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 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
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, by default set to 256K.
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.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel_low=size[KMG]
600 [KNL, x86] parts under 4G.
602 crashkernel=range1:size1[,range2:size2,...][@offset]
603 [KNL] Same as above, but depends on the memory
604 in the running system. The syntax of range is
605 start-[end] where start and end are both
606 a memory unit (amount[KMG]). See also
607 Documentation/kdump/kdump.txt for an example.
612 cs89x0_media= [HW,NET]
613 Format: { rj45 | aui | bnc }
616 See header of drivers/s390/block/dasd_devmap.c.
618 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
619 (one device per port)
620 Format: <port#>,<type>
621 See also Documentation/input/joystick-parport.txt
623 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
624 time. See Documentation/dynamic-debug-howto.txt for
625 details. Deprecated, see dyndbg.
627 debug [KNL] Enable kernel debugging (events log level).
630 [KNL] verbose self-tests
632 Print debugging info while doing the locking API
634 We default to 0 (no extra messages), setting it to
635 1 will print _a lot_ more information - normally
636 only useful to kernel developers.
638 debug_objects [KNL] Enable object debugging
641 [KNL] Disable object debugging
643 debug_guardpage_minorder=
644 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
645 parameter allows control of the order of pages that will
646 be intentionally kept free (and hence protected) by the
647 buddy allocator. Bigger value increase the probability
648 of catching random memory corruption, but reduce the
649 amount of memory for normal system use. The maximum
650 possible value is MAX_ORDER/2. Setting this parameter
651 to 1 or 2 should be enough to identify most random
652 memory corruption problems caused by bugs in kernel or
653 driver code when a CPU writes to (or reads from) a
654 random memory location. Note that there exists a class
655 of memory corruptions problems caused by buggy H/W or
656 F/W or by drivers badly programing DMA (basically when
657 memory is written at bus level and the CPU MMU is
658 bypassed) which are not detectable by
659 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
660 tracking down these problems.
662 debugpat [X86] Enable PAT debugging
664 decnet.addr= [HW,NET]
665 Format: <area>[,<node>]
666 See also Documentation/networking/decnet.txt.
669 [same as hugepagesz=] The size of the default
670 HugeTLB page size. This is the size represented by
671 the legacy /proc/ hugepages APIs, used for SHM, and
672 default size when mounting hugetlbfs filesystems.
673 Defaults to the default architecture's huge page size
677 Set number of hash buckets for dentry cache.
680 IO parameters + enable/disable command.
682 digiepca= [HW,SERIAL]
683 See drivers/char/README.epca and
684 Documentation/serial/digiepca.txt.
687 See Documentation/networking/ipv6.txt.
689 disable_ddw [PPC/PSERIES]
690 Disable Dynamic DMA Window support. Use this if
691 to workaround buggy firmware.
694 See Documentation/networking/ipv6.txt.
696 disable_mtrr_cleanup [X86]
697 The kernel tries to adjust MTRR layout from continuous
698 to discrete, to make X server driver able to add WB
699 entry later. This parameter disables that.
701 disable_mtrr_trim [X86, Intel and AMD only]
702 By default the kernel will trim any uncacheable
703 memory out of your available memory pool based on
704 MTRR settings. This parameter disables that behavior,
705 possibly causing your machine to run very slowly.
707 disable_timer_pin_1 [X86]
708 Disable PIN 1 of APIC timer
709 Can be useful to work around chipset bugs.
711 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
712 this option disables the debugging code at boot.
714 dma_debug_entries=<number>
715 This option allows to tune the number of preallocated
716 entries for DMA-API debugging code. One entry is
717 required per DMA-API allocation. Use this if the
718 DMA-API debugging code disables itself because the
719 architectural default is too low.
721 dma_debug_driver=<driver_name>
722 With this option the DMA-API debugging driver
723 filter feature can be enabled at boot time. Just
724 pass the driver to filter for as the parameter.
725 The filter can be disabled or changed to another
726 driver later using sysfs.
728 drm_kms_helper.edid_firmware=[<connector>:]<file>
729 Broken monitors, graphic adapters and KVMs may
730 send no or incorrect EDID data sets. This parameter
731 allows to specify an EDID data set in the
732 /lib/firmware directory that is used instead.
733 Generic built-in EDID data sets are used, if one of
734 edid/1024x768.bin, edid/1280x1024.bin,
735 edid/1680x1050.bin, or edid/1920x1080.bin is given
736 and no file with the same name exists. Details and
737 instructions how to build your own EDID data are
738 available in Documentation/EDID/HOWTO.txt. An EDID
739 data set will only be used for a particular connector,
740 if its name and a colon are prepended to the EDID
745 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
746 module.dyndbg[="val"]
747 Enable debug messages at boot time. See
748 Documentation/dynamic-debug-howto.txt for details.
750 earlycon= [KNL] Output early console device and options.
751 uart[8250],io,<addr>[,options]
752 uart[8250],mmio,<addr>[,options]
753 uart[8250],mmio32,<addr>[,options]
754 Start an early, polled-mode console on the 8250/16550
755 UART at the specified I/O port or MMIO address.
756 MMIO inter-register address stride is either 8-bit
757 (mmio) or 32-bit (mmio32).
758 The options are the same as for ttyS, above.
760 earlyprintk= [X86,SH,BLACKFIN]
763 earlyprintk=serial[,ttySn[,baudrate]]
764 earlyprintk=ttySn[,baudrate]
765 earlyprintk=dbgp[debugController#]
767 Append ",keep" to not disable it when the real console
770 Only vga or serial or usb debug port at a time.
772 Currently only ttyS0 and ttyS1 are supported.
774 Interaction with the standard serial driver is not
777 The VGA output is eventually overwritten by the real
780 The xen output can only be used by Xen PV guests.
782 ekgdboc= [X86,KGDB] Allow early kernel console debugging
785 This is designed to be used in conjunction with
786 the boot argument: earlyprintk=vga
789 Format: {"off" | "on" | "skip[mbr]"}
791 eisa_irq_edge= [PARISC,HW]
792 See header of drivers/parisc/eisa.c.
795 See comment before function elanfreq_setup() in
796 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
799 Format: {"cfq" | "deadline" | "noop"}
800 See Documentation/block/cfq-iosched.txt and
801 Documentation/block/deadline-iosched.txt for details.
803 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
804 Specifies physical address of start of kernel core
805 image elf header and optionally the size. Generally
806 kexec loader will pass this option to capture kernel.
807 See Documentation/kdump/kdump.txt for details.
809 enable_mtrr_cleanup [X86]
810 The kernel tries to adjust MTRR layout from continuous
811 to discrete, to make X server driver able to add WB
812 entry later. This parameter enables that.
814 enable_timer_pin_1 [X86]
815 Enable PIN 1 of APIC timer
816 Can be useful to work around chipset bugs
817 (in particular on some ATI chipsets).
818 The kernel tries to set a reasonable default.
820 enforcing [SELINUX] Set initial enforcing status.
822 See security/selinux/Kconfig help text.
823 0 -- permissive (log only, no denials).
824 1 -- enforcing (deny and log).
826 Value can be changed at runtime via /selinux/enforce.
829 Disable Error Record Serialization Table (ERST)
832 ether= [HW,NET] Ethernet cards parameters
833 This option is obsoleted by the "netdev=" option, which
834 has equivalent usage. See its documentation for details.
838 Permit 'security.evm' to be updated regardless of
839 current integrity status.
843 fail_make_request=[KNL]
844 General fault injection mechanism.
845 Format: <interval>,<probability>,<space>,<times>
846 See also Documentation/fault-injection/.
849 See Documentation/blockdev/floppy.txt.
851 force_pal_cache_flush
852 [IA-64] Avoid check_sal_cache_flush which may hang on
853 buggy SAL_CACHE_FLUSH implementations. Using this
854 parameter will force ia64_sal_cache_flush to call
855 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
858 [FTRACE] will set and start the specified tracer
859 as early as possible in order to facilitate early
862 ftrace_dump_on_oops[=orig_cpu]
863 [FTRACE] will dump the trace buffers on oops.
864 If no parameter is passed, ftrace will dump
865 buffers of all CPUs, but if you pass orig_cpu, it will
866 dump only the buffer of the CPU that triggered the
869 ftrace_filter=[function-list]
870 [FTRACE] Limit the functions traced by the function
871 tracer at boot up. function-list is a comma separated
872 list of functions. This list can be changed at run
873 time by the set_ftrace_filter file in the debugfs
876 ftrace_notrace=[function-list]
877 [FTRACE] Do not trace the functions specified in
878 function-list. This list can be changed at run time
879 by the set_ftrace_notrace file in the debugfs
882 ftrace_graph_filter=[function-list]
883 [FTRACE] Limit the top level callers functions traced
884 by the function graph tracer at boot up.
885 function-list is a comma separated list of functions
886 that can be changed at run time by the
887 set_graph_function file in the debugfs tracing directory.
890 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
891 support via parallel port (up to 5 devices per port)
892 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
893 See also Documentation/input/joystick-parport.txt
897 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
901 gcov_persist= [GCOV] When non-zero (default), profiling data for
902 kernel modules is saved and remains accessible via
903 debugfs, even when the module is unloaded/reloaded.
904 When zero, profiling data is discarded and associated
905 debugfs files are removed at module unload time.
907 gpt [EFI] Forces disk with valid GPT signature but
908 invalid Protective MBR to be treated as GPT.
910 grcan.enable0= [HW] Configuration of physical interface 0. Determines
911 the "Enable 0" bit of the configuration register.
914 grcan.enable1= [HW] Configuration of physical interface 1. Determines
915 the "Enable 0" bit of the configuration register.
918 grcan.select= [HW] Select which physical interface to use.
921 grcan.txsize= [HW] Sets the size of the tx buffer.
922 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
924 grcan.rxsize= [HW] Sets the size of the rx buffer.
925 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
928 hashdist= [KNL,NUMA] Large hashes allocated during boot
929 are distributed across NUMA nodes. Defaults on
930 for 64-bit NUMA, off otherwise.
931 Format: 0 | 1 (for off | on)
933 hcl= [IA-64] SGI's Hardware Graph compatibility layer
935 hd= [EIDE] (E)IDE hard drive subsystem geometry
936 Format: <cyl>,<head>,<sect>
939 Disable Hardware Error Source Table (HEST) support;
940 corresponding firmware-first mode error processing
941 logic will be disabled.
943 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
944 size of <nn>. This works even on boxes that have no
945 highmem otherwise. This also works to reduce highmem
946 size on bigger boxes.
948 highres= [KNL] Enable/disable high resolution timer mode.
949 Valid parameters: "on", "off"
953 See Documentation/isdn/README.HiSax.
957 hpet= [X86-32,HPET] option to control HPET usage
958 Format: { enable (default) | disable | force |
960 disable: disable HPET and use PIT instead
961 force: allow force enabled of undocumented chips (ICH4,
963 verbose: show contents of HPET registers during setup
965 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
966 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
967 On x86-64 and powerpc, this option can be specified
968 multiple times interleaved with hugepages= to reserve
969 huge pages of different sizes. Valid pages sizes on
970 x86-64 are 2M (when the CPU supports "pse") and 1G
971 (when the CPU supports the "pdpe1gb" cpuinfo flag)
972 Note that 1GB pages can only be allocated at boot time
973 using hugepages= and not freed afterwards.
975 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
976 terminal devices. Valid values: 0..8
977 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
978 If specified, z/VM IUCV HVC accepts connections
979 from listed z/VM user IDs only.
981 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
982 hardware thread id mappings.
983 Format: <cpu>:<hwthread>
986 Do not unregister boot console at start. This is only
987 useful for debugging when something happens in the window
988 between unregistering the boot console and initializing
991 i2c_bus= [HW] Override the default board specific I2C bus speed
992 or register an additional I2C bus that is not
993 registered from board initialization code.
997 i8042.debug [HW] Toggle i8042 debug mode
998 i8042.direct [HW] Put keyboard port into non-translated mode
999 i8042.dumbkbd [HW] Pretend that controller can only read data from
1000 keyboard and cannot control its state
1001 (Don't attempt to blink the leds)
1002 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1003 i8042.nokbd [HW] Don't check/create keyboard port
1004 i8042.noloop [HW] Disable the AUX Loopback command while probing
1006 i8042.nomux [HW] Don't check presence of an active multiplexing
1008 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1010 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1011 i8042.reset [HW] Reset the controller during init and cleanup
1012 i8042.unlock [HW] Unlock (ignore) the keylock
1016 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1017 indicates that the driver is running on unsupported
1019 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1020 does not match list of supported models.
1022 [HW] Report power status in /proc/i8k
1023 (disabled by default)
1024 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1027 i915.invert_brightness=
1028 [DRM] Invert the sense of the variable that is used to
1029 set the brightness of the panel backlight. Normally a
1030 brightness value of 0 indicates backlight switched off,
1031 and the maximum of the brightness value sets the backlight
1032 to maximum brightness. If this parameter is set to 0
1033 (default) and the machine requires it, or this parameter
1034 is set to 1, a brightness value of 0 sets the backlight
1035 to maximum brightness, and the maximum of the brightness
1036 value switches the backlight off.
1037 -1 -- never invert brightness
1038 0 -- machine default
1039 1 -- force brightness inversion
1042 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1044 ide-core.nodma= [HW] (E)IDE subsystem
1045 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1046 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1047 .cdrom .chs .ignore_cable are additional options
1048 See Documentation/ide/ide.txt.
1050 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1051 Claim all unknown PCI IDE storage controllers.
1054 Format: idle=poll, idle=halt, idle=nomwait
1055 Poll forces a polling idle loop that can slightly
1056 improve the performance of waking up a idle CPU, but
1057 will use a lot of power and make the system run hot.
1059 idle=halt: Halt is forced to be used for CPU idle.
1060 In such case C2/C3 won't be used again.
1061 idle=nomwait: Disable mwait for CPU C-states
1063 ignore_loglevel [KNL]
1064 Ignore loglevel setting - this will print /all/
1065 kernel messages to the console. Useful for debugging.
1066 We also add it as printk module parameter, so users
1067 could change it dynamically, usually by
1068 /sys/module/printk/parameters/ignore_loglevel.
1070 ihash_entries= [KNL]
1071 Set number of hash buckets for inode cache.
1073 ima_appraise= [IMA] appraise integrity measurements
1074 Format: { "off" | "enforce" | "fix" }
1077 ima_appraise_tcb [IMA]
1078 The builtin appraise policy appraises all files
1082 Format: { "0" | "1" }
1083 0 -- integrity auditing messages. (Default)
1084 1 -- enable informational integrity auditing messages.
1087 Format: { "sha1" | "md5" }
1091 Load a policy which meets the needs of the Trusted
1092 Computing Base. This means IMA will measure all
1093 programs exec'd, files mmap'd for exec, and all files
1094 opened for read by uid=0.
1098 Run specified binary instead of /sbin/init as init
1101 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1102 for working out where the kernel is dying during
1105 initrd= [BOOT] Specify the location of the initial ramdisk
1107 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1110 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1112 Enable intel iommu driver.
1114 Disable intel iommu driver.
1115 igfx_off [Default Off]
1116 By default, gfx is mapped as normal device. If a gfx
1117 device has a dedicated DMAR unit, the DMAR unit is
1118 bypassed by not enabling DMAR with this option. In
1119 this case, gfx device will use physical address for
1122 With this option iommu will not optimize to look
1123 for io virtual address below 32-bit forcing dual
1124 address cycle on pci bus for cards supporting greater
1125 than 32-bit addressing. The default is to look
1126 for translation below 32-bit and if not available
1127 then look in the higher range.
1128 strict [Default Off]
1129 With this option on every unmap_single operation will
1130 result in a hardware IOTLB flush operation as opposed
1131 to batching them for performance.
1132 sp_off [Default Off]
1133 By default, super page will be supported if Intel IOMMU
1134 has the capability. With this option, super page will
1137 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1138 0 disables intel_idle and fall back on acpi_idle.
1139 1 to 6 specify maximum depth of C-state.
1143 Do not enable intel_pstate as the default
1144 scaling driver for the supported processors
1146 intremap= [X86-64, Intel-IOMMU]
1147 on enable Interrupt Remapping (default)
1148 off disable Interrupt Remapping
1149 nosid disable Source ID checking
1151 BIOS x2APIC opt-out request will be ignored
1153 iomem= Disable strict checking of access to MMIO memory
1154 strict regions from userspace.
1171 io7= [HW] IO7 for Marvel based alpha systems
1172 See comment before marvel_specify_io7 in
1173 arch/alpha/kernel/core_marvel.c.
1175 io_delay= [X86] I/O delay method
1177 Standard port 0x80 based delay
1179 Alternate port 0xed based delay (needed on some systems)
1181 Simple two microseconds delay
1186 See Documentation/filesystems/nfs/nfsroot.txt.
1188 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1189 See comment before ip2_setup() in
1190 drivers/char/ip2/ip2base.c.
1193 When an interrupt is not handled search all handlers
1194 for it. Intended to get systems with badly broken
1198 When an interrupt is not handled search all handlers
1199 for it. Also check all handlers each timer
1200 interrupt. Intended to get systems with badly broken
1204 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1206 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1208 <cpu number>,...,<cpu number>
1210 <cpu number>-<cpu number>
1211 (must be a positive range in ascending order)
1213 <cpu number>,...,<cpu number>-<cpu number>
1215 This option can be used to specify one or more CPUs
1216 to isolate from the general SMP balancing and scheduling
1217 algorithms. You can move a process onto or off an
1218 "isolated" CPU via the CPU affinity syscalls or cpuset.
1219 <cpu number> begins at 0 and the maximum value is
1220 "number of CPUs in system - 1".
1222 This option is the preferred way to isolate CPUs. The
1223 alternative -- manually setting the CPU mask of all
1224 tasks in the system -- can cause problems and
1225 suboptimal load balancer performance.
1229 ivrs_ioapic [HW,X86_64]
1230 Provide an override to the IOAPIC-ID<->DEVICE-ID
1231 mapping provided in the IVRS ACPI table. For
1232 example, to map IOAPIC-ID decimal 10 to
1233 PCI device 00:14.0 write the parameter as:
1234 ivrs_ioapic[10]=00:14.0
1236 ivrs_hpet [HW,X86_64]
1237 Provide an override to the HPET-ID<->DEVICE-ID
1238 mapping provided in the IVRS ACPI table. For
1239 example, to map HPET-ID decimal 0 to
1240 PCI device 00:14.0 write the parameter as:
1241 ivrs_hpet[0]=00:14.0
1243 js= [HW,JOY] Analog joystick
1244 See Documentation/input/joystick.txt.
1248 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1249 specifies the amount of memory usable by the kernel
1250 for non-movable allocations. The requested amount is
1251 spread evenly throughout all nodes in the system. The
1252 remaining memory in each node is used for Movable
1253 pages. In the event, a node is too small to have both
1254 kernelcore and Movable pages, kernelcore pages will
1255 take priority and other nodes will have a larger number
1256 of kernelcore pages. The Movable zone is used for the
1257 allocation of pages that may be reclaimed or moved
1258 by the page migration subsystem. This means that
1259 HugeTLB pages may not be allocated from this zone.
1260 Note that allocations like PTEs-from-HighMem still
1261 use the HighMem zone if it exists, and the Normal
1262 zone if it does not.
1264 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1265 Format: <Controller#>[,poll interval]
1266 The controller # is the number of the ehci usb debug
1267 port as it is probed via PCI. The poll interval is
1268 optional and is the number seconds in between
1269 each poll cycle to the debug port in case you need
1270 the functionality for interrupting the kernel with
1271 gdb or control-c on the dbgp connection. When
1272 not using this parameter you use sysrq-g to break into
1273 the kernel debugger.
1275 kgdboc= [KGDB,HW] kgdb over consoles.
1276 Requires a tty driver that supports console polling,
1277 or a supported polling keyboard driver (non-usb).
1278 Serial only format: <serial_device>[,baud]
1279 keyboard only format: kbd
1280 keyboard and serial format: kbd,<serial_device>[,baud]
1281 Optional Kernel mode setting:
1282 kms, kbd format: kms,kbd
1283 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1285 kgdbwait [KGDB] Stop kernel execution and enter the
1286 kernel debugger at the earliest opportunity.
1288 kmac= [MIPS] korina ethernet MAC address.
1289 Configure the RouterBoard 532 series on-chip
1290 Ethernet adapter MAC address.
1292 kmemleak= [KNL] Boot-time kmemleak enable/disable
1293 Valid arguments: on, off
1296 kstack=N [X86] Print N words from the kernel stack
1299 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1300 Default is 0 (don't ignore, but inject #GP)
1302 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1306 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1307 Default is 1 (enabled)
1309 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1311 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1313 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1314 (virtualized MMU) support on capable Intel chips.
