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           The  Linux  kernel accepts certain 'command-line options' or 'boot time
           parameters' at the moment it is started.  In general this  is  used  to
           supply  the  kernel with information about hardware parameters that the
           kernel would not be able to determine on its own, or to  avoid/override
           the values that the kernel would otherwise detect.
           When  the  kernel  is booted directly by the BIOS (say from a floppy to
           which you copied a kernel using 'cp  zImage  /dev/fd0'),  you  have  no
           opportunity  to specify any parameters.  So, in order to take advantage
           of this possibility you have to use a boot loader that is able to  pass
           parameters, such as GRUB.
       The argument list
           The  kernel  command  line is parsed into a list of strings (boot argu-
           ments) separated by spaces.  Most of the boot arguments take  have  the
           where  'name' is a unique keyword that is used to identify what part of
           the kernel the associated values (if any) are to be given to.  Note the
           limit  of  10  is real, as the present code handles only 10 comma sepa-
           rated parameters per keyword.  (However, you can reuse the same keyword
           with  up to an additional 10 parameters in unusually complicated situa-
           tions, assuming the setup function supports it.)
           Most of the sorting is coded in the  kernel  source  file  init/main.c.
           First,  the  kernel checks to see if the argument is any of the special
           arguments 'root=', 'nfsroot=',  '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 argu-
           Any  remaining arguments that were not picked up by the kernel and were
           not interpreted as environment variables are then passed  onto  process
           one,  which  is  usually the init(1) program.  The most common argument
           that is passed to the init process is the word 'single' which instructs
           it  to  boot  the  computer in single user mode, and not launch all the
                  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 argument causes Linux to ignore the maths coproces-
                  sor  even  if  you  have one.  Of course you must then have your
                  kernel compiled with math emulation support!
                  (Only when  CONFIG_BUGi386  is  defined.)   Some  of  the  early
                  i486DX-100  chips  have a problem with the 'hlt' instruction, in
                  that they can't reliably return to  operating  mode  after  this
                  instruction is used.  Using the 'no-hlt' instruction tells Linux
                  to just run an infinite loop when there is nothing else  to  do,
                  and  to  not halt the CPU.  This allows people with these broken
                  chips to use Linux.
                  This argument tells the kernel what device is to be used as  the
                  root  filesystem  while booting.  The default of this setting is
                  determined at compile time, and usually is the value of the root
                  device  of the system that the kernel was built on.  To override
                  this value, and select the  second  floppy  drive  as  the  root
                  device, one would use 'root=/dev/fd1'.
                  The root device can be specified symbolically or numerically.  A
                  symbolic specification has the form /dev/XXYN, where  XX  desig-
                  nates  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 num-
                  ber, 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 filesystem.  The '/dev/' part is purely conven-
                  The more awkward and less portable numeric specification of  the
                  above  possible  root  devices  in  major/minor  format  is also
                  can do their work on a quiescent filesystem.  No  processes  can
                  write  to  files  on  the  filesystem  in  question  until it is
                  'remounted' as read/write capable, for example, by 'mount -w  -n
                  -o remount /'.  (See also mount(8).)
                  The  'rw'  option  tells the kernel to mount the root filesystem
                  read/write.  This is the default.
                  This tells the kernel the location of the  suspend-to-disk  data
                  that  you  want  the  machine  to resume from after hibernation.
                  Usually, it is the same as your swap partition or file. Example:
                  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  prob-
                  ing,  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 prob-
                  ing 0x300-0x31f.
                  The BIOS call defined in the PC specification that  returns  the
                  amount  of  installed  memory  was  designed  only to be able to
                  report up to 64MB.  Linux uses this BIOS call at boot to  deter-
                  mine  how  much memory is installed.  If you have more than 64MB
                  of RAM installed, you can use this boot argument to  tell  Linux
                  how  much memory you have.  The value is in decimal or hexadeci-
                  mal (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,
                       surely eventually.
                  You can also use the boot argument 'mem=nopentium' to turn off 4
                  MB page tables on kernels configured for  IA32  systems  with  a
                  pentium or newer CPU.
                  By  default  the  kernel will not reboot after a panic, but this
                  option will cause a kernel reboot  after  N  seconds  (if  N  is
                  greater than zero).  This panic timeout can also be set by
                      echo N > /proc/sys/kernel/panic
                  (Only when CONFIG_BUGi386 is defined.)  Since 2.0.22 a reboot is
                  by default a cold reboot.  One asks for  the  old  default  with
                  'reboot=warm'.   (A cold reboot may be required to reset certain
                  hardware, but might destroy not  yet  written  data  in  a  disk
                  cache.   A  warm  reboot may be faster.)  By default a reboot is
                  hard, by asking the keyboard controller to pulse the reset  line
                  low,  but  there  is at least one type of motherboard where that
                  doesn't  work.   The  option  'reboot=bios'  will  instead  jump
                  through the BIOS.
           'nosmp' and 'maxcpus=N'
                  (Only  when  __SMP__  is  defined.)   A  command-line  option of
                  'nosmp' or 'maxcpus=0' will disable SMP activation entirely;  an
                  option  'maxcpus=N'  limits the maximum number of CPUs activated
                  in SMP mode to N.
       Boot arguments for use by kernel developers
                  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_PRO-
                  FILE_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:
                  Set the six parameters max_buff_age, buff_advance, buff_decline,
                  buff_initial_age, bufferout_weight, buffermem_grace that control
                  kernel buffer memory management.  For kernel tuners only.
       Boot arguments for ramdisk use
           (Only  if the kernel was compiled with CONFIG_BLK_DEV_RAM.)  In general
           it is a bad idea to use a  ramdisk  under  Linux--the  system  will  use
           available  memory more efficiently itself.  But while booting (or while
           constructing boot floppies) it is often useful to load the floppy  con-
           tents 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' param-
           eter  to tell its size.  (This could also be set in the kernel image at
           compile time.)  These days ram disks use the  buffer  cache,  and  grow
           dynamically.   For  a  lot  of  information in conjunction with the new
           ramdisk  setup,  see  the  kernel  source   file   Documentation/block-
           dev/ramdisk.txt (Documentation/ramdisk.txt in older kernels).
           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;
                  afterward  the "real" root filesystem is mounted, and the initrd
                  filesystem is moved over to  /initrd;  finally  the  usual  boot
                  sequence (e.g., invocation of /sbin/init) is performed.
           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 usu-
           ally be 5, 7, 9, 10, 11, 12, and 15.  The other values are usually used
           for common peripherals like IDE hard disks, floppies, serial ports, and
           so on.
           scsi-id -- the ID that the host adapter uses to identify itself on  the
           SCSI  bus.   Only some host adapters allow you to change this value, as
           most have it permanently specified internally.  The usual default value
           is 7, but the Seagate and Future Domain TMC-950 boards use 6.
           parity -- whether the SCSI host adapter expects the attached devices to
           supply a parity value with all information exchanges.  Specifying a one
           indicates parity checking is enabled, and a zero disables parity check-
           ing.  Again, not all adapters will support selection of parity behavior
           as a boot argument.
                  A SCSI device can have a number of 'subdevices' contained within
                  itself.  The most common example is one of the new SCSI  CD-ROMs
                  that  handle more than one disk at a time.  Each CD is addressed
                  as a 'Logical Unit Number' (LUN) of that particular device.  But
                  most  devices, such as hard disks, tape drives and such are only
                  one device, and will be assigned to LUN zero.
                  Some poorly designed SCSI devices cannot handle being probed for
                  LUNs  not  equal  to  zero.  Therefore, if the compile-time flag
                  CONFIG_SCSI_MULTI_LUN is not set, newer kernels will by  default
                  only probe LUN zero.
                  To  specify  the  number  of  probed  LUNs  at  boot, one enters
                  'max_scsi_luns=n' as a boot arg, where n is a number between one
                  and  eight.  To avoid problems as described above, one would use
                  n=1 to avoid upsetting such broken devices.
           SCSI tape configuration
                  Some boot time configuration of the  SCSI  tape  driver  can  be
                  achieved by using the following:
                  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:
                  If the driver was compiled with debugging enabled, a sixth value
                  can be specified to set the debug level.
                  All  the parameters are as described at the top of this section,
                  and the reconnect value will allow  device  disconnect/reconnect
                  if a nonzero value is used.  An example usage is as follows:
                  Note  that  the  parameters  must be specified in order, meaning
                  that if you want to specify a parity setting, then you will have
                  to  specify an iobase, irq, scsi-id and reconnect value as well.
           Adaptec aha154x configuration
                  The aha1542  series  cards  have  an  i82077  floppy  controller
                  onboard,  while the aha1540 series cards do not.  These are bus-
                  mastering cards, and have parameters to set the "fairness"  that
                  is  used to share the bus with other devices.  The boot argument
                  looks like the following.
                  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
           Adaptec aha274x, aha284x, aic7xxx configuration
                  These boards can accept an argument of the form:
                  The extended value, if nonzero, indicates that extended transla-
                  tion  for  large  disks  is  enabled.   The  no_reset  value, if
                  nonzero, tells the driver not to reset the SCSI bus when setting
                  up the host adapter at boot.
           AdvanSys SCSI Hosts configuration ('advansys=')
                  The  AdvanSys  driver  can  accept up to four I/O addresses that
                  will be probed for an AdvanSys SCSI card.  Note that these  val-
                  For an extensive discussion of the BusLogic command line parame-
                  ters,  see  the kernel source file drivers/scsi/BusLogic.c.  The
                  text below is a very much abbreviated extract.
                  The parameters N1-N5 are integers.  The  parameters  S1,...  are
                  strings.   N1  is  the  I/O Address at which the Host Adapter is
                  located.  N2 is the Tagged Queue Depth to use for Target Devices
                  that  support Tagged Queuing.  N3 is the Bus Settle Time in sec-
                  onds.  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 Queu-
                  ing (TQ:Default, TQ:Enable,  TQ:Disable,  TQ:<Per-Target-Spec>),
                  over  Error  Recovery (ER:Default, ER:HardReset, ER:BusDeviceRe-
                  set, ER:None, ER:<Per-Target-Spec>), and over Host Adapter Prob-
                  ing (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, 0xde000.
           IN2000 configuration
                  where  S  is  a comma-separated string of items keyword[:value].
                  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 Documenta-
                  tion/scsi/g_NCR5380.txt  (or  drivers/scsi/README.g_NCR5380  for
                  older kernels) in the Linux kernel source.
           NCR53C8xx configuration
                  where  S  is  a  comma-separated  string of items keyword:value.
                  Recognized keywords are: mpar (master_parity),  spar  (scsi_par-
                  ity),  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  the
                  kernel source file drivers/scsi/ncr53c8xx.c.
           NCR53c406a configuration
                  Specify  irq  = 0 for noninterrupt driven mode.  Set fastpio = 1
                  for fast pio mode, 0 for slow mode.
           Pro Audio Spectrum configuration
                  The PAS16 uses a NC5380 SCSI  chip,  and  newer  models  support
                  jumperless configuration.  The boot argument is of the form:
                  The only difference is that you can specify an IRQ value of 255,
                  which will tell the driver to  work  without  using  interrupts,
                  albeit at a performance loss.  The iobase is usually 0x388.
           Seagate ST-0x configuration
                  If your card is not detected at boot time, you will then have to
                  use a boot argument 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:
           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 the kernel source file
       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'.
                  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
                  Also  note  that 'hd=' can be used to refer to the next unspeci-
                  fied drive in the (a, ..., h) sequence.  For the following  dis-
                  cussions,  the  'hd=' option will be cited for brevity.  See the
                  file  Documentation/ide.txt  (or  drivers/block/README.ide   for
                  older kernels) in the Linux kernel source for more details.
           The 'hd=cyls,heads,sects[,wpcom[,irq]]' options
                  These  options  are used to specify the physical geometry of the
                  disk.  Only the first three values  are  required.   The  cylin-
                  der/head/sectors  values will be those used by fdisk.  The write
                  precompensation value is ignored for IDE disks.  The  IRQ  value
                  specified  will be the IRQ used for the interface that the drive
                  resides on, and is not really a drive-specific parameter.
           The 'hd=serialize' option
                  The dual IDE interface CMD-640 chip is broken as  designed  such
                  that when drives on the secondary interface are used at the same
                  time as drives on the primary interface, it  will  corrupt  your
                  data.  Using this option tells the driver to make sure that both
                  interfaces are never used at the same time.
           The 'hd=dtc2278' option
                  This option tells the driver  that  you  have  a  DTC-2278D  IDE
                  interface.   The driver then tries to do DTC-specific operations
                  to enable the second interface and  to  enable  faster  transfer
           The 'hd=noprobe' option
                  Do not probe for this drive.  For example,
                  this may help.
           Standard ST-506 Disk Driver Options ('hd=')
                  The  standard  disk driver can accept geometry arguments for the
                  disks similar to the IDE driver.  Note however that  it  expects
                  only  three  values  (C/H/S);  any  more or any less and it will
                  silently ignore you.  Also, it accepts only 'hd='  as  an  argu-
                  ment,  that is, 'hda=' and so on are not valid here.  The format
                  is as follows:
                  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 recognized, you will have to use a
                  boot argument of the form:
                  The type value specifies  the  particular  manufacturer  of  the
                  card,  overriding  autodetection.  For the types to use, consult
                  the drivers/block/xd.c source file of the kernel you are  using.
                  The  type  is  an index in the list xd_sigs and in the course of
                  time types have been added to or deleted from the middle of  the
                  list,  changing all type numbers.  Today (Linux 2.5.0) the types
                  are 0=generic; 1=DTC 5150cx; 2,3=DTC 5150x; 4,5=Western Digital;
                  6,7,8=Seagate;  9=Omti;  10=XEBEC,  and where here several types
                  are given with the same designation, they are equivalent.
                  The xd_setup() function does no  checking  on  the  values,  and
                  assumes  that you entered all four values.  Don't disappoint it.
                  Here is an example usage for a WD1002 controller with  the  BIOS
                  disabled/removed, using the 'default' XT controller parameters:
           Syquest's EZ* removable disks
       IBM MCA bus devices
           See also the kernel source file Documentation/mca.txt.
           PS/2 ESDI hard disks
                  It is possible to specify the desired geometry at boot time:
                  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 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 syn-
                  tax 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 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 value.
           The GoldStar Interface
                  The syntax for this CD-ROM interface is:
           The ISP16 CD-ROM Interface
           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  spec-
                  ify  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
       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:
           The first nonnumeric argument is taken as the name.  The param_n values
           (if applicable) usually have  different  meanings  for  each  different
           card/driver.   Typical  param_n  values are used to specify things like
           shared memory address, interface selection, DMA channel and the like.
           The most common use of this parameter is to force probing for a  second
           ethercard, as the default is to probe only for one.  This can be accom-
           mentation/floppy.txt  (or drivers/block/README.fd for older kernels) in
           the Linux kernel source.  This information is taken directly from  that
                  Sets  the  bit mask of allowed drives to mask.  By default, only
                  units 0 and 1 of each floppy controller are  allowed.   This  is
                  done  because  certain  nonstandard  hardware  (ASUS PCI mother-
                  boards) mess up the keyboard when accessing units 2 or 3.   This
                  option is somewhat obsoleted by the cmos option.
                  Sets  the bit mask of allowed drives to all drives.  Use this if
                  you have more than two drives connected to a floppy  controller.
                  Sets the bit mask to allow only units 0 and 1.  (The default)
                  Tells the floppy driver that you have a well behaved floppy con-
                  troller.  This allows more efficient and smoother operation, but
                  may  fail  on  certain  controllers.   This may speed up certain
                  Tells the floppy driver that your floppy  controller  should  be
                  used with caution.
                  Tells  the  floppy  driver  that you have only floppy controller
           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 bit mask.  This is useful  if  you  have  more
                  than  two floppy drives (only two can be described in the physi-
                  cal cmos), or if your BIOS uses nonstandard CMOS types.  Setting
                  the  CMOS  to  0  for  the  first two drives (default) makes the
                  floppy driver read the physical cmos for those drives.
           is   described   in   the   Linux   kernel   source   file   Documenta-
           tion/sound/oss/README.OSS (drivers/sound/Readme.linux in  older  kernel
           versions).  It accepts a boot argument of the form:
                  where each deviceN value is of the following format 0xTaaaId and
                  the bytes are used as follows:
                  T - device type: 1=FM, 2=SB,  3=PAS,  4=GUS,  5=MPU401,  6=SB16,
                  aaa - I/O address in hex.
                  I - interrupt line in hex (i.e 10=a, 11=b, ...)
                  d - DMA channel.
                  As  you  can see it gets pretty messy, and you are better off to
                  compile in your own personal values  as  recommended.   Using  a
                  boot  argument  of  'sound=0'  will  disable  the  sound  driver
       ISDN drivers
           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
       Serial port drivers
                  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 the kernel source  file  Documenta-
           The Baycom Serial/Parallel Radio Modem
                  There  are  precisely 3 parameters; for several cards, give sev-
                  eral '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    the    file    Documentation/networking/baycom.txt    (or
                  drivers/net/README.baycom for older kernels) in the Linux kernel
           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,
                  or wssfdx, and modem is one of afsk1200 or fsk9600.
       The line printer driver
                  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
                  The  busmouse  driver accepts only 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-thresh-
                  old, and the second the  y-threshold.   These  values  must  lie
                  between 1 and 20 (inclusive); the default is 2.
       Video hardware
                  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.


           klogd(8), mount(8)
           Large parts of this man page have been derived from the Boot  Parameter
           HOWTO  (version 1.0.1) written by Paul Gortmaker.  More information may
           be found in this (or a more recent) HOWTO.   An  up-to-date  source  of
           information  is  the  kernel  source  file Documentation/kernel-parame-

    Linux 2013-08-01 BOOTPARAM(7)


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