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 checkreqprot [SELINUX] Set initial checkreqprot flag value.
612 Format: { "0" | "1" }
613 See security/selinux/Kconfig help text.
614 0 -- check protection applied by kernel (includes
615 any implied execute protection).
616 1 -- check protection requested by application.
617 Default value is set via a kernel config option.
618 Value can be changed at runtime via
619 /selinux/checkreqprot.
622 See Documentation/s390/CommonIO for details.
625 Prevents the clock framework from automatically gating
626 clocks that have not been explicitly enabled by a Linux
627 device driver but are enabled in hardware at reset or
628 by the bootloader/firmware. Note that this does not
629 force such clocks to be always-on nor does it reserve
630 those clocks in any way. This parameter is useful for
631 debug and development, but should not be needed on a
632 platform with proper driver support. For more
633 information, see Documentation/clk.txt.
635 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
637 Forces specified clocksource (if available) to be used
638 when calculating gettimeofday(). If specified
639 clocksource is not available, it defaults to PIT.
640 Format: { pit | tsc | cyclone | pmtmr }
642 clocksource= Override the default clocksource
644 Override the default clocksource and use the clocksource
645 with the name specified.
646 Some clocksource names to choose from, depending on
648 [all] jiffies (this is the base, fallback clocksource)
650 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
651 pxa_timer,timer3,32k_counter,timer0_1
653 [X86-32] pit,hpet,tsc;
654 scx200_hrt on Geode; cyclone on IBM x440
662 clearcpuid=BITNUM [X86]
663 Disable CPUID feature X for the kernel. See
664 arch/x86/include/asm/cpufeature.h for the valid bit
665 numbers. Note the Linux specific bits are not necessarily
666 stable over kernel options, but the vendor specific
668 Also note that user programs calling CPUID directly
669 or using the feature without checking anything
670 will still see it. This just prevents it from
671 being used by the kernel or shown in /proc/cpuinfo.
672 Also note the kernel might malfunction if you disable
675 cma=nn[MG]@[start[MG][-end[MG]]]
677 Sets the size of kernel global memory area for
678 contiguous memory allocations and optionally the
679 placement constraint by the physical address range of
680 memory allocations. A value of 0 disables CMA
681 altogether. For more information, see
682 include/linux/dma-contiguous.h
684 cmo_free_hint= [PPC] Format: { yes | no }
685 Specify whether pages are marked as being inactive
686 when they are freed. This is used in CMO environments
687 to determine OS memory pressure for page stealing by
691 coherent_pool=nn[KMG] [ARM,KNL]
692 Sets the size of memory pool for coherent, atomic dma
693 allocations, by default set to 256K.
695 code_bytes [X86] How many bytes of object code to print
700 com20020= [HW,NET] ARCnet - COM20020 chipset
702 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
704 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
708 ARCnet - COM90xx chipset (memory-mapped buffers)
709 Format: <io>[,<irq>[,<memstart>]]
711 condev= [HW,S390] console device
714 console= [KNL] Output console device and options.
716 tty<n> Use the virtual console device <n>.
720 Use the specified serial port. The options are of
721 the form "bbbbpnf", where "bbbb" is the baud rate,
722 "p" is parity ("n", "o", or "e"), "n" is number of
723 bits, and "f" is flow control ("r" for RTS or
724 omit it). Default is "9600n8".
726 See Documentation/serial-console.txt for more
728 Documentation/networking/netconsole.txt for an
731 uart[8250],io,<addr>[,options]
732 uart[8250],mmio,<addr>[,options]
733 uart[8250],mmio16,<addr>[,options]
734 uart[8250],mmio32,<addr>[,options]
735 uart[8250],0x<addr>[,options]
736 Start an early, polled-mode console on the 8250/16550
737 UART at the specified I/O port or MMIO address,
738 switching to the matching ttyS device later.
739 MMIO inter-register address stride is either 8-bit
740 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
741 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
742 to be equivalent to 'mmio'. 'options' are specified in
743 the same format described for ttyS above; if unspecified,
744 the h/w is not re-initialized.
746 hvc<n> Use the hypervisor console device <n>. This is for
747 both Xen and PowerPC hypervisors.
749 If the device connected to the port is not a TTY but a braille
750 device, prepend "brl," before the device type, for instance
752 For now, only VisioBraille is supported.
754 consoleblank= [KNL] The console blank (screen saver) timeout in
755 seconds. Defaults to 10*60 = 10mins. A value of 0
756 disables the blank timer.
759 [KNL] Change the default value for
760 /proc/<pid>/coredump_filter.
761 See also Documentation/filesystems/proc.txt.
763 cpuidle.off=1 [CPU_IDLE]
764 disable the cpuidle sub-system
767 [X86] Delay for N microsec between assert and de-assert
768 of APIC INIT to start processors. This delay occurs
769 on every CPU online, such as boot, and resume from suspend.
772 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
774 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
776 crashkernel=size[KMG][@offset[KMG]]
777 [KNL] Using kexec, Linux can switch to a 'crash kernel'
778 upon panic. This parameter reserves the physical
779 memory region [offset, offset + size] for that kernel
780 image. If '@offset' is omitted, then a suitable offset
781 is selected automatically. Check
782 Documentation/kdump/kdump.txt for further details.
784 crashkernel=range1:size1[,range2:size2,...][@offset]
785 [KNL] Same as above, but depends on the memory
786 in the running system. The syntax of range is
787 start-[end] where start and end are both
788 a memory unit (amount[KMG]). See also
789 Documentation/kdump/kdump.txt for an example.
791 crashkernel=size[KMG],high
792 [KNL, x86_64] range could be above 4G. Allow kernel
793 to allocate physical memory region from top, so could
794 be above 4G if system have more than 4G ram installed.
795 Otherwise memory region will be allocated below 4G, if
797 It will be ignored if crashkernel=X is specified.
798 crashkernel=size[KMG],low
799 [KNL, x86_64] range under 4G. When crashkernel=X,high
800 is passed, kernel could allocate physical memory region
801 above 4G, that cause second kernel crash on system
802 that require some amount of low memory, e.g. swiotlb
803 requires at least 64M+32K low memory, also enough extra
804 low memory is needed to make sure DMA buffers for 32-bit
805 devices won't run out. Kernel would try to allocate at
806 at least 256M below 4G automatically.
807 This one let user to specify own low range under 4G
808 for second kernel instead.
809 0: to disable low allocation.
810 It will be ignored when crashkernel=X,high is not used
811 or memory reserved is below 4G.
816 cs89x0_media= [HW,NET]
817 Format: { rj45 | aui | bnc }
820 See header of drivers/s390/block/dasd_devmap.c.
822 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
823 (one device per port)
824 Format: <port#>,<type>
825 See also Documentation/input/joystick-parport.txt
827 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
828 time. See Documentation/dynamic-debug-howto.txt for
829 details. Deprecated, see dyndbg.
831 debug [KNL] Enable kernel debugging (events log level).
834 [KNL] verbose self-tests
836 Print debugging info while doing the locking API
838 We default to 0 (no extra messages), setting it to
839 1 will print _a lot_ more information - normally
840 only useful to kernel developers.
842 debug_objects [KNL] Enable object debugging
845 [KNL] Disable object debugging
847 debug_guardpage_minorder=
848 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
849 parameter allows control of the order of pages that will
850 be intentionally kept free (and hence protected) by the
851 buddy allocator. Bigger value increase the probability
852 of catching random memory corruption, but reduce the
853 amount of memory for normal system use. The maximum
854 possible value is MAX_ORDER/2. Setting this parameter
855 to 1 or 2 should be enough to identify most random
856 memory corruption problems caused by bugs in kernel or
857 driver code when a CPU writes to (or reads from) a
858 random memory location. Note that there exists a class
859 of memory corruptions problems caused by buggy H/W or
860 F/W or by drivers badly programing DMA (basically when
861 memory is written at bus level and the CPU MMU is
862 bypassed) which are not detectable by
863 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
864 tracking down these problems.
867 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
868 parameter enables the feature at boot time. In
869 default, it is disabled. We can avoid allocating huge
870 chunk of memory for debug pagealloc if we don't enable
871 it at boot time and the system will work mostly same
872 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
873 on: enable the feature
875 debugpat [X86] Enable PAT debugging
877 decnet.addr= [HW,NET]
878 Format: <area>[,<node>]
879 See also Documentation/networking/decnet.txt.
882 [same as hugepagesz=] The size of the default
883 HugeTLB page size. This is the size represented by
884 the legacy /proc/ hugepages APIs, used for SHM, and
885 default size when mounting hugetlbfs filesystems.
886 Defaults to the default architecture's huge page size
890 Set number of hash buckets for dentry cache.
893 See Documentation/networking/ipv6.txt.
895 disable_cpu_apicid= [X86,APIC,SMP]
897 The number of initial APIC ID for the
898 corresponding CPU to be disabled at boot,
899 mostly used for the kdump 2nd kernel to
900 disable BSP to wake up multiple CPUs without
901 causing system reset or hang due to sending
904 disable_ddw [PPC/PSERIES]
905 Disable Dynamic DMA Window support. Use this if
906 to workaround buggy firmware.
909 See Documentation/networking/ipv6.txt.
911 disable_mtrr_cleanup [X86]
912 The kernel tries to adjust MTRR layout from continuous
913 to discrete, to make X server driver able to add WB
914 entry later. This parameter disables that.
916 disable_mtrr_trim [X86, Intel and AMD only]
917 By default the kernel will trim any uncacheable
918 memory out of your available memory pool based on
919 MTRR settings. This parameter disables that behavior,
920 possibly causing your machine to run very slowly.
922 disable_timer_pin_1 [X86]
923 Disable PIN 1 of APIC timer
924 Can be useful to work around chipset bugs.
926 dis_ucode_ldr [X86] Disable the microcode loader.
928 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
929 this option disables the debugging code at boot.
931 dma_debug_entries=<number>
932 This option allows to tune the number of preallocated
933 entries for DMA-API debugging code. One entry is
934 required per DMA-API allocation. Use this if the
935 DMA-API debugging code disables itself because the
936 architectural default is too low.
938 dma_debug_driver=<driver_name>
939 With this option the DMA-API debugging driver
940 filter feature can be enabled at boot time. Just
941 pass the driver to filter for as the parameter.
942 The filter can be disabled or changed to another
943 driver later using sysfs.
945 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
946 Broken monitors, graphic adapters, KVMs and EDIDless
947 panels may send no or incorrect EDID data sets.
948 This parameter allows to specify an EDID data sets
949 in the /lib/firmware directory that are used instead.
950 Generic built-in EDID data sets are used, if one of
951 edid/1024x768.bin, edid/1280x1024.bin,
952 edid/1680x1050.bin, or edid/1920x1080.bin is given
953 and no file with the same name exists. Details and
954 instructions how to build your own EDID data are
955 available in Documentation/EDID/HOWTO.txt. An EDID
956 data set will only be used for a particular connector,
957 if its name and a colon are prepended to the EDID
958 name. Each connector may use a unique EDID data
959 set by separating the files with a comma. An EDID
960 data set with no connector name will be used for
961 any connectors not explicitly specified.
965 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
966 module.dyndbg[="val"]
967 Enable debug messages at boot time. See
968 Documentation/dynamic-debug-howto.txt for details.
970 nompx [X86] Disables Intel Memory Protection Extensions.
971 See Documentation/x86/intel_mpx.txt for more
972 information about the feature.
975 on enable eager fpu restore
976 off disable eager fpu restore
977 auto selects the default scheme, which automatically
978 enables eagerfpu restore for xsaveopt.
980 module.async_probe [KNL]
981 Enable asynchronous probe on this module.
983 early_ioremap_debug [KNL]
984 Enable debug messages in early_ioremap support. This
985 is useful for tracking down temporary early mappings
986 which are not unmapped.
988 earlycon= [KNL] Output early console device and options.
990 When used with no options, the early console is
991 determined by the stdout-path property in device
995 Start an early, polled-mode console on a cadence serial
996 port at the specified address. The cadence serial port
997 must already be setup and configured. Options are not
1000 uart[8250],io,<addr>[,options]
1001 uart[8250],mmio,<addr>[,options]
1002 uart[8250],mmio32,<addr>[,options]
1003 uart[8250],mmio32be,<addr>[,options]
1004 uart[8250],0x<addr>[,options]
1005 Start an early, polled-mode console on the 8250/16550
1006 UART at the specified I/O port or MMIO address.
1007 MMIO inter-register address stride is either 8-bit
1008 (mmio) or 32-bit (mmio32 or mmio32be).
1009 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1010 to be equivalent to 'mmio'. 'options' are specified
1011 in the same format described for "console=ttyS<n>"; if
1012 unspecified, the h/w is not initialized.
1016 Start an early, polled-mode console on a pl011 serial
1017 port at the specified address. The pl011 serial port
1018 must already be setup and configured. Options are not
1019 yet supported. If 'mmio32' is specified, then only
1020 the driver will use only 32-bit accessors to read/write
1021 the device registers.
1024 Start an early, polled-mode console on an msm serial
1025 port at the specified address. The serial port
1026 must already be setup and configured. Options are not
1029 msm_serial_dm,<addr>
1030 Start an early, polled-mode console on an msm serial
1031 dm port at the specified address. The serial port
1032 must already be setup and configured. Options are not
1035 smh Use ARM semihosting calls for early console.
1043 Use early console provided by serial driver available
1044 on Samsung SoCs, requires selecting proper type and
1045 a correct base address of the selected UART port. The
1046 serial port must already be setup and configured.
1047 Options are not yet supported.
1051 Use early console provided by Freescale LP UART driver
1052 found on Freescale Vybrid and QorIQ LS1021A processors.
1053 A valid base address must be provided, and the serial
1054 port must already be setup and configured.
1056 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1060 earlyprintk=serial[,ttySn[,baudrate]]
1061 earlyprintk=serial[,0x...[,baudrate]]
1062 earlyprintk=ttySn[,baudrate]
1063 earlyprintk=dbgp[debugController#]
1064 earlyprintk=pciserial,bus:device.function[,baudrate]
1066 earlyprintk is useful when the kernel crashes before
1067 the normal console is initialized. It is not enabled by
1068 default because it has some cosmetic problems.
1070 Append ",keep" to not disable it when the real console
1073 Only one of vga, efi, serial, or usb debug port can
1076 Currently only ttyS0 and ttyS1 may be specified by
1077 name. Other I/O ports may be explicitly specified
1078 on some architectures (x86 and arm at least) by
1079 replacing ttySn with an I/O port address, like this:
1080 earlyprintk=serial,0x1008,115200
1081 You can find the port for a given device in
1082 /proc/tty/driver/serial:
1083 2: uart:ST16650V2 port:00001008 irq:18 ...
1085 Interaction with the standard serial driver is not
1088 The VGA and EFI output is eventually overwritten by
1091 The xen output can only be used by Xen PV guests.
1093 edac_report= [HW,EDAC] Control how to report EDAC event
1094 Format: {"on" | "off" | "force"}
1095 on: enable EDAC to report H/W event. May be overridden
1096 by other higher priority error reporting module.
1097 off: disable H/W event reporting through EDAC.
1098 force: enforce the use of EDAC to report H/W event.
1101 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1104 This is designed to be used in conjunction with
1105 the boot argument: earlyprintk=vga
1108 Format: {"off" | "on" | "skip[mbr]"}
1111 Format: { "old_map", "nochunk", "noruntime", "debug" }
1112 old_map [X86-64]: switch to the old ioremap-based EFI
1113 runtime services mapping. 32-bit still uses this one by
1115 nochunk: disable reading files in "chunks" in the EFI
1116 boot stub, as chunking can cause problems with some
1117 firmware implementations.
1118 noruntime : disable EFI runtime services support
1119 debug: enable misc debug output
1121 efi_no_storage_paranoia [EFI; X86]
1122 Using this parameter you can use more than 50% of
1123 your efi variable storage. Use this parameter only if
1124 you are really sure that your UEFI does sane gc and
1125 fulfills the spec otherwise your board may brick.
1127 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1128 Add arbitrary attribute to specific memory range by
1129 updating original EFI memory map.
1130 Region of memory which aa attribute is added to is
1132 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1133 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1134 attribute is added to range 0x100000000-0x180000000 and
1135 0x10a0000000-0x1120000000.
1137 Using this parameter you can do debugging of EFI memmap
1138 related feature. For example, you can do debugging of
1139 Address Range Mirroring feature even if your box
1142 eisa_irq_edge= [PARISC,HW]
1143 See header of drivers/parisc/eisa.c.
1146 See comment before function elanfreq_setup() in
1147 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1150 Format: {"cfq" | "deadline" | "noop"}
1151 See Documentation/block/cfq-iosched.txt and
1152 Documentation/block/deadline-iosched.txt for details.
1154 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1155 Specifies physical address of start of kernel core
1156 image elf header and optionally the size. Generally
1157 kexec loader will pass this option to capture kernel.
1158 See Documentation/kdump/kdump.txt for details.
1160 enable_mtrr_cleanup [X86]
1161 The kernel tries to adjust MTRR layout from continuous
1162 to discrete, to make X server driver able to add WB
1163 entry later. This parameter enables that.
1165 enable_timer_pin_1 [X86]
1166 Enable PIN 1 of APIC timer
1167 Can be useful to work around chipset bugs
1168 (in particular on some ATI chipsets).
1169 The kernel tries to set a reasonable default.
1171 enforcing [SELINUX] Set initial enforcing status.
1173 See security/selinux/Kconfig help text.
1174 0 -- permissive (log only, no denials).
1175 1 -- enforcing (deny and log).
1177 Value can be changed at runtime via /selinux/enforce.
1180 Disable Error Record Serialization Table (ERST)
1183 ether= [HW,NET] Ethernet cards parameters
1184 This option is obsoleted by the "netdev=" option, which
1185 has equivalent usage. See its documentation for details.
1189 Permit 'security.evm' to be updated regardless of
1190 current integrity status.
1194 fail_make_request=[KNL]
1195 General fault injection mechanism.
1196 Format: <interval>,<probability>,<space>,<times>
1197 See also Documentation/fault-injection/.
1200 See Documentation/blockdev/floppy.txt.
1202 force_pal_cache_flush
1203 [IA-64] Avoid check_sal_cache_flush which may hang on
1204 buggy SAL_CACHE_FLUSH implementations. Using this
1205 parameter will force ia64_sal_cache_flush to call
1206 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1209 Forcefully enable Physical Address Extension (PAE).
1210 Many Pentium M systems disable PAE but may have a
1211 functionally usable PAE implementation.
1212 Warning: use of this parameter will taint the kernel
1213 and may cause unknown problems.
1216 [FTRACE] will set and start the specified tracer
1217 as early as possible in order to facilitate early
1220 ftrace_dump_on_oops[=orig_cpu]
1221 [FTRACE] will dump the trace buffers on oops.
1222 If no parameter is passed, ftrace will dump
1223 buffers of all CPUs, but if you pass orig_cpu, it will
1224 dump only the buffer of the CPU that triggered the
1227 ftrace_filter=[function-list]
1228 [FTRACE] Limit the functions traced by the function
1229 tracer at boot up. function-list is a comma separated
1230 list of functions. This list can be changed at run
1231 time by the set_ftrace_filter file in the debugfs
1234 ftrace_notrace=[function-list]
1235 [FTRACE] Do not trace the functions specified in
1236 function-list. This list can be changed at run time
1237 by the set_ftrace_notrace file in the debugfs
1240 ftrace_graph_filter=[function-list]
1241 [FTRACE] Limit the top level callers functions traced
1242 by the function graph tracer at boot up.
1243 function-list is a comma separated list of functions
1244 that can be changed at run time by the
1245 set_graph_function file in the debugfs tracing directory.
1247 ftrace_graph_notrace=[function-list]
1248 [FTRACE] Do not trace from the functions specified in
1249 function-list. This list is a comma separated list of
1250 functions that can be changed at run time by the
1251 set_graph_notrace file in the debugfs tracing directory.
1254 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1255 support via parallel port (up to 5 devices per port)
1256 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1257 See also Documentation/input/joystick-parport.txt
1261 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1265 gcov_persist= [GCOV] When non-zero (default), profiling data for
1266 kernel modules is saved and remains accessible via
1267 debugfs, even when the module is unloaded/reloaded.
1268 When zero, profiling data is discarded and associated
1269 debugfs files are removed at module unload time.
1271 gpt [EFI] Forces disk with valid GPT signature but
1272 invalid Protective MBR to be treated as GPT. If the
1273 primary GPT is corrupted, it enables the backup/alternate
1274 GPT to be used instead.
1276 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1277 the "Enable 0" bit of the configuration register.
1280 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1281 the "Enable 0" bit of the configuration register.
1284 grcan.select= [HW] Select which physical interface to use.
1287 grcan.txsize= [HW] Sets the size of the tx buffer.
1288 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1290 grcan.rxsize= [HW] Sets the size of the rx buffer.
1291 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1294 hardlockup_all_cpu_backtrace=
1295 [KNL] Should the hard-lockup detector generate
1296 backtraces on all cpus.
1299 hashdist= [KNL,NUMA] Large hashes allocated during boot
1300 are distributed across NUMA nodes. Defaults on
1301 for 64-bit NUMA, off otherwise.
1302 Format: 0 | 1 (for off | on)
1304 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1306 hd= [EIDE] (E)IDE hard drive subsystem geometry
1307 Format: <cyl>,<head>,<sect>
1310 Disable Hardware Error Source Table (HEST) support;
1311 corresponding firmware-first mode error processing
1312 logic will be disabled.
1314 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1315 size of <nn>. This works even on boxes that have no
1316 highmem otherwise. This also works to reduce highmem
1317 size on bigger boxes.
1319 highres= [KNL] Enable/disable high resolution timer mode.
1320 Valid parameters: "on", "off"
1324 See Documentation/isdn/README.HiSax.
1328 hpet= [X86-32,HPET] option to control HPET usage
1329 Format: { enable (default) | disable | force |
1331 disable: disable HPET and use PIT instead
1332 force: allow force enabled of undocumented chips (ICH4,
1334 verbose: show contents of HPET registers during setup
1336 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1337 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1339 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1340 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1341 On x86-64 and powerpc, this option can be specified
1342 multiple times interleaved with hugepages= to reserve
1343 huge pages of different sizes. Valid pages sizes on
1344 x86-64 are 2M (when the CPU supports "pse") and 1G
1345 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1347 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1348 terminal devices. Valid values: 0..8
1349 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1350 If specified, z/VM IUCV HVC accepts connections
1351 from listed z/VM user IDs only.
1353 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1354 hardware thread id mappings.
1355 Format: <cpu>:<hwthread>
1358 Do not unregister boot console at start. This is only
1359 useful for debugging when something happens in the window
1360 between unregistering the boot console and initializing
1363 i2c_bus= [HW] Override the default board specific I2C bus speed
1364 or register an additional I2C bus that is not
1365 registered from board initialization code.
1369 i8042.debug [HW] Toggle i8042 debug mode
1370 i8042.unmask_kbd_data
1371 [HW] Enable printing of interrupt data from the KBD port
1372 (disabled by default, and as a pre-condition
1373 requires that i8042.debug=1 be enabled)
1374 i8042.direct [HW] Put keyboard port into non-translated mode
1375 i8042.dumbkbd [HW] Pretend that controller can only read data from
1376 keyboard and cannot control its state
1377 (Don't attempt to blink the leds)
1378 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1379 i8042.nokbd [HW] Don't check/create keyboard port
1380 i8042.noloop [HW] Disable the AUX Loopback command while probing
1382 i8042.nomux [HW] Don't check presence of an active multiplexing
1384 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1386 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1387 i8042.reset [HW] Reset the controller during init and cleanup
1388 i8042.unlock [HW] Unlock (ignore) the keylock
1389 i8042.kbdreset [HW] Reset device connected to KBD port
1393 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1394 indicates that the driver is running on unsupported
1396 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1397 does not match list of supported models.
1399 [HW] Report power status in /proc/i8k
1400 (disabled by default)
1401 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1404 i915.invert_brightness=
1405 [DRM] Invert the sense of the variable that is used to
1406 set the brightness of the panel backlight. Normally a
1407 brightness value of 0 indicates backlight switched off,
1408 and the maximum of the brightness value sets the backlight
1409 to maximum brightness. If this parameter is set to 0
1410 (default) and the machine requires it, or this parameter
1411 is set to 1, a brightness value of 0 sets the backlight
1412 to maximum brightness, and the maximum of the brightness
1413 value switches the backlight off.
1414 -1 -- never invert brightness
1415 0 -- machine default
1416 1 -- force brightness inversion
1419 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1421 ide-core.nodma= [HW] (E)IDE subsystem
1422 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1423 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1424 .cdrom .chs .ignore_cable are additional options
1425 See Documentation/ide/ide.txt.
1427 ide-generic.probe-mask= [HW] (E)IDE subsystem
1429 Probe mask for legacy ISA IDE ports. Depending on
1430 platform up to 6 ports are supported, enabled by
1431 setting corresponding bits in the mask to 1. The
1432 default value is 0x0, which has a special meaning.
1433 On systems that have PCI, it triggers scanning the
1434 PCI bus for the first and the second port, which
1435 are then probed. On systems without PCI the value
1436 of 0x0 enables probing the two first ports as if it
1439 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1440 Claim all unknown PCI IDE storage controllers.
1443 Format: idle=poll, idle=halt, idle=nomwait
1444 Poll forces a polling idle loop that can slightly
1445 improve the performance of waking up a idle CPU, but
1446 will use a lot of power and make the system run hot.
1448 idle=halt: Halt is forced to be used for CPU idle.
1449 In such case C2/C3 won't be used again.
1450 idle=nomwait: Disable mwait for CPU C-states
1452 ignore_loglevel [KNL]
1453 Ignore loglevel setting - this will print /all/
1454 kernel messages to the console. Useful for debugging.
1455 We also add it as printk module parameter, so users
1456 could change it dynamically, usually by
1457 /sys/module/printk/parameters/ignore_loglevel.
1459 ihash_entries= [KNL]
1460 Set number of hash buckets for inode cache.
1462 ima_appraise= [IMA] appraise integrity measurements
1463 Format: { "off" | "enforce" | "fix" | "log" }
1466 ima_appraise_tcb [IMA]
1467 The builtin appraise policy appraises all files
1471 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1475 The list of supported hash algorithms is defined
1476 in crypto/hash_info.h.
1479 The builtin measurement policy to load during IMA
1480 setup. Specyfing "tcb" as the value, measures all
1481 programs exec'd, files mmap'd for exec, and all files
1482 opened with the read mode bit set by either the
1483 effective uid (euid=0) or uid=0.
1486 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1487 Load a policy which meets the needs of the Trusted
1488 Computing Base. This means IMA will measure all
1489 programs exec'd, files mmap'd for exec, and all files
1490 opened for read by uid=0.
1493 Select one of defined IMA measurements template formats.
1494 Formats: { "ima" | "ima-ng" | "ima-sig" }
1498 [IMA] Define a custom template format.
1499 Format: { "field1|...|fieldN" }
1501 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1502 Format: <min_file_size>
1503 Set the minimal file size for using asynchronous hash.
1504 If left unspecified, ahash usage is disabled.
1506 ahash performance varies for different data sizes on
1507 different crypto accelerators. This option can be used
1508 to achieve the best performance for a particular HW.
1510 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1512 Set hashing buffer size. Default: 4k.
1514 ahash performance varies for different chunk sizes on
1515 different crypto accelerators. This option can be used
1516 to achieve best performance for particular HW.
1520 Run specified binary instead of /sbin/init as init
1523 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1524 for working out where the kernel is dying during
1527 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1528 initcall functions. Useful for debugging built-in
1529 modules and initcalls.
1531 initrd= [BOOT] Specify the location of the initial ramdisk
1533 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1536 int_pln_enable [x86] Enable power limit notification interrupt
1538 integrity_audit=[IMA]
1539 Format: { "0" | "1" }
1540 0 -- basic integrity auditing messages. (Default)
1541 1 -- additional integrity auditing messages.
1543 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1545 Enable intel iommu driver.
1547 Disable intel iommu driver.
1548 igfx_off [Default Off]
1549 By default, gfx is mapped as normal device. If a gfx
1550 device has a dedicated DMAR unit, the DMAR unit is
1551 bypassed by not enabling DMAR with this option. In
1552 this case, gfx device will use physical address for
1555 With this option iommu will not optimize to look
1556 for io virtual address below 32-bit forcing dual
1557 address cycle on pci bus for cards supporting greater
1558 than 32-bit addressing. The default is to look
1559 for translation below 32-bit and if not available
1560 then look in the higher range.
1561 strict [Default Off]
1562 With this option on every unmap_single operation will
1563 result in a hardware IOTLB flush operation as opposed
1564 to batching them for performance.
1565 sp_off [Default Off]
1566 By default, super page will be supported if Intel IOMMU
1567 has the capability. With this option, super page will
1569 ecs_off [Default Off]
1570 By default, extended context tables will be supported if
1571 the hardware advertises that it has support both for the
1572 extended tables themselves, and also PASID support. With
1573 this option set, extended tables will not be used even
1574 on hardware which claims to support them.
1576 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1577 0 disables intel_idle and fall back on acpi_idle.
1578 1 to 6 specify maximum depth of C-state.
1582 Do not enable intel_pstate as the default
1583 scaling driver for the supported processors
1585 Enable intel_pstate on systems that prohibit it by default
1586 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1587 instead of acpi-cpufreq may disable platform features, such
1588 as thermal controls and power capping, that rely on ACPI
1589 P-States information being indicated to OSPM and therefore
1590 should be used with caution. This option does not work with
1591 processors that aren't supported by the intel_pstate driver
1592 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1594 Do not enable hardware P state control (HWP)
1597 Only load intel_pstate on systems which support
1598 hardware P state control (HWP) if available.
1600 intremap= [X86-64, Intel-IOMMU]
1601 on enable Interrupt Remapping (default)
1602 off disable Interrupt Remapping
1603 nosid disable Source ID checking
1605 BIOS x2APIC opt-out request will be ignored
1606 nopost disable Interrupt Posting
1608 iomem= Disable strict checking of access to MMIO memory
1609 strict regions from userspace.
1624 nobypass [PPC/POWERNV]
1625 Disable IOMMU bypass, using IOMMU for PCI devices.
1628 io7= [HW] IO7 for Marvel based alpha systems
1629 See comment before marvel_specify_io7 in
1630 arch/alpha/kernel/core_marvel.c.
1632 io_delay= [X86] I/O delay method
1634 Standard port 0x80 based delay
1636 Alternate port 0xed based delay (needed on some systems)
1638 Simple two microseconds delay
1643 See Documentation/filesystems/nfs/nfsroot.txt.
1646 When an interrupt is not handled search all handlers
1647 for it. Intended to get systems with badly broken
1651 When an interrupt is not handled search all handlers
1652 for it. Also check all handlers each timer
1653 interrupt. Intended to get systems with badly broken
1657 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1659 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1661 <cpu number>,...,<cpu number>
1663 <cpu number>-<cpu number>
1664 (must be a positive range in ascending order)
1666 <cpu number>,...,<cpu number>-<cpu number>
1668 This option can be used to specify one or more CPUs
1669 to isolate from the general SMP balancing and scheduling
1670 algorithms. You can move a process onto or off an
1671 "isolated" CPU via the CPU affinity syscalls or cpuset.
1672 <cpu number> begins at 0 and the maximum value is
1673 "number of CPUs in system - 1".
1675 This option is the preferred way to isolate CPUs. The
1676 alternative -- manually setting the CPU mask of all
1677 tasks in the system -- can cause problems and
1678 suboptimal load balancer performance.
1682 ivrs_ioapic [HW,X86_64]
1683 Provide an override to the IOAPIC-ID<->DEVICE-ID
1684 mapping provided in the IVRS ACPI table. For
1685 example, to map IOAPIC-ID decimal 10 to
1686 PCI device 00:14.0 write the parameter as:
1687 ivrs_ioapic[10]=00:14.0
1689 ivrs_hpet [HW,X86_64]
1690 Provide an override to the HPET-ID<->DEVICE-ID
1691 mapping provided in the IVRS ACPI table. For
1692 example, to map HPET-ID decimal 0 to
1693 PCI device 00:14.0 write the parameter as:
1694 ivrs_hpet[0]=00:14.0
1696 js= [HW,JOY] Analog joystick
1697 See Documentation/input/joystick.txt.
1700 Enable/disable kernel and module base offset ASLR
1701 (Address Space Layout Randomization) if built into
1702 the kernel. When CONFIG_HIBERNATION is selected,
1703 kASLR is disabled by default. When kASLR is enabled,
1704 hibernation will be disabled.
1708 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1709 specifies the amount of memory usable by the kernel
1710 for non-movable allocations. The requested amount is
1711 spread evenly throughout all nodes in the system. The
1712 remaining memory in each node is used for Movable
1713 pages. In the event, a node is too small to have both
1714 kernelcore and Movable pages, kernelcore pages will
1715 take priority and other nodes will have a larger number
1716 of Movable pages. The Movable zone is used for the
1717 allocation of pages that may be reclaimed or moved
1718 by the page migration subsystem. This means that
1719 HugeTLB pages may not be allocated from this zone.
1720 Note that allocations like PTEs-from-HighMem still
1721 use the HighMem zone if it exists, and the Normal
1722 zone if it does not.
1724 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1725 Format: <Controller#>[,poll interval]
1726 The controller # is the number of the ehci usb debug
1727 port as it is probed via PCI. The poll interval is
1728 optional and is the number seconds in between
1729 each poll cycle to the debug port in case you need
1730 the functionality for interrupting the kernel with
1731 gdb or control-c on the dbgp connection. When
1732 not using this parameter you use sysrq-g to break into
1733 the kernel debugger.
1735 kgdboc= [KGDB,HW] kgdb over consoles.
1736 Requires a tty driver that supports console polling,
1737 or a supported polling keyboard driver (non-usb).
1738 Serial only format: <serial_device>[,baud]
1739 keyboard only format: kbd
1740 keyboard and serial format: kbd,<serial_device>[,baud]
1741 Optional Kernel mode setting:
1742 kms, kbd format: kms,kbd
1743 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1745 kgdbwait [KGDB] Stop kernel execution and enter the
1746 kernel debugger at the earliest opportunity.
1748 kmac= [MIPS] korina ethernet MAC address.
1749 Configure the RouterBoard 532 series on-chip
1750 Ethernet adapter MAC address.
1752 kmemleak= [KNL] Boot-time kmemleak enable/disable
1753 Valid arguments: on, off
1755 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1758 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1759 Valid arguments: 0, 1, 2
1760 kmemcheck=0 (disabled)
1761 kmemcheck=1 (enabled)
1762 kmemcheck=2 (one-shot mode)
1763 Default: 2 (one-shot mode)
1765 kstack=N [X86] Print N words from the kernel stack
1768 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1769 Default is 0 (don't ignore, but inject #GP)
1771 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1775 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1776 Default is 1 (enabled)
1778 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1780 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1782 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1783 (virtualized MMU) support on capable Intel chips.
1784 Default is 1 (enabled)
1786 kvm-intel.emulate_invalid_guest_state=
1787 [KVM,Intel] Enable emulation of invalid guest states
1788 Default is 0 (disabled)
1790 kvm-intel.flexpriority=
1791 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1792 Default is 1 (enabled)
1795 [KVM,Intel] Enable VMX nesting (nVMX).
1796 Default is 0 (disabled)
1798 kvm-intel.unrestricted_guest=
1799 [KVM,Intel] Disable unrestricted guest feature
1800 (virtualized real and unpaged mode) on capable
1801 Intel chips. Default is 1 (enabled)
1803 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1804 feature (tagged TLBs) on capable Intel chips.
1805 Default is 1 (enabled)
1811 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1814 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1815 value for LAPIC timer one-shot implementation. Default
1816 back to the programmable timer unit in the LAPIC.
1818 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1821 libata.dma= [LIBATA] DMA control
1822 libata.dma=0 Disable all PATA and SATA DMA
1823 libata.dma=1 PATA and SATA Disk DMA only
1824 libata.dma=2 ATAPI (CDROM) DMA only
1825 libata.dma=4 Compact Flash DMA only
1826 Combinations also work, so libata.dma=3 enables DMA
1827 for disks and CDROMs, but not CFs.
1829 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1830 libata.ignore_hpa=0 keep BIOS limits (default)
1831 libata.ignore_hpa=1 ignore limits, using full disk
1833 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1837 libata.force= [LIBATA] Force configurations. The format is comma
1838 separated list of "[ID:]VAL" where ID is
1839 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1840 matching port, link or device. Basically, it matches
1841 the ATA ID string printed on console by libata. If
1842 the whole ID part is omitted, the last PORT and DEVICE
1843 values are used. If ID hasn't been specified yet, the
1844 configuration applies to all ports, links and devices.
1846 If only DEVICE is omitted, the parameter applies to
1847 the port and all links and devices behind it. DEVICE
1848 number of 0 either selects the first device or the
1849 first fan-out link behind PMP device. It does not
1850 select the host link. DEVICE number of 15 selects the
1851 host link and device attached to it.
1853 The VAL specifies the configuration to force. As long
1854 as there's no ambiguity shortcut notation is allowed.
1855 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1856 The following configurations can be forced.
1858 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1859 Any ID with matching PORT is used.
1861 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1863 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1864 udma[/][16,25,33,44,66,100,133] notation is also
1867 * [no]ncq: Turn on or off NCQ.
1869 * [no]ncqtrim: Turn off queued DSM TRIM.
1871 * nohrst, nosrst, norst: suppress hard, soft
1874 * rstonce: only attempt one reset during
1875 hot-unplug link recovery
1877 * dump_id: dump IDENTIFY data.
1879 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1881 * disable: Disable this device.
1883 If there are multiple matching configurations changing
1884 the same attribute, the last one is used.
1886 memblock=debug [KNL] Enable memblock debug messages.
1888 load_ramdisk= [RAM] List of ramdisks to load from floppy
1889 See Documentation/blockdev/ramdisk.txt.
1891 lockd.nlm_grace_period=P [NFS] Assign grace period.
1894 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1897 lockd.nlm_timeout=T [NFS] Assign timeout value.
1900 lockd.nlm_udpport=M [NFS] Assign UDP port.
1903 locktorture.nreaders_stress= [KNL]
1904 Set the number of locking read-acquisition kthreads.
1905 Defaults to being automatically set based on the
1906 number of online CPUs.
1908 locktorture.nwriters_stress= [KNL]
1909 Set the number of locking write-acquisition kthreads.
1911 locktorture.onoff_holdoff= [KNL]
1912 Set time (s) after boot for CPU-hotplug testing.
1914 locktorture.onoff_interval= [KNL]
1915 Set time (s) between CPU-hotplug operations, or
1916 zero to disable CPU-hotplug testing.
1918 locktorture.shuffle_interval= [KNL]
1919 Set task-shuffle interval (jiffies). Shuffling
1920 tasks allows some CPUs to go into dyntick-idle
1921 mode during the locktorture test.
1923 locktorture.shutdown_secs= [KNL]
1924 Set time (s) after boot system shutdown. This
1925 is useful for hands-off automated testing.
1927 locktorture.stat_interval= [KNL]
1928 Time (s) between statistics printk()s.
1930 locktorture.stutter= [KNL]
1931 Time (s) to stutter testing, for example,
1932 specifying five seconds causes the test to run for
1933 five seconds, wait for five seconds, and so on.
1934 This tests the locking primitive's ability to
1935 transition abruptly to and from idle.
1937 locktorture.torture_runnable= [BOOT]
1938 Start locktorture running at boot time.
1940 locktorture.torture_type= [KNL]
1941 Specify the locking implementation to test.
1943 locktorture.verbose= [KNL]
1944 Enable additional printk() statements.
1946 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1949 loglevel= All Kernel Messages with a loglevel smaller than the
1950 console loglevel will be printed to the console. It can
1951 also be changed with klogd or other programs. The
1952 loglevels are defined as follows:
1954 0 (KERN_EMERG) system is unusable
1955 1 (KERN_ALERT) action must be taken immediately
1956 2 (KERN_CRIT) critical conditions
1957 3 (KERN_ERR) error conditions
1958 4 (KERN_WARNING) warning conditions
1959 5 (KERN_NOTICE) normal but significant condition
1960 6 (KERN_INFO) informational
1961 7 (KERN_DEBUG) debug-level messages
1963 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1964 in bytes. n must be a power of two and greater
1965 than the minimal size. The minimal size is defined
1966 by LOG_BUF_SHIFT kernel config parameter. There is
1967 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1968 that allows to increase the default size depending on
1969 the number of CPUs. See init/Kconfig for more details.
1971 logo.nologo [FB] Disables display of the built-in Linux logo.
1972 This may be used to provide more screen space for
1973 kernel log messages and is useful when debugging
1974 kernel boot problems.
1976 lp=0 [LP] Specify parallel ports to use, e.g,
1977 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1978 lp=reset first parallel port). 'lp=0' disables the
1979 lp=auto printer driver. 'lp=reset' (which can be
1980 specified in addition to the ports) causes
1981 attached printers to be reset. Using
1982 lp=port1,port2,... specifies the parallel ports
1983 to associate lp devices with, starting with
1984 lp0. A port specification may be 'none' to skip
1985 that lp device, or a parport name such as
1986 'parport0'. Specifying 'lp=auto' instead of a
1987 port specification list means that device IDs
1988 from each port should be examined, to see if
1989 an IEEE 1284-compliant printer is attached; if
1990 so, the driver will manage that printer.
1991 See also header of drivers/char/lp.c.
1994 Sets loops_per_jiffy to given constant, thus avoiding
1995 time-consuming boot-time autodetection (up to 250 ms per
1996 CPU). 0 enables autodetection (default). To determine
1997 the correct value for your kernel, boot with normal
1998 autodetection and see what value is printed. Note that
1999 on SMP systems the preset will be applied to all CPUs,
2000 which is likely to cause problems if your CPUs need
2001 significantly divergent settings. An incorrect value
2002 will cause delays in the kernel to be wrong, leading to
2003 unpredictable I/O errors and other breakage. Although
2004 unlikely, in the extreme case this might damage your
2008 Format: <io>,<irq>,<dma>
2010 machvec= [IA-64] Force the use of a particular machine-vector
2011 (machvec) in a generic kernel.
2012 Example: machvec=hpzx1_swiotlb
2014 machtype= [Loongson] Share the same kernel image file between different
2016 Example: machtype=lemote-yeeloong-2f-7inch
2018 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2019 than or equal to this physical address is ignored.
2021 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2022 should make use of. maxcpus=n : n >= 0 limits the
2023 kernel to using 'n' processors. n=0 is a special case,
2024 it is equivalent to "nosmp", which also disables
2027 max_loop= [LOOP] The number of loop block devices that get
2028 (loop.max_loop) unconditionally pre-created at init time. The default
2029 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2030 of statically allocating a predefined number, loop
2031 devices can be requested on-demand with the
2032 /dev/loop-control interface.
2034 mce [X86-32] Machine Check Exception
2036 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2038 md= [HW] RAID subsystems devices and level
2039 See Documentation/md.txt.
2042 Format: <first>,<last>
2043 Specifies range of consoles to be captured by the MDA.
2045 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2046 Amount of memory to be used when the kernel is not able
2047 to see the whole system memory or for test.
2048 [X86] Work as limiting max address. Use together
2049 with memmap= to avoid physical address space collisions.
2050 Without memmap= PCI devices could be placed at addresses
2051 belonging to unused RAM.
2053 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2057 [KNL,SH] Allow user to override the default size for
2058 per-device physically contiguous DMA buffers.
2060 memmap=exactmap [KNL,X86] Enable setting of an exact
2061 E820 memory map, as specified by the user.
2062 Such memmap=exactmap lines can be constructed based on
2063 BIOS output or other requirements. See the memmap=nn@ss
2066 memmap=nn[KMG]@ss[KMG]
2067 [KNL] Force usage of a specific region of memory.
2068 Region of memory to be used is from ss to ss+nn.
2070 memmap=nn[KMG]#ss[KMG]
2071 [KNL,ACPI] Mark specific memory as ACPI data.
2072 Region of memory to be marked is from ss to ss+nn.
2074 memmap=nn[KMG]$ss[KMG]
2075 [KNL,ACPI] Mark specific memory as reserved.
2076 Region of memory to be reserved is from ss to ss+nn.
2077 Example: Exclude memory from 0x18690000-0x1869ffff
2078 memmap=64K$0x18690000
2080 memmap=0x10000$0x18690000
2082 memmap=nn[KMG]!ss[KMG]
2083 [KNL,X86] Mark specific memory as protected.
2084 Region of memory to be used, from ss to ss+nn.
2085 The memory region may be marked as e820 type 12 (0xc)
2086 and is NVDIMM or ADR memory.
2088 memory_corruption_check=0/1 [X86]
2089 Some BIOSes seem to corrupt the first 64k of
2090 memory when doing things like suspend/resume.
2091 Setting this option will scan the memory
2092 looking for corruption. Enabling this will
2093 both detect corruption and prevent the kernel
2094 from using the memory being corrupted.
2095 However, its intended as a diagnostic tool; if
2096 repeatable BIOS-originated corruption always
2097 affects the same memory, you can use memmap=
2098 to prevent the kernel from using that memory.
2100 memory_corruption_check_size=size [X86]
2101 By default it checks for corruption in the low
2102 64k, making this memory unavailable for normal
2103 use. Use this parameter to scan for
2104 corruption in more or less memory.
2106 memory_corruption_check_period=seconds [X86]
2107 By default it checks for corruption every 60
2108 seconds. Use this parameter to check at some
2109 other rate. 0 disables periodic checking.
2111 memtest= [KNL,X86,ARM] Enable memtest
2113 default : 0 <disable>
2114 Specifies the number of memtest passes to be
2115 performed. Each pass selects another test
2116 pattern from a given set of patterns. Memtest
2117 fills the memory with this pattern, validates
2118 memory contents and reserves bad memory
2119 regions that are detected.
2121 meye.*= [HW] Set MotionEye Camera parameters
2122 See Documentation/video4linux/meye.txt.
2124 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2125 Multi-Function General Purpose Timers on AMD Geode
2128 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2129 the BIOS has incorrectly applied a workaround. TinyBIOS
2130 version 0.98 is known to be affected, 0.99 fixes the
2131 problem by letting the user disable the workaround.
2135 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2136 physical address is ignored.
2138 mini2440= [ARM,HW,KNL]
2139 Format:[0..2][b][c][t]
2141 MINI2440 configuration specification:
2142 0 - The attached screen is the 3.5" TFT
2143 1 - The attached screen is the 7" TFT
2144 2 - The VGA Shield is attached (1024x768)
2145 Leaving out the screen size parameter will not load
2146 the TFT driver, and the framebuffer will be left
2148 b - Enable backlight. The TFT backlight pin will be
2149 linked to the kernel VESA blanking code and a GPIO
2150 LED. This parameter is not necessary when using the
2152 c - Enable the s3c camera interface.
2153 t - Reserved for enabling touchscreen support. The
2154 touchscreen support is not enabled in the mainstream
2155 kernel as of 2.6.30, a preliminary port can be found
2156 in the "bleeding edge" mini2440 support kernel at
2157 http://repo.or.cz/w/linux-2.6/mini2440.git
2160 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2161 parameter allows control of the logging verbosity for
2162 the additional memory initialisation checks. A value
2163 of 0 disables mminit logging and a level of 4 will
2164 log everything. Information is printed at KERN_DEBUG
2165 so loglevel=8 may also need to be specified.
2168 [KNL] When CONFIG_MODULE_SIG is set, this means that
2169 modules without (valid) signatures will fail to load.
2170 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2171 is always true, so this option does nothing.
2174 [MOUSE] Maximum time between finger touching and
2175 leaving touchpad surface for touch to be considered
2176 a tap and be reported as a left button click (for
2177 touchpads working in absolute mode only).
2179 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2180 reporting absolute coordinates, such as tablets
2181 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2182 reporting absolute coordinates, such as tablets
2184 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2185 is similar to kernelcore except it specifies the
2186 amount of memory used for migratable allocations.
2187 If both kernelcore and movablecore is specified,
2188 then kernelcore will be at *least* the specified
2189 value but may be more. If movablecore on its own
2190 is specified, the administrator must be careful
2191 that the amount of memory usable for all allocations
2194 movable_node [KNL,X86] Boot-time switch to enable the effects
2195 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2197 MTD_Partition= [MTD]
2198 Format: <name>,<region-number>,<size>,<offset>
2200 MTD_Region= [MTD] Format:
2201 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2204 See drivers/mtd/cmdlinepart.c.
2206 multitce=off [PPC] This parameter disables the use of the pSeries
2207 firmware feature for updating multiple TCE entries
2210 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2212 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2214 boundary - index of last SLC block on Flex-OneNAND.
2215 The remaining blocks are configured as MLC blocks.
2216 lock - Configure if Flex-OneNAND boundary should be locked.
2217 Once locked, the boundary cannot be changed.
2218 1 indicates lock status, 0 indicates unlock status.
2221 ARM/S3C2412 JIVE boot control
2223 See arch/arm/mach-s3c2412/mach-jive.c
2225 mtouchusb.raw_coordinates=
2226 [HW] Make the MicroTouch USB driver use raw coordinates
2227 ('y', default) or cooked coordinates ('n')
2229 mtrr_chunk_size=nn[KMG] [X86]
2230 used for mtrr cleanup. It is largest continuous chunk
2231 that could hold holes aka. UC entries.
2233 mtrr_gran_size=nn[KMG] [X86]
2234 Used for mtrr cleanup. It is granularity of mtrr block.
2236 Large value could prevent small alignment from
2239 mtrr_spare_reg_nr=n [X86]
2241 Range: 0,7 : spare reg number
2243 Used for mtrr cleanup. It is spare mtrr entries number.
2244 Set to 2 or more if your graphical card needs more.
2246 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2248 netdev= [NET] Network devices parameters
2249 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2250 Note that mem_start is often overloaded to mean
2251 something different and driver-specific.
2252 This usage is only documented in each driver source
2256 [NETFILTER] Enable connection tracking flow accounting
2257 0 to disable accounting
2258 1 to enable accounting
2261 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2262 See Documentation/filesystems/nfs/nfsroot.txt.
2264 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2265 See Documentation/filesystems/nfs/nfsroot.txt.
2267 nfsrootdebug [NFS] enable nfsroot debugging messages.
2268 See Documentation/filesystems/nfs/nfsroot.txt.
2270 nfs.callback_tcpport=
2271 [NFS] set the TCP port on which the NFSv4 callback
2272 channel should listen.
2275 [NFS] sets the pathname to the program which is used
2276 to update the NFS client cache entries.
2278 nfs.cache_getent_timeout=
2279 [NFS] sets the timeout after which an attempt to
2280 update a cache entry is deemed to have failed.
2282 nfs.idmap_cache_timeout=
2283 [NFS] set the maximum lifetime for idmapper cache
2287 [NFS] enable 64-bit inode numbers.
2288 If zero, the NFS client will fake up a 32-bit inode
2289 number for the readdir() and stat() syscalls instead
2290 of returning the full 64-bit number.
2291 The default is to return 64-bit inode numbers.
2293 nfs.max_session_slots=
2294 [NFSv4.1] Sets the maximum number of session slots
2295 the client will attempt to negotiate with the server.
2296 This limits the number of simultaneous RPC requests
2297 that the client can send to the NFSv4.1 server.
2298 Note that there is little point in setting this
2299 value higher than the max_tcp_slot_table_limit.
2301 nfs.nfs4_disable_idmapping=
2302 [NFSv4] When set to the default of '1', this option
2303 ensures that both the RPC level authentication
2304 scheme and the NFS level operations agree to use
2305 numeric uids/gids if the mount is using the
2306 'sec=sys' security flavour. In effect it is
2307 disabling idmapping, which can make migration from
2308 legacy NFSv2/v3 systems to NFSv4 easier.
2309 Servers that do not support this mode of operation
2310 will be autodetected by the client, and it will fall
2311 back to using the idmapper.
2312 To turn off this behaviour, set the value to '0'.
2314 [NFS4] Specify an additional fixed unique ident-
2315 ification string that NFSv4 clients can insert into
2316 their nfs_client_id4 string. This is typically a
2317 UUID that is generated at system install time.
2319 nfs.send_implementation_id =
2320 [NFSv4.1] Send client implementation identification
2321 information in exchange_id requests.
2322 If zero, no implementation identification information
2324 The default is to send the implementation identification
2327 nfs.recover_lost_locks =
2328 [NFSv4] Attempt to recover locks that were lost due
2329 to a lease timeout on the server. Please note that
2330 doing this risks data corruption, since there are
2331 no guarantees that the file will remain unchanged
2332 after the locks are lost.
2333 If you want to enable the kernel legacy behaviour of
2334 attempting to recover these locks, then set this
2336 The default parameter value of '0' causes the kernel
2337 not to attempt recovery of lost locks.
2339 nfs4.layoutstats_timer =
2340 [NFSv4.2] Change the rate at which the kernel sends
2341 layoutstats to the pNFS metadata server.
2343 Setting this to value to 0 causes the kernel to use
2344 whatever value is the default set by the layout
2345 driver. A non-zero value sets the minimum interval
2346 in seconds between layoutstats transmissions.
2348 nfsd.nfs4_disable_idmapping=
2349 [NFSv4] When set to the default of '1', the NFSv4
2350 server will return only numeric uids and gids to
2351 clients using auth_sys, and will accept numeric uids
2352 and gids from such clients. This is intended to ease
2353 migration from NFSv2/v3.
2355 objlayoutdriver.osd_login_prog=
2356 [NFS] [OBJLAYOUT] sets the pathname to the program which
2357 is used to automatically discover and login into new
2358 osd-targets. Please see:
2359 Documentation/filesystems/pnfs.txt for more explanations
2361 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2362 when a NMI is triggered.
2363 Format: [state][,regs][,debounce][,die]
2365 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2366 Format: [panic,][nopanic,][num]
2368 0 - turn hardlockup detector in nmi_watchdog off
2369 1 - turn hardlockup detector in nmi_watchdog on
2370 When panic is specified, panic when an NMI watchdog
2371 timeout occurs (or 'nopanic' to override the opposite
2372 default). To disable both hard and soft lockup detectors,
2373 please see 'nowatchdog'.
2374 This is useful when you use a panic=... timeout and
2375 need the box quickly up again.
2377 netpoll.carrier_timeout=
2378 [NET] Specifies amount of time (in seconds) that
2379 netpoll should wait for a carrier. By default netpoll
2382 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2383 emulation library even if a 387 maths coprocessor
2387 [HW] Never suspend the console
2388 Disable suspending of consoles during suspend and
2389 hibernate operations. Once disabled, debugging
2390 messages can reach various consoles while the rest
2391 of the system is being put to sleep (ie, while
2392 debugging driver suspend/resume hooks). This may
2393 not work reliably with all consoles, but is known
2394 to work with serial and VGA consoles.
2395 To facilitate more flexible debugging, we also add
2396 console_suspend, a printk module parameter to control
2397 it. Users could use console_suspend (usually
2398 /sys/module/printk/parameters/console_suspend) to
2399 turn on/off it dynamically.
2401 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2402 caches in the slab allocator. Saves per-node memory,
2403 but will impact performance.
2407 noapic [SMP,APIC] Tells the kernel to not make use of any
2408 IOAPICs that may be present in the system.
2410 noautogroup Disable scheduler automatic task group creation.
2412 nobats [PPC] Do not use BATs for mapping kernel lowmem
2413 on "Classic" PPC cores.
2417 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2419 nodelayacct [KNL] Disable per-task delay accounting
2421 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2423 nodsp [SH] Disable hardware DSP at boot time.
2425 noefi Disable EFI runtime services support.
2430 On X86-32 available only on PAE configured kernels.
2431 noexec=on: enable non-executable mappings (default)
2432 noexec=off: disable non-executable mappings
2435 Disable SMAP (Supervisor Mode Access Prevention)
2436 even if it is supported by processor.
2439 Disable SMEP (Supervisor Mode Execution Prevention)
2440 even if it is supported by processor.
2443 This affects only 32-bit executables.
2444 noexec32=on: enable non-executable mappings (default)
2445 read doesn't imply executable mappings
2446 noexec32=off: disable non-executable mappings
2447 read implies executable mappings
2449 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2451 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2452 register save and restore. The kernel will only save
2453 legacy floating-point registers on task switch.
2455 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2457 noxsave [BUGS=X86] Disables x86 extended register state save
2458 and restore using xsave. The kernel will fallback to
2459 enabling legacy floating-point and sse state.
2461 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2462 register states. The kernel will fall back to use
2463 xsave to save the states. By using this parameter,
2464 performance of saving the states is degraded because
2465 xsave doesn't support modified optimization while
2466 xsaveopt supports it on xsaveopt enabled systems.
2468 noxsaves [X86] Disables xsaves and xrstors used in saving and
2469 restoring x86 extended register state in compacted
2470 form of xsave area. The kernel will fall back to use
2471 xsaveopt and xrstor to save and restore the states
2472 in standard form of xsave area. By using this
2473 parameter, xsave area per process might occupy more
2474 memory on xsaves enabled systems.
2476 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2477 wfi(ARM) instruction doesn't work correctly and not to
2478 use it. This is also useful when using JTAG debugger.
2480 no_file_caps Tells the kernel not to honor file capabilities. The
2481 only way then for a file to be executed with privilege
2482 is to be setuid root or executed by root.
2484 nohalt [IA-64] Tells the kernel not to use the power saving
2485 function PAL_HALT_LIGHT when idle. This increases
2486 power-consumption. On the positive side, it reduces
2487 interrupt wake-up latency, which may improve performance
2488 in certain environments such as networked servers or
2491 nohibernate [HIBERNATION] Disable hibernation and resume.
2493 nohz= [KNL] Boottime enable/disable dynamic ticks
2494 Valid arguments: on, off
2497 nohz_full= [KNL,BOOT]
2498 In kernels built with CONFIG_NO_HZ_FULL=y, set
2499 the specified list of CPUs whose tick will be stopped
2500 whenever possible. The boot CPU will be forced outside
2501 the range to maintain the timekeeping.
2502 The CPUs in this range must also be included in the
2505 noiotrap [SH] Disables trapped I/O port accesses.
2507 noirqdebug [X86-32] Disables the code which attempts to detect and
2508 disable unhandled interrupt sources.
2510 no_timer_check [X86,APIC] Disables the code which tests for
2511 broken timer IRQ sources.
2513 noisapnp [ISAPNP] Disables ISA PnP code.
2515 noinitrd [RAM] Tells the kernel not to load any configured
2518 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2520 [Deprecated - use intremap=off]
2524 nojitter [IA-64] Disables jitter checking for ITC timers.
2526 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2528 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2531 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2532 steal time is computed, but won't influence scheduler
2535 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2537 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2539 noltlbs [PPC] Do not use large page/tlb entries for kernel
2540 lowmem mapping on PPC40x.
2542 nomca [IA-64] Disable machine check abort handling
2544 nomce [X86-32] Disable Machine Check Exception
2546 nomfgpt [X86-32] Disable Multi-Function General Purpose
2547 Timer usage (for AMD Geode machines).
2549 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2550 shutdown the other cpus. Instead use the REBOOT_VECTOR
2553 nomodule Disable module load
2555 nopat [X86] Disable PAT (page attribute table extension of
2556 pagetables) support.
2558 norandmaps Don't use address space randomization. Equivalent to
2559 echo 0 > /proc/sys/kernel/randomize_va_space
2561 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2563 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2564 with UP alternatives
2566 nordrand [X86] Disable kernel use of the RDRAND and
2567 RDSEED instructions even if they are supported
2568 by the processor. RDRAND and RDSEED are still
2569 available to user space applications.
2571 noresume [SWSUSP] Disables resume and restores original swap
2574 no-scroll [VGA] Disables scrollback.
2575 This is required for the Braillex ib80-piezo Braille
2576 reader made by F.H. Papenmeier (Germany).
2580 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2582 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2583 and disable the IO APIC. legacy for "maxcpus=0".
2585 nosoftlockup [KNL] Disable the soft-lockup detector.
2587 nosync [HW,M68K] Disables sync negotiation for all devices.
2589 notsc [BUGS=X86-32] Disable Time Stamp Counter
2591 nowatchdog [KNL] Disable both lockup detectors, i.e.
2592 soft-lockup and NMI watchdog (hard-lockup).
2596 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2598 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2599 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2600 Some features depend on CPU0. Known dependencies are:
2601 1. Resume from suspend/hibernate depends on CPU0.
2602 Suspend/hibernate will fail if CPU0 is offline and you
2603 need to online CPU0 before suspend/hibernate.
2604 2. PIC interrupts also depend on CPU0. CPU0 can't be
2605 removed if a PIC interrupt is detected.
2606 It's said poweroff/reboot may depend on CPU0 on some
2607 machines although I haven't seen such issues so far
2608 after CPU0 is offline on a few tested machines.
2609 If the dependencies are under your control, you can
2610 turn on cpu0_hotplug.
2612 nptcg= [IA-64] Override max number of concurrent global TLB
2613 purges which is reported from either PAL_VM_SUMMARY or
2616 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2617 could support. nr_cpus=n : n >= 1 limits the kernel to
2618 supporting 'n' processors. Later in runtime you can not
2619 use hotplug cpu feature to put more cpu back to online.
2620 just like you compile the kernel NR_CPUS=n
2622 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2624 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2625 Allowed values are enable and disable
2627 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2628 one of ['zone', 'node', 'default'] can be specified
2629 This can be set from sysctl after boot.
2630 See Documentation/sysctl/vm.txt for details.
2632 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2633 See Documentation/debugging-via-ohci1394.txt for more
2636 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2637 Rather than timing out after 20 ms if an EC
2638 command is not properly ACKed, override the length
2639 of the timeout. We have interrupts disabled while
2640 waiting for the ACK, so if this is set too high
2641 interrupts *may* be lost!
2643 omap_mux= [OMAP] Override bootloader pin multiplexing.
2644 Format: <mux_mode0.mode_name=value>...
2645 For example, to override I2C bus2:
2646 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2648 oprofile.timer= [HW]
2649 Use timer interrupt instead of performance counters
2651 oprofile.cpu_type= Force an oprofile cpu type
2652 This might be useful if you have an older oprofile
2653 userland or if you want common events.
2654 Format: { arch_perfmon }
2655 arch_perfmon: [X86] Force use of architectural
2656 perfmon on Intel CPUs instead of the
2657 CPU specific event set.
2658 timer: [X86] Force use of architectural NMI
2659 timer mode (see also oprofile.timer
2660 for generic hr timer mode)
2661 [s390] Force legacy basic mode sampling
2662 (report cpu_type "timer")
2664 oops=panic Always panic on oopses. Default is to just kill the
2665 process, but there is a small probability of
2666 deadlocking the machine.
2667 This will also cause panics on machine check exceptions.
2668 Useful together with panic=30 to trigger a reboot.
2671 See Documentation/sound/oss/oss-parameters.txt
2673 page_owner= [KNL] Boot-time page_owner enabling option.
2674 Storage of the information about who allocated
2675 each page is disabled in default. With this switch,
2677 on: enable the feature
2679 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2680 timeout > 0: seconds before rebooting
2681 timeout = 0: wait forever
2682 timeout < 0: reboot immediately
2685 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2688 crash_kexec_post_notifiers
2689 Run kdump after running panic-notifiers and dumping
2690 kmsg. This only for the users who doubt kdump always
2691 succeeds in any situation.
2692 Note that this also increases risks of kdump failure,
2693 because some panic notifiers can make the crashed
2694 kernel more unstable.
2696 parkbd.port= [HW] Parallel port number the keyboard adapter is
2697 connected to, default is 0.
2699 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2700 0 for XT, 1 for AT (default is AT).
2703 parport= [HW,PPT] Specify parallel ports. 0 disables.
2704 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2705 Use 'auto' to force the driver to use any
2706 IRQ/DMA settings detected (the default is to
2707 ignore detected IRQ/DMA settings because of
2708 possible conflicts). You can specify the base
2709 address, IRQ, and DMA settings; IRQ and DMA
2710 should be numbers, or 'auto' (for using detected
2711 settings on that particular port), or 'nofifo'
2712 (to avoid using a FIFO even if it is detected).
2713 Parallel ports are assigned in the order they
2714 are specified on the command line, starting
2717 parport_init_mode= [HW,PPT]
2718 Configure VIA parallel port to operate in
2719 a specific mode. This is necessary on Pegasos
2720 computer where firmware has no options for setting
2721 up parallel port mode and sets it to spp.
2722 Currently this function knows 686a and 8231 chips.
2723 Format: [spp|ps2|epp|ecp|ecpepp]
2726 Halt all CPUs after the first oops has been printed for
2727 the specified number of seconds. This is to be used if
2728 your oopses keep scrolling off the screen.
2733 See header of drivers/block/paride/pcd.c.
2734 See also Documentation/blockdev/paride.txt.
2736 pci=option[,option...] [PCI] various PCI subsystem options:
2737 earlydump [X86] dump PCI config space before the kernel
2739 off [X86] don't probe for the PCI bus
2740 bios [X86-32] force use of PCI BIOS, don't access
2741 the hardware directly. Use this if your machine
2742 has a non-standard PCI host bridge.
2743 nobios [X86-32] disallow use of PCI BIOS, only direct
2744 hardware access methods are allowed. Use this
2745 if you experience crashes upon bootup and you
2746 suspect they are caused by the BIOS.
2747 conf1 [X86] Force use of PCI Configuration
2749 conf2 [X86] Force use of PCI Configuration
2751 noaer [PCIE] If the PCIEAER kernel config parameter is
2752 enabled, this kernel boot option can be used to
2753 disable the use of PCIE advanced error reporting.
2754 nodomains [PCI] Disable support for multiple PCI
2755 root domains (aka PCI segments, in ACPI-speak).
2756 nommconf [X86] Disable use of MMCONFIG for PCI
2758 check_enable_amd_mmconf [X86] check for and enable
2759 properly configured MMIO access to PCI
2760 config space on AMD family 10h CPU
2761 nomsi [MSI] If the PCI_MSI kernel config parameter is
2762 enabled, this kernel boot option can be used to
2763 disable the use of MSI interrupts system-wide.
2764 noioapicquirk [APIC] Disable all boot interrupt quirks.
2765 Safety option to keep boot IRQs enabled. This
2766 should never be necessary.
2767 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2768 primary IO-APIC for bridges that cannot disable
2769 boot IRQs. This fixes a source of spurious IRQs
2770 when the system masks IRQs.
2771 noioapicreroute [APIC] Disable workaround that uses the
2772 boot IRQ equivalent of an IRQ that connects to
2773 a chipset where boot IRQs cannot be disabled.
2774 The opposite of ioapicreroute.
2775 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2776 routing table. These calls are known to be buggy
2777 on several machines and they hang the machine
2778 when used, but on other computers it's the only
2779 way to get the interrupt routing table. Try
2780 this option if the kernel is unable to allocate
2781 IRQs or discover secondary PCI buses on your
2783 rom [X86] Assign address space to expansion ROMs.
2784 Use with caution as certain devices share
2785 address decoders between ROMs and other
2787 norom [X86] Do not assign address space to
2788 expansion ROMs that do not already have
2789 BIOS assigned address ranges.
2790 nobar [X86] Do not assign address space to the
2791 BARs that weren't assigned by the BIOS.
2792 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2793 assigned automatically to PCI devices. You can
2794 make the kernel exclude IRQs of your ISA cards
2796 pirqaddr=0xAAAAA [X86] Specify the physical address
2797 of the PIRQ table (normally generated
2798 by the BIOS) if it is outside the
2799 F0000h-100000h range.
2800 lastbus=N [X86] Scan all buses thru bus #N. Can be
2801 useful if the kernel is unable to find your
2802 secondary buses and you want to tell it
2803 explicitly which ones they are.
2804 assign-busses [X86] Always assign all PCI bus
2805 numbers ourselves, overriding
2806 whatever the firmware may have done.
2807 usepirqmask [X86] Honor the possible IRQ mask stored
2808 in the BIOS $PIR table. This is needed on
2809 some systems with broken BIOSes, notably
2810 some HP Pavilion N5400 and Omnibook XE3
2811 notebooks. This will have no effect if ACPI
2812 IRQ routing is enabled.
2813 noacpi [X86] Do not use ACPI for IRQ routing
2814 or for PCI scanning.
2815 use_crs [X86] Use PCI host bridge window information
2816 from ACPI. On BIOSes from 2008 or later, this
2817 is enabled by default. If you need to use this,
2818 please report a bug.
2819 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2820 If you need to use this, please report a bug.
2821 routeirq Do IRQ routing for all PCI devices.
2822 This is normally done in pci_enable_device(),
2823 so this option is a temporary workaround
2824 for broken drivers that don't call it.
2825 skip_isa_align [X86] do not align io start addr, so can
2826 handle more pci cards
2827 firmware [ARM] Do not re-enumerate the bus but instead
2828 just use the configuration from the
2829 bootloader. This is currently used on
2830 IXP2000 systems where the bus has to be
2831 configured a certain way for adjunct CPUs.
2832 noearly [X86] Don't do any early type 1 scanning.
2833 This might help on some broken boards which
2834 machine check when some devices' config space
2835 is read. But various workarounds are disabled
2836 and some IOMMU drivers will not work.
2837 bfsort Sort PCI devices into breadth-first order.
2838 This sorting is done to get a device
2839 order compatible with older (<= 2.4) kernels.
2840 nobfsort Don't sort PCI devices into breadth-first order.
2841 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2842 tuning and use the BIOS-configured MPS defaults.
2843 pcie_bus_safe Set every device's MPS to the largest value
2844 supported by all devices below the root complex.
2845 pcie_bus_perf Set device MPS to the largest allowable MPS
2846 based on its parent bus. Also set MRRS (Max
2847 Read Request Size) to the largest supported
2848 value (no larger than the MPS that the device
2849 or bus can support) for best performance.
2850 pcie_bus_peer2peer Set every device's MPS to 128B, which
2851 every device is guaranteed to support. This
2852 configuration allows peer-to-peer DMA between
2853 any pair of devices, possibly at the cost of
2854 reduced performance. This also guarantees
2855 that hot-added devices will work.
2856 cbiosize=nn[KMG] The fixed amount of bus space which is
2857 reserved for the CardBus bridge's IO window.
2858 The default value is 256 bytes.
2859 cbmemsize=nn[KMG] The fixed amount of bus space which is
2860 reserved for the CardBus bridge's memory
2861 window. The default value is 64 megabytes.
2864 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2865 Specifies alignment and device to reassign
2866 aligned memory resources.
2867 If <order of align> is not specified,
2868 PAGE_SIZE is used as alignment.
2869 PCI-PCI bridge can be specified, if resource
2870 windows need to be expanded.
2871 ecrc= Enable/disable PCIe ECRC (transaction layer
2872 end-to-end CRC checking).
2873 bios: Use BIOS/firmware settings. This is the
2877 hpiosize=nn[KMG] The fixed amount of bus space which is
2878 reserved for hotplug bridge's IO window.
2879 Default size is 256 bytes.
2880 hpmemsize=nn[KMG] The fixed amount of bus space which is
2881 reserved for hotplug bridge's memory window.
2882 Default size is 2 megabytes.
2883 realloc= Enable/disable reallocating PCI bridge resources
2884 if allocations done by BIOS are too small to
2885 accommodate resources required by all child
2887 off: Turn realloc off
2889 realloc same as realloc=on
2890 noari do not use PCIe ARI.
2891 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2892 only look for one device below a PCIe downstream
2895 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2898 force Enable ASPM even on devices that claim not to support it.
2899 WARNING: Forcing ASPM on may cause system lockups.
2901 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2902 nomsi Do not use MSI for PCI Express Native Hotplug (this
2903 makes all PCIe ports use INTx for hotplug services).
2905 pcie_ports= [PCIE] PCIe ports handling:
2906 auto Ask the BIOS whether or not to use native PCIe services
2907 associated with PCIe ports (PME, hot-plug, AER). Use
2908 them only if that is allowed by the BIOS.
2909 native Use native PCIe services associated with PCIe ports
2911 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2914 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2915 nomsi Do not use MSI for native PCIe PME signaling (this makes
2916 all PCIe root ports use INTx for all services).
2918 pcmv= [HW,PCMCIA] BadgePAD 4
2922 Keep all power-domains already enabled by bootloader on,
2923 even if no driver has claimed them. This is useful
2924 for debug and development, but should not be
2925 needed on a platform with proper driver support.
2928 See Documentation/blockdev/paride.txt.
2930 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2933 See arch/parisc/kernel/pdc_chassis.c
2935 percpu_alloc= Select which percpu first chunk allocator to use.
2936 Currently supported values are "embed" and "page".
2937 Archs may support subset or none of the selections.
2938 See comments in mm/percpu.c for details on each
2939 allocator. This parameter is primarily for debugging
2940 and performance comparison.
2943 See Documentation/blockdev/paride.txt.
2946 See Documentation/blockdev/paride.txt.
2948 pirq= [SMP,APIC] Manual mp-table setup
2949 See Documentation/x86/i386/IO-APIC.txt.
2951 plip= [PPT,NET] Parallel port network link
2952 Format: { parport<nr> | timid | 0 }
2953 See also Documentation/parport.txt.
2955 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2956 Override pmtimer IOPort with a hex value.
2960 Enable PNP debug messages (depends on the
2961 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2962 via /sys/module/pnp/parameters/debug. We always show
2963 current resource usage; turning this on also shows
2964 possible settings and some assignment information.
2970 { on | off | curr | res | no-curr | no-res }
2973 [ISAPNP] Exclude IRQs for the autoconfiguration
2976 [ISAPNP] Exclude DMAs for the autoconfiguration
2978 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2979 Ranges are in pairs (I/O port base and size).
2982 [ISAPNP] Exclude memory regions for the
2984 Ranges are in pairs (memory base and size).
2986 ports= [IP_VS_FTP] IPVS ftp helper module
2988 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2990 Format: <port>,<port>....
2992 print-fatal-signals=
2993 [KNL] debug: print fatal signals
2995 If enabled, warn about various signal handling
2996 related application anomalies: too many signals,
2997 too many POSIX.1 timers, fatal signals causing a
3000 If you hit the warning due to signal overflow,
3001 you might want to try "ulimit -i unlimited".
3005 printk.always_kmsg_dump=
3006 Trigger kmsg_dump for cases other than kernel oops or
3008 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3011 printk.time= Show timing data prefixed to each printk message line
3012 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3014 processor.max_cstate= [HW,ACPI]
3015 Limit processor to maximum C-state
3016 max_cstate=9 overrides any DMI blacklist limit.
3018 processor.nocst [HW,ACPI]
3019 Ignore the _CST method to determine C-states,
3020 instead using the legacy FADT method
3022 profile= [KNL] Enable kernel profiling via /proc/profile
3023 Format: [schedule,]<number>
3024 Param: "schedule" - profile schedule points.
3025 Param: <number> - step/bucket size as a power of 2 for
3026 statistical time based profiling.
3027 Param: "sleep" - profile D-state sleeping (millisecs).
3028 Requires CONFIG_SCHEDSTATS
3029 Param: "kvm" - profile VM exits.
3031 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3033 See Documentation/blockdev/ramdisk.txt.
3035 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3036 probe for; one of (bare|imps|exps|lifebook|any).
3037 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3039 psmouse.resetafter= [HW,MOUSE]
3040 Try to reset the device after so many bad packets
3043 [HW,MOUSE] Set desired mouse resolution, in dpi.
3044 psmouse.smartscroll=
3045 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3046 0 = disabled, 1 = enabled (default).
3048 pstore.backend= Specify the name of the pstore backend to use
3051 See Documentation/blockdev/paride.txt.
3054 [KNL] Number of legacy pty's. Overwrites compiled-in
3057 quiet [KNL] Disable most log messages
3062 See Documentation/md.txt.
3064 ramdisk_blocksize= [RAM]
3065 See Documentation/blockdev/ramdisk.txt.
3067 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3068 See Documentation/blockdev/ramdisk.txt.
3071 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3072 the specified list of CPUs to be no-callback CPUs.
3073 Invocation of these CPUs' RCU callbacks will
3074 be offloaded to "rcuox/N" kthreads created for
3075 that purpose, where "x" is "b" for RCU-bh, "p"
3076 for RCU-preempt, and "s" for RCU-sched, and "N"
3077 is the CPU number. This reduces OS jitter on the
3078 offloaded CPUs, which can be useful for HPC and
3079 real-time workloads. It can also improve energy
3080 efficiency for asymmetric multiprocessors.
3083 Rather than requiring that offloaded CPUs
3084 (specified by rcu_nocbs= above) explicitly
3085 awaken the corresponding "rcuoN" kthreads,
3086 make these kthreads poll for callbacks.
3087 This improves the real-time response for the
3088 offloaded CPUs by relieving them of the need to
3089 wake up the corresponding kthread, but degrades
3090 energy efficiency by requiring that the kthreads
3091 periodically wake up to do the polling.
3093 rcutree.blimit= [KNL]
3094 Set maximum number of finished RCU callbacks to
3095 process in one batch.
3097 rcutree.dump_tree= [KNL]
3098 Dump the structure of the rcu_node combining tree
3099 out at early boot. This is used for diagnostic
3100 purposes, to verify correct tree setup.
3102 rcutree.gp_cleanup_delay= [KNL]
3103 Set the number of jiffies to delay each step of
3104 RCU grace-period cleanup. This only has effect
3105 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3107 rcutree.gp_init_delay= [KNL]
3108 Set the number of jiffies to delay each step of
3109 RCU grace-period initialization. This only has
3110 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3113 rcutree.gp_preinit_delay= [KNL]
3114 Set the number of jiffies to delay each step of
3115 RCU grace-period pre-initialization, that is,
3116 the propagation of recent CPU-hotplug changes up
3117 the rcu_node combining tree. This only has effect
3118 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3120 rcutree.rcu_fanout_exact= [KNL]
3121 Disable autobalancing of the rcu_node combining
3122 tree. This is used by rcutorture, and might
3123 possibly be useful for architectures having high
3124 cache-to-cache transfer latencies.
3126 rcutree.rcu_fanout_leaf= [KNL]
3127 Change the number of CPUs assigned to each
3128 leaf rcu_node structure. Useful for very
3129 large systems, which will choose the value 64,
3130 and for NUMA systems with large remote-access
3131 latencies, which will choose a value aligned
3132 with the appropriate hardware boundaries.
3134 rcutree.jiffies_till_sched_qs= [KNL]
3135 Set required age in jiffies for a
3136 given grace period before RCU starts
3137 soliciting quiescent-state help from
3138 rcu_note_context_switch().
3140 rcutree.jiffies_till_first_fqs= [KNL]
3141 Set delay from grace-period initialization to
3142 first attempt to force quiescent states.
3143 Units are jiffies, minimum value is zero,
3144 and maximum value is HZ.
3146 rcutree.jiffies_till_next_fqs= [KNL]
3147 Set delay between subsequent attempts to force
3148 quiescent states. Units are jiffies, minimum
3149 value is one, and maximum value is HZ.
3151 rcutree.kthread_prio= [KNL,BOOT]
3152 Set the SCHED_FIFO priority of the RCU per-CPU
3153 kthreads (rcuc/N). This value is also used for
3154 the priority of the RCU boost threads (rcub/N)
3155 and for the RCU grace-period kthreads (rcu_bh,
3156 rcu_preempt, and rcu_sched). If RCU_BOOST is
3157 set, valid values are 1-99 and the default is 1
3158 (the least-favored priority). Otherwise, when
3159 RCU_BOOST is not set, valid values are 0-99 and
3160 the default is zero (non-realtime operation).
3162 rcutree.rcu_nocb_leader_stride= [KNL]
3163 Set the number of NOCB kthread groups, which
3164 defaults to the square root of the number of
3165 CPUs. Larger numbers reduces the wakeup overhead
3166 on the per-CPU grace-period kthreads, but increases
3167 that same overhead on each group's leader.
3169 rcutree.qhimark= [KNL]
3170 Set threshold of queued RCU callbacks beyond which
3171 batch limiting is disabled.
3173 rcutree.qlowmark= [KNL]
3174 Set threshold of queued RCU callbacks below which
3175 batch limiting is re-enabled.
3177 rcutree.rcu_idle_gp_delay= [KNL]
3178 Set wakeup interval for idle CPUs that have
3179 RCU callbacks (RCU_FAST_NO_HZ=y).
3181 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3182 Set wakeup interval for idle CPUs that have
3183 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3184 Lazy RCU callbacks are those which RCU can
3185 prove do nothing more than free memory.
3187 rcutorture.cbflood_inter_holdoff= [KNL]
3188 Set holdoff time (jiffies) between successive
3189 callback-flood tests.
3191 rcutorture.cbflood_intra_holdoff= [KNL]
3192 Set holdoff time (jiffies) between successive
3193 bursts of callbacks within a given callback-flood
3196 rcutorture.cbflood_n_burst= [KNL]
3197 Set the number of bursts making up a given
3198 callback-flood test. Set this to zero to
3199 disable callback-flood testing.
3201 rcutorture.cbflood_n_per_burst= [KNL]
3202 Set the number of callbacks to be registered
3203 in a given burst of a callback-flood test.
3205 rcutorture.fqs_duration= [KNL]
3206 Set duration of force_quiescent_state bursts
3209 rcutorture.fqs_holdoff= [KNL]
3210 Set holdoff time within force_quiescent_state bursts
3213 rcutorture.fqs_stutter= [KNL]
3214 Set wait time between force_quiescent_state bursts
3217 rcutorture.gp_cond= [KNL]
3218 Use conditional/asynchronous update-side
3219 primitives, if available.
3221 rcutorture.gp_exp= [KNL]
3222 Use expedited update-side primitives, if available.
3224 rcutorture.gp_normal= [KNL]
3225 Use normal (non-expedited) asynchronous
3226 update-side primitives, if available.
3228 rcutorture.gp_sync= [KNL]
3229 Use normal (non-expedited) synchronous
3230 update-side primitives, if available. If all
3231 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3232 rcutorture.gp_normal=, and rcutorture.gp_sync=
3233 are zero, rcutorture acts as if is interpreted
3234 they are all non-zero.
3236 rcutorture.n_barrier_cbs= [KNL]
3237 Set callbacks/threads for rcu_barrier() testing.
3239 rcutorture.nfakewriters= [KNL]
3240 Set number of concurrent RCU writers. These just
3241 stress RCU, they don't participate in the actual
3242 test, hence the "fake".
3244 rcutorture.nreaders= [KNL]
3245 Set number of RCU readers. The value -1 selects
3246 N-1, where N is the number of CPUs. A value
3247 "n" less than -1 selects N-n-2, where N is again
3248 the number of CPUs. For example, -2 selects N
3249 (the number of CPUs), -3 selects N+1, and so on.
3251 rcutorture.object_debug= [KNL]
3252 Enable debug-object double-call_rcu() testing.
3254 rcutorture.onoff_holdoff= [KNL]
3255 Set time (s) after boot for CPU-hotplug testing.
3257 rcutorture.onoff_interval= [KNL]
3258 Set time (s) between CPU-hotplug operations, or
3259 zero to disable CPU-hotplug testing.
3261 rcutorture.shuffle_interval= [KNL]
3262 Set task-shuffle interval (s). Shuffling tasks
3263 allows some CPUs to go into dyntick-idle mode
3264 during the rcutorture test.
3266 rcutorture.shutdown_secs= [KNL]
3267 Set time (s) after boot system shutdown. This
3268 is useful for hands-off automated testing.
3270 rcutorture.stall_cpu= [KNL]
3271 Duration of CPU stall (s) to test RCU CPU stall
3272 warnings, zero to disable.
3274 rcutorture.stall_cpu_holdoff= [KNL]
3275 Time to wait (s) after boot before inducing stall.
3277 rcutorture.stat_interval= [KNL]
3278 Time (s) between statistics printk()s.
3280 rcutorture.stutter= [KNL]
3281 Time (s) to stutter testing, for example, specifying
3282 five seconds causes the test to run for five seconds,
3283 wait for five seconds, and so on. This tests RCU's
3284 ability to transition abruptly to and from idle.
3286 rcutorture.test_boost= [KNL]
3287 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3288 "Maybe" means test if the RCU implementation
3289 under test support RCU priority boosting.
3291 rcutorture.test_boost_duration= [KNL]
3292 Duration (s) of each individual boost test.
3294 rcutorture.test_boost_interval= [KNL]
3295 Interval (s) between each boost test.
3297 rcutorture.test_no_idle_hz= [KNL]
3298 Test RCU's dyntick-idle handling. See also the
3299 rcutorture.shuffle_interval parameter.
3301 rcutorture.torture_runnable= [BOOT]
3302 Start rcutorture running at boot time.
3304 rcutorture.torture_type= [KNL]
3305 Specify the RCU implementation to test.
3307 rcutorture.verbose= [KNL]
3308 Enable additional printk() statements.
3310 rcupdate.rcu_cpu_stall_suppress= [KNL]
3311 Suppress RCU CPU stall warning messages.
3313 rcupdate.rcu_cpu_stall_timeout= [KNL]
3314 Set timeout for RCU CPU stall warning messages.
3316 rcupdate.rcu_expedited= [KNL]
3317 Use expedited grace-period primitives, for
3318 example, synchronize_rcu_expedited() instead
3319 of synchronize_rcu(). This reduces latency,
3320 but can increase CPU utilization, degrade
3321 real-time latency, and degrade energy efficiency.
