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 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 GENERIC_TIME The generic timeofday code is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 In addition, the following text indicates that the option:
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
125 Parameters denoted with BOOT are actually interpreted by the boot
126 loader, and have no meaning to the kernel directly.
127 Do not modify the syntax of boot loader parameters without extreme
128 need or coordination with <Documentation/x86/boot.txt>.
130 There are also arch-specific kernel-parameters not documented here.
131 See for example <Documentation/x86/x86_64/boot-options.txt>.
133 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134 a trailing = on the name of any parameter states that that parameter will
135 be entered as an environment variable, whereas its absence indicates that
136 it will appear as a kernel argument readable via /proc/cmdline by programs
137 running once the system is up.
139 The number of kernel parameters is not limited, but the length of the
140 complete command line (parameters including spaces etc.) is limited to
141 a fixed number of characters. This limit depends on the architecture
142 and is between 256 and 4096 characters. It is defined in the file
143 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Advanced Configuration and Power Interface
148 Format: { force | off | ht | strict | noirq | rsdt }
149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
152 ht -- run only enough ACPI to enable Hyper Threading
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 s4_nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during hibernation.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
291 See header of drivers/scsi/advansys.c.
293 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
713 ekgdboc= [X86,KGDB] Allow early kernel console debugging
716 This is desgined to be used in conjunction with
717 the boot argument: earlyprintk=vga
722 Format: {"off" | "on" | "skip[mbr]"}
724 eisa_irq_edge= [PARISC,HW]
725 See header of drivers/parisc/eisa.c.
728 See comment before function elanfreq_setup() in
729 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
732 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
733 See Documentation/block/as-iosched.txt and
734 Documentation/block/deadline-iosched.txt for details.
736 elfcorehdr= [IA64,PPC,SH,X86]
737 Specifies physical address of start of kernel core
738 image elf header. Generally kexec loader will
739 pass this option to capture kernel.
740 See Documentation/kdump/kdump.txt for details.
742 enable_mtrr_cleanup [X86]
743 The kernel tries to adjust MTRR layout from continuous
744 to discrete, to make X server driver able to add WB
745 entry later. This parameter enables that.
747 enable_timer_pin_1 [X86]
748 Enable PIN 1 of APIC timer
749 Can be useful to work around chipset bugs
750 (in particular on some ATI chipsets).
751 The kernel tries to set a reasonable default.
753 enforcing [SELINUX] Set initial enforcing status.
755 See security/selinux/Kconfig help text.
756 0 -- permissive (log only, no denials).
757 1 -- enforcing (deny and log).
759 Value can be changed at runtime via /selinux/enforce.
761 ether= [HW,NET] Ethernet cards parameters
762 This option is obsoleted by the "netdev=" option, which
763 has equivalent usage. See its documentation for details.
767 fail_make_request=[KNL]
768 General fault injection mechanism.
769 Format: <interval>,<probability>,<space>,<times>
770 See also /Documentation/fault-injection/.
773 See header of drivers/scsi/fd_mcs.c.
776 See header of drivers/scsi/fdomain.c.
779 See Documentation/blockdev/floppy.txt.
781 force_pal_cache_flush
782 [IA-64] Avoid check_sal_cache_flush which may hang on
783 buggy SAL_CACHE_FLUSH implementations. Using this
784 parameter will force ia64_sal_cache_flush to call
785 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
788 [FTRACE] will set and start the specified tracer
789 as early as possible in order to facilitate early
792 ftrace_dump_on_oops[=orig_cpu]
793 [FTRACE] will dump the trace buffers on oops.
794 If no parameter is passed, ftrace will dump
795 buffers of all CPUs, but if you pass orig_cpu, it will
796 dump only the buffer of the CPU that triggered the
799 ftrace_filter=[function-list]
800 [FTRACE] Limit the functions traced by the function
801 tracer at boot up. function-list is a comma separated
802 list of functions. This list can be changed at run
803 time by the set_ftrace_filter file in the debugfs
806 ftrace_notrace=[function-list]
807 [FTRACE] Do not trace the functions specified in
808 function-list. This list can be changed at run time
809 by the set_ftrace_notrace file in the debugfs
812 ftrace_graph_filter=[function-list]
813 [FTRACE] Limit the top level callers functions traced
814 by the function graph tracer at boot up.
815 function-list is a comma separated list of functions
816 that can be changed at run time by the
817 set_graph_function file in the debugfs tracing directory.
820 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
821 support via parallel port (up to 5 devices per port)
822 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
823 See also Documentation/input/joystick-parport.txt
827 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
831 gcov_persist= [GCOV] When non-zero (default), profiling data for
832 kernel modules is saved and remains accessible via
833 debugfs, even when the module is unloaded/reloaded.
834 When zero, profiling data is discarded and associated
835 debugfs files are removed at module unload time.
838 See header of drivers/scsi/gdth.c.
840 gpt [EFI] Forces disk with valid GPT signature but
841 invalid Protective MBR to be treated as GPT.
845 hashdist= [KNL,NUMA] Large hashes allocated during boot
846 are distributed across NUMA nodes. Defaults on
847 for 64bit NUMA, off otherwise.
848 Format: 0 | 1 (for off | on)
850 hcl= [IA-64] SGI's Hardware Graph compatibility layer
852 hd= [EIDE] (E)IDE hard drive subsystem geometry
853 Format: <cyl>,<head>,<sect>
855 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
856 size of <nn>. This works even on boxes that have no
857 highmem otherwise. This also works to reduce highmem
858 size on bigger boxes.
860 highres= [KNL] Enable/disable high resolution timer mode.
861 Valid parameters: "on", "off"
865 See Documentation/isdn/README.HiSax.
869 hpet= [X86-32,HPET] option to control HPET usage
870 Format: { enable (default) | disable | force |
872 disable: disable HPET and use PIT instead
873 force: allow force enabled of undocumented chips (ICH4,
875 verbose: show contents of HPET registers during setup
877 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
878 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
879 On x86-64 and powerpc, this option can be specified
880 multiple times interleaved with hugepages= to reserve
881 huge pages of different sizes. Valid pages sizes on
882 x86-64 are 2M (when the CPU supports "pse") and 1G
883 (when the CPU supports the "pdpe1gb" cpuinfo flag)
884 Note that 1GB pages can only be allocated at boot time
885 using hugepages= and not freed afterwards.
887 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
888 terminal devices. Valid values: 0..8
889 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
890 If specified, z/VM IUCV HVC accepts connections
891 from listed z/VM user IDs only.
893 i2c_bus= [HW] Override the default board specific I2C bus speed
894 or register an additional I2C bus that is not
895 registered from board initialization code.
899 i8042.debug [HW] Toggle i8042 debug mode
900 i8042.direct [HW] Put keyboard port into non-translated mode
901 i8042.dumbkbd [HW] Pretend that controller can only read data from
902 keyboard and cannot control its state
903 (Don't attempt to blink the leds)
904 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
905 i8042.nokbd [HW] Don't check/create keyboard port
906 i8042.noloop [HW] Disable the AUX Loopback command while probing
908 i8042.nomux [HW] Don't check presence of an active multiplexing
910 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
913 [HW] Frequency with which keyboard LEDs should blink
914 when kernel panics (default is 0.5 sec)
915 i8042.reset [HW] Reset the controller during init and cleanup
916 i8042.unlock [HW] Unlock (ignore) the keylock
920 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
921 indicates that the driver is running on unsupported
923 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
924 does not match list of supported models.
926 [HW] Report power status in /proc/i8k
927 (disabled by default)
928 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
931 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
932 See Documentation/mca.txt.
935 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
937 ide-core.nodma= [HW] (E)IDE subsystem
938 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
939 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
940 .cdrom .chs .ignore_cable are additional options
941 See Documentation/ide/ide.txt.
943 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
944 Claim all unknown PCI IDE storage controllers.
947 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
948 Poll forces a polling idle loop that can slightly
949 improve the performance of waking up a idle CPU, but
950 will use a lot of power and make the system run hot.
952 idle=mwait: On systems which support MONITOR/MWAIT but
953 the kernel chose to not use it because it doesn't save
954 as much power as a normal idle loop, use the
955 MONITOR/MWAIT idle loop anyways. Performance should be
956 the same as idle=poll.
