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.
168 acpi= [HW,ACPI,X86,ARM64]
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
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_apic_instance= [ACPI, IOAPIC]
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 Format: <irq>,<irq>...
267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
272 This feature is enabled by default.
273 This option allows to turn off the feature.
275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
305 acpi_osi=!* # remove all strings
306 acpi_osi=! # disable all built-in OS vendor
308 acpi_osi= # disable all strings
310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372 old_ordering, nonvs, sci_force_enable }
373 See Documentation/power/video.txt for information on
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
403 See Documentation/sound/alsa/alsa-parameters.txt
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
418 32: only for 32-bit processes
419 64: only for 64-bit processes
420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
430 amd_iommu= [HW,X86-64]
431 Pass parameters to the AMD IOMMU driver in the system.
433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
437 off - do not initialize any AMD IOMMU found in
439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
454 See also Documentation/input/joystick.txt
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
462 Power management functions (SPARCstation-4/5 + deriv.)
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
469 Change the output verbosity whilst booting
470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
475 See Documentation/networking/ipv6.txt.
477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
486 apm= [APM] Advanced Power Management
487 See header of arch/x86/kernel/apm_32.c.
489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
494 atarimouse= [HW,MOUSE] Atari Mouse
496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
499 atkbd.reset= [HW] Reset keyboard during initialization
501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
529 baycom_epp= [HW,AX25]
532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
534 See header of drivers/net/hamradio/baycom_par.c.
536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
558 bttv.radio= Most important insmod options are available as
560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
567 c101= [NET] Moxa C101 synchronous serial card
569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
579 format: { id:<keyid> | builtin }
581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
595 - foo isn't visible as an individually mountable
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
608 Value can be changed at runtime via
609 /selinux/checkreqprot.
612 See Documentation/s390/CommonIO for details.
615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
627 Forces specified clocksource (if available) to be used
628 when calculating gettimeofday(). If specified
629 clocksource is not available, it defaults to PIT.
630 Format: { pit | tsc | cyclone | pmtmr }
632 clocksource= Override the default clocksource
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
638 [all] jiffies (this is the base, fallback clocksource)
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
643 [X86-32] pit,hpet,tsc;
644 scx200_hrt on Geode; cyclone on IBM x440
652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
656 stable over kernel options, but the vendor specific
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
665 cma=nn[MG]@[start[MG][-end[MG]]]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
672 include/linux/dma-contiguous.h
674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
683 allocations, by default set to 256K.
685 code_bytes [X86] How many bytes of object code to print
690 com20020= [HW,NET] ARCnet - COM20020 chipset
692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
698 ARCnet - COM90xx chipset (memory-mapped buffers)
699 Format: <io>[,<irq>[,<memstart>]]
701 condev= [HW,S390] console device
704 console= [KNL] Output console device and options.
706 tty<n> Use the virtual console device <n>.
710 Use the specified serial port. The options are of
711 the form "bbbbpnf", where "bbbb" is the baud rate,
712 "p" is parity ("n", "o", or "e"), "n" is number of
713 bits, and "f" is flow control ("r" for RTS or
714 omit it). Default is "9600n8".
716 See Documentation/serial-console.txt for more
718 Documentation/networking/netconsole.txt for an
721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
741 For now, only VisioBraille is supported.
743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
778 Documentation/kdump/kdump.txt for an example.
780 crashkernel=size[KMG],high
781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
786 It will be ignored if crashkernel=X is specified.
787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
792 requires at least 64M+32K low memory. Kernel would
793 try to allocate 72M below 4G automatically.
794 This one let user to specify own low range under 4G
795 for second kernel instead.
796 0: to disable low allocation.
797 It will be ignored when crashkernel=X,high is not used
798 or memory reserved is below 4G.
803 cs89x0_media= [HW,NET]
804 Format: { rj45 | aui | bnc }
807 See header of drivers/s390/block/dasd_devmap.c.
809 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
810 (one device per port)
811 Format: <port#>,<type>
812 See also Documentation/input/joystick-parport.txt
814 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815 time. See Documentation/dynamic-debug-howto.txt for
816 details. Deprecated, see dyndbg.
818 debug [KNL] Enable kernel debugging (events log level).
821 [KNL] verbose self-tests
823 Print debugging info while doing the locking API
825 We default to 0 (no extra messages), setting it to
826 1 will print _a lot_ more information - normally
827 only useful to kernel developers.
829 debug_objects [KNL] Enable object debugging
832 [KNL] Disable object debugging
834 debug_guardpage_minorder=
835 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836 parameter allows control of the order of pages that will
837 be intentionally kept free (and hence protected) by the
838 buddy allocator. Bigger value increase the probability
839 of catching random memory corruption, but reduce the
840 amount of memory for normal system use. The maximum
841 possible value is MAX_ORDER/2. Setting this parameter
842 to 1 or 2 should be enough to identify most random
843 memory corruption problems caused by bugs in kernel or
844 driver code when a CPU writes to (or reads from) a
845 random memory location. Note that there exists a class
846 of memory corruptions problems caused by buggy H/W or
847 F/W or by drivers badly programing DMA (basically when
848 memory is written at bus level and the CPU MMU is
849 bypassed) which are not detectable by
850 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851 tracking down these problems.
854 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855 parameter enables the feature at boot time. In
856 default, it is disabled. We can avoid allocating huge
857 chunk of memory for debug pagealloc if we don't enable
858 it at boot time and the system will work mostly same
859 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860 on: enable the feature
862 debugpat [X86] Enable PAT debugging
864 decnet.addr= [HW,NET]
865 Format: <area>[,<node>]
866 See also Documentation/networking/decnet.txt.
869 [same as hugepagesz=] The size of the default
870 HugeTLB page size. This is the size represented by
871 the legacy /proc/ hugepages APIs, used for SHM, and
872 default size when mounting hugetlbfs filesystems.
873 Defaults to the default architecture's huge page size
877 Set number of hash buckets for dentry cache.
880 See Documentation/networking/ipv6.txt.
882 disable_cpu_apicid= [X86,APIC,SMP]
884 The number of initial APIC ID for the
885 corresponding CPU to be disabled at boot,
886 mostly used for the kdump 2nd kernel to
887 disable BSP to wake up multiple CPUs without
888 causing system reset or hang due to sending
891 disable_ddw [PPC/PSERIES]
892 Disable Dynamic DMA Window support. Use this if
893 to workaround buggy firmware.
896 See Documentation/networking/ipv6.txt.
898 disable_mtrr_cleanup [X86]
899 The kernel tries to adjust MTRR layout from continuous
900 to discrete, to make X server driver able to add WB
901 entry later. This parameter disables that.
903 disable_mtrr_trim [X86, Intel and AMD only]
904 By default the kernel will trim any uncacheable
905 memory out of your available memory pool based on
906 MTRR settings. This parameter disables that behavior,
907 possibly causing your machine to run very slowly.
909 disable_timer_pin_1 [X86]
910 Disable PIN 1 of APIC timer
911 Can be useful to work around chipset bugs.
913 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
914 this option disables the debugging code at boot.
916 dma_debug_entries=<number>
917 This option allows to tune the number of preallocated
918 entries for DMA-API debugging code. One entry is
919 required per DMA-API allocation. Use this if the
920 DMA-API debugging code disables itself because the
921 architectural default is too low.
923 dma_debug_driver=<driver_name>
924 With this option the DMA-API debugging driver
925 filter feature can be enabled at boot time. Just
926 pass the driver to filter for as the parameter.
927 The filter can be disabled or changed to another
928 driver later using sysfs.
930 drm_kms_helper.edid_firmware=[<connector>:]<file>
931 Broken monitors, graphic adapters and KVMs may
932 send no or incorrect EDID data sets. This parameter
933 allows to specify an EDID data set in the
934 /lib/firmware directory that is used instead.
935 Generic built-in EDID data sets are used, if one of
936 edid/1024x768.bin, edid/1280x1024.bin,
937 edid/1680x1050.bin, or edid/1920x1080.bin is given
938 and no file with the same name exists. Details and
939 instructions how to build your own EDID data are
940 available in Documentation/EDID/HOWTO.txt. An EDID
941 data set will only be used for a particular connector,
942 if its name and a colon are prepended to the EDID
947 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
948 module.dyndbg[="val"]
949 Enable debug messages at boot time. See
950 Documentation/dynamic-debug-howto.txt for details.
952 nompx [X86] Disables Intel Memory Protection Extensions.
953 See Documentation/x86/intel_mpx.txt for more
954 information about the feature.
957 on enable eager fpu restore
958 off disable eager fpu restore
959 auto selects the default scheme, which automatically
960 enables eagerfpu restore for xsaveopt.
962 module.async_probe [KNL]
963 Enable asynchronous probe on this module.
965 early_ioremap_debug [KNL]
966 Enable debug messages in early_ioremap support. This
967 is useful for tracking down temporary early mappings
968 which are not unmapped.
970 earlycon= [KNL] Output early console device and options.
973 Start an early, polled-mode console on a cadence serial
974 port at the specified address. The cadence serial port
975 must already be setup and configured. Options are not
978 uart[8250],io,<addr>[,options]
979 uart[8250],mmio,<addr>[,options]
980 uart[8250],mmio32,<addr>[,options]
981 uart[8250],mmio32be,<addr>[,options]
982 uart[8250],0x<addr>[,options]
983 Start an early, polled-mode console on the 8250/16550
984 UART at the specified I/O port or MMIO address.
985 MMIO inter-register address stride is either 8-bit
986 (mmio) or 32-bit (mmio32 or mmio32be).
987 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
988 to be equivalent to 'mmio'. 'options' are specified
989 in the same format described for "console=ttyS<n>"; if
990 unspecified, the h/w is not initialized.
993 Start an early, polled-mode console on a pl011 serial
994 port at the specified address. The pl011 serial port
995 must already be setup and configured. Options are not
999 Start an early, polled-mode console on an msm serial
1000 port at the specified address. The serial port
1001 must already be setup and configured. Options are not
1004 msm_serial_dm,<addr>
1005 Start an early, polled-mode console on an msm serial
1006 dm port at the specified address. The serial port
1007 must already be setup and configured. Options are not
1010 smh Use ARM semihosting calls for early console.
1018 Use early console provided by serial driver available
1019 on Samsung SoCs, requires selecting proper type and
1020 a correct base address of the selected UART port. The
1021 serial port must already be setup and configured.
1022 Options are not yet supported.
1024 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1028 earlyprintk=serial[,ttySn[,baudrate]]
1029 earlyprintk=serial[,0x...[,baudrate]]
1030 earlyprintk=ttySn[,baudrate]
1031 earlyprintk=dbgp[debugController#]
1032 earlyprintk=pciserial,bus:device.function[,baudrate]
1034 earlyprintk is useful when the kernel crashes before
1035 the normal console is initialized. It is not enabled by
1036 default because it has some cosmetic problems.
1038 Append ",keep" to not disable it when the real console
1041 Only one of vga, efi, serial, or usb debug port can
1044 Currently only ttyS0 and ttyS1 may be specified by
1045 name. Other I/O ports may be explicitly specified
1046 on some architectures (x86 and arm at least) by
1047 replacing ttySn with an I/O port address, like this:
1048 earlyprintk=serial,0x1008,115200
1049 You can find the port for a given device in
1050 /proc/tty/driver/serial:
1051 2: uart:ST16650V2 port:00001008 irq:18 ...
1053 Interaction with the standard serial driver is not
1056 The VGA and EFI output is eventually overwritten by
1059 The xen output can only be used by Xen PV guests.
1061 edac_report= [HW,EDAC] Control how to report EDAC event
1062 Format: {"on" | "off" | "force"}
1063 on: enable EDAC to report H/W event. May be overridden
1064 by other higher priority error reporting module.
1065 off: disable H/W event reporting through EDAC.
1066 force: enforce the use of EDAC to report H/W event.
1069 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1072 This is designed to be used in conjunction with
1073 the boot argument: earlyprintk=vga
1076 Format: {"off" | "on" | "skip[mbr]"}
1079 Format: { "old_map", "nochunk", "noruntime", "debug" }
1080 old_map [X86-64]: switch to the old ioremap-based EFI
1081 runtime services mapping. 32-bit still uses this one by
1083 nochunk: disable reading files in "chunks" in the EFI
1084 boot stub, as chunking can cause problems with some
1085 firmware implementations.
1086 noruntime : disable EFI runtime services support
1087 debug: enable misc debug output
1089 efi_no_storage_paranoia [EFI; X86]
1090 Using this parameter you can use more than 50% of
1091 your efi variable storage. Use this parameter only if
1092 you are really sure that your UEFI does sane gc and
1093 fulfills the spec otherwise your board may brick.
1095 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1096 Add arbitrary attribute to specific memory range by
1097 updating original EFI memory map.
1098 Region of memory which aa attribute is added to is
1100 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1101 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1102 attribute is added to range 0x100000000-0x180000000 and
1103 0x10a0000000-0x1120000000.
1105 Using this parameter you can do debugging of EFI memmap
1106 related feature. For example, you can do debugging of
1107 Address Range Mirroring feature even if your box
1110 eisa_irq_edge= [PARISC,HW]
1111 See header of drivers/parisc/eisa.c.
1114 See comment before function elanfreq_setup() in
1115 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1118 Format: {"cfq" | "deadline" | "noop"}
1119 See Documentation/block/cfq-iosched.txt and
1120 Documentation/block/deadline-iosched.txt for details.
1122 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1123 Specifies physical address of start of kernel core
1124 image elf header and optionally the size. Generally
1125 kexec loader will pass this option to capture kernel.
