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 |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
475 apic_extnmi= [APIC,X86] External NMI delivery setting
476 Format: { bsp (default) | all | none }
477 bsp: External NMI is delivered only to CPU 0
478 all: External NMIs are broadcast to all CPUs as a
480 none: External NMI is masked for all CPUs. This is
481 useful so that a dump capture kernel won't be
485 See Documentation/networking/ipv6.txt.
487 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
488 Limit apic dumping. The parameter defines the maximal
489 number of local apics being dumped. Also it is possible
490 to set it to "all" by meaning -- no limit here.
491 Format: { 1 (default) | 2 | ... | all }.
492 The parameter valid if only apic=debug or
493 apic=verbose is specified.
494 Example: apic=debug show_lapic=all
496 apm= [APM] Advanced Power Management
497 See header of arch/x86/kernel/apm_32.c.
499 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
500 Format: <io>,<irq>,<nodeID>
504 atarimouse= [HW,MOUSE] Atari Mouse
506 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
507 EzKey and similar keyboards
509 atkbd.reset= [HW] Reset keyboard during initialization
511 atkbd.set= [HW] Select keyboard code set
512 Format: <int> (2 = AT (default), 3 = PS/2)
514 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
517 atkbd.softraw= [HW] Choose between synthetic and real raw mode
518 Format: <bool> (0 = real, 1 = synthetic (default))
520 atkbd.softrepeat= [HW]
521 Use software keyboard repeat
523 audit= [KNL] Enable the audit sub-system
524 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
525 0 - kernel audit is disabled and can not be enabled
526 until the next reboot
527 unset - kernel audit is initialized but disabled and
528 will be fully enabled by the userspace auditd.
529 1 - kernel audit is initialized and partially enabled,
530 storing at most audit_backlog_limit messages in
531 RAM until it is fully enabled by the userspace
535 audit_backlog_limit= [KNL] Set the audit queue size limit.
536 Format: <int> (must be >=0)
539 baycom_epp= [HW,AX25]
542 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
544 See header of drivers/net/hamradio/baycom_par.c.
546 baycom_ser_fdx= [HW,AX25]
547 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
548 Format: <io>,<irq>,<mode>[,<baud>]
549 See header of drivers/net/hamradio/baycom_ser_fdx.c.
551 baycom_ser_hdx= [HW,AX25]
552 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
553 Format: <io>,<irq>,<mode>
554 See header of drivers/net/hamradio/baycom_ser_hdx.c.
556 blkdevparts= Manual partition parsing of block device(s) for
557 embedded devices based on command line input.
558 See Documentation/block/cmdline-partition.txt
560 boot_delay= Milliseconds to delay each printk during boot.
561 Values larger than 10 seconds (10000) are changed to
565 bootmem_debug [KNL] Enable bootmem allocator debug messages.
567 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
568 bttv.radio= Most important insmod options are available as
570 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
573 bulk_remove=off [PPC] This parameter disables the use of the pSeries
574 firmware feature for flushing multiple hpte entries
577 c101= [NET] Moxa C101 synchronous serial card
579 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
580 Sometimes CPU hardware bugs make them report the cache
581 size incorrectly. The kernel will attempt work arounds
582 to fix known problems, but for some CPUs it is not
583 possible to determine what the correct size should be.
584 This option provides an override for these situations.
586 ca_keys= [KEYS] This parameter identifies a specific key(s) on
587 the system trusted keyring to be used for certificate
589 format: { id:<keyid> | builtin }
591 cca= [MIPS] Override the kernel pages' cache coherency
592 algorithm. Accepted values range from 0 to 7
593 inclusive. See arch/mips/include/asm/pgtable-bits.h
594 for platform specific values (SB1, Loongson3 and
597 ccw_timeout_log [S390]
598 See Documentation/s390/CommonIO for details.
600 cgroup_disable= [KNL] Disable a particular controller
601 Format: {name of the controller(s) to disable}
602 The effects of cgroup_disable=foo are:
603 - foo isn't auto-mounted if you mount all cgroups in
605 - foo isn't visible as an individually mountable
607 {Currently only "memory" controller deal with this and
608 cut the overhead, others just disable the usage. So
609 only cgroup_disable=memory is actually worthy}
611 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
613 nosocket -- Disable socket memory accounting.
615 checkreqprot [SELINUX] Set initial checkreqprot flag value.
616 Format: { "0" | "1" }
617 See security/selinux/Kconfig help text.
618 0 -- check protection applied by kernel (includes
619 any implied execute protection).
620 1 -- check protection requested by application.
621 Default value is set via a kernel config option.
622 Value can be changed at runtime via
623 /selinux/checkreqprot.
626 See Documentation/s390/CommonIO for details.
629 Prevents the clock framework from automatically gating
630 clocks that have not been explicitly enabled by a Linux
631 device driver but are enabled in hardware at reset or
632 by the bootloader/firmware. Note that this does not
633 force such clocks to be always-on nor does it reserve
634 those clocks in any way. This parameter is useful for
635 debug and development, but should not be needed on a
636 platform with proper driver support. For more
637 information, see Documentation/clk.txt.
639 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
641 Forces specified clocksource (if available) to be used
642 when calculating gettimeofday(). If specified
643 clocksource is not available, it defaults to PIT.
644 Format: { pit | tsc | cyclone | pmtmr }
646 clocksource= Override the default clocksource
648 Override the default clocksource and use the clocksource
649 with the name specified.
650 Some clocksource names to choose from, depending on
652 [all] jiffies (this is the base, fallback clocksource)
654 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
655 pxa_timer,timer3,32k_counter,timer0_1
657 [X86-32] pit,hpet,tsc;
658 scx200_hrt on Geode; cyclone on IBM x440
666 clearcpuid=BITNUM [X86]
667 Disable CPUID feature X for the kernel. See
668 arch/x86/include/asm/cpufeature.h for the valid bit
669 numbers. Note the Linux specific bits are not necessarily
670 stable over kernel options, but the vendor specific
672 Also note that user programs calling CPUID directly
673 or using the feature without checking anything
674 will still see it. This just prevents it from
675 being used by the kernel or shown in /proc/cpuinfo.
676 Also note the kernel might malfunction if you disable
679 cma=nn[MG]@[start[MG][-end[MG]]]
681 Sets the size of kernel global memory area for
682 contiguous memory allocations and optionally the
683 placement constraint by the physical address range of
684 memory allocations. A value of 0 disables CMA
685 altogether. For more information, see
686 include/linux/dma-contiguous.h
688 cmo_free_hint= [PPC] Format: { yes | no }
689 Specify whether pages are marked as being inactive
690 when they are freed. This is used in CMO environments
691 to determine OS memory pressure for page stealing by
695 coherent_pool=nn[KMG] [ARM,KNL]
696 Sets the size of memory pool for coherent, atomic dma
697 allocations, by default set to 256K.
699 code_bytes [X86] How many bytes of object code to print
704 com20020= [HW,NET] ARCnet - COM20020 chipset
706 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
708 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
712 ARCnet - COM90xx chipset (memory-mapped buffers)
713 Format: <io>[,<irq>[,<memstart>]]
715 condev= [HW,S390] console device
718 console= [KNL] Output console device and options.
720 tty<n> Use the virtual console device <n>.
724 Use the specified serial port. The options are of
725 the form "bbbbpnf", where "bbbb" is the baud rate,
726 "p" is parity ("n", "o", or "e"), "n" is number of
727 bits, and "f" is flow control ("r" for RTS or
728 omit it). Default is "9600n8".
730 See Documentation/serial-console.txt for more
732 Documentation/networking/netconsole.txt for an
735 uart[8250],io,<addr>[,options]
736 uart[8250],mmio,<addr>[,options]
737 uart[8250],mmio16,<addr>[,options]
738 uart[8250],mmio32,<addr>[,options]
739 uart[8250],0x<addr>[,options]
740 Start an early, polled-mode console on the 8250/16550
741 UART at the specified I/O port or MMIO address,
742 switching to the matching ttyS device later.
743 MMIO inter-register address stride is either 8-bit
744 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
745 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
746 to be equivalent to 'mmio'. 'options' are specified in
747 the same format described for ttyS above; if unspecified,
748 the h/w is not re-initialized.
750 hvc<n> Use the hypervisor console device <n>. This is for
751 both Xen and PowerPC hypervisors.
753 If the device connected to the port is not a TTY but a braille
754 device, prepend "brl," before the device type, for instance
756 For now, only VisioBraille is supported.
758 consoleblank= [KNL] The console blank (screen saver) timeout in
759 seconds. Defaults to 10*60 = 10mins. A value of 0
760 disables the blank timer.
763 [KNL] Change the default value for
764 /proc/<pid>/coredump_filter.
765 See also Documentation/filesystems/proc.txt.
767 cpuidle.off=1 [CPU_IDLE]
768 disable the cpuidle sub-system
771 [X86] Delay for N microsec between assert and de-assert
772 of APIC INIT to start processors. This delay occurs
773 on every CPU online, such as boot, and resume from suspend.
776 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
778 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
780 crashkernel=size[KMG][@offset[KMG]]
781 [KNL] Using kexec, Linux can switch to a 'crash kernel'
782 upon panic. This parameter reserves the physical
783 memory region [offset, offset + size] for that kernel
784 image. If '@offset' is omitted, then a suitable offset
785 is selected automatically. Check
786 Documentation/kdump/kdump.txt for further details.
788 crashkernel=range1:size1[,range2:size2,...][@offset]
789 [KNL] Same as above, but depends on the memory
790 in the running system. The syntax of range is
791 start-[end] where start and end are both
792 a memory unit (amount[KMG]). See also
793 Documentation/kdump/kdump.txt for an example.
795 crashkernel=size[KMG],high
796 [KNL, x86_64] range could be above 4G. Allow kernel
797 to allocate physical memory region from top, so could
798 be above 4G if system have more than 4G ram installed.
799 Otherwise memory region will be allocated below 4G, if
801 It will be ignored if crashkernel=X is specified.
802 crashkernel=size[KMG],low
803 [KNL, x86_64] range under 4G. When crashkernel=X,high
804 is passed, kernel could allocate physical memory region
805 above 4G, that cause second kernel crash on system
806 that require some amount of low memory, e.g. swiotlb
807 requires at least 64M+32K low memory, also enough extra
808 low memory is needed to make sure DMA buffers for 32-bit
809 devices won't run out. Kernel would try to allocate at
810 at least 256M below 4G automatically.
811 This one let user to specify own low range under 4G
812 for second kernel instead.
813 0: to disable low allocation.
814 It will be ignored when crashkernel=X,high is not used
815 or memory reserved is below 4G.
820 cs89x0_media= [HW,NET]
821 Format: { rj45 | aui | bnc }
824 See header of drivers/s390/block/dasd_devmap.c.
826 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
827 (one device per port)
828 Format: <port#>,<type>
829 See also Documentation/input/joystick-parport.txt
831 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
832 time. See Documentation/dynamic-debug-howto.txt for
833 details. Deprecated, see dyndbg.
835 debug [KNL] Enable kernel debugging (events log level).
838 [KNL] verbose self-tests
840 Print debugging info while doing the locking API
842 We default to 0 (no extra messages), setting it to
843 1 will print _a lot_ more information - normally
844 only useful to kernel developers.
846 debug_objects [KNL] Enable object debugging
849 [KNL] Disable object debugging
851 debug_guardpage_minorder=
852 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
853 parameter allows control of the order of pages that will
854 be intentionally kept free (and hence protected) by the
855 buddy allocator. Bigger value increase the probability
856 of catching random memory corruption, but reduce the
857 amount of memory for normal system use. The maximum
858 possible value is MAX_ORDER/2. Setting this parameter
859 to 1 or 2 should be enough to identify most random
860 memory corruption problems caused by bugs in kernel or
861 driver code when a CPU writes to (or reads from) a
862 random memory location. Note that there exists a class
863 of memory corruptions problems caused by buggy H/W or
864 F/W or by drivers badly programing DMA (basically when
865 memory is written at bus level and the CPU MMU is
866 bypassed) which are not detectable by
867 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
868 tracking down these problems.
871 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
872 parameter enables the feature at boot time. In
873 default, it is disabled. We can avoid allocating huge
874 chunk of memory for debug pagealloc if we don't enable
875 it at boot time and the system will work mostly same
876 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
877 on: enable the feature
879 debugpat [X86] Enable PAT debugging
881 decnet.addr= [HW,NET]
882 Format: <area>[,<node>]
883 See also Documentation/networking/decnet.txt.
886 [same as hugepagesz=] The size of the default
887 HugeTLB page size. This is the size represented by
888 the legacy /proc/ hugepages APIs, used for SHM, and
889 default size when mounting hugetlbfs filesystems.
890 Defaults to the default architecture's huge page size
894 Set number of hash buckets for dentry cache.
897 See Documentation/networking/ipv6.txt.
899 disable_cpu_apicid= [X86,APIC,SMP]
901 The number of initial APIC ID for the
902 corresponding CPU to be disabled at boot,
903 mostly used for the kdump 2nd kernel to
904 disable BSP to wake up multiple CPUs without
905 causing system reset or hang due to sending
908 disable_ddw [PPC/PSERIES]
909 Disable Dynamic DMA Window support. Use this if
910 to workaround buggy firmware.
913 See Documentation/networking/ipv6.txt.
915 disable_mtrr_cleanup [X86]
916 The kernel tries to adjust MTRR layout from continuous
917 to discrete, to make X server driver able to add WB
918 entry later. This parameter disables that.
920 disable_mtrr_trim [X86, Intel and AMD only]
921 By default the kernel will trim any uncacheable
922 memory out of your available memory pool based on
923 MTRR settings. This parameter disables that behavior,
924 possibly causing your machine to run very slowly.
926 disable_timer_pin_1 [X86]
927 Disable PIN 1 of APIC timer
928 Can be useful to work around chipset bugs.
930 dis_ucode_ldr [X86] Disable the microcode loader.
932 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
933 this option disables the debugging code at boot.
935 dma_debug_entries=<number>
936 This option allows to tune the number of preallocated
937 entries for DMA-API debugging code. One entry is
938 required per DMA-API allocation. Use this if the
939 DMA-API debugging code disables itself because the
940 architectural default is too low.
942 dma_debug_driver=<driver_name>
943 With this option the DMA-API debugging driver
944 filter feature can be enabled at boot time. Just
945 pass the driver to filter for as the parameter.
946 The filter can be disabled or changed to another
947 driver later using sysfs.
949 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
950 Broken monitors, graphic adapters, KVMs and EDIDless
951 panels may send no or incorrect EDID data sets.
952 This parameter allows to specify an EDID data sets
953 in the /lib/firmware directory that are used instead.
954 Generic built-in EDID data sets are used, if one of
955 edid/1024x768.bin, edid/1280x1024.bin,
956 edid/1680x1050.bin, or edid/1920x1080.bin is given
957 and no file with the same name exists. Details and
958 instructions how to build your own EDID data are
959 available in Documentation/EDID/HOWTO.txt. An EDID
960 data set will only be used for a particular connector,
961 if its name and a colon are prepended to the EDID
962 name. Each connector may use a unique EDID data
963 set by separating the files with a comma. An EDID
964 data set with no connector name will be used for
965 any connectors not explicitly specified.
969 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
970 module.dyndbg[="val"]
971 Enable debug messages at boot time. See
972 Documentation/dynamic-debug-howto.txt for details.
974 nompx [X86] Disables Intel Memory Protection Extensions.
975 See Documentation/x86/intel_mpx.txt for more
976 information about the feature.
979 on enable eager fpu restore
980 off disable eager fpu restore
981 auto selects the default scheme, which automatically
982 enables eagerfpu restore for xsaveopt.
984 module.async_probe [KNL]
985 Enable asynchronous probe on this module.
987 early_ioremap_debug [KNL]
988 Enable debug messages in early_ioremap support. This
989 is useful for tracking down temporary early mappings
990 which are not unmapped.
992 earlycon= [KNL] Output early console device and options.
994 When used with no options, the early console is
995 determined by the stdout-path property in device
999 Start an early, polled-mode console on a cadence serial
1000 port at the specified address. The cadence serial port
1001 must already be setup and configured. Options are not
1004 uart[8250],io,<addr>[,options]
1005 uart[8250],mmio,<addr>[,options]
1006 uart[8250],mmio32,<addr>[,options]
1007 uart[8250],mmio32be,<addr>[,options]
1008 uart[8250],0x<addr>[,options]
1009 Start an early, polled-mode console on the 8250/16550
1010 UART at the specified I/O port or MMIO address.
1011 MMIO inter-register address stride is either 8-bit
1012 (mmio) or 32-bit (mmio32 or mmio32be).
1013 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1014 to be equivalent to 'mmio'. 'options' are specified
1015 in the same format described for "console=ttyS<n>"; if
1016 unspecified, the h/w is not initialized.
1020 Start an early, polled-mode console on a pl011 serial
1021 port at the specified address. The pl011 serial port
1022 must already be setup and configured. Options are not
1023 yet supported. If 'mmio32' is specified, then only
1024 the driver will use only 32-bit accessors to read/write
1025 the device registers.
1028 Start an early, polled-mode console on an msm serial
1029 port at the specified address. The serial port
1030 must already be setup and configured. Options are not
1033 msm_serial_dm,<addr>
1034 Start an early, polled-mode console on an msm serial
1035 dm port at the specified address. The serial port
1036 must already be setup and configured. Options are not
1039 smh Use ARM semihosting calls for early console.
1047 Use early console provided by serial driver available
1048 on Samsung SoCs, requires selecting proper type and
1049 a correct base address of the selected UART port. The
1050 serial port must already be setup and configured.
1051 Options are not yet supported.
1055 Use early console provided by Freescale LP UART driver
1056 found on Freescale Vybrid and QorIQ LS1021A processors.
1057 A valid base address must be provided, and the serial
1058 port must already be setup and configured.
1060 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1064 earlyprintk=serial[,ttySn[,baudrate]]
1065 earlyprintk=serial[,0x...[,baudrate]]
1066 earlyprintk=ttySn[,baudrate]
1067 earlyprintk=dbgp[debugController#]
1068 earlyprintk=pciserial,bus:device.function[,baudrate]
1070 earlyprintk is useful when the kernel crashes before
1071 the normal console is initialized. It is not enabled by
1072 default because it has some cosmetic problems.
1074 Append ",keep" to not disable it when the real console
1077 Only one of vga, efi, serial, or usb debug port can
1080 Currently only ttyS0 and ttyS1 may be specified by
1081 name. Other I/O ports may be explicitly specified
1082 on some architectures (x86 and arm at least) by
1083 replacing ttySn with an I/O port address, like this:
1084 earlyprintk=serial,0x1008,115200
1085 You can find the port for a given device in
1086 /proc/tty/driver/serial:
1087 2: uart:ST16650V2 port:00001008 irq:18 ...
1089 Interaction with the standard serial driver is not
1092 The VGA and EFI output is eventually overwritten by
1095 The xen output can only be used by Xen PV guests.
1097 edac_report= [HW,EDAC] Control how to report EDAC event
1098 Format: {"on" | "off" | "force"}
1099 on: enable EDAC to report H/W event. May be overridden
1100 by other higher priority error reporting module.
1101 off: disable H/W event reporting through EDAC.
1102 force: enforce the use of EDAC to report H/W event.
1105 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1108 This is designed to be used in conjunction with
1109 the boot argument: earlyprintk=vga
1112 Format: {"off" | "on" | "skip[mbr]"}
1115 Format: { "old_map", "nochunk", "noruntime", "debug" }
1116 old_map [X86-64]: switch to the old ioremap-based EFI
1117 runtime services mapping. 32-bit still uses this one by
1119 nochunk: disable reading files in "chunks" in the EFI
1120 boot stub, as chunking can cause problems with some
1121 firmware implementations.
1122 noruntime : disable EFI runtime services support
1123 debug: enable misc debug output
1125 efi_no_storage_paranoia [EFI; X86]
1126 Using this parameter you can use more than 50% of
1127 your efi variable storage. Use this parameter only if
1128 you are really sure that your UEFI does sane gc and
1129 fulfills the spec otherwise your board may brick.
1131 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1132 Add arbitrary attribute to specific memory range by
1133 updating original EFI memory map.
1134 Region of memory which aa attribute is added to is
1136 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1137 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1138 attribute is added to range 0x100000000-0x180000000 and
1139 0x10a0000000-0x1120000000.
1141 Using this parameter you can do debugging of EFI memmap
1142 related feature. For example, you can do debugging of
1143 Address Range Mirroring feature even if your box
1146 eisa_irq_edge= [PARISC,HW]
1147 See header of drivers/parisc/eisa.c.
1150 See comment before function elanfreq_setup() in
1151 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1154 Format: {"cfq" | "deadline" | "noop"}
1155 See Documentation/block/cfq-iosched.txt and
1156 Documentation/block/deadline-iosched.txt for details.
1158 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1159 Specifies physical address of start of kernel core
1160 image elf header and optionally the size. Generally
1161 kexec loader will pass this option to capture kernel.
1162 See Documentation/kdump/kdump.txt for details.
1164 enable_mtrr_cleanup [X86]
1165 The kernel tries to adjust MTRR layout from continuous
1166 to discrete, to make X server driver able to add WB
1167 entry later. This parameter enables that.
1169 enable_timer_pin_1 [X86]
1170 Enable PIN 1 of APIC timer
1171 Can be useful to work around chipset bugs
1172 (in particular on some ATI chipsets).
1173 The kernel tries to set a reasonable default.
1175 enforcing [SELINUX] Set initial enforcing status.
1177 See security/selinux/Kconfig help text.
1178 0 -- permissive (log only, no denials).
1179 1 -- enforcing (deny and log).
1181 Value can be changed at runtime via /selinux/enforce.
1184 Disable Error Record Serialization Table (ERST)
1187 ether= [HW,NET] Ethernet cards parameters
1188 This option is obsoleted by the "netdev=" option, which
1189 has equivalent usage. See its documentation for details.
1193 Permit 'security.evm' to be updated regardless of
1194 current integrity status.
1198 fail_make_request=[KNL]
1199 General fault injection mechanism.
1200 Format: <interval>,<probability>,<space>,<times>
1201 See also Documentation/fault-injection/.
1204 See Documentation/blockdev/floppy.txt.
1206 force_pal_cache_flush
1207 [IA-64] Avoid check_sal_cache_flush which may hang on
1208 buggy SAL_CACHE_FLUSH implementations. Using this
1209 parameter will force ia64_sal_cache_flush to call
1210 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1213 Forcefully enable Physical Address Extension (PAE).
1214 Many Pentium M systems disable PAE but may have a
1215 functionally usable PAE implementation.
1216 Warning: use of this parameter will taint the kernel
1217 and may cause unknown problems.
1220 [FTRACE] will set and start the specified tracer
1221 as early as possible in order to facilitate early
1224 ftrace_dump_on_oops[=orig_cpu]
1225 [FTRACE] will dump the trace buffers on oops.
1226 If no parameter is passed, ftrace will dump
1227 buffers of all CPUs, but if you pass orig_cpu, it will
1228 dump only the buffer of the CPU that triggered the
1231 ftrace_filter=[function-list]
1232 [FTRACE] Limit the functions traced by the function
1233 tracer at boot up. function-list is a comma separated
1234 list of functions. This list can be changed at run
1235 time by the set_ftrace_filter file in the debugfs
1238 ftrace_notrace=[function-list]
1239 [FTRACE] Do not trace the functions specified in
1240 function-list. This list can be changed at run time
1241 by the set_ftrace_notrace file in the debugfs
1244 ftrace_graph_filter=[function-list]
1245 [FTRACE] Limit the top level callers functions traced
1246 by the function graph tracer at boot up.
1247 function-list is a comma separated list of functions
1248 that can be changed at run time by the
1249 set_graph_function file in the debugfs tracing directory.
1251 ftrace_graph_notrace=[function-list]
1252 [FTRACE] Do not trace from the functions specified in
1253 function-list. This list is a comma separated list of
1254 functions that can be changed at run time by the
1255 set_graph_notrace file in the debugfs tracing directory.
1258 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1259 support via parallel port (up to 5 devices per port)
1260 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1261 See also Documentation/input/joystick-parport.txt
1265 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1269 gcov_persist= [GCOV] When non-zero (default), profiling data for
1270 kernel modules is saved and remains accessible via
1271 debugfs, even when the module is unloaded/reloaded.
1272 When zero, profiling data is discarded and associated
1273 debugfs files are removed at module unload time.
1275 gpt [EFI] Forces disk with valid GPT signature but
1276 invalid Protective MBR to be treated as GPT. If the
1277 primary GPT is corrupted, it enables the backup/alternate
1278 GPT to be used instead.
1280 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1281 the "Enable 0" bit of the configuration register.
1284 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1285 the "Enable 0" bit of the configuration register.
1288 grcan.select= [HW] Select which physical interface to use.
1291 grcan.txsize= [HW] Sets the size of the tx buffer.
1292 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1294 grcan.rxsize= [HW] Sets the size of the rx buffer.
1295 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1298 hardlockup_all_cpu_backtrace=
1299 [KNL] Should the hard-lockup detector generate
1300 backtraces on all cpus.
1303 hashdist= [KNL,NUMA] Large hashes allocated during boot
1304 are distributed across NUMA nodes. Defaults on
1305 for 64-bit NUMA, off otherwise.
1306 Format: 0 | 1 (for off | on)
1308 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1310 hd= [EIDE] (E)IDE hard drive subsystem geometry
1311 Format: <cyl>,<head>,<sect>
1314 Disable Hardware Error Source Table (HEST) support;
1315 corresponding firmware-first mode error processing
1316 logic will be disabled.
1318 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1319 size of <nn>. This works even on boxes that have no
1320 highmem otherwise. This also works to reduce highmem
1321 size on bigger boxes.
1323 highres= [KNL] Enable/disable high resolution timer mode.
1324 Valid parameters: "on", "off"
1328 See Documentation/isdn/README.HiSax.
1332 hpet= [X86-32,HPET] option to control HPET usage
1333 Format: { enable (default) | disable | force |
1335 disable: disable HPET and use PIT instead
1336 force: allow force enabled of undocumented chips (ICH4,
1338 verbose: show contents of HPET registers during setup
1340 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1341 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1343 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1344 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1345 On x86-64 and powerpc, this option can be specified
1346 multiple times interleaved with hugepages= to reserve
1347 huge pages of different sizes. Valid pages sizes on
1348 x86-64 are 2M (when the CPU supports "pse") and 1G
1349 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1351 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1352 terminal devices. Valid values: 0..8
1353 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1354 If specified, z/VM IUCV HVC accepts connections
1355 from listed z/VM user IDs only.
1357 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1358 hardware thread id mappings.
1359 Format: <cpu>:<hwthread>
1362 Do not unregister boot console at start. This is only
1363 useful for debugging when something happens in the window
1364 between unregistering the boot console and initializing
1367 i2c_bus= [HW] Override the default board specific I2C bus speed
1368 or register an additional I2C bus that is not
1369 registered from board initialization code.
1373 i8042.debug [HW] Toggle i8042 debug mode
1374 i8042.unmask_kbd_data
1375 [HW] Enable printing of interrupt data from the KBD port
1376 (disabled by default, and as a pre-condition
1377 requires that i8042.debug=1 be enabled)
1378 i8042.direct [HW] Put keyboard port into non-translated mode
1379 i8042.dumbkbd [HW] Pretend that controller can only read data from
1380 keyboard and cannot control its state
1381 (Don't attempt to blink the leds)
1382 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1383 i8042.nokbd [HW] Don't check/create keyboard port
1384 i8042.noloop [HW] Disable the AUX Loopback command while probing
1386 i8042.nomux [HW] Don't check presence of an active multiplexing
1388 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1390 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1391 i8042.reset [HW] Reset the controller during init and cleanup
1392 i8042.unlock [HW] Unlock (ignore) the keylock
1393 i8042.kbdreset [HW] Reset device connected to KBD port
1397 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1398 indicates that the driver is running on unsupported
1400 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1401 does not match list of supported models.
1403 [HW] Report power status in /proc/i8k
1404 (disabled by default)
1405 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1408 i915.invert_brightness=
1409 [DRM] Invert the sense of the variable that is used to
1410 set the brightness of the panel backlight. Normally a
1411 brightness value of 0 indicates backlight switched off,
1412 and the maximum of the brightness value sets the backlight
1413 to maximum brightness. If this parameter is set to 0
1414 (default) and the machine requires it, or this parameter
1415 is set to 1, a brightness value of 0 sets the backlight
1416 to maximum brightness, and the maximum of the brightness
1417 value switches the backlight off.
1418 -1 -- never invert brightness
1419 0 -- machine default
1420 1 -- force brightness inversion
1423 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1425 ide-core.nodma= [HW] (E)IDE subsystem
1426 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1427 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1428 .cdrom .chs .ignore_cable are additional options
1429 See Documentation/ide/ide.txt.
1431 ide-generic.probe-mask= [HW] (E)IDE subsystem
1433 Probe mask for legacy ISA IDE ports. Depending on
1434 platform up to 6 ports are supported, enabled by
1435 setting corresponding bits in the mask to 1. The
1436 default value is 0x0, which has a special meaning.
1437 On systems that have PCI, it triggers scanning the
1438 PCI bus for the first and the second port, which
1439 are then probed. On systems without PCI the value
1440 of 0x0 enables probing the two first ports as if it
1443 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1444 Claim all unknown PCI IDE storage controllers.
1447 Format: idle=poll, idle=halt, idle=nomwait
1448 Poll forces a polling idle loop that can slightly
1449 improve the performance of waking up a idle CPU, but
1450 will use a lot of power and make the system run hot.
1452 idle=halt: Halt is forced to be used for CPU idle.
