Boot parameters are specified using
a three-part directive that includes the name of the parameter and an
optional list of options, which consists of an equal sign
(=
) followed by a comma-separated list of option
values
No spaces may appear in the directive. As an example, the following directive specifies the identity of the Linux root partition:
root=/dev/hda1
You can specify multiple directives by separating them with a space. For example, the following specifies the identity of the Linux root partition and that the root partition is initially mounted read-only, so that a thorough check of its filesystem can be performed:
root=/dev/hda1 ro
Most directives are interpreted by the kernel, though GRUB
is also capable of processing directives. If you specify a
directive that neither the kernel nor GRUB
understands (assuming you’re using GRUB), a
directive that includes an equal sign is passed to the
init
process as an environment variable. You
learned about environment variables in Chapter 7.
A nonkernel directive that doesn’t include an equal sign is
passed to the init
process. An example of this
usage is specifying the directive single
, which
causes init
to start your system in single-user
mode:
root=/dev/hda1 ro single
Table C-2 describes some of the most popular and
useful boot arguments. These arguments apply to your system as a
whole; in subsequent sections, you’ll learn about other boot
arguments that apply to specific devices or functions. In addition to
boot arguments previously introduced, the table describes the
reserve
argument, which is helpful in avoiding
system memory conflicts.
Table C-2. Selected General Boot Arguments
Table C-3 describes four boot arguments used in working with RAM disks. You won’t likely need to specify any of these, but knowing about them may help you understand boot specifications written by others, including those used by Red Hat Linux.
Table C-3. Selected RAM Disk Arguments
Table C-4 describes the most often used boot arguments related to SCSI host adapters. Table C-5 describes the options used by the SCSI host adapter boot arguments and other boot arguments.
Table C-4. Selected SCSI Host Adapter Arguments
Argument |
Description and options |
---|---|
advansys= |
Advansys SCSI host adapter:
|
aha152x= |
Adaptec aha151x, ada152x, aic6260, aic6360, and SB16-SCSI SCSI host adapters:
|
aha1542= |
Adaptec aha154x SCSI host adapter:
|
aic7xxx= |
Adaptec aha274x, aha284x, aic7xxx SCSI host adapters:
|
AM53C974= |
AMD AM53C974-based SCSI host adapters:
See the file |
buslogic= |
BusLogic SCSI controller Many options are available. See the
|
eata= |
EATA SCSI host adapter:
|
fdomain= |
Future Domain SCSI controller:
|
in2000= |
Always SCSI host adapter The driver for the Always SCSI controller accepts options in somewhat
different format than other drivers. See the |
max-scsi-luns= |
Specifies the maximum number of SCSI logical units to be probed; lets you avoid probing devices that might lock up the SCSI bus. |
ncr5380= |
NCR 5380-based SCSI host adapters:
|
ncr53c400= |
NCR 53c400-based SCSI host adapters:
|
ncr53c406a= |
NCR 53c406a-based SCSI host adapters:
|
pas16= |
Pro Audio Spectrum SCSI host adapter:
|
ppa= |
Iomega parallel port SCSI adapter for ZIP drive:
|
st0x= |
Seagate ST-0x SCSI host adapter:
|
t128= |
Trantor T128 SCSI host adapter:
|
tmc8xx= |
Future Domain TMC-8xx and TMC-950 SCSI host adapters:
|
u14-34f= |
Ultrastor SCSI host adapter:
|
wd7000= |
Western Digital WD7000 SCSI host adapter:
|
[a] Don't include the square brackets in your boot argument; they merely indicate which options must be present. |
For example, from Table C-4 you can learn that Adaptec aha154x SCSI host adapters use a boot argument having the form:
iobase
[,buson
,busoff
[,dmaspeed
]]
Table C-5 helps you understand the form of the
iobase
option and the other italicized options. The
iobase
option, for example, lets you
specify the I/O port associated with the SCSI host adapter. For
example, you can specify a boot argument for an Adaptec aha154x SCSI
host adapter by writing only an iobase
option; the remaining options are optional. However, as indicated by
the square brackets, if you include a
buson
option, you must include a
busoff
option. Similarly, to include the
dmaspeed
option, you must include each of
the other options. Here’s an example of a complete boot
argument:
aha1542=0x300,11,4
Table C-5. Selected Boot Prompt Options
To determine a proper value for options described in Table C-5, you must often know something about the hardware structure of your system. The procedures described in Chapter 2 will help you.
Table C-6 describes the most commonly used boot arguments associated with IDE hard drives and CD-ROM drives. Refer to Table C-7 to determine the form of the italicized options.
Table C-6. Selected IDE Hard Drive Arguments
Table C-7 describes the most common boot arguments for non-IDE CD-ROM drives. Refer to Table C-5 to determine the form of the italicized options.
Table C-7. Selected CD-ROM Arguments
Argument |
Description and options |
---|---|
aztcd= |
Aztech CD-ROM:
[a] |
cdu31a= |
Sony CDU-31A or CDU-33A CD-ROM:
|
sonycd535= |
Sony CDU-535 CD-ROM:
|
gscd= |
Goldstar CD-ROM:
|
isp16= |
ISP16 CD-ROM: [ |
mcd= |
Mitsumi CD-ROM:
|
optcd= |
Optical Storage CD-ROM:
|
cm206= |
Phillips CD206 CD-ROM: [ |
sjcd= |
Sanyo CD-ROM:
|
sbpcd= |
SoundBlaster Pro CD-ROM:
|
[a] Don’t include the square brackets in your boot argument; they merely indicate which options must be present. |
A
few systems require special boot arguments to best use their floppy
drives. Table C-8 describes the most common boot
arguments related to floppy drives. Floppy drives that are not well
behaved may malfunction if you specify the daring
option, which you should use only with care. For additional boot
arguments related to floppy drives, see
/usr/src/linux/Documentation/floppy.txt
.
Table C-8. Selected Floppy Disk Arguments and Options
Two boot arguments provide bus mouse support. The first supports the Microsoft bus mouse:
msmouse=irq
The second supports any non-Microsoft bus mouse:
bmouse=irq
Each argument accepts a single option specifying the IRQ associated with the mouse.
The Linux printer driver claims all
available parallel ports. If you want to access a device other than a
printer attached to a parallel port, you must instruct the printer
driver to reserve only the ports associated with printers. To do so,
use the lp
boot argument, which takes as its
options a list of ports and IRQs used to support printers. For
example, the following boot argument specifies two printers:
lp=0x3bc,0,0x378,7
The first printer is on port 0x3bc
and the second
is on port 0x378
. The first printer uses a special
IRQ-less mode known as polling, so its IRQ is specified as
0
. The second printer uses IRQ
7
.
To disable all printers, specify lp=0
.
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