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 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 HW Appropriate hardware is enabled.
52 IA-64 IA-64 architecture is enabled.
53 IMA Integrity measurement architecture is enabled.
54 IOSCHED More than one I/O scheduler is enabled.
55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
59 LIBATA Libata driver is enabled
60 LP Printer support is enabled.
61 LOOP Loopback device support is enabled.
62 M68k M68k architecture is enabled.
63 These options have more detailed description inside of
64 Documentation/m68k/kernel-options.txt.
65 MCA MCA bus support is enabled.
66 MDA MDA console support is enabled.
67 MOUSE Appropriate mouse support is enabled.
68 MSI Message Signaled Interrupts (PCI).
69 MTD MTD (Memory Technology Device) support is enabled.
70 NET Appropriate network support is enabled.
71 NUMA NUMA support is enabled.
72 GENERIC_TIME The generic timeofday code is enabled.
73 NFS Appropriate NFS support is enabled.
74 OSS OSS sound support is enabled.
75 PV_OPS A paravirtualized kernel is enabled.
76 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
77 PARISC The PA-RISC architecture is enabled.
78 PCI PCI bus support is enabled.
79 PCIE PCI Express support is enabled.
80 PCMCIA The PCMCIA subsystem is enabled.
81 PNP Plug & Play support is enabled.
82 PPC PowerPC architecture is enabled.
83 PPT Parallel port support is enabled.
84 PS2 Appropriate PS/2 support is enabled.
85 RAM RAM disk support is enabled.
86 ROOTPLUG The example Root Plug LSM is enabled.
87 S390 S390 architecture is enabled.
88 SCSI Appropriate SCSI support is enabled.
89 A lot of drivers has their options described inside of
91 SECURITY Different security models are enabled.
92 SELINUX SELinux support is enabled.
93 SERIAL Serial support is enabled.
94 SH SuperH architecture is enabled.
95 SMP The kernel is an SMP kernel.
96 SPARC Sparc architecture is enabled.
97 SWSUSP Software suspend (hibernation) is enabled.
98 SUSPEND System suspend states are enabled.
99 FTRACE Function tracing enabled.
100 TS Appropriate touchscreen support is enabled.
101 UMS USB Mass Storage support is enabled.
102 USB USB support is enabled.
103 USBHID USB Human Interface Device support is enabled.
104 V4L Video For Linux support is enabled.
105 VGA The VGA console has been enabled.
106 VT Virtual terminal support is enabled.
107 WDT Watchdog support is enabled.
108 XT IBM PC/XT MFM hard disk support is enabled.
109 X86-32 X86-32, aka i386 architecture is enabled.
110 X86-64 X86-64 architecture is enabled.
111 More X86-64 boot options can be found in
112 Documentation/x86/x86_64/boot-options.txt .
113 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
115 In addition, the following text indicates that the option:
117 BUGS= Relates to possible processor bugs on the said processor.
118 KNL Is a kernel start-up parameter.
119 BOOT Is a boot loader parameter.
121 Parameters denoted with BOOT are actually interpreted by the boot
122 loader, and have no meaning to the kernel directly.
123 Do not modify the syntax of boot loader parameters without extreme
124 need or coordination with <Documentation/x86/boot.txt>.
126 There are also arch-specific kernel-parameters not documented here.
127 See for example <Documentation/x86/x86_64/boot-options.txt>.
129 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
130 a trailing = on the name of any parameter states that that parameter will
131 be entered as an environment variable, whereas its absence indicates that
132 it will appear as a kernel argument readable via /proc/cmdline by programs
133 running once the system is up.
135 The number of kernel parameters is not limited, but the length of the
136 complete command line (parameters including spaces etc.) is limited to
137 a fixed number of characters. This limit depends on the architecture
138 and is between 256 and 4096 characters. It is defined in the file
139 ./include/asm/setup.h as COMMAND_LINE_SIZE.
143 Advanced Configuration and Power Interface
144 Format: { force | off | ht | strict | noirq | rsdt }
145 force -- enable ACPI if default was off
146 off -- disable ACPI if default was on
147 noirq -- do not use ACPI for IRQ routing
148 ht -- run only enough ACPI to enable Hyper Threading
149 strict -- Be less tolerant of platforms that are not
150 strictly ACPI specification compliant.
151 rsdt -- prefer RSDT over (default) XSDT
153 See also Documentation/power/pm.txt, pci=noacpi
155 acpi_apic_instance= [ACPI, IOAPIC]
157 2: use 2nd APIC table, if available
158 1,0: use 1st APIC table
161 acpi_backlight= [HW,ACPI]
162 acpi_backlight=vendor
164 If set to vendor, prefer vendor specific driver
165 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
166 of the ACPI video.ko driver.
168 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
169 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
171 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
172 debug output. Bits in debug_layer correspond to a
173 _COMPONENT in an ACPI source file, e.g.,
174 #define _COMPONENT ACPI_PCI_COMPONENT
175 Bits in debug_level correspond to a level in
176 ACPI_DEBUG_PRINT statements, e.g.,
177 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
178 The debug_level mask defaults to "info". See
179 Documentation/acpi/debug.txt for more information about
180 debug layers and levels.
182 Enable processor driver info messages:
183 acpi.debug_layer=0x20000000
184 Enable PCI/PCI interrupt routing info messages:
185 acpi.debug_layer=0x400000
186 Enable AML "Debug" output, i.e., stores to the Debug
187 object while interpreting AML:
188 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
189 Enable all messages related to ACPI hardware:
190 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
192 Some values produce so much output that the system is
193 unusable. The "log_buf_len" parameter may be useful
194 if you need to capture more output.
196 acpi_display_output= [HW,ACPI]
197 acpi_display_output=vendor
198 acpi_display_output=video
201 acpi_irq_balance [HW,ACPI]
202 ACPI will balance active IRQs
205 acpi_irq_nobalance [HW,ACPI]
206 ACPI will not move active IRQs (default)
209 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
210 Format: <irq>,<irq>...
212 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 Format: <irq>,<irq>...
216 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
218 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
219 Format: To spoof as Windows 98: ="Microsoft Windows"
221 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
222 acpi_osi="string1" # add string1 -- only one string
223 acpi_osi="!string2" # remove built-in string2
224 acpi_osi= # disable all strings
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.
231 acpi.power_nocheck= [HW,ACPI]
232 Format: 1/0 enable/disable the check of power state.
233 On some bogus BIOS the _PSC object/_STA object of
234 power resource can't return the correct device power
235 state. In such case it is unneccessary to check its
236 power state again in power transition.
237 1 : disable the power state check
239 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
240 Format: { level | edge | high | low }
242 acpi_serialize [HW,ACPI] force serialization of AML methods
244 acpi_skip_timer_override [HW,ACPI]
245 Recognize and ignore IRQ0/pin2 Interrupt Override.
246 For broken nForce2 BIOS resulting in XT-PIC timer.
248 acpi_sleep= [HW,ACPI] Sleep options
249 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
250 old_ordering, s4_nonvs }
251 See Documentation/power/video.txt for information on
253 s3_beep is for debugging; it makes the PC's speaker beep
254 as soon as the kernel's real-mode entry point is called.
255 s4_nohwsig prevents ACPI hardware signature from being
256 used during resume from hibernation.
257 old_ordering causes the ACPI 1.0 ordering of the _PTS
258 control method, with respect to putting devices into
259 low power states, to be enforced (the ACPI 2.0 ordering
260 of _PTS is used by default).
261 s4_nonvs prevents the kernel from saving/restoring the
262 ACPI NVS memory during hibernation.
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
291 See header of drivers/scsi/advansys.c.
293 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
307 See Documentation/scsi/aha152x.txt.
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
313 See Documentation/scsi/aic7xxx.txt.
316 See Documentation/scsi/aic79xx.txt.
318 amd_iommu= [HW,X86-84]
319 Pass parameters to the AMD IOMMU driver in the system.
321 isolate - enable device isolation (each device, as far
322 as possible, will get its own protection
324 share - put every device behind one IOMMU into the
325 same protection domain
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
334 See also Documentation/kernel/input/joystick.txt
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
342 Power management functions (SPARCstation-4/5 + deriv.)
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
348 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
349 Change the output verbosity whilst booting
350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
354 apm= [APM] Advanced Power Management
355 See header of arch/x86/kernel/apm_32.c.
357 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
358 Format: <io>,<irq>,<nodeID>
362 atarimouse= [HW,MOUSE] Atari Mouse
364 atascsi= [HW,SCSI] Atari SCSI
366 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
367 EzKey and similar keyboards
369 atkbd.reset= [HW] Reset keyboard during initialization
371 atkbd.set= [HW] Select keyboard code set
372 Format: <int> (2 = AT (default), 3 = PS/2)
374 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 atkbd.softraw= [HW] Choose between synthetic and real raw mode
378 Format: <bool> (0 = real, 1 = synthetic (default))
380 atkbd.softrepeat= [HW]
381 Use software keyboard repeat
385 baycom_epp= [HW,AX25]
388 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
390 See header of drivers/net/hamradio/baycom_par.c.
392 baycom_ser_fdx= [HW,AX25]
393 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
394 Format: <io>,<irq>,<mode>[,<baud>]
395 See header of drivers/net/hamradio/baycom_ser_fdx.c.
397 baycom_ser_hdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
399 Format: <io>,<irq>,<mode>
400 See header of drivers/net/hamradio/baycom_ser_hdx.c.
402 boot_delay= Milliseconds to delay each printk during boot.
