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/power/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, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
183 acpi_serialize [HW,ACPI] force serialization of AML methods
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
193 acpi.debug_layer= [HW,ACPI]
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
210 acpi.debug_level= [HW,ACPI]
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
228 acpi_pm_good [X86-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
263 See Documentation/scsi/aha152x.txt.
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
269 See Documentation/scsi/aic7xxx.txt.
272 See Documentation/scsi/aic79xx.txt.
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
277 See also Documentation/kernel/input/joystick.txt
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
285 Power management functions (SPARCstation-4/5 + deriv.)
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
328 baycom_epp= [HW,AX25]
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
395 Value can be changed at runtime via
396 /selinux/checkreqprot.
399 See Documentation/s390/CommonIO for details.
402 See Documentation/s390/CommonIO for details.
404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
406 Forces specified clocksource (if available) to be used
407 when calculating gettimeofday(). If specified
408 clocksource is not available, it defaults to PIT.
409 Format: { pit | tsc | cyclone | pmtmr }
411 clocksource= [GENERIC_TIME] Override the default clocksource
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
417 [all] jiffies (this is the base, fallback clocksource)
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
422 [X86-32] pit,hpet,tsc,vmi-timer;
423 scx200_hrt on Geode; cyclone on IBM x440
431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
444 code_bytes [IA32/X86_64] How many bytes of object code to print
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
458 force: allow force enabled of undocumented chips (ICH4,
461 com20020= [HW,NET] ARCnet - COM20020 chipset
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
469 ARCnet - COM90xx chipset (memory-mapped buffers)
470 Format: <io>[,<irq>[,<memstart>]]
472 condev= [HW,S390] console device
475 console= [KNL] Output console device and options.
477 tty<n> Use the virtual console device <n>.
481 Use the specified serial port. The options are of
482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
487 See Documentation/serial-console.txt for more
489 Documentation/networking/netconsole.txt for an
492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
499 If the device connected to the port is not a TTY but a braille
500 device, prepend "brl," before the device type, for instance
502 For now, only VisioBraille is supported.
504 earlycon= [KNL] Output early console device and options.
505 uart[8250],io,<addr>[,options]
506 uart[8250],mmio,<addr>[,options]
507 Start an early, polled-mode console on the 8250/16550
508 UART at the specified I/O port or MMIO address.
509 The options are the same as for ttyS, above.
512 [HW] Never suspend the console
513 Disable suspending of consoles during suspend and
514 hibernate operations. Once disabled, debugging
515 messages can reach various consoles while the rest
516 of the system is being put to sleep (ie, while
517 debugging driver suspend/resume hooks). This may
518 not work reliably with all consoles, but is known
519 to work with serial and VGA consoles.
521 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
523 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
525 crashkernel=nn[KMG]@ss[KMG]
526 [KNL] Reserve a chunk of physical memory to
527 hold a kernel to switch to with kexec on panic.
529 crashkernel=range1:size1[,range2:size2,...][@offset]
530 [KNL] Same as above, but depends on the memory
531 in the running system. The syntax of range is
532 start-[end] where start and end are both
533 a memory unit (amount[KMG]). See also
534 Documentation/kdump/kdump.txt for a example.
537 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
542 cs89x0_media= [HW,NET]
543 Format: { rj45 | aui | bnc }
546 See header of drivers/s390/block/dasd_devmap.c.
548 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
549 (one device per port)
550 Format: <port#>,<type>
551 See also Documentation/input/joystick-parport.txt
553 debug [KNL] Enable kernel debugging (events log level).
556 [KNL] verbose self-tests
558 Print debugging info while doing the locking API
560 We default to 0 (no extra messages), setting it to
561 1 will print _a lot_ more information - normally
562 only useful to kernel developers.
564 decnet.addr= [HW,NET]
565 Format: <area>[,<node>]
566 See also Documentation/networking/decnet.txt.
569 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
570 Change the default blue palette of the console.
571 This is a 16-member array composed of values
575 Format: <green0>,<green1>,<green2>,...,<green15>
576 Change the default green palette of the console.
577 This is a 16-member array composed of values
581 Format: <red0>,<red1>,<red2>,...,<red15>
582 Change the default red palette of the console.
583 This is a 16-member array composed of values
589 Set system-wide default UTF-8 mode for all tty's.
590 Default is 1, i.e. UTF-8 mode is enabled for all
591 newly opened terminals.
594 Set number of hash buckets for dentry cache.
597 IO parameters + enable/disable command.
599 digiepca= [HW,SERIAL]
600 See drivers/char/README.epca and
601 Documentation/digiepca.txt.
603 disable_mtrr_trim [X86, Intel and AMD only]
604 By default the kernel will trim any uncacheable
605 memory out of your available memory pool based on
606 MTRR settings. This parameter disables that behavior,
607 possibly causing your machine to run very slowly.
609 dmasound= [HW,OSS] Sound subsystem buffers
615 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
617 earlyprintk=serial[,ttySn[,baudrate]]
619 Append ",keep" to not disable it when the real console
622 Only vga or serial at a time, not both.
624 Currently only ttyS0 and ttyS1 are supported.
626 Interaction with the standard serial driver is not
629 The VGA output is eventually overwritten by the real
635 Format: {"off" | "on" | "skip[mbr]"}
637 eisa_irq_edge= [PARISC,HW]
638 See header of drivers/parisc/eisa.c.
641 See comment before function elanfreq_setup() in
642 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
645 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
646 See Documentation/block/as-iosched.txt and
647 Documentation/block/deadline-iosched.txt for details.
649 elfcorehdr= [X86-32, X86_64]
650 Specifies physical address of start of kernel core
651 image elf header. Generally kexec loader will
652 pass this option to capture kernel.
653 See Documentation/kdump/kdump.txt for details.
655 enforcing [SELINUX] Set initial enforcing status.
657 See security/selinux/Kconfig help text.
658 0 -- permissive (log only, no denials).
659 1 -- enforcing (deny and log).
661 Value can be changed at runtime via /selinux/enforce.
664 Format: <spdif>,[<nomix>,[<amplifier>]]
665 See also header of sound/oss/es1371.c.
667 ether= [HW,NET] Ethernet cards parameters
668 This option is obsoleted by the "netdev=" option, which
669 has equivalent usage. See its documentation for details.
671 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
676 fail_make_request=[KNL]
677 General fault injection mechanism.
678 Format: <interval>,<probability>,<space>,<times>
679 See also /Documentation/fault-injection/.
682 See header of drivers/scsi/fd_mcs.c.
685 See header of drivers/scsi/fdomain.c.
688 See Documentation/floppy.txt.
691 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
692 support via parallel port (up to 5 devices per port)
693 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
694 See also Documentation/input/joystick-parport.txt
698 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
703 See header of drivers/scsi/gdth.c.
705 gpt [EFI] Forces disk with valid GPT signature but
706 invalid Protective MBR to be treated as GPT.
710 hashdist= [KNL,NUMA] Large hashes allocated during boot
711 are distributed across NUMA nodes. Defaults on
712 for IA-64, off otherwise.
713 Format: 0 | 1 (for off | on)
715 hcl= [IA-64] SGI's Hardware Graph compatibility layer
717 hd= [EIDE] (E)IDE hard drive subsystem geometry
718 Format: <cyl>,<head>,<sect>
720 hd?= [HW] (E)IDE subsystem
721 hd?lun= See Documentation/ide/ide.txt.
723 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
724 size of <nn>. This works even on boxes that have no
725 highmem otherwise. This also works to reduce highmem
726 size on bigger boxes.
728 highres= [KNL] Enable/disable high resolution timer mode.
729 Valid parameters: "on", "off"
733 See Documentation/isdn/README.HiSax.
735 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
736 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
738 i8042.direct [HW] Put keyboard port into non-translated mode
739 i8042.dumbkbd [HW] Pretend that controller can only read data from
740 keyboard and cannot control its state
741 (Don't attempt to blink the leds)
742 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
743 i8042.nokbd [HW] Don't check/create keyboard port
744 i8042.noloop [HW] Disable the AUX Loopback command while probing
746 i8042.nomux [HW] Don't check presence of an active multiplexing
748 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
751 [HW] Frequency with which keyboard LEDs should blink
752 when kernel panics (default is 0.5 sec)
753 i8042.reset [HW] Reset the controller during init and cleanup
754 i8042.unlock [HW] Unlock (ignore) the keylock
758 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
759 indicates that the driver is running on unsupported
761 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
762 does not match list of supported models.
764 [HW] Report power status in /proc/i8k
765 (disabled by default)
766 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
769 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
770 See Documentation/mca.txt.
773 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
775 ide= [HW] (E)IDE subsystem
776 Format: ide=nodma or ide=doubler
777 See Documentation/ide/ide.txt.
779 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
780 See Documentation/ide/ide.txt.
783 Format: idle=poll or idle=mwait
784 Poll forces a polling idle loop that can slightly improves the performance
785 of waking up a idle CPU, but will use a lot of power and make the system
786 run hot. Not recommended.
787 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
788 to not use it because it doesn't save as much power as a normal idle
789 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
792 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
793 Claim all unknown PCI IDE storage controllers.
795 ignore_loglevel [KNL]
796 Ignore loglevel setting - this will print /all/
797 kernel messages to the console. Useful for debugging.
800 Set number of hash buckets for inode cache.
803 See header of drivers/scsi/in2000.c.
807 Run specified binary instead of /sbin/init as init
810 initcall_debug [KNL] Trace initcalls as they are executed. Useful
811 for working out where the kernel is dying during
814 initrd= [BOOT] Specify the location of the initial ramdisk
816 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
834 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
836 Disable intel iommu driver.
837 igfx_off [Default Off]
838 By default, gfx is mapped as normal device. If a gfx
839 device has a dedicated DMAR unit, the DMAR unit is
840 bypassed by not enabling DMAR with this option. In
841 this case, gfx device will use physical address for
844 With this option iommu will not optimize to look
845 for io virtual address below 32 bit forcing dual
846 address cycle on pci bus for cards supporting greater
847 than 32 bit addressing. The default is to look
848 for translation below 32 bit and if not available
849 then look in the higher range.
851 With this option on every unmap_single operation will
852 result in a hardware IOTLB flush operation as opposed
853 to batching them for performance.
855 io_delay= [X86-32,X86-64] I/O delay method
857 Standard port 0x80 based delay
859 Alternate port 0xed based delay (needed on some systems)
861 Simple two microseconds delay
865 io7= [HW] IO7 for Marvel based alpha systems
866 See comment before marvel_specify_io7 in
867 arch/alpha/kernel/core_marvel.c.
870 See Documentation/filesystems/nfsroot.txt.
872 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
873 See comment before ip2_setup() in
874 drivers/char/ip2/ip2base.c.
876 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
877 See header of drivers/scsi/ips.c.
879 ports= [IP_VS_FTP] IPVS ftp helper module
881 Up to 8 (IP_VS_APP_MAX_PORTS) ports
883 Format: <port>,<port>....
886 When an interrupt is not handled search all handlers
887 for it. Intended to get systems with badly broken
891 When an interrupt is not handled search all handlers
892 for it. Also check all handlers each timer
893 interrupt. Intended to get systems with badly broken
897 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
899 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
901 <cpu number>,...,<cpu number>
903 <cpu number>-<cpu number> (must be a positive range in ascending order)
905 <cpu number>,...,<cpu number>-<cpu number>
906 This option can be used to specify one or more CPUs
907 to isolate from the general SMP balancing and scheduling
908 algorithms. The only way to move a process onto or off
909 an "isolated" CPU is via the CPU affinity syscalls.
910 <cpu number> begins at 0 and the maximum value is
911 "number of CPUs in system - 1".
913 This option is the preferred way to isolate CPUs. The
914 alternative -- manually setting the CPU mask of all
915 tasks in the system -- can cause problems and
916 suboptimal load balancer performance.
920 js= [HW,JOY] Analog joystick
921 See Documentation/input/joystick.txt.
923 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
924 specifies the amount of memory usable by the kernel
925 for non-movable allocations. The requested amount is
926 spread evenly throughout all nodes in the system. The
927 remaining memory in each node is used for Movable
928 pages. In the event, a node is too small to have both
929 kernelcore and Movable pages, kernelcore pages will
930 take priority and other nodes will have a larger number
931 of kernelcore pages. The Movable zone is used for the
932 allocation of pages that may be reclaimed or moved
933 by the page migration subsystem. This means that
934 HugeTLB pages may not be allocated from this zone.
935 Note that allocations like PTEs-from-HighMem still
936 use the HighMem zone if it exists, and the Normal
939 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
940 is similar to kernelcore except it specifies the
941 amount of memory used for migratable allocations.
942 If both kernelcore and movablecore is specified,
943 then kernelcore will be at *least* the specified
944 value but may be more. If movablecore on its own
945 is specified, the administrator must be careful
946 that the amount of memory usable for all allocations
951 kstack=N [X86-32,X86-64] Print N words from the kernel stack
954 kgdboc= [HW] kgdb over consoles.
955 Requires a tty driver that supports console polling.
956 (only serial suported for now)
957 Format: <serial_device>[,baud]
963 lapic [X86-32,APIC] Enable the local APIC even if BIOS
966 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
969 libata.dma= [LIBATA] DMA control
970 libata.dma=0 Disable all PATA and SATA DMA
971 libata.dma=1 PATA and SATA Disk DMA only
972 libata.dma=2 ATAPI (CDROM) DMA only
973 libata.dma=4 Compact Flash DMA only
974 Combinations also work, so libata.dma=3 enables DMA
975 for disks and CDROMs, but not CFs.
977 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
981 libata.force= [LIBATA] Force configurations. The format is comma
982 separated list of "[ID:]VAL" where ID is
983 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
984 matching port, link or device. Basically, it matches
985 the ATA ID string printed on console by libata. If
986 the whole ID part is omitted, the last PORT and DEVICE
987 values are used. If ID hasn't been specified yet, the
988 configuration applies to all ports, links and devices.
990 If only DEVICE is omitted, the parameter applies to
991 the port and all links and devices behind it. DEVICE
992 number of 0 either selects the first device or the
993 first fan-out link behind PMP device. It does not
994 select the host link. DEVICE number of 15 selects the
995 host link and device attached to it.
997 The VAL specifies the configuration to force. As long
998 as there's no ambiguity shortcut notation is allowed.
999 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1000 The following configurations can be forced.
1002 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1003 Any ID with matching PORT is used.
1005 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1007 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1008 udma[/][16,25,33,44,66,100,133] notation is also
1011 * [no]ncq: Turn on or off NCQ.
1013 If there are multiple matching configurations changing
1014 the same attribute, the last one is used.
1016 load_ramdisk= [RAM] List of ramdisks to load from floppy
1017 See Documentation/ramdisk.txt.
1019 lockd.nlm_grace_period=P [NFS] Assign grace period.
1022 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1025 lockd.nlm_timeout=T [NFS] Assign timeout value.
1028 lockd.nlm_udpport=M [NFS] Assign UDP port.
1031 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1034 loglevel= All Kernel Messages with a loglevel smaller than the
1035 console loglevel will be printed to the console. It can
1036 also be changed with klogd or other programs. The
1037 loglevels are defined as follows:
1039 0 (KERN_EMERG) system is unusable
1040 1 (KERN_ALERT) action must be taken immediately
1041 2 (KERN_CRIT) critical conditions
1042 3 (KERN_ERR) error conditions
1043 4 (KERN_WARNING) warning conditions
1044 5 (KERN_NOTICE) normal but significant condition
1045 6 (KERN_INFO) informational
1046 7 (KERN_DEBUG) debug-level messages
1048 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1049 Format: { n | nk | nM }
1050 n must be a power of two. The default size
1051 is set in the kernel config file.
1053 logo.nologo [FB] Disables display of the built-in Linux logo.
1054 This may be used to provide more screen space for
1055 kernel log messages and is useful when debugging
1056 kernel boot problems.
1058 lp=0 [LP] Specify parallel ports to use, e.g,
1059 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1060 lp=reset first parallel port). 'lp=0' disables the
1061 lp=auto printer driver. 'lp=reset' (which can be
1062 specified in addition to the ports) causes
1063 attached printers to be reset. Using
1064 lp=port1,port2,... specifies the parallel ports
1065 to associate lp devices with, starting with
1066 lp0. A port specification may be 'none' to skip
1067 that lp device, or a parport name such as
1068 'parport0'. Specifying 'lp=auto' instead of a
1069 port specification list means that device IDs
1070 from each port should be examined, to see if
1071 an IEEE 1284-compliant printer is attached; if
1072 so, the driver will manage that printer.
1073 See also header of drivers/char/lp.c.
1076 Sets loops_per_jiffy to given constant, thus avoiding
1077 time-consuming boot-time autodetection (up to 250 ms per
1078 CPU). 0 enables autodetection (default). To determine
1079 the correct value for your kernel, boot with normal
1080 autodetection and see what value is printed. Note that
1081 on SMP systems the preset will be applied to all CPUs,
1082 which is likely to cause problems if your CPUs need
1083 significantly divergent settings. An incorrect value
1084 will cause delays in the kernel to be wrong, leading to
1085 unpredictable I/O errors and other breakage. Although
1086 unlikely, in the extreme case this might damage your
1090 Format: <io>,<irq>,<dma>
1092 mac5380= [HW,SCSI] Format:
1093 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1095 mac53c9x= [HW,SCSI] Format:
1096 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1098 machvec= [IA64] Force the use of a particular machine-vector
1099 (machvec) in a generic kernel.
1100 Example: machvec=hpzx1_swiotlb
1102 max_loop= [LOOP] Maximum number of loopback devices that can
1106 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1107 should make use of. maxcpus=n : n >= 0 limits the
1108 kernel to using 'n' processors. n=0 is a special case,
1109 it is equivalent to "nosmp", which also disables
1112 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1113 equal to this physical address is ignored.
1115 max_luns= [SCSI] Maximum number of LUNs to probe.
1116 Should be between 1 and 2^32-1.
1119 [SCSI] Maximum number of LUNs received.
1120 Should be between 1 and 16384.
1124 mce [X86-32] Machine Check Exception
1126 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1128 md= [HW] RAID subsystems devices and level
1129 See Documentation/md.txt.
1132 Format: <first>,<last>
1133 Specifies range of consoles to be captured by the MDA.
1135 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1136 Amount of memory to be used when the kernel is not able
1137 to see the whole system memory or for test.
1138 [X86-32] Use together with memmap= to avoid physical
1139 address space collisions. Without memmap= PCI devices
1140 could be placed at addresses belonging to unused RAM.
1142 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1145 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1146 E820 memory map, as specified by the user.
1147 Such memmap=exactmap lines can be constructed based on
1148 BIOS output or other requirements. See the memmap=nn@ss
1151 memmap=nn[KMG]@ss[KMG]
1152 [KNL] Force usage of a specific region of memory
1153 Region of memory to be used, from ss to ss+nn.
1155 memmap=nn[KMG]#ss[KMG]
1156 [KNL,ACPI] Mark specific memory as ACPI data.
1157 Region of memory to be used, from ss to ss+nn.
1159 memmap=nn[KMG]$ss[KMG]
1160 [KNL,ACPI] Mark specific memory as reserved.
1161 Region of memory to be used, from ss to ss+nn.
1162 Example: Exclude memory from 0x18690000-0x1869ffff
1163 memmap=64K$0x18690000
1165 memmap=0x10000$0x18690000
1167 memtest= [KNL,X86_64] Enable memtest
1169 range: 0,4 : pattern number
1170 default : 0 <disable>
1172 meye.*= [HW] Set MotionEye Camera parameters
1173 See Documentation/video4linux/meye.txt.
1175 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1176 Multi-Function General Purpose Timers on AMD Geode
1179 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1180 the BIOS has incorrectly applied a workaround. TinyBIOS
1181 version 0.98 is known to be affected, 0.99 fixes the
1182 problem by letting the user disable the workaround.
1187 [MOUSE] Maximum time between finger touching and
1188 leaving touchpad surface for touch to be considered
1189 a tap and be reported as a left button click (for
1190 touchpads working in absolute mode only).
1192 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1193 reporting absolute coordinates, such as tablets
1194 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1195 reporting absolute coordinates, such as tablets
1200 MTD_Partition= [MTD]
1201 Format: <name>,<region-number>,<size>,<offset>
1203 MTD_Region= [MTD] Format:
1204 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1207 See drivers/mtd/cmdlinepart.c.
1209 mtouchusb.raw_coordinates=
1210 [HW] Make the MicroTouch USB driver use raw coordinates
1211 ('y', default) or cooked coordinates ('n')
1213 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1216 See header of drivers/scsi/NCR_D700.c.
1220 ncr53c400= [HW,SCSI]
1222 ncr53c400a= [HW,SCSI]
1224 ncr53c406a= [HW,SCSI]
1226 ncr53c8xx= [HW,SCSI]
1228 netdev= [NET] Network devices parameters
1229 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1230 Note that mem_start is often overloaded to mean
1231 something different and driver-specific.
1232 This usage is only documented in each driver source
1236 See Documentation/filesystems/nfsroot.txt.
1238 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1239 See Documentation/filesystems/nfsroot.txt.
1241 nfs.callback_tcpport=
1242 [NFS] set the TCP port on which the NFSv4 callback
1243 channel should listen.
1245 nfs.idmap_cache_timeout=
1246 [NFS] set the maximum lifetime for idmapper cache
1250 [NFS] enable 64-bit inode numbers.
1251 If zero, the NFS client will fake up a 32-bit inode
1252 number for the readdir() and stat() syscalls instead
1253 of returning the full 64-bit number.
1254 The default is to return 64-bit inode numbers.
1256 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1257 when a NMI is triggered.
1258 Format: [state][,regs][,debounce][,die]
1260 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1262 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1263 emulation library even if a 387 maths coprocessor
1266 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1267 caches in the slab allocator. Saves per-node memory,
1268 but will impact performance.
1272 noapic [SMP,APIC] Tells the kernel to not make use of any
1273 IOAPICs that may be present in the system.
1275 nobats [PPC] Do not use BATs for mapping kernel lowmem
1276 on "Classic" PPC cores.
1280 nodelayacct [KNL] Disable per-task delay accounting
1282 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1284 noefi [X86-32,X86-64] Disable EFI runtime services support.
1288 noexec [X86-32,X86-64]
1289 On X86-32 available only on PAE configured kernels.
1290 noexec=on: enable non-executable mappings (default)
1291 noexec=off: disable non-executable mappings
1294 This affects only 32-bit executables.
1295 noexec32=on: enable non-executable mappings (default)
1296 read doesn't imply executable mappings
1297 noexec32=off: disable non-executable mappings
1298 read implies executable mappings
1300 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1301 register save and restore. The kernel will only save
1302 legacy floating-point registers on task switch.
1304 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1308 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1309 instruction doesn't work correctly and not to
1312 nohalt [IA-64] Tells the kernel not to use the power saving
1313 function PAL_HALT_LIGHT when idle. This increases
1314 power-consumption. On the positive side, it reduces
1315 interrupt wake-up latency, which may improve performance
1316 in certain environments such as networked servers or
1319 nohz= [KNL] Boottime enable/disable dynamic ticks
1320 Valid arguments: on, off
1323 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1325 noirqdebug [X86-32] Disables the code which attempts to detect and
1326 disable unhandled interrupt sources.
1328 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1329 broken timer IRQ sources.
1331 noisapnp [ISAPNP] Disables ISA PnP code.
1333 noinitrd [RAM] Tells the kernel not to load any configured
1338 nojitter [IA64] Disables jitter checking for ITC timers.
1340 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1342 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1344 noltlbs [PPC] Do not use large page/tlb entries for kernel
1345 lowmem mapping on PPC40x.
1347 nomca [IA-64] Disable machine check abort handling
1349 nomce [X86-32] Machine Check Exception
1351 nomfgpt [X86-32] Disable Multi-Function General Purpose
1352 Timer usage (for AMD Geode machines).
1354 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1356 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1357 with UP alternatives
1359 noresidual [PPC] Don't use residual data on PReP machines.
1361 noresume [SWSUSP] Disables resume and restores original swap
1364 no-scroll [VGA] Disables scrollback.
1365 This is required for the Braillex ib80-piezo Braille
1366 reader made by F.H. Papenmeier (Germany).
1370 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1372 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1373 and disable the IO APIC. legacy for "maxcpus=0".
1375 nosoftlockup [KNL] Disable the soft-lockup detector.
1377 nosync [HW,M68K] Disables sync negotiation for all devices.
1379 notsc [BUGS=X86-32] Disable Time Stamp Counter
1381 nousb [USB] Disable the USB subsystem
1385 nptcg= [IA64] Override max number of concurrent global TLB
1386 purges which is reported from either PAL_VM_SUMMARY or
1389 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1390 one of ['zone', 'node', 'default'] can be specified
1391 This can be set from sysctl after boot.
1392 See Documentation/sysctl/vm.txt for details.
1394 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1396 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1397 Rather than timing out after 20 ms if an EC
1398 command is not properly ACKed, override the length
1399 of the timeout. We have interrupts disabled while
1400 waiting for the ACK, so if this is set too high
1401 interrupts *may* be lost!
1406 oprofile.timer= [HW]
1407 Use timer interrupt instead of performance counters
1409 osst= [HW,SCSI] SCSI Tape Driver
1410 Format: <buffer_size>,<write_threshold>
1411 See also Documentation/scsi/st.txt.
1413 panic= [KNL] Kernel behaviour on panic
1416 parkbd.port= [HW] Parallel port number the keyboard adapter is
1417 connected to, default is 0.
1419 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1420 0 for XT, 1 for AT (default is AT).
1423 parport= [HW,PPT] Specify parallel ports. 0 disables.
1424 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1425 Use 'auto' to force the driver to use any
1426 IRQ/DMA settings detected (the default is to
1427 ignore detected IRQ/DMA settings because of
1428 possible conflicts). You can specify the base
1429 address, IRQ, and DMA settings; IRQ and DMA
1430 should be numbers, or 'auto' (for using detected
1431 settings on that particular port), or 'nofifo'
1432 (to avoid using a FIFO even if it is detected).
1433 Parallel ports are assigned in the order they
1434 are specified on the command line, starting
1437 parport_init_mode= [HW,PPT]
1438 Configure VIA parallel port to operate in
1439 a specific mode. This is necessary on Pegasos
1440 computer where firmware has no options for setting
1441 up parallel port mode and sets it to spp.
1442 Currently this function knows 686a and 8231 chips.
1443 Format: [spp|ps2|epp|ecp|ecpepp]
1445 pas2= [HW,OSS] Format:
1446 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1449 See header of drivers/scsi/pas16.c.
1452 Halt all CPUs after the first oops has been printed for
1453 the specified number of seconds. This is to be used if
1454 your oopses keep scrolling off the screen.
1459 See header of drivers/block/paride/pcd.c.
1460 See also Documentation/paride.txt.
1462 pci=option[,option...] [PCI] various PCI subsystem options:
1463 off [X86-32] don't probe for the PCI bus
1464 bios [X86-32] force use of PCI BIOS, don't access
1465 the hardware directly. Use this if your machine
1466 has a non-standard PCI host bridge.
1467 nobios [X86-32] disallow use of PCI BIOS, only direct
1468 hardware access methods are allowed. Use this
1469 if you experience crashes upon bootup and you
1470 suspect they are caused by the BIOS.
1471 conf1 [X86-32] Force use of PCI Configuration
1473 conf2 [X86-32] Force use of PCI Configuration
1475 noaer [PCIE] If the PCIEAER kernel config parameter is
1476 enabled, this kernel boot option can be used to
1477 disable the use of PCIE advanced error reporting.
1478 nodomains [PCI] Disable support for multiple PCI
1479 root domains (aka PCI segments, in ACPI-speak).
1480 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1482 nomsi [MSI] If the PCI_MSI kernel config parameter is
1483 enabled, this kernel boot option can be used to
1484 disable the use of MSI interrupts system-wide.
1485 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1486 routing table. These calls are known to be buggy
1487 on several machines and they hang the machine
1488 when used, but on other computers it's the only
1489 way to get the interrupt routing table. Try
1490 this option if the kernel is unable to allocate
1491 IRQs or discover secondary PCI buses on your
1493 rom [X86-32] Assign address space to expansion ROMs.
1494 Use with caution as certain devices share
1495 address decoders between ROMs and other
1497 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1498 assigned automatically to PCI devices. You can
1499 make the kernel exclude IRQs of your ISA cards
1501 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1502 of the PIRQ table (normally generated
1503 by the BIOS) if it is outside the
1504 F0000h-100000h range.
1505 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1506 useful if the kernel is unable to find your
1507 secondary buses and you want to tell it
1508 explicitly which ones they are.
1509 assign-busses [X86-32] Always assign all PCI bus
1510 numbers ourselves, overriding
1511 whatever the firmware may have done.
1512 usepirqmask [X86-32] Honor the possible IRQ mask stored
1513 in the BIOS $PIR table. This is needed on
1514 some systems with broken BIOSes, notably
1515 some HP Pavilion N5400 and Omnibook XE3
1516 notebooks. This will have no effect if ACPI
1517 IRQ routing is enabled.
1518 noacpi [X86-32] Do not use ACPI for IRQ routing
1519 or for PCI scanning.
1520 use_crs [X86-32] Use _CRS for PCI resource
1522 routeirq Do IRQ routing for all PCI devices.
1523 This is normally done in pci_enable_device(),
1524 so this option is a temporary workaround
1525 for broken drivers that don't call it.
1526 firmware [ARM] Do not re-enumerate the bus but instead
1527 just use the configuration from the
1528 bootloader. This is currently used on
1529 IXP2000 systems where the bus has to be
1530 configured a certain way for adjunct CPUs.
1531 noearly [X86] Don't do any early type 1 scanning.
1532 This might help on some broken boards which
1533 machine check when some devices' config space
1534 is read. But various workarounds are disabled
1535 and some IOMMU drivers will not work.
1536 bfsort Sort PCI devices into breadth-first order.
1537 This sorting is done to get a device
1538 order compatible with older (<= 2.4) kernels.
1539 nobfsort Don't sort PCI devices into breadth-first order.
1540 cbiosize=nn[KMG] The fixed amount of bus space which is
1541 reserved for the CardBus bridge's IO window.
1542 The default value is 256 bytes.
1543 cbmemsize=nn[KMG] The fixed amount of bus space which is
1544 reserved for the CardBus bridge's memory
1545 window. The default value is 64 megabytes.
1547 pcmv= [HW,PCMCIA] BadgePAD 4
1550 See Documentation/paride.txt.
1552 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1555 See arch/parisc/kernel/pdc_chassis.c
1558 See Documentation/paride.txt.
1561 See Documentation/paride.txt.
1563 pirq= [SMP,APIC] Manual mp-table setup
1564 See Documentation/i386/IO-APIC.txt.
1566 plip= [PPT,NET] Parallel port network link
1567 Format: { parport<nr> | timid | 0 }
1568 See also Documentation/parport.txt.
1574 { on | off | curr | res | no-curr | no-res }
1577 [ISAPNP] Exclude IRQs for the autoconfiguration
1580 [ISAPNP] Exclude DMAs for the autoconfiguration
1582 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1583 Ranges are in pairs (I/O port base and size).
1586 [ISAPNP] Exclude memory regions for the
1588 Ranges are in pairs (memory base and size).
1590 print-fatal-signals=
1591 [KNL] debug: print fatal signals
1592 print-fatal-signals=1: print segfault info to
1596 printk.time= Show timing data prefixed to each printk message line
1597 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1599 profile= [KNL] Enable kernel profiling via /proc/profile
1600 Format: [schedule,]<number>
1601 Param: "schedule" - profile schedule points.
1602 Param: <number> - step/bucket size as a power of 2 for
1603 statistical time based profiling.
1604 Param: "sleep" - profile D-state sleeping (millisecs).
1605 Requires CONFIG_SCHEDSTATS
1606 Param: "kvm" - profile VM exits.
1608 processor.max_cstate= [HW,ACPI]
1609 Limit processor to maximum C-state
1610 max_cstate=9 overrides any DMI blacklist limit.
1612 processor.nocst [HW,ACPI]
1613 Ignore the _CST method to determine C-states,
1614 instead using the legacy FADT method
1616 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1618 See Documentation/ramdisk.txt.
1620 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1621 probe for; one of (bare|imps|exps|lifebook|any).
1622 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1624 psmouse.resetafter= [HW,MOUSE]
1625 Try to reset the device after so many bad packets
1628 [HW,MOUSE] Set desired mouse resolution, in dpi.
1629 psmouse.smartscroll=
1630 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1631 0 = disabled, 1 = enabled (default).
1633 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1635 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1638 See Documentation/paride.txt.
1641 [KNL] Number of legacy pty's. Overwrites compiled-in
1644 quiet [KNL] Disable most log messages
1649 See Documentation/md.txt.
1651 ramdisk_blocksize= [RAM]
1652 See Documentation/ramdisk.txt.
1654 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1655 See Documentation/ramdisk.txt.
1657 rcupdate.blimit= [KNL,BOOT]
1658 Set maximum number of finished RCU callbacks to process
1661 rcupdate.qhimark= [KNL,BOOT]
1662 Set threshold of queued
1663 RCU callbacks over which batch limiting is disabled.
1665 rcupdate.qlowmark= [KNL,BOOT]
1666 Set threshold of queued RCU callbacks below which
1667 batch limiting is re-enabled.
1671 Run specified binary instead of /init from the ramdisk,
1672 used for early userspace startup. See initrd.
1674 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1675 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1676 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1678 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1680 reservetop= [X86-32]
1682 Reserves a hole at the top of the kernel virtual
1685 reset_devices [KNL] Force drivers to reset the underlying device
1686 during initialization.
1689 Specify the partition device for software suspend
1691 resume_offset= [SWSUSP]
1692 Specify the offset from the beginning of the partition
1693 given by "resume=" at which the swap header is located,
1694 in <PAGE_SIZE> units (needed only for swap files).
1695 See Documentation/power/swsusp-and-swap-files.txt
1697 retain_initrd [RAM] Keep initrd memory after extraction
1699 rhash_entries= [KNL,NET]
1700 Set number of hash buckets for route cache
1702 riscom8= [HW,SERIAL]
1703 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1705 ro [KNL] Mount root device read-only on boot
1707 root= [KNL] Root filesystem
1709 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1710 mount the root filesystem
1712 rootflags= [KNL] Set root filesystem mount option string
1714 rootfstype= [KNL] Set root filesystem type
1716 rootwait [KNL] Wait (indefinitely) for root device to show up.
1717 Useful for devices that are detected asynchronously
1718 (e.g. USB and MMC devices).
1720 root_plug.vendor_id=
1721 [ROOTPLUG] Override the default vendor ID
1723 root_plug.product_id=
1724 [ROOTPLUG] Override the default product ID
1727 [ROOTPLUG] Enable debugging output
1729 rw [KNL] Mount root device read-write on boot
1731 S [KNL] Run init in single mode
1734 See drivers/net/irda/sa1100_ir.c.
1736 sbni= [NET] Granch SBNI12 leased line adapter
1738 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1739 Format: <io>[,<timeout>[,<isapnp>]]
1741 scsi_debug_*= [SCSI]
1742 See drivers/scsi/scsi_debug.c.
1744 scsi_default_dev_flags=
1745 [SCSI] SCSI default device flags
1748 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1749 Format: <vendor>:<model>:<flags>
1750 (flags are integer value)
1752 scsi_logging_level= [SCSI] a bit mask of logging levels
1753 See drivers/scsi/scsi_logging.h for bits. Also
1754 settable via sysctl at dev.scsi.logging_level
1755 (/proc/sys/dev/scsi/logging_level).
1756 There is also a nice 'scsi_logging_level' script in the
1757 S390-tools package, available for download at
1758 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1760 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1761 discovered. async scans them in kernel threads,
1762 allowing boot to proceed. none ignores them, expecting
1763 user space to do the scan.
1765 selinux [SELINUX] Disable or enable SELinux at boot time.
1766 Format: { "0" | "1" }
1767 See security/selinux/Kconfig help text.
1770 Default value is set via kernel config option.
1771 If enabled at boot time, /selinux/disable can be used
1772 later to disable prior to initial policy load.
1774 selinux_compat_net =
1775 [SELINUX] Set initial selinux_compat_net flag value.
1776 Format: { "0" | "1" }
1777 0 -- use new secmark-based packet controls
1778 1 -- use legacy packet controls
1779 Default value is 0 (preferred).
1780 Value can be changed at runtime via
1781 /selinux/compat_net.
1783 serialnumber [BUGS=X86-32]
1786 Maximal number of shapers.
1789 See header of drivers/scsi/sim710.c.
1796 slub_debug[=options[,slabs]] [MM, SLUB]
1797 Enabling slub_debug allows one to determine the
1798 culprit if slab objects become corrupted. Enabling
1799 slub_debug can create guard zones around objects and
1800 may poison objects when not in use. Also tracks the
1801 last alloc / free. For more information see
1802 Documentation/vm/slub.txt.
1804 slub_max_order= [MM, SLUB]
1805 Determines the maximum allowed order for slabs.
1806 A high setting may cause OOMs due to memory
1807 fragmentation. For more information see
1808 Documentation/vm/slub.txt.
1810 slub_min_objects= [MM, SLUB]
1811 The minimum number of objects per slab. SLUB will
1812 increase the slab order up to slub_max_order to
1813 generate a sufficiently large slab able to contain
1814 the number of objects indicated. The higher the number
1815 of objects the smaller the overhead of tracking slabs
1816 and the less frequently locks need to be acquired.
1817 For more information see Documentation/vm/slub.txt.
1819 slub_min_order= [MM, SLUB]
1820 Determines the mininum page order for slabs. Must be
1821 lower than slub_max_order.
1822 For more information see Documentation/vm/slub.txt.
1824 slub_nomerge [MM, SLUB]
1825 Disable merging of slabs with similar size. May be
1826 necessary if there is some reason to distinguish
1827 allocs to different slabs. Debug options disable
1828 merging on their own.
1829 For more information see Documentation/vm/slub.txt.
1832 Format: <io1>[,<io2>[,...,<io8>]]
1834 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1835 attempt to substitute SMP alternatives once at boot.
1837 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1838 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1839 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1840 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1841 smsc-ircc2.ircc_irq= [HW] IRQ line
1842 smsc-ircc2.ircc_dma= [HW] DMA channel
1843 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1844 0: Toshiba Satellite 1800 (GP data pin select)
1845 1: Fast pin select (default)
1848 snd-ad1816a= [HW,ALSA]
1850 snd-ad1848= [HW,ALSA]
1852 snd-ali5451= [HW,ALSA]
1854 snd-als100= [HW,ALSA]
1856 snd-als4000= [HW,ALSA]
1858 snd-azt2320= [HW,ALSA]
1860 snd-cmi8330= [HW,ALSA]
1862 snd-cmipci= [HW,ALSA]
1864 snd-cs4231= [HW,ALSA]
1866 snd-cs4232= [HW,ALSA]
1868 snd-cs4236= [HW,ALSA]
1870 snd-cs4281= [HW,ALSA]
1872 snd-cs46xx= [HW,ALSA]
1874 snd-dt019x= [HW,ALSA]
1876 snd-dummy= [HW,ALSA]
1878 snd-emu10k1= [HW,ALSA]
1880 snd-ens1370= [HW,ALSA]
1882 snd-ens1371= [HW,ALSA]
1884 snd-es968= [HW,ALSA]
1886 snd-es1688= [HW,ALSA]
1888 snd-es18xx= [HW,ALSA]
1890 snd-es1938= [HW,ALSA]
1892 snd-es1968= [HW,ALSA]
1894 snd-fm801= [HW,ALSA]
1896 snd-gusclassic= [HW,ALSA]
1898 snd-gusextreme= [HW,ALSA]
1900 snd-gusmax= [HW,ALSA]
1904 snd-ice1712= [HW,ALSA]
1906 snd-intel8x0= [HW,ALSA]
1908 snd-interwave= [HW,ALSA]
1913 snd-korg1212= [HW,ALSA]
1915 snd-maestro3= [HW,ALSA]
1917 snd-mpu401= [HW,ALSA]
1919 snd-mtpav= [HW,ALSA]
1921 snd-nm256= [HW,ALSA]
1923 snd-opl3sa2= [HW,ALSA]
1931 snd-opti93x= [HW,ALSA]
1935 snd-rme32= [HW,ALSA]
1937 snd-rme96= [HW,ALSA]
1939 snd-rme9652= [HW,ALSA]
1945 snd-sbawe= [HW,ALSA]
1947 snd-serial= [HW,ALSA]
1949 snd-sgalaxy= [HW,ALSA]
1951 snd-sonicvibes= [HW,ALSA]
1956 snd-sun-cs4231= [HW,ALSA]
1958 snd-trident= [HW,ALSA]
1960 snd-usb-audio= [HW,ALSA,USB]
1962 snd-via82xx= [HW,ALSA]
1964 snd-virmidi= [HW,ALSA]
1966 snd-wavefront= [HW,ALSA]
1968 snd-ymfpci= [HW,ALSA]
1970 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1971 See Documentation/sonypi.txt
1973 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1974 See Documentation/specialix.txt.
1976 spia_io_base= [HW,MTD]
1982 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1984 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1985 See Documentation/scsi/st.txt.
1989 Set the STI (builtin display/keyboard on the HP-PARISC
1990 machines) console (graphic card) which should be used
1991 as the initial boot-console.
1992 See also comment in drivers/video/console/sticore.c.
1995 See comment in drivers/video/console/sticore.c.
1998 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2002 Control how the NFS server code allocates CPUs to
2003 service thread pools. Depending on how many NICs
2004 you have and where their interrupts are bound, this
2005 option will affect which CPUs will do NFS serving.
2006 Note: this parameter cannot be changed while the
2007 NFS server is running.
2009 auto the server chooses an appropriate mode
2010 automatically using heuristics
2011 global a single global pool contains all CPUs
2012 percpu one pool for each CPU
2013 pernode one pool for each NUMA node (equivalent
2014 to global on non-NUMA machines)
2016 swiotlb= [IA-64] Number of I/O TLB slabs
2020 sym53c416= [HW,SCSI]
2021 See header of drivers/scsi/sym53c416.c.
2023 sysrq_always_enabled
2025 Ignore sysrq setting - this boot parameter will
2026 neutralize any effect of /proc/sys/kernel/sysrq.
2027 Useful for debugging.
2030 See header of drivers/scsi/t128.c.
2034 thash_entries= [KNL,NET]
2035 Set number of hash buckets for TCP connection
2037 thermal.act= [HW,ACPI]
2038 -1: disable all active trip points in all thermal zones
2039 <degrees C>: override all lowest active trip points
2041 thermal.crt= [HW,ACPI]
2042 -1: disable all critical trip points in all thermal zones
2043 <degrees C>: lower all critical trip points
2045 thermal.nocrt= [HW,ACPI]
2046 Set to disable actions on ACPI thermal zone
2047 critical and hot trip points.
2049 thermal.off= [HW,ACPI]
2050 1: disable ACPI thermal control
2052 thermal.psv= [HW,ACPI]
2053 -1: disable all passive trip points
2054 <degrees C>: override all passive trip points to this value
2056 thermal.tzp= [HW,ACPI]
2057 Specify global default ACPI thermal zone polling rate
2058 <deci-seconds>: poll all this frequency
2059 0: no polling (default)
2061 tipar.timeout= [HW,PPT]
2062 Set communications timeout in tenths of a second
2065 tipar.delay= [HW,PPT]
2066 Set inter-bit delay in microseconds (default 10).
2069 See comment before function dc390_setup() in
2070 drivers/scsi/tmscsim.c.
2074 trix= [HW,OSS] MediaTrix AudioTrix Pro
2076 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2078 turbografx.map[2|3]= [HW,JOY]
2079 TurboGraFX parallel port interface
2081 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2082 See also Documentation/input/joystick-parport.txt
2084 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2085 See header of drivers/scsi/u14-34f.c.
2094 [USB] Ignore overcurrent events (default N).
2095 Some badly-designed motherboards generate lots of
2096 bogus events, for ports that aren't wired to
2097 anything. Set this parameter to avoid log spamming.
2098 Note that genuine overcurrent events won't be
2101 usbcore.autosuspend=
2102 [USB] The autosuspend time delay (in seconds) used
2103 for newly-detected USB devices (default 2). This
2104 is the time required before an idle device will be
2105 autosuspended. Devices for which the delay is set
2106 to a negative value won't be autosuspended at all.
2109 [USBHID] The interval which mice are to be polled at.
2111 vdso= [X86-32,SH,x86-64]
2112 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2113 vdso=1: enable VDSO (default)
2114 vdso=0: disable VDSO mapping
2116 vdso32= [X86-32,X86-64]
2117 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2118 vdso32=1: enable 32-bit VDSO (default)
2119 vdso32=0: disable 32-bit VDSO mapping
2122 vector=percpu: enable percpu vector domain
2124 video= [FB] Frame buffer configuration
2125 See Documentation/fb/modedb.txt.
2127 vga= [BOOT,X86-32] Select a particular video mode
2128 See Documentation/i386/boot.txt and
2129 Documentation/svga.txt.
2130 Use vga=ask for menu.
2131 This is actually a boot loader parameter; the value is
2132 passed to the kernel using a special protocol.
2134 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2135 size of <nn>. This can be used to increase the
2136 minimum size (128MB on x86). It can also be used to
2137 decrease the size and leave more room for directly
2140 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2143 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2146 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2149 waveartist= [HW,OSS]
2150 Format: <io>,<irq>,<dma>,<dma2>
2153 See header of drivers/scsi/wd33c93.c.
2156 See header of drivers/scsi/wd7000.c.
2159 See Documentation/watchdog/wdt.txt.
2161 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2162 xd_geo= See header of drivers/block/xd.c.
2164 xirc2ps_cs= [NET,PCMCIA]
2166 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2168 norandmaps Don't use address space randomization
2169 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2171 ______________________________________________________________________
2175 Add documentation for ALSA options.
2176 Add more DRM drivers.
projects / linux-2.6 / blob