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 S390 S390 architecture is enabled.
79 SCSI Appropriate SCSI support is enabled.
80 A lot of drivers has their options described inside of
82 SELINUX SELinux support is enabled.
83 SERIAL Serial support is enabled.
84 SH SuperH architecture is enabled.
85 SMP The kernel is an SMP kernel.
86 SPARC Sparc architecture is enabled.
87 SWSUSP Software suspend is enabled.
88 TS Appropriate touchscreen support is enabled.
89 USB USB support is enabled.
90 USBHID USB Human Interface Device support is enabled.
91 V4L Video For Linux support is enabled.
92 VGA The VGA console has been enabled.
93 VT Virtual terminal support is enabled.
94 WDT Watchdog support is enabled.
95 XT IBM PC/XT MFM hard disk support is enabled.
96 X86-32 X86-32, aka i386 architecture is enabled.
97 X86-64 X86-64 architecture is enabled.
98 More X86-64 boot options can be found in
99 Documentation/x86_64/boot-options.txt .
101 In addition, the following text indicates that the option:
103 BUGS= Relates to possible processor bugs on the said processor.
104 KNL Is a kernel start-up parameter.
105 BOOT Is a boot loader parameter.
107 Parameters denoted with BOOT are actually interpreted by the boot
108 loader, and have no meaning to the kernel directly.
109 Do not modify the syntax of boot loader parameters without extreme
110 need or coordination with <Documentation/i386/boot.txt>.
112 There are also arch-specific kernel-parameters not documented here.
113 See for example <Documentation/x86_64/boot-options.txt>.
115 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
116 a trailing = on the name of any parameter states that that parameter will
117 be entered as an environment variable, whereas its absence indicates that
118 it will appear as a kernel argument readable via /proc/cmdline by programs
119 running once the system is up.
121 The number of kernel parameters is not limited, but the length of the
122 complete command line (parameters including spaces etc.) is limited to
123 a fixed number of characters. This limit depends on the architecture
124 and is between 256 and 4096 characters. It is defined in the file
125 ./include/asm/setup.h as COMMAND_LINE_SIZE.
128 acpi= [HW,ACPI,X86-64,i386]
129 Advanced Configuration and Power Interface
130 Format: { force | off | ht | strict | noirq }
131 force -- enable ACPI if default was off
132 off -- disable ACPI if default was on
133 noirq -- do not use ACPI for IRQ routing
134 ht -- run only enough ACPI to enable Hyper Threading
135 strict -- Be less tolerant of platforms that are not
136 strictly ACPI specification compliant.
138 See also Documentation/pm.txt, pci=noacpi
140 acpi_apic_instance= [ACPI, IOAPIC]
142 2: use 2nd APIC table, if available
143 1,0: use 1st APIC table
146 acpi_sleep= [HW,ACPI] Sleep options
147 Format: { s3_bios, s3_mode }
148 See Documentation/power/video.txt
150 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
151 Format: { level | edge | high | low }
153 acpi_irq_balance [HW,ACPI]
154 ACPI will balance active IRQs
157 acpi_irq_nobalance [HW,ACPI]
158 ACPI will not move active IRQs (default)
161 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
163 Format: <irq>,<irq>...
165 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
166 Format: <irq>,<irq>...
168 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
174 acpi_osi="string1" # add string1 -- only one string
175 acpi_osi="!string2" # remove built-in string2
176 acpi_osi= # disable all strings
178 acpi_serialize [HW,ACPI] force serialization of AML methods
180 acpi_skip_timer_override [HW,ACPI]
181 Recognize and ignore IRQ0/pin2 Interrupt Override.
182 For broken nForce2 BIOS resulting in XT-PIC timer.
183 acpi_use_timer_override [HW,ACPI}
184 Use timer override. For some broken Nvidia NF5 boards
185 that require a timer override, but don't have
188 acpi.debug_layer= [HW,ACPI]
190 Each bit of the <int> indicates an ACPI debug layer,
191 1: enable, 0: disable. It is useful for boot time
192 debugging. After system has booted up, it can be set
193 via /sys/module/acpi/parameters/debug_layer.
194 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
195 Available bits (add the numbers together) to enable debug output
196 for specific parts of the ACPI subsystem:
197 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
198 0x10 namespace 0x20 parser 0x40 dispatcher
199 0x80 executer 0x100 resources 0x200 acpica debugger
200 0x400 os services 0x800 acpica disassembler.
201 The number can be in decimal or prefixed with 0x in hex.
202 Warning: Many of these options can produce a lot of
203 output and make your system unusable. Be very careful.
205 acpi.debug_level= [HW,ACPI]
207 Each bit of the <int> indicates an ACPI debug level,
208 1: enable, 0: disable. It is useful for boot time
209 debugging. After system has booted up, it can be set
210 via /sys/module/acpi/parameters/debug_level.
211 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
212 Available bits (add the numbers together) to enable different
213 debug output levels of the ACPI subsystem:
214 0x01 error 0x02 warn 0x04 init 0x08 debug object
215 0x10 info 0x20 init names 0x40 parse 0x80 load
216 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
217 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
218 0x10000 resources 0x20000 user requests 0x40000 package.
219 The number can be in decimal or prefixed with 0x in hex.
220 Warning: Many of these options can produce a lot of
221 output and make your system unusable. Be very careful.
224 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
261 See Documentation/scsi/aha152x.txt.
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267 See Documentation/scsi/aic7xxx.txt.
