4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
833 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
834 parameter enables the feature at boot time. In
835 default, it is disabled. We can avoid allocating huge
836 chunk of memory for debug pagealloc if we don't enable
837 it at boot time and the system will work mostly same
838 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
839 on: enable the feature
841 debugpat [X86] Enable PAT debugging
843 decnet.addr= [HW,NET]
844 Format: <area>[,<node>]
845 See also Documentation/networking/decnet.txt.
848 [same as hugepagesz=] The size of the default
849 HugeTLB page size. This is the size represented by
850 the legacy /proc/ hugepages APIs, used for SHM, and
851 default size when mounting hugetlbfs filesystems.
852 Defaults to the default architecture's huge page size
856 Set number of hash buckets for dentry cache.
859 See Documentation/networking/ipv6.txt.
861 disable_cpu_apicid= [X86,APIC,SMP]
863 The number of initial APIC ID for the
864 corresponding CPU to be disabled at boot,
865 mostly used for the kdump 2nd kernel to
866 disable BSP to wake up multiple CPUs without
867 causing system reset or hang due to sending
870 disable_ddw [PPC/PSERIES]
871 Disable Dynamic DMA Window support. Use this if
872 to workaround buggy firmware.
875 See Documentation/networking/ipv6.txt.
877 disable_mtrr_cleanup [X86]
878 The kernel tries to adjust MTRR layout from continuous
879 to discrete, to make X server driver able to add WB
880 entry later. This parameter disables that.
882 disable_mtrr_trim [X86, Intel and AMD only]
883 By default the kernel will trim any uncacheable
884 memory out of your available memory pool based on
885 MTRR settings. This parameter disables that behavior,
886 possibly causing your machine to run very slowly.
888 disable_timer_pin_1 [X86]
889 Disable PIN 1 of APIC timer
890 Can be useful to work around chipset bugs.
892 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
893 this option disables the debugging code at boot.
895 dma_debug_entries=<number>
896 This option allows to tune the number of preallocated
897 entries for DMA-API debugging code. One entry is
898 required per DMA-API allocation. Use this if the
899 DMA-API debugging code disables itself because the
900 architectural default is too low.
902 dma_debug_driver=<driver_name>
903 With this option the DMA-API debugging driver
904 filter feature can be enabled at boot time. Just
905 pass the driver to filter for as the parameter.
906 The filter can be disabled or changed to another
907 driver later using sysfs.
909 drm_kms_helper.edid_firmware=[<connector>:]<file>
910 Broken monitors, graphic adapters and KVMs may
911 send no or incorrect EDID data sets. This parameter
912 allows to specify an EDID data set in the
913 /lib/firmware directory that is used instead.
914 Generic built-in EDID data sets are used, if one of
915 edid/1024x768.bin, edid/1280x1024.bin,
916 edid/1680x1050.bin, or edid/1920x1080.bin is given
917 and no file with the same name exists. Details and
918 instructions how to build your own EDID data are
919 available in Documentation/EDID/HOWTO.txt. An EDID
920 data set will only be used for a particular connector,
921 if its name and a colon are prepended to the EDID
926 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
927 module.dyndbg[="val"]
928 Enable debug messages at boot time. See
929 Documentation/dynamic-debug-howto.txt for details.
932 on enable eager fpu restore
933 off disable eager fpu restore
934 auto selects the default scheme, which automatically
935 enables eagerfpu restore for xsaveopt.
937 early_ioremap_debug [KNL]
938 Enable debug messages in early_ioremap support. This
939 is useful for tracking down temporary early mappings
940 which are not unmapped.
942 earlycon= [KNL] Output early console device and options.
945 Start an early, polled-mode console on a cadence serial
946 port at the specified address. The cadence serial port
947 must already be setup and configured. Options are not
950 uart[8250],io,<addr>[,options]
951 uart[8250],mmio,<addr>[,options]
952 uart[8250],mmio32,<addr>[,options]
953 Start an early, polled-mode console on the 8250/16550
954 UART at the specified I/O port or MMIO address.
955 MMIO inter-register address stride is either 8-bit
956 (mmio) or 32-bit (mmio32).
957 The options are the same as for ttyS, above.
960 Start an early, polled-mode console on a pl011 serial
961 port at the specified address. The pl011 serial port
962 must already be setup and configured. Options are not
966 Start an early, polled-mode console on an msm serial
967 port at the specified address. The serial port
968 must already be setup and configured. Options are not
972 Start an early, polled-mode console on an msm serial
973 dm port at the specified address. The serial port
974 must already be setup and configured. Options are not
977 smh Use ARM semihosting calls for early console.
985 Use early console provided by serial driver available
986 on Samsung SoCs, requires selecting proper type and
987 a correct base address of the selected UART port. The
988 serial port must already be setup and configured.
989 Options are not yet supported.
991 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
995 earlyprintk=serial[,ttySn[,baudrate]]
996 earlyprintk=serial[,0x...[,baudrate]]
997 earlyprintk=ttySn[,baudrate]
998 earlyprintk=dbgp[debugController#]
1000 earlyprintk is useful when the kernel crashes before
1001 the normal console is initialized. It is not enabled by
1002 default because it has some cosmetic problems.
1004 Append ",keep" to not disable it when the real console
1007 Only one of vga, efi, serial, or usb debug port can
1010 Currently only ttyS0 and ttyS1 may be specified by
1011 name. Other I/O ports may be explicitly specified
1012 on some architectures (x86 and arm at least) by
1013 replacing ttySn with an I/O port address, like this:
1014 earlyprintk=serial,0x1008,115200
1015 You can find the port for a given device in
1016 /proc/tty/driver/serial:
1017 2: uart:ST16650V2 port:00001008 irq:18 ...
1019 Interaction with the standard serial driver is not
1022 The VGA and EFI output is eventually overwritten by
1025 The xen output can only be used by Xen PV guests.
1027 edac_report= [HW,EDAC] Control how to report EDAC event
1028 Format: {"on" | "off" | "force"}
1029 on: enable EDAC to report H/W event. May be overridden
1030 by other higher priority error reporting module.
1031 off: disable H/W event reporting through EDAC.
1032 force: enforce the use of EDAC to report H/W event.
1035 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1038 This is designed to be used in conjunction with
1039 the boot argument: earlyprintk=vga
1042 Format: {"off" | "on" | "skip[mbr]"}
1045 Format: { "old_map", "nochunk", "noruntime", "debug" }
1046 old_map [X86-64]: switch to the old ioremap-based EFI
1047 runtime services mapping. 32-bit still uses this one by
1049 nochunk: disable reading files in "chunks" in the EFI
1050 boot stub, as chunking can cause problems with some
1051 firmware implementations.
1052 noruntime : disable EFI runtime services support
1053 debug: enable misc debug output
1055 efi_no_storage_paranoia [EFI; X86]
1056 Using this parameter you can use more than 50% of
1057 your efi variable storage. Use this parameter only if
1058 you are really sure that your UEFI does sane gc and
1059 fulfills the spec otherwise your board may brick.
1061 eisa_irq_edge= [PARISC,HW]
1062 See header of drivers/parisc/eisa.c.
1065 See comment before function elanfreq_setup() in
1066 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1069 Format: {"cfq" | "deadline" | "noop"}
1070 See Documentation/block/cfq-iosched.txt and
1071 Documentation/block/deadline-iosched.txt for details.
1073 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1074 Specifies physical address of start of kernel core
1075 image elf header and optionally the size. Generally
1076 kexec loader will pass this option to capture kernel.
1077 See Documentation/kdump/kdump.txt for details.
1079 enable_mtrr_cleanup [X86]
1080 The kernel tries to adjust MTRR layout from continuous
1081 to discrete, to make X server driver able to add WB
1082 entry later. This parameter enables that.
1084 enable_timer_pin_1 [X86]
1085 Enable PIN 1 of APIC timer
1086 Can be useful to work around chipset bugs
1087 (in particular on some ATI chipsets).
1088 The kernel tries to set a reasonable default.
1090 enforcing [SELINUX] Set initial enforcing status.
1092 See security/selinux/Kconfig help text.
1093 0 -- permissive (log only, no denials).
1094 1 -- enforcing (deny and log).
1096 Value can be changed at runtime via /selinux/enforce.
1099 Disable Error Record Serialization Table (ERST)
1102 ether= [HW,NET] Ethernet cards parameters
1103 This option is obsoleted by the "netdev=" option, which
1104 has equivalent usage. See its documentation for details.
1108 Permit 'security.evm' to be updated regardless of
1109 current integrity status.
1113 fail_make_request=[KNL]
1114 General fault injection mechanism.
1115 Format: <interval>,<probability>,<space>,<times>
1116 See also Documentation/fault-injection/.
1119 See Documentation/blockdev/floppy.txt.
1121 force_pal_cache_flush
1122 [IA-64] Avoid check_sal_cache_flush which may hang on
1123 buggy SAL_CACHE_FLUSH implementations. Using this
1124 parameter will force ia64_sal_cache_flush to call
1125 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1128 Forcefully enable Physical Address Extension (PAE).
1129 Many Pentium M systems disable PAE but may have a
1130 functionally usable PAE implementation.
1131 Warning: use of this parameter will taint the kernel
1132 and may cause unknown problems.
1135 [FTRACE] will set and start the specified tracer
1136 as early as possible in order to facilitate early
1139 ftrace_dump_on_oops[=orig_cpu]
1140 [FTRACE] will dump the trace buffers on oops.
1141 If no parameter is passed, ftrace will dump
1142 buffers of all CPUs, but if you pass orig_cpu, it will
1143 dump only the buffer of the CPU that triggered the
1146 ftrace_filter=[function-list]
1147 [FTRACE] Limit the functions traced by the function
1148 tracer at boot up. function-list is a comma separated
1149 list of functions. This list can be changed at run
1150 time by the set_ftrace_filter file in the debugfs
1153 ftrace_notrace=[function-list]
1154 [FTRACE] Do not trace the functions specified in
1155 function-list. This list can be changed at run time
1156 by the set_ftrace_notrace file in the debugfs
1159 ftrace_graph_filter=[function-list]
1160 [FTRACE] Limit the top level callers functions traced
1161 by the function graph tracer at boot up.
1162 function-list is a comma separated list of functions
1163 that can be changed at run time by the
1164 set_graph_function file in the debugfs tracing directory.
1166 ftrace_graph_notrace=[function-list]
1167 [FTRACE] Do not trace from the functions specified in
1168 function-list. This list is a comma separated list of
1169 functions that can be changed at run time by the
1170 set_graph_notrace file in the debugfs tracing directory.
1173 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1174 support via parallel port (up to 5 devices per port)
1175 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1176 See also Documentation/input/joystick-parport.txt
1180 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1184 gcov_persist= [GCOV] When non-zero (default), profiling data for
1185 kernel modules is saved and remains accessible via
1186 debugfs, even when the module is unloaded/reloaded.
1187 When zero, profiling data is discarded and associated
1188 debugfs files are removed at module unload time.
1190 gpt [EFI] Forces disk with valid GPT signature but
1191 invalid Protective MBR to be treated as GPT. If the
1192 primary GPT is corrupted, it enables the backup/alternate
1193 GPT to be used instead.
1195 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1196 the "Enable 0" bit of the configuration register.
1199 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1200 the "Enable 0" bit of the configuration register.
1203 grcan.select= [HW] Select which physical interface to use.
1206 grcan.txsize= [HW] Sets the size of the tx buffer.
1207 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1209 grcan.rxsize= [HW] Sets the size of the rx buffer.
1210 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1213 hashdist= [KNL,NUMA] Large hashes allocated during boot
1214 are distributed across NUMA nodes. Defaults on
1215 for 64-bit NUMA, off otherwise.
1216 Format: 0 | 1 (for off | on)
1218 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1220 hd= [EIDE] (E)IDE hard drive subsystem geometry
1221 Format: <cyl>,<head>,<sect>
1224 Disable Hardware Error Source Table (HEST) support;
1225 corresponding firmware-first mode error processing
1226 logic will be disabled.
1228 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1229 size of <nn>. This works even on boxes that have no
1230 highmem otherwise. This also works to reduce highmem
1231 size on bigger boxes.
1233 highres= [KNL] Enable/disable high resolution timer mode.
1234 Valid parameters: "on", "off"
1238 See Documentation/isdn/README.HiSax.
1242 hpet= [X86-32,HPET] option to control HPET usage
1243 Format: { enable (default) | disable | force |
1245 disable: disable HPET and use PIT instead
1246 force: allow force enabled of undocumented chips (ICH4,
1248 verbose: show contents of HPET registers during setup
1250 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1251 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1253 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1254 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1255 On x86-64 and powerpc, this option can be specified
1256 multiple times interleaved with hugepages= to reserve
1257 huge pages of different sizes. Valid pages sizes on
1258 x86-64 are 2M (when the CPU supports "pse") and 1G
1259 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1261 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1262 terminal devices. Valid values: 0..8
1263 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1264 If specified, z/VM IUCV HVC accepts connections
1265 from listed z/VM user IDs only.