1126 See Documentation/kdump/kdump.txt for details.
1128 enable_mtrr_cleanup [X86]
1129 The kernel tries to adjust MTRR layout from continuous
1130 to discrete, to make X server driver able to add WB
1131 entry later. This parameter enables that.
1133 enable_timer_pin_1 [X86]
1134 Enable PIN 1 of APIC timer
1135 Can be useful to work around chipset bugs
1136 (in particular on some ATI chipsets).
1137 The kernel tries to set a reasonable default.
1139 enforcing [SELINUX] Set initial enforcing status.
1141 See security/selinux/Kconfig help text.
1142 0 -- permissive (log only, no denials).
1143 1 -- enforcing (deny and log).
1145 Value can be changed at runtime via /selinux/enforce.
1148 Disable Error Record Serialization Table (ERST)
1151 ether= [HW,NET] Ethernet cards parameters
1152 This option is obsoleted by the "netdev=" option, which
1153 has equivalent usage. See its documentation for details.
1157 Permit 'security.evm' to be updated regardless of
1158 current integrity status.
1162 fail_make_request=[KNL]
1163 General fault injection mechanism.
1164 Format: <interval>,<probability>,<space>,<times>
1165 See also Documentation/fault-injection/.
1168 See Documentation/blockdev/floppy.txt.
1170 force_pal_cache_flush
1171 [IA-64] Avoid check_sal_cache_flush which may hang on
1172 buggy SAL_CACHE_FLUSH implementations. Using this
1173 parameter will force ia64_sal_cache_flush to call
1174 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1177 Forcefully enable Physical Address Extension (PAE).
1178 Many Pentium M systems disable PAE but may have a
1179 functionally usable PAE implementation.
1180 Warning: use of this parameter will taint the kernel
1181 and may cause unknown problems.
1184 [FTRACE] will set and start the specified tracer
1185 as early as possible in order to facilitate early
1188 ftrace_dump_on_oops[=orig_cpu]
1189 [FTRACE] will dump the trace buffers on oops.
1190 If no parameter is passed, ftrace will dump
1191 buffers of all CPUs, but if you pass orig_cpu, it will
1192 dump only the buffer of the CPU that triggered the
1195 ftrace_filter=[function-list]
1196 [FTRACE] Limit the functions traced by the function
1197 tracer at boot up. function-list is a comma separated
1198 list of functions. This list can be changed at run
1199 time by the set_ftrace_filter file in the debugfs
1202 ftrace_notrace=[function-list]
1203 [FTRACE] Do not trace the functions specified in
1204 function-list. This list can be changed at run time
1205 by the set_ftrace_notrace file in the debugfs
1208 ftrace_graph_filter=[function-list]
1209 [FTRACE] Limit the top level callers functions traced
1210 by the function graph tracer at boot up.
1211 function-list is a comma separated list of functions
1212 that can be changed at run time by the
1213 set_graph_function file in the debugfs tracing directory.
1215 ftrace_graph_notrace=[function-list]
1216 [FTRACE] Do not trace from the functions specified in
1217 function-list. This list is a comma separated list of
1218 functions that can be changed at run time by the
1219 set_graph_notrace file in the debugfs tracing directory.
1222 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1223 support via parallel port (up to 5 devices per port)
1224 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1225 See also Documentation/input/joystick-parport.txt
1229 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1233 gcov_persist= [GCOV] When non-zero (default), profiling data for
1234 kernel modules is saved and remains accessible via
1235 debugfs, even when the module is unloaded/reloaded.
1236 When zero, profiling data is discarded and associated
1237 debugfs files are removed at module unload time.
1239 gpt [EFI] Forces disk with valid GPT signature but
1240 invalid Protective MBR to be treated as GPT. If the
1241 primary GPT is corrupted, it enables the backup/alternate
1242 GPT to be used instead.
1244 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1245 the "Enable 0" bit of the configuration register.
1248 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1249 the "Enable 0" bit of the configuration register.
1252 grcan.select= [HW] Select which physical interface to use.
1255 grcan.txsize= [HW] Sets the size of the tx buffer.
1256 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1258 grcan.rxsize= [HW] Sets the size of the rx buffer.
1259 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1262 hashdist= [KNL,NUMA] Large hashes allocated during boot
1263 are distributed across NUMA nodes. Defaults on
1264 for 64-bit NUMA, off otherwise.
1265 Format: 0 | 1 (for off | on)
1267 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1269 hd= [EIDE] (E)IDE hard drive subsystem geometry
1270 Format: <cyl>,<head>,<sect>
1273 Disable Hardware Error Source Table (HEST) support;
1274 corresponding firmware-first mode error processing
1275 logic will be disabled.
1277 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1278 size of <nn>. This works even on boxes that have no
1279 highmem otherwise. This also works to reduce highmem
1280 size on bigger boxes.
1282 highres= [KNL] Enable/disable high resolution timer mode.
1283 Valid parameters: "on", "off"
1287 See Documentation/isdn/README.HiSax.
1291 hpet= [X86-32,HPET] option to control HPET usage
1292 Format: { enable (default) | disable | force |
1294 disable: disable HPET and use PIT instead
1295 force: allow force enabled of undocumented chips (ICH4,
1297 verbose: show contents of HPET registers during setup
1299 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1300 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1302 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1303 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1304 On x86-64 and powerpc, this option can be specified
1305 multiple times interleaved with hugepages= to reserve
1306 huge pages of different sizes. Valid pages sizes on
1307 x86-64 are 2M (when the CPU supports "pse") and 1G
1308 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1310 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1311 terminal devices. Valid values: 0..8
1312 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1313 If specified, z/VM IUCV HVC accepts connections
1314 from listed z/VM user IDs only.
1316 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1317 hardware thread id mappings.
1318 Format: <cpu>:<hwthread>
1321 Do not unregister boot console at start. This is only
1322 useful for debugging when something happens in the window
1323 between unregistering the boot console and initializing
1326 i2c_bus= [HW] Override the default board specific I2C bus speed
1327 or register an additional I2C bus that is not
1328 registered from board initialization code.
1332 i8042.debug [HW] Toggle i8042 debug mode
1333 i8042.direct [HW] Put keyboard port into non-translated mode
1334 i8042.dumbkbd [HW] Pretend that controller can only read data from
1335 keyboard and cannot control its state
1336 (Don't attempt to blink the leds)
1337 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1338 i8042.nokbd [HW] Don't check/create keyboard port
1339 i8042.noloop [HW] Disable the AUX Loopback command while probing
1341 i8042.nomux [HW] Don't check presence of an active multiplexing
1343 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1345 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1346 i8042.reset [HW] Reset the controller during init and cleanup
1347 i8042.unlock [HW] Unlock (ignore) the keylock
1348 i8042.kbdreset [HW] Reset device connected to KBD port
1352 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1353 indicates that the driver is running on unsupported
1355 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1356 does not match list of supported models.
1358 [HW] Report power status in /proc/i8k
1359 (disabled by default)
1360 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1363 i915.invert_brightness=
1364 [DRM] Invert the sense of the variable that is used to
1365 set the brightness of the panel backlight. Normally a
1366 brightness value of 0 indicates backlight switched off,
1367 and the maximum of the brightness value sets the backlight
1368 to maximum brightness. If this parameter is set to 0
1369 (default) and the machine requires it, or this parameter
1370 is set to 1, a brightness value of 0 sets the backlight
1371 to maximum brightness, and the maximum of the brightness
1372 value switches the backlight off.
1373 -1 -- never invert brightness
1374 0 -- machine default
1375 1 -- force brightness inversion
1378 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1380 ide-core.nodma= [HW] (E)IDE subsystem
1381 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1382 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1383 .cdrom .chs .ignore_cable are additional options
1384 See Documentation/ide/ide.txt.
1386 ide-generic.probe-mask= [HW] (E)IDE subsystem
1388 Probe mask for legacy ISA IDE ports. Depending on
1389 platform up to 6 ports are supported, enabled by
1390 setting corresponding bits in the mask to 1. The
1391 default value is 0x0, which has a special meaning.
1392 On systems that have PCI, it triggers scanning the
1393 PCI bus for the first and the second port, which
1394 are then probed. On systems without PCI the value
1395 of 0x0 enables probing the two first ports as if it
1398 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1399 Claim all unknown PCI IDE storage controllers.
1402 Format: idle=poll, idle=halt, idle=nomwait
1403 Poll forces a polling idle loop that can slightly
1404 improve the performance of waking up a idle CPU, but
1405 will use a lot of power and make the system run hot.
1407 idle=halt: Halt is forced to be used for CPU idle.
1408 In such case C2/C3 won't be used again.
1409 idle=nomwait: Disable mwait for CPU C-states
1411 ignore_loglevel [KNL]
1412 Ignore loglevel setting - this will print /all/
1413 kernel messages to the console. Useful for debugging.
1414 We also add it as printk module parameter, so users
1415 could change it dynamically, usually by
1416 /sys/module/printk/parameters/ignore_loglevel.
1418 ihash_entries= [KNL]
1419 Set number of hash buckets for inode cache.
1421 ima_appraise= [IMA] appraise integrity measurements
1422 Format: { "off" | "enforce" | "fix" | "log" }
1425 ima_appraise_tcb [IMA]
1426 The builtin appraise policy appraises all files
1430 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1434 The list of supported hash algorithms is defined
1435 in crypto/hash_info.h.
1438 The builtin measurement policy to load during IMA
1439 setup. Specyfing "tcb" as the value, measures all
1440 programs exec'd, files mmap'd for exec, and all files
1441 opened with the read mode bit set by either the
1442 effective uid (euid=0) or uid=0.
1445 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1446 Load a policy which meets the needs of the Trusted
1447 Computing Base. This means IMA will measure all
1448 programs exec'd, files mmap'd for exec, and all files
1449 opened for read by uid=0.
1452 Select one of defined IMA measurements template formats.
1453 Formats: { "ima" | "ima-ng" | "ima-sig" }
1457 [IMA] Define a custom template format.
1458 Format: { "field1|...|fieldN" }
1460 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1461 Format: <min_file_size>
1462 Set the minimal file size for using asynchronous hash.
1463 If left unspecified, ahash usage is disabled.
1465 ahash performance varies for different data sizes on
1466 different crypto accelerators. This option can be used
1467 to achieve the best performance for a particular HW.
1469 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1471 Set hashing buffer size. Default: 4k.
1473 ahash performance varies for different chunk sizes on
1474 different crypto accelerators. This option can be used
1475 to achieve best performance for particular HW.
1479 Run specified binary instead of /sbin/init as init
1482 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1483 for working out where the kernel is dying during
1486 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1487 initcall functions. Useful for debugging built-in
1488 modules and initcalls.
1490 initrd= [BOOT] Specify the location of the initial ramdisk
1492 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1495 int_pln_enable [x86] Enable power limit notification interrupt
1497 integrity_audit=[IMA]
1498 Format: { "0" | "1" }
1499 0 -- basic integrity auditing messages. (Default)
1500 1 -- additional integrity auditing messages.
1502 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1504 Enable intel iommu driver.
1506 Disable intel iommu driver.
1507 igfx_off [Default Off]
1508 By default, gfx is mapped as normal device. If a gfx
1509 device has a dedicated DMAR unit, the DMAR unit is
1510 bypassed by not enabling DMAR with this option. In
1511 this case, gfx device will use physical address for
1514 With this option iommu will not optimize to look
1515 for io virtual address below 32-bit forcing dual
1516 address cycle on pci bus for cards supporting greater
1517 than 32-bit addressing. The default is to look
1518 for translation below 32-bit and if not available
1519 then look in the higher range.
1520 strict [Default Off]
1521 With this option on every unmap_single operation will
1522 result in a hardware IOTLB flush operation as opposed
1523 to batching them for performance.
1524 sp_off [Default Off]
1525 By default, super page will be supported if Intel IOMMU
1526 has the capability. With this option, super page will
1528 ecs_off [Default Off]
1529 By default, extended context tables will be supported if
1530 the hardware advertises that it has support both for the
1531 extended tables themselves, and also PASID support. With
1532 this option set, extended tables will not be used even
1533 on hardware which claims to support them.
1535 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1536 0 disables intel_idle and fall back on acpi_idle.
1537 1 to 6 specify maximum depth of C-state.
1541 Do not enable intel_pstate as the default
1542 scaling driver for the supported processors
1544 Enable intel_pstate on systems that prohibit it by default
1545 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1546 instead of acpi-cpufreq may disable platform features, such
1547 as thermal controls and power capping, that rely on ACPI
1548 P-States information being indicated to OSPM and therefore
1549 should be used with caution. This option does not work with
1550 processors that aren't supported by the intel_pstate driver
1551 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1553 Do not enable hardware P state control (HWP)
1556 Only load intel_pstate on systems which support
1557 hardware P state control (HWP) if available.
1559 intremap= [X86-64, Intel-IOMMU]
1560 on enable Interrupt Remapping (default)
1561 off disable Interrupt Remapping
1562 nosid disable Source ID checking
1564 BIOS x2APIC opt-out request will be ignored
1566 iomem= Disable strict checking of access to MMIO memory
1567 strict regions from userspace.
1582 nobypass [PPC/POWERNV]
1583 Disable IOMMU bypass, using IOMMU for PCI devices.
1586 io7= [HW] IO7 for Marvel based alpha systems
1587 See comment before marvel_specify_io7 in
1588 arch/alpha/kernel/core_marvel.c.
