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 dis_ucode_ldr [X86] Disable the microcode loader.
915 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
916 this option disables the debugging code at boot.
918 dma_debug_entries=<number>
919 This option allows to tune the number of preallocated
920 entries for DMA-API debugging code. One entry is
921 required per DMA-API allocation. Use this if the
922 DMA-API debugging code disables itself because the
923 architectural default is too low.
925 dma_debug_driver=<driver_name>
926 With this option the DMA-API debugging driver
927 filter feature can be enabled at boot time. Just
928 pass the driver to filter for as the parameter.
929 The filter can be disabled or changed to another
930 driver later using sysfs.
932 drm_kms_helper.edid_firmware=[<connector>:]<file>
933 Broken monitors, graphic adapters and KVMs may
934 send no or incorrect EDID data sets. This parameter
935 allows to specify an EDID data set in the
936 /lib/firmware directory that is used instead.
937 Generic built-in EDID data sets are used, if one of
938 edid/1024x768.bin, edid/1280x1024.bin,
939 edid/1680x1050.bin, or edid/1920x1080.bin is given
940 and no file with the same name exists. Details and
941 instructions how to build your own EDID data are
942 available in Documentation/EDID/HOWTO.txt. An EDID
943 data set will only be used for a particular connector,
944 if its name and a colon are prepended to the EDID
949 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
950 module.dyndbg[="val"]
951 Enable debug messages at boot time. See
952 Documentation/dynamic-debug-howto.txt for details.
954 nompx [X86] Disables Intel Memory Protection Extensions.
955 See Documentation/x86/intel_mpx.txt for more
956 information about the feature.
959 on enable eager fpu restore
960 off disable eager fpu restore
961 auto selects the default scheme, which automatically
962 enables eagerfpu restore for xsaveopt.
964 module.async_probe [KNL]
965 Enable asynchronous probe on this module.
967 early_ioremap_debug [KNL]
968 Enable debug messages in early_ioremap support. This
969 is useful for tracking down temporary early mappings
970 which are not unmapped.
972 earlycon= [KNL] Output early console device and options.
975 Start an early, polled-mode console on a cadence serial
976 port at the specified address. The cadence serial port
977 must already be setup and configured. Options are not
980 uart[8250],io,<addr>[,options]
981 uart[8250],mmio,<addr>[,options]
982 uart[8250],mmio32,<addr>[,options]
983 uart[8250],mmio32be,<addr>[,options]
984 uart[8250],0x<addr>[,options]
985 Start an early, polled-mode console on the 8250/16550
986 UART at the specified I/O port or MMIO address.
987 MMIO inter-register address stride is either 8-bit
988 (mmio) or 32-bit (mmio32 or mmio32be).
989 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
990 to be equivalent to 'mmio'. 'options' are specified
991 in the same format described for "console=ttyS<n>"; if
992 unspecified, the h/w is not initialized.
995 Start an early, polled-mode console on a pl011 serial
996 port at the specified address. The pl011 serial port
997 must already be setup and configured. Options are not
1001 Start an early, polled-mode console on an msm serial
1002 port at the specified address. The serial port
1003 must already be setup and configured. Options are not
1006 msm_serial_dm,<addr>
1007 Start an early, polled-mode console on an msm serial
1008 dm port at the specified address. The serial port
1009 must already be setup and configured. Options are not
1012 smh Use ARM semihosting calls for early console.
1020 Use early console provided by serial driver available
1021 on Samsung SoCs, requires selecting proper type and
1022 a correct base address of the selected UART port. The
1023 serial port must already be setup and configured.
1024 Options are not yet supported.
1026 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1030 earlyprintk=serial[,ttySn[,baudrate]]
1031 earlyprintk=serial[,0x...[,baudrate]]
1032 earlyprintk=ttySn[,baudrate]
1033 earlyprintk=dbgp[debugController#]
1034 earlyprintk=pciserial,bus:device.function[,baudrate]
1036 earlyprintk is useful when the kernel crashes before
1037 the normal console is initialized. It is not enabled by
1038 default because it has some cosmetic problems.
1040 Append ",keep" to not disable it when the real console
1043 Only one of vga, efi, serial, or usb debug port can
1046 Currently only ttyS0 and ttyS1 may be specified by
1047 name. Other I/O ports may be explicitly specified
1048 on some architectures (x86 and arm at least) by
1049 replacing ttySn with an I/O port address, like this:
1050 earlyprintk=serial,0x1008,115200
1051 You can find the port for a given device in
1052 /proc/tty/driver/serial:
1053 2: uart:ST16650V2 port:00001008 irq:18 ...
1055 Interaction with the standard serial driver is not
1058 The VGA and EFI output is eventually overwritten by
1061 The xen output can only be used by Xen PV guests.
1063 edac_report= [HW,EDAC] Control how to report EDAC event
1064 Format: {"on" | "off" | "force"}
1065 on: enable EDAC to report H/W event. May be overridden
1066 by other higher priority error reporting module.
1067 off: disable H/W event reporting through EDAC.
1068 force: enforce the use of EDAC to report H/W event.
1071 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1074 This is designed to be used in conjunction with
1075 the boot argument: earlyprintk=vga
1078 Format: {"off" | "on" | "skip[mbr]"}
1081 Format: { "old_map", "nochunk", "noruntime", "debug" }
1082 old_map [X86-64]: switch to the old ioremap-based EFI
1083 runtime services mapping. 32-bit still uses this one by
1085 nochunk: disable reading files in "chunks" in the EFI
1086 boot stub, as chunking can cause problems with some
1087 firmware implementations.
1088 noruntime : disable EFI runtime services support
1089 debug: enable misc debug output
1091 efi_no_storage_paranoia [EFI; X86]
1092 Using this parameter you can use more than 50% of
1093 your efi variable storage. Use this parameter only if
1094 you are really sure that your UEFI does sane gc and
1095 fulfills the spec otherwise your board may brick.
1097 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1098 Add arbitrary attribute to specific memory range by
1099 updating original EFI memory map.
1100 Region of memory which aa attribute is added to is
1102 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1103 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1104 attribute is added to range 0x100000000-0x180000000 and
1105 0x10a0000000-0x1120000000.
1107 Using this parameter you can do debugging of EFI memmap
1108 related feature. For example, you can do debugging of
1109 Address Range Mirroring feature even if your box
1112 eisa_irq_edge= [PARISC,HW]
1113 See header of drivers/parisc/eisa.c.
1116 See comment before function elanfreq_setup() in
1117 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1120 Format: {"cfq" | "deadline" | "noop"}
1121 See Documentation/block/cfq-iosched.txt and
1122 Documentation/block/deadline-iosched.txt for details.
1124 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1125 Specifies physical address of start of kernel core
1126 image elf header and optionally the size. Generally
1127 kexec loader will pass this option to capture kernel.
1128 See Documentation/kdump/kdump.txt for details.
1130 enable_mtrr_cleanup [X86]
1131 The kernel tries to adjust MTRR layout from continuous
1132 to discrete, to make X server driver able to add WB
1133 entry later. This parameter enables that.
1135 enable_timer_pin_1 [X86]
1136 Enable PIN 1 of APIC timer
1137 Can be useful to work around chipset bugs
1138 (in particular on some ATI chipsets).
1139 The kernel tries to set a reasonable default.
1141 enforcing [SELINUX] Set initial enforcing status.
1143 See security/selinux/Kconfig help text.
1144 0 -- permissive (log only, no denials).
1145 1 -- enforcing (deny and log).
1147 Value can be changed at runtime via /selinux/enforce.
1150 Disable Error Record Serialization Table (ERST)
1153 ether= [HW,NET] Ethernet cards parameters
1154 This option is obsoleted by the "netdev=" option, which
1155 has equivalent usage. See its documentation for details.
1159 Permit 'security.evm' to be updated regardless of
1160 current integrity status.
1164 fail_make_request=[KNL]
1165 General fault injection mechanism.
1166 Format: <interval>,<probability>,<space>,<times>
1167 See also Documentation/fault-injection/.
1170 See Documentation/blockdev/floppy.txt.
1172 force_pal_cache_flush
1173 [IA-64] Avoid check_sal_cache_flush which may hang on
1174 buggy SAL_CACHE_FLUSH implementations. Using this
1175 parameter will force ia64_sal_cache_flush to call
1176 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1179 Forcefully enable Physical Address Extension (PAE).
1180 Many Pentium M systems disable PAE but may have a
1181 functionally usable PAE implementation.
1182 Warning: use of this parameter will taint the kernel
1183 and may cause unknown problems.
1186 [FTRACE] will set and start the specified tracer
1187 as early as possible in order to facilitate early
1190 ftrace_dump_on_oops[=orig_cpu]
1191 [FTRACE] will dump the trace buffers on oops.
1192 If no parameter is passed, ftrace will dump
1193 buffers of all CPUs, but if you pass orig_cpu, it will
1194 dump only the buffer of the CPU that triggered the
1197 ftrace_filter=[function-list]
1198 [FTRACE] Limit the functions traced by the function
1199 tracer at boot up. function-list is a comma separated
1200 list of functions. This list can be changed at run
1201 time by the set_ftrace_filter file in the debugfs
1204 ftrace_notrace=[function-list]
1205 [FTRACE] Do not trace the functions specified in
1206 function-list. This list can be changed at run time
1207 by the set_ftrace_notrace file in the debugfs
1210 ftrace_graph_filter=[function-list]
1211 [FTRACE] Limit the top level callers functions traced
1212 by the function graph tracer at boot up.
1213 function-list is a comma separated list of functions
1214 that can be changed at run time by the
1215 set_graph_function file in the debugfs tracing directory.
1217 ftrace_graph_notrace=[function-list]
1218 [FTRACE] Do not trace from the functions specified in
1219 function-list. This list is a comma separated list of
1220 functions that can be changed at run time by the
1221 set_graph_notrace file in the debugfs tracing directory.
1224 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1225 support via parallel port (up to 5 devices per port)
1226 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1227 See also Documentation/input/joystick-parport.txt
1231 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1235 gcov_persist= [GCOV] When non-zero (default), profiling data for
1236 kernel modules is saved and remains accessible via
1237 debugfs, even when the module is unloaded/reloaded.
1238 When zero, profiling data is discarded and associated
1239 debugfs files are removed at module unload time.
1241 gpt [EFI] Forces disk with valid GPT signature but
1242 invalid Protective MBR to be treated as GPT. If the
1243 primary GPT is corrupted, it enables the backup/alternate
1244 GPT to be used instead.
1246 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1247 the "Enable 0" bit of the configuration register.
1250 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1251 the "Enable 0" bit of the configuration register.
1254 grcan.select= [HW] Select which physical interface to use.
1257 grcan.txsize= [HW] Sets the size of the tx buffer.
1258 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1260 grcan.rxsize= [HW] Sets the size of the rx buffer.
1261 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1264 hashdist= [KNL,NUMA] Large hashes allocated during boot
1265 are distributed across NUMA nodes. Defaults on
1266 for 64-bit NUMA, off otherwise.
1267 Format: 0 | 1 (for off | on)
1269 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1271 hd= [EIDE] (E)IDE hard drive subsystem geometry
1272 Format: <cyl>,<head>,<sect>
1275 Disable Hardware Error Source Table (HEST) support;
1276 corresponding firmware-first mode error processing
1277 logic will be disabled.
1279 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1280 size of <nn>. This works even on boxes that have no
1281 highmem otherwise. This also works to reduce highmem
1282 size on bigger boxes.
1284 highres= [KNL] Enable/disable high resolution timer mode.
1285 Valid parameters: "on", "off"
1289 See Documentation/isdn/README.HiSax.
1293 hpet= [X86-32,HPET] option to control HPET usage
1294 Format: { enable (default) | disable | force |
1296 disable: disable HPET and use PIT instead
1297 force: allow force enabled of undocumented chips (ICH4,
1299 verbose: show contents of HPET registers during setup
1301 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1302 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1304 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1305 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1306 On x86-64 and powerpc, this option can be specified
1307 multiple times interleaved with hugepages= to reserve
1308 huge pages of different sizes. Valid pages sizes on
1309 x86-64 are 2M (when the CPU supports "pse") and 1G
1310 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1312 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1313 terminal devices. Valid values: 0..8
1314 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1315 If specified, z/VM IUCV HVC accepts connections
1316 from listed z/VM user IDs only.
1318 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1319 hardware thread id mappings.
1320 Format: <cpu>:<hwthread>
1323 Do not unregister boot console at start. This is only
1324 useful for debugging when something happens in the window
1325 between unregistering the boot console and initializing
1328 i2c_bus= [HW] Override the default board specific I2C bus speed
1329 or register an additional I2C bus that is not
1330 registered from board initialization code.
