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
1587 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1588 Valid arguments: 0, 1, 2
1589 kmemcheck=0 (disabled)
1590 kmemcheck=1 (enabled)
1591 kmemcheck=2 (one-shot mode)
1592 Default: 2 (one-shot mode)
1594 kstack=N [X86] Print N words from the kernel stack
1597 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1598 Default is 0 (don't ignore, but inject #GP)
1600 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1604 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1605 Default is 1 (enabled)
1607 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1609 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1611 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1612 (virtualized MMU) support on capable Intel chips.
1613 Default is 1 (enabled)
1615 kvm-intel.emulate_invalid_guest_state=
1616 [KVM,Intel] Enable emulation of invalid guest states
1617 Default is 0 (disabled)
1619 kvm-intel.flexpriority=
1620 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1621 Default is 1 (enabled)
1624 [KVM,Intel] Enable VMX nesting (nVMX).
1625 Default is 0 (disabled)
1627 kvm-intel.unrestricted_guest=
1628 [KVM,Intel] Disable unrestricted guest feature
1629 (virtualized real and unpaged mode) on capable
1630 Intel chips. Default is 1 (enabled)
1632 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1633 feature (tagged TLBs) on capable Intel chips.
1634 Default is 1 (enabled)
1640 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1643 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1644 value for LAPIC timer one-shot implementation. Default
1645 back to the programmable timer unit in the LAPIC.
1647 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1650 libata.dma= [LIBATA] DMA control
1651 libata.dma=0 Disable all PATA and SATA DMA
1652 libata.dma=1 PATA and SATA Disk DMA only
1653 libata.dma=2 ATAPI (CDROM) DMA only
1654 libata.dma=4 Compact Flash DMA only
1655 Combinations also work, so libata.dma=3 enables DMA
1656 for disks and CDROMs, but not CFs.
1658 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1659 libata.ignore_hpa=0 keep BIOS limits (default)
1660 libata.ignore_hpa=1 ignore limits, using full disk
1662 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1666 libata.force= [LIBATA] Force configurations. The format is comma
1667 separated list of "[ID:]VAL" where ID is
1668 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1669 matching port, link or device. Basically, it matches
1670 the ATA ID string printed on console by libata. If
1671 the whole ID part is omitted, the last PORT and DEVICE
1672 values are used. If ID hasn't been specified yet, the
1673 configuration applies to all ports, links and devices.
1675 If only DEVICE is omitted, the parameter applies to
1676 the port and all links and devices behind it. DEVICE
1677 number of 0 either selects the first device or the
1678 first fan-out link behind PMP device. It does not
1679 select the host link. DEVICE number of 15 selects the
1680 host link and device attached to it.
1682 The VAL specifies the configuration to force. As long
1683 as there's no ambiguity shortcut notation is allowed.
1684 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1685 The following configurations can be forced.
1687 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1688 Any ID with matching PORT is used.
1690 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1692 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1693 udma[/][16,25,33,44,66,100,133] notation is also
1696 * [no]ncq: Turn on or off NCQ.
1698 * nohrst, nosrst, norst: suppress hard, soft
1701 * rstonce: only attempt one reset during
1702 hot-unplug link recovery
1704 * dump_id: dump IDENTIFY data.
1706 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1708 * disable: Disable this device.
1710 If there are multiple matching configurations changing
1711 the same attribute, the last one is used.
1713 memblock=debug [KNL] Enable memblock debug messages.
1715 load_ramdisk= [RAM] List of ramdisks to load from floppy
1716 See Documentation/blockdev/ramdisk.txt.
1718 lockd.nlm_grace_period=P [NFS] Assign grace period.
1721 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1724 lockd.nlm_timeout=T [NFS] Assign timeout value.
1727 lockd.nlm_udpport=M [NFS] Assign UDP port.
1730 locktorture.nreaders_stress= [KNL]
1731 Set the number of locking read-acquisition kthreads.
1732 Defaults to being automatically set based on the
1733 number of online CPUs.
1735 locktorture.nwriters_stress= [KNL]
1736 Set the number of locking write-acquisition kthreads.
1738 locktorture.onoff_holdoff= [KNL]
1739 Set time (s) after boot for CPU-hotplug testing.
1741 locktorture.onoff_interval= [KNL]
1742 Set time (s) between CPU-hotplug operations, or
1743 zero to disable CPU-hotplug testing.
1745 locktorture.shuffle_interval= [KNL]
1746 Set task-shuffle interval (jiffies). Shuffling
1747 tasks allows some CPUs to go into dyntick-idle
1748 mode during the locktorture test.
1750 locktorture.shutdown_secs= [KNL]
1751 Set time (s) after boot system shutdown. This
1752 is useful for hands-off automated testing.
1754 locktorture.stat_interval= [KNL]
1755 Time (s) between statistics printk()s.
1757 locktorture.stutter= [KNL]
1758 Time (s) to stutter testing, for example,
1759 specifying five seconds causes the test to run for
1760 five seconds, wait for five seconds, and so on.
1761 This tests the locking primitive's ability to
1762 transition abruptly to and from idle.
1764 locktorture.torture_runnable= [BOOT]
1765 Start locktorture running at boot time.
1767 locktorture.torture_type= [KNL]
1768 Specify the locking implementation to test.
1770 locktorture.verbose= [KNL]
1771 Enable additional printk() statements.
1773 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1776 loglevel= All Kernel Messages with a loglevel smaller than the
1777 console loglevel will be printed to the console. It can
1778 also be changed with klogd or other programs. The
1779 loglevels are defined as follows:
1781 0 (KERN_EMERG) system is unusable
1782 1 (KERN_ALERT) action must be taken immediately
1783 2 (KERN_CRIT) critical conditions
1784 3 (KERN_ERR) error conditions
1785 4 (KERN_WARNING) warning conditions
1786 5 (KERN_NOTICE) normal but significant condition
1787 6 (KERN_INFO) informational
1788 7 (KERN_DEBUG) debug-level messages
1790 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1791 in bytes. n must be a power of two and greater
1792 than the minimal size. The minimal size is defined
1793 by LOG_BUF_SHIFT kernel config parameter. There is
1794 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1795 that allows to increase the default size depending on
1796 the number of CPUs. See init/Kconfig for more details.
1798 logo.nologo [FB] Disables display of the built-in Linux logo.
1799 This may be used to provide more screen space for
1800 kernel log messages and is useful when debugging
1801 kernel boot problems.
1803 lp=0 [LP] Specify parallel ports to use, e.g,
1804 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1805 lp=reset first parallel port). 'lp=0' disables the
1806 lp=auto printer driver. 'lp=reset' (which can be
1807 specified in addition to the ports) causes
1808 attached printers to be reset. Using
1809 lp=port1,port2,... specifies the parallel ports
1810 to associate lp devices with, starting with
1811 lp0. A port specification may be 'none' to skip
1812 that lp device, or a parport name such as
1813 'parport0'. Specifying 'lp=auto' instead of a
1814 port specification list means that device IDs
1815 from each port should be examined, to see if
1816 an IEEE 1284-compliant printer is attached; if
1817 so, the driver will manage that printer.
1818 See also header of drivers/char/lp.c.
1821 Sets loops_per_jiffy to given constant, thus avoiding
1822 time-consuming boot-time autodetection (up to 250 ms per
1823 CPU). 0 enables autodetection (default). To determine
1824 the correct value for your kernel, boot with normal
1825 autodetection and see what value is printed. Note that
1826 on SMP systems the preset will be applied to all CPUs,
1827 which is likely to cause problems if your CPUs need
1828 significantly divergent settings. An incorrect value
1829 will cause delays in the kernel to be wrong, leading to
1830 unpredictable I/O errors and other breakage. Although
1831 unlikely, in the extreme case this might damage your
1835 Format: <io>,<irq>,<dma>
1837 machvec= [IA-64] Force the use of a particular machine-vector
1838 (machvec) in a generic kernel.
1839 Example: machvec=hpzx1_swiotlb
1841 machtype= [Loongson] Share the same kernel image file between different
1843 Example: machtype=lemote-yeeloong-2f-7inch
1845 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1846 than or equal to this physical address is ignored.
1848 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1849 should make use of. maxcpus=n : n >= 0 limits the
1850 kernel to using 'n' processors. n=0 is a special case,
1851 it is equivalent to "nosmp", which also disables
1854 max_loop= [LOOP] The number of loop block devices that get
1855 (loop.max_loop) unconditionally pre-created at init time. The default
1856 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1857 of statically allocating a predefined number, loop
1858 devices can be requested on-demand with the
1859 /dev/loop-control interface.
1861 mce [X86-32] Machine Check Exception
1863 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1865 md= [HW] RAID subsystems devices and level
1866 See Documentation/md.txt.
1869 Format: <first>,<last>
1870 Specifies range of consoles to be captured by the MDA.
1872 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1873 Amount of memory to be used when the kernel is not able
1874 to see the whole system memory or for test.
1875 [X86] Work as limiting max address. Use together
1876 with memmap= to avoid physical address space collisions.
1877 Without memmap= PCI devices could be placed at addresses
1878 belonging to unused RAM.
1880 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1884 [KNL,SH] Allow user to override the default size for
1885 per-device physically contiguous DMA buffers.