403 Values larger than 10 seconds (10000) are changed to
407 bootmem_debug [KNL] Enable bootmem allocator debug messages.
409 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
410 bttv.radio= Most important insmod options are available as
412 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
413 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
416 See drivers/scsi/BusLogic.c, comment before function
417 BusLogic_ParseDriverOptions().
419 c101= [NET] Moxa C101 synchronous serial card
421 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
422 Sometimes CPU hardware bugs make them report the cache
423 size incorrectly. The kernel will attempt work arounds
424 to fix known problems, but for some CPUs it is not
425 possible to determine what the correct size should be.
426 This option provides an override for these situations.
429 [SECURITY] Disable capabilities. This would normally
430 be used only if an alternative security model is to be
431 configured. Potentially dangerous and should only be
432 used if you are entirely sure of the consequences.
434 ccw_timeout_log [S390]
435 See Documentation/s390/CommonIO for details.
437 cgroup_disable= [KNL] Disable a particular controller
438 Format: {name of the controller(s) to disable}
439 {Currently supported controllers - "memory"}
441 checkreqprot [SELINUX] Set initial checkreqprot flag value.
442 Format: { "0" | "1" }
443 See security/selinux/Kconfig help text.
444 0 -- check protection applied by kernel (includes
445 any implied execute protection).
446 1 -- check protection requested by application.
447 Default value is set via a kernel config option.
448 Value can be changed at runtime via
449 /selinux/checkreqprot.
452 See Documentation/s390/CommonIO for details.
454 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
456 Forces specified clocksource (if available) to be used
457 when calculating gettimeofday(). If specified
458 clocksource is not available, it defaults to PIT.
459 Format: { pit | tsc | cyclone | pmtmr }
461 clocksource= [GENERIC_TIME] Override the default clocksource
463 Override the default clocksource and use the clocksource
464 with the name specified.
465 Some clocksource names to choose from, depending on
467 [all] jiffies (this is the base, fallback clocksource)
469 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
470 pxa_timer,timer3,32k_counter,timer0_1
472 [X86-32] pit,hpet,tsc,vmi-timer;
473 scx200_hrt on Geode; cyclone on IBM x440
481 clearcpuid=BITNUM [X86]
482 Disable CPUID feature X for the kernel. See
483 arch/x86/include/asm/cpufeature.h for the valid bit
484 numbers. Note the Linux specific bits are not necessarily
485 stable over kernel options, but the vendor specific
487 Also note that user programs calling CPUID directly
488 or using the feature without checking anything
489 will still see it. This just prevents it from
490 being used by the kernel or shown in /proc/cpuinfo.
491 Also note the kernel might malfunction if you disable
494 code_bytes [X86] How many bytes of object code to print
499 com20020= [HW,NET] ARCnet - COM20020 chipset
501 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
503 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
507 ARCnet - COM90xx chipset (memory-mapped buffers)
508 Format: <io>[,<irq>[,<memstart>]]
510 condev= [HW,S390] console device
513 console= [KNL] Output console device and options.
515 tty<n> Use the virtual console device <n>.
519 Use the specified serial port. The options are of
520 the form "bbbbpnf", where "bbbb" is the baud rate,
521 "p" is parity ("n", "o", or "e"), "n" is number of
522 bits, and "f" is flow control ("r" for RTS or
523 omit it). Default is "9600n8".
525 See Documentation/serial-console.txt for more
527 Documentation/networking/netconsole.txt for an
530 uart[8250],io,<addr>[,options]
531 uart[8250],mmio,<addr>[,options]
532 Start an early, polled-mode console on the 8250/16550
533 UART at the specified I/O port or MMIO address,
534 switching to the matching ttyS device later. The
535 options are the same as for ttyS, above.
537 If the device connected to the port is not a TTY but a braille
538 device, prepend "brl," before the device type, for instance
540 For now, only VisioBraille is supported.
543 [KNL] Change the default value for
544 /proc/<pid>/coredump_filter.
545 See also Documentation/filesystems/proc.txt.
547 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
549 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
551 crashkernel=nn[KMG]@ss[KMG]
552 [KNL] Reserve a chunk of physical memory to
553 hold a kernel to switch to with kexec on panic.
555 crashkernel=range1:size1[,range2:size2,...][@offset]
556 [KNL] Same as above, but depends on the memory
557 in the running system. The syntax of range is
558 start-[end] where start and end are both
559 a memory unit (amount[KMG]). See also
560 Documentation/kdump/kdump.txt for a example.
565 cs89x0_media= [HW,NET]
566 Format: { rj45 | aui | bnc }
569 See header of drivers/s390/block/dasd_devmap.c.
571 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
572 (one device per port)
573 Format: <port#>,<type>
574 See also Documentation/input/joystick-parport.txt
576 debug [KNL] Enable kernel debugging (events log level).
579 [KNL] verbose self-tests
581 Print debugging info while doing the locking API
583 We default to 0 (no extra messages), setting it to
584 1 will print _a lot_ more information - normally
585 only useful to kernel developers.
587 debug_objects [KNL] Enable object debugging
590 [KNL] Disable object debugging
592 debugpat [X86] Enable PAT debugging
594 decnet.addr= [HW,NET]
595 Format: <area>[,<node>]
596 See also Documentation/networking/decnet.txt.
599 [same as hugepagesz=] The size of the default
600 HugeTLB page size. This is the size represented by
601 the legacy /proc/ hugepages APIs, used for SHM, and
602 default size when mounting hugetlbfs filesystems.
603 Defaults to the default architecture's huge page size
607 Set number of hash buckets for dentry cache.
610 IO parameters + enable/disable command.
612 digiepca= [HW,SERIAL]
613 See drivers/char/README.epca and
614 Documentation/serial/digiepca.txt.
616 disable_mtrr_cleanup [X86]
617 The kernel tries to adjust MTRR layout from continuous
618 to discrete, to make X server driver able to add WB
619 entry later. This parameter disables that.
621 disable_mtrr_trim [X86, Intel and AMD only]
622 By default the kernel will trim any uncacheable
623 memory out of your available memory pool based on
624 MTRR settings. This parameter disables that behavior,
625 possibly causing your machine to run very slowly.
627 disable_timer_pin_1 [X86]
628 Disable PIN 1 of APIC timer
629 Can be useful to work around chipset bugs.
631 dmasound= [HW,OSS] Sound subsystem buffers
633 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
634 this option disables the debugging code at boot.
636 dma_debug_entries=<number>
637 This option allows to tune the number of preallocated
638 entries for DMA-API debugging code. One entry is
639 required per DMA-API allocation. Use this if the
640 DMA-API debugging code disables itself because the
641 architectural default is too low.
643 dma_debug_driver=<driver_name>
644 With this option the DMA-API debugging driver
645 filter feature can be enabled at boot time. Just
646 pass the driver to filter for as the parameter.
647 The filter can be disabled or changed to another
648 driver later using sysfs.
654 dynamic_printk Enables pr_debug()/dev_dbg() calls if
655 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
656 These can also be switched on/off via
657 <debugfs>/dynamic_printk/modules
659 earlycon= [KNL] Output early console device and options.
660 uart[8250],io,<addr>[,options]
661 uart[8250],mmio,<addr>[,options]
662 Start an early, polled-mode console on the 8250/16550
663 UART at the specified I/O port or MMIO address.
664 The options are the same as for ttyS, above.
666 earlyprintk= [X86,SH,BLACKFIN]
668 earlyprintk=serial[,ttySn[,baudrate]]
671 Append ",keep" to not disable it when the real console
674 Only vga or serial or usb debug port at a time.
676 Currently only ttyS0 and ttyS1 are supported.
678 Interaction with the standard serial driver is not
681 The VGA output is eventually overwritten by the real
687 Format: {"off" | "on" | "skip[mbr]"}
689 eisa_irq_edge= [PARISC,HW]
690 See header of drivers/parisc/eisa.c.
693 See comment before function elanfreq_setup() in
694 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
697 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
698 See Documentation/block/as-iosched.txt and
699 Documentation/block/deadline-iosched.txt for details.
701 elfcorehdr= [IA64,PPC,SH,X86]
702 Specifies physical address of start of kernel core
703 image elf header. Generally kexec loader will
704 pass this option to capture kernel.
705 See Documentation/kdump/kdump.txt for details.
707 enable_mtrr_cleanup [X86]
708 The kernel tries to adjust MTRR layout from continuous
709 to discrete, to make X server driver able to add WB
710 entry later. This parameter enables that.
