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.
832 debugpat [X86] Enable PAT debugging
834 decnet.addr= [HW,NET]
835 Format: <area>[,<node>]
836 See also Documentation/networking/decnet.txt.
839 [same as hugepagesz=] The size of the default
840 HugeTLB page size. This is the size represented by
841 the legacy /proc/ hugepages APIs, used for SHM, and
842 default size when mounting hugetlbfs filesystems.
843 Defaults to the default architecture's huge page size
847 Set number of hash buckets for dentry cache.
850 See Documentation/networking/ipv6.txt.
852 disable_cpu_apicid= [X86,APIC,SMP]
854 The number of initial APIC ID for the
855 corresponding CPU to be disabled at boot,
856 mostly used for the kdump 2nd kernel to
857 disable BSP to wake up multiple CPUs without
858 causing system reset or hang due to sending
861 disable_ddw [PPC/PSERIES]
862 Disable Dynamic DMA Window support. Use this if
863 to workaround buggy firmware.
866 See Documentation/networking/ipv6.txt.
868 disable_mtrr_cleanup [X86]
869 The kernel tries to adjust MTRR layout from continuous
870 to discrete, to make X server driver able to add WB
871 entry later. This parameter disables that.
873 disable_mtrr_trim [X86, Intel and AMD only]
874 By default the kernel will trim any uncacheable
875 memory out of your available memory pool based on
876 MTRR settings. This parameter disables that behavior,
877 possibly causing your machine to run very slowly.
879 disable_timer_pin_1 [X86]
880 Disable PIN 1 of APIC timer
881 Can be useful to work around chipset bugs.
883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
900 drm_kms_helper.edid_firmware=[<connector>:]<file>
901 Broken monitors, graphic adapters and KVMs may
902 send no or incorrect EDID data sets. This parameter
903 allows to specify an EDID data set in the
904 /lib/firmware directory that is used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
917 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
918 module.dyndbg[="val"]
919 Enable debug messages at boot time. See
920 Documentation/dynamic-debug-howto.txt for details.
922 early_ioremap_debug [KNL]
923 Enable debug messages in early_ioremap support. This
924 is useful for tracking down temporary early mappings
925 which are not unmapped.
927 earlycon= [KNL] Output early console device and options.
930 Start an early, polled-mode console on a cadence serial
931 port at the specified address. The cadence serial port
932 must already be setup and configured. Options are not
935 uart[8250],io,<addr>[,options]
936 uart[8250],mmio,<addr>[,options]
937 uart[8250],mmio32,<addr>[,options]
938 Start an early, polled-mode console on the 8250/16550
939 UART at the specified I/O port or MMIO address.
940 MMIO inter-register address stride is either 8-bit
941 (mmio) or 32-bit (mmio32).
942 The options are the same as for ttyS, above.
945 Start an early, polled-mode console on a pl011 serial
946 port at the specified address. The pl011 serial port
947 must already be setup and configured. Options are not
951 Start an early, polled-mode console on an msm serial
952 port at the specified address. The serial port
953 must already be setup and configured. Options are not
957 Start an early, polled-mode console on an msm serial
958 dm port at the specified address. The serial port
959 must already be setup and configured. Options are not
962 smh Use ARM semihosting calls for early console.
964 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
968 earlyprintk=serial[,ttySn[,baudrate]]
969 earlyprintk=serial[,0x...[,baudrate]]
970 earlyprintk=ttySn[,baudrate]
971 earlyprintk=dbgp[debugController#]
973 earlyprintk is useful when the kernel crashes before
974 the normal console is initialized. It is not enabled by
975 default because it has some cosmetic problems.
977 Append ",keep" to not disable it when the real console
980 Only one of vga, efi, serial, or usb debug port can
983 Currently only ttyS0 and ttyS1 may be specified by
984 name. Other I/O ports may be explicitly specified
985 on some architectures (x86 and arm at least) by
986 replacing ttySn with an I/O port address, like this:
987 earlyprintk=serial,0x1008,115200
988 You can find the port for a given device in
989 /proc/tty/driver/serial:
990 2: uart:ST16650V2 port:00001008 irq:18 ...
992 Interaction with the standard serial driver is not
995 The VGA and EFI output is eventually overwritten by
998 The xen output can only be used by Xen PV guests.
1000 edac_report= [HW,EDAC] Control how to report EDAC event
1001 Format: {"on" | "off" | "force"}
1002 on: enable EDAC to report H/W event. May be overridden
1003 by other higher priority error reporting module.
1004 off: disable H/W event reporting through EDAC.
1005 force: enforce the use of EDAC to report H/W event.
1008 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1011 This is designed to be used in conjunction with
1012 the boot argument: earlyprintk=vga
1015 Format: {"off" | "on" | "skip[mbr]"}
1018 Format: { "old_map" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1023 efi_no_storage_paranoia [EFI; X86]
1024 Using this parameter you can use more than 50% of
1025 your efi variable storage. Use this parameter only if
1026 you are really sure that your UEFI does sane gc and
1027 fulfills the spec otherwise your board may brick.
1029 eisa_irq_edge= [PARISC,HW]
1030 See header of drivers/parisc/eisa.c.
1033 See comment before function elanfreq_setup() in
1034 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1037 Format: {"cfq" | "deadline" | "noop"}
1038 See Documentation/block/cfq-iosched.txt and
1039 Documentation/block/deadline-iosched.txt for details.
1041 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1042 Specifies physical address of start of kernel core
1043 image elf header and optionally the size. Generally
1044 kexec loader will pass this option to capture kernel.
1045 See Documentation/kdump/kdump.txt for details.
1047 enable_mtrr_cleanup [X86]
1048 The kernel tries to adjust MTRR layout from continuous
1049 to discrete, to make X server driver able to add WB
1050 entry later. This parameter enables that.
1052 enable_timer_pin_1 [X86]
1053 Enable PIN 1 of APIC timer
1054 Can be useful to work around chipset bugs
1055 (in particular on some ATI chipsets).
1056 The kernel tries to set a reasonable default.
1058 enforcing [SELINUX] Set initial enforcing status.
1060 See security/selinux/Kconfig help text.
1061 0 -- permissive (log only, no denials).
1062 1 -- enforcing (deny and log).
1064 Value can be changed at runtime via /selinux/enforce.
1067 Disable Error Record Serialization Table (ERST)
1070 ether= [HW,NET] Ethernet cards parameters
1071 This option is obsoleted by the "netdev=" option, which
1072 has equivalent usage. See its documentation for details.
1076 Permit 'security.evm' to be updated regardless of
1077 current integrity status.
1081 fail_make_request=[KNL]
1082 General fault injection mechanism.
1083 Format: <interval>,<probability>,<space>,<times>
1084 See also Documentation/fault-injection/.
1087 See Documentation/blockdev/floppy.txt.
1089 force_pal_cache_flush
1090 [IA-64] Avoid check_sal_cache_flush which may hang on
1091 buggy SAL_CACHE_FLUSH implementations. Using this
1092 parameter will force ia64_sal_cache_flush to call
1093 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1096 Forcefully enable Physical Address Extension (PAE).
1097 Many Pentium M systems disable PAE but may have a
1098 functionally usable PAE implementation.
1099 Warning: use of this parameter will taint the kernel
1100 and may cause unknown problems.
1103 [FTRACE] will set and start the specified tracer
1104 as early as possible in order to facilitate early
1107 ftrace_dump_on_oops[=orig_cpu]
1108 [FTRACE] will dump the trace buffers on oops.
1109 If no parameter is passed, ftrace will dump
1110 buffers of all CPUs, but if you pass orig_cpu, it will
1111 dump only the buffer of the CPU that triggered the
1114 ftrace_filter=[function-list]
1115 [FTRACE] Limit the functions traced by the function
1116 tracer at boot up. function-list is a comma separated
1117 list of functions. This list can be changed at run
1118 time by the set_ftrace_filter file in the debugfs
1121 ftrace_notrace=[function-list]
1122 [FTRACE] Do not trace the functions specified in
1123 function-list. This list can be changed at run time
1124 by the set_ftrace_notrace file in the debugfs
1127 ftrace_graph_filter=[function-list]
1128 [FTRACE] Limit the top level callers functions traced
1129 by the function graph tracer at boot up.
1130 function-list is a comma separated list of functions
1131 that can be changed at run time by the
1132 set_graph_function file in the debugfs tracing directory.
1134 ftrace_graph_notrace=[function-list]
1135 [FTRACE] Do not trace from the functions specified in
1136 function-list. This list is a comma separated list of
1137 functions that can be changed at run time by the
1138 set_graph_notrace file in the debugfs tracing directory.
1141 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1142 support via parallel port (up to 5 devices per port)
1143 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1144 See also Documentation/input/joystick-parport.txt
1148 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1152 gcov_persist= [GCOV] When non-zero (default), profiling data for
1153 kernel modules is saved and remains accessible via
1154 debugfs, even when the module is unloaded/reloaded.
1155 When zero, profiling data is discarded and associated
1156 debugfs files are removed at module unload time.
1158 gpt [EFI] Forces disk with valid GPT signature but
1159 invalid Protective MBR to be treated as GPT. If the
1160 primary GPT is corrupted, it enables the backup/alternate
1161 GPT to be used instead.
1163 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1164 the "Enable 0" bit of the configuration register.
1167 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1168 the "Enable 0" bit of the configuration register.
1171 grcan.select= [HW] Select which physical interface to use.
1174 grcan.txsize= [HW] Sets the size of the tx buffer.
1175 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1177 grcan.rxsize= [HW] Sets the size of the rx buffer.
1178 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1181 hashdist= [KNL,NUMA] Large hashes allocated during boot
1182 are distributed across NUMA nodes. Defaults on
1183 for 64-bit NUMA, off otherwise.
1184 Format: 0 | 1 (for off | on)
1186 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1188 hd= [EIDE] (E)IDE hard drive subsystem geometry
1189 Format: <cyl>,<head>,<sect>
1192 Disable Hardware Error Source Table (HEST) support;
1193 corresponding firmware-first mode error processing
1194 logic will be disabled.
1196 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1197 size of <nn>. This works even on boxes that have no
1198 highmem otherwise. This also works to reduce highmem
1199 size on bigger boxes.
1201 highres= [KNL] Enable/disable high resolution timer mode.
1202 Valid parameters: "on", "off"
1206 See Documentation/isdn/README.HiSax.
1210 hpet= [X86-32,HPET] option to control HPET usage
1211 Format: { enable (default) | disable | force |
1213 disable: disable HPET and use PIT instead
1214 force: allow force enabled of undocumented chips (ICH4,
1216 verbose: show contents of HPET registers during setup
1218 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1219 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1221 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1222 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1223 On x86-64 and powerpc, this option can be specified
1224 multiple times interleaved with hugepages= to reserve
1225 huge pages of different sizes. Valid pages sizes on
1226 x86-64 are 2M (when the CPU supports "pse") and 1G
1227 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1228 Note that 1GB pages can only be allocated at boot time
1229 using hugepages= and not freed afterwards.
1231 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1232 terminal devices. Valid values: 0..8
1233 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1234 If specified, z/VM IUCV HVC accepts connections
1235 from listed z/VM user IDs only.
1237 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1238 hardware thread id mappings.
1239 Format: <cpu>:<hwthread>
1242 Do not unregister boot console at start. This is only
1243 useful for debugging when something happens in the window
1244 between unregistering the boot console and initializing
1247 i2c_bus= [HW] Override the default board specific I2C bus speed
1248 or register an additional I2C bus that is not
1249 registered from board initialization code.
1253 i8042.debug [HW] Toggle i8042 debug mode
1254 i8042.direct [HW] Put keyboard port into non-translated mode
1255 i8042.dumbkbd [HW] Pretend that controller can only read data from
1256 keyboard and cannot control its state
1257 (Don't attempt to blink the leds)
1258 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1259 i8042.nokbd [HW] Don't check/create keyboard port
1260 i8042.noloop [HW] Disable the AUX Loopback command while probing
1262 i8042.nomux [HW] Don't check presence of an active multiplexing
1263 controller. Default: true.
