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
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 is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode }
151 See Documentation/power/video.txt
153 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
154 Format: { level | edge | high | low }
156 acpi_irq_balance [HW,ACPI]
157 ACPI will balance active IRQs
160 acpi_irq_nobalance [HW,ACPI]
161 ACPI will not move active IRQs (default)
164 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
166 Format: <irq>,<irq>...
168 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
169 Format: <irq>,<irq>...
171 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
173 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
174 Format: To spoof as Windows 98: ="Microsoft Windows"
176 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
177 acpi_osi="string1" # add string1 -- only one string
178 acpi_osi="!string2" # remove built-in string2
179 acpi_osi= # disable all strings
181 acpi_serialize [HW,ACPI] force serialization of AML methods
183 acpi_skip_timer_override [HW,ACPI]
184 Recognize and ignore IRQ0/pin2 Interrupt Override.
185 For broken nForce2 BIOS resulting in XT-PIC timer.
186 acpi_use_timer_override [HW,ACPI}
187 Use timer override. For some broken Nvidia NF5 boards
188 that require a timer override, but don't have
191 acpi.debug_layer= [HW,ACPI]
193 Each bit of the <int> indicates an ACPI debug layer,
194 1: enable, 0: disable. It is useful for boot time
195 debugging. After system has booted up, it can be set
196 via /sys/module/acpi/parameters/debug_layer.
197 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
198 Available bits (add the numbers together) to enable debug output
199 for specific parts of the ACPI subsystem:
200 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
201 0x10 namespace 0x20 parser 0x40 dispatcher
202 0x80 executer 0x100 resources 0x200 acpica debugger
203 0x400 os services 0x800 acpica disassembler.
204 The number can be in decimal or prefixed with 0x in hex.
205 Warning: Many of these options can produce a lot of
206 output and make your system unusable. Be very careful.
208 acpi.debug_level= [HW,ACPI]
210 Each bit of the <int> indicates an ACPI debug level,
211 1: enable, 0: disable. It is useful for boot time
212 debugging. After system has booted up, it can be set
213 via /sys/module/acpi/parameters/debug_level.
214 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
215 Available bits (add the numbers together) to enable different
216 debug output levels of the ACPI subsystem:
217 0x01 error 0x02 warn 0x04 init 0x08 debug object
218 0x10 info 0x20 init names 0x40 parse 0x80 load
219 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
220 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
221 0x10000 resources 0x20000 user requests 0x40000 package.
222 The number can be in decimal or prefixed with 0x in hex.
223 Warning: Many of these options can produce a lot of
224 output and make your system unusable. Be very careful.
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
261 See Documentation/scsi/aha152x.txt.
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267 See Documentation/scsi/aic7xxx.txt.
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
283 Power management functions (SPARCstation-4/5 + deriv.)
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
299 Format: <io>,<irq>,<nodeID>
303 atarimouse= [HW,MOUSE] Atari Mouse
305 atascsi= [HW,SCSI] Atari SCSI
307 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
308 EzKey and similar keyboards
310 atkbd.reset= [HW] Reset keyboard during initialization
312 atkbd.set= [HW] Select keyboard code set
313 Format: <int> (2 = AT (default), 3 = PS/2)
315 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 atkbd.softraw= [HW] Choose between synthetic and real raw mode
319 Format: <bool> (0 = real, 1 = synthetic (default))
321 atkbd.softrepeat= [HW]
322 Use software keyboard repeat
326 baycom_epp= [HW,AX25]
329 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
331 See header of drivers/net/hamradio/baycom_par.c.
333 baycom_ser_fdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
335 Format: <io>,<irq>,<mode>[,<baud>]
336 See header of drivers/net/hamradio/baycom_ser_fdx.c.
338 baycom_ser_hdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
340 Format: <io>,<irq>,<mode>
341 See header of drivers/net/hamradio/baycom_ser_hdx.c.
343 boot_delay= Milliseconds to delay each printk during boot.
344 Values larger than 10 seconds (10000) are changed to
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
368 [SECURITY] Disable capabilities. This would normally
369 be used only if an alternative security model is to be
370 configured. Potentially dangerous and should only be
371 used if you are entirely sure of the consequences.
373 ccw_timeout_log [S390]
374 See Documentation/s390/CommonIO for details.
376 checkreqprot [SELINUX] Set initial checkreqprot flag value.
377 Format: { "0" | "1" }
378 See security/selinux/Kconfig help text.
379 0 -- check protection applied by kernel (includes
380 any implied execute protection).
381 1 -- check protection requested by application.
382 Default value is set via a kernel config option.
383 Value can be changed at runtime via
384 /selinux/checkreqprot.
387 See Documentation/s390/CommonIO for details.
390 See Documentation/s390/CommonIO for details.
392 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
394 Forces specified clocksource (if available) to be used
395 when calculating gettimeofday(). If specified
396 clocksource is not available, it defaults to PIT.
397 Format: { pit | tsc | cyclone | pmtmr }
399 clocksource= [GENERIC_TIME] Override the default clocksource
401 Override the default clocksource and use the clocksource
402 with the name specified.
403 Some clocksource names to choose from, depending on
405 [all] jiffies (this is the base, fallback clocksource)
407 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
408 pxa_timer,timer3,32k_counter,timer0_1
410 [X86-32] pit,hpet,tsc,vmi-timer;
411 scx200_hrt on Geode; cyclone on IBM x440
419 code_bytes [IA32/X86_64] How many bytes of object code to print
426 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
427 over the 8254 in addition to over the IO-APIC. The
428 kernel tries to set a sensible default.
430 hpet= [X86-32,HPET] option to control HPET usage
431 Format: { enable (default) | disable | force }
432 disable: disable HPET and use PIT instead
433 force: allow force enabled of undocumented chips (ICH4,
436 com20020= [HW,NET] ARCnet - COM20020 chipset
438 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
440 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
444 ARCnet - COM90xx chipset (memory-mapped buffers)
445 Format: <io>[,<irq>[,<memstart>]]
447 condev= [HW,S390] console device
450 console= [KNL] Output console device and options.
452 tty<n> Use the virtual console device <n>.