1334 i8042.debug [HW] Toggle i8042 debug mode
1335 i8042.unmask_kbd_data
1336 [HW] Enable printing of interrupt data from the KBD port
1337 (disabled by default, and as a pre-condition
1338 requires that i8042.debug=1 be enabled)
1339 i8042.direct [HW] Put keyboard port into non-translated mode
1340 i8042.dumbkbd [HW] Pretend that controller can only read data from
1341 keyboard and cannot control its state
1342 (Don't attempt to blink the leds)
1343 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1344 i8042.nokbd [HW] Don't check/create keyboard port
1345 i8042.noloop [HW] Disable the AUX Loopback command while probing
1347 i8042.nomux [HW] Don't check presence of an active multiplexing
1349 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1351 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1352 i8042.reset [HW] Reset the controller during init and cleanup
1353 i8042.unlock [HW] Unlock (ignore) the keylock
1354 i8042.kbdreset [HW] Reset device connected to KBD port
1358 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1359 indicates that the driver is running on unsupported
1361 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1362 does not match list of supported models.
1364 [HW] Report power status in /proc/i8k
1365 (disabled by default)
1366 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1369 i915.invert_brightness=
1370 [DRM] Invert the sense of the variable that is used to
1371 set the brightness of the panel backlight. Normally a
1372 brightness value of 0 indicates backlight switched off,
1373 and the maximum of the brightness value sets the backlight
1374 to maximum brightness. If this parameter is set to 0
1375 (default) and the machine requires it, or this parameter
1376 is set to 1, a brightness value of 0 sets the backlight
1377 to maximum brightness, and the maximum of the brightness
1378 value switches the backlight off.
1379 -1 -- never invert brightness
1380 0 -- machine default
1381 1 -- force brightness inversion
1384 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1386 ide-core.nodma= [HW] (E)IDE subsystem
1387 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1388 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1389 .cdrom .chs .ignore_cable are additional options
1390 See Documentation/ide/ide.txt.
1392 ide-generic.probe-mask= [HW] (E)IDE subsystem
1394 Probe mask for legacy ISA IDE ports. Depending on
1395 platform up to 6 ports are supported, enabled by
1396 setting corresponding bits in the mask to 1. The
1397 default value is 0x0, which has a special meaning.
1398 On systems that have PCI, it triggers scanning the
1399 PCI bus for the first and the second port, which
1400 are then probed. On systems without PCI the value
1401 of 0x0 enables probing the two first ports as if it
1404 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1405 Claim all unknown PCI IDE storage controllers.
1408 Format: idle=poll, idle=halt, idle=nomwait
1409 Poll forces a polling idle loop that can slightly
1410 improve the performance of waking up a idle CPU, but
1411 will use a lot of power and make the system run hot.
1413 idle=halt: Halt is forced to be used for CPU idle.
1414 In such case C2/C3 won't be used again.
1415 idle=nomwait: Disable mwait for CPU C-states
1417 ignore_loglevel [KNL]
1418 Ignore loglevel setting - this will print /all/
1419 kernel messages to the console. Useful for debugging.
1420 We also add it as printk module parameter, so users
1421 could change it dynamically, usually by
1422 /sys/module/printk/parameters/ignore_loglevel.
1424 ihash_entries= [KNL]
1425 Set number of hash buckets for inode cache.
1427 ima_appraise= [IMA] appraise integrity measurements
1428 Format: { "off" | "enforce" | "fix" | "log" }
1431 ima_appraise_tcb [IMA]
1432 The builtin appraise policy appraises all files
1436 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1440 The list of supported hash algorithms is defined
1441 in crypto/hash_info.h.
1444 The builtin measurement policy to load during IMA
1445 setup. Specyfing "tcb" as the value, measures all
1446 programs exec'd, files mmap'd for exec, and all files
1447 opened with the read mode bit set by either the
1448 effective uid (euid=0) or uid=0.
1451 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1452 Load a policy which meets the needs of the Trusted
1453 Computing Base. This means IMA will measure all
1454 programs exec'd, files mmap'd for exec, and all files
1455 opened for read by uid=0.
1458 Select one of defined IMA measurements template formats.
1459 Formats: { "ima" | "ima-ng" | "ima-sig" }
1463 [IMA] Define a custom template format.
1464 Format: { "field1|...|fieldN" }
1466 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1467 Format: <min_file_size>
1468 Set the minimal file size for using asynchronous hash.
1469 If left unspecified, ahash usage is disabled.
1471 ahash performance varies for different data sizes on
1472 different crypto accelerators. This option can be used
1473 to achieve the best performance for a particular HW.
1475 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1477 Set hashing buffer size. Default: 4k.
1479 ahash performance varies for different chunk sizes on
1480 different crypto accelerators. This option can be used
1481 to achieve best performance for particular HW.
1485 Run specified binary instead of /sbin/init as init
1488 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1489 for working out where the kernel is dying during
1492 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1493 initcall functions. Useful for debugging built-in
1494 modules and initcalls.
1496 initrd= [BOOT] Specify the location of the initial ramdisk
1498 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1501 int_pln_enable [x86] Enable power limit notification interrupt
1503 integrity_audit=[IMA]
1504 Format: { "0" | "1" }
1505 0 -- basic integrity auditing messages. (Default)
1506 1 -- additional integrity auditing messages.
1508 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1510 Enable intel iommu driver.
1512 Disable intel iommu driver.
1513 igfx_off [Default Off]
1514 By default, gfx is mapped as normal device. If a gfx
1515 device has a dedicated DMAR unit, the DMAR unit is
1516 bypassed by not enabling DMAR with this option. In
1517 this case, gfx device will use physical address for
1520 With this option iommu will not optimize to look
1521 for io virtual address below 32-bit forcing dual
1522 address cycle on pci bus for cards supporting greater
1523 than 32-bit addressing. The default is to look
1524 for translation below 32-bit and if not available
1525 then look in the higher range.
1526 strict [Default Off]
1527 With this option on every unmap_single operation will
1528 result in a hardware IOTLB flush operation as opposed
1529 to batching them for performance.
1530 sp_off [Default Off]
1531 By default, super page will be supported if Intel IOMMU
1532 has the capability. With this option, super page will
1534 ecs_off [Default Off]
1535 By default, extended context tables will be supported if
1536 the hardware advertises that it has support both for the
1537 extended tables themselves, and also PASID support. With
1538 this option set, extended tables will not be used even
1539 on hardware which claims to support them.
1541 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1542 0 disables intel_idle and fall back on acpi_idle.
1543 1 to 6 specify maximum depth of C-state.
1547 Do not enable intel_pstate as the default
1548 scaling driver for the supported processors
1550 Enable intel_pstate on systems that prohibit it by default
1551 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1552 instead of acpi-cpufreq may disable platform features, such
1553 as thermal controls and power capping, that rely on ACPI
1554 P-States information being indicated to OSPM and therefore
1555 should be used with caution. This option does not work with
1556 processors that aren't supported by the intel_pstate driver
1557 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1559 Do not enable hardware P state control (HWP)
1562 Only load intel_pstate on systems which support
1563 hardware P state control (HWP) if available.
1565 intremap= [X86-64, Intel-IOMMU]
1566 on enable Interrupt Remapping (default)
1567 off disable Interrupt Remapping
1568 nosid disable Source ID checking
1570 BIOS x2APIC opt-out request will be ignored
1572 iomem= Disable strict checking of access to MMIO memory
1573 strict regions from userspace.
1588 nobypass [PPC/POWERNV]
1589 Disable IOMMU bypass, using IOMMU for PCI devices.
1592 io7= [HW] IO7 for Marvel based alpha systems
1593 See comment before marvel_specify_io7 in
1594 arch/alpha/kernel/core_marvel.c.
1596 io_delay= [X86] I/O delay method
1598 Standard port 0x80 based delay
1600 Alternate port 0xed based delay (needed on some systems)
1602 Simple two microseconds delay
1607 See Documentation/filesystems/nfs/nfsroot.txt.
1610 When an interrupt is not handled search all handlers
1611 for it. Intended to get systems with badly broken
1615 When an interrupt is not handled search all handlers
1616 for it. Also check all handlers each timer
1617 interrupt. Intended to get systems with badly broken
1621 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1623 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1625 <cpu number>,...,<cpu number>
1627 <cpu number>-<cpu number>
1628 (must be a positive range in ascending order)
1630 <cpu number>,...,<cpu number>-<cpu number>
1632 This option can be used to specify one or more CPUs
1633 to isolate from the general SMP balancing and scheduling
1634 algorithms. You can move a process onto or off an
1635 "isolated" CPU via the CPU affinity syscalls or cpuset.
1636 <cpu number> begins at 0 and the maximum value is
1637 "number of CPUs in system - 1".
1639 This option is the preferred way to isolate CPUs. The
1640 alternative -- manually setting the CPU mask of all
1641 tasks in the system -- can cause problems and
1642 suboptimal load balancer performance.
1646 ivrs_ioapic [HW,X86_64]
1647 Provide an override to the IOAPIC-ID<->DEVICE-ID
1648 mapping provided in the IVRS ACPI table. For
1649 example, to map IOAPIC-ID decimal 10 to
1650 PCI device 00:14.0 write the parameter as:
1651 ivrs_ioapic[10]=00:14.0
1653 ivrs_hpet [HW,X86_64]
1654 Provide an override to the HPET-ID<->DEVICE-ID
1655 mapping provided in the IVRS ACPI table. For
1656 example, to map HPET-ID decimal 0 to
1657 PCI device 00:14.0 write the parameter as:
1658 ivrs_hpet[0]=00:14.0
1660 js= [HW,JOY] Analog joystick
1661 See Documentation/input/joystick.txt.
1664 Enable/disable kernel and module base offset ASLR
1665 (Address Space Layout Randomization) if built into
1666 the kernel. When CONFIG_HIBERNATION is selected,
1667 kASLR is disabled by default. When kASLR is enabled,
1668 hibernation will be disabled.
1672 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1673 specifies the amount of memory usable by the kernel
1674 for non-movable allocations. The requested amount is
1675 spread evenly throughout all nodes in the system. The
1676 remaining memory in each node is used for Movable
1677 pages. In the event, a node is too small to have both
1678 kernelcore and Movable pages, kernelcore pages will
1679 take priority and other nodes will have a larger number
1680 of Movable pages. The Movable zone is used for the
1681 allocation of pages that may be reclaimed or moved
1682 by the page migration subsystem. This means that
1683 HugeTLB pages may not be allocated from this zone.
1684 Note that allocations like PTEs-from-HighMem still
1685 use the HighMem zone if it exists, and the Normal
1686 zone if it does not.
1688 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1689 Format: <Controller#>[,poll interval]
1690 The controller # is the number of the ehci usb debug
1691 port as it is probed via PCI. The poll interval is
1692 optional and is the number seconds in between
1693 each poll cycle to the debug port in case you need
1694 the functionality for interrupting the kernel with
1695 gdb or control-c on the dbgp connection. When
1696 not using this parameter you use sysrq-g to break into
1697 the kernel debugger.
1699 kgdboc= [KGDB,HW] kgdb over consoles.
1700 Requires a tty driver that supports console polling,
1701 or a supported polling keyboard driver (non-usb).
1702 Serial only format: <serial_device>[,baud]
1703 keyboard only format: kbd
1704 keyboard and serial format: kbd,<serial_device>[,baud]
1705 Optional Kernel mode setting:
1706 kms, kbd format: kms,kbd
1707 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1709 kgdbwait [KGDB] Stop kernel execution and enter the
1710 kernel debugger at the earliest opportunity.
1712 kmac= [MIPS] korina ethernet MAC address.
1713 Configure the RouterBoard 532 series on-chip
1714 Ethernet adapter MAC address.
1716 kmemleak= [KNL] Boot-time kmemleak enable/disable
1717 Valid arguments: on, off
1719 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1722 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1723 Valid arguments: 0, 1, 2
1724 kmemcheck=0 (disabled)
1725 kmemcheck=1 (enabled)
1726 kmemcheck=2 (one-shot mode)
1727 Default: 2 (one-shot mode)
1729 kstack=N [X86] Print N words from the kernel stack
1732 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1733 Default is 0 (don't ignore, but inject #GP)
1735 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1739 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1740 Default is 1 (enabled)
1742 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1744 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1746 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1747 (virtualized MMU) support on capable Intel chips.
1748 Default is 1 (enabled)
1750 kvm-intel.emulate_invalid_guest_state=
1751 [KVM,Intel] Enable emulation of invalid guest states
1752 Default is 0 (disabled)
1754 kvm-intel.flexpriority=
1755 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1756 Default is 1 (enabled)
1759 [KVM,Intel] Enable VMX nesting (nVMX).
1760 Default is 0 (disabled)
1762 kvm-intel.unrestricted_guest=
1763 [KVM,Intel] Disable unrestricted guest feature
1764 (virtualized real and unpaged mode) on capable
1765 Intel chips. Default is 1 (enabled)
1767 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1768 feature (tagged TLBs) on capable Intel chips.
1769 Default is 1 (enabled)
1775 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1778 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1779 value for LAPIC timer one-shot implementation. Default
1780 back to the programmable timer unit in the LAPIC.