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
283 Power management functions (SPARCstation-4/5 + deriv.)
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
301 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
302 Format: <io>,<irq>,<nodeID>
306 atarimouse= [HW,MOUSE] Atari Mouse
308 atascsi= [HW,SCSI] Atari SCSI
310 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
311 EzKey and similar keyboards
313 atkbd.reset= [HW] Reset keyboard during initialization
315 atkbd.set= [HW] Select keyboard code set
316 Format: <int> (2 = AT (default), 3 = PS/2)
318 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
321 atkbd.softraw= [HW] Choose between synthetic and real raw mode
322 Format: <bool> (0 = real, 1 = synthetic (default))
324 atkbd.softrepeat= [HW]
325 Use software keyboard repeat
329 baycom_epp= [HW,AX25]
332 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
334 See header of drivers/net/hamradio/baycom_par.c.
336 baycom_ser_fdx= [HW,AX25]
337 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
338 Format: <io>,<irq>,<mode>[,<baud>]
339 See header of drivers/net/hamradio/baycom_ser_fdx.c.
341 baycom_ser_hdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
343 Format: <io>,<irq>,<mode>
344 See header of drivers/net/hamradio/baycom_ser_hdx.c.
346 blkmtd_device= [HW,MTD]
352 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
353 bttv.radio= Most important insmod options are available as
355 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
356 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
359 See drivers/scsi/BusLogic.c, comment before function
360 BusLogic_ParseDriverOptions().
362 c101= [NET] Moxa C101 synchronous serial card
364 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
365 Sometimes CPU hardware bugs make them report the cache
366 size incorrectly. The kernel will attempt work arounds
367 to fix known problems, but for some CPUs it is not
368 possible to determine what the correct size should be.
369 This option provides an override for these situations.
371 chandev= [HW,NET] Generic channel device initialisation
373 checkreqprot [SELINUX] Set initial checkreqprot flag value.
374 Format: { "0" | "1" }
375 See security/selinux/Kconfig help text.
376 0 -- check protection applied by kernel (includes
377 any implied execute protection).
378 1 -- check protection requested by application.
379 Default value is set via a kernel config option.
380 Value can be changed at runtime via
381 /selinux/checkreqprot.
383 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
385 Forces specified clocksource (if available) to be used
386 when calculating gettimeofday(). If specified
387 clocksource is not available, it defaults to PIT.
388 Format: { pit | tsc | cyclone | pmtmr }
390 clocksource= [GENERIC_TIME] Override the default clocksource
392 Override the default clocksource and use the clocksource
393 with the name specified.
394 Some clocksource names to choose from, depending on
396 [all] jiffies (this is the base, fallback clocksource)
398 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
399 pxa_timer,timer3,32k_counter,timer0_1
401 [X86-32] pit,hpet,tsc,vmi-timer;
402 scx200_hrt on Geode; cyclone on IBM x440
410 code_bytes [IA32] How many bytes of object code to print in an
417 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
418 over the 8254 in addition to over the IO-APIC. The
419 kernel tries to set a sensible default.
421 hpet= [X86-32,HPET] option to disable HPET and use PIT.
424 com20020= [HW,NET] ARCnet - COM20020 chipset
426 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
428 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
432 ARCnet - COM90xx chipset (memory-mapped buffers)
433 Format: <io>[,<irq>[,<memstart>]]
435 condev= [HW,S390] console device
438 console= [KNL] Output console device and options.
440 tty<n> Use the virtual console device <n>.
444 Use the specified serial port. The options are of
445 the form "bbbbpnf", where "bbbb" is the baud rate,
446 "p" is parity ("n", "o", or "e"), "n" is number of
447 bits, and "f" is flow control ("r" for RTS or
448 omit it). Default is "9600n8".
450 See Documentation/serial-console.txt for more
452 Documentation/networking/netconsole.txt for an
455 uart[8250],io,<addr>[,options]
456 uart[8250],mmio,<addr>[,options]
457 Start an early, polled-mode console on the 8250/16550
458 UART at the specified I/O port or MMIO address,
459 switching to the matching ttyS device later. The
460 options are the same as for ttyS, above.
462 earlycon= [KNL] Output early console device and options.
463 uart[8250],io,<addr>[,options]
464 uart[8250],mmio,<addr>[,options]
465 Start an early, polled-mode console on the 8250/16550
466 UART at the specified I/O port or MMIO address.
467 The options are the same as for ttyS, above.
469 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
471 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
473 crashkernel=nn[KMG]@ss[KMG]
474 [KNL] Reserve a chunk of physical memory to
475 hold a kernel to switch to with kexec on panic.
478 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
483 cs89x0_media= [HW,NET]
484 Format: { rj45 | aui | bnc }
486 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
489 See header of drivers/s390/block/dasd_devmap.c.
491 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
492 (one device per port)
493 Format: <port#>,<type>
494 See also Documentation/input/joystick-parport.txt
496 debug [KNL] Enable kernel debugging (events log level).
499 [KNL] verbose self-tests
501 Print debugging info while doing the locking API
503 We default to 0 (no extra messages), setting it to
504 1 will print _a lot_ more information - normally
505 only useful to kernel developers.
508 Format: <area>[,<node>]
509 See also Documentation/networking/decnet.txt.
512 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
513 Change the default blue palette of the console.
514 This is a 16-member array composed of values
518 Format: <green0>,<green1>,<green2>,...,<green15>
519 Change the default green palette of the console.
520 This is a 16-member array composed of values
524 Format: <red0>,<red1>,<red2>,...,<red15>
525 Change the default red palette of the console.
526 This is a 16-member array composed of values
531 Set system-wide default UTF-8 mode for all tty's.
532 Default is 0 and by setting to 1, it enables UTF-8
533 mode for all newly opened or allocated terminals.
536 Set number of hash buckets for dentry cache.
539 IO parameters + enable/disable command.
541 digiepca= [HW,SERIAL]
542 See drivers/char/README.epca and
543 Documentation/digiepca.txt.
545 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
547 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
549 dmasound= [HW,OSS] Sound subsystem buffers
555 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
557 earlyprintk=serial[,ttySn[,baudrate]]
559 Append ",keep" to not disable it when the real console
562 Only vga or serial at a time, not both.
564 Currently only ttyS0 and ttyS1 are supported.
566 Interaction with the standard serial driver is not
569 The VGA output is eventually overwritten by the real
574 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
577 non-0: interrupt mode (default)
584 Format: {"of[f]" | "sk[ipmbr]"}
585 See comment in arch/i386/boot/edd.S
588 Format: <id>,<membase>,<irq>
590 eisa_irq_edge= [PARISC,HW]
591 See header of drivers/parisc/eisa.c.
594 See comment before function elanfreq_setup() in
595 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
598 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
599 See Documentation/block/as-iosched.txt and
600 Documentation/block/deadline-iosched.txt for details.
602 elfcorehdr= [X86-32, X86_64]
603 Specifies physical address of start of kernel core
604 image elf header. Generally kexec loader will
605 pass this option to capture kernel.
606 See Documentation/kdump/kdump.txt for details.
608 enforcing [SELINUX] Set initial enforcing status.
610 See security/selinux/Kconfig help text.
611 0 -- permissive (log only, no denials).
612 1 -- enforcing (deny and log).
614 Value can be changed at runtime via /selinux/enforce.
617 Format: <spdif>,[<nomix>,[<amplifier>]]
618 See also header of sound/oss/es1371.c.
620 ether= [HW,NET] Ethernet cards parameters
621 This option is obsoleted by the "netdev=" option, which
622 has equivalent usage. See its documentation for details.
624 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
629 fail_make_request=[KNL]
630 General fault injection mechanism.
631 Format: <interval>,<probability>,<space>,<times>
632 See also /Documentation/fault-injection/.
635 See header of drivers/scsi/fd_mcs.c.
638 See header of drivers/scsi/fdomain.c.
641 See Documentation/floppy.txt.
644 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
645 support via parallel port (up to 5 devices per port)
646 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
647 See also Documentation/input/joystick-parport.txt
652 See header of drivers/scsi/gdth.c.
654 gpt [EFI] Forces disk with valid GPT signature but
655 invalid Protective MBR to be treated as GPT.
659 hashdist= [KNL,NUMA] Large hashes allocated during boot
660 are distributed across NUMA nodes. Defaults on
661 for IA-64, off otherwise.
662 Format: 0 | 1 (for off | on)
664 hcl= [IA-64] SGI's Hardware Graph compatibility layer
666 hd= [EIDE] (E)IDE hard drive subsystem geometry
667 Format: <cyl>,<head>,<sect>
669 hd?= [HW] (E)IDE subsystem
670 hd?lun= See Documentation/ide.txt.
672 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
673 size of <nn>. This works even on boxes that have no
674 highmem otherwise. This also works to reduce highmem
675 size on bigger boxes.
677 highres= [KNL] Enable/disable high resolution timer mode.
678 Valid parameters: "on", "off"
682 See Documentation/isdn/README.HiSax.
684 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
686 i8042.direct [HW] Put keyboard port into non-translated mode
687 i8042.dumbkbd [HW] Pretend that controller can only read data from
688 keyboard and cannot control its state
689 (Don't attempt to blink the leds)
690 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
691 i8042.nokbd [HW] Don't check/create keyboard port
692 i8042.nomux [HW] Don't check presence of an active multiplexing
694 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
697 [HW] Frequency with which keyboard LEDs should blink
698 when kernel panics (default is 0.5 sec)
699 i8042.reset [HW] Reset the controller during init and cleanup
700 i8042.unlock [HW] Unlock (ignore) the keylock
704 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
705 indicates that the driver is running on unsupported
707 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
708 does not match list of supported models.
710 [HW] Report power status in /proc/i8k
711 (disabled by default)
712 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
715 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
716 See Documentation/mca.txt.
719 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
721 ide= [HW] (E)IDE subsystem
722 Format: ide=nodma or ide=doubler or ide=reverse
723 See Documentation/ide.txt.
725 ide?= [HW] (E)IDE subsystem
726 Format: ide?=noprobe or chipset specific parameters.
727 See Documentation/ide.txt.
729 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
730 See Documentation/ide.txt.
733 Format: idle=poll or idle=mwait
734 Poll forces a polling idle loop that can slightly improves the performance
735 of waking up a idle CPU, but will use a lot of power and make the system
736 run hot. Not recommended.
737 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
738 to not use it because it doesn't save as much power as a normal idle
739 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
742 ignore_loglevel [KNL]
743 Ignore loglevel setting - this will print /all/
744 kernel messages to the console. Useful for debugging.
747 Set number of hash buckets for inode cache.
750 See header of drivers/scsi/in2000.c.
754 Run specified binary instead of /sbin/init as init
757 initcall_debug [KNL] Trace initcalls as they are executed. Useful
758 for working out where the kernel is dying during
761 initrd= [BOOT] Specify the location of the initial ramdisk
763 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
768 io7= [HW] IO7 for Marvel based alpha systems
769 See comment before marvel_specify_io7 in
770 arch/alpha/kernel/core_marvel.c.
773 See Documentation/nfsroot.txt.
775 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
776 See comment before ip2_setup() in
777 drivers/char/ip2/ip2base.c.
779 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
780 See header of drivers/scsi/ips.c.
782 ports= [IP_VS_FTP] IPVS ftp helper module
784 Up to 8 (IP_VS_APP_MAX_PORTS) ports
786 Format: <port>,<port>....
789 When an interrupt is not handled search all handlers
790 for it. Intended to get systems with badly broken
794 When an interrupt is not handled search all handlers
795 for it. Also check all handlers each timer
796 interrupt. Intended to get systems with badly broken
800 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
802 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
804 <cpu number>,...,<cpu number>
806 <cpu number>-<cpu number> (must be a positive range in ascending order)
808 <cpu number>,...,<cpu number>-<cpu number>
809 This option can be used to specify one or more CPUs
810 to isolate from the general SMP balancing and scheduling
811 algorithms. The only way to move a process onto or off
812 an "isolated" CPU is via the CPU affinity syscalls.
813 <cpu number> begins at 0 and the maximum value is
814 "number of CPUs in system - 1".
816 This option is the preferred way to isolate CPUs. The
817 alternative -- manually setting the CPU mask of all
818 tasks in the system -- can cause problems and
819 suboptimal load balancer performance.
823 js= [HW,JOY] Analog joystick
824 See Documentation/input/joystick.txt.
826 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
827 specifies the amount of memory usable by the kernel
828 for non-movable allocations. The requested amount is
829 spread evenly throughout all nodes in the system. The
830 remaining memory in each node is used for Movable
831 pages. In the event, a node is too small to have both
832 kernelcore and Movable pages, kernelcore pages will
833 take priority and other nodes will have a larger number
834 of kernelcore pages. The Movable zone is used for the
835 allocation of pages that may be reclaimed or moved
836 by the page migration subsystem. This means that
837 HugeTLB pages may not be allocated from this zone.
838 Note that allocations like PTEs-from-HighMem still
839 use the HighMem zone if it exists, and the Normal
842 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
843 is similar to kernelcore except it specifies the
844 amount of memory used for migratable allocations.
