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_new_pts_ordering [HW,ACPI]
172 Enforce the ACPI 2.0 ordering of the _PTS control
173 method wrt putting devices into low power states
174 default: pre ACPI 2.0 ordering of _PTS
176 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
178 acpi_no_initrd_override [KNL,ACPI]
179 Disable loading custom ACPI tables from the initramfs
181 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
182 Format: To spoof as Windows 98: ="Microsoft Windows"
184 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
185 acpi_osi="string1" # add string1 -- only one string
186 acpi_osi="!string2" # remove built-in string2
187 acpi_osi= # disable all strings
189 acpi_serialize [HW,ACPI] force serialization of AML methods
191 acpi_skip_timer_override [HW,ACPI]
192 Recognize and ignore IRQ0/pin2 Interrupt Override.
193 For broken nForce2 BIOS resulting in XT-PIC timer.
194 acpi_use_timer_override [HW,ACPI}
195 Use timer override. For some broken Nvidia NF5 boards
196 that require a timer override, but don't have
199 acpi.debug_layer= [HW,ACPI]
201 Each bit of the <int> indicates an ACPI debug layer,
202 1: enable, 0: disable. It is useful for boot time
203 debugging. After system has booted up, it can be set
204 via /sys/module/acpi/parameters/debug_layer.
205 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
206 Available bits (add the numbers together) to enable debug output
207 for specific parts of the ACPI subsystem:
208 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
209 0x10 namespace 0x20 parser 0x40 dispatcher
210 0x80 executer 0x100 resources 0x200 acpica debugger
211 0x400 os services 0x800 acpica disassembler.
212 The number can be in decimal or prefixed with 0x in hex.
213 Warning: Many of these options can produce a lot of
214 output and make your system unusable. Be very careful.
216 acpi.debug_level= [HW,ACPI]
218 Each bit of the <int> indicates an ACPI debug level,
219 1: enable, 0: disable. It is useful for boot time
220 debugging. After system has booted up, it can be set
221 via /sys/module/acpi/parameters/debug_level.
222 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
223 Available bits (add the numbers together) to enable different
224 debug output levels of the ACPI subsystem:
225 0x01 error 0x02 warn 0x04 init 0x08 debug object
226 0x10 info 0x20 init names 0x40 parse 0x80 load
227 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
228 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
229 0x10000 resources 0x20000 user requests 0x40000 package.
230 The number can be in decimal or prefixed with 0x in hex.
231 Warning: Many of these options can produce a lot of
232 output and make your system unusable. Be very careful.
234 acpi_pm_good [X86-32,X86-64]
235 Override the pmtimer bug detection: force the kernel
236 to assume that this machine's pmtimer latches its value
237 and always returns good values.
240 { off | try_unsupported }
241 off: disable AGP support
242 try_unsupported: try to drive unsupported chipsets
243 (may crash computer or cause data corruption)
245 enable_timer_pin_1 [i386,x86-64]
246 Enable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs
248 (in particular on some ATI chipsets).
249 The kernel tries to set a reasonable default.
251 disable_timer_pin_1 [i386,x86-64]
252 Disable PIN 1 of APIC timer
253 Can be useful to work around chipset bugs.
256 Format: <io>,<irq>,<dma>,<dma2>,<type>
259 See header of drivers/scsi/advansys.c.
261 advwdt= [HW,WDT] Advantech WDT
262 Format: <iostart>,<iostop>
264 aedsp16= [HW,OSS] Audio Excel DSP 16
265 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
266 See also header of sound/oss/aedsp16.c.
269 See Documentation/scsi/aha152x.txt.
272 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
275 See Documentation/scsi/aic7xxx.txt.
278 See Documentation/scsi/aic79xx.txt.
280 amijoy.map= [HW,JOY] Amiga joystick support
281 Map of devices attached to JOY0DAT and JOY1DAT
283 See also Documentation/kernel/input/joystick.txt
285 analog.map= [HW,JOY] Analog joystick and gamepad support
286 Specifies type or capabilities of an analog joystick
287 connected to one of 16 gameports
288 Format: <type1>,<type2>,..<type16>
291 Power management functions (SPARCstation-4/5 + deriv.)
293 Disable APC CPU standby support. SPARCstation-Fox does
294 not play well with APC CPU idle - disable it if you have
295 APC and your system crashes randomly.
297 apic= [APIC,i386] Advanced Programmable Interrupt Controller
298 Change the output verbosity whilst booting
299 Format: { quiet (default) | verbose | debug }
300 Change the amount of debugging information output
301 when initialising the APIC and IO-APIC components.
303 apm= [APM] Advanced Power Management
304 See header of arch/i386/kernel/apm.c.
306 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
307 Format: <io>,<irq>,<nodeID>
311 atarimouse= [HW,MOUSE] Atari Mouse
313 atascsi= [HW,SCSI] Atari SCSI
315 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
316 EzKey and similar keyboards
318 atkbd.reset= [HW] Reset keyboard during initialization
320 atkbd.set= [HW] Select keyboard code set
321 Format: <int> (2 = AT (default), 3 = PS/2)
323 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
326 atkbd.softraw= [HW] Choose between synthetic and real raw mode
327 Format: <bool> (0 = real, 1 = synthetic (default))
329 atkbd.softrepeat= [HW]
330 Use software keyboard repeat
334 baycom_epp= [HW,AX25]
337 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
339 See header of drivers/net/hamradio/baycom_par.c.
341 baycom_ser_fdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
343 Format: <io>,<irq>,<mode>[,<baud>]
344 See header of drivers/net/hamradio/baycom_ser_fdx.c.
346 baycom_ser_hdx= [HW,AX25]
347 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
348 Format: <io>,<irq>,<mode>
349 See header of drivers/net/hamradio/baycom_ser_hdx.c.
351 boot_delay= Milliseconds to delay each printk during boot.
352 Values larger than 10 seconds (10000) are changed to
356 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
357 bttv.radio= Most important insmod options are available as
359 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
360 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
363 See drivers/scsi/BusLogic.c, comment before function
364 BusLogic_ParseDriverOptions().
366 c101= [NET] Moxa C101 synchronous serial card
368 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
369 Sometimes CPU hardware bugs make them report the cache
370 size incorrectly. The kernel will attempt work arounds
371 to fix known problems, but for some CPUs it is not
372 possible to determine what the correct size should be.
373 This option provides an override for these situations.
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 checkreqprot [SELINUX] Set initial checkreqprot flag value.
