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.
225 acpi_pm_good [X86-32,X86-64]
226 Override the pmtimer bug detection: force the kernel
227 to assume that this machine's pmtimer latches its value
228 and always returns good values.
231 { off | try_unsupported }
232 off: disable AGP support
233 try_unsupported: try to drive unsupported chipsets
234 (may crash computer or cause data corruption)
236 enable_timer_pin_1 [i386,x86-64]
237 Enable PIN 1 of APIC timer
238 Can be useful to work around chipset bugs
239 (in particular on some ATI chipsets).
240 The kernel tries to set a reasonable default.
242 disable_timer_pin_1 [i386,x86-64]
243 Disable PIN 1 of APIC timer
244 Can be useful to work around chipset bugs.
247 Format: <io>,<irq>,<dma>,<dma2>,<type>
250 See header of drivers/scsi/advansys.c.
252 advwdt= [HW,WDT] Advantech WDT
253 Format: <iostart>,<iostop>
255 aedsp16= [HW,OSS] Audio Excel DSP 16
256 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
257 See also header of sound/oss/aedsp16.c.
260 See Documentation/scsi/aha152x.txt.
263 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
266 See Documentation/scsi/aic7xxx.txt.
269 See Documentation/scsi/aic79xx.txt.
271 amijoy.map= [HW,JOY] Amiga joystick support
272 Map of devices attached to JOY0DAT and JOY1DAT
274 See also Documentation/kernel/input/joystick.txt
276 analog.map= [HW,JOY] Analog joystick and gamepad support
277 Specifies type or capabilities of an analog joystick
278 connected to one of 16 gameports
279 Format: <type1>,<type2>,..<type16>
282 Power management functions (SPARCstation-4/5 + deriv.)
284 Disable APC CPU standby support. SPARCstation-Fox does
285 not play well with APC CPU idle - disable it if you have
286 APC and your system crashes randomly.
288 apic= [APIC,i386] Advanced Programmable Interrupt Controller
289 Change the output verbosity whilst booting
290 Format: { quiet (default) | verbose | debug }
291 Change the amount of debugging information output
292 when initialising the APIC and IO-APIC components.
294 apm= [APM] Advanced Power Management
295 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 boot_delay= Milliseconds to delay each printk during boot.
349 Values larger than 10 seconds (10000) are changed to
353 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
354 bttv.radio= Most important insmod options are available as
356 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
357 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
360 See drivers/scsi/BusLogic.c, comment before function
361 BusLogic_ParseDriverOptions().
363 c101= [NET] Moxa C101 synchronous serial card
365 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
366 Sometimes CPU hardware bugs make them report the cache
367 size incorrectly. The kernel will attempt work arounds
368 to fix known problems, but for some CPUs it is not
369 possible to determine what the correct size should be.
370 This option provides an override for these situations.
373 [SECURITY] Disable capabilities. This would normally
374 be used only if an alternative security model is to be
375 configured. Potentially dangerous and should only be
376 used if you are entirely sure of the consequences.
378 chandev= [HW,NET] Generic channel device initialisation
380 checkreqprot [SELINUX] Set initial checkreqprot flag value.
381 Format: { "0" | "1" }
382 See security/selinux/Kconfig help text.
383 0 -- check protection applied by kernel (includes
384 any implied execute protection).
385 1 -- check protection requested by application.
386 Default value is set via a kernel config option.
387 Value can be changed at runtime via
388 /selinux/checkreqprot.
390 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
392 Forces specified clocksource (if available) to be used
393 when calculating gettimeofday(). If specified
394 clocksource is not available, it defaults to PIT.
395 Format: { pit | tsc | cyclone | pmtmr }
397 clocksource= [GENERIC_TIME] Override the default clocksource
399 Override the default clocksource and use the clocksource
400 with the name specified.
401 Some clocksource names to choose from, depending on
403 [all] jiffies (this is the base, fallback clocksource)
405 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
406 pxa_timer,timer3,32k_counter,timer0_1
408 [X86-32] pit,hpet,tsc,vmi-timer;
409 scx200_hrt on Geode; cyclone on IBM x440
417 code_bytes [IA32] How many bytes of object code to print in an
424 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
425 over the 8254 in addition to over the IO-APIC. The
426 kernel tries to set a sensible default.
428 hpet= [X86-32,HPET] option to disable HPET and use PIT.
431 com20020= [HW,NET] ARCnet - COM20020 chipset
433 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
435 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
439 ARCnet - COM90xx chipset (memory-mapped buffers)
440 Format: <io>[,<irq>[,<memstart>]]
442 condev= [HW,S390] console device
445 console= [KNL] Output console device and options.
447 tty<n> Use the virtual console device <n>.
451 Use the specified serial port. The options are of
452 the form "bbbbpnf", where "bbbb" is the baud rate,
453 "p" is parity ("n", "o", or "e"), "n" is number of
454 bits, and "f" is flow control ("r" for RTS or
455 omit it). Default is "9600n8".
457 See Documentation/serial-console.txt for more
459 Documentation/networking/netconsole.txt for an
462 uart[8250],io,<addr>[,options]
463 uart[8250],mmio,<addr>[,options]
464 Start an early, polled-mode console on the 8250/16550
465 UART at the specified I/O port or MMIO address,
466 switching to the matching ttyS device later. The
467 options are the same as for ttyS, above.
469 earlycon= [KNL] Output early console device and options.
470 uart[8250],io,<addr>[,options]
471 uart[8250],mmio,<addr>[,options]
472 Start an early, polled-mode console on the 8250/16550
473 UART at the specified I/O port or MMIO address.
474 The options are the same as for ttyS, above.
477 [HW] Never suspend the console
478 Disable suspending of consoles during suspend and
479 hibernate operations. Once disabled, debugging
480 messages can reach various consoles while the rest
481 of the system is being put to sleep (ie, while
482 debugging driver suspend/resume hooks). This may
483 not work reliably with all consoles, but is known
484 to work with serial and VGA consoles.
486 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
488 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
490 crashkernel=nn[KMG]@ss[KMG]
491 [KNL] Reserve a chunk of physical memory to
492 hold a kernel to switch to with kexec on panic.
494 crashkernel=range1:size1[,range2:size2,...][@offset]
495 [KNL] Same as above, but depends on the memory
496 in the running system. The syntax of range is
497 start-[end] where start and end are both
498 a memory unit (amount[KMG]). See also
499 Documentation/kdump/kdump.txt for a example.
502 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
507 cs89x0_media= [HW,NET]
508 Format: { rj45 | aui | bnc }
511 See header of drivers/s390/block/dasd_devmap.c.
513 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
514 (one device per port)
515 Format: <port#>,<type>
516 See also Documentation/input/joystick-parport.txt
518 debug [KNL] Enable kernel debugging (events log level).
521 [KNL] verbose self-tests
523 Print debugging info while doing the locking API
525 We default to 0 (no extra messages), setting it to
526 1 will print _a lot_ more information - normally
527 only useful to kernel developers.
530 Format: <area>[,<node>]
531 See also Documentation/networking/decnet.txt.
534 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
535 Change the default blue palette of the console.
536 This is a 16-member array composed of values
540 Format: <green0>,<green1>,<green2>,...,<green15>
541 Change the default green palette of the console.
542 This is a 16-member array composed of values
546 Format: <red0>,<red1>,<red2>,...,<red15>
547 Change the default red palette of the console.
548 This is a 16-member array composed of values
553 Set system-wide default UTF-8 mode for all tty's.
554 Default is 0 and by setting to 1, it enables UTF-8
555 mode for all newly opened or allocated terminals.
558 Set number of hash buckets for dentry cache.
561 IO parameters + enable/disable command.
563 digiepca= [HW,SERIAL]
564 See drivers/char/README.epca and
565 Documentation/digiepca.txt.
567 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
569 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
571 dmasound= [HW,OSS] Sound subsystem buffers
577 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
579 earlyprintk=serial[,ttySn[,baudrate]]
581 Append ",keep" to not disable it when the real console
584 Only vga or serial at a time, not both.
586 Currently only ttyS0 and ttyS1 are supported.
588 Interaction with the standard serial driver is not
591 The VGA output is eventually overwritten by the real
596 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
599 non-0: interrupt mode (default)
602 Format: {"of[f]" | "sk[ipmbr]"}
603 See comment in arch/i386/boot/edd.S
605 eisa_irq_edge= [PARISC,HW]
606 See header of drivers/parisc/eisa.c.
609 See comment before function elanfreq_setup() in
610 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
613 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
614 See Documentation/block/as-iosched.txt and
615 Documentation/block/deadline-iosched.txt for details.
617 elfcorehdr= [X86-32, X86_64]
618 Specifies physical address of start of kernel core
619 image elf header. Generally kexec loader will
620 pass this option to capture kernel.
621 See Documentation/kdump/kdump.txt for details.
623 enforcing [SELINUX] Set initial enforcing status.
625 See security/selinux/Kconfig help text.
626 0 -- permissive (log only, no denials).
627 1 -- enforcing (deny and log).
629 Value can be changed at runtime via /selinux/enforce.
632 Format: <spdif>,[<nomix>,[<amplifier>]]
633 See also header of sound/oss/es1371.c.
635 ether= [HW,NET] Ethernet cards parameters
636 This option is obsoleted by the "netdev=" option, which
637 has equivalent usage. See its documentation for details.
639 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
644 fail_make_request=[KNL]
645 General fault injection mechanism.
646 Format: <interval>,<probability>,<space>,<times>
647 See also /Documentation/fault-injection/.
650 See header of drivers/scsi/fd_mcs.c.
653 See header of drivers/scsi/fdomain.c.
656 See Documentation/floppy.txt.
659 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
660 support via parallel port (up to 5 devices per port)
661 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
662 See also Documentation/input/joystick-parport.txt
667 See header of drivers/scsi/gdth.c.
669 gpt [EFI] Forces disk with valid GPT signature but
670 invalid Protective MBR to be treated as GPT.
674 hashdist= [KNL,NUMA] Large hashes allocated during boot
675 are distributed across NUMA nodes. Defaults on
676 for IA-64, off otherwise.
677 Format: 0 | 1 (for off | on)
679 hcl= [IA-64] SGI's Hardware Graph compatibility layer
681 hd= [EIDE] (E)IDE hard drive subsystem geometry
682 Format: <cyl>,<head>,<sect>
684 hd?= [HW] (E)IDE subsystem
685 hd?lun= See Documentation/ide.txt.
687 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
688 size of <nn>. This works even on boxes that have no
689 highmem otherwise. This also works to reduce highmem
690 size on bigger boxes.
692 highres= [KNL] Enable/disable high resolution timer mode.
693 Valid parameters: "on", "off"
697 See Documentation/isdn/README.HiSax.
699 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
701 i8042.direct [HW] Put keyboard port into non-translated mode
702 i8042.dumbkbd [HW] Pretend that controller can only read data from
703 keyboard and cannot control its state
704 (Don't attempt to blink the leds)
705 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
706 i8042.nokbd [HW] Don't check/create keyboard port
707 i8042.nomux [HW] Don't check presence of an active multiplexing
709 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
712 [HW] Frequency with which keyboard LEDs should blink
713 when kernel panics (default is 0.5 sec)
714 i8042.reset [HW] Reset the controller during init and cleanup
715 i8042.unlock [HW] Unlock (ignore) the keylock
719 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
720 indicates that the driver is running on unsupported
722 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
723 does not match list of supported models.
725 [HW] Report power status in /proc/i8k
726 (disabled by default)
727 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
730 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
731 See Documentation/mca.txt.
734 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
736 ide= [HW] (E)IDE subsystem
737 Format: ide=nodma or ide=doubler or ide=reverse
738 See Documentation/ide.txt.
740 ide?= [HW] (E)IDE subsystem
741 Format: ide?=noprobe or chipset specific parameters.
742 See Documentation/ide.txt.
744 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
745 See Documentation/ide.txt.
748 Format: idle=poll or idle=mwait
749 Poll forces a polling idle loop that can slightly improves the performance
750 of waking up a idle CPU, but will use a lot of power and make the system
751 run hot. Not recommended.
752 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
753 to not use it because it doesn't save as much power as a normal idle
754 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
757 ignore_loglevel [KNL]
758 Ignore loglevel setting - this will print /all/
759 kernel messages to the console. Useful for debugging.
762 Set number of hash buckets for inode cache.
765 See header of drivers/scsi/in2000.c.
769 Run specified binary instead of /sbin/init as init
772 initcall_debug [KNL] Trace initcalls as they are executed. Useful
773 for working out where the kernel is dying during
776 initrd= [BOOT] Specify the location of the initial ramdisk
778 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
783 io7= [HW] IO7 for Marvel based alpha systems
784 See comment before marvel_specify_io7 in
785 arch/alpha/kernel/core_marvel.c.
788 See Documentation/nfsroot.txt.
790 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
791 See comment before ip2_setup() in
792 drivers/char/ip2/ip2base.c.
794 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
795 See header of drivers/scsi/ips.c.
797 ports= [IP_VS_FTP] IPVS ftp helper module
799 Up to 8 (IP_VS_APP_MAX_PORTS) ports
801 Format: <port>,<port>....
804 When an interrupt is not handled search all handlers
805 for it. Intended to get systems with badly broken
809 When an interrupt is not handled search all handlers
810 for it. Also check all handlers each timer
811 interrupt. Intended to get systems with badly broken
815 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
817 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
819 <cpu number>,...,<cpu number>
821 <cpu number>-<cpu number> (must be a positive range in ascending order)
823 <cpu number>,...,<cpu number>-<cpu number>
824 This option can be used to specify one or more CPUs
825 to isolate from the general SMP balancing and scheduling
826 algorithms. The only way to move a process onto or off
827 an "isolated" CPU is via the CPU affinity syscalls.
828 <cpu number> begins at 0 and the maximum value is
829 "number of CPUs in system - 1".
831 This option is the preferred way to isolate CPUs. The
832 alternative -- manually setting the CPU mask of all
833 tasks in the system -- can cause problems and
834 suboptimal load balancer performance.
838 js= [HW,JOY] Analog joystick
839 See Documentation/input/joystick.txt.
841 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
842 specifies the amount of memory usable by the kernel
843 for non-movable allocations. The requested amount is
844 spread evenly throughout all nodes in the system. The
845 remaining memory in each node is used for Movable
846 pages. In the event, a node is too small to have both
847 kernelcore and Movable pages, kernelcore pages will
848 take priority and other nodes will have a larger number
849 of kernelcore pages. The Movable zone is used for the
850 allocation of pages that may be reclaimed or moved
851 by the page migration subsystem. This means that
852 HugeTLB pages may not be allocated from this zone.
853 Note that allocations like PTEs-from-HighMem still
854 use the HighMem zone if it exists, and the Normal
857 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
858 is similar to kernelcore except it specifies the
859 amount of memory used for migratable allocations.
860 If both kernelcore and movablecore is specified,
861 then kernelcore will be at *least* the specified
862 value but may be more. If movablecore on its own
863 is specified, the administrator must be careful
864 that the amount of memory usable for all allocations
869 kstack=N [X86-32,X86-64] Print N words from the kernel stack
874 lapic [X86-32,APIC] Enable the local APIC even if BIOS
877 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
880 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
884 load_ramdisk= [RAM] List of ramdisks to load from floppy
885 See Documentation/ramdisk.txt.
887 lockd.nlm_grace_period=P [NFS] Assign grace period.
890 lockd.nlm_tcpport=N [NFS] Assign TCP port.
893 lockd.nlm_timeout=T [NFS] Assign timeout value.
896 lockd.nlm_udpport=M [NFS] Assign UDP port.
899 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
902 loglevel= All Kernel Messages with a loglevel smaller than the
903 console loglevel will be printed to the console. It can
904 also be changed with klogd or other programs. The
905 loglevels are defined as follows:
907 0 (KERN_EMERG) system is unusable
908 1 (KERN_ALERT) action must be taken immediately
909 2 (KERN_CRIT) critical conditions
910 3 (KERN_ERR) error conditions
911 4 (KERN_WARNING) warning conditions
912 5 (KERN_NOTICE) normal but significant condition
913 6 (KERN_INFO) informational
914 7 (KERN_DEBUG) debug-level messages
916 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
917 Format: { n | nk | nM }
918 n must be a power of two. The default size
919 is set in the kernel config file.
921 logo.nologo [FB] Disables display of the built-in Linux logo.
922 This may be used to provide more screen space for
923 kernel log messages and is useful when debugging
924 kernel boot problems.
926 lp=0 [LP] Specify parallel ports to use, e.g,
927 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
928 lp=reset first parallel port). 'lp=0' disables the
929 lp=auto printer driver. 'lp=reset' (which can be
930 specified in addition to the ports) causes
931 attached printers to be reset. Using
932 lp=port1,port2,... specifies the parallel ports
933 to associate lp devices with, starting with
934 lp0. A port specification may be 'none' to skip
935 that lp device, or a parport name such as
936 'parport0'. Specifying 'lp=auto' instead of a
937 port specification list means that device IDs
938 from each port should be examined, to see if
939 an IEEE 1284-compliant printer is attached; if
940 so, the driver will manage that printer.
941 See also header of drivers/char/lp.c.
944 Sets loops_per_jiffy to given constant, thus avoiding
945 time-consuming boot-time autodetection (up to 250 ms per
946 CPU). 0 enables autodetection (default). To determine
947 the correct value for your kernel, boot with normal
948 autodetection and see what value is printed. Note that
949 on SMP systems the preset will be applied to all CPUs,
950 which is likely to cause problems if your CPUs need
951 significantly divergent settings. An incorrect value
952 will cause delays in the kernel to be wrong, leading to
953 unpredictable I/O errors and other breakage. Although
954 unlikely, in the extreme case this might damage your
958 Format: <io>,<irq>,<dma>
960 mac5380= [HW,SCSI] Format:
961 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
963 mac53c9x= [HW,SCSI] Format:
964 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
966 machvec= [IA64] Force the use of a particular machine-vector
967 (machvec) in a generic kernel.
968 Example: machvec=hpzx1_swiotlb
970 max_loop= [LOOP] Maximum number of loopback devices that can
974 maxcpus= [SMP] Maximum number of processors that an SMP kernel
975 should make use of. maxcpus=n : n >= 0 limits the
976 kernel to using 'n' processors. n=0 is a special case,
977 it is equivalent to "nosmp", which also disables
980 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
981 equal to this physical address is ignored.
983 max_luns= [SCSI] Maximum number of LUNs to probe.
984 Should be between 1 and 2^32-1.
987 [SCSI] Maximum number of LUNs received.
988 Should be between 1 and 16384.
990 mca-pentium [BUGS=X86-32]
994 mce [X86-32] Machine Check Exception
996 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
998 md= [HW] RAID subsystems devices and level
999 See Documentation/md.txt.
1002 Format: <first>,<last>
1003 Specifies range of consoles to be captured by the MDA.
1005 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1006 Amount of memory to be used when the kernel is not able
1007 to see the whole system memory or for test.
1008 [X86-32] Use together with memmap= to avoid physical
1009 address space collisions. Without memmap= PCI devices
1010 could be placed at addresses belonging to unused RAM.
1012 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1015 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1016 E820 memory map, as specified by the user.
1017 Such memmap=exactmap lines can be constructed based on
1018 BIOS output or other requirements. See the memmap=nn@ss
1021 memmap=nn[KMG]@ss[KMG]
1022 [KNL] Force usage of a specific region of memory
1023 Region of memory to be used, from ss to ss+nn.
1025 memmap=nn[KMG]#ss[KMG]
1026 [KNL,ACPI] Mark specific memory as ACPI data.
1027 Region of memory to be used, from ss to ss+nn.
1029 memmap=nn[KMG]$ss[KMG]
1030 [KNL,ACPI] Mark specific memory as reserved.
1031 Region of memory to be used, from ss to ss+nn.
1033 meye.*= [HW] Set MotionEye Camera parameters
1034 See Documentation/video4linux/meye.txt.
1036 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1037 Multi-Function General Purpose Timers on AMD Geode
1043 [MOUSE] Maximum time between finger touching and
1044 leaving touchpad surface for touch to be considered
1045 a tap and be reported as a left button click (for
1046 touchpads working in absolute mode only).
1048 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1049 reporting absolute coordinates, such as tablets
1050 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1051 reporting absolute coordinates, such as tablets
1056 MTD_Partition= [MTD]
1057 Format: <name>,<region-number>,<size>,<offset>
1059 MTD_Region= [MTD] Format:
1060 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1063 See drivers/mtd/cmdlinepart.c.
1065 mtouchusb.raw_coordinates=
1066 [HW] Make the MicroTouch USB driver use raw coordinates
1067 ('y', default) or cooked coordinates ('n')
1069 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1072 See header of drivers/scsi/NCR_D700.c.
1076 ncr53c400= [HW,SCSI]
1078 ncr53c400a= [HW,SCSI]
1080 ncr53c406a= [HW,SCSI]
1082 ncr53c8xx= [HW,SCSI]
1084 netdev= [NET] Network devices parameters
1085 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1086 Note that mem_start is often overloaded to mean
1087 something different and driver-specific.
1088 This usage is only documented in each driver source
1092 See Documentation/nfsroot.txt.
1094 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1095 See Documentation/nfsroot.txt.
1097 nfs.callback_tcpport=
1098 [NFS] set the TCP port on which the NFSv4 callback
1099 channel should listen.
1101 nfs.idmap_cache_timeout=
1102 [NFS] set the maximum lifetime for idmapper cache
1106 [NFS] enable 64-bit inode numbers.
1107 If zero, the NFS client will fake up a 32-bit inode
1108 number for the readdir() and stat() syscalls instead
1109 of returning the full 64-bit number.
1110 The default is to return 64-bit inode numbers.
1112 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1114 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1115 emulation library even if a 387 maths coprocessor
1118 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1119 caches in the slab allocator. Saves per-node memory,
1120 but will impact performance.
1124 noapic [SMP,APIC] Tells the kernel to not make use of any
1125 IOAPICs that may be present in the system.
1127 nobats [PPC] Do not use BATs for mapping kernel lowmem
1128 on "Classic" PPC cores.
1132 nodelayacct [KNL] Disable per-task delay accounting
1134 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1138 noexec [X86-32,X86-64]
1139 noexec=on: enable non-executable mappings (default)
1140 noexec=off: disable nn-executable mappings
1142 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1143 register save and restore. The kernel will only save
1144 legacy floating-point registers on task switch.
1148 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1149 instruction doesn't work correctly and not to
1152 nohalt [IA-64] Tells the kernel not to use the power saving
1153 function PAL_HALT_LIGHT when idle. This increases
1154 power-consumption. On the positive side, it reduces
1155 interrupt wake-up latency, which may improve performance
1156 in certain environments such as networked servers or
1159 nohz= [KNL] Boottime enable/disable dynamic ticks
1160 Valid arguments: on, off
1163 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1165 noirqdebug [X86-32] Disables the code which attempts to detect and
1166 disable unhandled interrupt sources.
1168 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1169 broken timer IRQ sources.
1171 noisapnp [ISAPNP] Disables ISA PnP code.
1173 noinitrd [RAM] Tells the kernel not to load any configured
1178 nojitter [IA64] Disables jitter checking for ITC timers.
1180 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1182 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1184 noltlbs [PPC] Do not use large page/tlb entries for kernel
1185 lowmem mapping on PPC40x.
1187 nomca [IA-64] Disable machine check abort handling
1189 nomce [X86-32] Machine Check Exception
1191 nomfgpt [X86-32] Disable Multi-Function General Purpose
1192 Timer usage (for AMD Geode machines).
1194 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1196 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1197 with UP alternatives
1199 noresidual [PPC] Don't use residual data on PReP machines.
1201 noresume [SWSUSP] Disables resume and restores original swap
1204 no-scroll [VGA] Disables scrollback.
1205 This is required for the Braillex ib80-piezo Braille
1206 reader made by F.H. Papenmeier (Germany).
1210 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1212 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1213 and disable the IO APIC. legacy for "maxcpus=0".
1215 nosoftlockup [KNL] Disable the soft-lockup detector.
1217 nosync [HW,M68K] Disables sync negotiation for all devices.
1219 notsc [BUGS=X86-32] Disable Time Stamp Counter
1221 nousb [USB] Disable the USB subsystem
1225 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1226 one of ['zone', 'node', 'default'] can be specified
1227 This can be set from sysctl after boot.
1228 See Documentation/sysctl/vm.txt for details.
1230 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1235 oprofile.timer= [HW]
1236 Use timer interrupt instead of performance counters
1238 osst= [HW,SCSI] SCSI Tape Driver
1239 Format: <buffer_size>,<write_threshold>
1240 See also Documentation/scsi/st.txt.
1242 panic= [KNL] Kernel behaviour on panic
1245 parkbd.port= [HW] Parallel port number the keyboard adapter is
1246 connected to, default is 0.
1248 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1249 0 for XT, 1 for AT (default is AT).
1252 parport= [HW,PPT] Specify parallel ports. 0 disables.
1253 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1254 Use 'auto' to force the driver to use any
1255 IRQ/DMA settings detected (the default is to
1256 ignore detected IRQ/DMA settings because of
1257 possible conflicts). You can specify the base
1258 address, IRQ, and DMA settings; IRQ and DMA
1259 should be numbers, or 'auto' (for using detected
1260 settings on that particular port), or 'nofifo'
1261 (to avoid using a FIFO even if it is detected).
1262 Parallel ports are assigned in the order they
1263 are specified on the command line, starting
1266 parport_init_mode= [HW,PPT]
1267 Configure VIA parallel port to operate in
1268 a specific mode. This is necessary on Pegasos
1269 computer where firmware has no options for setting
1270 up parallel port mode and sets it to spp.
1271 Currently this function knows 686a and 8231 chips.
1272 Format: [spp|ps2|epp|ecp|ecpepp]
1274 pas2= [HW,OSS] Format:
1275 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1278 See header of drivers/scsi/pas16.c.
1281 Halt all CPUs after the first oops has been printed for
1282 the specified number of seconds. This is to be used if
1283 your oopses keep scrolling off the screen.
1288 See header of drivers/block/paride/pcd.c.
1289 See also Documentation/paride.txt.
1291 pci=option[,option...] [PCI] various PCI subsystem options:
1292 off [X86-32] don't probe for the PCI bus
1293 bios [X86-32] force use of PCI BIOS, don't access
1294 the hardware directly. Use this if your machine
1295 has a non-standard PCI host bridge.
1296 nobios [X86-32] disallow use of PCI BIOS, only direct
1297 hardware access methods are allowed. Use this
1298 if you experience crashes upon bootup and you
1299 suspect they are caused by the BIOS.
1300 conf1 [X86-32] Force use of PCI Configuration
1302 conf2 [X86-32] Force use of PCI Configuration
1304 noaer [PCIE] If the PCIEAER kernel config parameter is
1305 enabled, this kernel boot option can be used to
1306 disable the use of PCIE advanced error reporting.
1307 nodomains [PCI] Disable support for multiple PCI
1308 root domains (aka PCI segments, in ACPI-speak).
1309 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1311 nomsi [MSI] If the PCI_MSI kernel config parameter is
1312 enabled, this kernel boot option can be used to
1313 disable the use of MSI interrupts system-wide.
1314 nosort [X86-32] Don't sort PCI devices according to
1315 order given by the PCI BIOS. This sorting is
1316 done to get a device order compatible with
1318 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1319 routing table. These calls are known to be buggy
1320 on several machines and they hang the machine
1321 when used, but on other computers it's the only
1322 way to get the interrupt routing table. Try
1323 this option if the kernel is unable to allocate
1324 IRQs or discover secondary PCI buses on your
1326 rom [X86-32] Assign address space to expansion ROMs.
1327 Use with caution as certain devices share
1328 address decoders between ROMs and other
1330 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1331 assigned automatically to PCI devices. You can
1332 make the kernel exclude IRQs of your ISA cards
1334 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1335 of the PIRQ table (normally generated
1336 by the BIOS) if it is outside the
1337 F0000h-100000h range.
1338 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1339 useful if the kernel is unable to find your
1340 secondary buses and you want to tell it
1341 explicitly which ones they are.
1342 assign-busses [X86-32] Always assign all PCI bus
1343 numbers ourselves, overriding
1344 whatever the firmware may have done.
1345 usepirqmask [X86-32] Honor the possible IRQ mask stored
1346 in the BIOS $PIR table. This is needed on
1347 some systems with broken BIOSes, notably
1348 some HP Pavilion N5400 and Omnibook XE3
1349 notebooks. This will have no effect if ACPI
1350 IRQ routing is enabled.
1351 noacpi [X86-32] Do not use ACPI for IRQ routing
1352 or for PCI scanning.
1353 use_crs [X86-32] Use _CRS for PCI resource
1355 routeirq Do IRQ routing for all PCI devices.
1356 This is normally done in pci_enable_device(),
1357 so this option is a temporary workaround
1358 for broken drivers that don't call it.
1359 firmware [ARM] Do not re-enumerate the bus but instead
1360 just use the configuration from the
1361 bootloader. This is currently used on
1362 IXP2000 systems where the bus has to be
1363 configured a certain way for adjunct CPUs.
1364 noearly [X86] Don't do any early type 1 scanning.
1365 This might help on some broken boards which
1366 machine check when some devices' config space
1367 is read. But various workarounds are disabled
1368 and some IOMMU drivers will not work.
1369 bfsort Sort PCI devices into breadth-first order.
1370 This sorting is done to get a device
1371 order compatible with older (<= 2.4) kernels.
1372 nobfsort Don't sort PCI devices into breadth-first order.
1373 cbiosize=nn[KMG] The fixed amount of bus space which is
1374 reserved for the CardBus bridge's IO window.
1375 The default value is 256 bytes.
1376 cbmemsize=nn[KMG] The fixed amount of bus space which is
1377 reserved for the CardBus bridge's memory
1378 window. The default value is 64 megabytes.
1380 pcmv= [HW,PCMCIA] BadgePAD 4
1383 See Documentation/paride.txt.
1385 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1388 See arch/parisc/kernel/pdc_chassis.c
1391 See Documentation/paride.txt.
1394 See Documentation/paride.txt.
1396 pirq= [SMP,APIC] Manual mp-table setup
1397 See Documentation/i386/IO-APIC.txt.
1399 plip= [PPT,NET] Parallel port network link
1400 Format: { parport<nr> | timid | 0 }
1401 See also Documentation/parport.txt.
1407 { on | off | curr | res | no-curr | no-res }
1410 [ISAPNP] Exclude IRQs for the autoconfiguration
1413 [ISAPNP] Exclude DMAs for the autoconfiguration
1415 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1416 Ranges are in pairs (I/O port base and size).
1419 [ISAPNP] Exclude memory regions for the
1421 Ranges are in pairs (memory base and size).
1423 print-fatal-signals=
1424 [KNL] debug: print fatal signals
1425 print-fatal-signals=1: print segfault info to
1429 printk.time= Show timing data prefixed to each printk message line
1430 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1432 profile= [KNL] Enable kernel profiling via /proc/profile
1433 Format: [schedule,]<number>
1434 Param: "schedule" - profile schedule points.
1435 Param: <number> - step/bucket size as a power of 2 for
1436 statistical time based profiling.
1437 Param: "sleep" - profile D-state sleeping (millisecs)
1439 processor.max_cstate= [HW,ACPI]
1440 Limit processor to maximum C-state
1441 max_cstate=9 overrides any DMI blacklist limit.
1443 processor.nocst [HW,ACPI]
1444 Ignore the _CST method to determine C-states,
1445 instead using the legacy FADT method
1447 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1449 See Documentation/ramdisk.txt.
1451 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1452 probe for; one of (bare|imps|exps|lifebook|any).
1453 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1455 psmouse.resetafter= [HW,MOUSE]
1456 Try to reset the device after so many bad packets
1459 [HW,MOUSE] Set desired mouse resolution, in dpi.
1460 psmouse.smartscroll=
1461 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1462 0 = disabled, 1 = enabled (default).
1464 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1466 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1469 See Documentation/paride.txt.
1472 [KNL] Number of legacy pty's. Overwrites compiled-in
1475 quiet [KNL] Disable most log messages
1480 See Documentation/md.txt.
1482 ramdisk_blocksize= [RAM]
1483 See Documentation/ramdisk.txt.
1485 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1486 See Documentation/ramdisk.txt.
1488 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1489 RCU callbacks to process in one batch.
1491 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1492 RCU callbacks over which batch limiting is disabled.
1494 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1495 RCU callbacks below which batch limiting is re-enabled.
1499 Run specified binary instead of /init from the ramdisk,
1500 used for early userspace startup. See initrd.
1502 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1503 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1504 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1506 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1508 reservetop= [X86-32]
1510 Reserves a hole at the top of the kernel virtual
1513 reset_devices [KNL] Force drivers to reset the underlying device
1514 during initialization.
1517 Specify the partition device for software suspend
1519 resume_offset= [SWSUSP]
1520 Specify the offset from the beginning of the partition
1521 given by "resume=" at which the swap header is located,
1522 in <PAGE_SIZE> units (needed only for swap files).
1523 See Documentation/power/swsusp-and-swap-files.txt
1525 retain_initrd [RAM] Keep initrd memory after extraction
1527 rhash_entries= [KNL,NET]
1528 Set number of hash buckets for route cache
1530 riscom8= [HW,SERIAL]
1531 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1533 ro [KNL] Mount root device read-only on boot
1535 root= [KNL] Root filesystem
1537 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1538 mount the root filesystem
1540 rootflags= [KNL] Set root filesystem mount option string
1542 rootfstype= [KNL] Set root filesystem type
1544 rootwait [KNL] Wait (indefinitely) for root device to show up.
1545 Useful for devices that are detected asynchronously
1546 (e.g. USB and MMC devices).
1548 root_plug.vendor_id=
1549 [ROOTPLUG] Override the default vendor ID
1551 root_plug.product_id=
1552 [ROOTPLUG] Override the default product ID
1555 [ROOTPLUG] Enable debugging output
1557 rw [KNL] Mount root device read-write on boot
1559 S [KNL] Run init in single mode
1562 See drivers/net/irda/sa1100_ir.c.
1564 sbni= [NET] Granch SBNI12 leased line adapter
1566 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1567 Format: <io>[,<timeout>[,<isapnp>]]
1569 scsi_debug_*= [SCSI]
1570 See drivers/scsi/scsi_debug.c.
1572 scsi_default_dev_flags=
1573 [SCSI] SCSI default device flags
1576 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1577 Format: <vendor>:<model>:<flags>
1578 (flags are integer value)
1580 scsi_logging= [SCSI]
1582 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1583 discovered. async scans them in kernel threads,
1584 allowing boot to proceed. none ignores them, expecting
1585 user space to do the scan.
1587 selinux [SELINUX] Disable or enable SELinux at boot time.
1588 Format: { "0" | "1" }
1589 See security/selinux/Kconfig help text.
1592 Default value is set via kernel config option.
1593 If enabled at boot time, /selinux/disable can be used
1594 later to disable prior to initial policy load.
1596 selinux_compat_net =
1597 [SELINUX] Set initial selinux_compat_net flag value.
1598 Format: { "0" | "1" }
1599 0 -- use new secmark-based packet controls
1600 1 -- use legacy packet controls
1601 Default value is 0 (preferred).
1602 Value can be changed at runtime via
1603 /selinux/compat_net.
1605 serialnumber [BUGS=X86-32]
1608 Maximal number of shapers.
1611 See header of drivers/scsi/sim710.c.
1618 slub_debug[=options[,slabs]] [MM, SLUB]
1619 Enabling slub_debug allows one to determine the
1620 culprit if slab objects become corrupted. Enabling
1621 slub_debug can create guard zones around objects and
1622 may poison objects when not in use. Also tracks the
1623 last alloc / free. For more information see
1624 Documentation/vm/slub.txt.
1626 slub_max_order= [MM, SLUB]
1627 Determines the maximum allowed order for slabs.
1628 A high setting may cause OOMs due to memory
1629 fragmentation. For more information see
1630 Documentation/vm/slub.txt.
1632 slub_min_objects= [MM, SLUB]
1633 The minimum number of objects per slab. SLUB will
1634 increase the slab order up to slub_max_order to
1635 generate a sufficiently large slab able to contain
1636 the number of objects indicated. The higher the number
1637 of objects the smaller the overhead of tracking slabs
1638 and the less frequently locks need to be acquired.
1639 For more information see Documentation/vm/slub.txt.
1641 slub_min_order= [MM, SLUB]
1642 Determines the mininum page order for slabs. Must be
1643 lower than slub_max_order.
1644 For more information see Documentation/vm/slub.txt.
1646 slub_nomerge [MM, SLUB]
1647 Disable merging of slabs with similar size. May be
1648 necessary if there is some reason to distinguish
1649 allocs to different slabs. Debug options disable
1650 merging on their own.
1651 For more information see Documentation/vm/slub.txt.
1654 Format: <io1>[,<io2>[,...,<io8>]]
1656 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1657 attempt to substitute SMP alternatives once at boot.
1659 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1660 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1661 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1662 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1663 smsc-ircc2.ircc_irq= [HW] IRQ line
1664 smsc-ircc2.ircc_dma= [HW] DMA channel
1665 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1666 0: Toshiba Satellite 1800 (GP data pin select)
1667 1: Fast pin select (default)
1670 snd-ad1816a= [HW,ALSA]
1672 snd-ad1848= [HW,ALSA]
1674 snd-ali5451= [HW,ALSA]
1676 snd-als100= [HW,ALSA]
1678 snd-als4000= [HW,ALSA]
1680 snd-azt2320= [HW,ALSA]
1682 snd-cmi8330= [HW,ALSA]
1684 snd-cmipci= [HW,ALSA]
1686 snd-cs4231= [HW,ALSA]
1688 snd-cs4232= [HW,ALSA]
1690 snd-cs4236= [HW,ALSA]
1692 snd-cs4281= [HW,ALSA]
1694 snd-cs46xx= [HW,ALSA]
1696 snd-dt019x= [HW,ALSA]
1698 snd-dummy= [HW,ALSA]
1700 snd-emu10k1= [HW,ALSA]
1702 snd-ens1370= [HW,ALSA]
1704 snd-ens1371= [HW,ALSA]
1706 snd-es968= [HW,ALSA]
1708 snd-es1688= [HW,ALSA]
1710 snd-es18xx= [HW,ALSA]
1712 snd-es1938= [HW,ALSA]
1714 snd-es1968= [HW,ALSA]
1716 snd-fm801= [HW,ALSA]
1718 snd-gusclassic= [HW,ALSA]
1720 snd-gusextreme= [HW,ALSA]
1722 snd-gusmax= [HW,ALSA]
1726 snd-ice1712= [HW,ALSA]
1728 snd-intel8x0= [HW,ALSA]
1730 snd-interwave= [HW,ALSA]
1735 snd-korg1212= [HW,ALSA]
1737 snd-maestro3= [HW,ALSA]
1739 snd-mpu401= [HW,ALSA]
1741 snd-mtpav= [HW,ALSA]
1743 snd-nm256= [HW,ALSA]
1745 snd-opl3sa2= [HW,ALSA]
1753 snd-opti93x= [HW,ALSA]
1757 snd-rme32= [HW,ALSA]
1759 snd-rme96= [HW,ALSA]
1761 snd-rme9652= [HW,ALSA]
1767 snd-sbawe= [HW,ALSA]
1769 snd-serial= [HW,ALSA]
1771 snd-sgalaxy= [HW,ALSA]
1773 snd-sonicvibes= [HW,ALSA]
1778 snd-sun-cs4231= [HW,ALSA]
1780 snd-trident= [HW,ALSA]
1782 snd-usb-audio= [HW,ALSA,USB]
1784 snd-via82xx= [HW,ALSA]
1786 snd-virmidi= [HW,ALSA]
1788 snd-wavefront= [HW,ALSA]
1790 snd-ymfpci= [HW,ALSA]
1792 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1793 See Documentation/sonypi.txt
1795 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1796 See Documentation/specialix.txt.
1798 spia_io_base= [HW,MTD]
1804 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1806 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1807 See Documentation/scsi/st.txt.
1810 See header of drivers/scsi/seagate.c.
1814 Set the STI (builtin display/keyboard on the HP-PARISC
1815 machines) console (graphic card) which should be used
1816 as the initial boot-console.
1817 See also comment in drivers/video/console/sticore.c.
1820 See comment in drivers/video/console/sticore.c.
1823 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1827 Control how the NFS server code allocates CPUs to
1828 service thread pools. Depending on how many NICs
1829 you have and where their interrupts are bound, this
1830 option will affect which CPUs will do NFS serving.
1831 Note: this parameter cannot be changed while the
1832 NFS server is running.
1834 auto the server chooses an appropriate mode
1835 automatically using heuristics
1836 global a single global pool contains all CPUs
1837 percpu one pool for each CPU
1838 pernode one pool for each NUMA node (equivalent
1839 to global on non-NUMA machines)
1841 swiotlb= [IA-64] Number of I/O TLB slabs
1845 sym53c416= [HW,SCSI]
1846 See header of drivers/scsi/sym53c416.c.
1848 sysrq_always_enabled
1850 Ignore sysrq setting - this boot parameter will
1851 neutralize any effect of /proc/sys/kernel/sysrq.
1852 Useful for debugging.
1855 See header of drivers/scsi/t128.c.
1859 thash_entries= [KNL,NET]
1860 Set number of hash buckets for TCP connection
1862 thermal.act= [HW,ACPI]
1863 -1: disable all active trip points in all thermal zones
1864 <degrees C>: override all lowest active trip points
1866 thermal.crt= [HW,ACPI]
1867 -1: disable all critical trip points in all thermal zones
1868 <degrees C>: lower all critical trip points
1870 thermal.nocrt= [HW,ACPI]
1871 Set to disable actions on ACPI thermal zone
1872 critical and hot trip points.
1874 thermal.off= [HW,ACPI]
1875 1: disable ACPI thermal control
1877 thermal.psv= [HW,ACPI]
1878 -1: disable all passive trip points
1879 <degrees C>: override all passive trip points to this value
1881 thermal.tzp= [HW,ACPI]
1882 Specify global default ACPI thermal zone polling rate
1883 <deci-seconds>: poll all this frequency
1884 0: no polling (default)
1886 time Show timing data prefixed to each printk message line
1887 [deprecated, see 'printk.time']
1889 tipar.timeout= [HW,PPT]
1890 Set communications timeout in tenths of a second
1893 tipar.delay= [HW,PPT]
1894 Set inter-bit delay in microseconds (default 10).
1897 See header of drivers/scsi/seagate.c.
1900 See comment before function dc390_setup() in
1901 drivers/scsi/tmscsim.c.
1905 trix= [HW,OSS] MediaTrix AudioTrix Pro
1907 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1909 turbografx.map[2|3]= [HW,JOY]
1910 TurboGraFX parallel port interface
1912 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1913 See also Documentation/input/joystick-parport.txt
1915 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1916 See header of drivers/scsi/u14-34f.c.
1925 [USB] Ignore overcurrent events (default N).
1926 Some badly-designed motherboards generate lots of
1927 bogus events, for ports that aren't wired to
1928 anything. Set this parameter to avoid log spamming.
1929 Note that genuine overcurrent events won't be
1932 usbcore.autosuspend=
1933 [USB] The autosuspend time delay (in seconds) used
1934 for newly-detected USB devices (default 2). This
1935 is the time required before an idle device will be
1936 autosuspended. Devices for which the delay is set
1937 to a negative value won't be autosuspended at all.
1940 [USBHID] The interval which mice are to be polled at.
1942 vdso= [X86-32,SH,x86-64]
1943 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1944 vdso=1: enable VDSO (default)
1945 vdso=0: disable VDSO mapping
1948 vector=percpu: enable percpu vector domain
1950 video= [FB] Frame buffer configuration
1951 See Documentation/fb/modedb.txt.
1953 vga= [BOOT,X86-32] Select a particular video mode
1954 See Documentation/i386/boot.txt and
1955 Documentation/svga.txt.
1956 Use vga=ask for menu.
1957 This is actually a boot loader parameter; the value is
1958 passed to the kernel using a special protocol.
1960 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1961 size of <nn>. This can be used to increase the
1962 minimum size (128MB on x86). It can also be used to
1963 decrease the size and leave more room for directly
1966 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1969 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1972 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1975 waveartist= [HW,OSS]
1976 Format: <io>,<irq>,<dma>,<dma2>
1979 See header of drivers/scsi/wd33c93.c.
1982 See header of drivers/scsi/wd7000.c.
1985 See Documentation/watchdog/wdt.txt.
1987 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1988 xd_geo= See header of drivers/block/xd.c.
1990 xirc2ps_cs= [NET,PCMCIA]
1992 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1994 norandmaps Don't use address space randomization
1995 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1997 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1998 This is useful to get more information why
1999 you got a "dwarf2 unwinder stuck"
2001 ______________________________________________________________________
2005 Add documentation for ALSA options.
2006 Add more DRM drivers.