4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VMMIO Driver for memory mapped virtio devices is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amijoy.map= [HW,JOY] Amiga joystick support
340 Map of devices attached to JOY0DAT and JOY1DAT
342 See also Documentation/input/joystick.txt
344 analog.map= [HW,JOY] Analog joystick and gamepad support
345 Specifies type or capabilities of an analog joystick
346 connected to one of 16 gameports
347 Format: <type1>,<type2>,..<type16>
350 Power management functions (SPARCstation-4/5 + deriv.)
352 Disable APC CPU standby support. SPARCstation-Fox does
353 not play well with APC CPU idle - disable it if you have
354 APC and your system crashes randomly.
356 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
357 Change the output verbosity whilst booting
358 Format: { quiet (default) | verbose | debug }
359 Change the amount of debugging information output
360 when initialising the APIC and IO-APIC components.
363 See Documentation/networking/ipv6.txt.
365 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
366 Limit apic dumping. The parameter defines the maximal
367 number of local apics being dumped. Also it is possible
368 to set it to "all" by meaning -- no limit here.
369 Format: { 1 (default) | 2 | ... | all }.
370 The parameter valid if only apic=debug or
371 apic=verbose is specified.
372 Example: apic=debug show_lapic=all
374 apm= [APM] Advanced Power Management
375 See header of arch/x86/kernel/apm_32.c.
377 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
378 Format: <io>,<irq>,<nodeID>
382 atarimouse= [HW,MOUSE] Atari Mouse
384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
385 EzKey and similar keyboards
387 atkbd.reset= [HW] Reset keyboard during initialization
389 atkbd.set= [HW] Select keyboard code set
390 Format: <int> (2 = AT (default), 3 = PS/2)
392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
396 Format: <bool> (0 = real, 1 = synthetic (default))
398 atkbd.softrepeat= [HW]
399 Use software keyboard repeat
403 baycom_epp= [HW,AX25]
406 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
408 See header of drivers/net/hamradio/baycom_par.c.
410 baycom_ser_fdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
412 Format: <io>,<irq>,<mode>[,<baud>]
413 See header of drivers/net/hamradio/baycom_ser_fdx.c.
415 baycom_ser_hdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
417 Format: <io>,<irq>,<mode>
418 See header of drivers/net/hamradio/baycom_ser_hdx.c.
420 boot_delay= Milliseconds to delay each printk during boot.
421 Values larger than 10 seconds (10000) are changed to
425 bootmem_debug [KNL] Enable bootmem allocator debug messages.
427 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
428 bttv.radio= Most important insmod options are available as
430 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
433 bulk_remove=off [PPC] This parameter disables the use of the pSeries
434 firmware feature for flushing multiple hpte entries
437 c101= [NET] Moxa C101 synchronous serial card
439 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
440 Sometimes CPU hardware bugs make them report the cache
441 size incorrectly. The kernel will attempt work arounds
442 to fix known problems, but for some CPUs it is not
443 possible to determine what the correct size should be.
444 This option provides an override for these situations.
447 [SECURITY] Disable capabilities. This would normally
448 be used only if an alternative security model is to be
449 configured. Potentially dangerous and should only be
450 used if you are entirely sure of the consequences.
452 ccw_timeout_log [S390]
453 See Documentation/s390/CommonIO for details.
455 cgroup_disable= [KNL] Disable a particular controller
456 Format: {name of the controller(s) to disable}
457 {Currently supported controllers - "memory"}
459 checkreqprot [SELINUX] Set initial checkreqprot flag value.
460 Format: { "0" | "1" }
461 See security/selinux/Kconfig help text.
462 0 -- check protection applied by kernel (includes
463 any implied execute protection).
464 1 -- check protection requested by application.
465 Default value is set via a kernel config option.
466 Value can be changed at runtime via
467 /selinux/checkreqprot.
470 See Documentation/s390/CommonIO for details.
472 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
474 Forces specified clocksource (if available) to be used
475 when calculating gettimeofday(). If specified
476 clocksource is not available, it defaults to PIT.
477 Format: { pit | tsc | cyclone | pmtmr }
479 clocksource= Override the default clocksource
481 Override the default clocksource and use the clocksource
482 with the name specified.
483 Some clocksource names to choose from, depending on
485 [all] jiffies (this is the base, fallback clocksource)
487 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
488 pxa_timer,timer3,32k_counter,timer0_1
490 [X86-32] pit,hpet,tsc;
491 scx200_hrt on Geode; cyclone on IBM x440
499 clearcpuid=BITNUM [X86]
500 Disable CPUID feature X for the kernel. See
501 arch/x86/include/asm/cpufeature.h for the valid bit
502 numbers. Note the Linux specific bits are not necessarily
503 stable over kernel options, but the vendor specific
505 Also note that user programs calling CPUID directly
506 or using the feature without checking anything
507 will still see it. This just prevents it from
508 being used by the kernel or shown in /proc/cpuinfo.
509 Also note the kernel might malfunction if you disable
512 cmo_free_hint= [PPC] Format: { yes | no }
513 Specify whether pages are marked as being inactive
514 when they are freed. This is used in CMO environments
515 to determine OS memory pressure for page stealing by
519 code_bytes [X86] How many bytes of object code to print
524 com20020= [HW,NET] ARCnet - COM20020 chipset
526 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
528 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
532 ARCnet - COM90xx chipset (memory-mapped buffers)
533 Format: <io>[,<irq>[,<memstart>]]
535 condev= [HW,S390] console device
538 console= [KNL] Output console device and options.
540 tty<n> Use the virtual console device <n>.
544 Use the specified serial port. The options are of
545 the form "bbbbpnf", where "bbbb" is the baud rate,
546 "p" is parity ("n", "o", or "e"), "n" is number of
547 bits, and "f" is flow control ("r" for RTS or
548 omit it). Default is "9600n8".
550 See Documentation/serial-console.txt for more
552 Documentation/networking/netconsole.txt for an
555 uart[8250],io,<addr>[,options]
556 uart[8250],mmio,<addr>[,options]
557 Start an early, polled-mode console on the 8250/16550
558 UART at the specified I/O port or MMIO address,
559 switching to the matching ttyS device later. The
560 options are the same as for ttyS, above.
562 If the device connected to the port is not a TTY but a braille
563 device, prepend "brl," before the device type, for instance
565 For now, only VisioBraille is supported.
567 consoleblank= [KNL] The console blank (screen saver) timeout in
568 seconds. Defaults to 10*60 = 10mins. A value of 0
569 disables the blank timer.
572 [KNL] Change the default value for
573 /proc/<pid>/coredump_filter.
574 See also Documentation/filesystems/proc.txt.
576 cpuidle.off=1 [CPU_IDLE]
577 disable the cpuidle sub-system
579 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
581 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
583 crashkernel=size[KMG][@offset[KMG]]
584 [KNL] Using kexec, Linux can switch to a 'crash kernel'
585 upon panic. This parameter reserves the physical
586 memory region [offset, offset + size] for that kernel
587 image. If '@offset' is omitted, then a suitable offset
588 is selected automatically. Check
589 Documentation/kdump/kdump.txt for further details.
591 crashkernel=range1:size1[,range2:size2,...][@offset]
592 [KNL] Same as above, but depends on the memory
593 in the running system. The syntax of range is
594 start-[end] where start and end are both
595 a memory unit (amount[KMG]). See also
596 Documentation/kdump/kdump.txt for an example.
601 cs89x0_media= [HW,NET]
602 Format: { rj45 | aui | bnc }
605 See header of drivers/s390/block/dasd_devmap.c.
607 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
608 (one device per port)
609 Format: <port#>,<type>
610 See also Documentation/input/joystick-parport.txt
612 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
613 time. See Documentation/dynamic-debug-howto.txt for
616 debug [KNL] Enable kernel debugging (events log level).
619 [KNL] verbose self-tests
621 Print debugging info while doing the locking API
623 We default to 0 (no extra messages), setting it to
624 1 will print _a lot_ more information - normally
625 only useful to kernel developers.
627 debug_objects [KNL] Enable object debugging
630 [KNL] Disable object debugging
632 debug_guardpage_minorder=
633 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
634 parameter allows control of the order of pages that will
635 be intentionally kept free (and hence protected) by the
636 buddy allocator. Bigger value increase the probability
637 of catching random memory corruption, but reduce the
638 amount of memory for normal system use. The maximum
639 possible value is MAX_ORDER/2. Setting this parameter
640 to 1 or 2 should be enough to identify most random
641 memory corruption problems caused by bugs in kernel or
642 driver code when a CPU writes to (or reads from) a
643 random memory location. Note that there exists a class
644 of memory corruptions problems caused by buggy H/W or
645 F/W or by drivers badly programing DMA (basically when
646 memory is written at bus level and the CPU MMU is
647 bypassed) which are not detectable by
648 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
649 tracking down these problems.
651 debugpat [X86] Enable PAT debugging
653 decnet.addr= [HW,NET]
654 Format: <area>[,<node>]
655 See also Documentation/networking/decnet.txt.
658 [same as hugepagesz=] The size of the default
659 HugeTLB page size. This is the size represented by
660 the legacy /proc/ hugepages APIs, used for SHM, and
661 default size when mounting hugetlbfs filesystems.
662 Defaults to the default architecture's huge page size
666 Set number of hash buckets for dentry cache.
669 IO parameters + enable/disable command.
671 digiepca= [HW,SERIAL]
672 See drivers/char/README.epca and
673 Documentation/serial/digiepca.txt.
676 See Documentation/networking/ipv6.txt.
678 disable_ddw [PPC/PSERIES]
679 Disable Dynamic DMA Window support. Use this if
680 to workaround buggy firmware.
683 See Documentation/networking/ipv6.txt.
685 disable_mtrr_cleanup [X86]
686 The kernel tries to adjust MTRR layout from continuous
687 to discrete, to make X server driver able to add WB
688 entry later. This parameter disables that.
690 disable_mtrr_trim [X86, Intel and AMD only]
691 By default the kernel will trim any uncacheable
692 memory out of your available memory pool based on
693 MTRR settings. This parameter disables that behavior,
694 possibly causing your machine to run very slowly.
696 disable_timer_pin_1 [X86]
697 Disable PIN 1 of APIC timer
698 Can be useful to work around chipset bugs.
700 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
701 this option disables the debugging code at boot.
703 dma_debug_entries=<number>
704 This option allows to tune the number of preallocated
705 entries for DMA-API debugging code. One entry is
706 required per DMA-API allocation. Use this if the
707 DMA-API debugging code disables itself because the
708 architectural default is too low.