1590 io_delay= [X86] I/O delay method
1592 Standard port 0x80 based delay
1594 Alternate port 0xed based delay (needed on some systems)
1596 Simple two microseconds delay
1601 See Documentation/filesystems/nfs/nfsroot.txt.
1604 When an interrupt is not handled search all handlers
1605 for it. Intended to get systems with badly broken
1609 When an interrupt is not handled search all handlers
1610 for it. Also check all handlers each timer
1611 interrupt. Intended to get systems with badly broken
1615 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1617 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1619 <cpu number>,...,<cpu number>
1621 <cpu number>-<cpu number>
1622 (must be a positive range in ascending order)
1624 <cpu number>,...,<cpu number>-<cpu number>
1626 This option can be used to specify one or more CPUs
1627 to isolate from the general SMP balancing and scheduling
1628 algorithms. You can move a process onto or off an
1629 "isolated" CPU via the CPU affinity syscalls or cpuset.
1630 <cpu number> begins at 0 and the maximum value is
1631 "number of CPUs in system - 1".
1633 This option is the preferred way to isolate CPUs. The
1634 alternative -- manually setting the CPU mask of all
1635 tasks in the system -- can cause problems and
1636 suboptimal load balancer performance.
1640 ivrs_ioapic [HW,X86_64]
1641 Provide an override to the IOAPIC-ID<->DEVICE-ID
1642 mapping provided in the IVRS ACPI table. For
1643 example, to map IOAPIC-ID decimal 10 to
1644 PCI device 00:14.0 write the parameter as:
1645 ivrs_ioapic[10]=00:14.0
1647 ivrs_hpet [HW,X86_64]
1648 Provide an override to the HPET-ID<->DEVICE-ID
1649 mapping provided in the IVRS ACPI table. For
1650 example, to map HPET-ID decimal 0 to
1651 PCI device 00:14.0 write the parameter as:
1652 ivrs_hpet[0]=00:14.0
1654 js= [HW,JOY] Analog joystick
1655 See Documentation/input/joystick.txt.
1658 Enable/disable kernel and module base offset ASLR
1659 (Address Space Layout Randomization) if built into
1660 the kernel. When CONFIG_HIBERNATION is selected,
1661 kASLR is disabled by default. When kASLR is enabled,
1662 hibernation will be disabled.
1666 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1667 specifies the amount of memory usable by the kernel
1668 for non-movable allocations. The requested amount is
1669 spread evenly throughout all nodes in the system. The
1670 remaining memory in each node is used for Movable
1671 pages. In the event, a node is too small to have both
1672 kernelcore and Movable pages, kernelcore pages will
1673 take priority and other nodes will have a larger number
1674 of Movable pages. The Movable zone is used for the
1675 allocation of pages that may be reclaimed or moved
1676 by the page migration subsystem. This means that
1677 HugeTLB pages may not be allocated from this zone.
1678 Note that allocations like PTEs-from-HighMem still
1679 use the HighMem zone if it exists, and the Normal
1680 zone if it does not.
1682 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1683 Format: <Controller#>[,poll interval]
1684 The controller # is the number of the ehci usb debug
1685 port as it is probed via PCI. The poll interval is
1686 optional and is the number seconds in between
1687 each poll cycle to the debug port in case you need
1688 the functionality for interrupting the kernel with
1689 gdb or control-c on the dbgp connection. When
1690 not using this parameter you use sysrq-g to break into
1691 the kernel debugger.
1693 kgdboc= [KGDB,HW] kgdb over consoles.
1694 Requires a tty driver that supports console polling,
1695 or a supported polling keyboard driver (non-usb).
1696 Serial only format: <serial_device>[,baud]
1697 keyboard only format: kbd
1698 keyboard and serial format: kbd,<serial_device>[,baud]
1699 Optional Kernel mode setting:
1700 kms, kbd format: kms,kbd
1701 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1703 kgdbwait [KGDB] Stop kernel execution and enter the
1704 kernel debugger at the earliest opportunity.
1706 kmac= [MIPS] korina ethernet MAC address.
1707 Configure the RouterBoard 532 series on-chip
1708 Ethernet adapter MAC address.
1710 kmemleak= [KNL] Boot-time kmemleak enable/disable
1711 Valid arguments: on, off
1713 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1716 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1717 Valid arguments: 0, 1, 2
1718 kmemcheck=0 (disabled)
1719 kmemcheck=1 (enabled)
1720 kmemcheck=2 (one-shot mode)
1721 Default: 2 (one-shot mode)
1723 kstack=N [X86] Print N words from the kernel stack
1726 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1727 Default is 0 (don't ignore, but inject #GP)
1729 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1733 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1734 Default is 1 (enabled)
1736 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1738 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1740 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1741 (virtualized MMU) support on capable Intel chips.
1742 Default is 1 (enabled)
1744 kvm-intel.emulate_invalid_guest_state=
1745 [KVM,Intel] Enable emulation of invalid guest states
1746 Default is 0 (disabled)
1748 kvm-intel.flexpriority=
1749 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1750 Default is 1 (enabled)
1753 [KVM,Intel] Enable VMX nesting (nVMX).
1754 Default is 0 (disabled)
1756 kvm-intel.unrestricted_guest=
1757 [KVM,Intel] Disable unrestricted guest feature
1758 (virtualized real and unpaged mode) on capable
1759 Intel chips. Default is 1 (enabled)
1761 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1762 feature (tagged TLBs) on capable Intel chips.
1763 Default is 1 (enabled)
1769 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1772 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1773 value for LAPIC timer one-shot implementation. Default
1774 back to the programmable timer unit in the LAPIC.
1776 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1779 libata.dma= [LIBATA] DMA control
1780 libata.dma=0 Disable all PATA and SATA DMA
1781 libata.dma=1 PATA and SATA Disk DMA only
1782 libata.dma=2 ATAPI (CDROM) DMA only
1783 libata.dma=4 Compact Flash DMA only
1784 Combinations also work, so libata.dma=3 enables DMA
1785 for disks and CDROMs, but not CFs.
1787 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1788 libata.ignore_hpa=0 keep BIOS limits (default)
1789 libata.ignore_hpa=1 ignore limits, using full disk
1791 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1795 libata.force= [LIBATA] Force configurations. The format is comma
1796 separated list of "[ID:]VAL" where ID is
1797 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1798 matching port, link or device. Basically, it matches
1799 the ATA ID string printed on console by libata. If
1800 the whole ID part is omitted, the last PORT and DEVICE
1801 values are used. If ID hasn't been specified yet, the
1802 configuration applies to all ports, links and devices.
1804 If only DEVICE is omitted, the parameter applies to
1805 the port and all links and devices behind it. DEVICE
1806 number of 0 either selects the first device or the
1807 first fan-out link behind PMP device. It does not
1808 select the host link. DEVICE number of 15 selects the
1809 host link and device attached to it.
1811 The VAL specifies the configuration to force. As long
1812 as there's no ambiguity shortcut notation is allowed.
1813 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1814 The following configurations can be forced.
1816 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1817 Any ID with matching PORT is used.
1819 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1821 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1822 udma[/][16,25,33,44,66,100,133] notation is also
1825 * [no]ncq: Turn on or off NCQ.
1827 * [no]ncqtrim: Turn off queued DSM TRIM.
1829 * nohrst, nosrst, norst: suppress hard, soft
1832 * rstonce: only attempt one reset during
1833 hot-unplug link recovery
1835 * dump_id: dump IDENTIFY data.
1837 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1839 * disable: Disable this device.
1841 If there are multiple matching configurations changing
1842 the same attribute, the last one is used.
1844 memblock=debug [KNL] Enable memblock debug messages.
1846 load_ramdisk= [RAM] List of ramdisks to load from floppy
1847 See Documentation/blockdev/ramdisk.txt.
1849 lockd.nlm_grace_period=P [NFS] Assign grace period.
1852 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1855 lockd.nlm_timeout=T [NFS] Assign timeout value.
1858 lockd.nlm_udpport=M [NFS] Assign UDP port.
1861 locktorture.nreaders_stress= [KNL]
1862 Set the number of locking read-acquisition kthreads.
1863 Defaults to being automatically set based on the
1864 number of online CPUs.
1866 locktorture.nwriters_stress= [KNL]
1867 Set the number of locking write-acquisition kthreads.
1869 locktorture.onoff_holdoff= [KNL]
1870 Set time (s) after boot for CPU-hotplug testing.
1872 locktorture.onoff_interval= [KNL]
1873 Set time (s) between CPU-hotplug operations, or
1874 zero to disable CPU-hotplug testing.
1876 locktorture.shuffle_interval= [KNL]
1877 Set task-shuffle interval (jiffies). Shuffling
1878 tasks allows some CPUs to go into dyntick-idle
1879 mode during the locktorture test.
1881 locktorture.shutdown_secs= [KNL]
1882 Set time (s) after boot system shutdown. This
1883 is useful for hands-off automated testing.
1885 locktorture.stat_interval= [KNL]
1886 Time (s) between statistics printk()s.
1888 locktorture.stutter= [KNL]
1889 Time (s) to stutter testing, for example,
1890 specifying five seconds causes the test to run for
1891 five seconds, wait for five seconds, and so on.
1892 This tests the locking primitive's ability to
1893 transition abruptly to and from idle.
1895 locktorture.torture_runnable= [BOOT]
1896 Start locktorture running at boot time.
1898 locktorture.torture_type= [KNL]
1899 Specify the locking implementation to test.
1901 locktorture.verbose= [KNL]
1902 Enable additional printk() statements.
1904 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1907 loglevel= All Kernel Messages with a loglevel smaller than the
1908 console loglevel will be printed to the console. It can
1909 also be changed with klogd or other programs. The
1910 loglevels are defined as follows:
1912 0 (KERN_EMERG) system is unusable
1913 1 (KERN_ALERT) action must be taken immediately
1914 2 (KERN_CRIT) critical conditions
1915 3 (KERN_ERR) error conditions
1916 4 (KERN_WARNING) warning conditions
1917 5 (KERN_NOTICE) normal but significant condition
1918 6 (KERN_INFO) informational
1919 7 (KERN_DEBUG) debug-level messages
1921 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1922 in bytes. n must be a power of two and greater
1923 than the minimal size. The minimal size is defined
1924 by LOG_BUF_SHIFT kernel config parameter. There is
1925 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1926 that allows to increase the default size depending on
1927 the number of CPUs. See init/Kconfig for more details.
1929 logo.nologo [FB] Disables display of the built-in Linux logo.
1930 This may be used to provide more screen space for
1931 kernel log messages and is useful when debugging
1932 kernel boot problems.
1934 lp=0 [LP] Specify parallel ports to use, e.g,
1935 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1936 lp=reset first parallel port). 'lp=0' disables the
1937 lp=auto printer driver. 'lp=reset' (which can be
1938 specified in addition to the ports) causes
1939 attached printers to be reset. Using
1940 lp=port1,port2,... specifies the parallel ports
1941 to associate lp devices with, starting with
1942 lp0. A port specification may be 'none' to skip
1943 that lp device, or a parport name such as
1944 'parport0'. Specifying 'lp=auto' instead of a
1945 port specification list means that device IDs
1946 from each port should be examined, to see if
1947 an IEEE 1284-compliant printer is attached; if
1948 so, the driver will manage that printer.
1949 See also header of drivers/char/lp.c.
1952 Sets loops_per_jiffy to given constant, thus avoiding
1953 time-consuming boot-time autodetection (up to 250 ms per
1954 CPU). 0 enables autodetection (default). To determine
1955 the correct value for your kernel, boot with normal
1956 autodetection and see what value is printed. Note that
1957 on SMP systems the preset will be applied to all CPUs,
1958 which is likely to cause problems if your CPUs need
1959 significantly divergent settings. An incorrect value
1960 will cause delays in the kernel to be wrong, leading to
1961 unpredictable I/O errors and other breakage. Although
1962 unlikely, in the extreme case this might damage your
1966 Format: <io>,<irq>,<dma>
1968 machvec= [IA-64] Force the use of a particular machine-vector
1969 (machvec) in a generic kernel.
1970 Example: machvec=hpzx1_swiotlb
1972 machtype= [Loongson] Share the same kernel image file between different
1974 Example: machtype=lemote-yeeloong-2f-7inch
1976 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1977 than or equal to this physical address is ignored.
1979 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1980 should make use of. maxcpus=n : n >= 0 limits the
1981 kernel to using 'n' processors. n=0 is a special case,
1982 it is equivalent to "nosmp", which also disables
1985 max_loop= [LOOP] The number of loop block devices that get
1986 (loop.max_loop) unconditionally pre-created at init time. The default
1987 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1988 of statically allocating a predefined number, loop
1989 devices can be requested on-demand with the
1990 /dev/loop-control interface.
1992 mce [X86-32] Machine Check Exception
1994 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1996 md= [HW] RAID subsystems devices and level
1997 See Documentation/md.txt.
2000 Format: <first>,<last>
2001 Specifies range of consoles to be captured by the MDA.
2003 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2004 Amount of memory to be used when the kernel is not able
2005 to see the whole system memory or for test.
2006 [X86] Work as limiting max address. Use together
2007 with memmap= to avoid physical address space collisions.
2008 Without memmap= PCI devices could be placed at addresses
2009 belonging to unused RAM.
2011 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2015 [KNL,SH] Allow user to override the default size for
2016 per-device physically contiguous DMA buffers.
2018 memmap=exactmap [KNL,X86] Enable setting of an exact
2019 E820 memory map, as specified by the user.
2020 Such memmap=exactmap lines can be constructed based on
2021 BIOS output or other requirements. See the memmap=nn@ss
2024 memmap=nn[KMG]@ss[KMG]
2025 [KNL] Force usage of a specific region of memory.
2026 Region of memory to be used is from ss to ss+nn.
2028 memmap=nn[KMG]#ss[KMG]
2029 [KNL,ACPI] Mark specific memory as ACPI data.