957 idle=halt: Halt is forced to be used for CPU idle.
958 In such case C2/C3 won't be used again.
959 idle=nomwait: Disable mwait for CPU C-states
961 ignore_loglevel [KNL]
962 Ignore loglevel setting - this will print /all/
963 kernel messages to the console. Useful for debugging.
966 Set number of hash buckets for inode cache.
969 Format: { "0" | "1" }
970 0 -- integrity auditing messages. (Default)
971 1 -- enable informational integrity auditing messages.
974 Format: { "sha1" | "md5" }
978 Load a policy which meets the needs of the Trusted
979 Computing Base. This means IMA will measure all
980 programs exec'd, files mmap'd for exec, and all files
981 opened for read by uid=0.
984 See header of drivers/scsi/in2000.c.
988 Run specified binary instead of /sbin/init as init
991 initcall_debug [KNL] Trace initcalls as they are executed. Useful
992 for working out where the kernel is dying during
995 initrd= [BOOT] Specify the location of the initial ramdisk
997 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1000 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1002 Enable intel iommu driver.
1004 Disable intel iommu driver.
1005 igfx_off [Default Off]
1006 By default, gfx is mapped as normal device. If a gfx
1007 device has a dedicated DMAR unit, the DMAR unit is
1008 bypassed by not enabling DMAR with this option. In
1009 this case, gfx device will use physical address for
1012 With this option iommu will not optimize to look
1013 for io virtual address below 32 bit forcing dual
1014 address cycle on pci bus for cards supporting greater
1015 than 32 bit addressing. The default is to look
1016 for translation below 32 bit and if not available
1017 then look in the higher range.
1018 strict [Default Off]
1019 With this option on every unmap_single operation will
1020 result in a hardware IOTLB flush operation as opposed
1021 to batching them for performance.
1025 iomem= Disable strict checking of access to MMIO memory
1026 strict regions from userspace.
1042 io7= [HW] IO7 for Marvel based alpha systems
1043 See comment before marvel_specify_io7 in
1044 arch/alpha/kernel/core_marvel.c.
1046 io_delay= [X86] I/O delay method
1048 Standard port 0x80 based delay
1050 Alternate port 0xed based delay (needed on some systems)
1052 Simple two microseconds delay
1057 See Documentation/filesystems/nfs/nfsroot.txt.
1059 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1060 See comment before ip2_setup() in
1061 drivers/char/ip2/ip2base.c.
1063 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1064 See header of drivers/scsi/ips.c.
1067 When an interrupt is not handled search all handlers
1068 for it. Intended to get systems with badly broken
1072 When an interrupt is not handled search all handlers
1073 for it. Also check all handlers each timer
1074 interrupt. Intended to get systems with badly broken
1078 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1080 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1082 <cpu number>,...,<cpu number>
1084 <cpu number>-<cpu number>
1085 (must be a positive range in ascending order)
1087 <cpu number>,...,<cpu number>-<cpu number>
1089 This option can be used to specify one or more CPUs
1090 to isolate from the general SMP balancing and scheduling
1091 algorithms. You can move a process onto or off an
1092 "isolated" CPU via the CPU affinity syscalls or cpuset.
1093 <cpu number> begins at 0 and the maximum value is
1094 "number of CPUs in system - 1".
1096 This option is the preferred way to isolate CPUs. The
1097 alternative -- manually setting the CPU mask of all
1098 tasks in the system -- can cause problems and
1099 suboptimal load balancer performance.
1103 js= [HW,JOY] Analog joystick
1104 See Documentation/input/joystick.txt.
1108 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1109 specifies the amount of memory usable by the kernel
1110 for non-movable allocations. The requested amount is
1111 spread evenly throughout all nodes in the system. The
1112 remaining memory in each node is used for Movable
1113 pages. In the event, a node is too small to have both
1114 kernelcore and Movable pages, kernelcore pages will
1115 take priority and other nodes will have a larger number
1116 of kernelcore pages. The Movable zone is used for the
1117 allocation of pages that may be reclaimed or moved
1118 by the page migration subsystem. This means that
1119 HugeTLB pages may not be allocated from this zone.
1120 Note that allocations like PTEs-from-HighMem still
1121 use the HighMem zone if it exists, and the Normal
1122 zone if it does not.
1124 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1125 Format: <Controller#>[,poll interval]
1126 The controller # is the number of the ehci usb debug
1127 port as it is probed via PCI. The poll interval is
1128 optional and is the number seconds in between
1129 each poll cycle to the debug port in case you need
1130 the functionality for interrupting the kernel with
1131 gdb or control-c on the dbgp connection. When
1132 not using this parameter you use sysrq-g to break into
1133 the kernel debugger.
1135 kgdboc= [KGDB,HW] kgdb over consoles.
1136 Requires a tty driver that supports console polling,
1137 or a supported polling keyboard driver (non-usb).
1138 Serial only format: <serial_device>[,baud]
1139 keyboard only format: kbd
1140 keyboard and serial format: kbd,<serial_device>[,baud]
1142 kgdbwait [KGDB] Stop kernel execution and enter the
1143 kernel debugger at the earliest opportunity.
1145 kmac= [MIPS] korina ethernet MAC address.
1146 Configure the RouterBoard 532 series on-chip
1147 Ethernet adapter MAC address.
1149 kmemleak= [KNL] Boot-time kmemleak enable/disable
1150 Valid arguments: on, off
1153 kstack=N [X86] Print N words from the kernel stack
1156 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1157 Default is 0 (don't ignore, but inject #GP)
1159 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1160 Default is 1 (enabled)
1162 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1165 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1167 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1169 kvm-intel.bypass_guest_pf=
1170 [KVM,Intel] Disables bypassing of guest page faults
1171 on Intel chips. Default is 1 (enabled)
1173 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1174 (virtualized MMU) support on capable Intel chips.
1175 Default is 1 (enabled)
1177 kvm-intel.emulate_invalid_guest_state=
1178 [KVM,Intel] Enable emulation of invalid guest states
1179 Default is 0 (disabled)
1181 kvm-intel.flexpriority=
1182 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1183 Default is 1 (enabled)
1185 kvm-intel.unrestricted_guest=
1186 [KVM,Intel] Disable unrestricted guest feature
1187 (virtualized real and unpaged mode) on capable
1188 Intel chips. Default is 1 (enabled)
1190 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1191 feature (tagged TLBs) on capable Intel chips.
1192 Default is 1 (enabled)
1198 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1201 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1204 libata.dma= [LIBATA] DMA control
1205 libata.dma=0 Disable all PATA and SATA DMA
1206 libata.dma=1 PATA and SATA Disk DMA only
1207 libata.dma=2 ATAPI (CDROM) DMA only
1208 libata.dma=4 Compact Flash DMA only
1209 Combinations also work, so libata.dma=3 enables DMA
1210 for disks and CDROMs, but not CFs.
1212 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1213 libata.ignore_hpa=0 keep BIOS limits (default)
1214 libata.ignore_hpa=1 ignore limits, using full disk
1216 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1220 libata.force= [LIBATA] Force configurations. The format is comma
1221 separated list of "[ID:]VAL" where ID is
1222 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1223 matching port, link or device. Basically, it matches
1224 the ATA ID string printed on console by libata. If
1225 the whole ID part is omitted, the last PORT and DEVICE
1226 values are used. If ID hasn't been specified yet, the
1227 configuration applies to all ports, links and devices.
1229 If only DEVICE is omitted, the parameter applies to
1230 the port and all links and devices behind it. DEVICE
1231 number of 0 either selects the first device or the
1232 first fan-out link behind PMP device. It does not
1233 select the host link. DEVICE number of 15 selects the
1234 host link and device attached to it.
1236 The VAL specifies the configuration to force. As long
1237 as there's no ambiguity shortcut notation is allowed.
1238 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1239 The following configurations can be forced.
1241 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1242 Any ID with matching PORT is used.
1244 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1246 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1247 udma[/][16,25,33,44,66,100,133] notation is also
1250 * [no]ncq: Turn on or off NCQ.
1252 * nohrst, nosrst, norst: suppress hard, soft
1255 * dump_id: dump IDENTIFY data.
1257 If there are multiple matching configurations changing
1258 the same attribute, the last one is used.
1260 lmb=debug [KNL] Enable lmb debug messages.
1262 load_ramdisk= [RAM] List of ramdisks to load from floppy
1263 See Documentation/blockdev/ramdisk.txt.
1265 lockd.nlm_grace_period=P [NFS] Assign grace period.
1268 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1271 lockd.nlm_timeout=T [NFS] Assign timeout value.
1274 lockd.nlm_udpport=M [NFS] Assign UDP port.
1277 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1280 loglevel= All Kernel Messages with a loglevel smaller than the
1281 console loglevel will be printed to the console. It can
1282 also be changed with klogd or other programs. The
1283 loglevels are defined as follows:
1285 0 (KERN_EMERG) system is unusable
1286 1 (KERN_ALERT) action must be taken immediately
1287 2 (KERN_CRIT) critical conditions
1288 3 (KERN_ERR) error conditions
1289 4 (KERN_WARNING) warning conditions
1290 5 (KERN_NOTICE) normal but significant condition
1291 6 (KERN_INFO) informational
1292 7 (KERN_DEBUG) debug-level messages
1294 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1295 Format: { n | nk | nM }
1296 n must be a power of two. The default size
1297 is set in the kernel config file.
1299 logo.nologo [FB] Disables display of the built-in Linux logo.
1300 This may be used to provide more screen space for
1301 kernel log messages and is useful when debugging
1302 kernel boot problems.
1304 lp=0 [LP] Specify parallel ports to use, e.g,
1305 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1306 lp=reset first parallel port). 'lp=0' disables the
1307 lp=auto printer driver. 'lp=reset' (which can be
1308 specified in addition to the ports) causes
1309 attached printers to be reset. Using
1310 lp=port1,port2,... specifies the parallel ports
1311 to associate lp devices with, starting with
1312 lp0. A port specification may be 'none' to skip
1313 that lp device, or a parport name such as
1314 'parport0'. Specifying 'lp=auto' instead of a
1315 port specification list means that device IDs
1316 from each port should be examined, to see if
1317 an IEEE 1284-compliant printer is attached; if
1318 so, the driver will manage that printer.
1319 See also header of drivers/char/lp.c.
1322 Sets loops_per_jiffy to given constant, thus avoiding
1323 time-consuming boot-time autodetection (up to 250 ms per
1324 CPU). 0 enables autodetection (default). To determine
1325 the correct value for your kernel, boot with normal
1326 autodetection and see what value is printed. Note that
1327 on SMP systems the preset will be applied to all CPUs,
1328 which is likely to cause problems if your CPUs need
1329 significantly divergent settings. An incorrect value
1330 will cause delays in the kernel to be wrong, leading to
1331 unpredictable I/O errors and other breakage. Although
1332 unlikely, in the extreme case this might damage your
1336 Format: <io>,<irq>,<dma>
1338 mac5380= [HW,SCSI] Format:
1339 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1341 machvec= [IA64] Force the use of a particular machine-vector
1342 (machvec) in a generic kernel.
1343 Example: machvec=hpzx1_swiotlb
1345 machtype= [Loongson] Share the same kernel image file between different
1347 Example: machtype=lemote-yeeloong-2f-7inch
1349 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1350 than or equal to this physical address is ignored.
1352 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1353 should make use of. maxcpus=n : n >= 0 limits the
1354 kernel to using 'n' processors. n=0 is a special case,
1355 it is equivalent to "nosmp", which also disables
1358 max_loop= [LOOP] Maximum number of loopback devices that can
1362 max_luns= [SCSI] Maximum number of LUNs to probe.
1363 Should be between 1 and 2^32-1.
1366 [SCSI] Maximum number of LUNs received.
1367 Should be between 1 and 16384.
1371 mce [X86-32] Machine Check Exception
1373 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1375 md= [HW] RAID subsystems devices and level
1376 See Documentation/md.txt.
1379 Format: <first>,<last>
1380 Specifies range of consoles to be captured by the MDA.
1382 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1383 Amount of memory to be used when the kernel is not able
1384 to see the whole system memory or for test.
1385 [X86-32] Use together with memmap= to avoid physical
1386 address space collisions. Without memmap= PCI devices
1387 could be placed at addresses belonging to unused RAM.
1389 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1393 [KNL,SH] Allow user to override the default size for
1394 per-device physically contiguous DMA buffers.
1396 memmap=exactmap [KNL,X86] Enable setting of an exact
1397 E820 memory map, as specified by the user.
1398 Such memmap=exactmap lines can be constructed based on
1399 BIOS output or other requirements. See the memmap=nn@ss
1402 memmap=nn[KMG]@ss[KMG]
1403 [KNL] Force usage of a specific region of memory
1404 Region of memory to be used, from ss to ss+nn.
1406 memmap=nn[KMG]#ss[KMG]
1407 [KNL,ACPI] Mark specific memory as ACPI data.
1408 Region of memory to be used, from ss to ss+nn.
1410 memmap=nn[KMG]$ss[KMG]
1411 [KNL,ACPI] Mark specific memory as reserved.
1412 Region of memory to be used, from ss to ss+nn.
1413 Example: Exclude memory from 0x18690000-0x1869ffff
1414 memmap=64K$0x18690000
1416 memmap=0x10000$0x18690000
1418 memory_corruption_check=0/1 [X86]
1419 Some BIOSes seem to corrupt the first 64k of
1420 memory when doing things like suspend/resume.
1421 Setting this option will scan the memory
1422 looking for corruption. Enabling this will
1423 both detect corruption and prevent the kernel
1424 from using the memory being corrupted.
1425 However, its intended as a diagnostic tool; if
1426 repeatable BIOS-originated corruption always
1427 affects the same memory, you can use memmap=
1428 to prevent the kernel from using that memory.
1430 memory_corruption_check_size=size [X86]
1431 By default it checks for corruption in the low
1432 64k, making this memory unavailable for normal
1433 use. Use this parameter to scan for
1434 corruption in more or less memory.
1436 memory_corruption_check_period=seconds [X86]
1437 By default it checks for corruption every 60
1438 seconds. Use this parameter to check at some
1439 other rate. 0 disables periodic checking.
1441 memtest= [KNL,X86] Enable memtest
1443 default : 0 <disable>
1444 Specifies the number of memtest passes to be
1445 performed. Each pass selects another test
1446 pattern from a given set of patterns. Memtest
1447 fills the memory with this pattern, validates
1448 memory contents and reserves bad memory
1449 regions that are detected.
1451 meye.*= [HW] Set MotionEye Camera parameters
1452 See Documentation/video4linux/meye.txt.
1454 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1455 Multi-Function General Purpose Timers on AMD Geode
1458 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1459 the BIOS has incorrectly applied a workaround. TinyBIOS
1460 version 0.98 is known to be affected, 0.99 fixes the
1461 problem by letting the user disable the workaround.
1465 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1466 physical address is ignored.
1468 mini2440= [ARM,HW,KNL]
1469 Format:[0..2][b][c][t]
1471 MINI2440 configuration specification:
1472 0 - The attached screen is the 3.5" TFT
1473 1 - The attached screen is the 7" TFT
1474 2 - The VGA Shield is attached (1024x768)
1475 Leaving out the screen size parameter will not load
1476 the TFT driver, and the framebuffer will be left
1478 b - Enable backlight. The TFT backlight pin will be
1479 linked to the kernel VESA blanking code and a GPIO
1480 LED. This parameter is not necessary when using the
1482 c - Enable the s3c camera interface.
1483 t - Reserved for enabling touchscreen support. The
1484 touchscreen support is not enabled in the mainstream
1485 kernel as of 2.6.30, a preliminary port can be found
1486 in the "bleeding edge" mini2440 support kernel at
1487 http://repo.or.cz/w/linux-2.6/mini2440.git
1490 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1491 parameter allows control of the logging verbosity for
1492 the additional memory initialisation checks. A value
1493 of 0 disables mminit logging and a level of 4 will
1494 log everything. Information is printed at KERN_DEBUG
1495 so loglevel=8 may also need to be specified.