1782 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1785 libata.dma= [LIBATA] DMA control
1786 libata.dma=0 Disable all PATA and SATA DMA
1787 libata.dma=1 PATA and SATA Disk DMA only
1788 libata.dma=2 ATAPI (CDROM) DMA only
1789 libata.dma=4 Compact Flash DMA only
1790 Combinations also work, so libata.dma=3 enables DMA
1791 for disks and CDROMs, but not CFs.
1793 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1794 libata.ignore_hpa=0 keep BIOS limits (default)
1795 libata.ignore_hpa=1 ignore limits, using full disk
1797 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1801 libata.force= [LIBATA] Force configurations. The format is comma
1802 separated list of "[ID:]VAL" where ID is
1803 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1804 matching port, link or device. Basically, it matches
1805 the ATA ID string printed on console by libata. If
1806 the whole ID part is omitted, the last PORT and DEVICE
1807 values are used. If ID hasn't been specified yet, the
1808 configuration applies to all ports, links and devices.
1810 If only DEVICE is omitted, the parameter applies to
1811 the port and all links and devices behind it. DEVICE
1812 number of 0 either selects the first device or the
1813 first fan-out link behind PMP device. It does not
1814 select the host link. DEVICE number of 15 selects the
1815 host link and device attached to it.
1817 The VAL specifies the configuration to force. As long
1818 as there's no ambiguity shortcut notation is allowed.
1819 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1820 The following configurations can be forced.
1822 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1823 Any ID with matching PORT is used.
1825 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1827 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1828 udma[/][16,25,33,44,66,100,133] notation is also
1831 * [no]ncq: Turn on or off NCQ.
1833 * [no]ncqtrim: Turn off queued DSM TRIM.
1835 * nohrst, nosrst, norst: suppress hard, soft
1838 * rstonce: only attempt one reset during
1839 hot-unplug link recovery
1841 * dump_id: dump IDENTIFY data.
1843 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1845 * disable: Disable this device.
1847 If there are multiple matching configurations changing
1848 the same attribute, the last one is used.
1850 memblock=debug [KNL] Enable memblock debug messages.
1852 load_ramdisk= [RAM] List of ramdisks to load from floppy
1853 See Documentation/blockdev/ramdisk.txt.
1855 lockd.nlm_grace_period=P [NFS] Assign grace period.
1858 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1861 lockd.nlm_timeout=T [NFS] Assign timeout value.
1864 lockd.nlm_udpport=M [NFS] Assign UDP port.
1867 locktorture.nreaders_stress= [KNL]
1868 Set the number of locking read-acquisition kthreads.
1869 Defaults to being automatically set based on the
1870 number of online CPUs.
1872 locktorture.nwriters_stress= [KNL]
1873 Set the number of locking write-acquisition kthreads.
1875 locktorture.onoff_holdoff= [KNL]
1876 Set time (s) after boot for CPU-hotplug testing.
1878 locktorture.onoff_interval= [KNL]
1879 Set time (s) between CPU-hotplug operations, or
1880 zero to disable CPU-hotplug testing.
1882 locktorture.shuffle_interval= [KNL]
1883 Set task-shuffle interval (jiffies). Shuffling
1884 tasks allows some CPUs to go into dyntick-idle
1885 mode during the locktorture test.
1887 locktorture.shutdown_secs= [KNL]
1888 Set time (s) after boot system shutdown. This
1889 is useful for hands-off automated testing.
1891 locktorture.stat_interval= [KNL]
1892 Time (s) between statistics printk()s.
1894 locktorture.stutter= [KNL]
1895 Time (s) to stutter testing, for example,
1896 specifying five seconds causes the test to run for
1897 five seconds, wait for five seconds, and so on.
1898 This tests the locking primitive's ability to
1899 transition abruptly to and from idle.
1901 locktorture.torture_runnable= [BOOT]
1902 Start locktorture running at boot time.
1904 locktorture.torture_type= [KNL]
1905 Specify the locking implementation to test.
1907 locktorture.verbose= [KNL]
1908 Enable additional printk() statements.
1910 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1913 loglevel= All Kernel Messages with a loglevel smaller than the
1914 console loglevel will be printed to the console. It can
1915 also be changed with klogd or other programs. The
1916 loglevels are defined as follows:
1918 0 (KERN_EMERG) system is unusable
1919 1 (KERN_ALERT) action must be taken immediately
1920 2 (KERN_CRIT) critical conditions
1921 3 (KERN_ERR) error conditions
1922 4 (KERN_WARNING) warning conditions
1923 5 (KERN_NOTICE) normal but significant condition
1924 6 (KERN_INFO) informational
1925 7 (KERN_DEBUG) debug-level messages
1927 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1928 in bytes. n must be a power of two and greater
1929 than the minimal size. The minimal size is defined
1930 by LOG_BUF_SHIFT kernel config parameter. There is
1931 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1932 that allows to increase the default size depending on
1933 the number of CPUs. See init/Kconfig for more details.
1935 logo.nologo [FB] Disables display of the built-in Linux logo.
1936 This may be used to provide more screen space for
1937 kernel log messages and is useful when debugging
1938 kernel boot problems.
1940 lp=0 [LP] Specify parallel ports to use, e.g,
1941 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1942 lp=reset first parallel port). 'lp=0' disables the
1943 lp=auto printer driver. 'lp=reset' (which can be
1944 specified in addition to the ports) causes
1945 attached printers to be reset. Using
1946 lp=port1,port2,... specifies the parallel ports
1947 to associate lp devices with, starting with
1948 lp0. A port specification may be 'none' to skip
1949 that lp device, or a parport name such as
1950 'parport0'. Specifying 'lp=auto' instead of a
1951 port specification list means that device IDs
1952 from each port should be examined, to see if
1953 an IEEE 1284-compliant printer is attached; if
1954 so, the driver will manage that printer.
1955 See also header of drivers/char/lp.c.
1958 Sets loops_per_jiffy to given constant, thus avoiding
1959 time-consuming boot-time autodetection (up to 250 ms per
1960 CPU). 0 enables autodetection (default). To determine
1961 the correct value for your kernel, boot with normal
1962 autodetection and see what value is printed. Note that
1963 on SMP systems the preset will be applied to all CPUs,
1964 which is likely to cause problems if your CPUs need
1965 significantly divergent settings. An incorrect value
1966 will cause delays in the kernel to be wrong, leading to
1967 unpredictable I/O errors and other breakage. Although
1968 unlikely, in the extreme case this might damage your
1972 Format: <io>,<irq>,<dma>
1974 machvec= [IA-64] Force the use of a particular machine-vector
1975 (machvec) in a generic kernel.
1976 Example: machvec=hpzx1_swiotlb
1978 machtype= [Loongson] Share the same kernel image file between different
1980 Example: machtype=lemote-yeeloong-2f-7inch
1982 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1983 than or equal to this physical address is ignored.
1985 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1986 should make use of. maxcpus=n : n >= 0 limits the
1987 kernel to using 'n' processors. n=0 is a special case,
1988 it is equivalent to "nosmp", which also disables
1991 max_loop= [LOOP] The number of loop block devices that get
1992 (loop.max_loop) unconditionally pre-created at init time. The default
1993 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1994 of statically allocating a predefined number, loop
1995 devices can be requested on-demand with the
1996 /dev/loop-control interface.
1998 mce [X86-32] Machine Check Exception
2000 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2002 md= [HW] RAID subsystems devices and level
2003 See Documentation/md.txt.
2006 Format: <first>,<last>
2007 Specifies range of consoles to be captured by the MDA.
2009 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2010 Amount of memory to be used when the kernel is not able
2011 to see the whole system memory or for test.
2012 [X86] Work as limiting max address. Use together
2013 with memmap= to avoid physical address space collisions.
2014 Without memmap= PCI devices could be placed at addresses
2015 belonging to unused RAM.
2017 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2021 [KNL,SH] Allow user to override the default size for
2022 per-device physically contiguous DMA buffers.
2024 memmap=exactmap [KNL,X86] Enable setting of an exact
2025 E820 memory map, as specified by the user.
2026 Such memmap=exactmap lines can be constructed based on
2027 BIOS output or other requirements. See the memmap=nn@ss
2030 memmap=nn[KMG]@ss[KMG]
2031 [KNL] Force usage of a specific region of memory.
2032 Region of memory to be used is from ss to ss+nn.
2034 memmap=nn[KMG]#ss[KMG]
2035 [KNL,ACPI] Mark specific memory as ACPI data.
2036 Region of memory to be marked is from ss to ss+nn.
2038 memmap=nn[KMG]$ss[KMG]
2039 [KNL,ACPI] Mark specific memory as reserved.
2040 Region of memory to be reserved is from ss to ss+nn.
2041 Example: Exclude memory from 0x18690000-0x1869ffff
2042 memmap=64K$0x18690000
2044 memmap=0x10000$0x18690000
2046 memmap=nn[KMG]!ss[KMG]
2047 [KNL,X86] Mark specific memory as protected.
2048 Region of memory to be used, from ss to ss+nn.
2049 The memory region may be marked as e820 type 12 (0xc)
2050 and is NVDIMM or ADR memory.
2052 memory_corruption_check=0/1 [X86]
2053 Some BIOSes seem to corrupt the first 64k of
2054 memory when doing things like suspend/resume.
2055 Setting this option will scan the memory
2056 looking for corruption. Enabling this will
2057 both detect corruption and prevent the kernel
2058 from using the memory being corrupted.
2059 However, its intended as a diagnostic tool; if
2060 repeatable BIOS-originated corruption always
2061 affects the same memory, you can use memmap=
2062 to prevent the kernel from using that memory.
2064 memory_corruption_check_size=size [X86]
2065 By default it checks for corruption in the low
2066 64k, making this memory unavailable for normal
2067 use. Use this parameter to scan for
2068 corruption in more or less memory.
2070 memory_corruption_check_period=seconds [X86]
2071 By default it checks for corruption every 60
2072 seconds. Use this parameter to check at some
2073 other rate. 0 disables periodic checking.
2075 memtest= [KNL,X86,ARM] Enable memtest
2077 default : 0 <disable>
2078 Specifies the number of memtest passes to be
2079 performed. Each pass selects another test
2080 pattern from a given set of patterns. Memtest
2081 fills the memory with this pattern, validates
2082 memory contents and reserves bad memory
2083 regions that are detected.
2085 meye.*= [HW] Set MotionEye Camera parameters
2086 See Documentation/video4linux/meye.txt.
2088 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2089 Multi-Function General Purpose Timers on AMD Geode
2092 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2093 the BIOS has incorrectly applied a workaround. TinyBIOS
2094 version 0.98 is known to be affected, 0.99 fixes the
2095 problem by letting the user disable the workaround.
2099 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2100 physical address is ignored.
2102 mini2440= [ARM,HW,KNL]
2103 Format:[0..2][b][c][t]
2105 MINI2440 configuration specification:
2106 0 - The attached screen is the 3.5" TFT
2107 1 - The attached screen is the 7" TFT
2108 2 - The VGA Shield is attached (1024x768)
2109 Leaving out the screen size parameter will not load
2110 the TFT driver, and the framebuffer will be left
2112 b - Enable backlight. The TFT backlight pin will be
2113 linked to the kernel VESA blanking code and a GPIO
2114 LED. This parameter is not necessary when using the
2116 c - Enable the s3c camera interface.
2117 t - Reserved for enabling touchscreen support. The
2118 touchscreen support is not enabled in the mainstream
2119 kernel as of 2.6.30, a preliminary port can be found
2120 in the "bleeding edge" mini2440 support kernel at
2121 http://repo.or.cz/w/linux-2.6/mini2440.git
2124 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2125 parameter allows control of the logging verbosity for
2126 the additional memory initialisation checks. A value
2127 of 0 disables mminit logging and a level of 4 will
2128 log everything. Information is printed at KERN_DEBUG
2129 so loglevel=8 may also need to be specified.
2132 [KNL] When CONFIG_MODULE_SIG is set, this means that
2133 modules without (valid) signatures will fail to load.
2134 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2135 is always true, so this option does nothing.
2138 [MOUSE] Maximum time between finger touching and
2139 leaving touchpad surface for touch to be considered
2140 a tap and be reported as a left button click (for
2141 touchpads working in absolute mode only).
2143 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2144 reporting absolute coordinates, such as tablets
2145 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2146 reporting absolute coordinates, such as tablets
2148 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2149 is similar to kernelcore except it specifies the
2150 amount of memory used for migratable allocations.
2151 If both kernelcore and movablecore is specified,
2152 then kernelcore will be at *least* the specified
2153 value but may be more. If movablecore on its own
2154 is specified, the administrator must be careful
2155 that the amount of memory usable for all allocations
2158 movable_node [KNL,X86] Boot-time switch to enable the effects
2159 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2161 MTD_Partition= [MTD]
2162 Format: <name>,<region-number>,<size>,<offset>
2164 MTD_Region= [MTD] Format:
2165 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2168 See drivers/mtd/cmdlinepart.c.
2170 multitce=off [PPC] This parameter disables the use of the pSeries
2171 firmware feature for updating multiple TCE entries
2174 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2176 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2178 boundary - index of last SLC block on Flex-OneNAND.
2179 The remaining blocks are configured as MLC blocks.
2180 lock - Configure if Flex-OneNAND boundary should be locked.
2181 Once locked, the boundary cannot be changed.
2182 1 indicates lock status, 0 indicates unlock status.
2185 ARM/S3C2412 JIVE boot control
2187 See arch/arm/mach-s3c2412/mach-jive.c
2189 mtouchusb.raw_coordinates=
2190 [HW] Make the MicroTouch USB driver use raw coordinates
2191 ('y', default) or cooked coordinates ('n')
2193 mtrr_chunk_size=nn[KMG] [X86]
2194 used for mtrr cleanup. It is largest continuous chunk
2195 that could hold holes aka. UC entries.
2197 mtrr_gran_size=nn[KMG] [X86]
2198 Used for mtrr cleanup. It is granularity of mtrr block.
2200 Large value could prevent small alignment from
2203 mtrr_spare_reg_nr=n [X86]
2205 Range: 0,7 : spare reg number
2207 Used for mtrr cleanup. It is spare mtrr entries number.
2208 Set to 2 or more if your graphical card needs more.
2210 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2212 netdev= [NET] Network devices parameters
2213 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2214 Note that mem_start is often overloaded to mean
2215 something different and driver-specific.
2216 This usage is only documented in each driver source
2220 [NETFILTER] Enable connection tracking flow accounting
2221 0 to disable accounting
2222 1 to enable accounting
2225 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2226 See Documentation/filesystems/nfs/nfsroot.txt.
2228 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2229 See Documentation/filesystems/nfs/nfsroot.txt.
2231 nfsrootdebug [NFS] enable nfsroot debugging messages.
2232 See Documentation/filesystems/nfs/nfsroot.txt.
2234 nfs.callback_tcpport=
2235 [NFS] set the TCP port on which the NFSv4 callback
2236 channel should listen.
2239 [NFS] sets the pathname to the program which is used
2240 to update the NFS client cache entries.
2242 nfs.cache_getent_timeout=
2243 [NFS] sets the timeout after which an attempt to
2244 update a cache entry is deemed to have failed.
2246 nfs.idmap_cache_timeout=
2247 [NFS] set the maximum lifetime for idmapper cache
2251 [NFS] enable 64-bit inode numbers.
2252 If zero, the NFS client will fake up a 32-bit inode
2253 number for the readdir() and stat() syscalls instead
2254 of returning the full 64-bit number.
2255 The default is to return 64-bit inode numbers.
2257 nfs.max_session_slots=
2258 [NFSv4.1] Sets the maximum number of session slots
2259 the client will attempt to negotiate with the server.
2260 This limits the number of simultaneous RPC requests
2261 that the client can send to the NFSv4.1 server.
2262 Note that there is little point in setting this
2263 value higher than the max_tcp_slot_table_limit.
2265 nfs.nfs4_disable_idmapping=
2266 [NFSv4] When set to the default of '1', this option
2267 ensures that both the RPC level authentication
2268 scheme and the NFS level operations agree to use
2269 numeric uids/gids if the mount is using the
2270 'sec=sys' security flavour. In effect it is
2271 disabling idmapping, which can make migration from
2272 legacy NFSv2/v3 systems to NFSv4 easier.
2273 Servers that do not support this mode of operation
2274 will be autodetected by the client, and it will fall
2275 back to using the idmapper.
2276 To turn off this behaviour, set the value to '0'.
2278 [NFS4] Specify an additional fixed unique ident-
2279 ification string that NFSv4 clients can insert into
2280 their nfs_client_id4 string. This is typically a
2281 UUID that is generated at system install time.
2283 nfs.send_implementation_id =
2284 [NFSv4.1] Send client implementation identification
2285 information in exchange_id requests.
2286 If zero, no implementation identification information
2288 The default is to send the implementation identification
2291 nfs.recover_lost_locks =
2292 [NFSv4] Attempt to recover locks that were lost due
2293 to a lease timeout on the server. Please note that
2294 doing this risks data corruption, since there are
2295 no guarantees that the file will remain unchanged
2296 after the locks are lost.
2297 If you want to enable the kernel legacy behaviour of
2298 attempting to recover these locks, then set this
2300 The default parameter value of '0' causes the kernel
2301 not to attempt recovery of lost locks.
2303 nfs4.layoutstats_timer =
2304 [NFSv4.2] Change the rate at which the kernel sends
2305 layoutstats to the pNFS metadata server.
2307 Setting this to value to 0 causes the kernel to use
2308 whatever value is the default set by the layout
2309 driver. A non-zero value sets the minimum interval
2310 in seconds between layoutstats transmissions.
2312 nfsd.nfs4_disable_idmapping=
2313 [NFSv4] When set to the default of '1', the NFSv4
2314 server will return only numeric uids and gids to
2315 clients using auth_sys, and will accept numeric uids
2316 and gids from such clients. This is intended to ease
2317 migration from NFSv2/v3.
2319 objlayoutdriver.osd_login_prog=
2320 [NFS] [OBJLAYOUT] sets the pathname to the program which
2321 is used to automatically discover and login into new
2322 osd-targets. Please see:
2323 Documentation/filesystems/pnfs.txt for more explanations
2325 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2326 when a NMI is triggered.
2327 Format: [state][,regs][,debounce][,die]
2329 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2330 Format: [panic,][nopanic,][num]
2332 0 - turn nmi_watchdog off
2333 1 - turn nmi_watchdog on
2334 When panic is specified, panic when an NMI watchdog
2335 timeout occurs (or 'nopanic' to override the opposite
2337 This is useful when you use a panic=... timeout and
2338 need the box quickly up again.
2340 netpoll.carrier_timeout=
2341 [NET] Specifies amount of time (in seconds) that
2342 netpoll should wait for a carrier. By default netpoll
2345 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2346 emulation library even if a 387 maths coprocessor
2350 [HW] Never suspend the console
2351 Disable suspending of consoles during suspend and
2352 hibernate operations. Once disabled, debugging
2353 messages can reach various consoles while the rest
2354 of the system is being put to sleep (ie, while
2355 debugging driver suspend/resume hooks). This may
2356 not work reliably with all consoles, but is known
2357 to work with serial and VGA consoles.
2358 To facilitate more flexible debugging, we also add
2359 console_suspend, a printk module parameter to control
2360 it. Users could use console_suspend (usually
2361 /sys/module/printk/parameters/console_suspend) to
2362 turn on/off it dynamically.
2364 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2365 caches in the slab allocator. Saves per-node memory,
2366 but will impact performance.
2370 noapic [SMP,APIC] Tells the kernel to not make use of any
2371 IOAPICs that may be present in the system.
2373 noautogroup Disable scheduler automatic task group creation.
2375 nobats [PPC] Do not use BATs for mapping kernel lowmem
2376 on "Classic" PPC cores.
2380 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2382 nodelayacct [KNL] Disable per-task delay accounting
2384 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2386 nodsp [SH] Disable hardware DSP at boot time.
2388 noefi Disable EFI runtime services support.
2393 On X86-32 available only on PAE configured kernels.
2394 noexec=on: enable non-executable mappings (default)
2395 noexec=off: disable non-executable mappings
2398 Disable SMAP (Supervisor Mode Access Prevention)
2399 even if it is supported by processor.
2402 Disable SMEP (Supervisor Mode Execution Prevention)
2403 even if it is supported by processor.
2406 This affects only 32-bit executables.
2407 noexec32=on: enable non-executable mappings (default)
2408 read doesn't imply executable mappings
2409 noexec32=off: disable non-executable mappings
2410 read implies executable mappings
2412 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2414 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2415 register save and restore. The kernel will only save
2416 legacy floating-point registers on task switch.
2418 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2420 noxsave [BUGS=X86] Disables x86 extended register state save
2421 and restore using xsave. The kernel will fallback to
2422 enabling legacy floating-point and sse state.
2424 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2425 register states. The kernel will fall back to use
2426 xsave to save the states. By using this parameter,
2427 performance of saving the states is degraded because
2428 xsave doesn't support modified optimization while
2429 xsaveopt supports it on xsaveopt enabled systems.
2431 noxsaves [X86] Disables xsaves and xrstors used in saving and
2432 restoring x86 extended register state in compacted
2433 form of xsave area. The kernel will fall back to use
2434 xsaveopt and xrstor to save and restore the states
2435 in standard form of xsave area. By using this
2436 parameter, xsave area per process might occupy more
2437 memory on xsaves enabled systems.
2439 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2440 wfi(ARM) instruction doesn't work correctly and not to
2441 use it. This is also useful when using JTAG debugger.
2443 no_file_caps Tells the kernel not to honor file capabilities. The
2444 only way then for a file to be executed with privilege
2445 is to be setuid root or executed by root.
2447 nohalt [IA-64] Tells the kernel not to use the power saving
2448 function PAL_HALT_LIGHT when idle. This increases
2449 power-consumption. On the positive side, it reduces
2450 interrupt wake-up latency, which may improve performance
2451 in certain environments such as networked servers or
2454 nohibernate [HIBERNATION] Disable hibernation and resume.
2456 nohz= [KNL] Boottime enable/disable dynamic ticks
2457 Valid arguments: on, off
2460 nohz_full= [KNL,BOOT]
2461 In kernels built with CONFIG_NO_HZ_FULL=y, set
2462 the specified list of CPUs whose tick will be stopped
2463 whenever possible. The boot CPU will be forced outside
2464 the range to maintain the timekeeping.
2465 The CPUs in this range must also be included in the
2468 noiotrap [SH] Disables trapped I/O port accesses.
2470 noirqdebug [X86-32] Disables the code which attempts to detect and
2471 disable unhandled interrupt sources.
2473 no_timer_check [X86,APIC] Disables the code which tests for
2474 broken timer IRQ sources.
2476 noisapnp [ISAPNP] Disables ISA PnP code.
2478 noinitrd [RAM] Tells the kernel not to load any configured
2481 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2483 [Deprecated - use intremap=off]
2487 nojitter [IA-64] Disables jitter checking for ITC timers.
2489 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2491 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2494 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2495 steal time is computed, but won't influence scheduler
2498 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2500 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2502 noltlbs [PPC] Do not use large page/tlb entries for kernel
2503 lowmem mapping on PPC40x.
2505 nomca [IA-64] Disable machine check abort handling
2507 nomce [X86-32] Disable Machine Check Exception
2509 nomfgpt [X86-32] Disable Multi-Function General Purpose
2510 Timer usage (for AMD Geode machines).
2512 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2513 shutdown the other cpus. Instead use the REBOOT_VECTOR
2516 nomodule Disable module load
2518 nopat [X86] Disable PAT (page attribute table extension of
2519 pagetables) support.
2521 norandmaps Don't use address space randomization. Equivalent to
2522 echo 0 > /proc/sys/kernel/randomize_va_space
2524 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2526 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2527 with UP alternatives
2529 nordrand [X86] Disable kernel use of the RDRAND and
2530 RDSEED instructions even if they are supported
2531 by the processor. RDRAND and RDSEED are still
2532 available to user space applications.
2534 noresume [SWSUSP] Disables resume and restores original swap
2537 no-scroll [VGA] Disables scrollback.
2538 This is required for the Braillex ib80-piezo Braille
2539 reader made by F.H. Papenmeier (Germany).
2543 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2545 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2546 and disable the IO APIC. legacy for "maxcpus=0".
2548 nosoftlockup [KNL] Disable the soft-lockup detector.
2550 nosync [HW,M68K] Disables sync negotiation for all devices.
2552 notsc [BUGS=X86-32] Disable Time Stamp Counter
2554 nousb [USB] Disable the USB subsystem
2556 nowatchdog [KNL] Disable both lockup detectors, i.e.
2557 soft-lockup and NMI watchdog (hard-lockup).
2561 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2563 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2564 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2565 Some features depend on CPU0. Known dependencies are:
2566 1. Resume from suspend/hibernate depends on CPU0.
2567 Suspend/hibernate will fail if CPU0 is offline and you
2568 need to online CPU0 before suspend/hibernate.
2569 2. PIC interrupts also depend on CPU0. CPU0 can't be
2570 removed if a PIC interrupt is detected.
2571 It's said poweroff/reboot may depend on CPU0 on some
2572 machines although I haven't seen such issues so far
2573 after CPU0 is offline on a few tested machines.
2574 If the dependencies are under your control, you can
2575 turn on cpu0_hotplug.
2577 nptcg= [IA-64] Override max number of concurrent global TLB
2578 purges which is reported from either PAL_VM_SUMMARY or
2581 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2582 could support. nr_cpus=n : n >= 1 limits the kernel to
2583 supporting 'n' processors. Later in runtime you can not
2584 use hotplug cpu feature to put more cpu back to online.
