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 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs, sci_force_enable }
245 See Documentation/power/video.txt for information on
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/scsi/aha152x.txt.
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
310 See Documentation/scsi/aic7xxx.txt.
313 See Documentation/scsi/aic79xx.txt.
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
327 off - do not initialize any AMD IOMMU found in
330 amijoy.map= [HW,JOY] Amiga joystick support
331 Map of devices attached to JOY0DAT and JOY1DAT
333 See also Documentation/kernel/input/joystick.txt
335 analog.map= [HW,JOY] Analog joystick and gamepad support
336 Specifies type or capabilities of an analog joystick
337 connected to one of 16 gameports
338 Format: <type1>,<type2>,..<type16>
341 Power management functions (SPARCstation-4/5 + deriv.)
343 Disable APC CPU standby support. SPARCstation-Fox does
344 not play well with APC CPU idle - disable it if you have
345 APC and your system crashes randomly.
347 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
348 Change the output verbosity whilst booting
349 Format: { quiet (default) | verbose | debug }
350 Change the amount of debugging information output
351 when initialising the APIC and IO-APIC components.
354 See Documentation/networking/ipv6.txt.
356 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
357 Limit apic dumping. The parameter defines the maximal
358 number of local apics being dumped. Also it is possible
359 to set it to "all" by meaning -- no limit here.
360 Format: { 1 (default) | 2 | ... | all }.
361 The parameter valid if only apic=debug or
362 apic=verbose is specified.
363 Example: apic=debug show_lapic=all
365 apm= [APM] Advanced Power Management
366 See header of arch/x86/kernel/apm_32.c.
368 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
369 Format: <io>,<irq>,<nodeID>
373 atarimouse= [HW,MOUSE] Atari Mouse
375 atascsi= [HW,SCSI] Atari SCSI
377 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
378 EzKey and similar keyboards
380 atkbd.reset= [HW] Reset keyboard during initialization
382 atkbd.set= [HW] Select keyboard code set
383 Format: <int> (2 = AT (default), 3 = PS/2)
385 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
388 atkbd.softraw= [HW] Choose between synthetic and real raw mode
389 Format: <bool> (0 = real, 1 = synthetic (default))
391 atkbd.softrepeat= [HW]
392 Use software keyboard repeat
396 baycom_epp= [HW,AX25]
399 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
401 See header of drivers/net/hamradio/baycom_par.c.
403 baycom_ser_fdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
405 Format: <io>,<irq>,<mode>[,<baud>]
406 See header of drivers/net/hamradio/baycom_ser_fdx.c.
408 baycom_ser_hdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
410 Format: <io>,<irq>,<mode>
411 See header of drivers/net/hamradio/baycom_ser_hdx.c.
413 boot_delay= Milliseconds to delay each printk during boot.
414 Values larger than 10 seconds (10000) are changed to
418 bootmem_debug [KNL] Enable bootmem allocator debug messages.
420 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
421 bttv.radio= Most important insmod options are available as
423 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
424 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
427 See drivers/scsi/BusLogic.c, comment before function
428 BusLogic_ParseDriverOptions().
430 c101= [NET] Moxa C101 synchronous serial card
432 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
433 Sometimes CPU hardware bugs make them report the cache
434 size incorrectly. The kernel will attempt work arounds
435 to fix known problems, but for some CPUs it is not
436 possible to determine what the correct size should be.
437 This option provides an override for these situations.
440 [SECURITY] Disable capabilities. This would normally
441 be used only if an alternative security model is to be
442 configured. Potentially dangerous and should only be
443 used if you are entirely sure of the consequences.
445 ccw_timeout_log [S390]
446 See Documentation/s390/CommonIO for details.
448 cgroup_disable= [KNL] Disable a particular controller
449 Format: {name of the controller(s) to disable}
450 {Currently supported controllers - "memory"}
452 checkreqprot [SELINUX] Set initial checkreqprot flag value.
453 Format: { "0" | "1" }
454 See security/selinux/Kconfig help text.
455 0 -- check protection applied by kernel (includes
456 any implied execute protection).
457 1 -- check protection requested by application.
458 Default value is set via a kernel config option.
459 Value can be changed at runtime via
460 /selinux/checkreqprot.
463 See Documentation/s390/CommonIO for details.
465 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
467 Forces specified clocksource (if available) to be used
468 when calculating gettimeofday(). If specified
469 clocksource is not available, it defaults to PIT.
470 Format: { pit | tsc | cyclone | pmtmr }
472 clocksource= [GENERIC_TIME] Override the default clocksource
474 Override the default clocksource and use the clocksource
475 with the name specified.
476 Some clocksource names to choose from, depending on
478 [all] jiffies (this is the base, fallback clocksource)
480 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
481 pxa_timer,timer3,32k_counter,timer0_1
483 [X86-32] pit,hpet,tsc,vmi-timer;
484 scx200_hrt on Geode; cyclone on IBM x440
492 clearcpuid=BITNUM [X86]
493 Disable CPUID feature X for the kernel. See
494 arch/x86/include/asm/cpufeature.h for the valid bit
495 numbers. Note the Linux specific bits are not necessarily
496 stable over kernel options, but the vendor specific
498 Also note that user programs calling CPUID directly
499 or using the feature without checking anything
500 will still see it. This just prevents it from
501 being used by the kernel or shown in /proc/cpuinfo.
502 Also note the kernel might malfunction if you disable
505 cmo_free_hint= [PPC] Format: { yes | no }
506 Specify whether pages are marked as being inactive
507 when they are freed. This is used in CMO environments
508 to determine OS memory pressure for page stealing by
512 code_bytes [X86] How many bytes of object code to print
517 com20020= [HW,NET] ARCnet - COM20020 chipset
519 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
521 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
525 ARCnet - COM90xx chipset (memory-mapped buffers)
526 Format: <io>[,<irq>[,<memstart>]]
528 condev= [HW,S390] console device
531 console= [KNL] Output console device and options.
533 tty<n> Use the virtual console device <n>.
537 Use the specified serial port. The options are of
538 the form "bbbbpnf", where "bbbb" is the baud rate,
539 "p" is parity ("n", "o", or "e"), "n" is number of
540 bits, and "f" is flow control ("r" for RTS or
541 omit it). Default is "9600n8".
543 See Documentation/serial-console.txt for more
545 Documentation/networking/netconsole.txt for an
548 uart[8250],io,<addr>[,options]
549 uart[8250],mmio,<addr>[,options]
550 Start an early, polled-mode console on the 8250/16550
551 UART at the specified I/O port or MMIO address,
552 switching to the matching ttyS device later. The
553 options are the same as for ttyS, above.
555 If the device connected to the port is not a TTY but a braille
556 device, prepend "brl," before the device type, for instance
558 For now, only VisioBraille is supported.
560 consoleblank= [KNL] The console blank (screen saver) timeout in
561 seconds. Defaults to 10*60 = 10mins. A value of 0
562 disables the blank timer.
565 [KNL] Change the default value for
566 /proc/<pid>/coredump_filter.
567 See also Documentation/filesystems/proc.txt.
569 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
571 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
573 crashkernel=nn[KMG]@ss[KMG]
574 [KNL] Reserve a chunk of physical memory to
575 hold a kernel to switch to with kexec on panic.
577 crashkernel=range1:size1[,range2:size2,...][@offset]
578 [KNL] Same as above, but depends on the memory
579 in the running system. The syntax of range is
580 start-[end] where start and end are both
581 a memory unit (amount[KMG]). See also
582 Documentation/kdump/kdump.txt for a example.
587 cs89x0_media= [HW,NET]
588 Format: { rj45 | aui | bnc }
591 See header of drivers/s390/block/dasd_devmap.c.
593 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
594 (one device per port)
595 Format: <port#>,<type>
596 See also Documentation/input/joystick-parport.txt
598 debug [KNL] Enable kernel debugging (events log level).
601 [KNL] verbose self-tests
603 Print debugging info while doing the locking API
605 We default to 0 (no extra messages), setting it to
606 1 will print _a lot_ more information - normally
607 only useful to kernel developers.
609 debug_objects [KNL] Enable object debugging
612 [KNL] Disable object debugging
614 debugpat [X86] Enable PAT debugging
616 decnet.addr= [HW,NET]
617 Format: <area>[,<node>]
618 See also Documentation/networking/decnet.txt.
621 [same as hugepagesz=] The size of the default
622 HugeTLB page size. This is the size represented by
623 the legacy /proc/ hugepages APIs, used for SHM, and
624 default size when mounting hugetlbfs filesystems.
625 Defaults to the default architecture's huge page size
629 Set number of hash buckets for dentry cache.
632 IO parameters + enable/disable command.
634 digiepca= [HW,SERIAL]
635 See drivers/char/README.epca and
636 Documentation/serial/digiepca.txt.
639 See Documentation/networking/ipv6.txt.
642 See Documentation/networking/ipv6.txt.
644 disable_mtrr_cleanup [X86]
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
647 entry later. This parameter disables that.
649 disable_mtrr_trim [X86, Intel and AMD only]
650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
655 disable_timer_pin_1 [X86]
656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
659 dmasound= [HW,OSS] Sound subsystem buffers
661 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
662 this option disables the debugging code at boot.
