4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_apic_instance= [ACPI, IOAPIC]
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 Format: <irq>,<irq>...
267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
272 This feature is enabled by default.
273 This option allows to turn off the feature.
275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
305 acpi_osi=!* # remove all strings
306 acpi_osi=! # disable all built-in OS vendor
308 acpi_osi= # disable all strings
310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372 old_ordering, nonvs, sci_force_enable }
373 See Documentation/power/video.txt for information on
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
403 See Documentation/sound/alsa/alsa-parameters.txt
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
418 32: only for 32-bit processes
419 64: only for 64-bit processes
420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
430 amd_iommu= [HW,X86-64]
431 Pass parameters to the AMD IOMMU driver in the system.
433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
437 off - do not initialize any AMD IOMMU found in
439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
454 See also Documentation/input/joystick.txt
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
462 Power management functions (SPARCstation-4/5 + deriv.)
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
469 Change the output verbosity whilst booting
470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
475 See Documentation/networking/ipv6.txt.
477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
486 apm= [APM] Advanced Power Management
487 See header of arch/x86/kernel/apm_32.c.
489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
494 atarimouse= [HW,MOUSE] Atari Mouse
496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
499 atkbd.reset= [HW] Reset keyboard during initialization
501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
529 baycom_epp= [HW,AX25]
532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
534 See header of drivers/net/hamradio/baycom_par.c.
536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
558 bttv.radio= Most important insmod options are available as
560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
567 c101= [NET] Moxa C101 synchronous serial card
569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
579 format: { id:<keyid> | builtin }
581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
595 - foo isn't visible as an individually mountable
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
608 Value can be changed at runtime via
609 /selinux/checkreqprot.
612 See Documentation/s390/CommonIO for details.
615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
627 Forces specified clocksource (if available) to be used
628 when calculating gettimeofday(). If specified
629 clocksource is not available, it defaults to PIT.
630 Format: { pit | tsc | cyclone | pmtmr }
632 clocksource= Override the default clocksource
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
638 [all] jiffies (this is the base, fallback clocksource)
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
643 [X86-32] pit,hpet,tsc;
644 scx200_hrt on Geode; cyclone on IBM x440
652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
656 stable over kernel options, but the vendor specific
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
665 cma=nn[MG]@[start[MG][-end[MG]]]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
672 include/linux/dma-contiguous.h
674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
683 allocations, by default set to 256K.
685 code_bytes [X86] How many bytes of object code to print
690 com20020= [HW,NET] ARCnet - COM20020 chipset
692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
698 ARCnet - COM90xx chipset (memory-mapped buffers)
699 Format: <io>[,<irq>[,<memstart>]]
701 condev= [HW,S390] console device
704 console= [KNL] Output console device and options.
706 tty<n> Use the virtual console device <n>.
710 Use the specified serial port. The options are of
711 the form "bbbbpnf", where "bbbb" is the baud rate,
712 "p" is parity ("n", "o", or "e"), "n" is number of
713 bits, and "f" is flow control ("r" for RTS or
714 omit it). Default is "9600n8".
716 See Documentation/serial-console.txt for more
718 Documentation/networking/netconsole.txt for an
721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
741 For now, only VisioBraille is supported.
743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
778 Documentation/kdump/kdump.txt for an example.
780 crashkernel=size[KMG],high
781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
786 It will be ignored if crashkernel=X is specified.
787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
792 requires at least 64M+32K low memory. Kernel would
793 try to allocate 72M below 4G automatically.
794 This one let user to specify own low range under 4G
795 for second kernel instead.
796 0: to disable low allocation.
797 It will be ignored when crashkernel=X,high is not used
798 or memory reserved is below 4G.
803 cs89x0_media= [HW,NET]
804 Format: { rj45 | aui | bnc }
807 See header of drivers/s390/block/dasd_devmap.c.
809 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
810 (one device per port)
811 Format: <port#>,<type>
812 See also Documentation/input/joystick-parport.txt
814 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815 time. See Documentation/dynamic-debug-howto.txt for
816 details. Deprecated, see dyndbg.
818 debug [KNL] Enable kernel debugging (events log level).
821 [KNL] verbose self-tests
823 Print debugging info while doing the locking API
825 We default to 0 (no extra messages), setting it to
826 1 will print _a lot_ more information - normally
827 only useful to kernel developers.
829 debug_objects [KNL] Enable object debugging
832 [KNL] Disable object debugging
834 debug_guardpage_minorder=
835 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836 parameter allows control of the order of pages that will
837 be intentionally kept free (and hence protected) by the
838 buddy allocator. Bigger value increase the probability
839 of catching random memory corruption, but reduce the
840 amount of memory for normal system use. The maximum
841 possible value is MAX_ORDER/2. Setting this parameter
842 to 1 or 2 should be enough to identify most random
843 memory corruption problems caused by bugs in kernel or
844 driver code when a CPU writes to (or reads from) a
845 random memory location. Note that there exists a class
846 of memory corruptions problems caused by buggy H/W or
847 F/W or by drivers badly programing DMA (basically when
848 memory is written at bus level and the CPU MMU is
849 bypassed) which are not detectable by
850 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851 tracking down these problems.
854 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855 parameter enables the feature at boot time. In
856 default, it is disabled. We can avoid allocating huge
857 chunk of memory for debug pagealloc if we don't enable
858 it at boot time and the system will work mostly same
859 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860 on: enable the feature
862 debugpat [X86] Enable PAT debugging
864 decnet.addr= [HW,NET]
865 Format: <area>[,<node>]
866 See also Documentation/networking/decnet.txt.
869 [same as hugepagesz=] The size of the default
870 HugeTLB page size. This is the size represented by
871 the legacy /proc/ hugepages APIs, used for SHM, and
872 default size when mounting hugetlbfs filesystems.
873 Defaults to the default architecture's huge page size
877 Set number of hash buckets for dentry cache.
880 See Documentation/networking/ipv6.txt.
882 disable_cpu_apicid= [X86,APIC,SMP]
884 The number of initial APIC ID for the
885 corresponding CPU to be disabled at boot,
886 mostly used for the kdump 2nd kernel to
887 disable BSP to wake up multiple CPUs without
888 causing system reset or hang due to sending
891 disable_ddw [PPC/PSERIES]
892 Disable Dynamic DMA Window support. Use this if
893 to workaround buggy firmware.
896 See Documentation/networking/ipv6.txt.
898 disable_mtrr_cleanup [X86]
899 The kernel tries to adjust MTRR layout from continuous
900 to discrete, to make X server driver able to add WB
901 entry later. This parameter disables that.
903 disable_mtrr_trim [X86, Intel and AMD only]
904 By default the kernel will trim any uncacheable
905 memory out of your available memory pool based on
906 MTRR settings. This parameter disables that behavior,
907 possibly causing your machine to run very slowly.
909 disable_timer_pin_1 [X86]
910 Disable PIN 1 of APIC timer
911 Can be useful to work around chipset bugs.
913 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
914 this option disables the debugging code at boot.
916 dma_debug_entries=<number>
917 This option allows to tune the number of preallocated
918 entries for DMA-API debugging code. One entry is
919 required per DMA-API allocation. Use this if the
920 DMA-API debugging code disables itself because the
921 architectural default is too low.
923 dma_debug_driver=<driver_name>
924 With this option the DMA-API debugging driver
925 filter feature can be enabled at boot time. Just
926 pass the driver to filter for as the parameter.
927 The filter can be disabled or changed to another
928 driver later using sysfs.
930 drm_kms_helper.edid_firmware=[<connector>:]<file>
931 Broken monitors, graphic adapters and KVMs may
932 send no or incorrect EDID data sets. This parameter
933 allows to specify an EDID data set in the
934 /lib/firmware directory that is used instead.
935 Generic built-in EDID data sets are used, if one of
936 edid/1024x768.bin, edid/1280x1024.bin,
937 edid/1680x1050.bin, or edid/1920x1080.bin is given
938 and no file with the same name exists. Details and
939 instructions how to build your own EDID data are
940 available in Documentation/EDID/HOWTO.txt. An EDID
941 data set will only be used for a particular connector,
942 if its name and a colon are prepended to the EDID
947 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
948 module.dyndbg[="val"]
949 Enable debug messages at boot time. See
950 Documentation/dynamic-debug-howto.txt for details.
952 nompx [X86] Disables Intel Memory Protection Extensions.
953 See Documentation/x86/intel_mpx.txt for more
954 information about the feature.
957 on enable eager fpu restore
958 off disable eager fpu restore
959 auto selects the default scheme, which automatically
960 enables eagerfpu restore for xsaveopt.
962 module.async_probe [KNL]
963 Enable asynchronous probe on this module.
965 early_ioremap_debug [KNL]
966 Enable debug messages in early_ioremap support. This
967 is useful for tracking down temporary early mappings
968 which are not unmapped.
970 earlycon= [KNL] Output early console device and options.
973 Start an early, polled-mode console on a cadence serial
974 port at the specified address. The cadence serial port
975 must already be setup and configured. Options are not
978 uart[8250],io,<addr>[,options]
979 uart[8250],mmio,<addr>[,options]
980 uart[8250],mmio32,<addr>[,options]
981 uart[8250],mmio32be,<addr>[,options]
982 uart[8250],0x<addr>[,options]
983 Start an early, polled-mode console on the 8250/16550
984 UART at the specified I/O port or MMIO address.
985 MMIO inter-register address stride is either 8-bit
986 (mmio) or 32-bit (mmio32 or mmio32be).
987 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
988 to be equivalent to 'mmio'. 'options' are specified
989 in the same format described for "console=ttyS<n>"; if
990 unspecified, the h/w is not initialized.
993 Start an early, polled-mode console on a pl011 serial
994 port at the specified address. The pl011 serial port
995 must already be setup and configured. Options are not
999 Start an early, polled-mode console on an msm serial
1000 port at the specified address. The serial port
1001 must already be setup and configured. Options are not
1004 msm_serial_dm,<addr>
1005 Start an early, polled-mode console on an msm serial
1006 dm port at the specified address. The serial port
1007 must already be setup and configured. Options are not
1010 smh Use ARM semihosting calls for early console.
1018 Use early console provided by serial driver available
1019 on Samsung SoCs, requires selecting proper type and
1020 a correct base address of the selected UART port. The
1021 serial port must already be setup and configured.
1022 Options are not yet supported.
1024 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1028 earlyprintk=serial[,ttySn[,baudrate]]
1029 earlyprintk=serial[,0x...[,baudrate]]
1030 earlyprintk=ttySn[,baudrate]
1031 earlyprintk=dbgp[debugController#]
1032 earlyprintk=pciserial,bus:device.function[,baudrate]
1034 earlyprintk is useful when the kernel crashes before
1035 the normal console is initialized. It is not enabled by
1036 default because it has some cosmetic problems.
1038 Append ",keep" to not disable it when the real console
1041 Only one of vga, efi, serial, or usb debug port can
1044 Currently only ttyS0 and ttyS1 may be specified by
1045 name. Other I/O ports may be explicitly specified
1046 on some architectures (x86 and arm at least) by
1047 replacing ttySn with an I/O port address, like this:
1048 earlyprintk=serial,0x1008,115200
1049 You can find the port for a given device in
1050 /proc/tty/driver/serial:
1051 2: uart:ST16650V2 port:00001008 irq:18 ...
1053 Interaction with the standard serial driver is not
1056 The VGA and EFI output is eventually overwritten by
1059 The xen output can only be used by Xen PV guests.
1061 edac_report= [HW,EDAC] Control how to report EDAC event
1062 Format: {"on" | "off" | "force"}
1063 on: enable EDAC to report H/W event. May be overridden
1064 by other higher priority error reporting module.
1065 off: disable H/W event reporting through EDAC.
1066 force: enforce the use of EDAC to report H/W event.
1069 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1072 This is designed to be used in conjunction with
1073 the boot argument: earlyprintk=vga
1076 Format: {"off" | "on" | "skip[mbr]"}
1079 Format: { "old_map", "nochunk", "noruntime", "debug" }
1080 old_map [X86-64]: switch to the old ioremap-based EFI
1081 runtime services mapping. 32-bit still uses this one by
1083 nochunk: disable reading files in "chunks" in the EFI
1084 boot stub, as chunking can cause problems with some
1085 firmware implementations.
1086 noruntime : disable EFI runtime services support
1087 debug: enable misc debug output
1089 efi_no_storage_paranoia [EFI; X86]
1090 Using this parameter you can use more than 50% of
1091 your efi variable storage. Use this parameter only if
1092 you are really sure that your UEFI does sane gc and
1093 fulfills the spec otherwise your board may brick.
1095 eisa_irq_edge= [PARISC,HW]
1096 See header of drivers/parisc/eisa.c.
1099 See comment before function elanfreq_setup() in
1100 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1103 Format: {"cfq" | "deadline" | "noop"}
1104 See Documentation/block/cfq-iosched.txt and
1105 Documentation/block/deadline-iosched.txt for details.
1107 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1108 Specifies physical address of start of kernel core
1109 image elf header and optionally the size. Generally
1110 kexec loader will pass this option to capture kernel.
1111 See Documentation/kdump/kdump.txt for details.
1113 enable_mtrr_cleanup [X86]
1114 The kernel tries to adjust MTRR layout from continuous
1115 to discrete, to make X server driver able to add WB
1116 entry later. This parameter enables that.
1118 enable_timer_pin_1 [X86]
1119 Enable PIN 1 of APIC timer
1120 Can be useful to work around chipset bugs
1121 (in particular on some ATI chipsets).
1122 The kernel tries to set a reasonable default.
1124 enforcing [SELINUX] Set initial enforcing status.