1453 In such case C2/C3 won't be used again.
1454 idle=nomwait: Disable mwait for CPU C-states
1456 ignore_loglevel [KNL]
1457 Ignore loglevel setting - this will print /all/
1458 kernel messages to the console. Useful for debugging.
1459 We also add it as printk module parameter, so users
1460 could change it dynamically, usually by
1461 /sys/module/printk/parameters/ignore_loglevel.
1463 ihash_entries= [KNL]
1464 Set number of hash buckets for inode cache.
1466 ima_appraise= [IMA] appraise integrity measurements
1467 Format: { "off" | "enforce" | "fix" | "log" }
1470 ima_appraise_tcb [IMA]
1471 The builtin appraise policy appraises all files
1475 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1479 The list of supported hash algorithms is defined
1480 in crypto/hash_info.h.
1483 The builtin measurement policy to load during IMA
1484 setup. Specyfing "tcb" as the value, measures all
1485 programs exec'd, files mmap'd for exec, and all files
1486 opened with the read mode bit set by either the
1487 effective uid (euid=0) or uid=0.
1490 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1491 Load a policy which meets the needs of the Trusted
1492 Computing Base. This means IMA will measure all
1493 programs exec'd, files mmap'd for exec, and all files
1494 opened for read by uid=0.
1497 Select one of defined IMA measurements template formats.
1498 Formats: { "ima" | "ima-ng" | "ima-sig" }
1502 [IMA] Define a custom template format.
1503 Format: { "field1|...|fieldN" }
1505 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1506 Format: <min_file_size>
1507 Set the minimal file size for using asynchronous hash.
1508 If left unspecified, ahash usage is disabled.
1510 ahash performance varies for different data sizes on
1511 different crypto accelerators. This option can be used
1512 to achieve the best performance for a particular HW.
1514 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1516 Set hashing buffer size. Default: 4k.
1518 ahash performance varies for different chunk sizes on
1519 different crypto accelerators. This option can be used
1520 to achieve best performance for particular HW.
1524 Run specified binary instead of /sbin/init as init
1527 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1528 for working out where the kernel is dying during
1531 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1532 initcall functions. Useful for debugging built-in
1533 modules and initcalls.
1535 initrd= [BOOT] Specify the location of the initial ramdisk
1537 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1540 int_pln_enable [x86] Enable power limit notification interrupt
1542 integrity_audit=[IMA]
1543 Format: { "0" | "1" }
1544 0 -- basic integrity auditing messages. (Default)
1545 1 -- additional integrity auditing messages.
1547 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1549 Enable intel iommu driver.
1551 Disable intel iommu driver.
1552 igfx_off [Default Off]
1553 By default, gfx is mapped as normal device. If a gfx
1554 device has a dedicated DMAR unit, the DMAR unit is
1555 bypassed by not enabling DMAR with this option. In
1556 this case, gfx device will use physical address for
1559 With this option iommu will not optimize to look
1560 for io virtual address below 32-bit forcing dual
1561 address cycle on pci bus for cards supporting greater
1562 than 32-bit addressing. The default is to look
1563 for translation below 32-bit and if not available
1564 then look in the higher range.
1565 strict [Default Off]
1566 With this option on every unmap_single operation will
1567 result in a hardware IOTLB flush operation as opposed
1568 to batching them for performance.
1569 sp_off [Default Off]
1570 By default, super page will be supported if Intel IOMMU
1571 has the capability. With this option, super page will
1573 ecs_off [Default Off]
1574 By default, extended context tables will be supported if
1575 the hardware advertises that it has support both for the
1576 extended tables themselves, and also PASID support. With
1577 this option set, extended tables will not be used even
1578 on hardware which claims to support them.
1580 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1581 0 disables intel_idle and fall back on acpi_idle.
1582 1 to 6 specify maximum depth of C-state.
1586 Do not enable intel_pstate as the default
1587 scaling driver for the supported processors
1589 Enable intel_pstate on systems that prohibit it by default
1590 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1591 instead of acpi-cpufreq may disable platform features, such
1592 as thermal controls and power capping, that rely on ACPI
1593 P-States information being indicated to OSPM and therefore
1594 should be used with caution. This option does not work with
1595 processors that aren't supported by the intel_pstate driver
1596 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1598 Do not enable hardware P state control (HWP)
1601 Only load intel_pstate on systems which support
1602 hardware P state control (HWP) if available.
1604 intremap= [X86-64, Intel-IOMMU]
1605 on enable Interrupt Remapping (default)
1606 off disable Interrupt Remapping
1607 nosid disable Source ID checking
1609 BIOS x2APIC opt-out request will be ignored
1610 nopost disable Interrupt Posting
1612 iomem= Disable strict checking of access to MMIO memory
1613 strict regions from userspace.
1628 nobypass [PPC/POWERNV]
1629 Disable IOMMU bypass, using IOMMU for PCI devices.
1632 io7= [HW] IO7 for Marvel based alpha systems
1633 See comment before marvel_specify_io7 in
1634 arch/alpha/kernel/core_marvel.c.
1636 io_delay= [X86] I/O delay method
1638 Standard port 0x80 based delay
1640 Alternate port 0xed based delay (needed on some systems)
1642 Simple two microseconds delay
1647 See Documentation/filesystems/nfs/nfsroot.txt.
1650 When an interrupt is not handled search all handlers
1651 for it. Intended to get systems with badly broken
1655 When an interrupt is not handled search all handlers
1656 for it. Also check all handlers each timer
1657 interrupt. Intended to get systems with badly broken
1661 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1663 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1665 <cpu number>,...,<cpu number>
1667 <cpu number>-<cpu number>
1668 (must be a positive range in ascending order)
1670 <cpu number>,...,<cpu number>-<cpu number>
1672 This option can be used to specify one or more CPUs
1673 to isolate from the general SMP balancing and scheduling
1674 algorithms. You can move a process onto or off an
1675 "isolated" CPU via the CPU affinity syscalls or cpuset.
1676 <cpu number> begins at 0 and the maximum value is
1677 "number of CPUs in system - 1".
1679 This option is the preferred way to isolate CPUs. The
1680 alternative -- manually setting the CPU mask of all
1681 tasks in the system -- can cause problems and
1682 suboptimal load balancer performance.
1686 ivrs_ioapic [HW,X86_64]
1687 Provide an override to the IOAPIC-ID<->DEVICE-ID
1688 mapping provided in the IVRS ACPI table. For
1689 example, to map IOAPIC-ID decimal 10 to
1690 PCI device 00:14.0 write the parameter as:
1691 ivrs_ioapic[10]=00:14.0
1693 ivrs_hpet [HW,X86_64]
1694 Provide an override to the HPET-ID<->DEVICE-ID
1695 mapping provided in the IVRS ACPI table. For
1696 example, to map HPET-ID decimal 0 to
1697 PCI device 00:14.0 write the parameter as:
1698 ivrs_hpet[0]=00:14.0
1700 js= [HW,JOY] Analog joystick
1701 See Documentation/input/joystick.txt.
1704 Enable/disable kernel and module base offset ASLR
1705 (Address Space Layout Randomization) if built into
1706 the kernel. When CONFIG_HIBERNATION is selected,
1707 kASLR is disabled by default. When kASLR is enabled,
1708 hibernation will be disabled.
1712 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1713 specifies the amount of memory usable by the kernel
1714 for non-movable allocations. The requested amount is
1715 spread evenly throughout all nodes in the system. The
1716 remaining memory in each node is used for Movable
1717 pages. In the event, a node is too small to have both
1718 kernelcore and Movable pages, kernelcore pages will
1719 take priority and other nodes will have a larger number
1720 of Movable pages. The Movable zone is used for the
1721 allocation of pages that may be reclaimed or moved
1722 by the page migration subsystem. This means that
1723 HugeTLB pages may not be allocated from this zone.
1724 Note that allocations like PTEs-from-HighMem still
1725 use the HighMem zone if it exists, and the Normal
1726 zone if it does not.
1728 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1729 Format: <Controller#>[,poll interval]
1730 The controller # is the number of the ehci usb debug
1731 port as it is probed via PCI. The poll interval is
1732 optional and is the number seconds in between
1733 each poll cycle to the debug port in case you need
1734 the functionality for interrupting the kernel with
1735 gdb or control-c on the dbgp connection. When
1736 not using this parameter you use sysrq-g to break into
1737 the kernel debugger.
1739 kgdboc= [KGDB,HW] kgdb over consoles.
1740 Requires a tty driver that supports console polling,
1741 or a supported polling keyboard driver (non-usb).
1742 Serial only format: <serial_device>[,baud]
1743 keyboard only format: kbd
1744 keyboard and serial format: kbd,<serial_device>[,baud]
1745 Optional Kernel mode setting:
1746 kms, kbd format: kms,kbd
1747 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1749 kgdbwait [KGDB] Stop kernel execution and enter the
1750 kernel debugger at the earliest opportunity.
1752 kmac= [MIPS] korina ethernet MAC address.
1753 Configure the RouterBoard 532 series on-chip
1754 Ethernet adapter MAC address.
1756 kmemleak= [KNL] Boot-time kmemleak enable/disable
1757 Valid arguments: on, off
1759 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1762 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1763 Valid arguments: 0, 1, 2
1764 kmemcheck=0 (disabled)
1765 kmemcheck=1 (enabled)
1766 kmemcheck=2 (one-shot mode)
1767 Default: 2 (one-shot mode)
1769 kstack=N [X86] Print N words from the kernel stack
1772 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1773 Default is 0 (don't ignore, but inject #GP)
1775 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1779 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1780 Default is 1 (enabled)
1782 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1784 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1786 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1787 (virtualized MMU) support on capable Intel chips.
1788 Default is 1 (enabled)
1790 kvm-intel.emulate_invalid_guest_state=
1791 [KVM,Intel] Enable emulation of invalid guest states
1792 Default is 0 (disabled)
1794 kvm-intel.flexpriority=
1795 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1796 Default is 1 (enabled)
1799 [KVM,Intel] Enable VMX nesting (nVMX).
1800 Default is 0 (disabled)
1802 kvm-intel.unrestricted_guest=
1803 [KVM,Intel] Disable unrestricted guest feature
1804 (virtualized real and unpaged mode) on capable
1805 Intel chips. Default is 1 (enabled)
1807 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1808 feature (tagged TLBs) on capable Intel chips.
1809 Default is 1 (enabled)
1815 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1818 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1819 value for LAPIC timer one-shot implementation. Default
1820 back to the programmable timer unit in the LAPIC.
1822 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1825 libata.dma= [LIBATA] DMA control
1826 libata.dma=0 Disable all PATA and SATA DMA
1827 libata.dma=1 PATA and SATA Disk DMA only
1828 libata.dma=2 ATAPI (CDROM) DMA only
1829 libata.dma=4 Compact Flash DMA only
1830 Combinations also work, so libata.dma=3 enables DMA
1831 for disks and CDROMs, but not CFs.
1833 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1834 libata.ignore_hpa=0 keep BIOS limits (default)
1835 libata.ignore_hpa=1 ignore limits, using full disk
1837 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1841 libata.force= [LIBATA] Force configurations. The format is comma
1842 separated list of "[ID:]VAL" where ID is
1843 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1844 matching port, link or device. Basically, it matches
1845 the ATA ID string printed on console by libata. If
1846 the whole ID part is omitted, the last PORT and DEVICE
1847 values are used. If ID hasn't been specified yet, the
1848 configuration applies to all ports, links and devices.
1850 If only DEVICE is omitted, the parameter applies to
1851 the port and all links and devices behind it. DEVICE
1852 number of 0 either selects the first device or the
1853 first fan-out link behind PMP device. It does not
1854 select the host link. DEVICE number of 15 selects the
1855 host link and device attached to it.
1857 The VAL specifies the configuration to force. As long
1858 as there's no ambiguity shortcut notation is allowed.
1859 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1860 The following configurations can be forced.
1862 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1863 Any ID with matching PORT is used.
1865 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1867 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1868 udma[/][16,25,33,44,66,100,133] notation is also
1871 * [no]ncq: Turn on or off NCQ.
1873 * [no]ncqtrim: Turn off queued DSM TRIM.
1875 * nohrst, nosrst, norst: suppress hard, soft
1878 * rstonce: only attempt one reset during
1879 hot-unplug link recovery
1881 * dump_id: dump IDENTIFY data.
1883 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1885 * disable: Disable this device.
1887 If there are multiple matching configurations changing
1888 the same attribute, the last one is used.
1890 memblock=debug [KNL] Enable memblock debug messages.
1892 load_ramdisk= [RAM] List of ramdisks to load from floppy
1893 See Documentation/blockdev/ramdisk.txt.
1895 lockd.nlm_grace_period=P [NFS] Assign grace period.
1898 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1901 lockd.nlm_timeout=T [NFS] Assign timeout value.
1904 lockd.nlm_udpport=M [NFS] Assign UDP port.
1907 locktorture.nreaders_stress= [KNL]
1908 Set the number of locking read-acquisition kthreads.
1909 Defaults to being automatically set based on the
1910 number of online CPUs.
1912 locktorture.nwriters_stress= [KNL]
1913 Set the number of locking write-acquisition kthreads.
1915 locktorture.onoff_holdoff= [KNL]
1916 Set time (s) after boot for CPU-hotplug testing.
1918 locktorture.onoff_interval= [KNL]
1919 Set time (s) between CPU-hotplug operations, or
1920 zero to disable CPU-hotplug testing.
1922 locktorture.shuffle_interval= [KNL]
1923 Set task-shuffle interval (jiffies). Shuffling
1924 tasks allows some CPUs to go into dyntick-idle
1925 mode during the locktorture test.
1927 locktorture.shutdown_secs= [KNL]
1928 Set time (s) after boot system shutdown. This
1929 is useful for hands-off automated testing.
1931 locktorture.stat_interval= [KNL]
1932 Time (s) between statistics printk()s.
1934 locktorture.stutter= [KNL]
1935 Time (s) to stutter testing, for example,
1936 specifying five seconds causes the test to run for
1937 five seconds, wait for five seconds, and so on.
1938 This tests the locking primitive's ability to
1939 transition abruptly to and from idle.
1941 locktorture.torture_runnable= [BOOT]
1942 Start locktorture running at boot time.
1944 locktorture.torture_type= [KNL]
1945 Specify the locking implementation to test.
1947 locktorture.verbose= [KNL]
1948 Enable additional printk() statements.
1950 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1953 loglevel= All Kernel Messages with a loglevel smaller than the
1954 console loglevel will be printed to the console. It can
1955 also be changed with klogd or other programs. The
1956 loglevels are defined as follows:
1958 0 (KERN_EMERG) system is unusable
1959 1 (KERN_ALERT) action must be taken immediately
1960 2 (KERN_CRIT) critical conditions
1961 3 (KERN_ERR) error conditions
1962 4 (KERN_WARNING) warning conditions
1963 5 (KERN_NOTICE) normal but significant condition
1964 6 (KERN_INFO) informational
1965 7 (KERN_DEBUG) debug-level messages
1967 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1968 in bytes. n must be a power of two and greater
1969 than the minimal size. The minimal size is defined
1970 by LOG_BUF_SHIFT kernel config parameter. There is
1971 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1972 that allows to increase the default size depending on
1973 the number of CPUs. See init/Kconfig for more details.
1975 logo.nologo [FB] Disables display of the built-in Linux logo.
1976 This may be used to provide more screen space for
1977 kernel log messages and is useful when debugging
1978 kernel boot problems.
1980 lp=0 [LP] Specify parallel ports to use, e.g,
1981 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1982 lp=reset first parallel port). 'lp=0' disables the
1983 lp=auto printer driver. 'lp=reset' (which can be
1984 specified in addition to the ports) causes
1985 attached printers to be reset. Using
1986 lp=port1,port2,... specifies the parallel ports
1987 to associate lp devices with, starting with
1988 lp0. A port specification may be 'none' to skip
1989 that lp device, or a parport name such as
1990 'parport0'. Specifying 'lp=auto' instead of a
1991 port specification list means that device IDs
1992 from each port should be examined, to see if
1993 an IEEE 1284-compliant printer is attached; if
1994 so, the driver will manage that printer.
1995 See also header of drivers/char/lp.c.
1998 Sets loops_per_jiffy to given constant, thus avoiding
1999 time-consuming boot-time autodetection (up to 250 ms per
2000 CPU). 0 enables autodetection (default). To determine
2001 the correct value for your kernel, boot with normal
2002 autodetection and see what value is printed. Note that
2003 on SMP systems the preset will be applied to all CPUs,
2004 which is likely to cause problems if your CPUs need
2005 significantly divergent settings. An incorrect value
2006 will cause delays in the kernel to be wrong, leading to
2007 unpredictable I/O errors and other breakage. Although
2008 unlikely, in the extreme case this might damage your
2012 Format: <io>,<irq>,<dma>
2014 machvec= [IA-64] Force the use of a particular machine-vector
2015 (machvec) in a generic kernel.
2016 Example: machvec=hpzx1_swiotlb
2018 machtype= [Loongson] Share the same kernel image file between different
2020 Example: machtype=lemote-yeeloong-2f-7inch
2022 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2023 than or equal to this physical address is ignored.
2025 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2026 should make use of. maxcpus=n : n >= 0 limits the
2027 kernel to using 'n' processors. n=0 is a special case,
2028 it is equivalent to "nosmp", which also disables
2031 max_loop= [LOOP] The number of loop block devices that get
2032 (loop.max_loop) unconditionally pre-created at init time. The default
2033 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2034 of statically allocating a predefined number, loop
2035 devices can be requested on-demand with the
2036 /dev/loop-control interface.
2038 mce [X86-32] Machine Check Exception
2040 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2042 md= [HW] RAID subsystems devices and level
2043 See Documentation/md.txt.
2046 Format: <first>,<last>
2047 Specifies range of consoles to be captured by the MDA.
2049 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2050 Amount of memory to be used when the kernel is not able
2051 to see the whole system memory or for test.
2052 [X86] Work as limiting max address. Use together
2053 with memmap= to avoid physical address space collisions.
2054 Without memmap= PCI devices could be placed at addresses
2055 belonging to unused RAM.
2057 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2061 [KNL,SH] Allow user to override the default size for
2062 per-device physically contiguous DMA buffers.
2064 memmap=exactmap [KNL,X86] Enable setting of an exact
2065 E820 memory map, as specified by the user.
2066 Such memmap=exactmap lines can be constructed based on
2067 BIOS output or other requirements. See the memmap=nn@ss
2070 memmap=nn[KMG]@ss[KMG]
2071 [KNL] Force usage of a specific region of memory.
2072 Region of memory to be used is from ss to ss+nn.
2074 memmap=nn[KMG]#ss[KMG]
2075 [KNL,ACPI] Mark specific memory as ACPI data.
2076 Region of memory to be marked is from ss to ss+nn.
2078 memmap=nn[KMG]$ss[KMG]
2079 [KNL,ACPI] Mark specific memory as reserved.
2080 Region of memory to be reserved is from ss to ss+nn.
2081 Example: Exclude memory from 0x18690000-0x1869ffff
2082 memmap=64K$0x18690000
2084 memmap=0x10000$0x18690000
2086 memmap=nn[KMG]!ss[KMG]
2087 [KNL,X86] Mark specific memory as protected.
2088 Region of memory to be used, from ss to ss+nn.
2089 The memory region may be marked as e820 type 12 (0xc)
2090 and is NVDIMM or ADR memory.
2092 memory_corruption_check=0/1 [X86]
2093 Some BIOSes seem to corrupt the first 64k of
2094 memory when doing things like suspend/resume.
2095 Setting this option will scan the memory
2096 looking for corruption. Enabling this will
2097 both detect corruption and prevent the kernel
2098 from using the memory being corrupted.
2099 However, its intended as a diagnostic tool; if
2100 repeatable BIOS-originated corruption always
2101 affects the same memory, you can use memmap=
2102 to prevent the kernel from using that memory.
2104 memory_corruption_check_size=size [X86]
2105 By default it checks for corruption in the low
2106 64k, making this memory unavailable for normal
2107 use. Use this parameter to scan for
2108 corruption in more or less memory.
2110 memory_corruption_check_period=seconds [X86]
2111 By default it checks for corruption every 60
2112 seconds. Use this parameter to check at some
2113 other rate. 0 disables periodic checking.
2115 memtest= [KNL,X86,ARM] Enable memtest
2117 default : 0 <disable>
2118 Specifies the number of memtest passes to be
2119 performed. Each pass selects another test
2120 pattern from a given set of patterns. Memtest
2121 fills the memory with this pattern, validates
2122 memory contents and reserves bad memory
2123 regions that are detected.
2125 meye.*= [HW] Set MotionEye Camera parameters
2126 See Documentation/video4linux/meye.txt.
2128 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2129 Multi-Function General Purpose Timers on AMD Geode
2132 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2133 the BIOS has incorrectly applied a workaround. TinyBIOS
2134 version 0.98 is known to be affected, 0.99 fixes the
2135 problem by letting the user disable the workaround.
2139 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2140 physical address is ignored.
2142 mini2440= [ARM,HW,KNL]
2143 Format:[0..2][b][c][t]
2145 MINI2440 configuration specification:
2146 0 - The attached screen is the 3.5" TFT
2147 1 - The attached screen is the 7" TFT
2148 2 - The VGA Shield is attached (1024x768)
2149 Leaving out the screen size parameter will not load
2150 the TFT driver, and the framebuffer will be left
2152 b - Enable backlight. The TFT backlight pin will be
2153 linked to the kernel VESA blanking code and a GPIO
2154 LED. This parameter is not necessary when using the
2156 c - Enable the s3c camera interface.
2157 t - Reserved for enabling touchscreen support. The
2158 touchscreen support is not enabled in the mainstream
2159 kernel as of 2.6.30, a preliminary port can be found
2160 in the "bleeding edge" mini2440 support kernel at
2161 http://repo.or.cz/w/linux-2.6/mini2440.git
2164 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2165 parameter allows control of the logging verbosity for
2166 the additional memory initialisation checks. A value
2167 of 0 disables mminit logging and a level of 4 will
2168 log everything. Information is printed at KERN_DEBUG
2169 so loglevel=8 may also need to be specified.
2172 [KNL] When CONFIG_MODULE_SIG is set, this means that
2173 modules without (valid) signatures will fail to load.
2174 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2175 is always true, so this option does nothing.
2178 [MOUSE] Maximum time between finger touching and
2179 leaving touchpad surface for touch to be considered
2180 a tap and be reported as a left button click (for
2181 touchpads working in absolute mode only).
2183 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2184 reporting absolute coordinates, such as tablets
2185 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2186 reporting absolute coordinates, such as tablets
2188 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2189 is similar to kernelcore except it specifies the
2190 amount of memory used for migratable allocations.
2191 If both kernelcore and movablecore is specified,
2192 then kernelcore will be at *least* the specified
2193 value but may be more. If movablecore on its own
2194 is specified, the administrator must be careful
2195 that the amount of memory usable for all allocations
2198 movable_node [KNL,X86] Boot-time switch to enable the effects
2199 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2201 MTD_Partition= [MTD]
2202 Format: <name>,<region-number>,<size>,<offset>
2204 MTD_Region= [MTD] Format:
2205 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2208 See drivers/mtd/cmdlinepart.c.
2210 multitce=off [PPC] This parameter disables the use of the pSeries
2211 firmware feature for updating multiple TCE entries
2214 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2216 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2218 boundary - index of last SLC block on Flex-OneNAND.
2219 The remaining blocks are configured as MLC blocks.
2220 lock - Configure if Flex-OneNAND boundary should be locked.
2221 Once locked, the boundary cannot be changed.
2222 1 indicates lock status, 0 indicates unlock status.
2225 ARM/S3C2412 JIVE boot control
2227 See arch/arm/mach-s3c2412/mach-jive.c
2229 mtouchusb.raw_coordinates=
2230 [HW] Make the MicroTouch USB driver use raw coordinates
2231 ('y', default) or cooked coordinates ('n')
2233 mtrr_chunk_size=nn[KMG] [X86]
2234 used for mtrr cleanup. It is largest continuous chunk
2235 that could hold holes aka. UC entries.
2237 mtrr_gran_size=nn[KMG] [X86]
2238 Used for mtrr cleanup. It is granularity of mtrr block.
2240 Large value could prevent small alignment from
2243 mtrr_spare_reg_nr=n [X86]
2245 Range: 0,7 : spare reg number
2247 Used for mtrr cleanup. It is spare mtrr entries number.
2248 Set to 2 or more if your graphical card needs more.
2250 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2252 netdev= [NET] Network devices parameters
2253 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2254 Note that mem_start is often overloaded to mean
2255 something different and driver-specific.
2256 This usage is only documented in each driver source
2260 [NETFILTER] Enable connection tracking flow accounting
2261 0 to disable accounting
2262 1 to enable accounting
2265 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2266 See Documentation/filesystems/nfs/nfsroot.txt.
2268 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2269 See Documentation/filesystems/nfs/nfsroot.txt.
2271 nfsrootdebug [NFS] enable nfsroot debugging messages.
2272 See Documentation/filesystems/nfs/nfsroot.txt.
2274 nfs.callback_tcpport=
2275 [NFS] set the TCP port on which the NFSv4 callback
2276 channel should listen.
2279 [NFS] sets the pathname to the program which is used
2280 to update the NFS client cache entries.
2282 nfs.cache_getent_timeout=
2283 [NFS] sets the timeout after which an attempt to
2284 update a cache entry is deemed to have failed.
2286 nfs.idmap_cache_timeout=
2287 [NFS] set the maximum lifetime for idmapper cache
2291 [NFS] enable 64-bit inode numbers.
2292 If zero, the NFS client will fake up a 32-bit inode
2293 number for the readdir() and stat() syscalls instead
2294 of returning the full 64-bit number.
2295 The default is to return 64-bit inode numbers.
2297 nfs.max_session_slots=
2298 [NFSv4.1] Sets the maximum number of session slots
2299 the client will attempt to negotiate with the server.
2300 This limits the number of simultaneous RPC requests
2301 that the client can send to the NFSv4.1 server.
2302 Note that there is little point in setting this
2303 value higher than the max_tcp_slot_table_limit.
2305 nfs.nfs4_disable_idmapping=
2306 [NFSv4] When set to the default of '1', this option
2307 ensures that both the RPC level authentication
2308 scheme and the NFS level operations agree to use
2309 numeric uids/gids if the mount is using the
2310 'sec=sys' security flavour. In effect it is
2311 disabling idmapping, which can make migration from
2312 legacy NFSv2/v3 systems to NFSv4 easier.
2313 Servers that do not support this mode of operation
2314 will be autodetected by the client, and it will fall
2315 back to using the idmapper.
2316 To turn off this behaviour, set the value to '0'.
2318 [NFS4] Specify an additional fixed unique ident-
2319 ification string that NFSv4 clients can insert into
2320 their nfs_client_id4 string. This is typically a
2321 UUID that is generated at system install time.
2323 nfs.send_implementation_id =
2324 [NFSv4.1] Send client implementation identification
2325 information in exchange_id requests.
2326 If zero, no implementation identification information
2328 The default is to send the implementation identification
2331 nfs.recover_lost_locks =
2332 [NFSv4] Attempt to recover locks that were lost due
2333 to a lease timeout on the server. Please note that
2334 doing this risks data corruption, since there are
2335 no guarantees that the file will remain unchanged
2336 after the locks are lost.
2337 If you want to enable the kernel legacy behaviour of
2338 attempting to recover these locks, then set this
2340 The default parameter value of '0' causes the kernel
2341 not to attempt recovery of lost locks.
2343 nfs4.layoutstats_timer =
2344 [NFSv4.2] Change the rate at which the kernel sends
2345 layoutstats to the pNFS metadata server.
2347 Setting this to value to 0 causes the kernel to use
2348 whatever value is the default set by the layout
2349 driver. A non-zero value sets the minimum interval
2350 in seconds between layoutstats transmissions.
2352 nfsd.nfs4_disable_idmapping=
2353 [NFSv4] When set to the default of '1', the NFSv4
2354 server will return only numeric uids and gids to
2355 clients using auth_sys, and will accept numeric uids
2356 and gids from such clients. This is intended to ease
2357 migration from NFSv2/v3.
2359 objlayoutdriver.osd_login_prog=
2360 [NFS] [OBJLAYOUT] sets the pathname to the program which
2361 is used to automatically discover and login into new
2362 osd-targets. Please see:
2363 Documentation/filesystems/pnfs.txt for more explanations
2365 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2366 when a NMI is triggered.
2367 Format: [state][,regs][,debounce][,die]
2369 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2370 Format: [panic,][nopanic,][num]
2372 0 - turn hardlockup detector in nmi_watchdog off
2373 1 - turn hardlockup detector in nmi_watchdog on
2374 When panic is specified, panic when an NMI watchdog
2375 timeout occurs (or 'nopanic' to override the opposite
2376 default). To disable both hard and soft lockup detectors,
2377 please see 'nowatchdog'.
2378 This is useful when you use a panic=... timeout and
2379 need the box quickly up again.
2381 netpoll.carrier_timeout=
2382 [NET] Specifies amount of time (in seconds) that
2383 netpoll should wait for a carrier. By default netpoll
2386 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2387 emulation library even if a 387 maths coprocessor
2391 [HW] Never suspend the console
2392 Disable suspending of consoles during suspend and
2393 hibernate operations. Once disabled, debugging
2394 messages can reach various consoles while the rest
2395 of the system is being put to sleep (ie, while
2396 debugging driver suspend/resume hooks). This may
2397 not work reliably with all consoles, but is known
2398 to work with serial and VGA consoles.
2399 To facilitate more flexible debugging, we also add
2400 console_suspend, a printk module parameter to control
2401 it. Users could use console_suspend (usually
2402 /sys/module/printk/parameters/console_suspend) to
2403 turn on/off it dynamically.
