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.
648 dynamic_printk Enables pr_debug()/dev_dbg() calls if
649 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
650 These can also be switched on/off via
651 <debugfs>/dynamic_printk/modules
653 earlycon= [KNL] Output early console device and options.
654 uart[8250],io,<addr>[,options]
655 uart[8250],mmio,<addr>[,options]
656 Start an early, polled-mode console on the 8250/16550
657 UART at the specified I/O port or MMIO address.
658 The options are the same as for ttyS, above.
660 earlyprintk= [X86,SH,BLACKFIN]
662 earlyprintk=serial[,ttySn[,baudrate]]
665 Append ",keep" to not disable it when the real console
668 Only vga or serial or usb debug port at a time.
670 Currently only ttyS0 and ttyS1 are supported.
672 Interaction with the standard serial driver is not
675 The VGA output is eventually overwritten by the real
681 Format: {"off" | "on" | "skip[mbr]"}
683 eisa_irq_edge= [PARISC,HW]
684 See header of drivers/parisc/eisa.c.
687 See comment before function elanfreq_setup() in
688 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
691 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
692 See Documentation/block/as-iosched.txt and
693 Documentation/block/deadline-iosched.txt for details.
695 elfcorehdr= [IA64,PPC,SH,X86]
696 Specifies physical address of start of kernel core
697 image elf header. Generally kexec loader will
698 pass this option to capture kernel.
699 See Documentation/kdump/kdump.txt for details.
701 enable_mtrr_cleanup [X86]
702 The kernel tries to adjust MTRR layout from continuous
703 to discrete, to make X server driver able to add WB
704 entry later. This parameter enables that.
706 enable_timer_pin_1 [X86]
707 Enable PIN 1 of APIC timer
708 Can be useful to work around chipset bugs
709 (in particular on some ATI chipsets).
710 The kernel tries to set a reasonable default.
712 enforcing [SELINUX] Set initial enforcing status.
714 See security/selinux/Kconfig help text.
715 0 -- permissive (log only, no denials).
716 1 -- enforcing (deny and log).
718 Value can be changed at runtime via /selinux/enforce.
720 ether= [HW,NET] Ethernet cards parameters
721 This option is obsoleted by the "netdev=" option, which
722 has equivalent usage. See its documentation for details.
724 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
729 fail_make_request=[KNL]
730 General fault injection mechanism.
731 Format: <interval>,<probability>,<space>,<times>
732 See also /Documentation/fault-injection/.
735 See header of drivers/scsi/fd_mcs.c.
738 See header of drivers/scsi/fdomain.c.
741 See Documentation/blockdev/floppy.txt.
743 force_pal_cache_flush
744 [IA-64] Avoid check_sal_cache_flush which may hang on
745 buggy SAL_CACHE_FLUSH implementations. Using this
746 parameter will force ia64_sal_cache_flush to call
747 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
750 [ftrace] will set and start the specified tracer
751 as early as possible in order to facilitate early
755 [ftrace] will dump the trace buffers on oops.
758 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
759 support via parallel port (up to 5 devices per port)
760 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
761 See also Documentation/input/joystick-parport.txt
765 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
770 See header of drivers/scsi/gdth.c.
772 gpt [EFI] Forces disk with valid GPT signature but
773 invalid Protective MBR to be treated as GPT.
777 hashdist= [KNL,NUMA] Large hashes allocated during boot
778 are distributed across NUMA nodes. Defaults on
779 for 64bit NUMA, off otherwise.
780 Format: 0 | 1 (for off | on)
782 hcl= [IA-64] SGI's Hardware Graph compatibility layer
784 hd= [EIDE] (E)IDE hard drive subsystem geometry
785 Format: <cyl>,<head>,<sect>
787 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
788 size of <nn>. This works even on boxes that have no
789 highmem otherwise. This also works to reduce highmem
790 size on bigger boxes.
792 highres= [KNL] Enable/disable high resolution timer mode.
793 Valid parameters: "on", "off"
797 See Documentation/isdn/README.HiSax.
801 hpet= [X86-32,HPET] option to control HPET usage
802 Format: { enable (default) | disable | force |
804 disable: disable HPET and use PIT instead
805 force: allow force enabled of undocumented chips (ICH4,
807 verbose: show contents of HPET registers during setup
809 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
810 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
811 On x86-64 and powerpc, this option can be specified
812 multiple times interleaved with hugepages= to reserve
813 huge pages of different sizes. Valid pages sizes on
814 x86-64 are 2M (when the CPU supports "pse") and 1G
815 (when the CPU supports the "pdpe1gb" cpuinfo flag)
816 Note that 1GB pages can only be allocated at boot time
817 using hugepages= and not freed afterwards.
819 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
820 terminal devices. Valid values: 0..8
821 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
822 If specified, z/VM IUCV HVC accepts connections
823 from listed z/VM user IDs only.
825 i2c_bus= [HW] Override the default board specific I2C bus speed
826 or register an additional I2C bus that is not
827 registered from board initialization code.
831 i8042.debug [HW] Toggle i8042 debug mode
832 i8042.direct [HW] Put keyboard port into non-translated mode
833 i8042.dumbkbd [HW] Pretend that controller can only read data from
834 keyboard and cannot control its state
835 (Don't attempt to blink the leds)
836 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
837 i8042.nokbd [HW] Don't check/create keyboard port
838 i8042.noloop [HW] Disable the AUX Loopback command while probing
840 i8042.nomux [HW] Don't check presence of an active multiplexing
842 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
845 [HW] Frequency with which keyboard LEDs should blink
846 when kernel panics (default is 0.5 sec)
847 i8042.reset [HW] Reset the controller during init and cleanup
848 i8042.unlock [HW] Unlock (ignore) the keylock
852 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
853 indicates that the driver is running on unsupported
855 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
856 does not match list of supported models.
858 [HW] Report power status in /proc/i8k
859 (disabled by default)
860 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
863 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
864 See Documentation/mca.txt.
867 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
869 ide-core.nodma= [HW] (E)IDE subsystem
870 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
871 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
872 .chs .ignore_cable are additional options
873 See Documentation/ide/ide.txt.
875 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
876 See Documentation/ide/ide.txt.
878 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
879 Claim all unknown PCI IDE storage controllers.
882 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
883 Poll forces a polling idle loop that can slightly
884 improve the performance of waking up a idle CPU, but
885 will use a lot of power and make the system run hot.
887 idle=mwait: On systems which support MONITOR/MWAIT but
888 the kernel chose to not use it because it doesn't save
889 as much power as a normal idle loop, use the
890 MONITOR/MWAIT idle loop anyways. Performance should be
891 the same as idle=poll.
892 idle=halt: Halt is forced to be used for CPU idle.
893 In such case C2/C3 won't be used again.
894 idle=nomwait: Disable mwait for CPU C-states
896 ignore_loglevel [KNL]
897 Ignore loglevel setting - this will print /all/
898 kernel messages to the console. Useful for debugging.
901 Set number of hash buckets for inode cache.
904 Format: { "0" | "1" }
905 0 -- integrity auditing messages. (Default)
906 1 -- enable informational integrity auditing messages.
909 Formt: { "sha1" | "md5" }
913 See header of drivers/scsi/in2000.c.
917 Run specified binary instead of /sbin/init as init
920 initcall_debug [KNL] Trace initcalls as they are executed. Useful
921 for working out where the kernel is dying during
924 initrd= [BOOT] Specify the location of the initial ramdisk
926 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
929 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
931 Enable intel iommu driver.
933 Disable intel iommu driver.
934 igfx_off [Default Off]
935 By default, gfx is mapped as normal device. If a gfx
936 device has a dedicated DMAR unit, the DMAR unit is
937 bypassed by not enabling DMAR with this option. In
938 this case, gfx device will use physical address for
941 With this option iommu will not optimize to look
942 for io virtual address below 32 bit forcing dual
943 address cycle on pci bus for cards supporting greater
944 than 32 bit addressing. The default is to look
945 for translation below 32 bit and if not available
946 then look in the higher range.
948 With this option on every unmap_single operation will
949 result in a hardware IOTLB flush operation as opposed
950 to batching them for performance.
954 iomem= Disable strict checking of access to MMIO memory
955 strict regions from userspace.
970 io7= [HW] IO7 for Marvel based alpha systems
971 See comment before marvel_specify_io7 in
972 arch/alpha/kernel/core_marvel.c.
974 io_delay= [X86] I/O delay method
976 Standard port 0x80 based delay
978 Alternate port 0xed based delay (needed on some systems)
980 Simple two microseconds delay
985 See Documentation/filesystems/nfsroot.txt.
987 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
988 See comment before ip2_setup() in
989 drivers/char/ip2/ip2base.c.
991 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
992 See header of drivers/scsi/ips.c.
995 When an interrupt is not handled search all handlers
996 for it. Intended to get systems with badly broken
1000 When an interrupt is not handled search all handlers
1001 for it. Also check all handlers each timer
1002 interrupt. Intended to get systems with badly broken
1006 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1008 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1010 <cpu number>,...,<cpu number>
1012 <cpu number>-<cpu number>
1013 (must be a positive range in ascending order)
1015 <cpu number>,...,<cpu number>-<cpu number>
1017 This option can be used to specify one or more CPUs
1018 to isolate from the general SMP balancing and scheduling
1019 algorithms. You can move a process onto or off an
1020 "isolated" CPU via the CPU affinity syscalls or cpuset.
1021 <cpu number> begins at 0 and the maximum value is
1022 "number of CPUs in system - 1".
1024 This option is the preferred way to isolate CPUs. The
1025 alternative -- manually setting the CPU mask of all
1026 tasks in the system -- can cause problems and
1027 suboptimal load balancer performance.
1031 js= [HW,JOY] Analog joystick
1032 See Documentation/input/joystick.txt.
1036 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1037 specifies the amount of memory usable by the kernel
1038 for non-movable allocations. The requested amount is
1039 spread evenly throughout all nodes in the system. The
1040 remaining memory in each node is used for Movable
1041 pages. In the event, a node is too small to have both
1042 kernelcore and Movable pages, kernelcore pages will
1043 take priority and other nodes will have a larger number
1044 of kernelcore pages. The Movable zone is used for the
1045 allocation of pages that may be reclaimed or moved
1046 by the page migration subsystem. This means that
1047 HugeTLB pages may not be allocated from this zone.
1048 Note that allocations like PTEs-from-HighMem still
1049 use the HighMem zone if it exists, and the Normal
1050 zone if it does not.
1052 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1053 Controls whether kmemtrace is enabled
1056 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1057 subbufs kmemtrace's relay channel has. Set this
1058 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1059 you experience buffer overruns.
1061 kgdboc= [HW] kgdb over consoles.
1062 Requires a tty driver that supports console polling.
1063 (only serial suported for now)
1064 Format: <serial_device>[,baud]
1066 kmac= [MIPS] korina ethernet MAC address.
1067 Configure the RouterBoard 532 series on-chip
1068 Ethernet adapter MAC address.
1070 kstack=N [X86] Print N words from the kernel stack
1077 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1080 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1083 libata.dma= [LIBATA] DMA control
1084 libata.dma=0 Disable all PATA and SATA DMA
1085 libata.dma=1 PATA and SATA Disk DMA only
1086 libata.dma=2 ATAPI (CDROM) DMA only
1087 libata.dma=4 Compact Flash DMA only
1088 Combinations also work, so libata.dma=3 enables DMA
1089 for disks and CDROMs, but not CFs.
1091 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1095 libata.force= [LIBATA] Force configurations. The format is comma
1096 separated list of "[ID:]VAL" where ID is
1097 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1098 matching port, link or device. Basically, it matches
1099 the ATA ID string printed on console by libata. If
1100 the whole ID part is omitted, the last PORT and DEVICE
1101 values are used. If ID hasn't been specified yet, the
1102 configuration applies to all ports, links and devices.
1104 If only DEVICE is omitted, the parameter applies to
1105 the port and all links and devices behind it. DEVICE
1106 number of 0 either selects the first device or the
1107 first fan-out link behind PMP device. It does not
1108 select the host link. DEVICE number of 15 selects the
1109 host link and device attached to it.
1111 The VAL specifies the configuration to force. As long
1112 as there's no ambiguity shortcut notation is allowed.
1113 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1114 The following configurations can be forced.
1116 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1117 Any ID with matching PORT is used.
1119 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1121 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1122 udma[/][16,25,33,44,66,100,133] notation is also
1125 * [no]ncq: Turn on or off NCQ.
1127 * nohrst, nosrst, norst: suppress hard, soft
1130 If there are multiple matching configurations changing
1131 the same attribute, the last one is used.
1133 lmb=debug [KNL] Enable lmb debug messages.
1135 load_ramdisk= [RAM] List of ramdisks to load from floppy
1136 See Documentation/blockdev/ramdisk.txt.
1138 lockd.nlm_grace_period=P [NFS] Assign grace period.
1141 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1144 lockd.nlm_timeout=T [NFS] Assign timeout value.
1147 lockd.nlm_udpport=M [NFS] Assign UDP port.
1150 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1153 loglevel= All Kernel Messages with a loglevel smaller than the
1154 console loglevel will be printed to the console. It can
1155 also be changed with klogd or other programs. The
1156 loglevels are defined as follows:
1158 0 (KERN_EMERG) system is unusable
1159 1 (KERN_ALERT) action must be taken immediately
1160 2 (KERN_CRIT) critical conditions
1161 3 (KERN_ERR) error conditions
1162 4 (KERN_WARNING) warning conditions
1163 5 (KERN_NOTICE) normal but significant condition
1164 6 (KERN_INFO) informational
1165 7 (KERN_DEBUG) debug-level messages
1167 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1168 Format: { n | nk | nM }
1169 n must be a power of two. The default size
1170 is set in the kernel config file.
1172 logo.nologo [FB] Disables display of the built-in Linux logo.
1173 This may be used to provide more screen space for
1174 kernel log messages and is useful when debugging
1175 kernel boot problems.
1177 lp=0 [LP] Specify parallel ports to use, e.g,
1178 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1179 lp=reset first parallel port). 'lp=0' disables the
1180 lp=auto printer driver. 'lp=reset' (which can be
1181 specified in addition to the ports) causes
1182 attached printers to be reset. Using
1183 lp=port1,port2,... specifies the parallel ports
1184 to associate lp devices with, starting with
1185 lp0. A port specification may be 'none' to skip
1186 that lp device, or a parport name such as
1187 'parport0'. Specifying 'lp=auto' instead of a
1188 port specification list means that device IDs
1189 from each port should be examined, to see if
1190 an IEEE 1284-compliant printer is attached; if
1191 so, the driver will manage that printer.
1192 See also header of drivers/char/lp.c.
1195 Sets loops_per_jiffy to given constant, thus avoiding
1196 time-consuming boot-time autodetection (up to 250 ms per
1197 CPU). 0 enables autodetection (default). To determine
1198 the correct value for your kernel, boot with normal
1199 autodetection and see what value is printed. Note that
1200 on SMP systems the preset will be applied to all CPUs,
1201 which is likely to cause problems if your CPUs need
1202 significantly divergent settings. An incorrect value
1203 will cause delays in the kernel to be wrong, leading to
1204 unpredictable I/O errors and other breakage. Although
1205 unlikely, in the extreme case this might damage your
1209 Format: <io>,<irq>,<dma>
1211 mac5380= [HW,SCSI] Format:
1212 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1214 machvec= [IA64] Force the use of a particular machine-vector
1215 (machvec) in a generic kernel.
1216 Example: machvec=hpzx1_swiotlb
1218 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1219 than or equal to this physical address is ignored.
1221 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1222 should make use of. maxcpus=n : n >= 0 limits the
1223 kernel to using 'n' processors. n=0 is a special case,
1224 it is equivalent to "nosmp", which also disables
1227 max_loop= [LOOP] Maximum number of loopback devices that can
1231 max_luns= [SCSI] Maximum number of LUNs to probe.
1232 Should be between 1 and 2^32-1.
1235 [SCSI] Maximum number of LUNs received.
1236 Should be between 1 and 16384.
1240 mce [X86-32] Machine Check Exception
1242 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1244 md= [HW] RAID subsystems devices and level
1245 See Documentation/md.txt.
1248 Format: <first>,<last>
1249 Specifies range of consoles to be captured by the MDA.
1251 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1252 Amount of memory to be used when the kernel is not able
1253 to see the whole system memory or for test.
1254 [X86-32] Use together with memmap= to avoid physical
1255 address space collisions. Without memmap= PCI devices
1256 could be placed at addresses belonging to unused RAM.
1258 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1262 [KNL,SH] Allow user to override the default size for
1263 per-device physically contiguous DMA buffers.
1265 memmap=exactmap [KNL,X86] Enable setting of an exact
1266 E820 memory map, as specified by the user.
1267 Such memmap=exactmap lines can be constructed based on
1268 BIOS output or other requirements. See the memmap=nn@ss
1271 memmap=nn[KMG]@ss[KMG]
1272 [KNL] Force usage of a specific region of memory
1273 Region of memory to be used, from ss to ss+nn.
1275 memmap=nn[KMG]#ss[KMG]
1276 [KNL,ACPI] Mark specific memory as ACPI data.
1277 Region of memory to be used, from ss to ss+nn.
1279 memmap=nn[KMG]$ss[KMG]
1280 [KNL,ACPI] Mark specific memory as reserved.
1281 Region of memory to be used, from ss to ss+nn.
1282 Example: Exclude memory from 0x18690000-0x1869ffff
1283 memmap=64K$0x18690000
1285 memmap=0x10000$0x18690000
1287 memory_corruption_check=0/1 [X86]
1288 Some BIOSes seem to corrupt the first 64k of
1289 memory when doing things like suspend/resume.
1290 Setting this option will scan the memory
1291 looking for corruption. Enabling this will
1292 both detect corruption and prevent the kernel
1293 from using the memory being corrupted.
1294 However, its intended as a diagnostic tool; if
1295 repeatable BIOS-originated corruption always
1296 affects the same memory, you can use memmap=
1297 to prevent the kernel from using that memory.
1299 memory_corruption_check_size=size [X86]
1300 By default it checks for corruption in the low
1301 64k, making this memory unavailable for normal
1302 use. Use this parameter to scan for
1303 corruption in more or less memory.
1305 memory_corruption_check_period=seconds [X86]
1306 By default it checks for corruption every 60
1307 seconds. Use this parameter to check at some
1308 other rate. 0 disables periodic checking.
1310 memtest= [KNL,X86] Enable memtest
1312 default : 0 <disable>
1313 Specifies the number of memtest passes to be
1314 performed. Each pass selects another test
1315 pattern from a given set of patterns. Memtest
1316 fills the memory with this pattern, validates
1317 memory contents and reserves bad memory
1318 regions that are detected.
1320 meye.*= [HW] Set MotionEye Camera parameters
1321 See Documentation/video4linux/meye.txt.
1323 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1324 Multi-Function General Purpose Timers on AMD Geode
1327 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1328 the BIOS has incorrectly applied a workaround. TinyBIOS
1329 version 0.98 is known to be affected, 0.99 fixes the
1330 problem by letting the user disable the workaround.
1334 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1335 physical address is ignored.
1338 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1339 parameter allows control of the logging verbosity for
1340 the additional memory initialisation checks. A value
1341 of 0 disables mminit logging and a level of 4 will
1342 log everything. Information is printed at KERN_DEBUG
1343 so loglevel=8 may also need to be specified.
1346 [MOUSE] Maximum time between finger touching and
1347 leaving touchpad surface for touch to be considered
1348 a tap and be reported as a left button click (for
1349 touchpads working in absolute mode only).
1351 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1352 reporting absolute coordinates, such as tablets
1353 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1354 reporting absolute coordinates, such as tablets
1356 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1357 is similar to kernelcore except it specifies the
1358 amount of memory used for migratable allocations.
1359 If both kernelcore and movablecore is specified,
1360 then kernelcore will be at *least* the specified
1361 value but may be more. If movablecore on its own
1362 is specified, the administrator must be careful
1363 that the amount of memory usable for all allocations
1369 MTD_Partition= [MTD]
1370 Format: <name>,<region-number>,<size>,<offset>
1372 MTD_Region= [MTD] Format:
1373 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1376 See drivers/mtd/cmdlinepart.c.
1379 ARM/S3C2412 JIVE boot control
1381 See arch/arm/mach-s3c2412/mach-jive.c
1383 mtouchusb.raw_coordinates=
1384 [HW] Make the MicroTouch USB driver use raw coordinates
1385 ('y', default) or cooked coordinates ('n')
1387 mtrr_chunk_size=nn[KMG] [X86]
1388 used for mtrr cleanup. It is largest continous chunk
1389 that could hold holes aka. UC entries.
1391 mtrr_gran_size=nn[KMG] [X86]
1392 Used for mtrr cleanup. It is granularity of mtrr block.
1394 Large value could prevent small alignment from
1397 mtrr_spare_reg_nr=n [X86]
1399 Range: 0,7 : spare reg number
1401 Used for mtrr cleanup. It is spare mtrr entries number.
1402 Set to 2 or more if your graphical card needs more.
1404 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1407 See header of drivers/scsi/NCR_D700.c.
1411 ncr53c400= [HW,SCSI]
1413 ncr53c400a= [HW,SCSI]
1415 ncr53c406a= [HW,SCSI]
1417 ncr53c8xx= [HW,SCSI]
1419 netdev= [NET] Network devices parameters
1420 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1421 Note that mem_start is often overloaded to mean
1422 something different and driver-specific.
1423 This usage is only documented in each driver source
1427 [NETFILTER] Enable connection tracking flow accounting
1428 0 to disable accounting
1429 1 to enable accounting
1430 Default value depends on CONFIG_NF_CT_ACCT that is
1431 going to be removed in 2.6.29.
1434 See Documentation/filesystems/nfsroot.txt.
1436 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1437 See Documentation/filesystems/nfsroot.txt.
1439 nfs.callback_tcpport=
1440 [NFS] set the TCP port on which the NFSv4 callback
1441 channel should listen.
1443 nfs.idmap_cache_timeout=
1444 [NFS] set the maximum lifetime for idmapper cache
1448 [NFS] enable 64-bit inode numbers.
1449 If zero, the NFS client will fake up a 32-bit inode
1450 number for the readdir() and stat() syscalls instead
1451 of returning the full 64-bit number.
1452 The default is to return 64-bit inode numbers.
1454 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1455 when a NMI is triggered.
1456 Format: [state][,regs][,debounce][,die]
1458 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1459 Format: [panic,][num]
1461 0 - turn nmi_watchdog off
1462 1 - use the IO-APIC timer for the NMI watchdog
1463 2 - use the local APIC for the NMI watchdog using
1464 a performance counter. Note: This will use one
1465 performance counter and the local APIC's performance
1467 When panic is specified, panic when an NMI watchdog
1469 This is useful when you use a panic=... timeout and
1470 need the box quickly up again.
1471 Instead of 1 and 2 it is possible to use the following
1472 symbolic names: lapic and ioapic
1473 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1475 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1476 emulation library even if a 387 maths coprocessor
1480 [HW] Never suspend the console
1481 Disable suspending of consoles during suspend and
1482 hibernate operations. Once disabled, debugging
1483 messages can reach various consoles while the rest
1484 of the system is being put to sleep (ie, while
1485 debugging driver suspend/resume hooks). This may
1486 not work reliably with all consoles, but is known
1487 to work with serial and VGA consoles.
1489 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1490 caches in the slab allocator. Saves per-node memory,
1491 but will impact performance.
1495 noapic [SMP,APIC] Tells the kernel to not make use of any
1496 IOAPICs that may be present in the system.
1498 nobats [PPC] Do not use BATs for mapping kernel lowmem
1499 on "Classic" PPC cores.
1503 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1505 nodelayacct [KNL] Disable per-task delay accounting
1507 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1509 nodsp [SH] Disable hardware DSP at boot time.
1511 noefi [X86] Disable EFI runtime services support.
1516 On X86-32 available only on PAE configured kernels.
1517 noexec=on: enable non-executable mappings (default)
1518 noexec=off: disable non-executable mappings
1521 This affects only 32-bit executables.
1522 noexec32=on: enable non-executable mappings (default)
1523 read doesn't imply executable mappings
1524 noexec32=off: disable non-executable mappings
1525 read implies executable mappings
1527 nofpu [SH] Disable hardware FPU at boot time.
1529 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1530 register save and restore. The kernel will only save
1531 legacy floating-point registers on task switch.
1533 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1534 wfi(ARM) instruction doesn't work correctly and not to
1535 use it. This is also useful when using JTAG debugger.
1537 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1538 instruction doesn't work correctly and not to
1541 no_file_caps Tells the kernel not to honor file capabilities. The
1542 only way then for a file to be executed with privilege
1543 is to be setuid root or executed by root.
1545 nohalt [IA-64] Tells the kernel not to use the power saving
1546 function PAL_HALT_LIGHT when idle. This increases
1547 power-consumption. On the positive side, it reduces
1548 interrupt wake-up latency, which may improve performance
1549 in certain environments such as networked servers or
1552 nohz= [KNL] Boottime enable/disable dynamic ticks
1553 Valid arguments: on, off
1556 noiotrap [SH] Disables trapped I/O port accesses.
1558 noirqdebug [X86-32] Disables the code which attempts to detect and
1559 disable unhandled interrupt sources.
1561 no_timer_check [X86,APIC] Disables the code which tests for
1562 broken timer IRQ sources.
1564 noisapnp [ISAPNP] Disables ISA PnP code.
1566 noinitrd [RAM] Tells the kernel not to load any configured
1571 nojitter [IA64] Disables jitter checking for ITC timers.
1573 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1575 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1577 noltlbs [PPC] Do not use large page/tlb entries for kernel
1578 lowmem mapping on PPC40x.
1580 nomca [IA-64] Disable machine check abort handling
1582 nomce [X86-32] Machine Check Exception
1584 nomfgpt [X86-32] Disable Multi-Function General Purpose
1585 Timer usage (for AMD Geode machines).
1587 norandmaps Don't use address space randomization. Equivalent to
1588 echo 0 > /proc/sys/kernel/randomize_va_space
1590 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1592 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1593 with UP alternatives
1595 noresidual [PPC] Don't use residual data on PReP machines.
1597 noresume [SWSUSP] Disables resume and restores original swap
1600 no-scroll [VGA] Disables scrollback.
1601 This is required for the Braillex ib80-piezo Braille
1602 reader made by F.H. Papenmeier (Germany).
1606 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1608 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1609 and disable the IO APIC. legacy for "maxcpus=0".
1611 nosoftlockup [KNL] Disable the soft-lockup detector.
1613 noswapaccount [KNL] Disable accounting of swap in memory resource
1614 controller. (See Documentation/cgroups/memory.txt)
1616 nosync [HW,M68K] Disables sync negotiation for all devices.
1618 notsc [BUGS=X86-32] Disable Time Stamp Counter
1620 nousb [USB] Disable the USB subsystem
1624 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1626 nptcg= [IA64] Override max number of concurrent global TLB
1627 purges which is reported from either PAL_VM_SUMMARY or
1630 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1632 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1633 one of ['zone', 'node', 'default'] can be specified
1634 This can be set from sysctl after boot.
1635 See Documentation/sysctl/vm.txt for details.
1637 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1638 See Documentation/debugging-via-ohci1394.txt for more
1641 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1642 Rather than timing out after 20 ms if an EC
1643 command is not properly ACKed, override the length
1644 of the timeout. We have interrupts disabled while
1645 waiting for the ACK, so if this is set too high
1646 interrupts *may* be lost!
1651 oprofile.timer= [HW]
1652 Use timer interrupt instead of performance counters
1654 osst= [HW,SCSI] SCSI Tape Driver
1655 Format: <buffer_size>,<write_threshold>
1656 See also Documentation/scsi/st.txt.
1658 panic= [KNL] Kernel behaviour on panic
1661 parkbd.port= [HW] Parallel port number the keyboard adapter is
1662 connected to, default is 0.
1664 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1665 0 for XT, 1 for AT (default is AT).
1668 parport= [HW,PPT] Specify parallel ports. 0 disables.
1669 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1670 Use 'auto' to force the driver to use any
1671 IRQ/DMA settings detected (the default is to
1672 ignore detected IRQ/DMA settings because of
1673 possible conflicts). You can specify the base
1674 address, IRQ, and DMA settings; IRQ and DMA
1675 should be numbers, or 'auto' (for using detected
1676 settings on that particular port), or 'nofifo'
1677 (to avoid using a FIFO even if it is detected).
1678 Parallel ports are assigned in the order they
1679 are specified on the command line, starting
1682 parport_init_mode= [HW,PPT]
1683 Configure VIA parallel port to operate in
1684 a specific mode. This is necessary on Pegasos
1685 computer where firmware has no options for setting
1686 up parallel port mode and sets it to spp.
1687 Currently this function knows 686a and 8231 chips.
1688 Format: [spp|ps2|epp|ecp|ecpepp]
1690 pas2= [HW,OSS] Format:
1691 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1694 See header of drivers/scsi/pas16.c.
1697 Halt all CPUs after the first oops has been printed for
1698 the specified number of seconds. This is to be used if
1699 your oopses keep scrolling off the screen.
1704 See header of drivers/block/paride/pcd.c.
1705 See also Documentation/blockdev/paride.txt.
1707 pci=option[,option...] [PCI] various PCI subsystem options:
1708 earlydump [X86] dump PCI config space before the kernel
1710 off [X86] don't probe for the PCI bus
1711 bios [X86-32] force use of PCI BIOS, don't access
1712 the hardware directly. Use this if your machine
1713 has a non-standard PCI host bridge.
1714 nobios [X86-32] disallow use of PCI BIOS, only direct
1715 hardware access methods are allowed. Use this
1716 if you experience crashes upon bootup and you
1717 suspect they are caused by the BIOS.
1718 conf1 [X86] Force use of PCI Configuration
1720 conf2 [X86] Force use of PCI Configuration
1722 noaer [PCIE] If the PCIEAER kernel config parameter is
1723 enabled, this kernel boot option can be used to
1724 disable the use of PCIE advanced error reporting.
1725 nodomains [PCI] Disable support for multiple PCI
1726 root domains (aka PCI segments, in ACPI-speak).
1727 nommconf [X86] Disable use of MMCONFIG for PCI
1729 nomsi [MSI] If the PCI_MSI kernel config parameter is
1730 enabled, this kernel boot option can be used to
1731 disable the use of MSI interrupts system-wide.
1732 noioapicquirk [APIC] Disable all boot interrupt quirks.
1733 Safety option to keep boot IRQs enabled. This
1734 should never be necessary.
1735 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1736 primary IO-APIC for bridges that cannot disable
1737 boot IRQs. This fixes a source of spurious IRQs
1738 when the system masks IRQs.
1739 noioapicreroute [APIC] Disable workaround that uses the
1740 boot IRQ equivalent of an IRQ that connects to
1741 a chipset where boot IRQs cannot be disabled.
1742 The opposite of ioapicreroute.
1743 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1744 routing table. These calls are known to be buggy
1745 on several machines and they hang the machine
1746 when used, but on other computers it's the only
1747 way to get the interrupt routing table. Try
1748 this option if the kernel is unable to allocate
1749 IRQs or discover secondary PCI buses on your
1751 rom [X86] Assign address space to expansion ROMs.
1752 Use with caution as certain devices share
1753 address decoders between ROMs and other
1755 norom [X86] Do not assign address space to
1756 expansion ROMs that do not already have
1757 BIOS assigned address ranges.
1758 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1759 assigned automatically to PCI devices. You can
1760 make the kernel exclude IRQs of your ISA cards
1762 pirqaddr=0xAAAAA [X86] Specify the physical address
1763 of the PIRQ table (normally generated
1764 by the BIOS) if it is outside the
1765 F0000h-100000h range.
1766 lastbus=N [X86] Scan all buses thru bus #N. Can be
1767 useful if the kernel is unable to find your
1768 secondary buses and you want to tell it
1769 explicitly which ones they are.
1770 assign-busses [X86] Always assign all PCI bus
1771 numbers ourselves, overriding
1772 whatever the firmware may have done.
1773 usepirqmask [X86] Honor the possible IRQ mask stored
1774 in the BIOS $PIR table. This is needed on
1775 some systems with broken BIOSes, notably
1776 some HP Pavilion N5400 and Omnibook XE3
1777 notebooks. This will have no effect if ACPI
1778 IRQ routing is enabled.
1779 noacpi [X86] Do not use ACPI for IRQ routing
1780 or for PCI scanning.
1781 use_crs [X86] Use _CRS for PCI resource
1783 routeirq Do IRQ routing for all PCI devices.
1784 This is normally done in pci_enable_device(),
1785 so this option is a temporary workaround
1786 for broken drivers that don't call it.
1787 skip_isa_align [X86] do not align io start addr, so can
1788 handle more pci cards
1789 firmware [ARM] Do not re-enumerate the bus but instead
1790 just use the configuration from the
1791 bootloader. This is currently used on
1792 IXP2000 systems where the bus has to be
1793 configured a certain way for adjunct CPUs.
1794 noearly [X86] Don't do any early type 1 scanning.
1795 This might help on some broken boards which
1796 machine check when some devices' config space
1797 is read. But various workarounds are disabled
1798 and some IOMMU drivers will not work.
1799 bfsort Sort PCI devices into breadth-first order.
1800 This sorting is done to get a device
1801 order compatible with older (<= 2.4) kernels.
1802 nobfsort Don't sort PCI devices into breadth-first order.
1803 cbiosize=nn[KMG] The fixed amount of bus space which is
1804 reserved for the CardBus bridge's IO window.
1805 The default value is 256 bytes.
1806 cbmemsize=nn[KMG] The fixed amount of bus space which is
1807 reserved for the CardBus bridge's memory
1808 window. The default value is 64 megabytes.
1811 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1812 Specifies alignment and device to reassign
1813 aligned memory resources.
1814 If <order of align> is not specified,
1815 PAGE_SIZE is used as alignment.
1816 PCI-PCI bridge can be specified, if resource
1817 windows need to be expanded.
1819 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1822 force Enable ASPM even on devices that claim not to support it.
1823 WARNING: Forcing ASPM on may cause system lockups.
1825 pcmv= [HW,PCMCIA] BadgePAD 4
1828 See Documentation/blockdev/paride.txt.
1830 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1833 See arch/parisc/kernel/pdc_chassis.c
1836 See Documentation/blockdev/paride.txt.
1839 See Documentation/blockdev/paride.txt.
1841 pirq= [SMP,APIC] Manual mp-table setup
1842 See Documentation/x86/i386/IO-APIC.txt.
1844 plip= [PPT,NET] Parallel port network link
1845 Format: { parport<nr> | timid | 0 }
1846 See also Documentation/parport.txt.
1848 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1849 Override pmtimer IOPort with a hex value.
1853 Enable PNP debug messages. This depends on the
1854 CONFIG_PNP_DEBUG_MESSAGES option.
1860 { on | off | curr | res | no-curr | no-res }
1863 [ISAPNP] Exclude IRQs for the autoconfiguration
1866 [ISAPNP] Exclude DMAs for the autoconfiguration
1868 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1869 Ranges are in pairs (I/O port base and size).
1872 [ISAPNP] Exclude memory regions for the
1874 Ranges are in pairs (memory base and size).
1876 ports= [IP_VS_FTP] IPVS ftp helper module
1878 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1880 Format: <port>,<port>....
1882 print-fatal-signals=
1883 [KNL] debug: print fatal signals
1884 print-fatal-signals=1: print segfault info to
1888 printk.time= Show timing data prefixed to each printk message line
1889 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1891 processor.max_cstate= [HW,ACPI]
1892 Limit processor to maximum C-state
1893 max_cstate=9 overrides any DMI blacklist limit.
1895 processor.nocst [HW,ACPI]
1896 Ignore the _CST method to determine C-states,
1897 instead using the legacy FADT method
1899 profile= [KNL] Enable kernel profiling via /proc/profile
1900 Format: [schedule,]<number>
1901 Param: "schedule" - profile schedule points.
1902 Param: <number> - step/bucket size as a power of 2 for
1903 statistical time based profiling.
1904 Param: "sleep" - profile D-state sleeping (millisecs).
1905 Requires CONFIG_SCHEDSTATS
1906 Param: "kvm" - profile VM exits.
1908 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1910 See Documentation/blockdev/ramdisk.txt.
1912 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1913 probe for; one of (bare|imps|exps|lifebook|any).
1914 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1916 psmouse.resetafter= [HW,MOUSE]
1917 Try to reset the device after so many bad packets
1920 [HW,MOUSE] Set desired mouse resolution, in dpi.
1921 psmouse.smartscroll=
1922 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1923 0 = disabled, 1 = enabled (default).
1925 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1927 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1930 See Documentation/blockdev/paride.txt.
1933 [KNL] Number of legacy pty's. Overwrites compiled-in
1936 quiet [KNL] Disable most log messages
1941 See Documentation/md.txt.
1943 ramdisk_blocksize= [RAM]
1944 See Documentation/blockdev/ramdisk.txt.
1946 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1947 See Documentation/blockdev/ramdisk.txt.
1949 rcupdate.blimit= [KNL,BOOT]
1950 Set maximum number of finished RCU callbacks to process
1953 rcupdate.qhimark= [KNL,BOOT]
1954 Set threshold of queued
1955 RCU callbacks over which batch limiting is disabled.
1957 rcupdate.qlowmark= [KNL,BOOT]
1958 Set threshold of queued RCU callbacks below which
1959 batch limiting is re-enabled.
1963 Run specified binary instead of /init from the ramdisk,
1964 used for early userspace startup. See initrd.
1966 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1967 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1968 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1971 [KNL, SMP] Set scheduler's default relax_domain_level.
1972 See Documentation/cgroups/cpusets.txt.
1974 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1976 reservetop= [X86-32]
1978 Reserves a hole at the top of the kernel virtual
1981 reset_devices [KNL] Force drivers to reset the underlying device
1982 during initialization.
1985 Specify the partition device for software suspend
1987 resume_offset= [SWSUSP]
1988 Specify the offset from the beginning of the partition
1989 given by "resume=" at which the swap header is located,
1990 in <PAGE_SIZE> units (needed only for swap files).
1991 See Documentation/power/swsusp-and-swap-files.txt
1993 retain_initrd [RAM] Keep initrd memory after extraction
1995 rhash_entries= [KNL,NET]
1996 Set number of hash buckets for route cache
1998 riscom8= [HW,SERIAL]
1999 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2001 ro [KNL] Mount root device read-only on boot
2003 root= [KNL] Root filesystem
2005 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2006 mount the root filesystem
2008 rootflags= [KNL] Set root filesystem mount option string
2010 rootfstype= [KNL] Set root filesystem type
2012 rootwait [KNL] Wait (indefinitely) for root device to show up.
2013 Useful for devices that are detected asynchronously
2014 (e.g. USB and MMC devices).
2016 root_plug.vendor_id=
2017 [ROOTPLUG] Override the default vendor ID
2019 root_plug.product_id=
2020 [ROOTPLUG] Override the default product ID
2023 [ROOTPLUG] Enable debugging output
2025 rw [KNL] Mount root device read-write on boot
2027 S [KNL] Run init in single mode
2030 See drivers/net/irda/sa1100_ir.c.
2032 sbni= [NET] Granch SBNI12 leased line adapter
2034 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2035 Format: <io>[,<timeout>[,<isapnp>]]
2037 scsi_debug_*= [SCSI]
2038 See drivers/scsi/scsi_debug.c.
2040 scsi_default_dev_flags=
2041 [SCSI] SCSI default device flags
2044 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2045 Format: <vendor>:<model>:<flags>
2046 (flags are integer value)
2048 scsi_logging_level= [SCSI] a bit mask of logging levels
2049 See drivers/scsi/scsi_logging.h for bits. Also
2050 settable via sysctl at dev.scsi.logging_level
2051 (/proc/sys/dev/scsi/logging_level).
2052 There is also a nice 'scsi_logging_level' script in the
2053 S390-tools package, available for download at
2054 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2056 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2057 discovered. async scans them in kernel threads,
2058 allowing boot to proceed. none ignores them, expecting
2059 user space to do the scan.
2061 security= [SECURITY] Choose a security module to enable at boot.
2062 If this boot parameter is not specified, only the first
2063 security module asking for security registration will be
2064 loaded. An invalid security module name will be treated
2065 as if no module has been chosen.
2067 selinux= [SELINUX] Disable or enable SELinux at boot time.
2068 Format: { "0" | "1" }
2069 See security/selinux/Kconfig help text.
2072 Default value is set via kernel config option.
2073 If enabled at boot time, /selinux/disable can be used
2074 later to disable prior to initial policy load.
2076 serialnumber [BUGS=X86-32]
2079 Maximal number of shapers.
2081 show_msr= [x86] show boot-time MSR settings
2082 Format: { <integer> }
2083 Show boot-time (BIOS-initialized) MSR settings.
2084 The parameter means the number of CPUs to show,
2085 for example 1 means boot CPU only.
2088 See header of drivers/scsi/sim710.c.
2095 slub_debug[=options[,slabs]] [MM, SLUB]
2096 Enabling slub_debug allows one to determine the
2097 culprit if slab objects become corrupted. Enabling
2098 slub_debug can create guard zones around objects and
2099 may poison objects when not in use. Also tracks the
2100 last alloc / free. For more information see
2101 Documentation/vm/slub.txt.
2103 slub_max_order= [MM, SLUB]
2104 Determines the maximum allowed order for slabs.
2105 A high setting may cause OOMs due to memory
2106 fragmentation. For more information see
2107 Documentation/vm/slub.txt.
2109 slub_min_objects= [MM, SLUB]
2110 The minimum number of objects per slab. SLUB will
2111 increase the slab order up to slub_max_order to
2112 generate a sufficiently large slab able to contain
2113 the number of objects indicated. The higher the number
2114 of objects the smaller the overhead of tracking slabs
2115 and the less frequently locks need to be acquired.
2116 For more information see Documentation/vm/slub.txt.
2118 slub_min_order= [MM, SLUB]
2119 Determines the mininum page order for slabs. Must be
2120 lower than slub_max_order.
2121 For more information see Documentation/vm/slub.txt.
2123 slub_nomerge [MM, SLUB]
2124 Disable merging of slabs with similar size. May be
2125 necessary if there is some reason to distinguish
2126 allocs to different slabs. Debug options disable
2127 merging on their own.
2128 For more information see Documentation/vm/slub.txt.
2131 Format: <io1>[,<io2>[,...,<io8>]]
2133 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2134 attempt to substitute SMP alternatives once at boot.
2136 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2137 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2138 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2139 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2140 smsc-ircc2.ircc_irq= [HW] IRQ line
2141 smsc-ircc2.ircc_dma= [HW] DMA channel
2142 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2143 0: Toshiba Satellite 1800 (GP data pin select)
2144 1: Fast pin select (default)
2147 snd-ad1816a= [HW,ALSA]
2149 snd-ad1848= [HW,ALSA]
2151 snd-ali5451= [HW,ALSA]
2153 snd-als100= [HW,ALSA]
2155 snd-als4000= [HW,ALSA]
2157 snd-azt2320= [HW,ALSA]
2159 snd-cmi8330= [HW,ALSA]
2161 snd-cmipci= [HW,ALSA]
2163 snd-cs4231= [HW,ALSA]
2165 snd-cs4232= [HW,ALSA]
2167 snd-cs4236= [HW,ALSA]
2169 snd-cs4281= [HW,ALSA]
2171 snd-cs46xx= [HW,ALSA]
2173 snd-dt019x= [HW,ALSA]
2175 snd-dummy= [HW,ALSA]
2177 snd-emu10k1= [HW,ALSA]
2179 snd-ens1370= [HW,ALSA]
2181 snd-ens1371= [HW,ALSA]
2183 snd-es968= [HW,ALSA]
2185 snd-es1688= [HW,ALSA]
2187 snd-es18xx= [HW,ALSA]
2189 snd-es1938= [HW,ALSA]
2191 snd-es1968= [HW,ALSA]
2193 snd-fm801= [HW,ALSA]
2195 snd-gusclassic= [HW,ALSA]
2197 snd-gusextreme= [HW,ALSA]
2199 snd-gusmax= [HW,ALSA]
2203 snd-ice1712= [HW,ALSA]
2205 snd-intel8x0= [HW,ALSA]
2207 snd-interwave= [HW,ALSA]
2212 snd-korg1212= [HW,ALSA]
2214 snd-maestro3= [HW,ALSA]
2216 snd-mpu401= [HW,ALSA]
2218 snd-mtpav= [HW,ALSA]
2220 snd-nm256= [HW,ALSA]
2222 snd-opl3sa2= [HW,ALSA]
2230 snd-opti93x= [HW,ALSA]
2234 snd-rme32= [HW,ALSA]
2236 snd-rme96= [HW,ALSA]
2238 snd-rme9652= [HW,ALSA]
2244 snd-sbawe= [HW,ALSA]
2246 snd-serial= [HW,ALSA]
2248 snd-sgalaxy= [HW,ALSA]
2250 snd-sonicvibes= [HW,ALSA]
2255 snd-sun-cs4231= [HW,ALSA]
2257 snd-trident= [HW,ALSA]
2259 snd-usb-audio= [HW,ALSA,USB]
2261 snd-via82xx= [HW,ALSA]
2263 snd-virmidi= [HW,ALSA]
2265 snd-wavefront= [HW,ALSA]
2267 snd-ymfpci= [HW,ALSA]
2270 [KNL] Should the soft-lockup detector generate panics.
2272 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2273 See Documentation/sonypi.txt
2275 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2276 See Documentation/serial/specialix.txt.
2278 spia_io_base= [HW,MTD]
2284 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2286 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2287 See Documentation/scsi/st.txt.
2290 Enabled the stack tracer on boot up.
2294 Set the STI (builtin display/keyboard on the HP-PARISC
2295 machines) console (graphic card) which should be used
2296 as the initial boot-console.
2297 See also comment in drivers/video/console/sticore.c.
2300 See comment in drivers/video/console/sticore.c.
2303 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2307 Control how the NFS server code allocates CPUs to
2308 service thread pools. Depending on how many NICs
2309 you have and where their interrupts are bound, this
2310 option will affect which CPUs will do NFS serving.
2311 Note: this parameter cannot be changed while the
2312 NFS server is running.
2314 auto the server chooses an appropriate mode
2315 automatically using heuristics
2316 global a single global pool contains all CPUs
2317 percpu one pool for each CPU
2318 pernode one pool for each NUMA node (equivalent
2319 to global on non-NUMA machines)
2321 swiotlb= [IA-64] Number of I/O TLB slabs
2325 sym53c416= [HW,SCSI]
2326 See header of drivers/scsi/sym53c416.c.
2328 sysrq_always_enabled
2330 Ignore sysrq setting - this boot parameter will
2331 neutralize any effect of /proc/sys/kernel/sysrq.
2332 Useful for debugging.
2335 See header of drivers/scsi/t128.c.
2339 test_suspend= [SUSPEND]
2340 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2341 standby suspend) as the system sleep state to briefly
2342 enter during system startup. The system is woken from
2343 this state using a wakeup-capable RTC alarm.
2345 thash_entries= [KNL,NET]
2346 Set number of hash buckets for TCP connection
2348 thermal.act= [HW,ACPI]
2349 -1: disable all active trip points in all thermal zones
2350 <degrees C>: override all lowest active trip points
2352 thermal.crt= [HW,ACPI]
2353 -1: disable all critical trip points in all thermal zones
2354 <degrees C>: override all critical trip points
2356 thermal.nocrt= [HW,ACPI]
2357 Set to disable actions on ACPI thermal zone
2358 critical and hot trip points.
2360 thermal.off= [HW,ACPI]
2361 1: disable ACPI thermal control
2363 thermal.psv= [HW,ACPI]
2364 -1: disable all passive trip points
2365 <degrees C>: override all passive trip points to this
2368 thermal.tzp= [HW,ACPI]
2369 Specify global default ACPI thermal zone polling rate
2370 <deci-seconds>: poll all this frequency
2371 0: no polling (default)
2374 See comment before function dc390_setup() in
2375 drivers/scsi/tmscsim.c.
2379 Specify if the kernel should make use of the cpu
2380 topology informations if the hardware supports these.
2381 The scheduler will make use of these informations and
2382 e.g. base its process migration decisions on it.
2387 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2389 trix= [HW,OSS] MediaTrix AudioTrix Pro
2391 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2393 tsc= Disable clocksource-must-verify flag for TSC.
2395 [x86] reliable: mark tsc clocksource as reliable, this
2396 disables clocksource verification at runtime.
2397 Used to enable high-resolution timer mode on older
2398 hardware, and in virtualized environment.
2400 turbografx.map[2|3]= [HW,JOY]
2401 TurboGraFX parallel port interface
2403 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2404 See also Documentation/input/joystick-parport.txt
2406 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2407 See header of drivers/scsi/u14-34f.c.
2416 [USB] Ignore overcurrent events (default N).
2417 Some badly-designed motherboards generate lots of
2418 bogus events, for ports that aren't wired to
2419 anything. Set this parameter to avoid log spamming.
2420 Note that genuine overcurrent events won't be
2425 Set unknown_nmi_panic=1 early on boot.
2427 usbcore.autosuspend=
2428 [USB] The autosuspend time delay (in seconds) used
2429 for newly-detected USB devices (default 2). This
2430 is the time required before an idle device will be
2431 autosuspended. Devices for which the delay is set
2432 to a negative value won't be autosuspended at all.
2434 usbcore.usbfs_snoop=
2435 [USB] Set to log all usbfs traffic (default 0 = off).
2437 usbcore.blinkenlights=
2438 [USB] Set to cycle leds on hubs (default 0 = off).
2440 usbcore.old_scheme_first=
2441 [USB] Start with the old device initialization
2442 scheme (default 0 = off).
2444 usbcore.use_both_schemes=
2445 [USB] Try the other device initialization scheme
2446 if the first one fails (default 1 = enabled).
2448 usbcore.initial_descriptor_timeout=
2449 [USB] Specifies timeout for the initial 64-byte
2450 USB_REQ_GET_DESCRIPTOR request in milliseconds
2451 (default 5000 = 5.0 seconds).
2454 [USBHID] The interval which mice are to be polled at.
2456 usb-storage.delay_use=
2457 [UMS] The delay in seconds before a new device is
2458 scanned for Logical Units (default 5).
2461 [UMS] A list of quirks entries to supplement or
2462 override the built-in unusual_devs list. List
2463 entries are separated by commas. Each entry has
2464 the form VID:PID:Flags where VID and PID are Vendor
2465 and Product ID values (4-digit hex numbers) and
2466 Flags is a set of characters, each corresponding
2467 to a common usb-storage quirk flag as follows:
2468 a = SANE_SENSE (collect more than 18 bytes
2470 c = FIX_CAPACITY (decrease the reported
2471 device capacity by one sector);
2472 h = CAPACITY_HEURISTICS (decrease the
2473 reported device capacity by one
2474 sector if the number is odd);
2475 i = IGNORE_DEVICE (don't bind to this
2477 l = NOT_LOCKABLE (don't try to lock and
2478 unlock ejectable media);
2479 m = MAX_SECTORS_64 (don't transfer more
2480 than 64 sectors = 32 KB at a time);
2481 o = CAPACITY_OK (accept the capacity
2482 reported by the device);
2483 r = IGNORE_RESIDUE (the device reports
2484 bogus residue values);
2485 s = SINGLE_LUN (the device has only one
2487 w = NO_WP_DETECT (don't test whether the
2488 medium is write-protected).
2489 Example: quirks=0419:aaf5:rl,0421:0433:rc
2492 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2493 vdso=1: enable VDSO (default)
2494 vdso=0: disable VDSO mapping
2497 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2498 vdso32=1: enable 32-bit VDSO (default)
2499 vdso32=0: disable 32-bit VDSO mapping
2502 vector=percpu: enable percpu vector domain
2504 video= [FB] Frame buffer configuration
2505 See Documentation/fb/modedb.txt.
2507 vga= [BOOT,X86-32] Select a particular video mode
2508 See Documentation/x86/boot.txt and
2509 Documentation/svga.txt.
2510 Use vga=ask for menu.
2511 This is actually a boot loader parameter; the value is
2512 passed to the kernel using a special protocol.
2514 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2515 size of <nn>. This can be used to increase the
2516 minimum size (128MB on x86). It can also be used to
2517 decrease the size and leave more room for directly
2520 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2523 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2526 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2529 vt.default_blu= [VT]
2530 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2531 Change the default blue palette of the console.
2532 This is a 16-member array composed of values
2535 vt.default_grn= [VT]
2536 Format: <green0>,<green1>,<green2>,...,<green15>
2537 Change the default green palette of the console.
2538 This is a 16-member array composed of values
2541 vt.default_red= [VT]
2542 Format: <red0>,<red1>,<red2>,...,<red15>
2543 Change the default red palette of the console.
2544 This is a 16-member array composed of values
2550 Set system-wide default UTF-8 mode for all tty's.
2551 Default is 1, i.e. UTF-8 mode is enabled for all
2552 newly opened terminals.
2554 waveartist= [HW,OSS]
2555 Format: <io>,<irq>,<dma>,<dma2>
2558 See header of drivers/scsi/wd33c93.c.
2561 See header of drivers/scsi/wd7000.c.
2564 See Documentation/watchdog/wdt.txt.
2566 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2567 default x2apic cluster mode on platforms
2570 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2571 xd_geo= See header of drivers/block/xd.c.
2573 xirc2ps_cs= [NET,PCMCIA]
2575 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2577 ______________________________________________________________________
2581 Add documentation for ALSA options.
2582 Add more DRM drivers.
projects / linux-2.6 / blob