1126 See security/selinux/Kconfig help text.
1127 0 -- permissive (log only, no denials).
1128 1 -- enforcing (deny and log).
1130 Value can be changed at runtime via /selinux/enforce.
1133 Disable Error Record Serialization Table (ERST)
1136 ether= [HW,NET] Ethernet cards parameters
1137 This option is obsoleted by the "netdev=" option, which
1138 has equivalent usage. See its documentation for details.
1142 Permit 'security.evm' to be updated regardless of
1143 current integrity status.
1147 fail_make_request=[KNL]
1148 General fault injection mechanism.
1149 Format: <interval>,<probability>,<space>,<times>
1150 See also Documentation/fault-injection/.
1153 See Documentation/blockdev/floppy.txt.
1155 force_pal_cache_flush
1156 [IA-64] Avoid check_sal_cache_flush which may hang on
1157 buggy SAL_CACHE_FLUSH implementations. Using this
1158 parameter will force ia64_sal_cache_flush to call
1159 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1162 Forcefully enable Physical Address Extension (PAE).
1163 Many Pentium M systems disable PAE but may have a
1164 functionally usable PAE implementation.
1165 Warning: use of this parameter will taint the kernel
1166 and may cause unknown problems.
1169 [FTRACE] will set and start the specified tracer
1170 as early as possible in order to facilitate early
1173 ftrace_dump_on_oops[=orig_cpu]
1174 [FTRACE] will dump the trace buffers on oops.
1175 If no parameter is passed, ftrace will dump
1176 buffers of all CPUs, but if you pass orig_cpu, it will
1177 dump only the buffer of the CPU that triggered the
1180 ftrace_filter=[function-list]
1181 [FTRACE] Limit the functions traced by the function
1182 tracer at boot up. function-list is a comma separated
1183 list of functions. This list can be changed at run
1184 time by the set_ftrace_filter file in the debugfs
1187 ftrace_notrace=[function-list]
1188 [FTRACE] Do not trace the functions specified in
1189 function-list. This list can be changed at run time
1190 by the set_ftrace_notrace file in the debugfs
1193 ftrace_graph_filter=[function-list]
1194 [FTRACE] Limit the top level callers functions traced
1195 by the function graph tracer at boot up.
1196 function-list is a comma separated list of functions
1197 that can be changed at run time by the
1198 set_graph_function file in the debugfs tracing directory.
1200 ftrace_graph_notrace=[function-list]
1201 [FTRACE] Do not trace from the functions specified in
1202 function-list. This list is a comma separated list of
1203 functions that can be changed at run time by the
1204 set_graph_notrace file in the debugfs tracing directory.
1207 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1208 support via parallel port (up to 5 devices per port)
1209 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1210 See also Documentation/input/joystick-parport.txt
1214 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1218 gcov_persist= [GCOV] When non-zero (default), profiling data for
1219 kernel modules is saved and remains accessible via
1220 debugfs, even when the module is unloaded/reloaded.
1221 When zero, profiling data is discarded and associated
1222 debugfs files are removed at module unload time.
1224 gpt [EFI] Forces disk with valid GPT signature but
1225 invalid Protective MBR to be treated as GPT. If the
1226 primary GPT is corrupted, it enables the backup/alternate
1227 GPT to be used instead.
1229 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1230 the "Enable 0" bit of the configuration register.
1233 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1234 the "Enable 0" bit of the configuration register.
1237 grcan.select= [HW] Select which physical interface to use.
1240 grcan.txsize= [HW] Sets the size of the tx buffer.
1241 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1243 grcan.rxsize= [HW] Sets the size of the rx buffer.
1244 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1247 hashdist= [KNL,NUMA] Large hashes allocated during boot
1248 are distributed across NUMA nodes. Defaults on
1249 for 64-bit NUMA, off otherwise.
1250 Format: 0 | 1 (for off | on)
1252 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1254 hd= [EIDE] (E)IDE hard drive subsystem geometry
1255 Format: <cyl>,<head>,<sect>
1258 Disable Hardware Error Source Table (HEST) support;
1259 corresponding firmware-first mode error processing
1260 logic will be disabled.
1262 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1263 size of <nn>. This works even on boxes that have no
1264 highmem otherwise. This also works to reduce highmem
1265 size on bigger boxes.
1267 highres= [KNL] Enable/disable high resolution timer mode.
1268 Valid parameters: "on", "off"
1272 See Documentation/isdn/README.HiSax.
1276 hpet= [X86-32,HPET] option to control HPET usage
1277 Format: { enable (default) | disable | force |
1279 disable: disable HPET and use PIT instead
1280 force: allow force enabled of undocumented chips (ICH4,
1282 verbose: show contents of HPET registers during setup
1284 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1285 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1287 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1288 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1289 On x86-64 and powerpc, this option can be specified
1290 multiple times interleaved with hugepages= to reserve
1291 huge pages of different sizes. Valid pages sizes on
1292 x86-64 are 2M (when the CPU supports "pse") and 1G
1293 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1295 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1296 terminal devices. Valid values: 0..8
1297 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1298 If specified, z/VM IUCV HVC accepts connections
1299 from listed z/VM user IDs only.
1301 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1302 hardware thread id mappings.
1303 Format: <cpu>:<hwthread>
1306 Do not unregister boot console at start. This is only
1307 useful for debugging when something happens in the window
1308 between unregistering the boot console and initializing
1311 i2c_bus= [HW] Override the default board specific I2C bus speed
1312 or register an additional I2C bus that is not
1313 registered from board initialization code.
1317 i8042.debug [HW] Toggle i8042 debug mode
1318 i8042.unmask_kbd_data
1319 [HW] Enable printing of interrupt data from the KBD port
1320 (disabled by default, and as a pre-condition
1321 requires that i8042.debug=1 be enabled)
1322 i8042.direct [HW] Put keyboard port into non-translated mode
1323 i8042.dumbkbd [HW] Pretend that controller can only read data from
1324 keyboard and cannot control its state
1325 (Don't attempt to blink the leds)
1326 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1327 i8042.nokbd [HW] Don't check/create keyboard port
1328 i8042.noloop [HW] Disable the AUX Loopback command while probing
1330 i8042.nomux [HW] Don't check presence of an active multiplexing
1332 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1334 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1335 i8042.reset [HW] Reset the controller during init and cleanup
1336 i8042.unlock [HW] Unlock (ignore) the keylock
1337 i8042.kbdreset [HW] Reset device connected to KBD port
1341 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1342 indicates that the driver is running on unsupported
1344 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1345 does not match list of supported models.
1347 [HW] Report power status in /proc/i8k
1348 (disabled by default)
1349 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1352 i915.invert_brightness=
1353 [DRM] Invert the sense of the variable that is used to
1354 set the brightness of the panel backlight. Normally a
1355 brightness value of 0 indicates backlight switched off,
1356 and the maximum of the brightness value sets the backlight
1357 to maximum brightness. If this parameter is set to 0
1358 (default) and the machine requires it, or this parameter
1359 is set to 1, a brightness value of 0 sets the backlight
1360 to maximum brightness, and the maximum of the brightness
1361 value switches the backlight off.
1362 -1 -- never invert brightness
1363 0 -- machine default
1364 1 -- force brightness inversion
1367 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1369 ide-core.nodma= [HW] (E)IDE subsystem
1370 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1371 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1372 .cdrom .chs .ignore_cable are additional options
1373 See Documentation/ide/ide.txt.
1375 ide-generic.probe-mask= [HW] (E)IDE subsystem
1377 Probe mask for legacy ISA IDE ports. Depending on
1378 platform up to 6 ports are supported, enabled by
1379 setting corresponding bits in the mask to 1. The
1380 default value is 0x0, which has a special meaning.
1381 On systems that have PCI, it triggers scanning the
1382 PCI bus for the first and the second port, which
1383 are then probed. On systems without PCI the value
1384 of 0x0 enables probing the two first ports as if it
1387 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1388 Claim all unknown PCI IDE storage controllers.
1391 Format: idle=poll, idle=halt, idle=nomwait
1392 Poll forces a polling idle loop that can slightly
1393 improve the performance of waking up a idle CPU, but
1394 will use a lot of power and make the system run hot.
1396 idle=halt: Halt is forced to be used for CPU idle.
1397 In such case C2/C3 won't be used again.
1398 idle=nomwait: Disable mwait for CPU C-states
1400 ignore_loglevel [KNL]
1401 Ignore loglevel setting - this will print /all/
1402 kernel messages to the console. Useful for debugging.
1403 We also add it as printk module parameter, so users
1404 could change it dynamically, usually by
1405 /sys/module/printk/parameters/ignore_loglevel.
1407 ihash_entries= [KNL]
1408 Set number of hash buckets for inode cache.
1410 ima_appraise= [IMA] appraise integrity measurements
1411 Format: { "off" | "enforce" | "fix" | "log" }
1414 ima_appraise_tcb [IMA]
1415 The builtin appraise policy appraises all files
1419 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1423 The list of supported hash algorithms is defined
1424 in crypto/hash_info.h.
1427 The builtin measurement policy to load during IMA
1428 setup. Specyfing "tcb" as the value, measures all
1429 programs exec'd, files mmap'd for exec, and all files
1430 opened with the read mode bit set by either the
1431 effective uid (euid=0) or uid=0.
1434 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1435 Load a policy which meets the needs of the Trusted
1436 Computing Base. This means IMA will measure all
1437 programs exec'd, files mmap'd for exec, and all files
1438 opened for read by uid=0.
1441 Select one of defined IMA measurements template formats.
1442 Formats: { "ima" | "ima-ng" | "ima-sig" }
1446 [IMA] Define a custom template format.
1447 Format: { "field1|...|fieldN" }
1449 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1450 Format: <min_file_size>
1451 Set the minimal file size for using asynchronous hash.
1452 If left unspecified, ahash usage is disabled.
1454 ahash performance varies for different data sizes on
1455 different crypto accelerators. This option can be used
1456 to achieve the best performance for a particular HW.
1458 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1460 Set hashing buffer size. Default: 4k.
1462 ahash performance varies for different chunk sizes on
1463 different crypto accelerators. This option can be used
1464 to achieve best performance for particular HW.
1468 Run specified binary instead of /sbin/init as init
1471 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1472 for working out where the kernel is dying during
1475 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1476 initcall functions. Useful for debugging built-in
1477 modules and initcalls.
1479 initrd= [BOOT] Specify the location of the initial ramdisk
1481 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1484 int_pln_enable [x86] Enable power limit notification interrupt
1486 integrity_audit=[IMA]
1487 Format: { "0" | "1" }
1488 0 -- basic integrity auditing messages. (Default)
1489 1 -- additional integrity auditing messages.
1491 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1493 Enable intel iommu driver.
1495 Disable intel iommu driver.
1496 igfx_off [Default Off]
1497 By default, gfx is mapped as normal device. If a gfx
1498 device has a dedicated DMAR unit, the DMAR unit is
1499 bypassed by not enabling DMAR with this option. In
1500 this case, gfx device will use physical address for
1503 With this option iommu will not optimize to look
1504 for io virtual address below 32-bit forcing dual
1505 address cycle on pci bus for cards supporting greater
1506 than 32-bit addressing. The default is to look
1507 for translation below 32-bit and if not available
1508 then look in the higher range.
1509 strict [Default Off]
1510 With this option on every unmap_single operation will
1511 result in a hardware IOTLB flush operation as opposed
1512 to batching them for performance.
1513 sp_off [Default Off]
1514 By default, super page will be supported if Intel IOMMU
1515 has the capability. With this option, super page will
1517 ecs_off [Default Off]
1518 By default, extended context tables will be supported if
1519 the hardware advertises that it has support both for the
1520 extended tables themselves, and also PASID support. With
1521 this option set, extended tables will not be used even
1522 on hardware which claims to support them.
1524 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1525 0 disables intel_idle and fall back on acpi_idle.
1526 1 to 6 specify maximum depth of C-state.
1530 Do not enable intel_pstate as the default
1531 scaling driver for the supported processors
1533 Enable intel_pstate on systems that prohibit it by default
1534 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1535 instead of acpi-cpufreq may disable platform features, such
1536 as thermal controls and power capping, that rely on ACPI
1537 P-States information being indicated to OSPM and therefore
1538 should be used with caution. This option does not work with
1539 processors that aren't supported by the intel_pstate driver
1540 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1542 Do not enable hardware P state control (HWP)
1545 Only load intel_pstate on systems which support
1546 hardware P state control (HWP) if available.
1548 intremap= [X86-64, Intel-IOMMU]
1549 on enable Interrupt Remapping (default)
1550 off disable Interrupt Remapping
1551 nosid disable Source ID checking
1553 BIOS x2APIC opt-out request will be ignored
1555 iomem= Disable strict checking of access to MMIO memory
1556 strict regions from userspace.
1571 nobypass [PPC/POWERNV]
1572 Disable IOMMU bypass, using IOMMU for PCI devices.
1575 io7= [HW] IO7 for Marvel based alpha systems
1576 See comment before marvel_specify_io7 in
1577 arch/alpha/kernel/core_marvel.c.
1579 io_delay= [X86] I/O delay method
1581 Standard port 0x80 based delay
1583 Alternate port 0xed based delay (needed on some systems)
1585 Simple two microseconds delay
1590 See Documentation/filesystems/nfs/nfsroot.txt.
1593 When an interrupt is not handled search all handlers
1594 for it. Intended to get systems with badly broken
1598 When an interrupt is not handled search all handlers
1599 for it. Also check all handlers each timer
1600 interrupt. Intended to get systems with badly broken
1604 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1606 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1608 <cpu number>,...,<cpu number>
1610 <cpu number>-<cpu number>
1611 (must be a positive range in ascending order)
1613 <cpu number>,...,<cpu number>-<cpu number>
1615 This option can be used to specify one or more CPUs
1616 to isolate from the general SMP balancing and scheduling
1617 algorithms. You can move a process onto or off an
1618 "isolated" CPU via the CPU affinity syscalls or cpuset.