1887 memmap=exactmap [KNL,X86] Enable setting of an exact
1888 E820 memory map, as specified by the user.
1889 Such memmap=exactmap lines can be constructed based on
1890 BIOS output or other requirements. See the memmap=nn@ss
1893 memmap=nn[KMG]@ss[KMG]
1894 [KNL] Force usage of a specific region of memory.
1895 Region of memory to be used is from ss to ss+nn.
1897 memmap=nn[KMG]#ss[KMG]
1898 [KNL,ACPI] Mark specific memory as ACPI data.
1899 Region of memory to be marked is from ss to ss+nn.
1901 memmap=nn[KMG]$ss[KMG]
1902 [KNL,ACPI] Mark specific memory as reserved.
1903 Region of memory to be reserved is from ss to ss+nn.
1904 Example: Exclude memory from 0x18690000-0x1869ffff
1905 memmap=64K$0x18690000
1907 memmap=0x10000$0x18690000
1909 memory_corruption_check=0/1 [X86]
1910 Some BIOSes seem to corrupt the first 64k of
1911 memory when doing things like suspend/resume.
1912 Setting this option will scan the memory
1913 looking for corruption. Enabling this will
1914 both detect corruption and prevent the kernel
1915 from using the memory being corrupted.
1916 However, its intended as a diagnostic tool; if
1917 repeatable BIOS-originated corruption always
1918 affects the same memory, you can use memmap=
1919 to prevent the kernel from using that memory.
1921 memory_corruption_check_size=size [X86]
1922 By default it checks for corruption in the low
1923 64k, making this memory unavailable for normal
1924 use. Use this parameter to scan for
1925 corruption in more or less memory.
1927 memory_corruption_check_period=seconds [X86]
1928 By default it checks for corruption every 60
1929 seconds. Use this parameter to check at some
1930 other rate. 0 disables periodic checking.
1932 memtest= [KNL,X86] Enable memtest
1934 default : 0 <disable>
1935 Specifies the number of memtest passes to be
1936 performed. Each pass selects another test
1937 pattern from a given set of patterns. Memtest
1938 fills the memory with this pattern, validates
1939 memory contents and reserves bad memory
1940 regions that are detected.
1942 meye.*= [HW] Set MotionEye Camera parameters
1943 See Documentation/video4linux/meye.txt.
1945 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1946 Multi-Function General Purpose Timers on AMD Geode
1949 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1950 the BIOS has incorrectly applied a workaround. TinyBIOS
1951 version 0.98 is known to be affected, 0.99 fixes the
1952 problem by letting the user disable the workaround.
1956 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1957 physical address is ignored.
1959 mini2440= [ARM,HW,KNL]
1960 Format:[0..2][b][c][t]
1962 MINI2440 configuration specification:
1963 0 - The attached screen is the 3.5" TFT
1964 1 - The attached screen is the 7" TFT
1965 2 - The VGA Shield is attached (1024x768)
1966 Leaving out the screen size parameter will not load
1967 the TFT driver, and the framebuffer will be left
1969 b - Enable backlight. The TFT backlight pin will be
1970 linked to the kernel VESA blanking code and a GPIO
1971 LED. This parameter is not necessary when using the
1973 c - Enable the s3c camera interface.
1974 t - Reserved for enabling touchscreen support. The
1975 touchscreen support is not enabled in the mainstream
1976 kernel as of 2.6.30, a preliminary port can be found
1977 in the "bleeding edge" mini2440 support kernel at
1978 http://repo.or.cz/w/linux-2.6/mini2440.git
1981 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1982 parameter allows control of the logging verbosity for
1983 the additional memory initialisation checks. A value
1984 of 0 disables mminit logging and a level of 4 will
1985 log everything. Information is printed at KERN_DEBUG
1986 so loglevel=8 may also need to be specified.
1989 [KNL] When CONFIG_MODULE_SIG is set, this means that
1990 modules without (valid) signatures will fail to load.
1991 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1992 is always true, so this option does nothing.
1995 [MOUSE] Maximum time between finger touching and
1996 leaving touchpad surface for touch to be considered
1997 a tap and be reported as a left button click (for
1998 touchpads working in absolute mode only).
2000 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2001 reporting absolute coordinates, such as tablets
2002 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2003 reporting absolute coordinates, such as tablets
2005 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2006 is similar to kernelcore except it specifies the
2007 amount of memory used for migratable allocations.
2008 If both kernelcore and movablecore is specified,
2009 then kernelcore will be at *least* the specified
2010 value but may be more. If movablecore on its own
2011 is specified, the administrator must be careful
2012 that the amount of memory usable for all allocations
2015 movable_node [KNL,X86] Boot-time switch to enable the effects
2016 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2018 MTD_Partition= [MTD]
2019 Format: <name>,<region-number>,<size>,<offset>
2021 MTD_Region= [MTD] Format:
2022 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2025 See drivers/mtd/cmdlinepart.c.
2027 multitce=off [PPC] This parameter disables the use of the pSeries
2028 firmware feature for updating multiple TCE entries
2031 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2033 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2035 boundary - index of last SLC block on Flex-OneNAND.
2036 The remaining blocks are configured as MLC blocks.
2037 lock - Configure if Flex-OneNAND boundary should be locked.
2038 Once locked, the boundary cannot be changed.
2039 1 indicates lock status, 0 indicates unlock status.
2042 ARM/S3C2412 JIVE boot control
2044 See arch/arm/mach-s3c2412/mach-jive.c
2046 mtouchusb.raw_coordinates=
2047 [HW] Make the MicroTouch USB driver use raw coordinates
2048 ('y', default) or cooked coordinates ('n')
2050 mtrr_chunk_size=nn[KMG] [X86]
2051 used for mtrr cleanup. It is largest continuous chunk
2052 that could hold holes aka. UC entries.
2054 mtrr_gran_size=nn[KMG] [X86]
2055 Used for mtrr cleanup. It is granularity of mtrr block.
2057 Large value could prevent small alignment from
2060 mtrr_spare_reg_nr=n [X86]
2062 Range: 0,7 : spare reg number
2064 Used for mtrr cleanup. It is spare mtrr entries number.
2065 Set to 2 or more if your graphical card needs more.
2067 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2069 netdev= [NET] Network devices parameters
2070 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2071 Note that mem_start is often overloaded to mean
2072 something different and driver-specific.
2073 This usage is only documented in each driver source
2077 [NETFILTER] Enable connection tracking flow accounting
2078 0 to disable accounting
2079 1 to enable accounting
2082 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2083 See Documentation/filesystems/nfs/nfsroot.txt.
2085 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2086 See Documentation/filesystems/nfs/nfsroot.txt.
2088 nfsrootdebug [NFS] enable nfsroot debugging messages.
2089 See Documentation/filesystems/nfs/nfsroot.txt.
2091 nfs.callback_tcpport=
2092 [NFS] set the TCP port on which the NFSv4 callback
2093 channel should listen.
2096 [NFS] sets the pathname to the program which is used
2097 to update the NFS client cache entries.
2099 nfs.cache_getent_timeout=
2100 [NFS] sets the timeout after which an attempt to
2101 update a cache entry is deemed to have failed.
2103 nfs.idmap_cache_timeout=
2104 [NFS] set the maximum lifetime for idmapper cache
2108 [NFS] enable 64-bit inode numbers.
2109 If zero, the NFS client will fake up a 32-bit inode
2110 number for the readdir() and stat() syscalls instead
2111 of returning the full 64-bit number.
2112 The default is to return 64-bit inode numbers.
2114 nfs.max_session_slots=
2115 [NFSv4.1] Sets the maximum number of session slots
2116 the client will attempt to negotiate with the server.
2117 This limits the number of simultaneous RPC requests
2118 that the client can send to the NFSv4.1 server.
2119 Note that there is little point in setting this
2120 value higher than the max_tcp_slot_table_limit.
2122 nfs.nfs4_disable_idmapping=
2123 [NFSv4] When set to the default of '1', this option
2124 ensures that both the RPC level authentication
2125 scheme and the NFS level operations agree to use
2126 numeric uids/gids if the mount is using the
2127 'sec=sys' security flavour. In effect it is
2128 disabling idmapping, which can make migration from
2129 legacy NFSv2/v3 systems to NFSv4 easier.
2130 Servers that do not support this mode of operation
2131 will be autodetected by the client, and it will fall
2132 back to using the idmapper.
2133 To turn off this behaviour, set the value to '0'.
2135 [NFS4] Specify an additional fixed unique ident-
2136 ification string that NFSv4 clients can insert into
2137 their nfs_client_id4 string. This is typically a
2138 UUID that is generated at system install time.
2140 nfs.send_implementation_id =
2141 [NFSv4.1] Send client implementation identification
2142 information in exchange_id requests.
2143 If zero, no implementation identification information
2145 The default is to send the implementation identification
2148 nfs.recover_lost_locks =
2149 [NFSv4] Attempt to recover locks that were lost due
2150 to a lease timeout on the server. Please note that
2151 doing this risks data corruption, since there are
2152 no guarantees that the file will remain unchanged
2153 after the locks are lost.
2154 If you want to enable the kernel legacy behaviour of
2155 attempting to recover these locks, then set this
2157 The default parameter value of '0' causes the kernel
2158 not to attempt recovery of lost locks.
2160 nfsd.nfs4_disable_idmapping=
2161 [NFSv4] When set to the default of '1', the NFSv4
2162 server will return only numeric uids and gids to
2163 clients using auth_sys, and will accept numeric uids
2164 and gids from such clients. This is intended to ease
2165 migration from NFSv2/v3.
2167 objlayoutdriver.osd_login_prog=
2168 [NFS] [OBJLAYOUT] sets the pathname to the program which
2169 is used to automatically discover and login into new
2170 osd-targets. Please see:
2171 Documentation/filesystems/pnfs.txt for more explanations
2173 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2174 when a NMI is triggered.
2175 Format: [state][,regs][,debounce][,die]
2177 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2178 Format: [panic,][nopanic,][num]
2180 0 - turn nmi_watchdog off
2181 When panic is specified, panic when an NMI watchdog
2182 timeout occurs (or 'nopanic' to override the opposite
2184 This is useful when you use a panic=... timeout and
2185 need the box quickly up again.
2187 netpoll.carrier_timeout=
2188 [NET] Specifies amount of time (in seconds) that
2189 netpoll should wait for a carrier. By default netpoll
2192 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2193 emulation library even if a 387 maths coprocessor
2197 [HW] Never suspend the console
2198 Disable suspending of consoles during suspend and
2199 hibernate operations. Once disabled, debugging
2200 messages can reach various consoles while the rest
2201 of the system is being put to sleep (ie, while
2202 debugging driver suspend/resume hooks). This may
2203 not work reliably with all consoles, but is known
2204 to work with serial and VGA consoles.
2205 To facilitate more flexible debugging, we also add
2206 console_suspend, a printk module parameter to control
2207 it. Users could use console_suspend (usually
2208 /sys/module/printk/parameters/console_suspend) to
2209 turn on/off it dynamically.
2211 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2212 caches in the slab allocator. Saves per-node memory,
2213 but will impact performance.
2217 noapic [SMP,APIC] Tells the kernel to not make use of any
2218 IOAPICs that may be present in the system.
2220 noautogroup Disable scheduler automatic task group creation.
2222 nobats [PPC] Do not use BATs for mapping kernel lowmem
2223 on "Classic" PPC cores.
2227 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2229 nodelayacct [KNL] Disable per-task delay accounting
2231 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2233 nodsp [SH] Disable hardware DSP at boot time.
2235 noefi [X86] Disable EFI runtime services support.
2240 On X86-32 available only on PAE configured kernels.
2241 noexec=on: enable non-executable mappings (default)
2242 noexec=off: disable non-executable mappings
2245 Disable SMAP (Supervisor Mode Access Prevention)
2246 even if it is supported by processor.
2249 Disable SMEP (Supervisor Mode Execution Prevention)
2250 even if it is supported by processor.
2253 This affects only 32-bit executables.
2254 noexec32=on: enable non-executable mappings (default)
2255 read doesn't imply executable mappings
2256 noexec32=off: disable non-executable mappings
2257 read implies executable mappings
2259 nofpu [SH] Disable hardware FPU at boot time.
2261 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2262 register save and restore. The kernel will only save
2263 legacy floating-point registers on task switch.
2265 noxsave [BUGS=X86] Disables x86 extended register state save
2266 and restore using xsave. The kernel will fallback to
2267 enabling legacy floating-point and sse state.
2269 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2270 register states. The kernel will fall back to use
2271 xsave to save the states. By using this parameter,
2272 performance of saving the states is degraded because
2273 xsave doesn't support modified optimization while
2274 xsaveopt supports it on xsaveopt enabled systems.
2276 noxsaves [X86] Disables xsaves and xrstors used in saving and
2277 restoring x86 extended register state in compacted
2278 form of xsave area. The kernel will fall back to use
2279 xsaveopt and xrstor to save and restore the states
2280 in standard form of xsave area. By using this
2281 parameter, xsave area per process might occupy more
2282 memory on xsaves enabled systems.
2285 on enable eager fpu restore
2286 off disable eager fpu restore
2287 auto selects the default scheme, which automatically
2288 enables eagerfpu restore for xsaveopt.
2290 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2291 wfi(ARM) instruction doesn't work correctly and not to
2292 use it. This is also useful when using JTAG debugger.
2294 no_file_caps Tells the kernel not to honor file capabilities. The
2295 only way then for a file to be executed with privilege
2296 is to be setuid root or executed by root.
2298 nohalt [IA-64] Tells the kernel not to use the power saving
2299 function PAL_HALT_LIGHT when idle. This increases
2300 power-consumption. On the positive side, it reduces
2301 interrupt wake-up latency, which may improve performance
2302 in certain environments such as networked servers or
2305 nohibernate [HIBERNATION] Disable hibernation and resume.
2307 nohz= [KNL] Boottime enable/disable dynamic ticks
2308 Valid arguments: on, off
2311 nohz_full= [KNL,BOOT]
2312 In kernels built with CONFIG_NO_HZ_FULL=y, set
2313 the specified list of CPUs whose tick will be stopped
2314 whenever possible. The boot CPU will be forced outside
2315 the range to maintain the timekeeping.
2316 The CPUs in this range must also be included in the
2319 noiotrap [SH] Disables trapped I/O port accesses.
2321 noirqdebug [X86-32] Disables the code which attempts to detect and
2322 disable unhandled interrupt sources.
2324 no_timer_check [X86,APIC] Disables the code which tests for
2325 broken timer IRQ sources.
2327 noisapnp [ISAPNP] Disables ISA PnP code.
2329 noinitrd [RAM] Tells the kernel not to load any configured
2332 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2334 [Deprecated - use intremap=off]
2338 nojitter [IA-64] Disables jitter checking for ITC timers.
2340 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2342 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2345 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2346 steal time is computed, but won't influence scheduler
2349 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2351 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2353 noltlbs [PPC] Do not use large page/tlb entries for kernel
2354 lowmem mapping on PPC40x.
2356 nomca [IA-64] Disable machine check abort handling
2358 nomce [X86-32] Machine Check Exception
2360 nomfgpt [X86-32] Disable Multi-Function General Purpose
2361 Timer usage (for AMD Geode machines).
2363 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2364 shutdown the other cpus. Instead use the REBOOT_VECTOR
2367 nomodule Disable module load
2369 nopat [X86] Disable PAT (page attribute table extension of
2370 pagetables) support.
2372 norandmaps Don't use address space randomization. Equivalent to
2373 echo 0 > /proc/sys/kernel/randomize_va_space
2375 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2377 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2378 with UP alternatives
2380 nordrand [X86] Disable kernel use of the RDRAND and
2381 RDSEED instructions even if they are supported
2382 by the processor. RDRAND and RDSEED are still
2383 available to user space applications.
2385 noresume [SWSUSP] Disables resume and restores original swap
2388 no-scroll [VGA] Disables scrollback.
2389 This is required for the Braillex ib80-piezo Braille
2390 reader made by F.H. Papenmeier (Germany).
2394 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2396 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2397 and disable the IO APIC. legacy for "maxcpus=0".
2399 nosoftlockup [KNL] Disable the soft-lockup detector.
2401 nosync [HW,M68K] Disables sync negotiation for all devices.
2403 notsc [BUGS=X86-32] Disable Time Stamp Counter
2405 nousb [USB] Disable the USB subsystem
2407 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2411 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2413 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2414 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2415 Some features depend on CPU0. Known dependencies are:
2416 1. Resume from suspend/hibernate depends on CPU0.
2417 Suspend/hibernate will fail if CPU0 is offline and you
2418 need to online CPU0 before suspend/hibernate.
2419 2. PIC interrupts also depend on CPU0. CPU0 can't be
2420 removed if a PIC interrupt is detected.
2421 It's said poweroff/reboot may depend on CPU0 on some
2422 machines although I haven't seen such issues so far
2423 after CPU0 is offline on a few tested machines.
2424 If the dependencies are under your control, you can
2425 turn on cpu0_hotplug.
2427 nptcg= [IA-64] Override max number of concurrent global TLB
2428 purges which is reported from either PAL_VM_SUMMARY or
2431 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2432 could support. nr_cpus=n : n >= 1 limits the kernel to
2433 supporting 'n' processors. Later in runtime you can not
2434 use hotplug cpu feature to put more cpu back to online.
2435 just like you compile the kernel NR_CPUS=n
2437 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2439 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2440 Allowed values are enable and disable
2442 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2443 one of ['zone', 'node', 'default'] can be specified
2444 This can be set from sysctl after boot.
2445 See Documentation/sysctl/vm.txt for details.
2447 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2448 See Documentation/debugging-via-ohci1394.txt for more
2451 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2452 Rather than timing out after 20 ms if an EC
2453 command is not properly ACKed, override the length
2454 of the timeout. We have interrupts disabled while
2455 waiting for the ACK, so if this is set too high
2456 interrupts *may* be lost!
2458 omap_mux= [OMAP] Override bootloader pin multiplexing.
2459 Format: <mux_mode0.mode_name=value>...
2460 For example, to override I2C bus2:
2461 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2463 oprofile.timer= [HW]
2464 Use timer interrupt instead of performance counters
2466 oprofile.cpu_type= Force an oprofile cpu type
2467 This might be useful if you have an older oprofile
2468 userland or if you want common events.
2469 Format: { arch_perfmon }
2470 arch_perfmon: [X86] Force use of architectural
2471 perfmon on Intel CPUs instead of the
2472 CPU specific event set.
2473 timer: [X86] Force use of architectural NMI
2474 timer mode (see also oprofile.timer
2475 for generic hr timer mode)
2476 [s390] Force legacy basic mode sampling
2477 (report cpu_type "timer")
2479 oops=panic Always panic on oopses. Default is to just kill the
2480 process, but there is a small probability of
2481 deadlocking the machine.
2482 This will also cause panics on machine check exceptions.
2483 Useful together with panic=30 to trigger a reboot.
2486 See Documentation/sound/oss/oss-parameters.txt
2488 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2489 timeout > 0: seconds before rebooting
2490 timeout = 0: wait forever
2491 timeout < 0: reboot immediately
2494 crash_kexec_post_notifiers
2495 Run kdump after running panic-notifiers and dumping
2496 kmsg. This only for the users who doubt kdump always
2497 succeeds in any situation.
2498 Note that this also increases risks of kdump failure,
2499 because some panic notifiers can make the crashed
2500 kernel more unstable.
2502 parkbd.port= [HW] Parallel port number the keyboard adapter is
2503 connected to, default is 0.
2505 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2506 0 for XT, 1 for AT (default is AT).
2509 parport= [HW,PPT] Specify parallel ports. 0 disables.
2510 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2511 Use 'auto' to force the driver to use any
2512 IRQ/DMA settings detected (the default is to
2513 ignore detected IRQ/DMA settings because of
2514 possible conflicts). You can specify the base
2515 address, IRQ, and DMA settings; IRQ and DMA
2516 should be numbers, or 'auto' (for using detected
2517 settings on that particular port), or 'nofifo'
2518 (to avoid using a FIFO even if it is detected).
2519 Parallel ports are assigned in the order they
2520 are specified on the command line, starting
2523 parport_init_mode= [HW,PPT]
2524 Configure VIA parallel port to operate in
2525 a specific mode. This is necessary on Pegasos
2526 computer where firmware has no options for setting
2527 up parallel port mode and sets it to spp.
2528 Currently this function knows 686a and 8231 chips.
2529 Format: [spp|ps2|epp|ecp|ecpepp]
2532 Halt all CPUs after the first oops has been printed for
2533 the specified number of seconds. This is to be used if
2534 your oopses keep scrolling off the screen.
2539 See header of drivers/block/paride/pcd.c.
2540 See also Documentation/blockdev/paride.txt.
2542 pci=option[,option...] [PCI] various PCI subsystem options:
2543 earlydump [X86] dump PCI config space before the kernel
2545 off [X86] don't probe for the PCI bus
2546 bios [X86-32] force use of PCI BIOS, don't access
2547 the hardware directly. Use this if your machine
2548 has a non-standard PCI host bridge.
2549 nobios [X86-32] disallow use of PCI BIOS, only direct
2550 hardware access methods are allowed. Use this
2551 if you experience crashes upon bootup and you
2552 suspect they are caused by the BIOS.
2553 conf1 [X86] Force use of PCI Configuration
2555 conf2 [X86] Force use of PCI Configuration
2557 noaer [PCIE] If the PCIEAER kernel config parameter is
2558 enabled, this kernel boot option can be used to
2559 disable the use of PCIE advanced error reporting.
2560 nodomains [PCI] Disable support for multiple PCI
2561 root domains (aka PCI segments, in ACPI-speak).
2562 nommconf [X86] Disable use of MMCONFIG for PCI
2564 check_enable_amd_mmconf [X86] check for and enable
2565 properly configured MMIO access to PCI
2566 config space on AMD family 10h CPU
2567 nomsi [MSI] If the PCI_MSI kernel config parameter is
2568 enabled, this kernel boot option can be used to
2569 disable the use of MSI interrupts system-wide.
2570 noioapicquirk [APIC] Disable all boot interrupt quirks.
2571 Safety option to keep boot IRQs enabled. This
2572 should never be necessary.
2573 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2574 primary IO-APIC for bridges that cannot disable
2575 boot IRQs. This fixes a source of spurious IRQs
2576 when the system masks IRQs.
2577 noioapicreroute [APIC] Disable workaround that uses the
2578 boot IRQ equivalent of an IRQ that connects to
2579 a chipset where boot IRQs cannot be disabled.
2580 The opposite of ioapicreroute.
2581 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2582 routing table. These calls are known to be buggy
2583 on several machines and they hang the machine
2584 when used, but on other computers it's the only
2585 way to get the interrupt routing table. Try
2586 this option if the kernel is unable to allocate
2587 IRQs or discover secondary PCI buses on your
2589 rom [X86] Assign address space to expansion ROMs.
2590 Use with caution as certain devices share
2591 address decoders between ROMs and other
2593 norom [X86] Do not assign address space to
2594 expansion ROMs that do not already have
2595 BIOS assigned address ranges.
2596 nobar [X86] Do not assign address space to the
2597 BARs that weren't assigned by the BIOS.
2598 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2599 assigned automatically to PCI devices. You can
2600 make the kernel exclude IRQs of your ISA cards
2602 pirqaddr=0xAAAAA [X86] Specify the physical address
2603 of the PIRQ table (normally generated
2604 by the BIOS) if it is outside the
2605 F0000h-100000h range.
2606 lastbus=N [X86] Scan all buses thru bus #N. Can be
2607 useful if the kernel is unable to find your
2608 secondary buses and you want to tell it
2609 explicitly which ones they are.
2610 assign-busses [X86] Always assign all PCI bus
2611 numbers ourselves, overriding
2612 whatever the firmware may have done.
2613 usepirqmask [X86] Honor the possible IRQ mask stored
2614 in the BIOS $PIR table. This is needed on
2615 some systems with broken BIOSes, notably
2616 some HP Pavilion N5400 and Omnibook XE3
2617 notebooks. This will have no effect if ACPI
2618 IRQ routing is enabled.
2619 noacpi [X86] Do not use ACPI for IRQ routing
2620 or for PCI scanning.
2621 use_crs [X86] Use PCI host bridge window information
2622 from ACPI. On BIOSes from 2008 or later, this
2623 is enabled by default. If you need to use this,
2624 please report a bug.
2625 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2626 If you need to use this, please report a bug.
2627 routeirq Do IRQ routing for all PCI devices.
2628 This is normally done in pci_enable_device(),
2629 so this option is a temporary workaround
2630 for broken drivers that don't call it.
2631 skip_isa_align [X86] do not align io start addr, so can
2632 handle more pci cards
2633 firmware [ARM] Do not re-enumerate the bus but instead
2634 just use the configuration from the
2635 bootloader. This is currently used on
2636 IXP2000 systems where the bus has to be
2637 configured a certain way for adjunct CPUs.
2638 noearly [X86] Don't do any early type 1 scanning.
2639 This might help on some broken boards which
2640 machine check when some devices' config space
2641 is read. But various workarounds are disabled
2642 and some IOMMU drivers will not work.
2643 bfsort Sort PCI devices into breadth-first order.
2644 This sorting is done to get a device
2645 order compatible with older (<= 2.4) kernels.
2646 nobfsort Don't sort PCI devices into breadth-first order.
2647 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2648 tuning and use the BIOS-configured MPS defaults.
2649 pcie_bus_safe Set every device's MPS to the largest value
2650 supported by all devices below the root complex.
2651 pcie_bus_perf Set device MPS to the largest allowable MPS
2652 based on its parent bus. Also set MRRS (Max
2653 Read Request Size) to the largest supported
2654 value (no larger than the MPS that the device
2655 or bus can support) for best performance.
2656 pcie_bus_peer2peer Set every device's MPS to 128B, which
2657 every device is guaranteed to support. This
2658 configuration allows peer-to-peer DMA between
2659 any pair of devices, possibly at the cost of
2660 reduced performance. This also guarantees
2661 that hot-added devices will work.
2662 cbiosize=nn[KMG] The fixed amount of bus space which is
2663 reserved for the CardBus bridge's IO window.
2664 The default value is 256 bytes.
2665 cbmemsize=nn[KMG] The fixed amount of bus space which is
2666 reserved for the CardBus bridge's memory
2667 window. The default value is 64 megabytes.
2670 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2671 Specifies alignment and device to reassign
2672 aligned memory resources.
2673 If <order of align> is not specified,
2674 PAGE_SIZE is used as alignment.
2675 PCI-PCI bridge can be specified, if resource
2676 windows need to be expanded.
2677 ecrc= Enable/disable PCIe ECRC (transaction layer
2678 end-to-end CRC checking).
2679 bios: Use BIOS/firmware settings. This is the
2683 hpiosize=nn[KMG] The fixed amount of bus space which is
2684 reserved for hotplug bridge's IO window.
2685 Default size is 256 bytes.
2686 hpmemsize=nn[KMG] The fixed amount of bus space which is
2687 reserved for hotplug bridge's memory window.
2688 Default size is 2 megabytes.
2689 realloc= Enable/disable reallocating PCI bridge resources
2690 if allocations done by BIOS are too small to
2691 accommodate resources required by all child
2693 off: Turn realloc off
2695 realloc same as realloc=on
2696 noari do not use PCIe ARI.
2697 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2698 only look for one device below a PCIe downstream
2701 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2704 force Enable ASPM even on devices that claim not to support it.
2705 WARNING: Forcing ASPM on may cause system lockups.
2707 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2708 nomsi Do not use MSI for PCI Express Native Hotplug (this
2709 makes all PCIe ports use INTx for hotplug services).
2711 pcie_ports= [PCIE] PCIe ports handling:
2712 auto Ask the BIOS whether or not to use native PCIe services
2713 associated with PCIe ports (PME, hot-plug, AER). Use
2714 them only if that is allowed by the BIOS.
2715 native Use native PCIe services associated with PCIe ports
2717 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2720 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2721 nomsi Do not use MSI for native PCIe PME signaling (this makes
2722 all PCIe root ports use INTx for all services).
2724 pcmv= [HW,PCMCIA] BadgePAD 4
2728 Keep all power-domains already enabled by bootloader on,
2729 even if no driver has claimed them. This is useful
2730 for debug and development, but should not be
2731 needed on a platform with proper driver support.
2734 See Documentation/blockdev/paride.txt.
2736 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2739 See arch/parisc/kernel/pdc_chassis.c
2741 percpu_alloc= Select which percpu first chunk allocator to use.
2742 Currently supported values are "embed" and "page".
2743 Archs may support subset or none of the selections.
2744 See comments in mm/percpu.c for details on each
2745 allocator. This parameter is primarily for debugging
2746 and performance comparison.
2749 See Documentation/blockdev/paride.txt.
2752 See Documentation/blockdev/paride.txt.
2754 pirq= [SMP,APIC] Manual mp-table setup
2755 See Documentation/x86/i386/IO-APIC.txt.
2757 plip= [PPT,NET] Parallel port network link
2758 Format: { parport<nr> | timid | 0 }
2759 See also Documentation/parport.txt.
2761 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2762 Override pmtimer IOPort with a hex value.
2766 Enable PNP debug messages (depends on the
2767 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2768 via /sys/module/pnp/parameters/debug. We always show
2769 current resource usage; turning this on also shows
2770 possible settings and some assignment information.
2776 { on | off | curr | res | no-curr | no-res }
2779 [ISAPNP] Exclude IRQs for the autoconfiguration
2782 [ISAPNP] Exclude DMAs for the autoconfiguration
2784 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2785 Ranges are in pairs (I/O port base and size).
2788 [ISAPNP] Exclude memory regions for the
2790 Ranges are in pairs (memory base and size).
2792 ports= [IP_VS_FTP] IPVS ftp helper module
2794 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2796 Format: <port>,<port>....
2798 print-fatal-signals=
2799 [KNL] debug: print fatal signals
2801 If enabled, warn about various signal handling
2802 related application anomalies: too many signals,
2803 too many POSIX.1 timers, fatal signals causing a
2806 If you hit the warning due to signal overflow,
2807 you might want to try "ulimit -i unlimited".
2811 printk.always_kmsg_dump=
2812 Trigger kmsg_dump for cases other than kernel oops or
2814 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2817 printk.time= Show timing data prefixed to each printk message line
2818 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2820 processor.max_cstate= [HW,ACPI]
2821 Limit processor to maximum C-state
2822 max_cstate=9 overrides any DMI blacklist limit.
2824 processor.nocst [HW,ACPI]
2825 Ignore the _CST method to determine C-states,
2826 instead using the legacy FADT method
2828 profile= [KNL] Enable kernel profiling via /proc/profile
2829 Format: [schedule,]<number>
2830 Param: "schedule" - profile schedule points.
2831 Param: <number> - step/bucket size as a power of 2 for
2832 statistical time based profiling.
2833 Param: "sleep" - profile D-state sleeping (millisecs).
2834 Requires CONFIG_SCHEDSTATS
2835 Param: "kvm" - profile VM exits.
2837 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2839 See Documentation/blockdev/ramdisk.txt.
2841 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2842 probe for; one of (bare|imps|exps|lifebook|any).
2843 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2845 psmouse.resetafter= [HW,MOUSE]
2846 Try to reset the device after so many bad packets
2849 [HW,MOUSE] Set desired mouse resolution, in dpi.
2850 psmouse.smartscroll=
2851 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2852 0 = disabled, 1 = enabled (default).
2854 pstore.backend= Specify the name of the pstore backend to use
2857 See Documentation/blockdev/paride.txt.
2860 [KNL] Number of legacy pty's. Overwrites compiled-in
2863 quiet [KNL] Disable most log messages
2868 See Documentation/md.txt.
2870 ramdisk_blocksize= [RAM]
2871 See Documentation/blockdev/ramdisk.txt.
2873 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2874 See Documentation/blockdev/ramdisk.txt.
2877 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2878 the specified list of CPUs to be no-callback CPUs.
2879 Invocation of these CPUs' RCU callbacks will
2880 be offloaded to "rcuox/N" kthreads created for
2881 that purpose, where "x" is "b" for RCU-bh, "p"
2882 for RCU-preempt, and "s" for RCU-sched, and "N"
2883 is the CPU number. This reduces OS jitter on the
2884 offloaded CPUs, which can be useful for HPC and
2885 real-time workloads. It can also improve energy
2886 efficiency for asymmetric multiprocessors.
2889 Rather than requiring that offloaded CPUs
2890 (specified by rcu_nocbs= above) explicitly
2891 awaken the corresponding "rcuoN" kthreads,
2892 make these kthreads poll for callbacks.
2893 This improves the real-time response for the
2894 offloaded CPUs by relieving them of the need to
2895 wake up the corresponding kthread, but degrades
2896 energy efficiency by requiring that the kthreads
2897 periodically wake up to do the polling.
2899 rcutree.blimit= [KNL]
2900 Set maximum number of finished RCU callbacks to
2901 process in one batch.
2903 rcutree.rcu_fanout_leaf= [KNL]
2904 Increase the number of CPUs assigned to each
2905 leaf rcu_node structure. Useful for very large
2908 rcutree.jiffies_till_sched_qs= [KNL]
2909 Set required age in jiffies for a
2910 given grace period before RCU starts
2911 soliciting quiescent-state help from
2912 rcu_note_context_switch().
2914 rcutree.jiffies_till_first_fqs= [KNL]
2915 Set delay from grace-period initialization to
2916 first attempt to force quiescent states.
2917 Units are jiffies, minimum value is zero,
2918 and maximum value is HZ.
2920 rcutree.jiffies_till_next_fqs= [KNL]
2921 Set delay between subsequent attempts to force
2922 quiescent states. Units are jiffies, minimum
2923 value is one, and maximum value is HZ.
2925 rcutree.rcu_nocb_leader_stride= [KNL]
2926 Set the number of NOCB kthread groups, which
2927 defaults to the square root of the number of
2928 CPUs. Larger numbers reduces the wakeup overhead
2929 on the per-CPU grace-period kthreads, but increases
2930 that same overhead on each group's leader.
2932 rcutree.qhimark= [KNL]
2933 Set threshold of queued RCU callbacks beyond which
2934 batch limiting is disabled.
2936 rcutree.qlowmark= [KNL]
2937 Set threshold of queued RCU callbacks below which
2938 batch limiting is re-enabled.
2940 rcutree.rcu_idle_gp_delay= [KNL]
2941 Set wakeup interval for idle CPUs that have
2942 RCU callbacks (RCU_FAST_NO_HZ=y).
2944 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2945 Set wakeup interval for idle CPUs that have
2946 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2947 Lazy RCU callbacks are those which RCU can
2948 prove do nothing more than free memory.
2950 rcutorture.cbflood_inter_holdoff= [KNL]
2951 Set holdoff time (jiffies) between successive
2952 callback-flood tests.
2954 rcutorture.cbflood_intra_holdoff= [KNL]
2955 Set holdoff time (jiffies) between successive
2956 bursts of callbacks within a given callback-flood
2959 rcutorture.cbflood_n_burst= [KNL]
2960 Set the number of bursts making up a given
2961 callback-flood test. Set this to zero to
2962 disable callback-flood testing.
2964 rcutorture.cbflood_n_per_burst= [KNL]
2965 Set the number of callbacks to be registered
2966 in a given burst of a callback-flood test.
2968 rcutorture.fqs_duration= [KNL]
2969 Set duration of force_quiescent_state bursts.
2971 rcutorture.fqs_holdoff= [KNL]
2972 Set holdoff time within force_quiescent_state bursts.
2974 rcutorture.fqs_stutter= [KNL]
2975 Set wait time between force_quiescent_state bursts.
2977 rcutorture.gp_exp= [KNL]
2978 Use expedited update-side primitives.
2980 rcutorture.gp_normal= [KNL]
2981 Use normal (non-expedited) update-side primitives.
2982 If both gp_exp and gp_normal are set, do both.
2983 If neither gp_exp nor gp_normal are set, still
2986 rcutorture.n_barrier_cbs= [KNL]
2987 Set callbacks/threads for rcu_barrier() testing.
2989 rcutorture.nfakewriters= [KNL]
2990 Set number of concurrent RCU writers. These just
2991 stress RCU, they don't participate in the actual
2992 test, hence the "fake".
2994 rcutorture.nreaders= [KNL]
2995 Set number of RCU readers.
2997 rcutorture.object_debug= [KNL]
2998 Enable debug-object double-call_rcu() testing.
3000 rcutorture.onoff_holdoff= [KNL]
3001 Set time (s) after boot for CPU-hotplug testing.
3003 rcutorture.onoff_interval= [KNL]
3004 Set time (s) between CPU-hotplug operations, or
3005 zero to disable CPU-hotplug testing.
3007 rcutorture.torture_runnable= [BOOT]
3008 Start rcutorture running at boot time.
3010 rcutorture.shuffle_interval= [KNL]
3011 Set task-shuffle interval (s). Shuffling tasks
3012 allows some CPUs to go into dyntick-idle mode
3013 during the rcutorture test.
3015 rcutorture.shutdown_secs= [KNL]
3016 Set time (s) after boot system shutdown. This
3017 is useful for hands-off automated testing.
3019 rcutorture.stall_cpu= [KNL]
3020 Duration of CPU stall (s) to test RCU CPU stall
3021 warnings, zero to disable.
3023 rcutorture.stall_cpu_holdoff= [KNL]
3024 Time to wait (s) after boot before inducing stall.
3026 rcutorture.stat_interval= [KNL]
3027 Time (s) between statistics printk()s.
3029 rcutorture.stutter= [KNL]
3030 Time (s) to stutter testing, for example, specifying
3031 five seconds causes the test to run for five seconds,
3032 wait for five seconds, and so on. This tests RCU's
3033 ability to transition abruptly to and from idle.
3035 rcutorture.test_boost= [KNL]
3036 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3037 "Maybe" means test if the RCU implementation
3038 under test support RCU priority boosting.
3040 rcutorture.test_boost_duration= [KNL]
3041 Duration (s) of each individual boost test.
3043 rcutorture.test_boost_interval= [KNL]
3044 Interval (s) between each boost test.
3046 rcutorture.test_no_idle_hz= [KNL]
3047 Test RCU's dyntick-idle handling. See also the
3048 rcutorture.shuffle_interval parameter.
3050 rcutorture.torture_type= [KNL]
3051 Specify the RCU implementation to test.
3053 rcutorture.verbose= [KNL]
3054 Enable additional printk() statements.
3056 rcupdate.rcu_expedited= [KNL]
3057 Use expedited grace-period primitives, for
3058 example, synchronize_rcu_expedited() instead
3059 of synchronize_rcu(). This reduces latency,
3060 but can increase CPU utilization, degrade
3061 real-time latency, and degrade energy efficiency.
3063 rcupdate.rcu_cpu_stall_suppress= [KNL]
3064 Suppress RCU CPU stall warning messages.
3066 rcupdate.rcu_cpu_stall_timeout= [KNL]
3067 Set timeout for RCU CPU stall warning messages.
3069 rcupdate.rcu_task_stall_timeout= [KNL]
3070 Set timeout in jiffies for RCU task stall warning
3071 messages. Disable with a value less than or equal
3076 Run specified binary instead of /init from the ramdisk,
3077 used for early userspace startup. See initrd.
3080 Format (x86 or x86_64):
3081 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3083 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3085 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3086 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3087 reboot_force is either force or not specified,
3088 reboot_cpu is s[mp]#### with #### being the processor
3089 to be used for rebooting.
3092 [KNL, SMP] Set scheduler's default relax_domain_level.
3093 See Documentation/cgroups/cpusets.txt.
3095 relative_sleep_states=
3096 [SUSPEND] Use sleep state labeling where the deepest
3097 state available other than hibernation is always "mem".
3098 Format: { "0" | "1" }
3099 0 -- Traditional sleep state labels.
3100 1 -- Relative sleep state labels.
3102 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3104 reservetop= [X86-32]
3106 Reserves a hole at the top of the kernel virtual
3111 Set the amount of memory to reserve for BIOS at
3112 the bottom of the address space.
3114 reset_devices [KNL] Force drivers to reset the underlying device
3115 during initialization.
3118 Specify the partition device for software suspend
3120 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3122 resume_offset= [SWSUSP]
3123 Specify the offset from the beginning of the partition
3124 given by "resume=" at which the swap header is located,
3125 in <PAGE_SIZE> units (needed only for swap files).
3126 See Documentation/power/swsusp-and-swap-files.txt
3128 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3129 read the resume files
3131 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3132 Useful for devices that are detected asynchronously
3133 (e.g. USB and MMC devices).
3135 hibernate= [HIBERNATION]
3136 noresume Don't check if there's a hibernation image
3137 present during boot.
3138 nocompress Don't compress/decompress hibernation images.
3139 no Disable hibernation and resume.
3141 retain_initrd [RAM] Keep initrd memory after extraction
3143 rhash_entries= [KNL,NET]
3144 Set number of hash buckets for route cache
3146 ro [KNL] Mount root device read-only on boot
3148 root= [KNL] Root filesystem
3149 See name_to_dev_t comment in init/do_mounts.c.
3151 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3152 mount the root filesystem
3154 rootflags= [KNL] Set root filesystem mount option string
3156 rootfstype= [KNL] Set root filesystem type
3158 rootwait [KNL] Wait (indefinitely) for root device to show up.
3159 Useful for devices that are detected asynchronously
3160 (e.g. USB and MMC devices).
3162 rproc_mem=nn[KMG][@address]
3163 [KNL,ARM,CMA] Remoteproc physical memory block.
3164 Memory area to be used by remote processor image,
3167 rw [KNL] Mount root device read-write on boot
3169 S [KNL] Run init in single mode
3171 s390_iommu= [HW,S390]
3172 Set s390 IOTLB flushing mode
3174 With strict flushing every unmap operation will result in
3175 an IOTLB flush. Default is lazy flushing before reuse,
3179 See drivers/net/irda/sa1100_ir.c.
3181 sbni= [NET] Granch SBNI12 leased line adapter
3183 sched_debug [KNL] Enables verbose scheduler debug messages.
3185 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3186 xtime_lock contention on larger systems, and/or RCU lock
3187 contention on all systems with CONFIG_MAXSMP set.
3188 Format: { "0" | "1" }
3189 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3191 Note: increases power consumption, thus should only be
3192 enabled if running jitter sensitive (HPC/RT) workloads.
3194 security= [SECURITY] Choose a security module to enable at boot.
3195 If this boot parameter is not specified, only the first
3196 security module asking for security registration will be
3197 loaded. An invalid security module name will be treated
3198 as if no module has been chosen.
3200 selinux= [SELINUX] Disable or enable SELinux at boot time.
3201 Format: { "0" | "1" }
3202 See security/selinux/Kconfig help text.
3205 Default value is set via kernel config option.
3206 If enabled at boot time, /selinux/disable can be used
3207 later to disable prior to initial policy load.
3209 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3210 Format: { "0" | "1" }
3211 See security/apparmor/Kconfig help text
3214 Default value is set via kernel config option.
3216 serialnumber [BUGS=X86-32]
3219 Maximal number of shapers.
3221 show_msr= [x86] show boot-time MSR settings
3222 Format: { <integer> }
3223 Show boot-time (BIOS-initialized) MSR settings.
3224 The parameter means the number of CPUs to show,
3225 for example 1 means boot CPU only.
3233 Disable merging of slabs with similar size. May be
3234 necessary if there is some reason to distinguish
3235 allocs to different slabs. Debug options disable
3236 merging on their own.
3237 For more information see Documentation/vm/slub.txt.
3239 slab_max_order= [MM, SLAB]
3240 Determines the maximum allowed order for slabs.
3241 A high setting may cause OOMs due to memory
3242 fragmentation. Defaults to 1 for systems with
3243 more than 32MB of RAM, 0 otherwise.
3245 slub_debug[=options[,slabs]] [MM, SLUB]
3246 Enabling slub_debug allows one to determine the
3247 culprit if slab objects become corrupted. Enabling
3248 slub_debug can create guard zones around objects and
3249 may poison objects when not in use. Also tracks the
3250 last alloc / free. For more information see
3251 Documentation/vm/slub.txt.
3253 slub_max_order= [MM, SLUB]
3254 Determines the maximum allowed order for slabs.
3255 A high setting may cause OOMs due to memory
3256 fragmentation. For more information see
3257 Documentation/vm/slub.txt.
3259 slub_min_objects= [MM, SLUB]
3260 The minimum number of objects per slab. SLUB will
3261 increase the slab order up to slub_max_order to
3262 generate a sufficiently large slab able to contain
3263 the number of objects indicated. The higher the number
3264 of objects the smaller the overhead of tracking slabs
3265 and the less frequently locks need to be acquired.
3266 For more information see Documentation/vm/slub.txt.
3268 slub_min_order= [MM, SLUB]
3269 Determines the minimum page order for slabs. Must be
3270 lower than slub_max_order.
3271 For more information see Documentation/vm/slub.txt.
3273 slub_nomerge [MM, SLUB]
3274 Same with slab_nomerge. This is supported for legacy.
3275 See slab_nomerge for more information.
3278 Format: <io1>[,<io2>[,...,<io8>]]
3280 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3281 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3282 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3283 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3284 smsc-ircc2.ircc_irq= [HW] IRQ line
3285 smsc-ircc2.ircc_dma= [HW] DMA channel
3286 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3287 0: Toshiba Satellite 1800 (GP data pin select)
3288 1: Fast pin select (default)
3292 [KNL] Should the soft-lockup detector generate panics.
3295 softlockup_all_cpu_backtrace=
3296 [KNL] Should the soft-lockup detector generate
3297 backtraces on all cpus.
3300 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3301 See Documentation/laptops/sonypi.txt
3303 spia_io_base= [HW,MTD]
3309 Enabled the stack tracer on boot up.
3311 stacktrace_filter=[function-list]
3312 [FTRACE] Limit the functions that the stack tracer
3313 will trace at boot up. function-list is a comma separated
3314 list of functions. This list can be changed at run
3315 time by the stack_trace_filter file in the debugfs
3316 tracing directory. Note, this enables stack tracing
3317 and the stacktrace above is not needed.
3321 Set the STI (builtin display/keyboard on the HP-PARISC
3322 machines) console (graphic card) which should be used
3323 as the initial boot-console.
3324 See also comment in drivers/video/console/sticore.c.
3327 See comment in drivers/video/console/sticore.c.
3330 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3332 sunrpc.min_resvport=
3333 sunrpc.max_resvport=
3335 SunRPC servers often require that client requests
3336 originate from a privileged port (i.e. a port in the
3337 range 0 < portnr < 1024).
3338 An administrator who wishes to reserve some of these
3339 ports for other uses may adjust the range that the
3340 kernel's sunrpc client considers to be privileged
3341 using these two parameters to set the minimum and
3342 maximum port values.
3346 Control how the NFS server code allocates CPUs to
3347 service thread pools. Depending on how many NICs
3348 you have and where their interrupts are bound, this
3349 option will affect which CPUs will do NFS serving.
3350 Note: this parameter cannot be changed while the
3351 NFS server is running.
3353 auto the server chooses an appropriate mode
3354 automatically using heuristics
3355 global a single global pool contains all CPUs
3356 percpu one pool for each CPU
3357 pernode one pool for each NUMA node (equivalent
3358 to global on non-NUMA machines)
3360 sunrpc.tcp_slot_table_entries=
3361 sunrpc.udp_slot_table_entries=
3363 Sets the upper limit on the number of simultaneous
3364 RPC calls that can be sent from the client to a
3365 server. Increasing these values may allow you to
3366 improve throughput, but will also increase the
3367 amount of memory reserved for use by the client.
3370 [KNL] Enable accounting of swap in memory resource
3371 controller if no parameter or 1 is given or disable
3372 it if 0 is given (See Documentation/cgroups/memory.txt)
3374 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3375 Format: { <int> | force }
3376 <int> -- Number of I/O TLB slabs
3377 force -- force using of bounce buffers even if they
3378 wouldn't be automatically used by the kernel
3382 sysfs.deprecated=0|1 [KNL]
3383 Enable/disable old style sysfs layout for old udev
3384 on older distributions. When this option is enabled
3385 very new udev will not work anymore. When this option
3386 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3387 in older udev will not work anymore.
3388 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3389 the kernel configuration.
3391 sysrq_always_enabled
3393 Ignore sysrq setting - this boot parameter will
3394 neutralize any effect of /proc/sys/kernel/sysrq.
3395 Useful for debugging.
3399 test_suspend= [SUSPEND][,N]
3400 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3401 standby suspend) or "freeze" (for suspend type freeze)
3402 as the system sleep state during system startup with
3403 the optional capability to repeat N number of times.
3404 The system is woken from this state using a
3405 wakeup-capable RTC alarm.
3407 thash_entries= [KNL,NET]
3408 Set number of hash buckets for TCP connection
3410 thermal.act= [HW,ACPI]
3411 -1: disable all active trip points in all thermal zones
3412 <degrees C>: override all lowest active trip points
3414 thermal.crt= [HW,ACPI]
3415 -1: disable all critical trip points in all thermal zones
3416 <degrees C>: override all critical trip points
3418 thermal.nocrt= [HW,ACPI]
3419 Set to disable actions on ACPI thermal zone
3420 critical and hot trip points.
3422 thermal.off= [HW,ACPI]
3423 1: disable ACPI thermal control
3425 thermal.psv= [HW,ACPI]
3426 -1: disable all passive trip points
3427 <degrees C>: override all passive trip points to this
3430 thermal.tzp= [HW,ACPI]
3431 Specify global default ACPI thermal zone polling rate
3432 <deci-seconds>: poll all this frequency
3433 0: no polling (default)
3436 Force threading of all interrupt handlers except those
3437 marked explicitly IRQF_NO_THREAD.
3440 Enable the Transcendent memory driver if built-in.
3442 tmem.cleancache=0|1 [KNL, XEN]
3443 Default is on (1). Disable the usage of the cleancache
3444 API to send anonymous pages to the hypervisor.
3446 tmem.frontswap=0|1 [KNL, XEN]
3447 Default is on (1). Disable the usage of the frontswap
3448 API to send swap pages to the hypervisor. If disabled
3449 the selfballooning and selfshrinking are force disabled.
3451 tmem.selfballooning=0|1 [KNL, XEN]
3452 Default is on (1). Disable the driving of swap pages
3455 tmem.selfshrinking=0|1 [KNL, XEN]
3456 Default is on (1). Partial swapoff that immediately
3457 transfers pages from Xen hypervisor back to the
3458 kernel based on different criteria.
3462 Specify if the kernel should make use of the cpu
3463 topology information if the hardware supports this.
3464 The scheduler will make use of this information and
3465 e.g. base its process migration decisions on it.
3468 topology_updates= [KNL, PPC, NUMA]
3470 Specify if the kernel should ignore (off)
3471 topology updates sent by the hypervisor to this
3476 tpm_suspend_pcr=[HW,TPM]
3477 Format: integer pcr id
3478 Specify that at suspend time, the tpm driver
3479 should extend the specified pcr with zeros,
3480 as a workaround for some chips which fail to
3481 flush the last written pcr on TPM_SaveState.
3482 This will guarantee that all the other pcrs
3485 trace_buf_size=nn[KMG]
3486 [FTRACE] will set tracing buffer size.
3488 trace_event=[event-list]
3489 [FTRACE] Set and start specified trace events in order
3490 to facilitate early boot debugging.
3491 See also Documentation/trace/events.txt
3493 trace_options=[option-list]
3494 [FTRACE] Enable or disable tracer options at boot.
3495 The option-list is a comma delimited list of options
3496 that can be enabled or disabled just as if you were
3497 to echo the option name into
3499 /sys/kernel/debug/tracing/trace_options
3501 For example, to enable stacktrace option (to dump the
3502 stack trace of each event), add to the command line:
3504 trace_options=stacktrace
3506 See also Documentation/trace/ftrace.txt "trace options"
3510 [FTRACE] enable this option to disable tracing when a
3511 warning is hit. This turns off "tracing_on". Tracing can
3512 be enabled again by echoing '1' into the "tracing_on"
3513 file located in /sys/kernel/debug/tracing/
3515 This option is useful, as it disables the trace before
3516 the WARNING dump is called, which prevents the trace to
3517 be filled with content caused by the warning output.
3519 This option can also be set at run time via the sysctl
3520 option: kernel/traceoff_on_warning
3522 transparent_hugepage=
3524 Format: [always|madvise|never]
3525 Can be used to control the default behavior of the system
3526 with respect to transparent hugepages.
3527 See Documentation/vm/transhuge.txt for more details.
3529 tsc= Disable clocksource stability checks for TSC.
3531 [x86] reliable: mark tsc clocksource as reliable, this
3532 disables clocksource verification at runtime, as well
3533 as the stability checks done at bootup. Used to enable
3534 high-resolution timer mode on older hardware, and in
3535 virtualized environment.
3536 [x86] noirqtime: Do not use TSC to do irq accounting.
3537 Used to run time disable IRQ_TIME_ACCOUNTING on any
3538 platforms where RDTSC is slow and this accounting
3541 turbografx.map[2|3]= [HW,JOY]
3542 TurboGraFX parallel port interface
3544 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3545 See also Documentation/input/joystick-parport.txt
3547 udbg-immortal [PPC] When debugging early kernel crashes that
3548 happen after console_init() and before a proper
3549 console driver takes over, this boot options might
3550 help "seeing" what's going on.
3552 uhash_entries= [KNL,NET]
3553 Set number of hash buckets for UDP/UDP-Lite connections
3556 [USB] Ignore overcurrent events (default N).
3557 Some badly-designed motherboards generate lots of
3558 bogus events, for ports that aren't wired to
3559 anything. Set this parameter to avoid log spamming.
3560 Note that genuine overcurrent events won't be
3564 [X86] Cause panic on unknown NMI.
3566 usbcore.authorized_default=
3567 [USB] Default USB device authorization:
3568 (default -1 = authorized except for wireless USB,
3569 0 = not authorized, 1 = authorized)
3571 usbcore.autosuspend=
3572 [USB] The autosuspend time delay (in seconds) used
3573 for newly-detected USB devices (default 2). This
3574 is the time required before an idle device will be
3575 autosuspended. Devices for which the delay is set
3576 to a negative value won't be autosuspended at all.
3578 usbcore.usbfs_snoop=
3579 [USB] Set to log all usbfs traffic (default 0 = off).
3581 usbcore.blinkenlights=
3582 [USB] Set to cycle leds on hubs (default 0 = off).
3584 usbcore.old_scheme_first=
3585 [USB] Start with the old device initialization
3586 scheme (default 0 = off).
3588 usbcore.usbfs_memory_mb=
3589 [USB] Memory limit (in MB) for buffers allocated by
3590 usbfs (default = 16, 0 = max = 2047).
3592 usbcore.use_both_schemes=
3593 [USB] Try the other device initialization scheme
3594 if the first one fails (default 1 = enabled).
3596 usbcore.initial_descriptor_timeout=
3597 [USB] Specifies timeout for the initial 64-byte
3598 USB_REQ_GET_DESCRIPTOR request in milliseconds
3599 (default 5000 = 5.0 seconds).
3602 [USBHID] The interval which mice are to be polled at.
3604 usb-storage.delay_use=
3605 [UMS] The delay in seconds before a new device is
3606 scanned for Logical Units (default 5).
3609 [UMS] A list of quirks entries to supplement or
3610 override the built-in unusual_devs list. List
3611 entries are separated by commas. Each entry has
3612 the form VID:PID:Flags where VID and PID are Vendor
3613 and Product ID values (4-digit hex numbers) and
3614 Flags is a set of characters, each corresponding
3615 to a common usb-storage quirk flag as follows:
3616 a = SANE_SENSE (collect more than 18 bytes
3618 b = BAD_SENSE (don't collect more than 18
3619 bytes of sense data);
3620 c = FIX_CAPACITY (decrease the reported
3621 device capacity by one sector);
3622 d = NO_READ_DISC_INFO (don't use
3623 READ_DISC_INFO command);
3624 e = NO_READ_CAPACITY_16 (don't use
3625 READ_CAPACITY_16 command);
3626 f = NO_REPORT_OPCODES (don't use report opcodes
3628 h = CAPACITY_HEURISTICS (decrease the
3629 reported device capacity by one
3630 sector if the number is odd);
3631 i = IGNORE_DEVICE (don't bind to this
3633 l = NOT_LOCKABLE (don't try to lock and
3634 unlock ejectable media);
3635 m = MAX_SECTORS_64 (don't transfer more
3636 than 64 sectors = 32 KB at a time);
3637 n = INITIAL_READ10 (force a retry of the
3638 initial READ(10) command);
3639 o = CAPACITY_OK (accept the capacity
3640 reported by the device);
3641 p = WRITE_CACHE (the device cache is ON
3643 r = IGNORE_RESIDUE (the device reports
3644 bogus residue values);
3645 s = SINGLE_LUN (the device has only one
3647 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3648 commands, uas only);
3649 u = IGNORE_UAS (don't bind to the uas driver);
3650 w = NO_WP_DETECT (don't test whether the
3651 medium is write-protected).
3652 Example: quirks=0419:aaf5:rl,0421:0433:rc
3654 user_debug= [KNL,ARM]
3656 See arch/arm/Kconfig.debug help text.
3657 1 - undefined instruction events
3659 4 - invalid data aborts
3662 Example: user_debug=31
3665 [X86] Flags controlling user PTE allocations.
3667 nohigh = do not allocate PTE pages in
3668 HIGHMEM regardless of setting
3672 On X86_32, this is an alias for vdso32=. Otherwise:
3674 vdso=1: enable VDSO (the default)
3675 vdso=0: disable VDSO mapping
3677 vdso32= [X86] Control the 32-bit vDSO
3678 vdso32=1: enable 32-bit VDSO
3679 vdso32=0 or vdso32=2: disable 32-bit VDSO
3681 See the help text for CONFIG_COMPAT_VDSO for more
3682 details. If CONFIG_COMPAT_VDSO is set, the default is
3683 vdso32=0; otherwise, the default is vdso32=1.
3685 For compatibility with older kernels, vdso32=2 is an
3688 Try vdso32=0 if you encounter an error that says:
3689 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3692 vector=percpu: enable percpu vector domain
3694 video= [FB] Frame buffer configuration
3695 See Documentation/fb/modedb.txt.
3697 video.brightness_switch_enabled= [0,1]
3698 If set to 1, on receiving an ACPI notify event
3699 generated by hotkey, video driver will adjust brightness
3700 level and then send out the event to user space through
3701 the allocated input device; If set to 0, video driver
3702 will only send out the event without touching backlight
3707 [VMMIO] Memory mapped virtio (platform) device.
3709 <size>@<baseaddr>:<irq>[:<id>]
3711 <size> := size (can use standard suffixes
3713 <baseaddr> := physical base address
3714 <irq> := interrupt number (as passed to
3716 <id> := (optional) platform device id
3718 virtio_mmio.device=1K@0x100b0000:48:7
3720 Can be used multiple times for multiple devices.
3722 vga= [BOOT,X86-32] Select a particular video mode
3723 See Documentation/x86/boot.txt and
3724 Documentation/svga.txt.
3725 Use vga=ask for menu.
3726 This is actually a boot loader parameter; the value is
3727 passed to the kernel using a special protocol.
3729 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3730 size of <nn>. This can be used to increase the
3731 minimum size (128MB on x86). It can also be used to
3732 decrease the size and leave more room for directly
3735 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3738 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3741 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3745 Controls the behavior of vsyscalls (i.e. calls to
3746 fixed addresses of 0xffffffffff600x00 from legacy
3747 code). Most statically-linked binaries and older
3748 versions of glibc use these calls. Because these
3749 functions are at fixed addresses, they make nice
3750 targets for exploits that can control RIP.
3752 emulate [default] Vsyscalls turn into traps and are
3753 emulated reasonably safely.
3755 native Vsyscalls are native syscall instructions.
3756 This is a little bit faster than trapping
3757 and makes a few dynamic recompilers work
3758 better than they would in emulation mode.
3759 It also makes exploits much easier to write.
3761 none Vsyscalls don't work at all. This makes
3762 them quite hard to use for exploits but
3763 might break your system.
3765 vt.color= [VT] Default text color.
3766 Format: 0xYX, X = foreground, Y = background.
3767 Default: 0x07 = light gray on black.
3769 vt.cur_default= [VT] Default cursor shape.
3770 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3771 the parameters of the <Esc>[?A;B;Cc escape sequence;
3772 see VGA-softcursor.txt. Default: 2 = underline.
3774 vt.default_blu= [VT]
3775 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3776 Change the default blue palette of the console.
3777 This is a 16-member array composed of values
3780 vt.default_grn= [VT]
3781 Format: <green0>,<green1>,<green2>,...,<green15>
3782 Change the default green palette of the console.
3783 This is a 16-member array composed of values
3786 vt.default_red= [VT]
3787 Format: <red0>,<red1>,<red2>,...,<red15>
3788 Change the default red palette of the console.
3789 This is a 16-member array composed of values
3795 Set system-wide default UTF-8 mode for all tty's.
3796 Default is 1, i.e. UTF-8 mode is enabled for all
3797 newly opened terminals.
3799 vt.global_cursor_default=
3802 Set system-wide default for whether a cursor
3803 is shown on new VTs. Default is -1,
3804 i.e. cursors will be created by default unless
3805 overridden by individual drivers. 0 will hide
3806 cursors, 1 will display them.
3808 vt.italic= [VT] Default color for italic text; 0-15.
3811 vt.underline= [VT] Default color for underlined text; 0-15.
3814 watchdog timers [HW,WDT] For information on watchdog timers,
3815 see Documentation/watchdog/watchdog-parameters.txt
3816 or other driver-specific files in the
3817 Documentation/watchdog/ directory.
3819 workqueue.disable_numa
3820 By default, all work items queued to unbound
3821 workqueues are affine to the NUMA nodes they're
3822 issued on, which results in better behavior in
3823 general. If NUMA affinity needs to be disabled for
3824 whatever reason, this option can be used. Note
3825 that this also can be controlled per-workqueue for
3826 workqueues visible under /sys/bus/workqueue/.
3828 workqueue.power_efficient
3829 Per-cpu workqueues are generally preferred because
3830 they show better performance thanks to cache
3831 locality; unfortunately, per-cpu workqueues tend to
3832 be more power hungry than unbound workqueues.
3834 Enabling this makes the per-cpu workqueues which
3835 were observed to contribute significantly to power
3836 consumption unbound, leading to measurably lower
3837 power usage at the cost of small performance
3840 The default value of this parameter is determined by
3841 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3843 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3844 default x2apic cluster mode on platforms
3847 x86_intel_mid_timer= [X86-32,APBT]
3848 Choose timer option for x86 Intel MID platform.
3849 Two valid options are apbt timer only and lapic timer
3850 plus one apbt timer for broadcast timer.
3851 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3853 xen_emul_unplug= [HW,X86,XEN]
3854 Unplug Xen emulated devices
3855 Format: [unplug0,][unplug1]
3856 ide-disks -- unplug primary master IDE devices
3857 aux-ide-disks -- unplug non-primary-master IDE devices
3858 nics -- unplug network devices
3859 all -- unplug all emulated devices (NICs and IDE disks)
3860 unnecessary -- unplugging emulated devices is
3861 unnecessary even if the host did not respond to
3863 never -- do not unplug even if version check succeeds
3865 xen_nopvspin [X86,XEN]
3866 Disables the ticketlock slowpath using Xen PV
3870 Disables the PV optimizations forcing the HVM guest to
3871 run as generic HVM guest with no PV drivers.
3873 xirc2ps_cs= [NET,PCMCIA]
3875 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3877 ______________________________________________________________________
3881 Add more DRM drivers.
projects / cascardo / linux.git / blob