4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VMMIO Driver for memory mapped virtio devices is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amijoy.map= [HW,JOY] Amiga joystick support
340 Map of devices attached to JOY0DAT and JOY1DAT
342 See also Documentation/input/joystick.txt
344 analog.map= [HW,JOY] Analog joystick and gamepad support
345 Specifies type or capabilities of an analog joystick
346 connected to one of 16 gameports
347 Format: <type1>,<type2>,..<type16>
350 Power management functions (SPARCstation-4/5 + deriv.)
352 Disable APC CPU standby support. SPARCstation-Fox does
353 not play well with APC CPU idle - disable it if you have
354 APC and your system crashes randomly.
356 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
357 Change the output verbosity whilst booting
358 Format: { quiet (default) | verbose | debug }
359 Change the amount of debugging information output
360 when initialising the APIC and IO-APIC components.
363 See Documentation/networking/ipv6.txt.
365 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
366 Limit apic dumping. The parameter defines the maximal
367 number of local apics being dumped. Also it is possible
368 to set it to "all" by meaning -- no limit here.
369 Format: { 1 (default) | 2 | ... | all }.
370 The parameter valid if only apic=debug or
371 apic=verbose is specified.
372 Example: apic=debug show_lapic=all
374 apm= [APM] Advanced Power Management
375 See header of arch/x86/kernel/apm_32.c.
377 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
378 Format: <io>,<irq>,<nodeID>
382 atarimouse= [HW,MOUSE] Atari Mouse
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
401 baycom_epp= [HW,AX25]
404 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
406 See header of drivers/net/hamradio/baycom_par.c.
408 baycom_ser_fdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
410 Format: <io>,<irq>,<mode>[,<baud>]
411 See header of drivers/net/hamradio/baycom_ser_fdx.c.
413 baycom_ser_hdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
415 Format: <io>,<irq>,<mode>
416 See header of drivers/net/hamradio/baycom_ser_hdx.c.
418 boot_delay= Milliseconds to delay each printk during boot.
419 Values larger than 10 seconds (10000) are changed to
423 bootmem_debug [KNL] Enable bootmem allocator debug messages.
425 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
426 bttv.radio= Most important insmod options are available as
428 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
431 bulk_remove=off [PPC] This parameter disables the use of the pSeries
432 firmware feature for flushing multiple hpte entries
435 c101= [NET] Moxa C101 synchronous serial card
437 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
438 Sometimes CPU hardware bugs make them report the cache
439 size incorrectly. The kernel will attempt work arounds
440 to fix known problems, but for some CPUs it is not
441 possible to determine what the correct size should be.
442 This option provides an override for these situations.
445 [SECURITY] Disable capabilities. This would normally
446 be used only if an alternative security model is to be
447 configured. Potentially dangerous and should only be
448 used if you are entirely sure of the consequences.
450 ccw_timeout_log [S390]
451 See Documentation/s390/CommonIO for details.
453 cgroup_disable= [KNL] Disable a particular controller
454 Format: {name of the controller(s) to disable}
455 {Currently supported controllers - "memory"}
457 checkreqprot [SELINUX] Set initial checkreqprot flag value.
458 Format: { "0" | "1" }
459 See security/selinux/Kconfig help text.
460 0 -- check protection applied by kernel (includes
461 any implied execute protection).
462 1 -- check protection requested by application.
463 Default value is set via a kernel config option.
464 Value can be changed at runtime via
465 /selinux/checkreqprot.
468 See Documentation/s390/CommonIO for details.
470 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
472 Forces specified clocksource (if available) to be used
473 when calculating gettimeofday(). If specified
474 clocksource is not available, it defaults to PIT.
475 Format: { pit | tsc | cyclone | pmtmr }
477 clocksource= Override the default clocksource
479 Override the default clocksource and use the clocksource
480 with the name specified.
481 Some clocksource names to choose from, depending on
483 [all] jiffies (this is the base, fallback clocksource)
485 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
486 pxa_timer,timer3,32k_counter,timer0_1
488 [X86-32] pit,hpet,tsc;
489 scx200_hrt on Geode; cyclone on IBM x440
497 clearcpuid=BITNUM [X86]
498 Disable CPUID feature X for the kernel. See
499 arch/x86/include/asm/cpufeature.h for the valid bit
500 numbers. Note the Linux specific bits are not necessarily
501 stable over kernel options, but the vendor specific
503 Also note that user programs calling CPUID directly
504 or using the feature without checking anything
505 will still see it. This just prevents it from
506 being used by the kernel or shown in /proc/cpuinfo.
507 Also note the kernel might malfunction if you disable
510 cmo_free_hint= [PPC] Format: { yes | no }
511 Specify whether pages are marked as being inactive
512 when they are freed. This is used in CMO environments
513 to determine OS memory pressure for page stealing by
517 code_bytes [X86] How many bytes of object code to print
522 com20020= [HW,NET] ARCnet - COM20020 chipset
524 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
526 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
530 ARCnet - COM90xx chipset (memory-mapped buffers)
531 Format: <io>[,<irq>[,<memstart>]]
533 condev= [HW,S390] console device
536 console= [KNL] Output console device and options.
538 tty<n> Use the virtual console device <n>.
542 Use the specified serial port. The options are of
543 the form "bbbbpnf", where "bbbb" is the baud rate,
544 "p" is parity ("n", "o", or "e"), "n" is number of
545 bits, and "f" is flow control ("r" for RTS or
546 omit it). Default is "9600n8".
548 See Documentation/serial-console.txt for more
550 Documentation/networking/netconsole.txt for an
553 uart[8250],io,<addr>[,options]
554 uart[8250],mmio,<addr>[,options]
555 Start an early, polled-mode console on the 8250/16550
556 UART at the specified I/O port or MMIO address,
557 switching to the matching ttyS device later. The
558 options are the same as for ttyS, above.
560 If the device connected to the port is not a TTY but a braille
561 device, prepend "brl," before the device type, for instance
563 For now, only VisioBraille is supported.
565 consoleblank= [KNL] The console blank (screen saver) timeout in
566 seconds. Defaults to 10*60 = 10mins. A value of 0
567 disables the blank timer.
570 [KNL] Change the default value for
571 /proc/<pid>/coredump_filter.
572 See also Documentation/filesystems/proc.txt.
574 cpuidle.off=1 [CPU_IDLE]
575 disable the cpuidle sub-system
577 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
579 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
581 crashkernel=size[KMG][@offset[KMG]]
582 [KNL] Using kexec, Linux can switch to a 'crash kernel'
583 upon panic. This parameter reserves the physical
584 memory region [offset, offset + size] for that kernel
585 image. If '@offset' is omitted, then a suitable offset
586 is selected automatically. Check
587 Documentation/kdump/kdump.txt for further details.
589 crashkernel=range1:size1[,range2:size2,...][@offset]
590 [KNL] Same as above, but depends on the memory
591 in the running system. The syntax of range is
592 start-[end] where start and end are both
593 a memory unit (amount[KMG]). See also
594 Documentation/kdump/kdump.txt for an example.
599 cs89x0_media= [HW,NET]
600 Format: { rj45 | aui | bnc }
603 See header of drivers/s390/block/dasd_devmap.c.
605 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
606 (one device per port)
607 Format: <port#>,<type>
608 See also Documentation/input/joystick-parport.txt
610 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
611 time. See Documentation/dynamic-debug-howto.txt for
612 details. Deprecated, see dyndbg.
614 debug [KNL] Enable kernel debugging (events log level).
617 [KNL] verbose self-tests
619 Print debugging info while doing the locking API
621 We default to 0 (no extra messages), setting it to
622 1 will print _a lot_ more information - normally
623 only useful to kernel developers.
625 debug_objects [KNL] Enable object debugging
628 [KNL] Disable object debugging
630 debug_guardpage_minorder=
631 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
632 parameter allows control of the order of pages that will
633 be intentionally kept free (and hence protected) by the
634 buddy allocator. Bigger value increase the probability
635 of catching random memory corruption, but reduce the
636 amount of memory for normal system use. The maximum
637 possible value is MAX_ORDER/2. Setting this parameter
638 to 1 or 2 should be enough to identify most random
639 memory corruption problems caused by bugs in kernel or
640 driver code when a CPU writes to (or reads from) a
641 random memory location. Note that there exists a class
642 of memory corruptions problems caused by buggy H/W or
643 F/W or by drivers badly programing DMA (basically when
644 memory is written at bus level and the CPU MMU is
645 bypassed) which are not detectable by
646 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
647 tracking down these problems.
649 debugpat [X86] Enable PAT debugging
651 decnet.addr= [HW,NET]
652 Format: <area>[,<node>]
653 See also Documentation/networking/decnet.txt.
656 [same as hugepagesz=] The size of the default
657 HugeTLB page size. This is the size represented by
658 the legacy /proc/ hugepages APIs, used for SHM, and
659 default size when mounting hugetlbfs filesystems.
660 Defaults to the default architecture's huge page size
664 Set number of hash buckets for dentry cache.
667 IO parameters + enable/disable command.
669 digiepca= [HW,SERIAL]
670 See drivers/char/README.epca and
671 Documentation/serial/digiepca.txt.
674 See Documentation/networking/ipv6.txt.
676 disable_ddw [PPC/PSERIES]
677 Disable Dynamic DMA Window support. Use this if
678 to workaround buggy firmware.
681 See Documentation/networking/ipv6.txt.
683 disable_mtrr_cleanup [X86]
684 The kernel tries to adjust MTRR layout from continuous
685 to discrete, to make X server driver able to add WB
686 entry later. This parameter disables that.
688 disable_mtrr_trim [X86, Intel and AMD only]
689 By default the kernel will trim any uncacheable
690 memory out of your available memory pool based on
691 MTRR settings. This parameter disables that behavior,
692 possibly causing your machine to run very slowly.
694 disable_timer_pin_1 [X86]
695 Disable PIN 1 of APIC timer
696 Can be useful to work around chipset bugs.
698 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
699 this option disables the debugging code at boot.
701 dma_debug_entries=<number>
702 This option allows to tune the number of preallocated
703 entries for DMA-API debugging code. One entry is
704 required per DMA-API allocation. Use this if the
705 DMA-API debugging code disables itself because the
706 architectural default is too low.
708 dma_debug_driver=<driver_name>
709 With this option the DMA-API debugging driver
710 filter feature can be enabled at boot time. Just
711 pass the driver to filter for as the parameter.
712 The filter can be disabled or changed to another
713 driver later using sysfs.
715 drm_kms_helper.edid_firmware=[<connector>:]<file>
716 Broken monitors, graphic adapters and KVMs may
717 send no or incorrect EDID data sets. This parameter
718 allows to specify an EDID data set in the
719 /lib/firmware directory that is used instead.
720 Generic built-in EDID data sets are used, if one of
721 edid/1024x768.bin, edid/1280x1024.bin,
722 edid/1680x1050.bin, or edid/1920x1080.bin is given
723 and no file with the same name exists. Details and
724 instructions how to build your own EDID data are
725 available in Documentation/EDID/HOWTO.txt. An EDID
726 data set will only be used for a particular connector,
727 if its name and a colon are prepended to the EDID
732 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
733 module.dyndbg[="val"]
734 Enable debug messages at boot time. See
735 Documentation/dynamic-debug-howto.txt for details.
737 earlycon= [KNL] Output early console device and options.
738 uart[8250],io,<addr>[,options]
739 uart[8250],mmio,<addr>[,options]
740 uart[8250],mmio32,<addr>[,options]
741 Start an early, polled-mode console on the 8250/16550
742 UART at the specified I/O port or MMIO address.
743 MMIO inter-register address stride is either 8-bit
744 (mmio) or 32-bit (mmio32).
745 The options are the same as for ttyS, above.
747 earlyprintk= [X86,SH,BLACKFIN]
749 earlyprintk=serial[,ttySn[,baudrate]]
750 earlyprintk=ttySn[,baudrate]
751 earlyprintk=dbgp[debugController#]
753 Append ",keep" to not disable it when the real console
756 Only vga or serial or usb debug port at a time.
758 Currently only ttyS0 and ttyS1 are supported.
760 Interaction with the standard serial driver is not
763 The VGA output is eventually overwritten by the real
766 ekgdboc= [X86,KGDB] Allow early kernel console debugging
769 This is designed to be used in conjunction with
770 the boot argument: earlyprintk=vga
773 Format: {"off" | "on" | "skip[mbr]"}
775 eisa_irq_edge= [PARISC,HW]
776 See header of drivers/parisc/eisa.c.
779 See comment before function elanfreq_setup() in
780 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
783 Format: {"cfq" | "deadline" | "noop"}
784 See Documentation/block/cfq-iosched.txt and
785 Documentation/block/deadline-iosched.txt for details.
787 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
788 Specifies physical address of start of kernel core
789 image elf header and optionally the size. Generally
790 kexec loader will pass this option to capture kernel.
791 See Documentation/kdump/kdump.txt for details.
793 enable_mtrr_cleanup [X86]
794 The kernel tries to adjust MTRR layout from continuous
795 to discrete, to make X server driver able to add WB
796 entry later. This parameter enables that.
798 enable_timer_pin_1 [X86]
799 Enable PIN 1 of APIC timer
800 Can be useful to work around chipset bugs
801 (in particular on some ATI chipsets).
802 The kernel tries to set a reasonable default.
804 enforcing [SELINUX] Set initial enforcing status.
806 See security/selinux/Kconfig help text.
807 0 -- permissive (log only, no denials).
808 1 -- enforcing (deny and log).
810 Value can be changed at runtime via /selinux/enforce.
813 Disable Error Record Serialization Table (ERST)
816 ether= [HW,NET] Ethernet cards parameters
817 This option is obsoleted by the "netdev=" option, which
818 has equivalent usage. See its documentation for details.
822 Permit 'security.evm' to be updated regardless of
823 current integrity status.
827 fail_make_request=[KNL]
828 General fault injection mechanism.
829 Format: <interval>,<probability>,<space>,<times>
830 See also Documentation/fault-injection/.
833 See Documentation/blockdev/floppy.txt.
835 force_pal_cache_flush
836 [IA-64] Avoid check_sal_cache_flush which may hang on
837 buggy SAL_CACHE_FLUSH implementations. Using this
838 parameter will force ia64_sal_cache_flush to call
839 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
842 [FTRACE] will set and start the specified tracer
843 as early as possible in order to facilitate early
846 ftrace_dump_on_oops[=orig_cpu]
847 [FTRACE] will dump the trace buffers on oops.
848 If no parameter is passed, ftrace will dump
849 buffers of all CPUs, but if you pass orig_cpu, it will
850 dump only the buffer of the CPU that triggered the
853 ftrace_filter=[function-list]
854 [FTRACE] Limit the functions traced by the function
855 tracer at boot up. function-list is a comma separated
856 list of functions. This list can be changed at run
857 time by the set_ftrace_filter file in the debugfs
860 ftrace_notrace=[function-list]
861 [FTRACE] Do not trace the functions specified in
862 function-list. This list can be changed at run time
863 by the set_ftrace_notrace file in the debugfs
866 ftrace_graph_filter=[function-list]
867 [FTRACE] Limit the top level callers functions traced
868 by the function graph tracer at boot up.
869 function-list is a comma separated list of functions
870 that can be changed at run time by the
871 set_graph_function file in the debugfs tracing directory.
874 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
875 support via parallel port (up to 5 devices per port)
876 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
877 See also Documentation/input/joystick-parport.txt
881 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
885 gcov_persist= [GCOV] When non-zero (default), profiling data for
886 kernel modules is saved and remains accessible via
887 debugfs, even when the module is unloaded/reloaded.
888 When zero, profiling data is discarded and associated
889 debugfs files are removed at module unload time.
891 gpt [EFI] Forces disk with valid GPT signature but
892 invalid Protective MBR to be treated as GPT.
894 hashdist= [KNL,NUMA] Large hashes allocated during boot
895 are distributed across NUMA nodes. Defaults on
896 for 64-bit NUMA, off otherwise.
897 Format: 0 | 1 (for off | on)
899 hcl= [IA-64] SGI's Hardware Graph compatibility layer
901 hd= [EIDE] (E)IDE hard drive subsystem geometry
902 Format: <cyl>,<head>,<sect>
905 Disable Hardware Error Source Table (HEST) support;
906 corresponding firmware-first mode error processing
907 logic will be disabled.
909 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
910 size of <nn>. This works even on boxes that have no
911 highmem otherwise. This also works to reduce highmem
912 size on bigger boxes.
914 highres= [KNL] Enable/disable high resolution timer mode.
915 Valid parameters: "on", "off"
919 See Documentation/isdn/README.HiSax.
923 hpet= [X86-32,HPET] option to control HPET usage
924 Format: { enable (default) | disable | force |
926 disable: disable HPET and use PIT instead
927 force: allow force enabled of undocumented chips (ICH4,
929 verbose: show contents of HPET registers during setup
931 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
932 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
933 On x86-64 and powerpc, this option can be specified
934 multiple times interleaved with hugepages= to reserve
935 huge pages of different sizes. Valid pages sizes on
936 x86-64 are 2M (when the CPU supports "pse") and 1G
937 (when the CPU supports the "pdpe1gb" cpuinfo flag)
938 Note that 1GB pages can only be allocated at boot time
939 using hugepages= and not freed afterwards.
941 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
942 terminal devices. Valid values: 0..8
943 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
944 If specified, z/VM IUCV HVC accepts connections
945 from listed z/VM user IDs only.
948 Do not unregister boot console at start. This is only
949 useful for debugging when something happens in the window
950 between unregistering the boot console and initializing
953 i2c_bus= [HW] Override the default board specific I2C bus speed
954 or register an additional I2C bus that is not
955 registered from board initialization code.
959 i8042.debug [HW] Toggle i8042 debug mode
960 i8042.direct [HW] Put keyboard port into non-translated mode
961 i8042.dumbkbd [HW] Pretend that controller can only read data from
962 keyboard and cannot control its state
963 (Don't attempt to blink the leds)
964 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
965 i8042.nokbd [HW] Don't check/create keyboard port
966 i8042.noloop [HW] Disable the AUX Loopback command while probing
968 i8042.nomux [HW] Don't check presence of an active multiplexing
970 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
972 i8042.notimeout [HW] Ignore timeout condition signalled by controller
973 i8042.reset [HW] Reset the controller during init and cleanup
974 i8042.unlock [HW] Unlock (ignore) the keylock
978 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
979 indicates that the driver is running on unsupported
981 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
982 does not match list of supported models.
984 [HW] Report power status in /proc/i8k
985 (disabled by default)
986 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
990 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
992 ide-core.nodma= [HW] (E)IDE subsystem
993 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
994 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
995 .cdrom .chs .ignore_cable are additional options
996 See Documentation/ide/ide.txt.
998 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
999 Claim all unknown PCI IDE storage controllers.
1002 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1003 Poll forces a polling idle loop that can slightly
1004 improve the performance of waking up a idle CPU, but
1005 will use a lot of power and make the system run hot.
1007 idle=mwait: On systems which support MONITOR/MWAIT but
1008 the kernel chose to not use it because it doesn't save
1009 as much power as a normal idle loop, use the
1010 MONITOR/MWAIT idle loop anyways. Performance should be
1011 the same as idle=poll.
1012 idle=halt: Halt is forced to be used for CPU idle.
1013 In such case C2/C3 won't be used again.
1014 idle=nomwait: Disable mwait for CPU C-states
1016 ignore_loglevel [KNL]
1017 Ignore loglevel setting - this will print /all/
1018 kernel messages to the console. Useful for debugging.
1019 We also add it as printk module parameter, so users
1020 could change it dynamically, usually by
1021 /sys/module/printk/parameters/ignore_loglevel.
1023 ihash_entries= [KNL]
1024 Set number of hash buckets for inode cache.
1027 Format: { "0" | "1" }
1028 0 -- integrity auditing messages. (Default)
1029 1 -- enable informational integrity auditing messages.
1032 Format: { "sha1" | "md5" }
1036 Load a policy which meets the needs of the Trusted
1037 Computing Base. This means IMA will measure all
1038 programs exec'd, files mmap'd for exec, and all files
1039 opened for read by uid=0.
1043 Run specified binary instead of /sbin/init as init
1046 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1047 for working out where the kernel is dying during
1050 initrd= [BOOT] Specify the location of the initial ramdisk
1052 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1055 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1057 Enable intel iommu driver.
1059 Disable intel iommu driver.
1060 igfx_off [Default Off]
1061 By default, gfx is mapped as normal device. If a gfx
1062 device has a dedicated DMAR unit, the DMAR unit is
1063 bypassed by not enabling DMAR with this option. In
1064 this case, gfx device will use physical address for
1067 With this option iommu will not optimize to look
1068 for io virtual address below 32-bit forcing dual
1069 address cycle on pci bus for cards supporting greater
1070 than 32-bit addressing. The default is to look
1071 for translation below 32-bit and if not available
1072 then look in the higher range.
1073 strict [Default Off]
1074 With this option on every unmap_single operation will
1075 result in a hardware IOTLB flush operation as opposed
1076 to batching them for performance.
1077 sp_off [Default Off]
1078 By default, super page will be supported if Intel IOMMU
1079 has the capability. With this option, super page will
1082 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1083 0 disables intel_idle and fall back on acpi_idle.
1084 1 to 6 specify maximum depth of C-state.
1086 intremap= [X86-64, Intel-IOMMU]
1087 on enable Interrupt Remapping (default)
1088 off disable Interrupt Remapping
1089 nosid disable Source ID checking
1091 BIOS x2APIC opt-out request will be ignored
1093 iomem= Disable strict checking of access to MMIO memory
1094 strict regions from userspace.
1109 group_mf [x86, IA-64]
1112 io7= [HW] IO7 for Marvel based alpha systems
1113 See comment before marvel_specify_io7 in
1114 arch/alpha/kernel/core_marvel.c.
1116 io_delay= [X86] I/O delay method
1118 Standard port 0x80 based delay
1120 Alternate port 0xed based delay (needed on some systems)
1122 Simple two microseconds delay
1127 See Documentation/filesystems/nfs/nfsroot.txt.
1129 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1130 See comment before ip2_setup() in
1131 drivers/char/ip2/ip2base.c.
1134 When an interrupt is not handled search all handlers
1135 for it. Intended to get systems with badly broken
1139 When an interrupt is not handled search all handlers
1140 for it. Also check all handlers each timer
1141 interrupt. Intended to get systems with badly broken
1145 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1147 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1149 <cpu number>,...,<cpu number>
1151 <cpu number>-<cpu number>
1152 (must be a positive range in ascending order)
1154 <cpu number>,...,<cpu number>-<cpu number>
1156 This option can be used to specify one or more CPUs
1157 to isolate from the general SMP balancing and scheduling
1158 algorithms. You can move a process onto or off an
1159 "isolated" CPU via the CPU affinity syscalls or cpuset.
1160 <cpu number> begins at 0 and the maximum value is
1161 "number of CPUs in system - 1".
1163 This option is the preferred way to isolate CPUs. The
1164 alternative -- manually setting the CPU mask of all
1165 tasks in the system -- can cause problems and
1166 suboptimal load balancer performance.
1170 js= [HW,JOY] Analog joystick
1171 See Documentation/input/joystick.txt.
1175 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1176 specifies the amount of memory usable by the kernel
1177 for non-movable allocations. The requested amount is
1178 spread evenly throughout all nodes in the system. The
1179 remaining memory in each node is used for Movable
1180 pages. In the event, a node is too small to have both
1181 kernelcore and Movable pages, kernelcore pages will
1182 take priority and other nodes will have a larger number
1183 of kernelcore pages. The Movable zone is used for the
1184 allocation of pages that may be reclaimed or moved
1185 by the page migration subsystem. This means that
1186 HugeTLB pages may not be allocated from this zone.
1187 Note that allocations like PTEs-from-HighMem still
1188 use the HighMem zone if it exists, and the Normal
1189 zone if it does not.
1191 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1192 Format: <Controller#>[,poll interval]
1193 The controller # is the number of the ehci usb debug
1194 port as it is probed via PCI. The poll interval is
1195 optional and is the number seconds in between
1196 each poll cycle to the debug port in case you need
1197 the functionality for interrupting the kernel with
1198 gdb or control-c on the dbgp connection. When
1199 not using this parameter you use sysrq-g to break into
1200 the kernel debugger.
1202 kgdboc= [KGDB,HW] kgdb over consoles.
1203 Requires a tty driver that supports console polling,
1204 or a supported polling keyboard driver (non-usb).
1205 Serial only format: <serial_device>[,baud]
1206 keyboard only format: kbd
1207 keyboard and serial format: kbd,<serial_device>[,baud]
1208 Optional Kernel mode setting:
1209 kms, kbd format: kms,kbd
1210 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1212 kgdbwait [KGDB] Stop kernel execution and enter the
1213 kernel debugger at the earliest opportunity.
1215 kmac= [MIPS] korina ethernet MAC address.
1216 Configure the RouterBoard 532 series on-chip
1217 Ethernet adapter MAC address.
1219 kmemleak= [KNL] Boot-time kmemleak enable/disable
1220 Valid arguments: on, off
1223 kstack=N [X86] Print N words from the kernel stack
1226 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1227 Default is 0 (don't ignore, but inject #GP)
1229 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1233 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1234 Default is 1 (enabled)
1236 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1238 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1240 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1241 (virtualized MMU) support on capable Intel chips.
1242 Default is 1 (enabled)
1244 kvm-intel.emulate_invalid_guest_state=
1245 [KVM,Intel] Enable emulation of invalid guest states
1246 Default is 0 (disabled)
1248 kvm-intel.flexpriority=
1249 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1250 Default is 1 (enabled)
1253 [KVM,Intel] Enable VMX nesting (nVMX).
1254 Default is 0 (disabled)
1256 kvm-intel.unrestricted_guest=
1257 [KVM,Intel] Disable unrestricted guest feature
1258 (virtualized real and unpaged mode) on capable
1259 Intel chips. Default is 1 (enabled)
1261 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1262 feature (tagged TLBs) on capable Intel chips.
1263 Default is 1 (enabled)
1269 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1272 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1275 libata.dma= [LIBATA] DMA control
1276 libata.dma=0 Disable all PATA and SATA DMA
1277 libata.dma=1 PATA and SATA Disk DMA only
1278 libata.dma=2 ATAPI (CDROM) DMA only
1279 libata.dma=4 Compact Flash DMA only
1280 Combinations also work, so libata.dma=3 enables DMA
1281 for disks and CDROMs, but not CFs.
1283 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1284 libata.ignore_hpa=0 keep BIOS limits (default)
1285 libata.ignore_hpa=1 ignore limits, using full disk
1287 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1291 libata.force= [LIBATA] Force configurations. The format is comma
1292 separated list of "[ID:]VAL" where ID is
1293 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1294 matching port, link or device. Basically, it matches
1295 the ATA ID string printed on console by libata. If
1296 the whole ID part is omitted, the last PORT and DEVICE
1297 values are used. If ID hasn't been specified yet, the
1298 configuration applies to all ports, links and devices.
1300 If only DEVICE is omitted, the parameter applies to
1301 the port and all links and devices behind it. DEVICE
1302 number of 0 either selects the first device or the
1303 first fan-out link behind PMP device. It does not
1304 select the host link. DEVICE number of 15 selects the
1305 host link and device attached to it.
1307 The VAL specifies the configuration to force. As long
1308 as there's no ambiguity shortcut notation is allowed.
1309 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1310 The following configurations can be forced.
1312 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1313 Any ID with matching PORT is used.
1315 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1317 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1318 udma[/][16,25,33,44,66,100,133] notation is also
1321 * [no]ncq: Turn on or off NCQ.
1323 * nohrst, nosrst, norst: suppress hard, soft
1326 * dump_id: dump IDENTIFY data.
1328 If there are multiple matching configurations changing
1329 the same attribute, the last one is used.
1331 memblock=debug [KNL] Enable memblock debug messages.
1333 load_ramdisk= [RAM] List of ramdisks to load from floppy
1334 See Documentation/blockdev/ramdisk.txt.
1336 lockd.nlm_grace_period=P [NFS] Assign grace period.
1339 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1342 lockd.nlm_timeout=T [NFS] Assign timeout value.
1345 lockd.nlm_udpport=M [NFS] Assign UDP port.
1348 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1351 loglevel= All Kernel Messages with a loglevel smaller than the
1352 console loglevel will be printed to the console. It can
1353 also be changed with klogd or other programs. The
1354 loglevels are defined as follows:
1356 0 (KERN_EMERG) system is unusable
1357 1 (KERN_ALERT) action must be taken immediately
1358 2 (KERN_CRIT) critical conditions
1359 3 (KERN_ERR) error conditions
1360 4 (KERN_WARNING) warning conditions
1361 5 (KERN_NOTICE) normal but significant condition
1362 6 (KERN_INFO) informational
1363 7 (KERN_DEBUG) debug-level messages
1365 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1366 in bytes. n must be a power of two. The default
1367 size is set in the kernel config file.
1369 logo.nologo [FB] Disables display of the built-in Linux logo.
1370 This may be used to provide more screen space for
1371 kernel log messages and is useful when debugging
1372 kernel boot problems.
1374 lp=0 [LP] Specify parallel ports to use, e.g,
1375 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1376 lp=reset first parallel port). 'lp=0' disables the
1377 lp=auto printer driver. 'lp=reset' (which can be
1378 specified in addition to the ports) causes
1379 attached printers to be reset. Using
1380 lp=port1,port2,... specifies the parallel ports
1381 to associate lp devices with, starting with
1382 lp0. A port specification may be 'none' to skip
1383 that lp device, or a parport name such as
1384 'parport0'. Specifying 'lp=auto' instead of a
1385 port specification list means that device IDs
1386 from each port should be examined, to see if
1387 an IEEE 1284-compliant printer is attached; if
1388 so, the driver will manage that printer.
1389 See also header of drivers/char/lp.c.
1392 Sets loops_per_jiffy to given constant, thus avoiding
1393 time-consuming boot-time autodetection (up to 250 ms per
1394 CPU). 0 enables autodetection (default). To determine
1395 the correct value for your kernel, boot with normal
1396 autodetection and see what value is printed. Note that
1397 on SMP systems the preset will be applied to all CPUs,
1398 which is likely to cause problems if your CPUs need
1399 significantly divergent settings. An incorrect value
1400 will cause delays in the kernel to be wrong, leading to
1401 unpredictable I/O errors and other breakage. Although
1402 unlikely, in the extreme case this might damage your
1406 Format: <io>,<irq>,<dma>
1408 machvec= [IA-64] Force the use of a particular machine-vector
1409 (machvec) in a generic kernel.
1410 Example: machvec=hpzx1_swiotlb
1412 machtype= [Loongson] Share the same kernel image file between different
1414 Example: machtype=lemote-yeeloong-2f-7inch
1416 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1417 than or equal to this physical address is ignored.
1419 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1420 should make use of. maxcpus=n : n >= 0 limits the
1421 kernel to using 'n' processors. n=0 is a special case,
1422 it is equivalent to "nosmp", which also disables
1425 max_loop= [LOOP] The number of loop block devices that get
1426 (loop.max_loop) unconditionally pre-created at init time. The default
1427 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1428 of statically allocating a predefined number, loop
1429 devices can be requested on-demand with the
1430 /dev/loop-control interface.
1432 mce [X86-32] Machine Check Exception
1434 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1436 md= [HW] RAID subsystems devices and level
1437 See Documentation/md.txt.
1440 Format: <first>,<last>
1441 Specifies range of consoles to be captured by the MDA.
1443 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1444 Amount of memory to be used when the kernel is not able
1445 to see the whole system memory or for test.
1446 [X86-32] Use together with memmap= to avoid physical
1447 address space collisions. Without memmap= PCI devices
1448 could be placed at addresses belonging to unused RAM.
1450 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1454 [KNL,SH] Allow user to override the default size for
1455 per-device physically contiguous DMA buffers.
1457 memmap=exactmap [KNL,X86] Enable setting of an exact
1458 E820 memory map, as specified by the user.
1459 Such memmap=exactmap lines can be constructed based on
1460 BIOS output or other requirements. See the memmap=nn@ss
1463 memmap=nn[KMG]@ss[KMG]
1464 [KNL] Force usage of a specific region of memory
1465 Region of memory to be used, from ss to ss+nn.
1467 memmap=nn[KMG]#ss[KMG]
1468 [KNL,ACPI] Mark specific memory as ACPI data.
1469 Region of memory to be used, from ss to ss+nn.
1471 memmap=nn[KMG]$ss[KMG]
1472 [KNL,ACPI] Mark specific memory as reserved.
1473 Region of memory to be used, from ss to ss+nn.
1474 Example: Exclude memory from 0x18690000-0x1869ffff
1475 memmap=64K$0x18690000
1477 memmap=0x10000$0x18690000
1479 memory_corruption_check=0/1 [X86]
1480 Some BIOSes seem to corrupt the first 64k of
1481 memory when doing things like suspend/resume.
1482 Setting this option will scan the memory
1483 looking for corruption. Enabling this will
1484 both detect corruption and prevent the kernel
1485 from using the memory being corrupted.
1486 However, its intended as a diagnostic tool; if
1487 repeatable BIOS-originated corruption always
1488 affects the same memory, you can use memmap=
1489 to prevent the kernel from using that memory.
1491 memory_corruption_check_size=size [X86]
1492 By default it checks for corruption in the low
1493 64k, making this memory unavailable for normal
1494 use. Use this parameter to scan for
1495 corruption in more or less memory.
1497 memory_corruption_check_period=seconds [X86]
1498 By default it checks for corruption every 60
1499 seconds. Use this parameter to check at some
1500 other rate. 0 disables periodic checking.
1502 memtest= [KNL,X86] Enable memtest
1504 default : 0 <disable>
1505 Specifies the number of memtest passes to be
1506 performed. Each pass selects another test
1507 pattern from a given set of patterns. Memtest
1508 fills the memory with this pattern, validates
1509 memory contents and reserves bad memory
1510 regions that are detected.
1512 meye.*= [HW] Set MotionEye Camera parameters
1513 See Documentation/video4linux/meye.txt.
1515 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1516 Multi-Function General Purpose Timers on AMD Geode
1519 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1520 the BIOS has incorrectly applied a workaround. TinyBIOS
1521 version 0.98 is known to be affected, 0.99 fixes the
1522 problem by letting the user disable the workaround.
1526 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1527 physical address is ignored.
1529 mini2440= [ARM,HW,KNL]
1530 Format:[0..2][b][c][t]
1532 MINI2440 configuration specification:
1533 0 - The attached screen is the 3.5" TFT
1534 1 - The attached screen is the 7" TFT
1535 2 - The VGA Shield is attached (1024x768)
1536 Leaving out the screen size parameter will not load
1537 the TFT driver, and the framebuffer will be left
1539 b - Enable backlight. The TFT backlight pin will be
1540 linked to the kernel VESA blanking code and a GPIO
1541 LED. This parameter is not necessary when using the
1543 c - Enable the s3c camera interface.
1544 t - Reserved for enabling touchscreen support. The
1545 touchscreen support is not enabled in the mainstream
1546 kernel as of 2.6.30, a preliminary port can be found
1547 in the "bleeding edge" mini2440 support kernel at
1548 http://repo.or.cz/w/linux-2.6/mini2440.git
1551 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1552 parameter allows control of the logging verbosity for
1553 the additional memory initialisation checks. A value
1554 of 0 disables mminit logging and a level of 4 will
1555 log everything. Information is printed at KERN_DEBUG
1556 so loglevel=8 may also need to be specified.
1559 [MOUSE] Maximum time between finger touching and
1560 leaving touchpad surface for touch to be considered
1561 a tap and be reported as a left button click (for
1562 touchpads working in absolute mode only).
1564 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1565 reporting absolute coordinates, such as tablets
1566 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1567 reporting absolute coordinates, such as tablets
1569 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1570 is similar to kernelcore except it specifies the
1571 amount of memory used for migratable allocations.
1572 If both kernelcore and movablecore is specified,
1573 then kernelcore will be at *least* the specified
1574 value but may be more. If movablecore on its own
1575 is specified, the administrator must be careful
1576 that the amount of memory usable for all allocations
1579 MTD_Partition= [MTD]
1580 Format: <name>,<region-number>,<size>,<offset>
1582 MTD_Region= [MTD] Format:
1583 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1586 See drivers/mtd/cmdlinepart.c.
1588 multitce=off [PPC] This parameter disables the use of the pSeries
1589 firmware feature for updating multiple TCE entries
1592 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1594 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1596 boundary - index of last SLC block on Flex-OneNAND.
1597 The remaining blocks are configured as MLC blocks.
1598 lock - Configure if Flex-OneNAND boundary should be locked.
1599 Once locked, the boundary cannot be changed.
1600 1 indicates lock status, 0 indicates unlock status.
1603 ARM/S3C2412 JIVE boot control
1605 See arch/arm/mach-s3c2412/mach-jive.c
1607 mtouchusb.raw_coordinates=
1608 [HW] Make the MicroTouch USB driver use raw coordinates
1609 ('y', default) or cooked coordinates ('n')
1611 mtrr_chunk_size=nn[KMG] [X86]
1612 used for mtrr cleanup. It is largest continuous chunk
1613 that could hold holes aka. UC entries.
1615 mtrr_gran_size=nn[KMG] [X86]
1616 Used for mtrr cleanup. It is granularity of mtrr block.
1618 Large value could prevent small alignment from
1621 mtrr_spare_reg_nr=n [X86]
1623 Range: 0,7 : spare reg number
1625 Used for mtrr cleanup. It is spare mtrr entries number.
1626 Set to 2 or more if your graphical card needs more.
1628 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1630 netdev= [NET] Network devices parameters
1631 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1632 Note that mem_start is often overloaded to mean
1633 something different and driver-specific.
1634 This usage is only documented in each driver source
1638 [NETFILTER] Enable connection tracking flow accounting
1639 0 to disable accounting
1640 1 to enable accounting
1643 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1644 See Documentation/filesystems/nfs/nfsroot.txt.
1646 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1647 See Documentation/filesystems/nfs/nfsroot.txt.
1649 nfsrootdebug [NFS] enable nfsroot debugging messages.
1650 See Documentation/filesystems/nfs/nfsroot.txt.
1652 nfs.callback_tcpport=
1653 [NFS] set the TCP port on which the NFSv4 callback
1654 channel should listen.
1657 [NFS] sets the pathname to the program which is used
1658 to update the NFS client cache entries.
1660 nfs.cache_getent_timeout=
1661 [NFS] sets the timeout after which an attempt to
1662 update a cache entry is deemed to have failed.
1664 nfs.idmap_cache_timeout=
1665 [NFS] set the maximum lifetime for idmapper cache
1669 [NFS] enable 64-bit inode numbers.
1670 If zero, the NFS client will fake up a 32-bit inode
1671 number for the readdir() and stat() syscalls instead
1672 of returning the full 64-bit number.
1673 The default is to return 64-bit inode numbers.
1675 nfs.max_session_slots=
1676 [NFSv4.1] Sets the maximum number of session slots
1677 the client will attempt to negotiate with the server.
1678 This limits the number of simultaneous RPC requests
1679 that the client can send to the NFSv4.1 server.
1680 Note that there is little point in setting this
1681 value higher than the max_tcp_slot_table_limit.
1683 nfs.nfs4_disable_idmapping=
1684 [NFSv4] When set to the default of '1', this option
1685 ensures that both the RPC level authentication
1686 scheme and the NFS level operations agree to use
1687 numeric uids/gids if the mount is using the
1688 'sec=sys' security flavour. In effect it is
1689 disabling idmapping, which can make migration from
1690 legacy NFSv2/v3 systems to NFSv4 easier.
1691 Servers that do not support this mode of operation
1692 will be autodetected by the client, and it will fall
1693 back to using the idmapper.
1694 To turn off this behaviour, set the value to '0'.
1696 nfs.send_implementation_id =
1697 [NFSv4.1] Send client implementation identification
1698 information in exchange_id requests.
1699 If zero, no implementation identification information
1701 The default is to send the implementation identification
1704 nfsd.nfs4_disable_idmapping=
1705 [NFSv4] When set to the default of '1', the NFSv4
1706 server will return only numeric uids and gids to
1707 clients using auth_sys, and will accept numeric uids
1708 and gids from such clients. This is intended to ease
1709 migration from NFSv2/v3.
1711 objlayoutdriver.osd_login_prog=
1712 [NFS] [OBJLAYOUT] sets the pathname to the program which
1713 is used to automatically discover and login into new
1714 osd-targets. Please see:
1715 Documentation/filesystems/pnfs.txt for more explanations
1717 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1718 when a NMI is triggered.
1719 Format: [state][,regs][,debounce][,die]
1721 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1722 Format: [panic,][nopanic,][num]
1724 0 - turn nmi_watchdog off
1725 When panic is specified, panic when an NMI watchdog
1726 timeout occurs (or 'nopanic' to override the opposite
1728 This is useful when you use a panic=... timeout and
1729 need the box quickly up again.
1731 netpoll.carrier_timeout=
1732 [NET] Specifies amount of time (in seconds) that
1733 netpoll should wait for a carrier. By default netpoll
1736 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1737 emulation library even if a 387 maths coprocessor
1741 [HW] Never suspend the console
1742 Disable suspending of consoles during suspend and
1743 hibernate operations. Once disabled, debugging
1744 messages can reach various consoles while the rest
1745 of the system is being put to sleep (ie, while
1746 debugging driver suspend/resume hooks). This may
1747 not work reliably with all consoles, but is known
1748 to work with serial and VGA consoles.
1749 To facilitate more flexible debugging, we also add
1750 console_suspend, a printk module parameter to control
1751 it. Users could use console_suspend (usually
1752 /sys/module/printk/parameters/console_suspend) to
1753 turn on/off it dynamically.
1755 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1756 caches in the slab allocator. Saves per-node memory,
1757 but will impact performance.
1761 noapic [SMP,APIC] Tells the kernel to not make use of any
1762 IOAPICs that may be present in the system.
1764 noautogroup Disable scheduler automatic task group creation.
1766 nobats [PPC] Do not use BATs for mapping kernel lowmem
1767 on "Classic" PPC cores.
1771 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1773 nodelayacct [KNL] Disable per-task delay accounting
1775 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1777 nodsp [SH] Disable hardware DSP at boot time.
1779 noefi [X86] Disable EFI runtime services support.
1784 On X86-32 available only on PAE configured kernels.
1785 noexec=on: enable non-executable mappings (default)
1786 noexec=off: disable non-executable mappings
1789 Disable SMEP (Supervisor Mode Execution Protection)
1790 even if it is supported by processor.
1793 This affects only 32-bit executables.
1794 noexec32=on: enable non-executable mappings (default)
1795 read doesn't imply executable mappings
1796 noexec32=off: disable non-executable mappings
1797 read implies executable mappings
1799 nofpu [SH] Disable hardware FPU at boot time.
1801 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1802 register save and restore. The kernel will only save
1803 legacy floating-point registers on task switch.
1805 noxsave [BUGS=X86] Disables x86 extended register state save
1806 and restore using xsave. The kernel will fallback to
1807 enabling legacy floating-point and sse state.
1809 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1810 wfi(ARM) instruction doesn't work correctly and not to
1811 use it. This is also useful when using JTAG debugger.
1813 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1814 instruction doesn't work correctly and not to
1817 no_file_caps Tells the kernel not to honor file capabilities. The
1818 only way then for a file to be executed with privilege
1819 is to be setuid root or executed by root.
1821 nohalt [IA-64] Tells the kernel not to use the power saving
1822 function PAL_HALT_LIGHT when idle. This increases
1823 power-consumption. On the positive side, it reduces
1824 interrupt wake-up latency, which may improve performance
1825 in certain environments such as networked servers or
1828 nohz= [KNL] Boottime enable/disable dynamic ticks
1829 Valid arguments: on, off
1832 noiotrap [SH] Disables trapped I/O port accesses.
1834 noirqdebug [X86-32] Disables the code which attempts to detect and
1835 disable unhandled interrupt sources.
1837 no_timer_check [X86,APIC] Disables the code which tests for
1838 broken timer IRQ sources.
1840 noisapnp [ISAPNP] Disables ISA PnP code.
1842 noinitrd [RAM] Tells the kernel not to load any configured
1845 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1847 [Deprecated - use intremap=off]
1851 nojitter [IA-64] Disables jitter checking for ITC timers.
1853 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1855 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1858 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1859 steal time is computed, but won't influence scheduler
1862 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1864 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1866 noltlbs [PPC] Do not use large page/tlb entries for kernel
1867 lowmem mapping on PPC40x.
1869 nomca [IA-64] Disable machine check abort handling
1871 nomce [X86-32] Machine Check Exception
1873 nomfgpt [X86-32] Disable Multi-Function General Purpose
1874 Timer usage (for AMD Geode machines).
1876 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1877 shutdown the other cpus. Instead use the REBOOT_VECTOR
1880 nomodule Disable module load
1882 nopat [X86] Disable PAT (page attribute table extension of
1883 pagetables) support.
1885 norandmaps Don't use address space randomization. Equivalent to
1886 echo 0 > /proc/sys/kernel/randomize_va_space
1888 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1890 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1891 with UP alternatives
1893 noresidual [PPC] Don't use residual data on PReP machines.
1895 nordrand [X86] Disable the direct use of the RDRAND
1896 instruction even if it is supported by the
1897 processor. RDRAND is still available to user
1900 noresume [SWSUSP] Disables resume and restores original swap
1903 no-scroll [VGA] Disables scrollback.
1904 This is required for the Braillex ib80-piezo Braille
1905 reader made by F.H. Papenmeier (Germany).
1909 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1911 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1912 and disable the IO APIC. legacy for "maxcpus=0".
1914 nosoftlockup [KNL] Disable the soft-lockup detector.
1916 nosync [HW,M68K] Disables sync negotiation for all devices.
1918 notsc [BUGS=X86-32] Disable Time Stamp Counter
1920 nousb [USB] Disable the USB subsystem
1922 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1926 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1928 nptcg= [IA-64] Override max number of concurrent global TLB
1929 purges which is reported from either PAL_VM_SUMMARY or
1932 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1933 could support. nr_cpus=n : n >= 1 limits the kernel to
1934 supporting 'n' processors. Later in runtime you can not
1935 use hotplug cpu feature to put more cpu back to online.
1936 just like you compile the kernel NR_CPUS=n
1938 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1940 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1941 one of ['zone', 'node', 'default'] can be specified
1942 This can be set from sysctl after boot.
1943 See Documentation/sysctl/vm.txt for details.
1945 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1946 See Documentation/debugging-via-ohci1394.txt for more
1949 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1950 Rather than timing out after 20 ms if an EC
1951 command is not properly ACKed, override the length
1952 of the timeout. We have interrupts disabled while
1953 waiting for the ACK, so if this is set too high
1954 interrupts *may* be lost!
1956 omap_mux= [OMAP] Override bootloader pin multiplexing.
1957 Format: <mux_mode0.mode_name=value>...
1958 For example, to override I2C bus2:
1959 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1961 oprofile.timer= [HW]
1962 Use timer interrupt instead of performance counters
1964 oprofile.cpu_type= Force an oprofile cpu type
1965 This might be useful if you have an older oprofile
1966 userland or if you want common events.
1967 Format: { arch_perfmon }
1968 arch_perfmon: [X86] Force use of architectural
1969 perfmon on Intel CPUs instead of the
1970 CPU specific event set.
1971 timer: [X86] Force use of architectural NMI
1972 timer mode (see also oprofile.timer
1973 for generic hr timer mode)
1974 [s390] Force legacy basic mode sampling
1975 (report cpu_type "timer")
1977 oops=panic Always panic on oopses. Default is to just kill the
1978 process, but there is a small probability of
1979 deadlocking the machine.
1980 This will also cause panics on machine check exceptions.
1981 Useful together with panic=30 to trigger a reboot.
1984 See Documentation/sound/oss/oss-parameters.txt
1986 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1987 timeout > 0: seconds before rebooting
1988 timeout = 0: wait forever
1989 timeout < 0: reboot immediately
1992 parkbd.port= [HW] Parallel port number the keyboard adapter is
1993 connected to, default is 0.
1995 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1996 0 for XT, 1 for AT (default is AT).
1999 parport= [HW,PPT] Specify parallel ports. 0 disables.
2000 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2001 Use 'auto' to force the driver to use any
2002 IRQ/DMA settings detected (the default is to
2003 ignore detected IRQ/DMA settings because of
2004 possible conflicts). You can specify the base
2005 address, IRQ, and DMA settings; IRQ and DMA
2006 should be numbers, or 'auto' (for using detected
2007 settings on that particular port), or 'nofifo'
2008 (to avoid using a FIFO even if it is detected).
2009 Parallel ports are assigned in the order they
2010 are specified on the command line, starting
2013 parport_init_mode= [HW,PPT]
2014 Configure VIA parallel port to operate in
2015 a specific mode. This is necessary on Pegasos
2016 computer where firmware has no options for setting
2017 up parallel port mode and sets it to spp.
2018 Currently this function knows 686a and 8231 chips.
2019 Format: [spp|ps2|epp|ecp|ecpepp]
2022 Halt all CPUs after the first oops has been printed for
2023 the specified number of seconds. This is to be used if
2024 your oopses keep scrolling off the screen.
2029 See header of drivers/block/paride/pcd.c.
2030 See also Documentation/blockdev/paride.txt.
2032 pci=option[,option...] [PCI] various PCI subsystem options:
2033 earlydump [X86] dump PCI config space before the kernel
2035 off [X86] don't probe for the PCI bus
2036 bios [X86-32] force use of PCI BIOS, don't access
2037 the hardware directly. Use this if your machine
2038 has a non-standard PCI host bridge.
2039 nobios [X86-32] disallow use of PCI BIOS, only direct
2040 hardware access methods are allowed. Use this
2041 if you experience crashes upon bootup and you
2042 suspect they are caused by the BIOS.
2043 conf1 [X86] Force use of PCI Configuration
2045 conf2 [X86] Force use of PCI Configuration
2047 noaer [PCIE] If the PCIEAER kernel config parameter is
2048 enabled, this kernel boot option can be used to
2049 disable the use of PCIE advanced error reporting.
2050 nodomains [PCI] Disable support for multiple PCI
2051 root domains (aka PCI segments, in ACPI-speak).
2052 nommconf [X86] Disable use of MMCONFIG for PCI
2054 check_enable_amd_mmconf [X86] check for and enable
2055 properly configured MMIO access to PCI
2056 config space on AMD family 10h CPU
2057 nomsi [MSI] If the PCI_MSI kernel config parameter is
2058 enabled, this kernel boot option can be used to
2059 disable the use of MSI interrupts system-wide.
2060 noioapicquirk [APIC] Disable all boot interrupt quirks.
2061 Safety option to keep boot IRQs enabled. This
2062 should never be necessary.
2063 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2064 primary IO-APIC for bridges that cannot disable
2065 boot IRQs. This fixes a source of spurious IRQs
2066 when the system masks IRQs.
2067 noioapicreroute [APIC] Disable workaround that uses the
2068 boot IRQ equivalent of an IRQ that connects to
2069 a chipset where boot IRQs cannot be disabled.
2070 The opposite of ioapicreroute.
2071 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2072 routing table. These calls are known to be buggy
2073 on several machines and they hang the machine
2074 when used, but on other computers it's the only
2075 way to get the interrupt routing table. Try
2076 this option if the kernel is unable to allocate
2077 IRQs or discover secondary PCI buses on your
2079 rom [X86] Assign address space to expansion ROMs.
2080 Use with caution as certain devices share
2081 address decoders between ROMs and other
2083 norom [X86] Do not assign address space to
2084 expansion ROMs that do not already have
2085 BIOS assigned address ranges.
2086 nobar [X86] Do not assign address space to the
2087 BARs that weren't assigned by the BIOS.
2088 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2089 assigned automatically to PCI devices. You can
2090 make the kernel exclude IRQs of your ISA cards
2092 pirqaddr=0xAAAAA [X86] Specify the physical address
2093 of the PIRQ table (normally generated
2094 by the BIOS) if it is outside the
2095 F0000h-100000h range.
2096 lastbus=N [X86] Scan all buses thru bus #N. Can be
2097 useful if the kernel is unable to find your
2098 secondary buses and you want to tell it
2099 explicitly which ones they are.
2100 assign-busses [X86] Always assign all PCI bus
2101 numbers ourselves, overriding
2102 whatever the firmware may have done.
2103 usepirqmask [X86] Honor the possible IRQ mask stored
2104 in the BIOS $PIR table. This is needed on
2105 some systems with broken BIOSes, notably
2106 some HP Pavilion N5400 and Omnibook XE3
2107 notebooks. This will have no effect if ACPI
2108 IRQ routing is enabled.
2109 noacpi [X86] Do not use ACPI for IRQ routing
2110 or for PCI scanning.
2111 use_crs [X86] Use PCI host bridge window information
2112 from ACPI. On BIOSes from 2008 or later, this
2113 is enabled by default. If you need to use this,
2114 please report a bug.
2115 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2116 If you need to use this, please report a bug.
2117 routeirq Do IRQ routing for all PCI devices.
2118 This is normally done in pci_enable_device(),
2119 so this option is a temporary workaround
2120 for broken drivers that don't call it.
2121 skip_isa_align [X86] do not align io start addr, so can
2122 handle more pci cards
2123 firmware [ARM] Do not re-enumerate the bus but instead
2124 just use the configuration from the
2125 bootloader. This is currently used on
2126 IXP2000 systems where the bus has to be
2127 configured a certain way for adjunct CPUs.
2128 noearly [X86] Don't do any early type 1 scanning.
2129 This might help on some broken boards which
2130 machine check when some devices' config space
2131 is read. But various workarounds are disabled
2132 and some IOMMU drivers will not work.
2133 bfsort Sort PCI devices into breadth-first order.
2134 This sorting is done to get a device
2135 order compatible with older (<= 2.4) kernels.
2136 nobfsort Don't sort PCI devices into breadth-first order.
2137 cbiosize=nn[KMG] The fixed amount of bus space which is
2138 reserved for the CardBus bridge's IO window.
2139 The default value is 256 bytes.
2140 cbmemsize=nn[KMG] The fixed amount of bus space which is
2141 reserved for the CardBus bridge's memory
2142 window. The default value is 64 megabytes.
2145 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2146 Specifies alignment and device to reassign
2147 aligned memory resources.
2148 If <order of align> is not specified,
2149 PAGE_SIZE is used as alignment.
2150 PCI-PCI bridge can be specified, if resource
2151 windows need to be expanded.
2152 ecrc= Enable/disable PCIe ECRC (transaction layer
2153 end-to-end CRC checking).
2154 bios: Use BIOS/firmware settings. This is the
2158 realloc= Enable/disable reallocating PCI bridge resources
2159 if allocations done by BIOS are too small to
2160 accommodate resources required by all child
2162 off: Turn realloc off
2164 realloc same as realloc=on
2165 noari do not use PCIe ARI.
2166 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2167 only look for one device below a PCIe downstream
2170 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2173 force Enable ASPM even on devices that claim not to support it.
2174 WARNING: Forcing ASPM on may cause system lockups.
2176 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2177 nomsi Do not use MSI for PCI Express Native Hotplug (this
2178 makes all PCIe ports use INTx for hotplug services).
2180 pcie_ports= [PCIE] PCIe ports handling:
2181 auto Ask the BIOS whether or not to use native PCIe services
2182 associated with PCIe ports (PME, hot-plug, AER). Use
2183 them only if that is allowed by the BIOS.
2184 native Use native PCIe services associated with PCIe ports
2186 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2189 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2190 nomsi Do not use MSI for native PCIe PME signaling (this makes
2191 all PCIe root ports use INTx for all services).
2193 pcmv= [HW,PCMCIA] BadgePAD 4
2196 See Documentation/blockdev/paride.txt.
2198 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2201 See arch/parisc/kernel/pdc_chassis.c
2203 percpu_alloc= Select which percpu first chunk allocator to use.
2204 Currently supported values are "embed" and "page".
2205 Archs may support subset or none of the selections.
2206 See comments in mm/percpu.c for details on each
2207 allocator. This parameter is primarily for debugging
2208 and performance comparison.
2211 See Documentation/blockdev/paride.txt.
2214 See Documentation/blockdev/paride.txt.
2216 pirq= [SMP,APIC] Manual mp-table setup
2217 See Documentation/x86/i386/IO-APIC.txt.
2219 plip= [PPT,NET] Parallel port network link
2220 Format: { parport<nr> | timid | 0 }
2221 See also Documentation/parport.txt.
2223 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2224 Override pmtimer IOPort with a hex value.
2228 Enable PNP debug messages (depends on the
2229 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2230 via /sys/module/pnp/parameters/debug. We always show
2231 current resource usage; turning this on also shows
2232 possible settings and some assignment information.
2238 { on | off | curr | res | no-curr | no-res }
2241 [ISAPNP] Exclude IRQs for the autoconfiguration
2244 [ISAPNP] Exclude DMAs for the autoconfiguration
2246 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2247 Ranges are in pairs (I/O port base and size).
2250 [ISAPNP] Exclude memory regions for the
2252 Ranges are in pairs (memory base and size).
2254 ports= [IP_VS_FTP] IPVS ftp helper module
2256 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2258 Format: <port>,<port>....
2260 print-fatal-signals=
2261 [KNL] debug: print fatal signals
2263 If enabled, warn about various signal handling
2264 related application anomalies: too many signals,
2265 too many POSIX.1 timers, fatal signals causing a
2268 If you hit the warning due to signal overflow,
2269 you might want to try "ulimit -i unlimited".
2273 printk.always_kmsg_dump=
2274 Trigger kmsg_dump for cases other than kernel oops or
2276 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2279 printk.time= Show timing data prefixed to each printk message line
2280 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2282 processor.max_cstate= [HW,ACPI]
2283 Limit processor to maximum C-state
2284 max_cstate=9 overrides any DMI blacklist limit.
2286 processor.nocst [HW,ACPI]
2287 Ignore the _CST method to determine C-states,
2288 instead using the legacy FADT method
2290 profile= [KNL] Enable kernel profiling via /proc/profile
2291 Format: [schedule,]<number>
2292 Param: "schedule" - profile schedule points.
2293 Param: <number> - step/bucket size as a power of 2 for
2294 statistical time based profiling.
2295 Param: "sleep" - profile D-state sleeping (millisecs).
2296 Requires CONFIG_SCHEDSTATS
2297 Param: "kvm" - profile VM exits.
2299 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2301 See Documentation/blockdev/ramdisk.txt.
2303 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2304 probe for; one of (bare|imps|exps|lifebook|any).
2305 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2307 psmouse.resetafter= [HW,MOUSE]
2308 Try to reset the device after so many bad packets
2311 [HW,MOUSE] Set desired mouse resolution, in dpi.
2312 psmouse.smartscroll=
2313 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2314 0 = disabled, 1 = enabled (default).
2316 pstore.backend= Specify the name of the pstore backend to use
2319 See Documentation/blockdev/paride.txt.
2322 [KNL] Number of legacy pty's. Overwrites compiled-in
2325 quiet [KNL] Disable most log messages
2330 See Documentation/md.txt.
2332 ramdisk_blocksize= [RAM]
2333 See Documentation/blockdev/ramdisk.txt.
2335 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2336 See Documentation/blockdev/ramdisk.txt.
2338 rcutree.blimit= [KNL,BOOT]
2339 Set maximum number of finished RCU callbacks to process
2342 rcutree.qhimark= [KNL,BOOT]
2343 Set threshold of queued
2344 RCU callbacks over which batch limiting is disabled.
2346 rcutree.qlowmark= [KNL,BOOT]
2347 Set threshold of queued RCU callbacks below which
2348 batch limiting is re-enabled.
2350 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2351 Suppress RCU CPU stall warning messages.
2353 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2354 Set timeout for RCU CPU stall warning messages.
2356 rcutorture.fqs_duration= [KNL,BOOT]
2357 Set duration of force_quiescent_state bursts.
2359 rcutorture.fqs_holdoff= [KNL,BOOT]
2360 Set holdoff time within force_quiescent_state bursts.
2362 rcutorture.fqs_stutter= [KNL,BOOT]
2363 Set wait time between force_quiescent_state bursts.
2365 rcutorture.irqreader= [KNL,BOOT]
2366 Test RCU readers from irq handlers.
2368 rcutorture.n_barrier_cbs= [KNL,BOOT]
2369 Set callbacks/threads for rcu_barrier() testing.
2371 rcutorture.nfakewriters= [KNL,BOOT]
2372 Set number of concurrent RCU writers. These just
2373 stress RCU, they don't participate in the actual
2374 test, hence the "fake".
2376 rcutorture.nreaders= [KNL,BOOT]
2377 Set number of RCU readers.
2379 rcutorture.onoff_holdoff= [KNL,BOOT]
2380 Set time (s) after boot for CPU-hotplug testing.
2382 rcutorture.onoff_interval= [KNL,BOOT]
2383 Set time (s) between CPU-hotplug operations, or
2384 zero to disable CPU-hotplug testing.
2386 rcutorture.shuffle_interval= [KNL,BOOT]
2387 Set task-shuffle interval (s). Shuffling tasks
2388 allows some CPUs to go into dyntick-idle mode
2389 during the rcutorture test.
2391 rcutorture.shutdown_secs= [KNL,BOOT]
2392 Set time (s) after boot system shutdown. This
2393 is useful for hands-off automated testing.
2395 rcutorture.stall_cpu= [KNL,BOOT]
2396 Duration of CPU stall (s) to test RCU CPU stall
2397 warnings, zero to disable.
2399 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2400 Time to wait (s) after boot before inducing stall.
2402 rcutorture.stat_interval= [KNL,BOOT]
2403 Time (s) between statistics printk()s.
2405 rcutorture.stutter= [KNL,BOOT]
2406 Time (s) to stutter testing, for example, specifying
2407 five seconds causes the test to run for five seconds,
2408 wait for five seconds, and so on. This tests RCU's
2409 ability to transition abruptly to and from idle.
2411 rcutorture.test_boost= [KNL,BOOT]
2412 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2413 "Maybe" means test if the RCU implementation
2414 under test support RCU priority boosting.
2416 rcutorture.test_boost_duration= [KNL,BOOT]
2417 Duration (s) of each individual boost test.
2419 rcutorture.test_boost_interval= [KNL,BOOT]
2420 Interval (s) between each boost test.
2422 rcutorture.test_no_idle_hz= [KNL,BOOT]
2423 Test RCU's dyntick-idle handling. See also the
2424 rcutorture.shuffle_interval parameter.
2426 rcutorture.torture_type= [KNL,BOOT]
2427 Specify the RCU implementation to test.
2429 rcutorture.verbose= [KNL,BOOT]
2430 Enable additional printk() statements.
2434 Run specified binary instead of /init from the ramdisk,
2435 used for early userspace startup. See initrd.
2437 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2438 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2439 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2442 [KNL, SMP] Set scheduler's default relax_domain_level.
2443 See Documentation/cgroups/cpusets.txt.
2445 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2447 reservetop= [X86-32]
2449 Reserves a hole at the top of the kernel virtual
2454 Set the amount of memory to reserve for BIOS at
2455 the bottom of the address space.
2457 reset_devices [KNL] Force drivers to reset the underlying device
2458 during initialization.
2461 Specify the partition device for software suspend
2463 resume_offset= [SWSUSP]
2464 Specify the offset from the beginning of the partition
2465 given by "resume=" at which the swap header is located,
2466 in <PAGE_SIZE> units (needed only for swap files).
2467 See Documentation/power/swsusp-and-swap-files.txt
2469 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2470 read the resume files
2472 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2473 Useful for devices that are detected asynchronously
2474 (e.g. USB and MMC devices).
2476 hibernate= [HIBERNATION]
2477 noresume Don't check if there's a hibernation image
2478 present during boot.
2479 nocompress Don't compress/decompress hibernation images.
2481 retain_initrd [RAM] Keep initrd memory after extraction
2483 rhash_entries= [KNL,NET]
2484 Set number of hash buckets for route cache
2486 riscom8= [HW,SERIAL]
2487 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2489 ro [KNL] Mount root device read-only on boot
2491 root= [KNL] Root filesystem
2492 See name_to_dev_t comment in init/do_mounts.c.
2494 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2495 mount the root filesystem
2497 rootflags= [KNL] Set root filesystem mount option string
2499 rootfstype= [KNL] Set root filesystem type
2501 rootwait [KNL] Wait (indefinitely) for root device to show up.
2502 Useful for devices that are detected asynchronously
2503 (e.g. USB and MMC devices).
2505 rw [KNL] Mount root device read-write on boot
2507 S [KNL] Run init in single mode
2510 See drivers/net/irda/sa1100_ir.c.
2512 sbni= [NET] Granch SBNI12 leased line adapter
2514 sched_debug [KNL] Enables verbose scheduler debug messages.
2516 security= [SECURITY] Choose a security module to enable at boot.
2517 If this boot parameter is not specified, only the first
2518 security module asking for security registration will be
2519 loaded. An invalid security module name will be treated
2520 as if no module has been chosen.
2522 selinux= [SELINUX] Disable or enable SELinux at boot time.
2523 Format: { "0" | "1" }
2524 See security/selinux/Kconfig help text.
2527 Default value is set via kernel config option.
2528 If enabled at boot time, /selinux/disable can be used
2529 later to disable prior to initial policy load.
2531 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2532 Format: { "0" | "1" }
2533 See security/apparmor/Kconfig help text
2536 Default value is set via kernel config option.
2538 serialnumber [BUGS=X86-32]
2541 Maximal number of shapers.
2543 show_msr= [x86] show boot-time MSR settings
2544 Format: { <integer> }
2545 Show boot-time (BIOS-initialized) MSR settings.
2546 The parameter means the number of CPUs to show,
2547 for example 1 means boot CPU only.
2554 slab_max_order= [MM, SLAB]
2555 Determines the maximum allowed order for slabs.
2556 A high setting may cause OOMs due to memory
2557 fragmentation. Defaults to 1 for systems with
2558 more than 32MB of RAM, 0 otherwise.
2560 slub_debug[=options[,slabs]] [MM, SLUB]
2561 Enabling slub_debug allows one to determine the
2562 culprit if slab objects become corrupted. Enabling
2563 slub_debug can create guard zones around objects and
2564 may poison objects when not in use. Also tracks the
2565 last alloc / free. For more information see
2566 Documentation/vm/slub.txt.
2568 slub_max_order= [MM, SLUB]
2569 Determines the maximum allowed order for slabs.
2570 A high setting may cause OOMs due to memory
2571 fragmentation. For more information see
2572 Documentation/vm/slub.txt.
2574 slub_min_objects= [MM, SLUB]
2575 The minimum number of objects per slab. SLUB will
2576 increase the slab order up to slub_max_order to
2577 generate a sufficiently large slab able to contain
2578 the number of objects indicated. The higher the number
2579 of objects the smaller the overhead of tracking slabs
2580 and the less frequently locks need to be acquired.
2581 For more information see Documentation/vm/slub.txt.
2583 slub_min_order= [MM, SLUB]
2584 Determines the minimum page order for slabs. Must be
2585 lower than slub_max_order.
2586 For more information see Documentation/vm/slub.txt.
2588 slub_nomerge [MM, SLUB]
2589 Disable merging of slabs with similar size. May be
2590 necessary if there is some reason to distinguish
2591 allocs to different slabs. Debug options disable
2592 merging on their own.
2593 For more information see Documentation/vm/slub.txt.
2596 Format: <io1>[,<io2>[,...,<io8>]]
2598 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2599 attempt to substitute SMP alternatives once at boot.
2601 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2602 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2603 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2604 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2605 smsc-ircc2.ircc_irq= [HW] IRQ line
2606 smsc-ircc2.ircc_dma= [HW] DMA channel
2607 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2608 0: Toshiba Satellite 1800 (GP data pin select)
2609 1: Fast pin select (default)
2613 [KNL] Should the soft-lockup detector generate panics.
2616 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2617 See Documentation/laptops/sonypi.txt
2619 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2620 See Documentation/serial/specialix.txt.
2622 spia_io_base= [HW,MTD]
2628 Enabled the stack tracer on boot up.
2630 stacktrace_filter=[function-list]
2631 [FTRACE] Limit the functions that the stack tracer
2632 will trace at boot up. function-list is a comma separated
2633 list of functions. This list can be changed at run
2634 time by the stack_trace_filter file in the debugfs
2635 tracing directory. Note, this enables stack tracing
2636 and the stacktrace above is not needed.
2640 Set the STI (builtin display/keyboard on the HP-PARISC
2641 machines) console (graphic card) which should be used
2642 as the initial boot-console.
2643 See also comment in drivers/video/console/sticore.c.
2646 See comment in drivers/video/console/sticore.c.
2649 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2651 sunrpc.min_resvport=
2652 sunrpc.max_resvport=
2654 SunRPC servers often require that client requests
2655 originate from a privileged port (i.e. a port in the
2656 range 0 < portnr < 1024).
2657 An administrator who wishes to reserve some of these
2658 ports for other uses may adjust the range that the
2659 kernel's sunrpc client considers to be privileged
2660 using these two parameters to set the minimum and
2661 maximum port values.
2665 Control how the NFS server code allocates CPUs to
2666 service thread pools. Depending on how many NICs
2667 you have and where their interrupts are bound, this
2668 option will affect which CPUs will do NFS serving.
2669 Note: this parameter cannot be changed while the
2670 NFS server is running.
2672 auto the server chooses an appropriate mode
2673 automatically using heuristics
2674 global a single global pool contains all CPUs
2675 percpu one pool for each CPU
2676 pernode one pool for each NUMA node (equivalent
2677 to global on non-NUMA machines)
2679 sunrpc.tcp_slot_table_entries=
2680 sunrpc.udp_slot_table_entries=
2682 Sets the upper limit on the number of simultaneous
2683 RPC calls that can be sent from the client to a
2684 server. Increasing these values may allow you to
2685 improve throughput, but will also increase the
2686 amount of memory reserved for use by the client.
2689 [KNL] Enable accounting of swap in memory resource
2690 controller if no parameter or 1 is given or disable
2691 it if 0 is given (See Documentation/cgroups/memory.txt)
2693 swiotlb= [IA-64] Number of I/O TLB slabs
2697 sysfs.deprecated=0|1 [KNL]
2698 Enable/disable old style sysfs layout for old udev
2699 on older distributions. When this option is enabled
2700 very new udev will not work anymore. When this option
2701 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2702 in older udev will not work anymore.
2703 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2704 the kernel configuration.
2706 sysrq_always_enabled
2708 Ignore sysrq setting - this boot parameter will
2709 neutralize any effect of /proc/sys/kernel/sysrq.
2710 Useful for debugging.
2714 test_suspend= [SUSPEND]
2715 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2716 standby suspend) as the system sleep state to briefly
2717 enter during system startup. The system is woken from
2718 this state using a wakeup-capable RTC alarm.
2720 thash_entries= [KNL,NET]
2721 Set number of hash buckets for TCP connection
2723 thermal.act= [HW,ACPI]
2724 -1: disable all active trip points in all thermal zones
2725 <degrees C>: override all lowest active trip points
2727 thermal.crt= [HW,ACPI]
2728 -1: disable all critical trip points in all thermal zones
2729 <degrees C>: override all critical trip points
2731 thermal.nocrt= [HW,ACPI]
2732 Set to disable actions on ACPI thermal zone
2733 critical and hot trip points.
2735 thermal.off= [HW,ACPI]
2736 1: disable ACPI thermal control
2738 thermal.psv= [HW,ACPI]
2739 -1: disable all passive trip points
2740 <degrees C>: override all passive trip points to this
2743 thermal.tzp= [HW,ACPI]
2744 Specify global default ACPI thermal zone polling rate
2745 <deci-seconds>: poll all this frequency
2746 0: no polling (default)
2749 Force threading of all interrupt handlers except those
2750 marked explicitly IRQF_NO_THREAD.
2754 Specify if the kernel should make use of the cpu
2755 topology information if the hardware supports this.
2756 The scheduler will make use of this information and
2757 e.g. base its process migration decisions on it.
2762 tpm_suspend_pcr=[HW,TPM]
2763 Format: integer pcr id
2764 Specify that at suspend time, the tpm driver
2765 should extend the specified pcr with zeros,
2766 as a workaround for some chips which fail to
2767 flush the last written pcr on TPM_SaveState.
2768 This will guarantee that all the other pcrs
2771 trace_buf_size=nn[KMG]
2772 [FTRACE] will set tracing buffer size.
2774 trace_event=[event-list]
2775 [FTRACE] Set and start specified trace events in order
2776 to facilitate early boot debugging.
2777 See also Documentation/trace/events.txt
2779 transparent_hugepage=
2781 Format: [always|madvise|never]
2782 Can be used to control the default behavior of the system
2783 with respect to transparent hugepages.
2784 See Documentation/vm/transhuge.txt for more details.
2786 tsc= Disable clocksource stability checks for TSC.
2788 [x86] reliable: mark tsc clocksource as reliable, this
2789 disables clocksource verification at runtime, as well
2790 as the stability checks done at bootup. Used to enable
2791 high-resolution timer mode on older hardware, and in
2792 virtualized environment.
2793 [x86] noirqtime: Do not use TSC to do irq accounting.
2794 Used to run time disable IRQ_TIME_ACCOUNTING on any
2795 platforms where RDTSC is slow and this accounting
2798 turbografx.map[2|3]= [HW,JOY]
2799 TurboGraFX parallel port interface
2801 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2802 See also Documentation/input/joystick-parport.txt
2804 udbg-immortal [PPC] When debugging early kernel crashes that
2805 happen after console_init() and before a proper
2806 console driver takes over, this boot options might
2807 help "seeing" what's going on.
2809 uhash_entries= [KNL,NET]
2810 Set number of hash buckets for UDP/UDP-Lite connections
2813 [USB] Ignore overcurrent events (default N).
2814 Some badly-designed motherboards generate lots of
2815 bogus events, for ports that aren't wired to
2816 anything. Set this parameter to avoid log spamming.
2817 Note that genuine overcurrent events won't be
2821 [X86] Cause panic on unknown NMI.
2823 usbcore.authorized_default=
2824 [USB] Default USB device authorization:
2825 (default -1 = authorized except for wireless USB,
2826 0 = not authorized, 1 = authorized)
2828 usbcore.autosuspend=
2829 [USB] The autosuspend time delay (in seconds) used
2830 for newly-detected USB devices (default 2). This
2831 is the time required before an idle device will be
2832 autosuspended. Devices for which the delay is set
2833 to a negative value won't be autosuspended at all.
2835 usbcore.usbfs_snoop=
2836 [USB] Set to log all usbfs traffic (default 0 = off).
2838 usbcore.blinkenlights=
2839 [USB] Set to cycle leds on hubs (default 0 = off).
2841 usbcore.old_scheme_first=
2842 [USB] Start with the old device initialization
2843 scheme (default 0 = off).
2845 usbcore.usbfs_memory_mb=
2846 [USB] Memory limit (in MB) for buffers allocated by
2847 usbfs (default = 16, 0 = max = 2047).
2849 usbcore.use_both_schemes=
2850 [USB] Try the other device initialization scheme
2851 if the first one fails (default 1 = enabled).
2853 usbcore.initial_descriptor_timeout=
2854 [USB] Specifies timeout for the initial 64-byte
2855 USB_REQ_GET_DESCRIPTOR request in milliseconds
2856 (default 5000 = 5.0 seconds).
2859 [USBHID] The interval which mice are to be polled at.
2861 usb-storage.delay_use=
2862 [UMS] The delay in seconds before a new device is
2863 scanned for Logical Units (default 5).
2866 [UMS] A list of quirks entries to supplement or
2867 override the built-in unusual_devs list. List
2868 entries are separated by commas. Each entry has
2869 the form VID:PID:Flags where VID and PID are Vendor
2870 and Product ID values (4-digit hex numbers) and
2871 Flags is a set of characters, each corresponding
2872 to a common usb-storage quirk flag as follows:
2873 a = SANE_SENSE (collect more than 18 bytes
2875 b = BAD_SENSE (don't collect more than 18
2876 bytes of sense data);
2877 c = FIX_CAPACITY (decrease the reported
2878 device capacity by one sector);
2879 d = NO_READ_DISC_INFO (don't use
2880 READ_DISC_INFO command);
2881 e = NO_READ_CAPACITY_16 (don't use
2882 READ_CAPACITY_16 command);
2883 h = CAPACITY_HEURISTICS (decrease the
2884 reported device capacity by one
2885 sector if the number is odd);
2886 i = IGNORE_DEVICE (don't bind to this
2888 l = NOT_LOCKABLE (don't try to lock and
2889 unlock ejectable media);
2890 m = MAX_SECTORS_64 (don't transfer more
2891 than 64 sectors = 32 KB at a time);
2892 n = INITIAL_READ10 (force a retry of the
2893 initial READ(10) command);
2894 o = CAPACITY_OK (accept the capacity
2895 reported by the device);
2896 r = IGNORE_RESIDUE (the device reports
2897 bogus residue values);
2898 s = SINGLE_LUN (the device has only one
2900 w = NO_WP_DETECT (don't test whether the
2901 medium is write-protected).
2902 Example: quirks=0419:aaf5:rl,0421:0433:rc
2904 user_debug= [KNL,ARM]
2906 See arch/arm/Kconfig.debug help text.
2907 1 - undefined instruction events
2909 4 - invalid data aborts
2912 Example: user_debug=31
2915 [X86] Flags controlling user PTE allocations.
2917 nohigh = do not allocate PTE pages in
2918 HIGHMEM regardless of setting
2922 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2923 vdso=1: enable VDSO (default)
2924 vdso=0: disable VDSO mapping
2927 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2928 vdso32=1: enable 32-bit VDSO (default)
2929 vdso32=0: disable 32-bit VDSO mapping
2932 vector=percpu: enable percpu vector domain
2934 video= [FB] Frame buffer configuration
2935 See Documentation/fb/modedb.txt.
2938 [VMMIO] Memory mapped virtio (platform) device.
2940 <size>@<baseaddr>:<irq>[:<id>]
2942 <size> := size (can use standard suffixes
2944 <baseaddr> := physical base address
2945 <irq> := interrupt number (as passed to
2947 <id> := (optional) platform device id
2949 virtio_mmio.device=1K@0x100b0000:48:7
2951 Can be used multiple times for multiple devices.
2953 vga= [BOOT,X86-32] Select a particular video mode
2954 See Documentation/x86/boot.txt and
2955 Documentation/svga.txt.
2956 Use vga=ask for menu.
2957 This is actually a boot loader parameter; the value is
2958 passed to the kernel using a special protocol.
2960 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2961 size of <nn>. This can be used to increase the
2962 minimum size (128MB on x86). It can also be used to
2963 decrease the size and leave more room for directly
2966 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2969 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2972 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2976 Controls the behavior of vsyscalls (i.e. calls to
2977 fixed addresses of 0xffffffffff600x00 from legacy
2978 code). Most statically-linked binaries and older
2979 versions of glibc use these calls. Because these
2980 functions are at fixed addresses, they make nice
2981 targets for exploits that can control RIP.
2983 emulate [default] Vsyscalls turn into traps and are
2984 emulated reasonably safely.
2986 native Vsyscalls are native syscall instructions.
2987 This is a little bit faster than trapping
2988 and makes a few dynamic recompilers work
2989 better than they would in emulation mode.
2990 It also makes exploits much easier to write.
2992 none Vsyscalls don't work at all. This makes
2993 them quite hard to use for exploits but
2994 might break your system.
2996 vt.cur_default= [VT] Default cursor shape.
2997 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2998 the parameters of the <Esc>[?A;B;Cc escape sequence;
2999 see VGA-softcursor.txt. Default: 2 = underline.
3001 vt.default_blu= [VT]
3002 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3003 Change the default blue palette of the console.
3004 This is a 16-member array composed of values
3007 vt.default_grn= [VT]
3008 Format: <green0>,<green1>,<green2>,...,<green15>
3009 Change the default green palette of the console.
3010 This is a 16-member array composed of values
3013 vt.default_red= [VT]
3014 Format: <red0>,<red1>,<red2>,...,<red15>
3015 Change the default red palette of the console.
3016 This is a 16-member array composed of values
3022 Set system-wide default UTF-8 mode for all tty's.
3023 Default is 1, i.e. UTF-8 mode is enabled for all
3024 newly opened terminals.
3026 vt.global_cursor_default=
3029 Set system-wide default for whether a cursor
3030 is shown on new VTs. Default is -1,
3031 i.e. cursors will be created by default unless
3032 overridden by individual drivers. 0 will hide
3033 cursors, 1 will display them.
3035 watchdog timers [HW,WDT] For information on watchdog timers,
3036 see Documentation/watchdog/watchdog-parameters.txt
3037 or other driver-specific files in the
3038 Documentation/watchdog/ directory.
3040 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3041 default x2apic cluster mode on platforms
3044 x86_mrst_timer= [X86-32,APBT]
3045 Choose timer option for x86 Moorestown MID platform.
3046 Two valid options are apbt timer only and lapic timer
3047 plus one apbt timer for broadcast timer.
3048 x86_mrst_timer=apbt_only | lapic_and_apbt
3050 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3051 xd_geo= See header of drivers/block/xd.c.
3053 xen_emul_unplug= [HW,X86,XEN]
3054 Unplug Xen emulated devices
3055 Format: [unplug0,][unplug1]
3056 ide-disks -- unplug primary master IDE devices
3057 aux-ide-disks -- unplug non-primary-master IDE devices
3058 nics -- unplug network devices
3059 all -- unplug all emulated devices (NICs and IDE disks)
3060 unnecessary -- unplugging emulated devices is
3061 unnecessary even if the host did not respond to
3063 never -- do not unplug even if version check succeeds
3065 xirc2ps_cs= [NET,PCMCIA]
3067 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3069 ______________________________________________________________________
3073 Add more DRM drivers.
projects / cascardo / linux.git / blob