1619 <cpu number> begins at 0 and the maximum value is
1620 "number of CPUs in system - 1".
1622 This option is the preferred way to isolate CPUs. The
1623 alternative -- manually setting the CPU mask of all
1624 tasks in the system -- can cause problems and
1625 suboptimal load balancer performance.
1629 ivrs_ioapic [HW,X86_64]
1630 Provide an override to the IOAPIC-ID<->DEVICE-ID
1631 mapping provided in the IVRS ACPI table. For
1632 example, to map IOAPIC-ID decimal 10 to
1633 PCI device 00:14.0 write the parameter as:
1634 ivrs_ioapic[10]=00:14.0
1636 ivrs_hpet [HW,X86_64]
1637 Provide an override to the HPET-ID<->DEVICE-ID
1638 mapping provided in the IVRS ACPI table. For
1639 example, to map HPET-ID decimal 0 to
1640 PCI device 00:14.0 write the parameter as:
1641 ivrs_hpet[0]=00:14.0
1643 js= [HW,JOY] Analog joystick
1644 See Documentation/input/joystick.txt.
1647 Enable/disable kernel and module base offset ASLR
1648 (Address Space Layout Randomization) if built into
1649 the kernel. When CONFIG_HIBERNATION is selected,
1650 kASLR is disabled by default. When kASLR is enabled,
1651 hibernation will be disabled.
1655 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1656 specifies the amount of memory usable by the kernel
1657 for non-movable allocations. The requested amount is
1658 spread evenly throughout all nodes in the system. The
1659 remaining memory in each node is used for Movable
1660 pages. In the event, a node is too small to have both
1661 kernelcore and Movable pages, kernelcore pages will
1662 take priority and other nodes will have a larger number
1663 of Movable pages. The Movable zone is used for the
1664 allocation of pages that may be reclaimed or moved
1665 by the page migration subsystem. This means that
1666 HugeTLB pages may not be allocated from this zone.
1667 Note that allocations like PTEs-from-HighMem still
1668 use the HighMem zone if it exists, and the Normal
1669 zone if it does not.
1671 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1672 Format: <Controller#>[,poll interval]
1673 The controller # is the number of the ehci usb debug
1674 port as it is probed via PCI. The poll interval is
1675 optional and is the number seconds in between
1676 each poll cycle to the debug port in case you need
1677 the functionality for interrupting the kernel with
1678 gdb or control-c on the dbgp connection. When
1679 not using this parameter you use sysrq-g to break into
1680 the kernel debugger.
1682 kgdboc= [KGDB,HW] kgdb over consoles.
1683 Requires a tty driver that supports console polling,
1684 or a supported polling keyboard driver (non-usb).
1685 Serial only format: <serial_device>[,baud]
1686 keyboard only format: kbd
1687 keyboard and serial format: kbd,<serial_device>[,baud]
1688 Optional Kernel mode setting:
1689 kms, kbd format: kms,kbd
1690 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1692 kgdbwait [KGDB] Stop kernel execution and enter the
1693 kernel debugger at the earliest opportunity.
1695 kmac= [MIPS] korina ethernet MAC address.
1696 Configure the RouterBoard 532 series on-chip
1697 Ethernet adapter MAC address.
1699 kmemleak= [KNL] Boot-time kmemleak enable/disable
1700 Valid arguments: on, off
1702 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1705 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1706 Valid arguments: 0, 1, 2
1707 kmemcheck=0 (disabled)
1708 kmemcheck=1 (enabled)
1709 kmemcheck=2 (one-shot mode)
1710 Default: 2 (one-shot mode)
1712 kstack=N [X86] Print N words from the kernel stack
1715 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1716 Default is 0 (don't ignore, but inject #GP)
1718 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1722 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1723 Default is 1 (enabled)
1725 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1727 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1729 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1730 (virtualized MMU) support on capable Intel chips.
1731 Default is 1 (enabled)
1733 kvm-intel.emulate_invalid_guest_state=
1734 [KVM,Intel] Enable emulation of invalid guest states
1735 Default is 0 (disabled)
1737 kvm-intel.flexpriority=
1738 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1739 Default is 1 (enabled)
1742 [KVM,Intel] Enable VMX nesting (nVMX).
1743 Default is 0 (disabled)
1745 kvm-intel.unrestricted_guest=
1746 [KVM,Intel] Disable unrestricted guest feature
1747 (virtualized real and unpaged mode) on capable
1748 Intel chips. Default is 1 (enabled)
1750 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1751 feature (tagged TLBs) on capable Intel chips.
1752 Default is 1 (enabled)
1758 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1761 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1762 value for LAPIC timer one-shot implementation. Default
1763 back to the programmable timer unit in the LAPIC.
1765 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1768 libata.dma= [LIBATA] DMA control
1769 libata.dma=0 Disable all PATA and SATA DMA
1770 libata.dma=1 PATA and SATA Disk DMA only
1771 libata.dma=2 ATAPI (CDROM) DMA only
1772 libata.dma=4 Compact Flash DMA only
1773 Combinations also work, so libata.dma=3 enables DMA
1774 for disks and CDROMs, but not CFs.
1776 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1777 libata.ignore_hpa=0 keep BIOS limits (default)
1778 libata.ignore_hpa=1 ignore limits, using full disk
1780 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1784 libata.force= [LIBATA] Force configurations. The format is comma
1785 separated list of "[ID:]VAL" where ID is
1786 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1787 matching port, link or device. Basically, it matches
1788 the ATA ID string printed on console by libata. If
1789 the whole ID part is omitted, the last PORT and DEVICE
1790 values are used. If ID hasn't been specified yet, the
1791 configuration applies to all ports, links and devices.
1793 If only DEVICE is omitted, the parameter applies to
1794 the port and all links and devices behind it. DEVICE
1795 number of 0 either selects the first device or the
1796 first fan-out link behind PMP device. It does not
1797 select the host link. DEVICE number of 15 selects the
1798 host link and device attached to it.
1800 The VAL specifies the configuration to force. As long
1801 as there's no ambiguity shortcut notation is allowed.
1802 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1803 The following configurations can be forced.
1805 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1806 Any ID with matching PORT is used.
1808 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1810 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1811 udma[/][16,25,33,44,66,100,133] notation is also
1814 * [no]ncq: Turn on or off NCQ.
1816 * [no]ncqtrim: Turn off queued DSM TRIM.
1818 * nohrst, nosrst, norst: suppress hard, soft
1821 * rstonce: only attempt one reset during
1822 hot-unplug link recovery
1824 * dump_id: dump IDENTIFY data.
1826 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1828 * disable: Disable this device.
1830 If there are multiple matching configurations changing
1831 the same attribute, the last one is used.
1833 memblock=debug [KNL] Enable memblock debug messages.
1835 load_ramdisk= [RAM] List of ramdisks to load from floppy
1836 See Documentation/blockdev/ramdisk.txt.
1838 lockd.nlm_grace_period=P [NFS] Assign grace period.
1841 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1844 lockd.nlm_timeout=T [NFS] Assign timeout value.
1847 lockd.nlm_udpport=M [NFS] Assign UDP port.
1850 locktorture.nreaders_stress= [KNL]
1851 Set the number of locking read-acquisition kthreads.
1852 Defaults to being automatically set based on the
1853 number of online CPUs.
1855 locktorture.nwriters_stress= [KNL]
1856 Set the number of locking write-acquisition kthreads.
1858 locktorture.onoff_holdoff= [KNL]
1859 Set time (s) after boot for CPU-hotplug testing.
1861 locktorture.onoff_interval= [KNL]
1862 Set time (s) between CPU-hotplug operations, or
1863 zero to disable CPU-hotplug testing.
1865 locktorture.shuffle_interval= [KNL]
1866 Set task-shuffle interval (jiffies). Shuffling
1867 tasks allows some CPUs to go into dyntick-idle
1868 mode during the locktorture test.
1870 locktorture.shutdown_secs= [KNL]
1871 Set time (s) after boot system shutdown. This
1872 is useful for hands-off automated testing.
1874 locktorture.stat_interval= [KNL]
1875 Time (s) between statistics printk()s.
1877 locktorture.stutter= [KNL]
1878 Time (s) to stutter testing, for example,
1879 specifying five seconds causes the test to run for
1880 five seconds, wait for five seconds, and so on.
1881 This tests the locking primitive's ability to
1882 transition abruptly to and from idle.
1884 locktorture.torture_runnable= [BOOT]
1885 Start locktorture running at boot time.
1887 locktorture.torture_type= [KNL]
1888 Specify the locking implementation to test.
1890 locktorture.verbose= [KNL]
1891 Enable additional printk() statements.
1893 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1896 loglevel= All Kernel Messages with a loglevel smaller than the
1897 console loglevel will be printed to the console. It can
1898 also be changed with klogd or other programs. The
1899 loglevels are defined as follows:
1901 0 (KERN_EMERG) system is unusable
1902 1 (KERN_ALERT) action must be taken immediately
1903 2 (KERN_CRIT) critical conditions
1904 3 (KERN_ERR) error conditions
1905 4 (KERN_WARNING) warning conditions
1906 5 (KERN_NOTICE) normal but significant condition
1907 6 (KERN_INFO) informational
1908 7 (KERN_DEBUG) debug-level messages
1910 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1911 in bytes. n must be a power of two and greater
1912 than the minimal size. The minimal size is defined
1913 by LOG_BUF_SHIFT kernel config parameter. There is
1914 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1915 that allows to increase the default size depending on
1916 the number of CPUs. See init/Kconfig for more details.
1918 logo.nologo [FB] Disables display of the built-in Linux logo.
1919 This may be used to provide more screen space for
1920 kernel log messages and is useful when debugging
1921 kernel boot problems.
1923 lp=0 [LP] Specify parallel ports to use, e.g,
1924 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1925 lp=reset first parallel port). 'lp=0' disables the
1926 lp=auto printer driver. 'lp=reset' (which can be
1927 specified in addition to the ports) causes
1928 attached printers to be reset. Using
1929 lp=port1,port2,... specifies the parallel ports
1930 to associate lp devices with, starting with
1931 lp0. A port specification may be 'none' to skip
1932 that lp device, or a parport name such as
1933 'parport0'. Specifying 'lp=auto' instead of a
1934 port specification list means that device IDs
1935 from each port should be examined, to see if
1936 an IEEE 1284-compliant printer is attached; if
1937 so, the driver will manage that printer.
1938 See also header of drivers/char/lp.c.
1941 Sets loops_per_jiffy to given constant, thus avoiding
1942 time-consuming boot-time autodetection (up to 250 ms per
1943 CPU). 0 enables autodetection (default). To determine
1944 the correct value for your kernel, boot with normal
1945 autodetection and see what value is printed. Note that
1946 on SMP systems the preset will be applied to all CPUs,
1947 which is likely to cause problems if your CPUs need
1948 significantly divergent settings. An incorrect value
1949 will cause delays in the kernel to be wrong, leading to
1950 unpredictable I/O errors and other breakage. Although
1951 unlikely, in the extreme case this might damage your
1955 Format: <io>,<irq>,<dma>
1957 machvec= [IA-64] Force the use of a particular machine-vector
1958 (machvec) in a generic kernel.
1959 Example: machvec=hpzx1_swiotlb
1961 machtype= [Loongson] Share the same kernel image file between different
1963 Example: machtype=lemote-yeeloong-2f-7inch
1965 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1966 than or equal to this physical address is ignored.
1968 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1969 should make use of. maxcpus=n : n >= 0 limits the
1970 kernel to using 'n' processors. n=0 is a special case,
1971 it is equivalent to "nosmp", which also disables
1974 max_loop= [LOOP] The number of loop block devices that get
1975 (loop.max_loop) unconditionally pre-created at init time. The default
1976 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1977 of statically allocating a predefined number, loop
1978 devices can be requested on-demand with the
1979 /dev/loop-control interface.
1981 mce [X86-32] Machine Check Exception
1983 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1985 md= [HW] RAID subsystems devices and level
1986 See Documentation/md.txt.
1989 Format: <first>,<last>
1990 Specifies range of consoles to be captured by the MDA.
1992 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1993 Amount of memory to be used when the kernel is not able
1994 to see the whole system memory or for test.
1995 [X86] Work as limiting max address. Use together
1996 with memmap= to avoid physical address space collisions.
1997 Without memmap= PCI devices could be placed at addresses
1998 belonging to unused RAM.
2000 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2004 [KNL,SH] Allow user to override the default size for
2005 per-device physically contiguous DMA buffers.
2007 memmap=exactmap [KNL,X86] Enable setting of an exact
2008 E820 memory map, as specified by the user.
2009 Such memmap=exactmap lines can be constructed based on
2010 BIOS output or other requirements. See the memmap=nn@ss
2013 memmap=nn[KMG]@ss[KMG]
2014 [KNL] Force usage of a specific region of memory.
2015 Region of memory to be used is from ss to ss+nn.
2017 memmap=nn[KMG]#ss[KMG]
2018 [KNL,ACPI] Mark specific memory as ACPI data.
2019 Region of memory to be marked is from ss to ss+nn.
2021 memmap=nn[KMG]$ss[KMG]
2022 [KNL,ACPI] Mark specific memory as reserved.
2023 Region of memory to be reserved is from ss to ss+nn.
2024 Example: Exclude memory from 0x18690000-0x1869ffff
2025 memmap=64K$0x18690000
2027 memmap=0x10000$0x18690000
2029 memmap=nn[KMG]!ss[KMG]
2030 [KNL,X86] Mark specific memory as protected.
2031 Region of memory to be used, from ss to ss+nn.
2032 The memory region may be marked as e820 type 12 (0xc)
2033 and is NVDIMM or ADR memory.
2035 memory_corruption_check=0/1 [X86]
2036 Some BIOSes seem to corrupt the first 64k of
2037 memory when doing things like suspend/resume.
2038 Setting this option will scan the memory
2039 looking for corruption. Enabling this will
2040 both detect corruption and prevent the kernel
2041 from using the memory being corrupted.
2042 However, its intended as a diagnostic tool; if
2043 repeatable BIOS-originated corruption always
2044 affects the same memory, you can use memmap=
2045 to prevent the kernel from using that memory.
2047 memory_corruption_check_size=size [X86]
2048 By default it checks for corruption in the low
2049 64k, making this memory unavailable for normal
2050 use. Use this parameter to scan for
2051 corruption in more or less memory.
2053 memory_corruption_check_period=seconds [X86]
2054 By default it checks for corruption every 60
2055 seconds. Use this parameter to check at some
2056 other rate. 0 disables periodic checking.
2058 memtest= [KNL,X86,ARM] Enable memtest
2060 default : 0 <disable>
2061 Specifies the number of memtest passes to be
2062 performed. Each pass selects another test
2063 pattern from a given set of patterns. Memtest
2064 fills the memory with this pattern, validates
2065 memory contents and reserves bad memory
2066 regions that are detected.
2068 meye.*= [HW] Set MotionEye Camera parameters
2069 See Documentation/video4linux/meye.txt.
2071 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2072 Multi-Function General Purpose Timers on AMD Geode
2075 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2076 the BIOS has incorrectly applied a workaround. TinyBIOS
2077 version 0.98 is known to be affected, 0.99 fixes the
2078 problem by letting the user disable the workaround.
2082 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2083 physical address is ignored.
2085 mini2440= [ARM,HW,KNL]
2086 Format:[0..2][b][c][t]
2088 MINI2440 configuration specification:
2089 0 - The attached screen is the 3.5" TFT
2090 1 - The attached screen is the 7" TFT
2091 2 - The VGA Shield is attached (1024x768)
2092 Leaving out the screen size parameter will not load
2093 the TFT driver, and the framebuffer will be left
2095 b - Enable backlight. The TFT backlight pin will be
2096 linked to the kernel VESA blanking code and a GPIO
2097 LED. This parameter is not necessary when using the
2099 c - Enable the s3c camera interface.
2100 t - Reserved for enabling touchscreen support. The
2101 touchscreen support is not enabled in the mainstream
2102 kernel as of 2.6.30, a preliminary port can be found
2103 in the "bleeding edge" mini2440 support kernel at
2104 http://repo.or.cz/w/linux-2.6/mini2440.git
2107 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2108 parameter allows control of the logging verbosity for
2109 the additional memory initialisation checks. A value
2110 of 0 disables mminit logging and a level of 4 will
2111 log everything. Information is printed at KERN_DEBUG
2112 so loglevel=8 may also need to be specified.
2115 [KNL] When CONFIG_MODULE_SIG is set, this means that
2116 modules without (valid) signatures will fail to load.
2117 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2118 is always true, so this option does nothing.
2121 [MOUSE] Maximum time between finger touching and
2122 leaving touchpad surface for touch to be considered
2123 a tap and be reported as a left button click (for
2124 touchpads working in absolute mode only).
2126 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2127 reporting absolute coordinates, such as tablets
2128 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2129 reporting absolute coordinates, such as tablets
2131 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2132 is similar to kernelcore except it specifies the
2133 amount of memory used for migratable allocations.
2134 If both kernelcore and movablecore is specified,
2135 then kernelcore will be at *least* the specified
2136 value but may be more. If movablecore on its own
2137 is specified, the administrator must be careful
2138 that the amount of memory usable for all allocations
2141 movable_node [KNL,X86] Boot-time switch to enable the effects
2142 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2144 MTD_Partition= [MTD]
2145 Format: <name>,<region-number>,<size>,<offset>
2147 MTD_Region= [MTD] Format:
2148 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2151 See drivers/mtd/cmdlinepart.c.
2153 multitce=off [PPC] This parameter disables the use of the pSeries
2154 firmware feature for updating multiple TCE entries
2157 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2159 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2161 boundary - index of last SLC block on Flex-OneNAND.
2162 The remaining blocks are configured as MLC blocks.
2163 lock - Configure if Flex-OneNAND boundary should be locked.
2164 Once locked, the boundary cannot be changed.
2165 1 indicates lock status, 0 indicates unlock status.
2168 ARM/S3C2412 JIVE boot control
2170 See arch/arm/mach-s3c2412/mach-jive.c
2172 mtouchusb.raw_coordinates=
2173 [HW] Make the MicroTouch USB driver use raw coordinates
2174 ('y', default) or cooked coordinates ('n')
2176 mtrr_chunk_size=nn[KMG] [X86]
2177 used for mtrr cleanup. It is largest continuous chunk
2178 that could hold holes aka. UC entries.
2180 mtrr_gran_size=nn[KMG] [X86]
2181 Used for mtrr cleanup. It is granularity of mtrr block.
2183 Large value could prevent small alignment from
2186 mtrr_spare_reg_nr=n [X86]
2188 Range: 0,7 : spare reg number
2190 Used for mtrr cleanup. It is spare mtrr entries number.
2191 Set to 2 or more if your graphical card needs more.
2193 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2195 netdev= [NET] Network devices parameters
2196 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2197 Note that mem_start is often overloaded to mean
2198 something different and driver-specific.
2199 This usage is only documented in each driver source
2203 [NETFILTER] Enable connection tracking flow accounting
2204 0 to disable accounting
2205 1 to enable accounting
2208 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2209 See Documentation/filesystems/nfs/nfsroot.txt.
2211 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2212 See Documentation/filesystems/nfs/nfsroot.txt.
2214 nfsrootdebug [NFS] enable nfsroot debugging messages.
2215 See Documentation/filesystems/nfs/nfsroot.txt.
2217 nfs.callback_tcpport=
2218 [NFS] set the TCP port on which the NFSv4 callback
2219 channel should listen.
2222 [NFS] sets the pathname to the program which is used
2223 to update the NFS client cache entries.
2225 nfs.cache_getent_timeout=
2226 [NFS] sets the timeout after which an attempt to
2227 update a cache entry is deemed to have failed.
2229 nfs.idmap_cache_timeout=
2230 [NFS] set the maximum lifetime for idmapper cache
2234 [NFS] enable 64-bit inode numbers.
2235 If zero, the NFS client will fake up a 32-bit inode
2236 number for the readdir() and stat() syscalls instead
2237 of returning the full 64-bit number.
2238 The default is to return 64-bit inode numbers.
2240 nfs.max_session_slots=
2241 [NFSv4.1] Sets the maximum number of session slots
2242 the client will attempt to negotiate with the server.
2243 This limits the number of simultaneous RPC requests
2244 that the client can send to the NFSv4.1 server.
2245 Note that there is little point in setting this
2246 value higher than the max_tcp_slot_table_limit.
2248 nfs.nfs4_disable_idmapping=
2249 [NFSv4] When set to the default of '1', this option
2250 ensures that both the RPC level authentication
2251 scheme and the NFS level operations agree to use
2252 numeric uids/gids if the mount is using the
2253 'sec=sys' security flavour. In effect it is
2254 disabling idmapping, which can make migration from
2255 legacy NFSv2/v3 systems to NFSv4 easier.
2256 Servers that do not support this mode of operation
2257 will be autodetected by the client, and it will fall
2258 back to using the idmapper.
2259 To turn off this behaviour, set the value to '0'.
2261 [NFS4] Specify an additional fixed unique ident-
2262 ification string that NFSv4 clients can insert into
2263 their nfs_client_id4 string. This is typically a
2264 UUID that is generated at system install time.
2266 nfs.send_implementation_id =
2267 [NFSv4.1] Send client implementation identification
2268 information in exchange_id requests.
2269 If zero, no implementation identification information
2271 The default is to send the implementation identification
2274 nfs.recover_lost_locks =
2275 [NFSv4] Attempt to recover locks that were lost due
2276 to a lease timeout on the server. Please note that
2277 doing this risks data corruption, since there are
2278 no guarantees that the file will remain unchanged
2279 after the locks are lost.
2280 If you want to enable the kernel legacy behaviour of
2281 attempting to recover these locks, then set this
2283 The default parameter value of '0' causes the kernel
2284 not to attempt recovery of lost locks.
2286 nfsd.nfs4_disable_idmapping=
2287 [NFSv4] When set to the default of '1', the NFSv4
2288 server will return only numeric uids and gids to
2289 clients using auth_sys, and will accept numeric uids
2290 and gids from such clients. This is intended to ease
2291 migration from NFSv2/v3.
2293 objlayoutdriver.osd_login_prog=
2294 [NFS] [OBJLAYOUT] sets the pathname to the program which
2295 is used to automatically discover and login into new
2296 osd-targets. Please see:
2297 Documentation/filesystems/pnfs.txt for more explanations
2299 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2300 when a NMI is triggered.
2301 Format: [state][,regs][,debounce][,die]
2303 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2304 Format: [panic,][nopanic,][num]
2306 0 - turn nmi_watchdog off
2307 1 - turn nmi_watchdog on
2308 When panic is specified, panic when an NMI watchdog
2309 timeout occurs (or 'nopanic' to override the opposite
2311 This is useful when you use a panic=... timeout and
2312 need the box quickly up again.
2314 netpoll.carrier_timeout=
2315 [NET] Specifies amount of time (in seconds) that
2316 netpoll should wait for a carrier. By default netpoll
2319 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2320 emulation library even if a 387 maths coprocessor
2324 [HW] Never suspend the console
2325 Disable suspending of consoles during suspend and
2326 hibernate operations. Once disabled, debugging
2327 messages can reach various consoles while the rest
2328 of the system is being put to sleep (ie, while
2329 debugging driver suspend/resume hooks). This may
2330 not work reliably with all consoles, but is known
2331 to work with serial and VGA consoles.
2332 To facilitate more flexible debugging, we also add
2333 console_suspend, a printk module parameter to control
2334 it. Users could use console_suspend (usually
2335 /sys/module/printk/parameters/console_suspend) to
2336 turn on/off it dynamically.
2338 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2339 caches in the slab allocator. Saves per-node memory,
2340 but will impact performance.
2344 noapic [SMP,APIC] Tells the kernel to not make use of any
2345 IOAPICs that may be present in the system.
2347 noautogroup Disable scheduler automatic task group creation.
2349 nobats [PPC] Do not use BATs for mapping kernel lowmem
2350 on "Classic" PPC cores.
2354 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2356 nodelayacct [KNL] Disable per-task delay accounting
2358 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2360 nodsp [SH] Disable hardware DSP at boot time.
2362 noefi Disable EFI runtime services support.
2367 On X86-32 available only on PAE configured kernels.
2368 noexec=on: enable non-executable mappings (default)
2369 noexec=off: disable non-executable mappings
2372 Disable SMAP (Supervisor Mode Access Prevention)
2373 even if it is supported by processor.
2376 Disable SMEP (Supervisor Mode Execution Prevention)
2377 even if it is supported by processor.
2380 This affects only 32-bit executables.
2381 noexec32=on: enable non-executable mappings (default)
2382 read doesn't imply executable mappings
2383 noexec32=off: disable non-executable mappings
2384 read implies executable mappings
2386 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2388 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2389 register save and restore. The kernel will only save
2390 legacy floating-point registers on task switch.
2392 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2394 noxsave [BUGS=X86] Disables x86 extended register state save
2395 and restore using xsave. The kernel will fallback to
2396 enabling legacy floating-point and sse state.
2398 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2399 register states. The kernel will fall back to use
2400 xsave to save the states. By using this parameter,
2401 performance of saving the states is degraded because
2402 xsave doesn't support modified optimization while
2403 xsaveopt supports it on xsaveopt enabled systems.
2405 noxsaves [X86] Disables xsaves and xrstors used in saving and
2406 restoring x86 extended register state in compacted
2407 form of xsave area. The kernel will fall back to use
2408 xsaveopt and xrstor to save and restore the states
2409 in standard form of xsave area. By using this
2410 parameter, xsave area per process might occupy more
2411 memory on xsaves enabled systems.
2413 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2414 wfi(ARM) instruction doesn't work correctly and not to
2415 use it. This is also useful when using JTAG debugger.
2417 no_file_caps Tells the kernel not to honor file capabilities. The
2418 only way then for a file to be executed with privilege
2419 is to be setuid root or executed by root.
2421 nohalt [IA-64] Tells the kernel not to use the power saving
2422 function PAL_HALT_LIGHT when idle. This increases
2423 power-consumption. On the positive side, it reduces
2424 interrupt wake-up latency, which may improve performance
2425 in certain environments such as networked servers or
2428 nohibernate [HIBERNATION] Disable hibernation and resume.
2430 nohz= [KNL] Boottime enable/disable dynamic ticks
2431 Valid arguments: on, off
2434 nohz_full= [KNL,BOOT]
2435 In kernels built with CONFIG_NO_HZ_FULL=y, set
2436 the specified list of CPUs whose tick will be stopped
2437 whenever possible. The boot CPU will be forced outside
2438 the range to maintain the timekeeping.
2439 The CPUs in this range must also be included in the
2442 noiotrap [SH] Disables trapped I/O port accesses.
2444 noirqdebug [X86-32] Disables the code which attempts to detect and
2445 disable unhandled interrupt sources.
2447 no_timer_check [X86,APIC] Disables the code which tests for
2448 broken timer IRQ sources.
2450 noisapnp [ISAPNP] Disables ISA PnP code.
2452 noinitrd [RAM] Tells the kernel not to load any configured
2455 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2457 [Deprecated - use intremap=off]
2461 nojitter [IA-64] Disables jitter checking for ITC timers.
2463 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2465 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2468 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2469 steal time is computed, but won't influence scheduler
2472 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2474 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2476 noltlbs [PPC] Do not use large page/tlb entries for kernel
2477 lowmem mapping on PPC40x.
2479 nomca [IA-64] Disable machine check abort handling
2481 nomce [X86-32] Disable Machine Check Exception
2483 nomfgpt [X86-32] Disable Multi-Function General Purpose
2484 Timer usage (for AMD Geode machines).
2486 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2487 shutdown the other cpus. Instead use the REBOOT_VECTOR
2490 nomodule Disable module load
2492 nopat [X86] Disable PAT (page attribute table extension of
2493 pagetables) support.
2495 norandmaps Don't use address space randomization. Equivalent to
2496 echo 0 > /proc/sys/kernel/randomize_va_space
2498 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2500 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2501 with UP alternatives
2503 nordrand [X86] Disable kernel use of the RDRAND and
2504 RDSEED instructions even if they are supported
2505 by the processor. RDRAND and RDSEED are still
2506 available to user space applications.
2508 noresume [SWSUSP] Disables resume and restores original swap
2511 no-scroll [VGA] Disables scrollback.
2512 This is required for the Braillex ib80-piezo Braille
2513 reader made by F.H. Papenmeier (Germany).
2517 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2519 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2520 and disable the IO APIC. legacy for "maxcpus=0".
2522 nosoftlockup [KNL] Disable the soft-lockup detector.
2524 nosync [HW,M68K] Disables sync negotiation for all devices.
2526 notsc [BUGS=X86-32] Disable Time Stamp Counter
2528 nousb [USB] Disable the USB subsystem
2530 nowatchdog [KNL] Disable both lockup detectors, i.e.
2531 soft-lockup and NMI watchdog (hard-lockup).
2535 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2537 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2538 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2539 Some features depend on CPU0. Known dependencies are:
2540 1. Resume from suspend/hibernate depends on CPU0.
2541 Suspend/hibernate will fail if CPU0 is offline and you
2542 need to online CPU0 before suspend/hibernate.
2543 2. PIC interrupts also depend on CPU0. CPU0 can't be
2544 removed if a PIC interrupt is detected.
2545 It's said poweroff/reboot may depend on CPU0 on some
2546 machines although I haven't seen such issues so far
2547 after CPU0 is offline on a few tested machines.
2548 If the dependencies are under your control, you can
2549 turn on cpu0_hotplug.
2551 nptcg= [IA-64] Override max number of concurrent global TLB
2552 purges which is reported from either PAL_VM_SUMMARY or
2555 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2556 could support. nr_cpus=n : n >= 1 limits the kernel to
2557 supporting 'n' processors. Later in runtime you can not
2558 use hotplug cpu feature to put more cpu back to online.
2559 just like you compile the kernel NR_CPUS=n
2561 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2563 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2564 Allowed values are enable and disable
2566 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2567 one of ['zone', 'node', 'default'] can be specified
2568 This can be set from sysctl after boot.
2569 See Documentation/sysctl/vm.txt for details.
2571 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2572 See Documentation/debugging-via-ohci1394.txt for more
2575 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2576 Rather than timing out after 20 ms if an EC
2577 command is not properly ACKed, override the length
2578 of the timeout. We have interrupts disabled while
2579 waiting for the ACK, so if this is set too high
2580 interrupts *may* be lost!
2582 omap_mux= [OMAP] Override bootloader pin multiplexing.
2583 Format: <mux_mode0.mode_name=value>...
2584 For example, to override I2C bus2:
2585 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2587 oprofile.timer= [HW]
2588 Use timer interrupt instead of performance counters
2590 oprofile.cpu_type= Force an oprofile cpu type
2591 This might be useful if you have an older oprofile
2592 userland or if you want common events.
2593 Format: { arch_perfmon }
2594 arch_perfmon: [X86] Force use of architectural
2595 perfmon on Intel CPUs instead of the
2596 CPU specific event set.
2597 timer: [X86] Force use of architectural NMI
2598 timer mode (see also oprofile.timer
2599 for generic hr timer mode)
2600 [s390] Force legacy basic mode sampling
2601 (report cpu_type "timer")
2603 oops=panic Always panic on oopses. Default is to just kill the
2604 process, but there is a small probability of
2605 deadlocking the machine.
2606 This will also cause panics on machine check exceptions.
2607 Useful together with panic=30 to trigger a reboot.
2610 See Documentation/sound/oss/oss-parameters.txt
2612 page_owner= [KNL] Boot-time page_owner enabling option.
2613 Storage of the information about who allocated
2614 each page is disabled in default. With this switch,
2616 on: enable the feature
2618 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2619 timeout > 0: seconds before rebooting
2620 timeout = 0: wait forever
2621 timeout < 0: reboot immediately
2624 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2627 crash_kexec_post_notifiers
2628 Run kdump after running panic-notifiers and dumping
2629 kmsg. This only for the users who doubt kdump always
2630 succeeds in any situation.
2631 Note that this also increases risks of kdump failure,
2632 because some panic notifiers can make the crashed
2633 kernel more unstable.
2635 parkbd.port= [HW] Parallel port number the keyboard adapter is
2636 connected to, default is 0.
2638 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2639 0 for XT, 1 for AT (default is AT).
2642 parport= [HW,PPT] Specify parallel ports. 0 disables.
2643 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2644 Use 'auto' to force the driver to use any
2645 IRQ/DMA settings detected (the default is to
2646 ignore detected IRQ/DMA settings because of
2647 possible conflicts). You can specify the base
2648 address, IRQ, and DMA settings; IRQ and DMA
2649 should be numbers, or 'auto' (for using detected
2650 settings on that particular port), or 'nofifo'
2651 (to avoid using a FIFO even if it is detected).
2652 Parallel ports are assigned in the order they
2653 are specified on the command line, starting
2656 parport_init_mode= [HW,PPT]
2657 Configure VIA parallel port to operate in
2658 a specific mode. This is necessary on Pegasos
2659 computer where firmware has no options for setting
2660 up parallel port mode and sets it to spp.
2661 Currently this function knows 686a and 8231 chips.
2662 Format: [spp|ps2|epp|ecp|ecpepp]
2665 Halt all CPUs after the first oops has been printed for
2666 the specified number of seconds. This is to be used if
2667 your oopses keep scrolling off the screen.
2672 See header of drivers/block/paride/pcd.c.
2673 See also Documentation/blockdev/paride.txt.
2675 pci=option[,option...] [PCI] various PCI subsystem options:
2676 earlydump [X86] dump PCI config space before the kernel
2678 off [X86] don't probe for the PCI bus
2679 bios [X86-32] force use of PCI BIOS, don't access
2680 the hardware directly. Use this if your machine
2681 has a non-standard PCI host bridge.
2682 nobios [X86-32] disallow use of PCI BIOS, only direct
2683 hardware access methods are allowed. Use this
2684 if you experience crashes upon bootup and you
2685 suspect they are caused by the BIOS.
2686 conf1 [X86] Force use of PCI Configuration
2688 conf2 [X86] Force use of PCI Configuration
2690 noaer [PCIE] If the PCIEAER kernel config parameter is
2691 enabled, this kernel boot option can be used to
2692 disable the use of PCIE advanced error reporting.
2693 nodomains [PCI] Disable support for multiple PCI
2694 root domains (aka PCI segments, in ACPI-speak).
2695 nommconf [X86] Disable use of MMCONFIG for PCI
2697 check_enable_amd_mmconf [X86] check for and enable
2698 properly configured MMIO access to PCI
2699 config space on AMD family 10h CPU
2700 nomsi [MSI] If the PCI_MSI kernel config parameter is
2701 enabled, this kernel boot option can be used to
2702 disable the use of MSI interrupts system-wide.
2703 noioapicquirk [APIC] Disable all boot interrupt quirks.
2704 Safety option to keep boot IRQs enabled. This
2705 should never be necessary.
2706 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2707 primary IO-APIC for bridges that cannot disable
2708 boot IRQs. This fixes a source of spurious IRQs
2709 when the system masks IRQs.
2710 noioapicreroute [APIC] Disable workaround that uses the
2711 boot IRQ equivalent of an IRQ that connects to
2712 a chipset where boot IRQs cannot be disabled.
2713 The opposite of ioapicreroute.
2714 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2715 routing table. These calls are known to be buggy
2716 on several machines and they hang the machine
2717 when used, but on other computers it's the only
2718 way to get the interrupt routing table. Try
2719 this option if the kernel is unable to allocate
2720 IRQs or discover secondary PCI buses on your
2722 rom [X86] Assign address space to expansion ROMs.
2723 Use with caution as certain devices share
2724 address decoders between ROMs and other
2726 norom [X86] Do not assign address space to
2727 expansion ROMs that do not already have
2728 BIOS assigned address ranges.
2729 nobar [X86] Do not assign address space to the
2730 BARs that weren't assigned by the BIOS.
2731 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2732 assigned automatically to PCI devices. You can
2733 make the kernel exclude IRQs of your ISA cards
2735 pirqaddr=0xAAAAA [X86] Specify the physical address
2736 of the PIRQ table (normally generated
2737 by the BIOS) if it is outside the
2738 F0000h-100000h range.
2739 lastbus=N [X86] Scan all buses thru bus #N. Can be
2740 useful if the kernel is unable to find your
2741 secondary buses and you want to tell it
2742 explicitly which ones they are.
2743 assign-busses [X86] Always assign all PCI bus
2744 numbers ourselves, overriding
2745 whatever the firmware may have done.
2746 usepirqmask [X86] Honor the possible IRQ mask stored
2747 in the BIOS $PIR table. This is needed on
2748 some systems with broken BIOSes, notably
2749 some HP Pavilion N5400 and Omnibook XE3
2750 notebooks. This will have no effect if ACPI
2751 IRQ routing is enabled.
2752 noacpi [X86] Do not use ACPI for IRQ routing
2753 or for PCI scanning.
2754 use_crs [X86] Use PCI host bridge window information
2755 from ACPI. On BIOSes from 2008 or later, this
2756 is enabled by default. If you need to use this,
2757 please report a bug.
2758 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2759 If you need to use this, please report a bug.
2760 routeirq Do IRQ routing for all PCI devices.
2761 This is normally done in pci_enable_device(),
2762 so this option is a temporary workaround
2763 for broken drivers that don't call it.
2764 skip_isa_align [X86] do not align io start addr, so can
2765 handle more pci cards
2766 firmware [ARM] Do not re-enumerate the bus but instead
2767 just use the configuration from the
2768 bootloader. This is currently used on
2769 IXP2000 systems where the bus has to be
2770 configured a certain way for adjunct CPUs.
2771 noearly [X86] Don't do any early type 1 scanning.
2772 This might help on some broken boards which
2773 machine check when some devices' config space
2774 is read. But various workarounds are disabled
2775 and some IOMMU drivers will not work.
2776 bfsort Sort PCI devices into breadth-first order.
2777 This sorting is done to get a device
2778 order compatible with older (<= 2.4) kernels.
2779 nobfsort Don't sort PCI devices into breadth-first order.
2780 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2781 tuning and use the BIOS-configured MPS defaults.
2782 pcie_bus_safe Set every device's MPS to the largest value
2783 supported by all devices below the root complex.
2784 pcie_bus_perf Set device MPS to the largest allowable MPS
2785 based on its parent bus. Also set MRRS (Max
2786 Read Request Size) to the largest supported
2787 value (no larger than the MPS that the device
2788 or bus can support) for best performance.
2789 pcie_bus_peer2peer Set every device's MPS to 128B, which
2790 every device is guaranteed to support. This
2791 configuration allows peer-to-peer DMA between
2792 any pair of devices, possibly at the cost of
2793 reduced performance. This also guarantees
2794 that hot-added devices will work.
2795 cbiosize=nn[KMG] The fixed amount of bus space which is
2796 reserved for the CardBus bridge's IO window.
2797 The default value is 256 bytes.
2798 cbmemsize=nn[KMG] The fixed amount of bus space which is
2799 reserved for the CardBus bridge's memory
2800 window. The default value is 64 megabytes.
2803 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2804 Specifies alignment and device to reassign
2805 aligned memory resources.
2806 If <order of align> is not specified,
2807 PAGE_SIZE is used as alignment.
2808 PCI-PCI bridge can be specified, if resource
2809 windows need to be expanded.
2810 ecrc= Enable/disable PCIe ECRC (transaction layer
2811 end-to-end CRC checking).
2812 bios: Use BIOS/firmware settings. This is the
2816 hpiosize=nn[KMG] The fixed amount of bus space which is
2817 reserved for hotplug bridge's IO window.
2818 Default size is 256 bytes.
2819 hpmemsize=nn[KMG] The fixed amount of bus space which is
2820 reserved for hotplug bridge's memory window.
2821 Default size is 2 megabytes.
2822 realloc= Enable/disable reallocating PCI bridge resources
2823 if allocations done by BIOS are too small to
2824 accommodate resources required by all child
2826 off: Turn realloc off
2828 realloc same as realloc=on
2829 noari do not use PCIe ARI.
2830 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2831 only look for one device below a PCIe downstream
2834 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2837 force Enable ASPM even on devices that claim not to support it.
2838 WARNING: Forcing ASPM on may cause system lockups.
2840 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2841 nomsi Do not use MSI for PCI Express Native Hotplug (this
2842 makes all PCIe ports use INTx for hotplug services).
2844 pcie_ports= [PCIE] PCIe ports handling:
2845 auto Ask the BIOS whether or not to use native PCIe services
2846 associated with PCIe ports (PME, hot-plug, AER). Use
2847 them only if that is allowed by the BIOS.
2848 native Use native PCIe services associated with PCIe ports
2850 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2853 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2854 nomsi Do not use MSI for native PCIe PME signaling (this makes
2855 all PCIe root ports use INTx for all services).
2857 pcmv= [HW,PCMCIA] BadgePAD 4
2861 Keep all power-domains already enabled by bootloader on,
2862 even if no driver has claimed them. This is useful
2863 for debug and development, but should not be
2864 needed on a platform with proper driver support.
2867 See Documentation/blockdev/paride.txt.
2869 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2872 See arch/parisc/kernel/pdc_chassis.c
2874 percpu_alloc= Select which percpu first chunk allocator to use.
2875 Currently supported values are "embed" and "page".
2876 Archs may support subset or none of the selections.
2877 See comments in mm/percpu.c for details on each
2878 allocator. This parameter is primarily for debugging
2879 and performance comparison.
2882 See Documentation/blockdev/paride.txt.
2885 See Documentation/blockdev/paride.txt.
2887 pirq= [SMP,APIC] Manual mp-table setup
2888 See Documentation/x86/i386/IO-APIC.txt.
2890 plip= [PPT,NET] Parallel port network link
2891 Format: { parport<nr> | timid | 0 }
2892 See also Documentation/parport.txt.
2894 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2895 Override pmtimer IOPort with a hex value.
2899 Enable PNP debug messages (depends on the
2900 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2901 via /sys/module/pnp/parameters/debug. We always show
2902 current resource usage; turning this on also shows
2903 possible settings and some assignment information.
2909 { on | off | curr | res | no-curr | no-res }
2912 [ISAPNP] Exclude IRQs for the autoconfiguration
2915 [ISAPNP] Exclude DMAs for the autoconfiguration
2917 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2918 Ranges are in pairs (I/O port base and size).
2921 [ISAPNP] Exclude memory regions for the
2923 Ranges are in pairs (memory base and size).
2925 ports= [IP_VS_FTP] IPVS ftp helper module
2927 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2929 Format: <port>,<port>....
2931 print-fatal-signals=
2932 [KNL] debug: print fatal signals
2934 If enabled, warn about various signal handling
2935 related application anomalies: too many signals,
2936 too many POSIX.1 timers, fatal signals causing a
2939 If you hit the warning due to signal overflow,
2940 you might want to try "ulimit -i unlimited".
2944 printk.always_kmsg_dump=
2945 Trigger kmsg_dump for cases other than kernel oops or
2947 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2950 printk.time= Show timing data prefixed to each printk message line
2951 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2953 processor.max_cstate= [HW,ACPI]
2954 Limit processor to maximum C-state
2955 max_cstate=9 overrides any DMI blacklist limit.
2957 processor.nocst [HW,ACPI]
2958 Ignore the _CST method to determine C-states,
2959 instead using the legacy FADT method
2961 profile= [KNL] Enable kernel profiling via /proc/profile
2962 Format: [schedule,]<number>
2963 Param: "schedule" - profile schedule points.
2964 Param: <number> - step/bucket size as a power of 2 for
2965 statistical time based profiling.
2966 Param: "sleep" - profile D-state sleeping (millisecs).
2967 Requires CONFIG_SCHEDSTATS
2968 Param: "kvm" - profile VM exits.
2970 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2972 See Documentation/blockdev/ramdisk.txt.
2974 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2975 probe for; one of (bare|imps|exps|lifebook|any).
2976 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2978 psmouse.resetafter= [HW,MOUSE]
2979 Try to reset the device after so many bad packets
2982 [HW,MOUSE] Set desired mouse resolution, in dpi.
2983 psmouse.smartscroll=
2984 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2985 0 = disabled, 1 = enabled (default).
2987 pstore.backend= Specify the name of the pstore backend to use
2990 See Documentation/blockdev/paride.txt.
2993 [KNL] Number of legacy pty's. Overwrites compiled-in
2996 quiet [KNL] Disable most log messages
3001 See Documentation/md.txt.
3003 ramdisk_blocksize= [RAM]
3004 See Documentation/blockdev/ramdisk.txt.
3006 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3007 See Documentation/blockdev/ramdisk.txt.
3010 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3011 the specified list of CPUs to be no-callback CPUs.
3012 Invocation of these CPUs' RCU callbacks will
3013 be offloaded to "rcuox/N" kthreads created for
3014 that purpose, where "x" is "b" for RCU-bh, "p"
3015 for RCU-preempt, and "s" for RCU-sched, and "N"
3016 is the CPU number. This reduces OS jitter on the
3017 offloaded CPUs, which can be useful for HPC and
3018 real-time workloads. It can also improve energy
3019 efficiency for asymmetric multiprocessors.
3022 Rather than requiring that offloaded CPUs
3023 (specified by rcu_nocbs= above) explicitly
3024 awaken the corresponding "rcuoN" kthreads,
3025 make these kthreads poll for callbacks.
3026 This improves the real-time response for the
3027 offloaded CPUs by relieving them of the need to
3028 wake up the corresponding kthread, but degrades
3029 energy efficiency by requiring that the kthreads
3030 periodically wake up to do the polling.
3032 rcutree.blimit= [KNL]
3033 Set maximum number of finished RCU callbacks to
3034 process in one batch.
3036 rcutree.dump_tree= [KNL]
3037 Dump the structure of the rcu_node combining tree
3038 out at early boot. This is used for diagnostic
3039 purposes, to verify correct tree setup.
3041 rcutree.gp_cleanup_delay= [KNL]
3042 Set the number of jiffies to delay each step of
3043 RCU grace-period cleanup. This only has effect
3044 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3046 rcutree.gp_init_delay= [KNL]
3047 Set the number of jiffies to delay each step of
3048 RCU grace-period initialization. This only has
3049 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3052 rcutree.gp_preinit_delay= [KNL]
3053 Set the number of jiffies to delay each step of
3054 RCU grace-period pre-initialization, that is,
3055 the propagation of recent CPU-hotplug changes up
3056 the rcu_node combining tree. This only has effect
3057 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3059 rcutree.rcu_fanout_exact= [KNL]
3060 Disable autobalancing of the rcu_node combining
3061 tree. This is used by rcutorture, and might
3062 possibly be useful for architectures having high
3063 cache-to-cache transfer latencies.
3065 rcutree.rcu_fanout_leaf= [KNL]
3066 Increase the number of CPUs assigned to each
3067 leaf rcu_node structure. Useful for very large
3070 rcutree.jiffies_till_sched_qs= [KNL]
3071 Set required age in jiffies for a
3072 given grace period before RCU starts
3073 soliciting quiescent-state help from
3074 rcu_note_context_switch().
3076 rcutree.jiffies_till_first_fqs= [KNL]
3077 Set delay from grace-period initialization to
3078 first attempt to force quiescent states.
3079 Units are jiffies, minimum value is zero,
3080 and maximum value is HZ.
3082 rcutree.jiffies_till_next_fqs= [KNL]
3083 Set delay between subsequent attempts to force
3084 quiescent states. Units are jiffies, minimum
3085 value is one, and maximum value is HZ.
3087 rcutree.kthread_prio= [KNL,BOOT]
3088 Set the SCHED_FIFO priority of the RCU per-CPU
3089 kthreads (rcuc/N). This value is also used for
3090 the priority of the RCU boost threads (rcub/N)
3091 and for the RCU grace-period kthreads (rcu_bh,
3092 rcu_preempt, and rcu_sched). If RCU_BOOST is
3093 set, valid values are 1-99 and the default is 1
3094 (the least-favored priority). Otherwise, when
3095 RCU_BOOST is not set, valid values are 0-99 and
3096 the default is zero (non-realtime operation).
3098 rcutree.rcu_nocb_leader_stride= [KNL]
3099 Set the number of NOCB kthread groups, which
3100 defaults to the square root of the number of
3101 CPUs. Larger numbers reduces the wakeup overhead
3102 on the per-CPU grace-period kthreads, but increases
3103 that same overhead on each group's leader.
3105 rcutree.qhimark= [KNL]
3106 Set threshold of queued RCU callbacks beyond which
3107 batch limiting is disabled.
3109 rcutree.qlowmark= [KNL]
3110 Set threshold of queued RCU callbacks below which
3111 batch limiting is re-enabled.
3113 rcutree.rcu_idle_gp_delay= [KNL]
3114 Set wakeup interval for idle CPUs that have
3115 RCU callbacks (RCU_FAST_NO_HZ=y).
3117 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3118 Set wakeup interval for idle CPUs that have
3119 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3120 Lazy RCU callbacks are those which RCU can
3121 prove do nothing more than free memory.
3123 rcutorture.cbflood_inter_holdoff= [KNL]
3124 Set holdoff time (jiffies) between successive
3125 callback-flood tests.
3127 rcutorture.cbflood_intra_holdoff= [KNL]
3128 Set holdoff time (jiffies) between successive
3129 bursts of callbacks within a given callback-flood
3132 rcutorture.cbflood_n_burst= [KNL]
3133 Set the number of bursts making up a given
3134 callback-flood test. Set this to zero to
3135 disable callback-flood testing.
3137 rcutorture.cbflood_n_per_burst= [KNL]
3138 Set the number of callbacks to be registered
3139 in a given burst of a callback-flood test.
3141 rcutorture.fqs_duration= [KNL]
3142 Set duration of force_quiescent_state bursts.
3144 rcutorture.fqs_holdoff= [KNL]
3145 Set holdoff time within force_quiescent_state bursts.
3147 rcutorture.fqs_stutter= [KNL]
3148 Set wait time between force_quiescent_state bursts.
3150 rcutorture.gp_exp= [KNL]
3151 Use expedited update-side primitives.
3153 rcutorture.gp_normal= [KNL]
3154 Use normal (non-expedited) update-side primitives.
3155 If both gp_exp and gp_normal are set, do both.
3156 If neither gp_exp nor gp_normal are set, still
3159 rcutorture.n_barrier_cbs= [KNL]
3160 Set callbacks/threads for rcu_barrier() testing.
3162 rcutorture.nfakewriters= [KNL]
3163 Set number of concurrent RCU writers. These just
3164 stress RCU, they don't participate in the actual
3165 test, hence the "fake".
3167 rcutorture.nreaders= [KNL]
3168 Set number of RCU readers. The value -1 selects
3169 N-1, where N is the number of CPUs. A value
3170 "n" less than -1 selects N-n-2, where N is again
3171 the number of CPUs. For example, -2 selects N
3172 (the number of CPUs), -3 selects N+1, and so on.
3174 rcutorture.object_debug= [KNL]
3175 Enable debug-object double-call_rcu() testing.
3177 rcutorture.onoff_holdoff= [KNL]
3178 Set time (s) after boot for CPU-hotplug testing.
3180 rcutorture.onoff_interval= [KNL]
3181 Set time (s) between CPU-hotplug operations, or
3182 zero to disable CPU-hotplug testing.
3184 rcutorture.torture_runnable= [BOOT]
3185 Start rcutorture running at boot time.
3187 rcutorture.shuffle_interval= [KNL]
3188 Set task-shuffle interval (s). Shuffling tasks
3189 allows some CPUs to go into dyntick-idle mode
3190 during the rcutorture test.
3192 rcutorture.shutdown_secs= [KNL]
3193 Set time (s) after boot system shutdown. This
3194 is useful for hands-off automated testing.
3196 rcutorture.stall_cpu= [KNL]
3197 Duration of CPU stall (s) to test RCU CPU stall
3198 warnings, zero to disable.
3200 rcutorture.stall_cpu_holdoff= [KNL]
3201 Time to wait (s) after boot before inducing stall.
3203 rcutorture.stat_interval= [KNL]
3204 Time (s) between statistics printk()s.
3206 rcutorture.stutter= [KNL]
3207 Time (s) to stutter testing, for example, specifying
3208 five seconds causes the test to run for five seconds,
3209 wait for five seconds, and so on. This tests RCU's
3210 ability to transition abruptly to and from idle.
3212 rcutorture.test_boost= [KNL]
3213 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3214 "Maybe" means test if the RCU implementation
3215 under test support RCU priority boosting.
3217 rcutorture.test_boost_duration= [KNL]
3218 Duration (s) of each individual boost test.
3220 rcutorture.test_boost_interval= [KNL]
3221 Interval (s) between each boost test.
3223 rcutorture.test_no_idle_hz= [KNL]
3224 Test RCU's dyntick-idle handling. See also the
3225 rcutorture.shuffle_interval parameter.
3227 rcutorture.torture_type= [KNL]
3228 Specify the RCU implementation to test.
3230 rcutorture.verbose= [KNL]
3231 Enable additional printk() statements.
3233 rcupdate.rcu_expedited= [KNL]
3234 Use expedited grace-period primitives, for
3235 example, synchronize_rcu_expedited() instead
3236 of synchronize_rcu(). This reduces latency,
3237 but can increase CPU utilization, degrade
3238 real-time latency, and degrade energy efficiency.
3240 rcupdate.rcu_cpu_stall_suppress= [KNL]
3241 Suppress RCU CPU stall warning messages.
3243 rcupdate.rcu_cpu_stall_timeout= [KNL]
3244 Set timeout for RCU CPU stall warning messages.
3246 rcupdate.rcu_task_stall_timeout= [KNL]
3247 Set timeout in jiffies for RCU task stall warning
3248 messages. Disable with a value less than or equal
3251 rcupdate.rcu_self_test= [KNL]
3252 Run the RCU early boot self tests
3254 rcupdate.rcu_self_test_bh= [KNL]
3255 Run the RCU bh early boot self tests
3257 rcupdate.rcu_self_test_sched= [KNL]
3258 Run the RCU sched early boot self tests
3262 Run specified binary instead of /init from the ramdisk,
3263 used for early userspace startup. See initrd.
3266 Format (x86 or x86_64):
3267 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3269 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3271 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3272 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3273 reboot_force is either force or not specified,
3274 reboot_cpu is s[mp]#### with #### being the processor
3275 to be used for rebooting.
3278 [KNL, SMP] Set scheduler's default relax_domain_level.
3279 See Documentation/cgroups/cpusets.txt.
3281 relative_sleep_states=
3282 [SUSPEND] Use sleep state labeling where the deepest
3283 state available other than hibernation is always "mem".
3284 Format: { "0" | "1" }
3285 0 -- Traditional sleep state labels.
3286 1 -- Relative sleep state labels.
3288 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3290 reservetop= [X86-32]
3292 Reserves a hole at the top of the kernel virtual
3297 Set the amount of memory to reserve for BIOS at
3298 the bottom of the address space.
3300 reset_devices [KNL] Force drivers to reset the underlying device
3301 during initialization.
3304 Specify the partition device for software suspend
3306 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3308 resume_offset= [SWSUSP]
3309 Specify the offset from the beginning of the partition
3310 given by "resume=" at which the swap header is located,
3311 in <PAGE_SIZE> units (needed only for swap files).
3312 See Documentation/power/swsusp-and-swap-files.txt
3314 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3315 read the resume files
3317 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3318 Useful for devices that are detected asynchronously
3319 (e.g. USB and MMC devices).
3321 hibernate= [HIBERNATION]
3322 noresume Don't check if there's a hibernation image
3323 present during boot.
3324 nocompress Don't compress/decompress hibernation images.
3325 no Disable hibernation and resume.
3327 retain_initrd [RAM] Keep initrd memory after extraction
3329 rfkill.default_state=
3330 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3331 etc. communication is blocked by default.
3334 rfkill.master_switch_mode=
3335 0 The "airplane mode" button does nothing.
3336 1 The "airplane mode" button toggles between everything
3337 blocked and the previous configuration.
3338 2 The "airplane mode" button toggles between everything
3339 blocked and everything unblocked.
3341 rhash_entries= [KNL,NET]
3342 Set number of hash buckets for route cache
3344 ro [KNL] Mount root device read-only on boot
3346 root= [KNL] Root filesystem
3347 See name_to_dev_t comment in init/do_mounts.c.
3349 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3350 mount the root filesystem
3352 rootflags= [KNL] Set root filesystem mount option string
3354 rootfstype= [KNL] Set root filesystem type
3356 rootwait [KNL] Wait (indefinitely) for root device to show up.
3357 Useful for devices that are detected asynchronously
3358 (e.g. USB and MMC devices).
3360 rproc_mem=nn[KMG][@address]
3361 [KNL,ARM,CMA] Remoteproc physical memory block.
3362 Memory area to be used by remote processor image,
3365 rw [KNL] Mount root device read-write on boot
3367 S [KNL] Run init in single mode
3369 s390_iommu= [HW,S390]
3370 Set s390 IOTLB flushing mode
3372 With strict flushing every unmap operation will result in
3373 an IOTLB flush. Default is lazy flushing before reuse,
3377 See drivers/net/irda/sa1100_ir.c.
3379 sbni= [NET] Granch SBNI12 leased line adapter
3381 sched_debug [KNL] Enables verbose scheduler debug messages.
3383 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3384 xtime_lock contention on larger systems, and/or RCU lock
3385 contention on all systems with CONFIG_MAXSMP set.
3386 Format: { "0" | "1" }
3387 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3389 Note: increases power consumption, thus should only be
3390 enabled if running jitter sensitive (HPC/RT) workloads.
3392 security= [SECURITY] Choose a security module to enable at boot.
3393 If this boot parameter is not specified, only the first
3394 security module asking for security registration will be
3395 loaded. An invalid security module name will be treated
3396 as if no module has been chosen.
3398 selinux= [SELINUX] Disable or enable SELinux at boot time.
3399 Format: { "0" | "1" }
3400 See security/selinux/Kconfig help text.
3403 Default value is set via kernel config option.
3404 If enabled at boot time, /selinux/disable can be used
3405 later to disable prior to initial policy load.
3407 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3408 Format: { "0" | "1" }
3409 See security/apparmor/Kconfig help text
3412 Default value is set via kernel config option.
3414 serialnumber [BUGS=X86-32]
3417 Maximal number of shapers.
3419 show_msr= [x86] show boot-time MSR settings
3420 Format: { <integer> }
3421 Show boot-time (BIOS-initialized) MSR settings.
3422 The parameter means the number of CPUs to show,
3423 for example 1 means boot CPU only.
3431 Disable merging of slabs with similar size. May be
3432 necessary if there is some reason to distinguish
3433 allocs to different slabs. Debug options disable
3434 merging on their own.
3435 For more information see Documentation/vm/slub.txt.
3437 slab_max_order= [MM, SLAB]
3438 Determines the maximum allowed order for slabs.
3439 A high setting may cause OOMs due to memory
3440 fragmentation. Defaults to 1 for systems with
3441 more than 32MB of RAM, 0 otherwise.
3443 slub_debug[=options[,slabs]] [MM, SLUB]
3444 Enabling slub_debug allows one to determine the
3445 culprit if slab objects become corrupted. Enabling
3446 slub_debug can create guard zones around objects and
3447 may poison objects when not in use. Also tracks the
3448 last alloc / free. For more information see
3449 Documentation/vm/slub.txt.
3451 slub_max_order= [MM, SLUB]
3452 Determines the maximum allowed order for slabs.
3453 A high setting may cause OOMs due to memory
3454 fragmentation. For more information see
3455 Documentation/vm/slub.txt.
3457 slub_min_objects= [MM, SLUB]
3458 The minimum number of objects per slab. SLUB will
3459 increase the slab order up to slub_max_order to
3460 generate a sufficiently large slab able to contain
3461 the number of objects indicated. The higher the number
3462 of objects the smaller the overhead of tracking slabs
3463 and the less frequently locks need to be acquired.
3464 For more information see Documentation/vm/slub.txt.
3466 slub_min_order= [MM, SLUB]
3467 Determines the minimum page order for slabs. Must be
3468 lower than slub_max_order.
3469 For more information see Documentation/vm/slub.txt.
3471 slub_nomerge [MM, SLUB]
3472 Same with slab_nomerge. This is supported for legacy.
3473 See slab_nomerge for more information.
3476 Format: <io1>[,<io2>[,...,<io8>]]
3478 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3479 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3480 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3481 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3482 smsc-ircc2.ircc_irq= [HW] IRQ line
3483 smsc-ircc2.ircc_dma= [HW] DMA channel
3484 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3485 0: Toshiba Satellite 1800 (GP data pin select)
3486 1: Fast pin select (default)
3490 [KNL] Should the soft-lockup detector generate panics.
3493 softlockup_all_cpu_backtrace=
3494 [KNL] Should the soft-lockup detector generate
3495 backtraces on all cpus.
3498 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3499 See Documentation/laptops/sonypi.txt
3501 spia_io_base= [HW,MTD]
3507 Enabled the stack tracer on boot up.
3509 stacktrace_filter=[function-list]
3510 [FTRACE] Limit the functions that the stack tracer
3511 will trace at boot up. function-list is a comma separated
3512 list of functions. This list can be changed at run
3513 time by the stack_trace_filter file in the debugfs
3514 tracing directory. Note, this enables stack tracing
3515 and the stacktrace above is not needed.
3519 Set the STI (builtin display/keyboard on the HP-PARISC
3520 machines) console (graphic card) which should be used
3521 as the initial boot-console.
3522 See also comment in drivers/video/console/sticore.c.
3525 See comment in drivers/video/console/sticore.c.
3528 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3530 sunrpc.min_resvport=
3531 sunrpc.max_resvport=
3533 SunRPC servers often require that client requests
3534 originate from a privileged port (i.e. a port in the
3535 range 0 < portnr < 1024).
3536 An administrator who wishes to reserve some of these
3537 ports for other uses may adjust the range that the
3538 kernel's sunrpc client considers to be privileged
3539 using these two parameters to set the minimum and
3540 maximum port values.
3544 Control how the NFS server code allocates CPUs to
3545 service thread pools. Depending on how many NICs
3546 you have and where their interrupts are bound, this
3547 option will affect which CPUs will do NFS serving.
3548 Note: this parameter cannot be changed while the
3549 NFS server is running.
3551 auto the server chooses an appropriate mode
3552 automatically using heuristics
3553 global a single global pool contains all CPUs
3554 percpu one pool for each CPU
3555 pernode one pool for each NUMA node (equivalent
3556 to global on non-NUMA machines)
3558 sunrpc.tcp_slot_table_entries=
3559 sunrpc.udp_slot_table_entries=
3561 Sets the upper limit on the number of simultaneous
3562 RPC calls that can be sent from the client to a
3563 server. Increasing these values may allow you to
3564 improve throughput, but will also increase the
3565 amount of memory reserved for use by the client.
3567 suspend.pm_test_delay=
3569 Sets the number of seconds to remain in a suspend test
3570 mode before resuming the system (see
3571 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3572 is set. Default value is 5.
3575 [KNL] Enable accounting of swap in memory resource
3576 controller if no parameter or 1 is given or disable
3577 it if 0 is given (See Documentation/cgroups/memory.txt)
3579 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3580 Format: { <int> | force }
3581 <int> -- Number of I/O TLB slabs
3582 force -- force using of bounce buffers even if they
3583 wouldn't be automatically used by the kernel
3587 sysfs.deprecated=0|1 [KNL]
3588 Enable/disable old style sysfs layout for old udev
3589 on older distributions. When this option is enabled
3590 very new udev will not work anymore. When this option
3591 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3592 in older udev will not work anymore.
3593 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3594 the kernel configuration.
3596 sysrq_always_enabled
3598 Ignore sysrq setting - this boot parameter will
3599 neutralize any effect of /proc/sys/kernel/sysrq.
3600 Useful for debugging.
3602 tcpmhash_entries= [KNL,NET]
3603 Set the number of tcp_metrics_hash slots.
3604 Default value is 8192 or 16384 depending on total
3605 ram pages. This is used to specify the TCP metrics
3606 cache size. See Documentation/networking/ip-sysctl.txt
3607 "tcp_no_metrics_save" section for more details.
3611 test_suspend= [SUSPEND][,N]
3612 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3613 standby suspend) or "freeze" (for suspend type freeze)
3614 as the system sleep state during system startup with
3615 the optional capability to repeat N number of times.
3616 The system is woken from this state using a
3617 wakeup-capable RTC alarm.
3619 thash_entries= [KNL,NET]
3620 Set number of hash buckets for TCP connection
3622 thermal.act= [HW,ACPI]
3623 -1: disable all active trip points in all thermal zones
3624 <degrees C>: override all lowest active trip points
3626 thermal.crt= [HW,ACPI]
3627 -1: disable all critical trip points in all thermal zones
3628 <degrees C>: override all critical trip points
3630 thermal.nocrt= [HW,ACPI]
3631 Set to disable actions on ACPI thermal zone
3632 critical and hot trip points.
3634 thermal.off= [HW,ACPI]
3635 1: disable ACPI thermal control
3637 thermal.psv= [HW,ACPI]
3638 -1: disable all passive trip points
3639 <degrees C>: override all passive trip points to this
3642 thermal.tzp= [HW,ACPI]
3643 Specify global default ACPI thermal zone polling rate
3644 <deci-seconds>: poll all this frequency
3645 0: no polling (default)
3648 Force threading of all interrupt handlers except those
3649 marked explicitly IRQF_NO_THREAD.
3652 Enable the Transcendent memory driver if built-in.
3654 tmem.cleancache=0|1 [KNL, XEN]
3655 Default is on (1). Disable the usage of the cleancache
3656 API to send anonymous pages to the hypervisor.
3658 tmem.frontswap=0|1 [KNL, XEN]
3659 Default is on (1). Disable the usage of the frontswap
3660 API to send swap pages to the hypervisor. If disabled
3661 the selfballooning and selfshrinking are force disabled.
3663 tmem.selfballooning=0|1 [KNL, XEN]
3664 Default is on (1). Disable the driving of swap pages
3667 tmem.selfshrinking=0|1 [KNL, XEN]
3668 Default is on (1). Partial swapoff that immediately
3669 transfers pages from Xen hypervisor back to the
3670 kernel based on different criteria.
3674 Specify if the kernel should make use of the cpu
3675 topology information if the hardware supports this.
3676 The scheduler will make use of this information and
3677 e.g. base its process migration decisions on it.
3680 topology_updates= [KNL, PPC, NUMA]
3682 Specify if the kernel should ignore (off)
3683 topology updates sent by the hypervisor to this
3688 tpm_suspend_pcr=[HW,TPM]
3689 Format: integer pcr id
3690 Specify that at suspend time, the tpm driver
3691 should extend the specified pcr with zeros,
3692 as a workaround for some chips which fail to
3693 flush the last written pcr on TPM_SaveState.
3694 This will guarantee that all the other pcrs
3697 trace_buf_size=nn[KMG]
3698 [FTRACE] will set tracing buffer size on each cpu.
3700 trace_event=[event-list]
3701 [FTRACE] Set and start specified trace events in order
3702 to facilitate early boot debugging.
3703 See also Documentation/trace/events.txt
3705 trace_options=[option-list]
3706 [FTRACE] Enable or disable tracer options at boot.
3707 The option-list is a comma delimited list of options
3708 that can be enabled or disabled just as if you were
3709 to echo the option name into
3711 /sys/kernel/debug/tracing/trace_options
3713 For example, to enable stacktrace option (to dump the
3714 stack trace of each event), add to the command line:
3716 trace_options=stacktrace
3718 See also Documentation/trace/ftrace.txt "trace options"
3722 Have the tracepoints sent to printk as well as the
3723 tracing ring buffer. This is useful for early boot up
3724 where the system hangs or reboots and does not give the
3725 option for reading the tracing buffer or performing a
3726 ftrace_dump_on_oops.
3728 To turn off having tracepoints sent to printk,
3729 echo 0 > /proc/sys/kernel/tracepoint_printk
3730 Note, echoing 1 into this file without the
3731 tracepoint_printk kernel cmdline option has no effect.
3735 Having tracepoints sent to printk() and activating high
3736 frequency tracepoints such as irq or sched, can cause
3737 the system to live lock.
3740 [FTRACE] enable this option to disable tracing when a
3741 warning is hit. This turns off "tracing_on". Tracing can
3742 be enabled again by echoing '1' into the "tracing_on"
3743 file located in /sys/kernel/debug/tracing/
3745 This option is useful, as it disables the trace before
3746 the WARNING dump is called, which prevents the trace to
3747 be filled with content caused by the warning output.
3749 This option can also be set at run time via the sysctl
3750 option: kernel/traceoff_on_warning
3752 transparent_hugepage=
3754 Format: [always|madvise|never]
3755 Can be used to control the default behavior of the system
3756 with respect to transparent hugepages.
3757 See Documentation/vm/transhuge.txt for more details.
3759 tsc= Disable clocksource stability checks for TSC.
3761 [x86] reliable: mark tsc clocksource as reliable, this
3762 disables clocksource verification at runtime, as well
3763 as the stability checks done at bootup. Used to enable
3764 high-resolution timer mode on older hardware, and in
3765 virtualized environment.
3766 [x86] noirqtime: Do not use TSC to do irq accounting.
3767 Used to run time disable IRQ_TIME_ACCOUNTING on any
3768 platforms where RDTSC is slow and this accounting
3771 turbografx.map[2|3]= [HW,JOY]
3772 TurboGraFX parallel port interface
3774 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3775 See also Documentation/input/joystick-parport.txt
3777 udbg-immortal [PPC] When debugging early kernel crashes that
3778 happen after console_init() and before a proper
3779 console driver takes over, this boot options might
3780 help "seeing" what's going on.
3782 uhash_entries= [KNL,NET]
3783 Set number of hash buckets for UDP/UDP-Lite connections
3786 [USB] Ignore overcurrent events (default N).
3787 Some badly-designed motherboards generate lots of
3788 bogus events, for ports that aren't wired to
3789 anything. Set this parameter to avoid log spamming.
3790 Note that genuine overcurrent events won't be
3794 [X86] Cause panic on unknown NMI.
3796 usbcore.authorized_default=
3797 [USB] Default USB device authorization:
3798 (default -1 = authorized except for wireless USB,
3799 0 = not authorized, 1 = authorized)
3801 usbcore.autosuspend=
3802 [USB] The autosuspend time delay (in seconds) used
3803 for newly-detected USB devices (default 2). This
3804 is the time required before an idle device will be
3805 autosuspended. Devices for which the delay is set
3806 to a negative value won't be autosuspended at all.
3808 usbcore.usbfs_snoop=
3809 [USB] Set to log all usbfs traffic (default 0 = off).
3811 usbcore.blinkenlights=
3812 [USB] Set to cycle leds on hubs (default 0 = off).
3814 usbcore.old_scheme_first=
3815 [USB] Start with the old device initialization
3816 scheme (default 0 = off).
3818 usbcore.usbfs_memory_mb=
3819 [USB] Memory limit (in MB) for buffers allocated by
3820 usbfs (default = 16, 0 = max = 2047).
3822 usbcore.use_both_schemes=
3823 [USB] Try the other device initialization scheme
3824 if the first one fails (default 1 = enabled).
3826 usbcore.initial_descriptor_timeout=
3827 [USB] Specifies timeout for the initial 64-byte
3828 USB_REQ_GET_DESCRIPTOR request in milliseconds
3829 (default 5000 = 5.0 seconds).
3832 [USBHID] The interval which mice are to be polled at.
3834 usb-storage.delay_use=
3835 [UMS] The delay in seconds before a new device is
3836 scanned for Logical Units (default 1).
3839 [UMS] A list of quirks entries to supplement or
3840 override the built-in unusual_devs list. List
3841 entries are separated by commas. Each entry has
3842 the form VID:PID:Flags where VID and PID are Vendor
3843 and Product ID values (4-digit hex numbers) and
3844 Flags is a set of characters, each corresponding
3845 to a common usb-storage quirk flag as follows:
3846 a = SANE_SENSE (collect more than 18 bytes
3848 b = BAD_SENSE (don't collect more than 18
3849 bytes of sense data);
3850 c = FIX_CAPACITY (decrease the reported
3851 device capacity by one sector);
3852 d = NO_READ_DISC_INFO (don't use
3853 READ_DISC_INFO command);
3854 e = NO_READ_CAPACITY_16 (don't use
3855 READ_CAPACITY_16 command);
3856 f = NO_REPORT_OPCODES (don't use report opcodes
3858 g = MAX_SECTORS_240 (don't transfer more than
3859 240 sectors at a time, uas only);
3860 h = CAPACITY_HEURISTICS (decrease the
3861 reported device capacity by one
3862 sector if the number is odd);
3863 i = IGNORE_DEVICE (don't bind to this
3865 l = NOT_LOCKABLE (don't try to lock and
3866 unlock ejectable media);
3867 m = MAX_SECTORS_64 (don't transfer more
3868 than 64 sectors = 32 KB at a time);
3869 n = INITIAL_READ10 (force a retry of the
3870 initial READ(10) command);
3871 o = CAPACITY_OK (accept the capacity
3872 reported by the device);
3873 p = WRITE_CACHE (the device cache is ON
3875 r = IGNORE_RESIDUE (the device reports
3876 bogus residue values);
3877 s = SINGLE_LUN (the device has only one
3879 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3880 commands, uas only);
3881 u = IGNORE_UAS (don't bind to the uas driver);
3882 w = NO_WP_DETECT (don't test whether the
3883 medium is write-protected).
3884 Example: quirks=0419:aaf5:rl,0421:0433:rc
3886 user_debug= [KNL,ARM]
3888 See arch/arm/Kconfig.debug help text.
3889 1 - undefined instruction events
3891 4 - invalid data aborts
3894 Example: user_debug=31
3897 [X86] Flags controlling user PTE allocations.
3899 nohigh = do not allocate PTE pages in
3900 HIGHMEM regardless of setting
3904 On X86_32, this is an alias for vdso32=. Otherwise:
3906 vdso=1: enable VDSO (the default)
3907 vdso=0: disable VDSO mapping
3909 vdso32= [X86] Control the 32-bit vDSO
3910 vdso32=1: enable 32-bit VDSO
3911 vdso32=0 or vdso32=2: disable 32-bit VDSO
3913 See the help text for CONFIG_COMPAT_VDSO for more
3914 details. If CONFIG_COMPAT_VDSO is set, the default is
3915 vdso32=0; otherwise, the default is vdso32=1.
3917 For compatibility with older kernels, vdso32=2 is an
3920 Try vdso32=0 if you encounter an error that says:
3921 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3924 vector=percpu: enable percpu vector domain
3926 video= [FB] Frame buffer configuration
3927 See Documentation/fb/modedb.txt.
3929 video.brightness_switch_enabled= [0,1]
3930 If set to 1, on receiving an ACPI notify event
3931 generated by hotkey, video driver will adjust brightness
3932 level and then send out the event to user space through
3933 the allocated input device; If set to 0, video driver
3934 will only send out the event without touching backlight
3939 [VMMIO] Memory mapped virtio (platform) device.
3941 <size>@<baseaddr>:<irq>[:<id>]
3943 <size> := size (can use standard suffixes
3945 <baseaddr> := physical base address
3946 <irq> := interrupt number (as passed to
3948 <id> := (optional) platform device id
3950 virtio_mmio.device=1K@0x100b0000:48:7
3952 Can be used multiple times for multiple devices.
3954 vga= [BOOT,X86-32] Select a particular video mode
3955 See Documentation/x86/boot.txt and
3956 Documentation/svga.txt.
3957 Use vga=ask for menu.
3958 This is actually a boot loader parameter; the value is
3959 passed to the kernel using a special protocol.
3961 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3962 size of <nn>. This can be used to increase the
3963 minimum size (128MB on x86). It can also be used to
3964 decrease the size and leave more room for directly
3967 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3970 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3973 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3977 Controls the behavior of vsyscalls (i.e. calls to
3978 fixed addresses of 0xffffffffff600x00 from legacy
3979 code). Most statically-linked binaries and older
3980 versions of glibc use these calls. Because these
3981 functions are at fixed addresses, they make nice
3982 targets for exploits that can control RIP.
3984 emulate [default] Vsyscalls turn into traps and are
3985 emulated reasonably safely.
3987 native Vsyscalls are native syscall instructions.
3988 This is a little bit faster than trapping
3989 and makes a few dynamic recompilers work
3990 better than they would in emulation mode.
3991 It also makes exploits much easier to write.
3993 none Vsyscalls don't work at all. This makes
3994 them quite hard to use for exploits but
3995 might break your system.
3997 vt.color= [VT] Default text color.
3998 Format: 0xYX, X = foreground, Y = background.
3999 Default: 0x07 = light gray on black.
4001 vt.cur_default= [VT] Default cursor shape.
4002 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4003 the parameters of the <Esc>[?A;B;Cc escape sequence;
4004 see VGA-softcursor.txt. Default: 2 = underline.
4006 vt.default_blu= [VT]
4007 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4008 Change the default blue palette of the console.
4009 This is a 16-member array composed of values
4012 vt.default_grn= [VT]
4013 Format: <green0>,<green1>,<green2>,...,<green15>
4014 Change the default green palette of the console.
4015 This is a 16-member array composed of values
4018 vt.default_red= [VT]
4019 Format: <red0>,<red1>,<red2>,...,<red15>
4020 Change the default red palette of the console.
4021 This is a 16-member array composed of values
4027 Set system-wide default UTF-8 mode for all tty's.
4028 Default is 1, i.e. UTF-8 mode is enabled for all
4029 newly opened terminals.
4031 vt.global_cursor_default=
4034 Set system-wide default for whether a cursor
4035 is shown on new VTs. Default is -1,
4036 i.e. cursors will be created by default unless
4037 overridden by individual drivers. 0 will hide
4038 cursors, 1 will display them.
4040 vt.italic= [VT] Default color for italic text; 0-15.
4043 vt.underline= [VT] Default color for underlined text; 0-15.
4046 watchdog timers [HW,WDT] For information on watchdog timers,
4047 see Documentation/watchdog/watchdog-parameters.txt
4048 or other driver-specific files in the
4049 Documentation/watchdog/ directory.
4051 workqueue.disable_numa
4052 By default, all work items queued to unbound
4053 workqueues are affine to the NUMA nodes they're
4054 issued on, which results in better behavior in
4055 general. If NUMA affinity needs to be disabled for
4056 whatever reason, this option can be used. Note
4057 that this also can be controlled per-workqueue for
4058 workqueues visible under /sys/bus/workqueue/.
4060 workqueue.power_efficient
4061 Per-cpu workqueues are generally preferred because
4062 they show better performance thanks to cache
4063 locality; unfortunately, per-cpu workqueues tend to
4064 be more power hungry than unbound workqueues.
4066 Enabling this makes the per-cpu workqueues which
4067 were observed to contribute significantly to power
4068 consumption unbound, leading to measurably lower
4069 power usage at the cost of small performance
4072 The default value of this parameter is determined by
4073 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4075 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4076 default x2apic cluster mode on platforms
4079 x86_intel_mid_timer= [X86-32,APBT]
4080 Choose timer option for x86 Intel MID platform.
4081 Two valid options are apbt timer only and lapic timer
4082 plus one apbt timer for broadcast timer.
4083 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4085 xen_emul_unplug= [HW,X86,XEN]
4086 Unplug Xen emulated devices
4087 Format: [unplug0,][unplug1]
4088 ide-disks -- unplug primary master IDE devices
4089 aux-ide-disks -- unplug non-primary-master IDE devices
4090 nics -- unplug network devices
4091 all -- unplug all emulated devices (NICs and IDE disks)
4092 unnecessary -- unplugging emulated devices is
4093 unnecessary even if the host did not respond to
4095 never -- do not unplug even if version check succeeds
4097 xen_nopvspin [X86,XEN]
4098 Disables the ticketlock slowpath using Xen PV
4102 Disables the PV optimizations forcing the HVM guest to
4103 run as generic HVM guest with no PV drivers.
4105 xirc2ps_cs= [NET,PCMCIA]
4107 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4109 ______________________________________________________________________
4113 Add more DRM drivers.
projects / cascardo / linux.git / blob