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 AX25 Appropriate AX.25 support is enabled.
38 BLACKFIN Blackfin architecture is enabled.
39 DRM Direct Rendering Management support is enabled.
40 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
41 EFI EFI Partitioning (GPT) is enabled
42 EIDE EIDE/ATAPI support is enabled.
43 FB The frame buffer device is enabled.
44 HW Appropriate hardware is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD (Memory Technology Device) support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel is enabled.
68 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCIE PCI Express support is enabled.
72 PCMCIA The PCMCIA subsystem is enabled.
73 PNP Plug & Play support is enabled.
74 PPC PowerPC architecture is enabled.
75 PPT Parallel port support is enabled.
76 PS2 Appropriate PS/2 support is enabled.
77 RAM RAM disk support is enabled.
78 ROOTPLUG The example Root Plug LSM is enabled.
79 S390 S390 architecture is enabled.
80 SCSI Appropriate SCSI support is enabled.
81 A lot of drivers has their options described inside of
83 SECURITY Different security models are enabled.
84 SELINUX SELinux support is enabled.
85 SERIAL Serial support is enabled.
86 SH SuperH architecture is enabled.
87 SMP The kernel is an SMP kernel.
88 SPARC Sparc architecture is enabled.
89 SWSUSP Software suspend is enabled.
90 TS Appropriate touchscreen support is enabled.
91 USB USB support is enabled.
92 USBHID USB Human Interface Device support is enabled.
93 V4L Video For Linux support is enabled.
94 VGA The VGA console has been enabled.
95 VT Virtual terminal support is enabled.
96 WDT Watchdog support is enabled.
97 XT IBM PC/XT MFM hard disk support is enabled.
98 X86-32 X86-32, aka i386 architecture is enabled.
99 X86-64 X86-64 architecture is enabled.
100 More X86-64 boot options can be found in
101 Documentation/x86_64/boot-options.txt .
103 In addition, the following text indicates that the option:
105 BUGS= Relates to possible processor bugs on the said processor.
106 KNL Is a kernel start-up parameter.
107 BOOT Is a boot loader parameter.
109 Parameters denoted with BOOT are actually interpreted by the boot
110 loader, and have no meaning to the kernel directly.
111 Do not modify the syntax of boot loader parameters without extreme
112 need or coordination with <Documentation/i386/boot.txt>.
114 There are also arch-specific kernel-parameters not documented here.
115 See for example <Documentation/x86_64/boot-options.txt>.
117 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
118 a trailing = on the name of any parameter states that that parameter will
119 be entered as an environment variable, whereas its absence indicates that
120 it will appear as a kernel argument readable via /proc/cmdline by programs
121 running once the system is up.
123 The number of kernel parameters is not limited, but the length of the
124 complete command line (parameters including spaces etc.) is limited to
125 a fixed number of characters. This limit depends on the architecture
126 and is between 256 and 4096 characters. It is defined in the file
127 ./include/asm/setup.h as COMMAND_LINE_SIZE.
130 acpi= [HW,ACPI,X86-64,i386]
131 Advanced Configuration and Power Interface
132 Format: { force | off | ht | strict | noirq }
133 force -- enable ACPI if default was off
134 off -- disable ACPI if default was on
135 noirq -- do not use ACPI for IRQ routing
136 ht -- run only enough ACPI to enable Hyper Threading
137 strict -- Be less tolerant of platforms that are not
138 strictly ACPI specification compliant.
140 See also Documentation/pm.txt, pci=noacpi
142 acpi_apic_instance= [ACPI, IOAPIC]
144 2: use 2nd APIC table, if available
145 1,0: use 1st APIC table
148 acpi_sleep= [HW,ACPI] Sleep options
149 Format: { s3_bios, s3_mode }
150 See Documentation/power/video.txt
152 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
153 Format: { level | edge | high | low }
155 acpi_irq_balance [HW,ACPI]
156 ACPI will balance active IRQs
159 acpi_irq_nobalance [HW,ACPI]
160 ACPI will not move active IRQs (default)
163 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
165 Format: <irq>,<irq>...
167 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
168 Format: <irq>,<irq>...
170 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
172 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
173 Format: To spoof as Windows 98: ="Microsoft Windows"
175 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
176 acpi_osi="string1" # add string1 -- only one string
177 acpi_osi="!string2" # remove built-in string2
178 acpi_osi= # disable all strings
180 acpi_serialize [HW,ACPI] force serialization of AML methods
182 acpi_skip_timer_override [HW,ACPI]
183 Recognize and ignore IRQ0/pin2 Interrupt Override.
184 For broken nForce2 BIOS resulting in XT-PIC timer.
185 acpi_use_timer_override [HW,ACPI}
186 Use timer override. For some broken Nvidia NF5 boards
187 that require a timer override, but don't have
190 acpi.debug_layer= [HW,ACPI]
192 Each bit of the <int> indicates an ACPI debug layer,
193 1: enable, 0: disable. It is useful for boot time
194 debugging. After system has booted up, it can be set
195 via /sys/module/acpi/parameters/debug_layer.
196 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
197 Available bits (add the numbers together) to enable debug output
198 for specific parts of the ACPI subsystem:
199 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
200 0x10 namespace 0x20 parser 0x40 dispatcher
201 0x80 executer 0x100 resources 0x200 acpica debugger
202 0x400 os services 0x800 acpica disassembler.
203 The number can be in decimal or prefixed with 0x in hex.
204 Warning: Many of these options can produce a lot of
205 output and make your system unusable. Be very careful.
207 acpi.debug_level= [HW,ACPI]
209 Each bit of the <int> indicates an ACPI debug level,
210 1: enable, 0: disable. It is useful for boot time
211 debugging. After system has booted up, it can be set
212 via /sys/module/acpi/parameters/debug_level.
213 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
214 Available bits (add the numbers together) to enable different
215 debug output levels of the ACPI subsystem:
216 0x01 error 0x02 warn 0x04 init 0x08 debug object
217 0x10 info 0x20 init names 0x40 parse 0x80 load
218 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
219 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
220 0x10000 resources 0x20000 user requests 0x40000 package.
221 The number can be in decimal or prefixed with 0x in hex.
222 Warning: Many of these options can produce a lot of
223 output and make your system unusable. Be very careful.
226 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
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.
303 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
304 Format: <io>,<irq>,<nodeID>
308 atarimouse= [HW,MOUSE] Atari Mouse
310 atascsi= [HW,SCSI] Atari SCSI
312 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
313 EzKey and similar keyboards
315 atkbd.reset= [HW] Reset keyboard during initialization
317 atkbd.set= [HW] Select keyboard code set
318 Format: <int> (2 = AT (default), 3 = PS/2)
320 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
323 atkbd.softraw= [HW] Choose between synthetic and real raw mode
324 Format: <bool> (0 = real, 1 = synthetic (default))
326 atkbd.softrepeat= [HW]
327 Use software keyboard repeat
331 baycom_epp= [HW,AX25]
334 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
336 See header of drivers/net/hamradio/baycom_par.c.
338 baycom_ser_fdx= [HW,AX25]
339 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
340 Format: <io>,<irq>,<mode>[,<baud>]
341 See header of drivers/net/hamradio/baycom_ser_fdx.c.
343 baycom_ser_hdx= [HW,AX25]
344 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
345 Format: <io>,<irq>,<mode>
346 See header of drivers/net/hamradio/baycom_ser_hdx.c.
348 blkmtd_device= [HW,MTD]
354 boot_delay= Milliseconds to delay each printk during boot.
355 Values larger than 10 seconds (10000) are changed to
359 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
360 bttv.radio= Most important insmod options are available as
362 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
363 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
366 See drivers/scsi/BusLogic.c, comment before function
367 BusLogic_ParseDriverOptions().
369 c101= [NET] Moxa C101 synchronous serial card
371 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
372 Sometimes CPU hardware bugs make them report the cache
373 size incorrectly. The kernel will attempt work arounds
374 to fix known problems, but for some CPUs it is not
375 possible to determine what the correct size should be.
376 This option provides an override for these situations.
379 [SECURITY] Disable capabilities. This would normally
380 be used only if an alternative security model is to be
381 configured. Potentially dangerous and should only be
382 used if you are entirely sure of the consequences.
384 chandev= [HW,NET] Generic channel device initialisation
386 checkreqprot [SELINUX] Set initial checkreqprot flag value.
387 Format: { "0" | "1" }
388 See security/selinux/Kconfig help text.
389 0 -- check protection applied by kernel (includes
390 any implied execute protection).
391 1 -- check protection requested by application.
392 Default value is set via a kernel config option.
393 Value can be changed at runtime via
394 /selinux/checkreqprot.
396 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
398 Forces specified clocksource (if available) to be used
399 when calculating gettimeofday(). If specified
400 clocksource is not available, it defaults to PIT.
401 Format: { pit | tsc | cyclone | pmtmr }
403 clocksource= [GENERIC_TIME] Override the default clocksource
405 Override the default clocksource and use the clocksource
406 with the name specified.
407 Some clocksource names to choose from, depending on
409 [all] jiffies (this is the base, fallback clocksource)
411 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
412 pxa_timer,timer3,32k_counter,timer0_1
414 [X86-32] pit,hpet,tsc,vmi-timer;
415 scx200_hrt on Geode; cyclone on IBM x440
423 code_bytes [IA32] How many bytes of object code to print in an
430 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
431 over the 8254 in addition to over the IO-APIC. The
432 kernel tries to set a sensible default.
434 hpet= [X86-32,HPET] option to disable HPET and use PIT.
437 com20020= [HW,NET] ARCnet - COM20020 chipset
439 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
441 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
445 ARCnet - COM90xx chipset (memory-mapped buffers)
446 Format: <io>[,<irq>[,<memstart>]]
448 condev= [HW,S390] console device
451 console= [KNL] Output console device and options.
453 tty<n> Use the virtual console device <n>.
457 Use the specified serial port. The options are of
458 the form "bbbbpnf", where "bbbb" is the baud rate,
459 "p" is parity ("n", "o", or "e"), "n" is number of
460 bits, and "f" is flow control ("r" for RTS or
461 omit it). Default is "9600n8".
463 See Documentation/serial-console.txt for more
465 Documentation/networking/netconsole.txt for an
468 uart[8250],io,<addr>[,options]
469 uart[8250],mmio,<addr>[,options]
470 Start an early, polled-mode console on the 8250/16550
471 UART at the specified I/O port or MMIO address,
472 switching to the matching ttyS device later. The
473 options are the same as for ttyS, above.
475 earlycon= [KNL] Output early console device and options.
476 uart[8250],io,<addr>[,options]
477 uart[8250],mmio,<addr>[,options]
478 Start an early, polled-mode console on the 8250/16550
479 UART at the specified I/O port or MMIO address.
480 The options are the same as for ttyS, above.
483 [HW] Never suspend the console
484 Disable suspending of consoles during suspend and
485 hibernate operations. Once disabled, debugging
486 messages can reach various consoles while the rest
487 of the system is being put to sleep (ie, while
488 debugging driver suspend/resume hooks). This may
489 not work reliably with all consoles, but is known
490 to work with serial and VGA consoles.
492 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
494 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
496 crashkernel=nn[KMG]@ss[KMG]
497 [KNL] Reserve a chunk of physical memory to
498 hold a kernel to switch to with kexec on panic.
500 crashkernel=range1:size1[,range2:size2,...][@offset]
501 [KNL] Same as above, but depends on the memory
502 in the running system. The syntax of range is
503 start-[end] where start and end are both
504 a memory unit (amount[KMG]). See also
505 Documentation/kdump/kdump.txt for a example.
508 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
513 cs89x0_media= [HW,NET]
514 Format: { rj45 | aui | bnc }
516 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
519 See header of drivers/s390/block/dasd_devmap.c.
521 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
522 (one device per port)
523 Format: <port#>,<type>
524 See also Documentation/input/joystick-parport.txt
526 debug [KNL] Enable kernel debugging (events log level).
529 [KNL] verbose self-tests
531 Print debugging info while doing the locking API
533 We default to 0 (no extra messages), setting it to
534 1 will print _a lot_ more information - normally
535 only useful to kernel developers.
538 Format: <area>[,<node>]
539 See also Documentation/networking/decnet.txt.
542 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
543 Change the default blue palette of the console.
544 This is a 16-member array composed of values
548 Format: <green0>,<green1>,<green2>,...,<green15>
549 Change the default green palette of the console.
550 This is a 16-member array composed of values
554 Format: <red0>,<red1>,<red2>,...,<red15>
555 Change the default red palette of the console.
556 This is a 16-member array composed of values
561 Set system-wide default UTF-8 mode for all tty's.
562 Default is 0 and by setting to 1, it enables UTF-8
563 mode for all newly opened or allocated terminals.
