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 ccw_timeout_log [S390]
570 See Documentation/s390/CommonIO for details.
572 cgroup_disable= [KNL] Disable a particular controller
573 Format: {name of the controller(s) to disable}
574 The effects of cgroup_disable=foo are:
575 - foo isn't auto-mounted if you mount all cgroups in
577 - foo isn't visible as an individually mountable
579 {Currently only "memory" controller deal with this and
580 cut the overhead, others just disable the usage. So
581 only cgroup_disable=memory is actually worthy}
583 checkreqprot [SELINUX] Set initial checkreqprot flag value.
584 Format: { "0" | "1" }
585 See security/selinux/Kconfig help text.
586 0 -- check protection applied by kernel (includes
587 any implied execute protection).
588 1 -- check protection requested by application.
589 Default value is set via a kernel config option.
590 Value can be changed at runtime via
591 /selinux/checkreqprot.
594 See Documentation/s390/CommonIO for details.
597 Keep all clocks already enabled by bootloader on,
598 even if no driver has claimed them. This is useful
599 for debug and development, but should not be
600 needed on a platform with proper driver support.
601 For more information, see Documentation/clk.txt.
603 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
605 Forces specified clocksource (if available) to be used
606 when calculating gettimeofday(). If specified
607 clocksource is not available, it defaults to PIT.
608 Format: { pit | tsc | cyclone | pmtmr }
610 clocksource= Override the default clocksource
612 Override the default clocksource and use the clocksource
613 with the name specified.
614 Some clocksource names to choose from, depending on
616 [all] jiffies (this is the base, fallback clocksource)
618 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
619 pxa_timer,timer3,32k_counter,timer0_1
621 [X86-32] pit,hpet,tsc;
622 scx200_hrt on Geode; cyclone on IBM x440
630 clearcpuid=BITNUM [X86]
631 Disable CPUID feature X for the kernel. See
632 arch/x86/include/asm/cpufeature.h for the valid bit
633 numbers. Note the Linux specific bits are not necessarily
634 stable over kernel options, but the vendor specific
636 Also note that user programs calling CPUID directly
637 or using the feature without checking anything
638 will still see it. This just prevents it from
639 being used by the kernel or shown in /proc/cpuinfo.
640 Also note the kernel might malfunction if you disable
643 cma=nn[MG]@[start[MG][-end[MG]]]
645 Sets the size of kernel global memory area for
646 contiguous memory allocations and optionally the
647 placement constraint by the physical address range of
648 memory allocations. For more information, see
649 include/linux/dma-contiguous.h
651 cmo_free_hint= [PPC] Format: { yes | no }
652 Specify whether pages are marked as being inactive
653 when they are freed. This is used in CMO environments
654 to determine OS memory pressure for page stealing by
658 coherent_pool=nn[KMG] [ARM,KNL]
659 Sets the size of memory pool for coherent, atomic dma
660 allocations, by default set to 256K.
662 code_bytes [X86] How many bytes of object code to print
667 com20020= [HW,NET] ARCnet - COM20020 chipset
669 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
671 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
675 ARCnet - COM90xx chipset (memory-mapped buffers)
676 Format: <io>[,<irq>[,<memstart>]]
678 condev= [HW,S390] console device
681 console= [KNL] Output console device and options.
683 tty<n> Use the virtual console device <n>.
687 Use the specified serial port. The options are of
688 the form "bbbbpnf", where "bbbb" is the baud rate,
689 "p" is parity ("n", "o", or "e"), "n" is number of
690 bits, and "f" is flow control ("r" for RTS or
691 omit it). Default is "9600n8".
693 See Documentation/serial-console.txt for more
695 Documentation/networking/netconsole.txt for an
698 uart[8250],io,<addr>[,options]
699 uart[8250],mmio,<addr>[,options]
700 Start an early, polled-mode console on the 8250/16550
701 UART at the specified I/O port or MMIO address,
702 switching to the matching ttyS device later. The
703 options are the same as for ttyS, above.
704 hvc<n> Use the hypervisor console device <n>. This is for
705 both Xen and PowerPC hypervisors.
707 If the device connected to the port is not a TTY but a braille
708 device, prepend "brl," before the device type, for instance
710 For now, only VisioBraille is supported.
712 consoleblank= [KNL] The console blank (screen saver) timeout in
713 seconds. Defaults to 10*60 = 10mins. A value of 0
714 disables the blank timer.
717 [KNL] Change the default value for
718 /proc/<pid>/coredump_filter.
719 See also Documentation/filesystems/proc.txt.
721 cpuidle.off=1 [CPU_IDLE]
722 disable the cpuidle sub-system
724 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
726 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
728 crashkernel=size[KMG][@offset[KMG]]
729 [KNL] Using kexec, Linux can switch to a 'crash kernel'
730 upon panic. This parameter reserves the physical
731 memory region [offset, offset + size] for that kernel
732 image. If '@offset' is omitted, then a suitable offset
733 is selected automatically. Check
734 Documentation/kdump/kdump.txt for further details.
736 crashkernel=range1:size1[,range2:size2,...][@offset]
737 [KNL] Same as above, but depends on the memory
738 in the running system. The syntax of range is
739 start-[end] where start and end are both
740 a memory unit (amount[KMG]). See also
741 Documentation/kdump/kdump.txt for an example.
743 crashkernel=size[KMG],high
744 [KNL, x86_64] range could be above 4G. Allow kernel
745 to allocate physical memory region from top, so could
746 be above 4G if system have more than 4G ram installed.
747 Otherwise memory region will be allocated below 4G, if
749 It will be ignored if crashkernel=X is specified.
750 crashkernel=size[KMG],low
751 [KNL, x86_64] range under 4G. When crashkernel=X,high
752 is passed, kernel could allocate physical memory region
753 above 4G, that cause second kernel crash on system
754 that require some amount of low memory, e.g. swiotlb
755 requires at least 64M+32K low memory. Kernel would
756 try to allocate 72M below 4G automatically.
757 This one let user to specify own low range under 4G
758 for second kernel instead.
759 0: to disable low allocation.
760 It will be ignored when crashkernel=X,high is not used
761 or memory reserved is below 4G.
766 cs89x0_media= [HW,NET]
767 Format: { rj45 | aui | bnc }
770 See header of drivers/s390/block/dasd_devmap.c.
772 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
773 (one device per port)
774 Format: <port#>,<type>
775 See also Documentation/input/joystick-parport.txt
777 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
778 time. See Documentation/dynamic-debug-howto.txt for
779 details. Deprecated, see dyndbg.
781 debug [KNL] Enable kernel debugging (events log level).
784 [KNL] verbose self-tests
786 Print debugging info while doing the locking API
788 We default to 0 (no extra messages), setting it to
789 1 will print _a lot_ more information - normally
790 only useful to kernel developers.
792 debug_objects [KNL] Enable object debugging
795 [KNL] Disable object debugging
797 debug_guardpage_minorder=
798 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
799 parameter allows control of the order of pages that will
800 be intentionally kept free (and hence protected) by the
801 buddy allocator. Bigger value increase the probability
802 of catching random memory corruption, but reduce the
803 amount of memory for normal system use. The maximum
804 possible value is MAX_ORDER/2. Setting this parameter
805 to 1 or 2 should be enough to identify most random
806 memory corruption problems caused by bugs in kernel or
807 driver code when a CPU writes to (or reads from) a
808 random memory location. Note that there exists a class
809 of memory corruptions problems caused by buggy H/W or
810 F/W or by drivers badly programing DMA (basically when
811 memory is written at bus level and the CPU MMU is
812 bypassed) which are not detectable by
813 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
814 tracking down these problems.
816 debugpat [X86] Enable PAT debugging
818 decnet.addr= [HW,NET]
819 Format: <area>[,<node>]
820 See also Documentation/networking/decnet.txt.
823 [same as hugepagesz=] The size of the default
824 HugeTLB page size. This is the size represented by
825 the legacy /proc/ hugepages APIs, used for SHM, and
826 default size when mounting hugetlbfs filesystems.
827 Defaults to the default architecture's huge page size
831 Set number of hash buckets for dentry cache.
834 See Documentation/networking/ipv6.txt.
836 disable_cpu_apicid= [X86,APIC,SMP]
838 The number of initial APIC ID for the
839 corresponding CPU to be disabled at boot,
840 mostly used for the kdump 2nd kernel to
841 disable BSP to wake up multiple CPUs without
842 causing system reset or hang due to sending
845 disable_ddw [PPC/PSERIES]
846 Disable Dynamic DMA Window support. Use this if
847 to workaround buggy firmware.
850 See Documentation/networking/ipv6.txt.
852 disable_mtrr_cleanup [X86]
853 The kernel tries to adjust MTRR layout from continuous
854 to discrete, to make X server driver able to add WB
855 entry later. This parameter disables that.
857 disable_mtrr_trim [X86, Intel and AMD only]
858 By default the kernel will trim any uncacheable
859 memory out of your available memory pool based on
860 MTRR settings. This parameter disables that behavior,
861 possibly causing your machine to run very slowly.
863 disable_timer_pin_1 [X86]
864 Disable PIN 1 of APIC timer
865 Can be useful to work around chipset bugs.
867 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
868 this option disables the debugging code at boot.
870 dma_debug_entries=<number>
871 This option allows to tune the number of preallocated
872 entries for DMA-API debugging code. One entry is
873 required per DMA-API allocation. Use this if the
874 DMA-API debugging code disables itself because the
875 architectural default is too low.
877 dma_debug_driver=<driver_name>
878 With this option the DMA-API debugging driver
879 filter feature can be enabled at boot time. Just
880 pass the driver to filter for as the parameter.
881 The filter can be disabled or changed to another
882 driver later using sysfs.
884 drm_kms_helper.edid_firmware=[<connector>:]<file>
885 Broken monitors, graphic adapters and KVMs may
886 send no or incorrect EDID data sets. This parameter
887 allows to specify an EDID data set in the
888 /lib/firmware directory that is used instead.
889 Generic built-in EDID data sets are used, if one of
890 edid/1024x768.bin, edid/1280x1024.bin,
891 edid/1680x1050.bin, or edid/1920x1080.bin is given
892 and no file with the same name exists. Details and
893 instructions how to build your own EDID data are
894 available in Documentation/EDID/HOWTO.txt. An EDID
895 data set will only be used for a particular connector,
896 if its name and a colon are prepended to the EDID
901 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
902 module.dyndbg[="val"]
903 Enable debug messages at boot time. See
904 Documentation/dynamic-debug-howto.txt for details.
906 early_ioremap_debug [KNL]
907 Enable debug messages in early_ioremap support. This
908 is useful for tracking down temporary early mappings
909 which are not unmapped.
911 earlycon= [KNL] Output early console device and options.
913 uart[8250],io,<addr>[,options]
914 uart[8250],mmio,<addr>[,options]
915 uart[8250],mmio32,<addr>[,options]
916 Start an early, polled-mode console on the 8250/16550
917 UART at the specified I/O port or MMIO address.
918 MMIO inter-register address stride is either 8-bit
919 (mmio) or 32-bit (mmio32).
920 The options are the same as for ttyS, above.
923 Start an early, polled-mode console on a pl011 serial
924 port at the specified address. The pl011 serial port
925 must already be setup and configured. Options are not
928 smh Use ARM semihosting calls for early console.
930 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
934 earlyprintk=serial[,ttySn[,baudrate]]
935 earlyprintk=serial[,0x...[,baudrate]]
936 earlyprintk=ttySn[,baudrate]
937 earlyprintk=dbgp[debugController#]
939 earlyprintk is useful when the kernel crashes before
940 the normal console is initialized. It is not enabled by
941 default because it has some cosmetic problems.
943 Append ",keep" to not disable it when the real console
946 Only one of vga, efi, serial, or usb debug port can
949 Currently only ttyS0 and ttyS1 may be specified by
950 name. Other I/O ports may be explicitly specified
951 on some architectures (x86 and arm at least) by
952 replacing ttySn with an I/O port address, like this:
953 earlyprintk=serial,0x1008,115200
954 You can find the port for a given device in
955 /proc/tty/driver/serial:
956 2: uart:ST16650V2 port:00001008 irq:18 ...
958 Interaction with the standard serial driver is not
961 The VGA and EFI output is eventually overwritten by
964 The xen output can only be used by Xen PV guests.
966 edac_report= [HW,EDAC] Control how to report EDAC event
967 Format: {"on" | "off" | "force"}
968 on: enable EDAC to report H/W event. May be overridden
969 by other higher priority error reporting module.
970 off: disable H/W event reporting through EDAC.
971 force: enforce the use of EDAC to report H/W event.
974 ekgdboc= [X86,KGDB] Allow early kernel console debugging
977 This is designed to be used in conjunction with
978 the boot argument: earlyprintk=vga
981 Format: {"off" | "on" | "skip[mbr]"}
984 Format: { "old_map" }
985 old_map [X86-64]: switch to the old ioremap-based EFI
986 runtime services mapping. 32-bit still uses this one by
989 efi_no_storage_paranoia [EFI; X86]
990 Using this parameter you can use more than 50% of
991 your efi variable storage. Use this parameter only if
992 you are really sure that your UEFI does sane gc and
993 fulfills the spec otherwise your board may brick.
995 eisa_irq_edge= [PARISC,HW]
996 See header of drivers/parisc/eisa.c.
999 See comment before function elanfreq_setup() in
1000 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1003 Format: {"cfq" | "deadline" | "noop"}
1004 See Documentation/block/cfq-iosched.txt and
1005 Documentation/block/deadline-iosched.txt for details.
1007 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1008 Specifies physical address of start of kernel core
1009 image elf header and optionally the size. Generally
1010 kexec loader will pass this option to capture kernel.
1011 See Documentation/kdump/kdump.txt for details.
1013 enable_mtrr_cleanup [X86]
1014 The kernel tries to adjust MTRR layout from continuous
1015 to discrete, to make X server driver able to add WB
1016 entry later. This parameter enables that.
1018 enable_timer_pin_1 [X86]
1019 Enable PIN 1 of APIC timer
1020 Can be useful to work around chipset bugs
1021 (in particular on some ATI chipsets).
1022 The kernel tries to set a reasonable default.
1024 enforcing [SELINUX] Set initial enforcing status.
1026 See security/selinux/Kconfig help text.
1027 0 -- permissive (log only, no denials).
1028 1 -- enforcing (deny and log).
1030 Value can be changed at runtime via /selinux/enforce.
1033 Disable Error Record Serialization Table (ERST)
1036 ether= [HW,NET] Ethernet cards parameters
1037 This option is obsoleted by the "netdev=" option, which
1038 has equivalent usage. See its documentation for details.
1042 Permit 'security.evm' to be updated regardless of
1043 current integrity status.
1047 fail_make_request=[KNL]
1048 General fault injection mechanism.
1049 Format: <interval>,<probability>,<space>,<times>
1050 See also Documentation/fault-injection/.
1053 See Documentation/blockdev/floppy.txt.
1055 force_pal_cache_flush
1056 [IA-64] Avoid check_sal_cache_flush which may hang on
1057 buggy SAL_CACHE_FLUSH implementations. Using this
1058 parameter will force ia64_sal_cache_flush to call
1059 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1062 Forcefully enable Physical Address Extension (PAE).
1063 Many Pentium M systems disable PAE but may have a
1064 functionally usable PAE implementation.
1065 Warning: use of this parameter will taint the kernel
1066 and may cause unknown problems.
1069 [FTRACE] will set and start the specified tracer
1070 as early as possible in order to facilitate early
1073 ftrace_dump_on_oops[=orig_cpu]
1074 [FTRACE] will dump the trace buffers on oops.
1075 If no parameter is passed, ftrace will dump
1076 buffers of all CPUs, but if you pass orig_cpu, it will
1077 dump only the buffer of the CPU that triggered the
1080 ftrace_filter=[function-list]
1081 [FTRACE] Limit the functions traced by the function
1082 tracer at boot up. function-list is a comma separated
1083 list of functions. This list can be changed at run
1084 time by the set_ftrace_filter file in the debugfs
1087 ftrace_notrace=[function-list]
1088 [FTRACE] Do not trace the functions specified in
1089 function-list. This list can be changed at run time
1090 by the set_ftrace_notrace file in the debugfs
1093 ftrace_graph_filter=[function-list]
1094 [FTRACE] Limit the top level callers functions traced
1095 by the function graph tracer at boot up.
1096 function-list is a comma separated list of functions
1097 that can be changed at run time by the
1098 set_graph_function file in the debugfs tracing directory.
1101 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1102 support via parallel port (up to 5 devices per port)
1103 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1104 See also Documentation/input/joystick-parport.txt
1108 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1112 gcov_persist= [GCOV] When non-zero (default), profiling data for
1113 kernel modules is saved and remains accessible via
1114 debugfs, even when the module is unloaded/reloaded.
1115 When zero, profiling data is discarded and associated
1116 debugfs files are removed at module unload time.
1118 gpt [EFI] Forces disk with valid GPT signature but
1119 invalid Protective MBR to be treated as GPT. If the
1120 primary GPT is corrupted, it enables the backup/alternate
1121 GPT to be used instead.
1123 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1124 the "Enable 0" bit of the configuration register.
1127 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1128 the "Enable 0" bit of the configuration register.
1131 grcan.select= [HW] Select which physical interface to use.
1134 grcan.txsize= [HW] Sets the size of the tx buffer.
1135 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1137 grcan.rxsize= [HW] Sets the size of the rx buffer.
1138 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1141 hashdist= [KNL,NUMA] Large hashes allocated during boot
1142 are distributed across NUMA nodes. Defaults on
1143 for 64-bit NUMA, off otherwise.
1144 Format: 0 | 1 (for off | on)
1146 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1148 hd= [EIDE] (E)IDE hard drive subsystem geometry
1149 Format: <cyl>,<head>,<sect>
1152 Disable Hardware Error Source Table (HEST) support;
1153 corresponding firmware-first mode error processing
1154 logic will be disabled.
1156 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1157 size of <nn>. This works even on boxes that have no
1158 highmem otherwise. This also works to reduce highmem
1159 size on bigger boxes.
1161 highres= [KNL] Enable/disable high resolution timer mode.
1162 Valid parameters: "on", "off"
1166 See Documentation/isdn/README.HiSax.
1170 hpet= [X86-32,HPET] option to control HPET usage
1171 Format: { enable (default) | disable | force |
1173 disable: disable HPET and use PIT instead
1174 force: allow force enabled of undocumented chips (ICH4,
1176 verbose: show contents of HPET registers during setup
1178 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1179 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1181 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1182 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1183 On x86-64 and powerpc, this option can be specified
1184 multiple times interleaved with hugepages= to reserve
1185 huge pages of different sizes. Valid pages sizes on
1186 x86-64 are 2M (when the CPU supports "pse") and 1G
1187 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1188 Note that 1GB pages can only be allocated at boot time
1189 using hugepages= and not freed afterwards.
1191 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1192 terminal devices. Valid values: 0..8
1193 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1194 If specified, z/VM IUCV HVC accepts connections
1195 from listed z/VM user IDs only.
1197 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1198 hardware thread id mappings.
1199 Format: <cpu>:<hwthread>
1202 Do not unregister boot console at start. This is only
1203 useful for debugging when something happens in the window
1204 between unregistering the boot console and initializing
1207 i2c_bus= [HW] Override the default board specific I2C bus speed
1208 or register an additional I2C bus that is not
1209 registered from board initialization code.
1213 i8042.debug [HW] Toggle i8042 debug mode
1214 i8042.direct [HW] Put keyboard port into non-translated mode
1215 i8042.dumbkbd [HW] Pretend that controller can only read data from
1216 keyboard and cannot control its state
1217 (Don't attempt to blink the leds)
1218 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1219 i8042.nokbd [HW] Don't check/create keyboard port
1220 i8042.noloop [HW] Disable the AUX Loopback command while probing
1222 i8042.nomux [HW] Don't check presence of an active multiplexing
1224 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1226 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1227 i8042.reset [HW] Reset the controller during init and cleanup
1228 i8042.unlock [HW] Unlock (ignore) the keylock
1232 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1233 indicates that the driver is running on unsupported
1235 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1236 does not match list of supported models.
1238 [HW] Report power status in /proc/i8k
1239 (disabled by default)
1240 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1243 i915.invert_brightness=
1244 [DRM] Invert the sense of the variable that is used to
1245 set the brightness of the panel backlight. Normally a
1246 brightness value of 0 indicates backlight switched off,
1247 and the maximum of the brightness value sets the backlight
1248 to maximum brightness. If this parameter is set to 0
1249 (default) and the machine requires it, or this parameter
1250 is set to 1, a brightness value of 0 sets the backlight
1251 to maximum brightness, and the maximum of the brightness
1252 value switches the backlight off.
1253 -1 -- never invert brightness
1254 0 -- machine default
1255 1 -- force brightness inversion
1258 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1260 ide-core.nodma= [HW] (E)IDE subsystem
1261 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1262 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1263 .cdrom .chs .ignore_cable are additional options
1264 See Documentation/ide/ide.txt.
1266 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1267 Claim all unknown PCI IDE storage controllers.
1270 Format: idle=poll, idle=halt, idle=nomwait
1271 Poll forces a polling idle loop that can slightly
1272 improve the performance of waking up a idle CPU, but
1273 will use a lot of power and make the system run hot.
1275 idle=halt: Halt is forced to be used for CPU idle.
1276 In such case C2/C3 won't be used again.
1277 idle=nomwait: Disable mwait for CPU C-states
1279 ignore_loglevel [KNL]
1280 Ignore loglevel setting - this will print /all/
1281 kernel messages to the console. Useful for debugging.
1282 We also add it as printk module parameter, so users
1283 could change it dynamically, usually by
1284 /sys/module/printk/parameters/ignore_loglevel.
1286 ihash_entries= [KNL]
1287 Set number of hash buckets for inode cache.
1289 ima_appraise= [IMA] appraise integrity measurements
1290 Format: { "off" | "enforce" | "fix" }
1293 ima_appraise_tcb [IMA]
1294 The builtin appraise policy appraises all files
1298 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1302 The list of supported hash algorithms is defined
1303 in crypto/hash_info.h.
1306 Load a policy which meets the needs of the Trusted
1307 Computing Base. This means IMA will measure all
1308 programs exec'd, files mmap'd for exec, and all files
1309 opened for read by uid=0.
1312 Select one of defined IMA measurements template formats.
1313 Formats: { "ima" | "ima-ng" }
1318 Run specified binary instead of /sbin/init as init
1321 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1322 for working out where the kernel is dying during
1325 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1326 initcall functions. Useful for debugging built-in
1327 modules and initcalls.
1329 initrd= [BOOT] Specify the location of the initial ramdisk
1331 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1334 int_pln_enable [x86] Enable power limit notification interrupt
1336 integrity_audit=[IMA]
1337 Format: { "0" | "1" }
1338 0 -- basic integrity auditing messages. (Default)
1339 1 -- additional integrity auditing messages.
1341 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1343 Enable intel iommu driver.
1345 Disable intel iommu driver.
1346 igfx_off [Default Off]
1347 By default, gfx is mapped as normal device. If a gfx
1348 device has a dedicated DMAR unit, the DMAR unit is
1349 bypassed by not enabling DMAR with this option. In
1350 this case, gfx device will use physical address for
1353 With this option iommu will not optimize to look
1354 for io virtual address below 32-bit forcing dual
1355 address cycle on pci bus for cards supporting greater
1356 than 32-bit addressing. The default is to look
1357 for translation below 32-bit and if not available
1358 then look in the higher range.
1359 strict [Default Off]
1360 With this option on every unmap_single operation will
1361 result in a hardware IOTLB flush operation as opposed
1362 to batching them for performance.
1363 sp_off [Default Off]
1364 By default, super page will be supported if Intel IOMMU
1365 has the capability. With this option, super page will
1368 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1369 0 disables intel_idle and fall back on acpi_idle.
1370 1 to 6 specify maximum depth of C-state.
1374 Do not enable intel_pstate as the default
1375 scaling driver for the supported processors
1377 intremap= [X86-64, Intel-IOMMU]
1378 on enable Interrupt Remapping (default)
1379 off disable Interrupt Remapping
1380 nosid disable Source ID checking
1382 BIOS x2APIC opt-out request will be ignored
1384 iomem= Disable strict checking of access to MMIO memory
1385 strict regions from userspace.
1402 io7= [HW] IO7 for Marvel based alpha systems
1403 See comment before marvel_specify_io7 in
1404 arch/alpha/kernel/core_marvel.c.
1406 io_delay= [X86] I/O delay method
1408 Standard port 0x80 based delay
1410 Alternate port 0xed based delay (needed on some systems)
1412 Simple two microseconds delay
1417 See Documentation/filesystems/nfs/nfsroot.txt.
1420 When an interrupt is not handled search all handlers
1421 for it. Intended to get systems with badly broken
1425 When an interrupt is not handled search all handlers
1426 for it. Also check all handlers each timer
1427 interrupt. Intended to get systems with badly broken
1431 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1433 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1435 <cpu number>,...,<cpu number>
1437 <cpu number>-<cpu number>
1438 (must be a positive range in ascending order)
1440 <cpu number>,...,<cpu number>-<cpu number>
1442 This option can be used to specify one or more CPUs
1443 to isolate from the general SMP balancing and scheduling
1444 algorithms. You can move a process onto or off an
1445 "isolated" CPU via the CPU affinity syscalls or cpuset.
1446 <cpu number> begins at 0 and the maximum value is
1447 "number of CPUs in system - 1".
1449 This option is the preferred way to isolate CPUs. The
1450 alternative -- manually setting the CPU mask of all
1451 tasks in the system -- can cause problems and
1452 suboptimal load balancer performance.
1456 ivrs_ioapic [HW,X86_64]
1457 Provide an override to the IOAPIC-ID<->DEVICE-ID
1458 mapping provided in the IVRS ACPI table. For
1459 example, to map IOAPIC-ID decimal 10 to
1460 PCI device 00:14.0 write the parameter as:
1461 ivrs_ioapic[10]=00:14.0
1463 ivrs_hpet [HW,X86_64]
1464 Provide an override to the HPET-ID<->DEVICE-ID
1465 mapping provided in the IVRS ACPI table. For
1466 example, to map HPET-ID decimal 0 to
1467 PCI device 00:14.0 write the parameter as:
1468 ivrs_hpet[0]=00:14.0
1470 js= [HW,JOY] Analog joystick
1471 See Documentation/input/joystick.txt.
1474 Enable/disable kernel and module base offset ASLR
1475 (Address Space Layout Randomization) if built into
1476 the kernel. When CONFIG_HIBERNATION is selected,
1477 kASLR is disabled by default. When kASLR is enabled,
1478 hibernation will be disabled.
1482 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1483 specifies the amount of memory usable by the kernel
1484 for non-movable allocations. The requested amount is
1485 spread evenly throughout all nodes in the system. The
1486 remaining memory in each node is used for Movable
1487 pages. In the event, a node is too small to have both
1488 kernelcore and Movable pages, kernelcore pages will
1489 take priority and other nodes will have a larger number
1490 of Movable pages. The Movable zone is used for the
1491 allocation of pages that may be reclaimed or moved
1492 by the page migration subsystem. This means that
1493 HugeTLB pages may not be allocated from this zone.
1494 Note that allocations like PTEs-from-HighMem still
1495 use the HighMem zone if it exists, and the Normal
1496 zone if it does not.
1498 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1499 Format: <Controller#>[,poll interval]
1500 The controller # is the number of the ehci usb debug
1501 port as it is probed via PCI. The poll interval is
1502 optional and is the number seconds in between
1503 each poll cycle to the debug port in case you need
1504 the functionality for interrupting the kernel with
1505 gdb or control-c on the dbgp connection. When
1506 not using this parameter you use sysrq-g to break into
1507 the kernel debugger.
1509 kgdboc= [KGDB,HW] kgdb over consoles.
1510 Requires a tty driver that supports console polling,
1511 or a supported polling keyboard driver (non-usb).
1512 Serial only format: <serial_device>[,baud]
1513 keyboard only format: kbd
1514 keyboard and serial format: kbd,<serial_device>[,baud]
1515 Optional Kernel mode setting:
1516 kms, kbd format: kms,kbd
1517 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1519 kgdbwait [KGDB] Stop kernel execution and enter the
1520 kernel debugger at the earliest opportunity.
1522 kmac= [MIPS] korina ethernet MAC address.
1523 Configure the RouterBoard 532 series on-chip
1524 Ethernet adapter MAC address.
1526 kmemleak= [KNL] Boot-time kmemleak enable/disable
1527 Valid arguments: on, off
1530 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1531 Valid arguments: 0, 1, 2
1532 kmemcheck=0 (disabled)
1533 kmemcheck=1 (enabled)
1534 kmemcheck=2 (one-shot mode)
1535 Default: 2 (one-shot mode)
1537 kstack=N [X86] Print N words from the kernel stack
1540 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1541 Default is 0 (don't ignore, but inject #GP)
1543 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1547 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1548 Default is 1 (enabled)
1550 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1552 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1554 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1555 (virtualized MMU) support on capable Intel chips.
1556 Default is 1 (enabled)
1558 kvm-intel.emulate_invalid_guest_state=
1559 [KVM,Intel] Enable emulation of invalid guest states
1560 Default is 0 (disabled)
1562 kvm-intel.flexpriority=
1563 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1564 Default is 1 (enabled)
1567 [KVM,Intel] Enable VMX nesting (nVMX).
1568 Default is 0 (disabled)
1570 kvm-intel.unrestricted_guest=
1571 [KVM,Intel] Disable unrestricted guest feature
1572 (virtualized real and unpaged mode) on capable
1573 Intel chips. Default is 1 (enabled)
1575 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1576 feature (tagged TLBs) on capable Intel chips.
1577 Default is 1 (enabled)
1583 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1586 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1587 value for LAPIC timer one-shot implementation. Default
1588 back to the programmable timer unit in the LAPIC.
1590 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1593 libata.dma= [LIBATA] DMA control
1594 libata.dma=0 Disable all PATA and SATA DMA
1595 libata.dma=1 PATA and SATA Disk DMA only
1596 libata.dma=2 ATAPI (CDROM) DMA only
1597 libata.dma=4 Compact Flash DMA only
1598 Combinations also work, so libata.dma=3 enables DMA
1599 for disks and CDROMs, but not CFs.
1601 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1602 libata.ignore_hpa=0 keep BIOS limits (default)
1603 libata.ignore_hpa=1 ignore limits, using full disk
1605 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1609 libata.force= [LIBATA] Force configurations. The format is comma
1610 separated list of "[ID:]VAL" where ID is
1611 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1612 matching port, link or device. Basically, it matches
1613 the ATA ID string printed on console by libata. If
1614 the whole ID part is omitted, the last PORT and DEVICE
1615 values are used. If ID hasn't been specified yet, the
1616 configuration applies to all ports, links and devices.
1618 If only DEVICE is omitted, the parameter applies to
1619 the port and all links and devices behind it. DEVICE
1620 number of 0 either selects the first device or the
1621 first fan-out link behind PMP device. It does not
1622 select the host link. DEVICE number of 15 selects the
1623 host link and device attached to it.
1625 The VAL specifies the configuration to force. As long
1626 as there's no ambiguity shortcut notation is allowed.
1627 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1628 The following configurations can be forced.
1630 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1631 Any ID with matching PORT is used.
1633 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1635 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1636 udma[/][16,25,33,44,66,100,133] notation is also
1639 * [no]ncq: Turn on or off NCQ.
1641 * nohrst, nosrst, norst: suppress hard, soft
1644 * rstonce: only attempt one reset during
1645 hot-unplug link recovery
1647 * dump_id: dump IDENTIFY data.
1649 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1651 * disable: Disable this device.
1653 If there are multiple matching configurations changing
1654 the same attribute, the last one is used.
1656 memblock=debug [KNL] Enable memblock debug messages.
1658 load_ramdisk= [RAM] List of ramdisks to load from floppy
1659 See Documentation/blockdev/ramdisk.txt.
1661 lockd.nlm_grace_period=P [NFS] Assign grace period.
1664 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1667 lockd.nlm_timeout=T [NFS] Assign timeout value.
1670 lockd.nlm_udpport=M [NFS] Assign UDP port.
1673 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1676 loglevel= All Kernel Messages with a loglevel smaller than the
1677 console loglevel will be printed to the console. It can
1678 also be changed with klogd or other programs. The
1679 loglevels are defined as follows:
1681 0 (KERN_EMERG) system is unusable
1682 1 (KERN_ALERT) action must be taken immediately
1683 2 (KERN_CRIT) critical conditions
1684 3 (KERN_ERR) error conditions
1685 4 (KERN_WARNING) warning conditions
1686 5 (KERN_NOTICE) normal but significant condition
1687 6 (KERN_INFO) informational
1688 7 (KERN_DEBUG) debug-level messages
1690 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1691 in bytes. n must be a power of two. The default
1692 size is set in the kernel config file.
1694 logo.nologo [FB] Disables display of the built-in Linux logo.
1695 This may be used to provide more screen space for
1696 kernel log messages and is useful when debugging
1697 kernel boot problems.
1699 lp=0 [LP] Specify parallel ports to use, e.g,
1700 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1701 lp=reset first parallel port). 'lp=0' disables the
1702 lp=auto printer driver. 'lp=reset' (which can be
1703 specified in addition to the ports) causes
1704 attached printers to be reset. Using
1705 lp=port1,port2,... specifies the parallel ports
1706 to associate lp devices with, starting with
1707 lp0. A port specification may be 'none' to skip
1708 that lp device, or a parport name such as
1709 'parport0'. Specifying 'lp=auto' instead of a
1710 port specification list means that device IDs
1711 from each port should be examined, to see if
1712 an IEEE 1284-compliant printer is attached; if
1713 so, the driver will manage that printer.
1714 See also header of drivers/char/lp.c.
1717 Sets loops_per_jiffy to given constant, thus avoiding
1718 time-consuming boot-time autodetection (up to 250 ms per
1719 CPU). 0 enables autodetection (default). To determine
1720 the correct value for your kernel, boot with normal
1721 autodetection and see what value is printed. Note that
1722 on SMP systems the preset will be applied to all CPUs,
1723 which is likely to cause problems if your CPUs need
1724 significantly divergent settings. An incorrect value
1725 will cause delays in the kernel to be wrong, leading to
1726 unpredictable I/O errors and other breakage. Although
1727 unlikely, in the extreme case this might damage your
1731 Format: <io>,<irq>,<dma>
1733 machvec= [IA-64] Force the use of a particular machine-vector
1734 (machvec) in a generic kernel.
1735 Example: machvec=hpzx1_swiotlb
1737 machtype= [Loongson] Share the same kernel image file between different
1739 Example: machtype=lemote-yeeloong-2f-7inch
1741 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1742 than or equal to this physical address is ignored.
1744 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1745 should make use of. maxcpus=n : n >= 0 limits the
1746 kernel to using 'n' processors. n=0 is a special case,
1747 it is equivalent to "nosmp", which also disables
1750 max_loop= [LOOP] The number of loop block devices that get
1751 (loop.max_loop) unconditionally pre-created at init time. The default
1752 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1753 of statically allocating a predefined number, loop
1754 devices can be requested on-demand with the
1755 /dev/loop-control interface.
1757 mce [X86-32] Machine Check Exception
1759 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1761 md= [HW] RAID subsystems devices and level
1762 See Documentation/md.txt.
1765 Format: <first>,<last>
1766 Specifies range of consoles to be captured by the MDA.
1768 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1769 Amount of memory to be used when the kernel is not able
1770 to see the whole system memory or for test.
1771 [X86] Work as limiting max address. Use together
1772 with memmap= to avoid physical address space collisions.
1773 Without memmap= PCI devices could be placed at addresses
1774 belonging to unused RAM.
1776 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1780 [KNL,SH] Allow user to override the default size for
1781 per-device physically contiguous DMA buffers.
1783 memmap=exactmap [KNL,X86] Enable setting of an exact
1784 E820 memory map, as specified by the user.
1785 Such memmap=exactmap lines can be constructed based on
1786 BIOS output or other requirements. See the memmap=nn@ss
1789 memmap=nn[KMG]@ss[KMG]
1790 [KNL] Force usage of a specific region of memory.
1791 Region of memory to be used is from ss to ss+nn.
1793 memmap=nn[KMG]#ss[KMG]
1794 [KNL,ACPI] Mark specific memory as ACPI data.
