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 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
386 atkbd.reset= [HW] Reset keyboard during initialization
388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
400 baycom_epp= [HW,AX25]
403 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
405 See header of drivers/net/hamradio/baycom_par.c.
407 baycom_ser_fdx= [HW,AX25]
408 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
409 Format: <io>,<irq>,<mode>[,<baud>]
410 See header of drivers/net/hamradio/baycom_ser_fdx.c.
412 baycom_ser_hdx= [HW,AX25]
413 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
414 Format: <io>,<irq>,<mode>
415 See header of drivers/net/hamradio/baycom_ser_hdx.c.
417 boot_delay= Milliseconds to delay each printk during boot.
418 Values larger than 10 seconds (10000) are changed to
422 bootmem_debug [KNL] Enable bootmem allocator debug messages.
424 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
425 bttv.radio= Most important insmod options are available as
427 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
430 bulk_remove=off [PPC] This parameter disables the use of the pSeries
431 firmware feature for flushing multiple hpte entries
434 c101= [NET] Moxa C101 synchronous serial card
436 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
437 Sometimes CPU hardware bugs make them report the cache
438 size incorrectly. The kernel will attempt work arounds
439 to fix known problems, but for some CPUs it is not
440 possible to determine what the correct size should be.
441 This option provides an override for these situations.
444 [SECURITY] Disable capabilities. This would normally
445 be used only if an alternative security model is to be
446 configured. Potentially dangerous and should only be
447 used if you are entirely sure of the consequences.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations if Contiguous Memory Allocator (CMA) is used.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel=range1:size1[,range2:size2,...][@offset]
598 [KNL] Same as above, but depends on the memory
599 in the running system. The syntax of range is
600 start-[end] where start and end are both
601 a memory unit (amount[KMG]). See also
602 Documentation/kdump/kdump.txt for an example.
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
620 details. Deprecated, see dyndbg.
622 debug [KNL] Enable kernel debugging (events log level).
625 [KNL] verbose self-tests
627 Print debugging info while doing the locking API
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
672 Set number of hash buckets for dentry cache.
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
707 this option disables the debugging code at boot.
709 dma_debug_entries=<number>
710 This option allows to tune the number of preallocated
711 entries for DMA-API debugging code. One entry is
712 required per DMA-API allocation. Use this if the
713 DMA-API debugging code disables itself because the
714 architectural default is too low.
716 dma_debug_driver=<driver_name>
717 With this option the DMA-API debugging driver
718 filter feature can be enabled at boot time. Just
719 pass the driver to filter for as the parameter.
720 The filter can be disabled or changed to another
721 driver later using sysfs.
723 drm_kms_helper.edid_firmware=[<connector>:]<file>
724 Broken monitors, graphic adapters and KVMs may
725 send no or incorrect EDID data sets. This parameter
726 allows to specify an EDID data set in the
727 /lib/firmware directory that is used instead.
728 Generic built-in EDID data sets are used, if one of
729 edid/1024x768.bin, edid/1280x1024.bin,
730 edid/1680x1050.bin, or edid/1920x1080.bin is given
731 and no file with the same name exists. Details and
732 instructions how to build your own EDID data are
733 available in Documentation/EDID/HOWTO.txt. An EDID
734 data set will only be used for a particular connector,
735 if its name and a colon are prepended to the EDID
740 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
741 module.dyndbg[="val"]
742 Enable debug messages at boot time. See
743 Documentation/dynamic-debug-howto.txt for details.
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
757 earlyprintk=serial[,ttySn[,baudrate]]
758 earlyprintk=ttySn[,baudrate]
759 earlyprintk=dbgp[debugController#]
761 Append ",keep" to not disable it when the real console
764 Only vga or serial or usb debug port at a time.
766 Currently only ttyS0 and ttyS1 are supported.
768 Interaction with the standard serial driver is not
771 The VGA output is eventually overwritten by the real
774 ekgdboc= [X86,KGDB] Allow early kernel console debugging
777 This is designed to be used in conjunction with
778 the boot argument: earlyprintk=vga
781 Format: {"off" | "on" | "skip[mbr]"}
783 eisa_irq_edge= [PARISC,HW]
784 See header of drivers/parisc/eisa.c.
787 See comment before function elanfreq_setup() in
788 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
791 Format: {"cfq" | "deadline" | "noop"}
792 See Documentation/block/cfq-iosched.txt and
793 Documentation/block/deadline-iosched.txt for details.
795 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
796 Specifies physical address of start of kernel core
797 image elf header and optionally the size. Generally
798 kexec loader will pass this option to capture kernel.
799 See Documentation/kdump/kdump.txt for details.
801 enable_mtrr_cleanup [X86]
802 The kernel tries to adjust MTRR layout from continuous
803 to discrete, to make X server driver able to add WB
804 entry later. This parameter enables that.
806 enable_timer_pin_1 [X86]
807 Enable PIN 1 of APIC timer
808 Can be useful to work around chipset bugs
809 (in particular on some ATI chipsets).
810 The kernel tries to set a reasonable default.
812 enforcing [SELINUX] Set initial enforcing status.
814 See security/selinux/Kconfig help text.
815 0 -- permissive (log only, no denials).
816 1 -- enforcing (deny and log).
818 Value can be changed at runtime via /selinux/enforce.
821 Disable Error Record Serialization Table (ERST)
824 ether= [HW,NET] Ethernet cards parameters
825 This option is obsoleted by the "netdev=" option, which
826 has equivalent usage. See its documentation for details.
830 Permit 'security.evm' to be updated regardless of
831 current integrity status.
835 fail_make_request=[KNL]
836 General fault injection mechanism.
837 Format: <interval>,<probability>,<space>,<times>
838 See also Documentation/fault-injection/.
841 See Documentation/blockdev/floppy.txt.
843 force_pal_cache_flush
844 [IA-64] Avoid check_sal_cache_flush which may hang on
845 buggy SAL_CACHE_FLUSH implementations. Using this
846 parameter will force ia64_sal_cache_flush to call
847 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
850 [FTRACE] will set and start the specified tracer
851 as early as possible in order to facilitate early
854 ftrace_dump_on_oops[=orig_cpu]
855 [FTRACE] will dump the trace buffers on oops.
856 If no parameter is passed, ftrace will dump
857 buffers of all CPUs, but if you pass orig_cpu, it will
858 dump only the buffer of the CPU that triggered the
861 ftrace_filter=[function-list]
862 [FTRACE] Limit the functions traced by the function
863 tracer at boot up. function-list is a comma separated
864 list of functions. This list can be changed at run
865 time by the set_ftrace_filter file in the debugfs
868 ftrace_notrace=[function-list]
869 [FTRACE] Do not trace the functions specified in
870 function-list. This list can be changed at run time
871 by the set_ftrace_notrace file in the debugfs
874 ftrace_graph_filter=[function-list]
875 [FTRACE] Limit the top level callers functions traced
876 by the function graph tracer at boot up.
877 function-list is a comma separated list of functions
878 that can be changed at run time by the
879 set_graph_function file in the debugfs tracing directory.
882 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
883 support via parallel port (up to 5 devices per port)
884 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
885 See also Documentation/input/joystick-parport.txt
889 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
893 gcov_persist= [GCOV] When non-zero (default), profiling data for
894 kernel modules is saved and remains accessible via
895 debugfs, even when the module is unloaded/reloaded.
896 When zero, profiling data is discarded and associated
897 debugfs files are removed at module unload time.
899 gpt [EFI] Forces disk with valid GPT signature but
900 invalid Protective MBR to be treated as GPT.
902 hashdist= [KNL,NUMA] Large hashes allocated during boot
903 are distributed across NUMA nodes. Defaults on
904 for 64-bit NUMA, off otherwise.
905 Format: 0 | 1 (for off | on)
907 hcl= [IA-64] SGI's Hardware Graph compatibility layer
909 hd= [EIDE] (E)IDE hard drive subsystem geometry
910 Format: <cyl>,<head>,<sect>
913 Disable Hardware Error Source Table (HEST) support;
914 corresponding firmware-first mode error processing
915 logic will be disabled.
917 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
918 size of <nn>. This works even on boxes that have no
919 highmem otherwise. This also works to reduce highmem
920 size on bigger boxes.
922 highres= [KNL] Enable/disable high resolution timer mode.
923 Valid parameters: "on", "off"
927 See Documentation/isdn/README.HiSax.
931 hpet= [X86-32,HPET] option to control HPET usage
932 Format: { enable (default) | disable | force |
934 disable: disable HPET and use PIT instead
935 force: allow force enabled of undocumented chips (ICH4,
937 verbose: show contents of HPET registers during setup
939 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
940 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
941 On x86-64 and powerpc, this option can be specified
942 multiple times interleaved with hugepages= to reserve
943 huge pages of different sizes. Valid pages sizes on
944 x86-64 are 2M (when the CPU supports "pse") and 1G
945 (when the CPU supports the "pdpe1gb" cpuinfo flag)
946 Note that 1GB pages can only be allocated at boot time
947 using hugepages= and not freed afterwards.
949 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
950 terminal devices. Valid values: 0..8
951 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
952 If specified, z/VM IUCV HVC accepts connections
953 from listed z/VM user IDs only.
956 Do not unregister boot console at start. This is only
957 useful for debugging when something happens in the window
958 between unregistering the boot console and initializing
961 i2c_bus= [HW] Override the default board specific I2C bus speed
962 or register an additional I2C bus that is not
963 registered from board initialization code.