2585 just like you compile the kernel NR_CPUS=n
2587 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2589 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2590 Allowed values are enable and disable
2592 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2593 one of ['zone', 'node', 'default'] can be specified
2594 This can be set from sysctl after boot.
2595 See Documentation/sysctl/vm.txt for details.
2597 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2598 See Documentation/debugging-via-ohci1394.txt for more
2601 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2602 Rather than timing out after 20 ms if an EC
2603 command is not properly ACKed, override the length
2604 of the timeout. We have interrupts disabled while
2605 waiting for the ACK, so if this is set too high
2606 interrupts *may* be lost!
2608 omap_mux= [OMAP] Override bootloader pin multiplexing.
2609 Format: <mux_mode0.mode_name=value>...
2610 For example, to override I2C bus2:
2611 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2613 oprofile.timer= [HW]
2614 Use timer interrupt instead of performance counters
2616 oprofile.cpu_type= Force an oprofile cpu type
2617 This might be useful if you have an older oprofile
2618 userland or if you want common events.
2619 Format: { arch_perfmon }
2620 arch_perfmon: [X86] Force use of architectural
2621 perfmon on Intel CPUs instead of the
2622 CPU specific event set.
2623 timer: [X86] Force use of architectural NMI
2624 timer mode (see also oprofile.timer
2625 for generic hr timer mode)
2626 [s390] Force legacy basic mode sampling
2627 (report cpu_type "timer")
2629 oops=panic Always panic on oopses. Default is to just kill the
2630 process, but there is a small probability of
2631 deadlocking the machine.
2632 This will also cause panics on machine check exceptions.
2633 Useful together with panic=30 to trigger a reboot.
2636 See Documentation/sound/oss/oss-parameters.txt
2638 page_owner= [KNL] Boot-time page_owner enabling option.
2639 Storage of the information about who allocated
2640 each page is disabled in default. With this switch,
2642 on: enable the feature
2644 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2645 timeout > 0: seconds before rebooting
2646 timeout = 0: wait forever
2647 timeout < 0: reboot immediately
2650 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2653 crash_kexec_post_notifiers
2654 Run kdump after running panic-notifiers and dumping
2655 kmsg. This only for the users who doubt kdump always
2656 succeeds in any situation.
2657 Note that this also increases risks of kdump failure,
2658 because some panic notifiers can make the crashed
2659 kernel more unstable.
2661 parkbd.port= [HW] Parallel port number the keyboard adapter is
2662 connected to, default is 0.
2664 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2665 0 for XT, 1 for AT (default is AT).
2668 parport= [HW,PPT] Specify parallel ports. 0 disables.
2669 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2670 Use 'auto' to force the driver to use any
2671 IRQ/DMA settings detected (the default is to
2672 ignore detected IRQ/DMA settings because of
2673 possible conflicts). You can specify the base
2674 address, IRQ, and DMA settings; IRQ and DMA
2675 should be numbers, or 'auto' (for using detected
2676 settings on that particular port), or 'nofifo'
2677 (to avoid using a FIFO even if it is detected).
2678 Parallel ports are assigned in the order they
2679 are specified on the command line, starting
2682 parport_init_mode= [HW,PPT]
2683 Configure VIA parallel port to operate in
2684 a specific mode. This is necessary on Pegasos
2685 computer where firmware has no options for setting
2686 up parallel port mode and sets it to spp.
2687 Currently this function knows 686a and 8231 chips.
2688 Format: [spp|ps2|epp|ecp|ecpepp]
2691 Halt all CPUs after the first oops has been printed for
2692 the specified number of seconds. This is to be used if
2693 your oopses keep scrolling off the screen.
2698 See header of drivers/block/paride/pcd.c.
2699 See also Documentation/blockdev/paride.txt.
2701 pci=option[,option...] [PCI] various PCI subsystem options:
2702 earlydump [X86] dump PCI config space before the kernel
2704 off [X86] don't probe for the PCI bus
2705 bios [X86-32] force use of PCI BIOS, don't access
2706 the hardware directly. Use this if your machine
2707 has a non-standard PCI host bridge.
2708 nobios [X86-32] disallow use of PCI BIOS, only direct
2709 hardware access methods are allowed. Use this
2710 if you experience crashes upon bootup and you
2711 suspect they are caused by the BIOS.
2712 conf1 [X86] Force use of PCI Configuration
2714 conf2 [X86] Force use of PCI Configuration
2716 noaer [PCIE] If the PCIEAER kernel config parameter is
2717 enabled, this kernel boot option can be used to
2718 disable the use of PCIE advanced error reporting.
2719 nodomains [PCI] Disable support for multiple PCI
2720 root domains (aka PCI segments, in ACPI-speak).
2721 nommconf [X86] Disable use of MMCONFIG for PCI
2723 check_enable_amd_mmconf [X86] check for and enable
2724 properly configured MMIO access to PCI
2725 config space on AMD family 10h CPU
2726 nomsi [MSI] If the PCI_MSI kernel config parameter is
2727 enabled, this kernel boot option can be used to
2728 disable the use of MSI interrupts system-wide.
2729 noioapicquirk [APIC] Disable all boot interrupt quirks.
2730 Safety option to keep boot IRQs enabled. This
2731 should never be necessary.
2732 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2733 primary IO-APIC for bridges that cannot disable
2734 boot IRQs. This fixes a source of spurious IRQs
2735 when the system masks IRQs.
2736 noioapicreroute [APIC] Disable workaround that uses the
2737 boot IRQ equivalent of an IRQ that connects to
2738 a chipset where boot IRQs cannot be disabled.
2739 The opposite of ioapicreroute.
2740 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2741 routing table. These calls are known to be buggy
2742 on several machines and they hang the machine
2743 when used, but on other computers it's the only
2744 way to get the interrupt routing table. Try
2745 this option if the kernel is unable to allocate
2746 IRQs or discover secondary PCI buses on your
2748 rom [X86] Assign address space to expansion ROMs.
2749 Use with caution as certain devices share
2750 address decoders between ROMs and other
2752 norom [X86] Do not assign address space to
2753 expansion ROMs that do not already have
2754 BIOS assigned address ranges.
2755 nobar [X86] Do not assign address space to the
2756 BARs that weren't assigned by the BIOS.
2757 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2758 assigned automatically to PCI devices. You can
2759 make the kernel exclude IRQs of your ISA cards
2761 pirqaddr=0xAAAAA [X86] Specify the physical address
2762 of the PIRQ table (normally generated
2763 by the BIOS) if it is outside the
2764 F0000h-100000h range.
2765 lastbus=N [X86] Scan all buses thru bus #N. Can be
2766 useful if the kernel is unable to find your
2767 secondary buses and you want to tell it
2768 explicitly which ones they are.
2769 assign-busses [X86] Always assign all PCI bus
2770 numbers ourselves, overriding
2771 whatever the firmware may have done.
2772 usepirqmask [X86] Honor the possible IRQ mask stored
2773 in the BIOS $PIR table. This is needed on
2774 some systems with broken BIOSes, notably
2775 some HP Pavilion N5400 and Omnibook XE3
2776 notebooks. This will have no effect if ACPI
2777 IRQ routing is enabled.
2778 noacpi [X86] Do not use ACPI for IRQ routing
2779 or for PCI scanning.
2780 use_crs [X86] Use PCI host bridge window information
2781 from ACPI. On BIOSes from 2008 or later, this
2782 is enabled by default. If you need to use this,
2783 please report a bug.
2784 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2785 If you need to use this, please report a bug.
2786 routeirq Do IRQ routing for all PCI devices.
2787 This is normally done in pci_enable_device(),
2788 so this option is a temporary workaround
2789 for broken drivers that don't call it.
2790 skip_isa_align [X86] do not align io start addr, so can
2791 handle more pci cards
2792 firmware [ARM] Do not re-enumerate the bus but instead
2793 just use the configuration from the
2794 bootloader. This is currently used on
2795 IXP2000 systems where the bus has to be
2796 configured a certain way for adjunct CPUs.
2797 noearly [X86] Don't do any early type 1 scanning.
2798 This might help on some broken boards which
2799 machine check when some devices' config space
2800 is read. But various workarounds are disabled
2801 and some IOMMU drivers will not work.
2802 bfsort Sort PCI devices into breadth-first order.
2803 This sorting is done to get a device
2804 order compatible with older (<= 2.4) kernels.
2805 nobfsort Don't sort PCI devices into breadth-first order.
2806 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2807 tuning and use the BIOS-configured MPS defaults.
2808 pcie_bus_safe Set every device's MPS to the largest value
2809 supported by all devices below the root complex.
2810 pcie_bus_perf Set device MPS to the largest allowable MPS
2811 based on its parent bus. Also set MRRS (Max
2812 Read Request Size) to the largest supported
2813 value (no larger than the MPS that the device
2814 or bus can support) for best performance.
2815 pcie_bus_peer2peer Set every device's MPS to 128B, which
2816 every device is guaranteed to support. This
2817 configuration allows peer-to-peer DMA between
2818 any pair of devices, possibly at the cost of
2819 reduced performance. This also guarantees
2820 that hot-added devices will work.
2821 cbiosize=nn[KMG] The fixed amount of bus space which is
2822 reserved for the CardBus bridge's IO window.
2823 The default value is 256 bytes.
2824 cbmemsize=nn[KMG] The fixed amount of bus space which is
2825 reserved for the CardBus bridge's memory
2826 window. The default value is 64 megabytes.
2829 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2830 Specifies alignment and device to reassign
2831 aligned memory resources.
2832 If <order of align> is not specified,
2833 PAGE_SIZE is used as alignment.
2834 PCI-PCI bridge can be specified, if resource
2835 windows need to be expanded.
2836 ecrc= Enable/disable PCIe ECRC (transaction layer
2837 end-to-end CRC checking).
2838 bios: Use BIOS/firmware settings. This is the
2842 hpiosize=nn[KMG] The fixed amount of bus space which is
2843 reserved for hotplug bridge's IO window.
2844 Default size is 256 bytes.
2845 hpmemsize=nn[KMG] The fixed amount of bus space which is
2846 reserved for hotplug bridge's memory window.
2847 Default size is 2 megabytes.
2848 realloc= Enable/disable reallocating PCI bridge resources
2849 if allocations done by BIOS are too small to
2850 accommodate resources required by all child
2852 off: Turn realloc off
2854 realloc same as realloc=on
2855 noari do not use PCIe ARI.
2856 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2857 only look for one device below a PCIe downstream
2860 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2863 force Enable ASPM even on devices that claim not to support it.
2864 WARNING: Forcing ASPM on may cause system lockups.
2866 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2867 nomsi Do not use MSI for PCI Express Native Hotplug (this
2868 makes all PCIe ports use INTx for hotplug services).
2870 pcie_ports= [PCIE] PCIe ports handling:
2871 auto Ask the BIOS whether or not to use native PCIe services
2872 associated with PCIe ports (PME, hot-plug, AER). Use
2873 them only if that is allowed by the BIOS.
2874 native Use native PCIe services associated with PCIe ports
2876 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2879 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2880 nomsi Do not use MSI for native PCIe PME signaling (this makes
2881 all PCIe root ports use INTx for all services).
2883 pcmv= [HW,PCMCIA] BadgePAD 4
2887 Keep all power-domains already enabled by bootloader on,
2888 even if no driver has claimed them. This is useful
2889 for debug and development, but should not be
2890 needed on a platform with proper driver support.
2893 See Documentation/blockdev/paride.txt.
2895 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2898 See arch/parisc/kernel/pdc_chassis.c
2900 percpu_alloc= Select which percpu first chunk allocator to use.
2901 Currently supported values are "embed" and "page".
2902 Archs may support subset or none of the selections.
2903 See comments in mm/percpu.c for details on each
2904 allocator. This parameter is primarily for debugging
2905 and performance comparison.
2908 See Documentation/blockdev/paride.txt.
2911 See Documentation/blockdev/paride.txt.
2913 pirq= [SMP,APIC] Manual mp-table setup
2914 See Documentation/x86/i386/IO-APIC.txt.
2916 plip= [PPT,NET] Parallel port network link
2917 Format: { parport<nr> | timid | 0 }
2918 See also Documentation/parport.txt.
2920 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2921 Override pmtimer IOPort with a hex value.
2925 Enable PNP debug messages (depends on the
2926 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2927 via /sys/module/pnp/parameters/debug. We always show
2928 current resource usage; turning this on also shows
2929 possible settings and some assignment information.
2935 { on | off | curr | res | no-curr | no-res }
2938 [ISAPNP] Exclude IRQs for the autoconfiguration
2941 [ISAPNP] Exclude DMAs for the autoconfiguration
2943 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2944 Ranges are in pairs (I/O port base and size).
2947 [ISAPNP] Exclude memory regions for the
2949 Ranges are in pairs (memory base and size).
2951 ports= [IP_VS_FTP] IPVS ftp helper module
2953 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2955 Format: <port>,<port>....
2957 print-fatal-signals=
2958 [KNL] debug: print fatal signals
2960 If enabled, warn about various signal handling
2961 related application anomalies: too many signals,
2962 too many POSIX.1 timers, fatal signals causing a
2965 If you hit the warning due to signal overflow,
2966 you might want to try "ulimit -i unlimited".
2970 printk.always_kmsg_dump=
2971 Trigger kmsg_dump for cases other than kernel oops or
2973 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2976 printk.time= Show timing data prefixed to each printk message line
2977 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2979 processor.max_cstate= [HW,ACPI]
2980 Limit processor to maximum C-state
2981 max_cstate=9 overrides any DMI blacklist limit.
2983 processor.nocst [HW,ACPI]
2984 Ignore the _CST method to determine C-states,
2985 instead using the legacy FADT method
2987 profile= [KNL] Enable kernel profiling via /proc/profile
2988 Format: [schedule,]<number>
2989 Param: "schedule" - profile schedule points.
2990 Param: <number> - step/bucket size as a power of 2 for
2991 statistical time based profiling.
2992 Param: "sleep" - profile D-state sleeping (millisecs).
2993 Requires CONFIG_SCHEDSTATS
2994 Param: "kvm" - profile VM exits.
2996 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2998 See Documentation/blockdev/ramdisk.txt.
3000 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3001 probe for; one of (bare|imps|exps|lifebook|any).
3002 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3004 psmouse.resetafter= [HW,MOUSE]
3005 Try to reset the device after so many bad packets
3008 [HW,MOUSE] Set desired mouse resolution, in dpi.
3009 psmouse.smartscroll=
3010 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3011 0 = disabled, 1 = enabled (default).
3013 pstore.backend= Specify the name of the pstore backend to use
3016 See Documentation/blockdev/paride.txt.
3019 [KNL] Number of legacy pty's. Overwrites compiled-in
3022 quiet [KNL] Disable most log messages
3027 See Documentation/md.txt.
3029 ramdisk_blocksize= [RAM]
3030 See Documentation/blockdev/ramdisk.txt.
3032 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3033 See Documentation/blockdev/ramdisk.txt.
3036 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3037 the specified list of CPUs to be no-callback CPUs.
3038 Invocation of these CPUs' RCU callbacks will
3039 be offloaded to "rcuox/N" kthreads created for
3040 that purpose, where "x" is "b" for RCU-bh, "p"
3041 for RCU-preempt, and "s" for RCU-sched, and "N"
3042 is the CPU number. This reduces OS jitter on the
3043 offloaded CPUs, which can be useful for HPC and
3044 real-time workloads. It can also improve energy
3045 efficiency for asymmetric multiprocessors.
3048 Rather than requiring that offloaded CPUs
3049 (specified by rcu_nocbs= above) explicitly
3050 awaken the corresponding "rcuoN" kthreads,
3051 make these kthreads poll for callbacks.
3052 This improves the real-time response for the
3053 offloaded CPUs by relieving them of the need to
3054 wake up the corresponding kthread, but degrades
3055 energy efficiency by requiring that the kthreads
3056 periodically wake up to do the polling.
3058 rcutree.blimit= [KNL]
3059 Set maximum number of finished RCU callbacks to
3060 process in one batch.
3062 rcutree.dump_tree= [KNL]
3063 Dump the structure of the rcu_node combining tree
3064 out at early boot. This is used for diagnostic
3065 purposes, to verify correct tree setup.
3067 rcutree.gp_cleanup_delay= [KNL]
3068 Set the number of jiffies to delay each step of
3069 RCU grace-period cleanup. This only has effect
3070 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3072 rcutree.gp_init_delay= [KNL]
3073 Set the number of jiffies to delay each step of
3074 RCU grace-period initialization. This only has
3075 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3078 rcutree.gp_preinit_delay= [KNL]
3079 Set the number of jiffies to delay each step of
3080 RCU grace-period pre-initialization, that is,
3081 the propagation of recent CPU-hotplug changes up
3082 the rcu_node combining tree. This only has effect
3083 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3085 rcutree.rcu_fanout_exact= [KNL]
3086 Disable autobalancing of the rcu_node combining
3087 tree. This is used by rcutorture, and might
3088 possibly be useful for architectures having high
3089 cache-to-cache transfer latencies.
3091 rcutree.rcu_fanout_leaf= [KNL]
3092 Change the number of CPUs assigned to each
3093 leaf rcu_node structure. Useful for very
3094 large systems, which will choose the value 64,
3095 and for NUMA systems with large remote-access
3096 latencies, which will choose a value aligned
3097 with the appropriate hardware boundaries.
3099 rcutree.jiffies_till_sched_qs= [KNL]
3100 Set required age in jiffies for a
3101 given grace period before RCU starts
3102 soliciting quiescent-state help from
3103 rcu_note_context_switch().
3105 rcutree.jiffies_till_first_fqs= [KNL]
3106 Set delay from grace-period initialization to
3107 first attempt to force quiescent states.
3108 Units are jiffies, minimum value is zero,
3109 and maximum value is HZ.
3111 rcutree.jiffies_till_next_fqs= [KNL]
3112 Set delay between subsequent attempts to force
3113 quiescent states. Units are jiffies, minimum
3114 value is one, and maximum value is HZ.
3116 rcutree.kthread_prio= [KNL,BOOT]
3117 Set the SCHED_FIFO priority of the RCU per-CPU
3118 kthreads (rcuc/N). This value is also used for
3119 the priority of the RCU boost threads (rcub/N)
3120 and for the RCU grace-period kthreads (rcu_bh,
3121 rcu_preempt, and rcu_sched). If RCU_BOOST is
3122 set, valid values are 1-99 and the default is 1
3123 (the least-favored priority). Otherwise, when
3124 RCU_BOOST is not set, valid values are 0-99 and
3125 the default is zero (non-realtime operation).
3127 rcutree.rcu_nocb_leader_stride= [KNL]
3128 Set the number of NOCB kthread groups, which
3129 defaults to the square root of the number of
3130 CPUs. Larger numbers reduces the wakeup overhead
3131 on the per-CPU grace-period kthreads, but increases
3132 that same overhead on each group's leader.
3134 rcutree.qhimark= [KNL]
3135 Set threshold of queued RCU callbacks beyond which
3136 batch limiting is disabled.
3138 rcutree.qlowmark= [KNL]
3139 Set threshold of queued RCU callbacks below which
3140 batch limiting is re-enabled.
3142 rcutree.rcu_idle_gp_delay= [KNL]
3143 Set wakeup interval for idle CPUs that have
3144 RCU callbacks (RCU_FAST_NO_HZ=y).
3146 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3147 Set wakeup interval for idle CPUs that have
3148 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3149 Lazy RCU callbacks are those which RCU can
3150 prove do nothing more than free memory.
3152 rcutorture.cbflood_inter_holdoff= [KNL]
3153 Set holdoff time (jiffies) between successive
3154 callback-flood tests.
3156 rcutorture.cbflood_intra_holdoff= [KNL]
3157 Set holdoff time (jiffies) between successive
3158 bursts of callbacks within a given callback-flood
3161 rcutorture.cbflood_n_burst= [KNL]
3162 Set the number of bursts making up a given
3163 callback-flood test. Set this to zero to
3164 disable callback-flood testing.
3166 rcutorture.cbflood_n_per_burst= [KNL]
3167 Set the number of callbacks to be registered
3168 in a given burst of a callback-flood test.
3170 rcutorture.fqs_duration= [KNL]
3171 Set duration of force_quiescent_state bursts
3174 rcutorture.fqs_holdoff= [KNL]
3175 Set holdoff time within force_quiescent_state bursts
3178 rcutorture.fqs_stutter= [KNL]
3179 Set wait time between force_quiescent_state bursts
3182 rcutorture.gp_cond= [KNL]
3183 Use conditional/asynchronous update-side
3184 primitives, if available.
3186 rcutorture.gp_exp= [KNL]
3187 Use expedited update-side primitives, if available.
3189 rcutorture.gp_normal= [KNL]
3190 Use normal (non-expedited) asynchronous
3191 update-side primitives, if available.
3193 rcutorture.gp_sync= [KNL]
3194 Use normal (non-expedited) synchronous
3195 update-side primitives, if available. If all
3196 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3197 rcutorture.gp_normal=, and rcutorture.gp_sync=
3198 are zero, rcutorture acts as if is interpreted
3199 they are all non-zero.
3201 rcutorture.n_barrier_cbs= [KNL]
3202 Set callbacks/threads for rcu_barrier() testing.
3204 rcutorture.nfakewriters= [KNL]
3205 Set number of concurrent RCU writers. These just
3206 stress RCU, they don't participate in the actual
3207 test, hence the "fake".
3209 rcutorture.nreaders= [KNL]
3210 Set number of RCU readers. The value -1 selects
3211 N-1, where N is the number of CPUs. A value
3212 "n" less than -1 selects N-n-2, where N is again
3213 the number of CPUs. For example, -2 selects N
3214 (the number of CPUs), -3 selects N+1, and so on.
3216 rcutorture.object_debug= [KNL]
3217 Enable debug-object double-call_rcu() testing.
3219 rcutorture.onoff_holdoff= [KNL]
3220 Set time (s) after boot for CPU-hotplug testing.
3222 rcutorture.onoff_interval= [KNL]
3223 Set time (s) between CPU-hotplug operations, or
3224 zero to disable CPU-hotplug testing.
3226 rcutorture.shuffle_interval= [KNL]
3227 Set task-shuffle interval (s). Shuffling tasks
3228 allows some CPUs to go into dyntick-idle mode
3229 during the rcutorture test.
3231 rcutorture.shutdown_secs= [KNL]
3232 Set time (s) after boot system shutdown. This
3233 is useful for hands-off automated testing.
3235 rcutorture.stall_cpu= [KNL]
3236 Duration of CPU stall (s) to test RCU CPU stall
3237 warnings, zero to disable.
3239 rcutorture.stall_cpu_holdoff= [KNL]
3240 Time to wait (s) after boot before inducing stall.
3242 rcutorture.stat_interval= [KNL]
3243 Time (s) between statistics printk()s.
3245 rcutorture.stutter= [KNL]
3246 Time (s) to stutter testing, for example, specifying
3247 five seconds causes the test to run for five seconds,
3248 wait for five seconds, and so on. This tests RCU's
3249 ability to transition abruptly to and from idle.
3251 rcutorture.test_boost= [KNL]
3252 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3253 "Maybe" means test if the RCU implementation
3254 under test support RCU priority boosting.
3256 rcutorture.test_boost_duration= [KNL]
3257 Duration (s) of each individual boost test.
3259 rcutorture.test_boost_interval= [KNL]
3260 Interval (s) between each boost test.
3262 rcutorture.test_no_idle_hz= [KNL]
3263 Test RCU's dyntick-idle handling. See also the
3264 rcutorture.shuffle_interval parameter.
3266 rcutorture.torture_runnable= [BOOT]
3267 Start rcutorture running at boot time.
3269 rcutorture.torture_type= [KNL]
3270 Specify the RCU implementation to test.
3272 rcutorture.verbose= [KNL]
3273 Enable additional printk() statements.
3275 rcupdate.rcu_expedited= [KNL]
3276 Use expedited grace-period primitives, for
3277 example, synchronize_rcu_expedited() instead
3278 of synchronize_rcu(). This reduces latency,
3279 but can increase CPU utilization, degrade
3280 real-time latency, and degrade energy efficiency.
3282 rcupdate.rcu_cpu_stall_suppress= [KNL]
3283 Suppress RCU CPU stall warning messages.
3285 rcupdate.rcu_cpu_stall_timeout= [KNL]
3286 Set timeout for RCU CPU stall warning messages.
3288 rcupdate.rcu_task_stall_timeout= [KNL]
3289 Set timeout in jiffies for RCU task stall warning
3290 messages. Disable with a value less than or equal
3293 rcupdate.rcu_self_test= [KNL]
3294 Run the RCU early boot self tests
3296 rcupdate.rcu_self_test_bh= [KNL]
3297 Run the RCU bh early boot self tests
3299 rcupdate.rcu_self_test_sched= [KNL]
3300 Run the RCU sched early boot self tests
3304 Run specified binary instead of /init from the ramdisk,
3305 used for early userspace startup. See initrd.
3308 Format (x86 or x86_64):
3309 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3311 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3313 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3314 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3315 reboot_force is either force or not specified,
3316 reboot_cpu is s[mp]#### with #### being the processor
3317 to be used for rebooting.
3320 [KNL, SMP] Set scheduler's default relax_domain_level.
3321 See Documentation/cgroups/cpusets.txt.
3323 relative_sleep_states=
3324 [SUSPEND] Use sleep state labeling where the deepest
3325 state available other than hibernation is always "mem".
3326 Format: { "0" | "1" }
3327 0 -- Traditional sleep state labels.
3328 1 -- Relative sleep state labels.
3330 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3332 reservetop= [X86-32]
3334 Reserves a hole at the top of the kernel virtual
3339 Set the amount of memory to reserve for BIOS at
3340 the bottom of the address space.
3342 reset_devices [KNL] Force drivers to reset the underlying device
3343 during initialization.
3346 Specify the partition device for software suspend
3348 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3350 resume_offset= [SWSUSP]
3351 Specify the offset from the beginning of the partition
3352 given by "resume=" at which the swap header is located,
3353 in <PAGE_SIZE> units (needed only for swap files).
3354 See Documentation/power/swsusp-and-swap-files.txt
3356 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3357 read the resume files
3359 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3360 Useful for devices that are detected asynchronously
3361 (e.g. USB and MMC devices).
3363 hibernate= [HIBERNATION]
3364 noresume Don't check if there's a hibernation image
3365 present during boot.
3366 nocompress Don't compress/decompress hibernation images.
3367 no Disable hibernation and resume.
3369 retain_initrd [RAM] Keep initrd memory after extraction
3371 rfkill.default_state=
3372 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3373 etc. communication is blocked by default.
3376 rfkill.master_switch_mode=
3377 0 The "airplane mode" button does nothing.
3378 1 The "airplane mode" button toggles between everything
3379 blocked and the previous configuration.
3380 2 The "airplane mode" button toggles between everything
3381 blocked and everything unblocked.
3383 rhash_entries= [KNL,NET]
3384 Set number of hash buckets for route cache
3386 ro [KNL] Mount root device read-only on boot
3388 root= [KNL] Root filesystem
3389 See name_to_dev_t comment in init/do_mounts.c.
3391 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3392 mount the root filesystem
3394 rootflags= [KNL] Set root filesystem mount option string
3396 rootfstype= [KNL] Set root filesystem type
3398 rootwait [KNL] Wait (indefinitely) for root device to show up.
3399 Useful for devices that are detected asynchronously
3400 (e.g. USB and MMC devices).
3402 rproc_mem=nn[KMG][@address]
3403 [KNL,ARM,CMA] Remoteproc physical memory block.
3404 Memory area to be used by remote processor image,
3407 rw [KNL] Mount root device read-write on boot
3409 S [KNL] Run init in single mode
3411 s390_iommu= [HW,S390]
3412 Set s390 IOTLB flushing mode
3414 With strict flushing every unmap operation will result in
3415 an IOTLB flush. Default is lazy flushing before reuse,
3419 See drivers/net/irda/sa1100_ir.c.
3421 sbni= [NET] Granch SBNI12 leased line adapter
3423 sched_debug [KNL] Enables verbose scheduler debug messages.
3425 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3426 xtime_lock contention on larger systems, and/or RCU lock
3427 contention on all systems with CONFIG_MAXSMP set.
3428 Format: { "0" | "1" }
3429 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3431 Note: increases power consumption, thus should only be
3432 enabled if running jitter sensitive (HPC/RT) workloads.
3434 security= [SECURITY] Choose a security module to enable at boot.
3435 If this boot parameter is not specified, only the first
3436 security module asking for security registration will be
3437 loaded. An invalid security module name will be treated
3438 as if no module has been chosen.
3440 selinux= [SELINUX] Disable or enable SELinux at boot time.
3441 Format: { "0" | "1" }
3442 See security/selinux/Kconfig help text.
3445 Default value is set via kernel config option.
3446 If enabled at boot time, /selinux/disable can be used
3447 later to disable prior to initial policy load.
3449 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3450 Format: { "0" | "1" }
3451 See security/apparmor/Kconfig help text
3454 Default value is set via kernel config option.
3456 serialnumber [BUGS=X86-32]
3459 Maximal number of shapers.
3461 show_msr= [x86] show boot-time MSR settings
3462 Format: { <integer> }
3463 Show boot-time (BIOS-initialized) MSR settings.
3464 The parameter means the number of CPUs to show,
3465 for example 1 means boot CPU only.
3473 Disable merging of slabs with similar size. May be
3474 necessary if there is some reason to distinguish
3475 allocs to different slabs. Debug options disable
3476 merging on their own.
3477 For more information see Documentation/vm/slub.txt.
3479 slab_max_order= [MM, SLAB]
3480 Determines the maximum allowed order for slabs.
3481 A high setting may cause OOMs due to memory
3482 fragmentation. Defaults to 1 for systems with
3483 more than 32MB of RAM, 0 otherwise.
3485 slub_debug[=options[,slabs]] [MM, SLUB]
3486 Enabling slub_debug allows one to determine the
3487 culprit if slab objects become corrupted. Enabling
3488 slub_debug can create guard zones around objects and
3489 may poison objects when not in use. Also tracks the
3490 last alloc / free. For more information see
3491 Documentation/vm/slub.txt.
3493 slub_max_order= [MM, SLUB]
3494 Determines the maximum allowed order for slabs.
3495 A high setting may cause OOMs due to memory
3496 fragmentation. For more information see
3497 Documentation/vm/slub.txt.
3499 slub_min_objects= [MM, SLUB]
3500 The minimum number of objects per slab. SLUB will
3501 increase the slab order up to slub_max_order to
3502 generate a sufficiently large slab able to contain
3503 the number of objects indicated. The higher the number
3504 of objects the smaller the overhead of tracking slabs
3505 and the less frequently locks need to be acquired.
3506 For more information see Documentation/vm/slub.txt.
3508 slub_min_order= [MM, SLUB]
3509 Determines the minimum page order for slabs. Must be
3510 lower than slub_max_order.
3511 For more information see Documentation/vm/slub.txt.
3513 slub_nomerge [MM, SLUB]
3514 Same with slab_nomerge. This is supported for legacy.
3515 See slab_nomerge for more information.
3518 Format: <io1>[,<io2>[,...,<io8>]]
3520 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3521 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3522 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3523 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3524 smsc-ircc2.ircc_irq= [HW] IRQ line
3525 smsc-ircc2.ircc_dma= [HW] DMA channel
3526 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3527 0: Toshiba Satellite 1800 (GP data pin select)
3528 1: Fast pin select (default)
3532 [KNL] Should the soft-lockup detector generate panics.
3535 softlockup_all_cpu_backtrace=
3536 [KNL] Should the soft-lockup detector generate
3537 backtraces on all cpus.
3540 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3541 See Documentation/laptops/sonypi.txt
3543 spia_io_base= [HW,MTD]
3549 Enabled the stack tracer on boot up.
3551 stacktrace_filter=[function-list]
3552 [FTRACE] Limit the functions that the stack tracer
3553 will trace at boot up. function-list is a comma separated
3554 list of functions. This list can be changed at run
3555 time by the stack_trace_filter file in the debugfs
3556 tracing directory. Note, this enables stack tracing
3557 and the stacktrace above is not needed.
3561 Set the STI (builtin display/keyboard on the HP-PARISC
3562 machines) console (graphic card) which should be used
3563 as the initial boot-console.
3564 See also comment in drivers/video/console/sticore.c.
3567 See comment in drivers/video/console/sticore.c.
3570 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3572 sunrpc.min_resvport=
3573 sunrpc.max_resvport=
3575 SunRPC servers often require that client requests
3576 originate from a privileged port (i.e. a port in the
3577 range 0 < portnr < 1024).
3578 An administrator who wishes to reserve some of these
3579 ports for other uses may adjust the range that the
3580 kernel's sunrpc client considers to be privileged
3581 using these two parameters to set the minimum and
3582 maximum port values.
3586 Control how the NFS server code allocates CPUs to
3587 service thread pools. Depending on how many NICs
3588 you have and where their interrupts are bound, this
3589 option will affect which CPUs will do NFS serving.
3590 Note: this parameter cannot be changed while the
3591 NFS server is running.
3593 auto the server chooses an appropriate mode
3594 automatically using heuristics
3595 global a single global pool contains all CPUs
3596 percpu one pool for each CPU
3597 pernode one pool for each NUMA node (equivalent
3598 to global on non-NUMA machines)
3600 sunrpc.tcp_slot_table_entries=
3601 sunrpc.udp_slot_table_entries=
3603 Sets the upper limit on the number of simultaneous
3604 RPC calls that can be sent from the client to a
3605 server. Increasing these values may allow you to
3606 improve throughput, but will also increase the
3607 amount of memory reserved for use by the client.
3609 suspend.pm_test_delay=
3611 Sets the number of seconds to remain in a suspend test
3612 mode before resuming the system (see
3613 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3614 is set. Default value is 5.
3617 [KNL] Enable accounting of swap in memory resource
3618 controller if no parameter or 1 is given or disable
3619 it if 0 is given (See Documentation/cgroups/memory.txt)
3621 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3622 Format: { <int> | force }
3623 <int> -- Number of I/O TLB slabs
3624 force -- force using of bounce buffers even if they
3625 wouldn't be automatically used by the kernel
3629 sysfs.deprecated=0|1 [KNL]
3630 Enable/disable old style sysfs layout for old udev
3631 on older distributions. When this option is enabled
3632 very new udev will not work anymore. When this option
3633 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3634 in older udev will not work anymore.
3635 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3636 the kernel configuration.
3638 sysrq_always_enabled
3640 Ignore sysrq setting - this boot parameter will
3641 neutralize any effect of /proc/sys/kernel/sysrq.
3642 Useful for debugging.
3644 tcpmhash_entries= [KNL,NET]
3645 Set the number of tcp_metrics_hash slots.
3646 Default value is 8192 or 16384 depending on total
3647 ram pages. This is used to specify the TCP metrics
3648 cache size. See Documentation/networking/ip-sysctl.txt
3649 "tcp_no_metrics_save" section for more details.
3653 test_suspend= [SUSPEND][,N]
3654 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3655 standby suspend) or "freeze" (for suspend type freeze)
3656 as the system sleep state during system startup with
3657 the optional capability to repeat N number of times.
3658 The system is woken from this state using a
3659 wakeup-capable RTC alarm.
3661 thash_entries= [KNL,NET]
3662 Set number of hash buckets for TCP connection
3664 thermal.act= [HW,ACPI]
3665 -1: disable all active trip points in all thermal zones
3666 <degrees C>: override all lowest active trip points
3668 thermal.crt= [HW,ACPI]
3669 -1: disable all critical trip points in all thermal zones
3670 <degrees C>: override all critical trip points
3672 thermal.nocrt= [HW,ACPI]
3673 Set to disable actions on ACPI thermal zone
3674 critical and hot trip points.
3676 thermal.off= [HW,ACPI]
3677 1: disable ACPI thermal control
3679 thermal.psv= [HW,ACPI]
3680 -1: disable all passive trip points
3681 <degrees C>: override all passive trip points to this
3684 thermal.tzp= [HW,ACPI]
3685 Specify global default ACPI thermal zone polling rate
3686 <deci-seconds>: poll all this frequency
3687 0: no polling (default)
3690 Force threading of all interrupt handlers except those
3691 marked explicitly IRQF_NO_THREAD.
3694 Enable the Transcendent memory driver if built-in.
3696 tmem.cleancache=0|1 [KNL, XEN]
3697 Default is on (1). Disable the usage of the cleancache
3698 API to send anonymous pages to the hypervisor.
3700 tmem.frontswap=0|1 [KNL, XEN]
3701 Default is on (1). Disable the usage of the frontswap
3702 API to send swap pages to the hypervisor. If disabled
3703 the selfballooning and selfshrinking are force disabled.
3705 tmem.selfballooning=0|1 [KNL, XEN]
3706 Default is on (1). Disable the driving of swap pages
3709 tmem.selfshrinking=0|1 [KNL, XEN]
3710 Default is on (1). Partial swapoff that immediately
3711 transfers pages from Xen hypervisor back to the
3712 kernel based on different criteria.
3716 Specify if the kernel should make use of the cpu
3717 topology information if the hardware supports this.
3718 The scheduler will make use of this information and
3719 e.g. base its process migration decisions on it.
3722 topology_updates= [KNL, PPC, NUMA]
3724 Specify if the kernel should ignore (off)
3725 topology updates sent by the hypervisor to this
3730 tpm_suspend_pcr=[HW,TPM]
3731 Format: integer pcr id
3732 Specify that at suspend time, the tpm driver
3733 should extend the specified pcr with zeros,
3734 as a workaround for some chips which fail to
3735 flush the last written pcr on TPM_SaveState.
3736 This will guarantee that all the other pcrs
3739 trace_buf_size=nn[KMG]
3740 [FTRACE] will set tracing buffer size on each cpu.
3742 trace_event=[event-list]
3743 [FTRACE] Set and start specified trace events in order
3744 to facilitate early boot debugging.
3745 See also Documentation/trace/events.txt
3747 trace_options=[option-list]
3748 [FTRACE] Enable or disable tracer options at boot.
3749 The option-list is a comma delimited list of options
3750 that can be enabled or disabled just as if you were
3751 to echo the option name into
3753 /sys/kernel/debug/tracing/trace_options
3755 For example, to enable stacktrace option (to dump the
3756 stack trace of each event), add to the command line:
3758 trace_options=stacktrace
3760 See also Documentation/trace/ftrace.txt "trace options"
3764 Have the tracepoints sent to printk as well as the
3765 tracing ring buffer. This is useful for early boot up
3766 where the system hangs or reboots and does not give the
3767 option for reading the tracing buffer or performing a
3768 ftrace_dump_on_oops.
3770 To turn off having tracepoints sent to printk,
3771 echo 0 > /proc/sys/kernel/tracepoint_printk
3772 Note, echoing 1 into this file without the
3773 tracepoint_printk kernel cmdline option has no effect.
3777 Having tracepoints sent to printk() and activating high
3778 frequency tracepoints such as irq or sched, can cause
3779 the system to live lock.
3782 [FTRACE] enable this option to disable tracing when a
3783 warning is hit. This turns off "tracing_on". Tracing can
3784 be enabled again by echoing '1' into the "tracing_on"
3785 file located in /sys/kernel/debug/tracing/
3787 This option is useful, as it disables the trace before
3788 the WARNING dump is called, which prevents the trace to
3789 be filled with content caused by the warning output.
3791 This option can also be set at run time via the sysctl
3792 option: kernel/traceoff_on_warning
3794 transparent_hugepage=
3796 Format: [always|madvise|never]
3797 Can be used to control the default behavior of the system
3798 with respect to transparent hugepages.
3799 See Documentation/vm/transhuge.txt for more details.
3801 tsc= Disable clocksource stability checks for TSC.
3803 [x86] reliable: mark tsc clocksource as reliable, this
3804 disables clocksource verification at runtime, as well
3805 as the stability checks done at bootup. Used to enable
3806 high-resolution timer mode on older hardware, and in
3807 virtualized environment.
3808 [x86] noirqtime: Do not use TSC to do irq accounting.
3809 Used to run time disable IRQ_TIME_ACCOUNTING on any
3810 platforms where RDTSC is slow and this accounting
3813 turbografx.map[2|3]= [HW,JOY]
3814 TurboGraFX parallel port interface
3816 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3817 See also Documentation/input/joystick-parport.txt
3819 udbg-immortal [PPC] When debugging early kernel crashes that
3820 happen after console_init() and before a proper
3821 console driver takes over, this boot options might
3822 help "seeing" what's going on.
3824 uhash_entries= [KNL,NET]
3825 Set number of hash buckets for UDP/UDP-Lite connections
3828 [USB] Ignore overcurrent events (default N).
3829 Some badly-designed motherboards generate lots of
3830 bogus events, for ports that aren't wired to
3831 anything. Set this parameter to avoid log spamming.
3832 Note that genuine overcurrent events won't be
3836 [X86] Cause panic on unknown NMI.
3838 usbcore.authorized_default=
3839 [USB] Default USB device authorization:
3840 (default -1 = authorized except for wireless USB,
3841 0 = not authorized, 1 = authorized)
3843 usbcore.autosuspend=
3844 [USB] The autosuspend time delay (in seconds) used
3845 for newly-detected USB devices (default 2). This
3846 is the time required before an idle device will be
3847 autosuspended. Devices for which the delay is set
3848 to a negative value won't be autosuspended at all.
3850 usbcore.usbfs_snoop=
3851 [USB] Set to log all usbfs traffic (default 0 = off).
3853 usbcore.blinkenlights=
3854 [USB] Set to cycle leds on hubs (default 0 = off).
3856 usbcore.old_scheme_first=
3857 [USB] Start with the old device initialization
3858 scheme (default 0 = off).
3860 usbcore.usbfs_memory_mb=
3861 [USB] Memory limit (in MB) for buffers allocated by
3862 usbfs (default = 16, 0 = max = 2047).
3864 usbcore.use_both_schemes=
3865 [USB] Try the other device initialization scheme
3866 if the first one fails (default 1 = enabled).
3868 usbcore.initial_descriptor_timeout=
3869 [USB] Specifies timeout for the initial 64-byte
3870 USB_REQ_GET_DESCRIPTOR request in milliseconds
3871 (default 5000 = 5.0 seconds).
3874 [USBHID] The interval which mice are to be polled at.
3876 usb-storage.delay_use=
3877 [UMS] The delay in seconds before a new device is
3878 scanned for Logical Units (default 1).
3881 [UMS] A list of quirks entries to supplement or
3882 override the built-in unusual_devs list. List
3883 entries are separated by commas. Each entry has
3884 the form VID:PID:Flags where VID and PID are Vendor
3885 and Product ID values (4-digit hex numbers) and
3886 Flags is a set of characters, each corresponding
3887 to a common usb-storage quirk flag as follows:
3888 a = SANE_SENSE (collect more than 18 bytes
3890 b = BAD_SENSE (don't collect more than 18
3891 bytes of sense data);
3892 c = FIX_CAPACITY (decrease the reported
3893 device capacity by one sector);
3894 d = NO_READ_DISC_INFO (don't use
3895 READ_DISC_INFO command);
3896 e = NO_READ_CAPACITY_16 (don't use
3897 READ_CAPACITY_16 command);
3898 f = NO_REPORT_OPCODES (don't use report opcodes
3900 g = MAX_SECTORS_240 (don't transfer more than
3901 240 sectors at a time, uas only);
3902 h = CAPACITY_HEURISTICS (decrease the
3903 reported device capacity by one
3904 sector if the number is odd);
3905 i = IGNORE_DEVICE (don't bind to this
3907 l = NOT_LOCKABLE (don't try to lock and
3908 unlock ejectable media);
3909 m = MAX_SECTORS_64 (don't transfer more
3910 than 64 sectors = 32 KB at a time);
3911 n = INITIAL_READ10 (force a retry of the
3912 initial READ(10) command);
3913 o = CAPACITY_OK (accept the capacity
3914 reported by the device);
3915 p = WRITE_CACHE (the device cache is ON
3917 r = IGNORE_RESIDUE (the device reports
3918 bogus residue values);
3919 s = SINGLE_LUN (the device has only one
3921 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3922 commands, uas only);
3923 u = IGNORE_UAS (don't bind to the uas driver);
3924 w = NO_WP_DETECT (don't test whether the
3925 medium is write-protected).
3926 Example: quirks=0419:aaf5:rl,0421:0433:rc
3928 user_debug= [KNL,ARM]
3930 See arch/arm/Kconfig.debug help text.
3931 1 - undefined instruction events
3933 4 - invalid data aborts
3936 Example: user_debug=31
3939 [X86] Flags controlling user PTE allocations.
3941 nohigh = do not allocate PTE pages in
3942 HIGHMEM regardless of setting
3946 On X86_32, this is an alias for vdso32=. Otherwise:
3948 vdso=1: enable VDSO (the default)
3949 vdso=0: disable VDSO mapping
3951 vdso32= [X86] Control the 32-bit vDSO
3952 vdso32=1: enable 32-bit VDSO
3953 vdso32=0 or vdso32=2: disable 32-bit VDSO
3955 See the help text for CONFIG_COMPAT_VDSO for more
3956 details. If CONFIG_COMPAT_VDSO is set, the default is
3957 vdso32=0; otherwise, the default is vdso32=1.
3959 For compatibility with older kernels, vdso32=2 is an
3962 Try vdso32=0 if you encounter an error that says:
3963 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3966 vector=percpu: enable percpu vector domain
3968 video= [FB] Frame buffer configuration
3969 See Documentation/fb/modedb.txt.
3971 video.brightness_switch_enabled= [0,1]
3972 If set to 1, on receiving an ACPI notify event
3973 generated by hotkey, video driver will adjust brightness
3974 level and then send out the event to user space through
3975 the allocated input device; If set to 0, video driver
3976 will only send out the event without touching backlight
3981 [VMMIO] Memory mapped virtio (platform) device.
3983 <size>@<baseaddr>:<irq>[:<id>]
3985 <size> := size (can use standard suffixes
3987 <baseaddr> := physical base address
3988 <irq> := interrupt number (as passed to
3990 <id> := (optional) platform device id
3992 virtio_mmio.device=1K@0x100b0000:48:7
3994 Can be used multiple times for multiple devices.
3996 vga= [BOOT,X86-32] Select a particular video mode
3997 See Documentation/x86/boot.txt and
3998 Documentation/svga.txt.
3999 Use vga=ask for menu.
4000 This is actually a boot loader parameter; the value is
4001 passed to the kernel using a special protocol.
4003 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4004 size of <nn>. This can be used to increase the
4005 minimum size (128MB on x86). It can also be used to
4006 decrease the size and leave more room for directly
4009 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4012 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4015 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4019 Controls the behavior of vsyscalls (i.e. calls to
4020 fixed addresses of 0xffffffffff600x00 from legacy
4021 code). Most statically-linked binaries and older
4022 versions of glibc use these calls. Because these
4023 functions are at fixed addresses, they make nice
4024 targets for exploits that can control RIP.
4026 emulate [default] Vsyscalls turn into traps and are
4027 emulated reasonably safely.
4029 native Vsyscalls are native syscall instructions.
4030 This is a little bit faster than trapping
4031 and makes a few dynamic recompilers work
4032 better than they would in emulation mode.
4033 It also makes exploits much easier to write.
4035 none Vsyscalls don't work at all. This makes
4036 them quite hard to use for exploits but
4037 might break your system.
4039 vt.color= [VT] Default text color.
4040 Format: 0xYX, X = foreground, Y = background.
4041 Default: 0x07 = light gray on black.
4043 vt.cur_default= [VT] Default cursor shape.
4044 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4045 the parameters of the <Esc>[?A;B;Cc escape sequence;
4046 see VGA-softcursor.txt. Default: 2 = underline.
4048 vt.default_blu= [VT]
4049 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4050 Change the default blue palette of the console.
4051 This is a 16-member array composed of values
4054 vt.default_grn= [VT]
4055 Format: <green0>,<green1>,<green2>,...,<green15>
4056 Change the default green palette of the console.
4057 This is a 16-member array composed of values
4060 vt.default_red= [VT]
4061 Format: <red0>,<red1>,<red2>,...,<red15>
4062 Change the default red palette of the console.
4063 This is a 16-member array composed of values
4069 Set system-wide default UTF-8 mode for all tty's.
4070 Default is 1, i.e. UTF-8 mode is enabled for all
4071 newly opened terminals.
4073 vt.global_cursor_default=
4076 Set system-wide default for whether a cursor
4077 is shown on new VTs. Default is -1,
4078 i.e. cursors will be created by default unless
4079 overridden by individual drivers. 0 will hide
4080 cursors, 1 will display them.
4082 vt.italic= [VT] Default color for italic text; 0-15.
4085 vt.underline= [VT] Default color for underlined text; 0-15.
4088 watchdog timers [HW,WDT] For information on watchdog timers,
4089 see Documentation/watchdog/watchdog-parameters.txt
4090 or other driver-specific files in the
4091 Documentation/watchdog/ directory.
4093 workqueue.disable_numa
4094 By default, all work items queued to unbound
4095 workqueues are affine to the NUMA nodes they're
4096 issued on, which results in better behavior in
4097 general. If NUMA affinity needs to be disabled for
4098 whatever reason, this option can be used. Note
4099 that this also can be controlled per-workqueue for
4100 workqueues visible under /sys/bus/workqueue/.
4102 workqueue.power_efficient
4103 Per-cpu workqueues are generally preferred because
4104 they show better performance thanks to cache
4105 locality; unfortunately, per-cpu workqueues tend to
4106 be more power hungry than unbound workqueues.
4108 Enabling this makes the per-cpu workqueues which
4109 were observed to contribute significantly to power
4110 consumption unbound, leading to measurably lower
4111 power usage at the cost of small performance
4114 The default value of this parameter is determined by
4115 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4117 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4118 default x2apic cluster mode on platforms
4121 x86_intel_mid_timer= [X86-32,APBT]
4122 Choose timer option for x86 Intel MID platform.
4123 Two valid options are apbt timer only and lapic timer
4124 plus one apbt timer for broadcast timer.
4125 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4127 xen_512gb_limit [KNL,X86-64,XEN]
4128 Restricts the kernel running paravirtualized under Xen
4129 to use only up to 512 GB of RAM. The reason to do so is
4130 crash analysis tools and Xen tools for doing domain
4131 save/restore/migration must be enabled to handle larger
4134 xen_emul_unplug= [HW,X86,XEN]
4135 Unplug Xen emulated devices
4136 Format: [unplug0,][unplug1]
4137 ide-disks -- unplug primary master IDE devices
4138 aux-ide-disks -- unplug non-primary-master IDE devices
4139 nics -- unplug network devices
4140 all -- unplug all emulated devices (NICs and IDE disks)
4141 unnecessary -- unplugging emulated devices is
4142 unnecessary even if the host did not respond to
4144 never -- do not unplug even if version check succeeds
4146 xen_nopvspin [X86,XEN]
4147 Disables the ticketlock slowpath using Xen PV
4151 Disables the PV optimizations forcing the HVM guest to
4152 run as generic HVM guest with no PV drivers.
4154 xirc2ps_cs= [NET,PCMCIA]
4156 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4158 ______________________________________________________________________
4162 Add more DRM drivers.
projects / karo-tx-linux.git / blob