1795 Region of memory to be marked is from ss to ss+nn.
1797 memmap=nn[KMG]$ss[KMG]
1798 [KNL,ACPI] Mark specific memory as reserved.
1799 Region of memory to be reserved is from ss to ss+nn.
1800 Example: Exclude memory from 0x18690000-0x1869ffff
1801 memmap=64K$0x18690000
1803 memmap=0x10000$0x18690000
1805 memory_corruption_check=0/1 [X86]
1806 Some BIOSes seem to corrupt the first 64k of
1807 memory when doing things like suspend/resume.
1808 Setting this option will scan the memory
1809 looking for corruption. Enabling this will
1810 both detect corruption and prevent the kernel
1811 from using the memory being corrupted.
1812 However, its intended as a diagnostic tool; if
1813 repeatable BIOS-originated corruption always
1814 affects the same memory, you can use memmap=
1815 to prevent the kernel from using that memory.
1817 memory_corruption_check_size=size [X86]
1818 By default it checks for corruption in the low
1819 64k, making this memory unavailable for normal
1820 use. Use this parameter to scan for
1821 corruption in more or less memory.
1823 memory_corruption_check_period=seconds [X86]
1824 By default it checks for corruption every 60
1825 seconds. Use this parameter to check at some
1826 other rate. 0 disables periodic checking.
1828 memtest= [KNL,X86] Enable memtest
1830 default : 0 <disable>
1831 Specifies the number of memtest passes to be
1832 performed. Each pass selects another test
1833 pattern from a given set of patterns. Memtest
1834 fills the memory with this pattern, validates
1835 memory contents and reserves bad memory
1836 regions that are detected.
1838 meye.*= [HW] Set MotionEye Camera parameters
1839 See Documentation/video4linux/meye.txt.
1841 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1842 Multi-Function General Purpose Timers on AMD Geode
1845 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1846 the BIOS has incorrectly applied a workaround. TinyBIOS
1847 version 0.98 is known to be affected, 0.99 fixes the
1848 problem by letting the user disable the workaround.
1852 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1853 physical address is ignored.
1855 mini2440= [ARM,HW,KNL]
1856 Format:[0..2][b][c][t]
1858 MINI2440 configuration specification:
1859 0 - The attached screen is the 3.5" TFT
1860 1 - The attached screen is the 7" TFT
1861 2 - The VGA Shield is attached (1024x768)
1862 Leaving out the screen size parameter will not load
1863 the TFT driver, and the framebuffer will be left
1865 b - Enable backlight. The TFT backlight pin will be
1866 linked to the kernel VESA blanking code and a GPIO
1867 LED. This parameter is not necessary when using the
1869 c - Enable the s3c camera interface.
1870 t - Reserved for enabling touchscreen support. The
1871 touchscreen support is not enabled in the mainstream
1872 kernel as of 2.6.30, a preliminary port can be found
1873 in the "bleeding edge" mini2440 support kernel at
1874 http://repo.or.cz/w/linux-2.6/mini2440.git
1877 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1878 parameter allows control of the logging verbosity for
1879 the additional memory initialisation checks. A value
1880 of 0 disables mminit logging and a level of 4 will
1881 log everything. Information is printed at KERN_DEBUG
1882 so loglevel=8 may also need to be specified.
1885 [KNL] When CONFIG_MODULE_SIG is set, this means that
1886 modules without (valid) signatures will fail to load.
1887 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1888 is always true, so this option does nothing.
1891 [MOUSE] Maximum time between finger touching and
1892 leaving touchpad surface for touch to be considered
1893 a tap and be reported as a left button click (for
1894 touchpads working in absolute mode only).
1896 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1897 reporting absolute coordinates, such as tablets
1898 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1899 reporting absolute coordinates, such as tablets
1901 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1902 is similar to kernelcore except it specifies the
1903 amount of memory used for migratable allocations.
1904 If both kernelcore and movablecore is specified,
1905 then kernelcore will be at *least* the specified
1906 value but may be more. If movablecore on its own
1907 is specified, the administrator must be careful
1908 that the amount of memory usable for all allocations
1911 movable_node [KNL,X86] Boot-time switch to enable the effects
1912 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1914 MTD_Partition= [MTD]
1915 Format: <name>,<region-number>,<size>,<offset>
1917 MTD_Region= [MTD] Format:
1918 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1921 See drivers/mtd/cmdlinepart.c.
1923 multitce=off [PPC] This parameter disables the use of the pSeries
1924 firmware feature for updating multiple TCE entries
1927 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1929 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1931 boundary - index of last SLC block on Flex-OneNAND.
1932 The remaining blocks are configured as MLC blocks.
1933 lock - Configure if Flex-OneNAND boundary should be locked.
1934 Once locked, the boundary cannot be changed.
1935 1 indicates lock status, 0 indicates unlock status.
1938 ARM/S3C2412 JIVE boot control
1940 See arch/arm/mach-s3c2412/mach-jive.c
1942 mtouchusb.raw_coordinates=
1943 [HW] Make the MicroTouch USB driver use raw coordinates
1944 ('y', default) or cooked coordinates ('n')
1946 mtrr_chunk_size=nn[KMG] [X86]
1947 used for mtrr cleanup. It is largest continuous chunk
1948 that could hold holes aka. UC entries.
1950 mtrr_gran_size=nn[KMG] [X86]
1951 Used for mtrr cleanup. It is granularity of mtrr block.
1953 Large value could prevent small alignment from
1956 mtrr_spare_reg_nr=n [X86]
1958 Range: 0,7 : spare reg number
1960 Used for mtrr cleanup. It is spare mtrr entries number.
1961 Set to 2 or more if your graphical card needs more.
1963 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1965 netdev= [NET] Network devices parameters
1966 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1967 Note that mem_start is often overloaded to mean
1968 something different and driver-specific.
1969 This usage is only documented in each driver source
1973 [NETFILTER] Enable connection tracking flow accounting
1974 0 to disable accounting
1975 1 to enable accounting
1978 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1979 See Documentation/filesystems/nfs/nfsroot.txt.
1981 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1982 See Documentation/filesystems/nfs/nfsroot.txt.
1984 nfsrootdebug [NFS] enable nfsroot debugging messages.
1985 See Documentation/filesystems/nfs/nfsroot.txt.
1987 nfs.callback_tcpport=
1988 [NFS] set the TCP port on which the NFSv4 callback
1989 channel should listen.
1992 [NFS] sets the pathname to the program which is used
1993 to update the NFS client cache entries.
1995 nfs.cache_getent_timeout=
1996 [NFS] sets the timeout after which an attempt to
1997 update a cache entry is deemed to have failed.
1999 nfs.idmap_cache_timeout=
2000 [NFS] set the maximum lifetime for idmapper cache
2004 [NFS] enable 64-bit inode numbers.
2005 If zero, the NFS client will fake up a 32-bit inode
2006 number for the readdir() and stat() syscalls instead
2007 of returning the full 64-bit number.
2008 The default is to return 64-bit inode numbers.
2010 nfs.max_session_slots=
2011 [NFSv4.1] Sets the maximum number of session slots
2012 the client will attempt to negotiate with the server.
2013 This limits the number of simultaneous RPC requests
2014 that the client can send to the NFSv4.1 server.
2015 Note that there is little point in setting this
2016 value higher than the max_tcp_slot_table_limit.
2018 nfs.nfs4_disable_idmapping=
2019 [NFSv4] When set to the default of '1', this option
2020 ensures that both the RPC level authentication
2021 scheme and the NFS level operations agree to use
2022 numeric uids/gids if the mount is using the
2023 'sec=sys' security flavour. In effect it is
2024 disabling idmapping, which can make migration from
2025 legacy NFSv2/v3 systems to NFSv4 easier.
2026 Servers that do not support this mode of operation
2027 will be autodetected by the client, and it will fall
2028 back to using the idmapper.
2029 To turn off this behaviour, set the value to '0'.
2031 [NFS4] Specify an additional fixed unique ident-
2032 ification string that NFSv4 clients can insert into
2033 their nfs_client_id4 string. This is typically a
2034 UUID that is generated at system install time.
2036 nfs.send_implementation_id =
2037 [NFSv4.1] Send client implementation identification
2038 information in exchange_id requests.
2039 If zero, no implementation identification information
2041 The default is to send the implementation identification
2044 nfs.recover_lost_locks =
2045 [NFSv4] Attempt to recover locks that were lost due
2046 to a lease timeout on the server. Please note that
2047 doing this risks data corruption, since there are
2048 no guarantees that the file will remain unchanged
2049 after the locks are lost.
2050 If you want to enable the kernel legacy behaviour of
2051 attempting to recover these locks, then set this
2053 The default parameter value of '0' causes the kernel
2054 not to attempt recovery of lost locks.
2056 nfsd.nfs4_disable_idmapping=
2057 [NFSv4] When set to the default of '1', the NFSv4
2058 server will return only numeric uids and gids to
2059 clients using auth_sys, and will accept numeric uids
2060 and gids from such clients. This is intended to ease
2061 migration from NFSv2/v3.
2063 objlayoutdriver.osd_login_prog=
2064 [NFS] [OBJLAYOUT] sets the pathname to the program which
2065 is used to automatically discover and login into new
2066 osd-targets. Please see:
2067 Documentation/filesystems/pnfs.txt for more explanations
2069 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2070 when a NMI is triggered.
2071 Format: [state][,regs][,debounce][,die]
2073 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2074 Format: [panic,][nopanic,][num]
2076 0 - turn nmi_watchdog off
2077 When panic is specified, panic when an NMI watchdog
2078 timeout occurs (or 'nopanic' to override the opposite
2080 This is useful when you use a panic=... timeout and
2081 need the box quickly up again.
2083 netpoll.carrier_timeout=
2084 [NET] Specifies amount of time (in seconds) that
2085 netpoll should wait for a carrier. By default netpoll
2088 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2089 emulation library even if a 387 maths coprocessor
2093 [HW] Never suspend the console
2094 Disable suspending of consoles during suspend and
2095 hibernate operations. Once disabled, debugging
2096 messages can reach various consoles while the rest
2097 of the system is being put to sleep (ie, while
2098 debugging driver suspend/resume hooks). This may
2099 not work reliably with all consoles, but is known
2100 to work with serial and VGA consoles.
2101 To facilitate more flexible debugging, we also add
2102 console_suspend, a printk module parameter to control
2103 it. Users could use console_suspend (usually
2104 /sys/module/printk/parameters/console_suspend) to
2105 turn on/off it dynamically.
2107 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2108 caches in the slab allocator. Saves per-node memory,
2109 but will impact performance.
2113 noapic [SMP,APIC] Tells the kernel to not make use of any
2114 IOAPICs that may be present in the system.
2116 noautogroup Disable scheduler automatic task group creation.
2118 nobats [PPC] Do not use BATs for mapping kernel lowmem
2119 on "Classic" PPC cores.
2123 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2125 nodelayacct [KNL] Disable per-task delay accounting
2127 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2129 nodsp [SH] Disable hardware DSP at boot time.
2131 noefi [X86] Disable EFI runtime services support.
2136 On X86-32 available only on PAE configured kernels.
2137 noexec=on: enable non-executable mappings (default)
2138 noexec=off: disable non-executable mappings
2141 Disable SMAP (Supervisor Mode Access Prevention)
2142 even if it is supported by processor.
2145 Disable SMEP (Supervisor Mode Execution Prevention)
2146 even if it is supported by processor.
2149 This affects only 32-bit executables.
2150 noexec32=on: enable non-executable mappings (default)
2151 read doesn't imply executable mappings
2152 noexec32=off: disable non-executable mappings
2153 read implies executable mappings
2155 nofpu [SH] Disable hardware FPU at boot time.
2157 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2158 register save and restore. The kernel will only save
2159 legacy floating-point registers on task switch.
2161 noxsave [BUGS=X86] Disables x86 extended register state save
2162 and restore using xsave. The kernel will fallback to
2163 enabling legacy floating-point and sse state.
2166 on enable eager fpu restore
2167 off disable eager fpu restore
2168 auto selects the default scheme, which automatically
2169 enables eagerfpu restore for xsaveopt.
2171 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2172 wfi(ARM) instruction doesn't work correctly and not to
2173 use it. This is also useful when using JTAG debugger.
2175 no_file_caps Tells the kernel not to honor file capabilities. The
2176 only way then for a file to be executed with privilege
2177 is to be setuid root or executed by root.
2179 nohalt [IA-64] Tells the kernel not to use the power saving
2180 function PAL_HALT_LIGHT when idle. This increases
2181 power-consumption. On the positive side, it reduces
2182 interrupt wake-up latency, which may improve performance
2183 in certain environments such as networked servers or
2186 nohibernate [HIBERNATION] Disable hibernation and resume.
2188 nohz= [KNL] Boottime enable/disable dynamic ticks
2189 Valid arguments: on, off
2192 nohz_full= [KNL,BOOT]
2193 In kernels built with CONFIG_NO_HZ_FULL=y, set
2194 the specified list of CPUs whose tick will be stopped
2195 whenever possible. The boot CPU will be forced outside
2196 the range to maintain the timekeeping.
2197 The CPUs in this range must also be included in the
2200 noiotrap [SH] Disables trapped I/O port accesses.
2202 noirqdebug [X86-32] Disables the code which attempts to detect and
2203 disable unhandled interrupt sources.
2205 no_timer_check [X86,APIC] Disables the code which tests for
2206 broken timer IRQ sources.
2208 noisapnp [ISAPNP] Disables ISA PnP code.
2210 noinitrd [RAM] Tells the kernel not to load any configured
2213 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2215 [Deprecated - use intremap=off]
2219 nojitter [IA-64] Disables jitter checking for ITC timers.
2221 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2223 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2226 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2227 steal time is computed, but won't influence scheduler
2230 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2232 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2234 noltlbs [PPC] Do not use large page/tlb entries for kernel
2235 lowmem mapping on PPC40x.
2237 nomca [IA-64] Disable machine check abort handling
2239 nomce [X86-32] Machine Check Exception
2241 nomfgpt [X86-32] Disable Multi-Function General Purpose
2242 Timer usage (for AMD Geode machines).
2244 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2245 shutdown the other cpus. Instead use the REBOOT_VECTOR
2248 nomodule Disable module load
2250 nopat [X86] Disable PAT (page attribute table extension of
2251 pagetables) support.
2253 norandmaps Don't use address space randomization. Equivalent to
2254 echo 0 > /proc/sys/kernel/randomize_va_space
2256 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2258 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2259 with UP alternatives
2261 nordrand [X86] Disable kernel use of the RDRAND and
2262 RDSEED instructions even if they are supported
2263 by the processor. RDRAND and RDSEED are still
2264 available to user space applications.
2266 noresume [SWSUSP] Disables resume and restores original swap
2269 no-scroll [VGA] Disables scrollback.
2270 This is required for the Braillex ib80-piezo Braille
2271 reader made by F.H. Papenmeier (Germany).
2275 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2277 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2278 and disable the IO APIC. legacy for "maxcpus=0".
2280 nosoftlockup [KNL] Disable the soft-lockup detector.
2282 nosync [HW,M68K] Disables sync negotiation for all devices.
2284 notsc [BUGS=X86-32] Disable Time Stamp Counter
2286 nousb [USB] Disable the USB subsystem
2288 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2292 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2294 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2295 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2296 Some features depend on CPU0. Known dependencies are:
2297 1. Resume from suspend/hibernate depends on CPU0.
2298 Suspend/hibernate will fail if CPU0 is offline and you
2299 need to online CPU0 before suspend/hibernate.
2300 2. PIC interrupts also depend on CPU0. CPU0 can't be
2301 removed if a PIC interrupt is detected.
2302 It's said poweroff/reboot may depend on CPU0 on some
2303 machines although I haven't seen such issues so far
2304 after CPU0 is offline on a few tested machines.
2305 If the dependencies are under your control, you can
2306 turn on cpu0_hotplug.
2308 nptcg= [IA-64] Override max number of concurrent global TLB
2309 purges which is reported from either PAL_VM_SUMMARY or
2312 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2313 could support. nr_cpus=n : n >= 1 limits the kernel to
2314 supporting 'n' processors. Later in runtime you can not
2315 use hotplug cpu feature to put more cpu back to online.
2316 just like you compile the kernel NR_CPUS=n
2318 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2320 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2321 Allowed values are enable and disable
2323 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2324 one of ['zone', 'node', 'default'] can be specified
2325 This can be set from sysctl after boot.
2326 See Documentation/sysctl/vm.txt for details.
2328 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2329 See Documentation/debugging-via-ohci1394.txt for more
2332 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2333 Rather than timing out after 20 ms if an EC
2334 command is not properly ACKed, override the length
2335 of the timeout. We have interrupts disabled while
2336 waiting for the ACK, so if this is set too high
2337 interrupts *may* be lost!
2339 omap_mux= [OMAP] Override bootloader pin multiplexing.
2340 Format: <mux_mode0.mode_name=value>...
2341 For example, to override I2C bus2:
2342 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2344 oprofile.timer= [HW]
2345 Use timer interrupt instead of performance counters
2347 oprofile.cpu_type= Force an oprofile cpu type
2348 This might be useful if you have an older oprofile
2349 userland or if you want common events.
2350 Format: { arch_perfmon }
2351 arch_perfmon: [X86] Force use of architectural
2352 perfmon on Intel CPUs instead of the
2353 CPU specific event set.
2354 timer: [X86] Force use of architectural NMI
2355 timer mode (see also oprofile.timer
2356 for generic hr timer mode)
2357 [s390] Force legacy basic mode sampling
2358 (report cpu_type "timer")
2360 oops=panic Always panic on oopses. Default is to just kill the
2361 process, but there is a small probability of
2362 deadlocking the machine.
2363 This will also cause panics on machine check exceptions.
2364 Useful together with panic=30 to trigger a reboot.
2367 See Documentation/sound/oss/oss-parameters.txt
2369 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2370 timeout > 0: seconds before rebooting
2371 timeout = 0: wait forever
2372 timeout < 0: reboot immediately
2375 crash_kexec_post_notifiers
2376 Run kdump after running panic-notifiers and dumping
2377 kmsg. This only for the users who doubt kdump always
2378 succeeds in any situation.
2379 Note that this also increases risks of kdump failure,
2380 because some panic notifiers can make the crashed
2381 kernel more unstable.
2383 parkbd.port= [HW] Parallel port number the keyboard adapter is
2384 connected to, default is 0.
2386 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2387 0 for XT, 1 for AT (default is AT).
2390 parport= [HW,PPT] Specify parallel ports. 0 disables.
2391 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2392 Use 'auto' to force the driver to use any
2393 IRQ/DMA settings detected (the default is to
2394 ignore detected IRQ/DMA settings because of
2395 possible conflicts). You can specify the base
2396 address, IRQ, and DMA settings; IRQ and DMA
2397 should be numbers, or 'auto' (for using detected
2398 settings on that particular port), or 'nofifo'
2399 (to avoid using a FIFO even if it is detected).
2400 Parallel ports are assigned in the order they
2401 are specified on the command line, starting
2404 parport_init_mode= [HW,PPT]
2405 Configure VIA parallel port to operate in
2406 a specific mode. This is necessary on Pegasos
2407 computer where firmware has no options for setting
2408 up parallel port mode and sets it to spp.
2409 Currently this function knows 686a and 8231 chips.
2410 Format: [spp|ps2|epp|ecp|ecpepp]
2413 Halt all CPUs after the first oops has been printed for
2414 the specified number of seconds. This is to be used if
2415 your oopses keep scrolling off the screen.
2420 See header of drivers/block/paride/pcd.c.
2421 See also Documentation/blockdev/paride.txt.
2423 pci=option[,option...] [PCI] various PCI subsystem options:
2424 earlydump [X86] dump PCI config space before the kernel
2426 off [X86] don't probe for the PCI bus
2427 bios [X86-32] force use of PCI BIOS, don't access
2428 the hardware directly. Use this if your machine
2429 has a non-standard PCI host bridge.
2430 nobios [X86-32] disallow use of PCI BIOS, only direct
2431 hardware access methods are allowed. Use this
2432 if you experience crashes upon bootup and you
2433 suspect they are caused by the BIOS.
2434 conf1 [X86] Force use of PCI Configuration
2436 conf2 [X86] Force use of PCI Configuration
2438 noaer [PCIE] If the PCIEAER kernel config parameter is
2439 enabled, this kernel boot option can be used to
2440 disable the use of PCIE advanced error reporting.
2441 nodomains [PCI] Disable support for multiple PCI
2442 root domains (aka PCI segments, in ACPI-speak).
2443 nommconf [X86] Disable use of MMCONFIG for PCI
2445 check_enable_amd_mmconf [X86] check for and enable
2446 properly configured MMIO access to PCI
2447 config space on AMD family 10h CPU
2448 nomsi [MSI] If the PCI_MSI kernel config parameter is
2449 enabled, this kernel boot option can be used to
2450 disable the use of MSI interrupts system-wide.
2451 noioapicquirk [APIC] Disable all boot interrupt quirks.
2452 Safety option to keep boot IRQs enabled. This
2453 should never be necessary.
2454 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2455 primary IO-APIC for bridges that cannot disable
2456 boot IRQs. This fixes a source of spurious IRQs
2457 when the system masks IRQs.
2458 noioapicreroute [APIC] Disable workaround that uses the
2459 boot IRQ equivalent of an IRQ that connects to
2460 a chipset where boot IRQs cannot be disabled.
2461 The opposite of ioapicreroute.
2462 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2463 routing table. These calls are known to be buggy
2464 on several machines and they hang the machine
2465 when used, but on other computers it's the only
2466 way to get the interrupt routing table. Try
2467 this option if the kernel is unable to allocate
2468 IRQs or discover secondary PCI buses on your
2470 rom [X86] Assign address space to expansion ROMs.
2471 Use with caution as certain devices share
2472 address decoders between ROMs and other
2474 norom [X86] Do not assign address space to
2475 expansion ROMs that do not already have
2476 BIOS assigned address ranges.
2477 nobar [X86] Do not assign address space to the
2478 BARs that weren't assigned by the BIOS.
2479 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2480 assigned automatically to PCI devices. You can
2481 make the kernel exclude IRQs of your ISA cards
2483 pirqaddr=0xAAAAA [X86] Specify the physical address
2484 of the PIRQ table (normally generated
2485 by the BIOS) if it is outside the
2486 F0000h-100000h range.
2487 lastbus=N [X86] Scan all buses thru bus #N. Can be
2488 useful if the kernel is unable to find your
2489 secondary buses and you want to tell it
2490 explicitly which ones they are.
2491 assign-busses [X86] Always assign all PCI bus
2492 numbers ourselves, overriding
2493 whatever the firmware may have done.
2494 usepirqmask [X86] Honor the possible IRQ mask stored
2495 in the BIOS $PIR table. This is needed on
2496 some systems with broken BIOSes, notably
2497 some HP Pavilion N5400 and Omnibook XE3
2498 notebooks. This will have no effect if ACPI
2499 IRQ routing is enabled.
2500 noacpi [X86] Do not use ACPI for IRQ routing
2501 or for PCI scanning.
2502 use_crs [X86] Use PCI host bridge window information
2503 from ACPI. On BIOSes from 2008 or later, this
2504 is enabled by default. If you need to use this,
2505 please report a bug.
2506 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2507 If you need to use this, please report a bug.
2508 routeirq Do IRQ routing for all PCI devices.
2509 This is normally done in pci_enable_device(),
2510 so this option is a temporary workaround
2511 for broken drivers that don't call it.
2512 skip_isa_align [X86] do not align io start addr, so can
2513 handle more pci cards
2514 firmware [ARM] Do not re-enumerate the bus but instead
2515 just use the configuration from the
2516 bootloader. This is currently used on
2517 IXP2000 systems where the bus has to be
2518 configured a certain way for adjunct CPUs.
2519 noearly [X86] Don't do any early type 1 scanning.
2520 This might help on some broken boards which
2521 machine check when some devices' config space
2522 is read. But various workarounds are disabled
2523 and some IOMMU drivers will not work.
2524 bfsort Sort PCI devices into breadth-first order.
2525 This sorting is done to get a device
2526 order compatible with older (<= 2.4) kernels.
2527 nobfsort Don't sort PCI devices into breadth-first order.
2528 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2529 tuning and use the BIOS-configured MPS defaults.
2530 pcie_bus_safe Set every device's MPS to the largest value
2531 supported by all devices below the root complex.
2532 pcie_bus_perf Set device MPS to the largest allowable MPS
2533 based on its parent bus. Also set MRRS (Max
2534 Read Request Size) to the largest supported
2535 value (no larger than the MPS that the device
2536 or bus can support) for best performance.
2537 pcie_bus_peer2peer Set every device's MPS to 128B, which
2538 every device is guaranteed to support. This
2539 configuration allows peer-to-peer DMA between
2540 any pair of devices, possibly at the cost of
2541 reduced performance. This also guarantees
2542 that hot-added devices will work.
2543 cbiosize=nn[KMG] The fixed amount of bus space which is
2544 reserved for the CardBus bridge's IO window.
2545 The default value is 256 bytes.
2546 cbmemsize=nn[KMG] The fixed amount of bus space which is
2547 reserved for the CardBus bridge's memory
2548 window. The default value is 64 megabytes.
2551 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2552 Specifies alignment and device to reassign
2553 aligned memory resources.
2554 If <order of align> is not specified,
2555 PAGE_SIZE is used as alignment.
2556 PCI-PCI bridge can be specified, if resource
2557 windows need to be expanded.
2558 ecrc= Enable/disable PCIe ECRC (transaction layer
2559 end-to-end CRC checking).
2560 bios: Use BIOS/firmware settings. This is the
2564 hpiosize=nn[KMG] The fixed amount of bus space which is
2565 reserved for hotplug bridge's IO window.
2566 Default size is 256 bytes.
2567 hpmemsize=nn[KMG] The fixed amount of bus space which is
2568 reserved for hotplug bridge's memory window.
2569 Default size is 2 megabytes.
2570 realloc= Enable/disable reallocating PCI bridge resources
2571 if allocations done by BIOS are too small to
2572 accommodate resources required by all child
2574 off: Turn realloc off
2576 realloc same as realloc=on
2577 noari do not use PCIe ARI.
2578 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2579 only look for one device below a PCIe downstream
2582 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2585 force Enable ASPM even on devices that claim not to support it.
2586 WARNING: Forcing ASPM on may cause system lockups.
2588 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2589 nomsi Do not use MSI for PCI Express Native Hotplug (this
2590 makes all PCIe ports use INTx for hotplug services).
2592 pcie_ports= [PCIE] PCIe ports handling:
2593 auto Ask the BIOS whether or not to use native PCIe services
2594 associated with PCIe ports (PME, hot-plug, AER). Use
2595 them only if that is allowed by the BIOS.
2596 native Use native PCIe services associated with PCIe ports
2598 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2601 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2602 nomsi Do not use MSI for native PCIe PME signaling (this makes
2603 all PCIe root ports use INTx for all services).
2605 pcmv= [HW,PCMCIA] BadgePAD 4
2609 Keep all power-domains already enabled by bootloader on,
2610 even if no driver has claimed them. This is useful
2611 for debug and development, but should not be
2612 needed on a platform with proper driver support.
2615 See Documentation/blockdev/paride.txt.
2617 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2620 See arch/parisc/kernel/pdc_chassis.c
2622 percpu_alloc= Select which percpu first chunk allocator to use.
2623 Currently supported values are "embed" and "page".
2624 Archs may support subset or none of the selections.
2625 See comments in mm/percpu.c for details on each
2626 allocator. This parameter is primarily for debugging
2627 and performance comparison.
2630 See Documentation/blockdev/paride.txt.
2633 See Documentation/blockdev/paride.txt.
2635 pirq= [SMP,APIC] Manual mp-table setup
2636 See Documentation/x86/i386/IO-APIC.txt.
2638 plip= [PPT,NET] Parallel port network link
2639 Format: { parport<nr> | timid | 0 }
2640 See also Documentation/parport.txt.
2642 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2643 Override pmtimer IOPort with a hex value.
2647 Enable PNP debug messages (depends on the
2648 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2649 via /sys/module/pnp/parameters/debug. We always show
2650 current resource usage; turning this on also shows
2651 possible settings and some assignment information.
2657 { on | off | curr | res | no-curr | no-res }
2660 [ISAPNP] Exclude IRQs for the autoconfiguration
2663 [ISAPNP] Exclude DMAs for the autoconfiguration
2665 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2666 Ranges are in pairs (I/O port base and size).
2669 [ISAPNP] Exclude memory regions for the
2671 Ranges are in pairs (memory base and size).
2673 ports= [IP_VS_FTP] IPVS ftp helper module
2675 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2677 Format: <port>,<port>....
2679 print-fatal-signals=
2680 [KNL] debug: print fatal signals
2682 If enabled, warn about various signal handling
2683 related application anomalies: too many signals,
2684 too many POSIX.1 timers, fatal signals causing a
2687 If you hit the warning due to signal overflow,
2688 you might want to try "ulimit -i unlimited".
2692 printk.always_kmsg_dump=
2693 Trigger kmsg_dump for cases other than kernel oops or
2695 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2698 printk.time= Show timing data prefixed to each printk message line
2699 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2701 processor.max_cstate= [HW,ACPI]
2702 Limit processor to maximum C-state
2703 max_cstate=9 overrides any DMI blacklist limit.
2705 processor.nocst [HW,ACPI]
2706 Ignore the _CST method to determine C-states,
2707 instead using the legacy FADT method
2709 profile= [KNL] Enable kernel profiling via /proc/profile
2710 Format: [schedule,]<number>
2711 Param: "schedule" - profile schedule points.
2712 Param: <number> - step/bucket size as a power of 2 for
2713 statistical time based profiling.
2714 Param: "sleep" - profile D-state sleeping (millisecs).
2715 Requires CONFIG_SCHEDSTATS
2716 Param: "kvm" - profile VM exits.
2718 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2720 See Documentation/blockdev/ramdisk.txt.
2722 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2723 probe for; one of (bare|imps|exps|lifebook|any).
2724 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2726 psmouse.resetafter= [HW,MOUSE]
2727 Try to reset the device after so many bad packets
2730 [HW,MOUSE] Set desired mouse resolution, in dpi.
2731 psmouse.smartscroll=
2732 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2733 0 = disabled, 1 = enabled (default).
2735 pstore.backend= Specify the name of the pstore backend to use
2738 See Documentation/blockdev/paride.txt.
2741 [KNL] Number of legacy pty's. Overwrites compiled-in
2744 quiet [KNL] Disable most log messages
2749 See Documentation/md.txt.
2751 ramdisk_blocksize= [RAM]
2752 See Documentation/blockdev/ramdisk.txt.
2754 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2755 See Documentation/blockdev/ramdisk.txt.
2758 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2759 the specified list of CPUs to be no-callback CPUs.
2760 Invocation of these CPUs' RCU callbacks will
2761 be offloaded to "rcuox/N" kthreads created for
2762 that purpose, where "x" is "b" for RCU-bh, "p"
2763 for RCU-preempt, and "s" for RCU-sched, and "N"
2764 is the CPU number. This reduces OS jitter on the
2765 offloaded CPUs, which can be useful for HPC and
2766 real-time workloads. It can also improve energy
2767 efficiency for asymmetric multiprocessors.
2770 Rather than requiring that offloaded CPUs
2771 (specified by rcu_nocbs= above) explicitly
2772 awaken the corresponding "rcuoN" kthreads,
2773 make these kthreads poll for callbacks.
2774 This improves the real-time response for the
2775 offloaded CPUs by relieving them of the need to
2776 wake up the corresponding kthread, but degrades
2777 energy efficiency by requiring that the kthreads
2778 periodically wake up to do the polling.
2780 rcutree.blimit= [KNL]
2781 Set maximum number of finished RCU callbacks to
2782 process in one batch.
2784 rcutree.rcu_fanout_leaf= [KNL]
2785 Increase the number of CPUs assigned to each
2786 leaf rcu_node structure. Useful for very large
2789 rcutree.jiffies_till_first_fqs= [KNL]
2790 Set delay from grace-period initialization to
2791 first attempt to force quiescent states.
2792 Units are jiffies, minimum value is zero,
2793 and maximum value is HZ.
2795 rcutree.jiffies_till_next_fqs= [KNL]
2796 Set delay between subsequent attempts to force
2797 quiescent states. Units are jiffies, minimum
2798 value is one, and maximum value is HZ.
2800 rcutree.qhimark= [KNL]
2801 Set threshold of queued RCU callbacks beyond which
2802 batch limiting is disabled.
2804 rcutree.qlowmark= [KNL]
2805 Set threshold of queued RCU callbacks below which
2806 batch limiting is re-enabled.
2808 rcutree.rcu_idle_gp_delay= [KNL]
2809 Set wakeup interval for idle CPUs that have
2810 RCU callbacks (RCU_FAST_NO_HZ=y).
2812 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2813 Set wakeup interval for idle CPUs that have
2814 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2815 Lazy RCU callbacks are those which RCU can
2816 prove do nothing more than free memory.
2818 rcutorture.fqs_duration= [KNL]
2819 Set duration of force_quiescent_state bursts.
2821 rcutorture.fqs_holdoff= [KNL]
2822 Set holdoff time within force_quiescent_state bursts.
2824 rcutorture.fqs_stutter= [KNL]
2825 Set wait time between force_quiescent_state bursts.
2827 rcutorture.gp_exp= [KNL]
2828 Use expedited update-side primitives.
2830 rcutorture.gp_normal= [KNL]
2831 Use normal (non-expedited) update-side primitives.
2832 If both gp_exp and gp_normal are set, do both.
2833 If neither gp_exp nor gp_normal are set, still
2836 rcutorture.n_barrier_cbs= [KNL]
2837 Set callbacks/threads for rcu_barrier() testing.
2839 rcutorture.nfakewriters= [KNL]
2840 Set number of concurrent RCU writers. These just
2841 stress RCU, they don't participate in the actual
2842 test, hence the "fake".
2844 rcutorture.nreaders= [KNL]
2845 Set number of RCU readers.
2847 rcutorture.object_debug= [KNL]
2848 Enable debug-object double-call_rcu() testing.
2850 rcutorture.onoff_holdoff= [KNL]
2851 Set time (s) after boot for CPU-hotplug testing.
2853 rcutorture.onoff_interval= [KNL]
2854 Set time (s) between CPU-hotplug operations, or
2855 zero to disable CPU-hotplug testing.
2857 rcutorture.rcutorture_runnable= [BOOT]
2858 Start rcutorture running at boot time.
2860 rcutorture.shuffle_interval= [KNL]
2861 Set task-shuffle interval (s). Shuffling tasks
2862 allows some CPUs to go into dyntick-idle mode
2863 during the rcutorture test.
2865 rcutorture.shutdown_secs= [KNL]
2866 Set time (s) after boot system shutdown. This
2867 is useful for hands-off automated testing.
2869 rcutorture.stall_cpu= [KNL]
2870 Duration of CPU stall (s) to test RCU CPU stall
2871 warnings, zero to disable.
2873 rcutorture.stall_cpu_holdoff= [KNL]
2874 Time to wait (s) after boot before inducing stall.
2876 rcutorture.stat_interval= [KNL]
2877 Time (s) between statistics printk()s.
2879 rcutorture.stutter= [KNL]
2880 Time (s) to stutter testing, for example, specifying
2881 five seconds causes the test to run for five seconds,
2882 wait for five seconds, and so on. This tests RCU's
2883 ability to transition abruptly to and from idle.
2885 rcutorture.test_boost= [KNL]
2886 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2887 "Maybe" means test if the RCU implementation
2888 under test support RCU priority boosting.
2890 rcutorture.test_boost_duration= [KNL]
2891 Duration (s) of each individual boost test.
2893 rcutorture.test_boost_interval= [KNL]
2894 Interval (s) between each boost test.
2896 rcutorture.test_no_idle_hz= [KNL]
2897 Test RCU's dyntick-idle handling. See also the
2898 rcutorture.shuffle_interval parameter.
2900 rcutorture.torture_type= [KNL]
2901 Specify the RCU implementation to test.
2903 rcutorture.verbose= [KNL]
2904 Enable additional printk() statements.
2906 rcupdate.rcu_expedited= [KNL]
2907 Use expedited grace-period primitives, for
2908 example, synchronize_rcu_expedited() instead
2909 of synchronize_rcu(). This reduces latency,
2910 but can increase CPU utilization, degrade
2911 real-time latency, and degrade energy efficiency.
2913 rcupdate.rcu_cpu_stall_suppress= [KNL]
2914 Suppress RCU CPU stall warning messages.
2916 rcupdate.rcu_cpu_stall_timeout= [KNL]
2917 Set timeout for RCU CPU stall warning messages.
2921 Run specified binary instead of /init from the ramdisk,
2922 used for early userspace startup. See initrd.
2925 Format (x86 or x86_64):
2926 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2928 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2930 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2931 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2932 reboot_force is either force or not specified,
2933 reboot_cpu is s[mp]#### with #### being the processor
2934 to be used for rebooting.
2937 [KNL, SMP] Set scheduler's default relax_domain_level.
2938 See Documentation/cgroups/cpusets.txt.
2940 relative_sleep_states=
2941 [SUSPEND] Use sleep state labeling where the deepest
2942 state available other than hibernation is always "mem".
2943 Format: { "0" | "1" }
2944 0 -- Traditional sleep state labels.
2945 1 -- Relative sleep state labels.
2947 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2949 reservetop= [X86-32]
2951 Reserves a hole at the top of the kernel virtual
2956 Set the amount of memory to reserve for BIOS at
2957 the bottom of the address space.
2959 reset_devices [KNL] Force drivers to reset the underlying device
2960 during initialization.
2963 Specify the partition device for software suspend
2965 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2967 resume_offset= [SWSUSP]
2968 Specify the offset from the beginning of the partition
2969 given by "resume=" at which the swap header is located,
2970 in <PAGE_SIZE> units (needed only for swap files).
2971 See Documentation/power/swsusp-and-swap-files.txt
2973 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2974 read the resume files
2976 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2977 Useful for devices that are detected asynchronously
2978 (e.g. USB and MMC devices).
2980 hibernate= [HIBERNATION]
2981 noresume Don't check if there's a hibernation image
2982 present during boot.
2983 nocompress Don't compress/decompress hibernation images.
2984 no Disable hibernation and resume.
2986 retain_initrd [RAM] Keep initrd memory after extraction
2988 rhash_entries= [KNL,NET]
2989 Set number of hash buckets for route cache
2991 ro [KNL] Mount root device read-only on boot
2993 root= [KNL] Root filesystem
2994 See name_to_dev_t comment in init/do_mounts.c.
2996 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2997 mount the root filesystem
2999 rootflags= [KNL] Set root filesystem mount option string
3001 rootfstype= [KNL] Set root filesystem type
3003 rootwait [KNL] Wait (indefinitely) for root device to show up.
3004 Useful for devices that are detected asynchronously
3005 (e.g. USB and MMC devices).
3007 rproc_mem=nn[KMG][@address]
3008 [KNL,ARM,CMA] Remoteproc physical memory block.
3009 Memory area to be used by remote processor image,
3012 rw [KNL] Mount root device read-write on boot
3014 S [KNL] Run init in single mode
3017 See drivers/net/irda/sa1100_ir.c.
3019 sbni= [NET] Granch SBNI12 leased line adapter
3021 sched_debug [KNL] Enables verbose scheduler debug messages.
3023 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3024 xtime_lock contention on larger systems, and/or RCU lock
3025 contention on all systems with CONFIG_MAXSMP set.
3026 Format: { "0" | "1" }
3027 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3029 Note: increases power consumption, thus should only be
3030 enabled if running jitter sensitive (HPC/RT) workloads.
3032 security= [SECURITY] Choose a security module to enable at boot.
3033 If this boot parameter is not specified, only the first
3034 security module asking for security registration will be
3035 loaded. An invalid security module name will be treated
3036 as if no module has been chosen.
3038 selinux= [SELINUX] Disable or enable SELinux at boot time.
3039 Format: { "0" | "1" }
3040 See security/selinux/Kconfig help text.
3043 Default value is set via kernel config option.
3044 If enabled at boot time, /selinux/disable can be used
3045 later to disable prior to initial policy load.
3047 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3048 Format: { "0" | "1" }
3049 See security/apparmor/Kconfig help text
3052 Default value is set via kernel config option.
3054 serialnumber [BUGS=X86-32]
3057 Maximal number of shapers.
3059 show_msr= [x86] show boot-time MSR settings
3060 Format: { <integer> }
3061 Show boot-time (BIOS-initialized) MSR settings.
3062 The parameter means the number of CPUs to show,
3063 for example 1 means boot CPU only.
3070 slab_max_order= [MM, SLAB]
3071 Determines the maximum allowed order for slabs.
3072 A high setting may cause OOMs due to memory
3073 fragmentation. Defaults to 1 for systems with
3074 more than 32MB of RAM, 0 otherwise.
3076 slub_debug[=options[,slabs]] [MM, SLUB]
3077 Enabling slub_debug allows one to determine the
3078 culprit if slab objects become corrupted. Enabling
3079 slub_debug can create guard zones around objects and
3080 may poison objects when not in use. Also tracks the
3081 last alloc / free. For more information see
3082 Documentation/vm/slub.txt.
3084 slub_max_order= [MM, SLUB]
3085 Determines the maximum allowed order for slabs.
3086 A high setting may cause OOMs due to memory
3087 fragmentation. For more information see
3088 Documentation/vm/slub.txt.
3090 slub_min_objects= [MM, SLUB]
3091 The minimum number of objects per slab. SLUB will
3092 increase the slab order up to slub_max_order to
3093 generate a sufficiently large slab able to contain
3094 the number of objects indicated. The higher the number
3095 of objects the smaller the overhead of tracking slabs
3096 and the less frequently locks need to be acquired.
3097 For more information see Documentation/vm/slub.txt.
3099 slub_min_order= [MM, SLUB]
3100 Determines the minimum page order for slabs. Must be
3101 lower than slub_max_order.
3102 For more information see Documentation/vm/slub.txt.
3104 slub_nomerge [MM, SLUB]
3105 Disable merging of slabs with similar size. May be
3106 necessary if there is some reason to distinguish
3107 allocs to different slabs. Debug options disable
3108 merging on their own.
3109 For more information see Documentation/vm/slub.txt.
3112 Format: <io1>[,<io2>[,...,<io8>]]
3114 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3115 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3116 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3117 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3118 smsc-ircc2.ircc_irq= [HW] IRQ line
3119 smsc-ircc2.ircc_dma= [HW] DMA channel
3120 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3121 0: Toshiba Satellite 1800 (GP data pin select)
3122 1: Fast pin select (default)
3126 [KNL] Should the soft-lockup detector generate panics.
3129 softlockup_all_cpu_backtrace=
3130 [KNL] Should the soft-lockup detector generate
3131 backtraces on all cpus.
3134 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3135 See Documentation/laptops/sonypi.txt
3137 spia_io_base= [HW,MTD]
3143 Enabled the stack tracer on boot up.
3145 stacktrace_filter=[function-list]
3146 [FTRACE] Limit the functions that the stack tracer
3147 will trace at boot up. function-list is a comma separated
3148 list of functions. This list can be changed at run
3149 time by the stack_trace_filter file in the debugfs
3150 tracing directory. Note, this enables stack tracing
3151 and the stacktrace above is not needed.
3155 Set the STI (builtin display/keyboard on the HP-PARISC
3156 machines) console (graphic card) which should be used
3157 as the initial boot-console.
3158 See also comment in drivers/video/console/sticore.c.
3161 See comment in drivers/video/console/sticore.c.
3164 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3166 sunrpc.min_resvport=
3167 sunrpc.max_resvport=
3169 SunRPC servers often require that client requests
3170 originate from a privileged port (i.e. a port in the
3171 range 0 < portnr < 1024).
3172 An administrator who wishes to reserve some of these
3173 ports for other uses may adjust the range that the
3174 kernel's sunrpc client considers to be privileged
3175 using these two parameters to set the minimum and
3176 maximum port values.
3180 Control how the NFS server code allocates CPUs to
3181 service thread pools. Depending on how many NICs
3182 you have and where their interrupts are bound, this
3183 option will affect which CPUs will do NFS serving.
3184 Note: this parameter cannot be changed while the
3185 NFS server is running.
3187 auto the server chooses an appropriate mode
3188 automatically using heuristics
3189 global a single global pool contains all CPUs
3190 percpu one pool for each CPU
3191 pernode one pool for each NUMA node (equivalent
3192 to global on non-NUMA machines)
3194 sunrpc.tcp_slot_table_entries=
3195 sunrpc.udp_slot_table_entries=
3197 Sets the upper limit on the number of simultaneous
3198 RPC calls that can be sent from the client to a
3199 server. Increasing these values may allow you to
3200 improve throughput, but will also increase the
3201 amount of memory reserved for use by the client.
3204 [KNL] Enable accounting of swap in memory resource
3205 controller if no parameter or 1 is given or disable
3206 it if 0 is given (See Documentation/cgroups/memory.txt)
3208 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3209 Format: { <int> | force }
3210 <int> -- Number of I/O TLB slabs
3211 force -- force using of bounce buffers even if they
3212 wouldn't be automatically used by the kernel
3216 sysfs.deprecated=0|1 [KNL]
3217 Enable/disable old style sysfs layout for old udev
3218 on older distributions. When this option is enabled
3219 very new udev will not work anymore. When this option
3220 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3221 in older udev will not work anymore.
3222 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3223 the kernel configuration.
3225 sysrq_always_enabled
3227 Ignore sysrq setting - this boot parameter will
3228 neutralize any effect of /proc/sys/kernel/sysrq.
3229 Useful for debugging.
3233 test_suspend= [SUSPEND]
3234 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3235 standby suspend) as the system sleep state to briefly
3236 enter during system startup. The system is woken from
3237 this state using a wakeup-capable RTC alarm.
3239 thash_entries= [KNL,NET]
3240 Set number of hash buckets for TCP connection
3242 thermal.act= [HW,ACPI]
3243 -1: disable all active trip points in all thermal zones
3244 <degrees C>: override all lowest active trip points
3246 thermal.crt= [HW,ACPI]
3247 -1: disable all critical trip points in all thermal zones
3248 <degrees C>: override all critical trip points
3250 thermal.nocrt= [HW,ACPI]
3251 Set to disable actions on ACPI thermal zone
3252 critical and hot trip points.
3254 thermal.off= [HW,ACPI]
3255 1: disable ACPI thermal control
3257 thermal.psv= [HW,ACPI]
3258 -1: disable all passive trip points
3259 <degrees C>: override all passive trip points to this
3262 thermal.tzp= [HW,ACPI]
3263 Specify global default ACPI thermal zone polling rate
3264 <deci-seconds>: poll all this frequency
3265 0: no polling (default)
3268 Force threading of all interrupt handlers except those
3269 marked explicitly IRQF_NO_THREAD.
3272 Enable the Transcendent memory driver if built-in.
3274 tmem.cleancache=0|1 [KNL, XEN]
3275 Default is on (1). Disable the usage of the cleancache
3276 API to send anonymous pages to the hypervisor.
3278 tmem.frontswap=0|1 [KNL, XEN]
3279 Default is on (1). Disable the usage of the frontswap
3280 API to send swap pages to the hypervisor. If disabled
3281 the selfballooning and selfshrinking are force disabled.
3283 tmem.selfballooning=0|1 [KNL, XEN]
3284 Default is on (1). Disable the driving of swap pages
3287 tmem.selfshrinking=0|1 [KNL, XEN]
3288 Default is on (1). Partial swapoff that immediately
3289 transfers pages from Xen hypervisor back to the
3290 kernel based on different criteria.
3294 Specify if the kernel should make use of the cpu
3295 topology information if the hardware supports this.
3296 The scheduler will make use of this information and
3297 e.g. base its process migration decisions on it.
3302 tpm_suspend_pcr=[HW,TPM]
3303 Format: integer pcr id
3304 Specify that at suspend time, the tpm driver
3305 should extend the specified pcr with zeros,
3306 as a workaround for some chips which fail to
3307 flush the last written pcr on TPM_SaveState.
3308 This will guarantee that all the other pcrs
3311 trace_buf_size=nn[KMG]
3312 [FTRACE] will set tracing buffer size.
3314 trace_event=[event-list]
3315 [FTRACE] Set and start specified trace events in order
3316 to facilitate early boot debugging.
3317 See also Documentation/trace/events.txt
3319 trace_options=[option-list]
3320 [FTRACE] Enable or disable tracer options at boot.
3321 The option-list is a comma delimited list of options
3322 that can be enabled or disabled just as if you were
3323 to echo the option name into
3325 /sys/kernel/debug/tracing/trace_options
3327 For example, to enable stacktrace option (to dump the
3328 stack trace of each event), add to the command line:
3330 trace_options=stacktrace
3332 See also Documentation/trace/ftrace.txt "trace options"
3336 [FTRACE] enable this option to disable tracing when a
3337 warning is hit. This turns off "tracing_on". Tracing can
3338 be enabled again by echoing '1' into the "tracing_on"
3339 file located in /sys/kernel/debug/tracing/
3341 This option is useful, as it disables the trace before
3342 the WARNING dump is called, which prevents the trace to
3343 be filled with content caused by the warning output.
3345 This option can also be set at run time via the sysctl
3346 option: kernel/traceoff_on_warning
3348 transparent_hugepage=
3350 Format: [always|madvise|never]
3351 Can be used to control the default behavior of the system
3352 with respect to transparent hugepages.
3353 See Documentation/vm/transhuge.txt for more details.
3355 tsc= Disable clocksource stability checks for TSC.
3357 [x86] reliable: mark tsc clocksource as reliable, this
3358 disables clocksource verification at runtime, as well
3359 as the stability checks done at bootup. Used to enable
3360 high-resolution timer mode on older hardware, and in
3361 virtualized environment.
3362 [x86] noirqtime: Do not use TSC to do irq accounting.
3363 Used to run time disable IRQ_TIME_ACCOUNTING on any
3364 platforms where RDTSC is slow and this accounting
3367 turbografx.map[2|3]= [HW,JOY]
3368 TurboGraFX parallel port interface
3370 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3371 See also Documentation/input/joystick-parport.txt
3373 udbg-immortal [PPC] When debugging early kernel crashes that
3374 happen after console_init() and before a proper
3375 console driver takes over, this boot options might
3376 help "seeing" what's going on.
3378 uhash_entries= [KNL,NET]
3379 Set number of hash buckets for UDP/UDP-Lite connections
3382 [USB] Ignore overcurrent events (default N).
3383 Some badly-designed motherboards generate lots of
3384 bogus events, for ports that aren't wired to
3385 anything. Set this parameter to avoid log spamming.
3386 Note that genuine overcurrent events won't be
3390 [X86] Cause panic on unknown NMI.
3392 usbcore.authorized_default=
3393 [USB] Default USB device authorization:
3394 (default -1 = authorized except for wireless USB,
3395 0 = not authorized, 1 = authorized)
3397 usbcore.autosuspend=
3398 [USB] The autosuspend time delay (in seconds) used
3399 for newly-detected USB devices (default 2). This
3400 is the time required before an idle device will be
3401 autosuspended. Devices for which the delay is set
3402 to a negative value won't be autosuspended at all.
3404 usbcore.usbfs_snoop=
3405 [USB] Set to log all usbfs traffic (default 0 = off).
3407 usbcore.blinkenlights=
3408 [USB] Set to cycle leds on hubs (default 0 = off).
3410 usbcore.old_scheme_first=
3411 [USB] Start with the old device initialization
3412 scheme (default 0 = off).
3414 usbcore.usbfs_memory_mb=
3415 [USB] Memory limit (in MB) for buffers allocated by
3416 usbfs (default = 16, 0 = max = 2047).
3418 usbcore.use_both_schemes=
3419 [USB] Try the other device initialization scheme
3420 if the first one fails (default 1 = enabled).
3422 usbcore.initial_descriptor_timeout=
3423 [USB] Specifies timeout for the initial 64-byte
3424 USB_REQ_GET_DESCRIPTOR request in milliseconds
3425 (default 5000 = 5.0 seconds).
3428 [USBHID] The interval which mice are to be polled at.
3430 usb-storage.delay_use=
3431 [UMS] The delay in seconds before a new device is
3432 scanned for Logical Units (default 5).
3435 [UMS] A list of quirks entries to supplement or
3436 override the built-in unusual_devs list. List
3437 entries are separated by commas. Each entry has
3438 the form VID:PID:Flags where VID and PID are Vendor
3439 and Product ID values (4-digit hex numbers) and
3440 Flags is a set of characters, each corresponding
3441 to a common usb-storage quirk flag as follows:
3442 a = SANE_SENSE (collect more than 18 bytes
3444 b = BAD_SENSE (don't collect more than 18
3445 bytes of sense data);
3446 c = FIX_CAPACITY (decrease the reported
3447 device capacity by one sector);
3448 d = NO_READ_DISC_INFO (don't use
3449 READ_DISC_INFO command);
3450 e = NO_READ_CAPACITY_16 (don't use
3451 READ_CAPACITY_16 command);
3452 h = CAPACITY_HEURISTICS (decrease the
3453 reported device capacity by one
3454 sector if the number is odd);
3455 i = IGNORE_DEVICE (don't bind to this
3457 l = NOT_LOCKABLE (don't try to lock and
3458 unlock ejectable media);
3459 m = MAX_SECTORS_64 (don't transfer more
3460 than 64 sectors = 32 KB at a time);
3461 n = INITIAL_READ10 (force a retry of the
3462 initial READ(10) command);
3463 o = CAPACITY_OK (accept the capacity
3464 reported by the device);
3465 p = WRITE_CACHE (the device cache is ON
3467 r = IGNORE_RESIDUE (the device reports
3468 bogus residue values);
3469 s = SINGLE_LUN (the device has only one
3471 w = NO_WP_DETECT (don't test whether the
3472 medium is write-protected).
3473 Example: quirks=0419:aaf5:rl,0421:0433:rc
3475 user_debug= [KNL,ARM]
3477 See arch/arm/Kconfig.debug help text.
3478 1 - undefined instruction events
3480 4 - invalid data aborts
3483 Example: user_debug=31
3486 [X86] Flags controlling user PTE allocations.
3488 nohigh = do not allocate PTE pages in
3489 HIGHMEM regardless of setting
3493 On X86_32, this is an alias for vdso32=. Otherwise:
3495 vdso=1: enable VDSO (the default)
3496 vdso=0: disable VDSO mapping
3498 vdso32= [X86] Control the 32-bit vDSO
3499 vdso32=1: enable 32-bit VDSO
3500 vdso32=0 or vdso32=2: disable 32-bit VDSO
3502 See the help text for CONFIG_COMPAT_VDSO for more
3503 details. If CONFIG_COMPAT_VDSO is set, the default is
3504 vdso32=0; otherwise, the default is vdso32=1.
3506 For compatibility with older kernels, vdso32=2 is an
3509 Try vdso32=0 if you encounter an error that says:
3510 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3513 vector=percpu: enable percpu vector domain
3515 video= [FB] Frame buffer configuration
3516 See Documentation/fb/modedb.txt.
3518 video.brightness_switch_enabled= [0,1]
3519 If set to 1, on receiving an ACPI notify event
3520 generated by hotkey, video driver will adjust brightness
3521 level and then send out the event to user space through
3522 the allocated input device; If set to 0, video driver
3523 will only send out the event without touching backlight
3528 [VMMIO] Memory mapped virtio (platform) device.
3530 <size>@<baseaddr>:<irq>[:<id>]
3532 <size> := size (can use standard suffixes
3534 <baseaddr> := physical base address
3535 <irq> := interrupt number (as passed to
3537 <id> := (optional) platform device id
3539 virtio_mmio.device=1K@0x100b0000:48:7
3541 Can be used multiple times for multiple devices.
3543 vga= [BOOT,X86-32] Select a particular video mode
3544 See Documentation/x86/boot.txt and
3545 Documentation/svga.txt.
3546 Use vga=ask for menu.
3547 This is actually a boot loader parameter; the value is
3548 passed to the kernel using a special protocol.
3550 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3551 size of <nn>. This can be used to increase the
3552 minimum size (128MB on x86). It can also be used to
3553 decrease the size and leave more room for directly
3556 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3559 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3562 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3566 Controls the behavior of vsyscalls (i.e. calls to
3567 fixed addresses of 0xffffffffff600x00 from legacy
3568 code). Most statically-linked binaries and older
3569 versions of glibc use these calls. Because these
3570 functions are at fixed addresses, they make nice
3571 targets for exploits that can control RIP.
3573 emulate [default] Vsyscalls turn into traps and are
3574 emulated reasonably safely.
3576 native Vsyscalls are native syscall instructions.
3577 This is a little bit faster than trapping
3578 and makes a few dynamic recompilers work
3579 better than they would in emulation mode.
3580 It also makes exploits much easier to write.
3582 none Vsyscalls don't work at all. This makes
3583 them quite hard to use for exploits but
3584 might break your system.
3586 vt.color= [VT] Default text color.
3587 Format: 0xYX, X = foreground, Y = background.
3588 Default: 0x07 = light gray on black.
3590 vt.cur_default= [VT] Default cursor shape.
3591 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3592 the parameters of the <Esc>[?A;B;Cc escape sequence;
3593 see VGA-softcursor.txt. Default: 2 = underline.
3595 vt.default_blu= [VT]
3596 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3597 Change the default blue palette of the console.
3598 This is a 16-member array composed of values
3601 vt.default_grn= [VT]
3602 Format: <green0>,<green1>,<green2>,...,<green15>
3603 Change the default green palette of the console.
3604 This is a 16-member array composed of values
3607 vt.default_red= [VT]
3608 Format: <red0>,<red1>,<red2>,...,<red15>
3609 Change the default red palette of the console.
3610 This is a 16-member array composed of values
3616 Set system-wide default UTF-8 mode for all tty's.
3617 Default is 1, i.e. UTF-8 mode is enabled for all
3618 newly opened terminals.
3620 vt.global_cursor_default=
3623 Set system-wide default for whether a cursor
3624 is shown on new VTs. Default is -1,
3625 i.e. cursors will be created by default unless
3626 overridden by individual drivers. 0 will hide
3627 cursors, 1 will display them.
3629 vt.italic= [VT] Default color for italic text; 0-15.
3632 vt.underline= [VT] Default color for underlined text; 0-15.
3635 watchdog timers [HW,WDT] For information on watchdog timers,
3636 see Documentation/watchdog/watchdog-parameters.txt
3637 or other driver-specific files in the
3638 Documentation/watchdog/ directory.
3640 workqueue.disable_numa
3641 By default, all work items queued to unbound
3642 workqueues are affine to the NUMA nodes they're
3643 issued on, which results in better behavior in
3644 general. If NUMA affinity needs to be disabled for
3645 whatever reason, this option can be used. Note
3646 that this also can be controlled per-workqueue for
3647 workqueues visible under /sys/bus/workqueue/.
3649 workqueue.power_efficient
3650 Per-cpu workqueues are generally preferred because
3651 they show better performance thanks to cache
3652 locality; unfortunately, per-cpu workqueues tend to
3653 be more power hungry than unbound workqueues.
3655 Enabling this makes the per-cpu workqueues which
3656 were observed to contribute significantly to power
3657 consumption unbound, leading to measurably lower
3658 power usage at the cost of small performance
3661 The default value of this parameter is determined by
3662 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3664 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3665 default x2apic cluster mode on platforms
3668 x86_intel_mid_timer= [X86-32,APBT]
3669 Choose timer option for x86 Intel MID platform.
3670 Two valid options are apbt timer only and lapic timer
3671 plus one apbt timer for broadcast timer.
3672 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3674 xen_emul_unplug= [HW,X86,XEN]
3675 Unplug Xen emulated devices
3676 Format: [unplug0,][unplug1]
3677 ide-disks -- unplug primary master IDE devices
3678 aux-ide-disks -- unplug non-primary-master IDE devices
3679 nics -- unplug network devices
3680 all -- unplug all emulated devices (NICs and IDE disks)
3681 unnecessary -- unplugging emulated devices is
3682 unnecessary even if the host did not respond to
3684 never -- do not unplug even if version check succeeds
3686 xen_nopvspin [X86,XEN]
3687 Disables the ticketlock slowpath using Xen PV
3690 xirc2ps_cs= [NET,PCMCIA]
3692 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3694 ______________________________________________________________________
3698 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob