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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 a boot loader  that  is
       able to pass parameters, such as GRUB.

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

	   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 handles only 10 comma separated parameters per keyword.   (However,  you  can
       reuse  the  same  keyword  with up to an additional 10 parameters in unusually complicated
       situations, assuming the setup function supports it.)

       Most of the sorting is coded in the kernel source file  init/main.c.   First,  the  kernel
       checks to see if the argument is any of the special arguments 'root=', 'nfsroot=', 'nfsad-
       drs=', '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 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(1) pro-
       gram.  The most common argument that is passed to the init process is  the  word  'single'
       which  instructs it to boot the computer in single user mode, and not launch all the usual
       daemons.  Check the manual page for the version of init(1) 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  calcula-
	      tions.   Using the 'no387' boot argument causes Linux to ignore the maths coproces-
	      sor 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 filesystem
	      while booting.  The default of this setting is determined at compile time, and usu-
	      ally  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 be specified symbolically or numerically.  A symbolic specifi-
	      cation 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 par-
	      allel  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  flop-
	      pies).   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
	      filesystem.  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 alternative.)

       'rootfstype=...'
	      The 'rootfstype' option tells the kernel to mount the  root  filesystem  as  if  it
	      where  of  the  type  specified.	This can be useful (for example) to mount an ext3
	      filesystem as ext2 and then remove the journal in  the  root  filesystem,  in  fact
	      reverting its format from ext3 to ext2 without the need to boot the box from alter-
	      nate media.

       'ro' and 'rw'
	      The 'ro' option tells the kernel to mount the root  filesystem  as  'read-only'  so
	      that  filesystem consistency check programs (fsck) can do their work on a quiescent
	      filesystem.  No processes can write to files on the filesystem 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 filesystem read/write.  This  is
	      the default.

       'resume=...'
	      This  tells  the	kernel the location of the suspend-to-disk data that you want the
	      machine to resume from after hibernation.  Usually, it is the  same  as  your  swap
	      partition or file. Example:

		  resume=/dev/hda2

       '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 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 0x300-0x31f.

       'mem=...'
	      The BIOS call defined in the PC specification that returns the amount of	installed
	      memory  was  designed  only  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 argument 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: 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 num-
	      ber 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 vari-
	      able 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 nonzero value.  This is done  either  by  specifying  CON-
	      FIG_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.

       'swap=N1,N2,N3,N4,N5,N6,N7,N8'
	      Set  the	eight  parameters  max_page_age,  page_advance,  page_decline,	page_ini-
	      tial_age, age_cluster_fract, age_cluster_min, pageout_weight, bufferout_weight that
	      control the kernel 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 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 allo-
       cated statically, and there was a 'ramdisk=N' parameter to tell	its  size.   (This  could
       also  be  set  in  the kernel image at compile time.)  These days ram disks use the buffer
       cache, and grow dynamically.  For a lot of information in conjunction with the new ramdisk
       setup,	see   the   kernel  source  file  Documentation/blockdev/ramdisk.txt  (Documenta-
       tion/ramdisk.txt in older kernels).

       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_INI-
	      TRD.)   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; afterward the "real" root filesys-
	      tem  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 kernel source file  Docu-
	      mentation/initrd.txt.

	      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.)

   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 hexadec-
       imal 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, and so on.

       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 selec-
       tion of parity behavior as a boot argument.

       'max_scsi_luns=...'
	      A SCSI device can have a number of 'subdevices' 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  file  Documentation/scsi/st.txt  (or  driv-
	      ers/scsi/README.st for older kernels) in the Linux kernel source.

       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 argu-
	      ment 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 nonzero value is used.  An exam-
	      ple 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 busmastering cards, and have parameters to
	      set the "fairness" that is used to share the bus	with  other  devices.	The  boot
	      argument 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  domi-
	      nates  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 han-
	      dling 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 nonzero, indicates that extended translation for large disks
	      is enabled.  The no_reset value, if nonzero, 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 values (if used) do not effect EISA or PCI
	      probing in any way.  They are used only for probing ISA and VLB  cards.	In  addi-
	      tion,  if  the driver has been compiled with debugging enabled, the level of debug-
	      ging 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
	      Syntax:

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

       BusLogic SCSI Hosts configuration ('BusLogic=')

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

	      For an extensive discussion of the BusLogic command line parameters, see the kernel
	      source file drivers/scsi/BusLogic.c.  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
	      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

		  eata=iobase,iobase,....

       Future Domain TMC-16x0 configuration
	      Syntax:

		  fdomain=iobase,irq[,adapter_id]

       Great Valley Products (GVP) SCSI controller configuration
	      Syntax:

		  gvp11=dma_transfer_bitmask

       Future Domain TMC-8xx, TMC-950 configuration
	      Syntax:

		  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
	      Syntax:

		  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 the kernel source file
	      drivers/scsi/in2000.c.

       NCR5380 and NCR53C400 configuration
	      The boot argument 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	Documentation/scsi/g_NCR5380.txt  (or  drivers/scsi/README.g_NCR5380  for
	      older kernels) in the Linux kernel source.

       NCR53C8xx configuration
	      Syntax:

		  ncr53c8xx=S

	      where  S	is  a comma-separated string of items keyword:value.  Recognized keywords
	      are: mpar (master_parity), spar (scsi_parity), disc  (disconnection),  specf  (spe-
	      cial_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   the   kernel   source  file  driv-
	      ers/scsi/ncr53c8xx.c.

       NCR53c406a configuration
	      Syntax:

		  ncr53c406a=iobase[,irq[,fastpio]]

	      Specify irq = 0 for noninterrupt 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 configura-
	      tion.  The boot argument 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  argu-
	      ment 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
	      Syntax:

		  wd7000=irq,dma,iobase

       Commodore Amiga A2091/590 SCSI controller configuration
	      Syntax:

		  wd33c93=S

	      where S is a comma-separated string of options.  Recognized options are nosync:bit-
	      mask, nodma:x, period:ns, disconnect:x, debug:x, clock:x, next.  For  details,  see
	      the kernel source file 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 spec-
	      ifications, 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 Documentation/ide.txt (or drivers/block/README.ide for
	      older kernels) in the Linux kernel source 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 inter-
	      face, 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 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	automati-
	      cally, 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 expects only three values (C/H/S);  any  more  or
	      any  less and it will silently ignore you.  Also, it accepts only '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  parame-
	      ters 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 argument 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
	      Syntax:

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

   IBM MCA bus devices
       See also the kernel source file 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
	      Syntax:

		  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  auto-
	      matically),  '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 syntax 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 recognized 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 prob-
	      lems  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.  Syn-
	      tax:

		  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 nonnumeric 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 probe only 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 Documentation/floppy.txt
       (or drivers/block/README.fd for older kernels) in the Linux kernel source.  This  informa-
       tion 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 nonstandard hard-
	      ware  (ASUS  PCI	motherboards)  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 controller.  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  con-
	      vention 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 physical cmos), or if your BIOS uses nonstandard 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 arguments to override the compiled in values.   This
       is  not	recommended, as it is rather complex.  It is described in the Linux kernel source
       file Documentation/sound/oss/README.OSS (drivers/sound/Readme.linux in older  kernel  ver-
       sions).	It accepts a boot argument 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 argument 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  inter-
	      rupt 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 the kernel source file 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) alter-
	      nate  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 the kernel source file Documentation/digiboard.txt.

       The Baycom Serial/Parallel Radio Modem
	      Syntax:

		  baycom=iobase,irq,modem

	      There  are  precisely  3 parameters; for several cards, give several 'baycom=' com-
	      mands.  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  Documentation/networking/baycom.txt  (or  drivers/net/README.baycom for older
	      kernels) in the Linux kernel source.

       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 accepts only 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
	      Syntax:

		  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-threshold, 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
       klogd(8), mount(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 the kernel source file Documenta-
       tion/kernel-parameters.txt.

COLOPHON
       This page is part of release 3.55 of the Linux man-pages project.  A  description  of  the
       project,     and    information	  about    reporting	bugs,	 can	be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux					    2013-08-01				     BOOTPARAM(7)
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