710 dma_debug_driver=<driver_name>
711 With this option the DMA-API debugging driver
712 filter feature can be enabled at boot time. Just
713 pass the driver to filter for as the parameter.
714 The filter can be disabled or changed to another
715 driver later using sysfs.
717 drm_kms_helper.edid_firmware=[<connector>:]<file>
718 Broken monitors, graphic adapters and KVMs may
719 send no or incorrect EDID data sets. This parameter
720 allows to specify an EDID data set in the
721 /lib/firmware directory that is used instead.
722 Generic built-in EDID data sets are used, if one of
723 edid/1024x768.bin, edid/1280x1024.bin,
724 edid/1680x1050.bin, or edid/1920x1080.bin is given
725 and no file with the same name exists. Details and
726 instructions how to build your own EDID data are
727 available in Documentation/EDID/HOWTO.txt. An EDID
728 data set will only be used for a particular connector,
729 if its name and a colon are prepended to the EDID
734 earlycon= [KNL] Output early console device and options.
735 uart[8250],io,<addr>[,options]
736 uart[8250],mmio,<addr>[,options]
737 uart[8250],mmio32,<addr>[,options]
738 Start an early, polled-mode console on the 8250/16550
739 UART at the specified I/O port or MMIO address.
740 MMIO inter-register address stride is either 8-bit
741 (mmio) or 32-bit (mmio32).
742 The options are the same as for ttyS, above.
744 earlyprintk= [X86,SH,BLACKFIN]
746 earlyprintk=serial[,ttySn[,baudrate]]
747 earlyprintk=ttySn[,baudrate]
748 earlyprintk=dbgp[debugController#]
750 Append ",keep" to not disable it when the real console
753 Only vga or serial or usb debug port at a time.
755 Currently only ttyS0 and ttyS1 are supported.
757 Interaction with the standard serial driver is not
760 The VGA output is eventually overwritten by the real
763 ekgdboc= [X86,KGDB] Allow early kernel console debugging
766 This is designed to be used in conjunction with
767 the boot argument: earlyprintk=vga
770 Format: {"off" | "on" | "skip[mbr]"}
772 eisa_irq_edge= [PARISC,HW]
773 See header of drivers/parisc/eisa.c.
776 See comment before function elanfreq_setup() in
777 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
780 Format: {"cfq" | "deadline" | "noop"}
781 See Documentation/block/cfq-iosched.txt and
782 Documentation/block/deadline-iosched.txt for details.
784 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
785 Specifies physical address of start of kernel core
786 image elf header and optionally the size. Generally
787 kexec loader will pass this option to capture kernel.
788 See Documentation/kdump/kdump.txt for details.
790 enable_mtrr_cleanup [X86]
791 The kernel tries to adjust MTRR layout from continuous
792 to discrete, to make X server driver able to add WB
793 entry later. This parameter enables that.
795 enable_timer_pin_1 [X86]
796 Enable PIN 1 of APIC timer
797 Can be useful to work around chipset bugs
798 (in particular on some ATI chipsets).
799 The kernel tries to set a reasonable default.
801 enforcing [SELINUX] Set initial enforcing status.
803 See security/selinux/Kconfig help text.
804 0 -- permissive (log only, no denials).
805 1 -- enforcing (deny and log).
807 Value can be changed at runtime via /selinux/enforce.
810 Disable Error Record Serialization Table (ERST)
813 ether= [HW,NET] Ethernet cards parameters
814 This option is obsoleted by the "netdev=" option, which
815 has equivalent usage. See its documentation for details.
819 Permit 'security.evm' to be updated regardless of
820 current integrity status.
824 fail_make_request=[KNL]
825 General fault injection mechanism.
826 Format: <interval>,<probability>,<space>,<times>
827 See also Documentation/fault-injection/.
830 See Documentation/blockdev/floppy.txt.
832 force_pal_cache_flush
833 [IA-64] Avoid check_sal_cache_flush which may hang on
834 buggy SAL_CACHE_FLUSH implementations. Using this
835 parameter will force ia64_sal_cache_flush to call
836 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
839 [FTRACE] will set and start the specified tracer
840 as early as possible in order to facilitate early
843 ftrace_dump_on_oops[=orig_cpu]
844 [FTRACE] will dump the trace buffers on oops.
845 If no parameter is passed, ftrace will dump
846 buffers of all CPUs, but if you pass orig_cpu, it will
847 dump only the buffer of the CPU that triggered the
850 ftrace_filter=[function-list]
851 [FTRACE] Limit the functions traced by the function
852 tracer at boot up. function-list is a comma separated
853 list of functions. This list can be changed at run
854 time by the set_ftrace_filter file in the debugfs
857 ftrace_notrace=[function-list]
858 [FTRACE] Do not trace the functions specified in
859 function-list. This list can be changed at run time
860 by the set_ftrace_notrace file in the debugfs
863 ftrace_graph_filter=[function-list]
864 [FTRACE] Limit the top level callers functions traced
865 by the function graph tracer at boot up.
866 function-list is a comma separated list of functions
867 that can be changed at run time by the
868 set_graph_function file in the debugfs tracing directory.
871 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
872 support via parallel port (up to 5 devices per port)
873 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
874 See also Documentation/input/joystick-parport.txt
878 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
882 gcov_persist= [GCOV] When non-zero (default), profiling data for
883 kernel modules is saved and remains accessible via
884 debugfs, even when the module is unloaded/reloaded.
885 When zero, profiling data is discarded and associated
886 debugfs files are removed at module unload time.
888 gpt [EFI] Forces disk with valid GPT signature but
889 invalid Protective MBR to be treated as GPT.
891 hashdist= [KNL,NUMA] Large hashes allocated during boot
892 are distributed across NUMA nodes. Defaults on
893 for 64-bit NUMA, off otherwise.
894 Format: 0 | 1 (for off | on)
896 hcl= [IA-64] SGI's Hardware Graph compatibility layer
898 hd= [EIDE] (E)IDE hard drive subsystem geometry
899 Format: <cyl>,<head>,<sect>
902 Disable Hardware Error Source Table (HEST) support;
903 corresponding firmware-first mode error processing
904 logic will be disabled.
906 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
907 size of <nn>. This works even on boxes that have no
908 highmem otherwise. This also works to reduce highmem
909 size on bigger boxes.
911 highres= [KNL] Enable/disable high resolution timer mode.
912 Valid parameters: "on", "off"
916 See Documentation/isdn/README.HiSax.
920 hpet= [X86-32,HPET] option to control HPET usage
921 Format: { enable (default) | disable | force |
923 disable: disable HPET and use PIT instead
924 force: allow force enabled of undocumented chips (ICH4,
926 verbose: show contents of HPET registers during setup
928 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
929 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
930 On x86-64 and powerpc, this option can be specified
931 multiple times interleaved with hugepages= to reserve
932 huge pages of different sizes. Valid pages sizes on
933 x86-64 are 2M (when the CPU supports "pse") and 1G
934 (when the CPU supports the "pdpe1gb" cpuinfo flag)
935 Note that 1GB pages can only be allocated at boot time
936 using hugepages= and not freed afterwards.
938 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
939 terminal devices. Valid values: 0..8
940 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
941 If specified, z/VM IUCV HVC accepts connections
942 from listed z/VM user IDs only.
945 Do not unregister boot console at start. This is only
946 useful for debugging when something happens in the window
947 between unregistering the boot console and initializing
950 i2c_bus= [HW] Override the default board specific I2C bus speed
951 or register an additional I2C bus that is not
952 registered from board initialization code.
956 i8042.debug [HW] Toggle i8042 debug mode
957 i8042.direct [HW] Put keyboard port into non-translated mode
958 i8042.dumbkbd [HW] Pretend that controller can only read data from
959 keyboard and cannot control its state
960 (Don't attempt to blink the leds)
961 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
962 i8042.nokbd [HW] Don't check/create keyboard port
963 i8042.noloop [HW] Disable the AUX Loopback command while probing
965 i8042.nomux [HW] Don't check presence of an active multiplexing
967 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
969 i8042.notimeout [HW] Ignore timeout condition signalled by controller
970 i8042.reset [HW] Reset the controller during init and cleanup
971 i8042.unlock [HW] Unlock (ignore) the keylock
975 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
976 indicates that the driver is running on unsupported
978 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
979 does not match list of supported models.
981 [HW] Report power status in /proc/i8k
982 (disabled by default)
983 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
987 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
989 ide-core.nodma= [HW] (E)IDE subsystem
990 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
991 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
992 .cdrom .chs .ignore_cable are additional options
993 See Documentation/ide/ide.txt.
995 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
996 Claim all unknown PCI IDE storage controllers.
999 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1000 Poll forces a polling idle loop that can slightly
1001 improve the performance of waking up a idle CPU, but
1002 will use a lot of power and make the system run hot.
1004 idle=mwait: On systems which support MONITOR/MWAIT but
1005 the kernel chose to not use it because it doesn't save
1006 as much power as a normal idle loop, use the
1007 MONITOR/MWAIT idle loop anyways. Performance should be
1008 the same as idle=poll.
1009 idle=halt: Halt is forced to be used for CPU idle.
1010 In such case C2/C3 won't be used again.
1011 idle=nomwait: Disable mwait for CPU C-states
1013 ignore_loglevel [KNL]
1014 Ignore loglevel setting - this will print /all/
1015 kernel messages to the console. Useful for debugging.
1016 We also add it as printk module parameter, so users
1017 could change it dynamically, usually by
1018 /sys/module/printk/parameters/ignore_loglevel.
1020 ihash_entries= [KNL]
1021 Set number of hash buckets for inode cache.
1024 Format: { "0" | "1" }
1025 0 -- integrity auditing messages. (Default)
1026 1 -- enable informational integrity auditing messages.
1029 Format: { "sha1" | "md5" }
1033 Load a policy which meets the needs of the Trusted
1034 Computing Base. This means IMA will measure all
1035 programs exec'd, files mmap'd for exec, and all files
1036 opened for read by uid=0.
1040 Run specified binary instead of /sbin/init as init
1043 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1044 for working out where the kernel is dying during
1047 initrd= [BOOT] Specify the location of the initial ramdisk
1049 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1052 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1054 Enable intel iommu driver.
1056 Disable intel iommu driver.
1057 igfx_off [Default Off]
1058 By default, gfx is mapped as normal device. If a gfx
1059 device has a dedicated DMAR unit, the DMAR unit is
1060 bypassed by not enabling DMAR with this option. In
1061 this case, gfx device will use physical address for
1064 With this option iommu will not optimize to look
1065 for io virtual address below 32-bit forcing dual
1066 address cycle on pci bus for cards supporting greater
1067 than 32-bit addressing. The default is to look
1068 for translation below 32-bit and if not available
1069 then look in the higher range.
1070 strict [Default Off]
1071 With this option on every unmap_single operation will
1072 result in a hardware IOTLB flush operation as opposed
1073 to batching them for performance.
1074 sp_off [Default Off]
1075 By default, super page will be supported if Intel IOMMU
1076 has the capability. With this option, super page will
1079 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1080 0 disables intel_idle and fall back on acpi_idle.
1081 1 to 6 specify maximum depth of C-state.
1083 intremap= [X86-64, Intel-IOMMU]
1084 on enable Interrupt Remapping (default)
1085 off disable Interrupt Remapping
1086 nosid disable Source ID checking
1088 BIOS x2APIC opt-out request will be ignored
1090 iomem= Disable strict checking of access to MMIO memory
1091 strict regions from userspace.
1106 group_mf [x86, IA-64]
1109 io7= [HW] IO7 for Marvel based alpha systems
1110 See comment before marvel_specify_io7 in
1111 arch/alpha/kernel/core_marvel.c.
1113 io_delay= [X86] I/O delay method
1115 Standard port 0x80 based delay
1117 Alternate port 0xed based delay (needed on some systems)
1119 Simple two microseconds delay
1124 See Documentation/filesystems/nfs/nfsroot.txt.
1126 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1127 See comment before ip2_setup() in
1128 drivers/char/ip2/ip2base.c.
1131 When an interrupt is not handled search all handlers
1132 for it. Intended to get systems with badly broken
1136 When an interrupt is not handled search all handlers
1137 for it. Also check all handlers each timer
1138 interrupt. Intended to get systems with badly broken
1142 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1144 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1146 <cpu number>,...,<cpu number>
1148 <cpu number>-<cpu number>
1149 (must be a positive range in ascending order)
1151 <cpu number>,...,<cpu number>-<cpu number>
1153 This option can be used to specify one or more CPUs
1154 to isolate from the general SMP balancing and scheduling
1155 algorithms. You can move a process onto or off an
1156 "isolated" CPU via the CPU affinity syscalls or cpuset.
1157 <cpu number> begins at 0 and the maximum value is
1158 "number of CPUs in system - 1".
1160 This option is the preferred way to isolate CPUs. The
1161 alternative -- manually setting the CPU mask of all
1162 tasks in the system -- can cause problems and
1163 suboptimal load balancer performance.
1167 js= [HW,JOY] Analog joystick
1168 See Documentation/input/joystick.txt.
1172 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1173 specifies the amount of memory usable by the kernel
1174 for non-movable allocations. The requested amount is
1175 spread evenly throughout all nodes in the system. The
1176 remaining memory in each node is used for Movable
1177 pages. In the event, a node is too small to have both
1178 kernelcore and Movable pages, kernelcore pages will
1179 take priority and other nodes will have a larger number
1180 of kernelcore pages. The Movable zone is used for the
1181 allocation of pages that may be reclaimed or moved
1182 by the page migration subsystem. This means that
1183 HugeTLB pages may not be allocated from this zone.
1184 Note that allocations like PTEs-from-HighMem still
1185 use the HighMem zone if it exists, and the Normal
1186 zone if it does not.
1188 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1189 Format: <Controller#>[,poll interval]
1190 The controller # is the number of the ehci usb debug
1191 port as it is probed via PCI. The poll interval is
1192 optional and is the number seconds in between
1193 each poll cycle to the debug port in case you need
1194 the functionality for interrupting the kernel with
1195 gdb or control-c on the dbgp connection. When
1196 not using this parameter you use sysrq-g to break into
1197 the kernel debugger.
1199 kgdboc= [KGDB,HW] kgdb over consoles.
1200 Requires a tty driver that supports console polling,
1201 or a supported polling keyboard driver (non-usb).
1202 Serial only format: <serial_device>[,baud]
1203 keyboard only format: kbd
1204 keyboard and serial format: kbd,<serial_device>[,baud]
1205 Optional Kernel mode setting:
1206 kms, kbd format: kms,kbd
1207 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1209 kgdbwait [KGDB] Stop kernel execution and enter the
1210 kernel debugger at the earliest opportunity.
1212 kmac= [MIPS] korina ethernet MAC address.
1213 Configure the RouterBoard 532 series on-chip
1214 Ethernet adapter MAC address.
1216 kmemleak= [KNL] Boot-time kmemleak enable/disable
1217 Valid arguments: on, off
1220 kstack=N [X86] Print N words from the kernel stack
1223 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1224 Default is 0 (don't ignore, but inject #GP)
1226 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1230 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1231 Default is 1 (enabled)
1233 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1235 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1237 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1238 (virtualized MMU) support on capable Intel chips.
1239 Default is 1 (enabled)
1241 kvm-intel.emulate_invalid_guest_state=
1242 [KVM,Intel] Enable emulation of invalid guest states
1243 Default is 0 (disabled)
1245 kvm-intel.flexpriority=
1246 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1247 Default is 1 (enabled)
1250 [KVM,Intel] Enable VMX nesting (nVMX).
1251 Default is 0 (disabled)
1253 kvm-intel.unrestricted_guest=
1254 [KVM,Intel] Disable unrestricted guest feature
1255 (virtualized real and unpaged mode) on capable
1256 Intel chips. Default is 1 (enabled)
1258 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1259 feature (tagged TLBs) on capable Intel chips.
1260 Default is 1 (enabled)
1266 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1269 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1272 libata.dma= [LIBATA] DMA control
1273 libata.dma=0 Disable all PATA and SATA DMA
1274 libata.dma=1 PATA and SATA Disk DMA only
1275 libata.dma=2 ATAPI (CDROM) DMA only
1276 libata.dma=4 Compact Flash DMA only
1277 Combinations also work, so libata.dma=3 enables DMA
1278 for disks and CDROMs, but not CFs.
1280 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1281 libata.ignore_hpa=0 keep BIOS limits (default)
1282 libata.ignore_hpa=1 ignore limits, using full disk
1284 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1288 libata.force= [LIBATA] Force configurations. The format is comma
1289 separated list of "[ID:]VAL" where ID is
1290 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1291 matching port, link or device. Basically, it matches
1292 the ATA ID string printed on console by libata. If
1293 the whole ID part is omitted, the last PORT and DEVICE
1294 values are used. If ID hasn't been specified yet, the
1295 configuration applies to all ports, links and devices.
1297 If only DEVICE is omitted, the parameter applies to
1298 the port and all links and devices behind it. DEVICE
1299 number of 0 either selects the first device or the
1300 first fan-out link behind PMP device. It does not
1301 select the host link. DEVICE number of 15 selects the
1302 host link and device attached to it.
1304 The VAL specifies the configuration to force. As long
1305 as there's no ambiguity shortcut notation is allowed.
1306 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1307 The following configurations can be forced.
1309 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1310 Any ID with matching PORT is used.
1312 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1314 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1315 udma[/][16,25,33,44,66,100,133] notation is also
1318 * [no]ncq: Turn on or off NCQ.
1320 * nohrst, nosrst, norst: suppress hard, soft
1323 * dump_id: dump IDENTIFY data.
1325 If there are multiple matching configurations changing
1326 the same attribute, the last one is used.
1328 memblock=debug [KNL] Enable memblock debug messages.
1330 load_ramdisk= [RAM] List of ramdisks to load from floppy
1331 See Documentation/blockdev/ramdisk.txt.
1333 lockd.nlm_grace_period=P [NFS] Assign grace period.
1336 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1339 lockd.nlm_timeout=T [NFS] Assign timeout value.
1342 lockd.nlm_udpport=M [NFS] Assign UDP port.
1345 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1348 loglevel= All Kernel Messages with a loglevel smaller than the
1349 console loglevel will be printed to the console. It can
1350 also be changed with klogd or other programs. The
1351 loglevels are defined as follows:
1353 0 (KERN_EMERG) system is unusable
1354 1 (KERN_ALERT) action must be taken immediately
1355 2 (KERN_CRIT) critical conditions
1356 3 (KERN_ERR) error conditions
1357 4 (KERN_WARNING) warning conditions
1358 5 (KERN_NOTICE) normal but significant condition
1359 6 (KERN_INFO) informational
1360 7 (KERN_DEBUG) debug-level messages
1362 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1363 in bytes. n must be a power of two. The default
1364 size is set in the kernel config file.
1366 logo.nologo [FB] Disables display of the built-in Linux logo.
1367 This may be used to provide more screen space for
1368 kernel log messages and is useful when debugging
1369 kernel boot problems.
1371 lp=0 [LP] Specify parallel ports to use, e.g,
1372 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1373 lp=reset first parallel port). 'lp=0' disables the
1374 lp=auto printer driver. 'lp=reset' (which can be
1375 specified in addition to the ports) causes
1376 attached printers to be reset. Using
1377 lp=port1,port2,... specifies the parallel ports
1378 to associate lp devices with, starting with
1379 lp0. A port specification may be 'none' to skip
1380 that lp device, or a parport name such as
1381 'parport0'. Specifying 'lp=auto' instead of a
1382 port specification list means that device IDs
1383 from each port should be examined, to see if
1384 an IEEE 1284-compliant printer is attached; if
1385 so, the driver will manage that printer.
1386 See also header of drivers/char/lp.c.
1389 Sets loops_per_jiffy to given constant, thus avoiding
1390 time-consuming boot-time autodetection (up to 250 ms per
1391 CPU). 0 enables autodetection (default). To determine
1392 the correct value for your kernel, boot with normal
1393 autodetection and see what value is printed. Note that
1394 on SMP systems the preset will be applied to all CPUs,
1395 which is likely to cause problems if your CPUs need
1396 significantly divergent settings. An incorrect value
1397 will cause delays in the kernel to be wrong, leading to
1398 unpredictable I/O errors and other breakage. Although
1399 unlikely, in the extreme case this might damage your
1403 Format: <io>,<irq>,<dma>
1405 machvec= [IA-64] Force the use of a particular machine-vector
1406 (machvec) in a generic kernel.
1407 Example: machvec=hpzx1_swiotlb
1409 machtype= [Loongson] Share the same kernel image file between different
1411 Example: machtype=lemote-yeeloong-2f-7inch
1413 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1414 than or equal to this physical address is ignored.