385 Format: { "0" | "1" }
386 See security/selinux/Kconfig help text.
387 0 -- check protection applied by kernel (includes
388 any implied execute protection).
389 1 -- check protection requested by application.
390 Default value is set via a kernel config option.
391 Value can be changed at runtime via
392 /selinux/checkreqprot.
395 See Documentation/s390/CommonIO for details.
398 See Documentation/s390/CommonIO for details.
400 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
402 Forces specified clocksource (if available) to be used
403 when calculating gettimeofday(). If specified
404 clocksource is not available, it defaults to PIT.
405 Format: { pit | tsc | cyclone | pmtmr }
407 clocksource= [GENERIC_TIME] Override the default clocksource
409 Override the default clocksource and use the clocksource
410 with the name specified.
411 Some clocksource names to choose from, depending on
413 [all] jiffies (this is the base, fallback clocksource)
415 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
416 pxa_timer,timer3,32k_counter,timer0_1
418 [X86-32] pit,hpet,tsc,vmi-timer;
419 scx200_hrt on Geode; cyclone on IBM x440
427 clearcpuid=BITNUM [X86]
428 Disable CPUID feature X for the kernel. See
429 include/asm-x86/cpufeature.h for the valid bit numbers.
430 Note the Linux specific bits are not necessarily
431 stable over kernel options, but the vendor specific
433 Also note that user programs calling CPUID directly
434 or using the feature without checking anything
435 will still see it. This just prevents it from
436 being used by the kernel or shown in /proc/cpuinfo.
437 Also note the kernel might malfunction if you disable
440 code_bytes [IA32/X86_64] How many bytes of object code to print
447 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
448 over the 8254 in addition to over the IO-APIC. The
449 kernel tries to set a sensible default.
451 hpet= [X86-32,HPET] option to control HPET usage
452 Format: { enable (default) | disable | force }
453 disable: disable HPET and use PIT instead
454 force: allow force enabled of undocumented chips (ICH4,
457 com20020= [HW,NET] ARCnet - COM20020 chipset
459 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
461 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
465 ARCnet - COM90xx chipset (memory-mapped buffers)
466 Format: <io>[,<irq>[,<memstart>]]
468 condev= [HW,S390] console device
471 console= [KNL] Output console device and options.
473 tty<n> Use the virtual console device <n>.
477 Use the specified serial port. The options are of
478 the form "bbbbpnf", where "bbbb" is the baud rate,
479 "p" is parity ("n", "o", or "e"), "n" is number of
480 bits, and "f" is flow control ("r" for RTS or
481 omit it). Default is "9600n8".
483 See Documentation/serial-console.txt for more
485 Documentation/networking/netconsole.txt for an
488 uart[8250],io,<addr>[,options]
489 uart[8250],mmio,<addr>[,options]
490 Start an early, polled-mode console on the 8250/16550
491 UART at the specified I/O port or MMIO address,
492 switching to the matching ttyS device later. The
493 options are the same as for ttyS, above.
495 earlycon= [KNL] Output early console device and options.
496 uart[8250],io,<addr>[,options]
497 uart[8250],mmio,<addr>[,options]
498 Start an early, polled-mode console on the 8250/16550
499 UART at the specified I/O port or MMIO address.
500 The options are the same as for ttyS, above.
503 [HW] Never suspend the console
504 Disable suspending of consoles during suspend and
505 hibernate operations. Once disabled, debugging
506 messages can reach various consoles while the rest
507 of the system is being put to sleep (ie, while
508 debugging driver suspend/resume hooks). This may
509 not work reliably with all consoles, but is known
510 to work with serial and VGA consoles.
512 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
514 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
516 crashkernel=nn[KMG]@ss[KMG]
517 [KNL] Reserve a chunk of physical memory to
518 hold a kernel to switch to with kexec on panic.
520 crashkernel=range1:size1[,range2:size2,...][@offset]
521 [KNL] Same as above, but depends on the memory
522 in the running system. The syntax of range is
523 start-[end] where start and end are both
524 a memory unit (amount[KMG]). See also
525 Documentation/kdump/kdump.txt for a example.
528 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
533 cs89x0_media= [HW,NET]
534 Format: { rj45 | aui | bnc }
537 See header of drivers/s390/block/dasd_devmap.c.
539 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
540 (one device per port)
541 Format: <port#>,<type>
542 See also Documentation/input/joystick-parport.txt
544 debug [KNL] Enable kernel debugging (events log level).
547 [KNL] verbose self-tests
549 Print debugging info while doing the locking API
551 We default to 0 (no extra messages), setting it to
552 1 will print _a lot_ more information - normally
553 only useful to kernel developers.
555 decnet.addr= [HW,NET]
556 Format: <area>[,<node>]
557 See also Documentation/networking/decnet.txt.
560 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
561 Change the default blue palette of the console.
562 This is a 16-member array composed of values
566 Format: <green0>,<green1>,<green2>,...,<green15>
567 Change the default green palette of the console.
568 This is a 16-member array composed of values
572 Format: <red0>,<red1>,<red2>,...,<red15>
573 Change the default red palette of the console.
574 This is a 16-member array composed of values
580 Set system-wide default UTF-8 mode for all tty's.
581 Default is 1, i.e. UTF-8 mode is enabled for all
582 newly opened terminals.
585 Set number of hash buckets for dentry cache.
588 IO parameters + enable/disable command.
590 digiepca= [HW,SERIAL]
591 See drivers/char/README.epca and
592 Documentation/digiepca.txt.
594 disable_mtrr_trim [X86, Intel and AMD only]
595 By default the kernel will trim any uncacheable
596 memory out of your available memory pool based on
597 MTRR settings. This parameter disables that behavior,
598 possibly causing your machine to run very slowly.
600 dmasound= [HW,OSS] Sound subsystem buffers
606 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
608 earlyprintk=serial[,ttySn[,baudrate]]
610 Append ",keep" to not disable it when the real console
613 Only vga or serial at a time, not both.
615 Currently only ttyS0 and ttyS1 are supported.
617 Interaction with the standard serial driver is not
620 The VGA output is eventually overwritten by the real
626 Format: {"of[f]" | "sk[ipmbr]"}
627 See comment in arch/i386/boot/edd.S
629 eisa_irq_edge= [PARISC,HW]
630 See header of drivers/parisc/eisa.c.
633 See comment before function elanfreq_setup() in
634 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
637 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
638 See Documentation/block/as-iosched.txt and
639 Documentation/block/deadline-iosched.txt for details.
641 elfcorehdr= [X86-32, X86_64]
642 Specifies physical address of start of kernel core
643 image elf header. Generally kexec loader will
644 pass this option to capture kernel.
645 See Documentation/kdump/kdump.txt for details.
647 enforcing [SELINUX] Set initial enforcing status.
649 See security/selinux/Kconfig help text.
650 0 -- permissive (log only, no denials).
651 1 -- enforcing (deny and log).
653 Value can be changed at runtime via /selinux/enforce.
656 Format: <spdif>,[<nomix>,[<amplifier>]]
657 See also header of sound/oss/es1371.c.
659 ether= [HW,NET] Ethernet cards parameters
660 This option is obsoleted by the "netdev=" option, which
661 has equivalent usage. See its documentation for details.
663 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
668 fail_make_request=[KNL]
669 General fault injection mechanism.
670 Format: <interval>,<probability>,<space>,<times>
671 See also /Documentation/fault-injection/.
674 See header of drivers/scsi/fd_mcs.c.
677 See header of drivers/scsi/fdomain.c.
680 See Documentation/floppy.txt.
683 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
684 support via parallel port (up to 5 devices per port)
685 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
686 See also Documentation/input/joystick-parport.txt
690 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
695 See header of drivers/scsi/gdth.c.
697 gpt [EFI] Forces disk with valid GPT signature but
698 invalid Protective MBR to be treated as GPT.
702 hashdist= [KNL,NUMA] Large hashes allocated during boot
703 are distributed across NUMA nodes. Defaults on
704 for IA-64, off otherwise.
705 Format: 0 | 1 (for off | on)
707 hcl= [IA-64] SGI's Hardware Graph compatibility layer
709 hd= [EIDE] (E)IDE hard drive subsystem geometry
710 Format: <cyl>,<head>,<sect>
712 hd?= [HW] (E)IDE subsystem
713 hd?lun= See Documentation/ide.txt.
715 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
716 size of <nn>. This works even on boxes that have no
717 highmem otherwise. This also works to reduce highmem
718 size on bigger boxes.
720 highres= [KNL] Enable/disable high resolution timer mode.
721 Valid parameters: "on", "off"
725 See Documentation/isdn/README.HiSax.
727 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
728 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
730 i8042.direct [HW] Put keyboard port into non-translated mode
731 i8042.dumbkbd [HW] Pretend that controller can only read data from
732 keyboard and cannot control its state
733 (Don't attempt to blink the leds)
734 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
735 i8042.nokbd [HW] Don't check/create keyboard port
736 i8042.nomux [HW] Don't check presence of an active multiplexing
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler or ide=reverse
767 See Documentation/ide.txt.
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
771 See Documentation/ide.txt.
773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
774 See Documentation/ide.txt.
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
794 Set number of hash buckets for inode cache.
797 See header of drivers/scsi/in2000.c.
801 Run specified binary instead of /sbin/init as init
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
808 initrd= [BOOT] Specify the location of the initial ramdisk
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
815 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
817 Disable intel iommu driver.
818 igfx_off [Default Off]
819 By default, gfx is mapped as normal device. If a gfx
820 device has a dedicated DMAR unit, the DMAR unit is
821 bypassed by not enabling DMAR with this option. In
822 this case, gfx device will use physical address for
825 With this option iommu will not optimize to look
826 for io virtual address below 32 bit forcing dual
827 address cycle on pci bus for cards supporting greater
828 than 32 bit addressing. The default is to look
829 for translation below 32 bit and if not available
830 then look in the higher range.
832 io_delay= [X86-32,X86-64] I/O delay method
834 Standard port 0x80 based delay
836 Alternate port 0xed based delay (needed on some systems)
838 Simple two microseconds delay
842 io7= [HW] IO7 for Marvel based alpha systems
843 See comment before marvel_specify_io7 in
844 arch/alpha/kernel/core_marvel.c.
847 See Documentation/nfsroot.txt.
849 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
850 See comment before ip2_setup() in
851 drivers/char/ip2/ip2base.c.
853 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
854 See header of drivers/scsi/ips.c.
856 ports= [IP_VS_FTP] IPVS ftp helper module
858 Up to 8 (IP_VS_APP_MAX_PORTS) ports
860 Format: <port>,<port>....
863 When an interrupt is not handled search all handlers
864 for it. Intended to get systems with badly broken
868 When an interrupt is not handled search all handlers
869 for it. Also check all handlers each timer
870 interrupt. Intended to get systems with badly broken
874 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
876 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
878 <cpu number>,...,<cpu number>
880 <cpu number>-<cpu number> (must be a positive range in ascending order)
882 <cpu number>,...,<cpu number>-<cpu number>
883 This option can be used to specify one or more CPUs
884 to isolate from the general SMP balancing and scheduling
885 algorithms. The only way to move a process onto or off
886 an "isolated" CPU is via the CPU affinity syscalls.
887 <cpu number> begins at 0 and the maximum value is
888 "number of CPUs in system - 1".
890 This option is the preferred way to isolate CPUs. The
891 alternative -- manually setting the CPU mask of all
892 tasks in the system -- can cause problems and
893 suboptimal load balancer performance.
897 js= [HW,JOY] Analog joystick
898 See Documentation/input/joystick.txt.
900 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
901 specifies the amount of memory usable by the kernel
902 for non-movable allocations. The requested amount is
903 spread evenly throughout all nodes in the system. The
904 remaining memory in each node is used for Movable
905 pages. In the event, a node is too small to have both
906 kernelcore and Movable pages, kernelcore pages will
907 take priority and other nodes will have a larger number
908 of kernelcore pages. The Movable zone is used for the
909 allocation of pages that may be reclaimed or moved
910 by the page migration subsystem. This means that
911 HugeTLB pages may not be allocated from this zone.
912 Note that allocations like PTEs-from-HighMem still
913 use the HighMem zone if it exists, and the Normal
916 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
917 is similar to kernelcore except it specifies the
918 amount of memory used for migratable allocations.
919 If both kernelcore and movablecore is specified,
920 then kernelcore will be at *least* the specified
921 value but may be more. If movablecore on its own
922 is specified, the administrator must be careful
923 that the amount of memory usable for all allocations
928 kstack=N [X86-32,X86-64] Print N words from the kernel stack
933 lapic [X86-32,APIC] Enable the local APIC even if BIOS
936 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
939 libata.dma= [LIBATA] DMA control
940 libata.dma=0 Disable all PATA and SATA DMA
941 libata.dma=1 PATA and SATA Disk DMA only
942 libata.dma=2 ATAPI (CDROM) DMA only
943 libata.dma=4 Compact Flash DMA only
944 Combinations also work, so libata.dma=3 enables DMA
945 for disks and CDROMs, but not CFs.
947 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
951 load_ramdisk= [RAM] List of ramdisks to load from floppy
952 See Documentation/ramdisk.txt.
954 lockd.nlm_grace_period=P [NFS] Assign grace period.
957 lockd.nlm_tcpport=N [NFS] Assign TCP port.
960 lockd.nlm_timeout=T [NFS] Assign timeout value.
963 lockd.nlm_udpport=M [NFS] Assign UDP port.
966 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
969 loglevel= All Kernel Messages with a loglevel smaller than the
970 console loglevel will be printed to the console. It can
971 also be changed with klogd or other programs. The
972 loglevels are defined as follows:
974 0 (KERN_EMERG) system is unusable
975 1 (KERN_ALERT) action must be taken immediately
976 2 (KERN_CRIT) critical conditions
977 3 (KERN_ERR) error conditions
978 4 (KERN_WARNING) warning conditions
979 5 (KERN_NOTICE) normal but significant condition
980 6 (KERN_INFO) informational
981 7 (KERN_DEBUG) debug-level messages
983 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
984 Format: { n | nk | nM }
985 n must be a power of two. The default size
986 is set in the kernel config file.
988 logo.nologo [FB] Disables display of the built-in Linux logo.
989 This may be used to provide more screen space for
990 kernel log messages and is useful when debugging
991 kernel boot problems.
993 lp=0 [LP] Specify parallel ports to use, e.g,
994 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
995 lp=reset first parallel port). 'lp=0' disables the
996 lp=auto printer driver. 'lp=reset' (which can be
997 specified in addition to the ports) causes
998 attached printers to be reset. Using
999 lp=port1,port2,... specifies the parallel ports
1000 to associate lp devices with, starting with
1001 lp0. A port specification may be 'none' to skip
1002 that lp device, or a parport name such as
1003 'parport0'. Specifying 'lp=auto' instead of a
1004 port specification list means that device IDs
1005 from each port should be examined, to see if
1006 an IEEE 1284-compliant printer is attached; if
1007 so, the driver will manage that printer.
1008 See also header of drivers/char/lp.c.
1011 Sets loops_per_jiffy to given constant, thus avoiding
1012 time-consuming boot-time autodetection (up to 250 ms per
1013 CPU). 0 enables autodetection (default). To determine
1014 the correct value for your kernel, boot with normal
1015 autodetection and see what value is printed. Note that
1016 on SMP systems the preset will be applied to all CPUs,
1017 which is likely to cause problems if your CPUs need
1018 significantly divergent settings. An incorrect value
1019 will cause delays in the kernel to be wrong, leading to
1020 unpredictable I/O errors and other breakage. Although
1021 unlikely, in the extreme case this might damage your
1025 Format: <io>,<irq>,<dma>
1027 mac5380= [HW,SCSI] Format:
1028 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1030 mac53c9x= [HW,SCSI] Format:
1031 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1033 machvec= [IA64] Force the use of a particular machine-vector
1034 (machvec) in a generic kernel.
1035 Example: machvec=hpzx1_swiotlb
1037 max_loop= [LOOP] Maximum number of loopback devices that can
1041 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1042 should make use of. maxcpus=n : n >= 0 limits the
1043 kernel to using 'n' processors. n=0 is a special case,
1044 it is equivalent to "nosmp", which also disables
1047 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1048 equal to this physical address is ignored.
1050 max_luns= [SCSI] Maximum number of LUNs to probe.
1051 Should be between 1 and 2^32-1.
1054 [SCSI] Maximum number of LUNs received.
1055 Should be between 1 and 16384.
1057 mca-pentium [BUGS=X86-32]
1061 mce [X86-32] Machine Check Exception
1063 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1065 md= [HW] RAID subsystems devices and level
1066 See Documentation/md.txt.
1069 Format: <first>,<last>
1070 Specifies range of consoles to be captured by the MDA.
1072 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1073 Amount of memory to be used when the kernel is not able
1074 to see the whole system memory or for test.
1075 [X86-32] Use together with memmap= to avoid physical
1076 address space collisions. Without memmap= PCI devices
1077 could be placed at addresses belonging to unused RAM.
1079 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1082 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1083 E820 memory map, as specified by the user.
1084 Such memmap=exactmap lines can be constructed based on
1085 BIOS output or other requirements. See the memmap=nn@ss
1088 memmap=nn[KMG]@ss[KMG]
1089 [KNL] Force usage of a specific region of memory
1090 Region of memory to be used, from ss to ss+nn.
1092 memmap=nn[KMG]#ss[KMG]
1093 [KNL,ACPI] Mark specific memory as ACPI data.
1094 Region of memory to be used, from ss to ss+nn.
1096 memmap=nn[KMG]$ss[KMG]
1097 [KNL,ACPI] Mark specific memory as reserved.
1098 Region of memory to be used, from ss to ss+nn.
1100 meye.*= [HW] Set MotionEye Camera parameters
1101 See Documentation/video4linux/meye.txt.
1103 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1104 Multi-Function General Purpose Timers on AMD Geode
1107 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1108 the BIOS has incorrectly applied a workaround. TinyBIOS
1109 version 0.98 is known to be affected, 0.99 fixes the
1110 problem by letting the user disable the workaround.
1115 [MOUSE] Maximum time between finger touching and
1116 leaving touchpad surface for touch to be considered
1117 a tap and be reported as a left button click (for
1118 touchpads working in absolute mode only).
1120 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1121 reporting absolute coordinates, such as tablets
1122 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1123 reporting absolute coordinates, such as tablets
1128 MTD_Partition= [MTD]
1129 Format: <name>,<region-number>,<size>,<offset>
1131 MTD_Region= [MTD] Format:
1132 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1135 See drivers/mtd/cmdlinepart.c.
1137 mtouchusb.raw_coordinates=
1138 [HW] Make the MicroTouch USB driver use raw coordinates
1139 ('y', default) or cooked coordinates ('n')
1141 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1144 See header of drivers/scsi/NCR_D700.c.
1148 ncr53c400= [HW,SCSI]
1150 ncr53c400a= [HW,SCSI]
1152 ncr53c406a= [HW,SCSI]
1154 ncr53c8xx= [HW,SCSI]
1156 netdev= [NET] Network devices parameters
1157 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1158 Note that mem_start is often overloaded to mean
1159 something different and driver-specific.
1160 This usage is only documented in each driver source
1164 See Documentation/nfsroot.txt.
1166 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1167 See Documentation/nfsroot.txt.
1169 nfs.callback_tcpport=
1170 [NFS] set the TCP port on which the NFSv4 callback
1171 channel should listen.
1173 nfs.idmap_cache_timeout=
1174 [NFS] set the maximum lifetime for idmapper cache
1178 [NFS] enable 64-bit inode numbers.
1179 If zero, the NFS client will fake up a 32-bit inode
1180 number for the readdir() and stat() syscalls instead
1181 of returning the full 64-bit number.
1182 The default is to return 64-bit inode numbers.
1184 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1185 when a NMI is triggered.
1186 Format: [state][,regs][,debounce][,die]
1188 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1190 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1191 emulation library even if a 387 maths coprocessor
1194 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1195 caches in the slab allocator. Saves per-node memory,
1196 but will impact performance.
1200 noapic [SMP,APIC] Tells the kernel to not make use of any
1201 IOAPICs that may be present in the system.
1203 nobats [PPC] Do not use BATs for mapping kernel lowmem
1204 on "Classic" PPC cores.
1208 nodelayacct [KNL] Disable per-task delay accounting
1210 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1212 noefi [X86-32,X86-64] Disable EFI runtime services support.
1216 noexec [X86-32,X86-64]
1217 noexec=on: enable non-executable mappings (default)
1218 noexec=off: disable nn-executable mappings
1220 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1221 register save and restore. The kernel will only save
1222 legacy floating-point registers on task switch.
1224 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1228 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1229 instruction doesn't work correctly and not to
1232 nohalt [IA-64] Tells the kernel not to use the power saving
1233 function PAL_HALT_LIGHT when idle. This increases
1234 power-consumption. On the positive side, it reduces
1235 interrupt wake-up latency, which may improve performance
1236 in certain environments such as networked servers or
1239 nohz= [KNL] Boottime enable/disable dynamic ticks
1240 Valid arguments: on, off
1243 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1245 noirqdebug [X86-32] Disables the code which attempts to detect and
1246 disable unhandled interrupt sources.
1248 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1249 broken timer IRQ sources.
1251 noisapnp [ISAPNP] Disables ISA PnP code.
1253 noinitrd [RAM] Tells the kernel not to load any configured
1258 nojitter [IA64] Disables jitter checking for ITC timers.
1260 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1262 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1264 noltlbs [PPC] Do not use large page/tlb entries for kernel
1265 lowmem mapping on PPC40x.
1267 nomca [IA-64] Disable machine check abort handling
1269 nomce [X86-32] Machine Check Exception
1271 nomfgpt [X86-32] Disable Multi-Function General Purpose
1272 Timer usage (for AMD Geode machines).
1274 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1276 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1277 with UP alternatives
1279 noresidual [PPC] Don't use residual data on PReP machines.
1281 noresume [SWSUSP] Disables resume and restores original swap
1284 no-scroll [VGA] Disables scrollback.
1285 This is required for the Braillex ib80-piezo Braille
1286 reader made by F.H. Papenmeier (Germany).
1290 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1292 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1293 and disable the IO APIC. legacy for "maxcpus=0".
1295 nosoftlockup [KNL] Disable the soft-lockup detector.
1297 nosync [HW,M68K] Disables sync negotiation for all devices.
1299 notsc [BUGS=X86-32] Disable Time Stamp Counter
1301 nousb [USB] Disable the USB subsystem
1305 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1306 one of ['zone', 'node', 'default'] can be specified
1307 This can be set from sysctl after boot.
1308 See Documentation/sysctl/vm.txt for details.
1310 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1315 oprofile.timer= [HW]
1316 Use timer interrupt instead of performance counters
1318 osst= [HW,SCSI] SCSI Tape Driver
1319 Format: <buffer_size>,<write_threshold>
1320 See also Documentation/scsi/st.txt.
1322 panic= [KNL] Kernel behaviour on panic
1325 parkbd.port= [HW] Parallel port number the keyboard adapter is
1326 connected to, default is 0.
1328 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1329 0 for XT, 1 for AT (default is AT).
1332 parport= [HW,PPT] Specify parallel ports. 0 disables.
1333 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1334 Use 'auto' to force the driver to use any
1335 IRQ/DMA settings detected (the default is to
1336 ignore detected IRQ/DMA settings because of
1337 possible conflicts). You can specify the base
1338 address, IRQ, and DMA settings; IRQ and DMA
1339 should be numbers, or 'auto' (for using detected
1340 settings on that particular port), or 'nofifo'
1341 (to avoid using a FIFO even if it is detected).
1342 Parallel ports are assigned in the order they
1343 are specified on the command line, starting
1346 parport_init_mode= [HW,PPT]
1347 Configure VIA parallel port to operate in
1348 a specific mode. This is necessary on Pegasos
1349 computer where firmware has no options for setting
1350 up parallel port mode and sets it to spp.
1351 Currently this function knows 686a and 8231 chips.
1352 Format: [spp|ps2|epp|ecp|ecpepp]
1354 pas2= [HW,OSS] Format:
1355 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1358 See header of drivers/scsi/pas16.c.
1361 Halt all CPUs after the first oops has been printed for
1362 the specified number of seconds. This is to be used if
1363 your oopses keep scrolling off the screen.
1368 See header of drivers/block/paride/pcd.c.
1369 See also Documentation/paride.txt.
1371 pci=option[,option...] [PCI] various PCI subsystem options:
1372 off [X86-32] don't probe for the PCI bus
1373 bios [X86-32] force use of PCI BIOS, don't access
1374 the hardware directly. Use this if your machine
1375 has a non-standard PCI host bridge.
1376 nobios [X86-32] disallow use of PCI BIOS, only direct
1377 hardware access methods are allowed. Use this
1378 if you experience crashes upon bootup and you
1379 suspect they are caused by the BIOS.
1380 conf1 [X86-32] Force use of PCI Configuration
1382 conf2 [X86-32] Force use of PCI Configuration
1384 noaer [PCIE] If the PCIEAER kernel config parameter is
1385 enabled, this kernel boot option can be used to
1386 disable the use of PCIE advanced error reporting.
1387 nodomains [PCI] Disable support for multiple PCI
1388 root domains (aka PCI segments, in ACPI-speak).
1389 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1391 nomsi [MSI] If the PCI_MSI kernel config parameter is
1392 enabled, this kernel boot option can be used to
1393 disable the use of MSI interrupts system-wide.
1394 nosort [X86-32] Don't sort PCI devices according to
1395 order given by the PCI BIOS. This sorting is
1396 done to get a device order compatible with
1398 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1399 routing table. These calls are known to be buggy
1400 on several machines and they hang the machine
1401 when used, but on other computers it's the only
1402 way to get the interrupt routing table. Try
1403 this option if the kernel is unable to allocate
1404 IRQs or discover secondary PCI buses on your
1406 rom [X86-32] Assign address space to expansion ROMs.
1407 Use with caution as certain devices share
1408 address decoders between ROMs and other
1410 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1411 assigned automatically to PCI devices. You can
1412 make the kernel exclude IRQs of your ISA cards
1414 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1415 of the PIRQ table (normally generated
1416 by the BIOS) if it is outside the
1417 F0000h-100000h range.
1418 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1419 useful if the kernel is unable to find your
1420 secondary buses and you want to tell it
1421 explicitly which ones they are.
1422 assign-busses [X86-32] Always assign all PCI bus
1423 numbers ourselves, overriding
1424 whatever the firmware may have done.
1425 usepirqmask [X86-32] Honor the possible IRQ mask stored
1426 in the BIOS $PIR table. This is needed on
1427 some systems with broken BIOSes, notably
1428 some HP Pavilion N5400 and Omnibook XE3
1429 notebooks. This will have no effect if ACPI
1430 IRQ routing is enabled.
1431 noacpi [X86-32] Do not use ACPI for IRQ routing
1432 or for PCI scanning.
1433 use_crs [X86-32] Use _CRS for PCI resource
1435 routeirq Do IRQ routing for all PCI devices.
1436 This is normally done in pci_enable_device(),
1437 so this option is a temporary workaround
1438 for broken drivers that don't call it.
1439 firmware [ARM] Do not re-enumerate the bus but instead
1440 just use the configuration from the
1441 bootloader. This is currently used on
1442 IXP2000 systems where the bus has to be
1443 configured a certain way for adjunct CPUs.
1444 noearly [X86] Don't do any early type 1 scanning.
1445 This might help on some broken boards which
1446 machine check when some devices' config space
1447 is read. But various workarounds are disabled
1448 and some IOMMU drivers will not work.
1449 bfsort Sort PCI devices into breadth-first order.
1450 This sorting is done to get a device
1451 order compatible with older (<= 2.4) kernels.
1452 nobfsort Don't sort PCI devices into breadth-first order.
1453 cbiosize=nn[KMG] The fixed amount of bus space which is
1454 reserved for the CardBus bridge's IO window.
1455 The default value is 256 bytes.
1456 cbmemsize=nn[KMG] The fixed amount of bus space which is
1457 reserved for the CardBus bridge's memory
1458 window. The default value is 64 megabytes.
1460 pcmv= [HW,PCMCIA] BadgePAD 4
1463 See Documentation/paride.txt.
1465 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1468 See arch/parisc/kernel/pdc_chassis.c
1471 See Documentation/paride.txt.
1474 See Documentation/paride.txt.
1476 pirq= [SMP,APIC] Manual mp-table setup
1477 See Documentation/i386/IO-APIC.txt.
1479 plip= [PPT,NET] Parallel port network link
1480 Format: { parport<nr> | timid | 0 }
1481 See also Documentation/parport.txt.
1487 { on | off | curr | res | no-curr | no-res }
1490 [ISAPNP] Exclude IRQs for the autoconfiguration
1493 [ISAPNP] Exclude DMAs for the autoconfiguration
1495 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1496 Ranges are in pairs (I/O port base and size).
1499 [ISAPNP] Exclude memory regions for the
1501 Ranges are in pairs (memory base and size).
1503 print-fatal-signals=
1504 [KNL] debug: print fatal signals
1505 print-fatal-signals=1: print segfault info to
1509 printk.time= Show timing data prefixed to each printk message line
1510 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1512 profile= [KNL] Enable kernel profiling via /proc/profile
1513 Format: [schedule,]<number>
1514 Param: "schedule" - profile schedule points.
1515 Param: <number> - step/bucket size as a power of 2 for
1516 statistical time based profiling.
1517 Param: "sleep" - profile D-state sleeping (millisecs).
1518 Requires CONFIG_SCHEDSTATS
1519 Param: "kvm" - profile VM exits.
1521 processor.max_cstate= [HW,ACPI]
1522 Limit processor to maximum C-state
1523 max_cstate=9 overrides any DMI blacklist limit.
1525 processor.nocst [HW,ACPI]
1526 Ignore the _CST method to determine C-states,
1527 instead using the legacy FADT method
1529 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1531 See Documentation/ramdisk.txt.
1533 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1534 probe for; one of (bare|imps|exps|lifebook|any).
1535 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1537 psmouse.resetafter= [HW,MOUSE]
1538 Try to reset the device after so many bad packets
1541 [HW,MOUSE] Set desired mouse resolution, in dpi.
1542 psmouse.smartscroll=
1543 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1544 0 = disabled, 1 = enabled (default).
1546 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1548 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1551 See Documentation/paride.txt.
1554 [KNL] Number of legacy pty's. Overwrites compiled-in
1557 quiet [KNL] Disable most log messages
1562 See Documentation/md.txt.
1564 ramdisk_blocksize= [RAM]
1565 See Documentation/ramdisk.txt.
1567 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1568 See Documentation/ramdisk.txt.
1570 rcupdate.blimit= [KNL,BOOT]
1571 Set maximum number of finished RCU callbacks to process
1574 rcupdate.qhimark= [KNL,BOOT]
1575 Set threshold of queued
1576 RCU callbacks over which batch limiting is disabled.
1578 rcupdate.qlowmark= [KNL,BOOT]
1579 Set threshold of queued RCU callbacks below which
1580 batch limiting is re-enabled.
1584 Run specified binary instead of /init from the ramdisk,
1585 used for early userspace startup. See initrd.
1587 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1588 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1589 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1591 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1593 reservetop= [X86-32]
1595 Reserves a hole at the top of the kernel virtual
1598 reset_devices [KNL] Force drivers to reset the underlying device
1599 during initialization.
1602 Specify the partition device for software suspend
1604 resume_offset= [SWSUSP]
1605 Specify the offset from the beginning of the partition
1606 given by "resume=" at which the swap header is located,
1607 in <PAGE_SIZE> units (needed only for swap files).
1608 See Documentation/power/swsusp-and-swap-files.txt
1610 retain_initrd [RAM] Keep initrd memory after extraction
1612 rhash_entries= [KNL,NET]
1613 Set number of hash buckets for route cache
1615 riscom8= [HW,SERIAL]
1616 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1618 ro [KNL] Mount root device read-only on boot
1620 root= [KNL] Root filesystem
1622 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1623 mount the root filesystem
1625 rootflags= [KNL] Set root filesystem mount option string
1627 rootfstype= [KNL] Set root filesystem type
1629 rootwait [KNL] Wait (indefinitely) for root device to show up.
1630 Useful for devices that are detected asynchronously
1631 (e.g. USB and MMC devices).
1633 root_plug.vendor_id=
1634 [ROOTPLUG] Override the default vendor ID
1636 root_plug.product_id=
1637 [ROOTPLUG] Override the default product ID
1640 [ROOTPLUG] Enable debugging output
1642 rw [KNL] Mount root device read-write on boot
1644 S [KNL] Run init in single mode
1647 See drivers/net/irda/sa1100_ir.c.
1649 sbni= [NET] Granch SBNI12 leased line adapter
1651 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1652 Format: <io>[,<timeout>[,<isapnp>]]
1654 scsi_debug_*= [SCSI]
1655 See drivers/scsi/scsi_debug.c.
1657 scsi_default_dev_flags=
1658 [SCSI] SCSI default device flags
1661 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1662 Format: <vendor>:<model>:<flags>
1663 (flags are integer value)
1665 scsi_logging_level= [SCSI] a bit mask of logging levels
1666 See drivers/scsi/scsi_logging.h for bits. Also
1667 settable via sysctl at dev.scsi.logging_level
1668 (/proc/sys/dev/scsi/logging_level).
1669 There is also a nice 'scsi_logging_level' script in the
1670 S390-tools package, available for download at
1671 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1673 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1674 discovered. async scans them in kernel threads,
1675 allowing boot to proceed. none ignores them, expecting
1676 user space to do the scan.
1678 selinux [SELINUX] Disable or enable SELinux at boot time.
1679 Format: { "0" | "1" }
1680 See security/selinux/Kconfig help text.
1683 Default value is set via kernel config option.
1684 If enabled at boot time, /selinux/disable can be used
1685 later to disable prior to initial policy load.
1687 selinux_compat_net =
1688 [SELINUX] Set initial selinux_compat_net flag value.
1689 Format: { "0" | "1" }
1690 0 -- use new secmark-based packet controls
1691 1 -- use legacy packet controls
1692 Default value is 0 (preferred).
1693 Value can be changed at runtime via
1694 /selinux/compat_net.
1696 serialnumber [BUGS=X86-32]
1699 Maximal number of shapers.
1702 See header of drivers/scsi/sim710.c.
1709 slub_debug[=options[,slabs]] [MM, SLUB]
1710 Enabling slub_debug allows one to determine the
1711 culprit if slab objects become corrupted. Enabling
1712 slub_debug can create guard zones around objects and
1713 may poison objects when not in use. Also tracks the
1714 last alloc / free. For more information see
1715 Documentation/vm/slub.txt.
1717 slub_max_order= [MM, SLUB]
1718 Determines the maximum allowed order for slabs.
1719 A high setting may cause OOMs due to memory
1720 fragmentation. For more information see
1721 Documentation/vm/slub.txt.
1723 slub_min_objects= [MM, SLUB]
1724 The minimum number of objects per slab. SLUB will
1725 increase the slab order up to slub_max_order to
1726 generate a sufficiently large slab able to contain
1727 the number of objects indicated. The higher the number
1728 of objects the smaller the overhead of tracking slabs
1729 and the less frequently locks need to be acquired.
1730 For more information see Documentation/vm/slub.txt.
1732 slub_min_order= [MM, SLUB]
1733 Determines the mininum page order for slabs. Must be
1734 lower than slub_max_order.
1735 For more information see Documentation/vm/slub.txt.
1737 slub_nomerge [MM, SLUB]
1738 Disable merging of slabs with similar size. May be
1739 necessary if there is some reason to distinguish
1740 allocs to different slabs. Debug options disable
1741 merging on their own.
1742 For more information see Documentation/vm/slub.txt.
1745 Format: <io1>[,<io2>[,...,<io8>]]
1747 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1748 attempt to substitute SMP alternatives once at boot.
1750 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1751 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1752 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1753 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1754 smsc-ircc2.ircc_irq= [HW] IRQ line
1755 smsc-ircc2.ircc_dma= [HW] DMA channel
1756 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1757 0: Toshiba Satellite 1800 (GP data pin select)
1758 1: Fast pin select (default)
1761 snd-ad1816a= [HW,ALSA]
1763 snd-ad1848= [HW,ALSA]
1765 snd-ali5451= [HW,ALSA]
1767 snd-als100= [HW,ALSA]
1769 snd-als4000= [HW,ALSA]
1771 snd-azt2320= [HW,ALSA]
1773 snd-cmi8330= [HW,ALSA]
1775 snd-cmipci= [HW,ALSA]
1777 snd-cs4231= [HW,ALSA]
1779 snd-cs4232= [HW,ALSA]
1781 snd-cs4236= [HW,ALSA]
1783 snd-cs4281= [HW,ALSA]
1785 snd-cs46xx= [HW,ALSA]
1787 snd-dt019x= [HW,ALSA]
1789 snd-dummy= [HW,ALSA]
1791 snd-emu10k1= [HW,ALSA]
1793 snd-ens1370= [HW,ALSA]
1795 snd-ens1371= [HW,ALSA]
1797 snd-es968= [HW,ALSA]
1799 snd-es1688= [HW,ALSA]
1801 snd-es18xx= [HW,ALSA]
1803 snd-es1938= [HW,ALSA]
1805 snd-es1968= [HW,ALSA]
1807 snd-fm801= [HW,ALSA]
1809 snd-gusclassic= [HW,ALSA]
1811 snd-gusextreme= [HW,ALSA]
1813 snd-gusmax= [HW,ALSA]
1817 snd-ice1712= [HW,ALSA]
1819 snd-intel8x0= [HW,ALSA]
1821 snd-interwave= [HW,ALSA]
1826 snd-korg1212= [HW,ALSA]
1828 snd-maestro3= [HW,ALSA]
1830 snd-mpu401= [HW,ALSA]
1832 snd-mtpav= [HW,ALSA]
1834 snd-nm256= [HW,ALSA]
1836 snd-opl3sa2= [HW,ALSA]
1844 snd-opti93x= [HW,ALSA]
1848 snd-rme32= [HW,ALSA]
1850 snd-rme96= [HW,ALSA]
1852 snd-rme9652= [HW,ALSA]
1858 snd-sbawe= [HW,ALSA]
1860 snd-serial= [HW,ALSA]
1862 snd-sgalaxy= [HW,ALSA]
1864 snd-sonicvibes= [HW,ALSA]
1869 snd-sun-cs4231= [HW,ALSA]
1871 snd-trident= [HW,ALSA]
1873 snd-usb-audio= [HW,ALSA,USB]
1875 snd-via82xx= [HW,ALSA]
1877 snd-virmidi= [HW,ALSA]
1879 snd-wavefront= [HW,ALSA]
1881 snd-ymfpci= [HW,ALSA]
1883 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1884 See Documentation/sonypi.txt
1886 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1887 See Documentation/specialix.txt.
1889 spia_io_base= [HW,MTD]
1895 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1897 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1898 See Documentation/scsi/st.txt.
1902 Set the STI (builtin display/keyboard on the HP-PARISC
1903 machines) console (graphic card) which should be used
1904 as the initial boot-console.
1905 See also comment in drivers/video/console/sticore.c.
1908 See comment in drivers/video/console/sticore.c.
1911 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1915 Control how the NFS server code allocates CPUs to
1916 service thread pools. Depending on how many NICs
1917 you have and where their interrupts are bound, this
1918 option will affect which CPUs will do NFS serving.
1919 Note: this parameter cannot be changed while the
1920 NFS server is running.
1922 auto the server chooses an appropriate mode
1923 automatically using heuristics
1924 global a single global pool contains all CPUs
1925 percpu one pool for each CPU
1926 pernode one pool for each NUMA node (equivalent
1927 to global on non-NUMA machines)
1929 swiotlb= [IA-64] Number of I/O TLB slabs
1933 sym53c416= [HW,SCSI]
1934 See header of drivers/scsi/sym53c416.c.
1936 sysrq_always_enabled
1938 Ignore sysrq setting - this boot parameter will
1939 neutralize any effect of /proc/sys/kernel/sysrq.
1940 Useful for debugging.
1943 See header of drivers/scsi/t128.c.
1947 thash_entries= [KNL,NET]
1948 Set number of hash buckets for TCP connection
1950 thermal.act= [HW,ACPI]
1951 -1: disable all active trip points in all thermal zones
1952 <degrees C>: override all lowest active trip points
1954 thermal.crt= [HW,ACPI]
1955 -1: disable all critical trip points in all thermal zones
1956 <degrees C>: lower all critical trip points
1958 thermal.nocrt= [HW,ACPI]
1959 Set to disable actions on ACPI thermal zone
1960 critical and hot trip points.
1962 thermal.off= [HW,ACPI]
1963 1: disable ACPI thermal control
1965 thermal.psv= [HW,ACPI]
1966 -1: disable all passive trip points
1967 <degrees C>: override all passive trip points to this value
1969 thermal.tzp= [HW,ACPI]
1970 Specify global default ACPI thermal zone polling rate
1971 <deci-seconds>: poll all this frequency
1972 0: no polling (default)
1974 time Show timing data prefixed to each printk message line
1975 [deprecated, see 'printk.time']
1977 tipar.timeout= [HW,PPT]
1978 Set communications timeout in tenths of a second
1981 tipar.delay= [HW,PPT]
1982 Set inter-bit delay in microseconds (default 10).
1985 See comment before function dc390_setup() in
1986 drivers/scsi/tmscsim.c.
1990 trix= [HW,OSS] MediaTrix AudioTrix Pro
1992 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1994 turbografx.map[2|3]= [HW,JOY]
1995 TurboGraFX parallel port interface
1997 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1998 See also Documentation/input/joystick-parport.txt
2000 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2001 See header of drivers/scsi/u14-34f.c.
2010 [USB] Ignore overcurrent events (default N).
2011 Some badly-designed motherboards generate lots of
2012 bogus events, for ports that aren't wired to
2013 anything. Set this parameter to avoid log spamming.
2014 Note that genuine overcurrent events won't be
2017 usbcore.autosuspend=
2018 [USB] The autosuspend time delay (in seconds) used
2019 for newly-detected USB devices (default 2). This
2020 is the time required before an idle device will be
2021 autosuspended. Devices for which the delay is set
2022 to a negative value won't be autosuspended at all.
2025 [USBHID] The interval which mice are to be polled at.
2027 vdso= [X86-32,SH,x86-64]
2028 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2029 vdso=1: enable VDSO (default)
2030 vdso=0: disable VDSO mapping
2032 vdso32= [X86-32,X86-64]
2033 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2034 vdso32=1: enable 32-bit VDSO (default)
2035 vdso32=0: disable 32-bit VDSO mapping
2038 vector=percpu: enable percpu vector domain
2040 video= [FB] Frame buffer configuration
2041 See Documentation/fb/modedb.txt.
2043 vga= [BOOT,X86-32] Select a particular video mode
2044 See Documentation/i386/boot.txt and
2045 Documentation/svga.txt.
2046 Use vga=ask for menu.
2047 This is actually a boot loader parameter; the value is
2048 passed to the kernel using a special protocol.
2050 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2051 size of <nn>. This can be used to increase the
2052 minimum size (128MB on x86). It can also be used to
2053 decrease the size and leave more room for directly
2056 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2059 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2062 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2065 waveartist= [HW,OSS]
2066 Format: <io>,<irq>,<dma>,<dma2>
2069 See header of drivers/scsi/wd33c93.c.
2072 See header of drivers/scsi/wd7000.c.
2075 See Documentation/watchdog/wdt.txt.
2077 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2078 xd_geo= See header of drivers/block/xd.c.
2080 xirc2ps_cs= [NET,PCMCIA]
2082 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2084 norandmaps Don't use address space randomization
2085 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2087 ______________________________________________________________________
2091 Add documentation for ALSA options.
2092 Add more DRM drivers.