1315 Default is 1 (enabled)
1317 kvm-intel.emulate_invalid_guest_state=
1318 [KVM,Intel] Enable emulation of invalid guest states
1319 Default is 0 (disabled)
1321 kvm-intel.flexpriority=
1322 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1323 Default is 1 (enabled)
1326 [KVM,Intel] Enable VMX nesting (nVMX).
1327 Default is 0 (disabled)
1329 kvm-intel.unrestricted_guest=
1330 [KVM,Intel] Disable unrestricted guest feature
1331 (virtualized real and unpaged mode) on capable
1332 Intel chips. Default is 1 (enabled)
1334 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1335 feature (tagged TLBs) on capable Intel chips.
1336 Default is 1 (enabled)
1342 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1345 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1346 value for LAPIC timer one-shot implementation. Default
1347 back to the programmable timer unit in the LAPIC.
1349 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1352 libata.dma= [LIBATA] DMA control
1353 libata.dma=0 Disable all PATA and SATA DMA
1354 libata.dma=1 PATA and SATA Disk DMA only
1355 libata.dma=2 ATAPI (CDROM) DMA only
1356 libata.dma=4 Compact Flash DMA only
1357 Combinations also work, so libata.dma=3 enables DMA
1358 for disks and CDROMs, but not CFs.
1360 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1361 libata.ignore_hpa=0 keep BIOS limits (default)
1362 libata.ignore_hpa=1 ignore limits, using full disk
1364 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1368 libata.force= [LIBATA] Force configurations. The format is comma
1369 separated list of "[ID:]VAL" where ID is
1370 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1371 matching port, link or device. Basically, it matches
1372 the ATA ID string printed on console by libata. If
1373 the whole ID part is omitted, the last PORT and DEVICE
1374 values are used. If ID hasn't been specified yet, the
1375 configuration applies to all ports, links and devices.
1377 If only DEVICE is omitted, the parameter applies to
1378 the port and all links and devices behind it. DEVICE
1379 number of 0 either selects the first device or the
1380 first fan-out link behind PMP device. It does not
1381 select the host link. DEVICE number of 15 selects the
1382 host link and device attached to it.
1384 The VAL specifies the configuration to force. As long
1385 as there's no ambiguity shortcut notation is allowed.
1386 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1387 The following configurations can be forced.
1389 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1390 Any ID with matching PORT is used.
1392 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1394 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1395 udma[/][16,25,33,44,66,100,133] notation is also
1398 * [no]ncq: Turn on or off NCQ.
1400 * nohrst, nosrst, norst: suppress hard, soft
1403 * rstonce: only attempt one reset during
1404 hot-unplug link recovery
1406 * dump_id: dump IDENTIFY data.
1408 If there are multiple matching configurations changing
1409 the same attribute, the last one is used.
1411 memblock=debug [KNL] Enable memblock debug messages.
1413 load_ramdisk= [RAM] List of ramdisks to load from floppy
1414 See Documentation/blockdev/ramdisk.txt.
1416 lockd.nlm_grace_period=P [NFS] Assign grace period.
1419 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1422 lockd.nlm_timeout=T [NFS] Assign timeout value.
1425 lockd.nlm_udpport=M [NFS] Assign UDP port.
1428 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1431 loglevel= All Kernel Messages with a loglevel smaller than the
1432 console loglevel will be printed to the console. It can
1433 also be changed with klogd or other programs. The
1434 loglevels are defined as follows:
1436 0 (KERN_EMERG) system is unusable
1437 1 (KERN_ALERT) action must be taken immediately
1438 2 (KERN_CRIT) critical conditions
1439 3 (KERN_ERR) error conditions
1440 4 (KERN_WARNING) warning conditions
1441 5 (KERN_NOTICE) normal but significant condition
1442 6 (KERN_INFO) informational
1443 7 (KERN_DEBUG) debug-level messages
1445 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1446 in bytes. n must be a power of two. The default
1447 size is set in the kernel config file.
1449 logo.nologo [FB] Disables display of the built-in Linux logo.
1450 This may be used to provide more screen space for
1451 kernel log messages and is useful when debugging
1452 kernel boot problems.
1454 lp=0 [LP] Specify parallel ports to use, e.g,
1455 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1456 lp=reset first parallel port). 'lp=0' disables the
1457 lp=auto printer driver. 'lp=reset' (which can be
1458 specified in addition to the ports) causes
1459 attached printers to be reset. Using
1460 lp=port1,port2,... specifies the parallel ports
1461 to associate lp devices with, starting with
1462 lp0. A port specification may be 'none' to skip
1463 that lp device, or a parport name such as
1464 'parport0'. Specifying 'lp=auto' instead of a
1465 port specification list means that device IDs
1466 from each port should be examined, to see if
1467 an IEEE 1284-compliant printer is attached; if
1468 so, the driver will manage that printer.
1469 See also header of drivers/char/lp.c.
1472 Sets loops_per_jiffy to given constant, thus avoiding
1473 time-consuming boot-time autodetection (up to 250 ms per
1474 CPU). 0 enables autodetection (default). To determine
1475 the correct value for your kernel, boot with normal
1476 autodetection and see what value is printed. Note that
1477 on SMP systems the preset will be applied to all CPUs,
1478 which is likely to cause problems if your CPUs need
1479 significantly divergent settings. An incorrect value
1480 will cause delays in the kernel to be wrong, leading to
1481 unpredictable I/O errors and other breakage. Although
1482 unlikely, in the extreme case this might damage your
1486 Format: <io>,<irq>,<dma>
1488 machvec= [IA-64] Force the use of a particular machine-vector
1489 (machvec) in a generic kernel.
1490 Example: machvec=hpzx1_swiotlb
1492 machtype= [Loongson] Share the same kernel image file between different
1494 Example: machtype=lemote-yeeloong-2f-7inch
1496 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1497 than or equal to this physical address is ignored.
1499 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1500 should make use of. maxcpus=n : n >= 0 limits the
1501 kernel to using 'n' processors. n=0 is a special case,
1502 it is equivalent to "nosmp", which also disables
1505 max_loop= [LOOP] The number of loop block devices that get
1506 (loop.max_loop) unconditionally pre-created at init time. The default
1507 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1508 of statically allocating a predefined number, loop
1509 devices can be requested on-demand with the
1510 /dev/loop-control interface.
1512 mce [X86-32] Machine Check Exception
1514 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1516 md= [HW] RAID subsystems devices and level
1517 See Documentation/md.txt.
1520 Format: <first>,<last>
1521 Specifies range of consoles to be captured by the MDA.
1523 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1524 Amount of memory to be used when the kernel is not able
1525 to see the whole system memory or for test.
1526 [X86] Work as limiting max address. Use together
1527 with memmap= to avoid physical address space collisions.
1528 Without memmap= PCI devices could be placed at addresses
1529 belonging to unused RAM.
1531 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1535 [KNL,SH] Allow user to override the default size for
1536 per-device physically contiguous DMA buffers.
1538 memmap=exactmap [KNL,X86] Enable setting of an exact
1539 E820 memory map, as specified by the user.
1540 Such memmap=exactmap lines can be constructed based on
1541 BIOS output or other requirements. See the memmap=nn@ss
1544 memmap=nn[KMG]@ss[KMG]
1545 [KNL] Force usage of a specific region of memory
1546 Region of memory to be used, from ss to ss+nn.
1548 memmap=nn[KMG]#ss[KMG]
1549 [KNL,ACPI] Mark specific memory as ACPI data.
1550 Region of memory to be used, from ss to ss+nn.
1552 memmap=nn[KMG]$ss[KMG]
1553 [KNL,ACPI] Mark specific memory as reserved.
1554 Region of memory to be used, from ss to ss+nn.
1555 Example: Exclude memory from 0x18690000-0x1869ffff
1556 memmap=64K$0x18690000
1558 memmap=0x10000$0x18690000
1560 memory_corruption_check=0/1 [X86]
1561 Some BIOSes seem to corrupt the first 64k of
1562 memory when doing things like suspend/resume.
1563 Setting this option will scan the memory
1564 looking for corruption. Enabling this will
1565 both detect corruption and prevent the kernel
1566 from using the memory being corrupted.
1567 However, its intended as a diagnostic tool; if
1568 repeatable BIOS-originated corruption always
1569 affects the same memory, you can use memmap=
1570 to prevent the kernel from using that memory.
1572 memory_corruption_check_size=size [X86]
1573 By default it checks for corruption in the low
1574 64k, making this memory unavailable for normal
1575 use. Use this parameter to scan for
1576 corruption in more or less memory.
1578 memory_corruption_check_period=seconds [X86]
1579 By default it checks for corruption every 60
1580 seconds. Use this parameter to check at some
1581 other rate. 0 disables periodic checking.
1583 memtest= [KNL,X86] Enable memtest
1585 default : 0 <disable>
1586 Specifies the number of memtest passes to be
1587 performed. Each pass selects another test
1588 pattern from a given set of patterns. Memtest
1589 fills the memory with this pattern, validates
1590 memory contents and reserves bad memory
1591 regions that are detected.
1593 meye.*= [HW] Set MotionEye Camera parameters
1594 See Documentation/video4linux/meye.txt.
1596 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1597 Multi-Function General Purpose Timers on AMD Geode
1600 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1601 the BIOS has incorrectly applied a workaround. TinyBIOS
1602 version 0.98 is known to be affected, 0.99 fixes the
1603 problem by letting the user disable the workaround.
1607 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1608 physical address is ignored.
1610 mini2440= [ARM,HW,KNL]
1611 Format:[0..2][b][c][t]
1613 MINI2440 configuration specification:
1614 0 - The attached screen is the 3.5" TFT
1615 1 - The attached screen is the 7" TFT
1616 2 - The VGA Shield is attached (1024x768)
1617 Leaving out the screen size parameter will not load
1618 the TFT driver, and the framebuffer will be left
1620 b - Enable backlight. The TFT backlight pin will be
1621 linked to the kernel VESA blanking code and a GPIO
1622 LED. This parameter is not necessary when using the
1624 c - Enable the s3c camera interface.