1267 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1268 hardware thread id mappings.
1269 Format: <cpu>:<hwthread>
1272 Do not unregister boot console at start. This is only
1273 useful for debugging when something happens in the window
1274 between unregistering the boot console and initializing
1277 i2c_bus= [HW] Override the default board specific I2C bus speed
1278 or register an additional I2C bus that is not
1279 registered from board initialization code.
1283 i8042.debug [HW] Toggle i8042 debug mode
1284 i8042.direct [HW] Put keyboard port into non-translated mode
1285 i8042.dumbkbd [HW] Pretend that controller can only read data from
1286 keyboard and cannot control its state
1287 (Don't attempt to blink the leds)
1288 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1289 i8042.nokbd [HW] Don't check/create keyboard port
1290 i8042.noloop [HW] Disable the AUX Loopback command while probing
1292 i8042.nomux [HW] Don't check presence of an active multiplexing
1294 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1296 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1297 i8042.reset [HW] Reset the controller during init and cleanup
1298 i8042.unlock [HW] Unlock (ignore) the keylock
1299 i8042.kbdreset [HW] Reset device connected to KBD port
1303 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1304 indicates that the driver is running on unsupported
1306 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1307 does not match list of supported models.
1309 [HW] Report power status in /proc/i8k
1310 (disabled by default)
1311 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1314 i915.invert_brightness=
1315 [DRM] Invert the sense of the variable that is used to
1316 set the brightness of the panel backlight. Normally a
1317 brightness value of 0 indicates backlight switched off,
1318 and the maximum of the brightness value sets the backlight
1319 to maximum brightness. If this parameter is set to 0
1320 (default) and the machine requires it, or this parameter
1321 is set to 1, a brightness value of 0 sets the backlight
1322 to maximum brightness, and the maximum of the brightness
1323 value switches the backlight off.
1324 -1 -- never invert brightness
1325 0 -- machine default
1326 1 -- force brightness inversion
1329 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1331 ide-core.nodma= [HW] (E)IDE subsystem
1332 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1333 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1334 .cdrom .chs .ignore_cable are additional options
1335 See Documentation/ide/ide.txt.
1337 ide-generic.probe-mask= [HW] (E)IDE subsystem
1339 Probe mask for legacy ISA IDE ports. Depending on
1340 platform up to 6 ports are supported, enabled by
1341 setting corresponding bits in the mask to 1. The
1342 default value is 0x0, which has a special meaning.
1343 On systems that have PCI, it triggers scanning the
1344 PCI bus for the first and the second port, which
1345 are then probed. On systems without PCI the value
1346 of 0x0 enables probing the two first ports as if it
1349 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1350 Claim all unknown PCI IDE storage controllers.
1353 Format: idle=poll, idle=halt, idle=nomwait
1354 Poll forces a polling idle loop that can slightly
1355 improve the performance of waking up a idle CPU, but
1356 will use a lot of power and make the system run hot.
1358 idle=halt: Halt is forced to be used for CPU idle.
1359 In such case C2/C3 won't be used again.
1360 idle=nomwait: Disable mwait for CPU C-states
1362 ignore_loglevel [KNL]
1363 Ignore loglevel setting - this will print /all/
1364 kernel messages to the console. Useful for debugging.
1365 We also add it as printk module parameter, so users
1366 could change it dynamically, usually by
1367 /sys/module/printk/parameters/ignore_loglevel.
1369 ihash_entries= [KNL]
1370 Set number of hash buckets for inode cache.
1372 ima_appraise= [IMA] appraise integrity measurements
1373 Format: { "off" | "enforce" | "fix" | "log" }
1376 ima_appraise_tcb [IMA]
1377 The builtin appraise policy appraises all files
1381 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1385 The list of supported hash algorithms is defined
1386 in crypto/hash_info.h.
1389 Load a policy which meets the needs of the Trusted
1390 Computing Base. This means IMA will measure all
1391 programs exec'd, files mmap'd for exec, and all files
1392 opened for read by uid=0.
1395 Select one of defined IMA measurements template formats.
1396 Formats: { "ima" | "ima-ng" }
1400 [IMA] Define a custom template format.
1401 Format: { "field1|...|fieldN" }
1403 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1404 Format: <min_file_size>
1405 Set the minimal file size for using asynchronous hash.
1406 If left unspecified, ahash usage is disabled.
1408 ahash performance varies for different data sizes on
1409 different crypto accelerators. This option can be used
1410 to achieve the best performance for a particular HW.
1412 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1414 Set hashing buffer size. Default: 4k.
1416 ahash performance varies for different chunk sizes on
1417 different crypto accelerators. This option can be used
1418 to achieve best performance for particular HW.
1422 Run specified binary instead of /sbin/init as init
1425 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1426 for working out where the kernel is dying during
1429 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1430 initcall functions. Useful for debugging built-in
1431 modules and initcalls.
1433 initrd= [BOOT] Specify the location of the initial ramdisk
1435 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1438 int_pln_enable [x86] Enable power limit notification interrupt
1440 integrity_audit=[IMA]
1441 Format: { "0" | "1" }
1442 0 -- basic integrity auditing messages. (Default)
1443 1 -- additional integrity auditing messages.
1445 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1447 Enable intel iommu driver.
1449 Disable intel iommu driver.
1450 igfx_off [Default Off]
1451 By default, gfx is mapped as normal device. If a gfx
1452 device has a dedicated DMAR unit, the DMAR unit is
1453 bypassed by not enabling DMAR with this option. In
1454 this case, gfx device will use physical address for
1457 With this option iommu will not optimize to look
1458 for io virtual address below 32-bit forcing dual
1459 address cycle on pci bus for cards supporting greater
1460 than 32-bit addressing. The default is to look
1461 for translation below 32-bit and if not available
1462 then look in the higher range.
1463 strict [Default Off]
1464 With this option on every unmap_single operation will
1465 result in a hardware IOTLB flush operation as opposed
1466 to batching them for performance.
1467 sp_off [Default Off]
1468 By default, super page will be supported if Intel IOMMU
1469 has the capability. With this option, super page will
1472 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1473 0 disables intel_idle and fall back on acpi_idle.
1474 1 to 6 specify maximum depth of C-state.
1478 Do not enable intel_pstate as the default
1479 scaling driver for the supported processors
1481 Enable intel_pstate on systems that prohibit it by default
1482 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1483 instead of acpi-cpufreq may disable platform features, such
1484 as thermal controls and power capping, that rely on ACPI
1485 P-States information being indicated to OSPM and therefore
1486 should be used with caution. This option does not work with
1487 processors that aren't supported by the intel_pstate driver
1488 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1490 Do not enable hardware P state control (HWP)
1493 Only load intel_pstate on systems which support
1494 hardware P state control (HWP) if available.
1496 intremap= [X86-64, Intel-IOMMU]
1497 on enable Interrupt Remapping (default)
1498 off disable Interrupt Remapping
1499 nosid disable Source ID checking
1501 BIOS x2APIC opt-out request will be ignored
1503 iomem= Disable strict checking of access to MMIO memory
1504 strict regions from userspace.
1519 nobypass [PPC/POWERNV]
1520 Disable IOMMU bypass, using IOMMU for PCI devices.
1523 io7= [HW] IO7 for Marvel based alpha systems
1524 See comment before marvel_specify_io7 in
1525 arch/alpha/kernel/core_marvel.c.
1527 io_delay= [X86] I/O delay method
1529 Standard port 0x80 based delay
1531 Alternate port 0xed based delay (needed on some systems)
1533 Simple two microseconds delay
1538 See Documentation/filesystems/nfs/nfsroot.txt.
1541 When an interrupt is not handled search all handlers
1542 for it. Intended to get systems with badly broken
1546 When an interrupt is not handled search all handlers
1547 for it. Also check all handlers each timer
1548 interrupt. Intended to get systems with badly broken
1552 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1554 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1556 <cpu number>,...,<cpu number>
1558 <cpu number>-<cpu number>
1559 (must be a positive range in ascending order)
1561 <cpu number>,...,<cpu number>-<cpu number>
1563 This option can be used to specify one or more CPUs
1564 to isolate from the general SMP balancing and scheduling
1565 algorithms. You can move a process onto or off an
1566 "isolated" CPU via the CPU affinity syscalls or cpuset.
1567 <cpu number> begins at 0 and the maximum value is
1568 "number of CPUs in system - 1".
1570 This option is the preferred way to isolate CPUs. The
1571 alternative -- manually setting the CPU mask of all
1572 tasks in the system -- can cause problems and
1573 suboptimal load balancer performance.
1577 ivrs_ioapic [HW,X86_64]
1578 Provide an override to the IOAPIC-ID<->DEVICE-ID
1579 mapping provided in the IVRS ACPI table. For
1580 example, to map IOAPIC-ID decimal 10 to
1581 PCI device 00:14.0 write the parameter as:
1582 ivrs_ioapic[10]=00:14.0
1584 ivrs_hpet [HW,X86_64]
1585 Provide an override to the HPET-ID<->DEVICE-ID
1586 mapping provided in the IVRS ACPI table. For
1587 example, to map HPET-ID decimal 0 to
1588 PCI device 00:14.0 write the parameter as:
1589 ivrs_hpet[0]=00:14.0
1591 js= [HW,JOY] Analog joystick
1592 See Documentation/input/joystick.txt.
1595 Enable/disable kernel and module base offset ASLR
1596 (Address Space Layout Randomization) if built into
1597 the kernel. When CONFIG_HIBERNATION is selected,
1598 kASLR is disabled by default. When kASLR is enabled,
1599 hibernation will be disabled.
1603 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1604 specifies the amount of memory usable by the kernel
1605 for non-movable allocations. The requested amount is
1606 spread evenly throughout all nodes in the system. The
1607 remaining memory in each node is used for Movable
1608 pages. In the event, a node is too small to have both
1609 kernelcore and Movable pages, kernelcore pages will
1610 take priority and other nodes will have a larger number
1611 of Movable pages. The Movable zone is used for the
1612 allocation of pages that may be reclaimed or moved
1613 by the page migration subsystem. This means that
1614 HugeTLB pages may not be allocated from this zone.
1615 Note that allocations like PTEs-from-HighMem still
1616 use the HighMem zone if it exists, and the Normal
1617 zone if it does not.
1619 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1620 Format: <Controller#>[,poll interval]
1621 The controller # is the number of the ehci usb debug
1622 port as it is probed via PCI. The poll interval is
1623 optional and is the number seconds in between
1624 each poll cycle to the debug port in case you need
1625 the functionality for interrupting the kernel with
1626 gdb or control-c on the dbgp connection. When
1627 not using this parameter you use sysrq-g to break into
1628 the kernel debugger.
1630 kgdboc= [KGDB,HW] kgdb over consoles.
1631 Requires a tty driver that supports console polling,
1632 or a supported polling keyboard driver (non-usb).
1633 Serial only format: <serial_device>[,baud]
1634 keyboard only format: kbd
1635 keyboard and serial format: kbd,<serial_device>[,baud]
1636 Optional Kernel mode setting:
1637 kms, kbd format: kms,kbd
1638 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1640 kgdbwait [KGDB] Stop kernel execution and enter the
1641 kernel debugger at the earliest opportunity.
1643 kmac= [MIPS] korina ethernet MAC address.
1644 Configure the RouterBoard 532 series on-chip
1645 Ethernet adapter MAC address.
1647 kmemleak= [KNL] Boot-time kmemleak enable/disable
1648 Valid arguments: on, off
1650 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1653 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1654 Valid arguments: 0, 1, 2
1655 kmemcheck=0 (disabled)
1656 kmemcheck=1 (enabled)
1657 kmemcheck=2 (one-shot mode)
1658 Default: 2 (one-shot mode)
1660 kstack=N [X86] Print N words from the kernel stack
1663 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1664 Default is 0 (don't ignore, but inject #GP)
1666 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1670 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1671 Default is 1 (enabled)
1673 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1675 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1677 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1678 (virtualized MMU) support on capable Intel chips.
1679 Default is 1 (enabled)
1681 kvm-intel.emulate_invalid_guest_state=
1682 [KVM,Intel] Enable emulation of invalid guest states
1683 Default is 0 (disabled)
1685 kvm-intel.flexpriority=
1686 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1687 Default is 1 (enabled)
1690 [KVM,Intel] Enable VMX nesting (nVMX).
