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 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
386 atkbd.reset= [HW] Reset keyboard during initialization
388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
402 baycom_epp= [HW,AX25]
405 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
407 See header of drivers/net/hamradio/baycom_par.c.
409 baycom_ser_fdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
411 Format: <io>,<irq>,<mode>[,<baud>]
412 See header of drivers/net/hamradio/baycom_ser_fdx.c.
414 baycom_ser_hdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
416 Format: <io>,<irq>,<mode>
417 See header of drivers/net/hamradio/baycom_ser_hdx.c.
419 boot_delay= Milliseconds to delay each printk during boot.
420 Values larger than 10 seconds (10000) are changed to
424 bootmem_debug [KNL] Enable bootmem allocator debug messages.
426 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
427 bttv.radio= Most important insmod options are available as
429 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
432 bulk_remove=off [PPC] This parameter disables the use of the pSeries
433 firmware feature for flushing multiple hpte entries
436 c101= [NET] Moxa C101 synchronous serial card
438 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
439 Sometimes CPU hardware bugs make them report the cache
440 size incorrectly. The kernel will attempt work arounds
441 to fix known problems, but for some CPUs it is not
442 possible to determine what the correct size should be.
443 This option provides an override for these situations.
446 [SECURITY] Disable capabilities. This would normally
447 be used only if an alternative security model is to be
448 configured. Potentially dangerous and should only be
449 used if you are entirely sure of the consequences.
451 ccw_timeout_log [S390]
452 See Documentation/s390/CommonIO for details.
454 cgroup_disable= [KNL] Disable a particular controller
455 Format: {name of the controller(s) to disable}
456 {Currently supported controllers - "memory"}
458 checkreqprot [SELINUX] Set initial checkreqprot flag value.
459 Format: { "0" | "1" }
460 See security/selinux/Kconfig help text.
461 0 -- check protection applied by kernel (includes
462 any implied execute protection).
463 1 -- check protection requested by application.
464 Default value is set via a kernel config option.
465 Value can be changed at runtime via
466 /selinux/checkreqprot.
469 See Documentation/s390/CommonIO for details.
471 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
473 Forces specified clocksource (if available) to be used
474 when calculating gettimeofday(). If specified
475 clocksource is not available, it defaults to PIT.
476 Format: { pit | tsc | cyclone | pmtmr }
478 clocksource= Override the default clocksource
480 Override the default clocksource and use the clocksource
481 with the name specified.
482 Some clocksource names to choose from, depending on
484 [all] jiffies (this is the base, fallback clocksource)
486 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
487 pxa_timer,timer3,32k_counter,timer0_1
489 [X86-32] pit,hpet,tsc;
490 scx200_hrt on Geode; cyclone on IBM x440
498 clearcpuid=BITNUM [X86]
499 Disable CPUID feature X for the kernel. See
500 arch/x86/include/asm/cpufeature.h for the valid bit
501 numbers. Note the Linux specific bits are not necessarily
502 stable over kernel options, but the vendor specific
504 Also note that user programs calling CPUID directly
505 or using the feature without checking anything
506 will still see it. This just prevents it from
507 being used by the kernel or shown in /proc/cpuinfo.
508 Also note the kernel might malfunction if you disable
512 Sets the size of kernel global memory area for contiguous
513 memory allocations. For more information, see
514 include/linux/dma-contiguous.h
516 cmo_free_hint= [PPC] Format: { yes | no }
517 Specify whether pages are marked as being inactive
518 when they are freed. This is used in CMO environments
519 to determine OS memory pressure for page stealing by
523 coherent_pool=nn[KMG] [ARM,KNL]
524 Sets the size of memory pool for coherent, atomic dma
525 allocations if Contiguous Memory Allocator (CMA) is used.
527 code_bytes [X86] How many bytes of object code to print
532 com20020= [HW,NET] ARCnet - COM20020 chipset
534 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
536 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
540 ARCnet - COM90xx chipset (memory-mapped buffers)
541 Format: <io>[,<irq>[,<memstart>]]
543 condev= [HW,S390] console device
546 console= [KNL] Output console device and options.
548 tty<n> Use the virtual console device <n>.
552 Use the specified serial port. The options are of
553 the form "bbbbpnf", where "bbbb" is the baud rate,
554 "p" is parity ("n", "o", or "e"), "n" is number of
555 bits, and "f" is flow control ("r" for RTS or
556 omit it). Default is "9600n8".
558 See Documentation/serial-console.txt for more
560 Documentation/networking/netconsole.txt for an
563 uart[8250],io,<addr>[,options]
564 uart[8250],mmio,<addr>[,options]
565 Start an early, polled-mode console on the 8250/16550
566 UART at the specified I/O port or MMIO address,
567 switching to the matching ttyS device later. The
568 options are the same as for ttyS, above.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel=range1:size1[,range2:size2,...][@offset]
600 [KNL] Same as above, but depends on the memory
601 in the running system. The syntax of range is
602 start-[end] where start and end are both
603 a memory unit (amount[KMG]). See also
604 Documentation/kdump/kdump.txt for an example.
609 cs89x0_media= [HW,NET]
610 Format: { rj45 | aui | bnc }
613 See header of drivers/s390/block/dasd_devmap.c.
615 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
616 (one device per port)
617 Format: <port#>,<type>
618 See also Documentation/input/joystick-parport.txt
620 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
621 time. See Documentation/dynamic-debug-howto.txt for
624 debug [KNL] Enable kernel debugging (events log level).
627 [KNL] verbose self-tests
629 Print debugging info while doing the locking API
631 We default to 0 (no extra messages), setting it to
632 1 will print _a lot_ more information - normally
633 only useful to kernel developers.
635 debug_objects [KNL] Enable object debugging
638 [KNL] Disable object debugging
640 debug_guardpage_minorder=
641 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
642 parameter allows control of the order of pages that will
643 be intentionally kept free (and hence protected) by the
644 buddy allocator. Bigger value increase the probability
645 of catching random memory corruption, but reduce the
646 amount of memory for normal system use. The maximum
647 possible value is MAX_ORDER/2. Setting this parameter
648 to 1 or 2 should be enough to identify most random
649 memory corruption problems caused by bugs in kernel or
650 driver code when a CPU writes to (or reads from) a
651 random memory location. Note that there exists a class
652 of memory corruptions problems caused by buggy H/W or
653 F/W or by drivers badly programing DMA (basically when
654 memory is written at bus level and the CPU MMU is
655 bypassed) which are not detectable by
656 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
657 tracking down these problems.
659 debugpat [X86] Enable PAT debugging
661 decnet.addr= [HW,NET]
662 Format: <area>[,<node>]
663 See also Documentation/networking/decnet.txt.
666 [same as hugepagesz=] The size of the default
667 HugeTLB page size. This is the size represented by
668 the legacy /proc/ hugepages APIs, used for SHM, and
669 default size when mounting hugetlbfs filesystems.
670 Defaults to the default architecture's huge page size
674 Set number of hash buckets for dentry cache.
677 IO parameters + enable/disable command.
679 digiepca= [HW,SERIAL]
680 See drivers/char/README.epca and
681 Documentation/serial/digiepca.txt.
684 See Documentation/networking/ipv6.txt.
686 disable_ddw [PPC/PSERIES]
687 Disable Dynamic DMA Window support. Use this if
688 to workaround buggy firmware.
691 See Documentation/networking/ipv6.txt.
693 disable_mtrr_cleanup [X86]
694 The kernel tries to adjust MTRR layout from continuous
695 to discrete, to make X server driver able to add WB
696 entry later. This parameter disables that.
698 disable_mtrr_trim [X86, Intel and AMD only]
699 By default the kernel will trim any uncacheable
700 memory out of your available memory pool based on
701 MTRR settings. This parameter disables that behavior,
702 possibly causing your machine to run very slowly.
704 disable_timer_pin_1 [X86]
705 Disable PIN 1 of APIC timer
706 Can be useful to work around chipset bugs.
708 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
709 this option disables the debugging code at boot.
711 dma_debug_entries=<number>
712 This option allows to tune the number of preallocated
713 entries for DMA-API debugging code. One entry is
714 required per DMA-API allocation. Use this if the
715 DMA-API debugging code disables itself because the
716 architectural default is too low.
718 dma_debug_driver=<driver_name>
719 With this option the DMA-API debugging driver
720 filter feature can be enabled at boot time. Just
721 pass the driver to filter for as the parameter.
722 The filter can be disabled or changed to another
723 driver later using sysfs.
725 drm_kms_helper.edid_firmware=[<connector>:]<file>
726 Broken monitors, graphic adapters and KVMs may
727 send no or incorrect EDID data sets. This parameter
728 allows to specify an EDID data set in the
729 /lib/firmware directory that is used instead.
730 Generic built-in EDID data sets are used, if one of
731 edid/1024x768.bin, edid/1280x1024.bin,
732 edid/1680x1050.bin, or edid/1920x1080.bin is given
733 and no file with the same name exists. Details and
734 instructions how to build your own EDID data are
735 available in Documentation/EDID/HOWTO.txt. An EDID
736 data set will only be used for a particular connector,
737 if its name and a colon are prepended to the EDID
742 earlycon= [KNL] Output early console device and options.
743 uart[8250],io,<addr>[,options]
744 uart[8250],mmio,<addr>[,options]
745 uart[8250],mmio32,<addr>[,options]
746 Start an early, polled-mode console on the 8250/16550
747 UART at the specified I/O port or MMIO address.
748 MMIO inter-register address stride is either 8-bit
749 (mmio) or 32-bit (mmio32).
750 The options are the same as for ttyS, above.
752 earlyprintk= [X86,SH,BLACKFIN]
754 earlyprintk=serial[,ttySn[,baudrate]]
755 earlyprintk=ttySn[,baudrate]
756 earlyprintk=dbgp[debugController#]
758 Append ",keep" to not disable it when the real console
761 Only vga or serial or usb debug port at a time.
763 Currently only ttyS0 and ttyS1 are supported.
765 Interaction with the standard serial driver is not
768 The VGA output is eventually overwritten by the real
771 ekgdboc= [X86,KGDB] Allow early kernel console debugging
774 This is designed to be used in conjunction with
775 the boot argument: earlyprintk=vga
778 Format: {"off" | "on" | "skip[mbr]"}
780 eisa_irq_edge= [PARISC,HW]
781 See header of drivers/parisc/eisa.c.
784 See comment before function elanfreq_setup() in
785 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
788 Format: {"cfq" | "deadline" | "noop"}
789 See Documentation/block/cfq-iosched.txt and
790 Documentation/block/deadline-iosched.txt for details.
792 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
793 Specifies physical address of start of kernel core
794 image elf header and optionally the size. Generally
795 kexec loader will pass this option to capture kernel.
796 See Documentation/kdump/kdump.txt for details.
798 enable_mtrr_cleanup [X86]
799 The kernel tries to adjust MTRR layout from continuous
800 to discrete, to make X server driver able to add WB
801 entry later. This parameter enables that.
803 enable_timer_pin_1 [X86]
804 Enable PIN 1 of APIC timer
805 Can be useful to work around chipset bugs
806 (in particular on some ATI chipsets).
807 The kernel tries to set a reasonable default.
809 enforcing [SELINUX] Set initial enforcing status.
811 See security/selinux/Kconfig help text.
812 0 -- permissive (log only, no denials).
813 1 -- enforcing (deny and log).
815 Value can be changed at runtime via /selinux/enforce.
818 Disable Error Record Serialization Table (ERST)
821 ether= [HW,NET] Ethernet cards parameters
822 This option is obsoleted by the "netdev=" option, which
823 has equivalent usage. See its documentation for details.
827 Permit 'security.evm' to be updated regardless of
828 current integrity status.
832 fail_make_request=[KNL]
833 General fault injection mechanism.
834 Format: <interval>,<probability>,<space>,<times>
835 See also Documentation/fault-injection/.
838 See Documentation/blockdev/floppy.txt.
840 force_pal_cache_flush
841 [IA-64] Avoid check_sal_cache_flush which may hang on
842 buggy SAL_CACHE_FLUSH implementations. Using this
843 parameter will force ia64_sal_cache_flush to call
844 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
847 [FTRACE] will set and start the specified tracer
848 as early as possible in order to facilitate early
851 ftrace_dump_on_oops[=orig_cpu]
852 [FTRACE] will dump the trace buffers on oops.
853 If no parameter is passed, ftrace will dump
854 buffers of all CPUs, but if you pass orig_cpu, it will
855 dump only the buffer of the CPU that triggered the
858 ftrace_filter=[function-list]
859 [FTRACE] Limit the functions traced by the function
860 tracer at boot up. function-list is a comma separated
861 list of functions. This list can be changed at run
862 time by the set_ftrace_filter file in the debugfs
865 ftrace_notrace=[function-list]
866 [FTRACE] Do not trace the functions specified in
867 function-list. This list can be changed at run time
868 by the set_ftrace_notrace file in the debugfs
871 ftrace_graph_filter=[function-list]
872 [FTRACE] Limit the top level callers functions traced
873 by the function graph tracer at boot up.
874 function-list is a comma separated list of functions
875 that can be changed at run time by the
876 set_graph_function file in the debugfs tracing directory.
879 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
880 support via parallel port (up to 5 devices per port)
881 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
882 See also Documentation/input/joystick-parport.txt
886 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
890 gcov_persist= [GCOV] When non-zero (default), profiling data for
891 kernel modules is saved and remains accessible via
892 debugfs, even when the module is unloaded/reloaded.
893 When zero, profiling data is discarded and associated
894 debugfs files are removed at module unload time.
896 gpt [EFI] Forces disk with valid GPT signature but
897 invalid Protective MBR to be treated as GPT.
899 hashdist= [KNL,NUMA] Large hashes allocated during boot
900 are distributed across NUMA nodes. Defaults on
901 for 64-bit NUMA, off otherwise.
902 Format: 0 | 1 (for off | on)
904 hcl= [IA-64] SGI's Hardware Graph compatibility layer
906 hd= [EIDE] (E)IDE hard drive subsystem geometry
907 Format: <cyl>,<head>,<sect>
910 Disable Hardware Error Source Table (HEST) support;
911 corresponding firmware-first mode error processing
912 logic will be disabled.
914 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
915 size of <nn>. This works even on boxes that have no
916 highmem otherwise. This also works to reduce highmem
917 size on bigger boxes.
919 highres= [KNL] Enable/disable high resolution timer mode.
920 Valid parameters: "on", "off"
924 See Documentation/isdn/README.HiSax.
928 hpet= [X86-32,HPET] option to control HPET usage
929 Format: { enable (default) | disable | force |
931 disable: disable HPET and use PIT instead
932 force: allow force enabled of undocumented chips (ICH4,
934 verbose: show contents of HPET registers during setup
936 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
937 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
938 On x86-64 and powerpc, this option can be specified
939 multiple times interleaved with hugepages= to reserve
940 huge pages of different sizes. Valid pages sizes on
941 x86-64 are 2M (when the CPU supports "pse") and 1G
942 (when the CPU supports the "pdpe1gb" cpuinfo flag)
943 Note that 1GB pages can only be allocated at boot time
944 using hugepages= and not freed afterwards.
946 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
947 terminal devices. Valid values: 0..8
948 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
949 If specified, z/VM IUCV HVC accepts connections
950 from listed z/VM user IDs only.
953 Do not unregister boot console at start. This is only
954 useful for debugging when something happens in the window
955 between unregistering the boot console and initializing
958 i2c_bus= [HW] Override the default board specific I2C bus speed
959 or register an additional I2C bus that is not
960 registered from board initialization code.
964 i8042.debug [HW] Toggle i8042 debug mode
965 i8042.direct [HW] Put keyboard port into non-translated mode
966 i8042.dumbkbd [HW] Pretend that controller can only read data from
967 keyboard and cannot control its state
968 (Don't attempt to blink the leds)
969 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
970 i8042.nokbd [HW] Don't check/create keyboard port
971 i8042.noloop [HW] Disable the AUX Loopback command while probing
973 i8042.nomux [HW] Don't check presence of an active multiplexing
975 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
977 i8042.notimeout [HW] Ignore timeout condition signalled by controller
978 i8042.reset [HW] Reset the controller during init and cleanup
979 i8042.unlock [HW] Unlock (ignore) the keylock
983 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
984 indicates that the driver is running on unsupported
986 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
987 does not match list of supported models.
989 [HW] Report power status in /proc/i8k
990 (disabled by default)
991 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
995 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
997 ide-core.nodma= [HW] (E)IDE subsystem
998 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
999 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1000 .cdrom .chs .ignore_cable are additional options
1001 See Documentation/ide/ide.txt.
1003 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1004 Claim all unknown PCI IDE storage controllers.
1007 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1008 Poll forces a polling idle loop that can slightly
1009 improve the performance of waking up a idle CPU, but
1010 will use a lot of power and make the system run hot.
1012 idle=mwait: On systems which support MONITOR/MWAIT but
1013 the kernel chose to not use it because it doesn't save
1014 as much power as a normal idle loop, use the
1015 MONITOR/MWAIT idle loop anyways. Performance should be
1016 the same as idle=poll.
1017 idle=halt: Halt is forced to be used for CPU idle.
1018 In such case C2/C3 won't be used again.
1019 idle=nomwait: Disable mwait for CPU C-states
1021 ignore_loglevel [KNL]
1022 Ignore loglevel setting - this will print /all/
1023 kernel messages to the console. Useful for debugging.
1024 We also add it as printk module parameter, so users
1025 could change it dynamically, usually by
1026 /sys/module/printk/parameters/ignore_loglevel.
1028 ihash_entries= [KNL]
1029 Set number of hash buckets for inode cache.
1032 Format: { "0" | "1" }
1033 0 -- integrity auditing messages. (Default)
1034 1 -- enable informational integrity auditing messages.
1037 Format: { "sha1" | "md5" }
1041 Load a policy which meets the needs of the Trusted
1042 Computing Base. This means IMA will measure all
1043 programs exec'd, files mmap'd for exec, and all files
1044 opened for read by uid=0.
1048 Run specified binary instead of /sbin/init as init
1051 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1052 for working out where the kernel is dying during
1055 initrd= [BOOT] Specify the location of the initial ramdisk
1057 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1060 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1062 Enable intel iommu driver.
1064 Disable intel iommu driver.
1065 igfx_off [Default Off]
1066 By default, gfx is mapped as normal device. If a gfx
1067 device has a dedicated DMAR unit, the DMAR unit is
1068 bypassed by not enabling DMAR with this option. In
1069 this case, gfx device will use physical address for
1072 With this option iommu will not optimize to look
1073 for io virtual address below 32-bit forcing dual
1074 address cycle on pci bus for cards supporting greater
1075 than 32-bit addressing. The default is to look
1076 for translation below 32-bit and if not available
1077 then look in the higher range.
1078 strict [Default Off]
1079 With this option on every unmap_single operation will
1080 result in a hardware IOTLB flush operation as opposed
1081 to batching them for performance.
1082 sp_off [Default Off]
1083 By default, super page will be supported if Intel IOMMU
1084 has the capability. With this option, super page will
1087 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1088 0 disables intel_idle and fall back on acpi_idle.
1089 1 to 6 specify maximum depth of C-state.
1091 intremap= [X86-64, Intel-IOMMU]
1092 on enable Interrupt Remapping (default)
1093 off disable Interrupt Remapping
1094 nosid disable Source ID checking
1096 BIOS x2APIC opt-out request will be ignored
1098 iomem= Disable strict checking of access to MMIO memory
1099 strict regions from userspace.
1114 group_mf [x86, IA-64]
1117 io7= [HW] IO7 for Marvel based alpha systems
1118 See comment before marvel_specify_io7 in
1119 arch/alpha/kernel/core_marvel.c.
1121 io_delay= [X86] I/O delay method
1123 Standard port 0x80 based delay
1125 Alternate port 0xed based delay (needed on some systems)
1127 Simple two microseconds delay
1132 See Documentation/filesystems/nfs/nfsroot.txt.
1134 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1135 See comment before ip2_setup() in
1136 drivers/char/ip2/ip2base.c.
1139 When an interrupt is not handled search all handlers
1140 for it. Intended to get systems with badly broken
1144 When an interrupt is not handled search all handlers
1145 for it. Also check all handlers each timer
1146 interrupt. Intended to get systems with badly broken
1150 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1152 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1154 <cpu number>,...,<cpu number>
1156 <cpu number>-<cpu number>
1157 (must be a positive range in ascending order)
1159 <cpu number>,...,<cpu number>-<cpu number>
1161 This option can be used to specify one or more CPUs
1162 to isolate from the general SMP balancing and scheduling
1163 algorithms. You can move a process onto or off an
1164 "isolated" CPU via the CPU affinity syscalls or cpuset.
1165 <cpu number> begins at 0 and the maximum value is
1166 "number of CPUs in system - 1".
1168 This option is the preferred way to isolate CPUs. The
1169 alternative -- manually setting the CPU mask of all
1170 tasks in the system -- can cause problems and
1171 suboptimal load balancer performance.
1175 js= [HW,JOY] Analog joystick
1176 See Documentation/input/joystick.txt.
1180 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1181 specifies the amount of memory usable by the kernel
1182 for non-movable allocations. The requested amount is
1183 spread evenly throughout all nodes in the system. The
1184 remaining memory in each node is used for Movable
1185 pages. In the event, a node is too small to have both
1186 kernelcore and Movable pages, kernelcore pages will
1187 take priority and other nodes will have a larger number
1188 of kernelcore pages. The Movable zone is used for the
1189 allocation of pages that may be reclaimed or moved
1190 by the page migration subsystem. This means that
1191 HugeTLB pages may not be allocated from this zone.
1192 Note that allocations like PTEs-from-HighMem still
1193 use the HighMem zone if it exists, and the Normal
1194 zone if it does not.
1196 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1197 Format: <Controller#>[,poll interval]
1198 The controller # is the number of the ehci usb debug
1199 port as it is probed via PCI. The poll interval is
1200 optional and is the number seconds in between
1201 each poll cycle to the debug port in case you need
1202 the functionality for interrupting the kernel with
1203 gdb or control-c on the dbgp connection. When
1204 not using this parameter you use sysrq-g to break into
1205 the kernel debugger.
1207 kgdboc= [KGDB,HW] kgdb over consoles.
1208 Requires a tty driver that supports console polling,
1209 or a supported polling keyboard driver (non-usb).
1210 Serial only format: <serial_device>[,baud]
1211 keyboard only format: kbd
1212 keyboard and serial format: kbd,<serial_device>[,baud]
1213 Optional Kernel mode setting:
1214 kms, kbd format: kms,kbd
1215 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1217 kgdbwait [KGDB] Stop kernel execution and enter the
1218 kernel debugger at the earliest opportunity.
1220 kmac= [MIPS] korina ethernet MAC address.
1221 Configure the RouterBoard 532 series on-chip
1222 Ethernet adapter MAC address.
1224 kmemleak= [KNL] Boot-time kmemleak enable/disable
1225 Valid arguments: on, off
1228 kstack=N [X86] Print N words from the kernel stack
1231 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1232 Default is 0 (don't ignore, but inject #GP)
1234 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1238 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1239 Default is 1 (enabled)
1241 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1243 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1245 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1246 (virtualized MMU) support on capable Intel chips.
1247 Default is 1 (enabled)
1249 kvm-intel.emulate_invalid_guest_state=
1250 [KVM,Intel] Enable emulation of invalid guest states
1251 Default is 0 (disabled)
1253 kvm-intel.flexpriority=
1254 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1255 Default is 1 (enabled)
1258 [KVM,Intel] Enable VMX nesting (nVMX).
1259 Default is 0 (disabled)
1261 kvm-intel.unrestricted_guest=
1262 [KVM,Intel] Disable unrestricted guest feature
1263 (virtualized real and unpaged mode) on capable
1264 Intel chips. Default is 1 (enabled)
1266 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1267 feature (tagged TLBs) on capable Intel chips.
1268 Default is 1 (enabled)
1274 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1277 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1280 libata.dma= [LIBATA] DMA control
1281 libata.dma=0 Disable all PATA and SATA DMA
1282 libata.dma=1 PATA and SATA Disk DMA only
1283 libata.dma=2 ATAPI (CDROM) DMA only
1284 libata.dma=4 Compact Flash DMA only
1285 Combinations also work, so libata.dma=3 enables DMA
1286 for disks and CDROMs, but not CFs.
1288 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1289 libata.ignore_hpa=0 keep BIOS limits (default)
1290 libata.ignore_hpa=1 ignore limits, using full disk
1292 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1296 libata.force= [LIBATA] Force configurations. The format is comma
1297 separated list of "[ID:]VAL" where ID is
1298 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1299 matching port, link or device. Basically, it matches
1300 the ATA ID string printed on console by libata. If
1301 the whole ID part is omitted, the last PORT and DEVICE
1302 values are used. If ID hasn't been specified yet, the
1303 configuration applies to all ports, links and devices.
1305 If only DEVICE is omitted, the parameter applies to
1306 the port and all links and devices behind it. DEVICE
1307 number of 0 either selects the first device or the
1308 first fan-out link behind PMP device. It does not
1309 select the host link. DEVICE number of 15 selects the
1310 host link and device attached to it.
1312 The VAL specifies the configuration to force. As long
1313 as there's no ambiguity shortcut notation is allowed.
1314 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1315 The following configurations can be forced.
1317 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1318 Any ID with matching PORT is used.
1320 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1322 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1323 udma[/][16,25,33,44,66,100,133] notation is also
1326 * [no]ncq: Turn on or off NCQ.
1328 * nohrst, nosrst, norst: suppress hard, soft
1331 * dump_id: dump IDENTIFY data.
1333 If there are multiple matching configurations changing
1334 the same attribute, the last one is used.
1336 memblock=debug [KNL] Enable memblock debug messages.
1338 load_ramdisk= [RAM] List of ramdisks to load from floppy
1339 See Documentation/blockdev/ramdisk.txt.
1341 lockd.nlm_grace_period=P [NFS] Assign grace period.
1344 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1347 lockd.nlm_timeout=T [NFS] Assign timeout value.
1350 lockd.nlm_udpport=M [NFS] Assign UDP port.
1353 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1356 loglevel= All Kernel Messages with a loglevel smaller than the
1357 console loglevel will be printed to the console. It can
1358 also be changed with klogd or other programs. The
1359 loglevels are defined as follows:
1361 0 (KERN_EMERG) system is unusable
1362 1 (KERN_ALERT) action must be taken immediately
1363 2 (KERN_CRIT) critical conditions
1364 3 (KERN_ERR) error conditions
1365 4 (KERN_WARNING) warning conditions
1366 5 (KERN_NOTICE) normal but significant condition
1367 6 (KERN_INFO) informational
1368 7 (KERN_DEBUG) debug-level messages
1370 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1371 in bytes. n must be a power of two. The default
1372 size is set in the kernel config file.
1374 logo.nologo [FB] Disables display of the built-in Linux logo.
1375 This may be used to provide more screen space for
1376 kernel log messages and is useful when debugging
1377 kernel boot problems.
1379 lp=0 [LP] Specify parallel ports to use, e.g,
1380 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1381 lp=reset first parallel port). 'lp=0' disables the
1382 lp=auto printer driver. 'lp=reset' (which can be
1383 specified in addition to the ports) causes
1384 attached printers to be reset. Using
1385 lp=port1,port2,... specifies the parallel ports
1386 to associate lp devices with, starting with
1387 lp0. A port specification may be 'none' to skip
1388 that lp device, or a parport name such as
1389 'parport0'. Specifying 'lp=auto' instead of a
1390 port specification list means that device IDs
1391 from each port should be examined, to see if
1392 an IEEE 1284-compliant printer is attached; if
1393 so, the driver will manage that printer.
1394 See also header of drivers/char/lp.c.
1397 Sets loops_per_jiffy to given constant, thus avoiding
1398 time-consuming boot-time autodetection (up to 250 ms per
1399 CPU). 0 enables autodetection (default). To determine
1400 the correct value for your kernel, boot with normal
1401 autodetection and see what value is printed. Note that
1402 on SMP systems the preset will be applied to all CPUs,
1403 which is likely to cause problems if your CPUs need
1404 significantly divergent settings. An incorrect value
1405 will cause delays in the kernel to be wrong, leading to
1406 unpredictable I/O errors and other breakage. Although
1407 unlikely, in the extreme case this might damage your
1411 Format: <io>,<irq>,<dma>
1413 machvec= [IA-64] Force the use of a particular machine-vector
1414 (machvec) in a generic kernel.
1415 Example: machvec=hpzx1_swiotlb
1417 machtype= [Loongson] Share the same kernel image file between different
1419 Example: machtype=lemote-yeeloong-2f-7inch
1421 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1422 than or equal to this physical address is ignored.
1424 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1425 should make use of. maxcpus=n : n >= 0 limits the
1426 kernel to using 'n' processors. n=0 is a special case,
1427 it is equivalent to "nosmp", which also disables
1430 max_loop= [LOOP] The number of loop block devices that get
1431 (loop.max_loop) unconditionally pre-created at init time. The default
1432 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1433 of statically allocating a predefined number, loop
1434 devices can be requested on-demand with the
1435 /dev/loop-control interface.
1439 mce [X86-32] Machine Check Exception
1441 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1443 md= [HW] RAID subsystems devices and level
1444 See Documentation/md.txt.
1447 Format: <first>,<last>
1448 Specifies range of consoles to be captured by the MDA.
1450 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1451 Amount of memory to be used when the kernel is not able
1452 to see the whole system memory or for test.
1453 [X86-32] Use together with memmap= to avoid physical
1454 address space collisions. Without memmap= PCI devices
1455 could be placed at addresses belonging to unused RAM.
1457 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1461 [KNL,SH] Allow user to override the default size for
1462 per-device physically contiguous DMA buffers.
1464 memmap=exactmap [KNL,X86] Enable setting of an exact
1465 E820 memory map, as specified by the user.
1466 Such memmap=exactmap lines can be constructed based on
1467 BIOS output or other requirements. See the memmap=nn@ss
1470 memmap=nn[KMG]@ss[KMG]
1471 [KNL] Force usage of a specific region of memory
1472 Region of memory to be used, from ss to ss+nn.
1474 memmap=nn[KMG]#ss[KMG]
1475 [KNL,ACPI] Mark specific memory as ACPI data.
1476 Region of memory to be used, from ss to ss+nn.
1478 memmap=nn[KMG]$ss[KMG]
1479 [KNL,ACPI] Mark specific memory as reserved.
1480 Region of memory to be used, from ss to ss+nn.
1481 Example: Exclude memory from 0x18690000-0x1869ffff
1482 memmap=64K$0x18690000
1484 memmap=0x10000$0x18690000
1486 memory_corruption_check=0/1 [X86]
1487 Some BIOSes seem to corrupt the first 64k of
1488 memory when doing things like suspend/resume.
1489 Setting this option will scan the memory
1490 looking for corruption. Enabling this will
1491 both detect corruption and prevent the kernel
1492 from using the memory being corrupted.
1493 However, its intended as a diagnostic tool; if
1494 repeatable BIOS-originated corruption always
1495 affects the same memory, you can use memmap=
1496 to prevent the kernel from using that memory.
1498 memory_corruption_check_size=size [X86]
1499 By default it checks for corruption in the low
1500 64k, making this memory unavailable for normal
1501 use. Use this parameter to scan for
1502 corruption in more or less memory.
1504 memory_corruption_check_period=seconds [X86]
1505 By default it checks for corruption every 60
1506 seconds. Use this parameter to check at some
1507 other rate. 0 disables periodic checking.
1509 memtest= [KNL,X86] Enable memtest
1511 default : 0 <disable>
1512 Specifies the number of memtest passes to be
1513 performed. Each pass selects another test
1514 pattern from a given set of patterns. Memtest
1515 fills the memory with this pattern, validates
1516 memory contents and reserves bad memory
1517 regions that are detected.
1519 meye.*= [HW] Set MotionEye Camera parameters
1520 See Documentation/video4linux/meye.txt.
1522 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1523 Multi-Function General Purpose Timers on AMD Geode
1526 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1527 the BIOS has incorrectly applied a workaround. TinyBIOS
1528 version 0.98 is known to be affected, 0.99 fixes the
1529 problem by letting the user disable the workaround.
1533 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1534 physical address is ignored.
1536 mini2440= [ARM,HW,KNL]
1537 Format:[0..2][b][c][t]
1539 MINI2440 configuration specification:
1540 0 - The attached screen is the 3.5" TFT
1541 1 - The attached screen is the 7" TFT
1542 2 - The VGA Shield is attached (1024x768)
1543 Leaving out the screen size parameter will not load
1544 the TFT driver, and the framebuffer will be left
1546 b - Enable backlight. The TFT backlight pin will be
1547 linked to the kernel VESA blanking code and a GPIO
1548 LED. This parameter is not necessary when using the
1550 c - Enable the s3c camera interface.
1551 t - Reserved for enabling touchscreen support. The
1552 touchscreen support is not enabled in the mainstream
1553 kernel as of 2.6.30, a preliminary port can be found
1554 in the "bleeding edge" mini2440 support kernel at
1555 http://repo.or.cz/w/linux-2.6/mini2440.git
1558 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1559 parameter allows control of the logging verbosity for
1560 the additional memory initialisation checks. A value
1561 of 0 disables mminit logging and a level of 4 will
1562 log everything. Information is printed at KERN_DEBUG
1563 so loglevel=8 may also need to be specified.
1566 [MOUSE] Maximum time between finger touching and
1567 leaving touchpad surface for touch to be considered
1568 a tap and be reported as a left button click (for
1569 touchpads working in absolute mode only).
1571 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1572 reporting absolute coordinates, such as tablets
1573 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1574 reporting absolute coordinates, such as tablets
1576 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1577 is similar to kernelcore except it specifies the
1578 amount of memory used for migratable allocations.
1579 If both kernelcore and movablecore is specified,
1580 then kernelcore will be at *least* the specified
1581 value but may be more. If movablecore on its own
1582 is specified, the administrator must be careful
1583 that the amount of memory usable for all allocations
1586 MTD_Partition= [MTD]
1587 Format: <name>,<region-number>,<size>,<offset>
1589 MTD_Region= [MTD] Format:
1590 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1593 See drivers/mtd/cmdlinepart.c.
1595 multitce=off [PPC] This parameter disables the use of the pSeries
1596 firmware feature for updating multiple TCE entries
1599 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1601 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1603 boundary - index of last SLC block on Flex-OneNAND.
1604 The remaining blocks are configured as MLC blocks.
1605 lock - Configure if Flex-OneNAND boundary should be locked.
1606 Once locked, the boundary cannot be changed.
1607 1 indicates lock status, 0 indicates unlock status.
1610 ARM/S3C2412 JIVE boot control
1612 See arch/arm/mach-s3c2412/mach-jive.c
1614 mtouchusb.raw_coordinates=
1615 [HW] Make the MicroTouch USB driver use raw coordinates
1616 ('y', default) or cooked coordinates ('n')
1618 mtrr_chunk_size=nn[KMG] [X86]
1619 used for mtrr cleanup. It is largest continuous chunk
1620 that could hold holes aka. UC entries.
1622 mtrr_gran_size=nn[KMG] [X86]
1623 Used for mtrr cleanup. It is granularity of mtrr block.
1625 Large value could prevent small alignment from
1628 mtrr_spare_reg_nr=n [X86]
1630 Range: 0,7 : spare reg number
1632 Used for mtrr cleanup. It is spare mtrr entries number.
1633 Set to 2 or more if your graphical card needs more.
1635 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1637 netdev= [NET] Network devices parameters
1638 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1639 Note that mem_start is often overloaded to mean
1640 something different and driver-specific.
1641 This usage is only documented in each driver source
1645 [NETFILTER] Enable connection tracking flow accounting
1646 0 to disable accounting
1647 1 to enable accounting
1650 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1651 See Documentation/filesystems/nfs/nfsroot.txt.
1653 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1654 See Documentation/filesystems/nfs/nfsroot.txt.
1656 nfsrootdebug [NFS] enable nfsroot debugging messages.
1657 See Documentation/filesystems/nfs/nfsroot.txt.
1659 nfs.callback_tcpport=
1660 [NFS] set the TCP port on which the NFSv4 callback
1661 channel should listen.
1664 [NFS] sets the pathname to the program which is used
1665 to update the NFS client cache entries.
1667 nfs.cache_getent_timeout=
1668 [NFS] sets the timeout after which an attempt to
1669 update a cache entry is deemed to have failed.
1671 nfs.idmap_cache_timeout=
1672 [NFS] set the maximum lifetime for idmapper cache
1676 [NFS] enable 64-bit inode numbers.
1677 If zero, the NFS client will fake up a 32-bit inode
1678 number for the readdir() and stat() syscalls instead
1679 of returning the full 64-bit number.
1680 The default is to return 64-bit inode numbers.
1682 nfs.max_session_slots=
1683 [NFSv4.1] Sets the maximum number of session slots
1684 the client will attempt to negotiate with the server.
1685 This limits the number of simultaneous RPC requests
1686 that the client can send to the NFSv4.1 server.
1687 Note that there is little point in setting this
1688 value higher than the max_tcp_slot_table_limit.
1690 nfs.nfs4_disable_idmapping=
1691 [NFSv4] When set to the default of '1', this option
1692 ensures that both the RPC level authentication
1693 scheme and the NFS level operations agree to use
1694 numeric uids/gids if the mount is using the
1695 'sec=sys' security flavour. In effect it is
1696 disabling idmapping, which can make migration from
1697 legacy NFSv2/v3 systems to NFSv4 easier.
1698 Servers that do not support this mode of operation
1699 will be autodetected by the client, and it will fall
1700 back to using the idmapper.
1701 To turn off this behaviour, set the value to '0'.
1703 nfs.send_implementation_id =
1704 [NFSv4.1] Send client implementation identification
1705 information in exchange_id requests.
1706 If zero, no implementation identification information
1708 The default is to send the implementation identification
1711 nfsd.nfs4_disable_idmapping=
1712 [NFSv4] When set to the default of '1', the NFSv4
1713 server will return only numeric uids and gids to
1714 clients using auth_sys, and will accept numeric uids
1715 and gids from such clients. This is intended to ease
1716 migration from NFSv2/v3.
1718 objlayoutdriver.osd_login_prog=
1719 [NFS] [OBJLAYOUT] sets the pathname to the program which
1720 is used to automatically discover and login into new
1721 osd-targets. Please see:
1722 Documentation/filesystems/pnfs.txt for more explanations
1724 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1725 when a NMI is triggered.
1726 Format: [state][,regs][,debounce][,die]
1728 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1729 Format: [panic,][nopanic,][num]
1731 0 - turn nmi_watchdog off
1732 When panic is specified, panic when an NMI watchdog
1733 timeout occurs (or 'nopanic' to override the opposite
1735 This is useful when you use a panic=... timeout and
1736 need the box quickly up again.
1738 netpoll.carrier_timeout=
1739 [NET] Specifies amount of time (in seconds) that
1740 netpoll should wait for a carrier. By default netpoll
1743 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1744 emulation library even if a 387 maths coprocessor
1748 [HW] Never suspend the console
1749 Disable suspending of consoles during suspend and
1750 hibernate operations. Once disabled, debugging
1751 messages can reach various consoles while the rest
1752 of the system is being put to sleep (ie, while
1753 debugging driver suspend/resume hooks). This may
1754 not work reliably with all consoles, but is known
1755 to work with serial and VGA consoles.
1756 To facilitate more flexible debugging, we also add
1757 console_suspend, a printk module parameter to control
1758 it. Users could use console_suspend (usually
1759 /sys/module/printk/parameters/console_suspend) to
1760 turn on/off it dynamically.
1762 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1763 caches in the slab allocator. Saves per-node memory,
1764 but will impact performance.
1768 noapic [SMP,APIC] Tells the kernel to not make use of any
1769 IOAPICs that may be present in the system.
1771 noautogroup Disable scheduler automatic task group creation.
1773 nobats [PPC] Do not use BATs for mapping kernel lowmem
1774 on "Classic" PPC cores.
1778 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1780 nodelayacct [KNL] Disable per-task delay accounting
1782 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1784 nodsp [SH] Disable hardware DSP at boot time.
1786 noefi [X86] Disable EFI runtime services support.
1791 On X86-32 available only on PAE configured kernels.
1792 noexec=on: enable non-executable mappings (default)
1793 noexec=off: disable non-executable mappings
1796 Disable SMEP (Supervisor Mode Execution Protection)
1797 even if it is supported by processor.
1800 This affects only 32-bit executables.
1801 noexec32=on: enable non-executable mappings (default)
1802 read doesn't imply executable mappings
1803 noexec32=off: disable non-executable mappings
1804 read implies executable mappings
1806 nofpu [SH] Disable hardware FPU at boot time.
1808 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1809 register save and restore. The kernel will only save
1810 legacy floating-point registers on task switch.
1812 noxsave [BUGS=X86] Disables x86 extended register state save
1813 and restore using xsave. The kernel will fallback to
1814 enabling legacy floating-point and sse state.
1816 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1817 wfi(ARM) instruction doesn't work correctly and not to
1818 use it. This is also useful when using JTAG debugger.
1820 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1821 instruction doesn't work correctly and not to
1824 no_file_caps Tells the kernel not to honor file capabilities. The
1825 only way then for a file to be executed with privilege
1826 is to be setuid root or executed by root.
1828 nohalt [IA-64] Tells the kernel not to use the power saving
1829 function PAL_HALT_LIGHT when idle. This increases
1830 power-consumption. On the positive side, it reduces
1831 interrupt wake-up latency, which may improve performance
1832 in certain environments such as networked servers or
1835 nohz= [KNL] Boottime enable/disable dynamic ticks
1836 Valid arguments: on, off
1839 noiotrap [SH] Disables trapped I/O port accesses.
1841 noirqdebug [X86-32] Disables the code which attempts to detect and
1842 disable unhandled interrupt sources.
1844 no_timer_check [X86,APIC] Disables the code which tests for
1845 broken timer IRQ sources.
1847 noisapnp [ISAPNP] Disables ISA PnP code.
1849 noinitrd [RAM] Tells the kernel not to load any configured
1852 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1854 [Deprecated - use intremap=off]
1858 nojitter [IA-64] Disables jitter checking for ITC timers.
1860 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1862 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1865 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1866 steal time is computed, but won't influence scheduler
1869 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1871 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1873 noltlbs [PPC] Do not use large page/tlb entries for kernel
1874 lowmem mapping on PPC40x.
1876 nomca [IA-64] Disable machine check abort handling
1878 nomce [X86-32] Machine Check Exception
1880 nomfgpt [X86-32] Disable Multi-Function General Purpose
1881 Timer usage (for AMD Geode machines).
1883 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1884 shutdown the other cpus. Instead use the REBOOT_VECTOR
1887 nomodule Disable module load
1889 nopat [X86] Disable PAT (page attribute table extension of
1890 pagetables) support.
1892 norandmaps Don't use address space randomization. Equivalent to
1893 echo 0 > /proc/sys/kernel/randomize_va_space
1895 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1897 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1898 with UP alternatives
1900 noresidual [PPC] Don't use residual data on PReP machines.
1902 nordrand [X86] Disable the direct use of the RDRAND
1903 instruction even if it is supported by the
1904 processor. RDRAND is still available to user
1907 noresume [SWSUSP] Disables resume and restores original swap
1910 no-scroll [VGA] Disables scrollback.
1911 This is required for the Braillex ib80-piezo Braille
1912 reader made by F.H. Papenmeier (Germany).
1916 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1918 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1919 and disable the IO APIC. legacy for "maxcpus=0".
1921 nosoftlockup [KNL] Disable the soft-lockup detector.
1923 nosync [HW,M68K] Disables sync negotiation for all devices.
1925 notsc [BUGS=X86-32] Disable Time Stamp Counter
1927 nousb [USB] Disable the USB subsystem
1929 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1933 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1935 nptcg= [IA-64] Override max number of concurrent global TLB
1936 purges which is reported from either PAL_VM_SUMMARY or
1939 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1940 could support. nr_cpus=n : n >= 1 limits the kernel to
1941 supporting 'n' processors. Later in runtime you can not
1942 use hotplug cpu feature to put more cpu back to online.
1943 just like you compile the kernel NR_CPUS=n
1945 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1947 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1948 one of ['zone', 'node', 'default'] can be specified
1949 This can be set from sysctl after boot.
1950 See Documentation/sysctl/vm.txt for details.
1952 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1953 See Documentation/debugging-via-ohci1394.txt for more
1956 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1957 Rather than timing out after 20 ms if an EC
1958 command is not properly ACKed, override the length
1959 of the timeout. We have interrupts disabled while
1960 waiting for the ACK, so if this is set too high
1961 interrupts *may* be lost!
1963 omap_mux= [OMAP] Override bootloader pin multiplexing.
1964 Format: <mux_mode0.mode_name=value>...
1965 For example, to override I2C bus2:
1966 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1968 oprofile.timer= [HW]
1969 Use timer interrupt instead of performance counters
1971 oprofile.cpu_type= Force an oprofile cpu type
1972 This might be useful if you have an older oprofile
1973 userland or if you want common events.
1974 Format: { arch_perfmon }
1975 arch_perfmon: [X86] Force use of architectural
1976 perfmon on Intel CPUs instead of the
1977 CPU specific event set.
1978 timer: [X86] Force use of architectural NMI
1979 timer mode (see also oprofile.timer
1980 for generic hr timer mode)
1981 [s390] Force legacy basic mode sampling
1982 (report cpu_type "timer")
1984 oops=panic Always panic on oopses. Default is to just kill the
1985 process, but there is a small probability of
1986 deadlocking the machine.
1987 This will also cause panics on machine check exceptions.
1988 Useful together with panic=30 to trigger a reboot.
1991 See Documentation/sound/oss/oss-parameters.txt
1993 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1994 timeout > 0: seconds before rebooting
1995 timeout = 0: wait forever
1996 timeout < 0: reboot immediately
1999 parkbd.port= [HW] Parallel port number the keyboard adapter is
2000 connected to, default is 0.
2002 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2003 0 for XT, 1 for AT (default is AT).
2006 parport= [HW,PPT] Specify parallel ports. 0 disables.
2007 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2008 Use 'auto' to force the driver to use any
2009 IRQ/DMA settings detected (the default is to
2010 ignore detected IRQ/DMA settings because of
2011 possible conflicts). You can specify the base
2012 address, IRQ, and DMA settings; IRQ and DMA
2013 should be numbers, or 'auto' (for using detected
2014 settings on that particular port), or 'nofifo'
2015 (to avoid using a FIFO even if it is detected).
2016 Parallel ports are assigned in the order they
2017 are specified on the command line, starting
2020 parport_init_mode= [HW,PPT]
2021 Configure VIA parallel port to operate in
2022 a specific mode. This is necessary on Pegasos
2023 computer where firmware has no options for setting
2024 up parallel port mode and sets it to spp.
2025 Currently this function knows 686a and 8231 chips.
2026 Format: [spp|ps2|epp|ecp|ecpepp]
2029 Halt all CPUs after the first oops has been printed for
2030 the specified number of seconds. This is to be used if
2031 your oopses keep scrolling off the screen.
2036 See header of drivers/block/paride/pcd.c.
2037 See also Documentation/blockdev/paride.txt.
2039 pci=option[,option...] [PCI] various PCI subsystem options:
2040 earlydump [X86] dump PCI config space before the kernel
2042 off [X86] don't probe for the PCI bus
2043 bios [X86-32] force use of PCI BIOS, don't access
2044 the hardware directly. Use this if your machine
2045 has a non-standard PCI host bridge.
2046 nobios [X86-32] disallow use of PCI BIOS, only direct
2047 hardware access methods are allowed. Use this
2048 if you experience crashes upon bootup and you
2049 suspect they are caused by the BIOS.
2050 conf1 [X86] Force use of PCI Configuration
2052 conf2 [X86] Force use of PCI Configuration
2054 noaer [PCIE] If the PCIEAER kernel config parameter is
2055 enabled, this kernel boot option can be used to
2056 disable the use of PCIE advanced error reporting.
2057 nodomains [PCI] Disable support for multiple PCI
2058 root domains (aka PCI segments, in ACPI-speak).
2059 nommconf [X86] Disable use of MMCONFIG for PCI
2061 check_enable_amd_mmconf [X86] check for and enable
2062 properly configured MMIO access to PCI
2063 config space on AMD family 10h CPU
2064 nomsi [MSI] If the PCI_MSI kernel config parameter is
2065 enabled, this kernel boot option can be used to
2066 disable the use of MSI interrupts system-wide.
2067 noioapicquirk [APIC] Disable all boot interrupt quirks.
2068 Safety option to keep boot IRQs enabled. This
2069 should never be necessary.
2070 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2071 primary IO-APIC for bridges that cannot disable
2072 boot IRQs. This fixes a source of spurious IRQs
2073 when the system masks IRQs.
2074 noioapicreroute [APIC] Disable workaround that uses the
2075 boot IRQ equivalent of an IRQ that connects to
2076 a chipset where boot IRQs cannot be disabled.
2077 The opposite of ioapicreroute.
2078 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2079 routing table. These calls are known to be buggy
2080 on several machines and they hang the machine
2081 when used, but on other computers it's the only
2082 way to get the interrupt routing table. Try
2083 this option if the kernel is unable to allocate
2084 IRQs or discover secondary PCI buses on your
2086 rom [X86] Assign address space to expansion ROMs.
2087 Use with caution as certain devices share
2088 address decoders between ROMs and other
2090 norom [X86] Do not assign address space to
2091 expansion ROMs that do not already have
2092 BIOS assigned address ranges.
2093 nobar [X86] Do not assign address space to the
2094 BARs that weren't assigned by the BIOS.
2095 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2096 assigned automatically to PCI devices. You can
2097 make the kernel exclude IRQs of your ISA cards
2099 pirqaddr=0xAAAAA [X86] Specify the physical address
2100 of the PIRQ table (normally generated
2101 by the BIOS) if it is outside the
2102 F0000h-100000h range.
2103 lastbus=N [X86] Scan all buses thru bus #N. Can be
2104 useful if the kernel is unable to find your
2105 secondary buses and you want to tell it
2106 explicitly which ones they are.
2107 assign-busses [X86] Always assign all PCI bus
2108 numbers ourselves, overriding
2109 whatever the firmware may have done.
2110 usepirqmask [X86] Honor the possible IRQ mask stored
2111 in the BIOS $PIR table. This is needed on
2112 some systems with broken BIOSes, notably
2113 some HP Pavilion N5400 and Omnibook XE3
2114 notebooks. This will have no effect if ACPI
2115 IRQ routing is enabled.
2116 noacpi [X86] Do not use ACPI for IRQ routing
2117 or for PCI scanning.
2118 use_crs [X86] Use PCI host bridge window information
2119 from ACPI. On BIOSes from 2008 or later, this
2120 is enabled by default. If you need to use this,
2121 please report a bug.
2122 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2123 If you need to use this, please report a bug.
2124 routeirq Do IRQ routing for all PCI devices.
2125 This is normally done in pci_enable_device(),
2126 so this option is a temporary workaround
2127 for broken drivers that don't call it.
2128 skip_isa_align [X86] do not align io start addr, so can
2129 handle more pci cards
2130 firmware [ARM] Do not re-enumerate the bus but instead
2131 just use the configuration from the
2132 bootloader. This is currently used on
2133 IXP2000 systems where the bus has to be
2134 configured a certain way for adjunct CPUs.
2135 noearly [X86] Don't do any early type 1 scanning.
2136 This might help on some broken boards which
2137 machine check when some devices' config space
2138 is read. But various workarounds are disabled
2139 and some IOMMU drivers will not work.
2140 bfsort Sort PCI devices into breadth-first order.
2141 This sorting is done to get a device
2142 order compatible with older (<= 2.4) kernels.
2143 nobfsort Don't sort PCI devices into breadth-first order.
2144 cbiosize=nn[KMG] The fixed amount of bus space which is
2145 reserved for the CardBus bridge's IO window.
2146 The default value is 256 bytes.
2147 cbmemsize=nn[KMG] The fixed amount of bus space which is
2148 reserved for the CardBus bridge's memory
2149 window. The default value is 64 megabytes.
2152 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2153 Specifies alignment and device to reassign
2154 aligned memory resources.
2155 If <order of align> is not specified,
2156 PAGE_SIZE is used as alignment.
2157 PCI-PCI bridge can be specified, if resource
2158 windows need to be expanded.
2159 ecrc= Enable/disable PCIe ECRC (transaction layer
2160 end-to-end CRC checking).
2161 bios: Use BIOS/firmware settings. This is the
2165 realloc= Enable/disable reallocating PCI bridge resources
2166 if allocations done by BIOS are too small to
2167 accommodate resources required by all child
2169 off: Turn realloc off
2171 realloc same as realloc=on
2172 noari do not use PCIe ARI.
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 rcupdate.blimit= [KNL,BOOT]
2343 Set maximum number of finished RCU callbacks to process
2346 rcupdate.qhimark= [KNL,BOOT]
2347 Set threshold of queued
2348 RCU callbacks over which batch limiting is disabled.
2350 rcupdate.qlowmark= [KNL,BOOT]
2351 Set threshold of queued RCU callbacks below which
2352 batch limiting is re-enabled.
2356 Run specified binary instead of /init from the ramdisk,
2357 used for early userspace startup. See initrd.
2359 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2360 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2361 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2364 [KNL, SMP] Set scheduler's default relax_domain_level.
2365 See Documentation/cgroups/cpusets.txt.
2367 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2369 reservetop= [X86-32]
2371 Reserves a hole at the top of the kernel virtual
2376 Set the amount of memory to reserve for BIOS at
2377 the bottom of the address space.
2379 reset_devices [KNL] Force drivers to reset the underlying device
2380 during initialization.
2383 Specify the partition device for software suspend
2385 resume_offset= [SWSUSP]
2386 Specify the offset from the beginning of the partition
2387 given by "resume=" at which the swap header is located,
2388 in <PAGE_SIZE> units (needed only for swap files).
2389 See Documentation/power/swsusp-and-swap-files.txt
2391 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2392 read the resume files
2394 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2395 Useful for devices that are detected asynchronously
2396 (e.g. USB and MMC devices).
2398 hibernate= [HIBERNATION]
2399 noresume Don't check if there's a hibernation image
2400 present during boot.
2401 nocompress Don't compress/decompress hibernation images.
2403 retain_initrd [RAM] Keep initrd memory after extraction
2405 rhash_entries= [KNL,NET]
2406 Set number of hash buckets for route cache
2408 riscom8= [HW,SERIAL]
2409 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2411 ro [KNL] Mount root device read-only on boot
2413 root= [KNL] Root filesystem
2414 See name_to_dev_t comment in init/do_mounts.c.
2416 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2417 mount the root filesystem
2419 rootflags= [KNL] Set root filesystem mount option string
2421 rootfstype= [KNL] Set root filesystem type
2423 rootwait [KNL] Wait (indefinitely) for root device to show up.
2424 Useful for devices that are detected asynchronously
2425 (e.g. USB and MMC devices).
2427 rw [KNL] Mount root device read-write on boot
2429 S [KNL] Run init in single mode
2432 See drivers/net/irda/sa1100_ir.c.
2434 sbni= [NET] Granch SBNI12 leased line adapter
2436 sched_debug [KNL] Enables verbose scheduler debug messages.
2438 security= [SECURITY] Choose a security module to enable at boot.
2439 If this boot parameter is not specified, only the first
2440 security module asking for security registration will be
2441 loaded. An invalid security module name will be treated
2442 as if no module has been chosen.
2444 selinux= [SELINUX] Disable or enable SELinux at boot time.
2445 Format: { "0" | "1" }
2446 See security/selinux/Kconfig help text.
2449 Default value is set via kernel config option.
2450 If enabled at boot time, /selinux/disable can be used
2451 later to disable prior to initial policy load.
2453 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2454 Format: { "0" | "1" }
2455 See security/apparmor/Kconfig help text
2458 Default value is set via kernel config option.
2460 serialnumber [BUGS=X86-32]
2463 Maximal number of shapers.
2465 show_msr= [x86] show boot-time MSR settings
2466 Format: { <integer> }
2467 Show boot-time (BIOS-initialized) MSR settings.
2468 The parameter means the number of CPUs to show,
2469 for example 1 means boot CPU only.
2476 slab_max_order= [MM, SLAB]
2477 Determines the maximum allowed order for slabs.
2478 A high setting may cause OOMs due to memory
2479 fragmentation. Defaults to 1 for systems with
2480 more than 32MB of RAM, 0 otherwise.
2482 slub_debug[=options[,slabs]] [MM, SLUB]
2483 Enabling slub_debug allows one to determine the
2484 culprit if slab objects become corrupted. Enabling
2485 slub_debug can create guard zones around objects and
2486 may poison objects when not in use. Also tracks the
2487 last alloc / free. For more information see
2488 Documentation/vm/slub.txt.
2490 slub_max_order= [MM, SLUB]
2491 Determines the maximum allowed order for slabs.
2492 A high setting may cause OOMs due to memory
2493 fragmentation. For more information see
2494 Documentation/vm/slub.txt.
2496 slub_min_objects= [MM, SLUB]
2497 The minimum number of objects per slab. SLUB will
2498 increase the slab order up to slub_max_order to
2499 generate a sufficiently large slab able to contain
2500 the number of objects indicated. The higher the number
2501 of objects the smaller the overhead of tracking slabs
2502 and the less frequently locks need to be acquired.
2503 For more information see Documentation/vm/slub.txt.
2505 slub_min_order= [MM, SLUB]
2506 Determines the minimum page order for slabs. Must be
2507 lower than slub_max_order.
2508 For more information see Documentation/vm/slub.txt.
2510 slub_nomerge [MM, SLUB]
2511 Disable merging of slabs with similar size. May be
2512 necessary if there is some reason to distinguish
2513 allocs to different slabs. Debug options disable
2514 merging on their own.
2515 For more information see Documentation/vm/slub.txt.
2518 Format: <io1>[,<io2>[,...,<io8>]]
2520 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2521 attempt to substitute SMP alternatives once at boot.
2523 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2524 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2525 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2526 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2527 smsc-ircc2.ircc_irq= [HW] IRQ line
2528 smsc-ircc2.ircc_dma= [HW] DMA channel
2529 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2530 0: Toshiba Satellite 1800 (GP data pin select)
2531 1: Fast pin select (default)
2535 [KNL] Should the soft-lockup detector generate panics.
2538 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2539 See Documentation/laptops/sonypi.txt
2541 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2542 See Documentation/serial/specialix.txt.
2544 spia_io_base= [HW,MTD]
2550 Enabled the stack tracer on boot up.
2552 stacktrace_filter=[function-list]
2553 [FTRACE] Limit the functions that the stack tracer
2554 will trace at boot up. function-list is a comma separated
2555 list of functions. This list can be changed at run
2556 time by the stack_trace_filter file in the debugfs
2557 tracing directory. Note, this enables stack tracing
2558 and the stacktrace above is not needed.
2562 Set the STI (builtin display/keyboard on the HP-PARISC
2563 machines) console (graphic card) which should be used
2564 as the initial boot-console.
2565 See also comment in drivers/video/console/sticore.c.
2568 See comment in drivers/video/console/sticore.c.
2571 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2573 sunrpc.min_resvport=
2574 sunrpc.max_resvport=
2576 SunRPC servers often require that client requests
2577 originate from a privileged port (i.e. a port in the
2578 range 0 < portnr < 1024).
2579 An administrator who wishes to reserve some of these
2580 ports for other uses may adjust the range that the
2581 kernel's sunrpc client considers to be privileged
2582 using these two parameters to set the minimum and
2583 maximum port values.
2587 Control how the NFS server code allocates CPUs to
2588 service thread pools. Depending on how many NICs
2589 you have and where their interrupts are bound, this
2590 option will affect which CPUs will do NFS serving.
2591 Note: this parameter cannot be changed while the
2592 NFS server is running.
2594 auto the server chooses an appropriate mode
2595 automatically using heuristics
2596 global a single global pool contains all CPUs
2597 percpu one pool for each CPU
2598 pernode one pool for each NUMA node (equivalent
2599 to global on non-NUMA machines)
2601 sunrpc.tcp_slot_table_entries=
2602 sunrpc.udp_slot_table_entries=
2604 Sets the upper limit on the number of simultaneous
2605 RPC calls that can be sent from the client to a
2606 server. Increasing these values may allow you to
2607 improve throughput, but will also increase the
2608 amount of memory reserved for use by the client.
2611 [KNL] Enable accounting of swap in memory resource
2612 controller if no parameter or 1 is given or disable
2613 it if 0 is given (See Documentation/cgroups/memory.txt)
2615 swiotlb= [IA-64] Number of I/O TLB slabs
2619 sysfs.deprecated=0|1 [KNL]
2620 Enable/disable old style sysfs layout for old udev
2621 on older distributions. When this option is enabled
2622 very new udev will not work anymore. When this option
2623 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2624 in older udev will not work anymore.
2625 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2626 the kernel configuration.
2628 sysrq_always_enabled
2630 Ignore sysrq setting - this boot parameter will
2631 neutralize any effect of /proc/sys/kernel/sysrq.
2632 Useful for debugging.
2636 test_suspend= [SUSPEND]
2637 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2638 standby suspend) as the system sleep state to briefly
2639 enter during system startup. The system is woken from
2640 this state using a wakeup-capable RTC alarm.
2642 thash_entries= [KNL,NET]
2643 Set number of hash buckets for TCP connection
2645 thermal.act= [HW,ACPI]
2646 -1: disable all active trip points in all thermal zones
2647 <degrees C>: override all lowest active trip points
2649 thermal.crt= [HW,ACPI]
2650 -1: disable all critical trip points in all thermal zones
2651 <degrees C>: override all critical trip points
2653 thermal.nocrt= [HW,ACPI]
2654 Set to disable actions on ACPI thermal zone
2655 critical and hot trip points.
2657 thermal.off= [HW,ACPI]
2658 1: disable ACPI thermal control
2660 thermal.psv= [HW,ACPI]
2661 -1: disable all passive trip points
2662 <degrees C>: override all passive trip points to this
2665 thermal.tzp= [HW,ACPI]
2666 Specify global default ACPI thermal zone polling rate
2667 <deci-seconds>: poll all this frequency
2668 0: no polling (default)
2671 Force threading of all interrupt handlers except those
2672 marked explicitly IRQF_NO_THREAD.
2676 Specify if the kernel should make use of the cpu
2677 topology information if the hardware supports this.
2678 The scheduler will make use of this information and
2679 e.g. base its process migration decisions on it.
2684 tpm_suspend_pcr=[HW,TPM]
2685 Format: integer pcr id
2686 Specify that at suspend time, the tpm driver
2687 should extend the specified pcr with zeros,
2688 as a workaround for some chips which fail to
2689 flush the last written pcr on TPM_SaveState.
2690 This will guarantee that all the other pcrs
2693 trace_buf_size=nn[KMG]
2694 [FTRACE] will set tracing buffer size.
2696 trace_event=[event-list]
2697 [FTRACE] Set and start specified trace events in order
2698 to facilitate early boot debugging.
2699 See also Documentation/trace/events.txt
2701 transparent_hugepage=
2703 Format: [always|madvise|never]
2704 Can be used to control the default behavior of the system
2705 with respect to transparent hugepages.
2706 See Documentation/vm/transhuge.txt for more details.
2708 tsc= Disable clocksource stability checks for TSC.
2710 [x86] reliable: mark tsc clocksource as reliable, this
2711 disables clocksource verification at runtime, as well
2712 as the stability checks done at bootup. Used to enable
2713 high-resolution timer mode on older hardware, and in
2714 virtualized environment.
2715 [x86] noirqtime: Do not use TSC to do irq accounting.
2716 Used to run time disable IRQ_TIME_ACCOUNTING on any
2717 platforms where RDTSC is slow and this accounting
2720 turbografx.map[2|3]= [HW,JOY]
2721 TurboGraFX parallel port interface
2723 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2724 See also Documentation/input/joystick-parport.txt
2726 udbg-immortal [PPC] When debugging early kernel crashes that
2727 happen after console_init() and before a proper
2728 console driver takes over, this boot options might
2729 help "seeing" what's going on.
2731 uhash_entries= [KNL,NET]
2732 Set number of hash buckets for UDP/UDP-Lite connections
2735 [USB] Ignore overcurrent events (default N).
2736 Some badly-designed motherboards generate lots of
2737 bogus events, for ports that aren't wired to
2738 anything. Set this parameter to avoid log spamming.
2739 Note that genuine overcurrent events won't be
2743 [X86] Cause panic on unknown NMI.
2745 usbcore.authorized_default=
2746 [USB] Default USB device authorization:
2747 (default -1 = authorized except for wireless USB,
2748 0 = not authorized, 1 = authorized)
2750 usbcore.autosuspend=
2751 [USB] The autosuspend time delay (in seconds) used
2752 for newly-detected USB devices (default 2). This
2753 is the time required before an idle device will be
2754 autosuspended. Devices for which the delay is set
2755 to a negative value won't be autosuspended at all.
2757 usbcore.usbfs_snoop=
2758 [USB] Set to log all usbfs traffic (default 0 = off).
2760 usbcore.blinkenlights=
2761 [USB] Set to cycle leds on hubs (default 0 = off).
2763 usbcore.old_scheme_first=
2764 [USB] Start with the old device initialization
2765 scheme (default 0 = off).
2767 usbcore.usbfs_memory_mb=
2768 [USB] Memory limit (in MB) for buffers allocated by
2769 usbfs (default = 16, 0 = max = 2047).
2771 usbcore.use_both_schemes=
2772 [USB] Try the other device initialization scheme
2773 if the first one fails (default 1 = enabled).
2775 usbcore.initial_descriptor_timeout=
2776 [USB] Specifies timeout for the initial 64-byte
2777 USB_REQ_GET_DESCRIPTOR request in milliseconds
2778 (default 5000 = 5.0 seconds).
2781 [USBHID] The interval which mice are to be polled at.
2783 usb-storage.delay_use=
2784 [UMS] The delay in seconds before a new device is
2785 scanned for Logical Units (default 5).
2788 [UMS] A list of quirks entries to supplement or
2789 override the built-in unusual_devs list. List
2790 entries are separated by commas. Each entry has
2791 the form VID:PID:Flags where VID and PID are Vendor
2792 and Product ID values (4-digit hex numbers) and
2793 Flags is a set of characters, each corresponding
2794 to a common usb-storage quirk flag as follows:
2795 a = SANE_SENSE (collect more than 18 bytes
2797 b = BAD_SENSE (don't collect more than 18
2798 bytes of sense data);
2799 c = FIX_CAPACITY (decrease the reported
2800 device capacity by one sector);
2801 d = NO_READ_DISC_INFO (don't use
2802 READ_DISC_INFO command);
2803 e = NO_READ_CAPACITY_16 (don't use
2804 READ_CAPACITY_16 command);
2805 h = CAPACITY_HEURISTICS (decrease the
2806 reported device capacity by one
2807 sector if the number is odd);
2808 i = IGNORE_DEVICE (don't bind to this
2810 l = NOT_LOCKABLE (don't try to lock and
2811 unlock ejectable media);
2812 m = MAX_SECTORS_64 (don't transfer more
2813 than 64 sectors = 32 KB at a time);
2814 n = INITIAL_READ10 (force a retry of the
2815 initial READ(10) command);
2816 o = CAPACITY_OK (accept the capacity
2817 reported by the device);
2818 r = IGNORE_RESIDUE (the device reports
2819 bogus residue values);
2820 s = SINGLE_LUN (the device has only one
2822 w = NO_WP_DETECT (don't test whether the
2823 medium is write-protected).
2824 Example: quirks=0419:aaf5:rl,0421:0433:rc
2826 user_debug= [KNL,ARM]
2828 See arch/arm/Kconfig.debug help text.
2829 1 - undefined instruction events
2831 4 - invalid data aborts
2834 Example: user_debug=31
2837 [X86] Flags controlling user PTE allocations.
2839 nohigh = do not allocate PTE pages in
2840 HIGHMEM regardless of setting
2844 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2845 vdso=1: enable VDSO (default)
2846 vdso=0: disable VDSO mapping
2849 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2850 vdso32=1: enable 32-bit VDSO (default)
2851 vdso32=0: disable 32-bit VDSO mapping
2854 vector=percpu: enable percpu vector domain
2856 video= [FB] Frame buffer configuration
2857 See Documentation/fb/modedb.txt.
2859 vga= [BOOT,X86-32] Select a particular video mode
2860 See Documentation/x86/boot.txt and
2861 Documentation/svga.txt.
2862 Use vga=ask for menu.
2863 This is actually a boot loader parameter; the value is
2864 passed to the kernel using a special protocol.
2866 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2867 size of <nn>. This can be used to increase the
2868 minimum size (128MB on x86). It can also be used to
2869 decrease the size and leave more room for directly
2872 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2875 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2878 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2882 Controls the behavior of vsyscalls (i.e. calls to
2883 fixed addresses of 0xffffffffff600x00 from legacy
2884 code). Most statically-linked binaries and older
2885 versions of glibc use these calls. Because these
2886 functions are at fixed addresses, they make nice
2887 targets for exploits that can control RIP.
2889 emulate [default] Vsyscalls turn into traps and are
2890 emulated reasonably safely.
2892 native Vsyscalls are native syscall instructions.
2893 This is a little bit faster than trapping
2894 and makes a few dynamic recompilers work
2895 better than they would in emulation mode.
2896 It also makes exploits much easier to write.
2898 none Vsyscalls don't work at all. This makes
2899 them quite hard to use for exploits but
2900 might break your system.
2902 vt.cur_default= [VT] Default cursor shape.
2903 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2904 the parameters of the <Esc>[?A;B;Cc escape sequence;
2905 see VGA-softcursor.txt. Default: 2 = underline.
2907 vt.default_blu= [VT]
2908 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2909 Change the default blue palette of the console.
2910 This is a 16-member array composed of values
2913 vt.default_grn= [VT]
2914 Format: <green0>,<green1>,<green2>,...,<green15>
2915 Change the default green palette of the console.
2916 This is a 16-member array composed of values
2919 vt.default_red= [VT]
2920 Format: <red0>,<red1>,<red2>,...,<red15>
2921 Change the default red palette of the console.
2922 This is a 16-member array composed of values
2928 Set system-wide default UTF-8 mode for all tty's.
2929 Default is 1, i.e. UTF-8 mode is enabled for all
2930 newly opened terminals.
2932 vt.global_cursor_default=
2935 Set system-wide default for whether a cursor
2936 is shown on new VTs. Default is -1,
2937 i.e. cursors will be created by default unless
2938 overridden by individual drivers. 0 will hide
2939 cursors, 1 will display them.
2941 watchdog timers [HW,WDT] For information on watchdog timers,
2942 see Documentation/watchdog/watchdog-parameters.txt
2943 or other driver-specific files in the
2944 Documentation/watchdog/ directory.
2946 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2947 default x2apic cluster mode on platforms
2950 x86_mrst_timer= [X86-32,APBT]
2951 Choose timer option for x86 Moorestown MID platform.
2952 Two valid options are apbt timer only and lapic timer
2953 plus one apbt timer for broadcast timer.
2954 x86_mrst_timer=apbt_only | lapic_and_apbt
2956 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2957 xd_geo= See header of drivers/block/xd.c.
2959 xen_emul_unplug= [HW,X86,XEN]
2960 Unplug Xen emulated devices
2961 Format: [unplug0,][unplug1]
2962 ide-disks -- unplug primary master IDE devices
2963 aux-ide-disks -- unplug non-primary-master IDE devices
2964 nics -- unplug network devices
2965 all -- unplug all emulated devices (NICs and IDE disks)
2966 unnecessary -- unplugging emulated devices is
2967 unnecessary even if the host did not respond to
2969 never -- do not unplug even if version check succeeds
2971 xirc2ps_cs= [NET,PCMCIA]
2973 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2975 ______________________________________________________________________
2979 Add more DRM drivers.
projects / can-eth-gw-linux.git / blob