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 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VMMIO Driver for memory mapped virtio devices is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
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/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amijoy.map= [HW,JOY] Amiga joystick support
340 Map of devices attached to JOY0DAT and JOY1DAT
342 See also Documentation/input/joystick.txt
344 analog.map= [HW,JOY] Analog joystick and gamepad support
345 Specifies type or capabilities of an analog joystick
346 connected to one of 16 gameports
347 Format: <type1>,<type2>,..<type16>
350 Power management functions (SPARCstation-4/5 + deriv.)
352 Disable APC CPU standby support. SPARCstation-Fox does
353 not play well with APC CPU idle - disable it if you have
354 APC and your system crashes randomly.
356 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
357 Change the output verbosity whilst booting
358 Format: { quiet (default) | verbose | debug }
359 Change the amount of debugging information output
360 when initialising the APIC and IO-APIC components.
363 See Documentation/networking/ipv6.txt.
365 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
366 Limit apic dumping. The parameter defines the maximal
367 number of local apics being dumped. Also it is possible
368 to set it to "all" by meaning -- no limit here.
369 Format: { 1 (default) | 2 | ... | all }.
370 The parameter valid if only apic=debug or
371 apic=verbose is specified.
372 Example: apic=debug show_lapic=all
374 apm= [APM] Advanced Power Management
375 See header of arch/x86/kernel/apm_32.c.
377 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
378 Format: <io>,<irq>,<nodeID>
382 atarimouse= [HW,MOUSE] Atari Mouse
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
403 baycom_epp= [HW,AX25]
406 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
408 See header of drivers/net/hamradio/baycom_par.c.
410 baycom_ser_fdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
412 Format: <io>,<irq>,<mode>[,<baud>]
413 See header of drivers/net/hamradio/baycom_ser_fdx.c.
415 baycom_ser_hdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
417 Format: <io>,<irq>,<mode>
418 See header of drivers/net/hamradio/baycom_ser_hdx.c.
420 boot_delay= Milliseconds to delay each printk during boot.
421 Values larger than 10 seconds (10000) are changed to
425 bootmem_debug [KNL] Enable bootmem allocator debug messages.
427 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
428 bttv.radio= Most important insmod options are available as
430 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
433 bulk_remove=off [PPC] This parameter disables the use of the pSeries
434 firmware feature for flushing multiple hpte entries
437 c101= [NET] Moxa C101 synchronous serial card
439 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
440 Sometimes CPU hardware bugs make them report the cache
441 size incorrectly. The kernel will attempt work arounds
442 to fix known problems, but for some CPUs it is not
443 possible to determine what the correct size should be.
444 This option provides an override for these situations.
447 [SECURITY] Disable capabilities. This would normally
448 be used only if an alternative security model is to be
449 configured. Potentially dangerous and should only be
450 used if you are entirely sure of the consequences.
452 ccw_timeout_log [S390]
453 See Documentation/s390/CommonIO for details.
455 cgroup_disable= [KNL] Disable a particular controller
456 Format: {name of the controller(s) to disable}
457 {Currently supported controllers - "memory"}
459 checkreqprot [SELINUX] Set initial checkreqprot flag value.
460 Format: { "0" | "1" }
461 See security/selinux/Kconfig help text.
462 0 -- check protection applied by kernel (includes
463 any implied execute protection).
464 1 -- check protection requested by application.
465 Default value is set via a kernel config option.
466 Value can be changed at runtime via
467 /selinux/checkreqprot.
470 See Documentation/s390/CommonIO for details.
472 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
474 Forces specified clocksource (if available) to be used
475 when calculating gettimeofday(). If specified
476 clocksource is not available, it defaults to PIT.
477 Format: { pit | tsc | cyclone | pmtmr }
479 clocksource= Override the default clocksource
481 Override the default clocksource and use the clocksource
482 with the name specified.
483 Some clocksource names to choose from, depending on
485 [all] jiffies (this is the base, fallback clocksource)
487 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
488 pxa_timer,timer3,32k_counter,timer0_1
490 [X86-32] pit,hpet,tsc;
491 scx200_hrt on Geode; cyclone on IBM x440
499 clearcpuid=BITNUM [X86]
500 Disable CPUID feature X for the kernel. See
501 arch/x86/include/asm/cpufeature.h for the valid bit
502 numbers. Note the Linux specific bits are not necessarily
503 stable over kernel options, but the vendor specific
505 Also note that user programs calling CPUID directly
506 or using the feature without checking anything
507 will still see it. This just prevents it from
508 being used by the kernel or shown in /proc/cpuinfo.
509 Also note the kernel might malfunction if you disable
512 cmo_free_hint= [PPC] Format: { yes | no }
513 Specify whether pages are marked as being inactive
514 when they are freed. This is used in CMO environments
515 to determine OS memory pressure for page stealing by
519 code_bytes [X86] How many bytes of object code to print
524 com20020= [HW,NET] ARCnet - COM20020 chipset
526 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
528 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
532 ARCnet - COM90xx chipset (memory-mapped buffers)
533 Format: <io>[,<irq>[,<memstart>]]
535 condev= [HW,S390] console device
538 console= [KNL] Output console device and options.
540 tty<n> Use the virtual console device <n>.
544 Use the specified serial port. The options are of
545 the form "bbbbpnf", where "bbbb" is the baud rate,
546 "p" is parity ("n", "o", or "e"), "n" is number of
547 bits, and "f" is flow control ("r" for RTS or
548 omit it). Default is "9600n8".
550 See Documentation/serial-console.txt for more
552 Documentation/networking/netconsole.txt for an
555 uart[8250],io,<addr>[,options]
556 uart[8250],mmio,<addr>[,options]
557 Start an early, polled-mode console on the 8250/16550
558 UART at the specified I/O port or MMIO address,
559 switching to the matching ttyS device later. The
560 options are the same as for ttyS, above.
562 If the device connected to the port is not a TTY but a braille
563 device, prepend "brl," before the device type, for instance
565 For now, only VisioBraille is supported.
567 consoleblank= [KNL] The console blank (screen saver) timeout in
568 seconds. Defaults to 10*60 = 10mins. A value of 0
569 disables the blank timer.
572 [KNL] Change the default value for
573 /proc/<pid>/coredump_filter.
574 See also Documentation/filesystems/proc.txt.
576 cpuidle.off=1 [CPU_IDLE]
577 disable the cpuidle sub-system
579 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
581 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
583 crashkernel=size[KMG][@offset[KMG]]
584 [KNL] Using kexec, Linux can switch to a 'crash kernel'
585 upon panic. This parameter reserves the physical
586 memory region [offset, offset + size] for that kernel
587 image. If '@offset' is omitted, then a suitable offset
588 is selected automatically. Check
589 Documentation/kdump/kdump.txt for further details.
591 crashkernel=range1:size1[,range2:size2,...][@offset]
592 [KNL] Same as above, but depends on the memory
593 in the running system. The syntax of range is
594 start-[end] where start and end are both
595 a memory unit (amount[KMG]). See also
596 Documentation/kdump/kdump.txt for an example.
601 cs89x0_media= [HW,NET]
602 Format: { rj45 | aui | bnc }
605 See header of drivers/s390/block/dasd_devmap.c.
607 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
608 (one device per port)
609 Format: <port#>,<type>
610 See also Documentation/input/joystick-parport.txt
612 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
613 time. See Documentation/dynamic-debug-howto.txt for
614 details. Deprecated, see dyndbg.
616 debug [KNL] Enable kernel debugging (events log level).
619 [KNL] verbose self-tests
621 Print debugging info while doing the locking API
623 We default to 0 (no extra messages), setting it to
624 1 will print _a lot_ more information - normally
625 only useful to kernel developers.
627 debug_objects [KNL] Enable object debugging
630 [KNL] Disable object debugging
632 debug_guardpage_minorder=
633 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
634 parameter allows control of the order of pages that will
635 be intentionally kept free (and hence protected) by the
636 buddy allocator. Bigger value increase the probability
637 of catching random memory corruption, but reduce the
638 amount of memory for normal system use. The maximum
639 possible value is MAX_ORDER/2. Setting this parameter
640 to 1 or 2 should be enough to identify most random
641 memory corruption problems caused by bugs in kernel or
642 driver code when a CPU writes to (or reads from) a
643 random memory location. Note that there exists a class
644 of memory corruptions problems caused by buggy H/W or
645 F/W or by drivers badly programing DMA (basically when
646 memory is written at bus level and the CPU MMU is
647 bypassed) which are not detectable by
648 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
649 tracking down these problems.
651 debugpat [X86] Enable PAT debugging
653 decnet.addr= [HW,NET]
654 Format: <area>[,<node>]
655 See also Documentation/networking/decnet.txt.
658 [same as hugepagesz=] The size of the default
659 HugeTLB page size. This is the size represented by
660 the legacy /proc/ hugepages APIs, used for SHM, and
661 default size when mounting hugetlbfs filesystems.
662 Defaults to the default architecture's huge page size
666 Set number of hash buckets for dentry cache.
669 IO parameters + enable/disable command.
671 digiepca= [HW,SERIAL]
672 See drivers/char/README.epca and
673 Documentation/serial/digiepca.txt.
676 See Documentation/networking/ipv6.txt.
678 disable_ddw [PPC/PSERIES]
679 Disable Dynamic DMA Window support. Use this if
680 to workaround buggy firmware.
683 See Documentation/networking/ipv6.txt.
685 disable_mtrr_cleanup [X86]
686 The kernel tries to adjust MTRR layout from continuous
687 to discrete, to make X server driver able to add WB
688 entry later. This parameter disables that.
690 disable_mtrr_trim [X86, Intel and AMD only]
691 By default the kernel will trim any uncacheable
692 memory out of your available memory pool based on
693 MTRR settings. This parameter disables that behavior,
694 possibly causing your machine to run very slowly.
696 disable_timer_pin_1 [X86]
697 Disable PIN 1 of APIC timer
698 Can be useful to work around chipset bugs.
700 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
701 this option disables the debugging code at boot.
703 dma_debug_entries=<number>
704 This option allows to tune the number of preallocated
705 entries for DMA-API debugging code. One entry is
706 required per DMA-API allocation. Use this if the
707 DMA-API debugging code disables itself because the
708 architectural default is too low.
710 dma_debug_driver=<driver_name>
711 With this option the DMA-API debugging driver
712 filter feature can be enabled at boot time. Just
713 pass the driver to filter for as the parameter.
714 The filter can be disabled or changed to another
715 driver later using sysfs.
717 drm_kms_helper.edid_firmware=[<connector>:]<file>
718 Broken monitors, graphic adapters and KVMs may
719 send no or incorrect EDID data sets. This parameter
720 allows to specify an EDID data set in the
721 /lib/firmware directory that is used instead.
722 Generic built-in EDID data sets are used, if one of
723 edid/1024x768.bin, edid/1280x1024.bin,
724 edid/1680x1050.bin, or edid/1920x1080.bin is given
725 and no file with the same name exists. Details and
726 instructions how to build your own EDID data are
727 available in Documentation/EDID/HOWTO.txt. An EDID
728 data set will only be used for a particular connector,
729 if its name and a colon are prepended to the EDID
734 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
735 module.dyndbg[="val"]
736 Enable debug messages at boot time. See
737 Documentation/dynamic-debug-howto.txt for details.
739 earlycon= [KNL] Output early console device and options.
740 uart[8250],io,<addr>[,options]
741 uart[8250],mmio,<addr>[,options]
742 uart[8250],mmio32,<addr>[,options]
743 Start an early, polled-mode console on the 8250/16550
744 UART at the specified I/O port or MMIO address.
745 MMIO inter-register address stride is either 8-bit
746 (mmio) or 32-bit (mmio32).
747 The options are the same as for ttyS, above.
749 earlyprintk= [X86,SH,BLACKFIN]
751 earlyprintk=serial[,ttySn[,baudrate]]
752 earlyprintk=ttySn[,baudrate]
753 earlyprintk=dbgp[debugController#]
755 Append ",keep" to not disable it when the real console
758 Only vga or serial or usb debug port at a time.
760 Currently only ttyS0 and ttyS1 are supported.
762 Interaction with the standard serial driver is not
765 The VGA output is eventually overwritten by the real
768 ekgdboc= [X86,KGDB] Allow early kernel console debugging
771 This is designed to be used in conjunction with
772 the boot argument: earlyprintk=vga
775 Format: {"off" | "on" | "skip[mbr]"}
777 eisa_irq_edge= [PARISC,HW]
778 See header of drivers/parisc/eisa.c.
781 See comment before function elanfreq_setup() in
782 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
785 Format: {"cfq" | "deadline" | "noop"}
786 See Documentation/block/cfq-iosched.txt and
787 Documentation/block/deadline-iosched.txt for details.
789 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
790 Specifies physical address of start of kernel core
791 image elf header and optionally the size. Generally
792 kexec loader will pass this option to capture kernel.
793 See Documentation/kdump/kdump.txt for details.
795 enable_mtrr_cleanup [X86]
796 The kernel tries to adjust MTRR layout from continuous
797 to discrete, to make X server driver able to add WB
798 entry later. This parameter enables that.
800 enable_timer_pin_1 [X86]
801 Enable PIN 1 of APIC timer
802 Can be useful to work around chipset bugs
803 (in particular on some ATI chipsets).
804 The kernel tries to set a reasonable default.
806 enforcing [SELINUX] Set initial enforcing status.
808 See security/selinux/Kconfig help text.
809 0 -- permissive (log only, no denials).
810 1 -- enforcing (deny and log).
812 Value can be changed at runtime via /selinux/enforce.
815 Disable Error Record Serialization Table (ERST)
818 ether= [HW,NET] Ethernet cards parameters
819 This option is obsoleted by the "netdev=" option, which
820 has equivalent usage. See its documentation for details.
824 Permit 'security.evm' to be updated regardless of
825 current integrity status.
829 fail_make_request=[KNL]
830 General fault injection mechanism.
831 Format: <interval>,<probability>,<space>,<times>
832 See also Documentation/fault-injection/.
835 See Documentation/blockdev/floppy.txt.
837 force_pal_cache_flush
838 [IA-64] Avoid check_sal_cache_flush which may hang on
839 buggy SAL_CACHE_FLUSH implementations. Using this
840 parameter will force ia64_sal_cache_flush to call
841 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
844 [FTRACE] will set and start the specified tracer
845 as early as possible in order to facilitate early
848 ftrace_dump_on_oops[=orig_cpu]
849 [FTRACE] will dump the trace buffers on oops.
850 If no parameter is passed, ftrace will dump
851 buffers of all CPUs, but if you pass orig_cpu, it will
852 dump only the buffer of the CPU that triggered the
855 ftrace_filter=[function-list]
856 [FTRACE] Limit the functions traced by the function
857 tracer at boot up. function-list is a comma separated
858 list of functions. This list can be changed at run
859 time by the set_ftrace_filter file in the debugfs
862 ftrace_notrace=[function-list]
863 [FTRACE] Do not trace the functions specified in
864 function-list. This list can be changed at run time
865 by the set_ftrace_notrace file in the debugfs
868 ftrace_graph_filter=[function-list]
869 [FTRACE] Limit the top level callers functions traced
870 by the function graph tracer at boot up.
871 function-list is a comma separated list of functions
872 that can be changed at run time by the
873 set_graph_function file in the debugfs tracing directory.
876 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
877 support via parallel port (up to 5 devices per port)
878 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
879 See also Documentation/input/joystick-parport.txt
883 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
887 gcov_persist= [GCOV] When non-zero (default), profiling data for
888 kernel modules is saved and remains accessible via
889 debugfs, even when the module is unloaded/reloaded.
890 When zero, profiling data is discarded and associated
891 debugfs files are removed at module unload time.
893 gpt [EFI] Forces disk with valid GPT signature but
894 invalid Protective MBR to be treated as GPT.
896 hashdist= [KNL,NUMA] Large hashes allocated during boot
897 are distributed across NUMA nodes. Defaults on
898 for 64-bit NUMA, off otherwise.
899 Format: 0 | 1 (for off | on)
901 hcl= [IA-64] SGI's Hardware Graph compatibility layer
903 hd= [EIDE] (E)IDE hard drive subsystem geometry
904 Format: <cyl>,<head>,<sect>
907 Disable Hardware Error Source Table (HEST) support;
908 corresponding firmware-first mode error processing
909 logic will be disabled.
911 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
912 size of <nn>. This works even on boxes that have no
913 highmem otherwise. This also works to reduce highmem
914 size on bigger boxes.
916 highres= [KNL] Enable/disable high resolution timer mode.
917 Valid parameters: "on", "off"
921 See Documentation/isdn/README.HiSax.
925 hpet= [X86-32,HPET] option to control HPET usage
926 Format: { enable (default) | disable | force |
928 disable: disable HPET and use PIT instead
929 force: allow force enabled of undocumented chips (ICH4,
931 verbose: show contents of HPET registers during setup
933 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
934 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
935 On x86-64 and powerpc, this option can be specified
936 multiple times interleaved with hugepages= to reserve
937 huge pages of different sizes. Valid pages sizes on
938 x86-64 are 2M (when the CPU supports "pse") and 1G
939 (when the CPU supports the "pdpe1gb" cpuinfo flag)
940 Note that 1GB pages can only be allocated at boot time
941 using hugepages= and not freed afterwards.
943 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
944 terminal devices. Valid values: 0..8
945 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
946 If specified, z/VM IUCV HVC accepts connections
947 from listed z/VM user IDs only.
950 Do not unregister boot console at start. This is only
951 useful for debugging when something happens in the window
952 between unregistering the boot console and initializing
955 i2c_bus= [HW] Override the default board specific I2C bus speed
956 or register an additional I2C bus that is not
957 registered from board initialization code.
961 i8042.debug [HW] Toggle i8042 debug mode
962 i8042.direct [HW] Put keyboard port into non-translated mode
963 i8042.dumbkbd [HW] Pretend that controller can only read data from
964 keyboard and cannot control its state
965 (Don't attempt to blink the leds)
966 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
967 i8042.nokbd [HW] Don't check/create keyboard port
968 i8042.noloop [HW] Disable the AUX Loopback command while probing
970 i8042.nomux [HW] Don't check presence of an active multiplexing
972 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
974 i8042.notimeout [HW] Ignore timeout condition signalled by controller
975 i8042.reset [HW] Reset the controller during init and cleanup
976 i8042.unlock [HW] Unlock (ignore) the keylock
980 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
981 indicates that the driver is running on unsupported
983 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
984 does not match list of supported models.
986 [HW] Report power status in /proc/i8k
987 (disabled by default)
988 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
992 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
994 ide-core.nodma= [HW] (E)IDE subsystem
995 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
996 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
997 .cdrom .chs .ignore_cable are additional options
998 See Documentation/ide/ide.txt.
1000 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1001 Claim all unknown PCI IDE storage controllers.
1004 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1005 Poll forces a polling idle loop that can slightly
1006 improve the performance of waking up a idle CPU, but
1007 will use a lot of power and make the system run hot.
1009 idle=mwait: On systems which support MONITOR/MWAIT but
1010 the kernel chose to not use it because it doesn't save
1011 as much power as a normal idle loop, use the
1012 MONITOR/MWAIT idle loop anyways. Performance should be
1013 the same as idle=poll.
1014 idle=halt: Halt is forced to be used for CPU idle.
1015 In such case C2/C3 won't be used again.
1016 idle=nomwait: Disable mwait for CPU C-states
1018 ignore_loglevel [KNL]
1019 Ignore loglevel setting - this will print /all/
1020 kernel messages to the console. Useful for debugging.
1021 We also add it as printk module parameter, so users
1022 could change it dynamically, usually by
1023 /sys/module/printk/parameters/ignore_loglevel.
1025 ihash_entries= [KNL]
1026 Set number of hash buckets for inode cache.
1029 Format: { "0" | "1" }
1030 0 -- integrity auditing messages. (Default)
1031 1 -- enable informational integrity auditing messages.
1034 Format: { "sha1" | "md5" }
1038 Load a policy which meets the needs of the Trusted
1039 Computing Base. This means IMA will measure all
1040 programs exec'd, files mmap'd for exec, and all files
1041 opened for read by uid=0.
1045 Run specified binary instead of /sbin/init as init
1048 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1049 for working out where the kernel is dying during
1052 initrd= [BOOT] Specify the location of the initial ramdisk
1054 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1057 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1059 Enable intel iommu driver.
1061 Disable intel iommu driver.
1062 igfx_off [Default Off]
1063 By default, gfx is mapped as normal device. If a gfx
1064 device has a dedicated DMAR unit, the DMAR unit is
1065 bypassed by not enabling DMAR with this option. In
1066 this case, gfx device will use physical address for
1069 With this option iommu will not optimize to look
1070 for io virtual address below 32-bit forcing dual
1071 address cycle on pci bus for cards supporting greater
1072 than 32-bit addressing. The default is to look
1073 for translation below 32-bit and if not available
1074 then look in the higher range.
1075 strict [Default Off]
1076 With this option on every unmap_single operation will
1077 result in a hardware IOTLB flush operation as opposed
1078 to batching them for performance.
1079 sp_off [Default Off]
1080 By default, super page will be supported if Intel IOMMU
1081 has the capability. With this option, super page will
1084 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1085 0 disables intel_idle and fall back on acpi_idle.
1086 1 to 6 specify maximum depth of C-state.
1088 intremap= [X86-64, Intel-IOMMU]
1089 on enable Interrupt Remapping (default)
1090 off disable Interrupt Remapping
1091 nosid disable Source ID checking
1093 BIOS x2APIC opt-out request will be ignored
1095 iomem= Disable strict checking of access to MMIO memory
1096 strict regions from userspace.
1111 group_mf [x86, IA-64]
1114 io7= [HW] IO7 for Marvel based alpha systems
1115 See comment before marvel_specify_io7 in
1116 arch/alpha/kernel/core_marvel.c.
1118 io_delay= [X86] I/O delay method
1120 Standard port 0x80 based delay
1122 Alternate port 0xed based delay (needed on some systems)
1124 Simple two microseconds delay
1129 See Documentation/filesystems/nfs/nfsroot.txt.
1131 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1132 See comment before ip2_setup() in
1133 drivers/char/ip2/ip2base.c.
1136 When an interrupt is not handled search all handlers
1137 for it. Intended to get systems with badly broken
1141 When an interrupt is not handled search all handlers
1142 for it. Also check all handlers each timer
1143 interrupt. Intended to get systems with badly broken
1147 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1149 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1151 <cpu number>,...,<cpu number>
1153 <cpu number>-<cpu number>
1154 (must be a positive range in ascending order)
1156 <cpu number>,...,<cpu number>-<cpu number>
1158 This option can be used to specify one or more CPUs
1159 to isolate from the general SMP balancing and scheduling
1160 algorithms. You can move a process onto or off an
1161 "isolated" CPU via the CPU affinity syscalls or cpuset.
1162 <cpu number> begins at 0 and the maximum value is
1163 "number of CPUs in system - 1".
1165 This option is the preferred way to isolate CPUs. The
1166 alternative -- manually setting the CPU mask of all
1167 tasks in the system -- can cause problems and
1168 suboptimal load balancer performance.
1172 js= [HW,JOY] Analog joystick
1173 See Documentation/input/joystick.txt.
1177 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1178 specifies the amount of memory usable by the kernel
1179 for non-movable allocations. The requested amount is
1180 spread evenly throughout all nodes in the system. The
1181 remaining memory in each node is used for Movable
1182 pages. In the event, a node is too small to have both
1183 kernelcore and Movable pages, kernelcore pages will
1184 take priority and other nodes will have a larger number
1185 of kernelcore pages. The Movable zone is used for the
1186 allocation of pages that may be reclaimed or moved
1187 by the page migration subsystem. This means that
1188 HugeTLB pages may not be allocated from this zone.
1189 Note that allocations like PTEs-from-HighMem still
1190 use the HighMem zone if it exists, and the Normal
1191 zone if it does not.
1193 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1194 Format: <Controller#>[,poll interval]
1195 The controller # is the number of the ehci usb debug
1196 port as it is probed via PCI. The poll interval is
1197 optional and is the number seconds in between
1198 each poll cycle to the debug port in case you need
1199 the functionality for interrupting the kernel with
1200 gdb or control-c on the dbgp connection. When
1201 not using this parameter you use sysrq-g to break into
1202 the kernel debugger.
1204 kgdboc= [KGDB,HW] kgdb over consoles.
1205 Requires a tty driver that supports console polling,
1206 or a supported polling keyboard driver (non-usb).
1207 Serial only format: <serial_device>[,baud]
1208 keyboard only format: kbd
1209 keyboard and serial format: kbd,<serial_device>[,baud]
1210 Optional Kernel mode setting:
1211 kms, kbd format: kms,kbd
1212 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1214 kgdbwait [KGDB] Stop kernel execution and enter the
1215 kernel debugger at the earliest opportunity.
1217 kmac= [MIPS] korina ethernet MAC address.
1218 Configure the RouterBoard 532 series on-chip
1219 Ethernet adapter MAC address.
1221 kmemleak= [KNL] Boot-time kmemleak enable/disable
1222 Valid arguments: on, off
1225 kstack=N [X86] Print N words from the kernel stack
1228 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1229 Default is 0 (don't ignore, but inject #GP)
1231 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1235 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1236 Default is 1 (enabled)
1238 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1240 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1242 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1243 (virtualized MMU) support on capable Intel chips.
1244 Default is 1 (enabled)
1246 kvm-intel.emulate_invalid_guest_state=
1247 [KVM,Intel] Enable emulation of invalid guest states
1248 Default is 0 (disabled)
1250 kvm-intel.flexpriority=
1251 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1252 Default is 1 (enabled)
1255 [KVM,Intel] Enable VMX nesting (nVMX).
1256 Default is 0 (disabled)
1258 kvm-intel.unrestricted_guest=
1259 [KVM,Intel] Disable unrestricted guest feature
1260 (virtualized real and unpaged mode) on capable
1261 Intel chips. Default is 1 (enabled)
1263 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1264 feature (tagged TLBs) on capable Intel chips.
1265 Default is 1 (enabled)
1271 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1274 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1277 libata.dma= [LIBATA] DMA control
1278 libata.dma=0 Disable all PATA and SATA DMA
1279 libata.dma=1 PATA and SATA Disk DMA only
1280 libata.dma=2 ATAPI (CDROM) DMA only
1281 libata.dma=4 Compact Flash DMA only
1282 Combinations also work, so libata.dma=3 enables DMA
1283 for disks and CDROMs, but not CFs.
1285 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1286 libata.ignore_hpa=0 keep BIOS limits (default)
1287 libata.ignore_hpa=1 ignore limits, using full disk
1289 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1293 libata.force= [LIBATA] Force configurations. The format is comma
1294 separated list of "[ID:]VAL" where ID is
1295 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1296 matching port, link or device. Basically, it matches
1297 the ATA ID string printed on console by libata. If
1298 the whole ID part is omitted, the last PORT and DEVICE
1299 values are used. If ID hasn't been specified yet, the
1300 configuration applies to all ports, links and devices.
1302 If only DEVICE is omitted, the parameter applies to
1303 the port and all links and devices behind it. DEVICE
1304 number of 0 either selects the first device or the
1305 first fan-out link behind PMP device. It does not
1306 select the host link. DEVICE number of 15 selects the
1307 host link and device attached to it.
1309 The VAL specifies the configuration to force. As long
1310 as there's no ambiguity shortcut notation is allowed.
1311 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1312 The following configurations can be forced.
1314 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1315 Any ID with matching PORT is used.
1317 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1319 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1320 udma[/][16,25,33,44,66,100,133] notation is also
1323 * [no]ncq: Turn on or off NCQ.
1325 * nohrst, nosrst, norst: suppress hard, soft
1328 * dump_id: dump IDENTIFY data.
1330 If there are multiple matching configurations changing
1331 the same attribute, the last one is used.
1333 memblock=debug [KNL] Enable memblock debug messages.
1335 load_ramdisk= [RAM] List of ramdisks to load from floppy
1336 See Documentation/blockdev/ramdisk.txt.
1338 lockd.nlm_grace_period=P [NFS] Assign grace period.
1341 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1344 lockd.nlm_timeout=T [NFS] Assign timeout value.
1347 lockd.nlm_udpport=M [NFS] Assign UDP port.
1350 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1353 loglevel= All Kernel Messages with a loglevel smaller than the
1354 console loglevel will be printed to the console. It can
1355 also be changed with klogd or other programs. The
1356 loglevels are defined as follows:
1358 0 (KERN_EMERG) system is unusable
1359 1 (KERN_ALERT) action must be taken immediately
1360 2 (KERN_CRIT) critical conditions
1361 3 (KERN_ERR) error conditions
1362 4 (KERN_WARNING) warning conditions
1363 5 (KERN_NOTICE) normal but significant condition
1364 6 (KERN_INFO) informational
1365 7 (KERN_DEBUG) debug-level messages
1367 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1368 in bytes. n must be a power of two. The default
1369 size is set in the kernel config file.
1371 logo.nologo [FB] Disables display of the built-in Linux logo.
1372 This may be used to provide more screen space for
1373 kernel log messages and is useful when debugging
1374 kernel boot problems.
1376 lp=0 [LP] Specify parallel ports to use, e.g,
1377 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1378 lp=reset first parallel port). 'lp=0' disables the
1379 lp=auto printer driver. 'lp=reset' (which can be
1380 specified in addition to the ports) causes
1381 attached printers to be reset. Using
1382 lp=port1,port2,... specifies the parallel ports
1383 to associate lp devices with, starting with
1384 lp0. A port specification may be 'none' to skip
1385 that lp device, or a parport name such as
1386 'parport0'. Specifying 'lp=auto' instead of a
1387 port specification list means that device IDs
1388 from each port should be examined, to see if
1389 an IEEE 1284-compliant printer is attached; if
1390 so, the driver will manage that printer.
1391 See also header of drivers/char/lp.c.
1394 Sets loops_per_jiffy to given constant, thus avoiding
1395 time-consuming boot-time autodetection (up to 250 ms per
1396 CPU). 0 enables autodetection (default). To determine
1397 the correct value for your kernel, boot with normal
1398 autodetection and see what value is printed. Note that
1399 on SMP systems the preset will be applied to all CPUs,
1400 which is likely to cause problems if your CPUs need
1401 significantly divergent settings. An incorrect value
1402 will cause delays in the kernel to be wrong, leading to
1403 unpredictable I/O errors and other breakage. Although
1404 unlikely, in the extreme case this might damage your
1408 Format: <io>,<irq>,<dma>
1410 machvec= [IA-64] Force the use of a particular machine-vector
1411 (machvec) in a generic kernel.
1412 Example: machvec=hpzx1_swiotlb
1414 machtype= [Loongson] Share the same kernel image file between different
1416 Example: machtype=lemote-yeeloong-2f-7inch
1418 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1419 than or equal to this physical address is ignored.
1421 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1422 should make use of. maxcpus=n : n >= 0 limits the
1423 kernel to using 'n' processors. n=0 is a special case,
1424 it is equivalent to "nosmp", which also disables
1427 max_loop= [LOOP] The number of loop block devices that get
1428 (loop.max_loop) unconditionally pre-created at init time. The default
1429 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1430 of statically allocating a predefined number, loop
1431 devices can be requested on-demand with the
1432 /dev/loop-control interface.
1436 mce [X86-32] Machine Check Exception
1438 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1440 md= [HW] RAID subsystems devices and level
1441 See Documentation/md.txt.
1444 Format: <first>,<last>
1445 Specifies range of consoles to be captured by the MDA.
1447 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1448 Amount of memory to be used when the kernel is not able
1449 to see the whole system memory or for test.
1450 [X86-32] Use together with memmap= to avoid physical
1451 address space collisions. Without memmap= PCI devices
1452 could be placed at addresses belonging to unused RAM.
1454 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1458 [KNL,SH] Allow user to override the default size for
1459 per-device physically contiguous DMA buffers.
1461 memmap=exactmap [KNL,X86] Enable setting of an exact
1462 E820 memory map, as specified by the user.
1463 Such memmap=exactmap lines can be constructed based on
1464 BIOS output or other requirements. See the memmap=nn@ss
1467 memmap=nn[KMG]@ss[KMG]
1468 [KNL] Force usage of a specific region of memory
1469 Region of memory to be used, from ss to ss+nn.
1471 memmap=nn[KMG]#ss[KMG]
1472 [KNL,ACPI] Mark specific memory as ACPI data.
1473 Region of memory to be used, from ss to ss+nn.
1475 memmap=nn[KMG]$ss[KMG]
1476 [KNL,ACPI] Mark specific memory as reserved.
1477 Region of memory to be used, from ss to ss+nn.
1478 Example: Exclude memory from 0x18690000-0x1869ffff
1479 memmap=64K$0x18690000
1481 memmap=0x10000$0x18690000
1483 memory_corruption_check=0/1 [X86]
1484 Some BIOSes seem to corrupt the first 64k of
1485 memory when doing things like suspend/resume.
1486 Setting this option will scan the memory
1487 looking for corruption. Enabling this will
1488 both detect corruption and prevent the kernel
1489 from using the memory being corrupted.
1490 However, its intended as a diagnostic tool; if
1491 repeatable BIOS-originated corruption always
1492 affects the same memory, you can use memmap=
1493 to prevent the kernel from using that memory.
1495 memory_corruption_check_size=size [X86]
1496 By default it checks for corruption in the low
1497 64k, making this memory unavailable for normal
1498 use. Use this parameter to scan for
1499 corruption in more or less memory.
1501 memory_corruption_check_period=seconds [X86]
1502 By default it checks for corruption every 60
1503 seconds. Use this parameter to check at some
1504 other rate. 0 disables periodic checking.
1506 memtest= [KNL,X86] Enable memtest
1508 default : 0 <disable>
1509 Specifies the number of memtest passes to be
1510 performed. Each pass selects another test
1511 pattern from a given set of patterns. Memtest
1512 fills the memory with this pattern, validates
1513 memory contents and reserves bad memory
1514 regions that are detected.
1516 meye.*= [HW] Set MotionEye Camera parameters
1517 See Documentation/video4linux/meye.txt.
1519 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1520 Multi-Function General Purpose Timers on AMD Geode
1523 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1524 the BIOS has incorrectly applied a workaround. TinyBIOS
1525 version 0.98 is known to be affected, 0.99 fixes the
1526 problem by letting the user disable the workaround.
1530 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1531 physical address is ignored.
1533 mini2440= [ARM,HW,KNL]
1534 Format:[0..2][b][c][t]
1536 MINI2440 configuration specification:
1537 0 - The attached screen is the 3.5" TFT
1538 1 - The attached screen is the 7" TFT
1539 2 - The VGA Shield is attached (1024x768)
1540 Leaving out the screen size parameter will not load
1541 the TFT driver, and the framebuffer will be left
1543 b - Enable backlight. The TFT backlight pin will be
1544 linked to the kernel VESA blanking code and a GPIO
1545 LED. This parameter is not necessary when using the
1547 c - Enable the s3c camera interface.
1548 t - Reserved for enabling touchscreen support. The
1549 touchscreen support is not enabled in the mainstream
1550 kernel as of 2.6.30, a preliminary port can be found
1551 in the "bleeding edge" mini2440 support kernel at
1552 http://repo.or.cz/w/linux-2.6/mini2440.git
1555 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1556 parameter allows control of the logging verbosity for
1557 the additional memory initialisation checks. A value
1558 of 0 disables mminit logging and a level of 4 will
1559 log everything. Information is printed at KERN_DEBUG
1560 so loglevel=8 may also need to be specified.
1563 [MOUSE] Maximum time between finger touching and
1564 leaving touchpad surface for touch to be considered
1565 a tap and be reported as a left button click (for
1566 touchpads working in absolute mode only).
1568 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1569 reporting absolute coordinates, such as tablets
1570 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1571 reporting absolute coordinates, such as tablets
1573 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1574 is similar to kernelcore except it specifies the
1575 amount of memory used for migratable allocations.
1576 If both kernelcore and movablecore is specified,
1577 then kernelcore will be at *least* the specified
1578 value but may be more. If movablecore on its own
1579 is specified, the administrator must be careful
1580 that the amount of memory usable for all allocations
1583 MTD_Partition= [MTD]
1584 Format: <name>,<region-number>,<size>,<offset>
1586 MTD_Region= [MTD] Format:
1587 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1590 See drivers/mtd/cmdlinepart.c.
1592 multitce=off [PPC] This parameter disables the use of the pSeries
1593 firmware feature for updating multiple TCE entries
1596 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1598 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1600 boundary - index of last SLC block on Flex-OneNAND.
1601 The remaining blocks are configured as MLC blocks.
1602 lock - Configure if Flex-OneNAND boundary should be locked.
1603 Once locked, the boundary cannot be changed.
1604 1 indicates lock status, 0 indicates unlock status.
1607 ARM/S3C2412 JIVE boot control
1609 See arch/arm/mach-s3c2412/mach-jive.c
1611 mtouchusb.raw_coordinates=
1612 [HW] Make the MicroTouch USB driver use raw coordinates
1613 ('y', default) or cooked coordinates ('n')
1615 mtrr_chunk_size=nn[KMG] [X86]
1616 used for mtrr cleanup. It is largest continuous chunk
1617 that could hold holes aka. UC entries.
1619 mtrr_gran_size=nn[KMG] [X86]
1620 Used for mtrr cleanup. It is granularity of mtrr block.
1622 Large value could prevent small alignment from
1625 mtrr_spare_reg_nr=n [X86]
1627 Range: 0,7 : spare reg number
1629 Used for mtrr cleanup. It is spare mtrr entries number.
1630 Set to 2 or more if your graphical card needs more.
1632 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1634 netdev= [NET] Network devices parameters
1635 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1636 Note that mem_start is often overloaded to mean
1637 something different and driver-specific.
1638 This usage is only documented in each driver source
1642 [NETFILTER] Enable connection tracking flow accounting
1643 0 to disable accounting
1644 1 to enable accounting
1647 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1648 See Documentation/filesystems/nfs/nfsroot.txt.
1650 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1651 See Documentation/filesystems/nfs/nfsroot.txt.
1653 nfsrootdebug [NFS] enable nfsroot debugging messages.
1654 See Documentation/filesystems/nfs/nfsroot.txt.
1656 nfs.callback_tcpport=
1657 [NFS] set the TCP port on which the NFSv4 callback
1658 channel should listen.
1661 [NFS] sets the pathname to the program which is used
1662 to update the NFS client cache entries.
1664 nfs.cache_getent_timeout=
1665 [NFS] sets the timeout after which an attempt to
1666 update a cache entry is deemed to have failed.
1668 nfs.idmap_cache_timeout=
1669 [NFS] set the maximum lifetime for idmapper cache
1673 [NFS] enable 64-bit inode numbers.
1674 If zero, the NFS client will fake up a 32-bit inode
1675 number for the readdir() and stat() syscalls instead
1676 of returning the full 64-bit number.
1677 The default is to return 64-bit inode numbers.
1679 nfs.max_session_slots=
1680 [NFSv4.1] Sets the maximum number of session slots
1681 the client will attempt to negotiate with the server.
1682 This limits the number of simultaneous RPC requests
1683 that the client can send to the NFSv4.1 server.
1684 Note that there is little point in setting this
1685 value higher than the max_tcp_slot_table_limit.
1687 nfs.nfs4_disable_idmapping=
1688 [NFSv4] When set to the default of '1', this option
1689 ensures that both the RPC level authentication
1690 scheme and the NFS level operations agree to use
1691 numeric uids/gids if the mount is using the
1692 'sec=sys' security flavour. In effect it is
1693 disabling idmapping, which can make migration from
1694 legacy NFSv2/v3 systems to NFSv4 easier.
1695 Servers that do not support this mode of operation
1696 will be autodetected by the client, and it will fall
1697 back to using the idmapper.
1698 To turn off this behaviour, set the value to '0'.
1700 nfs.send_implementation_id =
1701 [NFSv4.1] Send client implementation identification
1702 information in exchange_id requests.
1703 If zero, no implementation identification information
1705 The default is to send the implementation identification
1708 nfsd.nfs4_disable_idmapping=
1709 [NFSv4] When set to the default of '1', the NFSv4
1710 server will return only numeric uids and gids to
1711 clients using auth_sys, and will accept numeric uids
1712 and gids from such clients. This is intended to ease
1713 migration from NFSv2/v3.
1715 objlayoutdriver.osd_login_prog=
1716 [NFS] [OBJLAYOUT] sets the pathname to the program which
1717 is used to automatically discover and login into new
1718 osd-targets. Please see:
1719 Documentation/filesystems/pnfs.txt for more explanations
1721 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1722 when a NMI is triggered.
1723 Format: [state][,regs][,debounce][,die]
1725 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1726 Format: [panic,][nopanic,][num]
1728 0 - turn nmi_watchdog off
1729 When panic is specified, panic when an NMI watchdog
1730 timeout occurs (or 'nopanic' to override the opposite
1732 This is useful when you use a panic=... timeout and
1733 need the box quickly up again.
1735 netpoll.carrier_timeout=
1736 [NET] Specifies amount of time (in seconds) that
1737 netpoll should wait for a carrier. By default netpoll
1740 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1741 emulation library even if a 387 maths coprocessor
1745 [HW] Never suspend the console
1746 Disable suspending of consoles during suspend and
1747 hibernate operations. Once disabled, debugging
1748 messages can reach various consoles while the rest
1749 of the system is being put to sleep (ie, while
1750 debugging driver suspend/resume hooks). This may
1751 not work reliably with all consoles, but is known
1752 to work with serial and VGA consoles.
1753 To facilitate more flexible debugging, we also add
1754 console_suspend, a printk module parameter to control
1755 it. Users could use console_suspend (usually
1756 /sys/module/printk/parameters/console_suspend) to
1757 turn on/off it dynamically.
1759 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1760 caches in the slab allocator. Saves per-node memory,
1761 but will impact performance.
1765 noapic [SMP,APIC] Tells the kernel to not make use of any
1766 IOAPICs that may be present in the system.
1768 noautogroup Disable scheduler automatic task group creation.
1770 nobats [PPC] Do not use BATs for mapping kernel lowmem
1771 on "Classic" PPC cores.
1775 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1777 nodelayacct [KNL] Disable per-task delay accounting
1779 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1781 nodsp [SH] Disable hardware DSP at boot time.
1783 noefi [X86] Disable EFI runtime services support.
1788 On X86-32 available only on PAE configured kernels.
1789 noexec=on: enable non-executable mappings (default)
1790 noexec=off: disable non-executable mappings
1793 Disable SMEP (Supervisor Mode Execution Protection)
1794 even if it is supported by processor.
1797 This affects only 32-bit executables.
1798 noexec32=on: enable non-executable mappings (default)
1799 read doesn't imply executable mappings
1800 noexec32=off: disable non-executable mappings
1801 read implies executable mappings
1803 nofpu [SH] Disable hardware FPU at boot time.
1805 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1806 register save and restore. The kernel will only save
1807 legacy floating-point registers on task switch.
1809 noxsave [BUGS=X86] Disables x86 extended register state save
1810 and restore using xsave. The kernel will fallback to
1811 enabling legacy floating-point and sse state.
1813 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1814 wfi(ARM) instruction doesn't work correctly and not to
1815 use it. This is also useful when using JTAG debugger.
1817 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1818 instruction doesn't work correctly and not to
1821 no_file_caps Tells the kernel not to honor file capabilities. The
1822 only way then for a file to be executed with privilege
1823 is to be setuid root or executed by root.
1825 nohalt [IA-64] Tells the kernel not to use the power saving
1826 function PAL_HALT_LIGHT when idle. This increases
1827 power-consumption. On the positive side, it reduces
1828 interrupt wake-up latency, which may improve performance
1829 in certain environments such as networked servers or
1832 nohz= [KNL] Boottime enable/disable dynamic ticks
1833 Valid arguments: on, off
1836 noiotrap [SH] Disables trapped I/O port accesses.
1838 noirqdebug [X86-32] Disables the code which attempts to detect and
1839 disable unhandled interrupt sources.
1841 no_timer_check [X86,APIC] Disables the code which tests for
1842 broken timer IRQ sources.
1844 noisapnp [ISAPNP] Disables ISA PnP code.
1846 noinitrd [RAM] Tells the kernel not to load any configured
1849 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1851 [Deprecated - use intremap=off]
1855 nojitter [IA-64] Disables jitter checking for ITC timers.
1857 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1859 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1862 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1863 steal time is computed, but won't influence scheduler
1866 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1868 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1870 noltlbs [PPC] Do not use large page/tlb entries for kernel
1871 lowmem mapping on PPC40x.
1873 nomca [IA-64] Disable machine check abort handling
1875 nomce [X86-32] Machine Check Exception
1877 nomfgpt [X86-32] Disable Multi-Function General Purpose
1878 Timer usage (for AMD Geode machines).
1880 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1881 shutdown the other cpus. Instead use the REBOOT_VECTOR
1884 nomodule Disable module load
1886 nopat [X86] Disable PAT (page attribute table extension of
1887 pagetables) support.
1889 norandmaps Don't use address space randomization. Equivalent to
1890 echo 0 > /proc/sys/kernel/randomize_va_space
1892 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1894 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1895 with UP alternatives
1897 noresidual [PPC] Don't use residual data on PReP machines.
1899 nordrand [X86] Disable the direct use of the RDRAND
1900 instruction even if it is supported by the
1901 processor. RDRAND is still available to user
1904 noresume [SWSUSP] Disables resume and restores original swap
1907 no-scroll [VGA] Disables scrollback.
1908 This is required for the Braillex ib80-piezo Braille
1909 reader made by F.H. Papenmeier (Germany).
1913 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1915 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1916 and disable the IO APIC. legacy for "maxcpus=0".
1918 nosoftlockup [KNL] Disable the soft-lockup detector.
1920 nosync [HW,M68K] Disables sync negotiation for all devices.
1922 notsc [BUGS=X86-32] Disable Time Stamp Counter
1924 nousb [USB] Disable the USB subsystem
1926 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1930 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1932 nptcg= [IA-64] Override max number of concurrent global TLB
1933 purges which is reported from either PAL_VM_SUMMARY or
1936 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1937 could support. nr_cpus=n : n >= 1 limits the kernel to
1938 supporting 'n' processors. Later in runtime you can not
1939 use hotplug cpu feature to put more cpu back to online.
1940 just like you compile the kernel NR_CPUS=n
1942 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1944 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1945 one of ['zone', 'node', 'default'] can be specified
1946 This can be set from sysctl after boot.
1947 See Documentation/sysctl/vm.txt for details.
1949 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1950 See Documentation/debugging-via-ohci1394.txt for more
1953 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1954 Rather than timing out after 20 ms if an EC
1955 command is not properly ACKed, override the length
1956 of the timeout. We have interrupts disabled while
1957 waiting for the ACK, so if this is set too high
1958 interrupts *may* be lost!
1960 omap_mux= [OMAP] Override bootloader pin multiplexing.
1961 Format: <mux_mode0.mode_name=value>...
1962 For example, to override I2C bus2:
1963 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1965 oprofile.timer= [HW]
1966 Use timer interrupt instead of performance counters
1968 oprofile.cpu_type= Force an oprofile cpu type
1969 This might be useful if you have an older oprofile
1970 userland or if you want common events.
1971 Format: { arch_perfmon }
1972 arch_perfmon: [X86] Force use of architectural
1973 perfmon on Intel CPUs instead of the
1974 CPU specific event set.
1975 timer: [X86] Force use of architectural NMI
1976 timer mode (see also oprofile.timer
1977 for generic hr timer mode)
1978 [s390] Force legacy basic mode sampling
1979 (report cpu_type "timer")
1981 oops=panic Always panic on oopses. Default is to just kill the
1982 process, but there is a small probability of
1983 deadlocking the machine.
1984 This will also cause panics on machine check exceptions.
1985 Useful together with panic=30 to trigger a reboot.
1988 See Documentation/sound/oss/oss-parameters.txt
1990 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1991 timeout > 0: seconds before rebooting
1992 timeout = 0: wait forever
1993 timeout < 0: reboot immediately
1996 parkbd.port= [HW] Parallel port number the keyboard adapter is
1997 connected to, default is 0.
1999 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2000 0 for XT, 1 for AT (default is AT).
2003 parport= [HW,PPT] Specify parallel ports. 0 disables.
2004 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2005 Use 'auto' to force the driver to use any
2006 IRQ/DMA settings detected (the default is to
2007 ignore detected IRQ/DMA settings because of
2008 possible conflicts). You can specify the base
2009 address, IRQ, and DMA settings; IRQ and DMA
2010 should be numbers, or 'auto' (for using detected
2011 settings on that particular port), or 'nofifo'
2012 (to avoid using a FIFO even if it is detected).
2013 Parallel ports are assigned in the order they
2014 are specified on the command line, starting
2017 parport_init_mode= [HW,PPT]
2018 Configure VIA parallel port to operate in
2019 a specific mode. This is necessary on Pegasos
2020 computer where firmware has no options for setting
2021 up parallel port mode and sets it to spp.
2022 Currently this function knows 686a and 8231 chips.
2023 Format: [spp|ps2|epp|ecp|ecpepp]
2026 Halt all CPUs after the first oops has been printed for
2027 the specified number of seconds. This is to be used if
2028 your oopses keep scrolling off the screen.
2033 See header of drivers/block/paride/pcd.c.
2034 See also Documentation/blockdev/paride.txt.
2036 pci=option[,option...] [PCI] various PCI subsystem options:
2037 earlydump [X86] dump PCI config space before the kernel
2039 off [X86] don't probe for the PCI bus
2040 bios [X86-32] force use of PCI BIOS, don't access
2041 the hardware directly. Use this if your machine
2042 has a non-standard PCI host bridge.
2043 nobios [X86-32] disallow use of PCI BIOS, only direct
2044 hardware access methods are allowed. Use this
2045 if you experience crashes upon bootup and you
2046 suspect they are caused by the BIOS.
2047 conf1 [X86] Force use of PCI Configuration
2049 conf2 [X86] Force use of PCI Configuration
2051 noaer [PCIE] If the PCIEAER kernel config parameter is
2052 enabled, this kernel boot option can be used to
2053 disable the use of PCIE advanced error reporting.
2054 nodomains [PCI] Disable support for multiple PCI
2055 root domains (aka PCI segments, in ACPI-speak).
2056 nommconf [X86] Disable use of MMCONFIG for PCI
2058 check_enable_amd_mmconf [X86] check for and enable
2059 properly configured MMIO access to PCI
2060 config space on AMD family 10h CPU
2061 nomsi [MSI] If the PCI_MSI kernel config parameter is
2062 enabled, this kernel boot option can be used to
2063 disable the use of MSI interrupts system-wide.
2064 noioapicquirk [APIC] Disable all boot interrupt quirks.
2065 Safety option to keep boot IRQs enabled. This
2066 should never be necessary.
2067 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2068 primary IO-APIC for bridges that cannot disable
2069 boot IRQs. This fixes a source of spurious IRQs
2070 when the system masks IRQs.
2071 noioapicreroute [APIC] Disable workaround that uses the
2072 boot IRQ equivalent of an IRQ that connects to
2073 a chipset where boot IRQs cannot be disabled.
2074 The opposite of ioapicreroute.
2075 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2076 routing table. These calls are known to be buggy
2077 on several machines and they hang the machine
2078 when used, but on other computers it's the only
2079 way to get the interrupt routing table. Try
2080 this option if the kernel is unable to allocate
2081 IRQs or discover secondary PCI buses on your
2083 rom [X86] Assign address space to expansion ROMs.
2084 Use with caution as certain devices share
2085 address decoders between ROMs and other
2087 norom [X86] Do not assign address space to
2088 expansion ROMs that do not already have
2089 BIOS assigned address ranges.
2090 nobar [X86] Do not assign address space to the
2091 BARs that weren't assigned by the BIOS.
2092 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2093 assigned automatically to PCI devices. You can
2094 make the kernel exclude IRQs of your ISA cards
2096 pirqaddr=0xAAAAA [X86] Specify the physical address
2097 of the PIRQ table (normally generated
2098 by the BIOS) if it is outside the
2099 F0000h-100000h range.
2100 lastbus=N [X86] Scan all buses thru bus #N. Can be
2101 useful if the kernel is unable to find your
2102 secondary buses and you want to tell it
2103 explicitly which ones they are.
2104 assign-busses [X86] Always assign all PCI bus
2105 numbers ourselves, overriding
2106 whatever the firmware may have done.
2107 usepirqmask [X86] Honor the possible IRQ mask stored
2108 in the BIOS $PIR table. This is needed on
2109 some systems with broken BIOSes, notably
2110 some HP Pavilion N5400 and Omnibook XE3
2111 notebooks. This will have no effect if ACPI
2112 IRQ routing is enabled.
2113 noacpi [X86] Do not use ACPI for IRQ routing
2114 or for PCI scanning.
2115 use_crs [X86] Use PCI host bridge window information
2116 from ACPI. On BIOSes from 2008 or later, this
2117 is enabled by default. If you need to use this,
2118 please report a bug.
2119 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2120 If you need to use this, please report a bug.
2121 routeirq Do IRQ routing for all PCI devices.
2122 This is normally done in pci_enable_device(),
2123 so this option is a temporary workaround
2124 for broken drivers that don't call it.
2125 skip_isa_align [X86] do not align io start addr, so can
2126 handle more pci cards
2127 firmware [ARM] Do not re-enumerate the bus but instead
2128 just use the configuration from the
2129 bootloader. This is currently used on
2130 IXP2000 systems where the bus has to be
2131 configured a certain way for adjunct CPUs.
2132 noearly [X86] Don't do any early type 1 scanning.
2133 This might help on some broken boards which
2134 machine check when some devices' config space
2135 is read. But various workarounds are disabled
2136 and some IOMMU drivers will not work.
2137 bfsort Sort PCI devices into breadth-first order.
2138 This sorting is done to get a device
2139 order compatible with older (<= 2.4) kernels.
2140 nobfsort Don't sort PCI devices into breadth-first order.
2141 cbiosize=nn[KMG] The fixed amount of bus space which is
2142 reserved for the CardBus bridge's IO window.
2143 The default value is 256 bytes.
2144 cbmemsize=nn[KMG] The fixed amount of bus space which is
2145 reserved for the CardBus bridge's memory
2146 window. The default value is 64 megabytes.
2149 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2150 Specifies alignment and device to reassign
2151 aligned memory resources.
2152 If <order of align> is not specified,
2153 PAGE_SIZE is used as alignment.
2154 PCI-PCI bridge can be specified, if resource
2155 windows need to be expanded.
2156 ecrc= Enable/disable PCIe ECRC (transaction layer
2157 end-to-end CRC checking).
2158 bios: Use BIOS/firmware settings. This is the
2162 realloc= Enable/disable reallocating PCI bridge resources
2163 if allocations done by BIOS are too small to
2164 accommodate resources required by all child
2166 off: Turn realloc off
2168 realloc same as realloc=on
2169 noari do not use PCIe ARI.
2170 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2171 only look for one device below a PCIe downstream
2174 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2177 force Enable ASPM even on devices that claim not to support it.
2178 WARNING: Forcing ASPM on may cause system lockups.
2180 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2181 nomsi Do not use MSI for PCI Express Native Hotplug (this
2182 makes all PCIe ports use INTx for hotplug services).
2184 pcie_ports= [PCIE] PCIe ports handling:
2185 auto Ask the BIOS whether or not to use native PCIe services
2186 associated with PCIe ports (PME, hot-plug, AER). Use
2187 them only if that is allowed by the BIOS.
2188 native Use native PCIe services associated with PCIe ports
2190 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2193 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2194 nomsi Do not use MSI for native PCIe PME signaling (this makes
2195 all PCIe root ports use INTx for all services).
2197 pcmv= [HW,PCMCIA] BadgePAD 4
2200 See Documentation/blockdev/paride.txt.
2202 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2205 See arch/parisc/kernel/pdc_chassis.c
2207 percpu_alloc= Select which percpu first chunk allocator to use.
2208 Currently supported values are "embed" and "page".
2209 Archs may support subset or none of the selections.
2210 See comments in mm/percpu.c for details on each
2211 allocator. This parameter is primarily for debugging
2212 and performance comparison.
2215 See Documentation/blockdev/paride.txt.
2218 See Documentation/blockdev/paride.txt.
2220 pirq= [SMP,APIC] Manual mp-table setup
2221 See Documentation/x86/i386/IO-APIC.txt.
2223 plip= [PPT,NET] Parallel port network link
2224 Format: { parport<nr> | timid | 0 }
2225 See also Documentation/parport.txt.
2227 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2228 Override pmtimer IOPort with a hex value.
2232 Enable PNP debug messages (depends on the
2233 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2234 via /sys/module/pnp/parameters/debug. We always show
2235 current resource usage; turning this on also shows
2236 possible settings and some assignment information.
2242 { on | off | curr | res | no-curr | no-res }
2245 [ISAPNP] Exclude IRQs for the autoconfiguration
2248 [ISAPNP] Exclude DMAs for the autoconfiguration
2250 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2251 Ranges are in pairs (I/O port base and size).
2254 [ISAPNP] Exclude memory regions for the
2256 Ranges are in pairs (memory base and size).
2258 ports= [IP_VS_FTP] IPVS ftp helper module
2260 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2262 Format: <port>,<port>....
2264 print-fatal-signals=
2265 [KNL] debug: print fatal signals
2267 If enabled, warn about various signal handling
2268 related application anomalies: too many signals,
2269 too many POSIX.1 timers, fatal signals causing a
2272 If you hit the warning due to signal overflow,
2273 you might want to try "ulimit -i unlimited".
2277 printk.always_kmsg_dump=
2278 Trigger kmsg_dump for cases other than kernel oops or
2280 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2283 printk.time= Show timing data prefixed to each printk message line
2284 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2286 processor.max_cstate= [HW,ACPI]
2287 Limit processor to maximum C-state
2288 max_cstate=9 overrides any DMI blacklist limit.
2290 processor.nocst [HW,ACPI]
2291 Ignore the _CST method to determine C-states,
2292 instead using the legacy FADT method
2294 profile= [KNL] Enable kernel profiling via /proc/profile
2295 Format: [schedule,]<number>
2296 Param: "schedule" - profile schedule points.
2297 Param: <number> - step/bucket size as a power of 2 for
2298 statistical time based profiling.
2299 Param: "sleep" - profile D-state sleeping (millisecs).
2300 Requires CONFIG_SCHEDSTATS
2301 Param: "kvm" - profile VM exits.
2303 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2305 See Documentation/blockdev/ramdisk.txt.
2307 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2308 probe for; one of (bare|imps|exps|lifebook|any).
2309 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2311 psmouse.resetafter= [HW,MOUSE]
2312 Try to reset the device after so many bad packets
2315 [HW,MOUSE] Set desired mouse resolution, in dpi.
2316 psmouse.smartscroll=
2317 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2318 0 = disabled, 1 = enabled (default).
2320 pstore.backend= Specify the name of the pstore backend to use
2323 See Documentation/blockdev/paride.txt.
2326 [KNL] Number of legacy pty's. Overwrites compiled-in
2329 quiet [KNL] Disable most log messages
2334 See Documentation/md.txt.
2336 ramdisk_blocksize= [RAM]
2337 See Documentation/blockdev/ramdisk.txt.
2339 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2340 See Documentation/blockdev/ramdisk.txt.
2342 rcutree.blimit= [KNL,BOOT]
2343 Set maximum number of finished RCU callbacks to process
2346 rcutree.qhimark= [KNL,BOOT]
2347 Set threshold of queued
2348 RCU callbacks over which batch limiting is disabled.
2350 rcutree.qlowmark= [KNL,BOOT]
2351 Set threshold of queued RCU callbacks below which
2352 batch limiting is re-enabled.
2354 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2355 Suppress RCU CPU stall warning messages.
2357 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2358 Set timeout for RCU CPU stall warning messages.
2360 rcutorture.fqs_duration= [KNL,BOOT]
2361 Set duration of force_quiescent_state bursts.
2363 rcutorture.fqs_holdoff= [KNL,BOOT]
2364 Set holdoff time within force_quiescent_state bursts.
2366 rcutorture.fqs_stutter= [KNL,BOOT]
2367 Set wait time between force_quiescent_state bursts.
2369 rcutorture.irqreader= [KNL,BOOT]
2370 Test RCU readers from irq handlers.
2372 rcutorture.n_barrier_cbs= [KNL,BOOT]
2373 Set callbacks/threads for rcu_barrier() testing.
2375 rcutorture.nfakewriters= [KNL,BOOT]
2376 Set number of concurrent RCU writers. These just
2377 stress RCU, they don't participate in the actual
2378 test, hence the "fake".
2380 rcutorture.nreaders= [KNL,BOOT]
2381 Set number of RCU readers.
2383 rcutorture.onoff_holdoff= [KNL,BOOT]
2384 Set time (s) after boot for CPU-hotplug testing.
2386 rcutorture.onoff_interval= [KNL,BOOT]
2387 Set time (s) between CPU-hotplug operations, or
2388 zero to disable CPU-hotplug testing.
2390 rcutorture.shuffle_interval= [KNL,BOOT]
2391 Set task-shuffle interval (s). Shuffling tasks
2392 allows some CPUs to go into dyntick-idle mode
2393 during the rcutorture test.
2395 rcutorture.shutdown_secs= [KNL,BOOT]
2396 Set time (s) after boot system shutdown. This
2397 is useful for hands-off automated testing.
2399 rcutorture.stall_cpu= [KNL,BOOT]
2400 Duration of CPU stall (s) to test RCU CPU stall
2401 warnings, zero to disable.
2403 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2404 Time to wait (s) after boot before inducing stall.
2406 rcutorture.stat_interval= [KNL,BOOT]
2407 Time (s) between statistics printk()s.
2409 rcutorture.stutter= [KNL,BOOT]
2410 Time (s) to stutter testing, for example, specifying
2411 five seconds causes the test to run for five seconds,
2412 wait for five seconds, and so on. This tests RCU's
2413 ability to transition abruptly to and from idle.
2415 rcutorture.test_boost= [KNL,BOOT]
2416 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2417 "Maybe" means test if the RCU implementation
2418 under test support RCU priority boosting.
2420 rcutorture.test_boost_duration= [KNL,BOOT]
2421 Duration (s) of each individual boost test.
2423 rcutorture.test_boost_interval= [KNL,BOOT]
2424 Interval (s) between each boost test.
2426 rcutorture.test_no_idle_hz= [KNL,BOOT]
2427 Test RCU's dyntick-idle handling. See also the
2428 rcutorture.shuffle_interval parameter.
2430 rcutorture.torture_type= [KNL,BOOT]
2431 Specify the RCU implementation to test.
2433 rcutorture.verbose= [KNL,BOOT]
2434 Enable additional printk() statements.
2438 Run specified binary instead of /init from the ramdisk,
2439 used for early userspace startup. See initrd.
2441 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2442 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2443 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2446 [KNL, SMP] Set scheduler's default relax_domain_level.
2447 See Documentation/cgroups/cpusets.txt.
2449 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2451 reservetop= [X86-32]
2453 Reserves a hole at the top of the kernel virtual
2458 Set the amount of memory to reserve for BIOS at
2459 the bottom of the address space.
2461 reset_devices [KNL] Force drivers to reset the underlying device
2462 during initialization.
2465 Specify the partition device for software suspend
2467 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2469 resume_offset= [SWSUSP]
2470 Specify the offset from the beginning of the partition
2471 given by "resume=" at which the swap header is located,
2472 in <PAGE_SIZE> units (needed only for swap files).
2473 See Documentation/power/swsusp-and-swap-files.txt
2475 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2476 read the resume files
2478 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2479 Useful for devices that are detected asynchronously
2480 (e.g. USB and MMC devices).
2482 hibernate= [HIBERNATION]
2483 noresume Don't check if there's a hibernation image
2484 present during boot.
2485 nocompress Don't compress/decompress hibernation images.
2487 retain_initrd [RAM] Keep initrd memory after extraction
2489 rhash_entries= [KNL,NET]
2490 Set number of hash buckets for route cache
2492 riscom8= [HW,SERIAL]
2493 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2495 ro [KNL] Mount root device read-only on boot
2497 root= [KNL] Root filesystem
2498 See name_to_dev_t comment in init/do_mounts.c.
2500 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2501 mount the root filesystem
2503 rootflags= [KNL] Set root filesystem mount option string
2505 rootfstype= [KNL] Set root filesystem type
2507 rootwait [KNL] Wait (indefinitely) for root device to show up.
2508 Useful for devices that are detected asynchronously
2509 (e.g. USB and MMC devices).
2511 rw [KNL] Mount root device read-write on boot
2513 S [KNL] Run init in single mode
2516 See drivers/net/irda/sa1100_ir.c.
2518 sbni= [NET] Granch SBNI12 leased line adapter
2520 sched_debug [KNL] Enables verbose scheduler debug messages.
2522 security= [SECURITY] Choose a security module to enable at boot.
2523 If this boot parameter is not specified, only the first
2524 security module asking for security registration will be
2525 loaded. An invalid security module name will be treated
2526 as if no module has been chosen.
2528 selinux= [SELINUX] Disable or enable SELinux at boot time.
2529 Format: { "0" | "1" }
2530 See security/selinux/Kconfig help text.
2533 Default value is set via kernel config option.
2534 If enabled at boot time, /selinux/disable can be used
2535 later to disable prior to initial policy load.
2537 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2538 Format: { "0" | "1" }
2539 See security/apparmor/Kconfig help text
2542 Default value is set via kernel config option.
2544 serialnumber [BUGS=X86-32]
2547 Maximal number of shapers.
2549 show_msr= [x86] show boot-time MSR settings
2550 Format: { <integer> }
2551 Show boot-time (BIOS-initialized) MSR settings.
2552 The parameter means the number of CPUs to show,
2553 for example 1 means boot CPU only.
2560 slab_max_order= [MM, SLAB]
2561 Determines the maximum allowed order for slabs.
2562 A high setting may cause OOMs due to memory
2563 fragmentation. Defaults to 1 for systems with
2564 more than 32MB of RAM, 0 otherwise.
2566 slub_debug[=options[,slabs]] [MM, SLUB]
2567 Enabling slub_debug allows one to determine the
2568 culprit if slab objects become corrupted. Enabling
2569 slub_debug can create guard zones around objects and
2570 may poison objects when not in use. Also tracks the
2571 last alloc / free. For more information see
2572 Documentation/vm/slub.txt.
2574 slub_max_order= [MM, SLUB]
2575 Determines the maximum allowed order for slabs.
2576 A high setting may cause OOMs due to memory
2577 fragmentation. For more information see
2578 Documentation/vm/slub.txt.
2580 slub_min_objects= [MM, SLUB]
2581 The minimum number of objects per slab. SLUB will
2582 increase the slab order up to slub_max_order to
2583 generate a sufficiently large slab able to contain
2584 the number of objects indicated. The higher the number
2585 of objects the smaller the overhead of tracking slabs
2586 and the less frequently locks need to be acquired.
2587 For more information see Documentation/vm/slub.txt.
2589 slub_min_order= [MM, SLUB]
2590 Determines the minimum page order for slabs. Must be
2591 lower than slub_max_order.
2592 For more information see Documentation/vm/slub.txt.
2594 slub_nomerge [MM, SLUB]
2595 Disable merging of slabs with similar size. May be
2596 necessary if there is some reason to distinguish
2597 allocs to different slabs. Debug options disable
2598 merging on their own.
2599 For more information see Documentation/vm/slub.txt.
2602 Format: <io1>[,<io2>[,...,<io8>]]
2604 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2605 attempt to substitute SMP alternatives once at boot.
2607 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2608 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2609 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2610 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2611 smsc-ircc2.ircc_irq= [HW] IRQ line
2612 smsc-ircc2.ircc_dma= [HW] DMA channel
2613 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2614 0: Toshiba Satellite 1800 (GP data pin select)
2615 1: Fast pin select (default)
2619 [KNL] Should the soft-lockup detector generate panics.
2622 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2623 See Documentation/laptops/sonypi.txt
2625 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2626 See Documentation/serial/specialix.txt.
2628 spia_io_base= [HW,MTD]
2634 Enabled the stack tracer on boot up.
2636 stacktrace_filter=[function-list]
2637 [FTRACE] Limit the functions that the stack tracer
2638 will trace at boot up. function-list is a comma separated
2639 list of functions. This list can be changed at run
2640 time by the stack_trace_filter file in the debugfs
2641 tracing directory. Note, this enables stack tracing
2642 and the stacktrace above is not needed.
2646 Set the STI (builtin display/keyboard on the HP-PARISC
2647 machines) console (graphic card) which should be used
2648 as the initial boot-console.
2649 See also comment in drivers/video/console/sticore.c.
2652 See comment in drivers/video/console/sticore.c.
2655 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2657 sunrpc.min_resvport=
2658 sunrpc.max_resvport=
2660 SunRPC servers often require that client requests
2661 originate from a privileged port (i.e. a port in the
2662 range 0 < portnr < 1024).
2663 An administrator who wishes to reserve some of these
2664 ports for other uses may adjust the range that the
2665 kernel's sunrpc client considers to be privileged
2666 using these two parameters to set the minimum and
2667 maximum port values.
2671 Control how the NFS server code allocates CPUs to
2672 service thread pools. Depending on how many NICs
2673 you have and where their interrupts are bound, this
2674 option will affect which CPUs will do NFS serving.
2675 Note: this parameter cannot be changed while the
2676 NFS server is running.
2678 auto the server chooses an appropriate mode
2679 automatically using heuristics
2680 global a single global pool contains all CPUs
2681 percpu one pool for each CPU
2682 pernode one pool for each NUMA node (equivalent
2683 to global on non-NUMA machines)
2685 sunrpc.tcp_slot_table_entries=
2686 sunrpc.udp_slot_table_entries=
2688 Sets the upper limit on the number of simultaneous
2689 RPC calls that can be sent from the client to a
2690 server. Increasing these values may allow you to
2691 improve throughput, but will also increase the
2692 amount of memory reserved for use by the client.
2695 [KNL] Enable accounting of swap in memory resource
2696 controller if no parameter or 1 is given or disable
2697 it if 0 is given (See Documentation/cgroups/memory.txt)
2699 swiotlb= [IA-64] Number of I/O TLB slabs
2703 sysfs.deprecated=0|1 [KNL]
2704 Enable/disable old style sysfs layout for old udev
2705 on older distributions. When this option is enabled
2706 very new udev will not work anymore. When this option
2707 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2708 in older udev will not work anymore.
2709 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2710 the kernel configuration.
2712 sysrq_always_enabled
2714 Ignore sysrq setting - this boot parameter will
2715 neutralize any effect of /proc/sys/kernel/sysrq.
2716 Useful for debugging.
2720 test_suspend= [SUSPEND]
2721 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2722 standby suspend) as the system sleep state to briefly
2723 enter during system startup. The system is woken from
2724 this state using a wakeup-capable RTC alarm.
2726 thash_entries= [KNL,NET]
2727 Set number of hash buckets for TCP connection
2729 thermal.act= [HW,ACPI]
2730 -1: disable all active trip points in all thermal zones
2731 <degrees C>: override all lowest active trip points
2733 thermal.crt= [HW,ACPI]
2734 -1: disable all critical trip points in all thermal zones
2735 <degrees C>: override all critical trip points
2737 thermal.nocrt= [HW,ACPI]
2738 Set to disable actions on ACPI thermal zone
2739 critical and hot trip points.
2741 thermal.off= [HW,ACPI]
2742 1: disable ACPI thermal control
2744 thermal.psv= [HW,ACPI]
2745 -1: disable all passive trip points
2746 <degrees C>: override all passive trip points to this
2749 thermal.tzp= [HW,ACPI]
2750 Specify global default ACPI thermal zone polling rate
2751 <deci-seconds>: poll all this frequency
2752 0: no polling (default)
2755 Force threading of all interrupt handlers except those
2756 marked explicitly IRQF_NO_THREAD.
2760 Specify if the kernel should make use of the cpu
2761 topology information if the hardware supports this.
2762 The scheduler will make use of this information and
2763 e.g. base its process migration decisions on it.
2768 tpm_suspend_pcr=[HW,TPM]
2769 Format: integer pcr id
2770 Specify that at suspend time, the tpm driver
2771 should extend the specified pcr with zeros,
2772 as a workaround for some chips which fail to
2773 flush the last written pcr on TPM_SaveState.
2774 This will guarantee that all the other pcrs
2777 trace_buf_size=nn[KMG]
2778 [FTRACE] will set tracing buffer size.
2780 trace_event=[event-list]
2781 [FTRACE] Set and start specified trace events in order
2782 to facilitate early boot debugging.
2783 See also Documentation/trace/events.txt
2785 transparent_hugepage=
2787 Format: [always|madvise|never]
2788 Can be used to control the default behavior of the system
2789 with respect to transparent hugepages.
2790 See Documentation/vm/transhuge.txt for more details.
2792 tsc= Disable clocksource stability checks for TSC.
2794 [x86] reliable: mark tsc clocksource as reliable, this
2795 disables clocksource verification at runtime, as well
2796 as the stability checks done at bootup. Used to enable
2797 high-resolution timer mode on older hardware, and in
2798 virtualized environment.
2799 [x86] noirqtime: Do not use TSC to do irq accounting.
2800 Used to run time disable IRQ_TIME_ACCOUNTING on any
2801 platforms where RDTSC is slow and this accounting
2804 turbografx.map[2|3]= [HW,JOY]
2805 TurboGraFX parallel port interface
2807 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2808 See also Documentation/input/joystick-parport.txt
2810 udbg-immortal [PPC] When debugging early kernel crashes that
2811 happen after console_init() and before a proper
2812 console driver takes over, this boot options might
2813 help "seeing" what's going on.
2815 uhash_entries= [KNL,NET]
2816 Set number of hash buckets for UDP/UDP-Lite connections
2819 [USB] Ignore overcurrent events (default N).
2820 Some badly-designed motherboards generate lots of
2821 bogus events, for ports that aren't wired to
2822 anything. Set this parameter to avoid log spamming.
2823 Note that genuine overcurrent events won't be
2827 [X86] Cause panic on unknown NMI.
2829 usbcore.authorized_default=
2830 [USB] Default USB device authorization:
2831 (default -1 = authorized except for wireless USB,
2832 0 = not authorized, 1 = authorized)
2834 usbcore.autosuspend=
2835 [USB] The autosuspend time delay (in seconds) used
2836 for newly-detected USB devices (default 2). This
2837 is the time required before an idle device will be
2838 autosuspended. Devices for which the delay is set
2839 to a negative value won't be autosuspended at all.
2841 usbcore.usbfs_snoop=
2842 [USB] Set to log all usbfs traffic (default 0 = off).
2844 usbcore.blinkenlights=
2845 [USB] Set to cycle leds on hubs (default 0 = off).
2847 usbcore.old_scheme_first=
2848 [USB] Start with the old device initialization
2849 scheme (default 0 = off).
2851 usbcore.usbfs_memory_mb=
2852 [USB] Memory limit (in MB) for buffers allocated by
2853 usbfs (default = 16, 0 = max = 2047).
2855 usbcore.use_both_schemes=
2856 [USB] Try the other device initialization scheme
2857 if the first one fails (default 1 = enabled).
2859 usbcore.initial_descriptor_timeout=
2860 [USB] Specifies timeout for the initial 64-byte
2861 USB_REQ_GET_DESCRIPTOR request in milliseconds
2862 (default 5000 = 5.0 seconds).
2865 [USBHID] The interval which mice are to be polled at.
2867 usb-storage.delay_use=
2868 [UMS] The delay in seconds before a new device is
2869 scanned for Logical Units (default 5).
2872 [UMS] A list of quirks entries to supplement or
2873 override the built-in unusual_devs list. List
2874 entries are separated by commas. Each entry has
2875 the form VID:PID:Flags where VID and PID are Vendor
2876 and Product ID values (4-digit hex numbers) and
2877 Flags is a set of characters, each corresponding
2878 to a common usb-storage quirk flag as follows:
2879 a = SANE_SENSE (collect more than 18 bytes
2881 b = BAD_SENSE (don't collect more than 18
2882 bytes of sense data);
2883 c = FIX_CAPACITY (decrease the reported
2884 device capacity by one sector);
2885 d = NO_READ_DISC_INFO (don't use
2886 READ_DISC_INFO command);
2887 e = NO_READ_CAPACITY_16 (don't use
2888 READ_CAPACITY_16 command);
2889 h = CAPACITY_HEURISTICS (decrease the
2890 reported device capacity by one
2891 sector if the number is odd);
2892 i = IGNORE_DEVICE (don't bind to this
2894 l = NOT_LOCKABLE (don't try to lock and
2895 unlock ejectable media);
2896 m = MAX_SECTORS_64 (don't transfer more
2897 than 64 sectors = 32 KB at a time);
2898 n = INITIAL_READ10 (force a retry of the
2899 initial READ(10) command);
2900 o = CAPACITY_OK (accept the capacity
2901 reported by the device);
2902 r = IGNORE_RESIDUE (the device reports
2903 bogus residue values);
2904 s = SINGLE_LUN (the device has only one
2906 w = NO_WP_DETECT (don't test whether the
2907 medium is write-protected).
2908 Example: quirks=0419:aaf5:rl,0421:0433:rc
2910 user_debug= [KNL,ARM]
2912 See arch/arm/Kconfig.debug help text.
2913 1 - undefined instruction events
2915 4 - invalid data aborts
2918 Example: user_debug=31
2921 [X86] Flags controlling user PTE allocations.
2923 nohigh = do not allocate PTE pages in
2924 HIGHMEM regardless of setting
2928 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2929 vdso=1: enable VDSO (default)
2930 vdso=0: disable VDSO mapping
2933 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2934 vdso32=1: enable 32-bit VDSO (default)
2935 vdso32=0: disable 32-bit VDSO mapping
2938 vector=percpu: enable percpu vector domain
2940 video= [FB] Frame buffer configuration
2941 See Documentation/fb/modedb.txt.
2944 [VMMIO] Memory mapped virtio (platform) device.
2946 <size>@<baseaddr>:<irq>[:<id>]
2948 <size> := size (can use standard suffixes
2950 <baseaddr> := physical base address
2951 <irq> := interrupt number (as passed to
2953 <id> := (optional) platform device id
2955 virtio_mmio.device=1K@0x100b0000:48:7
2957 Can be used multiple times for multiple devices.
2959 vga= [BOOT,X86-32] Select a particular video mode
2960 See Documentation/x86/boot.txt and
2961 Documentation/svga.txt.
2962 Use vga=ask for menu.
2963 This is actually a boot loader parameter; the value is
2964 passed to the kernel using a special protocol.
2966 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2967 size of <nn>. This can be used to increase the
2968 minimum size (128MB on x86). It can also be used to
2969 decrease the size and leave more room for directly
2972 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2975 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2978 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2982 Controls the behavior of vsyscalls (i.e. calls to
2983 fixed addresses of 0xffffffffff600x00 from legacy
2984 code). Most statically-linked binaries and older
2985 versions of glibc use these calls. Because these
2986 functions are at fixed addresses, they make nice
2987 targets for exploits that can control RIP.
2989 emulate [default] Vsyscalls turn into traps and are
2990 emulated reasonably safely.
2992 native Vsyscalls are native syscall instructions.
2993 This is a little bit faster than trapping
2994 and makes a few dynamic recompilers work
2995 better than they would in emulation mode.
2996 It also makes exploits much easier to write.
2998 none Vsyscalls don't work at all. This makes
2999 them quite hard to use for exploits but
3000 might break your system.
3002 vt.cur_default= [VT] Default cursor shape.
3003 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3004 the parameters of the <Esc>[?A;B;Cc escape sequence;
3005 see VGA-softcursor.txt. Default: 2 = underline.
3007 vt.default_blu= [VT]
3008 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3009 Change the default blue palette of the console.
3010 This is a 16-member array composed of values
3013 vt.default_grn= [VT]
3014 Format: <green0>,<green1>,<green2>,...,<green15>
3015 Change the default green palette of the console.
3016 This is a 16-member array composed of values
3019 vt.default_red= [VT]
3020 Format: <red0>,<red1>,<red2>,...,<red15>
3021 Change the default red palette of the console.
3022 This is a 16-member array composed of values
3028 Set system-wide default UTF-8 mode for all tty's.
3029 Default is 1, i.e. UTF-8 mode is enabled for all
3030 newly opened terminals.
3032 vt.global_cursor_default=
3035 Set system-wide default for whether a cursor
3036 is shown on new VTs. Default is -1,
3037 i.e. cursors will be created by default unless
3038 overridden by individual drivers. 0 will hide
3039 cursors, 1 will display them.
3041 watchdog timers [HW,WDT] For information on watchdog timers,
3042 see Documentation/watchdog/watchdog-parameters.txt
3043 or other driver-specific files in the
3044 Documentation/watchdog/ directory.
3046 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3047 default x2apic cluster mode on platforms
3050 x86_mrst_timer= [X86-32,APBT]
3051 Choose timer option for x86 Moorestown MID platform.
3052 Two valid options are apbt timer only and lapic timer
3053 plus one apbt timer for broadcast timer.
3054 x86_mrst_timer=apbt_only | lapic_and_apbt
3056 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3057 xd_geo= See header of drivers/block/xd.c.
3059 xen_emul_unplug= [HW,X86,XEN]
3060 Unplug Xen emulated devices
3061 Format: [unplug0,][unplug1]
3062 ide-disks -- unplug primary master IDE devices
3063 aux-ide-disks -- unplug non-primary-master IDE devices
3064 nics -- unplug network devices
3065 all -- unplug all emulated devices (NICs and IDE disks)
3066 unnecessary -- unplugging emulated devices is
3067 unnecessary even if the host did not respond to
3069 never -- do not unplug even if version check succeeds
3071 xirc2ps_cs= [NET,PCMCIA]
3073 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3075 ______________________________________________________________________
3079 Add more DRM drivers.
git.openpandora.org / pandora-kernel.git / blob