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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The 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
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IMA Integrity measurement architecture is enabled.
48 IOSCHED More than one I/O scheduler is enabled.
49 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
50 ISAPNP ISA PnP code is enabled.
51 ISDN Appropriate ISDN support is enabled.
52 JOY Appropriate joystick support is enabled.
53 LIBATA Libata driver is enabled
54 LP Printer support is enabled.
55 LOOP Loopback device support is enabled.
56 M68k M68k architecture is enabled.
57 These options have more detailed description inside of
58 Documentation/m68k/kernel-options.txt.
59 MCA MCA bus support is enabled.
60 MDA MDA console support is enabled.
61 MOUSE Appropriate mouse support is enabled.
62 MSI Message Signaled Interrupts (PCI).
63 MTD MTD (Memory Technology Device) support is enabled.
64 NET Appropriate network support is enabled.
65 NUMA NUMA support is enabled.
66 GENERIC_TIME The generic timeofday code is enabled.
67 NFS Appropriate NFS support is enabled.
68 OSS OSS sound support is enabled.
69 PV_OPS A paravirtualized kernel is enabled.
70 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
71 PARISC The PA-RISC architecture is enabled.
72 PCI PCI bus support is enabled.
73 PCIE PCI Express support is enabled.
74 PCMCIA The PCMCIA subsystem is enabled.
75 PNP Plug & Play support is enabled.
76 PPC PowerPC architecture is enabled.
77 PPT Parallel port support is enabled.
78 PS2 Appropriate PS/2 support is enabled.
79 RAM RAM disk support is enabled.
80 ROOTPLUG The example Root Plug LSM is enabled.
81 S390 S390 architecture is enabled.
82 SCSI Appropriate SCSI support is enabled.
83 A lot of drivers has their options described inside of
84 Documentation/scsi/.
85 SECURITY Different security models are enabled.
86 SELINUX SELinux support is enabled.
87 SERIAL Serial support is enabled.
88 SH SuperH architecture is enabled.
89 SMP The kernel is an SMP kernel.
90 SPARC Sparc architecture is enabled.
91 SWSUSP Software suspend (hibernation) is enabled.
92 SUSPEND System suspend states are enabled.
93 FTRACE Function tracing enabled.
94 TS Appropriate touchscreen support is enabled.
95 UMS USB Mass Storage support is enabled.
96 USB USB support is enabled.
97 USBHID USB Human Interface Device support is enabled.
98 V4L Video For Linux support is enabled.
99 VGA The VGA console has been enabled.
100 VT Virtual terminal support is enabled.
101 WDT Watchdog support is enabled.
102 XT IBM PC/XT MFM hard disk support is enabled.
103 X86-32 X86-32, aka i386 architecture is enabled.
104 X86-64 X86-64 architecture is enabled.
105 More X86-64 boot options can be found in
106 Documentation/x86/x86_64/boot-options.txt .
107 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
109 In addition, the following text indicates that the option:
111 BUGS= Relates to possible processor bugs on the said processor.
112 KNL Is a kernel start-up parameter.
113 BOOT Is a boot loader parameter.
115 Parameters denoted with BOOT are actually interpreted by the boot
116 loader, and have no meaning to the kernel directly.
117 Do not modify the syntax of boot loader parameters without extreme
118 need or coordination with <Documentation/x86/boot.txt>.
120 There are also arch-specific kernel-parameters not documented here.
121 See for example <Documentation/x86/x86_64/boot-options.txt>.
123 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
124 a trailing = on the name of any parameter states that that parameter will
125 be entered as an environment variable, whereas its absence indicates that
126 it will appear as a kernel argument readable via /proc/cmdline by programs
127 running once the system is up.
129 The number of kernel parameters is not limited, but the length of the
130 complete command line (parameters including spaces etc.) is limited to
131 a fixed number of characters. This limit depends on the architecture
132 and is between 256 and 4096 characters. It is defined in the file
133 ./include/asm/setup.h as COMMAND_LINE_SIZE.
136 acpi= [HW,ACPI,X86-64,i386]
137 Advanced Configuration and Power Interface
138 Format: { force | off | ht | strict | noirq | rsdt }
139 force -- enable ACPI if default was off
140 off -- disable ACPI if default was on
141 noirq -- do not use ACPI for IRQ routing
142 ht -- run only enough ACPI to enable Hyper Threading
143 strict -- Be less tolerant of platforms that are not
144 strictly ACPI specification compliant.
145 rsdt -- prefer RSDT over (default) XSDT
147 See also Documentation/power/pm.txt, pci=noacpi
149 acpi_apic_instance= [ACPI, IOAPIC]
150 Format: <int>
151 2: use 2nd APIC table, if available
152 1,0: use 1st APIC table
153 default: 0
155 acpi_sleep= [HW,ACPI] Sleep options
156 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
157 old_ordering, s4_nonvs }
158 See Documentation/power/video.txt for information on
159 s3_bios and s3_mode.
160 s3_beep is for debugging; it makes the PC's speaker beep
161 as soon as the kernel's real-mode entry point is called.
162 s4_nohwsig prevents ACPI hardware signature from being
163 used during resume from hibernation.
164 old_ordering causes the ACPI 1.0 ordering of the _PTS
165 control method, with respect to putting devices into
166 low power states, to be enforced (the ACPI 2.0 ordering
167 of _PTS is used by default).
168 s4_nonvs prevents the kernel from saving/restoring the
169 ACPI NVS memory during hibernation.
171 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
172 Format: { level | edge | high | low }
174 acpi_irq_balance [HW,ACPI]
175 ACPI will balance active IRQs
176 default in APIC mode
178 acpi_irq_nobalance [HW,ACPI]
179 ACPI will not move active IRQs (default)
180 default in PIC mode
182 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
183 use by PCI
184 Format: <irq>,<irq>...
186 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
187 Format: <irq>,<irq>...
189 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
191 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
192 Format: To spoof as Windows 98: ="Microsoft Windows"
194 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
195 acpi_osi="string1" # add string1 -- only one string
196 acpi_osi="!string2" # remove built-in string2
197 acpi_osi= # disable all strings
199 acpi_serialize [HW,ACPI] force serialization of AML methods
201 acpi_skip_timer_override [HW,ACPI]
202 Recognize and ignore IRQ0/pin2 Interrupt Override.
203 For broken nForce2 BIOS resulting in XT-PIC timer.
204 acpi_use_timer_override [HW,ACPI]
205 Use timer override. For some broken Nvidia NF5 boards
206 that require a timer override, but don't have
207 HPET
209 acpi_backlight= [HW,ACPI]
210 acpi_backlight=vendor
211 acpi_backlight=video
212 If set to vendor, prefer vendor specific driver
213 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
214 of the ACPI video.ko driver.
216 acpi_display_output= [HW,ACPI]
217 acpi_display_output=vendor
218 acpi_display_output=video
219 See above.
221 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
222 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
223 Format: <int>
224 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
225 debug output. Bits in debug_layer correspond to a
226 _COMPONENT in an ACPI source file, e.g.,
227 #define _COMPONENT ACPI_PCI_COMPONENT
228 Bits in debug_level correspond to a level in
229 ACPI_DEBUG_PRINT statements, e.g.,
230 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
231 The debug_level mask defaults to "info". See
232 Documentation/acpi/debug.txt for more information about
233 debug layers and levels.
235 Enable processor driver info messages:
236 acpi.debug_layer=0x20000000
237 Enable PCI/PCI interrupt routing info messages:
238 acpi.debug_layer=0x400000
239 Enable AML "Debug" output, i.e., stores to the Debug
240 object while interpreting AML:
241 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
242 Enable all messages related to ACPI hardware:
243 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
245 Some values produce so much output that the system is
246 unusable. The "log_buf_len" parameter may be useful
247 if you need to capture more output.
249 acpi.power_nocheck= [HW,ACPI]
250 Format: 1/0 enable/disable the check of power state.
251 On some bogus BIOS the _PSC object/_STA object of
252 power resource can't return the correct device power
253 state. In such case it is unneccessary to check its
254 power state again in power transition.
255 1 : disable the power state check
257 acpi_pm_good [X86-32,X86-64]
258 Override the pmtimer bug detection: force the kernel
259 to assume that this machine's pmtimer latches its value
260 and always returns good values.
262 agp= [AGP]
263 { off | try_unsupported }
264 off: disable AGP support
265 try_unsupported: try to drive unsupported chipsets
266 (may crash computer or cause data corruption)
268 enable_timer_pin_1 [i386,x86-64]
269 Enable PIN 1 of APIC timer
270 Can be useful to work around chipset bugs
271 (in particular on some ATI chipsets).
272 The kernel tries to set a reasonable default.
274 disable_timer_pin_1 [i386,x86-64]
275 Disable PIN 1 of APIC timer
276 Can be useful to work around chipset bugs.
278 ad1848= [HW,OSS]
279 Format: <io>,<irq>,<dma>,<dma2>,<type>
281 advansys= [HW,SCSI]
282 See header of drivers/scsi/advansys.c.
284 advwdt= [HW,WDT] Advantech WDT
285 Format: <iostart>,<iostop>
287 aedsp16= [HW,OSS] Audio Excel DSP 16
288 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
289 See also header of sound/oss/aedsp16.c.
291 aha152x= [HW,SCSI]
292 See Documentation/scsi/aha152x.txt.
294 aha1542= [HW,SCSI]
295 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
297 aic7xxx= [HW,SCSI]
298 See Documentation/scsi/aic7xxx.txt.
300 aic79xx= [HW,SCSI]
301 See Documentation/scsi/aic79xx.txt.
303 amd_iommu= [HW,X86-84]
304 Pass parameters to the AMD IOMMU driver in the system.
305 Possible values are:
306 isolate - enable device isolation (each device, as far
307 as possible, will get its own protection
308 domain) [default]
309 share - put every device behind one IOMMU into the
310 same protection domain
311 fullflush - enable flushing of IO/TLB entries when
312 they are unmapped. Otherwise they are
313 flushed before they will be reused, which
314 is a lot of faster
316 amd_iommu_size= [HW,X86-64]
317 Define the size of the aperture for the AMD IOMMU
318 driver. Possible values are:
319 '32M', '64M' (default), '128M', '256M', '512M', '1G'
321 amijoy.map= [HW,JOY] Amiga joystick support
322 Map of devices attached to JOY0DAT and JOY1DAT
323 Format: <a>,<b>
324 See also Documentation/kernel/input/joystick.txt
326 analog.map= [HW,JOY] Analog joystick and gamepad support
327 Specifies type or capabilities of an analog joystick
328 connected to one of 16 gameports
329 Format: <type1>,<type2>,..<type16>
331 apc= [HW,SPARC]
332 Power management functions (SPARCstation-4/5 + deriv.)
333 Format: noidle
334 Disable APC CPU standby support. SPARCstation-Fox does
335 not play well with APC CPU idle - disable it if you have
336 APC and your system crashes randomly.
338 apic= [APIC,i386] Advanced Programmable Interrupt Controller
339 Change the output verbosity whilst booting
340 Format: { quiet (default) | verbose | debug }
341 Change the amount of debugging information output
342 when initialising the APIC and IO-APIC components.
344 apm= [APM] Advanced Power Management
345 See header of arch/x86/kernel/apm_32.c.
347 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
348 Format: <io>,<irq>,<nodeID>
350 ataflop= [HW,M68k]
352 atarimouse= [HW,MOUSE] Atari Mouse
354 atascsi= [HW,SCSI] Atari SCSI
356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
357 EzKey and similar keyboards
359 atkbd.reset= [HW] Reset keyboard during initialization
361 atkbd.set= [HW] Select keyboard code set
362 Format: <int> (2 = AT (default), 3 = PS/2)
364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
365 keyboards
367 atkbd.softraw= [HW] Choose between synthetic and real raw mode
368 Format: <bool> (0 = real, 1 = synthetic (default))
370 atkbd.softrepeat= [HW]
371 Use software keyboard repeat
373 autotest [IA64]
375 baycom_epp= [HW,AX25]
376 Format: <io>,<mode>
378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
379 Format: <io>,<mode>
380 See header of drivers/net/hamradio/baycom_par.c.
382 baycom_ser_fdx= [HW,AX25]
383 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
384 Format: <io>,<irq>,<mode>[,<baud>]
385 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387 baycom_ser_hdx= [HW,AX25]
388 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
389 Format: <io>,<irq>,<mode>
390 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392 boot_delay= Milliseconds to delay each printk during boot.
393 Values larger than 10 seconds (10000) are changed to
394 no delay (0).
395 Format: integer
397 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
400 bttv.radio= Most important insmod options are available as
401 kernel args too.
402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405 BusLogic= [HW,SCSI]
406 See drivers/scsi/BusLogic.c, comment before function
407 BusLogic_ParseDriverOptions().
409 c101= [NET] Moxa C101 synchronous serial card
411 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
412 Sometimes CPU hardware bugs make them report the cache
413 size incorrectly. The kernel will attempt work arounds
414 to fix known problems, but for some CPUs it is not
415 possible to determine what the correct size should be.
416 This option provides an override for these situations.
418 security= [SECURITY] Choose a security module to enable at boot.
419 If this boot parameter is not specified, only the first
420 security module asking for security registration will be
421 loaded. An invalid security module name will be treated
422 as if no module has been chosen.
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.
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
447 cio_ignore= [S390]
448 See Documentation/s390/CommonIO for details.
450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
451 [Deprecated]
452 Forces specified clocksource (if available) to be used
453 when calculating gettimeofday(). If specified
454 clocksource is not available, it defaults to PIT.
455 Format: { pit | tsc | cyclone | pmtmr }
457 clocksource= [GENERIC_TIME] Override the default clocksource
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
468 [X86-32] pit,hpet,tsc,vmi-timer;
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
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
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.
490 code_bytes [IA32/X86_64] How many bytes of object code to print
491 in an oops report.
492 Range: 0 - 8192
493 Default: 64
495 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support
496 this option disables the debugging code at boot.
498 dma_debug_entries=<number>
499 This option allows to tune the number of preallocated
500 entries for DMA-API debugging code. One entry is
501 required per DMA-API allocation. Use this if the
502 DMA-API debugging code disables itself because the
503 architectural default is too low.
505 hpet= [X86-32,HPET] option to control HPET usage
506 Format: { enable (default) | disable | force |
507 verbose }
508 disable: disable HPET and use PIT instead
509 force: allow force enabled of undocumented chips (ICH4,
510 VIA, nVidia)
511 verbose: show contents of HPET registers during setup
513 com20020= [HW,NET] ARCnet - COM20020 chipset
514 Format:
515 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
517 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
518 Format: <io>[,<irq>]
520 com90xx= [HW,NET]
521 ARCnet - COM90xx chipset (memory-mapped buffers)
522 Format: <io>[,<irq>[,<memstart>]]
524 condev= [HW,S390] console device
525 conmode=
527 console= [KNL] Output console device and options.
529 tty<n> Use the virtual console device <n>.
531 ttyS<n>[,options]
532 ttyUSB0[,options]
533 Use the specified serial port. The options are of
534 the form "bbbbpnf", where "bbbb" is the baud rate,
535 "p" is parity ("n", "o", or "e"), "n" is number of
536 bits, and "f" is flow control ("r" for RTS or
537 omit it). Default is "9600n8".
539 See Documentation/serial-console.txt for more
540 information. See
541 Documentation/networking/netconsole.txt for an
542 alternative.
544 uart[8250],io,<addr>[,options]
545 uart[8250],mmio,<addr>[,options]
546 Start an early, polled-mode console on the 8250/16550
547 UART at the specified I/O port or MMIO address,
548 switching to the matching ttyS device later. The
549 options are the same as for ttyS, above.
551 If the device connected to the port is not a TTY but a braille
552 device, prepend "brl," before the device type, for instance
553 console=brl,ttyS0
554 For now, only VisioBraille is supported.
556 earlycon= [KNL] Output early console device and options.
557 uart[8250],io,<addr>[,options]
558 uart[8250],mmio,<addr>[,options]
559 Start an early, polled-mode console on the 8250/16550
560 UART at the specified I/O port or MMIO address.
561 The options are the same as for ttyS, above.
563 no_console_suspend
564 [HW] Never suspend the console
565 Disable suspending of consoles during suspend and
566 hibernate operations. Once disabled, debugging
567 messages can reach various consoles while the rest
568 of the system is being put to sleep (ie, while
569 debugging driver suspend/resume hooks). This may
570 not work reliably with all consoles, but is known
571 to work with serial and VGA consoles.
573 coredump_filter=
574 [KNL] Change the default value for
575 /proc/<pid>/coredump_filter.
576 See also Documentation/filesystems/proc.txt.
578 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
579 Format:
580 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
582 crashkernel=nn[KMG]@ss[KMG]
583 [KNL] Reserve a chunk of physical memory to
584 hold a kernel to switch to with kexec on panic.
586 crashkernel=range1:size1[,range2:size2,...][@offset]
587 [KNL] Same as above, but depends on the memory
588 in the running system. The syntax of range is
589 start-[end] where start and end are both
590 a memory unit (amount[KMG]). See also
591 Documentation/kdump/kdump.txt for a example.
593 cs89x0_dma= [HW,NET]
594 Format: <dma>
596 cs89x0_media= [HW,NET]
597 Format: { rj45 | aui | bnc }
599 dasd= [HW,NET]
600 See header of drivers/s390/block/dasd_devmap.c.
602 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
603 (one device per port)
604 Format: <port#>,<type>
605 See also Documentation/input/joystick-parport.txt
607 debug [KNL] Enable kernel debugging (events log level).
609 debug_locks_verbose=
610 [KNL] verbose self-tests
611 Format=<0|1>
612 Print debugging info while doing the locking API
613 self-tests.
614 We default to 0 (no extra messages), setting it to
615 1 will print _a lot_ more information - normally
616 only useful to kernel developers.
618 debug_objects [KNL] Enable object debugging
620 debugpat [X86] Enable PAT debugging
622 decnet.addr= [HW,NET]
623 Format: <area>[,<node>]
624 See also Documentation/networking/decnet.txt.
626 vt.default_blu= [VT]
627 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
628 Change the default blue palette of the console.
629 This is a 16-member array composed of values
630 ranging from 0-255.
632 vt.default_grn= [VT]
633 Format: <green0>,<green1>,<green2>,...,<green15>
634 Change the default green palette of the console.
635 This is a 16-member array composed of values
636 ranging from 0-255.
638 vt.default_red= [VT]
639 Format: <red0>,<red1>,<red2>,...,<red15>
640 Change the default red palette of the console.
641 This is a 16-member array composed of values
642 ranging from 0-255.
644 vt.default_utf8=
645 [VT]
646 Format=<0|1>
647 Set system-wide default UTF-8 mode for all tty's.
648 Default is 1, i.e. UTF-8 mode is enabled for all
649 newly opened terminals.
651 dhash_entries= [KNL]
652 Set number of hash buckets for dentry cache.
654 digi= [HW,SERIAL]
655 IO parameters + enable/disable command.
657 digiepca= [HW,SERIAL]
658 See drivers/char/README.epca and
659 Documentation/serial/digiepca.txt.
661 disable_mtrr_cleanup [X86]
662 enable_mtrr_cleanup [X86]
663 The kernel tries to adjust MTRR layout from continuous
664 to discrete, to make X server driver able to add WB
665 entry later. This parameter enables/disables that.
667 mtrr_chunk_size=nn[KMG] [X86]
668 used for mtrr cleanup. It is largest continous chunk
669 that could hold holes aka. UC entries.
671 mtrr_gran_size=nn[KMG] [X86]
672 Used for mtrr cleanup. It is granularity of mtrr block.
673 Default is 1.
674 Large value could prevent small alignment from
675 using up MTRRs.
677 mtrr_spare_reg_nr=n [X86]
678 Format: <integer>
679 Range: 0,7 : spare reg number
680 Default : 1
681 Used for mtrr cleanup. It is spare mtrr entries number.
682 Set to 2 or more if your graphical card needs more.
684 disable_mtrr_trim [X86, Intel and AMD only]
685 By default the kernel will trim any uncacheable
686 memory out of your available memory pool based on
687 MTRR settings. This parameter disables that behavior,
688 possibly causing your machine to run very slowly.
690 dmasound= [HW,OSS] Sound subsystem buffers
692 dscc4.setup= [NET]
694 dtc3181e= [HW,SCSI]
696 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
697 earlyprintk=vga
698 earlyprintk=serial[,ttySn[,baudrate]]
699 earlyprintk=dbgp
701 Append ",keep" to not disable it when the real console
702 takes over.
704 Only vga or serial or usb debug port at a time.
706 Currently only ttyS0 and ttyS1 are supported.
708 Interaction with the standard serial driver is not
709 very good.
711 The VGA output is eventually overwritten by the real
712 console.
714 eata= [HW,SCSI]
716 edd= [EDD]
717 Format: {"off" | "on" | "skip[mbr]"}
719 eisa_irq_edge= [PARISC,HW]
720 See header of drivers/parisc/eisa.c.
722 elanfreq= [X86-32]
723 See comment before function elanfreq_setup() in
724 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
726 elevator= [IOSCHED]
727 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
728 See Documentation/block/as-iosched.txt and
729 Documentation/block/deadline-iosched.txt for details.
731 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
732 Specifies physical address of start of kernel core
733 image elf header. Generally kexec loader will
734 pass this option to capture kernel.
735 See Documentation/kdump/kdump.txt for details.
737 enforcing [SELINUX] Set initial enforcing status.
738 Format: {"0" | "1"}
739 See security/selinux/Kconfig help text.
740 0 -- permissive (log only, no denials).
741 1 -- enforcing (deny and log).
742 Default value is 0.
743 Value can be changed at runtime via /selinux/enforce.
745 ether= [HW,NET] Ethernet cards parameters
746 This option is obsoleted by the "netdev=" option, which
747 has equivalent usage. See its documentation for details.
749 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
750 Format: <io>[,<irq>]
752 failslab=
753 fail_page_alloc=
754 fail_make_request=[KNL]
755 General fault injection mechanism.
756 Format: <interval>,<probability>,<space>,<times>
757 See also /Documentation/fault-injection/.
759 fd_mcs= [HW,SCSI]
760 See header of drivers/scsi/fd_mcs.c.
762 fdomain= [HW,SCSI]
763 See header of drivers/scsi/fdomain.c.
765 floppy= [HW]
766 See Documentation/blockdev/floppy.txt.
768 force_pal_cache_flush
769 [IA-64] Avoid check_sal_cache_flush which may hang on
770 buggy SAL_CACHE_FLUSH implementations. Using this
771 parameter will force ia64_sal_cache_flush to call
772 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
774 ftrace=[tracer]
775 [ftrace] will set and start the specified tracer
776 as early as possible in order to facilitate early
777 boot debugging.
779 ftrace_dump_on_oops
780 [ftrace] will dump the trace buffers on oops.
782 gamecon.map[2|3]=
783 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
784 support via parallel port (up to 5 devices per port)
785 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
786 See also Documentation/input/joystick-parport.txt
788 gamma= [HW,DRM]
790 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
791 Format: off | on
792 default: on
794 gdth= [HW,SCSI]
795 See header of drivers/scsi/gdth.c.
797 gpt [EFI] Forces disk with valid GPT signature but
798 invalid Protective MBR to be treated as GPT.
800 gvp11= [HW,SCSI]
802 hashdist= [KNL,NUMA] Large hashes allocated during boot
803 are distributed across NUMA nodes. Defaults on
804 for IA-64, off otherwise.
805 Format: 0 | 1 (for off | on)
807 hcl= [IA-64] SGI's Hardware Graph compatibility layer
809 hd= [EIDE] (E)IDE hard drive subsystem geometry
810 Format: <cyl>,<head>,<sect>
812 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
813 size of <nn>. This works even on boxes that have no
814 highmem otherwise. This also works to reduce highmem
815 size on bigger boxes.
817 highres= [KNL] Enable/disable high resolution timer mode.
818 Valid parameters: "on", "off"
819 Default: "on"
821 hisax= [HW,ISDN]
822 See Documentation/isdn/README.HiSax.
824 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
825 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
826 On x86-64 and powerpc, this option can be specified
827 multiple times interleaved with hugepages= to reserve
828 huge pages of different sizes. Valid pages sizes on
829 x86-64 are 2M (when the CPU supports "pse") and 1G
830 (when the CPU supports the "pdpe1gb" cpuinfo flag)
831 Note that 1GB pages can only be allocated at boot time
832 using hugepages= and not freed afterwards.
833 default_hugepagesz=
834 [same as hugepagesz=] The size of the default
835 HugeTLB page size. This is the size represented by
836 the legacy /proc/ hugepages APIs, used for SHM, and
837 default size when mounting hugetlbfs filesystems.
838 Defaults to the default architecture's huge page size
839 if not specified.
841 hlt [BUGS=ARM,SH]
843 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
844 terminal devices. Valid values: 0..8
845 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
846 If specified, z/VM IUCV HVC accepts connections
847 from listed z/VM user IDs only.
849 i2c_bus= [HW] Override the default board specific I2C bus speed
850 or register an additional I2C bus that is not
851 registered from board initialization code.
852 Format:
853 <bus_id>,<clkrate>
855 i8042.debug [HW] Toggle i8042 debug mode
856 i8042.direct [HW] Put keyboard port into non-translated mode
857 i8042.dumbkbd [HW] Pretend that controller can only read data from
858 keyboard and cannot control its state
859 (Don't attempt to blink the leds)
860 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
861 i8042.nokbd [HW] Don't check/create keyboard port
862 i8042.noloop [HW] Disable the AUX Loopback command while probing
863 for the AUX port
864 i8042.nomux [HW] Don't check presence of an active multiplexing
865 controller
866 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
867 controllers
868 i8042.panicblink=
869 [HW] Frequency with which keyboard LEDs should blink
870 when kernel panics (default is 0.5 sec)
871 i8042.reset [HW] Reset the controller during init and cleanup
872 i8042.unlock [HW] Unlock (ignore) the keylock
874 i810= [HW,DRM]
876 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
877 indicates that the driver is running on unsupported
878 hardware.
879 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
880 does not match list of supported models.
881 i8k.power_status
882 [HW] Report power status in /proc/i8k
883 (disabled by default)
884 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
885 capability is set.
887 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
888 See Documentation/mca.txt.
890 icn= [HW,ISDN]
891 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
893 ide-core.nodma= [HW] (E)IDE subsystem
894 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
895 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
896 .chs .ignore_cable are additional options
897 See Documentation/ide/ide.txt.
899 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
900 See Documentation/ide/ide.txt.
902 idle= [X86]
903 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
904 Poll forces a polling idle loop that can slightly
905 improve the performance of waking up a idle CPU, but
906 will use a lot of power and make the system run hot.
907 Not recommended.
908 idle=mwait: On systems which support MONITOR/MWAIT but
909 the kernel chose to not use it because it doesn't save
910 as much power as a normal idle loop, use the
911 MONITOR/MWAIT idle loop anyways. Performance should be
912 the same as idle=poll.
913 idle=halt: Halt is forced to be used for CPU idle.
914 In such case C2/C3 won't be used again.
915 idle=nomwait: Disable mwait for CPU C-states
917 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
918 Claim all unknown PCI IDE storage controllers.
920 ignore_loglevel [KNL]
921 Ignore loglevel setting - this will print /all/
922 kernel messages to the console. Useful for debugging.
924 ihash_entries= [KNL]
925 Set number of hash buckets for inode cache.
927 ima_audit= [IMA]
928 Format: { "0" | "1" }
929 0 -- integrity auditing messages. (Default)
930 1 -- enable informational integrity auditing messages.
932 ima_hash= [IMA]
933 Formt: { "sha1" | "md5" }
934 default: "sha1"
936 in2000= [HW,SCSI]
937 See header of drivers/scsi/in2000.c.
939 init= [KNL]
940 Format: <full_path>
941 Run specified binary instead of /sbin/init as init
942 process.
944 initcall_debug [KNL] Trace initcalls as they are executed. Useful
945 for working out where the kernel is dying during
946 startup.
948 initrd= [BOOT] Specify the location of the initial ramdisk
950 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
951 Format: <irq>
953 inttest= [IA64]
955 iomem= Disable strict checking of access to MMIO memory
956 strict regions from userspace.
957 relaxed
959 iommu= [x86]
960 off
961 force
962 noforce
963 biomerge
964 panic
965 nopanic
966 merge
967 nomerge
968 forcesac
969 soft
972 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
973 on
974 Enable intel iommu driver.
975 off
976 Disable intel iommu driver.
977 igfx_off [Default Off]
978 By default, gfx is mapped as normal device. If a gfx
979 device has a dedicated DMAR unit, the DMAR unit is
980 bypassed by not enabling DMAR with this option. In
981 this case, gfx device will use physical address for
982 DMA.
983 forcedac [x86_64]
984 With this option iommu will not optimize to look
985 for io virtual address below 32 bit forcing dual
986 address cycle on pci bus for cards supporting greater
987 than 32 bit addressing. The default is to look
988 for translation below 32 bit and if not available
989 then look in the higher range.
990 strict [Default Off]
991 With this option on every unmap_single operation will
992 result in a hardware IOTLB flush operation as opposed
993 to batching them for performance.
995 io_delay= [X86-32,X86-64] I/O delay method
996 0x80
997 Standard port 0x80 based delay
998 0xed
999 Alternate port 0xed based delay (needed on some systems)
1000 udelay
1001 Simple two microseconds delay
1002 none
1003 No delay
1005 io7= [HW] IO7 for Marvel based alpha systems
1006 See comment before marvel_specify_io7 in
1007 arch/alpha/kernel/core_marvel.c.
1009 ip= [IP_PNP]
1010 See Documentation/filesystems/nfsroot.txt.
1012 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1013 See comment before ip2_setup() in
1014 drivers/char/ip2/ip2base.c.
1016 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1017 See header of drivers/scsi/ips.c.
1019 ports= [IP_VS_FTP] IPVS ftp helper module
1020 Default is 21.
1021 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1022 may be specified.
1023 Format: <port>,<port>....
1025 irqfixup [HW]
1026 When an interrupt is not handled search all handlers
1027 for it. Intended to get systems with badly broken
1028 firmware running.
1030 irqpoll [HW]
1031 When an interrupt is not handled search all handlers
1032 for it. Also check all handlers each timer
1033 interrupt. Intended to get systems with badly broken
1034 firmware running.
1036 isapnp= [ISAPNP]
1037 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1039 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1040 Format:
1041 <cpu number>,...,<cpu number>
1042 or
1043 <cpu number>-<cpu number>
1044 (must be a positive range in ascending order)
1045 or a mixture
1046 <cpu number>,...,<cpu number>-<cpu number>
1048 This option can be used to specify one or more CPUs
1049 to isolate from the general SMP balancing and scheduling
1050 algorithms. You can move a process onto or off an
1051 "isolated" CPU via the CPU affinity syscalls or cpuset.
1052 <cpu number> begins at 0 and the maximum value is
1053 "number of CPUs in system - 1".
1055 This option is the preferred way to isolate CPUs. The
1056 alternative -- manually setting the CPU mask of all
1057 tasks in the system -- can cause problems and
1058 suboptimal load balancer performance.
1060 iucv= [HW,NET]
1062 js= [HW,JOY] Analog joystick
1063 See Documentation/input/joystick.txt.
1065 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1066 specifies the amount of memory usable by the kernel
1067 for non-movable allocations. The requested amount is
1068 spread evenly throughout all nodes in the system. The
1069 remaining memory in each node is used for Movable
1070 pages. In the event, a node is too small to have both
1071 kernelcore and Movable pages, kernelcore pages will
1072 take priority and other nodes will have a larger number
1073 of kernelcore pages. The Movable zone is used for the
1074 allocation of pages that may be reclaimed or moved
1075 by the page migration subsystem. This means that
1076 HugeTLB pages may not be allocated from this zone.
1077 Note that allocations like PTEs-from-HighMem still
1078 use the HighMem zone if it exists, and the Normal
1079 zone if it does not.
1081 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1082 is similar to kernelcore except it specifies the
1083 amount of memory used for migratable allocations.
1084 If both kernelcore and movablecore is specified,
1085 then kernelcore will be at *least* the specified
1086 value but may be more. If movablecore on its own
1087 is specified, the administrator must be careful
1088 that the amount of memory usable for all allocations
1089 is not too small.
1091 keepinitrd [HW,ARM]
1093 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1094 in oops dumps.
1096 kgdboc= [HW] kgdb over consoles.
1097 Requires a tty driver that supports console polling.
1098 (only serial suported for now)
1099 Format: <serial_device>[,baud]
1101 kmac= [MIPS] korina ethernet MAC address.
1102 Configure the RouterBoard 532 series on-chip
1103 Ethernet adapter MAC address.
1105 l2cr= [PPC]
1107 l3cr= [PPC]
1109 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1110 disabled it.
1112 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1113 in C2 power state.
1115 libata.dma= [LIBATA] DMA control
1116 libata.dma=0 Disable all PATA and SATA DMA
1117 libata.dma=1 PATA and SATA Disk DMA only
1118 libata.dma=2 ATAPI (CDROM) DMA only
1119 libata.dma=4 Compact Flash DMA only
1120 Combinations also work, so libata.dma=3 enables DMA
1121 for disks and CDROMs, but not CFs.
1123 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1124 when set.
1125 Format: <int>
1127 libata.force= [LIBATA] Force configurations. The format is comma
1128 separated list of "[ID:]VAL" where ID is
1129 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1130 matching port, link or device. Basically, it matches
1131 the ATA ID string printed on console by libata. If
1132 the whole ID part is omitted, the last PORT and DEVICE
1133 values are used. If ID hasn't been specified yet, the
1134 configuration applies to all ports, links and devices.
1136 If only DEVICE is omitted, the parameter applies to
1137 the port and all links and devices behind it. DEVICE
1138 number of 0 either selects the first device or the
1139 first fan-out link behind PMP device. It does not
1140 select the host link. DEVICE number of 15 selects the
1141 host link and device attached to it.
1143 The VAL specifies the configuration to force. As long
1144 as there's no ambiguity shortcut notation is allowed.
1145 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1146 The following configurations can be forced.
1148 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1149 Any ID with matching PORT is used.
1151 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1153 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1154 udma[/][16,25,33,44,66,100,133] notation is also
1155 allowed.
1157 * [no]ncq: Turn on or off NCQ.
1159 * nohrst, nosrst, norst: suppress hard, soft
1160 and both resets.
1162 If there are multiple matching configurations changing
1163 the same attribute, the last one is used.
1165 lmb=debug [KNL] Enable lmb debug messages.
1167 load_ramdisk= [RAM] List of ramdisks to load from floppy
1168 See Documentation/blockdev/ramdisk.txt.
1170 lockd.nlm_grace_period=P [NFS] Assign grace period.
1171 Format: <integer>
1173 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1174 Format: <integer>
1176 lockd.nlm_timeout=T [NFS] Assign timeout value.
1177 Format: <integer>
1179 lockd.nlm_udpport=M [NFS] Assign UDP port.
1180 Format: <integer>
1182 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1183 Format: <irq>
1185 loglevel= All Kernel Messages with a loglevel smaller than the
1186 console loglevel will be printed to the console. It can
1187 also be changed with klogd or other programs. The
1188 loglevels are defined as follows:
1190 0 (KERN_EMERG) system is unusable
1191 1 (KERN_ALERT) action must be taken immediately
1192 2 (KERN_CRIT) critical conditions
1193 3 (KERN_ERR) error conditions
1194 4 (KERN_WARNING) warning conditions
1195 5 (KERN_NOTICE) normal but significant condition
1196 6 (KERN_INFO) informational
1197 7 (KERN_DEBUG) debug-level messages
1199 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1200 Format: { n | nk | nM }
1201 n must be a power of two. The default size
1202 is set in the kernel config file.
1204 logo.nologo [FB] Disables display of the built-in Linux logo.
1205 This may be used to provide more screen space for
1206 kernel log messages and is useful when debugging
1207 kernel boot problems.
1209 lp=0 [LP] Specify parallel ports to use, e.g,
1210 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1211 lp=reset first parallel port). 'lp=0' disables the
1212 lp=auto printer driver. 'lp=reset' (which can be
1213 specified in addition to the ports) causes
1214 attached printers to be reset. Using
1215 lp=port1,port2,... specifies the parallel ports
1216 to associate lp devices with, starting with
1217 lp0. A port specification may be 'none' to skip
1218 that lp device, or a parport name such as
1219 'parport0'. Specifying 'lp=auto' instead of a
1220 port specification list means that device IDs
1221 from each port should be examined, to see if
1222 an IEEE 1284-compliant printer is attached; if
1223 so, the driver will manage that printer.
1224 See also header of drivers/char/lp.c.
1226 lpj=n [KNL]
1227 Sets loops_per_jiffy to given constant, thus avoiding
1228 time-consuming boot-time autodetection (up to 250 ms per
1229 CPU). 0 enables autodetection (default). To determine
1230 the correct value for your kernel, boot with normal
1231 autodetection and see what value is printed. Note that
1232 on SMP systems the preset will be applied to all CPUs,
1233 which is likely to cause problems if your CPUs need
1234 significantly divergent settings. An incorrect value
1235 will cause delays in the kernel to be wrong, leading to
1236 unpredictable I/O errors and other breakage. Although
1237 unlikely, in the extreme case this might damage your
1238 hardware.
1240 ltpc= [NET]
1241 Format: <io>,<irq>,<dma>
1243 mac5380= [HW,SCSI] Format:
1244 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1246 machvec= [IA64] Force the use of a particular machine-vector
1247 (machvec) in a generic kernel.
1248 Example: machvec=hpzx1_swiotlb
1250 max_loop= [LOOP] Maximum number of loopback devices that can
1251 be mounted
1252 Format: <1-256>
1254 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1255 should make use of. maxcpus=n : n >= 0 limits the
1256 kernel to using 'n' processors. n=0 is a special case,
1257 it is equivalent to "nosmp", which also disables
1258 the IO APIC.
1260 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1261 or equal to this physical address is ignored.
1263 max_luns= [SCSI] Maximum number of LUNs to probe.
1264 Should be between 1 and 2^32-1.
1266 max_report_luns=
1267 [SCSI] Maximum number of LUNs received.
1268 Should be between 1 and 16384.
1270 mcatest= [IA-64]
1272 mce [X86-32] Machine Check Exception
1274 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1276 md= [HW] RAID subsystems devices and level
1277 See Documentation/md.txt.
1279 mdacon= [MDA]
1280 Format: <first>,<last>
1281 Specifies range of consoles to be captured by the MDA.
1283 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1284 Amount of memory to be used when the kernel is not able
1285 to see the whole system memory or for test.
1286 [X86-32] Use together with memmap= to avoid physical
1287 address space collisions. Without memmap= PCI devices
1288 could be placed at addresses belonging to unused RAM.
1290 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1291 memory.
1293 memchunk=nn[KMG]
1294 [KNL,SH] Allow user to override the default size for
1295 per-device physically contiguous DMA buffers.
1297 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1298 E820 memory map, as specified by the user.
1299 Such memmap=exactmap lines can be constructed based on
1300 BIOS output or other requirements. See the memmap=nn@ss
1301 option description.
1303 memmap=nn[KMG]@ss[KMG]
1304 [KNL] Force usage of a specific region of memory
1305 Region of memory to be used, from ss to ss+nn.
1307 memmap=nn[KMG]#ss[KMG]
1308 [KNL,ACPI] Mark specific memory as ACPI data.
1309 Region of memory to be used, from ss to ss+nn.
1311 memmap=nn[KMG]$ss[KMG]
1312 [KNL,ACPI] Mark specific memory as reserved.
1313 Region of memory to be used, from ss to ss+nn.
1314 Example: Exclude memory from 0x18690000-0x1869ffff
1315 memmap=64K$0x18690000
1316 or
1317 memmap=0x10000$0x18690000
1319 memory_corruption_check=0/1 [X86]
1320 Some BIOSes seem to corrupt the first 64k of
1321 memory when doing things like suspend/resume.
1322 Setting this option will scan the memory
1323 looking for corruption. Enabling this will
1324 both detect corruption and prevent the kernel
1325 from using the memory being corrupted.
1326 However, its intended as a diagnostic tool; if
1327 repeatable BIOS-originated corruption always
1328 affects the same memory, you can use memmap=
1329 to prevent the kernel from using that memory.
1331 memory_corruption_check_size=size [X86]
1332 By default it checks for corruption in the low
1333 64k, making this memory unavailable for normal
1334 use. Use this parameter to scan for
1335 corruption in more or less memory.
1337 memory_corruption_check_period=seconds [X86]
1338 By default it checks for corruption every 60
1339 seconds. Use this parameter to check at some
1340 other rate. 0 disables periodic checking.
1342 memtest= [KNL,X86] Enable memtest
1343 Format: <integer>
1344 default : 0 <disable>
1345 Specifies the number of memtest passes to be
1346 performed. Each pass selects another test
1347 pattern from a given set of patterns. Memtest
1348 fills the memory with this pattern, validates
1349 memory contents and reserves bad memory
1350 regions that are detected.
1352 meye.*= [HW] Set MotionEye Camera parameters
1353 See Documentation/video4linux/meye.txt.
1355 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1356 Multi-Function General Purpose Timers on AMD Geode
1357 platforms.
1359 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1360 the BIOS has incorrectly applied a workaround. TinyBIOS
1361 version 0.98 is known to be affected, 0.99 fixes the
1362 problem by letting the user disable the workaround.
1364 mga= [HW,DRM]
1366 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1367 physical address is ignored.
1369 mminit_loglevel=
1370 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1371 parameter allows control of the logging verbosity for
1372 the additional memory initialisation checks. A value
1373 of 0 disables mminit logging and a level of 4 will
1374 log everything. Information is printed at KERN_DEBUG
1375 so loglevel=8 may also need to be specified.
1377 mousedev.tap_time=
1378 [MOUSE] Maximum time between finger touching and
1379 leaving touchpad surface for touch to be considered
1380 a tap and be reported as a left button click (for
1381 touchpads working in absolute mode only).
1382 Format: <msecs>
1383 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1384 reporting absolute coordinates, such as tablets
1385 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1386 reporting absolute coordinates, such as tablets
1388 mpu401= [HW,OSS]
1389 Format: <io>,<irq>
1391 MTD_Partition= [MTD]
1392 Format: <name>,<region-number>,<size>,<offset>
1394 MTD_Region= [MTD] Format:
1395 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1397 mtdparts= [MTD]
1398 See drivers/mtd/cmdlinepart.c.
1400 mtdset= [ARM]
1401 ARM/S3C2412 JIVE boot control
1403 See arch/arm/mach-s3c2412/mach-jive.c
1405 mtouchusb.raw_coordinates=
1406 [HW] Make the MicroTouch USB driver use raw coordinates
1407 ('y', default) or cooked coordinates ('n')
1409 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1411 NCR_D700= [HW,SCSI]
1412 See header of drivers/scsi/NCR_D700.c.
1414 ncr5380= [HW,SCSI]
1416 ncr53c400= [HW,SCSI]
1418 ncr53c400a= [HW,SCSI]
1420 ncr53c406a= [HW,SCSI]
1422 ncr53c8xx= [HW,SCSI]
1424 netdev= [NET] Network devices parameters
1425 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1426 Note that mem_start is often overloaded to mean
1427 something different and driver-specific.
1428 This usage is only documented in each driver source
1429 file if at all.
1431 nf_conntrack.acct=
1432 [NETFILTER] Enable connection tracking flow accounting
1433 0 to disable accounting
1434 1 to enable accounting
1435 Default value depends on CONFIG_NF_CT_ACCT that is
1436 going to be removed in 2.6.29.
1438 nfsaddrs= [NFS]
1439 See Documentation/filesystems/nfsroot.txt.
1441 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1442 See Documentation/filesystems/nfsroot.txt.
1444 nfs.callback_tcpport=
1445 [NFS] set the TCP port on which the NFSv4 callback
1446 channel should listen.
1448 nfs.idmap_cache_timeout=
1449 [NFS] set the maximum lifetime for idmapper cache
1450 entries.
1452 nfs.enable_ino64=
1453 [NFS] enable 64-bit inode numbers.
1454 If zero, the NFS client will fake up a 32-bit inode
1455 number for the readdir() and stat() syscalls instead
1456 of returning the full 64-bit number.
1457 The default is to return 64-bit inode numbers.
1459 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1460 when a NMI is triggered.
1461 Format: [state][,regs][,debounce][,die]
1463 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1464 Format: [panic,][num]
1465 Valid num: 0,1,2
1466 0 - turn nmi_watchdog off
1467 1 - use the IO-APIC timer for the NMI watchdog
1468 2 - use the local APIC for the NMI watchdog using
1469 a performance counter. Note: This will use one performance
1470 counter and the local APIC's performance vector.
1471 When panic is specified panic when an NMI watchdog timeout occurs.
1472 This is useful when you use a panic=... timeout and need the box
1473 quickly up again.
1474 Instead of 1 and 2 it is possible to use the following
1475 symbolic names: lapic and ioapic
1476 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1478 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1479 emulation library even if a 387 maths coprocessor
1480 is present.
1482 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1483 caches in the slab allocator. Saves per-node memory,
1484 but will impact performance.
1486 noalign [KNL,ARM]
1488 noapic [SMP,APIC] Tells the kernel to not make use of any
1489 IOAPICs that may be present in the system.
1491 nobats [PPC] Do not use BATs for mapping kernel lowmem
1492 on "Classic" PPC cores.
1494 nocache [ARM]
1496 nodelayacct [KNL] Disable per-task delay accounting
1498 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1500 nodsp [SH] Disable hardware DSP at boot time.
1502 noefi [X86-32,X86-64] Disable EFI runtime services support.
1504 noexec [IA-64]
1506 noexec [X86-32,X86-64]
1507 On X86-32 available only on PAE configured kernels.
1508 noexec=on: enable non-executable mappings (default)
1509 noexec=off: disable non-executable mappings
1511 noexec32 [X86-64]
1512 This affects only 32-bit executables.
1513 noexec32=on: enable non-executable mappings (default)
1514 read doesn't imply executable mappings
1515 noexec32=off: disable non-executable mappings
1516 read implies executable mappings
1518 nofpu [SH] Disable hardware FPU at boot time.
1520 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1521 register save and restore. The kernel will only save
1522 legacy floating-point registers on task switch.
1524 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1526 nohlt [BUGS=ARM,SH]
1528 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1529 instruction doesn't work correctly and not to
1530 use it.
1532 no_file_caps Tells the kernel not to honor file capabilities. The
1533 only way then for a file to be executed with privilege
1534 is to be setuid root or executed by root.
1536 nohalt [IA-64] Tells the kernel not to use the power saving
1537 function PAL_HALT_LIGHT when idle. This increases
1538 power-consumption. On the positive side, it reduces
1539 interrupt wake-up latency, which may improve performance
1540 in certain environments such as networked servers or
1541 real-time systems.
1543 nohz= [KNL] Boottime enable/disable dynamic ticks
1544 Valid arguments: on, off
1545 Default: on
1547 noirqdebug [X86-32] Disables the code which attempts to detect and
1548 disable unhandled interrupt sources.
1550 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1551 broken timer IRQ sources.
1553 noisapnp [ISAPNP] Disables ISA PnP code.
1555 noinitrd [RAM] Tells the kernel not to load any configured
1556 initial RAM disk.
1558 nointroute [IA-64]
1560 nojitter [IA64] Disables jitter checking for ITC timers.
1562 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1564 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1566 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1568 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1569 default x2apic cluster mode on platforms
1570 supporting x2apic.
1572 noltlbs [PPC] Do not use large page/tlb entries for kernel
1573 lowmem mapping on PPC40x.
1575 nomca [IA-64] Disable machine check abort handling
1577 nomce [X86-32] Machine Check Exception
1579 nomfgpt [X86-32] Disable Multi-Function General Purpose
1580 Timer usage (for AMD Geode machines).
1582 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1584 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1585 with UP alternatives
1587 noresidual [PPC] Don't use residual data on PReP machines.
1589 noresume [SWSUSP] Disables resume and restores original swap
1590 space.
1592 no-scroll [VGA] Disables scrollback.
1593 This is required for the Braillex ib80-piezo Braille
1594 reader made by F.H. Papenmeier (Germany).
1596 nosbagart [IA-64]
1598 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1600 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1601 and disable the IO APIC. legacy for "maxcpus=0".
1603 nosoftlockup [KNL] Disable the soft-lockup detector.
1605 noswapaccount [KNL] Disable accounting of swap in memory resource
1606 controller. (See Documentation/controllers/memory.txt)
1608 nosync [HW,M68K] Disables sync negotiation for all devices.
1610 notsc [BUGS=X86-32] Disable Time Stamp Counter
1612 nousb [USB] Disable the USB subsystem
1614 nowb [ARM]
1616 nptcg= [IA64] Override max number of concurrent global TLB
1617 purges which is reported from either PAL_VM_SUMMARY or
1618 SAL PALO.
1620 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1621 one of ['zone', 'node', 'default'] can be specified
1622 This can be set from sysctl after boot.
1623 See Documentation/sysctl/vm.txt for details.
1625 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1627 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1628 See Documentation/debugging-via-ohci1394.txt for more
1629 info.
1631 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1632 Rather than timing out after 20 ms if an EC
1633 command is not properly ACKed, override the length
1634 of the timeout. We have interrupts disabled while
1635 waiting for the ACK, so if this is set too high
1636 interrupts *may* be lost!
1638 opl3= [HW,OSS]
1639 Format: <io>
1641 oprofile.timer= [HW]
1642 Use timer interrupt instead of performance counters
1644 osst= [HW,SCSI] SCSI Tape Driver
1645 Format: <buffer_size>,<write_threshold>
1646 See also Documentation/scsi/st.txt.
1648 panic= [KNL] Kernel behaviour on panic
1649 Format: <timeout>
1651 parkbd.port= [HW] Parallel port number the keyboard adapter is
1652 connected to, default is 0.
1653 Format: <parport#>
1654 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1655 0 for XT, 1 for AT (default is AT).
1656 Format: <mode>
1658 parport= [HW,PPT] Specify parallel ports. 0 disables.
1659 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1660 Use 'auto' to force the driver to use any
1661 IRQ/DMA settings detected (the default is to
1662 ignore detected IRQ/DMA settings because of
1663 possible conflicts). You can specify the base
1664 address, IRQ, and DMA settings; IRQ and DMA
1665 should be numbers, or 'auto' (for using detected
1666 settings on that particular port), or 'nofifo'
1667 (to avoid using a FIFO even if it is detected).
1668 Parallel ports are assigned in the order they
1669 are specified on the command line, starting
1670 with parport0.
1672 parport_init_mode= [HW,PPT]
1673 Configure VIA parallel port to operate in
1674 a specific mode. This is necessary on Pegasos
1675 computer where firmware has no options for setting
1676 up parallel port mode and sets it to spp.
1677 Currently this function knows 686a and 8231 chips.
1678 Format: [spp|ps2|epp|ecp|ecpepp]
1680 pas2= [HW,OSS] Format:
1681 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1683 pas16= [HW,SCSI]
1684 See header of drivers/scsi/pas16.c.
1686 pause_on_oops=
1687 Halt all CPUs after the first oops has been printed for
1688 the specified number of seconds. This is to be used if
1689 your oopses keep scrolling off the screen.
1691 pcbit= [HW,ISDN]
1693 pcd. [PARIDE]
1694 See header of drivers/block/paride/pcd.c.
1695 See also Documentation/blockdev/paride.txt.
1697 pci=option[,option...] [PCI] various PCI subsystem options:
1698 off [X86] don't probe for the PCI bus
1699 bios [X86-32] force use of PCI BIOS, don't access
1700 the hardware directly. Use this if your machine
1701 has a non-standard PCI host bridge.
1702 nobios [X86-32] disallow use of PCI BIOS, only direct
1703 hardware access methods are allowed. Use this
1704 if you experience crashes upon bootup and you
1705 suspect they are caused by the BIOS.
1706 conf1 [X86] Force use of PCI Configuration
1707 Mechanism 1.
1708 conf2 [X86] Force use of PCI Configuration
1709 Mechanism 2.
1710 noaer [PCIE] If the PCIEAER kernel config parameter is
1711 enabled, this kernel boot option can be used to
1712 disable the use of PCIE advanced error reporting.
1713 nodomains [PCI] Disable support for multiple PCI
1714 root domains (aka PCI segments, in ACPI-speak).
1715 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1716 Configuration
1717 nomsi [MSI] If the PCI_MSI kernel config parameter is
1718 enabled, this kernel boot option can be used to
1719 disable the use of MSI interrupts system-wide.
1720 noioapicquirk [APIC] Disable all boot interrupt quirks.
1721 Safety option to keep boot IRQs enabled. This
1722 should never be necessary.
1723 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1724 primary IO-APIC for bridges that cannot disable
1725 boot IRQs. This fixes a source of spurious IRQs
1726 when the system masks IRQs.
1727 noioapicreroute [APIC] Disable workaround that uses the
1728 boot IRQ equivalent of an IRQ that connects to
1729 a chipset where boot IRQs cannot be disabled.
1730 The opposite of ioapicreroute.
1731 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1732 routing table. These calls are known to be buggy
1733 on several machines and they hang the machine
1734 when used, but on other computers it's the only
1735 way to get the interrupt routing table. Try
1736 this option if the kernel is unable to allocate
1737 IRQs or discover secondary PCI buses on your
1738 motherboard.
1739 rom [X86] Assign address space to expansion ROMs.
1740 Use with caution as certain devices share
1741 address decoders between ROMs and other
1742 resources.
1743 norom [X86] Do not assign address space to
1744 expansion ROMs that do not already have
1745 BIOS assigned address ranges.
1746 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1747 assigned automatically to PCI devices. You can
1748 make the kernel exclude IRQs of your ISA cards
1749 this way.
1750 pirqaddr=0xAAAAA [X86] Specify the physical address
1751 of the PIRQ table (normally generated
1752 by the BIOS) if it is outside the
1753 F0000h-100000h range.
1754 lastbus=N [X86] Scan all buses thru bus #N. Can be
1755 useful if the kernel is unable to find your
1756 secondary buses and you want to tell it
1757 explicitly which ones they are.
1758 assign-busses [X86] Always assign all PCI bus
1759 numbers ourselves, overriding
1760 whatever the firmware may have done.
1761 usepirqmask [X86] Honor the possible IRQ mask stored
1762 in the BIOS $PIR table. This is needed on
1763 some systems with broken BIOSes, notably
1764 some HP Pavilion N5400 and Omnibook XE3
1765 notebooks. This will have no effect if ACPI
1766 IRQ routing is enabled.
1767 noacpi [X86] Do not use ACPI for IRQ routing
1768 or for PCI scanning.
1769 use_crs [X86] Use _CRS for PCI resource
1770 allocation.
1771 routeirq Do IRQ routing for all PCI devices.
1772 This is normally done in pci_enable_device(),
1773 so this option is a temporary workaround
1774 for broken drivers that don't call it.
1775 skip_isa_align [X86] do not align io start addr, so can
1776 handle more pci cards
1777 firmware [ARM] Do not re-enumerate the bus but instead
1778 just use the configuration from the
1779 bootloader. This is currently used on
1780 IXP2000 systems where the bus has to be
1781 configured a certain way for adjunct CPUs.
1782 noearly [X86] Don't do any early type 1 scanning.
1783 This might help on some broken boards which
1784 machine check when some devices' config space
1785 is read. But various workarounds are disabled
1786 and some IOMMU drivers will not work.
1787 bfsort Sort PCI devices into breadth-first order.
1788 This sorting is done to get a device
1789 order compatible with older (<= 2.4) kernels.
1790 nobfsort Don't sort PCI devices into breadth-first order.
1791 cbiosize=nn[KMG] The fixed amount of bus space which is
1792 reserved for the CardBus bridge's IO window.
1793 The default value is 256 bytes.
1794 cbmemsize=nn[KMG] The fixed amount of bus space which is
1795 reserved for the CardBus bridge's memory
1796 window. The default value is 64 megabytes.
1798 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1799 Management.
1800 off Disable ASPM.
1801 force Enable ASPM even on devices that claim not to support it.
1802 WARNING: Forcing ASPM on may cause system lockups.
1804 pcmv= [HW,PCMCIA] BadgePAD 4
1806 pd. [PARIDE]
1807 See Documentation/blockdev/paride.txt.
1809 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1810 boot time.
1811 Format: { 0 | 1 }
1812 See arch/parisc/kernel/pdc_chassis.c
1814 pf. [PARIDE]
1815 See Documentation/blockdev/paride.txt.
1817 pg. [PARIDE]
1818 See Documentation/blockdev/paride.txt.
1820 pirq= [SMP,APIC] Manual mp-table setup
1821 See Documentation/x86/i386/IO-APIC.txt.
1823 plip= [PPT,NET] Parallel port network link
1824 Format: { parport<nr> | timid | 0 }
1825 See also Documentation/parport.txt.
1827 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1828 Override pmtimer IOPort with a hex value.
1829 e.g. pmtmr=0x508
1831 pnp.debug [PNP]
1832 Enable PNP debug messages. This depends on the
1833 CONFIG_PNP_DEBUG_MESSAGES option.
1835 pnpacpi= [ACPI]
1836 { off }
1838 pnpbios= [ISAPNP]
1839 { on | off | curr | res | no-curr | no-res }
1841 pnp_reserve_irq=
1842 [ISAPNP] Exclude IRQs for the autoconfiguration
1844 pnp_reserve_dma=
1845 [ISAPNP] Exclude DMAs for the autoconfiguration
1847 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1848 Ranges are in pairs (I/O port base and size).
1850 pnp_reserve_mem=
1851 [ISAPNP] Exclude memory regions for the
1852 autoconfiguration.
1853 Ranges are in pairs (memory base and size).
1855 print-fatal-signals=
1856 [KNL] debug: print fatal signals
1857 print-fatal-signals=1: print segfault info to
1858 the kernel console.
1859 default: off.
1861 printk.time= Show timing data prefixed to each printk message line
1862 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1864 profile= [KNL] Enable kernel profiling via /proc/profile
1865 Format: [schedule,]<number>
1866 Param: "schedule" - profile schedule points.
1867 Param: <number> - step/bucket size as a power of 2 for
1868 statistical time based profiling.
1869 Param: "sleep" - profile D-state sleeping (millisecs).
1870 Requires CONFIG_SCHEDSTATS
1871 Param: "kvm" - profile VM exits.
1873 processor.max_cstate= [HW,ACPI]
1874 Limit processor to maximum C-state
1875 max_cstate=9 overrides any DMI blacklist limit.
1877 processor.nocst [HW,ACPI]
1878 Ignore the _CST method to determine C-states,
1879 instead using the legacy FADT method
1881 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1882 before loading.
1883 See Documentation/blockdev/ramdisk.txt.
1885 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1886 probe for; one of (bare|imps|exps|lifebook|any).
1887 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1888 per second.
1889 psmouse.resetafter= [HW,MOUSE]
1890 Try to reset the device after so many bad packets
1891 (0 = never).
1892 psmouse.resolution=
1893 [HW,MOUSE] Set desired mouse resolution, in dpi.
1894 psmouse.smartscroll=
1895 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1896 0 = disabled, 1 = enabled (default).
1898 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1899 Format:
1900 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1902 pt. [PARIDE]
1903 See Documentation/blockdev/paride.txt.
1905 pty.legacy_count=
1906 [KNL] Number of legacy pty's. Overwrites compiled-in
1907 default number.
1909 quiet [KNL] Disable most log messages
1911 r128= [HW,DRM]
1913 raid= [HW,RAID]
1914 See Documentation/md.txt.
1916 ramdisk_blocksize= [RAM]
1917 See Documentation/blockdev/ramdisk.txt.
1919 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1920 See Documentation/blockdev/ramdisk.txt.
1922 rcupdate.blimit= [KNL,BOOT]
1923 Set maximum number of finished RCU callbacks to process
1924 in one batch.
1926 rcupdate.qhimark= [KNL,BOOT]
1927 Set threshold of queued
1928 RCU callbacks over which batch limiting is disabled.
1930 rcupdate.qlowmark= [KNL,BOOT]
1931 Set threshold of queued RCU callbacks below which
1932 batch limiting is re-enabled.
1934 rdinit= [KNL]
1935 Format: <full_path>
1936 Run specified binary instead of /init from the ramdisk,
1937 used for early userspace startup. See initrd.
1939 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1940 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1941 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1943 relax_domain_level=
1944 [KNL, SMP] Set scheduler's default relax_domain_level.
1945 See Documentation/cpusets.txt.
1947 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1949 reservetop= [X86-32]
1950 Format: nn[KMG]
1951 Reserves a hole at the top of the kernel virtual
1952 address space.
1954 reset_devices [KNL] Force drivers to reset the underlying device
1955 during initialization.
1957 resume= [SWSUSP]
1958 Specify the partition device for software suspend
1960 resume_offset= [SWSUSP]
1961 Specify the offset from the beginning of the partition
1962 given by "resume=" at which the swap header is located,
1963 in <PAGE_SIZE> units (needed only for swap files).
1964 See Documentation/power/swsusp-and-swap-files.txt
1966 retain_initrd [RAM] Keep initrd memory after extraction
1968 rhash_entries= [KNL,NET]
1969 Set number of hash buckets for route cache
1971 riscom8= [HW,SERIAL]
1972 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1974 ro [KNL] Mount root device read-only on boot
1976 root= [KNL] Root filesystem
1978 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1979 mount the root filesystem
1981 rootflags= [KNL] Set root filesystem mount option string
1983 rootfstype= [KNL] Set root filesystem type
1985 rootwait [KNL] Wait (indefinitely) for root device to show up.
1986 Useful for devices that are detected asynchronously
1987 (e.g. USB and MMC devices).
1989 root_plug.vendor_id=
1990 [ROOTPLUG] Override the default vendor ID
1992 root_plug.product_id=
1993 [ROOTPLUG] Override the default product ID
1995 root_plug.debug=
1996 [ROOTPLUG] Enable debugging output
1998 rw [KNL] Mount root device read-write on boot
2000 S [KNL] Run init in single mode
2002 sa1100ir [NET]
2003 See drivers/net/irda/sa1100_ir.c.
2005 sbni= [NET] Granch SBNI12 leased line adapter
2007 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2008 Format: <io>[,<timeout>[,<isapnp>]]
2010 scsi_debug_*= [SCSI]
2011 See drivers/scsi/scsi_debug.c.
2013 scsi_default_dev_flags=
2014 [SCSI] SCSI default device flags
2015 Format: <integer>
2017 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2018 Format: <vendor>:<model>:<flags>
2019 (flags are integer value)
2021 scsi_logging_level= [SCSI] a bit mask of logging levels
2022 See drivers/scsi/scsi_logging.h for bits. Also
2023 settable via sysctl at dev.scsi.logging_level
2024 (/proc/sys/dev/scsi/logging_level).
2025 There is also a nice 'scsi_logging_level' script in the
2026 S390-tools package, available for download at
2027 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2029 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2030 discovered. async scans them in kernel threads,
2031 allowing boot to proceed. none ignores them, expecting
2032 user space to do the scan.
2034 selinux [SELINUX] Disable or enable SELinux at boot time.
2035 Format: { "0" | "1" }
2036 See security/selinux/Kconfig help text.
2037 0 -- disable.
2038 1 -- enable.
2039 Default value is set via kernel config option.
2040 If enabled at boot time, /selinux/disable can be used
2041 later to disable prior to initial policy load.
2043 serialnumber [BUGS=X86-32]
2045 shapers= [NET]
2046 Maximal number of shapers.
2048 show_msr= [x86] show boot-time MSR settings
2049 Format: { <integer> }
2050 Show boot-time (BIOS-initialized) MSR settings.
2051 The parameter means the number of CPUs to show,
2052 for example 1 means boot CPU only.
2054 sim710= [SCSI,HW]
2055 See header of drivers/scsi/sim710.c.
2057 simeth= [IA-64]
2058 simscsi=
2060 slram= [HW,MTD]
2062 slub_debug[=options[,slabs]] [MM, SLUB]
2063 Enabling slub_debug allows one to determine the
2064 culprit if slab objects become corrupted. Enabling
2065 slub_debug can create guard zones around objects and
2066 may poison objects when not in use. Also tracks the
2067 last alloc / free. For more information see
2068 Documentation/vm/slub.txt.
2070 slub_max_order= [MM, SLUB]
2071 Determines the maximum allowed order for slabs.
2072 A high setting may cause OOMs due to memory
2073 fragmentation. For more information see
2074 Documentation/vm/slub.txt.
2076 slub_min_objects= [MM, SLUB]
2077 The minimum number of objects per slab. SLUB will
2078 increase the slab order up to slub_max_order to
2079 generate a sufficiently large slab able to contain
2080 the number of objects indicated. The higher the number
2081 of objects the smaller the overhead of tracking slabs
2082 and the less frequently locks need to be acquired.
2083 For more information see Documentation/vm/slub.txt.
2085 slub_min_order= [MM, SLUB]
2086 Determines the mininum page order for slabs. Must be
2087 lower than slub_max_order.
2088 For more information see Documentation/vm/slub.txt.
2090 slub_nomerge [MM, SLUB]
2091 Disable merging of slabs with similar size. May be
2092 necessary if there is some reason to distinguish
2093 allocs to different slabs. Debug options disable
2094 merging on their own.
2095 For more information see Documentation/vm/slub.txt.
2097 smart2= [HW]
2098 Format: <io1>[,<io2>[,...,<io8>]]
2100 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2101 attempt to substitute SMP alternatives once at boot.
2103 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2104 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2105 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2106 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2107 smsc-ircc2.ircc_irq= [HW] IRQ line
2108 smsc-ircc2.ircc_dma= [HW] DMA channel
2109 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2110 0: Toshiba Satellite 1800 (GP data pin select)
2111 1: Fast pin select (default)
2112 2: ATC IRMode
2114 snd-ad1816a= [HW,ALSA]
2116 snd-ad1848= [HW,ALSA]
2118 snd-ali5451= [HW,ALSA]
2120 snd-als100= [HW,ALSA]
2122 snd-als4000= [HW,ALSA]
2124 snd-azt2320= [HW,ALSA]
2126 snd-cmi8330= [HW,ALSA]
2128 snd-cmipci= [HW,ALSA]
2130 snd-cs4231= [HW,ALSA]
2132 snd-cs4232= [HW,ALSA]
2134 snd-cs4236= [HW,ALSA]
2136 snd-cs4281= [HW,ALSA]
2138 snd-cs46xx= [HW,ALSA]
2140 snd-dt019x= [HW,ALSA]
2142 snd-dummy= [HW,ALSA]
2144 snd-emu10k1= [HW,ALSA]
2146 snd-ens1370= [HW,ALSA]
2148 snd-ens1371= [HW,ALSA]
2150 snd-es968= [HW,ALSA]
2152 snd-es1688= [HW,ALSA]
2154 snd-es18xx= [HW,ALSA]
2156 snd-es1938= [HW,ALSA]
2158 snd-es1968= [HW,ALSA]
2160 snd-fm801= [HW,ALSA]
2162 snd-gusclassic= [HW,ALSA]
2164 snd-gusextreme= [HW,ALSA]
2166 snd-gusmax= [HW,ALSA]
2168 snd-hdsp= [HW,ALSA]
2170 snd-ice1712= [HW,ALSA]
2172 snd-intel8x0= [HW,ALSA]
2174 snd-interwave= [HW,ALSA]
2176 snd-interwave-stb=
2177 [HW,ALSA]
2179 snd-korg1212= [HW,ALSA]
2181 snd-maestro3= [HW,ALSA]
2183 snd-mpu401= [HW,ALSA]
2185 snd-mtpav= [HW,ALSA]
2187 snd-nm256= [HW,ALSA]
2189 snd-opl3sa2= [HW,ALSA]
2191 snd-opti92x-ad1848=
2192 [HW,ALSA]
2194 snd-opti92x-cs4231=
2195 [HW,ALSA]
2197 snd-opti93x= [HW,ALSA]
2199 snd-pmac= [HW,ALSA]
2201 snd-rme32= [HW,ALSA]
2203 snd-rme96= [HW,ALSA]
2205 snd-rme9652= [HW,ALSA]
2207 snd-sb8= [HW,ALSA]
2209 snd-sb16= [HW,ALSA]
2211 snd-sbawe= [HW,ALSA]
2213 snd-serial= [HW,ALSA]
2215 snd-sgalaxy= [HW,ALSA]
2217 snd-sonicvibes= [HW,ALSA]
2219 snd-sun-amd7930=
2220 [HW,ALSA]
2222 snd-sun-cs4231= [HW,ALSA]
2224 snd-trident= [HW,ALSA]
2226 snd-usb-audio= [HW,ALSA,USB]
2228 snd-via82xx= [HW,ALSA]
2230 snd-virmidi= [HW,ALSA]
2232 snd-wavefront= [HW,ALSA]
2234 snd-ymfpci= [HW,ALSA]
2236 softlockup_panic=
2237 [KNL] Should the soft-lockup detector generate panics.
2239 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2240 See Documentation/sonypi.txt
2242 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2243 See Documentation/serial/specialix.txt.
2245 spia_io_base= [HW,MTD]
2246 spia_fio_base=
2247 spia_pedr=
2248 spia_peddr=
2250 sscape= [HW,OSS]
2251 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2253 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2254 See Documentation/scsi/st.txt.
2256 stacktrace [FTRACE]
2257 Enabled the stack tracer on boot up.
2259 sti= [PARISC,HW]
2260 Format: <num>
2261 Set the STI (builtin display/keyboard on the HP-PARISC
2262 machines) console (graphic card) which should be used
2263 as the initial boot-console.
2264 See also comment in drivers/video/console/sticore.c.
2266 sti_font= [HW]
2267 See comment in drivers/video/console/sticore.c.
2269 stifb= [HW]
2270 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2272 sunrpc.pool_mode=
2273 [NFS]
2274 Control how the NFS server code allocates CPUs to
2275 service thread pools. Depending on how many NICs
2276 you have and where their interrupts are bound, this
2277 option will affect which CPUs will do NFS serving.
2278 Note: this parameter cannot be changed while the
2279 NFS server is running.
2281 auto the server chooses an appropriate mode
2282 automatically using heuristics
2283 global a single global pool contains all CPUs
2284 percpu one pool for each CPU
2285 pernode one pool for each NUMA node (equivalent
2286 to global on non-NUMA machines)
2288 swiotlb= [IA-64] Number of I/O TLB slabs
2290 switches= [HW,M68k]
2292 sym53c416= [HW,SCSI]
2293 See header of drivers/scsi/sym53c416.c.
2295 sysrq_always_enabled
2296 [KNL]
2297 Ignore sysrq setting - this boot parameter will
2298 neutralize any effect of /proc/sys/kernel/sysrq.
2299 Useful for debugging.
2301 t128= [HW,SCSI]
2302 See header of drivers/scsi/t128.c.
2304 tdfx= [HW,DRM]
2306 test_suspend= [SUSPEND]
2307 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2308 standby suspend) as the system sleep state to briefly
2309 enter during system startup. The system is woken from
2310 this state using a wakeup-capable RTC alarm.
2312 thash_entries= [KNL,NET]
2313 Set number of hash buckets for TCP connection
2315 thermal.act= [HW,ACPI]
2316 -1: disable all active trip points in all thermal zones
2317 <degrees C>: override all lowest active trip points
2319 thermal.crt= [HW,ACPI]
2320 -1: disable all critical trip points in all thermal zones
2321 <degrees C>: override all critical trip points
2323 thermal.nocrt= [HW,ACPI]
2324 Set to disable actions on ACPI thermal zone
2325 critical and hot trip points.
2327 thermal.off= [HW,ACPI]
2328 1: disable ACPI thermal control
2330 thermal.psv= [HW,ACPI]
2331 -1: disable all passive trip points
2332 <degrees C>: override all passive trip points to this
2333 value
2335 thermal.tzp= [HW,ACPI]
2336 Specify global default ACPI thermal zone polling rate
2337 <deci-seconds>: poll all this frequency
2338 0: no polling (default)
2340 tmscsim= [HW,SCSI]
2341 See comment before function dc390_setup() in
2342 drivers/scsi/tmscsim.c.
2344 topology= [S390]
2345 Format: {off | on}
2346 Specify if the kernel should make use of the cpu
2347 topology informations if the hardware supports these.
2348 The scheduler will make use of these informations and
2349 e.g. base its process migration decisions on it.
2350 Default is off.
2352 tp720= [HW,PS2]
2354 trix= [HW,OSS] MediaTrix AudioTrix Pro
2355 Format:
2356 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2358 tsc= Disable clocksource-must-verify flag for TSC.
2359 Format: <string>
2360 [x86] reliable: mark tsc clocksource as reliable, this
2361 disables clocksource verification at runtime.
2362 Used to enable high-resolution timer mode on older
2363 hardware, and in virtualized environment.
2365 turbografx.map[2|3]= [HW,JOY]
2366 TurboGraFX parallel port interface
2367 Format:
2368 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2369 See also Documentation/input/joystick-parport.txt
2371 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2372 See header of drivers/scsi/u14-34f.c.
2374 uart401= [HW,OSS]
2375 Format: <io>,<irq>
2377 uart6850= [HW,OSS]
2378 Format: <io>,<irq>
2380 uhci-hcd.ignore_oc=
2381 [USB] Ignore overcurrent events (default N).
2382 Some badly-designed motherboards generate lots of
2383 bogus events, for ports that aren't wired to
2384 anything. Set this parameter to avoid log spamming.
2385 Note that genuine overcurrent events won't be
2386 reported either.
2388 unknown_nmi_panic
2389 [X86-32,X86-64]
2390 Set unknown_nmi_panic=1 early on boot.
2392 usbcore.autosuspend=
2393 [USB] The autosuspend time delay (in seconds) used
2394 for newly-detected USB devices (default 2). This
2395 is the time required before an idle device will be
2396 autosuspended. Devices for which the delay is set
2397 to a negative value won't be autosuspended at all.
2399 usbcore.usbfs_snoop=
2400 [USB] Set to log all usbfs traffic (default 0 = off).
2402 usbcore.blinkenlights=
2403 [USB] Set to cycle leds on hubs (default 0 = off).
2405 usbcore.old_scheme_first=
2406 [USB] Start with the old device initialization
2407 scheme (default 0 = off).
2409 usbcore.use_both_schemes=
2410 [USB] Try the other device initialization scheme
2411 if the first one fails (default 1 = enabled).
2413 usbcore.initial_descriptor_timeout=
2414 [USB] Specifies timeout for the initial 64-byte
2415 USB_REQ_GET_DESCRIPTOR request in milliseconds
2416 (default 5000 = 5.0 seconds).
2418 usbhid.mousepoll=
2419 [USBHID] The interval which mice are to be polled at.
2421 usb-storage.delay_use=
2422 [UMS] The delay in seconds before a new device is
2423 scanned for Logical Units (default 5).
2425 usb-storage.quirks=
2426 [UMS] A list of quirks entries to supplement or
2427 override the built-in unusual_devs list. List
2428 entries are separated by commas. Each entry has
2429 the form VID:PID:Flags where VID and PID are Vendor
2430 and Product ID values (4-digit hex numbers) and
2431 Flags is a set of characters, each corresponding
2432 to a common usb-storage quirk flag as follows:
2433 a = SANE_SENSE (collect more than 18 bytes
2434 of sense data);
2435 c = FIX_CAPACITY (decrease the reported
2436 device capacity by one sector);
2437 h = CAPACITY_HEURISTICS (decrease the
2438 reported device capacity by one
2439 sector if the number is odd);
2440 i = IGNORE_DEVICE (don't bind to this
2441 device);
2442 l = NOT_LOCKABLE (don't try to lock and
2443 unlock ejectable media);
2444 m = MAX_SECTORS_64 (don't transfer more
2445 than 64 sectors = 32 KB at a time);
2446 o = CAPACITY_OK (accept the capacity
2447 reported by the device);
2448 r = IGNORE_RESIDUE (the device reports
2449 bogus residue values);
2450 s = SINGLE_LUN (the device has only one
2451 Logical Unit);
2452 w = NO_WP_DETECT (don't test whether the
2453 medium is write-protected).
2454 Example: quirks=0419:aaf5:rl,0421:0433:rc
2456 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2457 kernel's map of available physical RAM.
2459 vdso= [X86-32,SH,x86-64]
2460 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2461 vdso=1: enable VDSO (default)
2462 vdso=0: disable VDSO mapping
2464 vdso32= [X86-32,X86-64]
2465 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2466 vdso32=1: enable 32-bit VDSO (default)
2467 vdso32=0: disable 32-bit VDSO mapping
2469 vector= [IA-64,SMP]
2470 vector=percpu: enable percpu vector domain
2472 video= [FB] Frame buffer configuration
2473 See Documentation/fb/modedb.txt.
2475 vga= [BOOT,X86-32] Select a particular video mode
2476 See Documentation/x86/boot.txt and
2477 Documentation/svga.txt.
2478 Use vga=ask for menu.
2479 This is actually a boot loader parameter; the value is
2480 passed to the kernel using a special protocol.
2482 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2483 size of <nn>. This can be used to increase the
2484 minimum size (128MB on x86). It can also be used to
2485 decrease the size and leave more room for directly
2486 mapped kernel RAM.
2488 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2489 Format: <command>
2491 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2492 Format: <command>
2494 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2495 Format: <command>
2497 waveartist= [HW,OSS]
2498 Format: <io>,<irq>,<dma>,<dma2>
2500 wd33c93= [HW,SCSI]
2501 See header of drivers/scsi/wd33c93.c.
2503 wd7000= [HW,SCSI]
2504 See header of drivers/scsi/wd7000.c.
2506 wdt= [WDT] Watchdog
2507 See Documentation/watchdog/wdt.txt.
2509 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2510 xd_geo= See header of drivers/block/xd.c.
2512 xirc2ps_cs= [NET,PCMCIA]
2513 Format:
2514 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2516 norandmaps Don't use address space randomization. Equivalent to
2517 echo 0 > /proc/sys/kernel/randomize_va_space
2519 ______________________________________________________________________
2521 TODO:
2523 Add documentation for ALSA options.
2524 Add more DRM drivers.