]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blame - Documentation/kernel-parameters.txt
Hibernate: Replace unnecessary evaluation of pfn_to_page()
[mirror_ubuntu-bionic-kernel.git] / Documentation / kernel-parameters.txt
CommitLineData
e53dd083
MCC
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
1da177e4
LT
3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
a901ebb9
SR
20This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
6585fa8a
SR
27The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
1da177e4
LT
31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
1da177e4
LT
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
1da177e4
LT
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
1da177e4
LT
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
1da177e4
LT
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
1da177e4
LT
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
1da177e4
LT
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
1da177e4
LT
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
c8facbb6
RD
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
1da177e4
LT
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
1da177e4
LT
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
1da177e4
LT
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
20510f2f 84 SECURITY Different security models are enabled.
1da177e4
LT
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
1da177e4
LT
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
77437fd4
DB
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
1da177e4
LT
92 TS Appropriate touchscreen support is enabled.
93 USB USB support is enabled.
94 USBHID USB Human Interface Device support is enabled.
95 V4L Video For Linux support is enabled.
96 VGA The VGA console has been enabled.
97 VT Virtual terminal support is enabled.
98 WDT Watchdog support is enabled.
99 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 100 X86-32 X86-32, aka i386 architecture is enabled.
1da177e4
LT
101 X86-64 X86-64 architecture is enabled.
102 More X86-64 boot options can be found in
71cced6e 103 Documentation/x86/x86_64/boot-options.txt .
c0115606 104 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
1da177e4
LT
105
106In addition, the following text indicates that the option:
107
108 BUGS= Relates to possible processor bugs on the said processor.
109 KNL Is a kernel start-up parameter.
110 BOOT Is a boot loader parameter.
111
112Parameters denoted with BOOT are actually interpreted by the boot
113loader, and have no meaning to the kernel directly.
114Do not modify the syntax of boot loader parameters without extreme
71cced6e 115need or coordination with <Documentation/x86/i386/boot.txt>.
1da177e4 116
5558870b 117There are also arch-specific kernel-parameters not documented here.
71cced6e 118See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 119
1da177e4
LT
120Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
121a trailing = on the name of any parameter states that that parameter will
122be entered as an environment variable, whereas its absence indicates that
123it will appear as a kernel argument readable via /proc/cmdline by programs
124running once the system is up.
125
9c4751fd 126The number of kernel parameters is not limited, but the length of the
127complete command line (parameters including spaces etc.) is limited to
128a fixed number of characters. This limit depends on the architecture
129and is between 256 and 4096 characters. It is defined in the file
130./include/asm/setup.h as COMMAND_LINE_SIZE.
131
132
03d926f8
BW
133 acpi= [HW,ACPI,X86-64,i386]
134 Advanced Configuration and Power Interface
a9913044 135 Format: { force | off | ht | strict | noirq }
1da177e4
LT
136 force -- enable ACPI if default was off
137 off -- disable ACPI if default was on
138 noirq -- do not use ACPI for IRQ routing
139 ht -- run only enough ACPI to enable Hyper Threading
a9913044 140 strict -- Be less tolerant of platforms that are not
1da177e4
LT
141 strictly ACPI specification compliant.
142
53471121 143 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 144
a1fdcc0d
LB
145 acpi_apic_instance= [ACPI, IOAPIC]
146 Format: <int>
147 2: use 2nd APIC table, if available
148 1,0: use 1st APIC table
4e381a4f 149 default: 0
a1fdcc0d 150
1da177e4 151 acpi_sleep= [HW,ACPI] Sleep options
ba84ed95
RW
152 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
153 old_ordering, s4_nonvs }
23b168d4
PM
154 See Documentation/power/video.txt for s3_bios and s3_mode.
155 s3_beep is for debugging; it makes the PC's speaker beep
156 as soon as the kernel's real-mode entry point is called.
bdfe6b7c
SL
157 s4_nohwsig prevents ACPI hardware signature from being
158 used during resume from hibernation.
d8f3de0d
RW
159 old_ordering causes the ACPI 1.0 ordering of the _PTS
160 control method, wrt putting devices into low power
161 states, to be enforced (the ACPI 2.0 ordering of _PTS is
162 used by default).
ba84ed95
RW
163 s4_nonvs prevents the kernel from saving/restoring the
164 ACPI NVS memory during hibernation.
a9913044 165
1da177e4 166 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 167 Format: { level | edge | high | low }
1da177e4 168
a9913044
RD
169 acpi_irq_balance [HW,ACPI]
170 ACPI will balance active IRQs
171 default in APIC mode
1da177e4 172
a9913044
RD
173 acpi_irq_nobalance [HW,ACPI]
174 ACPI will not move active IRQs (default)
175 default in PIC mode
1da177e4 176
a9913044
RD
177 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
178 use by PCI
1da177e4
LT
179 Format: <irq>,<irq>...
180
a9913044 181 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
1da177e4
LT
182 Format: <irq>,<irq>...
183
67effe8f
LB
184 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
185
a1f9e65e
LB
186 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
187 Format: To spoof as Windows 98: ="Microsoft Windows"
188
ae00d812
LB
189 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
190 acpi_osi="string1" # add string1 -- only one string
191 acpi_osi="!string2" # remove built-in string2
192 acpi_osi= # disable all strings
1da177e4
LT
193
194 acpi_serialize [HW,ACPI] force serialization of AML methods
195
196 acpi_skip_timer_override [HW,ACPI]
197 Recognize and ignore IRQ0/pin2 Interrupt Override.
198 For broken nForce2 BIOS resulting in XT-PIC timer.
fa18f477
AK
199 acpi_use_timer_override [HW,ACPI}
200 Use timer override. For some broken Nvidia NF5 boards
201 that require a timer override, but don't have
202 HPET
1da177e4 203
c3d6de69
TR
204 acpi_backlight= [HW,ACPI]
205 acpi_backlight=vendor
206 acpi_backlight=video
207 If set to vendor, prefer vendor specific driver
208 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
209 of the ACPI video.ko driver.
210
211 acpi_display_output= [HW,ACPI]
212 acpi_display_output=vendor
213 acpi_display_output=video
214 See above.
215
a0d84a92
BH
216 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
217 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 218 Format: <int>
a0d84a92
BH
219 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
220 debug output. Bits in debug_layer correspond to a
221 _COMPONENT in an ACPI source file, e.g.,
222 #define _COMPONENT ACPI_PCI_COMPONENT
223 Bits in debug_level correspond to a level in
224 ACPI_DEBUG_PRINT statements, e.g.,
225 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
226 See Documentation/acpi/debug.txt for more information
227 about debug layers and levels.
228
229 Enable AML "Debug" output, i.e., stores to the Debug
230 object while interpreting AML:
231 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
232 Enable PCI/PCI interrupt routing info messages:
233 acpi.debug_layer=0x400000 acpi.debug_level=0x4
234 Enable all messages related to ACPI hardware:
235 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
236
237 Some values produce so much output that the system is
238 unusable. The "log_buf_len" parameter may be useful
239 if you need to capture more output.
f989106c 240
f5adfaa3
ZY
241 acpi.power_nocheck= [HW,ACPI]
242 Format: 1/0 enable/disable the check of power state.
243 On some bogus BIOS the _PSC object/_STA object of
244 power resource can't return the correct device power
245 state. In such case it is unneccessary to check its
246 power state again in power transition.
247 1 : disable the power state check
248
cd4f0ef7 249 acpi_pm_good [X86-32,X86-64]
5d0cf410
JS
250 Override the pmtimer bug detection: force the kernel
251 to assume that this machine's pmtimer latches its value
252 and always returns good values.
253
c99c108a
CE
254 agp= [AGP]
255 { off | try_unsupported }
256 off: disable AGP support
257 try_unsupported: try to drive unsupported chipsets
258 (may crash computer or cause data corruption)
259
66759a01
CE
260 enable_timer_pin_1 [i386,x86-64]
261 Enable PIN 1 of APIC timer
a9913044
RD
262 Can be useful to work around chipset bugs
263 (in particular on some ATI chipsets).
66759a01
CE
264 The kernel tries to set a reasonable default.
265
266 disable_timer_pin_1 [i386,x86-64]
267 Disable PIN 1 of APIC timer
268 Can be useful to work around chipset bugs.
269
1da177e4
LT
270 ad1848= [HW,OSS]
271 Format: <io>,<irq>,<dma>,<dma2>,<type>
272
1da177e4
LT
273 advansys= [HW,SCSI]
274 See header of drivers/scsi/advansys.c.
275
276 advwdt= [HW,WDT] Advantech WDT
277 Format: <iostart>,<iostop>
278
279 aedsp16= [HW,OSS] Audio Excel DSP 16
280 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
281 See also header of sound/oss/aedsp16.c.
a9913044 282
1da177e4
LT
283 aha152x= [HW,SCSI]
284 See Documentation/scsi/aha152x.txt.
285
286 aha1542= [HW,SCSI]
287 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
288
289 aic7xxx= [HW,SCSI]
290 See Documentation/scsi/aic7xxx.txt.
291
292 aic79xx= [HW,SCSI]
293 See Documentation/scsi/aic79xx.txt.
294
54b4cbd2
JR
295 amd_iommu= [HW,X86-84]
296 Pass parameters to the AMD IOMMU driver in the system.
297 Possible values are:
54b4cbd2
JR
298 isolate - enable device isolation (each device, as far
299 as possible, will get its own protection
3ce1f93c 300 domain) [default]
e5e1f606
JR
301 share - put every device behind one IOMMU into the
302 same protection domain
afa9fdc2
FT
303 fullflush - enable flushing of IO/TLB entries when
304 they are unmapped. Otherwise they are
305 flushed before they will be reused, which
306 is a lot of faster
307
54b4cbd2
JR
308 amd_iommu_size= [HW,X86-64]
309 Define the size of the aperture for the AMD IOMMU
310 driver. Possible values are:
311 '32M', '64M' (default), '128M', '256M', '512M', '1G'
312
1da177e4
LT
313 amijoy.map= [HW,JOY] Amiga joystick support
314 Map of devices attached to JOY0DAT and JOY1DAT
315 Format: <a>,<b>
316 See also Documentation/kernel/input/joystick.txt
317
318 analog.map= [HW,JOY] Analog joystick and gamepad support
319 Specifies type or capabilities of an analog joystick
320 connected to one of 16 gameports
321 Format: <type1>,<type2>,..<type16>
322
a9913044
RD
323 apc= [HW,SPARC]
324 Power management functions (SPARCstation-4/5 + deriv.)
1da177e4
LT
325 Format: noidle
326 Disable APC CPU standby support. SPARCstation-Fox does
327 not play well with APC CPU idle - disable it if you have
328 APC and your system crashes randomly.
329
c8facbb6
RD
330 apic= [APIC,i386] Advanced Programmable Interrupt Controller
331 Change the output verbosity whilst booting
1da177e4
LT
332 Format: { quiet (default) | verbose | debug }
333 Change the amount of debugging information output
334 when initialising the APIC and IO-APIC components.
a9913044 335
1da177e4 336 apm= [APM] Advanced Power Management
71f77055 337 See header of arch/x86/kernel/apm_32.c.
1da177e4 338
1da177e4
LT
339 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
340 Format: <io>,<irq>,<nodeID>
341
342 ataflop= [HW,M68k]
343
344 atarimouse= [HW,MOUSE] Atari Mouse
345
346 atascsi= [HW,SCSI] Atari SCSI
347
348 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
349 EzKey and similar keyboards
350
351 atkbd.reset= [HW] Reset keyboard during initialization
352
a9913044
RD
353 atkbd.set= [HW] Select keyboard code set
354 Format: <int> (2 = AT (default), 3 = PS/2)
1da177e4
LT
355
356 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
357 keyboards
358
359 atkbd.softraw= [HW] Choose between synthetic and real raw mode
360 Format: <bool> (0 = real, 1 = synthetic (default))
a9913044
RD
361
362 atkbd.softrepeat= [HW]
363 Use software keyboard repeat
1da177e4
LT
364
365 autotest [IA64]
366
1da177e4
LT
367 baycom_epp= [HW,AX25]
368 Format: <io>,<mode>
a9913044 369
1da177e4
LT
370 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
371 Format: <io>,<mode>
372 See header of drivers/net/hamradio/baycom_par.c.
373
a9913044
RD
374 baycom_ser_fdx= [HW,AX25]
375 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
1da177e4
LT
376 Format: <io>,<irq>,<mode>[,<baud>]
377 See header of drivers/net/hamradio/baycom_ser_fdx.c.
378
a9913044
RD
379 baycom_ser_hdx= [HW,AX25]
380 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
1da177e4
LT
381 Format: <io>,<irq>,<mode>
382 See header of drivers/net/hamradio/baycom_ser_hdx.c.
383
bfe8df3d
RD
384 boot_delay= Milliseconds to delay each printk during boot.
385 Values larger than 10 seconds (10000) are changed to
386 no delay (0).
387 Format: integer
388
35fc908d
AH
389 bootmem_debug [KNL] Enable bootmem allocator debug messages.
390
1da177e4 391 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
a9913044
RD
392 bttv.radio= Most important insmod options are available as
393 kernel args too.
1da177e4
LT
394 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
395 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
396
397 BusLogic= [HW,SCSI]
398 See drivers/scsi/BusLogic.c, comment before function
399 BusLogic_ParseDriverOptions().
400
401 c101= [NET] Moxa C101 synchronous serial card
402
cd4f0ef7 403 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
1da177e4
LT
404 Sometimes CPU hardware bugs make them report the cache
405 size incorrectly. The kernel will attempt work arounds
406 to fix known problems, but for some CPUs it is not
407 possible to determine what the correct size should be.
408 This option provides an override for these situations.
409
076c54c5
AD
410 security= [SECURITY] Choose a security module to enable at boot.
411 If this boot parameter is not specified, only the first
412 security module asking for security registration will be
413 loaded. An invalid security module name will be treated
414 as if no module has been chosen.
415
20510f2f
JM
416 capability.disable=
417 [SECURITY] Disable capabilities. This would normally
418 be used only if an alternative security model is to be
419 configured. Potentially dangerous and should only be
420 used if you are entirely sure of the consequences.
421
14ff56bb
SO
422 ccw_timeout_log [S390]
423 See Documentation/s390/CommonIO for details.
1da177e4 424
8bab8dde
PM
425 cgroup_disable= [KNL] Disable a particular controller
426 Format: {name of the controller(s) to disable}
427 {Currently supported controllers - "memory"}
428
1da177e4
LT
429 checkreqprot [SELINUX] Set initial checkreqprot flag value.
430 Format: { "0" | "1" }
431 See security/selinux/Kconfig help text.
a9913044
RD
432 0 -- check protection applied by kernel (includes
433 any implied execute protection).
1da177e4
LT
434 1 -- check protection requested by application.
435 Default value is set via a kernel config option.
a9913044
RD
436 Value can be changed at runtime via
437 /selinux/checkreqprot.
438
661ca0da
SO
439 cio_ignore= [S390]
440 See Documentation/s390/CommonIO for details.
441
cd4f0ef7 442 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 443 [Deprecated]
3f6dee9b 444 Forces specified clocksource (if available) to be used
734efb46 445 when calculating gettimeofday(). If specified
3f6dee9b 446 clocksource is not available, it defaults to PIT.
1da177e4
LT
447 Format: { pit | tsc | cyclone | pmtmr }
448
3d6ac984
RD
449 clocksource= [GENERIC_TIME] Override the default clocksource
450 Format: <string>
451 Override the default clocksource and use the clocksource
452 with the name specified.
453 Some clocksource names to choose from, depending on
454 the platform:
455 [all] jiffies (this is the base, fallback clocksource)
456 [ACPI] acpi_pm
457 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
458 pxa_timer,timer3,32k_counter,timer0_1
459 [AVR32] avr32
cd4f0ef7 460 [X86-32] pit,hpet,tsc,vmi-timer;
3d6ac984
RD
461 scx200_hrt on Geode; cyclone on IBM x440
462 [MIPS] MIPS
463 [PARISC] cr16
464 [S390] tod
465 [SH] SuperH
466 [SPARC64] tick
467 [X86-64] hpet,tsc
468
ac72e788
AK
469 clearcpuid=BITNUM [X86]
470 Disable CPUID feature X for the kernel. See
471 include/asm-x86/cpufeature.h for the valid bit numbers.
472 Note the Linux specific bits are not necessarily
473 stable over kernel options, but the vendor specific
474 ones should be.
475 Also note that user programs calling CPUID directly
476 or using the feature without checking anything
477 will still see it. This just prevents it from
478 being used by the kernel or shown in /proc/cpuinfo.
479 Also note the kernel might malfunction if you disable
480 some critical bits.
481
a25bd949
AV
482 code_bytes [IA32/X86_64] How many bytes of object code to print
483 in an oops report.
86c41837
CE
484 Range: 0 - 8192
485 Default: 64
486
b17530bd
TG
487 hpet= [X86-32,HPET] option to control HPET usage
488 Format: { enable (default) | disable | force }
489 disable: disable HPET and use PIT instead
d79a5f80
CC
490 force: allow force enabled of undocumented chips (ICH4,
491 VIA, nVidia)
1da177e4 492
1da177e4 493 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
494 Format:
495 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
496
497 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
498 Format: <io>[,<irq>]
499
a9913044
RD
500 com90xx= [HW,NET]
501 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
502 Format: <io>[,<irq>[,<memstart>]]
503
504 condev= [HW,S390] console device
505 conmode=
a9913044 506
1da177e4
LT
507 console= [KNL] Output console device and options.
508
509 tty<n> Use the virtual console device <n>.
510
511 ttyS<n>[,options]
f1a1c2dc 512 ttyUSB0[,options]
1da177e4 513 Use the specified serial port. The options are of
f1a1c2dc
RD
514 the form "bbbbpnf", where "bbbb" is the baud rate,
515 "p" is parity ("n", "o", or "e"), "n" is number of
516 bits, and "f" is flow control ("r" for RTS or
517 omit it). Default is "9600n8".
518
519 See Documentation/serial-console.txt for more
520 information. See
521 Documentation/networking/netconsole.txt for an
522 alternative.
1da177e4 523
18a8bd94
YL
524 uart[8250],io,<addr>[,options]
525 uart[8250],mmio,<addr>[,options]
1da177e4
LT
526 Start an early, polled-mode console on the 8250/16550
527 UART at the specified I/O port or MMIO address,
528 switching to the matching ttyS device later. The
529 options are the same as for ttyS, above.
530
f7511d5f
ST
531 If the device connected to the port is not a TTY but a braille
532 device, prepend "brl," before the device type, for instance
533 console=brl,ttyS0
534 For now, only VisioBraille is supported.
535
18a8bd94
YL
536 earlycon= [KNL] Output early console device and options.
537 uart[8250],io,<addr>[,options]
538 uart[8250],mmio,<addr>[,options]
539 Start an early, polled-mode console on the 8250/16550
540 UART at the specified I/O port or MMIO address.
541 The options are the same as for ttyS, above.
542
8f4ce8c3
AS
543 no_console_suspend
544 [HW] Never suspend the console
545 Disable suspending of consoles during suspend and
546 hibernate operations. Once disabled, debugging
547 messages can reach various consoles while the rest
548 of the system is being put to sleep (ie, while
549 debugging driver suspend/resume hooks). This may
550 not work reliably with all consoles, but is known
551 to work with serial and VGA consoles.
552
1da177e4 553 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
554 Format:
555 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 556
dc009d92
EB
557 crashkernel=nn[KMG]@ss[KMG]
558 [KNL] Reserve a chunk of physical memory to
559 hold a kernel to switch to with kexec on panic.
560
fb391599
BW
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for a example.
567
1da177e4
LT
568 cs4232= [HW,OSS]
569 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
570
571 cs89x0_dma= [HW,NET]
572 Format: <dma>
573
574 cs89x0_media= [HW,NET]
575 Format: { rj45 | aui | bnc }
a9913044 576
a9913044 577 dasd= [HW,NET]
1da177e4
LT
578 See header of drivers/s390/block/dasd_devmap.c.
579
580 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
581 (one device per port)
582 Format: <port#>,<type>
583 See also Documentation/input/joystick-parport.txt
584
585 debug [KNL] Enable kernel debugging (events log level).
586
cae2ed9a
IM
587 debug_locks_verbose=
588 [KNL] verbose self-tests
589 Format=<0|1>
590 Print debugging info while doing the locking API
591 self-tests.
592 We default to 0 (no extra messages), setting it to
593 1 will print _a lot_ more information - normally
594 only useful to kernel developers.
595
3ac7fe5a
TG
596 debug_objects [KNL] Enable object debugging
597
d3af01f1
TG
598 debugpat [X86] Enable PAT debugging
599
2d27a966 600 decnet.addr= [HW,NET]
1da177e4
LT
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
603
ecb77fa9 604 vt.default_blu= [VT]
55ff9780
AD
605 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
606 Change the default blue palette of the console.
607 This is a 16-member array composed of values
608 ranging from 0-255.
609
ecb77fa9 610 vt.default_grn= [VT]
55ff9780
AD
611 Format: <green0>,<green1>,<green2>,...,<green15>
612 Change the default green palette of the console.
613 This is a 16-member array composed of values
614 ranging from 0-255.
615
ecb77fa9 616 vt.default_red= [VT]
55ff9780
AD
617 Format: <red0>,<red1>,<red2>,...,<red15>
618 Change the default red palette of the console.
619 This is a 16-member array composed of values
620 ranging from 0-255.
621
ecb77fa9
ST
622 vt.default_utf8=
623 [VT]
55ff9780
AD
624 Format=<0|1>
625 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
626 Default is 1, i.e. UTF-8 mode is enabled for all
627 newly opened terminals.
55ff9780 628
1da177e4
LT
629 dhash_entries= [KNL]
630 Set number of hash buckets for dentry cache.
a9913044 631
1da177e4
LT
632 digi= [HW,SERIAL]
633 IO parameters + enable/disable command.
634
635 digiepca= [HW,SERIAL]
636 See drivers/char/README.epca and
31c00fc1 637 Documentation/serial/digiepca.txt.
1da177e4 638
95ffa243
YL
639 disable_mtrr_cleanup [X86]
640 enable_mtrr_cleanup [X86]
641 The kernel tries to adjust MTRR layout from continuous
642 to discrete, to make X server driver able to add WB
643 entry later. This parameter enables/disables that.
644
645 mtrr_chunk_size=nn[KMG] [X86]
646 used for mtrr cleanup. It is largest continous chunk
647 that could hold holes aka. UC entries.
648
649 mtrr_gran_size=nn[KMG] [X86]
12031a62
YL
650 Used for mtrr cleanup. It is granularity of mtrr block.
651 Default is 1.
652 Large value could prevent small alignment from
653 using up MTRRs.
654
655 mtrr_spare_reg_nr=n [X86]
656 Format: <integer>
657 Range: 0,7 : spare reg number
658 Default : 1
659 Used for mtrr cleanup. It is spare mtrr entries number.
660 Set to 2 or more if your graphical card needs more.
95ffa243 661
093af8d7 662 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
663 By default the kernel will trim any uncacheable
664 memory out of your available memory pool based on
665 MTRR settings. This parameter disables that behavior,
666 possibly causing your machine to run very slowly.
667
1da177e4
LT
668 dmasound= [HW,OSS] Sound subsystem buffers
669
670 dscc4.setup= [NET]
671
672 dtc3181e= [HW,SCSI]
673
0ae53640 674 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
675 earlyprintk=vga
676 earlyprintk=serial[,ttySn[,baudrate]]
5c05917e 677 earlyprintk=dbgp
1da177e4 678
a9913044 679 Append ",keep" to not disable it when the real console
1da177e4
LT
680 takes over.
681
5c05917e 682 Only vga or serial or usb debug port at a time.
1da177e4
LT
683
684 Currently only ttyS0 and ttyS1 are supported.
685
686 Interaction with the standard serial driver is not
687 very good.
688
689 The VGA output is eventually overwritten by the real
690 console.
691
692 eata= [HW,SCSI]
693
1da177e4 694 edd= [EDD]
8c4dd606 695 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 696
1da177e4
LT
697 eisa_irq_edge= [PARISC,HW]
698 See header of drivers/parisc/eisa.c.
699
cd4f0ef7 700 elanfreq= [X86-32]
1da177e4 701 See comment before function elanfreq_setup() in
71f77055 702 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
703
704 elevator= [IOSCHED]
16ab3adf 705 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
706 See Documentation/block/as-iosched.txt and
707 Documentation/block/deadline-iosched.txt for details.
708
e515a0d6 709 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
a9913044 710 Specifies physical address of start of kernel core
aac04b32
VG
711 image elf header. Generally kexec loader will
712 pass this option to capture kernel.
713 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
714
715 enforcing [SELINUX] Set initial enforcing status.
716 Format: {"0" | "1"}
717 See security/selinux/Kconfig help text.
718 0 -- permissive (log only, no denials).
719 1 -- enforcing (deny and log).
720 Default value is 0.
721 Value can be changed at runtime via /selinux/enforce.
722
1da177e4
LT
723 es1371= [HW,OSS]
724 Format: <spdif>,[<nomix>,[<amplifier>]]
725 See also header of sound/oss/es1371.c.
a9913044 726
1da177e4
LT
727 ether= [HW,NET] Ethernet cards parameters
728 This option is obsoleted by the "netdev=" option, which
729 has equivalent usage. See its documentation for details.
730
731 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
732 Format: <io>[,<irq>]
733
de1ba09b
AM
734 failslab=
735 fail_page_alloc=
736 fail_make_request=[KNL]
737 General fault injection mechanism.
738 Format: <interval>,<probability>,<space>,<times>
739 See also /Documentation/fault-injection/.
740
1da177e4
LT
741 fd_mcs= [HW,SCSI]
742 See header of drivers/scsi/fd_mcs.c.
743
744 fdomain= [HW,SCSI]
745 See header of drivers/scsi/fdomain.c.
746
747 floppy= [HW]
31c00fc1 748 See Documentation/blockdev/floppy.txt.
1da177e4 749
f13ae30e
AC
750 force_pal_cache_flush
751 [IA-64] Avoid check_sal_cache_flush which may hang on
752 buggy SAL_CACHE_FLUSH implementations. Using this
753 parameter will force ia64_sal_cache_flush to call
754 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
755
1da177e4
LT
756 gamecon.map[2|3]=
757 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
758 support via parallel port (up to 5 devices per port)
759 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
760 See also Documentation/input/joystick-parport.txt
761
762 gamma= [HW,DRM]
763
aaf23042
YL
764 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
765 Format: off | on
766 default: on
767
1da177e4
LT
768 gdth= [HW,SCSI]
769 See header of drivers/scsi/gdth.c.
770
771 gpt [EFI] Forces disk with valid GPT signature but
772 invalid Protective MBR to be treated as GPT.
773
1da177e4
LT
774 gvp11= [HW,SCSI]
775
776 hashdist= [KNL,NUMA] Large hashes allocated during boot
777 are distributed across NUMA nodes. Defaults on
778 for IA-64, off otherwise.
a9913044 779 Format: 0 | 1 (for off | on)
1da177e4
LT
780
781 hcl= [IA-64] SGI's Hardware Graph compatibility layer
782
783 hd= [EIDE] (E)IDE hard drive subsystem geometry
784 Format: <cyl>,<head>,<sect>
785
1da177e4
LT
786 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
787 size of <nn>. This works even on boxes that have no
788 highmem otherwise. This also works to reduce highmem
789 size on bigger boxes.
790
54cdfdb4
TG
791 highres= [KNL] Enable/disable high resolution timer mode.
792 Valid parameters: "on", "off"
793 Default: "on"
794
1da177e4
LT
795 hisax= [HW,ISDN]
796 See Documentation/isdn/README.HiSax.
797
b4718e62
AK
798 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
799 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
800 On x86-64 and powerpc, this option can be specified
801 multiple times interleaved with hugepages= to reserve
802 huge pages of different sizes. Valid pages sizes on
803 x86-64 are 2M (when the CPU supports "pse") and 1G
804 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
805 Note that 1GB pages can only be allocated at boot time
806 using hugepages= and not freed afterwards.
e11bfbfc
NP
807 default_hugepagesz=
808 [same as hugepagesz=] The size of the default
809 HugeTLB page size. This is the size represented by
810 the legacy /proc/ hugepages APIs, used for SHM, and
811 default size when mounting hugetlbfs filesystems.
812 Defaults to the default architecture's huge page size
813 if not specified.
1da177e4 814
6902aa84
PM
815 hlt [BUGS=ARM,SH]
816
36d95739 817 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 818 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
819 i8042.dumbkbd [HW] Pretend that controller can only read data from
820 keyboard and cannot control its state
1da177e4
LT
821 (Don't attempt to blink the leds)
822 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 823 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
824 i8042.noloop [HW] Disable the AUX Loopback command while probing
825 for the AUX port
1da177e4
LT
826 i8042.nomux [HW] Don't check presence of an active multiplexing
827 controller
828 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
829 controllers
830 i8042.panicblink=
831 [HW] Frequency with which keyboard LEDs should blink
832 when kernel panics (default is 0.5 sec)
833 i8042.reset [HW] Reset the controller during init and cleanup
834 i8042.unlock [HW] Unlock (ignore) the keylock
835
836 i810= [HW,DRM]
837
e70c9d5e
DT
838 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
839 indicates that the driver is running on unsupported
840 hardware.
1da177e4
LT
841 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
842 does not match list of supported models.
843 i8k.power_status
844 [HW] Report power status in /proc/i8k
845 (disabled by default)
846 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
847 capability is set.
848
849 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
850 See Documentation/mca.txt.
851
852 icn= [HW,ISDN]
853 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
854
855 ide= [HW] (E)IDE subsystem
a594eeb1 856 Format: ide=nodma or ide=doubler
1c10e938 857 See Documentation/ide/ide.txt.
1da177e4 858
1da177e4 859 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 860 See Documentation/ide/ide.txt.
1da177e4 861
f039b754 862 idle= [X86]
da5e09a1 863 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
f039b754
AK
864 Poll forces a polling idle loop that can slightly improves the performance
865 of waking up a idle CPU, but will use a lot of power and make the system
866 run hot. Not recommended.
867 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
868 to not use it because it doesn't save as much power as a normal idle
869 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
870 as idle=poll.
c1e3b377
ZY
871 idle=halt. Halt is forced to be used for CPU idle.
872 In such case C2/C3 won't be used again.
da5e09a1 873 idle=nomwait. Disable mwait for CPU C-states
a9913044 874
594765a7
DC
875 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
876 Claim all unknown PCI IDE storage controllers.
877
79290822
IM
878 ignore_loglevel [KNL]
879 Ignore loglevel setting - this will print /all/
880 kernel messages to the console. Useful for debugging.
881
1da177e4
LT
882 ihash_entries= [KNL]
883 Set number of hash buckets for inode cache.
884
885 in2000= [HW,SCSI]
886 See header of drivers/scsi/in2000.c.
887
888 init= [KNL]
889 Format: <full_path>
890 Run specified binary instead of /sbin/init as init
891 process.
892
893 initcall_debug [KNL] Trace initcalls as they are executed. Useful
894 for working out where the kernel is dying during
895 startup.
896
897 initrd= [BOOT] Specify the location of the initial ramdisk
898
899 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
900 Format: <irq>
901
902 inttest= [IA64]
903
b552da87
PM
904 iommu= [x86]
905 off
906 force
907 noforce
908 biomerge
909 panic
910 nopanic
911 merge
912 nomerge
913 forcesac
914 soft
915
916
ba395927
KA
917 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
918 off
919 Disable intel iommu driver.
920 igfx_off [Default Off]
921 By default, gfx is mapped as normal device. If a gfx
922 device has a dedicated DMAR unit, the DMAR unit is
923 bypassed by not enabling DMAR with this option. In
924 this case, gfx device will use physical address for
925 DMA.
7d3b03ce
KA
926 forcedac [x86_64]
927 With this option iommu will not optimize to look
928 for io virtual address below 32 bit forcing dual
929 address cycle on pci bus for cards supporting greater
930 than 32 bit addressing. The default is to look
931 for translation below 32 bit and if not available
932 then look in the higher range.
5e0d2a6f 933 strict [Default Off]
934 With this option on every unmap_single operation will
935 result in a hardware IOTLB flush operation as opposed
936 to batching them for performance.
ba395927 937
b02aae9c 938 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
939 0x80
940 Standard port 0x80 based delay
941 0xed
942 Alternate port 0xed based delay (needed on some systems)
b02aae9c 943 udelay
6e7c4025
IM
944 Simple two microseconds delay
945 none
946 No delay
b02aae9c 947
1da177e4
LT
948 io7= [HW] IO7 for Marvel based alpha systems
949 See comment before marvel_specify_io7 in
950 arch/alpha/kernel/core_marvel.c.
951
952 ip= [IP_PNP]
6ded55da 953 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
954
955 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
956 See comment before ip2_setup() in
957 drivers/char/ip2/ip2base.c.
1da177e4
LT
958
959 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
960 See header of drivers/scsi/ips.c.
961
72c4a13a
SH
962 ports= [IP_VS_FTP] IPVS ftp helper module
963 Default is 21.
964 Up to 8 (IP_VS_APP_MAX_PORTS) ports
965 may be specified.
966 Format: <port>,<port>....
967
200803df
AC
968 irqfixup [HW]
969 When an interrupt is not handled search all handlers
970 for it. Intended to get systems with badly broken
971 firmware running.
972
973 irqpoll [HW]
974 When an interrupt is not handled search all handlers
975 for it. Also check all handlers each timer
976 interrupt. Intended to get systems with badly broken
977 firmware running.
978
1da177e4 979 isapnp= [ISAPNP]
a9913044 980 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
981
982 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
983 Format:
984 <cpu number>,...,<cpu number>
985 or
b225d44e
LZ
986 <cpu number>-<cpu number>
987 (must be a positive range in ascending order)
22f2e280
DF
988 or a mixture
989 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 990
1da177e4
LT
991 This option can be used to specify one or more CPUs
992 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
993 algorithms. You can move a process onto or off an
994 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
995 <cpu number> begins at 0 and the maximum value is
996 "number of CPUs in system - 1".
997
998 This option is the preferred way to isolate CPUs. The
a9913044
RD
999 alternative -- manually setting the CPU mask of all
1000 tasks in the system -- can cause problems and
1001 suboptimal load balancer performance.
1da177e4 1002
a9913044 1003 iucv= [HW,NET]
1da177e4
LT
1004
1005 js= [HW,JOY] Analog joystick
1006 See Documentation/input/joystick.txt.
1007
cd4f0ef7 1008 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
1009 specifies the amount of memory usable by the kernel
1010 for non-movable allocations. The requested amount is
1011 spread evenly throughout all nodes in the system. The
1012 remaining memory in each node is used for Movable
1013 pages. In the event, a node is too small to have both
1014 kernelcore and Movable pages, kernelcore pages will
1015 take priority and other nodes will have a larger number
1016 of kernelcore pages. The Movable zone is used for the
1017 allocation of pages that may be reclaimed or moved
1018 by the page migration subsystem. This means that
1019 HugeTLB pages may not be allocated from this zone.
1020 Note that allocations like PTEs-from-HighMem still
1021 use the HighMem zone if it exists, and the Normal
1022 zone if it does not.
1023
cd4f0ef7 1024 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
1025 is similar to kernelcore except it specifies the
1026 amount of memory used for migratable allocations.
1027 If both kernelcore and movablecore is specified,
1028 then kernelcore will be at *least* the specified
1029 value but may be more. If movablecore on its own
1030 is specified, the administrator must be careful
1031 that the amount of memory usable for all allocations
1032 is not too small.
1033
1da177e4
LT
1034 keepinitrd [HW,ARM]
1035
cd4f0ef7 1036 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
1037 in oops dumps.
1038
6cdf6e06
JW
1039 kgdboc= [HW] kgdb over consoles.
1040 Requires a tty driver that supports console polling.
1041 (only serial suported for now)
1042 Format: <serial_device>[,baud]
1043
9bed90c6
FF
1044 kmac= [MIPS] korina ethernet MAC address.
1045 Configure the RouterBoard 532 series on-chip
1046 Ethernet adapter MAC address.
1047
1da177e4
LT
1048 l2cr= [PPC]
1049
a78bfbfc
RB
1050 l3cr= [PPC]
1051
cd4f0ef7 1052 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1053 disabled it.
1da177e4 1054
cd4f0ef7 1055 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
1056 C2 power state.
1057
fcb71f6f
FC
1058 libata.dma= [LIBATA] DMA control
1059 libata.dma=0 Disable all PATA and SATA DMA
1060 libata.dma=1 PATA and SATA Disk DMA only
1061 libata.dma=2 ATAPI (CDROM) DMA only
1062 libata.dma=4 Compact Flash DMA only
1063 Combinations also work, so libata.dma=3 enables DMA
1064 for disks and CDROMs, but not CFs.
1065
78e70c23
DJ
1066 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1067 when set.
1068 Format: <int>
1069
33267325
TH
1070 libata.force= [LIBATA] Force configurations. The format is comma
1071 separated list of "[ID:]VAL" where ID is
1072 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1073 matching port, link or device. Basically, it matches
1074 the ATA ID string printed on console by libata. If
1075 the whole ID part is omitted, the last PORT and DEVICE
1076 values are used. If ID hasn't been specified yet, the
1077 configuration applies to all ports, links and devices.
1078
1079 If only DEVICE is omitted, the parameter applies to
1080 the port and all links and devices behind it. DEVICE
1081 number of 0 either selects the first device or the
1082 first fan-out link behind PMP device. It does not
1083 select the host link. DEVICE number of 15 selects the
1084 host link and device attached to it.
1085
1086 The VAL specifies the configuration to force. As long
1087 as there's no ambiguity shortcut notation is allowed.
1088 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1089 The following configurations can be forced.
1090
1091 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1092 Any ID with matching PORT is used.
1093
1094 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1095
1096 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1097 udma[/][16,25,33,44,66,100,133] notation is also
1098 allowed.
1099
1100 * [no]ncq: Turn on or off NCQ.
1101
05944bdf
TH
1102 * nohrst, nosrst, norst: suppress hard, soft
1103 and both resets.
1104
33267325
TH
1105 If there are multiple matching configurations changing
1106 the same attribute, the last one is used.
1107
1da177e4 1108 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1109 See Documentation/blockdev/ramdisk.txt.
1da177e4 1110
a6b25b67
RD
1111 lockd.nlm_grace_period=P [NFS] Assign grace period.
1112 Format: <integer>
1da177e4 1113
a6b25b67
RD
1114 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1115 Format: <integer>
1116
1117 lockd.nlm_timeout=T [NFS] Assign timeout value.
1118 Format: <integer>
1119
1120 lockd.nlm_udpport=M [NFS] Assign UDP port.
1121 Format: <integer>
1da177e4
LT
1122
1123 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1124 Format: <irq>
1125
1126 loglevel= All Kernel Messages with a loglevel smaller than the
1127 console loglevel will be printed to the console. It can
1128 also be changed with klogd or other programs. The
1129 loglevels are defined as follows:
1130
1131 0 (KERN_EMERG) system is unusable
1132 1 (KERN_ALERT) action must be taken immediately
1133 2 (KERN_CRIT) critical conditions
1134 3 (KERN_ERR) error conditions
1135 4 (KERN_WARNING) warning conditions
1136 5 (KERN_NOTICE) normal but significant condition
1137 6 (KERN_INFO) informational
1138 7 (KERN_DEBUG) debug-level messages
1139
1140 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1141 Format: { n | nk | nM }
1142 n must be a power of two. The default size
1143 is set in the kernel config file.
1da177e4 1144
accaa24c
RD
1145 logo.nologo [FB] Disables display of the built-in Linux logo.
1146 This may be used to provide more screen space for
1147 kernel log messages and is useful when debugging
1148 kernel boot problems.
1149
1da177e4
LT
1150 lp=0 [LP] Specify parallel ports to use, e.g,
1151 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1152 lp=reset first parallel port). 'lp=0' disables the
1153 lp=auto printer driver. 'lp=reset' (which can be
1154 specified in addition to the ports) causes
1155 attached printers to be reset. Using
1156 lp=port1,port2,... specifies the parallel ports
1157 to associate lp devices with, starting with
1158 lp0. A port specification may be 'none' to skip
1159 that lp device, or a parport name such as
1160 'parport0'. Specifying 'lp=auto' instead of a
1161 port specification list means that device IDs
1162 from each port should be examined, to see if
1163 an IEEE 1284-compliant printer is attached; if
1164 so, the driver will manage that printer.
1165 See also header of drivers/char/lp.c.
1166
1167 lpj=n [KNL]
1168 Sets loops_per_jiffy to given constant, thus avoiding
1169 time-consuming boot-time autodetection (up to 250 ms per
1170 CPU). 0 enables autodetection (default). To determine
1171 the correct value for your kernel, boot with normal
1172 autodetection and see what value is printed. Note that
1173 on SMP systems the preset will be applied to all CPUs,
1174 which is likely to cause problems if your CPUs need
1175 significantly divergent settings. An incorrect value
1176 will cause delays in the kernel to be wrong, leading to
1177 unpredictable I/O errors and other breakage. Although
1178 unlikely, in the extreme case this might damage your
1179 hardware.
1180
1181 ltpc= [NET]
1182 Format: <io>,<irq>,<dma>
1183
a9913044
RD
1184 mac5380= [HW,SCSI] Format:
1185 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1186
a9913044
RD
1187 machvec= [IA64] Force the use of a particular machine-vector
1188 (machvec) in a generic kernel.
1189 Example: machvec=hpzx1_swiotlb
1da177e4 1190
a9913044 1191 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1192 be mounted
1193 Format: <1-256>
1194
1195 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1196 should make use of. maxcpus=n : n >= 0 limits the
1197 kernel to using 'n' processors. n=0 is a special case,
1198 it is equivalent to "nosmp", which also disables
1199 the IO APIC.
1da177e4 1200
1c207f95
RD
1201 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1202 or equal to this physical address is ignored.
2b2c3750 1203
a9913044 1204 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1205 Should be between 1 and 2^32-1.
1206
1207 max_report_luns=
a9913044 1208 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1209 Should be between 1 and 16384.
1210
1da177e4
LT
1211 mcatest= [IA-64]
1212
cd4f0ef7 1213 mce [X86-32] Machine Check Exception
1da177e4 1214
71cced6e 1215 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1216
1da177e4
LT
1217 md= [HW] RAID subsystems devices and level
1218 See Documentation/md.txt.
a9913044 1219
1da177e4
LT
1220 mdacon= [MDA]
1221 Format: <first>,<last>
1222 Specifies range of consoles to be captured by the MDA.
a9913044 1223
1da177e4
LT
1224 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1225 Amount of memory to be used when the kernel is not able
1226 to see the whole system memory or for test.
cd4f0ef7 1227 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1228 address space collisions. Without memmap= PCI devices
1229 could be placed at addresses belonging to unused RAM.
1230
cd4f0ef7 1231 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1232 memory.
1233
6902aa84
PM
1234 memchunk=nn[KMG]
1235 [KNL,SH] Allow user to override the default size for
1236 per-device physically contiguous DMA buffers.
1237
cd4f0ef7 1238 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1239 E820 memory map, as specified by the user.
1240 Such memmap=exactmap lines can be constructed based on
1241 BIOS output or other requirements. See the memmap=nn@ss
1242 option description.
1243
1244 memmap=nn[KMG]@ss[KMG]
1245 [KNL] Force usage of a specific region of memory
1246 Region of memory to be used, from ss to ss+nn.
1247
1248 memmap=nn[KMG]#ss[KMG]
1249 [KNL,ACPI] Mark specific memory as ACPI data.
1250 Region of memory to be used, from ss to ss+nn.
1251
1252 memmap=nn[KMG]$ss[KMG]
1253 [KNL,ACPI] Mark specific memory as reserved.
1254 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1255 Example: Exclude memory from 0x18690000-0x1869ffff
1256 memmap=64K$0x18690000
1257 or
1258 memmap=0x10000$0x18690000
1da177e4 1259
9f077871
JF
1260 memory_corruption_check=0/1 [X86]
1261 Some BIOSes seem to corrupt the first 64k of
1262 memory when doing things like suspend/resume.
1263 Setting this option will scan the memory
1264 looking for corruption. Enabling this will
1265 both detect corruption and prevent the kernel
1266 from using the memory being corrupted.
1267 However, its intended as a diagnostic tool; if
1268 repeatable BIOS-originated corruption always
1269 affects the same memory, you can use memmap=
1270 to prevent the kernel from using that memory.
1271
1272 memory_corruption_check_size=size [X86]
1273 By default it checks for corruption in the low
1274 64k, making this memory unavailable for normal
1275 use. Use this parameter to scan for
1276 corruption in more or less memory.
1277
1278 memory_corruption_check_period=seconds [X86]
1279 By default it checks for corruption every 60
1280 seconds. Use this parameter to check at some
1281 other rate. 0 disables periodic checking.
1282
caadbdce 1283 memtest= [KNL,X86] Enable memtest
c64df707
YL
1284 Format: <integer>
1285 range: 0,4 : pattern number
1286 default : 0 <disable>
1287
1da177e4
LT
1288 meye.*= [HW] Set MotionEye Camera parameters
1289 See Documentation/video4linux/meye.txt.
1290
8f36881b
AS
1291 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1292 Multi-Function General Purpose Timers on AMD Geode
1293 platforms.
1294
e6c4dc6c
WT
1295 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1296 the BIOS has incorrectly applied a workaround. TinyBIOS
1297 version 0.98 is known to be affected, 0.99 fixes the
1298 problem by letting the user disable the workaround.
1299
1da177e4
LT
1300 mga= [HW,DRM]
1301
1c207f95
RD
1302 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1303 physical address is ignored.
1304
6b74ab97
MG
1305 mminit_loglevel=
1306 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1307 parameter allows control of the logging verbosity for
1308 the additional memory initialisation checks. A value
1309 of 0 disables mminit logging and a level of 4 will
1310 log everything. Information is printed at KERN_DEBUG
1311 so loglevel=8 may also need to be specified.
1312
1da177e4
LT
1313 mousedev.tap_time=
1314 [MOUSE] Maximum time between finger touching and
1315 leaving touchpad surface for touch to be considered
1316 a tap and be reported as a left button click (for
1317 touchpads working in absolute mode only).
1318 Format: <msecs>
1319 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1320 reporting absolute coordinates, such as tablets
1321 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1322 reporting absolute coordinates, such as tablets
1323
1324 mpu401= [HW,OSS]
1325 Format: <io>,<irq>
1326
1327 MTD_Partition= [MTD]
1328 Format: <name>,<region-number>,<size>,<offset>
1329
a9913044
RD
1330 MTD_Region= [MTD] Format:
1331 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1332
1333 mtdparts= [MTD]
c8facbb6 1334 See drivers/mtd/cmdlinepart.c.
1da177e4 1335
9db829f4
BD
1336 mtdset= [ARM]
1337 ARM/S3C2412 JIVE boot control
1338
1339 See arch/arm/mach-s3c2412/mach-jive.c
1340
1da177e4 1341 mtouchusb.raw_coordinates=
a9913044
RD
1342 [HW] Make the MicroTouch USB driver use raw coordinates
1343 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1344
1345 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1346
1347 NCR_D700= [HW,SCSI]
1348 See header of drivers/scsi/NCR_D700.c.
1349
1350 ncr5380= [HW,SCSI]
1351
1352 ncr53c400= [HW,SCSI]
1353
1354 ncr53c400a= [HW,SCSI]
1355
1356 ncr53c406a= [HW,SCSI]
1357
1358 ncr53c8xx= [HW,SCSI]
1359
1360 netdev= [NET] Network devices parameters
1361 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1362 Note that mem_start is often overloaded to mean
1363 something different and driver-specific.
a9913044
RD
1364 This usage is only documented in each driver source
1365 file if at all.
1366
58401572
KPO
1367 nf_conntrack.acct=
1368 [NETFILTER] Enable connection tracking flow accounting
1369 0 to disable accounting
1370 1 to enable accounting
1371 Default value depends on CONFIG_NF_CT_ACCT that is
1372 going to be removed in 2.6.29.
1373
1da177e4 1374 nfsaddrs= [NFS]
6ded55da 1375 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1376
1377 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1378 See Documentation/filesystems/nfsroot.txt.
1da177e4 1379
a72b4422
TM
1380 nfs.callback_tcpport=
1381 [NFS] set the TCP port on which the NFSv4 callback
1382 channel should listen.
1383
58df095b
TM
1384 nfs.idmap_cache_timeout=
1385 [NFS] set the maximum lifetime for idmapper cache
1386 entries.
1387
f43bf0be
TM
1388 nfs.enable_ino64=
1389 [NFS] enable 64-bit inode numbers.
1390 If zero, the NFS client will fake up a 32-bit inode
1391 number for the readdir() and stat() syscalls instead
1392 of returning the full 64-bit number.
1393 The default is to return 64-bit inode numbers.
1394
e7ba176b
HS
1395 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1396 when a NMI is triggered.
1397 Format: [state][,regs][,debounce][,die]
1398
cd4f0ef7 1399 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1da177e4 1400
cd4f0ef7 1401 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1402 emulation library even if a 387 maths coprocessor
1403 is present.
1404
c1aee215
CL
1405 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1406 caches in the slab allocator. Saves per-node memory,
1407 but will impact performance.
3395ee05 1408
a9913044
RD
1409 noalign [KNL,ARM]
1410
1da177e4
LT
1411 noapic [SMP,APIC] Tells the kernel to not make use of any
1412 IOAPICs that may be present in the system.
1413
1da177e4
LT
1414 nobats [PPC] Do not use BATs for mapping kernel lowmem
1415 on "Classic" PPC cores.
1416
1417 nocache [ARM]
a9913044 1418
163ecdff
SN
1419 nodelayacct [KNL] Disable per-task delay accounting
1420
1da177e4
LT
1421 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1422
6902aa84
PM
1423 nodsp [SH] Disable hardware DSP at boot time.
1424
8b2cb7a8
HY
1425 noefi [X86-32,X86-64] Disable EFI runtime services support.
1426
1da177e4
LT
1427 noexec [IA-64]
1428
cd4f0ef7 1429 noexec [X86-32,X86-64]
f5a1b191 1430 On X86-32 available only on PAE configured kernels.
1da177e4 1431 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1432 noexec=off: disable non-executable mappings
1433
1434 noexec32 [X86-64]
1435 This affects only 32-bit executables.
1436 noexec32=on: enable non-executable mappings (default)
1437 read doesn't imply executable mappings
1438 noexec32=off: disable non-executable mappings
1439 read implies executable mappings
1da177e4 1440
6902aa84
PM
1441 nofpu [SH] Disable hardware FPU at boot time.
1442
cd4f0ef7 1443 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1444 register save and restore. The kernel will only save
1445 legacy floating-point registers on task switch.
1da177e4 1446
191679fd
AK
1447 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1448
6902aa84 1449 nohlt [BUGS=ARM,SH]
a9913044 1450
cd4f0ef7 1451 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1452 instruction doesn't work correctly and not to
1453 use it.
1454
1455 nohalt [IA-64] Tells the kernel not to use the power saving
1456 function PAL_HALT_LIGHT when idle. This increases
1457 power-consumption. On the positive side, it reduces
1458 interrupt wake-up latency, which may improve performance
1459 in certain environments such as networked servers or
1460 real-time systems.
1461
79bf2bb3
TG
1462 nohz= [KNL] Boottime enable/disable dynamic ticks
1463 Valid arguments: on, off
1464 Default: on
1465
cd4f0ef7 1466 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1467 disable unhandled interrupt sources.
1468
cd4f0ef7 1469 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1470 broken timer IRQ sources.
1471
1da177e4
LT
1472 noisapnp [ISAPNP] Disables ISA PnP code.
1473
1474 noinitrd [RAM] Tells the kernel not to load any configured
1475 initial RAM disk.
1476
1477 nointroute [IA-64]
1478
0aa366f3
TL
1479 nojitter [IA64] Disables jitter checking for ITC timers.
1480
cd4f0ef7 1481 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1482
cd4f0ef7 1483 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1484
6e1cb38a
SS
1485 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1486
af9d1388
SS
1487 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1488 default x2apic cluster mode on platforms
1489 supporting x2apic.
1490
1da177e4
LT
1491 noltlbs [PPC] Do not use large page/tlb entries for kernel
1492 lowmem mapping on PPC40x.
1493
312f1f01
H
1494 nomca [IA-64] Disable machine check abort handling
1495
cd4f0ef7 1496 nomce [X86-32] Machine Check Exception
abe37e5a 1497
83d7384f
AS
1498 nomfgpt [X86-32] Disable Multi-Function General Purpose
1499 Timer usage (for AMD Geode machines).
1500
cd4f0ef7 1501 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1502
cd4f0ef7 1503 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1504 with UP alternatives
1505
1da177e4
LT
1506 noresidual [PPC] Don't use residual data on PReP machines.
1507
a9913044
RD
1508 noresume [SWSUSP] Disables resume and restores original swap
1509 space.
1510
1da177e4
LT
1511 no-scroll [VGA] Disables scrollback.
1512 This is required for the Braillex ib80-piezo Braille
1513 reader made by F.H. Papenmeier (Germany).
1514
1515 nosbagart [IA-64]
1516
cd4f0ef7 1517 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1518
61ec7567
LB
1519 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1520 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1521
97842216
DJ
1522 nosoftlockup [KNL] Disable the soft-lockup detector.
1523
1da177e4
LT
1524 nosync [HW,M68K] Disables sync negotiation for all devices.
1525
cd4f0ef7 1526 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1527
1528 nousb [USB] Disable the USB subsystem
1529
1530 nowb [ARM]
a9913044 1531
a6c75b86
FY
1532 nptcg= [IA64] Override max number of concurrent global TLB
1533 purges which is reported from either PAL_VM_SUMMARY or
1534 SAL PALO.
1535
f0c0b2b8
KH
1536 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1537 one of ['zone', 'node', 'default'] can be specified
1538 This can be set from sysctl after boot.
1539 See Documentation/sysctl/vm.txt for details.
1540
a61c2d78
DJ
1541 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1542
3ef0e1f8
AS
1543 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1544 Rather than timing out after 20 ms if an EC
1545 command is not properly ACKed, override the length
1546 of the timeout. We have interrupts disabled while
1547 waiting for the ACK, so if this is set too high
1548 interrupts *may* be lost!
1549
1da177e4
LT
1550 opl3= [HW,OSS]
1551 Format: <io>
1552
1da177e4
LT
1553 oprofile.timer= [HW]
1554 Use timer interrupt instead of performance counters
1555
1da177e4
LT
1556 osst= [HW,SCSI] SCSI Tape Driver
1557 Format: <buffer_size>,<write_threshold>
1558 See also Documentation/scsi/st.txt.
1559
1560 panic= [KNL] Kernel behaviour on panic
1561 Format: <timeout>
1562
1563 parkbd.port= [HW] Parallel port number the keyboard adapter is
1564 connected to, default is 0.
1565 Format: <parport#>
1566 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1567 0 for XT, 1 for AT (default is AT).
a9913044
RD
1568 Format: <mode>
1569
1570 parport= [HW,PPT] Specify parallel ports. 0 disables.
1571 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1572 Use 'auto' to force the driver to use any
1573 IRQ/DMA settings detected (the default is to
1574 ignore detected IRQ/DMA settings because of
1575 possible conflicts). You can specify the base
1576 address, IRQ, and DMA settings; IRQ and DMA
1577 should be numbers, or 'auto' (for using detected
1578 settings on that particular port), or 'nofifo'
1579 (to avoid using a FIFO even if it is detected).
1580 Parallel ports are assigned in the order they
1581 are specified on the command line, starting
1582 with parport0.
1583
1584 parport_init_mode= [HW,PPT]
1585 Configure VIA parallel port to operate in
1586 a specific mode. This is necessary on Pegasos
1587 computer where firmware has no options for setting
1588 up parallel port mode and sets it to spp.
1589 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1590 Format: [spp|ps2|epp|ecp|ecpepp]
1591
a9913044
RD
1592 pas2= [HW,OSS] Format:
1593 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1594
1da177e4
LT
1595 pas16= [HW,SCSI]
1596 See header of drivers/scsi/pas16.c.
1597
dd287796
AM
1598 pause_on_oops=
1599 Halt all CPUs after the first oops has been printed for
1600 the specified number of seconds. This is to be used if
1601 your oopses keep scrolling off the screen.
1602
1da177e4
LT
1603 pcbit= [HW,ISDN]
1604
1605 pcd. [PARIDE]
1606 See header of drivers/block/paride/pcd.c.
31c00fc1 1607 See also Documentation/blockdev/paride.txt.
1da177e4 1608
a9913044 1609 pci=option[,option...] [PCI] various PCI subsystem options:
c0115606 1610 off [X86] don't probe for the PCI bus
cd4f0ef7 1611 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1612 the hardware directly. Use this if your machine
1613 has a non-standard PCI host bridge.
cd4f0ef7 1614 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1615 hardware access methods are allowed. Use this
1616 if you experience crashes upon bootup and you
1617 suspect they are caused by the BIOS.
c0115606 1618 conf1 [X86] Force use of PCI Configuration
a9913044 1619 Mechanism 1.
c0115606 1620 conf2 [X86] Force use of PCI Configuration
a9913044 1621 Mechanism 2.
7f785763
RD
1622 noaer [PCIE] If the PCIEAER kernel config parameter is
1623 enabled, this kernel boot option can be used to
1624 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1625 nodomains [PCI] Disable support for multiple PCI
1626 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1627 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1628 Configuration
309e57df
MW
1629 nomsi [MSI] If the PCI_MSI kernel config parameter is
1630 enabled, this kernel boot option can be used to
1631 disable the use of MSI interrupts system-wide.
cd4f0ef7 1632 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1633 routing table. These calls are known to be buggy
1634 on several machines and they hang the machine
1635 when used, but on other computers it's the only
1636 way to get the interrupt routing table. Try
1637 this option if the kernel is unable to allocate
1638 IRQs or discover secondary PCI buses on your
1639 motherboard.
c0115606 1640 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1641 Use with caution as certain devices share
1642 address decoders between ROMs and other
1643 resources.
c0115606 1644 norom [X86] Do not assign address space to
bb71ad88
GH
1645 expansion ROMs that do not already have
1646 BIOS assigned address ranges.
c0115606 1647 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1648 assigned automatically to PCI devices. You can
1649 make the kernel exclude IRQs of your ISA cards
1650 this way.
c0115606 1651 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1652 of the PIRQ table (normally generated
1653 by the BIOS) if it is outside the
1654 F0000h-100000h range.
c0115606 1655 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1656 useful if the kernel is unable to find your
1657 secondary buses and you want to tell it
1658 explicitly which ones they are.
c0115606 1659 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1660 numbers ourselves, overriding
1661 whatever the firmware may have done.
c0115606 1662 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1663 in the BIOS $PIR table. This is needed on
1664 some systems with broken BIOSes, notably
1665 some HP Pavilion N5400 and Omnibook XE3
1666 notebooks. This will have no effect if ACPI
1667 IRQ routing is enabled.
c0115606 1668 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1669 or for PCI scanning.
c0115606 1670 use_crs [X86] Use _CRS for PCI resource
62f420f8 1671 allocation.
a9913044
RD
1672 routeirq Do IRQ routing for all PCI devices.
1673 This is normally done in pci_enable_device(),
1674 so this option is a temporary workaround
1675 for broken drivers that don't call it.
13a6ddb0
YL
1676 skip_isa_align [X86] do not align io start addr, so can
1677 handle more pci cards
a9913044
RD
1678 firmware [ARM] Do not re-enumerate the bus but instead
1679 just use the configuration from the
1680 bootloader. This is currently used on
1681 IXP2000 systems where the bus has to be
1682 configured a certain way for adjunct CPUs.
0637a70a
AK
1683 noearly [X86] Don't do any early type 1 scanning.
1684 This might help on some broken boards which
1685 machine check when some devices' config space
1686 is read. But various workarounds are disabled
1687 and some IOMMU drivers will not work.
6b4b78fe
MD
1688 bfsort Sort PCI devices into breadth-first order.
1689 This sorting is done to get a device
1690 order compatible with older (<= 2.4) kernels.
1691 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1692 cbiosize=nn[KMG] The fixed amount of bus space which is
1693 reserved for the CardBus bridge's IO window.
1694 The default value is 256 bytes.
1695 cbmemsize=nn[KMG] The fixed amount of bus space which is
1696 reserved for the CardBus bridge's memory
1697 window. The default value is 64 megabytes.
6b4b78fe 1698
e5665a45
CE
1699 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1700 Management.
1701 off Disable ASPM.
1702 force Enable ASPM even on devices that claim not to support it.
1703 WARNING: Forcing ASPM on may cause system lockups.
1704
1da177e4
LT
1705 pcmv= [HW,PCMCIA] BadgePAD 4
1706
1707 pd. [PARIDE]
31c00fc1 1708 See Documentation/blockdev/paride.txt.
1da177e4
LT
1709
1710 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1711 boot time.
1712 Format: { 0 | 1 }
1713 See arch/parisc/kernel/pdc_chassis.c
1714
1715 pf. [PARIDE]
31c00fc1 1716 See Documentation/blockdev/paride.txt.
1da177e4
LT
1717
1718 pg. [PARIDE]
31c00fc1 1719 See Documentation/blockdev/paride.txt.
1da177e4
LT
1720
1721 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 1722 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
1723
1724 plip= [PPT,NET] Parallel port network link
1725 Format: { parport<nr> | timid | 0 }
1726 See also Documentation/parport.txt.
1727
de32a243
TG
1728 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1729 Override pmtimer IOPort with a hex value.
1730 e.g. pmtmr=0x508
1731
97ef062b
BH
1732 pnp.debug [PNP]
1733 Enable PNP debug messages. This depends on the
1734 CONFIG_PNP_DEBUG_MESSAGES option.
1735
1da177e4
LT
1736 pnpacpi= [ACPI]
1737 { off }
1738
1739 pnpbios= [ISAPNP]
1740 { on | off | curr | res | no-curr | no-res }
1741
1742 pnp_reserve_irq=
1743 [ISAPNP] Exclude IRQs for the autoconfiguration
1744
1745 pnp_reserve_dma=
1746 [ISAPNP] Exclude DMAs for the autoconfiguration
1747
1748 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1749 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1750
1751 pnp_reserve_mem=
a9913044
RD
1752 [ISAPNP] Exclude memory regions for the
1753 autoconfiguration.
1da177e4
LT
1754 Ranges are in pairs (memory base and size).
1755
346e15be
JB
1756 dynamic_printk
1757 Enables pr_debug()/dev_dbg() calls if
1758 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
1759 be switched on/off via <debugfs>/dynamic_printk/modules
1760
45807a1d
IM
1761 print-fatal-signals=
1762 [KNL] debug: print fatal signals
1763 print-fatal-signals=1: print segfault info to
1764 the kernel console.
1765 default: off.
1766
e84845c4
RD
1767 printk.time= Show timing data prefixed to each printk message line
1768 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1769
1da177e4 1770 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1771 Format: [schedule,]<number>
1772 Param: "schedule" - profile schedule points.
1773 Param: <number> - step/bucket size as a power of 2 for
1774 statistical time based profiling.
b3da2a73
MG
1775 Param: "sleep" - profile D-state sleeping (millisecs).
1776 Requires CONFIG_SCHEDSTATS
c0fe2e69 1777 Param: "kvm" - profile VM exits.
1da177e4 1778
a9913044 1779 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1780 Limit processor to maximum C-state
1781 max_cstate=9 overrides any DMI blacklist limit.
1782
41c0d868
LB
1783 processor.nocst [HW,ACPI]
1784 Ignore the _CST method to determine C-states,
1785 instead using the legacy FADT method
1786
1da177e4
LT
1787 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1788 before loading.
31c00fc1 1789 See Documentation/blockdev/ramdisk.txt.
1da177e4 1790
a9913044
RD
1791 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1792 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1793 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1794 per second.
a9913044
RD
1795 psmouse.resetafter= [HW,MOUSE]
1796 Try to reset the device after so many bad packets
1da177e4
LT
1797 (0 = never).
1798 psmouse.resolution=
1799 [HW,MOUSE] Set desired mouse resolution, in dpi.
1800 psmouse.smartscroll=
a9913044 1801 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1802 0 = disabled, 1 = enabled (default).
1803
1804 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1805 Format:
1806 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1807
1808 pt. [PARIDE]
31c00fc1 1809 See Documentation/blockdev/paride.txt.
1da177e4 1810
dc8c8587
KS
1811 pty.legacy_count=
1812 [KNL] Number of legacy pty's. Overwrites compiled-in
1813 default number.
1814
7d2c502f 1815 quiet [KNL] Disable most log messages
a9913044 1816
1da177e4
LT
1817 r128= [HW,DRM]
1818
1819 raid= [HW,RAID]
1820 See Documentation/md.txt.
1821
a9913044 1822 ramdisk_blocksize= [RAM]
31c00fc1 1823 See Documentation/blockdev/ramdisk.txt.
a9913044 1824
1da177e4 1825 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 1826 See Documentation/blockdev/ramdisk.txt.
1da177e4 1827
24aaef8d
RD
1828 rcupdate.blimit= [KNL,BOOT]
1829 Set maximum number of finished RCU callbacks to process
1830 in one batch.
21a1ea9e 1831
24aaef8d
RD
1832 rcupdate.qhimark= [KNL,BOOT]
1833 Set threshold of queued
21a1ea9e
DS
1834 RCU callbacks over which batch limiting is disabled.
1835
24aaef8d
RD
1836 rcupdate.qlowmark= [KNL,BOOT]
1837 Set threshold of queued RCU callbacks below which
1838 batch limiting is re-enabled.
21a1ea9e 1839
ffdfc409
OJ
1840 rdinit= [KNL]
1841 Format: <full_path>
1842 Run specified binary instead of /init from the ramdisk,
1843 used for early userspace startup. See initrd.
1844
cd4f0ef7 1845 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1846 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1847 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1848
46b6d94e
PJ
1849 relax_domain_level=
1850 [KNL, SMP] Set scheduler's default relax_domain_level.
1851 See Documentation/cpusets.txt.
1852
1da177e4
LT
1853 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1854
cd4f0ef7 1855 reservetop= [X86-32]
461a9aff
ZA
1856 Format: nn[KMG]
1857 Reserves a hole at the top of the kernel virtual
1858 address space.
1859
7e96287d
VG
1860 reset_devices [KNL] Force drivers to reset the underlying device
1861 during initialization.
1862
a9913044
RD
1863 resume= [SWSUSP]
1864 Specify the partition device for software suspend
1da177e4 1865
ecbd0da1
RW
1866 resume_offset= [SWSUSP]
1867 Specify the offset from the beginning of the partition
1868 given by "resume=" at which the swap header is located,
1869 in <PAGE_SIZE> units (needed only for swap files).
1870 See Documentation/power/swsusp-and-swap-files.txt
1871
0a7b35cb
MN
1872 retain_initrd [RAM] Keep initrd memory after extraction
1873
1da177e4
LT
1874 rhash_entries= [KNL,NET]
1875 Set number of hash buckets for route cache
1876
1877 riscom8= [HW,SERIAL]
1878 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1879
1880 ro [KNL] Mount root device read-only on boot
1881
1882 root= [KNL] Root filesystem
1883
1884 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1885 mount the root filesystem
1886
1887 rootflags= [KNL] Set root filesystem mount option string
1888
1889 rootfstype= [KNL] Set root filesystem type
1890
cc1ed754
PO
1891 rootwait [KNL] Wait (indefinitely) for root device to show up.
1892 Useful for devices that are detected asynchronously
1893 (e.g. USB and MMC devices).
1894
20510f2f
JM
1895 root_plug.vendor_id=
1896 [ROOTPLUG] Override the default vendor ID
1897
1898 root_plug.product_id=
1899 [ROOTPLUG] Override the default product ID
1900
1901 root_plug.debug=
1902 [ROOTPLUG] Enable debugging output
1903
1da177e4
LT
1904 rw [KNL] Mount root device read-write on boot
1905
1906 S [KNL] Run init in single mode
1907
1908 sa1100ir [NET]
1909 See drivers/net/irda/sa1100_ir.c.
1910
1da177e4 1911 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1912
1da177e4
LT
1913 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1914 Format: <io>[,<timeout>[,<isapnp>]]
1915
1916 scsi_debug_*= [SCSI]
1917 See drivers/scsi/scsi_debug.c.
1918
1919 scsi_default_dev_flags=
1920 [SCSI] SCSI default device flags
1921 Format: <integer>
1922
1923 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1924 Format: <vendor>:<model>:<flags>
1925 (flags are integer value)
1926
6af6632a
RD
1927 scsi_logging_level= [SCSI] a bit mask of logging levels
1928 See drivers/scsi/scsi_logging.h for bits. Also
1929 settable via sysctl at dev.scsi.logging_level
1930 (/proc/sys/dev/scsi/logging_level).
1931 There is also a nice 'scsi_logging_level' script in the
1932 S390-tools package, available for download at
1933 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1934
3e082a91
MW
1935 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1936 discovered. async scans them in kernel threads,
1937 allowing boot to proceed. none ignores them, expecting
1938 user space to do the scan.
1939
1da177e4
LT
1940 selinux [SELINUX] Disable or enable SELinux at boot time.
1941 Format: { "0" | "1" }
1942 See security/selinux/Kconfig help text.
1943 0 -- disable.
1944 1 -- enable.
1945 Default value is set via kernel config option.
1946 If enabled at boot time, /selinux/disable can be used
1947 later to disable prior to initial policy load.
1948
4e5ab4cb
JM
1949 selinux_compat_net =
1950 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1951 Format: { "0" | "1" }
1952 0 -- use new secmark-based packet controls
1953 1 -- use legacy packet controls
1954 Default value is 0 (preferred).
1955 Value can be changed at runtime via
1956 /selinux/compat_net.
4e5ab4cb 1957
cd4f0ef7 1958 serialnumber [BUGS=X86-32]
1da177e4 1959
1da177e4
LT
1960 shapers= [NET]
1961 Maximal number of shapers.
a9913044 1962
b05f78f5
YL
1963 show_msr= [x86] show boot-time MSR settings
1964 Format: { <integer> }
1965 Show boot-time (BIOS-initialized) MSR settings.
1966 The parameter means the number of CPUs to show,
1967 for example 1 means boot CPU only.
1968
1da177e4
LT
1969 sim710= [SCSI,HW]
1970 See header of drivers/scsi/sim710.c.
1971
1972 simeth= [IA-64]
1973 simscsi=
a9913044 1974
1da177e4
LT
1975 slram= [HW,MTD]
1976
f0630fff
CL
1977 slub_debug[=options[,slabs]] [MM, SLUB]
1978 Enabling slub_debug allows one to determine the
1979 culprit if slab objects become corrupted. Enabling
1980 slub_debug can create guard zones around objects and
1981 may poison objects when not in use. Also tracks the
1982 last alloc / free. For more information see
1983 Documentation/vm/slub.txt.
c1aee215
CL
1984
1985 slub_max_order= [MM, SLUB]
f0630fff
CL
1986 Determines the maximum allowed order for slabs.
1987 A high setting may cause OOMs due to memory
1988 fragmentation. For more information see
1989 Documentation/vm/slub.txt.
c1aee215
CL
1990
1991 slub_min_objects= [MM, SLUB]
f0630fff
CL
1992 The minimum number of objects per slab. SLUB will
1993 increase the slab order up to slub_max_order to
1994 generate a sufficiently large slab able to contain
1995 the number of objects indicated. The higher the number
1996 of objects the smaller the overhead of tracking slabs
1997 and the less frequently locks need to be acquired.
c1aee215
CL
1998 For more information see Documentation/vm/slub.txt.
1999
2000 slub_min_order= [MM, SLUB]
2001 Determines the mininum page order for slabs. Must be
f0630fff 2002 lower than slub_max_order.
c1aee215
CL
2003 For more information see Documentation/vm/slub.txt.
2004
2005 slub_nomerge [MM, SLUB]
f0630fff 2006 Disable merging of slabs with similar size. May be
c1aee215 2007 necessary if there is some reason to distinguish
f0630fff
CL
2008 allocs to different slabs. Debug options disable
2009 merging on their own.
c1aee215
CL
2010 For more information see Documentation/vm/slub.txt.
2011
1da177e4
LT
2012 smart2= [HW]
2013 Format: <io1>[,<io2>[,...,<io8>]]
2014
cd4f0ef7 2015 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2016 attempt to substitute SMP alternatives once at boot.
2017
d0d4f69b
BH
2018 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2019 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2020 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2021 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2022 smsc-ircc2.ircc_irq= [HW] IRQ line
2023 smsc-ircc2.ircc_dma= [HW] DMA channel
2024 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2025 0: Toshiba Satellite 1800 (GP data pin select)
2026 1: Fast pin select (default)
2027 2: ATC IRMode
2028
1da177e4
LT
2029 snd-ad1816a= [HW,ALSA]
2030
2031 snd-ad1848= [HW,ALSA]
2032
2033 snd-ali5451= [HW,ALSA]
2034
2035 snd-als100= [HW,ALSA]
2036
2037 snd-als4000= [HW,ALSA]
2038
2039 snd-azt2320= [HW,ALSA]
2040
2041 snd-cmi8330= [HW,ALSA]
2042
2043 snd-cmipci= [HW,ALSA]
2044
2045 snd-cs4231= [HW,ALSA]
2046
2047 snd-cs4232= [HW,ALSA]
2048
2049 snd-cs4236= [HW,ALSA]
2050
2051 snd-cs4281= [HW,ALSA]
2052
2053 snd-cs46xx= [HW,ALSA]
2054
2055 snd-dt019x= [HW,ALSA]
2056
2057 snd-dummy= [HW,ALSA]
2058
2059 snd-emu10k1= [HW,ALSA]
2060
2061 snd-ens1370= [HW,ALSA]
2062
2063 snd-ens1371= [HW,ALSA]
2064
2065 snd-es968= [HW,ALSA]
2066
2067 snd-es1688= [HW,ALSA]
2068
2069 snd-es18xx= [HW,ALSA]
2070
2071 snd-es1938= [HW,ALSA]
2072
2073 snd-es1968= [HW,ALSA]
2074
2075 snd-fm801= [HW,ALSA]
2076
2077 snd-gusclassic= [HW,ALSA]
2078
2079 snd-gusextreme= [HW,ALSA]
2080
2081 snd-gusmax= [HW,ALSA]
2082
2083 snd-hdsp= [HW,ALSA]
2084
2085 snd-ice1712= [HW,ALSA]
2086
2087 snd-intel8x0= [HW,ALSA]
2088
2089 snd-interwave= [HW,ALSA]
2090
2091 snd-interwave-stb=
2092 [HW,ALSA]
2093
2094 snd-korg1212= [HW,ALSA]
2095
2096 snd-maestro3= [HW,ALSA]
2097
2098 snd-mpu401= [HW,ALSA]
2099
2100 snd-mtpav= [HW,ALSA]
2101
2102 snd-nm256= [HW,ALSA]
2103
2104 snd-opl3sa2= [HW,ALSA]
2105
2106 snd-opti92x-ad1848=
2107 [HW,ALSA]
2108
2109 snd-opti92x-cs4231=
2110 [HW,ALSA]
2111
2112 snd-opti93x= [HW,ALSA]
2113
2114 snd-pmac= [HW,ALSA]
2115
2116 snd-rme32= [HW,ALSA]
2117
2118 snd-rme96= [HW,ALSA]
2119
2120 snd-rme9652= [HW,ALSA]
2121
2122 snd-sb8= [HW,ALSA]
2123
2124 snd-sb16= [HW,ALSA]
2125
2126 snd-sbawe= [HW,ALSA]
2127
2128 snd-serial= [HW,ALSA]
2129
2130 snd-sgalaxy= [HW,ALSA]
2131
2132 snd-sonicvibes= [HW,ALSA]
2133
2134 snd-sun-amd7930=
2135 [HW,ALSA]
2136
2137 snd-sun-cs4231= [HW,ALSA]
2138
2139 snd-trident= [HW,ALSA]
2140
2141 snd-usb-audio= [HW,ALSA,USB]
2142
2143 snd-via82xx= [HW,ALSA]
2144
2145 snd-virmidi= [HW,ALSA]
2146
2147 snd-wavefront= [HW,ALSA]
2148
2149 snd-ymfpci= [HW,ALSA]
a9913044 2150
9c44bc03
IM
2151 softlockup_panic=
2152 [KNL] Should the soft-lockup detector generate panics.
2153
1da177e4
LT
2154 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2155 See Documentation/sonypi.txt
2156
2157 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2158 See Documentation/serial/specialix.txt.
1da177e4
LT
2159
2160 spia_io_base= [HW,MTD]
2161 spia_fio_base=
2162 spia_pedr=
2163 spia_peddr=
2164
2165 sscape= [HW,OSS]
2166 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2167
1da177e4
LT
2168 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2169 See Documentation/scsi/st.txt.
2170
1da177e4
LT
2171 sti= [PARISC,HW]
2172 Format: <num>
2173 Set the STI (builtin display/keyboard on the HP-PARISC
2174 machines) console (graphic card) which should be used
2175 as the initial boot-console.
2176 See also comment in drivers/video/console/sticore.c.
2177
2178 sti_font= [HW]
2179 See comment in drivers/video/console/sticore.c.
2180
2181 stifb= [HW]
2182 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2183
42a7fc4a
GB
2184 sunrpc.pool_mode=
2185 [NFS]
2186 Control how the NFS server code allocates CPUs to
2187 service thread pools. Depending on how many NICs
2188 you have and where their interrupts are bound, this
2189 option will affect which CPUs will do NFS serving.
2190 Note: this parameter cannot be changed while the
2191 NFS server is running.
2192
2193 auto the server chooses an appropriate mode
2194 automatically using heuristics
2195 global a single global pool contains all CPUs
2196 percpu one pool for each CPU
2197 pernode one pool for each NUMA node (equivalent
2198 to global on non-NUMA machines)
2199
1da177e4 2200 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2201
1da177e4
LT
2202 switches= [HW,M68k]
2203
2204 sym53c416= [HW,SCSI]
2205 See header of drivers/scsi/sym53c416.c.
2206
5d6f647f
IM
2207 sysrq_always_enabled
2208 [KNL]
2209 Ignore sysrq setting - this boot parameter will
2210 neutralize any effect of /proc/sys/kernel/sysrq.
2211 Useful for debugging.
2212
1da177e4
LT
2213 t128= [HW,SCSI]
2214 See header of drivers/scsi/t128.c.
2215
2216 tdfx= [HW,DRM]
2217
77437fd4
DB
2218 test_suspend= [SUSPEND]
2219 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2220 standby suspend) as the system sleep state to briefly
2221 enter during system startup. The system is woken from
2222 this state using a wakeup-capable RTC alarm.
2223
1da177e4
LT
2224 thash_entries= [KNL,NET]
2225 Set number of hash buckets for TCP connection
2226
f8707ec9
LB
2227 thermal.act= [HW,ACPI]
2228 -1: disable all active trip points in all thermal zones
2229 <degrees C>: override all lowest active trip points
2230
c52a7419
LB
2231 thermal.crt= [HW,ACPI]
2232 -1: disable all critical trip points in all thermal zones
22a94d79 2233 <degrees C>: override all critical trip points
c52a7419 2234
f5487145
LB
2235 thermal.nocrt= [HW,ACPI]
2236 Set to disable actions on ACPI thermal zone
2237 critical and hot trip points.
2238
72b33ef8
LB
2239 thermal.off= [HW,ACPI]
2240 1: disable ACPI thermal control
2241
a70cdc52
LB
2242 thermal.psv= [HW,ACPI]
2243 -1: disable all passive trip points
2244 <degrees C>: override all passive trip points to this value
2245
730ff34d
LB
2246 thermal.tzp= [HW,ACPI]
2247 Specify global default ACPI thermal zone polling rate
2248 <deci-seconds>: poll all this frequency
2249 0: no polling (default)
2250
1da177e4
LT
2251 tmscsim= [HW,SCSI]
2252 See comment before function dc390_setup() in
2253 drivers/scsi/tmscsim.c.
2254
2255 tp720= [HW,PS2]
2256
2257 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2258 Format:
2259 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2260
a9913044
RD
2261 turbografx.map[2|3]= [HW,JOY]
2262 TurboGraFX parallel port interface
2263 Format:
2264 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2265 See also Documentation/input/joystick-parport.txt
2266
2267 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2268 See header of drivers/scsi/u14-34f.c.
2269
2270 uart401= [HW,OSS]
2271 Format: <io>,<irq>
2272
2273 uart6850= [HW,OSS]
2274 Format: <io>,<irq>
2275
5f8364b7
AS
2276 uhci-hcd.ignore_oc=
2277 [USB] Ignore overcurrent events (default N).
2278 Some badly-designed motherboards generate lots of
2279 bogus events, for ports that aren't wired to
2280 anything. Set this parameter to avoid log spamming.
2281 Note that genuine overcurrent events won't be
2282 reported either.
2283
e3a61b0a
SA
2284 unknown_nmi_panic
2285 [X86-32,X86-64]
2286 Set unknown_nmi_panic=1 early on boot.
2287
b5e795f8
AS
2288 usbcore.autosuspend=
2289 [USB] The autosuspend time delay (in seconds) used
2290 for newly-detected USB devices (default 2). This
2291 is the time required before an idle device will be
2292 autosuspended. Devices for which the delay is set
eaafbc3a 2293 to a negative value won't be autosuspended at all.
b5e795f8 2294
fd7c519d
JK
2295 usbcore.usbfs_snoop=
2296 [USB] Set to log all usbfs traffic (default 0 = off).
2297
2298 usbcore.blinkenlights=
2299 [USB] Set to cycle leds on hubs (default 0 = off).
2300
2301 usbcore.old_scheme_first=
2302 [USB] Start with the old device initialization
2303 scheme (default 0 = off).
2304
2305 usbcore.use_both_schemes=
2306 [USB] Try the other device initialization scheme
2307 if the first one fails (default 1 = enabled).
2308
2309 usbcore.initial_descriptor_timeout=
2310 [USB] Specifies timeout for the initial 64-byte
2311 USB_REQ_GET_DESCRIPTOR request in milliseconds
2312 (default 5000 = 5.0 seconds).
2313
1da177e4
LT
2314 usbhid.mousepoll=
2315 [USBHID] The interval which mice are to be polled at.
a9913044 2316
200001eb
PJ
2317 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2318 kernel's map of available physical RAM.
2319
cd4f0ef7 2320 vdso= [X86-32,SH,x86-64]
1dbf527c 2321 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2322 vdso=1: enable VDSO (default)
2323 vdso=0: disable VDSO mapping
2324
af65d648
RM
2325 vdso32= [X86-32,X86-64]
2326 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2327 vdso32=1: enable 32-bit VDSO (default)
2328 vdso32=0: disable 32-bit VDSO mapping
2329
d080d397
YI
2330 vector= [IA-64,SMP]
2331 vector=percpu: enable percpu vector domain
2332
1da177e4
LT
2333 video= [FB] Frame buffer configuration
2334 See Documentation/fb/modedb.txt.
2335
cd4f0ef7 2336 vga= [BOOT,X86-32] Select a particular video mode
71cced6e 2337 See Documentation/x86/i386/boot.txt and
a9913044 2338 Documentation/svga.txt.
1da177e4
LT
2339 Use vga=ask for menu.
2340 This is actually a boot loader parameter; the value is
2341 passed to the kernel using a special protocol.
2342
a9913044 2343 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2344 size of <nn>. This can be used to increase the
2345 minimum size (128MB on x86). It can also be used to
2346 decrease the size and leave more room for directly
2347 mapped kernel RAM.
2348
585c3047
PO
2349 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2350 Format: <command>
1da177e4 2351
585c3047
PO
2352 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2353 Format: <command>
2354
2355 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2356 Format: <command>
a9913044 2357
1da177e4
LT
2358 waveartist= [HW,OSS]
2359 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2360
1da177e4
LT
2361 wd33c93= [HW,SCSI]
2362 See header of drivers/scsi/wd33c93.c.
2363
2364 wd7000= [HW,SCSI]
2365 See header of drivers/scsi/wd7000.c.
2366
2367 wdt= [WDT] Watchdog
8dfe9c21 2368 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2369
2370 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2371 xd_geo= See header of drivers/block/xd.c.
2372
2373 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2374 Format:
2375 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2376
a62eaf15
AK
2377 norandmaps Don't use address space randomization
2378 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2379
a9913044 2380______________________________________________________________________
1da177e4
LT
2381
2382TODO:
2383
2384 Add documentation for ALSA options.
2385 Add more DRM drivers.