967 i8042.debug [HW] Toggle i8042 debug mode
968 i8042.direct [HW] Put keyboard port into non-translated mode
969 i8042.dumbkbd [HW] Pretend that controller can only read data from
970 keyboard and cannot control its state
971 (Don't attempt to blink the leds)
972 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
973 i8042.nokbd [HW] Don't check/create keyboard port
974 i8042.noloop [HW] Disable the AUX Loopback command while probing
976 i8042.nomux [HW] Don't check presence of an active multiplexing
978 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
980 i8042.notimeout [HW] Ignore timeout condition signalled by controller
981 i8042.reset [HW] Reset the controller during init and cleanup
982 i8042.unlock [HW] Unlock (ignore) the keylock
986 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
987 indicates that the driver is running on unsupported
989 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
990 does not match list of supported models.
992 [HW] Report power status in /proc/i8k
993 (disabled by default)
994 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
997 i915.invert_brightness=
998 [DRM] Invert the sense of the variable that is used to
999 set the brightness of the panel backlight. Normally a
1000 brightness value of 0 indicates backlight switched off,
1001 and the maximum of the brightness value sets the backlight
1002 to maximum brightness. If this parameter is set to 0
1003 (default) and the machine requires it, or this parameter
1004 is set to 1, a brightness value of 0 sets the backlight
1005 to maximum brightness, and the maximum of the brightness
1006 value switches the backlight off.
1007 -1 -- never invert brightness
1008 0 -- machine default
1009 1 -- force brightness inversion
1012 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1014 ide-core.nodma= [HW] (E)IDE subsystem
1015 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1016 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1017 .cdrom .chs .ignore_cable are additional options
1018 See Documentation/ide/ide.txt.
1020 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1021 Claim all unknown PCI IDE storage controllers.
1024 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1025 Poll forces a polling idle loop that can slightly
1026 improve the performance of waking up a idle CPU, but
1027 will use a lot of power and make the system run hot.
1029 idle=mwait: On systems which support MONITOR/MWAIT but
1030 the kernel chose to not use it because it doesn't save
1031 as much power as a normal idle loop, use the
1032 MONITOR/MWAIT idle loop anyways. Performance should be
1033 the same as idle=poll.
1034 idle=halt: Halt is forced to be used for CPU idle.
1035 In such case C2/C3 won't be used again.
1036 idle=nomwait: Disable mwait for CPU C-states
1038 ignore_loglevel [KNL]
1039 Ignore loglevel setting - this will print /all/
1040 kernel messages to the console. Useful for debugging.
1041 We also add it as printk module parameter, so users
1042 could change it dynamically, usually by
1043 /sys/module/printk/parameters/ignore_loglevel.
1045 ihash_entries= [KNL]
1046 Set number of hash buckets for inode cache.
1049 Format: { "0" | "1" }
1050 0 -- integrity auditing messages. (Default)
1051 1 -- enable informational integrity auditing messages.
1054 Format: { "sha1" | "md5" }
1058 Load a policy which meets the needs of the Trusted
1059 Computing Base. This means IMA will measure all
1060 programs exec'd, files mmap'd for exec, and all files
1061 opened for read by uid=0.
1065 Run specified binary instead of /sbin/init as init
1068 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1069 for working out where the kernel is dying during
1072 initrd= [BOOT] Specify the location of the initial ramdisk
1074 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1077 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1079 Enable intel iommu driver.
1081 Disable intel iommu driver.
1082 igfx_off [Default Off]
1083 By default, gfx is mapped as normal device. If a gfx
1084 device has a dedicated DMAR unit, the DMAR unit is
1085 bypassed by not enabling DMAR with this option. In
1086 this case, gfx device will use physical address for
1089 With this option iommu will not optimize to look
1090 for io virtual address below 32-bit forcing dual
1091 address cycle on pci bus for cards supporting greater
1092 than 32-bit addressing. The default is to look
1093 for translation below 32-bit and if not available
1094 then look in the higher range.
1095 strict [Default Off]
1096 With this option on every unmap_single operation will
1097 result in a hardware IOTLB flush operation as opposed
1098 to batching them for performance.
1099 sp_off [Default Off]
1100 By default, super page will be supported if Intel IOMMU
1101 has the capability. With this option, super page will
1104 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1105 0 disables intel_idle and fall back on acpi_idle.
1106 1 to 6 specify maximum depth of C-state.
1108 intremap= [X86-64, Intel-IOMMU]
1109 on enable Interrupt Remapping (default)
1110 off disable Interrupt Remapping
1111 nosid disable Source ID checking
1113 BIOS x2APIC opt-out request will be ignored
1115 iomem= Disable strict checking of access to MMIO memory
1116 strict regions from userspace.
1131 group_mf [x86, IA-64]
1134 io7= [HW] IO7 for Marvel based alpha systems
1135 See comment before marvel_specify_io7 in
1136 arch/alpha/kernel/core_marvel.c.
1138 io_delay= [X86] I/O delay method
1140 Standard port 0x80 based delay
1142 Alternate port 0xed based delay (needed on some systems)
1144 Simple two microseconds delay
1149 See Documentation/filesystems/nfs/nfsroot.txt.
1151 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1152 See comment before ip2_setup() in
1153 drivers/char/ip2/ip2base.c.
1156 When an interrupt is not handled search all handlers
1157 for it. Intended to get systems with badly broken
1161 When an interrupt is not handled search all handlers
1162 for it. Also check all handlers each timer
1163 interrupt. Intended to get systems with badly broken
1167 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1169 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1171 <cpu number>,...,<cpu number>
1173 <cpu number>-<cpu number>
1174 (must be a positive range in ascending order)
1176 <cpu number>,...,<cpu number>-<cpu number>
1178 This option can be used to specify one or more CPUs
1179 to isolate from the general SMP balancing and scheduling
1180 algorithms. You can move a process onto or off an
1181 "isolated" CPU via the CPU affinity syscalls or cpuset.
1182 <cpu number> begins at 0 and the maximum value is
1183 "number of CPUs in system - 1".
1185 This option is the preferred way to isolate CPUs. The
1186 alternative -- manually setting the CPU mask of all
1187 tasks in the system -- can cause problems and
1188 suboptimal load balancer performance.
1192 js= [HW,JOY] Analog joystick
1193 See Documentation/input/joystick.txt.
1197 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1198 specifies the amount of memory usable by the kernel
1199 for non-movable allocations. The requested amount is
1200 spread evenly throughout all nodes in the system. The
1201 remaining memory in each node is used for Movable
1202 pages. In the event, a node is too small to have both
1203 kernelcore and Movable pages, kernelcore pages will
1204 take priority and other nodes will have a larger number
1205 of kernelcore pages. The Movable zone is used for the
1206 allocation of pages that may be reclaimed or moved
1207 by the page migration subsystem. This means that
1208 HugeTLB pages may not be allocated from this zone.
1209 Note that allocations like PTEs-from-HighMem still
1210 use the HighMem zone if it exists, and the Normal
1211 zone if it does not.
1213 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1214 Format: <Controller#>[,poll interval]
1215 The controller # is the number of the ehci usb debug
1216 port as it is probed via PCI. The poll interval is
1217 optional and is the number seconds in between
1218 each poll cycle to the debug port in case you need
1219 the functionality for interrupting the kernel with
1220 gdb or control-c on the dbgp connection. When
1221 not using this parameter you use sysrq-g to break into
1222 the kernel debugger.
1224 kgdboc= [KGDB,HW] kgdb over consoles.
1225 Requires a tty driver that supports console polling,
1226 or a supported polling keyboard driver (non-usb).
1227 Serial only format: <serial_device>[,baud]
1228 keyboard only format: kbd
1229 keyboard and serial format: kbd,<serial_device>[,baud]
1230 Optional Kernel mode setting:
1231 kms, kbd format: kms,kbd
1232 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1234 kgdbwait [KGDB] Stop kernel execution and enter the
1235 kernel debugger at the earliest opportunity.
1237 kmac= [MIPS] korina ethernet MAC address.
1238 Configure the RouterBoard 532 series on-chip
1239 Ethernet adapter MAC address.
1241 kmemleak= [KNL] Boot-time kmemleak enable/disable
1242 Valid arguments: on, off
1245 kstack=N [X86] Print N words from the kernel stack
1248 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1249 Default is 0 (don't ignore, but inject #GP)
1251 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1255 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1256 Default is 1 (enabled)
1258 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1260 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1262 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1263 (virtualized MMU) support on capable Intel chips.
1264 Default is 1 (enabled)
1266 kvm-intel.emulate_invalid_guest_state=
1267 [KVM,Intel] Enable emulation of invalid guest states
1268 Default is 0 (disabled)
1270 kvm-intel.flexpriority=
1271 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1272 Default is 1 (enabled)
1275 [KVM,Intel] Enable VMX nesting (nVMX).
1276 Default is 0 (disabled)
1278 kvm-intel.unrestricted_guest=
1279 [KVM,Intel] Disable unrestricted guest feature
1280 (virtualized real and unpaged mode) on capable
1281 Intel chips. Default is 1 (enabled)
1283 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1284 feature (tagged TLBs) on capable Intel chips.
1285 Default is 1 (enabled)
1291 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1294 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1297 libata.dma= [LIBATA] DMA control
1298 libata.dma=0 Disable all PATA and SATA DMA
1299 libata.dma=1 PATA and SATA Disk DMA only
1300 libata.dma=2 ATAPI (CDROM) DMA only
1301 libata.dma=4 Compact Flash DMA only
1302 Combinations also work, so libata.dma=3 enables DMA
1303 for disks and CDROMs, but not CFs.
1305 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1306 libata.ignore_hpa=0 keep BIOS limits (default)
1307 libata.ignore_hpa=1 ignore limits, using full disk
1309 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1313 libata.force= [LIBATA] Force configurations. The format is comma
1314 separated list of "[ID:]VAL" where ID is
1315 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1316 matching port, link or device. Basically, it matches
1317 the ATA ID string printed on console by libata. If
1318 the whole ID part is omitted, the last PORT and DEVICE
1319 values are used. If ID hasn't been specified yet, the
1320 configuration applies to all ports, links and devices.
1322 If only DEVICE is omitted, the parameter applies to
1323 the port and all links and devices behind it. DEVICE
1324 number of 0 either selects the first device or the
1325 first fan-out link behind PMP device. It does not
1326 select the host link. DEVICE number of 15 selects the
1327 host link and device attached to it.
1329 The VAL specifies the configuration to force. As long
1330 as there's no ambiguity shortcut notation is allowed.
1331 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1332 The following configurations can be forced.
1334 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1335 Any ID with matching PORT is used.
1337 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1339 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1340 udma[/][16,25,33,44,66,100,133] notation is also
1343 * [no]ncq: Turn on or off NCQ.
1345 * nohrst, nosrst, norst: suppress hard, soft
1348 * dump_id: dump IDENTIFY data.
1350 If there are multiple matching configurations changing
1351 the same attribute, the last one is used.
1353 memblock=debug [KNL] Enable memblock debug messages.
1355 load_ramdisk= [RAM] List of ramdisks to load from floppy
1356 See Documentation/blockdev/ramdisk.txt.
1358 lockd.nlm_grace_period=P [NFS] Assign grace period.
1361 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1364 lockd.nlm_timeout=T [NFS] Assign timeout value.
1367 lockd.nlm_udpport=M [NFS] Assign UDP port.
1370 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1373 loglevel= All Kernel Messages with a loglevel smaller than the
1374 console loglevel will be printed to the console. It can
1375 also be changed with klogd or other programs. The
1376 loglevels are defined as follows:
1378 0 (KERN_EMERG) system is unusable
1379 1 (KERN_ALERT) action must be taken immediately
1380 2 (KERN_CRIT) critical conditions
1381 3 (KERN_ERR) error conditions
1382 4 (KERN_WARNING) warning conditions
1383 5 (KERN_NOTICE) normal but significant condition
1384 6 (KERN_INFO) informational
1385 7 (KERN_DEBUG) debug-level messages
1387 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1388 in bytes. n must be a power of two. The default
1389 size is set in the kernel config file.
1391 logo.nologo [FB] Disables display of the built-in Linux logo.
1392 This may be used to provide more screen space for
1393 kernel log messages and is useful when debugging
1394 kernel boot problems.
1396 lp=0 [LP] Specify parallel ports to use, e.g,
1397 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1398 lp=reset first parallel port). 'lp=0' disables the
1399 lp=auto printer driver. 'lp=reset' (which can be
1400 specified in addition to the ports) causes
1401 attached printers to be reset. Using
1402 lp=port1,port2,... specifies the parallel ports
1403 to associate lp devices with, starting with
1404 lp0. A port specification may be 'none' to skip
1405 that lp device, or a parport name such as
1406 'parport0'. Specifying 'lp=auto' instead of a
1407 port specification list means that device IDs
1408 from each port should be examined, to see if
1409 an IEEE 1284-compliant printer is attached; if
1410 so, the driver will manage that printer.
1411 See also header of drivers/char/lp.c.
1414 Sets loops_per_jiffy to given constant, thus avoiding
1415 time-consuming boot-time autodetection (up to 250 ms per
1416 CPU). 0 enables autodetection (default). To determine
1417 the correct value for your kernel, boot with normal
1418 autodetection and see what value is printed. Note that
1419 on SMP systems the preset will be applied to all CPUs,
1420 which is likely to cause problems if your CPUs need
1421 significantly divergent settings. An incorrect value
1422 will cause delays in the kernel to be wrong, leading to
1423 unpredictable I/O errors and other breakage. Although
1424 unlikely, in the extreme case this might damage your
1428 Format: <io>,<irq>,<dma>
1430 machvec= [IA-64] Force the use of a particular machine-vector
1431 (machvec) in a generic kernel.
1432 Example: machvec=hpzx1_swiotlb
1434 machtype= [Loongson] Share the same kernel image file between different
1436 Example: machtype=lemote-yeeloong-2f-7inch
1438 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1439 than or equal to this physical address is ignored.
1441 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1442 should make use of. maxcpus=n : n >= 0 limits the
1443 kernel to using 'n' processors. n=0 is a special case,
1444 it is equivalent to "nosmp", which also disables
1447 max_loop= [LOOP] The number of loop block devices that get
1448 (loop.max_loop) unconditionally pre-created at init time. The default
1449 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1450 of statically allocating a predefined number, loop
1451 devices can be requested on-demand with the
1452 /dev/loop-control interface.
1454 mce [X86-32] Machine Check Exception
1456 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1458 md= [HW] RAID subsystems devices and level
1459 See Documentation/md.txt.
1462 Format: <first>,<last>
1463 Specifies range of consoles to be captured by the MDA.
1465 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1466 Amount of memory to be used when the kernel is not able
1467 to see the whole system memory or for test.
1468 [X86-32] Use together with memmap= to avoid physical
1469 address space collisions. Without memmap= PCI devices
1470 could be placed at addresses belonging to unused RAM.
1472 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1476 [KNL,SH] Allow user to override the default size for
1477 per-device physically contiguous DMA buffers.
1479 memmap=exactmap [KNL,X86] Enable setting of an exact
1480 E820 memory map, as specified by the user.
1481 Such memmap=exactmap lines can be constructed based on
1482 BIOS output or other requirements. See the memmap=nn@ss
1485 memmap=nn[KMG]@ss[KMG]
1486 [KNL] Force usage of a specific region of memory
1487 Region of memory to be used, from ss to ss+nn.
1489 memmap=nn[KMG]#ss[KMG]
1490 [KNL,ACPI] Mark specific memory as ACPI data.
1491 Region of memory to be used, from ss to ss+nn.
1493 memmap=nn[KMG]$ss[KMG]
1494 [KNL,ACPI] Mark specific memory as reserved.
1495 Region of memory to be used, from ss to ss+nn.
1496 Example: Exclude memory from 0x18690000-0x1869ffff
1497 memmap=64K$0x18690000
1499 memmap=0x10000$0x18690000
1501 memory_corruption_check=0/1 [X86]
1502 Some BIOSes seem to corrupt the first 64k of
1503 memory when doing things like suspend/resume.
1504 Setting this option will scan the memory
1505 looking for corruption. Enabling this will
1506 both detect corruption and prevent the kernel
1507 from using the memory being corrupted.
1508 However, its intended as a diagnostic tool; if
1509 repeatable BIOS-originated corruption always
1510 affects the same memory, you can use memmap=
1511 to prevent the kernel from using that memory.
1513 memory_corruption_check_size=size [X86]
1514 By default it checks for corruption in the low
1515 64k, making this memory unavailable for normal
1516 use. Use this parameter to scan for
1517 corruption in more or less memory.
1519 memory_corruption_check_period=seconds [X86]
1520 By default it checks for corruption every 60
1521 seconds. Use this parameter to check at some
1522 other rate. 0 disables periodic checking.
1524 memtest= [KNL,X86] Enable memtest
1526 default : 0 <disable>
1527 Specifies the number of memtest passes to be
1528 performed. Each pass selects another test
1529 pattern from a given set of patterns. Memtest
1530 fills the memory with this pattern, validates
1531 memory contents and reserves bad memory
1532 regions that are detected.
1534 meye.*= [HW] Set MotionEye Camera parameters
1535 See Documentation/video4linux/meye.txt.
1537 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1538 Multi-Function General Purpose Timers on AMD Geode
1541 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1542 the BIOS has incorrectly applied a workaround. TinyBIOS
1543 version 0.98 is known to be affected, 0.99 fixes the
1544 problem by letting the user disable the workaround.
1548 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1549 physical address is ignored.
1551 mini2440= [ARM,HW,KNL]
1552 Format:[0..2][b][c][t]
1554 MINI2440 configuration specification:
1555 0 - The attached screen is the 3.5" TFT
1556 1 - The attached screen is the 7" TFT
1557 2 - The VGA Shield is attached (1024x768)
1558 Leaving out the screen size parameter will not load
1559 the TFT driver, and the framebuffer will be left
1561 b - Enable backlight. The TFT backlight pin will be
1562 linked to the kernel VESA blanking code and a GPIO
1563 LED. This parameter is not necessary when using the
1565 c - Enable the s3c camera interface.
1566 t - Reserved for enabling touchscreen support. The
1567 touchscreen support is not enabled in the mainstream
1568 kernel as of 2.6.30, a preliminary port can be found
1569 in the "bleeding edge" mini2440 support kernel at
1570 http://repo.or.cz/w/linux-2.6/mini2440.git
1573 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1574 parameter allows control of the logging verbosity for
1575 the additional memory initialisation checks. A value
1576 of 0 disables mminit logging and a level of 4 will
1577 log everything. Information is printed at KERN_DEBUG
1578 so loglevel=8 may also need to be specified.
1581 [MOUSE] Maximum time between finger touching and
1582 leaving touchpad surface for touch to be considered
1583 a tap and be reported as a left button click (for
1584 touchpads working in absolute mode only).
1586 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1587 reporting absolute coordinates, such as tablets
1588 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1589 reporting absolute coordinates, such as tablets
1591 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1592 is similar to kernelcore except it specifies the
1593 amount of memory used for migratable allocations.
1594 If both kernelcore and movablecore is specified,
1595 then kernelcore will be at *least* the specified
1596 value but may be more. If movablecore on its own
1597 is specified, the administrator must be careful
1598 that the amount of memory usable for all allocations
1601 MTD_Partition= [MTD]
1602 Format: <name>,<region-number>,<size>,<offset>
1604 MTD_Region= [MTD] Format:
1605 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1608 See drivers/mtd/cmdlinepart.c.
1610 multitce=off [PPC] This parameter disables the use of the pSeries
1611 firmware feature for updating multiple TCE entries
1614 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1616 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1618 boundary - index of last SLC block on Flex-OneNAND.
1619 The remaining blocks are configured as MLC blocks.
1620 lock - Configure if Flex-OneNAND boundary should be locked.
1621 Once locked, the boundary cannot be changed.
1622 1 indicates lock status, 0 indicates unlock status.
1625 ARM/S3C2412 JIVE boot control
1627 See arch/arm/mach-s3c2412/mach-jive.c
1629 mtouchusb.raw_coordinates=
1630 [HW] Make the MicroTouch USB driver use raw coordinates
1631 ('y', default) or cooked coordinates ('n')
1633 mtrr_chunk_size=nn[KMG] [X86]
1634 used for mtrr cleanup. It is largest continuous chunk
1635 that could hold holes aka. UC entries.
1637 mtrr_gran_size=nn[KMG] [X86]
1638 Used for mtrr cleanup. It is granularity of mtrr block.
1640 Large value could prevent small alignment from
1643 mtrr_spare_reg_nr=n [X86]
1645 Range: 0,7 : spare reg number
1647 Used for mtrr cleanup. It is spare mtrr entries number.
1648 Set to 2 or more if your graphical card needs more.
1650 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1652 netdev= [NET] Network devices parameters
1653 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1654 Note that mem_start is often overloaded to mean
1655 something different and driver-specific.
1656 This usage is only documented in each driver source
1660 [NETFILTER] Enable connection tracking flow accounting
1661 0 to disable accounting
1662 1 to enable accounting
1665 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1666 See Documentation/filesystems/nfs/nfsroot.txt.
1668 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1669 See Documentation/filesystems/nfs/nfsroot.txt.
1671 nfsrootdebug [NFS] enable nfsroot debugging messages.
1672 See Documentation/filesystems/nfs/nfsroot.txt.
1674 nfs.callback_tcpport=
1675 [NFS] set the TCP port on which the NFSv4 callback
1676 channel should listen.
1679 [NFS] sets the pathname to the program which is used
1680 to update the NFS client cache entries.
1682 nfs.cache_getent_timeout=
1683 [NFS] sets the timeout after which an attempt to
1684 update a cache entry is deemed to have failed.
1686 nfs.idmap_cache_timeout=
1687 [NFS] set the maximum lifetime for idmapper cache
1691 [NFS] enable 64-bit inode numbers.
1692 If zero, the NFS client will fake up a 32-bit inode
1693 number for the readdir() and stat() syscalls instead
1694 of returning the full 64-bit number.
1695 The default is to return 64-bit inode numbers.
1697 nfs.max_session_slots=
1698 [NFSv4.1] Sets the maximum number of session slots
1699 the client will attempt to negotiate with the server.
1700 This limits the number of simultaneous RPC requests
1701 that the client can send to the NFSv4.1 server.
1702 Note that there is little point in setting this
1703 value higher than the max_tcp_slot_table_limit.
1705 nfs.nfs4_disable_idmapping=
1706 [NFSv4] When set to the default of '1', this option
1707 ensures that both the RPC level authentication
1708 scheme and the NFS level operations agree to use
1709 numeric uids/gids if the mount is using the
1710 'sec=sys' security flavour. In effect it is
1711 disabling idmapping, which can make migration from
1712 legacy NFSv2/v3 systems to NFSv4 easier.
1713 Servers that do not support this mode of operation
1714 will be autodetected by the client, and it will fall
1715 back to using the idmapper.
1716 To turn off this behaviour, set the value to '0'.
1718 nfs.send_implementation_id =
1719 [NFSv4.1] Send client implementation identification
1720 information in exchange_id requests.
1721 If zero, no implementation identification information
1723 The default is to send the implementation identification
1726 nfsd.nfs4_disable_idmapping=
1727 [NFSv4] When set to the default of '1', the NFSv4
1728 server will return only numeric uids and gids to
1729 clients using auth_sys, and will accept numeric uids
1730 and gids from such clients. This is intended to ease
1731 migration from NFSv2/v3.
1733 objlayoutdriver.osd_login_prog=
1734 [NFS] [OBJLAYOUT] sets the pathname to the program which
1735 is used to automatically discover and login into new
1736 osd-targets. Please see:
1737 Documentation/filesystems/pnfs.txt for more explanations
1739 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1740 when a NMI is triggered.
1741 Format: [state][,regs][,debounce][,die]
1743 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1744 Format: [panic,][nopanic,][num]
1746 0 - turn nmi_watchdog off
1747 When panic is specified, panic when an NMI watchdog
1748 timeout occurs (or 'nopanic' to override the opposite
1750 This is useful when you use a panic=... timeout and
1751 need the box quickly up again.
1753 netpoll.carrier_timeout=
1754 [NET] Specifies amount of time (in seconds) that
1755 netpoll should wait for a carrier. By default netpoll
1758 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1759 emulation library even if a 387 maths coprocessor
1763 [HW] Never suspend the console
1764 Disable suspending of consoles during suspend and
1765 hibernate operations. Once disabled, debugging
1766 messages can reach various consoles while the rest
1767 of the system is being put to sleep (ie, while
1768 debugging driver suspend/resume hooks). This may
1769 not work reliably with all consoles, but is known
1770 to work with serial and VGA consoles.
1771 To facilitate more flexible debugging, we also add
1772 console_suspend, a printk module parameter to control
1773 it. Users could use console_suspend (usually
1774 /sys/module/printk/parameters/console_suspend) to
1775 turn on/off it dynamically.
1777 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1778 caches in the slab allocator. Saves per-node memory,
1779 but will impact performance.
1783 noapic [SMP,APIC] Tells the kernel to not make use of any
1784 IOAPICs that may be present in the system.
1786 noautogroup Disable scheduler automatic task group creation.
1788 nobats [PPC] Do not use BATs for mapping kernel lowmem
1789 on "Classic" PPC cores.
1793 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1795 nodelayacct [KNL] Disable per-task delay accounting
1797 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1799 nodsp [SH] Disable hardware DSP at boot time.
1801 noefi [X86] Disable EFI runtime services support.
1806 On X86-32 available only on PAE configured kernels.
1807 noexec=on: enable non-executable mappings (default)
1808 noexec=off: disable non-executable mappings
1811 Disable SMEP (Supervisor Mode Execution Protection)
1812 even if it is supported by processor.
1815 This affects only 32-bit executables.
1816 noexec32=on: enable non-executable mappings (default)
1817 read doesn't imply executable mappings
1818 noexec32=off: disable non-executable mappings
1819 read implies executable mappings
1821 nofpu [SH] Disable hardware FPU at boot time.
1823 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1824 register save and restore. The kernel will only save
1825 legacy floating-point registers on task switch.
1827 noxsave [BUGS=X86] Disables x86 extended register state save
1828 and restore using xsave. The kernel will fallback to
1829 enabling legacy floating-point and sse state.
1831 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1832 wfi(ARM) instruction doesn't work correctly and not to
1833 use it. This is also useful when using JTAG debugger.
1835 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1836 instruction doesn't work correctly and not to
1839 no_file_caps Tells the kernel not to honor file capabilities. The
1840 only way then for a file to be executed with privilege
1841 is to be setuid root or executed by root.
1843 nohalt [IA-64] Tells the kernel not to use the power saving
1844 function PAL_HALT_LIGHT when idle. This increases
1845 power-consumption. On the positive side, it reduces
1846 interrupt wake-up latency, which may improve performance
1847 in certain environments such as networked servers or
1850 nohz= [KNL] Boottime enable/disable dynamic ticks
1851 Valid arguments: on, off
1854 noiotrap [SH] Disables trapped I/O port accesses.
1856 noirqdebug [X86-32] Disables the code which attempts to detect and
1857 disable unhandled interrupt sources.
1859 no_timer_check [X86,APIC] Disables the code which tests for
1860 broken timer IRQ sources.
1862 noisapnp [ISAPNP] Disables ISA PnP code.
1864 noinitrd [RAM] Tells the kernel not to load any configured
1867 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1869 [Deprecated - use intremap=off]
1873 nojitter [IA-64] Disables jitter checking for ITC timers.
1875 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1877 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1880 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1881 steal time is computed, but won't influence scheduler
1884 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1886 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1888 noltlbs [PPC] Do not use large page/tlb entries for kernel
1889 lowmem mapping on PPC40x.
1891 nomca [IA-64] Disable machine check abort handling
1893 nomce [X86-32] Machine Check Exception
1895 nomfgpt [X86-32] Disable Multi-Function General Purpose
1896 Timer usage (for AMD Geode machines).
1898 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1899 shutdown the other cpus. Instead use the REBOOT_VECTOR
1902 nomodule Disable module load
1904 nopat [X86] Disable PAT (page attribute table extension of
1905 pagetables) support.
1907 norandmaps Don't use address space randomization. Equivalent to
1908 echo 0 > /proc/sys/kernel/randomize_va_space
1910 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1912 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1913 with UP alternatives
1915 noresidual [PPC] Don't use residual data on PReP machines.
1917 nordrand [X86] Disable the direct use of the RDRAND
1918 instruction even if it is supported by the
1919 processor. RDRAND is still available to user
1922 noresume [SWSUSP] Disables resume and restores original swap
1925 no-scroll [VGA] Disables scrollback.
1926 This is required for the Braillex ib80-piezo Braille
1927 reader made by F.H. Papenmeier (Germany).
1931 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1933 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1934 and disable the IO APIC. legacy for "maxcpus=0".
1936 nosoftlockup [KNL] Disable the soft-lockup detector.
1938 nosync [HW,M68K] Disables sync negotiation for all devices.
1940 notsc [BUGS=X86-32] Disable Time Stamp Counter
1942 nousb [USB] Disable the USB subsystem
1944 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1948 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1950 nptcg= [IA-64] Override max number of concurrent global TLB
1951 purges which is reported from either PAL_VM_SUMMARY or
1954 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1955 could support. nr_cpus=n : n >= 1 limits the kernel to
1956 supporting 'n' processors. Later in runtime you can not
1957 use hotplug cpu feature to put more cpu back to online.
1958 just like you compile the kernel NR_CPUS=n
1960 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1962 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1963 one of ['zone', 'node', 'default'] can be specified
1964 This can be set from sysctl after boot.
1965 See Documentation/sysctl/vm.txt for details.
1967 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1968 See Documentation/debugging-via-ohci1394.txt for more
1971 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1972 Rather than timing out after 20 ms if an EC
1973 command is not properly ACKed, override the length
1974 of the timeout. We have interrupts disabled while
1975 waiting for the ACK, so if this is set too high
1976 interrupts *may* be lost!
1978 omap_mux= [OMAP] Override bootloader pin multiplexing.
1979 Format: <mux_mode0.mode_name=value>...
1980 For example, to override I2C bus2:
1981 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1983 oprofile.timer= [HW]
1984 Use timer interrupt instead of performance counters
1986 oprofile.cpu_type= Force an oprofile cpu type
1987 This might be useful if you have an older oprofile
1988 userland or if you want common events.
1989 Format: { arch_perfmon }
1990 arch_perfmon: [X86] Force use of architectural
1991 perfmon on Intel CPUs instead of the
1992 CPU specific event set.
1993 timer: [X86] Force use of architectural NMI
1994 timer mode (see also oprofile.timer
1995 for generic hr timer mode)
1996 [s390] Force legacy basic mode sampling
1997 (report cpu_type "timer")
1999 oops=panic Always panic on oopses. Default is to just kill the
2000 process, but there is a small probability of
2001 deadlocking the machine.
2002 This will also cause panics on machine check exceptions.
2003 Useful together with panic=30 to trigger a reboot.
2006 See Documentation/sound/oss/oss-parameters.txt
2008 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2009 timeout > 0: seconds before rebooting
2010 timeout = 0: wait forever
2011 timeout < 0: reboot immediately
2014 parkbd.port= [HW] Parallel port number the keyboard adapter is
2015 connected to, default is 0.
2017 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2018 0 for XT, 1 for AT (default is AT).
2021 parport= [HW,PPT] Specify parallel ports. 0 disables.
2022 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2023 Use 'auto' to force the driver to use any
2024 IRQ/DMA settings detected (the default is to
2025 ignore detected IRQ/DMA settings because of
2026 possible conflicts). You can specify the base
2027 address, IRQ, and DMA settings; IRQ and DMA
2028 should be numbers, or 'auto' (for using detected
2029 settings on that particular port), or 'nofifo'
2030 (to avoid using a FIFO even if it is detected).
2031 Parallel ports are assigned in the order they
2032 are specified on the command line, starting
2035 parport_init_mode= [HW,PPT]
2036 Configure VIA parallel port to operate in
2037 a specific mode. This is necessary on Pegasos
2038 computer where firmware has no options for setting
2039 up parallel port mode and sets it to spp.
2040 Currently this function knows 686a and 8231 chips.
2041 Format: [spp|ps2|epp|ecp|ecpepp]
2044 Halt all CPUs after the first oops has been printed for
2045 the specified number of seconds. This is to be used if
2046 your oopses keep scrolling off the screen.
2051 See header of drivers/block/paride/pcd.c.
2052 See also Documentation/blockdev/paride.txt.
2054 pci=option[,option...] [PCI] various PCI subsystem options:
2055 earlydump [X86] dump PCI config space before the kernel
2057 off [X86] don't probe for the PCI bus
2058 bios [X86-32] force use of PCI BIOS, don't access
2059 the hardware directly. Use this if your machine
2060 has a non-standard PCI host bridge.
2061 nobios [X86-32] disallow use of PCI BIOS, only direct
2062 hardware access methods are allowed. Use this
2063 if you experience crashes upon bootup and you
2064 suspect they are caused by the BIOS.
2065 conf1 [X86] Force use of PCI Configuration
2067 conf2 [X86] Force use of PCI Configuration
2069 noaer [PCIE] If the PCIEAER kernel config parameter is
2070 enabled, this kernel boot option can be used to
2071 disable the use of PCIE advanced error reporting.
2072 nodomains [PCI] Disable support for multiple PCI
2073 root domains (aka PCI segments, in ACPI-speak).
2074 nommconf [X86] Disable use of MMCONFIG for PCI
2076 check_enable_amd_mmconf [X86] check for and enable
2077 properly configured MMIO access to PCI
2078 config space on AMD family 10h CPU
2079 nomsi [MSI] If the PCI_MSI kernel config parameter is
2080 enabled, this kernel boot option can be used to
2081 disable the use of MSI interrupts system-wide.
2082 noioapicquirk [APIC] Disable all boot interrupt quirks.
2083 Safety option to keep boot IRQs enabled. This
2084 should never be necessary.
2085 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2086 primary IO-APIC for bridges that cannot disable
2087 boot IRQs. This fixes a source of spurious IRQs
2088 when the system masks IRQs.
2089 noioapicreroute [APIC] Disable workaround that uses the
2090 boot IRQ equivalent of an IRQ that connects to
2091 a chipset where boot IRQs cannot be disabled.
2092 The opposite of ioapicreroute.
2093 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2094 routing table. These calls are known to be buggy
2095 on several machines and they hang the machine
2096 when used, but on other computers it's the only
2097 way to get the interrupt routing table. Try
2098 this option if the kernel is unable to allocate
2099 IRQs or discover secondary PCI buses on your
2101 rom [X86] Assign address space to expansion ROMs.
2102 Use with caution as certain devices share
2103 address decoders between ROMs and other
2105 norom [X86] Do not assign address space to
2106 expansion ROMs that do not already have
2107 BIOS assigned address ranges.
2108 nobar [X86] Do not assign address space to the
2109 BARs that weren't assigned by the BIOS.
2110 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2111 assigned automatically to PCI devices. You can
2112 make the kernel exclude IRQs of your ISA cards
2114 pirqaddr=0xAAAAA [X86] Specify the physical address
2115 of the PIRQ table (normally generated
2116 by the BIOS) if it is outside the
2117 F0000h-100000h range.
2118 lastbus=N [X86] Scan all buses thru bus #N. Can be
2119 useful if the kernel is unable to find your
2120 secondary buses and you want to tell it
2121 explicitly which ones they are.
2122 assign-busses [X86] Always assign all PCI bus
2123 numbers ourselves, overriding
2124 whatever the firmware may have done.
2125 usepirqmask [X86] Honor the possible IRQ mask stored
2126 in the BIOS $PIR table. This is needed on
2127 some systems with broken BIOSes, notably
2128 some HP Pavilion N5400 and Omnibook XE3
2129 notebooks. This will have no effect if ACPI
2130 IRQ routing is enabled.
2131 noacpi [X86] Do not use ACPI for IRQ routing
2132 or for PCI scanning.
2133 use_crs [X86] Use PCI host bridge window information
2134 from ACPI. On BIOSes from 2008 or later, this
2135 is enabled by default. If you need to use this,
2136 please report a bug.
2137 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2138 If you need to use this, please report a bug.
2139 routeirq Do IRQ routing for all PCI devices.
2140 This is normally done in pci_enable_device(),
2141 so this option is a temporary workaround
2142 for broken drivers that don't call it.
2143 skip_isa_align [X86] do not align io start addr, so can
2144 handle more pci cards
2145 firmware [ARM] Do not re-enumerate the bus but instead
2146 just use the configuration from the
2147 bootloader. This is currently used on
2148 IXP2000 systems where the bus has to be
2149 configured a certain way for adjunct CPUs.
2150 noearly [X86] Don't do any early type 1 scanning.
2151 This might help on some broken boards which
2152 machine check when some devices' config space
2153 is read. But various workarounds are disabled
2154 and some IOMMU drivers will not work.
2155 bfsort Sort PCI devices into breadth-first order.
2156 This sorting is done to get a device
2157 order compatible with older (<= 2.4) kernels.
2158 nobfsort Don't sort PCI devices into breadth-first order.
2159 cbiosize=nn[KMG] The fixed amount of bus space which is
2160 reserved for the CardBus bridge's IO window.
2161 The default value is 256 bytes.
2162 cbmemsize=nn[KMG] The fixed amount of bus space which is
2163 reserved for the CardBus bridge's memory
2164 window. The default value is 64 megabytes.
2167 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2168 Specifies alignment and device to reassign
2169 aligned memory resources.
2170 If <order of align> is not specified,
2171 PAGE_SIZE is used as alignment.
2172 PCI-PCI bridge can be specified, if resource
2173 windows need to be expanded.
2174 ecrc= Enable/disable PCIe ECRC (transaction layer
2175 end-to-end CRC checking).
2176 bios: Use BIOS/firmware settings. This is the
2180 realloc= Enable/disable reallocating PCI bridge resources
2181 if allocations done by BIOS are too small to
2182 accommodate resources required by all child
2184 off: Turn realloc off
2186 realloc same as realloc=on
2187 noari do not use PCIe ARI.
2188 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2189 only look for one device below a PCIe downstream
2192 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2195 force Enable ASPM even on devices that claim not to support it.
2196 WARNING: Forcing ASPM on may cause system lockups.
2198 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2199 nomsi Do not use MSI for PCI Express Native Hotplug (this
2200 makes all PCIe ports use INTx for hotplug services).
2202 pcie_ports= [PCIE] PCIe ports handling:
2203 auto Ask the BIOS whether or not to use native PCIe services
2204 associated with PCIe ports (PME, hot-plug, AER). Use
2205 them only if that is allowed by the BIOS.
2206 native Use native PCIe services associated with PCIe ports
2208 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2211 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2212 nomsi Do not use MSI for native PCIe PME signaling (this makes
2213 all PCIe root ports use INTx for all services).
2215 pcmv= [HW,PCMCIA] BadgePAD 4
2218 See Documentation/blockdev/paride.txt.
2220 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2223 See arch/parisc/kernel/pdc_chassis.c
2225 percpu_alloc= Select which percpu first chunk allocator to use.
2226 Currently supported values are "embed" and "page".
2227 Archs may support subset or none of the selections.
2228 See comments in mm/percpu.c for details on each
2229 allocator. This parameter is primarily for debugging
2230 and performance comparison.
2233 See Documentation/blockdev/paride.txt.
2236 See Documentation/blockdev/paride.txt.
2238 pirq= [SMP,APIC] Manual mp-table setup
2239 See Documentation/x86/i386/IO-APIC.txt.
2241 plip= [PPT,NET] Parallel port network link
2242 Format: { parport<nr> | timid | 0 }
2243 See also Documentation/parport.txt.
2245 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2246 Override pmtimer IOPort with a hex value.
2250 Enable PNP debug messages (depends on the
2251 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2252 via /sys/module/pnp/parameters/debug. We always show
2253 current resource usage; turning this on also shows
2254 possible settings and some assignment information.
2260 { on | off | curr | res | no-curr | no-res }
2263 [ISAPNP] Exclude IRQs for the autoconfiguration
2266 [ISAPNP] Exclude DMAs for the autoconfiguration
2268 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2269 Ranges are in pairs (I/O port base and size).
2272 [ISAPNP] Exclude memory regions for the
2274 Ranges are in pairs (memory base and size).
2276 ports= [IP_VS_FTP] IPVS ftp helper module
2278 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2280 Format: <port>,<port>....
2282 print-fatal-signals=
2283 [KNL] debug: print fatal signals
2285 If enabled, warn about various signal handling
2286 related application anomalies: too many signals,
2287 too many POSIX.1 timers, fatal signals causing a
2290 If you hit the warning due to signal overflow,
2291 you might want to try "ulimit -i unlimited".
2295 printk.always_kmsg_dump=
2296 Trigger kmsg_dump for cases other than kernel oops or
2298 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2301 printk.time= Show timing data prefixed to each printk message line
2302 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2304 processor.max_cstate= [HW,ACPI]
2305 Limit processor to maximum C-state
2306 max_cstate=9 overrides any DMI blacklist limit.
2308 processor.nocst [HW,ACPI]
2309 Ignore the _CST method to determine C-states,
2310 instead using the legacy FADT method
2312 profile= [KNL] Enable kernel profiling via /proc/profile
2313 Format: [schedule,]<number>
2314 Param: "schedule" - profile schedule points.
2315 Param: <number> - step/bucket size as a power of 2 for
2316 statistical time based profiling.
2317 Param: "sleep" - profile D-state sleeping (millisecs).
2318 Requires CONFIG_SCHEDSTATS
2319 Param: "kvm" - profile VM exits.
2321 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2323 See Documentation/blockdev/ramdisk.txt.
2325 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2326 probe for; one of (bare|imps|exps|lifebook|any).
2327 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2329 psmouse.resetafter= [HW,MOUSE]
2330 Try to reset the device after so many bad packets
2333 [HW,MOUSE] Set desired mouse resolution, in dpi.
2334 psmouse.smartscroll=
2335 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2336 0 = disabled, 1 = enabled (default).
2338 pstore.backend= Specify the name of the pstore backend to use
2341 See Documentation/blockdev/paride.txt.
2344 [KNL] Number of legacy pty's. Overwrites compiled-in
2347 quiet [KNL] Disable most log messages
2352 See Documentation/md.txt.
2354 ramdisk_blocksize= [RAM]
2355 See Documentation/blockdev/ramdisk.txt.
2357 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2358 See Documentation/blockdev/ramdisk.txt.
2360 rcutree.blimit= [KNL,BOOT]
2361 Set maximum number of finished RCU callbacks to process
2364 rcutree.qhimark= [KNL,BOOT]
2365 Set threshold of queued
2366 RCU callbacks over which batch limiting is disabled.
2368 rcutree.qlowmark= [KNL,BOOT]
2369 Set threshold of queued RCU callbacks below which
2370 batch limiting is re-enabled.
2372 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2373 Suppress RCU CPU stall warning messages.
2375 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2376 Set timeout for RCU CPU stall warning messages.
2378 rcutorture.fqs_duration= [KNL,BOOT]
2379 Set duration of force_quiescent_state bursts.
2381 rcutorture.fqs_holdoff= [KNL,BOOT]
2382 Set holdoff time within force_quiescent_state bursts.
2384 rcutorture.fqs_stutter= [KNL,BOOT]
2385 Set wait time between force_quiescent_state bursts.
2387 rcutorture.irqreader= [KNL,BOOT]
2388 Test RCU readers from irq handlers.
2390 rcutorture.n_barrier_cbs= [KNL,BOOT]
2391 Set callbacks/threads for rcu_barrier() testing.
2393 rcutorture.nfakewriters= [KNL,BOOT]
2394 Set number of concurrent RCU writers. These just
2395 stress RCU, they don't participate in the actual
2396 test, hence the "fake".
2398 rcutorture.nreaders= [KNL,BOOT]
2399 Set number of RCU readers.
2401 rcutorture.onoff_holdoff= [KNL,BOOT]
2402 Set time (s) after boot for CPU-hotplug testing.
2404 rcutorture.onoff_interval= [KNL,BOOT]
2405 Set time (s) between CPU-hotplug operations, or
2406 zero to disable CPU-hotplug testing.
2408 rcutorture.shuffle_interval= [KNL,BOOT]
2409 Set task-shuffle interval (s). Shuffling tasks
2410 allows some CPUs to go into dyntick-idle mode
2411 during the rcutorture test.
2413 rcutorture.shutdown_secs= [KNL,BOOT]
2414 Set time (s) after boot system shutdown. This
2415 is useful for hands-off automated testing.
2417 rcutorture.stall_cpu= [KNL,BOOT]
2418 Duration of CPU stall (s) to test RCU CPU stall
2419 warnings, zero to disable.
2421 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2422 Time to wait (s) after boot before inducing stall.
2424 rcutorture.stat_interval= [KNL,BOOT]
2425 Time (s) between statistics printk()s.
2427 rcutorture.stutter= [KNL,BOOT]
2428 Time (s) to stutter testing, for example, specifying
2429 five seconds causes the test to run for five seconds,
2430 wait for five seconds, and so on. This tests RCU's
2431 ability to transition abruptly to and from idle.
2433 rcutorture.test_boost= [KNL,BOOT]
2434 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2435 "Maybe" means test if the RCU implementation
2436 under test support RCU priority boosting.
2438 rcutorture.test_boost_duration= [KNL,BOOT]
2439 Duration (s) of each individual boost test.
2441 rcutorture.test_boost_interval= [KNL,BOOT]
2442 Interval (s) between each boost test.
2444 rcutorture.test_no_idle_hz= [KNL,BOOT]
2445 Test RCU's dyntick-idle handling. See also the
2446 rcutorture.shuffle_interval parameter.
2448 rcutorture.torture_type= [KNL,BOOT]
2449 Specify the RCU implementation to test.
2451 rcutorture.verbose= [KNL,BOOT]
2452 Enable additional printk() statements.
2456 Run specified binary instead of /init from the ramdisk,
2457 used for early userspace startup. See initrd.
2459 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2460 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2461 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2464 [KNL, SMP] Set scheduler's default relax_domain_level.
2465 See Documentation/cgroups/cpusets.txt.
2467 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2469 reservetop= [X86-32]
2471 Reserves a hole at the top of the kernel virtual
2476 Set the amount of memory to reserve for BIOS at
2477 the bottom of the address space.
2479 reset_devices [KNL] Force drivers to reset the underlying device
2480 during initialization.
2483 Specify the partition device for software suspend
2485 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2487 resume_offset= [SWSUSP]
2488 Specify the offset from the beginning of the partition
2489 given by "resume=" at which the swap header is located,
2490 in <PAGE_SIZE> units (needed only for swap files).
2491 See Documentation/power/swsusp-and-swap-files.txt
2493 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2494 read the resume files
2496 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2497 Useful for devices that are detected asynchronously
2498 (e.g. USB and MMC devices).
2500 hibernate= [HIBERNATION]
2501 noresume Don't check if there's a hibernation image
2502 present during boot.
2503 nocompress Don't compress/decompress hibernation images.
2505 retain_initrd [RAM] Keep initrd memory after extraction
2507 rhash_entries= [KNL,NET]
2508 Set number of hash buckets for route cache
2510 riscom8= [HW,SERIAL]
2511 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2513 ro [KNL] Mount root device read-only on boot
2515 root= [KNL] Root filesystem
2516 See name_to_dev_t comment in init/do_mounts.c.
2518 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2519 mount the root filesystem
2521 rootflags= [KNL] Set root filesystem mount option string
2523 rootfstype= [KNL] Set root filesystem type
2525 rootwait [KNL] Wait (indefinitely) for root device to show up.
2526 Useful for devices that are detected asynchronously
2527 (e.g. USB and MMC devices).
2529 rw [KNL] Mount root device read-write on boot
2531 S [KNL] Run init in single mode
2534 See drivers/net/irda/sa1100_ir.c.
2536 sbni= [NET] Granch SBNI12 leased line adapter
2538 sched_debug [KNL] Enables verbose scheduler debug messages.
2540 security= [SECURITY] Choose a security module to enable at boot.
2541 If this boot parameter is not specified, only the first
2542 security module asking for security registration will be
2543 loaded. An invalid security module name will be treated
2544 as if no module has been chosen.
2546 selinux= [SELINUX] Disable or enable SELinux at boot time.
2547 Format: { "0" | "1" }
2548 See security/selinux/Kconfig help text.
2551 Default value is set via kernel config option.
2552 If enabled at boot time, /selinux/disable can be used
2553 later to disable prior to initial policy load.
2555 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2556 Format: { "0" | "1" }
2557 See security/apparmor/Kconfig help text
2560 Default value is set via kernel config option.
2562 serialnumber [BUGS=X86-32]
2565 Maximal number of shapers.
2567 show_msr= [x86] show boot-time MSR settings
2568 Format: { <integer> }
2569 Show boot-time (BIOS-initialized) MSR settings.
2570 The parameter means the number of CPUs to show,
2571 for example 1 means boot CPU only.
2578 slab_max_order= [MM, SLAB]
2579 Determines the maximum allowed order for slabs.
2580 A high setting may cause OOMs due to memory
2581 fragmentation. Defaults to 1 for systems with
2582 more than 32MB of RAM, 0 otherwise.
2584 slub_debug[=options[,slabs]] [MM, SLUB]
2585 Enabling slub_debug allows one to determine the
2586 culprit if slab objects become corrupted. Enabling
2587 slub_debug can create guard zones around objects and
2588 may poison objects when not in use. Also tracks the
2589 last alloc / free. For more information see
2590 Documentation/vm/slub.txt.
2592 slub_max_order= [MM, SLUB]
2593 Determines the maximum allowed order for slabs.
2594 A high setting may cause OOMs due to memory
2595 fragmentation. For more information see
2596 Documentation/vm/slub.txt.
2598 slub_min_objects= [MM, SLUB]
2599 The minimum number of objects per slab. SLUB will
2600 increase the slab order up to slub_max_order to
2601 generate a sufficiently large slab able to contain
2602 the number of objects indicated. The higher the number
2603 of objects the smaller the overhead of tracking slabs
2604 and the less frequently locks need to be acquired.
2605 For more information see Documentation/vm/slub.txt.
2607 slub_min_order= [MM, SLUB]
2608 Determines the minimum page order for slabs. Must be
2609 lower than slub_max_order.
2610 For more information see Documentation/vm/slub.txt.
2612 slub_nomerge [MM, SLUB]
2613 Disable merging of slabs with similar size. May be
2614 necessary if there is some reason to distinguish
2615 allocs to different slabs. Debug options disable
2616 merging on their own.
2617 For more information see Documentation/vm/slub.txt.
2620 Format: <io1>[,<io2>[,...,<io8>]]
2622 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2623 attempt to substitute SMP alternatives once at boot.
2625 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2626 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2627 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2628 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2629 smsc-ircc2.ircc_irq= [HW] IRQ line
2630 smsc-ircc2.ircc_dma= [HW] DMA channel
2631 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2632 0: Toshiba Satellite 1800 (GP data pin select)
2633 1: Fast pin select (default)
2637 [KNL] Should the soft-lockup detector generate panics.
2640 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2641 See Documentation/laptops/sonypi.txt
2643 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2644 See Documentation/serial/specialix.txt.
2646 spia_io_base= [HW,MTD]
2652 Enabled the stack tracer on boot up.
2654 stacktrace_filter=[function-list]
2655 [FTRACE] Limit the functions that the stack tracer
2656 will trace at boot up. function-list is a comma separated
2657 list of functions. This list can be changed at run
2658 time by the stack_trace_filter file in the debugfs
2659 tracing directory. Note, this enables stack tracing
2660 and the stacktrace above is not needed.
2664 Set the STI (builtin display/keyboard on the HP-PARISC
2665 machines) console (graphic card) which should be used
2666 as the initial boot-console.
2667 See also comment in drivers/video/console/sticore.c.
2670 See comment in drivers/video/console/sticore.c.
2673 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2675 sunrpc.min_resvport=
2676 sunrpc.max_resvport=
2678 SunRPC servers often require that client requests
2679 originate from a privileged port (i.e. a port in the
2680 range 0 < portnr < 1024).
2681 An administrator who wishes to reserve some of these
2682 ports for other uses may adjust the range that the
2683 kernel's sunrpc client considers to be privileged
2684 using these two parameters to set the minimum and
2685 maximum port values.
2689 Control how the NFS server code allocates CPUs to
2690 service thread pools. Depending on how many NICs
2691 you have and where their interrupts are bound, this
2692 option will affect which CPUs will do NFS serving.
2693 Note: this parameter cannot be changed while the
2694 NFS server is running.
2696 auto the server chooses an appropriate mode
2697 automatically using heuristics
2698 global a single global pool contains all CPUs
2699 percpu one pool for each CPU
2700 pernode one pool for each NUMA node (equivalent
2701 to global on non-NUMA machines)
2703 sunrpc.tcp_slot_table_entries=
2704 sunrpc.udp_slot_table_entries=
2706 Sets the upper limit on the number of simultaneous
2707 RPC calls that can be sent from the client to a
2708 server. Increasing these values may allow you to
2709 improve throughput, but will also increase the
2710 amount of memory reserved for use by the client.
2713 [KNL] Enable accounting of swap in memory resource
2714 controller if no parameter or 1 is given or disable
2715 it if 0 is given (See Documentation/cgroups/memory.txt)
2717 swiotlb= [IA-64] Number of I/O TLB slabs
2721 sysfs.deprecated=0|1 [KNL]
2722 Enable/disable old style sysfs layout for old udev
2723 on older distributions. When this option is enabled
2724 very new udev will not work anymore. When this option
2725 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2726 in older udev will not work anymore.
2727 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2728 the kernel configuration.
2730 sysrq_always_enabled
2732 Ignore sysrq setting - this boot parameter will
2733 neutralize any effect of /proc/sys/kernel/sysrq.
2734 Useful for debugging.
2738 test_suspend= [SUSPEND]
2739 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2740 standby suspend) as the system sleep state to briefly
2741 enter during system startup. The system is woken from
2742 this state using a wakeup-capable RTC alarm.
2744 thash_entries= [KNL,NET]
2745 Set number of hash buckets for TCP connection
2747 thermal.act= [HW,ACPI]
2748 -1: disable all active trip points in all thermal zones
2749 <degrees C>: override all lowest active trip points
2751 thermal.crt= [HW,ACPI]
2752 -1: disable all critical trip points in all thermal zones
2753 <degrees C>: override all critical trip points
2755 thermal.nocrt= [HW,ACPI]
2756 Set to disable actions on ACPI thermal zone
2757 critical and hot trip points.
2759 thermal.off= [HW,ACPI]
2760 1: disable ACPI thermal control
2762 thermal.psv= [HW,ACPI]
2763 -1: disable all passive trip points
2764 <degrees C>: override all passive trip points to this
2767 thermal.tzp= [HW,ACPI]
2768 Specify global default ACPI thermal zone polling rate
2769 <deci-seconds>: poll all this frequency
2770 0: no polling (default)
2773 Force threading of all interrupt handlers except those
2774 marked explicitly IRQF_NO_THREAD.
2778 Specify if the kernel should make use of the cpu
2779 topology information if the hardware supports this.
2780 The scheduler will make use of this information and
2781 e.g. base its process migration decisions on it.
2786 tpm_suspend_pcr=[HW,TPM]
2787 Format: integer pcr id
2788 Specify that at suspend time, the tpm driver
2789 should extend the specified pcr with zeros,
2790 as a workaround for some chips which fail to
2791 flush the last written pcr on TPM_SaveState.
2792 This will guarantee that all the other pcrs
2795 trace_buf_size=nn[KMG]
2796 [FTRACE] will set tracing buffer size.
2798 trace_event=[event-list]
2799 [FTRACE] Set and start specified trace events in order
2800 to facilitate early boot debugging.
2801 See also Documentation/trace/events.txt
2803 transparent_hugepage=
2805 Format: [always|madvise|never]
2806 Can be used to control the default behavior of the system
2807 with respect to transparent hugepages.
2808 See Documentation/vm/transhuge.txt for more details.
2810 tsc= Disable clocksource stability checks for TSC.
2812 [x86] reliable: mark tsc clocksource as reliable, this
2813 disables clocksource verification at runtime, as well
2814 as the stability checks done at bootup. Used to enable
2815 high-resolution timer mode on older hardware, and in
2816 virtualized environment.
2817 [x86] noirqtime: Do not use TSC to do irq accounting.
2818 Used to run time disable IRQ_TIME_ACCOUNTING on any
2819 platforms where RDTSC is slow and this accounting
2822 turbografx.map[2|3]= [HW,JOY]
2823 TurboGraFX parallel port interface
2825 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2826 See also Documentation/input/joystick-parport.txt
2828 udbg-immortal [PPC] When debugging early kernel crashes that
2829 happen after console_init() and before a proper
2830 console driver takes over, this boot options might
2831 help "seeing" what's going on.
2833 uhash_entries= [KNL,NET]
2834 Set number of hash buckets for UDP/UDP-Lite connections
2837 [USB] Ignore overcurrent events (default N).
2838 Some badly-designed motherboards generate lots of
2839 bogus events, for ports that aren't wired to
2840 anything. Set this parameter to avoid log spamming.
2841 Note that genuine overcurrent events won't be
2845 [X86] Cause panic on unknown NMI.
2847 usbcore.authorized_default=
2848 [USB] Default USB device authorization:
2849 (default -1 = authorized except for wireless USB,
2850 0 = not authorized, 1 = authorized)
2852 usbcore.autosuspend=
2853 [USB] The autosuspend time delay (in seconds) used
2854 for newly-detected USB devices (default 2). This
2855 is the time required before an idle device will be
2856 autosuspended. Devices for which the delay is set
2857 to a negative value won't be autosuspended at all.
2859 usbcore.usbfs_snoop=
2860 [USB] Set to log all usbfs traffic (default 0 = off).
2862 usbcore.blinkenlights=
2863 [USB] Set to cycle leds on hubs (default 0 = off).
2865 usbcore.old_scheme_first=
2866 [USB] Start with the old device initialization
2867 scheme (default 0 = off).
2869 usbcore.usbfs_memory_mb=
2870 [USB] Memory limit (in MB) for buffers allocated by
2871 usbfs (default = 16, 0 = max = 2047).
2873 usbcore.use_both_schemes=
2874 [USB] Try the other device initialization scheme
2875 if the first one fails (default 1 = enabled).
2877 usbcore.initial_descriptor_timeout=
2878 [USB] Specifies timeout for the initial 64-byte
2879 USB_REQ_GET_DESCRIPTOR request in milliseconds
2880 (default 5000 = 5.0 seconds).
2883 [USBHID] The interval which mice are to be polled at.
2885 usb-storage.delay_use=
2886 [UMS] The delay in seconds before a new device is
2887 scanned for Logical Units (default 5).
2890 [UMS] A list of quirks entries to supplement or
2891 override the built-in unusual_devs list. List
2892 entries are separated by commas. Each entry has
2893 the form VID:PID:Flags where VID and PID are Vendor
2894 and Product ID values (4-digit hex numbers) and
2895 Flags is a set of characters, each corresponding
2896 to a common usb-storage quirk flag as follows:
2897 a = SANE_SENSE (collect more than 18 bytes
2899 b = BAD_SENSE (don't collect more than 18
2900 bytes of sense data);
2901 c = FIX_CAPACITY (decrease the reported
2902 device capacity by one sector);
2903 d = NO_READ_DISC_INFO (don't use
2904 READ_DISC_INFO command);
2905 e = NO_READ_CAPACITY_16 (don't use
2906 READ_CAPACITY_16 command);
2907 h = CAPACITY_HEURISTICS (decrease the
2908 reported device capacity by one
2909 sector if the number is odd);
2910 i = IGNORE_DEVICE (don't bind to this
2912 l = NOT_LOCKABLE (don't try to lock and
2913 unlock ejectable media);
2914 m = MAX_SECTORS_64 (don't transfer more
2915 than 64 sectors = 32 KB at a time);
2916 n = INITIAL_READ10 (force a retry of the
2917 initial READ(10) command);
2918 o = CAPACITY_OK (accept the capacity
2919 reported by the device);
2920 r = IGNORE_RESIDUE (the device reports
2921 bogus residue values);
2922 s = SINGLE_LUN (the device has only one
2924 w = NO_WP_DETECT (don't test whether the
2925 medium is write-protected).
2926 Example: quirks=0419:aaf5:rl,0421:0433:rc
2928 user_debug= [KNL,ARM]
2930 See arch/arm/Kconfig.debug help text.
2931 1 - undefined instruction events
2933 4 - invalid data aborts
2936 Example: user_debug=31
2939 [X86] Flags controlling user PTE allocations.
2941 nohigh = do not allocate PTE pages in
2942 HIGHMEM regardless of setting
2946 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2947 vdso=1: enable VDSO (default)
2948 vdso=0: disable VDSO mapping
2951 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2952 vdso32=1: enable 32-bit VDSO (default)
2953 vdso32=0: disable 32-bit VDSO mapping
2956 vector=percpu: enable percpu vector domain
2958 video= [FB] Frame buffer configuration
2959 See Documentation/fb/modedb.txt.
2962 [VMMIO] Memory mapped virtio (platform) device.
2964 <size>@<baseaddr>:<irq>[:<id>]
2966 <size> := size (can use standard suffixes
2968 <baseaddr> := physical base address
2969 <irq> := interrupt number (as passed to
2971 <id> := (optional) platform device id
2973 virtio_mmio.device=1K@0x100b0000:48:7
2975 Can be used multiple times for multiple devices.
2977 vga= [BOOT,X86-32] Select a particular video mode
2978 See Documentation/x86/boot.txt and
2979 Documentation/svga.txt.
2980 Use vga=ask for menu.
2981 This is actually a boot loader parameter; the value is
2982 passed to the kernel using a special protocol.
2984 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2985 size of <nn>. This can be used to increase the
2986 minimum size (128MB on x86). It can also be used to
2987 decrease the size and leave more room for directly
2990 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2993 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2996 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3000 Controls the behavior of vsyscalls (i.e. calls to
3001 fixed addresses of 0xffffffffff600x00 from legacy
3002 code). Most statically-linked binaries and older
3003 versions of glibc use these calls. Because these
3004 functions are at fixed addresses, they make nice
3005 targets for exploits that can control RIP.
3007 emulate [default] Vsyscalls turn into traps and are
3008 emulated reasonably safely.
3010 native Vsyscalls are native syscall instructions.
3011 This is a little bit faster than trapping
3012 and makes a few dynamic recompilers work
3013 better than they would in emulation mode.
3014 It also makes exploits much easier to write.
3016 none Vsyscalls don't work at all. This makes
3017 them quite hard to use for exploits but
3018 might break your system.
3020 vt.cur_default= [VT] Default cursor shape.
3021 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3022 the parameters of the <Esc>[?A;B;Cc escape sequence;
3023 see VGA-softcursor.txt. Default: 2 = underline.
3025 vt.default_blu= [VT]
3026 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3027 Change the default blue palette of the console.
3028 This is a 16-member array composed of values
3031 vt.default_grn= [VT]
3032 Format: <green0>,<green1>,<green2>,...,<green15>
3033 Change the default green palette of the console.
3034 This is a 16-member array composed of values
3037 vt.default_red= [VT]
3038 Format: <red0>,<red1>,<red2>,...,<red15>
3039 Change the default red palette of the console.
3040 This is a 16-member array composed of values
3046 Set system-wide default UTF-8 mode for all tty's.
3047 Default is 1, i.e. UTF-8 mode is enabled for all
3048 newly opened terminals.
3050 vt.global_cursor_default=
3053 Set system-wide default for whether a cursor
3054 is shown on new VTs. Default is -1,
3055 i.e. cursors will be created by default unless
3056 overridden by individual drivers. 0 will hide
3057 cursors, 1 will display them.
3059 watchdog timers [HW,WDT] For information on watchdog timers,
3060 see Documentation/watchdog/watchdog-parameters.txt
3061 or other driver-specific files in the
3062 Documentation/watchdog/ directory.
3064 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3065 default x2apic cluster mode on platforms
3068 x86_mrst_timer= [X86-32,APBT]
3069 Choose timer option for x86 Moorestown MID platform.
3070 Two valid options are apbt timer only and lapic timer
3071 plus one apbt timer for broadcast timer.
3072 x86_mrst_timer=apbt_only | lapic_and_apbt
3074 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3075 xd_geo= See header of drivers/block/xd.c.
3077 xen_emul_unplug= [HW,X86,XEN]
3078 Unplug Xen emulated devices
3079 Format: [unplug0,][unplug1]
3080 ide-disks -- unplug primary master IDE devices
3081 aux-ide-disks -- unplug non-primary-master IDE devices
3082 nics -- unplug network devices
3083 all -- unplug all emulated devices (NICs and IDE disks)
3084 unnecessary -- unplugging emulated devices is
3085 unnecessary even if the host did not respond to
3087 never -- do not unplug even if version check succeeds
3089 xirc2ps_cs= [NET,PCMCIA]
3091 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3093 ______________________________________________________________________
3097 Add more DRM drivers.
projects / mirror_ubuntu-zesty-kernel.git / blob