| blob | e0f346d201edb70fae654c55f6be842c4465a5ff |
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 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
92 TS Appropriate touchscreen support is enabled.
93 USB USB support is enabled.
94 USBHID USB Human Interface Device support is enabled.
95 V4L Video For Linux support is enabled.
96 VGA The VGA console has been enabled.
97 VT Virtual terminal support is enabled.
98 WDT Watchdog support is enabled.
99 XT IBM PC/XT MFM hard disk support is enabled.
100 X86-32 X86-32, aka i386 architecture is enabled.
101 X86-64 X86-64 architecture is enabled.
102 More X86-64 boot options can be found in
103 Documentation/x86/x86_64/boot-options.txt .
104 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
106 In addition, the following text indicates that the option:
108 BUGS= Relates to possible processor bugs on the said processor.
109 KNL Is a kernel start-up parameter.
110 BOOT Is a boot loader parameter.
112 Parameters denoted with BOOT are actually interpreted by the boot
113 loader, and have no meaning to the kernel directly.
114 Do not modify the syntax of boot loader parameters without extreme
115 need or coordination with <Documentation/x86/i386/boot.txt>.
117 There are also arch-specific kernel-parameters not documented here.
118 See for example <Documentation/x86/x86_64/boot-options.txt>.
120 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
121 a trailing = on the name of any parameter states that that parameter will
122 be entered as an environment variable, whereas its absence indicates that
123 it will appear as a kernel argument readable via /proc/cmdline by programs
124 running once the system is up.
126 The number of kernel parameters is not limited, but the length of the
127 complete command line (parameters including spaces etc.) is limited to
128 a fixed number of characters. This limit depends on the architecture
129 and is between 256 and 4096 characters. It is defined in the file
130 ./include/asm/setup.h as COMMAND_LINE_SIZE.
133 acpi= [HW,ACPI,X86-64,i386]
134 Advanced Configuration and Power Interface
135 Format: { force | off | ht | strict | noirq }
136 force -- enable ACPI if default was off
137 off -- disable ACPI if default was on
138 noirq -- do not use ACPI for IRQ routing
139 ht -- run only enough ACPI to enable Hyper Threading
140 strict -- Be less tolerant of platforms that are not
141 strictly ACPI specification compliant.
143 See also Documentation/power/pm.txt, pci=noacpi
145 acpi_apic_instance= [ACPI, IOAPIC]
146 Format: <int>
147 2: use 2nd APIC table, if available
148 1,0: use 1st APIC table
149 default: 0
151 acpi_sleep= [HW,ACPI] Sleep options
152 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
153 See Documentation/power/video.txt for s3_bios and s3_mode.
154 s3_beep is for debugging; it makes the PC's speaker beep
155 as soon as the kernel's real-mode entry point is called.
156 s4_nohwsig prevents ACPI hardware signature from being
157 used during resume from hibernation.
158 old_ordering causes the ACPI 1.0 ordering of the _PTS
159 control method, wrt putting devices into low power
160 states, to be enforced (the ACPI 2.0 ordering of _PTS is
161 used by default).
163 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
164 Format: { level | edge | high | low }
166 acpi_irq_balance [HW,ACPI]
167 ACPI will balance active IRQs
168 default in APIC mode
170 acpi_irq_nobalance [HW,ACPI]
171 ACPI will not move active IRQs (default)
172 default in PIC mode
174 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
175 use by PCI
176 Format: <irq>,<irq>...
178 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
179 Format: <irq>,<irq>...
181 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
183 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
184 Format: To spoof as Windows 98: ="Microsoft Windows"
186 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
187 acpi_osi="string1" # add string1 -- only one string
188 acpi_osi="!string2" # remove built-in string2
189 acpi_osi= # disable all strings
191 acpi_serialize [HW,ACPI] force serialization of AML methods
193 acpi_skip_timer_override [HW,ACPI]
194 Recognize and ignore IRQ0/pin2 Interrupt Override.
195 For broken nForce2 BIOS resulting in XT-PIC timer.
196 acpi_use_timer_override [HW,ACPI}
197 Use timer override. For some broken Nvidia NF5 boards
198 that require a timer override, but don't have
199 HPET
201 acpi_backlight= [HW,ACPI]
202 acpi_backlight=vendor
203 acpi_backlight=video
204 If set to vendor, prefer vendor specific driver
205 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
206 of the ACPI video.ko driver.
208 acpi_display_output= [HW,ACPI]
209 acpi_display_output=vendor
210 acpi_display_output=video
211 See above.
213 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
214 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
215 Format: <int>
216 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
217 debug output. Bits in debug_layer correspond to a
218 _COMPONENT in an ACPI source file, e.g.,
219 #define _COMPONENT ACPI_PCI_COMPONENT
220 Bits in debug_level correspond to a level in
221 ACPI_DEBUG_PRINT statements, e.g.,
222 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
223 See Documentation/acpi/debug.txt for more information
224 about debug layers and levels.
226 Enable AML "Debug" output, i.e., stores to the Debug
227 object while interpreting AML:
228 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
229 Enable PCI/PCI interrupt routing info messages:
230 acpi.debug_layer=0x400000 acpi.debug_level=0x4
231 Enable all messages related to ACPI hardware:
232 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
234 Some values produce so much output that the system is
235 unusable. The "log_buf_len" parameter may be useful
236 if you need to capture more output.
238 acpi.power_nocheck= [HW,ACPI]
239 Format: 1/0 enable/disable the check of power state.
240 On some bogus BIOS the _PSC object/_STA object of
241 power resource can't return the correct device power
242 state. In such case it is unneccessary to check its
243 power state again in power transition.
244 1 : disable the power state check
246 acpi_pm_good [X86-32,X86-64]
247 Override the pmtimer bug detection: force the kernel
248 to assume that this machine's pmtimer latches its value
249 and always returns good values.
251 agp= [AGP]
252 { off | try_unsupported }
253 off: disable AGP support
254 try_unsupported: try to drive unsupported chipsets
255 (may crash computer or cause data corruption)
257 enable_timer_pin_1 [i386,x86-64]
258 Enable PIN 1 of APIC timer
259 Can be useful to work around chipset bugs
260 (in particular on some ATI chipsets).
261 The kernel tries to set a reasonable default.
263 disable_timer_pin_1 [i386,x86-64]
264 Disable PIN 1 of APIC timer
265 Can be useful to work around chipset bugs.
267 ad1848= [HW,OSS]
268 Format: <io>,<irq>,<dma>,<dma2>,<type>
270 advansys= [HW,SCSI]
271 See header of drivers/scsi/advansys.c.
273 advwdt= [HW,WDT] Advantech WDT
274 Format: <iostart>,<iostop>
276 aedsp16= [HW,OSS] Audio Excel DSP 16
277 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
278 See also header of sound/oss/aedsp16.c.
280 aha152x= [HW,SCSI]
281 See Documentation/scsi/aha152x.txt.
283 aha1542= [HW,SCSI]
284 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
286 aic7xxx= [HW,SCSI]
287 See Documentation/scsi/aic7xxx.txt.
289 aic79xx= [HW,SCSI]
290 See Documentation/scsi/aic79xx.txt.
292 amd_iommu= [HW,X86-84]
293 Pass parameters to the AMD IOMMU driver in the system.
294 Possible values are:
295 isolate - enable device isolation (each device, as far
296 as possible, will get its own protection
297 domain) [default]
298 share - put every device behind one IOMMU into the
299 same protection domain
300 fullflush - enable flushing of IO/TLB entries when
301 they are unmapped. Otherwise they are
302 flushed before they will be reused, which
303 is a lot of faster
305 amd_iommu_size= [HW,X86-64]
306 Define the size of the aperture for the AMD IOMMU
307 driver. Possible values are:
308 '32M', '64M' (default), '128M', '256M', '512M', '1G'
310 amijoy.map= [HW,JOY] Amiga joystick support
311 Map of devices attached to JOY0DAT and JOY1DAT
312 Format: <a>,<b>
313 See also Documentation/kernel/input/joystick.txt
315 analog.map= [HW,JOY] Analog joystick and gamepad support
316 Specifies type or capabilities of an analog joystick
317 connected to one of 16 gameports
318 Format: <type1>,<type2>,..<type16>
320 apc= [HW,SPARC]
321 Power management functions (SPARCstation-4/5 + deriv.)
322 Format: noidle
323 Disable APC CPU standby support. SPARCstation-Fox does
324 not play well with APC CPU idle - disable it if you have
325 APC and your system crashes randomly.
327 apic= [APIC,i386] Advanced Programmable Interrupt Controller
328 Change the output verbosity whilst booting
329 Format: { quiet (default) | verbose | debug }
330 Change the amount of debugging information output
331 when initialising the APIC and IO-APIC components.
333 apm= [APM] Advanced Power Management
334 See header of arch/x86/kernel/apm_32.c.
336 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
337 Format: <io>,<irq>,<nodeID>
339 ataflop= [HW,M68k]
341 atarimouse= [HW,MOUSE] Atari Mouse
343 atascsi= [HW,SCSI] Atari SCSI
345 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
346 EzKey and similar keyboards
348 atkbd.reset= [HW] Reset keyboard during initialization
350 atkbd.set= [HW] Select keyboard code set
351 Format: <int> (2 = AT (default), 3 = PS/2)
353 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
354 keyboards
356 atkbd.softraw= [HW] Choose between synthetic and real raw mode
357 Format: <bool> (0 = real, 1 = synthetic (default))
359 atkbd.softrepeat= [HW]
360 Use software keyboard repeat
362 autotest [IA64]
364 baycom_epp= [HW,AX25]
365 Format: <io>,<mode>
367 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
368 Format: <io>,<mode>
369 See header of drivers/net/hamradio/baycom_par.c.
371 baycom_ser_fdx= [HW,AX25]
372 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
373 Format: <io>,<irq>,<mode>[,<baud>]
374 See header of drivers/net/hamradio/baycom_ser_fdx.c.
376 baycom_ser_hdx= [HW,AX25]
377 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
378 Format: <io>,<irq>,<mode>
379 See header of drivers/net/hamradio/baycom_ser_hdx.c.
381 boot_delay= Milliseconds to delay each printk during boot.
382 Values larger than 10 seconds (10000) are changed to
383 no delay (0).
384 Format: integer
386 bootmem_debug [KNL] Enable bootmem allocator debug messages.
388 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
389 bttv.radio= Most important insmod options are available as
390 kernel args too.
391 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
392 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
394 BusLogic= [HW,SCSI]
395 See drivers/scsi/BusLogic.c, comment before function
396 BusLogic_ParseDriverOptions().
398 c101= [NET] Moxa C101 synchronous serial card
400 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
401 Sometimes CPU hardware bugs make them report the cache
402 size incorrectly. The kernel will attempt work arounds
403 to fix known problems, but for some CPUs it is not
404 possible to determine what the correct size should be.
405 This option provides an override for these situations.
407 security= [SECURITY] Choose a security module to enable at boot.
408 If this boot parameter is not specified, only the first
409 security module asking for security registration will be
410 loaded. An invalid security module name will be treated
411 as if no module has been chosen.
413 capability.disable=
414 [SECURITY] Disable capabilities. This would normally
415 be used only if an alternative security model is to be
416 configured. Potentially dangerous and should only be
417 used if you are entirely sure of the consequences.
419 ccw_timeout_log [S390]
420 See Documentation/s390/CommonIO for details.
422 cgroup_disable= [KNL] Disable a particular controller
423 Format: {name of the controller(s) to disable}
424 {Currently supported controllers - "memory"}
426 checkreqprot [SELINUX] Set initial checkreqprot flag value.
427 Format: { "0" | "1" }
428 See security/selinux/Kconfig help text.
429 0 -- check protection applied by kernel (includes
430 any implied execute protection).
431 1 -- check protection requested by application.
432 Default value is set via a kernel config option.
433 Value can be changed at runtime via
434 /selinux/checkreqprot.
436 cio_ignore= [S390]
437 See Documentation/s390/CommonIO for details.
439 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
440 [Deprecated]
441 Forces specified clocksource (if available) to be used
442 when calculating gettimeofday(). If specified
443 clocksource is not available, it defaults to PIT.
444 Format: { pit | tsc | cyclone | pmtmr }
446 clocksource= [GENERIC_TIME] Override the default clocksource
447 Format: <string>
448 Override the default clocksource and use the clocksource
449 with the name specified.
450 Some clocksource names to choose from, depending on
451 the platform:
452 [all] jiffies (this is the base, fallback clocksource)
453 [ACPI] acpi_pm
454 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
455 pxa_timer,timer3,32k_counter,timer0_1
456 [AVR32] avr32
457 [X86-32] pit,hpet,tsc,vmi-timer;
458 scx200_hrt on Geode; cyclone on IBM x440
459 [MIPS] MIPS
460 [PARISC] cr16
461 [S390] tod
462 [SH] SuperH
463 [SPARC64] tick
464 [X86-64] hpet,tsc
466 clearcpuid=BITNUM [X86]
467 Disable CPUID feature X for the kernel. See
468 include/asm-x86/cpufeature.h for the valid bit numbers.
469 Note the Linux specific bits are not necessarily
470 stable over kernel options, but the vendor specific
471 ones should be.
472 Also note that user programs calling CPUID directly
473 or using the feature without checking anything
474 will still see it. This just prevents it from
475 being used by the kernel or shown in /proc/cpuinfo.
476 Also note the kernel might malfunction if you disable
477 some critical bits.
479 code_bytes [IA32/X86_64] How many bytes of object code to print
480 in an oops report.
481 Range: 0 - 8192
482 Default: 64
484 hpet= [X86-32,HPET] option to control HPET usage
485 Format: { enable (default) | disable | force }
486 disable: disable HPET and use PIT instead
487 force: allow force enabled of undocumented chips (ICH4,
488 VIA, nVidia)
490 com20020= [HW,NET] ARCnet - COM20020 chipset
491 Format:
492 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
494 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
495 Format: <io>[,<irq>]
497 com90xx= [HW,NET]
498 ARCnet - COM90xx chipset (memory-mapped buffers)
499 Format: <io>[,<irq>[,<memstart>]]
501 condev= [HW,S390] console device
502 conmode=
504 console= [KNL] Output console device and options.
506 tty<n> Use the virtual console device <n>.
508 ttyS<n>[,options]
509 ttyUSB0[,options]
510 Use the specified serial port. The options are of
511 the form "bbbbpnf", where "bbbb" is the baud rate,
512 "p" is parity ("n", "o", or "e"), "n" is number of
513 bits, and "f" is flow control ("r" for RTS or
514 omit it). Default is "9600n8".
516 See Documentation/serial-console.txt for more
517 information. See
518 Documentation/networking/netconsole.txt for an
519 alternative.
521 uart[8250],io,<addr>[,options]
522 uart[8250],mmio,<addr>[,options]
523 Start an early, polled-mode console on the 8250/16550
524 UART at the specified I/O port or MMIO address,
525 switching to the matching ttyS device later. The
526 options are the same as for ttyS, above.
528 If the device connected to the port is not a TTY but a braille
529 device, prepend "brl," before the device type, for instance
530 console=brl,ttyS0
531 For now, only VisioBraille is supported.
533 earlycon= [KNL] Output early console device and options.
534 uart[8250],io,<addr>[,options]
535 uart[8250],mmio,<addr>[,options]
536 Start an early, polled-mode console on the 8250/16550
537 UART at the specified I/O port or MMIO address.
538 The options are the same as for ttyS, above.
540 no_console_suspend
541 [HW] Never suspend the console
542 Disable suspending of consoles during suspend and
543 hibernate operations. Once disabled, debugging
544 messages can reach various consoles while the rest
545 of the system is being put to sleep (ie, while
546 debugging driver suspend/resume hooks). This may
547 not work reliably with all consoles, but is known
548 to work with serial and VGA consoles.
550 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
551 Format:
552 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
554 crashkernel=nn[KMG]@ss[KMG]
555 [KNL] Reserve a chunk of physical memory to
556 hold a kernel to switch to with kexec on panic.
558 crashkernel=range1:size1[,range2:size2,...][@offset]
559 [KNL] Same as above, but depends on the memory
560 in the running system. The syntax of range is
561 start-[end] where start and end are both
562 a memory unit (amount[KMG]). See also
563 Documentation/kdump/kdump.txt for a example.
565 cs4232= [HW,OSS]
566 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 debug [KNL] Enable kernel debugging (events log level).
584 debug_locks_verbose=
585 [KNL] verbose self-tests
586 Format=<0|1>
587 Print debugging info while doing the locking API
588 self-tests.
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
593 debug_objects [KNL] Enable object debugging
595 debugpat [X86] Enable PAT debugging
597 decnet.addr= [HW,NET]
598 Format: <area>[,<node>]
599 See also Documentation/networking/decnet.txt.
601 vt.default_blu= [VT]
602 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
603 Change the default blue palette of the console.
604 This is a 16-member array composed of values
605 ranging from 0-255.
607 vt.default_grn= [VT]
608 Format: <green0>,<green1>,<green2>,...,<green15>
609 Change the default green palette of the console.
610 This is a 16-member array composed of values
611 ranging from 0-255.
613 vt.default_red= [VT]
614 Format: <red0>,<red1>,<red2>,...,<red15>
615 Change the default red palette of the console.
616 This is a 16-member array composed of values
617 ranging from 0-255.
619 vt.default_utf8=
620 [VT]
621 Format=<0|1>
622 Set system-wide default UTF-8 mode for all tty's.
623 Default is 1, i.e. UTF-8 mode is enabled for all
624 newly opened terminals.
626 dhash_entries= [KNL]
627 Set number of hash buckets for dentry cache.
629 digi= [HW,SERIAL]
630 IO parameters + enable/disable command.
632 digiepca= [HW,SERIAL]
633 See drivers/char/README.epca and
634 Documentation/serial/digiepca.txt.
636 disable_mtrr_cleanup [X86]
637 enable_mtrr_cleanup [X86]
638 The kernel tries to adjust MTRR layout from continuous
639 to discrete, to make X server driver able to add WB
640 entry later. This parameter enables/disables that.
642 mtrr_chunk_size=nn[KMG] [X86]
643 used for mtrr cleanup. It is largest continous chunk
644 that could hold holes aka. UC entries.
646 mtrr_gran_size=nn[KMG] [X86]
647 Used for mtrr cleanup. It is granularity of mtrr block.
648 Default is 1.
649 Large value could prevent small alignment from
650 using up MTRRs.
652 mtrr_spare_reg_nr=n [X86]
653 Format: <integer>
654 Range: 0,7 : spare reg number
655 Default : 1
656 Used for mtrr cleanup. It is spare mtrr entries number.
657 Set to 2 or more if your graphical card needs more.
659 disable_mtrr_trim [X86, Intel and AMD only]
660 By default the kernel will trim any uncacheable
661 memory out of your available memory pool based on
662 MTRR settings. This parameter disables that behavior,
663 possibly causing your machine to run very slowly.
665 dmasound= [HW,OSS] Sound subsystem buffers
667 dscc4.setup= [NET]
669 dtc3181e= [HW,SCSI]
671 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
672 earlyprintk=vga
673 earlyprintk=serial[,ttySn[,baudrate]]
674 earlyprintk=dbgp
676 Append ",keep" to not disable it when the real console
677 takes over.
679 Only vga or serial or usb debug port at a time.
681 Currently only ttyS0 and ttyS1 are supported.
683 Interaction with the standard serial driver is not
684 very good.
686 The VGA output is eventually overwritten by the real
687 console.
689 eata= [HW,SCSI]
691 edd= [EDD]
692 Format: {"off" | "on" | "skip[mbr]"}
694 eisa_irq_edge= [PARISC,HW]
695 See header of drivers/parisc/eisa.c.
697 elanfreq= [X86-32]
698 See comment before function elanfreq_setup() in
699 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
701 elevator= [IOSCHED]
702 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
703 See Documentation/block/as-iosched.txt and
704 Documentation/block/deadline-iosched.txt for details.
706 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
707 Specifies physical address of start of kernel core
708 image elf header. Generally kexec loader will
709 pass this option to capture kernel.
710 See Documentation/kdump/kdump.txt for details.
712 enforcing [SELINUX] Set initial enforcing status.
713 Format: {"0" | "1"}
714 See security/selinux/Kconfig help text.
715 0 -- permissive (log only, no denials).
716 1 -- enforcing (deny and log).
717 Default value is 0.
718 Value can be changed at runtime via /selinux/enforce.
720 es1371= [HW,OSS]
721 Format: <spdif>,[<nomix>,[<amplifier>]]
722 See also header of sound/oss/es1371.c.
724 ether= [HW,NET] Ethernet cards parameters
725 This option is obsoleted by the "netdev=" option, which
726 has equivalent usage. See its documentation for details.
728 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
729 Format: <io>[,<irq>]
731 failslab=
732 fail_page_alloc=
733 fail_make_request=[KNL]
734 General fault injection mechanism.
735 Format: <interval>,<probability>,<space>,<times>
736 See also /Documentation/fault-injection/.
738 fd_mcs= [HW,SCSI]
739 See header of drivers/scsi/fd_mcs.c.
741 fdomain= [HW,SCSI]
742 See header of drivers/scsi/fdomain.c.
744 floppy= [HW]
745 See Documentation/blockdev/floppy.txt.
747 force_pal_cache_flush
748 [IA-64] Avoid check_sal_cache_flush which may hang on
749 buggy SAL_CACHE_FLUSH implementations. Using this
750 parameter will force ia64_sal_cache_flush to call
751 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
753 gamecon.map[2|3]=
754 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
755 support via parallel port (up to 5 devices per port)
756 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
757 See also Documentation/input/joystick-parport.txt
759 gamma= [HW,DRM]
761 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
762 Format: off | on
763 default: on
765 gdth= [HW,SCSI]
766 See header of drivers/scsi/gdth.c.
768 gpt [EFI] Forces disk with valid GPT signature but
769 invalid Protective MBR to be treated as GPT.
771 gvp11= [HW,SCSI]
773 hashdist= [KNL,NUMA] Large hashes allocated during boot
774 are distributed across NUMA nodes. Defaults on
775 for IA-64, off otherwise.
776 Format: 0 | 1 (for off | on)
778 hcl= [IA-64] SGI's Hardware Graph compatibility layer
780 hd= [EIDE] (E)IDE hard drive subsystem geometry
781 Format: <cyl>,<head>,<sect>
783 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
784 size of <nn>. This works even on boxes that have no
785 highmem otherwise. This also works to reduce highmem
786 size on bigger boxes.
788 highres= [KNL] Enable/disable high resolution timer mode.
789 Valid parameters: "on", "off"
790 Default: "on"
792 hisax= [HW,ISDN]
793 See Documentation/isdn/README.HiSax.
795 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
796 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
797 On x86-64 and powerpc, this option can be specified
798 multiple times interleaved with hugepages= to reserve
799 huge pages of different sizes. Valid pages sizes on
800 x86-64 are 2M (when the CPU supports "pse") and 1G
801 (when the CPU supports the "pdpe1gb" cpuinfo flag)
802 Note that 1GB pages can only be allocated at boot time
803 using hugepages= and not freed afterwards.
804 default_hugepagesz=
805 [same as hugepagesz=] The size of the default
806 HugeTLB page size. This is the size represented by
807 the legacy /proc/ hugepages APIs, used for SHM, and
808 default size when mounting hugetlbfs filesystems.
809 Defaults to the default architecture's huge page size
810 if not specified.
812 hlt [BUGS=ARM,SH]
814 i8042.debug [HW] Toggle i8042 debug mode
815 i8042.direct [HW] Put keyboard port into non-translated mode
816 i8042.dumbkbd [HW] Pretend that controller can only read data from
817 keyboard and cannot control its state
818 (Don't attempt to blink the leds)
819 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
820 i8042.nokbd [HW] Don't check/create keyboard port
821 i8042.noloop [HW] Disable the AUX Loopback command while probing
822 for the AUX port
823 i8042.nomux [HW] Don't check presence of an active multiplexing
824 controller
825 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
826 controllers
827 i8042.panicblink=
828 [HW] Frequency with which keyboard LEDs should blink
829 when kernel panics (default is 0.5 sec)
830 i8042.reset [HW] Reset the controller during init and cleanup
831 i8042.unlock [HW] Unlock (ignore) the keylock
833 i810= [HW,DRM]
835 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
836 indicates that the driver is running on unsupported
837 hardware.
838 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
839 does not match list of supported models.
840 i8k.power_status
841 [HW] Report power status in /proc/i8k
842 (disabled by default)
843 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
844 capability is set.
846 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
847 See Documentation/mca.txt.
849 icn= [HW,ISDN]
850 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
852 ide= [HW] (E)IDE subsystem
853 Format: ide=nodma or ide=doubler
854 See Documentation/ide/ide.txt.
856 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
857 See Documentation/ide/ide.txt.
859 idle= [X86]
860 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
861 Poll forces a polling idle loop that can slightly improves the performance
862 of waking up a idle CPU, but will use a lot of power and make the system
863 run hot. Not recommended.
864 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
865 to not use it because it doesn't save as much power as a normal idle
866 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
867 as idle=poll.
868 idle=halt. Halt is forced to be used for CPU idle.
869 In such case C2/C3 won't be used again.
870 idle=nomwait. Disable mwait for CPU C-states
872 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
873 Claim all unknown PCI IDE storage controllers.
875 ignore_loglevel [KNL]
876 Ignore loglevel setting - this will print /all/
877 kernel messages to the console. Useful for debugging.
879 ihash_entries= [KNL]
880 Set number of hash buckets for inode cache.
882 in2000= [HW,SCSI]
883 See header of drivers/scsi/in2000.c.
885 init= [KNL]
886 Format: <full_path>
887 Run specified binary instead of /sbin/init as init
888 process.
890 initcall_debug [KNL] Trace initcalls as they are executed. Useful
891 for working out where the kernel is dying during
892 startup.
894 initrd= [BOOT] Specify the location of the initial ramdisk
896 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
897 Format: <irq>
899 inttest= [IA64]
901 iommu= [x86]
902 off
903 force
904 noforce
905 biomerge
906 panic
907 nopanic
908 merge
909 nomerge
910 forcesac
911 soft
914 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
915 off
916 Disable intel iommu driver.
917 igfx_off [Default Off]
918 By default, gfx is mapped as normal device. If a gfx
919 device has a dedicated DMAR unit, the DMAR unit is
920 bypassed by not enabling DMAR with this option. In
921 this case, gfx device will use physical address for
922 DMA.
923 forcedac [x86_64]
924 With this option iommu will not optimize to look
925 for io virtual address below 32 bit forcing dual
926 address cycle on pci bus for cards supporting greater
927 than 32 bit addressing. The default is to look
928 for translation below 32 bit and if not available
929 then look in the higher range.
930 strict [Default Off]
931 With this option on every unmap_single operation will
932 result in a hardware IOTLB flush operation as opposed
933 to batching them for performance.
935 io_delay= [X86-32,X86-64] I/O delay method
936 0x80
937 Standard port 0x80 based delay
938 0xed
939 Alternate port 0xed based delay (needed on some systems)
940 udelay
941 Simple two microseconds delay
942 none
943 No delay
945 io7= [HW] IO7 for Marvel based alpha systems
946 See comment before marvel_specify_io7 in
947 arch/alpha/kernel/core_marvel.c.
949 ip= [IP_PNP]
950 See Documentation/filesystems/nfsroot.txt.
952 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
953 See comment before ip2_setup() in
954 drivers/char/ip2/ip2base.c.
956 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
957 See header of drivers/scsi/ips.c.
959 ports= [IP_VS_FTP] IPVS ftp helper module
960 Default is 21.
961 Up to 8 (IP_VS_APP_MAX_PORTS) ports
962 may be specified.
963 Format: <port>,<port>....
965 irqfixup [HW]
966 When an interrupt is not handled search all handlers
967 for it. Intended to get systems with badly broken
968 firmware running.
970 irqpoll [HW]
971 When an interrupt is not handled search all handlers
972 for it. Also check all handlers each timer
973 interrupt. Intended to get systems with badly broken
974 firmware running.
976 isapnp= [ISAPNP]
977 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
979 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
980 Format:
981 <cpu number>,...,<cpu number>
982 or
983 <cpu number>-<cpu number>
984 (must be a positive range in ascending order)
985 or a mixture
986 <cpu number>,...,<cpu number>-<cpu number>
988 This option can be used to specify one or more CPUs
989 to isolate from the general SMP balancing and scheduling
990 algorithms. You can move a process onto or off an
991 "isolated" CPU via the CPU affinity syscalls or cpuset.
992 <cpu number> begins at 0 and the maximum value is
993 "number of CPUs in system - 1".
995 This option is the preferred way to isolate CPUs. The
996 alternative -- manually setting the CPU mask of all
997 tasks in the system -- can cause problems and
998 suboptimal load balancer performance.
1000 iucv= [HW,NET]
1002 js= [HW,JOY] Analog joystick
1003 See Documentation/input/joystick.txt.
1005 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1006 specifies the amount of memory usable by the kernel
1007 for non-movable allocations. The requested amount is
1008 spread evenly throughout all nodes in the system. The
1009 remaining memory in each node is used for Movable
1010 pages. In the event, a node is too small to have both
1011 kernelcore and Movable pages, kernelcore pages will
1012 take priority and other nodes will have a larger number
1013 of kernelcore pages. The Movable zone is used for the
1014 allocation of pages that may be reclaimed or moved
1015 by the page migration subsystem. This means that
1016 HugeTLB pages may not be allocated from this zone.
1017 Note that allocations like PTEs-from-HighMem still
1018 use the HighMem zone if it exists, and the Normal
1019 zone if it does not.
1021 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1022 is similar to kernelcore except it specifies the
1023 amount of memory used for migratable allocations.
1024 If both kernelcore and movablecore is specified,
1025 then kernelcore will be at *least* the specified
1026 value but may be more. If movablecore on its own
1027 is specified, the administrator must be careful
1028 that the amount of memory usable for all allocations
1029 is not too small.
1031 keepinitrd [HW,ARM]
1033 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1034 in oops dumps.
1036 kgdboc= [HW] kgdb over consoles.
1037 Requires a tty driver that supports console polling.
1038 (only serial suported for now)
1039 Format: <serial_device>[,baud]
1041 kmac= [MIPS] korina ethernet MAC address.
1042 Configure the RouterBoard 532 series on-chip
1043 Ethernet adapter MAC address.
1045 l2cr= [PPC]
1047 l3cr= [PPC]
1049 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1050 disabled it.
1052 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1053 C2 power state.
1055 libata.dma= [LIBATA] DMA control
1056 libata.dma=0 Disable all PATA and SATA DMA
1057 libata.dma=1 PATA and SATA Disk DMA only
1058 libata.dma=2 ATAPI (CDROM) DMA only
1059 libata.dma=4 Compact Flash DMA only
1060 Combinations also work, so libata.dma=3 enables DMA
1061 for disks and CDROMs, but not CFs.
1063 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1064 when set.
1065 Format: <int>
1067 libata.force= [LIBATA] Force configurations. The format is comma
1068 separated list of "[ID:]VAL" where ID is
1069 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1070 matching port, link or device. Basically, it matches
1071 the ATA ID string printed on console by libata. If
1072 the whole ID part is omitted, the last PORT and DEVICE
1073 values are used. If ID hasn't been specified yet, the
1074 configuration applies to all ports, links and devices.
1076 If only DEVICE is omitted, the parameter applies to
1077 the port and all links and devices behind it. DEVICE
1078 number of 0 either selects the first device or the
1079 first fan-out link behind PMP device. It does not
1080 select the host link. DEVICE number of 15 selects the
1081 host link and device attached to it.
1083 The VAL specifies the configuration to force. As long
1084 as there's no ambiguity shortcut notation is allowed.
1085 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1086 The following configurations can be forced.
1088 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1089 Any ID with matching PORT is used.
1091 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1093 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1094 udma[/][16,25,33,44,66,100,133] notation is also
1095 allowed.
1097 * [no]ncq: Turn on or off NCQ.
1099 * nohrst, nosrst, norst: suppress hard, soft
1100 and both resets.
1102 If there are multiple matching configurations changing
1103 the same attribute, the last one is used.
1105 load_ramdisk= [RAM] List of ramdisks to load from floppy
1106 See Documentation/blockdev/ramdisk.txt.
1108 lockd.nlm_grace_period=P [NFS] Assign grace period.
1109 Format: <integer>
1111 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1112 Format: <integer>
1114 lockd.nlm_timeout=T [NFS] Assign timeout value.
1115 Format: <integer>
1117 lockd.nlm_udpport=M [NFS] Assign UDP port.
1118 Format: <integer>
1120 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1121 Format: <irq>
1123 loglevel= All Kernel Messages with a loglevel smaller than the
1124 console loglevel will be printed to the console. It can
1125 also be changed with klogd or other programs. The
1126 loglevels are defined as follows:
1128 0 (KERN_EMERG) system is unusable
1129 1 (KERN_ALERT) action must be taken immediately
1130 2 (KERN_CRIT) critical conditions
1131 3 (KERN_ERR) error conditions
1132 4 (KERN_WARNING) warning conditions
1133 5 (KERN_NOTICE) normal but significant condition
1134 6 (KERN_INFO) informational
1135 7 (KERN_DEBUG) debug-level messages
1137 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1138 Format: { n | nk | nM }
1139 n must be a power of two. The default size
1140 is set in the kernel config file.
1142 logo.nologo [FB] Disables display of the built-in Linux logo.
1143 This may be used to provide more screen space for
1144 kernel log messages and is useful when debugging
1145 kernel boot problems.
1147 lp=0 [LP] Specify parallel ports to use, e.g,
1148 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1149 lp=reset first parallel port). 'lp=0' disables the
1150 lp=auto printer driver. 'lp=reset' (which can be
1151 specified in addition to the ports) causes
1152 attached printers to be reset. Using
1153 lp=port1,port2,... specifies the parallel ports
1154 to associate lp devices with, starting with
1155 lp0. A port specification may be 'none' to skip
1156 that lp device, or a parport name such as
1157 'parport0'. Specifying 'lp=auto' instead of a
1158 port specification list means that device IDs
1159 from each port should be examined, to see if
1160 an IEEE 1284-compliant printer is attached; if
1161 so, the driver will manage that printer.
1162 See also header of drivers/char/lp.c.
1164 lpj=n [KNL]
1165 Sets loops_per_jiffy to given constant, thus avoiding
1166 time-consuming boot-time autodetection (up to 250 ms per
1167 CPU). 0 enables autodetection (default). To determine
1168 the correct value for your kernel, boot with normal
1169 autodetection and see what value is printed. Note that
1170 on SMP systems the preset will be applied to all CPUs,
1171 which is likely to cause problems if your CPUs need
1172 significantly divergent settings. An incorrect value
1173 will cause delays in the kernel to be wrong, leading to
1174 unpredictable I/O errors and other breakage. Although
1175 unlikely, in the extreme case this might damage your
1176 hardware.
1178 ltpc= [NET]
1179 Format: <io>,<irq>,<dma>
1181 mac5380= [HW,SCSI] Format:
1182 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1184 machvec= [IA64] Force the use of a particular machine-vector
1185 (machvec) in a generic kernel.
1186 Example: machvec=hpzx1_swiotlb
1188 max_loop= [LOOP] Maximum number of loopback devices that can
1189 be mounted
1190 Format: <1-256>
1192 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1193 should make use of. maxcpus=n : n >= 0 limits the
1194 kernel to using 'n' processors. n=0 is a special case,
1195 it is equivalent to "nosmp", which also disables
1196 the IO APIC.
1198 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1199 or equal to this physical address is ignored.
1201 max_luns= [SCSI] Maximum number of LUNs to probe.
1202 Should be between 1 and 2^32-1.
1204 max_report_luns=
1205 [SCSI] Maximum number of LUNs received.
1206 Should be between 1 and 16384.
1208 mcatest= [IA-64]
1210 mce [X86-32] Machine Check Exception
1212 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1214 md= [HW] RAID subsystems devices and level
1215 See Documentation/md.txt.
1217 mdacon= [MDA]
1218 Format: <first>,<last>
1219 Specifies range of consoles to be captured by the MDA.
1221 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1222 Amount of memory to be used when the kernel is not able
1223 to see the whole system memory or for test.
1224 [X86-32] Use together with memmap= to avoid physical
1225 address space collisions. Without memmap= PCI devices
1226 could be placed at addresses belonging to unused RAM.
1228 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1229 memory.
1231 memchunk=nn[KMG]
1232 [KNL,SH] Allow user to override the default size for
1233 per-device physically contiguous DMA buffers.
1235 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1236 E820 memory map, as specified by the user.
1237 Such memmap=exactmap lines can be constructed based on
1238 BIOS output or other requirements. See the memmap=nn@ss
1239 option description.
1241 memmap=nn[KMG]@ss[KMG]
1242 [KNL] Force usage of a specific region of memory
1243 Region of memory to be used, from ss to ss+nn.
1245 memmap=nn[KMG]#ss[KMG]
1246 [KNL,ACPI] Mark specific memory as ACPI data.
1247 Region of memory to be used, from ss to ss+nn.
1249 memmap=nn[KMG]$ss[KMG]
1250 [KNL,ACPI] Mark specific memory as reserved.
1251 Region of memory to be used, from ss to ss+nn.
1252 Example: Exclude memory from 0x18690000-0x1869ffff
1253 memmap=64K$0x18690000
1254 or
1255 memmap=0x10000$0x18690000
1257 memory_corruption_check=0/1 [X86]
1258 Some BIOSes seem to corrupt the first 64k of
1259 memory when doing things like suspend/resume.
1260 Setting this option will scan the memory
1261 looking for corruption. Enabling this will
1262 both detect corruption and prevent the kernel
1263 from using the memory being corrupted.
1264 However, its intended as a diagnostic tool; if
1265 repeatable BIOS-originated corruption always
1266 affects the same memory, you can use memmap=
1267 to prevent the kernel from using that memory.
1269 memory_corruption_check_size=size [X86]
1270 By default it checks for corruption in the low
1271 64k, making this memory unavailable for normal
1272 use. Use this parameter to scan for
1273 corruption in more or less memory.
1275 memory_corruption_check_period=seconds [X86]
1276 By default it checks for corruption every 60
1277 seconds. Use this parameter to check at some
1278 other rate. 0 disables periodic checking.
1280 memtest= [KNL,X86] Enable memtest
1281 Format: <integer>
1282 range: 0,4 : pattern number
1283 default : 0 <disable>
1285 meye.*= [HW] Set MotionEye Camera parameters
1286 See Documentation/video4linux/meye.txt.
1288 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1289 Multi-Function General Purpose Timers on AMD Geode
1290 platforms.
1292 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1293 the BIOS has incorrectly applied a workaround. TinyBIOS
1294 version 0.98 is known to be affected, 0.99 fixes the
1295 problem by letting the user disable the workaround.
1297 mga= [HW,DRM]
1299 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1300 physical address is ignored.
1302 mminit_loglevel=
1303 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1304 parameter allows control of the logging verbosity for
1305 the additional memory initialisation checks. A value
1306 of 0 disables mminit logging and a level of 4 will
1307 log everything. Information is printed at KERN_DEBUG
1308 so loglevel=8 may also need to be specified.
1310 mousedev.tap_time=
1311 [MOUSE] Maximum time between finger touching and
1312 leaving touchpad surface for touch to be considered
1313 a tap and be reported as a left button click (for
1314 touchpads working in absolute mode only).
1315 Format: <msecs>
1316 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1317 reporting absolute coordinates, such as tablets
1318 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1319 reporting absolute coordinates, such as tablets
1321 mpu401= [HW,OSS]
1322 Format: <io>,<irq>
1324 MTD_Partition= [MTD]
1325 Format: <name>,<region-number>,<size>,<offset>
1327 MTD_Region= [MTD] Format:
1328 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1330 mtdparts= [MTD]
1331 See drivers/mtd/cmdlinepart.c.
1333 mtdset= [ARM]
1334 ARM/S3C2412 JIVE boot control
1336 See arch/arm/mach-s3c2412/mach-jive.c
1338 mtouchusb.raw_coordinates=
1339 [HW] Make the MicroTouch USB driver use raw coordinates
1340 ('y', default) or cooked coordinates ('n')
1342 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1344 NCR_D700= [HW,SCSI]
1345 See header of drivers/scsi/NCR_D700.c.
1347 ncr5380= [HW,SCSI]
1349 ncr53c400= [HW,SCSI]
1351 ncr53c400a= [HW,SCSI]
1353 ncr53c406a= [HW,SCSI]
1355 ncr53c8xx= [HW,SCSI]
1357 netdev= [NET] Network devices parameters
1358 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1359 Note that mem_start is often overloaded to mean
1360 something different and driver-specific.
1361 This usage is only documented in each driver source
1362 file if at all.
1364 nf_conntrack.acct=
1365 [NETFILTER] Enable connection tracking flow accounting
1366 0 to disable accounting
1367 1 to enable accounting
1368 Default value depends on CONFIG_NF_CT_ACCT that is
1369 going to be removed in 2.6.29.
1371 nfsaddrs= [NFS]
1372 See Documentation/filesystems/nfsroot.txt.
1374 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1375 See Documentation/filesystems/nfsroot.txt.
1377 nfs.callback_tcpport=
1378 [NFS] set the TCP port on which the NFSv4 callback
1379 channel should listen.
1381 nfs.idmap_cache_timeout=
1382 [NFS] set the maximum lifetime for idmapper cache
1383 entries.
1385 nfs.enable_ino64=
1386 [NFS] enable 64-bit inode numbers.
1387 If zero, the NFS client will fake up a 32-bit inode
1388 number for the readdir() and stat() syscalls instead
1389 of returning the full 64-bit number.
1390 The default is to return 64-bit inode numbers.
1392 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1393 when a NMI is triggered.
1394 Format: [state][,regs][,debounce][,die]
1396 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1398 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1399 emulation library even if a 387 maths coprocessor
1400 is present.
1402 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1403 caches in the slab allocator. Saves per-node memory,
1404 but will impact performance.
1406 noalign [KNL,ARM]
1408 noapic [SMP,APIC] Tells the kernel to not make use of any
1409 IOAPICs that may be present in the system.
1411 nobats [PPC] Do not use BATs for mapping kernel lowmem
1412 on "Classic" PPC cores.
1414 nocache [ARM]
1416 nodelayacct [KNL] Disable per-task delay accounting
1418 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1420 nodsp [SH] Disable hardware DSP at boot time.
1422 noefi [X86-32,X86-64] Disable EFI runtime services support.
1424 noexec [IA-64]
1426 noexec [X86-32,X86-64]
1427 On X86-32 available only on PAE configured kernels.
1428 noexec=on: enable non-executable mappings (default)
1429 noexec=off: disable non-executable mappings
1431 noexec32 [X86-64]
1432 This affects only 32-bit executables.
1433 noexec32=on: enable non-executable mappings (default)
1434 read doesn't imply executable mappings
1435 noexec32=off: disable non-executable mappings
1436 read implies executable mappings
1438 nofpu [SH] Disable hardware FPU at boot time.
1440 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1441 register save and restore. The kernel will only save
1442 legacy floating-point registers on task switch.
1444 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1446 nohlt [BUGS=ARM,SH]
1448 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1449 instruction doesn't work correctly and not to
1450 use it.
1452 nohalt [IA-64] Tells the kernel not to use the power saving
1453 function PAL_HALT_LIGHT when idle. This increases
1454 power-consumption. On the positive side, it reduces
1455 interrupt wake-up latency, which may improve performance
1456 in certain environments such as networked servers or
1457 real-time systems.
1459 nohz= [KNL] Boottime enable/disable dynamic ticks
1460 Valid arguments: on, off
1461 Default: on
1463 noirqdebug [X86-32] Disables the code which attempts to detect and
1464 disable unhandled interrupt sources.
1466 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1467 broken timer IRQ sources.
1469 noisapnp [ISAPNP] Disables ISA PnP code.
1471 noinitrd [RAM] Tells the kernel not to load any configured
1472 initial RAM disk.
1474 nointroute [IA-64]
1476 nojitter [IA64] Disables jitter checking for ITC timers.
1478 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1480 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1482 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1484 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1485 default x2apic cluster mode on platforms
1486 supporting x2apic.
1488 noltlbs [PPC] Do not use large page/tlb entries for kernel
1489 lowmem mapping on PPC40x.
1491 nomca [IA-64] Disable machine check abort handling
1493 nomce [X86-32] Machine Check Exception
1495 nomfgpt [X86-32] Disable Multi-Function General Purpose
1496 Timer usage (for AMD Geode machines).
1498 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1500 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1501 with UP alternatives
1503 noresidual [PPC] Don't use residual data on PReP machines.
1505 noresume [SWSUSP] Disables resume and restores original swap
1506 space.
1508 no-scroll [VGA] Disables scrollback.
1509 This is required for the Braillex ib80-piezo Braille
1510 reader made by F.H. Papenmeier (Germany).
1512 nosbagart [IA-64]
1514 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1516 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1517 and disable the IO APIC. legacy for "maxcpus=0".
1519 nosoftlockup [KNL] Disable the soft-lockup detector.
1521 nosync [HW,M68K] Disables sync negotiation for all devices.
1523 notsc [BUGS=X86-32] Disable Time Stamp Counter
1525 nousb [USB] Disable the USB subsystem
1527 nowb [ARM]
1529 nptcg= [IA64] Override max number of concurrent global TLB
1530 purges which is reported from either PAL_VM_SUMMARY or
1531 SAL PALO.
1533 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1534 one of ['zone', 'node', 'default'] can be specified
1535 This can be set from sysctl after boot.
1536 See Documentation/sysctl/vm.txt for details.
1538 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1540 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1541 Rather than timing out after 20 ms if an EC
1542 command is not properly ACKed, override the length
1543 of the timeout. We have interrupts disabled while
1544 waiting for the ACK, so if this is set too high
1545 interrupts *may* be lost!
1547 opl3= [HW,OSS]
1548 Format: <io>
1550 oprofile.timer= [HW]
1551 Use timer interrupt instead of performance counters
1553 osst= [HW,SCSI] SCSI Tape Driver
1554 Format: <buffer_size>,<write_threshold>
1555 See also Documentation/scsi/st.txt.
1557 panic= [KNL] Kernel behaviour on panic
1558 Format: <timeout>
1560 parkbd.port= [HW] Parallel port number the keyboard adapter is
1561 connected to, default is 0.
1562 Format: <parport#>
1563 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1564 0 for XT, 1 for AT (default is AT).
1565 Format: <mode>
1567 parport= [HW,PPT] Specify parallel ports. 0 disables.
1568 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1569 Use 'auto' to force the driver to use any
1570 IRQ/DMA settings detected (the default is to
1571 ignore detected IRQ/DMA settings because of
1572 possible conflicts). You can specify the base
1573 address, IRQ, and DMA settings; IRQ and DMA
1574 should be numbers, or 'auto' (for using detected
1575 settings on that particular port), or 'nofifo'
1576 (to avoid using a FIFO even if it is detected).
1577 Parallel ports are assigned in the order they
1578 are specified on the command line, starting
1579 with parport0.
1581 parport_init_mode= [HW,PPT]
1582 Configure VIA parallel port to operate in
1583 a specific mode. This is necessary on Pegasos
1584 computer where firmware has no options for setting
1585 up parallel port mode and sets it to spp.
1586 Currently this function knows 686a and 8231 chips.
1587 Format: [spp|ps2|epp|ecp|ecpepp]
1589 pas2= [HW,OSS] Format:
1590 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1592 pas16= [HW,SCSI]
1593 See header of drivers/scsi/pas16.c.
1595 pause_on_oops=
1596 Halt all CPUs after the first oops has been printed for
1597 the specified number of seconds. This is to be used if
1598 your oopses keep scrolling off the screen.
1600 pcbit= [HW,ISDN]
1602 pcd. [PARIDE]
1603 See header of drivers/block/paride/pcd.c.
1604 See also Documentation/blockdev/paride.txt.
1606 pci=option[,option...] [PCI] various PCI subsystem options:
1607 off [X86] don't probe for the PCI bus
1608 bios [X86-32] force use of PCI BIOS, don't access
1609 the hardware directly. Use this if your machine
1610 has a non-standard PCI host bridge.
1611 nobios [X86-32] disallow use of PCI BIOS, only direct
1612 hardware access methods are allowed. Use this
1613 if you experience crashes upon bootup and you
1614 suspect they are caused by the BIOS.
1615 conf1 [X86] Force use of PCI Configuration
1616 Mechanism 1.
1617 conf2 [X86] Force use of PCI Configuration
1618 Mechanism 2.
1619 noaer [PCIE] If the PCIEAER kernel config parameter is
1620 enabled, this kernel boot option can be used to
1621 disable the use of PCIE advanced error reporting.
1622 nodomains [PCI] Disable support for multiple PCI
1623 root domains (aka PCI segments, in ACPI-speak).
1624 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1625 Configuration
1626 nomsi [MSI] If the PCI_MSI kernel config parameter is
1627 enabled, this kernel boot option can be used to
1628 disable the use of MSI interrupts system-wide.
1629 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1630 routing table. These calls are known to be buggy
1631 on several machines and they hang the machine
1632 when used, but on other computers it's the only
1633 way to get the interrupt routing table. Try
1634 this option if the kernel is unable to allocate
1635 IRQs or discover secondary PCI buses on your
1636 motherboard.
1637 rom [X86] Assign address space to expansion ROMs.
1638 Use with caution as certain devices share
1639 address decoders between ROMs and other
1640 resources.
1641 norom [X86] Do not assign address space to
1642 expansion ROMs that do not already have
1643 BIOS assigned address ranges.
1644 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1645 assigned automatically to PCI devices. You can
1646 make the kernel exclude IRQs of your ISA cards
1647 this way.
1648 pirqaddr=0xAAAAA [X86] Specify the physical address
1649 of the PIRQ table (normally generated
1650 by the BIOS) if it is outside the
1651 F0000h-100000h range.
1652 lastbus=N [X86] Scan all buses thru bus #N. Can be
1653 useful if the kernel is unable to find your
1654 secondary buses and you want to tell it
1655 explicitly which ones they are.
1656 assign-busses [X86] Always assign all PCI bus
1657 numbers ourselves, overriding
1658 whatever the firmware may have done.
1659 usepirqmask [X86] Honor the possible IRQ mask stored
1660 in the BIOS $PIR table. This is needed on
1661 some systems with broken BIOSes, notably
1662 some HP Pavilion N5400 and Omnibook XE3
1663 notebooks. This will have no effect if ACPI
1664 IRQ routing is enabled.
1665 noacpi [X86] Do not use ACPI for IRQ routing
1666 or for PCI scanning.
1667 use_crs [X86] Use _CRS for PCI resource
1668 allocation.
1669 routeirq Do IRQ routing for all PCI devices.
1670 This is normally done in pci_enable_device(),
1671 so this option is a temporary workaround
1672 for broken drivers that don't call it.
1673 skip_isa_align [X86] do not align io start addr, so can
1674 handle more pci cards
1675 firmware [ARM] Do not re-enumerate the bus but instead
1676 just use the configuration from the
1677 bootloader. This is currently used on
1678 IXP2000 systems where the bus has to be
1679 configured a certain way for adjunct CPUs.
1680 noearly [X86] Don't do any early type 1 scanning.
1681 This might help on some broken boards which
1682 machine check when some devices' config space
1683 is read. But various workarounds are disabled
1684 and some IOMMU drivers will not work.
1685 bfsort Sort PCI devices into breadth-first order.
1686 This sorting is done to get a device
1687 order compatible with older (<= 2.4) kernels.
1688 nobfsort Don't sort PCI devices into breadth-first order.
1689 cbiosize=nn[KMG] The fixed amount of bus space which is
1690 reserved for the CardBus bridge's IO window.
1691 The default value is 256 bytes.
1692 cbmemsize=nn[KMG] The fixed amount of bus space which is
1693 reserved for the CardBus bridge's memory
1694 window. The default value is 64 megabytes.
1696 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1697 Management.
1698 off Disable ASPM.
1699 force Enable ASPM even on devices that claim not to support it.
1700 WARNING: Forcing ASPM on may cause system lockups.
1702 pcmv= [HW,PCMCIA] BadgePAD 4
1704 pd. [PARIDE]
1705 See Documentation/blockdev/paride.txt.
1707 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1708 boot time.
1709 Format: { 0 | 1 }
1710 See arch/parisc/kernel/pdc_chassis.c
1712 pf. [PARIDE]
1713 See Documentation/blockdev/paride.txt.
1715 pg. [PARIDE]
1716 See Documentation/blockdev/paride.txt.
1718 pirq= [SMP,APIC] Manual mp-table setup
1719 See Documentation/x86/i386/IO-APIC.txt.
1721 plip= [PPT,NET] Parallel port network link
1722 Format: { parport<nr> | timid | 0 }
1723 See also Documentation/parport.txt.
1725 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1726 Override pmtimer IOPort with a hex value.
1727 e.g. pmtmr=0x508
1729 pnp.debug [PNP]
1730 Enable PNP debug messages. This depends on the
1731 CONFIG_PNP_DEBUG_MESSAGES option.
1733 pnpacpi= [ACPI]
1734 { off }
1736 pnpbios= [ISAPNP]
1737 { on | off | curr | res | no-curr | no-res }
1739 pnp_reserve_irq=
1740 [ISAPNP] Exclude IRQs for the autoconfiguration
1742 pnp_reserve_dma=
1743 [ISAPNP] Exclude DMAs for the autoconfiguration
1745 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1746 Ranges are in pairs (I/O port base and size).
1748 pnp_reserve_mem=
1749 [ISAPNP] Exclude memory regions for the
1750 autoconfiguration.
1751 Ranges are in pairs (memory base and size).
1753 dynamic_printk
1754 Enables pr_debug()/dev_dbg() calls if
1755 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
1756 be switched on/off via <debugfs>/dynamic_printk/modules
1758 print-fatal-signals=
1759 [KNL] debug: print fatal signals
1760 print-fatal-signals=1: print segfault info to
1761 the kernel console.
1762 default: off.
1764 printk.time= Show timing data prefixed to each printk message line
1765 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1767 profile= [KNL] Enable kernel profiling via /proc/profile
1768 Format: [schedule,]<number>
1769 Param: "schedule" - profile schedule points.
1770 Param: <number> - step/bucket size as a power of 2 for
1771 statistical time based profiling.
1772 Param: "sleep" - profile D-state sleeping (millisecs).
1773 Requires CONFIG_SCHEDSTATS
1774 Param: "kvm" - profile VM exits.
1776 processor.max_cstate= [HW,ACPI]
1777 Limit processor to maximum C-state
1778 max_cstate=9 overrides any DMI blacklist limit.
1780 processor.nocst [HW,ACPI]
1781 Ignore the _CST method to determine C-states,
1782 instead using the legacy FADT method
1784 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1785 before loading.
1786 See Documentation/blockdev/ramdisk.txt.
1788 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1789 probe for; one of (bare|imps|exps|lifebook|any).
1790 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1791 per second.
1792 psmouse.resetafter= [HW,MOUSE]
1793 Try to reset the device after so many bad packets
1794 (0 = never).
1795 psmouse.resolution=
1796 [HW,MOUSE] Set desired mouse resolution, in dpi.
1797 psmouse.smartscroll=
1798 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1799 0 = disabled, 1 = enabled (default).
1801 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1802 Format:
1803 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1805 pt. [PARIDE]
1806 See Documentation/blockdev/paride.txt.
1808 pty.legacy_count=
1809 [KNL] Number of legacy pty's. Overwrites compiled-in
1810 default number.
1812 quiet [KNL] Disable most log messages
1814 r128= [HW,DRM]
1816 raid= [HW,RAID]
1817 See Documentation/md.txt.
1819 ramdisk_blocksize= [RAM]
1820 See Documentation/blockdev/ramdisk.txt.
1822 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1823 See Documentation/blockdev/ramdisk.txt.
1825 rcupdate.blimit= [KNL,BOOT]
1826 Set maximum number of finished RCU callbacks to process
1827 in one batch.
1829 rcupdate.qhimark= [KNL,BOOT]
1830 Set threshold of queued
1831 RCU callbacks over which batch limiting is disabled.
1833 rcupdate.qlowmark= [KNL,BOOT]
1834 Set threshold of queued RCU callbacks below which
1835 batch limiting is re-enabled.
1837 rdinit= [KNL]
1838 Format: <full_path>
1839 Run specified binary instead of /init from the ramdisk,
1840 used for early userspace startup. See initrd.
1842 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1843 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1844 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1846 relax_domain_level=
1847 [KNL, SMP] Set scheduler's default relax_domain_level.
1848 See Documentation/cpusets.txt.
1850 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1852 reservetop= [X86-32]
1853 Format: nn[KMG]
1854 Reserves a hole at the top of the kernel virtual
1855 address space.
1857 reset_devices [KNL] Force drivers to reset the underlying device
1858 during initialization.
1860 resume= [SWSUSP]
1861 Specify the partition device for software suspend
1863 resume_offset= [SWSUSP]
1864 Specify the offset from the beginning of the partition
1865 given by "resume=" at which the swap header is located,
1866 in <PAGE_SIZE> units (needed only for swap files).
1867 See Documentation/power/swsusp-and-swap-files.txt
1869 retain_initrd [RAM] Keep initrd memory after extraction
1871 rhash_entries= [KNL,NET]
1872 Set number of hash buckets for route cache
1874 riscom8= [HW,SERIAL]
1875 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1877 ro [KNL] Mount root device read-only on boot
1879 root= [KNL] Root filesystem
1881 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1882 mount the root filesystem
1884 rootflags= [KNL] Set root filesystem mount option string
1886 rootfstype= [KNL] Set root filesystem type
1888 rootwait [KNL] Wait (indefinitely) for root device to show up.
1889 Useful for devices that are detected asynchronously
1890 (e.g. USB and MMC devices).
1892 root_plug.vendor_id=
1893 [ROOTPLUG] Override the default vendor ID
1895 root_plug.product_id=
1896 [ROOTPLUG] Override the default product ID
1898 root_plug.debug=
1899 [ROOTPLUG] Enable debugging output
1901 rw [KNL] Mount root device read-write on boot
1903 S [KNL] Run init in single mode
1905 sa1100ir [NET]
1906 See drivers/net/irda/sa1100_ir.c.
1908 sbni= [NET] Granch SBNI12 leased line adapter
1910 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1911 Format: <io>[,<timeout>[,<isapnp>]]
1913 scsi_debug_*= [SCSI]
1914 See drivers/scsi/scsi_debug.c.
1916 scsi_default_dev_flags=
1917 [SCSI] SCSI default device flags
1918 Format: <integer>
1920 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1921 Format: <vendor>:<model>:<flags>
1922 (flags are integer value)
1924 scsi_logging_level= [SCSI] a bit mask of logging levels
1925 See drivers/scsi/scsi_logging.h for bits. Also
1926 settable via sysctl at dev.scsi.logging_level
1927 (/proc/sys/dev/scsi/logging_level).
1928 There is also a nice 'scsi_logging_level' script in the
1929 S390-tools package, available for download at
1930 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1932 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1933 discovered. async scans them in kernel threads,
1934 allowing boot to proceed. none ignores them, expecting
1935 user space to do the scan.
1937 selinux [SELINUX] Disable or enable SELinux at boot time.
1938 Format: { "0" | "1" }
1939 See security/selinux/Kconfig help text.
1940 0 -- disable.
1941 1 -- enable.
1942 Default value is set via kernel config option.
1943 If enabled at boot time, /selinux/disable can be used
1944 later to disable prior to initial policy load.
1946 selinux_compat_net =
1947 [SELINUX] Set initial selinux_compat_net flag value.
1948 Format: { "0" | "1" }
1949 0 -- use new secmark-based packet controls
1950 1 -- use legacy packet controls
1951 Default value is 0 (preferred).
1952 Value can be changed at runtime via
1953 /selinux/compat_net.
1955 serialnumber [BUGS=X86-32]
1957 shapers= [NET]
1958 Maximal number of shapers.
1960 show_msr= [x86] show boot-time MSR settings
1961 Format: { <integer> }
1962 Show boot-time (BIOS-initialized) MSR settings.
1963 The parameter means the number of CPUs to show,
1964 for example 1 means boot CPU only.
1966 sim710= [SCSI,HW]
1967 See header of drivers/scsi/sim710.c.
1969 simeth= [IA-64]
1970 simscsi=
1972 slram= [HW,MTD]
1974 slub_debug[=options[,slabs]] [MM, SLUB]
1975 Enabling slub_debug allows one to determine the
1976 culprit if slab objects become corrupted. Enabling
1977 slub_debug can create guard zones around objects and
1978 may poison objects when not in use. Also tracks the
1979 last alloc / free. For more information see
1980 Documentation/vm/slub.txt.
1982 slub_max_order= [MM, SLUB]
1983 Determines the maximum allowed order for slabs.
1984 A high setting may cause OOMs due to memory
1985 fragmentation. For more information see
1986 Documentation/vm/slub.txt.
1988 slub_min_objects= [MM, SLUB]
1989 The minimum number of objects per slab. SLUB will
1990 increase the slab order up to slub_max_order to
1991 generate a sufficiently large slab able to contain
1992 the number of objects indicated. The higher the number
1993 of objects the smaller the overhead of tracking slabs
1994 and the less frequently locks need to be acquired.
1995 For more information see Documentation/vm/slub.txt.
1997 slub_min_order= [MM, SLUB]
1998 Determines the mininum page order for slabs. Must be
1999 lower than slub_max_order.
2000 For more information see Documentation/vm/slub.txt.
2002 slub_nomerge [MM, SLUB]
2003 Disable merging of slabs with similar size. May be
2004 necessary if there is some reason to distinguish
2005 allocs to different slabs. Debug options disable
2006 merging on their own.
2007 For more information see Documentation/vm/slub.txt.
2009 smart2= [HW]
2010 Format: <io1>[,<io2>[,...,<io8>]]
2012 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2013 attempt to substitute SMP alternatives once at boot.
2015 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2016 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2017 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2018 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2019 smsc-ircc2.ircc_irq= [HW] IRQ line
2020 smsc-ircc2.ircc_dma= [HW] DMA channel
2021 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2022 0: Toshiba Satellite 1800 (GP data pin select)
2023 1: Fast pin select (default)
2024 2: ATC IRMode
2026 snd-ad1816a= [HW,ALSA]
2028 snd-ad1848= [HW,ALSA]
2030 snd-ali5451= [HW,ALSA]
2032 snd-als100= [HW,ALSA]
2034 snd-als4000= [HW,ALSA]
2036 snd-azt2320= [HW,ALSA]
2038 snd-cmi8330= [HW,ALSA]
2040 snd-cmipci= [HW,ALSA]
2042 snd-cs4231= [HW,ALSA]
2044 snd-cs4232= [HW,ALSA]
2046 snd-cs4236= [HW,ALSA]
2048 snd-cs4281= [HW,ALSA]
2050 snd-cs46xx= [HW,ALSA]
2052 snd-dt019x= [HW,ALSA]
2054 snd-dummy= [HW,ALSA]
2056 snd-emu10k1= [HW,ALSA]
2058 snd-ens1370= [HW,ALSA]
2060 snd-ens1371= [HW,ALSA]
2062 snd-es968= [HW,ALSA]
2064 snd-es1688= [HW,ALSA]
2066 snd-es18xx= [HW,ALSA]
2068 snd-es1938= [HW,ALSA]
2070 snd-es1968= [HW,ALSA]
2072 snd-fm801= [HW,ALSA]
2074 snd-gusclassic= [HW,ALSA]
2076 snd-gusextreme= [HW,ALSA]
2078 snd-gusmax= [HW,ALSA]
2080 snd-hdsp= [HW,ALSA]
2082 snd-ice1712= [HW,ALSA]
2084 snd-intel8x0= [HW,ALSA]
2086 snd-interwave= [HW,ALSA]
2088 snd-interwave-stb=
2089 [HW,ALSA]
2091 snd-korg1212= [HW,ALSA]
2093 snd-maestro3= [HW,ALSA]
2095 snd-mpu401= [HW,ALSA]
2097 snd-mtpav= [HW,ALSA]
2099 snd-nm256= [HW,ALSA]
2101 snd-opl3sa2= [HW,ALSA]
2103 snd-opti92x-ad1848=
2104 [HW,ALSA]
2106 snd-opti92x-cs4231=
2107 [HW,ALSA]
2109 snd-opti93x= [HW,ALSA]
2111 snd-pmac= [HW,ALSA]
2113 snd-rme32= [HW,ALSA]
2115 snd-rme96= [HW,ALSA]
2117 snd-rme9652= [HW,ALSA]
2119 snd-sb8= [HW,ALSA]
2121 snd-sb16= [HW,ALSA]
2123 snd-sbawe= [HW,ALSA]
2125 snd-serial= [HW,ALSA]
2127 snd-sgalaxy= [HW,ALSA]
2129 snd-sonicvibes= [HW,ALSA]
2131 snd-sun-amd7930=
2132 [HW,ALSA]
2134 snd-sun-cs4231= [HW,ALSA]
2136 snd-trident= [HW,ALSA]
2138 snd-usb-audio= [HW,ALSA,USB]
2140 snd-via82xx= [HW,ALSA]
2142 snd-virmidi= [HW,ALSA]
2144 snd-wavefront= [HW,ALSA]
2146 snd-ymfpci= [HW,ALSA]
2148 softlockup_panic=
2149 [KNL] Should the soft-lockup detector generate panics.
2151 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2152 See Documentation/sonypi.txt
2154 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2155 See Documentation/serial/specialix.txt.
2157 spia_io_base= [HW,MTD]
2158 spia_fio_base=
2159 spia_pedr=
2160 spia_peddr=
2162 sscape= [HW,OSS]
2163 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2165 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2166 See Documentation/scsi/st.txt.
2168 sti= [PARISC,HW]
2169 Format: <num>
2170 Set the STI (builtin display/keyboard on the HP-PARISC
2171 machines) console (graphic card) which should be used
2172 as the initial boot-console.
2173 See also comment in drivers/video/console/sticore.c.
2175 sti_font= [HW]
2176 See comment in drivers/video/console/sticore.c.
2178 stifb= [HW]
2179 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2181 sunrpc.pool_mode=
2182 [NFS]
2183 Control how the NFS server code allocates CPUs to
2184 service thread pools. Depending on how many NICs
2185 you have and where their interrupts are bound, this
2186 option will affect which CPUs will do NFS serving.
2187 Note: this parameter cannot be changed while the
2188 NFS server is running.
2190 auto the server chooses an appropriate mode
2191 automatically using heuristics
2192 global a single global pool contains all CPUs
2193 percpu one pool for each CPU
2194 pernode one pool for each NUMA node (equivalent
2195 to global on non-NUMA machines)
2197 swiotlb= [IA-64] Number of I/O TLB slabs
2199 switches= [HW,M68k]
2201 sym53c416= [HW,SCSI]
2202 See header of drivers/scsi/sym53c416.c.
2204 sysrq_always_enabled
2205 [KNL]
2206 Ignore sysrq setting - this boot parameter will
2207 neutralize any effect of /proc/sys/kernel/sysrq.
2208 Useful for debugging.
2210 t128= [HW,SCSI]
2211 See header of drivers/scsi/t128.c.
2213 tdfx= [HW,DRM]
2215 test_suspend= [SUSPEND]
2216 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2217 standby suspend) as the system sleep state to briefly
2218 enter during system startup. The system is woken from
2219 this state using a wakeup-capable RTC alarm.
2221 thash_entries= [KNL,NET]
2222 Set number of hash buckets for TCP connection
2224 thermal.act= [HW,ACPI]
2225 -1: disable all active trip points in all thermal zones
2226 <degrees C>: override all lowest active trip points
2228 thermal.crt= [HW,ACPI]
2229 -1: disable all critical trip points in all thermal zones
2230 <degrees C>: override all critical trip points
2232 thermal.nocrt= [HW,ACPI]
2233 Set to disable actions on ACPI thermal zone
2234 critical and hot trip points.
2236 thermal.off= [HW,ACPI]
2237 1: disable ACPI thermal control
2239 thermal.psv= [HW,ACPI]
2240 -1: disable all passive trip points
2241 <degrees C>: override all passive trip points to this value
2243 thermal.tzp= [HW,ACPI]
2244 Specify global default ACPI thermal zone polling rate
2245 <deci-seconds>: poll all this frequency
2246 0: no polling (default)
2248 tmscsim= [HW,SCSI]
2249 See comment before function dc390_setup() in
2250 drivers/scsi/tmscsim.c.
2252 tp720= [HW,PS2]
2254 trix= [HW,OSS] MediaTrix AudioTrix Pro
2255 Format:
2256 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2258 turbografx.map[2|3]= [HW,JOY]
2259 TurboGraFX parallel port interface
2260 Format:
2261 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2262 See also Documentation/input/joystick-parport.txt
2264 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2265 See header of drivers/scsi/u14-34f.c.
2267 uart401= [HW,OSS]
2268 Format: <io>,<irq>
2270 uart6850= [HW,OSS]
2271 Format: <io>,<irq>
2273 uhci-hcd.ignore_oc=
2274 [USB] Ignore overcurrent events (default N).
2275 Some badly-designed motherboards generate lots of
2276 bogus events, for ports that aren't wired to
2277 anything. Set this parameter to avoid log spamming.
2278 Note that genuine overcurrent events won't be
2279 reported either.
2281 unknown_nmi_panic
2282 [X86-32,X86-64]
2283 Set unknown_nmi_panic=1 early on boot.
2285 usbcore.autosuspend=
2286 [USB] The autosuspend time delay (in seconds) used
2287 for newly-detected USB devices (default 2). This
2288 is the time required before an idle device will be
2289 autosuspended. Devices for which the delay is set
2290 to a negative value won't be autosuspended at all.
2292 usbcore.usbfs_snoop=
2293 [USB] Set to log all usbfs traffic (default 0 = off).
2295 usbcore.blinkenlights=
2296 [USB] Set to cycle leds on hubs (default 0 = off).
2298 usbcore.old_scheme_first=
2299 [USB] Start with the old device initialization
2300 scheme (default 0 = off).
2302 usbcore.use_both_schemes=
2303 [USB] Try the other device initialization scheme
2304 if the first one fails (default 1 = enabled).
2306 usbcore.initial_descriptor_timeout=
2307 [USB] Specifies timeout for the initial 64-byte
2308 USB_REQ_GET_DESCRIPTOR request in milliseconds
2309 (default 5000 = 5.0 seconds).
2311 usbhid.mousepoll=
2312 [USBHID] The interval which mice are to be polled at.
2314 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2315 kernel's map of available physical RAM.
2317 vdso= [X86-32,SH,x86-64]
2318 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2319 vdso=1: enable VDSO (default)
2320 vdso=0: disable VDSO mapping
2322 vdso32= [X86-32,X86-64]
2323 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2324 vdso32=1: enable 32-bit VDSO (default)
2325 vdso32=0: disable 32-bit VDSO mapping
2327 vector= [IA-64,SMP]
2328 vector=percpu: enable percpu vector domain
2330 video= [FB] Frame buffer configuration
2331 See Documentation/fb/modedb.txt.
2333 vga= [BOOT,X86-32] Select a particular video mode
2334 See Documentation/x86/i386/boot.txt and
2335 Documentation/svga.txt.
2336 Use vga=ask for menu.
2337 This is actually a boot loader parameter; the value is
2338 passed to the kernel using a special protocol.
2340 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2341 size of <nn>. This can be used to increase the
2342 minimum size (128MB on x86). It can also be used to
2343 decrease the size and leave more room for directly
2344 mapped kernel RAM.
2346 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2347 Format: <command>
2349 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2350 Format: <command>
2352 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2353 Format: <command>
2355 waveartist= [HW,OSS]
2356 Format: <io>,<irq>,<dma>,<dma2>
2358 wd33c93= [HW,SCSI]
2359 See header of drivers/scsi/wd33c93.c.
2361 wd7000= [HW,SCSI]
2362 See header of drivers/scsi/wd7000.c.
2364 wdt= [WDT] Watchdog
2365 See Documentation/watchdog/wdt.txt.
2367 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2368 xd_geo= See header of drivers/block/xd.c.
2370 xirc2ps_cs= [NET,PCMCIA]
2371 Format:
2372 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2374 norandmaps Don't use address space randomization
2375 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2377 ______________________________________________________________________
2379 TODO:
2381 Add documentation for ALSA options.
2382 Add more DRM drivers.