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 KMEMTRACE kmemtrace is enabled.
60 LIBATA Libata driver is enabled
61 LP Printer support is enabled.
62 LOOP Loopback device support is enabled.
63 M68k M68k architecture is enabled.
64 These options have more detailed description inside of
65 Documentation/m68k/kernel-options.txt.
66 MCA MCA bus support is enabled.
67 MDA MDA console support is enabled.
68 MOUSE Appropriate mouse support is enabled.
69 MSI Message Signaled Interrupts (PCI).
70 MTD MTD (Memory Technology Device) support is enabled.
71 NET Appropriate network support is enabled.
72 NUMA NUMA support is enabled.
73 GENERIC_TIME The generic timeofday code is enabled.
74 NFS Appropriate NFS support is enabled.
75 OSS OSS sound support is enabled.
76 PV_OPS A paravirtualized kernel is enabled.
77 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
78 PARISC The PA-RISC architecture is enabled.
79 PCI PCI bus support is enabled.
80 PCIE PCI Express support is enabled.
81 PCMCIA The PCMCIA subsystem is enabled.
82 PNP Plug & Play support is enabled.
83 PPC PowerPC architecture is enabled.
84 PPT Parallel port support is enabled.
85 PS2 Appropriate PS/2 support is enabled.
86 RAM RAM disk support is enabled.
87 ROOTPLUG The example Root Plug LSM is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
92 SECURITY Different security models are enabled.
93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
95 SH SuperH architecture is enabled.
96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
100 FTRACE Function tracing enabled.
101 TS Appropriate touchscreen support is enabled.
102 UMS USB Mass Storage support is enabled.
103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
110 X86-32 X86-32, aka i386 architecture is enabled.
111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
113 Documentation/x86/x86_64/boot-options.txt .
114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116 In addition, the following text indicates that the option:
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
122 Parameters denoted with BOOT are actually interpreted by the boot
123 loader, and have no meaning to the kernel directly.
124 Do not modify the syntax of boot loader parameters without extreme
125 need or coordination with <Documentation/x86/boot.txt>.
127 There are also arch-specific kernel-parameters not documented here.
128 See for example <Documentation/x86/x86_64/boot-options.txt>.
130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131 a trailing = on the name of any parameter states that that parameter will
132 be entered as an environment variable, whereas its absence indicates that
133 it will appear as a kernel argument readable via /proc/cmdline by programs
134 running once the system is up.
136 The number of kernel parameters is not limited, but the length of the
137 complete command line (parameters including spaces etc.) is limited to
138 a fixed number of characters. This limit depends on the architecture
139 and is between 256 and 4096 characters. It is defined in the file
140 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 Advanced Configuration and Power Interface
145 Format: { force | off | ht | strict | noirq | rsdt }
146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
150 strict -- Be less tolerant of platforms that are not
151 strictly ACPI specification compliant.
152 rsdt -- prefer RSDT over (default) XSDT
154 See also Documentation/power/pm.txt, pci=noacpi
156 acpi_apic_instance= [ACPI, IOAPIC]
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi.power_nocheck= [HW,ACPI]
233 Format: 1/0 enable/disable the check of power state.
234 On some bogus BIOS the _PSC object/_STA object of
235 power resource can't return the correct device power
236 state. In such case it is unneccessary to check its
237 power state again in power transition.
238 1 : disable the power state check
240 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
241 Format: { level | edge | high | low }
243 acpi_serialize [HW,ACPI] force serialization of AML methods
245 acpi_skip_timer_override [HW,ACPI]
246 Recognize and ignore IRQ0/pin2 Interrupt Override.
247 For broken nForce2 BIOS resulting in XT-PIC timer.
249 acpi_sleep= [HW,ACPI] Sleep options
250 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
251 old_ordering, s4_nonvs }
252 See Documentation/power/video.txt for information on
254 s3_beep is for debugging; it makes the PC's speaker beep
255 as soon as the kernel's real-mode entry point is called.
256 s4_nohwsig prevents ACPI hardware signature from being
257 used during resume from hibernation.
258 old_ordering causes the ACPI 1.0 ordering of the _PTS
259 control method, with respect to putting devices into
260 low power states, to be enforced (the ACPI 2.0 ordering
261 of _PTS is used by default).
262 s4_nonvs prevents the kernel from saving/restoring the
263 ACPI NVS memory during hibernation.
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
292 See header of drivers/scsi/advansys.c.
294 advwdt= [HW,WDT] Advantech WDT
295 Format: <iostart>,<iostop>
297 aedsp16= [HW,OSS] Audio Excel DSP 16
298 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
299 See also header of sound/oss/aedsp16.c.
302 { off | try_unsupported }
303 off: disable AGP support
304 try_unsupported: try to drive unsupported chipsets
305 (may crash computer or cause data corruption)
308 See Documentation/scsi/aha152x.txt.
311 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
314 See Documentation/scsi/aic7xxx.txt.
317 See Documentation/scsi/aic79xx.txt.
319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
322 isolate - enable device isolation (each device, as far
323 as possible, will get its own protection
325 share - put every device behind one IOMMU into the
326 same protection domain
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
332 amijoy.map= [HW,JOY] Amiga joystick support
333 Map of devices attached to JOY0DAT and JOY1DAT
335 See also Documentation/kernel/input/joystick.txt
337 analog.map= [HW,JOY] Analog joystick and gamepad support
338 Specifies type or capabilities of an analog joystick
339 connected to one of 16 gameports
340 Format: <type1>,<type2>,..<type16>
343 Power management functions (SPARCstation-4/5 + deriv.)
345 Disable APC CPU standby support. SPARCstation-Fox does
346 not play well with APC CPU idle - disable it if you have
347 APC and your system crashes randomly.
349 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
350 Change the output verbosity whilst booting
351 Format: { quiet (default) | verbose | debug }
352 Change the amount of debugging information output
353 when initialising the APIC and IO-APIC components.
355 apm= [APM] Advanced Power Management
356 See header of arch/x86/kernel/apm_32.c.
358 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
359 Format: <io>,<irq>,<nodeID>
363 atarimouse= [HW,MOUSE] Atari Mouse
365 atascsi= [HW,SCSI] Atari SCSI
367 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
368 EzKey and similar keyboards
370 atkbd.reset= [HW] Reset keyboard during initialization
372 atkbd.set= [HW] Select keyboard code set
373 Format: <int> (2 = AT (default), 3 = PS/2)
375 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
378 atkbd.softraw= [HW] Choose between synthetic and real raw mode
379 Format: <bool> (0 = real, 1 = synthetic (default))
381 atkbd.softrepeat= [HW]
382 Use software keyboard repeat
386 baycom_epp= [HW,AX25]
389 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
391 See header of drivers/net/hamradio/baycom_par.c.
393 baycom_ser_fdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
395 Format: <io>,<irq>,<mode>[,<baud>]
396 See header of drivers/net/hamradio/baycom_ser_fdx.c.
398 baycom_ser_hdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
400 Format: <io>,<irq>,<mode>
401 See header of drivers/net/hamradio/baycom_ser_hdx.c.
403 boot_delay= Milliseconds to delay each printk during boot.
404 Values larger than 10 seconds (10000) are changed to
408 bootmem_debug [KNL] Enable bootmem allocator debug messages.
410 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
411 bttv.radio= Most important insmod options are available as
413 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
414 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
417 See drivers/scsi/BusLogic.c, comment before function
418 BusLogic_ParseDriverOptions().
420 c101= [NET] Moxa C101 synchronous serial card
422 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
423 Sometimes CPU hardware bugs make them report the cache
424 size incorrectly. The kernel will attempt work arounds
425 to fix known problems, but for some CPUs it is not
426 possible to determine what the correct size should be.
427 This option provides an override for these situations.
430 [SECURITY] Disable capabilities. This would normally
431 be used only if an alternative security model is to be
432 configured. Potentially dangerous and should only be
433 used if you are entirely sure of the consequences.
435 ccw_timeout_log [S390]
436 See Documentation/s390/CommonIO for details.
438 cgroup_disable= [KNL] Disable a particular controller
439 Format: {name of the controller(s) to disable}
440 {Currently supported controllers - "memory"}
442 checkreqprot [SELINUX] Set initial checkreqprot flag value.
443 Format: { "0" | "1" }
444 See security/selinux/Kconfig help text.
445 0 -- check protection applied by kernel (includes
446 any implied execute protection).
447 1 -- check protection requested by application.
448 Default value is set via a kernel config option.
449 Value can be changed at runtime via
450 /selinux/checkreqprot.