456 Use the specified serial port. The options are of
457 the form "bbbbpnf", where "bbbb" is the baud rate,
458 "p" is parity ("n", "o", or "e"), "n" is number of
459 bits, and "f" is flow control ("r" for RTS or
460 omit it). Default is "9600n8".
462 See Documentation/serial-console.txt for more
464 Documentation/networking/netconsole.txt for an
467 uart[8250],io,<addr>[,options]
468 uart[8250],mmio,<addr>[,options]
469 Start an early, polled-mode console on the 8250/16550
470 UART at the specified I/O port or MMIO address,
471 switching to the matching ttyS device later. The
472 options are the same as for ttyS, above.
474 earlycon= [KNL] Output early console device and options.
475 uart[8250],io,<addr>[,options]
476 uart[8250],mmio,<addr>[,options]
477 Start an early, polled-mode console on the 8250/16550
478 UART at the specified I/O port or MMIO address.
479 The options are the same as for ttyS, above.
482 [HW] Never suspend the console
483 Disable suspending of consoles during suspend and
484 hibernate operations. Once disabled, debugging
485 messages can reach various consoles while the rest
486 of the system is being put to sleep (ie, while
487 debugging driver suspend/resume hooks). This may
488 not work reliably with all consoles, but is known
489 to work with serial and VGA consoles.
491 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
493 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
495 crashkernel=nn[KMG]@ss[KMG]
496 [KNL] Reserve a chunk of physical memory to
497 hold a kernel to switch to with kexec on panic.
499 crashkernel=range1:size1[,range2:size2,...][@offset]
500 [KNL] Same as above, but depends on the memory
501 in the running system. The syntax of range is
502 start-[end] where start and end are both
503 a memory unit (amount[KMG]). See also
504 Documentation/kdump/kdump.txt for a example.
507 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
512 cs89x0_media= [HW,NET]
513 Format: { rj45 | aui | bnc }
516 See header of drivers/s390/block/dasd_devmap.c.
518 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
519 (one device per port)
520 Format: <port#>,<type>
521 See also Documentation/input/joystick-parport.txt
523 debug [KNL] Enable kernel debugging (events log level).
526 [KNL] verbose self-tests
528 Print debugging info while doing the locking API
530 We default to 0 (no extra messages), setting it to
531 1 will print _a lot_ more information - normally
532 only useful to kernel developers.
535 Format: <area>[,<node>]
536 See also Documentation/networking/decnet.txt.
539 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
540 Change the default blue palette of the console.
541 This is a 16-member array composed of values
545 Format: <green0>,<green1>,<green2>,...,<green15>
546 Change the default green palette of the console.
547 This is a 16-member array composed of values
551 Format: <red0>,<red1>,<red2>,...,<red15>
552 Change the default red palette of the console.
553 This is a 16-member array composed of values
559 Set system-wide default UTF-8 mode for all tty's.
560 Default is 1, i.e. UTF-8 mode is enabled for all
561 newly opened terminals.
564 Set number of hash buckets for dentry cache.
567 IO parameters + enable/disable command.
569 digiepca= [HW,SERIAL]
570 See drivers/char/README.epca and
571 Documentation/digiepca.txt.
573 disable_mtrr_trim [X86-64, Intel only]
574 By default the kernel will trim any uncacheable
575 memory out of your available memory pool based on
576 MTRR settings. This parameter disables that behavior,
577 possibly causing your machine to run very slowly.
579 dmasound= [HW,OSS] Sound subsystem buffers
585 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
587 earlyprintk=serial[,ttySn[,baudrate]]
589 Append ",keep" to not disable it when the real console
592 Only vga or serial at a time, not both.
594 Currently only ttyS0 and ttyS1 are supported.
596 Interaction with the standard serial driver is not
599 The VGA output is eventually overwritten by the real
605 Format: {"of[f]" | "sk[ipmbr]"}
606 See comment in arch/i386/boot/edd.S
608 eisa_irq_edge= [PARISC,HW]
609 See header of drivers/parisc/eisa.c.
612 See comment before function elanfreq_setup() in
613 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
616 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
617 See Documentation/block/as-iosched.txt and
618 Documentation/block/deadline-iosched.txt for details.
620 elfcorehdr= [X86-32, X86_64]
621 Specifies physical address of start of kernel core
622 image elf header. Generally kexec loader will
623 pass this option to capture kernel.
624 See Documentation/kdump/kdump.txt for details.
626 enforcing [SELINUX] Set initial enforcing status.
628 See security/selinux/Kconfig help text.
629 0 -- permissive (log only, no denials).
630 1 -- enforcing (deny and log).
632 Value can be changed at runtime via /selinux/enforce.
635 Format: <spdif>,[<nomix>,[<amplifier>]]
636 See also header of sound/oss/es1371.c.
638 ether= [HW,NET] Ethernet cards parameters
639 This option is obsoleted by the "netdev=" option, which
640 has equivalent usage. See its documentation for details.
642 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
647 fail_make_request=[KNL]
648 General fault injection mechanism.
649 Format: <interval>,<probability>,<space>,<times>
650 See also /Documentation/fault-injection/.
653 See header of drivers/scsi/fd_mcs.c.
656 See header of drivers/scsi/fdomain.c.
659 See Documentation/floppy.txt.
662 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
663 support via parallel port (up to 5 devices per port)
664 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
665 See also Documentation/input/joystick-parport.txt
669 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
674 See header of drivers/scsi/gdth.c.
676 gpt [EFI] Forces disk with valid GPT signature but
677 invalid Protective MBR to be treated as GPT.
681 hashdist= [KNL,NUMA] Large hashes allocated during boot
682 are distributed across NUMA nodes. Defaults on
683 for IA-64, off otherwise.
684 Format: 0 | 1 (for off | on)
686 hcl= [IA-64] SGI's Hardware Graph compatibility layer
688 hd= [EIDE] (E)IDE hard drive subsystem geometry
689 Format: <cyl>,<head>,<sect>
691 hd?= [HW] (E)IDE subsystem
692 hd?lun= See Documentation/ide.txt.
694 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
695 size of <nn>. This works even on boxes that have no
696 highmem otherwise. This also works to reduce highmem
697 size on bigger boxes.
699 highres= [KNL] Enable/disable high resolution timer mode.
700 Valid parameters: "on", "off"
704 See Documentation/isdn/README.HiSax.
706 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
708 i8042.direct [HW] Put keyboard port into non-translated mode
709 i8042.dumbkbd [HW] Pretend that controller can only read data from
710 keyboard and cannot control its state
711 (Don't attempt to blink the leds)
712 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
713 i8042.nokbd [HW] Don't check/create keyboard port
714 i8042.nomux [HW] Don't check presence of an active multiplexing
716 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
719 [HW] Frequency with which keyboard LEDs should blink
720 when kernel panics (default is 0.5 sec)
721 i8042.reset [HW] Reset the controller during init and cleanup
722 i8042.unlock [HW] Unlock (ignore) the keylock
726 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
727 indicates that the driver is running on unsupported
729 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
730 does not match list of supported models.
732 [HW] Report power status in /proc/i8k
733 (disabled by default)
734 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
737 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
738 See Documentation/mca.txt.
741 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
743 ide= [HW] (E)IDE subsystem
744 Format: ide=nodma or ide=doubler or ide=reverse
745 See Documentation/ide.txt.
747 ide?= [HW] (E)IDE subsystem
748 Format: ide?=noprobe or chipset specific parameters.
749 See Documentation/ide.txt.
751 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
752 See Documentation/ide.txt.
755 Format: idle=poll or idle=mwait
756 Poll forces a polling idle loop that can slightly improves the performance
757 of waking up a idle CPU, but will use a lot of power and make the system
758 run hot. Not recommended.
759 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
760 to not use it because it doesn't save as much power as a normal idle
761 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
764 ignore_loglevel [KNL]
765 Ignore loglevel setting - this will print /all/
766 kernel messages to the console. Useful for debugging.
769 Set number of hash buckets for inode cache.
772 See header of drivers/scsi/in2000.c.
776 Run specified binary instead of /sbin/init as init
779 initcall_debug [KNL] Trace initcalls as they are executed. Useful
780 for working out where the kernel is dying during
783 initrd= [BOOT] Specify the location of the initial ramdisk
785 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
790 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
792 Disable intel iommu driver.
793 igfx_off [Default Off]
794 By default, gfx is mapped as normal device. If a gfx
795 device has a dedicated DMAR unit, the DMAR unit is
796 bypassed by not enabling DMAR with this option. In
797 this case, gfx device will use physical address for
800 With this option iommu will not optimize to look
801 for io virtual address below 32 bit forcing dual
802 address cycle on pci bus for cards supporting greater
803 than 32 bit addressing. The default is to look
804 for translation below 32 bit and if not available
805 then look in the higher range.
807 io_delay= [X86-32,X86-64] I/O delay method
809 Standard port 0x80 based delay
811 Alternate port 0xed based delay (needed on some systems)
813 Simple two microseconds delay
817 io7= [HW] IO7 for Marvel based alpha systems
818 See comment before marvel_specify_io7 in
819 arch/alpha/kernel/core_marvel.c.
822 See Documentation/nfsroot.txt.
824 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
825 See comment before ip2_setup() in
826 drivers/char/ip2/ip2base.c.
828 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
829 See header of drivers/scsi/ips.c.
831 ports= [IP_VS_FTP] IPVS ftp helper module
833 Up to 8 (IP_VS_APP_MAX_PORTS) ports
835 Format: <port>,<port>....
838 When an interrupt is not handled search all handlers
839 for it. Intended to get systems with badly broken
843 When an interrupt is not handled search all handlers
844 for it. Also check all handlers each timer
845 interrupt. Intended to get systems with badly broken
849 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
851 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
853 <cpu number>,...,<cpu number>
855 <cpu number>-<cpu number> (must be a positive range in ascending order)
857 <cpu number>,...,<cpu number>-<cpu number>
858 This option can be used to specify one or more CPUs
859 to isolate from the general SMP balancing and scheduling
860 algorithms. The only way to move a process onto or off
861 an "isolated" CPU is via the CPU affinity syscalls.
862 <cpu number> begins at 0 and the maximum value is
863 "number of CPUs in system - 1".
865 This option is the preferred way to isolate CPUs. The
866 alternative -- manually setting the CPU mask of all
867 tasks in the system -- can cause problems and
868 suboptimal load balancer performance.
872 js= [HW,JOY] Analog joystick
873 See Documentation/input/joystick.txt.
875 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
876 specifies the amount of memory usable by the kernel
877 for non-movable allocations. The requested amount is
878 spread evenly throughout all nodes in the system. The
879 remaining memory in each node is used for Movable
880 pages. In the event, a node is too small to have both
881 kernelcore and Movable pages, kernelcore pages will
882 take priority and other nodes will have a larger number
883 of kernelcore pages. The Movable zone is used for the
884 allocation of pages that may be reclaimed or moved
885 by the page migration subsystem. This means that
886 HugeTLB pages may not be allocated from this zone.
887 Note that allocations like PTEs-from-HighMem still
888 use the HighMem zone if it exists, and the Normal
891 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
892 is similar to kernelcore except it specifies the
893 amount of memory used for migratable allocations.
894 If both kernelcore and movablecore is specified,
895 then kernelcore will be at *least* the specified
896 value but may be more. If movablecore on its own
897 is specified, the administrator must be careful
898 that the amount of memory usable for all allocations
903 kstack=N [X86-32,X86-64] Print N words from the kernel stack
908 lapic [X86-32,APIC] Enable the local APIC even if BIOS
911 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
914 libata.dma= [LIBATA] DMA control
915 libata.dma=0 Disable all PATA and SATA DMA
916 libata.dma=1 PATA and SATA Disk DMA only
917 libata.dma=2 ATAPI (CDROM) DMA only
918 libata.dma=4 Compact Flash DMA only
919 Combinations also work, so libata.dma=3 enables DMA
920 for disks and CDROMs, but not CFs.
922 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
926 load_ramdisk= [RAM] List of ramdisks to load from floppy
927 See Documentation/ramdisk.txt.
929 lockd.nlm_grace_period=P [NFS] Assign grace period.
932 lockd.nlm_tcpport=N [NFS] Assign TCP port.
935 lockd.nlm_timeout=T [NFS] Assign timeout value.
938 lockd.nlm_udpport=M [NFS] Assign UDP port.
941 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
944 loglevel= All Kernel Messages with a loglevel smaller than the
945 console loglevel will be printed to the console. It can
946 also be changed with klogd or other programs. The
947 loglevels are defined as follows:
949 0 (KERN_EMERG) system is unusable
950 1 (KERN_ALERT) action must be taken immediately
951 2 (KERN_CRIT) critical conditions
952 3 (KERN_ERR) error conditions
953 4 (KERN_WARNING) warning conditions
954 5 (KERN_NOTICE) normal but significant condition
955 6 (KERN_INFO) informational
956 7 (KERN_DEBUG) debug-level messages
958 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
959 Format: { n | nk | nM }
960 n must be a power of two. The default size
961 is set in the kernel config file.
963 logo.nologo [FB] Disables display of the built-in Linux logo.
964 This may be used to provide more screen space for
965 kernel log messages and is useful when debugging
966 kernel boot problems.
968 lp=0 [LP] Specify parallel ports to use, e.g,
969 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
970 lp=reset first parallel port). 'lp=0' disables the
971 lp=auto printer driver. 'lp=reset' (which can be
972 specified in addition to the ports) causes
973 attached printers to be reset. Using
974 lp=port1,port2,... specifies the parallel ports
975 to associate lp devices with, starting with
976 lp0. A port specification may be 'none' to skip
977 that lp device, or a parport name such as
978 'parport0'. Specifying 'lp=auto' instead of a
979 port specification list means that device IDs
980 from each port should be examined, to see if
981 an IEEE 1284-compliant printer is attached; if
982 so, the driver will manage that printer.
983 See also header of drivers/char/lp.c.
986 Sets loops_per_jiffy to given constant, thus avoiding
987 time-consuming boot-time autodetection (up to 250 ms per
988 CPU). 0 enables autodetection (default). To determine
989 the correct value for your kernel, boot with normal
990 autodetection and see what value is printed. Note that
991 on SMP systems the preset will be applied to all CPUs,
992 which is likely to cause problems if your CPUs need
993 significantly divergent settings. An incorrect value
994 will cause delays in the kernel to be wrong, leading to
995 unpredictable I/O errors and other breakage. Although
996 unlikely, in the extreme case this might damage your
1000 Format: <io>,<irq>,<dma>
1002 mac5380= [HW,SCSI] Format:
1003 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1005 mac53c9x= [HW,SCSI] Format:
1006 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1008 machvec= [IA64] Force the use of a particular machine-vector
1009 (machvec) in a generic kernel.
1010 Example: machvec=hpzx1_swiotlb
1012 max_loop= [LOOP] Maximum number of loopback devices that can
1016 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1017 should make use of. maxcpus=n : n >= 0 limits the
1018 kernel to using 'n' processors. n=0 is a special case,
1019 it is equivalent to "nosmp", which also disables
1022 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1023 equal to this physical address is ignored.
1025 max_luns= [SCSI] Maximum number of LUNs to probe.
1026 Should be between 1 and 2^32-1.
1029 [SCSI] Maximum number of LUNs received.
1030 Should be between 1 and 16384.
1032 mca-pentium [BUGS=X86-32]
1036 mce [X86-32] Machine Check Exception
1038 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1040 md= [HW] RAID subsystems devices and level
1041 See Documentation/md.txt.
1044 Format: <first>,<last>
1045 Specifies range of consoles to be captured by the MDA.
1047 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1048 Amount of memory to be used when the kernel is not able
1049 to see the whole system memory or for test.
1050 [X86-32] Use together with memmap= to avoid physical
1051 address space collisions. Without memmap= PCI devices
1052 could be placed at addresses belonging to unused RAM.
1054 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1057 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1058 E820 memory map, as specified by the user.
1059 Such memmap=exactmap lines can be constructed based on
1060 BIOS output or other requirements. See the memmap=nn@ss
1063 memmap=nn[KMG]@ss[KMG]
1064 [KNL] Force usage of a specific region of memory
1065 Region of memory to be used, from ss to ss+nn.
1067 memmap=nn[KMG]#ss[KMG]
1068 [KNL,ACPI] Mark specific memory as ACPI data.
1069 Region of memory to be used, from ss to ss+nn.
1071 memmap=nn[KMG]$ss[KMG]
1072 [KNL,ACPI] Mark specific memory as reserved.
1073 Region of memory to be used, from ss to ss+nn.
1075 meye.*= [HW] Set MotionEye Camera parameters
1076 See Documentation/video4linux/meye.txt.
1078 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1079 Multi-Function General Purpose Timers on AMD Geode
1085 [MOUSE] Maximum time between finger touching and
1086 leaving touchpad surface for touch to be considered
1087 a tap and be reported as a left button click (for
1088 touchpads working in absolute mode only).
1090 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1091 reporting absolute coordinates, such as tablets
1092 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1093 reporting absolute coordinates, such as tablets
1098 MTD_Partition= [MTD]
1099 Format: <name>,<region-number>,<size>,<offset>
1101 MTD_Region= [MTD] Format:
1102 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1105 See drivers/mtd/cmdlinepart.c.
1107 mtouchusb.raw_coordinates=
1108 [HW] Make the MicroTouch USB driver use raw coordinates
1109 ('y', default) or cooked coordinates ('n')
1111 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1114 See header of drivers/scsi/NCR_D700.c.
1118 ncr53c400= [HW,SCSI]
1120 ncr53c400a= [HW,SCSI]
1122 ncr53c406a= [HW,SCSI]
1124 ncr53c8xx= [HW,SCSI]
1126 netdev= [NET] Network devices parameters
1127 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1128 Note that mem_start is often overloaded to mean
1129 something different and driver-specific.
1130 This usage is only documented in each driver source
1134 See Documentation/nfsroot.txt.
1136 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1137 See Documentation/nfsroot.txt.
1139 nfs.callback_tcpport=
1140 [NFS] set the TCP port on which the NFSv4 callback
1141 channel should listen.
1143 nfs.idmap_cache_timeout=
1144 [NFS] set the maximum lifetime for idmapper cache
1148 [NFS] enable 64-bit inode numbers.
1149 If zero, the NFS client will fake up a 32-bit inode
1150 number for the readdir() and stat() syscalls instead
1151 of returning the full 64-bit number.
