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 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TPM TPM drivers are enabled.
103 TS Appropriate touchscreen support is enabled.
104 UMS USB Mass Storage support is enabled.
105 USB USB support is enabled.
106 USBHID USB Human Interface Device support is enabled.
107 V4L Video For Linux support is enabled.
108 VGA The VGA console has been enabled.
109 VT Virtual terminal support is enabled.
110 WDT Watchdog support is enabled.
111 XT IBM PC/XT MFM hard disk support is enabled.
112 X86-32 X86-32, aka i386 architecture is enabled.
113 X86-64 X86-64 architecture is enabled.
114 More X86-64 boot options can be found in
115 Documentation/x86/x86_64/boot-options.txt .
116 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 In addition, the following text indicates that the option:
120 BUGS= Relates to possible processor bugs on the said processor.
121 KNL Is a kernel start-up parameter.
122 BOOT Is a boot loader parameter.
124 Parameters denoted with BOOT are actually interpreted by the boot
125 loader, and have no meaning to the kernel directly.
126 Do not modify the syntax of boot loader parameters without extreme
127 need or coordination with <Documentation/x86/boot.txt>.
129 There are also arch-specific kernel-parameters not documented here.
130 See for example <Documentation/x86/x86_64/boot-options.txt>.
132 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
133 a trailing = on the name of any parameter states that that parameter will
134 be entered as an environment variable, whereas its absence indicates that
135 it will appear as a kernel argument readable via /proc/cmdline by programs
136 running once the system is up.
138 The number of kernel parameters is not limited, but the length of the
139 complete command line (parameters including spaces etc.) is limited to
140 a fixed number of characters. This limit depends on the architecture
141 and is between 256 and 4096 characters. It is defined in the file
142 ./include/asm/setup.h as COMMAND_LINE_SIZE.
146 Advanced Configuration and Power Interface
147 Format: { force | off | ht | strict | noirq | rsdt }
148 force -- enable ACPI if default was off
149 off -- disable ACPI if default was on
150 noirq -- do not use ACPI for IRQ routing
151 ht -- run only enough ACPI to enable Hyper Threading
152 strict -- Be less tolerant of platforms that are not
153 strictly ACPI specification compliant.
154 rsdt -- prefer RSDT over (default) XSDT
156 See also Documentation/power/pm.txt, pci=noacpi
158 acpi_apic_instance= [ACPI, IOAPIC]
160 2: use 2nd APIC table, if available
161 1,0: use 1st APIC table
164 acpi_backlight= [HW,ACPI]
165 acpi_backlight=vendor
167 If set to vendor, prefer vendor specific driver
168 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
169 of the ACPI video.ko driver.
171 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
172 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
174 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
175 debug output. Bits in debug_layer correspond to a
176 _COMPONENT in an ACPI source file, e.g.,
177 #define _COMPONENT ACPI_PCI_COMPONENT
178 Bits in debug_level correspond to a level in
179 ACPI_DEBUG_PRINT statements, e.g.,
180 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
181 The debug_level mask defaults to "info". See
182 Documentation/acpi/debug.txt for more information about
183 debug layers and levels.
185 Enable processor driver info messages:
186 acpi.debug_layer=0x20000000
187 Enable PCI/PCI interrupt routing info messages:
188 acpi.debug_layer=0x400000
189 Enable AML "Debug" output, i.e., stores to the Debug
190 object while interpreting AML:
191 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
192 Enable all messages related to ACPI hardware:
193 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
195 Some values produce so much output that the system is
196 unusable. The "log_buf_len" parameter may be useful
197 if you need to capture more output.
199 acpi_display_output= [HW,ACPI]
200 acpi_display_output=vendor
201 acpi_display_output=video
204 acpi_irq_balance [HW,ACPI]
205 ACPI will balance active IRQs
208 acpi_irq_nobalance [HW,ACPI]
209 ACPI will not move active IRQs (default)
212 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
213 Format: <irq>,<irq>...
215 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
217 Format: <irq>,<irq>...
219 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
221 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
222 Format: To spoof as Windows 98: ="Microsoft Windows"
224 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
225 acpi_osi="string1" # add string1 -- only one string
226 acpi_osi="!string2" # remove built-in string2
227 acpi_osi= # disable all strings
230 Override the pmtimer bug detection: force the kernel
231 to assume that this machine's pmtimer latches its value
232 and always returns good values.
234 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
235 Format: { level | edge | high | low }
237 acpi_serialize [HW,ACPI] force serialization of AML methods
239 acpi_skip_timer_override [HW,ACPI]
240 Recognize and ignore IRQ0/pin2 Interrupt Override.
241 For broken nForce2 BIOS resulting in XT-PIC timer.
243 acpi_sleep= [HW,ACPI] Sleep options
244 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
245 old_ordering, s4_nonvs, sci_force_enable }
246 See Documentation/power/video.txt for information on
248 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel's real-mode entry point is called.
250 s4_nohwsig prevents ACPI hardware signature from being
251 used during resume from hibernation.
252 old_ordering causes the ACPI 1.0 ordering of the _PTS
253 control method, with respect to putting devices into
254 low power states, to be enforced (the ACPI 2.0 ordering
255 of _PTS is used by default).
256 s4_nonvs prevents the kernel from saving/restoring the
257 ACPI NVS memory during hibernation.
258 sci_force_enable causes the kernel to set SCI_EN directly
259 on resume from S1/S3 (which is against the ACPI spec,
260 but some broken systems don't work without it).
262 acpi_use_timer_override [HW,ACPI]
263 Use timer override. For some broken Nvidia NF5 boards
264 that require a timer override, but don't have HPET
266 acpi_enforce_resources= [ACPI]
267 { strict | lax | no }
268 Check for resource conflicts between native drivers
269 and ACPI OperationRegions (SystemIO and SystemMemory
270 only). IO ports and memory declared in ACPI might be
271 used by the ACPI subsystem in arbitrary AML code and
272 can interfere with legacy drivers.
273 strict (default): access to resources claimed by ACPI
274 is denied; legacy drivers trying to access reserved
275 resources will fail to bind to device using them.
276 lax: access to resources claimed by ACPI is allowed;
277 legacy drivers trying to access reserved resources
278 will bind successfully but a warning message is logged.
279 no: ACPI OperationRegions are not marked as reserved,
280 no further checks are performed.
283 Format: <io>,<irq>,<dma>,<dma2>,<type>
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
289 See header of drivers/scsi/advansys.c.
291 advwdt= [HW,WDT] Advantech WDT
292 Format: <iostart>,<iostop>
294 aedsp16= [HW,OSS] Audio Excel DSP 16
295 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
296 See also header of sound/oss/aedsp16.c.
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
305 See Documentation/scsi/aha152x.txt.
308 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
311 See Documentation/scsi/aic7xxx.txt.
314 See Documentation/scsi/aic79xx.txt.
317 Allow the default userspace alignment fault handler
318 behaviour to be specified. Bit 0 enables warnings,
319 bit 1 enables fixups, and bit 2 sends a segfault.
321 amd_iommu= [HW,X86-84]
322 Pass parameters to the AMD IOMMU driver in the system.
324 fullflush - enable flushing of IO/TLB entries when
325 they are unmapped. Otherwise they are
326 flushed before they will be reused, which
328 off - do not initialize any AMD IOMMU found in
331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
334 See also Documentation/kernel/input/joystick.txt
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
342 Power management functions (SPARCstation-4/5 + deriv.)
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
348 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
349 Change the output verbosity whilst booting
350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
355 See Documentation/networking/ipv6.txt.
357 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
358 Limit apic dumping. The parameter defines the maximal
359 number of local apics being dumped. Also it is possible
360 to set it to "all" by meaning -- no limit here.
361 Format: { 1 (default) | 2 | ... | all }.
362 The parameter valid if only apic=debug or
363 apic=verbose is specified.
364 Example: apic=debug show_lapic=all
366 apm= [APM] Advanced Power Management
367 See header of arch/x86/kernel/apm_32.c.
369 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
370 Format: <io>,<irq>,<nodeID>
374 atarimouse= [HW,MOUSE] Atari Mouse
376 atascsi= [HW,SCSI] Atari SCSI
378 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
379 EzKey and similar keyboards
381 atkbd.reset= [HW] Reset keyboard during initialization
383 atkbd.set= [HW] Select keyboard code set
384 Format: <int> (2 = AT (default), 3 = PS/2)
386 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 atkbd.softraw= [HW] Choose between synthetic and real raw mode
390 Format: <bool> (0 = real, 1 = synthetic (default))
392 atkbd.softrepeat= [HW]
393 Use software keyboard repeat
397 baycom_epp= [HW,AX25]
400 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
402 See header of drivers/net/hamradio/baycom_par.c.
404 baycom_ser_fdx= [HW,AX25]
405 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
406 Format: <io>,<irq>,<mode>[,<baud>]
407 See header of drivers/net/hamradio/baycom_ser_fdx.c.
409 baycom_ser_hdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
411 Format: <io>,<irq>,<mode>
412 See header of drivers/net/hamradio/baycom_ser_hdx.c.
414 boot_delay= Milliseconds to delay each printk during boot.
415 Values larger than 10 seconds (10000) are changed to
419 bootmem_debug [KNL] Enable bootmem allocator debug messages.
421 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
422 bttv.radio= Most important insmod options are available as
424 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
425 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
428 See drivers/scsi/BusLogic.c, comment before function
429 BusLogic_ParseDriverOptions().
431 c101= [NET] Moxa C101 synchronous serial card
433 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
434 Sometimes CPU hardware bugs make them report the cache
435 size incorrectly. The kernel will attempt work arounds
436 to fix known problems, but for some CPUs it is not
437 possible to determine what the correct size should be.
438 This option provides an override for these situations.
441 [SECURITY] Disable capabilities. This would normally
442 be used only if an alternative security model is to be
443 configured. Potentially dangerous and should only be
444 used if you are entirely sure of the consequences.
446 ccw_timeout_log [S390]
447 See Documentation/s390/CommonIO for details.
449 cgroup_disable= [KNL] Disable a particular controller
450 Format: {name of the controller(s) to disable}
451 {Currently supported controllers - "memory"}
453 checkreqprot [SELINUX] Set initial checkreqprot flag value.
454 Format: { "0" | "1" }
455 See security/selinux/Kconfig help text.
456 0 -- check protection applied by kernel (includes
457 any implied execute protection).
458 1 -- check protection requested by application.
459 Default value is set via a kernel config option.
460 Value can be changed at runtime via
461 /selinux/checkreqprot.
464 See Documentation/s390/CommonIO for details.
466 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
468 Forces specified clocksource (if available) to be used
469 when calculating gettimeofday(). If specified
470 clocksource is not available, it defaults to PIT.
471 Format: { pit | tsc | cyclone | pmtmr }
473 clocksource= [GENERIC_TIME] Override the default clocksource
475 Override the default clocksource and use the clocksource
476 with the name specified.
477 Some clocksource names to choose from, depending on
479 [all] jiffies (this is the base, fallback clocksource)
481 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
482 pxa_timer,timer3,32k_counter,timer0_1
484 [X86-32] pit,hpet,tsc,vmi-timer;
485 scx200_hrt on Geode; cyclone on IBM x440
493 clearcpuid=BITNUM [X86]
494 Disable CPUID feature X for the kernel. See
495 arch/x86/include/asm/cpufeature.h for the valid bit
496 numbers. Note the Linux specific bits are not necessarily
497 stable over kernel options, but the vendor specific
499 Also note that user programs calling CPUID directly
500 or using the feature without checking anything
501 will still see it. This just prevents it from
502 being used by the kernel or shown in /proc/cpuinfo.
503 Also note the kernel might malfunction if you disable
506 cmo_free_hint= [PPC] Format: { yes | no }
507 Specify whether pages are marked as being inactive
508 when they are freed. This is used in CMO environments
509 to determine OS memory pressure for page stealing by
513 code_bytes [X86] How many bytes of object code to print
518 com20020= [HW,NET] ARCnet - COM20020 chipset
520 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
522 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
526 ARCnet - COM90xx chipset (memory-mapped buffers)
527 Format: <io>[,<irq>[,<memstart>]]
529 condev= [HW,S390] console device
532 console= [KNL] Output console device and options.
534 tty<n> Use the virtual console device <n>.
538 Use the specified serial port. The options are of
539 the form "bbbbpnf", where "bbbb" is the baud rate,
540 "p" is parity ("n", "o", or "e"), "n" is number of
541 bits, and "f" is flow control ("r" for RTS or
542 omit it). Default is "9600n8".
544 See Documentation/serial-console.txt for more
546 Documentation/networking/netconsole.txt for an
549 uart[8250],io,<addr>[,options]
550 uart[8250],mmio,<addr>[,options]
551 Start an early, polled-mode console on the 8250/16550
552 UART at the specified I/O port or MMIO address,
553 switching to the matching ttyS device later. The
554 options are the same as for ttyS, above.
556 If the device connected to the port is not a TTY but a braille
557 device, prepend "brl," before the device type, for instance
559 For now, only VisioBraille is supported.
561 consoleblank= [KNL] The console blank (screen saver) timeout in
562 seconds. Defaults to 10*60 = 10mins. A value of 0
563 disables the blank timer.
566 [KNL] Change the default value for
567 /proc/<pid>/coredump_filter.
568 See also Documentation/filesystems/proc.txt.
570 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
572 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
574 crashkernel=nn[KMG]@ss[KMG]
575 [KNL] Reserve a chunk of physical memory to
576 hold a kernel to switch to with kexec on panic.
578 crashkernel=range1:size1[,range2:size2,...][@offset]
579 [KNL] Same as above, but depends on the memory
580 in the running system. The syntax of range is
581 start-[end] where start and end are both
582 a memory unit (amount[KMG]). See also
583 Documentation/kdump/kdump.txt for a example.
588 cs89x0_media= [HW,NET]
589 Format: { rj45 | aui | bnc }
592 See header of drivers/s390/block/dasd_devmap.c.
594 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
595 (one device per port)
596 Format: <port#>,<type>
597 See also Documentation/input/joystick-parport.txt
599 debug [KNL] Enable kernel debugging (events log level).
602 [KNL] verbose self-tests
604 Print debugging info while doing the locking API
606 We default to 0 (no extra messages), setting it to
607 1 will print _a lot_ more information - normally
608 only useful to kernel developers.
610 debug_objects [KNL] Enable object debugging
613 [KNL] Disable object debugging
615 debugpat [X86] Enable PAT debugging
617 decnet.addr= [HW,NET]
618 Format: <area>[,<node>]
619 See also Documentation/networking/decnet.txt.
622 [same as hugepagesz=] The size of the default
623 HugeTLB page size. This is the size represented by
624 the legacy /proc/ hugepages APIs, used for SHM, and
625 default size when mounting hugetlbfs filesystems.
626 Defaults to the default architecture's huge page size
630 Set number of hash buckets for dentry cache.
633 IO parameters + enable/disable command.
635 digiepca= [HW,SERIAL]
636 See drivers/char/README.epca and
637 Documentation/serial/digiepca.txt.
640 See Documentation/networking/ipv6.txt.
643 See Documentation/networking/ipv6.txt.
645 disable_mtrr_cleanup [X86]
646 The kernel tries to adjust MTRR layout from continuous
647 to discrete, to make X server driver able to add WB
648 entry later. This parameter disables that.
650 disable_mtrr_trim [X86, Intel and AMD only]
651 By default the kernel will trim any uncacheable
652 memory out of your available memory pool based on
653 MTRR settings. This parameter disables that behavior,
654 possibly causing your machine to run very slowly.
656 disable_timer_pin_1 [X86]
657 Disable PIN 1 of APIC timer
658 Can be useful to work around chipset bugs.
660 dmasound= [HW,OSS] Sound subsystem buffers
662 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
663 this option disables the debugging code at boot.
665 dma_debug_entries=<number>
666 This option allows to tune the number of preallocated
667 entries for DMA-API debugging code. One entry is
668 required per DMA-API allocation. Use this if the
669 DMA-API debugging code disables itself because the
670 architectural default is too low.
672 dma_debug_driver=<driver_name>
673 With this option the DMA-API debugging driver
674 filter feature can be enabled at boot time. Just
675 pass the driver to filter for as the parameter.
676 The filter can be disabled or changed to another
677 driver later using sysfs.
683 dynamic_printk Enables pr_debug()/dev_dbg() calls if
684 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
685 These can also be switched on/off via
686 <debugfs>/dynamic_printk/modules
688 earlycon= [KNL] Output early console device and options.
689 uart[8250],io,<addr>[,options]
690 uart[8250],mmio,<addr>[,options]
691 Start an early, polled-mode console on the 8250/16550
692 UART at the specified I/O port or MMIO address.
693 The options are the same as for ttyS, above.
695 earlyprintk= [X86,SH,BLACKFIN]
697 earlyprintk=serial[,ttySn[,baudrate]]
698 earlyprintk=ttySn[,baudrate]
699 earlyprintk=dbgp[debugController#]
701 Append ",keep" to not disable it when the real console
704 Only vga or serial or usb debug port at a time.
706 Currently only ttyS0 and ttyS1 are supported.
708 Interaction with the standard serial driver is not
711 The VGA output is eventually overwritten by the real
717 Format: {"off" | "on" | "skip[mbr]"}
719 eisa_irq_edge= [PARISC,HW]
720 See header of drivers/parisc/eisa.c.
723 See comment before function elanfreq_setup() in
724 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
727 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
728 See Documentation/block/as-iosched.txt and
729 Documentation/block/deadline-iosched.txt for details.
731 elfcorehdr= [IA64,PPC,SH,X86]
732 Specifies physical address of start of kernel core
733 image elf header. Generally kexec loader will
734 pass this option to capture kernel.
735 See Documentation/kdump/kdump.txt for details.
737 enable_mtrr_cleanup [X86]
738 The kernel tries to adjust MTRR layout from continuous
739 to discrete, to make X server driver able to add WB
740 entry later. This parameter enables that.
742 enable_timer_pin_1 [X86]
743 Enable PIN 1 of APIC timer
744 Can be useful to work around chipset bugs
745 (in particular on some ATI chipsets).
746 The kernel tries to set a reasonable default.
748 enforcing [SELINUX] Set initial enforcing status.
750 See security/selinux/Kconfig help text.
751 0 -- permissive (log only, no denials).
752 1 -- enforcing (deny and log).
754 Value can be changed at runtime via /selinux/enforce.
756 ether= [HW,NET] Ethernet cards parameters
757 This option is obsoleted by the "netdev=" option, which
758 has equivalent usage. See its documentation for details.
760 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
765 fail_make_request=[KNL]
766 General fault injection mechanism.
767 Format: <interval>,<probability>,<space>,<times>
768 See also /Documentation/fault-injection/.
771 See header of drivers/scsi/fd_mcs.c.
774 See header of drivers/scsi/fdomain.c.
777 See Documentation/blockdev/floppy.txt.
779 force_pal_cache_flush
780 [IA-64] Avoid check_sal_cache_flush which may hang on
781 buggy SAL_CACHE_FLUSH implementations. Using this
782 parameter will force ia64_sal_cache_flush to call
783 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
786 [FTRACE] will set and start the specified tracer
787 as early as possible in order to facilitate early
790 ftrace_dump_on_oops[=orig_cpu]
791 [FTRACE] will dump the trace buffers on oops.
792 If no parameter is passed, ftrace will dump
793 buffers of all CPUs, but if you pass orig_cpu, it will
794 dump only the buffer of the CPU that triggered the
797 ftrace_filter=[function-list]
798 [FTRACE] Limit the functions traced by the function
799 tracer at boot up. function-list is a comma separated
800 list of functions. This list can be changed at run
801 time by the set_ftrace_filter file in the debugfs
804 ftrace_notrace=[function-list]
805 [FTRACE] Do not trace the functions specified in
806 function-list. This list can be changed at run time
807 by the set_ftrace_notrace file in the debugfs
810 ftrace_graph_filter=[function-list]
811 [FTRACE] Limit the top level callers functions traced
812 by the function graph tracer at boot up.
813 function-list is a comma separated list of functions
814 that can be changed at run time by the
815 set_graph_function file in the debugfs tracing directory.
818 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
819 support via parallel port (up to 5 devices per port)
820 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
821 See also Documentation/input/joystick-parport.txt
825 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
829 gcov_persist= [GCOV] When non-zero (default), profiling data for
830 kernel modules is saved and remains accessible via
831 debugfs, even when the module is unloaded/reloaded.
832 When zero, profiling data is discarded and associated
833 debugfs files are removed at module unload time.
836 See header of drivers/scsi/gdth.c.
838 gpt [EFI] Forces disk with valid GPT signature but
839 invalid Protective MBR to be treated as GPT.
843 hashdist= [KNL,NUMA] Large hashes allocated during boot
844 are distributed across NUMA nodes. Defaults on
845 for 64bit NUMA, off otherwise.
846 Format: 0 | 1 (for off | on)
848 hcl= [IA-64] SGI's Hardware Graph compatibility layer
850 hd= [EIDE] (E)IDE hard drive subsystem geometry
851 Format: <cyl>,<head>,<sect>
853 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
854 size of <nn>. This works even on boxes that have no
855 highmem otherwise. This also works to reduce highmem
856 size on bigger boxes.
858 highres= [KNL] Enable/disable high resolution timer mode.
859 Valid parameters: "on", "off"
863 See Documentation/isdn/README.HiSax.
867 hpet= [X86-32,HPET] option to control HPET usage
868 Format: { enable (default) | disable | force |
870 disable: disable HPET and use PIT instead
871 force: allow force enabled of undocumented chips (ICH4,
873 verbose: show contents of HPET registers during setup
875 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
876 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
877 On x86-64 and powerpc, this option can be specified
878 multiple times interleaved with hugepages= to reserve
879 huge pages of different sizes. Valid pages sizes on
880 x86-64 are 2M (when the CPU supports "pse") and 1G
881 (when the CPU supports the "pdpe1gb" cpuinfo flag)
882 Note that 1GB pages can only be allocated at boot time
883 using hugepages= and not freed afterwards.
885 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
886 terminal devices. Valid values: 0..8
887 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
888 If specified, z/VM IUCV HVC accepts connections
889 from listed z/VM user IDs only.
891 i2c_bus= [HW] Override the default board specific I2C bus speed
892 or register an additional I2C bus that is not
893 registered from board initialization code.
897 i8042.debug [HW] Toggle i8042 debug mode
898 i8042.direct [HW] Put keyboard port into non-translated mode
899 i8042.dumbkbd [HW] Pretend that controller can only read data from
900 keyboard and cannot control its state
901 (Don't attempt to blink the leds)
902 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
903 i8042.nokbd [HW] Don't check/create keyboard port
904 i8042.noloop [HW] Disable the AUX Loopback command while probing
906 i8042.nomux [HW] Don't check presence of an active multiplexing
908 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
911 [HW] Frequency with which keyboard LEDs should blink
912 when kernel panics (default is 0.5 sec)
913 i8042.reset [HW] Reset the controller during init and cleanup
914 i8042.unlock [HW] Unlock (ignore) the keylock
918 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
919 indicates that the driver is running on unsupported
921 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
922 does not match list of supported models.
924 [HW] Report power status in /proc/i8k
925 (disabled by default)
926 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
929 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
930 See Documentation/mca.txt.
933 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
935 ide-core.nodma= [HW] (E)IDE subsystem
936 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
937 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
938 .cdrom .chs .ignore_cable are additional options
939 See Documentation/ide/ide.txt.
941 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
942 Claim all unknown PCI IDE storage controllers.
945 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
946 Poll forces a polling idle loop that can slightly
947 improve the performance of waking up a idle CPU, but
948 will use a lot of power and make the system run hot.
950 idle=mwait: On systems which support MONITOR/MWAIT but
951 the kernel chose to not use it because it doesn't save
952 as much power as a normal idle loop, use the
953 MONITOR/MWAIT idle loop anyways. Performance should be
954 the same as idle=poll.
955 idle=halt: Halt is forced to be used for CPU idle.
956 In such case C2/C3 won't be used again.
957 idle=nomwait: Disable mwait for CPU C-states
959 ignore_loglevel [KNL]
960 Ignore loglevel setting - this will print /all/
961 kernel messages to the console. Useful for debugging.
964 Set number of hash buckets for inode cache.
967 Format: { "0" | "1" }
968 0 -- integrity auditing messages. (Default)
969 1 -- enable informational integrity auditing messages.
972 Format: { "sha1" | "md5" }
976 Load a policy which meets the needs of the Trusted
977 Computing Base. This means IMA will measure all
978 programs exec'd, files mmap'd for exec, and all files
979 opened for read by uid=0.
982 See header of drivers/scsi/in2000.c.
986 Run specified binary instead of /sbin/init as init
989 initcall_debug [KNL] Trace initcalls as they are executed. Useful
990 for working out where the kernel is dying during
993 initrd= [BOOT] Specify the location of the initial ramdisk
995 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
998 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1000 Enable intel iommu driver.
1002 Disable intel iommu driver.
1003 igfx_off [Default Off]
1004 By default, gfx is mapped as normal device. If a gfx
1005 device has a dedicated DMAR unit, the DMAR unit is
1006 bypassed by not enabling DMAR with this option. In
1007 this case, gfx device will use physical address for
1010 With this option iommu will not optimize to look
1011 for io virtual address below 32 bit forcing dual
1012 address cycle on pci bus for cards supporting greater
1013 than 32 bit addressing. The default is to look
1014 for translation below 32 bit and if not available
1015 then look in the higher range.
1016 strict [Default Off]
1017 With this option on every unmap_single operation will
1018 result in a hardware IOTLB flush operation as opposed
1019 to batching them for performance.
1023 iomem= Disable strict checking of access to MMIO memory
1024 strict regions from userspace.
1040 io7= [HW] IO7 for Marvel based alpha systems
1041 See comment before marvel_specify_io7 in
1042 arch/alpha/kernel/core_marvel.c.
1044 io_delay= [X86] I/O delay method
1046 Standard port 0x80 based delay
1048 Alternate port 0xed based delay (needed on some systems)
1050 Simple two microseconds delay
1055 See Documentation/filesystems/nfs/nfsroot.txt.
1057 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1058 See comment before ip2_setup() in
1059 drivers/char/ip2/ip2base.c.
1061 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1062 See header of drivers/scsi/ips.c.
1065 When an interrupt is not handled search all handlers
1066 for it. Intended to get systems with badly broken
1070 When an interrupt is not handled search all handlers
1071 for it. Also check all handlers each timer
1072 interrupt. Intended to get systems with badly broken
1076 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1078 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1080 <cpu number>,...,<cpu number>
1082 <cpu number>-<cpu number>
1083 (must be a positive range in ascending order)
1085 <cpu number>,...,<cpu number>-<cpu number>
1087 This option can be used to specify one or more CPUs
1088 to isolate from the general SMP balancing and scheduling
1089 algorithms. You can move a process onto or off an
1090 "isolated" CPU via the CPU affinity syscalls or cpuset.
1091 <cpu number> begins at 0 and the maximum value is
1092 "number of CPUs in system - 1".
1094 This option is the preferred way to isolate CPUs. The
1095 alternative -- manually setting the CPU mask of all
1096 tasks in the system -- can cause problems and
1097 suboptimal load balancer performance.
1101 js= [HW,JOY] Analog joystick
1102 See Documentation/input/joystick.txt.
1106 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1107 specifies the amount of memory usable by the kernel
1108 for non-movable allocations. The requested amount is
1109 spread evenly throughout all nodes in the system. The
1110 remaining memory in each node is used for Movable
1111 pages. In the event, a node is too small to have both
1112 kernelcore and Movable pages, kernelcore pages will
1113 take priority and other nodes will have a larger number
1114 of kernelcore pages. The Movable zone is used for the
1115 allocation of pages that may be reclaimed or moved
1116 by the page migration subsystem. This means that
1117 HugeTLB pages may not be allocated from this zone.
1118 Note that allocations like PTEs-from-HighMem still
1119 use the HighMem zone if it exists, and the Normal
1120 zone if it does not.
1122 kgdboc= [HW] kgdb over consoles.
1123 Requires a tty driver that supports console polling.
1124 (only serial supported for now)
1125 Format: <serial_device>[,baud]
1127 kmac= [MIPS] korina ethernet MAC address.
1128 Configure the RouterBoard 532 series on-chip
1129 Ethernet adapter MAC address.
1131 kmemleak= [KNL] Boot-time kmemleak enable/disable
1132 Valid arguments: on, off
1135 kstack=N [X86] Print N words from the kernel stack
1138 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1139 Default is 0 (don't ignore, but inject #GP)
1141 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1142 Default is 1 (enabled)
1144 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1147 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1149 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1151 kvm-intel.bypass_guest_pf=
1152 [KVM,Intel] Disables bypassing of guest page faults
1153 on Intel chips. Default is 1 (enabled)
1155 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1156 (virtualized MMU) support on capable Intel chips.
1157 Default is 1 (enabled)
1159 kvm-intel.emulate_invalid_guest_state=
1160 [KVM,Intel] Enable emulation of invalid guest states
1161 Default is 0 (disabled)
1163 kvm-intel.flexpriority=
1164 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1165 Default is 1 (enabled)
1167 kvm-intel.unrestricted_guest=
1168 [KVM,Intel] Disable unrestricted guest feature
1169 (virtualized real and unpaged mode) on capable
1170 Intel chips. Default is 1 (enabled)
1172 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1173 feature (tagged TLBs) on capable Intel chips.
1174 Default is 1 (enabled)
1180 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1183 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1186 libata.dma= [LIBATA] DMA control
1187 libata.dma=0 Disable all PATA and SATA DMA
1188 libata.dma=1 PATA and SATA Disk DMA only
1189 libata.dma=2 ATAPI (CDROM) DMA only
1190 libata.dma=4 Compact Flash DMA only
1191 Combinations also work, so libata.dma=3 enables DMA
1192 for disks and CDROMs, but not CFs.
1194 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1195 libata.ignore_hpa=0 keep BIOS limits (default)
1196 libata.ignore_hpa=1 ignore limits, using full disk
1198 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1202 libata.force= [LIBATA] Force configurations. The format is comma
1203 separated list of "[ID:]VAL" where ID is
1204 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1205 matching port, link or device. Basically, it matches
1206 the ATA ID string printed on console by libata. If
1207 the whole ID part is omitted, the last PORT and DEVICE
1208 values are used. If ID hasn't been specified yet, the
1209 configuration applies to all ports, links and devices.
1211 If only DEVICE is omitted, the parameter applies to
1212 the port and all links and devices behind it. DEVICE
1213 number of 0 either selects the first device or the
1214 first fan-out link behind PMP device. It does not
1215 select the host link. DEVICE number of 15 selects the
1216 host link and device attached to it.
1218 The VAL specifies the configuration to force. As long
1219 as there's no ambiguity shortcut notation is allowed.
1220 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1221 The following configurations can be forced.
1223 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1224 Any ID with matching PORT is used.
1226 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1228 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1229 udma[/][16,25,33,44,66,100,133] notation is also
1232 * [no]ncq: Turn on or off NCQ.
1234 * nohrst, nosrst, norst: suppress hard, soft
1237 If there are multiple matching configurations changing
1238 the same attribute, the last one is used.
1240 lmb=debug [KNL] Enable lmb debug messages.
1242 load_ramdisk= [RAM] List of ramdisks to load from floppy
1243 See Documentation/blockdev/ramdisk.txt.
1245 lockd.nlm_grace_period=P [NFS] Assign grace period.
1248 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1251 lockd.nlm_timeout=T [NFS] Assign timeout value.
1254 lockd.nlm_udpport=M [NFS] Assign UDP port.
1257 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1260 loglevel= All Kernel Messages with a loglevel smaller than the
1261 console loglevel will be printed to the console. It can
1262 also be changed with klogd or other programs. The
1263 loglevels are defined as follows:
1265 0 (KERN_EMERG) system is unusable
1266 1 (KERN_ALERT) action must be taken immediately
1267 2 (KERN_CRIT) critical conditions
1268 3 (KERN_ERR) error conditions
1269 4 (KERN_WARNING) warning conditions
1270 5 (KERN_NOTICE) normal but significant condition
1271 6 (KERN_INFO) informational
1272 7 (KERN_DEBUG) debug-level messages
1274 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1275 Format: { n | nk | nM }
1276 n must be a power of two. The default size
1277 is set in the kernel config file.
1279 logo.nologo [FB] Disables display of the built-in Linux logo.
1280 This may be used to provide more screen space for
1281 kernel log messages and is useful when debugging
1282 kernel boot problems.
1284 lp=0 [LP] Specify parallel ports to use, e.g,
1285 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1286 lp=reset first parallel port). 'lp=0' disables the
1287 lp=auto printer driver. 'lp=reset' (which can be
1288 specified in addition to the ports) causes
1289 attached printers to be reset. Using
1290 lp=port1,port2,... specifies the parallel ports
1291 to associate lp devices with, starting with
1292 lp0. A port specification may be 'none' to skip
1293 that lp device, or a parport name such as
1294 'parport0'. Specifying 'lp=auto' instead of a
1295 port specification list means that device IDs
1296 from each port should be examined, to see if
1297 an IEEE 1284-compliant printer is attached; if
1298 so, the driver will manage that printer.
1299 See also header of drivers/char/lp.c.
1302 Sets loops_per_jiffy to given constant, thus avoiding
1303 time-consuming boot-time autodetection (up to 250 ms per
1304 CPU). 0 enables autodetection (default). To determine
1305 the correct value for your kernel, boot with normal
1306 autodetection and see what value is printed. Note that
1307 on SMP systems the preset will be applied to all CPUs,
1308 which is likely to cause problems if your CPUs need
1309 significantly divergent settings. An incorrect value
1310 will cause delays in the kernel to be wrong, leading to
1311 unpredictable I/O errors and other breakage. Although
1312 unlikely, in the extreme case this might damage your
1316 Format: <io>,<irq>,<dma>
1318 mac5380= [HW,SCSI] Format:
1319 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1321 machvec= [IA64] Force the use of a particular machine-vector
1322 (machvec) in a generic kernel.
1323 Example: machvec=hpzx1_swiotlb
1325 machtype= [Loongson] Share the same kernel image file between different
1327 Example: machtype=lemote-yeeloong-2f-7inch
1329 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1330 than or equal to this physical address is ignored.
1332 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1333 should make use of. maxcpus=n : n >= 0 limits the
1334 kernel to using 'n' processors. n=0 is a special case,
1335 it is equivalent to "nosmp", which also disables
1338 max_loop= [LOOP] Maximum number of loopback devices that can
1342 max_luns= [SCSI] Maximum number of LUNs to probe.
1343 Should be between 1 and 2^32-1.
1346 [SCSI] Maximum number of LUNs received.
1347 Should be between 1 and 16384.
1351 mce [X86-32] Machine Check Exception
1353 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1355 md= [HW] RAID subsystems devices and level
1356 See Documentation/md.txt.
1359 Format: <first>,<last>
1360 Specifies range of consoles to be captured by the MDA.
1362 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1363 Amount of memory to be used when the kernel is not able
1364 to see the whole system memory or for test.
1365 [X86-32] Use together with memmap= to avoid physical
1366 address space collisions. Without memmap= PCI devices
1367 could be placed at addresses belonging to unused RAM.
1369 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1373 [KNL,SH] Allow user to override the default size for
1374 per-device physically contiguous DMA buffers.
1376 memmap=exactmap [KNL,X86] Enable setting of an exact
1377 E820 memory map, as specified by the user.
1378 Such memmap=exactmap lines can be constructed based on
1379 BIOS output or other requirements. See the memmap=nn@ss
1382 memmap=nn[KMG]@ss[KMG]
1383 [KNL] Force usage of a specific region of memory
1384 Region of memory to be used, from ss to ss+nn.
1386 memmap=nn[KMG]#ss[KMG]
1387 [KNL,ACPI] Mark specific memory as ACPI data.
1388 Region of memory to be used, from ss to ss+nn.
1390 memmap=nn[KMG]$ss[KMG]
1391 [KNL,ACPI] Mark specific memory as reserved.
1392 Region of memory to be used, from ss to ss+nn.
1393 Example: Exclude memory from 0x18690000-0x1869ffff
1394 memmap=64K$0x18690000
1396 memmap=0x10000$0x18690000
1398 memory_corruption_check=0/1 [X86]
1399 Some BIOSes seem to corrupt the first 64k of
1400 memory when doing things like suspend/resume.
1401 Setting this option will scan the memory
1402 looking for corruption. Enabling this will
1403 both detect corruption and prevent the kernel
1404 from using the memory being corrupted.
1405 However, its intended as a diagnostic tool; if
1406 repeatable BIOS-originated corruption always
1407 affects the same memory, you can use memmap=
1408 to prevent the kernel from using that memory.
1410 memory_corruption_check_size=size [X86]
1411 By default it checks for corruption in the low
1412 64k, making this memory unavailable for normal
1413 use. Use this parameter to scan for
1414 corruption in more or less memory.
1416 memory_corruption_check_period=seconds [X86]
1417 By default it checks for corruption every 60
1418 seconds. Use this parameter to check at some
1419 other rate. 0 disables periodic checking.
1421 memtest= [KNL,X86] Enable memtest
1423 default : 0 <disable>
1424 Specifies the number of memtest passes to be
1425 performed. Each pass selects another test
1426 pattern from a given set of patterns. Memtest
1427 fills the memory with this pattern, validates
1428 memory contents and reserves bad memory
1429 regions that are detected.
1431 meye.*= [HW] Set MotionEye Camera parameters
1432 See Documentation/video4linux/meye.txt.
1434 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1435 Multi-Function General Purpose Timers on AMD Geode
1438 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1439 the BIOS has incorrectly applied a workaround. TinyBIOS
1440 version 0.98 is known to be affected, 0.99 fixes the
1441 problem by letting the user disable the workaround.
1445 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1446 physical address is ignored.
1448 mini2440= [ARM,HW,KNL]
1449 Format:[0..2][b][c][t]
1451 MINI2440 configuration specification:
1452 0 - The attached screen is the 3.5" TFT
1453 1 - The attached screen is the 7" TFT
1454 2 - The VGA Shield is attached (1024x768)
1455 Leaving out the screen size parameter will not load
1456 the TFT driver, and the framebuffer will be left
1458 b - Enable backlight. The TFT backlight pin will be
1459 linked to the kernel VESA blanking code and a GPIO
1460 LED. This parameter is not necessary when using the
1462 c - Enable the s3c camera interface.
1463 t - Reserved for enabling touchscreen support. The
1464 touchscreen support is not enabled in the mainstream
1465 kernel as of 2.6.30, a preliminary port can be found
1466 in the "bleeding edge" mini2440 support kernel at
1467 http://repo.or.cz/w/linux-2.6/mini2440.git
1470 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1471 parameter allows control of the logging verbosity for
1472 the additional memory initialisation checks. A value
1473 of 0 disables mminit logging and a level of 4 will
1474 log everything. Information is printed at KERN_DEBUG
1475 so loglevel=8 may also need to be specified.
1478 [MOUSE] Maximum time between finger touching and
1479 leaving touchpad surface for touch to be considered
1480 a tap and be reported as a left button click (for
1481 touchpads working in absolute mode only).
1483 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1484 reporting absolute coordinates, such as tablets
1485 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1486 reporting absolute coordinates, such as tablets
1488 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1489 is similar to kernelcore except it specifies the
1490 amount of memory used for migratable allocations.
1491 If both kernelcore and movablecore is specified,
1492 then kernelcore will be at *least* the specified
1493 value but may be more. If movablecore on its own
1494 is specified, the administrator must be careful
1495 that the amount of memory usable for all allocations
1501 MTD_Partition= [MTD]
1502 Format: <name>,<region-number>,<size>,<offset>
1504 MTD_Region= [MTD] Format:
1505 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1508 See drivers/mtd/cmdlinepart.c.
1510 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1512 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1514 boundary - index of last SLC block on Flex-OneNAND.
1515 The remaining blocks are configured as MLC blocks.
1516 lock - Configure if Flex-OneNAND boundary should be locked.
1517 Once locked, the boundary cannot be changed.
1518 1 indicates lock status, 0 indicates unlock status.
1521 ARM/S3C2412 JIVE boot control
1523 See arch/arm/mach-s3c2412/mach-jive.c
1525 mtouchusb.raw_coordinates=
1526 [HW] Make the MicroTouch USB driver use raw coordinates
1527 ('y', default) or cooked coordinates ('n')
1529 mtrr_chunk_size=nn[KMG] [X86]
1530 used for mtrr cleanup. It is largest continuous chunk
1531 that could hold holes aka. UC entries.
1533 mtrr_gran_size=nn[KMG] [X86]
1534 Used for mtrr cleanup. It is granularity of mtrr block.
1536 Large value could prevent small alignment from
1539 mtrr_spare_reg_nr=n [X86]
1541 Range: 0,7 : spare reg number
1543 Used for mtrr cleanup. It is spare mtrr entries number.
1544 Set to 2 or more if your graphical card needs more.
1546 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1549 See header of drivers/scsi/NCR_D700.c.
1553 ncr53c400= [HW,SCSI]
1555 ncr53c400a= [HW,SCSI]
1557 ncr53c406a= [HW,SCSI]
1559 ncr53c8xx= [HW,SCSI]
1561 netdev= [NET] Network devices parameters
1562 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1563 Note that mem_start is often overloaded to mean
1564 something different and driver-specific.
1565 This usage is only documented in each driver source
1569 [NETFILTER] Enable connection tracking flow accounting
1570 0 to disable accounting
1571 1 to enable accounting
1572 Default value depends on CONFIG_NF_CT_ACCT that is
1573 going to be removed in 2.6.29.
1576 See Documentation/filesystems/nfs/nfsroot.txt.
1578 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1579 See Documentation/filesystems/nfs/nfsroot.txt.
1581 nfs.callback_tcpport=
1582 [NFS] set the TCP port on which the NFSv4 callback
1583 channel should listen.
1586 [NFS] sets the pathname to the program which is used
1587 to update the NFS client cache entries.
1589 nfs.cache_getent_timeout=
1590 [NFS] sets the timeout after which an attempt to
1591 update a cache entry is deemed to have failed.
1593 nfs.idmap_cache_timeout=
1594 [NFS] set the maximum lifetime for idmapper cache
1598 [NFS] enable 64-bit inode numbers.
1599 If zero, the NFS client will fake up a 32-bit inode
1600 number for the readdir() and stat() syscalls instead
1601 of returning the full 64-bit number.
1602 The default is to return 64-bit inode numbers.
1604 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1605 when a NMI is triggered.
1606 Format: [state][,regs][,debounce][,die]
1608 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1609 Format: [panic,][num]
1611 0 - turn nmi_watchdog off
1612 1 - use the IO-APIC timer for the NMI watchdog
1613 2 - use the local APIC for the NMI watchdog using
1614 a performance counter. Note: This will use one
1615 performance counter and the local APIC's performance
1617 When panic is specified, panic when an NMI watchdog
1619 This is useful when you use a panic=... timeout and
1620 need the box quickly up again.
1621 Instead of 1 and 2 it is possible to use the following
1622 symbolic names: lapic and ioapic
1623 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1625 netpoll.carrier_timeout=
1626 [NET] Specifies amount of time (in seconds) that
1627 netpoll should wait for a carrier. By default netpoll
1630 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1631 emulation library even if a 387 maths coprocessor
1635 [HW] Never suspend the console
1636 Disable suspending of consoles during suspend and
1637 hibernate operations. Once disabled, debugging
1638 messages can reach various consoles while the rest
1639 of the system is being put to sleep (ie, while
1640 debugging driver suspend/resume hooks). This may
1641 not work reliably with all consoles, but is known
1642 to work with serial and VGA consoles.
1644 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1645 caches in the slab allocator. Saves per-node memory,
1646 but will impact performance.
1650 noapic [SMP,APIC] Tells the kernel to not make use of any
1651 IOAPICs that may be present in the system.
1653 nobats [PPC] Do not use BATs for mapping kernel lowmem
1654 on "Classic" PPC cores.
1658 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1660 nodelayacct [KNL] Disable per-task delay accounting
1662 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1664 nodsp [SH] Disable hardware DSP at boot time.
1666 noefi [X86] Disable EFI runtime services support.
1671 On X86-32 available only on PAE configured kernels.
1672 noexec=on: enable non-executable mappings (default)
1673 noexec=off: disable non-executable mappings
1676 This affects only 32-bit executables.
1677 noexec32=on: enable non-executable mappings (default)
1678 read doesn't imply executable mappings
1679 noexec32=off: disable non-executable mappings
1680 read implies executable mappings
1682 nofpu [SH] Disable hardware FPU at boot time.
1684 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1685 register save and restore. The kernel will only save
1686 legacy floating-point registers on task switch.
1688 noxsave [BUGS=X86] Disables x86 extended register state save
1689 and restore using xsave. The kernel will fallback to
1690 enabling legacy floating-point and sse state.
1692 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1693 wfi(ARM) instruction doesn't work correctly and not to
1694 use it. This is also useful when using JTAG debugger.
1696 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1697 instruction doesn't work correctly and not to
1700 no_file_caps Tells the kernel not to honor file capabilities. The
1701 only way then for a file to be executed with privilege
1702 is to be setuid root or executed by root.
1704 nohalt [IA-64] Tells the kernel not to use the power saving
1705 function PAL_HALT_LIGHT when idle. This increases
1706 power-consumption. On the positive side, it reduces
1707 interrupt wake-up latency, which may improve performance
1708 in certain environments such as networked servers or
1711 nohz= [KNL] Boottime enable/disable dynamic ticks
1712 Valid arguments: on, off
1715 noiotrap [SH] Disables trapped I/O port accesses.
1717 noirqdebug [X86-32] Disables the code which attempts to detect and
1718 disable unhandled interrupt sources.
1720 no_timer_check [X86,APIC] Disables the code which tests for
1721 broken timer IRQ sources.
1723 noisapnp [ISAPNP] Disables ISA PnP code.
1725 noinitrd [RAM] Tells the kernel not to load any configured
1728 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1733 nojitter [IA64] Disables jitter checking for ITC timers.
1735 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1737 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1739 noltlbs [PPC] Do not use large page/tlb entries for kernel
1740 lowmem mapping on PPC40x.
1742 nomca [IA-64] Disable machine check abort handling
1744 nomce [X86-32] Machine Check Exception
1746 nomfgpt [X86-32] Disable Multi-Function General Purpose
1747 Timer usage (for AMD Geode machines).
1749 nopat [X86] Disable PAT (page attribute table extension of
1750 pagetables) support.
1752 norandmaps Don't use address space randomization. Equivalent to
1753 echo 0 > /proc/sys/kernel/randomize_va_space
1755 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1757 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1758 with UP alternatives
1760 noresidual [PPC] Don't use residual data on PReP machines.
1762 noresume [SWSUSP] Disables resume and restores original swap
1765 no-scroll [VGA] Disables scrollback.
1766 This is required for the Braillex ib80-piezo Braille
1767 reader made by F.H. Papenmeier (Germany).
1771 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1773 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1774 and disable the IO APIC. legacy for "maxcpus=0".
1776 nosoftlockup [KNL] Disable the soft-lockup detector.
1778 noswapaccount [KNL] Disable accounting of swap in memory resource
1779 controller. (See Documentation/cgroups/memory.txt)
1781 nosync [HW,M68K] Disables sync negotiation for all devices.
1783 notsc [BUGS=X86-32] Disable Time Stamp Counter
1785 nousb [USB] Disable the USB subsystem
1789 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1791 nptcg= [IA64] Override max number of concurrent global TLB
1792 purges which is reported from either PAL_VM_SUMMARY or
1795 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1796 could support. nr_cpus=n : n >= 1 limits the kernel to
1797 supporting 'n' processors. Later in runtime you can not
1798 use hotplug cpu feature to put more cpu back to online.
1799 just like you compile the kernel NR_CPUS=n
1801 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1803 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1804 one of ['zone', 'node', 'default'] can be specified
1805 This can be set from sysctl after boot.
1806 See Documentation/sysctl/vm.txt for details.
1808 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1809 See Documentation/debugging-via-ohci1394.txt for more
1812 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1813 Rather than timing out after 20 ms if an EC
1814 command is not properly ACKed, override the length
1815 of the timeout. We have interrupts disabled while
1816 waiting for the ACK, so if this is set too high
1817 interrupts *may* be lost!
1819 omap_mux= [OMAP] Override bootloader pin multiplexing.
1820 Format: <mux_mode0.mode_name=value>...
1821 For example, to override I2C bus2:
1822 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1827 oprofile.timer= [HW]
1828 Use timer interrupt instead of performance counters
1830 oprofile.cpu_type= Force an oprofile cpu type
1831 This might be useful if you have an older oprofile
1832 userland or if you want common events.
1833 Format: { arch_perfmon }
1834 arch_perfmon: [X86] Force use of architectural
1835 perfmon on Intel CPUs instead of the
1836 CPU specific event set.
1838 osst= [HW,SCSI] SCSI Tape Driver
1839 Format: <buffer_size>,<write_threshold>
1840 See also Documentation/scsi/st.txt.
1842 panic= [KNL] Kernel behaviour on panic
1845 parkbd.port= [HW] Parallel port number the keyboard adapter is
1846 connected to, default is 0.
1848 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1849 0 for XT, 1 for AT (default is AT).
1852 parport= [HW,PPT] Specify parallel ports. 0 disables.
1853 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1854 Use 'auto' to force the driver to use any
1855 IRQ/DMA settings detected (the default is to
1856 ignore detected IRQ/DMA settings because of
1857 possible conflicts). You can specify the base
1858 address, IRQ, and DMA settings; IRQ and DMA
1859 should be numbers, or 'auto' (for using detected
1860 settings on that particular port), or 'nofifo'
1861 (to avoid using a FIFO even if it is detected).
1862 Parallel ports are assigned in the order they
1863 are specified on the command line, starting
1866 parport_init_mode= [HW,PPT]
1867 Configure VIA parallel port to operate in
1868 a specific mode. This is necessary on Pegasos
1869 computer where firmware has no options for setting
1870 up parallel port mode and sets it to spp.
1871 Currently this function knows 686a and 8231 chips.
1872 Format: [spp|ps2|epp|ecp|ecpepp]
1874 pas2= [HW,OSS] Format:
1875 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1878 See header of drivers/scsi/pas16.c.
1881 Halt all CPUs after the first oops has been printed for
1882 the specified number of seconds. This is to be used if
1883 your oopses keep scrolling off the screen.
1888 See header of drivers/block/paride/pcd.c.
1889 See also Documentation/blockdev/paride.txt.
1891 pci=option[,option...] [PCI] various PCI subsystem options:
1892 earlydump [X86] dump PCI config space before the kernel
1894 off [X86] don't probe for the PCI bus
1895 bios [X86-32] force use of PCI BIOS, don't access
1896 the hardware directly. Use this if your machine
1897 has a non-standard PCI host bridge.
1898 nobios [X86-32] disallow use of PCI BIOS, only direct
1899 hardware access methods are allowed. Use this
1900 if you experience crashes upon bootup and you
1901 suspect they are caused by the BIOS.
1902 conf1 [X86] Force use of PCI Configuration
1904 conf2 [X86] Force use of PCI Configuration
1906 noaer [PCIE] If the PCIEAER kernel config parameter is
1907 enabled, this kernel boot option can be used to
1908 disable the use of PCIE advanced error reporting.
1909 nodomains [PCI] Disable support for multiple PCI
1910 root domains (aka PCI segments, in ACPI-speak).
1911 nommconf [X86] Disable use of MMCONFIG for PCI
1913 check_enable_amd_mmconf [X86] check for and enable
1914 properly configured MMIO access to PCI
1915 config space on AMD family 10h CPU
1916 nomsi [MSI] If the PCI_MSI kernel config parameter is
1917 enabled, this kernel boot option can be used to
1918 disable the use of MSI interrupts system-wide.
1919 noioapicquirk [APIC] Disable all boot interrupt quirks.
1920 Safety option to keep boot IRQs enabled. This
1921 should never be necessary.
1922 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1923 primary IO-APIC for bridges that cannot disable
1924 boot IRQs. This fixes a source of spurious IRQs
1925 when the system masks IRQs.
1926 noioapicreroute [APIC] Disable workaround that uses the
1927 boot IRQ equivalent of an IRQ that connects to
1928 a chipset where boot IRQs cannot be disabled.
1929 The opposite of ioapicreroute.
1930 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1931 routing table. These calls are known to be buggy
1932 on several machines and they hang the machine
1933 when used, but on other computers it's the only
1934 way to get the interrupt routing table. Try
1935 this option if the kernel is unable to allocate
1936 IRQs or discover secondary PCI buses on your
1938 rom [X86] Assign address space to expansion ROMs.
1939 Use with caution as certain devices share
1940 address decoders between ROMs and other
1942 norom [X86] Do not assign address space to
1943 expansion ROMs that do not already have
1944 BIOS assigned address ranges.
1945 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1946 assigned automatically to PCI devices. You can
1947 make the kernel exclude IRQs of your ISA cards
1949 pirqaddr=0xAAAAA [X86] Specify the physical address
1950 of the PIRQ table (normally generated
1951 by the BIOS) if it is outside the
1952 F0000h-100000h range.
1953 lastbus=N [X86] Scan all buses thru bus #N. Can be
1954 useful if the kernel is unable to find your
1955 secondary buses and you want to tell it
1956 explicitly which ones they are.
1957 assign-busses [X86] Always assign all PCI bus
1958 numbers ourselves, overriding
1959 whatever the firmware may have done.
1960 usepirqmask [X86] Honor the possible IRQ mask stored
1961 in the BIOS $PIR table. This is needed on
1962 some systems with broken BIOSes, notably
1963 some HP Pavilion N5400 and Omnibook XE3
1964 notebooks. This will have no effect if ACPI
1965 IRQ routing is enabled.
1966 noacpi [X86] Do not use ACPI for IRQ routing
1967 or for PCI scanning.
1968 use_crs [X86] Use PCI host bridge window information
1969 from ACPI. On BIOSes from 2008 or later, this
1970 is enabled by default. If you need to use this,
1971 please report a bug.
1972 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1973 If you need to use this, please report a bug.
1974 routeirq Do IRQ routing for all PCI devices.
1975 This is normally done in pci_enable_device(),
1976 so this option is a temporary workaround
1977 for broken drivers that don't call it.
1978 skip_isa_align [X86] do not align io start addr, so can
1979 handle more pci cards
1980 firmware [ARM] Do not re-enumerate the bus but instead
1981 just use the configuration from the
1982 bootloader. This is currently used on
1983 IXP2000 systems where the bus has to be
1984 configured a certain way for adjunct CPUs.
1985 noearly [X86] Don't do any early type 1 scanning.
1986 This might help on some broken boards which
1987 machine check when some devices' config space
1988 is read. But various workarounds are disabled
1989 and some IOMMU drivers will not work.
1990 bfsort Sort PCI devices into breadth-first order.
1991 This sorting is done to get a device
1992 order compatible with older (<= 2.4) kernels.
1993 nobfsort Don't sort PCI devices into breadth-first order.
1994 cbiosize=nn[KMG] The fixed amount of bus space which is
1995 reserved for the CardBus bridge's IO window.
1996 The default value is 256 bytes.
1997 cbmemsize=nn[KMG] The fixed amount of bus space which is
1998 reserved for the CardBus bridge's memory
1999 window. The default value is 64 megabytes.
2002 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2003 Specifies alignment and device to reassign
2004 aligned memory resources.
2005 If <order of align> is not specified,
2006 PAGE_SIZE is used as alignment.
2007 PCI-PCI bridge can be specified, if resource
2008 windows need to be expanded.
2009 ecrc= Enable/disable PCIe ECRC (transaction layer
2010 end-to-end CRC checking).
2011 bios: Use BIOS/firmware settings. This is the
2016 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2019 force Enable ASPM even on devices that claim not to support it.
2020 WARNING: Forcing ASPM on may cause system lockups.
2022 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2023 off Do not use native PCIe PME signaling.
2024 force Use native PCIe PME signaling even if the BIOS refuses
2025 to allow the kernel to control the relevant PCIe config
2027 nomsi Do not use MSI for native PCIe PME signaling (this makes
2028 all PCIe root ports use INTx for everything).
2030 pcmv= [HW,PCMCIA] BadgePAD 4
2033 See Documentation/blockdev/paride.txt.
2035 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2038 See arch/parisc/kernel/pdc_chassis.c
2040 percpu_alloc= Select which percpu first chunk allocator to use.
2041 Currently supported values are "embed" and "page".
2042 Archs may support subset or none of the selections.
2043 See comments in mm/percpu.c for details on each
2044 allocator. This parameter is primarily for debugging
2045 and performance comparison.
2048 See Documentation/blockdev/paride.txt.
2051 See Documentation/blockdev/paride.txt.
2053 pirq= [SMP,APIC] Manual mp-table setup
2054 See Documentation/x86/i386/IO-APIC.txt.
2056 plip= [PPT,NET] Parallel port network link
2057 Format: { parport<nr> | timid | 0 }
2058 See also Documentation/parport.txt.
2060 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2061 Override pmtimer IOPort with a hex value.
2065 Enable PNP debug messages. This depends on the
2066 CONFIG_PNP_DEBUG_MESSAGES option.
2072 { on | off | curr | res | no-curr | no-res }
2075 [ISAPNP] Exclude IRQs for the autoconfiguration
2078 [ISAPNP] Exclude DMAs for the autoconfiguration
2080 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2081 Ranges are in pairs (I/O port base and size).
2084 [ISAPNP] Exclude memory regions for the
2086 Ranges are in pairs (memory base and size).
2088 ports= [IP_VS_FTP] IPVS ftp helper module
2090 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2092 Format: <port>,<port>....
2094 print-fatal-signals=
2095 [KNL] debug: print fatal signals
2097 If enabled, warn about various signal handling
2098 related application anomalies: too many signals,
2099 too many POSIX.1 timers, fatal signals causing a
2102 If you hit the warning due to signal overflow,
2103 you might want to try "ulimit -i unlimited".
2107 printk.time= Show timing data prefixed to each printk message line
2108 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2110 processor.max_cstate= [HW,ACPI]
2111 Limit processor to maximum C-state
2112 max_cstate=9 overrides any DMI blacklist limit.
2114 processor.nocst [HW,ACPI]
2115 Ignore the _CST method to determine C-states,
2116 instead using the legacy FADT method
2118 profile= [KNL] Enable kernel profiling via /proc/profile
2119 Format: [schedule,]<number>
2120 Param: "schedule" - profile schedule points.
2121 Param: <number> - step/bucket size as a power of 2 for
2122 statistical time based profiling.
2123 Param: "sleep" - profile D-state sleeping (millisecs).
2124 Requires CONFIG_SCHEDSTATS
2125 Param: "kvm" - profile VM exits.
2127 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2129 See Documentation/blockdev/ramdisk.txt.
2131 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2132 probe for; one of (bare|imps|exps|lifebook|any).
2133 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2135 psmouse.resetafter= [HW,MOUSE]
2136 Try to reset the device after so many bad packets
2139 [HW,MOUSE] Set desired mouse resolution, in dpi.
2140 psmouse.smartscroll=
2141 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2142 0 = disabled, 1 = enabled (default).
2144 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2146 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2149 See Documentation/blockdev/paride.txt.
2152 [KNL] Number of legacy pty's. Overwrites compiled-in
2155 quiet [KNL] Disable most log messages
2160 See Documentation/md.txt.
2162 ramdisk_blocksize= [RAM]
2163 See Documentation/blockdev/ramdisk.txt.
2165 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2166 See Documentation/blockdev/ramdisk.txt.
2168 rcupdate.blimit= [KNL,BOOT]
2169 Set maximum number of finished RCU callbacks to process
2172 rcupdate.qhimark= [KNL,BOOT]
2173 Set threshold of queued
2174 RCU callbacks over which batch limiting is disabled.
2176 rcupdate.qlowmark= [KNL,BOOT]
2177 Set threshold of queued RCU callbacks below which
2178 batch limiting is re-enabled.
2182 Run specified binary instead of /init from the ramdisk,
2183 used for early userspace startup. See initrd.
2185 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2186 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2187 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2190 [KNL, SMP] Set scheduler's default relax_domain_level.
2191 See Documentation/cgroups/cpusets.txt.
2193 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2195 reservetop= [X86-32]
2197 Reserves a hole at the top of the kernel virtual
2200 reset_devices [KNL] Force drivers to reset the underlying device
2201 during initialization.
2204 Specify the partition device for software suspend
2206 resume_offset= [SWSUSP]
2207 Specify the offset from the beginning of the partition
2208 given by "resume=" at which the swap header is located,
2209 in <PAGE_SIZE> units (needed only for swap files).
2210 See Documentation/power/swsusp-and-swap-files.txt
2212 retain_initrd [RAM] Keep initrd memory after extraction
2214 rhash_entries= [KNL,NET]
2215 Set number of hash buckets for route cache
2217 riscom8= [HW,SERIAL]
2218 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2220 ro [KNL] Mount root device read-only on boot
2222 root= [KNL] Root filesystem
2224 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2225 mount the root filesystem
2227 rootflags= [KNL] Set root filesystem mount option string
2229 rootfstype= [KNL] Set root filesystem type
2231 rootwait [KNL] Wait (indefinitely) for root device to show up.
2232 Useful for devices that are detected asynchronously
2233 (e.g. USB and MMC devices).
2235 rw [KNL] Mount root device read-write on boot
2237 S [KNL] Run init in single mode
2240 See drivers/net/irda/sa1100_ir.c.
2242 sbni= [NET] Granch SBNI12 leased line adapter
2244 sched_debug [KNL] Enables verbose scheduler debug messages.
2246 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2247 Format: <io>[,<timeout>[,<isapnp>]]
2249 scsi_debug_*= [SCSI]
2250 See drivers/scsi/scsi_debug.c.
2252 scsi_default_dev_flags=
2253 [SCSI] SCSI default device flags
2256 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2257 Format: <vendor>:<model>:<flags>
2258 (flags are integer value)
2260 scsi_logging_level= [SCSI] a bit mask of logging levels
2261 See drivers/scsi/scsi_logging.h for bits. Also
2262 settable via sysctl at dev.scsi.logging_level
2263 (/proc/sys/dev/scsi/logging_level).
2264 There is also a nice 'scsi_logging_level' script in the
2265 S390-tools package, available for download at
2266 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2268 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2269 discovered. async scans them in kernel threads,
2270 allowing boot to proceed. none ignores them, expecting
2271 user space to do the scan.
2273 security= [SECURITY] Choose a security module to enable at boot.
2274 If this boot parameter is not specified, only the first
2275 security module asking for security registration will be
2276 loaded. An invalid security module name will be treated
2277 as if no module has been chosen.
2279 selinux= [SELINUX] Disable or enable SELinux at boot time.
2280 Format: { "0" | "1" }
2281 See security/selinux/Kconfig help text.
2284 Default value is set via kernel config option.
2285 If enabled at boot time, /selinux/disable can be used
2286 later to disable prior to initial policy load.
2288 serialnumber [BUGS=X86-32]
2291 Maximal number of shapers.
2293 show_msr= [x86] show boot-time MSR settings
2294 Format: { <integer> }
2295 Show boot-time (BIOS-initialized) MSR settings.
2296 The parameter means the number of CPUs to show,
2297 for example 1 means boot CPU only.
2300 See header of drivers/scsi/sim710.c.
2307 slub_debug[=options[,slabs]] [MM, SLUB]
2308 Enabling slub_debug allows one to determine the
2309 culprit if slab objects become corrupted. Enabling
2310 slub_debug can create guard zones around objects and
2311 may poison objects when not in use. Also tracks the
2312 last alloc / free. For more information see
2313 Documentation/vm/slub.txt.
2315 slub_max_order= [MM, SLUB]
2316 Determines the maximum allowed order for slabs.
2317 A high setting may cause OOMs due to memory
2318 fragmentation. For more information see
2319 Documentation/vm/slub.txt.
2321 slub_min_objects= [MM, SLUB]
2322 The minimum number of objects per slab. SLUB will
2323 increase the slab order up to slub_max_order to
2324 generate a sufficiently large slab able to contain
2325 the number of objects indicated. The higher the number
2326 of objects the smaller the overhead of tracking slabs
2327 and the less frequently locks need to be acquired.
2328 For more information see Documentation/vm/slub.txt.
2330 slub_min_order= [MM, SLUB]
2331 Determines the mininum page order for slabs. Must be
2332 lower than slub_max_order.
2333 For more information see Documentation/vm/slub.txt.
2335 slub_nomerge [MM, SLUB]
2336 Disable merging of slabs with similar size. May be
2337 necessary if there is some reason to distinguish
2338 allocs to different slabs. Debug options disable
2339 merging on their own.
2340 For more information see Documentation/vm/slub.txt.
2343 Format: <io1>[,<io2>[,...,<io8>]]
2345 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2346 attempt to substitute SMP alternatives once at boot.
2348 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2349 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2350 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2351 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2352 smsc-ircc2.ircc_irq= [HW] IRQ line
2353 smsc-ircc2.ircc_dma= [HW] DMA channel
2354 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2355 0: Toshiba Satellite 1800 (GP data pin select)
2356 1: Fast pin select (default)
2359 snd-ad1816a= [HW,ALSA]
2361 snd-ad1848= [HW,ALSA]
2363 snd-ali5451= [HW,ALSA]
2365 snd-als100= [HW,ALSA]
2367 snd-als4000= [HW,ALSA]
2369 snd-azt2320= [HW,ALSA]
2371 snd-cmi8330= [HW,ALSA]
2373 snd-cmipci= [HW,ALSA]
2375 snd-cs4231= [HW,ALSA]
2377 snd-cs4232= [HW,ALSA]
2379 snd-cs4236= [HW,ALSA]
2381 snd-cs4281= [HW,ALSA]
2383 snd-cs46xx= [HW,ALSA]
2385 snd-dt019x= [HW,ALSA]
2387 snd-dummy= [HW,ALSA]
2389 snd-emu10k1= [HW,ALSA]
2391 snd-ens1370= [HW,ALSA]
2393 snd-ens1371= [HW,ALSA]
2395 snd-es968= [HW,ALSA]
2397 snd-es1688= [HW,ALSA]
2399 snd-es18xx= [HW,ALSA]
2401 snd-es1938= [HW,ALSA]
2403 snd-es1968= [HW,ALSA]
2405 snd-fm801= [HW,ALSA]
2407 snd-gusclassic= [HW,ALSA]
2409 snd-gusextreme= [HW,ALSA]
2411 snd-gusmax= [HW,ALSA]
2415 snd-ice1712= [HW,ALSA]
2417 snd-intel8x0= [HW,ALSA]
2419 snd-interwave= [HW,ALSA]
2424 snd-korg1212= [HW,ALSA]
2426 snd-maestro3= [HW,ALSA]
2428 snd-mpu401= [HW,ALSA]
2430 snd-mtpav= [HW,ALSA]
2432 snd-nm256= [HW,ALSA]
2434 snd-opl3sa2= [HW,ALSA]
2442 snd-opti93x= [HW,ALSA]
2446 snd-rme32= [HW,ALSA]
2448 snd-rme96= [HW,ALSA]
2450 snd-rme9652= [HW,ALSA]
2456 snd-sbawe= [HW,ALSA]
2458 snd-serial= [HW,ALSA]
2460 snd-sgalaxy= [HW,ALSA]
2462 snd-sonicvibes= [HW,ALSA]
2467 snd-sun-cs4231= [HW,ALSA]
2469 snd-trident= [HW,ALSA]
2471 snd-usb-audio= [HW,ALSA,USB]
2473 snd-via82xx= [HW,ALSA]
2475 snd-virmidi= [HW,ALSA]
2477 snd-wavefront= [HW,ALSA]
2479 snd-ymfpci= [HW,ALSA]
2482 [KNL] Should the soft-lockup detector generate panics.
2484 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2485 See Documentation/sonypi.txt
2487 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2488 See Documentation/serial/specialix.txt.
2490 spia_io_base= [HW,MTD]
2496 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2498 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2499 See Documentation/scsi/st.txt.
2502 Enabled the stack tracer on boot up.
2506 Set the STI (builtin display/keyboard on the HP-PARISC
2507 machines) console (graphic card) which should be used
2508 as the initial boot-console.
2509 See also comment in drivers/video/console/sticore.c.
2512 See comment in drivers/video/console/sticore.c.
2515 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2517 sunrpc.min_resvport=
2518 sunrpc.max_resvport=
2520 SunRPC servers often require that client requests
2521 originate from a privileged port (i.e. a port in the
2522 range 0 < portnr < 1024).
2523 An administrator who wishes to reserve some of these
2524 ports for other uses may adjust the range that the
2525 kernel's sunrpc client considers to be privileged
2526 using these two parameters to set the minimum and
2527 maximum port values.
2531 Control how the NFS server code allocates CPUs to
2532 service thread pools. Depending on how many NICs
2533 you have and where their interrupts are bound, this
2534 option will affect which CPUs will do NFS serving.
2535 Note: this parameter cannot be changed while the
2536 NFS server is running.
2538 auto the server chooses an appropriate mode
2539 automatically using heuristics
2540 global a single global pool contains all CPUs
2541 percpu one pool for each CPU
2542 pernode one pool for each NUMA node (equivalent
2543 to global on non-NUMA machines)
2545 sunrpc.tcp_slot_table_entries=
2546 sunrpc.udp_slot_table_entries=
2548 Sets the upper limit on the number of simultaneous
2549 RPC calls that can be sent from the client to a
2550 server. Increasing these values may allow you to
2551 improve throughput, but will also increase the
2552 amount of memory reserved for use by the client.
2554 swiotlb= [IA-64] Number of I/O TLB slabs
2558 sym53c416= [HW,SCSI]
2559 See header of drivers/scsi/sym53c416.c.
2561 sysrq_always_enabled
2563 Ignore sysrq setting - this boot parameter will
2564 neutralize any effect of /proc/sys/kernel/sysrq.
2565 Useful for debugging.
2568 See header of drivers/scsi/t128.c.
2572 test_suspend= [SUSPEND]
2573 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2574 standby suspend) as the system sleep state to briefly
2575 enter during system startup. The system is woken from
2576 this state using a wakeup-capable RTC alarm.
2578 thash_entries= [KNL,NET]
2579 Set number of hash buckets for TCP connection
2581 thermal.act= [HW,ACPI]
2582 -1: disable all active trip points in all thermal zones
2583 <degrees C>: override all lowest active trip points
2585 thermal.crt= [HW,ACPI]
2586 -1: disable all critical trip points in all thermal zones
2587 <degrees C>: override all critical trip points
2589 thermal.nocrt= [HW,ACPI]
2590 Set to disable actions on ACPI thermal zone
2591 critical and hot trip points.
2593 thermal.off= [HW,ACPI]
2594 1: disable ACPI thermal control
2596 thermal.psv= [HW,ACPI]
2597 -1: disable all passive trip points
2598 <degrees C>: override all passive trip points to this
2601 thermal.tzp= [HW,ACPI]
2602 Specify global default ACPI thermal zone polling rate
2603 <deci-seconds>: poll all this frequency
2604 0: no polling (default)
2607 See comment before function dc390_setup() in
2608 drivers/scsi/tmscsim.c.
2612 Specify if the kernel should make use of the cpu
2613 topology informations if the hardware supports these.
2614 The scheduler will make use of these informations and
2615 e.g. base its process migration decisions on it.
2620 tpm_suspend_pcr=[HW,TPM]
2621 Format: integer pcr id
2622 Specify that at suspend time, the tpm driver
2623 should extend the specified pcr with zeros,
2624 as a workaround for some chips which fail to
2625 flush the last written pcr on TPM_SaveState.
2626 This will guarantee that all the other pcrs
2629 trace_buf_size=nn[KMG]
2630 [FTRACE] will set tracing buffer size.
2632 trace_event=[event-list]
2633 [FTRACE] Set and start specified trace events in order
2634 to facilitate early boot debugging.
2635 See also Documentation/trace/events.txt
2637 trix= [HW,OSS] MediaTrix AudioTrix Pro
2639 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2641 tsc= Disable clocksource-must-verify flag for TSC.
2643 [x86] reliable: mark tsc clocksource as reliable, this
2644 disables clocksource verification at runtime.
2645 Used to enable high-resolution timer mode on older
2646 hardware, and in virtualized environment.
2648 turbografx.map[2|3]= [HW,JOY]
2649 TurboGraFX parallel port interface
2651 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2652 See also Documentation/input/joystick-parport.txt
2654 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2655 See header of drivers/scsi/u14-34f.c.
2663 uhash_entries= [KNL,NET]
2664 Set number of hash buckets for UDP/UDP-Lite connections
2667 [USB] Ignore overcurrent events (default N).
2668 Some badly-designed motherboards generate lots of
2669 bogus events, for ports that aren't wired to
2670 anything. Set this parameter to avoid log spamming.
2671 Note that genuine overcurrent events won't be
2676 Set unknown_nmi_panic=1 early on boot.
2678 usbcore.autosuspend=
2679 [USB] The autosuspend time delay (in seconds) used
2680 for newly-detected USB devices (default 2). This
2681 is the time required before an idle device will be
2682 autosuspended. Devices for which the delay is set
2683 to a negative value won't be autosuspended at all.
2685 usbcore.usbfs_snoop=
2686 [USB] Set to log all usbfs traffic (default 0 = off).
2688 usbcore.blinkenlights=
2689 [USB] Set to cycle leds on hubs (default 0 = off).
2691 usbcore.old_scheme_first=
2692 [USB] Start with the old device initialization
2693 scheme (default 0 = off).
2695 usbcore.use_both_schemes=
2696 [USB] Try the other device initialization scheme
2697 if the first one fails (default 1 = enabled).
2699 usbcore.initial_descriptor_timeout=
2700 [USB] Specifies timeout for the initial 64-byte
2701 USB_REQ_GET_DESCRIPTOR request in milliseconds
2702 (default 5000 = 5.0 seconds).
2705 [USBHID] The interval which mice are to be polled at.
2707 usb-storage.delay_use=
2708 [UMS] The delay in seconds before a new device is
2709 scanned for Logical Units (default 5).
2712 [UMS] A list of quirks entries to supplement or
2713 override the built-in unusual_devs list. List
2714 entries are separated by commas. Each entry has
2715 the form VID:PID:Flags where VID and PID are Vendor
2716 and Product ID values (4-digit hex numbers) and
2717 Flags is a set of characters, each corresponding
2718 to a common usb-storage quirk flag as follows:
2719 a = SANE_SENSE (collect more than 18 bytes
2721 b = BAD_SENSE (don't collect more than 18
2722 bytes of sense data);
2723 c = FIX_CAPACITY (decrease the reported
2724 device capacity by one sector);
2725 h = CAPACITY_HEURISTICS (decrease the
2726 reported device capacity by one
2727 sector if the number is odd);
2728 i = IGNORE_DEVICE (don't bind to this
2730 l = NOT_LOCKABLE (don't try to lock and
2731 unlock ejectable media);
2732 m = MAX_SECTORS_64 (don't transfer more
2733 than 64 sectors = 32 KB at a time);
2734 o = CAPACITY_OK (accept the capacity
2735 reported by the device);
2736 r = IGNORE_RESIDUE (the device reports
2737 bogus residue values);
2738 s = SINGLE_LUN (the device has only one
2740 w = NO_WP_DETECT (don't test whether the
2741 medium is write-protected).
2742 Example: quirks=0419:aaf5:rl,0421:0433:rc
2745 [X86] Flags controlling user PTE allocations.
2747 nohigh = do not allocate PTE pages in
2748 HIGHMEM regardless of setting
2752 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2753 vdso=1: enable VDSO (default)
2754 vdso=0: disable VDSO mapping
2757 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2758 vdso32=1: enable 32-bit VDSO (default)
2759 vdso32=0: disable 32-bit VDSO mapping
2762 vector=percpu: enable percpu vector domain
2764 video= [FB] Frame buffer configuration
2765 See Documentation/fb/modedb.txt.
2767 vga= [BOOT,X86-32] Select a particular video mode
2768 See Documentation/x86/boot.txt and
2769 Documentation/svga.txt.
2770 Use vga=ask for menu.
2771 This is actually a boot loader parameter; the value is
2772 passed to the kernel using a special protocol.
2774 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2775 size of <nn>. This can be used to increase the
2776 minimum size (128MB on x86). It can also be used to
2777 decrease the size and leave more room for directly
2780 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2783 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2786 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2789 vt.cur_default= [VT] Default cursor shape.
2790 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2791 the parameters of the <Esc>[?A;B;Cc escape sequence;
2792 see VGA-softcursor.txt. Default: 2 = underline.
2794 vt.default_blu= [VT]
2795 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2796 Change the default blue palette of the console.
2797 This is a 16-member array composed of values
2800 vt.default_grn= [VT]
2801 Format: <green0>,<green1>,<green2>,...,<green15>
2802 Change the default green palette of the console.
2803 This is a 16-member array composed of values
2806 vt.default_red= [VT]
2807 Format: <red0>,<red1>,<red2>,...,<red15>
2808 Change the default red palette of the console.
2809 This is a 16-member array composed of values
2815 Set system-wide default UTF-8 mode for all tty's.
2816 Default is 1, i.e. UTF-8 mode is enabled for all
2817 newly opened terminals.
2819 vt.global_cursor_default=
2822 Set system-wide default for whether a cursor
2823 is shown on new VTs. Default is -1,
2824 i.e. cursors will be created by default unless
2825 overridden by individual drivers. 0 will hide
2826 cursors, 1 will display them.
2828 waveartist= [HW,OSS]
2829 Format: <io>,<irq>,<dma>,<dma2>
2832 See header of drivers/scsi/wd33c93.c.
2835 See header of drivers/scsi/wd7000.c.
2838 See Documentation/watchdog/wdt.txt.
2840 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2841 default x2apic cluster mode on platforms
2844 x86_mrst_timer= [X86-32,APBT]
2845 Choose timer option for x86 Moorestown MID platform.
2846 Two valid options are apbt timer only and lapic timer
2847 plus one apbt timer for broadcast timer.
2848 x86_mrst_timer=apbt_only | lapic_and_apbt
2850 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2851 xd_geo= See header of drivers/block/xd.c.
2853 xirc2ps_cs= [NET,PCMCIA]
2855 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2857 ______________________________________________________________________
2861 Add documentation for ALSA options.
2862 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob