Yolinux.com

bootparam manpage

Search topic Section
Get manual page for the search topic
List all commands matching the search topic
List all topics in the manpage index

BOOTPARAM(7)		   Linux Programmer's Manual		  BOOTPARAM(7)



NAME
       bootparam - Introduction to boot time parameters of the Linux kernel

DESCRIPTION
       The  Linux  kernel accepts certain 'command-line options' or 'boot time
       parameters' at the moment it is started.	 In general this  is  used  to
       supply  the  kernel with information about hardware parameters that the
       kernel would not be able to determine on its own, or to	avoid/override
       the values that the kernel would otherwise detect.

       When  the  kernel  is booted directly by the BIOS (say from a floppy to
       which you copied a kernel using 'cp  zImage  /dev/fd0'),	 you  have  no
       opportunity  to specify any parameters.	So, in order to take advantage
       of this possibility you have to use  software  that  is	able  to  pass
       parameters,  like  LILO	or loadlin.  For a few parameters one can also
       modify the kernel image itself, using rdev,  see	 rdev(8)  for  further
       details.

       The  LILO  program  (LInux LOader) written by Werner Almesberger is the
       most commonly used.  It has the ability to boot	various	 kernels,  and
       stores  the  configuration  information	in  a  plain  text file.  (See
       lilo(8) and lilo.conf(5).)  LILO can boot DOS,  OS/2,  Linux,  FreeBSD,
       UnixWare, etc., and is quite flexible.

       The  other  commonly used Linux loader is 'LoadLin' which is a DOS pro-
       gram that has the capability to launch a	 Linux	kernel	from  the  DOS
       prompt  (with boot-args) assuming that certain resources are available.
       This is good for people that want to launch Linux from DOS.

       It is also very useful if you have certain hardware which relies on the
       supplied	 DOS  driver to put the hardware into a known state.  A common
       example is 'SoundBlaster Compatible' sound cards that require  the  DOS
       driver  to  twiddle  a few mystical registers to put the card into a SB
       compatible mode.	 Booting DOS with the supplied driver, and then	 load-
       ing Linux from the DOS prompt with loadlin avoids the reset of the card
       that happens if one rebooted instead.

   The Argument List
       The kernel command line is parsed into a list of	 strings  (boot	 argu-
       ments) separated by spaces.  Most of the boot args take the form of:

	      name[=value_1][,value_2]...[,value_10]

       where  'name' is a unique keyword that is used to identify what part of
       the kernel the associated values (if any) are to be given to.  Note the
       limit  of  10  is real, as the present code only handles 10 comma sepa-
       rated parameters per keyword.  (However, you can re-use the  same  key-
       word  with  up  to an additional 10 parameters in unusually complicated
       situations, assuming the setup function supports it.)

       Most of the sorting goes on in linux/init/main.c.   First,  the	kernel
       checks  to see if the argument is any of the special arguments 'root=',
       'nfsroot=', 'nfsaddrs=', 'ro', 'rw', 'debug' or 'init'.	The meaning of
       these special arguments is described below.

       Then  it	 walks	a list of setup functions (contained in the bootsetups
       array) to see if the specified argument string (such as 'foo') has been
       associated  with	 a  setup  function  ('foo_setup()')  for a particular
       device or part of the kernel.   If  you	passed	the  kernel  the  line
       foo=3,4,5,6 then the kernel would search the bootsetups array to see if
       'foo' was registered.  If it was, then it would call the setup function
       associated  with	 'foo' (foo_setup()) and hand it the arguments 3, 4, 5
       and 6 as given on the kernel command line.

       Anything of the form 'foo=bar' that is not accepted as a setup function
       as described above is then interpreted as an environment variable to be
       set.  A (useless?) example would be to use 'TERM=vt100' as a boot argu-
       ment.

       Any  remaining arguments that were not picked up by the kernel and were
       not interpreted as environment variables are then passed	 onto  process
       one,  which is usually the init program.	 The most common argument that
       is passed to the init process is the word 'single' which instructs init
       to  boot the computer in single user mode, and not launch all the usual
       daemons.	 Check the manual page for the version of  init	 installed  on
       your system to see what arguments it accepts.

   General Non-device Specific Boot Arguments
       'init=...'
	      This  sets the initial command to be executed by the kernel.  If
	      this is not set,	or  cannot  be	found,	the  kernel  will  try
	      /sbin/init,  then	 /etc/init,  then  /bin/init, then /bin/sh and
	      panic if all of this fails.

       'nfsaddrs=...'
	      This sets the nfs boot address to the given string.   This  boot
	      address is used in case of a net boot.

       'nfsroot=...'
	      This sets the nfs root name to the given string.	If this string
	      does not begin with '/' or ',' or a digit, then it  is  prefixed
	      by  '/tftpboot/'.	 This root name is used in case of a net boot.

       'no387'
	      (Only when CONFIG_BUGi386 is defined.)   Some  i387  coprocessor
	      chips have bugs that show up when used in 32 bit protected mode.
	      For example, some of the early ULSI-387 chips would cause	 solid
	      lockups while performing floating-point calculations.  Using the
	      'no387' boot arg causes Linux to ignore  the  maths  coprocessor
	      even  if you have one.  Of course you must then have your kernel
	      compiled with math emulation support!

       'no-hlt'
	      (Only when  CONFIG_BUGi386  is  defined.)	  Some	of  the	 early
	      i486DX-100  chips	 have a problem with the 'hlt' instruction, in
	      that they can't reliably return to  operating  mode  after  this
	      instruction is used.  Using the 'no-hlt' instruction tells Linux
	      to just run an infinite loop when there is nothing else  to  do,
	      and  to  not halt the CPU.  This allows people with these broken
	      chips to use Linux.

       'root=...'
	      This argument tells the kernel what device is to be used as  the
	      root  file system while booting.	The default of this setting is
	      determined at compile time, and usually is the value of the root
	      device  of the system that the kernel was built on.  To override
	      this value, and select the  second  floppy  drive	 as  the  root
	      device,  one  would  use	'root=/dev/fd1'.  (The root device can
	      also be set using rdev(8).)

	      The root device can be specified symbolically or numerically.  A
	      symbolic	specification  has the form /dev/XXYN, where XX desig-
	      nates the device type ('hd' for  ST-506  compatible  hard	 disk,
	      with  Y  in  'a'-'d';  'sd'  for SCSI compatible disk, with Y in
	      'a'-'e'; 'ad' for Atari ACSI disk, with Y in 'a'-'e', 'ez' for a
	      Syquest  EZ135  parallel	port removable drive, with Y='a', 'xd'
	      for XT compatible disk, with Y  either  'a'  or  'b';  'fd'  for
	      floppy  disk,  with Y the floppy drive number -- fd0 would be the
	      DOS 'A:' drive, and fd1 would be 'B:'), Y the driver  letter  or
	      number,  and  N the number (in decimal) of the partition on this
	      device (absent in the case of floppies).	Recent	kernels	 allow
	      many  other  types,  mostly  for	CD-ROMs:  nfs,	ram, scd, mcd,
	      cdu535, aztcd, cm206cd, gscd, sbpcd, sonycd,  bpcd.   (The  type
	      nfs specifies a net boot; ram refers to a ram disk.)

	      Note  that  this has nothing to do with the designation of these
	      devices on your file system.  The '/dev/' part is purely conven-
	      tional.

	      The  more awkward and less portable numeric specification of the
	      above possible  root  devices  in	 major/minor  format  is  also
	      accepted.	  (E.g.,  /dev/sda3  is major 8, minor 3, so you could
	      use 'root=0x803' as an alternative.)

       'ro' and 'rw'
	      The 'ro' option tells the kernel to mount the root  file	system
	      as  'read-only'  so  that file system consistency check programs
	      (fsck) can do their work on a quiescent file  system.   No  pro-
	      cesses  can  write to files on the file system in question until
	      it is 'remounted' as read/write capable, for example, by	'mount
	      -w -n -o remount /'.  (See also mount(8).)

	      The  'rw'	 option tells the kernel to mount the root file system
	      read/write.  This is the default.

	      The choice between read-only and	read/write  can	 also  be  set
	      using rdev(8).

       'reserve=...'
	      This  is used to protect I/O port regions from probes.  The form
	      of the command is:

	      reserve=iobase,extent[,iobase,extent]...

	      In some machines it may be necessary to prevent  device  drivers
	      from  checking  for devices (auto-probing) in a specific region.
	      This may be because of hardware that reacts badly to  the	 prob-
	      ing,  or hardware that would be mistakenly identified, or merely
	      hardware you don't want the kernel to initialize.

	      The reserve boot-time argument specifies an I/O port region that
	      shouldn't	 be probed.  A device driver will not probe a reserved
	      region, unless another boot argument explicitly  specifies  that
	      it do so.

	      For example, the boot line

	      reserve=0x300,32	blah=0x300

	      keeps all device drivers except the driver for 'blah' from prob-
	      ing 0x300-0x31f.

       'mem=...'
	      The BIOS call defined in the PC specification that  returns  the
	      amount  of  installed  memory  was  only	designed to be able to
	      report up to 64MB.  Linux uses this BIOS call at boot to	deter-
	      mine  how	 much memory is installed.  If you have more than 64MB
	      of RAM installed, you can use this boot arg to  tell  Linux  how
	      much  memory  you	 have.	The value is in decimal or hexadecimal
	      (prefix 0x), and the suffixes 'k' (times	1024)  or  'M'	(times
	      1048576)	can  be	 used.	Here is a quote from Linus on usage of
	      the 'mem=' parameter.

		   The kernel will accept any 'mem=xx' parameter you give  it,
		   and if it turns out that you lied to it, it will crash hor-
		   ribly sooner or later.  The parameter indicates the highest
		   addressable	RAM address, so 'mem=0x1000000' means you have
		   16MB of memory, for example.	 For a 96MB machine this would
		   be 'mem=0x6000000'.

		   NOTE	 NOTE  NOTE: some machines might use the top of memory
		   for BIOS caching or whatever, so  you  might	 not  actually
		   have	 up to the full 96MB addressable.  The reverse is also
		   true: some chipsets will map the physical  memory  that  is
		   covered by the BIOS area into the area just past the top of
		   memory, so the top-of-mem might actually be	96MB  +	 384kB
		   for	example.   If  you  tell linux that it has more memory
		   than it actually does have, bad things will	happen:	 maybe
		   not at once, but surely eventually.

	      You can also use the boot argument 'mem=nopentium' to turn off 4
	      MB page tables on kernels configured for	IA32  systems  with  a
	      pentium or newer CPU.

       'panic=N'
	      By  default  the	kernel will not reboot after a panic, but this
	      option will cause a kernel reboot	 after	N  seconds  (if	 N  is
	      greater than zero).  This panic timeout can also be set by "echo
	      N > /proc/sys/kernel/panic".

       'reboot=[warm|cold][,[bios|hard]]'
	      (Only when CONFIG_BUGi386 is defined.)  Since 2.0.22 a reboot is
	      by  default  a  cold  reboot.  One asks for the old default with
	      'reboot=warm'.  (A cold reboot may be required to reset  certain
	      hardware,	 but  might  destroy  not  yet	written data in a disk
	      cache.  A warm reboot may be faster.)  By default	 a  reboot  is
	      hard,  by asking the keyboard controller to pulse the reset line
	      low, but there is at least one type of  motherboard  where  that
	      doesn't  work.   The  option  'reboot=bios'  will	 instead  jump
	      through the BIOS.

       'nosmp' and 'maxcpus=N'
	      (Only when  __SMP__  is  defined.)   A  command-line  option  of
	      'nosmp'  or 'maxcpus=0' will disable SMP activation entirely; an
	      option 'maxcpus=N' limits the maximum number of  CPUs  activated
	      in SMP mode to N.

   Boot Arguments for Use by Kernel Developers
       'debug'
	      Kernel messages are handed off to the kernel log daemon klogd so
	      that they may be logged to disk.	Messages with a priority above
	      console_loglevel	are  also  printed on the console.  (For these
	      levels, see <linux/kernel.h>.)  By default this variable is  set
	      to  log  anything more important than debug messages.  This boot
	      argument will cause the kernel to also  print  the  messages  of
	      DEBUG  priority.	 The  console  loglevel can also be set at run
	      time via an option to klogd.  See klogd(8).

       'profile=N'
	      It is possible to enable a kernel	 profiling  function,  if  one
	      wishes  to find out where the kernel is spending its CPU cycles.
	      Profiling is enabled by setting the  variable  prof_shift	 to  a
	      non-zero	value.	 This is done either by specifying CONFIG_PRO-
	      FILE at compile time, or by giving the 'profile='	 option.   Now
	      the  value  that	prof_shift gets will be N, when given, or CON-
	      FIG_PROFILE_SHIFT, when that is given, or 2, the	default.   The
	      significance  of	this variable is that it gives the granularity
	      of the profiling: each clock tick, if the system	was  executing
	      kernel code, a counter is incremented:

	      profile[address >> prof_shift]++;

	      The  raw	profiling  information can be read from /proc/profile.
	      Probably you'll want to use a  tool  such	 as  readprofile.c  to
	      digest it.  Writing to /proc/profile will clear the counters.

       'swap=N1,N2,N3,N4,N5,N6,N7,N8'
	      Set    the    eight   parameters	 max_page_age,	 page_advance,
	      page_decline,  page_initial_age,	age_cluster_fract,   age_clus-
	      ter_min,	pageout_weight, bufferout_weight that control the ker-
	      nel swap algorithm.  For kernel tuners only.

       'buff=N1,N2,N3,N4,N5,N6'
	      Set the six parameters max_buff_age, buff_advance, buff_decline,
	      buff_initial_age, bufferout_weight, buffermem_grace that control
	      kernel buffer memory management.	For kernel tuners only.

   Boot Arguments for Ramdisk Use
       (Only if the kernel was compiled with CONFIG_BLK_DEV_RAM.)  In  general
       it  is  a  bad  idea to use a ramdisk under Linux -- the system will use
       available memory more efficiently itself.  But while booting (or	 while
       constructing  boot floppies) it is often useful to load the floppy con-
       tents into a ramdisk.  One might also have a system in which first some
       modules	(for  file  system or hardware) must be loaded before the main
       disk can be accessed.

       In Linux 1.3.48, ramdisk handling was  changed  drastically.   Earlier,
       the memory was allocated statically, and there was a 'ramdisk=N' param-
       eter to tell its size.  (This could also be set in the kernel image  at
       compile	time,  or  by  use  of rdev(8).)  These days ram disks use the
       buffer cache, and grow dynamically.  For a lot  of  information	(e.g.,
       how  to	use  rdev(8)  in  conjunction with the new ramdisk setup), see
       /usr/share/doc/kernel-doc-2.6.18/Documentation/ramdisk.txt.

       There are four parameters, two boolean and two integral.

       'load_ramdisk=N'
	      If N=1, do load a ramdisk.  If  N=0,  do	not  load  a  ramdisk.
	      (This is the default.)

       'prompt_ramdisk=N'
	      If  N=1,	do  prompt  for insertion of the floppy.  (This is the
	      default.)	 If N=0, do not	 prompt.   (Thus,  this	 parameter  is
	      never needed.)

       'ramdisk_size=N' or (obsolete) 'ramdisk=N'
	      Set  the maximal size of the ramdisk(s) to N kB.	The default is
	      4096 (4 MB).

       'ramdisk_start=N'
	      Sets the starting block number (the offset on the	 floppy	 where
	      the  ramdisk  starts)  to N.  This is needed in case the ramdisk
	      follows a kernel image.

       'noinitrd'
	      (Only if the kernel was  compiled	 with  CONFIG_BLK_DEV_RAM  and
	      CONFIG_BLK_DEV_INITRD.)	These  days  it is possible to compile
	      the kernel to use initrd.	 When this  feature  is	 enabled,  the
	      boot  process  will load the kernel and an initial ramdisk; then
	      the kernel converts initrd into a	 "normal"  ramdisk,  which  is
	      mounted  read-write  as  root device; then /linuxrc is executed;
	      afterwards the "real" root file system is mounted, and the  ini-
	      trd file system is moved over to /initrd; finally the usual boot
	      sequence (e.g., invocation of /sbin/init) is performed.

	      For  a  detailed	description  of	 the   initrd	feature,   see
	      /usr/share/doc/kernel-doc-2.6.18/Documentation/initrd.txt.

	      The 'noinitrd' option tells the kernel that although it was com-
	      piled for operation with initrd, it should not  go  through  the
	      above steps, but leave the initrd data under /dev/initrd.	 (This
	      device can be used only once: the data is freed as soon  as  the
	      last process that used it has closed /dev/initrd.)

   Boot Arguments for SCSI Devices
       General notation for this section:

       iobase  --  the	first I/O port that the SCSI host occupies.  These are
       specified in hexadecimal notation, and usually lie in  the  range  from
       0x200 to 0x3ff.

       irq  --	the  hardware  interrupt  that	the card is configured to use.
       Valid values will be dependent on the card in question, but  will  usu-
       ally be 5, 7, 9, 10, 11, 12, and 15.  The other values are usually used
       for common peripherals like IDE hard  disks,  floppies,	serial	ports,
       etc.

       scsi-id	-- the ID that the host adapter uses to identify itself on the
       SCSI bus.  Only some host adapters allow you to change this  value,  as
       most have it permanently specified internally.  The usual default value
       is 7, but the Seagate and Future Domain TMC-950 boards use 6.

       parity -- whether the SCSI host adapter expects the attached devices to
       supply a parity value with all information exchanges.  Specifying a one
       indicates parity checking is enabled, and a zero disables parity check-
       ing.  Again, not all adapters will support selection of parity behavior
       as a boot argument.

       'max_scsi_luns=...'
	      A SCSI device can	 have  a  number  of  'sub-devices'  contained
	      within  itself.	The most common example is one of the new SCSI
	      CD-ROMs that handle more than one disk at a time.	  Each	CD  is
	      addressed	 as  a	'Logical Unit Number' (LUN) of that particular
	      device.  But most devices, such as hard disks, tape  drives  and
	      such are only one device, and will be assigned to LUN zero.

	      Some poorly designed SCSI devices cannot handle being probed for
	      LUNs not equal to zero.  Therefore,  if  the  compile-time  flag
	      CONFIG_SCSI_MULTI_LUN  is not set, newer kernels will by default
	      only probe LUN zero.

	      To specify the  number  of  probed  LUNs	at  boot,  one	enters
	      'max_scsi_luns=n' as a boot arg, where n is a number between one
	      and eight.  To avoid problems as described above, one would  use
	      n=1 to avoid upsetting such broken devices.

       SCSI tape configuration
	      Some  boot  time	configuration  of  the SCSI tape driver can be
	      achieved by using the following:

	      st=buf_size[,write_threshold[,max_bufs]]

	      The first two numbers are specified in units of kB.  The default
	      buf_size	is 32kB, and the maximum size that can be specified is
	      a ridiculous 16384kB.  The write_threshold is the value at which
	      the  buffer  is committed to tape, with a default value of 30kB.
	      The maximum number of buffers varies with the number  of	drives
	      detected, and has a default of two.  An example usage would be:

	      st=32,30,2

	      Full  details  can be found in the README.st file that is in the
	      scsi directory of the kernel source tree.

       Adaptec aha151x, aha152x, aic6260, aic6360, SB16-SCSI configuration
	      The aha numbers refer to cards and the aic numbers refer to  the
	      actual  SCSI  chip  on these type of cards, including the Sound-
	      blaster-16 SCSI.

	      The probe code for these SCSI hosts looks for an installed BIOS,
	      and if none is present, the probe will not find your card.  Then
	      you will have to use a boot arg of the form:

	      aha152x=iobase[,irq[,scsi-id[,reconnect[,parity]]]]

	      If the driver was compiled with debugging enabled, a sixth value
	      can be specified to set the debug level.

	      All  the parameters are as described at the top of this section,
	      and the reconnect value will allow  device  disconnect/reconnect
	      if a non-zero value is used.  An example usage is as follows:

	      aha152x=0x340,11,7,1

	      Note  that  the  parameters  must be specified in order, meaning
	      that if you want to specify a parity setting, then you will have
	      to  specify an iobase, irq, scsi-id and reconnect value as well.

       Adaptec aha154x configuration
	      The aha1542  series  cards  have	an  i82077  floppy  controller
	      onboard,	while the aha1540 series cards do not.	These are bus-
	      mastering cards, and have parameters to set the "fairness"  that
	      is used to share the bus with other devices.  The boot arg looks
	      like the following.

	      aha1542=iobase[,buson,busoff[,dmaspeed]]

	      Valid iobase values are usually one  of:	0x130,	0x134,	0x230,
	      0x234, 0x330, 0x334.  Clone cards may permit other values.

	      The  buson,  busoff  values  refer to the number of microseconds
	      that the card dominates the ISA bus.  The defaults are 11us  on,
	      and  4us off, so that other cards (such as an ISA LANCE Ethernet
	      card) have a chance to get access to the ISA bus.

	      The dmaspeed value refers to the rate (in MB/s) at which the DMA
	      (Direct Memory Access) transfers proceed.	 The default is 5MB/s.
	      Newer revision cards allow you to select this value as  part  of
	      the  soft-configuration,	older  cards use jumpers.  You can use
	      values up to 10MB/s assuming that your motherboard is capable of
	      handling	it.   Experiment  with	caution	 if  using values over
	      5MB/s.

       Adaptec aha274x, aha284x, aic7xxx configuration
	      These boards can accept an argument of the form:

	      aic7xxx=extended,no_reset

	      The extended value, if non-zero, indicates that extended	trans-
	      lation  for large disks is enabled.  The no_reset value, if non-
	      zero, tells the driver not to reset the SCSI bus when setting up
	      the host adapter at boot.

       AdvanSys SCSI Hosts configuration ('advansys=')
	      The  AdvanSys  driver  can  accept up to four i/o addresses that
	      will be probed for an AdvanSys SCSI card.	 Note that these  val-
	      ues  (if	used)  do  not	effect EISA or PCI probing in any way.
	      They are only used for probing ISA and VLB cards.	 In  addition,
	      if  the  driver  has  been  compiled with debugging enabled, the
	      level of debugging output can be set  by	adding	an  0xdeb[0-f]
	      parameter.   The	0-f  allows setting the level of the debugging
	      messages to any of 16 levels of verbosity.

       AM53C974

	      AM53C974=host-scsi-id,target-scsi-id,max-rate,max-offset

       BusLogic SCSI Hosts configuration ('BusLogic=')

	      BusLogic=N1,N2,N3,N4,N5,S1,S2,...

	      For an extensive discussion of the BusLogic command line parame-
	      ters,    see    /usr/src/linux/drivers/scsi/BusLogic.c	(lines
	      3149-3270 in the kernel version I	 am  looking  at).   The  text
	      below is a very much abbreviated extract.

	      The  parameters  N1-N5  are integers.  The parameters S1,... are
	      strings.	N1 is the I/O Address at which	the  Host  Adapter  is
	      located.	N2 is the Tagged Queue Depth to use for Target Devices
	      that support Tagged Queuing.  N3 is the Bus Settle Time in  sec-
	      onds.  This is the amount of time to wait between a Host Adapter
	      Hard Reset which initiates a SCSI Bus Reset and issuing any SCSI
	      Commands.	  N4  is the Local Options (for one Host Adapter).  N5
	      is the Global Options (for all Host Adapters).

	      The string options are used to provide control over Tagged Queu-
	      ing  (TQ:Default,	 TQ:Enable, TQ:Disable, TQ:<Per-Target-Spec>),
	      over Error Recovery (ER:Default,	ER:HardReset,  ER:BusDeviceRe-
	      set, ER:None, ER:<Per-Target-Spec>), and over Host Adapter Prob-
	      ing (NoProbe, NoProbeISA, NoSortPCI).

       EATA/DMA configuration
	      The default list of i/o ports to be probed can be changed by

	      eata=iobase,iobase,....

       Future Domain TMC-16x0 configuration

	      fdomain=iobase,irq[,adapter_id]

       Great Valley Products (GVP) SCSI controller configuration

	      gvp11=dma_transfer_bitmask

       Future Domain TMC-8xx, TMC-950 configuration

	      tmc8xx=mem_base,irq

	      The mem_base value is the value of the memory mapped I/O	region
	      that  the	 card uses.  This will usually be one of the following
	      values: 0xc8000, 0xca000, 0xcc000, 0xce000, 0xdc000, 0xde000.

       IN2000 configuration

	      in2000=S

	      where S is a comma-separated string  of  items  keyword[:value].
	      Recognized  keywords  (possibly  with  value)  are: ioport:addr,
	      noreset, nosync:x,  period:ns,  disconnect:x,  debug:x,  proc:x.
	      For     the     function	   of	  these	    parameters,	   see
	      /usr/src/linux/drivers/scsi/in2000.c.

       NCR5380 and NCR53C400 configuration
	      The boot arg is of the form

	      ncr5380=iobase,irq,dma

	      or

	      ncr53c400=iobase,irq

	      If the card doesn't use interrupts, then an  IRQ	value  of  255
	      (0xff)  will  disable  interrupts.  An IRQ value of 254 means to
	      autoprobe.   More	  details   can	  be   found   in   the	  file
	      /usr/src/linux/drivers/scsi/README.g_NCR5380 .

       NCR53C8xx configuration

	      ncr53c8xx=S

	      where  S	is  a  comma-separated	string of items keyword:value.
	      Recognized keywords are: mpar (master_parity),  spar  (scsi_par-
	      ity),  disc  (disconnection),  specf  (special_features),	 ultra
	      (ultra_scsi), fsn (force_sync_nego), tags	 (default_tags),  sync
	      (default_sync),	 verb	 (verbose),   debug   (debug),	 burst
	      (burst_max).  For the  function  of  the	assigned  values,  see
	      /usr/src/linux/drivers/scsi/ncr53c8xx.c.

       NCR53c406a configuration

	      ncr53c406a=iobase[,irq[,fastpio]]

	      Specify  irq = 0 for non-interrupt driven mode.  Set fastpio = 1
	      for fast pio mode, 0 for slow mode.

       Pro Audio Spectrum configuration
	      The PAS16 uses a NC5380 SCSI  chip,  and	newer  models  support
	      jumperless configuration.	 The boot arg is of the form:

	      pas16=iobase,irq

	      The only difference is that you can specify an IRQ value of 255,
	      which will tell the driver to  work  without  using  interrupts,
	      albeit at a performance loss.  The iobase is usually 0x388.

       Seagate ST-0x configuration
	      If your card is not detected at boot time, you will then have to
	      use a boot arg of the form:

	      st0x=mem_base,irq

	      The mem_base value is the value of the memory mapped I/O	region
	      that  the	 card uses.  This will usually be one of the following
	      values: 0xc8000, 0xca000, 0xcc000, 0xce000, 0xdc000, 0xde000.

       Trantor T128 configuration
	      These cards are also based on the NCR5380 chip, and  accept  the
	      following options:

	      t128=mem_base,irq

	      The  valid values for mem_base are as follows: 0xcc000, 0xc8000,
	      0xdc000, 0xd8000.

       UltraStor 14F/34F configuration
	      The default list of i/o ports to be probed can be changed by

	      eata=iobase,iobase,....

       WD7000 configuration

	      wd7000=irq,dma,iobase

       Commodore Amiga A2091/590 SCSI controller configuration

	      wd33c93=S

	      where S is a  comma-separated  string  of	 options.   Recognized
	      options  are  nosync:bitmask,  nodma:x, period:ns, disconnect:x,
	      debug:x,	   clock:x,	next.	    For	     details,	   see
	      /usr/src/linux/drivers/scsi/wd33c93.c.

   Hard Disks
       IDE Disk/CD-ROM Driver Parameters
	      The  IDE driver accepts a number of parameters, which range from
	      disk geometry specifications, to support for  broken  controller
	      chips.   Drive-specific  options	are  specified by using 'hdX='
	      with X in 'a'-'h'.

	      Non-drive-specific options are specified with the prefix	'hd='.
	      Note that using a drive-specific prefix for a non-drive-specific
	      option will still work, and the option will just be  applied  as
	      expected.

	      Also  note  that 'hd=' can be used to refer to the next unspeci-
	      fied drive in the (a, ..., h) sequence.  For the following  dis-
	      cussions,	 the  'hd=' option will be cited for brevity.  See the
	      file README.ide in linux/drivers/block for more details.

       The 'hd=cyls,heads,sects[,wpcom[,irq]]' options
	      These options are used to specify the physical geometry  of  the
	      disk.   Only  the	 first	three values are required.  The cylin-
	      der/head/sectors values will be those used by fdisk.  The	 write
	      precompensation  value  is ignored for IDE disks.	 The IRQ value
	      specified will be the IRQ used for the interface that the	 drive
	      resides on, and is not really a drive-specific parameter.

       The 'hd=serialize' option
	      The  dual	 IDE interface CMD-640 chip is broken as designed such
	      that when drives on the secondary interface are used at the same
	      time  as	drives	on the primary interface, it will corrupt your
	      data.  Using this option tells the driver to make sure that both
	      interfaces are never used at the same time.

       The 'hd=dtc2278' option
	      This  option  tells  the	driver	that  you have a DTC-2278D IDE
	      interface.  The driver then tries to do DTC-specific  operations
	      to  enable  the  second  interface and to enable faster transfer
	      modes.

       The 'hd=noprobe' option
	      Do not probe for this drive.  For example,

	      hdb=noprobe hdb=1166,7,17

	      would disable the probe, but still specify the drive geometry so
	      that  it	would be registered as a valid block device, and hence
	      usable.

       The 'hd=nowerr' option
	      Some drives apparently have the WRERR_STAT bit stuck  on	perma-
	      nently.  This enables a work-around for these broken devices.

       The 'hd=cdrom' option
	      This  tells the IDE driver that there is an ATAPI compatible CD-
	      ROM attached in place of a normal IDE hard disk.	In most	 cases
	      the  CD-ROM  is  identified  automatically, but if it isn't then
	      this may help.

       Standard ST-506 Disk Driver Options ('hd=')
	      The standard disk driver can accept geometry arguments  for  the
	      disks  similar  to  the  IDE  driver.  Note however that it only
	      expects three values (C/H/S); any more or any less and  it  will
	      silently	ignore	you.   Also, it only accepts 'hd=' as an argu-
	      ment, that is, 'hda=' and so on are not valid here.  The	format
	      is as follows:

	      hd=cyls,heads,sects

	      If there are two disks installed, the above is repeated with the
	      geometry parameters of the second disk.

       XT Disk Driver Options ('xd=')
	      If you are unfortunate enough to be using one of these old 8 bit
	      cards  that  move	 data  at  a whopping 125kB/s then here is the
	      scoop.  If the card is not recognized, you will have  to	use  a
	      boot arg of the form:

	      xd=type,irq,iobase,dma_chan

	      The  type	 value	specifies  the	particular manufacturer of the
	      card, overriding autodetection.  For the types to	 use,  consult
	      the  drivers/block/xd.c source file of the kernel you are using.
	      The type is an index in the list xd_sigs and in  the  course  of
	      time  types have been added to or deleted from the middle of the
	      list, changing all type numbers.	Today (Linux 2.5.0) the	 types
	      are 0=generic; 1=DTC 5150cx; 2,3=DTC 5150x; 4,5=Western Digital;
	      6,7,8=Seagate; 9=Omti; 10=XEBEC, and where  here	several	 types
	      are given with the same designation, they are equivalent.

	      The  xd_setup()  function	 does  no  checking on the values, and
	      assumes that you entered all four values.	 Don't disappoint  it.
	      Here  is	an example usage for a WD1002 controller with the BIOS
	      disabled/removed, using the 'default' XT controller parameters:

	      xd=2,5,0x320,3

       Syquest's EZ* removable disks

	      ez=iobase[,irq[,rep[,nybble]]]

   IBM MCA Bus Devices
       See also /usr/share/doc/kernel-doc-2.6.18/Documentation/mca.txt.

       PS/2 ESDI hard disks
	      It is possible to specify the desired geometry at boot time:

	      ed=cyls,heads,sectors.

	      For a ThinkPad-720, add the option

	      tp720=1.

       IBM Microchannel SCSI Subsystem configuration

	      ibmmcascsi=N

	      where N is the pun (SCSI ID) of the subsystem.

       The Aztech Interface
	      The syntax for this type of card is:

	      aztcd=iobase[,magic_number]

	      If you set the magic_number to 0x79 then the driver will try and
	      run  anyway  in  the  event of an unknown firmware version.  All
	      other values are ignored.

       Parallel port CD-ROM drives
	      Syntax:

	      pcd.driveN=prt,pro,uni,mod,slv,dly
	      pcd.nice=nice

	      where 'port' is the base address, 'pro' is the protocol  number,
	      'uni'  is	 the unit selector (for chained devices), 'mod' is the
	      mode (or -1 to choose the best automatically), 'slv' is 1 if  it
	      should be a slave, and 'dly' is a small integer for slowing down
	      port accesses.  The 'nice' parameter controls the	 driver's  use
	      of idle CPU time, at the expense of some speed.

       The CDU-31A and CDU-33A Sony Interface
	      This CD-ROM interface is found on some of the Pro Audio Spectrum
	      sound cards, and other Sony supplied interface cards.  The  syn-
	      tax is as follows:

	      cdu31a=iobase,[irq[,is_pas_card]]

	      Specifying  an  IRQ value of zero tells the driver that hardware
	      interrupts aren't supported (as on some  PAS  cards).   If  your
	      card supports interrupts, you should use them as it cuts down on
	      the CPU usage of the driver.

	      The is_pas_card should be entered as 'PAS' if using a Pro	 Audio
	      Spectrum	card, and otherwise it should not be specified at all.

       The CDU-535 Sony Interface
	      The syntax for this CD-ROM interface is:

	      sonycd535=iobase[,irq]

	      A zero can be used for the I/O base as a	'placeholder'  if  one
	      wishes to specify an IRQ value.

       The GoldStar Interface
	      The syntax for this CD-ROM interface is:

	      gscd=iobase

       The ISP16 CD-ROM Interface
	      Syntax:

	      isp16=[iobase[,irq[,dma[,type]]]]

	      (three  integers	and  a	string).   If  the  type  is  given as
	      'noisp16', the interface will not be configured.	 Other	recog-
	      nized types are: 'Sanyo", 'Sony', 'Panasonic' and 'Mitsumi'.

       The Mitsumi Standard Interface
	      The syntax for this CD-ROM interface is:

	      mcd=iobase,[irq[,wait_value]]

	      The  wait_value  is used as an internal timeout value for people
	      who are having problems with their drive, and may or may not  be
	      implemented  depending  on  a compile-time #define.  The Mitsumi
	      FX400 is an IDE/ATAPI CD-ROM player and does  not	 use  the  mcd
	      driver.

       The Mitsumi XA/MultiSession Interface
	      This  is	for  the  same	hardware  as above, but the driver has
	      extended features.  Syntax:

	      mcdx=iobase[,irq]

       The Optics Storage Interface
	      The syntax for this type of card is:

	      optcd=iobase

       The Phillips CM206 Interface
	      The syntax for this type of card is:

	      cm206=[iobase][,irq]

	      The driver assumes numbers between 3 and 11 are IRQ values,  and
	      numbers  between	0x300  and  0x370  are	I/O  ports, so you can
	      specify one, or both numbers, in any  order.   It	 also  accepts
	      'cm206=auto' to enable autoprobing.

       The Sanyo Interface
	      The syntax for this type of card is:

	      sjcd=iobase[,irq[,dma_channel]]

       The SoundBlaster Pro Interface
	      The syntax for this type of card is:

	      sbpcd=iobase,type

	      where  type  is  one  of the following (case sensitive) strings:
	      'SoundBlaster', 'LaserMate', or 'SPEA'.  The I/O base is that of
	      the  CD-ROM  interface, and not that of the sound portion of the
	      card.

   Ethernet Devices
       Different drivers make use of different parameters,  but	 they  all  at
       least  share having an IRQ, an I/O port base value, and a name.	In its
       most generic form, it looks something like this:

	      ether=irq,iobase[,param_1[,...param_8]],name

	      The first non-numeric  argument  is  taken  as  the  name.   The
	      param_n  values  (if applicable) usually have different meanings
	      for each different card/driver.  Typical param_n values are used
	      to  specify  things like shared memory address, interface selec-
	      tion, DMA channel and the like.

	      The most common use of this parameter is to force probing for  a
	      second ethercard, as the default is to only probe for one.  This
	      can be accomplished with a simple:

	      ether=0,0,eth1

	      Note that the values of zero for the IRQ and  I/O	 base  in  the
	      above example tell the driver(s) to autoprobe.

	      The Ethernet-HowTo has extensive documentation on using multiple
	      cards and on  the	 card/driver-specific  implementation  of  the
	      param_n  values  where used.  Interested readers should refer to
	      the section in that document on their particular card.

   The Floppy Disk Driver
       There are many floppy driver  options,  and  they  are  all  listed  in
       README.fd  in  linux/drivers/block.  This information is taken directly
       from that file.

       floppy=mask,allowed_drive_mask
	      Sets the bit mask of allowed drives to mask.  By	default,  only
	      units  0	and  1 of each floppy controller are allowed.  This is
	      done because certain non-standard	 hardware  (ASUS  PCI  mother-
	      boards)  mess up the keyboard when accessing units 2 or 3.  This
	      option is somewhat obsoleted by the cmos option.

       floppy=all_drives
	      Sets the bit mask of allowed drives to all drives.  Use this  if
	      you  have more than two drives connected to a floppy controller.

       floppy=asus_pci
	      Sets the bit mask to allow only units 0 and 1.  (The default)

       floppy=daring
	      Tells the floppy driver that you have a well behaved floppy con-
	      troller.	This allows more efficient and smoother operation, but
	      may fail on certain controllers.	 This  may  speed  up  certain
	      operations.

       floppy=0,daring
	      Tells  the  floppy  driver that your floppy controller should be
	      used with caution.

       floppy=one_fdc
	      Tells the floppy driver that you	have  only  floppy  controller
	      (default)

       floppy=two_fdc or floppy=address,two_fdc
	      Tells  the  floppy  driver that you have two floppy controllers.
	      The second floppy controller is assumed to be  at	 address.   If
	      address is not given, 0x370 is assumed.

       floppy=thinkpad
	      Tells the floppy driver that you have a Thinkpad.	 Thinkpads use
	      an inverted convention for the disk change line.

       floppy=0,thinkpad
	      Tells the floppy driver that you don't have a Thinkpad.

       floppy=drive,type,cmos
	      Sets the cmos type of drive to type.  Additionally,  this	 drive
	      is  allowed  in  the  bit mask.  This is useful if you have more
	      than two floppy drives (only two can be described in the	physi-
	      cal  cmos),  or if your BIOS uses non-standard CMOS types.  Set-
	      ting the CMOS to 0 for the first two drives (default) makes  the
	      floppy driver read the physical cmos for those drives.

       floppy=unexpected_interrupts
	      Print a warning message when an unexpected interrupt is received
	      (default behavior)

       floppy=no_unexpected_interrupts or floppy=L40SX
	      Don't print a message when an unexpected interrupt is  received.
	      This  is	needed	on  IBM	 L40SX laptops in certain video modes.
	      (There seems to be an interaction between video and floppy.  The
	      unexpected interrupts only affect performance, and can safely be
	      ignored.)

   The Sound Driver
       The sound driver can also accept boot args to override the compiled  in
       values.	 This  is  not	recommended,  as  it is rather complex.	 It is
       described in the Readme.Linux file, in linux/drivers/sound.  It accepts
       a boot arg of the form:

	      sound=device1[,device2[,device3...[,device10]]]

	      where each deviceN value is of the following format 0xTaaaId and
	      the bytes are used as follows:

	      T - device type: 1=FM, 2=SB,  3=PAS,  4=GUS,  5=MPU401,  6=SB16,
	      7=SB16-MPU401

	      aaa - I/O address in hex.

	      I - interrupt line in hex (i.e 10=a, 11=b, ...)

	      d - DMA channel.

	      As  you  can see it gets pretty messy, and you are better off to
	      compile in your own personal values  as  recommended.   Using  a
	      boot arg of 'sound=0' will disable the sound driver entirely.

   ISDN Drivers
       The ICN ISDN driver
	      Syntax:

	      icn=iobase,membase,icn_id1,icn_id2

	      where  icn_id1,icn_id2 are two strings used to identify the card
	      in kernel messages.

       The PCBIT ISDN driver
	      Syntax:

	      pcbit=membase1,irq1[,membase2,irq2]

	      where membaseN is the shared memory base of the N'th  card,  and
	      irqN  is the interrupt setting of the N'th card.	The default is
	      IRQ 5 and membase 0xD0000.

       The Teles ISDN driver
	      Syntax:

	      teles=iobase,irq,membase,protocol,teles_id

	      where iobase is the i/o port address of the card, membase is the
	      shared  memory  base  address  of the card, irq is the interrupt
	      channel the card uses, and teles_id is the unique	 ASCII	string
	      identifier.

   Serial Port Drivers
       The RISCom/8 Multiport Serial Driver ('riscom8=')
	      Syntax:

	      riscom=iobase1[,iobase2[,iobase3[,iobase4]]]

	      More    details	can   be   found   in	/usr/share/doc/kernel-
	      doc-2.6.18/Documentation/riscom8.txt.

       The DigiBoard Driver ('digi=')
	      If this option is used, it should have precisely six parameters.
	      Syntax:

	      digi=status,type,altpin,numports,iobase,membase

	      The  parameters  maybe  given  as	 integers,  or as strings.  If
	      strings are used, then iobase and membase	 should	 be  given  in
	      hexadecimal.   The integer arguments (fewer may be given) are in
	      order:  status  (Enable(1)  or  Disable(0)  this	 card),	  type
	      (PC/Xi(0),  PC/Xe(1),  PC/Xeve(2), PC/Xem(3)), altpin (Enable(1)
	      or Disable(0) alternate pin arrangement),	 numports  (number  of
	      ports  on	 this card), iobase (I/O Port where card is configured
	      (in HEX)), membase (base of memory window (in HEX)).  Thus,  the
	      following two boot prompt arguments are equivalent:

	      digi=E,PC/Xi,D,16,200,D0000
	      digi=1,0,0,16,0x200,851968

	      More    details	can   be   found   in	/usr/share/doc/kernel-
	      doc-2.6.18/Documentation/digiboard.txt.

       The Baycom Serial/Parallel Radio Modem
	      Syntax:

	      baycom=iobase,irq,modem

	      There are precisely 3 parameters; for several cards,  give  sev-
	      eral  'baycom='  commands.  The modem parameter is a string that
	      can take one of the values ser12, ser12*, par96,	par96*.	  Here
	      the  *  denotes that software DCD is to be used, and ser12/par96
	      chooses between the supported modem types.   For	more  details,
	      see the file /usr/src/linux/drivers/net/README.baycom .

       Soundcard radio modem driver
	      Syntax:

	      soundmodem=iobase,irq,dma[,dma2[,serio[,pario]]],0,mode

	      All  parameters  except  the  last  are integers; the dummy 0 is
	      required because of a bug in the setup code.  The mode parameter
	      is  a  string with syntax hw:modem, where hw is one of sbc, wss,
	      wssfdx and modem is one of afsk1200, fsk9600.

   The Line Printer Driver
       'lp='  Syntax:

	      lp=0
	      lp=auto
	      lp=reset
	      lp=port[,port...]

	      You can tell the printer driver what ports to use and what ports
	      not  to  use.   The  latter comes in handy if you don't want the
	      printer driver to claim all available parallel  ports,  so  that
	      other drivers (e.g., PLIP, PPA) can use them instead.

	      The format of the argument is multiple port names.  For example,
	      lp=none,parport0 would use the first parallel port for lp1,  and
	      disable  lp0.   To  disable the printer driver entirely, one can
	      use lp=0.

       WDT500/501 driver
	      Syntax:

	      wdt=io,irq

   Mouse Drivers
       'bmouse=irq'
	      The busmouse driver only accepts one parameter, that  being  the
	      hardware IRQ value to be used.

       'msmouse=irq'
	      And precisely the same is true for the msmouse driver.

       ATARI mouse setup

	      atamouse=threshold[,y-threshold]

	      If  only	one argument is given, it is used for both x-threshold
	      and y-threshold.	Otherwise, the first argument is the x-thresh-
	      old,  and	 the  second  the  y-threshold.	 These values must lie
	      between 1 and 20 (inclusive); the default is 2.

   Video Hardware
       'no-scroll'
	      This option tells the console driver not to use hardware	scroll
	      (where a scroll is effected by moving the screen origin in video
	      memory, instead of moving the data).  It is required by  certain
	      Braille machines.

SEE ALSO
       lilo.conf(5), klogd(8), lilo(8), mount(8), rdev(8)

       Large  parts of this man page have been derived from the Boot Parameter
       HOWTO (version 1.0.1) written by Paul Gortmaker.	 More information  may
       be  found  in  this  (or a more recent) HOWTO.  An up-to-date source of
       information  is	/usr/share/doc/kernel-doc-2.6.18/Documentation/kernel-
       parameters.txt.



Linux				  2007-12-16			  BOOTPARAM(7)
YoLinux.com Home Page
YoLinux Tutorial Index
Privacy Policy | Advertise with us | Feedback Form |
Unauthorized copying or redistribution prohibited.
    Bookmark and Share