1625 t - Reserved for enabling touchscreen support. The
1626 touchscreen support is not enabled in the mainstream
1627 kernel as of 2.6.30, a preliminary port can be found
1628 in the "bleeding edge" mini2440 support kernel at
1629 http://repo.or.cz/w/linux-2.6/mini2440.git
1632 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1633 parameter allows control of the logging verbosity for
1634 the additional memory initialisation checks. A value
1635 of 0 disables mminit logging and a level of 4 will
1636 log everything. Information is printed at KERN_DEBUG
1637 so loglevel=8 may also need to be specified.
1640 [KNL] When CONFIG_MODULE_SIG is set, this means that
1641 modules without (valid) signatures will fail to load.
1642 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1643 is always true, so this option does nothing.
1646 [MOUSE] Maximum time between finger touching and
1647 leaving touchpad surface for touch to be considered
1648 a tap and be reported as a left button click (for
1649 touchpads working in absolute mode only).
1651 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1652 reporting absolute coordinates, such as tablets
1653 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1654 reporting absolute coordinates, such as tablets
1656 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1657 is similar to kernelcore except it specifies the
1658 amount of memory used for migratable allocations.
1659 If both kernelcore and movablecore is specified,
1660 then kernelcore will be at *least* the specified
1661 value but may be more. If movablecore on its own
1662 is specified, the administrator must be careful
1663 that the amount of memory usable for all allocations
1666 MTD_Partition= [MTD]
1667 Format: <name>,<region-number>,<size>,<offset>
1669 MTD_Region= [MTD] Format:
1670 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1673 See drivers/mtd/cmdlinepart.c.
1675 multitce=off [PPC] This parameter disables the use of the pSeries
1676 firmware feature for updating multiple TCE entries
1679 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1681 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1683 boundary - index of last SLC block on Flex-OneNAND.
1684 The remaining blocks are configured as MLC blocks.
1685 lock - Configure if Flex-OneNAND boundary should be locked.
1686 Once locked, the boundary cannot be changed.
1687 1 indicates lock status, 0 indicates unlock status.
1690 ARM/S3C2412 JIVE boot control
1692 See arch/arm/mach-s3c2412/mach-jive.c
1694 mtouchusb.raw_coordinates=
1695 [HW] Make the MicroTouch USB driver use raw coordinates
1696 ('y', default) or cooked coordinates ('n')
1698 mtrr_chunk_size=nn[KMG] [X86]
1699 used for mtrr cleanup. It is largest continuous chunk
1700 that could hold holes aka. UC entries.
1702 mtrr_gran_size=nn[KMG] [X86]
1703 Used for mtrr cleanup. It is granularity of mtrr block.
1705 Large value could prevent small alignment from
1708 mtrr_spare_reg_nr=n [X86]
1710 Range: 0,7 : spare reg number
1712 Used for mtrr cleanup. It is spare mtrr entries number.
1713 Set to 2 or more if your graphical card needs more.
1715 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1717 netdev= [NET] Network devices parameters
1718 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1719 Note that mem_start is often overloaded to mean
1720 something different and driver-specific.
1721 This usage is only documented in each driver source
1725 [NETFILTER] Enable connection tracking flow accounting
1726 0 to disable accounting
1727 1 to enable accounting
1730 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1731 See Documentation/filesystems/nfs/nfsroot.txt.
1733 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1734 See Documentation/filesystems/nfs/nfsroot.txt.
1736 nfsrootdebug [NFS] enable nfsroot debugging messages.
1737 See Documentation/filesystems/nfs/nfsroot.txt.
1739 nfs.callback_tcpport=
1740 [NFS] set the TCP port on which the NFSv4 callback
1741 channel should listen.
1744 [NFS] sets the pathname to the program which is used
1745 to update the NFS client cache entries.
1747 nfs.cache_getent_timeout=
1748 [NFS] sets the timeout after which an attempt to
1749 update a cache entry is deemed to have failed.
1751 nfs.idmap_cache_timeout=
1752 [NFS] set the maximum lifetime for idmapper cache
1756 [NFS] enable 64-bit inode numbers.
1757 If zero, the NFS client will fake up a 32-bit inode
1758 number for the readdir() and stat() syscalls instead
1759 of returning the full 64-bit number.
1760 The default is to return 64-bit inode numbers.
1762 nfs.max_session_slots=
1763 [NFSv4.1] Sets the maximum number of session slots
1764 the client will attempt to negotiate with the server.
1765 This limits the number of simultaneous RPC requests
1766 that the client can send to the NFSv4.1 server.
1767 Note that there is little point in setting this
1768 value higher than the max_tcp_slot_table_limit.
1770 nfs.nfs4_disable_idmapping=
1771 [NFSv4] When set to the default of '1', this option
1772 ensures that both the RPC level authentication
1773 scheme and the NFS level operations agree to use
1774 numeric uids/gids if the mount is using the
1775 'sec=sys' security flavour. In effect it is
1776 disabling idmapping, which can make migration from
1777 legacy NFSv2/v3 systems to NFSv4 easier.
1778 Servers that do not support this mode of operation
1779 will be autodetected by the client, and it will fall
1780 back to using the idmapper.
1781 To turn off this behaviour, set the value to '0'.
1783 [NFS4] Specify an additional fixed unique ident-
1784 ification string that NFSv4 clients can insert into
1785 their nfs_client_id4 string. This is typically a
1786 UUID that is generated at system install time.
1788 nfs.send_implementation_id =
1789 [NFSv4.1] Send client implementation identification
1790 information in exchange_id requests.
1791 If zero, no implementation identification information
1793 The default is to send the implementation identification
1796 nfsd.nfs4_disable_idmapping=
1797 [NFSv4] When set to the default of '1', the NFSv4
1798 server will return only numeric uids and gids to
1799 clients using auth_sys, and will accept numeric uids
1800 and gids from such clients. This is intended to ease
1801 migration from NFSv2/v3.
1803 objlayoutdriver.osd_login_prog=
1804 [NFS] [OBJLAYOUT] sets the pathname to the program which
1805 is used to automatically discover and login into new
1806 osd-targets. Please see:
1807 Documentation/filesystems/pnfs.txt for more explanations
1809 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1810 when a NMI is triggered.
1811 Format: [state][,regs][,debounce][,die]
1813 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1814 Format: [panic,][nopanic,][num]
1816 0 - turn nmi_watchdog off
1817 When panic is specified, panic when an NMI watchdog
1818 timeout occurs (or 'nopanic' to override the opposite
1820 This is useful when you use a panic=... timeout and
1821 need the box quickly up again.
1823 netpoll.carrier_timeout=
1824 [NET] Specifies amount of time (in seconds) that
1825 netpoll should wait for a carrier. By default netpoll
1828 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1829 emulation library even if a 387 maths coprocessor
1833 [HW] Never suspend the console
1834 Disable suspending of consoles during suspend and
1835 hibernate operations. Once disabled, debugging
1836 messages can reach various consoles while the rest
1837 of the system is being put to sleep (ie, while
1838 debugging driver suspend/resume hooks). This may
1839 not work reliably with all consoles, but is known
1840 to work with serial and VGA consoles.
1841 To facilitate more flexible debugging, we also add
1842 console_suspend, a printk module parameter to control
1843 it. Users could use console_suspend (usually
1844 /sys/module/printk/parameters/console_suspend) to
1845 turn on/off it dynamically.
1847 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1848 caches in the slab allocator. Saves per-node memory,
1849 but will impact performance.
1853 noapic [SMP,APIC] Tells the kernel to not make use of any
1854 IOAPICs that may be present in the system.
1856 noautogroup Disable scheduler automatic task group creation.
1858 nobats [PPC] Do not use BATs for mapping kernel lowmem
1859 on "Classic" PPC cores.
1863 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1865 nodelayacct [KNL] Disable per-task delay accounting
1867 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1869 nodsp [SH] Disable hardware DSP at boot time.
1871 noefi [X86] Disable EFI runtime services support.
1876 On X86-32 available only on PAE configured kernels.
1877 noexec=on: enable non-executable mappings (default)
1878 noexec=off: disable non-executable mappings
1881 Disable SMAP (Supervisor Mode Access Prevention)
1882 even if it is supported by processor.
1885 Disable SMEP (Supervisor Mode Execution Prevention)
1886 even if it is supported by processor.
1889 This affects only 32-bit executables.
1890 noexec32=on: enable non-executable mappings (default)
1891 read doesn't imply executable mappings
1892 noexec32=off: disable non-executable mappings
1893 read implies executable mappings
1895 nofpu [SH] Disable hardware FPU at boot time.
1897 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1898 register save and restore. The kernel will only save
1899 legacy floating-point registers on task switch.
1901 noxsave [BUGS=X86] Disables x86 extended register state save
1902 and restore using xsave. The kernel will fallback to
1903 enabling legacy floating-point and sse state.
1906 on enable eager fpu restore
1907 off disable eager fpu restore
1908 auto selects the default scheme, which automatically
1909 enables eagerfpu restore for xsaveopt.
1911 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1912 wfi(ARM) instruction doesn't work correctly and not to
1913 use it. This is also useful when using JTAG debugger.
1915 no_file_caps Tells the kernel not to honor file capabilities. The
1916 only way then for a file to be executed with privilege
1917 is to be setuid root or executed by root.
1919 nohalt [IA-64] Tells the kernel not to use the power saving
1920 function PAL_HALT_LIGHT when idle. This increases
1921 power-consumption. On the positive side, it reduces
1922 interrupt wake-up latency, which may improve performance
1923 in certain environments such as networked servers or
1926 nohz= [KNL] Boottime enable/disable dynamic ticks
1927 Valid arguments: on, off
1930 noiotrap [SH] Disables trapped I/O port accesses.
1932 noirqdebug [X86-32] Disables the code which attempts to detect and
1933 disable unhandled interrupt sources.
1935 no_timer_check [X86,APIC] Disables the code which tests for
1936 broken timer IRQ sources.
1938 noisapnp [ISAPNP] Disables ISA PnP code.
1940 noinitrd [RAM] Tells the kernel not to load any configured
1943 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1945 [Deprecated - use intremap=off]
1949 nojitter [IA-64] Disables jitter checking for ITC timers.
1951 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1953 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1956 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1957 steal time is computed, but won't influence scheduler
1960 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1962 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1964 noltlbs [PPC] Do not use large page/tlb entries for kernel
1965 lowmem mapping on PPC40x.
1967 nomca [IA-64] Disable machine check abort handling
1969 nomce [X86-32] Machine Check Exception
1971 nomfgpt [X86-32] Disable Multi-Function General Purpose
1972 Timer usage (for AMD Geode machines).
1974 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1975 shutdown the other cpus. Instead use the REBOOT_VECTOR
1978 nomodule Disable module load
1980 nopat [X86] Disable PAT (page attribute table extension of
1981 pagetables) support.
1983 norandmaps Don't use address space randomization. Equivalent to
1984 echo 0 > /proc/sys/kernel/randomize_va_space
1986 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1988 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1989 with UP alternatives
1991 noresidual [PPC] Don't use residual data on PReP machines.
1993 nordrand [X86] Disable the direct use of the RDRAND
1994 instruction even if it is supported by the
1995 processor. RDRAND is still available to user
1998 noresume [SWSUSP] Disables resume and restores original swap
2001 no-scroll [VGA] Disables scrollback.
2002 This is required for the Braillex ib80-piezo Braille
2003 reader made by F.H. Papenmeier (Germany).
2007 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2009 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2010 and disable the IO APIC. legacy for "maxcpus=0".
2012 nosoftlockup [KNL] Disable the soft-lockup detector.
2014 nosync [HW,M68K] Disables sync negotiation for all devices.
2016 notsc [BUGS=X86-32] Disable Time Stamp Counter
2018 nousb [USB] Disable the USB subsystem
2020 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2024 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2026 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2027 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2028 Some features depend on CPU0. Known dependencies are:
2029 1. Resume from suspend/hibernate depends on CPU0.
2030 Suspend/hibernate will fail if CPU0 is offline and you
2031 need to online CPU0 before suspend/hibernate.
2032 2. PIC interrupts also depend on CPU0. CPU0 can't be
2033 removed if a PIC interrupt is detected.
2034 It's said poweroff/reboot may depend on CPU0 on some
2035 machines although I haven't seen such issues so far
2036 after CPU0 is offline on a few tested machines.
2037 If the dependencies are under your control, you can
2038 turn on cpu0_hotplug.
2040 nptcg= [IA-64] Override max number of concurrent global TLB
2041 purges which is reported from either PAL_VM_SUMMARY or
2044 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2045 could support. nr_cpus=n : n >= 1 limits the kernel to
2046 supporting 'n' processors. Later in runtime you can not
2047 use hotplug cpu feature to put more cpu back to online.
2048 just like you compile the kernel NR_CPUS=n
2050 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2052 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2053 Allowed values are enable and disable
2055 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2056 one of ['zone', 'node', 'default'] can be specified
2057 This can be set from sysctl after boot.
2058 See Documentation/sysctl/vm.txt for details.
2060 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2061 See Documentation/debugging-via-ohci1394.txt for more
2064 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2065 Rather than timing out after 20 ms if an EC
2066 command is not properly ACKed, override the length
2067 of the timeout. We have interrupts disabled while
2068 waiting for the ACK, so if this is set too high
2069 interrupts *may* be lost!
2071 omap_mux= [OMAP] Override bootloader pin multiplexing.
2072 Format: <mux_mode0.mode_name=value>...
2073 For example, to override I2C bus2:
2074 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2076 oprofile.timer= [HW]
2077 Use timer interrupt instead of performance counters
2079 oprofile.cpu_type= Force an oprofile cpu type
2080 This might be useful if you have an older oprofile
2081 userland or if you want common events.
2082 Format: { arch_perfmon }
2083 arch_perfmon: [X86] Force use of architectural
2084 perfmon on Intel CPUs instead of the
2085 CPU specific event set.
2086 timer: [X86] Force use of architectural NMI
2087 timer mode (see also oprofile.timer
2088 for generic hr timer mode)
2089 [s390] Force legacy basic mode sampling
2090 (report cpu_type "timer")
2092 oops=panic Always panic on oopses. Default is to just kill the
2093 process, but there is a small probability of
2094 deadlocking the machine.
2095 This will also cause panics on machine check exceptions.
2096 Useful together with panic=30 to trigger a reboot.
2099 See Documentation/sound/oss/oss-parameters.txt
2101 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2102 timeout > 0: seconds before rebooting
2103 timeout = 0: wait forever
2104 timeout < 0: reboot immediately
2107 parkbd.port= [HW] Parallel port number the keyboard adapter is
2108 connected to, default is 0.
2110 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2111 0 for XT, 1 for AT (default is AT).
2114 parport= [HW,PPT] Specify parallel ports. 0 disables.
2115 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2116 Use 'auto' to force the driver to use any
2117 IRQ/DMA settings detected (the default is to
2118 ignore detected IRQ/DMA settings because of
2119 possible conflicts). You can specify the base
2120 address, IRQ, and DMA settings; IRQ and DMA
2121 should be numbers, or 'auto' (for using detected
2122 settings on that particular port), or 'nofifo'
2123 (to avoid using a FIFO even if it is detected).
2124 Parallel ports are assigned in the order they
2125 are specified on the command line, starting
2128 parport_init_mode= [HW,PPT]
2129 Configure VIA parallel port to operate in
2130 a specific mode. This is necessary on Pegasos
2131 computer where firmware has no options for setting
2132 up parallel port mode and sets it to spp.
2133 Currently this function knows 686a and 8231 chips.
2134 Format: [spp|ps2|epp|ecp|ecpepp]
2137 Halt all CPUs after the first oops has been printed for
2138 the specified number of seconds. This is to be used if
2139 your oopses keep scrolling off the screen.
2144 See header of drivers/block/paride/pcd.c.
2145 See also Documentation/blockdev/paride.txt.
2147 pci=option[,option...] [PCI] various PCI subsystem options:
2148 earlydump [X86] dump PCI config space before the kernel
2150 off [X86] don't probe for the PCI bus
2151 bios [X86-32] force use of PCI BIOS, don't access
2152 the hardware directly. Use this if your machine
2153 has a non-standard PCI host bridge.
2154 nobios [X86-32] disallow use of PCI BIOS, only direct
2155 hardware access methods are allowed. Use this
2156 if you experience crashes upon bootup and you
2157 suspect they are caused by the BIOS.
2158 conf1 [X86] Force use of PCI Configuration
2160 conf2 [X86] Force use of PCI Configuration
2162 noaer [PCIE] If the PCIEAER kernel config parameter is
2163 enabled, this kernel boot option can be used to
2164 disable the use of PCIE advanced error reporting.
2165 nodomains [PCI] Disable support for multiple PCI
2166 root domains (aka PCI segments, in ACPI-speak).
2167 nommconf [X86] Disable use of MMCONFIG for PCI
2169 check_enable_amd_mmconf [X86] check for and enable
2170 properly configured MMIO access to PCI
2171 config space on AMD family 10h CPU
2172 nomsi [MSI] If the PCI_MSI kernel config parameter is
2173 enabled, this kernel boot option can be used to
2174 disable the use of MSI interrupts system-wide.
2175 noioapicquirk [APIC] Disable all boot interrupt quirks.
2176 Safety option to keep boot IRQs enabled. This
2177 should never be necessary.
2178 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2179 primary IO-APIC for bridges that cannot disable
2180 boot IRQs. This fixes a source of spurious IRQs
2181 when the system masks IRQs.
2182 noioapicreroute [APIC] Disable workaround that uses the
2183 boot IRQ equivalent of an IRQ that connects to
2184 a chipset where boot IRQs cannot be disabled.
2185 The opposite of ioapicreroute.
2186 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2187 routing table. These calls are known to be buggy
2188 on several machines and they hang the machine
2189 when used, but on other computers it's the only
2190 way to get the interrupt routing table. Try
2191 this option if the kernel is unable to allocate
2192 IRQs or discover secondary PCI buses on your
2194 rom [X86] Assign address space to expansion ROMs.
2195 Use with caution as certain devices share
2196 address decoders between ROMs and other
2198 norom [X86] Do not assign address space to
2199 expansion ROMs that do not already have
2200 BIOS assigned address ranges.
2201 nobar [X86] Do not assign address space to the
2202 BARs that weren't assigned by the BIOS.
2203 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2204 assigned automatically to PCI devices. You can
2205 make the kernel exclude IRQs of your ISA cards
2207 pirqaddr=0xAAAAA [X86] Specify the physical address
2208 of the PIRQ table (normally generated
2209 by the BIOS) if it is outside the
2210 F0000h-100000h range.
2211 lastbus=N [X86] Scan all buses thru bus #N. Can be
2212 useful if the kernel is unable to find your
2213 secondary buses and you want to tell it
2214 explicitly which ones they are.
2215 assign-busses [X86] Always assign all PCI bus
2216 numbers ourselves, overriding
2217 whatever the firmware may have done.
2218 usepirqmask [X86] Honor the possible IRQ mask stored
2219 in the BIOS $PIR table. This is needed on
2220 some systems with broken BIOSes, notably
2221 some HP Pavilion N5400 and Omnibook XE3
2222 notebooks. This will have no effect if ACPI
2223 IRQ routing is enabled.
2224 noacpi [X86] Do not use ACPI for IRQ routing
2225 or for PCI scanning.
2226 use_crs [X86] Use PCI host bridge window information
2227 from ACPI. On BIOSes from 2008 or later, this
2228 is enabled by default. If you need to use this,
2229 please report a bug.
2230 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2231 If you need to use this, please report a bug.
2232 routeirq Do IRQ routing for all PCI devices.
2233 This is normally done in pci_enable_device(),
2234 so this option is a temporary workaround
2235 for broken drivers that don't call it.
2236 skip_isa_align [X86] do not align io start addr, so can
2237 handle more pci cards
2238 firmware [ARM] Do not re-enumerate the bus but instead
2239 just use the configuration from the
2240 bootloader. This is currently used on
2241 IXP2000 systems where the bus has to be
2242 configured a certain way for adjunct CPUs.
2243 noearly [X86] Don't do any early type 1 scanning.
2244 This might help on some broken boards which
2245 machine check when some devices' config space
2246 is read. But various workarounds are disabled
2247 and some IOMMU drivers will not work.
2248 bfsort Sort PCI devices into breadth-first order.
2249 This sorting is done to get a device
2250 order compatible with older (<= 2.4) kernels.
2251 nobfsort Don't sort PCI devices into breadth-first order.
2252 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2253 tuning and use the BIOS-configured MPS defaults.
2254 pcie_bus_safe Set every device's MPS to the largest value
2255 supported by all devices below the root complex.
2256 pcie_bus_perf Set device MPS to the largest allowable MPS
2257 based on its parent bus. Also set MRRS (Max
2258 Read Request Size) to the largest supported
2259 value (no larger than the MPS that the device
2260 or bus can support) for best performance.
2261 pcie_bus_peer2peer Set every device's MPS to 128B, which
2262 every device is guaranteed to support. This
2263 configuration allows peer-to-peer DMA between
2264 any pair of devices, possibly at the cost of
2265 reduced performance. This also guarantees
2266 that hot-added devices will work.
2267 cbiosize=nn[KMG] The fixed amount of bus space which is
2268 reserved for the CardBus bridge's IO window.
2269 The default value is 256 bytes.
2270 cbmemsize=nn[KMG] The fixed amount of bus space which is
2271 reserved for the CardBus bridge's memory
2272 window. The default value is 64 megabytes.
2275 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2276 Specifies alignment and device to reassign
2277 aligned memory resources.
2278 If <order of align> is not specified,
2279 PAGE_SIZE is used as alignment.
2280 PCI-PCI bridge can be specified, if resource
2281 windows need to be expanded.
2282 ecrc= Enable/disable PCIe ECRC (transaction layer
2283 end-to-end CRC checking).
2284 bios: Use BIOS/firmware settings. This is the
2288 hpiosize=nn[KMG] The fixed amount of bus space which is
2289 reserved for hotplug bridge's IO window.
2290 Default size is 256 bytes.
2291 hpmemsize=nn[KMG] The fixed amount of bus space which is
2292 reserved for hotplug bridge's memory window.
2293 Default size is 2 megabytes.
2294 realloc= Enable/disable reallocating PCI bridge resources
2295 if allocations done by BIOS are too small to
2296 accommodate resources required by all child
2298 off: Turn realloc off
2300 realloc same as realloc=on
2301 noari do not use PCIe ARI.
2302 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2303 only look for one device below a PCIe downstream
2306 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2309 force Enable ASPM even on devices that claim not to support it.
2310 WARNING: Forcing ASPM on may cause system lockups.
2312 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2313 nomsi Do not use MSI for PCI Express Native Hotplug (this
2314 makes all PCIe ports use INTx for hotplug services).
2316 pcie_ports= [PCIE] PCIe ports handling:
2317 auto Ask the BIOS whether or not to use native PCIe services
2318 associated with PCIe ports (PME, hot-plug, AER). Use
2319 them only if that is allowed by the BIOS.
2320 native Use native PCIe services associated with PCIe ports
2322 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2325 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2326 nomsi Do not use MSI for native PCIe PME signaling (this makes
2327 all PCIe root ports use INTx for all services).
2329 pcmv= [HW,PCMCIA] BadgePAD 4
2332 See Documentation/blockdev/paride.txt.
2334 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2337 See arch/parisc/kernel/pdc_chassis.c
2339 percpu_alloc= Select which percpu first chunk allocator to use.
2340 Currently supported values are "embed" and "page".
2341 Archs may support subset or none of the selections.
2342 See comments in mm/percpu.c for details on each
2343 allocator. This parameter is primarily for debugging
2344 and performance comparison.
2347 See Documentation/blockdev/paride.txt.
2350 See Documentation/blockdev/paride.txt.
2352 pirq= [SMP,APIC] Manual mp-table setup
2353 See Documentation/x86/i386/IO-APIC.txt.
2355 plip= [PPT,NET] Parallel port network link
2356 Format: { parport<nr> | timid | 0 }
2357 See also Documentation/parport.txt.
2359 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2360 Override pmtimer IOPort with a hex value.
2364 Enable PNP debug messages (depends on the
2365 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2366 via /sys/module/pnp/parameters/debug. We always show
2367 current resource usage; turning this on also shows
2368 possible settings and some assignment information.
2374 { on | off | curr | res | no-curr | no-res }
2377 [ISAPNP] Exclude IRQs for the autoconfiguration
2380 [ISAPNP] Exclude DMAs for the autoconfiguration
2382 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2383 Ranges are in pairs (I/O port base and size).
2386 [ISAPNP] Exclude memory regions for the
2388 Ranges are in pairs (memory base and size).
2390 ports= [IP_VS_FTP] IPVS ftp helper module
2392 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2394 Format: <port>,<port>....
2396 print-fatal-signals=
2397 [KNL] debug: print fatal signals
2399 If enabled, warn about various signal handling
2400 related application anomalies: too many signals,
2401 too many POSIX.1 timers, fatal signals causing a
2404 If you hit the warning due to signal overflow,
2405 you might want to try "ulimit -i unlimited".
2409 printk.always_kmsg_dump=
2410 Trigger kmsg_dump for cases other than kernel oops or
2412 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2415 printk.time= Show timing data prefixed to each printk message line
2416 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2418 processor.max_cstate= [HW,ACPI]
2419 Limit processor to maximum C-state
2420 max_cstate=9 overrides any DMI blacklist limit.
2422 processor.nocst [HW,ACPI]
2423 Ignore the _CST method to determine C-states,
2424 instead using the legacy FADT method
2426 profile= [KNL] Enable kernel profiling via /proc/profile
2427 Format: [schedule,]<number>
2428 Param: "schedule" - profile schedule points.
2429 Param: <number> - step/bucket size as a power of 2 for
2430 statistical time based profiling.
2431 Param: "sleep" - profile D-state sleeping (millisecs).
2432 Requires CONFIG_SCHEDSTATS
2433 Param: "kvm" - profile VM exits.
2435 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2437 See Documentation/blockdev/ramdisk.txt.
2439 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2440 probe for; one of (bare|imps|exps|lifebook|any).
2441 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2443 psmouse.resetafter= [HW,MOUSE]
2444 Try to reset the device after so many bad packets
2447 [HW,MOUSE] Set desired mouse resolution, in dpi.
2448 psmouse.smartscroll=
2449 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2450 0 = disabled, 1 = enabled (default).
2452 pstore.backend= Specify the name of the pstore backend to use
2455 See Documentation/blockdev/paride.txt.
2458 [KNL] Number of legacy pty's. Overwrites compiled-in
2461 quiet [KNL] Disable most log messages
2466 See Documentation/md.txt.
2468 ramdisk_blocksize= [RAM]
2469 See Documentation/blockdev/ramdisk.txt.
2471 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2472 See Documentation/blockdev/ramdisk.txt.
2474 rcu_nocbs= [KNL,BOOT]
2475 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2476 the specified list of CPUs to be no-callback CPUs.
2477 Invocation of these CPUs' RCU callbacks will
2478 be offloaded to "rcuoN" kthreads created for
2479 that purpose. This reduces OS jitter on the
2480 offloaded CPUs, which can be useful for HPC and
2481 real-time workloads. It can also improve energy
2482 efficiency for asymmetric multiprocessors.
2484 rcu_nocb_poll [KNL,BOOT]
2485 Rather than requiring that offloaded CPUs
2486 (specified by rcu_nocbs= above) explicitly
2487 awaken the corresponding "rcuoN" kthreads,
2488 make these kthreads poll for callbacks.
2489 This improves the real-time response for the
2490 offloaded CPUs by relieving them of the need to
2491 wake up the corresponding kthread, but degrades
2492 energy efficiency by requiring that the kthreads
2493 periodically wake up to do the polling.
2495 rcutree.blimit= [KNL,BOOT]
2496 Set maximum number of finished RCU callbacks to process
2499 rcutree.fanout_leaf= [KNL,BOOT]
2500 Increase the number of CPUs assigned to each
2501 leaf rcu_node structure. Useful for very large
2504 rcutree.qhimark= [KNL,BOOT]
2505 Set threshold of queued
2506 RCU callbacks over which batch limiting is disabled.
2508 rcutree.qlowmark= [KNL,BOOT]
2509 Set threshold of queued RCU callbacks below which
2510 batch limiting is re-enabled.
2512 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2513 Suppress RCU CPU stall warning messages.
2515 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2516 Set timeout for RCU CPU stall warning messages.
2518 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2519 Set delay from grace-period initialization to
2520 first attempt to force quiescent states.
2521 Units are jiffies, minimum value is zero,
2522 and maximum value is HZ.
2524 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2525 Set delay between subsequent attempts to force
2526 quiescent states. Units are jiffies, minimum
2527 value is one, and maximum value is HZ.
2529 rcutorture.fqs_duration= [KNL,BOOT]
2530 Set duration of force_quiescent_state bursts.
2532 rcutorture.fqs_holdoff= [KNL,BOOT]
2533 Set holdoff time within force_quiescent_state bursts.
2535 rcutorture.fqs_stutter= [KNL,BOOT]
2536 Set wait time between force_quiescent_state bursts.
2538 rcutorture.irqreader= [KNL,BOOT]
2539 Test RCU readers from irq handlers.
2541 rcutorture.n_barrier_cbs= [KNL,BOOT]
2542 Set callbacks/threads for rcu_barrier() testing.
2544 rcutorture.nfakewriters= [KNL,BOOT]
2545 Set number of concurrent RCU writers. These just
2546 stress RCU, they don't participate in the actual
2547 test, hence the "fake".
2549 rcutorture.nreaders= [KNL,BOOT]
2550 Set number of RCU readers.
2552 rcutorture.onoff_holdoff= [KNL,BOOT]
2553 Set time (s) after boot for CPU-hotplug testing.
2555 rcutorture.onoff_interval= [KNL,BOOT]
2556 Set time (s) between CPU-hotplug operations, or
2557 zero to disable CPU-hotplug testing.
2559 rcutorture.shuffle_interval= [KNL,BOOT]
2560 Set task-shuffle interval (s). Shuffling tasks
2561 allows some CPUs to go into dyntick-idle mode
2562 during the rcutorture test.
2564 rcutorture.shutdown_secs= [KNL,BOOT]
2565 Set time (s) after boot system shutdown. This
2566 is useful for hands-off automated testing.
2568 rcutorture.stall_cpu= [KNL,BOOT]
2569 Duration of CPU stall (s) to test RCU CPU stall
2570 warnings, zero to disable.
2572 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2573 Time to wait (s) after boot before inducing stall.
2575 rcutorture.stat_interval= [KNL,BOOT]
2576 Time (s) between statistics printk()s.
2578 rcutorture.stutter= [KNL,BOOT]
2579 Time (s) to stutter testing, for example, specifying
2580 five seconds causes the test to run for five seconds,
2581 wait for five seconds, and so on. This tests RCU's
2582 ability to transition abruptly to and from idle.
2584 rcutorture.test_boost= [KNL,BOOT]
2585 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2586 "Maybe" means test if the RCU implementation
2587 under test support RCU priority boosting.
2589 rcutorture.test_boost_duration= [KNL,BOOT]
2590 Duration (s) of each individual boost test.
2592 rcutorture.test_boost_interval= [KNL,BOOT]
2593 Interval (s) between each boost test.
2595 rcutorture.test_no_idle_hz= [KNL,BOOT]
2596 Test RCU's dyntick-idle handling. See also the
2597 rcutorture.shuffle_interval parameter.
2599 rcutorture.torture_type= [KNL,BOOT]
2600 Specify the RCU implementation to test.
2602 rcutorture.verbose= [KNL,BOOT]
2603 Enable additional printk() statements.
2607 Run specified binary instead of /init from the ramdisk,
2608 used for early userspace startup. See initrd.
2610 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2611 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2612 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2615 [KNL, SMP] Set scheduler's default relax_domain_level.
2616 See Documentation/cgroups/cpusets.txt.
2618 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2620 reservetop= [X86-32]
2622 Reserves a hole at the top of the kernel virtual
2627 Set the amount of memory to reserve for BIOS at
2628 the bottom of the address space.
2630 reset_devices [KNL] Force drivers to reset the underlying device
2631 during initialization.
2634 Specify the partition device for software suspend
2636 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2638 resume_offset= [SWSUSP]
2639 Specify the offset from the beginning of the partition
2640 given by "resume=" at which the swap header is located,
2641 in <PAGE_SIZE> units (needed only for swap files).
2642 See Documentation/power/swsusp-and-swap-files.txt
2644 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2645 read the resume files
2647 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2648 Useful for devices that are detected asynchronously
2649 (e.g. USB and MMC devices).
2651 hibernate= [HIBERNATION]
2652 noresume Don't check if there's a hibernation image
2653 present during boot.
2654 nocompress Don't compress/decompress hibernation images.
2656 retain_initrd [RAM] Keep initrd memory after extraction
2658 rhash_entries= [KNL,NET]
2659 Set number of hash buckets for route cache
2661 riscom8= [HW,SERIAL]
2662 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2664 ro [KNL] Mount root device read-only on boot
2666 root= [KNL] Root filesystem
2667 See name_to_dev_t comment in init/do_mounts.c.
2669 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2670 mount the root filesystem
2672 rootflags= [KNL] Set root filesystem mount option string
2674 rootfstype= [KNL] Set root filesystem type
2676 rootwait [KNL] Wait (indefinitely) for root device to show up.
2677 Useful for devices that are detected asynchronously
2678 (e.g. USB and MMC devices).
2680 rw [KNL] Mount root device read-write on boot
2682 S [KNL] Run init in single mode
2685 See drivers/net/irda/sa1100_ir.c.
2687 sbni= [NET] Granch SBNI12 leased line adapter
2689 sched_debug [KNL] Enables verbose scheduler debug messages.
2691 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2692 xtime_lock contention on larger systems, and/or RCU lock
2693 contention on all systems with CONFIG_MAXSMP set.
2694 Format: { "0" | "1" }
2695 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2697 Note: increases power consumption, thus should only be
2698 enabled if running jitter sensitive (HPC/RT) workloads.
2700 security= [SECURITY] Choose a security module to enable at boot.
2701 If this boot parameter is not specified, only the first
2702 security module asking for security registration will be
2703 loaded. An invalid security module name will be treated
2704 as if no module has been chosen.
2706 selinux= [SELINUX] Disable or enable SELinux at boot time.
2707 Format: { "0" | "1" }
2708 See security/selinux/Kconfig help text.
2711 Default value is set via kernel config option.
2712 If enabled at boot time, /selinux/disable can be used
2713 later to disable prior to initial policy load.
2715 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2716 Format: { "0" | "1" }
2717 See security/apparmor/Kconfig help text
2720 Default value is set via kernel config option.
2722 serialnumber [BUGS=X86-32]
2725 Maximal number of shapers.
2727 show_msr= [x86] show boot-time MSR settings
2728 Format: { <integer> }
2729 Show boot-time (BIOS-initialized) MSR settings.
2730 The parameter means the number of CPUs to show,
2731 for example 1 means boot CPU only.
2738 slab_max_order= [MM, SLAB]
2739 Determines the maximum allowed order for slabs.
2740 A high setting may cause OOMs due to memory
2741 fragmentation. Defaults to 1 for systems with
2742 more than 32MB of RAM, 0 otherwise.
2744 slub_debug[=options[,slabs]] [MM, SLUB]
2745 Enabling slub_debug allows one to determine the
2746 culprit if slab objects become corrupted. Enabling
2747 slub_debug can create guard zones around objects and
2748 may poison objects when not in use. Also tracks the
2749 last alloc / free. For more information see
2750 Documentation/vm/slub.txt.
2752 slub_max_order= [MM, SLUB]
2753 Determines the maximum allowed order for slabs.
2754 A high setting may cause OOMs due to memory
2755 fragmentation. For more information see
2756 Documentation/vm/slub.txt.
2758 slub_min_objects= [MM, SLUB]
2759 The minimum number of objects per slab. SLUB will
2760 increase the slab order up to slub_max_order to
2761 generate a sufficiently large slab able to contain
2762 the number of objects indicated. The higher the number
2763 of objects the smaller the overhead of tracking slabs
2764 and the less frequently locks need to be acquired.
2765 For more information see Documentation/vm/slub.txt.
2767 slub_min_order= [MM, SLUB]
2768 Determines the minimum page order for slabs. Must be
2769 lower than slub_max_order.
2770 For more information see Documentation/vm/slub.txt.
2772 slub_nomerge [MM, SLUB]
2773 Disable merging of slabs with similar size. May be
2774 necessary if there is some reason to distinguish
2775 allocs to different slabs. Debug options disable
2776 merging on their own.
2777 For more information see Documentation/vm/slub.txt.
2780 Format: <io1>[,<io2>[,...,<io8>]]
2782 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2783 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2784 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2785 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2786 smsc-ircc2.ircc_irq= [HW] IRQ line
2787 smsc-ircc2.ircc_dma= [HW] DMA channel
2788 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2789 0: Toshiba Satellite 1800 (GP data pin select)
2790 1: Fast pin select (default)
2794 [KNL] Should the soft-lockup detector generate panics.
2797 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2798 See Documentation/laptops/sonypi.txt
2800 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2801 See Documentation/serial/specialix.txt.
2803 spia_io_base= [HW,MTD]
2809 Enabled the stack tracer on boot up.
2811 stacktrace_filter=[function-list]
2812 [FTRACE] Limit the functions that the stack tracer
2813 will trace at boot up. function-list is a comma separated
2814 list of functions. This list can be changed at run
2815 time by the stack_trace_filter file in the debugfs
2816 tracing directory. Note, this enables stack tracing
2817 and the stacktrace above is not needed.
2821 Set the STI (builtin display/keyboard on the HP-PARISC
2822 machines) console (graphic card) which should be used
2823 as the initial boot-console.
2824 See also comment in drivers/video/console/sticore.c.
2827 See comment in drivers/video/console/sticore.c.
2830 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2832 sunrpc.min_resvport=
2833 sunrpc.max_resvport=
2835 SunRPC servers often require that client requests
2836 originate from a privileged port (i.e. a port in the
2837 range 0 < portnr < 1024).
2838 An administrator who wishes to reserve some of these
2839 ports for other uses may adjust the range that the
2840 kernel's sunrpc client considers to be privileged
2841 using these two parameters to set the minimum and
2842 maximum port values.
2846 Control how the NFS server code allocates CPUs to
2847 service thread pools. Depending on how many NICs
2848 you have and where their interrupts are bound, this
2849 option will affect which CPUs will do NFS serving.
2850 Note: this parameter cannot be changed while the
2851 NFS server is running.
2853 auto the server chooses an appropriate mode
2854 automatically using heuristics
2855 global a single global pool contains all CPUs
2856 percpu one pool for each CPU
2857 pernode one pool for each NUMA node (equivalent
2858 to global on non-NUMA machines)
2860 sunrpc.tcp_slot_table_entries=
2861 sunrpc.udp_slot_table_entries=
2863 Sets the upper limit on the number of simultaneous
2864 RPC calls that can be sent from the client to a
2865 server. Increasing these values may allow you to
2866 improve throughput, but will also increase the
2867 amount of memory reserved for use by the client.
2870 [KNL] Enable accounting of swap in memory resource
2871 controller if no parameter or 1 is given or disable
2872 it if 0 is given (See Documentation/cgroups/memory.txt)
2874 swiotlb= [IA-64] Number of I/O TLB slabs
2878 sysfs.deprecated=0|1 [KNL]
2879 Enable/disable old style sysfs layout for old udev
2880 on older distributions. When this option is enabled
2881 very new udev will not work anymore. When this option
2882 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2883 in older udev will not work anymore.
2884 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2885 the kernel configuration.
2887 sysrq_always_enabled
2889 Ignore sysrq setting - this boot parameter will
2890 neutralize any effect of /proc/sys/kernel/sysrq.
2891 Useful for debugging.
2895 test_suspend= [SUSPEND]
2896 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2897 standby suspend) as the system sleep state to briefly
2898 enter during system startup. The system is woken from
2899 this state using a wakeup-capable RTC alarm.
2901 thash_entries= [KNL,NET]
2902 Set number of hash buckets for TCP connection
2904 thermal.act= [HW,ACPI]
2905 -1: disable all active trip points in all thermal zones
2906 <degrees C>: override all lowest active trip points
2908 thermal.crt= [HW,ACPI]
2909 -1: disable all critical trip points in all thermal zones
2910 <degrees C>: override all critical trip points
2912 thermal.nocrt= [HW,ACPI]
2913 Set to disable actions on ACPI thermal zone
2914 critical and hot trip points.
2916 thermal.off= [HW,ACPI]
2917 1: disable ACPI thermal control
2919 thermal.psv= [HW,ACPI]
2920 -1: disable all passive trip points
2921 <degrees C>: override all passive trip points to this
2924 thermal.tzp= [HW,ACPI]
2925 Specify global default ACPI thermal zone polling rate
2926 <deci-seconds>: poll all this frequency
2927 0: no polling (default)
2930 Force threading of all interrupt handlers except those
2931 marked explicitly IRQF_NO_THREAD.
2935 Specify if the kernel should make use of the cpu
2936 topology information if the hardware supports this.
2937 The scheduler will make use of this information and
2938 e.g. base its process migration decisions on it.
2943 tpm_suspend_pcr=[HW,TPM]
2944 Format: integer pcr id
2945 Specify that at suspend time, the tpm driver
2946 should extend the specified pcr with zeros,
2947 as a workaround for some chips which fail to
2948 flush the last written pcr on TPM_SaveState.
2949 This will guarantee that all the other pcrs
2952 trace_buf_size=nn[KMG]
2953 [FTRACE] will set tracing buffer size.
2955 trace_event=[event-list]
2956 [FTRACE] Set and start specified trace events in order
2957 to facilitate early boot debugging.
2958 See also Documentation/trace/events.txt
2960 trace_options=[option-list]
2961 [FTRACE] Enable or disable tracer options at boot.
2962 The option-list is a comma delimited list of options
2963 that can be enabled or disabled just as if you were
2964 to echo the option name into
2966 /sys/kernel/debug/tracing/trace_options
2968 For example, to enable stacktrace option (to dump the
2969 stack trace of each event), add to the command line:
2971 trace_options=stacktrace
2973 See also Documentation/trace/ftrace.txt "trace options"
2976 transparent_hugepage=
2978 Format: [always|madvise|never]
2979 Can be used to control the default behavior of the system
2980 with respect to transparent hugepages.
2981 See Documentation/vm/transhuge.txt for more details.
2983 tsc= Disable clocksource stability checks for TSC.
2985 [x86] reliable: mark tsc clocksource as reliable, this
2986 disables clocksource verification at runtime, as well
2987 as the stability checks done at bootup. Used to enable
2988 high-resolution timer mode on older hardware, and in
2989 virtualized environment.
2990 [x86] noirqtime: Do not use TSC to do irq accounting.
2991 Used to run time disable IRQ_TIME_ACCOUNTING on any
2992 platforms where RDTSC is slow and this accounting
2995 turbografx.map[2|3]= [HW,JOY]
2996 TurboGraFX parallel port interface
2998 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2999 See also Documentation/input/joystick-parport.txt
3001 udbg-immortal [PPC] When debugging early kernel crashes that
3002 happen after console_init() and before a proper
3003 console driver takes over, this boot options might
3004 help "seeing" what's going on.
3006 uhash_entries= [KNL,NET]
3007 Set number of hash buckets for UDP/UDP-Lite connections
3010 [USB] Ignore overcurrent events (default N).
3011 Some badly-designed motherboards generate lots of
3012 bogus events, for ports that aren't wired to
3013 anything. Set this parameter to avoid log spamming.
3014 Note that genuine overcurrent events won't be
3018 [X86] Cause panic on unknown NMI.
3020 usbcore.authorized_default=
3021 [USB] Default USB device authorization:
3022 (default -1 = authorized except for wireless USB,
3023 0 = not authorized, 1 = authorized)
3025 usbcore.autosuspend=
3026 [USB] The autosuspend time delay (in seconds) used
3027 for newly-detected USB devices (default 2). This
3028 is the time required before an idle device will be
3029 autosuspended. Devices for which the delay is set
3030 to a negative value won't be autosuspended at all.
3032 usbcore.usbfs_snoop=
3033 [USB] Set to log all usbfs traffic (default 0 = off).
3035 usbcore.blinkenlights=
3036 [USB] Set to cycle leds on hubs (default 0 = off).
3038 usbcore.old_scheme_first=
3039 [USB] Start with the old device initialization
3040 scheme (default 0 = off).
3042 usbcore.usbfs_memory_mb=
3043 [USB] Memory limit (in MB) for buffers allocated by
3044 usbfs (default = 16, 0 = max = 2047).
3046 usbcore.use_both_schemes=
3047 [USB] Try the other device initialization scheme
3048 if the first one fails (default 1 = enabled).
3050 usbcore.initial_descriptor_timeout=
3051 [USB] Specifies timeout for the initial 64-byte
3052 USB_REQ_GET_DESCRIPTOR request in milliseconds
3053 (default 5000 = 5.0 seconds).
3056 [USBHID] The interval which mice are to be polled at.
3058 usb-storage.delay_use=
3059 [UMS] The delay in seconds before a new device is
3060 scanned for Logical Units (default 5).
3063 [UMS] A list of quirks entries to supplement or
3064 override the built-in unusual_devs list. List
3065 entries are separated by commas. Each entry has
3066 the form VID:PID:Flags where VID and PID are Vendor
3067 and Product ID values (4-digit hex numbers) and
3068 Flags is a set of characters, each corresponding
3069 to a common usb-storage quirk flag as follows:
3070 a = SANE_SENSE (collect more than 18 bytes
3072 b = BAD_SENSE (don't collect more than 18
3073 bytes of sense data);
3074 c = FIX_CAPACITY (decrease the reported
3075 device capacity by one sector);
3076 d = NO_READ_DISC_INFO (don't use
3077 READ_DISC_INFO command);
3078 e = NO_READ_CAPACITY_16 (don't use
3079 READ_CAPACITY_16 command);
3080 h = CAPACITY_HEURISTICS (decrease the
3081 reported device capacity by one
3082 sector if the number is odd);
3083 i = IGNORE_DEVICE (don't bind to this
3085 l = NOT_LOCKABLE (don't try to lock and
3086 unlock ejectable media);
3087 m = MAX_SECTORS_64 (don't transfer more
3088 than 64 sectors = 32 KB at a time);
3089 n = INITIAL_READ10 (force a retry of the
3090 initial READ(10) command);
3091 o = CAPACITY_OK (accept the capacity
3092 reported by the device);
3093 p = WRITE_CACHE (the device cache is ON
3095 r = IGNORE_RESIDUE (the device reports
3096 bogus residue values);
3097 s = SINGLE_LUN (the device has only one
3099 w = NO_WP_DETECT (don't test whether the
3100 medium is write-protected).
3101 Example: quirks=0419:aaf5:rl,0421:0433:rc
3103 user_debug= [KNL,ARM]
3105 See arch/arm/Kconfig.debug help text.
3106 1 - undefined instruction events
3108 4 - invalid data aborts
3111 Example: user_debug=31
3114 [X86] Flags controlling user PTE allocations.
3116 nohigh = do not allocate PTE pages in
3117 HIGHMEM regardless of setting
3121 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3122 vdso=1: enable VDSO (default)
3123 vdso=0: disable VDSO mapping
3126 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3127 vdso32=1: enable 32-bit VDSO (default)
3128 vdso32=0: disable 32-bit VDSO mapping
3131 vector=percpu: enable percpu vector domain
3133 video= [FB] Frame buffer configuration
3134 See Documentation/fb/modedb.txt.
3137 [VMMIO] Memory mapped virtio (platform) device.
3139 <size>@<baseaddr>:<irq>[:<id>]
3141 <size> := size (can use standard suffixes
3143 <baseaddr> := physical base address
3144 <irq> := interrupt number (as passed to
3146 <id> := (optional) platform device id
3148 virtio_mmio.device=1K@0x100b0000:48:7
3150 Can be used multiple times for multiple devices.
3152 vga= [BOOT,X86-32] Select a particular video mode
3153 See Documentation/x86/boot.txt and
3154 Documentation/svga.txt.
3155 Use vga=ask for menu.
3156 This is actually a boot loader parameter; the value is
3157 passed to the kernel using a special protocol.
3159 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3160 size of <nn>. This can be used to increase the
3161 minimum size (128MB on x86). It can also be used to
3162 decrease the size and leave more room for directly
3165 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3168 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3171 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3175 Controls the behavior of vsyscalls (i.e. calls to
3176 fixed addresses of 0xffffffffff600x00 from legacy
3177 code). Most statically-linked binaries and older
3178 versions of glibc use these calls. Because these
3179 functions are at fixed addresses, they make nice
3180 targets for exploits that can control RIP.
3182 emulate [default] Vsyscalls turn into traps and are
3183 emulated reasonably safely.
3185 native Vsyscalls are native syscall instructions.
3186 This is a little bit faster than trapping
3187 and makes a few dynamic recompilers work
3188 better than they would in emulation mode.
3189 It also makes exploits much easier to write.
3191 none Vsyscalls don't work at all. This makes
3192 them quite hard to use for exploits but
3193 might break your system.
3195 vt.cur_default= [VT] Default cursor shape.
3196 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3197 the parameters of the <Esc>[?A;B;Cc escape sequence;
3198 see VGA-softcursor.txt. Default: 2 = underline.
3200 vt.default_blu= [VT]
3201 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3202 Change the default blue palette of the console.
3203 This is a 16-member array composed of values
3206 vt.default_grn= [VT]
3207 Format: <green0>,<green1>,<green2>,...,<green15>
3208 Change the default green palette of the console.
3209 This is a 16-member array composed of values
3212 vt.default_red= [VT]
3213 Format: <red0>,<red1>,<red2>,...,<red15>
3214 Change the default red palette of the console.
3215 This is a 16-member array composed of values
3221 Set system-wide default UTF-8 mode for all tty's.
3222 Default is 1, i.e. UTF-8 mode is enabled for all
3223 newly opened terminals.
3225 vt.global_cursor_default=
3228 Set system-wide default for whether a cursor
3229 is shown on new VTs. Default is -1,
3230 i.e. cursors will be created by default unless
3231 overridden by individual drivers. 0 will hide
3232 cursors, 1 will display them.
3234 watchdog timers [HW,WDT] For information on watchdog timers,
3235 see Documentation/watchdog/watchdog-parameters.txt
3236 or other driver-specific files in the
3237 Documentation/watchdog/ directory.
3239 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3240 default x2apic cluster mode on platforms
3243 x86_mrst_timer= [X86-32,APBT]
3244 Choose timer option for x86 Moorestown MID platform.
3245 Two valid options are apbt timer only and lapic timer
3246 plus one apbt timer for broadcast timer.
3247 x86_mrst_timer=apbt_only | lapic_and_apbt
3249 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3250 xd_geo= See header of drivers/block/xd.c.
3252 xen_emul_unplug= [HW,X86,XEN]
3253 Unplug Xen emulated devices
3254 Format: [unplug0,][unplug1]
3255 ide-disks -- unplug primary master IDE devices
3256 aux-ide-disks -- unplug non-primary-master IDE devices
3257 nics -- unplug network devices
3258 all -- unplug all emulated devices (NICs and IDE disks)
3259 unnecessary -- unplugging emulated devices is
3260 unnecessary even if the host did not respond to
3262 never -- do not unplug even if version check succeeds
3264 xirc2ps_cs= [NET,PCMCIA]
3266 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3268 ______________________________________________________________________
3272 Add more DRM drivers.
projects / ~andy / linux / blob