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1 | .\" Copyright (c) 1995,1997 Paul Gortmaker and Andries Brouwer |
2 | .\" | |
1dd72f9c | 3 | .\" %%%LICENSE_START(GPLv2+_DOC_FULL) |
fea681da MK |
4 | .\" This is free documentation; you can redistribute it and/or |
5 | .\" modify it under the terms of the GNU General Public License as | |
6 | .\" published by the Free Software Foundation; either version 2 of | |
7 | .\" the License, or (at your option) any later version. | |
8 | .\" | |
9 | .\" The GNU General Public License's references to "object code" | |
10 | .\" and "executables" are to be interpreted as the output of any | |
11 | .\" document formatting or typesetting system, including | |
12 | .\" intermediate and printed output. | |
13 | .\" | |
14 | .\" This manual is distributed in the hope that it will be useful, | |
15 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
17 | .\" GNU General Public License for more details. | |
18 | .\" | |
19 | .\" You should have received a copy of the GNU General Public | |
c715f741 MK |
20 | .\" License along with this manual; if not, see |
21 | .\" <http://www.gnu.org/licenses/>. | |
6a8d8745 | 22 | .\" %%%LICENSE_END |
fea681da MK |
23 | .\" |
24 | .\" This man page written 950814 by aeb, based on Paul Gortmaker's HOWTO | |
25 | .\" (dated v1.0.1, 15/08/95). | |
26 | .\" Major update, aeb, 970114. | |
27 | .\" | |
ad5b45ab | 28 | .TH BOOTPARAM 7 2014-06-13 "Linux" "Linux Programmer's Manual" |
fea681da | 29 | .SH NAME |
f68512e9 | 30 | bootparam \- introduction to boot time parameters of the Linux kernel |
fea681da | 31 | .SH DESCRIPTION |
76c44d83 | 32 | The Linux kernel accepts certain 'command-line options' or 'boot time |
c13182ef MK |
33 | parameters' at the moment it is started. |
34 | In general this is used to | |
fea681da MK |
35 | supply the kernel with information about hardware parameters that |
36 | the kernel would not be able to determine on its own, or to avoid/override | |
37 | the values that the kernel would otherwise detect. | |
38 | ||
ad8fe082 | 39 | When the kernel is booted directly by the BIOS, |
fea681da MK |
40 | you have no opportunity to specify any parameters. |
41 | So, in order to take advantage of this possibility you have to | |
122a101a | 42 | use a boot loader that is able to pass parameters, such as GRUB. |
fea681da | 43 | |
18299dfc MK |
44 | .\" The LILO program (LInux LOader) written by Werner Almesberger is the |
45 | .\" most commonly used. | |
46 | .\" It has the ability to boot various kernels, and | |
47 | .\" stores the configuration information in a plain text file. | |
48 | .\" (See | |
49 | .\" .BR lilo (8) | |
50 | .\" and | |
51 | .\" .BR lilo.conf (5).) | |
52 | .\" LILO can boot DOS, OS/2, Linux, FreeBSD, UnixWare, etc., and is quite flexible. | |
51700fd7 | 53 | .\" |
18299dfc MK |
54 | .\" The other commonly used Linux loader is 'LoadLin', which is a DOS |
55 | .\" program that has the capability to launch a Linux kernel from the DOS | |
56 | .\" prompt (with boot-args) assuming that certain resources are available. | |
57 | .\" This is good for people that want to launch Linux from DOS. | |
51700fd7 | 58 | .\" |
18299dfc MK |
59 | .\" It is also very useful if you have certain hardware which relies on |
60 | .\" the supplied DOS driver to put the hardware into a known state. | |
61 | .\" A common example is 'SoundBlaster Compatible' sound cards that require | |
62 | .\" the DOS driver to twiddle a few mystical registers to put the card | |
63 | .\" into a SB compatible mode. | |
64 | .\" Booting DOS with the supplied driver, and | |
65 | .\" then loading Linux from the DOS prompt with loadlin avoids the reset | |
66 | .\" of the card that happens if one rebooted instead. | |
73d8cece | 67 | .SS The argument list |
fea681da | 68 | The kernel command line is parsed into a list of strings |
c13182ef | 69 | (boot arguments) separated by spaces. |
36267a51 | 70 | Most of the boot arguments have the form: |
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71 | |
72 | .in +4n | |
73 | .nf | |
fea681da | 74 | name[=value_1][,value_2]...[,value_10] |
77bda21c MK |
75 | .fi |
76 | .in | |
fea681da | 77 | .LP |
40dedbfe | 78 | where 'name' is a unique keyword that is used to identify what part of |
fea681da | 79 | the kernel the associated values (if any) are to be given to. |
33a0ccb2 | 80 | Note the limit of 10 is real, as the present code handles only 10 comma |
c13182ef | 81 | separated parameters per keyword. |
3b777aff | 82 | (However, you can reuse the same |
fea681da MK |
83 | keyword with up to an additional 10 parameters in unusually |
84 | complicated situations, assuming the setup function supports it.) | |
85 | ||
e57fca5a MK |
86 | Most of the sorting is coded in the kernel source file |
87 | .IR init/main.c . | |
c13182ef | 88 | First, the kernel |
40dedbfe | 89 | checks to see if the argument is any of the special arguments 'root=', |
25715c96 | 90 | \&'nfsroot=', 'nfsaddrs=', 'ro', 'rw', 'debug' or 'init'. |
c13182ef | 91 | The meaning of these special arguments is described below. |
fea681da | 92 | |
b46a2f4a MK |
93 | Then it walks a list of setup functions |
94 | to see if the specified argument string (such as 'foo') has | |
40dedbfe | 95 | been associated with a setup function ('foo_setup()') for a particular |
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96 | device or part of the kernel. |
97 | If you passed the kernel the line | |
fea681da | 98 | foo=3,4,5,6 then the kernel would search the bootsetups array to see |
40dedbfe | 99 | if 'foo' was registered. |
c13182ef | 100 | If it was, then it would call the setup |
40dedbfe | 101 | function associated with 'foo' (foo_setup()) and hand it the arguments |
31df5734 | 102 | 3, 4, 5, and 6 as given on the kernel command line. |
fea681da | 103 | |
40dedbfe | 104 | Anything of the form 'foo=bar' that is not accepted as a setup function |
fea681da | 105 | as described above is then interpreted as an environment variable to |
c13182ef | 106 | be set. |
40dedbfe | 107 | A (useless?) example would be to use 'TERM=vt100' as a boot |
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108 | argument. |
109 | ||
110 | Any remaining arguments that were not picked up by the kernel and were | |
f184a1c3 MK |
111 | not interpreted as environment variables are then passed onto PID 1, |
112 | which is usually the | |
1aedd258 MK |
113 | .BR init (1) |
114 | program. | |
c13182ef | 115 | The most common argument that |
1aedd258 MK |
116 | is passed to the |
117 | .I init | |
118 | process is the word 'single' which instructs it | |
fea681da | 119 | to boot the computer in single user mode, and not launch all the usual |
c13182ef | 120 | daemons. |
1aedd258 MK |
121 | Check the manual page for the version of |
122 | .BR init (1) | |
123 | installed on | |
fea681da | 124 | your system to see what arguments it accepts. |
76c637e1 | 125 | .SS General non-device-specific boot arguments |
bebbbd1f | 126 | .TP |
40dedbfe | 127 | .B "'init=...'" |
fea681da MK |
128 | This sets the initial command to be executed by the kernel. |
129 | If this is not set, or cannot be found, the kernel will try | |
5ce89119 MK |
130 | .IR /sbin/init , |
131 | then | |
fea681da MK |
132 | .IR /etc/init , |
133 | then | |
134 | .IR /bin/init , | |
135 | then | |
0daa9e92 | 136 | .I /bin/sh |
fea681da | 137 | and panic if all of this fails. |
bebbbd1f | 138 | .TP |
40dedbfe | 139 | .B "'nfsaddrs=...'" |
32ae2e17 | 140 | This sets the NFS boot address to the given string. |
fea681da | 141 | This boot address is used in case of a net boot. |
bebbbd1f | 142 | .TP |
40dedbfe | 143 | .B "'nfsroot=...'" |
5d6aa84a | 144 | This sets the NFS root name to the given string. |
c13182ef | 145 | If this string |
fea681da | 146 | does not begin with '/' or ',' or a digit, then it is prefixed by |
25715c96 | 147 | \&'/tftpboot/'. |
c13182ef | 148 | This root name is used in case of a net boot. |
bebbbd1f | 149 | .TP |
40dedbfe MK |
150 | .B "'no387'" |
151 | (Only when | |
152 | .B CONFIG_BUGi386 | |
153 | is defined.) | |
fea681da | 154 | Some i387 coprocessor chips have bugs that show up when used in 32 bit |
c13182ef MK |
155 | protected mode. |
156 | For example, some of the early ULSI-387 chips would | |
c45bd688 | 157 | cause solid lockups while performing floating-point calculations. |
77bda21c | 158 | Using the 'no387' boot argument causes Linux to ignore the maths |
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159 | coprocessor even if you have one. |
160 | Of course you must then have your | |
fea681da | 161 | kernel compiled with math emulation support! |
bebbbd1f | 162 | .TP |
40dedbfe MK |
163 | .B "'no-hlt'" |
164 | (Only when | |
165 | .B CONFIG_BUGi386 | |
166 | is defined.) | |
167 | Some of the early i486DX-100 chips have a problem with the 'hlt' | |
fea681da | 168 | instruction, in that they can't reliably return to operating mode |
c13182ef | 169 | after this instruction is used. |
40dedbfe | 170 | Using the 'no-hlt' instruction tells |
fea681da | 171 | Linux to just run an infinite loop when there is nothing else to do, |
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172 | and to not halt the CPU. |
173 | This allows people with these broken chips | |
fea681da | 174 | to use Linux. |
bebbbd1f | 175 | .TP |
40dedbfe | 176 | .B "'root=...'" |
fea681da | 177 | This argument tells the kernel what device is to be used as the root |
9ee4a2b6 | 178 | filesystem while booting. |
c13182ef | 179 | The default of this setting is determined |
fea681da | 180 | at compile time, and usually is the value of the root device of the |
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181 | system that the kernel was built on. |
182 | To override this value, and | |
fea681da | 183 | select the second floppy drive as the root device, one would |
6387216b | 184 | use 'root=/dev/fd1'. |
fea681da MK |
185 | |
186 | The root device can be specified symbolically or numerically. | |
e57fca5a | 187 | A symbolic specification has the form |
21e79503 | 188 | .IR /dev/XXYN , |
e57fca5a | 189 | where XX designates |
af26ce0f MK |
190 | the device type (e.g., 'hd' for ST-506 compatible hard disk, with Y in |
191 | \&'a'-'d'; 'sd' for SCSI compatible disk, with Y in 'a'-'e'), | |
192 | Y the driver letter or | |
193 | number, and N the number (in decimal) of the partition on this device. | |
fea681da MK |
194 | |
195 | Note that this has nothing to do with the designation of these | |
9ee4a2b6 | 196 | devices on your filesystem. |
40dedbfe | 197 | The '/dev/' part is purely conventional. |
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198 | |
199 | The more awkward and less portable numeric specification of the above | |
c13182ef | 200 | possible root devices in major/minor format is also accepted. |
59dc509c | 201 | (For example, |
e57fca5a MK |
202 | .I /dev/sda3 |
203 | is major 8, minor 3, so you could use 'root=0x803' as an | |
fea681da | 204 | alternative.) |
bebbbd1f | 205 | .TP |
1c137827 | 206 | .BR "'rootdelay='" |
91085d85 | 207 | This parameter sets the delay (in seconds) to pause before attempting |
1c137827 PG |
208 | to mount the root filesystem. |
209 | .TP | |
210 | .BR "'rootflags=...'" | |
ffe8d0b1 MK |
211 | This parameter sets the mount option string for the root filesystem |
212 | (see also | |
1c137827 PG |
213 | .BR fstab (5)). |
214 | .TP | |
6c8adf48 JLDL |
215 | .BR "'rootfstype=...'" |
216 | The 'rootfstype' option tells the kernel to mount the root filesystem as | |
217 | if it where of the type specified. | |
218 | This can be useful (for example) to | |
219 | mount an ext3 filesystem as ext2 and then remove the journal in the root | |
220 | filesystem, in fact reverting its format from ext3 to ext2 without the | |
221 | need to boot the box from alternate media. | |
222 | .TP | |
40dedbfe | 223 | .BR 'ro' " and " 'rw' |
9ee4a2b6 MK |
224 | The 'ro' option tells the kernel to mount the root filesystem |
225 | as 'read-only' so that filesystem consistency check programs (fsck) | |
226 | can do their work on a quiescent filesystem. | |
c13182ef | 227 | No processes can |
9ee4a2b6 | 228 | write to files on the filesystem in question until it is 'remounted' |
40dedbfe | 229 | as read/write capable, for example, by 'mount \-w \-n \-o remount /'. |
fea681da MK |
230 | (See also |
231 | .BR mount (8).) | |
232 | ||
9ee4a2b6 | 233 | The 'rw' option tells the kernel to mount the root filesystem read/write. |
fea681da MK |
234 | This is the default. |
235 | ||
bebbbd1f | 236 | .TP |
d11f367d AR |
237 | .B "'resume=...'" |
238 | This tells the kernel the location of the suspend-to-disk data that you want the machine to resume from after hibernation. | |
063692c0 MK |
239 | Usually, it is the same as your swap partition or file. |
240 | Example: | |
77bda21c MK |
241 | |
242 | .in +4n | |
243 | .nf | |
244 | resume=/dev/hda2 | |
245 | .fi | |
246 | .in | |
d11f367d | 247 | .TP |
40dedbfe | 248 | .B "'reserve=...'" |
c13182ef MK |
249 | This is used to protect I/O port regions from probes. |
250 | The form of the command is: | |
77bda21c MK |
251 | |
252 | .in +4n | |
253 | .nf | |
fea681da | 254 | .BI reserve= iobase,extent[,iobase,extent]... |
77bda21c MK |
255 | .fi |
256 | .in | |
bebbbd1f | 257 | .sp |
fea681da | 258 | In some machines it may be necessary to prevent device drivers from |
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259 | checking for devices (auto-probing) in a specific region. |
260 | This may be | |
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261 | because of hardware that reacts badly to the probing, or hardware |
262 | that would be mistakenly identified, or merely | |
263 | hardware you don't want the kernel to initialize. | |
264 | ||
265 | The reserve boot-time argument specifies an I/O port region that | |
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266 | shouldn't be probed. |
267 | A device driver will not probe a reserved region, | |
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268 | unless another boot argument explicitly specifies that it do so. |
269 | ||
270 | For example, the boot line | |
77bda21c MK |
271 | |
272 | .in +4n | |
273 | .nf | |
fea681da | 274 | reserve=0x300,32 blah=0x300 |
77bda21c MK |
275 | .fi |
276 | .in | |
bebbbd1f | 277 | .IP |
40dedbfe | 278 | keeps all device drivers except the driver for 'blah' from probing |
94e9d9fe | 279 | 0x300\-0x31f. |
bebbbd1f | 280 | .TP |
40dedbfe | 281 | .B "'panic=N'" |
b9aee8fe | 282 | By default, the kernel will not reboot after a panic, but this option |
f7ceac86 | 283 | will cause a kernel reboot after N seconds (if N is greater than zero). |
77bda21c MK |
284 | This panic timeout can also be set by |
285 | ||
286 | .in +4n | |
287 | .nf | |
1322e836 | 288 | echo N > /proc/sys/kernel/panic |
77bda21c MK |
289 | .fi |
290 | .in | |
bebbbd1f | 291 | .TP |
40dedbfe | 292 | .B "'reboot=[warm|cold][,[bios|hard]]'" |
66d2031a | 293 | Since Linux 2.0.22, a reboot is by default a cold reboot. |
40dedbfe | 294 | One asks for the old default with 'reboot=warm'. |
fea681da MK |
295 | (A cold reboot may be required to reset certain hardware, |
296 | but might destroy not yet written data in a disk cache. | |
297 | A warm reboot may be faster.) | |
b9aee8fe | 298 | By default, a reboot is hard, by asking the keyboard controller |
fea681da | 299 | to pulse the reset line low, but there is at least one type |
c13182ef | 300 | of motherboard where that doesn't work. |
40dedbfe | 301 | The option 'reboot=bios' will |
fea681da | 302 | instead jump through the BIOS. |
bebbbd1f | 303 | .TP |
40dedbfe | 304 | .BR 'nosmp' " and " 'maxcpus=N' |
fea681da | 305 | (Only when __SMP__ is defined.) |
40dedbfe MK |
306 | A command-line option of 'nosmp' or 'maxcpus=0' will disable SMP |
307 | activation entirely; an option 'maxcpus=N' limits the maximum number | |
fea681da | 308 | of CPUs activated in SMP mode to N. |
73d8cece | 309 | .SS Boot arguments for use by kernel developers |
bebbbd1f | 310 | .TP |
40dedbfe | 311 | .B "'debug'" |
fea681da | 312 | Kernel messages are handed off to the kernel log daemon klogd so that they |
c13182ef MK |
313 | may be logged to disk. |
314 | Messages with a priority above | |
fea681da | 315 | .I console_loglevel |
c13182ef | 316 | are also printed on the console. |
e57fca5a MK |
317 | (For these levels, see |
318 | .IR <linux/kernel.h> .) | |
b9aee8fe | 319 | By default, this variable is set to log anything more important than |
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320 | debug messages. |
321 | This boot argument will cause the kernel to also | |
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322 | print the messages of DEBUG priority. |
323 | The console loglevel can also be set at run time via an option | |
c13182ef MK |
324 | to klogd. |
325 | See | |
fea681da | 326 | .BR klogd (8). |
bebbbd1f | 327 | .TP |
40dedbfe | 328 | .B "'profile=N'" |
fea681da MK |
329 | It is possible to enable a kernel profiling function, |
330 | if one wishes to find out where the kernel is spending its CPU cycles. | |
331 | Profiling is enabled by setting the variable | |
332 | .I prof_shift | |
c7094399 | 333 | to a nonzero value. |
40dedbfe MK |
334 | This is done either by specifying |
335 | .B CONFIG_PROFILE | |
336 | at compile time, or by giving the 'profile=' option. | |
fea681da MK |
337 | Now the value that |
338 | .I prof_shift | |
40dedbfe MK |
339 | gets will be N, when given, or |
340 | .BR CONFIG_PROFILE_SHIFT , | |
341 | when that is given, or 2, the default. | |
c13182ef | 342 | The significance of this variable is that it |
fea681da MK |
343 | gives the granularity of the profiling: each clock tick, if the |
344 | system was executing kernel code, a counter is incremented: | |
77bda21c MK |
345 | |
346 | .in +4n | |
347 | .nf | |
fea681da | 348 | profile[address >> prof_shift]++; |
77bda21c MK |
349 | .fi |
350 | .in | |
bebbbd1f | 351 | .sp |
fea681da MK |
352 | The raw profiling information can be read from |
353 | .IR /proc/profile . | |
354 | Probably you'll want to use a tool such as readprofile.c to digest it. | |
355 | Writing to | |
356 | .I /proc/profile | |
357 | will clear the counters. | |
bebbbd1f | 358 | .TP |
73d8cece | 359 | .SS Boot arguments for ramdisk use |
40dedbfe MK |
360 | (Only if the kernel was compiled with |
361 | .BR CONFIG_BLK_DEV_RAM .) | |
5503c85e MK |
362 | In general it is a bad idea to use a ramdisk under Linux\(emthe |
363 | system will use available memory more efficiently itself. | |
1aa04a53 | 364 | But while booting, |
fea681da | 365 | it is often useful to load the floppy contents into a |
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366 | ramdisk. |
367 | One might also have a system in which first | |
9ee4a2b6 | 368 | some modules (for filesystem or hardware) must be loaded |
fea681da MK |
369 | before the main disk can be accessed. |
370 | ||
371 | In Linux 1.3.48, ramdisk handling was changed drastically. | |
372 | Earlier, the memory was allocated statically, and there was | |
40dedbfe | 373 | a 'ramdisk=N' parameter to tell its size. |
421405f9 | 374 | (This could also be set in the kernel image at compile time.) |
fea681da | 375 | These days ram disks use the buffer cache, and grow dynamically. |
1aa04a53 | 376 | For a lot of information on the current ramdisk |
22367af2 | 377 | setup, see the kernel source file |
51700fd7 | 378 | .IR Documentation/blockdev/ramdisk.txt |
e57fca5a MK |
379 | .RI ( Documentation/ramdisk.txt |
380 | in older kernels). | |
fea681da MK |
381 | |
382 | There are four parameters, two boolean and two integral. | |
bebbbd1f | 383 | .TP |
40dedbfe | 384 | .B "'load_ramdisk=N'" |
c13182ef MK |
385 | If N=1, do load a ramdisk. |
386 | If N=0, do not load a ramdisk. | |
fea681da | 387 | (This is the default.) |
bebbbd1f | 388 | .TP |
40dedbfe | 389 | .B "'prompt_ramdisk=N'" |
c13182ef MK |
390 | If N=1, do prompt for insertion of the floppy. |
391 | (This is the default.) | |
392 | If N=0, do not prompt. | |
393 | (Thus, this parameter is never needed.) | |
bebbbd1f | 394 | .TP |
40dedbfe | 395 | .BR 'ramdisk_size=N' " or (obsolete) " 'ramdisk=N' |
c13182ef MK |
396 | Set the maximal size of the ramdisk(s) to N kB. |
397 | The default is 4096 (4 MB). | |
bebbbd1f | 398 | .TP |
40dedbfe | 399 | .B "'ramdisk_start=N'" |
fea681da MK |
400 | Sets the starting block number (the offset on the floppy where |
401 | the ramdisk starts) to N. | |
402 | This is needed in case the ramdisk follows a kernel image. | |
bebbbd1f | 403 | .TP |
40dedbfe MK |
404 | .B "'noinitrd'" |
405 | (Only if the kernel was compiled with | |
406 | .B CONFIG_BLK_DEV_RAM | |
407 | and | |
408 | .BR CONFIG_BLK_DEV_INITRD .) | |
fea681da MK |
409 | These days it is possible to compile the kernel to use initrd. |
410 | When this feature is enabled, the boot process will load the kernel | |
411 | and an initial ramdisk; then the kernel converts initrd into | |
412 | a "normal" ramdisk, which is mounted read-write as root device; | |
e57fca5a MK |
413 | then |
414 | .I /linuxrc | |
9ee4a2b6 MK |
415 | is executed; afterward the "real" root filesystem is mounted, |
416 | and the initrd filesystem is moved over to | |
e57fca5a MK |
417 | .IR /initrd ; |
418 | finally | |
419 | the usual boot sequence (e.g., invocation of | |
420 | .IR /sbin/init ) | |
421 | is performed. | |
fea681da | 422 | |
e57fca5a MK |
423 | For a detailed description of the initrd feature, see the kernel source file |
424 | .IR Documentation/initrd.txt . | |
fea681da | 425 | |
40dedbfe | 426 | The 'noinitrd' option tells the kernel that although it was compiled for |
fea681da MK |
427 | operation with initrd, it should not go through the above steps, but |
428 | leave the initrd data under | |
429 | .IR /dev/initrd . | |
4d9b6984 | 430 | (This device can be used only once: the data is freed as soon as |
fea681da MK |
431 | the last process that used it has closed |
432 | .IR /dev/initrd .) | |
73d8cece | 433 | .SS Boot arguments for SCSI devices |
fea681da MK |
434 | General notation for this section: |
435 | ||
436 | .I iobase | |
c13182ef MK |
437 | -- the first I/O port that the SCSI host occupies. |
438 | These are specified in hexadecimal notation, | |
439 | and usually lie in the range from 0x200 to 0x3ff. | |
fea681da MK |
440 | |
441 | .I irq | |
442 | -- the hardware interrupt that the card is configured to use. | |
443 | Valid values will be dependent on the card in question, but will | |
c13182ef MK |
444 | usually be 5, 7, 9, 10, 11, 12, and 15. |
445 | The other values are usually | |
fea681da | 446 | used for common peripherals like IDE hard disks, floppies, serial |
fb3969cd | 447 | ports, and so on. |
fea681da MK |
448 | |
449 | .I scsi-id | |
450 | -- the ID that the host adapter uses to identify itself on the | |
c13182ef MK |
451 | SCSI bus. |
452 | Only some host adapters allow you to change this value, as | |
453 | most have it permanently specified internally. | |
454 | The usual default value | |
fea681da MK |
455 | is 7, but the Seagate and Future Domain TMC-950 boards use 6. |
456 | ||
457 | .I parity | |
458 | -- whether the SCSI host adapter expects the attached devices | |
c13182ef MK |
459 | to supply a parity value with all information exchanges. |
460 | Specifying a one indicates parity checking is enabled, | |
461 | and a zero disables parity checking. | |
462 | Again, not all adapters will support selection of parity | |
d9bfdb9c | 463 | behavior as a boot argument. |
bebbbd1f | 464 | .TP |
40dedbfe | 465 | .B "'max_scsi_luns=...'" |
310672d6 | 466 | A SCSI device can have a number of 'subdevices' contained within |
c13182ef MK |
467 | itself. |
468 | The most common example is one of the new SCSI CD-ROMs that | |
469 | handle more than one disk at a time. | |
470 | Each CD is addressed as a | |
25715c96 | 471 | \&'Logical Unit Number' (LUN) of that particular device. |
c13182ef | 472 | But most |
fea681da MK |
473 | devices, such as hard disks, tape drives and such are only one device, |
474 | and will be assigned to LUN zero. | |
475 | ||
476 | Some poorly designed SCSI devices cannot handle being probed for | |
c13182ef | 477 | LUNs not equal to zero. |
29aceda4 | 478 | Therefore, if the compile-time flag |
40dedbfe | 479 | .B CONFIG_SCSI_MULTI_LUN |
e0a06014 | 480 | is not set, newer kernels will by default probe only LUN zero. |
fea681da MK |
481 | |
482 | To specify the number of probed LUNs at boot, one enters | |
25715c96 | 483 | \&'max_scsi_luns=n' as a boot arg, where n is a number between one and |
c13182ef MK |
484 | eight. |
485 | To avoid problems as described above, one would use n=1 to | |
fea681da | 486 | avoid upsetting such broken devices. |
bebbbd1f MK |
487 | .TP |
488 | .B "SCSI tape configuration" | |
fea681da MK |
489 | Some boot time configuration of the SCSI tape driver can be achieved |
490 | by using the following: | |
77bda21c MK |
491 | |
492 | .in +4n | |
493 | .nf | |
fea681da | 494 | .BI st= buf_size[,write_threshold[,max_bufs]] |
77bda21c MK |
495 | .fi |
496 | .in | |
bebbbd1f | 497 | .sp |
c13182ef MK |
498 | The first two numbers are specified in units of kB. |
499 | The default | |
fea681da MK |
500 | .I buf_size |
501 | is 32kB, and the maximum size that can be specified is a | |
c13182ef MK |
502 | ridiculous 16384kB. |
503 | The | |
fea681da MK |
504 | .I write_threshold |
505 | is the value at which the buffer is committed to tape, with a | |
c13182ef MK |
506 | default value of 30kB. |
507 | The maximum number of buffers varies | |
fea681da MK |
508 | with the number of drives detected, and has a default of two. |
509 | An example usage would be: | |
77bda21c MK |
510 | |
511 | .in +4n | |
512 | .nf | |
fea681da | 513 | st=32,30,2 |
77bda21c MK |
514 | .fi |
515 | .in | |
bebbbd1f | 516 | .IP |
4568d084 MK |
517 | Full details can be found in the file |
518 | .I Documentation/scsi/st.txt | |
519 | (or | |
520 | .I drivers/scsi/README.st | |
66a9882e | 521 | for older kernels) in the Linux kernel source. |
73d8cece | 522 | .SS Hard disks |
bebbbd1f MK |
523 | .TP |
524 | .B "IDE Disk/CD-ROM Driver Parameters" | |
fea681da | 525 | The IDE driver accepts a number of parameters, which range from disk |
c13182ef | 526 | geometry specifications, to support for broken controller chips. |
e2badfdf | 527 | Drive-specific options are specified by using 'hdX=' with X in 'a'-'h'. |
fea681da | 528 | |
e2badfdf MK |
529 | Non-drive-specific options are specified with the prefix 'hd='. |
530 | Note that using a drive-specific prefix for a non-drive-specific option | |
fea681da MK |
531 | will still work, and the option will just be applied as expected. |
532 | ||
40dedbfe | 533 | Also note that 'hd=' can be used to refer to the next unspecified |
c13182ef MK |
534 | drive in the (a, ..., h) sequence. |
535 | For the following discussions, | |
40dedbfe | 536 | the 'hd=' option will be cited for brevity. |
c13182ef | 537 | See the file |
0eb9025a | 538 | .I Documentation/ide/ide.txt |
4568d084 | 539 | (or |
0eb9025a MK |
540 | .I Documentation/ide.txt |
541 | .\" Linux 2.0, 2.2, 2.4 | |
542 | in older kernels, or | |
4568d084 | 543 | .I drivers/block/README.ide |
0eb9025a | 544 | in ancient kernels) in the Linux kernel source for more details. |
bebbbd1f | 545 | .TP |
40dedbfe | 546 | .B "The 'hd=cyls,heads,sects[,wpcom[,irq]]' options" |
fea681da | 547 | These options are used to specify the physical geometry of the disk. |
c13182ef MK |
548 | Only the first three values are required. |
549 | The cylinder/head/sectors | |
550 | values will be those used by fdisk. | |
551 | The write precompensation value | |
552 | is ignored for IDE disks. | |
553 | The IRQ value specified will be the IRQ | |
fea681da | 554 | used for the interface that the drive resides on, and is not really a |
e2badfdf | 555 | drive-specific parameter. |
bebbbd1f | 556 | .TP |
40dedbfe | 557 | .B "The 'hd=serialize' option" |
fea681da MK |
558 | The dual IDE interface CMD-640 chip is broken as designed such that |
559 | when drives on the secondary interface are used at the same time as | |
c13182ef MK |
560 | drives on the primary interface, it will corrupt your data. |
561 | Using this | |
fea681da MK |
562 | option tells the driver to make sure that both interfaces are never |
563 | used at the same time. | |
bebbbd1f | 564 | .TP |
40dedbfe | 565 | .B "The 'hd=noprobe' option" |
c13182ef MK |
566 | Do not probe for this drive. |
567 | For example, | |
77bda21c MK |
568 | |
569 | .in +4n | |
570 | .nf | |
fea681da | 571 | hdb=noprobe hdb=1166,7,17 |
77bda21c MK |
572 | .fi |
573 | .in | |
bebbbd1f | 574 | .IP |
fea681da MK |
575 | would disable the probe, but still specify the drive geometry so |
576 | that it would be registered as a valid block device, and hence | |
577 | usable. | |
bebbbd1f | 578 | .TP |
40dedbfe MK |
579 | .B "The 'hd=nowerr' option" |
580 | Some drives apparently have the | |
581 | .B WRERR_STAT | |
582 | bit stuck on permanently. | |
fea681da | 583 | This enables a work-around for these broken devices. |
bebbbd1f | 584 | .TP |
40dedbfe | 585 | .B "The 'hd=cdrom' option" |
fea681da | 586 | This tells the IDE driver that there is an ATAPI compatible CD-ROM |
c13182ef MK |
587 | attached in place of a normal IDE hard disk. |
588 | In most cases the CD-ROM | |
fea681da | 589 | is identified automatically, but if it isn't then this may help. |
bebbbd1f | 590 | .TP |
40dedbfe | 591 | .B "Standard ST-506 Disk Driver Options ('hd=')" |
fea681da | 592 | The standard disk driver can accept geometry arguments for the disks |
c13182ef | 593 | similar to the IDE driver. |
33a0ccb2 | 594 | Note however that it expects only three |
c13182ef | 595 | values (C/H/S); any more or any less and it will silently ignore you. |
33a0ccb2 | 596 | Also, it accepts only 'hd=' as an argument, that is, 'hda=' |
c13182ef MK |
597 | and so on are not valid here. |
598 | The format is as follows: | |
77bda21c MK |
599 | |
600 | .in +4n | |
601 | .nf | |
fea681da | 602 | hd=cyls,heads,sects |
77bda21c MK |
603 | .fi |
604 | .in | |
bebbbd1f | 605 | .IP |
fea681da MK |
606 | If there are two disks installed, the above is repeated with the |
607 | geometry parameters of the second disk. | |
73d8cece | 608 | .SS Ethernet devices |
fea681da | 609 | Different drivers make use of different parameters, but they all at |
c13182ef MK |
610 | least share having an IRQ, an I/O port base value, and a name. |
611 | In its most generic form, it looks something like this: | |
77bda21c MK |
612 | |
613 | .in +4n | |
614 | .nf | |
fea681da | 615 | ether=irq,iobase[,param_1[,...param_8]],name |
77bda21c MK |
616 | .fi |
617 | .in | |
618 | ||
80c9146c | 619 | The first nonnumeric argument is taken as the name. |
c13182ef MK |
620 | The param_n values (if applicable) usually have different meanings for each |
621 | different card/driver. | |
622 | Typical param_n values are used to specify | |
fea681da MK |
623 | things like shared memory address, interface selection, DMA channel |
624 | and the like. | |
625 | ||
626 | The most common use of this parameter is to force probing for a second | |
33a0ccb2 | 627 | ethercard, as the default is to probe only for one. |
c13182ef | 628 | This can be accomplished with a simple: |
77bda21c MK |
629 | |
630 | .in +4n | |
631 | .nf | |
fea681da | 632 | ether=0,0,eth1 |
77bda21c MK |
633 | .fi |
634 | .in | |
635 | ||
fea681da MK |
636 | Note that the values of zero for the IRQ and I/O base in the above |
637 | example tell the driver(s) to autoprobe. | |
638 | ||
639 | The Ethernet-HowTo has extensive documentation on using multiple | |
e2badfdf | 640 | cards and on the card/driver-specific implementation |
c13182ef MK |
641 | of the param_n values where used. |
642 | Interested readers should refer to | |
fea681da | 643 | the section in that document on their particular card. |
73d8cece | 644 | .SS The floppy disk driver |
fea681da | 645 | There are many floppy driver options, and they are all listed in |
cb6cb860 | 646 | .I Documentation/blockdev/floppy.txt |
4568d084 | 647 | (or |
cb6cb860 MK |
648 | .I Documentation/floppy.txt |
649 | in oplder kernels, or | |
4568d084 | 650 | .I drivers/block/README.fd |
cb6cb860 | 651 | for ancient kernels) in the Linux kernel source. |
3dd80946 | 652 | See that file for the details. |
73d8cece | 653 | .SS The sound driver |
92b451e5 | 654 | The sound driver can also accept boot arguments to override the compiled-in |
c13182ef MK |
655 | values. |
656 | This is not recommended, as it is rather complex. | |
66a9882e | 657 | It is described in the Linux kernel source file |
ef505ff0 MK |
658 | .IR Documentation/sound/oss/README.OSS |
659 | .RI ( drivers/sound/Readme.linux | |
660 | in older kernel versions). | |
c13182ef | 661 | It accepts |
77bda21c MK |
662 | a boot argument of the form: |
663 | ||
664 | .in +4n | |
665 | .nf | |
fea681da | 666 | sound=device1[,device2[,device3...[,device10]]] |
77bda21c MK |
667 | .fi |
668 | .in | |
bebbbd1f | 669 | .IP |
fea681da MK |
670 | where each deviceN value is of the following format 0xTaaaId and the |
671 | bytes are used as follows: | |
672 | ||
4d9b6984 | 673 | T \- device type: 1=FM, 2=SB, 3=PAS, 4=GUS, 5=MPU401, 6=SB16, |
fea681da MK |
674 | 7=SB16-MPU401 |
675 | ||
4d9b6984 | 676 | aaa \- I/O address in hex. |
fea681da | 677 | |
4d9b6984 | 678 | I \- interrupt line in hex (i.e 10=a, 11=b, ...) |
fea681da | 679 | |
4d9b6984 | 680 | d \- DMA channel. |
fea681da | 681 | |
92b451e5 | 682 | As you can see, it gets pretty messy, and you are better off to compile |
c13182ef | 683 | in your own personal values as recommended. |
77bda21c | 684 | Using a boot argument of |
25715c96 | 685 | \&'sound=0' will disable the sound driver entirely. |
73d8cece | 686 | .SS The line printer driver |
bebbbd1f | 687 | .TP |
40dedbfe | 688 | .B "'lp='" |
77bda21c | 689 | .br |
fea681da | 690 | Syntax: |
77bda21c MK |
691 | |
692 | .in +4n | |
693 | .nf | |
fea681da | 694 | lp=0 |
fea681da | 695 | lp=auto |
fea681da | 696 | lp=reset |
fea681da | 697 | lp=port[,port...] |
77bda21c MK |
698 | .fi |
699 | .in | |
bebbbd1f | 700 | .IP |
fea681da | 701 | You can tell the printer driver what ports to use and what ports not |
c13182ef MK |
702 | to use. |
703 | The latter comes in handy if you don't want the printer driver | |
fea681da | 704 | to claim all available parallel ports, so that other drivers |
75b94dc3 | 705 | (e.g., PLIP, PPA) can use them instead. |
fea681da | 706 | |
c13182ef MK |
707 | The format of the argument is multiple port names. |
708 | For example, | |
fea681da | 709 | lp=none,parport0 would use the first parallel port for lp1, and |
c13182ef MK |
710 | disable lp0. |
711 | To disable the printer driver entirely, one can use | |
fea681da | 712 | lp=0. |
fd7f0a7f MK |
713 | .\" .SH AUTHORS |
714 | .\" Linus Torvalds (and many others) | |
47297adb | 715 | .SH SEE ALSO |
fea681da | 716 | .BR klogd (8), |
421405f9 | 717 | .BR mount (8) |
fea681da MK |
718 | |
719 | Large parts of this man page have been derived from the | |
720 | Boot Parameter HOWTO (version 1.0.1) written by Paul Gortmaker. | |
721 | More information may be found in this (or a more recent) HOWTO. | |
e57fca5a MK |
722 | An up-to-date source of information is the kernel source file |
723 | .IR Documentation/kernel-parameters.txt . |