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

       bootparam  -  Introduction  to boot time parameters of the
       Linux kernel

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


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

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

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

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

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

       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.

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

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

       (Only  when  CONFIG_BUGi386 is defined.)  Some i387 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!

       (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.

       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

       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
       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.)

   `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).

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


       In some machines it may be  necessary  to  prevent  device
       drivers from checking for devices (auto-probing) in a 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.

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

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

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

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

       (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

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

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

       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.

       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

       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.

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

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

       There are four parameters, two boolean and two integral.

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

       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).

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

       (Only if the kernel was compiled  with  CONFIG_BLK_DEV_RAM
       and  CONFIG_BLK_DEV_INITRD.)  These days it is possible to
       compile the kernel to use initrd.  When  this  feature  is
       enabled, the boot process will load the kernel and an 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.)

       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.

       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
       between  one  and  eight.  To  avoid problems as described
       above, one would use n=1 to avoid  upsetting  such  broken

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


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


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

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

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


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

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


       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.

   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 ``fair-
       ness''  that  is used to share the bus with other devices.
       The boot arg looks like the following.


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

       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:


       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.


   BusLogic SCSI Hosts configuration (`BusLogic=')

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

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


   Future Domain TMC-16x0 configuration

   Great Valley Products (GVP) SCSI controller configuration

   Future Domain TMC-8xx, TMC-950 configuration

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

   IN2000 configuration

       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




       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

   NCR53C8xx configuration

       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

   NCR53c406a configuration

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

   IOMEGA PPA3 configuration

       Here  iobase is the parallel port address (default 0x378),
       speed_high is the port delay in data phase in microseconds
       (default 1), speed_low is the port delay (in microseconds)
       otherwise (default 6), and nybble is a boolean `force nyb-
       ble   (4-bit)   mode'   (default   0=false).    See   also

   Pro Audio Spectrum configuration
       The PAS16 uses a NC5380 SCSI chip, and newer  models  sup-
       port  jumperless  configuration.  The  boot  arg is of the


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

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


       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:


       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


   WD7000 configuration

   Commodore Amiga A2091/590 SCSI controller configuration

       where S is a comma-separated string of options. Recognized
       options  are  nosync:bitmask,  nodma:x, period:ns, discon-
       nect:x,  debug:x,  clock:x,   next.   For   details,   see

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

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

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

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

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

   The `hd=dtc2278' option
       This option tells the driver that you have a DTC-2278D IDE
       interface.  The driver then tries to do DTC specific 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

   The `hd=cdrom' option
       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:


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

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


       The  type  value  specifies the particular manufacturer of
       the  card,  and  are   as   follows:   0=generic;   1=DTC;
       2,3,4=Western  Digital,  5,6,7=Seagate;  8=OMTI.  The only
       difference between multiple types from the  same  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:


   Syquest's EZ* removable disks

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

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


       For a ThinkPad-720, add the option


   IBM Microchannel SCSI Subsystem configuration

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

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


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

   The MicroSolutions `backpack' CDrom


   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:


       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 speci-
       fied at all.

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


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

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


   The ISP16 CD-ROM Interface


       (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

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


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

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


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


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


       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:


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


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

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


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

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


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

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

       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.

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

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

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

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

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

       Tells  the  floppy  driver  that you have only floppy con-
       troller (default)

   floppy=two_fdc or floppy=address,two_fdc
       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.

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

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

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

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

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

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


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

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

       aaa - I/O address in hex.

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

       d - DMA channel.

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

   The ICN ISDN driver


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

   The PCBIT ISDN driver


       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


       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.

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


       More details can  be  found  in  /usr/src/linux/Documenta-

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


       The parameters maybe given as integers, or as strings.  If
       strings  are used, then iobase and membase should be given
       in hexadecimal.   The  integer  arguments  (fewer  may  be
       given)  are in order: status (Enable(1) or Disable(0) this
       card), type (PC/Xi(0), PC/Xe(1),  PC/Xeve(2),  PC/Xem(3)),
       altpin  (Enable(1)  or  Disable(0)  alternate pin 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:


       More  details  can  be  found in /usr/src/linux/Documenta-

   The Baycom Serial/Parallel Radio Modem


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

   Soundcard radio modem driver


       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,

       As  of kernels newer than 1.3.75, 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 i/o, IRQ pairs. For
       example, lp=0x3bc,0,0x378,7 would use the port at 0x3bc in
       IRQ-less  (polling)  mode,  and  use IRQ 7 for the port at
       0x378. The port at 0x278 (if any)  would  not  be  probed,
       since  autoprobing  only  takes  place in the absence of a
       `lp=' argument. To disable the  printer  driver  entirely,
       one can use lp=0.

   WDT500/501 driver


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

       And precisely the same is true for the msmouse driver.

   ATARI mouse setup

              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.

       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.

       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.  Slightly more information may be found in this (or
       a more recent) HOWTO.

Linux 2.1.21             14 January 1995                        1