845 If both kernelcore and movablecore is specified,
846 then kernelcore will be at *least* the specified
847 value but may be more. If movablecore on its own
848 is specified, the administrator must be careful
849 that the amount of memory usable for all allocations
854 kstack=N [X86-32,X86-64] Print N words from the kernel stack
859 lapic [X86-32,APIC] Enable the local APIC even if BIOS
862 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
865 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
866 Format: addr:<io>,irq:<irq>
868 load_ramdisk= [RAM] List of ramdisks to load from floppy
869 See Documentation/ramdisk.txt.
871 lockd.nlm_grace_period=P [NFS] Assign grace period.
874 lockd.nlm_tcpport=N [NFS] Assign TCP port.
877 lockd.nlm_timeout=T [NFS] Assign timeout value.
880 lockd.nlm_udpport=M [NFS] Assign UDP port.
883 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
886 loglevel= All Kernel Messages with a loglevel smaller than the
887 console loglevel will be printed to the console. It can
888 also be changed with klogd or other programs. The
889 loglevels are defined as follows:
891 0 (KERN_EMERG) system is unusable
892 1 (KERN_ALERT) action must be taken immediately
893 2 (KERN_CRIT) critical conditions
894 3 (KERN_ERR) error conditions
895 4 (KERN_WARNING) warning conditions
896 5 (KERN_NOTICE) normal but significant condition
897 6 (KERN_INFO) informational
898 7 (KERN_DEBUG) debug-level messages
900 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
901 Format: { n | nk | nM }
902 n must be a power of two. The default size
903 is set in the kernel config file.
905 lp=0 [LP] Specify parallel ports to use, e.g,
906 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
907 lp=reset first parallel port). 'lp=0' disables the
908 lp=auto printer driver. 'lp=reset' (which can be
909 specified in addition to the ports) causes
910 attached printers to be reset. Using
911 lp=port1,port2,... specifies the parallel ports
912 to associate lp devices with, starting with
913 lp0. A port specification may be 'none' to skip
914 that lp device, or a parport name such as
915 'parport0'. Specifying 'lp=auto' instead of a
916 port specification list means that device IDs
917 from each port should be examined, to see if
918 an IEEE 1284-compliant printer is attached; if
919 so, the driver will manage that printer.
920 See also header of drivers/char/lp.c.
923 Sets loops_per_jiffy to given constant, thus avoiding
924 time-consuming boot-time autodetection (up to 250 ms per
925 CPU). 0 enables autodetection (default). To determine
926 the correct value for your kernel, boot with normal
927 autodetection and see what value is printed. Note that
928 on SMP systems the preset will be applied to all CPUs,
929 which is likely to cause problems if your CPUs need
930 significantly divergent settings. An incorrect value
931 will cause delays in the kernel to be wrong, leading to
932 unpredictable I/O errors and other breakage. Although
933 unlikely, in the extreme case this might damage your
937 Format: <io>,<irq>,<dma>
939 mac5380= [HW,SCSI] Format:
940 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
942 mac53c9x= [HW,SCSI] Format:
943 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
945 machvec= [IA64] Force the use of a particular machine-vector
946 (machvec) in a generic kernel.
947 Example: machvec=hpzx1_swiotlb
949 max_loop= [LOOP] Maximum number of loopback devices that can
953 maxcpus= [SMP] Maximum number of processors that an SMP kernel
954 should make use of. maxcpus=n : n >= 0 limits the
955 kernel to using 'n' processors. n=0 is a special case,
956 it is equivalent to "nosmp", which also disables
959 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
960 equal to this physical address is ignored.
962 max_luns= [SCSI] Maximum number of LUNs to probe.
963 Should be between 1 and 2^32-1.
966 [SCSI] Maximum number of LUNs received.
967 Should be between 1 and 16384.
969 mca-pentium [BUGS=X86-32]
973 mce [X86-32] Machine Check Exception
975 md= [HW] RAID subsystems devices and level
976 See Documentation/md.txt.
979 Format: <first>,<last>
980 Specifies range of consoles to be captured by the MDA.
982 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
983 Amount of memory to be used when the kernel is not able
984 to see the whole system memory or for test.
985 [X86-32] Use together with memmap= to avoid physical
986 address space collisions. Without memmap= PCI devices
987 could be placed at addresses belonging to unused RAM.
989 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
992 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
993 E820 memory map, as specified by the user.
994 Such memmap=exactmap lines can be constructed based on
995 BIOS output or other requirements. See the memmap=nn@ss
998 memmap=nn[KMG]@ss[KMG]
999 [KNL] Force usage of a specific region of memory
1000 Region of memory to be used, from ss to ss+nn.
1002 memmap=nn[KMG]#ss[KMG]
1003 [KNL,ACPI] Mark specific memory as ACPI data.
1004 Region of memory to be used, from ss to ss+nn.
1006 memmap=nn[KMG]$ss[KMG]
1007 [KNL,ACPI] Mark specific memory as reserved.
1008 Region of memory to be used, from ss to ss+nn.
1010 meye.*= [HW] Set MotionEye Camera parameters
1011 See Documentation/video4linux/meye.txt.
1016 [MOUSE] Maximum time between finger touching and
1017 leaving touchpad surface for touch to be considered
1018 a tap and be reported as a left button click (for
1019 touchpads working in absolute mode only).
1021 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1022 reporting absolute coordinates, such as tablets
1023 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1024 reporting absolute coordinates, such as tablets
1029 MTD_Partition= [MTD]
1030 Format: <name>,<region-number>,<size>,<offset>
1032 MTD_Region= [MTD] Format:
1033 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1036 See drivers/mtd/cmdlinepart.c.
1038 mtouchusb.raw_coordinates=
1039 [HW] Make the MicroTouch USB driver use raw coordinates
1040 ('y', default) or cooked coordinates ('n')
1042 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1045 See header of drivers/scsi/NCR_D700.c.
1049 ncr53c400= [HW,SCSI]
1051 ncr53c400a= [HW,SCSI]
1053 ncr53c406a= [HW,SCSI]
1055 ncr53c8xx= [HW,SCSI]
1057 netdev= [NET] Network devices parameters
1058 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1059 Note that mem_start is often overloaded to mean
1060 something different and driver-specific.
1061 This usage is only documented in each driver source
1065 See Documentation/nfsroot.txt.
1067 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1068 See Documentation/nfsroot.txt.
1070 nfs.callback_tcpport=
1071 [NFS] set the TCP port on which the NFSv4 callback
1072 channel should listen.
1074 nfs.idmap_cache_timeout=
1075 [NFS] set the maximum lifetime for idmapper cache
1078 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1080 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1081 emulation library even if a 387 maths coprocessor
1084 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1088 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1089 caches in the slab allocator. Saves per-node memory,
1090 but will impact performance.
1094 noapic [SMP,APIC] Tells the kernel to not make use of any
1095 IOAPICs that may be present in the system.
1097 noasync [HW,M68K] Disables async and sync negotiation for
1100 nobats [PPC] Do not use BATs for mapping kernel lowmem
1101 on "Classic" PPC cores.
1105 nodelayacct [KNL] Disable per-task delay accounting
1107 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1111 noexec [X86-32,X86-64]
1112 noexec=on: enable non-executable mappings (default)
1113 noexec=off: disable nn-executable mappings
1115 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1116 register save and restore. The kernel will only save
1117 legacy floating-point registers on task switch.
1121 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1122 instruction doesn't work correctly and not to
1125 nohalt [IA-64] Tells the kernel not to use the power saving
1126 function PAL_HALT_LIGHT when idle. This increases
1127 power-consumption. On the positive side, it reduces
1128 interrupt wake-up latency, which may improve performance
1129 in certain environments such as networked servers or
1132 nohz= [KNL] Boottime enable/disable dynamic ticks
1133 Valid arguments: on, off
1136 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1138 noirqdebug [X86-32] Disables the code which attempts to detect and
1139 disable unhandled interrupt sources.
1141 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1142 broken timer IRQ sources.
1144 noisapnp [ISAPNP] Disables ISA PnP code.
1146 noinitrd [RAM] Tells the kernel not to load any configured
1151 nojitter [IA64] Disables jitter checking for ITC timers.
1153 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1155 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1157 noltlbs [PPC] Do not use large page/tlb entries for kernel
1158 lowmem mapping on PPC40x.
1160 nomca [IA-64] Disable machine check abort handling
1162 nomce [X86-32] Machine Check Exception
1164 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1166 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1167 with UP alternatives
1169 noresidual [PPC] Don't use residual data on PReP machines.
1171 noresume [SWSUSP] Disables resume and restores original swap
1174 no-scroll [VGA] Disables scrollback.
1175 This is required for the Braillex ib80-piezo Braille
1176 reader made by F.H. Papenmeier (Germany).
1180 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1182 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1183 and disable the IO APIC. legacy for "maxcpus=0".
1185 nosoftlockup [KNL] Disable the soft-lockup detector.
1187 nosync [HW,M68K] Disables sync negotiation for all devices.
1189 notsc [BUGS=X86-32] Disable Time Stamp Counter
1191 nousb [USB] Disable the USB subsystem
1195 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1196 one of ['zone', 'node', 'default'] can be specified
1197 This can be set from sysctl after boot.
1198 See Documentation/sysctl/vm.txt for details.
1200 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1205 oprofile.timer= [HW]
1206 Use timer interrupt instead of performance counters
1208 osst= [HW,SCSI] SCSI Tape Driver
1209 Format: <buffer_size>,<write_threshold>
1210 See also Documentation/scsi/st.txt.
1212 panic= [KNL] Kernel behaviour on panic
1215 parkbd.port= [HW] Parallel port number the keyboard adapter is
1216 connected to, default is 0.
1218 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1219 0 for XT, 1 for AT (default is AT).
1222 parport= [HW,PPT] Specify parallel ports. 0 disables.
1223 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1224 Use 'auto' to force the driver to use any
1225 IRQ/DMA settings detected (the default is to
1226 ignore detected IRQ/DMA settings because of
1227 possible conflicts). You can specify the base
1228 address, IRQ, and DMA settings; IRQ and DMA
1229 should be numbers, or 'auto' (for using detected
1230 settings on that particular port), or 'nofifo'
1231 (to avoid using a FIFO even if it is detected).
1232 Parallel ports are assigned in the order they
1233 are specified on the command line, starting
1236 parport_init_mode= [HW,PPT]
1237 Configure VIA parallel port to operate in
1238 a specific mode. This is necessary on Pegasos
1239 computer where firmware has no options for setting
1240 up parallel port mode and sets it to spp.
1241 Currently this function knows 686a and 8231 chips.
1242 Format: [spp|ps2|epp|ecp|ecpepp]
1244 pas2= [HW,OSS] Format:
1245 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1248 See header of drivers/scsi/pas16.c.
1251 Halt all CPUs after the first oops has been printed for
1252 the specified number of seconds. This is to be used if
1253 your oopses keep scrolling off the screen.
1258 See header of drivers/block/paride/pcd.c.
1259 See also Documentation/paride.txt.
1261 pci=option[,option...] [PCI] various PCI subsystem options:
1262 off [X86-32] don't probe for the PCI bus
1263 bios [X86-32] force use of PCI BIOS, don't access
1264 the hardware directly. Use this if your machine
1265 has a non-standard PCI host bridge.
1266 nobios [X86-32] disallow use of PCI BIOS, only direct
1267 hardware access methods are allowed. Use this
1268 if you experience crashes upon bootup and you
1269 suspect they are caused by the BIOS.
1270 conf1 [X86-32] Force use of PCI Configuration
1272 conf2 [X86-32] Force use of PCI Configuration
1274 noaer [PCIE] If the PCIEAER kernel config parameter is
1275 enabled, this kernel boot option can be used to
1276 disable the use of PCIE advanced error reporting.
1277 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1279 nomsi [MSI] If the PCI_MSI kernel config parameter is
1280 enabled, this kernel boot option can be used to
1281 disable the use of MSI interrupts system-wide.
1282 nosort [X86-32] Don't sort PCI devices according to
1283 order given by the PCI BIOS. This sorting is
1284 done to get a device order compatible with
1286 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1287 routing table. These calls are known to be buggy
1288 on several machines and they hang the machine
1289 when used, but on other computers it's the only
1290 way to get the interrupt routing table. Try
1291 this option if the kernel is unable to allocate
1292 IRQs or discover secondary PCI buses on your
1294 rom [X86-32] Assign address space to expansion ROMs.
1295 Use with caution as certain devices share
1296 address decoders between ROMs and other
1298 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1299 assigned automatically to PCI devices. You can
1300 make the kernel exclude IRQs of your ISA cards
1302 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1303 of the PIRQ table (normally generated
1304 by the BIOS) if it is outside the
1305 F0000h-100000h range.
1306 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1307 useful if the kernel is unable to find your
1308 secondary buses and you want to tell it
1309 explicitly which ones they are.
1310 assign-busses [X86-32] Always assign all PCI bus
1311 numbers ourselves, overriding
1312 whatever the firmware may have done.
1313 usepirqmask [X86-32] Honor the possible IRQ mask stored
1314 in the BIOS $PIR table. This is needed on
1315 some systems with broken BIOSes, notably
1316 some HP Pavilion N5400 and Omnibook XE3
1317 notebooks. This will have no effect if ACPI
1318 IRQ routing is enabled.
1319 noacpi [X86-32] Do not use ACPI for IRQ routing
1320 or for PCI scanning.
1321 use_crs [X86-32] Use _CRS for PCI resource
1323 routeirq Do IRQ routing for all PCI devices.
1324 This is normally done in pci_enable_device(),
1325 so this option is a temporary workaround
1326 for broken drivers that don't call it.
1327 firmware [ARM] Do not re-enumerate the bus but instead
1328 just use the configuration from the
1329 bootloader. This is currently used on
1330 IXP2000 systems where the bus has to be
1331 configured a certain way for adjunct CPUs.
1332 noearly [X86] Don't do any early type 1 scanning.
1333 This might help on some broken boards which
1334 machine check when some devices' config space
1335 is read. But various workarounds are disabled
1336 and some IOMMU drivers will not work.
1337 bfsort Sort PCI devices into breadth-first order.
1338 This sorting is done to get a device
1339 order compatible with older (<= 2.4) kernels.
1340 nobfsort Don't sort PCI devices into breadth-first order.
1341 cbiosize=nn[KMG] The fixed amount of bus space which is
1342 reserved for the CardBus bridge's IO window.
1343 The default value is 256 bytes.
1344 cbmemsize=nn[KMG] The fixed amount of bus space which is
1345 reserved for the CardBus bridge's memory
1346 window. The default value is 64 megabytes.
1348 pcmv= [HW,PCMCIA] BadgePAD 4
1351 See Documentation/paride.txt.
1353 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1356 See arch/parisc/kernel/pdc_chassis.c
1359 See Documentation/paride.txt.
1362 See Documentation/paride.txt.
1364 pirq= [SMP,APIC] Manual mp-table setup
1365 See Documentation/i386/IO-APIC.txt.
1367 plip= [PPT,NET] Parallel port network link
1368 Format: { parport<nr> | timid | 0 }
1369 See also Documentation/parport.txt.
1375 { on | off | curr | res | no-curr | no-res }
1378 [ISAPNP] Exclude IRQs for the autoconfiguration
1381 [ISAPNP] Exclude DMAs for the autoconfiguration
1383 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1384 Ranges are in pairs (I/O port base and size).
1387 [ISAPNP] Exclude memory regions for the
1389 Ranges are in pairs (memory base and size).
1391 print-fatal-signals=
1392 [KNL] debug: print fatal signals
1393 print-fatal-signals=1: print segfault info to
1397 printk.time= Show timing data prefixed to each printk message line
1398 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1400 profile= [KNL] Enable kernel profiling via /proc/profile
1401 Format: [schedule,]<number>
1402 Param: "schedule" - profile schedule points.
1403 Param: <number> - step/bucket size as a power of 2 for
1404 statistical time based profiling.
1405 Param: "sleep" - profile D-state sleeping (millisecs)
1407 processor.max_cstate= [HW,ACPI]
1408 Limit processor to maximum C-state
1409 max_cstate=9 overrides any DMI blacklist limit.
1411 processor.nocst [HW,ACPI]
1412 Ignore the _CST method to determine C-states,
1413 instead using the legacy FADT method
1415 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1417 See Documentation/ramdisk.txt.
1419 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1420 probe for; one of (bare|imps|exps|lifebook|any).
1421 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1423 psmouse.resetafter= [HW,MOUSE]
1424 Try to reset the device after so many bad packets
1427 [HW,MOUSE] Set desired mouse resolution, in dpi.
1428 psmouse.smartscroll=
1429 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1430 0 = disabled, 1 = enabled (default).
1432 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1434 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1437 See Documentation/paride.txt.
1439 quiet [KNL] Disable most log messages
1444 See Documentation/md.txt.
1446 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1447 See Documentation/ramdisk.txt.
1449 ramdisk_blocksize= [RAM]
1450 See Documentation/ramdisk.txt.
1452 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1453 New name for the ramdisk parameter.
1454 See Documentation/ramdisk.txt.
1456 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1457 RCU callbacks to process in one batch.
1459 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1460 RCU callbacks over which batch limiting is disabled.
1462 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1463 RCU callbacks below which batch limiting is re-enabled.
1467 Run specified binary instead of /init from the ramdisk,
1468 used for early userspace startup. See initrd.
1470 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1471 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1472 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1474 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1476 reservetop= [X86-32]
1478 Reserves a hole at the top of the kernel virtual
1481 reset_devices [KNL] Force drivers to reset the underlying device
1482 during initialization.
1485 Specify the partition device for software suspend
1487 resume_offset= [SWSUSP]
1488 Specify the offset from the beginning of the partition
1489 given by "resume=" at which the swap header is located,
1490 in <PAGE_SIZE> units (needed only for swap files).
1491 See Documentation/power/swsusp-and-swap-files.txt
1493 retain_initrd [RAM] Keep initrd memory after extraction
1495 rhash_entries= [KNL,NET]
1496 Set number of hash buckets for route cache
1498 riscom8= [HW,SERIAL]
1499 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1501 ro [KNL] Mount root device read-only on boot
1503 root= [KNL] Root filesystem
1505 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1506 mount the root filesystem
1508 rootflags= [KNL] Set root filesystem mount option string
1510 rootfstype= [KNL] Set root filesystem type
1512 rootwait [KNL] Wait (indefinitely) for root device to show up.
1513 Useful for devices that are detected asynchronously
1514 (e.g. USB and MMC devices).
1516 rw [KNL] Mount root device read-write on boot
1518 S [KNL] Run init in single mode
1521 See drivers/net/irda/sa1100_ir.c.
1524 Format: <io>,<irq>,<dma>,<dma2>
1526 sbni= [NET] Granch SBNI12 leased line adapter
1528 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1529 Format: <io>[,<timeout>[,<isapnp>]]
1531 scsi_debug_*= [SCSI]
1532 See drivers/scsi/scsi_debug.c.
1534 scsi_default_dev_flags=
1535 [SCSI] SCSI default device flags
1538 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1539 Format: <vendor>:<model>:<flags>
1540 (flags are integer value)
1542 scsi_logging= [SCSI]
1544 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1545 discovered. async scans them in kernel threads,
1546 allowing boot to proceed. none ignores them, expecting
1547 user space to do the scan.
1549 selinux [SELINUX] Disable or enable SELinux at boot time.
1550 Format: { "0" | "1" }
1551 See security/selinux/Kconfig help text.
1554 Default value is set via kernel config option.
1555 If enabled at boot time, /selinux/disable can be used
1556 later to disable prior to initial policy load.
1558 selinux_compat_net =
1559 [SELINUX] Set initial selinux_compat_net flag value.
1560 Format: { "0" | "1" }
1561 0 -- use new secmark-based packet controls
1562 1 -- use legacy packet controls
1563 Default value is 0 (preferred).
1564 Value can be changed at runtime via
1565 /selinux/compat_net.
1567 serialnumber [BUGS=X86-32]
1569 sg_def_reserved_size= [SCSI]
1572 Maximal number of shapers.
1575 See header of drivers/scsi/sim710.c.
1582 slub_debug[=options[,slabs]] [MM, SLUB]
1583 Enabling slub_debug allows one to determine the
1584 culprit if slab objects become corrupted. Enabling
1585 slub_debug can create guard zones around objects and
1586 may poison objects when not in use. Also tracks the
1587 last alloc / free. For more information see
1588 Documentation/vm/slub.txt.
1590 slub_max_order= [MM, SLUB]
1591 Determines the maximum allowed order for slabs.
1592 A high setting may cause OOMs due to memory
1593 fragmentation. For more information see
1594 Documentation/vm/slub.txt.
1596 slub_min_objects= [MM, SLUB]
1597 The minimum number of objects per slab. SLUB will
1598 increase the slab order up to slub_max_order to
1599 generate a sufficiently large slab able to contain
1600 the number of objects indicated. The higher the number
1601 of objects the smaller the overhead of tracking slabs
1602 and the less frequently locks need to be acquired.
1603 For more information see Documentation/vm/slub.txt.
1605 slub_min_order= [MM, SLUB]
1606 Determines the mininum page order for slabs. Must be
1607 lower than slub_max_order.
1608 For more information see Documentation/vm/slub.txt.
1610 slub_nomerge [MM, SLUB]
1611 Disable merging of slabs with similar size. May be
1612 necessary if there is some reason to distinguish
1613 allocs to different slabs. Debug options disable
1614 merging on their own.
1615 For more information see Documentation/vm/slub.txt.
1618 Format: <io1>[,<io2>[,...,<io8>]]
1620 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1621 attempt to substitute SMP alternatives once at boot.
1623 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1624 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1625 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1626 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1627 smsc-ircc2.ircc_irq= [HW] IRQ line
1628 smsc-ircc2.ircc_dma= [HW] DMA channel
1629 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1630 0: Toshiba Satellite 1800 (GP data pin select)
1631 1: Fast pin select (default)
1634 snd-ad1816a= [HW,ALSA]
1636 snd-ad1848= [HW,ALSA]
1638 snd-ali5451= [HW,ALSA]
1640 snd-als100= [HW,ALSA]
1642 snd-als4000= [HW,ALSA]
1644 snd-azt2320= [HW,ALSA]
1646 snd-cmi8330= [HW,ALSA]
1648 snd-cmipci= [HW,ALSA]
1650 snd-cs4231= [HW,ALSA]
1652 snd-cs4232= [HW,ALSA]
1654 snd-cs4236= [HW,ALSA]
1656 snd-cs4281= [HW,ALSA]
1658 snd-cs46xx= [HW,ALSA]
1660 snd-dt019x= [HW,ALSA]
1662 snd-dummy= [HW,ALSA]
1664 snd-emu10k1= [HW,ALSA]
1666 snd-ens1370= [HW,ALSA]
1668 snd-ens1371= [HW,ALSA]
1670 snd-es968= [HW,ALSA]
1672 snd-es1688= [HW,ALSA]
1674 snd-es18xx= [HW,ALSA]
1676 snd-es1938= [HW,ALSA]
1678 snd-es1968= [HW,ALSA]
1680 snd-fm801= [HW,ALSA]
1682 snd-gusclassic= [HW,ALSA]
1684 snd-gusextreme= [HW,ALSA]
1686 snd-gusmax= [HW,ALSA]
1690 snd-ice1712= [HW,ALSA]
1692 snd-intel8x0= [HW,ALSA]
1694 snd-interwave= [HW,ALSA]
1699 snd-korg1212= [HW,ALSA]
1701 snd-maestro3= [HW,ALSA]
1703 snd-mpu401= [HW,ALSA]
1705 snd-mtpav= [HW,ALSA]
1707 snd-nm256= [HW,ALSA]
1709 snd-opl3sa2= [HW,ALSA]
1717 snd-opti93x= [HW,ALSA]
1721 snd-rme32= [HW,ALSA]
1723 snd-rme96= [HW,ALSA]
1725 snd-rme9652= [HW,ALSA]
1731 snd-sbawe= [HW,ALSA]
1733 snd-serial= [HW,ALSA]
1735 snd-sgalaxy= [HW,ALSA]
1737 snd-sonicvibes= [HW,ALSA]
1742 snd-sun-cs4231= [HW,ALSA]
1744 snd-trident= [HW,ALSA]
1746 snd-usb-audio= [HW,ALSA,USB]
1748 snd-via82xx= [HW,ALSA]
1750 snd-virmidi= [HW,ALSA]
1752 snd-wavefront= [HW,ALSA]
1754 snd-ymfpci= [HW,ALSA]
1756 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1757 See Documentation/sonypi.txt
1759 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1760 See Documentation/specialix.txt.
1762 spia_io_base= [HW,MTD]
1768 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1770 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1771 See Documentation/scsi/st.txt.
1774 See header of drivers/scsi/seagate.c.
1778 Set the STI (builtin display/keyboard on the HP-PARISC
1779 machines) console (graphic card) which should be used
1780 as the initial boot-console.
1781 See also comment in drivers/video/console/sticore.c.
1784 See comment in drivers/video/console/sticore.c.
1787 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1791 Control how the NFS server code allocates CPUs to
1792 service thread pools. Depending on how many NICs
1793 you have and where their interrupts are bound, this
1794 option will affect which CPUs will do NFS serving.
1795 Note: this parameter cannot be changed while the
1796 NFS server is running.
1798 auto the server chooses an appropriate mode
1799 automatically using heuristics
1800 global a single global pool contains all CPUs
1801 percpu one pool for each CPU
1802 pernode one pool for each NUMA node (equivalent
1803 to global on non-NUMA machines)
1805 swiotlb= [IA-64] Number of I/O TLB slabs
1809 sym53c416= [HW,SCSI]
1810 See header of drivers/scsi/sym53c416.c.
1812 sysrq_always_enabled
1814 Ignore sysrq setting - this boot parameter will
1815 neutralize any effect of /proc/sys/kernel/sysrq.
1816 Useful for debugging.
1819 See header of drivers/scsi/t128.c.
1823 thash_entries= [KNL,NET]
1824 Set number of hash buckets for TCP connection
1826 thermal.act= [HW,ACPI]
1827 -1: disable all active trip points in all thermal zones
1828 <degrees C>: override all lowest active trip points
1830 thermal.crt= [HW,ACPI]
1831 -1: disable all critical trip points in all thermal zones
1832 <degrees C>: lower all critical trip points
1834 thermal.nocrt= [HW,ACPI]
1835 Set to disable actions on ACPI thermal zone
1836 critical and hot trip points.
1838 thermal.off= [HW,ACPI]
1839 1: disable ACPI thermal control
1841 thermal.psv= [HW,ACPI]
1842 -1: disable all passive trip points
1843 <degrees C>: override all passive trip points to this value
1845 thermal.tzp= [HW,ACPI]
1846 Specify global default ACPI thermal zone polling rate
1847 <deci-seconds>: poll all this frequency
1848 0: no polling (default)
1850 time Show timing data prefixed to each printk message line
1851 [deprecated, see 'printk.time']
1853 tipar.timeout= [HW,PPT]
1854 Set communications timeout in tenths of a second
1857 tipar.delay= [HW,PPT]
1858 Set inter-bit delay in microseconds (default 10).
1861 See header of drivers/scsi/seagate.c.
1864 See comment before function dc390_setup() in
1865 drivers/scsi/tmscsim.c.
1869 trix= [HW,OSS] MediaTrix AudioTrix Pro
1871 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1873 tsdev.xres= [TS] Horizontal screen resolution.
1874 tsdev.yres= [TS] Vertical screen resolution.
1876 turbografx.map[2|3]= [HW,JOY]
1877 TurboGraFX parallel port interface
1879 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1880 See also Documentation/input/joystick-parport.txt
1882 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1883 See header of drivers/scsi/u14-34f.c.
1892 [USB] Ignore overcurrent events (default N).
1893 Some badly-designed motherboards generate lots of
1894 bogus events, for ports that aren't wired to
1895 anything. Set this parameter to avoid log spamming.
1896 Note that genuine overcurrent events won't be
1899 usbcore.autosuspend=
1900 [USB] The autosuspend time delay (in seconds) used
1901 for newly-detected USB devices (default 2). This
1902 is the time required before an idle device will be
1903 autosuspended. Devices for which the delay is set
1904 to a negative value won't be autosuspended at all.
1907 [USBHID] The interval which mice are to be polled at.
1909 vdso= [X86-32,SH,x86-64]
1910 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1911 vdso=1: enable VDSO (default)
1912 vdso=0: disable VDSO mapping
1915 vector=percpu: enable percpu vector domain
1917 video= [FB] Frame buffer configuration
1918 See Documentation/fb/modedb.txt.
1920 vga= [BOOT,X86-32] Select a particular video mode
1921 See Documentation/i386/boot.txt and
1922 Documentation/svga.txt.
1923 Use vga=ask for menu.
1924 This is actually a boot loader parameter; the value is
1925 passed to the kernel using a special protocol.
1927 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1928 size of <nn>. This can be used to increase the
1929 minimum size (128MB on x86). It can also be used to
1930 decrease the size and leave more room for directly
1933 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1936 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1939 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1942 waveartist= [HW,OSS]
1943 Format: <io>,<irq>,<dma>,<dma2>
1946 See header of drivers/scsi/wd33c93.c.
1949 See header of drivers/scsi/wd7000.c.
1952 See Documentation/watchdog/wdt.txt.
1954 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1955 xd_geo= See header of drivers/block/xd.c.
1957 xirc2ps_cs= [NET,PCMCIA]
1959 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1961 norandmaps Don't use address space randomization
1962 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1964 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1965 This is useful to get more information why
1966 you got a "dwarf2 unwinder stuck"
1968 ______________________________________________________________________
1972 Add documentation for ALSA options.
1973 Add more DRM drivers.