DMSETUP(8)		     MAINTENANCE COMMANDS		    DMSETUP(8)



NAME
       dmsetup -- low level logical volume management

SYNOPSIS
       dmsetup clear device_name
       dmsetup create device_name [-u|--uuid uuid]
		[--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
		{table|table_file}] [--readahead {[+]sectors|auto|none}]
       dmsetup deps [-o options] [device_name]
       dmsetup help [-c|-C|--columns]
       dmsetup info [device_name]
       dmsetup info -c|-C|--columns [--count count] [--interval seconds]
		[--nameprefixes] [--noheadings] [-o fields] [-O|--sort
		sort_fields] [--separator separator] [device_name]
       dmsetup load device_name [--table {table|table_file}]
       dmsetup ls [--target target_type] [--exec command] [--tree] [-o
		options]
       dmsetup mangle [device_name]
       dmsetup message device_name sector message
       dmsetup mknodes [device_name]
       dmsetup reload device_name [--table {table|table_file}]
       dmsetup remove [-f|--force] [--retry] [--deferred] device_name
       dmsetup remove_all [-f|--force] [--deferred]
       dmsetup rename device_name new_name
       dmsetup rename device_name --setuuid uuid
       dmsetup resume device_name [--addnodeoncreate|--addnodeonresume]
		[--noflush] [--nolockfs] [--readahead {[+]sectors|auto|none}]
       dmsetup setgeometry device_name cyl head sect start
       dmsetup splitname device_name [subsystem]
       dmsetup stats command [options]
       dmsetup status [--target target_type] [--noflush] [device_name]
       dmsetup suspend [--nolockfs] [--noflush] device_name
       dmsetup table [--target target_type] [--showkeys] [device_name]
       dmsetup targets
       dmsetup udevcomplete cookie
       dmsetup udevcomplete_all [age_in_minutes]
       dmsetup udevcookie
       dmsetup udevcreatecookie
       dmsetup udevflags cookie
       dmsetup udevreleasecookie [cookie]
       dmsetup version
       dmsetup wait [--noflush] device_name [event_nr]
       dmsetup wipe_table device_name [-f|--force] [--noflush] [--nolockfs]

       devmap_name major minor
       devmap_name major:minor

DESCRIPTION
       dmsetup	manages	 logical  devices  that	 use the device-mapper driver.
       Devices are created by loading a table that specifies a target for each
       sector (512 bytes) in the logical device.

       The first argument to dmsetup is a command.  The second argument is the
       logical device name or uuid.

       Invoking the dmsetup tool as devmap_name (which is  not	normally  dis-
       tributed and is supported only for historical reasons) is equivalent to
       dmsetup info -c --noheadings -j major -m minor.

OPTIONS
       --addnodeoncreate
	      Ensure /dev/mapper node exists after dmsetup create.

       --addnodeonresume
	      Ensure /dev/mapper node exists  after  dmsetup  resume  (default
	      with udev).

       --checks
	      Perform additional checks on the operations requested and report
	      potential problems.  Useful when	debugging  scripts.   In  some
	      cases these checks may slow down operations noticeably.

       -c|-C|--columns
	      Display output in columns rather than as Field: Value lines.

       --count count
	      Specify the number of times to repeat a report. Set this to zero
	      continue until interrupted.  The default interval is one second.

       -f|--force
	      Try harder to complete operation.

       -h|--help
	      Outputs a summary of the commands available, optionally  includ-
	      ing the list of report fields (synonym with help command).

       --inactive
	      When  returning  any table information from the kernel report on
	      the inactive table instead of the live table.   Requires	kernel
	      driver version 4.16.0 or above.

       --interval seconds
	      Specify  the  interval  in seconds between successive iterations
	      for repeating reports. If --interval is specified but --count is
	      not,  reports  will  continue  to repeat until interrupted.  The
	      default interval is one second.

       --manglename {auto|hex|none}
	      Mangle any character not on a whitelist using mangling_mode when
	      processing  device-mapper	 device names and UUIDs. The names and
	      UUIDs are mangled on input and unmangled	on  output  where  the
	      mangling	mode is one of: auto (only do the mangling if not man-
	      gled yet, do nothing if already mangled, error  on  mixed),  hex
	      (always  do  the mangling) and none (no mangling).  Default mode
	      is auto.	Character whitelist: 0-9,  A-Z,	 a-z,  #+-.:=@_.  This
	      whitelist	 is  also  supported  by  udev. Any character not on a
	      whitelist is replaced with its hex value (two  digits)  prefixed
	      by    \x.	   Mangling   mode   could   be	  also	 set   through
	      DM_DEFAULT_NAME_MANGLING_MODE environment variable.

       -j|--major major
	      Specify the major number.

       -m|--minor minor
	      Specify the minor number.

       -n|--notable
	      When creating a device, don't load any table.

       --nameprefixes
	      Add a "DM_" prefix plus the field name to	 the  output.	Useful
	      with  --noheadings  to  produce a list of field=value pairs that
	      can be used  to  set  environment	 variables  (for  example,  in
	      udev(7) rules).

       --noheadings Suppress the headings line when using columnar output.

       --noflush  Do  not flush outstading I/O when suspending a device, or do
	      not commit thin-pool metadata when obtaining thin-pool status.

       --nolockfs
	      Do not attempt to synchronize filesystem eg, when	 suspending  a
	      device.

       --noopencount
	      Tell  the	 kernel not to supply the open reference count for the
	      device.

       --noudevrules
	      Do not allow udev to manage nodes for devices  in	 device-mapper
	      directory.

       --noudevsync
	      Do not synchronise with udev when creating, renaming or removing
	      devices.

       -o|--options options
	      Specify which fields to display.

       --readahead {[+]sectors|auto|none}
	      Specify read ahead size in units of sectors.  The default	 value
	      is auto which allows the kernel to choose a suitable value auto-
	      matically.  The + prefix lets you specify a minimum value	 which
	      will  not	 be used if it is smaller than the value chosen by the
	      kernel.  The value none is equivalent to specifying zero.

       -r|--readonly
	      Set the table being loaded read-only.

       -S|--select selection
	      Display only rows that match selection criteria.	All  rows  are
	      displayed	 with  the  additional "selected" column (-o selected)
	      showing 1 if the row matches the selection and 0 otherwise.  The
	      selection	 criteria  are	defined by specifying column names and
	      their valid values while	making	use  of	 supported  comparison
	      operators.  As a quick help and to see full list of column names
	      that can be used in selection and the set of supported selection
	      operators, check the output of dmsetup info -c -S help command.

       --table table
	      Specify  a  one-line  table  directly  on the command line.  See
	      below for more information on the table format.

       --udevcookie cookie
	      Use cookie for udev synchronisation.  Note: Same	cookie	should
	      be  used	for  same type of operations i.e. creation of multiple
	      different devices. It's not adviced to combine different	opera-
	      tions on the single device.

       -u|--uuid
	      Specify the uuid.

       -y|--yes
	      Answer yes to all prompts automatically.

       -v|--verbose [-v|--verbose]
	      Produce additional output.

       --verifyudev
	      If  udev synchronisation is enabled, verify that udev operations
	      get performed correctly and try  to  fix	up  the	 device	 nodes
	      afterwards if not.

       --version
	      Display the library and kernel driver version.

COMMANDS
       clear device_name
	      Destroys the table in the inactive table slot for device_name.

       create device_name [-u|--uuid uuid]
	      [--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
	      {table|table_file}] [--readahead {[+]sectors|auto|none}]
	      Creates a device with the given name.  If table or table_file is
	      supplied, the table is loaded and made live.  Otherwise a	 table
	      is  read	from  standard	input  unless  --notable is used.  The
	      optional uuid can be used in place of device_name in  subsequent
	      dmsetup commands.	 If successful the device will appear in table
	      and for live device the node /dev/mapper/device_name is created.
	      See below for more information on the table format.

       deps [-o options] [device_name]
	      Outputs  a  list of devices referenced by the live table for the
	      specified device. Device names on output can  be	customised  by
	      following	  options:  devno  (major  and	minor  pair,  used  by
	      default), blkdevname (block device name), devname (map name  for
	      device-mapper devices, equal to blkdevname otherwise).

       help [-c|-C|--columns]
	      Outputs  a summary of the commands available, optionally includ-
	      ing the list of report fields.

       info [device_name]
	      Outputs some brief information about the device in the form:
		      State: SUSPENDED|ACTIVE, READ-ONLY
		      Tables present: LIVE and/or INACTIVE
		      Open reference count
		      Last event sequence number (used by wait)
		      Major and minor device number
		      Number of targets in the live table
		      UUID

       info -c|-C|--columns [--count count] [--interval seconds]
	      [--nameprefixes] [--noheadings] [-o fields] [-O|--sort
	      sort_fields] [--separator separator] [device_name]
	      Output you can customise.	 Fields are comma-separated and chosen
	      from  the	 following  list: name, major, minor, attr, open, seg-
	      ments,  events,  uuid.   Attributes  are:	 (L)ive,   (I)nactive,
	      (s)uspended,  (r)ead-only,  read-(w)rite.	 Precede the list with
	      '+' to append to the default selection  of  columns  instead  of
	      replacing	 it.   Precede	any  sort field with '-' for a reverse
	      sort on that column.

       ls [--target target_type] [--exec command] [--tree] [-o options]
	      List device names.  Optionally only list devices	that  have  at
	      least  one  target  of the specified type.  Optionally execute a
	      command for each device.	The device name	 is  appended  to  the
	      supplied	command.   Device names on output can be customised by
	      following	 options:  devno  (major  and  minor  pair,  used   by
	      default),	 blkdevname (block device name), devname (map name for
	      device-mapper devices, equal to blkdevname  otherwise).	--tree
	      displays	dependencies  between devices as a tree.  It accepts a
	      comma-separate list of options.  Some  specify  the  information
	      displayed	  against   each  node:	 device/nodevice;  blkdevname;
	      active, open, rw, uuid.  Others specify how  the	tree  is  dis-
	      played: ascii, utf, vt100; compact, inverted, notrunc.

       load|reload device_name [--table {table|table_file}]
	      Loads  table  or	table_file  into  the  inactive table slot for
	      device_name.  If neither is supplied, reads a table  from	 stan-
	      dard input.

       mangle [device_name]
	      Ensure  existing	device-mapper  device_name  and UUID is in the
	      correct mangled  form  containing	 only  whitelisted  characters
	      (supported  by udev) and do a rename if necessary. Any character
	      not on the whitelist will be mangled based on  the  --manglename
	      setting.	Automatic  rename  works only for device names and not
	      for device UUIDs because the kernel does not allow changing  the
	      UUID  of	active	devices. Any incorrect UUIDs are reported only
	      and they must be manually corrected by deactivating  the	device
	      first  and  then	reactivating it with proper mangling mode used
	      (see also --manglename).

       message device_name sector message
	      Send message to target. If sector not needed use 0.

       mknodes [device_name]
	      Ensure that the node in /dev/mapper for device_name is  correct.
	      If  no  device_name  is  supplied,  ensure  that	all  nodes  in
	      /dev/mapper correspond to mapped devices currently loaded by the
	      device-mapper  kernel driver, adding, changing or removing nodes
	      as necessary.

       remove [-f|--force] [--retry] [--deferred] device_name
	      Removes a device.	 It will no  longer  be	 visible  to  dmsetup.
	      Open  devices cannot be removed, but adding --force will replace
	      the table with one that fails all I/O.  --deferred  will	enable
	      deferred	removal	 of  open devices - the device will be removed
	      when the last user closes it. The deferred  removal  feature  is
	      supported	 since	version	 4.27.0	 of  the  device-mapper driver
	      available in upstream kernel version 3.13.  (Use dmsetup version
	      to check this.)  If an attempt to remove a device fails, perhaps
	      because a process run from a quick udev rule temporarily	opened
	      the  device,  the	 --retry option will cause the operation to be
	      retried for a  few  seconds  before  failing.   Do  NOT  combine
	      --force  and  --udevcookie,  as  udev  may start to process udev
	      rules in the middle of error target replacement  and  result  in
	      nondeterministic result.

       remove_all [-f|--force] [--deferred]
	      Attempts to remove all device definitions i.e. reset the driver.
	      This also runs mknodes afterwards.  Use with care!  Open devices
	      cannot  be  removed,  but	 adding --force will replace the table
	      with one that fails all I/O.  --deferred	will  enable  deferred
	      removal  of  open	 devices - the device will be removed when the
	      last user closes it.  The deferred removal feature is  supported
	      since  version  4.27.0  of the device-mapper driver available in
	      upstream kernel version 3.13.

       rename device_name new_name
	      Renames a device.

       rename device_name --setuuid uuid
	      Sets the uuid of a device	 that  was  created  without  a	 uuid.
	      After a uuid has been set it cannot be changed.

       resume device_name [--addnodeoncreate|--addnodeonresume] [--noflush]
	      [--nolockfs] [--readahead {[+]sectors|auto|none}]
	      Un-suspends a device.  If an inactive table has been loaded,  it
	      becomes live.  Postponed I/O then gets re-queued for processing.

       setgeometry device_name cyl head sect start
	      Sets the device geometry to C/H/S.

       splitname device_name [subsystem]
	      Splits  given  device  name  into	 subsystem  constituents.  The
	      default subsystem is LVM.	 LVM currently generates device	 names
	      by  concatenating	 the names of the Volume Group, Logical Volume
	      and any internal Layer with a hyphen as separator.  Any  hyphens
	      within the names are doubled to escape them.  The precise encod-
	      ing might change without notice in any  future  release,	so  we
	      recommend	 you  always  decode using the current version of this
	      command.

       stats command [options]
	      Manages IO statistics regions for devices.  See  dmstats(8)  for
	      more details.

       status [--target target_type] [--noflush] [device_name]
	      Outputs  status  information  for	 each of the device's targets.
	      With --target, only information relating to the specified target
	      type  any	 is  displayed.	 With --noflush, the thin target (from
	      version 1.3.0) doesn't commit any outstanding  changes  to  disk
	      before reporting its statistics.


       suspend [--nolockfs] [--noflush] device_name
	      Suspends	a device.  Any I/O that has already been mapped by the
	      device but has not yet completed will be flushed.	  Any  further
	      I/O  to  that device will be postponed for as long as the device
	      is suspended.  If there's a filesystem on the device which  sup-
	      ports  the  operation,  an attempt will be made to sync it first
	      unless --nolockfs is specified.  Some  targets  such  as	recent
	      (October	2006)  versions of multipath may support the --noflush
	      option.  This lets outstanding I/O that has not yet reached  the
	      device to remain unflushed.

       table [--target target_type] [--showkeys] [device_name]
	      Outputs the current table for the device in a format that can be
	      fed back in using the create or load commands.   With  --target,
	      only  information	 relating to the specified target type is dis-
	      played.  Encryption keys are suppressed in the table output  for
	      the crypt target unless the --showkeys parameter is supplied.

       targets
	      Displays the names and versions of the currently-loaded targets.

       udevcomplete cookie
	      Wake  any	 processes  that are waiting for udev to complete pro-
	      cessing the specified cookie.

       udevcomplete_all [age_in_minutes]
	      Remove all cookies older than the specified number  of  minutes.
	      Any process waiting on a cookie will be resumed immediately.

       udevcookie
	      List  all	 existing  cookies. Cookies are system-wide semaphores
	      with keys prefixed by two predefined bytes (0x0D4D).

       udevcreatecookie
	      Creates a new cookie to synchronize actions with	udev  process-
	      ing.   The  output  is a cookie value. Normally we don't need to
	      create cookies since dmsetup creates and destroys them for  each
	      action automatically. However, we can generate one explicitly to
	      group several actions together and use only one cookie  instead.
	      We can define a cookie to use for each relevant command by using
	      --udevcookie option. Alternatively, we  can  export  this	 value
	      into  the	 environment  of the dmsetup process as DM_UDEV_COOKIE
	      variable and it will be used automatically with  all  subsequent
	      commands	until  it is unset.  Invoking this command will create
	      system-wide semaphore that needs to be cleaned up explicitly  by
	      calling udevreleasecookie command.

       udevflags cookie
	      Parses  given  cookie  value and extracts any udev control flags
	      encoded.	The output is in environment key format that is	 suit-
	      able  for	 use  in udev rules. If the flag has its symbolic name
	      assigned then the	 output	 is  DM_UDEV_FLAG_<flag_name>  =  '1',
	      DM_UDEV_FLAG<flag_position>  =  '1'  otherwise.	Subsystem udev
	      flags don't have symbolic names  assigned	 and  these  ones  are
	      always  reported as DM_SUBSYSTEM_UDEV_FLAG<flag_position> = '1'.
	      There are 16 udev flags altogether.

       udevreleasecookie [cookie]
	      Waits for all pending udev  processing  bound  to	 given	cookie
	      value  and clean up the cookie with underlying semaphore. If the
	      cookie is not given directly, the command	 will  try  to	use  a
	      value defined by DM_UDEV_COOKIE environment variable.

       version
	      Outputs version information.

       wait [--noflush] device_name [event_nr]
	      Sleeps until the event counter for device_name exceeds event_nr.
	      Use -v to see the event number returned.	To wait until the next
	      event  is	 triggered,  use  info	to find the last event number.
	      With --noflush, the thin target  (from  version  1.3.0)  doesn't
	      commit any outstanding changes to disk before reporting its sta-
	      tistics.

       wipe_table device_name [-f|--force] [--noflush] [--nolockfs]
	      Wait for any I/O in-flight through the device to complete,  then
	      replace  the  table with a new table that fails any new I/O sent
	      to the device.  If successful, this should release  any  devices
	      held open by the device's table(s).

TABLE FORMAT
       Each line of the table specifies a single target and is of the form:

       logical_start_sector num_sectors target_type target_args

       Simple target types and target args include:

       linear destination_device start_sector
	      The traditional linear mapping.

       striped num_stripes chunk_size [destination start_sector]...
	      Creates a striped area.
	      e.g.  striped  2	32  /dev/hda1 0 /dev/hdb1 0 will map the first
	      chunk (16k) as follows:
		      LV chunk 1 -> hda1, chunk 1
		      LV chunk 2 -> hdb1, chunk 1
		      LV chunk 3 -> hda1, chunk 2
		      LV chunk 4 -> hdb1, chunk 2
		      etc.

       error  Errors any I/O that goes to this area.  Useful  for  testing  or
	      for creating devices with holes in them.

       zero   Returns  blocks  of  zeroes  on reads.  Any data written is dis-
	      carded silently.	This  is  a  block-device  equivalent  of  the
	      /dev/zero character-device data sink described in null(4).

       More complex targets include:

       cache  Improves performance of a block device (eg, a spindle) by dynam-
	      ically migrating some of its data to  a  faster  smaller	device
	      (eg, an SSD).

       crypt  Transparent  encryption of block devices using the kernel crypto
	      API.

       delay  Delays reads and/or writes to  different	devices.   Useful  for
	      testing.

       flakey Creates  a  similar  mapping  to	the linear target but exhibits
	      unreliable behaviour periodically.  Useful for simulating	 fail-
	      ing devices when testing.

       mirror Mirrors data across two or more devices.

       multipath
	      Mediates access through multiple paths to the same device.

       raid   Offers an interface to the kernel's software raid driver, md.

       snapshot
	      Supports snapshots of devices.

       thin, thin-pool
	      Supports thin provisioning of devices and also provides a better
	      snapshot support.

       To find out more about the various targets and their table formats  and
       status  lines, please read the files in the Documentation/device-mapper
       directory in the kernel source tree.  (Your distribution might  include
       a  copy	of  this  information  in  the documentation directory for the
       device-mapper package.)

EXAMPLES
       # A table to join two disks together
       0 1028160 linear /dev/hda 0
       1028160 3903762 linear /dev/hdb 0
       # A table to stripe across the two disks,
       # and add the spare space from
       # hdb to the back of the volume
       0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
       2056320 2875602 linear /dev/hdb 1028160

ENVIRONMENT VARIABLES
       DM_DEV_DIR
	      The device directory name.  Defaults to "/dev" and  must	be  an
	      absolute path.

       DM_UDEV_COOKIE
	      A	 cookie	 to  use for all relevant commands to synchronize with
	      udev processing.	It is an  alternative  to  using  --udevcookie
	      option.

       DM_DEFAULT_NAME_MANGLING_MODE
	      A	 default mangling mode. Defaults to "auto" and it is an alter-
	      native to using --manglename option.

AUTHORS
       Original version: Joe Thornber <thornber@redhat.com>

SEE ALSO
       dmstats(8), udev(7), udevadm(8)

       LVM2 resource page: https://www.sourceware.org/lvm2/
       Device-mapper resource page: http://sources.redhat.com/dm/



Linux				  Apr 06 2006			    DMSETUP(8)