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PROC(5)			   Linux Programmer's Manual		       PROC(5)



NAME
       proc - process information pseudo-filesystem

DESCRIPTION
       The  proc filesystem is a pseudo-filesystem which provides an interface
       to kernel data structures.  It is commonly mounted at /proc.   Most  of
       it is read-only, but some files allow kernel variables to be changed.

   Mount options
       The proc filesystem supports the following mount options:

       hidepid=n (since Linux 3.3)
	      This   option   controls	who  can  access  the  information  in
	      /proc/[pid] directories.	The argument, n, is one of the follow-
	      ing values:

	      0	  Everybody  may  access all /proc/[pid] directories.  This is
		  the traditional behavior, and	 the  default  if  this	 mount
		  option is not specified.

	      1	  Users	 may  not  access  files and subdirectories inside any
		  /proc/[pid]  directories  but	 their	own  (the  /proc/[pid]
		  directories  themselves  remain  visible).   Sensitive files
		  such as /proc/[pid]/cmdline and /proc/[pid]/status  are  now
		  protected  against other users.  This makes it impossible to
		  learn whether any user is running  a	specific  program  (so
		  long	as  the program doesn't otherwise reveal itself by its
		  behavior).

	      2	  As for mode 1, but in addition the  /proc/[pid]  directories
		  belonging  to other users become invisible.  This means that
		  /proc/[pid] entries can no longer be used  to	 discover  the
		  PIDs	on  the	 system.   This	 doesn't  hide the fact that a
		  process with a specific PID value exists (it can be  learned
		  by  other  means,  for  example,  by "kill -0 $PID"), but it
		  hides a process's UID and  GID,  which  could	 otherwise  be
		  learned  by  employing  stat(2)  on a /proc/[pid] directory.
		  This greatly complicates an  attacker's  task	 of  gathering
		  information	about  running	processes  (e.g.,  discovering
		  whether some daemon is  running  with	 elevated  privileges,
		  whether  another  user  is  running  some sensitive program,
		  whether other users are running any program at all,  and  so
		  on).

       gid=gid (since Linux 3.3)
	      Specifies	 the  ID  of  a	 group whose members are authorized to
	      learn process information otherwise prohibited by hidepid (i.e.,
	      users  in	 this  group  behave  as though /proc was mounted with
	      hidepid=0).  This group should be	 used  instead	of  approaches
	      such as putting nonroot users into the sudoers(5) file.

   Files and directories
       The  following  list  describes many of the files and directories under
       the /proc hierarchy.

       /proc/[pid]
	      There is a numerical subdirectory for each running process;  the
	      subdirectory is named by the process ID.

	      Each  /proc/[pid]	 subdirectory  contains	 the  pseudo-files and
	      directories described below.  These files are normally owned  by
	      the  effective user and effective group ID of the process.  How-
	      ever, as a security measure, the ownership is made root:root  if
	      the  process's "dumpable" attribute is set to a value other than
	      1.  This attribute may change for the following reasons:

	      *	 The  attribute	 was   explicitly   set	  via	the   prctl(2)
		 PR_SET_DUMPABLE operation.

	      *	 The   attribute   was	 reset	 to  the  value	 in  the  file
		 /proc/sys/fs/suid_dumpable (described below), for the reasons
		 described in prctl(2).

	      Resetting the "dumpable" attribute to 1 reverts the ownership of
	      the /proc/[pid]/* files to the process's real UID and real GID.

       /proc/[pid]/attr
	      The files in this directory provide an API for security modules.
	      The  contents  of	 this directory are files that can be read and
	      written in  order	 to  set  security-related  attributes.	  This
	      directory	 was  added  to support SELinux, but the intention was
	      that the API be general enough to support	 other	security  mod-
	      ules.   For  the purpose of explanation, examples of how SELinux
	      uses these files are provided below.

	      This directory is present only if the kernel was configured with
	      CONFIG_SECURITY.

       /proc/[pid]/attr/current (since Linux 2.6.0)
	      The  contents  of	 this  file  represent	the  current  security
	      attributes of the process.

	      In SELinux, this file is used to get the security context	 of  a
	      process.	 Prior to Linux 2.6.11, this file could not be used to
	      set the security context (a  write  was  always  denied),	 since
	      SELinux  limited	process security transitions to execve(2) (see
	      the description of /proc/[pid]/attr/exec, below).	  Since	 Linux
	      2.6.11,  SELinux	lifted	this  restriction and began supporting
	      "set" operations via writes to this node if authorized  by  pol-
	      icy,  although use of this operation is only suitable for appli-
	      cations that are trusted	to  maintain  any  desired  separation
	      between  the  old	 and  new  security  contexts.	Prior to Linux
	      2.6.28, SELinux did not allow threads  within  a	multi-threaded
	      process  to set their security context via this node as it would
	      yield an	inconsistency  among  the  security  contexts  of  the
	      threads  sharing	the  same  memory  space.  Since Linux 2.6.28,
	      SELinux lifted this restriction and began supporting "set" oper-
	      ations  for  threads  within  a multithreaded process if the new
	      security context is bounded by the old security  context,	 where
	      the  bounded  relation  is defined in policy and guarantees that
	      the new security context has a subset of the permissions of  the
	      old security context.  Other security modules may choose to sup-
	      port "set" operations via writes to this node.

       /proc/[pid]/attr/exec (since Linux 2.6.0)
	      This file represents the attributes to  assign  to  the  process
	      upon a subsequent execve(2).

	      In  SELinux,  this is needed to support role/domain transitions,
	      and execve(2) is the preferred point to  make  such  transitions
	      because  it offers better control over the initialization of the
	      process in the new security label and the inheritance of	state.
	      In SELinux, this attribute is reset on execve(2) so that the new
	      program reverts to the default behavior for any execve(2)	 calls
	      that  it	may  make.  In SELinux, a process can set only its own
	      /proc/[pid]/attr/exec attribute.

       /proc/[pid]/attr/fscreate (since Linux 2.6.0)
	      This file represents the attributes to assign to	files  created
	      by  subsequent  calls  to	 open(2),  mkdir(2),  symlink(2),  and
	      mknod(2)

	      SELinux employs this file to support creation of a  file	(using
	      the  aforementioned  system  calls)  in  a secure state, so that
	      there is no risk of inappropriate access being obtained  between
	      the  time	 of creation and the time that attributes are set.  In
	      SELinux, this attribute is reset on execve(2), so that  the  new
	      program  reverts	to  the default behavior for any file creation
	      calls it may make, but the attribute will persist across	multi-
	      ple file creation calls within a program unless it is explicitly
	      reset.   In  SELinux,  a	process	  can	set   only   its   own
	      /proc/[pid]/attr/fscreate attribute.

       /proc/[pid]/attr/keycreate (since Linux 2.6.18)
	      If  a process writes a security context into this file, all sub-
	      sequently created keys (add_key(2)) will be  labeled  with  this
	      context.	 For  further  information, see the kernel source file
	      Documentation/keys.txt.

       /proc/[pid]/attr/prev (since Linux 2.6.0)
	      This file contains the security context of  the  process	before
	      the   last   execve(2);	that   is,   the   previous  value  of
	      /proc/[pid]/attr/current.

       /proc/[pid]/attr/socketcreate (since Linux 2.6.18)
	      If a process writes a security context into this file, all  sub-
	      sequently created sockets will be labeled with this context.

       /proc/[pid]/autogroup (since Linux 2.6.38)
	      See sched(7).

       /proc/[pid]/auxv (since 2.6.0-test7)
	      This  contains  the  contents of the ELF interpreter information
	      passed to the process at exec time.  The format is one  unsigned
	      long  ID	plus one unsigned long value for each entry.  The last
	      entry contains two zeros.	 See also getauxval(3).

	      Permission to access this file is governed by  a	ptrace	access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/cgroup (since Linux 2.6.24)
	      See cgroups(7).

       /proc/[pid]/clear_refs (since Linux 2.6.22)

	      This  is	a  write-only  file,  writable	only  by  owner of the
	      process.

	      The following values may be written to the file:

	      1 (since Linux 2.6.22)
		     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all
		     the  pages	 associated  with the process.	(Before kernel
		     2.6.32, writing any nonzero value to this file  had  this
		     effect.)

	      2 (since Linux 2.6.32)
		     Reset  the	 PG_Referenced and ACCESSED/YOUNG bits for all
		     anonymous pages associated with the process.

	      3 (since Linux 2.6.32)
		     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all
		     file-mapped pages associated with the process.

	      Clearing	the  PG_Referenced  and ACCESSED/YOUNG bits provides a
	      method to measure approximately how much	memory	a  process  is
	      using.  One first inspects the values in the "Referenced" fields
	      for the VMAs shown in /proc/[pid]/smaps to get an	 idea  of  the
	      memory  footprint of the process.	 One then clears the PG_Refer-
	      enced and ACCESSED/YOUNG bits  and,  after  some	measured  time
	      interval,	 once  again  inspects	the values in the "Referenced"
	      fields to get an idea of the change in memory footprint  of  the
	      process during the measured interval.  If one is interested only
	      in inspecting the selected mapping types, then the value 2 or  3
	      can be used instead of 1.

	      Further values can be written to affect different properties:

	      4 (since Linux 3.11)
		     Clear  the	 soft-dirty  bit  for all the pages associated
		     with the process.	This  is  used	(in  conjunction  with
		     /proc/[pid]/pagemap) by the check-point restore system to
		     discover which pages of a process have been dirtied since
		     the file /proc/[pid]/clear_refs was written to.

	      5 (since Linux 4.0)
		     Reset  the	 peak resident set size ("high water mark") to
		     the process's current resident set size value.

	      Writing any value to  /proc/[pid]/clear_refs  other  than	 those
	      listed above has no effect.

	      The  /proc/[pid]/clear_refs  file	 is  present  only if the CON-
	      FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/cmdline
	      This read-only file holds the  complete  command	line  for  the
	      process,	unless	the  process is a zombie.  In the latter case,
	      there is nothing in this file: that is, a read on this file will
	      return  0 characters.  The command-line arguments appear in this
	      file as a set of strings separated by null bytes ('\0'), with  a
	      further null byte after the last string.

       /proc/[pid]/comm (since Linux 2.6.33)
	      This file exposes the process's comm value--that is, the command
	      name associated with the process.	 Different threads in the same
	      process	may   have   different	comm  values,  accessible  via
	      /proc/[pid]/task/[tid]/comm.   A	thread	may  modify  its  comm
	      value,  or  that of any of other thread in the same thread group
	      (see the discussion of CLONE_THREAD in clone(2)), by writing  to
	      the   file   /proc/self/task/[tid]/comm.	 Strings  longer  than
	      TASK_COMM_LEN (16) characters are silently truncated.

	      This file provides a superset of the  prctl(2)  PR_SET_NAME  and
	      PR_GET_NAME operations, and is employed by pthread_setname_np(3)
	      when used to rename threads other than the caller.

       /proc/[pid]/coredump_filter (since Linux 2.6.23)
	      See core(5).

       /proc/[pid]/cpuset (since Linux 2.6.12)
	      See cpuset(7).

       /proc/[pid]/cwd
	      This is a symbolic link to the current working directory of  the
	      process.	 To  find out the current working directory of process
	      20, for instance, you can do this:

		  $ cd /proc/20/cwd; /bin/pwd

	      Note that the pwd command is often a shell built-in,  and	 might
	      not work properly.  In bash(1), you may use pwd -P.

	      In  a  multithreaded process, the contents of this symbolic link
	      are not available if the	main  thread  has  already  terminated
	      (typically by calling pthread_exit(3)).

	      Permission  to  dereference  or read (readlink(2)) this symbolic
	      link    is    governed	by    a	    ptrace     access	  mode
	      PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/environ
	      This file contains the initial environment that was set when the
	      currently executing program  was	started	 via  execve(2).   The
	      entries  are  separated by null bytes ('\0'), and there may be a
	      null byte at the end.  Thus, to print  out  the  environment  of
	      process 1, you would do:

		  $ strings /proc/1/environ

	      If,  after  an  execve(2),  the process modifies its environment
	      (e.g., by calling functions such as putenv(3) or	modifying  the
	      environ(7)  variable directly), this file will not reflect those
	      changes.

	      Furthermore, a process may change the memory location that  this
	      file refers via prctl(2) operations such as PR_SET_MM_ENV_START.

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/exe
	      Under Linux 2.2 and later, this file is a symbolic link contain-
	      ing  the actual pathname of the executed command.	 This symbolic
	      link can be dereferenced normally; attempting to	open  it  will
	      open  the	 executable.  You can even type /proc/[pid]/exe to run
	      another copy of the same executable that is being run by process
	      [pid].   If  the	pathname  has been unlinked, the symbolic link
	      will contain the string '(deleted)'  appended  to	 the  original
	      pathname.	 In a multithreaded process, the contents of this sym-
	      bolic link are not available if the main thread has already ter-
	      minated (typically by calling pthread_exit(3)).

	      Permission  to  dereference  or read (readlink(2)) this symbolic
	      link    is    governed	by    a	    ptrace     access	  mode
	      PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

	      Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the
	      binary which was executed, and appears as a  symbolic  link.   A
	      readlink(2)  call	 on this file under Linux 2.0 returns a string
	      in the format:

		  [device]:inode

	      For example, [0301]:1502 would be inode 1502 on device major  03
	      (IDE,  MFM,  etc. drives) minor 01 (first partition on the first
	      drive).

	      find(1) with the -inum option can be used to locate the file.

       /proc/[pid]/fd/
	      This is a subdirectory containing one entry for each file	 which
	      the process has open, named by its file descriptor, and which is
	      a symbolic link to the actual file.  Thus, 0 is standard	input,
	      1 standard output, 2 standard error, and so on.

	      For  file descriptors for pipes and sockets, the entries will be
	      symbolic links whose content is the file type with the inode.  A
	      readlink(2) call on this file returns a string in the format:

		  type:[inode]

	      For  example, socket:[2248868] will be a socket and its inode is
	      2248868.	For sockets, that inode	 can  be  used	to  find  more
	      information in one of the files under /proc/net/.

	      For  file	 descriptors  that  have no corresponding inode (e.g.,
	      file   descriptors   produced   by   bpf(2),    epoll_create(2),
	      eventfd(2),  inotify_init(2),  perf_event_open(2),  signalfd(2),
	      timerfd_create(2), and userfautfd(2)), the entry will be a  sym-
	      bolic link with contents of the form

		  anon_inode:<file-type>

	      In  many	cases  (but  not  all), the file-type is surrounded by
	      square brackets.

	      For example, an epoll file descriptor will have a symbolic  link
	      whose content is the string anon_inode:[eventpoll].

	      In  a  multithreaded process, the contents of this directory are
	      not available if the main thread has already  terminated	(typi-
	      cally by calling pthread_exit(3)).

	      Programs	that  take  a filename as a command-line argument, but
	      don't take input from standard input if no argument is supplied,
	      and  programs that write to a file named as a command-line argu-
	      ment, but don't send their output to standard output if no argu-
	      ment is supplied, can nevertheless be made to use standard input
	      or standard output by using /proc/[pid]/fd files as command-line
	      arguments.   For example, assuming that -i is the flag designat-
	      ing an input file and -o is the flag designating an output file:

		  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

	      and you have a working filter.

	      /proc/self/fd/N is approximately the same as /dev/fd/N  in  some
	      UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts symboli-
	      cally link /dev/fd to /proc/self/fd, in fact.

	      Most systems provide symbolic links /dev/stdin, /dev/stdout, and
	      /dev/stderr, which respectively link to the files 0, 1, and 2 in
	      /proc/self/fd.  Thus the example command above could be  written
	      as:

		  $ foobar -i /dev/stdin -o /dev/stdout ...

	      Permission  to  dereference  or  read (readlink(2)) the symbolic
	      links in this directory is governed  by  a  ptrace  access  mode
	      PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/fdinfo/ (since Linux 2.6.22)
	      This  is a subdirectory containing one entry for each file which
	      the process has open, named by its file descriptor.   The	 files
	      in this directory are readable only by the owner of the process.
	      The contents of each file can  be	 read  to  obtain  information
	      about the corresponding file descriptor.	The content depends on
	      the type of file referred to by the corresponding file  descrip-
	      tor.

	      For regular files and directories, we see something like:

		  $ cat /proc/12015/fdinfo/4
		  pos:	  1000
		  flags:  01002002
		  mnt_id: 21

	      The fields are as follows:

	      pos    This is a decimal number showing the file offset.

	      flags  This  is  an  octal  number that displays the file access
		     mode and file status flags (see open(2)).	If the	close-
		     on-exec file descriptor flag is set, then flags will also
		     include the value O_CLOEXEC.

		     Before Linux 3.1, this field  incorrectly	displayed  the
		     setting  of  O_CLOEXEC  at	 the time the file was opened,
		     rather than the  current  setting	of  the	 close-on-exec
		     flag.

	      mnt_id This  field,  present  since Linux 3.15, is the ID of the
		     mount point containing this file.	See the description of
		     /proc/[pid]/mountinfo.

	      For  eventfd  file  descriptors  (see eventfd(2)), we see (since
	      Linux 3.8) the following fields:

		  pos: 0
		  flags:    02
		  mnt_id:   10
		  eventfd-count:	       40

	      eventfd-count is the current value of the	 eventfd  counter,  in
	      hexadecimal.

	      For  epoll  file descriptors (see epoll(7)), we see (since Linux
	      3.8) the following fields:

		  pos: 0
		  flags:    02
		  mnt_id:   10
		  tfd:	      9 events:	      19 data: 74253d2500000009
		  tfd:	      7 events:	      19 data: 74253d2500000007

	      Each of the lines	 beginning  tfd	 describes  one	 of  the  file
	      descriptors  being  monitored via the epoll file descriptor (see
	      epoll_ctl(2) for some details).  The tfd field is the number  of
	      the  file descriptor.  The events field is a hexadecimal mask of
	      the events being monitored for this file descriptor.   The  data
	      field is the data value associated with this file descriptor.

	      For  signalfd  file descriptors (see signalfd(2)), we see (since
	      Linux 3.8) the following fields:

		  pos: 0
		  flags:    02
		  mnt_id:   10
		  sigmask:  0000000000000006

	      sigmask is the hexadecimal mask of signals that are accepted via
	      this  signalfd  file descriptor.	(In this example, bits 2 and 3
	      are set, corresponding to the signals SIGINT  and	 SIGQUIT;  see
	      signal(7).)

	      For  inotify  file  descriptors  (see inotify(7)), we see (since
	      Linux 3.8) the following fields:

		  pos: 0
		  flags:    00
		  mnt_id:   11
		  inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73
		  inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73

	      Each of the lines beginning with "inotify" displays  information
	      about one file or directory that is being monitored.  The fields
	      in this line are as follows:

	      wd     A watch descriptor number (in decimal).

	      ino    The inode number of the target file (in hexadecimal).

	      sdev   The ID of the device where the target  file  resides  (in
		     hexadecimal).

	      mask   The  mask	of  events being monitored for the target file
		     (in hexadecimal).

	      If the kernel was built with exportfs support, the path  to  the
	      target  file  is exposed as a file handle, via three hexadecimal
	      fields: fhandle-bytes, fhandle-type, and f_handle.

	      For fanotify file descriptors (see fanotify(7)), we  see	(since
	      Linux 3.8) the following fields:

		  pos: 0
		  flags:    02
		  mnt_id:   11
		  fanotify flags:0 event-flags:88002
		  fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73

	      The  fourth  line displays information defined when the fanotify
	      group was created via fanotify_init(2):

	      flags  The flags argument given to  fanotify_init(2)  (expressed
		     in hexadecimal).

	      event-flags
		     The  event_f_flags	 argument  given  to  fanotify_init(2)
		     (expressed in hexadecimal).

	      Each additional line shown  in  the  file	 contains  information
	      about  one  of  the  marks in the fanotify group.	 Most of these
	      fields are as for inotify, except:

	      mflags The flags associated with the mark (expressed in hexadec-
		     imal).

	      mask   The events mask for this mark (expressed in hexadecimal).

	      ignored_mask
		     The  mask	of  events  that  are  ignored	for  this mark
		     (expressed in hexadecimal).

	      For details on these fields, see fanotify_mark(2).

       /proc/[pid]/gid_map (since Linux 3.5)
	      See user_namespaces(7).

       /proc/[pid]/io (since kernel 2.6.20)
	      This file contains I/O statistics for the process, for example:

		  # cat /proc/3828/io
		  rchar: 323934931
		  wchar: 323929600
		  syscr: 632687
		  syscw: 632675
		  read_bytes: 0
		  write_bytes: 323932160
		  cancelled_write_bytes: 0

	      The fields are as follows:

	      rchar: characters read
		     The number of bytes which this task has caused to be read
		     from storage.  This is simply the sum of bytes which this
		     process passed to read(2) and similar system  calls.   It
		     includes things such as terminal I/O and is unaffected by
		     whether or not actual physical disk I/O was required (the
		     read might have been satisfied from pagecache).

	      wchar: characters written
		     The  number of bytes which this task has caused, or shall
		     cause to be written to disk.  Similar caveats apply  here
		     as with rchar.

	      syscr: read syscalls
		     Attempt  to count the number of read I/O operations--that
		     is, system calls such as read(2) and pread(2).

	      syscw: write syscalls
		     Attempt to count the number of write I/O operations--that
		     is, system calls such as write(2) and pwrite(2).

	      read_bytes: bytes read
		     Attempt  to  count the number of bytes which this process
		     really did cause to be fetched from  the  storage	layer.
		     This is accurate for block-backed filesystems.

	      write_bytes: bytes written
		     Attempt  to  count the number of bytes which this process
		     caused to be sent to the storage layer.

	      cancelled_write_bytes:
		     The big inaccuracy here is truncate.  If a process writes
		     1MB  to a file and then deletes the file, it will in fact
		     perform no writeout.  But it will have been accounted  as
		     having  caused  1MB of write.  In other words: this field
		     represents the number of bytes which this process	caused
		     to not happen, by truncating pagecache.  A task can cause
		     "negative" I/O too.  If this task	truncates  some	 dirty
		     pagecache, some I/O which another task has been accounted
		     for (in its write_bytes) will not be happening.

	      Note: In the current implementation, things are a	 bit  racy  on
	      32-bit  systems:	if  process A reads process B's /proc/[pid]/io
	      while process B  is  updating  one  of  these  64-bit  counters,
	      process A could see an intermediate result.

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/limits (since Linux 2.6.24)
	      This file displays the soft limit, hard limit, and units of mea-
	      surement	for  each  of the process's resource limits (see getr-
	      limit(2)).  Up to and including Linux 2.6.35, this file is  pro-
	      tected  to  allow	 reading  only by the real UID of the process.
	      Since Linux 2.6.36, this file is readable by all	users  on  the
	      system.

       /proc/[pid]/map_files/ (since kernel 3.3)
	      This  subdirectory  contains  entries  corresponding  to memory-
	      mapped files (see mmap(2)).  Entries are named by memory	region
	      start  and  end address pair (expressed as hexadecimal numbers),
	      and are symbolic links to the mapped files themselves.  Here  is
	      an example, with the output wrapped and reformatted to fit on an
	      80-column display:

		  # ls -l /proc/self/map_files/
		  lr--------. 1 root root 64 Apr 16 21:31
			      3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
		  ...

	      Although these entries are present for memory regions that  were
	      mapped  with  the MAP_FILE flag, the way anonymous shared memory
	      (regions created with the MAP_ANON | MAP_SHARED flags) is imple-
	      mented  in  Linux	 means	that  such regions also appear on this
	      directory.  Here is an example where  the	 target	 file  is  the
	      deleted /dev/zero one:

		  lrw-------. 1 root root 64 Apr 16 21:33
			      7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

	      This  directory  appears	only  if the CONFIG_CHECKPOINT_RESTORE
	      kernel   configuration	option	  is	enabled.     Privilege
	      (CAP_SYS_ADMIN)  is required to view the contents of this direc-
	      tory.

       /proc/[pid]/maps
	      A file containing the currently mapped memory regions and	 their
	      access  permissions.   See  mmap(2) for some further information
	      about memory mappings.

	      Permission to access this file is governed by  a	ptrace	access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

	      The format of the file is:

       address		 perms offset  dev   inode	 pathname
       00400000-00452000 r-xp 00000000 08:02 173521	 /usr/bin/dbus-daemon
       00651000-00652000 r--p 00051000 08:02 173521	 /usr/bin/dbus-daemon
       00652000-00655000 rw-p 00052000 08:02 173521	 /usr/bin/dbus-daemon
       00e03000-00e24000 rw-p 00000000 00:00 0		 [heap]
       00e24000-011f7000 rw-p 00000000 00:00 0		 [heap]
       ...
       35b1800000-35b1820000 r-xp 00000000 08:02 135522	 /usr/lib64/ld-2.15.so
       35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522	 /usr/lib64/ld-2.15.so
       35b1a20000-35b1a21000 rw-p 00020000 08:02 135522	 /usr/lib64/ld-2.15.so
       35b1a21000-35b1a22000 rw-p 00000000 00:00 0
       35b1c00000-35b1dac000 r-xp 00000000 08:02 135870	 /usr/lib64/libc-2.15.so
       35b1dac000-35b1fac000 ---p 001ac000 08:02 135870	 /usr/lib64/libc-2.15.so
       35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870	 /usr/lib64/libc-2.15.so
       35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870	 /usr/lib64/libc-2.15.so
       ...
       f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0	 [stack:986]
       ...
       7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0	 [stack]
       7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0	 [vdso]

	      The  address  field is the address space in the process that the
	      mapping occupies.	 The perms field is a set of permissions:

		   r = read
		   w = write
		   x = execute
		   s = shared
		   p = private (copy on write)

	      The offset field is the offset into the  file/whatever;  dev  is
	      the  device (major:minor); inode is the inode on that device.  0
	      indicates that no inode is associated with the memory region, as
	      would be the case with BSS (uninitialized data).

	      The  pathname field will usually be the file that is backing the
	      mapping.	For ELF files, you can easily coordinate with the off-
	      set  field  by  looking  at  the Offset field in the ELF program
	      headers (readelf -l).

	      There are additional helpful pseudo-paths:

		   [stack]
			  The  initial	process's  (also  known	 as  the  main
			  thread's) stack.

		   [stack:<tid>] (since Linux 3.4)
			  A  thread's  stack (where the <tid> is a thread ID).
			  It corresponds to the /proc/[pid]/task/[tid]/ path.

		   [vdso] The virtual dynamically linked shared	 object.   See
			  vdso(7).

		   [heap] The process's heap.

	      If  the pathname field is blank, this is an anonymous mapping as
	      obtained via mmap(2).  There is no easy way to  coordinate  this
	      back  to a process's source, short of running it through gdb(1),
	      strace(1), or similar.

	      Under Linux 2.0, there is no field giving pathname.

       /proc/[pid]/mem
	      This file can be used to access the pages of a process's	memory
	      through open(2), read(2), and lseek(2).

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
	      This  file  contains  information	 about	mount  points  in  the
	      process's	 mount	namespace  (see mount_namespaces(7)).  It sup-
	      plies various information	 (e.g.,	 propagation  state,  root  of
	      mount for bind mounts, identifier for each mount and its parent)
	      that is missing from the (older)	/proc/[pid]/mounts  file,  and
	      fixes  various  other problems with that file (e.g., nonextensi-
	      bility, failure to distinguish per-mount	versus	per-superblock
	      options).

	      The file contains lines of the form:

	      36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
	      (1)(2)(3)	  (4)	(5)	 (6)	  (7)	(8) (9)	  (10)	       (11)

	      The  numbers  in	parentheses  are  labels  for the descriptions
	      below:

	      (1)  mount ID: a unique ID for the mount (may  be	 reused	 after
		   umount(2)).

	      (2)  parent  ID:	the ID of the parent mount (or of self for the
		   top of the mount tree).

	      (3)  major:minor: the value of st_dev for files on this filesys-
		   tem (see stat(2)).

	      (4)  root: the pathname of the directory in the filesystem which
		   forms the root of this mount.

	      (5)  mount point: the pathname of the mount  point  relative  to
		   the process's root directory.

	      (6)  mount options: per-mount options.

	      (7)  optional   fields:	zero   or  more	 fields	 of  the  form
		   "tag[:value]"; see below.

	      (8)  separator: the end of the optional fields is	 marked	 by  a
		   single hyphen.

	      (9)  filesystem	type:	the   filesystem   type	 in  the  form
		   "type[.subtype]".

	      (10) mount source: filesystem-specific information or "none".

	      (11) super options: per-superblock options.

	      Currently, the possible  optional	 fields	 are  shared,  master,
	      propagate_from,  and  unbindable.	 See mount_namespaces(7) for a
	      description of these fields.  Parsers should ignore all unrecog-
	      nized optional fields.

	      For  more	 information  on  mount	 propagation  see:  Documenta-
	      tion/filesystems/sharedsubtree.txt in the	 Linux	kernel	source
	      tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
	      This  file  lists	 all  the filesystems currently mounted in the
	      process's mount namespace (see mount_namespaces(7)).  The format
	      of this file is documented in fstab(5).

	      Since  kernel version 2.6.15, this file is pollable: after open-
	      ing the file for	reading,  a  change  in	 this  file  (i.e.,  a
	      filesystem  mount	 or unmount) causes select(2) to mark the file
	      descriptor as having an exceptional condition, and  poll(2)  and
	      epoll_wait(2)  mark  the	file as having a priority event (POLL-
	      PRI).  (Before Linux 2.6.30, a change in this file was indicated
	      by  the  file descriptor being marked as readable for select(2),
	      and being marked as having an error condition  for  poll(2)  and
	      epoll_wait(2).)

       /proc/[pid]/mountstats (since Linux 2.6.17)
	      This  file exports information (statistics, configuration infor-
	      mation) about the mount points in the process's mount  namespace
	      (see mount_namespaces(7)).  Lines in this file have the form:

	      device /dev/sda7 mounted on /home with fstype ext3 [statistics]
	      (	      1	     )		  ( 2 )		    (3 ) (4)

	      The fields in each line are:

	      (1)  The	name  of the mounted device (or "nodevice" if there is
		   no corresponding device).

	      (2)  The mount point within the filesystem tree.

	      (3)  The filesystem type.

	      (4)  Optional statistics and  configuration  information.	  Cur-
		   rently  (as	at  Linux 2.6.26), only NFS filesystems export
		   information via this field.

	      This file is readable only by the owner of the process.

       /proc/[pid]/net " (since Linux 2.6.25)"
	      See the description of /proc/net.

       /proc/[pid]/ns/ (since Linux 3.0)
	      This is a subdirectory containing one entry for  each  namespace
	      that  supports being manipulated by setns(2).  For more informa-
	      tion, see namespaces(7).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
	      See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
	      This file can be used to adjust the score used to	 select	 which
	      process  should  be  killed in an out-of-memory (OOM) situation.
	      The kernel uses this value for  a	 bit-shift  operation  of  the
	      process's	 oom_score value: valid values are in the range -16 to
	      +15, plus the special  value  -17,  which	 disables  OOM-killing
	      altogether  for  this  process.	A positive score increases the
	      likelihood of this process being killed  by  the	OOM-killer;  a
	      negative score decreases the likelihood.

	      The default value for this file is 0; a new process inherits its
	      parent's	oom_adj	 setting.   A  process	must   be   privileged
	      (CAP_SYS_RESOURCE) to update this file.

	      Since  Linux  2.6.36, use of this file is deprecated in favor of
	      /proc/[pid]/oom_score_adj.

       /proc/[pid]/oom_score (since Linux 2.6.11)
	      This file displays the current score that the  kernel  gives  to
	      this process for the purpose of selecting a process for the OOM-
	      killer.  A higher score means that the process is more likely to
	      be  selected by the OOM-killer.  The basis for this score is the
	      amount of memory used by the  process,  with  increases  (+)  or
	      decreases (-) for factors including:

	      * whether	 the  process  creates a lot of children using fork(2)
		(+);

	      * whether the process has been running a long time, or has  used
		a lot of CPU time (-);

	      * whether the process has a low nice value (i.e., > 0) (+);

	      * whether the process is privileged (-); and

	      * whether the process is making direct hardware access (-).

	      The  oom_score  also  reflects  the  adjustment specified by the
	      oom_score_adj or oom_adj setting for the process.

       /proc/[pid]/oom_score_adj (since Linux 2.6.36)
	      This file can be used to adjust the badness  heuristic  used  to
	      select which process gets killed in out-of-memory conditions.

	      The  badness  heuristic  assigns	a value to each candidate task
	      ranging from 0 (never kill) to 1000 (always kill)	 to  determine
	      which  process  is targeted.  The units are roughly a proportion
	      along that range of allowed  memory  the	process	 may  allocate
	      from, based on an estimation of its current memory and swap use.
	      For example, if a task is using all allowed memory, its  badness
	      score  will be 1000.  If it is using half of its allowed memory,
	      its score will be 500.

	      There is an additional factor included  in  the  badness	score:
	      root processes are given 3% extra memory over other tasks.

	      The  amount  of "allowed" memory depends on the context in which
	      the OOM-killer was called.  If it is due to the memory  assigned
	      to  the  allocating  task's  cpuset being exhausted, the allowed
	      memory represents the set of mems assigned to that  cpuset  (see
	      cpuset(7)).   If	it  is	due  to	 a  mempolicy's	 node(s) being
	      exhausted, the allowed memory represents the  set	 of  mempolicy
	      nodes.   If  it  is  due to a memory limit (or swap limit) being
	      reached, the allowed memory is that configured limit.   Finally,
	      if  it  is  due  to  the	entire system being out of memory, the
	      allowed memory represents all allocatable resources.

	      The value of oom_score_adj is added to the badness score	before
	      it  is  used to determine which task to kill.  Acceptable values
	      range    from	-1000	  (OOM_SCORE_ADJ_MIN)	  to	 +1000
	      (OOM_SCORE_ADJ_MAX).   This  allows  user	 space	to control the
	      preference for OOM-killing, ranging  from	 always	 preferring  a
	      certain  task  or completely disabling it from OOM killing.  The
	      lowest possible value, -1000, is equivalent  to  disabling  OOM-
	      killing  entirely	 for  that task, since it will always report a
	      badness score of 0.

	      Consequently, it is very simple for user	space  to  define  the
	      amount  of  memory  to  consider	for  each  task.   Setting  an
	      oom_score_adj value of +500, for example, is roughly  equivalent
	      to  allowing  the	 remainder  of	tasks sharing the same system,
	      cpuset, mempolicy, or memory  controller	resources  to  use  at
	      least  50%  more	memory.	  A  value of -500, on the other hand,
	      would be roughly equivalent to discounting  50%  of  the	task's
	      allowed  memory  from  being  considered	as scoring against the
	      task.

	      For    backward	 compatibility	  with	  previous    kernels,
	      /proc/[pid]/oom_adj can still be used to tune the badness score.
	      Its value is scaled linearly with oom_score_adj.

	      Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
	      change the other with its scaled value.

       /proc/[pid]/pagemap (since Linux 2.6.25)
	      This  file  shows	 the  mapping of each of the process's virtual
	      pages into physical page frames or swap area.  It	 contains  one
	      64-bit  value  for  each virtual page, with the bits set as fol-
	      lows:

		   63	  If set, the page is present in RAM.

		   62	  If set, the page is in swap space

		   61 (since Linux 3.5)
			  The page is a file-mapped page or a shared anonymous
			  page.

		   60-56 (since Linux 3.11)
			  Zero

		   55 (Since Linux 3.11)
			  PTE  is soft-dirty (see the kernel source file Docu-
			  mentation/vm/soft-dirty.txt).

		   54-0	  If the page is present in RAM (bit 63),  then	 these
			  bits	provide	 the  page  frame number, which can be
			  used to index /proc/kpageflags and /proc/kpagecount.
			  If  the  page is present in swap (bit 62), then bits
			  4-0 give the swap type, and  bits  54-5  encode  the
			  swap offset.

	      Before Linux 3.11, bits 60-55 were used to encode the base-2 log
	      of the page size.

	      To employ /proc/[pid]/pagemap efficiently, use  /proc/[pid]/maps
	      to  determine which areas of memory are actually mapped and seek
	      to skip over unmapped regions.

	      The  /proc/[pid]/pagemap	file  is  present  only	 if  the  CON-
	      FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/personality (since Linux 2.6.28)
	      This read-only file exposes the process's execution  domain,  as
	      set  by  personality(2).	 The value is displayed in hexadecimal
	      notation.

	      Permission to access this file is governed by  a	ptrace	access
	      mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/root
	      UNIX  and	 Linux	support	 the idea of a per-process root of the
	      filesystem, set by the chroot(2) system call.  This  file	 is  a
	      symbolic	link  that points to the process's root directory, and
	      behaves in the same way as exe, and fd/*.

	      Note however that this file is not merely a symbolic  link.   It
	      provides	the  same view of the filesystem (including namespaces
	      and the set of per-process mounts) as the	 process  itself.   An
	      example  illustrates  this  point.   In one terminal, we start a
	      shell in new user and mount namespaces, and  in  that  shell  we
	      create some new mount points:

		  $ PS1='sh1# ' unshare -Urnm
		  sh1# mount -t tmpfs tmpfs /etc  # Mount empty tmpfs at /etc
		  sh1# mount --bind /usr /dev	  # Mount /usr at /dev
		  sh1# echo $$
		  27123

	      In  a second terminal window, in the initial mount namespace, we
	      look at the contents of the corresponding mounts in the  initial
	      and new namespaces:

		  $ PS1='sh2# ' sudo sh
		  sh2# ls /etc | wc -l			# In initial NS
		  309
		  sh2# ls /proc/27123/root/etc | wc -l	# /etc in other NS
		  0					# The empty tmpfs dir
		  sh2# ls /dev | wc -l			# In initial NS
		  205
		  sh2# ls /proc/27123/root/dev | wc -l	# /dev in other NS
		  11					# Actually bind
							# mounted to /usr
		  sh2# ls /usr | wc -l			# /usr in initial NS
		  11

	      In a multithreaded process, the contents of the /proc/[pid]/root
	      symbolic link are not available if the main thread  has  already
	      terminated (typically by calling pthread_exit(3)).

	      Permission  to  dereference  or read (readlink(2)) this symbolic
	      link    is    governed	by    a	    ptrace     access	  mode
	      PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)
	      This  file  can  be used to read and change the process's secure
	      computing (seccomp) mode setting.	 It contains the  value	 0  if
	      the  process  is not in seccomp mode, and 1 if the process is in
	      strict seccomp mode (see seccomp(2)).  Writing 1	to  this  file
	      places  the  process irreversibly in strict seccomp mode.	 (Fur-
	      ther attempts to write to the file fail with the EPERM error.)

	      In Linux 2.6.23, this file went away,  to	 be  replaced  by  the
	      prctl(2) PR_GET_SECCOMP and PR_SET_SECCOMP operations (and later
	      by seccomp(2) and the Seccomp field in /proc/[pid]/status).

       /proc/[pid]/setgroups (since Linux 3.19)
	      See user_namespaces(7).

       /proc/[pid]/smaps (since Linux 2.6.14)
	      This file shows memory consumption for  each  of	the  process's
	      mappings.	 (The pmap(1) command displays similar information, in
	      a form that may be easier for parsing.)  For each mapping	 there
	      is a series of lines such as the following:

		  00400000-0048a000 r-xp 00000000 fd:03 960637	     /bin/bash
		  Size:		       552 kB
		  Rss:		       460 kB
		  Pss:		       100 kB
		  Shared_Clean:	       452 kB
		  Shared_Dirty:		 0 kB
		  Private_Clean:	 8 kB
		  Private_Dirty:	 0 kB
		  Referenced:	       460 kB
		  Anonymous:		 0 kB
		  AnonHugePages:	 0 kB
		  ShmemHugePages:	 0 kB
		  ShmemPmdMapped:	 0 kB
		  Swap:			 0 kB
		  KernelPageSize:	 4 kB
		  MMUPageSize:		 4 kB
		  KernelPageSize:	 4 kB
		  MMUPageSize:		 4 kB
		  Locked:		 0 kB
		  ProtectionKey:	 0
		  VmFlags: rd ex mr mw me dw

	      The  first  of these lines shows the same information as is dis-
	      played for the mapping in /proc/[pid]/maps.  The following lines
	      show  the size of the mapping, the amount of the mapping that is
	      currently resident in RAM ("Rss"),  the  process's  proportional
	      share  of	 this  mapping	("Pss"), the number of clean and dirty
	      shared pages in the mapping, and the number of clean  and	 dirty
	      private pages in the mapping.  "Referenced" indicates the amount
	      of memory currently marked as referenced or  accessed.   "Anony-
	      mous"  shows  the	 amount	 of memory that does not belong to any
	      file.  "Swap" shows how much would-be-anonymous memory  is  also
	      used, but out on swap.

	      The  "KernelPageSize" line (available since Linux 2.6.29) is the
	      page size used by the kernel to back the	virtual	 memory	 area.
	      This  matches the size used by the MMU in the majority of cases.
	      However, one counter-example occurs on PPC64 kernels  whereby  a
	      kernel  using  64kB  as a base page size may still use 4kB pages
	      for the  MMU  on	older  processors.   To	 distinguish  the  two
	      attributes,  the	"MMUPageSize" line (also available since Linux
	      2.6.29) reports the page size used by the MMU.

	      The "Locked" indicates whether the mapping is locked  in	memory
	      or not.

	      The  "ProtectionKey"  line  (available  since  Linux 4.9, on x86
	      only) contains the memory protection key (see pkeys(7))  associ-
	      ated  with  the virtual memory area.  This entry is present only
	      if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-
	      TION_KEYS configuration option.

	      The  "VmFlags"  line  (available since Linux 3.8) represents the
	      kernel flags associated with the virtual	memory	area,  encoded
	      using the following two-letter codes:

		  rd  - readable
		  wr  - writable
		  ex  - executable
		  sh  - shared
		  mr  - may read
		  mw  - may write
		  me  - may execute
		  ms  - may share
		  gd  - stack segment grows down
		  pf  - pure PFN range
		  dw  - disabled write to the mapped file
		  lo  - pages are locked in memory
		  io  - memory mapped I/O area
		  sr  - sequential read advise provided
		  rr  - random read advise provided
		  dc  - do not copy area on fork
		  de  - do not expand area on remapping
		  ac  - area is accountable
		  nr  - swap space is not reserved for the area
		  ht  - area uses huge tlb pages
		  nl  - non-linear mapping
		  ar  - architecture specific flag
		  dd  - do not include area into core dump
		  sd  - soft-dirty flag
		  mm  - mixed map area
		  hg  - huge page advise flag
		  nh  - no-huge page advise flag
		  mg  - mergeable advise flag

	      "ProtectionKey"  field  contains	the memory protection key (see
	      pkeys(5)) associated with the virtual memory area.  Present only
	      if the kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTEC-
	      TION_KEYS configuration option. (since Linux 4.6)

	      The  /proc/[pid]/smaps  file  is	present	 only  if   the	  CON-
	      FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/stack (since Linux 2.6.29)
	      This  file  provides  a  symbolic trace of the function calls in
	      this process's kernel stack.  This file is provided only if  the
	      kernel   was  built  with	 the  CONFIG_STACKTRACE	 configuration
	      option.

	      Permission to access this file is governed by  a	ptrace	access
	      mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/stat
	      Status  information  about  the process.	This is used by ps(1).
	      It is defined in the kernel source file fs/proc/array.c.

	      The fields, in order, with their proper scanf(3)	format	speci-
	      fiers, are listed below.	Whether or not certain of these fields
	      display valid information is governed by a  ptrace  access  mode
	      PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT  check  (refer to
	      ptrace(2)).  If the check denies access, then the field value is
	      displayed	 as  0.	  The  affected	 fields are indicated with the
	      marking [PT].


	      (1) pid  %d
			The process ID.

	      (2) comm	%s
			The filename of the executable, in parentheses.	  This
			is  visible  whether  or not the executable is swapped
			out.

	      (3) state	 %c
			One of the following  characters,  indicating  process
			state:

			R  Running

			S  Sleeping in an interruptible wait

			D  Waiting in uninterruptible disk sleep

			Z  Zombie

			T  Stopped  (on	 a  signal)  or	 (before Linux 2.6.33)
			   trace stopped

			t  Tracing stop (Linux 2.6.33 onward)

			W  Paging (only before Linux 2.6.0)

			X  Dead (from Linux 2.6.0 onward)

			x  Dead (Linux 2.6.33 to 3.13 only)

			K  Wakekill (Linux 2.6.33 to 3.13 only)

			W  Waking (Linux 2.6.33 to 3.13 only)

			P  Parked (Linux 3.9 to 3.13 only)

	      (4) ppid	%d
			The PID of the parent of this process.

	      (5) pgrp	%d
			The process group ID of the process.

	      (6) session  %d
			The session ID of the process.

	      (7) tty_nr  %d
			The controlling terminal of the process.   (The	 minor
			device	number is contained in the combination of bits
			31 to 20 and 7 to 0; the major	device	number	is  in
			bits 15 to 8.)

	      (8) tpgid	 %d
			The ID of the foreground process group of the control-
			ling terminal of the process.

	      (9) flags	 %u
			The kernel flags word of the process.  For  bit	 mean-
			ings,  see the PF_* defines in the Linux kernel source
			file include/linux/sched.h.   Details  depend  on  the
			kernel version.

			The format for this field was %lu before Linux 2.6.

	      (10) minflt  %lu
			The  number of minor faults the process has made which
			have not required loading a memory page from disk.

	      (11) cminflt  %lu
			The number of minor faults that the process's  waited-
			for children have made.

	      (12) majflt  %lu
			The  number of major faults the process has made which
			have required loading a memory page from disk.

	      (13) cmajflt  %lu
			The number of major faults that the process's  waited-
			for children have made.

	      (14) utime  %lu
			Amount of time that this process has been scheduled in
			user  mode,  measured  in  clock  ticks	  (divide   by
			sysconf(_SC_CLK_TCK)).	  This	includes  guest	 time,
			guest_time (time spent	running	 a  virtual  CPU,  see
			below), so that applications that are not aware of the
			guest time field do not lose that time from their cal-
			culations.

	      (15) stime  %lu
			Amount of time that this process has been scheduled in
			kernel	mode,  measured	 in  clock  ticks  (divide  by
			sysconf(_SC_CLK_TCK)).

	      (16) cutime  %ld
			Amount of time that this process's waited-for children
			have been scheduled in user mode,  measured  in	 clock
			ticks  (divide	by  sysconf(_SC_CLK_TCK)).   (See also
			times(2).)   This  includes  guest  time,  cguest_time
			(time spent running a virtual CPU, see below).

	      (17) cstime  %ld
			Amount of time that this process's waited-for children
			have been scheduled in kernel mode, measured in	 clock
			ticks (divide by sysconf(_SC_CLK_TCK)).

	      (18) priority  %ld
			(Explanation  for  Linux  2.6) For processes running a
			real-time  scheduling  policy	(policy	  below;   see
			sched_setscheduler(2)), this is the negated scheduling
			priority, minus one; that is, a number in the range -2
			to  -100,  corresponding  to real-time priorities 1 to
			99.   For  processes  running  under  a	 non-real-time
			scheduling policy, this is the raw nice value (setpri-
			ority(2)) as represented in the	 kernel.   The	kernel
			stores nice values as numbers in the range 0 (high) to
			39 (low), corresponding to the user-visible nice range
			of -20 to 19.

			Before Linux 2.6, this was a scaled value based on the
			scheduler weighting given to this process.

	      (19) nice	 %ld
			The nice value (see setpriority(2)), a	value  in  the
			range 19 (low priority) to -20 (high priority).

	      (20) num_threads	%ld
			Number	of  threads in this process (since Linux 2.6).
			Before kernel 2.6, this field was hard coded to 0 as a
			placeholder for an earlier removed field.

	      (21) itrealvalue	%ld
			The time in jiffies before the next SIGALRM is sent to
			the process due to an interval	timer.	 Since	kernel
			2.6.17,	 this  field  is  no longer maintained, and is
			hard coded as 0.

	      (22) starttime  %llu
			The time the process started after  system  boot.   In
			kernels	 before Linux 2.6, this value was expressed in
			jiffies.  Since Linux 2.6, the value is	 expressed  in
			clock ticks (divide by sysconf(_SC_CLK_TCK)).

			The format for this field was %lu before Linux 2.6.

	      (23) vsize  %lu
			Virtual memory size in bytes.

	      (24) rss	%ld
			Resident  Set Size: number of pages the process has in
			real memory.  This  is	just  the  pages  which	 count
			toward	text,  data,  or  stack	 space.	 This does not
			include pages which have not been demand-loaded in, or
			which are swapped out.

	      (25) rsslim  %lu
			Current soft limit in bytes on the rss of the process;
			see the description of RLIMIT_RSS in getrlimit(2).

	      (26) startcode  %lu  [PT]
			The address above which program text can run.

	      (27) endcode  %lu	 [PT]
			The address below which program text can run.

	      (28) startstack  %lu  [PT]
			The address of the start (i.e., bottom) of the stack.

	      (29) kstkesp  %lu	 [PT]
			The current value of ESP (stack pointer), as found  in
			the kernel stack page for the process.

	      (30) kstkeip  %lu	 [PT]
			The current EIP (instruction pointer).

	      (31) signal  %lu
			The  bitmap of pending signals, displayed as a decimal
			number.	 Obsolete, because it does not provide	infor-
			mation	on  real-time  signals; use /proc/[pid]/status
			instead.

	      (32) blocked  %lu
			The bitmap of blocked signals, displayed as a  decimal
			number.	  Obsolete, because it does not provide infor-
			mation on real-time  signals;  use  /proc/[pid]/status
			instead.

	      (33) sigignore  %lu
			The  bitmap of ignored signals, displayed as a decimal
			number.	 Obsolete, because it does not provide	infor-
			mation	on  real-time  signals; use /proc/[pid]/status
			instead.

	      (34) sigcatch  %lu
			The bitmap of caught signals, displayed as  a  decimal
			number.	  Obsolete, because it does not provide infor-
			mation on real-time  signals;  use  /proc/[pid]/status
			instead.

	      (35) wchan  %lu  [PT]
			This is the "channel" in which the process is waiting.
			It is the address of a location in  the	 kernel	 where
			the  process  is sleeping.  The corresponding symbolic
			name can be found in /proc/[pid]/wchan.

	      (36) nswap  %lu
			Number of pages swapped (not maintained).

	      (37) cnswap  %lu
			Cumulative nswap for child processes (not maintained).

	      (38) exit_signal	%d  (since Linux 2.1.22)
			Signal to be sent to parent when we die.

	      (39) processor  %d  (since Linux 2.2.8)
			CPU number last executed on.

	      (40) rt_priority	%u  (since Linux 2.5.19)
			Real-time scheduling priority, a number in the range 1
			to  99	for processes scheduled under a real-time pol-
			icy,  or   0,	for   non-real-time   processes	  (see
			sched_setscheduler(2)).

	      (41) policy  %u  (since Linux 2.5.19)
			Scheduling policy (see sched_setscheduler(2)).	Decode
			using the SCHED_* constants in linux/sched.h.

			The format for this field was %lu before Linux 2.6.22.

	      (42) delayacct_blkio_ticks  %llu	(since Linux 2.6.18)
			Aggregated block I/O delays, measured in  clock	 ticks
			(centiseconds).

	      (43) guest_time  %lu  (since Linux 2.6.24)
			Guest  time  of the process (time spent running a vir-
			tual CPU for a guest operating	system),  measured  in
			clock ticks (divide by sysconf(_SC_CLK_TCK)).

	      (44) cguest_time	%ld  (since Linux 2.6.24)
			Guest  time  of	 the  process's	 children, measured in
			clock ticks (divide by sysconf(_SC_CLK_TCK)).

	      (45) start_data  %lu  (since Linux 3.3)  [PT]
			Address above which program initialized and uninitial-
			ized (BSS) data are placed.

	      (46) end_data  %lu  (since Linux 3.3)  [PT]
			Address below which program initialized and uninitial-
			ized (BSS) data are placed.

	      (47) start_brk  %lu  (since Linux 3.3)  [PT]
			Address above which program heap can be expanded  with
			brk(2).

	      (48) arg_start  %lu  (since Linux 3.5)  [PT]
			Address	 above	which  program	command-line arguments
			(argv) are placed.

	      (49) arg_end  %lu	 (since Linux 3.5)  [PT]
			Address below program  command-line  arguments	(argv)
			are placed.

	      (50) env_start  %lu  (since Linux 3.5)  [PT]
			Address above which program environment is placed.

	      (51) env_end  %lu	 (since Linux 3.5)  [PT]
			Address below which program environment is placed.

	      (52) exit_code  %d  (since Linux 3.5)  [PT]
			The thread's exit status in the form reported by wait-
			pid(2).

       /proc/[pid]/statm
	      Provides information about memory usage, measured in pages.  The
	      columns are:

		  size	     (1) total program size
			     (same as VmSize in /proc/[pid]/status)
		  resident   (2) resident set size
			     (same as VmRSS in /proc/[pid]/status)
		  shared     (3) number of resident shared pages (i.e., backed by a file)
			     (same as RssFile+RssShmem in /proc/[pid]/status)
		  text	     (4) text (code)
		  lib	     (5) library (unused since Linux 2.6; always 0)
		  data	     (6) data + stack
		  dt	     (7) dirty pages (unused since Linux 2.6; always 0)

       /proc/[pid]/status
	      Provides	 much  of  the	information  in	 /proc/[pid]/stat  and
	      /proc/[pid]/statm in a format that's easier for humans to parse.
	      Here's an example:

		  $ cat /proc/$$/status
		  Name:	  bash
		  Umask:  0022
		  State:  S (sleeping)
		  Tgid:	  17248
		  Ngid:	  0
		  Pid:	  17248
		  PPid:	  17200
		  TracerPid:	  0
		  Uid:	  1000	  1000	  1000	  1000
		  Gid:	  100	  100	  100	  100
		  FDSize: 256
		  Groups: 16 33 100
		  NStgid: 17248
		  NSpid:  17248
		  NSpgid: 17248
		  NSsid:  17200
		  VmPeak:     131168 kB
		  VmSize:     131168 kB
		  VmLck:	   0 kB
		  VmPin:	   0 kB
		  VmHWM:       13484 kB
		  VmRSS:       13484 kB
		  RssAnon:     10264 kB
		  RssFile:	3220 kB
		  RssShmem:	   0 kB
		  VmData:      10332 kB
		  VmStk:	 136 kB
		  VmExe:	 992 kB
		  VmLib:	2104 kB
		  VmPTE:	  76 kB
		  VmPMD:	  12 kB
		  VmSwap:	   0 kB
		  HugetlbPages:		 0 kB	     # 4.4
		  Threads:	  1
		  SigQ:	  0/3067
		  SigPnd: 0000000000000000
		  ShdPnd: 0000000000000000
		  SigBlk: 0000000000010000
		  SigIgn: 0000000000384004
		  SigCgt: 000000004b813efb
		  CapInh: 0000000000000000
		  CapPrm: 0000000000000000
		  CapEff: 0000000000000000
		  CapBnd: ffffffffffffffff
		  CapAmb:   0000000000000000
		  NoNewPrivs:	  0
		  Seccomp:	  0
		  Cpus_allowed:	  00000001
		  Cpus_allowed_list:	  0
		  Mems_allowed:	  1
		  Mems_allowed_list:	  0
		  voluntary_ctxt_switches:	  150
		  nonvoluntary_ctxt_switches:	  545

	      The fields are as follows:

	      * Name: Command run by this process.

	      * Umask:	Process umask, expressed in octal with a leading zero;
		see umask(2).  (Since Linux 4.7.)

	      * State: Current state of the process.  One of "R (running)", "S
		(sleeping)",  "D  (disk	 sleep)",  "T  (stopped)", "T (tracing
		stop)", "Z (zombie)", or "X (dead)".

	      * Tgid: Thread group ID (i.e., Process ID).

	      * Ngid: NUMA group ID (0 if none; since Linux 3.13).

	      * Pid: Thread ID (see gettid(2)).

	      * PPid: PID of parent process.

	      * TracerPid: PID of process tracing this process (0 if not being
		traced).

	      * Uid,  Gid:  Real,  effective,  saved  set, and filesystem UIDs
		(GIDs).

	      * FDSize: Number of file descriptor slots currently allocated.

	      * Groups: Supplementary group list.

	      * NStgid : Thread group ID (i.e., PID) in each of the PID names-
		paces  of  which  [pid] is a member.  The leftmost entry shows
		the value with respect to the PID  namespace  of  the  reading
		process,  followed  by	the value in successively nested inner
		namespaces.  (Since Linux 4.1.)

	      * NSpid: Thread ID in each of the PID namespaces of which	 [pid]
		is  a  member.	 The fields are ordered as for NStgid.	(Since
		Linux 4.1.)

	      * NSpgid: Process group ID in each  of  the  PID	namespaces  of
		which  [pid]  is a member.  The fields are ordered as for NSt-
		gid.  (Since Linux 4.1.)

	      * NSsid: descendant namespace session ID hierarchy Session ID in
		each  of  the  PID namespaces of which [pid] is a member.  The
		fields are ordered as for NStgid.  (Since Linux 4.1.)

	      * VmPeak: Peak virtual memory size.

	      * VmSize: Virtual memory size.

	      * VmLck: Locked memory size (see mlock(3)).

	      * VmPin: Pinned memory size (since Linux 3.2).  These are	 pages
		that can't be moved because something needs to directly access
		physical memory.

	      * VmHWM: Peak resident set size ("high water mark").

	      * VmRSS: Resident set size.  Note that the value here is the sum
		of RssAnon, RssFile, and RssShmem.

	      * RssAnon:  Size	of  resident  anonymous	 memory.  (since Linux
		4.5).

	      * RssFile: Size of resident file mappings.  (since Linux 4.5).

	      * RssShmem: Size of resident shared memory  (includes  System  V
		shared	memory,	 mappings  from tmpfs(5), and shared anonymous
		mappings).  (since Linux 4.5).

	      * VmData, VmStk, VmExe: Size of data, stack, and text segments.

	      * VmLib: Shared library code size.

	      * VmPTE: Page table entries size (since Linux 2.6.10).

	      * VmPMD: Size of second-level page tables (since Linux 4.0).

	      * VmSwap: Swapped-out virtual memory size by  anonymous  private
		pages; shmem swap usage is not included (since Linux 2.6.34).

	      * HugetlbPages:  Size  of hugetlb memory portions.  (since Linux
		4.4).

	      * Threads: Number of threads in process containing this thread.

	      * SigQ: This field contains  two	slash-separated	 numbers  that
		relate to queued signals for the real user ID of this process.
		The first of these is the number of currently  queued  signals
		for this real user ID, and the second is the resource limit on
		the number  of	queued	signals	 for  this  process  (see  the
		description of RLIMIT_SIGPENDING in getrlimit(2)).

	      * SigPnd,	 ShdPnd:  Number of signals pending for thread and for
		process as a whole (see pthreads(7) and signal(7)).

	      * SigBlk,	 SigIgn,  SigCgt:  Masks  indicating   signals	 being
		blocked, ignored, and caught (see signal(7)).

	      * CapInh,	 CapPrm,  CapEff:  Masks  of  capabilities  enabled in
		inheritable, permitted,	 and  effective	 sets  (see  capabili-
		ties(7)).

	      * CapBnd: Capability Bounding set (since Linux 2.6.26, see capa-
		bilities(7)).

	      * CapAmb: Ambient capability set (since Linux 4.3, see capabili-
		ties(7)).

	      * NoNewPrivs:  Value  of the no_new_privs bit (since Linux 4.10,
		see prctl(2)).

	      * Seccomp: Seccomp mode of the process  (since  Linux  3.8,  see
		seccomp(2)).   0  means	 SECCOMP_MODE_DISABLED;	 1  means SEC-
		COMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER.	This field  is
		provided  only if the kernel was built with the CONFIG_SECCOMP
		kernel configuration option enabled.

	      * Cpus_allowed: Mask of CPUs  on	which  this  process  may  run
		(since Linux 2.6.24, see cpuset(7)).

	      * Cpus_allowed_list:  Same  as  previous,	 but  in "list format"
		(since Linux 2.6.26, see cpuset(7)).

	      * Mems_allowed: Mask of memory nodes  allowed  to	 this  process
		(since Linux 2.6.24, see cpuset(7)).

	      * Mems_allowed_list:  Same  as  previous,	 but  in "list format"
		(since Linux 2.6.26, see cpuset(7)).

	      * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of
		voluntary   and	 involuntary  context  switches	 (since	 Linux
		2.6.23).

       /proc/[pid]/syscall (since Linux 2.6.27)
	      This file exposes the system call number and argument  registers
	      for  the	system	call  currently being executed by the process,
	      followed by the values of the stack pointer and program  counter
	      registers.   The	values	of  all	 six  argument	registers  are
	      exposed, although most system calls use fewer registers.

	      If the process is blocked, but not in a system  call,  then  the
	      file displays -1 in place of the system call number, followed by
	      just the values of the stack pointer and	program	 counter.   If
	      process  is  not blocked, then the file contains just the string
	      "running".

	      This file is present only if the kernel was configured with CON-
	      FIG_HAVE_ARCH_TRACEHOOK.

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/task (since Linux 2.6.0-test6)
	      This is a directory that	contains  one  subdirectory  for  each
	      thread  in  the  process.	  The name of each subdirectory is the
	      numerical thread ID  ([tid])  of	the  thread  (see  gettid(2)).
	      Within  each  of	these  subdirectories, there is a set of files
	      with the same names and contents as under the /proc/[pid] direc-
	      tories.  For attributes that are shared by all threads, the con-
	      tents for each of the files under the task/[tid]	subdirectories
	      will  be	the  same  as  in the corresponding file in the parent
	      /proc/[pid] directory (e.g., in a multithreaded process, all  of
	      the  task/[tid]/cwd  files  will	have  the  same	 value	as the
	      /proc/[pid]/cwd file in the parent directory, since all  of  the
	      threads in a process share a working directory).	For attributes
	      that are distinct for each thread, the corresponding files under
	      task/[tid]  may  have  different values (e.g., various fields in
	      each of the task/[tid]/status files may be  different  for  each
	      thread),	or  they  might not exist in /proc/[pid] at all.  In a
	      multithreaded process,  the  contents  of	 the  /proc/[pid]/task
	      directory	 are not available if the main thread has already ter-
	      minated (typically by calling pthread_exit(3)).


       /proc/[pid]/task/[tid]/children (since Linux 3.5)
	      A space-separated list of child tasks of this task.  Each	 child
	      task is represented by its TID.

	      This option is intended for use by the checkpoint-restore (CRIU)
	      system, and reliably provides a list of children only if all  of
	      the  child  processes  are  stopped or frozen.  It does not work
	      properly if children of the target task exit while the  file  is
	      being  read!  Exiting children may cause non-exiting children to
	      be omitted from the list.	 This makes this interface  even  more
	      unreliable  than	classic	 PID-based approaches if the inspected
	      task and its children aren't frozen, and most code should proba-
	      bly not use this interface.

	      Until  Linux  4.2, the presence of this file was governed by the
	      CONFIG_CHECKPOINT_RESTORE kernel	configuration  option.	 Since
	      Linux 4.2, it is governed by the CONFIG_PROC_CHILDREN option.

       /proc/[pid]/timers (since Linux 3.10)
	      A	 list  of  the	POSIX  timers for this process.	 Each timer is
	      listed with a line that starts with the string "ID:".  For exam-
	      ple:

		  ID: 1
		  signal: 60/00007fff86e452a8
		  notify: signal/pid.2634
		  ClockID: 0
		  ID: 0
		  signal: 60/00007fff86e452a8
		  notify: signal/pid.2634
		  ClockID: 1

	      The lines shown for each timer have the following meanings:

	      ID     The ID for this timer.  This is not the same as the timer
		     ID returned by timer_create(2); rather, it	 is  the  same
		     kernel-internal  ID  that is available via the si_timerid
		     field of the siginfo_t structure (see sigaction(2)).

	      signal This is the signal number that this timer uses to deliver
		     notifications   followed	by   a	slash,	and  then  the
		     sigev_value value supplied to the signal handler.	 Valid
		     only for timers that notify via a signal.

	      notify The  part	before	the slash specifies the mechanism that
		     this timer uses to deliver notifications, and is  one  of
		     "thread", "signal", or "none".  Immediately following the
		     slash  is	either	the  string  "tid"  for	 timers	  with
		     SIGEV_THREAD_ID  notification,  or	 "pid" for timers that
		     notify by other mechanisms.  Following the "." is the PID
		     of	 the  process  (or the kernel thread ID of the thread)
		     that will be delivered a signal  if  the  timer  delivers
		     notifications via a signal.

	      ClockID
		     This  field  identifies the clock that the timer uses for
		     measuring time.  For most clocks, this is a  number  that
		     matches  one  of the user-space CLOCK_* constants exposed
		     via <time.h>.   CLOCK_PROCESS_CPUTIME_ID  timers  display
		     with     a	    value     of    -6	  in	this	field.
		     CLOCK_THREAD_CPUTIME_ID timers display with a value of -2
		     in this field.

	      This  file is available only when the kernel was configured with
	      CONFIG_CHECKPOINT_RESTORE.

       /proc/[pid]/timerslack_ns (since Linux 4.6)
	      This file exposes the process's  "current"  timer	 slack	value,
	      expressed	 in  nanoseconds.   The file is writable, allowing the
	      process's timer slack value to be changed.  Writing  0  to  this
	      file  resets  the	 "current"  timer slack to the "default" timer
	      slack  value.   For  further  details,  see  the	discussion  of
	      PR_SET_TIMERSLACK in prctl(2).

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_ATTACH_FSCREDS check; see ptrace(2).

       /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)
	      See user_namespaces(7).

       /proc/[pid]/wchan (since Linux 2.6.0)
	      The symbolic name corresponding to the location  in  the	kernel
	      where the process is sleeping.

	      Permission  to  access  this file is governed by a ptrace access
	      mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/apm
	      Advanced power management version and battery  information  when
	      CONFIG_APM is defined at kernel compilation time.

       /proc/buddyinfo
	      This file contains information which is used for diagnosing mem-
	      ory fragmentation issues.	 Each line starts with the identifica-
	      tion  of	the node and the name of the zone which together iden-
	      tify a memory region This is  then  followed  by	the  count  of
	      available	 chunks	 of  a	certain order in which these zones are
	      split.  The size in bytes of a certain order  is	given  by  the
	      formula:

		  (2^order) * PAGE_SIZE

	      The  binary  buddy  allocator  algorithm	inside the kernel will
	      split one chunk into two chunks of a smaller  order  (thus  with
	      half  the size) or combine two contiguous chunks into one larger
	      chunk of a higher order (thus with double the size)  to  satisfy
	      allocation  requests  and	 to counter memory fragmentation.  The
	      order matches the column number, when starting to count at zero.

	      For example on a x86_64 system:

  Node 0, zone	   DMA	   1	1    1	  0    2    1	 1    0	   1	1    3
  Node 0, zone	 DMA32	  65   47    4	 81   52   28	13   10	   5	1  404
  Node 0, zone	Normal	 216   55  189	101   84   38	37   27	   5	3  587

	      In this example, there is one node containing  three  zones  and
	      there are 11 different chunk sizes.  If the page size is 4 kilo-
	      bytes, then the first zone called	 DMA  (on  x86	the  first  16
	      megabyte	of memory) has 1 chunk of 4 kilobytes (order 0) avail-
	      able and has 3 chunks of 4 megabytes (order 10) available.

	      If the memory is heavily fragmented,  the	 counters  for	higher
	      order  chunks  will  be  zero and allocation of large contiguous
	      areas will fail.

	      Further information about the zones can be found in  /proc/zone-
	      info.

       /proc/bus
	      Contains subdirectories for installed busses.

       /proc/bus/pccard
	      Subdirectory  for	 PCMCIA	 devices  when CONFIG_PCMCIA is set at
	      kernel compilation time.

       /proc/bus/pccard/drivers

       /proc/bus/pci
	      Contains various bus subdirectories and pseudo-files  containing
	      information  about  PCI  busses,	installed  devices, and device
	      drivers.	Some of these files are not ASCII.

       /proc/bus/pci/devices
	      Information about PCI devices.  They  may	 be  accessed  through
	      lspci(8) and setpci(8).

       /proc/cgroups (since Linux 2.6.24)
	      See cgroups(7).

       /proc/cmdline
	      Arguments	 passed	 to the Linux kernel at boot time.  Often done
	      via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
	      This file exposes the configuration options that	were  used  to
	      build  the  currently running kernel, in the same format as they
	      would be shown in the .config file that resulted when  configur-
	      ing  the	kernel	(using make xconfig, make config, or similar).
	      The file contents are compressed;	 view  or  search  them	 using
	      zcat(1)  and  zgrep(1).  As long as no changes have been made to
	      the following file, the contents of /proc/config.gz are the same
	      as those provided by :

		  cat /lib/modules/$(uname -r)/build/.config

	      /proc/config.gz  is  provided  only  if the kernel is configured
	      with CONFIG_IKCONFIG_PROC.

       /proc/crypto
	      A list of the ciphers provided by the kernel  crypto  API.   For
	      details,	see  the  kernel Linux Kernel Crypto API documentation
	      available under the kernel source	 directory  Documentation/Doc-
	      Book.   (That documentation can be built using a command such as
	      make htmldocs in the root directory of the kernel source tree.)

       /proc/cpuinfo
	      This is a collection of CPU and  system  architecture  dependent
	      items,  for  each	 supported architecture a different list.  Two
	      common  entries  are  processor  which  gives  CPU  number   and
	      bogomips;	 a  system  constant  that is calculated during kernel
	      initialization.  SMP machines have  information  for  each  CPU.
	      The lscpu(1) command gathers its information from this file.

       /proc/devices
	      Text  listing  of	 major numbers and device groups.  This can be
	      used by MAKEDEV scripts for consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
	      This file contains disk I/O statistics  for  each	 disk  device.
	      See  the	Linux kernel source file Documentation/iostats.txt for
	      further information.

       /proc/dma
	      This is a list of the registered ISA DMA (direct memory  access)
	      channels in use.

       /proc/driver
	      Empty subdirectory.

       /proc/execdomains
	      List of the execution domains (ABI personalities).

       /proc/fb
	      Frame buffer information when CONFIG_FB is defined during kernel
	      compilation.

       /proc/filesystems
	      A text listing of the filesystems which  are  supported  by  the
	      kernel,  namely  filesystems which were compiled into the kernel
	      or  whose	 kernel	 modules  are  currently  loaded.   (See  also
	      filesystems(5).)	 If  a filesystem is marked with "nodev", this
	      means that it does not require a	block  device  to  be  mounted
	      (e.g., virtual filesystem, network filesystem).

	      Incidentally, this file may be used by mount(8) when no filesys-
	      tem is specified and it didn't manage to determine the  filesys-
	      tem  type.   Then	 filesystems  contained in this file are tried
	      (excepted those that are marked with "nodev").

       /proc/fs
	      Contains subdirectories that in turn contain files with informa-
	      tion about (certain) mounted filesystems.

       /proc/ide
	      This  directory  exists  on systems with the IDE bus.  There are
	      directories for each IDE channel	and  attached  device.	 Files
	      include:

		  cache		     buffer size in KB
		  capacity	     number of sectors
		  driver	     driver version
		  geometry	     physical and logical geometry
		  identify	     in hexadecimal
		  media		     media type
		  model		     manufacturer's model number
		  settings	     drive settings
		  smart_thresholds   in hexadecimal
		  smart_values	     in hexadecimal

	      The  hdparm(8)  utility provides access to this information in a
	      friendly format.

       /proc/interrupts
	      This is used to record the number of interrupts per CPU  per  IO
	      device.	Since  Linux 2.6.24, for the i386 and x86_64 architec-
	      tures, at least, this also includes interrupts internal  to  the
	      system  (that is, not associated with a device as such), such as
	      NMI (nonmaskable interrupt), LOC (local  timer  interrupt),  and
	      for  SMP	systems,  TLB (TLB flush interrupt), RES (rescheduling
	      interrupt), CAL (remote function call interrupt),	 and  possibly
	      others.  Very easy to read formatting, done in ASCII.

       /proc/iomem
	      I/O memory map in Linux 2.4.

       /proc/ioports
	      This is a list of currently registered Input-Output port regions
	      that are in use.

       /proc/kallsyms (since Linux 2.5.71)
	      This holds the kernel exported symbol definitions	 used  by  the
	      modules(X)  tools to dynamically link and bind loadable modules.
	      In Linux 2.5.47 and earlier, a similar file with	slightly  dif-
	      ferent syntax was named ksyms.

       /proc/kcore
	      This  file  represents  the physical memory of the system and is
	      stored in the ELF core file format.  With this pseudo-file,  and
	      an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
	      used to examine the current state of any kernel data structures.

	      The total length of the file is  the  size  of  physical	memory
	      (RAM) plus 4KB.

       /proc/keys (since Linux 2.6.10)
	      See keyrings(7).

       /proc/key-users (since Linux 2.6.10)
	      See keyrings(7).

       /proc/kmsg
	      This  file  can  be used instead of the syslog(2) system call to
	      read kernel messages.  A process must have superuser  privileges
	      to  read	this file, and only one process should read this file.
	      This file should not be read if  a  syslog  process  is  running
	      which uses the syslog(2) system call facility to log kernel mes-
	      sages.

	      Information in this file is retrieved with the dmesg(1) program.

       /proc/kpagecount (since Linux 2.6.25)
	      This file contains a 64-bit count of the number  of  times  each
	      physical page frame is mapped, indexed by page frame number (see
	      the discussion of /proc/[pid]/pagemap).

	      The  /proc/kpagecount  file  is  present	only   if   the	  CON-
	      FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/kpageflags (since Linux 2.6.25)
	      This  file  contains 64-bit masks corresponding to each physical
	      page frame; it is indexed by page frame number (see the  discus-
	      sion of /proc/[pid]/pagemap).  The bits are as follows:

		   0 - KPF_LOCKED
		   1 - KPF_ERROR
		   2 - KPF_REFERENCED
		   3 - KPF_UPTODATE
		   4 - KPF_DIRTY
		   5 - KPF_LRU
		   6 - KPF_ACTIVE
		   7 - KPF_SLAB
		   8 - KPF_WRITEBACK
		   9 - KPF_RECLAIM
		  10 - KPF_BUDDY
		  11 - KPF_MMAP		  (since Linux 2.6.31)
		  12 - KPF_ANON		  (since Linux 2.6.31)
		  13 - KPF_SWAPCACHE	  (since Linux 2.6.31)
		  14 - KPF_SWAPBACKED	  (since Linux 2.6.31)
		  15 - KPF_COMPOUND_HEAD  (since Linux 2.6.31)
		  16 - KPF_COMPOUND_TAIL  (since Linux 2.6.31)
		  16 - KPF_HUGE		  (since Linux 2.6.31)
		  18 - KPF_UNEVICTABLE	  (since Linux 2.6.31)
		  19 - KPF_HWPOISON	  (since Linux 2.6.31)
		  20 - KPF_NOPAGE	  (since Linux 2.6.31)
		  21 - KPF_KSM		  (since Linux 2.6.32)
		  22 - KPF_THP		  (since Linux 3.4)

	      For  further details on the meanings of these bits, see the ker-
	      nel source  file	Documentation/vm/pagemap.txt.	Before	kernel
	      2.6.29,  KPF_WRITEBACK,  KPF_RECLAIM,  KPF_BUDDY, and KPF_LOCKED
	      did not report correctly.

	      The  /proc/kpageflags  file  is  present	only   if   the	  CON-
	      FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/ksyms (Linux 1.1.23-2.5.47)
	      See /proc/kallsyms.

       /proc/loadavg
	      The  first  three	 fields	 in this file are load average figures
	      giving the number of jobs in the run queue (state R) or  waiting
	      for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
	      are the same as the load average numbers given by uptime(1)  and
	      other  programs.	The fourth field consists of two numbers sepa-
	      rated by a slash (/).  The first of these is the number of  cur-
	      rently runnable kernel scheduling entities (processes, threads).
	      The value after the slash is the	number	of  kernel  scheduling
	      entities that currently exist on the system.  The fifth field is
	      the PID of the process that was most  recently  created  on  the
	      system.

       /proc/locks
	      This  file  shows current file locks (flock(2) and fcntl(2)) and
	      leases (fcntl(2)).  The lslocks(8) command provides a  bit  more
	      information about each lock.

       /proc/malloc (only up to and including Linux 2.2)
	      This  file  is  present  only if CONFIG_DEBUG_MALLOC was defined
	      during compilation.

       /proc/meminfo
	      This file reports statistics about memory usage on  the  system.
	      It is used by free(1) to report the amount of free and used mem-
	      ory (both physical and swap) on the system as well as the shared
	      memory  and  buffers  used by the kernel.	 Each line of the file
	      consists of a parameter name, followed by a colon, the value  of
	      the  parameter,  and an option unit of measurement (e.g., "kB").
	      The list below describes the  parameter  names  and  the	format
	      specifier	 required  to  read  the field value.  Except as noted
	      below, all of the fields have been present since at least	 Linux
	      2.6.0.  Some fields are displayed only if the kernel was config-
	      ured with various options; those dependencies are noted  in  the
	      list.

	      MemTotal %lu
		     Total usable RAM (i.e., physical RAM minus a few reserved
		     bits and the kernel binary code).

	      MemFree %lu
		     The sum of LowFree+HighFree.

	      MemAvailable %lu (since Linux 3.14)
		     An estimate of how much memory is available for  starting
		     new applications, without swapping.

	      Buffers %lu
		     Relatively	 temporary  storage  for  raw disk blocks that
		     shouldn't get tremendously large (20MB or so).

	      Cached %lu
		     In-memory cache for files read from the  disk  (the  page
		     cache).  Doesn't include SwapCached.

	      SwapCached %lu
		     Memory  that once was swapped out, is swapped back in but
		     still also is in the swap file.  (If memory  pressure  is
		     high,  these  pages  don't	 need  to be swapped out again
		     because they are already in the swap  file.   This	 saves
		     I/O.)

	      Active %lu
		     Memory  that  has been used more recently and usually not
		     reclaimed unless absolutely necessary.

	      Inactive %lu
		     Memory which has been less recently  used.	  It  is  more
		     eligible to be reclaimed for other purposes.

	      Active(anon) %lu (since Linux 2.6.28)
		     [To be documented.]

	      Inactive(anon) %lu (since Linux 2.6.28)
		     [To be documented.]

	      Active(file) %lu (since Linux 2.6.28)
		     [To be documented.]

	      Inactive(file) %lu (since Linux 2.6.28)
		     [To be documented.]

	      Unevictable %lu (since Linux 2.6.28)
		     (From  Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
		     required.)	 [To be documented.]

	      Mlocked %lu (since Linux 2.6.28)
		     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU  was
		     required.)	 [To be documented.]

	      HighTotal %lu
		     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
		     Total amount of highmem.  Highmem	is  all	 memory	 above
		     ~860MB  of physical memory.  Highmem areas are for use by
		     user-space programs, or for the page cache.   The	kernel
		     must  use	tricks to access this memory, making it slower
		     to access than lowmem.

	      HighFree %lu
		     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
		     Amount of free highmem.

	      LowTotal %lu
		     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
		     Total amount of lowmem.  Lowmem is memory	which  can  be
		     used  for everything that highmem can be used for, but it
		     is also available for the kernel's use for its  own  data
		     structures.   Among many other things, it is where every-
		     thing from Slab is allocated.   Bad  things  happen  when
		     you're out of lowmem.

	      LowFree %lu
		     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
		     Amount of free lowmem.

	      MmapCopy %lu (since Linux 2.6.29)
		     (CONFIG_MMU is required.)	[To be documented.]

	      SwapTotal %lu
		     Total amount of swap space available.

	      SwapFree %lu
		     Amount of swap space that is currently unused.

	      Dirty %lu
		     Memory which is waiting to get written back to the disk.

	      Writeback %lu
		     Memory which is actively being written back to the disk.

	      AnonPages %lu (since Linux 2.6.18)
		     Non-file backed pages mapped into user-space page tables.

	      Mapped %lu
		     Files which have been mapped into memory (with  mmap(2)),
		     such as libraries.

	      Shmem %lu (since Linux 2.6.32)
		     Amount of memory consumed in tmpfs(5) filesystems.

	      Slab %lu
		     In-kernel data structures cache.  (See slabinfo(5).)

	      SReclaimable %lu (since Linux 2.6.19)
		     Part of Slab, that might be reclaimed, such as caches.

	      SUnreclaim %lu (since Linux 2.6.19)
		     Part  of  Slab,  that cannot be reclaimed on memory pres-
		     sure.

	      KernelStack %lu (since Linux 2.6.32)
		     Amount of memory allocated to kernel stacks.

	      PageTables %lu (since Linux 2.6.18)
		     Amount of memory dedicated to the lowest  level  of  page
		     tables.

	      Quicklists %lu (since Linux 2.6.27)
		     (CONFIG_QUICKLIST is required.)  [To be documented.]

	      NFS_Unstable %lu (since Linux 2.6.18)
		     NFS  pages	 sent  to the server, but not yet committed to
		     stable storage.

	      Bounce %lu (since Linux 2.6.18)
		     Memory used for block device "bounce buffers".

	      WritebackTmp %lu (since Linux 2.6.26)
		     Memory used by FUSE for temporary writeback buffers.

	      CommitLimit %lu (since Linux 2.6.10)
		     This is the total amount of memory currently available to
		     be allocated on the system, expressed in kilobytes.  This
		     limit is adhered to only if strict overcommit  accounting
		     is	 enabled  (mode	 2 in /proc/sys/vm/overcommit_memory).
		     The  limit	 is  calculated	 according  to	 the   formula
		     described under /proc/sys/vm/overcommit_memory.  For fur-
		     ther details,  see	 the  kernel  source  file  Documenta-
		     tion/vm/overcommit-accounting.

	      Committed_AS %lu
		     The  amount  of memory presently allocated on the system.
		     The committed memory is a sum of all of the memory	 which
		     has  been allocated by processes, even if it has not been
		     "used" by them as of yet.	A process which allocates  1GB
		     of	 memory (using malloc(3) or similar), but touches only
		     300MB of that memory will show up as using only 300MB  of
		     memory even if it has the address space allocated for the
		     entire 1GB.

		     This 1GB is memory which has been "committed" to  by  the
		     VM and can be used at any time by the allocating applica-
		     tion.  With strict overcommit enabled on the system (mode
		     2	in  /proc/sys/vm/overcommit_memory), allocations which
		     would exceed the CommitLimit will not be permitted.  This
		     is	 useful	 if one needs to guarantee that processes will
		     not fail due to lack of memory once that memory has  been
		     successfully allocated.

	      VmallocTotal %lu
		     Total size of vmalloc memory area.

	      VmallocUsed %lu
		     Amount of vmalloc area which is used.

	      VmallocChunk %lu
		     Largest contiguous block of vmalloc area which is free.

	      HardwareCorrupted %lu (since Linux 2.6.32)
		     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]

	      AnonHugePages %lu (since Linux 2.6.38)
		     (CONFIG_TRANSPARENT_HUGEPAGE   is	 required.)   Non-file
		     backed huge pages mapped into user-space page tables.

	      ShmemHugePages %lu (since Linux 4.8)
		     (CONFIG_TRANSPARENT_HUGEPAGE is required.)	  Memory  used
		     by shared memory (shmem) and tmpfs(5) allocated with huge
		     pages

	      ShmemPmdMapped %lu (since Linux 4.8)
		     (CONFIG_TRANSPARENT_HUGEPAGE is required.)	 Shared memory
		     mapped into user space with huge pages.

	      CmaTotal %lu (since Linux 3.1)
		     Total  CMA	 (Contiguous  Memory  Allocator) pages.	 (CON-
		     FIG_CMA is required.)

	      CmaFree %lu (since Linux 3.1)
		     Free CMA  (Contiguous  Memory  Allocator)	pages.	 (CON-
		     FIG_CMA is required.)

	      HugePages_Total %lu
		     (CONFIG_HUGETLB_PAGE  is required.)  The size of the pool
		     of huge pages.

	      HugePages_Free %lu
		     (CONFIG_HUGETLB_PAGE is required.)	 The  number  of  huge
		     pages in the pool that are not yet allocated.

	      HugePages_Rsvd %lu (since Linux 2.6.17)
		     (CONFIG_HUGETLB_PAGE is required.)	 This is the number of
		     huge pages for which a commitment to  allocate  from  the
		     pool  has been made, but no allocation has yet been made.
		     These reserved huge pages guarantee that  an  application
		     will  be  able  to	 allocate a huge page from the pool of
		     huge pages at fault time.

	      HugePages_Surp %lu (since Linux 2.6.24)
		     (CONFIG_HUGETLB_PAGE is required.)	 This is the number of
		     huge   pages   in	 the   pool   above   the   value   in
		     /proc/sys/vm/nr_hugepages.	 The maximum number of surplus
		     huge  pages  is  controlled  by  /proc/sys/vm/nr_overcom-
		     mit_hugepages.

	      Hugepagesize %lu
		     (CONFIG_HUGETLB_PAGE is  required.)   The	size  of  huge
		     pages.

	      DirectMap4k %lu (since Linux 2.6.27)
		     Number  of	 bytes of RAM linearly mapped by kernel in 4kB
		     pages.  (x86.)

	      DirectMap4M %lu (since Linux 2.6.27)
		     Number of bytes of RAM linearly mapped by kernel  in  4MB
		     pages.    (x86   with   CONFIG_X86_64  or	CONFIG_X86_PAE
		     enabled.)

	      DirectMap2M %lu (since Linux 2.6.27)
		     Number of bytes of RAM linearly mapped by kernel  in  2MB
		     pages.    (x86   with   neither  CONFIG_X86_64  nor  CON-
		     FIG_X86_PAE enabled.)

	      DirectMap1G %lu (since Linux 2.6.27)
		     (x86  with	 CONFIG_X86_64	and  CONFIG_X86_DIRECT_GBPAGES
		     enabled.)

       /proc/modules
	      A	 text list of the modules that have been loaded by the system.
	      See also lsmod(8).

       /proc/mounts
	      Before kernel 2.4.19, this file was a list of all	 the  filesys-
	      tems  currently mounted on the system.  With the introduction of
	      per-process mount namespaces in Linux 2.4.19  (see  mount_names-
	      paces(7)),  this	file became a link to /proc/self/mounts, which
	      lists the mount points of the  process's	own  mount  namespace.
	      The format of this file is documented in fstab(5).

       /proc/mtrr
	      Memory  Type  Range Registers.  See the Linux kernel source file
	      Documentation/mtrr.txt for details.

       /proc/net
	      This directory contains various files  and  subdirectories  con-
	      taining  information about the networking layer.	The files con-
	      tain ASCII structures and are, therefore, readable with  cat(1).
	      However,	the  standard  netstat(8)  suite provides much cleaner
	      access to these files.

	      With the	advent	of  network  namespaces,  various  information
	      relating	to  the	 network  stack	 is  virtualized  (see	names-
	      paces(7)).  Thus, since Linux 2.6.25, /proc/net  is  a  symbolic
	      link  to	the  directory /proc/self/net, which contains the same
	      files and directories as listed below.  However, these files and
	      directories  now expose information for the network namespace of
	      which the process is a member.

       /proc/net/arp
	      This holds an ASCII readable dump of the kernel ARP  table  used
	      for  address resolutions.	 It will show both dynamically learned
	      and preprogrammed ARP entries.  The format is:

	IP address     HW type	 Flags	   HW address	       Mask   Device
	192.168.0.50   0x1	 0x2	   00:50:BF:25:68:F3   *      eth0
	192.168.0.250  0x1	 0xc	   00:00:00:00:00:00   *      eth0

	      Here "IP address" is the IPv4 address of the machine and the "HW
	      type"  is	 the  hardware	type of the address from RFC 826.  The
	      flags are the internal flags of the ARP structure (as defined in
	      /usr/include/linux/if_arp.h)  and	 the  "HW address" is the data
	      link layer mapping for that IP address if it is known.

       /proc/net/dev
	      The dev pseudo-file contains network device status  information.
	      This  gives  the number of received and sent packets, the number
	      of errors and collisions and other basic statistics.  These  are
	      used  by	the  ifconfig(8) program to report device status.  The
	      format is:

 Inter-|   Receive						  |  Transmit
  face |bytes	 packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0	 0    0	    0	       0	 0  2776770   11307    0    0	 0     0       0	  0
   eth0: 1215645    2751    0	 0    0	    0	       0	 0  1782404    4324    0    0	 0   427       0	  0
   ppp0: 1622270    5552    1	 0    0	    0	       0	 0   354130    5669    0    0	 0     0       0	  0
   tap0:    7714      81    0	 0    0	    0	       0	 0     7714	 81    0    0	 0     0       0	  0

       /proc/net/dev_mcast
	      Defined in /usr/src/linux/net/core/dev_mcast.c:
		   indx interface_name	dmi_u dmi_g dmi_address
		   2	eth0		1     0	    01005e000001
		   3	eth1		1     0	    01005e000001
		   4	eth2		1     0	    01005e000001

       /proc/net/igmp
	      Internet	  Group	   Management	 Protocol.	Defined	    in
	      /usr/src/linux/net/core/igmp.c.

       /proc/net/rarp
	      This  file uses the same format as the arp file and contains the
	      current reverse mapping database used to provide rarp(8) reverse
	      address  lookup  services.   If  RARP is not configured into the
	      kernel, this file will not be present.

       /proc/net/raw
	      Holds a dump of the RAW socket table.  Much of  the  information
	      is  not of use apart from debugging.  The "sl" value is the ker-
	      nel hash slot for the socket, the "local_address" is  the	 local
	      address  and  protocol number pair.  "St" is the internal status
	      of the socket.  The "tx_queue" and "rx_queue" are	 the  outgoing
	      and  incoming  data  queue in terms of kernel memory usage.  The
	      "tr", "tm->when", and "rexmits" fields are not used by RAW.  The
	      "uid"  field  holds  the	effective  UID	of  the creator of the
	      socket.

       /proc/net/snmp
	      This file holds the ASCII data needed for the IP, ICMP, TCP, and
	      UDP management information bases for an SNMP agent.

       /proc/net/tcp
	      Holds  a	dump of the TCP socket table.  Much of the information
	      is not of use apart from debugging.  The "sl" value is the  ker-
	      nel  hash	 slot for the socket, the "local_address" is the local
	      address and port number pair.  The "rem_address" is  the	remote
	      address and port number pair (if connected).  "St" is the inter-
	      nal status of the socket.	 The "tx_queue" and "rx_queue" are the
	      outgoing	and  incoming  data  queue  in	terms of kernel memory
	      usage.  The "tr", "tm->when", and "rexmits" fields hold internal
	      information  of  the kernel socket state and are useful only for
	      debugging.  The "uid" field holds the effective UID of the  cre-
	      ator of the socket.

       /proc/net/udp
	      Holds  a	dump of the UDP socket table.  Much of the information
	      is not of use apart from debugging.  The "sl" value is the  ker-
	      nel  hash	 slot for the socket, the "local_address" is the local
	      address and port number pair.  The "rem_address" is  the	remote
	      address and port number pair (if connected).  "St" is the inter-
	      nal status of the socket.	 The "tx_queue" and "rx_queue" are the
	      outgoing	and  incoming  data  queue  in	terms of kernel memory
	      usage.  The "tr", "tm->when", and "rexmits" fields are not  used
	      by  UDP.	The "uid" field holds the effective UID of the creator
	      of the socket.  The format is:

 sl  local_address rem_address	 st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

       /proc/net/unix
	      Lists the UNIX domain sockets  present  within  the  system  and
	      their status.  The format is:
	      Num RefCount Protocol Flags    Type St Path
	       0: 00000002 00000000 00000000 0001 03
	       1: 00000001 00000000 00010000 0001 01 /dev/printer

	      The fields are as follows:

	      Num:	the kernel table slot number.

	      RefCount: the number of users of the socket.

	      Protocol: currently always 0.

	      Flags:	the  internal  kernel  flags holding the status of the
			socket.

	      Type:	the socket type.  For  SOCK_STREAM  sockets,  this  is
			0001;  for  SOCK_DGRAM	sockets,  it  is 0002; and for
			SOCK_SEQPACKET sockets, it is 0005.

	      St:	the internal state of the socket.

	      Path:	the bound path (if any) of the socket.	Sockets in the
			abstract  namespace  are included in the list, and are
			shown with a Path that commences  with	the  character
			'@'.

       /proc/net/netfilter/nfnetlink_queue
	      This file contains information about netfilter user-space queue-
	      ing, if used.  Each line represents a queue.  Queues  that  have
	      not been subscribed to by user space are not shown.

		 1   4207     0	 2 65535     0	   0	    0  1
		(1)   (2)    (3)(4)  (5)    (6)	  (7)	   (8)

	      The fields in each line are:

	      (1)  The ID of the queue.	 This matches what is specified in the
		   --queue-num or --queue-balance options to  the  iptables(8)
		   NFQUEUE target.  See iptables-extensions(8) for more infor-
		   mation.

	      (2)  The netlink port ID subscribed to the queue.

	      (3)  The number of packets currently queued and  waiting	to  be
		   processed by the application.

	      (4)  The copy mode of the queue.	It is either 1 (metadata only)
		   or 2 (also copy payload data to user space).

	      (5)  Copy range; that is,	 how  many  bytes  of  packet  payload
		   should be copied to user space at most.

	      (6)  queue dropped.  Number of packets that had to be dropped by
		   the kernel because too many packets are already waiting for
		   user space to send back the mandatory accept/drop verdicts.

	      (7)  queue  user	dropped.   Number of packets that were dropped
		   within the netlink subsystem.  Such	drops  usually	happen
		   when the corresponding socket buffer is full; that is, user
		   space is not able to read messages fast enough.

	      (8)  sequence number.  Every queued packet is associated with  a
		   (32-bit)  monotonically-increasing  sequence	 number.  This
		   shows the ID of the most recent packet queued.

	      The last number exists only for  compatibility  reasons  and  is
	      always 1.

       /proc/partitions
	      Contains	the  major and minor numbers of each partition as well
	      as the number of 1024-byte blocks and the partition name.

       /proc/pci
	      This is a listing of all PCI devices found  during  kernel  ini-
	      tialization and their configuration.

	      This  file has been deprecated in favor of a new /proc interface
	      for PCI  (/proc/bus/pci).	  It  became  optional	in  Linux  2.2
	      (available  with CONFIG_PCI_OLD_PROC set at kernel compilation).
	      It became once more nonoptionally enabled in Linux  2.4.	 Next,
	      it  was  deprecated  in  Linux  2.6  (still  available with CON-
	      FIG_PCI_LEGACY_PROC set), and finally removed  altogether	 since
	      Linux 2.6.17.

       /proc/profile (since Linux 2.4)
	      This file is present only if the kernel was booted with the pro-
	      file=1 command-line option.  It exposes kernel profiling	infor-
	      mation  in  a  binary format for use by readprofile(1).  Writing
	      (e.g., an empty string) to this file resets the profiling	 coun-
	      ters; on some architectures, writing a binary integer "profiling
	      multiplier" of size sizeof(int)  sets  the  profiling  interrupt
	      frequency.

       /proc/scsi
	      A directory with the scsi mid-level pseudo-file and various SCSI
	      low-level driver directories, which contain a file for each SCSI
	      host  in	this system, all of which give the status of some part
	      of the SCSI IO subsystem.	 These files contain ASCII  structures
	      and are, therefore, readable with cat(1).

	      You  can also write to some of the files to reconfigure the sub-
	      system or switch certain features on or off.

       /proc/scsi/scsi
	      This is a listing of all SCSI devices known to the kernel.   The
	      listing  is  similar  to	the one seen during bootup.  scsi cur-
	      rently supports only the add-single-device command which	allows
	      root to add a hotplugged device to the list of known devices.

	      The command

		  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

	      will  cause host scsi1 to scan on SCSI channel 0 for a device on
	      ID 5 LUN 0.  If there is already a device known on this  address
	      or the address is invalid, an error will be returned.

       /proc/scsi/[drivername]
	      [drivername]  can	 currently  be	NCR53c7xx,  aha152x,  aha1542,
	      aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
	      pas16,  qlogic,  scsi_debug, seagate, t128, u15-24f, ultrastore,
	      or wd7000.  These directories show up for all drivers that  reg-
	      istered  at  least  one  SCSI HBA.  Every directory contains one
	      file per registered host.	 Every host-file is  named  after  the
	      number the host was assigned during initialization.

	      Reading these files will usually show driver and host configura-
	      tion, statistics, and so on.

	      Writing to these files  allows  different	 things	 on  different
	      hosts.   For  example,  with the latency and nolatency commands,
	      root can switch on and off command latency measurement  code  in
	      the  eata_dma driver.  With the lockup and unlock commands, root
	      can control bus lockups simulated by the scsi_debug driver.

       /proc/self
	      This  directory  refers  to  the	process	 accessing  the	 /proc
	      filesystem, and is identical to the /proc directory named by the
	      process ID of the same process.

       /proc/slabinfo
	      Information about kernel caches.	Since Linux 2.6.16  this  file
	      is  present  only if the CONFIG_SLAB kernel configuration option
	      is enabled.  The columns in /proc/slabinfo are:

		  cache-name
		  num-active-objs
		  total-objs
		  object-size
		  num-active-slabs
		  total-slabs
		  num-pages-per-slab

	      See slabinfo(5) for details.

       /proc/stat
	      kernel/system statistics.	  Varies  with	architecture.	Common
	      entries include:

	      cpu  3357 0 4313 1362393
		     The   amount  of  time,  measured	in  units  of  USER_HZ
		     (1/100ths	of  a  second  on  most	  architectures,   use
		     sysconf(_SC_CLK_TCK) to obtain the right value), that the
		     system spent in various states:

		     user   (1) Time spent in user mode.

		     nice   (2) Time spent in  user  mode  with	 low  priority
			    (nice).

		     system (3) Time spent in system mode.

		     idle   (4)	 Time  spent  in  the  idle  task.  This value
			    should be USER_HZ times the second	entry  in  the
			    /proc/uptime pseudo-file.

		     iowait (since Linux 2.5.41)
			    (5) Time waiting for I/O to complete.

		     irq (since Linux 2.6.0-test4)
			    (6) Time servicing interrupts.

		     softirq (since Linux 2.6.0-test4)
			    (7) Time servicing softirqs.

		     steal (since Linux 2.6.11)
			    (8)	 Stolen time, which is the time spent in other
			    operating systems when running  in	a  virtualized
			    environment

		     guest (since Linux 2.6.24)
			    (9)	 Time  spent  running  a virtual CPU for guest
			    operating systems under the control of  the	 Linux
			    kernel.

		     guest_nice (since Linux 2.6.33)
			    (10) Time spent running a niced guest (virtual CPU
			    for guest operating systems under the  control  of
			    the Linux kernel).

	      page 5741 1808
		     The  number  of  pages the system paged in and the number
		     that were paged out (from disk).

	      swap 1 0
		     The number of swap pages that have been  brought  in  and
		     out.

	      intr 1462898
		     This  line shows counts of interrupts serviced since boot
		     time, for each of the possible  system  interrupts.   The
		     first  column  is	the  total  of all interrupts serviced
		     including unnumbered  architecture	 specific  interrupts;
		     each  subsequent  column is the total for that particular
		     numbered interrupt.  Unnumbered interrupts are not shown,
		     only summed into the total.

	      disk_io: (2,0):(31,30,5764,1,2) (3,0):...
		     (major,disk_idx):(noinfo,	   read_io_ops,	    blks_read,
		     write_io_ops, blks_written)
		     (Linux 2.4 only)

	      ctxt 115315
		     The number of context switches that the system underwent.

	      btime 769041601
		     boot  time,  in  seconds  since  the  Epoch,   1970-01-01
		     00:00:00 +0000 (UTC).

	      processes 86031
		     Number of forks since boot.

	      procs_running 6
		     Number  of	 processes  in	runnable state.	 (Linux 2.5.45
		     onward.)

	      procs_blocked 2
		     Number of processes blocked waiting for I/O to  complete.
		     (Linux 2.5.45 onward.)

       /proc/swaps
	      Swap areas in use.  See also swapon(8).

       /proc/sys
	      This directory (present since 1.3.57) contains a number of files
	      and subdirectories corresponding	to  kernel  variables.	 These
	      variables	 can  be  read	and sometimes modified using the /proc
	      filesystem, and the (deprecated) sysctl(2) system call.

	      String values may be terminated by either '\0' or '\n'.

	      Integer and long values may be written either in decimal	or  in
	      hexadecimal notation (e.g. 0x3FFF).  When writing multiple inte-
	      ger or long values, these may be separated by any of the follow-
	      ing whitespace characters: ' ', '\t', or '\n'.  Using other sep-
	      arators leads to the error EINVAL.

       /proc/sys/abi (since Linux 2.4.10)
	      This directory may contain files with application binary	infor-
	      mation.	 See   the   Linux   kernel   source  file  Documenta-
	      tion/sysctl/abi.txt for more information.

       /proc/sys/debug
	      This directory may be empty.

       /proc/sys/dev
	      This  directory  contains	 device-specific  information	(e.g.,
	      dev/cdrom/info).	On some systems, it may be empty.

       /proc/sys/fs
	      This  directory contains the files and subdirectories for kernel
	      variables related to filesystems.

       /proc/sys/fs/binfmt_misc
	      Documentation for files in this directory can be	found  in  the
	      Linux kernel sources in Documentation/binfmt_misc.txt.

       /proc/sys/fs/dentry-state (since Linux 2.2)
	      This file contains information about the status of the directory
	      cache (dcache).	The  file  contains  six  numbers,  nr_dentry,
	      nr_unused,   age_limit   (age  in	 seconds),  want_pages	(pages
	      requested by system) and two dummy values.

	      * nr_dentry  is  the  number  of	allocated   dentries   (dcache
		entries).  This field is unused in Linux 2.2.

	      * nr_unused is the number of unused dentries.

	      * age_limit is the age in seconds after which dcache entries can
		be reclaimed when memory is short.

	      * want_pages   is	  nonzero   when   the	 kernel	  has	called
		shrink_dcache_pages() and the dcache isn't pruned yet.

       /proc/sys/fs/dir-notify-enable
	      This file can be used to disable or enable the dnotify interface
	      described in fcntl(2) on a system-wide basis.  A value of	 0  in
	      this file disables the interface, and a value of 1 enables it.

       /proc/sys/fs/dquot-max
	      This file shows the maximum number of cached disk quota entries.
	      On some (2.4) systems, it is not present.	 If the number of free
	      cached  disk quota entries is very low and you have some awesome
	      number of simultaneous system users, you might want to raise the
	      limit.

       /proc/sys/fs/dquot-nr
	      This  file  shows the number of allocated disk quota entries and
	      the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
	      This directory contains the file max_user_watches, which can  be
	      used  to limit the amount of kernel memory consumed by the epoll
	      interface.  For further details, see epoll(7).

       /proc/sys/fs/file-max
	      This file defines a system-wide limit  on	 the  number  of  open
	      files for all processes.	System calls that fail when encounter-
	      ing this limit fail with the  error  ENFILE.   (See  also	 setr-
	      limit(2),	 which can be used by a process to set the per-process
	      limit, RLIMIT_NOFILE, on the number of files it may  open.)   If
	      you  get	lots of error messages in the kernel log about running
	      out of file handles (look	 for  "VFS:  file-max  limit  <number>
	      reached"), try increasing this value:

		  echo 100000 > /proc/sys/fs/file-max

	      Privileged  processes  (CAP_SYS_ADMIN) can override the file-max
	      limit.

       /proc/sys/fs/file-nr
	      This (read-only) file contains  three  numbers:  the  number  of
	      allocated	 file  handles	(i.e.,	the  number of files presently
	      opened); the number of free file handles; and the maximum number
	      of file handles (i.e., the same value as /proc/sys/fs/file-max).
	      If the number of allocated file handles is close to the maximum,
	      you  should  consider increasing the maximum.  Before Linux 2.6,
	      the kernel allocated file handles	 dynamically,  but  it	didn't
	      free  them  again.  Instead the free file handles were kept in a
	      list for reallocation; the "free file handles"  value  indicates
	      the  size	 of  that  list.   A large number of free file handles
	      indicates that there was a past peak in the usage of  open  file
	      handles.	Since Linux 2.6, the kernel does deallocate freed file
	      handles, and the "free file handles" value is always zero.

       /proc/sys/fs/inode-max (only present until Linux 2.2)
	      This file contains the maximum number of in-memory inodes.  This
	      value  should  be	 3-4  times larger than the value in file-max,
	      since stdin, stdout and network sockets also need	 an  inode  to
	      handle  them.  When you regularly run out of inodes, you need to
	      increase this value.

	      Starting with Linux 2.4, there is no longer a  static  limit  on
	      the number of inodes, and this file is removed.

       /proc/sys/fs/inode-nr
	      This file contains the first two values from inode-state.

       /proc/sys/fs/inode-state
	      This  file  contains  seven  numbers: nr_inodes, nr_free_inodes,
	      preshrink, and four dummy values (always zero).

	      nr_inodes is the number of  inodes  the  system  has  allocated.
	      nr_free_inodes represents the number of free inodes.

	      preshrink is nonzero when the nr_inodes > inode-max and the sys-
	      tem needs to prune the inode list instead	 of  allocating	 more;
	      since Linux 2.4, this field is a dummy value (always zero).

       /proc/sys/fs/inotify (since Linux 2.6.13)
	      This     directory     contains	  files	    max_queued_events,
	      max_user_instances, and max_user_watches, that can  be  used  to
	      limit the amount of kernel memory consumed by the inotify inter-
	      face.  For further details, see inotify(7).

       /proc/sys/fs/lease-break-time
	      This file specifies the grace period that the kernel grants to a
	      process holding a file lease (fcntl(2)) after it has sent a sig-
	      nal to that process notifying it that another process is waiting
	      to  open the file.  If the lease holder does not remove or down-
	      grade the lease within this grace period,	 the  kernel  forcibly
	      breaks the lease.

       /proc/sys/fs/leases-enable
	      This  file  can  be  used	 to  enable  or	 disable  file	leases
	      (fcntl(2)) on a system-wide basis.  If this  file	 contains  the
	      value 0, leases are disabled.  A nonzero value enables leases.

       /proc/sys/fs/mount-max (since Linux 4.9)
	      The  value  in  this file specifies the maximum number of mounts
	      that may exist in a mount namespace.  The default value in  this
	      file is 100,000.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
	      This   directory	 contains   files  msg_max,  msgsize_max,  and
	      queues_max, controlling the  resources  used  by	POSIX  message
	      queues.  See mq_overview(7) for details.

       /proc/sys/fs/nr_open (since Linux 2.6.25)
	      This   file   imposes   ceiling	on  the	 value	to  which  the
	      RLIMIT_NOFILE resource limit can be raised  (see	getrlimit(2)).
	      This  ceiling  is	 enforced for both unprivileged and privileged
	      process.	The default value in this file	is  1048576.   (Before
	      Linux  2.6.25,  the  ceiling for RLIMIT_NOFILE was hard-coded to
	      the same value.)

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
	      These files allow you to change the value of the fixed  UID  and
	      GID.   The  default  is  65534.	Some  filesystems support only
	      16-bit UIDs and GIDs, although in Linux UIDs  and	 GIDs  are  32
	      bits.   When  one	 of  these  filesystems is mounted with writes
	      enabled, any UID or GID that would exceed 65535 is translated to
	      the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
	      See pipe(7).

       /proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)
	      See pipe(7).

       /proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)
	      See pipe(7).

       /proc/sys/fs/protected_hardlinks (since Linux 3.6)
	      When  the value in this file is 0, no restrictions are placed on
	      the creation of hard links (i.e., this is the historical	behav-
	      ior before Linux 3.6).  When the value in this file is 1, a hard
	      link can be created to a target file only if one of the  follow-
	      ing conditions is true:

	      *	 The calling process has the CAP_FOWNER capability in its user
		 namespace and the file UID has a mapping in the namespace.

	      *	 The filesystem UID of the process creating the	 link  matches
		 the  owner  (UID) of the target file (as described in creden-
		 tials(7), a process's filesystem UID is normally the same  as
		 its effective UID).

	      *	 All of the following conditions are true:

		  o  the target is a regular file;

		  o  the  target  file	does not have its set-user-ID mode bit
		     enabled;

		  o  the target file does not have both its  set-group-ID  and
		     group-executable mode bits enabled; and

		  o  the  caller  has  permission to read and write the target
		     file (either via the file's permissions mask  or  because
		     it has suitable capabilities).

	      The  default  value  in  this file is 0.	Setting the value to 1
	      prevents a longstanding class of security issues caused by hard-
	      link-based  time-of-check, time-of-use races, most commonly seen
	      in world-writable directories such as /tmp.  The	common	method
	      of  exploiting  this  flaw is to cross privilege boundaries when
	      following a given hard link (i.e., a root process follows a hard
	      link created by another user).  Additionally, on systems without
	      separated partitions, this stops unauthorized users  from	 "pin-
	      ning"  vulnerable	 set-user-ID  and  set-group-ID	 files against
	      being upgraded by	 the  administrator,  or  linking  to  special
	      files.

       /proc/sys/fs/protected_symlinks (since Linux 3.6)
	      When  the value in this file is 0, no restrictions are placed on
	      following symbolic links (i.e., this is the historical  behavior
	      before  Linux  3.6).  When the value in this file is 1, symbolic
	      links are followed only in the following circumstances:

	      *	 the filesystem UID of the process following the link  matches
		 the owner (UID) of the symbolic link (as described in creden-
		 tials(7), a process's filesystem UID is normally the same  as
		 its effective UID);

	      *	 the link is not in a sticky world-writable directory; or

	      *	 the  symbolic	link  and  its	parent directory have the same
		 owner (UID)

	      A system call that fails to follow a symbolic  link  because  of
	      the above restrictions returns the error EACCES in errno.

	      The  default  value  in  this file is 0.	Setting the value to 1
	      avoids a longstanding class of security issues based on time-of-
	      check, time-of-use races when accessing symbolic links.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
	      The  value  in  this  file is assigned to a process's "dumpable"
	      flag in the circumstances described in prctl(2).	In effect, the
	      value  in	 this file determines whether core dump files are pro-
	      duced for set-user-ID or otherwise  protected/tainted  binaries.
	      The  "dumpable" setting also affects the ownership of files in a
	      process's /proc/[pid] directory, as described above.

	      Three different integer values can be specified:

	      0 (default)
		     This provides the traditional (pre-Linux  2.6.13)	behav-
		     ior.   A  core  dump  will	 not be produced for a process
		     which has changed	credentials  (by  calling  seteuid(2),
		     setgid(2),	 or  similar, or by executing a set-user-ID or
		     set-group-ID program) or whose binary does not have  read
		     permission enabled.

	      1 ("debug")
		     All  processes  dump  core when possible.	(Reasons why a
		     process might nevertheless not dump core are described in
		     core(5).)	 The core dump is owned by the filesystem user
		     ID of the dumping process and  no	security  is  applied.
		     This  is  intended	 for system debugging situations only:
		     this mode is  insecure  because  it  allows  unprivileged
		     users  to	examine the memory contents of privileged pro-
		     cesses.

	      2 ("suidsafe")
		     Any binary which normally would not be  dumped  (see  "0"
		     above)  is dumped readable by root only.  This allows the
		     user to remove the core dump file but  not	 to  read  it.
		     For  security  reasons  core  dumps in this mode will not
		     overwrite one another  or	other  files.	This  mode  is
		     appropriate  when	administrators are attempting to debug
		     problems in a normal environment.

		     Additionally, since Linux 3.6, /proc/sys/kernel/core_pat-
		     tern  must	 either be an absolute pathname or a pipe com-
		     mand, as detailed in core(5).  Warnings will  be  written
		     to	 the  kernel log if core_pattern does not follow these
		     rules, and no core dump will be produced.

	      For details of the effect of a process's "dumpable"  setting  on
	      ptrace access mode checking, see ptrace(2).

       /proc/sys/fs/super-max
	      This  file  controls the maximum number of superblocks, and thus
	      the maximum number of mounted filesystems the kernel  can	 have.
	      You  need	 increase  only	 super-max  if	you need to mount more
	      filesystems than the current value in super-max allows you to.

       /proc/sys/fs/super-nr
	      This file contains the number of filesystems currently mounted.

       /proc/sys/kernel
	      This directory contains files  controlling  a  range  of	kernel
	      parameters, as described below.

       /proc/sys/kernel/acct
	      This  file contains three numbers: highwater, lowwater, and fre-
	      quency.  If BSD-style process accounting is enabled, these  val-
	      ues control its behavior.	 If free space on filesystem where the
	      log lives goes below lowwater percent, accounting suspends.   If
	      free  space  gets	 above	highwater percent, accounting resumes.
	      frequency determines how often the kernel checks the  amount  of
	      free  space  (value is in seconds).  Default values are 4, 2 and
	      30.  That is, suspend accounting if 2% or less  space  is	 free;
	      resume  it  if  4%  or  more space is free; consider information
	      about amount of free space valid for 30 seconds.

       /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
	      From Linux 2.6.27 to 3.18, this file was used to control	recom-
	      puting of the value in /proc/sys/kernel/msgmni upon the addition
	      or removal of memory or  upon  IPC  namespace  creation/removal.
	      Echoing  "1" into this file enabled msgmni automatic recomputing
	      (and triggered a recomputation of msgmni based  on  the  current
	      amount of available memory and number of IPC namespaces).	 Echo-
	      ing "0" disabled automatic recomputing.  (Automatic  recomputing
	      was  also	 disabled  if  a  value	 was  explicitly  assigned  to
	      /proc/sys/kernel/msgmni.)	 The default value in auto_msgmni  was
	      1.

	      Since  Linux  3.19,  the	content	 of  this  file	 has no effect
	      (because msgmni defaults to near the  maximum  value  possible),
	      and reads from this file always return the value "0".

       /proc/sys/kernel/cap_last_cap (since Linux 3.2)
	      See capabilities(7).

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
	      This  file holds the value of the kernel capability bounding set
	      (expressed as a signed  decimal  number).	  This	set  is	 ANDed
	      against	the   capabilities   permitted	to  a  process	during
	      execve(2).  Starting with Linux 2.6.25, the system-wide capabil-
	      ity  bounding  set disappeared, and was replaced by a per-thread
	      bounding set; see capabilities(7).

       /proc/sys/kernel/core_pattern
	      See core(5).

       /proc/sys/kernel/core_pipe_limit
	      See core(5).

       /proc/sys/kernel/core_uses_pid
	      See core(5).

       /proc/sys/kernel/ctrl-alt-del
	      This file controls the handling of Ctrl-Alt-Del  from  the  key-
	      board.   When  the  value	 in  this  file	 is 0, Ctrl-Alt-Del is
	      trapped and sent to the init(1) program  to  handle  a  graceful
	      restart.	 When the value is greater than zero, Linux's reaction
	      to a Vulcan Nerve Pinch (tm) will be an immediate reboot,	 with-
	      out  even syncing its dirty buffers.  Note: when a program (like
	      dosemu) has the keyboard in  "raw"  mode,	 the  ctrl-alt-del  is
	      intercepted by the program before it ever reaches the kernel tty
	      layer, and it's up to the program to decide what to do with it.

       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
	      The value in this file determines who can see kernel syslog con-
	      tents.   A  value of 0 in this file imposes no restrictions.  If
	      the value is 1, only privileged users can read the  kernel  sys-
	      log.   (See  syslog(2) for more details.)	 Since Linux 3.4, only
	      users with the CAP_SYS_ADMIN capability may change the value  in
	      this file.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
	      can  be  used  to	 set the NIS/YP domainname and the hostname of
	      your box in exactly the same way as the  commands	 domainname(1)
	      and hostname(1), that is:

		  # echo 'darkstar' > /proc/sys/kernel/hostname
		  # echo 'mydomain' > /proc/sys/kernel/domainname

	      has the same effect as

		  # hostname 'darkstar'
		  # domainname 'mydomain'

	      Note,  however, that the classic darkstar.frop.org has the host-
	      name "darkstar" and DNS (Internet Domain Name Server) domainname
	      "frop.org", not to be confused with the NIS (Network Information
	      Service) or YP (Yellow  Pages)  domainname.   These  two	domain
	      names  are  in general different.	 For a detailed discussion see
	      the hostname(1) man page.

       /proc/sys/kernel/hotplug
	      This file contains the path for the hotplug policy  agent.   The
	      default value in this file is /sbin/hotplug.

       /proc/sys/kernel/htab-reclaim
	      (PowerPC	only) If this file is set to a nonzero value, the Pow-
	      erPC htab (see kernel  file  Documentation/powerpc/ppc_htab.txt)
	      is pruned each time the system hits the idle loop.

       /proc/sys/kernel/keys/*
	      This directory contains various files that define parameters and
	      limits  for  the	key-management	facility.   These  files   are
	      described in keyrings(7).

       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
	      The  value  in this file determines whether kernel addresses are
	      exposed via /proc files and other interfaces.  A value of	 0  in
	      this  file  imposes  no restrictions.  If the value is 1, kernel
	      pointers printed using the %pK format specifier will be replaced
	      with  zeros  unless  the user has the CAP_SYSLOG capability.  If
	      the value is 2, kernel pointers printed  using  the  %pK	format
	      specifier	 will  be replaced with zeros regardless of the user's
	      capabilities.  The initial default value for this	 file  was  1,
	      but  the	default was changed to 0 in Linux 2.6.39.  Since Linux
	      3.4, only users with the CAP_SYS_ADMIN capability can change the
	      value in this file.

       /proc/sys/kernel/l2cr
	      (PowerPC	only)  This  file contains a flag that controls the L2
	      cache of G3 processor boards.  If	 0,  the  cache	 is  disabled.
	      Enabled if nonzero.

       /proc/sys/kernel/modprobe
	      This  file  contains the path for the kernel module loader.  The
	      default value is /sbin/modprobe.	The file is  present  only  if
	      the  kernel  is  built  with  the CONFIG_MODULES (CONFIG_KMOD in
	      Linux 2.6.26 and earlier) option enabled.	 It  is	 described  by
	      the  Linux  kernel  source  file Documentation/kmod.txt (present
	      only in kernel 2.4 and earlier).

       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
	      A toggle value indicating if modules are allowed to be loaded in
	      an  otherwise  modular kernel.  This toggle defaults to off (0),
	      but can be set true (1).	Once  true,  modules  can  be  neither
	      loaded nor unloaded, and the toggle cannot be set back to false.
	      The file is present only if the kernel is built  with  the  CON-
	      FIG_MODULES option enabled.

       /proc/sys/kernel/msgmax (since Linux 2.2)
	      This  file  defines  a  system-wide limit specifying the maximum
	      number of bytes in a single message written on a System  V  mes-
	      sage queue.

       /proc/sys/kernel/msgmni (since Linux 2.4)
	      This file defines the system-wide limit on the number of message
	      queue identifiers.  See also /proc/sys/kernel/auto_msgmni.

       /proc/sys/kernel/msgmnb (since Linux 2.2)
	      This file defines a system-wide parameter used to initialize the
	      msg_qbytes setting for subsequently created message queues.  The
	      msg_qbytes setting specifies the maximum number  of  bytes  that
	      may be written to the message queue.

       /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
	      This  is	a  read-only file that displays the upper limit on the
	      number of a process's group memberships.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
	      These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
	      These files duplicate  the  files	 /proc/sys/fs/overflowgid  and
	      /proc/sys/fs/overflowuid.

       /proc/sys/kernel/panic
	      This  file  gives	 read/write  access  to	 the  kernel  variable
	      panic_timeout.  If this is zero,	the  kernel  will  loop	 on  a
	      panic;  if  nonzero, it indicates that the kernel should autore-
	      boot after this number of seconds.  When you  use	 the  software
	      watchdog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
	      This  file controls the kernel's behavior when an oops or BUG is
	      encountered.  If this file contains 0, then the system tries  to
	      continue	operation.  If it contains 1, then the system delays a
	      few seconds (to give klogd time to record the oops  output)  and
	      then   panics.   If  the	/proc/sys/kernel/panic	file  is  also
	      nonzero, then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
	      This file specifies the value at which PIDs wrap	around	(i.e.,
	      the  value  in  this  file is one greater than the maximum PID).
	      PIDs greater than this value are not allocated; thus, the	 value
	      in  this file also acts as a system-wide limit on the total num-
	      ber of processes and threads.  The default value for this	 file,
	      32768,  results in the same range of PIDs as on earlier kernels.
	      On 32-bit platforms, 32768 is the maximum value for pid_max.  On
	      64-bit  systems,	pid_max	 can  be  set  to any value up to 2^22
	      (PID_MAX_LIMIT, approximately 4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
	      This file contains a flag.  If set, Linux-PPC will use the "nap"
	      mode of powersaving, otherwise the "doze" mode will be used.

       /proc/sys/kernel/printk
	      See syslog(2).

       /proc/sys/kernel/pty (since Linux 2.6.4)
	      This directory contains two files relating to the number of UNIX
	      98 pseudoterminals (see pts(4)) on the system.

       /proc/sys/kernel/pty/max
	      This file defines the maximum number of pseudoterminals.

       /proc/sys/kernel/pty/nr
	      This read-only file indicates how many pseudoterminals are  cur-
	      rently in use.

       /proc/sys/kernel/random
	      This directory contains various parameters controlling the oper-
	      ation of the file /dev/random.  See random(4) for further infor-
	      mation.

       /proc/sys/kernel/random/uuid (since Linux 2.4)
	      Each  read from this read-only file returns a randomly generated
	      128-bit UUID, as a string in the standard UUID format.

       /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
	      Select the address space layout randomization (ASLR) policy  for
	      the  system  (on architectures that support ASLR).  Three values
	      are supported for this file:

	      0	 Turn ASLR off.	 This is the default  for  architectures  that
		 don't	support	 ASLR,	and when the kernel is booted with the
		 norandmaps parameter.

	      1	 Make the addresses of mmap(2) allocations, the stack, and the
		 VDSO  page  randomized.   Among other things, this means that
		 shared libraries will be loaded at randomized addresses.  The
		 text  segment of PIE-linked binaries will also be loaded at a
		 randomized address.  This value is the default if the	kernel
		 was configured with CONFIG_COMPAT_BRK.

	      2	 (Since	 Linux	2.6.25) Also support heap randomization.  This
		 value is the default if the kernel was	 not  configured  with
		 CONFIG_COMPAT_BRK.

       /proc/sys/kernel/real-root-dev
	      This file is documented in the Linux kernel source file Documen-
	      tation/initrd.txt.

       /proc/sys/kernel/reboot-cmd (Sparc only)
	      This file seems to be a way to give an  argument	to  the	 SPARC
	      ROM/Flash	 boot  loader.	 Maybe	to  tell  it  what to do after
	      rebooting?

       /proc/sys/kernel/rtsig-max
	      (Only in kernels up to and including  2.6.7;  see	 setrlimit(2))
	      This  file can be used to tune the maximum number of POSIX real-
	      time (queued) signals that can be outstanding in the system.

       /proc/sys/kernel/rtsig-nr
	      (Only in kernels up to and including 2.6.7.)   This  file	 shows
	      the number of POSIX real-time signals currently queued.

       /proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)
	      See sched(7).

       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
	      See sched_rr_get_interval(2).

       /proc/sys/kernel/sched_rt_period_us (Since Linux 2.6.25)
	      See sched(7).

       /proc/sys/kernel/sched_rt_runtime_us (Since Linux 2.6.25)
	      See sched(7).

       /proc/sys/kernel/sem (since Linux 2.4)
	      This  file  contains  4 numbers defining limits for System V IPC
	      semaphores.  These fields are, in order:

	      SEMMSL  The maximum semaphores per semaphore set.

	      SEMMNS  A system-wide limit on the number of semaphores  in  all
		      semaphore sets.

	      SEMOPM  The  maximum  number of operations that may be specified
		      in a semop(2) call.

	      SEMMNI  A system-wide limit on the maximum number	 of  semaphore
		      identifiers.

       /proc/sys/kernel/sg-big-buff
	      This file shows the size of the generic SCSI device (sg) buffer.
	      You can't tune it just yet, but you could change it  at  compile
	      time  by	editing	 include/scsi/sg.h  and	 changing the value of
	      SG_BIG_BUFF.  However, there shouldn't be any reason  to	change
	      this value.

       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
	      If  this	file  is set to 1, all System V shared memory segments
	      will be marked for destruction as soon as the number of attached
	      processes	 falls to zero; in other words, it is no longer possi-
	      ble to create shared memory segments that exist independently of
	      any attached process.

	      The effect is as though a shmctl(2) IPC_RMID is performed on all
	      existing segments as well as all segments created in the	future
	      (until  this  file  is reset to 0).  Note that existing segments
	      that are attached to no process will  be	immediately  destroyed
	      when  this  file	is  set	 to  1.	 Setting this option will also
	      destroy segments that were created,  but	never  attached,  upon
	      termination  of  the  process  that  created  the	 segment  with
	      shmget(2).

	      Setting this file to 1 provides a way of ensuring that all  Sys-
	      tem  V  shared  memory segments are counted against the resource
	      usage and resource limits (see the description of	 RLIMIT_AS  in
	      getrlimit(2)) of at least one process.

	      Because  setting	this  file to 1 produces behavior that is non-
	      standard and could also break existing applications, the default
	      value  in this file is 0.	 Set this file to 1 only if you have a
	      good understanding of the semantics of  the  applications	 using
	      System V shared memory on your system.

       /proc/sys/kernel/shmall (since Linux 2.2)
	      This  file contains the system-wide limit on the total number of
	      pages of System V shared memory.

       /proc/sys/kernel/shmmax (since Linux 2.2)
	      This file can be used to query and set the run-time limit on the
	      maximum  (System	V  IPC) shared memory segment size that can be
	      created.	Shared memory segments up to 1GB are now supported  in
	      the kernel.  This value defaults to SHMMAX.

       /proc/sys/kernel/shmmni (since Linux 2.4)
	      This  file  specifies the system-wide maximum number of System V
	      shared memory segments that can be created.

       /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
	      The value in this file determines how the	 file  offset  affects
	      the  behavior of updating entries in files under /proc/sys.  The
	      file has three possible values:

	      -1  This provides legacy	handling,  with	 no  printk  warnings.
		  Each	write(2)  must	fully contain the value to be written,
		  and multiple writes on the same file descriptor  will	 over-
		  write the entire value, regardless of the file position.

	      0	  (default)  This  provides  the  same behavior as for -1, but
		  printk warnings  are	written	 for  processes	 that  perform
		  writes when the file offset is not 0.

	      1	  Respect  the file offset when writing strings into /proc/sys
		  files.  Multiple writes will append  to  the	value  buffer.
		  Anything written beyond the maximum length of the value buf-
		  fer will be ignored.	Writes to  numeric  /proc/sys  entries
		  must	always be at file offset 0 and the value must be fully
		  contained in the buffer provided to write(2).

       /proc/sys/kernel/sysrq
	      This file controls the functions allowed to be  invoked  by  the
	      SysRq  key.   By default, the file contains 1 meaning that every
	      possible SysRq request is allowed	 (in  older  kernel  versions,
	      SysRq was disabled by default, and you were required to specifi-
	      cally enable it at run-time, but this is not the case any more).
	      Possible values in this file are:

	      0	   Disable sysrq completely

	      1	   Enable all functions of sysrq

	      > 1  Bit mask of allowed sysrq functions, as follows:
		     2	Enable control of console logging level
		     4	Enable control of keyboard (SAK, unraw)
		     8	Enable debugging dumps of processes etc.
		    16	Enable sync command
		    32	Enable remount read-only
		    64	Enable signaling of processes (term, kill, oom-kill)
		   128	Allow reboot/poweroff
		   256	Allow nicing of all real-time tasks

	      This  file is present only if the CONFIG_MAGIC_SYSRQ kernel con-
	      figuration option is enabled.  For further details see the Linux
	      kernel source file Documentation/sysrq.txt.

       /proc/sys/kernel/version
	      This file contains a string such as:

		  #5 Wed Feb 25 21:49:24 MET 1998

	      The  "#5"	 means	that  this is the fifth kernel built from this
	      source base and the date following it  indicates	the  time  the
	      kernel was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
	      This  file  specifies  the  system-wide  limit  on the number of
	      threads (tasks) that can be created on the system.

	      Since Linux 4.1, the value that can be written to threads-max is
	      bounded.	The minimum value that can be written is 20.  The max-
	      imum value  that	can  be	 written  is  given  by	 the  constant
	      FUTEX_TID_MASK  (0x3fffffff).   If a value outside of this range
	      is written to threads-max, the error EINVAL occurs.

	      The value written is checked against the	available  RAM	pages.
	      If the thread structures would occupy too much (more than 1/8th)
	      of the available RAM pages, threads-max is reduced accordingly.

       /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
	      See ptrace(2).

       /proc/sys/kernel/zero-paged (PowerPC only)
	      This file contains a flag.  When	enabled	 (nonzero),  Linux-PPC
	      will  pre-zero  pages  in	 the  idle  loop, possibly speeding up
	      get_free_pages.

       /proc/sys/net
	      This directory contains networking stuff.	 Explanations for some
	      of  the  files  under  this directory can be found in tcp(7) and
	      ip(7).

       /proc/sys/net/core/bpf_jit_enable
	      See bpf(2).

       /proc/sys/net/core/somaxconn
	      This file defines a ceiling value for the	 backlog  argument  of
	      listen(2); see the listen(2) manual page for details.

       /proc/sys/proc
	      This directory may be empty.

       /proc/sys/sunrpc
	      This  directory  supports	 Sun remote procedure call for network
	      filesystem (NFS).	 On some systems, it is not present.

       /proc/sys/vm
	      This directory contains files for memory management tuning, buf-
	      fer and cache management.

       /proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)
	      This file defines the amount of free memory (in KiB) on the sys-
	      tem that that should be reserved for users with  the  capability
	      CAP_SYS_ADMIN.

	      The  default  value  in  this file is the minimum of [3% of free
	      pages, 8MiB] expressed as KiB.  The default is intended to  pro-
	      vide  enough  for the superuser to log in and kill a process, if
	      necessary, under the default overcommit 'guess' mode (i.e., 0 in
	      /proc/sys/vm/overcommit_memory).

	      Systems	running	  in  "overcommit  never"  mode	 (i.e.,	 2  in
	      /proc/sys/vm/overcommit_memory) should  increase	the  value  in
	      this  file  to  account  for the full virtual memory size of the
	      programs used to recover (e.g.,  login(1)	 ssh(1),  and  top(1))
	      Otherwise,  the  superuser  may not be able to log in to recover
	      the system.  For example, on x86_64 a suitable value  is	131072
	      (128MiB reserved).

	      Changing	the value in this file takes effect whenever an appli-
	      cation requests memory.

       /proc/sys/vm/compact_memory (since Linux 2.6.35)
	      When 1 is written to this file, all  zones  are  compacted  such
	      that  free memory is available in contiguous blocks where possi-
	      ble.  The effect	of  this  action  can  be  seen	 by  examining
	      /proc/buddyinfo.

	      Present  only  if	 the  kernel  was  configured with CONFIG_COM-
	      PACTION.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
	      Writing to this file causes the kernel  to  drop	clean  caches,
	      dentries,	 and inodes from memory, causing that memory to become
	      free.  This can be useful for memory management testing and per-
	      forming  reproducible filesystem benchmarks.  Because writing to
	      this file causes the benefits of caching	to  be	lost,  it  can
	      degrade overall system performance.

	      To free pagecache, use:

		  echo 1 > /proc/sys/vm/drop_caches

	      To free dentries and inodes, use:

		  echo 2 > /proc/sys/vm/drop_caches

	      To free pagecache, dentries and inodes, use:

		  echo 3 > /proc/sys/vm/drop_caches

	      Because  writing	to this file is a nondestructive operation and
	      dirty objects are not freeable,  the  user  should  run  sync(1)
	      first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
	      If  nonzero, this disables the new 32-bit memory-mapping layout;
	      the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
	      Control how to kill processes when an uncorrected	 memory	 error
	      (typically a 2-bit error in a memory module) that cannot be han-
	      dled by the kernel is detected in the  background	 by  hardware.
	      In some cases (like the page still having a valid copy on disk),
	      the kernel will handle the failure transparently without affect-
	      ing  any applications.  But if there is no other up-to-date copy
	      of the data, it will kill processes to prevent any data  corrup-
	      tions from propagating.

	      The file has one of the following values:

	      1:  Kill	all  processes that have the corrupted-and-not-reload-
		  able page mapped as soon  as	the  corruption	 is  detected.
		  Note	that  this  is not supported for a few types of pages,
		  such as kernel internally allocated data or the swap	cache,
		  but works for the majority of user pages.

	      0:  Unmap	 the  corrupted	 page  from  all  processes and kill a
		  process only if it tries to access the page.

	      The kill is performed using a SIGBUS signal with si_code set  to
	      BUS_MCEERR_AO.   Processes  can handle this if they want to; see
	      sigaction(2) for more details.

	      This feature is  active  only  on	 architectures/platforms  with
	      advanced	machine	 check	handling  and  depends on the hardware
	      capabilities.

	      Applications can override the memory_failure_early_kill  setting
	      individually with the prctl(2) PR_MCE_KILL operation.

	      Present  only  if	 the  kernel  was  configured with CONFIG_MEM-
	      ORY_FAILURE.

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
	      Enable memory failure recovery (when supported by the platform)

	      1:  Attempt recovery.

	      0:  Always panic on a memory failure.

	      Present only if  the  kernel  was	 configured  with  CONFIG_MEM-
	      ORY_FAILURE.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
	      Enables a system-wide task dump (excluding kernel threads) to be
	      produced when the kernel	performs  an  OOM-killing.   The  dump
	      includes	the  following	information  for  each	task  (thread,
	      process): thread ID, real user ID, thread group ID (process ID),
	      virtual memory size, resident set size, the CPU that the task is
	      scheduled	 on,   oom_adj	 score	 (see	the   description   of
	      /proc/[pid]/oom_adj),  and  command  name.   This	 is helpful to
	      determine why the OOM-killer was invoked	and  to	 identify  the
	      rogue task that caused it.

	      If this contains the value zero, this information is suppressed.
	      On very large systems with thousands of tasks,  it  may  not  be
	      feasible	to  dump  the  memory  state information for each one.
	      Such systems should not be forced to incur a performance penalty
	      in OOM situations when the information may not be desired.

	      If  this	is  set to nonzero, this information is shown whenever
	      the OOM-killer actually kills a memory-hogging task.

	      The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
	      This enables or disables killing the OOM-triggering task in out-
	      of-memory situations.

	      If  this	is  set	 to zero, the OOM-killer will scan through the
	      entire tasklist and select a task based on heuristics  to	 kill.
	      This  normally selects a rogue memory-hogging task that frees up
	      a large amount of memory when killed.

	      If this is set to nonzero, the OOM-killer simply kills the  task
	      that  triggered the out-of-memory condition.  This avoids a pos-
	      sibly expensive tasklist scan.

	      If /proc/sys/vm/panic_on_oom is  nonzero,	 it  takes  precedence
	      over  whatever  value  is used in /proc/sys/vm/oom_kill_allocat-
	      ing_task.

	      The default value is 0.

       /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
	      This writable file provides an alternative to /proc/sys/vm/over-
	      commit_ratio    for    controlling    the	   CommitLimit	  when
	      /proc/sys/vm/overcommit_memory has the value 2.  It  allows  the
	      amount  of  memory overcommitting to be specified as an absolute
	      value (in kB), rather than as a  percentage,  as	is  done  with
	      overcommit_ratio.	 This allows for finer-grained control of Com-
	      mitLimit on systems with extremely large memory sizes.

	      Only one of overcommit_kbytes or overcommit_ratio	 can  have  an
	      effect:  if  overcommit_kbytes  has  a nonzero value, then it is
	      used to calculate	 CommitLimit,  otherwise  overcommit_ratio  is
	      used.  Writing a value to either of these files causes the value
	      in the other file to be set to zero.

       /proc/sys/vm/overcommit_memory
	      This file contains the kernel virtual  memory  accounting	 mode.
	      Values are:

		     0: heuristic overcommit (this is the default)
		     1: always overcommit, never check
		     2: always check, never overcommit

	      In  mode 0, calls of mmap(2) with MAP_NORESERVE are not checked,
	      and the default check is very weak, leading to the risk of  get-
	      ting a process "OOM-killed".

	      In  mode	1,  the kernel pretends there is always enough memory,
	      until memory actually runs out.  One use case for this  mode  is
	      scientific  computing  applications  that	 employ	 large	sparse
	      arrays.  In Linux kernel	versions  before  2.6.0,  any  nonzero
	      value implies mode 1.

	      In mode 2 (available since Linux 2.6), the total virtual address
	      space that can be allocated (CommitLimit	in  /proc/meminfo)  is
	      calculated as

		  CommitLimit = (total_RAM - total_huge_TLB) *
				overcommit_ratio / 100 + total_swap

	      where:

		   *  total_RAM is the total amount of RAM on the system;

		   *  total_huge_TLB  is  the  amount  of memory set aside for
		      huge pages;

		   *  overcommit_ratio is the value  in	 /proc/sys/vm/overcom-
		      mit_ratio; and

		   *  total_swap is the amount of swap space.

	      For  example,  on	 a  system  with 16GB of physical RAM, 16GB of
	      swap, no space dedicated to huge pages, and an  overcommit_ratio
	      of 50, this formula yields a CommitLimit of 24GB.

	      Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes
	      is nonzero, then CommitLimit is instead calculated as:

		  CommitLimit = overcommit_kbytes + total_swap

	      See also the description	of  /proc/sys/vm/admiin_reserve_kbytes
	      and /proc/sys/vm/user_reserve_kbytes.

       /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
	      This  writable  file defines a percentage by which memory can be
	      overcommitted.  The default value in the file is	50.   See  the
	      description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
	      This enables or disables a kernel panic in an out-of-memory sit-
	      uation.

	      If this file is set to the value 0, the kernel's OOM-killer will
	      kill  some  rogue	 process.   Usually, the OOM-killer is able to
	      kill a rogue process and the system will survive.

	      If this file is set to the value 1,  then	 the  kernel  normally
	      panics when out-of-memory happens.  However, if a process limits
	      allocations to certain nodes  using  memory  policies  (mbind(2)
	      MPOL_BIND)  or  cpusets (cpuset(7)) and those nodes reach memory
	      exhaustion status, one process may be killed by the  OOM-killer.
	      No panic occurs in this case: because other nodes' memory may be
	      free, this means the system as a whole may not have  reached  an
	      out-of-memory situation yet.

	      If  this	file  is  set to the value 2, the kernel always panics
	      when an out-of-memory condition occurs.

	      The default value is 0.  1 and 2 are for failover of clustering.
	      Select either according to your policy of failover.

       /proc/sys/vm/swappiness
	      The value in this file controls how aggressively the kernel will
	      swap memory pages.  Higher values increase aggressiveness, lower
	      values decrease aggressiveness.  The default value is 60.

       /proc/sys/vm/user_reserve_kbytes (since Linux 3.10)
	      Specifies	 an amount of memory (in KiB) to reserve for user pro-
	      cesses, This is intended to prevent a user from starting a  sin-
	      gle  memory hogging process, such that they cannot recover (kill
	      the hog).	 The value in  this  file  has	an  effect  only  when
	      /proc/sys/vm/overcommit_memory  is  set to 2 ("overcommit never"
	      mode).  In this case, the system reserves an  amount  of	memory
	      that   is	  the	minimum	  of  [3%  of  current	process	 size,
	      user_reserve_kbytes].

	      The default value in this file is the minimum  of	 [3%  of  free
	      pages, 128MiB] expressed as KiB.

	      If  the  value  in this file is set to zero, then a user will be
	      allowed to allocate all free memory with a single process (minus
	      the  amount reserved by /proc/sys/vm/admin_reserve_kbytes).  Any
	      subsequent attempts to execute a command will result  in	"fork:
	      Cannot allocate memory".

	      Changing	the value in this file takes effect whenever an appli-
	      cation requests memory.

       /proc/sysrq-trigger (since Linux 2.4.21)
	      Writing a character to this file triggers the same  SysRq	 func-
	      tion  as	typing	ALT-SysRq-<character>  (see the description of
	      /proc/sys/kernel/sysrq).	This file is normally writable only by
	      root.  For further details see the Linux kernel source file Doc-
	      umentation/sysrq.txt.

       /proc/sysvipc
	      Subdirectory containing  the  pseudo-files  msg,	sem  and  shm.
	      These  files  list the System V Interprocess Communication (IPC)
	      objects (respectively: message queues,  semaphores,  and	shared
	      memory)  that  currently	exist on the system, providing similar
	      information to that available via	 ipcs(1).   These  files  have
	      headers  and  are	 formatted  (one IPC object per line) for easy
	      understanding.  svipc(7)	provides  further  background  on  the
	      information shown by these files.

       /proc/thread-self (since Linux 3.17)
	      This directory refers to the thread accessing the /proc filesys-
	      tem, and is identical  to	 the  /proc/self/task/[tid]  directory
	      named by the process thread ID ([tid]) of the same thread.

       /proc/timer_list (since Linux 2.6.21)
	      This  read-only  file  exposes  a	 list of all currently pending
	      (high-resolution) timers, all  clock-event  sources,  and	 their
	      parameters in a human-readable form.

       /proc/timer_stats (since Linux 2.6.21)
	      This  is	a  debugging facility to make timer (ab)use in a Linux
	      system visible to kernel and user-space developers.  It  can  be
	      used  by	kernel	and user-space developers to verify that their
	      code does not make undue use of timers.  The goal	 is  to	 avoid
	      unnecessary wakeups, thereby optimizing power consumption.

	      If  enabled in the kernel (CONFIG_TIMER_STATS), but not used, it
	      has almost zero runtime overhead and a  relatively  small	 data-
	      structure	 overhead.   Even if collection is enabled at runtime,
	      overhead is low: all  the	 locking  is  per-CPU  and  lookup  is
	      hashed.

	      The  /proc/timer_stats  file  is	used  both to control sampling
	      facility and to read out the sampled information.

	      The timer_stats functionality is inactive on bootup.  A sampling
	      period can be started using the following command:

		  # echo 1 > /proc/timer_stats

	      The following command stops a sampling period:

		  # echo 0 > /proc/timer_stats

	      The statistics can be retrieved by:

		  $ cat /proc/timer_stats

	      While  sampling  is enabled, each readout from /proc/timer_stats
	      will see newly updated statistics.  Once sampling	 is  disabled,
	      the  sampled  information	 is  kept until a new sample period is
	      started.	This allows multiple readouts.

	      Sample output from /proc/timer_stats:

   $ cat /proc/timer_stats
   Timer Stats Version: v0.3
   Sample period: 1.764 s
   Collection: active
     255,     0 swapper/3	 hrtimer_start_range_ns (tick_sched_timer)
      71,     0 swapper/1	 hrtimer_start_range_ns (tick_sched_timer)
      58,     0 swapper/0	 hrtimer_start_range_ns (tick_sched_timer)
       4,  1694 gnome-shell	 mod_delayed_work_on (delayed_work_timer_fn)
      17,     7 rcu_sched	 rcu_gp_kthread (process_timeout)
   ...
       1,  4911 kworker/u16:0	 mod_delayed_work_on (delayed_work_timer_fn)
      1D,  2522 kworker/0:0	 queue_delayed_work_on (delayed_work_timer_fn)
   1029 total events, 583.333 events/sec

	      The output columns are:

	      *	 a count of the number	of  events,  optionally	 (since	 Linux
		 2.6.23)  followed  by	the letter 'D' if this is a deferrable
		 timer;

	      *	 the PID of the process that initialized the timer;

	      *	 the name of the process that initialized the timer;

	      *	 the function where the timer was initialized; and

	      *	 (in parentheses) the callback	function  that	is  associated
		 with the timer.

       /proc/tty
	      Subdirectory  containing the pseudo-files and subdirectories for
	      tty drivers and line disciplines.

       /proc/uptime
	      This file contains two numbers: the uptime of the	 system	 (sec-
	      onds), and the amount of time spent in idle process (seconds).

       /proc/version
	      This string identifies the kernel version that is currently run-
	      ning.  It	 includes  the	contents  of  /proc/sys/kernel/ostype,
	      /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For
	      example:
	    Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6.0)
	      This file displays various virtual memory statistics.  Each line
	      of  this	file  contains	a single name-value pair, delimited by
	      white space.  Some files are present only if the kernel was con-
	      figured  with  suitable  options.	  (In  some cases, the options
	      required for particular files have changed  across  kernel  ver-
	      sions,  so  they	are  not listed here.  Details can be found by
	      consulting the kernel source code.)  The following fields may be
	      present:

	      nr_free_pages (since Linux 2.6.31)

	      nr_alloc_batch (since Linux 3.12)

	      nr_inactive_anon (since Linux 2.6.28)

	      nr_active_anon (since Linux 2.6.28)

	      nr_inactive_file (since Linux 2.6.28)

	      nr_active_file (since Linux 2.6.28)

	      nr_unevictable (since Linux 2.6.28)

	      nr_mlock (since Linux 2.6.28)

	      nr_anon_pages (since Linux 2.6.18)

	      nr_mapped (since Linux 2.6.0)

	      nr_file_pages (since Linux 2.6.18)

	      nr_dirty (since Linux 2.6.0)

	      nr_writeback (since Linux 2.6.0)

	      nr_slab_reclaimable (since Linux 2.6.19)

	      nr_slab_unreclaimable (since Linux 2.6.19)

	      nr_page_table_pages (since Linux 2.6.0)

	      nr_kernel_stack (since Linux 2.6.32)
		     Amount of memory allocated to kernel stacks.

	      nr_unstable (since Linux 2.6.0)

	      nr_bounce (since Linux 2.6.12)

	      nr_vmscan_write (since Linux 2.6.19)

	      nr_vmscan_immediate_reclaim (since Linux 3.2)

	      nr_writeback_temp (since Linux 2.6.26)

	      nr_isolated_anon (since Linux 2.6.32)

	      nr_isolated_file (since Linux 2.6.32)

	      nr_shmem (since Linux 2.6.32)
		     Pages used by shmem and tmpfs(5).

	      nr_dirtied (since Linux 2.6.37)

	      nr_written (since Linux 2.6.37)

	      nr_pages_scanned (since Linux 3.17)

	      numa_hit (since Linux 2.6.18)

	      numa_miss (since Linux 2.6.18)

	      numa_foreign (since Linux 2.6.18)

	      numa_interleave (since Linux 2.6.18)

	      numa_local (since Linux 2.6.18)

	      numa_other (since Linux 2.6.18)

	      workingset_refault (since Linux 3.15)

	      workingset_activate (since Linux 3.15)

	      workingset_nodereclaim (since Linux 3.15)

	      nr_anon_transparent_hugepages (since Linux 2.6.38)

	      nr_free_cma (since Linux 3.7)
		     Number of free CMA (Contiguous Memory Allocator) pages.

	      nr_dirty_threshold (since Linux 2.6.37)

	      nr_dirty_background_threshold (since Linux 2.6.37)

	      pgpgin (since Linux 2.6.0)

	      pgpgout (since Linux 2.6.0)

	      pswpin (since Linux 2.6.0)

	      pswpout (since Linux 2.6.0)

	      pgalloc_dma (since Linux 2.6.5)

	      pgalloc_dma32 (since Linux 2.6.16)

	      pgalloc_normal (since Linux 2.6.5)

	      pgalloc_high (since Linux 2.6.5)

	      pgalloc_movable (since Linux 2.6.23)

	      pgfree (since Linux 2.6.0)

	      pgactivate (since Linux 2.6.0)

	      pgdeactivate (since Linux 2.6.0)

	      pgfault (since Linux 2.6.0)

	      pgmajfault (since Linux 2.6.0)

	      pgrefill_dma (since Linux 2.6.5)

	      pgrefill_dma32 (since Linux 2.6.16)

	      pgrefill_normal (since Linux 2.6.5)

	      pgrefill_high (since Linux 2.6.5)

	      pgrefill_movable (since Linux 2.6.23)

	      pgsteal_kswapd_dma (since Linux 3.4)

	      pgsteal_kswapd_dma32 (since Linux 3.4)

	      pgsteal_kswapd_normal (since Linux 3.4)

	      pgsteal_kswapd_high (since Linux 3.4)

	      pgsteal_kswapd_movable (since Linux 3.4)

	      pgsteal_direct_dma

	      pgsteal_direct_dma32 (since Linux 3.4)

	      pgsteal_direct_normal (since Linux 3.4)

	      pgsteal_direct_high (since Linux 3.4)

	      pgsteal_direct_movable (since Linux 2.6.23)

	      pgscan_kswapd_dma

	      pgscan_kswapd_dma32 (since Linux 2.6.16)

	      pgscan_kswapd_normal (since Linux 2.6.5)

	      pgscan_kswapd_high

	      pgscan_kswapd_movable (since Linux 2.6.23)

	      pgscan_direct_dma

	      pgscan_direct_dma32 (since Linux 2.6.16)

	      pgscan_direct_normal

	      pgscan_direct_high

	      pgscan_direct_movable (since Linux 2.6.23)

	      pgscan_direct_throttle (since Linux 3.6)

	      zone_reclaim_failed (since linux 2.6.31)

	      pginodesteal (since linux 2.6.0)

	      slabs_scanned (since linux 2.6.5)

	      kswapd_inodesteal (since linux 2.6.0)

	      kswapd_low_wmark_hit_quickly (since 2.6.33)

	      kswapd_high_wmark_hit_quickly (since 2.6.33)

	      pageoutrun (since Linux 2.6.0)

	      allocstall (since Linux 2.6.0)

	      pgrotated (since Linux 2.6.0)

	      drop_pagecache (since Linux 3.15)

	      drop_slab (since Linux 3.15)

	      numa_pte_updates (since Linux 3.8)

	      numa_huge_pte_updates (since Linux 3.13)

	      numa_hint_faults (since Linux 3.8)

	      numa_hint_faults_local (since Linux 3.8)

	      numa_pages_migrated (since Linux 3.8)

	      pgmigrate_success (since Linux 3.8)

	      pgmigrate_fail (since Linux 3.8)

	      compact_migrate_scanned (since Linux 3.8)

	      compact_free_scanned (since Linux 3.8)

	      compact_isolated (since Linux 3.8)

	      compact_stall (since Linux 2.6.35)
		     See   the	 kernel	  source  file	Documentation/vm/tran-
		     shuge.txt.

	      compact_fail (since Linux 2.6.35)
		     See  the  kernel	source	 file	Documentation/vm/tran-
		     shuge.txt.

	      compact_success (since Linux 2.6.35)
		     See   the	 kernel	  source  file	Documentation/vm/tran-
		     shuge.txt.

	      htlb_buddy_alloc_success (since Linux 2.6.26)

	      htlb_buddy_alloc_fail (since Linux 2.6.26)

	      unevictable_pgs_culled (since Linux 2.6.28)

	      unevictable_pgs_scanned (since Linux 2.6.28)

	      unevictable_pgs_rescued (since Linux 2.6.28)

	      unevictable_pgs_mlocked (since Linux 2.6.28)

	      unevictable_pgs_munlocked (since Linux 2.6.28)

	      unevictable_pgs_cleared (since Linux 2.6.28)

	      unevictable_pgs_stranded (since Linux 2.6.28)

	      thp_fault_alloc (since Linux 2.6.39)
		     See  the  kernel	source	 file	Documentation/vm/tran-
		     shuge.txt.

	      thp_fault_fallback (since Linux 2.6.39)
		     See   the	 kernel	  source  file	Documentation/vm/tran-
		     shuge.txt.

	      thp_collapse_alloc (since Linux 2.6.39)
		     See  the  kernel	source	 file	Documentation/vm/tran-
		     shuge.txt.

	      thp_collapse_alloc_failed (since Linux 2.6.39)
		     See   the	 kernel	  source  file	Documentation/vm/tran-
		     shuge.txt.

	      thp_split (since Linux 2.6.39)
		     See  the  kernel	source	 file	Documentation/vm/tran-
		     shuge.txt.

	      thp_zero_page_alloc (since Linux 3.8)
		     See   the	 kernel	  source  file	Documentation/vm/tran-
		     shuge.txt.

	      thp_zero_page_alloc_failed (since Linux 3.8)
		     See  the  kernel	source	 file	Documentation/vm/tran-
		     shuge.txt.

	      balloon_inflate (since Linux 3.18)

	      balloon_deflate (since Linux 3.18)

	      balloon_migrate (since Linux 3.18)

	      nr_tlb_remote_flush (since Linux 3.12)

	      nr_tlb_remote_flush_received (since Linux 3.12)

	      nr_tlb_local_flush_all (since Linux 3.12)

	      nr_tlb_local_flush_one (since Linux 3.12)

	      vmacache_find_calls (since Linux 3.16)

	      vmacache_find_hits (since Linux 3.16)

	      vmacache_full_flushes (since Linux 3.19)

       /proc/zoneinfo (since Linux 2.6.13)
	      This  file display information about memory zones.  This is use-
	      ful for analyzing virtual memory behavior.

NOTES
       Many strings (i.e., the environment and command line) are in the inter-
       nal  format, with subfields terminated by null bytes ('\0'), so you may
       find that things are more readable if you use od -c or tr  "\000"  "\n"
       to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

SEE ALSO
       cat(1), dmesg(1), find(1), free(1), init(1), ps(1),  tr(1),  uptime(1),
       chroot(2),   mmap(2),  readlink(2),  syslog(2),	slabinfo(5),  hier(7),
       namespaces(7),  time(7),	 arp(8),  hdparm(8),  ifconfig(8),   lsmod(8),
       lspci(8), mount(8), netstat(8), procinfo(8), route(8), sysctl(8)

       The Linux kernel source files: Documentation/filesystems/proc.txt Docu-
       mentation/sysctl/fs.txt,	 Documentation/sysctl/kernel.txt,   Documenta-
       tion/sysctl/net.txt, and Documentation/sysctl/vm.txt.

COLOPHON
       This  page  is  part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-12-12			       PROC(5)