566 Set number of hash buckets for dentry cache.
569 IO parameters + enable/disable command.
571 digiepca= [HW,SERIAL]
572 See drivers/char/README.epca and
573 Documentation/digiepca.txt.
575 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
577 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
579 dmasound= [HW,OSS] Sound subsystem buffers
585 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
587 earlyprintk=serial[,ttySn[,baudrate]]
589 Append ",keep" to not disable it when the real console
592 Only vga or serial at a time, not both.
594 Currently only ttyS0 and ttyS1 are supported.
596 Interaction with the standard serial driver is not
599 The VGA output is eventually overwritten by the real
604 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
607 non-0: interrupt mode (default)
614 Format: {"of[f]" | "sk[ipmbr]"}
615 See comment in arch/i386/boot/edd.S
617 eisa_irq_edge= [PARISC,HW]
618 See header of drivers/parisc/eisa.c.
621 See comment before function elanfreq_setup() in
622 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
625 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
626 See Documentation/block/as-iosched.txt and
627 Documentation/block/deadline-iosched.txt for details.
629 elfcorehdr= [X86-32, X86_64]
630 Specifies physical address of start of kernel core
631 image elf header. Generally kexec loader will
632 pass this option to capture kernel.
633 See Documentation/kdump/kdump.txt for details.
635 enforcing [SELINUX] Set initial enforcing status.
637 See security/selinux/Kconfig help text.
638 0 -- permissive (log only, no denials).
639 1 -- enforcing (deny and log).
641 Value can be changed at runtime via /selinux/enforce.
644 Format: <spdif>,[<nomix>,[<amplifier>]]
645 See also header of sound/oss/es1371.c.
647 ether= [HW,NET] Ethernet cards parameters
648 This option is obsoleted by the "netdev=" option, which
649 has equivalent usage. See its documentation for details.
651 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
656 fail_make_request=[KNL]
657 General fault injection mechanism.
658 Format: <interval>,<probability>,<space>,<times>
659 See also /Documentation/fault-injection/.
662 See header of drivers/scsi/fd_mcs.c.
665 See header of drivers/scsi/fdomain.c.
668 See Documentation/floppy.txt.
671 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
672 support via parallel port (up to 5 devices per port)
673 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
674 See also Documentation/input/joystick-parport.txt
679 See header of drivers/scsi/gdth.c.
681 gpt [EFI] Forces disk with valid GPT signature but
682 invalid Protective MBR to be treated as GPT.
686 hashdist= [KNL,NUMA] Large hashes allocated during boot
687 are distributed across NUMA nodes. Defaults on
688 for IA-64, off otherwise.
689 Format: 0 | 1 (for off | on)
691 hcl= [IA-64] SGI's Hardware Graph compatibility layer
693 hd= [EIDE] (E)IDE hard drive subsystem geometry
694 Format: <cyl>,<head>,<sect>
696 hd?= [HW] (E)IDE subsystem
697 hd?lun= See Documentation/ide.txt.
699 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
700 size of <nn>. This works even on boxes that have no
701 highmem otherwise. This also works to reduce highmem
702 size on bigger boxes.
704 highres= [KNL] Enable/disable high resolution timer mode.
705 Valid parameters: "on", "off"
709 See Documentation/isdn/README.HiSax.
711 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
713 i8042.direct [HW] Put keyboard port into non-translated mode
714 i8042.dumbkbd [HW] Pretend that controller can only read data from
715 keyboard and cannot control its state
716 (Don't attempt to blink the leds)
717 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
718 i8042.nokbd [HW] Don't check/create keyboard port
719 i8042.nomux [HW] Don't check presence of an active multiplexing
721 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
724 [HW] Frequency with which keyboard LEDs should blink
725 when kernel panics (default is 0.5 sec)
726 i8042.reset [HW] Reset the controller during init and cleanup
727 i8042.unlock [HW] Unlock (ignore) the keylock
731 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
732 indicates that the driver is running on unsupported
734 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
735 does not match list of supported models.
737 [HW] Report power status in /proc/i8k
738 (disabled by default)
739 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
742 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
743 See Documentation/mca.txt.
746 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
748 ide= [HW] (E)IDE subsystem
749 Format: ide=nodma or ide=doubler or ide=reverse
750 See Documentation/ide.txt.
752 ide?= [HW] (E)IDE subsystem
753 Format: ide?=noprobe or chipset specific parameters.
754 See Documentation/ide.txt.
756 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
757 See Documentation/ide.txt.
760 Format: idle=poll or idle=mwait
761 Poll forces a polling idle loop that can slightly improves the performance
762 of waking up a idle CPU, but will use a lot of power and make the system
763 run hot. Not recommended.
764 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
765 to not use it because it doesn't save as much power as a normal idle
766 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
769 ignore_loglevel [KNL]
770 Ignore loglevel setting - this will print /all/
771 kernel messages to the console. Useful for debugging.
774 Set number of hash buckets for inode cache.
777 See header of drivers/scsi/in2000.c.
781 Run specified binary instead of /sbin/init as init
784 initcall_debug [KNL] Trace initcalls as they are executed. Useful
785 for working out where the kernel is dying during
788 initrd= [BOOT] Specify the location of the initial ramdisk
790 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
795 io7= [HW] IO7 for Marvel based alpha systems
796 See comment before marvel_specify_io7 in
797 arch/alpha/kernel/core_marvel.c.
800 See Documentation/nfsroot.txt.
802 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
803 See comment before ip2_setup() in
804 drivers/char/ip2/ip2base.c.
806 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
807 See header of drivers/scsi/ips.c.
809 ports= [IP_VS_FTP] IPVS ftp helper module
811 Up to 8 (IP_VS_APP_MAX_PORTS) ports
813 Format: <port>,<port>....
816 When an interrupt is not handled search all handlers
817 for it. Intended to get systems with badly broken
821 When an interrupt is not handled search all handlers
822 for it. Also check all handlers each timer
823 interrupt. Intended to get systems with badly broken
827 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
829 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
831 <cpu number>,...,<cpu number>
833 <cpu number>-<cpu number> (must be a positive range in ascending order)
835 <cpu number>,...,<cpu number>-<cpu number>
836 This option can be used to specify one or more CPUs
837 to isolate from the general SMP balancing and scheduling
838 algorithms. The only way to move a process onto or off
839 an "isolated" CPU is via the CPU affinity syscalls.
840 <cpu number> begins at 0 and the maximum value is
841 "number of CPUs in system - 1".
843 This option is the preferred way to isolate CPUs. The
844 alternative -- manually setting the CPU mask of all
845 tasks in the system -- can cause problems and
846 suboptimal load balancer performance.
850 js= [HW,JOY] Analog joystick
851 See Documentation/input/joystick.txt.
853 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
854 specifies the amount of memory usable by the kernel
855 for non-movable allocations. The requested amount is
856 spread evenly throughout all nodes in the system. The
857 remaining memory in each node is used for Movable
858 pages. In the event, a node is too small to have both
859 kernelcore and Movable pages, kernelcore pages will
860 take priority and other nodes will have a larger number
861 of kernelcore pages. The Movable zone is used for the
862 allocation of pages that may be reclaimed or moved
863 by the page migration subsystem. This means that
864 HugeTLB pages may not be allocated from this zone.
865 Note that allocations like PTEs-from-HighMem still
866 use the HighMem zone if it exists, and the Normal
869 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
870 is similar to kernelcore except it specifies the
871 amount of memory used for migratable allocations.
872 If both kernelcore and movablecore is specified,
873 then kernelcore will be at *least* the specified
874 value but may be more. If movablecore on its own
875 is specified, the administrator must be careful
876 that the amount of memory usable for all allocations
881 kstack=N [X86-32,X86-64] Print N words from the kernel stack
886 lapic [X86-32,APIC] Enable the local APIC even if BIOS
889 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
892 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
893 Format: addr:<io>,irq:<irq>
895 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
899 load_ramdisk= [RAM] List of ramdisks to load from floppy
900 See Documentation/ramdisk.txt.
902 lockd.nlm_grace_period=P [NFS] Assign grace period.
905 lockd.nlm_tcpport=N [NFS] Assign TCP port.
908 lockd.nlm_timeout=T [NFS] Assign timeout value.
911 lockd.nlm_udpport=M [NFS] Assign UDP port.
914 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
917 loglevel= All Kernel Messages with a loglevel smaller than the
918 console loglevel will be printed to the console. It can
919 also be changed with klogd or other programs. The
920 loglevels are defined as follows:
922 0 (KERN_EMERG) system is unusable
923 1 (KERN_ALERT) action must be taken immediately
924 2 (KERN_CRIT) critical conditions
925 3 (KERN_ERR) error conditions
926 4 (KERN_WARNING) warning conditions
927 5 (KERN_NOTICE) normal but significant condition
928 6 (KERN_INFO) informational
929 7 (KERN_DEBUG) debug-level messages
931 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
932 Format: { n | nk | nM }
933 n must be a power of two. The default size
934 is set in the kernel config file.
936 logo.nologo [FB] Disables display of the built-in Linux logo.
937 This may be used to provide more screen space for
938 kernel log messages and is useful when debugging
939 kernel boot problems.
941 lp=0 [LP] Specify parallel ports to use, e.g,
942 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
943 lp=reset first parallel port). 'lp=0' disables the
944 lp=auto printer driver. 'lp=reset' (which can be
945 specified in addition to the ports) causes
946 attached printers to be reset. Using
947 lp=port1,port2,... specifies the parallel ports
948 to associate lp devices with, starting with
949 lp0. A port specification may be 'none' to skip
950 that lp device, or a parport name such as
951 'parport0'. Specifying 'lp=auto' instead of a
952 port specification list means that device IDs
953 from each port should be examined, to see if
954 an IEEE 1284-compliant printer is attached; if
955 so, the driver will manage that printer.
956 See also header of drivers/char/lp.c.
959 Sets loops_per_jiffy to given constant, thus avoiding
960 time-consuming boot-time autodetection (up to 250 ms per
961 CPU). 0 enables autodetection (default). To determine
962 the correct value for your kernel, boot with normal
963 autodetection and see what value is printed. Note that
964 on SMP systems the preset will be applied to all CPUs,
965 which is likely to cause problems if your CPUs need
966 significantly divergent settings. An incorrect value
967 will cause delays in the kernel to be wrong, leading to
968 unpredictable I/O errors and other breakage. Although
969 unlikely, in the extreme case this might damage your
973 Format: <io>,<irq>,<dma>
975 mac5380= [HW,SCSI] Format:
976 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
978 mac53c9x= [HW,SCSI] Format:
979 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
981 machvec= [IA64] Force the use of a particular machine-vector
982 (machvec) in a generic kernel.
983 Example: machvec=hpzx1_swiotlb
985 max_loop= [LOOP] Maximum number of loopback devices that can
989 maxcpus= [SMP] Maximum number of processors that an SMP kernel
990 should make use of. maxcpus=n : n >= 0 limits the
991 kernel to using 'n' processors. n=0 is a special case,
992 it is equivalent to "nosmp", which also disables
995 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
996 equal to this physical address is ignored.
998 max_luns= [SCSI] Maximum number of LUNs to probe.
999 Should be between 1 and 2^32-1.
1002 [SCSI] Maximum number of LUNs received.
1003 Should be between 1 and 16384.
1005 mca-pentium [BUGS=X86-32]
1009 mce [X86-32] Machine Check Exception
1011 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1013 md= [HW] RAID subsystems devices and level
1014 See Documentation/md.txt.
1017 Format: <first>,<last>
1018 Specifies range of consoles to be captured by the MDA.
1020 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1021 Amount of memory to be used when the kernel is not able
1022 to see the whole system memory or for test.
1023 [X86-32] Use together with memmap= to avoid physical
1024 address space collisions. Without memmap= PCI devices
1025 could be placed at addresses belonging to unused RAM.
1027 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1030 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1031 E820 memory map, as specified by the user.
1032 Such memmap=exactmap lines can be constructed based on
1033 BIOS output or other requirements. See the memmap=nn@ss
1036 memmap=nn[KMG]@ss[KMG]
1037 [KNL] Force usage of a specific region of memory
1038 Region of memory to be used, from ss to ss+nn.
1040 memmap=nn[KMG]#ss[KMG]
1041 [KNL,ACPI] Mark specific memory as ACPI data.
1042 Region of memory to be used, from ss to ss+nn.
1044 memmap=nn[KMG]$ss[KMG]
1045 [KNL,ACPI] Mark specific memory as reserved.
1046 Region of memory to be used, from ss to ss+nn.
1048 meye.*= [HW] Set MotionEye Camera parameters
1049 See Documentation/video4linux/meye.txt.
1051 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1052 Multi-Function General Purpose Timers on AMD Geode
1058 [MOUSE] Maximum time between finger touching and
1059 leaving touchpad surface for touch to be considered
1060 a tap and be reported as a left button click (for
1061 touchpads working in absolute mode only).
1063 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1064 reporting absolute coordinates, such as tablets
1065 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1066 reporting absolute coordinates, such as tablets
1071 MTD_Partition= [MTD]
1072 Format: <name>,<region-number>,<size>,<offset>
1074 MTD_Region= [MTD] Format:
1075 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1078 See drivers/mtd/cmdlinepart.c.
1080 mtouchusb.raw_coordinates=
1081 [HW] Make the MicroTouch USB driver use raw coordinates
1082 ('y', default) or cooked coordinates ('n')
1084 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1087 See header of drivers/scsi/NCR_D700.c.
1091 ncr53c400= [HW,SCSI]
1093 ncr53c400a= [HW,SCSI]
1095 ncr53c406a= [HW,SCSI]
1097 ncr53c8xx= [HW,SCSI]
1099 netdev= [NET] Network devices parameters
1100 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1101 Note that mem_start is often overloaded to mean
1102 something different and driver-specific.
1103 This usage is only documented in each driver source
1107 See Documentation/nfsroot.txt.
1109 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1110 See Documentation/nfsroot.txt.
1112 nfs.callback_tcpport=
1113 [NFS] set the TCP port on which the NFSv4 callback
1114 channel should listen.
1116 nfs.idmap_cache_timeout=
1117 [NFS] set the maximum lifetime for idmapper cache
1121 [NFS] enable 64-bit inode numbers.
1122 If zero, the NFS client will fake up a 32-bit inode
1123 number for the readdir() and stat() syscalls instead
1124 of returning the full 64-bit number.
1125 The default is to return 64-bit inode numbers.
1127 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1129 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1130 emulation library even if a 387 maths coprocessor
1133 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1134 caches in the slab allocator. Saves per-node memory,
1135 but will impact performance.
1139 noapic [SMP,APIC] Tells the kernel to not make use of any
1140 IOAPICs that may be present in the system.
1142 noasync [HW,M68K] Disables async and sync negotiation for
1145 nobats [PPC] Do not use BATs for mapping kernel lowmem
1146 on "Classic" PPC cores.
1150 nodelayacct [KNL] Disable per-task delay accounting
1152 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1156 noexec [X86-32,X86-64]
1157 noexec=on: enable non-executable mappings (default)
1158 noexec=off: disable nn-executable mappings
1160 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1161 register save and restore. The kernel will only save
1162 legacy floating-point registers on task switch.
1166 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1167 instruction doesn't work correctly and not to
1170 nohalt [IA-64] Tells the kernel not to use the power saving
1171 function PAL_HALT_LIGHT when idle. This increases
1172 power-consumption. On the positive side, it reduces
1173 interrupt wake-up latency, which may improve performance
1174 in certain environments such as networked servers or
1177 nohz= [KNL] Boottime enable/disable dynamic ticks
1178 Valid arguments: on, off
1181 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1183 noirqdebug [X86-32] Disables the code which attempts to detect and
1184 disable unhandled interrupt sources.
1186 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1187 broken timer IRQ sources.
1189 noisapnp [ISAPNP] Disables ISA PnP code.
1191 noinitrd [RAM] Tells the kernel not to load any configured
1196 nojitter [IA64] Disables jitter checking for ITC timers.
1198 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1200 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1202 noltlbs [PPC] Do not use large page/tlb entries for kernel
1203 lowmem mapping on PPC40x.
1205 nomca [IA-64] Disable machine check abort handling
1207 nomce [X86-32] Machine Check Exception
1209 nomfgpt [X86-32] Disable Multi-Function General Purpose
1210 Timer usage (for AMD Geode machines).
1212 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1214 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1215 with UP alternatives
1217 noresidual [PPC] Don't use residual data on PReP machines.
1219 noresume [SWSUSP] Disables resume and restores original swap
1222 no-scroll [VGA] Disables scrollback.
1223 This is required for the Braillex ib80-piezo Braille
1224 reader made by F.H. Papenmeier (Germany).
1228 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1230 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1231 and disable the IO APIC. legacy for "maxcpus=0".
1233 nosoftlockup [KNL] Disable the soft-lockup detector.
1235 nosync [HW,M68K] Disables sync negotiation for all devices.
1237 notsc [BUGS=X86-32] Disable Time Stamp Counter
1239 nousb [USB] Disable the USB subsystem
1243 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1244 one of ['zone', 'node', 'default'] can be specified
1245 This can be set from sysctl after boot.
1246 See Documentation/sysctl/vm.txt for details.
1248 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1253 oprofile.timer= [HW]
1254 Use timer interrupt instead of performance counters
1256 osst= [HW,SCSI] SCSI Tape Driver
1257 Format: <buffer_size>,<write_threshold>
1258 See also Documentation/scsi/st.txt.
1260 panic= [KNL] Kernel behaviour on panic
1263 parkbd.port= [HW] Parallel port number the keyboard adapter is
1264 connected to, default is 0.
1266 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1267 0 for XT, 1 for AT (default is AT).
1270 parport= [HW,PPT] Specify parallel ports. 0 disables.
1271 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1272 Use 'auto' to force the driver to use any
1273 IRQ/DMA settings detected (the default is to
1274 ignore detected IRQ/DMA settings because of
1275 possible conflicts). You can specify the base
1276 address, IRQ, and DMA settings; IRQ and DMA
1277 should be numbers, or 'auto' (for using detected
1278 settings on that particular port), or 'nofifo'
1279 (to avoid using a FIFO even if it is detected).
1280 Parallel ports are assigned in the order they
1281 are specified on the command line, starting
1284 parport_init_mode= [HW,PPT]
1285 Configure VIA parallel port to operate in
1286 a specific mode. This is necessary on Pegasos
1287 computer where firmware has no options for setting
1288 up parallel port mode and sets it to spp.
1289 Currently this function knows 686a and 8231 chips.
1290 Format: [spp|ps2|epp|ecp|ecpepp]
1292 pas2= [HW,OSS] Format:
1293 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1296 See header of drivers/scsi/pas16.c.
1299 Halt all CPUs after the first oops has been printed for
1300 the specified number of seconds. This is to be used if
1301 your oopses keep scrolling off the screen.
1306 See header of drivers/block/paride/pcd.c.
1307 See also Documentation/paride.txt.
1309 pci=option[,option...] [PCI] various PCI subsystem options:
1310 off [X86-32] don't probe for the PCI bus
1311 bios [X86-32] force use of PCI BIOS, don't access
1312 the hardware directly. Use this if your machine
1313 has a non-standard PCI host bridge.
1314 nobios [X86-32] disallow use of PCI BIOS, only direct
1315 hardware access methods are allowed. Use this
1316 if you experience crashes upon bootup and you
1317 suspect they are caused by the BIOS.
1318 conf1 [X86-32] Force use of PCI Configuration
1320 conf2 [X86-32] Force use of PCI Configuration
1322 noaer [PCIE] If the PCIEAER kernel config parameter is
1323 enabled, this kernel boot option can be used to
1324 disable the use of PCIE advanced error reporting.
1325 nodomains [PCI] Disable support for multiple PCI
1326 root domains (aka PCI segments, in ACPI-speak).
1327 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1329 nomsi [MSI] If the PCI_MSI kernel config parameter is
1330 enabled, this kernel boot option can be used to
1331 disable the use of MSI interrupts system-wide.
1332 nosort [X86-32] Don't sort PCI devices according to
1333 order given by the PCI BIOS. This sorting is
1334 done to get a device order compatible with
1336 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1337 routing table. These calls are known to be buggy
1338 on several machines and they hang the machine
1339 when used, but on other computers it's the only
1340 way to get the interrupt routing table. Try
1341 this option if the kernel is unable to allocate
1342 IRQs or discover secondary PCI buses on your
1344 rom [X86-32] Assign address space to expansion ROMs.
1345 Use with caution as certain devices share
1346 address decoders between ROMs and other
1348 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1349 assigned automatically to PCI devices. You can
1350 make the kernel exclude IRQs of your ISA cards
1352 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1353 of the PIRQ table (normally generated
1354 by the BIOS) if it is outside the
1355 F0000h-100000h range.
1356 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1357 useful if the kernel is unable to find your
1358 secondary buses and you want to tell it
1359 explicitly which ones they are.
1360 assign-busses [X86-32] Always assign all PCI bus
1361 numbers ourselves, overriding
1362 whatever the firmware may have done.
1363 usepirqmask [X86-32] Honor the possible IRQ mask stored
1364 in the BIOS $PIR table. This is needed on
1365 some systems with broken BIOSes, notably
1366 some HP Pavilion N5400 and Omnibook XE3
1367 notebooks. This will have no effect if ACPI
1368 IRQ routing is enabled.
1369 noacpi [X86-32] Do not use ACPI for IRQ routing
1370 or for PCI scanning.
1371 use_crs [X86-32] Use _CRS for PCI resource
1373 routeirq Do IRQ routing for all PCI devices.
1374 This is normally done in pci_enable_device(),
1375 so this option is a temporary workaround
1376 for broken drivers that don't call it.
1377 firmware [ARM] Do not re-enumerate the bus but instead
1378 just use the configuration from the
1379 bootloader. This is currently used on
1380 IXP2000 systems where the bus has to be
1381 configured a certain way for adjunct CPUs.
1382 noearly [X86] Don't do any early type 1 scanning.
1383 This might help on some broken boards which
1384 machine check when some devices' config space
1385 is read. But various workarounds are disabled
1386 and some IOMMU drivers will not work.
1387 bfsort Sort PCI devices into breadth-first order.
1388 This sorting is done to get a device
1389 order compatible with older (<= 2.4) kernels.
1390 nobfsort Don't sort PCI devices into breadth-first order.
1391 cbiosize=nn[KMG] The fixed amount of bus space which is
1392 reserved for the CardBus bridge's IO window.
1393 The default value is 256 bytes.
1394 cbmemsize=nn[KMG] The fixed amount of bus space which is
1395 reserved for the CardBus bridge's memory
1396 window. The default value is 64 megabytes.
1398 pcmv= [HW,PCMCIA] BadgePAD 4
1401 See Documentation/paride.txt.
1403 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1406 See arch/parisc/kernel/pdc_chassis.c
1409 See Documentation/paride.txt.
1412 See Documentation/paride.txt.
1414 pirq= [SMP,APIC] Manual mp-table setup
1415 See Documentation/i386/IO-APIC.txt.
1417 plip= [PPT,NET] Parallel port network link
1418 Format: { parport<nr> | timid | 0 }
1419 See also Documentation/parport.txt.
1425 { on | off | curr | res | no-curr | no-res }
1428 [ISAPNP] Exclude IRQs for the autoconfiguration
1431 [ISAPNP] Exclude DMAs for the autoconfiguration
1433 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1434 Ranges are in pairs (I/O port base and size).
1437 [ISAPNP] Exclude memory regions for the
1439 Ranges are in pairs (memory base and size).
1441 print-fatal-signals=
1442 [KNL] debug: print fatal signals
1443 print-fatal-signals=1: print segfault info to
1447 printk.time= Show timing data prefixed to each printk message line
1448 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1450 profile= [KNL] Enable kernel profiling via /proc/profile
1451 Format: [schedule,]<number>
1452 Param: "schedule" - profile schedule points.
1453 Param: <number> - step/bucket size as a power of 2 for
1454 statistical time based profiling.
1455 Param: "sleep" - profile D-state sleeping (millisecs)
1457 processor.max_cstate= [HW,ACPI]
1458 Limit processor to maximum C-state
1459 max_cstate=9 overrides any DMI blacklist limit.
1461 processor.nocst [HW,ACPI]
1462 Ignore the _CST method to determine C-states,
1463 instead using the legacy FADT method
1465 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1467 See Documentation/ramdisk.txt.
1469 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1470 probe for; one of (bare|imps|exps|lifebook|any).
1471 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1473 psmouse.resetafter= [HW,MOUSE]
1474 Try to reset the device after so many bad packets
1477 [HW,MOUSE] Set desired mouse resolution, in dpi.
1478 psmouse.smartscroll=
1479 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1480 0 = disabled, 1 = enabled (default).
1482 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1484 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1487 See Documentation/paride.txt.
1490 [KNL] Number of legacy pty's. Overwrites compiled-in
1493 quiet [KNL] Disable most log messages
1498 See Documentation/md.txt.
1500 ramdisk_blocksize= [RAM]
1501 See Documentation/ramdisk.txt.
1503 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1504 See Documentation/ramdisk.txt.
1506 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1507 RCU callbacks to process in one batch.
1509 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1510 RCU callbacks over which batch limiting is disabled.
1512 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1513 RCU callbacks below which batch limiting is re-enabled.
1517 Run specified binary instead of /init from the ramdisk,
1518 used for early userspace startup. See initrd.
1520 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1521 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1522 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1524 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1526 reservetop= [X86-32]
1528 Reserves a hole at the top of the kernel virtual
1531 reset_devices [KNL] Force drivers to reset the underlying device
1532 during initialization.
1535 Specify the partition device for software suspend
1537 resume_offset= [SWSUSP]
1538 Specify the offset from the beginning of the partition
1539 given by "resume=" at which the swap header is located,
1540 in <PAGE_SIZE> units (needed only for swap files).
1541 See Documentation/power/swsusp-and-swap-files.txt
1543 retain_initrd [RAM] Keep initrd memory after extraction
1545 rhash_entries= [KNL,NET]
1546 Set number of hash buckets for route cache
1548 riscom8= [HW,SERIAL]
1549 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1551 ro [KNL] Mount root device read-only on boot
1553 root= [KNL] Root filesystem
1555 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1556 mount the root filesystem
1558 rootflags= [KNL] Set root filesystem mount option string
1560 rootfstype= [KNL] Set root filesystem type
1562 rootwait [KNL] Wait (indefinitely) for root device to show up.
1563 Useful for devices that are detected asynchronously
1564 (e.g. USB and MMC devices).
1566 root_plug.vendor_id=
1567 [ROOTPLUG] Override the default vendor ID
1569 root_plug.product_id=
1570 [ROOTPLUG] Override the default product ID
1573 [ROOTPLUG] Enable debugging output
1575 rw [KNL] Mount root device read-write on boot
1577 S [KNL] Run init in single mode
1580 See drivers/net/irda/sa1100_ir.c.
1582 sbni= [NET] Granch SBNI12 leased line adapter
1584 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1585 Format: <io>[,<timeout>[,<isapnp>]]
1587 scsi_debug_*= [SCSI]
1588 See drivers/scsi/scsi_debug.c.
1590 scsi_default_dev_flags=
1591 [SCSI] SCSI default device flags
1594 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1595 Format: <vendor>:<model>:<flags>
1596 (flags are integer value)
1598 scsi_logging= [SCSI]
1600 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1601 discovered. async scans them in kernel threads,
1602 allowing boot to proceed. none ignores them, expecting
1603 user space to do the scan.
1605 selinux [SELINUX] Disable or enable SELinux at boot time.
1606 Format: { "0" | "1" }
1607 See security/selinux/Kconfig help text.
1610 Default value is set via kernel config option.
1611 If enabled at boot time, /selinux/disable can be used
1612 later to disable prior to initial policy load.
1614 selinux_compat_net =
1615 [SELINUX] Set initial selinux_compat_net flag value.
1616 Format: { "0" | "1" }
1617 0 -- use new secmark-based packet controls
1618 1 -- use legacy packet controls
1619 Default value is 0 (preferred).
1620 Value can be changed at runtime via
1621 /selinux/compat_net.
1623 serialnumber [BUGS=X86-32]
1625 sg_def_reserved_size= [SCSI]
1628 Maximal number of shapers.
1631 See header of drivers/scsi/sim710.c.
1638 slub_debug[=options[,slabs]] [MM, SLUB]
1639 Enabling slub_debug allows one to determine the
1640 culprit if slab objects become corrupted. Enabling
1641 slub_debug can create guard zones around objects and
1642 may poison objects when not in use. Also tracks the
1643 last alloc / free. For more information see
1644 Documentation/vm/slub.txt.
1646 slub_max_order= [MM, SLUB]
1647 Determines the maximum allowed order for slabs.
1648 A high setting may cause OOMs due to memory
1649 fragmentation. For more information see
1650 Documentation/vm/slub.txt.
1652 slub_min_objects= [MM, SLUB]
1653 The minimum number of objects per slab. SLUB will
1654 increase the slab order up to slub_max_order to
1655 generate a sufficiently large slab able to contain
1656 the number of objects indicated. The higher the number
1657 of objects the smaller the overhead of tracking slabs
1658 and the less frequently locks need to be acquired.
1659 For more information see Documentation/vm/slub.txt.
1661 slub_min_order= [MM, SLUB]
1662 Determines the mininum page order for slabs. Must be
1663 lower than slub_max_order.
1664 For more information see Documentation/vm/slub.txt.
1666 slub_nomerge [MM, SLUB]
1667 Disable merging of slabs with similar size. May be
1668 necessary if there is some reason to distinguish
1669 allocs to different slabs. Debug options disable
1670 merging on their own.
1671 For more information see Documentation/vm/slub.txt.
1674 Format: <io1>[,<io2>[,...,<io8>]]
1676 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1677 attempt to substitute SMP alternatives once at boot.
1679 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1680 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1681 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1682 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1683 smsc-ircc2.ircc_irq= [HW] IRQ line
1684 smsc-ircc2.ircc_dma= [HW] DMA channel
1685 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1686 0: Toshiba Satellite 1800 (GP data pin select)
1687 1: Fast pin select (default)
1690 snd-ad1816a= [HW,ALSA]
1692 snd-ad1848= [HW,ALSA]
1694 snd-ali5451= [HW,ALSA]
1696 snd-als100= [HW,ALSA]
1698 snd-als4000= [HW,ALSA]
1700 snd-azt2320= [HW,ALSA]
1702 snd-cmi8330= [HW,ALSA]
1704 snd-cmipci= [HW,ALSA]
1706 snd-cs4231= [HW,ALSA]
1708 snd-cs4232= [HW,ALSA]
1710 snd-cs4236= [HW,ALSA]
1712 snd-cs4281= [HW,ALSA]
1714 snd-cs46xx= [HW,ALSA]
1716 snd-dt019x= [HW,ALSA]
1718 snd-dummy= [HW,ALSA]
1720 snd-emu10k1= [HW,ALSA]
1722 snd-ens1370= [HW,ALSA]
1724 snd-ens1371= [HW,ALSA]
1726 snd-es968= [HW,ALSA]
1728 snd-es1688= [HW,ALSA]
1730 snd-es18xx= [HW,ALSA]
1732 snd-es1938= [HW,ALSA]
1734 snd-es1968= [HW,ALSA]
1736 snd-fm801= [HW,ALSA]
1738 snd-gusclassic= [HW,ALSA]
1740 snd-gusextreme= [HW,ALSA]
1742 snd-gusmax= [HW,ALSA]
1746 snd-ice1712= [HW,ALSA]
1748 snd-intel8x0= [HW,ALSA]
1750 snd-interwave= [HW,ALSA]
1755 snd-korg1212= [HW,ALSA]
1757 snd-maestro3= [HW,ALSA]
1759 snd-mpu401= [HW,ALSA]
1761 snd-mtpav= [HW,ALSA]
1763 snd-nm256= [HW,ALSA]
1765 snd-opl3sa2= [HW,ALSA]
1773 snd-opti93x= [HW,ALSA]
1777 snd-rme32= [HW,ALSA]
1779 snd-rme96= [HW,ALSA]
1781 snd-rme9652= [HW,ALSA]
1787 snd-sbawe= [HW,ALSA]
1789 snd-serial= [HW,ALSA]
1791 snd-sgalaxy= [HW,ALSA]
1793 snd-sonicvibes= [HW,ALSA]
1798 snd-sun-cs4231= [HW,ALSA]
1800 snd-trident= [HW,ALSA]
1802 snd-usb-audio= [HW,ALSA,USB]
1804 snd-via82xx= [HW,ALSA]
1806 snd-virmidi= [HW,ALSA]
1808 snd-wavefront= [HW,ALSA]
1810 snd-ymfpci= [HW,ALSA]
1812 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1813 See Documentation/sonypi.txt
1815 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1816 See Documentation/specialix.txt.
1818 spia_io_base= [HW,MTD]
1824 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1826 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1827 See Documentation/scsi/st.txt.
1830 See header of drivers/scsi/seagate.c.
1834 Set the STI (builtin display/keyboard on the HP-PARISC
1835 machines) console (graphic card) which should be used
1836 as the initial boot-console.
1837 See also comment in drivers/video/console/sticore.c.
1840 See comment in drivers/video/console/sticore.c.
1843 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1847 Control how the NFS server code allocates CPUs to
1848 service thread pools. Depending on how many NICs
1849 you have and where their interrupts are bound, this
1850 option will affect which CPUs will do NFS serving.
1851 Note: this parameter cannot be changed while the
1852 NFS server is running.
1854 auto the server chooses an appropriate mode
1855 automatically using heuristics
1856 global a single global pool contains all CPUs
1857 percpu one pool for each CPU
1858 pernode one pool for each NUMA node (equivalent
1859 to global on non-NUMA machines)
1861 swiotlb= [IA-64] Number of I/O TLB slabs
1865 sym53c416= [HW,SCSI]
1866 See header of drivers/scsi/sym53c416.c.
1868 sysrq_always_enabled
1870 Ignore sysrq setting - this boot parameter will
1871 neutralize any effect of /proc/sys/kernel/sysrq.
1872 Useful for debugging.
1875 See header of drivers/scsi/t128.c.
1879 thash_entries= [KNL,NET]
1880 Set number of hash buckets for TCP connection
1882 thermal.act= [HW,ACPI]
1883 -1: disable all active trip points in all thermal zones
1884 <degrees C>: override all lowest active trip points
1886 thermal.crt= [HW,ACPI]
1887 -1: disable all critical trip points in all thermal zones
1888 <degrees C>: lower all critical trip points
1890 thermal.nocrt= [HW,ACPI]
1891 Set to disable actions on ACPI thermal zone
1892 critical and hot trip points.
1894 thermal.off= [HW,ACPI]
1895 1: disable ACPI thermal control
1897 thermal.psv= [HW,ACPI]
1898 -1: disable all passive trip points
1899 <degrees C>: override all passive trip points to this value
1901 thermal.tzp= [HW,ACPI]
1902 Specify global default ACPI thermal zone polling rate
1903 <deci-seconds>: poll all this frequency
1904 0: no polling (default)
1906 time Show timing data prefixed to each printk message line
1907 [deprecated, see 'printk.time']
1909 tipar.timeout= [HW,PPT]
1910 Set communications timeout in tenths of a second
1913 tipar.delay= [HW,PPT]
1914 Set inter-bit delay in microseconds (default 10).
1917 See header of drivers/scsi/seagate.c.
1920 See comment before function dc390_setup() in
1921 drivers/scsi/tmscsim.c.
1925 trix= [HW,OSS] MediaTrix AudioTrix Pro
1927 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1929 turbografx.map[2|3]= [HW,JOY]
1930 TurboGraFX parallel port interface
1932 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1933 See also Documentation/input/joystick-parport.txt
1935 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1936 See header of drivers/scsi/u14-34f.c.
1945 [USB] Ignore overcurrent events (default N).
1946 Some badly-designed motherboards generate lots of
1947 bogus events, for ports that aren't wired to
1948 anything. Set this parameter to avoid log spamming.
1949 Note that genuine overcurrent events won't be
1952 usbcore.autosuspend=
1953 [USB] The autosuspend time delay (in seconds) used
1954 for newly-detected USB devices (default 2). This
1955 is the time required before an idle device will be
1956 autosuspended. Devices for which the delay is set
1957 to a negative value won't be autosuspended at all.
1960 [USBHID] The interval which mice are to be polled at.
1962 vdso= [X86-32,SH,x86-64]
1963 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1964 vdso=1: enable VDSO (default)
1965 vdso=0: disable VDSO mapping
1968 vector=percpu: enable percpu vector domain
1970 video= [FB] Frame buffer configuration
1971 See Documentation/fb/modedb.txt.
1973 vga= [BOOT,X86-32] Select a particular video mode
1974 See Documentation/i386/boot.txt and
1975 Documentation/svga.txt.
1976 Use vga=ask for menu.
1977 This is actually a boot loader parameter; the value is
1978 passed to the kernel using a special protocol.
1980 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1981 size of <nn>. This can be used to increase the
1982 minimum size (128MB on x86). It can also be used to
1983 decrease the size and leave more room for directly
1986 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1989 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1992 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1995 waveartist= [HW,OSS]
1996 Format: <io>,<irq>,<dma>,<dma2>
1999 See header of drivers/scsi/wd33c93.c.
2002 See header of drivers/scsi/wd7000.c.
2005 See Documentation/watchdog/wdt.txt.
2007 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2008 xd_geo= See header of drivers/block/xd.c.
2010 xirc2ps_cs= [NET,PCMCIA]
2012 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2014 norandmaps Don't use address space randomization
2015 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2017 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
2018 This is useful to get more information why
2019 you got a "dwarf2 unwinder stuck"
2021 ______________________________________________________________________
2025 Add documentation for ALSA options.
2026 Add more DRM drivers.