*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->Linux man pages -> bootparam (7)              



NAME    [Toc]    [Back]

       bootparam - Introduction to boot time parameters of the Linux kernel

DESCRIPTION    [Toc]    [Back]

       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

       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 program
 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 loading
       Linux  from  the  DOS  prompt with loadlin avoids the reset of the card
       that happens if one rebooted instead.

THE ARGUMENT LIST    [Toc]    [Back]

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


       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 separated
 parameters per keyword. (However, you can re-use the same keyword
       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  funtion
       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  argument.

       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.


       This sets the initial command to be executed by the kernel.  If this is
       not set, or cannot be  found,  the  kernel  will  try  /etc/init,  then
       /bin/init,  then  /sbin/init,  then  /bin/sh  and  panic if all of this

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

       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.

       (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!

       (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.

       This  argument  tells  the kernel what device is to be used as the root
       filesystem 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 designates 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 conventional.

       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

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

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

       The  choice  between  read-only	and  read/write  can also be set using

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


       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 probing, 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 probing

       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  determine  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 horribly 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
       cacheing 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.''

       By default the kernel will not reboot after a panic,  but  this	option
       will  cause  a  kernel  reboot  after N seconds (if N > 0).  This panic
       timeout can also be set by "echo N > /proc/sys/kernel/panic".

       (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.


       Kernel  messages  are handed off to the kernel log daemon klogd so that
       they may be logged  to  disk.  Messages	with  a  priority  above  con-
       sole_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

       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 nonzero value. This  is
       done  either by specifying CONFIG_PROFILE at compile time, or by giving
       the `profile=' option.  Now the value that prof_shift gets will	be  N,
       when  given,  or  CONFIG_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.

       Set the	eight  parameters  max_page_age,  page_advance,  page_decline,
       page_initial_age,  age_cluster_fract,  age_cluster_min, pageout_weight,
       bufferout_weight that control the kernel swap  algorithm.   For	kernel
       tuners only.

       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.


       (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  contents
  into a ramdisk. One might also have a system in which first some
       modules (for filesystem 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' parameter
  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

       There are four parameters, two boolean and two integral.

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

       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

       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.

       (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 initrd filesystem 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

       The `noinitrd' option tells the kernel that although  it  was  compiled
       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.)


       General notation for this section:

       iobase -- the first I/O port that the SCSI host	occupies.   These  are
       specified  in  hexidecimal  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 usually
 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,

       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 checking.
 Again, not all adapters will support selection of parity behaviour
       as a boot argument.

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


       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:


       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 Soundblaster-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:


       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:


       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    [Toc]    [Back]
       The  aha1542  series  cards  have  an i82077 floppy controller onboard,
       while the aha1540 series cards do not. These  are  busmastering	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.


       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:


       The  extended  value,  if non-zero, indicates that extended translation
       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 adaptor at

   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 values (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    [Toc]    [Back]

   BusLogic SCSI Hosts configuration (`BusLogic=')

       For an extensive discussion of the BusLogic  command  line  parameters,
       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

       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 seconds.  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 Queuing
       (TQ:Default, TQ:Enable, TQ:Disable, TQ:<Per-Target-Spec>),  over  Error
       Recovery   (ER:Default,	 ER:HardReset,	 ER:BusDeviceReset,   ER:None,
       ER:<Per-Target-Spec>),  and  over  Host	 Adapter   Probing   (NoProbe,
       NoProbeISA, NoSortPCI).

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


   Future Domain TMC-16x0 configuration    [Toc]    [Back]

   Great Valley Products (GVP) SCSI controller configuration    [Toc]    [Back]

   Future Domain TMC-8xx, TMC-950 configuration

       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    [Toc]    [Back]

       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    [Toc]    [Back]
       The boot arg is of the form




       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/driv-

   NCR53C8xx configuration    [Toc]    [Back]

       where S is a comma-separated string of items keyword:value.  Recognized
       keywords are: mpar (master_parity), spar (scsi_parity),	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    [Toc]    [Back]

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

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


       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    [Toc]    [Back]
       If your card is not detected at boot time, you will then have to use  a
       boot arg of the form:


       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    [Toc]    [Back]
       These  cards are also based on the NCR5380 chip, and accept the following


       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


   WD7000 configuration    [Toc]    [Back]

   Commodore Amiga A2091/590 SCSI controller configuration

       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    [Toc]    [Back]

   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 unspecified drive
       in the (a, ..., h) sequence.  For the following discussions, 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 cylinder/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 useable.

   The `hd=nowerr' option
       Some drives apparently have the WRERR_STAT bit  stuck  on  permanently.
       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 argument, i.e. `hda=' and so  on  are
       not valid here. The format is as follows:


       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 recognised, you will have to use a boot arg of the form:


       The type value specifies the particular manufacturer of the  card,  and
       are as follows: 0=generic; 1=DTC; 2,3,4=Western Digital, 5,6,7=Seagate;
       8=OMTI. The only difference between multiple types from the same  manufacturer
  is  the  BIOS string used for detection, which is not used if
       the type is specified.

       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:


   Syquest's EZ* removable disks

IBM MCA BUS DEVICES    [Toc]    [Back]

       See also /usr/src/linux/Documentation/mca.txt.

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


       For a ThinkPad-720, add the option


   IBM Microchannel SCSI Subsystem configuration    [Toc]    [Back]

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

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


       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    [Toc]    [Back]


       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    [Toc]    [Back]
       This CD-ROM interface is found on some of the Pro Audio Spectrum  sound
       cards,  and other Sony supplied interface cards.  The syntax is as follows:


       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

       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    [Toc]    [Back]
       The syntax for this CD-ROM interface is:


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

   The GoldStar Interface    [Toc]    [Back]
       The syntax for this CD-ROM interface is:


   The ISP16 CD-ROM Interface    [Toc]    [Back]


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

   The Mitsumi Standard Interface    [Toc]    [Back]
       The syntax for this CD-ROM interface is:


       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:


   The Optics Storage Interface    [Toc]    [Back]
       The syntax for this type of card is:


   The Phillips CM206 Interface    [Toc]    [Back]
       The syntax for this type of card is:


       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    [Toc]    [Back]
       The syntax for this type of card is:


   The SoundBlaster Pro Interface    [Toc]    [Back]
       The syntax for this type of card is:


       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    [Toc]    [Back]

       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:


       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 selection, 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:


       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.


       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.

       Sets  the  bitmask  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 motherboards) mess up the keyboard
       when accessing units 2 or 3. This option is somewhat obsoleted  by  the
       cmos option.

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

       Sets the bitmask to allow only units 0 and 1. (The default)

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

       Tells the floppy driver that your floppy controller should be used with

       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.

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

       Tells the floppy driver that you don't have a Thinkpad.

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

       Print  a  warning  message  when  an  unexpected  interrupt is received
       (default behaviour)

   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    [Toc]    [Back]

       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:


       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,

       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    [Toc]    [Back]

   The ICN ISDN driver


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

   The PCBIT ISDN driver    [Toc]    [Back]


       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

   The Teles ISDN driver    [Toc]    [Back]


       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    [Toc]    [Back]

   The RISCom/8 Multiport Serial Driver (`riscom8=')


       More  details can be found in /usr/src/linux/Documentation/riscom8.txt.

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


       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:


       More  details  can  be  found   in   /usr/src/linux/Documentation/digi-

   The Baycom Serial/Parallel Radio Modem


       There are precisely 3 parameters; for several cards, give several `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   /usr/src/linux/driv-

   Soundcard radio modem driver    [Toc]    [Back]


       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.




       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


MOUSE DRIVERS    [Toc]    [Back]

       The busmouse driver only accepts one parameter, that being the hardware
       IRQ value to be used.

       And precisely the same is true for the msmouse driver.

   ATARI mouse setup    [Toc]    [Back]

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

VIDEO HARDWARE    [Toc]    [Back]

       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

AUTHORS    [Toc]    [Back]

       Linus Torvalds (and many others)

SEE ALSO    [Toc]    [Back]

       klogd(8), lilo.conf(5), 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 uptodate source of
       information is /usr/src/linux/Documentation/kernel-parameters.txt.

Linux 2.1.21			  1995-01-14			  BOOTPARAM(7)
[ Back ]
 Similar pages
Name OS Title
modules Linux kernel modules to load at boot time
rcS Linux defaults used at boot time
microuptime FreeBSD get the time elapsed since boot
getmicrouptime FreeBSD get the time elapsed since boot
getnanouptime FreeBSD get the time elapsed since boot
nanouptime FreeBSD get the time elapsed since boot
arp Linux Linux ARP kernel module.
getbootfile FreeBSD get kernel boot file name
sema HP-UX enable or disable System V IPC semaphores at boot time
mesg HP-UX enable or disable System V IPC messages at boot time
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service