4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AX25 Appropriate AX.25 support is enabled.
38 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-64 IA-64 architecture is enabled.
45 IOSCHED More than one I/O scheduler is enabled.
46 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
47 ISAPNP ISA PnP code is enabled.
48 ISDN Appropriate ISDN support is enabled.
49 JOY Appropriate joystick support is enabled.
50 LIBATA Libata driver is enabled
51 LP Printer support is enabled.
52 LOOP Loopback device support is enabled.
53 M68k M68k architecture is enabled.
54 These options have more detailed description inside of
55 Documentation/m68k/kernel-options.txt.
56 MCA MCA bus support is enabled.
57 MDA MDA console support is enabled.
58 MOUSE Appropriate mouse support is enabled.
59 MSI Message Signaled Interrupts (PCI).
60 MTD MTD (Memory Technology Device) support is enabled.
61 NET Appropriate network support is enabled.
62 NUMA NUMA support is enabled.
63 GENERIC_TIME The generic timeofday code is enabled.
64 NFS Appropriate NFS support is enabled.
65 OSS OSS sound support is enabled.
66 PV_OPS A paravirtualized kernel is enabled.
67 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
68 PARISC The PA-RISC architecture is enabled.
69 PCI PCI bus support is enabled.
70 PCMCIA The PCMCIA subsystem is enabled.
71 PNP Plug & Play support is enabled.
72 PPC PowerPC architecture is enabled.
73 PPT Parallel port support is enabled.
74 PS2 Appropriate PS/2 support is enabled.
75 RAM RAM disk support is enabled.
76 S390 S390 architecture is enabled.
77 SCSI Appropriate SCSI support is enabled.
78 A lot of drivers has their options described inside of
80 SELINUX SELinux support is enabled.
81 SERIAL Serial support is enabled.
82 SH SuperH architecture is enabled.
83 SMP The kernel is an SMP kernel.
84 SPARC Sparc architecture is enabled.
85 SWSUSP Software suspend is enabled.
86 TS Appropriate touchscreen support is enabled.
87 USB USB support is enabled.
88 USBHID USB Human Interface Device support is enabled.
89 V4L Video For Linux support is enabled.
90 VGA The VGA console has been enabled.
91 VT Virtual terminal support is enabled.
92 WDT Watchdog support is enabled.
93 XT IBM PC/XT MFM hard disk support is enabled.
94 X86-32 X86-32, aka i386 architecture is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 acpi= [HW,ACPI,X86-64,i386]
127 Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
133 strict -- Be less tolerant of platforms that are not
134 strictly ACPI specification compliant.
136 See also Documentation/pm.txt, pci=noacpi
138 acpi_apic_instance= [ACPI, IOAPIC]
140 2: use 2nd APIC table, if available
141 1,0: use 1st APIC table
144 acpi_sleep= [HW,ACPI] Sleep options
145 Format: { s3_bios, s3_mode }
146 See Documentation/power/video.txt
148 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
149 Format: { level | edge | high | low }
151 acpi_irq_balance [HW,ACPI]
152 ACPI will balance active IRQs
155 acpi_irq_nobalance [HW,ACPI]
156 ACPI will not move active IRQs (default)
159 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
161 Format: <irq>,<irq>...
163 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
164 Format: <irq>,<irq>...
166 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
168 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
169 Format: To spoof as Windows 98: ="Microsoft Windows"
171 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
172 acpi_osi="string1" # add string1 -- only one string
173 acpi_osi="!string2" # remove built-in string2
174 acpi_osi= # disable all strings
176 acpi_serialize [HW,ACPI] force serialization of AML methods
178 acpi_skip_timer_override [HW,ACPI]
179 Recognize and ignore IRQ0/pin2 Interrupt Override.
180 For broken nForce2 BIOS resulting in XT-PIC timer.
181 acpi_use_timer_override [HW,ACPI}
182 Use timer override. For some broken Nvidia NF5 boards
183 that require a timer override, but don't have
186 acpi.debug_layer= [HW,ACPI]
188 Each bit of the <int> indicates an ACPI debug layer,
189 1: enable, 0: disable. It is useful for boot time
190 debugging. After system has booted up, it can be set
191 via /sys/module/acpi/parameters/debug_layer.
192 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
193 Available bits (add the numbers together) to enable debug output
194 for specific parts of the ACPI subsystem:
195 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
196 0x10 namespace 0x20 parser 0x40 dispatcher
197 0x80 executer 0x100 resources 0x200 acpica debugger
198 0x400 os services 0x800 acpica disassembler.
199 The number can be in decimal or prefixed with 0x in hex.
200 Warning: Many of these options can produce a lot of
201 output and make your system unusable. Be very careful.
203 acpi.debug_level= [HW,ACPI]
205 Each bit of the <int> indicates an ACPI debug level,
206 1: enable, 0: disable. It is useful for boot time
207 debugging. After system has booted up, it can be set
208 via /sys/module/acpi/parameters/debug_level.
209 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
210 Available bits (add the numbers together) to enable different
211 debug output levels of the ACPI subsystem:
212 0x01 error 0x02 warn 0x04 init 0x08 debug object
213 0x10 info 0x20 init names 0x40 parse 0x80 load
214 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
215 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
216 0x10000 resources 0x20000 user requests 0x40000 package.
217 The number can be in decimal or prefixed with 0x in hex.
218 Warning: Many of these options can produce a lot of
219 output and make your system unusable. Be very careful.
222 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
224 acpi_pm_good [X86-32,X86-64]
225 Override the pmtimer bug detection: force the kernel
226 to assume that this machine's pmtimer latches its value
227 and always returns good values.
230 { off | try_unsupported }
231 off: disable AGP support
232 try_unsupported: try to drive unsupported chipsets
233 (may crash computer or cause data corruption)
235 enable_timer_pin_1 [i386,x86-64]
236 Enable PIN 1 of APIC timer
237 Can be useful to work around chipset bugs
238 (in particular on some ATI chipsets).
239 The kernel tries to set a reasonable default.
241 disable_timer_pin_1 [i386,x86-64]
242 Disable PIN 1 of APIC timer
243 Can be useful to work around chipset bugs.
246 Format: <io>,<irq>,<dma>,<dma2>,<type>
249 See header of drivers/scsi/advansys.c.
251 advwdt= [HW,WDT] Advantech WDT
252 Format: <iostart>,<iostop>
254 aedsp16= [HW,OSS] Audio Excel DSP 16
255 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
256 See also header of sound/oss/aedsp16.c.
259 See Documentation/scsi/aha152x.txt.
262 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
265 See Documentation/scsi/aic7xxx.txt.
268 See Documentation/scsi/aic79xx.txt.
270 amijoy.map= [HW,JOY] Amiga joystick support
271 Map of devices attached to JOY0DAT and JOY1DAT
273 See also Documentation/kernel/input/joystick.txt
275 analog.map= [HW,JOY] Analog joystick and gamepad support
276 Specifies type or capabilities of an analog joystick
277 connected to one of 16 gameports
278 Format: <type1>,<type2>,..<type16>
281 Power management functions (SPARCstation-4/5 + deriv.)
283 Disable APC CPU standby support. SPARCstation-Fox does
284 not play well with APC CPU idle - disable it if you have
285 APC and your system crashes randomly.
287 apic= [APIC,i386] Advanced Programmable Interrupt Controller
288 Change the output verbosity whilst booting
289 Format: { quiet (default) | verbose | debug }
290 Change the amount of debugging information output
291 when initialising the APIC and IO-APIC components.
293 apm= [APM] Advanced Power Management
294 See header of arch/i386/kernel/apm.c.
299 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
300 Format: <io>,<irq>,<nodeID>
304 atarimouse= [HW,MOUSE] Atari Mouse
306 atascsi= [HW,SCSI] Atari SCSI
308 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
309 EzKey and similar keyboards
311 atkbd.reset= [HW] Reset keyboard during initialization
313 atkbd.set= [HW] Select keyboard code set
314 Format: <int> (2 = AT (default), 3 = PS/2)
316 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
319 atkbd.softraw= [HW] Choose between synthetic and real raw mode
320 Format: <bool> (0 = real, 1 = synthetic (default))
322 atkbd.softrepeat= [HW]
323 Use software keyboard repeat
327 baycom_epp= [HW,AX25]
330 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 See header of drivers/net/hamradio/baycom_par.c.
334 baycom_ser_fdx= [HW,AX25]
335 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
336 Format: <io>,<irq>,<mode>[,<baud>]
337 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339 baycom_ser_hdx= [HW,AX25]
340 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
341 Format: <io>,<irq>,<mode>
342 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344 blkmtd_device= [HW,MTD]
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 chandev= [HW,NET] Generic channel device initialisation
371 checkreqprot [SELINUX] Set initial checkreqprot flag value.
372 Format: { "0" | "1" }
373 See security/selinux/Kconfig help text.
374 0 -- check protection applied by kernel (includes
375 any implied execute protection).
376 1 -- check protection requested by application.
377 Default value is set via a kernel config option.
378 Value can be changed at runtime via
379 /selinux/checkreqprot.
381 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
383 Forces specified clocksource (if available) to be used
384 when calculating gettimeofday(). If specified
385 clocksource is not available, it defaults to PIT.
386 Format: { pit | tsc | cyclone | pmtmr }
388 clocksource= [GENERIC_TIME] Override the default clocksource
390 Override the default clocksource and use the clocksource
391 with the name specified.
392 Some clocksource names to choose from, depending on
394 [all] jiffies (this is the base, fallback clocksource)
396 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
397 pxa_timer,timer3,32k_counter,timer0_1
399 [X86-32] pit,hpet,tsc,vmi-timer;
400 scx200_hrt on Geode; cyclone on IBM x440
408 code_bytes [IA32] How many bytes of object code to print in an
415 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
416 over the 8254 in addition to over the IO-APIC. The
417 kernel tries to set a sensible default.
419 hpet= [X86-32,HPET] option to disable HPET and use PIT.
422 com20020= [HW,NET] ARCnet - COM20020 chipset
424 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
426 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
430 ARCnet - COM90xx chipset (memory-mapped buffers)
431 Format: <io>[,<irq>[,<memstart>]]
433 condev= [HW,S390] console device
436 console= [KNL] Output console device and options.
438 tty<n> Use the virtual console device <n>.
442 Use the specified serial port. The options are of
443 the form "bbbbpnf", where "bbbb" is the baud rate,
444 "p" is parity ("n", "o", or "e"), "n" is number of
445 bits, and "f" is flow control ("r" for RTS or
446 omit it). Default is "9600n8".
448 See Documentation/serial-console.txt for more
450 Documentation/networking/netconsole.txt for an
453 uart[8250],io,<addr>[,options]
454 uart[8250],mmio,<addr>[,options]
455 Start an early, polled-mode console on the 8250/16550
456 UART at the specified I/O port or MMIO address,
457 switching to the matching ttyS device later. The
458 options are the same as for ttyS, above.
460 earlycon= [KNL] Output early console device and options.
461 uart[8250],io,<addr>[,options]
462 uart[8250],mmio,<addr>[,options]
463 Start an early, polled-mode console on the 8250/16550
464 UART at the specified I/O port or MMIO address.
465 The options are the same as for ttyS, above.
467 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
469 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
471 crashkernel=nn[KMG]@ss[KMG]
472 [KNL] Reserve a chunk of physical memory to
473 hold a kernel to switch to with kexec on panic.
476 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
481 cs89x0_media= [HW,NET]
482 Format: { rj45 | aui | bnc }
484 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
487 See header of drivers/s390/block/dasd_devmap.c.
489 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
490 (one device per port)
491 Format: <port#>,<type>
492 See also Documentation/input/joystick-parport.txt
494 debug [KNL] Enable kernel debugging (events log level).
497 [KNL] verbose self-tests
499 Print debugging info while doing the locking API
501 We default to 0 (no extra messages), setting it to
502 1 will print _a lot_ more information - normally
503 only useful to kernel developers.
506 Format: <area>[,<node>]
507 See also Documentation/networking/decnet.txt.
510 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
511 Change the default blue palette of the console.
512 This is a 16-member array composed of values
516 Format: <green0>,<green1>,<green2>,...,<green15>
517 Change the default green palette of the console.
518 This is a 16-member array composed of values
522 Format: <red0>,<red1>,<red2>,...,<red15>
523 Change the default red palette of the console.
524 This is a 16-member array composed of values
529 Set system-wide default UTF-8 mode for all tty's.
530 Default is 0 and by setting to 1, it enables UTF-8
531 mode for all newly opened or allocated terminals.
534 Set number of hash buckets for dentry cache.
537 IO parameters + enable/disable command.
539 digiepca= [HW,SERIAL]
540 See drivers/char/README.epca and
541 Documentation/digiepca.txt.
543 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
545 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
547 dmasound= [HW,OSS] Sound subsystem buffers
553 earlyprintk= [X86-32,X86-64,SH]
555 earlyprintk=serial[,ttySn[,baudrate]]
557 Append ",keep" to not disable it when the real console
560 Only vga or serial at a time, not both.
562 Currently only ttyS0 and ttyS1 are supported.
564 Interaction with the standard serial driver is not
567 The VGA output is eventually overwritten by the real
572 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
575 non-0: interrupt mode (default)
582 Format: {"of[f]" | "sk[ipmbr]"}
583 See comment in arch/i386/boot/edd.S
586 Format: <id>,<membase>,<irq>
588 eisa_irq_edge= [PARISC,HW]
589 See header of drivers/parisc/eisa.c.
592 See comment before function elanfreq_setup() in
593 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
596 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
597 See Documentation/block/as-iosched.txt and
598 Documentation/block/deadline-iosched.txt for details.
600 elfcorehdr= [X86-32, X86_64]
601 Specifies physical address of start of kernel core
602 image elf header. Generally kexec loader will
603 pass this option to capture kernel.
604 See Documentation/kdump/kdump.txt for details.
606 enforcing [SELINUX] Set initial enforcing status.
608 See security/selinux/Kconfig help text.
609 0 -- permissive (log only, no denials).
610 1 -- enforcing (deny and log).
612 Value can be changed at runtime via /selinux/enforce.
615 Format: <spdif>,[<nomix>,[<amplifier>]]
616 See also header of sound/oss/es1371.c.
618 ether= [HW,NET] Ethernet cards parameters
619 This option is obsoleted by the "netdev=" option, which
620 has equivalent usage. See its documentation for details.
622 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
627 fail_make_request=[KNL]
628 General fault injection mechanism.
629 Format: <interval>,<probability>,<space>,<times>
630 See also /Documentation/fault-injection/.
633 See header of drivers/scsi/fd_mcs.c.
636 See header of drivers/scsi/fdomain.c.
639 See Documentation/floppy.txt.
642 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
643 support via parallel port (up to 5 devices per port)
644 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
645 See also Documentation/input/joystick-parport.txt
650 See header of drivers/scsi/gdth.c.
652 gpt [EFI] Forces disk with valid GPT signature but
653 invalid Protective MBR to be treated as GPT.
657 hashdist= [KNL,NUMA] Large hashes allocated during boot
658 are distributed across NUMA nodes. Defaults on
659 for IA-64, off otherwise.
660 Format: 0 | 1 (for off | on)
662 hcl= [IA-64] SGI's Hardware Graph compatibility layer
664 hd= [EIDE] (E)IDE hard drive subsystem geometry
665 Format: <cyl>,<head>,<sect>
667 hd?= [HW] (E)IDE subsystem
668 hd?lun= See Documentation/ide.txt.
670 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
671 size of <nn>. This works even on boxes that have no
672 highmem otherwise. This also works to reduce highmem
673 size on bigger boxes.
675 highres= [KNL] Enable/disable high resolution timer mode.
676 Valid parameters: "on", "off"
680 See Documentation/isdn/README.HiSax.
682 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
684 i8042.direct [HW] Put keyboard port into non-translated mode
685 i8042.dumbkbd [HW] Pretend that controller can only read data from
686 keyboard and cannot control its state
687 (Don't attempt to blink the leds)
688 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
689 i8042.nokbd [HW] Don't check/create keyboard port
690 i8042.nomux [HW] Don't check presence of an active multiplexing
692 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
695 [HW] Frequency with which keyboard LEDs should blink
696 when kernel panics (default is 0.5 sec)
697 i8042.reset [HW] Reset the controller during init and cleanup
698 i8042.unlock [HW] Unlock (ignore) the keylock
702 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
703 indicates that the driver is running on unsupported
705 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
706 does not match list of supported models.
708 [HW] Report power status in /proc/i8k
709 (disabled by default)
710 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
713 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
714 See Documentation/mca.txt.
717 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
719 ide= [HW] (E)IDE subsystem
720 Format: ide=nodma or ide=doubler or ide=reverse
721 See Documentation/ide.txt.
723 ide?= [HW] (E)IDE subsystem
724 Format: ide?=noprobe or chipset specific parameters.
725 See Documentation/ide.txt.
727 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
728 See Documentation/ide.txt.
731 Format: idle=poll or idle=mwait
732 Poll forces a polling idle loop that can slightly improves the performance
733 of waking up a idle CPU, but will use a lot of power and make the system
734 run hot. Not recommended.
735 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
736 to not use it because it doesn't save as much power as a normal idle
737 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
740 ignore_loglevel [KNL]
741 Ignore loglevel setting - this will print /all/
742 kernel messages to the console. Useful for debugging.
745 Set number of hash buckets for inode cache.
748 See header of drivers/scsi/in2000.c.
752 Run specified binary instead of /sbin/init as init
755 initcall_debug [KNL] Trace initcalls as they are executed. Useful
756 for working out where the kernel is dying during
759 initrd= [BOOT] Specify the location of the initial ramdisk
761 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
766 io7= [HW] IO7 for Marvel based alpha systems
767 See comment before marvel_specify_io7 in
768 arch/alpha/kernel/core_marvel.c.
771 See Documentation/nfsroot.txt.
773 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
774 See comment before ip2_setup() in
775 drivers/char/ip2/ip2base.c.
777 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
778 See header of drivers/scsi/ips.c.
780 ports= [IP_VS_FTP] IPVS ftp helper module
782 Up to 8 (IP_VS_APP_MAX_PORTS) ports
784 Format: <port>,<port>....
787 When an interrupt is not handled search all handlers
788 for it. Intended to get systems with badly broken
792 When an interrupt is not handled search all handlers
793 for it. Also check all handlers each timer
794 interrupt. Intended to get systems with badly broken
798 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
800 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
802 <cpu number>,...,<cpu number>
804 <cpu number>-<cpu number> (must be a positive range in ascending order)
806 <cpu number>,...,<cpu number>-<cpu number>
807 This option can be used to specify one or more CPUs
808 to isolate from the general SMP balancing and scheduling
809 algorithms. The only way to move a process onto or off
810 an "isolated" CPU is via the CPU affinity syscalls.
811 <cpu number> begins at 0 and the maximum value is
812 "number of CPUs in system - 1".
814 This option is the preferred way to isolate CPUs. The
815 alternative -- manually setting the CPU mask of all
816 tasks in the system -- can cause problems and
817 suboptimal load balancer performance.
821 js= [HW,JOY] Analog joystick
822 See Documentation/input/joystick.txt.
824 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
825 specifies the amount of memory usable by the kernel
826 for non-movable allocations. The requested amount is
827 spread evenly throughout all nodes in the system. The
828 remaining memory in each node is used for Movable
829 pages. In the event, a node is too small to have both
830 kernelcore and Movable pages, kernelcore pages will
831 take priority and other nodes will have a larger number
832 of kernelcore pages. The Movable zone is used for the
833 allocation of pages that may be reclaimed or moved
834 by the page migration subsystem. This means that
835 HugeTLB pages may not be allocated from this zone.
836 Note that allocations like PTEs-from-HighMem still
837 use the HighMem zone if it exists, and the Normal
840 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
841 is similar to kernelcore except it specifies the
842 amount of memory used for migratable allocations.
843 If both kernelcore and movablecore is specified,
844 then kernelcore will be at *least* the specified
845 value but may be more. If movablecore on its own
846 is specified, the administrator must be careful
847 that the amount of memory usable for all allocations
852 kstack=N [X86-32,X86-64] Print N words from the kernel stack
857 lapic [X86-32,APIC] Enable the local APIC even if BIOS
860 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
863 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
864 Format: addr:<io>,irq:<irq>
866 load_ramdisk= [RAM] List of ramdisks to load from floppy
867 See Documentation/ramdisk.txt.
869 lockd.nlm_grace_period=P [NFS] Assign grace period.
872 lockd.nlm_tcpport=N [NFS] Assign TCP port.
875 lockd.nlm_timeout=T [NFS] Assign timeout value.
878 lockd.nlm_udpport=M [NFS] Assign UDP port.
881 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
884 loglevel= All Kernel Messages with a loglevel smaller than the
885 console loglevel will be printed to the console. It can
886 also be changed with klogd or other programs. The
887 loglevels are defined as follows:
889 0 (KERN_EMERG) system is unusable
890 1 (KERN_ALERT) action must be taken immediately
891 2 (KERN_CRIT) critical conditions
892 3 (KERN_ERR) error conditions
893 4 (KERN_WARNING) warning conditions
894 5 (KERN_NOTICE) normal but significant condition
895 6 (KERN_INFO) informational
896 7 (KERN_DEBUG) debug-level messages
898 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
899 Format: { n | nk | nM }
900 n must be a power of two. The default size
901 is set in the kernel config file.
903 lp=0 [LP] Specify parallel ports to use, e.g,
904 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
905 lp=reset first parallel port). 'lp=0' disables the
906 lp=auto printer driver. 'lp=reset' (which can be
907 specified in addition to the ports) causes
908 attached printers to be reset. Using
909 lp=port1,port2,... specifies the parallel ports
910 to associate lp devices with, starting with
911 lp0. A port specification may be 'none' to skip
912 that lp device, or a parport name such as
913 'parport0'. Specifying 'lp=auto' instead of a
914 port specification list means that device IDs
915 from each port should be examined, to see if
916 an IEEE 1284-compliant printer is attached; if
917 so, the driver will manage that printer.
918 See also header of drivers/char/lp.c.
921 Sets loops_per_jiffy to given constant, thus avoiding
922 time-consuming boot-time autodetection (up to 250 ms per
923 CPU). 0 enables autodetection (default). To determine
924 the correct value for your kernel, boot with normal
925 autodetection and see what value is printed. Note that
926 on SMP systems the preset will be applied to all CPUs,
927 which is likely to cause problems if your CPUs need
928 significantly divergent settings. An incorrect value
929 will cause delays in the kernel to be wrong, leading to
930 unpredictable I/O errors and other breakage. Although
931 unlikely, in the extreme case this might damage your
935 Format: <io>,<irq>,<dma>
937 mac5380= [HW,SCSI] Format:
938 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
940 mac53c9x= [HW,SCSI] Format:
941 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
943 machvec= [IA64] Force the use of a particular machine-vector
944 (machvec) in a generic kernel.
945 Example: machvec=hpzx1_swiotlb
947 max_loop= [LOOP] Maximum number of loopback devices that can
951 maxcpus= [SMP] Maximum number of processors that an SMP kernel
952 should make use of. maxcpus=n : n >= 0 limits the
953 kernel to using 'n' processors. n=0 is a special case,
954 it is equivalent to "nosmp", which also disables
957 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
958 equal to this physical address is ignored.
960 max_luns= [SCSI] Maximum number of LUNs to probe.
961 Should be between 1 and 2^32-1.
964 [SCSI] Maximum number of LUNs received.
965 Should be between 1 and 16384.
967 mca-pentium [BUGS=X86-32]
971 mce [X86-32] Machine Check Exception
973 md= [HW] RAID subsystems devices and level
974 See Documentation/md.txt.
977 Format: <first>,<last>
978 Specifies range of consoles to be captured by the MDA.
980 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
981 Amount of memory to be used when the kernel is not able
982 to see the whole system memory or for test.
983 [X86-32] Use together with memmap= to avoid physical
984 address space collisions. Without memmap= PCI devices
985 could be placed at addresses belonging to unused RAM.
987 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
990 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
991 E820 memory map, as specified by the user.
992 Such memmap=exactmap lines can be constructed based on
993 BIOS output or other requirements. See the memmap=nn@ss
996 memmap=nn[KMG]@ss[KMG]
997 [KNL] Force usage of a specific region of memory
998 Region of memory to be used, from ss to ss+nn.
1000 memmap=nn[KMG]#ss[KMG]
1001 [KNL,ACPI] Mark specific memory as ACPI data.
1002 Region of memory to be used, from ss to ss+nn.
1004 memmap=nn[KMG]$ss[KMG]
1005 [KNL,ACPI] Mark specific memory as reserved.
1006 Region of memory to be used, from ss to ss+nn.
1008 meye.*= [HW] Set MotionEye Camera parameters
1009 See Documentation/video4linux/meye.txt.
1014 [MOUSE] Maximum time between finger touching and
1015 leaving touchpad surface for touch to be considered
1016 a tap and be reported as a left button click (for
1017 touchpads working in absolute mode only).
1019 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1020 reporting absolute coordinates, such as tablets
1021 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1022 reporting absolute coordinates, such as tablets
1027 MTD_Partition= [MTD]
1028 Format: <name>,<region-number>,<size>,<offset>
1030 MTD_Region= [MTD] Format:
1031 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1034 See drivers/mtd/cmdlinepart.c.
1036 mtouchusb.raw_coordinates=
1037 [HW] Make the MicroTouch USB driver use raw coordinates
1038 ('y', default) or cooked coordinates ('n')
1040 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1043 See header of drivers/scsi/NCR_D700.c.
1047 ncr53c400= [HW,SCSI]
1049 ncr53c400a= [HW,SCSI]
1051 ncr53c406a= [HW,SCSI]
1053 ncr53c8xx= [HW,SCSI]
1055 netdev= [NET] Network devices parameters
1056 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1057 Note that mem_start is often overloaded to mean
1058 something different and driver-specific.
1059 This usage is only documented in each driver source
1063 See Documentation/nfsroot.txt.
1065 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1066 See Documentation/nfsroot.txt.
1068 nfs.callback_tcpport=
1069 [NFS] set the TCP port on which the NFSv4 callback
1070 channel should listen.
1072 nfs.idmap_cache_timeout=
1073 [NFS] set the maximum lifetime for idmapper cache
1077 [NFS] enable 64-bit inode numbers.
1078 If zero, the NFS client will fake up a 32-bit inode
1079 number for the readdir() and stat() syscalls instead
1080 of returning the full 64-bit number.
1081 The default is to return 64-bit inode numbers.
1083 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1085 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1086 emulation library even if a 387 maths coprocessor
1089 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1093 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1094 caches in the slab allocator. Saves per-node memory,
1095 but will impact performance.
1099 noapic [SMP,APIC] Tells the kernel to not make use of any
1100 IOAPICs that may be present in the system.
1102 noasync [HW,M68K] Disables async and sync negotiation for
1105 nobats [PPC] Do not use BATs for mapping kernel lowmem
1106 on "Classic" PPC cores.
1110 nodelayacct [KNL] Disable per-task delay accounting
1112 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1116 noexec [X86-32,X86-64]
1117 noexec=on: enable non-executable mappings (default)
1118 noexec=off: disable nn-executable mappings
1120 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1121 register save and restore. The kernel will only save
1122 legacy floating-point registers on task switch.
1126 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1127 instruction doesn't work correctly and not to
1130 nohalt [IA-64] Tells the kernel not to use the power saving
1131 function PAL_HALT_LIGHT when idle. This increases
1132 power-consumption. On the positive side, it reduces
1133 interrupt wake-up latency, which may improve performance
1134 in certain environments such as networked servers or
1137 nohz= [KNL] Boottime enable/disable dynamic ticks
1138 Valid arguments: on, off
1141 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1143 noirqdebug [X86-32] Disables the code which attempts to detect and
1144 disable unhandled interrupt sources.
1146 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1147 broken timer IRQ sources.
1149 noisapnp [ISAPNP] Disables ISA PnP code.
1151 noinitrd [RAM] Tells the kernel not to load any configured
1156 nojitter [IA64] Disables jitter checking for ITC timers.
1158 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1160 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1162 noltlbs [PPC] Do not use large page/tlb entries for kernel
1163 lowmem mapping on PPC40x.
1165 nomca [IA-64] Disable machine check abort handling
1167 nomce [X86-32] Machine Check Exception
1169 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1171 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1172 with UP alternatives
1174 noresidual [PPC] Don't use residual data on PReP machines.
1176 noresume [SWSUSP] Disables resume and restores original swap
1179 no-scroll [VGA] Disables scrollback.
1180 This is required for the Braillex ib80-piezo Braille
1181 reader made by F.H. Papenmeier (Germany).
1185 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1187 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1188 and disable the IO APIC. legacy for "maxcpus=0".
1190 nosoftlockup [KNL] Disable the soft-lockup detector.
1192 nosync [HW,M68K] Disables sync negotiation for all devices.
1194 notsc [BUGS=X86-32] Disable Time Stamp Counter
1196 nousb [USB] Disable the USB subsystem
1200 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1201 one of ['zone', 'node', 'default'] can be specified
1202 This can be set from sysctl after boot.
1203 See Documentation/sysctl/vm.txt for details.
1205 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1210 oprofile.timer= [HW]
1211 Use timer interrupt instead of performance counters
1213 osst= [HW,SCSI] SCSI Tape Driver
1214 Format: <buffer_size>,<write_threshold>
1215 See also Documentation/scsi/st.txt.
1217 panic= [KNL] Kernel behaviour on panic
1220 parkbd.port= [HW] Parallel port number the keyboard adapter is
1221 connected to, default is 0.
1223 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1224 0 for XT, 1 for AT (default is AT).
1227 parport= [HW,PPT] Specify parallel ports. 0 disables.
1228 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1229 Use 'auto' to force the driver to use any
1230 IRQ/DMA settings detected (the default is to
1231 ignore detected IRQ/DMA settings because of
1232 possible conflicts). You can specify the base
1233 address, IRQ, and DMA settings; IRQ and DMA
1234 should be numbers, or 'auto' (for using detected
1235 settings on that particular port), or 'nofifo'
1236 (to avoid using a FIFO even if it is detected).
1237 Parallel ports are assigned in the order they
1238 are specified on the command line, starting
1241 parport_init_mode= [HW,PPT]
1242 Configure VIA parallel port to operate in
1243 a specific mode. This is necessary on Pegasos
1244 computer where firmware has no options for setting
1245 up parallel port mode and sets it to spp.
1246 Currently this function knows 686a and 8231 chips.
1247 Format: [spp|ps2|epp|ecp|ecpepp]
1249 pas2= [HW,OSS] Format:
1250 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1253 See header of drivers/scsi/pas16.c.
1256 Halt all CPUs after the first oops has been printed for
1257 the specified number of seconds. This is to be used if
1258 your oopses keep scrolling off the screen.
1263 See header of drivers/block/paride/pcd.c.
1264 See also Documentation/paride.txt.
1266 pci=option[,option...] [PCI] various PCI subsystem options:
1267 off [X86-32] don't probe for the PCI bus
1268 bios [X86-32] force use of PCI BIOS, don't access
1269 the hardware directly. Use this if your machine
1270 has a non-standard PCI host bridge.
1271 nobios [X86-32] disallow use of PCI BIOS, only direct
1272 hardware access methods are allowed. Use this
1273 if you experience crashes upon bootup and you
1274 suspect they are caused by the BIOS.
1275 conf1 [X86-32] Force use of PCI Configuration
1277 conf2 [X86-32] Force use of PCI Configuration
1279 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1281 nomsi [MSI] If the PCI_MSI kernel config parameter is
1282 enabled, this kernel boot option can be used to
1283 disable the use of MSI interrupts system-wide.
1284 nosort [X86-32] Don't sort PCI devices according to
1285 order given by the PCI BIOS. This sorting is
1286 done to get a device order compatible with
1288 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1289 routing table. These calls are known to be buggy
1290 on several machines and they hang the machine
1291 when used, but on other computers it's the only
1292 way to get the interrupt routing table. Try
1293 this option if the kernel is unable to allocate
1294 IRQs or discover secondary PCI buses on your
1296 rom [X86-32] Assign address space to expansion ROMs.
1297 Use with caution as certain devices share
1298 address decoders between ROMs and other
1300 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1301 assigned automatically to PCI devices. You can
1302 make the kernel exclude IRQs of your ISA cards
1304 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1305 of the PIRQ table (normally generated
1306 by the BIOS) if it is outside the
1307 F0000h-100000h range.
1308 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1309 useful if the kernel is unable to find your
1310 secondary buses and you want to tell it
1311 explicitly which ones they are.
1312 assign-busses [X86-32] Always assign all PCI bus
1313 numbers ourselves, overriding
1314 whatever the firmware may have done.
1315 usepirqmask [X86-32] Honor the possible IRQ mask stored
1316 in the BIOS $PIR table. This is needed on
1317 some systems with broken BIOSes, notably
1318 some HP Pavilion N5400 and Omnibook XE3
1319 notebooks. This will have no effect if ACPI
1320 IRQ routing is enabled.
1321 noacpi [X86-32] Do not use ACPI for IRQ routing
1322 or for PCI scanning.
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.