3322 No effect on CONFIG_TINY_RCU kernels.
3324 rcupdate.rcu_normal= [KNL]
3325 Use only normal grace-period primitives,
3326 for example, synchronize_rcu() instead of
3327 synchronize_rcu_expedited(). This improves
3328 real-time latency, CPU utilization, and
3329 energy efficiency, but can expose users to
3330 increased grace-period latency. This parameter
3331 overrides rcupdate.rcu_expedited. No effect on
3332 CONFIG_TINY_RCU kernels.
3334 rcupdate.rcu_normal_after_boot= [KNL]
3335 Once boot has completed (that is, after
3336 rcu_end_inkernel_boot() has been invoked), use
3337 only normal grace-period primitives. No effect
3338 on CONFIG_TINY_RCU kernels.
3340 rcupdate.rcu_task_stall_timeout= [KNL]
3341 Set timeout in jiffies for RCU task stall warning
3342 messages. Disable with a value less than or equal
3345 rcupdate.rcu_self_test= [KNL]
3346 Run the RCU early boot self tests
3348 rcupdate.rcu_self_test_bh= [KNL]
3349 Run the RCU bh early boot self tests
3351 rcupdate.rcu_self_test_sched= [KNL]
3352 Run the RCU sched early boot self tests
3356 Run specified binary instead of /init from the ramdisk,
3357 used for early userspace startup. See initrd.
3360 Format (x86 or x86_64):
3361 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3363 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3365 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3366 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3367 reboot_force is either force or not specified,
3368 reboot_cpu is s[mp]#### with #### being the processor
3369 to be used for rebooting.
3372 [KNL, SMP] Set scheduler's default relax_domain_level.
3373 See Documentation/cgroups/cpusets.txt.
3375 relative_sleep_states=
3376 [SUSPEND] Use sleep state labeling where the deepest
3377 state available other than hibernation is always "mem".
3378 Format: { "0" | "1" }
3379 0 -- Traditional sleep state labels.
3380 1 -- Relative sleep state labels.
3382 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3384 reservetop= [X86-32]
3386 Reserves a hole at the top of the kernel virtual
3391 Set the amount of memory to reserve for BIOS at
3392 the bottom of the address space.
3394 reset_devices [KNL] Force drivers to reset the underlying device
3395 during initialization.
3398 Specify the partition device for software suspend
3400 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3402 resume_offset= [SWSUSP]
3403 Specify the offset from the beginning of the partition
3404 given by "resume=" at which the swap header is located,
3405 in <PAGE_SIZE> units (needed only for swap files).
3406 See Documentation/power/swsusp-and-swap-files.txt
3408 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3409 read the resume files
3411 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3412 Useful for devices that are detected asynchronously
3413 (e.g. USB and MMC devices).
3415 hibernate= [HIBERNATION]
3416 noresume Don't check if there's a hibernation image
3417 present during boot.
3418 nocompress Don't compress/decompress hibernation images.
3419 no Disable hibernation and resume.
3421 retain_initrd [RAM] Keep initrd memory after extraction
3423 rfkill.default_state=
3424 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3425 etc. communication is blocked by default.
3428 rfkill.master_switch_mode=
3429 0 The "airplane mode" button does nothing.
3430 1 The "airplane mode" button toggles between everything
3431 blocked and the previous configuration.
3432 2 The "airplane mode" button toggles between everything
3433 blocked and everything unblocked.
3435 rhash_entries= [KNL,NET]
3436 Set number of hash buckets for route cache
3438 ro [KNL] Mount root device read-only on boot
3440 root= [KNL] Root filesystem
3441 See name_to_dev_t comment in init/do_mounts.c.
3443 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3444 mount the root filesystem
3446 rootflags= [KNL] Set root filesystem mount option string
3448 rootfstype= [KNL] Set root filesystem type
3450 rootwait [KNL] Wait (indefinitely) for root device to show up.
3451 Useful for devices that are detected asynchronously
3452 (e.g. USB and MMC devices).
3454 rproc_mem=nn[KMG][@address]
3455 [KNL,ARM,CMA] Remoteproc physical memory block.
3456 Memory area to be used by remote processor image,
3459 rw [KNL] Mount root device read-write on boot
3461 S [KNL] Run init in single mode
3463 s390_iommu= [HW,S390]
3464 Set s390 IOTLB flushing mode
3466 With strict flushing every unmap operation will result in
3467 an IOTLB flush. Default is lazy flushing before reuse,
3471 See drivers/net/irda/sa1100_ir.c.
3473 sbni= [NET] Granch SBNI12 leased line adapter
3475 sched_debug [KNL] Enables verbose scheduler debug messages.
3477 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3478 xtime_lock contention on larger systems, and/or RCU lock
3479 contention on all systems with CONFIG_MAXSMP set.
3480 Format: { "0" | "1" }
3481 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3483 Note: increases power consumption, thus should only be
3484 enabled if running jitter sensitive (HPC/RT) workloads.
3486 security= [SECURITY] Choose a security module to enable at boot.
3487 If this boot parameter is not specified, only the first
3488 security module asking for security registration will be
3489 loaded. An invalid security module name will be treated
3490 as if no module has been chosen.
3492 selinux= [SELINUX] Disable or enable SELinux at boot time.
3493 Format: { "0" | "1" }
3494 See security/selinux/Kconfig help text.
3497 Default value is set via kernel config option.
3498 If enabled at boot time, /selinux/disable can be used
3499 later to disable prior to initial policy load.
3501 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3502 Format: { "0" | "1" }
3503 See security/apparmor/Kconfig help text
3506 Default value is set via kernel config option.
3508 serialnumber [BUGS=X86-32]
3511 Maximal number of shapers.
3513 show_msr= [x86] show boot-time MSR settings
3514 Format: { <integer> }
3515 Show boot-time (BIOS-initialized) MSR settings.
3516 The parameter means the number of CPUs to show,
3517 for example 1 means boot CPU only.
3525 Disable merging of slabs with similar size. May be
3526 necessary if there is some reason to distinguish
3527 allocs to different slabs. Debug options disable
3528 merging on their own.
3529 For more information see Documentation/vm/slub.txt.
3531 slab_max_order= [MM, SLAB]
3532 Determines the maximum allowed order for slabs.
3533 A high setting may cause OOMs due to memory
3534 fragmentation. Defaults to 1 for systems with
3535 more than 32MB of RAM, 0 otherwise.
3537 slub_debug[=options[,slabs]] [MM, SLUB]
3538 Enabling slub_debug allows one to determine the
3539 culprit if slab objects become corrupted. Enabling
3540 slub_debug can create guard zones around objects and
3541 may poison objects when not in use. Also tracks the
3542 last alloc / free. For more information see
3543 Documentation/vm/slub.txt.
3545 slub_max_order= [MM, SLUB]
3546 Determines the maximum allowed order for slabs.
3547 A high setting may cause OOMs due to memory
3548 fragmentation. For more information see
3549 Documentation/vm/slub.txt.
3551 slub_min_objects= [MM, SLUB]
3552 The minimum number of objects per slab. SLUB will
3553 increase the slab order up to slub_max_order to
3554 generate a sufficiently large slab able to contain
3555 the number of objects indicated. The higher the number
3556 of objects the smaller the overhead of tracking slabs
3557 and the less frequently locks need to be acquired.
3558 For more information see Documentation/vm/slub.txt.
3560 slub_min_order= [MM, SLUB]
3561 Determines the minimum page order for slabs. Must be
3562 lower than slub_max_order.
3563 For more information see Documentation/vm/slub.txt.
3565 slub_nomerge [MM, SLUB]
3566 Same with slab_nomerge. This is supported for legacy.
3567 See slab_nomerge for more information.
3570 Format: <io1>[,<io2>[,...,<io8>]]
3572 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3573 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3574 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3575 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3576 smsc-ircc2.ircc_irq= [HW] IRQ line
3577 smsc-ircc2.ircc_dma= [HW] DMA channel
3578 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3579 0: Toshiba Satellite 1800 (GP data pin select)
3580 1: Fast pin select (default)
3584 [KNL] Should the soft-lockup detector generate panics.
3587 softlockup_all_cpu_backtrace=
3588 [KNL] Should the soft-lockup detector generate
3589 backtraces on all cpus.
3592 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3593 See Documentation/laptops/sonypi.txt
3595 spia_io_base= [HW,MTD]
3601 Enabled the stack tracer on boot up.
3603 stacktrace_filter=[function-list]
3604 [FTRACE] Limit the functions that the stack tracer
3605 will trace at boot up. function-list is a comma separated
3606 list of functions. This list can be changed at run
3607 time by the stack_trace_filter file in the debugfs
3608 tracing directory. Note, this enables stack tracing
3609 and the stacktrace above is not needed.
3613 Set the STI (builtin display/keyboard on the HP-PARISC
3614 machines) console (graphic card) which should be used
3615 as the initial boot-console.
3616 See also comment in drivers/video/console/sticore.c.
3619 See comment in drivers/video/console/sticore.c.
3622 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3624 sunrpc.min_resvport=
3625 sunrpc.max_resvport=
3627 SunRPC servers often require that client requests
3628 originate from a privileged port (i.e. a port in the
3629 range 0 < portnr < 1024).
3630 An administrator who wishes to reserve some of these
3631 ports for other uses may adjust the range that the
3632 kernel's sunrpc client considers to be privileged
3633 using these two parameters to set the minimum and
3634 maximum port values.
3638 Control how the NFS server code allocates CPUs to
3639 service thread pools. Depending on how many NICs
3640 you have and where their interrupts are bound, this
3641 option will affect which CPUs will do NFS serving.
3642 Note: this parameter cannot be changed while the
3643 NFS server is running.
3645 auto the server chooses an appropriate mode
3646 automatically using heuristics
3647 global a single global pool contains all CPUs
3648 percpu one pool for each CPU
3649 pernode one pool for each NUMA node (equivalent
3650 to global on non-NUMA machines)
3652 sunrpc.tcp_slot_table_entries=
3653 sunrpc.udp_slot_table_entries=
3655 Sets the upper limit on the number of simultaneous
3656 RPC calls that can be sent from the client to a
3657 server. Increasing these values may allow you to
3658 improve throughput, but will also increase the
3659 amount of memory reserved for use by the client.
3661 suspend.pm_test_delay=
3663 Sets the number of seconds to remain in a suspend test
3664 mode before resuming the system (see
3665 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3666 is set. Default value is 5.
3669 [KNL] Enable accounting of swap in memory resource
3670 controller if no parameter or 1 is given or disable
3671 it if 0 is given (See Documentation/cgroups/memory.txt)
3673 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3674 Format: { <int> | force }
3675 <int> -- Number of I/O TLB slabs
3676 force -- force using of bounce buffers even if they
3677 wouldn't be automatically used by the kernel
3681 sysfs.deprecated=0|1 [KNL]
3682 Enable/disable old style sysfs layout for old udev
3683 on older distributions. When this option is enabled
3684 very new udev will not work anymore. When this option
3685 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3686 in older udev will not work anymore.
3687 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3688 the kernel configuration.
3690 sysrq_always_enabled
3692 Ignore sysrq setting - this boot parameter will
3693 neutralize any effect of /proc/sys/kernel/sysrq.
3694 Useful for debugging.
3696 tcpmhash_entries= [KNL,NET]
3697 Set the number of tcp_metrics_hash slots.
3698 Default value is 8192 or 16384 depending on total
3699 ram pages. This is used to specify the TCP metrics
3700 cache size. See Documentation/networking/ip-sysctl.txt
3701 "tcp_no_metrics_save" section for more details.
3705 test_suspend= [SUSPEND][,N]
3706 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3707 standby suspend) or "freeze" (for suspend type freeze)
3708 as the system sleep state during system startup with
3709 the optional capability to repeat N number of times.
3710 The system is woken from this state using a
3711 wakeup-capable RTC alarm.
3713 thash_entries= [KNL,NET]
3714 Set number of hash buckets for TCP connection
3716 thermal.act= [HW,ACPI]
3717 -1: disable all active trip points in all thermal zones
3718 <degrees C>: override all lowest active trip points
3720 thermal.crt= [HW,ACPI]
3721 -1: disable all critical trip points in all thermal zones
3722 <degrees C>: override all critical trip points
3724 thermal.nocrt= [HW,ACPI]
3725 Set to disable actions on ACPI thermal zone
3726 critical and hot trip points.
3728 thermal.off= [HW,ACPI]
3729 1: disable ACPI thermal control
3731 thermal.psv= [HW,ACPI]
3732 -1: disable all passive trip points
3733 <degrees C>: override all passive trip points to this
3736 thermal.tzp= [HW,ACPI]
3737 Specify global default ACPI thermal zone polling rate
3738 <deci-seconds>: poll all this frequency
3739 0: no polling (default)
3742 Force threading of all interrupt handlers except those
3743 marked explicitly IRQF_NO_THREAD.
3746 Enable the Transcendent memory driver if built-in.
3748 tmem.cleancache=0|1 [KNL, XEN]
3749 Default is on (1). Disable the usage of the cleancache
3750 API to send anonymous pages to the hypervisor.
3752 tmem.frontswap=0|1 [KNL, XEN]
3753 Default is on (1). Disable the usage of the frontswap
3754 API to send swap pages to the hypervisor. If disabled
3755 the selfballooning and selfshrinking are force disabled.
3757 tmem.selfballooning=0|1 [KNL, XEN]
3758 Default is on (1). Disable the driving of swap pages
3761 tmem.selfshrinking=0|1 [KNL, XEN]
3762 Default is on (1). Partial swapoff that immediately
3763 transfers pages from Xen hypervisor back to the
3764 kernel based on different criteria.
3768 Specify if the kernel should make use of the cpu
3769 topology information if the hardware supports this.
3770 The scheduler will make use of this information and
3771 e.g. base its process migration decisions on it.
3774 topology_updates= [KNL, PPC, NUMA]
3776 Specify if the kernel should ignore (off)
3777 topology updates sent by the hypervisor to this
3782 tpm_suspend_pcr=[HW,TPM]
3783 Format: integer pcr id
3784 Specify that at suspend time, the tpm driver
3785 should extend the specified pcr with zeros,
3786 as a workaround for some chips which fail to
3787 flush the last written pcr on TPM_SaveState.
3788 This will guarantee that all the other pcrs
3791 trace_buf_size=nn[KMG]
3792 [FTRACE] will set tracing buffer size on each cpu.
3794 trace_event=[event-list]
3795 [FTRACE] Set and start specified trace events in order
3796 to facilitate early boot debugging.
3797 See also Documentation/trace/events.txt
3799 trace_options=[option-list]
3800 [FTRACE] Enable or disable tracer options at boot.
3801 The option-list is a comma delimited list of options
3802 that can be enabled or disabled just as if you were
3803 to echo the option name into
3805 /sys/kernel/debug/tracing/trace_options
3807 For example, to enable stacktrace option (to dump the
3808 stack trace of each event), add to the command line:
3810 trace_options=stacktrace
3812 See also Documentation/trace/ftrace.txt "trace options"
3816 Have the tracepoints sent to printk as well as the
3817 tracing ring buffer. This is useful for early boot up
3818 where the system hangs or reboots and does not give the
3819 option for reading the tracing buffer or performing a
3820 ftrace_dump_on_oops.
3822 To turn off having tracepoints sent to printk,
3823 echo 0 > /proc/sys/kernel/tracepoint_printk
3824 Note, echoing 1 into this file without the
3825 tracepoint_printk kernel cmdline option has no effect.
3829 Having tracepoints sent to printk() and activating high
3830 frequency tracepoints such as irq or sched, can cause
3831 the system to live lock.
3834 [FTRACE] enable this option to disable tracing when a
3835 warning is hit. This turns off "tracing_on". Tracing can
3836 be enabled again by echoing '1' into the "tracing_on"
3837 file located in /sys/kernel/debug/tracing/
3839 This option is useful, as it disables the trace before
3840 the WARNING dump is called, which prevents the trace to
3841 be filled with content caused by the warning output.
3843 This option can also be set at run time via the sysctl
3844 option: kernel/traceoff_on_warning
3846 transparent_hugepage=
3848 Format: [always|madvise|never]
3849 Can be used to control the default behavior of the system
3850 with respect to transparent hugepages.
3851 See Documentation/vm/transhuge.txt for more details.
3853 tsc= Disable clocksource stability checks for TSC.
3855 [x86] reliable: mark tsc clocksource as reliable, this
3856 disables clocksource verification at runtime, as well
3857 as the stability checks done at bootup. Used to enable
3858 high-resolution timer mode on older hardware, and in
3859 virtualized environment.
3860 [x86] noirqtime: Do not use TSC to do irq accounting.
3861 Used to run time disable IRQ_TIME_ACCOUNTING on any
3862 platforms where RDTSC is slow and this accounting
3865 turbografx.map[2|3]= [HW,JOY]
3866 TurboGraFX parallel port interface
3868 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3869 See also Documentation/input/joystick-parport.txt
3871 udbg-immortal [PPC] When debugging early kernel crashes that
3872 happen after console_init() and before a proper
3873 console driver takes over, this boot options might
3874 help "seeing" what's going on.
3876 uhash_entries= [KNL,NET]
3877 Set number of hash buckets for UDP/UDP-Lite connections
3880 [USB] Ignore overcurrent events (default N).
3881 Some badly-designed motherboards generate lots of
3882 bogus events, for ports that aren't wired to
3883 anything. Set this parameter to avoid log spamming.
3884 Note that genuine overcurrent events won't be
3888 [X86] Cause panic on unknown NMI.
3890 usbcore.authorized_default=
3891 [USB] Default USB device authorization:
3892 (default -1 = authorized except for wireless USB,
3893 0 = not authorized, 1 = authorized)
3895 usbcore.autosuspend=
3896 [USB] The autosuspend time delay (in seconds) used
3897 for newly-detected USB devices (default 2). This
3898 is the time required before an idle device will be
3899 autosuspended. Devices for which the delay is set
3900 to a negative value won't be autosuspended at all.
3902 usbcore.usbfs_snoop=
3903 [USB] Set to log all usbfs traffic (default 0 = off).
3905 usbcore.usbfs_snoop_max=
3906 [USB] Maximum number of bytes to snoop in each URB
3909 usbcore.blinkenlights=
3910 [USB] Set to cycle leds on hubs (default 0 = off).
3912 usbcore.old_scheme_first=
3913 [USB] Start with the old device initialization
3914 scheme (default 0 = off).
3916 usbcore.usbfs_memory_mb=
3917 [USB] Memory limit (in MB) for buffers allocated by
3918 usbfs (default = 16, 0 = max = 2047).
3920 usbcore.use_both_schemes=
3921 [USB] Try the other device initialization scheme
3922 if the first one fails (default 1 = enabled).
3924 usbcore.initial_descriptor_timeout=
3925 [USB] Specifies timeout for the initial 64-byte
3926 USB_REQ_GET_DESCRIPTOR request in milliseconds
3927 (default 5000 = 5.0 seconds).
3929 usbcore.nousb [USB] Disable the USB subsystem
3932 [USBHID] The interval which mice are to be polled at.
3934 usb-storage.delay_use=
3935 [UMS] The delay in seconds before a new device is
3936 scanned for Logical Units (default 1).
3939 [UMS] A list of quirks entries to supplement or
3940 override the built-in unusual_devs list. List
3941 entries are separated by commas. Each entry has
3942 the form VID:PID:Flags where VID and PID are Vendor
3943 and Product ID values (4-digit hex numbers) and
3944 Flags is a set of characters, each corresponding
3945 to a common usb-storage quirk flag as follows:
3946 a = SANE_SENSE (collect more than 18 bytes
3948 b = BAD_SENSE (don't collect more than 18
3949 bytes of sense data);
3950 c = FIX_CAPACITY (decrease the reported
3951 device capacity by one sector);
3952 d = NO_READ_DISC_INFO (don't use
3953 READ_DISC_INFO command);
3954 e = NO_READ_CAPACITY_16 (don't use
3955 READ_CAPACITY_16 command);
3956 f = NO_REPORT_OPCODES (don't use report opcodes
3958 g = MAX_SECTORS_240 (don't transfer more than
3959 240 sectors at a time, uas only);
3960 h = CAPACITY_HEURISTICS (decrease the
3961 reported device capacity by one
3962 sector if the number is odd);
3963 i = IGNORE_DEVICE (don't bind to this
3965 l = NOT_LOCKABLE (don't try to lock and
3966 unlock ejectable media);
3967 m = MAX_SECTORS_64 (don't transfer more
3968 than 64 sectors = 32 KB at a time);
3969 n = INITIAL_READ10 (force a retry of the
3970 initial READ(10) command);
3971 o = CAPACITY_OK (accept the capacity
3972 reported by the device);
3973 p = WRITE_CACHE (the device cache is ON
3975 r = IGNORE_RESIDUE (the device reports
3976 bogus residue values);
3977 s = SINGLE_LUN (the device has only one
3979 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3980 commands, uas only);
3981 u = IGNORE_UAS (don't bind to the uas driver);
3982 w = NO_WP_DETECT (don't test whether the
3983 medium is write-protected).
3984 Example: quirks=0419:aaf5:rl,0421:0433:rc
3986 user_debug= [KNL,ARM]
3988 See arch/arm/Kconfig.debug help text.
3989 1 - undefined instruction events
3991 4 - invalid data aborts
3994 Example: user_debug=31
3997 [X86] Flags controlling user PTE allocations.
3999 nohigh = do not allocate PTE pages in
4000 HIGHMEM regardless of setting
4004 On X86_32, this is an alias for vdso32=. Otherwise:
4006 vdso=1: enable VDSO (the default)
4007 vdso=0: disable VDSO mapping
4009 vdso32= [X86] Control the 32-bit vDSO
4010 vdso32=1: enable 32-bit VDSO
4011 vdso32=0 or vdso32=2: disable 32-bit VDSO
4013 See the help text for CONFIG_COMPAT_VDSO for more
4014 details. If CONFIG_COMPAT_VDSO is set, the default is
4015 vdso32=0; otherwise, the default is vdso32=1.
4017 For compatibility with older kernels, vdso32=2 is an
4020 Try vdso32=0 if you encounter an error that says:
4021 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4024 vector=percpu: enable percpu vector domain
4026 video= [FB] Frame buffer configuration
4027 See Documentation/fb/modedb.txt.
4029 video.brightness_switch_enabled= [0,1]
4030 If set to 1, on receiving an ACPI notify event
4031 generated by hotkey, video driver will adjust brightness
4032 level and then send out the event to user space through
4033 the allocated input device; If set to 0, video driver
4034 will only send out the event without touching backlight
4039 [VMMIO] Memory mapped virtio (platform) device.
4041 <size>@<baseaddr>:<irq>[:<id>]
4043 <size> := size (can use standard suffixes
4045 <baseaddr> := physical base address
4046 <irq> := interrupt number (as passed to
4048 <id> := (optional) platform device id
4050 virtio_mmio.device=1K@0x100b0000:48:7
4052 Can be used multiple times for multiple devices.
4054 vga= [BOOT,X86-32] Select a particular video mode
4055 See Documentation/x86/boot.txt and
4056 Documentation/svga.txt.
4057 Use vga=ask for menu.
4058 This is actually a boot loader parameter; the value is
4059 passed to the kernel using a special protocol.
4061 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4062 size of <nn>. This can be used to increase the
4063 minimum size (128MB on x86). It can also be used to
4064 decrease the size and leave more room for directly
4067 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4070 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4073 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4077 Controls the behavior of vsyscalls (i.e. calls to
4078 fixed addresses of 0xffffffffff600x00 from legacy
4079 code). Most statically-linked binaries and older
4080 versions of glibc use these calls. Because these
4081 functions are at fixed addresses, they make nice
4082 targets for exploits that can control RIP.
4084 emulate [default] Vsyscalls turn into traps and are
4085 emulated reasonably safely.
4087 native Vsyscalls are native syscall instructions.
4088 This is a little bit faster than trapping
4089 and makes a few dynamic recompilers work
4090 better than they would in emulation mode.
4091 It also makes exploits much easier to write.
4093 none Vsyscalls don't work at all. This makes
4094 them quite hard to use for exploits but
4095 might break your system.
4097 vt.color= [VT] Default text color.
4098 Format: 0xYX, X = foreground, Y = background.
4099 Default: 0x07 = light gray on black.
4101 vt.cur_default= [VT] Default cursor shape.
4102 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4103 the parameters of the <Esc>[?A;B;Cc escape sequence;
4104 see VGA-softcursor.txt. Default: 2 = underline.
4106 vt.default_blu= [VT]
4107 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4108 Change the default blue palette of the console.
4109 This is a 16-member array composed of values
4112 vt.default_grn= [VT]
4113 Format: <green0>,<green1>,<green2>,...,<green15>
4114 Change the default green palette of the console.
4115 This is a 16-member array composed of values
4118 vt.default_red= [VT]
4119 Format: <red0>,<red1>,<red2>,...,<red15>
4120 Change the default red palette of the console.
4121 This is a 16-member array composed of values
4127 Set system-wide default UTF-8 mode for all tty's.
4128 Default is 1, i.e. UTF-8 mode is enabled for all
4129 newly opened terminals.
4131 vt.global_cursor_default=
4134 Set system-wide default for whether a cursor
4135 is shown on new VTs. Default is -1,
4136 i.e. cursors will be created by default unless
4137 overridden by individual drivers. 0 will hide
4138 cursors, 1 will display them.
4140 vt.italic= [VT] Default color for italic text; 0-15.
4143 vt.underline= [VT] Default color for underlined text; 0-15.
4146 watchdog timers [HW,WDT] For information on watchdog timers,
4147 see Documentation/watchdog/watchdog-parameters.txt
4148 or other driver-specific files in the
4149 Documentation/watchdog/ directory.
4151 workqueue.watchdog_thresh=
4152 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4153 warn stall conditions and dump internal state to
4154 help debugging. 0 disables workqueue stall
4155 detection; otherwise, it's the stall threshold
4156 duration in seconds. The default value is 30 and
4157 it can be updated at runtime by writing to the
4158 corresponding sysfs file.
4160 workqueue.disable_numa
4161 By default, all work items queued to unbound
4162 workqueues are affine to the NUMA nodes they're
4163 issued on, which results in better behavior in
4164 general. If NUMA affinity needs to be disabled for
4165 whatever reason, this option can be used. Note
4166 that this also can be controlled per-workqueue for
4167 workqueues visible under /sys/bus/workqueue/.
4169 workqueue.power_efficient
4170 Per-cpu workqueues are generally preferred because
4171 they show better performance thanks to cache
4172 locality; unfortunately, per-cpu workqueues tend to
4173 be more power hungry than unbound workqueues.
4175 Enabling this makes the per-cpu workqueues which
4176 were observed to contribute significantly to power
4177 consumption unbound, leading to measurably lower
4178 power usage at the cost of small performance
4181 The default value of this parameter is determined by
4182 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4184 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4185 default x2apic cluster mode on platforms
4188 x86_intel_mid_timer= [X86-32,APBT]
4189 Choose timer option for x86 Intel MID platform.
4190 Two valid options are apbt timer only and lapic timer
4191 plus one apbt timer for broadcast timer.
4192 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4194 xen_512gb_limit [KNL,X86-64,XEN]
4195 Restricts the kernel running paravirtualized under Xen
4196 to use only up to 512 GB of RAM. The reason to do so is
4197 crash analysis tools and Xen tools for doing domain
4198 save/restore/migration must be enabled to handle larger
4201 xen_emul_unplug= [HW,X86,XEN]
4202 Unplug Xen emulated devices
4203 Format: [unplug0,][unplug1]
4204 ide-disks -- unplug primary master IDE devices
4205 aux-ide-disks -- unplug non-primary-master IDE devices
4206 nics -- unplug network devices
4207 all -- unplug all emulated devices (NICs and IDE disks)
4208 unnecessary -- unplugging emulated devices is
4209 unnecessary even if the host did not respond to
4211 never -- do not unplug even if version check succeeds
4213 xen_nopvspin [X86,XEN]
4214 Disables the ticketlock slowpath using Xen PV
4218 Disables the PV optimizations forcing the HVM guest to
4219 run as generic HVM guest with no PV drivers.
4221 xirc2ps_cs= [NET,PCMCIA]
4223 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4225 ______________________________________________________________________
4229 Add more DRM drivers.
projects / cascardo / linux.git / blob