1152 The default is to return 64-bit inode numbers.
1154 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1155 when a NMI is triggered.
1156 Format: [state][,regs][,debounce][,die]
1158 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1160 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1161 emulation library even if a 387 maths coprocessor
1164 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1165 caches in the slab allocator. Saves per-node memory,
1166 but will impact performance.
1170 noapic [SMP,APIC] Tells the kernel to not make use of any
1171 IOAPICs that may be present in the system.
1173 nobats [PPC] Do not use BATs for mapping kernel lowmem
1174 on "Classic" PPC cores.
1178 nodelayacct [KNL] Disable per-task delay accounting
1180 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1182 noefi [X86-32,X86-64] Disable EFI runtime services support.
1186 noexec [X86-32,X86-64]
1187 noexec=on: enable non-executable mappings (default)
1188 noexec=off: disable nn-executable mappings
1190 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1191 register save and restore. The kernel will only save
1192 legacy floating-point registers on task switch.
1194 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1198 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1199 instruction doesn't work correctly and not to
1202 nohalt [IA-64] Tells the kernel not to use the power saving
1203 function PAL_HALT_LIGHT when idle. This increases
1204 power-consumption. On the positive side, it reduces
1205 interrupt wake-up latency, which may improve performance
1206 in certain environments such as networked servers or
1209 nohz= [KNL] Boottime enable/disable dynamic ticks
1210 Valid arguments: on, off
1213 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1215 noirqdebug [X86-32] Disables the code which attempts to detect and
1216 disable unhandled interrupt sources.
1218 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1219 broken timer IRQ sources.
1221 noisapnp [ISAPNP] Disables ISA PnP code.
1223 noinitrd [RAM] Tells the kernel not to load any configured
1228 nojitter [IA64] Disables jitter checking for ITC timers.
1230 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1232 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1234 noltlbs [PPC] Do not use large page/tlb entries for kernel
1235 lowmem mapping on PPC40x.
1237 nomca [IA-64] Disable machine check abort handling
1239 nomce [X86-32] Machine Check Exception
1241 nomfgpt [X86-32] Disable Multi-Function General Purpose
1242 Timer usage (for AMD Geode machines).
1244 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1246 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1247 with UP alternatives
1249 noresidual [PPC] Don't use residual data on PReP machines.
1251 noresume [SWSUSP] Disables resume and restores original swap
1254 no-scroll [VGA] Disables scrollback.
1255 This is required for the Braillex ib80-piezo Braille
1256 reader made by F.H. Papenmeier (Germany).
1260 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1262 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1263 and disable the IO APIC. legacy for "maxcpus=0".
1265 nosoftlockup [KNL] Disable the soft-lockup detector.
1267 nosync [HW,M68K] Disables sync negotiation for all devices.
1269 notsc [BUGS=X86-32] Disable Time Stamp Counter
1271 nousb [USB] Disable the USB subsystem
1275 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1276 one of ['zone', 'node', 'default'] can be specified
1277 This can be set from sysctl after boot.
1278 See Documentation/sysctl/vm.txt for details.
1280 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1285 oprofile.timer= [HW]
1286 Use timer interrupt instead of performance counters
1288 osst= [HW,SCSI] SCSI Tape Driver
1289 Format: <buffer_size>,<write_threshold>
1290 See also Documentation/scsi/st.txt.
1292 panic= [KNL] Kernel behaviour on panic
1295 parkbd.port= [HW] Parallel port number the keyboard adapter is
1296 connected to, default is 0.
1298 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1299 0 for XT, 1 for AT (default is AT).
1302 parport= [HW,PPT] Specify parallel ports. 0 disables.
1303 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1304 Use 'auto' to force the driver to use any
1305 IRQ/DMA settings detected (the default is to
1306 ignore detected IRQ/DMA settings because of
1307 possible conflicts). You can specify the base
1308 address, IRQ, and DMA settings; IRQ and DMA
1309 should be numbers, or 'auto' (for using detected
1310 settings on that particular port), or 'nofifo'
1311 (to avoid using a FIFO even if it is detected).
1312 Parallel ports are assigned in the order they
1313 are specified on the command line, starting
1316 parport_init_mode= [HW,PPT]
1317 Configure VIA parallel port to operate in
1318 a specific mode. This is necessary on Pegasos
1319 computer where firmware has no options for setting
1320 up parallel port mode and sets it to spp.
1321 Currently this function knows 686a and 8231 chips.
1322 Format: [spp|ps2|epp|ecp|ecpepp]
1324 pas2= [HW,OSS] Format:
1325 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1328 See header of drivers/scsi/pas16.c.
1331 Halt all CPUs after the first oops has been printed for
1332 the specified number of seconds. This is to be used if
1333 your oopses keep scrolling off the screen.
1338 See header of drivers/block/paride/pcd.c.
1339 See also Documentation/paride.txt.
1341 pci=option[,option...] [PCI] various PCI subsystem options:
1342 off [X86-32] don't probe for the PCI bus
1343 bios [X86-32] force use of PCI BIOS, don't access
1344 the hardware directly. Use this if your machine
1345 has a non-standard PCI host bridge.
1346 nobios [X86-32] disallow use of PCI BIOS, only direct
1347 hardware access methods are allowed. Use this
1348 if you experience crashes upon bootup and you
1349 suspect they are caused by the BIOS.
1350 conf1 [X86-32] Force use of PCI Configuration
1352 conf2 [X86-32] Force use of PCI Configuration
1354 noaer [PCIE] If the PCIEAER kernel config parameter is
1355 enabled, this kernel boot option can be used to
1356 disable the use of PCIE advanced error reporting.
1357 nodomains [PCI] Disable support for multiple PCI
1358 root domains (aka PCI segments, in ACPI-speak).
1359 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1361 nomsi [MSI] If the PCI_MSI kernel config parameter is
1362 enabled, this kernel boot option can be used to
1363 disable the use of MSI interrupts system-wide.
1364 nosort [X86-32] Don't sort PCI devices according to
1365 order given by the PCI BIOS. This sorting is
1366 done to get a device order compatible with
1368 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1369 routing table. These calls are known to be buggy
1370 on several machines and they hang the machine
1371 when used, but on other computers it's the only
1372 way to get the interrupt routing table. Try
1373 this option if the kernel is unable to allocate
1374 IRQs or discover secondary PCI buses on your
1376 rom [X86-32] Assign address space to expansion ROMs.
1377 Use with caution as certain devices share
1378 address decoders between ROMs and other
1380 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1381 assigned automatically to PCI devices. You can
1382 make the kernel exclude IRQs of your ISA cards
1384 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1385 of the PIRQ table (normally generated
1386 by the BIOS) if it is outside the
1387 F0000h-100000h range.
1388 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1389 useful if the kernel is unable to find your
1390 secondary buses and you want to tell it
1391 explicitly which ones they are.
1392 assign-busses [X86-32] Always assign all PCI bus
1393 numbers ourselves, overriding
1394 whatever the firmware may have done.
1395 usepirqmask [X86-32] Honor the possible IRQ mask stored
1396 in the BIOS $PIR table. This is needed on
1397 some systems with broken BIOSes, notably
1398 some HP Pavilion N5400 and Omnibook XE3
1399 notebooks. This will have no effect if ACPI
1400 IRQ routing is enabled.
1401 noacpi [X86-32] Do not use ACPI for IRQ routing
1402 or for PCI scanning.
1403 use_crs [X86-32] Use _CRS for PCI resource
1405 routeirq Do IRQ routing for all PCI devices.
1406 This is normally done in pci_enable_device(),
1407 so this option is a temporary workaround
1408 for broken drivers that don't call it.
1409 firmware [ARM] Do not re-enumerate the bus but instead
1410 just use the configuration from the
1411 bootloader. This is currently used on
1412 IXP2000 systems where the bus has to be
1413 configured a certain way for adjunct CPUs.
1414 noearly [X86] Don't do any early type 1 scanning.
1415 This might help on some broken boards which
1416 machine check when some devices' config space
1417 is read. But various workarounds are disabled
1418 and some IOMMU drivers will not work.
1419 bfsort Sort PCI devices into breadth-first order.
1420 This sorting is done to get a device
1421 order compatible with older (<= 2.4) kernels.
1422 nobfsort Don't sort PCI devices into breadth-first order.
1423 cbiosize=nn[KMG] The fixed amount of bus space which is
1424 reserved for the CardBus bridge's IO window.
1425 The default value is 256 bytes.
1426 cbmemsize=nn[KMG] The fixed amount of bus space which is
1427 reserved for the CardBus bridge's memory
1428 window. The default value is 64 megabytes.
1430 pcmv= [HW,PCMCIA] BadgePAD 4
1433 See Documentation/paride.txt.
1435 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1438 See arch/parisc/kernel/pdc_chassis.c
1441 See Documentation/paride.txt.
1444 See Documentation/paride.txt.
1446 pirq= [SMP,APIC] Manual mp-table setup
1447 See Documentation/i386/IO-APIC.txt.
1449 plip= [PPT,NET] Parallel port network link
1450 Format: { parport<nr> | timid | 0 }
1451 See also Documentation/parport.txt.
1457 { on | off | curr | res | no-curr | no-res }
1460 [ISAPNP] Exclude IRQs for the autoconfiguration
1463 [ISAPNP] Exclude DMAs for the autoconfiguration
1465 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1466 Ranges are in pairs (I/O port base and size).
1469 [ISAPNP] Exclude memory regions for the
1471 Ranges are in pairs (memory base and size).
1473 print-fatal-signals=
1474 [KNL] debug: print fatal signals
1475 print-fatal-signals=1: print segfault info to
1479 printk.time= Show timing data prefixed to each printk message line
1480 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1482 profile= [KNL] Enable kernel profiling via /proc/profile
1483 Format: [schedule,]<number>
1484 Param: "schedule" - profile schedule points.
1485 Param: <number> - step/bucket size as a power of 2 for
1486 statistical time based profiling.
1487 Param: "sleep" - profile D-state sleeping (millisecs).
1488 Requires CONFIG_SCHEDSTATS
1489 Param: "kvm" - profile VM exits.
1491 processor.max_cstate= [HW,ACPI]
1492 Limit processor to maximum C-state
1493 max_cstate=9 overrides any DMI blacklist limit.
1495 processor.nocst [HW,ACPI]
1496 Ignore the _CST method to determine C-states,
1497 instead using the legacy FADT method
1499 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1501 See Documentation/ramdisk.txt.
1503 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1504 probe for; one of (bare|imps|exps|lifebook|any).
1505 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1507 psmouse.resetafter= [HW,MOUSE]
1508 Try to reset the device after so many bad packets
1511 [HW,MOUSE] Set desired mouse resolution, in dpi.
1512 psmouse.smartscroll=
1513 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1514 0 = disabled, 1 = enabled (default).
1516 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1518 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1521 See Documentation/paride.txt.
1524 [KNL] Number of legacy pty's. Overwrites compiled-in
1527 quiet [KNL] Disable most log messages
1532 See Documentation/md.txt.
1534 ramdisk_blocksize= [RAM]
1535 See Documentation/ramdisk.txt.
1537 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1538 See Documentation/ramdisk.txt.
1540 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1541 RCU callbacks to process in one batch.
1543 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1544 RCU callbacks over which batch limiting is disabled.
1546 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1547 RCU callbacks below which batch limiting is re-enabled.
1551 Run specified binary instead of /init from the ramdisk,
1552 used for early userspace startup. See initrd.
1554 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1555 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1556 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1558 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1560 reservetop= [X86-32]
1562 Reserves a hole at the top of the kernel virtual
1565 reset_devices [KNL] Force drivers to reset the underlying device
1566 during initialization.
1569 Specify the partition device for software suspend
1571 resume_offset= [SWSUSP]
1572 Specify the offset from the beginning of the partition
1573 given by "resume=" at which the swap header is located,
1574 in <PAGE_SIZE> units (needed only for swap files).