453 See Documentation/s390/CommonIO for details.
455 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
457 Forces specified clocksource (if available) to be used
458 when calculating gettimeofday(). If specified
459 clocksource is not available, it defaults to PIT.
460 Format: { pit | tsc | cyclone | pmtmr }
462 clocksource= [GENERIC_TIME] Override the default clocksource
464 Override the default clocksource and use the clocksource
465 with the name specified.
466 Some clocksource names to choose from, depending on
468 [all] jiffies (this is the base, fallback clocksource)
470 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
471 pxa_timer,timer3,32k_counter,timer0_1
473 [X86-32] pit,hpet,tsc,vmi-timer;
474 scx200_hrt on Geode; cyclone on IBM x440
482 clearcpuid=BITNUM [X86]
483 Disable CPUID feature X for the kernel. See
484 arch/x86/include/asm/cpufeature.h for the valid bit
485 numbers. Note the Linux specific bits are not necessarily
486 stable over kernel options, but the vendor specific
488 Also note that user programs calling CPUID directly
489 or using the feature without checking anything
490 will still see it. This just prevents it from
491 being used by the kernel or shown in /proc/cpuinfo.
492 Also note the kernel might malfunction if you disable
495 code_bytes [X86] How many bytes of object code to print
500 com20020= [HW,NET] ARCnet - COM20020 chipset
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
508 ARCnet - COM90xx chipset (memory-mapped buffers)
509 Format: <io>[,<irq>[,<memstart>]]
511 condev= [HW,S390] console device
514 console= [KNL] Output console device and options.
516 tty<n> Use the virtual console device <n>.
520 Use the specified serial port. The options are of
521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
526 See Documentation/serial-console.txt for more
528 Documentation/networking/netconsole.txt for an
531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
541 For now, only VisioBraille is supported.
544 [KNL] Change the default value for
545 /proc/<pid>/coredump_filter.
546 See also Documentation/filesystems/proc.txt.
548 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
550 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
552 crashkernel=nn[KMG]@ss[KMG]
553 [KNL] Reserve a chunk of physical memory to
554 hold a kernel to switch to with kexec on panic.
556 crashkernel=range1:size1[,range2:size2,...][@offset]
557 [KNL] Same as above, but depends on the memory
558 in the running system. The syntax of range is
559 start-[end] where start and end are both
560 a memory unit (amount[KMG]). See also
561 Documentation/kdump/kdump.txt for a example.
566 cs89x0_media= [HW,NET]
567 Format: { rj45 | aui | bnc }
570 See header of drivers/s390/block/dasd_devmap.c.
572 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
573 (one device per port)
574 Format: <port#>,<type>
575 See also Documentation/input/joystick-parport.txt
577 debug [KNL] Enable kernel debugging (events log level).
580 [KNL] verbose self-tests
582 Print debugging info while doing the locking API
584 We default to 0 (no extra messages), setting it to
585 1 will print _a lot_ more information - normally
586 only useful to kernel developers.
588 debug_objects [KNL] Enable object debugging
591 [KNL] Disable object debugging
593 debugpat [X86] Enable PAT debugging
595 decnet.addr= [HW,NET]
596 Format: <area>[,<node>]
597 See also Documentation/networking/decnet.txt.
600 [same as hugepagesz=] The size of the default
601 HugeTLB page size. This is the size represented by
602 the legacy /proc/ hugepages APIs, used for SHM, and
603 default size when mounting hugetlbfs filesystems.
604 Defaults to the default architecture's huge page size
608 Set number of hash buckets for dentry cache.
611 IO parameters + enable/disable command.
613 digiepca= [HW,SERIAL]
614 See drivers/char/README.epca and
615 Documentation/serial/digiepca.txt.
617 disable_mtrr_cleanup [X86]
618 The kernel tries to adjust MTRR layout from continuous
619 to discrete, to make X server driver able to add WB
620 entry later. This parameter disables that.
622 disable_mtrr_trim [X86, Intel and AMD only]
623 By default the kernel will trim any uncacheable
624 memory out of your available memory pool based on
625 MTRR settings. This parameter disables that behavior,
626 possibly causing your machine to run very slowly.
628 disable_timer_pin_1 [X86]
629 Disable PIN 1 of APIC timer
630 Can be useful to work around chipset bugs.
632 dmasound= [HW,OSS] Sound subsystem buffers
634 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
635 this option disables the debugging code at boot.
637 dma_debug_entries=<number>
638 This option allows to tune the number of preallocated
639 entries for DMA-API debugging code. One entry is
640 required per DMA-API allocation. Use this if the
641 DMA-API debugging code disables itself because the
642 architectural default is too low.
644 dma_debug_driver=<driver_name>
645 With this option the DMA-API debugging driver
646 filter feature can be enabled at boot time. Just
647 pass the driver to filter for as the parameter.
648 The filter can be disabled or changed to another
649 driver later using sysfs.
655 dynamic_printk Enables pr_debug()/dev_dbg() calls if
656 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
657 These can also be switched on/off via
658 <debugfs>/dynamic_printk/modules
660 earlycon= [KNL] Output early console device and options.
661 uart[8250],io,<addr>[,options]
662 uart[8250],mmio,<addr>[,options]
663 Start an early, polled-mode console on the 8250/16550
664 UART at the specified I/O port or MMIO address.
665 The options are the same as for ttyS, above.
667 earlyprintk= [X86,SH,BLACKFIN]
669 earlyprintk=serial[,ttySn[,baudrate]]
672 Append ",keep" to not disable it when the real console
675 Only vga or serial or usb debug port at a time.
677 Currently only ttyS0 and ttyS1 are supported.
679 Interaction with the standard serial driver is not
682 The VGA output is eventually overwritten by the real
688 Format: {"off" | "on" | "skip[mbr]"}
690 eisa_irq_edge= [PARISC,HW]
691 See header of drivers/parisc/eisa.c.
694 See comment before function elanfreq_setup() in
695 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
698 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
699 See Documentation/block/as-iosched.txt and
700 Documentation/block/deadline-iosched.txt for details.
702 elfcorehdr= [IA64,PPC,SH,X86]
703 Specifies physical address of start of kernel core
704 image elf header. Generally kexec loader will
705 pass this option to capture kernel.
706 See Documentation/kdump/kdump.txt for details.
708 enable_mtrr_cleanup [X86]
709 The kernel tries to adjust MTRR layout from continuous
710 to discrete, to make X server driver able to add WB
711 entry later. This parameter enables that.
713 enable_timer_pin_1 [X86]
714 Enable PIN 1 of APIC timer
715 Can be useful to work around chipset bugs
716 (in particular on some ATI chipsets).
717 The kernel tries to set a reasonable default.
719 enforcing [SELINUX] Set initial enforcing status.
721 See security/selinux/Kconfig help text.
722 0 -- permissive (log only, no denials).
723 1 -- enforcing (deny and log).
725 Value can be changed at runtime via /selinux/enforce.
727 ether= [HW,NET] Ethernet cards parameters
728 This option is obsoleted by the "netdev=" option, which
729 has equivalent usage. See its documentation for details.
731 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
736 fail_make_request=[KNL]
737 General fault injection mechanism.
738 Format: <interval>,<probability>,<space>,<times>
739 See also /Documentation/fault-injection/.
742 See header of drivers/scsi/fd_mcs.c.
745 See header of drivers/scsi/fdomain.c.
748 See Documentation/blockdev/floppy.txt.
750 force_pal_cache_flush
751 [IA-64] Avoid check_sal_cache_flush which may hang on
752 buggy SAL_CACHE_FLUSH implementations. Using this
753 parameter will force ia64_sal_cache_flush to call
754 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
757 [ftrace] will set and start the specified tracer
758 as early as possible in order to facilitate early
762 [ftrace] will dump the trace buffers on oops.
765 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
766 support via parallel port (up to 5 devices per port)
767 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
768 See also Documentation/input/joystick-parport.txt
772 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
777 See header of drivers/scsi/gdth.c.
779 gpt [EFI] Forces disk with valid GPT signature but
780 invalid Protective MBR to be treated as GPT.
784 hashdist= [KNL,NUMA] Large hashes allocated during boot
785 are distributed across NUMA nodes. Defaults on
786 for 64bit NUMA, off otherwise.
787 Format: 0 | 1 (for off | on)
789 hcl= [IA-64] SGI's Hardware Graph compatibility layer
791 hd= [EIDE] (E)IDE hard drive subsystem geometry
792 Format: <cyl>,<head>,<sect>
794 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
795 size of <nn>. This works even on boxes that have no
796 highmem otherwise. This also works to reduce highmem
797 size on bigger boxes.