1691 Default is 0 (disabled)
1693 kvm-intel.unrestricted_guest=
1694 [KVM,Intel] Disable unrestricted guest feature
1695 (virtualized real and unpaged mode) on capable
1696 Intel chips. Default is 1 (enabled)
1698 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1699 feature (tagged TLBs) on capable Intel chips.
1700 Default is 1 (enabled)
1706 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1709 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1710 value for LAPIC timer one-shot implementation. Default
1711 back to the programmable timer unit in the LAPIC.
1713 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1716 libata.dma= [LIBATA] DMA control
1717 libata.dma=0 Disable all PATA and SATA DMA
1718 libata.dma=1 PATA and SATA Disk DMA only
1719 libata.dma=2 ATAPI (CDROM) DMA only
1720 libata.dma=4 Compact Flash DMA only
1721 Combinations also work, so libata.dma=3 enables DMA
1722 for disks and CDROMs, but not CFs.
1724 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1725 libata.ignore_hpa=0 keep BIOS limits (default)
1726 libata.ignore_hpa=1 ignore limits, using full disk
1728 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1732 libata.force= [LIBATA] Force configurations. The format is comma
1733 separated list of "[ID:]VAL" where ID is
1734 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1735 matching port, link or device. Basically, it matches
1736 the ATA ID string printed on console by libata. If
1737 the whole ID part is omitted, the last PORT and DEVICE
1738 values are used. If ID hasn't been specified yet, the
1739 configuration applies to all ports, links and devices.
1741 If only DEVICE is omitted, the parameter applies to
1742 the port and all links and devices behind it. DEVICE
1743 number of 0 either selects the first device or the
1744 first fan-out link behind PMP device. It does not
1745 select the host link. DEVICE number of 15 selects the
1746 host link and device attached to it.
1748 The VAL specifies the configuration to force. As long
1749 as there's no ambiguity shortcut notation is allowed.
1750 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1751 The following configurations can be forced.
1753 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1754 Any ID with matching PORT is used.
1756 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1758 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1759 udma[/][16,25,33,44,66,100,133] notation is also
1762 * [no]ncq: Turn on or off NCQ.
1764 * nohrst, nosrst, norst: suppress hard, soft
1767 * rstonce: only attempt one reset during
1768 hot-unplug link recovery
1770 * dump_id: dump IDENTIFY data.
1772 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1774 * disable: Disable this device.
1776 If there are multiple matching configurations changing
1777 the same attribute, the last one is used.
1779 memblock=debug [KNL] Enable memblock debug messages.
1781 load_ramdisk= [RAM] List of ramdisks to load from floppy
1782 See Documentation/blockdev/ramdisk.txt.
1784 lockd.nlm_grace_period=P [NFS] Assign grace period.
1787 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1790 lockd.nlm_timeout=T [NFS] Assign timeout value.
1793 lockd.nlm_udpport=M [NFS] Assign UDP port.
1796 locktorture.nreaders_stress= [KNL]
1797 Set the number of locking read-acquisition kthreads.
1798 Defaults to being automatically set based on the
1799 number of online CPUs.
1801 locktorture.nwriters_stress= [KNL]
1802 Set the number of locking write-acquisition kthreads.
1804 locktorture.onoff_holdoff= [KNL]
1805 Set time (s) after boot for CPU-hotplug testing.
1807 locktorture.onoff_interval= [KNL]
1808 Set time (s) between CPU-hotplug operations, or
1809 zero to disable CPU-hotplug testing.
1811 locktorture.shuffle_interval= [KNL]
1812 Set task-shuffle interval (jiffies). Shuffling
1813 tasks allows some CPUs to go into dyntick-idle
1814 mode during the locktorture test.
1816 locktorture.shutdown_secs= [KNL]
1817 Set time (s) after boot system shutdown. This
1818 is useful for hands-off automated testing.
1820 locktorture.stat_interval= [KNL]
1821 Time (s) between statistics printk()s.
1823 locktorture.stutter= [KNL]
1824 Time (s) to stutter testing, for example,
1825 specifying five seconds causes the test to run for
1826 five seconds, wait for five seconds, and so on.
1827 This tests the locking primitive's ability to
1828 transition abruptly to and from idle.
1830 locktorture.torture_runnable= [BOOT]
1831 Start locktorture running at boot time.
1833 locktorture.torture_type= [KNL]
1834 Specify the locking implementation to test.
1836 locktorture.verbose= [KNL]
1837 Enable additional printk() statements.
1839 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1842 loglevel= All Kernel Messages with a loglevel smaller than the
1843 console loglevel will be printed to the console. It can
1844 also be changed with klogd or other programs. The
1845 loglevels are defined as follows:
1847 0 (KERN_EMERG) system is unusable
1848 1 (KERN_ALERT) action must be taken immediately
1849 2 (KERN_CRIT) critical conditions
1850 3 (KERN_ERR) error conditions
1851 4 (KERN_WARNING) warning conditions
1852 5 (KERN_NOTICE) normal but significant condition
1853 6 (KERN_INFO) informational
1854 7 (KERN_DEBUG) debug-level messages
1856 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1857 in bytes. n must be a power of two and greater
1858 than the minimal size. The minimal size is defined
1859 by LOG_BUF_SHIFT kernel config parameter. There is
1860 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1861 that allows to increase the default size depending on
1862 the number of CPUs. See init/Kconfig for more details.
1864 logo.nologo [FB] Disables display of the built-in Linux logo.
1865 This may be used to provide more screen space for
1866 kernel log messages and is useful when debugging
1867 kernel boot problems.
1869 lp=0 [LP] Specify parallel ports to use, e.g,
1870 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1871 lp=reset first parallel port). 'lp=0' disables the
1872 lp=auto printer driver. 'lp=reset' (which can be
1873 specified in addition to the ports) causes
1874 attached printers to be reset. Using
1875 lp=port1,port2,... specifies the parallel ports
1876 to associate lp devices with, starting with
1877 lp0. A port specification may be 'none' to skip
1878 that lp device, or a parport name such as
1879 'parport0'. Specifying 'lp=auto' instead of a
1880 port specification list means that device IDs
1881 from each port should be examined, to see if
1882 an IEEE 1284-compliant printer is attached; if
1883 so, the driver will manage that printer.
1884 See also header of drivers/char/lp.c.
1887 Sets loops_per_jiffy to given constant, thus avoiding
1888 time-consuming boot-time autodetection (up to 250 ms per
1889 CPU). 0 enables autodetection (default). To determine
1890 the correct value for your kernel, boot with normal
1891 autodetection and see what value is printed. Note that
1892 on SMP systems the preset will be applied to all CPUs,
1893 which is likely to cause problems if your CPUs need
1894 significantly divergent settings. An incorrect value
1895 will cause delays in the kernel to be wrong, leading to
1896 unpredictable I/O errors and other breakage. Although
1897 unlikely, in the extreme case this might damage your
1901 Format: <io>,<irq>,<dma>
1903 machvec= [IA-64] Force the use of a particular machine-vector
1904 (machvec) in a generic kernel.
1905 Example: machvec=hpzx1_swiotlb
1907 machtype= [Loongson] Share the same kernel image file between different
1909 Example: machtype=lemote-yeeloong-2f-7inch
1911 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1912 than or equal to this physical address is ignored.
1914 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1915 should make use of. maxcpus=n : n >= 0 limits the
1916 kernel to using 'n' processors. n=0 is a special case,
1917 it is equivalent to "nosmp", which also disables
1920 max_loop= [LOOP] The number of loop block devices that get
1921 (loop.max_loop) unconditionally pre-created at init time. The default
1922 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1923 of statically allocating a predefined number, loop
1924 devices can be requested on-demand with the
1925 /dev/loop-control interface.
1927 mce [X86-32] Machine Check Exception
1929 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1931 md= [HW] RAID subsystems devices and level
1932 See Documentation/md.txt.
1935 Format: <first>,<last>
1936 Specifies range of consoles to be captured by the MDA.
1938 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1939 Amount of memory to be used when the kernel is not able
1940 to see the whole system memory or for test.
1941 [X86] Work as limiting max address. Use together
1942 with memmap= to avoid physical address space collisions.
1943 Without memmap= PCI devices could be placed at addresses
1944 belonging to unused RAM.
1946 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1950 [KNL,SH] Allow user to override the default size for
1951 per-device physically contiguous DMA buffers.
1953 memmap=exactmap [KNL,X86] Enable setting of an exact
1954 E820 memory map, as specified by the user.
1955 Such memmap=exactmap lines can be constructed based on
1956 BIOS output or other requirements. See the memmap=nn@ss
1959 memmap=nn[KMG]@ss[KMG]
1960 [KNL] Force usage of a specific region of memory.
1961 Region of memory to be used is from ss to ss+nn.
1963 memmap=nn[KMG]#ss[KMG]
1964 [KNL,ACPI] Mark specific memory as ACPI data.
1965 Region of memory to be marked is from ss to ss+nn.
1967 memmap=nn[KMG]$ss[KMG]
1968 [KNL,ACPI] Mark specific memory as reserved.
1969 Region of memory to be reserved is from ss to ss+nn.
1970 Example: Exclude memory from 0x18690000-0x1869ffff
1971 memmap=64K$0x18690000
1973 memmap=0x10000$0x18690000
1975 memmap=nn[KMG]!ss[KMG]
1976 [KNL,X86] Mark specific memory as protected.
1977 Region of memory to be used, from ss to ss+nn.
1978 The memory region may be marked as e820 type 12 (0xc)
1979 and is NVDIMM or ADR memory.
1981 memory_corruption_check=0/1 [X86]
1982 Some BIOSes seem to corrupt the first 64k of
1983 memory when doing things like suspend/resume.
1984 Setting this option will scan the memory
1985 looking for corruption. Enabling this will
1986 both detect corruption and prevent the kernel
1987 from using the memory being corrupted.
1988 However, its intended as a diagnostic tool; if
1989 repeatable BIOS-originated corruption always
1990 affects the same memory, you can use memmap=
1991 to prevent the kernel from using that memory.
1993 memory_corruption_check_size=size [X86]
1994 By default it checks for corruption in the low
1995 64k, making this memory unavailable for normal
1996 use. Use this parameter to scan for
1997 corruption in more or less memory.
1999 memory_corruption_check_period=seconds [X86]
2000 By default it checks for corruption every 60
2001 seconds. Use this parameter to check at some
2002 other rate. 0 disables periodic checking.
2004 memtest= [KNL,X86,ARM] Enable memtest
2006 default : 0 <disable>
2007 Specifies the number of memtest passes to be
2008 performed. Each pass selects another test
2009 pattern from a given set of patterns. Memtest
2010 fills the memory with this pattern, validates
2011 memory contents and reserves bad memory
2012 regions that are detected.
2014 meye.*= [HW] Set MotionEye Camera parameters
2015 See Documentation/video4linux/meye.txt.
2017 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2018 Multi-Function General Purpose Timers on AMD Geode
2021 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2022 the BIOS has incorrectly applied a workaround. TinyBIOS
2023 version 0.98 is known to be affected, 0.99 fixes the
2024 problem by letting the user disable the workaround.
2028 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2029 physical address is ignored.
2031 mini2440= [ARM,HW,KNL]
2032 Format:[0..2][b][c][t]
2034 MINI2440 configuration specification:
2035 0 - The attached screen is the 3.5" TFT
2036 1 - The attached screen is the 7" TFT
2037 2 - The VGA Shield is attached (1024x768)
2038 Leaving out the screen size parameter will not load
2039 the TFT driver, and the framebuffer will be left
2041 b - Enable backlight. The TFT backlight pin will be
2042 linked to the kernel VESA blanking code and a GPIO
2043 LED. This parameter is not necessary when using the
2045 c - Enable the s3c camera interface.
2046 t - Reserved for enabling touchscreen support. The
2047 touchscreen support is not enabled in the mainstream
2048 kernel as of 2.6.30, a preliminary port can be found
2049 in the "bleeding edge" mini2440 support kernel at
2050 http://repo.or.cz/w/linux-2.6/mini2440.git
2053 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2054 parameter allows control of the logging verbosity for
2055 the additional memory initialisation checks. A value
2056 of 0 disables mminit logging and a level of 4 will
2057 log everything. Information is printed at KERN_DEBUG
2058 so loglevel=8 may also need to be specified.
2061 [KNL] When CONFIG_MODULE_SIG is set, this means that
2062 modules without (valid) signatures will fail to load.
2063 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2064 is always true, so this option does nothing.
2067 [MOUSE] Maximum time between finger touching and
2068 leaving touchpad surface for touch to be considered
2069 a tap and be reported as a left button click (for
2070 touchpads working in absolute mode only).