1498 [MOUSE] Maximum time between finger touching and
1499 leaving touchpad surface for touch to be considered
1500 a tap and be reported as a left button click (for
1501 touchpads working in absolute mode only).
1503 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1504 reporting absolute coordinates, such as tablets
1505 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1506 reporting absolute coordinates, such as tablets
1508 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1509 is similar to kernelcore except it specifies the
1510 amount of memory used for migratable allocations.
1511 If both kernelcore and movablecore is specified,
1512 then kernelcore will be at *least* the specified
1513 value but may be more. If movablecore on its own
1514 is specified, the administrator must be careful
1515 that the amount of memory usable for all allocations
1521 MTD_Partition= [MTD]
1522 Format: <name>,<region-number>,<size>,<offset>
1524 MTD_Region= [MTD] Format:
1525 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1528 See drivers/mtd/cmdlinepart.c.
1530 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1532 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1534 boundary - index of last SLC block on Flex-OneNAND.
1535 The remaining blocks are configured as MLC blocks.
1536 lock - Configure if Flex-OneNAND boundary should be locked.
1537 Once locked, the boundary cannot be changed.
1538 1 indicates lock status, 0 indicates unlock status.
1541 ARM/S3C2412 JIVE boot control
1543 See arch/arm/mach-s3c2412/mach-jive.c
1545 mtouchusb.raw_coordinates=
1546 [HW] Make the MicroTouch USB driver use raw coordinates
1547 ('y', default) or cooked coordinates ('n')
1549 mtrr_chunk_size=nn[KMG] [X86]
1550 used for mtrr cleanup. It is largest continuous chunk
1551 that could hold holes aka. UC entries.
1553 mtrr_gran_size=nn[KMG] [X86]
1554 Used for mtrr cleanup. It is granularity of mtrr block.
1556 Large value could prevent small alignment from
1559 mtrr_spare_reg_nr=n [X86]
1561 Range: 0,7 : spare reg number
1563 Used for mtrr cleanup. It is spare mtrr entries number.
1564 Set to 2 or more if your graphical card needs more.
1566 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1569 See header of drivers/scsi/NCR_D700.c.
1573 ncr53c400= [HW,SCSI]
1575 ncr53c400a= [HW,SCSI]
1577 ncr53c406a= [HW,SCSI]
1579 ncr53c8xx= [HW,SCSI]
1581 netdev= [NET] Network devices parameters
1582 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1583 Note that mem_start is often overloaded to mean
1584 something different and driver-specific.
1585 This usage is only documented in each driver source
1589 [NETFILTER] Enable connection tracking flow accounting
1590 0 to disable accounting
1591 1 to enable accounting
1592 Default value depends on CONFIG_NF_CT_ACCT that is
1593 going to be removed in 2.6.29.
1596 See Documentation/filesystems/nfs/nfsroot.txt.
1598 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1599 See Documentation/filesystems/nfs/nfsroot.txt.
1601 nfs.callback_tcpport=
1602 [NFS] set the TCP port on which the NFSv4 callback
1603 channel should listen.
1606 [NFS] sets the pathname to the program which is used
1607 to update the NFS client cache entries.
1609 nfs.cache_getent_timeout=
1610 [NFS] sets the timeout after which an attempt to
1611 update a cache entry is deemed to have failed.
1613 nfs.idmap_cache_timeout=
1614 [NFS] set the maximum lifetime for idmapper cache
1618 [NFS] enable 64-bit inode numbers.
1619 If zero, the NFS client will fake up a 32-bit inode
1620 number for the readdir() and stat() syscalls instead
1621 of returning the full 64-bit number.
1622 The default is to return 64-bit inode numbers.
1624 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1625 when a NMI is triggered.
1626 Format: [state][,regs][,debounce][,die]
1628 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1629 Format: [panic,][num]
1631 0 - turn nmi_watchdog off
1632 1 - use the IO-APIC timer for the NMI watchdog
1633 2 - use the local APIC for the NMI watchdog using
1634 a performance counter. Note: This will use one
1635 performance counter and the local APIC's performance
1637 When panic is specified, panic when an NMI watchdog
1639 This is useful when you use a panic=... timeout and
1640 need the box quickly up again.
1641 Instead of 1 and 2 it is possible to use the following
1642 symbolic names: lapic and ioapic
1643 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1645 netpoll.carrier_timeout=
1646 [NET] Specifies amount of time (in seconds) that
1647 netpoll should wait for a carrier. By default netpoll
1650 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1651 emulation library even if a 387 maths coprocessor
1655 [HW] Never suspend the console
1656 Disable suspending of consoles during suspend and
1657 hibernate operations. Once disabled, debugging
1658 messages can reach various consoles while the rest
1659 of the system is being put to sleep (ie, while
1660 debugging driver suspend/resume hooks). This may
1661 not work reliably with all consoles, but is known
1662 to work with serial and VGA consoles.
1664 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1665 caches in the slab allocator. Saves per-node memory,
1666 but will impact performance.
1670 noapic [SMP,APIC] Tells the kernel to not make use of any
1671 IOAPICs that may be present in the system.
1673 nobats [PPC] Do not use BATs for mapping kernel lowmem
1674 on "Classic" PPC cores.
1678 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1680 nodelayacct [KNL] Disable per-task delay accounting
1682 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1684 nodsp [SH] Disable hardware DSP at boot time.
1686 noefi [X86] Disable EFI runtime services support.
1691 On X86-32 available only on PAE configured kernels.
1692 noexec=on: enable non-executable mappings (default)
1693 noexec=off: disable non-executable mappings
1696 This affects only 32-bit executables.
1697 noexec32=on: enable non-executable mappings (default)
1698 read doesn't imply executable mappings
1699 noexec32=off: disable non-executable mappings
1700 read implies executable mappings
1702 nofpu [SH] Disable hardware FPU at boot time.
1704 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1705 register save and restore. The kernel will only save
1706 legacy floating-point registers on task switch.
1708 noxsave [BUGS=X86] Disables x86 extended register state save
1709 and restore using xsave. The kernel will fallback to
1710 enabling legacy floating-point and sse state.
1712 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1713 wfi(ARM) instruction doesn't work correctly and not to
1714 use it. This is also useful when using JTAG debugger.
1716 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1717 instruction doesn't work correctly and not to
1720 no_file_caps Tells the kernel not to honor file capabilities. The
1721 only way then for a file to be executed with privilege
1722 is to be setuid root or executed by root.
1724 nohalt [IA-64] Tells the kernel not to use the power saving
1725 function PAL_HALT_LIGHT when idle. This increases
1726 power-consumption. On the positive side, it reduces
1727 interrupt wake-up latency, which may improve performance
1728 in certain environments such as networked servers or
1731 nohz= [KNL] Boottime enable/disable dynamic ticks
1732 Valid arguments: on, off
1735 noiotrap [SH] Disables trapped I/O port accesses.
1737 noirqdebug [X86-32] Disables the code which attempts to detect and
1738 disable unhandled interrupt sources.
1740 no_timer_check [X86,APIC] Disables the code which tests for
1741 broken timer IRQ sources.
1743 noisapnp [ISAPNP] Disables ISA PnP code.
1745 noinitrd [RAM] Tells the kernel not to load any configured
1748 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1753 nojitter [IA64] Disables jitter checking for ITC timers.
1755 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1757 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1759 noltlbs [PPC] Do not use large page/tlb entries for kernel
1760 lowmem mapping on PPC40x.
1762 nomca [IA-64] Disable machine check abort handling
1764 nomce [X86-32] Machine Check Exception
1766 nomfgpt [X86-32] Disable Multi-Function General Purpose
1767 Timer usage (for AMD Geode machines).
1769 nopat [X86] Disable PAT (page attribute table extension of
1770 pagetables) support.
1772 norandmaps Don't use address space randomization. Equivalent to
1773 echo 0 > /proc/sys/kernel/randomize_va_space
1775 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1777 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1778 with UP alternatives
1780 noresidual [PPC] Don't use residual data on PReP machines.
1782 noresume [SWSUSP] Disables resume and restores original swap
1785 no-scroll [VGA] Disables scrollback.
1786 This is required for the Braillex ib80-piezo Braille
1787 reader made by F.H. Papenmeier (Germany).
1791 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1793 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1794 and disable the IO APIC. legacy for "maxcpus=0".
1796 nosoftlockup [KNL] Disable the soft-lockup detector.
1798 noswapaccount [KNL] Disable accounting of swap in memory resource
1799 controller. (See Documentation/cgroups/memory.txt)
1801 nosync [HW,M68K] Disables sync negotiation for all devices.
1803 notsc [BUGS=X86-32] Disable Time Stamp Counter
1805 nousb [USB] Disable the USB subsystem
1809 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1811 nptcg= [IA64] Override max number of concurrent global TLB
1812 purges which is reported from either PAL_VM_SUMMARY or
1815 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1816 could support. nr_cpus=n : n >= 1 limits the kernel to
1817 supporting 'n' processors. Later in runtime you can not
1818 use hotplug cpu feature to put more cpu back to online.
1819 just like you compile the kernel NR_CPUS=n
1821 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1823 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1824 one of ['zone', 'node', 'default'] can be specified
1825 This can be set from sysctl after boot.
1826 See Documentation/sysctl/vm.txt for details.
1828 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1829 See Documentation/debugging-via-ohci1394.txt for more
1832 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1833 Rather than timing out after 20 ms if an EC
1834 command is not properly ACKed, override the length
1835 of the timeout. We have interrupts disabled while
1836 waiting for the ACK, so if this is set too high
1837 interrupts *may* be lost!
1839 omap_mux= [OMAP] Override bootloader pin multiplexing.
1840 Format: <mux_mode0.mode_name=value>...
1841 For example, to override I2C bus2:
1842 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1847 oprofile.timer= [HW]
1848 Use timer interrupt instead of performance counters
1850 oprofile.cpu_type= Force an oprofile cpu type
1851 This might be useful if you have an older oprofile
1852 userland or if you want common events.
1853 Format: { arch_perfmon }
1854 arch_perfmon: [X86] Force use of architectural
1855 perfmon on Intel CPUs instead of the
1856 CPU specific event set.
1858 osst= [HW,SCSI] SCSI Tape Driver
1859 Format: <buffer_size>,<write_threshold>
1860 See also Documentation/scsi/st.txt.
1862 panic= [KNL] Kernel behaviour on panic
1865 parkbd.port= [HW] Parallel port number the keyboard adapter is
1866 connected to, default is 0.
1868 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1869 0 for XT, 1 for AT (default is AT).
1872 parport= [HW,PPT] Specify parallel ports. 0 disables.
1873 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1874 Use 'auto' to force the driver to use any
1875 IRQ/DMA settings detected (the default is to
1876 ignore detected IRQ/DMA settings because of
1877 possible conflicts). You can specify the base
1878 address, IRQ, and DMA settings; IRQ and DMA
1879 should be numbers, or 'auto' (for using detected
1880 settings on that particular port), or 'nofifo'
1881 (to avoid using a FIFO even if it is detected).
1882 Parallel ports are assigned in the order they
1883 are specified on the command line, starting
1886 parport_init_mode= [HW,PPT]
1887 Configure VIA parallel port to operate in
1888 a specific mode. This is necessary on Pegasos
1889 computer where firmware has no options for setting
1890 up parallel port mode and sets it to spp.
1891 Currently this function knows 686a and 8231 chips.
1892 Format: [spp|ps2|epp|ecp|ecpepp]
1894 pas2= [HW,OSS] Format:
1895 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1898 See header of drivers/scsi/pas16.c.
1901 Halt all CPUs after the first oops has been printed for
1902 the specified number of seconds. This is to be used if
1903 your oopses keep scrolling off the screen.
1908 See header of drivers/block/paride/pcd.c.
1909 See also Documentation/blockdev/paride.txt.
1911 pci=option[,option...] [PCI] various PCI subsystem options:
1912 earlydump [X86] dump PCI config space before the kernel
1914 off [X86] don't probe for the PCI bus
1915 bios [X86-32] force use of PCI BIOS, don't access
1916 the hardware directly. Use this if your machine
1917 has a non-standard PCI host bridge.
1918 nobios [X86-32] disallow use of PCI BIOS, only direct
1919 hardware access methods are allowed. Use this
1920 if you experience crashes upon bootup and you
1921 suspect they are caused by the BIOS.
1922 conf1 [X86] Force use of PCI Configuration
1924 conf2 [X86] Force use of PCI Configuration
1926 noaer [PCIE] If the PCIEAER kernel config parameter is
1927 enabled, this kernel boot option can be used to
1928 disable the use of PCIE advanced error reporting.
1929 nodomains [PCI] Disable support for multiple PCI
1930 root domains (aka PCI segments, in ACPI-speak).
1931 nommconf [X86] Disable use of MMCONFIG for PCI
1933 check_enable_amd_mmconf [X86] check for and enable
1934 properly configured MMIO access to PCI
1935 config space on AMD family 10h CPU
1936 nomsi [MSI] If the PCI_MSI kernel config parameter is
1937 enabled, this kernel boot option can be used to
1938 disable the use of MSI interrupts system-wide.
1939 noioapicquirk [APIC] Disable all boot interrupt quirks.
1940 Safety option to keep boot IRQs enabled. This
1941 should never be necessary.
1942 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1943 primary IO-APIC for bridges that cannot disable
1944 boot IRQs. This fixes a source of spurious IRQs
1945 when the system masks IRQs.
1946 noioapicreroute [APIC] Disable workaround that uses the
1947 boot IRQ equivalent of an IRQ that connects to
1948 a chipset where boot IRQs cannot be disabled.
1949 The opposite of ioapicreroute.
1950 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1951 routing table. These calls are known to be buggy
1952 on several machines and they hang the machine
1953 when used, but on other computers it's the only
1954 way to get the interrupt routing table. Try
1955 this option if the kernel is unable to allocate
1956 IRQs or discover secondary PCI buses on your
1958 rom [X86] Assign address space to expansion ROMs.
1959 Use with caution as certain devices share
1960 address decoders between ROMs and other
1962 norom [X86] Do not assign address space to
1963 expansion ROMs that do not already have
1964 BIOS assigned address ranges.
1965 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1966 assigned automatically to PCI devices. You can
1967 make the kernel exclude IRQs of your ISA cards
1969 pirqaddr=0xAAAAA [X86] Specify the physical address
1970 of the PIRQ table (normally generated
1971 by the BIOS) if it is outside the
1972 F0000h-100000h range.
1973 lastbus=N [X86] Scan all buses thru bus #N. Can be
1974 useful if the kernel is unable to find your
1975 secondary buses and you want to tell it
1976 explicitly which ones they are.
1977 assign-busses [X86] Always assign all PCI bus
1978 numbers ourselves, overriding
1979 whatever the firmware may have done.
1980 usepirqmask [X86] Honor the possible IRQ mask stored
1981 in the BIOS $PIR table. This is needed on
1982 some systems with broken BIOSes, notably
1983 some HP Pavilion N5400 and Omnibook XE3
1984 notebooks. This will have no effect if ACPI
1985 IRQ routing is enabled.
1986 noacpi [X86] Do not use ACPI for IRQ routing
1987 or for PCI scanning.
1988 use_crs [X86] Use PCI host bridge window information
1989 from ACPI. On BIOSes from 2008 or later, this
1990 is enabled by default. If you need to use this,
1991 please report a bug.
1992 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1993 If you need to use this, please report a bug.
1994 routeirq Do IRQ routing for all PCI devices.
1995 This is normally done in pci_enable_device(),
1996 so this option is a temporary workaround
1997 for broken drivers that don't call it.
1998 skip_isa_align [X86] do not align io start addr, so can
1999 handle more pci cards
2000 firmware [ARM] Do not re-enumerate the bus but instead
2001 just use the configuration from the
2002 bootloader. This is currently used on
2003 IXP2000 systems where the bus has to be
2004 configured a certain way for adjunct CPUs.
2005 noearly [X86] Don't do any early type 1 scanning.
2006 This might help on some broken boards which
2007 machine check when some devices' config space
2008 is read. But various workarounds are disabled
2009 and some IOMMU drivers will not work.
2010 bfsort Sort PCI devices into breadth-first order.
2011 This sorting is done to get a device
2012 order compatible with older (<= 2.4) kernels.
2013 nobfsort Don't sort PCI devices into breadth-first order.
2014 cbiosize=nn[KMG] The fixed amount of bus space which is
2015 reserved for the CardBus bridge's IO window.
2016 The default value is 256 bytes.
2017 cbmemsize=nn[KMG] The fixed amount of bus space which is
2018 reserved for the CardBus bridge's memory
2019 window. The default value is 64 megabytes.
2022 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2023 Specifies alignment and device to reassign
2024 aligned memory resources.
2025 If <order of align> is not specified,
2026 PAGE_SIZE is used as alignment.
2027 PCI-PCI bridge can be specified, if resource
2028 windows need to be expanded.
2029 ecrc= Enable/disable PCIe ECRC (transaction layer
2030 end-to-end CRC checking).
2031 bios: Use BIOS/firmware settings. This is the
2036 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2039 force Enable ASPM even on devices that claim not to support it.
2040 WARNING: Forcing ASPM on may cause system lockups.
2042 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2043 off Do not use native PCIe PME signaling.
2044 force Use native PCIe PME signaling even if the BIOS refuses
2045 to allow the kernel to control the relevant PCIe config
2047 nomsi Do not use MSI for native PCIe PME signaling (this makes
2048 all PCIe root ports use INTx for everything).
2050 pcmv= [HW,PCMCIA] BadgePAD 4
2053 See Documentation/blockdev/paride.txt.
2055 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2058 See arch/parisc/kernel/pdc_chassis.c
2060 percpu_alloc= Select which percpu first chunk allocator to use.
2061 Currently supported values are "embed" and "page".
2062 Archs may support subset or none of the selections.
2063 See comments in mm/percpu.c for details on each
2064 allocator. This parameter is primarily for debugging
2065 and performance comparison.
2068 See Documentation/blockdev/paride.txt.
2071 See Documentation/blockdev/paride.txt.
2073 pirq= [SMP,APIC] Manual mp-table setup
2074 See Documentation/x86/i386/IO-APIC.txt.
2076 plip= [PPT,NET] Parallel port network link
2077 Format: { parport<nr> | timid | 0 }
2078 See also Documentation/parport.txt.
2080 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2081 Override pmtimer IOPort with a hex value.
2085 Enable PNP debug messages. This depends on the
2086 CONFIG_PNP_DEBUG_MESSAGES option.
2092 { on | off | curr | res | no-curr | no-res }
2095 [ISAPNP] Exclude IRQs for the autoconfiguration
2098 [ISAPNP] Exclude DMAs for the autoconfiguration
2100 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2101 Ranges are in pairs (I/O port base and size).
2104 [ISAPNP] Exclude memory regions for the
2106 Ranges are in pairs (memory base and size).
2108 ports= [IP_VS_FTP] IPVS ftp helper module
2110 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2112 Format: <port>,<port>....
2114 print-fatal-signals=
2115 [KNL] debug: print fatal signals
2117 If enabled, warn about various signal handling
2118 related application anomalies: too many signals,
2119 too many POSIX.1 timers, fatal signals causing a
2122 If you hit the warning due to signal overflow,
2123 you might want to try "ulimit -i unlimited".
2127 printk.time= Show timing data prefixed to each printk message line
2128 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2130 processor.max_cstate= [HW,ACPI]
2131 Limit processor to maximum C-state
2132 max_cstate=9 overrides any DMI blacklist limit.
2134 processor.nocst [HW,ACPI]
2135 Ignore the _CST method to determine C-states,
2136 instead using the legacy FADT method
2138 profile= [KNL] Enable kernel profiling via /proc/profile
2139 Format: [schedule,]<number>
2140 Param: "schedule" - profile schedule points.
2141 Param: <number> - step/bucket size as a power of 2 for
2142 statistical time based profiling.
2143 Param: "sleep" - profile D-state sleeping (millisecs).
2144 Requires CONFIG_SCHEDSTATS
2145 Param: "kvm" - profile VM exits.
2147 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2149 See Documentation/blockdev/ramdisk.txt.
2151 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2152 probe for; one of (bare|imps|exps|lifebook|any).
2153 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2155 psmouse.resetafter= [HW,MOUSE]
2156 Try to reset the device after so many bad packets
2159 [HW,MOUSE] Set desired mouse resolution, in dpi.
2160 psmouse.smartscroll=
2161 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2162 0 = disabled, 1 = enabled (default).
2164 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2166 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2169 See Documentation/blockdev/paride.txt.
2172 [KNL] Number of legacy pty's. Overwrites compiled-in
2175 quiet [KNL] Disable most log messages
2180 See Documentation/md.txt.
2182 ramdisk_blocksize= [RAM]
2183 See Documentation/blockdev/ramdisk.txt.
2185 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2186 See Documentation/blockdev/ramdisk.txt.
2188 rcupdate.blimit= [KNL,BOOT]
2189 Set maximum number of finished RCU callbacks to process
2192 rcupdate.qhimark= [KNL,BOOT]
2193 Set threshold of queued
2194 RCU callbacks over which batch limiting is disabled.
2196 rcupdate.qlowmark= [KNL,BOOT]
2197 Set threshold of queued RCU callbacks below which
2198 batch limiting is re-enabled.
2202 Run specified binary instead of /init from the ramdisk,
2203 used for early userspace startup. See initrd.
2205 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2206 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2207 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2210 [KNL, SMP] Set scheduler's default relax_domain_level.
2211 See Documentation/cgroups/cpusets.txt.
2213 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2215 reservetop= [X86-32]
2217 Reserves a hole at the top of the kernel virtual
2220 reset_devices [KNL] Force drivers to reset the underlying device
2221 during initialization.
2224 Specify the partition device for software suspend
2226 resume_offset= [SWSUSP]
2227 Specify the offset from the beginning of the partition
2228 given by "resume=" at which the swap header is located,
2229 in <PAGE_SIZE> units (needed only for swap files).
2230 See Documentation/power/swsusp-and-swap-files.txt
2232 retain_initrd [RAM] Keep initrd memory after extraction
2234 rhash_entries= [KNL,NET]
2235 Set number of hash buckets for route cache
2237 riscom8= [HW,SERIAL]
2238 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2240 ro [KNL] Mount root device read-only on boot
2242 root= [KNL] Root filesystem
2244 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2245 mount the root filesystem
2247 rootflags= [KNL] Set root filesystem mount option string
2249 rootfstype= [KNL] Set root filesystem type
2251 rootwait [KNL] Wait (indefinitely) for root device to show up.
2252 Useful for devices that are detected asynchronously
2253 (e.g. USB and MMC devices).
2255 rw [KNL] Mount root device read-write on boot
2257 S [KNL] Run init in single mode
2260 See drivers/net/irda/sa1100_ir.c.
2262 sbni= [NET] Granch SBNI12 leased line adapter
2264 sched_debug [KNL] Enables verbose scheduler debug messages.
2266 scsi_debug_*= [SCSI]
2267 See drivers/scsi/scsi_debug.c.
2269 scsi_default_dev_flags=
2270 [SCSI] SCSI default device flags
2273 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2274 Format: <vendor>:<model>:<flags>
2275 (flags are integer value)
2277 scsi_logging_level= [SCSI] a bit mask of logging levels
2278 See drivers/scsi/scsi_logging.h for bits. Also
2279 settable via sysctl at dev.scsi.logging_level
2280 (/proc/sys/dev/scsi/logging_level).
2281 There is also a nice 'scsi_logging_level' script in the
2282 S390-tools package, available for download at
2283 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2285 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2286 discovered. async scans them in kernel threads,
2287 allowing boot to proceed. none ignores them, expecting
2288 user space to do the scan.
2290 security= [SECURITY] Choose a security module to enable at boot.
2291 If this boot parameter is not specified, only the first
2292 security module asking for security registration will be
2293 loaded. An invalid security module name will be treated
2294 as if no module has been chosen.
2296 selinux= [SELINUX] Disable or enable SELinux at boot time.
2297 Format: { "0" | "1" }
2298 See security/selinux/Kconfig help text.
2301 Default value is set via kernel config option.
2302 If enabled at boot time, /selinux/disable can be used
2303 later to disable prior to initial policy load.
2305 serialnumber [BUGS=X86-32]
2308 Maximal number of shapers.
2310 show_msr= [x86] show boot-time MSR settings
2311 Format: { <integer> }
2312 Show boot-time (BIOS-initialized) MSR settings.
2313 The parameter means the number of CPUs to show,
2314 for example 1 means boot CPU only.
2317 See header of drivers/scsi/sim710.c.
2324 slub_debug[=options[,slabs]] [MM, SLUB]
2325 Enabling slub_debug allows one to determine the
2326 culprit if slab objects become corrupted. Enabling
2327 slub_debug can create guard zones around objects and
2328 may poison objects when not in use. Also tracks the
2329 last alloc / free. For more information see
2330 Documentation/vm/slub.txt.
2332 slub_max_order= [MM, SLUB]
2333 Determines the maximum allowed order for slabs.
2334 A high setting may cause OOMs due to memory
2335 fragmentation. For more information see
2336 Documentation/vm/slub.txt.
2338 slub_min_objects= [MM, SLUB]
2339 The minimum number of objects per slab. SLUB will
2340 increase the slab order up to slub_max_order to
2341 generate a sufficiently large slab able to contain
2342 the number of objects indicated. The higher the number
2343 of objects the smaller the overhead of tracking slabs
2344 and the less frequently locks need to be acquired.
2345 For more information see Documentation/vm/slub.txt.
2347 slub_min_order= [MM, SLUB]
2348 Determines the mininum page order for slabs. Must be
2349 lower than slub_max_order.
2350 For more information see Documentation/vm/slub.txt.
2352 slub_nomerge [MM, SLUB]
2353 Disable merging of slabs with similar size. May be
2354 necessary if there is some reason to distinguish
2355 allocs to different slabs. Debug options disable
2356 merging on their own.
2357 For more information see Documentation/vm/slub.txt.
2360 Format: <io1>[,<io2>[,...,<io8>]]
2362 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2363 attempt to substitute SMP alternatives once at boot.
2365 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2366 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2367 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2368 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2369 smsc-ircc2.ircc_irq= [HW] IRQ line
2370 smsc-ircc2.ircc_dma= [HW] DMA channel
2371 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2372 0: Toshiba Satellite 1800 (GP data pin select)
2373 1: Fast pin select (default)
2376 snd-ad1816a= [HW,ALSA]
2378 snd-ad1848= [HW,ALSA]
2380 snd-ali5451= [HW,ALSA]
2382 snd-als100= [HW,ALSA]
2384 snd-als4000= [HW,ALSA]
2386 snd-azt2320= [HW,ALSA]
2388 snd-cmi8330= [HW,ALSA]
2390 snd-cmipci= [HW,ALSA]
2392 snd-cs4231= [HW,ALSA]
2394 snd-cs4232= [HW,ALSA]
2396 snd-cs4236= [HW,ALSA]
2398 snd-cs4281= [HW,ALSA]
2400 snd-cs46xx= [HW,ALSA]
2402 snd-dt019x= [HW,ALSA]
2404 snd-dummy= [HW,ALSA]
2406 snd-emu10k1= [HW,ALSA]
2408 snd-ens1370= [HW,ALSA]
2410 snd-ens1371= [HW,ALSA]
2412 snd-es968= [HW,ALSA]
2414 snd-es1688= [HW,ALSA]
2416 snd-es18xx= [HW,ALSA]
2418 snd-es1938= [HW,ALSA]
2420 snd-es1968= [HW,ALSA]
2422 snd-fm801= [HW,ALSA]
2424 snd-gusclassic= [HW,ALSA]
2426 snd-gusextreme= [HW,ALSA]
2428 snd-gusmax= [HW,ALSA]
2432 snd-ice1712= [HW,ALSA]
2434 snd-intel8x0= [HW,ALSA]
2436 snd-interwave= [HW,ALSA]
2441 snd-korg1212= [HW,ALSA]
2443 snd-maestro3= [HW,ALSA]
2445 snd-mpu401= [HW,ALSA]
2447 snd-mtpav= [HW,ALSA]
2449 snd-nm256= [HW,ALSA]
2451 snd-opl3sa2= [HW,ALSA]
2459 snd-opti93x= [HW,ALSA]
2463 snd-rme32= [HW,ALSA]
2465 snd-rme96= [HW,ALSA]
2467 snd-rme9652= [HW,ALSA]
2473 snd-sbawe= [HW,ALSA]
2475 snd-serial= [HW,ALSA]
2477 snd-sgalaxy= [HW,ALSA]
2479 snd-sonicvibes= [HW,ALSA]
2484 snd-sun-cs4231= [HW,ALSA]
2486 snd-trident= [HW,ALSA]
2488 snd-usb-audio= [HW,ALSA,USB]
2490 snd-via82xx= [HW,ALSA]
2492 snd-virmidi= [HW,ALSA]
2494 snd-wavefront= [HW,ALSA]
2496 snd-ymfpci= [HW,ALSA]
2499 [KNL] Should the soft-lockup detector generate panics.
2501 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2502 See Documentation/sonypi.txt
2504 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2505 See Documentation/serial/specialix.txt.
2507 spia_io_base= [HW,MTD]
2513 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2515 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2516 See Documentation/scsi/st.txt.
2519 Enabled the stack tracer on boot up.
2523 Set the STI (builtin display/keyboard on the HP-PARISC
2524 machines) console (graphic card) which should be used
2525 as the initial boot-console.
2526 See also comment in drivers/video/console/sticore.c.
2529 See comment in drivers/video/console/sticore.c.
2532 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2534 sunrpc.min_resvport=
2535 sunrpc.max_resvport=
2537 SunRPC servers often require that client requests
2538 originate from a privileged port (i.e. a port in the
2539 range 0 < portnr < 1024).
2540 An administrator who wishes to reserve some of these
2541 ports for other uses may adjust the range that the
2542 kernel's sunrpc client considers to be privileged
2543 using these two parameters to set the minimum and
2544 maximum port values.
2548 Control how the NFS server code allocates CPUs to
2549 service thread pools. Depending on how many NICs
2550 you have and where their interrupts are bound, this
2551 option will affect which CPUs will do NFS serving.
2552 Note: this parameter cannot be changed while the
2553 NFS server is running.
2555 auto the server chooses an appropriate mode
2556 automatically using heuristics
2557 global a single global pool contains all CPUs
2558 percpu one pool for each CPU
2559 pernode one pool for each NUMA node (equivalent
2560 to global on non-NUMA machines)
2562 sunrpc.tcp_slot_table_entries=
2563 sunrpc.udp_slot_table_entries=
2565 Sets the upper limit on the number of simultaneous
2566 RPC calls that can be sent from the client to a
2567 server. Increasing these values may allow you to
2568 improve throughput, but will also increase the
2569 amount of memory reserved for use by the client.
2571 swiotlb= [IA-64] Number of I/O TLB slabs
2575 sym53c416= [HW,SCSI]
2576 See header of drivers/scsi/sym53c416.c.
2578 sysrq_always_enabled
2580 Ignore sysrq setting - this boot parameter will
2581 neutralize any effect of /proc/sys/kernel/sysrq.
2582 Useful for debugging.
2585 See header of drivers/scsi/t128.c.
2589 test_suspend= [SUSPEND]
2590 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2591 standby suspend) as the system sleep state to briefly
2592 enter during system startup. The system is woken from
2593 this state using a wakeup-capable RTC alarm.
2595 thash_entries= [KNL,NET]
2596 Set number of hash buckets for TCP connection
2598 thermal.act= [HW,ACPI]
2599 -1: disable all active trip points in all thermal zones
2600 <degrees C>: override all lowest active trip points
2602 thermal.crt= [HW,ACPI]
2603 -1: disable all critical trip points in all thermal zones
2604 <degrees C>: override all critical trip points
2606 thermal.nocrt= [HW,ACPI]
2607 Set to disable actions on ACPI thermal zone
2608 critical and hot trip points.
2610 thermal.off= [HW,ACPI]
2611 1: disable ACPI thermal control
2613 thermal.psv= [HW,ACPI]
2614 -1: disable all passive trip points
2615 <degrees C>: override all passive trip points to this
2618 thermal.tzp= [HW,ACPI]
2619 Specify global default ACPI thermal zone polling rate
2620 <deci-seconds>: poll all this frequency
2621 0: no polling (default)
2624 See comment before function dc390_setup() in
2625 drivers/scsi/tmscsim.c.
2629 Specify if the kernel should make use of the cpu
2630 topology informations if the hardware supports these.
2631 The scheduler will make use of these informations and
2632 e.g. base its process migration decisions on it.
2637 tpm_suspend_pcr=[HW,TPM]
2638 Format: integer pcr id
2639 Specify that at suspend time, the tpm driver
2640 should extend the specified pcr with zeros,
2641 as a workaround for some chips which fail to
2642 flush the last written pcr on TPM_SaveState.
2643 This will guarantee that all the other pcrs
2646 trace_buf_size=nn[KMG]
2647 [FTRACE] will set tracing buffer size.
2649 trace_event=[event-list]
2650 [FTRACE] Set and start specified trace events in order
2651 to facilitate early boot debugging.
2652 See also Documentation/trace/events.txt
2654 trix= [HW,OSS] MediaTrix AudioTrix Pro
2656 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2658 tsc= Disable clocksource-must-verify flag for TSC.
2660 [x86] reliable: mark tsc clocksource as reliable, this
2661 disables clocksource verification at runtime.
2662 Used to enable high-resolution timer mode on older
2663 hardware, and in virtualized environment.
2665 turbografx.map[2|3]= [HW,JOY]
2666 TurboGraFX parallel port interface
2668 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2669 See also Documentation/input/joystick-parport.txt
2671 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2672 See header of drivers/scsi/u14-34f.c.
2680 uhash_entries= [KNL,NET]
2681 Set number of hash buckets for UDP/UDP-Lite connections
2684 [USB] Ignore overcurrent events (default N).
2685 Some badly-designed motherboards generate lots of
2686 bogus events, for ports that aren't wired to
2687 anything. Set this parameter to avoid log spamming.
2688 Note that genuine overcurrent events won't be
2693 Set unknown_nmi_panic=1 early on boot.
2695 usbcore.autosuspend=
2696 [USB] The autosuspend time delay (in seconds) used
2697 for newly-detected USB devices (default 2). This
2698 is the time required before an idle device will be
2699 autosuspended. Devices for which the delay is set
2700 to a negative value won't be autosuspended at all.
2702 usbcore.usbfs_snoop=
2703 [USB] Set to log all usbfs traffic (default 0 = off).
2705 usbcore.blinkenlights=
2706 [USB] Set to cycle leds on hubs (default 0 = off).
2708 usbcore.old_scheme_first=
2709 [USB] Start with the old device initialization
2710 scheme (default 0 = off).
2712 usbcore.use_both_schemes=
2713 [USB] Try the other device initialization scheme
2714 if the first one fails (default 1 = enabled).
2716 usbcore.initial_descriptor_timeout=
2717 [USB] Specifies timeout for the initial 64-byte
2718 USB_REQ_GET_DESCRIPTOR request in milliseconds
2719 (default 5000 = 5.0 seconds).
2722 [USBHID] The interval which mice are to be polled at.
2724 usb-storage.delay_use=
2725 [UMS] The delay in seconds before a new device is
2726 scanned for Logical Units (default 5).
2729 [UMS] A list of quirks entries to supplement or
2730 override the built-in unusual_devs list. List
2731 entries are separated by commas. Each entry has
2732 the form VID:PID:Flags where VID and PID are Vendor
2733 and Product ID values (4-digit hex numbers) and
2734 Flags is a set of characters, each corresponding
2735 to a common usb-storage quirk flag as follows:
2736 a = SANE_SENSE (collect more than 18 bytes
2738 b = BAD_SENSE (don't collect more than 18
2739 bytes of sense data);
2740 c = FIX_CAPACITY (decrease the reported
2741 device capacity by one sector);
2742 h = CAPACITY_HEURISTICS (decrease the
2743 reported device capacity by one
2744 sector if the number is odd);
2745 i = IGNORE_DEVICE (don't bind to this
2747 l = NOT_LOCKABLE (don't try to lock and
2748 unlock ejectable media);
2749 m = MAX_SECTORS_64 (don't transfer more
2750 than 64 sectors = 32 KB at a time);
2751 o = CAPACITY_OK (accept the capacity
2752 reported by the device);
2753 r = IGNORE_RESIDUE (the device reports
2754 bogus residue values);
2755 s = SINGLE_LUN (the device has only one
2757 w = NO_WP_DETECT (don't test whether the
2758 medium is write-protected).
2759 Example: quirks=0419:aaf5:rl,0421:0433:rc
2762 [X86] Flags controlling user PTE allocations.
2764 nohigh = do not allocate PTE pages in
2765 HIGHMEM regardless of setting
2769 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2770 vdso=1: enable VDSO (default)
2771 vdso=0: disable VDSO mapping
2774 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2775 vdso32=1: enable 32-bit VDSO (default)
2776 vdso32=0: disable 32-bit VDSO mapping
2779 vector=percpu: enable percpu vector domain
2781 video= [FB] Frame buffer configuration
2782 See Documentation/fb/modedb.txt.
2784 vga= [BOOT,X86-32] Select a particular video mode
2785 See Documentation/x86/boot.txt and
2786 Documentation/svga.txt.
2787 Use vga=ask for menu.
2788 This is actually a boot loader parameter; the value is
2789 passed to the kernel using a special protocol.
2791 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2792 size of <nn>. This can be used to increase the
2793 minimum size (128MB on x86). It can also be used to
2794 decrease the size and leave more room for directly
2797 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2800 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2803 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2806 vt.cur_default= [VT] Default cursor shape.
2807 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2808 the parameters of the <Esc>[?A;B;Cc escape sequence;
2809 see VGA-softcursor.txt. Default: 2 = underline.
2811 vt.default_blu= [VT]
2812 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2813 Change the default blue palette of the console.
2814 This is a 16-member array composed of values
2817 vt.default_grn= [VT]
2818 Format: <green0>,<green1>,<green2>,...,<green15>
2819 Change the default green palette of the console.
2820 This is a 16-member array composed of values
2823 vt.default_red= [VT]
2824 Format: <red0>,<red1>,<red2>,...,<red15>
2825 Change the default red palette of the console.
2826 This is a 16-member array composed of values
2832 Set system-wide default UTF-8 mode for all tty's.
2833 Default is 1, i.e. UTF-8 mode is enabled for all
2834 newly opened terminals.
2836 vt.global_cursor_default=
2839 Set system-wide default for whether a cursor
2840 is shown on new VTs. Default is -1,
2841 i.e. cursors will be created by default unless
2842 overridden by individual drivers. 0 will hide
2843 cursors, 1 will display them.
2845 waveartist= [HW,OSS]
2846 Format: <io>,<irq>,<dma>,<dma2>
2849 See header of drivers/scsi/wd33c93.c.
2852 See header of drivers/scsi/wd7000.c.
2854 watchdog timers [HW,WDT] For information on watchdog timers,
2855 see Documentation/watchdog/watchdog-parameters.txt
2856 or other driver-specific files in the
2857 Documentation/watchdog/ directory.
2859 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2860 default x2apic cluster mode on platforms
2863 x86_mrst_timer= [X86-32,APBT]
2864 Choose timer option for x86 Moorestown MID platform.
2865 Two valid options are apbt timer only and lapic timer
2866 plus one apbt timer for broadcast timer.
2867 x86_mrst_timer=apbt_only | lapic_and_apbt
2869 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2870 xd_geo= See header of drivers/block/xd.c.
2872 xirc2ps_cs= [NET,PCMCIA]
2874 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2876 ______________________________________________________________________
2880 Add documentation for ALSA options.
2881 Add more DRM drivers.