1416 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1417 should make use of. maxcpus=n : n >= 0 limits the
1418 kernel to using 'n' processors. n=0 is a special case,
1419 it is equivalent to "nosmp", which also disables
1422 max_loop= [LOOP] The number of loop block devices that get
1423 (loop.max_loop) unconditionally pre-created at init time. The default
1424 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1425 of statically allocating a predefined number, loop
1426 devices can be requested on-demand with the
1427 /dev/loop-control interface.
1431 mce [X86-32] Machine Check Exception
1433 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1435 md= [HW] RAID subsystems devices and level
1436 See Documentation/md.txt.
1439 Format: <first>,<last>
1440 Specifies range of consoles to be captured by the MDA.
1442 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1443 Amount of memory to be used when the kernel is not able
1444 to see the whole system memory or for test.
1445 [X86-32] Use together with memmap= to avoid physical
1446 address space collisions. Without memmap= PCI devices
1447 could be placed at addresses belonging to unused RAM.
1449 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1453 [KNL,SH] Allow user to override the default size for
1454 per-device physically contiguous DMA buffers.
1456 memmap=exactmap [KNL,X86] Enable setting of an exact
1457 E820 memory map, as specified by the user.
1458 Such memmap=exactmap lines can be constructed based on
1459 BIOS output or other requirements. See the memmap=nn@ss
1462 memmap=nn[KMG]@ss[KMG]
1463 [KNL] Force usage of a specific region of memory
1464 Region of memory to be used, from ss to ss+nn.
1466 memmap=nn[KMG]#ss[KMG]
1467 [KNL,ACPI] Mark specific memory as ACPI data.
1468 Region of memory to be used, from ss to ss+nn.
1470 memmap=nn[KMG]$ss[KMG]
1471 [KNL,ACPI] Mark specific memory as reserved.
1472 Region of memory to be used, from ss to ss+nn.
1473 Example: Exclude memory from 0x18690000-0x1869ffff
1474 memmap=64K$0x18690000
1476 memmap=0x10000$0x18690000
1478 memory_corruption_check=0/1 [X86]
1479 Some BIOSes seem to corrupt the first 64k of
1480 memory when doing things like suspend/resume.
1481 Setting this option will scan the memory
1482 looking for corruption. Enabling this will
1483 both detect corruption and prevent the kernel
1484 from using the memory being corrupted.
1485 However, its intended as a diagnostic tool; if
1486 repeatable BIOS-originated corruption always
1487 affects the same memory, you can use memmap=
1488 to prevent the kernel from using that memory.
1490 memory_corruption_check_size=size [X86]
1491 By default it checks for corruption in the low
1492 64k, making this memory unavailable for normal
1493 use. Use this parameter to scan for
1494 corruption in more or less memory.
1496 memory_corruption_check_period=seconds [X86]
1497 By default it checks for corruption every 60
1498 seconds. Use this parameter to check at some
1499 other rate. 0 disables periodic checking.
1501 memtest= [KNL,X86] Enable memtest
1503 default : 0 <disable>
1504 Specifies the number of memtest passes to be
1505 performed. Each pass selects another test
1506 pattern from a given set of patterns. Memtest
1507 fills the memory with this pattern, validates
1508 memory contents and reserves bad memory
1509 regions that are detected.
1511 meye.*= [HW] Set MotionEye Camera parameters
1512 See Documentation/video4linux/meye.txt.
1514 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1515 Multi-Function General Purpose Timers on AMD Geode
1518 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1519 the BIOS has incorrectly applied a workaround. TinyBIOS
1520 version 0.98 is known to be affected, 0.99 fixes the
1521 problem by letting the user disable the workaround.
1525 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1526 physical address is ignored.
1528 mini2440= [ARM,HW,KNL]
1529 Format:[0..2][b][c][t]
1531 MINI2440 configuration specification:
1532 0 - The attached screen is the 3.5" TFT
1533 1 - The attached screen is the 7" TFT
1534 2 - The VGA Shield is attached (1024x768)
1535 Leaving out the screen size parameter will not load
1536 the TFT driver, and the framebuffer will be left
1538 b - Enable backlight. The TFT backlight pin will be
1539 linked to the kernel VESA blanking code and a GPIO
1540 LED. This parameter is not necessary when using the
1542 c - Enable the s3c camera interface.
1543 t - Reserved for enabling touchscreen support. The
1544 touchscreen support is not enabled in the mainstream
1545 kernel as of 2.6.30, a preliminary port can be found
1546 in the "bleeding edge" mini2440 support kernel at
1547 http://repo.or.cz/w/linux-2.6/mini2440.git
1550 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1551 parameter allows control of the logging verbosity for
1552 the additional memory initialisation checks. A value
1553 of 0 disables mminit logging and a level of 4 will
1554 log everything. Information is printed at KERN_DEBUG
1555 so loglevel=8 may also need to be specified.
1558 [MOUSE] Maximum time between finger touching and
1559 leaving touchpad surface for touch to be considered
1560 a tap and be reported as a left button click (for
1561 touchpads working in absolute mode only).
1563 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1564 reporting absolute coordinates, such as tablets
1565 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1566 reporting absolute coordinates, such as tablets
1568 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1569 is similar to kernelcore except it specifies the
1570 amount of memory used for migratable allocations.
1571 If both kernelcore and movablecore is specified,
1572 then kernelcore will be at *least* the specified
1573 value but may be more. If movablecore on its own
1574 is specified, the administrator must be careful
1575 that the amount of memory usable for all allocations
1578 MTD_Partition= [MTD]
1579 Format: <name>,<region-number>,<size>,<offset>
1581 MTD_Region= [MTD] Format:
1582 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1585 See drivers/mtd/cmdlinepart.c.
1587 multitce=off [PPC] This parameter disables the use of the pSeries
1588 firmware feature for updating multiple TCE entries
1591 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1593 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1595 boundary - index of last SLC block on Flex-OneNAND.
1596 The remaining blocks are configured as MLC blocks.
1597 lock - Configure if Flex-OneNAND boundary should be locked.
1598 Once locked, the boundary cannot be changed.
1599 1 indicates lock status, 0 indicates unlock status.
1602 ARM/S3C2412 JIVE boot control
1604 See arch/arm/mach-s3c2412/mach-jive.c
1606 mtouchusb.raw_coordinates=
1607 [HW] Make the MicroTouch USB driver use raw coordinates
1608 ('y', default) or cooked coordinates ('n')
1610 mtrr_chunk_size=nn[KMG] [X86]
1611 used for mtrr cleanup. It is largest continuous chunk
1612 that could hold holes aka. UC entries.
1614 mtrr_gran_size=nn[KMG] [X86]
1615 Used for mtrr cleanup. It is granularity of mtrr block.
1617 Large value could prevent small alignment from
1620 mtrr_spare_reg_nr=n [X86]
1622 Range: 0,7 : spare reg number
1624 Used for mtrr cleanup. It is spare mtrr entries number.
1625 Set to 2 or more if your graphical card needs more.
1627 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1629 netdev= [NET] Network devices parameters
1630 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1631 Note that mem_start is often overloaded to mean
1632 something different and driver-specific.
1633 This usage is only documented in each driver source
1637 [NETFILTER] Enable connection tracking flow accounting
1638 0 to disable accounting
1639 1 to enable accounting
1642 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1643 See Documentation/filesystems/nfs/nfsroot.txt.
1645 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1646 See Documentation/filesystems/nfs/nfsroot.txt.
1648 nfsrootdebug [NFS] enable nfsroot debugging messages.
1649 See Documentation/filesystems/nfs/nfsroot.txt.
1651 nfs.callback_tcpport=
1652 [NFS] set the TCP port on which the NFSv4 callback
1653 channel should listen.
1656 [NFS] sets the pathname to the program which is used
1657 to update the NFS client cache entries.
1659 nfs.cache_getent_timeout=
1660 [NFS] sets the timeout after which an attempt to
1661 update a cache entry is deemed to have failed.
1663 nfs.idmap_cache_timeout=
1664 [NFS] set the maximum lifetime for idmapper cache
1668 [NFS] enable 64-bit inode numbers.
1669 If zero, the NFS client will fake up a 32-bit inode
1670 number for the readdir() and stat() syscalls instead
1671 of returning the full 64-bit number.
1672 The default is to return 64-bit inode numbers.
1674 nfs.max_session_slots=
1675 [NFSv4.1] Sets the maximum number of session slots
1676 the client will attempt to negotiate with the server.
1677 This limits the number of simultaneous RPC requests
1678 that the client can send to the NFSv4.1 server.
1679 Note that there is little point in setting this
1680 value higher than the max_tcp_slot_table_limit.
1682 nfs.nfs4_disable_idmapping=
1683 [NFSv4] When set to the default of '1', this option
1684 ensures that both the RPC level authentication
1685 scheme and the NFS level operations agree to use
1686 numeric uids/gids if the mount is using the
1687 'sec=sys' security flavour. In effect it is
1688 disabling idmapping, which can make migration from
1689 legacy NFSv2/v3 systems to NFSv4 easier.
1690 Servers that do not support this mode of operation
1691 will be autodetected by the client, and it will fall
1692 back to using the idmapper.
1693 To turn off this behaviour, set the value to '0'.
1695 nfs.send_implementation_id =
1696 [NFSv4.1] Send client implementation identification
1697 information in exchange_id requests.
1698 If zero, no implementation identification information
1700 The default is to send the implementation identification
1703 nfsd.nfs4_disable_idmapping=
1704 [NFSv4] When set to the default of '1', the NFSv4
1705 server will return only numeric uids and gids to
1706 clients using auth_sys, and will accept numeric uids
1707 and gids from such clients. This is intended to ease
1708 migration from NFSv2/v3.
1710 objlayoutdriver.osd_login_prog=
1711 [NFS] [OBJLAYOUT] sets the pathname to the program which
1712 is used to automatically discover and login into new
1713 osd-targets. Please see:
1714 Documentation/filesystems/pnfs.txt for more explanations
1716 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1717 when a NMI is triggered.
1718 Format: [state][,regs][,debounce][,die]
1720 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1721 Format: [panic,][nopanic,][num]
1723 0 - turn nmi_watchdog off
1724 When panic is specified, panic when an NMI watchdog
1725 timeout occurs (or 'nopanic' to override the opposite
1727 This is useful when you use a panic=... timeout and
1728 need the box quickly up again.
1730 netpoll.carrier_timeout=
1731 [NET] Specifies amount of time (in seconds) that
1732 netpoll should wait for a carrier. By default netpoll
1735 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1736 emulation library even if a 387 maths coprocessor
1740 [HW] Never suspend the console
1741 Disable suspending of consoles during suspend and
1742 hibernate operations. Once disabled, debugging
1743 messages can reach various consoles while the rest
1744 of the system is being put to sleep (ie, while
1745 debugging driver suspend/resume hooks). This may
1746 not work reliably with all consoles, but is known
1747 to work with serial and VGA consoles.
1748 To facilitate more flexible debugging, we also add
1749 console_suspend, a printk module parameter to control
1750 it. Users could use console_suspend (usually
1751 /sys/module/printk/parameters/console_suspend) to
1752 turn on/off it dynamically.
1754 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1755 caches in the slab allocator. Saves per-node memory,
1756 but will impact performance.
1760 noapic [SMP,APIC] Tells the kernel to not make use of any
1761 IOAPICs that may be present in the system.
1763 noautogroup Disable scheduler automatic task group creation.
1765 nobats [PPC] Do not use BATs for mapping kernel lowmem
1766 on "Classic" PPC cores.
1770 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1772 nodelayacct [KNL] Disable per-task delay accounting
1774 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1776 nodsp [SH] Disable hardware DSP at boot time.
1778 noefi [X86] Disable EFI runtime services support.
1783 On X86-32 available only on PAE configured kernels.
1784 noexec=on: enable non-executable mappings (default)
1785 noexec=off: disable non-executable mappings
1788 Disable SMEP (Supervisor Mode Execution Protection)
1789 even if it is supported by processor.
1792 This affects only 32-bit executables.
1793 noexec32=on: enable non-executable mappings (default)
1794 read doesn't imply executable mappings
1795 noexec32=off: disable non-executable mappings
1796 read implies executable mappings
1798 nofpu [SH] Disable hardware FPU at boot time.
1800 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1801 register save and restore. The kernel will only save
1802 legacy floating-point registers on task switch.
1804 noxsave [BUGS=X86] Disables x86 extended register state save
1805 and restore using xsave. The kernel will fallback to
1806 enabling legacy floating-point and sse state.
1808 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1809 wfi(ARM) instruction doesn't work correctly and not to
1810 use it. This is also useful when using JTAG debugger.
1812 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1813 instruction doesn't work correctly and not to
1816 no_file_caps Tells the kernel not to honor file capabilities. The
1817 only way then for a file to be executed with privilege
1818 is to be setuid root or executed by root.
1820 nohalt [IA-64] Tells the kernel not to use the power saving
1821 function PAL_HALT_LIGHT when idle. This increases
1822 power-consumption. On the positive side, it reduces
1823 interrupt wake-up latency, which may improve performance
1824 in certain environments such as networked servers or
1827 nohz= [KNL] Boottime enable/disable dynamic ticks
1828 Valid arguments: on, off
1831 noiotrap [SH] Disables trapped I/O port accesses.
1833 noirqdebug [X86-32] Disables the code which attempts to detect and
1834 disable unhandled interrupt sources.
1836 no_timer_check [X86,APIC] Disables the code which tests for
1837 broken timer IRQ sources.
1839 noisapnp [ISAPNP] Disables ISA PnP code.
1841 noinitrd [RAM] Tells the kernel not to load any configured
1844 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1846 [Deprecated - use intremap=off]
1850 nojitter [IA-64] Disables jitter checking for ITC timers.
1852 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1854 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1857 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1858 steal time is computed, but won't influence scheduler
1861 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1863 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1865 noltlbs [PPC] Do not use large page/tlb entries for kernel
1866 lowmem mapping on PPC40x.
1868 nomca [IA-64] Disable machine check abort handling
1870 nomce [X86-32] Machine Check Exception
1872 nomfgpt [X86-32] Disable Multi-Function General Purpose
1873 Timer usage (for AMD Geode machines).
1875 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1876 shutdown the other cpus. Instead use the REBOOT_VECTOR
1879 nomodule Disable module load
1881 nopat [X86] Disable PAT (page attribute table extension of
1882 pagetables) support.
1884 norandmaps Don't use address space randomization. Equivalent to
1885 echo 0 > /proc/sys/kernel/randomize_va_space
1887 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1889 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1890 with UP alternatives
1892 noresidual [PPC] Don't use residual data on PReP machines.
1894 nordrand [X86] Disable the direct use of the RDRAND
1895 instruction even if it is supported by the
1896 processor. RDRAND is still available to user
1899 noresume [SWSUSP] Disables resume and restores original swap
1902 no-scroll [VGA] Disables scrollback.
1903 This is required for the Braillex ib80-piezo Braille
1904 reader made by F.H. Papenmeier (Germany).
1908 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1910 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1911 and disable the IO APIC. legacy for "maxcpus=0".
1913 nosoftlockup [KNL] Disable the soft-lockup detector.
1915 nosync [HW,M68K] Disables sync negotiation for all devices.
1917 notsc [BUGS=X86-32] Disable Time Stamp Counter
1919 nousb [USB] Disable the USB subsystem
1921 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1925 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1927 nptcg= [IA-64] Override max number of concurrent global TLB
1928 purges which is reported from either PAL_VM_SUMMARY or
1931 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1932 could support. nr_cpus=n : n >= 1 limits the kernel to
1933 supporting 'n' processors. Later in runtime you can not
1934 use hotplug cpu feature to put more cpu back to online.
1935 just like you compile the kernel NR_CPUS=n
1937 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1939 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1940 one of ['zone', 'node', 'default'] can be specified
1941 This can be set from sysctl after boot.
1942 See Documentation/sysctl/vm.txt for details.
1944 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1945 See Documentation/debugging-via-ohci1394.txt for more
1948 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1949 Rather than timing out after 20 ms if an EC
1950 command is not properly ACKed, override the length
1951 of the timeout. We have interrupts disabled while
1952 waiting for the ACK, so if this is set too high
1953 interrupts *may* be lost!
1955 omap_mux= [OMAP] Override bootloader pin multiplexing.
1956 Format: <mux_mode0.mode_name=value>...
1957 For example, to override I2C bus2:
1958 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1960 oprofile.timer= [HW]
1961 Use timer interrupt instead of performance counters
1963 oprofile.cpu_type= Force an oprofile cpu type
1964 This might be useful if you have an older oprofile
1965 userland or if you want common events.
1966 Format: { arch_perfmon }
1967 arch_perfmon: [X86] Force use of architectural
1968 perfmon on Intel CPUs instead of the
1969 CPU specific event set.
1970 timer: [X86] Force use of architectural NMI
1971 timer mode (see also oprofile.timer
1972 for generic hr timer mode)
1973 [s390] Force legacy basic mode sampling
1974 (report cpu_type "timer")
1976 oops=panic Always panic on oopses. Default is to just kill the
1977 process, but there is a small probability of
1978 deadlocking the machine.
1979 This will also cause panics on machine check exceptions.
1980 Useful together with panic=30 to trigger a reboot.
1983 See Documentation/sound/oss/oss-parameters.txt
1985 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1986 timeout > 0: seconds before rebooting
1987 timeout = 0: wait forever
1988 timeout < 0: reboot immediately
1991 parkbd.port= [HW] Parallel port number the keyboard adapter is
1992 connected to, default is 0.
1994 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1995 0 for XT, 1 for AT (default is AT).
1998 parport= [HW,PPT] Specify parallel ports. 0 disables.
1999 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2000 Use 'auto' to force the driver to use any
2001 IRQ/DMA settings detected (the default is to
2002 ignore detected IRQ/DMA settings because of
2003 possible conflicts). You can specify the base
2004 address, IRQ, and DMA settings; IRQ and DMA
2005 should be numbers, or 'auto' (for using detected
2006 settings on that particular port), or 'nofifo'
2007 (to avoid using a FIFO even if it is detected).
2008 Parallel ports are assigned in the order they
2009 are specified on the command line, starting
2012 parport_init_mode= [HW,PPT]
2013 Configure VIA parallel port to operate in
2014 a specific mode. This is necessary on Pegasos
2015 computer where firmware has no options for setting
2016 up parallel port mode and sets it to spp.
2017 Currently this function knows 686a and 8231 chips.
2018 Format: [spp|ps2|epp|ecp|ecpepp]
2021 Halt all CPUs after the first oops has been printed for
2022 the specified number of seconds. This is to be used if
2023 your oopses keep scrolling off the screen.
2028 See header of drivers/block/paride/pcd.c.
2029 See also Documentation/blockdev/paride.txt.
2031 pci=option[,option...] [PCI] various PCI subsystem options:
2032 earlydump [X86] dump PCI config space before the kernel
2034 off [X86] don't probe for the PCI bus
2035 bios [X86-32] force use of PCI BIOS, don't access
2036 the hardware directly. Use this if your machine
2037 has a non-standard PCI host bridge.
2038 nobios [X86-32] disallow use of PCI BIOS, only direct
2039 hardware access methods are allowed. Use this
2040 if you experience crashes upon bootup and you
2041 suspect they are caused by the BIOS.
2042 conf1 [X86] Force use of PCI Configuration
2044 conf2 [X86] Force use of PCI Configuration
2046 noaer [PCIE] If the PCIEAER kernel config parameter is
2047 enabled, this kernel boot option can be used to
2048 disable the use of PCIE advanced error reporting.
2049 nodomains [PCI] Disable support for multiple PCI
2050 root domains (aka PCI segments, in ACPI-speak).
2051 nommconf [X86] Disable use of MMCONFIG for PCI
2053 check_enable_amd_mmconf [X86] check for and enable
2054 properly configured MMIO access to PCI
2055 config space on AMD family 10h CPU
2056 nomsi [MSI] If the PCI_MSI kernel config parameter is
2057 enabled, this kernel boot option can be used to
2058 disable the use of MSI interrupts system-wide.
2059 noioapicquirk [APIC] Disable all boot interrupt quirks.
2060 Safety option to keep boot IRQs enabled. This
2061 should never be necessary.
2062 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2063 primary IO-APIC for bridges that cannot disable
2064 boot IRQs. This fixes a source of spurious IRQs
2065 when the system masks IRQs.
2066 noioapicreroute [APIC] Disable workaround that uses the
2067 boot IRQ equivalent of an IRQ that connects to
2068 a chipset where boot IRQs cannot be disabled.
2069 The opposite of ioapicreroute.
2070 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2071 routing table. These calls are known to be buggy
2072 on several machines and they hang the machine
2073 when used, but on other computers it's the only
2074 way to get the interrupt routing table. Try
2075 this option if the kernel is unable to allocate
2076 IRQs or discover secondary PCI buses on your
2078 rom [X86] Assign address space to expansion ROMs.
2079 Use with caution as certain devices share
2080 address decoders between ROMs and other
2082 norom [X86] Do not assign address space to
2083 expansion ROMs that do not already have
2084 BIOS assigned address ranges.
2085 nobar [X86] Do not assign address space to the
2086 BARs that weren't assigned by the BIOS.
2087 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2088 assigned automatically to PCI devices. You can
2089 make the kernel exclude IRQs of your ISA cards
2091 pirqaddr=0xAAAAA [X86] Specify the physical address
2092 of the PIRQ table (normally generated
2093 by the BIOS) if it is outside the
2094 F0000h-100000h range.
2095 lastbus=N [X86] Scan all buses thru bus #N. Can be
2096 useful if the kernel is unable to find your
2097 secondary buses and you want to tell it
2098 explicitly which ones they are.
2099 assign-busses [X86] Always assign all PCI bus
2100 numbers ourselves, overriding
2101 whatever the firmware may have done.
2102 usepirqmask [X86] Honor the possible IRQ mask stored
2103 in the BIOS $PIR table. This is needed on
2104 some systems with broken BIOSes, notably
2105 some HP Pavilion N5400 and Omnibook XE3
2106 notebooks. This will have no effect if ACPI
2107 IRQ routing is enabled.
2108 noacpi [X86] Do not use ACPI for IRQ routing
2109 or for PCI scanning.
2110 use_crs [X86] Use PCI host bridge window information
2111 from ACPI. On BIOSes from 2008 or later, this
2112 is enabled by default. If you need to use this,
2113 please report a bug.
2114 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2115 If you need to use this, please report a bug.
2116 routeirq Do IRQ routing for all PCI devices.
2117 This is normally done in pci_enable_device(),
2118 so this option is a temporary workaround
2119 for broken drivers that don't call it.
2120 skip_isa_align [X86] do not align io start addr, so can
2121 handle more pci cards
2122 firmware [ARM] Do not re-enumerate the bus but instead
2123 just use the configuration from the
2124 bootloader. This is currently used on
2125 IXP2000 systems where the bus has to be
2126 configured a certain way for adjunct CPUs.
2127 noearly [X86] Don't do any early type 1 scanning.
2128 This might help on some broken boards which
2129 machine check when some devices' config space
2130 is read. But various workarounds are disabled
2131 and some IOMMU drivers will not work.
2132 bfsort Sort PCI devices into breadth-first order.
2133 This sorting is done to get a device
2134 order compatible with older (<= 2.4) kernels.
2135 nobfsort Don't sort PCI devices into breadth-first order.
2136 cbiosize=nn[KMG] The fixed amount of bus space which is
2137 reserved for the CardBus bridge's IO window.
2138 The default value is 256 bytes.
2139 cbmemsize=nn[KMG] The fixed amount of bus space which is
2140 reserved for the CardBus bridge's memory
2141 window. The default value is 64 megabytes.
2144 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2145 Specifies alignment and device to reassign
2146 aligned memory resources.
2147 If <order of align> is not specified,
2148 PAGE_SIZE is used as alignment.
2149 PCI-PCI bridge can be specified, if resource
2150 windows need to be expanded.
2151 ecrc= Enable/disable PCIe ECRC (transaction layer
2152 end-to-end CRC checking).
2153 bios: Use BIOS/firmware settings. This is the
2157 realloc= Enable/disable reallocating PCI bridge resources
2158 if allocations done by BIOS are too small to
2159 accommodate resources required by all child
2161 off: Turn realloc off
2163 realloc same as realloc=on
2164 noari do not use PCIe ARI.
2165 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2166 only look for one device below a PCIe downstream
2169 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2172 force Enable ASPM even on devices that claim not to support it.
2173 WARNING: Forcing ASPM on may cause system lockups.
2175 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2176 nomsi Do not use MSI for PCI Express Native Hotplug (this
2177 makes all PCIe ports use INTx for hotplug services).
2179 pcie_ports= [PCIE] PCIe ports handling:
2180 auto Ask the BIOS whether or not to use native PCIe services
2181 associated with PCIe ports (PME, hot-plug, AER). Use
2182 them only if that is allowed by the BIOS.
2183 native Use native PCIe services associated with PCIe ports
2185 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2188 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2189 nomsi Do not use MSI for native PCIe PME signaling (this makes
2190 all PCIe root ports use INTx for all services).
2192 pcmv= [HW,PCMCIA] BadgePAD 4
2195 See Documentation/blockdev/paride.txt.
2197 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2200 See arch/parisc/kernel/pdc_chassis.c
2202 percpu_alloc= Select which percpu first chunk allocator to use.
2203 Currently supported values are "embed" and "page".
2204 Archs may support subset or none of the selections.
2205 See comments in mm/percpu.c for details on each
2206 allocator. This parameter is primarily for debugging
2207 and performance comparison.
2210 See Documentation/blockdev/paride.txt.
2213 See Documentation/blockdev/paride.txt.
2215 pirq= [SMP,APIC] Manual mp-table setup
2216 See Documentation/x86/i386/IO-APIC.txt.
2218 plip= [PPT,NET] Parallel port network link
2219 Format: { parport<nr> | timid | 0 }
2220 See also Documentation/parport.txt.
2222 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2223 Override pmtimer IOPort with a hex value.
2227 Enable PNP debug messages (depends on the
2228 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2229 via /sys/module/pnp/parameters/debug. We always show
2230 current resource usage; turning this on also shows
2231 possible settings and some assignment information.
2237 { on | off | curr | res | no-curr | no-res }
2240 [ISAPNP] Exclude IRQs for the autoconfiguration
2243 [ISAPNP] Exclude DMAs for the autoconfiguration
2245 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2246 Ranges are in pairs (I/O port base and size).
2249 [ISAPNP] Exclude memory regions for the
2251 Ranges are in pairs (memory base and size).
2253 ports= [IP_VS_FTP] IPVS ftp helper module
2255 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2257 Format: <port>,<port>....
2259 print-fatal-signals=
2260 [KNL] debug: print fatal signals
2262 If enabled, warn about various signal handling
2263 related application anomalies: too many signals,
2264 too many POSIX.1 timers, fatal signals causing a
2267 If you hit the warning due to signal overflow,
2268 you might want to try "ulimit -i unlimited".
2272 printk.always_kmsg_dump=
2273 Trigger kmsg_dump for cases other than kernel oops or
2275 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2278 printk.time= Show timing data prefixed to each printk message line
2279 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2281 processor.max_cstate= [HW,ACPI]
2282 Limit processor to maximum C-state
2283 max_cstate=9 overrides any DMI blacklist limit.
2285 processor.nocst [HW,ACPI]
2286 Ignore the _CST method to determine C-states,
2287 instead using the legacy FADT method
2289 profile= [KNL] Enable kernel profiling via /proc/profile
2290 Format: [schedule,]<number>
2291 Param: "schedule" - profile schedule points.
2292 Param: <number> - step/bucket size as a power of 2 for
2293 statistical time based profiling.
2294 Param: "sleep" - profile D-state sleeping (millisecs).
2295 Requires CONFIG_SCHEDSTATS
2296 Param: "kvm" - profile VM exits.
2298 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2300 See Documentation/blockdev/ramdisk.txt.
2302 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2303 probe for; one of (bare|imps|exps|lifebook|any).
2304 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2306 psmouse.resetafter= [HW,MOUSE]
2307 Try to reset the device after so many bad packets
2310 [HW,MOUSE] Set desired mouse resolution, in dpi.
2311 psmouse.smartscroll=
2312 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2313 0 = disabled, 1 = enabled (default).
2315 pstore.backend= Specify the name of the pstore backend to use
2318 See Documentation/blockdev/paride.txt.
2321 [KNL] Number of legacy pty's. Overwrites compiled-in
2324 quiet [KNL] Disable most log messages
2329 See Documentation/md.txt.
2331 ramdisk_blocksize= [RAM]
2332 See Documentation/blockdev/ramdisk.txt.
2334 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2335 See Documentation/blockdev/ramdisk.txt.
2337 rcutree.blimit= [KNL,BOOT]
2338 Set maximum number of finished RCU callbacks to process
2341 rcutree.qhimark= [KNL,BOOT]
2342 Set threshold of queued
2343 RCU callbacks over which batch limiting is disabled.
2345 rcutree.qlowmark= [KNL,BOOT]
2346 Set threshold of queued RCU callbacks below which
2347 batch limiting is re-enabled.
2349 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2350 Suppress RCU CPU stall warning messages.
2352 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2353 Set timeout for RCU CPU stall warning messages.
2355 rcutorture.fqs_duration= [KNL,BOOT]
2356 Set duration of force_quiescent_state bursts.
2358 rcutorture.fqs_holdoff= [KNL,BOOT]
2359 Set holdoff time within force_quiescent_state bursts.
2361 rcutorture.fqs_stutter= [KNL,BOOT]
2362 Set wait time between force_quiescent_state bursts.
2364 rcutorture.irqreader= [KNL,BOOT]
2365 Test RCU readers from irq handlers.
2367 rcutorture.n_barrier_cbs= [KNL,BOOT]
2368 Set callbacks/threads for rcu_barrier() testing.
2370 rcutorture.nfakewriters= [KNL,BOOT]
2371 Set number of concurrent RCU writers. These just
2372 stress RCU, they don't participate in the actual
2373 test, hence the "fake".
2375 rcutorture.nreaders= [KNL,BOOT]
2376 Set number of RCU readers.
2378 rcutorture.onoff_holdoff= [KNL,BOOT]
2379 Set time (s) after boot for CPU-hotplug testing.
2381 rcutorture.onoff_interval= [KNL,BOOT]
2382 Set time (s) between CPU-hotplug operations, or
2383 zero to disable CPU-hotplug testing.
2385 rcutorture.shuffle_interval= [KNL,BOOT]
2386 Set task-shuffle interval (s). Shuffling tasks
2387 allows some CPUs to go into dyntick-idle mode
2388 during the rcutorture test.
2390 rcutorture.shutdown_secs= [KNL,BOOT]
2391 Set time (s) after boot system shutdown. This
2392 is useful for hands-off automated testing.
2394 rcutorture.stall_cpu= [KNL,BOOT]
2395 Duration of CPU stall (s) to test RCU CPU stall
2396 warnings, zero to disable.
2398 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2399 Time to wait (s) after boot before inducing stall.
2401 rcutorture.stat_interval= [KNL,BOOT]
2402 Time (s) between statistics printk()s.
2404 rcutorture.stutter= [KNL,BOOT]
2405 Time (s) to stutter testing, for example, specifying
2406 five seconds causes the test to run for five seconds,
2407 wait for five seconds, and so on. This tests RCU's
2408 ability to transition abruptly to and from idle.
2410 rcutorture.test_boost= [KNL,BOOT]
2411 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2412 "Maybe" means test if the RCU implementation
2413 under test support RCU priority boosting.
2415 rcutorture.test_boost_duration= [KNL,BOOT]
2416 Duration (s) of each individual boost test.
2418 rcutorture.test_boost_interval= [KNL,BOOT]
2419 Interval (s) between each boost test.
2421 rcutorture.test_no_idle_hz= [KNL,BOOT]
2422 Test RCU's dyntick-idle handling. See also the
2423 rcutorture.shuffle_interval parameter.
2425 rcutorture.torture_type= [KNL,BOOT]
2426 Specify the RCU implementation to test.
2428 rcutorture.verbose= [KNL,BOOT]
2429 Enable additional printk() statements.
2433 Run specified binary instead of /init from the ramdisk,
2434 used for early userspace startup. See initrd.
2436 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2437 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2438 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2441 [KNL, SMP] Set scheduler's default relax_domain_level.
2442 See Documentation/cgroups/cpusets.txt.
2444 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2446 reservetop= [X86-32]
2448 Reserves a hole at the top of the kernel virtual
2453 Set the amount of memory to reserve for BIOS at
2454 the bottom of the address space.
2456 reset_devices [KNL] Force drivers to reset the underlying device
2457 during initialization.
2460 Specify the partition device for software suspend
2462 resume_offset= [SWSUSP]
2463 Specify the offset from the beginning of the partition
2464 given by "resume=" at which the swap header is located,
2465 in <PAGE_SIZE> units (needed only for swap files).
2466 See Documentation/power/swsusp-and-swap-files.txt
2468 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2469 read the resume files
2471 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2472 Useful for devices that are detected asynchronously
2473 (e.g. USB and MMC devices).
2475 hibernate= [HIBERNATION]
2476 noresume Don't check if there's a hibernation image
2477 present during boot.
2478 nocompress Don't compress/decompress hibernation images.
2480 retain_initrd [RAM] Keep initrd memory after extraction
2482 rhash_entries= [KNL,NET]
2483 Set number of hash buckets for route cache
2485 riscom8= [HW,SERIAL]
2486 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2488 ro [KNL] Mount root device read-only on boot
2490 root= [KNL] Root filesystem
2491 See name_to_dev_t comment in init/do_mounts.c.
2493 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2494 mount the root filesystem
2496 rootflags= [KNL] Set root filesystem mount option string
2498 rootfstype= [KNL] Set root filesystem type
2500 rootwait [KNL] Wait (indefinitely) for root device to show up.
2501 Useful for devices that are detected asynchronously
2502 (e.g. USB and MMC devices).
2504 rw [KNL] Mount root device read-write on boot
2506 S [KNL] Run init in single mode
2509 See drivers/net/irda/sa1100_ir.c.
2511 sbni= [NET] Granch SBNI12 leased line adapter
2513 sched_debug [KNL] Enables verbose scheduler debug messages.
2515 security= [SECURITY] Choose a security module to enable at boot.
2516 If this boot parameter is not specified, only the first
2517 security module asking for security registration will be
2518 loaded. An invalid security module name will be treated
2519 as if no module has been chosen.
2521 selinux= [SELINUX] Disable or enable SELinux at boot time.
2522 Format: { "0" | "1" }
2523 See security/selinux/Kconfig help text.
2526 Default value is set via kernel config option.
2527 If enabled at boot time, /selinux/disable can be used
2528 later to disable prior to initial policy load.
2530 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2531 Format: { "0" | "1" }
2532 See security/apparmor/Kconfig help text
2535 Default value is set via kernel config option.
2537 serialnumber [BUGS=X86-32]
2540 Maximal number of shapers.
2542 show_msr= [x86] show boot-time MSR settings
2543 Format: { <integer> }
2544 Show boot-time (BIOS-initialized) MSR settings.
2545 The parameter means the number of CPUs to show,
2546 for example 1 means boot CPU only.
2553 slab_max_order= [MM, SLAB]
2554 Determines the maximum allowed order for slabs.
2555 A high setting may cause OOMs due to memory
2556 fragmentation. Defaults to 1 for systems with
2557 more than 32MB of RAM, 0 otherwise.
2559 slub_debug[=options[,slabs]] [MM, SLUB]
2560 Enabling slub_debug allows one to determine the
2561 culprit if slab objects become corrupted. Enabling
2562 slub_debug can create guard zones around objects and
2563 may poison objects when not in use. Also tracks the
2564 last alloc / free. For more information see
2565 Documentation/vm/slub.txt.
2567 slub_max_order= [MM, SLUB]
2568 Determines the maximum allowed order for slabs.
2569 A high setting may cause OOMs due to memory
2570 fragmentation. For more information see
2571 Documentation/vm/slub.txt.
2573 slub_min_objects= [MM, SLUB]
2574 The minimum number of objects per slab. SLUB will
2575 increase the slab order up to slub_max_order to
2576 generate a sufficiently large slab able to contain
2577 the number of objects indicated. The higher the number
2578 of objects the smaller the overhead of tracking slabs
2579 and the less frequently locks need to be acquired.
2580 For more information see Documentation/vm/slub.txt.
2582 slub_min_order= [MM, SLUB]
2583 Determines the minimum page order for slabs. Must be
2584 lower than slub_max_order.
2585 For more information see Documentation/vm/slub.txt.
2587 slub_nomerge [MM, SLUB]
2588 Disable merging of slabs with similar size. May be
2589 necessary if there is some reason to distinguish
2590 allocs to different slabs. Debug options disable
2591 merging on their own.
2592 For more information see Documentation/vm/slub.txt.
2595 Format: <io1>[,<io2>[,...,<io8>]]
2597 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2598 attempt to substitute SMP alternatives once at boot.
2600 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2601 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2602 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2603 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2604 smsc-ircc2.ircc_irq= [HW] IRQ line
2605 smsc-ircc2.ircc_dma= [HW] DMA channel
2606 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2607 0: Toshiba Satellite 1800 (GP data pin select)
2608 1: Fast pin select (default)
2612 [KNL] Should the soft-lockup detector generate panics.
2615 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2616 See Documentation/laptops/sonypi.txt
2618 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2619 See Documentation/serial/specialix.txt.
2621 spia_io_base= [HW,MTD]
2627 Enabled the stack tracer on boot up.
2629 stacktrace_filter=[function-list]
2630 [FTRACE] Limit the functions that the stack tracer
2631 will trace at boot up. function-list is a comma separated
2632 list of functions. This list can be changed at run
2633 time by the stack_trace_filter file in the debugfs
2634 tracing directory. Note, this enables stack tracing
2635 and the stacktrace above is not needed.
2639 Set the STI (builtin display/keyboard on the HP-PARISC
2640 machines) console (graphic card) which should be used
2641 as the initial boot-console.
2642 See also comment in drivers/video/console/sticore.c.
2645 See comment in drivers/video/console/sticore.c.
2648 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2650 sunrpc.min_resvport=
2651 sunrpc.max_resvport=
2653 SunRPC servers often require that client requests
2654 originate from a privileged port (i.e. a port in the
2655 range 0 < portnr < 1024).
2656 An administrator who wishes to reserve some of these
2657 ports for other uses may adjust the range that the
2658 kernel's sunrpc client considers to be privileged
2659 using these two parameters to set the minimum and
2660 maximum port values.
2664 Control how the NFS server code allocates CPUs to
2665 service thread pools. Depending on how many NICs
2666 you have and where their interrupts are bound, this
2667 option will affect which CPUs will do NFS serving.
2668 Note: this parameter cannot be changed while the
2669 NFS server is running.
2671 auto the server chooses an appropriate mode
2672 automatically using heuristics
2673 global a single global pool contains all CPUs
2674 percpu one pool for each CPU
2675 pernode one pool for each NUMA node (equivalent
2676 to global on non-NUMA machines)
2678 sunrpc.tcp_slot_table_entries=
2679 sunrpc.udp_slot_table_entries=
2681 Sets the upper limit on the number of simultaneous
2682 RPC calls that can be sent from the client to a
2683 server. Increasing these values may allow you to
2684 improve throughput, but will also increase the
2685 amount of memory reserved for use by the client.
2688 [KNL] Enable accounting of swap in memory resource
2689 controller if no parameter or 1 is given or disable
2690 it if 0 is given (See Documentation/cgroups/memory.txt)
2692 swiotlb= [IA-64] Number of I/O TLB slabs
2696 sysfs.deprecated=0|1 [KNL]
2697 Enable/disable old style sysfs layout for old udev
2698 on older distributions. When this option is enabled
2699 very new udev will not work anymore. When this option
2700 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2701 in older udev will not work anymore.
2702 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2703 the kernel configuration.
2705 sysrq_always_enabled
2707 Ignore sysrq setting - this boot parameter will
2708 neutralize any effect of /proc/sys/kernel/sysrq.
2709 Useful for debugging.
2713 test_suspend= [SUSPEND]
2714 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2715 standby suspend) as the system sleep state to briefly
2716 enter during system startup. The system is woken from
2717 this state using a wakeup-capable RTC alarm.
2719 thash_entries= [KNL,NET]
2720 Set number of hash buckets for TCP connection
2722 thermal.act= [HW,ACPI]
2723 -1: disable all active trip points in all thermal zones
2724 <degrees C>: override all lowest active trip points
2726 thermal.crt= [HW,ACPI]
2727 -1: disable all critical trip points in all thermal zones
2728 <degrees C>: override all critical trip points
2730 thermal.nocrt= [HW,ACPI]
2731 Set to disable actions on ACPI thermal zone
2732 critical and hot trip points.
2734 thermal.off= [HW,ACPI]
2735 1: disable ACPI thermal control
2737 thermal.psv= [HW,ACPI]
2738 -1: disable all passive trip points
2739 <degrees C>: override all passive trip points to this
2742 thermal.tzp= [HW,ACPI]
2743 Specify global default ACPI thermal zone polling rate
2744 <deci-seconds>: poll all this frequency
2745 0: no polling (default)
2748 Force threading of all interrupt handlers except those
2749 marked explicitly IRQF_NO_THREAD.
2753 Specify if the kernel should make use of the cpu
2754 topology information if the hardware supports this.
2755 The scheduler will make use of this information and
2756 e.g. base its process migration decisions on it.
2761 tpm_suspend_pcr=[HW,TPM]
2762 Format: integer pcr id
2763 Specify that at suspend time, the tpm driver
2764 should extend the specified pcr with zeros,
2765 as a workaround for some chips which fail to
2766 flush the last written pcr on TPM_SaveState.
2767 This will guarantee that all the other pcrs
2770 trace_buf_size=nn[KMG]
2771 [FTRACE] will set tracing buffer size.
2773 trace_event=[event-list]
2774 [FTRACE] Set and start specified trace events in order
2775 to facilitate early boot debugging.
2776 See also Documentation/trace/events.txt
2778 transparent_hugepage=
2780 Format: [always|madvise|never]
2781 Can be used to control the default behavior of the system
2782 with respect to transparent hugepages.
2783 See Documentation/vm/transhuge.txt for more details.
2785 tsc= Disable clocksource stability checks for TSC.
2787 [x86] reliable: mark tsc clocksource as reliable, this
2788 disables clocksource verification at runtime, as well
2789 as the stability checks done at bootup. Used to enable
2790 high-resolution timer mode on older hardware, and in
2791 virtualized environment.
2792 [x86] noirqtime: Do not use TSC to do irq accounting.
2793 Used to run time disable IRQ_TIME_ACCOUNTING on any
2794 platforms where RDTSC is slow and this accounting
2797 turbografx.map[2|3]= [HW,JOY]
2798 TurboGraFX parallel port interface
2800 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2801 See also Documentation/input/joystick-parport.txt
2803 udbg-immortal [PPC] When debugging early kernel crashes that
2804 happen after console_init() and before a proper
2805 console driver takes over, this boot options might
2806 help "seeing" what's going on.
2808 uhash_entries= [KNL,NET]
2809 Set number of hash buckets for UDP/UDP-Lite connections
2812 [USB] Ignore overcurrent events (default N).
2813 Some badly-designed motherboards generate lots of
2814 bogus events, for ports that aren't wired to
2815 anything. Set this parameter to avoid log spamming.
2816 Note that genuine overcurrent events won't be
2820 [X86] Cause panic on unknown NMI.
2822 usbcore.authorized_default=
2823 [USB] Default USB device authorization:
2824 (default -1 = authorized except for wireless USB,
2825 0 = not authorized, 1 = authorized)
2827 usbcore.autosuspend=
2828 [USB] The autosuspend time delay (in seconds) used
2829 for newly-detected USB devices (default 2). This
2830 is the time required before an idle device will be
2831 autosuspended. Devices for which the delay is set
2832 to a negative value won't be autosuspended at all.
2834 usbcore.usbfs_snoop=
2835 [USB] Set to log all usbfs traffic (default 0 = off).
2837 usbcore.blinkenlights=
2838 [USB] Set to cycle leds on hubs (default 0 = off).
2840 usbcore.old_scheme_first=
2841 [USB] Start with the old device initialization
2842 scheme (default 0 = off).
2844 usbcore.usbfs_memory_mb=
2845 [USB] Memory limit (in MB) for buffers allocated by
2846 usbfs (default = 16, 0 = max = 2047).
2848 usbcore.use_both_schemes=
2849 [USB] Try the other device initialization scheme
2850 if the first one fails (default 1 = enabled).
2852 usbcore.initial_descriptor_timeout=
2853 [USB] Specifies timeout for the initial 64-byte
2854 USB_REQ_GET_DESCRIPTOR request in milliseconds
2855 (default 5000 = 5.0 seconds).
2858 [USBHID] The interval which mice are to be polled at.
2860 usb-storage.delay_use=
2861 [UMS] The delay in seconds before a new device is
2862 scanned for Logical Units (default 5).
2865 [UMS] A list of quirks entries to supplement or
2866 override the built-in unusual_devs list. List
2867 entries are separated by commas. Each entry has
2868 the form VID:PID:Flags where VID and PID are Vendor
2869 and Product ID values (4-digit hex numbers) and
2870 Flags is a set of characters, each corresponding
2871 to a common usb-storage quirk flag as follows:
2872 a = SANE_SENSE (collect more than 18 bytes
2874 b = BAD_SENSE (don't collect more than 18
2875 bytes of sense data);
2876 c = FIX_CAPACITY (decrease the reported
2877 device capacity by one sector);
2878 d = NO_READ_DISC_INFO (don't use
2879 READ_DISC_INFO command);
2880 e = NO_READ_CAPACITY_16 (don't use
2881 READ_CAPACITY_16 command);
2882 h = CAPACITY_HEURISTICS (decrease the
2883 reported device capacity by one
2884 sector if the number is odd);
2885 i = IGNORE_DEVICE (don't bind to this
2887 l = NOT_LOCKABLE (don't try to lock and
2888 unlock ejectable media);
2889 m = MAX_SECTORS_64 (don't transfer more
2890 than 64 sectors = 32 KB at a time);
2891 n = INITIAL_READ10 (force a retry of the
2892 initial READ(10) command);
2893 o = CAPACITY_OK (accept the capacity
2894 reported by the device);
2895 r = IGNORE_RESIDUE (the device reports
2896 bogus residue values);
2897 s = SINGLE_LUN (the device has only one
2899 w = NO_WP_DETECT (don't test whether the
2900 medium is write-protected).
2901 Example: quirks=0419:aaf5:rl,0421:0433:rc
2903 user_debug= [KNL,ARM]
2905 See arch/arm/Kconfig.debug help text.
2906 1 - undefined instruction events
2908 4 - invalid data aborts
2911 Example: user_debug=31
2914 [X86] Flags controlling user PTE allocations.
2916 nohigh = do not allocate PTE pages in
2917 HIGHMEM regardless of setting
2921 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2922 vdso=1: enable VDSO (default)
2923 vdso=0: disable VDSO mapping
2926 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2927 vdso32=1: enable 32-bit VDSO (default)
2928 vdso32=0: disable 32-bit VDSO mapping
2931 vector=percpu: enable percpu vector domain
2933 video= [FB] Frame buffer configuration
2934 See Documentation/fb/modedb.txt.
2937 [VMMIO] Memory mapped virtio (platform) device.
2939 <size>@<baseaddr>:<irq>[:<id>]
2941 <size> := size (can use standard suffixes
2943 <baseaddr> := physical base address
2944 <irq> := interrupt number (as passed to
2946 <id> := (optional) platform device id
2948 virtio_mmio.device=1K@0x100b0000:48:7
2950 Can be used multiple times for multiple devices.
2952 vga= [BOOT,X86-32] Select a particular video mode
2953 See Documentation/x86/boot.txt and
2954 Documentation/svga.txt.
2955 Use vga=ask for menu.
2956 This is actually a boot loader parameter; the value is
2957 passed to the kernel using a special protocol.
2959 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2960 size of <nn>. This can be used to increase the
2961 minimum size (128MB on x86). It can also be used to
2962 decrease the size and leave more room for directly
2965 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2968 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2971 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2975 Controls the behavior of vsyscalls (i.e. calls to
2976 fixed addresses of 0xffffffffff600x00 from legacy
2977 code). Most statically-linked binaries and older
2978 versions of glibc use these calls. Because these
2979 functions are at fixed addresses, they make nice
2980 targets for exploits that can control RIP.
2982 emulate [default] Vsyscalls turn into traps and are
2983 emulated reasonably safely.
2985 native Vsyscalls are native syscall instructions.
2986 This is a little bit faster than trapping
2987 and makes a few dynamic recompilers work
2988 better than they would in emulation mode.
2989 It also makes exploits much easier to write.
2991 none Vsyscalls don't work at all. This makes
2992 them quite hard to use for exploits but
2993 might break your system.
2995 vt.cur_default= [VT] Default cursor shape.
2996 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2997 the parameters of the <Esc>[?A;B;Cc escape sequence;
2998 see VGA-softcursor.txt. Default: 2 = underline.
3000 vt.default_blu= [VT]
3001 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3002 Change the default blue palette of the console.
3003 This is a 16-member array composed of values
3006 vt.default_grn= [VT]
3007 Format: <green0>,<green1>,<green2>,...,<green15>
3008 Change the default green palette of the console.
3009 This is a 16-member array composed of values
3012 vt.default_red= [VT]
3013 Format: <red0>,<red1>,<red2>,...,<red15>
3014 Change the default red palette of the console.
3015 This is a 16-member array composed of values
3021 Set system-wide default UTF-8 mode for all tty's.
3022 Default is 1, i.e. UTF-8 mode is enabled for all
3023 newly opened terminals.
3025 vt.global_cursor_default=
3028 Set system-wide default for whether a cursor
3029 is shown on new VTs. Default is -1,
3030 i.e. cursors will be created by default unless
3031 overridden by individual drivers. 0 will hide
3032 cursors, 1 will display them.
3034 watchdog timers [HW,WDT] For information on watchdog timers,
3035 see Documentation/watchdog/watchdog-parameters.txt
3036 or other driver-specific files in the
3037 Documentation/watchdog/ directory.
3039 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3040 default x2apic cluster mode on platforms
3043 x86_mrst_timer= [X86-32,APBT]
3044 Choose timer option for x86 Moorestown MID platform.
3045 Two valid options are apbt timer only and lapic timer
3046 plus one apbt timer for broadcast timer.
3047 x86_mrst_timer=apbt_only | lapic_and_apbt
3049 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3050 xd_geo= See header of drivers/block/xd.c.
3052 xen_emul_unplug= [HW,X86,XEN]
3053 Unplug Xen emulated devices
3054 Format: [unplug0,][unplug1]
3055 ide-disks -- unplug primary master IDE devices
3056 aux-ide-disks -- unplug non-primary-master IDE devices
3057 nics -- unplug network devices
3058 all -- unplug all emulated devices (NICs and IDE disks)
3059 unnecessary -- unplugging emulated devices is
3060 unnecessary even if the host did not respond to
3062 never -- do not unplug even if version check succeeds
3064 xirc2ps_cs= [NET,PCMCIA]
3066 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3068 ______________________________________________________________________
3072 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob