PNP: update pnp.debug usage (needs value on command line)
[GitHub/mt8127/android_kernel_alcatel_ttab.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
ca1eda2d
RD
20Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
a901ebb9
SR
26This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
6585fa8a
SR
33The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
1da177e4
LT
37
38 ACPI ACPI support is enabled.
c99c108a 39 AGP AGP (Accelerated Graphics Port) is enabled.
1da177e4
LT
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
e7ba176b 43 AVR32 AVR32 architecture is enabled.
1da177e4 44 AX25 Appropriate AX.25 support is enabled.
0ae53640 45 BLACKFIN Blackfin architecture is enabled.
9cfe268e
AC
46 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
1da177e4
LT
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
2521f2c2 52 GCOV GCOV profiling is enabled.
1da177e4 53 HW Appropriate hardware is enabled.
1da177e4 54 IA-64 IA-64 architecture is enabled.
6146f0d5 55 IMA Integrity measurement architecture is enabled.
1da177e4 56 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 58 IPV6 IPv6 support is enabled.
1da177e4
LT
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
84c08fd6 62 KGDB Kernel debugger support is enabled.
fef07aae 63 KVM Kernel Virtual Machine support is enabled.
11ef697b 64 LIBATA Libata driver is enabled
1da177e4
LT
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
309e57df 73 MSI Message Signaled Interrupts (PCI).
c8facbb6 74 MTD MTD (Memory Technology Device) support is enabled.
1da177e4
LT
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
c8facbb6
RD
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
1da177e4
LT
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
7f785763 83 PCIE PCI Express support is enabled.
1da177e4
LT
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
163475fb
RD
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
20510f2f 94 SECURITY Different security models are enabled.
1da177e4 95 SELINUX SELinux support is enabled.
c1c124e9 96 APPARMOR AppArmor support is enabled.
1da177e4 97 SERIAL Serial support is enabled.
e523d93c 98 SH SuperH architecture is enabled.
1da177e4
LT
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
77437fd4
DB
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
f38f1d2a 103 FTRACE Function tracing enabled.
225a9be2 104 TPM TPM drivers are enabled.
1da177e4 105 TS Appropriate touchscreen support is enabled.
d4f373e5 106 UMS USB Mass Storage support is enabled.
1da177e4
LT
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 114 X86-32 X86-32, aka i386 architecture is enabled.
1da177e4
LT
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
71cced6e 117 Documentation/x86/x86_64/boot-options.txt .
c0115606 118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
c1c5413a 119 XEN Xen support is enabled
1da177e4
LT
120
121In addition, the following text indicates that the option:
122
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
954a8b81 130need or coordination with <Documentation/x86/boot.txt>.
1da177e4 131
5558870b 132There are also arch-specific kernel-parameters not documented here.
71cced6e 133See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 134
1da177e4
LT
135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
9c4751fd 141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
7a19a237
AD
147Finally, the [KMG] suffix is commonly described after a number of kernel
148parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150bytes respectively. Such letter suffixes can also be entirely omitted.
151
9c4751fd 152
6cececfc 153 acpi= [HW,ACPI,X86]
03d926f8 154 Advanced Configuration and Power Interface
68ca4069 155 Format: { force | off | strict | noirq | rsdt }
1da177e4
LT
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
a9913044 159 strict -- Be less tolerant of platforms that are not
1da177e4 160 strictly ACPI specification compliant.
237889bf 161 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 162 copy_dsdt -- copy DSDT to memory
1da177e4 163
53471121 164 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 165
4996c023
TI
166 acpi_rsdp= [ACPI,EFI,KEXEC]
167 Pass the RSDP address to the kernel, mostly used
168 on machines running EFI runtime service to boot the
169 second kernel for kdump.
170
a1fdcc0d
LB
171 acpi_apic_instance= [ACPI, IOAPIC]
172 Format: <int>
173 2: use 2nd APIC table, if available
174 1,0: use 1st APIC table
4e381a4f 175 default: 0
a1fdcc0d 176
c3d6de69
TR
177 acpi_backlight= [HW,ACPI]
178 acpi_backlight=vendor
179 acpi_backlight=video
180 If set to vendor, prefer vendor specific driver
181 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
182 of the ACPI video.ko driver.
183
a0d84a92
BH
184 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
185 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 186 Format: <int>
a0d84a92
BH
187 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
188 debug output. Bits in debug_layer correspond to a
189 _COMPONENT in an ACPI source file, e.g.,
190 #define _COMPONENT ACPI_PCI_COMPONENT
191 Bits in debug_level correspond to a level in
192 ACPI_DEBUG_PRINT statements, e.g.,
193 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
e76f4276
BH
194 The debug_level mask defaults to "info". See
195 Documentation/acpi/debug.txt for more information about
196 debug layers and levels.
a0d84a92 197
e76f4276
BH
198 Enable processor driver info messages:
199 acpi.debug_layer=0x20000000
200 Enable PCI/PCI interrupt routing info messages:
201 acpi.debug_layer=0x400000
a0d84a92
BH
202 Enable AML "Debug" output, i.e., stores to the Debug
203 object while interpreting AML:
204 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
a0d84a92
BH
205 Enable all messages related to ACPI hardware:
206 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
207
208 Some values produce so much output that the system is
209 unusable. The "log_buf_len" parameter may be useful
210 if you need to capture more output.
f989106c 211
0cb55ad2
RD
212 acpi_irq_balance [HW,ACPI]
213 ACPI will balance active IRQs
214 default in APIC mode
215
216 acpi_irq_nobalance [HW,ACPI]
217 ACPI will not move active IRQs (default)
218 default in PIC mode
219
220 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
221 Format: <irq>,<irq>...
222
223 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
224 use by PCI
225 Format: <irq>,<irq>...
226
227 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
228
229 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
230 Format: To spoof as Windows 98: ="Microsoft Windows"
231
232 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
233 acpi_osi="string1" # add string1 -- only one string
234 acpi_osi="!string2" # remove built-in string2
235 acpi_osi= # disable all strings
236
6cececfc 237 acpi_pm_good [X86]
0cb55ad2
RD
238 Override the pmtimer bug detection: force the kernel
239 to assume that this machine's pmtimer latches its value
240 and always returns good values.
241
4af94f39
RD
242 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
243 Format: { level | edge | high | low }
244
245 acpi_serialize [HW,ACPI] force serialization of AML methods
246
247 acpi_skip_timer_override [HW,ACPI]
248 Recognize and ignore IRQ0/pin2 Interrupt Override.
249 For broken nForce2 BIOS resulting in XT-PIC timer.
250
251 acpi_sleep= [HW,ACPI] Sleep options
252 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
c3b0795c 253 old_ordering, nonvs, sci_force_enable }
4af94f39
RD
254 See Documentation/power/video.txt for information on
255 s3_bios and s3_mode.
256 s3_beep is for debugging; it makes the PC's speaker beep
257 as soon as the kernel's real-mode entry point is called.
258 s4_nohwsig prevents ACPI hardware signature from being
259 used during resume from hibernation.
260 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with respect to putting devices into
262 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by default).
72ad5d77
RW
264 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during suspend/hibernation and resume.
d7f0eea9
ZR
266 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken systems don't work without it).
4af94f39
RD
269
270 acpi_use_timer_override [HW,ACPI]
271 Use timer override. For some broken Nvidia NF5 boards
272 that require a timer override, but don't have HPET
273
7e90560c
LT
274 acpi_enforce_resources= [ACPI]
275 { strict | lax | no }
276 Check for resource conflicts between native drivers
277 and ACPI OperationRegions (SystemIO and SystemMemory
278 only). IO ports and memory declared in ACPI might be
279 used by the ACPI subsystem in arbitrary AML code and
280 can interfere with legacy drivers.
281 strict (default): access to resources claimed by ACPI
282 is denied; legacy drivers trying to access reserved
283 resources will fail to bind to device using them.
284 lax: access to resources claimed by ACPI is allowed;
285 legacy drivers trying to access reserved resources
286 will bind successfully but a warning message is logged.
287 no: ACPI OperationRegions are not marked as reserved,
288 no further checks are performed.
289
4af94f39
RD
290 add_efi_memmap [EFI; X86] Include EFI memory map in
291 kernel's map of available physical RAM.
292
0cb55ad2
RD
293 agp= [AGP]
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
298
bcfde334
RD
299 ALSA [HW,ALSA]
300 See Documentation/sound/alsa/alsa-parameters.txt
301
d944d549
RK
302 alignment= [KNL,ARM]
303 Allow the default userspace alignment fault handler
304 behaviour to be specified. Bit 0 enables warnings,
305 bit 1 enables fixups, and bit 2 sends a segfault.
306
54b4cbd2
JR
307 amd_iommu= [HW,X86-84]
308 Pass parameters to the AMD IOMMU driver in the system.
309 Possible values are:
afa9fdc2
FT
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
313 is a lot of faster
a5235725
JR
314 off - do not initialize any AMD IOMMU found in
315 the system
afa9fdc2 316
1da177e4
LT
317 amijoy.map= [HW,JOY] Amiga joystick support
318 Map of devices attached to JOY0DAT and JOY1DAT
319 Format: <a>,<b>
320 See also Documentation/kernel/input/joystick.txt
321
322 analog.map= [HW,JOY] Analog joystick and gamepad support
323 Specifies type or capabilities of an analog joystick
324 connected to one of 16 gameports
325 Format: <type1>,<type2>,..<type16>
326
a9913044
RD
327 apc= [HW,SPARC]
328 Power management functions (SPARCstation-4/5 + deriv.)
1da177e4
LT
329 Format: noidle
330 Disable APC CPU standby support. SPARCstation-Fox does
331 not play well with APC CPU idle - disable it if you have
332 APC and your system crashes randomly.
333
ca1eda2d 334 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 335 Change the output verbosity whilst booting
1da177e4
LT
336 Format: { quiet (default) | verbose | debug }
337 Change the amount of debugging information output
338 when initialising the APIC and IO-APIC components.
a9913044 339
b0f83b28
BH
340 autoconf= [IPV6]
341 See Documentation/networking/ipv6.txt.
342
9636bc05
CG
343 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
344 Limit apic dumping. The parameter defines the maximal
345 number of local apics being dumped. Also it is possible
346 to set it to "all" by meaning -- no limit here.
347 Format: { 1 (default) | 2 | ... | all }.
348 The parameter valid if only apic=debug or
349 apic=verbose is specified.
350 Example: apic=debug show_lapic=all
351
1da177e4 352 apm= [APM] Advanced Power Management
71f77055 353 See header of arch/x86/kernel/apm_32.c.
1da177e4 354
1da177e4
LT
355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
357
358 ataflop= [HW,M68k]
359
360 atarimouse= [HW,MOUSE] Atari Mouse
361
1da177e4
LT
362 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
363 EzKey and similar keyboards
364
365 atkbd.reset= [HW] Reset keyboard during initialization
366
a9913044
RD
367 atkbd.set= [HW] Select keyboard code set
368 Format: <int> (2 = AT (default), 3 = PS/2)
1da177e4
LT
369
370 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
371 keyboards
372
373 atkbd.softraw= [HW] Choose between synthetic and real raw mode
374 Format: <bool> (0 = real, 1 = synthetic (default))
a9913044
RD
375
376 atkbd.softrepeat= [HW]
377 Use software keyboard repeat
1da177e4
LT
378
379 autotest [IA64]
380
1da177e4
LT
381 baycom_epp= [HW,AX25]
382 Format: <io>,<mode>
a9913044 383
1da177e4
LT
384 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
385 Format: <io>,<mode>
386 See header of drivers/net/hamradio/baycom_par.c.
387
a9913044
RD
388 baycom_ser_fdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
1da177e4
LT
390 Format: <io>,<irq>,<mode>[,<baud>]
391 See header of drivers/net/hamradio/baycom_ser_fdx.c.
392
a9913044
RD
393 baycom_ser_hdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
1da177e4
LT
395 Format: <io>,<irq>,<mode>
396 See header of drivers/net/hamradio/baycom_ser_hdx.c.
397
bfe8df3d
RD
398 boot_delay= Milliseconds to delay each printk during boot.
399 Values larger than 10 seconds (10000) are changed to
400 no delay (0).
401 Format: integer
402
35fc908d
AH
403 bootmem_debug [KNL] Enable bootmem allocator debug messages.
404
1da177e4 405 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
a9913044
RD
406 bttv.radio= Most important insmod options are available as
407 kernel args too.
1da177e4
LT
408 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
409 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
410
4e89a2d8
WS
411 bulk_remove=off [PPC] This parameter disables the use of the pSeries
412 firmware feature for flushing multiple hpte entries
413 at a time.