2405 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2406 caches in the slab allocator. Saves per-node memory,
2407 but will impact performance.
2411 noapic [SMP,APIC] Tells the kernel to not make use of any
2412 IOAPICs that may be present in the system.
2414 noautogroup Disable scheduler automatic task group creation.
2416 nobats [PPC] Do not use BATs for mapping kernel lowmem
2417 on "Classic" PPC cores.
2421 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2423 nodelayacct [KNL] Disable per-task delay accounting
2425 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2427 nodsp [SH] Disable hardware DSP at boot time.
2429 noefi Disable EFI runtime services support.
2434 On X86-32 available only on PAE configured kernels.
2435 noexec=on: enable non-executable mappings (default)
2436 noexec=off: disable non-executable mappings
2439 Disable SMAP (Supervisor Mode Access Prevention)
2440 even if it is supported by processor.
2443 Disable SMEP (Supervisor Mode Execution Prevention)
2444 even if it is supported by processor.
2447 This affects only 32-bit executables.
2448 noexec32=on: enable non-executable mappings (default)
2449 read doesn't imply executable mappings
2450 noexec32=off: disable non-executable mappings
2451 read implies executable mappings
2453 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2455 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2456 register save and restore. The kernel will only save
2457 legacy floating-point registers on task switch.
2459 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2461 noxsave [BUGS=X86] Disables x86 extended register state save
2462 and restore using xsave. The kernel will fallback to
2463 enabling legacy floating-point and sse state.
2465 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2466 register states. The kernel will fall back to use
2467 xsave to save the states. By using this parameter,
2468 performance of saving the states is degraded because
2469 xsave doesn't support modified optimization while
2470 xsaveopt supports it on xsaveopt enabled systems.
2472 noxsaves [X86] Disables xsaves and xrstors used in saving and
2473 restoring x86 extended register state in compacted
2474 form of xsave area. The kernel will fall back to use
2475 xsaveopt and xrstor to save and restore the states
2476 in standard form of xsave area. By using this
2477 parameter, xsave area per process might occupy more
2478 memory on xsaves enabled systems.
2480 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2481 wfi(ARM) instruction doesn't work correctly and not to
2482 use it. This is also useful when using JTAG debugger.
2484 no_file_caps Tells the kernel not to honor file capabilities. The
2485 only way then for a file to be executed with privilege
2486 is to be setuid root or executed by root.
2488 nohalt [IA-64] Tells the kernel not to use the power saving
2489 function PAL_HALT_LIGHT when idle. This increases
2490 power-consumption. On the positive side, it reduces
2491 interrupt wake-up latency, which may improve performance
2492 in certain environments such as networked servers or
2495 nohibernate [HIBERNATION] Disable hibernation and resume.
2497 nohz= [KNL] Boottime enable/disable dynamic ticks
2498 Valid arguments: on, off
2501 nohz_full= [KNL,BOOT]
2502 In kernels built with CONFIG_NO_HZ_FULL=y, set
2503 the specified list of CPUs whose tick will be stopped
2504 whenever possible. The boot CPU will be forced outside
2505 the range to maintain the timekeeping.
2506 The CPUs in this range must also be included in the
2509 noiotrap [SH] Disables trapped I/O port accesses.
2511 noirqdebug [X86-32] Disables the code which attempts to detect and
2512 disable unhandled interrupt sources.
2514 no_timer_check [X86,APIC] Disables the code which tests for
2515 broken timer IRQ sources.
2517 noisapnp [ISAPNP] Disables ISA PnP code.
2519 noinitrd [RAM] Tells the kernel not to load any configured
2522 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2524 [Deprecated - use intremap=off]
2528 nojitter [IA-64] Disables jitter checking for ITC timers.
2530 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2532 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2535 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2536 steal time is computed, but won't influence scheduler
2539 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2541 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2543 noltlbs [PPC] Do not use large page/tlb entries for kernel
2544 lowmem mapping on PPC40x.
2546 nomca [IA-64] Disable machine check abort handling
2548 nomce [X86-32] Disable Machine Check Exception
2550 nomfgpt [X86-32] Disable Multi-Function General Purpose
2551 Timer usage (for AMD Geode machines).
2553 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2554 shutdown the other cpus. Instead use the REBOOT_VECTOR
2557 nomodule Disable module load
2559 nopat [X86] Disable PAT (page attribute table extension of
2560 pagetables) support.
2562 norandmaps Don't use address space randomization. Equivalent to
2563 echo 0 > /proc/sys/kernel/randomize_va_space
2565 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2567 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2568 with UP alternatives
2570 nordrand [X86] Disable kernel use of the RDRAND and
2571 RDSEED instructions even if they are supported
2572 by the processor. RDRAND and RDSEED are still
2573 available to user space applications.
2575 noresume [SWSUSP] Disables resume and restores original swap
2578 no-scroll [VGA] Disables scrollback.
2579 This is required for the Braillex ib80-piezo Braille
2580 reader made by F.H. Papenmeier (Germany).
2584 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2586 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2587 and disable the IO APIC. legacy for "maxcpus=0".
2589 nosoftlockup [KNL] Disable the soft-lockup detector.
2591 nosync [HW,M68K] Disables sync negotiation for all devices.
2593 notsc [BUGS=X86-32] Disable Time Stamp Counter
2595 nowatchdog [KNL] Disable both lockup detectors, i.e.
2596 soft-lockup and NMI watchdog (hard-lockup).
2600 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2602 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2603 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2604 Some features depend on CPU0. Known dependencies are:
2605 1. Resume from suspend/hibernate depends on CPU0.
2606 Suspend/hibernate will fail if CPU0 is offline and you
2607 need to online CPU0 before suspend/hibernate.
2608 2. PIC interrupts also depend on CPU0. CPU0 can't be
2609 removed if a PIC interrupt is detected.
2610 It's said poweroff/reboot may depend on CPU0 on some
2611 machines although I haven't seen such issues so far
2612 after CPU0 is offline on a few tested machines.
2613 If the dependencies are under your control, you can
2614 turn on cpu0_hotplug.
2616 nptcg= [IA-64] Override max number of concurrent global TLB
2617 purges which is reported from either PAL_VM_SUMMARY or
2620 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2621 could support. nr_cpus=n : n >= 1 limits the kernel to
2622 supporting 'n' processors. Later in runtime you can not
2623 use hotplug cpu feature to put more cpu back to online.
2624 just like you compile the kernel NR_CPUS=n
2626 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2628 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2629 Allowed values are enable and disable
2631 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2632 one of ['zone', 'node', 'default'] can be specified
2633 This can be set from sysctl after boot.
2634 See Documentation/sysctl/vm.txt for details.
2636 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2637 See Documentation/debugging-via-ohci1394.txt for more
2640 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2641 Rather than timing out after 20 ms if an EC
2642 command is not properly ACKed, override the length
2643 of the timeout. We have interrupts disabled while
2644 waiting for the ACK, so if this is set too high
2645 interrupts *may* be lost!
2647 omap_mux= [OMAP] Override bootloader pin multiplexing.
2648 Format: <mux_mode0.mode_name=value>...
2649 For example, to override I2C bus2:
2650 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2652 oprofile.timer= [HW]
2653 Use timer interrupt instead of performance counters
2655 oprofile.cpu_type= Force an oprofile cpu type
2656 This might be useful if you have an older oprofile
2657 userland or if you want common events.
2658 Format: { arch_perfmon }
2659 arch_perfmon: [X86] Force use of architectural
2660 perfmon on Intel CPUs instead of the
2661 CPU specific event set.
2662 timer: [X86] Force use of architectural NMI
2663 timer mode (see also oprofile.timer
2664 for generic hr timer mode)
2665 [s390] Force legacy basic mode sampling
2666 (report cpu_type "timer")
2668 oops=panic Always panic on oopses. Default is to just kill the
2669 process, but there is a small probability of
2670 deadlocking the machine.
2671 This will also cause panics on machine check exceptions.
2672 Useful together with panic=30 to trigger a reboot.
2675 See Documentation/sound/oss/oss-parameters.txt
2677 page_owner= [KNL] Boot-time page_owner enabling option.
2678 Storage of the information about who allocated
2679 each page is disabled in default. With this switch,
2681 on: enable the feature
2683 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2684 timeout > 0: seconds before rebooting
2685 timeout = 0: wait forever
2686 timeout < 0: reboot immediately
2689 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2692 crash_kexec_post_notifiers
2693 Run kdump after running panic-notifiers and dumping
2694 kmsg. This only for the users who doubt kdump always
2695 succeeds in any situation.
2696 Note that this also increases risks of kdump failure,
2697 because some panic notifiers can make the crashed
2698 kernel more unstable.
2700 parkbd.port= [HW] Parallel port number the keyboard adapter is
2701 connected to, default is 0.
2703 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2704 0 for XT, 1 for AT (default is AT).
2707 parport= [HW,PPT] Specify parallel ports. 0 disables.
2708 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2709 Use 'auto' to force the driver to use any
2710 IRQ/DMA settings detected (the default is to
2711 ignore detected IRQ/DMA settings because of
2712 possible conflicts). You can specify the base
2713 address, IRQ, and DMA settings; IRQ and DMA
2714 should be numbers, or 'auto' (for using detected
2715 settings on that particular port), or 'nofifo'
2716 (to avoid using a FIFO even if it is detected).
2717 Parallel ports are assigned in the order they
2718 are specified on the command line, starting
2721 parport_init_mode= [HW,PPT]
2722 Configure VIA parallel port to operate in
2723 a specific mode. This is necessary on Pegasos
2724 computer where firmware has no options for setting
2725 up parallel port mode and sets it to spp.
2726 Currently this function knows 686a and 8231 chips.
2727 Format: [spp|ps2|epp|ecp|ecpepp]
2730 Halt all CPUs after the first oops has been printed for
2731 the specified number of seconds. This is to be used if
2732 your oopses keep scrolling off the screen.
2737 See header of drivers/block/paride/pcd.c.
2738 See also Documentation/blockdev/paride.txt.
2740 pci=option[,option...] [PCI] various PCI subsystem options:
2741 earlydump [X86] dump PCI config space before the kernel
2743 off [X86] don't probe for the PCI bus
2744 bios [X86-32] force use of PCI BIOS, don't access
2745 the hardware directly. Use this if your machine
2746 has a non-standard PCI host bridge.
2747 nobios [X86-32] disallow use of PCI BIOS, only direct
2748 hardware access methods are allowed. Use this
2749 if you experience crashes upon bootup and you
2750 suspect they are caused by the BIOS.
2751 conf1 [X86] Force use of PCI Configuration Access
2752 Mechanism 1 (config address in IO port 0xCF8,
2753 data in IO port 0xCFC, both 32-bit).
2754 conf2 [X86] Force use of PCI Configuration Access
2755 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2756 the function, IO port 0xCFA, also 8-bit, sets
2757 bus number. The config space is then accessed
2758 through ports 0xC000-0xCFFF).
2759 See http://wiki.osdev.org/PCI for more info
2760 on the configuration access mechanisms.
2761 noaer [PCIE] If the PCIEAER kernel config parameter is
2762 enabled, this kernel boot option can be used to
2763 disable the use of PCIE advanced error reporting.
2764 nodomains [PCI] Disable support for multiple PCI
2765 root domains (aka PCI segments, in ACPI-speak).
2766 nommconf [X86] Disable use of MMCONFIG for PCI
2768 check_enable_amd_mmconf [X86] check for and enable
2769 properly configured MMIO access to PCI
2770 config space on AMD family 10h CPU
2771 nomsi [MSI] If the PCI_MSI kernel config parameter is
2772 enabled, this kernel boot option can be used to
2773 disable the use of MSI interrupts system-wide.
2774 noioapicquirk [APIC] Disable all boot interrupt quirks.
2775 Safety option to keep boot IRQs enabled. This
2776 should never be necessary.
2777 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2778 primary IO-APIC for bridges that cannot disable
2779 boot IRQs. This fixes a source of spurious IRQs
2780 when the system masks IRQs.
2781 noioapicreroute [APIC] Disable workaround that uses the
2782 boot IRQ equivalent of an IRQ that connects to
2783 a chipset where boot IRQs cannot be disabled.
2784 The opposite of ioapicreroute.
2785 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2786 routing table. These calls are known to be buggy
2787 on several machines and they hang the machine
2788 when used, but on other computers it's the only
2789 way to get the interrupt routing table. Try
2790 this option if the kernel is unable to allocate
2791 IRQs or discover secondary PCI buses on your
2793 rom [X86] Assign address space to expansion ROMs.
2794 Use with caution as certain devices share
2795 address decoders between ROMs and other
2797 norom [X86] Do not assign address space to
2798 expansion ROMs that do not already have
2799 BIOS assigned address ranges.
2800 nobar [X86] Do not assign address space to the
2801 BARs that weren't assigned by the BIOS.
2802 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2803 assigned automatically to PCI devices. You can
2804 make the kernel exclude IRQs of your ISA cards
2806 pirqaddr=0xAAAAA [X86] Specify the physical address
2807 of the PIRQ table (normally generated
2808 by the BIOS) if it is outside the
2809 F0000h-100000h range.
2810 lastbus=N [X86] Scan all buses thru bus #N. Can be
2811 useful if the kernel is unable to find your
2812 secondary buses and you want to tell it
2813 explicitly which ones they are.
2814 assign-busses [X86] Always assign all PCI bus
2815 numbers ourselves, overriding
2816 whatever the firmware may have done.
2817 usepirqmask [X86] Honor the possible IRQ mask stored
2818 in the BIOS $PIR table. This is needed on
2819 some systems with broken BIOSes, notably
2820 some HP Pavilion N5400 and Omnibook XE3
2821 notebooks. This will have no effect if ACPI
2822 IRQ routing is enabled.
2823 noacpi [X86] Do not use ACPI for IRQ routing
2824 or for PCI scanning.
2825 use_crs [X86] Use PCI host bridge window information
2826 from ACPI. On BIOSes from 2008 or later, this
2827 is enabled by default. If you need to use this,
2828 please report a bug.
2829 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2830 If you need to use this, please report a bug.
2831 routeirq Do IRQ routing for all PCI devices.
2832 This is normally done in pci_enable_device(),
2833 so this option is a temporary workaround
2834 for broken drivers that don't call it.
2835 skip_isa_align [X86] do not align io start addr, so can
2836 handle more pci cards
2837 firmware [ARM] Do not re-enumerate the bus but instead
2838 just use the configuration from the
2839 bootloader. This is currently used on
2840 IXP2000 systems where the bus has to be
2841 configured a certain way for adjunct CPUs.
2842 noearly [X86] Don't do any early type 1 scanning.
2843 This might help on some broken boards which
2844 machine check when some devices' config space
2845 is read. But various workarounds are disabled
2846 and some IOMMU drivers will not work.
2847 bfsort Sort PCI devices into breadth-first order.
2848 This sorting is done to get a device
2849 order compatible with older (<= 2.4) kernels.