2030 Region of memory to be marked is from ss to ss+nn.
2032 memmap=nn[KMG]$ss[KMG]
2033 [KNL,ACPI] Mark specific memory as reserved.
2034 Region of memory to be reserved is from ss to ss+nn.
2035 Example: Exclude memory from 0x18690000-0x1869ffff
2036 memmap=64K$0x18690000
2038 memmap=0x10000$0x18690000
2040 memmap=nn[KMG]!ss[KMG]
2041 [KNL,X86] Mark specific memory as protected.
2042 Region of memory to be used, from ss to ss+nn.
2043 The memory region may be marked as e820 type 12 (0xc)
2044 and is NVDIMM or ADR memory.
2046 memory_corruption_check=0/1 [X86]
2047 Some BIOSes seem to corrupt the first 64k of
2048 memory when doing things like suspend/resume.
2049 Setting this option will scan the memory
2050 looking for corruption. Enabling this will
2051 both detect corruption and prevent the kernel
2052 from using the memory being corrupted.
2053 However, its intended as a diagnostic tool; if
2054 repeatable BIOS-originated corruption always
2055 affects the same memory, you can use memmap=
2056 to prevent the kernel from using that memory.
2058 memory_corruption_check_size=size [X86]
2059 By default it checks for corruption in the low
2060 64k, making this memory unavailable for normal
2061 use. Use this parameter to scan for
2062 corruption in more or less memory.
2064 memory_corruption_check_period=seconds [X86]
2065 By default it checks for corruption every 60
2066 seconds. Use this parameter to check at some
2067 other rate. 0 disables periodic checking.
2069 memtest= [KNL,X86,ARM] Enable memtest
2071 default : 0 <disable>
2072 Specifies the number of memtest passes to be
2073 performed. Each pass selects another test
2074 pattern from a given set of patterns. Memtest
2075 fills the memory with this pattern, validates
2076 memory contents and reserves bad memory
2077 regions that are detected.
2079 meye.*= [HW] Set MotionEye Camera parameters
2080 See Documentation/video4linux/meye.txt.
2082 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2083 Multi-Function General Purpose Timers on AMD Geode
2086 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2087 the BIOS has incorrectly applied a workaround. TinyBIOS
2088 version 0.98 is known to be affected, 0.99 fixes the
2089 problem by letting the user disable the workaround.
2093 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2094 physical address is ignored.
2096 mini2440= [ARM,HW,KNL]
2097 Format:[0..2][b][c][t]
2099 MINI2440 configuration specification:
2100 0 - The attached screen is the 3.5" TFT
2101 1 - The attached screen is the 7" TFT
2102 2 - The VGA Shield is attached (1024x768)
2103 Leaving out the screen size parameter will not load
2104 the TFT driver, and the framebuffer will be left
2106 b - Enable backlight. The TFT backlight pin will be
2107 linked to the kernel VESA blanking code and a GPIO
2108 LED. This parameter is not necessary when using the
2110 c - Enable the s3c camera interface.
2111 t - Reserved for enabling touchscreen support. The
2112 touchscreen support is not enabled in the mainstream
2113 kernel as of 2.6.30, a preliminary port can be found
2114 in the "bleeding edge" mini2440 support kernel at
2115 http://repo.or.cz/w/linux-2.6/mini2440.git
2118 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2119 parameter allows control of the logging verbosity for
2120 the additional memory initialisation checks. A value
2121 of 0 disables mminit logging and a level of 4 will
2122 log everything. Information is printed at KERN_DEBUG
2123 so loglevel=8 may also need to be specified.
2126 [KNL] When CONFIG_MODULE_SIG is set, this means that
2127 modules without (valid) signatures will fail to load.
2128 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2129 is always true, so this option does nothing.
2132 [MOUSE] Maximum time between finger touching and
2133 leaving touchpad surface for touch to be considered
2134 a tap and be reported as a left button click (for
2135 touchpads working in absolute mode only).
2137 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2138 reporting absolute coordinates, such as tablets
2139 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2140 reporting absolute coordinates, such as tablets
2142 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2143 is similar to kernelcore except it specifies the
2144 amount of memory used for migratable allocations.
2145 If both kernelcore and movablecore is specified,
2146 then kernelcore will be at *least* the specified
2147 value but may be more. If movablecore on its own
2148 is specified, the administrator must be careful
2149 that the amount of memory usable for all allocations
2152 movable_node [KNL,X86] Boot-time switch to enable the effects
2153 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2155 MTD_Partition= [MTD]
2156 Format: <name>,<region-number>,<size>,<offset>
2158 MTD_Region= [MTD] Format:
2159 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2162 See drivers/mtd/cmdlinepart.c.
2164 multitce=off [PPC] This parameter disables the use of the pSeries
2165 firmware feature for updating multiple TCE entries
2168 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2170 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2172 boundary - index of last SLC block on Flex-OneNAND.
2173 The remaining blocks are configured as MLC blocks.
2174 lock - Configure if Flex-OneNAND boundary should be locked.
2175 Once locked, the boundary cannot be changed.
2176 1 indicates lock status, 0 indicates unlock status.
2179 ARM/S3C2412 JIVE boot control
2181 See arch/arm/mach-s3c2412/mach-jive.c
2183 mtouchusb.raw_coordinates=
2184 [HW] Make the MicroTouch USB driver use raw coordinates
2185 ('y', default) or cooked coordinates ('n')
2187 mtrr_chunk_size=nn[KMG] [X86]
2188 used for mtrr cleanup. It is largest continuous chunk
2189 that could hold holes aka. UC entries.
2191 mtrr_gran_size=nn[KMG] [X86]
2192 Used for mtrr cleanup. It is granularity of mtrr block.
2194 Large value could prevent small alignment from
2197 mtrr_spare_reg_nr=n [X86]
2199 Range: 0,7 : spare reg number
2201 Used for mtrr cleanup. It is spare mtrr entries number.
2202 Set to 2 or more if your graphical card needs more.
2204 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2206 netdev= [NET] Network devices parameters
2207 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2208 Note that mem_start is often overloaded to mean
2209 something different and driver-specific.
2210 This usage is only documented in each driver source
2214 [NETFILTER] Enable connection tracking flow accounting
2215 0 to disable accounting
2216 1 to enable accounting
2219 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2220 See Documentation/filesystems/nfs/nfsroot.txt.
2222 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2223 See Documentation/filesystems/nfs/nfsroot.txt.
2225 nfsrootdebug [NFS] enable nfsroot debugging messages.
2226 See Documentation/filesystems/nfs/nfsroot.txt.
2228 nfs.callback_tcpport=
2229 [NFS] set the TCP port on which the NFSv4 callback
2230 channel should listen.
2233 [NFS] sets the pathname to the program which is used
2234 to update the NFS client cache entries.
2236 nfs.cache_getent_timeout=
2237 [NFS] sets the timeout after which an attempt to
2238 update a cache entry is deemed to have failed.
2240 nfs.idmap_cache_timeout=
2241 [NFS] set the maximum lifetime for idmapper cache
2245 [NFS] enable 64-bit inode numbers.
2246 If zero, the NFS client will fake up a 32-bit inode
2247 number for the readdir() and stat() syscalls instead
2248 of returning the full 64-bit number.
2249 The default is to return 64-bit inode numbers.
2251 nfs.max_session_slots=
2252 [NFSv4.1] Sets the maximum number of session slots
2253 the client will attempt to negotiate with the server.
2254 This limits the number of simultaneous RPC requests
2255 that the client can send to the NFSv4.1 server.
2256 Note that there is little point in setting this
2257 value higher than the max_tcp_slot_table_limit.
2259 nfs.nfs4_disable_idmapping=
2260 [NFSv4] When set to the default of '1', this option
2261 ensures that both the RPC level authentication
2262 scheme and the NFS level operations agree to use
2263 numeric uids/gids if the mount is using the
2264 'sec=sys' security flavour. In effect it is
2265 disabling idmapping, which can make migration from
2266 legacy NFSv2/v3 systems to NFSv4 easier.
2267 Servers that do not support this mode of operation
2268 will be autodetected by the client, and it will fall
2269 back to using the idmapper.
2270 To turn off this behaviour, set the value to '0'.
2272 [NFS4] Specify an additional fixed unique ident-
2273 ification string that NFSv4 clients can insert into
2274 their nfs_client_id4 string. This is typically a
2275 UUID that is generated at system install time.
2277 nfs.send_implementation_id =
2278 [NFSv4.1] Send client implementation identification
2279 information in exchange_id requests.
2280 If zero, no implementation identification information
2282 The default is to send the implementation identification
2285 nfs.recover_lost_locks =
2286 [NFSv4] Attempt to recover locks that were lost due
2287 to a lease timeout on the server. Please note that
2288 doing this risks data corruption, since there are
2289 no guarantees that the file will remain unchanged
2290 after the locks are lost.
2291 If you want to enable the kernel legacy behaviour of
2292 attempting to recover these locks, then set this
2294 The default parameter value of '0' causes the kernel
2295 not to attempt recovery of lost locks.
2297 nfsd.nfs4_disable_idmapping=
2298 [NFSv4] When set to the default of '1', the NFSv4
2299 server will return only numeric uids and gids to
2300 clients using auth_sys, and will accept numeric uids
2301 and gids from such clients. This is intended to ease
2302 migration from NFSv2/v3.
2304 objlayoutdriver.osd_login_prog=
2305 [NFS] [OBJLAYOUT] sets the pathname to the program which
2306 is used to automatically discover and login into new
2307 osd-targets. Please see:
2308 Documentation/filesystems/pnfs.txt for more explanations
2310 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2311 when a NMI is triggered.
2312 Format: [state][,regs][,debounce][,die]
2314 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2315 Format: [panic,][nopanic,][num]
2317 0 - turn nmi_watchdog off
2318 1 - turn nmi_watchdog on
2319 When panic is specified, panic when an NMI watchdog
2320 timeout occurs (or 'nopanic' to override the opposite
2322 This is useful when you use a panic=... timeout and
2323 need the box quickly up again.
2325 netpoll.carrier_timeout=
2326 [NET] Specifies amount of time (in seconds) that
2327 netpoll should wait for a carrier. By default netpoll
2330 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2331 emulation library even if a 387 maths coprocessor
2335 [HW] Never suspend the console
2336 Disable suspending of consoles during suspend and
2337 hibernate operations. Once disabled, debugging
2338 messages can reach various consoles while the rest
2339 of the system is being put to sleep (ie, while
2340 debugging driver suspend/resume hooks). This may
2341 not work reliably with all consoles, but is known
2342 to work with serial and VGA consoles.
2343 To facilitate more flexible debugging, we also add
2344 console_suspend, a printk module parameter to control
2345 it. Users could use console_suspend (usually
2346 /sys/module/printk/parameters/console_suspend) to
2347 turn on/off it dynamically.
2349 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2350 caches in the slab allocator. Saves per-node memory,
2351 but will impact performance.
2355 noapic [SMP,APIC] Tells the kernel to not make use of any
2356 IOAPICs that may be present in the system.
2358 noautogroup Disable scheduler automatic task group creation.
2360 nobats [PPC] Do not use BATs for mapping kernel lowmem
2361 on "Classic" PPC cores.
2365 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2367 nodelayacct [KNL] Disable per-task delay accounting
2369 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2371 nodsp [SH] Disable hardware DSP at boot time.
2373 noefi Disable EFI runtime services support.
2378 On X86-32 available only on PAE configured kernels.
2379 noexec=on: enable non-executable mappings (default)
2380 noexec=off: disable non-executable mappings
2383 Disable SMAP (Supervisor Mode Access Prevention)
2384 even if it is supported by processor.
2387 Disable SMEP (Supervisor Mode Execution Prevention)
2388 even if it is supported by processor.
2391 This affects only 32-bit executables.
2392 noexec32=on: enable non-executable mappings (default)
2393 read doesn't imply executable mappings
2394 noexec32=off: disable non-executable mappings
2395 read implies executable mappings
2397 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2399 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2400 register save and restore. The kernel will only save
2401 legacy floating-point registers on task switch.
2403 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2405 noxsave [BUGS=X86] Disables x86 extended register state save
2406 and restore using xsave. The kernel will fallback to
2407 enabling legacy floating-point and sse state.
2409 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2410 register states. The kernel will fall back to use
2411 xsave to save the states. By using this parameter,
2412 performance of saving the states is degraded because
2413 xsave doesn't support modified optimization while
2414 xsaveopt supports it on xsaveopt enabled systems.
2416 noxsaves [X86] Disables xsaves and xrstors used in saving and
2417 restoring x86 extended register state in compacted
2418 form of xsave area. The kernel will fall back to use
2419 xsaveopt and xrstor to save and restore the states
2420 in standard form of xsave area. By using this
2421 parameter, xsave area per process might occupy more
2422 memory on xsaves enabled systems.
2424 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2425 wfi(ARM) instruction doesn't work correctly and not to
2426 use it. This is also useful when using JTAG debugger.
2428 no_file_caps Tells the kernel not to honor file capabilities. The
2429 only way then for a file to be executed with privilege
2430 is to be setuid root or executed by root.
2432 nohalt [IA-64] Tells the kernel not to use the power saving
2433 function PAL_HALT_LIGHT when idle. This increases
2434 power-consumption. On the positive side, it reduces
2435 interrupt wake-up latency, which may improve performance
2436 in certain environments such as networked servers or
2439 nohibernate [HIBERNATION] Disable hibernation and resume.
2441 nohz= [KNL] Boottime enable/disable dynamic ticks
2442 Valid arguments: on, off
2445 nohz_full= [KNL,BOOT]
2446 In kernels built with CONFIG_NO_HZ_FULL=y, set
2447 the specified list of CPUs whose tick will be stopped
2448 whenever possible. The boot CPU will be forced outside
2449 the range to maintain the timekeeping.
2450 The CPUs in this range must also be included in the
2453 noiotrap [SH] Disables trapped I/O port accesses.
2455 noirqdebug [X86-32] Disables the code which attempts to detect and
2456 disable unhandled interrupt sources.
2458 no_timer_check [X86,APIC] Disables the code which tests for
2459 broken timer IRQ sources.
2461 noisapnp [ISAPNP] Disables ISA PnP code.
2463 noinitrd [RAM] Tells the kernel not to load any configured
2466 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2468 [Deprecated - use intremap=off]
2472 nojitter [IA-64] Disables jitter checking for ITC timers.
2474 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2476 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2479 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2480 steal time is computed, but won't influence scheduler
2483 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2485 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2487 noltlbs [PPC] Do not use large page/tlb entries for kernel
2488 lowmem mapping on PPC40x.
2490 nomca [IA-64] Disable machine check abort handling
2492 nomce [X86-32] Disable Machine Check Exception
2494 nomfgpt [X86-32] Disable Multi-Function General Purpose
2495 Timer usage (for AMD Geode machines).
2497 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2498 shutdown the other cpus. Instead use the REBOOT_VECTOR
2501 nomodule Disable module load
2503 nopat [X86] Disable PAT (page attribute table extension of
2504 pagetables) support.
2506 norandmaps Don't use address space randomization. Equivalent to
2507 echo 0 > /proc/sys/kernel/randomize_va_space
2509 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2511 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2512 with UP alternatives
2514 nordrand [X86] Disable kernel use of the RDRAND and
2515 RDSEED instructions even if they are supported
2516 by the processor. RDRAND and RDSEED are still
2517 available to user space applications.
2519 noresume [SWSUSP] Disables resume and restores original swap
2522 no-scroll [VGA] Disables scrollback.
2523 This is required for the Braillex ib80-piezo Braille
2524 reader made by F.H. Papenmeier (Germany).
2528 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2530 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2531 and disable the IO APIC. legacy for "maxcpus=0".
2533 nosoftlockup [KNL] Disable the soft-lockup detector.
2535 nosync [HW,M68K] Disables sync negotiation for all devices.
2537 notsc [BUGS=X86-32] Disable Time Stamp Counter
2539 nousb [USB] Disable the USB subsystem
2541 nowatchdog [KNL] Disable both lockup detectors, i.e.
2542 soft-lockup and NMI watchdog (hard-lockup).
2546 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2548 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2549 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2550 Some features depend on CPU0. Known dependencies are:
2551 1. Resume from suspend/hibernate depends on CPU0.
2552 Suspend/hibernate will fail if CPU0 is offline and you
2553 need to online CPU0 before suspend/hibernate.
2554 2. PIC interrupts also depend on CPU0. CPU0 can't be
2555 removed if a PIC interrupt is detected.
2556 It's said poweroff/reboot may depend on CPU0 on some
2557 machines although I haven't seen such issues so far
2558 after CPU0 is offline on a few tested machines.
2559 If the dependencies are under your control, you can
2560 turn on cpu0_hotplug.
2562 nptcg= [IA-64] Override max number of concurrent global TLB
2563 purges which is reported from either PAL_VM_SUMMARY or
2566 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2567 could support. nr_cpus=n : n >= 1 limits the kernel to
2568 supporting 'n' processors. Later in runtime you can not
2569 use hotplug cpu feature to put more cpu back to online.
2570 just like you compile the kernel NR_CPUS=n
2572 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2574 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2575 Allowed values are enable and disable
2577 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2578 one of ['zone', 'node', 'default'] can be specified
2579 This can be set from sysctl after boot.
2580 See Documentation/sysctl/vm.txt for details.
2582 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2583 See Documentation/debugging-via-ohci1394.txt for more
2586 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2587 Rather than timing out after 20 ms if an EC
2588 command is not properly ACKed, override the length
2589 of the timeout. We have interrupts disabled while
2590 waiting for the ACK, so if this is set too high
2591 interrupts *may* be lost!
2593 omap_mux= [OMAP] Override bootloader pin multiplexing.
2594 Format: <mux_mode0.mode_name=value>...
2595 For example, to override I2C bus2:
2596 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2598 oprofile.timer= [HW]
2599 Use timer interrupt instead of performance counters
2601 oprofile.cpu_type= Force an oprofile cpu type
2602 This might be useful if you have an older oprofile
2603 userland or if you want common events.
2604 Format: { arch_perfmon }
2605 arch_perfmon: [X86] Force use of architectural
2606 perfmon on Intel CPUs instead of the
2607 CPU specific event set.
2608 timer: [X86] Force use of architectural NMI
2609 timer mode (see also oprofile.timer
2610 for generic hr timer mode)
2611 [s390] Force legacy basic mode sampling
2612 (report cpu_type "timer")
2614 oops=panic Always panic on oopses. Default is to just kill the
2615 process, but there is a small probability of
2616 deadlocking the machine.
2617 This will also cause panics on machine check exceptions.
2618 Useful together with panic=30 to trigger a reboot.
2621 See Documentation/sound/oss/oss-parameters.txt
2623 page_owner= [KNL] Boot-time page_owner enabling option.
2624 Storage of the information about who allocated
2625 each page is disabled in default. With this switch,
2627 on: enable the feature
2629 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2630 timeout > 0: seconds before rebooting
2631 timeout = 0: wait forever
2632 timeout < 0: reboot immediately
2635 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2638 crash_kexec_post_notifiers
2639 Run kdump after running panic-notifiers and dumping
2640 kmsg. This only for the users who doubt kdump always
2641 succeeds in any situation.
2642 Note that this also increases risks of kdump failure,
2643 because some panic notifiers can make the crashed
2644 kernel more unstable.
2646 parkbd.port= [HW] Parallel port number the keyboard adapter is
2647 connected to, default is 0.
2649 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2650 0 for XT, 1 for AT (default is AT).
2653 parport= [HW,PPT] Specify parallel ports. 0 disables.
2654 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2655 Use 'auto' to force the driver to use any
2656 IRQ/DMA settings detected (the default is to
2657 ignore detected IRQ/DMA settings because of
2658 possible conflicts). You can specify the base
2659 address, IRQ, and DMA settings; IRQ and DMA
2660 should be numbers, or 'auto' (for using detected
2661 settings on that particular port), or 'nofifo'
2662 (to avoid using a FIFO even if it is detected).
2663 Parallel ports are assigned in the order they
2664 are specified on the command line, starting
2667 parport_init_mode= [HW,PPT]
2668 Configure VIA parallel port to operate in
2669 a specific mode. This is necessary on Pegasos
2670 computer where firmware has no options for setting
2671 up parallel port mode and sets it to spp.
2672 Currently this function knows 686a and 8231 chips.
2673 Format: [spp|ps2|epp|ecp|ecpepp]
2676 Halt all CPUs after the first oops has been printed for
2677 the specified number of seconds. This is to be used if
2678 your oopses keep scrolling off the screen.
2683 See header of drivers/block/paride/pcd.c.
2684 See also Documentation/blockdev/paride.txt.
2686 pci=option[,option...] [PCI] various PCI subsystem options:
2687 earlydump [X86] dump PCI config space before the kernel
2689 off [X86] don't probe for the PCI bus
2690 bios [X86-32] force use of PCI BIOS, don't access
2691 the hardware directly. Use this if your machine
2692 has a non-standard PCI host bridge.
2693 nobios [X86-32] disallow use of PCI BIOS, only direct
2694 hardware access methods are allowed. Use this
2695 if you experience crashes upon bootup and you
2696 suspect they are caused by the BIOS.
2697 conf1 [X86] Force use of PCI Configuration
2699 conf2 [X86] Force use of PCI Configuration
2701 noaer [PCIE] If the PCIEAER kernel config parameter is
2702 enabled, this kernel boot option can be used to
2703 disable the use of PCIE advanced error reporting.
2704 nodomains [PCI] Disable support for multiple PCI
2705 root domains (aka PCI segments, in ACPI-speak).
2706 nommconf [X86] Disable use of MMCONFIG for PCI
2708 check_enable_amd_mmconf [X86] check for and enable
2709 properly configured MMIO access to PCI
2710 config space on AMD family 10h CPU
2711 nomsi [MSI] If the PCI_MSI kernel config parameter is
2712 enabled, this kernel boot option can be used to
2713 disable the use of MSI interrupts system-wide.
2714 noioapicquirk [APIC] Disable all boot interrupt quirks.
2715 Safety option to keep boot IRQs enabled. This
2716 should never be necessary.
2717 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2718 primary IO-APIC for bridges that cannot disable
2719 boot IRQs. This fixes a source of spurious IRQs
2720 when the system masks IRQs.
2721 noioapicreroute [APIC] Disable workaround that uses the
2722 boot IRQ equivalent of an IRQ that connects to
2723 a chipset where boot IRQs cannot be disabled.
2724 The opposite of ioapicreroute.
2725 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2726 routing table. These calls are known to be buggy
2727 on several machines and they hang the machine
2728 when used, but on other computers it's the only
2729 way to get the interrupt routing table. Try
2730 this option if the kernel is unable to allocate
2731 IRQs or discover secondary PCI buses on your
2733 rom [X86] Assign address space to expansion ROMs.
2734 Use with caution as certain devices share
2735 address decoders between ROMs and other
2737 norom [X86] Do not assign address space to
2738 expansion ROMs that do not already have
2739 BIOS assigned address ranges.
2740 nobar [X86] Do not assign address space to the
2741 BARs that weren't assigned by the BIOS.
2742 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2743 assigned automatically to PCI devices. You can
2744 make the kernel exclude IRQs of your ISA cards
2746 pirqaddr=0xAAAAA [X86] Specify the physical address
2747 of the PIRQ table (normally generated
2748 by the BIOS) if it is outside the
2749 F0000h-100000h range.
2750 lastbus=N [X86] Scan all buses thru bus #N. Can be
2751 useful if the kernel is unable to find your
2752 secondary buses and you want to tell it
2753 explicitly which ones they are.
2754 assign-busses [X86] Always assign all PCI bus
2755 numbers ourselves, overriding
2756 whatever the firmware may have done.
2757 usepirqmask [X86] Honor the possible IRQ mask stored
2758 in the BIOS $PIR table. This is needed on
2759 some systems with broken BIOSes, notably
2760 some HP Pavilion N5400 and Omnibook XE3
2761 notebooks. This will have no effect if ACPI
2762 IRQ routing is enabled.
2763 noacpi [X86] Do not use ACPI for IRQ routing
2764 or for PCI scanning.
2765 use_crs [X86] Use PCI host bridge window information
2766 from ACPI. On BIOSes from 2008 or later, this
2767 is enabled by default. If you need to use this,
2768 please report a bug.
2769 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2770 If you need to use this, please report a bug.
2771 routeirq Do IRQ routing for all PCI devices.
2772 This is normally done in pci_enable_device(),
2773 so this option is a temporary workaround
2774 for broken drivers that don't call it.
2775 skip_isa_align [X86] do not align io start addr, so can
2776 handle more pci cards
2777 firmware [ARM] Do not re-enumerate the bus but instead
2778 just use the configuration from the
2779 bootloader. This is currently used on
2780 IXP2000 systems where the bus has to be
2781 configured a certain way for adjunct CPUs.
2782 noearly [X86] Don't do any early type 1 scanning.
2783 This might help on some broken boards which
2784 machine check when some devices' config space
2785 is read. But various workarounds are disabled
2786 and some IOMMU drivers will not work.
2787 bfsort Sort PCI devices into breadth-first order.
2788 This sorting is done to get a device
2789 order compatible with older (<= 2.4) kernels.
2790 nobfsort Don't sort PCI devices into breadth-first order.
2791 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2792 tuning and use the BIOS-configured MPS defaults.
2793 pcie_bus_safe Set every device's MPS to the largest value
2794 supported by all devices below the root complex.
2795 pcie_bus_perf Set device MPS to the largest allowable MPS
2796 based on its parent bus. Also set MRRS (Max
2797 Read Request Size) to the largest supported
2798 value (no larger than the MPS that the device
2799 or bus can support) for best performance.
2800 pcie_bus_peer2peer Set every device's MPS to 128B, which
2801 every device is guaranteed to support. This
2802 configuration allows peer-to-peer DMA between
2803 any pair of devices, possibly at the cost of
2804 reduced performance. This also guarantees
2805 that hot-added devices will work.
2806 cbiosize=nn[KMG] The fixed amount of bus space which is
2807 reserved for the CardBus bridge's IO window.
2808 The default value is 256 bytes.
2809 cbmemsize=nn[KMG] The fixed amount of bus space which is
2810 reserved for the CardBus bridge's memory
2811 window. The default value is 64 megabytes.
2814 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2815 Specifies alignment and device to reassign
2816 aligned memory resources.
2817 If <order of align> is not specified,
2818 PAGE_SIZE is used as alignment.
2819 PCI-PCI bridge can be specified, if resource
2820 windows need to be expanded.
2821 ecrc= Enable/disable PCIe ECRC (transaction layer
2822 end-to-end CRC checking).
2823 bios: Use BIOS/firmware settings. This is the
2827 hpiosize=nn[KMG] The fixed amount of bus space which is
2828 reserved for hotplug bridge's IO window.
2829 Default size is 256 bytes.
2830 hpmemsize=nn[KMG] The fixed amount of bus space which is
2831 reserved for hotplug bridge's memory window.
2832 Default size is 2 megabytes.
2833 realloc= Enable/disable reallocating PCI bridge resources
2834 if allocations done by BIOS are too small to
2835 accommodate resources required by all child
2837 off: Turn realloc off
2839 realloc same as realloc=on
2840 noari do not use PCIe ARI.
2841 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2842 only look for one device below a PCIe downstream
2845 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2848 force Enable ASPM even on devices that claim not to support it.
2849 WARNING: Forcing ASPM on may cause system lockups.
2851 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2852 nomsi Do not use MSI for PCI Express Native Hotplug (this
2853 makes all PCIe ports use INTx for hotplug services).
2855 pcie_ports= [PCIE] PCIe ports handling:
2856 auto Ask the BIOS whether or not to use native PCIe services
2857 associated with PCIe ports (PME, hot-plug, AER). Use
2858 them only if that is allowed by the BIOS.
2859 native Use native PCIe services associated with PCIe ports
2861 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2864 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2865 nomsi Do not use MSI for native PCIe PME signaling (this makes
2866 all PCIe root ports use INTx for all services).
2868 pcmv= [HW,PCMCIA] BadgePAD 4
2872 Keep all power-domains already enabled by bootloader on,
2873 even if no driver has claimed them. This is useful
2874 for debug and development, but should not be
2875 needed on a platform with proper driver support.
2878 See Documentation/blockdev/paride.txt.
2880 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2883 See arch/parisc/kernel/pdc_chassis.c
2885 percpu_alloc= Select which percpu first chunk allocator to use.
2886 Currently supported values are "embed" and "page".
2887 Archs may support subset or none of the selections.
2888 See comments in mm/percpu.c for details on each
2889 allocator. This parameter is primarily for debugging
2890 and performance comparison.
2893 See Documentation/blockdev/paride.txt.
2896 See Documentation/blockdev/paride.txt.
2898 pirq= [SMP,APIC] Manual mp-table setup
2899 See Documentation/x86/i386/IO-APIC.txt.
2901 plip= [PPT,NET] Parallel port network link
2902 Format: { parport<nr> | timid | 0 }
2903 See also Documentation/parport.txt.
2905 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2906 Override pmtimer IOPort with a hex value.
2910 Enable PNP debug messages (depends on the
2911 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2912 via /sys/module/pnp/parameters/debug. We always show
2913 current resource usage; turning this on also shows
2914 possible settings and some assignment information.
2920 { on | off | curr | res | no-curr | no-res }
2923 [ISAPNP] Exclude IRQs for the autoconfiguration
2926 [ISAPNP] Exclude DMAs for the autoconfiguration
2928 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2929 Ranges are in pairs (I/O port base and size).
2932 [ISAPNP] Exclude memory regions for the
2934 Ranges are in pairs (memory base and size).
2936 ports= [IP_VS_FTP] IPVS ftp helper module
2938 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2940 Format: <port>,<port>....
2942 print-fatal-signals=
2943 [KNL] debug: print fatal signals
2945 If enabled, warn about various signal handling
2946 related application anomalies: too many signals,
2947 too many POSIX.1 timers, fatal signals causing a
2950 If you hit the warning due to signal overflow,
2951 you might want to try "ulimit -i unlimited".
2955 printk.always_kmsg_dump=
2956 Trigger kmsg_dump for cases other than kernel oops or
2958 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2961 printk.time= Show timing data prefixed to each printk message line
2962 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2964 processor.max_cstate= [HW,ACPI]
2965 Limit processor to maximum C-state
2966 max_cstate=9 overrides any DMI blacklist limit.
2968 processor.nocst [HW,ACPI]
2969 Ignore the _CST method to determine C-states,
2970 instead using the legacy FADT method
2972 profile= [KNL] Enable kernel profiling via /proc/profile
2973 Format: [schedule,]<number>
2974 Param: "schedule" - profile schedule points.
2975 Param: <number> - step/bucket size as a power of 2 for
2976 statistical time based profiling.
2977 Param: "sleep" - profile D-state sleeping (millisecs).
2978 Requires CONFIG_SCHEDSTATS
2979 Param: "kvm" - profile VM exits.
2981 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2983 See Documentation/blockdev/ramdisk.txt.
2985 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2986 probe for; one of (bare|imps|exps|lifebook|any).
2987 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2989 psmouse.resetafter= [HW,MOUSE]
2990 Try to reset the device after so many bad packets
2993 [HW,MOUSE] Set desired mouse resolution, in dpi.
2994 psmouse.smartscroll=
2995 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2996 0 = disabled, 1 = enabled (default).
2998 pstore.backend= Specify the name of the pstore backend to use
3001 See Documentation/blockdev/paride.txt.
3004 [KNL] Number of legacy pty's. Overwrites compiled-in
3007 quiet [KNL] Disable most log messages
3012 See Documentation/md.txt.
3014 ramdisk_blocksize= [RAM]
3015 See Documentation/blockdev/ramdisk.txt.
3017 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3018 See Documentation/blockdev/ramdisk.txt.
3021 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3022 the specified list of CPUs to be no-callback CPUs.
3023 Invocation of these CPUs' RCU callbacks will
3024 be offloaded to "rcuox/N" kthreads created for
3025 that purpose, where "x" is "b" for RCU-bh, "p"
3026 for RCU-preempt, and "s" for RCU-sched, and "N"
3027 is the CPU number. This reduces OS jitter on the
3028 offloaded CPUs, which can be useful for HPC and
3029 real-time workloads. It can also improve energy
3030 efficiency for asymmetric multiprocessors.
3033 Rather than requiring that offloaded CPUs
3034 (specified by rcu_nocbs= above) explicitly
3035 awaken the corresponding "rcuoN" kthreads,
3036 make these kthreads poll for callbacks.
3037 This improves the real-time response for the
3038 offloaded CPUs by relieving them of the need to
3039 wake up the corresponding kthread, but degrades
3040 energy efficiency by requiring that the kthreads
3041 periodically wake up to do the polling.
3043 rcutree.blimit= [KNL]
3044 Set maximum number of finished RCU callbacks to
3045 process in one batch.
3047 rcutree.dump_tree= [KNL]
3048 Dump the structure of the rcu_node combining tree
3049 out at early boot. This is used for diagnostic
3050 purposes, to verify correct tree setup.
3052 rcutree.gp_cleanup_delay= [KNL]
3053 Set the number of jiffies to delay each step of
3054 RCU grace-period cleanup. This only has effect
3055 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3057 rcutree.gp_init_delay= [KNL]
3058 Set the number of jiffies to delay each step of
3059 RCU grace-period initialization. This only has
3060 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3063 rcutree.gp_preinit_delay= [KNL]
3064 Set the number of jiffies to delay each step of
3065 RCU grace-period pre-initialization, that is,
3066 the propagation of recent CPU-hotplug changes up
3067 the rcu_node combining tree. This only has effect
3068 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3070 rcutree.rcu_fanout_exact= [KNL]
3071 Disable autobalancing of the rcu_node combining
3072 tree. This is used by rcutorture, and might
3073 possibly be useful for architectures having high
3074 cache-to-cache transfer latencies.
3076 rcutree.rcu_fanout_leaf= [KNL]
3077 Increase the number of CPUs assigned to each
3078 leaf rcu_node structure. Useful for very large
3081 rcutree.jiffies_till_sched_qs= [KNL]
3082 Set required age in jiffies for a
3083 given grace period before RCU starts
3084 soliciting quiescent-state help from
3085 rcu_note_context_switch().
3087 rcutree.jiffies_till_first_fqs= [KNL]
3088 Set delay from grace-period initialization to
3089 first attempt to force quiescent states.
3090 Units are jiffies, minimum value is zero,
3091 and maximum value is HZ.
3093 rcutree.jiffies_till_next_fqs= [KNL]
3094 Set delay between subsequent attempts to force
3095 quiescent states. Units are jiffies, minimum
3096 value is one, and maximum value is HZ.
3098 rcutree.kthread_prio= [KNL,BOOT]
3099 Set the SCHED_FIFO priority of the RCU per-CPU
3100 kthreads (rcuc/N). This value is also used for
3101 the priority of the RCU boost threads (rcub/N)
3102 and for the RCU grace-period kthreads (rcu_bh,
3103 rcu_preempt, and rcu_sched). If RCU_BOOST is
3104 set, valid values are 1-99 and the default is 1
3105 (the least-favored priority). Otherwise, when
3106 RCU_BOOST is not set, valid values are 0-99 and
3107 the default is zero (non-realtime operation).
3109 rcutree.rcu_nocb_leader_stride= [KNL]
3110 Set the number of NOCB kthread groups, which
3111 defaults to the square root of the number of
3112 CPUs. Larger numbers reduces the wakeup overhead
3113 on the per-CPU grace-period kthreads, but increases
3114 that same overhead on each group's leader.
3116 rcutree.qhimark= [KNL]
3117 Set threshold of queued RCU callbacks beyond which
3118 batch limiting is disabled.
3120 rcutree.qlowmark= [KNL]
3121 Set threshold of queued RCU callbacks below which
3122 batch limiting is re-enabled.
3124 rcutree.rcu_idle_gp_delay= [KNL]
3125 Set wakeup interval for idle CPUs that have
3126 RCU callbacks (RCU_FAST_NO_HZ=y).
3128 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3129 Set wakeup interval for idle CPUs that have
3130 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3131 Lazy RCU callbacks are those which RCU can
3132 prove do nothing more than free memory.
3134 rcutorture.cbflood_inter_holdoff= [KNL]
3135 Set holdoff time (jiffies) between successive
3136 callback-flood tests.
3138 rcutorture.cbflood_intra_holdoff= [KNL]
3139 Set holdoff time (jiffies) between successive
3140 bursts of callbacks within a given callback-flood
3143 rcutorture.cbflood_n_burst= [KNL]
3144 Set the number of bursts making up a given
3145 callback-flood test. Set this to zero to
3146 disable callback-flood testing.
3148 rcutorture.cbflood_n_per_burst= [KNL]
3149 Set the number of callbacks to be registered
3150 in a given burst of a callback-flood test.
3152 rcutorture.fqs_duration= [KNL]
3153 Set duration of force_quiescent_state bursts.
3155 rcutorture.fqs_holdoff= [KNL]
3156 Set holdoff time within force_quiescent_state bursts.
3158 rcutorture.fqs_stutter= [KNL]
3159 Set wait time between force_quiescent_state bursts.
3161 rcutorture.gp_exp= [KNL]
3162 Use expedited update-side primitives.
3164 rcutorture.gp_normal= [KNL]
3165 Use normal (non-expedited) update-side primitives.
3166 If both gp_exp and gp_normal are set, do both.
3167 If neither gp_exp nor gp_normal are set, still
3170 rcutorture.n_barrier_cbs= [KNL]
3171 Set callbacks/threads for rcu_barrier() testing.
3173 rcutorture.nfakewriters= [KNL]
3174 Set number of concurrent RCU writers. These just
3175 stress RCU, they don't participate in the actual
3176 test, hence the "fake".
3178 rcutorture.nreaders= [KNL]
3179 Set number of RCU readers. The value -1 selects
3180 N-1, where N is the number of CPUs. A value
3181 "n" less than -1 selects N-n-2, where N is again
3182 the number of CPUs. For example, -2 selects N
3183 (the number of CPUs), -3 selects N+1, and so on.
3185 rcutorture.object_debug= [KNL]
3186 Enable debug-object double-call_rcu() testing.
3188 rcutorture.onoff_holdoff= [KNL]
3189 Set time (s) after boot for CPU-hotplug testing.
3191 rcutorture.onoff_interval= [KNL]
3192 Set time (s) between CPU-hotplug operations, or
3193 zero to disable CPU-hotplug testing.
3195 rcutorture.torture_runnable= [BOOT]
3196 Start rcutorture running at boot time.
3198 rcutorture.shuffle_interval= [KNL]
3199 Set task-shuffle interval (s). Shuffling tasks
3200 allows some CPUs to go into dyntick-idle mode
3201 during the rcutorture test.
3203 rcutorture.shutdown_secs= [KNL]
3204 Set time (s) after boot system shutdown. This
3205 is useful for hands-off automated testing.
3207 rcutorture.stall_cpu= [KNL]
3208 Duration of CPU stall (s) to test RCU CPU stall
3209 warnings, zero to disable.
3211 rcutorture.stall_cpu_holdoff= [KNL]
3212 Time to wait (s) after boot before inducing stall.
3214 rcutorture.stat_interval= [KNL]
3215 Time (s) between statistics printk()s.
3217 rcutorture.stutter= [KNL]
3218 Time (s) to stutter testing, for example, specifying
3219 five seconds causes the test to run for five seconds,
3220 wait for five seconds, and so on. This tests RCU's
3221 ability to transition abruptly to and from idle.
3223 rcutorture.test_boost= [KNL]
3224 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3225 "Maybe" means test if the RCU implementation
3226 under test support RCU priority boosting.
3228 rcutorture.test_boost_duration= [KNL]
3229 Duration (s) of each individual boost test.
3231 rcutorture.test_boost_interval= [KNL]
3232 Interval (s) between each boost test.
3234 rcutorture.test_no_idle_hz= [KNL]
3235 Test RCU's dyntick-idle handling. See also the
3236 rcutorture.shuffle_interval parameter.
3238 rcutorture.torture_type= [KNL]
3239 Specify the RCU implementation to test.
3241 rcutorture.verbose= [KNL]
3242 Enable additional printk() statements.
3244 rcupdate.rcu_expedited= [KNL]
3245 Use expedited grace-period primitives, for
3246 example, synchronize_rcu_expedited() instead
3247 of synchronize_rcu(). This reduces latency,
3248 but can increase CPU utilization, degrade
3249 real-time latency, and degrade energy efficiency.
3251 rcupdate.rcu_cpu_stall_suppress= [KNL]
3252 Suppress RCU CPU stall warning messages.
3254 rcupdate.rcu_cpu_stall_timeout= [KNL]
3255 Set timeout for RCU CPU stall warning messages.
3257 rcupdate.rcu_task_stall_timeout= [KNL]
3258 Set timeout in jiffies for RCU task stall warning
3259 messages. Disable with a value less than or equal
3262 rcupdate.rcu_self_test= [KNL]
3263 Run the RCU early boot self tests
3265 rcupdate.rcu_self_test_bh= [KNL]
3266 Run the RCU bh early boot self tests
3268 rcupdate.rcu_self_test_sched= [KNL]
3269 Run the RCU sched early boot self tests
3273 Run specified binary instead of /init from the ramdisk,
3274 used for early userspace startup. See initrd.
3277 Format (x86 or x86_64):
3278 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3280 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3282 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3283 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3284 reboot_force is either force or not specified,
3285 reboot_cpu is s[mp]#### with #### being the processor
3286 to be used for rebooting.
3289 [KNL, SMP] Set scheduler's default relax_domain_level.
3290 See Documentation/cgroups/cpusets.txt.
3292 relative_sleep_states=
3293 [SUSPEND] Use sleep state labeling where the deepest
3294 state available other than hibernation is always "mem".
3295 Format: { "0" | "1" }
3296 0 -- Traditional sleep state labels.
3297 1 -- Relative sleep state labels.
3299 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3301 reservetop= [X86-32]
3303 Reserves a hole at the top of the kernel virtual
3308 Set the amount of memory to reserve for BIOS at
3309 the bottom of the address space.
3311 reset_devices [KNL] Force drivers to reset the underlying device
3312 during initialization.
3315 Specify the partition device for software suspend
3317 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3319 resume_offset= [SWSUSP]
3320 Specify the offset from the beginning of the partition
3321 given by "resume=" at which the swap header is located,
3322 in <PAGE_SIZE> units (needed only for swap files).
3323 See Documentation/power/swsusp-and-swap-files.txt
3325 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3326 read the resume files
3328 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3329 Useful for devices that are detected asynchronously
3330 (e.g. USB and MMC devices).
3332 hibernate= [HIBERNATION]
3333 noresume Don't check if there's a hibernation image
3334 present during boot.
3335 nocompress Don't compress/decompress hibernation images.
3336 no Disable hibernation and resume.
3338 retain_initrd [RAM] Keep initrd memory after extraction
3340 rfkill.default_state=
3341 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3342 etc. communication is blocked by default.
3345 rfkill.master_switch_mode=
3346 0 The "airplane mode" button does nothing.
3347 1 The "airplane mode" button toggles between everything
3348 blocked and the previous configuration.
3349 2 The "airplane mode" button toggles between everything
3350 blocked and everything unblocked.
3352 rhash_entries= [KNL,NET]
3353 Set number of hash buckets for route cache
3355 ro [KNL] Mount root device read-only on boot
3357 root= [KNL] Root filesystem
3358 See name_to_dev_t comment in init/do_mounts.c.
3360 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3361 mount the root filesystem
3363 rootflags= [KNL] Set root filesystem mount option string
3365 rootfstype= [KNL] Set root filesystem type
3367 rootwait [KNL] Wait (indefinitely) for root device to show up.
3368 Useful for devices that are detected asynchronously
3369 (e.g. USB and MMC devices).
3371 rproc_mem=nn[KMG][@address]
3372 [KNL,ARM,CMA] Remoteproc physical memory block.
3373 Memory area to be used by remote processor image,
3376 rw [KNL] Mount root device read-write on boot
3378 S [KNL] Run init in single mode
3380 s390_iommu= [HW,S390]
3381 Set s390 IOTLB flushing mode
3383 With strict flushing every unmap operation will result in
3384 an IOTLB flush. Default is lazy flushing before reuse,
3388 See drivers/net/irda/sa1100_ir.c.
3390 sbni= [NET] Granch SBNI12 leased line adapter
3392 sched_debug [KNL] Enables verbose scheduler debug messages.
3394 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3395 xtime_lock contention on larger systems, and/or RCU lock
3396 contention on all systems with CONFIG_MAXSMP set.
3397 Format: { "0" | "1" }
3398 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3400 Note: increases power consumption, thus should only be
3401 enabled if running jitter sensitive (HPC/RT) workloads.
3403 security= [SECURITY] Choose a security module to enable at boot.
3404 If this boot parameter is not specified, only the first
3405 security module asking for security registration will be
3406 loaded. An invalid security module name will be treated
3407 as if no module has been chosen.
3409 selinux= [SELINUX] Disable or enable SELinux at boot time.
3410 Format: { "0" | "1" }
3411 See security/selinux/Kconfig help text.
3414 Default value is set via kernel config option.
3415 If enabled at boot time, /selinux/disable can be used
3416 later to disable prior to initial policy load.
3418 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3419 Format: { "0" | "1" }
3420 See security/apparmor/Kconfig help text
3423 Default value is set via kernel config option.
3425 serialnumber [BUGS=X86-32]
3428 Maximal number of shapers.
3430 show_msr= [x86] show boot-time MSR settings
3431 Format: { <integer> }
3432 Show boot-time (BIOS-initialized) MSR settings.
3433 The parameter means the number of CPUs to show,
3434 for example 1 means boot CPU only.
3442 Disable merging of slabs with similar size. May be
3443 necessary if there is some reason to distinguish
3444 allocs to different slabs. Debug options disable
3445 merging on their own.
3446 For more information see Documentation/vm/slub.txt.
3448 slab_max_order= [MM, SLAB]
3449 Determines the maximum allowed order for slabs.
3450 A high setting may cause OOMs due to memory
3451 fragmentation. Defaults to 1 for systems with
3452 more than 32MB of RAM, 0 otherwise.
3454 slub_debug[=options[,slabs]] [MM, SLUB]
3455 Enabling slub_debug allows one to determine the
3456 culprit if slab objects become corrupted. Enabling
3457 slub_debug can create guard zones around objects and
3458 may poison objects when not in use. Also tracks the
3459 last alloc / free. For more information see
3460 Documentation/vm/slub.txt.
3462 slub_max_order= [MM, SLUB]
3463 Determines the maximum allowed order for slabs.
3464 A high setting may cause OOMs due to memory
3465 fragmentation. For more information see
3466 Documentation/vm/slub.txt.
3468 slub_min_objects= [MM, SLUB]
3469 The minimum number of objects per slab. SLUB will
3470 increase the slab order up to slub_max_order to
3471 generate a sufficiently large slab able to contain
3472 the number of objects indicated. The higher the number
3473 of objects the smaller the overhead of tracking slabs
3474 and the less frequently locks need to be acquired.
3475 For more information see Documentation/vm/slub.txt.
3477 slub_min_order= [MM, SLUB]
3478 Determines the minimum page order for slabs. Must be
3479 lower than slub_max_order.
3480 For more information see Documentation/vm/slub.txt.
3482 slub_nomerge [MM, SLUB]
3483 Same with slab_nomerge. This is supported for legacy.
3484 See slab_nomerge for more information.
3487 Format: <io1>[,<io2>[,...,<io8>]]
3489 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3490 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3491 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3492 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3493 smsc-ircc2.ircc_irq= [HW] IRQ line
3494 smsc-ircc2.ircc_dma= [HW] DMA channel
3495 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3496 0: Toshiba Satellite 1800 (GP data pin select)
3497 1: Fast pin select (default)
3501 [KNL] Should the soft-lockup detector generate panics.
3504 softlockup_all_cpu_backtrace=
3505 [KNL] Should the soft-lockup detector generate
3506 backtraces on all cpus.
3509 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3510 See Documentation/laptops/sonypi.txt
3512 spia_io_base= [HW,MTD]
3518 Enabled the stack tracer on boot up.
3520 stacktrace_filter=[function-list]
3521 [FTRACE] Limit the functions that the stack tracer
3522 will trace at boot up. function-list is a comma separated
3523 list of functions. This list can be changed at run
3524 time by the stack_trace_filter file in the debugfs
3525 tracing directory. Note, this enables stack tracing
3526 and the stacktrace above is not needed.
3530 Set the STI (builtin display/keyboard on the HP-PARISC
3531 machines) console (graphic card) which should be used
3532 as the initial boot-console.
3533 See also comment in drivers/video/console/sticore.c.
3536 See comment in drivers/video/console/sticore.c.
3539 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3541 sunrpc.min_resvport=
3542 sunrpc.max_resvport=
3544 SunRPC servers often require that client requests
3545 originate from a privileged port (i.e. a port in the
3546 range 0 < portnr < 1024).
3547 An administrator who wishes to reserve some of these
3548 ports for other uses may adjust the range that the
3549 kernel's sunrpc client considers to be privileged
3550 using these two parameters to set the minimum and
3551 maximum port values.
3555 Control how the NFS server code allocates CPUs to
3556 service thread pools. Depending on how many NICs
3557 you have and where their interrupts are bound, this
3558 option will affect which CPUs will do NFS serving.
3559 Note: this parameter cannot be changed while the
3560 NFS server is running.
3562 auto the server chooses an appropriate mode
3563 automatically using heuristics
3564 global a single global pool contains all CPUs
3565 percpu one pool for each CPU
3566 pernode one pool for each NUMA node (equivalent
3567 to global on non-NUMA machines)
3569 sunrpc.tcp_slot_table_entries=
3570 sunrpc.udp_slot_table_entries=
3572 Sets the upper limit on the number of simultaneous
3573 RPC calls that can be sent from the client to a
3574 server. Increasing these values may allow you to
3575 improve throughput, but will also increase the
3576 amount of memory reserved for use by the client.
3578 suspend.pm_test_delay=
3580 Sets the number of seconds to remain in a suspend test
3581 mode before resuming the system (see
3582 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3583 is set. Default value is 5.
3586 [KNL] Enable accounting of swap in memory resource
3587 controller if no parameter or 1 is given or disable
3588 it if 0 is given (See Documentation/cgroups/memory.txt)
3590 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3591 Format: { <int> | force }
3592 <int> -- Number of I/O TLB slabs
3593 force -- force using of bounce buffers even if they
3594 wouldn't be automatically used by the kernel
3598 sysfs.deprecated=0|1 [KNL]
3599 Enable/disable old style sysfs layout for old udev
3600 on older distributions. When this option is enabled
3601 very new udev will not work anymore. When this option
3602 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3603 in older udev will not work anymore.
3604 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3605 the kernel configuration.
3607 sysrq_always_enabled
3609 Ignore sysrq setting - this boot parameter will
3610 neutralize any effect of /proc/sys/kernel/sysrq.
3611 Useful for debugging.
3613 tcpmhash_entries= [KNL,NET]
3614 Set the number of tcp_metrics_hash slots.
3615 Default value is 8192 or 16384 depending on total
3616 ram pages. This is used to specify the TCP metrics
3617 cache size. See Documentation/networking/ip-sysctl.txt
3618 "tcp_no_metrics_save" section for more details.
3622 test_suspend= [SUSPEND][,N]
3623 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3624 standby suspend) or "freeze" (for suspend type freeze)
3625 as the system sleep state during system startup with
3626 the optional capability to repeat N number of times.
3627 The system is woken from this state using a
3628 wakeup-capable RTC alarm.
3630 thash_entries= [KNL,NET]
3631 Set number of hash buckets for TCP connection
3633 thermal.act= [HW,ACPI]
3634 -1: disable all active trip points in all thermal zones
3635 <degrees C>: override all lowest active trip points
3637 thermal.crt= [HW,ACPI]
3638 -1: disable all critical trip points in all thermal zones
3639 <degrees C>: override all critical trip points
3641 thermal.nocrt= [HW,ACPI]
3642 Set to disable actions on ACPI thermal zone
3643 critical and hot trip points.
3645 thermal.off= [HW,ACPI]
3646 1: disable ACPI thermal control
3648 thermal.psv= [HW,ACPI]
3649 -1: disable all passive trip points
3650 <degrees C>: override all passive trip points to this
3653 thermal.tzp= [HW,ACPI]
3654 Specify global default ACPI thermal zone polling rate
3655 <deci-seconds>: poll all this frequency
3656 0: no polling (default)
3659 Force threading of all interrupt handlers except those
3660 marked explicitly IRQF_NO_THREAD.
3663 Enable the Transcendent memory driver if built-in.
3665 tmem.cleancache=0|1 [KNL, XEN]
3666 Default is on (1). Disable the usage of the cleancache
3667 API to send anonymous pages to the hypervisor.
3669 tmem.frontswap=0|1 [KNL, XEN]
3670 Default is on (1). Disable the usage of the frontswap
3671 API to send swap pages to the hypervisor. If disabled
3672 the selfballooning and selfshrinking are force disabled.
3674 tmem.selfballooning=0|1 [KNL, XEN]
3675 Default is on (1). Disable the driving of swap pages
3678 tmem.selfshrinking=0|1 [KNL, XEN]
3679 Default is on (1). Partial swapoff that immediately
3680 transfers pages from Xen hypervisor back to the
3681 kernel based on different criteria.
3685 Specify if the kernel should make use of the cpu
3686 topology information if the hardware supports this.
3687 The scheduler will make use of this information and
3688 e.g. base its process migration decisions on it.
3691 topology_updates= [KNL, PPC, NUMA]
3693 Specify if the kernel should ignore (off)
3694 topology updates sent by the hypervisor to this
3699 tpm_suspend_pcr=[HW,TPM]
3700 Format: integer pcr id
3701 Specify that at suspend time, the tpm driver
3702 should extend the specified pcr with zeros,
3703 as a workaround for some chips which fail to
3704 flush the last written pcr on TPM_SaveState.
3705 This will guarantee that all the other pcrs
3708 trace_buf_size=nn[KMG]
3709 [FTRACE] will set tracing buffer size on each cpu.
3711 trace_event=[event-list]
3712 [FTRACE] Set and start specified trace events in order
3713 to facilitate early boot debugging.
3714 See also Documentation/trace/events.txt
3716 trace_options=[option-list]
3717 [FTRACE] Enable or disable tracer options at boot.
3718 The option-list is a comma delimited list of options
3719 that can be enabled or disabled just as if you were
3720 to echo the option name into
3722 /sys/kernel/debug/tracing/trace_options
3724 For example, to enable stacktrace option (to dump the
3725 stack trace of each event), add to the command line:
3727 trace_options=stacktrace
3729 See also Documentation/trace/ftrace.txt "trace options"
3733 Have the tracepoints sent to printk as well as the
3734 tracing ring buffer. This is useful for early boot up
3735 where the system hangs or reboots and does not give the
3736 option for reading the tracing buffer or performing a
3737 ftrace_dump_on_oops.
3739 To turn off having tracepoints sent to printk,
3740 echo 0 > /proc/sys/kernel/tracepoint_printk
3741 Note, echoing 1 into this file without the
3742 tracepoint_printk kernel cmdline option has no effect.
3746 Having tracepoints sent to printk() and activating high
3747 frequency tracepoints such as irq or sched, can cause
3748 the system to live lock.
3751 [FTRACE] enable this option to disable tracing when a
3752 warning is hit. This turns off "tracing_on". Tracing can
3753 be enabled again by echoing '1' into the "tracing_on"
3754 file located in /sys/kernel/debug/tracing/
3756 This option is useful, as it disables the trace before
3757 the WARNING dump is called, which prevents the trace to
3758 be filled with content caused by the warning output.
3760 This option can also be set at run time via the sysctl
3761 option: kernel/traceoff_on_warning
3763 transparent_hugepage=
3765 Format: [always|madvise|never]
3766 Can be used to control the default behavior of the system
3767 with respect to transparent hugepages.
3768 See Documentation/vm/transhuge.txt for more details.
3770 tsc= Disable clocksource stability checks for TSC.
3772 [x86] reliable: mark tsc clocksource as reliable, this
3773 disables clocksource verification at runtime, as well
3774 as the stability checks done at bootup. Used to enable
3775 high-resolution timer mode on older hardware, and in
3776 virtualized environment.
3777 [x86] noirqtime: Do not use TSC to do irq accounting.
3778 Used to run time disable IRQ_TIME_ACCOUNTING on any
3779 platforms where RDTSC is slow and this accounting
3782 turbografx.map[2|3]= [HW,JOY]
3783 TurboGraFX parallel port interface
3785 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3786 See also Documentation/input/joystick-parport.txt
3788 udbg-immortal [PPC] When debugging early kernel crashes that
3789 happen after console_init() and before a proper
3790 console driver takes over, this boot options might
3791 help "seeing" what's going on.
3793 uhash_entries= [KNL,NET]
3794 Set number of hash buckets for UDP/UDP-Lite connections
3797 [USB] Ignore overcurrent events (default N).
3798 Some badly-designed motherboards generate lots of
3799 bogus events, for ports that aren't wired to
3800 anything. Set this parameter to avoid log spamming.
3801 Note that genuine overcurrent events won't be
3805 [X86] Cause panic on unknown NMI.
3807 usbcore.authorized_default=
3808 [USB] Default USB device authorization:
3809 (default -1 = authorized except for wireless USB,
3810 0 = not authorized, 1 = authorized)
3812 usbcore.autosuspend=
3813 [USB] The autosuspend time delay (in seconds) used
3814 for newly-detected USB devices (default 2). This
3815 is the time required before an idle device will be
3816 autosuspended. Devices for which the delay is set
3817 to a negative value won't be autosuspended at all.
3819 usbcore.usbfs_snoop=
3820 [USB] Set to log all usbfs traffic (default 0 = off).
3822 usbcore.blinkenlights=
3823 [USB] Set to cycle leds on hubs (default 0 = off).
3825 usbcore.old_scheme_first=
3826 [USB] Start with the old device initialization
3827 scheme (default 0 = off).
3829 usbcore.usbfs_memory_mb=
3830 [USB] Memory limit (in MB) for buffers allocated by
3831 usbfs (default = 16, 0 = max = 2047).
3833 usbcore.use_both_schemes=
3834 [USB] Try the other device initialization scheme
3835 if the first one fails (default 1 = enabled).
3837 usbcore.initial_descriptor_timeout=
3838 [USB] Specifies timeout for the initial 64-byte
3839 USB_REQ_GET_DESCRIPTOR request in milliseconds
3840 (default 5000 = 5.0 seconds).
3843 [USBHID] The interval which mice are to be polled at.
3845 usb-storage.delay_use=
3846 [UMS] The delay in seconds before a new device is
3847 scanned for Logical Units (default 1).
3850 [UMS] A list of quirks entries to supplement or
3851 override the built-in unusual_devs list. List
3852 entries are separated by commas. Each entry has
3853 the form VID:PID:Flags where VID and PID are Vendor
3854 and Product ID values (4-digit hex numbers) and
3855 Flags is a set of characters, each corresponding
3856 to a common usb-storage quirk flag as follows:
3857 a = SANE_SENSE (collect more than 18 bytes
3859 b = BAD_SENSE (don't collect more than 18
3860 bytes of sense data);
3861 c = FIX_CAPACITY (decrease the reported
3862 device capacity by one sector);
3863 d = NO_READ_DISC_INFO (don't use
3864 READ_DISC_INFO command);
3865 e = NO_READ_CAPACITY_16 (don't use
3866 READ_CAPACITY_16 command);
3867 f = NO_REPORT_OPCODES (don't use report opcodes
3869 g = MAX_SECTORS_240 (don't transfer more than
3870 240 sectors at a time, uas only);
3871 h = CAPACITY_HEURISTICS (decrease the
3872 reported device capacity by one
3873 sector if the number is odd);
3874 i = IGNORE_DEVICE (don't bind to this
3876 l = NOT_LOCKABLE (don't try to lock and
3877 unlock ejectable media);
3878 m = MAX_SECTORS_64 (don't transfer more
3879 than 64 sectors = 32 KB at a time);
3880 n = INITIAL_READ10 (force a retry of the
3881 initial READ(10) command);
3882 o = CAPACITY_OK (accept the capacity
3883 reported by the device);
3884 p = WRITE_CACHE (the device cache is ON
3886 r = IGNORE_RESIDUE (the device reports
3887 bogus residue values);
3888 s = SINGLE_LUN (the device has only one
3890 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3891 commands, uas only);
3892 u = IGNORE_UAS (don't bind to the uas driver);
3893 w = NO_WP_DETECT (don't test whether the
3894 medium is write-protected).
3895 Example: quirks=0419:aaf5:rl,0421:0433:rc
3897 user_debug= [KNL,ARM]
3899 See arch/arm/Kconfig.debug help text.
3900 1 - undefined instruction events
3902 4 - invalid data aborts
3905 Example: user_debug=31
3908 [X86] Flags controlling user PTE allocations.
3910 nohigh = do not allocate PTE pages in
3911 HIGHMEM regardless of setting
3915 On X86_32, this is an alias for vdso32=. Otherwise:
3917 vdso=1: enable VDSO (the default)
3918 vdso=0: disable VDSO mapping
3920 vdso32= [X86] Control the 32-bit vDSO
3921 vdso32=1: enable 32-bit VDSO
3922 vdso32=0 or vdso32=2: disable 32-bit VDSO
3924 See the help text for CONFIG_COMPAT_VDSO for more
3925 details. If CONFIG_COMPAT_VDSO is set, the default is
3926 vdso32=0; otherwise, the default is vdso32=1.
3928 For compatibility with older kernels, vdso32=2 is an
3931 Try vdso32=0 if you encounter an error that says:
3932 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3935 vector=percpu: enable percpu vector domain
3937 video= [FB] Frame buffer configuration
3938 See Documentation/fb/modedb.txt.
3940 video.brightness_switch_enabled= [0,1]
3941 If set to 1, on receiving an ACPI notify event
3942 generated by hotkey, video driver will adjust brightness
3943 level and then send out the event to user space through
3944 the allocated input device; If set to 0, video driver
3945 will only send out the event without touching backlight
3950 [VMMIO] Memory mapped virtio (platform) device.
3952 <size>@<baseaddr>:<irq>[:<id>]
3954 <size> := size (can use standard suffixes
3956 <baseaddr> := physical base address
3957 <irq> := interrupt number (as passed to
3959 <id> := (optional) platform device id
3961 virtio_mmio.device=1K@0x100b0000:48:7
3963 Can be used multiple times for multiple devices.
3965 vga= [BOOT,X86-32] Select a particular video mode
3966 See Documentation/x86/boot.txt and
3967 Documentation/svga.txt.
3968 Use vga=ask for menu.
3969 This is actually a boot loader parameter; the value is
3970 passed to the kernel using a special protocol.
3972 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3973 size of <nn>. This can be used to increase the
3974 minimum size (128MB on x86). It can also be used to
3975 decrease the size and leave more room for directly
3978 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3981 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3984 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3988 Controls the behavior of vsyscalls (i.e. calls to
3989 fixed addresses of 0xffffffffff600x00 from legacy
3990 code). Most statically-linked binaries and older
3991 versions of glibc use these calls. Because these
3992 functions are at fixed addresses, they make nice
3993 targets for exploits that can control RIP.
3995 emulate [default] Vsyscalls turn into traps and are
3996 emulated reasonably safely.
3998 native Vsyscalls are native syscall instructions.
3999 This is a little bit faster than trapping
4000 and makes a few dynamic recompilers work
4001 better than they would in emulation mode.
4002 It also makes exploits much easier to write.
4004 none Vsyscalls don't work at all. This makes
4005 them quite hard to use for exploits but
4006 might break your system.
4008 vt.color= [VT] Default text color.
4009 Format: 0xYX, X = foreground, Y = background.
4010 Default: 0x07 = light gray on black.
4012 vt.cur_default= [VT] Default cursor shape.
4013 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4014 the parameters of the <Esc>[?A;B;Cc escape sequence;
4015 see VGA-softcursor.txt. Default: 2 = underline.
4017 vt.default_blu= [VT]
4018 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4019 Change the default blue palette of the console.
4020 This is a 16-member array composed of values
4023 vt.default_grn= [VT]
4024 Format: <green0>,<green1>,<green2>,...,<green15>
4025 Change the default green palette of the console.
4026 This is a 16-member array composed of values
4029 vt.default_red= [VT]
4030 Format: <red0>,<red1>,<red2>,...,<red15>
4031 Change the default red palette of the console.
4032 This is a 16-member array composed of values
4038 Set system-wide default UTF-8 mode for all tty's.
4039 Default is 1, i.e. UTF-8 mode is enabled for all
4040 newly opened terminals.
4042 vt.global_cursor_default=
4045 Set system-wide default for whether a cursor
4046 is shown on new VTs. Default is -1,
4047 i.e. cursors will be created by default unless
4048 overridden by individual drivers. 0 will hide
4049 cursors, 1 will display them.
4051 vt.italic= [VT] Default color for italic text; 0-15.
4054 vt.underline= [VT] Default color for underlined text; 0-15.
4057 watchdog timers [HW,WDT] For information on watchdog timers,
4058 see Documentation/watchdog/watchdog-parameters.txt
4059 or other driver-specific files in the
4060 Documentation/watchdog/ directory.
4062 workqueue.disable_numa
4063 By default, all work items queued to unbound
4064 workqueues are affine to the NUMA nodes they're
4065 issued on, which results in better behavior in
4066 general. If NUMA affinity needs to be disabled for
4067 whatever reason, this option can be used. Note
4068 that this also can be controlled per-workqueue for
4069 workqueues visible under /sys/bus/workqueue/.
4071 workqueue.power_efficient
4072 Per-cpu workqueues are generally preferred because
4073 they show better performance thanks to cache
4074 locality; unfortunately, per-cpu workqueues tend to
4075 be more power hungry than unbound workqueues.
4077 Enabling this makes the per-cpu workqueues which
4078 were observed to contribute significantly to power
4079 consumption unbound, leading to measurably lower
4080 power usage at the cost of small performance
4083 The default value of this parameter is determined by
4084 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4086 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4087 default x2apic cluster mode on platforms
4090 x86_intel_mid_timer= [X86-32,APBT]
4091 Choose timer option for x86 Intel MID platform.
4092 Two valid options are apbt timer only and lapic timer
4093 plus one apbt timer for broadcast timer.
4094 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4096 xen_emul_unplug= [HW,X86,XEN]
4097 Unplug Xen emulated devices
4098 Format: [unplug0,][unplug1]
4099 ide-disks -- unplug primary master IDE devices
4100 aux-ide-disks -- unplug non-primary-master IDE devices
4101 nics -- unplug network devices
4102 all -- unplug all emulated devices (NICs and IDE disks)
4103 unnecessary -- unplugging emulated devices is
4104 unnecessary even if the host did not respond to
4106 never -- do not unplug even if version check succeeds
4108 xen_nopvspin [X86,XEN]
4109 Disables the ticketlock slowpath using Xen PV
4113 Disables the PV optimizations forcing the HVM guest to
4114 run as generic HVM guest with no PV drivers.
4116 xirc2ps_cs= [NET,PCMCIA]
4118 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4120 ______________________________________________________________________
4124 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob