BOOTPARAM(7)
NAME
bootparam - Introduction to boot time parameters of the
Linux kernel
DESCRIPTION
The Linux kernel accepts certain `command line options' or
`boot time parameters' at the moment it is started. In
general this is used to supply the kernel with information
about hardware parameters that the kernel would not be
able to determine on its own, or to avoid/override the
values that the kernel would otherwise detect.
When the kernel is booted directly by the BIOS (say from a
floppy to which you copied a kernel using `cp zImage
/dev/fd0'), you have no opportunity to specify any parame-
ters. So, in order to take advantage of this possibility
you have to use software that is able to pass parameters,
like LILO or loadlin. For a few parameters one can also
modify the kernel image itself, using rdev, see rdev(8)
for further details.
The LILO program (LInux LOader) written by Werner Almes-
berger is the most commonly used. It has the ability to
boot various kernels, and stores the configuration infor-
mation in a plain text file. (See lilo(8) and
lilo.conf(5).) LILO can boot DOS, OS/2 Linux, FreeBSD,
etc., and is quite flexible.
The other commonly used Linux loader is `LoadLin' which is
a DOS program that has the capability to launch a Linux
kernel from the DOS prompt (with boot-args) assuming that
certain resources are available. This is good for people
that want to launch Linux from DOS.
It is also very useful if you have certain hardware which
relies on the supplied DOS driver to put the hardware into
a known state. A common example is `SoundBlaster Compati-
ble' sound cards that require the DOS driver to twiddle a
few mystical registers to put the card into a SB compati-
ble mode. Booting DOS with the supplied driver, and then
loading Linux from the DOS prompt with loadlin avoids the
reset of the card that happens if one rebooted instead.
THE ARGUMENT LIST
The kernel command line is parsed into a list of strings
(boot arguments) separated by spaces. Most of the boot
args take the form of:
name[=value_1][,value_2]...[,value_10]
where `name' is a unique keyword that is used to identify
what part of the kernel the associated values (if any) are
to be given to. Note the limit of 10 is real, as the
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 com-
plicated situations, assuming the setup function supports
it.)
Most of the sorting goes on in linux/init/main.c. First,
the kernel checks to see if the argument is any of the
special arguments `root=', `nfsroot=', `nfsaddrs=', `ro',
`rw', `debug' or `init'. The meaning of these special
arguments is described below.
Then it walks a list of setup functions (contained in the
bootsetups array) to see if the specified argument string
(such as `foo') has been associated with a setup function
(`foo_setup()') for a particular device or part of the
kernel. If you passed the kernel the line foo=3,4,5,6 then
the kernel would search the bootsetups array to see if
`foo' was registered. If it was, then it would call the
setup function associated with `foo' (foo_setup()) and
hand it the arguments 3, 4, 5 and 6 as given on the kernel
command line.
Anything of the form `foo=bar' that is not accepted as a
setup funtion as described above is then interpreted as an
environment variable to be set. A (useless?) example would
be to use `TERM=vt100' as a boot argument.
Any remaining arguments that were not picked up by the
kernel and were not interpreted as environment variables
are then passed onto process one, which is usually the
init program. The most common argument that is passed to
the init process is the word `single' which instructs init
to boot the computer in single user mode, and not launch
all the usual daemons. Check the manual page for the ver-
sion of init installed on your system to see what argu-
ments it accepts.
GENERAL NON-DEVICE SPECIFIC BOOT ARGS
`init=...'
This sets the initial command to be executed by the ker-
nel. If this is not set, or cannot be found, the kernel
will try /etc/init, then /bin/init, then /sbin/init, then
/bin/sh and panic if all of this fails.
`nfsaddrs=...'
This sets the nfs boot address to the given string. This
boot address is used in case of a net boot.
`nfsroot=...'
This sets the nfs root name to the given string. If this
string does not begin with '/' or ',' or a digit, then it
is prefixed by `/tftpboot/'. This root name is used in
case of a net boot.
`no387'
(Only when CONFIG_BUGi386 is defined.) Some i387 copro-
cessor chips have bugs that show up when used in 32 bit
protected mode. For example, some of the early ULSI-387
chips would cause solid lockups while performing floating
point calculations. Using the `no387' boot arg causes
Linux to ignore the maths coprocessor even if you have
one. Of course you must then have your kernel compiled
with math emulation support!
`no-hlt'
(Only when CONFIG_BUGi386 is defined.) Some of the early
i486DX-100 chips have a problem with the `hlt' instruc-
tion, in that they can't reliably return to operating mode
after this instruction is used. Using the `no-hlt'
instruction tells Linux to just run an infinite loop when
there is nothing else to do, and to not halt the CPU. This
allows people with these broken chips to use Linux.
`root=...'
This argument tells the kernel what device is to be used
as the root filesystem while booting. The default of this
setting is determined at compile time, and usually is the
value of the root device of the system that the kernel was
built on. To override this value, and select the second
floppy drive as the root device, one would use
`root=/dev/fd1'. (The root device can also be set using
rdev(8).)
The root device can be specified symbolically or numeri-
cally. A symbolic specification has the form /dev/XXYN,
where XX designates the device type (`hd' for ST-506 com-
patible hard disk, with Y in `a'-`d'; `sd' for SCSI com-
patible disk, with Y in `a'-`e'; `ad' for Atari ACSI disk,
with Y in `a'-`e', `ez' for a Syquest EZ135 parallel port
removable drive, with Y=`a', `xd' for XT compatible disk,
with Y either `a' or `b'; `fd' for floppy disk, with Y the
floppy drive number - fd0 would be the DOS `A:' drive, and
fd1 would be `B:'), Y the driver letter or number, and N
the number (in decimal) of the partition on this device
(absent in the case of floppies). Recent kernels allow
many other types, mostly for CD-ROMs: nfs, ram, scd, mcd,
cdu535, aztcd, cm206cd, gscd, sbpcd, sonycd, bpcd. (The
type nfs specifies a net boot; ram refers to a ram disk.)
Note that this has nothing to do with the designation of
these devices on your file system. The `/dev/' part is
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).
`reserve=...'
This is used to protect I/O port regions from probes. The
form of the command is:
reserve=iobase,extent[,iobase,extent]...
In some machines it may be necessary to prevent device
drivers from checking for devices (auto-probing) in a spe-
cific region. This may be because of hardware that reacts
badly to the probing, or hardware that would be mistakenly
identified, or merely hardware you don't want the kernel
to initialize.
The reserve boot-time argument specifies an I/O port
region that shouldn't be probed. A device driver will not
probe a reserved region, unless another boot argument
explicitly specifies that it do so.
For example, the boot line
reserve=0x300,32 blah=0x300
keeps all device drivers except the driver for `blah' from
probing 0x300-0x31f.
`mem=...'
The BIOS call defined in the PC specification that returns
the amount of installed memory was only designed to be
able to report up to 64MB. Linux uses this BIOS call at
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 happen:
maybe not at once, but surely eventually.''
`panic=N'
By default the kernel will not reboot after a panic, but
this option will cause a kernel reboot after N seconds (if
N > 0). This panic timeout can also be set by "echo N >
/proc/sys/kernel/panic".
`reboot=[warm|cold][,[bios|hard]]'
(Only when CONFIG_BUGi386 is defined.) Since 2.0.22 a
reboot is by default a cold reboot. One asks for the old
default with `reboot=warm'. (A cold reboot may be
required to reset certain hardware, but might destroy not
yet written data in a disk cache. A warm reboot may be
faster.) By default a reboot is hard, by asking the key-
board controller to pulse the reset line low, but there is
at least one type of motherboard where that doesn't work.
The option `reboot=bios' will instead jump through the
BIOS.
`nosmp' and `maxcpus=N'
(Only when __SMP__ is defined.) A command-line option of
`nosmp' or `maxcpus=0' will disable SMP activation
entirely; an option `maxcpus=N' limits the maximum number
of CPUs activated in SMP mode to N.
BOOT ARGUMENTS FOR USE BY KERNEL DEVELOPERS
`debug'
Kernel messages are handed off to the kernel log daemon
klogd so that they may be logged to disk. Messages with a
priority above console_loglevel are also printed on the
console. (For these levels, see <linux/kernel.h>.) By
default this variable is set to log anything more impor-
tant than debug messages. This boot argument will cause
the kernel to also print the messages of DEBUG priority.
The console loglevel can also be set at run time via an
option to klogd. See klogd(8).
`profile=N'
It is possible to enable a kernel profiling function, if
one wishes to find out where the kernel is spending its
CPU cycles. Profiling is enabled by setting the variable
prof_shift to a nonzero value. This is done either by
specifying CONFIG_PROFILE at compile time, or by giving
the `profile=' option. Now the value that prof_shift gets
will be N, when given, or CONFIG_PROFILE_SHIFT, when that
is given, or 2, the default. The significance of this
variable is that it gives the granularity of the profil-
ing: each clock tick, if the system was executing kernel
code, a counter is incremented:
profile[address >> prof_shift]++;
The raw profiling information can be read from /proc/pro-
file. Probably you'll want to use a tool such as readpro-
file.c to digest it. Writing to /proc/profile will clear
the counters.
`swap=N1,N2,N3,N4,N5,N6,N7,N8'
Set the eight parameters max_page_age, page_advance,
page_decline, page_initial_age, age_cluster_fract,
age_cluster_min, pageout_weight, bufferout_weight that
control the kernel swap algorithm. For kernel tuners
only.
`buff=N1,N2,N3,N4,N5,N6'
Set the six parameters max_buff_age, buff_advance,
buff_decline, buff_initial_age, bufferout_weight, buffer-
mem_grace that control kernel buffer memory management.
For kernel tuners only.
BOOT ARGUMENTS FOR RAMDISK USE
(Only if the kernel was compiled with CONFIG_BLK_DEV_RAM.)
In general it is a bad idea to use a ramdisk under Linux -
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.
`load_ramdisk=N'
If N=1, do load a ramdisk. If N=0, do not load a ramdisk.
(This is the default.)
`prompt_ramdisk=N'
If N=1, do prompt for insertion of the floppy. (This is
the default.) If N=0, do not prompt. (Thus, this parame-
ter is never needed.)
`ramdisk_size=N' or (obsolete) `ramdisk=N'
Set the maximal size of the ramdisk(s) to N kB. The
default is 4096 (4 MB).
`ramdisk_start=N'
Sets the starting block number (the offset on the floppy
where the ramdisk starts) to N. This is needed in case
the ramdisk follows a kernel image.
`noinitrd'
(Only if the kernel was compiled with CONFIG_BLK_DEV_RAM
and CONFIG_BLK_DEV_INITRD.) These days it is possible to
compile the kernel to use initrd. When this feature is
enabled, the boot process will load the kernel and an ini-
tial ramdisk; then the kernel converts initrd into a "nor-
mal" ramdisk, which is mounted read-write as root device;
then /linuxrc is executed; afterwards the "real" root file
system is mounted, and the initrd filesystem is moved over
to /initrd; finally the usual boot sequence (e.g. invoca-
tion of /sbin/init) is performed.
For a detailed description of the initrd feature, see
/usr/src/linux/Documentation/initrd.txt.
The `noinitrd' option tells the kernel that although it
was compiled for operation with initrd, it should not go
through the above steps, but leave the initrd data under
/dev/initrd. (This device can be used only once - the
data is freed as soon as the last process that used it has
closed /dev/initrd.)
BOOT ARGUMENTS FOR SCSI DEVICES
General notation for this section:
iobase -- the first I/O port that the SCSI host occupies.
These are specified in hexidecimal notation, and usually
lie in the range from 0x200 to 0x3ff.
irq -- the hardware interrupt that the card is configured
to use. Valid values will be dependent on the card in
question, but will usually be 5, 7, 9, 10, 11, 12, and 15.
The other values are usually used for common peripherals
like IDE hard disks, floppies, serial ports, etc.
scsi-id -- the ID that the host adapter uses to identify
itself on the SCSI bus. Only some host adapters allow you
to change this value, as most have it permanently speci-
fied internally. The usual default value is 7, but the
Seagate and Future Domain TMC-950 boards use 6.
parity -- whether the SCSI host adapter expects the
attached devices to supply a parity value with all infor-
mation exchanges. Specifying a one indicates parity
checking is enabled, and a zero disables parity checking.
Again, not all adapters will support selection of parity
behaviour as a boot argument.
`max_scsi_luns=...'
A SCSI device can have a number of `sub-devices' contained
within itself. The most common example is one of the new
SCSI CD-ROMs that handle more than one disk at a time.
Each CD is addressed as a `Logical Unit Number' (LUN) of
that particular device. But most devices, such as hard
disks, tape drives and such are only one device, and will
be assigned to LUN zero.
Some poorly designed SCSI devices cannot handle being
probed for LUNs not equal to zero. Therefore, if the com-
pile time flag CONFIG_SCSI_MULTI_LUN is not set, newer
kernels will by default only probe LUN zero.
To specify the number of probed LUNs at boot, one enters
`max_scsi_luns=n' as a boot arg, where n is a number
between one and eight. To avoid problems as described
above, one would use n=1 to avoid upsetting such broken
devices.
SCSI tape configuration
Some boot time configuration of the SCSI tape driver can
be achieved by using the following:
st=buf_size[,write_threshold[,max_bufs]]
The first two numbers are specified in units of kB. The
default buf_size is 32kB, and the maximum size that can be
specified is a ridiculous 16384kB. The write_threshold is
the value at which the buffer is committed to tape, with a
default value of 30kB. The maximum number of buffers
varies with the number of drives detected, and has a
default of two. An example usage would be:
st=32,30,2
Full details can be found in the README.st file that is in
the scsi directory of the kernel source tree.
Adaptec aha151x, aha152x, aic6260, aic6360, SB16-SCSI configu-
ration
The aha numbers refer to cards and the aic numbers refer
to the actual SCSI chip on these type of cards, including
the Soundblaster-16 SCSI.
The probe code for these SCSI hosts looks for an installed
BIOS, and if none is present, the probe will not find your
card. Then you will have to use a boot arg of the form:
aha152x=iobase[,irq[,scsi-id[,reconnect[,parity]]]]
If the driver was compiled with debugging enabled, a sixth
value can be specified to set the debug level.
All the parameters are as described at the top of this
section, and the reconnect value will allow device discon-
nect/reconnect if a non-zero value is used. An example
usage is as follows:
aha152x=0x340,11,7,1
Note that the parameters must be specified in order, mean-
ing that if you want to specify a parity setting, then you
will have to specify an iobase, irq, scsi-id and reconnect
value as well.
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.
aha1542=iobase[,buson,busoff[,dmaspeed]]
Valid iobase values are usually one of: 0x130, 0x134,
0x230, 0x234, 0x330, 0x334. Clone cards may permit other
values.
The buson, busoff values refer to the number of microsec-
onds that the card dominates the ISA bus. The defaults are
11us on, and 4us off, so that other cards (such as an ISA
LANCE Ethernet card) have a chance to get access to the
ISA bus.
The dmaspeed value refers to the rate (in MB/s) at which
the DMA (Direct Memory Access) transfers proceed. The
default is 5MB/s. Newer revision cards allow you to
select this value as part of the soft-configuration, older
cards use jumpers. You can use values up to 10MB/s assum-
ing that your motherboard is capable of handling it.
Experiment with caution if using values over 5MB/s.
Adaptec aha274x, aha284x, aic7xxx configuration
These boards can accept an argument of the form:
aic7xxx=extended,no_reset
The extended value, if non-zero, indicates that extended
translation for large disks is enabled. The no_reset
value, if non-zero, tells the driver not to reset the SCSI
bus when setting up the host adaptor at boot.
AdvanSys SCSI Hosts configuration (`advansys=')
The AdvanSys driver can accept up to four i/o addresses
that will be probed for an AdvanSys SCSI card. Note that
these values (if used) do not effect EISA or PCI probing
in any way. They are only used for probing ISA and VLB
cards. In addition, if the driver has been compiled with
debugging enabled, the level of debugging output can be
set by adding an 0xdeb[0-f] parameter. The 0-f allows set-
ting the level of the debugging messages to any of 16 lev-
els of verbosity.
AM53C974
AM53C974=host-scsi-id,target-scsi-id,max-rate,max-
offset
BusLogic SCSI Hosts configuration (`BusLogic=')
BusLogic=N1,N2,N3,N4,N5,S1,S2,...
For an extensive discussion of the BusLogic command line
parameters, see /usr/src/linux/drivers/scsi/BusLogic.c
(lines 3149-3270 in the kernel version I am looking at).
The text below is a very much abbreviated extract.
The parameters N1-N5 are integers. The parameters S1,...
are strings. N1 is the I/O Address at which the Host
Adapter is located. N2 is the Tagged Queue Depth to use
for Target Devices that support Tagged Queuing. N3 is the
Bus Settle Time in seconds. This is the amount of time to
wait between a Host Adapter Hard Reset which initiates a
SCSI Bus Reset and issuing any SCSI Commands. N4 is the
Local Options (for one Host Adapter). N5 is the Global
Options (for all Host Adapters).
The string options are used to provide control over Tagged
Queuing (TQ:Default, TQ:Enable, TQ:Disable, TQ:), and
over Host Adapter Probing (NoProbe, NoProbeISA, NoSort-
PCI).
EATA/DMA configuration
The default list of i/o ports to be probed can be changed
by
eata=iobase,iobase,....
Future Domain TMC-16x0 configuration
fdomain=iobase,irq[,adapter_id]
Great Valley Products (GVP) SCSI controller configuration
gvp11=dma_transfer_bitmask
Future Domain TMC-8xx, TMC-950 configuration
tmc8xx=mem_base,irq
The mem_base value is the value of the memory mapped I/O
region that the card uses. This will usually be one of the
following values: 0xc8000, 0xca000, 0xcc000, 0xce000,
0xdc000, 0xde000.
IN2000 configuration
in2000=S
where S is a comma-separated string of items key-
word[:value]. Recognized keywords (possibly with value)
are: ioport:addr, noreset, nosync:x, period:ns, discon-
nect:x, debug:x, proc:x. For the function of these parame-
ters, see /usr/src/linux/drivers/scsi/in2000.c.
NCR5380 and NCR53C400 configuration
The boot arg is of the form
ncr5380=iobase,irq,dma
or
ncr53c400=iobase,irq
If the card doesn't use interrupts, then an IRQ value of
255 (0xff) will disable interrupts. An IRQ value of 254
means to autoprobe. More details can be found in the file
/usr/src/linux/drivers/scsi/README.g_NCR5380.
NCR53C8xx configuration
ncr53c8xx=S
where S is a comma-separated string of items key-
word:value. Recognized keywords are: mpar (master_par-
ity), spar (scsi_parity), disc (disconnection), specf
(special_features), ultra (ultra_scsi), fsn
(force_sync_nego), tags (default_tags), sync
(default_sync), verb (verbose), debug (debug), burst
(burst_max). For the function of the assigned values, see
/usr/src/linux/drivers/scsi/ncr53c8xx.c.
NCR53c406a configuration
ncr53c406a=iobase[,irq[,fastpio]]
Specify irq = 0 for non-interrupt driven mode. Set fast-
pio = 1 for fast pio mode, 0 for slow mode.
IOMEGA PPA3 configuration
ppa=iobase[,speed_high[,speed_low[,nybble]]]
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
/usr/src/linux/drivers/scsi/README.ppa.
Pro Audio Spectrum configuration
The PAS16 uses a NC5380 SCSI chip, and newer models sup-
port jumperless configuration. The boot arg is of the
form:
pas16=iobase,irq
The only difference is that you can specify an IRQ value
of 255, which will tell the driver to work without using
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:
st0x=mem_base,irq
The mem_base value is the value of the memory mapped I/O
region that the card uses. This will usually be one of the
following values: 0xc8000, 0xca000, 0xcc000, 0xce000,
0xdc000, 0xde000.
Trantor T128 configuration
These cards are also based on the NCR5380 chip, and accept
the following options:
t128=mem_base,irq
The valid values for mem_base are as follows: 0xcc000,
0xc8000, 0xdc000, 0xd8000.
UltraStor 14F/34F configuration
The default list of i/o ports to be probed can be changed
by
eata=iobase,iobase,....
WD7000 configuration
wd7000=irq,dma,iobase
Commodore Amiga A2091/590 SCSI controller configuration
wd33c93=S
where S is a comma-separated string of options. Recognized
options are nosync:bitmask, nodma:x, period:ns, discon-
nect:x, debug:x, clock:x, next. For details, see
/usr/src/linux/drivers/scsi/wd33c93.c.
HARD DISKS
IDE Disk/CD-ROM Driver Parameters
The IDE driver accepts a number of parameters, which range
from disk geometry specifications, to support for broken
controller chips. Drive specific options are specified by
using `hdX=' with X in `a'-`h'.
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
geometry so that it would be registered as a valid block
device, and hence useable.
The `hd=nowerr' option
Some drives apparently have the WRERR_STAT bit stuck on
permanently. This enables a work-around for these broken
devices.
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:
hd=cyls,heads,sects
If there are two disks installed, the above is repeated
with the geometry parameters of the second disk.
XT Disk Driver Options (`xd=')
If you are unfortunate enough to be using one of these old
8 bit cards that move data at a whopping 125kB/s then here
is the scoop. If the card is not recognised, you will
have to use a boot arg of the form:
xd=type,irq,iobase,dma_chan
The type value specifies the particular manufacturer of
the card, and are as follows: 0=generic; 1=DTC;
2,3,4=Western Digital, 5,6,7=Seagate; 8=OMTI. The only
difference between multiple types from the same manufac-
turer is the BIOS string used for detection, which is not
used if the type is specified.
The xd_setup() function does no checking on the values,
and assumes that you entered all four values. Don't disap-
point it. Here is an example usage for a WD1002 con-
troller with the BIOS disabled/removed, using the
`default' XT controller parameters:
xd=2,5,0x320,3
Syquest's EZ* removable disks
ez=iobase[,irq[,rep[,nybble]]]
IBM MCA BUS DEVICES
See also /usr/src/linux/Documentation/mca.txt.
PS/2 ESDI hard disks
It is possible to specify the desired geometry at boot
time:
ed=cyls,heads,sectors.
For a ThinkPad-720, add the option
tp720=1.
IBM Microchannel SCSI Subsystem configuration
ibmmcascsi=N
where N is the pun (SCSI ID) of the subsystem.
CD-ROMs (Non-SCSI/ATAPI/IDE)
The Aztech Interface
The syntax for this type of card is:
aztcd=iobase[,magic_number]
If you set the magic_number to 0x79 then the driver will
try and run anyway in the event of an unknown firmware
version. All other values are ignored.
The MicroSolutions `backpack' CDrom
Syntax:
bpcd=iobase
The CDU-31A and CDU-33A Sony Interface
This CD-ROM interface is found on some of the Pro Audio
Spectrum sound cards, and other Sony supplied interface
cards. The syntax is as follows:
cdu31a=iobase,[irq[,is_pas_card]]
Specifying an IRQ value of zero tells the driver that
hardware interrupts aren't supported (as on some PAS
cards). If your card supports interrupts, you should use
them as it cuts down on the CPU usage of the driver.
The is_pas_card should be entered as `PAS' if using a Pro
Audio Spectrum card, and otherwise it should not be speci-
fied at all.
The CDU-535 Sony Interface
The syntax for this CD-ROM interface is:
sonycd535=iobase[,irq]
A zero can be used for the I/O base as a `placeholder' if
one wishes to specify an IRQ value.
The GoldStar Interface
The syntax for this CD-ROM interface is:
gscd=iobase
The ISP16 CD-ROM Interface
Syntax:
isp16=[iobase[,irq[,dma[,type]]]]
(three integers and a string). If the type is given as
`noisp16', the interface will not be configured. Other
recognized types are: `Sanyo", `Sony', `Panasonic' and
`Mitsumi'.
The Mitsumi Standard Interface
The syntax for this CD-ROM interface is:
mcd=iobase,[irq[,wait_value]]
The wait_value is used as an internal timeout value for
people who are having problems with their drive, and may
or may not be implemented depending on a compile time
#define. The Mitsumi FX400 is an IDE/ATAPI CD-ROM player
and does not use the mcd driver.
The Mitsumi XA/MultiSession Interface
This is for the same hardware as above, but the driver has
extended features. Syntax:
mcdx=iobase[,irq]
The Optics Storage Interface
The syntax for this type of card is:
optcd=iobase
The Phillips CM206 Interface
The syntax for this type of card is:
cm206=[iobase][,irq]
The driver assumes numbers between 3 and 11 are IRQ val-
ues, and numbers between 0x300 and 0x370 are I/O ports, so
you can specify one, or both numbers, in any order. It
also accepts `cm206=auto' to enable autoprobing.
The Sanyo Interface
The syntax for this type of card is:
sjcd=iobase[,irq[,dma_channel]]
The SoundBlaster Pro Interface
The syntax for this type of card is:
sbpcd=iobase,type
where type is one of the following (case sensitive)
strings: `SoundBlaster', `LaserMate', or `SPEA'. The I/O
base is that of the CD-ROM interface, and not that of the
sound portion of the card.
ETHERNET DEVICES
Different drivers make use of different parameters, but
they all at least share having an IRQ, an I/O port base
value, and a name. In its most generic form, it looks
something like this:
ether=irq,iobase[,param_1[,...param_8]],name
The first non-numeric argument is taken as the name. The
param_n values (if applicable) usually have different
meanings for each different card/driver. Typical param_n
values are used to specify things like shared memory
address, interface selection, DMA channel and the like.
The most common use of this parameter is to force probing
for a second ethercard, as the default is to only probe
for one. This can be accomplished with a simple:
ether=0,0,eth1
Note that the values of zero for the IRQ and I/O base in
the above example tell the driver(s) to autoprobe.
The Ethernet-HowTo has extensive documentation on using
multiple cards and on the card/driver specific implementa-
tion of the param_n values where used. Interested readers
should refer to the section in that document on their par-
ticular card.
THE FLOPPY DISK DRIVER
There are many floppy driver options, and they are all
listed in README.fd in linux/drivers/block. This informa-
tion is taken directly from that file.
floppy=mask,allowed_drive_mask
Sets the bitmask of allowed drives to mask. By default,
only units 0 and 1 of each floppy controller are allowed.
This is done because certain non-standard hardware (ASUS
PCI motherboards) mess up the keyboard when accessing
units 2 or 3. This option is somewhat obsoleted by the
cmos option.
floppy=all_drives
Sets the bitmask of allowed drives to all drives. Use this
if you have more than two drives connected to a floppy
controller.
floppy=asus_pci
Sets the bitmask to allow only units 0 and 1. (The
default)
floppy=daring
Tells the floppy driver that you have a well behaved
floppy controller. This allows more efficient and
smoother operation, but may fail on certain controllers.
This may speed up certain operations.
floppy=0,daring
Tells the floppy driver that your floppy controller should
be used with caution.
floppy=one_fdc
Tells the floppy driver that you have only floppy con-
troller (default)
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.
floppy=thinkpad
Tells the floppy driver that you have a Thinkpad.
Thinkpads use an inverted convention for the disk change
line.
floppy=0,thinkpad
Tells the floppy driver that you don't have a Thinkpad.
floppy=drive,type,cmos
Sets the cmos type of drive to type. Additionally, this
drive is allowed in the bitmask. This is useful if you
have more than two floppy drives (only two can be
described in the physical cmos), or if your BIOS uses non-
standard CMOS types. Setting the CMOS to 0 for the first
two drives (default) makes the floppy driver read the
physical cmos for those drives.
floppy=unexpected_interrupts
Print a warning message when an unexpected interrupt is
received (default behaviour)
floppy=no_unexpected_interrupts or floppy=L40SX
Don't print a message when an unexpected interrupt is
received. This is needed on IBM L40SX laptops in certain
video modes. (There seems to be an interaction between
video and floppy. The unexpected interrupts only affect
performance, and can safely be ignored.)
THE SOUND DRIVER
The sound driver can also accept boot args to override the
compiled in values. This is not recommended, as it is
rather complex. It is described in the Readme.Linux file,
in linux/drivers/sound. It accepts a boot arg of the form:
sound=device1[,device2[,device3...[,device10]]]
where each deviceN value is of the following format
0xTaaaId and the bytes are used as follows:
T - device type: 1=FM, 2=SB, 3=PAS, 4=GUS, 5=MPU401,
6=SB16, 7=SB16-MPU401
aaa - I/O address in hex.
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.
ISDN DRIVERS
The ICN ISDN driver
Syntax:
icn=iobase,membase,icn_id1,icn_id2
where icn_id1,icn_id2 are two strings used to identify the
card in kernel messages.
The PCBIT ISDN driver
Syntax:
pcbit=membase1,irq1[,membase2,irq2]
where membaseN is the shared memory base of the N'th card,
and irqN is the interrupt setting of the N'th card. The
default is IRQ 5 and membase 0xD0000.
The Teles ISDN driver
Syntax:
teles=iobase,irq,membase,protocol,teles_id
where iobase is the i/o port address of the card, membase
is the shared memory base address of the card, irq is the
interrupt channel the card uses, and teles_id is the
unique ASCII string identifier.
SERIAL PORT DRIVERS
The RISCom/8 Multiport Serial Driver (`riscom8=')
Syntax:
riscom=iobase1[,iobase2[,iobase3[,iobase4]]]
More details can be found in /usr/src/linux/Documenta-
tion/riscom8.txt.
The DigiBoard Driver (`digi=')
If this option is used, it should have precisely six
parameters. Syntax:
digi=status,type,altpin,numports,iobase,membase
The parameters maybe given as integers, or as strings. If
strings are used, then iobase and membase should be given
in hexadecimal. The integer arguments (fewer may be
given) are in order: status (Enable(1) or Disable(0) this
card), type (PC/Xi(0), PC/Xe(1), PC/Xeve(2), PC/Xem(3)),
altpin (Enable(1) or Disable(0) alternate pin arrange-
ment), numports (number of ports on this card), iobase
(I/O Port where card is configured (in HEX)), membase
(base of memory window (in HEX)). Thus, the following two
boot prompt arguments are equivalent:
digi=E,PC/Xi,D,16,200,D0000
digi=1,0,0,16,0x200,851968
More details can be found in /usr/src/linux/Documenta-
tion/digiboard.txt.
The Baycom Serial/Parallel Radio Modem
Syntax:
baycom=iobase,irq,modem
There are precisely 3 parameters; for several cards, give
several `baycom=' commands. The modem parameter is a
string that can take one of the values ser12, ser12*,
par96, par96*. Here the * denotes that software DCD is to
be used, and ser12/par96 chooses between the supported
modem types. For more details, see
/usr/src/linux/drivers/net/README.baycom.
Soundcard radio modem driver
Syntax:
soundmo-
dem=iobase,irq,dma[,dma2[,serio[,pario]]],0,mode
All parameters except the last are integers; the dummy 0
is required because of a bug in the setup code. The mode
parameter is a string with syntax hw:modem, where hw is
one of sbc, wss, wssfdx and modem is one of afsk1200,
fsk9600.
THE LINE PRINTER DRIVER
`lp='
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
Syntax:
wdt=io,irq
MOUSE DRIVERS
`bmouse=irq'
The busmouse driver only accepts one parameter, that being
the hardware IRQ value to be used.
`msmouse=irq'
And precisely the same is true for the msmouse driver.
ATARI mouse setup
atamouse=threshold[,y-threshold]
If only one argument is given, it is used for both
x-threshold and y-threshold. Otherwise, the first
argument is the x-threshold, and the second the y-
threshold. These values must lie between 1 and 20
(inclusive); the default is 2.
VIDEO HARDWARE
`no-scroll'
This option tells the console driver not to use hardware
scroll (where a scroll is effected by moving the screen
origin in video memory, instead of moving the data). It is
required by certain Braille machines.
AUTHORS
Linus Torvalds (and many others)
SEE ALSO
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.