712 enable_timer_pin_1 [X86]
713 Enable PIN 1 of APIC timer
714 Can be useful to work around chipset bugs
715 (in particular on some ATI chipsets).
716 The kernel tries to set a reasonable default.
718 enforcing [SELINUX] Set initial enforcing status.
720 See security/selinux/Kconfig help text.
721 0 -- permissive (log only, no denials).
722 1 -- enforcing (deny and log).
724 Value can be changed at runtime via /selinux/enforce.
726 ether= [HW,NET] Ethernet cards parameters
727 This option is obsoleted by the "netdev=" option, which
728 has equivalent usage. See its documentation for details.
730 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
735 fail_make_request=[KNL]
736 General fault injection mechanism.
737 Format: <interval>,<probability>,<space>,<times>
738 See also /Documentation/fault-injection/.
741 See header of drivers/scsi/fd_mcs.c.
744 See header of drivers/scsi/fdomain.c.
747 See Documentation/blockdev/floppy.txt.
749 force_pal_cache_flush
750 [IA-64] Avoid check_sal_cache_flush which may hang on
751 buggy SAL_CACHE_FLUSH implementations. Using this
752 parameter will force ia64_sal_cache_flush to call
753 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
756 [FTRACE] will set and start the specified tracer
757 as early as possible in order to facilitate early
761 [FTRACE] will dump the trace buffers on oops.
763 ftrace_filter=[function-list]
764 [FTRACE] Limit the functions traced by the function
765 tracer at boot up. function-list is a comma separated
766 list of functions. This list can be changed at run
767 time by the set_ftrace_filter file in the debugfs
770 ftrace_notrace=[function-list]
771 [FTRACE] Do not trace the functions specified in
772 function-list. This list can be changed at run time
773 by the set_ftrace_notrace file in the debugfs
777 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
778 support via parallel port (up to 5 devices per port)
779 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
780 See also Documentation/input/joystick-parport.txt
784 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
789 See header of drivers/scsi/gdth.c.
791 gpt [EFI] Forces disk with valid GPT signature but
792 invalid Protective MBR to be treated as GPT.
796 hashdist= [KNL,NUMA] Large hashes allocated during boot
797 are distributed across NUMA nodes. Defaults on
798 for 64bit NUMA, off otherwise.
799 Format: 0 | 1 (for off | on)
801 hcl= [IA-64] SGI's Hardware Graph compatibility layer
803 hd= [EIDE] (E)IDE hard drive subsystem geometry
804 Format: <cyl>,<head>,<sect>
806 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
807 size of <nn>. This works even on boxes that have no
808 highmem otherwise. This also works to reduce highmem
809 size on bigger boxes.
811 highres= [KNL] Enable/disable high resolution timer mode.
812 Valid parameters: "on", "off"
816 See Documentation/isdn/README.HiSax.
820 hpet= [X86-32,HPET] option to control HPET usage
821 Format: { enable (default) | disable | force |
823 disable: disable HPET and use PIT instead
824 force: allow force enabled of undocumented chips (ICH4,
826 verbose: show contents of HPET registers during setup
828 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
829 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
830 On x86-64 and powerpc, this option can be specified
831 multiple times interleaved with hugepages= to reserve
832 huge pages of different sizes. Valid pages sizes on
833 x86-64 are 2M (when the CPU supports "pse") and 1G
834 (when the CPU supports the "pdpe1gb" cpuinfo flag)
835 Note that 1GB pages can only be allocated at boot time
836 using hugepages= and not freed afterwards.
838 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
839 terminal devices. Valid values: 0..8
840 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
841 If specified, z/VM IUCV HVC accepts connections
842 from listed z/VM user IDs only.
844 i2c_bus= [HW] Override the default board specific I2C bus speed
845 or register an additional I2C bus that is not
846 registered from board initialization code.
850 i8042.debug [HW] Toggle i8042 debug mode
851 i8042.direct [HW] Put keyboard port into non-translated mode
852 i8042.dumbkbd [HW] Pretend that controller can only read data from
853 keyboard and cannot control its state
854 (Don't attempt to blink the leds)
855 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
856 i8042.nokbd [HW] Don't check/create keyboard port
857 i8042.noloop [HW] Disable the AUX Loopback command while probing
859 i8042.nomux [HW] Don't check presence of an active multiplexing
861 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
864 [HW] Frequency with which keyboard LEDs should blink
865 when kernel panics (default is 0.5 sec)
866 i8042.reset [HW] Reset the controller during init and cleanup
867 i8042.unlock [HW] Unlock (ignore) the keylock
871 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
872 indicates that the driver is running on unsupported
874 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
875 does not match list of supported models.
877 [HW] Report power status in /proc/i8k
878 (disabled by default)
879 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
882 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
883 See Documentation/mca.txt.
886 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
888 ide-core.nodma= [HW] (E)IDE subsystem
889 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
890 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
891 .chs .ignore_cable are additional options
892 See Documentation/ide/ide.txt.
894 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
895 See Documentation/ide/ide.txt.
897 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
898 Claim all unknown PCI IDE storage controllers.
901 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
902 Poll forces a polling idle loop that can slightly
903 improve the performance of waking up a idle CPU, but
904 will use a lot of power and make the system run hot.
906 idle=mwait: On systems which support MONITOR/MWAIT but
907 the kernel chose to not use it because it doesn't save
908 as much power as a normal idle loop, use the
909 MONITOR/MWAIT idle loop anyways. Performance should be
910 the same as idle=poll.
911 idle=halt: Halt is forced to be used for CPU idle.
912 In such case C2/C3 won't be used again.
913 idle=nomwait: Disable mwait for CPU C-states
915 ignore_loglevel [KNL]
916 Ignore loglevel setting - this will print /all/
917 kernel messages to the console. Useful for debugging.
920 Set number of hash buckets for inode cache.
923 Format: { "0" | "1" }
924 0 -- integrity auditing messages. (Default)
925 1 -- enable informational integrity auditing messages.
928 Formt: { "sha1" | "md5" }
932 See header of drivers/scsi/in2000.c.
936 Run specified binary instead of /sbin/init as init
939 initcall_debug [KNL] Trace initcalls as they are executed. Useful
940 for working out where the kernel is dying during
943 initrd= [BOOT] Specify the location of the initial ramdisk
945 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
948 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
950 Enable intel iommu driver.
952 Disable intel iommu driver.
953 igfx_off [Default Off]
954 By default, gfx is mapped as normal device. If a gfx
955 device has a dedicated DMAR unit, the DMAR unit is
956 bypassed by not enabling DMAR with this option. In
957 this case, gfx device will use physical address for
960 With this option iommu will not optimize to look
961 for io virtual address below 32 bit forcing dual
962 address cycle on pci bus for cards supporting greater
963 than 32 bit addressing. The default is to look
964 for translation below 32 bit and if not available
965 then look in the higher range.
967 With this option on every unmap_single operation will
968 result in a hardware IOTLB flush operation as opposed
969 to batching them for performance.
973 iomem= Disable strict checking of access to MMIO memory
974 strict regions from userspace.
989 io7= [HW] IO7 for Marvel based alpha systems
990 See comment before marvel_specify_io7 in
991 arch/alpha/kernel/core_marvel.c.
993 io_delay= [X86] I/O delay method
995 Standard port 0x80 based delay
997 Alternate port 0xed based delay (needed on some systems)
999 Simple two microseconds delay
1004 See Documentation/filesystems/nfsroot.txt.
1006 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1007 See comment before ip2_setup() in
1008 drivers/char/ip2/ip2base.c.
1010 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1011 See header of drivers/scsi/ips.c.
1014 When an interrupt is not handled search all handlers
1015 for it. Intended to get systems with badly broken
1019 When an interrupt is not handled search all handlers
1020 for it. Also check all handlers each timer
1021 interrupt. Intended to get systems with badly broken
1025 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1027 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1029 <cpu number>,...,<cpu number>
1031 <cpu number>-<cpu number>
1032 (must be a positive range in ascending order)
1034 <cpu number>,...,<cpu number>-<cpu number>
1036 This option can be used to specify one or more CPUs
1037 to isolate from the general SMP balancing and scheduling
1038 algorithms. You can move a process onto or off an
1039 "isolated" CPU via the CPU affinity syscalls or cpuset.
1040 <cpu number> begins at 0 and the maximum value is
1041 "number of CPUs in system - 1".
1043 This option is the preferred way to isolate CPUs. The
1044 alternative -- manually setting the CPU mask of all
1045 tasks in the system -- can cause problems and
1046 suboptimal load balancer performance.
1050 js= [HW,JOY] Analog joystick
1051 See Documentation/input/joystick.txt.
1055 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1056 specifies the amount of memory usable by the kernel
1057 for non-movable allocations. The requested amount is
1058 spread evenly throughout all nodes in the system. The
1059 remaining memory in each node is used for Movable
1060 pages. In the event, a node is too small to have both
1061 kernelcore and Movable pages, kernelcore pages will
1062 take priority and other nodes will have a larger number
1063 of kernelcore pages. The Movable zone is used for the
1064 allocation of pages that may be reclaimed or moved
1065 by the page migration subsystem. This means that
1066 HugeTLB pages may not be allocated from this zone.
1067 Note that allocations like PTEs-from-HighMem still
1068 use the HighMem zone if it exists, and the Normal
1069 zone if it does not.