2072 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2073 reporting absolute coordinates, such as tablets
2074 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2075 reporting absolute coordinates, such as tablets
2077 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2078 is similar to kernelcore except it specifies the
2079 amount of memory used for migratable allocations.
2080 If both kernelcore and movablecore is specified,
2081 then kernelcore will be at *least* the specified
2082 value but may be more. If movablecore on its own
2083 is specified, the administrator must be careful
2084 that the amount of memory usable for all allocations
2087 movable_node [KNL,X86] Boot-time switch to enable the effects
2088 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2090 MTD_Partition= [MTD]
2091 Format: <name>,<region-number>,<size>,<offset>
2093 MTD_Region= [MTD] Format:
2094 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2097 See drivers/mtd/cmdlinepart.c.
2099 multitce=off [PPC] This parameter disables the use of the pSeries
2100 firmware feature for updating multiple TCE entries
2103 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2105 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2107 boundary - index of last SLC block on Flex-OneNAND.
2108 The remaining blocks are configured as MLC blocks.
2109 lock - Configure if Flex-OneNAND boundary should be locked.
2110 Once locked, the boundary cannot be changed.
2111 1 indicates lock status, 0 indicates unlock status.
2114 ARM/S3C2412 JIVE boot control
2116 See arch/arm/mach-s3c2412/mach-jive.c
2118 mtouchusb.raw_coordinates=
2119 [HW] Make the MicroTouch USB driver use raw coordinates
2120 ('y', default) or cooked coordinates ('n')
2122 mtrr_chunk_size=nn[KMG] [X86]
2123 used for mtrr cleanup. It is largest continuous chunk
2124 that could hold holes aka. UC entries.
2126 mtrr_gran_size=nn[KMG] [X86]
2127 Used for mtrr cleanup. It is granularity of mtrr block.
2129 Large value could prevent small alignment from
2132 mtrr_spare_reg_nr=n [X86]
2134 Range: 0,7 : spare reg number
2136 Used for mtrr cleanup. It is spare mtrr entries number.
2137 Set to 2 or more if your graphical card needs more.
2139 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2141 netdev= [NET] Network devices parameters
2142 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2143 Note that mem_start is often overloaded to mean
2144 something different and driver-specific.
2145 This usage is only documented in each driver source
2149 [NETFILTER] Enable connection tracking flow accounting
2150 0 to disable accounting
2151 1 to enable accounting
2154 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2155 See Documentation/filesystems/nfs/nfsroot.txt.
2157 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2158 See Documentation/filesystems/nfs/nfsroot.txt.
2160 nfsrootdebug [NFS] enable nfsroot debugging messages.
2161 See Documentation/filesystems/nfs/nfsroot.txt.
2163 nfs.callback_tcpport=
2164 [NFS] set the TCP port on which the NFSv4 callback
2165 channel should listen.
2168 [NFS] sets the pathname to the program which is used
2169 to update the NFS client cache entries.
2171 nfs.cache_getent_timeout=
2172 [NFS] sets the timeout after which an attempt to
2173 update a cache entry is deemed to have failed.
2175 nfs.idmap_cache_timeout=
2176 [NFS] set the maximum lifetime for idmapper cache
2180 [NFS] enable 64-bit inode numbers.
2181 If zero, the NFS client will fake up a 32-bit inode
2182 number for the readdir() and stat() syscalls instead
2183 of returning the full 64-bit number.
2184 The default is to return 64-bit inode numbers.
2186 nfs.max_session_slots=
2187 [NFSv4.1] Sets the maximum number of session slots
2188 the client will attempt to negotiate with the server.
2189 This limits the number of simultaneous RPC requests
2190 that the client can send to the NFSv4.1 server.
2191 Note that there is little point in setting this
2192 value higher than the max_tcp_slot_table_limit.
2194 nfs.nfs4_disable_idmapping=
2195 [NFSv4] When set to the default of '1', this option
2196 ensures that both the RPC level authentication
2197 scheme and the NFS level operations agree to use
2198 numeric uids/gids if the mount is using the
2199 'sec=sys' security flavour. In effect it is
2200 disabling idmapping, which can make migration from
2201 legacy NFSv2/v3 systems to NFSv4 easier.
2202 Servers that do not support this mode of operation
2203 will be autodetected by the client, and it will fall
2204 back to using the idmapper.
2205 To turn off this behaviour, set the value to '0'.
2207 [NFS4] Specify an additional fixed unique ident-
2208 ification string that NFSv4 clients can insert into
2209 their nfs_client_id4 string. This is typically a
2210 UUID that is generated at system install time.
2212 nfs.send_implementation_id =
2213 [NFSv4.1] Send client implementation identification
2214 information in exchange_id requests.
2215 If zero, no implementation identification information
2217 The default is to send the implementation identification
2220 nfs.recover_lost_locks =
2221 [NFSv4] Attempt to recover locks that were lost due
2222 to a lease timeout on the server. Please note that
2223 doing this risks data corruption, since there are
2224 no guarantees that the file will remain unchanged
2225 after the locks are lost.
2226 If you want to enable the kernel legacy behaviour of
2227 attempting to recover these locks, then set this
2229 The default parameter value of '0' causes the kernel
2230 not to attempt recovery of lost locks.
2232 nfsd.nfs4_disable_idmapping=
2233 [NFSv4] When set to the default of '1', the NFSv4
2234 server will return only numeric uids and gids to
2235 clients using auth_sys, and will accept numeric uids
2236 and gids from such clients. This is intended to ease
2237 migration from NFSv2/v3.
2239 objlayoutdriver.osd_login_prog=
2240 [NFS] [OBJLAYOUT] sets the pathname to the program which
2241 is used to automatically discover and login into new
2242 osd-targets. Please see:
2243 Documentation/filesystems/pnfs.txt for more explanations
2245 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2246 when a NMI is triggered.
2247 Format: [state][,regs][,debounce][,die]
2249 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2250 Format: [panic,][nopanic,][num]
2252 0 - turn nmi_watchdog off
2253 1 - turn nmi_watchdog on
2254 When panic is specified, panic when an NMI watchdog
2255 timeout occurs (or 'nopanic' to override the opposite
2257 This is useful when you use a panic=... timeout and
2258 need the box quickly up again.
2260 netpoll.carrier_timeout=
2261 [NET] Specifies amount of time (in seconds) that
2262 netpoll should wait for a carrier. By default netpoll
2265 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2266 emulation library even if a 387 maths coprocessor
2270 [HW] Never suspend the console
2271 Disable suspending of consoles during suspend and
2272 hibernate operations. Once disabled, debugging
2273 messages can reach various consoles while the rest
2274 of the system is being put to sleep (ie, while
2275 debugging driver suspend/resume hooks). This may
2276 not work reliably with all consoles, but is known
2277 to work with serial and VGA consoles.
2278 To facilitate more flexible debugging, we also add
2279 console_suspend, a printk module parameter to control
2280 it. Users could use console_suspend (usually
2281 /sys/module/printk/parameters/console_suspend) to
2282 turn on/off it dynamically.
2284 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2285 caches in the slab allocator. Saves per-node memory,
2286 but will impact performance.
2290 noapic [SMP,APIC] Tells the kernel to not make use of any
2291 IOAPICs that may be present in the system.
2293 noautogroup Disable scheduler automatic task group creation.
2295 nobats [PPC] Do not use BATs for mapping kernel lowmem
2296 on "Classic" PPC cores.
2300 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2302 nodelayacct [KNL] Disable per-task delay accounting
2304 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2306 nodsp [SH] Disable hardware DSP at boot time.
2308 noefi Disable EFI runtime services support.
2313 On X86-32 available only on PAE configured kernels.
2314 noexec=on: enable non-executable mappings (default)
2315 noexec=off: disable non-executable mappings
2318 Disable SMAP (Supervisor Mode Access Prevention)
2319 even if it is supported by processor.
2322 Disable SMEP (Supervisor Mode Execution Prevention)
2323 even if it is supported by processor.
2326 This affects only 32-bit executables.
2327 noexec32=on: enable non-executable mappings (default)
2328 read doesn't imply executable mappings
2329 noexec32=off: disable non-executable mappings
2330 read implies executable mappings
2332 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2334 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2335 register save and restore. The kernel will only save
2336 legacy floating-point registers on task switch.
2338 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2340 noxsave [BUGS=X86] Disables x86 extended register state save
2341 and restore using xsave. The kernel will fallback to
2342 enabling legacy floating-point and sse state.
2344 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2345 register states. The kernel will fall back to use
2346 xsave to save the states. By using this parameter,
2347 performance of saving the states is degraded because
2348 xsave doesn't support modified optimization while
2349 xsaveopt supports it on xsaveopt enabled systems.
2351 noxsaves [X86] Disables xsaves and xrstors used in saving and
2352 restoring x86 extended register state in compacted
2353 form of xsave area. The kernel will fall back to use
2354 xsaveopt and xrstor to save and restore the states
2355 in standard form of xsave area. By using this
2356 parameter, xsave area per process might occupy more
2357 memory on xsaves enabled systems.
2359 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2360 wfi(ARM) instruction doesn't work correctly and not to
2361 use it. This is also useful when using JTAG debugger.
2363 no_file_caps Tells the kernel not to honor file capabilities. The
2364 only way then for a file to be executed with privilege
2365 is to be setuid root or executed by root.
2367 nohalt [IA-64] Tells the kernel not to use the power saving
2368 function PAL_HALT_LIGHT when idle. This increases
2369 power-consumption. On the positive side, it reduces
2370 interrupt wake-up latency, which may improve performance
2371 in certain environments such as networked servers or
2374 nohibernate [HIBERNATION] Disable hibernation and resume.
2376 nohz= [KNL] Boottime enable/disable dynamic ticks
2377 Valid arguments: on, off
2380 nohz_full= [KNL,BOOT]
2381 In kernels built with CONFIG_NO_HZ_FULL=y, set
2382 the specified list of CPUs whose tick will be stopped
2383 whenever possible. The boot CPU will be forced outside
2384 the range to maintain the timekeeping.
2385 The CPUs in this range must also be included in the
2388 noiotrap [SH] Disables trapped I/O port accesses.
2390 noirqdebug [X86-32] Disables the code which attempts to detect and
2391 disable unhandled interrupt sources.
2393 no_timer_check [X86,APIC] Disables the code which tests for
2394 broken timer IRQ sources.
2396 noisapnp [ISAPNP] Disables ISA PnP code.
2398 noinitrd [RAM] Tells the kernel not to load any configured
2401 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2403 [Deprecated - use intremap=off]
2407 nojitter [IA-64] Disables jitter checking for ITC timers.
2409 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2411 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2414 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2415 steal time is computed, but won't influence scheduler
2418 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2420 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2422 noltlbs [PPC] Do not use large page/tlb entries for kernel
2423 lowmem mapping on PPC40x.
2425 nomca [IA-64] Disable machine check abort handling
2427 nomce [X86-32] Machine Check Exception
2429 nomfgpt [X86-32] Disable Multi-Function General Purpose
2430 Timer usage (for AMD Geode machines).
2432 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2433 shutdown the other cpus. Instead use the REBOOT_VECTOR
2436 nomodule Disable module load
2438 nopat [X86] Disable PAT (page attribute table extension of
2439 pagetables) support.
2441 norandmaps Don't use address space randomization. Equivalent to
2442 echo 0 > /proc/sys/kernel/randomize_va_space
2444 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2446 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2447 with UP alternatives
2449 nordrand [X86] Disable kernel use of the RDRAND and
2450 RDSEED instructions even if they are supported
2451 by the processor. RDRAND and RDSEED are still
2452 available to user space applications.
2454 noresume [SWSUSP] Disables resume and restores original swap
2457 no-scroll [VGA] Disables scrollback.
2458 This is required for the Braillex ib80-piezo Braille
2459 reader made by F.H. Papenmeier (Germany).
2463 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2465 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2466 and disable the IO APIC. legacy for "maxcpus=0".
2468 nosoftlockup [KNL] Disable the soft-lockup detector.
2470 nosync [HW,M68K] Disables sync negotiation for all devices.
2472 notsc [BUGS=X86-32] Disable Time Stamp Counter
2474 nousb [USB] Disable the USB subsystem
2476 nowatchdog [KNL] Disable both lockup detectors, i.e.
2477 soft-lockup and NMI watchdog (hard-lockup).
2481 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2483 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2484 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2485 Some features depend on CPU0. Known dependencies are:
2486 1. Resume from suspend/hibernate depends on CPU0.
2487 Suspend/hibernate will fail if CPU0 is offline and you
2488 need to online CPU0 before suspend/hibernate.
2489 2. PIC interrupts also depend on CPU0. CPU0 can't be
2490 removed if a PIC interrupt is detected.
2491 It's said poweroff/reboot may depend on CPU0 on some
2492 machines although I haven't seen such issues so far
2493 after CPU0 is offline on a few tested machines.
2494 If the dependencies are under your control, you can
2495 turn on cpu0_hotplug.
2497 nptcg= [IA-64] Override max number of concurrent global TLB
2498 purges which is reported from either PAL_VM_SUMMARY or
2501 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2502 could support. nr_cpus=n : n >= 1 limits the kernel to
2503 supporting 'n' processors. Later in runtime you can not
2504 use hotplug cpu feature to put more cpu back to online.
2505 just like you compile the kernel NR_CPUS=n
2507 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2509 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2510 Allowed values are enable and disable
2512 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2513 one of ['zone', 'node', 'default'] can be specified
2514 This can be set from sysctl after boot.
2515 See Documentation/sysctl/vm.txt for details.
2517 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2518 See Documentation/debugging-via-ohci1394.txt for more
2521 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2522 Rather than timing out after 20 ms if an EC
2523 command is not properly ACKed, override the length
2524 of the timeout. We have interrupts disabled while
2525 waiting for the ACK, so if this is set too high
2526 interrupts *may* be lost!
2528 omap_mux= [OMAP] Override bootloader pin multiplexing.
2529 Format: <mux_mode0.mode_name=value>...
2530 For example, to override I2C bus2:
2531 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2533 oprofile.timer= [HW]
2534 Use timer interrupt instead of performance counters
2536 oprofile.cpu_type= Force an oprofile cpu type
2537 This might be useful if you have an older oprofile
2538 userland or if you want common events.
2539 Format: { arch_perfmon }
2540 arch_perfmon: [X86] Force use of architectural
2541 perfmon on Intel CPUs instead of the
2542 CPU specific event set.
2543 timer: [X86] Force use of architectural NMI
2544 timer mode (see also oprofile.timer
2545 for generic hr timer mode)
2546 [s390] Force legacy basic mode sampling
2547 (report cpu_type "timer")
2549 oops=panic Always panic on oopses. Default is to just kill the
2550 process, but there is a small probability of
2551 deadlocking the machine.
2552 This will also cause panics on machine check exceptions.
2553 Useful together with panic=30 to trigger a reboot.
2556 See Documentation/sound/oss/oss-parameters.txt
2558 page_owner= [KNL] Boot-time page_owner enabling option.
2559 Storage of the information about who allocated
2560 each page is disabled in default. With this switch,
2562 on: enable the feature
2564 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2565 timeout > 0: seconds before rebooting
2566 timeout = 0: wait forever
2567 timeout < 0: reboot immediately
2570 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2573 crash_kexec_post_notifiers
2574 Run kdump after running panic-notifiers and dumping
2575 kmsg. This only for the users who doubt kdump always
2576 succeeds in any situation.
2577 Note that this also increases risks of kdump failure,
2578 because some panic notifiers can make the crashed
2579 kernel more unstable.
2581 parkbd.port= [HW] Parallel port number the keyboard adapter is
2582 connected to, default is 0.
2584 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2585 0 for XT, 1 for AT (default is AT).
2588 parport= [HW,PPT] Specify parallel ports. 0 disables.
2589 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2590 Use 'auto' to force the driver to use any
2591 IRQ/DMA settings detected (the default is to
2592 ignore detected IRQ/DMA settings because of
2593 possible conflicts). You can specify the base
2594 address, IRQ, and DMA settings; IRQ and DMA
2595 should be numbers, or 'auto' (for using detected
2596 settings on that particular port), or 'nofifo'
2597 (to avoid using a FIFO even if it is detected).
2598 Parallel ports are assigned in the order they
2599 are specified on the command line, starting
2602 parport_init_mode= [HW,PPT]
2603 Configure VIA parallel port to operate in
2604 a specific mode. This is necessary on Pegasos
2605 computer where firmware has no options for setting
2606 up parallel port mode and sets it to spp.
2607 Currently this function knows 686a and 8231 chips.
2608 Format: [spp|ps2|epp|ecp|ecpepp]
2611 Halt all CPUs after the first oops has been printed for
2612 the specified number of seconds. This is to be used if
2613 your oopses keep scrolling off the screen.
2618 See header of drivers/block/paride/pcd.c.
2619 See also Documentation/blockdev/paride.txt.
2621 pci=option[,option...] [PCI] various PCI subsystem options:
2622 earlydump [X86] dump PCI config space before the kernel
2624 off [X86] don't probe for the PCI bus
2625 bios [X86-32] force use of PCI BIOS, don't access
2626 the hardware directly. Use this if your machine
2627 has a non-standard PCI host bridge.
2628 nobios [X86-32] disallow use of PCI BIOS, only direct
2629 hardware access methods are allowed. Use this
2630 if you experience crashes upon bootup and you
2631 suspect they are caused by the BIOS.
2632 conf1 [X86] Force use of PCI Configuration
2634 conf2 [X86] Force use of PCI Configuration
2636 noaer [PCIE] If the PCIEAER kernel config parameter is
2637 enabled, this kernel boot option can be used to
2638 disable the use of PCIE advanced error reporting.
2639 nodomains [PCI] Disable support for multiple PCI
2640 root domains (aka PCI segments, in ACPI-speak).
2641 nommconf [X86] Disable use of MMCONFIG for PCI
2643 check_enable_amd_mmconf [X86] check for and enable
2644 properly configured MMIO access to PCI
2645 config space on AMD family 10h CPU
2646 nomsi [MSI] If the PCI_MSI kernel config parameter is
2647 enabled, this kernel boot option can be used to
2648 disable the use of MSI interrupts system-wide.
2649 noioapicquirk [APIC] Disable all boot interrupt quirks.
2650 Safety option to keep boot IRQs enabled. This
2651 should never be necessary.
2652 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2653 primary IO-APIC for bridges that cannot disable
2654 boot IRQs. This fixes a source of spurious IRQs
2655 when the system masks IRQs.
2656 noioapicreroute [APIC] Disable workaround that uses the
2657 boot IRQ equivalent of an IRQ that connects to
2658 a chipset where boot IRQs cannot be disabled.
2659 The opposite of ioapicreroute.
2660 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2661 routing table. These calls are known to be buggy
2662 on several machines and they hang the machine
2663 when used, but on other computers it's the only
2664 way to get the interrupt routing table. Try
2665 this option if the kernel is unable to allocate
2666 IRQs or discover secondary PCI buses on your
2668 rom [X86] Assign address space to expansion ROMs.
2669 Use with caution as certain devices share
2670 address decoders between ROMs and other
2672 norom [X86] Do not assign address space to
2673 expansion ROMs that do not already have
2674 BIOS assigned address ranges.
2675 nobar [X86] Do not assign address space to the
2676 BARs that weren't assigned by the BIOS.
2677 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2678 assigned automatically to PCI devices. You can
2679 make the kernel exclude IRQs of your ISA cards
2681 pirqaddr=0xAAAAA [X86] Specify the physical address
2682 of the PIRQ table (normally generated
2683 by the BIOS) if it is outside the
2684 F0000h-100000h range.
2685 lastbus=N [X86] Scan all buses thru bus #N. Can be
2686 useful if the kernel is unable to find your
2687 secondary buses and you want to tell it
2688 explicitly which ones they are.
2689 assign-busses [X86] Always assign all PCI bus
2690 numbers ourselves, overriding
2691 whatever the firmware may have done.
2692 usepirqmask [X86] Honor the possible IRQ mask stored
2693 in the BIOS $PIR table. This is needed on
2694 some systems with broken BIOSes, notably
2695 some HP Pavilion N5400 and Omnibook XE3
2696 notebooks. This will have no effect if ACPI
2697 IRQ routing is enabled.
2698 noacpi [X86] Do not use ACPI for IRQ routing
2699 or for PCI scanning.
2700 use_crs [X86] Use PCI host bridge window information
2701 from ACPI. On BIOSes from 2008 or later, this
2702 is enabled by default. If you need to use this,
2703 please report a bug.
2704 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2705 If you need to use this, please report a bug.
2706 routeirq Do IRQ routing for all PCI devices.
2707 This is normally done in pci_enable_device(),
2708 so this option is a temporary workaround
2709 for broken drivers that don't call it.
2710 skip_isa_align [X86] do not align io start addr, so can
2711 handle more pci cards
2712 firmware [ARM] Do not re-enumerate the bus but instead
2713 just use the configuration from the
2714 bootloader. This is currently used on
2715 IXP2000 systems where the bus has to be
2716 configured a certain way for adjunct CPUs.
2717 noearly [X86] Don't do any early type 1 scanning.
2718 This might help on some broken boards which
2719 machine check when some devices' config space
2720 is read. But various workarounds are disabled
2721 and some IOMMU drivers will not work.
2722 bfsort Sort PCI devices into breadth-first order.
2723 This sorting is done to get a device
2724 order compatible with older (<= 2.4) kernels.
2725 nobfsort Don't sort PCI devices into breadth-first order.
2726 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2727 tuning and use the BIOS-configured MPS defaults.
2728 pcie_bus_safe Set every device's MPS to the largest value
2729 supported by all devices below the root complex.
2730 pcie_bus_perf Set device MPS to the largest allowable MPS
2731 based on its parent bus. Also set MRRS (Max
2732 Read Request Size) to the largest supported
2733 value (no larger than the MPS that the device
2734 or bus can support) for best performance.
2735 pcie_bus_peer2peer Set every device's MPS to 128B, which
2736 every device is guaranteed to support. This
2737 configuration allows peer-to-peer DMA between
2738 any pair of devices, possibly at the cost of
2739 reduced performance. This also guarantees
2740 that hot-added devices will work.
2741 cbiosize=nn[KMG] The fixed amount of bus space which is
2742 reserved for the CardBus bridge's IO window.
2743 The default value is 256 bytes.
2744 cbmemsize=nn[KMG] The fixed amount of bus space which is
2745 reserved for the CardBus bridge's memory
2746 window. The default value is 64 megabytes.
2749 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2750 Specifies alignment and device to reassign
2751 aligned memory resources.
2752 If <order of align> is not specified,
2753 PAGE_SIZE is used as alignment.
2754 PCI-PCI bridge can be specified, if resource
2755 windows need to be expanded.
2756 ecrc= Enable/disable PCIe ECRC (transaction layer
2757 end-to-end CRC checking).
2758 bios: Use BIOS/firmware settings. This is the
2762 hpiosize=nn[KMG] The fixed amount of bus space which is
2763 reserved for hotplug bridge's IO window.
2764 Default size is 256 bytes.
2765 hpmemsize=nn[KMG] The fixed amount of bus space which is
2766 reserved for hotplug bridge's memory window.
2767 Default size is 2 megabytes.
2768 realloc= Enable/disable reallocating PCI bridge resources
2769 if allocations done by BIOS are too small to
2770 accommodate resources required by all child
2772 off: Turn realloc off
2774 realloc same as realloc=on
2775 noari do not use PCIe ARI.
2776 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2777 only look for one device below a PCIe downstream
2780 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2783 force Enable ASPM even on devices that claim not to support it.
2784 WARNING: Forcing ASPM on may cause system lockups.
2786 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2787 nomsi Do not use MSI for PCI Express Native Hotplug (this
2788 makes all PCIe ports use INTx for hotplug services).
2790 pcie_ports= [PCIE] PCIe ports handling:
2791 auto Ask the BIOS whether or not to use native PCIe services
2792 associated with PCIe ports (PME, hot-plug, AER). Use
2793 them only if that is allowed by the BIOS.
2794 native Use native PCIe services associated with PCIe ports
2796 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2799 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2800 nomsi Do not use MSI for native PCIe PME signaling (this makes
2801 all PCIe root ports use INTx for all services).
2803 pcmv= [HW,PCMCIA] BadgePAD 4
2807 Keep all power-domains already enabled by bootloader on,
2808 even if no driver has claimed them. This is useful
2809 for debug and development, but should not be
2810 needed on a platform with proper driver support.
2813 See Documentation/blockdev/paride.txt.
2815 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2818 See arch/parisc/kernel/pdc_chassis.c
2820 percpu_alloc= Select which percpu first chunk allocator to use.
2821 Currently supported values are "embed" and "page".
2822 Archs may support subset or none of the selections.
2823 See comments in mm/percpu.c for details on each
2824 allocator. This parameter is primarily for debugging
2825 and performance comparison.
2828 See Documentation/blockdev/paride.txt.
2831 See Documentation/blockdev/paride.txt.
2833 pirq= [SMP,APIC] Manual mp-table setup
2834 See Documentation/x86/i386/IO-APIC.txt.
2836 plip= [PPT,NET] Parallel port network link
2837 Format: { parport<nr> | timid | 0 }
2838 See also Documentation/parport.txt.
2840 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2841 Override pmtimer IOPort with a hex value.
2845 Enable PNP debug messages (depends on the
2846 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2847 via /sys/module/pnp/parameters/debug. We always show
2848 current resource usage; turning this on also shows
2849 possible settings and some assignment information.
2855 { on | off | curr | res | no-curr | no-res }
2858 [ISAPNP] Exclude IRQs for the autoconfiguration
2861 [ISAPNP] Exclude DMAs for the autoconfiguration
2863 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2864 Ranges are in pairs (I/O port base and size).
2867 [ISAPNP] Exclude memory regions for the
2869 Ranges are in pairs (memory base and size).
2871 ports= [IP_VS_FTP] IPVS ftp helper module
2873 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2875 Format: <port>,<port>....
2877 print-fatal-signals=
2878 [KNL] debug: print fatal signals
2880 If enabled, warn about various signal handling
2881 related application anomalies: too many signals,
2882 too many POSIX.1 timers, fatal signals causing a
2885 If you hit the warning due to signal overflow,
2886 you might want to try "ulimit -i unlimited".
2890 printk.always_kmsg_dump=
2891 Trigger kmsg_dump for cases other than kernel oops or
2893 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2896 printk.time= Show timing data prefixed to each printk message line
2897 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2899 processor.max_cstate= [HW,ACPI]
2900 Limit processor to maximum C-state
2901 max_cstate=9 overrides any DMI blacklist limit.
2903 processor.nocst [HW,ACPI]
2904 Ignore the _CST method to determine C-states,
2905 instead using the legacy FADT method
2907 profile= [KNL] Enable kernel profiling via /proc/profile
2908 Format: [schedule,]<number>
2909 Param: "schedule" - profile schedule points.
2910 Param: <number> - step/bucket size as a power of 2 for
2911 statistical time based profiling.
2912 Param: "sleep" - profile D-state sleeping (millisecs).
2913 Requires CONFIG_SCHEDSTATS
2914 Param: "kvm" - profile VM exits.
2916 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2918 See Documentation/blockdev/ramdisk.txt.
2920 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2921 probe for; one of (bare|imps|exps|lifebook|any).
2922 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2924 psmouse.resetafter= [HW,MOUSE]
2925 Try to reset the device after so many bad packets
2928 [HW,MOUSE] Set desired mouse resolution, in dpi.
2929 psmouse.smartscroll=
2930 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2931 0 = disabled, 1 = enabled (default).
2933 pstore.backend= Specify the name of the pstore backend to use
2936 See Documentation/blockdev/paride.txt.
2939 [KNL] Number of legacy pty's. Overwrites compiled-in
2942 quiet [KNL] Disable most log messages
2947 See Documentation/md.txt.
2949 ramdisk_blocksize= [RAM]
2950 See Documentation/blockdev/ramdisk.txt.
2952 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2953 See Documentation/blockdev/ramdisk.txt.
2956 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2957 the specified list of CPUs to be no-callback CPUs.
2958 Invocation of these CPUs' RCU callbacks will
2959 be offloaded to "rcuox/N" kthreads created for
2960 that purpose, where "x" is "b" for RCU-bh, "p"
2961 for RCU-preempt, and "s" for RCU-sched, and "N"
2962 is the CPU number. This reduces OS jitter on the
2963 offloaded CPUs, which can be useful for HPC and
2964 real-time workloads. It can also improve energy
2965 efficiency for asymmetric multiprocessors.
2968 Rather than requiring that offloaded CPUs
2969 (specified by rcu_nocbs= above) explicitly
2970 awaken the corresponding "rcuoN" kthreads,
2971 make these kthreads poll for callbacks.
2972 This improves the real-time response for the
2973 offloaded CPUs by relieving them of the need to
2974 wake up the corresponding kthread, but degrades
2975 energy efficiency by requiring that the kthreads
2976 periodically wake up to do the polling.
2978 rcutree.blimit= [KNL]
2979 Set maximum number of finished RCU callbacks to
2980 process in one batch.
2982 rcutree.gp_init_delay= [KNL]
2983 Set the number of jiffies to delay each step of
2984 RCU grace-period initialization. This only has
2985 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
2988 rcutree.rcu_fanout_leaf= [KNL]
2989 Increase the number of CPUs assigned to each
2990 leaf rcu_node structure. Useful for very large
2993 rcutree.jiffies_till_sched_qs= [KNL]
2994 Set required age in jiffies for a
2995 given grace period before RCU starts
2996 soliciting quiescent-state help from
2997 rcu_note_context_switch().
2999 rcutree.jiffies_till_first_fqs= [KNL]
3000 Set delay from grace-period initialization to
3001 first attempt to force quiescent states.
3002 Units are jiffies, minimum value is zero,
3003 and maximum value is HZ.
3005 rcutree.jiffies_till_next_fqs= [KNL]
3006 Set delay between subsequent attempts to force
3007 quiescent states. Units are jiffies, minimum
3008 value is one, and maximum value is HZ.
3010 rcutree.kthread_prio= [KNL,BOOT]
3011 Set the SCHED_FIFO priority of the RCU per-CPU
3012 kthreads (rcuc/N). This value is also used for
3013 the priority of the RCU boost threads (rcub/N)
3014 and for the RCU grace-period kthreads (rcu_bh,
3015 rcu_preempt, and rcu_sched). If RCU_BOOST is
3016 set, valid values are 1-99 and the default is 1
3017 (the least-favored priority). Otherwise, when
3018 RCU_BOOST is not set, valid values are 0-99 and
3019 the default is zero (non-realtime operation).
3021 rcutree.rcu_nocb_leader_stride= [KNL]
3022 Set the number of NOCB kthread groups, which
3023 defaults to the square root of the number of
3024 CPUs. Larger numbers reduces the wakeup overhead
3025 on the per-CPU grace-period kthreads, but increases
3026 that same overhead on each group's leader.
3028 rcutree.qhimark= [KNL]
3029 Set threshold of queued RCU callbacks beyond which
3030 batch limiting is disabled.
3032 rcutree.qlowmark= [KNL]
3033 Set threshold of queued RCU callbacks below which
3034 batch limiting is re-enabled.
3036 rcutree.rcu_idle_gp_delay= [KNL]
3037 Set wakeup interval for idle CPUs that have
3038 RCU callbacks (RCU_FAST_NO_HZ=y).
3040 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3041 Set wakeup interval for idle CPUs that have
3042 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3043 Lazy RCU callbacks are those which RCU can
3044 prove do nothing more than free memory.
3046 rcutorture.cbflood_inter_holdoff= [KNL]
3047 Set holdoff time (jiffies) between successive
3048 callback-flood tests.
3050 rcutorture.cbflood_intra_holdoff= [KNL]
3051 Set holdoff time (jiffies) between successive
3052 bursts of callbacks within a given callback-flood
3055 rcutorture.cbflood_n_burst= [KNL]
3056 Set the number of bursts making up a given
3057 callback-flood test. Set this to zero to
3058 disable callback-flood testing.
3060 rcutorture.cbflood_n_per_burst= [KNL]
3061 Set the number of callbacks to be registered
3062 in a given burst of a callback-flood test.
3064 rcutorture.fqs_duration= [KNL]
3065 Set duration of force_quiescent_state bursts.
3067 rcutorture.fqs_holdoff= [KNL]
3068 Set holdoff time within force_quiescent_state bursts.
3070 rcutorture.fqs_stutter= [KNL]
3071 Set wait time between force_quiescent_state bursts.
3073 rcutorture.gp_exp= [KNL]
3074 Use expedited update-side primitives.
3076 rcutorture.gp_normal= [KNL]
3077 Use normal (non-expedited) update-side primitives.
3078 If both gp_exp and gp_normal are set, do both.
3079 If neither gp_exp nor gp_normal are set, still
3082 rcutorture.n_barrier_cbs= [KNL]
3083 Set callbacks/threads for rcu_barrier() testing.
3085 rcutorture.nfakewriters= [KNL]
3086 Set number of concurrent RCU writers. These just
3087 stress RCU, they don't participate in the actual
3088 test, hence the "fake".
3090 rcutorture.nreaders= [KNL]
3091 Set number of RCU readers.
3093 rcutorture.object_debug= [KNL]
3094 Enable debug-object double-call_rcu() testing.
3096 rcutorture.onoff_holdoff= [KNL]
3097 Set time (s) after boot for CPU-hotplug testing.
3099 rcutorture.onoff_interval= [KNL]
3100 Set time (s) between CPU-hotplug operations, or
3101 zero to disable CPU-hotplug testing.
3103 rcutorture.torture_runnable= [BOOT]
3104 Start rcutorture running at boot time.
3106 rcutorture.shuffle_interval= [KNL]
3107 Set task-shuffle interval (s). Shuffling tasks
3108 allows some CPUs to go into dyntick-idle mode
3109 during the rcutorture test.
3111 rcutorture.shutdown_secs= [KNL]
3112 Set time (s) after boot system shutdown. This
3113 is useful for hands-off automated testing.
3115 rcutorture.stall_cpu= [KNL]
3116 Duration of CPU stall (s) to test RCU CPU stall
3117 warnings, zero to disable.
3119 rcutorture.stall_cpu_holdoff= [KNL]
3120 Time to wait (s) after boot before inducing stall.
3122 rcutorture.stat_interval= [KNL]
3123 Time (s) between statistics printk()s.
3125 rcutorture.stutter= [KNL]
3126 Time (s) to stutter testing, for example, specifying
3127 five seconds causes the test to run for five seconds,
3128 wait for five seconds, and so on. This tests RCU's
3129 ability to transition abruptly to and from idle.
3131 rcutorture.test_boost= [KNL]
3132 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3133 "Maybe" means test if the RCU implementation
3134 under test support RCU priority boosting.
3136 rcutorture.test_boost_duration= [KNL]
3137 Duration (s) of each individual boost test.
3139 rcutorture.test_boost_interval= [KNL]
3140 Interval (s) between each boost test.
3142 rcutorture.test_no_idle_hz= [KNL]
3143 Test RCU's dyntick-idle handling. See also the
3144 rcutorture.shuffle_interval parameter.
3146 rcutorture.torture_type= [KNL]
3147 Specify the RCU implementation to test.
3149 rcutorture.verbose= [KNL]
3150 Enable additional printk() statements.
3152 rcupdate.rcu_expedited= [KNL]
3153 Use expedited grace-period primitives, for
3154 example, synchronize_rcu_expedited() instead
3155 of synchronize_rcu(). This reduces latency,
3156 but can increase CPU utilization, degrade
3157 real-time latency, and degrade energy efficiency.
3159 rcupdate.rcu_cpu_stall_suppress= [KNL]
3160 Suppress RCU CPU stall warning messages.
3162 rcupdate.rcu_cpu_stall_timeout= [KNL]
3163 Set timeout for RCU CPU stall warning messages.
3165 rcupdate.rcu_task_stall_timeout= [KNL]
3166 Set timeout in jiffies for RCU task stall warning
3167 messages. Disable with a value less than or equal
3170 rcupdate.rcu_self_test= [KNL]
3171 Run the RCU early boot self tests
3173 rcupdate.rcu_self_test_bh= [KNL]
3174 Run the RCU bh early boot self tests
3176 rcupdate.rcu_self_test_sched= [KNL]
3177 Run the RCU sched early boot self tests
3181 Run specified binary instead of /init from the ramdisk,
3182 used for early userspace startup. See initrd.
3185 Format (x86 or x86_64):
3186 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3188 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3190 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3191 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3192 reboot_force is either force or not specified,
3193 reboot_cpu is s[mp]#### with #### being the processor
3194 to be used for rebooting.
3197 [KNL, SMP] Set scheduler's default relax_domain_level.
3198 See Documentation/cgroups/cpusets.txt.
3200 relative_sleep_states=
3201 [SUSPEND] Use sleep state labeling where the deepest
3202 state available other than hibernation is always "mem".
3203 Format: { "0" | "1" }
3204 0 -- Traditional sleep state labels.
3205 1 -- Relative sleep state labels.
3207 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3209 reservetop= [X86-32]
3211 Reserves a hole at the top of the kernel virtual
3216 Set the amount of memory to reserve for BIOS at
3217 the bottom of the address space.
3219 reset_devices [KNL] Force drivers to reset the underlying device
3220 during initialization.
3223 Specify the partition device for software suspend
3225 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3227 resume_offset= [SWSUSP]
3228 Specify the offset from the beginning of the partition
3229 given by "resume=" at which the swap header is located,
3230 in <PAGE_SIZE> units (needed only for swap files).
3231 See Documentation/power/swsusp-and-swap-files.txt
3233 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3234 read the resume files
3236 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3237 Useful for devices that are detected asynchronously
3238 (e.g. USB and MMC devices).
3240 hibernate= [HIBERNATION]
3241 noresume Don't check if there's a hibernation image
3242 present during boot.
3243 nocompress Don't compress/decompress hibernation images.
3244 no Disable hibernation and resume.
3246 retain_initrd [RAM] Keep initrd memory after extraction
3248 rfkill.default_state=
3249 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3250 etc. communication is blocked by default.
3253 rfkill.master_switch_mode=
3254 0 The "airplane mode" button does nothing.
3255 1 The "airplane mode" button toggles between everything
3256 blocked and the previous configuration.
3257 2 The "airplane mode" button toggles between everything
3258 blocked and everything unblocked.
3260 rhash_entries= [KNL,NET]
3261 Set number of hash buckets for route cache
3263 ro [KNL] Mount root device read-only on boot
3265 root= [KNL] Root filesystem
3266 See name_to_dev_t comment in init/do_mounts.c.
3268 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3269 mount the root filesystem
3271 rootflags= [KNL] Set root filesystem mount option string
3273 rootfstype= [KNL] Set root filesystem type
3275 rootwait [KNL] Wait (indefinitely) for root device to show up.
3276 Useful for devices that are detected asynchronously
3277 (e.g. USB and MMC devices).
3279 rproc_mem=nn[KMG][@address]
3280 [KNL,ARM,CMA] Remoteproc physical memory block.
3281 Memory area to be used by remote processor image,
3284 rw [KNL] Mount root device read-write on boot
3286 S [KNL] Run init in single mode
3288 s390_iommu= [HW,S390]
3289 Set s390 IOTLB flushing mode
3291 With strict flushing every unmap operation will result in
3292 an IOTLB flush. Default is lazy flushing before reuse,
3296 See drivers/net/irda/sa1100_ir.c.
3298 sbni= [NET] Granch SBNI12 leased line adapter
3300 sched_debug [KNL] Enables verbose scheduler debug messages.
3302 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3303 xtime_lock contention on larger systems, and/or RCU lock
3304 contention on all systems with CONFIG_MAXSMP set.
3305 Format: { "0" | "1" }
3306 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3308 Note: increases power consumption, thus should only be
3309 enabled if running jitter sensitive (HPC/RT) workloads.
3311 security= [SECURITY] Choose a security module to enable at boot.
3312 If this boot parameter is not specified, only the first
3313 security module asking for security registration will be
3314 loaded. An invalid security module name will be treated
3315 as if no module has been chosen.
3317 selinux= [SELINUX] Disable or enable SELinux at boot time.
3318 Format: { "0" | "1" }
3319 See security/selinux/Kconfig help text.
3322 Default value is set via kernel config option.
3323 If enabled at boot time, /selinux/disable can be used
3324 later to disable prior to initial policy load.
3326 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3327 Format: { "0" | "1" }
3328 See security/apparmor/Kconfig help text
3331 Default value is set via kernel config option.
3333 serialnumber [BUGS=X86-32]
3336 Maximal number of shapers.
3338 show_msr= [x86] show boot-time MSR settings
3339 Format: { <integer> }
3340 Show boot-time (BIOS-initialized) MSR settings.
3341 The parameter means the number of CPUs to show,
3342 for example 1 means boot CPU only.
3350 Disable merging of slabs with similar size. May be
3351 necessary if there is some reason to distinguish
3352 allocs to different slabs. Debug options disable
3353 merging on their own.
3354 For more information see Documentation/vm/slub.txt.
3356 slab_max_order= [MM, SLAB]
3357 Determines the maximum allowed order for slabs.
3358 A high setting may cause OOMs due to memory
3359 fragmentation. Defaults to 1 for systems with
3360 more than 32MB of RAM, 0 otherwise.
3362 slub_debug[=options[,slabs]] [MM, SLUB]
3363 Enabling slub_debug allows one to determine the
3364 culprit if slab objects become corrupted. Enabling
3365 slub_debug can create guard zones around objects and
3366 may poison objects when not in use. Also tracks the
3367 last alloc / free. For more information see
3368 Documentation/vm/slub.txt.
3370 slub_max_order= [MM, SLUB]
3371 Determines the maximum allowed order for slabs.
3372 A high setting may cause OOMs due to memory
3373 fragmentation. For more information see
3374 Documentation/vm/slub.txt.
3376 slub_min_objects= [MM, SLUB]
3377 The minimum number of objects per slab. SLUB will
3378 increase the slab order up to slub_max_order to
3379 generate a sufficiently large slab able to contain
3380 the number of objects indicated. The higher the number
3381 of objects the smaller the overhead of tracking slabs
3382 and the less frequently locks need to be acquired.
3383 For more information see Documentation/vm/slub.txt.
3385 slub_min_order= [MM, SLUB]
3386 Determines the minimum page order for slabs. Must be
3387 lower than slub_max_order.
3388 For more information see Documentation/vm/slub.txt.
3390 slub_nomerge [MM, SLUB]
3391 Same with slab_nomerge. This is supported for legacy.
3392 See slab_nomerge for more information.
3395 Format: <io1>[,<io2>[,...,<io8>]]
3397 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3398 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3399 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3400 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3401 smsc-ircc2.ircc_irq= [HW] IRQ line
3402 smsc-ircc2.ircc_dma= [HW] DMA channel
3403 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3404 0: Toshiba Satellite 1800 (GP data pin select)
3405 1: Fast pin select (default)
3409 [KNL] Should the soft-lockup detector generate panics.
3412 softlockup_all_cpu_backtrace=
3413 [KNL] Should the soft-lockup detector generate
3414 backtraces on all cpus.
3417 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3418 See Documentation/laptops/sonypi.txt
3420 spia_io_base= [HW,MTD]
3426 Enabled the stack tracer on boot up.
3428 stacktrace_filter=[function-list]
3429 [FTRACE] Limit the functions that the stack tracer
3430 will trace at boot up. function-list is a comma separated
3431 list of functions. This list can be changed at run
3432 time by the stack_trace_filter file in the debugfs
3433 tracing directory. Note, this enables stack tracing
3434 and the stacktrace above is not needed.
3438 Set the STI (builtin display/keyboard on the HP-PARISC
3439 machines) console (graphic card) which should be used
3440 as the initial boot-console.
3441 See also comment in drivers/video/console/sticore.c.
3444 See comment in drivers/video/console/sticore.c.
3447 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3449 sunrpc.min_resvport=
3450 sunrpc.max_resvport=
3452 SunRPC servers often require that client requests
3453 originate from a privileged port (i.e. a port in the
3454 range 0 < portnr < 1024).
3455 An administrator who wishes to reserve some of these
3456 ports for other uses may adjust the range that the
3457 kernel's sunrpc client considers to be privileged
3458 using these two parameters to set the minimum and
3459 maximum port values.
3463 Control how the NFS server code allocates CPUs to
3464 service thread pools. Depending on how many NICs
3465 you have and where their interrupts are bound, this
3466 option will affect which CPUs will do NFS serving.
3467 Note: this parameter cannot be changed while the
3468 NFS server is running.
3470 auto the server chooses an appropriate mode
3471 automatically using heuristics
3472 global a single global pool contains all CPUs
3473 percpu one pool for each CPU
3474 pernode one pool for each NUMA node (equivalent
3475 to global on non-NUMA machines)
3477 sunrpc.tcp_slot_table_entries=
3478 sunrpc.udp_slot_table_entries=
3480 Sets the upper limit on the number of simultaneous
3481 RPC calls that can be sent from the client to a
3482 server. Increasing these values may allow you to
3483 improve throughput, but will also increase the
3484 amount of memory reserved for use by the client.
3486 suspend.pm_test_delay=
3488 Sets the number of seconds to remain in a suspend test
3489 mode before resuming the system (see
3490 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3491 is set. Default value is 5.
3494 [KNL] Enable accounting of swap in memory resource
3495 controller if no parameter or 1 is given or disable
3496 it if 0 is given (See Documentation/cgroups/memory.txt)
3498 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3499 Format: { <int> | force }
3500 <int> -- Number of I/O TLB slabs
3501 force -- force using of bounce buffers even if they
3502 wouldn't be automatically used by the kernel
3506 sysfs.deprecated=0|1 [KNL]
3507 Enable/disable old style sysfs layout for old udev
3508 on older distributions. When this option is enabled
3509 very new udev will not work anymore. When this option
3510 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3511 in older udev will not work anymore.
3512 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3513 the kernel configuration.
3515 sysrq_always_enabled
3517 Ignore sysrq setting - this boot parameter will
3518 neutralize any effect of /proc/sys/kernel/sysrq.
3519 Useful for debugging.
3521 tcpmhash_entries= [KNL,NET]
3522 Set the number of tcp_metrics_hash slots.
3523 Default value is 8192 or 16384 depending on total
3524 ram pages. This is used to specify the TCP metrics
3525 cache size. See Documentation/networking/ip-sysctl.txt
3526 "tcp_no_metrics_save" section for more details.
3530 test_suspend= [SUSPEND][,N]
3531 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3532 standby suspend) or "freeze" (for suspend type freeze)
3533 as the system sleep state during system startup with
3534 the optional capability to repeat N number of times.
3535 The system is woken from this state using a
3536 wakeup-capable RTC alarm.
3538 thash_entries= [KNL,NET]
3539 Set number of hash buckets for TCP connection
3541 thermal.act= [HW,ACPI]
3542 -1: disable all active trip points in all thermal zones
3543 <degrees C>: override all lowest active trip points
3545 thermal.crt= [HW,ACPI]
3546 -1: disable all critical trip points in all thermal zones
3547 <degrees C>: override all critical trip points
3549 thermal.nocrt= [HW,ACPI]
3550 Set to disable actions on ACPI thermal zone
3551 critical and hot trip points.
3553 thermal.off= [HW,ACPI]
3554 1: disable ACPI thermal control
3556 thermal.psv= [HW,ACPI]
3557 -1: disable all passive trip points
3558 <degrees C>: override all passive trip points to this
3561 thermal.tzp= [HW,ACPI]
3562 Specify global default ACPI thermal zone polling rate
3563 <deci-seconds>: poll all this frequency
3564 0: no polling (default)
3567 Force threading of all interrupt handlers except those
3568 marked explicitly IRQF_NO_THREAD.
3571 Enable the Transcendent memory driver if built-in.
3573 tmem.cleancache=0|1 [KNL, XEN]
3574 Default is on (1). Disable the usage of the cleancache
3575 API to send anonymous pages to the hypervisor.
3577 tmem.frontswap=0|1 [KNL, XEN]
3578 Default is on (1). Disable the usage of the frontswap
3579 API to send swap pages to the hypervisor. If disabled
3580 the selfballooning and selfshrinking are force disabled.
3582 tmem.selfballooning=0|1 [KNL, XEN]
3583 Default is on (1). Disable the driving of swap pages
3586 tmem.selfshrinking=0|1 [KNL, XEN]
3587 Default is on (1). Partial swapoff that immediately
3588 transfers pages from Xen hypervisor back to the
3589 kernel based on different criteria.
3593 Specify if the kernel should make use of the cpu
3594 topology information if the hardware supports this.
3595 The scheduler will make use of this information and
3596 e.g. base its process migration decisions on it.
3599 topology_updates= [KNL, PPC, NUMA]
3601 Specify if the kernel should ignore (off)
3602 topology updates sent by the hypervisor to this
3607 tpm_suspend_pcr=[HW,TPM]
3608 Format: integer pcr id
3609 Specify that at suspend time, the tpm driver
3610 should extend the specified pcr with zeros,
3611 as a workaround for some chips which fail to
3612 flush the last written pcr on TPM_SaveState.
3613 This will guarantee that all the other pcrs
3616 trace_buf_size=nn[KMG]
3617 [FTRACE] will set tracing buffer size on each cpu.
3619 trace_event=[event-list]
3620 [FTRACE] Set and start specified trace events in order
3621 to facilitate early boot debugging.
3622 See also Documentation/trace/events.txt
3624 trace_options=[option-list]
3625 [FTRACE] Enable or disable tracer options at boot.
3626 The option-list is a comma delimited list of options
3627 that can be enabled or disabled just as if you were
3628 to echo the option name into
3630 /sys/kernel/debug/tracing/trace_options
3632 For example, to enable stacktrace option (to dump the
3633 stack trace of each event), add to the command line:
3635 trace_options=stacktrace
3637 See also Documentation/trace/ftrace.txt "trace options"
3641 Have the tracepoints sent to printk as well as the
3642 tracing ring buffer. This is useful for early boot up
3643 where the system hangs or reboots and does not give the
3644 option for reading the tracing buffer or performing a
3645 ftrace_dump_on_oops.
3647 To turn off having tracepoints sent to printk,
3648 echo 0 > /proc/sys/kernel/tracepoint_printk
3649 Note, echoing 1 into this file without the
3650 tracepoint_printk kernel cmdline option has no effect.
3654 Having tracepoints sent to printk() and activating high
3655 frequency tracepoints such as irq or sched, can cause
3656 the system to live lock.
3659 [FTRACE] enable this option to disable tracing when a
3660 warning is hit. This turns off "tracing_on". Tracing can
3661 be enabled again by echoing '1' into the "tracing_on"
3662 file located in /sys/kernel/debug/tracing/
3664 This option is useful, as it disables the trace before
3665 the WARNING dump is called, which prevents the trace to
3666 be filled with content caused by the warning output.
3668 This option can also be set at run time via the sysctl
3669 option: kernel/traceoff_on_warning
3671 transparent_hugepage=
3673 Format: [always|madvise|never]
3674 Can be used to control the default behavior of the system
3675 with respect to transparent hugepages.
3676 See Documentation/vm/transhuge.txt for more details.
3678 tsc= Disable clocksource stability checks for TSC.
3680 [x86] reliable: mark tsc clocksource as reliable, this
3681 disables clocksource verification at runtime, as well
3682 as the stability checks done at bootup. Used to enable
3683 high-resolution timer mode on older hardware, and in
3684 virtualized environment.
3685 [x86] noirqtime: Do not use TSC to do irq accounting.
3686 Used to run time disable IRQ_TIME_ACCOUNTING on any
3687 platforms where RDTSC is slow and this accounting
3690 turbografx.map[2|3]= [HW,JOY]
3691 TurboGraFX parallel port interface
3693 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3694 See also Documentation/input/joystick-parport.txt
3696 udbg-immortal [PPC] When debugging early kernel crashes that
3697 happen after console_init() and before a proper
3698 console driver takes over, this boot options might
3699 help "seeing" what's going on.
3701 uhash_entries= [KNL,NET]
3702 Set number of hash buckets for UDP/UDP-Lite connections
3705 [USB] Ignore overcurrent events (default N).
3706 Some badly-designed motherboards generate lots of
3707 bogus events, for ports that aren't wired to
3708 anything. Set this parameter to avoid log spamming.
3709 Note that genuine overcurrent events won't be
3713 [X86] Cause panic on unknown NMI.
3715 usbcore.authorized_default=
3716 [USB] Default USB device authorization:
3717 (default -1 = authorized except for wireless USB,
3718 0 = not authorized, 1 = authorized)
3720 usbcore.autosuspend=
3721 [USB] The autosuspend time delay (in seconds) used
3722 for newly-detected USB devices (default 2). This
3723 is the time required before an idle device will be
3724 autosuspended. Devices for which the delay is set
3725 to a negative value won't be autosuspended at all.
3727 usbcore.usbfs_snoop=
3728 [USB] Set to log all usbfs traffic (default 0 = off).
3730 usbcore.blinkenlights=
3731 [USB] Set to cycle leds on hubs (default 0 = off).
3733 usbcore.old_scheme_first=
3734 [USB] Start with the old device initialization
3735 scheme (default 0 = off).
3737 usbcore.usbfs_memory_mb=
3738 [USB] Memory limit (in MB) for buffers allocated by
3739 usbfs (default = 16, 0 = max = 2047).
3741 usbcore.use_both_schemes=
3742 [USB] Try the other device initialization scheme
3743 if the first one fails (default 1 = enabled).
3745 usbcore.initial_descriptor_timeout=
3746 [USB] Specifies timeout for the initial 64-byte
3747 USB_REQ_GET_DESCRIPTOR request in milliseconds
3748 (default 5000 = 5.0 seconds).
3751 [USBHID] The interval which mice are to be polled at.
3753 usb-storage.delay_use=
3754 [UMS] The delay in seconds before a new device is
3755 scanned for Logical Units (default 1).
3758 [UMS] A list of quirks entries to supplement or
3759 override the built-in unusual_devs list. List
3760 entries are separated by commas. Each entry has
3761 the form VID:PID:Flags where VID and PID are Vendor
3762 and Product ID values (4-digit hex numbers) and
3763 Flags is a set of characters, each corresponding
3764 to a common usb-storage quirk flag as follows:
3765 a = SANE_SENSE (collect more than 18 bytes
3767 b = BAD_SENSE (don't collect more than 18
3768 bytes of sense data);
3769 c = FIX_CAPACITY (decrease the reported
3770 device capacity by one sector);
3771 d = NO_READ_DISC_INFO (don't use
3772 READ_DISC_INFO command);
3773 e = NO_READ_CAPACITY_16 (don't use
3774 READ_CAPACITY_16 command);
3775 f = NO_REPORT_OPCODES (don't use report opcodes
3777 h = CAPACITY_HEURISTICS (decrease the
3778 reported device capacity by one
3779 sector if the number is odd);
3780 i = IGNORE_DEVICE (don't bind to this
3782 l = NOT_LOCKABLE (don't try to lock and
3783 unlock ejectable media);
3784 m = MAX_SECTORS_64 (don't transfer more
3785 than 64 sectors = 32 KB at a time);
3786 n = INITIAL_READ10 (force a retry of the
3787 initial READ(10) command);
3788 o = CAPACITY_OK (accept the capacity
3789 reported by the device);
3790 p = WRITE_CACHE (the device cache is ON
3792 r = IGNORE_RESIDUE (the device reports
3793 bogus residue values);
3794 s = SINGLE_LUN (the device has only one
3796 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3797 commands, uas only);
3798 u = IGNORE_UAS (don't bind to the uas driver);
3799 w = NO_WP_DETECT (don't test whether the
3800 medium is write-protected).
3801 Example: quirks=0419:aaf5:rl,0421:0433:rc
3803 user_debug= [KNL,ARM]
3805 See arch/arm/Kconfig.debug help text.
3806 1 - undefined instruction events
3808 4 - invalid data aborts
3811 Example: user_debug=31
3814 [X86] Flags controlling user PTE allocations.
3816 nohigh = do not allocate PTE pages in
3817 HIGHMEM regardless of setting
3821 On X86_32, this is an alias for vdso32=. Otherwise:
3823 vdso=1: enable VDSO (the default)
3824 vdso=0: disable VDSO mapping
3826 vdso32= [X86] Control the 32-bit vDSO
3827 vdso32=1: enable 32-bit VDSO
3828 vdso32=0 or vdso32=2: disable 32-bit VDSO
3830 See the help text for CONFIG_COMPAT_VDSO for more
3831 details. If CONFIG_COMPAT_VDSO is set, the default is
3832 vdso32=0; otherwise, the default is vdso32=1.
3834 For compatibility with older kernels, vdso32=2 is an
3837 Try vdso32=0 if you encounter an error that says:
3838 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3841 vector=percpu: enable percpu vector domain
3843 video= [FB] Frame buffer configuration
3844 See Documentation/fb/modedb.txt.
3846 video.brightness_switch_enabled= [0,1]
3847 If set to 1, on receiving an ACPI notify event
3848 generated by hotkey, video driver will adjust brightness
3849 level and then send out the event to user space through
3850 the allocated input device; If set to 0, video driver
3851 will only send out the event without touching backlight
3856 [VMMIO] Memory mapped virtio (platform) device.
3858 <size>@<baseaddr>:<irq>[:<id>]
3860 <size> := size (can use standard suffixes
3862 <baseaddr> := physical base address
3863 <irq> := interrupt number (as passed to
3865 <id> := (optional) platform device id
3867 virtio_mmio.device=1K@0x100b0000:48:7
3869 Can be used multiple times for multiple devices.
3871 vga= [BOOT,X86-32] Select a particular video mode
3872 See Documentation/x86/boot.txt and
3873 Documentation/svga.txt.
3874 Use vga=ask for menu.
3875 This is actually a boot loader parameter; the value is
3876 passed to the kernel using a special protocol.
3878 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3879 size of <nn>. This can be used to increase the
3880 minimum size (128MB on x86). It can also be used to
3881 decrease the size and leave more room for directly
3884 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3887 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3890 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3894 Controls the behavior of vsyscalls (i.e. calls to
3895 fixed addresses of 0xffffffffff600x00 from legacy
3896 code). Most statically-linked binaries and older
3897 versions of glibc use these calls. Because these
3898 functions are at fixed addresses, they make nice
3899 targets for exploits that can control RIP.
3901 emulate [default] Vsyscalls turn into traps and are
3902 emulated reasonably safely.
3904 native Vsyscalls are native syscall instructions.
3905 This is a little bit faster than trapping
3906 and makes a few dynamic recompilers work
3907 better than they would in emulation mode.
3908 It also makes exploits much easier to write.
3910 none Vsyscalls don't work at all. This makes
3911 them quite hard to use for exploits but
3912 might break your system.
3914 vt.color= [VT] Default text color.
3915 Format: 0xYX, X = foreground, Y = background.
3916 Default: 0x07 = light gray on black.
3918 vt.cur_default= [VT] Default cursor shape.
3919 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3920 the parameters of the <Esc>[?A;B;Cc escape sequence;
3921 see VGA-softcursor.txt. Default: 2 = underline.
3923 vt.default_blu= [VT]
3924 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3925 Change the default blue palette of the console.
3926 This is a 16-member array composed of values
3929 vt.default_grn= [VT]
3930 Format: <green0>,<green1>,<green2>,...,<green15>
3931 Change the default green palette of the console.
3932 This is a 16-member array composed of values
3935 vt.default_red= [VT]
3936 Format: <red0>,<red1>,<red2>,...,<red15>
3937 Change the default red palette of the console.
3938 This is a 16-member array composed of values
3944 Set system-wide default UTF-8 mode for all tty's.
3945 Default is 1, i.e. UTF-8 mode is enabled for all
3946 newly opened terminals.
3948 vt.global_cursor_default=
3951 Set system-wide default for whether a cursor
3952 is shown on new VTs. Default is -1,
3953 i.e. cursors will be created by default unless
3954 overridden by individual drivers. 0 will hide
3955 cursors, 1 will display them.
3957 vt.italic= [VT] Default color for italic text; 0-15.
3960 vt.underline= [VT] Default color for underlined text; 0-15.
3963 watchdog timers [HW,WDT] For information on watchdog timers,
3964 see Documentation/watchdog/watchdog-parameters.txt
3965 or other driver-specific files in the
3966 Documentation/watchdog/ directory.
3968 workqueue.disable_numa
3969 By default, all work items queued to unbound
3970 workqueues are affine to the NUMA nodes they're
3971 issued on, which results in better behavior in
3972 general. If NUMA affinity needs to be disabled for
3973 whatever reason, this option can be used. Note
3974 that this also can be controlled per-workqueue for
3975 workqueues visible under /sys/bus/workqueue/.
3977 workqueue.power_efficient
3978 Per-cpu workqueues are generally preferred because
3979 they show better performance thanks to cache
3980 locality; unfortunately, per-cpu workqueues tend to
3981 be more power hungry than unbound workqueues.
3983 Enabling this makes the per-cpu workqueues which
3984 were observed to contribute significantly to power
3985 consumption unbound, leading to measurably lower
3986 power usage at the cost of small performance
3989 The default value of this parameter is determined by
3990 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3992 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3993 default x2apic cluster mode on platforms
3996 x86_intel_mid_timer= [X86-32,APBT]
3997 Choose timer option for x86 Intel MID platform.
3998 Two valid options are apbt timer only and lapic timer
3999 plus one apbt timer for broadcast timer.
4000 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4002 xen_emul_unplug= [HW,X86,XEN]
4003 Unplug Xen emulated devices
4004 Format: [unplug0,][unplug1]
4005 ide-disks -- unplug primary master IDE devices
4006 aux-ide-disks -- unplug non-primary-master IDE devices
4007 nics -- unplug network devices
4008 all -- unplug all emulated devices (NICs and IDE disks)
4009 unnecessary -- unplugging emulated devices is
4010 unnecessary even if the host did not respond to
4012 never -- do not unplug even if version check succeeds
4014 xen_nopvspin [X86,XEN]
4015 Disables the ticketlock slowpath using Xen PV
4019 Disables the PV optimizations forcing the HVM guest to
4020 run as generic HVM guest with no PV drivers.
4022 xirc2ps_cs= [NET,PCMCIA]
4024 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4026 ______________________________________________________________________
4030 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob