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RedHat 9 (Linux i386) - man page for bootparam (redhat section 7)

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 parameters.
       So, in order to take advantage of this possibility you have to use software that  is  able
       to  pass  parameters,  like LILO or loadlin.  For a few parameters one can also modify the
       kernel image itself, using rdev, see rdev(8) for further details.

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

       The  other  commonly  used  Linux  loader is `LoadLin' which is a DOS 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

       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 compatible mode. Booting DOS with the supplied driver, and then loading
       Linux from the DOS prompt with loadlin avoids the reset of the card that  happens  if  one
       rebooted instead.

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


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

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

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

       Anything of the form `foo=bar' that is not accepted as a setup function as described above
       is then interpreted as an environment variable to be set. A (useless?) example would be to
       use `TERM=vt100' as a boot 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 dae-
       mons.  Check  the manual page for the version of init installed on your system to see what
       arguments it accepts.

       This sets the initial command to be executed by the kernel.  If this is not set, or cannot
       be found, the kernel will try /etc/init, then /bin/init, then /sbin/init, then /bin/sh and
       panic if all of this 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 coprocessor chips have bugs that show up
       when used in 32 bit protected mode. For example, some of the early  ULSI-387  chips  would
       cause  solid lockups while performing floating point calculations.  Using the `no387' boot
       arg causes Linux to ignore the maths coprocessor even if you have one. Of course you  must
       then have your kernel compiled with math emulation support!

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

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

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

       Note that this has nothing to do with the designation of these devices on your  file  sys-
       tem. 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

       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 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.

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

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

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

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

       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 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 dis-
       able 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 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).

       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  signifi-
       cance 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 coun-

       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 ker-
       nel swap algorithm.  For kernel tuners only.

       Set the six parameters max_buff_age, buff_advance, buff_decline, buff_initial_age, buffer-
       out_weight,  buffermem_grace  that  control  kernel  buffer  memory management. For kernel
       tuners only.

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

       In Linux 1.3.48, ramdisk handling was changed drastically.  Earlier, the memory was  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, 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/Documenta-

       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 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).

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

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

       For  a  detailed  description of the initrd feature, see /usr/src/linux/Documentation/ini-

       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 hexidec-
       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, etc.

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

       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 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

       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 follow-


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


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

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

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


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

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


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


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

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

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

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


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

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


   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-Target-Spec>), over Error Recovery (ER:Default, ER:HardReset, ER:Bus-
       DeviceReset, ER:None, ER:<Per-Target-Spec>),  and  over	Host  Adapter  Probing	(NoProbe,
       NoProbeISA, NoSortPCI).

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


   Future Domain TMC-16x0 configuration

   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,

   IN2000 configuration

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

   NCR5380 and NCR53C400 configuration
       The boot arg is of the form




       If  the	card  doesn't use interrupts, then an IRQ value of 255 (0xff) will disable inter-
       rupts. 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 keyword:value.  Recognized keywords are: mpar
       (master_parity), spar (scsi_parity), disc (disconnection), specf (special_features), ultra
       (ultra_scsi),  fsn (force_sync_nego), tags (default_tags), sync (default_sync), verb (ver-
       bose), debug (debug), burst (burst_max).  For the function of  the  assigned  values,  see

   NCR53c406a configuration

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

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


       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  usu-
       ally 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


       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,

   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 by


   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,   disconnect: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  specifica-
       tions,  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

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

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

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

	      hdb=noprobe hdb=1166,7,17

       would  disable  the probe, but still specify the drive geometry so that it would be regis-
       tered 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  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, overriding autodetec-
       tion. 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 des-
       ignation, 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:


   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 time:


       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.

   Parallel port CD-ROM drives


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

   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 other-
       wise it should not be specified 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

   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 `Mitsumi'.

   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 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:


   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 por-
       tion 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


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

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


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

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

       There  are many floppy driver options, and they are all listed in README.fd in linux/driv-
       ers/block. This information is taken directly from that file.

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

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

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

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

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

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

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

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

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

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

       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

       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 per-
       sonal values as recommended. Using a boot arg of `sound=0' will disable the  sound  driver

   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 set-
       ting 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/Documentation/riscom8.txt.

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


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


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

   The Baycom Serial/Parallel Radio Modem


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

   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, fsk9600.



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

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

   WDT500/501 driver


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

       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  Gortmaker.   More  information  may be found in this (or a more
       recent) HOWTO.  An uptodate source of information is  /usr/src/linux/Documentation/kernel-

Linux 2.1.21				    1995-01-14				     BOOTPARAM(7)

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