1071 kgdboc= [HW] kgdb over consoles.
1072 Requires a tty driver that supports console polling.
1073 (only serial suported for now)
1074 Format: <serial_device>[,baud]
1076 kmac= [MIPS] korina ethernet MAC address.
1077 Configure the RouterBoard 532 series on-chip
1078 Ethernet adapter MAC address.
1080 kstack=N [X86] Print N words from the kernel stack
1087 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1090 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1093 libata.dma= [LIBATA] DMA control
1094 libata.dma=0 Disable all PATA and SATA DMA
1095 libata.dma=1 PATA and SATA Disk DMA only
1096 libata.dma=2 ATAPI (CDROM) DMA only
1097 libata.dma=4 Compact Flash DMA only
1098 Combinations also work, so libata.dma=3 enables DMA
1099 for disks and CDROMs, but not CFs.
1101 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1105 libata.force= [LIBATA] Force configurations. The format is comma
1106 separated list of "[ID:]VAL" where ID is
1107 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1108 matching port, link or device. Basically, it matches
1109 the ATA ID string printed on console by libata. If
1110 the whole ID part is omitted, the last PORT and DEVICE
1111 values are used. If ID hasn't been specified yet, the
1112 configuration applies to all ports, links and devices.
1114 If only DEVICE is omitted, the parameter applies to
1115 the port and all links and devices behind it. DEVICE
1116 number of 0 either selects the first device or the
1117 first fan-out link behind PMP device. It does not
1118 select the host link. DEVICE number of 15 selects the
1119 host link and device attached to it.
1121 The VAL specifies the configuration to force. As long
1122 as there's no ambiguity shortcut notation is allowed.
1123 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1124 The following configurations can be forced.
1126 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1127 Any ID with matching PORT is used.
1129 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1131 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1132 udma[/][16,25,33,44,66,100,133] notation is also
1135 * [no]ncq: Turn on or off NCQ.
1137 * nohrst, nosrst, norst: suppress hard, soft
1140 If there are multiple matching configurations changing
1141 the same attribute, the last one is used.
1143 lmb=debug [KNL] Enable lmb debug messages.
1145 load_ramdisk= [RAM] List of ramdisks to load from floppy
1146 See Documentation/blockdev/ramdisk.txt.
1148 lockd.nlm_grace_period=P [NFS] Assign grace period.
1151 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1154 lockd.nlm_timeout=T [NFS] Assign timeout value.
1157 lockd.nlm_udpport=M [NFS] Assign UDP port.
1160 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1163 loglevel= All Kernel Messages with a loglevel smaller than the
1164 console loglevel will be printed to the console. It can
1165 also be changed with klogd or other programs. The
1166 loglevels are defined as follows:
1168 0 (KERN_EMERG) system is unusable
1169 1 (KERN_ALERT) action must be taken immediately
1170 2 (KERN_CRIT) critical conditions
1171 3 (KERN_ERR) error conditions
1172 4 (KERN_WARNING) warning conditions
1173 5 (KERN_NOTICE) normal but significant condition
1174 6 (KERN_INFO) informational
1175 7 (KERN_DEBUG) debug-level messages
1177 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1178 Format: { n | nk | nM }
1179 n must be a power of two. The default size
1180 is set in the kernel config file.
1182 logo.nologo [FB] Disables display of the built-in Linux logo.
1183 This may be used to provide more screen space for
1184 kernel log messages and is useful when debugging
1185 kernel boot problems.
1187 lp=0 [LP] Specify parallel ports to use, e.g,
1188 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1189 lp=reset first parallel port). 'lp=0' disables the
1190 lp=auto printer driver. 'lp=reset' (which can be
1191 specified in addition to the ports) causes
1192 attached printers to be reset. Using
1193 lp=port1,port2,... specifies the parallel ports
1194 to associate lp devices with, starting with
1195 lp0. A port specification may be 'none' to skip
1196 that lp device, or a parport name such as
1197 'parport0'. Specifying 'lp=auto' instead of a
1198 port specification list means that device IDs
1199 from each port should be examined, to see if
1200 an IEEE 1284-compliant printer is attached; if
1201 so, the driver will manage that printer.
1202 See also header of drivers/char/lp.c.
1205 Sets loops_per_jiffy to given constant, thus avoiding
1206 time-consuming boot-time autodetection (up to 250 ms per
1207 CPU). 0 enables autodetection (default). To determine
1208 the correct value for your kernel, boot with normal
1209 autodetection and see what value is printed. Note that
1210 on SMP systems the preset will be applied to all CPUs,
1211 which is likely to cause problems if your CPUs need
1212 significantly divergent settings. An incorrect value
1213 will cause delays in the kernel to be wrong, leading to
1214 unpredictable I/O errors and other breakage. Although
1215 unlikely, in the extreme case this might damage your
1219 Format: <io>,<irq>,<dma>
1221 mac5380= [HW,SCSI] Format:
1222 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1224 machvec= [IA64] Force the use of a particular machine-vector
1225 (machvec) in a generic kernel.
1226 Example: machvec=hpzx1_swiotlb
1228 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1229 than or equal to this physical address is ignored.
1231 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1232 should make use of. maxcpus=n : n >= 0 limits the
1233 kernel to using 'n' processors. n=0 is a special case,
1234 it is equivalent to "nosmp", which also disables
1237 max_loop= [LOOP] Maximum number of loopback devices that can
1241 max_luns= [SCSI] Maximum number of LUNs to probe.
1242 Should be between 1 and 2^32-1.
1245 [SCSI] Maximum number of LUNs received.
1246 Should be between 1 and 16384.
1250 mce [X86-32] Machine Check Exception
1252 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1254 md= [HW] RAID subsystems devices and level
1255 See Documentation/md.txt.
1258 Format: <first>,<last>
1259 Specifies range of consoles to be captured by the MDA.
1261 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1262 Amount of memory to be used when the kernel is not able
1263 to see the whole system memory or for test.
1264 [X86-32] Use together with memmap= to avoid physical
1265 address space collisions. Without memmap= PCI devices
1266 could be placed at addresses belonging to unused RAM.
1268 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1272 [KNL,SH] Allow user to override the default size for
1273 per-device physically contiguous DMA buffers.
1275 memmap=exactmap [KNL,X86] Enable setting of an exact
1276 E820 memory map, as specified by the user.
1277 Such memmap=exactmap lines can be constructed based on
1278 BIOS output or other requirements. See the memmap=nn@ss
1281 memmap=nn[KMG]@ss[KMG]
1282 [KNL] Force usage of a specific region of memory
1283 Region of memory to be used, from ss to ss+nn.
1285 memmap=nn[KMG]#ss[KMG]
1286 [KNL,ACPI] Mark specific memory as ACPI data.
1287 Region of memory to be used, from ss to ss+nn.
1289 memmap=nn[KMG]$ss[KMG]
1290 [KNL,ACPI] Mark specific memory as reserved.
1291 Region of memory to be used, from ss to ss+nn.
1292 Example: Exclude memory from 0x18690000-0x1869ffff
1293 memmap=64K$0x18690000
1295 memmap=0x10000$0x18690000
1297 memory_corruption_check=0/1 [X86]
1298 Some BIOSes seem to corrupt the first 64k of
1299 memory when doing things like suspend/resume.
1300 Setting this option will scan the memory
1301 looking for corruption. Enabling this will
1302 both detect corruption and prevent the kernel
1303 from using the memory being corrupted.
1304 However, its intended as a diagnostic tool; if
1305 repeatable BIOS-originated corruption always
1306 affects the same memory, you can use memmap=
1307 to prevent the kernel from using that memory.
1309 memory_corruption_check_size=size [X86]
1310 By default it checks for corruption in the low
1311 64k, making this memory unavailable for normal
1312 use. Use this parameter to scan for
1313 corruption in more or less memory.
1315 memory_corruption_check_period=seconds [X86]
1316 By default it checks for corruption every 60
1317 seconds. Use this parameter to check at some
1318 other rate. 0 disables periodic checking.
1320 memtest= [KNL,X86] Enable memtest
1322 default : 0 <disable>
1323 Specifies the number of memtest passes to be
1324 performed. Each pass selects another test
1325 pattern from a given set of patterns. Memtest
1326 fills the memory with this pattern, validates
1327 memory contents and reserves bad memory
1328 regions that are detected.
1330 meye.*= [HW] Set MotionEye Camera parameters
1331 See Documentation/video4linux/meye.txt.
1333 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1334 Multi-Function General Purpose Timers on AMD Geode
1337 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1338 the BIOS has incorrectly applied a workaround. TinyBIOS
1339 version 0.98 is known to be affected, 0.99 fixes the
1340 problem by letting the user disable the workaround.
1344 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1345 physical address is ignored.
1348 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1349 parameter allows control of the logging verbosity for
1350 the additional memory initialisation checks. A value
1351 of 0 disables mminit logging and a level of 4 will
1352 log everything. Information is printed at KERN_DEBUG
1353 so loglevel=8 may also need to be specified.
1356 [MOUSE] Maximum time between finger touching and
1357 leaving touchpad surface for touch to be considered
1358 a tap and be reported as a left button click (for
1359 touchpads working in absolute mode only).
1361 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1362 reporting absolute coordinates, such as tablets
1363 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1364 reporting absolute coordinates, such as tablets
1366 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1367 is similar to kernelcore except it specifies the
1368 amount of memory used for migratable allocations.
1369 If both kernelcore and movablecore is specified,
1370 then kernelcore will be at *least* the specified
1371 value but may be more. If movablecore on its own
1372 is specified, the administrator must be careful
1373 that the amount of memory usable for all allocations
1379 MTD_Partition= [MTD]
1380 Format: <name>,<region-number>,<size>,<offset>
1382 MTD_Region= [MTD] Format:
1383 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1386 See drivers/mtd/cmdlinepart.c.
1389 ARM/S3C2412 JIVE boot control
1391 See arch/arm/mach-s3c2412/mach-jive.c
1393 mtouchusb.raw_coordinates=
1394 [HW] Make the MicroTouch USB driver use raw coordinates
1395 ('y', default) or cooked coordinates ('n')
1397 mtrr_chunk_size=nn[KMG] [X86]
1398 used for mtrr cleanup. It is largest continous chunk
1399 that could hold holes aka. UC entries.
1401 mtrr_gran_size=nn[KMG] [X86]
1402 Used for mtrr cleanup. It is granularity of mtrr block.
1404 Large value could prevent small alignment from
1407 mtrr_spare_reg_nr=n [X86]
1409 Range: 0,7 : spare reg number
1411 Used for mtrr cleanup. It is spare mtrr entries number.
1412 Set to 2 or more if your graphical card needs more.
1414 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1417 See header of drivers/scsi/NCR_D700.c.
1421 ncr53c400= [HW,SCSI]
1423 ncr53c400a= [HW,SCSI]
1425 ncr53c406a= [HW,SCSI]
1427 ncr53c8xx= [HW,SCSI]
1429 netdev= [NET] Network devices parameters
1430 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1431 Note that mem_start is often overloaded to mean
1432 something different and driver-specific.
1433 This usage is only documented in each driver source
1437 [NETFILTER] Enable connection tracking flow accounting
1438 0 to disable accounting
1439 1 to enable accounting
1440 Default value depends on CONFIG_NF_CT_ACCT that is
1441 going to be removed in 2.6.29.
1444 See Documentation/filesystems/nfsroot.txt.
1446 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1447 See Documentation/filesystems/nfsroot.txt.
1449 nfs.callback_tcpport=
1450 [NFS] set the TCP port on which the NFSv4 callback
1451 channel should listen.
1453 nfs.idmap_cache_timeout=
1454 [NFS] set the maximum lifetime for idmapper cache
1458 [NFS] enable 64-bit inode numbers.
1459 If zero, the NFS client will fake up a 32-bit inode
1460 number for the readdir() and stat() syscalls instead
1461 of returning the full 64-bit number.
1462 The default is to return 64-bit inode numbers.
1464 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1465 when a NMI is triggered.
1466 Format: [state][,regs][,debounce][,die]
1468 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1469 Format: [panic,][num]
1471 0 - turn nmi_watchdog off
1472 1 - use the IO-APIC timer for the NMI watchdog
1473 2 - use the local APIC for the NMI watchdog using
1474 a performance counter. Note: This will use one
1475 performance counter and the local APIC's performance
1477 When panic is specified, panic when an NMI watchdog
1479 This is useful when you use a panic=... timeout and
1480 need the box quickly up again.
1481 Instead of 1 and 2 it is possible to use the following
1482 symbolic names: lapic and ioapic
1483 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1485 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1486 emulation library even if a 387 maths coprocessor
1490 [HW] Never suspend the console
1491 Disable suspending of consoles during suspend and
1492 hibernate operations. Once disabled, debugging
1493 messages can reach various consoles while the rest
1494 of the system is being put to sleep (ie, while
1495 debugging driver suspend/resume hooks). This may
1496 not work reliably with all consoles, but is known
1497 to work with serial and VGA consoles.
1499 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1500 caches in the slab allocator. Saves per-node memory,
1501 but will impact performance.
1505 noapic [SMP,APIC] Tells the kernel to not make use of any
1506 IOAPICs that may be present in the system.
1508 nobats [PPC] Do not use BATs for mapping kernel lowmem
1509 on "Classic" PPC cores.
1513 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1515 nodelayacct [KNL] Disable per-task delay accounting
1517 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1519 nodsp [SH] Disable hardware DSP at boot time.
1521 noefi [X86] Disable EFI runtime services support.
1526 On X86-32 available only on PAE configured kernels.
1527 noexec=on: enable non-executable mappings (default)
1528 noexec=off: disable non-executable mappings
1531 This affects only 32-bit executables.
1532 noexec32=on: enable non-executable mappings (default)
1533 read doesn't imply executable mappings
1534 noexec32=off: disable non-executable mappings
1535 read implies executable mappings
1537 nofpu [SH] Disable hardware FPU at boot time.
1539 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1540 register save and restore. The kernel will only save
1541 legacy floating-point registers on task switch.
1543 noxsave [BUGS=X86] Disables x86 extended register state save
1544 and restore using xsave. The kernel will fallback to
1545 enabling legacy floating-point and sse state.
1547 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1548 wfi(ARM) instruction doesn't work correctly and not to
1549 use it. This is also useful when using JTAG debugger.
1551 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1552 instruction doesn't work correctly and not to
1555 no_file_caps Tells the kernel not to honor file capabilities. The
1556 only way then for a file to be executed with privilege
1557 is to be setuid root or executed by root.
1559 nohalt [IA-64] Tells the kernel not to use the power saving
1560 function PAL_HALT_LIGHT when idle. This increases
1561 power-consumption. On the positive side, it reduces
1562 interrupt wake-up latency, which may improve performance
1563 in certain environments such as networked servers or
1566 nohz= [KNL] Boottime enable/disable dynamic ticks
1567 Valid arguments: on, off
1570 noiotrap [SH] Disables trapped I/O port accesses.
1572 noirqdebug [X86-32] Disables the code which attempts to detect and
1573 disable unhandled interrupt sources.
1575 no_timer_check [X86,APIC] Disables the code which tests for
1576 broken timer IRQ sources.
1578 noisapnp [ISAPNP] Disables ISA PnP code.
1580 noinitrd [RAM] Tells the kernel not to load any configured
1583 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1588 nojitter [IA64] Disables jitter checking for ITC timers.
1590 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1592 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1594 noltlbs [PPC] Do not use large page/tlb entries for kernel
1595 lowmem mapping on PPC40x.
1597 nomca [IA-64] Disable machine check abort handling
1599 nomce [X86-32] Machine Check Exception
1601 nomfgpt [X86-32] Disable Multi-Function General Purpose
1602 Timer usage (for AMD Geode machines).
1604 norandmaps Don't use address space randomization. Equivalent to
1605 echo 0 > /proc/sys/kernel/randomize_va_space
1607 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1609 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1610 with UP alternatives
1612 noresidual [PPC] Don't use residual data on PReP machines.
1614 noresume [SWSUSP] Disables resume and restores original swap
1617 no-scroll [VGA] Disables scrollback.
1618 This is required for the Braillex ib80-piezo Braille
1619 reader made by F.H. Papenmeier (Germany).
1623 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1625 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1626 and disable the IO APIC. legacy for "maxcpus=0".
1628 nosoftlockup [KNL] Disable the soft-lockup detector.
1630 noswapaccount [KNL] Disable accounting of swap in memory resource
1631 controller. (See Documentation/cgroups/memory.txt)
1633 nosync [HW,M68K] Disables sync negotiation for all devices.
1635 notsc [BUGS=X86-32] Disable Time Stamp Counter
1637 nousb [USB] Disable the USB subsystem
1641 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1643 nptcg= [IA64] Override max number of concurrent global TLB
1644 purges which is reported from either PAL_VM_SUMMARY or
1647 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1649 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1650 one of ['zone', 'node', 'default'] can be specified
1651 This can be set from sysctl after boot.
1652 See Documentation/sysctl/vm.txt for details.
1654 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1655 See Documentation/debugging-via-ohci1394.txt for more
1658 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1659 Rather than timing out after 20 ms if an EC
1660 command is not properly ACKed, override the length
1661 of the timeout. We have interrupts disabled while
1662 waiting for the ACK, so if this is set too high
1663 interrupts *may* be lost!
1668 oprofile.timer= [HW]
1669 Use timer interrupt instead of performance counters
1671 oprofile.cpu_type= Force an oprofile cpu type
1672 This might be useful if you have an older oprofile
1673 userland or if you want common events.
1674 Format: { archperfmon }
1675 archperfmon: [X86] Force use of architectural
1676 perfmon on Intel CPUs instead of the
1677 CPU specific event set.
1679 osst= [HW,SCSI] SCSI Tape Driver
1680 Format: <buffer_size>,<write_threshold>
1681 See also Documentation/scsi/st.txt.
1683 panic= [KNL] Kernel behaviour on panic
1686 parkbd.port= [HW] Parallel port number the keyboard adapter is
1687 connected to, default is 0.
1689 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1690 0 for XT, 1 for AT (default is AT).
1693 parport= [HW,PPT] Specify parallel ports. 0 disables.
1694 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1695 Use 'auto' to force the driver to use any
1696 IRQ/DMA settings detected (the default is to
1697 ignore detected IRQ/DMA settings because of
1698 possible conflicts). You can specify the base
1699 address, IRQ, and DMA settings; IRQ and DMA
1700 should be numbers, or 'auto' (for using detected
1701 settings on that particular port), or 'nofifo'
1702 (to avoid using a FIFO even if it is detected).
1703 Parallel ports are assigned in the order they
1704 are specified on the command line, starting
1707 parport_init_mode= [HW,PPT]
1708 Configure VIA parallel port to operate in
1709 a specific mode. This is necessary on Pegasos
1710 computer where firmware has no options for setting
1711 up parallel port mode and sets it to spp.
1712 Currently this function knows 686a and 8231 chips.
1713 Format: [spp|ps2|epp|ecp|ecpepp]
1715 pas2= [HW,OSS] Format:
1716 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1719 See header of drivers/scsi/pas16.c.
1722 Halt all CPUs after the first oops has been printed for
1723 the specified number of seconds. This is to be used if
1724 your oopses keep scrolling off the screen.
1729 See header of drivers/block/paride/pcd.c.
1730 See also Documentation/blockdev/paride.txt.
1732 pci=option[,option...] [PCI] various PCI subsystem options:
1733 earlydump [X86] dump PCI config space before the kernel
1735 off [X86] don't probe for the PCI bus
1736 bios [X86-32] force use of PCI BIOS, don't access
1737 the hardware directly. Use this if your machine
1738 has a non-standard PCI host bridge.
1739 nobios [X86-32] disallow use of PCI BIOS, only direct
1740 hardware access methods are allowed. Use this
1741 if you experience crashes upon bootup and you
1742 suspect they are caused by the BIOS.
1743 conf1 [X86] Force use of PCI Configuration
1745 conf2 [X86] Force use of PCI Configuration
1747 noaer [PCIE] If the PCIEAER kernel config parameter is
1748 enabled, this kernel boot option can be used to
1749 disable the use of PCIE advanced error reporting.
1750 nodomains [PCI] Disable support for multiple PCI
1751 root domains (aka PCI segments, in ACPI-speak).
1752 nommconf [X86] Disable use of MMCONFIG for PCI
1754 nomsi [MSI] If the PCI_MSI kernel config parameter is
1755 enabled, this kernel boot option can be used to
1756 disable the use of MSI interrupts system-wide.
1757 noioapicquirk [APIC] Disable all boot interrupt quirks.
1758 Safety option to keep boot IRQs enabled. This
1759 should never be necessary.
1760 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1761 primary IO-APIC for bridges that cannot disable
1762 boot IRQs. This fixes a source of spurious IRQs
1763 when the system masks IRQs.
1764 noioapicreroute [APIC] Disable workaround that uses the
1765 boot IRQ equivalent of an IRQ that connects to
1766 a chipset where boot IRQs cannot be disabled.
1767 The opposite of ioapicreroute.
1768 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1769 routing table. These calls are known to be buggy
1770 on several machines and they hang the machine
1771 when used, but on other computers it's the only
1772 way to get the interrupt routing table. Try
1773 this option if the kernel is unable to allocate
1774 IRQs or discover secondary PCI buses on your
1776 rom [X86] Assign address space to expansion ROMs.
1777 Use with caution as certain devices share
1778 address decoders between ROMs and other
1780 norom [X86] Do not assign address space to
1781 expansion ROMs that do not already have
1782 BIOS assigned address ranges.
1783 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1784 assigned automatically to PCI devices. You can
1785 make the kernel exclude IRQs of your ISA cards
1787 pirqaddr=0xAAAAA [X86] Specify the physical address
1788 of the PIRQ table (normally generated
1789 by the BIOS) if it is outside the
1790 F0000h-100000h range.
1791 lastbus=N [X86] Scan all buses thru bus #N. Can be
1792 useful if the kernel is unable to find your
1793 secondary buses and you want to tell it
1794 explicitly which ones they are.
1795 assign-busses [X86] Always assign all PCI bus
1796 numbers ourselves, overriding
1797 whatever the firmware may have done.
1798 usepirqmask [X86] Honor the possible IRQ mask stored
1799 in the BIOS $PIR table. This is needed on
1800 some systems with broken BIOSes, notably
1801 some HP Pavilion N5400 and Omnibook XE3
1802 notebooks. This will have no effect if ACPI
1803 IRQ routing is enabled.
1804 noacpi [X86] Do not use ACPI for IRQ routing
1805 or for PCI scanning.
1806 use_crs [X86] Use _CRS for PCI resource
1808 routeirq Do IRQ routing for all PCI devices.
1809 This is normally done in pci_enable_device(),
1810 so this option is a temporary workaround
1811 for broken drivers that don't call it.
1812 skip_isa_align [X86] do not align io start addr, so can
1813 handle more pci cards
1814 firmware [ARM] Do not re-enumerate the bus but instead
1815 just use the configuration from the
1816 bootloader. This is currently used on
1817 IXP2000 systems where the bus has to be
1818 configured a certain way for adjunct CPUs.
1819 noearly [X86] Don't do any early type 1 scanning.
1820 This might help on some broken boards which
1821 machine check when some devices' config space
1822 is read. But various workarounds are disabled
1823 and some IOMMU drivers will not work.
1824 bfsort Sort PCI devices into breadth-first order.
1825 This sorting is done to get a device
1826 order compatible with older (<= 2.4) kernels.
1827 nobfsort Don't sort PCI devices into breadth-first order.
1828 cbiosize=nn[KMG] The fixed amount of bus space which is
1829 reserved for the CardBus bridge's IO window.
1830 The default value is 256 bytes.
1831 cbmemsize=nn[KMG] The fixed amount of bus space which is
1832 reserved for the CardBus bridge's memory
1833 window. The default value is 64 megabytes.
1836 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1837 Specifies alignment and device to reassign
1838 aligned memory resources.
1839 If <order of align> is not specified,
1840 PAGE_SIZE is used as alignment.
1841 PCI-PCI bridge can be specified, if resource
1842 windows need to be expanded.
1844 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1847 force Enable ASPM even on devices that claim not to support it.
1848 WARNING: Forcing ASPM on may cause system lockups.
1850 pcmv= [HW,PCMCIA] BadgePAD 4
1853 See Documentation/blockdev/paride.txt.
1855 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1858 See arch/parisc/kernel/pdc_chassis.c
1861 See Documentation/blockdev/paride.txt.
1864 See Documentation/blockdev/paride.txt.
1866 pirq= [SMP,APIC] Manual mp-table setup
1867 See Documentation/x86/i386/IO-APIC.txt.
1869 plip= [PPT,NET] Parallel port network link
1870 Format: { parport<nr> | timid | 0 }
1871 See also Documentation/parport.txt.
1873 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1874 Override pmtimer IOPort with a hex value.
1878 Enable PNP debug messages. This depends on the
1879 CONFIG_PNP_DEBUG_MESSAGES option.
1885 { on | off | curr | res | no-curr | no-res }
1888 [ISAPNP] Exclude IRQs for the autoconfiguration
1891 [ISAPNP] Exclude DMAs for the autoconfiguration
1893 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1894 Ranges are in pairs (I/O port base and size).
1897 [ISAPNP] Exclude memory regions for the
1899 Ranges are in pairs (memory base and size).
1901 ports= [IP_VS_FTP] IPVS ftp helper module
1903 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1905 Format: <port>,<port>....
1907 print-fatal-signals=
1908 [KNL] debug: print fatal signals
1909 print-fatal-signals=1: print segfault info to
1913 printk.time= Show timing data prefixed to each printk message line
1914 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1916 processor.max_cstate= [HW,ACPI]
1917 Limit processor to maximum C-state
1918 max_cstate=9 overrides any DMI blacklist limit.
1920 processor.nocst [HW,ACPI]
1921 Ignore the _CST method to determine C-states,
1922 instead using the legacy FADT method
1924 profile= [KNL] Enable kernel profiling via /proc/profile
1925 Format: [schedule,]<number>
1926 Param: "schedule" - profile schedule points.
1927 Param: <number> - step/bucket size as a power of 2 for
1928 statistical time based profiling.
1929 Param: "sleep" - profile D-state sleeping (millisecs).
1930 Requires CONFIG_SCHEDSTATS
1931 Param: "kvm" - profile VM exits.
1933 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1935 See Documentation/blockdev/ramdisk.txt.
1937 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1938 probe for; one of (bare|imps|exps|lifebook|any).
1939 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1941 psmouse.resetafter= [HW,MOUSE]
1942 Try to reset the device after so many bad packets
1945 [HW,MOUSE] Set desired mouse resolution, in dpi.
1946 psmouse.smartscroll=
1947 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1948 0 = disabled, 1 = enabled (default).
1950 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1952 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1955 See Documentation/blockdev/paride.txt.
1958 [KNL] Number of legacy pty's. Overwrites compiled-in
1961 quiet [KNL] Disable most log messages
1966 See Documentation/md.txt.
1968 ramdisk_blocksize= [RAM]
1969 See Documentation/blockdev/ramdisk.txt.
1971 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1972 See Documentation/blockdev/ramdisk.txt.
1974 rcupdate.blimit= [KNL,BOOT]
1975 Set maximum number of finished RCU callbacks to process
1978 rcupdate.qhimark= [KNL,BOOT]
1979 Set threshold of queued
1980 RCU callbacks over which batch limiting is disabled.
1982 rcupdate.qlowmark= [KNL,BOOT]
1983 Set threshold of queued RCU callbacks below which
1984 batch limiting is re-enabled.
1988 Run specified binary instead of /init from the ramdisk,
1989 used for early userspace startup. See initrd.
1991 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1992 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1993 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1996 [KNL, SMP] Set scheduler's default relax_domain_level.
1997 See Documentation/cgroups/cpusets.txt.
1999 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2001 reservetop= [X86-32]
2003 Reserves a hole at the top of the kernel virtual
2006 reset_devices [KNL] Force drivers to reset the underlying device
2007 during initialization.
2010 Specify the partition device for software suspend
2012 resume_offset= [SWSUSP]
2013 Specify the offset from the beginning of the partition
2014 given by "resume=" at which the swap header is located,
2015 in <PAGE_SIZE> units (needed only for swap files).
2016 See Documentation/power/swsusp-and-swap-files.txt
2018 retain_initrd [RAM] Keep initrd memory after extraction
2020 rhash_entries= [KNL,NET]
2021 Set number of hash buckets for route cache
2023 riscom8= [HW,SERIAL]
2024 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2026 ro [KNL] Mount root device read-only on boot
2028 root= [KNL] Root filesystem
2030 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2031 mount the root filesystem
2033 rootflags= [KNL] Set root filesystem mount option string
2035 rootfstype= [KNL] Set root filesystem type
2037 rootwait [KNL] Wait (indefinitely) for root device to show up.
2038 Useful for devices that are detected asynchronously
2039 (e.g. USB and MMC devices).
2041 root_plug.vendor_id=
2042 [ROOTPLUG] Override the default vendor ID
2044 root_plug.product_id=
2045 [ROOTPLUG] Override the default product ID
2048 [ROOTPLUG] Enable debugging output
2050 rw [KNL] Mount root device read-write on boot
2052 S [KNL] Run init in single mode
2055 See drivers/net/irda/sa1100_ir.c.
2057 sbni= [NET] Granch SBNI12 leased line adapter
2059 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2060 Format: <io>[,<timeout>[,<isapnp>]]
2062 scsi_debug_*= [SCSI]
2063 See drivers/scsi/scsi_debug.c.
2065 scsi_default_dev_flags=
2066 [SCSI] SCSI default device flags
2069 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2070 Format: <vendor>:<model>:<flags>
2071 (flags are integer value)
2073 scsi_logging_level= [SCSI] a bit mask of logging levels
2074 See drivers/scsi/scsi_logging.h for bits. Also
2075 settable via sysctl at dev.scsi.logging_level
2076 (/proc/sys/dev/scsi/logging_level).
2077 There is also a nice 'scsi_logging_level' script in the
2078 S390-tools package, available for download at
2079 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2081 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2082 discovered. async scans them in kernel threads,
2083 allowing boot to proceed. none ignores them, expecting
2084 user space to do the scan.
2086 security= [SECURITY] Choose a security module to enable at boot.
2087 If this boot parameter is not specified, only the first
2088 security module asking for security registration will be
2089 loaded. An invalid security module name will be treated
2090 as if no module has been chosen.
2092 selinux= [SELINUX] Disable or enable SELinux at boot time.
2093 Format: { "0" | "1" }
2094 See security/selinux/Kconfig help text.
2097 Default value is set via kernel config option.
2098 If enabled at boot time, /selinux/disable can be used
2099 later to disable prior to initial policy load.
2101 serialnumber [BUGS=X86-32]
2104 Maximal number of shapers.
2106 show_msr= [x86] show boot-time MSR settings
2107 Format: { <integer> }
2108 Show boot-time (BIOS-initialized) MSR settings.
2109 The parameter means the number of CPUs to show,
2110 for example 1 means boot CPU only.
2113 See header of drivers/scsi/sim710.c.
2120 slub_debug[=options[,slabs]] [MM, SLUB]
2121 Enabling slub_debug allows one to determine the
2122 culprit if slab objects become corrupted. Enabling
2123 slub_debug can create guard zones around objects and
2124 may poison objects when not in use. Also tracks the
2125 last alloc / free. For more information see
2126 Documentation/vm/slub.txt.
2128 slub_max_order= [MM, SLUB]
2129 Determines the maximum allowed order for slabs.
2130 A high setting may cause OOMs due to memory
2131 fragmentation. For more information see
2132 Documentation/vm/slub.txt.
2134 slub_min_objects= [MM, SLUB]
2135 The minimum number of objects per slab. SLUB will
2136 increase the slab order up to slub_max_order to
2137 generate a sufficiently large slab able to contain
2138 the number of objects indicated. The higher the number
2139 of objects the smaller the overhead of tracking slabs
2140 and the less frequently locks need to be acquired.
2141 For more information see Documentation/vm/slub.txt.
2143 slub_min_order= [MM, SLUB]
2144 Determines the mininum page order for slabs. Must be
2145 lower than slub_max_order.
2146 For more information see Documentation/vm/slub.txt.
2148 slub_nomerge [MM, SLUB]
2149 Disable merging of slabs with similar size. May be
2150 necessary if there is some reason to distinguish
2151 allocs to different slabs. Debug options disable
2152 merging on their own.
2153 For more information see Documentation/vm/slub.txt.
2156 Format: <io1>[,<io2>[,...,<io8>]]
2158 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2159 attempt to substitute SMP alternatives once at boot.
2161 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2162 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2163 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2164 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2165 smsc-ircc2.ircc_irq= [HW] IRQ line
2166 smsc-ircc2.ircc_dma= [HW] DMA channel
2167 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2168 0: Toshiba Satellite 1800 (GP data pin select)
2169 1: Fast pin select (default)
2172 snd-ad1816a= [HW,ALSA]
2174 snd-ad1848= [HW,ALSA]
2176 snd-ali5451= [HW,ALSA]
2178 snd-als100= [HW,ALSA]
2180 snd-als4000= [HW,ALSA]
2182 snd-azt2320= [HW,ALSA]
2184 snd-cmi8330= [HW,ALSA]
2186 snd-cmipci= [HW,ALSA]
2188 snd-cs4231= [HW,ALSA]
2190 snd-cs4232= [HW,ALSA]
2192 snd-cs4236= [HW,ALSA]
2194 snd-cs4281= [HW,ALSA]
2196 snd-cs46xx= [HW,ALSA]
2198 snd-dt019x= [HW,ALSA]
2200 snd-dummy= [HW,ALSA]
2202 snd-emu10k1= [HW,ALSA]
2204 snd-ens1370= [HW,ALSA]
2206 snd-ens1371= [HW,ALSA]
2208 snd-es968= [HW,ALSA]
2210 snd-es1688= [HW,ALSA]
2212 snd-es18xx= [HW,ALSA]
2214 snd-es1938= [HW,ALSA]
2216 snd-es1968= [HW,ALSA]
2218 snd-fm801= [HW,ALSA]
2220 snd-gusclassic= [HW,ALSA]
2222 snd-gusextreme= [HW,ALSA]
2224 snd-gusmax= [HW,ALSA]
2228 snd-ice1712= [HW,ALSA]
2230 snd-intel8x0= [HW,ALSA]
2232 snd-interwave= [HW,ALSA]
2237 snd-korg1212= [HW,ALSA]
2239 snd-maestro3= [HW,ALSA]
2241 snd-mpu401= [HW,ALSA]
2243 snd-mtpav= [HW,ALSA]
2245 snd-nm256= [HW,ALSA]
2247 snd-opl3sa2= [HW,ALSA]
2255 snd-opti93x= [HW,ALSA]
2259 snd-rme32= [HW,ALSA]
2261 snd-rme96= [HW,ALSA]
2263 snd-rme9652= [HW,ALSA]
2269 snd-sbawe= [HW,ALSA]
2271 snd-serial= [HW,ALSA]
2273 snd-sgalaxy= [HW,ALSA]
2275 snd-sonicvibes= [HW,ALSA]
2280 snd-sun-cs4231= [HW,ALSA]
2282 snd-trident= [HW,ALSA]
2284 snd-usb-audio= [HW,ALSA,USB]
2286 snd-via82xx= [HW,ALSA]
2288 snd-virmidi= [HW,ALSA]
2290 snd-wavefront= [HW,ALSA]
2292 snd-ymfpci= [HW,ALSA]
2295 [KNL] Should the soft-lockup detector generate panics.