2850 nobfsort Don't sort PCI devices into breadth-first order.
2851 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2852 tuning and use the BIOS-configured MPS defaults.
2853 pcie_bus_safe Set every device's MPS to the largest value
2854 supported by all devices below the root complex.
2855 pcie_bus_perf Set device MPS to the largest allowable MPS
2856 based on its parent bus. Also set MRRS (Max
2857 Read Request Size) to the largest supported
2858 value (no larger than the MPS that the device
2859 or bus can support) for best performance.
2860 pcie_bus_peer2peer Set every device's MPS to 128B, which
2861 every device is guaranteed to support. This
2862 configuration allows peer-to-peer DMA between
2863 any pair of devices, possibly at the cost of
2864 reduced performance. This also guarantees
2865 that hot-added devices will work.
2866 cbiosize=nn[KMG] The fixed amount of bus space which is
2867 reserved for the CardBus bridge's IO window.
2868 The default value is 256 bytes.
2869 cbmemsize=nn[KMG] The fixed amount of bus space which is
2870 reserved for the CardBus bridge's memory
2871 window. The default value is 64 megabytes.
2874 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2875 Specifies alignment and device to reassign
2876 aligned memory resources.
2877 If <order of align> is not specified,
2878 PAGE_SIZE is used as alignment.
2879 PCI-PCI bridge can be specified, if resource
2880 windows need to be expanded.
2881 ecrc= Enable/disable PCIe ECRC (transaction layer
2882 end-to-end CRC checking).
2883 bios: Use BIOS/firmware settings. This is the
2887 hpiosize=nn[KMG] The fixed amount of bus space which is
2888 reserved for hotplug bridge's IO window.
2889 Default size is 256 bytes.
2890 hpmemsize=nn[KMG] The fixed amount of bus space which is
2891 reserved for hotplug bridge's memory window.
2892 Default size is 2 megabytes.
2893 realloc= Enable/disable reallocating PCI bridge resources
2894 if allocations done by BIOS are too small to
2895 accommodate resources required by all child
2897 off: Turn realloc off
2899 realloc same as realloc=on
2900 noari do not use PCIe ARI.
2901 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2902 only look for one device below a PCIe downstream
2905 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2908 force Enable ASPM even on devices that claim not to support it.
2909 WARNING: Forcing ASPM on may cause system lockups.
2911 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2912 nomsi Do not use MSI for PCI Express Native Hotplug (this
2913 makes all PCIe ports use INTx for hotplug services).
2915 pcie_ports= [PCIE] PCIe ports handling:
2916 auto Ask the BIOS whether or not to use native PCIe services
2917 associated with PCIe ports (PME, hot-plug, AER). Use
2918 them only if that is allowed by the BIOS.
2919 native Use native PCIe services associated with PCIe ports
2921 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2924 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2925 nomsi Do not use MSI for native PCIe PME signaling (this makes
2926 all PCIe root ports use INTx for all services).
2928 pcmv= [HW,PCMCIA] BadgePAD 4
2932 Keep all power-domains already enabled by bootloader on,
2933 even if no driver has claimed them. This is useful
2934 for debug and development, but should not be
2935 needed on a platform with proper driver support.
2938 See Documentation/blockdev/paride.txt.
2940 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2943 See arch/parisc/kernel/pdc_chassis.c
2945 percpu_alloc= Select which percpu first chunk allocator to use.
2946 Currently supported values are "embed" and "page".
2947 Archs may support subset or none of the selections.
2948 See comments in mm/percpu.c for details on each
2949 allocator. This parameter is primarily for debugging
2950 and performance comparison.
2953 See Documentation/blockdev/paride.txt.
2956 See Documentation/blockdev/paride.txt.
2958 pirq= [SMP,APIC] Manual mp-table setup
2959 See Documentation/x86/i386/IO-APIC.txt.
2961 plip= [PPT,NET] Parallel port network link
2962 Format: { parport<nr> | timid | 0 }
2963 See also Documentation/parport.txt.
2965 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2966 Override pmtimer IOPort with a hex value.
2970 Enable PNP debug messages (depends on the
2971 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2972 via /sys/module/pnp/parameters/debug. We always show
2973 current resource usage; turning this on also shows
2974 possible settings and some assignment information.
2980 { on | off | curr | res | no-curr | no-res }
2983 [ISAPNP] Exclude IRQs for the autoconfiguration
2986 [ISAPNP] Exclude DMAs for the autoconfiguration
2988 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2989 Ranges are in pairs (I/O port base and size).
2992 [ISAPNP] Exclude memory regions for the
2994 Ranges are in pairs (memory base and size).
2996 ports= [IP_VS_FTP] IPVS ftp helper module
2998 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3000 Format: <port>,<port>....
3002 ppc_strict_facility_enable
3003 [PPC] This option catches any kernel floating point,
3004 Altivec, VSX and SPE outside of regions specifically
3005 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3006 There is some performance impact when enabling this.
3008 print-fatal-signals=
3009 [KNL] debug: print fatal signals
3011 If enabled, warn about various signal handling
3012 related application anomalies: too many signals,
3013 too many POSIX.1 timers, fatal signals causing a
3016 If you hit the warning due to signal overflow,
3017 you might want to try "ulimit -i unlimited".
3021 printk.always_kmsg_dump=
3022 Trigger kmsg_dump for cases other than kernel oops or
3024 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3027 printk.time= Show timing data prefixed to each printk message line
3028 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3030 processor.max_cstate= [HW,ACPI]
3031 Limit processor to maximum C-state
3032 max_cstate=9 overrides any DMI blacklist limit.
3034 processor.nocst [HW,ACPI]
3035 Ignore the _CST method to determine C-states,
3036 instead using the legacy FADT method
3038 profile= [KNL] Enable kernel profiling via /proc/profile
3039 Format: [schedule,]<number>
3040 Param: "schedule" - profile schedule points.
3041 Param: <number> - step/bucket size as a power of 2 for
3042 statistical time based profiling.
3043 Param: "sleep" - profile D-state sleeping (millisecs).
3044 Requires CONFIG_SCHEDSTATS
3045 Param: "kvm" - profile VM exits.
3047 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3049 See Documentation/blockdev/ramdisk.txt.
3051 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3052 probe for; one of (bare|imps|exps|lifebook|any).
3053 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3055 psmouse.resetafter= [HW,MOUSE]
3056 Try to reset the device after so many bad packets
3059 [HW,MOUSE] Set desired mouse resolution, in dpi.
3060 psmouse.smartscroll=
3061 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3062 0 = disabled, 1 = enabled (default).
3064 pstore.backend= Specify the name of the pstore backend to use
3067 See Documentation/blockdev/paride.txt.
3070 [KNL] Number of legacy pty's. Overwrites compiled-in
3073 quiet [KNL] Disable most log messages
3078 See Documentation/md.txt.
3080 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3081 See Documentation/blockdev/ramdisk.txt.
3084 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3085 the specified list of CPUs to be no-callback CPUs.
3086 Invocation of these CPUs' RCU callbacks will
3087 be offloaded to "rcuox/N" kthreads created for
3088 that purpose, where "x" is "b" for RCU-bh, "p"
3089 for RCU-preempt, and "s" for RCU-sched, and "N"
3090 is the CPU number. This reduces OS jitter on the
3091 offloaded CPUs, which can be useful for HPC and
3092 real-time workloads. It can also improve energy
3093 efficiency for asymmetric multiprocessors.
3096 Rather than requiring that offloaded CPUs
3097 (specified by rcu_nocbs= above) explicitly
3098 awaken the corresponding "rcuoN" kthreads,
3099 make these kthreads poll for callbacks.
3100 This improves the real-time response for the
3101 offloaded CPUs by relieving them of the need to
3102 wake up the corresponding kthread, but degrades
3103 energy efficiency by requiring that the kthreads
3104 periodically wake up to do the polling.
3106 rcutree.blimit= [KNL]
3107 Set maximum number of finished RCU callbacks to
3108 process in one batch.
3110 rcutree.dump_tree= [KNL]
3111 Dump the structure of the rcu_node combining tree
3112 out at early boot. This is used for diagnostic
3113 purposes, to verify correct tree setup.
3115 rcutree.gp_cleanup_delay= [KNL]
3116 Set the number of jiffies to delay each step of
3117 RCU grace-period cleanup. This only has effect
3118 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3120 rcutree.gp_init_delay= [KNL]
3121 Set the number of jiffies to delay each step of
3122 RCU grace-period initialization. This only has
3123 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3126 rcutree.gp_preinit_delay= [KNL]
3127 Set the number of jiffies to delay each step of
3128 RCU grace-period pre-initialization, that is,
3129 the propagation of recent CPU-hotplug changes up
3130 the rcu_node combining tree. This only has effect
3131 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3133 rcutree.rcu_fanout_exact= [KNL]
3134 Disable autobalancing of the rcu_node combining
3135 tree. This is used by rcutorture, and might
3136 possibly be useful for architectures having high
3137 cache-to-cache transfer latencies.
3139 rcutree.rcu_fanout_leaf= [KNL]
3140 Change the number of CPUs assigned to each
3141 leaf rcu_node structure. Useful for very
3142 large systems, which will choose the value 64,
3143 and for NUMA systems with large remote-access
3144 latencies, which will choose a value aligned
3145 with the appropriate hardware boundaries.
3147 rcutree.jiffies_till_sched_qs= [KNL]
3148 Set required age in jiffies for a
3149 given grace period before RCU starts
3150 soliciting quiescent-state help from
3151 rcu_note_context_switch().
3153 rcutree.jiffies_till_first_fqs= [KNL]
3154 Set delay from grace-period initialization to
3155 first attempt to force quiescent states.
3156 Units are jiffies, minimum value is zero,
3157 and maximum value is HZ.
3159 rcutree.jiffies_till_next_fqs= [KNL]
3160 Set delay between subsequent attempts to force
3161 quiescent states. Units are jiffies, minimum
3162 value is one, and maximum value is HZ.
3164 rcutree.kthread_prio= [KNL,BOOT]
3165 Set the SCHED_FIFO priority of the RCU per-CPU
3166 kthreads (rcuc/N). This value is also used for
3167 the priority of the RCU boost threads (rcub/N)
3168 and for the RCU grace-period kthreads (rcu_bh,
3169 rcu_preempt, and rcu_sched). If RCU_BOOST is
3170 set, valid values are 1-99 and the default is 1
3171 (the least-favored priority). Otherwise, when
3172 RCU_BOOST is not set, valid values are 0-99 and
3173 the default is zero (non-realtime operation).
3175 rcutree.rcu_nocb_leader_stride= [KNL]
3176 Set the number of NOCB kthread groups, which
3177 defaults to the square root of the number of
3178 CPUs. Larger numbers reduces the wakeup overhead
3179 on the per-CPU grace-period kthreads, but increases
3180 that same overhead on each group's leader.
3182 rcutree.qhimark= [KNL]
3183 Set threshold of queued RCU callbacks beyond which
3184 batch limiting is disabled.
3186 rcutree.qlowmark= [KNL]
3187 Set threshold of queued RCU callbacks below which
3188 batch limiting is re-enabled.
3190 rcutree.rcu_idle_gp_delay= [KNL]
3191 Set wakeup interval for idle CPUs that have
3192 RCU callbacks (RCU_FAST_NO_HZ=y).
3194 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3195 Set wakeup interval for idle CPUs that have
3196 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3197 Lazy RCU callbacks are those which RCU can
3198 prove do nothing more than free memory.
3200 rcutorture.cbflood_inter_holdoff= [KNL]
3201 Set holdoff time (jiffies) between successive
3202 callback-flood tests.
3204 rcutorture.cbflood_intra_holdoff= [KNL]
3205 Set holdoff time (jiffies) between successive
3206 bursts of callbacks within a given callback-flood
3209 rcutorture.cbflood_n_burst= [KNL]
3210 Set the number of bursts making up a given
3211 callback-flood test. Set this to zero to
3212 disable callback-flood testing.
3214 rcutorture.cbflood_n_per_burst= [KNL]
3215 Set the number of callbacks to be registered
3216 in a given burst of a callback-flood test.
3218 rcutorture.fqs_duration= [KNL]
3219 Set duration of force_quiescent_state bursts
3222 rcutorture.fqs_holdoff= [KNL]
3223 Set holdoff time within force_quiescent_state bursts
3226 rcutorture.fqs_stutter= [KNL]
3227 Set wait time between force_quiescent_state bursts
3230 rcutorture.gp_cond= [KNL]
3231 Use conditional/asynchronous update-side
3232 primitives, if available.
3234 rcutorture.gp_exp= [KNL]
3235 Use expedited update-side primitives, if available.
3237 rcutorture.gp_normal= [KNL]
3238 Use normal (non-expedited) asynchronous
3239 update-side primitives, if available.
3241 rcutorture.gp_sync= [KNL]
3242 Use normal (non-expedited) synchronous
3243 update-side primitives, if available. If all
3244 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3245 rcutorture.gp_normal=, and rcutorture.gp_sync=
3246 are zero, rcutorture acts as if is interpreted
3247 they are all non-zero.
3249 rcutorture.n_barrier_cbs= [KNL]
3250 Set callbacks/threads for rcu_barrier() testing.
3252 rcutorture.nfakewriters= [KNL]
3253 Set number of concurrent RCU writers. These just
3254 stress RCU, they don't participate in the actual
3255 test, hence the "fake".
3257 rcutorture.nreaders= [KNL]
3258 Set number of RCU readers. The value -1 selects
3259 N-1, where N is the number of CPUs. A value
3260 "n" less than -1 selects N-n-2, where N is again
3261 the number of CPUs. For example, -2 selects N
3262 (the number of CPUs), -3 selects N+1, and so on.
3264 rcutorture.object_debug= [KNL]
3265 Enable debug-object double-call_rcu() testing.
3267 rcutorture.onoff_holdoff= [KNL]
3268 Set time (s) after boot for CPU-hotplug testing.
3270 rcutorture.onoff_interval= [KNL]
3271 Set time (s) between CPU-hotplug operations, or
3272 zero to disable CPU-hotplug testing.
3274 rcutorture.shuffle_interval= [KNL]
3275 Set task-shuffle interval (s). Shuffling tasks
3276 allows some CPUs to go into dyntick-idle mode
3277 during the rcutorture test.
3279 rcutorture.shutdown_secs= [KNL]
3280 Set time (s) after boot system shutdown. This
3281 is useful for hands-off automated testing.
3283 rcutorture.stall_cpu= [KNL]
3284 Duration of CPU stall (s) to test RCU CPU stall
3285 warnings, zero to disable.
3287 rcutorture.stall_cpu_holdoff= [KNL]
3288 Time to wait (s) after boot before inducing stall.
3290 rcutorture.stat_interval= [KNL]
3291 Time (s) between statistics printk()s.
3293 rcutorture.stutter= [KNL]
3294 Time (s) to stutter testing, for example, specifying
3295 five seconds causes the test to run for five seconds,
3296 wait for five seconds, and so on. This tests RCU's
3297 ability to transition abruptly to and from idle.
3299 rcutorture.test_boost= [KNL]
3300 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3301 "Maybe" means test if the RCU implementation
3302 under test support RCU priority boosting.
3304 rcutorture.test_boost_duration= [KNL]
3305 Duration (s) of each individual boost test.
3307 rcutorture.test_boost_interval= [KNL]
3308 Interval (s) between each boost test.
3310 rcutorture.test_no_idle_hz= [KNL]
3311 Test RCU's dyntick-idle handling. See also the
3312 rcutorture.shuffle_interval parameter.
3314 rcutorture.torture_runnable= [BOOT]
3315 Start rcutorture running at boot time.
3317 rcutorture.torture_type= [KNL]
3318 Specify the RCU implementation to test.
3320 rcutorture.verbose= [KNL]
3321 Enable additional printk() statements.
3323 rcupdate.rcu_cpu_stall_suppress= [KNL]
3324 Suppress RCU CPU stall warning messages.
3326 rcupdate.rcu_cpu_stall_timeout= [KNL]
3327 Set timeout for RCU CPU stall warning messages.
3329 rcupdate.rcu_expedited= [KNL]
3330 Use expedited grace-period primitives, for
3331 example, synchronize_rcu_expedited() instead
3332 of synchronize_rcu(). This reduces latency,
3333 but can increase CPU utilization, degrade
3334 real-time latency, and degrade energy efficiency.
3335 No effect on CONFIG_TINY_RCU kernels.
3337 rcupdate.rcu_normal= [KNL]
3338 Use only normal grace-period primitives,
3339 for example, synchronize_rcu() instead of
3340 synchronize_rcu_expedited(). This improves
3341 real-time latency, CPU utilization, and
3342 energy efficiency, but can expose users to
3343 increased grace-period latency. This parameter
3344 overrides rcupdate.rcu_expedited. No effect on
3345 CONFIG_TINY_RCU kernels.
3347 rcupdate.rcu_normal_after_boot= [KNL]
3348 Once boot has completed (that is, after
3349 rcu_end_inkernel_boot() has been invoked), use
3350 only normal grace-period primitives. No effect
3351 on CONFIG_TINY_RCU kernels.
3353 rcupdate.rcu_task_stall_timeout= [KNL]
3354 Set timeout in jiffies for RCU task stall warning
3355 messages. Disable with a value less than or equal
3358 rcupdate.rcu_self_test= [KNL]
3359 Run the RCU early boot self tests
3361 rcupdate.rcu_self_test_bh= [KNL]
3362 Run the RCU bh early boot self tests
3364 rcupdate.rcu_self_test_sched= [KNL]
3365 Run the RCU sched early boot self tests
3369 Run specified binary instead of /init from the ramdisk,
3370 used for early userspace startup. See initrd.
3373 Format (x86 or x86_64):
3374 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3376 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3378 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3379 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3380 reboot_force is either force or not specified,
3381 reboot_cpu is s[mp]#### with #### being the processor
3382 to be used for rebooting.
3385 [KNL, SMP] Set scheduler's default relax_domain_level.
3386 See Documentation/cgroups/cpusets.txt.
3388 relative_sleep_states=
3389 [SUSPEND] Use sleep state labeling where the deepest
3390 state available other than hibernation is always "mem".
3391 Format: { "0" | "1" }
3392 0 -- Traditional sleep state labels.
3393 1 -- Relative sleep state labels.
3395 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3397 reservetop= [X86-32]
3399 Reserves a hole at the top of the kernel virtual
3404 Set the amount of memory to reserve for BIOS at
3405 the bottom of the address space.
3407 reset_devices [KNL] Force drivers to reset the underlying device
3408 during initialization.
3411 Specify the partition device for software suspend
3413 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3415 resume_offset= [SWSUSP]
3416 Specify the offset from the beginning of the partition
3417 given by "resume=" at which the swap header is located,
3418 in <PAGE_SIZE> units (needed only for swap files).
3419 See Documentation/power/swsusp-and-swap-files.txt
3421 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3422 read the resume files
3424 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3425 Useful for devices that are detected asynchronously
3426 (e.g. USB and MMC devices).
3428 hibernate= [HIBERNATION]
3429 noresume Don't check if there's a hibernation image
3430 present during boot.
3431 nocompress Don't compress/decompress hibernation images.
3432 no Disable hibernation and resume.
3434 retain_initrd [RAM] Keep initrd memory after extraction
3436 rfkill.default_state=
3437 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3438 etc. communication is blocked by default.
3441 rfkill.master_switch_mode=
3442 0 The "airplane mode" button does nothing.
3443 1 The "airplane mode" button toggles between everything
3444 blocked and the previous configuration.
3445 2 The "airplane mode" button toggles between everything
3446 blocked and everything unblocked.
3448 rhash_entries= [KNL,NET]
3449 Set number of hash buckets for route cache
3451 ro [KNL] Mount root device read-only on boot
3453 root= [KNL] Root filesystem
3454 See name_to_dev_t comment in init/do_mounts.c.
3456 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3457 mount the root filesystem
3459 rootflags= [KNL] Set root filesystem mount option string
3461 rootfstype= [KNL] Set root filesystem type
3463 rootwait [KNL] Wait (indefinitely) for root device to show up.
3464 Useful for devices that are detected asynchronously
3465 (e.g. USB and MMC devices).
3467 rproc_mem=nn[KMG][@address]
3468 [KNL,ARM,CMA] Remoteproc physical memory block.
3469 Memory area to be used by remote processor image,
3472 rw [KNL] Mount root device read-write on boot
3474 S [KNL] Run init in single mode
3476 s390_iommu= [HW,S390]
3477 Set s390 IOTLB flushing mode
3479 With strict flushing every unmap operation will result in
3480 an IOTLB flush. Default is lazy flushing before reuse,
3484 See drivers/net/irda/sa1100_ir.c.
3486 sbni= [NET] Granch SBNI12 leased line adapter
3488 sched_debug [KNL] Enables verbose scheduler debug messages.
3490 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3491 xtime_lock contention on larger systems, and/or RCU lock
3492 contention on all systems with CONFIG_MAXSMP set.
3493 Format: { "0" | "1" }
3494 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3496 Note: increases power consumption, thus should only be
3497 enabled if running jitter sensitive (HPC/RT) workloads.
3499 security= [SECURITY] Choose a security module to enable at boot.
3500 If this boot parameter is not specified, only the first
3501 security module asking for security registration will be
3502 loaded. An invalid security module name will be treated
3503 as if no module has been chosen.
3505 selinux= [SELINUX] Disable or enable SELinux at boot time.
3506 Format: { "0" | "1" }
3507 See security/selinux/Kconfig help text.
3510 Default value is set via kernel config option.
3511 If enabled at boot time, /selinux/disable can be used
3512 later to disable prior to initial policy load.
3514 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3515 Format: { "0" | "1" }
3516 See security/apparmor/Kconfig help text
3519 Default value is set via kernel config option.
3521 serialnumber [BUGS=X86-32]
3524 Maximal number of shapers.
3526 show_msr= [x86] show boot-time MSR settings
3527 Format: { <integer> }
3528 Show boot-time (BIOS-initialized) MSR settings.
3529 The parameter means the number of CPUs to show,
3530 for example 1 means boot CPU only.
3538 Disable merging of slabs with similar size. May be
3539 necessary if there is some reason to distinguish
3540 allocs to different slabs. Debug options disable
3541 merging on their own.
3542 For more information see Documentation/vm/slub.txt.
3544 slab_max_order= [MM, SLAB]
3545 Determines the maximum allowed order for slabs.
3546 A high setting may cause OOMs due to memory
3547 fragmentation. Defaults to 1 for systems with
3548 more than 32MB of RAM, 0 otherwise.
3550 slub_debug[=options[,slabs]] [MM, SLUB]
3551 Enabling slub_debug allows one to determine the
3552 culprit if slab objects become corrupted. Enabling
3553 slub_debug can create guard zones around objects and
3554 may poison objects when not in use. Also tracks the
3555 last alloc / free. For more information see
3556 Documentation/vm/slub.txt.
3558 slub_max_order= [MM, SLUB]
3559 Determines the maximum allowed order for slabs.
3560 A high setting may cause OOMs due to memory
3561 fragmentation. For more information see
3562 Documentation/vm/slub.txt.
3564 slub_min_objects= [MM, SLUB]
3565 The minimum number of objects per slab. SLUB will
3566 increase the slab order up to slub_max_order to
3567 generate a sufficiently large slab able to contain
3568 the number of objects indicated. The higher the number
3569 of objects the smaller the overhead of tracking slabs
3570 and the less frequently locks need to be acquired.
3571 For more information see Documentation/vm/slub.txt.
3573 slub_min_order= [MM, SLUB]
3574 Determines the minimum page order for slabs. Must be
3575 lower than slub_max_order.
3576 For more information see Documentation/vm/slub.txt.
3578 slub_nomerge [MM, SLUB]
3579 Same with slab_nomerge. This is supported for legacy.
3580 See slab_nomerge for more information.
3583 Format: <io1>[,<io2>[,...,<io8>]]
3585 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3586 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3587 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3588 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3589 smsc-ircc2.ircc_irq= [HW] IRQ line
3590 smsc-ircc2.ircc_dma= [HW] DMA channel
3591 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3592 0: Toshiba Satellite 1800 (GP data pin select)
3593 1: Fast pin select (default)
3597 [KNL] Should the soft-lockup detector generate panics.
3600 softlockup_all_cpu_backtrace=
3601 [KNL] Should the soft-lockup detector generate
3602 backtraces on all cpus.
3605 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3606 See Documentation/laptops/sonypi.txt
3608 spia_io_base= [HW,MTD]
3614 Enabled the stack tracer on boot up.
3616 stacktrace_filter=[function-list]
3617 [FTRACE] Limit the functions that the stack tracer
3618 will trace at boot up. function-list is a comma separated
3619 list of functions. This list can be changed at run
3620 time by the stack_trace_filter file in the debugfs
3621 tracing directory. Note, this enables stack tracing
3622 and the stacktrace above is not needed.
3626 Set the STI (builtin display/keyboard on the HP-PARISC
3627 machines) console (graphic card) which should be used
3628 as the initial boot-console.
3629 See also comment in drivers/video/console/sticore.c.
3632 See comment in drivers/video/console/sticore.c.
3635 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3637 sunrpc.min_resvport=
3638 sunrpc.max_resvport=
3640 SunRPC servers often require that client requests
3641 originate from a privileged port (i.e. a port in the
3642 range 0 < portnr < 1024).
3643 An administrator who wishes to reserve some of these
3644 ports for other uses may adjust the range that the
3645 kernel's sunrpc client considers to be privileged
3646 using these two parameters to set the minimum and
3647 maximum port values.
3651 Control how the NFS server code allocates CPUs to
3652 service thread pools. Depending on how many NICs
3653 you have and where their interrupts are bound, this
3654 option will affect which CPUs will do NFS serving.
3655 Note: this parameter cannot be changed while the
3656 NFS server is running.
3658 auto the server chooses an appropriate mode
3659 automatically using heuristics
3660 global a single global pool contains all CPUs
3661 percpu one pool for each CPU
3662 pernode one pool for each NUMA node (equivalent
3663 to global on non-NUMA machines)
3665 sunrpc.tcp_slot_table_entries=
3666 sunrpc.udp_slot_table_entries=
3668 Sets the upper limit on the number of simultaneous
3669 RPC calls that can be sent from the client to a
3670 server. Increasing these values may allow you to
3671 improve throughput, but will also increase the
3672 amount of memory reserved for use by the client.
3674 suspend.pm_test_delay=
3676 Sets the number of seconds to remain in a suspend test
3677 mode before resuming the system (see
3678 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3679 is set. Default value is 5.
3682 [KNL] Enable accounting of swap in memory resource
3683 controller if no parameter or 1 is given or disable
3684 it if 0 is given (See Documentation/cgroups/memory.txt)
3686 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3687 Format: { <int> | force }
3688 <int> -- Number of I/O TLB slabs
3689 force -- force using of bounce buffers even if they
3690 wouldn't be automatically used by the kernel
3694 sysfs.deprecated=0|1 [KNL]
3695 Enable/disable old style sysfs layout for old udev
3696 on older distributions. When this option is enabled
3697 very new udev will not work anymore. When this option
3698 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3699 in older udev will not work anymore.
3700 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3701 the kernel configuration.
3703 sysrq_always_enabled
3705 Ignore sysrq setting - this boot parameter will
3706 neutralize any effect of /proc/sys/kernel/sysrq.
3707 Useful for debugging.
3709 tcpmhash_entries= [KNL,NET]
3710 Set the number of tcp_metrics_hash slots.
3711 Default value is 8192 or 16384 depending on total
3712 ram pages. This is used to specify the TCP metrics
3713 cache size. See Documentation/networking/ip-sysctl.txt
3714 "tcp_no_metrics_save" section for more details.
3718 test_suspend= [SUSPEND][,N]
3719 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3720 standby suspend) or "freeze" (for suspend type freeze)
3721 as the system sleep state during system startup with
3722 the optional capability to repeat N number of times.
3723 The system is woken from this state using a
3724 wakeup-capable RTC alarm.
3726 thash_entries= [KNL,NET]
3727 Set number of hash buckets for TCP connection
3729 thermal.act= [HW,ACPI]
3730 -1: disable all active trip points in all thermal zones
3731 <degrees C>: override all lowest active trip points
3733 thermal.crt= [HW,ACPI]
3734 -1: disable all critical trip points in all thermal zones
3735 <degrees C>: override all critical trip points
3737 thermal.nocrt= [HW,ACPI]
3738 Set to disable actions on ACPI thermal zone
3739 critical and hot trip points.
3741 thermal.off= [HW,ACPI]
3742 1: disable ACPI thermal control
3744 thermal.psv= [HW,ACPI]
3745 -1: disable all passive trip points
3746 <degrees C>: override all passive trip points to this
3749 thermal.tzp= [HW,ACPI]
3750 Specify global default ACPI thermal zone polling rate
3751 <deci-seconds>: poll all this frequency
3752 0: no polling (default)
3755 Force threading of all interrupt handlers except those
3756 marked explicitly IRQF_NO_THREAD.
3759 Enable the Transcendent memory driver if built-in.
3761 tmem.cleancache=0|1 [KNL, XEN]
3762 Default is on (1). Disable the usage of the cleancache
3763 API to send anonymous pages to the hypervisor.
3765 tmem.frontswap=0|1 [KNL, XEN]
3766 Default is on (1). Disable the usage of the frontswap
3767 API to send swap pages to the hypervisor. If disabled
3768 the selfballooning and selfshrinking are force disabled.
3770 tmem.selfballooning=0|1 [KNL, XEN]
3771 Default is on (1). Disable the driving of swap pages
3774 tmem.selfshrinking=0|1 [KNL, XEN]
3775 Default is on (1). Partial swapoff that immediately
3776 transfers pages from Xen hypervisor back to the
3777 kernel based on different criteria.
3781 Specify if the kernel should make use of the cpu
3782 topology information if the hardware supports this.
3783 The scheduler will make use of this information and
3784 e.g. base its process migration decisions on it.
3787 topology_updates= [KNL, PPC, NUMA]
3789 Specify if the kernel should ignore (off)
3790 topology updates sent by the hypervisor to this
3795 tpm_suspend_pcr=[HW,TPM]
3796 Format: integer pcr id
3797 Specify that at suspend time, the tpm driver
3798 should extend the specified pcr with zeros,
3799 as a workaround for some chips which fail to
3800 flush the last written pcr on TPM_SaveState.
3801 This will guarantee that all the other pcrs
3804 trace_buf_size=nn[KMG]
3805 [FTRACE] will set tracing buffer size on each cpu.
3807 trace_event=[event-list]
3808 [FTRACE] Set and start specified trace events in order
3809 to facilitate early boot debugging.
3810 See also Documentation/trace/events.txt
3812 trace_options=[option-list]
3813 [FTRACE] Enable or disable tracer options at boot.
3814 The option-list is a comma delimited list of options
3815 that can be enabled or disabled just as if you were
3816 to echo the option name into
3818 /sys/kernel/debug/tracing/trace_options
3820 For example, to enable stacktrace option (to dump the
3821 stack trace of each event), add to the command line:
3823 trace_options=stacktrace
3825 See also Documentation/trace/ftrace.txt "trace options"
3829 Have the tracepoints sent to printk as well as the
3830 tracing ring buffer. This is useful for early boot up
3831 where the system hangs or reboots and does not give the
3832 option for reading the tracing buffer or performing a
3833 ftrace_dump_on_oops.
3835 To turn off having tracepoints sent to printk,
3836 echo 0 > /proc/sys/kernel/tracepoint_printk
3837 Note, echoing 1 into this file without the
3838 tracepoint_printk kernel cmdline option has no effect.
3842 Having tracepoints sent to printk() and activating high
3843 frequency tracepoints such as irq or sched, can cause
3844 the system to live lock.
3847 [FTRACE] enable this option to disable tracing when a
3848 warning is hit. This turns off "tracing_on". Tracing can
3849 be enabled again by echoing '1' into the "tracing_on"
3850 file located in /sys/kernel/debug/tracing/
3852 This option is useful, as it disables the trace before
3853 the WARNING dump is called, which prevents the trace to
3854 be filled with content caused by the warning output.
3856 This option can also be set at run time via the sysctl
3857 option: kernel/traceoff_on_warning
3859 transparent_hugepage=
3861 Format: [always|madvise|never]
3862 Can be used to control the default behavior of the system
3863 with respect to transparent hugepages.
3864 See Documentation/vm/transhuge.txt for more details.
3866 tsc= Disable clocksource stability checks for TSC.
3868 [x86] reliable: mark tsc clocksource as reliable, this
3869 disables clocksource verification at runtime, as well
3870 as the stability checks done at bootup. Used to enable
3871 high-resolution timer mode on older hardware, and in
3872 virtualized environment.
3873 [x86] noirqtime: Do not use TSC to do irq accounting.
3874 Used to run time disable IRQ_TIME_ACCOUNTING on any
3875 platforms where RDTSC is slow and this accounting
3878 turbografx.map[2|3]= [HW,JOY]
3879 TurboGraFX parallel port interface
3881 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3882 See also Documentation/input/joystick-parport.txt
3884 udbg-immortal [PPC] When debugging early kernel crashes that
3885 happen after console_init() and before a proper
3886 console driver takes over, this boot options might
3887 help "seeing" what's going on.
3889 uhash_entries= [KNL,NET]
3890 Set number of hash buckets for UDP/UDP-Lite connections
3893 [USB] Ignore overcurrent events (default N).
3894 Some badly-designed motherboards generate lots of
3895 bogus events, for ports that aren't wired to
3896 anything. Set this parameter to avoid log spamming.
3897 Note that genuine overcurrent events won't be
3901 [X86] Cause panic on unknown NMI.
3903 usbcore.authorized_default=
3904 [USB] Default USB device authorization:
3905 (default -1 = authorized except for wireless USB,
3906 0 = not authorized, 1 = authorized)
3908 usbcore.autosuspend=
3909 [USB] The autosuspend time delay (in seconds) used
3910 for newly-detected USB devices (default 2). This
3911 is the time required before an idle device will be
3912 autosuspended. Devices for which the delay is set
3913 to a negative value won't be autosuspended at all.
3915 usbcore.usbfs_snoop=
3916 [USB] Set to log all usbfs traffic (default 0 = off).
3918 usbcore.usbfs_snoop_max=
3919 [USB] Maximum number of bytes to snoop in each URB
3922 usbcore.blinkenlights=
3923 [USB] Set to cycle leds on hubs (default 0 = off).
3925 usbcore.old_scheme_first=
3926 [USB] Start with the old device initialization
3927 scheme (default 0 = off).
3929 usbcore.usbfs_memory_mb=
3930 [USB] Memory limit (in MB) for buffers allocated by
3931 usbfs (default = 16, 0 = max = 2047).
3933 usbcore.use_both_schemes=
3934 [USB] Try the other device initialization scheme
3935 if the first one fails (default 1 = enabled).
3937 usbcore.initial_descriptor_timeout=
3938 [USB] Specifies timeout for the initial 64-byte
3939 USB_REQ_GET_DESCRIPTOR request in milliseconds
3940 (default 5000 = 5.0 seconds).
3942 usbcore.nousb [USB] Disable the USB subsystem
3945 [USBHID] The interval which mice are to be polled at.
3947 usb-storage.delay_use=
3948 [UMS] The delay in seconds before a new device is
3949 scanned for Logical Units (default 1).
3952 [UMS] A list of quirks entries to supplement or
3953 override the built-in unusual_devs list. List
3954 entries are separated by commas. Each entry has
3955 the form VID:PID:Flags where VID and PID are Vendor
3956 and Product ID values (4-digit hex numbers) and
3957 Flags is a set of characters, each corresponding
3958 to a common usb-storage quirk flag as follows:
3959 a = SANE_SENSE (collect more than 18 bytes
3961 b = BAD_SENSE (don't collect more than 18
3962 bytes of sense data);
3963 c = FIX_CAPACITY (decrease the reported
3964 device capacity by one sector);
3965 d = NO_READ_DISC_INFO (don't use
3966 READ_DISC_INFO command);
3967 e = NO_READ_CAPACITY_16 (don't use
3968 READ_CAPACITY_16 command);
3969 f = NO_REPORT_OPCODES (don't use report opcodes
3971 g = MAX_SECTORS_240 (don't transfer more than
3972 240 sectors at a time, uas only);
3973 h = CAPACITY_HEURISTICS (decrease the
3974 reported device capacity by one
3975 sector if the number is odd);
3976 i = IGNORE_DEVICE (don't bind to this
3978 l = NOT_LOCKABLE (don't try to lock and
3979 unlock ejectable media);
3980 m = MAX_SECTORS_64 (don't transfer more
3981 than 64 sectors = 32 KB at a time);
3982 n = INITIAL_READ10 (force a retry of the
3983 initial READ(10) command);
3984 o = CAPACITY_OK (accept the capacity
3985 reported by the device);
3986 p = WRITE_CACHE (the device cache is ON
3988 r = IGNORE_RESIDUE (the device reports
3989 bogus residue values);
3990 s = SINGLE_LUN (the device has only one
3992 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3993 commands, uas only);
3994 u = IGNORE_UAS (don't bind to the uas driver);
3995 w = NO_WP_DETECT (don't test whether the
3996 medium is write-protected).
3997 Example: quirks=0419:aaf5:rl,0421:0433:rc
3999 user_debug= [KNL,ARM]
4001 See arch/arm/Kconfig.debug help text.
4002 1 - undefined instruction events
4004 4 - invalid data aborts
4007 Example: user_debug=31
4010 [X86] Flags controlling user PTE allocations.
4012 nohigh = do not allocate PTE pages in
4013 HIGHMEM regardless of setting
4017 On X86_32, this is an alias for vdso32=. Otherwise:
4019 vdso=1: enable VDSO (the default)
4020 vdso=0: disable VDSO mapping
4022 vdso32= [X86] Control the 32-bit vDSO
4023 vdso32=1: enable 32-bit VDSO
4024 vdso32=0 or vdso32=2: disable 32-bit VDSO
4026 See the help text for CONFIG_COMPAT_VDSO for more
4027 details. If CONFIG_COMPAT_VDSO is set, the default is
4028 vdso32=0; otherwise, the default is vdso32=1.
4030 For compatibility with older kernels, vdso32=2 is an
4033 Try vdso32=0 if you encounter an error that says:
4034 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4037 vector=percpu: enable percpu vector domain
4039 video= [FB] Frame buffer configuration
4040 See Documentation/fb/modedb.txt.
4042 video.brightness_switch_enabled= [0,1]
4043 If set to 1, on receiving an ACPI notify event
4044 generated by hotkey, video driver will adjust brightness
4045 level and then send out the event to user space through
4046 the allocated input device; If set to 0, video driver
4047 will only send out the event without touching backlight
4052 [VMMIO] Memory mapped virtio (platform) device.
4054 <size>@<baseaddr>:<irq>[:<id>]
4056 <size> := size (can use standard suffixes
4058 <baseaddr> := physical base address
4059 <irq> := interrupt number (as passed to
4061 <id> := (optional) platform device id
4063 virtio_mmio.device=1K@0x100b0000:48:7
4065 Can be used multiple times for multiple devices.
4067 vga= [BOOT,X86-32] Select a particular video mode
4068 See Documentation/x86/boot.txt and
4069 Documentation/svga.txt.
4070 Use vga=ask for menu.
4071 This is actually a boot loader parameter; the value is
4072 passed to the kernel using a special protocol.
4074 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4075 size of <nn>. This can be used to increase the
4076 minimum size (128MB on x86). It can also be used to
4077 decrease the size and leave more room for directly
4080 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4083 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4086 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4090 Controls the behavior of vsyscalls (i.e. calls to
4091 fixed addresses of 0xffffffffff600x00 from legacy
4092 code). Most statically-linked binaries and older
4093 versions of glibc use these calls. Because these
4094 functions are at fixed addresses, they make nice
4095 targets for exploits that can control RIP.
4097 emulate [default] Vsyscalls turn into traps and are
4098 emulated reasonably safely.
4100 native Vsyscalls are native syscall instructions.
4101 This is a little bit faster than trapping
4102 and makes a few dynamic recompilers work
4103 better than they would in emulation mode.
4104 It also makes exploits much easier to write.
4106 none Vsyscalls don't work at all. This makes
4107 them quite hard to use for exploits but
4108 might break your system.
4110 vt.color= [VT] Default text color.
4111 Format: 0xYX, X = foreground, Y = background.
4112 Default: 0x07 = light gray on black.
4114 vt.cur_default= [VT] Default cursor shape.
4115 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4116 the parameters of the <Esc>[?A;B;Cc escape sequence;
4117 see VGA-softcursor.txt. Default: 2 = underline.
4119 vt.default_blu= [VT]
4120 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4121 Change the default blue palette of the console.
4122 This is a 16-member array composed of values
4125 vt.default_grn= [VT]
4126 Format: <green0>,<green1>,<green2>,...,<green15>
4127 Change the default green palette of the console.
4128 This is a 16-member array composed of values
4131 vt.default_red= [VT]
4132 Format: <red0>,<red1>,<red2>,...,<red15>
4133 Change the default red palette of the console.
4134 This is a 16-member array composed of values
4140 Set system-wide default UTF-8 mode for all tty's.
4141 Default is 1, i.e. UTF-8 mode is enabled for all
4142 newly opened terminals.
4144 vt.global_cursor_default=
4147 Set system-wide default for whether a cursor
4148 is shown on new VTs. Default is -1,
4149 i.e. cursors will be created by default unless
4150 overridden by individual drivers. 0 will hide
4151 cursors, 1 will display them.
4153 vt.italic= [VT] Default color for italic text; 0-15.
4156 vt.underline= [VT] Default color for underlined text; 0-15.
4159 watchdog timers [HW,WDT] For information on watchdog timers,
4160 see Documentation/watchdog/watchdog-parameters.txt
4161 or other driver-specific files in the
4162 Documentation/watchdog/ directory.
4164 workqueue.watchdog_thresh=
4165 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4166 warn stall conditions and dump internal state to
4167 help debugging. 0 disables workqueue stall
4168 detection; otherwise, it's the stall threshold
4169 duration in seconds. The default value is 30 and
4170 it can be updated at runtime by writing to the
4171 corresponding sysfs file.
4173 workqueue.disable_numa
4174 By default, all work items queued to unbound
4175 workqueues are affine to the NUMA nodes they're
4176 issued on, which results in better behavior in
4177 general. If NUMA affinity needs to be disabled for
4178 whatever reason, this option can be used. Note
4179 that this also can be controlled per-workqueue for
4180 workqueues visible under /sys/bus/workqueue/.
4182 workqueue.power_efficient
4183 Per-cpu workqueues are generally preferred because
4184 they show better performance thanks to cache
4185 locality; unfortunately, per-cpu workqueues tend to
4186 be more power hungry than unbound workqueues.
4188 Enabling this makes the per-cpu workqueues which
4189 were observed to contribute significantly to power
4190 consumption unbound, leading to measurably lower
4191 power usage at the cost of small performance
4194 The default value of this parameter is determined by
4195 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4197 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4198 default x2apic cluster mode on platforms
4201 x86_intel_mid_timer= [X86-32,APBT]
4202 Choose timer option for x86 Intel MID platform.
4203 Two valid options are apbt timer only and lapic timer
4204 plus one apbt timer for broadcast timer.
4205 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4207 xen_512gb_limit [KNL,X86-64,XEN]
4208 Restricts the kernel running paravirtualized under Xen
4209 to use only up to 512 GB of RAM. The reason to do so is
4210 crash analysis tools and Xen tools for doing domain
4211 save/restore/migration must be enabled to handle larger
4214 xen_emul_unplug= [HW,X86,XEN]
4215 Unplug Xen emulated devices
4216 Format: [unplug0,][unplug1]
4217 ide-disks -- unplug primary master IDE devices
4218 aux-ide-disks -- unplug non-primary-master IDE devices
4219 nics -- unplug network devices
4220 all -- unplug all emulated devices (NICs and IDE disks)
4221 unnecessary -- unplugging emulated devices is
4222 unnecessary even if the host did not respond to
4224 never -- do not unplug even if version check succeeds
4226 xen_nopvspin [X86,XEN]
4227 Disables the ticketlock slowpath using Xen PV
4231 Disables the PV optimizations forcing the HVM guest to
4232 run as generic HVM guest with no PV drivers.
4234 xirc2ps_cs= [NET,PCMCIA]
4236 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4238 ______________________________________________________________________
4242 Add more DRM drivers.
projects / cascardo / linux.git / blob