414
1da177e4
LT
415 c101= [NET] Moxa C101 synchronous serial card
416
cd4f0ef7 417 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
1da177e4
LT
418 Sometimes CPU hardware bugs make them report the cache
419 size incorrectly. The kernel will attempt work arounds
420 to fix known problems, but for some CPUs it is not
421 possible to determine what the correct size should be.
422 This option provides an override for these situations.
423
20510f2f
JM
424 capability.disable=
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
429
14ff56bb
SO
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
1da177e4 432
8bab8dde
PM
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
436
1da177e4
LT
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
a9913044
RD
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
1da177e4
LT
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
a9913044
RD
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
446
661ca0da
SO
447 cio_ignore= [S390]
448 See Documentation/s390/CommonIO for details.
449
cd4f0ef7 450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 451 [Deprecated]
3f6dee9b 452 Forces specified clocksource (if available) to be used
734efb46 453 when calculating gettimeofday(). If specified
3f6dee9b 454 clocksource is not available, it defaults to PIT.
1da177e4
LT
455 Format: { pit | tsc | cyclone | pmtmr }
456
592913ec 457 clocksource= Override the default clocksource
3d6ac984
RD
458 Format: <string>
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
462 the platform:
463 [all] jiffies (this is the base, fallback clocksource)
464 [ACPI] acpi_pm
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
467 [AVR32] avr32
9863c90f 468 [X86-32] pit,hpet,tsc;
3d6ac984
RD
469 scx200_hrt on Geode; cyclone on IBM x440
470 [MIPS] MIPS
471 [PARISC] cr16
472 [S390] tod
473 [SH] SuperH
474 [SPARC64] tick
475 [X86-64] hpet,tsc
476
ac72e788
AK
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
07983f0e
RD
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
ac72e788
AK
481 stable over kernel options, but the vendor specific
482 ones should be.
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
488 some critical bits.
489
14f966e7
RJ
490 cmo_free_hint= [PPC] Format: { yes | no }
491 Specify whether pages are marked as being inactive
492 when they are freed. This is used in CMO environments
493 to determine OS memory pressure for page stealing by
494 a hypervisor.
495 Default: yes
496
6cececfc 497 code_bytes [X86] How many bytes of object code to print
a25bd949 498 in an oops report.
86c41837
CE
499 Range: 0 - 8192
500 Default: 64
501
1da177e4 502 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
503 Format:
504 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
505
506 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
507 Format: <io>[,<irq>]
508
a9913044
RD
509 com90xx= [HW,NET]
510 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
511 Format: <io>[,<irq>[,<memstart>]]
512
513 condev= [HW,S390] console device
514 conmode=
a9913044 515
1da177e4
LT
516 console= [KNL] Output console device and options.
517
518 tty<n> Use the virtual console device <n>.
519
520 ttyS<n>[,options]
f1a1c2dc 521 ttyUSB0[,options]
1da177e4 522 Use the specified serial port. The options are of
f1a1c2dc
RD
523 the form "bbbbpnf", where "bbbb" is the baud rate,
524 "p" is parity ("n", "o", or "e"), "n" is number of
525 bits, and "f" is flow control ("r" for RTS or
526 omit it). Default is "9600n8".
527
528 See Documentation/serial-console.txt for more
529 information. See
530 Documentation/networking/netconsole.txt for an
531 alternative.
1da177e4 532
18a8bd94
YL
533 uart[8250],io,<addr>[,options]
534 uart[8250],mmio,<addr>[,options]
1da177e4
LT
535 Start an early, polled-mode console on the 8250/16550
536 UART at the specified I/O port or MMIO address,
537 switching to the matching ttyS device later. The
538 options are the same as for ttyS, above.
539
f7511d5f
ST
540 If the device connected to the port is not a TTY but a braille
541 device, prepend "brl," before the device type, for instance
542 console=brl,ttyS0
543 For now, only VisioBraille is supported.
544
f324edc8
DM
545 consoleblank= [KNL] The console blank (screen saver) timeout in
546 seconds. Defaults to 10*60 = 10mins. A value of 0
547 disables the blank timer.
548
4cb0e11b
HK
549 coredump_filter=
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
553
62027aea
LB
554 cpuidle.off=1 [CPU_IDLE]
555 disable the cpuidle sub-system
556
1da177e4 557 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
558 Format:
559 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 560
6f21e646
AD
561 crashkernel=size[KMG][@offset[KMG]]
562 [KNL] Using kexec, Linux can switch to a 'crash kernel'
563 upon panic. This parameter reserves the physical
564 memory region [offset, offset + size] for that kernel
565 image. If '@offset' is omitted, then a suitable offset
566 is selected automatically. Check
567 Documentation/kdump/kdump.txt for further details.
dc009d92 568
fb391599
BW
569 crashkernel=range1:size1[,range2:size2,...][@offset]
570 [KNL] Same as above, but depends on the memory
571 in the running system. The syntax of range is
572 start-[end] where start and end are both
573 a memory unit (amount[KMG]). See also
6f21e646 574 Documentation/kdump/kdump.txt for an example.
fb391599 575
1da177e4
LT
576 cs89x0_dma= [HW,NET]
577 Format: <dma>
578
579 cs89x0_media= [HW,NET]
580 Format: { rj45 | aui | bnc }
a9913044 581
a9913044 582 dasd= [HW,NET]
1da177e4
LT
583 See header of drivers/s390/block/dasd_devmap.c.
584
585 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
586 (one device per port)
587 Format: <port#>,<type>
588 See also Documentation/input/joystick-parport.txt
589
a648ec05
TR
590 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
591 time. See Documentation/dynamic-debug-howto.txt for
592 details.
593
1da177e4
LT
594 debug [KNL] Enable kernel debugging (events log level).
595
cae2ed9a
IM
596 debug_locks_verbose=
597 [KNL] verbose self-tests
598 Format=<0|1>
599 Print debugging info while doing the locking API
600 self-tests.
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
604
3ac7fe5a
TG
605 debug_objects [KNL] Enable object debugging
606
3e8ebb5c
KM
607 no_debug_objects
608 [KNL] Disable object debugging
609
d3af01f1
TG
610 debugpat [X86] Enable PAT debugging
611
2d27a966 612 decnet.addr= [HW,NET]
1da177e4
LT
613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
615
0cb55ad2
RD
616 default_hugepagesz=
617 [same as hugepagesz=] The size of the default
618 HugeTLB page size. This is the size represented by
619 the legacy /proc/ hugepages APIs, used for SHM, and
620 default size when mounting hugetlbfs filesystems.
621 Defaults to the default architecture's huge page size
622 if not specified.
55ff9780 623
1da177e4
LT
624 dhash_entries= [KNL]
625 Set number of hash buckets for dentry cache.
a9913044 626
1da177e4
LT
627 digi= [HW,SERIAL]
628 IO parameters + enable/disable command.
629
630 digiepca= [HW,SERIAL]
631 See drivers/char/README.epca and
31c00fc1 632 Documentation/serial/digiepca.txt.
1da177e4 633
b0f83b28
BH
634 disable= [IPV6]
635 See Documentation/networking/ipv6.txt.
636
4e8b0cf4
NA
637 disable_ddw [PPC/PSERIES]
638 Disable Dynamic DMA Window support. Use this if
639 to workaround buggy firmware.
640
b0f83b28
BH
641 disable_ipv6= [IPV6]
642 See Documentation/networking/ipv6.txt.
643
95ffa243 644 disable_mtrr_cleanup [X86]
95ffa243
YL
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
0cb55ad2 647 entry later. This parameter disables that.
95ffa243 648
093af8d7 649 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
654
6cececfc 655 disable_timer_pin_1 [X86]
0cb55ad2
RD
656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
658
0cb55ad2
RD
659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
661
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
668
1745de5e
JR
669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
675
1da177e4
LT
676 dscc4.setup= [NET]
677
0cb55ad2
RD
678 earlycon= [KNL] Output early console device and options.
679 uart[8250],io,<addr>[,options]
680 uart[8250],mmio,<addr>[,options]
1917ac76 681 uart[8250],mmio32,<addr>[,options]
0cb55ad2
RD
682 Start an early, polled-mode console on the 8250/16550
683 UART at the specified I/O port or MMIO address.
1917ac76
SG
684 MMIO inter-register address stride is either 8bit (mmio)
685 or 32bit (mmio32).
0cb55ad2
RD
686 The options are the same as for ttyS, above.
687
6cececfc 688 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
689 earlyprintk=vga
690 earlyprintk=serial[,ttySn[,baudrate]]
ea3acb19 691 earlyprintk=ttySn[,baudrate]
9780bc41 692 earlyprintk=dbgp[debugController#]
1da177e4 693
a9913044 694 Append ",keep" to not disable it when the real console
1da177e4
LT
695 takes over.
696
5c05917e 697 Only vga or serial or usb debug port at a time.
1da177e4
LT
698
699 Currently only ttyS0 and ttyS1 are supported.
700
701 Interaction with the standard serial driver is not
702 very good.
703
704 The VGA output is eventually overwritten by the real
705 console.
706
9731191f
JW
707 ekgdboc= [X86,KGDB] Allow early kernel console debugging
708 ekgdboc=kbd
709
25985edc 710 This is designed to be used in conjunction with
9731191f
JW
711 the boot argument: earlyprintk=vga
712
1da177e4 713 edd= [EDD]
8c4dd606 714 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 715
1da177e4
LT
716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
718
cd4f0ef7 719 elanfreq= [X86-32]
1da177e4 720 See comment before function elanfreq_setup() in
71f77055 721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
722
723 elevator= [IOSCHED]
17a9e7bb 724 Format: {"cfq" | "deadline" | "noop"}
a9913044
RD
725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
727
6cececfc 728 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 729 Specifies physical address of start of kernel core
aac04b32
VG
730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
1da177e4 733
0cb55ad2
RD
734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
738
ca1eda2d 739 enable_timer_pin_1 [X86]
0cb55ad2
RD
740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
744
1da177e4
LT
745 enforcing [SELINUX] Set initial enforcing status.
746 Format: {"0" | "1"}
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
750 Default value is 0.
751 Value can be changed at runtime via /selinux/enforce.
752
a08f82d0
HY
753 erst_disable [ACPI]
754 Disable Error Record Serialization Table (ERST)
755 support.
756
1da177e4
LT
757 ether= [HW,NET] Ethernet cards parameters
758 This option is obsoleted by the "netdev=" option, which
759 has equivalent usage. See its documentation for details.
760
de1ba09b
AM
761 failslab=
762 fail_page_alloc=
763 fail_make_request=[KNL]
764 General fault injection mechanism.
765 Format: <interval>,<probability>,<space>,<times>
766 See also /Documentation/fault-injection/.
767
1da177e4 768 floppy= [HW]
31c00fc1 769 See Documentation/blockdev/floppy.txt.
1da177e4 770
f13ae30e
AC
771 force_pal_cache_flush
772 [IA-64] Avoid check_sal_cache_flush which may hang on
773 buggy SAL_CACHE_FLUSH implementations. Using this
774 parameter will force ia64_sal_cache_flush to call
775 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
776
d9e54076 777 ftrace=[tracer]
2af15d6a 778 [FTRACE] will set and start the specified tracer
d9e54076
PZ
779 as early as possible in order to facilitate early
780 boot debugging.
781
cecbca96 782 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 783 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
784 If no parameter is passed, ftrace will dump
785 buffers of all CPUs, but if you pass orig_cpu, it will
786 dump only the buffer of the CPU that triggered the
787 oops.
2af15d6a
SR
788
789 ftrace_filter=[function-list]
790 [FTRACE] Limit the functions traced by the function
791 tracer at boot up. function-list is a comma separated
792 list of functions. This list can be changed at run
793 time by the set_ftrace_filter file in the debugfs
794 tracing directory.
795
796 ftrace_notrace=[function-list]
797 [FTRACE] Do not trace the functions specified in
798 function-list. This list can be changed at run time
799 by the set_ftrace_notrace file in the debugfs
800 tracing directory.
d9e54076 801
369bc18f
SA
802 ftrace_graph_filter=[function-list]
803 [FTRACE] Limit the top level callers functions traced
804 by the function graph tracer at boot up.
805 function-list is a comma separated list of functions
806 that can be changed at run time by the
807 set_graph_function file in the debugfs tracing directory.
808
1da177e4
LT
809 gamecon.map[2|3]=
810 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
811 support via parallel port (up to 5 devices per port)
812 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
813 See also Documentation/input/joystick-parport.txt
814
815 gamma= [HW,DRM]
816
aaf23042
YL
817 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
818 Format: off | on
819 default: on
820
2521f2c2
PO
821 gcov_persist= [GCOV] When non-zero (default), profiling data for
822 kernel modules is saved and remains accessible via
823 debugfs, even when the module is unloaded/reloaded.
824 When zero, profiling data is discarded and associated
825 debugfs files are removed at module unload time.
826
1da177e4
LT
827 gpt [EFI] Forces disk with valid GPT signature but
828 invalid Protective MBR to be treated as GPT.
829
1da177e4
LT
830 hashdist= [KNL,NUMA] Large hashes allocated during boot
831 are distributed across NUMA nodes. Defaults on
429aa0fc 832 for 64bit NUMA, off otherwise.
a9913044 833 Format: 0 | 1 (for off | on)
1da177e4
LT
834
835 hcl= [IA-64] SGI's Hardware Graph compatibility layer
836
837 hd= [EIDE] (E)IDE hard drive subsystem geometry
838 Format: <cyl>,<head>,<sect>
839
ea8c071c
HY
840 hest_disable [ACPI]
841 Disable Hardware Error Source Table (HEST) support;
842 corresponding firmware-first mode error processing
843 logic will be disabled.
844
1da177e4
LT
845 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
846 size of <nn>. This works even on boxes that have no
847 highmem otherwise. This also works to reduce highmem
848 size on bigger boxes.
849
54cdfdb4
TG
850 highres= [KNL] Enable/disable high resolution timer mode.
851 Valid parameters: "on", "off"
852 Default: "on"
853
1da177e4
LT
854 hisax= [HW,ISDN]
855 See Documentation/isdn/README.HiSax.
856
0cb55ad2
RD
857 hlt [BUGS=ARM,SH]
858
859 hpet= [X86-32,HPET] option to control HPET usage
860 Format: { enable (default) | disable | force |
861 verbose }
862 disable: disable HPET and use PIT instead
863 force: allow force enabled of undocumented chips (ICH4,
864 VIA, nVidia)
865 verbose: show contents of HPET registers during setup
866
b4718e62
AK
867 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
868 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
869 On x86-64 and powerpc, this option can be specified
870 multiple times interleaved with hugepages= to reserve
871 huge pages of different sizes. Valid pages sizes on
872 x86-64 are 2M (when the CPU supports "pse") and 1G
873 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
874 Note that 1GB pages can only be allocated at boot time
875 using hugepages= and not freed afterwards.
6902aa84 876
555d61d6
HB
877 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
878 terminal devices. Valid values: 0..8
431429ff
HB
879 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
880 If specified, z/VM IUCV HVC accepts connections
881 from listed z/VM user IDs only.
cef7125d 882
7bf69395
FDN
883 keep_bootcon [KNL]
884 Do not unregister boot console at start. This is only
885 useful for debugging when something happens in the window
886 between unregistering the boot console and initializing
887 the real console.
888
3a853fb9 889 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
890 or register an additional I2C bus that is not
891 registered from board initialization code.
3a853fb9
JN
892 Format:
893 <bus_id>,<clkrate>
894
36d95739 895 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 896 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
897 i8042.dumbkbd [HW] Pretend that controller can only read data from
898 keyboard and cannot control its state
1da177e4
LT
899 (Don't attempt to blink the leds)
900 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 901 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
902 i8042.noloop [HW] Disable the AUX Loopback command while probing
903 for the AUX port
1da177e4
LT
904 i8042.nomux [HW] Don't check presence of an active multiplexing
905 controller
906 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
907 controllers
f8313ef1 908 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
1da177e4
LT
909 i8042.reset [HW] Reset the controller during init and cleanup
910 i8042.unlock [HW] Unlock (ignore) the keylock
911
912 i810= [HW,DRM]
913
e70c9d5e
DT
914 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
915 indicates that the driver is running on unsupported
916 hardware.
1da177e4
LT
917 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
918 does not match list of supported models.
919 i8k.power_status
920 [HW] Report power status in /proc/i8k
921 (disabled by default)
922 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
923 capability is set.
924
1da177e4
LT
925 icn= [HW,ISDN]
926 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
927
0af80c04
DF
928 ide-core.nodma= [HW] (E)IDE subsystem
929 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
930 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
931 .cdrom .chs .ignore_cable are additional options
1c10e938 932 See Documentation/ide/ide.txt.
1da177e4 933
0cb55ad2
RD
934 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
935 Claim all unknown PCI IDE storage controllers.
936
f039b754 937 idle= [X86]
ada9cfdd
RD
938 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
939 Poll forces a polling idle loop that can slightly
940 improve the performance of waking up a idle CPU, but
941 will use a lot of power and make the system run hot.
942 Not recommended.
943 idle=mwait: On systems which support MONITOR/MWAIT but
944 the kernel chose to not use it because it doesn't save
945 as much power as a normal idle loop, use the
946 MONITOR/MWAIT idle loop anyways. Performance should be
947 the same as idle=poll.
948 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 949 In such case C2/C3 won't be used again.
ada9cfdd 950 idle=nomwait: Disable mwait for CPU C-states
a9913044 951
79290822
IM
952 ignore_loglevel [KNL]
953 Ignore loglevel setting - this will print /all/
954 kernel messages to the console. Useful for debugging.
955
1da177e4
LT
956 ihash_entries= [KNL]
957 Set number of hash buckets for inode cache.
958
3323eec9
MZ
959 ima_audit= [IMA]
960 Format: { "0" | "1" }
961 0 -- integrity auditing messages. (Default)
962 1 -- enable informational integrity auditing messages.
963
964 ima_hash= [IMA]
a9ed83a5 965 Format: { "sha1" | "md5" }
3323eec9
MZ
966 default: "sha1"
967
5789ba3b
EP
968 ima_tcb [IMA]
969 Load a policy which meets the needs of the Trusted
970 Computing Base. This means IMA will measure all
971 programs exec'd, files mmap'd for exec, and all files
972 opened for read by uid=0.
973
1da177e4
LT
974 init= [KNL]
975 Format: <full_path>
976 Run specified binary instead of /sbin/init as init
977 process.
978
979 initcall_debug [KNL] Trace initcalls as they are executed. Useful
980 for working out where the kernel is dying during
981 startup.
982
983 initrd= [BOOT] Specify the location of the initial ramdisk
984
985 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
986 Format: <irq>
987
ba395927 988 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
989 on
990 Enable intel iommu driver.
ba395927
KA
991 off
992 Disable intel iommu driver.
993 igfx_off [Default Off]
994 By default, gfx is mapped as normal device. If a gfx
995 device has a dedicated DMAR unit, the DMAR unit is
996 bypassed by not enabling DMAR with this option. In
997 this case, gfx device will use physical address for
998 DMA.
7d3b03ce
KA
999 forcedac [x86_64]
1000 With this option iommu will not optimize to look
1001 for io virtual address below 32 bit forcing dual
1002 address cycle on pci bus for cards supporting greater
1003 than 32 bit addressing. The default is to look
1004 for translation below 32 bit and if not available
1005 then look in the higher range.
5e0d2a6f 1006 strict [Default Off]
1007 With this option on every unmap_single operation will
1008 result in a hardware IOTLB flush operation as opposed
1009 to batching them for performance.
6dd9a7c7
YS
1010 sp_off [Default Off]
1011 By default, super page will be supported if Intel IOMMU
1012 has the capability. With this option, super page will
1013 not be supported.
d1423d56
CW
1014 intremap= [X86-64, Intel-IOMMU]
1015 Format: { on (default) | off | nosid }
1016 on enable Interrupt Remapping (default)
1017 off disable Interrupt Remapping
1018 nosid disable Source ID checking
1019
0cb55ad2
RD
1020 inttest= [IA64]
1021
1022 iomem= Disable strict checking of access to MMIO memory
1023 strict regions from userspace.
1024 relaxed
1025
1026 iommu= [x86]
1027 off
1028 force
1029 noforce
1030 biomerge
1031 panic
1032 nopanic
1033 merge
1034 nomerge
1035 forcesac
1036 soft
4ed0d3e6 1037 pt [x86, IA64]
0cb55ad2
RD
1038
1039 io7= [HW] IO7 for Marvel based alpha systems
1040 See comment before marvel_specify_io7 in
1041 arch/alpha/kernel/core_marvel.c.
1042
6cececfc 1043 io_delay= [X86] I/O delay method
6e7c4025
IM
1044 0x80
1045 Standard port 0x80 based delay
1046 0xed
1047 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1048 udelay
6e7c4025
IM
1049 Simple two microseconds delay
1050 none
1051 No delay
b02aae9c 1052
1da177e4 1053 ip= [IP_PNP]
dc7a0816 1054 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1055
1056 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1057 See comment before ip2_setup() in
1058 drivers/char/ip2/ip2base.c.
1da177e4 1059
200803df
AC
1060 irqfixup [HW]
1061 When an interrupt is not handled search all handlers
1062 for it. Intended to get systems with badly broken
1063 firmware running.
1064
1065 irqpoll [HW]
1066 When an interrupt is not handled search all handlers
1067 for it. Also check all handlers each timer
1068 interrupt. Intended to get systems with badly broken
1069 firmware running.
1070
1da177e4 1071 isapnp= [ISAPNP]
a9913044 1072 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1073
1074 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1075 Format:
1076 <cpu number>,...,<cpu number>
1077 or
b225d44e
LZ
1078 <cpu number>-<cpu number>
1079 (must be a positive range in ascending order)
22f2e280
DF
1080 or a mixture
1081 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1082
1da177e4
LT
1083 This option can be used to specify one or more CPUs
1084 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1085 algorithms. You can move a process onto or off an
1086 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1087 <cpu number> begins at 0 and the maximum value is
1088 "number of CPUs in system - 1".
1089
1090 This option is the preferred way to isolate CPUs. The
a9913044
RD
1091 alternative -- manually setting the CPU mask of all
1092 tasks in the system -- can cause problems and
1093 suboptimal load balancer performance.
1da177e4 1094
a9913044 1095 iucv= [HW,NET]
1da177e4
LT
1096
1097 js= [HW,JOY] Analog joystick
1098 See Documentation/input/joystick.txt.
1099
0cb55ad2
RD
1100 keepinitrd [HW,ARM]
1101
6cececfc 1102 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1103 specifies the amount of memory usable by the kernel
1104 for non-movable allocations. The requested amount is
1105 spread evenly throughout all nodes in the system. The
1106 remaining memory in each node is used for Movable
1107 pages. In the event, a node is too small to have both
1108 kernelcore and Movable pages, kernelcore pages will
1109 take priority and other nodes will have a larger number
1110 of kernelcore pages. The Movable zone is used for the
1111 allocation of pages that may be reclaimed or moved
1112 by the page migration subsystem. This means that
1113 HugeTLB pages may not be allocated from this zone.
1114 Note that allocations like PTEs-from-HighMem still
1115 use the HighMem zone if it exists, and the Normal
1116 zone if it does not.
1117
4fe1da4e
JW
1118 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1119 Format: <Controller#>[,poll interval]
1120 The controller # is the number of the ehci usb debug
1121 port as it is probed via PCI. The poll interval is
1122 optional and is the number seconds in between
1123 each poll cycle to the debug port in case you need
1124 the functionality for interrupting the kernel with
1125 gdb or control-c on the dbgp connection. When
1126 not using this parameter you use sysrq-g to break into
1127 the kernel debugger.
1128
84c08fd6 1129 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1130 Requires a tty driver that supports console polling,
1131 or a supported polling keyboard driver (non-usb).
65b5ac14
JW
1132 Serial only format: <serial_device>[,baud]
1133 keyboard only format: kbd
1134 keyboard and serial format: kbd,<serial_device>[,baud]
1135 Optional Kernel mode setting:
1136 kms, kbd format: kms,kbd
1137 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
6cdf6e06 1138
84c08fd6
JW
1139 kgdbwait [KGDB] Stop kernel execution and enter the
1140 kernel debugger at the earliest opportunity.
1141
9bed90c6
FF
1142 kmac= [MIPS] korina ethernet MAC address.
1143 Configure the RouterBoard 532 series on-chip
1144 Ethernet adapter MAC address.
1145
04f70336
CM
1146 kmemleak= [KNL] Boot-time kmemleak enable/disable
1147 Valid arguments: on, off
1148 Default: on
1149
6cececfc 1150 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1151 in oops dumps.
1152
fef07aae
AP
1153 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1154 Default is 0 (don't ignore, but inject #GP)
1155
1156 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1157 Default is 1 (enabled)
1158
a182d873
XG
1159 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1160 KVM MMU at runtime.
fef07aae
AP
1161 Default is 0 (off)
1162
fef07aae 1163 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
8475f94a 1164 Default is 1 (enabled)
fef07aae
AP
1165
1166 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1167 for all guests.
1168 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1169
fef07aae
AP
1170 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1171 (virtualized MMU) support on capable Intel chips.
1172 Default is 1 (enabled)
1173
1174 kvm-intel.emulate_invalid_guest_state=
1175 [KVM,Intel] Enable emulation of invalid guest states
1176 Default is 0 (disabled)
1177
1178 kvm-intel.flexpriority=
1179 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1180 Default is 1 (enabled)
1181
1182 kvm-intel.unrestricted_guest=
1183 [KVM,Intel] Disable unrestricted guest feature
1184 (virtualized real and unpaged mode) on capable
1185 Intel chips. Default is 1 (enabled)
1186
1187 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1188 feature (tagged TLBs) on capable Intel chips.
1189 Default is 1 (enabled)
1190
1da177e4
LT
1191 l2cr= [PPC]
1192
a78bfbfc
RB
1193 l3cr= [PPC]
1194
cd4f0ef7 1195 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1196 disabled it.
1da177e4 1197
6cececfc 1198 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1199 in C2 power state.
e585bef8 1200
fcb71f6f
FC
1201 libata.dma= [LIBATA] DMA control
1202 libata.dma=0 Disable all PATA and SATA DMA
1203 libata.dma=1 PATA and SATA Disk DMA only
1204 libata.dma=2 ATAPI (CDROM) DMA only
1205 libata.dma=4 Compact Flash DMA only
1206 Combinations also work, so libata.dma=3 enables DMA
1207 for disks and CDROMs, but not CFs.
20308871
MP
1208
1209 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1210 libata.ignore_hpa=0 keep BIOS limits (default)
1211 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1212
78e70c23
DJ
1213 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1214 when set.
1215 Format: <int>
1216
33267325
TH
1217 libata.force= [LIBATA] Force configurations. The format is comma
1218 separated list of "[ID:]VAL" where ID is
4c44f309 1219 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1220 matching port, link or device. Basically, it matches
1221 the ATA ID string printed on console by libata. If
1222 the whole ID part is omitted, the last PORT and DEVICE
1223 values are used. If ID hasn't been specified yet, the
1224 configuration applies to all ports, links and devices.
1225
1226 If only DEVICE is omitted, the parameter applies to
1227 the port and all links and devices behind it. DEVICE
1228 number of 0 either selects the first device or the
1229 first fan-out link behind PMP device. It does not
1230 select the host link. DEVICE number of 15 selects the
1231 host link and device attached to it.
1232
1233 The VAL specifies the configuration to force. As long
1234 as there's no ambiguity shortcut notation is allowed.
1235 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1236 The following configurations can be forced.
1237
1238 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1239 Any ID with matching PORT is used.
1240
1241 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1242
1243 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1244 udma[/][16,25,33,44,66,100,133] notation is also
1245 allowed.
1246
1247 * [no]ncq: Turn on or off NCQ.
1248
05944bdf
TH
1249 * nohrst, nosrst, norst: suppress hard, soft
1250 and both resets.
1251
43c9c591
TH
1252 * dump_id: dump IDENTIFY data.
1253
33267325
TH
1254 If there are multiple matching configurations changing
1255 the same attribute, the last one is used.
1256
95f72d1e 1257 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1258
1da177e4 1259 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1260 See Documentation/blockdev/ramdisk.txt.
1da177e4 1261
a6b25b67
RD
1262 lockd.nlm_grace_period=P [NFS] Assign grace period.
1263 Format: <integer>
1da177e4 1264
a6b25b67
RD
1265 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1266 Format: <integer>
1267
1268 lockd.nlm_timeout=T [NFS] Assign timeout value.
1269 Format: <integer>
1270
1271 lockd.nlm_udpport=M [NFS] Assign UDP port.
1272 Format: <integer>
1da177e4
LT
1273
1274 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1275 Format: <irq>
1276
1277 loglevel= All Kernel Messages with a loglevel smaller than the
1278 console loglevel will be printed to the console. It can
1279 also be changed with klogd or other programs. The
1280 loglevels are defined as follows:
1281
1282 0 (KERN_EMERG) system is unusable
1283 1 (KERN_ALERT) action must be taken immediately
1284 2 (KERN_CRIT) critical conditions
1285 3 (KERN_ERR) error conditions
1286 4 (KERN_WARNING) warning conditions
1287 5 (KERN_NOTICE) normal but significant condition
1288 6 (KERN_INFO) informational
1289 7 (KERN_DEBUG) debug-level messages
1290
c756d08a
RD
1291 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1292 in bytes. n must be a power of two. The default
1293 size is set in the kernel config file.
1da177e4 1294
accaa24c
RD
1295 logo.nologo [FB] Disables display of the built-in Linux logo.
1296 This may be used to provide more screen space for
1297 kernel log messages and is useful when debugging
1298 kernel boot problems.
1299
1da177e4
LT
1300 lp=0 [LP] Specify parallel ports to use, e.g,
1301 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1302 lp=reset first parallel port). 'lp=0' disables the
1303 lp=auto printer driver. 'lp=reset' (which can be
1304 specified in addition to the ports) causes
1305 attached printers to be reset. Using
1306 lp=port1,port2,... specifies the parallel ports
1307 to associate lp devices with, starting with
1308 lp0. A port specification may be 'none' to skip
1309 that lp device, or a parport name such as
1310 'parport0'. Specifying 'lp=auto' instead of a
1311 port specification list means that device IDs
1312 from each port should be examined, to see if
1313 an IEEE 1284-compliant printer is attached; if
1314 so, the driver will manage that printer.
1315 See also header of drivers/char/lp.c.
1316
1317 lpj=n [KNL]
1318 Sets loops_per_jiffy to given constant, thus avoiding
1319 time-consuming boot-time autodetection (up to 250 ms per
1320 CPU). 0 enables autodetection (default). To determine
1321 the correct value for your kernel, boot with normal
1322 autodetection and see what value is printed. Note that
1323 on SMP systems the preset will be applied to all CPUs,
1324 which is likely to cause problems if your CPUs need
1325 significantly divergent settings. An incorrect value
1326 will cause delays in the kernel to be wrong, leading to
1327 unpredictable I/O errors and other breakage. Although
1328 unlikely, in the extreme case this might damage your
1329 hardware.
1330
1331 ltpc= [NET]
1332 Format: <io>,<irq>,<dma>
1333
a9913044
RD
1334 machvec= [IA64] Force the use of a particular machine-vector
1335 (machvec) in a generic kernel.
1336 Example: machvec=hpzx1_swiotlb
1da177e4 1337
3209e70e
WZ
1338 machtype= [Loongson] Share the same kernel image file between different
1339 yeeloong laptop.
1340 Example: machtype=lemote-yeeloong-2f-7inch
1341
0cb55ad2
RD
1342 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1343 than or equal to this physical address is ignored.
1da177e4
LT
1344
1345 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1346 should make use of. maxcpus=n : n >= 0 limits the
1347 kernel to using 'n' processors. n=0 is a special case,
1348 it is equivalent to "nosmp", which also disables
1349 the IO APIC.
1da177e4 1350
0cb55ad2
RD
1351 max_loop= [LOOP] Maximum number of loopback devices that can
1352 be mounted
1353 Format: <1-256>
2b2c3750 1354
1da177e4
LT
1355 mcatest= [IA-64]
1356
cd4f0ef7 1357 mce [X86-32] Machine Check Exception
1da177e4 1358
71cced6e 1359 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1360
1da177e4
LT
1361 md= [HW] RAID subsystems devices and level
1362 See Documentation/md.txt.
a9913044 1363
1da177e4
LT
1364 mdacon= [MDA]
1365 Format: <first>,<last>
1366 Specifies range of consoles to be captured by the MDA.
a9913044 1367
1da177e4
LT
1368 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1369 Amount of memory to be used when the kernel is not able
1370 to see the whole system memory or for test.
cd4f0ef7 1371 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1372 address space collisions. Without memmap= PCI devices
1373 could be placed at addresses belonging to unused RAM.
1374
cd4f0ef7 1375 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1376 memory.
1377
6902aa84
PM
1378 memchunk=nn[KMG]
1379 [KNL,SH] Allow user to override the default size for
1380 per-device physically contiguous DMA buffers.
1381
6cececfc 1382 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1383 E820 memory map, as specified by the user.
1384 Such memmap=exactmap lines can be constructed based on
1385 BIOS output or other requirements. See the memmap=nn@ss
1386 option description.
1387
1388 memmap=nn[KMG]@ss[KMG]
1389 [KNL] Force usage of a specific region of memory
1390 Region of memory to be used, from ss to ss+nn.
1391
1392 memmap=nn[KMG]#ss[KMG]
1393 [KNL,ACPI] Mark specific memory as ACPI data.
1394 Region of memory to be used, from ss to ss+nn.
1395
1396 memmap=nn[KMG]$ss[KMG]
1397 [KNL,ACPI] Mark specific memory as reserved.
1398 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1399 Example: Exclude memory from 0x18690000-0x1869ffff
1400 memmap=64K$0x18690000
1401 or
1402 memmap=0x10000$0x18690000
1da177e4 1403
9f077871
JF
1404 memory_corruption_check=0/1 [X86]
1405 Some BIOSes seem to corrupt the first 64k of
1406 memory when doing things like suspend/resume.
1407 Setting this option will scan the memory
1408 looking for corruption. Enabling this will
1409 both detect corruption and prevent the kernel
1410 from using the memory being corrupted.
1411 However, its intended as a diagnostic tool; if
1412 repeatable BIOS-originated corruption always
1413 affects the same memory, you can use memmap=
1414 to prevent the kernel from using that memory.
1415
1416 memory_corruption_check_size=size [X86]
1417 By default it checks for corruption in the low
1418 64k, making this memory unavailable for normal
1419 use. Use this parameter to scan for
1420 corruption in more or less memory.
1421
1422 memory_corruption_check_period=seconds [X86]
1423 By default it checks for corruption every 60
1424 seconds. Use this parameter to check at some
1425 other rate. 0 disables periodic checking.
1426
caadbdce 1427 memtest= [KNL,X86] Enable memtest
c64df707 1428 Format: <integer>
c64df707 1429 default : 0 <disable>
9e5f6cf5
AH
1430 Specifies the number of memtest passes to be
1431 performed. Each pass selects another test
1432 pattern from a given set of patterns. Memtest
1433 fills the memory with this pattern, validates
1434 memory contents and reserves bad memory
1435 regions that are detected.
c64df707 1436
1da177e4
LT
1437 meye.*= [HW] Set MotionEye Camera parameters
1438 See Documentation/video4linux/meye.txt.
1439
8f36881b
AS
1440 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1441 Multi-Function General Purpose Timers on AMD Geode
1442 platforms.
1443
e6c4dc6c
WT
1444 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1445 the BIOS has incorrectly applied a workaround. TinyBIOS
1446 version 0.98 is known to be affected, 0.99 fixes the
1447 problem by letting the user disable the workaround.
1448
1da177e4
LT
1449 mga= [HW,DRM]
1450
1c207f95
RD
1451 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1452 physical address is ignored.
1453
39f45d7b
MP
1454 mini2440= [ARM,HW,KNL]
1455 Format:[0..2][b][c][t]
1456 Default: "0tb"
1457 MINI2440 configuration specification:
1458 0 - The attached screen is the 3.5" TFT
1459 1 - The attached screen is the 7" TFT
1460 2 - The VGA Shield is attached (1024x768)
1461 Leaving out the screen size parameter will not load
1462 the TFT driver, and the framebuffer will be left
1463 unconfigured.
1464 b - Enable backlight. The TFT backlight pin will be
1465 linked to the kernel VESA blanking code and a GPIO
1466 LED. This parameter is not necessary when using the
1467 VGA shield.
1468 c - Enable the s3c camera interface.
1469 t - Reserved for enabling touchscreen support. The
1470 touchscreen support is not enabled in the mainstream
1471 kernel as of 2.6.30, a preliminary port can be found
1472 in the "bleeding edge" mini2440 support kernel at
1473 http://repo.or.cz/w/linux-2.6/mini2440.git
1474
6b74ab97
MG
1475 mminit_loglevel=
1476 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1477 parameter allows control of the logging verbosity for
1478 the additional memory initialisation checks. A value
1479 of 0 disables mminit logging and a level of 4 will
1480 log everything. Information is printed at KERN_DEBUG
1481 so loglevel=8 may also need to be specified.
1482
1da177e4
LT
1483 mousedev.tap_time=
1484 [MOUSE] Maximum time between finger touching and
1485 leaving touchpad surface for touch to be considered
1486 a tap and be reported as a left button click (for
1487 touchpads working in absolute mode only).
1488 Format: <msecs>
1489 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1490 reporting absolute coordinates, such as tablets
1491 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1492 reporting absolute coordinates, such as tablets
1493
6cececfc 1494 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1495 is similar to kernelcore except it specifies the
1496 amount of memory used for migratable allocations.
1497 If both kernelcore and movablecore is specified,
1498 then kernelcore will be at *least* the specified
1499 value but may be more. If movablecore on its own
1500 is specified, the administrator must be careful
1501 that the amount of memory usable for all allocations
1502 is not too small.
1503
1da177e4
LT
1504 MTD_Partition= [MTD]
1505 Format: <name>,<region-number>,<size>,<offset>
1506
a9913044
RD
1507 MTD_Region= [MTD] Format:
1508 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1509
1510 mtdparts= [MTD]
c8facbb6 1511 See drivers/mtd/cmdlinepart.c.
1da177e4 1512
4e89a2d8
WS
1513 multitce=off [PPC] This parameter disables the use of the pSeries
1514 firmware feature for updating multiple TCE entries
1515 at a time.
1516
5988af23
RH
1517 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1518
1519 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1520
1521 boundary - index of last SLC block on Flex-OneNAND.
1522 The remaining blocks are configured as MLC blocks.
1523 lock - Configure if Flex-OneNAND boundary should be locked.
1524 Once locked, the boundary cannot be changed.
1525 1 indicates lock status, 0 indicates unlock status.
1526
9db829f4
BD
1527 mtdset= [ARM]
1528 ARM/S3C2412 JIVE boot control
1529
1530 See arch/arm/mach-s3c2412/mach-jive.c
1531
1da177e4 1532 mtouchusb.raw_coordinates=
a9913044
RD
1533 [HW] Make the MicroTouch USB driver use raw coordinates
1534 ('y', default) or cooked coordinates ('n')
1da177e4 1535
0cb55ad2 1536 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1537 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1538 that could hold holes aka. UC entries.
1539
1540 mtrr_gran_size=nn[KMG] [X86]
1541 Used for mtrr cleanup. It is granularity of mtrr block.
1542 Default is 1.
1543 Large value could prevent small alignment from
1544 using up MTRRs.
1545
1546 mtrr_spare_reg_nr=n [X86]
1547 Format: <integer>
1548 Range: 0,7 : spare reg number
1549 Default : 1
1550 Used for mtrr cleanup. It is spare mtrr entries number.
1551 Set to 2 or more if your graphical card needs more.
1552
1da177e4
LT
1553 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1554
1da177e4
LT
1555 netdev= [NET] Network devices parameters
1556 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1557 Note that mem_start is often overloaded to mean
1558 something different and driver-specific.
a9913044
RD
1559 This usage is only documented in each driver source
1560 file if at all.
1561
58401572
KPO
1562 nf_conntrack.acct=
1563 [NETFILTER] Enable connection tracking flow accounting
1564 0 to disable accounting
1565 1 to enable accounting
d70a011d 1566 Default value is 0.
58401572 1567
306a0753 1568 nfsaddrs= [NFS] Deprecated. Use ip= instead.
dc7a0816 1569 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1570
1571 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1572 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1573
306a0753
CL
1574 nfsrootdebug [NFS] enable nfsroot debugging messages.
1575 See Documentation/filesystems/nfs/nfsroot.txt.
1576
a72b4422
TM
1577 nfs.callback_tcpport=
1578 [NFS] set the TCP port on which the NFSv4 callback
1579 channel should listen.
1580
e571cbf1
TM
1581 nfs.cache_getent=
1582 [NFS] sets the pathname to the program which is used
1583 to update the NFS client cache entries.
1584
1585 nfs.cache_getent_timeout=
1586 [NFS] sets the timeout after which an attempt to
1587 update a cache entry is deemed to have failed.
1588
58df095b
TM
1589 nfs.idmap_cache_timeout=
1590 [NFS] set the maximum lifetime for idmapper cache
1591 entries.
1592
f43bf0be
TM
1593 nfs.enable_ino64=
1594 [NFS] enable 64-bit inode numbers.
1595 If zero, the NFS client will fake up a 32-bit inode
1596 number for the readdir() and stat() syscalls instead
1597 of returning the full 64-bit number.
1598 The default is to return 64-bit inode numbers.
1599
b064eca2
TM
1600 nfs.nfs4_disable_idmapping=
1601 [NFSv4] When set, this option disables the NFSv4
1602 idmapper on the client, but only if the mount
1603 is using the 'sec=sys' security flavour. This may
1604 make migration from legacy NFSv2/v3 systems easier
1605 provided that the server has the appropriate support.
1606 The default is to always enable NFSv4 idmapping.
1607
1e1030dc 1608 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1609 when a NMI is triggered.
1610 Format: [state][,regs][,debounce][,die]
1611
6cececfc 1612 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
fef2c9bc 1613 Format: [panic,][nopanic,][num]
5dc30558 1614 Valid num: 0
5b9a0e14 1615 0 - turn nmi_watchdog off
0cb55ad2 1616 When panic is specified, panic when an NMI watchdog
fef2c9bc
DZ
1617 timeout occurs (or 'nopanic' to override the opposite
1618 default).
0cb55ad2
RD
1619 This is useful when you use a panic=... timeout and
1620 need the box quickly up again.
1da177e4 1621
bff38771
AV
1622 netpoll.carrier_timeout=
1623 [NET] Specifies amount of time (in seconds) that
1624 netpoll should wait for a carrier. By default netpoll
1625 waits 4 seconds.
1626
cd4f0ef7 1627 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1628 emulation library even if a 387 maths coprocessor
1629 is present.
1630
0cb55ad2
RD
1631 no_console_suspend
1632 [HW] Never suspend the console
1633 Disable suspending of consoles during suspend and
1634 hibernate operations. Once disabled, debugging
1635 messages can reach various consoles while the rest
1636 of the system is being put to sleep (ie, while
1637 debugging driver suspend/resume hooks). This may
1638 not work reliably with all consoles, but is known
1639 to work with serial and VGA consoles.
1640
c1aee215
CL
1641 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1642 caches in the slab allocator. Saves per-node memory,
1643 but will impact performance.
3395ee05 1644
a9913044
RD
1645 noalign [KNL,ARM]
1646
1da177e4
LT
1647 noapic [SMP,APIC] Tells the kernel to not make use of any
1648 IOAPICs that may be present in the system.
1649
5091faa4
MG
1650 noautogroup Disable scheduler automatic task group creation.
1651
1da177e4
LT
1652 nobats [PPC] Do not use BATs for mapping kernel lowmem
1653 on "Classic" PPC cores.
1654
1655 nocache [ARM]
a9913044 1656
0cb55ad2
RD
1657 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1658
163ecdff
SN
1659 nodelayacct [KNL] Disable per-task delay accounting
1660
1da177e4
LT
1661 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1662
6902aa84
PM
1663 nodsp [SH] Disable hardware DSP at boot time.
1664
6cececfc 1665 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1666
1da177e4
LT
1667 noexec [IA-64]
1668
6cececfc 1669 noexec [X86]
f5a1b191 1670 On X86-32 available only on PAE configured kernels.
1da177e4 1671 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1672 noexec=off: disable non-executable mappings
1673
de5397ad
FY
1674 nosmep [X86]
1675 Disable SMEP (Supervisor Mode Execution Protection)
1676 even if it is supported by processor.
1677
f5a1b191
JS
1678 noexec32 [X86-64]
1679 This affects only 32-bit executables.
1680 noexec32=on: enable non-executable mappings (default)
1681 read doesn't imply executable mappings
1682 noexec32=off: disable non-executable mappings
1683 read implies executable mappings
1da177e4 1684
6902aa84
PM
1685 nofpu [SH] Disable hardware FPU at boot time.
1686
cd4f0ef7 1687 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1688 register save and restore. The kernel will only save
1689 legacy floating-point registers on task switch.
1da177e4 1690
0c752a93
SS
1691 noxsave [BUGS=X86] Disables x86 extended register state save
1692 and restore using xsave. The kernel will fallback to
1693 enabling legacy floating-point and sse state.
1694
01a24d2b
PZ
1695 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1696 wfi(ARM) instruction doesn't work correctly and not to
1697 use it. This is also useful when using JTAG debugger.
a9913044 1698
cd4f0ef7 1699 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1700 instruction doesn't work correctly and not to
1701 use it.
1702
1f29fae2
SH
1703 no_file_caps Tells the kernel not to honor file capabilities. The
1704 only way then for a file to be executed with privilege
1705 is to be setuid root or executed by root.
1706
1da177e4
LT
1707 nohalt [IA-64] Tells the kernel not to use the power saving
1708 function PAL_HALT_LIGHT when idle. This increases
1709 power-consumption. On the positive side, it reduces
1710 interrupt wake-up latency, which may improve performance
1711 in certain environments such as networked servers or
1712 real-time systems.
1713
79bf2bb3
TG
1714 nohz= [KNL] Boottime enable/disable dynamic ticks
1715 Valid arguments: on, off
1716 Default: on
1717
eeee7853
PM
1718 noiotrap [SH] Disables trapped I/O port accesses.
1719
cd4f0ef7 1720 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1721 disable unhandled interrupt sources.
1722
6cececfc 1723 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1724 broken timer IRQ sources.
1725
1da177e4
LT
1726 noisapnp [ISAPNP] Disables ISA PnP code.
1727
1728 noinitrd [RAM] Tells the kernel not to load any configured
1729 initial RAM disk.
1730
03ea8155
WH
1731 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1732 remapping.
d1423d56 1733 [Deprecated - use intremap=off]
03ea8155 1734
1da177e4
LT
1735 nointroute [IA-64]
1736
0aa366f3
TL
1737 nojitter [IA64] Disables jitter checking for ITC timers.
1738
9cf4c4fc
JK
1739 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1740
fd10cde9
GN
1741 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1742 fault handling.
1743
d910f5c1
GC
1744 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1745 steal time is computed, but won't influence scheduler
1746 behaviour
1747
cd4f0ef7 1748 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1749
cd4f0ef7 1750 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1751
1da177e4
LT
1752 noltlbs [PPC] Do not use large page/tlb entries for kernel
1753 lowmem mapping on PPC40x.
1754
312f1f01
H
1755 nomca [IA-64] Disable machine check abort handling
1756
cd4f0ef7 1757 nomce [X86-32] Machine Check Exception
abe37e5a 1758
83d7384f
AS
1759 nomfgpt [X86-32] Disable Multi-Function General Purpose
1760 Timer usage (for AMD Geode machines).
1761
016ddd9b
JK
1762 nopat [X86] Disable PAT (page attribute table extension of
1763 pagetables) support.
1764
0cb55ad2
RD
1765 norandmaps Don't use address space randomization. Equivalent to
1766 echo 0 > /proc/sys/kernel/randomize_va_space
1767
bbff2168 1768 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
959b4fdf 1769
cd4f0ef7 1770 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1771 with UP alternatives
1772
1da177e4
LT
1773 noresidual [PPC] Don't use residual data on PReP machines.
1774
a9913044
RD
1775 noresume [SWSUSP] Disables resume and restores original swap
1776 space.
1777
1da177e4
LT
1778 no-scroll [VGA] Disables scrollback.
1779 This is required for the Braillex ib80-piezo Braille
1780 reader made by F.H. Papenmeier (Germany).
1781
1782 nosbagart [IA-64]
1783
cd4f0ef7 1784 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1785
61ec7567
LB
1786 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1787 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1788
97842216
DJ
1789 nosoftlockup [KNL] Disable the soft-lockup detector.
1790
1da177e4
LT
1791 nosync [HW,M68K] Disables sync negotiation for all devices.
1792
cd4f0ef7 1793 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1794
1795 nousb [USB] Disable the USB subsystem
1796
55142374 1797 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
58687acb 1798
1da177e4 1799 nowb [ARM]
a9913044 1800
2b2fd87a
WH
1801 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1802
a6c75b86
FY
1803 nptcg= [IA64] Override max number of concurrent global TLB
1804 purges which is reported from either PAL_VM_SUMMARY or
1805 SAL PALO.
1806
2b633e3f
YL
1807 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1808 could support. nr_cpus=n : n >= 1 limits the kernel to
1809 supporting 'n' processors. Later in runtime you can not
1810 use hotplug cpu feature to put more cpu back to online.
1811 just like you compile the kernel NR_CPUS=n
1812
0cb55ad2
RD
1813 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1814
f0c0b2b8
KH
1815 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1816 one of ['zone', 'node', 'default'] can be specified
1817 This can be set from sysctl after boot.
1818 See Documentation/sysctl/vm.txt for details.
1819
7c4be253
RD
1820 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1821 See Documentation/debugging-via-ohci1394.txt for more
1822 info.
1823
3ef0e1f8
AS
1824 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1825 Rather than timing out after 20 ms if an EC
1826 command is not properly ACKed, override the length
1827 of the timeout. We have interrupts disabled while
1828 waiting for the ACK, so if this is set too high
1829 interrupts *may* be lost!
1830
15ac7afe
TL
1831 omap_mux= [OMAP] Override bootloader pin multiplexing.
1832 Format: <mux_mode0.mode_name=value>...
1833 For example, to override I2C bus2:
1834 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1835
1da177e4
LT
1836 oprofile.timer= [HW]
1837 Use timer interrupt instead of performance counters
1838
7e4e0bd5
RR
1839 oprofile.cpu_type= Force an oprofile cpu type
1840 This might be useful if you have an older oprofile
1841 userland or if you want common events.
8d7ff4f2
RR
1842 Format: { arch_perfmon }
1843 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
1844 perfmon on Intel CPUs instead of the
1845 CPU specific event set.
1dcdb5a9 1846
44a4dcf7
RD
1847 oops=panic Always panic on oopses. Default is to just kill the
1848 process, but there is a small probability of
1849 deadlocking the machine.
d404ab0a
OH
1850 This will also cause panics on machine check exceptions.
1851 Useful together with panic=30 to trigger a reboot.
1852
bcfde334
RD
1853 OSS [HW,OSS]
1854 See Documentation/sound/oss/oss-parameters.txt
1855
44a4dcf7 1856 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4302fbc8
HD
1857 timeout > 0: seconds before rebooting
1858 timeout = 0: wait forever
1859 timeout < 0: reboot immediately
1da177e4
LT
1860 Format: <timeout>
1861
1862 parkbd.port= [HW] Parallel port number the keyboard adapter is
1863 connected to, default is 0.
1864 Format: <parport#>
1865 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1866 0 for XT, 1 for AT (default is AT).
a9913044
RD
1867 Format: <mode>
1868
1869 parport= [HW,PPT] Specify parallel ports. 0 disables.
1870 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1871 Use 'auto' to force the driver to use any
1872 IRQ/DMA settings detected (the default is to
1873 ignore detected IRQ/DMA settings because of
1874 possible conflicts). You can specify the base
1875 address, IRQ, and DMA settings; IRQ and DMA
1876 should be numbers, or 'auto' (for using detected
1877 settings on that particular port), or 'nofifo'
1878 (to avoid using a FIFO even if it is detected).
1879 Parallel ports are assigned in the order they
1880 are specified on the command line, starting
1881 with parport0.
1882
1883 parport_init_mode= [HW,PPT]
1884 Configure VIA parallel port to operate in
1885 a specific mode. This is necessary on Pegasos
1886 computer where firmware has no options for setting
1887 up parallel port mode and sets it to spp.
1888 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1889 Format: [spp|ps2|epp|ecp|ecpepp]
1890
dd287796
AM
1891 pause_on_oops=
1892 Halt all CPUs after the first oops has been printed for
1893 the specified number of seconds. This is to be used if
1894 your oopses keep scrolling off the screen.
1895
1da177e4
LT
1896 pcbit= [HW,ISDN]
1897
1898 pcd. [PARIDE]
1899 See header of drivers/block/paride/pcd.c.
31c00fc1 1900 See also Documentation/blockdev/paride.txt.
1da177e4 1901
a9913044 1902 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1903 earlydump [X86] dump PCI config space before the kernel
1904 changes anything
c0115606 1905 off [X86] don't probe for the PCI bus
cd4f0ef7 1906 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1907 the hardware directly. Use this if your machine
1908 has a non-standard PCI host bridge.
cd4f0ef7 1909 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1910 hardware access methods are allowed. Use this
1911 if you experience crashes upon bootup and you
1912 suspect they are caused by the BIOS.
c0115606 1913 conf1 [X86] Force use of PCI Configuration
a9913044 1914 Mechanism 1.
c0115606 1915 conf2 [X86] Force use of PCI Configuration
a9913044 1916 Mechanism 2.
7f785763
RD
1917 noaer [PCIE] If the PCIEAER kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1920 nodomains [PCI] Disable support for multiple PCI
1921 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1922 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1923 Configuration
12983077
AH
1924 check_enable_amd_mmconf [X86] check for and enable
1925 properly configured MMIO access to PCI
1926 config space on AMD family 10h CPU
309e57df
MW
1927 nomsi [MSI] If the PCI_MSI kernel config parameter is
1928 enabled, this kernel boot option can be used to
1929 disable the use of MSI interrupts system-wide.
a9322f64
SA
1930 noioapicquirk [APIC] Disable all boot interrupt quirks.
1931 Safety option to keep boot IRQs enabled. This
1932 should never be necessary.
9197979b
SA
1933 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1934 primary IO-APIC for bridges that cannot disable
1935 boot IRQs. This fixes a source of spurious IRQs
1936 when the system masks IRQs.
41b9eb26
SA
1937 noioapicreroute [APIC] Disable workaround that uses the
1938 boot IRQ equivalent of an IRQ that connects to
1939 a chipset where boot IRQs cannot be disabled.
1940 The opposite of ioapicreroute.
cd4f0ef7 1941 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1942 routing table. These calls are known to be buggy
1943 on several machines and they hang the machine
1944 when used, but on other computers it's the only
1945 way to get the interrupt routing table. Try
1946 this option if the kernel is unable to allocate
1947 IRQs or discover secondary PCI buses on your
1948 motherboard.
c0115606 1949 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1950 Use with caution as certain devices share
1951 address decoders between ROMs and other
1952 resources.
c0115606 1953 norom [X86] Do not assign address space to
bb71ad88
GH
1954 expansion ROMs that do not already have
1955 BIOS assigned address ranges.
7bd1c365
MH
1956 nobar [X86] Do not assign address space to the
1957 BARs that weren't assigned by the BIOS.
c0115606 1958 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1959 assigned automatically to PCI devices. You can
1960 make the kernel exclude IRQs of your ISA cards
1961 this way.
c0115606 1962 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1963 of the PIRQ table (normally generated
1964 by the BIOS) if it is outside the
1965 F0000h-100000h range.
c0115606 1966 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1967 useful if the kernel is unable to find your
1968 secondary buses and you want to tell it
1969 explicitly which ones they are.
c0115606 1970 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1971 numbers ourselves, overriding
1972 whatever the firmware may have done.
c0115606 1973 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1974 in the BIOS $PIR table. This is needed on
1975 some systems with broken BIOSes, notably
1976 some HP Pavilion N5400 and Omnibook XE3
1977 notebooks. This will have no effect if ACPI
1978 IRQ routing is enabled.
c0115606 1979 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1980 or for PCI scanning.
7bc5e3f2
BH
1981 use_crs [X86] Use PCI host bridge window information
1982 from ACPI. On BIOSes from 2008 or later, this
1983 is enabled by default. If you need to use this,
1984 please report a bug.
1985 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1986 If you need to use this, please report a bug.
a9913044
RD
1987 routeirq Do IRQ routing for all PCI devices.
1988 This is normally done in pci_enable_device(),
1989 so this option is a temporary workaround
1990 for broken drivers that don't call it.
13a6ddb0
YL
1991 skip_isa_align [X86] do not align io start addr, so can
1992 handle more pci cards
a9913044
RD
1993 firmware [ARM] Do not re-enumerate the bus but instead
1994 just use the configuration from the
1995 bootloader. This is currently used on
1996 IXP2000 systems where the bus has to be
1997 configured a certain way for adjunct CPUs.
0637a70a
AK
1998 noearly [X86] Don't do any early type 1 scanning.
1999 This might help on some broken boards which
2000 machine check when some devices' config space
2001 is read. But various workarounds are disabled
2002 and some IOMMU drivers will not work.
6b4b78fe
MD
2003 bfsort Sort PCI devices into breadth-first order.
2004 This sorting is done to get a device
2005 order compatible with older (<= 2.4) kernels.
2006 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
2007 cbiosize=nn[KMG] The fixed amount of bus space which is
2008 reserved for the CardBus bridge's IO window.
2009 The default value is 256 bytes.
2010 cbmemsize=nn[KMG] The fixed amount of bus space which is
2011 reserved for the CardBus bridge's memory
2012 window. The default value is 64 megabytes.
32a9a682
YS
2013 resource_alignment=
2014 Format:
2015 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2016 Specifies alignment and device to reassign
2017 aligned memory resources.
2018 If <order of align> is not specified,
2019 PAGE_SIZE is used as alignment.
2020 PCI-PCI bridge can be specified, if resource
2021 windows need to be expanded.
43c16408
AP
2022 ecrc= Enable/disable PCIe ECRC (transaction layer
2023 end-to-end CRC checking).
2024 bios: Use BIOS/firmware settings. This is the
2025 the default.
2026 off: Turn ECRC off
2027 on: Turn ECRC on.
f483d392
RP
2028 realloc reallocate PCI resources if allocations done by BIOS
2029 are erroneous.
6b4b78fe 2030
e5665a45
CE
2031 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2032 Management.
2033 off Disable ASPM.
2034 force Enable ASPM even on devices that claim not to support it.
2035 WARNING: Forcing ASPM on may cause system lockups.
2036
79dd9182 2037 pcie_ports= [PCIE] PCIe ports handling:
28eb5f27
RW
2038 auto Ask the BIOS whether or not to use native PCIe services
2039 associated with PCIe ports (PME, hot-plug, AER). Use
2040 them only if that is allowed by the BIOS.
2041 native Use native PCIe services associated with PCIe ports
2042 unconditionally.
79dd9182
RW
2043 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2044 ports driver.
2045
c7f48656 2046 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
c39fae14 2047 nomsi Do not use MSI for native PCIe PME signaling (this makes
28eb5f27 2048 all PCIe root ports use INTx for all services).
c7f48656 2049
1da177e4
LT
2050 pcmv= [HW,PCMCIA] BadgePAD 4
2051
2052 pd. [PARIDE]
31c00fc1 2053 See Documentation/blockdev/paride.txt.
1da177e4
LT
2054
2055 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2056 boot time.
2057 Format: { 0 | 1 }
2058 See arch/parisc/kernel/pdc_chassis.c
2059
f58dc01b 2060 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2061 Currently supported values are "embed" and "page".
2062 Archs may support subset or none of the selections.
2063 See comments in mm/percpu.c for details on each
2064 allocator. This parameter is primarily for debugging
2065 and performance comparison.
fa8a7094 2066
1da177e4 2067 pf. [PARIDE]
31c00fc1 2068 See Documentation/blockdev/paride.txt.
1da177e4
LT
2069
2070 pg. [PARIDE]
31c00fc1 2071 See Documentation/blockdev/paride.txt.
1da177e4
LT
2072
2073 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2074 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2075
2076 plip= [PPT,NET] Parallel port network link
2077 Format: { parport<nr> | timid | 0 }
2078 See also Documentation/parport.txt.
2079
de32a243
TG
2080 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2081 Override pmtimer IOPort with a hex value.
2082 e.g. pmtmr=0x508
2083
96242116
BH
2084 pnp.debug=1 [PNP]
2085 Enable PNP debug messages (depends on the
2086 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2087 via /sys/module/pnp/parameters/debug. We always show
2088 current resource usage; turning this on also shows
2089 possible settings and some assignment information.
97ef062b 2090
1da177e4
LT
2091 pnpacpi= [ACPI]
2092 { off }
2093
2094 pnpbios= [ISAPNP]
2095 { on | off | curr | res | no-curr | no-res }
2096
2097 pnp_reserve_irq=
2098 [ISAPNP] Exclude IRQs for the autoconfiguration
2099
2100 pnp_reserve_dma=
2101 [ISAPNP] Exclude DMAs for the autoconfiguration
2102
2103 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2104 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2105
2106 pnp_reserve_mem=
a9913044
RD
2107 [ISAPNP] Exclude memory regions for the
2108 autoconfiguration.
1da177e4
LT
2109 Ranges are in pairs (memory base and size).
2110
4af94f39
RD
2111 ports= [IP_VS_FTP] IPVS ftp helper module
2112 Default is 21.
2113 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2114 may be specified.
2115 Format: <port>,<port>....
2116
45807a1d
IM
2117 print-fatal-signals=
2118 [KNL] debug: print fatal signals
f84d49b2
NO
2119
2120 If enabled, warn about various signal handling
2121 related application anomalies: too many signals,
2122 too many POSIX.1 timers, fatal signals causing a
2123 coredump - etc.
2124
2125 If you hit the warning due to signal overflow,
2126 you might want to try "ulimit -i unlimited".
2127
45807a1d
IM
2128 default: off.
2129
e84845c4
RD
2130 printk.time= Show timing data prefixed to each printk message line
2131 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2132
0cb55ad2
RD
2133 processor.max_cstate= [HW,ACPI]
2134 Limit processor to maximum C-state
2135 max_cstate=9 overrides any DMI blacklist limit.
2136
2137 processor.nocst [HW,ACPI]
2138 Ignore the _CST method to determine C-states,
2139 instead using the legacy FADT method
2140
1da177e4 2141 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2142 Format: [schedule,]<number>
2143 Param: "schedule" - profile schedule points.
2144 Param: <number> - step/bucket size as a power of 2 for
2145 statistical time based profiling.
b3da2a73
MG
2146 Param: "sleep" - profile D-state sleeping (millisecs).
2147 Requires CONFIG_SCHEDSTATS
c0fe2e69 2148 Param: "kvm" - profile VM exits.
1da177e4 2149
1da177e4
LT
2150 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2151 before loading.
31c00fc1 2152 See Documentation/blockdev/ramdisk.txt.
1da177e4 2153
a9913044
RD
2154 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2155 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2156 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2157 per second.
a9913044
RD
2158 psmouse.resetafter= [HW,MOUSE]
2159 Try to reset the device after so many bad packets
1da177e4
LT
2160 (0 = never).
2161 psmouse.resolution=
2162 [HW,MOUSE] Set desired mouse resolution, in dpi.
2163 psmouse.smartscroll=
a9913044 2164 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2165 0 = disabled, 1 = enabled (default).
2166
dee28e72
MG
2167 pstore.backend= Specify the name of the pstore backend to use
2168
1da177e4 2169 pt. [PARIDE]
31c00fc1 2170 See Documentation/blockdev/paride.txt.
1da177e4 2171
dc8c8587
KS
2172 pty.legacy_count=
2173 [KNL] Number of legacy pty's. Overwrites compiled-in
2174 default number.
2175
7d2c502f 2176 quiet [KNL] Disable most log messages
a9913044 2177
1da177e4
LT
2178 r128= [HW,DRM]
2179
2180 raid= [HW,RAID]
2181 See Documentation/md.txt.
2182
a9913044 2183 ramdisk_blocksize= [RAM]
31c00fc1 2184 See Documentation/blockdev/ramdisk.txt.
a9913044 2185
1da177e4 2186 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2187 See Documentation/blockdev/ramdisk.txt.
1da177e4 2188
24aaef8d
RD
2189 rcupdate.blimit= [KNL,BOOT]
2190 Set maximum number of finished RCU callbacks to process
2191 in one batch.
21a1ea9e 2192
24aaef8d
RD
2193 rcupdate.qhimark= [KNL,BOOT]
2194 Set threshold of queued
21a1ea9e
DS
2195 RCU callbacks over which batch limiting is disabled.
2196
24aaef8d
RD
2197 rcupdate.qlowmark= [KNL,BOOT]
2198 Set threshold of queued RCU callbacks below which
2199 batch limiting is re-enabled.
21a1ea9e 2200
ffdfc409
OJ
2201 rdinit= [KNL]
2202 Format: <full_path>
2203 Run specified binary instead of /init from the ramdisk,
2204 used for early userspace startup. See initrd.
2205
cd4f0ef7 2206 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2207 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2208 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2209
46b6d94e
PJ
2210 relax_domain_level=
2211 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2212 See Documentation/cgroups/cpusets.txt.
46b6d94e 2213
1da177e4
LT
2214 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2215
cd4f0ef7 2216 reservetop= [X86-32]
461a9aff
ZA
2217 Format: nn[KMG]
2218 Reserves a hole at the top of the kernel virtual
2219 address space.
2220
9ea77bdb
PA
2221 reservelow= [X86]
2222 Format: nn[K]
2223 Set the amount of memory to reserve for BIOS at
2224 the bottom of the address space.
2225
7e96287d
VG
2226 reset_devices [KNL] Force drivers to reset the underlying device
2227 during initialization.
2228
a9913044
RD
2229 resume= [SWSUSP]
2230 Specify the partition device for software suspend
1da177e4 2231
ecbd0da1
RW
2232 resume_offset= [SWSUSP]
2233 Specify the offset from the beginning of the partition
2234 given by "resume=" at which the swap header is located,
2235 in <PAGE_SIZE> units (needed only for swap files).
2236 See Documentation/power/swsusp-and-swap-files.txt
2237
f996fc96
BS
2238 hibernate= [HIBERNATION]
2239 noresume Don't check if there's a hibernation image
2240 present during boot.
2241 nocompress Don't compress/decompress hibernation images.
2242
0a7b35cb
MN
2243 retain_initrd [RAM] Keep initrd memory after extraction
2244
1da177e4
LT
2245 rhash_entries= [KNL,NET]
2246 Set number of hash buckets for route cache
2247
2248 riscom8= [HW,SERIAL]
2249 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2250
2251 ro [KNL] Mount root device read-only on boot
2252
2253 root= [KNL] Root filesystem
f2d34fd9 2254 See name_to_dev_t comment in init/do_mounts.c.
1da177e4
LT
2255
2256 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2257 mount the root filesystem
2258
2259 rootflags= [KNL] Set root filesystem mount option string
2260
2261 rootfstype= [KNL] Set root filesystem type
2262
cc1ed754
PO
2263 rootwait [KNL] Wait (indefinitely) for root device to show up.
2264 Useful for devices that are detected asynchronously
2265 (e.g. USB and MMC devices).
2266
1da177e4
LT
2267 rw [KNL] Mount root device read-write on boot
2268
2269 S [KNL] Run init in single mode
2270
2271 sa1100ir [NET]
2272 See drivers/net/irda/sa1100_ir.c.
2273
1da177e4 2274 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2275
f6630114
MT
2276 sched_debug [KNL] Enables verbose scheduler debug messages.
2277
0cb55ad2
RD
2278 security= [SECURITY] Choose a security module to enable at boot.
2279 If this boot parameter is not specified, only the first
2280 security module asking for security registration will be
2281 loaded. An invalid security module name will be treated
2282 as if no module has been chosen.
2283
2284 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2285 Format: { "0" | "1" }
2286 See security/selinux/Kconfig help text.
2287 0 -- disable.
2288 1 -- enable.
2289 Default value is set via kernel config option.
2290 If enabled at boot time, /selinux/disable can be used
2291 later to disable prior to initial policy load.
2292
c1c124e9
JJ
2293 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2294 Format: { "0" | "1" }
2295 See security/apparmor/Kconfig help text
2296 0 -- disable.
2297 1 -- enable.
2298 Default value is set via kernel config option.
2299
cd4f0ef7 2300 serialnumber [BUGS=X86-32]
1da177e4 2301
1da177e4
LT
2302 shapers= [NET]
2303 Maximal number of shapers.
a9913044 2304
b05f78f5
YL
2305 show_msr= [x86] show boot-time MSR settings
2306 Format: { <integer> }
2307 Show boot-time (BIOS-initialized) MSR settings.
2308 The parameter means the number of CPUs to show,
2309 for example 1 means boot CPU only.
2310
1da177e4
LT
2311 simeth= [IA-64]
2312 simscsi=
a9913044 2313
1da177e4
LT
2314 slram= [HW,MTD]
2315
f0630fff
CL
2316 slub_debug[=options[,slabs]] [MM, SLUB]
2317 Enabling slub_debug allows one to determine the
2318 culprit if slab objects become corrupted. Enabling
2319 slub_debug can create guard zones around objects and
2320 may poison objects when not in use. Also tracks the
2321 last alloc / free. For more information see
2322 Documentation/vm/slub.txt.
c1aee215
CL
2323
2324 slub_max_order= [MM, SLUB]
f0630fff
CL
2325 Determines the maximum allowed order for slabs.
2326 A high setting may cause OOMs due to memory
2327 fragmentation. For more information see
2328 Documentation/vm/slub.txt.
c1aee215
CL
2329
2330 slub_min_objects= [MM, SLUB]
f0630fff
CL
2331 The minimum number of objects per slab. SLUB will
2332 increase the slab order up to slub_max_order to
2333 generate a sufficiently large slab able to contain
2334 the number of objects indicated. The higher the number
2335 of objects the smaller the overhead of tracking slabs
2336 and the less frequently locks need to be acquired.
c1aee215
CL
2337 For more information see Documentation/vm/slub.txt.
2338
2339 slub_min_order= [MM, SLUB]
2340 Determines the mininum page order for slabs. Must be
f0630fff 2341 lower than slub_max_order.
c1aee215
CL
2342 For more information see Documentation/vm/slub.txt.
2343
2344 slub_nomerge [MM, SLUB]
f0630fff 2345 Disable merging of slabs with similar size. May be
c1aee215 2346 necessary if there is some reason to distinguish
f0630fff
CL
2347 allocs to different slabs. Debug options disable
2348 merging on their own.
c1aee215
CL
2349 For more information see Documentation/vm/slub.txt.
2350
1da177e4
LT
2351 smart2= [HW]
2352 Format: <io1>[,<io2>[,...,<io8>]]
2353
cd4f0ef7 2354 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2355 attempt to substitute SMP alternatives once at boot.
2356
d0d4f69b
BH
2357 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2358 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2359 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2360 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2361 smsc-ircc2.ircc_irq= [HW] IRQ line
2362 smsc-ircc2.ircc_dma= [HW] DMA channel
2363 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2364 0: Toshiba Satellite 1800 (GP data pin select)
2365 1: Fast pin select (default)
2366 2: ATC IRMode
2367
9c44bc03
IM
2368 softlockup_panic=
2369 [KNL] Should the soft-lockup detector generate panics.
44a4dcf7 2370 Format: <integer>
9c44bc03 2371
1da177e4
LT
2372 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2373 See Documentation/sonypi.txt
2374
2375 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2376 See Documentation/serial/specialix.txt.
1da177e4
LT
2377
2378 spia_io_base= [HW,MTD]
2379 spia_fio_base=
2380 spia_pedr=
2381 spia_peddr=
2382
f38f1d2a
SR
2383 stacktrace [FTRACE]
2384 Enabled the stack tracer on boot up.
2385
1da177e4
LT
2386 sti= [PARISC,HW]
2387 Format: <num>
2388 Set the STI (builtin display/keyboard on the HP-PARISC
2389 machines) console (graphic card) which should be used
2390 as the initial boot-console.
2391 See also comment in drivers/video/console/sticore.c.
2392
2393 sti_font= [HW]
2394 See comment in drivers/video/console/sticore.c.
2395
2396 stifb= [HW]
2397 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2398
cbf11071
TM
2399 sunrpc.min_resvport=
2400 sunrpc.max_resvport=
2401 [NFS,SUNRPC]
2402 SunRPC servers often require that client requests
2403 originate from a privileged port (i.e. a port in the
2404 range 0 < portnr < 1024).
2405 An administrator who wishes to reserve some of these
2406 ports for other uses may adjust the range that the
2407 kernel's sunrpc client considers to be privileged
2408 using these two parameters to set the minimum and
2409 maximum port values.
2410
42a7fc4a
GB
2411 sunrpc.pool_mode=
2412 [NFS]
2413 Control how the NFS server code allocates CPUs to
2414 service thread pools. Depending on how many NICs
2415 you have and where their interrupts are bound, this
2416 option will affect which CPUs will do NFS serving.
2417 Note: this parameter cannot be changed while the
2418 NFS server is running.
2419
2420 auto the server chooses an appropriate mode
2421 automatically using heuristics
2422 global a single global pool contains all CPUs
2423 percpu one pool for each CPU
2424 pernode one pool for each NUMA node (equivalent
2425 to global on non-NUMA machines)
2426
cbf11071
TM
2427 sunrpc.tcp_slot_table_entries=
2428 sunrpc.udp_slot_table_entries=
2429 [NFS,SUNRPC]
2430 Sets the upper limit on the number of simultaneous
2431 RPC calls that can be sent from the client to a
2432 server. Increasing these values may allow you to
2433 improve throughput, but will also increase the
2434 amount of memory reserved for use by the client.
2435
a42c390c
MH
2436 swapaccount[=0|1]
2437 [KNL] Enable accounting of swap in memory resource
2438 controller if no parameter or 1 is given or disable
2439 it if 0 is given (See Documentation/cgroups/memory.txt)
2440
1da177e4 2441 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2442
1da177e4
LT
2443 switches= [HW,M68k]
2444
e52eec13
AK
2445 sysfs.deprecated=0|1 [KNL]
2446 Enable/disable old style sysfs layout for old udev
2447 on older distributions. When this option is enabled
2448 very new udev will not work anymore. When this option
2449 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2450 in older udev will not work anymore.
2451 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2452 the kernel configuration.
2453
5d6f647f
IM
2454 sysrq_always_enabled
2455 [KNL]
2456 Ignore sysrq setting - this boot parameter will
2457 neutralize any effect of /proc/sys/kernel/sysrq.
2458 Useful for debugging.
2459
1da177e4
LT
2460 tdfx= [HW,DRM]
2461
77437fd4
DB
2462 test_suspend= [SUSPEND]
2463 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2464 standby suspend) as the system sleep state to briefly
2465 enter during system startup. The system is woken from
2466 this state using a wakeup-capable RTC alarm.
2467
1da177e4
LT
2468 thash_entries= [KNL,NET]
2469 Set number of hash buckets for TCP connection
2470
f8707ec9
LB
2471 thermal.act= [HW,ACPI]
2472 -1: disable all active trip points in all thermal zones
2473 <degrees C>: override all lowest active trip points
2474
c52a7419
LB
2475 thermal.crt= [HW,ACPI]
2476 -1: disable all critical trip points in all thermal zones
22a94d79 2477 <degrees C>: override all critical trip points
c52a7419 2478
f5487145
LB
2479 thermal.nocrt= [HW,ACPI]
2480 Set to disable actions on ACPI thermal zone
2481 critical and hot trip points.
2482
72b33ef8
LB
2483 thermal.off= [HW,ACPI]
2484 1: disable ACPI thermal control
2485
a70cdc52
LB
2486 thermal.psv= [HW,ACPI]
2487 -1: disable all passive trip points
ada9cfdd
RD
2488 <degrees C>: override all passive trip points to this
2489 value
a70cdc52 2490
730ff34d
LB
2491 thermal.tzp= [HW,ACPI]
2492 Specify global default ACPI thermal zone polling rate
2493 <deci-seconds>: poll all this frequency
2494 0: no polling (default)
2495
8d32a307
TG
2496 threadirqs [KNL]
2497 Force threading of all interrupt handlers except those
2498 marked explicitely IRQF_NO_THREAD.
2499
2b1a61f0
HC
2500 topology= [S390]
2501 Format: {off | on}
2502 Specify if the kernel should make use of the cpu
f65e51d7
SL
2503 topology information if the hardware supports this.
2504 The scheduler will make use of this information and
2b1a61f0 2505 e.g. base its process migration decisions on it.
c9af3fa9 2506 Default is on.
2b1a61f0 2507
1da177e4
LT
2508 tp720= [HW,PS2]
2509
225a9be2
RA
2510 tpm_suspend_pcr=[HW,TPM]
2511 Format: integer pcr id
2512 Specify that at suspend time, the tpm driver
2513 should extend the specified pcr with zeros,
2514 as a workaround for some chips which fail to
2515 flush the last written pcr on TPM_SaveState.
2516 This will guarantee that all the other pcrs
2517 are saved.
2518
9d612bef
LZ
2519 trace_buf_size=nn[KMG]
2520 [FTRACE] will set tracing buffer size.
631595fb 2521
020e5f85
LZ
2522 trace_event=[event-list]
2523 [FTRACE] Set and start specified trace events in order
2524 to facilitate early boot debugging.
2525 See also Documentation/trace/events.txt
2526
d3b8f889 2527 tsc= Disable clocksource stability checks for TSC.
395628ef
AK
2528 Format: <string>
2529 [x86] reliable: mark tsc clocksource as reliable, this
d3b8f889
JS
2530 disables clocksource verification at runtime, as well
2531 as the stability checks done at bootup. Used to enable
2532 high-resolution timer mode on older hardware, and in
2533 virtualized environment.
e82b8e4e
VP
2534 [x86] noirqtime: Do not use TSC to do irq accounting.
2535 Used to run time disable IRQ_TIME_ACCOUNTING on any
2536 platforms where RDTSC is slow and this accounting
2537 can add overhead.
395628ef 2538
a9913044
RD
2539 turbografx.map[2|3]= [HW,JOY]
2540 TurboGraFX parallel port interface
2541 Format:
2542 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2543 See also Documentation/input/joystick-parport.txt
2544
b6935f8c
CK
2545 udbg-immortal [PPC] When debugging early kernel crashes that
2546 happen after console_init() and before a proper
2547 console driver takes over, this boot options might
2548 help "seeing" what's going on.
2549
f86dcc5a
ED
2550 uhash_entries= [KNL,NET]
2551 Set number of hash buckets for UDP/UDP-Lite connections
2552
5f8364b7
AS
2553 uhci-hcd.ignore_oc=
2554 [USB] Ignore overcurrent events (default N).
2555 Some badly-designed motherboards generate lots of
2556 bogus events, for ports that aren't wired to
2557 anything. Set this parameter to avoid log spamming.
2558 Note that genuine overcurrent events won't be
2559 reported either.
2560
e3a61b0a 2561 unknown_nmi_panic
44a4dcf7 2562 [X86] Cause panic on unknown NMI.
e3a61b0a 2563
c4fc2342
CDH
2564 usbcore.authorized_default=
2565 [USB] Default USB device authorization:
2566 (default -1 = authorized except for wireless USB,
2567 0 = not authorized, 1 = authorized)
2568
b5e795f8
AS
2569 usbcore.autosuspend=
2570 [USB] The autosuspend time delay (in seconds) used
2571 for newly-detected USB devices (default 2). This
2572 is the time required before an idle device will be
2573 autosuspended. Devices for which the delay is set
eaafbc3a 2574 to a negative value won't be autosuspended at all.
b5e795f8 2575
fd7c519d
JK
2576 usbcore.usbfs_snoop=
2577 [USB] Set to log all usbfs traffic (default 0 = off).
2578
2579 usbcore.blinkenlights=
2580 [USB] Set to cycle leds on hubs (default 0 = off).
2581
2582 usbcore.old_scheme_first=
2583 [USB] Start with the old device initialization
2584 scheme (default 0 = off).
2585
2586 usbcore.use_both_schemes=
2587 [USB] Try the other device initialization scheme
2588 if the first one fails (default 1 = enabled).
2589
2590 usbcore.initial_descriptor_timeout=
2591 [USB] Specifies timeout for the initial 64-byte
2592 USB_REQ_GET_DESCRIPTOR request in milliseconds
2593 (default 5000 = 5.0 seconds).
2594
1da177e4
LT
2595 usbhid.mousepoll=
2596 [USBHID] The interval which mice are to be polled at.
a9913044 2597
d4f373e5
AS
2598 usb-storage.delay_use=
2599 [UMS] The delay in seconds before a new device is
2600 scanned for Logical Units (default 5).
2601
2602 usb-storage.quirks=
2603 [UMS] A list of quirks entries to supplement or
2604 override the built-in unusual_devs list. List
2605 entries are separated by commas. Each entry has
2606 the form VID:PID:Flags where VID and PID are Vendor
2607 and Product ID values (4-digit hex numbers) and
2608 Flags is a set of characters, each corresponding
2609 to a common usb-storage quirk flag as follows:
c838ea46
AS
2610 a = SANE_SENSE (collect more than 18 bytes
2611 of sense data);
a0bb1081
AS
2612 b = BAD_SENSE (don't collect more than 18
2613 bytes of sense data);
d4f373e5
AS
2614 c = FIX_CAPACITY (decrease the reported
2615 device capacity by one sector);
5116901d
KR
2616 d = NO_READ_DISC_INFO (don't use
2617 READ_DISC_INFO command);
2618 e = NO_READ_CAPACITY_16 (don't use
2619 READ_CAPACITY_16 command);
c838ea46
AS
2620 h = CAPACITY_HEURISTICS (decrease the
2621 reported device capacity by one
2622 sector if the number is odd);
d4f373e5
AS
2623 i = IGNORE_DEVICE (don't bind to this
2624 device);
2625 l = NOT_LOCKABLE (don't try to lock and
2626 unlock ejectable media);
2627 m = MAX_SECTORS_64 (don't transfer more
2628 than 64 sectors = 32 KB at a time);
21c13a4f
AS
2629 n = INITIAL_READ10 (force a retry of the
2630 initial READ(10) command);
c838ea46
AS
2631 o = CAPACITY_OK (accept the capacity
2632 reported by the device);
d4f373e5
AS
2633 r = IGNORE_RESIDUE (the device reports
2634 bogus residue values);
2635 s = SINGLE_LUN (the device has only one
2636 Logical Unit);
2637 w = NO_WP_DETECT (don't test whether the
2638 medium is write-protected).
2639 Example: quirks=0419:aaf5:rl,0421:0433:rc
2640
14315592
IC
2641 userpte=
2642 [X86] Flags controlling user PTE allocations.
2643
2644 nohigh = do not allocate PTE pages in
2645 HIGHMEM regardless of setting
2646 of CONFIG_HIGHPTE.
2647
6cececfc 2648 vdso= [X86,SH]
1dbf527c 2649 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2650 vdso=1: enable VDSO (default)
2651 vdso=0: disable VDSO mapping
2652
6cececfc 2653 vdso32= [X86]
af65d648
RM
2654 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2655 vdso32=1: enable 32-bit VDSO (default)
2656 vdso32=0: disable 32-bit VDSO mapping
2657
d080d397
YI
2658 vector= [IA-64,SMP]
2659 vector=percpu: enable percpu vector domain
2660
1da177e4
LT
2661 video= [FB] Frame buffer configuration
2662 See Documentation/fb/modedb.txt.
2663
cd4f0ef7 2664 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2665 See Documentation/x86/boot.txt and
a9913044 2666 Documentation/svga.txt.
1da177e4
LT
2667 Use vga=ask for menu.
2668 This is actually a boot loader parameter; the value is
2669 passed to the kernel using a special protocol.
2670
a9913044 2671 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2672 size of <nn>. This can be used to increase the
2673 minimum size (128MB on x86). It can also be used to
2674 decrease the size and leave more room for directly
2675 mapped kernel RAM.
2676
585c3047
PO
2677 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2678 Format: <command>
1da177e4 2679
585c3047
PO
2680 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2681 Format: <command>
2682
2683 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2684 Format: <command>
a9913044 2685
9ea9a886
CL
2686 vt.cur_default= [VT] Default cursor shape.
2687 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2688 the parameters of the <Esc>[?A;B;Cc escape sequence;
2689 see VGA-softcursor.txt. Default: 2 = underline.
2690
0cb55ad2
RD
2691 vt.default_blu= [VT]
2692 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2693 Change the default blue palette of the console.
2694 This is a 16-member array composed of values
2695 ranging from 0-255.
2696
2697 vt.default_grn= [VT]
2698 Format: <green0>,<green1>,<green2>,...,<green15>
2699 Change the default green palette of the console.
2700 This is a 16-member array composed of values
2701 ranging from 0-255.
2702
2703 vt.default_red= [VT]
2704 Format: <red0>,<red1>,<red2>,...,<red15>
2705 Change the default red palette of the console.
2706 This is a 16-member array composed of values
2707 ranging from 0-255.
2708
2709 vt.default_utf8=
2710 [VT]
2711 Format=<0|1>
2712 Set system-wide default UTF-8 mode for all tty's.
2713 Default is 1, i.e. UTF-8 mode is enabled for all
2714 newly opened terminals.
2715
f6c06b68
MG
2716 vt.global_cursor_default=
2717 [VT]
2718 Format=<-1|0|1>
2719 Set system-wide default for whether a cursor
2720 is shown on new VTs. Default is -1,
2721 i.e. cursors will be created by default unless
2722 overridden by individual drivers. 0 will hide
2723 cursors, 1 will display them.
2724
4724ba57
RD
2725 watchdog timers [HW,WDT] For information on watchdog timers,
2726 see Documentation/watchdog/watchdog-parameters.txt
2727 or other driver-specific files in the
2728 Documentation/watchdog/ directory.
1da177e4 2729
0cb55ad2
RD
2730 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2731 default x2apic cluster mode on platforms
2732 supporting x2apic.
2733
bb24c471
JP
2734 x86_mrst_timer= [X86-32,APBT]
2735 Choose timer option for x86 Moorestown MID platform.
2736 Two valid options are apbt timer only and lapic timer
2737 plus one apbt timer for broadcast timer.
2738 x86_mrst_timer=apbt_only | lapic_and_apbt
2739
1da177e4
LT
2740 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2741 xd_geo= See header of drivers/block/xd.c.
2742
c1c5413a
SS
2743 xen_emul_unplug= [HW,X86,XEN]
2744 Unplug Xen emulated devices
2745 Format: [unplug0,][unplug1]
2746 ide-disks -- unplug primary master IDE devices
2747 aux-ide-disks -- unplug non-primary-master IDE devices
2748 nics -- unplug network devices
2749 all -- unplug all emulated devices (NICs and IDE disks)
1dc7ce99
IC
2750 unnecessary -- unplugging emulated devices is
2751 unnecessary even if the host did not respond to
2752 the unplug protocol
c93a4dfb 2753 never -- do not unplug even if version check succeeds
c1c5413a 2754
1da177e4 2755 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2756 Format:
2757 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2758
a9913044 2759______________________________________________________________________
1da177e4
LT
2760
2761TODO:
2762
1da177e4 2763 Add more DRM drivers.