1264 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1266 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1267 i8042.reset [HW] Reset the controller during init and cleanup
1268 i8042.unlock [HW] Unlock (ignore) the keylock
1272 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1273 indicates that the driver is running on unsupported
1275 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1276 does not match list of supported models.
1278 [HW] Report power status in /proc/i8k
1279 (disabled by default)
1280 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1283 i915.invert_brightness=
1284 [DRM] Invert the sense of the variable that is used to
1285 set the brightness of the panel backlight. Normally a
1286 brightness value of 0 indicates backlight switched off,
1287 and the maximum of the brightness value sets the backlight
1288 to maximum brightness. If this parameter is set to 0
1289 (default) and the machine requires it, or this parameter
1290 is set to 1, a brightness value of 0 sets the backlight
1291 to maximum brightness, and the maximum of the brightness
1292 value switches the backlight off.
1293 -1 -- never invert brightness
1294 0 -- machine default
1295 1 -- force brightness inversion
1298 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1300 ide-core.nodma= [HW] (E)IDE subsystem
1301 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1302 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1303 .cdrom .chs .ignore_cable are additional options
1304 See Documentation/ide/ide.txt.
1306 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1307 Claim all unknown PCI IDE storage controllers.
1310 Format: idle=poll, idle=halt, idle=nomwait
1311 Poll forces a polling idle loop that can slightly
1312 improve the performance of waking up a idle CPU, but
1313 will use a lot of power and make the system run hot.
1315 idle=halt: Halt is forced to be used for CPU idle.
1316 In such case C2/C3 won't be used again.
1317 idle=nomwait: Disable mwait for CPU C-states
1319 ignore_loglevel [KNL]
1320 Ignore loglevel setting - this will print /all/
1321 kernel messages to the console. Useful for debugging.
1322 We also add it as printk module parameter, so users
1323 could change it dynamically, usually by
1324 /sys/module/printk/parameters/ignore_loglevel.
1326 ihash_entries= [KNL]
1327 Set number of hash buckets for inode cache.
1329 ima_appraise= [IMA] appraise integrity measurements
1330 Format: { "off" | "enforce" | "fix" | "log" }
1333 ima_appraise_tcb [IMA]
1334 The builtin appraise policy appraises all files
1338 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1342 The list of supported hash algorithms is defined
1343 in crypto/hash_info.h.
1346 Load a policy which meets the needs of the Trusted
1347 Computing Base. This means IMA will measure all
1348 programs exec'd, files mmap'd for exec, and all files
1349 opened for read by uid=0.
1352 Select one of defined IMA measurements template formats.
1353 Formats: { "ima" | "ima-ng" }
1356 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1357 Format: <min_file_size>
1358 Set the minimal file size for using asynchronous hash.
1359 If left unspecified, ahash usage is disabled.
1361 ahash performance varies for different data sizes on
1362 different crypto accelerators. This option can be used
1363 to achieve the best performance for a particular HW.
1365 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1367 Set hashing buffer size. Default: 4k.
1369 ahash performance varies for different chunk sizes on
1370 different crypto accelerators. This option can be used
1371 to achieve best performance for particular HW.
1375 Run specified binary instead of /sbin/init as init
1378 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1379 for working out where the kernel is dying during
1382 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1383 initcall functions. Useful for debugging built-in
1384 modules and initcalls.
1386 initrd= [BOOT] Specify the location of the initial ramdisk
1388 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1391 int_pln_enable [x86] Enable power limit notification interrupt
1393 integrity_audit=[IMA]
1394 Format: { "0" | "1" }
1395 0 -- basic integrity auditing messages. (Default)
1396 1 -- additional integrity auditing messages.
1398 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1400 Enable intel iommu driver.
1402 Disable intel iommu driver.
1403 igfx_off [Default Off]
1404 By default, gfx is mapped as normal device. If a gfx
1405 device has a dedicated DMAR unit, the DMAR unit is
1406 bypassed by not enabling DMAR with this option. In
1407 this case, gfx device will use physical address for
1410 With this option iommu will not optimize to look
1411 for io virtual address below 32-bit forcing dual
1412 address cycle on pci bus for cards supporting greater
1413 than 32-bit addressing. The default is to look
1414 for translation below 32-bit and if not available
1415 then look in the higher range.
1416 strict [Default Off]
1417 With this option on every unmap_single operation will
1418 result in a hardware IOTLB flush operation as opposed
1419 to batching them for performance.
1420 sp_off [Default Off]
1421 By default, super page will be supported if Intel IOMMU
1422 has the capability. With this option, super page will
1425 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1426 0 disables intel_idle and fall back on acpi_idle.
1427 1 to 6 specify maximum depth of C-state.
1431 Do not enable intel_pstate as the default
1432 scaling driver for the supported processors
1434 intremap= [X86-64, Intel-IOMMU]
1435 on enable Interrupt Remapping (default)
1436 off disable Interrupt Remapping
1437 nosid disable Source ID checking
1439 BIOS x2APIC opt-out request will be ignored
1441 iomem= Disable strict checking of access to MMIO memory
1442 strict regions from userspace.
1459 io7= [HW] IO7 for Marvel based alpha systems
1460 See comment before marvel_specify_io7 in
1461 arch/alpha/kernel/core_marvel.c.
1463 io_delay= [X86] I/O delay method
1465 Standard port 0x80 based delay
1467 Alternate port 0xed based delay (needed on some systems)
1469 Simple two microseconds delay
1474 See Documentation/filesystems/nfs/nfsroot.txt.
1477 When an interrupt is not handled search all handlers
1478 for it. Intended to get systems with badly broken
1482 When an interrupt is not handled search all handlers
1483 for it. Also check all handlers each timer
1484 interrupt. Intended to get systems with badly broken
1488 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1490 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1492 <cpu number>,...,<cpu number>
1494 <cpu number>-<cpu number>
1495 (must be a positive range in ascending order)
1497 <cpu number>,...,<cpu number>-<cpu number>
1499 This option can be used to specify one or more CPUs
1500 to isolate from the general SMP balancing and scheduling
1501 algorithms. You can move a process onto or off an
1502 "isolated" CPU via the CPU affinity syscalls or cpuset.
1503 <cpu number> begins at 0 and the maximum value is
1504 "number of CPUs in system - 1".
1506 This option is the preferred way to isolate CPUs. The
1507 alternative -- manually setting the CPU mask of all
1508 tasks in the system -- can cause problems and
1509 suboptimal load balancer performance.
1513 ivrs_ioapic [HW,X86_64]
1514 Provide an override to the IOAPIC-ID<->DEVICE-ID
1515 mapping provided in the IVRS ACPI table. For
1516 example, to map IOAPIC-ID decimal 10 to
1517 PCI device 00:14.0 write the parameter as:
1518 ivrs_ioapic[10]=00:14.0
1520 ivrs_hpet [HW,X86_64]
1521 Provide an override to the HPET-ID<->DEVICE-ID
1522 mapping provided in the IVRS ACPI table. For
1523 example, to map HPET-ID decimal 0 to
1524 PCI device 00:14.0 write the parameter as:
1525 ivrs_hpet[0]=00:14.0
1527 js= [HW,JOY] Analog joystick
1528 See Documentation/input/joystick.txt.
1531 Enable/disable kernel and module base offset ASLR
1532 (Address Space Layout Randomization) if built into
1533 the kernel. When CONFIG_HIBERNATION is selected,
1534 kASLR is disabled by default. When kASLR is enabled,
1535 hibernation will be disabled.
1539 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1540 specifies the amount of memory usable by the kernel
1541 for non-movable allocations. The requested amount is
1542 spread evenly throughout all nodes in the system. The
1543 remaining memory in each node is used for Movable
1544 pages. In the event, a node is too small to have both
1545 kernelcore and Movable pages, kernelcore pages will
1546 take priority and other nodes will have a larger number
1547 of Movable pages. The Movable zone is used for the
1548 allocation of pages that may be reclaimed or moved
1549 by the page migration subsystem. This means that
1550 HugeTLB pages may not be allocated from this zone.
1551 Note that allocations like PTEs-from-HighMem still
1552 use the HighMem zone if it exists, and the Normal
1553 zone if it does not.
1555 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1556 Format: <Controller#>[,poll interval]
1557 The controller # is the number of the ehci usb debug
1558 port as it is probed via PCI. The poll interval is
1559 optional and is the number seconds in between
1560 each poll cycle to the debug port in case you need
1561 the functionality for interrupting the kernel with
1562 gdb or control-c on the dbgp connection. When
1563 not using this parameter you use sysrq-g to break into
1564 the kernel debugger.
1566 kgdboc= [KGDB,HW] kgdb over consoles.
1567 Requires a tty driver that supports console polling,
1568 or a supported polling keyboard driver (non-usb).
1569 Serial only format: <serial_device>[,baud]
1570 keyboard only format: kbd
1571 keyboard and serial format: kbd,<serial_device>[,baud]
1572 Optional Kernel mode setting:
1573 kms, kbd format: kms,kbd
1574 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1576 kgdbwait [KGDB] Stop kernel execution and enter the
1577 kernel debugger at the earliest opportunity.
1579 kmac= [MIPS] korina ethernet MAC address.
1580 Configure the RouterBoard 532 series on-chip
1581 Ethernet adapter MAC address.
1583 kmemleak= [KNL] Boot-time kmemleak enable/disable
1584 Valid arguments: on, off
1586 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1589 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1590 Valid arguments: 0, 1, 2
1591 kmemcheck=0 (disabled)
1592 kmemcheck=1 (enabled)
1593 kmemcheck=2 (one-shot mode)
1594 Default: 2 (one-shot mode)
1596 kstack=N [X86] Print N words from the kernel stack
1599 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1600 Default is 0 (don't ignore, but inject #GP)
1602 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1606 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1607 Default is 1 (enabled)
1609 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1611 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1613 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1614 (virtualized MMU) support on capable Intel chips.
1615 Default is 1 (enabled)
1617 kvm-intel.emulate_invalid_guest_state=
1618 [KVM,Intel] Enable emulation of invalid guest states
1619 Default is 0 (disabled)
1621 kvm-intel.flexpriority=
1622 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1623 Default is 1 (enabled)
1626 [KVM,Intel] Enable VMX nesting (nVMX).
1627 Default is 0 (disabled)
1629 kvm-intel.unrestricted_guest=
1630 [KVM,Intel] Disable unrestricted guest feature
1631 (virtualized real and unpaged mode) on capable
1632 Intel chips. Default is 1 (enabled)
1634 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1635 feature (tagged TLBs) on capable Intel chips.
1636 Default is 1 (enabled)
1642 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1645 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1646 value for LAPIC timer one-shot implementation. Default
1647 back to the programmable timer unit in the LAPIC.
1649 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1652 libata.dma= [LIBATA] DMA control
1653 libata.dma=0 Disable all PATA and SATA DMA
1654 libata.dma=1 PATA and SATA Disk DMA only
1655 libata.dma=2 ATAPI (CDROM) DMA only
1656 libata.dma=4 Compact Flash DMA only
1657 Combinations also work, so libata.dma=3 enables DMA
1658 for disks and CDROMs, but not CFs.
1660 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1661 libata.ignore_hpa=0 keep BIOS limits (default)
1662 libata.ignore_hpa=1 ignore limits, using full disk
1664 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1668 libata.force= [LIBATA] Force configurations. The format is comma
1669 separated list of "[ID:]VAL" where ID is
1670 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1671 matching port, link or device. Basically, it matches
1672 the ATA ID string printed on console by libata. If
1673 the whole ID part is omitted, the last PORT and DEVICE
1674 values are used. If ID hasn't been specified yet, the
1675 configuration applies to all ports, links and devices.
1677 If only DEVICE is omitted, the parameter applies to
1678 the port and all links and devices behind it. DEVICE
1679 number of 0 either selects the first device or the
1680 first fan-out link behind PMP device. It does not
1681 select the host link. DEVICE number of 15 selects the
1682 host link and device attached to it.
1684 The VAL specifies the configuration to force. As long
1685 as there's no ambiguity shortcut notation is allowed.
1686 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1687 The following configurations can be forced.
1689 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1690 Any ID with matching PORT is used.
1692 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1694 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1695 udma[/][16,25,33,44,66,100,133] notation is also
1698 * [no]ncq: Turn on or off NCQ.
1700 * nohrst, nosrst, norst: suppress hard, soft
1703 * rstonce: only attempt one reset during
1704 hot-unplug link recovery
1706 * dump_id: dump IDENTIFY data.
1708 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1710 * disable: Disable this device.
1712 If there are multiple matching configurations changing
1713 the same attribute, the last one is used.
1715 memblock=debug [KNL] Enable memblock debug messages.
1717 load_ramdisk= [RAM] List of ramdisks to load from floppy
1718 See Documentation/blockdev/ramdisk.txt.
1720 lockd.nlm_grace_period=P [NFS] Assign grace period.
1723 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1726 lockd.nlm_timeout=T [NFS] Assign timeout value.
1729 lockd.nlm_udpport=M [NFS] Assign UDP port.
1732 locktorture.nreaders_stress= [KNL]
1733 Set the number of locking read-acquisition kthreads.
1734 Defaults to being automatically set based on the
1735 number of online CPUs.
1737 locktorture.nwriters_stress= [KNL]
1738 Set the number of locking write-acquisition kthreads.
1740 locktorture.onoff_holdoff= [KNL]
1741 Set time (s) after boot for CPU-hotplug testing.
1743 locktorture.onoff_interval= [KNL]
1744 Set time (s) between CPU-hotplug operations, or
1745 zero to disable CPU-hotplug testing.
1747 locktorture.shuffle_interval= [KNL]
1748 Set task-shuffle interval (jiffies). Shuffling
1749 tasks allows some CPUs to go into dyntick-idle
1750 mode during the locktorture test.
1752 locktorture.shutdown_secs= [KNL]
1753 Set time (s) after boot system shutdown. This
1754 is useful for hands-off automated testing.
1756 locktorture.stat_interval= [KNL]
1757 Time (s) between statistics printk()s.
1759 locktorture.stutter= [KNL]
1760 Time (s) to stutter testing, for example,
1761 specifying five seconds causes the test to run for
1762 five seconds, wait for five seconds, and so on.
1763 This tests the locking primitive's ability to
1764 transition abruptly to and from idle.
1766 locktorture.torture_runnable= [BOOT]
1767 Start locktorture running at boot time.
1769 locktorture.torture_type= [KNL]
1770 Specify the locking implementation to test.
1772 locktorture.verbose= [KNL]
1773 Enable additional printk() statements.
1775 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1778 loglevel= All Kernel Messages with a loglevel smaller than the
1779 console loglevel will be printed to the console. It can
1780 also be changed with klogd or other programs. The
1781 loglevels are defined as follows:
1783 0 (KERN_EMERG) system is unusable
1784 1 (KERN_ALERT) action must be taken immediately
1785 2 (KERN_CRIT) critical conditions
1786 3 (KERN_ERR) error conditions
1787 4 (KERN_WARNING) warning conditions
1788 5 (KERN_NOTICE) normal but significant condition
1789 6 (KERN_INFO) informational
1790 7 (KERN_DEBUG) debug-level messages
1792 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1793 in bytes. n must be a power of two and greater
1794 than the minimal size. The minimal size is defined
1795 by LOG_BUF_SHIFT kernel config parameter. There is
1796 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1797 that allows to increase the default size depending on
1798 the number of CPUs. See init/Kconfig for more details.
1800 logo.nologo [FB] Disables display of the built-in Linux logo.
1801 This may be used to provide more screen space for
1802 kernel log messages and is useful when debugging
1803 kernel boot problems.
1805 lp=0 [LP] Specify parallel ports to use, e.g,
1806 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1807 lp=reset first parallel port). 'lp=0' disables the
1808 lp=auto printer driver. 'lp=reset' (which can be
1809 specified in addition to the ports) causes
1810 attached printers to be reset. Using
1811 lp=port1,port2,... specifies the parallel ports
1812 to associate lp devices with, starting with
1813 lp0. A port specification may be 'none' to skip
1814 that lp device, or a parport name such as
1815 'parport0'. Specifying 'lp=auto' instead of a
1816 port specification list means that device IDs
1817 from each port should be examined, to see if
1818 an IEEE 1284-compliant printer is attached; if
1819 so, the driver will manage that printer.
1820 See also header of drivers/char/lp.c.
1823 Sets loops_per_jiffy to given constant, thus avoiding
1824 time-consuming boot-time autodetection (up to 250 ms per
1825 CPU). 0 enables autodetection (default). To determine
1826 the correct value for your kernel, boot with normal
1827 autodetection and see what value is printed. Note that
1828 on SMP systems the preset will be applied to all CPUs,
1829 which is likely to cause problems if your CPUs need
1830 significantly divergent settings. An incorrect value
1831 will cause delays in the kernel to be wrong, leading to
1832 unpredictable I/O errors and other breakage. Although
1833 unlikely, in the extreme case this might damage your
1837 Format: <io>,<irq>,<dma>
1839 machvec= [IA-64] Force the use of a particular machine-vector
1840 (machvec) in a generic kernel.
1841 Example: machvec=hpzx1_swiotlb
1843 machtype= [Loongson] Share the same kernel image file between different
1845 Example: machtype=lemote-yeeloong-2f-7inch
1847 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1848 than or equal to this physical address is ignored.
1850 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1851 should make use of. maxcpus=n : n >= 0 limits the
1852 kernel to using 'n' processors. n=0 is a special case,
1853 it is equivalent to "nosmp", which also disables
1856 max_loop= [LOOP] The number of loop block devices that get
1857 (loop.max_loop) unconditionally pre-created at init time. The default
1858 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1859 of statically allocating a predefined number, loop
1860 devices can be requested on-demand with the
1861 /dev/loop-control interface.
1863 mce [X86-32] Machine Check Exception
1865 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1867 md= [HW] RAID subsystems devices and level
1868 See Documentation/md.txt.
1871 Format: <first>,<last>
1872 Specifies range of consoles to be captured by the MDA.
1874 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1875 Amount of memory to be used when the kernel is not able
1876 to see the whole system memory or for test.
1877 [X86] Work as limiting max address. Use together
1878 with memmap= to avoid physical address space collisions.
1879 Without memmap= PCI devices could be placed at addresses
1880 belonging to unused RAM.
1882 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1886 [KNL,SH] Allow user to override the default size for
1887 per-device physically contiguous DMA buffers.
1889 memmap=exactmap [KNL,X86] Enable setting of an exact
1890 E820 memory map, as specified by the user.
1891 Such memmap=exactmap lines can be constructed based on
1892 BIOS output or other requirements. See the memmap=nn@ss
1895 memmap=nn[KMG]@ss[KMG]
1896 [KNL] Force usage of a specific region of memory.
1897 Region of memory to be used is from ss to ss+nn.
1899 memmap=nn[KMG]#ss[KMG]
1900 [KNL,ACPI] Mark specific memory as ACPI data.
1901 Region of memory to be marked is from ss to ss+nn.
1903 memmap=nn[KMG]$ss[KMG]
1904 [KNL,ACPI] Mark specific memory as reserved.
1905 Region of memory to be reserved is from ss to ss+nn.
1906 Example: Exclude memory from 0x18690000-0x1869ffff
1907 memmap=64K$0x18690000
1909 memmap=0x10000$0x18690000
1911 memory_corruption_check=0/1 [X86]
1912 Some BIOSes seem to corrupt the first 64k of
1913 memory when doing things like suspend/resume.
1914 Setting this option will scan the memory
1915 looking for corruption. Enabling this will
1916 both detect corruption and prevent the kernel
1917 from using the memory being corrupted.
1918 However, its intended as a diagnostic tool; if
1919 repeatable BIOS-originated corruption always
1920 affects the same memory, you can use memmap=
1921 to prevent the kernel from using that memory.
1923 memory_corruption_check_size=size [X86]
1924 By default it checks for corruption in the low
1925 64k, making this memory unavailable for normal
1926 use. Use this parameter to scan for
1927 corruption in more or less memory.
1929 memory_corruption_check_period=seconds [X86]
1930 By default it checks for corruption every 60
1931 seconds. Use this parameter to check at some
1932 other rate. 0 disables periodic checking.
1934 memtest= [KNL,X86] Enable memtest
1936 default : 0 <disable>
1937 Specifies the number of memtest passes to be
1938 performed. Each pass selects another test
1939 pattern from a given set of patterns. Memtest
1940 fills the memory with this pattern, validates
1941 memory contents and reserves bad memory
1942 regions that are detected.
1944 meye.*= [HW] Set MotionEye Camera parameters
1945 See Documentation/video4linux/meye.txt.
1947 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1948 Multi-Function General Purpose Timers on AMD Geode
1951 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1952 the BIOS has incorrectly applied a workaround. TinyBIOS
1953 version 0.98 is known to be affected, 0.99 fixes the
1954 problem by letting the user disable the workaround.
1958 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1959 physical address is ignored.
1961 mini2440= [ARM,HW,KNL]
1962 Format:[0..2][b][c][t]
1964 MINI2440 configuration specification:
1965 0 - The attached screen is the 3.5" TFT
1966 1 - The attached screen is the 7" TFT
1967 2 - The VGA Shield is attached (1024x768)
1968 Leaving out the screen size parameter will not load
1969 the TFT driver, and the framebuffer will be left
1971 b - Enable backlight. The TFT backlight pin will be
1972 linked to the kernel VESA blanking code and a GPIO
1973 LED. This parameter is not necessary when using the
1975 c - Enable the s3c camera interface.
1976 t - Reserved for enabling touchscreen support. The
1977 touchscreen support is not enabled in the mainstream
1978 kernel as of 2.6.30, a preliminary port can be found
1979 in the "bleeding edge" mini2440 support kernel at
1980 http://repo.or.cz/w/linux-2.6/mini2440.git
1983 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1984 parameter allows control of the logging verbosity for
1985 the additional memory initialisation checks. A value
1986 of 0 disables mminit logging and a level of 4 will
1987 log everything. Information is printed at KERN_DEBUG
1988 so loglevel=8 may also need to be specified.
1991 [KNL] When CONFIG_MODULE_SIG is set, this means that
1992 modules without (valid) signatures will fail to load.
1993 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1994 is always true, so this option does nothing.
1997 [MOUSE] Maximum time between finger touching and
1998 leaving touchpad surface for touch to be considered
1999 a tap and be reported as a left button click (for
2000 touchpads working in absolute mode only).
2002 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2003 reporting absolute coordinates, such as tablets
2004 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2005 reporting absolute coordinates, such as tablets
2007 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2008 is similar to kernelcore except it specifies the
2009 amount of memory used for migratable allocations.
2010 If both kernelcore and movablecore is specified,
2011 then kernelcore will be at *least* the specified
2012 value but may be more. If movablecore on its own
2013 is specified, the administrator must be careful
2014 that the amount of memory usable for all allocations
2017 movable_node [KNL,X86] Boot-time switch to enable the effects
2018 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2020 MTD_Partition= [MTD]
2021 Format: <name>,<region-number>,<size>,<offset>
2023 MTD_Region= [MTD] Format:
2024 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2027 See drivers/mtd/cmdlinepart.c.
2029 multitce=off [PPC] This parameter disables the use of the pSeries
2030 firmware feature for updating multiple TCE entries
2033 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2035 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2037 boundary - index of last SLC block on Flex-OneNAND.
2038 The remaining blocks are configured as MLC blocks.
2039 lock - Configure if Flex-OneNAND boundary should be locked.
2040 Once locked, the boundary cannot be changed.
2041 1 indicates lock status, 0 indicates unlock status.
2044 ARM/S3C2412 JIVE boot control
2046 See arch/arm/mach-s3c2412/mach-jive.c
2048 mtouchusb.raw_coordinates=
2049 [HW] Make the MicroTouch USB driver use raw coordinates
2050 ('y', default) or cooked coordinates ('n')
2052 mtrr_chunk_size=nn[KMG] [X86]
2053 used for mtrr cleanup. It is largest continuous chunk
2054 that could hold holes aka. UC entries.
2056 mtrr_gran_size=nn[KMG] [X86]
2057 Used for mtrr cleanup. It is granularity of mtrr block.
2059 Large value could prevent small alignment from
2062 mtrr_spare_reg_nr=n [X86]
2064 Range: 0,7 : spare reg number
2066 Used for mtrr cleanup. It is spare mtrr entries number.
2067 Set to 2 or more if your graphical card needs more.
2069 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2071 netdev= [NET] Network devices parameters
2072 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2073 Note that mem_start is often overloaded to mean
2074 something different and driver-specific.
2075 This usage is only documented in each driver source
2079 [NETFILTER] Enable connection tracking flow accounting
2080 0 to disable accounting
2081 1 to enable accounting
2084 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2085 See Documentation/filesystems/nfs/nfsroot.txt.
2087 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2088 See Documentation/filesystems/nfs/nfsroot.txt.
2090 nfsrootdebug [NFS] enable nfsroot debugging messages.
2091 See Documentation/filesystems/nfs/nfsroot.txt.
2093 nfs.callback_tcpport=
2094 [NFS] set the TCP port on which the NFSv4 callback
2095 channel should listen.
2098 [NFS] sets the pathname to the program which is used
2099 to update the NFS client cache entries.
2101 nfs.cache_getent_timeout=
2102 [NFS] sets the timeout after which an attempt to
2103 update a cache entry is deemed to have failed.
2105 nfs.idmap_cache_timeout=
2106 [NFS] set the maximum lifetime for idmapper cache
2110 [NFS] enable 64-bit inode numbers.
2111 If zero, the NFS client will fake up a 32-bit inode
2112 number for the readdir() and stat() syscalls instead
2113 of returning the full 64-bit number.
2114 The default is to return 64-bit inode numbers.
2116 nfs.max_session_slots=
2117 [NFSv4.1] Sets the maximum number of session slots
2118 the client will attempt to negotiate with the server.
2119 This limits the number of simultaneous RPC requests
2120 that the client can send to the NFSv4.1 server.
2121 Note that there is little point in setting this
2122 value higher than the max_tcp_slot_table_limit.
2124 nfs.nfs4_disable_idmapping=
2125 [NFSv4] When set to the default of '1', this option
2126 ensures that both the RPC level authentication
2127 scheme and the NFS level operations agree to use
2128 numeric uids/gids if the mount is using the
2129 'sec=sys' security flavour. In effect it is
2130 disabling idmapping, which can make migration from
2131 legacy NFSv2/v3 systems to NFSv4 easier.
2132 Servers that do not support this mode of operation
2133 will be autodetected by the client, and it will fall
2134 back to using the idmapper.
2135 To turn off this behaviour, set the value to '0'.
2137 [NFS4] Specify an additional fixed unique ident-
2138 ification string that NFSv4 clients can insert into
2139 their nfs_client_id4 string. This is typically a
2140 UUID that is generated at system install time.
2142 nfs.send_implementation_id =
2143 [NFSv4.1] Send client implementation identification
2144 information in exchange_id requests.
2145 If zero, no implementation identification information
2147 The default is to send the implementation identification
2150 nfs.recover_lost_locks =
2151 [NFSv4] Attempt to recover locks that were lost due
2152 to a lease timeout on the server. Please note that
2153 doing this risks data corruption, since there are
2154 no guarantees that the file will remain unchanged
2155 after the locks are lost.
2156 If you want to enable the kernel legacy behaviour of
2157 attempting to recover these locks, then set this
2159 The default parameter value of '0' causes the kernel
2160 not to attempt recovery of lost locks.
2162 nfsd.nfs4_disable_idmapping=
2163 [NFSv4] When set to the default of '1', the NFSv4
2164 server will return only numeric uids and gids to
2165 clients using auth_sys, and will accept numeric uids
2166 and gids from such clients. This is intended to ease
2167 migration from NFSv2/v3.
2169 objlayoutdriver.osd_login_prog=
2170 [NFS] [OBJLAYOUT] sets the pathname to the program which
2171 is used to automatically discover and login into new
2172 osd-targets. Please see:
2173 Documentation/filesystems/pnfs.txt for more explanations
2175 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2176 when a NMI is triggered.
2177 Format: [state][,regs][,debounce][,die]
2179 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2180 Format: [panic,][nopanic,][num]
2182 0 - turn nmi_watchdog off
2183 When panic is specified, panic when an NMI watchdog
2184 timeout occurs (or 'nopanic' to override the opposite
2186 This is useful when you use a panic=... timeout and
2187 need the box quickly up again.
2189 netpoll.carrier_timeout=
2190 [NET] Specifies amount of time (in seconds) that
2191 netpoll should wait for a carrier. By default netpoll
2194 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2195 emulation library even if a 387 maths coprocessor
2199 [HW] Never suspend the console
2200 Disable suspending of consoles during suspend and
2201 hibernate operations. Once disabled, debugging
2202 messages can reach various consoles while the rest
2203 of the system is being put to sleep (ie, while
2204 debugging driver suspend/resume hooks). This may
2205 not work reliably with all consoles, but is known
2206 to work with serial and VGA consoles.
2207 To facilitate more flexible debugging, we also add
2208 console_suspend, a printk module parameter to control
2209 it. Users could use console_suspend (usually
2210 /sys/module/printk/parameters/console_suspend) to
2211 turn on/off it dynamically.
2213 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2214 caches in the slab allocator. Saves per-node memory,
2215 but will impact performance.
2219 noapic [SMP,APIC] Tells the kernel to not make use of any
2220 IOAPICs that may be present in the system.
2222 noautogroup Disable scheduler automatic task group creation.
2224 nobats [PPC] Do not use BATs for mapping kernel lowmem
2225 on "Classic" PPC cores.
2229 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2231 nodelayacct [KNL] Disable per-task delay accounting
2233 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2235 nodsp [SH] Disable hardware DSP at boot time.
2237 noefi [X86] Disable EFI runtime services support.
2242 On X86-32 available only on PAE configured kernels.
2243 noexec=on: enable non-executable mappings (default)
2244 noexec=off: disable non-executable mappings
2247 Disable SMAP (Supervisor Mode Access Prevention)
2248 even if it is supported by processor.
2251 Disable SMEP (Supervisor Mode Execution Prevention)
2252 even if it is supported by processor.
2255 This affects only 32-bit executables.
2256 noexec32=on: enable non-executable mappings (default)
2257 read doesn't imply executable mappings
2258 noexec32=off: disable non-executable mappings
2259 read implies executable mappings
2261 nofpu [SH] Disable hardware FPU at boot time.
2263 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2264 register save and restore. The kernel will only save
2265 legacy floating-point registers on task switch.
2267 noxsave [BUGS=X86] Disables x86 extended register state save
2268 and restore using xsave. The kernel will fallback to
2269 enabling legacy floating-point and sse state.
2271 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2272 register states. The kernel will fall back to use
2273 xsave to save the states. By using this parameter,
2274 performance of saving the states is degraded because
2275 xsave doesn't support modified optimization while
2276 xsaveopt supports it on xsaveopt enabled systems.
2278 noxsaves [X86] Disables xsaves and xrstors used in saving and
2279 restoring x86 extended register state in compacted
2280 form of xsave area. The kernel will fall back to use
2281 xsaveopt and xrstor to save and restore the states
2282 in standard form of xsave area. By using this
2283 parameter, xsave area per process might occupy more
2284 memory on xsaves enabled systems.
2287 on enable eager fpu restore
2288 off disable eager fpu restore
2289 auto selects the default scheme, which automatically
2290 enables eagerfpu restore for xsaveopt.
2292 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2293 wfi(ARM) instruction doesn't work correctly and not to
2294 use it. This is also useful when using JTAG debugger.
2296 no_file_caps Tells the kernel not to honor file capabilities. The
2297 only way then for a file to be executed with privilege
2298 is to be setuid root or executed by root.
2300 nohalt [IA-64] Tells the kernel not to use the power saving
2301 function PAL_HALT_LIGHT when idle. This increases
2302 power-consumption. On the positive side, it reduces
2303 interrupt wake-up latency, which may improve performance
2304 in certain environments such as networked servers or
2307 nohibernate [HIBERNATION] Disable hibernation and resume.
2309 nohz= [KNL] Boottime enable/disable dynamic ticks
2310 Valid arguments: on, off
2313 nohz_full= [KNL,BOOT]
2314 In kernels built with CONFIG_NO_HZ_FULL=y, set
2315 the specified list of CPUs whose tick will be stopped
2316 whenever possible. The boot CPU will be forced outside
2317 the range to maintain the timekeeping.
2318 The CPUs in this range must also be included in the
2321 noiotrap [SH] Disables trapped I/O port accesses.
2323 noirqdebug [X86-32] Disables the code which attempts to detect and
2324 disable unhandled interrupt sources.
2326 no_timer_check [X86,APIC] Disables the code which tests for
2327 broken timer IRQ sources.
2329 noisapnp [ISAPNP] Disables ISA PnP code.
2331 noinitrd [RAM] Tells the kernel not to load any configured
2334 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2336 [Deprecated - use intremap=off]
2340 nojitter [IA-64] Disables jitter checking for ITC timers.
2342 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2344 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2347 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2348 steal time is computed, but won't influence scheduler
2351 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2353 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2355 noltlbs [PPC] Do not use large page/tlb entries for kernel
2356 lowmem mapping on PPC40x.
2358 nomca [IA-64] Disable machine check abort handling
2360 nomce [X86-32] Machine Check Exception
2362 nomfgpt [X86-32] Disable Multi-Function General Purpose
2363 Timer usage (for AMD Geode machines).
2365 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2366 shutdown the other cpus. Instead use the REBOOT_VECTOR
2369 nomodule Disable module load
2371 nopat [X86] Disable PAT (page attribute table extension of
2372 pagetables) support.
2374 norandmaps Don't use address space randomization. Equivalent to
2375 echo 0 > /proc/sys/kernel/randomize_va_space
2377 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2379 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2380 with UP alternatives
2382 nordrand [X86] Disable kernel use of the RDRAND and
2383 RDSEED instructions even if they are supported
2384 by the processor. RDRAND and RDSEED are still
2385 available to user space applications.
2387 noresume [SWSUSP] Disables resume and restores original swap
2390 no-scroll [VGA] Disables scrollback.
2391 This is required for the Braillex ib80-piezo Braille
2392 reader made by F.H. Papenmeier (Germany).
2396 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2398 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2399 and disable the IO APIC. legacy for "maxcpus=0".
2401 nosoftlockup [KNL] Disable the soft-lockup detector.
2403 nosync [HW,M68K] Disables sync negotiation for all devices.
2405 notsc [BUGS=X86-32] Disable Time Stamp Counter
2407 nousb [USB] Disable the USB subsystem
2409 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2413 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2415 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2416 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2417 Some features depend on CPU0. Known dependencies are:
2418 1. Resume from suspend/hibernate depends on CPU0.
2419 Suspend/hibernate will fail if CPU0 is offline and you
2420 need to online CPU0 before suspend/hibernate.
2421 2. PIC interrupts also depend on CPU0. CPU0 can't be
2422 removed if a PIC interrupt is detected.
2423 It's said poweroff/reboot may depend on CPU0 on some
2424 machines although I haven't seen such issues so far
2425 after CPU0 is offline on a few tested machines.
2426 If the dependencies are under your control, you can
2427 turn on cpu0_hotplug.
2429 nptcg= [IA-64] Override max number of concurrent global TLB
2430 purges which is reported from either PAL_VM_SUMMARY or
2433 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2434 could support. nr_cpus=n : n >= 1 limits the kernel to
2435 supporting 'n' processors. Later in runtime you can not
2436 use hotplug cpu feature to put more cpu back to online.
2437 just like you compile the kernel NR_CPUS=n
2439 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2441 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2442 Allowed values are enable and disable
2444 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2445 one of ['zone', 'node', 'default'] can be specified
2446 This can be set from sysctl after boot.
2447 See Documentation/sysctl/vm.txt for details.
2449 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2450 See Documentation/debugging-via-ohci1394.txt for more
2453 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2454 Rather than timing out after 20 ms if an EC
2455 command is not properly ACKed, override the length
2456 of the timeout. We have interrupts disabled while
2457 waiting for the ACK, so if this is set too high
2458 interrupts *may* be lost!
2460 omap_mux= [OMAP] Override bootloader pin multiplexing.
2461 Format: <mux_mode0.mode_name=value>...
2462 For example, to override I2C bus2:
2463 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2465 oprofile.timer= [HW]
2466 Use timer interrupt instead of performance counters
2468 oprofile.cpu_type= Force an oprofile cpu type
2469 This might be useful if you have an older oprofile
2470 userland or if you want common events.
2471 Format: { arch_perfmon }
2472 arch_perfmon: [X86] Force use of architectural
2473 perfmon on Intel CPUs instead of the
2474 CPU specific event set.
2475 timer: [X86] Force use of architectural NMI
2476 timer mode (see also oprofile.timer
2477 for generic hr timer mode)
2478 [s390] Force legacy basic mode sampling
2479 (report cpu_type "timer")
2481 oops=panic Always panic on oopses. Default is to just kill the
2482 process, but there is a small probability of
2483 deadlocking the machine.
2484 This will also cause panics on machine check exceptions.
2485 Useful together with panic=30 to trigger a reboot.
2488 See Documentation/sound/oss/oss-parameters.txt
2490 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2491 timeout > 0: seconds before rebooting
2492 timeout = 0: wait forever
2493 timeout < 0: reboot immediately
2496 crash_kexec_post_notifiers
2497 Run kdump after running panic-notifiers and dumping
2498 kmsg. This only for the users who doubt kdump always
2499 succeeds in any situation.
2500 Note that this also increases risks of kdump failure,
2501 because some panic notifiers can make the crashed
2502 kernel more unstable.
2504 parkbd.port= [HW] Parallel port number the keyboard adapter is
2505 connected to, default is 0.
2507 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2508 0 for XT, 1 for AT (default is AT).
2511 parport= [HW,PPT] Specify parallel ports. 0 disables.
2512 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2513 Use 'auto' to force the driver to use any
2514 IRQ/DMA settings detected (the default is to
2515 ignore detected IRQ/DMA settings because of
2516 possible conflicts). You can specify the base
2517 address, IRQ, and DMA settings; IRQ and DMA
2518 should be numbers, or 'auto' (for using detected
2519 settings on that particular port), or 'nofifo'
2520 (to avoid using a FIFO even if it is detected).
2521 Parallel ports are assigned in the order they
2522 are specified on the command line, starting
2525 parport_init_mode= [HW,PPT]
2526 Configure VIA parallel port to operate in
2527 a specific mode. This is necessary on Pegasos
2528 computer where firmware has no options for setting
2529 up parallel port mode and sets it to spp.
2530 Currently this function knows 686a and 8231 chips.
2531 Format: [spp|ps2|epp|ecp|ecpepp]
2534 Halt all CPUs after the first oops has been printed for
2535 the specified number of seconds. This is to be used if
2536 your oopses keep scrolling off the screen.
2541 See header of drivers/block/paride/pcd.c.
2542 See also Documentation/blockdev/paride.txt.
2544 pci=option[,option...] [PCI] various PCI subsystem options:
2545 earlydump [X86] dump PCI config space before the kernel
2547 off [X86] don't probe for the PCI bus
2548 bios [X86-32] force use of PCI BIOS, don't access
2549 the hardware directly. Use this if your machine
2550 has a non-standard PCI host bridge.
2551 nobios [X86-32] disallow use of PCI BIOS, only direct
2552 hardware access methods are allowed. Use this
2553 if you experience crashes upon bootup and you
2554 suspect they are caused by the BIOS.
2555 conf1 [X86] Force use of PCI Configuration
2557 conf2 [X86] Force use of PCI Configuration
2559 noaer [PCIE] If the PCIEAER kernel config parameter is
2560 enabled, this kernel boot option can be used to
2561 disable the use of PCIE advanced error reporting.
2562 nodomains [PCI] Disable support for multiple PCI
2563 root domains (aka PCI segments, in ACPI-speak).
2564 nommconf [X86] Disable use of MMCONFIG for PCI
2566 check_enable_amd_mmconf [X86] check for and enable
2567 properly configured MMIO access to PCI
2568 config space on AMD family 10h CPU
2569 nomsi [MSI] If the PCI_MSI kernel config parameter is
2570 enabled, this kernel boot option can be used to
2571 disable the use of MSI interrupts system-wide.
2572 noioapicquirk [APIC] Disable all boot interrupt quirks.
2573 Safety option to keep boot IRQs enabled. This
2574 should never be necessary.
2575 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2576 primary IO-APIC for bridges that cannot disable
2577 boot IRQs. This fixes a source of spurious IRQs
2578 when the system masks IRQs.
2579 noioapicreroute [APIC] Disable workaround that uses the
2580 boot IRQ equivalent of an IRQ that connects to
2581 a chipset where boot IRQs cannot be disabled.
2582 The opposite of ioapicreroute.
2583 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2584 routing table. These calls are known to be buggy
2585 on several machines and they hang the machine
2586 when used, but on other computers it's the only
2587 way to get the interrupt routing table. Try
2588 this option if the kernel is unable to allocate
2589 IRQs or discover secondary PCI buses on your
2591 rom [X86] Assign address space to expansion ROMs.
2592 Use with caution as certain devices share
2593 address decoders between ROMs and other
2595 norom [X86] Do not assign address space to
2596 expansion ROMs that do not already have
2597 BIOS assigned address ranges.
2598 nobar [X86] Do not assign address space to the
2599 BARs that weren't assigned by the BIOS.
2600 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2601 assigned automatically to PCI devices. You can
2602 make the kernel exclude IRQs of your ISA cards
2604 pirqaddr=0xAAAAA [X86] Specify the physical address
2605 of the PIRQ table (normally generated
2606 by the BIOS) if it is outside the
2607 F0000h-100000h range.
2608 lastbus=N [X86] Scan all buses thru bus #N. Can be
2609 useful if the kernel is unable to find your
2610 secondary buses and you want to tell it
2611 explicitly which ones they are.
2612 assign-busses [X86] Always assign all PCI bus
2613 numbers ourselves, overriding
2614 whatever the firmware may have done.
2615 usepirqmask [X86] Honor the possible IRQ mask stored
2616 in the BIOS $PIR table. This is needed on
2617 some systems with broken BIOSes, notably
2618 some HP Pavilion N5400 and Omnibook XE3
2619 notebooks. This will have no effect if ACPI
2620 IRQ routing is enabled.
2621 noacpi [X86] Do not use ACPI for IRQ routing
2622 or for PCI scanning.
2623 use_crs [X86] Use PCI host bridge window information
2624 from ACPI. On BIOSes from 2008 or later, this
2625 is enabled by default. If you need to use this,
2626 please report a bug.
2627 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2628 If you need to use this, please report a bug.
2629 routeirq Do IRQ routing for all PCI devices.
2630 This is normally done in pci_enable_device(),
2631 so this option is a temporary workaround
2632 for broken drivers that don't call it.
2633 skip_isa_align [X86] do not align io start addr, so can
2634 handle more pci cards
2635 firmware [ARM] Do not re-enumerate the bus but instead
2636 just use the configuration from the
2637 bootloader. This is currently used on
2638 IXP2000 systems where the bus has to be
2639 configured a certain way for adjunct CPUs.
2640 noearly [X86] Don't do any early type 1 scanning.
2641 This might help on some broken boards which
2642 machine check when some devices' config space
2643 is read. But various workarounds are disabled
2644 and some IOMMU drivers will not work.
2645 bfsort Sort PCI devices into breadth-first order.
2646 This sorting is done to get a device
2647 order compatible with older (<= 2.4) kernels.
2648 nobfsort Don't sort PCI devices into breadth-first order.
2649 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2650 tuning and use the BIOS-configured MPS defaults.
2651 pcie_bus_safe Set every device's MPS to the largest value
2652 supported by all devices below the root complex.
2653 pcie_bus_perf Set device MPS to the largest allowable MPS
2654 based on its parent bus. Also set MRRS (Max
2655 Read Request Size) to the largest supported
2656 value (no larger than the MPS that the device
2657 or bus can support) for best performance.
2658 pcie_bus_peer2peer Set every device's MPS to 128B, which
2659 every device is guaranteed to support. This
2660 configuration allows peer-to-peer DMA between
2661 any pair of devices, possibly at the cost of
2662 reduced performance. This also guarantees
2663 that hot-added devices will work.
2664 cbiosize=nn[KMG] The fixed amount of bus space which is
2665 reserved for the CardBus bridge's IO window.
2666 The default value is 256 bytes.
2667 cbmemsize=nn[KMG] The fixed amount of bus space which is
2668 reserved for the CardBus bridge's memory
2669 window. The default value is 64 megabytes.
2672 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2673 Specifies alignment and device to reassign
2674 aligned memory resources.
2675 If <order of align> is not specified,
2676 PAGE_SIZE is used as alignment.
2677 PCI-PCI bridge can be specified, if resource
2678 windows need to be expanded.
2679 ecrc= Enable/disable PCIe ECRC (transaction layer
2680 end-to-end CRC checking).
2681 bios: Use BIOS/firmware settings. This is the
2685 hpiosize=nn[KMG] The fixed amount of bus space which is
2686 reserved for hotplug bridge's IO window.
2687 Default size is 256 bytes.
2688 hpmemsize=nn[KMG] The fixed amount of bus space which is
2689 reserved for hotplug bridge's memory window.
2690 Default size is 2 megabytes.
2691 realloc= Enable/disable reallocating PCI bridge resources
2692 if allocations done by BIOS are too small to
2693 accommodate resources required by all child
2695 off: Turn realloc off
2697 realloc same as realloc=on
2698 noari do not use PCIe ARI.
2699 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2700 only look for one device below a PCIe downstream
2703 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2706 force Enable ASPM even on devices that claim not to support it.
2707 WARNING: Forcing ASPM on may cause system lockups.
2709 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2710 nomsi Do not use MSI for PCI Express Native Hotplug (this
2711 makes all PCIe ports use INTx for hotplug services).
2713 pcie_ports= [PCIE] PCIe ports handling:
2714 auto Ask the BIOS whether or not to use native PCIe services
2715 associated with PCIe ports (PME, hot-plug, AER). Use
2716 them only if that is allowed by the BIOS.
2717 native Use native PCIe services associated with PCIe ports
2719 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2722 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2723 nomsi Do not use MSI for native PCIe PME signaling (this makes
2724 all PCIe root ports use INTx for all services).
2726 pcmv= [HW,PCMCIA] BadgePAD 4
2730 Keep all power-domains already enabled by bootloader on,
2731 even if no driver has claimed them. This is useful
2732 for debug and development, but should not be
2733 needed on a platform with proper driver support.
2736 See Documentation/blockdev/paride.txt.
2738 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2741 See arch/parisc/kernel/pdc_chassis.c
2743 percpu_alloc= Select which percpu first chunk allocator to use.
2744 Currently supported values are "embed" and "page".
2745 Archs may support subset or none of the selections.
2746 See comments in mm/percpu.c for details on each
2747 allocator. This parameter is primarily for debugging
2748 and performance comparison.
2751 See Documentation/blockdev/paride.txt.
2754 See Documentation/blockdev/paride.txt.
2756 pirq= [SMP,APIC] Manual mp-table setup
2757 See Documentation/x86/i386/IO-APIC.txt.
2759 plip= [PPT,NET] Parallel port network link
2760 Format: { parport<nr> | timid | 0 }
2761 See also Documentation/parport.txt.
2763 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2764 Override pmtimer IOPort with a hex value.
2768 Enable PNP debug messages (depends on the
2769 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2770 via /sys/module/pnp/parameters/debug. We always show
2771 current resource usage; turning this on also shows
2772 possible settings and some assignment information.
2778 { on | off | curr | res | no-curr | no-res }
2781 [ISAPNP] Exclude IRQs for the autoconfiguration
2784 [ISAPNP] Exclude DMAs for the autoconfiguration
2786 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2787 Ranges are in pairs (I/O port base and size).
2790 [ISAPNP] Exclude memory regions for the
2792 Ranges are in pairs (memory base and size).
2794 ports= [IP_VS_FTP] IPVS ftp helper module
2796 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2798 Format: <port>,<port>....
2800 print-fatal-signals=
2801 [KNL] debug: print fatal signals
2803 If enabled, warn about various signal handling
2804 related application anomalies: too many signals,
2805 too many POSIX.1 timers, fatal signals causing a
2808 If you hit the warning due to signal overflow,
2809 you might want to try "ulimit -i unlimited".
2813 printk.always_kmsg_dump=
2814 Trigger kmsg_dump for cases other than kernel oops or
2816 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2819 printk.time= Show timing data prefixed to each printk message line
2820 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2822 processor.max_cstate= [HW,ACPI]
2823 Limit processor to maximum C-state
2824 max_cstate=9 overrides any DMI blacklist limit.
2826 processor.nocst [HW,ACPI]
2827 Ignore the _CST method to determine C-states,
2828 instead using the legacy FADT method
2830 profile= [KNL] Enable kernel profiling via /proc/profile
2831 Format: [schedule,]<number>
2832 Param: "schedule" - profile schedule points.
2833 Param: <number> - step/bucket size as a power of 2 for
2834 statistical time based profiling.
2835 Param: "sleep" - profile D-state sleeping (millisecs).
2836 Requires CONFIG_SCHEDSTATS
2837 Param: "kvm" - profile VM exits.
2839 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2841 See Documentation/blockdev/ramdisk.txt.
2843 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2844 probe for; one of (bare|imps|exps|lifebook|any).
2845 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2847 psmouse.resetafter= [HW,MOUSE]
2848 Try to reset the device after so many bad packets
2851 [HW,MOUSE] Set desired mouse resolution, in dpi.
2852 psmouse.smartscroll=
2853 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2854 0 = disabled, 1 = enabled (default).
2856 pstore.backend= Specify the name of the pstore backend to use
2859 See Documentation/blockdev/paride.txt.
2862 [KNL] Number of legacy pty's. Overwrites compiled-in
2865 quiet [KNL] Disable most log messages
2870 See Documentation/md.txt.
2872 ramdisk_blocksize= [RAM]
2873 See Documentation/blockdev/ramdisk.txt.
2875 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2876 See Documentation/blockdev/ramdisk.txt.
2879 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2880 the specified list of CPUs to be no-callback CPUs.
2881 Invocation of these CPUs' RCU callbacks will
2882 be offloaded to "rcuox/N" kthreads created for
2883 that purpose, where "x" is "b" for RCU-bh, "p"
2884 for RCU-preempt, and "s" for RCU-sched, and "N"
2885 is the CPU number. This reduces OS jitter on the
2886 offloaded CPUs, which can be useful for HPC and
2887 real-time workloads. It can also improve energy
2888 efficiency for asymmetric multiprocessors.
2891 Rather than requiring that offloaded CPUs
2892 (specified by rcu_nocbs= above) explicitly
2893 awaken the corresponding "rcuoN" kthreads,
2894 make these kthreads poll for callbacks.
2895 This improves the real-time response for the
2896 offloaded CPUs by relieving them of the need to
2897 wake up the corresponding kthread, but degrades
2898 energy efficiency by requiring that the kthreads
2899 periodically wake up to do the polling.
2901 rcutree.blimit= [KNL]
2902 Set maximum number of finished RCU callbacks to
2903 process in one batch.
2905 rcutree.rcu_fanout_leaf= [KNL]
2906 Increase the number of CPUs assigned to each
2907 leaf rcu_node structure. Useful for very large
2910 rcutree.jiffies_till_sched_qs= [KNL]
2911 Set required age in jiffies for a
2912 given grace period before RCU starts
2913 soliciting quiescent-state help from
2914 rcu_note_context_switch().
2916 rcutree.jiffies_till_first_fqs= [KNL]
2917 Set delay from grace-period initialization to
2918 first attempt to force quiescent states.
2919 Units are jiffies, minimum value is zero,
2920 and maximum value is HZ.
2922 rcutree.jiffies_till_next_fqs= [KNL]
2923 Set delay between subsequent attempts to force
2924 quiescent states. Units are jiffies, minimum
2925 value is one, and maximum value is HZ.
2927 rcutree.rcu_nocb_leader_stride= [KNL]
2928 Set the number of NOCB kthread groups, which
2929 defaults to the square root of the number of
2930 CPUs. Larger numbers reduces the wakeup overhead
2931 on the per-CPU grace-period kthreads, but increases
2932 that same overhead on each group's leader.
2934 rcutree.qhimark= [KNL]
2935 Set threshold of queued RCU callbacks beyond which
2936 batch limiting is disabled.
2938 rcutree.qlowmark= [KNL]
2939 Set threshold of queued RCU callbacks below which
2940 batch limiting is re-enabled.
2942 rcutree.rcu_idle_gp_delay= [KNL]
2943 Set wakeup interval for idle CPUs that have
2944 RCU callbacks (RCU_FAST_NO_HZ=y).
2946 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2947 Set wakeup interval for idle CPUs that have
2948 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2949 Lazy RCU callbacks are those which RCU can
2950 prove do nothing more than free memory.
2952 rcutorture.cbflood_inter_holdoff= [KNL]
2953 Set holdoff time (jiffies) between successive
2954 callback-flood tests.
2956 rcutorture.cbflood_intra_holdoff= [KNL]
2957 Set holdoff time (jiffies) between successive
2958 bursts of callbacks within a given callback-flood
2961 rcutorture.cbflood_n_burst= [KNL]
2962 Set the number of bursts making up a given
2963 callback-flood test. Set this to zero to
2964 disable callback-flood testing.
2966 rcutorture.cbflood_n_per_burst= [KNL]
2967 Set the number of callbacks to be registered
2968 in a given burst of a callback-flood test.
2970 rcutorture.fqs_duration= [KNL]
2971 Set duration of force_quiescent_state bursts.
2973 rcutorture.fqs_holdoff= [KNL]
2974 Set holdoff time within force_quiescent_state bursts.
2976 rcutorture.fqs_stutter= [KNL]
2977 Set wait time between force_quiescent_state bursts.
2979 rcutorture.gp_exp= [KNL]
2980 Use expedited update-side primitives.
2982 rcutorture.gp_normal= [KNL]
2983 Use normal (non-expedited) update-side primitives.
2984 If both gp_exp and gp_normal are set, do both.
2985 If neither gp_exp nor gp_normal are set, still
2988 rcutorture.n_barrier_cbs= [KNL]
2989 Set callbacks/threads for rcu_barrier() testing.
2991 rcutorture.nfakewriters= [KNL]
2992 Set number of concurrent RCU writers. These just
2993 stress RCU, they don't participate in the actual
2994 test, hence the "fake".
2996 rcutorture.nreaders= [KNL]
2997 Set number of RCU readers.
2999 rcutorture.object_debug= [KNL]
3000 Enable debug-object double-call_rcu() testing.
3002 rcutorture.onoff_holdoff= [KNL]
3003 Set time (s) after boot for CPU-hotplug testing.
3005 rcutorture.onoff_interval= [KNL]
3006 Set time (s) between CPU-hotplug operations, or
3007 zero to disable CPU-hotplug testing.
3009 rcutorture.torture_runnable= [BOOT]
3010 Start rcutorture running at boot time.
3012 rcutorture.shuffle_interval= [KNL]
3013 Set task-shuffle interval (s). Shuffling tasks
3014 allows some CPUs to go into dyntick-idle mode
3015 during the rcutorture test.
3017 rcutorture.shutdown_secs= [KNL]
3018 Set time (s) after boot system shutdown. This
3019 is useful for hands-off automated testing.
3021 rcutorture.stall_cpu= [KNL]
3022 Duration of CPU stall (s) to test RCU CPU stall
3023 warnings, zero to disable.
3025 rcutorture.stall_cpu_holdoff= [KNL]
3026 Time to wait (s) after boot before inducing stall.
3028 rcutorture.stat_interval= [KNL]
3029 Time (s) between statistics printk()s.
3031 rcutorture.stutter= [KNL]
3032 Time (s) to stutter testing, for example, specifying
3033 five seconds causes the test to run for five seconds,
3034 wait for five seconds, and so on. This tests RCU's
3035 ability to transition abruptly to and from idle.
3037 rcutorture.test_boost= [KNL]
3038 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3039 "Maybe" means test if the RCU implementation
3040 under test support RCU priority boosting.
3042 rcutorture.test_boost_duration= [KNL]
3043 Duration (s) of each individual boost test.
3045 rcutorture.test_boost_interval= [KNL]
3046 Interval (s) between each boost test.
3048 rcutorture.test_no_idle_hz= [KNL]
3049 Test RCU's dyntick-idle handling. See also the
3050 rcutorture.shuffle_interval parameter.
3052 rcutorture.torture_type= [KNL]
3053 Specify the RCU implementation to test.
3055 rcutorture.verbose= [KNL]
3056 Enable additional printk() statements.
3058 rcupdate.rcu_expedited= [KNL]
3059 Use expedited grace-period primitives, for
3060 example, synchronize_rcu_expedited() instead
3061 of synchronize_rcu(). This reduces latency,
3062 but can increase CPU utilization, degrade
3063 real-time latency, and degrade energy efficiency.
3065 rcupdate.rcu_cpu_stall_suppress= [KNL]
3066 Suppress RCU CPU stall warning messages.
3068 rcupdate.rcu_cpu_stall_timeout= [KNL]
3069 Set timeout for RCU CPU stall warning messages.
3071 rcupdate.rcu_task_stall_timeout= [KNL]
3072 Set timeout in jiffies for RCU task stall warning
3073 messages. Disable with a value less than or equal
3078 Run specified binary instead of /init from the ramdisk,
3079 used for early userspace startup. See initrd.
3082 Format (x86 or x86_64):
3083 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3085 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3087 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3088 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3089 reboot_force is either force or not specified,
3090 reboot_cpu is s[mp]#### with #### being the processor
3091 to be used for rebooting.
3094 [KNL, SMP] Set scheduler's default relax_domain_level.
3095 See Documentation/cgroups/cpusets.txt.
3097 relative_sleep_states=
3098 [SUSPEND] Use sleep state labeling where the deepest
3099 state available other than hibernation is always "mem".
3100 Format: { "0" | "1" }
3101 0 -- Traditional sleep state labels.
3102 1 -- Relative sleep state labels.
3104 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3106 reservetop= [X86-32]
3108 Reserves a hole at the top of the kernel virtual
3113 Set the amount of memory to reserve for BIOS at
3114 the bottom of the address space.
3116 reset_devices [KNL] Force drivers to reset the underlying device
3117 during initialization.
3120 Specify the partition device for software suspend
3122 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3124 resume_offset= [SWSUSP]
3125 Specify the offset from the beginning of the partition
3126 given by "resume=" at which the swap header is located,
3127 in <PAGE_SIZE> units (needed only for swap files).
3128 See Documentation/power/swsusp-and-swap-files.txt
3130 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3131 read the resume files
3133 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3134 Useful for devices that are detected asynchronously
3135 (e.g. USB and MMC devices).
3137 hibernate= [HIBERNATION]
3138 noresume Don't check if there's a hibernation image
3139 present during boot.
3140 nocompress Don't compress/decompress hibernation images.
3141 no Disable hibernation and resume.
3143 retain_initrd [RAM] Keep initrd memory after extraction
3145 rhash_entries= [KNL,NET]
3146 Set number of hash buckets for route cache
3148 ro [KNL] Mount root device read-only on boot
3150 root= [KNL] Root filesystem
3151 See name_to_dev_t comment in init/do_mounts.c.
3153 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3154 mount the root filesystem
3156 rootflags= [KNL] Set root filesystem mount option string
3158 rootfstype= [KNL] Set root filesystem type
3160 rootwait [KNL] Wait (indefinitely) for root device to show up.
3161 Useful for devices that are detected asynchronously
3162 (e.g. USB and MMC devices).
3164 rproc_mem=nn[KMG][@address]
3165 [KNL,ARM,CMA] Remoteproc physical memory block.
3166 Memory area to be used by remote processor image,
3169 rw [KNL] Mount root device read-write on boot
3171 S [KNL] Run init in single mode
3173 s390_iommu= [HW,S390]
3174 Set s390 IOTLB flushing mode
3176 With strict flushing every unmap operation will result in
3177 an IOTLB flush. Default is lazy flushing before reuse,
3181 See drivers/net/irda/sa1100_ir.c.
3183 sbni= [NET] Granch SBNI12 leased line adapter
3185 sched_debug [KNL] Enables verbose scheduler debug messages.
3187 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3188 xtime_lock contention on larger systems, and/or RCU lock
3189 contention on all systems with CONFIG_MAXSMP set.
3190 Format: { "0" | "1" }
3191 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3193 Note: increases power consumption, thus should only be
3194 enabled if running jitter sensitive (HPC/RT) workloads.
3196 security= [SECURITY] Choose a security module to enable at boot.
3197 If this boot parameter is not specified, only the first
3198 security module asking for security registration will be
3199 loaded. An invalid security module name will be treated
3200 as if no module has been chosen.
3202 selinux= [SELINUX] Disable or enable SELinux at boot time.
3203 Format: { "0" | "1" }
3204 See security/selinux/Kconfig help text.
3207 Default value is set via kernel config option.
3208 If enabled at boot time, /selinux/disable can be used
3209 later to disable prior to initial policy load.
3211 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3212 Format: { "0" | "1" }
3213 See security/apparmor/Kconfig help text
3216 Default value is set via kernel config option.
3218 serialnumber [BUGS=X86-32]
3221 Maximal number of shapers.
3223 show_msr= [x86] show boot-time MSR settings
3224 Format: { <integer> }
3225 Show boot-time (BIOS-initialized) MSR settings.
3226 The parameter means the number of CPUs to show,
3227 for example 1 means boot CPU only.
3235 Disable merging of slabs with similar size. May be
3236 necessary if there is some reason to distinguish
3237 allocs to different slabs. Debug options disable
3238 merging on their own.
3239 For more information see Documentation/vm/slub.txt.
3241 slab_max_order= [MM, SLAB]
3242 Determines the maximum allowed order for slabs.
3243 A high setting may cause OOMs due to memory
3244 fragmentation. Defaults to 1 for systems with
3245 more than 32MB of RAM, 0 otherwise.
3247 slub_debug[=options[,slabs]] [MM, SLUB]
3248 Enabling slub_debug allows one to determine the
3249 culprit if slab objects become corrupted. Enabling
3250 slub_debug can create guard zones around objects and
3251 may poison objects when not in use. Also tracks the
3252 last alloc / free. For more information see
3253 Documentation/vm/slub.txt.
3255 slub_max_order= [MM, SLUB]
3256 Determines the maximum allowed order for slabs.
3257 A high setting may cause OOMs due to memory
3258 fragmentation. For more information see
3259 Documentation/vm/slub.txt.
3261 slub_min_objects= [MM, SLUB]
3262 The minimum number of objects per slab. SLUB will
3263 increase the slab order up to slub_max_order to
3264 generate a sufficiently large slab able to contain
3265 the number of objects indicated. The higher the number
3266 of objects the smaller the overhead of tracking slabs
3267 and the less frequently locks need to be acquired.
3268 For more information see Documentation/vm/slub.txt.
3270 slub_min_order= [MM, SLUB]
3271 Determines the minimum page order for slabs. Must be
3272 lower than slub_max_order.
3273 For more information see Documentation/vm/slub.txt.
3275 slub_nomerge [MM, SLUB]
3276 Same with slab_nomerge. This is supported for legacy.
3277 See slab_nomerge for more information.
3280 Format: <io1>[,<io2>[,...,<io8>]]
3282 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3283 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3284 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3285 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3286 smsc-ircc2.ircc_irq= [HW] IRQ line
3287 smsc-ircc2.ircc_dma= [HW] DMA channel
3288 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3289 0: Toshiba Satellite 1800 (GP data pin select)
3290 1: Fast pin select (default)
3294 [KNL] Should the soft-lockup detector generate panics.
3297 softlockup_all_cpu_backtrace=
3298 [KNL] Should the soft-lockup detector generate
3299 backtraces on all cpus.
3302 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3303 See Documentation/laptops/sonypi.txt
3305 spia_io_base= [HW,MTD]
3311 Enabled the stack tracer on boot up.
3313 stacktrace_filter=[function-list]
3314 [FTRACE] Limit the functions that the stack tracer
3315 will trace at boot up. function-list is a comma separated
3316 list of functions. This list can be changed at run
3317 time by the stack_trace_filter file in the debugfs
3318 tracing directory. Note, this enables stack tracing
3319 and the stacktrace above is not needed.
3323 Set the STI (builtin display/keyboard on the HP-PARISC
3324 machines) console (graphic card) which should be used
3325 as the initial boot-console.
3326 See also comment in drivers/video/console/sticore.c.
3329 See comment in drivers/video/console/sticore.c.
3332 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3334 sunrpc.min_resvport=
3335 sunrpc.max_resvport=
3337 SunRPC servers often require that client requests
3338 originate from a privileged port (i.e. a port in the
3339 range 0 < portnr < 1024).
3340 An administrator who wishes to reserve some of these
3341 ports for other uses may adjust the range that the
3342 kernel's sunrpc client considers to be privileged
3343 using these two parameters to set the minimum and
3344 maximum port values.
3348 Control how the NFS server code allocates CPUs to
3349 service thread pools. Depending on how many NICs
3350 you have and where their interrupts are bound, this
3351 option will affect which CPUs will do NFS serving.
3352 Note: this parameter cannot be changed while the
3353 NFS server is running.
3355 auto the server chooses an appropriate mode
3356 automatically using heuristics
3357 global a single global pool contains all CPUs
3358 percpu one pool for each CPU
3359 pernode one pool for each NUMA node (equivalent
3360 to global on non-NUMA machines)
3362 sunrpc.tcp_slot_table_entries=
3363 sunrpc.udp_slot_table_entries=
3365 Sets the upper limit on the number of simultaneous
3366 RPC calls that can be sent from the client to a
3367 server. Increasing these values may allow you to
3368 improve throughput, but will also increase the
3369 amount of memory reserved for use by the client.
3372 [KNL] Enable accounting of swap in memory resource
3373 controller if no parameter or 1 is given or disable
3374 it if 0 is given (See Documentation/cgroups/memory.txt)
3376 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3377 Format: { <int> | force }
3378 <int> -- Number of I/O TLB slabs
3379 force -- force using of bounce buffers even if they
3380 wouldn't be automatically used by the kernel
3384 sysfs.deprecated=0|1 [KNL]
3385 Enable/disable old style sysfs layout for old udev
3386 on older distributions. When this option is enabled
3387 very new udev will not work anymore. When this option
3388 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3389 in older udev will not work anymore.
3390 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3391 the kernel configuration.
3393 sysrq_always_enabled
3395 Ignore sysrq setting - this boot parameter will
3396 neutralize any effect of /proc/sys/kernel/sysrq.
3397 Useful for debugging.
3401 test_suspend= [SUSPEND][,N]
3402 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3403 standby suspend) or "freeze" (for suspend type freeze)
3404 as the system sleep state during system startup with
3405 the optional capability to repeat N number of times.
3406 The system is woken from this state using a
3407 wakeup-capable RTC alarm.
3409 thash_entries= [KNL,NET]
3410 Set number of hash buckets for TCP connection
3412 thermal.act= [HW,ACPI]
3413 -1: disable all active trip points in all thermal zones
3414 <degrees C>: override all lowest active trip points
3416 thermal.crt= [HW,ACPI]
3417 -1: disable all critical trip points in all thermal zones
3418 <degrees C>: override all critical trip points
3420 thermal.nocrt= [HW,ACPI]
3421 Set to disable actions on ACPI thermal zone
3422 critical and hot trip points.
3424 thermal.off= [HW,ACPI]
3425 1: disable ACPI thermal control
3427 thermal.psv= [HW,ACPI]
3428 -1: disable all passive trip points
3429 <degrees C>: override all passive trip points to this
3432 thermal.tzp= [HW,ACPI]
3433 Specify global default ACPI thermal zone polling rate
3434 <deci-seconds>: poll all this frequency
3435 0: no polling (default)
3438 Force threading of all interrupt handlers except those
3439 marked explicitly IRQF_NO_THREAD.
3442 Enable the Transcendent memory driver if built-in.
3444 tmem.cleancache=0|1 [KNL, XEN]
3445 Default is on (1). Disable the usage of the cleancache
3446 API to send anonymous pages to the hypervisor.
3448 tmem.frontswap=0|1 [KNL, XEN]
3449 Default is on (1). Disable the usage of the frontswap
3450 API to send swap pages to the hypervisor. If disabled
3451 the selfballooning and selfshrinking are force disabled.
3453 tmem.selfballooning=0|1 [KNL, XEN]
3454 Default is on (1). Disable the driving of swap pages
3457 tmem.selfshrinking=0|1 [KNL, XEN]
3458 Default is on (1). Partial swapoff that immediately
3459 transfers pages from Xen hypervisor back to the
3460 kernel based on different criteria.
3464 Specify if the kernel should make use of the cpu
3465 topology information if the hardware supports this.
3466 The scheduler will make use of this information and
3467 e.g. base its process migration decisions on it.
3472 tpm_suspend_pcr=[HW,TPM]
3473 Format: integer pcr id
3474 Specify that at suspend time, the tpm driver
3475 should extend the specified pcr with zeros,
3476 as a workaround for some chips which fail to
3477 flush the last written pcr on TPM_SaveState.
3478 This will guarantee that all the other pcrs
3481 trace_buf_size=nn[KMG]
3482 [FTRACE] will set tracing buffer size.
3484 trace_event=[event-list]
3485 [FTRACE] Set and start specified trace events in order
3486 to facilitate early boot debugging.
3487 See also Documentation/trace/events.txt
3489 trace_options=[option-list]
3490 [FTRACE] Enable or disable tracer options at boot.
3491 The option-list is a comma delimited list of options
3492 that can be enabled or disabled just as if you were
3493 to echo the option name into
3495 /sys/kernel/debug/tracing/trace_options
3497 For example, to enable stacktrace option (to dump the
3498 stack trace of each event), add to the command line:
3500 trace_options=stacktrace
3502 See also Documentation/trace/ftrace.txt "trace options"
3506 [FTRACE] enable this option to disable tracing when a
3507 warning is hit. This turns off "tracing_on". Tracing can
3508 be enabled again by echoing '1' into the "tracing_on"
3509 file located in /sys/kernel/debug/tracing/
3511 This option is useful, as it disables the trace before
3512 the WARNING dump is called, which prevents the trace to
3513 be filled with content caused by the warning output.
3515 This option can also be set at run time via the sysctl
3516 option: kernel/traceoff_on_warning
3518 transparent_hugepage=
3520 Format: [always|madvise|never]
3521 Can be used to control the default behavior of the system
3522 with respect to transparent hugepages.
3523 See Documentation/vm/transhuge.txt for more details.
3525 tsc= Disable clocksource stability checks for TSC.
3527 [x86] reliable: mark tsc clocksource as reliable, this
3528 disables clocksource verification at runtime, as well
3529 as the stability checks done at bootup. Used to enable
3530 high-resolution timer mode on older hardware, and in
3531 virtualized environment.
3532 [x86] noirqtime: Do not use TSC to do irq accounting.
3533 Used to run time disable IRQ_TIME_ACCOUNTING on any
3534 platforms where RDTSC is slow and this accounting
3537 turbografx.map[2|3]= [HW,JOY]
3538 TurboGraFX parallel port interface
3540 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3541 See also Documentation/input/joystick-parport.txt
3543 udbg-immortal [PPC] When debugging early kernel crashes that
3544 happen after console_init() and before a proper
3545 console driver takes over, this boot options might
3546 help "seeing" what's going on.
3548 uhash_entries= [KNL,NET]
3549 Set number of hash buckets for UDP/UDP-Lite connections
3552 [USB] Ignore overcurrent events (default N).
3553 Some badly-designed motherboards generate lots of
3554 bogus events, for ports that aren't wired to
3555 anything. Set this parameter to avoid log spamming.
3556 Note that genuine overcurrent events won't be
3560 [X86] Cause panic on unknown NMI.
3562 usbcore.authorized_default=
3563 [USB] Default USB device authorization:
3564 (default -1 = authorized except for wireless USB,
3565 0 = not authorized, 1 = authorized)
3567 usbcore.autosuspend=
3568 [USB] The autosuspend time delay (in seconds) used
3569 for newly-detected USB devices (default 2). This
3570 is the time required before an idle device will be
3571 autosuspended. Devices for which the delay is set
3572 to a negative value won't be autosuspended at all.
3574 usbcore.usbfs_snoop=
3575 [USB] Set to log all usbfs traffic (default 0 = off).
3577 usbcore.blinkenlights=
3578 [USB] Set to cycle leds on hubs (default 0 = off).
3580 usbcore.old_scheme_first=
3581 [USB] Start with the old device initialization
3582 scheme (default 0 = off).
3584 usbcore.usbfs_memory_mb=
3585 [USB] Memory limit (in MB) for buffers allocated by
3586 usbfs (default = 16, 0 = max = 2047).
3588 usbcore.use_both_schemes=
3589 [USB] Try the other device initialization scheme
3590 if the first one fails (default 1 = enabled).
3592 usbcore.initial_descriptor_timeout=
3593 [USB] Specifies timeout for the initial 64-byte
3594 USB_REQ_GET_DESCRIPTOR request in milliseconds
3595 (default 5000 = 5.0 seconds).
3598 [USBHID] The interval which mice are to be polled at.
3600 usb-storage.delay_use=
3601 [UMS] The delay in seconds before a new device is
3602 scanned for Logical Units (default 5).
3605 [UMS] A list of quirks entries to supplement or
3606 override the built-in unusual_devs list. List
3607 entries are separated by commas. Each entry has
3608 the form VID:PID:Flags where VID and PID are Vendor
3609 and Product ID values (4-digit hex numbers) and
3610 Flags is a set of characters, each corresponding
3611 to a common usb-storage quirk flag as follows:
3612 a = SANE_SENSE (collect more than 18 bytes
3614 b = BAD_SENSE (don't collect more than 18
3615 bytes of sense data);
3616 c = FIX_CAPACITY (decrease the reported
3617 device capacity by one sector);
3618 d = NO_READ_DISC_INFO (don't use
3619 READ_DISC_INFO command);
3620 e = NO_READ_CAPACITY_16 (don't use
3621 READ_CAPACITY_16 command);
3622 f = NO_REPORT_OPCODES (don't use report opcodes
3624 h = CAPACITY_HEURISTICS (decrease the
3625 reported device capacity by one
3626 sector if the number is odd);
3627 i = IGNORE_DEVICE (don't bind to this
3629 l = NOT_LOCKABLE (don't try to lock and
3630 unlock ejectable media);
3631 m = MAX_SECTORS_64 (don't transfer more
3632 than 64 sectors = 32 KB at a time);
3633 n = INITIAL_READ10 (force a retry of the
3634 initial READ(10) command);
3635 o = CAPACITY_OK (accept the capacity
3636 reported by the device);
3637 p = WRITE_CACHE (the device cache is ON
3639 r = IGNORE_RESIDUE (the device reports
3640 bogus residue values);
3641 s = SINGLE_LUN (the device has only one
3643 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3644 commands, uas only);
3645 u = IGNORE_UAS (don't bind to the uas driver);
3646 w = NO_WP_DETECT (don't test whether the
3647 medium is write-protected).
3648 Example: quirks=0419:aaf5:rl,0421:0433:rc
3650 user_debug= [KNL,ARM]
3652 See arch/arm/Kconfig.debug help text.
3653 1 - undefined instruction events
3655 4 - invalid data aborts
3658 Example: user_debug=31
3661 [X86] Flags controlling user PTE allocations.
3663 nohigh = do not allocate PTE pages in
3664 HIGHMEM regardless of setting
3668 On X86_32, this is an alias for vdso32=. Otherwise:
3670 vdso=1: enable VDSO (the default)
3671 vdso=0: disable VDSO mapping
3673 vdso32= [X86] Control the 32-bit vDSO
3674 vdso32=1: enable 32-bit VDSO
3675 vdso32=0 or vdso32=2: disable 32-bit VDSO
3677 See the help text for CONFIG_COMPAT_VDSO for more
3678 details. If CONFIG_COMPAT_VDSO is set, the default is
3679 vdso32=0; otherwise, the default is vdso32=1.
3681 For compatibility with older kernels, vdso32=2 is an
3684 Try vdso32=0 if you encounter an error that says:
3685 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3688 vector=percpu: enable percpu vector domain
3690 video= [FB] Frame buffer configuration
3691 See Documentation/fb/modedb.txt.
3693 video.brightness_switch_enabled= [0,1]
3694 If set to 1, on receiving an ACPI notify event
3695 generated by hotkey, video driver will adjust brightness
3696 level and then send out the event to user space through
3697 the allocated input device; If set to 0, video driver
3698 will only send out the event without touching backlight
3703 [VMMIO] Memory mapped virtio (platform) device.
3705 <size>@<baseaddr>:<irq>[:<id>]
3707 <size> := size (can use standard suffixes
3709 <baseaddr> := physical base address
3710 <irq> := interrupt number (as passed to
3712 <id> := (optional) platform device id
3714 virtio_mmio.device=1K@0x100b0000:48:7
3716 Can be used multiple times for multiple devices.
3718 vga= [BOOT,X86-32] Select a particular video mode
3719 See Documentation/x86/boot.txt and
3720 Documentation/svga.txt.
3721 Use vga=ask for menu.
3722 This is actually a boot loader parameter; the value is
3723 passed to the kernel using a special protocol.
3725 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3726 size of <nn>. This can be used to increase the
3727 minimum size (128MB on x86). It can also be used to
3728 decrease the size and leave more room for directly
3731 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3734 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3737 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3741 Controls the behavior of vsyscalls (i.e. calls to
3742 fixed addresses of 0xffffffffff600x00 from legacy
3743 code). Most statically-linked binaries and older
3744 versions of glibc use these calls. Because these
3745 functions are at fixed addresses, they make nice
3746 targets for exploits that can control RIP.
3748 emulate [default] Vsyscalls turn into traps and are
3749 emulated reasonably safely.
3751 native Vsyscalls are native syscall instructions.
3752 This is a little bit faster than trapping
3753 and makes a few dynamic recompilers work
3754 better than they would in emulation mode.
3755 It also makes exploits much easier to write.
3757 none Vsyscalls don't work at all. This makes
3758 them quite hard to use for exploits but
3759 might break your system.
3761 vt.color= [VT] Default text color.
3762 Format: 0xYX, X = foreground, Y = background.
3763 Default: 0x07 = light gray on black.
3765 vt.cur_default= [VT] Default cursor shape.
3766 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3767 the parameters of the <Esc>[?A;B;Cc escape sequence;
3768 see VGA-softcursor.txt. Default: 2 = underline.
3770 vt.default_blu= [VT]
3771 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3772 Change the default blue palette of the console.
3773 This is a 16-member array composed of values
3776 vt.default_grn= [VT]
3777 Format: <green0>,<green1>,<green2>,...,<green15>
3778 Change the default green palette of the console.
3779 This is a 16-member array composed of values
3782 vt.default_red= [VT]
3783 Format: <red0>,<red1>,<red2>,...,<red15>
3784 Change the default red palette of the console.
3785 This is a 16-member array composed of values
3791 Set system-wide default UTF-8 mode for all tty's.
3792 Default is 1, i.e. UTF-8 mode is enabled for all
3793 newly opened terminals.
3795 vt.global_cursor_default=
3798 Set system-wide default for whether a cursor
3799 is shown on new VTs. Default is -1,
3800 i.e. cursors will be created by default unless
3801 overridden by individual drivers. 0 will hide
3802 cursors, 1 will display them.
3804 vt.italic= [VT] Default color for italic text; 0-15.
3807 vt.underline= [VT] Default color for underlined text; 0-15.
3810 watchdog timers [HW,WDT] For information on watchdog timers,
3811 see Documentation/watchdog/watchdog-parameters.txt
3812 or other driver-specific files in the
3813 Documentation/watchdog/ directory.
3815 workqueue.disable_numa
3816 By default, all work items queued to unbound
3817 workqueues are affine to the NUMA nodes they're
3818 issued on, which results in better behavior in
3819 general. If NUMA affinity needs to be disabled for
3820 whatever reason, this option can be used. Note
3821 that this also can be controlled per-workqueue for
3822 workqueues visible under /sys/bus/workqueue/.
3824 workqueue.power_efficient
3825 Per-cpu workqueues are generally preferred because
3826 they show better performance thanks to cache
3827 locality; unfortunately, per-cpu workqueues tend to
3828 be more power hungry than unbound workqueues.
3830 Enabling this makes the per-cpu workqueues which
3831 were observed to contribute significantly to power
3832 consumption unbound, leading to measurably lower
3833 power usage at the cost of small performance
3836 The default value of this parameter is determined by
3837 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3839 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3840 default x2apic cluster mode on platforms
3843 x86_intel_mid_timer= [X86-32,APBT]
3844 Choose timer option for x86 Intel MID platform.
3845 Two valid options are apbt timer only and lapic timer
3846 plus one apbt timer for broadcast timer.
3847 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3849 xen_emul_unplug= [HW,X86,XEN]
3850 Unplug Xen emulated devices
3851 Format: [unplug0,][unplug1]
3852 ide-disks -- unplug primary master IDE devices
3853 aux-ide-disks -- unplug non-primary-master IDE devices
3854 nics -- unplug network devices
3855 all -- unplug all emulated devices (NICs and IDE disks)
3856 unnecessary -- unplugging emulated devices is
3857 unnecessary even if the host did not respond to
3859 never -- do not unplug even if version check succeeds
3861 xen_nopvspin [X86,XEN]
3862 Disables the ticketlock slowpath using Xen PV
3866 Disables the PV optimizations forcing the HVM guest to
3867 run as generic HVM guest with no PV drivers.
3869 xirc2ps_cs= [NET,PCMCIA]
3871 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3873 ______________________________________________________________________
3877 Add more DRM drivers.