664 dma_debug_entries=<number>
665 This option allows to tune the number of preallocated
666 entries for DMA-API debugging code. One entry is
667 required per DMA-API allocation. Use this if the
668 DMA-API debugging code disables itself because the
669 architectural default is too low.
671 dma_debug_driver=<driver_name>
672 With this option the DMA-API debugging driver
673 filter feature can be enabled at boot time. Just
674 pass the driver to filter for as the parameter.
675 The filter can be disabled or changed to another
676 driver later using sysfs.
682 dynamic_printk Enables pr_debug()/dev_dbg() calls if
683 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
684 These can also be switched on/off via
685 <debugfs>/dynamic_printk/modules
687 earlycon= [KNL] Output early console device and options.
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address.
692 The options are the same as for ttyS, above.
694 earlyprintk= [X86,SH,BLACKFIN]
696 earlyprintk=serial[,ttySn[,baudrate]]
697 earlyprintk=ttySn[,baudrate]
698 earlyprintk=dbgp[debugController#]
700 Append ",keep" to not disable it when the real console
703 Only vga or serial or usb debug port at a time.
705 Currently only ttyS0 and ttyS1 are supported.
707 Interaction with the standard serial driver is not
710 The VGA output is eventually overwritten by the real
716 Format: {"off" | "on" | "skip[mbr]"}
718 eisa_irq_edge= [PARISC,HW]
719 See header of drivers/parisc/eisa.c.
722 See comment before function elanfreq_setup() in
723 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
726 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
727 See Documentation/block/as-iosched.txt and
728 Documentation/block/deadline-iosched.txt for details.
730 elfcorehdr= [IA64,PPC,SH,X86]
731 Specifies physical address of start of kernel core
732 image elf header. Generally kexec loader will
733 pass this option to capture kernel.
734 See Documentation/kdump/kdump.txt for details.
736 enable_mtrr_cleanup [X86]
737 The kernel tries to adjust MTRR layout from continuous
738 to discrete, to make X server driver able to add WB
739 entry later. This parameter enables that.
741 enable_timer_pin_1 [X86]
742 Enable PIN 1 of APIC timer
743 Can be useful to work around chipset bugs
744 (in particular on some ATI chipsets).
745 The kernel tries to set a reasonable default.
747 enforcing [SELINUX] Set initial enforcing status.
749 See security/selinux/Kconfig help text.
750 0 -- permissive (log only, no denials).
751 1 -- enforcing (deny and log).
753 Value can be changed at runtime via /selinux/enforce.
755 ether= [HW,NET] Ethernet cards parameters
756 This option is obsoleted by the "netdev=" option, which
757 has equivalent usage. See its documentation for details.
759 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
764 fail_make_request=[KNL]
765 General fault injection mechanism.
766 Format: <interval>,<probability>,<space>,<times>
767 See also /Documentation/fault-injection/.
770 See header of drivers/scsi/fd_mcs.c.
773 See header of drivers/scsi/fdomain.c.
776 See Documentation/blockdev/floppy.txt.
778 force_pal_cache_flush
779 [IA-64] Avoid check_sal_cache_flush which may hang on
780 buggy SAL_CACHE_FLUSH implementations. Using this
781 parameter will force ia64_sal_cache_flush to call
782 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
785 [FTRACE] will set and start the specified tracer
786 as early as possible in order to facilitate early
789 ftrace_dump_on_oops[=orig_cpu]
790 [FTRACE] will dump the trace buffers on oops.
791 If no parameter is passed, ftrace will dump
792 buffers of all CPUs, but if you pass orig_cpu, it will
793 dump only the buffer of the CPU that triggered the
796 ftrace_filter=[function-list]
797 [FTRACE] Limit the functions traced by the function
798 tracer at boot up. function-list is a comma separated
799 list of functions. This list can be changed at run
800 time by the set_ftrace_filter file in the debugfs
803 ftrace_notrace=[function-list]
804 [FTRACE] Do not trace the functions specified in
805 function-list. This list can be changed at run time
806 by the set_ftrace_notrace file in the debugfs
809 ftrace_graph_filter=[function-list]
810 [FTRACE] Limit the top level callers functions traced
811 by the function graph tracer at boot up.
812 function-list is a comma separated list of functions
813 that can be changed at run time by the
814 set_graph_function file in the debugfs tracing directory.
817 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
818 support via parallel port (up to 5 devices per port)
819 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
820 See also Documentation/input/joystick-parport.txt
824 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
828 gcov_persist= [GCOV] When non-zero (default), profiling data for
829 kernel modules is saved and remains accessible via
830 debugfs, even when the module is unloaded/reloaded.
831 When zero, profiling data is discarded and associated
832 debugfs files are removed at module unload time.
835 See header of drivers/scsi/gdth.c.
837 gpt [EFI] Forces disk with valid GPT signature but
838 invalid Protective MBR to be treated as GPT.
842 hashdist= [KNL,NUMA] Large hashes allocated during boot
843 are distributed across NUMA nodes. Defaults on
844 for 64bit NUMA, off otherwise.
845 Format: 0 | 1 (for off | on)
847 hcl= [IA-64] SGI's Hardware Graph compatibility layer
849 hd= [EIDE] (E)IDE hard drive subsystem geometry
850 Format: <cyl>,<head>,<sect>
852 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
853 size of <nn>. This works even on boxes that have no
854 highmem otherwise. This also works to reduce highmem
855 size on bigger boxes.
857 highres= [KNL] Enable/disable high resolution timer mode.
858 Valid parameters: "on", "off"
862 See Documentation/isdn/README.HiSax.
866 hpet= [X86-32,HPET] option to control HPET usage
867 Format: { enable (default) | disable | force |
869 disable: disable HPET and use PIT instead
870 force: allow force enabled of undocumented chips (ICH4,
872 verbose: show contents of HPET registers during setup
874 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
875 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
876 On x86-64 and powerpc, this option can be specified
877 multiple times interleaved with hugepages= to reserve
878 huge pages of different sizes. Valid pages sizes on
879 x86-64 are 2M (when the CPU supports "pse") and 1G
880 (when the CPU supports the "pdpe1gb" cpuinfo flag)
881 Note that 1GB pages can only be allocated at boot time
882 using hugepages= and not freed afterwards.
884 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
885 terminal devices. Valid values: 0..8
886 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
887 If specified, z/VM IUCV HVC accepts connections
888 from listed z/VM user IDs only.
890 i2c_bus= [HW] Override the default board specific I2C bus speed
891 or register an additional I2C bus that is not
892 registered from board initialization code.
896 i8042.debug [HW] Toggle i8042 debug mode
897 i8042.direct [HW] Put keyboard port into non-translated mode
898 i8042.dumbkbd [HW] Pretend that controller can only read data from
899 keyboard and cannot control its state
900 (Don't attempt to blink the leds)
901 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
902 i8042.nokbd [HW] Don't check/create keyboard port
903 i8042.noloop [HW] Disable the AUX Loopback command while probing
905 i8042.nomux [HW] Don't check presence of an active multiplexing
907 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
910 [HW] Frequency with which keyboard LEDs should blink
911 when kernel panics (default is 0.5 sec)
912 i8042.reset [HW] Reset the controller during init and cleanup
913 i8042.unlock [HW] Unlock (ignore) the keylock
917 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
918 indicates that the driver is running on unsupported
920 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
921 does not match list of supported models.
923 [HW] Report power status in /proc/i8k
924 (disabled by default)
925 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
928 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
929 See Documentation/mca.txt.
932 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
934 ide-core.nodma= [HW] (E)IDE subsystem
935 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
936 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
937 .cdrom .chs .ignore_cable are additional options
938 See Documentation/ide/ide.txt.
940 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
941 Claim all unknown PCI IDE storage controllers.
944 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
945 Poll forces a polling idle loop that can slightly
946 improve the performance of waking up a idle CPU, but
947 will use a lot of power and make the system run hot.
949 idle=mwait: On systems which support MONITOR/MWAIT but
950 the kernel chose to not use it because it doesn't save
951 as much power as a normal idle loop, use the
952 MONITOR/MWAIT idle loop anyways. Performance should be
953 the same as idle=poll.
954 idle=halt: Halt is forced to be used for CPU idle.
955 In such case C2/C3 won't be used again.
956 idle=nomwait: Disable mwait for CPU C-states
958 ignore_loglevel [KNL]
959 Ignore loglevel setting - this will print /all/
960 kernel messages to the console. Useful for debugging.
963 Set number of hash buckets for inode cache.
966 Format: { "0" | "1" }
967 0 -- integrity auditing messages. (Default)
968 1 -- enable informational integrity auditing messages.
971 Format: { "sha1" | "md5" }
975 Load a policy which meets the needs of the Trusted
976 Computing Base. This means IMA will measure all
977 programs exec'd, files mmap'd for exec, and all files
978 opened for read by uid=0.
981 See header of drivers/scsi/in2000.c.
985 Run specified binary instead of /sbin/init as init
988 initcall_debug [KNL] Trace initcalls as they are executed. Useful
989 for working out where the kernel is dying during
992 initrd= [BOOT] Specify the location of the initial ramdisk
994 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
997 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
999 Enable intel iommu driver.
1001 Disable intel iommu driver.
1002 igfx_off [Default Off]
1003 By default, gfx is mapped as normal device. If a gfx
1004 device has a dedicated DMAR unit, the DMAR unit is
1005 bypassed by not enabling DMAR with this option. In
1006 this case, gfx device will use physical address for
1009 With this option iommu will not optimize to look
1010 for io virtual address below 32 bit forcing dual
1011 address cycle on pci bus for cards supporting greater
1012 than 32 bit addressing. The default is to look
1013 for translation below 32 bit and if not available
1014 then look in the higher range.
1015 strict [Default Off]
1016 With this option on every unmap_single operation will
1017 result in a hardware IOTLB flush operation as opposed
1018 to batching them for performance.
1022 iomem= Disable strict checking of access to MMIO memory
1023 strict regions from userspace.
1039 io7= [HW] IO7 for Marvel based alpha systems
1040 See comment before marvel_specify_io7 in
1041 arch/alpha/kernel/core_marvel.c.
1043 io_delay= [X86] I/O delay method
1045 Standard port 0x80 based delay
1047 Alternate port 0xed based delay (needed on some systems)
1049 Simple two microseconds delay
1054 See Documentation/filesystems/nfs/nfsroot.txt.
1056 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1057 See comment before ip2_setup() in
1058 drivers/char/ip2/ip2base.c.
1060 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1061 See header of drivers/scsi/ips.c.
1064 When an interrupt is not handled search all handlers
1065 for it. Intended to get systems with badly broken
1069 When an interrupt is not handled search all handlers
1070 for it. Also check all handlers each timer
1071 interrupt. Intended to get systems with badly broken
1075 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1077 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1079 <cpu number>,...,<cpu number>
1081 <cpu number>-<cpu number>
1082 (must be a positive range in ascending order)
1084 <cpu number>,...,<cpu number>-<cpu number>
1086 This option can be used to specify one or more CPUs
1087 to isolate from the general SMP balancing and scheduling
1088 algorithms. You can move a process onto or off an
1089 "isolated" CPU via the CPU affinity syscalls or cpuset.
1090 <cpu number> begins at 0 and the maximum value is
1091 "number of CPUs in system - 1".
1093 This option is the preferred way to isolate CPUs. The
1094 alternative -- manually setting the CPU mask of all
1095 tasks in the system -- can cause problems and
1096 suboptimal load balancer performance.
1100 js= [HW,JOY] Analog joystick
1101 See Documentation/input/joystick.txt.
1105 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1106 specifies the amount of memory usable by the kernel
1107 for non-movable allocations. The requested amount is
1108 spread evenly throughout all nodes in the system. The
1109 remaining memory in each node is used for Movable
1110 pages. In the event, a node is too small to have both
1111 kernelcore and Movable pages, kernelcore pages will
1112 take priority and other nodes will have a larger number
1113 of kernelcore pages. The Movable zone is used for the
1114 allocation of pages that may be reclaimed or moved
1115 by the page migration subsystem. This means that
1116 HugeTLB pages may not be allocated from this zone.
1117 Note that allocations like PTEs-from-HighMem still
1118 use the HighMem zone if it exists, and the Normal
1119 zone if it does not.
1121 kgdboc= [HW] kgdb over consoles.
1122 Requires a tty driver that supports console polling.
1123 (only serial supported for now)
1124 Format: <serial_device>[,baud]
1126 kmac= [MIPS] korina ethernet MAC address.
1127 Configure the RouterBoard 532 series on-chip
1128 Ethernet adapter MAC address.
1130 kmemleak= [KNL] Boot-time kmemleak enable/disable
1131 Valid arguments: on, off
1134 kstack=N [X86] Print N words from the kernel stack
1137 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1138 Default is 0 (don't ignore, but inject #GP)
1140 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1141 Default is 1 (enabled)
1143 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1146 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1148 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1150 kvm-intel.bypass_guest_pf=
1151 [KVM,Intel] Disables bypassing of guest page faults
1152 on Intel chips. Default is 1 (enabled)
1154 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1155 (virtualized MMU) support on capable Intel chips.
1156 Default is 1 (enabled)
1158 kvm-intel.emulate_invalid_guest_state=
1159 [KVM,Intel] Enable emulation of invalid guest states
1160 Default is 0 (disabled)
1162 kvm-intel.flexpriority=
1163 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1164 Default is 1 (enabled)
1166 kvm-intel.unrestricted_guest=
1167 [KVM,Intel] Disable unrestricted guest feature
1168 (virtualized real and unpaged mode) on capable
1169 Intel chips. Default is 1 (enabled)
1171 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1172 feature (tagged TLBs) on capable Intel chips.
1173 Default is 1 (enabled)
1179 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1182 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1185 libata.dma= [LIBATA] DMA control
1186 libata.dma=0 Disable all PATA and SATA DMA
1187 libata.dma=1 PATA and SATA Disk DMA only
1188 libata.dma=2 ATAPI (CDROM) DMA only
1189 libata.dma=4 Compact Flash DMA only
1190 Combinations also work, so libata.dma=3 enables DMA
1191 for disks and CDROMs, but not CFs.
1193 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1194 libata.ignore_hpa=0 keep BIOS limits (default)
1195 libata.ignore_hpa=1 ignore limits, using full disk
1197 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1201 libata.force= [LIBATA] Force configurations. The format is comma
1202 separated list of "[ID:]VAL" where ID is
1203 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1204 matching port, link or device. Basically, it matches
1205 the ATA ID string printed on console by libata. If
1206 the whole ID part is omitted, the last PORT and DEVICE
1207 values are used. If ID hasn't been specified yet, the
1208 configuration applies to all ports, links and devices.
1210 If only DEVICE is omitted, the parameter applies to
1211 the port and all links and devices behind it. DEVICE
1212 number of 0 either selects the first device or the
1213 first fan-out link behind PMP device. It does not
1214 select the host link. DEVICE number of 15 selects the
1215 host link and device attached to it.
1217 The VAL specifies the configuration to force. As long
1218 as there's no ambiguity shortcut notation is allowed.
1219 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1220 The following configurations can be forced.
1222 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1223 Any ID with matching PORT is used.
1225 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1227 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1228 udma[/][16,25,33,44,66,100,133] notation is also
1231 * [no]ncq: Turn on or off NCQ.
1233 * nohrst, nosrst, norst: suppress hard, soft
1236 If there are multiple matching configurations changing
1237 the same attribute, the last one is used.
1239 lmb=debug [KNL] Enable lmb debug messages.
1241 load_ramdisk= [RAM] List of ramdisks to load from floppy
1242 See Documentation/blockdev/ramdisk.txt.
1244 lockd.nlm_grace_period=P [NFS] Assign grace period.
1247 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1250 lockd.nlm_timeout=T [NFS] Assign timeout value.
1253 lockd.nlm_udpport=M [NFS] Assign UDP port.
1256 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1259 loglevel= All Kernel Messages with a loglevel smaller than the
1260 console loglevel will be printed to the console. It can
1261 also be changed with klogd or other programs. The
1262 loglevels are defined as follows:
1264 0 (KERN_EMERG) system is unusable
1265 1 (KERN_ALERT) action must be taken immediately
1266 2 (KERN_CRIT) critical conditions
1267 3 (KERN_ERR) error conditions
1268 4 (KERN_WARNING) warning conditions
1269 5 (KERN_NOTICE) normal but significant condition
1270 6 (KERN_INFO) informational
1271 7 (KERN_DEBUG) debug-level messages
1273 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1274 Format: { n | nk | nM }
1275 n must be a power of two. The default size
1276 is set in the kernel config file.
1278 logo.nologo [FB] Disables display of the built-in Linux logo.
1279 This may be used to provide more screen space for
1280 kernel log messages and is useful when debugging
1281 kernel boot problems.
1283 lp=0 [LP] Specify parallel ports to use, e.g,
1284 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1285 lp=reset first parallel port). 'lp=0' disables the
1286 lp=auto printer driver. 'lp=reset' (which can be
1287 specified in addition to the ports) causes
1288 attached printers to be reset. Using
1289 lp=port1,port2,... specifies the parallel ports
1290 to associate lp devices with, starting with
1291 lp0. A port specification may be 'none' to skip
1292 that lp device, or a parport name such as
1293 'parport0'. Specifying 'lp=auto' instead of a
1294 port specification list means that device IDs
1295 from each port should be examined, to see if
1296 an IEEE 1284-compliant printer is attached; if
1297 so, the driver will manage that printer.
1298 See also header of drivers/char/lp.c.
1301 Sets loops_per_jiffy to given constant, thus avoiding
1302 time-consuming boot-time autodetection (up to 250 ms per
1303 CPU). 0 enables autodetection (default). To determine
1304 the correct value for your kernel, boot with normal
1305 autodetection and see what value is printed. Note that
1306 on SMP systems the preset will be applied to all CPUs,
1307 which is likely to cause problems if your CPUs need
1308 significantly divergent settings. An incorrect value
1309 will cause delays in the kernel to be wrong, leading to
1310 unpredictable I/O errors and other breakage. Although
1311 unlikely, in the extreme case this might damage your
1315 Format: <io>,<irq>,<dma>
1317 mac5380= [HW,SCSI] Format:
1318 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1320 machvec= [IA64] Force the use of a particular machine-vector
1321 (machvec) in a generic kernel.
1322 Example: machvec=hpzx1_swiotlb
1324 machtype= [Loongson] Share the same kernel image file between different
1326 Example: machtype=lemote-yeeloong-2f-7inch
1328 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1329 than or equal to this physical address is ignored.
1331 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1332 should make use of. maxcpus=n : n >= 0 limits the
1333 kernel to using 'n' processors. n=0 is a special case,
1334 it is equivalent to "nosmp", which also disables
1337 max_loop= [LOOP] Maximum number of loopback devices that can
1341 max_luns= [SCSI] Maximum number of LUNs to probe.
1342 Should be between 1 and 2^32-1.
1345 [SCSI] Maximum number of LUNs received.
1346 Should be between 1 and 16384.
1350 mce [X86-32] Machine Check Exception
1352 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1354 md= [HW] RAID subsystems devices and level
1355 See Documentation/md.txt.
1358 Format: <first>,<last>
1359 Specifies range of consoles to be captured by the MDA.
1361 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1362 Amount of memory to be used when the kernel is not able
1363 to see the whole system memory or for test.
1364 [X86-32] Use together with memmap= to avoid physical
1365 address space collisions. Without memmap= PCI devices
1366 could be placed at addresses belonging to unused RAM.
1368 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1372 [KNL,SH] Allow user to override the default size for
1373 per-device physically contiguous DMA buffers.
1375 memmap=exactmap [KNL,X86] Enable setting of an exact
1376 E820 memory map, as specified by the user.
1377 Such memmap=exactmap lines can be constructed based on
1378 BIOS output or other requirements. See the memmap=nn@ss
1381 memmap=nn[KMG]@ss[KMG]
1382 [KNL] Force usage of a specific region of memory
1383 Region of memory to be used, from ss to ss+nn.
1385 memmap=nn[KMG]#ss[KMG]
1386 [KNL,ACPI] Mark specific memory as ACPI data.
1387 Region of memory to be used, from ss to ss+nn.
1389 memmap=nn[KMG]$ss[KMG]
1390 [KNL,ACPI] Mark specific memory as reserved.
1391 Region of memory to be used, from ss to ss+nn.
1392 Example: Exclude memory from 0x18690000-0x1869ffff
1393 memmap=64K$0x18690000
1395 memmap=0x10000$0x18690000
1397 memory_corruption_check=0/1 [X86]
1398 Some BIOSes seem to corrupt the first 64k of
1399 memory when doing things like suspend/resume.
1400 Setting this option will scan the memory
1401 looking for corruption. Enabling this will
1402 both detect corruption and prevent the kernel
1403 from using the memory being corrupted.
1404 However, its intended as a diagnostic tool; if
1405 repeatable BIOS-originated corruption always
1406 affects the same memory, you can use memmap=
1407 to prevent the kernel from using that memory.
1409 memory_corruption_check_size=size [X86]
1410 By default it checks for corruption in the low
1411 64k, making this memory unavailable for normal
1412 use. Use this parameter to scan for
1413 corruption in more or less memory.
1415 memory_corruption_check_period=seconds [X86]
1416 By default it checks for corruption every 60
1417 seconds. Use this parameter to check at some
1418 other rate. 0 disables periodic checking.
1420 memtest= [KNL,X86] Enable memtest
1422 default : 0 <disable>
1423 Specifies the number of memtest passes to be
1424 performed. Each pass selects another test
1425 pattern from a given set of patterns. Memtest
1426 fills the memory with this pattern, validates
1427 memory contents and reserves bad memory
1428 regions that are detected.
1430 meye.*= [HW] Set MotionEye Camera parameters
1431 See Documentation/video4linux/meye.txt.
1433 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1434 Multi-Function General Purpose Timers on AMD Geode
1437 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1438 the BIOS has incorrectly applied a workaround. TinyBIOS
1439 version 0.98 is known to be affected, 0.99 fixes the
1440 problem by letting the user disable the workaround.
1444 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1445 physical address is ignored.
1447 mini2440= [ARM,HW,KNL]
1448 Format:[0..2][b][c][t]
1450 MINI2440 configuration specification:
1451 0 - The attached screen is the 3.5" TFT
1452 1 - The attached screen is the 7" TFT
1453 2 - The VGA Shield is attached (1024x768)
1454 Leaving out the screen size parameter will not load
1455 the TFT driver, and the framebuffer will be left
1457 b - Enable backlight. The TFT backlight pin will be
1458 linked to the kernel VESA blanking code and a GPIO
1459 LED. This parameter is not necessary when using the
1461 c - Enable the s3c camera interface.
1462 t - Reserved for enabling touchscreen support. The
1463 touchscreen support is not enabled in the mainstream
1464 kernel as of 2.6.30, a preliminary port can be found
1465 in the "bleeding edge" mini2440 support kernel at
1466 http://repo.or.cz/w/linux-2.6/mini2440.git
1469 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1470 parameter allows control of the logging verbosity for
1471 the additional memory initialisation checks. A value
1472 of 0 disables mminit logging and a level of 4 will
1473 log everything. Information is printed at KERN_DEBUG
1474 so loglevel=8 may also need to be specified.
1477 [MOUSE] Maximum time between finger touching and
1478 leaving touchpad surface for touch to be considered
1479 a tap and be reported as a left button click (for
1480 touchpads working in absolute mode only).
1482 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1483 reporting absolute coordinates, such as tablets
1484 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1485 reporting absolute coordinates, such as tablets
1487 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1488 is similar to kernelcore except it specifies the
1489 amount of memory used for migratable allocations.
1490 If both kernelcore and movablecore is specified,
1491 then kernelcore will be at *least* the specified
1492 value but may be more. If movablecore on its own
1493 is specified, the administrator must be careful
1494 that the amount of memory usable for all allocations
1500 MTD_Partition= [MTD]
1501 Format: <name>,<region-number>,<size>,<offset>
1503 MTD_Region= [MTD] Format:
1504 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1507 See drivers/mtd/cmdlinepart.c.
1509 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1511 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1513 boundary - index of last SLC block on Flex-OneNAND.
1514 The remaining blocks are configured as MLC blocks.
1515 lock - Configure if Flex-OneNAND boundary should be locked.
1516 Once locked, the boundary cannot be changed.
1517 1 indicates lock status, 0 indicates unlock status.
1520 ARM/S3C2412 JIVE boot control
1522 See arch/arm/mach-s3c2412/mach-jive.c
1524 mtouchusb.raw_coordinates=
1525 [HW] Make the MicroTouch USB driver use raw coordinates
1526 ('y', default) or cooked coordinates ('n')
1528 mtrr_chunk_size=nn[KMG] [X86]
1529 used for mtrr cleanup. It is largest continuous chunk
1530 that could hold holes aka. UC entries.
1532 mtrr_gran_size=nn[KMG] [X86]
1533 Used for mtrr cleanup. It is granularity of mtrr block.
1535 Large value could prevent small alignment from
1538 mtrr_spare_reg_nr=n [X86]
1540 Range: 0,7 : spare reg number
1542 Used for mtrr cleanup. It is spare mtrr entries number.
1543 Set to 2 or more if your graphical card needs more.
1545 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1548 See header of drivers/scsi/NCR_D700.c.
1552 ncr53c400= [HW,SCSI]
1554 ncr53c400a= [HW,SCSI]
1556 ncr53c406a= [HW,SCSI]
1558 ncr53c8xx= [HW,SCSI]
1560 netdev= [NET] Network devices parameters
1561 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1562 Note that mem_start is often overloaded to mean
1563 something different and driver-specific.
1564 This usage is only documented in each driver source
1568 [NETFILTER] Enable connection tracking flow accounting
1569 0 to disable accounting
1570 1 to enable accounting
1571 Default value depends on CONFIG_NF_CT_ACCT that is
1572 going to be removed in 2.6.29.
1575 See Documentation/filesystems/nfs/nfsroot.txt.
1577 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1578 See Documentation/filesystems/nfs/nfsroot.txt.
1580 nfs.callback_tcpport=
1581 [NFS] set the TCP port on which the NFSv4 callback
1582 channel should listen.
1585 [NFS] sets the pathname to the program which is used
1586 to update the NFS client cache entries.
1588 nfs.cache_getent_timeout=
1589 [NFS] sets the timeout after which an attempt to
1590 update a cache entry is deemed to have failed.
1592 nfs.idmap_cache_timeout=
1593 [NFS] set the maximum lifetime for idmapper cache
1597 [NFS] enable 64-bit inode numbers.
1598 If zero, the NFS client will fake up a 32-bit inode
1599 number for the readdir() and stat() syscalls instead
1600 of returning the full 64-bit number.
1601 The default is to return 64-bit inode numbers.
1603 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1604 when a NMI is triggered.
1605 Format: [state][,regs][,debounce][,die]
1607 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1608 Format: [panic,][num]
1610 0 - turn nmi_watchdog off
1611 1 - use the IO-APIC timer for the NMI watchdog
1612 2 - use the local APIC for the NMI watchdog using
1613 a performance counter. Note: This will use one
1614 performance counter and the local APIC's performance
1616 When panic is specified, panic when an NMI watchdog
1618 This is useful when you use a panic=... timeout and
1619 need the box quickly up again.
1620 Instead of 1 and 2 it is possible to use the following
1621 symbolic names: lapic and ioapic
1622 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1624 netpoll.carrier_timeout=
1625 [NET] Specifies amount of time (in seconds) that
1626 netpoll should wait for a carrier. By default netpoll
1629 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1630 emulation library even if a 387 maths coprocessor
1634 [HW] Never suspend the console
1635 Disable suspending of consoles during suspend and
1636 hibernate operations. Once disabled, debugging
1637 messages can reach various consoles while the rest
1638 of the system is being put to sleep (ie, while
1639 debugging driver suspend/resume hooks). This may
1640 not work reliably with all consoles, but is known
1641 to work with serial and VGA consoles.
1643 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1644 caches in the slab allocator. Saves per-node memory,
1645 but will impact performance.
1649 noapic [SMP,APIC] Tells the kernel to not make use of any
1650 IOAPICs that may be present in the system.
1652 nobats [PPC] Do not use BATs for mapping kernel lowmem
1653 on "Classic" PPC cores.
1657 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1659 nodelayacct [KNL] Disable per-task delay accounting
1661 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1663 nodsp [SH] Disable hardware DSP at boot time.
1665 noefi [X86] Disable EFI runtime services support.
1670 On X86-32 available only on PAE configured kernels.
1671 noexec=on: enable non-executable mappings (default)
1672 noexec=off: disable non-executable mappings
1675 This affects only 32-bit executables.
1676 noexec32=on: enable non-executable mappings (default)
1677 read doesn't imply executable mappings
1678 noexec32=off: disable non-executable mappings
1679 read implies executable mappings
1681 nofpu [SH] Disable hardware FPU at boot time.
1683 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1684 register save and restore. The kernel will only save
1685 legacy floating-point registers on task switch.
1687 noxsave [BUGS=X86] Disables x86 extended register state save
1688 and restore using xsave. The kernel will fallback to
1689 enabling legacy floating-point and sse state.
1691 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1692 wfi(ARM) instruction doesn't work correctly and not to
1693 use it. This is also useful when using JTAG debugger.
1695 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1696 instruction doesn't work correctly and not to
1699 no_file_caps Tells the kernel not to honor file capabilities. The
1700 only way then for a file to be executed with privilege
1701 is to be setuid root or executed by root.
1703 nohalt [IA-64] Tells the kernel not to use the power saving
1704 function PAL_HALT_LIGHT when idle. This increases
1705 power-consumption. On the positive side, it reduces
1706 interrupt wake-up latency, which may improve performance
1707 in certain environments such as networked servers or
1710 nohz= [KNL] Boottime enable/disable dynamic ticks
1711 Valid arguments: on, off
1714 noiotrap [SH] Disables trapped I/O port accesses.
1716 noirqdebug [X86-32] Disables the code which attempts to detect and
1717 disable unhandled interrupt sources.
1719 no_timer_check [X86,APIC] Disables the code which tests for
1720 broken timer IRQ sources.
1722 noisapnp [ISAPNP] Disables ISA PnP code.
1724 noinitrd [RAM] Tells the kernel not to load any configured
1727 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1732 nojitter [IA64] Disables jitter checking for ITC timers.
1734 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1736 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1738 noltlbs [PPC] Do not use large page/tlb entries for kernel
1739 lowmem mapping on PPC40x.
1741 nomca [IA-64] Disable machine check abort handling
1743 nomce [X86-32] Machine Check Exception
1745 nomfgpt [X86-32] Disable Multi-Function General Purpose
1746 Timer usage (for AMD Geode machines).
1748 nopat [X86] Disable PAT (page attribute table extension of
1749 pagetables) support.
1751 norandmaps Don't use address space randomization. Equivalent to
1752 echo 0 > /proc/sys/kernel/randomize_va_space
1754 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1756 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1757 with UP alternatives
1759 noresidual [PPC] Don't use residual data on PReP machines.
1761 noresume [SWSUSP] Disables resume and restores original swap
1764 no-scroll [VGA] Disables scrollback.
1765 This is required for the Braillex ib80-piezo Braille
1766 reader made by F.H. Papenmeier (Germany).
1770 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1772 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1773 and disable the IO APIC. legacy for "maxcpus=0".
1775 nosoftlockup [KNL] Disable the soft-lockup detector.
1777 noswapaccount [KNL] Disable accounting of swap in memory resource
1778 controller. (See Documentation/cgroups/memory.txt)
1780 nosync [HW,M68K] Disables sync negotiation for all devices.
1782 notsc [BUGS=X86-32] Disable Time Stamp Counter
1784 nousb [USB] Disable the USB subsystem
1788 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1790 nptcg= [IA64] Override max number of concurrent global TLB
1791 purges which is reported from either PAL_VM_SUMMARY or
1794 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1795 could support. nr_cpus=n : n >= 1 limits the kernel to
1796 supporting 'n' processors. Later in runtime you can not
1797 use hotplug cpu feature to put more cpu back to online.
1798 just like you compile the kernel NR_CPUS=n
1800 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1802 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1803 one of ['zone', 'node', 'default'] can be specified
1804 This can be set from sysctl after boot.
1805 See Documentation/sysctl/vm.txt for details.
1807 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1808 See Documentation/debugging-via-ohci1394.txt for more
1811 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1812 Rather than timing out after 20 ms if an EC
1813 command is not properly ACKed, override the length
1814 of the timeout. We have interrupts disabled while
1815 waiting for the ACK, so if this is set too high
1816 interrupts *may* be lost!
1818 omap_mux= [OMAP] Override bootloader pin multiplexing.
1819 Format: <mux_mode0.mode_name=value>...
1820 For example, to override I2C bus2:
1821 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1826 oprofile.timer= [HW]
1827 Use timer interrupt instead of performance counters
1829 oprofile.cpu_type= Force an oprofile cpu type
1830 This might be useful if you have an older oprofile
1831 userland or if you want common events.
1832 Format: { arch_perfmon }
1833 arch_perfmon: [X86] Force use of architectural
1834 perfmon on Intel CPUs instead of the
1835 CPU specific event set.
1837 osst= [HW,SCSI] SCSI Tape Driver
1838 Format: <buffer_size>,<write_threshold>
1839 See also Documentation/scsi/st.txt.
1841 panic= [KNL] Kernel behaviour on panic
1844 parkbd.port= [HW] Parallel port number the keyboard adapter is
1845 connected to, default is 0.
1847 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1848 0 for XT, 1 for AT (default is AT).
1851 parport= [HW,PPT] Specify parallel ports. 0 disables.
1852 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1853 Use 'auto' to force the driver to use any
1854 IRQ/DMA settings detected (the default is to
1855 ignore detected IRQ/DMA settings because of
1856 possible conflicts). You can specify the base
1857 address, IRQ, and DMA settings; IRQ and DMA
1858 should be numbers, or 'auto' (for using detected
1859 settings on that particular port), or 'nofifo'
1860 (to avoid using a FIFO even if it is detected).
1861 Parallel ports are assigned in the order they
1862 are specified on the command line, starting
1865 parport_init_mode= [HW,PPT]
1866 Configure VIA parallel port to operate in
1867 a specific mode. This is necessary on Pegasos
1868 computer where firmware has no options for setting
1869 up parallel port mode and sets it to spp.
1870 Currently this function knows 686a and 8231 chips.
1871 Format: [spp|ps2|epp|ecp|ecpepp]
1873 pas2= [HW,OSS] Format:
1874 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1877 See header of drivers/scsi/pas16.c.
1880 Halt all CPUs after the first oops has been printed for
1881 the specified number of seconds. This is to be used if
1882 your oopses keep scrolling off the screen.
1887 See header of drivers/block/paride/pcd.c.
1888 See also Documentation/blockdev/paride.txt.
1890 pci=option[,option...] [PCI] various PCI subsystem options:
1891 earlydump [X86] dump PCI config space before the kernel
1893 off [X86] don't probe for the PCI bus
1894 bios [X86-32] force use of PCI BIOS, don't access
1895 the hardware directly. Use this if your machine
1896 has a non-standard PCI host bridge.
1897 nobios [X86-32] disallow use of PCI BIOS, only direct
1898 hardware access methods are allowed. Use this
1899 if you experience crashes upon bootup and you
1900 suspect they are caused by the BIOS.
1901 conf1 [X86] Force use of PCI Configuration
1903 conf2 [X86] Force use of PCI Configuration
1905 noaer [PCIE] If the PCIEAER kernel config parameter is
1906 enabled, this kernel boot option can be used to
1907 disable the use of PCIE advanced error reporting.
1908 nodomains [PCI] Disable support for multiple PCI
1909 root domains (aka PCI segments, in ACPI-speak).
1910 nommconf [X86] Disable use of MMCONFIG for PCI
1912 check_enable_amd_mmconf [X86] check for and enable
1913 properly configured MMIO access to PCI
1914 config space on AMD family 10h CPU
1915 nomsi [MSI] If the PCI_MSI kernel config parameter is
1916 enabled, this kernel boot option can be used to
1917 disable the use of MSI interrupts system-wide.
1918 noioapicquirk [APIC] Disable all boot interrupt quirks.
1919 Safety option to keep boot IRQs enabled. This
1920 should never be necessary.
1921 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1922 primary IO-APIC for bridges that cannot disable
1923 boot IRQs. This fixes a source of spurious IRQs
1924 when the system masks IRQs.
1925 noioapicreroute [APIC] Disable workaround that uses the
1926 boot IRQ equivalent of an IRQ that connects to
1927 a chipset where boot IRQs cannot be disabled.
1928 The opposite of ioapicreroute.
1929 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1930 routing table. These calls are known to be buggy
1931 on several machines and they hang the machine
1932 when used, but on other computers it's the only
1933 way to get the interrupt routing table. Try
1934 this option if the kernel is unable to allocate
1935 IRQs or discover secondary PCI buses on your
1937 rom [X86] Assign address space to expansion ROMs.
1938 Use with caution as certain devices share
1939 address decoders between ROMs and other
1941 norom [X86] Do not assign address space to
1942 expansion ROMs that do not already have
1943 BIOS assigned address ranges.
1944 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1945 assigned automatically to PCI devices. You can
1946 make the kernel exclude IRQs of your ISA cards
1948 pirqaddr=0xAAAAA [X86] Specify the physical address
1949 of the PIRQ table (normally generated
1950 by the BIOS) if it is outside the
1951 F0000h-100000h range.
1952 lastbus=N [X86] Scan all buses thru bus #N. Can be
1953 useful if the kernel is unable to find your
1954 secondary buses and you want to tell it
1955 explicitly which ones they are.
1956 assign-busses [X86] Always assign all PCI bus
1957 numbers ourselves, overriding
1958 whatever the firmware may have done.
1959 usepirqmask [X86] Honor the possible IRQ mask stored
1960 in the BIOS $PIR table. This is needed on
1961 some systems with broken BIOSes, notably
1962 some HP Pavilion N5400 and Omnibook XE3
1963 notebooks. This will have no effect if ACPI
1964 IRQ routing is enabled.
1965 noacpi [X86] Do not use ACPI for IRQ routing
1966 or for PCI scanning.
1967 use_crs [X86] Use PCI host bridge window information
1968 from ACPI. On BIOSes from 2008 or later, this
1969 is enabled by default. If you need to use this,
1970 please report a bug.
1971 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1972 If you need to use this, please report a bug.
1973 routeirq Do IRQ routing for all PCI devices.
1974 This is normally done in pci_enable_device(),
1975 so this option is a temporary workaround
1976 for broken drivers that don't call it.
1977 skip_isa_align [X86] do not align io start addr, so can
1978 handle more pci cards
1979 firmware [ARM] Do not re-enumerate the bus but instead
1980 just use the configuration from the
1981 bootloader. This is currently used on
1982 IXP2000 systems where the bus has to be
1983 configured a certain way for adjunct CPUs.
1984 noearly [X86] Don't do any early type 1 scanning.
1985 This might help on some broken boards which
1986 machine check when some devices' config space
1987 is read. But various workarounds are disabled
1988 and some IOMMU drivers will not work.
1989 bfsort Sort PCI devices into breadth-first order.
1990 This sorting is done to get a device
1991 order compatible with older (<= 2.4) kernels.
1992 nobfsort Don't sort PCI devices into breadth-first order.
1993 cbiosize=nn[KMG] The fixed amount of bus space which is
1994 reserved for the CardBus bridge's IO window.
1995 The default value is 256 bytes.
1996 cbmemsize=nn[KMG] The fixed amount of bus space which is
1997 reserved for the CardBus bridge's memory
1998 window. The default value is 64 megabytes.
2001 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2002 Specifies alignment and device to reassign
2003 aligned memory resources.
2004 If <order of align> is not specified,
2005 PAGE_SIZE is used as alignment.
2006 PCI-PCI bridge can be specified, if resource
2007 windows need to be expanded.
2008 ecrc= Enable/disable PCIe ECRC (transaction layer
2009 end-to-end CRC checking).
2010 bios: Use BIOS/firmware settings. This is the
2015 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2018 force Enable ASPM even on devices that claim not to support it.
2019 WARNING: Forcing ASPM on may cause system lockups.
2021 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2022 off Do not use native PCIe PME signaling.
2023 force Use native PCIe PME signaling even if the BIOS refuses
2024 to allow the kernel to control the relevant PCIe config
2026 nomsi Do not use MSI for native PCIe PME signaling (this makes
2027 all PCIe root ports use INTx for everything).
2029 pcmv= [HW,PCMCIA] BadgePAD 4
2032 See Documentation/blockdev/paride.txt.
2034 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2037 See arch/parisc/kernel/pdc_chassis.c
2039 percpu_alloc= Select which percpu first chunk allocator to use.
2040 Currently supported values are "embed" and "page".
2041 Archs may support subset or none of the selections.
2042 See comments in mm/percpu.c for details on each
2043 allocator. This parameter is primarily for debugging
2044 and performance comparison.
2047 See Documentation/blockdev/paride.txt.
2050 See Documentation/blockdev/paride.txt.
2052 pirq= [SMP,APIC] Manual mp-table setup
2053 See Documentation/x86/i386/IO-APIC.txt.
2055 plip= [PPT,NET] Parallel port network link
2056 Format: { parport<nr> | timid | 0 }
2057 See also Documentation/parport.txt.
2059 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2060 Override pmtimer IOPort with a hex value.
2064 Enable PNP debug messages. This depends on the
2065 CONFIG_PNP_DEBUG_MESSAGES option.
2071 { on | off | curr | res | no-curr | no-res }
2074 [ISAPNP] Exclude IRQs for the autoconfiguration
2077 [ISAPNP] Exclude DMAs for the autoconfiguration
2079 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2080 Ranges are in pairs (I/O port base and size).
2083 [ISAPNP] Exclude memory regions for the
2085 Ranges are in pairs (memory base and size).
2087 ports= [IP_VS_FTP] IPVS ftp helper module
2089 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2091 Format: <port>,<port>....
2093 print-fatal-signals=
2094 [KNL] debug: print fatal signals
2096 If enabled, warn about various signal handling
2097 related application anomalies: too many signals,
2098 too many POSIX.1 timers, fatal signals causing a
2101 If you hit the warning due to signal overflow,
2102 you might want to try "ulimit -i unlimited".
2106 printk.time= Show timing data prefixed to each printk message line
2107 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2109 processor.max_cstate= [HW,ACPI]
2110 Limit processor to maximum C-state
2111 max_cstate=9 overrides any DMI blacklist limit.
2113 processor.nocst [HW,ACPI]
2114 Ignore the _CST method to determine C-states,
2115 instead using the legacy FADT method
2117 profile= [KNL] Enable kernel profiling via /proc/profile
2118 Format: [schedule,]<number>
2119 Param: "schedule" - profile schedule points.
2120 Param: <number> - step/bucket size as a power of 2 for
2121 statistical time based profiling.
2122 Param: "sleep" - profile D-state sleeping (millisecs).
2123 Requires CONFIG_SCHEDSTATS
2124 Param: "kvm" - profile VM exits.
2126 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2128 See Documentation/blockdev/ramdisk.txt.
2130 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2131 probe for; one of (bare|imps|exps|lifebook|any).
2132 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2134 psmouse.resetafter= [HW,MOUSE]
2135 Try to reset the device after so many bad packets
2138 [HW,MOUSE] Set desired mouse resolution, in dpi.
2139 psmouse.smartscroll=
2140 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2141 0 = disabled, 1 = enabled (default).
2143 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2145 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2148 See Documentation/blockdev/paride.txt.
2151 [KNL] Number of legacy pty's. Overwrites compiled-in
2154 quiet [KNL] Disable most log messages
2159 See Documentation/md.txt.
2161 ramdisk_blocksize= [RAM]
2162 See Documentation/blockdev/ramdisk.txt.
2164 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2165 See Documentation/blockdev/ramdisk.txt.
2167 rcupdate.blimit= [KNL,BOOT]
2168 Set maximum number of finished RCU callbacks to process
2171 rcupdate.qhimark= [KNL,BOOT]
2172 Set threshold of queued
2173 RCU callbacks over which batch limiting is disabled.
2175 rcupdate.qlowmark= [KNL,BOOT]
2176 Set threshold of queued RCU callbacks below which
2177 batch limiting is re-enabled.
2181 Run specified binary instead of /init from the ramdisk,
2182 used for early userspace startup. See initrd.
2184 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2185 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2186 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2189 [KNL, SMP] Set scheduler's default relax_domain_level.
2190 See Documentation/cgroups/cpusets.txt.
2192 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2194 reservetop= [X86-32]
2196 Reserves a hole at the top of the kernel virtual
2199 reset_devices [KNL] Force drivers to reset the underlying device
2200 during initialization.
2203 Specify the partition device for software suspend
2205 resume_offset= [SWSUSP]
2206 Specify the offset from the beginning of the partition
2207 given by "resume=" at which the swap header is located,
2208 in <PAGE_SIZE> units (needed only for swap files).
2209 See Documentation/power/swsusp-and-swap-files.txt
2211 retain_initrd [RAM] Keep initrd memory after extraction
2213 rhash_entries= [KNL,NET]
2214 Set number of hash buckets for route cache
2216 riscom8= [HW,SERIAL]
2217 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2219 ro [KNL] Mount root device read-only on boot
2221 root= [KNL] Root filesystem
2223 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2224 mount the root filesystem
2226 rootflags= [KNL] Set root filesystem mount option string
2228 rootfstype= [KNL] Set root filesystem type
2230 rootwait [KNL] Wait (indefinitely) for root device to show up.
2231 Useful for devices that are detected asynchronously
2232 (e.g. USB and MMC devices).
2234 rw [KNL] Mount root device read-write on boot
2236 S [KNL] Run init in single mode
2239 See drivers/net/irda/sa1100_ir.c.
2241 sbni= [NET] Granch SBNI12 leased line adapter
2243 sched_debug [KNL] Enables verbose scheduler debug messages.
2245 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2246 Format: <io>[,<timeout>[,<isapnp>]]
2248 scsi_debug_*= [SCSI]
2249 See drivers/scsi/scsi_debug.c.
2251 scsi_default_dev_flags=
2252 [SCSI] SCSI default device flags
2255 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2256 Format: <vendor>:<model>:<flags>
2257 (flags are integer value)
2259 scsi_logging_level= [SCSI] a bit mask of logging levels
2260 See drivers/scsi/scsi_logging.h for bits. Also
2261 settable via sysctl at dev.scsi.logging_level
2262 (/proc/sys/dev/scsi/logging_level).
2263 There is also a nice 'scsi_logging_level' script in the
2264 S390-tools package, available for download at
2265 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2267 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2268 discovered. async scans them in kernel threads,
2269 allowing boot to proceed. none ignores them, expecting
2270 user space to do the scan.
2272 security= [SECURITY] Choose a security module to enable at boot.
2273 If this boot parameter is not specified, only the first
2274 security module asking for security registration will be
2275 loaded. An invalid security module name will be treated
2276 as if no module has been chosen.
2278 selinux= [SELINUX] Disable or enable SELinux at boot time.
2279 Format: { "0" | "1" }
2280 See security/selinux/Kconfig help text.
2283 Default value is set via kernel config option.
2284 If enabled at boot time, /selinux/disable can be used
2285 later to disable prior to initial policy load.
2287 serialnumber [BUGS=X86-32]
2290 Maximal number of shapers.
2292 show_msr= [x86] show boot-time MSR settings
2293 Format: { <integer> }
2294 Show boot-time (BIOS-initialized) MSR settings.
2295 The parameter means the number of CPUs to show,
2296 for example 1 means boot CPU only.
2299 See header of drivers/scsi/sim710.c.
2306 slub_debug[=options[,slabs]] [MM, SLUB]
2307 Enabling slub_debug allows one to determine the
2308 culprit if slab objects become corrupted. Enabling
2309 slub_debug can create guard zones around objects and
2310 may poison objects when not in use. Also tracks the
2311 last alloc / free. For more information see
2312 Documentation/vm/slub.txt.
2314 slub_max_order= [MM, SLUB]
2315 Determines the maximum allowed order for slabs.
2316 A high setting may cause OOMs due to memory
2317 fragmentation. For more information see
2318 Documentation/vm/slub.txt.
2320 slub_min_objects= [MM, SLUB]
2321 The minimum number of objects per slab. SLUB will
2322 increase the slab order up to slub_max_order to
2323 generate a sufficiently large slab able to contain
2324 the number of objects indicated. The higher the number
2325 of objects the smaller the overhead of tracking slabs
2326 and the less frequently locks need to be acquired.
2327 For more information see Documentation/vm/slub.txt.
2329 slub_min_order= [MM, SLUB]
2330 Determines the mininum page order for slabs. Must be
2331 lower than slub_max_order.
2332 For more information see Documentation/vm/slub.txt.
2334 slub_nomerge [MM, SLUB]
2335 Disable merging of slabs with similar size. May be
2336 necessary if there is some reason to distinguish
2337 allocs to different slabs. Debug options disable
2338 merging on their own.
2339 For more information see Documentation/vm/slub.txt.
2342 Format: <io1>[,<io2>[,...,<io8>]]
2344 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2345 attempt to substitute SMP alternatives once at boot.
2347 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2348 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2349 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2350 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2351 smsc-ircc2.ircc_irq= [HW] IRQ line
2352 smsc-ircc2.ircc_dma= [HW] DMA channel
2353 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2354 0: Toshiba Satellite 1800 (GP data pin select)
2355 1: Fast pin select (default)
2358 snd-ad1816a= [HW,ALSA]
2360 snd-ad1848= [HW,ALSA]
2362 snd-ali5451= [HW,ALSA]
2364 snd-als100= [HW,ALSA]
2366 snd-als4000= [HW,ALSA]
2368 snd-azt2320= [HW,ALSA]
2370 snd-cmi8330= [HW,ALSA]
2372 snd-cmipci= [HW,ALSA]
2374 snd-cs4231= [HW,ALSA]
2376 snd-cs4232= [HW,ALSA]
2378 snd-cs4236= [HW,ALSA]
2380 snd-cs4281= [HW,ALSA]
2382 snd-cs46xx= [HW,ALSA]
2384 snd-dt019x= [HW,ALSA]
2386 snd-dummy= [HW,ALSA]
2388 snd-emu10k1= [HW,ALSA]
2390 snd-ens1370= [HW,ALSA]
2392 snd-ens1371= [HW,ALSA]
2394 snd-es968= [HW,ALSA]
2396 snd-es1688= [HW,ALSA]
2398 snd-es18xx= [HW,ALSA]
2400 snd-es1938= [HW,ALSA]
2402 snd-es1968= [HW,ALSA]
2404 snd-fm801= [HW,ALSA]
2406 snd-gusclassic= [HW,ALSA]
2408 snd-gusextreme= [HW,ALSA]
2410 snd-gusmax= [HW,ALSA]
2414 snd-ice1712= [HW,ALSA]
2416 snd-intel8x0= [HW,ALSA]
2418 snd-interwave= [HW,ALSA]
2423 snd-korg1212= [HW,ALSA]
2425 snd-maestro3= [HW,ALSA]
2427 snd-mpu401= [HW,ALSA]
2429 snd-mtpav= [HW,ALSA]
2431 snd-nm256= [HW,ALSA]
2433 snd-opl3sa2= [HW,ALSA]
2441 snd-opti93x= [HW,ALSA]
2445 snd-rme32= [HW,ALSA]
2447 snd-rme96= [HW,ALSA]
2449 snd-rme9652= [HW,ALSA]
2455 snd-sbawe= [HW,ALSA]
2457 snd-serial= [HW,ALSA]
2459 snd-sgalaxy= [HW,ALSA]
2461 snd-sonicvibes= [HW,ALSA]
2466 snd-sun-cs4231= [HW,ALSA]
2468 snd-trident= [HW,ALSA]
2470 snd-usb-audio= [HW,ALSA,USB]
2472 snd-via82xx= [HW,ALSA]
2474 snd-virmidi= [HW,ALSA]
2476 snd-wavefront= [HW,ALSA]
2478 snd-ymfpci= [HW,ALSA]
2481 [KNL] Should the soft-lockup detector generate panics.
2483 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2484 See Documentation/sonypi.txt
2486 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2487 See Documentation/serial/specialix.txt.
2489 spia_io_base= [HW,MTD]
2495 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2497 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2498 See Documentation/scsi/st.txt.
2501 Enabled the stack tracer on boot up.
2505 Set the STI (builtin display/keyboard on the HP-PARISC
2506 machines) console (graphic card) which should be used
2507 as the initial boot-console.
2508 See also comment in drivers/video/console/sticore.c.
2511 See comment in drivers/video/console/sticore.c.
2514 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2516 sunrpc.min_resvport=
2517 sunrpc.max_resvport=
2519 SunRPC servers often require that client requests
2520 originate from a privileged port (i.e. a port in the
2521 range 0 < portnr < 1024).
2522 An administrator who wishes to reserve some of these
2523 ports for other uses may adjust the range that the
2524 kernel's sunrpc client considers to be privileged
2525 using these two parameters to set the minimum and
2526 maximum port values.
2530 Control how the NFS server code allocates CPUs to
2531 service thread pools. Depending on how many NICs
2532 you have and where their interrupts are bound, this
2533 option will affect which CPUs will do NFS serving.
2534 Note: this parameter cannot be changed while the
2535 NFS server is running.
2537 auto the server chooses an appropriate mode
2538 automatically using heuristics
2539 global a single global pool contains all CPUs
2540 percpu one pool for each CPU
2541 pernode one pool for each NUMA node (equivalent
2542 to global on non-NUMA machines)
2544 sunrpc.tcp_slot_table_entries=
2545 sunrpc.udp_slot_table_entries=
2547 Sets the upper limit on the number of simultaneous
2548 RPC calls that can be sent from the client to a
2549 server. Increasing these values may allow you to
2550 improve throughput, but will also increase the
2551 amount of memory reserved for use by the client.
2553 swiotlb= [IA-64] Number of I/O TLB slabs
2557 sym53c416= [HW,SCSI]
2558 See header of drivers/scsi/sym53c416.c.
2560 sysrq_always_enabled
2562 Ignore sysrq setting - this boot parameter will
2563 neutralize any effect of /proc/sys/kernel/sysrq.
2564 Useful for debugging.
2567 See header of drivers/scsi/t128.c.
2571 test_suspend= [SUSPEND]
2572 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2573 standby suspend) as the system sleep state to briefly
2574 enter during system startup. The system is woken from
2575 this state using a wakeup-capable RTC alarm.
2577 thash_entries= [KNL,NET]
2578 Set number of hash buckets for TCP connection
2580 thermal.act= [HW,ACPI]
2581 -1: disable all active trip points in all thermal zones
2582 <degrees C>: override all lowest active trip points
2584 thermal.crt= [HW,ACPI]
2585 -1: disable all critical trip points in all thermal zones
2586 <degrees C>: override all critical trip points
2588 thermal.nocrt= [HW,ACPI]
2589 Set to disable actions on ACPI thermal zone
2590 critical and hot trip points.
2592 thermal.off= [HW,ACPI]
2593 1: disable ACPI thermal control
2595 thermal.psv= [HW,ACPI]
2596 -1: disable all passive trip points
2597 <degrees C>: override all passive trip points to this
2600 thermal.tzp= [HW,ACPI]
2601 Specify global default ACPI thermal zone polling rate
2602 <deci-seconds>: poll all this frequency
2603 0: no polling (default)
2606 See comment before function dc390_setup() in
2607 drivers/scsi/tmscsim.c.
2611 Specify if the kernel should make use of the cpu
2612 topology informations if the hardware supports these.
2613 The scheduler will make use of these informations and
2614 e.g. base its process migration decisions on it.
2619 trace_buf_size=nn[KMG]
2620 [FTRACE] will set tracing buffer size.
2622 trace_event=[event-list]
2623 [FTRACE] Set and start specified trace events in order
2624 to facilitate early boot debugging.
2625 See also Documentation/trace/events.txt
2627 trix= [HW,OSS] MediaTrix AudioTrix Pro
2629 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2631 tsc= Disable clocksource-must-verify flag for TSC.
2633 [x86] reliable: mark tsc clocksource as reliable, this
2634 disables clocksource verification at runtime.
2635 Used to enable high-resolution timer mode on older
2636 hardware, and in virtualized environment.
2638 turbografx.map[2|3]= [HW,JOY]
2639 TurboGraFX parallel port interface
2641 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2642 See also Documentation/input/joystick-parport.txt
2644 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2645 See header of drivers/scsi/u14-34f.c.
2653 uhash_entries= [KNL,NET]
2654 Set number of hash buckets for UDP/UDP-Lite connections
2657 [USB] Ignore overcurrent events (default N).
2658 Some badly-designed motherboards generate lots of
2659 bogus events, for ports that aren't wired to
2660 anything. Set this parameter to avoid log spamming.
2661 Note that genuine overcurrent events won't be
2666 Set unknown_nmi_panic=1 early on boot.
2668 usbcore.autosuspend=
2669 [USB] The autosuspend time delay (in seconds) used
2670 for newly-detected USB devices (default 2). This
2671 is the time required before an idle device will be
2672 autosuspended. Devices for which the delay is set
2673 to a negative value won't be autosuspended at all.
2675 usbcore.usbfs_snoop=
2676 [USB] Set to log all usbfs traffic (default 0 = off).
2678 usbcore.blinkenlights=
2679 [USB] Set to cycle leds on hubs (default 0 = off).
2681 usbcore.old_scheme_first=
2682 [USB] Start with the old device initialization
2683 scheme (default 0 = off).
2685 usbcore.use_both_schemes=
2686 [USB] Try the other device initialization scheme
2687 if the first one fails (default 1 = enabled).
2689 usbcore.initial_descriptor_timeout=
2690 [USB] Specifies timeout for the initial 64-byte
2691 USB_REQ_GET_DESCRIPTOR request in milliseconds
2692 (default 5000 = 5.0 seconds).
2695 [USBHID] The interval which mice are to be polled at.
2697 usb-storage.delay_use=
2698 [UMS] The delay in seconds before a new device is
2699 scanned for Logical Units (default 5).
2702 [UMS] A list of quirks entries to supplement or
2703 override the built-in unusual_devs list. List
2704 entries are separated by commas. Each entry has
2705 the form VID:PID:Flags where VID and PID are Vendor
2706 and Product ID values (4-digit hex numbers) and
2707 Flags is a set of characters, each corresponding
2708 to a common usb-storage quirk flag as follows:
2709 a = SANE_SENSE (collect more than 18 bytes
2711 b = BAD_SENSE (don't collect more than 18
2712 bytes of sense data);
2713 c = FIX_CAPACITY (decrease the reported
2714 device capacity by one sector);
2715 h = CAPACITY_HEURISTICS (decrease the
2716 reported device capacity by one
2717 sector if the number is odd);
2718 i = IGNORE_DEVICE (don't bind to this
2720 l = NOT_LOCKABLE (don't try to lock and
2721 unlock ejectable media);
2722 m = MAX_SECTORS_64 (don't transfer more
2723 than 64 sectors = 32 KB at a time);
2724 o = CAPACITY_OK (accept the capacity
2725 reported by the device);
2726 r = IGNORE_RESIDUE (the device reports
2727 bogus residue values);
2728 s = SINGLE_LUN (the device has only one
2730 w = NO_WP_DETECT (don't test whether the
2731 medium is write-protected).
2732 Example: quirks=0419:aaf5:rl,0421:0433:rc
2735 [X86] Flags controlling user PTE allocations.
2737 nohigh = do not allocate PTE pages in
2738 HIGHMEM regardless of setting
2742 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2743 vdso=1: enable VDSO (default)
2744 vdso=0: disable VDSO mapping
2747 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2748 vdso32=1: enable 32-bit VDSO (default)
2749 vdso32=0: disable 32-bit VDSO mapping
2752 vector=percpu: enable percpu vector domain
2754 video= [FB] Frame buffer configuration
2755 See Documentation/fb/modedb.txt.
2757 vga= [BOOT,X86-32] Select a particular video mode
2758 See Documentation/x86/boot.txt and
2759 Documentation/svga.txt.
2760 Use vga=ask for menu.
2761 This is actually a boot loader parameter; the value is
2762 passed to the kernel using a special protocol.
2764 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2765 size of <nn>. This can be used to increase the
2766 minimum size (128MB on x86). It can also be used to
2767 decrease the size and leave more room for directly
2770 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2773 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2776 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2779 vt.cur_default= [VT] Default cursor shape.
2780 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2781 the parameters of the <Esc>[?A;B;Cc escape sequence;
2782 see VGA-softcursor.txt. Default: 2 = underline.
2784 vt.default_blu= [VT]
2785 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2786 Change the default blue palette of the console.
2787 This is a 16-member array composed of values
2790 vt.default_grn= [VT]
2791 Format: <green0>,<green1>,<green2>,...,<green15>
2792 Change the default green palette of the console.
2793 This is a 16-member array composed of values
2796 vt.default_red= [VT]
2797 Format: <red0>,<red1>,<red2>,...,<red15>
2798 Change the default red palette of the console.
2799 This is a 16-member array composed of values
2805 Set system-wide default UTF-8 mode for all tty's.
2806 Default is 1, i.e. UTF-8 mode is enabled for all
2807 newly opened terminals.
2809 vt.global_cursor_default=
2812 Set system-wide default for whether a cursor
2813 is shown on new VTs. Default is -1,
2814 i.e. cursors will be created by default unless
2815 overridden by individual drivers. 0 will hide
2816 cursors, 1 will display them.
2818 waveartist= [HW,OSS]
2819 Format: <io>,<irq>,<dma>,<dma2>
2822 See header of drivers/scsi/wd33c93.c.
2825 See header of drivers/scsi/wd7000.c.
2828 See Documentation/watchdog/wdt.txt.
2830 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2831 default x2apic cluster mode on platforms
2834 x86_mrst_timer= [X86-32,APBT]
2835 Choose timer option for x86 Moorestown MID platform.
2836 Two valid options are apbt timer only and lapic timer
2837 plus one apbt timer for broadcast timer.
2838 x86_mrst_timer=apbt_only | lapic_and_apbt
2840 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2841 xd_geo= See header of drivers/block/xd.c.
2843 xirc2ps_cs= [NET,PCMCIA]
2845 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2847 ______________________________________________________________________
2851 Add documentation for ALSA options.
2852 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob