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 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-32 IA-32 aka i386 architecture 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 PCMCIA The PCMCIA subsystem is enabled.
72 PNP Plug & Play support is enabled.
73 PPC PowerPC architecture is enabled.
74 PPT Parallel port support is enabled.
75 PS2 Appropriate PS/2 support is enabled.
76 RAM RAM disk support is enabled.
77 S390 S390 architecture is enabled.
78 SCSI Appropriate SCSI support is enabled.
79 A lot of drivers has their options described inside of
81 SELINUX SELinux support is enabled.
82 SERIAL Serial support is enabled.
83 SH SuperH architecture is enabled.
84 SMP The kernel is an SMP kernel.
85 SPARC Sparc architecture is enabled.
86 SWSUSP Software suspend is enabled.
87 TS Appropriate touchscreen support is enabled.
88 USB USB support is enabled.
89 USBHID USB Human Interface Device support is enabled.
90 V4L Video For Linux support is enabled.
91 VGA The VGA console has been enabled.
92 VT Virtual terminal support is enabled.
93 WDT Watchdog support is enabled.
94 XT IBM PC/XT MFM hard disk support is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 acpi= [HW,ACPI,X86-64,i386]
127 Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
133 strict -- Be less tolerant of platforms that are not
134 strictly ACPI specification compliant.
136 See also Documentation/pm.txt, pci=noacpi
138 acpi_apic_instance= [ACPI, IOAPIC]
140 2: use 2nd APIC table, if available
141 1,0: use 1st APIC table
144 acpi_sleep= [HW,ACPI] Sleep options
145 Format: { s3_bios, s3_mode }
146 See Documentation/power/video.txt
148 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
149 Format: { level | edge | high | low }
151 acpi_irq_balance [HW,ACPI]
152 ACPI will balance active IRQs
155 acpi_irq_nobalance [HW,ACPI]
156 ACPI will not move active IRQs (default)
159 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
161 Format: <irq>,<irq>...
163 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
164 Format: <irq>,<irq>...
166 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
167 Format: To spoof as Windows 98: ="Microsoft Windows"
169 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
170 acpi_osi="string1" # add string1 -- only one string
171 acpi_osi="!string2" # remove built-in string2
172 acpi_osi= # disable all strings
174 acpi_serialize [HW,ACPI] force serialization of AML methods
176 acpi_skip_timer_override [HW,ACPI]
177 Recognize and ignore IRQ0/pin2 Interrupt Override.
178 For broken nForce2 BIOS resulting in XT-PIC timer.
179 acpi_use_timer_override [HW,ACPI}
180 Use timer override. For some broken Nvidia NF5 boards
181 that require a timer override, but don't have
184 acpi.debug_layer= [HW,ACPI]
186 Each bit of the <int> indicates an ACPI debug layer,
187 1: enable, 0: disable. It is useful for boot time
188 debugging. After system has booted up, it can be set
189 via /sys/module/acpi/parameters/debug_layer.
190 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
191 Available bits (add the numbers together) to enable debug output
192 for specific parts of the ACPI subsystem:
193 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
194 0x10 namespace 0x20 parser 0x40 dispatcher
195 0x80 executer 0x100 resources 0x200 acpica debugger
196 0x400 os services 0x800 acpica disassembler.
197 The number can be in decimal or prefixed with 0x in hex.
198 Warning: Many of these options can produce a lot of
199 output and make your system unusable. Be very careful.
201 acpi.debug_level= [HW,ACPI]
203 Each bit of the <int> indicates an ACPI debug level,
204 1: enable, 0: disable. It is useful for boot time
205 debugging. After system has booted up, it can be set
206 via /sys/module/acpi/parameters/debug_level.
207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
208 Available bits (add the numbers together) to enable different
209 debug output levels of the ACPI subsystem:
210 0x01 error 0x02 warn 0x04 init 0x08 debug object
211 0x10 info 0x20 init names 0x40 parse 0x80 load
212 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
213 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
214 0x10000 resources 0x20000 user requests 0x40000 package.
215 The number can be in decimal or prefixed with 0x in hex.
216 Warning: Many of these options can produce a lot of
217 output and make your system unusable. Be very careful.
220 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
222 acpi_pm_good [IA-32,X86-64]
223 Override the pmtimer bug detection: force the kernel
224 to assume that this machine's pmtimer latches its value
225 and always returns good values.
228 { off | try_unsupported }
229 off: disable AGP support
230 try_unsupported: try to drive unsupported chipsets
231 (may crash computer or cause data corruption)
233 enable_timer_pin_1 [i386,x86-64]
234 Enable PIN 1 of APIC timer
235 Can be useful to work around chipset bugs
236 (in particular on some ATI chipsets).
237 The kernel tries to set a reasonable default.
239 disable_timer_pin_1 [i386,x86-64]
240 Disable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs.
244 Format: <io>,<irq>,<dma>,<dma2>,<type>
247 See header of drivers/scsi/advansys.c.
249 advwdt= [HW,WDT] Advantech WDT
250 Format: <iostart>,<iostop>
252 aedsp16= [HW,OSS] Audio Excel DSP 16
253 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
254 See also header of sound/oss/aedsp16.c.
257 See Documentation/scsi/aha152x.txt.
260 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
263 See Documentation/scsi/aic7xxx.txt.
266 See Documentation/scsi/aic79xx.txt.
268 amijoy.map= [HW,JOY] Amiga joystick support
269 Map of devices attached to JOY0DAT and JOY1DAT
271 See also Documentation/kernel/input/joystick.txt
273 analog.map= [HW,JOY] Analog joystick and gamepad support
274 Specifies type or capabilities of an analog joystick
275 connected to one of 16 gameports
276 Format: <type1>,<type2>,..<type16>
279 Power management functions (SPARCstation-4/5 + deriv.)
281 Disable APC CPU standby support. SPARCstation-Fox does
282 not play well with APC CPU idle - disable it if you have
283 APC and your system crashes randomly.
285 apic= [APIC,i386] Advanced Programmable Interrupt Controller
286 Change the output verbosity whilst booting
287 Format: { quiet (default) | verbose | debug }
288 Change the amount of debugging information output
289 when initialising the APIC and IO-APIC components.
291 apm= [APM] Advanced Power Management
292 See header of arch/i386/kernel/apm.c.
297 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
298 Format: <io>,<irq>,<nodeID>
302 atarimouse= [HW,MOUSE] Atari Mouse
304 atascsi= [HW,SCSI] Atari SCSI
306 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
307 EzKey and similar keyboards
309 atkbd.reset= [HW] Reset keyboard during initialization
311 atkbd.set= [HW] Select keyboard code set
312 Format: <int> (2 = AT (default), 3 = PS/2)
314 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
317 atkbd.softraw= [HW] Choose between synthetic and real raw mode
318 Format: <bool> (0 = real, 1 = synthetic (default))
320 atkbd.softrepeat= [HW]
321 Use software keyboard repeat
325 baycom_epp= [HW,AX25]
328 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
330 See header of drivers/net/hamradio/baycom_par.c.
332 baycom_ser_fdx= [HW,AX25]
333 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
334 Format: <io>,<irq>,<mode>[,<baud>]
335 See header of drivers/net/hamradio/baycom_ser_fdx.c.
337 baycom_ser_hdx= [HW,AX25]
338 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
339 Format: <io>,<irq>,<mode>
340 See header of drivers/net/hamradio/baycom_ser_hdx.c.
342 blkmtd_device= [HW,MTD]
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
367 chandev= [HW,NET] Generic channel device initialisation
369 checkreqprot [SELINUX] Set initial checkreqprot flag value.
370 Format: { "0" | "1" }
371 See security/selinux/Kconfig help text.
372 0 -- check protection applied by kernel (includes
373 any implied execute protection).
374 1 -- check protection requested by application.
375 Default value is set via a kernel config option.
376 Value can be changed at runtime via
377 /selinux/checkreqprot.
379 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
381 Forces specified clocksource (if available) to be used
382 when calculating gettimeofday(). If specified
383 clocksource is not available, it defaults to PIT.
384 Format: { pit | tsc | cyclone | pmtmr }
386 clocksource= [GENERIC_TIME] Override the default clocksource
388 Override the default clocksource and use the clocksource
389 with the name specified.
390 Some clocksource names to choose from, depending on
392 [all] jiffies (this is the base, fallback clocksource)
394 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
395 pxa_timer,timer3,32k_counter,timer0_1
397 [IA-32] pit,hpet,tsc,vmi-timer;
398 scx200_hrt on Geode; cyclone on IBM x440
406 code_bytes [IA32] How many bytes of object code to print in an
413 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
414 over the 8254 in addition to over the IO-APIC. The
415 kernel tries to set a sensible default.
417 hpet= [IA-32,HPET] option to disable HPET and use PIT.
420 com20020= [HW,NET] ARCnet - COM20020 chipset
422 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
424 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
428 ARCnet - COM90xx chipset (memory-mapped buffers)
429 Format: <io>[,<irq>[,<memstart>]]
431 condev= [HW,S390] console device
434 console= [KNL] Output console device and options.
436 tty<n> Use the virtual console device <n>.
440 Use the specified serial port. The options are of
441 the form "bbbbpnf", where "bbbb" is the baud rate,
442 "p" is parity ("n", "o", or "e"), "n" is number of
443 bits, and "f" is flow control ("r" for RTS or
444 omit it). Default is "9600n8".
446 See Documentation/serial-console.txt for more
448 Documentation/networking/netconsole.txt for an
451 uart[8250],io,<addr>[,options]
452 uart[8250],mmio,<addr>[,options]
453 Start an early, polled-mode console on the 8250/16550
454 UART at the specified I/O port or MMIO address,
455 switching to the matching ttyS device later. The
456 options are the same as for ttyS, above.
458 earlycon= [KNL] Output early console device and options.
459 uart[8250],io,<addr>[,options]
460 uart[8250],mmio,<addr>[,options]
461 Start an early, polled-mode console on the 8250/16550
462 UART at the specified I/O port or MMIO address.
463 The options are the same as for ttyS, above.
465 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
467 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
470 Format: { parport<nr> | auto | none }
472 crashkernel=nn[KMG]@ss[KMG]
473 [KNL] Reserve a chunk of physical memory to
474 hold a kernel to switch to with kexec on panic.
477 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
482 cs89x0_media= [HW,NET]
483 Format: { rj45 | aui | bnc }
485 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
488 See header of drivers/s390/block/dasd_devmap.c.
490 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
491 (one device per port)
492 Format: <port#>,<type>
493 See also Documentation/input/joystick-parport.txt
495 debug [KNL] Enable kernel debugging (events log level).
498 [KNL] verbose self-tests
500 Print debugging info while doing the locking API
502 We default to 0 (no extra messages), setting it to
503 1 will print _a lot_ more information - normally
504 only useful to kernel developers.
507 Format: <area>[,<node>]
508 See also Documentation/networking/decnet.txt.
511 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
512 Change the default blue palette of the console.
513 This is a 16-member array composed of values
517 Format: <green0>,<green1>,<green2>,...,<green15>
518 Change the default green palette of the console.
519 This is a 16-member array composed of values
523 Format: <red0>,<red1>,<red2>,...,<red15>
524 Change the default red palette of the console.
525 This is a 16-member array composed of values
530 Set system-wide default UTF-8 mode for all tty's.
531 Default is 0 and by setting to 1, it enables UTF-8
532 mode for all newly opened or allocated terminals.
535 Set number of hash buckets for dentry cache.
538 IO parameters + enable/disable command.
540 digiepca= [HW,SERIAL]
541 See drivers/char/README.epca and
542 Documentation/digiepca.txt.
544 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
546 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
548 dmasound= [HW,OSS] Sound subsystem buffers
554 earlyprintk= [IA-32,X86-64,SH]
556 earlyprintk=serial[,ttySn[,baudrate]]
558 Append ",keep" to not disable it when the real console
561 Only vga or serial at a time, not both.
563 Currently only ttyS0 and ttyS1 are supported.
565 Interaction with the standard serial driver is not
568 The VGA output is eventually overwritten by the real
573 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
576 non-0: interrupt mode (default)
583 Format: {"of[f]" | "sk[ipmbr]"}
584 See comment in arch/i386/boot/edd.S
587 Format: <id>,<membase>,<irq>
589 eisa_irq_edge= [PARISC,HW]
590 See header of drivers/parisc/eisa.c.
593 See comment before function elanfreq_setup() in
594 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
597 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
598 See Documentation/block/as-iosched.txt and
599 Documentation/block/deadline-iosched.txt for details.
601 elfcorehdr= [IA-32, X86_64]
602 Specifies physical address of start of kernel core
603 image elf header. Generally kexec loader will
604 pass this option to capture kernel.
605 See Documentation/kdump/kdump.txt for details.
607 enforcing [SELINUX] Set initial enforcing status.
609 See security/selinux/Kconfig help text.
610 0 -- permissive (log only, no denials).
611 1 -- enforcing (deny and log).
613 Value can be changed at runtime via /selinux/enforce.
616 Format: <spdif>,[<nomix>,[<amplifier>]]
617 See also header of sound/oss/es1371.c.
619 ether= [HW,NET] Ethernet cards parameters
620 This option is obsoleted by the "netdev=" option, which
621 has equivalent usage. See its documentation for details.
623 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
628 fail_make_request=[KNL]
629 General fault injection mechanism.
630 Format: <interval>,<probability>,<space>,<times>
631 See also /Documentation/fault-injection/.
634 See header of drivers/scsi/fd_mcs.c.
637 See header of drivers/scsi/fdomain.c.
640 See Documentation/floppy.txt.
643 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
644 support via parallel port (up to 5 devices per port)
645 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
646 See also Documentation/input/joystick-parport.txt
651 See header of drivers/scsi/gdth.c.
653 gpt [EFI] Forces disk with valid GPT signature but
654 invalid Protective MBR to be treated as GPT.
658 hashdist= [KNL,NUMA] Large hashes allocated during boot
659 are distributed across NUMA nodes. Defaults on
660 for IA-64, off otherwise.
661 Format: 0 | 1 (for off | on)
663 hcl= [IA-64] SGI's Hardware Graph compatibility layer
665 hd= [EIDE] (E)IDE hard drive subsystem geometry
666 Format: <cyl>,<head>,<sect>
668 hd?= [HW] (E)IDE subsystem
669 hd?lun= See Documentation/ide.txt.
671 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
672 size of <nn>. This works even on boxes that have no
673 highmem otherwise. This also works to reduce highmem
674 size on bigger boxes.
676 highres= [KNL] Enable/disable high resolution timer mode.
677 Valid parameters: "on", "off"
681 See Documentation/isdn/README.HiSax.
683 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
685 i8042.direct [HW] Put keyboard port into non-translated mode
686 i8042.dumbkbd [HW] Pretend that controller can only read data from
687 keyboard and cannot control its state
688 (Don't attempt to blink the leds)
689 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
690 i8042.nokbd [HW] Don't check/create keyboard port
691 i8042.nomux [HW] Don't check presence of an active multiplexing
693 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
696 [HW] Frequency with which keyboard LEDs should blink
697 when kernel panics (default is 0.5 sec)
698 i8042.reset [HW] Reset the controller during init and cleanup
699 i8042.unlock [HW] Unlock (ignore) the keylock
703 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
704 indicates that the driver is running on unsupported
706 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
707 does not match list of supported models.
709 [HW] Report power status in /proc/i8k
710 (disabled by default)
711 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
714 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
715 See Documentation/mca.txt.
718 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
720 ide= [HW] (E)IDE subsystem
721 Format: ide=nodma or ide=doubler or ide=reverse
722 See Documentation/ide.txt.
724 ide?= [HW] (E)IDE subsystem
725 Format: ide?=noprobe or chipset specific parameters.
726 See Documentation/ide.txt.
728 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
729 See Documentation/ide.txt.
732 Format: idle=poll or idle=mwait
733 Poll forces a polling idle loop that can slightly improves the performance
734 of waking up a idle CPU, but will use a lot of power and make the system
735 run hot. Not recommended.
736 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
737 to not use it because it doesn't save as much power as a normal idle
738 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
741 ignore_loglevel [KNL]
742 Ignore loglevel setting - this will print /all/
743 kernel messages to the console. Useful for debugging.
746 Set number of hash buckets for inode cache.
749 See header of drivers/scsi/in2000.c.
753 Run specified binary instead of /sbin/init as init
756 initcall_debug [KNL] Trace initcalls as they are executed. Useful
757 for working out where the kernel is dying during
760 initrd= [BOOT] Specify the location of the initial ramdisk
762 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
767 io7= [HW] IO7 for Marvel based alpha systems
768 See comment before marvel_specify_io7 in
769 arch/alpha/kernel/core_marvel.c.
772 See Documentation/nfsroot.txt.
774 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
775 See comment before ip2_setup() in
776 drivers/char/ip2/ip2base.c.
778 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
779 See header of drivers/scsi/ips.c.
781 ports= [IP_VS_FTP] IPVS ftp helper module
783 Up to 8 (IP_VS_APP_MAX_PORTS) ports
785 Format: <port>,<port>....
788 When an interrupt is not handled search all handlers
789 for it. Intended to get systems with badly broken
793 When an interrupt is not handled search all handlers
794 for it. Also check all handlers each timer
795 interrupt. Intended to get systems with badly broken
799 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
801 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
803 <cpu number>,...,<cpu number>
805 <cpu number>-<cpu number> (must be a positive range in ascending order)
807 <cpu number>,...,<cpu number>-<cpu number>
808 This option can be used to specify one or more CPUs
809 to isolate from the general SMP balancing and scheduling
810 algorithms. The only way to move a process onto or off
811 an "isolated" CPU is via the CPU affinity syscalls.
812 <cpu number> begins at 0 and the maximum value is
813 "number of CPUs in system - 1".
815 This option is the preferred way to isolate CPUs. The
816 alternative -- manually setting the CPU mask of all
817 tasks in the system -- can cause problems and
818 suboptimal load balancer performance.
822 js= [HW,JOY] Analog joystick
823 See Documentation/input/joystick.txt.
825 kernelcore=nn[KMG] [KNL,IA-32,IA-64,PPC,X86-64] This parameter
826 specifies the amount of memory usable by the kernel
827 for non-movable allocations. The requested amount is
828 spread evenly throughout all nodes in the system. The
829 remaining memory in each node is used for Movable
830 pages. In the event, a node is too small to have both
831 kernelcore and Movable pages, kernelcore pages will
832 take priority and other nodes will have a larger number
833 of kernelcore pages. The Movable zone is used for the
834 allocation of pages that may be reclaimed or moved
835 by the page migration subsystem. This means that
836 HugeTLB pages may not be allocated from this zone.
837 Note that allocations like PTEs-from-HighMem still
838 use the HighMem zone if it exists, and the Normal
841 movablecore=nn[KMG] [KNL,IA-32,IA-64,PPC,X86-64] This parameter
842 is similar to kernelcore except it specifies the
843 amount of memory used for migratable allocations.
844 If both kernelcore and movablecore is specified,
845 then kernelcore will be at *least* the specified
846 value but may be more. If movablecore on its own
847 is specified, the administrator must be careful
848 that the amount of memory usable for all allocations
853 kstack=N [IA-32,X86-64] Print N words from the kernel stack
858 lapic [IA-32,APIC] Enable the local APIC even if BIOS
861 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
864 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
865 Format: addr:<io>,irq:<irq>
867 legacy_serial.force [HW,IA-32,X86-64]
868 Probe for COM ports at legacy addresses even
869 if PNPBIOS or ACPI should describe them. This
870 is for working around firmware defects.
872 load_ramdisk= [RAM] List of ramdisks to load from floppy
873 See Documentation/ramdisk.txt.
875 lockd.nlm_grace_period=P [NFS] Assign grace period.
878 lockd.nlm_tcpport=N [NFS] Assign TCP port.
881 lockd.nlm_timeout=T [NFS] Assign timeout value.
884 lockd.nlm_udpport=M [NFS] Assign UDP port.
887 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
890 loglevel= All Kernel Messages with a loglevel smaller than the
891 console loglevel will be printed to the console. It can
892 also be changed with klogd or other programs. The
893 loglevels are defined as follows:
895 0 (KERN_EMERG) system is unusable
896 1 (KERN_ALERT) action must be taken immediately
897 2 (KERN_CRIT) critical conditions
898 3 (KERN_ERR) error conditions
899 4 (KERN_WARNING) warning conditions
900 5 (KERN_NOTICE) normal but significant condition
901 6 (KERN_INFO) informational
902 7 (KERN_DEBUG) debug-level messages
904 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
905 Format: { n | nk | nM }
906 n must be a power of two. The default size
907 is set in the kernel config file.
909 lp=0 [LP] Specify parallel ports to use, e.g,
910 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
911 lp=reset first parallel port). 'lp=0' disables the
912 lp=auto printer driver. 'lp=reset' (which can be
913 specified in addition to the ports) causes
914 attached printers to be reset. Using
915 lp=port1,port2,... specifies the parallel ports
916 to associate lp devices with, starting with
917 lp0. A port specification may be 'none' to skip
918 that lp device, or a parport name such as
919 'parport0'. Specifying 'lp=auto' instead of a
920 port specification list means that device IDs
921 from each port should be examined, to see if
922 an IEEE 1284-compliant printer is attached; if
923 so, the driver will manage that printer.
924 See also header of drivers/char/lp.c.
927 Sets loops_per_jiffy to given constant, thus avoiding
928 time-consuming boot-time autodetection (up to 250 ms per
929 CPU). 0 enables autodetection (default). To determine
930 the correct value for your kernel, boot with normal
931 autodetection and see what value is printed. Note that
932 on SMP systems the preset will be applied to all CPUs,
933 which is likely to cause problems if your CPUs need
934 significantly divergent settings. An incorrect value
935 will cause delays in the kernel to be wrong, leading to
936 unpredictable I/O errors and other breakage. Although
937 unlikely, in the extreme case this might damage your
941 Format: <io>,<irq>,<dma>
943 mac5380= [HW,SCSI] Format:
944 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
946 mac53c9x= [HW,SCSI] Format:
947 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
949 machvec= [IA64] Force the use of a particular machine-vector
950 (machvec) in a generic kernel.
951 Example: machvec=hpzx1_swiotlb
953 max_loop= [LOOP] Maximum number of loopback devices that can
957 maxcpus= [SMP] Maximum number of processors that an SMP kernel
959 Using "nosmp" or "maxcpus=0" will disable SMP
960 entirely (the MPS table probe still happens, though).
961 A command-line option of "maxcpus=<NUM>", where <NUM>
962 is an integer greater than 0, limits the maximum number
963 of CPUs activated in SMP mode to <NUM>.
964 Using "maxcpus=1" on an SMP kernel is the trivial
965 case of an SMP kernel with only one CPU.
967 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
968 equal to this physical address is ignored.
970 max_luns= [SCSI] Maximum number of LUNs to probe.
971 Should be between 1 and 2^32-1.
974 [SCSI] Maximum number of LUNs received.
975 Should be between 1 and 16384.
977 mca-pentium [BUGS=IA-32]
981 mce [IA-32] Machine Check Exception
983 md= [HW] RAID subsystems devices and level
984 See Documentation/md.txt.
987 Format: <first>,<last>
988 Specifies range of consoles to be captured by the MDA.
990 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
991 Amount of memory to be used when the kernel is not able
992 to see the whole system memory or for test.
993 [IA-32] Use together with memmap= to avoid physical
994 address space collisions. Without memmap= PCI devices
995 could be placed at addresses belonging to unused RAM.
997 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
1000 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
1001 E820 memory map, as specified by the user.
1002 Such memmap=exactmap lines can be constructed based on
1003 BIOS output or other requirements. See the memmap=nn@ss
1006 memmap=nn[KMG]@ss[KMG]
1007 [KNL] Force usage of a specific region of memory
1008 Region of memory to be used, from ss to ss+nn.
1010 memmap=nn[KMG]#ss[KMG]
1011 [KNL,ACPI] Mark specific memory as ACPI data.
1012 Region of memory to be used, from ss to ss+nn.
1014 memmap=nn[KMG]$ss[KMG]
1015 [KNL,ACPI] Mark specific memory as reserved.
1016 Region of memory to be used, from ss to ss+nn.
1018 meye.*= [HW] Set MotionEye Camera parameters
1019 See Documentation/video4linux/meye.txt.
1024 [MOUSE] Maximum time between finger touching and
1025 leaving touchpad surface for touch to be considered
1026 a tap and be reported as a left button click (for
1027 touchpads working in absolute mode only).
1029 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1030 reporting absolute coordinates, such as tablets
1031 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1032 reporting absolute coordinates, such as tablets
1037 MTD_Partition= [MTD]
1038 Format: <name>,<region-number>,<size>,<offset>
1040 MTD_Region= [MTD] Format:
1041 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1044 See drivers/mtd/cmdlinepart.c.
1046 mtouchusb.raw_coordinates=
1047 [HW] Make the MicroTouch USB driver use raw coordinates
1048 ('y', default) or cooked coordinates ('n')
1050 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1053 See header of drivers/scsi/NCR_D700.c.
1057 ncr53c400= [HW,SCSI]
1059 ncr53c400a= [HW,SCSI]
1061 ncr53c406a= [HW,SCSI]
1063 ncr53c8xx= [HW,SCSI]
1065 netdev= [NET] Network devices parameters
1066 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1067 Note that mem_start is often overloaded to mean
1068 something different and driver-specific.
1069 This usage is only documented in each driver source
1073 See Documentation/nfsroot.txt.
1075 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1076 See Documentation/nfsroot.txt.
1078 nfs.callback_tcpport=
1079 [NFS] set the TCP port on which the NFSv4 callback
1080 channel should listen.
1082 nfs.idmap_cache_timeout=
1083 [NFS] set the maximum lifetime for idmapper cache
1086 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1088 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1089 emulation library even if a 387 maths coprocessor
1092 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1096 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1097 caches in the slab allocator. Saves per-node memory,
1098 but will impact performance.
1102 noapic [SMP,APIC] Tells the kernel to not make use of any
1103 IOAPICs that may be present in the system.
1105 noasync [HW,M68K] Disables async and sync negotiation for
1108 nobats [PPC] Do not use BATs for mapping kernel lowmem
1109 on "Classic" PPC cores.
1113 nodelayacct [KNL] Disable per-task delay accounting
1115 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1119 noexec [IA-32,X86-64]
1120 noexec=on: enable non-executable mappings (default)
1121 noexec=off: disable nn-executable mappings
1123 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1124 register save and restore. The kernel will only save
1125 legacy floating-point registers on task switch.
1129 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1130 instruction doesn't work correctly and not to
1133 nohalt [IA-64] Tells the kernel not to use the power saving
1134 function PAL_HALT_LIGHT when idle. This increases
1135 power-consumption. On the positive side, it reduces
1136 interrupt wake-up latency, which may improve performance
1137 in certain environments such as networked servers or
1140 nohz= [KNL] Boottime enable/disable dynamic ticks
1141 Valid arguments: on, off
1144 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1146 noirqdebug [IA-32] Disables the code which attempts to detect and
1147 disable unhandled interrupt sources.
1149 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1150 broken timer IRQ sources.
1152 noisapnp [ISAPNP] Disables ISA PnP code.
1154 noinitrd [RAM] Tells the kernel not to load any configured
1159 nojitter [IA64] Disables jitter checking for ITC timers.
1161 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1163 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1165 noltlbs [PPC] Do not use large page/tlb entries for kernel
1166 lowmem mapping on PPC40x.
1168 nomca [IA-64] Disable machine check abort handling
1170 nomce [IA-32] Machine Check Exception
1172 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1174 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1175 with UP alternatives
1177 noresidual [PPC] Don't use residual data on PReP machines.
1179 noresume [SWSUSP] Disables resume and restores original swap
1182 no-scroll [VGA] Disables scrollback.
1183 This is required for the Braillex ib80-piezo Braille
1184 reader made by F.H. Papenmeier (Germany).
1188 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1190 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1192 nosoftlockup [KNL] Disable the soft-lockup detector.
1194 nosync [HW,M68K] Disables sync negotiation for all devices.
1196 notsc [BUGS=IA-32] Disable Time Stamp Counter
1198 nousb [USB] Disable the USB subsystem
1202 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1203 one of ['zone', 'node', 'default'] can be specified
1204 This can be set from sysctl after boot.
1205 See Documentation/sysctl/vm.txt for details.
1207 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1212 oprofile.timer= [HW]
1213 Use timer interrupt instead of performance counters
1215 osst= [HW,SCSI] SCSI Tape Driver
1216 Format: <buffer_size>,<write_threshold>
1217 See also Documentation/scsi/st.txt.
1219 panic= [KNL] Kernel behaviour on panic
1222 parkbd.port= [HW] Parallel port number the keyboard adapter is
1223 connected to, default is 0.
1225 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1226 0 for XT, 1 for AT (default is AT).
1229 parport= [HW,PPT] Specify parallel ports. 0 disables.
1230 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1231 Use 'auto' to force the driver to use any
1232 IRQ/DMA settings detected (the default is to
1233 ignore detected IRQ/DMA settings because of
1234 possible conflicts). You can specify the base
1235 address, IRQ, and DMA settings; IRQ and DMA
1236 should be numbers, or 'auto' (for using detected
1237 settings on that particular port), or 'nofifo'
1238 (to avoid using a FIFO even if it is detected).
1239 Parallel ports are assigned in the order they
1240 are specified on the command line, starting
1243 parport_init_mode= [HW,PPT]
1244 Configure VIA parallel port to operate in
1245 a specific mode. This is necessary on Pegasos
1246 computer where firmware has no options for setting
1247 up parallel port mode and sets it to spp.
1248 Currently this function knows 686a and 8231 chips.
1249 Format: [spp|ps2|epp|ecp|ecpepp]
1251 pas2= [HW,OSS] Format:
1252 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1255 See header of drivers/scsi/pas16.c.
1258 Halt all CPUs after the first oops has been printed for
1259 the specified number of seconds. This is to be used if
1260 your oopses keep scrolling off the screen.
1265 See header of drivers/block/paride/pcd.c.
1266 See also Documentation/paride.txt.
1268 pci=option[,option...] [PCI] various PCI subsystem options:
1269 off [IA-32] don't probe for the PCI bus
1270 bios [IA-32] force use of PCI BIOS, don't access
1271 the hardware directly. Use this if your machine
1272 has a non-standard PCI host bridge.
1273 nobios [IA-32] disallow use of PCI BIOS, only direct
1274 hardware access methods are allowed. Use this
1275 if you experience crashes upon bootup and you
1276 suspect they are caused by the BIOS.
1277 conf1 [IA-32] Force use of PCI Configuration
1279 conf2 [IA-32] Force use of PCI Configuration
1281 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1283 nomsi [MSI] If the PCI_MSI kernel config parameter is
1284 enabled, this kernel boot option can be used to
1285 disable the use of MSI interrupts system-wide.
1286 nosort [IA-32] Don't sort PCI devices according to
1287 order given by the PCI BIOS. This sorting is
1288 done to get a device order compatible with
1290 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1291 routing table. These calls are known to be buggy
1292 on several machines and they hang the machine
1293 when used, but on other computers it's the only
1294 way to get the interrupt routing table. Try
1295 this option if the kernel is unable to allocate
1296 IRQs or discover secondary PCI buses on your
1298 rom [IA-32] Assign address space to expansion ROMs.
1299 Use with caution as certain devices share
1300 address decoders between ROMs and other
1302 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1303 assigned automatically to PCI devices. You can
1304 make the kernel exclude IRQs of your ISA cards
1306 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1307 of the PIRQ table (normally generated
1308 by the BIOS) if it is outside the
1309 F0000h-100000h range.
1310 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1311 useful if the kernel is unable to find your
1312 secondary buses and you want to tell it
1313 explicitly which ones they are.
1314 assign-busses [IA-32] Always assign all PCI bus
1315 numbers ourselves, overriding
1316 whatever the firmware may have done.
1317 usepirqmask [IA-32] Honor the possible IRQ mask stored
1318 in the BIOS $PIR table. This is needed on
1319 some systems with broken BIOSes, notably
1320 some HP Pavilion N5400 and Omnibook XE3
1321 notebooks. This will have no effect if ACPI
1322 IRQ routing is enabled.
1323 noacpi [IA-32] Do not use ACPI for IRQ routing
1324 or for PCI scanning.
1325 routeirq Do IRQ routing for all PCI devices.
1326 This is normally done in pci_enable_device(),
1327 so this option is a temporary workaround
1328 for broken drivers that don't call it.
1329 firmware [ARM] Do not re-enumerate the bus but instead
1330 just use the configuration from the
1331 bootloader. This is currently used on
1332 IXP2000 systems where the bus has to be
1333 configured a certain way for adjunct CPUs.
1334 noearly [X86] Don't do any early type 1 scanning.
1335 This might help on some broken boards which
1336 machine check when some devices' config space
1337 is read. But various workarounds are disabled
1338 and some IOMMU drivers will not work.
1339 bfsort Sort PCI devices into breadth-first order.
1340 This sorting is done to get a device
1341 order compatible with older (<= 2.4) kernels.
1342 nobfsort Don't sort PCI devices into breadth-first order.
1343 cbiosize=nn[KMG] The fixed amount of bus space which is
1344 reserved for the CardBus bridge's IO window.
1345 The default value is 256 bytes.
1346 cbmemsize=nn[KMG] The fixed amount of bus space which is
1347 reserved for the CardBus bridge's memory
1348 window. The default value is 64 megabytes.
1350 pcmv= [HW,PCMCIA] BadgePAD 4
1353 See Documentation/paride.txt.
1355 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1358 See arch/parisc/kernel/pdc_chassis.c
1361 See Documentation/paride.txt.
1364 See Documentation/paride.txt.
1366 pirq= [SMP,APIC] Manual mp-table setup
1367 See Documentation/i386/IO-APIC.txt.
1369 plip= [PPT,NET] Parallel port network link
1370 Format: { parport<nr> | timid | 0 }
1371 See also Documentation/parport.txt.
1377 { on | off | curr | res | no-curr | no-res }
1380 [ISAPNP] Exclude IRQs for the autoconfiguration
1383 [ISAPNP] Exclude DMAs for the autoconfiguration
1385 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1386 Ranges are in pairs (I/O port base and size).
1389 [ISAPNP] Exclude memory regions for the
1391 Ranges are in pairs (memory base and size).
1393 print-fatal-signals=
1394 [KNL] debug: print fatal signals
1395 print-fatal-signals=1: print segfault info to
1399 printk.time= Show timing data prefixed to each printk message line
1400 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1402 profile= [KNL] Enable kernel profiling via /proc/profile
1403 Format: [schedule,]<number>
1404 Param: "schedule" - profile schedule points.
1405 Param: <number> - step/bucket size as a power of 2 for
1406 statistical time based profiling.
1407 Param: "sleep" - profile D-state sleeping (millisecs)
1409 processor.max_cstate= [HW,ACPI]
1410 Limit processor to maximum C-state
1411 max_cstate=9 overrides any DMI blacklist limit.
1413 processor.nocst [HW,ACPI]
1414 Ignore the _CST method to determine C-states,
1415 instead using the legacy FADT method
1417 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1419 See Documentation/ramdisk.txt.
1421 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1422 probe for; one of (bare|imps|exps|lifebook|any).
1423 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1425 psmouse.resetafter= [HW,MOUSE]
1426 Try to reset the device after so many bad packets
1429 [HW,MOUSE] Set desired mouse resolution, in dpi.
1430 psmouse.smartscroll=
1431 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1432 0 = disabled, 1 = enabled (default).
1434 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1436 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1439 See Documentation/paride.txt.
1441 quiet [KNL] Disable most log messages
1446 See Documentation/md.txt.
1448 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1449 See Documentation/ramdisk.txt.
1451 ramdisk_blocksize= [RAM]
1452 See Documentation/ramdisk.txt.
1454 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1455 New name for the ramdisk parameter.
1456 See Documentation/ramdisk.txt.
1458 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1459 RCU callbacks to process in one batch.
1461 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1462 RCU callbacks over which batch limiting is disabled.
1464 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1465 RCU callbacks below which batch limiting is re-enabled.
1469 Run specified binary instead of /init from the ramdisk,
1470 used for early userspace startup. See initrd.
1472 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1473 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1474 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1476 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1480 Reserves a hole at the top of the kernel virtual
1483 reset_devices [KNL] Force drivers to reset the underlying device
1484 during initialization.
1487 Specify the partition device for software suspend
1489 resume_offset= [SWSUSP]
1490 Specify the offset from the beginning of the partition
1491 given by "resume=" at which the swap header is located,
1492 in <PAGE_SIZE> units (needed only for swap files).
1493 See Documentation/power/swsusp-and-swap-files.txt
1495 retain_initrd [RAM] Keep initrd memory after extraction
1497 rhash_entries= [KNL,NET]
1498 Set number of hash buckets for route cache
1500 riscom8= [HW,SERIAL]
1501 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1503 ro [KNL] Mount root device read-only on boot
1505 root= [KNL] Root filesystem
1507 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1508 mount the root filesystem
1510 rootflags= [KNL] Set root filesystem mount option string
1512 rootfstype= [KNL] Set root filesystem type
1514 rootwait [KNL] Wait (indefinitely) for root device to show up.
1515 Useful for devices that are detected asynchronously
1516 (e.g. USB and MMC devices).
1518 rw [KNL] Mount root device read-write on boot
1520 S [KNL] Run init in single mode
1523 See drivers/net/irda/sa1100_ir.c.
1526 Format: <io>,<irq>,<dma>,<dma2>
1528 sbni= [NET] Granch SBNI12 leased line adapter
1530 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1531 Format: <io>[,<timeout>[,<isapnp>]]
1533 scsi_debug_*= [SCSI]
1534 See drivers/scsi/scsi_debug.c.
1536 scsi_default_dev_flags=
1537 [SCSI] SCSI default device flags
1540 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1541 Format: <vendor>:<model>:<flags>
1542 (flags are integer value)
1544 scsi_logging= [SCSI]
1546 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1547 discovered. async scans them in kernel threads,
1548 allowing boot to proceed. none ignores them, expecting
1549 user space to do the scan.
1551 selinux [SELINUX] Disable or enable SELinux at boot time.
1552 Format: { "0" | "1" }
1553 See security/selinux/Kconfig help text.
1556 Default value is set via kernel config option.
1557 If enabled at boot time, /selinux/disable can be used
1558 later to disable prior to initial policy load.
1560 selinux_compat_net =
1561 [SELINUX] Set initial selinux_compat_net flag value.
1562 Format: { "0" | "1" }
1563 0 -- use new secmark-based packet controls
1564 1 -- use legacy packet controls
1565 Default value is 0 (preferred).
1566 Value can be changed at runtime via
1567 /selinux/compat_net.
1569 serialnumber [BUGS=IA-32]
1571 sg_def_reserved_size= [SCSI]
1574 Maximal number of shapers.
1577 See header of drivers/scsi/sim710.c.
1584 slub_debug[=options[,slabs]] [MM, SLUB]
1585 Enabling slub_debug allows one to determine the
1586 culprit if slab objects become corrupted. Enabling
1587 slub_debug can create guard zones around objects and
1588 may poison objects when not in use. Also tracks the
1589 last alloc / free. For more information see
1590 Documentation/vm/slub.txt.
1592 slub_max_order= [MM, SLUB]
1593 Determines the maximum allowed order for slabs.
1594 A high setting may cause OOMs due to memory
1595 fragmentation. For more information see
1596 Documentation/vm/slub.txt.
1598 slub_min_objects= [MM, SLUB]
1599 The minimum number of objects per slab. SLUB will
1600 increase the slab order up to slub_max_order to
1601 generate a sufficiently large slab able to contain
1602 the number of objects indicated. The higher the number
1603 of objects the smaller the overhead of tracking slabs
1604 and the less frequently locks need to be acquired.
1605 For more information see Documentation/vm/slub.txt.
1607 slub_min_order= [MM, SLUB]
1608 Determines the mininum page order for slabs. Must be
1609 lower than slub_max_order.
1610 For more information see Documentation/vm/slub.txt.
1612 slub_nomerge [MM, SLUB]
1613 Disable merging of slabs with similar size. May be
1614 necessary if there is some reason to distinguish
1615 allocs to different slabs. Debug options disable
1616 merging on their own.
1617 For more information see Documentation/vm/slub.txt.
1620 Format: <io1>[,<io2>[,...,<io8>]]
1622 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1623 attempt to substitute SMP alternatives once at boot.
1625 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1626 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1627 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1628 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1629 smsc-ircc2.ircc_irq= [HW] IRQ line
1630 smsc-ircc2.ircc_dma= [HW] DMA channel
1631 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1632 0: Toshiba Satellite 1800 (GP data pin select)
1633 1: Fast pin select (default)
1636 snd-ad1816a= [HW,ALSA]
1638 snd-ad1848= [HW,ALSA]
1640 snd-ali5451= [HW,ALSA]
1642 snd-als100= [HW,ALSA]
1644 snd-als4000= [HW,ALSA]
1646 snd-azt2320= [HW,ALSA]
1648 snd-cmi8330= [HW,ALSA]
1650 snd-cmipci= [HW,ALSA]
1652 snd-cs4231= [HW,ALSA]
1654 snd-cs4232= [HW,ALSA]
1656 snd-cs4236= [HW,ALSA]
1658 snd-cs4281= [HW,ALSA]
1660 snd-cs46xx= [HW,ALSA]
1662 snd-dt019x= [HW,ALSA]
1664 snd-dummy= [HW,ALSA]
1666 snd-emu10k1= [HW,ALSA]
1668 snd-ens1370= [HW,ALSA]
1670 snd-ens1371= [HW,ALSA]
1672 snd-es968= [HW,ALSA]
1674 snd-es1688= [HW,ALSA]
1676 snd-es18xx= [HW,ALSA]
1678 snd-es1938= [HW,ALSA]
1680 snd-es1968= [HW,ALSA]
1682 snd-fm801= [HW,ALSA]
1684 snd-gusclassic= [HW,ALSA]
1686 snd-gusextreme= [HW,ALSA]
1688 snd-gusmax= [HW,ALSA]
1692 snd-ice1712= [HW,ALSA]
1694 snd-intel8x0= [HW,ALSA]
1696 snd-interwave= [HW,ALSA]
1701 snd-korg1212= [HW,ALSA]
1703 snd-maestro3= [HW,ALSA]
1705 snd-mpu401= [HW,ALSA]
1707 snd-mtpav= [HW,ALSA]
1709 snd-nm256= [HW,ALSA]
1711 snd-opl3sa2= [HW,ALSA]
1719 snd-opti93x= [HW,ALSA]
1723 snd-rme32= [HW,ALSA]
1725 snd-rme96= [HW,ALSA]
1727 snd-rme9652= [HW,ALSA]
1733 snd-sbawe= [HW,ALSA]
1735 snd-serial= [HW,ALSA]
1737 snd-sgalaxy= [HW,ALSA]
1739 snd-sonicvibes= [HW,ALSA]
1744 snd-sun-cs4231= [HW,ALSA]
1746 snd-trident= [HW,ALSA]
1748 snd-usb-audio= [HW,ALSA,USB]
1750 snd-via82xx= [HW,ALSA]
1752 snd-virmidi= [HW,ALSA]
1754 snd-wavefront= [HW,ALSA]
1756 snd-ymfpci= [HW,ALSA]
1758 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1759 See Documentation/sonypi.txt
1761 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1762 See Documentation/specialix.txt.
1764 spia_io_base= [HW,MTD]
1770 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1772 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1773 See Documentation/scsi/st.txt.
1776 See header of drivers/scsi/seagate.c.
1780 Set the STI (builtin display/keyboard on the HP-PARISC
1781 machines) console (graphic card) which should be used
1782 as the initial boot-console.
1783 See also comment in drivers/video/console/sticore.c.
1786 See comment in drivers/video/console/sticore.c.
1789 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1793 Control how the NFS server code allocates CPUs to
1794 service thread pools. Depending on how many NICs
1795 you have and where their interrupts are bound, this
1796 option will affect which CPUs will do NFS serving.
1797 Note: this parameter cannot be changed while the
1798 NFS server is running.
1800 auto the server chooses an appropriate mode
1801 automatically using heuristics
1802 global a single global pool contains all CPUs
1803 percpu one pool for each CPU
1804 pernode one pool for each NUMA node (equivalent
1805 to global on non-NUMA machines)
1807 swiotlb= [IA-64] Number of I/O TLB slabs
1811 sym53c416= [HW,SCSI]
1812 See header of drivers/scsi/sym53c416.c.
1814 sysrq_always_enabled
1816 Ignore sysrq setting - this boot parameter will
1817 neutralize any effect of /proc/sys/kernel/sysrq.
1818 Useful for debugging.
1821 See header of drivers/scsi/t128.c.
1825 thash_entries= [KNL,NET]
1826 Set number of hash buckets for TCP connection
1828 time Show timing data prefixed to each printk message line
1829 [deprecated, see 'printk.time']
1831 tipar.timeout= [HW,PPT]
1832 Set communications timeout in tenths of a second
1835 tipar.delay= [HW,PPT]
1836 Set inter-bit delay in microseconds (default 10).
1839 See header of drivers/scsi/seagate.c.
1842 See comment before function dc390_setup() in
1843 drivers/scsi/tmscsim.c.
1847 trix= [HW,OSS] MediaTrix AudioTrix Pro
1849 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1851 tsdev.xres= [TS] Horizontal screen resolution.
1852 tsdev.yres= [TS] Vertical screen resolution.
1854 turbografx.map[2|3]= [HW,JOY]
1855 TurboGraFX parallel port interface
1857 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1858 See also Documentation/input/joystick-parport.txt
1860 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1861 See header of drivers/scsi/u14-34f.c.
1870 [USB] Ignore overcurrent events (default N).
1871 Some badly-designed motherboards generate lots of
1872 bogus events, for ports that aren't wired to
1873 anything. Set this parameter to avoid log spamming.
1874 Note that genuine overcurrent events won't be
1877 usbcore.autosuspend=
1878 [USB] The autosuspend time delay (in seconds) used
1879 for newly-detected USB devices (default 2). This
1880 is the time required before an idle device will be
1881 autosuspended. Devices for which the delay is set
1882 to a negative value won't be autosuspended at all.
1885 [USBHID] The interval which mice are to be polled at.
1887 vdso= [IA-32,SH,x86-64]
1888 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1889 vdso=1: enable VDSO (default)
1890 vdso=0: disable VDSO mapping
1893 vector=percpu: enable percpu vector domain
1895 video= [FB] Frame buffer configuration
1896 See Documentation/fb/modedb.txt.
1898 vga= [BOOT,IA-32] Select a particular video mode
1899 See Documentation/i386/boot.txt and
1900 Documentation/svga.txt.
1901 Use vga=ask for menu.
1902 This is actually a boot loader parameter; the value is
1903 passed to the kernel using a special protocol.
1905 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1906 size of <nn>. This can be used to increase the
1907 minimum size (128MB on x86). It can also be used to
1908 decrease the size and leave more room for directly
1911 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1914 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1917 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1920 waveartist= [HW,OSS]
1921 Format: <io>,<irq>,<dma>,<dma2>
1924 See header of drivers/scsi/wd33c93.c.
1927 See header of drivers/scsi/wd7000.c.
1930 See Documentation/watchdog/watchdog.txt.
1932 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1933 xd_geo= See header of drivers/block/xd.c.
1935 xirc2ps_cs= [NET,PCMCIA]
1937 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1939 norandmaps Don't use address space randomization
1940 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1942 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1943 This is useful to get more information why
1944 you got a "dwarf2 unwinder stuck"
1946 ______________________________________________________________________
1950 Add documentation for ALSA options.
1951 Add more DRM drivers.