2297 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2298 See Documentation/sonypi.txt
2300 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2301 See Documentation/serial/specialix.txt.
2303 spia_io_base= [HW,MTD]
2309 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2311 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2312 See Documentation/scsi/st.txt.
2315 Enabled the stack tracer on boot up.
2319 Set the STI (builtin display/keyboard on the HP-PARISC
2320 machines) console (graphic card) which should be used
2321 as the initial boot-console.
2322 See also comment in drivers/video/console/sticore.c.
2325 See comment in drivers/video/console/sticore.c.
2328 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2332 Control how the NFS server code allocates CPUs to
2333 service thread pools. Depending on how many NICs
2334 you have and where their interrupts are bound, this
2335 option will affect which CPUs will do NFS serving.
2336 Note: this parameter cannot be changed while the
2337 NFS server is running.
2339 auto the server chooses an appropriate mode
2340 automatically using heuristics
2341 global a single global pool contains all CPUs
2342 percpu one pool for each CPU
2343 pernode one pool for each NUMA node (equivalent
2344 to global on non-NUMA machines)
2346 swiotlb= [IA-64] Number of I/O TLB slabs
2350 sym53c416= [HW,SCSI]
2351 See header of drivers/scsi/sym53c416.c.
2353 sysrq_always_enabled
2355 Ignore sysrq setting - this boot parameter will
2356 neutralize any effect of /proc/sys/kernel/sysrq.
2357 Useful for debugging.
2360 See header of drivers/scsi/t128.c.
2364 test_suspend= [SUSPEND]
2365 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2366 standby suspend) as the system sleep state to briefly
2367 enter during system startup. The system is woken from
2368 this state using a wakeup-capable RTC alarm.
2370 thash_entries= [KNL,NET]
2371 Set number of hash buckets for TCP connection
2373 thermal.act= [HW,ACPI]
2374 -1: disable all active trip points in all thermal zones
2375 <degrees C>: override all lowest active trip points
2377 thermal.crt= [HW,ACPI]
2378 -1: disable all critical trip points in all thermal zones
2379 <degrees C>: override all critical trip points
2381 thermal.nocrt= [HW,ACPI]
2382 Set to disable actions on ACPI thermal zone
2383 critical and hot trip points.
2385 thermal.off= [HW,ACPI]
2386 1: disable ACPI thermal control
2388 thermal.psv= [HW,ACPI]
2389 -1: disable all passive trip points
2390 <degrees C>: override all passive trip points to this
2393 thermal.tzp= [HW,ACPI]
2394 Specify global default ACPI thermal zone polling rate
2395 <deci-seconds>: poll all this frequency
2396 0: no polling (default)
2399 See comment before function dc390_setup() in
2400 drivers/scsi/tmscsim.c.
2404 Specify if the kernel should make use of the cpu
2405 topology informations if the hardware supports these.
2406 The scheduler will make use of these informations and
2407 e.g. base its process migration decisions on it.
2412 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2414 trix= [HW,OSS] MediaTrix AudioTrix Pro
2416 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2418 tsc= Disable clocksource-must-verify flag for TSC.
2420 [x86] reliable: mark tsc clocksource as reliable, this
2421 disables clocksource verification at runtime.
2422 Used to enable high-resolution timer mode on older
2423 hardware, and in virtualized environment.
2425 turbografx.map[2|3]= [HW,JOY]
2426 TurboGraFX parallel port interface
2428 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2429 See also Documentation/input/joystick-parport.txt
2431 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2432 See header of drivers/scsi/u14-34f.c.
2441 [USB] Ignore overcurrent events (default N).
2442 Some badly-designed motherboards generate lots of
2443 bogus events, for ports that aren't wired to
2444 anything. Set this parameter to avoid log spamming.
2445 Note that genuine overcurrent events won't be
2450 Set unknown_nmi_panic=1 early on boot.
2452 usbcore.autosuspend=
2453 [USB] The autosuspend time delay (in seconds) used
2454 for newly-detected USB devices (default 2). This
2455 is the time required before an idle device will be
2456 autosuspended. Devices for which the delay is set
2457 to a negative value won't be autosuspended at all.
2459 usbcore.usbfs_snoop=
2460 [USB] Set to log all usbfs traffic (default 0 = off).
2462 usbcore.blinkenlights=
2463 [USB] Set to cycle leds on hubs (default 0 = off).
2465 usbcore.old_scheme_first=
2466 [USB] Start with the old device initialization
2467 scheme (default 0 = off).
2469 usbcore.use_both_schemes=
2470 [USB] Try the other device initialization scheme
2471 if the first one fails (default 1 = enabled).
2473 usbcore.initial_descriptor_timeout=
2474 [USB] Specifies timeout for the initial 64-byte
2475 USB_REQ_GET_DESCRIPTOR request in milliseconds
2476 (default 5000 = 5.0 seconds).
2479 [USBHID] The interval which mice are to be polled at.
2481 usb-storage.delay_use=
2482 [UMS] The delay in seconds before a new device is
2483 scanned for Logical Units (default 5).
2486 [UMS] A list of quirks entries to supplement or
2487 override the built-in unusual_devs list. List
2488 entries are separated by commas. Each entry has
2489 the form VID:PID:Flags where VID and PID are Vendor
2490 and Product ID values (4-digit hex numbers) and
2491 Flags is a set of characters, each corresponding
2492 to a common usb-storage quirk flag as follows:
2493 a = SANE_SENSE (collect more than 18 bytes
2495 c = FIX_CAPACITY (decrease the reported
2496 device capacity by one sector);
2497 h = CAPACITY_HEURISTICS (decrease the
2498 reported device capacity by one
2499 sector if the number is odd);
2500 i = IGNORE_DEVICE (don't bind to this
2502 l = NOT_LOCKABLE (don't try to lock and
2503 unlock ejectable media);
2504 m = MAX_SECTORS_64 (don't transfer more
2505 than 64 sectors = 32 KB at a time);
2506 o = CAPACITY_OK (accept the capacity
2507 reported by the device);
2508 r = IGNORE_RESIDUE (the device reports
2509 bogus residue values);
2510 s = SINGLE_LUN (the device has only one
2512 w = NO_WP_DETECT (don't test whether the
2513 medium is write-protected).
2514 Example: quirks=0419:aaf5:rl,0421:0433:rc
2517 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2518 vdso=1: enable VDSO (default)
2519 vdso=0: disable VDSO mapping
2522 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2523 vdso32=1: enable 32-bit VDSO (default)
2524 vdso32=0: disable 32-bit VDSO mapping
2527 vector=percpu: enable percpu vector domain
2529 video= [FB] Frame buffer configuration
2530 See Documentation/fb/modedb.txt.
2532 vga= [BOOT,X86-32] Select a particular video mode
2533 See Documentation/x86/boot.txt and
2534 Documentation/svga.txt.
2535 Use vga=ask for menu.
2536 This is actually a boot loader parameter; the value is
2537 passed to the kernel using a special protocol.
2539 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2540 size of <nn>. This can be used to increase the
2541 minimum size (128MB on x86). It can also be used to
2542 decrease the size and leave more room for directly
2545 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2548 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2551 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2554 vt.default_blu= [VT]
2555 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2556 Change the default blue palette of the console.
2557 This is a 16-member array composed of values
2560 vt.default_grn= [VT]
2561 Format: <green0>,<green1>,<green2>,...,<green15>
2562 Change the default green palette of the console.
2563 This is a 16-member array composed of values
2566 vt.default_red= [VT]
2567 Format: <red0>,<red1>,<red2>,...,<red15>
2568 Change the default red palette of the console.
2569 This is a 16-member array composed of values
2575 Set system-wide default UTF-8 mode for all tty's.
2576 Default is 1, i.e. UTF-8 mode is enabled for all
2577 newly opened terminals.
2579 waveartist= [HW,OSS]
2580 Format: <io>,<irq>,<dma>,<dma2>
2583 See header of drivers/scsi/wd33c93.c.
2586 See header of drivers/scsi/wd7000.c.
2589 See Documentation/watchdog/wdt.txt.
2591 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2592 default x2apic cluster mode on platforms
2595 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2596 xd_geo= See header of drivers/block/xd.c.
2598 xirc2ps_cs= [NET,PCMCIA]
2600 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2602 ______________________________________________________________________
2606 Add documentation for ALSA options.
2607 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob