4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 HW Appropriate hardware is enabled.
52 IA-64 IA-64 architecture is enabled.
53 IMA Integrity measurement architecture is enabled.
54 IOSCHED More than one I/O scheduler is enabled.
55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
59 LIBATA Libata driver is enabled
60 LP Printer support is enabled.
61 LOOP Loopback device support is enabled.
62 M68k M68k architecture is enabled.
63 These options have more detailed description inside of
64 Documentation/m68k/kernel-options.txt.
65 MCA MCA bus support is enabled.
66 MDA MDA console support is enabled.
67 MOUSE Appropriate mouse support is enabled.
68 MSI Message Signaled Interrupts (PCI).
69 MTD MTD (Memory Technology Device) support is enabled.
70 NET Appropriate network support is enabled.
71 NUMA NUMA support is enabled.
72 GENERIC_TIME The generic timeofday code is enabled.
73 NFS Appropriate NFS support is enabled.
74 OSS OSS sound support is enabled.
75 PV_OPS A paravirtualized kernel is enabled.
76 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
77 PARISC The PA-RISC architecture is enabled.
78 PCI PCI bus support is enabled.
79 PCIE PCI Express support is enabled.
80 PCMCIA The PCMCIA subsystem is enabled.
81 PNP Plug & Play support is enabled.
82 PPC PowerPC architecture is enabled.
83 PPT Parallel port support is enabled.
84 PS2 Appropriate PS/2 support is enabled.
85 RAM RAM disk support is enabled.
86 ROOTPLUG The example Root Plug LSM is enabled.
87 S390 S390 architecture is enabled.
88 SCSI Appropriate SCSI support is enabled.
89 A lot of drivers has their options described inside of
91 SECURITY Different security models are enabled.
92 SELINUX SELinux support is enabled.
93 SERIAL Serial support is enabled.
94 SH SuperH architecture is enabled.
95 SMP The kernel is an SMP kernel.
96 SPARC Sparc architecture is enabled.
97 SWSUSP Software suspend (hibernation) is enabled.
98 SUSPEND System suspend states are enabled.
99 FTRACE Function tracing enabled.
100 TS Appropriate touchscreen support is enabled.
101 UMS USB Mass Storage support is enabled.
102 USB USB support is enabled.
103 USBHID USB Human Interface Device support is enabled.
104 V4L Video For Linux support is enabled.
105 VGA The VGA console has been enabled.
106 VT Virtual terminal support is enabled.
107 WDT Watchdog support is enabled.
108 XT IBM PC/XT MFM hard disk support is enabled.
109 X86-32 X86-32, aka i386 architecture is enabled.
110 X86-64 X86-64 architecture is enabled.
111 More X86-64 boot options can be found in
112 Documentation/x86/x86_64/boot-options.txt .
113 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
115 In addition, the following text indicates that the option:
117 BUGS= Relates to possible processor bugs on the said processor.
118 KNL Is a kernel start-up parameter.
119 BOOT Is a boot loader parameter.
121 Parameters denoted with BOOT are actually interpreted by the boot
122 loader, and have no meaning to the kernel directly.
123 Do not modify the syntax of boot loader parameters without extreme
124 need or coordination with <Documentation/x86/boot.txt>.
126 There are also arch-specific kernel-parameters not documented here.
127 See for example <Documentation/x86/x86_64/boot-options.txt>.
129 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
130 a trailing = on the name of any parameter states that that parameter will
131 be entered as an environment variable, whereas its absence indicates that
132 it will appear as a kernel argument readable via /proc/cmdline by programs
133 running once the system is up.
135 The number of kernel parameters is not limited, but the length of the
136 complete command line (parameters including spaces etc.) is limited to
137 a fixed number of characters. This limit depends on the architecture
138 and is between 256 and 4096 characters. It is defined in the file
139 ./include/asm/setup.h as COMMAND_LINE_SIZE.
143 Advanced Configuration and Power Interface
144 Format: { force | off | ht | strict | noirq | rsdt }
145 force -- enable ACPI if default was off
146 off -- disable ACPI if default was on
147 noirq -- do not use ACPI for IRQ routing
148 ht -- run only enough ACPI to enable Hyper Threading
149 strict -- Be less tolerant of platforms that are not
150 strictly ACPI specification compliant.
151 rsdt -- prefer RSDT over (default) XSDT
153 See also Documentation/power/pm.txt, pci=noacpi
155 acpi_apic_instance= [ACPI, IOAPIC]
157 2: use 2nd APIC table, if available
158 1,0: use 1st APIC table
161 acpi_backlight= [HW,ACPI]
162 acpi_backlight=vendor
164 If set to vendor, prefer vendor specific driver
165 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
166 of the ACPI video.ko driver.
168 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
169 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
171 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
172 debug output. Bits in debug_layer correspond to a
173 _COMPONENT in an ACPI source file, e.g.,
174 #define _COMPONENT ACPI_PCI_COMPONENT
175 Bits in debug_level correspond to a level in
176 ACPI_DEBUG_PRINT statements, e.g.,
177 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
178 The debug_level mask defaults to "info". See
179 Documentation/acpi/debug.txt for more information about
180 debug layers and levels.
182 Enable processor driver info messages:
183 acpi.debug_layer=0x20000000
184 Enable PCI/PCI interrupt routing info messages:
185 acpi.debug_layer=0x400000
186 Enable AML "Debug" output, i.e., stores to the Debug
187 object while interpreting AML:
188 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
189 Enable all messages related to ACPI hardware:
190 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
192 Some values produce so much output that the system is
193 unusable. The "log_buf_len" parameter may be useful
194 if you need to capture more output.
196 acpi_display_output= [HW,ACPI]
197 acpi_display_output=vendor
198 acpi_display_output=video
201 acpi_irq_balance [HW,ACPI]
202 ACPI will balance active IRQs
205 acpi_irq_nobalance [HW,ACPI]
206 ACPI will not move active IRQs (default)
209 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
210 Format: <irq>,<irq>...
212 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 Format: <irq>,<irq>...
216 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
218 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
219 Format: To spoof as Windows 98: ="Microsoft Windows"
221 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
222 acpi_osi="string1" # add string1 -- only one string
223 acpi_osi="!string2" # remove built-in string2
224 acpi_osi= # disable all strings
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
231 acpi.power_nocheck= [HW,ACPI]
232 Format: 1/0 enable/disable the check of power state.
233 On some bogus BIOS the _PSC object/_STA object of
234 power resource can't return the correct device power
235 state. In such case it is unneccessary to check its
236 power state again in power transition.
237 1 : disable the power state check
239 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
240 Format: { level | edge | high | low }
242 acpi_serialize [HW,ACPI] force serialization of AML methods
244 acpi_skip_timer_override [HW,ACPI]
245 Recognize and ignore IRQ0/pin2 Interrupt Override.
246 For broken nForce2 BIOS resulting in XT-PIC timer.
248 acpi_sleep= [HW,ACPI] Sleep options
249 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
250 old_ordering, s4_nonvs }
251 See Documentation/power/video.txt for information on
253 s3_beep is for debugging; it makes the PC's speaker beep
254 as soon as the kernel's real-mode entry point is called.
255 s4_nohwsig prevents ACPI hardware signature from being
256 used during resume from hibernation.
257 old_ordering causes the ACPI 1.0 ordering of the _PTS
258 control method, with respect to putting devices into
259 low power states, to be enforced (the ACPI 2.0 ordering
260 of _PTS is used by default).
261 s4_nonvs prevents the kernel from saving/restoring the
262 ACPI NVS memory during hibernation.
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 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
307 See Documentation/scsi/aha152x.txt.
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
313 See Documentation/scsi/aic7xxx.txt.
316 See Documentation/scsi/aic79xx.txt.
318 amd_iommu= [HW,X86-84]
319 Pass parameters to the AMD IOMMU driver in the system.
321 isolate - enable device isolation (each device, as far
322 as possible, will get its own protection
324 share - put every device behind one IOMMU into the
325 same protection domain
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
334 See also Documentation/kernel/input/joystick.txt
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
342 Power management functions (SPARCstation-4/5 + deriv.)
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
348 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
349 Change the output verbosity whilst booting
350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
354 apm= [APM] Advanced Power Management
355 See header of arch/x86/kernel/apm_32.c.
357 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
358 Format: <io>,<irq>,<nodeID>
362 atarimouse= [HW,MOUSE] Atari Mouse
364 atascsi= [HW,SCSI] Atari SCSI
366 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
367 EzKey and similar keyboards
369 atkbd.reset= [HW] Reset keyboard during initialization
371 atkbd.set= [HW] Select keyboard code set
372 Format: <int> (2 = AT (default), 3 = PS/2)
374 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 atkbd.softraw= [HW] Choose between synthetic and real raw mode
378 Format: <bool> (0 = real, 1 = synthetic (default))
380 atkbd.softrepeat= [HW]
381 Use software keyboard repeat
385 baycom_epp= [HW,AX25]
388 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
390 See header of drivers/net/hamradio/baycom_par.c.
392 baycom_ser_fdx= [HW,AX25]
393 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
394 Format: <io>,<irq>,<mode>[,<baud>]
395 See header of drivers/net/hamradio/baycom_ser_fdx.c.
397 baycom_ser_hdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
399 Format: <io>,<irq>,<mode>
400 See header of drivers/net/hamradio/baycom_ser_hdx.c.
402 boot_delay= Milliseconds to delay each printk during boot.
403 Values larger than 10 seconds (10000) are changed to
407 bootmem_debug [KNL] Enable bootmem allocator debug messages.
409 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
410 bttv.radio= Most important insmod options are available as
412 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
413 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
416 See drivers/scsi/BusLogic.c, comment before function
417 BusLogic_ParseDriverOptions().
419 c101= [NET] Moxa C101 synchronous serial card
421 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
422 Sometimes CPU hardware bugs make them report the cache
423 size incorrectly. The kernel will attempt work arounds
424 to fix known problems, but for some CPUs it is not
425 possible to determine what the correct size should be.
426 This option provides an override for these situations.
429 [SECURITY] Disable capabilities. This would normally
430 be used only if an alternative security model is to be
431 configured. Potentially dangerous and should only be
432 used if you are entirely sure of the consequences.
434 ccw_timeout_log [S390]
435 See Documentation/s390/CommonIO for details.
437 cgroup_disable= [KNL] Disable a particular controller
438 Format: {name of the controller(s) to disable}
439 {Currently supported controllers - "memory"}
441 checkreqprot [SELINUX] Set initial checkreqprot flag value.
442 Format: { "0" | "1" }
443 See security/selinux/Kconfig help text.
444 0 -- check protection applied by kernel (includes
445 any implied execute protection).
446 1 -- check protection requested by application.
447 Default value is set via a kernel config option.
448 Value can be changed at runtime via
449 /selinux/checkreqprot.
452 See Documentation/s390/CommonIO for details.
454 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
456 Forces specified clocksource (if available) to be used
457 when calculating gettimeofday(). If specified
458 clocksource is not available, it defaults to PIT.
459 Format: { pit | tsc | cyclone | pmtmr }
461 clocksource= [GENERIC_TIME] Override the default clocksource
463 Override the default clocksource and use the clocksource
464 with the name specified.
465 Some clocksource names to choose from, depending on
467 [all] jiffies (this is the base, fallback clocksource)
469 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
470 pxa_timer,timer3,32k_counter,timer0_1
472 [X86-32] pit,hpet,tsc,vmi-timer;
473 scx200_hrt on Geode; cyclone on IBM x440
481 clearcpuid=BITNUM [X86]
482 Disable CPUID feature X for the kernel. See
483 arch/x86/include/asm/cpufeature.h for the valid bit
484 numbers. Note the Linux specific bits are not necessarily
485 stable over kernel options, but the vendor specific
487 Also note that user programs calling CPUID directly
488 or using the feature without checking anything
489 will still see it. This just prevents it from
490 being used by the kernel or shown in /proc/cpuinfo.
491 Also note the kernel might malfunction if you disable
494 cmo_free_hint= [PPC] Format: { yes | no }
495 Specify whether pages are marked as being inactive
496 when they are freed. This is used in CMO environments
497 to determine OS memory pressure for page stealing by
501 code_bytes [X86] How many bytes of object code to print
506 com20020= [HW,NET] ARCnet - COM20020 chipset
508 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
510 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
514 ARCnet - COM90xx chipset (memory-mapped buffers)
515 Format: <io>[,<irq>[,<memstart>]]
517 condev= [HW,S390] console device
520 console= [KNL] Output console device and options.
522 tty<n> Use the virtual console device <n>.
526 Use the specified serial port. The options are of
527 the form "bbbbpnf", where "bbbb" is the baud rate,
528 "p" is parity ("n", "o", or "e"), "n" is number of
529 bits, and "f" is flow control ("r" for RTS or
530 omit it). Default is "9600n8".
532 See Documentation/serial-console.txt for more
534 Documentation/networking/netconsole.txt for an
537 uart[8250],io,<addr>[,options]
538 uart[8250],mmio,<addr>[,options]
539 Start an early, polled-mode console on the 8250/16550
540 UART at the specified I/O port or MMIO address,
541 switching to the matching ttyS device later. The
542 options are the same as for ttyS, above.
544 If the device connected to the port is not a TTY but a braille
545 device, prepend "brl," before the device type, for instance
547 For now, only VisioBraille is supported.
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
554 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
556 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
558 crashkernel=nn[KMG]@ss[KMG]
559 [KNL] Reserve a chunk of physical memory to
560 hold a kernel to switch to with kexec on panic.
562 crashkernel=range1:size1[,range2:size2,...][@offset]
563 [KNL] Same as above, but depends on the memory
564 in the running system. The syntax of range is
565 start-[end] where start and end are both
566 a memory unit (amount[KMG]). See also
567 Documentation/kdump/kdump.txt for a example.
572 cs89x0_media= [HW,NET]
573 Format: { rj45 | aui | bnc }
576 See header of drivers/s390/block/dasd_devmap.c.
578 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
579 (one device per port)
580 Format: <port#>,<type>
581 See also Documentation/input/joystick-parport.txt
583 debug [KNL] Enable kernel debugging (events log level).
586 [KNL] verbose self-tests
588 Print debugging info while doing the locking API
590 We default to 0 (no extra messages), setting it to
591 1 will print _a lot_ more information - normally
592 only useful to kernel developers.
594 debug_objects [KNL] Enable object debugging
597 [KNL] Disable object debugging
599 debugpat [X86] Enable PAT debugging
601 decnet.addr= [HW,NET]
602 Format: <area>[,<node>]
603 See also Documentation/networking/decnet.txt.
606 [same as hugepagesz=] The size of the default
607 HugeTLB page size. This is the size represented by
608 the legacy /proc/ hugepages APIs, used for SHM, and
609 default size when mounting hugetlbfs filesystems.
610 Defaults to the default architecture's huge page size
614 Set number of hash buckets for dentry cache.
617 IO parameters + enable/disable command.
619 digiepca= [HW,SERIAL]
620 See drivers/char/README.epca and
621 Documentation/serial/digiepca.txt.
623 disable_mtrr_cleanup [X86]
624 The kernel tries to adjust MTRR layout from continuous
625 to discrete, to make X server driver able to add WB
626 entry later. This parameter disables that.
628 disable_mtrr_trim [X86, Intel and AMD only]
629 By default the kernel will trim any uncacheable
630 memory out of your available memory pool based on
631 MTRR settings. This parameter disables that behavior,
632 possibly causing your machine to run very slowly.
634 disable_timer_pin_1 [X86]
635 Disable PIN 1 of APIC timer
636 Can be useful to work around chipset bugs.
638 dmasound= [HW,OSS] Sound subsystem buffers
640 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
641 this option disables the debugging code at boot.
643 dma_debug_entries=<number>
644 This option allows to tune the number of preallocated
645 entries for DMA-API debugging code. One entry is
646 required per DMA-API allocation. Use this if the
647 DMA-API debugging code disables itself because the
648 architectural default is too low.
650 dma_debug_driver=<driver_name>
651 With this option the DMA-API debugging driver
652 filter feature can be enabled at boot time. Just
653 pass the driver to filter for as the parameter.
654 The filter can be disabled or changed to another
655 driver later using sysfs.
661 dynamic_printk Enables pr_debug()/dev_dbg() calls if
662 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
663 These can also be switched on/off via
664 <debugfs>/dynamic_printk/modules
666 earlycon= [KNL] Output early console device and options.
667 uart[8250],io,<addr>[,options]
668 uart[8250],mmio,<addr>[,options]
669 Start an early, polled-mode console on the 8250/16550
670 UART at the specified I/O port or MMIO address.
671 The options are the same as for ttyS, above.
673 earlyprintk= [X86,SH,BLACKFIN]
675 earlyprintk=serial[,ttySn[,baudrate]]
678 Append ",keep" to not disable it when the real console
681 Only vga or serial or usb debug port at a time.
683 Currently only ttyS0 and ttyS1 are supported.
685 Interaction with the standard serial driver is not
688 The VGA output is eventually overwritten by the real
694 Format: {"off" | "on" | "skip[mbr]"}
696 eisa_irq_edge= [PARISC,HW]
697 See header of drivers/parisc/eisa.c.
700 See comment before function elanfreq_setup() in
701 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
704 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
705 See Documentation/block/as-iosched.txt and
706 Documentation/block/deadline-iosched.txt for details.
708 elfcorehdr= [IA64,PPC,SH,X86]
709 Specifies physical address of start of kernel core
710 image elf header. Generally kexec loader will
711 pass this option to capture kernel.
712 See Documentation/kdump/kdump.txt for details.
714 enable_mtrr_cleanup [X86]
715 The kernel tries to adjust MTRR layout from continuous
716 to discrete, to make X server driver able to add WB
717 entry later. This parameter enables that.
719 enable_timer_pin_1 [X86]
720 Enable PIN 1 of APIC timer
721 Can be useful to work around chipset bugs
722 (in particular on some ATI chipsets).
723 The kernel tries to set a reasonable default.
725 enforcing [SELINUX] Set initial enforcing status.
727 See security/selinux/Kconfig help text.
728 0 -- permissive (log only, no denials).
729 1 -- enforcing (deny and log).
731 Value can be changed at runtime via /selinux/enforce.
733 ether= [HW,NET] Ethernet cards parameters
734 This option is obsoleted by the "netdev=" option, which
735 has equivalent usage. See its documentation for details.
737 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
742 fail_make_request=[KNL]
743 General fault injection mechanism.
744 Format: <interval>,<probability>,<space>,<times>
745 See also /Documentation/fault-injection/.
748 See header of drivers/scsi/fd_mcs.c.
751 See header of drivers/scsi/fdomain.c.
754 See Documentation/blockdev/floppy.txt.
756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
763 [FTRACE] will set and start the specified tracer
764 as early as possible in order to facilitate early
768 [FTRACE] will dump the trace buffers on oops.
770 ftrace_filter=[function-list]
771 [FTRACE] Limit the functions traced by the function
772 tracer at boot up. function-list is a comma separated
773 list of functions. This list can be changed at run
774 time by the set_ftrace_filter file in the debugfs
777 ftrace_notrace=[function-list]
778 [FTRACE] Do not trace the functions specified in
779 function-list. This list can be changed at run time
780 by the set_ftrace_notrace file in the debugfs
784 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
785 support via parallel port (up to 5 devices per port)
786 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
787 See also Documentation/input/joystick-parport.txt
791 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
796 See header of drivers/scsi/gdth.c.
798 gpt [EFI] Forces disk with valid GPT signature but
799 invalid Protective MBR to be treated as GPT.
803 hashdist= [KNL,NUMA] Large hashes allocated during boot
804 are distributed across NUMA nodes. Defaults on
805 for 64bit NUMA, off otherwise.
806 Format: 0 | 1 (for off | on)
808 hcl= [IA-64] SGI's Hardware Graph compatibility layer
810 hd= [EIDE] (E)IDE hard drive subsystem geometry
811 Format: <cyl>,<head>,<sect>
813 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
814 size of <nn>. This works even on boxes that have no
815 highmem otherwise. This also works to reduce highmem
816 size on bigger boxes.
818 highres= [KNL] Enable/disable high resolution timer mode.
819 Valid parameters: "on", "off"
823 See Documentation/isdn/README.HiSax.
827 hpet= [X86-32,HPET] option to control HPET usage
828 Format: { enable (default) | disable | force |
830 disable: disable HPET and use PIT instead
831 force: allow force enabled of undocumented chips (ICH4,
833 verbose: show contents of HPET registers during setup
835 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
836 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
837 On x86-64 and powerpc, this option can be specified
838 multiple times interleaved with hugepages= to reserve
839 huge pages of different sizes. Valid pages sizes on
840 x86-64 are 2M (when the CPU supports "pse") and 1G
841 (when the CPU supports the "pdpe1gb" cpuinfo flag)
842 Note that 1GB pages can only be allocated at boot time
843 using hugepages= and not freed afterwards.
845 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
846 terminal devices. Valid values: 0..8
847 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
848 If specified, z/VM IUCV HVC accepts connections
849 from listed z/VM user IDs only.
851 i2c_bus= [HW] Override the default board specific I2C bus speed
852 or register an additional I2C bus that is not
853 registered from board initialization code.
857 i8042.debug [HW] Toggle i8042 debug mode
858 i8042.direct [HW] Put keyboard port into non-translated mode
859 i8042.dumbkbd [HW] Pretend that controller can only read data from
860 keyboard and cannot control its state
861 (Don't attempt to blink the leds)
862 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
863 i8042.nokbd [HW] Don't check/create keyboard port
864 i8042.noloop [HW] Disable the AUX Loopback command while probing
866 i8042.nomux [HW] Don't check presence of an active multiplexing
868 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
871 [HW] Frequency with which keyboard LEDs should blink
872 when kernel panics (default is 0.5 sec)
873 i8042.reset [HW] Reset the controller during init and cleanup
874 i8042.unlock [HW] Unlock (ignore) the keylock
878 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
879 indicates that the driver is running on unsupported
881 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
882 does not match list of supported models.
884 [HW] Report power status in /proc/i8k
885 (disabled by default)
886 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
889 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
890 See Documentation/mca.txt.
893 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
895 ide-core.nodma= [HW] (E)IDE subsystem
896 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
897 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
898 .chs .ignore_cable are additional options
899 See Documentation/ide/ide.txt.
901 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
902 See Documentation/ide/ide.txt.
904 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
905 Claim all unknown PCI IDE storage controllers.
908 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
909 Poll forces a polling idle loop that can slightly
910 improve the performance of waking up a idle CPU, but
911 will use a lot of power and make the system run hot.
913 idle=mwait: On systems which support MONITOR/MWAIT but
914 the kernel chose to not use it because it doesn't save
915 as much power as a normal idle loop, use the
916 MONITOR/MWAIT idle loop anyways. Performance should be
917 the same as idle=poll.
918 idle=halt: Halt is forced to be used for CPU idle.
919 In such case C2/C3 won't be used again.
920 idle=nomwait: Disable mwait for CPU C-states
922 ignore_loglevel [KNL]
923 Ignore loglevel setting - this will print /all/
924 kernel messages to the console. Useful for debugging.
927 Set number of hash buckets for inode cache.
930 Format: { "0" | "1" }
931 0 -- integrity auditing messages. (Default)
932 1 -- enable informational integrity auditing messages.
935 Formt: { "sha1" | "md5" }
939 Load a policy which meets the needs of the Trusted
940 Computing Base. This means IMA will measure all
941 programs exec'd, files mmap'd for exec, and all files
942 opened for read by uid=0.
945 See header of drivers/scsi/in2000.c.
949 Run specified binary instead of /sbin/init as init
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
956 initrd= [BOOT] Specify the location of the initial ramdisk
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
963 Enable intel iommu driver.
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
986 iomem= Disable strict checking of access to MMIO memory
987 strict regions from userspace.
1002 io7= [HW] IO7 for Marvel based alpha systems
1003 See comment before marvel_specify_io7 in
1004 arch/alpha/kernel/core_marvel.c.
1006 io_delay= [X86] I/O delay method
1008 Standard port 0x80 based delay
1010 Alternate port 0xed based delay (needed on some systems)
1012 Simple two microseconds delay
1017 See Documentation/filesystems/nfsroot.txt.
1019 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1020 See comment before ip2_setup() in
1021 drivers/char/ip2/ip2base.c.
1023 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1024 See header of drivers/scsi/ips.c.
1027 When an interrupt is not handled search all handlers
1028 for it. Intended to get systems with badly broken
1032 When an interrupt is not handled search all handlers
1033 for it. Also check all handlers each timer
1034 interrupt. Intended to get systems with badly broken
1038 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1040 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1042 <cpu number>,...,<cpu number>
1044 <cpu number>-<cpu number>
1045 (must be a positive range in ascending order)
1047 <cpu number>,...,<cpu number>-<cpu number>
1049 This option can be used to specify one or more CPUs
1050 to isolate from the general SMP balancing and scheduling
1051 algorithms. You can move a process onto or off an
1052 "isolated" CPU via the CPU affinity syscalls or cpuset.
1053 <cpu number> begins at 0 and the maximum value is
1054 "number of CPUs in system - 1".
1056 This option is the preferred way to isolate CPUs. The
1057 alternative -- manually setting the CPU mask of all
1058 tasks in the system -- can cause problems and
1059 suboptimal load balancer performance.
1063 js= [HW,JOY] Analog joystick
1064 See Documentation/input/joystick.txt.
1068 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1069 specifies the amount of memory usable by the kernel
1070 for non-movable allocations. The requested amount is
1071 spread evenly throughout all nodes in the system. The
1072 remaining memory in each node is used for Movable
1073 pages. In the event, a node is too small to have both
1074 kernelcore and Movable pages, kernelcore pages will
1075 take priority and other nodes will have a larger number
1076 of kernelcore pages. The Movable zone is used for the
1077 allocation of pages that may be reclaimed or moved
1078 by the page migration subsystem. This means that
1079 HugeTLB pages may not be allocated from this zone.
1080 Note that allocations like PTEs-from-HighMem still
1081 use the HighMem zone if it exists, and the Normal
1082 zone if it does not.
1084 kgdboc= [HW] kgdb over consoles.
1085 Requires a tty driver that supports console polling.
1086 (only serial suported for now)
1087 Format: <serial_device>[,baud]
1089 kmac= [MIPS] korina ethernet MAC address.
1090 Configure the RouterBoard 532 series on-chip
1091 Ethernet adapter MAC address.
1093 kmemleak= [KNL] Boot-time kmemleak enable/disable
1094 Valid arguments: on, off
1097 kstack=N [X86] Print N words from the kernel stack
1104 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1107 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1110 libata.dma= [LIBATA] DMA control
1111 libata.dma=0 Disable all PATA and SATA DMA
1112 libata.dma=1 PATA and SATA Disk DMA only
1113 libata.dma=2 ATAPI (CDROM) DMA only
1114 libata.dma=4 Compact Flash DMA only
1115 Combinations also work, so libata.dma=3 enables DMA
1116 for disks and CDROMs, but not CFs.
1118 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1122 libata.force= [LIBATA] Force configurations. The format is comma
1123 separated list of "[ID:]VAL" where ID is
1124 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1125 matching port, link or device. Basically, it matches
1126 the ATA ID string printed on console by libata. If
1127 the whole ID part is omitted, the last PORT and DEVICE
1128 values are used. If ID hasn't been specified yet, the
1129 configuration applies to all ports, links and devices.
1131 If only DEVICE is omitted, the parameter applies to
1132 the port and all links and devices behind it. DEVICE
1133 number of 0 either selects the first device or the
1134 first fan-out link behind PMP device. It does not
1135 select the host link. DEVICE number of 15 selects the
1136 host link and device attached to it.
1138 The VAL specifies the configuration to force. As long
1139 as there's no ambiguity shortcut notation is allowed.
1140 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1141 The following configurations can be forced.
1143 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1144 Any ID with matching PORT is used.
1146 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1148 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1149 udma[/][16,25,33,44,66,100,133] notation is also
1152 * [no]ncq: Turn on or off NCQ.
1154 * nohrst, nosrst, norst: suppress hard, soft
1157 If there are multiple matching configurations changing
1158 the same attribute, the last one is used.
1160 lmb=debug [KNL] Enable lmb debug messages.
1162 load_ramdisk= [RAM] List of ramdisks to load from floppy
1163 See Documentation/blockdev/ramdisk.txt.
1165 lockd.nlm_grace_period=P [NFS] Assign grace period.
1168 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1171 lockd.nlm_timeout=T [NFS] Assign timeout value.
1174 lockd.nlm_udpport=M [NFS] Assign UDP port.
1177 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1180 loglevel= All Kernel Messages with a loglevel smaller than the
1181 console loglevel will be printed to the console. It can
1182 also be changed with klogd or other programs. The
1183 loglevels are defined as follows:
1185 0 (KERN_EMERG) system is unusable
1186 1 (KERN_ALERT) action must be taken immediately
1187 2 (KERN_CRIT) critical conditions
1188 3 (KERN_ERR) error conditions
1189 4 (KERN_WARNING) warning conditions
1190 5 (KERN_NOTICE) normal but significant condition
1191 6 (KERN_INFO) informational
1192 7 (KERN_DEBUG) debug-level messages
1194 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1195 Format: { n | nk | nM }
1196 n must be a power of two. The default size
1197 is set in the kernel config file.
1199 logo.nologo [FB] Disables display of the built-in Linux logo.
1200 This may be used to provide more screen space for
1201 kernel log messages and is useful when debugging
1202 kernel boot problems.
1204 lp=0 [LP] Specify parallel ports to use, e.g,
1205 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1206 lp=reset first parallel port). 'lp=0' disables the
1207 lp=auto printer driver. 'lp=reset' (which can be
1208 specified in addition to the ports) causes
1209 attached printers to be reset. Using
1210 lp=port1,port2,... specifies the parallel ports
1211 to associate lp devices with, starting with
1212 lp0. A port specification may be 'none' to skip
1213 that lp device, or a parport name such as
1214 'parport0'. Specifying 'lp=auto' instead of a
1215 port specification list means that device IDs
1216 from each port should be examined, to see if
1217 an IEEE 1284-compliant printer is attached; if
1218 so, the driver will manage that printer.
1219 See also header of drivers/char/lp.c.
1222 Sets loops_per_jiffy to given constant, thus avoiding
1223 time-consuming boot-time autodetection (up to 250 ms per
1224 CPU). 0 enables autodetection (default). To determine
1225 the correct value for your kernel, boot with normal
1226 autodetection and see what value is printed. Note that
1227 on SMP systems the preset will be applied to all CPUs,
1228 which is likely to cause problems if your CPUs need
1229 significantly divergent settings. An incorrect value
1230 will cause delays in the kernel to be wrong, leading to
1231 unpredictable I/O errors and other breakage. Although
1232 unlikely, in the extreme case this might damage your
1236 Format: <io>,<irq>,<dma>
1238 mac5380= [HW,SCSI] Format:
1239 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1241 machvec= [IA64] Force the use of a particular machine-vector
1242 (machvec) in a generic kernel.
1243 Example: machvec=hpzx1_swiotlb
1245 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1246 than or equal to this physical address is ignored.
1248 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1249 should make use of. maxcpus=n : n >= 0 limits the
1250 kernel to using 'n' processors. n=0 is a special case,
1251 it is equivalent to "nosmp", which also disables
1254 max_loop= [LOOP] Maximum number of loopback devices that can
1258 max_luns= [SCSI] Maximum number of LUNs to probe.
1259 Should be between 1 and 2^32-1.
1262 [SCSI] Maximum number of LUNs received.
1263 Should be between 1 and 16384.
1267 mce [X86-32] Machine Check Exception
1269 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1271 md= [HW] RAID subsystems devices and level
1272 See Documentation/md.txt.
1275 Format: <first>,<last>
1276 Specifies range of consoles to be captured by the MDA.
1278 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1279 Amount of memory to be used when the kernel is not able
1280 to see the whole system memory or for test.
1281 [X86-32] Use together with memmap= to avoid physical
1282 address space collisions. Without memmap= PCI devices
1283 could be placed at addresses belonging to unused RAM.
1285 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1289 [KNL,SH] Allow user to override the default size for
1290 per-device physically contiguous DMA buffers.
1292 memmap=exactmap [KNL,X86] Enable setting of an exact
1293 E820 memory map, as specified by the user.
1294 Such memmap=exactmap lines can be constructed based on
1295 BIOS output or other requirements. See the memmap=nn@ss
1298 memmap=nn[KMG]@ss[KMG]
1299 [KNL] Force usage of a specific region of memory
1300 Region of memory to be used, from ss to ss+nn.
1302 memmap=nn[KMG]#ss[KMG]
1303 [KNL,ACPI] Mark specific memory as ACPI data.
1304 Region of memory to be used, from ss to ss+nn.
1306 memmap=nn[KMG]$ss[KMG]
1307 [KNL,ACPI] Mark specific memory as reserved.
1308 Region of memory to be used, from ss to ss+nn.
1309 Example: Exclude memory from 0x18690000-0x1869ffff
1310 memmap=64K$0x18690000
1312 memmap=0x10000$0x18690000
1314 memory_corruption_check=0/1 [X86]
1315 Some BIOSes seem to corrupt the first 64k of
1316 memory when doing things like suspend/resume.
1317 Setting this option will scan the memory
1318 looking for corruption. Enabling this will
1319 both detect corruption and prevent the kernel
1320 from using the memory being corrupted.
1321 However, its intended as a diagnostic tool; if
1322 repeatable BIOS-originated corruption always
1323 affects the same memory, you can use memmap=
1324 to prevent the kernel from using that memory.
1326 memory_corruption_check_size=size [X86]
1327 By default it checks for corruption in the low
1328 64k, making this memory unavailable for normal
1329 use. Use this parameter to scan for
1330 corruption in more or less memory.
1332 memory_corruption_check_period=seconds [X86]
1333 By default it checks for corruption every 60
1334 seconds. Use this parameter to check at some
1335 other rate. 0 disables periodic checking.
1337 memtest= [KNL,X86] Enable memtest
1339 default : 0 <disable>
1340 Specifies the number of memtest passes to be
1341 performed. Each pass selects another test
1342 pattern from a given set of patterns. Memtest
1343 fills the memory with this pattern, validates
1344 memory contents and reserves bad memory
1345 regions that are detected.
1347 meye.*= [HW] Set MotionEye Camera parameters
1348 See Documentation/video4linux/meye.txt.
1350 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1351 Multi-Function General Purpose Timers on AMD Geode
1354 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1355 the BIOS has incorrectly applied a workaround. TinyBIOS
1356 version 0.98 is known to be affected, 0.99 fixes the
1357 problem by letting the user disable the workaround.
1361 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1362 physical address is ignored.
1365 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1366 parameter allows control of the logging verbosity for
1367 the additional memory initialisation checks. A value
1368 of 0 disables mminit logging and a level of 4 will
1369 log everything. Information is printed at KERN_DEBUG
1370 so loglevel=8 may also need to be specified.
1373 [MOUSE] Maximum time between finger touching and
1374 leaving touchpad surface for touch to be considered
1375 a tap and be reported as a left button click (for
1376 touchpads working in absolute mode only).
1378 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1379 reporting absolute coordinates, such as tablets
1380 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1381 reporting absolute coordinates, such as tablets
1383 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1384 is similar to kernelcore except it specifies the
1385 amount of memory used for migratable allocations.
1386 If both kernelcore and movablecore is specified,
1387 then kernelcore will be at *least* the specified
1388 value but may be more. If movablecore on its own
1389 is specified, the administrator must be careful
1390 that the amount of memory usable for all allocations
1396 MTD_Partition= [MTD]
1397 Format: <name>,<region-number>,<size>,<offset>
1399 MTD_Region= [MTD] Format:
1400 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1403 See drivers/mtd/cmdlinepart.c.
1406 ARM/S3C2412 JIVE boot control
1408 See arch/arm/mach-s3c2412/mach-jive.c
1410 mtouchusb.raw_coordinates=
1411 [HW] Make the MicroTouch USB driver use raw coordinates
1412 ('y', default) or cooked coordinates ('n')
1414 mtrr_chunk_size=nn[KMG] [X86]
1415 used for mtrr cleanup. It is largest continous chunk
1416 that could hold holes aka. UC entries.
1418 mtrr_gran_size=nn[KMG] [X86]
1419 Used for mtrr cleanup. It is granularity of mtrr block.
1421 Large value could prevent small alignment from
1424 mtrr_spare_reg_nr=n [X86]
1426 Range: 0,7 : spare reg number
1428 Used for mtrr cleanup. It is spare mtrr entries number.
1429 Set to 2 or more if your graphical card needs more.
1431 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1434 See header of drivers/scsi/NCR_D700.c.
1438 ncr53c400= [HW,SCSI]
1440 ncr53c400a= [HW,SCSI]
1442 ncr53c406a= [HW,SCSI]
1444 ncr53c8xx= [HW,SCSI]
1446 netdev= [NET] Network devices parameters
1447 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1448 Note that mem_start is often overloaded to mean
1449 something different and driver-specific.
1450 This usage is only documented in each driver source
1454 [NETFILTER] Enable connection tracking flow accounting
1455 0 to disable accounting
1456 1 to enable accounting
1457 Default value depends on CONFIG_NF_CT_ACCT that is
1458 going to be removed in 2.6.29.
1461 See Documentation/filesystems/nfsroot.txt.
1463 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1464 See Documentation/filesystems/nfsroot.txt.
1466 nfs.callback_tcpport=
1467 [NFS] set the TCP port on which the NFSv4 callback
1468 channel should listen.
1470 nfs.idmap_cache_timeout=
1471 [NFS] set the maximum lifetime for idmapper cache
1475 [NFS] enable 64-bit inode numbers.
1476 If zero, the NFS client will fake up a 32-bit inode
1477 number for the readdir() and stat() syscalls instead
1478 of returning the full 64-bit number.
1479 The default is to return 64-bit inode numbers.
1481 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1482 when a NMI is triggered.
1483 Format: [state][,regs][,debounce][,die]
1485 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1486 Format: [panic,][num]
1488 0 - turn nmi_watchdog off
1489 1 - use the IO-APIC timer for the NMI watchdog
1490 2 - use the local APIC for the NMI watchdog using
1491 a performance counter. Note: This will use one
1492 performance counter and the local APIC's performance
1494 When panic is specified, panic when an NMI watchdog
1496 This is useful when you use a panic=... timeout and
1497 need the box quickly up again.
1498 Instead of 1 and 2 it is possible to use the following
1499 symbolic names: lapic and ioapic
1500 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1502 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1503 emulation library even if a 387 maths coprocessor
1507 [HW] Never suspend the console
1508 Disable suspending of consoles during suspend and
1509 hibernate operations. Once disabled, debugging
1510 messages can reach various consoles while the rest
1511 of the system is being put to sleep (ie, while
1512 debugging driver suspend/resume hooks). This may
1513 not work reliably with all consoles, but is known
1514 to work with serial and VGA consoles.
1516 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1517 caches in the slab allocator. Saves per-node memory,
1518 but will impact performance.
1522 noapic [SMP,APIC] Tells the kernel to not make use of any
1523 IOAPICs that may be present in the system.
1525 nobats [PPC] Do not use BATs for mapping kernel lowmem
1526 on "Classic" PPC cores.
1530 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1532 nodelayacct [KNL] Disable per-task delay accounting
1534 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1536 nodsp [SH] Disable hardware DSP at boot time.
1538 noefi [X86] Disable EFI runtime services support.
1543 On X86-32 available only on PAE configured kernels.
1544 noexec=on: enable non-executable mappings (default)
1545 noexec=off: disable non-executable mappings
1548 This affects only 32-bit executables.
1549 noexec32=on: enable non-executable mappings (default)
1550 read doesn't imply executable mappings
1551 noexec32=off: disable non-executable mappings
1552 read implies executable mappings
1554 nofpu [SH] Disable hardware FPU at boot time.
1556 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1557 register save and restore. The kernel will only save
1558 legacy floating-point registers on task switch.
1560 noxsave [BUGS=X86] Disables x86 extended register state save
1561 and restore using xsave. The kernel will fallback to
1562 enabling legacy floating-point and sse state.
1564 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1565 wfi(ARM) instruction doesn't work correctly and not to
1566 use it. This is also useful when using JTAG debugger.
1568 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1569 instruction doesn't work correctly and not to
1572 no_file_caps Tells the kernel not to honor file capabilities. The
1573 only way then for a file to be executed with privilege
1574 is to be setuid root or executed by root.
1576 nohalt [IA-64] Tells the kernel not to use the power saving
1577 function PAL_HALT_LIGHT when idle. This increases
1578 power-consumption. On the positive side, it reduces
1579 interrupt wake-up latency, which may improve performance
1580 in certain environments such as networked servers or
1583 nohz= [KNL] Boottime enable/disable dynamic ticks
1584 Valid arguments: on, off
1587 noiotrap [SH] Disables trapped I/O port accesses.
1589 noirqdebug [X86-32] Disables the code which attempts to detect and
1590 disable unhandled interrupt sources.
1592 no_timer_check [X86,APIC] Disables the code which tests for
1593 broken timer IRQ sources.
1595 noisapnp [ISAPNP] Disables ISA PnP code.
1597 noinitrd [RAM] Tells the kernel not to load any configured
1600 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1605 nojitter [IA64] Disables jitter checking for ITC timers.
1607 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1609 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1611 noltlbs [PPC] Do not use large page/tlb entries for kernel
1612 lowmem mapping on PPC40x.
1614 nomca [IA-64] Disable machine check abort handling
1616 nomce [X86-32] Machine Check Exception
1618 nomfgpt [X86-32] Disable Multi-Function General Purpose
1619 Timer usage (for AMD Geode machines).
1621 norandmaps Don't use address space randomization. Equivalent to
1622 echo 0 > /proc/sys/kernel/randomize_va_space
1624 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1626 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1627 with UP alternatives
1629 noresidual [PPC] Don't use residual data on PReP machines.
1631 noresume [SWSUSP] Disables resume and restores original swap
1634 no-scroll [VGA] Disables scrollback.
1635 This is required for the Braillex ib80-piezo Braille
1636 reader made by F.H. Papenmeier (Germany).
1640 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1642 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1643 and disable the IO APIC. legacy for "maxcpus=0".
1645 nosoftlockup [KNL] Disable the soft-lockup detector.
1647 noswapaccount [KNL] Disable accounting of swap in memory resource
1648 controller. (See Documentation/cgroups/memory.txt)
1650 nosync [HW,M68K] Disables sync negotiation for all devices.
1652 notsc [BUGS=X86-32] Disable Time Stamp Counter
1654 nousb [USB] Disable the USB subsystem
1658 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1660 nptcg= [IA64] Override max number of concurrent global TLB
1661 purges which is reported from either PAL_VM_SUMMARY or
1664 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1666 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1667 one of ['zone', 'node', 'default'] can be specified
1668 This can be set from sysctl after boot.
1669 See Documentation/sysctl/vm.txt for details.
1671 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1672 See Documentation/debugging-via-ohci1394.txt for more
1675 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1676 Rather than timing out after 20 ms if an EC
1677 command is not properly ACKed, override the length
1678 of the timeout. We have interrupts disabled while
1679 waiting for the ACK, so if this is set too high
1680 interrupts *may* be lost!
1685 oprofile.timer= [HW]
1686 Use timer interrupt instead of performance counters
1688 oprofile.cpu_type= Force an oprofile cpu type
1689 This might be useful if you have an older oprofile
1690 userland or if you want common events.
1691 Format: { archperfmon }
1692 archperfmon: [X86] Force use of architectural
1693 perfmon on Intel CPUs instead of the
1694 CPU specific event set.
1696 osst= [HW,SCSI] SCSI Tape Driver
1697 Format: <buffer_size>,<write_threshold>
1698 See also Documentation/scsi/st.txt.
1700 panic= [KNL] Kernel behaviour on panic
1703 parkbd.port= [HW] Parallel port number the keyboard adapter is
1704 connected to, default is 0.
1706 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1707 0 for XT, 1 for AT (default is AT).
1710 parport= [HW,PPT] Specify parallel ports. 0 disables.
1711 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1712 Use 'auto' to force the driver to use any
1713 IRQ/DMA settings detected (the default is to
1714 ignore detected IRQ/DMA settings because of
1715 possible conflicts). You can specify the base
1716 address, IRQ, and DMA settings; IRQ and DMA
1717 should be numbers, or 'auto' (for using detected
1718 settings on that particular port), or 'nofifo'
1719 (to avoid using a FIFO even if it is detected).
1720 Parallel ports are assigned in the order they
1721 are specified on the command line, starting
1724 parport_init_mode= [HW,PPT]
1725 Configure VIA parallel port to operate in
1726 a specific mode. This is necessary on Pegasos
1727 computer where firmware has no options for setting
1728 up parallel port mode and sets it to spp.
1729 Currently this function knows 686a and 8231 chips.
1730 Format: [spp|ps2|epp|ecp|ecpepp]
1732 pas2= [HW,OSS] Format:
1733 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1736 See header of drivers/scsi/pas16.c.
1739 Halt all CPUs after the first oops has been printed for
1740 the specified number of seconds. This is to be used if
1741 your oopses keep scrolling off the screen.
1746 See header of drivers/block/paride/pcd.c.
1747 See also Documentation/blockdev/paride.txt.
1749 pci=option[,option...] [PCI] various PCI subsystem options:
1750 earlydump [X86] dump PCI config space before the kernel
1752 off [X86] don't probe for the PCI bus
1753 bios [X86-32] force use of PCI BIOS, don't access
1754 the hardware directly. Use this if your machine
1755 has a non-standard PCI host bridge.
1756 nobios [X86-32] disallow use of PCI BIOS, only direct
1757 hardware access methods are allowed. Use this
1758 if you experience crashes upon bootup and you
1759 suspect they are caused by the BIOS.
1760 conf1 [X86] Force use of PCI Configuration
1762 conf2 [X86] Force use of PCI Configuration
1764 noaer [PCIE] If the PCIEAER kernel config parameter is
1765 enabled, this kernel boot option can be used to
1766 disable the use of PCIE advanced error reporting.
1767 nodomains [PCI] Disable support for multiple PCI
1768 root domains (aka PCI segments, in ACPI-speak).
1769 nommconf [X86] Disable use of MMCONFIG for PCI
1771 nomsi [MSI] If the PCI_MSI kernel config parameter is
1772 enabled, this kernel boot option can be used to
1773 disable the use of MSI interrupts system-wide.
1774 noioapicquirk [APIC] Disable all boot interrupt quirks.
1775 Safety option to keep boot IRQs enabled. This
1776 should never be necessary.
1777 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1778 primary IO-APIC for bridges that cannot disable
1779 boot IRQs. This fixes a source of spurious IRQs
1780 when the system masks IRQs.
1781 noioapicreroute [APIC] Disable workaround that uses the
1782 boot IRQ equivalent of an IRQ that connects to
1783 a chipset where boot IRQs cannot be disabled.
1784 The opposite of ioapicreroute.
1785 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1786 routing table. These calls are known to be buggy
1787 on several machines and they hang the machine
1788 when used, but on other computers it's the only
1789 way to get the interrupt routing table. Try
1790 this option if the kernel is unable to allocate
1791 IRQs or discover secondary PCI buses on your
1793 rom [X86] Assign address space to expansion ROMs.
1794 Use with caution as certain devices share
1795 address decoders between ROMs and other
1797 norom [X86] Do not assign address space to
1798 expansion ROMs that do not already have
1799 BIOS assigned address ranges.
1800 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1801 assigned automatically to PCI devices. You can
1802 make the kernel exclude IRQs of your ISA cards
1804 pirqaddr=0xAAAAA [X86] Specify the physical address
1805 of the PIRQ table (normally generated
1806 by the BIOS) if it is outside the
1807 F0000h-100000h range.
1808 lastbus=N [X86] Scan all buses thru bus #N. Can be
1809 useful if the kernel is unable to find your
1810 secondary buses and you want to tell it
1811 explicitly which ones they are.
1812 assign-busses [X86] Always assign all PCI bus
1813 numbers ourselves, overriding
1814 whatever the firmware may have done.
1815 usepirqmask [X86] Honor the possible IRQ mask stored
1816 in the BIOS $PIR table. This is needed on
1817 some systems with broken BIOSes, notably
1818 some HP Pavilion N5400 and Omnibook XE3
1819 notebooks. This will have no effect if ACPI
1820 IRQ routing is enabled.
1821 noacpi [X86] Do not use ACPI for IRQ routing
1822 or for PCI scanning.
1823 use_crs [X86] Use _CRS for PCI resource
1825 routeirq Do IRQ routing for all PCI devices.
1826 This is normally done in pci_enable_device(),
1827 so this option is a temporary workaround
1828 for broken drivers that don't call it.
1829 skip_isa_align [X86] do not align io start addr, so can
1830 handle more pci cards
1831 firmware [ARM] Do not re-enumerate the bus but instead
1832 just use the configuration from the
1833 bootloader. This is currently used on
1834 IXP2000 systems where the bus has to be
1835 configured a certain way for adjunct CPUs.
1836 noearly [X86] Don't do any early type 1 scanning.
1837 This might help on some broken boards which
1838 machine check when some devices' config space
1839 is read. But various workarounds are disabled
1840 and some IOMMU drivers will not work.
1841 bfsort Sort PCI devices into breadth-first order.
1842 This sorting is done to get a device
1843 order compatible with older (<= 2.4) kernels.
1844 nobfsort Don't sort PCI devices into breadth-first order.
1845 cbiosize=nn[KMG] The fixed amount of bus space which is
1846 reserved for the CardBus bridge's IO window.
1847 The default value is 256 bytes.
1848 cbmemsize=nn[KMG] The fixed amount of bus space which is
1849 reserved for the CardBus bridge's memory
1850 window. The default value is 64 megabytes.
1853 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1854 Specifies alignment and device to reassign
1855 aligned memory resources.
1856 If <order of align> is not specified,
1857 PAGE_SIZE is used as alignment.
1858 PCI-PCI bridge can be specified, if resource
1859 windows need to be expanded.
1861 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1864 force Enable ASPM even on devices that claim not to support it.
1865 WARNING: Forcing ASPM on may cause system lockups.
1867 pcmv= [HW,PCMCIA] BadgePAD 4
1870 See Documentation/blockdev/paride.txt.
1872 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1875 See arch/parisc/kernel/pdc_chassis.c
1878 See Documentation/blockdev/paride.txt.
1881 See Documentation/blockdev/paride.txt.
1883 pirq= [SMP,APIC] Manual mp-table setup
1884 See Documentation/x86/i386/IO-APIC.txt.
1886 plip= [PPT,NET] Parallel port network link
1887 Format: { parport<nr> | timid | 0 }
1888 See also Documentation/parport.txt.
1890 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1891 Override pmtimer IOPort with a hex value.
1895 Enable PNP debug messages. This depends on the
1896 CONFIG_PNP_DEBUG_MESSAGES option.
1902 { on | off | curr | res | no-curr | no-res }
1905 [ISAPNP] Exclude IRQs for the autoconfiguration
1908 [ISAPNP] Exclude DMAs for the autoconfiguration
1910 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1911 Ranges are in pairs (I/O port base and size).
1914 [ISAPNP] Exclude memory regions for the
1916 Ranges are in pairs (memory base and size).
1918 ports= [IP_VS_FTP] IPVS ftp helper module
1920 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1922 Format: <port>,<port>....
1924 print-fatal-signals=
1925 [KNL] debug: print fatal signals
1926 print-fatal-signals=1: print segfault info to
1930 printk.time= Show timing data prefixed to each printk message line
1931 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1933 processor.max_cstate= [HW,ACPI]
1934 Limit processor to maximum C-state
1935 max_cstate=9 overrides any DMI blacklist limit.
1937 processor.nocst [HW,ACPI]
1938 Ignore the _CST method to determine C-states,
1939 instead using the legacy FADT method
1941 profile= [KNL] Enable kernel profiling via /proc/profile
1942 Format: [schedule,]<number>
1943 Param: "schedule" - profile schedule points.
1944 Param: <number> - step/bucket size as a power of 2 for
1945 statistical time based profiling.
1946 Param: "sleep" - profile D-state sleeping (millisecs).
1947 Requires CONFIG_SCHEDSTATS
1948 Param: "kvm" - profile VM exits.
1950 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1952 See Documentation/blockdev/ramdisk.txt.
1954 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1955 probe for; one of (bare|imps|exps|lifebook|any).
1956 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1958 psmouse.resetafter= [HW,MOUSE]
1959 Try to reset the device after so many bad packets
1962 [HW,MOUSE] Set desired mouse resolution, in dpi.
1963 psmouse.smartscroll=
1964 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1965 0 = disabled, 1 = enabled (default).
1967 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1969 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1972 See Documentation/blockdev/paride.txt.
1975 [KNL] Number of legacy pty's. Overwrites compiled-in
1978 quiet [KNL] Disable most log messages
1983 See Documentation/md.txt.
1985 ramdisk_blocksize= [RAM]
1986 See Documentation/blockdev/ramdisk.txt.
1988 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1989 See Documentation/blockdev/ramdisk.txt.
1991 rcupdate.blimit= [KNL,BOOT]
1992 Set maximum number of finished RCU callbacks to process
1995 rcupdate.qhimark= [KNL,BOOT]
1996 Set threshold of queued
1997 RCU callbacks over which batch limiting is disabled.
1999 rcupdate.qlowmark= [KNL,BOOT]
2000 Set threshold of queued RCU callbacks below which
2001 batch limiting is re-enabled.
2005 Run specified binary instead of /init from the ramdisk,
2006 used for early userspace startup. See initrd.
2008 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2009 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2010 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2013 [KNL, SMP] Set scheduler's default relax_domain_level.
2014 See Documentation/cgroups/cpusets.txt.
2016 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2018 reservetop= [X86-32]
2020 Reserves a hole at the top of the kernel virtual
2023 reset_devices [KNL] Force drivers to reset the underlying device
2024 during initialization.
2027 Specify the partition device for software suspend
2029 resume_offset= [SWSUSP]
2030 Specify the offset from the beginning of the partition
2031 given by "resume=" at which the swap header is located,
2032 in <PAGE_SIZE> units (needed only for swap files).
2033 See Documentation/power/swsusp-and-swap-files.txt
2035 retain_initrd [RAM] Keep initrd memory after extraction
2037 rhash_entries= [KNL,NET]
2038 Set number of hash buckets for route cache
2040 riscom8= [HW,SERIAL]
2041 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2043 ro [KNL] Mount root device read-only on boot
2045 root= [KNL] Root filesystem
2047 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2048 mount the root filesystem
2050 rootflags= [KNL] Set root filesystem mount option string
2052 rootfstype= [KNL] Set root filesystem type
2054 rootwait [KNL] Wait (indefinitely) for root device to show up.
2055 Useful for devices that are detected asynchronously
2056 (e.g. USB and MMC devices).
2058 root_plug.vendor_id=
2059 [ROOTPLUG] Override the default vendor ID
2061 root_plug.product_id=
2062 [ROOTPLUG] Override the default product ID
2065 [ROOTPLUG] Enable debugging output
2067 rw [KNL] Mount root device read-write on boot
2069 S [KNL] Run init in single mode
2072 See drivers/net/irda/sa1100_ir.c.
2074 sbni= [NET] Granch SBNI12 leased line adapter
2076 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2077 Format: <io>[,<timeout>[,<isapnp>]]
2079 scsi_debug_*= [SCSI]
2080 See drivers/scsi/scsi_debug.c.
2082 scsi_default_dev_flags=
2083 [SCSI] SCSI default device flags
2086 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2087 Format: <vendor>:<model>:<flags>
2088 (flags are integer value)
2090 scsi_logging_level= [SCSI] a bit mask of logging levels
2091 See drivers/scsi/scsi_logging.h for bits. Also
2092 settable via sysctl at dev.scsi.logging_level
2093 (/proc/sys/dev/scsi/logging_level).
2094 There is also a nice 'scsi_logging_level' script in the
2095 S390-tools package, available for download at
2096 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2098 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2099 discovered. async scans them in kernel threads,
2100 allowing boot to proceed. none ignores them, expecting
2101 user space to do the scan.
2103 security= [SECURITY] Choose a security module to enable at boot.
2104 If this boot parameter is not specified, only the first
2105 security module asking for security registration will be
2106 loaded. An invalid security module name will be treated
2107 as if no module has been chosen.
2109 selinux= [SELINUX] Disable or enable SELinux at boot time.
2110 Format: { "0" | "1" }
2111 See security/selinux/Kconfig help text.
2114 Default value is set via kernel config option.
2115 If enabled at boot time, /selinux/disable can be used
2116 later to disable prior to initial policy load.
2118 serialnumber [BUGS=X86-32]
2121 Maximal number of shapers.
2123 show_msr= [x86] show boot-time MSR settings
2124 Format: { <integer> }
2125 Show boot-time (BIOS-initialized) MSR settings.
2126 The parameter means the number of CPUs to show,
2127 for example 1 means boot CPU only.
2130 See header of drivers/scsi/sim710.c.
2137 slub_debug[=options[,slabs]] [MM, SLUB]
2138 Enabling slub_debug allows one to determine the
2139 culprit if slab objects become corrupted. Enabling
2140 slub_debug can create guard zones around objects and
2141 may poison objects when not in use. Also tracks the
2142 last alloc / free. For more information see
2143 Documentation/vm/slub.txt.
2145 slub_max_order= [MM, SLUB]
2146 Determines the maximum allowed order for slabs.
2147 A high setting may cause OOMs due to memory
2148 fragmentation. For more information see
2149 Documentation/vm/slub.txt.
2151 slub_min_objects= [MM, SLUB]
2152 The minimum number of objects per slab. SLUB will
2153 increase the slab order up to slub_max_order to
2154 generate a sufficiently large slab able to contain
2155 the number of objects indicated. The higher the number
2156 of objects the smaller the overhead of tracking slabs
2157 and the less frequently locks need to be acquired.
2158 For more information see Documentation/vm/slub.txt.
2160 slub_min_order= [MM, SLUB]
2161 Determines the mininum page order for slabs. Must be
2162 lower than slub_max_order.
2163 For more information see Documentation/vm/slub.txt.
2165 slub_nomerge [MM, SLUB]
2166 Disable merging of slabs with similar size. May be
2167 necessary if there is some reason to distinguish
2168 allocs to different slabs. Debug options disable
2169 merging on their own.
2170 For more information see Documentation/vm/slub.txt.
2173 Format: <io1>[,<io2>[,...,<io8>]]
2175 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2176 attempt to substitute SMP alternatives once at boot.
2178 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2179 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2180 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2181 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2182 smsc-ircc2.ircc_irq= [HW] IRQ line
2183 smsc-ircc2.ircc_dma= [HW] DMA channel
2184 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2185 0: Toshiba Satellite 1800 (GP data pin select)
2186 1: Fast pin select (default)
2189 snd-ad1816a= [HW,ALSA]
2191 snd-ad1848= [HW,ALSA]
2193 snd-ali5451= [HW,ALSA]
2195 snd-als100= [HW,ALSA]
2197 snd-als4000= [HW,ALSA]
2199 snd-azt2320= [HW,ALSA]
2201 snd-cmi8330= [HW,ALSA]
2203 snd-cmipci= [HW,ALSA]
2205 snd-cs4231= [HW,ALSA]
2207 snd-cs4232= [HW,ALSA]
2209 snd-cs4236= [HW,ALSA]
2211 snd-cs4281= [HW,ALSA]
2213 snd-cs46xx= [HW,ALSA]
2215 snd-dt019x= [HW,ALSA]
2217 snd-dummy= [HW,ALSA]
2219 snd-emu10k1= [HW,ALSA]
2221 snd-ens1370= [HW,ALSA]
2223 snd-ens1371= [HW,ALSA]
2225 snd-es968= [HW,ALSA]
2227 snd-es1688= [HW,ALSA]
2229 snd-es18xx= [HW,ALSA]
2231 snd-es1938= [HW,ALSA]
2233 snd-es1968= [HW,ALSA]
2235 snd-fm801= [HW,ALSA]
2237 snd-gusclassic= [HW,ALSA]
2239 snd-gusextreme= [HW,ALSA]
2241 snd-gusmax= [HW,ALSA]
2245 snd-ice1712= [HW,ALSA]
2247 snd-intel8x0= [HW,ALSA]
2249 snd-interwave= [HW,ALSA]
2254 snd-korg1212= [HW,ALSA]
2256 snd-maestro3= [HW,ALSA]
2258 snd-mpu401= [HW,ALSA]
2260 snd-mtpav= [HW,ALSA]
2262 snd-nm256= [HW,ALSA]
2264 snd-opl3sa2= [HW,ALSA]
2272 snd-opti93x= [HW,ALSA]
2276 snd-rme32= [HW,ALSA]
2278 snd-rme96= [HW,ALSA]
2280 snd-rme9652= [HW,ALSA]
2286 snd-sbawe= [HW,ALSA]
2288 snd-serial= [HW,ALSA]
2290 snd-sgalaxy= [HW,ALSA]
2292 snd-sonicvibes= [HW,ALSA]
2297 snd-sun-cs4231= [HW,ALSA]
2299 snd-trident= [HW,ALSA]
2301 snd-usb-audio= [HW,ALSA,USB]
2303 snd-via82xx= [HW,ALSA]
2305 snd-virmidi= [HW,ALSA]
2307 snd-wavefront= [HW,ALSA]
2309 snd-ymfpci= [HW,ALSA]
2312 [KNL] Should the soft-lockup detector generate panics.
2314 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2315 See Documentation/sonypi.txt
2317 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2318 See Documentation/serial/specialix.txt.
2320 spia_io_base= [HW,MTD]
2326 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2328 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2329 See Documentation/scsi/st.txt.
2332 Enabled the stack tracer on boot up.
2336 Set the STI (builtin display/keyboard on the HP-PARISC
2337 machines) console (graphic card) which should be used
2338 as the initial boot-console.
2339 See also comment in drivers/video/console/sticore.c.
2342 See comment in drivers/video/console/sticore.c.
2345 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2349 Control how the NFS server code allocates CPUs to
2350 service thread pools. Depending on how many NICs
2351 you have and where their interrupts are bound, this
2352 option will affect which CPUs will do NFS serving.
2353 Note: this parameter cannot be changed while the
2354 NFS server is running.
2356 auto the server chooses an appropriate mode
2357 automatically using heuristics
2358 global a single global pool contains all CPUs
2359 percpu one pool for each CPU
2360 pernode one pool for each NUMA node (equivalent
2361 to global on non-NUMA machines)
2363 swiotlb= [IA-64] Number of I/O TLB slabs
2367 sym53c416= [HW,SCSI]
2368 See header of drivers/scsi/sym53c416.c.
2370 sysrq_always_enabled
2372 Ignore sysrq setting - this boot parameter will
2373 neutralize any effect of /proc/sys/kernel/sysrq.
2374 Useful for debugging.
2377 See header of drivers/scsi/t128.c.
2381 test_suspend= [SUSPEND]
2382 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2383 standby suspend) as the system sleep state to briefly
2384 enter during system startup. The system is woken from
2385 this state using a wakeup-capable RTC alarm.
2387 thash_entries= [KNL,NET]
2388 Set number of hash buckets for TCP connection
2390 thermal.act= [HW,ACPI]
2391 -1: disable all active trip points in all thermal zones
2392 <degrees C>: override all lowest active trip points
2394 thermal.crt= [HW,ACPI]
2395 -1: disable all critical trip points in all thermal zones
2396 <degrees C>: override all critical trip points
2398 thermal.nocrt= [HW,ACPI]
2399 Set to disable actions on ACPI thermal zone
2400 critical and hot trip points.
2402 thermal.off= [HW,ACPI]
2403 1: disable ACPI thermal control
2405 thermal.psv= [HW,ACPI]
2406 -1: disable all passive trip points
2407 <degrees C>: override all passive trip points to this
2410 thermal.tzp= [HW,ACPI]
2411 Specify global default ACPI thermal zone polling rate
2412 <deci-seconds>: poll all this frequency
2413 0: no polling (default)
2416 See comment before function dc390_setup() in
2417 drivers/scsi/tmscsim.c.
2421 Specify if the kernel should make use of the cpu
2422 topology informations if the hardware supports these.
2423 The scheduler will make use of these informations and
2424 e.g. base its process migration decisions on it.
2429 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2431 trix= [HW,OSS] MediaTrix AudioTrix Pro
2433 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2435 tsc= Disable clocksource-must-verify flag for TSC.
2437 [x86] reliable: mark tsc clocksource as reliable, this
2438 disables clocksource verification at runtime.
2439 Used to enable high-resolution timer mode on older
2440 hardware, and in virtualized environment.
2442 turbografx.map[2|3]= [HW,JOY]
2443 TurboGraFX parallel port interface
2445 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2446 See also Documentation/input/joystick-parport.txt
2448 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2449 See header of drivers/scsi/u14-34f.c.
2458 [USB] Ignore overcurrent events (default N).
2459 Some badly-designed motherboards generate lots of
2460 bogus events, for ports that aren't wired to
2461 anything. Set this parameter to avoid log spamming.
2462 Note that genuine overcurrent events won't be
2467 Set unknown_nmi_panic=1 early on boot.
2469 usbcore.autosuspend=
2470 [USB] The autosuspend time delay (in seconds) used
2471 for newly-detected USB devices (default 2). This
2472 is the time required before an idle device will be
2473 autosuspended. Devices for which the delay is set
2474 to a negative value won't be autosuspended at all.
2476 usbcore.usbfs_snoop=
2477 [USB] Set to log all usbfs traffic (default 0 = off).
2479 usbcore.blinkenlights=
2480 [USB] Set to cycle leds on hubs (default 0 = off).
2482 usbcore.old_scheme_first=
2483 [USB] Start with the old device initialization
2484 scheme (default 0 = off).
2486 usbcore.use_both_schemes=
2487 [USB] Try the other device initialization scheme
2488 if the first one fails (default 1 = enabled).
2490 usbcore.initial_descriptor_timeout=
2491 [USB] Specifies timeout for the initial 64-byte
2492 USB_REQ_GET_DESCRIPTOR request in milliseconds
2493 (default 5000 = 5.0 seconds).
2496 [USBHID] The interval which mice are to be polled at.
2498 usb-storage.delay_use=
2499 [UMS] The delay in seconds before a new device is
2500 scanned for Logical Units (default 5).
2503 [UMS] A list of quirks entries to supplement or
2504 override the built-in unusual_devs list. List
2505 entries are separated by commas. Each entry has
2506 the form VID:PID:Flags where VID and PID are Vendor
2507 and Product ID values (4-digit hex numbers) and
2508 Flags is a set of characters, each corresponding
2509 to a common usb-storage quirk flag as follows:
2510 a = SANE_SENSE (collect more than 18 bytes
2512 c = FIX_CAPACITY (decrease the reported
2513 device capacity by one sector);
2514 h = CAPACITY_HEURISTICS (decrease the
2515 reported device capacity by one
2516 sector if the number is odd);
2517 i = IGNORE_DEVICE (don't bind to this
2519 l = NOT_LOCKABLE (don't try to lock and
2520 unlock ejectable media);
2521 m = MAX_SECTORS_64 (don't transfer more
2522 than 64 sectors = 32 KB at a time);
2523 o = CAPACITY_OK (accept the capacity
2524 reported by the device);
2525 r = IGNORE_RESIDUE (the device reports
2526 bogus residue values);
2527 s = SINGLE_LUN (the device has only one
2529 w = NO_WP_DETECT (don't test whether the
2530 medium is write-protected).
2531 Example: quirks=0419:aaf5:rl,0421:0433:rc
2534 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2535 vdso=1: enable VDSO (default)
2536 vdso=0: disable VDSO mapping
2539 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2540 vdso32=1: enable 32-bit VDSO (default)
2541 vdso32=0: disable 32-bit VDSO mapping
2544 vector=percpu: enable percpu vector domain
2546 video= [FB] Frame buffer configuration
2547 See Documentation/fb/modedb.txt.
2549 vga= [BOOT,X86-32] Select a particular video mode
2550 See Documentation/x86/boot.txt and
2551 Documentation/svga.txt.
2552 Use vga=ask for menu.
2553 This is actually a boot loader parameter; the value is
2554 passed to the kernel using a special protocol.
2556 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2557 size of <nn>. This can be used to increase the
2558 minimum size (128MB on x86). It can also be used to
2559 decrease the size and leave more room for directly
2562 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2565 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2568 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2571 vt.default_blu= [VT]
2572 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2573 Change the default blue palette of the console.
2574 This is a 16-member array composed of values
2577 vt.default_grn= [VT]
2578 Format: <green0>,<green1>,<green2>,...,<green15>
2579 Change the default green palette of the console.
2580 This is a 16-member array composed of values
2583 vt.default_red= [VT]
2584 Format: <red0>,<red1>,<red2>,...,<red15>
2585 Change the default red palette of the console.
2586 This is a 16-member array composed of values
2592 Set system-wide default UTF-8 mode for all tty's.
2593 Default is 1, i.e. UTF-8 mode is enabled for all
2594 newly opened terminals.
2596 waveartist= [HW,OSS]
2597 Format: <io>,<irq>,<dma>,<dma2>
2600 See header of drivers/scsi/wd33c93.c.
2603 See header of drivers/scsi/wd7000.c.
2606 See Documentation/watchdog/wdt.txt.
2608 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2609 default x2apic cluster mode on platforms
2612 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2613 xd_geo= See header of drivers/block/xd.c.
2615 xirc2ps_cs= [NET,PCMCIA]
2617 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2619 ______________________________________________________________________
2623 Add documentation for ALSA options.
2624 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob