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 parame­
       ters.  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  Almes­
       berger  is  the  most commonly used. It has the ability to
       boot various kernels, and stores the configuration  infor­
       mation   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 Compati­
       ble' sound cards that require the DOS driver to twiddle  a
       few  mystical registers to put the card into a SB compati­
       ble 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

       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:

              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

       per keyword. (However, you can  re-use  the  same  keyword
       with  up  to an additional 10 parameters in unusually com­
       plicated 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 ver­
       sion of init installed on your system to  see  what  argu­
       ments it accepts.


GENERAL NON-DEVICE SPECIFIC BOOT ARGS

   `init=...'
       This  sets  the initial command to be executed by the ker­
       nel.  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 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

       is  prefixed  by  `/tftpboot/'.  This root name is used in
       case of a net boot.

   `no387'
       (Only when CONFIG_BUGi386 is defined.)  Some  i387  copro­
       cessor  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'  instruc­
       tion, 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 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  numeri­
       cally.   A  symbolic specification has the form /dev/XXYN,
       where XX designates the device type (`hd' for ST-506  com­
       patible  hard  disk, with Y in `a'-`d'; `sd' for SCSI com­
       patible 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


       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
       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 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 spe­
       cific  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 only designed to be
       able to report up to 64MB.  Linux uses this BIOS  call  at

       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.''

   `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 > 0).  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  key­
       board 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.

   `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 impor­
       tant 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  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 profil­
       ing: 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/pro­
       file.  Probably you'll want to use a tool such as readpro­
       file.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_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, buffer­
       mem_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 -

       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 /usr/src/linux/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 parame­
       ter 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 ini­
       tial ramdisk; then the kernel converts initrd into a "nor­
       mal" 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. invoca­
       tion 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.)


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 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, 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  speci­
       fied  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 infor­
       mation  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.

   `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  com­
       pile  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

       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 configu­
       ration
       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:

              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 discon­
       nect/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, mean­
       ing 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.

       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 ``fair­
       ness'' 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 microsec­
       onds 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 assum­
       ing 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
       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 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 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 set­
       ting the level of the debugging messages to any of 16 lev­
       els of verbosity.

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

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

       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 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-Tar­
       get-Spec>), over Error Recovery (ER:Default, ER:HardReset,
       ER:BusDeviceReset,   ER:None,  ER:<Per-Target-Spec>),  and
       over Host Adapter Probing  (NoProbe,  NoProbeISA,  NoSort­
       PCI).

   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=S

       where   S  is  a  comma-separated  string  of  items  key­
       word[:value].  Recognized keywords (possibly  with  value)
       are:  ioport:addr,  noreset,  nosync:x, period:ns, discon­
       nect:x, debug:x, proc:x. For the function of these parame­
       ters, 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   key­
       word:value.   Recognized  keywords  are: mpar (master_par­
       ity),  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
              ncr53c406a=iobase[,irq[,fastpio]]

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

   Pro Audio Spectrum configuration
       The PAS16 uses a NC5380 SCSI chip, and newer  models  sup­
       port  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

       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, discon­
       nect: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'.

       `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 oper­
       ations 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 geom­
       etry 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.

       This  tells the IDE driver that there is an ATAPI compati­
       ble 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:

              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  recognised,  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,  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  manufac­
       turer  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 disap­
       point it.  Here is an example  usage  for  a  WD1002  con­
       troller   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/src/linux/Documentation/mca.txt.

       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.


CD-ROMs (Non-SCSI/ATAPI/IDE)

   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 automati­
       cally), `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


       The is_pas_card should be entered as `PAS' if using a  Pro
       Audio Spectrum card, and otherwise it should not be speci­
       fied 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 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 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 val­
       ues, 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 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 implementa­
       tion  of the param_n values where used. Interested readers
       should refer to the section in that document on their par­
       ticular card.


THE FLOPPY DISK DRIVER

       There  are  many  floppy  driver options, and they are all
       listed in README.fd in linux/drivers/block. This  informa­
       tion is taken directly from that file.

   floppy=mask,allowed_drive_mask
       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.

   floppy=all_drives
       Sets the bitmask 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 bitmask  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 con­
       troller (default)

       Tells the floppy driver that  you  have  two  floppy  con­
       trollers. 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 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.

   floppy=unexpected_interrupts
       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

       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.


       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/src/linux/Documenta­
       tion/riscom8.txt.

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


              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 arrange­
       ment), 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/src/linux/Documenta­
       tion/digiboard.txt.

   The Baycom Serial/Parallel Radio Modem
       Syntax:

              baycom=iobase,irq,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/drivers/net/README.baycom.

   Soundcard radio modem driver
       Syntax:

              soundmo­
              dem=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=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-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.


AUTHORS

       Linus Torvalds (and many others)

       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 Gort­
       maker.  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.


Man(1) output converted with man2html