1575 See Documentation/power/swsusp-and-swap-files.txt
1577 retain_initrd [RAM] Keep initrd memory after extraction
1579 rhash_entries= [KNL,NET]
1580 Set number of hash buckets for route cache
1582 riscom8= [HW,SERIAL]
1583 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1585 ro [KNL] Mount root device read-only on boot
1587 root= [KNL] Root filesystem
1589 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1590 mount the root filesystem
1592 rootflags= [KNL] Set root filesystem mount option string
1594 rootfstype= [KNL] Set root filesystem type
1596 rootwait [KNL] Wait (indefinitely) for root device to show up.
1597 Useful for devices that are detected asynchronously
1598 (e.g. USB and MMC devices).
1600 root_plug.vendor_id=
1601 [ROOTPLUG] Override the default vendor ID
1603 root_plug.product_id=
1604 [ROOTPLUG] Override the default product ID
1607 [ROOTPLUG] Enable debugging output
1609 rw [KNL] Mount root device read-write on boot
1611 S [KNL] Run init in single mode
1614 See drivers/net/irda/sa1100_ir.c.
1616 sbni= [NET] Granch SBNI12 leased line adapter
1618 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1619 Format: <io>[,<timeout>[,<isapnp>]]
1621 scsi_debug_*= [SCSI]
1622 See drivers/scsi/scsi_debug.c.
1624 scsi_default_dev_flags=
1625 [SCSI] SCSI default device flags
1628 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1629 Format: <vendor>:<model>:<flags>
1630 (flags are integer value)
1632 scsi_logging_level= [SCSI] a bit mask of logging levels
1633 See drivers/scsi/scsi_logging.h for bits. Also
1634 settable via sysctl at dev.scsi.logging_level
1635 (/proc/sys/dev/scsi/logging_level).
1636 There is also a nice 'scsi_logging_level' script in the
1637 S390-tools package, available for download at
1638 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1640 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1641 discovered. async scans them in kernel threads,
1642 allowing boot to proceed. none ignores them, expecting
1643 user space to do the scan.
1645 selinux [SELINUX] Disable or enable SELinux at boot time.
1646 Format: { "0" | "1" }
1647 See security/selinux/Kconfig help text.
1650 Default value is set via kernel config option.
1651 If enabled at boot time, /selinux/disable can be used
1652 later to disable prior to initial policy load.
1654 selinux_compat_net =
1655 [SELINUX] Set initial selinux_compat_net flag value.
1656 Format: { "0" | "1" }
1657 0 -- use new secmark-based packet controls
1658 1 -- use legacy packet controls
1659 Default value is 0 (preferred).
1660 Value can be changed at runtime via
1661 /selinux/compat_net.
1663 serialnumber [BUGS=X86-32]
1666 Maximal number of shapers.
1669 See header of drivers/scsi/sim710.c.
1676 slub_debug[=options[,slabs]] [MM, SLUB]
1677 Enabling slub_debug allows one to determine the
1678 culprit if slab objects become corrupted. Enabling
1679 slub_debug can create guard zones around objects and
1680 may poison objects when not in use. Also tracks the
1681 last alloc / free. For more information see
1682 Documentation/vm/slub.txt.
1684 slub_max_order= [MM, SLUB]
1685 Determines the maximum allowed order for slabs.
1686 A high setting may cause OOMs due to memory
1687 fragmentation. For more information see
1688 Documentation/vm/slub.txt.
1690 slub_min_objects= [MM, SLUB]
1691 The minimum number of objects per slab. SLUB will
1692 increase the slab order up to slub_max_order to
1693 generate a sufficiently large slab able to contain
1694 the number of objects indicated. The higher the number
1695 of objects the smaller the overhead of tracking slabs
1696 and the less frequently locks need to be acquired.
1697 For more information see Documentation/vm/slub.txt.
1699 slub_min_order= [MM, SLUB]
1700 Determines the mininum page order for slabs. Must be
1701 lower than slub_max_order.
1702 For more information see Documentation/vm/slub.txt.
1704 slub_nomerge [MM, SLUB]
1705 Disable merging of slabs with similar size. May be
1706 necessary if there is some reason to distinguish
1707 allocs to different slabs. Debug options disable
1708 merging on their own.
1709 For more information see Documentation/vm/slub.txt.
1712 Format: <io1>[,<io2>[,...,<io8>]]
1714 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1715 attempt to substitute SMP alternatives once at boot.
1717 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1718 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1719 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1720 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1721 smsc-ircc2.ircc_irq= [HW] IRQ line
1722 smsc-ircc2.ircc_dma= [HW] DMA channel
1723 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1724 0: Toshiba Satellite 1800 (GP data pin select)
1725 1: Fast pin select (default)
1728 snd-ad1816a= [HW,ALSA]
1730 snd-ad1848= [HW,ALSA]
1732 snd-ali5451= [HW,ALSA]
1734 snd-als100= [HW,ALSA]
1736 snd-als4000= [HW,ALSA]
1738 snd-azt2320= [HW,ALSA]
1740 snd-cmi8330= [HW,ALSA]
1742 snd-cmipci= [HW,ALSA]
1744 snd-cs4231= [HW,ALSA]
1746 snd-cs4232= [HW,ALSA]
1748 snd-cs4236= [HW,ALSA]
1750 snd-cs4281= [HW,ALSA]
1752 snd-cs46xx= [HW,ALSA]
1754 snd-dt019x= [HW,ALSA]
1756 snd-dummy= [HW,ALSA]
1758 snd-emu10k1= [HW,ALSA]
1760 snd-ens1370= [HW,ALSA]
1762 snd-ens1371= [HW,ALSA]
1764 snd-es968= [HW,ALSA]
1766 snd-es1688= [HW,ALSA]
1768 snd-es18xx= [HW,ALSA]
1770 snd-es1938= [HW,ALSA]
1772 snd-es1968= [HW,ALSA]
1774 snd-fm801= [HW,ALSA]
1776 snd-gusclassic= [HW,ALSA]
1778 snd-gusextreme= [HW,ALSA]
1780 snd-gusmax= [HW,ALSA]
1784 snd-ice1712= [HW,ALSA]
1786 snd-intel8x0= [HW,ALSA]
1788 snd-interwave= [HW,ALSA]
1793 snd-korg1212= [HW,ALSA]
1795 snd-maestro3= [HW,ALSA]
1797 snd-mpu401= [HW,ALSA]
1799 snd-mtpav= [HW,ALSA]
1801 snd-nm256= [HW,ALSA]
1803 snd-opl3sa2= [HW,ALSA]
1811 snd-opti93x= [HW,ALSA]
1815 snd-rme32= [HW,ALSA]
1817 snd-rme96= [HW,ALSA]
1819 snd-rme9652= [HW,ALSA]
1825 snd-sbawe= [HW,ALSA]
1827 snd-serial= [HW,ALSA]
1829 snd-sgalaxy= [HW,ALSA]
1831 snd-sonicvibes= [HW,ALSA]
1836 snd-sun-cs4231= [HW,ALSA]
1838 snd-trident= [HW,ALSA]
1840 snd-usb-audio= [HW,ALSA,USB]
1842 snd-via82xx= [HW,ALSA]
1844 snd-virmidi= [HW,ALSA]
1846 snd-wavefront= [HW,ALSA]
1848 snd-ymfpci= [HW,ALSA]
1850 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1851 See Documentation/sonypi.txt
1853 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1854 See Documentation/specialix.txt.
1856 spia_io_base= [HW,MTD]
1862 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1864 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1865 See Documentation/scsi/st.txt.
1868 See header of drivers/scsi/seagate.c.
1872 Set the STI (builtin display/keyboard on the HP-PARISC
1873 machines) console (graphic card) which should be used
1874 as the initial boot-console.
1875 See also comment in drivers/video/console/sticore.c.
1878 See comment in drivers/video/console/sticore.c.
1881 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1885 Control how the NFS server code allocates CPUs to
1886 service thread pools. Depending on how many NICs
1887 you have and where their interrupts are bound, this
1888 option will affect which CPUs will do NFS serving.
1889 Note: this parameter cannot be changed while the
1890 NFS server is running.
1892 auto the server chooses an appropriate mode
1893 automatically using heuristics
1894 global a single global pool contains all CPUs
1895 percpu one pool for each CPU
1896 pernode one pool for each NUMA node (equivalent
1897 to global on non-NUMA machines)
1899 swiotlb= [IA-64] Number of I/O TLB slabs
1903 sym53c416= [HW,SCSI]
1904 See header of drivers/scsi/sym53c416.c.
1906 sysrq_always_enabled
1908 Ignore sysrq setting - this boot parameter will
1909 neutralize any effect of /proc/sys/kernel/sysrq.
1910 Useful for debugging.
1913 See header of drivers/scsi/t128.c.
1917 thash_entries= [KNL,NET]
1918 Set number of hash buckets for TCP connection
1920 thermal.act= [HW,ACPI]
1921 -1: disable all active trip points in all thermal zones
1922 <degrees C>: override all lowest active trip points
1924 thermal.crt= [HW,ACPI]
1925 -1: disable all critical trip points in all thermal zones
1926 <degrees C>: lower all critical trip points
1928 thermal.nocrt= [HW,ACPI]
1929 Set to disable actions on ACPI thermal zone
1930 critical and hot trip points.
1932 thermal.off= [HW,ACPI]
1933 1: disable ACPI thermal control
1935 thermal.psv= [HW,ACPI]
1936 -1: disable all passive trip points
1937 <degrees C>: override all passive trip points to this value
1939 thermal.tzp= [HW,ACPI]
1940 Specify global default ACPI thermal zone polling rate
1941 <deci-seconds>: poll all this frequency
1942 0: no polling (default)
1944 time Show timing data prefixed to each printk message line
1945 [deprecated, see 'printk.time']
1947 tipar.timeout= [HW,PPT]
1948 Set communications timeout in tenths of a second
1951 tipar.delay= [HW,PPT]
1952 Set inter-bit delay in microseconds (default 10).
1955 See header of drivers/scsi/seagate.c.
1958 See comment before function dc390_setup() in
1959 drivers/scsi/tmscsim.c.
1963 trix= [HW,OSS] MediaTrix AudioTrix Pro
1965 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1967 turbografx.map[2|3]= [HW,JOY]
1968 TurboGraFX parallel port interface
1970 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1971 See also Documentation/input/joystick-parport.txt
1973 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1974 See header of drivers/scsi/u14-34f.c.
1983 [USB] Ignore overcurrent events (default N).
1984 Some badly-designed motherboards generate lots of
1985 bogus events, for ports that aren't wired to
1986 anything. Set this parameter to avoid log spamming.
1987 Note that genuine overcurrent events won't be
1990 usbcore.autosuspend=
1991 [USB] The autosuspend time delay (in seconds) used
1992 for newly-detected USB devices (default 2). This
1993 is the time required before an idle device will be
1994 autosuspended. Devices for which the delay is set
1995 to a negative value won't be autosuspended at all.
1998 [USBHID] The interval which mice are to be polled at.
2000 vdso= [X86-32,SH,x86-64]
2001 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2002 vdso=1: enable VDSO (default)
2003 vdso=0: disable VDSO mapping
2005 vdso32= [X86-32,X86-64]
2006 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2007 vdso32=1: enable 32-bit VDSO (default)
2008 vdso32=0: disable 32-bit VDSO mapping
2011 vector=percpu: enable percpu vector domain
2013 video= [FB] Frame buffer configuration
2014 See Documentation/fb/modedb.txt.
2016 vga= [BOOT,X86-32] Select a particular video mode
2017 See Documentation/i386/boot.txt and
2018 Documentation/svga.txt.
2019 Use vga=ask for menu.
2020 This is actually a boot loader parameter; the value is
2021 passed to the kernel using a special protocol.
2023 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2024 size of <nn>. This can be used to increase the
2025 minimum size (128MB on x86). It can also be used to
2026 decrease the size and leave more room for directly
2029 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2032 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2035 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2038 waveartist= [HW,OSS]
2039 Format: <io>,<irq>,<dma>,<dma2>
2042 See header of drivers/scsi/wd33c93.c.
2045 See header of drivers/scsi/wd7000.c.
2048 See Documentation/watchdog/wdt.txt.
2050 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2051 xd_geo= See header of drivers/block/xd.c.
2053 xirc2ps_cs= [NET,PCMCIA]
2055 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2057 norandmaps Don't use address space randomization
2058 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2060 ______________________________________________________________________
2064 Add documentation for ALSA options.
2065 Add more DRM drivers.