799 highres= [KNL] Enable/disable high resolution timer mode.
800 Valid parameters: "on", "off"
804 See Documentation/isdn/README.HiSax.
808 hpet= [X86-32,HPET] option to control HPET usage
809 Format: { enable (default) | disable | force |
811 disable: disable HPET and use PIT instead
812 force: allow force enabled of undocumented chips (ICH4,
814 verbose: show contents of HPET registers during setup
816 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
817 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
818 On x86-64 and powerpc, this option can be specified
819 multiple times interleaved with hugepages= to reserve
820 huge pages of different sizes. Valid pages sizes on
821 x86-64 are 2M (when the CPU supports "pse") and 1G
822 (when the CPU supports the "pdpe1gb" cpuinfo flag)
823 Note that 1GB pages can only be allocated at boot time
824 using hugepages= and not freed afterwards.
826 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
827 terminal devices. Valid values: 0..8
828 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
829 If specified, z/VM IUCV HVC accepts connections
830 from listed z/VM user IDs only.
832 i2c_bus= [HW] Override the default board specific I2C bus speed
833 or register an additional I2C bus that is not
834 registered from board initialization code.
838 i8042.debug [HW] Toggle i8042 debug mode
839 i8042.direct [HW] Put keyboard port into non-translated mode
840 i8042.dumbkbd [HW] Pretend that controller can only read data from
841 keyboard and cannot control its state
842 (Don't attempt to blink the leds)
843 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
844 i8042.nokbd [HW] Don't check/create keyboard port
845 i8042.noloop [HW] Disable the AUX Loopback command while probing
847 i8042.nomux [HW] Don't check presence of an active multiplexing
849 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
852 [HW] Frequency with which keyboard LEDs should blink
853 when kernel panics (default is 0.5 sec)
854 i8042.reset [HW] Reset the controller during init and cleanup
855 i8042.unlock [HW] Unlock (ignore) the keylock
859 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
860 indicates that the driver is running on unsupported
862 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
863 does not match list of supported models.
865 [HW] Report power status in /proc/i8k
866 (disabled by default)
867 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
870 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
871 See Documentation/mca.txt.
874 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
876 ide-core.nodma= [HW] (E)IDE subsystem
877 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
878 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
879 .chs .ignore_cable are additional options
880 See Documentation/ide/ide.txt.
882 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
883 See Documentation/ide/ide.txt.
885 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
886 Claim all unknown PCI IDE storage controllers.
889 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
890 Poll forces a polling idle loop that can slightly
891 improve the performance of waking up a idle CPU, but
892 will use a lot of power and make the system run hot.
894 idle=mwait: On systems which support MONITOR/MWAIT but
895 the kernel chose to not use it because it doesn't save
896 as much power as a normal idle loop, use the
897 MONITOR/MWAIT idle loop anyways. Performance should be
898 the same as idle=poll.
899 idle=halt: Halt is forced to be used for CPU idle.
900 In such case C2/C3 won't be used again.
901 idle=nomwait: Disable mwait for CPU C-states
903 ignore_loglevel [KNL]
904 Ignore loglevel setting - this will print /all/
905 kernel messages to the console. Useful for debugging.
908 Set number of hash buckets for inode cache.
911 Format: { "0" | "1" }
912 0 -- integrity auditing messages. (Default)
913 1 -- enable informational integrity auditing messages.
916 Formt: { "sha1" | "md5" }
920 Load a policy which meets the needs of the Trusted
921 Computing Base. This means IMA will measure all
922 programs exec'd, files mmap'd for exec, and all files
923 opened for read by uid=0.
926 See header of drivers/scsi/in2000.c.
930 Run specified binary instead of /sbin/init as init
933 initcall_debug [KNL] Trace initcalls as they are executed. Useful
934 for working out where the kernel is dying during
937 initrd= [BOOT] Specify the location of the initial ramdisk
939 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
942 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
944 Enable intel iommu driver.
946 Disable intel iommu driver.
947 igfx_off [Default Off]
948 By default, gfx is mapped as normal device. If a gfx
949 device has a dedicated DMAR unit, the DMAR unit is
950 bypassed by not enabling DMAR with this option. In
951 this case, gfx device will use physical address for
954 With this option iommu will not optimize to look
955 for io virtual address below 32 bit forcing dual
956 address cycle on pci bus for cards supporting greater
957 than 32 bit addressing. The default is to look
958 for translation below 32 bit and if not available
959 then look in the higher range.
961 With this option on every unmap_single operation will
962 result in a hardware IOTLB flush operation as opposed
963 to batching them for performance.
967 iomem= Disable strict checking of access to MMIO memory
968 strict regions from userspace.
983 io7= [HW] IO7 for Marvel based alpha systems
984 See comment before marvel_specify_io7 in
985 arch/alpha/kernel/core_marvel.c.
987 io_delay= [X86] I/O delay method
989 Standard port 0x80 based delay
991 Alternate port 0xed based delay (needed on some systems)
993 Simple two microseconds delay
998 See Documentation/filesystems/nfsroot.txt.
1000 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1001 See comment before ip2_setup() in
1002 drivers/char/ip2/ip2base.c.
1004 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1005 See header of drivers/scsi/ips.c.
1008 When an interrupt is not handled search all handlers
1009 for it. Intended to get systems with badly broken
1013 When an interrupt is not handled search all handlers
1014 for it. Also check all handlers each timer
1015 interrupt. Intended to get systems with badly broken
1019 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1021 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1023 <cpu number>,...,<cpu number>
1025 <cpu number>-<cpu number>
1026 (must be a positive range in ascending order)
1028 <cpu number>,...,<cpu number>-<cpu number>
1030 This option can be used to specify one or more CPUs
1031 to isolate from the general SMP balancing and scheduling
1032 algorithms. You can move a process onto or off an
1033 "isolated" CPU via the CPU affinity syscalls or cpuset.
1034 <cpu number> begins at 0 and the maximum value is
1035 "number of CPUs in system - 1".
1037 This option is the preferred way to isolate CPUs. The
1038 alternative -- manually setting the CPU mask of all
1039 tasks in the system -- can cause problems and
1040 suboptimal load balancer performance.
1044 js= [HW,JOY] Analog joystick
1045 See Documentation/input/joystick.txt.
1049 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1050 specifies the amount of memory usable by the kernel
1051 for non-movable allocations. The requested amount is
1052 spread evenly throughout all nodes in the system. The
1053 remaining memory in each node is used for Movable
1054 pages. In the event, a node is too small to have both
1055 kernelcore and Movable pages, kernelcore pages will
1056 take priority and other nodes will have a larger number
1057 of kernelcore pages. The Movable zone is used for the
1058 allocation of pages that may be reclaimed or moved
1059 by the page migration subsystem. This means that
1060 HugeTLB pages may not be allocated from this zone.
1061 Note that allocations like PTEs-from-HighMem still
1062 use the HighMem zone if it exists, and the Normal
1063 zone if it does not.
1065 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1066 Controls whether kmemtrace is enabled
1069 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1070 subbufs kmemtrace's relay channel has. Set this
1071 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1072 you experience buffer overruns.
1074 kgdboc= [HW] kgdb over consoles.
1075 Requires a tty driver that supports console polling.
1076 (only serial suported for now)
1077 Format: <serial_device>[,baud]
1079 kmac= [MIPS] korina ethernet MAC address.
1080 Configure the RouterBoard 532 series on-chip
1081 Ethernet adapter MAC address.
1083 kstack=N [X86] Print N words from the kernel stack
1090 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1093 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1096 libata.dma= [LIBATA] DMA control
1097 libata.dma=0 Disable all PATA and SATA DMA
1098 libata.dma=1 PATA and SATA Disk DMA only
1099 libata.dma=2 ATAPI (CDROM) DMA only
1100 libata.dma=4 Compact Flash DMA only
1101 Combinations also work, so libata.dma=3 enables DMA
1102 for disks and CDROMs, but not CFs.
1104 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1108 libata.force= [LIBATA] Force configurations. The format is comma
1109 separated list of "[ID:]VAL" where ID is
1110 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1111 matching port, link or device. Basically, it matches
1112 the ATA ID string printed on console by libata. If
1113 the whole ID part is omitted, the last PORT and DEVICE
1114 values are used. If ID hasn't been specified yet, the
1115 configuration applies to all ports, links and devices.
1117 If only DEVICE is omitted, the parameter applies to
1118 the port and all links and devices behind it. DEVICE
1119 number of 0 either selects the first device or the
1120 first fan-out link behind PMP device. It does not
1121 select the host link. DEVICE number of 15 selects the
1122 host link and device attached to it.
1124 The VAL specifies the configuration to force. As long
1125 as there's no ambiguity shortcut notation is allowed.
1126 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1127 The following configurations can be forced.
1129 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1130 Any ID with matching PORT is used.
1132 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1134 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1135 udma[/][16,25,33,44,66,100,133] notation is also
1138 * [no]ncq: Turn on or off NCQ.
1140 * nohrst, nosrst, norst: suppress hard, soft
1143 If there are multiple matching configurations changing
1144 the same attribute, the last one is used.
1146 lmb=debug [KNL] Enable lmb debug messages.
1148 load_ramdisk= [RAM] List of ramdisks to load from floppy
1149 See Documentation/blockdev/ramdisk.txt.
1151 lockd.nlm_grace_period=P [NFS] Assign grace period.
1154 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1157 lockd.nlm_timeout=T [NFS] Assign timeout value.
1160 lockd.nlm_udpport=M [NFS] Assign UDP port.
1163 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1166 loglevel= All Kernel Messages with a loglevel smaller than the
1167 console loglevel will be printed to the console. It can
1168 also be changed with klogd or other programs. The
1169 loglevels are defined as follows:
1171 0 (KERN_EMERG) system is unusable
1172 1 (KERN_ALERT) action must be taken immediately
1173 2 (KERN_CRIT) critical conditions
1174 3 (KERN_ERR) error conditions
1175 4 (KERN_WARNING) warning conditions
1176 5 (KERN_NOTICE) normal but significant condition
1177 6 (KERN_INFO) informational
1178 7 (KERN_DEBUG) debug-level messages
1180 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1181 Format: { n | nk | nM }
1182 n must be a power of two. The default size
1183 is set in the kernel config file.
1185 logo.nologo [FB] Disables display of the built-in Linux logo.
1186 This may be used to provide more screen space for
1187 kernel log messages and is useful when debugging
1188 kernel boot problems.
1190 lp=0 [LP] Specify parallel ports to use, e.g,
1191 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1192 lp=reset first parallel port). 'lp=0' disables the
1193 lp=auto printer driver. 'lp=reset' (which can be
1194 specified in addition to the ports) causes
1195 attached printers to be reset. Using
1196 lp=port1,port2,... specifies the parallel ports
1197 to associate lp devices with, starting with
1198 lp0. A port specification may be 'none' to skip
1199 that lp device, or a parport name such as
1200 'parport0'. Specifying 'lp=auto' instead of a
1201 port specification list means that device IDs
1202 from each port should be examined, to see if
1203 an IEEE 1284-compliant printer is attached; if
1204 so, the driver will manage that printer.
1205 See also header of drivers/char/lp.c.
1208 Sets loops_per_jiffy to given constant, thus avoiding
1209 time-consuming boot-time autodetection (up to 250 ms per
1210 CPU). 0 enables autodetection (default). To determine
1211 the correct value for your kernel, boot with normal
1212 autodetection and see what value is printed. Note that
1213 on SMP systems the preset will be applied to all CPUs,
1214 which is likely to cause problems if your CPUs need
1215 significantly divergent settings. An incorrect value
1216 will cause delays in the kernel to be wrong, leading to
1217 unpredictable I/O errors and other breakage. Although
1218 unlikely, in the extreme case this might damage your
1222 Format: <io>,<irq>,<dma>
1224 mac5380= [HW,SCSI] Format:
1225 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1227 machvec= [IA64] Force the use of a particular machine-vector
1228 (machvec) in a generic kernel.
1229 Example: machvec=hpzx1_swiotlb
1231 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1232 than or equal to this physical address is ignored.
1234 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1235 should make use of. maxcpus=n : n >= 0 limits the
1236 kernel to using 'n' processors. n=0 is a special case,
1237 it is equivalent to "nosmp", which also disables
1240 max_loop= [LOOP] Maximum number of loopback devices that can
1244 max_luns= [SCSI] Maximum number of LUNs to probe.
1245 Should be between 1 and 2^32-1.
1248 [SCSI] Maximum number of LUNs received.
1249 Should be between 1 and 16384.
1253 mce [X86-32] Machine Check Exception
1255 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1257 md= [HW] RAID subsystems devices and level
1258 See Documentation/md.txt.
1261 Format: <first>,<last>
1262 Specifies range of consoles to be captured by the MDA.
1264 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1265 Amount of memory to be used when the kernel is not able
1266 to see the whole system memory or for test.
1267 [X86-32] Use together with memmap= to avoid physical
1268 address space collisions. Without memmap= PCI devices
1269 could be placed at addresses belonging to unused RAM.
1271 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1275 [KNL,SH] Allow user to override the default size for
1276 per-device physically contiguous DMA buffers.
1278 memmap=exactmap [KNL,X86] Enable setting of an exact
1279 E820 memory map, as specified by the user.
1280 Such memmap=exactmap lines can be constructed based on
1281 BIOS output or other requirements. See the memmap=nn@ss
1284 memmap=nn[KMG]@ss[KMG]
1285 [KNL] Force usage of a specific region of memory
1286 Region of memory to be used, from ss to ss+nn.
1288 memmap=nn[KMG]#ss[KMG]
1289 [KNL,ACPI] Mark specific memory as ACPI data.
1290 Region of memory to be used, from ss to ss+nn.
1292 memmap=nn[KMG]$ss[KMG]
1293 [KNL,ACPI] Mark specific memory as reserved.
1294 Region of memory to be used, from ss to ss+nn.
1295 Example: Exclude memory from 0x18690000-0x1869ffff
1296 memmap=64K$0x18690000
1298 memmap=0x10000$0x18690000
1300 memory_corruption_check=0/1 [X86]
1301 Some BIOSes seem to corrupt the first 64k of
1302 memory when doing things like suspend/resume.
1303 Setting this option will scan the memory
1304 looking for corruption. Enabling this will
1305 both detect corruption and prevent the kernel
1306 from using the memory being corrupted.
1307 However, its intended as a diagnostic tool; if
1308 repeatable BIOS-originated corruption always
1309 affects the same memory, you can use memmap=
1310 to prevent the kernel from using that memory.
1312 memory_corruption_check_size=size [X86]
1313 By default it checks for corruption in the low
1314 64k, making this memory unavailable for normal
1315 use. Use this parameter to scan for
1316 corruption in more or less memory.
1318 memory_corruption_check_period=seconds [X86]
1319 By default it checks for corruption every 60
1320 seconds. Use this parameter to check at some
1321 other rate. 0 disables periodic checking.
1323 memtest= [KNL,X86] Enable memtest
1325 default : 0 <disable>
1326 Specifies the number of memtest passes to be
1327 performed. Each pass selects another test
1328 pattern from a given set of patterns. Memtest
1329 fills the memory with this pattern, validates
1330 memory contents and reserves bad memory
1331 regions that are detected.
1333 meye.*= [HW] Set MotionEye Camera parameters
1334 See Documentation/video4linux/meye.txt.
1336 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1337 Multi-Function General Purpose Timers on AMD Geode
1340 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1341 the BIOS has incorrectly applied a workaround. TinyBIOS
1342 version 0.98 is known to be affected, 0.99 fixes the
1343 problem by letting the user disable the workaround.
1347 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1348 physical address is ignored.
1351 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1352 parameter allows control of the logging verbosity for
1353 the additional memory initialisation checks. A value
1354 of 0 disables mminit logging and a level of 4 will
1355 log everything. Information is printed at KERN_DEBUG
1356 so loglevel=8 may also need to be specified.
1359 [MOUSE] Maximum time between finger touching and
1360 leaving touchpad surface for touch to be considered
1361 a tap and be reported as a left button click (for
1362 touchpads working in absolute mode only).
1364 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1365 reporting absolute coordinates, such as tablets
1366 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1367 reporting absolute coordinates, such as tablets
1369 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1370 is similar to kernelcore except it specifies the
1371 amount of memory used for migratable allocations.
1372 If both kernelcore and movablecore is specified,
1373 then kernelcore will be at *least* the specified
1374 value but may be more. If movablecore on its own
1375 is specified, the administrator must be careful
1376 that the amount of memory usable for all allocations
1382 MTD_Partition= [MTD]
1383 Format: <name>,<region-number>,<size>,<offset>
1385 MTD_Region= [MTD] Format:
1386 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1389 See drivers/mtd/cmdlinepart.c.
1392 ARM/S3C2412 JIVE boot control
1394 See arch/arm/mach-s3c2412/mach-jive.c
1396 mtouchusb.raw_coordinates=
1397 [HW] Make the MicroTouch USB driver use raw coordinates
1398 ('y', default) or cooked coordinates ('n')
1400 mtrr_chunk_size=nn[KMG] [X86]
1401 used for mtrr cleanup. It is largest continous chunk
1402 that could hold holes aka. UC entries.
1404 mtrr_gran_size=nn[KMG] [X86]
1405 Used for mtrr cleanup. It is granularity of mtrr block.
1407 Large value could prevent small alignment from
1410 mtrr_spare_reg_nr=n [X86]
1412 Range: 0,7 : spare reg number
1414 Used for mtrr cleanup. It is spare mtrr entries number.
1415 Set to 2 or more if your graphical card needs more.
1417 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1420 See header of drivers/scsi/NCR_D700.c.
1424 ncr53c400= [HW,SCSI]
1426 ncr53c400a= [HW,SCSI]
1428 ncr53c406a= [HW,SCSI]
1430 ncr53c8xx= [HW,SCSI]
1432 netdev= [NET] Network devices parameters
1433 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1434 Note that mem_start is often overloaded to mean
1435 something different and driver-specific.
1436 This usage is only documented in each driver source
1440 [NETFILTER] Enable connection tracking flow accounting
1441 0 to disable accounting
1442 1 to enable accounting
1443 Default value depends on CONFIG_NF_CT_ACCT that is
1444 going to be removed in 2.6.29.
1447 See Documentation/filesystems/nfsroot.txt.
1449 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1450 See Documentation/filesystems/nfsroot.txt.
1452 nfs.callback_tcpport=
1453 [NFS] set the TCP port on which the NFSv4 callback
1454 channel should listen.
1456 nfs.idmap_cache_timeout=
1457 [NFS] set the maximum lifetime for idmapper cache
1461 [NFS] enable 64-bit inode numbers.
1462 If zero, the NFS client will fake up a 32-bit inode
1463 number for the readdir() and stat() syscalls instead
1464 of returning the full 64-bit number.
1465 The default is to return 64-bit inode numbers.
1467 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1468 when a NMI is triggered.
1469 Format: [state][,regs][,debounce][,die]
1471 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1472 Format: [panic,][num]
1474 0 - turn nmi_watchdog off
1475 1 - use the IO-APIC timer for the NMI watchdog
1476 2 - use the local APIC for the NMI watchdog using
1477 a performance counter. Note: This will use one
1478 performance counter and the local APIC's performance
1480 When panic is specified, panic when an NMI watchdog
1482 This is useful when you use a panic=... timeout and
1483 need the box quickly up again.
1484 Instead of 1 and 2 it is possible to use the following
1485 symbolic names: lapic and ioapic
1486 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1488 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1489 emulation library even if a 387 maths coprocessor
1493 [HW] Never suspend the console
1494 Disable suspending of consoles during suspend and
1495 hibernate operations. Once disabled, debugging
1496 messages can reach various consoles while the rest
1497 of the system is being put to sleep (ie, while
1498 debugging driver suspend/resume hooks). This may
1499 not work reliably with all consoles, but is known
1500 to work with serial and VGA consoles.
1502 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1503 caches in the slab allocator. Saves per-node memory,
1504 but will impact performance.
1508 noapic [SMP,APIC] Tells the kernel to not make use of any
1509 IOAPICs that may be present in the system.
1511 nobats [PPC] Do not use BATs for mapping kernel lowmem
1512 on "Classic" PPC cores.
1516 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1518 nodelayacct [KNL] Disable per-task delay accounting
1520 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1522 nodsp [SH] Disable hardware DSP at boot time.
1524 noefi [X86] Disable EFI runtime services support.
1529 On X86-32 available only on PAE configured kernels.
1530 noexec=on: enable non-executable mappings (default)
1531 noexec=off: disable non-executable mappings
1534 This affects only 32-bit executables.
1535 noexec32=on: enable non-executable mappings (default)
1536 read doesn't imply executable mappings
1537 noexec32=off: disable non-executable mappings
1538 read implies executable mappings
1540 nofpu [SH] Disable hardware FPU at boot time.
1542 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1543 register save and restore. The kernel will only save
1544 legacy floating-point registers on task switch.
1546 noxsave [BUGS=X86] Disables x86 extended register state save
1547 and restore using xsave. The kernel will fallback to
1548 enabling legacy floating-point and sse state.
1550 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1551 wfi(ARM) instruction doesn't work correctly and not to
1552 use it. This is also useful when using JTAG debugger.
1554 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1555 instruction doesn't work correctly and not to
1558 no_file_caps Tells the kernel not to honor file capabilities. The
1559 only way then for a file to be executed with privilege
1560 is to be setuid root or executed by root.
1562 nohalt [IA-64] Tells the kernel not to use the power saving
1563 function PAL_HALT_LIGHT when idle. This increases
1564 power-consumption. On the positive side, it reduces
1565 interrupt wake-up latency, which may improve performance
1566 in certain environments such as networked servers or
1569 nohz= [KNL] Boottime enable/disable dynamic ticks
1570 Valid arguments: on, off
1573 noiotrap [SH] Disables trapped I/O port accesses.
1575 noirqdebug [X86-32] Disables the code which attempts to detect and
1576 disable unhandled interrupt sources.
1578 no_timer_check [X86,APIC] Disables the code which tests for
1579 broken timer IRQ sources.
1581 noisapnp [ISAPNP] Disables ISA PnP code.
1583 noinitrd [RAM] Tells the kernel not to load any configured
1586 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1591 nojitter [IA64] Disables jitter checking for ITC timers.
1593 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1595 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1597 noltlbs [PPC] Do not use large page/tlb entries for kernel
1598 lowmem mapping on PPC40x.
1600 nomca [IA-64] Disable machine check abort handling
1602 nomce [X86-32] Machine Check Exception
1604 nomfgpt [X86-32] Disable Multi-Function General Purpose
1605 Timer usage (for AMD Geode machines).
1607 norandmaps Don't use address space randomization. Equivalent to
1608 echo 0 > /proc/sys/kernel/randomize_va_space
1610 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1612 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1613 with UP alternatives
1615 noresidual [PPC] Don't use residual data on PReP machines.
1617 noresume [SWSUSP] Disables resume and restores original swap
1620 no-scroll [VGA] Disables scrollback.
1621 This is required for the Braillex ib80-piezo Braille
1622 reader made by F.H. Papenmeier (Germany).
1626 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1628 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1629 and disable the IO APIC. legacy for "maxcpus=0".
1631 nosoftlockup [KNL] Disable the soft-lockup detector.
1633 noswapaccount [KNL] Disable accounting of swap in memory resource
1634 controller. (See Documentation/cgroups/memory.txt)
1636 nosync [HW,M68K] Disables sync negotiation for all devices.
1638 notsc [BUGS=X86-32] Disable Time Stamp Counter
1640 nousb [USB] Disable the USB subsystem
1644 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1646 nptcg= [IA64] Override max number of concurrent global TLB
1647 purges which is reported from either PAL_VM_SUMMARY or
1650 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1652 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1653 one of ['zone', 'node', 'default'] can be specified
1654 This can be set from sysctl after boot.
1655 See Documentation/sysctl/vm.txt for details.
1657 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1658 See Documentation/debugging-via-ohci1394.txt for more
1661 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1662 Rather than timing out after 20 ms if an EC
1663 command is not properly ACKed, override the length
1664 of the timeout. We have interrupts disabled while
1665 waiting for the ACK, so if this is set too high
1666 interrupts *may* be lost!
1671 oprofile.timer= [HW]
1672 Use timer interrupt instead of performance counters
1674 osst= [HW,SCSI] SCSI Tape Driver
1675 Format: <buffer_size>,<write_threshold>
1676 See also Documentation/scsi/st.txt.
1678 panic= [KNL] Kernel behaviour on panic
1681 parkbd.port= [HW] Parallel port number the keyboard adapter is
1682 connected to, default is 0.
1684 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1685 0 for XT, 1 for AT (default is AT).
1688 parport= [HW,PPT] Specify parallel ports. 0 disables.
1689 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1690 Use 'auto' to force the driver to use any
1691 IRQ/DMA settings detected (the default is to
1692 ignore detected IRQ/DMA settings because of
1693 possible conflicts). You can specify the base
1694 address, IRQ, and DMA settings; IRQ and DMA
1695 should be numbers, or 'auto' (for using detected
1696 settings on that particular port), or 'nofifo'
1697 (to avoid using a FIFO even if it is detected).
1698 Parallel ports are assigned in the order they
1699 are specified on the command line, starting
1702 parport_init_mode= [HW,PPT]
1703 Configure VIA parallel port to operate in
1704 a specific mode. This is necessary on Pegasos
1705 computer where firmware has no options for setting
1706 up parallel port mode and sets it to spp.
1707 Currently this function knows 686a and 8231 chips.
1708 Format: [spp|ps2|epp|ecp|ecpepp]
1710 pas2= [HW,OSS] Format:
1711 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1714 See header of drivers/scsi/pas16.c.
1717 Halt all CPUs after the first oops has been printed for
1718 the specified number of seconds. This is to be used if
1719 your oopses keep scrolling off the screen.
1724 See header of drivers/block/paride/pcd.c.
1725 See also Documentation/blockdev/paride.txt.
1727 pci=option[,option...] [PCI] various PCI subsystem options:
1728 earlydump [X86] dump PCI config space before the kernel
1730 off [X86] don't probe for the PCI bus
1731 bios [X86-32] force use of PCI BIOS, don't access
1732 the hardware directly. Use this if your machine
1733 has a non-standard PCI host bridge.
1734 nobios [X86-32] disallow use of PCI BIOS, only direct
1735 hardware access methods are allowed. Use this
1736 if you experience crashes upon bootup and you
1737 suspect they are caused by the BIOS.
1738 conf1 [X86] Force use of PCI Configuration
1740 conf2 [X86] Force use of PCI Configuration
1742 noaer [PCIE] If the PCIEAER kernel config parameter is
1743 enabled, this kernel boot option can be used to
1744 disable the use of PCIE advanced error reporting.
1745 nodomains [PCI] Disable support for multiple PCI
1746 root domains (aka PCI segments, in ACPI-speak).
1747 nommconf [X86] Disable use of MMCONFIG for PCI
1749 nomsi [MSI] If the PCI_MSI kernel config parameter is
1750 enabled, this kernel boot option can be used to
1751 disable the use of MSI interrupts system-wide.
1752 noioapicquirk [APIC] Disable all boot interrupt quirks.
1753 Safety option to keep boot IRQs enabled. This
1754 should never be necessary.
1755 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1756 primary IO-APIC for bridges that cannot disable
1757 boot IRQs. This fixes a source of spurious IRQs
1758 when the system masks IRQs.
1759 noioapicreroute [APIC] Disable workaround that uses the
1760 boot IRQ equivalent of an IRQ that connects to
1761 a chipset where boot IRQs cannot be disabled.
1762 The opposite of ioapicreroute.
1763 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1764 routing table. These calls are known to be buggy
1765 on several machines and they hang the machine
1766 when used, but on other computers it's the only
1767 way to get the interrupt routing table. Try
1768 this option if the kernel is unable to allocate
1769 IRQs or discover secondary PCI buses on your
1771 rom [X86] Assign address space to expansion ROMs.
1772 Use with caution as certain devices share
1773 address decoders between ROMs and other
1775 norom [X86] Do not assign address space to
1776 expansion ROMs that do not already have
1777 BIOS assigned address ranges.
1778 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1779 assigned automatically to PCI devices. You can
1780 make the kernel exclude IRQs of your ISA cards
1782 pirqaddr=0xAAAAA [X86] Specify the physical address
1783 of the PIRQ table (normally generated
1784 by the BIOS) if it is outside the
1785 F0000h-100000h range.
1786 lastbus=N [X86] Scan all buses thru bus #N. Can be
1787 useful if the kernel is unable to find your
1788 secondary buses and you want to tell it
1789 explicitly which ones they are.
1790 assign-busses [X86] Always assign all PCI bus
1791 numbers ourselves, overriding
1792 whatever the firmware may have done.
1793 usepirqmask [X86] Honor the possible IRQ mask stored
1794 in the BIOS $PIR table. This is needed on
1795 some systems with broken BIOSes, notably
1796 some HP Pavilion N5400 and Omnibook XE3
1797 notebooks. This will have no effect if ACPI
1798 IRQ routing is enabled.
1799 noacpi [X86] Do not use ACPI for IRQ routing
1800 or for PCI scanning.
1801 use_crs [X86] Use _CRS for PCI resource
1803 routeirq Do IRQ routing for all PCI devices.
1804 This is normally done in pci_enable_device(),
1805 so this option is a temporary workaround
1806 for broken drivers that don't call it.
1807 skip_isa_align [X86] do not align io start addr, so can
1808 handle more pci cards
1809 firmware [ARM] Do not re-enumerate the bus but instead
1810 just use the configuration from the
1811 bootloader. This is currently used on
1812 IXP2000 systems where the bus has to be
1813 configured a certain way for adjunct CPUs.
1814 noearly [X86] Don't do any early type 1 scanning.
1815 This might help on some broken boards which
1816 machine check when some devices' config space
1817 is read. But various workarounds are disabled
1818 and some IOMMU drivers will not work.
1819 bfsort Sort PCI devices into breadth-first order.
1820 This sorting is done to get a device
1821 order compatible with older (<= 2.4) kernels.
1822 nobfsort Don't sort PCI devices into breadth-first order.
1823 cbiosize=nn[KMG] The fixed amount of bus space which is
1824 reserved for the CardBus bridge's IO window.
1825 The default value is 256 bytes.
1826 cbmemsize=nn[KMG] The fixed amount of bus space which is
1827 reserved for the CardBus bridge's memory
1828 window. The default value is 64 megabytes.
1831 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1832 Specifies alignment and device to reassign
1833 aligned memory resources.
1834 If <order of align> is not specified,
1835 PAGE_SIZE is used as alignment.
1836 PCI-PCI bridge can be specified, if resource
1837 windows need to be expanded.
1839 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1842 force Enable ASPM even on devices that claim not to support it.
1843 WARNING: Forcing ASPM on may cause system lockups.
1845 pcmv= [HW,PCMCIA] BadgePAD 4
1848 See Documentation/blockdev/paride.txt.
1850 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1853 See arch/parisc/kernel/pdc_chassis.c
1856 See Documentation/blockdev/paride.txt.
1859 See Documentation/blockdev/paride.txt.
1861 pirq= [SMP,APIC] Manual mp-table setup
1862 See Documentation/x86/i386/IO-APIC.txt.
1864 plip= [PPT,NET] Parallel port network link
1865 Format: { parport<nr> | timid | 0 }
1866 See also Documentation/parport.txt.
1868 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1869 Override pmtimer IOPort with a hex value.
1873 Enable PNP debug messages. This depends on the
1874 CONFIG_PNP_DEBUG_MESSAGES option.
1880 { on | off | curr | res | no-curr | no-res }
1883 [ISAPNP] Exclude IRQs for the autoconfiguration
1886 [ISAPNP] Exclude DMAs for the autoconfiguration
1888 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1889 Ranges are in pairs (I/O port base and size).
1892 [ISAPNP] Exclude memory regions for the
1894 Ranges are in pairs (memory base and size).
1896 ports= [IP_VS_FTP] IPVS ftp helper module
1898 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1900 Format: <port>,<port>....
1902 print-fatal-signals=
1903 [KNL] debug: print fatal signals
1904 print-fatal-signals=1: print segfault info to
1908 printk.time= Show timing data prefixed to each printk message line
1909 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1911 processor.max_cstate= [HW,ACPI]
1912 Limit processor to maximum C-state
1913 max_cstate=9 overrides any DMI blacklist limit.
1915 processor.nocst [HW,ACPI]
1916 Ignore the _CST method to determine C-states,
1917 instead using the legacy FADT method
1919 profile= [KNL] Enable kernel profiling via /proc/profile
1920 Format: [schedule,]<number>
1921 Param: "schedule" - profile schedule points.
1922 Param: <number> - step/bucket size as a power of 2 for
1923 statistical time based profiling.
1924 Param: "sleep" - profile D-state sleeping (millisecs).
1925 Requires CONFIG_SCHEDSTATS
1926 Param: "kvm" - profile VM exits.
1928 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1930 See Documentation/blockdev/ramdisk.txt.
1932 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1933 probe for; one of (bare|imps|exps|lifebook|any).
1934 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1936 psmouse.resetafter= [HW,MOUSE]
1937 Try to reset the device after so many bad packets
1940 [HW,MOUSE] Set desired mouse resolution, in dpi.
1941 psmouse.smartscroll=
1942 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1943 0 = disabled, 1 = enabled (default).
1945 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1947 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1950 See Documentation/blockdev/paride.txt.
1953 [KNL] Number of legacy pty's. Overwrites compiled-in
1956 quiet [KNL] Disable most log messages
1961 See Documentation/md.txt.
1963 ramdisk_blocksize= [RAM]
1964 See Documentation/blockdev/ramdisk.txt.
1966 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1967 See Documentation/blockdev/ramdisk.txt.
1969 rcupdate.blimit= [KNL,BOOT]
1970 Set maximum number of finished RCU callbacks to process
1973 rcupdate.qhimark= [KNL,BOOT]
1974 Set threshold of queued
1975 RCU callbacks over which batch limiting is disabled.
1977 rcupdate.qlowmark= [KNL,BOOT]
1978 Set threshold of queued RCU callbacks below which
1979 batch limiting is re-enabled.
1983 Run specified binary instead of /init from the ramdisk,
1984 used for early userspace startup. See initrd.
1986 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1987 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1988 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1991 [KNL, SMP] Set scheduler's default relax_domain_level.
1992 See Documentation/cgroups/cpusets.txt.
1994 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1996 reservetop= [X86-32]
1998 Reserves a hole at the top of the kernel virtual
2001 reset_devices [KNL] Force drivers to reset the underlying device
2002 during initialization.
2005 Specify the partition device for software suspend
2007 resume_offset= [SWSUSP]
2008 Specify the offset from the beginning of the partition
2009 given by "resume=" at which the swap header is located,
2010 in <PAGE_SIZE> units (needed only for swap files).
2011 See Documentation/power/swsusp-and-swap-files.txt
2013 retain_initrd [RAM] Keep initrd memory after extraction
2015 rhash_entries= [KNL,NET]
2016 Set number of hash buckets for route cache
2018 riscom8= [HW,SERIAL]
2019 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2021 ro [KNL] Mount root device read-only on boot
2023 root= [KNL] Root filesystem
2025 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2026 mount the root filesystem
2028 rootflags= [KNL] Set root filesystem mount option string
2030 rootfstype= [KNL] Set root filesystem type
2032 rootwait [KNL] Wait (indefinitely) for root device to show up.
2033 Useful for devices that are detected asynchronously
2034 (e.g. USB and MMC devices).
2036 root_plug.vendor_id=
2037 [ROOTPLUG] Override the default vendor ID
2039 root_plug.product_id=
2040 [ROOTPLUG] Override the default product ID
2043 [ROOTPLUG] Enable debugging output
2045 rw [KNL] Mount root device read-write on boot
2047 S [KNL] Run init in single mode
2050 See drivers/net/irda/sa1100_ir.c.
2052 sbni= [NET] Granch SBNI12 leased line adapter
2054 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2055 Format: <io>[,<timeout>[,<isapnp>]]
2057 scsi_debug_*= [SCSI]
2058 See drivers/scsi/scsi_debug.c.
2060 scsi_default_dev_flags=
2061 [SCSI] SCSI default device flags
2064 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2065 Format: <vendor>:<model>:<flags>
2066 (flags are integer value)
2068 scsi_logging_level= [SCSI] a bit mask of logging levels
2069 See drivers/scsi/scsi_logging.h for bits. Also
2070 settable via sysctl at dev.scsi.logging_level
2071 (/proc/sys/dev/scsi/logging_level).
2072 There is also a nice 'scsi_logging_level' script in the
2073 S390-tools package, available for download at
2074 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2076 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2077 discovered. async scans them in kernel threads,
2078 allowing boot to proceed. none ignores them, expecting
2079 user space to do the scan.
2081 security= [SECURITY] Choose a security module to enable at boot.
2082 If this boot parameter is not specified, only the first
2083 security module asking for security registration will be
2084 loaded. An invalid security module name will be treated
2085 as if no module has been chosen.
2087 selinux= [SELINUX] Disable or enable SELinux at boot time.
2088 Format: { "0" | "1" }
2089 See security/selinux/Kconfig help text.
2092 Default value is set via kernel config option.
2093 If enabled at boot time, /selinux/disable can be used
2094 later to disable prior to initial policy load.
2096 serialnumber [BUGS=X86-32]
2099 Maximal number of shapers.
2101 show_msr= [x86] show boot-time MSR settings
2102 Format: { <integer> }
2103 Show boot-time (BIOS-initialized) MSR settings.
2104 The parameter means the number of CPUs to show,
2105 for example 1 means boot CPU only.
2108 See header of drivers/scsi/sim710.c.
2115 slub_debug[=options[,slabs]] [MM, SLUB]
2116 Enabling slub_debug allows one to determine the
2117 culprit if slab objects become corrupted. Enabling
2118 slub_debug can create guard zones around objects and
2119 may poison objects when not in use. Also tracks the
2120 last alloc / free. For more information see
2121 Documentation/vm/slub.txt.
2123 slub_max_order= [MM, SLUB]
2124 Determines the maximum allowed order for slabs.
2125 A high setting may cause OOMs due to memory
2126 fragmentation. For more information see
2127 Documentation/vm/slub.txt.
2129 slub_min_objects= [MM, SLUB]
2130 The minimum number of objects per slab. SLUB will
2131 increase the slab order up to slub_max_order to
2132 generate a sufficiently large slab able to contain
2133 the number of objects indicated. The higher the number
2134 of objects the smaller the overhead of tracking slabs
2135 and the less frequently locks need to be acquired.
2136 For more information see Documentation/vm/slub.txt.
2138 slub_min_order= [MM, SLUB]
2139 Determines the mininum page order for slabs. Must be
2140 lower than slub_max_order.
2141 For more information see Documentation/vm/slub.txt.
2143 slub_nomerge [MM, SLUB]
2144 Disable merging of slabs with similar size. May be
2145 necessary if there is some reason to distinguish
2146 allocs to different slabs. Debug options disable
2147 merging on their own.
2148 For more information see Documentation/vm/slub.txt.
2151 Format: <io1>[,<io2>[,...,<io8>]]
2153 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2154 attempt to substitute SMP alternatives once at boot.
2156 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2157 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2158 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2159 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2160 smsc-ircc2.ircc_irq= [HW] IRQ line
2161 smsc-ircc2.ircc_dma= [HW] DMA channel
2162 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2163 0: Toshiba Satellite 1800 (GP data pin select)
2164 1: Fast pin select (default)
2167 snd-ad1816a= [HW,ALSA]
2169 snd-ad1848= [HW,ALSA]
2171 snd-ali5451= [HW,ALSA]
2173 snd-als100= [HW,ALSA]
2175 snd-als4000= [HW,ALSA]
2177 snd-azt2320= [HW,ALSA]
2179 snd-cmi8330= [HW,ALSA]
2181 snd-cmipci= [HW,ALSA]
2183 snd-cs4231= [HW,ALSA]
2185 snd-cs4232= [HW,ALSA]
2187 snd-cs4236= [HW,ALSA]
2189 snd-cs4281= [HW,ALSA]
2191 snd-cs46xx= [HW,ALSA]
2193 snd-dt019x= [HW,ALSA]
2195 snd-dummy= [HW,ALSA]
2197 snd-emu10k1= [HW,ALSA]
2199 snd-ens1370= [HW,ALSA]
2201 snd-ens1371= [HW,ALSA]
2203 snd-es968= [HW,ALSA]
2205 snd-es1688= [HW,ALSA]
2207 snd-es18xx= [HW,ALSA]
2209 snd-es1938= [HW,ALSA]
2211 snd-es1968= [HW,ALSA]
2213 snd-fm801= [HW,ALSA]
2215 snd-gusclassic= [HW,ALSA]
2217 snd-gusextreme= [HW,ALSA]
2219 snd-gusmax= [HW,ALSA]
2223 snd-ice1712= [HW,ALSA]
2225 snd-intel8x0= [HW,ALSA]
2227 snd-interwave= [HW,ALSA]
2232 snd-korg1212= [HW,ALSA]
2234 snd-maestro3= [HW,ALSA]
2236 snd-mpu401= [HW,ALSA]
2238 snd-mtpav= [HW,ALSA]
2240 snd-nm256= [HW,ALSA]
2242 snd-opl3sa2= [HW,ALSA]
2250 snd-opti93x= [HW,ALSA]
2254 snd-rme32= [HW,ALSA]
2256 snd-rme96= [HW,ALSA]
2258 snd-rme9652= [HW,ALSA]
2264 snd-sbawe= [HW,ALSA]
2266 snd-serial= [HW,ALSA]
2268 snd-sgalaxy= [HW,ALSA]
2270 snd-sonicvibes= [HW,ALSA]
2275 snd-sun-cs4231= [HW,ALSA]
2277 snd-trident= [HW,ALSA]
2279 snd-usb-audio= [HW,ALSA,USB]
2281 snd-via82xx= [HW,ALSA]
2283 snd-virmidi= [HW,ALSA]
2285 snd-wavefront= [HW,ALSA]
2287 snd-ymfpci= [HW,ALSA]
2290 [KNL] Should the soft-lockup detector generate panics.
2292 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2293 See Documentation/sonypi.txt
2295 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2296 See Documentation/serial/specialix.txt.
2298 spia_io_base= [HW,MTD]
2304 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2306 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2307 See Documentation/scsi/st.txt.
2310 Enabled the stack tracer on boot up.
2314 Set the STI (builtin display/keyboard on the HP-PARISC
2315 machines) console (graphic card) which should be used
2316 as the initial boot-console.
2317 See also comment in drivers/video/console/sticore.c.
2320 See comment in drivers/video/console/sticore.c.
2323 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2327 Control how the NFS server code allocates CPUs to
2328 service thread pools. Depending on how many NICs
2329 you have and where their interrupts are bound, this
2330 option will affect which CPUs will do NFS serving.
2331 Note: this parameter cannot be changed while the
2332 NFS server is running.
2334 auto the server chooses an appropriate mode
2335 automatically using heuristics
2336 global a single global pool contains all CPUs
2337 percpu one pool for each CPU
2338 pernode one pool for each NUMA node (equivalent
2339 to global on non-NUMA machines)
2341 swiotlb= [IA-64] Number of I/O TLB slabs
2345 sym53c416= [HW,SCSI]
2346 See header of drivers/scsi/sym53c416.c.
2348 sysrq_always_enabled
2350 Ignore sysrq setting - this boot parameter will
2351 neutralize any effect of /proc/sys/kernel/sysrq.
2352 Useful for debugging.
2355 See header of drivers/scsi/t128.c.
2359 test_suspend= [SUSPEND]
2360 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2361 standby suspend) as the system sleep state to briefly
2362 enter during system startup. The system is woken from
2363 this state using a wakeup-capable RTC alarm.
2365 thash_entries= [KNL,NET]
2366 Set number of hash buckets for TCP connection
2368 thermal.act= [HW,ACPI]
2369 -1: disable all active trip points in all thermal zones
2370 <degrees C>: override all lowest active trip points
2372 thermal.crt= [HW,ACPI]
2373 -1: disable all critical trip points in all thermal zones
2374 <degrees C>: override all critical trip points
2376 thermal.nocrt= [HW,ACPI]
2377 Set to disable actions on ACPI thermal zone
2378 critical and hot trip points.
2380 thermal.off= [HW,ACPI]
2381 1: disable ACPI thermal control
2383 thermal.psv= [HW,ACPI]
2384 -1: disable all passive trip points
2385 <degrees C>: override all passive trip points to this
2388 thermal.tzp= [HW,ACPI]
2389 Specify global default ACPI thermal zone polling rate
2390 <deci-seconds>: poll all this frequency
2391 0: no polling (default)
2394 See comment before function dc390_setup() in
2395 drivers/scsi/tmscsim.c.
2399 Specify if the kernel should make use of the cpu
2400 topology informations if the hardware supports these.
2401 The scheduler will make use of these informations and
2402 e.g. base its process migration decisions on it.
2407 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2409 trix= [HW,OSS] MediaTrix AudioTrix Pro
2411 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2413 tsc= Disable clocksource-must-verify flag for TSC.
2415 [x86] reliable: mark tsc clocksource as reliable, this
2416 disables clocksource verification at runtime.
2417 Used to enable high-resolution timer mode on older
2418 hardware, and in virtualized environment.
2420 turbografx.map[2|3]= [HW,JOY]
2421 TurboGraFX parallel port interface
2423 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2424 See also Documentation/input/joystick-parport.txt
2426 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2427 See header of drivers/scsi/u14-34f.c.
2436 [USB] Ignore overcurrent events (default N).
2437 Some badly-designed motherboards generate lots of
2438 bogus events, for ports that aren't wired to
2439 anything. Set this parameter to avoid log spamming.
2440 Note that genuine overcurrent events won't be
2445 Set unknown_nmi_panic=1 early on boot.
2447 usbcore.autosuspend=
2448 [USB] The autosuspend time delay (in seconds) used
2449 for newly-detected USB devices (default 2). This
2450 is the time required before an idle device will be
2451 autosuspended. Devices for which the delay is set
2452 to a negative value won't be autosuspended at all.
2454 usbcore.usbfs_snoop=
2455 [USB] Set to log all usbfs traffic (default 0 = off).
2457 usbcore.blinkenlights=
2458 [USB] Set to cycle leds on hubs (default 0 = off).
2460 usbcore.old_scheme_first=
2461 [USB] Start with the old device initialization
2462 scheme (default 0 = off).
2464 usbcore.use_both_schemes=
2465 [USB] Try the other device initialization scheme
2466 if the first one fails (default 1 = enabled).
2468 usbcore.initial_descriptor_timeout=
2469 [USB] Specifies timeout for the initial 64-byte
2470 USB_REQ_GET_DESCRIPTOR request in milliseconds
2471 (default 5000 = 5.0 seconds).
2474 [USBHID] The interval which mice are to be polled at.
2476 usb-storage.delay_use=
2477 [UMS] The delay in seconds before a new device is
2478 scanned for Logical Units (default 5).
2481 [UMS] A list of quirks entries to supplement or
2482 override the built-in unusual_devs list. List
2483 entries are separated by commas. Each entry has
2484 the form VID:PID:Flags where VID and PID are Vendor
2485 and Product ID values (4-digit hex numbers) and
2486 Flags is a set of characters, each corresponding
2487 to a common usb-storage quirk flag as follows:
2488 a = SANE_SENSE (collect more than 18 bytes
2490 c = FIX_CAPACITY (decrease the reported
2491 device capacity by one sector);
2492 h = CAPACITY_HEURISTICS (decrease the
2493 reported device capacity by one
2494 sector if the number is odd);
2495 i = IGNORE_DEVICE (don't bind to this
2497 l = NOT_LOCKABLE (don't try to lock and
2498 unlock ejectable media);
2499 m = MAX_SECTORS_64 (don't transfer more
2500 than 64 sectors = 32 KB at a time);
2501 o = CAPACITY_OK (accept the capacity
2502 reported by the device);
2503 r = IGNORE_RESIDUE (the device reports
2504 bogus residue values);
2505 s = SINGLE_LUN (the device has only one
2507 w = NO_WP_DETECT (don't test whether the
2508 medium is write-protected).
2509 Example: quirks=0419:aaf5:rl,0421:0433:rc
2512 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2513 vdso=1: enable VDSO (default)
2514 vdso=0: disable VDSO mapping
2517 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2518 vdso32=1: enable 32-bit VDSO (default)
2519 vdso32=0: disable 32-bit VDSO mapping
2522 vector=percpu: enable percpu vector domain
2524 video= [FB] Frame buffer configuration
2525 See Documentation/fb/modedb.txt.
2527 vga= [BOOT,X86-32] Select a particular video mode
2528 See Documentation/x86/boot.txt and
2529 Documentation/svga.txt.
2530 Use vga=ask for menu.
2531 This is actually a boot loader parameter; the value is
2532 passed to the kernel using a special protocol.
2534 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2535 size of <nn>. This can be used to increase the
2536 minimum size (128MB on x86). It can also be used to
2537 decrease the size and leave more room for directly
2540 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2543 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2546 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2549 vt.default_blu= [VT]
2550 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2551 Change the default blue palette of the console.
2552 This is a 16-member array composed of values
2555 vt.default_grn= [VT]
2556 Format: <green0>,<green1>,<green2>,...,<green15>
2557 Change the default green palette of the console.
2558 This is a 16-member array composed of values
2561 vt.default_red= [VT]
2562 Format: <red0>,<red1>,<red2>,...,<red15>
2563 Change the default red palette of the console.
2564 This is a 16-member array composed of values
2570 Set system-wide default UTF-8 mode for all tty's.
2571 Default is 1, i.e. UTF-8 mode is enabled for all
2572 newly opened terminals.
2574 waveartist= [HW,OSS]
2575 Format: <io>,<irq>,<dma>,<dma2>
2578 See header of drivers/scsi/wd33c93.c.
2581 See header of drivers/scsi/wd7000.c.
2584 See Documentation/watchdog/wdt.txt.
2586 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2587 default x2apic cluster mode on platforms
2590 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2591 xd_geo= See header of drivers/block/xd.c.
2593 xirc2ps_cs= [NET,PCMCIA]
2595 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2597 ______________________________________________________________________
2601 Add documentation for ALSA options.
2602 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob