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 acpi_force_32bit_fadt_addr
197 force FADT to use 32 bit addresses rather than the
198 64 bit X_* addresses. Some firmware have broken 64
199 bit addresses for force ACPI ignore these and use
200 the older legacy 32 bit addresses.
202 acpica_no_return_repair [HW, ACPI]
203 Disable AML predefined validation mechanism
204 This mechanism can repair the evaluation result to make
205 the return objects more ACPI specification compliant.
206 This option is useful for developers to identify the
207 root cause of an AML interpreter issue when the issue
208 has something to do with the repair mechanism.
210 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
211 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
213 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
214 debug output. Bits in debug_layer correspond to a
215 _COMPONENT in an ACPI source file, e.g.,
216 #define _COMPONENT ACPI_PCI_COMPONENT
217 Bits in debug_level correspond to a level in
218 ACPI_DEBUG_PRINT statements, e.g.,
219 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
220 The debug_level mask defaults to "info". See
221 Documentation/acpi/debug.txt for more information about
222 debug layers and levels.
224 Enable processor driver info messages:
225 acpi.debug_layer=0x20000000
226 Enable PCI/PCI interrupt routing info messages:
227 acpi.debug_layer=0x400000
228 Enable AML "Debug" output, i.e., stores to the Debug
229 object while interpreting AML:
230 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
231 Enable all messages related to ACPI hardware:
232 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
234 Some values produce so much output that the system is
235 unusable. The "log_buf_len" parameter may be useful
236 if you need to capture more output.
238 acpi_enforce_resources= [ACPI]
239 { strict | lax | no }
240 Check for resource conflicts between native drivers
241 and ACPI OperationRegions (SystemIO and SystemMemory
242 only). IO ports and memory declared in ACPI might be
243 used by the ACPI subsystem in arbitrary AML code and
244 can interfere with legacy drivers.
245 strict (default): access to resources claimed by ACPI
246 is denied; legacy drivers trying to access reserved
247 resources will fail to bind to device using them.
248 lax: access to resources claimed by ACPI is allowed;
249 legacy drivers trying to access reserved resources
250 will bind successfully but a warning message is logged.
251 no: ACPI OperationRegions are not marked as reserved,
252 no further checks are performed.
254 acpi_force_table_verification [HW,ACPI]
255 Enable table checksum verification during early stage.
256 By default, this is disabled due to x86 early mapping
259 acpi_irq_balance [HW,ACPI]
260 ACPI will balance active IRQs
263 acpi_irq_nobalance [HW,ACPI]
264 ACPI will not move active IRQs (default)
267 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
268 Format: <irq>,<irq>...
270 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
272 Format: <irq>,<irq>...
274 acpi_no_auto_serialize [HW,ACPI]
275 Disable auto-serialization of AML methods
276 AML control methods that contain the opcodes to create
277 named objects will be marked as "Serialized" by the
278 auto-serialization feature.
279 This feature is enabled by default.
280 This option allows to turn off the feature.
282 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
285 acpi_no_static_ssdt [HW,ACPI]
286 Disable installation of static SSDTs at early boot time
287 By default, SSDTs contained in the RSDT/XSDT will be
288 installed automatically and they will appear under
289 /sys/firmware/acpi/tables.
290 This option turns off this feature.
291 Note that specifying this option does not affect
292 dynamic table installation which will install SSDT
293 tables to /sys/firmware/acpi/tables/dynamic.
295 acpi_rsdp= [ACPI,EFI,KEXEC]
296 Pass the RSDP address to the kernel, mostly used
297 on machines running EFI runtime service to boot the
298 second kernel for kdump.
300 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
301 Format: To spoof as Windows 98: ="Microsoft Windows"
303 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
304 of 2 which is mandated by ACPI 6) as the supported ACPI
305 specification revision (when using this switch, it may
306 be necessary to carry out a cold reboot _twice_ in a
307 row to make it take effect on the platform firmware).
309 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
310 acpi_osi="string1" # add string1
311 acpi_osi="!string2" # remove string2
312 acpi_osi=!* # remove all strings
313 acpi_osi=! # disable all built-in OS vendor
315 acpi_osi= # disable all strings
317 'acpi_osi=!' can be used in combination with single or
318 multiple 'acpi_osi="string1"' to support specific OS
319 vendor string(s). Note that such command can only
320 affect the default state of the OS vendor strings, thus
321 it cannot affect the default state of the feature group
322 strings and the current state of the OS vendor strings,
323 specifying it multiple times through kernel command line
324 is meaningless. This command is useful when one do not
325 care about the state of the feature group strings which
326 should be controlled by the OSPM.
328 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
329 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
330 can make '_OSI("Windows 2000")' TRUE.
332 'acpi_osi=' cannot be used in combination with other
333 'acpi_osi=' command lines, the _OSI method will not
334 exist in the ACPI namespace. NOTE that such command can
335 only affect the _OSI support state, thus specifying it
336 multiple times through kernel command line is also
339 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
342 'acpi_osi=!*' can be used in combination with single or
343 multiple 'acpi_osi="string1"' to support specific
344 string(s). Note that such command can affect the
345 current state of both the OS vendor strings and the
346 feature group strings, thus specifying it multiple times
347 through kernel command line is meaningful. But it may
348 still not able to affect the final state of a string if
349 there are quirks related to this string. This command
350 is useful when one want to control the state of the
351 feature group strings to debug BIOS issues related to
354 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
355 '_OSI("Module Device")' FALSE.
356 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
357 '_OSI("Module Device")' TRUE.
358 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
360 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
362 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
363 they all will make '_OSI("Windows 2000")' TRUE.
366 Override the pmtimer bug detection: force the kernel
367 to assume that this machine's pmtimer latches its value
368 and always returns good values.
370 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
371 Format: { level | edge | high | low }
373 acpi_skip_timer_override [HW,ACPI]
374 Recognize and ignore IRQ0/pin2 Interrupt Override.
375 For broken nForce2 BIOS resulting in XT-PIC timer.
377 acpi_sleep= [HW,ACPI] Sleep options
378 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
379 old_ordering, nonvs, sci_force_enable }
380 See Documentation/power/video.txt for information on
382 s3_beep is for debugging; it makes the PC's speaker beep
383 as soon as the kernel's real-mode entry point is called.
384 s4_nohwsig prevents ACPI hardware signature from being
385 used during resume from hibernation.
386 old_ordering causes the ACPI 1.0 ordering of the _PTS
387 control method, with respect to putting devices into
388 low power states, to be enforced (the ACPI 2.0 ordering
389 of _PTS is used by default).
390 nonvs prevents the kernel from saving/restoring the
391 ACPI NVS memory during suspend/hibernation and resume.
392 sci_force_enable causes the kernel to set SCI_EN directly
393 on resume from S1/S3 (which is against the ACPI spec,
394 but some broken systems don't work without it).
396 acpi_use_timer_override [HW,ACPI]
397 Use timer override. For some broken Nvidia NF5 boards
398 that require a timer override, but don't have HPET
400 add_efi_memmap [EFI; X86] Include EFI memory map in
401 kernel's map of available physical RAM.
404 { off | try_unsupported }
405 off: disable AGP support
406 try_unsupported: try to drive unsupported chipsets
407 (may crash computer or cause data corruption)
410 See Documentation/sound/alsa/alsa-parameters.txt
413 Allow the default userspace alignment fault handler
414 behaviour to be specified. Bit 0 enables warnings,
415 bit 1 enables fixups, and bit 2 sends a segfault.
417 align_va_addr= [X86-64]
418 Align virtual addresses by clearing slice [14:12] when
419 allocating a VMA at process creation time. This option
420 gives you up to 3% performance improvement on AMD F15h
421 machines (where it is enabled by default) for a
422 CPU-intensive style benchmark, and it can vary highly in
423 a microbenchmark depending on workload and compiler.
425 32: only for 32-bit processes
426 64: only for 64-bit processes
427 on: enable for both 32- and 64-bit processes
428 off: disable for both 32- and 64-bit processes
430 alloc_snapshot [FTRACE]
431 Allocate the ftrace snapshot buffer on boot up when the
432 main buffer is allocated. This is handy if debugging
433 and you need to use tracing_snapshot() on boot up, and
434 do not want to use tracing_snapshot_alloc() as it needs
435 to be done where GFP_KERNEL allocations are allowed.
437 amd_iommu= [HW,X86-64]
438 Pass parameters to the AMD IOMMU driver in the system.
440 fullflush - enable flushing of IO/TLB entries when
441 they are unmapped. Otherwise they are
442 flushed before they will be reused, which
444 off - do not initialize any AMD IOMMU found in
446 force_isolation - Force device isolation for all
447 devices. The IOMMU driver is not
448 allowed anymore to lift isolation
449 requirements as needed. This option
450 does not override iommu=pt
452 amd_iommu_dump= [HW,X86-64]
453 Enable AMD IOMMU driver option to dump the ACPI table
454 for AMD IOMMU. With this option enabled, AMD IOMMU
455 driver will print ACPI tables for AMD IOMMU during
456 IOMMU initialization.
458 amijoy.map= [HW,JOY] Amiga joystick support
459 Map of devices attached to JOY0DAT and JOY1DAT
461 See also Documentation/input/joystick.txt
463 analog.map= [HW,JOY] Analog joystick and gamepad support
464 Specifies type or capabilities of an analog joystick
465 connected to one of 16 gameports
466 Format: <type1>,<type2>,..<type16>
469 Power management functions (SPARCstation-4/5 + deriv.)
471 Disable APC CPU standby support. SPARCstation-Fox does
472 not play well with APC CPU idle - disable it if you have
473 APC and your system crashes randomly.
475 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
476 Change the output verbosity whilst booting
477 Format: { quiet (default) | verbose | debug }
478 Change the amount of debugging information output
479 when initialising the APIC and IO-APIC components.
481 apic_extnmi= [APIC,X86] External NMI delivery setting
482 Format: { bsp (default) | all | none }
483 bsp: External NMI is delivered only to CPU 0
484 all: External NMIs are broadcast to all CPUs as a
486 none: External NMI is masked for all CPUs. This is
487 useful so that a dump capture kernel won't be
491 See Documentation/networking/ipv6.txt.
493 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
494 Limit apic dumping. The parameter defines the maximal
495 number of local apics being dumped. Also it is possible
496 to set it to "all" by meaning -- no limit here.
497 Format: { 1 (default) | 2 | ... | all }.
498 The parameter valid if only apic=debug or
499 apic=verbose is specified.
500 Example: apic=debug show_lapic=all
502 apm= [APM] Advanced Power Management
503 See header of arch/x86/kernel/apm_32.c.
505 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
506 Format: <io>,<irq>,<nodeID>
510 atarimouse= [HW,MOUSE] Atari Mouse
512 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
513 EzKey and similar keyboards
515 atkbd.reset= [HW] Reset keyboard during initialization
517 atkbd.set= [HW] Select keyboard code set
518 Format: <int> (2 = AT (default), 3 = PS/2)
520 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
523 atkbd.softraw= [HW] Choose between synthetic and real raw mode
524 Format: <bool> (0 = real, 1 = synthetic (default))
526 atkbd.softrepeat= [HW]
527 Use software keyboard repeat
529 audit= [KNL] Enable the audit sub-system
530 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
531 0 - kernel audit is disabled and can not be enabled
532 until the next reboot
533 unset - kernel audit is initialized but disabled and
534 will be fully enabled by the userspace auditd.
535 1 - kernel audit is initialized and partially enabled,
536 storing at most audit_backlog_limit messages in
537 RAM until it is fully enabled by the userspace
541 audit_backlog_limit= [KNL] Set the audit queue size limit.
542 Format: <int> (must be >=0)
545 baycom_epp= [HW,AX25]
548 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
550 See header of drivers/net/hamradio/baycom_par.c.
552 baycom_ser_fdx= [HW,AX25]
553 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
554 Format: <io>,<irq>,<mode>[,<baud>]
555 See header of drivers/net/hamradio/baycom_ser_fdx.c.
557 baycom_ser_hdx= [HW,AX25]
558 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
559 Format: <io>,<irq>,<mode>
560 See header of drivers/net/hamradio/baycom_ser_hdx.c.
562 blkdevparts= Manual partition parsing of block device(s) for
563 embedded devices based on command line input.
564 See Documentation/block/cmdline-partition.txt
566 boot_delay= Milliseconds to delay each printk during boot.
567 Values larger than 10 seconds (10000) are changed to
571 bootmem_debug [KNL] Enable bootmem allocator debug messages.
573 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
574 bttv.radio= Most important insmod options are available as
576 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
579 bulk_remove=off [PPC] This parameter disables the use of the pSeries
580 firmware feature for flushing multiple hpte entries
583 c101= [NET] Moxa C101 synchronous serial card
585 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
586 Sometimes CPU hardware bugs make them report the cache
587 size incorrectly. The kernel will attempt work arounds
588 to fix known problems, but for some CPUs it is not
589 possible to determine what the correct size should be.
590 This option provides an override for these situations.
592 ca_keys= [KEYS] This parameter identifies a specific key(s) on
593 the system trusted keyring to be used for certificate
595 format: { id:<keyid> | builtin }
597 cca= [MIPS] Override the kernel pages' cache coherency
598 algorithm. Accepted values range from 0 to 7
599 inclusive. See arch/mips/include/asm/pgtable-bits.h
600 for platform specific values (SB1, Loongson3 and
603 ccw_timeout_log [S390]
604 See Documentation/s390/CommonIO for details.
606 cgroup_disable= [KNL] Disable a particular controller
607 Format: {name of the controller(s) to disable}
608 The effects of cgroup_disable=foo are:
609 - foo isn't auto-mounted if you mount all cgroups in
611 - foo isn't visible as an individually mountable
613 {Currently only "memory" controller deal with this and
614 cut the overhead, others just disable the usage. So
615 only cgroup_disable=memory is actually worthy}
617 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
618 Format: { controller[,controller...] | "all" }
619 Like cgroup_disable, but only applies to cgroup v1;
620 the blacklisted controllers remain available in cgroup2.
622 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
624 nosocket -- Disable socket memory accounting.
625 nokmem -- Disable kernel memory accounting.
627 checkreqprot [SELINUX] Set initial checkreqprot flag value.
628 Format: { "0" | "1" }
629 See security/selinux/Kconfig help text.
630 0 -- check protection applied by kernel (includes
631 any implied execute protection).
632 1 -- check protection requested by application.
633 Default value is set via a kernel config option.
634 Value can be changed at runtime via
635 /selinux/checkreqprot.
638 See Documentation/s390/CommonIO for details.
641 Prevents the clock framework from automatically gating
642 clocks that have not been explicitly enabled by a Linux
643 device driver but are enabled in hardware at reset or
644 by the bootloader/firmware. Note that this does not
645 force such clocks to be always-on nor does it reserve
646 those clocks in any way. This parameter is useful for
647 debug and development, but should not be needed on a
648 platform with proper driver support. For more
649 information, see Documentation/clk.txt.
651 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
653 Forces specified clocksource (if available) to be used
654 when calculating gettimeofday(). If specified
655 clocksource is not available, it defaults to PIT.
656 Format: { pit | tsc | cyclone | pmtmr }
658 clocksource= Override the default clocksource
660 Override the default clocksource and use the clocksource
661 with the name specified.
662 Some clocksource names to choose from, depending on
664 [all] jiffies (this is the base, fallback clocksource)
666 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
667 pxa_timer,timer3,32k_counter,timer0_1
669 [X86-32] pit,hpet,tsc;
670 scx200_hrt on Geode; cyclone on IBM x440
678 clearcpuid=BITNUM [X86]
679 Disable CPUID feature X for the kernel. See
680 arch/x86/include/asm/cpufeatures.h for the valid bit
681 numbers. Note the Linux specific bits are not necessarily
682 stable over kernel options, but the vendor specific
684 Also note that user programs calling CPUID directly
685 or using the feature without checking anything
686 will still see it. This just prevents it from
687 being used by the kernel or shown in /proc/cpuinfo.
688 Also note the kernel might malfunction if you disable
691 cma=nn[MG]@[start[MG][-end[MG]]]
693 Sets the size of kernel global memory area for
694 contiguous memory allocations and optionally the
695 placement constraint by the physical address range of
696 memory allocations. A value of 0 disables CMA
697 altogether. For more information, see
698 include/linux/dma-contiguous.h
700 cmo_free_hint= [PPC] Format: { yes | no }
701 Specify whether pages are marked as being inactive
702 when they are freed. This is used in CMO environments
703 to determine OS memory pressure for page stealing by
707 coherent_pool=nn[KMG] [ARM,KNL]
708 Sets the size of memory pool for coherent, atomic dma
709 allocations, by default set to 256K.
711 code_bytes [X86] How many bytes of object code to print
716 com20020= [HW,NET] ARCnet - COM20020 chipset
718 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
720 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
724 ARCnet - COM90xx chipset (memory-mapped buffers)
725 Format: <io>[,<irq>[,<memstart>]]
727 condev= [HW,S390] console device
730 console= [KNL] Output console device and options.
732 tty<n> Use the virtual console device <n>.
736 Use the specified serial port. The options are of
737 the form "bbbbpnf", where "bbbb" is the baud rate,
738 "p" is parity ("n", "o", or "e"), "n" is number of
739 bits, and "f" is flow control ("r" for RTS or
740 omit it). Default is "9600n8".
742 See Documentation/serial-console.txt for more
744 Documentation/networking/netconsole.txt for an
747 uart[8250],io,<addr>[,options]
748 uart[8250],mmio,<addr>[,options]
749 uart[8250],mmio16,<addr>[,options]
750 uart[8250],mmio32,<addr>[,options]
751 uart[8250],0x<addr>[,options]
752 Start an early, polled-mode console on the 8250/16550
753 UART at the specified I/O port or MMIO address,
754 switching to the matching ttyS device later.
755 MMIO inter-register address stride is either 8-bit
756 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
757 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
758 to be equivalent to 'mmio'. 'options' are specified in
759 the same format described for ttyS above; if unspecified,
760 the h/w is not re-initialized.
762 hvc<n> Use the hypervisor console device <n>. This is for
763 both Xen and PowerPC hypervisors.
765 If the device connected to the port is not a TTY but a braille
766 device, prepend "brl," before the device type, for instance
768 For now, only VisioBraille is supported.
770 consoleblank= [KNL] The console blank (screen saver) timeout in
771 seconds. Defaults to 10*60 = 10mins. A value of 0
772 disables the blank timer.
775 [KNL] Change the default value for
776 /proc/<pid>/coredump_filter.
777 See also Documentation/filesystems/proc.txt.
779 cpuidle.off=1 [CPU_IDLE]
780 disable the cpuidle sub-system
783 [X86] Delay for N microsec between assert and de-assert
784 of APIC INIT to start processors. This delay occurs
785 on every CPU online, such as boot, and resume from suspend.
788 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
790 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
792 crashkernel=size[KMG][@offset[KMG]]
793 [KNL] Using kexec, Linux can switch to a 'crash kernel'
794 upon panic. This parameter reserves the physical
795 memory region [offset, offset + size] for that kernel
796 image. If '@offset' is omitted, then a suitable offset
797 is selected automatically. Check
798 Documentation/kdump/kdump.txt for further details.
800 crashkernel=range1:size1[,range2:size2,...][@offset]
801 [KNL] Same as above, but depends on the memory
802 in the running system. The syntax of range is
803 start-[end] where start and end are both
804 a memory unit (amount[KMG]). See also
805 Documentation/kdump/kdump.txt for an example.
807 crashkernel=size[KMG],high
808 [KNL, x86_64] range could be above 4G. Allow kernel
809 to allocate physical memory region from top, so could
810 be above 4G if system have more than 4G ram installed.
811 Otherwise memory region will be allocated below 4G, if
813 It will be ignored if crashkernel=X is specified.
814 crashkernel=size[KMG],low
815 [KNL, x86_64] range under 4G. When crashkernel=X,high
816 is passed, kernel could allocate physical memory region
817 above 4G, that cause second kernel crash on system
818 that require some amount of low memory, e.g. swiotlb
819 requires at least 64M+32K low memory, also enough extra
820 low memory is needed to make sure DMA buffers for 32-bit
821 devices won't run out. Kernel would try to allocate at
822 at least 256M below 4G automatically.
823 This one let user to specify own low range under 4G
824 for second kernel instead.
825 0: to disable low allocation.
826 It will be ignored when crashkernel=X,high is not used
827 or memory reserved is below 4G.
832 cs89x0_media= [HW,NET]
833 Format: { rj45 | aui | bnc }
836 See header of drivers/s390/block/dasd_devmap.c.
838 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
839 (one device per port)
840 Format: <port#>,<type>
841 See also Documentation/input/joystick-parport.txt
843 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
844 time. See Documentation/dynamic-debug-howto.txt for
845 details. Deprecated, see dyndbg.
847 debug [KNL] Enable kernel debugging (events log level).
850 [KNL] verbose self-tests
852 Print debugging info while doing the locking API
854 We default to 0 (no extra messages), setting it to
855 1 will print _a lot_ more information - normally
856 only useful to kernel developers.
858 debug_objects [KNL] Enable object debugging
861 [KNL] Disable object debugging
863 debug_guardpage_minorder=
864 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
865 parameter allows control of the order of pages that will
866 be intentionally kept free (and hence protected) by the
867 buddy allocator. Bigger value increase the probability
868 of catching random memory corruption, but reduce the
869 amount of memory for normal system use. The maximum
870 possible value is MAX_ORDER/2. Setting this parameter
871 to 1 or 2 should be enough to identify most random
872 memory corruption problems caused by bugs in kernel or
873 driver code when a CPU writes to (or reads from) a
874 random memory location. Note that there exists a class
875 of memory corruptions problems caused by buggy H/W or
876 F/W or by drivers badly programing DMA (basically when
877 memory is written at bus level and the CPU MMU is
878 bypassed) which are not detectable by
879 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
880 tracking down these problems.
883 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
884 parameter enables the feature at boot time. In
885 default, it is disabled. We can avoid allocating huge
886 chunk of memory for debug pagealloc if we don't enable
887 it at boot time and the system will work mostly same
888 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
889 on: enable the feature
891 debugpat [X86] Enable PAT debugging
893 decnet.addr= [HW,NET]
894 Format: <area>[,<node>]
895 See also Documentation/networking/decnet.txt.
898 [same as hugepagesz=] The size of the default
899 HugeTLB page size. This is the size represented by
900 the legacy /proc/ hugepages APIs, used for SHM, and
901 default size when mounting hugetlbfs filesystems.
902 Defaults to the default architecture's huge page size
906 Set number of hash buckets for dentry cache.
909 See Documentation/networking/ipv6.txt.
911 disable_cpu_apicid= [X86,APIC,SMP]
913 The number of initial APIC ID for the
914 corresponding CPU to be disabled at boot,
915 mostly used for the kdump 2nd kernel to
916 disable BSP to wake up multiple CPUs without
917 causing system reset or hang due to sending
920 disable_ddw [PPC/PSERIES]
921 Disable Dynamic DMA Window support. Use this if
922 to workaround buggy firmware.
925 See Documentation/networking/ipv6.txt.
927 disable_mtrr_cleanup [X86]
928 The kernel tries to adjust MTRR layout from continuous
929 to discrete, to make X server driver able to add WB
930 entry later. This parameter disables that.
932 disable_mtrr_trim [X86, Intel and AMD only]
933 By default the kernel will trim any uncacheable
934 memory out of your available memory pool based on
935 MTRR settings. This parameter disables that behavior,
936 possibly causing your machine to run very slowly.
938 disable_timer_pin_1 [X86]
939 Disable PIN 1 of APIC timer
940 Can be useful to work around chipset bugs.
942 dis_ucode_ldr [X86] Disable the microcode loader.
944 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
945 this option disables the debugging code at boot.
947 dma_debug_entries=<number>
948 This option allows to tune the number of preallocated
949 entries for DMA-API debugging code. One entry is
950 required per DMA-API allocation. Use this if the
951 DMA-API debugging code disables itself because the
952 architectural default is too low.
954 dma_debug_driver=<driver_name>
955 With this option the DMA-API debugging driver
956 filter feature can be enabled at boot time. Just
957 pass the driver to filter for as the parameter.
958 The filter can be disabled or changed to another
959 driver later using sysfs.
961 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
962 Broken monitors, graphic adapters, KVMs and EDIDless
963 panels may send no or incorrect EDID data sets.
964 This parameter allows to specify an EDID data sets
965 in the /lib/firmware directory that are used instead.
966 Generic built-in EDID data sets are used, if one of
967 edid/1024x768.bin, edid/1280x1024.bin,
968 edid/1680x1050.bin, or edid/1920x1080.bin is given
969 and no file with the same name exists. Details and
970 instructions how to build your own EDID data are
971 available in Documentation/EDID/HOWTO.txt. An EDID
972 data set will only be used for a particular connector,
973 if its name and a colon are prepended to the EDID
974 name. Each connector may use a unique EDID data
975 set by separating the files with a comma. An EDID
976 data set with no connector name will be used for
977 any connectors not explicitly specified.
981 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
982 module.dyndbg[="val"]
983 Enable debug messages at boot time. See
984 Documentation/dynamic-debug-howto.txt for details.
986 nompx [X86] Disables Intel Memory Protection Extensions.
987 See Documentation/x86/intel_mpx.txt for more
988 information about the feature.
991 on enable eager fpu restore
992 off disable eager fpu restore
993 auto selects the default scheme, which automatically
994 enables eagerfpu restore for xsaveopt.
996 module.async_probe [KNL]
997 Enable asynchronous probe on this module.
999 early_ioremap_debug [KNL]
1000 Enable debug messages in early_ioremap support. This
1001 is useful for tracking down temporary early mappings
1002 which are not unmapped.
1004 earlycon= [KNL] Output early console device and options.
1006 When used with no options, the early console is
1007 determined by the stdout-path property in device
1011 Start an early, polled-mode console on a cadence serial
1012 port at the specified address. The cadence serial port
1013 must already be setup and configured. Options are not
1016 uart[8250],io,<addr>[,options]
1017 uart[8250],mmio,<addr>[,options]
1018 uart[8250],mmio32,<addr>[,options]
1019 uart[8250],mmio32be,<addr>[,options]
1020 uart[8250],0x<addr>[,options]
1021 Start an early, polled-mode console on the 8250/16550
1022 UART at the specified I/O port or MMIO address.
1023 MMIO inter-register address stride is either 8-bit
1024 (mmio) or 32-bit (mmio32 or mmio32be).
1025 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1026 to be equivalent to 'mmio'. 'options' are specified
1027 in the same format described for "console=ttyS<n>"; if
1028 unspecified, the h/w is not initialized.
1032 Start an early, polled-mode console on a pl011 serial
1033 port at the specified address. The pl011 serial port
1034 must already be setup and configured. Options are not
1035 yet supported. If 'mmio32' is specified, then only
1036 the driver will use only 32-bit accessors to read/write
1037 the device registers.
1040 Start an early, polled-mode console on an msm serial
1041 port at the specified address. The serial port
1042 must already be setup and configured. Options are not
1045 msm_serial_dm,<addr>
1046 Start an early, polled-mode console on an msm serial
1047 dm port at the specified address. The serial port
1048 must already be setup and configured. Options are not
1051 smh Use ARM semihosting calls for early console.
1059 Use early console provided by serial driver available
1060 on Samsung SoCs, requires selecting proper type and
1061 a correct base address of the selected UART port. The
1062 serial port must already be setup and configured.
1063 Options are not yet supported.
1067 Use early console provided by Freescale LP UART driver
1068 found on Freescale Vybrid and QorIQ LS1021A processors.
1069 A valid base address must be provided, and the serial
1070 port must already be setup and configured.
1072 armada3700_uart,<addr>
1073 Start an early, polled-mode console on the
1074 Armada 3700 serial port at the specified
1075 address. The serial port must already be setup
1076 and configured. Options are not yet supported.
1078 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1082 earlyprintk=serial[,ttySn[,baudrate]]
1083 earlyprintk=serial[,0x...[,baudrate]]
1084 earlyprintk=ttySn[,baudrate]
1085 earlyprintk=dbgp[debugController#]
1086 earlyprintk=pciserial,bus:device.function[,baudrate]
1088 earlyprintk is useful when the kernel crashes before
1089 the normal console is initialized. It is not enabled by
1090 default because it has some cosmetic problems.
1092 Append ",keep" to not disable it when the real console
1095 Only one of vga, efi, serial, or usb debug port can
1098 Currently only ttyS0 and ttyS1 may be specified by
1099 name. Other I/O ports may be explicitly specified
1100 on some architectures (x86 and arm at least) by
1101 replacing ttySn with an I/O port address, like this:
1102 earlyprintk=serial,0x1008,115200
1103 You can find the port for a given device in
1104 /proc/tty/driver/serial:
1105 2: uart:ST16650V2 port:00001008 irq:18 ...
1107 Interaction with the standard serial driver is not
1110 The VGA and EFI output is eventually overwritten by
1113 The xen output can only be used by Xen PV guests.
1115 edac_report= [HW,EDAC] Control how to report EDAC event
1116 Format: {"on" | "off" | "force"}
1117 on: enable EDAC to report H/W event. May be overridden
1118 by other higher priority error reporting module.
1119 off: disable H/W event reporting through EDAC.
1120 force: enforce the use of EDAC to report H/W event.
1123 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1126 This is designed to be used in conjunction with
1127 the boot argument: earlyprintk=vga
1130 Format: {"off" | "on" | "skip[mbr]"}
1133 Format: { "old_map", "nochunk", "noruntime", "debug" }
1134 old_map [X86-64]: switch to the old ioremap-based EFI
1135 runtime services mapping. 32-bit still uses this one by
1137 nochunk: disable reading files in "chunks" in the EFI
1138 boot stub, as chunking can cause problems with some
1139 firmware implementations.
1140 noruntime : disable EFI runtime services support
1141 debug: enable misc debug output
1143 efi_no_storage_paranoia [EFI; X86]
1144 Using this parameter you can use more than 50% of
1145 your efi variable storage. Use this parameter only if
1146 you are really sure that your UEFI does sane gc and
1147 fulfills the spec otherwise your board may brick.
1149 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1150 Add arbitrary attribute to specific memory range by
1151 updating original EFI memory map.
1152 Region of memory which aa attribute is added to is
1154 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1155 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1156 attribute is added to range 0x100000000-0x180000000 and
1157 0x10a0000000-0x1120000000.
1159 Using this parameter you can do debugging of EFI memmap
1160 related feature. For example, you can do debugging of
1161 Address Range Mirroring feature even if your box
1164 eisa_irq_edge= [PARISC,HW]
1165 See header of drivers/parisc/eisa.c.
1168 See comment before function elanfreq_setup() in
1169 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1172 Format: {"cfq" | "deadline" | "noop"}
1173 See Documentation/block/cfq-iosched.txt and
1174 Documentation/block/deadline-iosched.txt for details.
1176 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1177 Specifies physical address of start of kernel core
1178 image elf header and optionally the size. Generally
1179 kexec loader will pass this option to capture kernel.
1180 See Documentation/kdump/kdump.txt for details.
1182 enable_mtrr_cleanup [X86]
1183 The kernel tries to adjust MTRR layout from continuous
1184 to discrete, to make X server driver able to add WB
1185 entry later. This parameter enables that.
1187 enable_timer_pin_1 [X86]
1188 Enable PIN 1 of APIC timer
1189 Can be useful to work around chipset bugs
1190 (in particular on some ATI chipsets).
1191 The kernel tries to set a reasonable default.
1193 enforcing [SELINUX] Set initial enforcing status.
1195 See security/selinux/Kconfig help text.
1196 0 -- permissive (log only, no denials).
1197 1 -- enforcing (deny and log).
1199 Value can be changed at runtime via /selinux/enforce.
1202 Disable Error Record Serialization Table (ERST)
1205 ether= [HW,NET] Ethernet cards parameters
1206 This option is obsoleted by the "netdev=" option, which
1207 has equivalent usage. See its documentation for details.
1211 Permit 'security.evm' to be updated regardless of
1212 current integrity status.
1216 fail_make_request=[KNL]
1217 General fault injection mechanism.
1218 Format: <interval>,<probability>,<space>,<times>
1219 See also Documentation/fault-injection/.
1222 See Documentation/blockdev/floppy.txt.
1224 force_pal_cache_flush
1225 [IA-64] Avoid check_sal_cache_flush which may hang on
1226 buggy SAL_CACHE_FLUSH implementations. Using this
1227 parameter will force ia64_sal_cache_flush to call
1228 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1231 Forcefully enable Physical Address Extension (PAE).
1232 Many Pentium M systems disable PAE but may have a
1233 functionally usable PAE implementation.
1234 Warning: use of this parameter will taint the kernel
1235 and may cause unknown problems.
1238 [FTRACE] will set and start the specified tracer
1239 as early as possible in order to facilitate early
1242 ftrace_dump_on_oops[=orig_cpu]
1243 [FTRACE] will dump the trace buffers on oops.
1244 If no parameter is passed, ftrace will dump
1245 buffers of all CPUs, but if you pass orig_cpu, it will
1246 dump only the buffer of the CPU that triggered the
1249 ftrace_filter=[function-list]
1250 [FTRACE] Limit the functions traced by the function
1251 tracer at boot up. function-list is a comma separated
1252 list of functions. This list can be changed at run
1253 time by the set_ftrace_filter file in the debugfs
1256 ftrace_notrace=[function-list]
1257 [FTRACE] Do not trace the functions specified in
1258 function-list. This list can be changed at run time
1259 by the set_ftrace_notrace file in the debugfs
1262 ftrace_graph_filter=[function-list]
1263 [FTRACE] Limit the top level callers functions traced
1264 by the function graph tracer at boot up.
1265 function-list is a comma separated list of functions
1266 that can be changed at run time by the
1267 set_graph_function file in the debugfs tracing directory.
1269 ftrace_graph_notrace=[function-list]
1270 [FTRACE] Do not trace from the functions specified in
1271 function-list. This list is a comma separated list of
1272 functions that can be changed at run time by the
1273 set_graph_notrace file in the debugfs tracing directory.
1276 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1277 support via parallel port (up to 5 devices per port)
1278 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1279 See also Documentation/input/joystick-parport.txt
1283 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1287 gcov_persist= [GCOV] When non-zero (default), profiling data for
1288 kernel modules is saved and remains accessible via
1289 debugfs, even when the module is unloaded/reloaded.
1290 When zero, profiling data is discarded and associated
1291 debugfs files are removed at module unload time.
1293 gpt [EFI] Forces disk with valid GPT signature but
1294 invalid Protective MBR to be treated as GPT. If the
1295 primary GPT is corrupted, it enables the backup/alternate
1296 GPT to be used instead.
1298 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1299 the "Enable 0" bit of the configuration register.
1302 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1303 the "Enable 0" bit of the configuration register.
1306 grcan.select= [HW] Select which physical interface to use.
1309 grcan.txsize= [HW] Sets the size of the tx buffer.
1310 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1312 grcan.rxsize= [HW] Sets the size of the rx buffer.
1313 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1316 hardlockup_all_cpu_backtrace=
1317 [KNL] Should the hard-lockup detector generate
1318 backtraces on all cpus.
1321 hashdist= [KNL,NUMA] Large hashes allocated during boot
1322 are distributed across NUMA nodes. Defaults on
1323 for 64-bit NUMA, off otherwise.
1324 Format: 0 | 1 (for off | on)
1326 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1328 hd= [EIDE] (E)IDE hard drive subsystem geometry
1329 Format: <cyl>,<head>,<sect>
1332 Disable Hardware Error Source Table (HEST) support;
1333 corresponding firmware-first mode error processing
1334 logic will be disabled.
1336 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1337 size of <nn>. This works even on boxes that have no
1338 highmem otherwise. This also works to reduce highmem
1339 size on bigger boxes.
1341 highres= [KNL] Enable/disable high resolution timer mode.
1342 Valid parameters: "on", "off"
1346 See Documentation/isdn/README.HiSax.
1350 hpet= [X86-32,HPET] option to control HPET usage
1351 Format: { enable (default) | disable | force |
1353 disable: disable HPET and use PIT instead
1354 force: allow force enabled of undocumented chips (ICH4,
1356 verbose: show contents of HPET registers during setup
1358 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1359 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1361 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1362 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1363 On x86-64 and powerpc, this option can be specified
1364 multiple times interleaved with hugepages= to reserve
1365 huge pages of different sizes. Valid pages sizes on
1366 x86-64 are 2M (when the CPU supports "pse") and 1G
1367 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1369 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1370 terminal devices. Valid values: 0..8
1371 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1372 If specified, z/VM IUCV HVC accepts connections
1373 from listed z/VM user IDs only.
1375 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1376 hardware thread id mappings.
1377 Format: <cpu>:<hwthread>
1380 Do not unregister boot console at start. This is only
1381 useful for debugging when something happens in the window
1382 between unregistering the boot console and initializing
1385 i2c_bus= [HW] Override the default board specific I2C bus speed
1386 or register an additional I2C bus that is not
1387 registered from board initialization code.
1391 i8042.debug [HW] Toggle i8042 debug mode
1392 i8042.unmask_kbd_data
1393 [HW] Enable printing of interrupt data from the KBD port
1394 (disabled by default, and as a pre-condition
1395 requires that i8042.debug=1 be enabled)
1396 i8042.direct [HW] Put keyboard port into non-translated mode
1397 i8042.dumbkbd [HW] Pretend that controller can only read data from
1398 keyboard and cannot control its state
1399 (Don't attempt to blink the leds)
1400 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1401 i8042.nokbd [HW] Don't check/create keyboard port
1402 i8042.noloop [HW] Disable the AUX Loopback command while probing
1404 i8042.nomux [HW] Don't check presence of an active multiplexing
1406 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1408 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1409 i8042.reset [HW] Reset the controller during init and cleanup
1410 i8042.unlock [HW] Unlock (ignore) the keylock
1411 i8042.kbdreset [HW] Reset device connected to KBD port
1415 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1416 indicates that the driver is running on unsupported
1418 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1419 does not match list of supported models.
1421 [HW] Report power status in /proc/i8k
1422 (disabled by default)
1423 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1426 i915.invert_brightness=
1427 [DRM] Invert the sense of the variable that is used to
1428 set the brightness of the panel backlight. Normally a
1429 brightness value of 0 indicates backlight switched off,
1430 and the maximum of the brightness value sets the backlight
1431 to maximum brightness. If this parameter is set to 0
1432 (default) and the machine requires it, or this parameter
1433 is set to 1, a brightness value of 0 sets the backlight
1434 to maximum brightness, and the maximum of the brightness
1435 value switches the backlight off.
1436 -1 -- never invert brightness
1437 0 -- machine default
1438 1 -- force brightness inversion
1441 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1443 ide-core.nodma= [HW] (E)IDE subsystem
1444 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1445 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1446 .cdrom .chs .ignore_cable are additional options
1447 See Documentation/ide/ide.txt.
1449 ide-generic.probe-mask= [HW] (E)IDE subsystem
1451 Probe mask for legacy ISA IDE ports. Depending on
1452 platform up to 6 ports are supported, enabled by
1453 setting corresponding bits in the mask to 1. The
1454 default value is 0x0, which has a special meaning.
1455 On systems that have PCI, it triggers scanning the
1456 PCI bus for the first and the second port, which
1457 are then probed. On systems without PCI the value
1458 of 0x0 enables probing the two first ports as if it
1461 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1462 Claim all unknown PCI IDE storage controllers.
1465 Format: idle=poll, idle=halt, idle=nomwait
1466 Poll forces a polling idle loop that can slightly
1467 improve the performance of waking up a idle CPU, but
1468 will use a lot of power and make the system run hot.
1470 idle=halt: Halt is forced to be used for CPU idle.
1471 In such case C2/C3 won't be used again.
1472 idle=nomwait: Disable mwait for CPU C-states
1474 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1475 Format: { strict | legacy | 2008 | relaxed }
1478 Choose which programs will be accepted for execution
1479 based on the IEEE 754 NaN encoding(s) supported by
1480 the FPU and the NaN encoding requested with the value
1481 of an ELF file header flag individually set by each
1482 binary. Hardware implementations are permitted to
1483 support either or both of the legacy and the 2008 NaN
1486 Available settings are as follows:
1487 strict accept binaries that request a NaN encoding
1488 supported by the FPU
1489 legacy only accept legacy-NaN binaries, if supported
1491 2008 only accept 2008-NaN binaries, if supported
1493 relaxed accept any binaries regardless of whether
1494 supported by the FPU
1496 The FPU emulator is always able to support both NaN
1497 encodings, so if no FPU hardware is present or it has
1498 been disabled with 'nofpu', then the settings of
1499 'legacy' and '2008' strap the emulator accordingly,
1500 'relaxed' straps the emulator for both legacy-NaN and
1501 2008-NaN, whereas 'strict' enables legacy-NaN only on
1502 legacy processors and both NaN encodings on MIPS32 or
1505 The setting for ABS.fmt/NEG.fmt instruction execution
1506 mode generally follows that for the NaN encoding,
1507 except where unsupported by hardware.
1509 ignore_loglevel [KNL]
1510 Ignore loglevel setting - this will print /all/
1511 kernel messages to the console. Useful for debugging.
1512 We also add it as printk module parameter, so users
1513 could change it dynamically, usually by
1514 /sys/module/printk/parameters/ignore_loglevel.
1517 Ignore RLIMIT_DATA setting for data mappings,
1518 print warning at first misuse. Can be changed via
1519 /sys/module/kernel/parameters/ignore_rlimit_data.
1521 ihash_entries= [KNL]
1522 Set number of hash buckets for inode cache.
1524 ima_appraise= [IMA] appraise integrity measurements
1525 Format: { "off" | "enforce" | "fix" | "log" }
1528 ima_appraise_tcb [IMA]
1529 The builtin appraise policy appraises all files
1533 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1537 The list of supported hash algorithms is defined
1538 in crypto/hash_info.h.
1541 The builtin measurement policy to load during IMA
1542 setup. Specyfing "tcb" as the value, measures all
1543 programs exec'd, files mmap'd for exec, and all files
1544 opened with the read mode bit set by either the
1545 effective uid (euid=0) or uid=0.
1548 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1549 Load a policy which meets the needs of the Trusted
1550 Computing Base. This means IMA will measure all
1551 programs exec'd, files mmap'd for exec, and all files
1552 opened for read by uid=0.
1555 Select one of defined IMA measurements template formats.
1556 Formats: { "ima" | "ima-ng" | "ima-sig" }
1560 [IMA] Define a custom template format.
1561 Format: { "field1|...|fieldN" }
1563 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1564 Format: <min_file_size>
1565 Set the minimal file size for using asynchronous hash.
1566 If left unspecified, ahash usage is disabled.
1568 ahash performance varies for different data sizes on
1569 different crypto accelerators. This option can be used
1570 to achieve the best performance for a particular HW.
1572 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1574 Set hashing buffer size. Default: 4k.
1576 ahash performance varies for different chunk sizes on
1577 different crypto accelerators. This option can be used
1578 to achieve best performance for particular HW.
1582 Run specified binary instead of /sbin/init as init
1585 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1586 for working out where the kernel is dying during
1589 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1590 initcall functions. Useful for debugging built-in
1591 modules and initcalls.
1593 initrd= [BOOT] Specify the location of the initial ramdisk
1595 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1598 int_pln_enable [x86] Enable power limit notification interrupt
1600 integrity_audit=[IMA]
1601 Format: { "0" | "1" }
1602 0 -- basic integrity auditing messages. (Default)
1603 1 -- additional integrity auditing messages.
1605 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1607 Enable intel iommu driver.
1609 Disable intel iommu driver.
1610 igfx_off [Default Off]
1611 By default, gfx is mapped as normal device. If a gfx
1612 device has a dedicated DMAR unit, the DMAR unit is
1613 bypassed by not enabling DMAR with this option. In
1614 this case, gfx device will use physical address for
1617 With this option iommu will not optimize to look
1618 for io virtual address below 32-bit forcing dual
1619 address cycle on pci bus for cards supporting greater
1620 than 32-bit addressing. The default is to look
1621 for translation below 32-bit and if not available
1622 then look in the higher range.
1623 strict [Default Off]
1624 With this option on every unmap_single operation will
1625 result in a hardware IOTLB flush operation as opposed
1626 to batching them for performance.
1627 sp_off [Default Off]
1628 By default, super page will be supported if Intel IOMMU
1629 has the capability. With this option, super page will
1631 ecs_off [Default Off]
1632 By default, extended context tables will be supported if
1633 the hardware advertises that it has support both for the
1634 extended tables themselves, and also PASID support. With
1635 this option set, extended tables will not be used even
1636 on hardware which claims to support them.
1638 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1639 0 disables intel_idle and fall back on acpi_idle.
1640 1 to 6 specify maximum depth of C-state.
1644 Do not enable intel_pstate as the default
1645 scaling driver for the supported processors
1647 Enable intel_pstate on systems that prohibit it by default
1648 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1649 instead of acpi-cpufreq may disable platform features, such
1650 as thermal controls and power capping, that rely on ACPI
1651 P-States information being indicated to OSPM and therefore
1652 should be used with caution. This option does not work with
1653 processors that aren't supported by the intel_pstate driver
1654 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1656 Do not enable hardware P state control (HWP)
1659 Only load intel_pstate on systems which support
1660 hardware P state control (HWP) if available.
1662 intremap= [X86-64, Intel-IOMMU]
1663 on enable Interrupt Remapping (default)
1664 off disable Interrupt Remapping
1665 nosid disable Source ID checking
1667 BIOS x2APIC opt-out request will be ignored
1668 nopost disable Interrupt Posting
1670 iomem= Disable strict checking of access to MMIO memory
1671 strict regions from userspace.
1686 nobypass [PPC/POWERNV]
1687 Disable IOMMU bypass, using IOMMU for PCI devices.
1690 io7= [HW] IO7 for Marvel based alpha systems
1691 See comment before marvel_specify_io7 in
1692 arch/alpha/kernel/core_marvel.c.
1694 io_delay= [X86] I/O delay method
1696 Standard port 0x80 based delay
1698 Alternate port 0xed based delay (needed on some systems)
1700 Simple two microseconds delay
1705 See Documentation/filesystems/nfs/nfsroot.txt.
1707 irqaffinity= [SMP] Set the default irq affinity mask
1709 <cpu number>,...,<cpu number>
1711 <cpu number>-<cpu number>
1712 (must be a positive range in ascending order)
1714 <cpu number>,...,<cpu number>-<cpu number>
1717 When an interrupt is not handled search all handlers
1718 for it. Intended to get systems with badly broken
1722 When an interrupt is not handled search all handlers
1723 for it. Also check all handlers each timer
1724 interrupt. Intended to get systems with badly broken
1728 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1730 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1732 <cpu number>,...,<cpu number>
1734 <cpu number>-<cpu number>
1735 (must be a positive range in ascending order)
1737 <cpu number>,...,<cpu number>-<cpu number>
1739 This option can be used to specify one or more CPUs
1740 to isolate from the general SMP balancing and scheduling
1741 algorithms. You can move a process onto or off an
1742 "isolated" CPU via the CPU affinity syscalls or cpuset.
1743 <cpu number> begins at 0 and the maximum value is
1744 "number of CPUs in system - 1".
1746 This option is the preferred way to isolate CPUs. The
1747 alternative -- manually setting the CPU mask of all
1748 tasks in the system -- can cause problems and
1749 suboptimal load balancer performance.
1753 ivrs_ioapic [HW,X86_64]
1754 Provide an override to the IOAPIC-ID<->DEVICE-ID
1755 mapping provided in the IVRS ACPI table. For
1756 example, to map IOAPIC-ID decimal 10 to
1757 PCI device 00:14.0 write the parameter as:
1758 ivrs_ioapic[10]=00:14.0
1760 ivrs_hpet [HW,X86_64]
1761 Provide an override to the HPET-ID<->DEVICE-ID
1762 mapping provided in the IVRS ACPI table. For
1763 example, to map HPET-ID decimal 0 to
1764 PCI device 00:14.0 write the parameter as:
1765 ivrs_hpet[0]=00:14.0
1767 js= [HW,JOY] Analog joystick
1768 See Documentation/input/joystick.txt.
1771 Enable/disable kernel and module base offset ASLR
1772 (Address Space Layout Randomization) if built into
1773 the kernel. When CONFIG_HIBERNATION is selected,
1774 kASLR is disabled by default. When kASLR is enabled,
1775 hibernation will be disabled.
1779 kernelcore= [KNL,X86,IA-64,PPC]
1780 Format: nn[KMGTPE] | "mirror"
1782 specifies the amount of memory usable by the kernel
1783 for non-movable allocations. The requested amount is
1784 spread evenly throughout all nodes in the system. The
1785 remaining memory in each node is used for Movable
1786 pages. In the event, a node is too small to have both
1787 kernelcore and Movable pages, kernelcore pages will
1788 take priority and other nodes will have a larger number
1789 of Movable pages. The Movable zone is used for the
1790 allocation of pages that may be reclaimed or moved
1791 by the page migration subsystem. This means that
1792 HugeTLB pages may not be allocated from this zone.
1793 Note that allocations like PTEs-from-HighMem still
1794 use the HighMem zone if it exists, and the Normal
1795 zone if it does not.
1797 Instead of specifying the amount of memory (nn[KMGTPE]),
1798 you can specify "mirror" option. In case "mirror"
1799 option is specified, mirrored (reliable) memory is used
1800 for non-movable allocations and remaining memory is used
1801 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1802 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1805 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1806 Format: <Controller#>[,poll interval]
1807 The controller # is the number of the ehci usb debug
1808 port as it is probed via PCI. The poll interval is
1809 optional and is the number seconds in between
1810 each poll cycle to the debug port in case you need
1811 the functionality for interrupting the kernel with
1812 gdb or control-c on the dbgp connection. When
1813 not using this parameter you use sysrq-g to break into
1814 the kernel debugger.
1816 kgdboc= [KGDB,HW] kgdb over consoles.
1817 Requires a tty driver that supports console polling,
1818 or a supported polling keyboard driver (non-usb).
1819 Serial only format: <serial_device>[,baud]
1820 keyboard only format: kbd
1821 keyboard and serial format: kbd,<serial_device>[,baud]
1822 Optional Kernel mode setting:
1823 kms, kbd format: kms,kbd
1824 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1826 kgdbwait [KGDB] Stop kernel execution and enter the
1827 kernel debugger at the earliest opportunity.
1829 kmac= [MIPS] korina ethernet MAC address.
1830 Configure the RouterBoard 532 series on-chip
1831 Ethernet adapter MAC address.
1833 kmemleak= [KNL] Boot-time kmemleak enable/disable
1834 Valid arguments: on, off
1836 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1839 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1840 Valid arguments: 0, 1, 2
1841 kmemcheck=0 (disabled)
1842 kmemcheck=1 (enabled)
1843 kmemcheck=2 (one-shot mode)
1844 Default: 2 (one-shot mode)
1846 kstack=N [X86] Print N words from the kernel stack
1849 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1850 Default is 0 (don't ignore, but inject #GP)
1852 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1856 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1857 Default is 1 (enabled)
1859 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1861 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1863 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1864 (virtualized MMU) support on capable Intel chips.
1865 Default is 1 (enabled)
1867 kvm-intel.emulate_invalid_guest_state=
1868 [KVM,Intel] Enable emulation of invalid guest states
1869 Default is 0 (disabled)
1871 kvm-intel.flexpriority=
1872 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1873 Default is 1 (enabled)
1876 [KVM,Intel] Enable VMX nesting (nVMX).
1877 Default is 0 (disabled)
1879 kvm-intel.unrestricted_guest=
1880 [KVM,Intel] Disable unrestricted guest feature
1881 (virtualized real and unpaged mode) on capable
1882 Intel chips. Default is 1 (enabled)
1884 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1885 feature (tagged TLBs) on capable Intel chips.
1886 Default is 1 (enabled)
1892 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1895 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1896 value for LAPIC timer one-shot implementation. Default
1897 back to the programmable timer unit in the LAPIC.
1899 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1902 libata.dma= [LIBATA] DMA control
1903 libata.dma=0 Disable all PATA and SATA DMA
1904 libata.dma=1 PATA and SATA Disk DMA only
1905 libata.dma=2 ATAPI (CDROM) DMA only
1906 libata.dma=4 Compact Flash DMA only
1907 Combinations also work, so libata.dma=3 enables DMA
1908 for disks and CDROMs, but not CFs.
1910 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1911 libata.ignore_hpa=0 keep BIOS limits (default)
1912 libata.ignore_hpa=1 ignore limits, using full disk
1914 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1918 libata.force= [LIBATA] Force configurations. The format is comma
1919 separated list of "[ID:]VAL" where ID is
1920 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1921 matching port, link or device. Basically, it matches
1922 the ATA ID string printed on console by libata. If
1923 the whole ID part is omitted, the last PORT and DEVICE
1924 values are used. If ID hasn't been specified yet, the
1925 configuration applies to all ports, links and devices.
1927 If only DEVICE is omitted, the parameter applies to
1928 the port and all links and devices behind it. DEVICE
1929 number of 0 either selects the first device or the
1930 first fan-out link behind PMP device. It does not
1931 select the host link. DEVICE number of 15 selects the
1932 host link and device attached to it.
1934 The VAL specifies the configuration to force. As long
1935 as there's no ambiguity shortcut notation is allowed.
1936 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1937 The following configurations can be forced.
1939 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1940 Any ID with matching PORT is used.
1942 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1944 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1945 udma[/][16,25,33,44,66,100,133] notation is also
1948 * [no]ncq: Turn on or off NCQ.
1950 * [no]ncqtrim: Turn off queued DSM TRIM.
1952 * nohrst, nosrst, norst: suppress hard, soft
1955 * rstonce: only attempt one reset during
1956 hot-unplug link recovery
1958 * dump_id: dump IDENTIFY data.
1960 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1962 * disable: Disable this device.
1964 If there are multiple matching configurations changing
1965 the same attribute, the last one is used.
1967 memblock=debug [KNL] Enable memblock debug messages.
1969 load_ramdisk= [RAM] List of ramdisks to load from floppy
1970 See Documentation/blockdev/ramdisk.txt.
1972 lockd.nlm_grace_period=P [NFS] Assign grace period.
1975 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1978 lockd.nlm_timeout=T [NFS] Assign timeout value.
1981 lockd.nlm_udpport=M [NFS] Assign UDP port.
1984 locktorture.nreaders_stress= [KNL]
1985 Set the number of locking read-acquisition kthreads.
1986 Defaults to being automatically set based on the
1987 number of online CPUs.
1989 locktorture.nwriters_stress= [KNL]
1990 Set the number of locking write-acquisition kthreads.
1992 locktorture.onoff_holdoff= [KNL]
1993 Set time (s) after boot for CPU-hotplug testing.
1995 locktorture.onoff_interval= [KNL]
1996 Set time (s) between CPU-hotplug operations, or
1997 zero to disable CPU-hotplug testing.
1999 locktorture.shuffle_interval= [KNL]
2000 Set task-shuffle interval (jiffies). Shuffling
2001 tasks allows some CPUs to go into dyntick-idle
2002 mode during the locktorture test.
2004 locktorture.shutdown_secs= [KNL]
2005 Set time (s) after boot system shutdown. This
2006 is useful for hands-off automated testing.
2008 locktorture.stat_interval= [KNL]
2009 Time (s) between statistics printk()s.
2011 locktorture.stutter= [KNL]
2012 Time (s) to stutter testing, for example,
2013 specifying five seconds causes the test to run for
2014 five seconds, wait for five seconds, and so on.
2015 This tests the locking primitive's ability to
2016 transition abruptly to and from idle.
2018 locktorture.torture_runnable= [BOOT]
2019 Start locktorture running at boot time.
2021 locktorture.torture_type= [KNL]
2022 Specify the locking implementation to test.
2024 locktorture.verbose= [KNL]
2025 Enable additional printk() statements.
2027 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2030 loglevel= All Kernel Messages with a loglevel smaller than the
2031 console loglevel will be printed to the console. It can
2032 also be changed with klogd or other programs. The
2033 loglevels are defined as follows:
2035 0 (KERN_EMERG) system is unusable
2036 1 (KERN_ALERT) action must be taken immediately
2037 2 (KERN_CRIT) critical conditions
2038 3 (KERN_ERR) error conditions
2039 4 (KERN_WARNING) warning conditions
2040 5 (KERN_NOTICE) normal but significant condition
2041 6 (KERN_INFO) informational
2042 7 (KERN_DEBUG) debug-level messages
2044 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2045 in bytes. n must be a power of two and greater
2046 than the minimal size. The minimal size is defined
2047 by LOG_BUF_SHIFT kernel config parameter. There is
2048 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2049 that allows to increase the default size depending on
2050 the number of CPUs. See init/Kconfig for more details.
2052 logo.nologo [FB] Disables display of the built-in Linux logo.
2053 This may be used to provide more screen space for
2054 kernel log messages and is useful when debugging
2055 kernel boot problems.
2057 lp=0 [LP] Specify parallel ports to use, e.g,
2058 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2059 lp=reset first parallel port). 'lp=0' disables the
2060 lp=auto printer driver. 'lp=reset' (which can be
2061 specified in addition to the ports) causes
2062 attached printers to be reset. Using
2063 lp=port1,port2,... specifies the parallel ports
2064 to associate lp devices with, starting with
2065 lp0. A port specification may be 'none' to skip
2066 that lp device, or a parport name such as
2067 'parport0'. Specifying 'lp=auto' instead of a
2068 port specification list means that device IDs
2069 from each port should be examined, to see if
2070 an IEEE 1284-compliant printer is attached; if
2071 so, the driver will manage that printer.
2072 See also header of drivers/char/lp.c.
2075 Sets loops_per_jiffy to given constant, thus avoiding
2076 time-consuming boot-time autodetection (up to 250 ms per
2077 CPU). 0 enables autodetection (default). To determine
2078 the correct value for your kernel, boot with normal
2079 autodetection and see what value is printed. Note that
2080 on SMP systems the preset will be applied to all CPUs,
2081 which is likely to cause problems if your CPUs need
2082 significantly divergent settings. An incorrect value
2083 will cause delays in the kernel to be wrong, leading to
2084 unpredictable I/O errors and other breakage. Although
2085 unlikely, in the extreme case this might damage your
2089 Format: <io>,<irq>,<dma>
2091 machvec= [IA-64] Force the use of a particular machine-vector
2092 (machvec) in a generic kernel.
2093 Example: machvec=hpzx1_swiotlb
2095 machtype= [Loongson] Share the same kernel image file between different
2097 Example: machtype=lemote-yeeloong-2f-7inch
2099 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2100 than or equal to this physical address is ignored.
2102 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2103 should make use of. maxcpus=n : n >= 0 limits the
2104 kernel to using 'n' processors. n=0 is a special case,
2105 it is equivalent to "nosmp", which also disables
2108 max_loop= [LOOP] The number of loop block devices that get
2109 (loop.max_loop) unconditionally pre-created at init time. The default
2110 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2111 of statically allocating a predefined number, loop
2112 devices can be requested on-demand with the
2113 /dev/loop-control interface.
2115 mce [X86-32] Machine Check Exception
2117 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2119 md= [HW] RAID subsystems devices and level
2120 See Documentation/md.txt.
2123 Format: <first>,<last>
2124 Specifies range of consoles to be captured by the MDA.
2126 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2127 Amount of memory to be used when the kernel is not able
2128 to see the whole system memory or for test.
2129 [X86] Work as limiting max address. Use together
2130 with memmap= to avoid physical address space collisions.
2131 Without memmap= PCI devices could be placed at addresses
2132 belonging to unused RAM.
2134 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2138 [KNL,SH] Allow user to override the default size for
2139 per-device physically contiguous DMA buffers.
2141 memmap=exactmap [KNL,X86] Enable setting of an exact
2142 E820 memory map, as specified by the user.
2143 Such memmap=exactmap lines can be constructed based on
2144 BIOS output or other requirements. See the memmap=nn@ss
2147 memmap=nn[KMG]@ss[KMG]
2148 [KNL] Force usage of a specific region of memory.
2149 Region of memory to be used is from ss to ss+nn.
2151 memmap=nn[KMG]#ss[KMG]
2152 [KNL,ACPI] Mark specific memory as ACPI data.
2153 Region of memory to be marked is from ss to ss+nn.
2155 memmap=nn[KMG]$ss[KMG]
2156 [KNL,ACPI] Mark specific memory as reserved.
2157 Region of memory to be reserved is from ss to ss+nn.
2158 Example: Exclude memory from 0x18690000-0x1869ffff
2159 memmap=64K$0x18690000
2161 memmap=0x10000$0x18690000
2163 memmap=nn[KMG]!ss[KMG]
2164 [KNL,X86] Mark specific memory as protected.
2165 Region of memory to be used, from ss to ss+nn.
2166 The memory region may be marked as e820 type 12 (0xc)
2167 and is NVDIMM or ADR memory.
2169 memory_corruption_check=0/1 [X86]
2170 Some BIOSes seem to corrupt the first 64k of
2171 memory when doing things like suspend/resume.
2172 Setting this option will scan the memory
2173 looking for corruption. Enabling this will
2174 both detect corruption and prevent the kernel
2175 from using the memory being corrupted.
2176 However, its intended as a diagnostic tool; if
2177 repeatable BIOS-originated corruption always
2178 affects the same memory, you can use memmap=
2179 to prevent the kernel from using that memory.
2181 memory_corruption_check_size=size [X86]
2182 By default it checks for corruption in the low
2183 64k, making this memory unavailable for normal
2184 use. Use this parameter to scan for
2185 corruption in more or less memory.
2187 memory_corruption_check_period=seconds [X86]
2188 By default it checks for corruption every 60
2189 seconds. Use this parameter to check at some
2190 other rate. 0 disables periodic checking.
2192 memtest= [KNL,X86,ARM] Enable memtest
2194 default : 0 <disable>
2195 Specifies the number of memtest passes to be
2196 performed. Each pass selects another test
2197 pattern from a given set of patterns. Memtest
2198 fills the memory with this pattern, validates
2199 memory contents and reserves bad memory
2200 regions that are detected.
2202 meye.*= [HW] Set MotionEye Camera parameters
2203 See Documentation/video4linux/meye.txt.
2205 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2206 Multi-Function General Purpose Timers on AMD Geode
2209 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2210 the BIOS has incorrectly applied a workaround. TinyBIOS
2211 version 0.98 is known to be affected, 0.99 fixes the
2212 problem by letting the user disable the workaround.
2216 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2217 physical address is ignored.
2219 mini2440= [ARM,HW,KNL]
2220 Format:[0..2][b][c][t]
2222 MINI2440 configuration specification:
2223 0 - The attached screen is the 3.5" TFT
2224 1 - The attached screen is the 7" TFT
2225 2 - The VGA Shield is attached (1024x768)
2226 Leaving out the screen size parameter will not load
2227 the TFT driver, and the framebuffer will be left
2229 b - Enable backlight. The TFT backlight pin will be
2230 linked to the kernel VESA blanking code and a GPIO
2231 LED. This parameter is not necessary when using the
2233 c - Enable the s3c camera interface.
2234 t - Reserved for enabling touchscreen support. The
2235 touchscreen support is not enabled in the mainstream
2236 kernel as of 2.6.30, a preliminary port can be found
2237 in the "bleeding edge" mini2440 support kernel at
2238 http://repo.or.cz/w/linux-2.6/mini2440.git
2241 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2242 parameter allows control of the logging verbosity for
2243 the additional memory initialisation checks. A value
2244 of 0 disables mminit logging and a level of 4 will
2245 log everything. Information is printed at KERN_DEBUG
2246 so loglevel=8 may also need to be specified.
2249 [KNL] When CONFIG_MODULE_SIG is set, this means that
2250 modules without (valid) signatures will fail to load.
2251 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2252 is always true, so this option does nothing.
2255 [MOUSE] Maximum time between finger touching and
2256 leaving touchpad surface for touch to be considered
2257 a tap and be reported as a left button click (for
2258 touchpads working in absolute mode only).
2260 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2261 reporting absolute coordinates, such as tablets
2262 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2263 reporting absolute coordinates, such as tablets
2265 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2266 is similar to kernelcore except it specifies the
2267 amount of memory used for migratable allocations.
2268 If both kernelcore and movablecore is specified,
2269 then kernelcore will be at *least* the specified
2270 value but may be more. If movablecore on its own
2271 is specified, the administrator must be careful
2272 that the amount of memory usable for all allocations
2275 movable_node [KNL,X86] Boot-time switch to enable the effects
2276 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2278 MTD_Partition= [MTD]
2279 Format: <name>,<region-number>,<size>,<offset>
2281 MTD_Region= [MTD] Format:
2282 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2285 See drivers/mtd/cmdlinepart.c.
2287 multitce=off [PPC] This parameter disables the use of the pSeries
2288 firmware feature for updating multiple TCE entries
2291 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2293 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2295 boundary - index of last SLC block on Flex-OneNAND.
2296 The remaining blocks are configured as MLC blocks.
2297 lock - Configure if Flex-OneNAND boundary should be locked.
2298 Once locked, the boundary cannot be changed.
2299 1 indicates lock status, 0 indicates unlock status.
2302 ARM/S3C2412 JIVE boot control
2304 See arch/arm/mach-s3c2412/mach-jive.c
2306 mtouchusb.raw_coordinates=
2307 [HW] Make the MicroTouch USB driver use raw coordinates
2308 ('y', default) or cooked coordinates ('n')
2310 mtrr_chunk_size=nn[KMG] [X86]
2311 used for mtrr cleanup. It is largest continuous chunk
2312 that could hold holes aka. UC entries.
2314 mtrr_gran_size=nn[KMG] [X86]
2315 Used for mtrr cleanup. It is granularity of mtrr block.
2317 Large value could prevent small alignment from
2320 mtrr_spare_reg_nr=n [X86]
2322 Range: 0,7 : spare reg number
2324 Used for mtrr cleanup. It is spare mtrr entries number.
2325 Set to 2 or more if your graphical card needs more.
2327 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2329 netdev= [NET] Network devices parameters
2330 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2331 Note that mem_start is often overloaded to mean
2332 something different and driver-specific.
2333 This usage is only documented in each driver source
2337 [NETFILTER] Enable connection tracking flow accounting
2338 0 to disable accounting
2339 1 to enable accounting
2342 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2343 See Documentation/filesystems/nfs/nfsroot.txt.
2345 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2346 See Documentation/filesystems/nfs/nfsroot.txt.
2348 nfsrootdebug [NFS] enable nfsroot debugging messages.
2349 See Documentation/filesystems/nfs/nfsroot.txt.
2351 nfs.callback_tcpport=
2352 [NFS] set the TCP port on which the NFSv4 callback
2353 channel should listen.
2356 [NFS] sets the pathname to the program which is used
2357 to update the NFS client cache entries.
2359 nfs.cache_getent_timeout=
2360 [NFS] sets the timeout after which an attempt to
2361 update a cache entry is deemed to have failed.
2363 nfs.idmap_cache_timeout=
2364 [NFS] set the maximum lifetime for idmapper cache
2368 [NFS] enable 64-bit inode numbers.
2369 If zero, the NFS client will fake up a 32-bit inode
2370 number for the readdir() and stat() syscalls instead
2371 of returning the full 64-bit number.
2372 The default is to return 64-bit inode numbers.
2374 nfs.max_session_slots=
2375 [NFSv4.1] Sets the maximum number of session slots
2376 the client will attempt to negotiate with the server.
2377 This limits the number of simultaneous RPC requests
2378 that the client can send to the NFSv4.1 server.
2379 Note that there is little point in setting this
2380 value higher than the max_tcp_slot_table_limit.
2382 nfs.nfs4_disable_idmapping=
2383 [NFSv4] When set to the default of '1', this option
2384 ensures that both the RPC level authentication
2385 scheme and the NFS level operations agree to use
2386 numeric uids/gids if the mount is using the
2387 'sec=sys' security flavour. In effect it is
2388 disabling idmapping, which can make migration from
2389 legacy NFSv2/v3 systems to NFSv4 easier.
2390 Servers that do not support this mode of operation
2391 will be autodetected by the client, and it will fall
2392 back to using the idmapper.
2393 To turn off this behaviour, set the value to '0'.
2395 [NFS4] Specify an additional fixed unique ident-
2396 ification string that NFSv4 clients can insert into
2397 their nfs_client_id4 string. This is typically a
2398 UUID that is generated at system install time.
2400 nfs.send_implementation_id =
2401 [NFSv4.1] Send client implementation identification
2402 information in exchange_id requests.
2403 If zero, no implementation identification information
2405 The default is to send the implementation identification
2408 nfs.recover_lost_locks =
2409 [NFSv4] Attempt to recover locks that were lost due
2410 to a lease timeout on the server. Please note that
2411 doing this risks data corruption, since there are
2412 no guarantees that the file will remain unchanged
2413 after the locks are lost.
2414 If you want to enable the kernel legacy behaviour of
2415 attempting to recover these locks, then set this
2417 The default parameter value of '0' causes the kernel
2418 not to attempt recovery of lost locks.
2420 nfs4.layoutstats_timer =
2421 [NFSv4.2] Change the rate at which the kernel sends
2422 layoutstats to the pNFS metadata server.
2424 Setting this to value to 0 causes the kernel to use
2425 whatever value is the default set by the layout
2426 driver. A non-zero value sets the minimum interval
2427 in seconds between layoutstats transmissions.
2429 nfsd.nfs4_disable_idmapping=
2430 [NFSv4] When set to the default of '1', the NFSv4
2431 server will return only numeric uids and gids to
2432 clients using auth_sys, and will accept numeric uids
2433 and gids from such clients. This is intended to ease
2434 migration from NFSv2/v3.
2436 objlayoutdriver.osd_login_prog=
2437 [NFS] [OBJLAYOUT] sets the pathname to the program which
2438 is used to automatically discover and login into new
2439 osd-targets. Please see:
2440 Documentation/filesystems/pnfs.txt for more explanations
2442 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2443 when a NMI is triggered.
2444 Format: [state][,regs][,debounce][,die]
2446 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2447 Format: [panic,][nopanic,][num]
2449 0 - turn hardlockup detector in nmi_watchdog off
2450 1 - turn hardlockup detector in nmi_watchdog on
2451 When panic is specified, panic when an NMI watchdog
2452 timeout occurs (or 'nopanic' to override the opposite
2453 default). To disable both hard and soft lockup detectors,
2454 please see 'nowatchdog'.
2455 This is useful when you use a panic=... timeout and
2456 need the box quickly up again.
2458 netpoll.carrier_timeout=
2459 [NET] Specifies amount of time (in seconds) that
2460 netpoll should wait for a carrier. By default netpoll
2463 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2464 emulation library even if a 387 maths coprocessor
2468 [HW] Never suspend the console
2469 Disable suspending of consoles during suspend and
2470 hibernate operations. Once disabled, debugging
2471 messages can reach various consoles while the rest
2472 of the system is being put to sleep (ie, while
2473 debugging driver suspend/resume hooks). This may
2474 not work reliably with all consoles, but is known
2475 to work with serial and VGA consoles.
2476 To facilitate more flexible debugging, we also add
2477 console_suspend, a printk module parameter to control
2478 it. Users could use console_suspend (usually
2479 /sys/module/printk/parameters/console_suspend) to
2480 turn on/off it dynamically.
2482 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2483 caches in the slab allocator. Saves per-node memory,
2484 but will impact performance.
2488 noapic [SMP,APIC] Tells the kernel to not make use of any
2489 IOAPICs that may be present in the system.
2491 noautogroup Disable scheduler automatic task group creation.
2493 nobats [PPC] Do not use BATs for mapping kernel lowmem
2494 on "Classic" PPC cores.
2498 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2500 nodelayacct [KNL] Disable per-task delay accounting
2502 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2504 nodsp [SH] Disable hardware DSP at boot time.
2506 noefi Disable EFI runtime services support.
2511 On X86-32 available only on PAE configured kernels.
2512 noexec=on: enable non-executable mappings (default)
2513 noexec=off: disable non-executable mappings
2516 Disable SMAP (Supervisor Mode Access Prevention)
2517 even if it is supported by processor.
2520 Disable SMEP (Supervisor Mode Execution Prevention)
2521 even if it is supported by processor.
2524 This affects only 32-bit executables.
2525 noexec32=on: enable non-executable mappings (default)
2526 read doesn't imply executable mappings
2527 noexec32=off: disable non-executable mappings
2528 read implies executable mappings
2530 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2532 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2533 register save and restore. The kernel will only save
2534 legacy floating-point registers on task switch.
2536 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2538 noxsave [BUGS=X86] Disables x86 extended register state save
2539 and restore using xsave. The kernel will fallback to
2540 enabling legacy floating-point and sse state.
2542 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2543 register states. The kernel will fall back to use
2544 xsave to save the states. By using this parameter,
2545 performance of saving the states is degraded because
2546 xsave doesn't support modified optimization while
2547 xsaveopt supports it on xsaveopt enabled systems.
2549 noxsaves [X86] Disables xsaves and xrstors used in saving and
2550 restoring x86 extended register state in compacted
2551 form of xsave area. The kernel will fall back to use
2552 xsaveopt and xrstor to save and restore the states
2553 in standard form of xsave area. By using this
2554 parameter, xsave area per process might occupy more
2555 memory on xsaves enabled systems.
2557 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2558 wfi(ARM) instruction doesn't work correctly and not to
2559 use it. This is also useful when using JTAG debugger.
2561 no_file_caps Tells the kernel not to honor file capabilities. The
2562 only way then for a file to be executed with privilege
2563 is to be setuid root or executed by root.
2565 nohalt [IA-64] Tells the kernel not to use the power saving
2566 function PAL_HALT_LIGHT when idle. This increases
2567 power-consumption. On the positive side, it reduces
2568 interrupt wake-up latency, which may improve performance
2569 in certain environments such as networked servers or
2572 nohibernate [HIBERNATION] Disable hibernation and resume.
2574 nohz= [KNL] Boottime enable/disable dynamic ticks
2575 Valid arguments: on, off
2578 nohz_full= [KNL,BOOT]
2579 In kernels built with CONFIG_NO_HZ_FULL=y, set
2580 the specified list of CPUs whose tick will be stopped
2581 whenever possible. The boot CPU will be forced outside
2582 the range to maintain the timekeeping.
2583 The CPUs in this range must also be included in the
2586 noiotrap [SH] Disables trapped I/O port accesses.
2588 noirqdebug [X86-32] Disables the code which attempts to detect and
2589 disable unhandled interrupt sources.
2591 no_timer_check [X86,APIC] Disables the code which tests for
2592 broken timer IRQ sources.
2594 noisapnp [ISAPNP] Disables ISA PnP code.
2596 noinitrd [RAM] Tells the kernel not to load any configured
2599 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2601 [Deprecated - use intremap=off]
2605 noinvpcid [X86] Disable the INVPCID cpu feature.
2607 nojitter [IA-64] Disables jitter checking for ITC timers.
2609 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2611 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2614 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2615 steal time is computed, but won't influence scheduler
2618 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2620 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2622 noltlbs [PPC] Do not use large page/tlb entries for kernel
2623 lowmem mapping on PPC40x.
2625 nomca [IA-64] Disable machine check abort handling
2627 nomce [X86-32] Disable Machine Check Exception
2629 nomfgpt [X86-32] Disable Multi-Function General Purpose
2630 Timer usage (for AMD Geode machines).
2632 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2633 shutdown the other cpus. Instead use the REBOOT_VECTOR
2636 nomodule Disable module load
2638 nopat [X86] Disable PAT (page attribute table extension of
2639 pagetables) support.
2641 norandmaps Don't use address space randomization. Equivalent to
2642 echo 0 > /proc/sys/kernel/randomize_va_space
2644 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2646 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2647 with UP alternatives
2649 nordrand [X86] Disable kernel use of the RDRAND and
2650 RDSEED instructions even if they are supported
2651 by the processor. RDRAND and RDSEED are still
2652 available to user space applications.
2654 noresume [SWSUSP] Disables resume and restores original swap
2657 no-scroll [VGA] Disables scrollback.
2658 This is required for the Braillex ib80-piezo Braille
2659 reader made by F.H. Papenmeier (Germany).
2663 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2665 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2666 and disable the IO APIC. legacy for "maxcpus=0".
2668 nosoftlockup [KNL] Disable the soft-lockup detector.
2670 nosync [HW,M68K] Disables sync negotiation for all devices.
2672 notsc [BUGS=X86-32] Disable Time Stamp Counter
2674 nowatchdog [KNL] Disable both lockup detectors, i.e.
2675 soft-lockup and NMI watchdog (hard-lockup).
2679 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2681 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2682 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2683 Some features depend on CPU0. Known dependencies are:
2684 1. Resume from suspend/hibernate depends on CPU0.
2685 Suspend/hibernate will fail if CPU0 is offline and you
2686 need to online CPU0 before suspend/hibernate.
2687 2. PIC interrupts also depend on CPU0. CPU0 can't be
2688 removed if a PIC interrupt is detected.
2689 It's said poweroff/reboot may depend on CPU0 on some
2690 machines although I haven't seen such issues so far
2691 after CPU0 is offline on a few tested machines.
2692 If the dependencies are under your control, you can
2693 turn on cpu0_hotplug.
2695 nptcg= [IA-64] Override max number of concurrent global TLB
2696 purges which is reported from either PAL_VM_SUMMARY or
2699 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2700 could support. nr_cpus=n : n >= 1 limits the kernel to
2701 supporting 'n' processors. Later in runtime you can not
2702 use hotplug cpu feature to put more cpu back to online.
2703 just like you compile the kernel NR_CPUS=n
2705 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2707 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2708 Allowed values are enable and disable
2710 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2711 one of ['zone', 'node', 'default'] can be specified
2712 This can be set from sysctl after boot.
2713 See Documentation/sysctl/vm.txt for details.
2715 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2716 See Documentation/debugging-via-ohci1394.txt for more
2719 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2720 Rather than timing out after 20 ms if an EC
2721 command is not properly ACKed, override the length
2722 of the timeout. We have interrupts disabled while
2723 waiting for the ACK, so if this is set too high
2724 interrupts *may* be lost!
2726 omap_mux= [OMAP] Override bootloader pin multiplexing.
2727 Format: <mux_mode0.mode_name=value>...
2728 For example, to override I2C bus2:
2729 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2731 oprofile.timer= [HW]
2732 Use timer interrupt instead of performance counters
2734 oprofile.cpu_type= Force an oprofile cpu type
2735 This might be useful if you have an older oprofile
2736 userland or if you want common events.
2737 Format: { arch_perfmon }
2738 arch_perfmon: [X86] Force use of architectural
2739 perfmon on Intel CPUs instead of the
2740 CPU specific event set.
2741 timer: [X86] Force use of architectural NMI
2742 timer mode (see also oprofile.timer
2743 for generic hr timer mode)
2744 [s390] Force legacy basic mode sampling
2745 (report cpu_type "timer")
2747 oops=panic Always panic on oopses. Default is to just kill the
2748 process, but there is a small probability of
2749 deadlocking the machine.
2750 This will also cause panics on machine check exceptions.
2751 Useful together with panic=30 to trigger a reboot.
2754 See Documentation/sound/oss/oss-parameters.txt
2756 page_owner= [KNL] Boot-time page_owner enabling option.
2757 Storage of the information about who allocated
2758 each page is disabled in default. With this switch,
2760 on: enable the feature
2762 page_poison= [KNL] Boot-time parameter changing the state of
2763 poisoning on the buddy allocator.
2764 off: turn off poisoning
2765 on: turn on poisoning
2767 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2768 timeout > 0: seconds before rebooting
2769 timeout = 0: wait forever
2770 timeout < 0: reboot immediately
2773 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2776 crash_kexec_post_notifiers
2777 Run kdump after running panic-notifiers and dumping
2778 kmsg. This only for the users who doubt kdump always
2779 succeeds in any situation.
2780 Note that this also increases risks of kdump failure,
2781 because some panic notifiers can make the crashed
2782 kernel more unstable.
2784 parkbd.port= [HW] Parallel port number the keyboard adapter is
2785 connected to, default is 0.
2787 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2788 0 for XT, 1 for AT (default is AT).
2791 parport= [HW,PPT] Specify parallel ports. 0 disables.
2792 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2793 Use 'auto' to force the driver to use any
2794 IRQ/DMA settings detected (the default is to
2795 ignore detected IRQ/DMA settings because of
2796 possible conflicts). You can specify the base
2797 address, IRQ, and DMA settings; IRQ and DMA
2798 should be numbers, or 'auto' (for using detected
2799 settings on that particular port), or 'nofifo'
2800 (to avoid using a FIFO even if it is detected).
2801 Parallel ports are assigned in the order they
2802 are specified on the command line, starting
2805 parport_init_mode= [HW,PPT]
2806 Configure VIA parallel port to operate in
2807 a specific mode. This is necessary on Pegasos
2808 computer where firmware has no options for setting
2809 up parallel port mode and sets it to spp.
2810 Currently this function knows 686a and 8231 chips.
2811 Format: [spp|ps2|epp|ecp|ecpepp]
2814 Halt all CPUs after the first oops has been printed for
2815 the specified number of seconds. This is to be used if
2816 your oopses keep scrolling off the screen.
2821 See header of drivers/block/paride/pcd.c.
2822 See also Documentation/blockdev/paride.txt.
2824 pci=option[,option...] [PCI] various PCI subsystem options:
2825 earlydump [X86] dump PCI config space before the kernel
2827 off [X86] don't probe for the PCI bus
2828 bios [X86-32] force use of PCI BIOS, don't access
2829 the hardware directly. Use this if your machine
2830 has a non-standard PCI host bridge.
2831 nobios [X86-32] disallow use of PCI BIOS, only direct
2832 hardware access methods are allowed. Use this
2833 if you experience crashes upon bootup and you
2834 suspect they are caused by the BIOS.
2835 conf1 [X86] Force use of PCI Configuration Access
2836 Mechanism 1 (config address in IO port 0xCF8,
2837 data in IO port 0xCFC, both 32-bit).
2838 conf2 [X86] Force use of PCI Configuration Access
2839 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2840 the function, IO port 0xCFA, also 8-bit, sets
2841 bus number. The config space is then accessed
2842 through ports 0xC000-0xCFFF).
2843 See http://wiki.osdev.org/PCI for more info
2844 on the configuration access mechanisms.
2845 noaer [PCIE] If the PCIEAER kernel config parameter is
2846 enabled, this kernel boot option can be used to
2847 disable the use of PCIE advanced error reporting.
2848 nodomains [PCI] Disable support for multiple PCI
2849 root domains (aka PCI segments, in ACPI-speak).
2850 nommconf [X86] Disable use of MMCONFIG for PCI
2852 check_enable_amd_mmconf [X86] check for and enable
2853 properly configured MMIO access to PCI
2854 config space on AMD family 10h CPU
2855 nomsi [MSI] If the PCI_MSI kernel config parameter is
2856 enabled, this kernel boot option can be used to
2857 disable the use of MSI interrupts system-wide.
2858 noioapicquirk [APIC] Disable all boot interrupt quirks.
2859 Safety option to keep boot IRQs enabled. This
2860 should never be necessary.
2861 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2862 primary IO-APIC for bridges that cannot disable
2863 boot IRQs. This fixes a source of spurious IRQs
2864 when the system masks IRQs.
2865 noioapicreroute [APIC] Disable workaround that uses the
2866 boot IRQ equivalent of an IRQ that connects to
2867 a chipset where boot IRQs cannot be disabled.
2868 The opposite of ioapicreroute.
2869 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2870 routing table. These calls are known to be buggy
2871 on several machines and they hang the machine
2872 when used, but on other computers it's the only
2873 way to get the interrupt routing table. Try
2874 this option if the kernel is unable to allocate
2875 IRQs or discover secondary PCI buses on your
2877 rom [X86] Assign address space to expansion ROMs.
2878 Use with caution as certain devices share
2879 address decoders between ROMs and other
2881 norom [X86] Do not assign address space to
2882 expansion ROMs that do not already have
2883 BIOS assigned address ranges.
2884 nobar [X86] Do not assign address space to the
2885 BARs that weren't assigned by the BIOS.
2886 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2887 assigned automatically to PCI devices. You can
2888 make the kernel exclude IRQs of your ISA cards
2890 pirqaddr=0xAAAAA [X86] Specify the physical address
2891 of the PIRQ table (normally generated
2892 by the BIOS) if it is outside the
2893 F0000h-100000h range.
2894 lastbus=N [X86] Scan all buses thru bus #N. Can be
2895 useful if the kernel is unable to find your
2896 secondary buses and you want to tell it
2897 explicitly which ones they are.
2898 assign-busses [X86] Always assign all PCI bus
2899 numbers ourselves, overriding
2900 whatever the firmware may have done.
2901 usepirqmask [X86] Honor the possible IRQ mask stored
2902 in the BIOS $PIR table. This is needed on
2903 some systems with broken BIOSes, notably
2904 some HP Pavilion N5400 and Omnibook XE3
2905 notebooks. This will have no effect if ACPI
2906 IRQ routing is enabled.
2907 noacpi [X86] Do not use ACPI for IRQ routing
2908 or for PCI scanning.
2909 use_crs [X86] Use PCI host bridge window information
2910 from ACPI. On BIOSes from 2008 or later, this
2911 is enabled by default. If you need to use this,
2912 please report a bug.
2913 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2914 If you need to use this, please report a bug.
2915 routeirq Do IRQ routing for all PCI devices.
2916 This is normally done in pci_enable_device(),
2917 so this option is a temporary workaround
2918 for broken drivers that don't call it.
2919 skip_isa_align [X86] do not align io start addr, so can
2920 handle more pci cards
2921 firmware [ARM] Do not re-enumerate the bus but instead
2922 just use the configuration from the
2923 bootloader. This is currently used on
2924 IXP2000 systems where the bus has to be
2925 configured a certain way for adjunct CPUs.
2926 noearly [X86] Don't do any early type 1 scanning.
2927 This might help on some broken boards which
2928 machine check when some devices' config space
2929 is read. But various workarounds are disabled
2930 and some IOMMU drivers will not work.
2931 bfsort Sort PCI devices into breadth-first order.
2932 This sorting is done to get a device
2933 order compatible with older (<= 2.4) kernels.
2934 nobfsort Don't sort PCI devices into breadth-first order.
2935 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2936 tuning and use the BIOS-configured MPS defaults.
2937 pcie_bus_safe Set every device's MPS to the largest value
2938 supported by all devices below the root complex.
2939 pcie_bus_perf Set device MPS to the largest allowable MPS
2940 based on its parent bus. Also set MRRS (Max
2941 Read Request Size) to the largest supported
2942 value (no larger than the MPS that the device
2943 or bus can support) for best performance.
2944 pcie_bus_peer2peer Set every device's MPS to 128B, which
2945 every device is guaranteed to support. This
2946 configuration allows peer-to-peer DMA between
2947 any pair of devices, possibly at the cost of
2948 reduced performance. This also guarantees
2949 that hot-added devices will work.
2950 cbiosize=nn[KMG] The fixed amount of bus space which is
2951 reserved for the CardBus bridge's IO window.
2952 The default value is 256 bytes.
2953 cbmemsize=nn[KMG] The fixed amount of bus space which is
2954 reserved for the CardBus bridge's memory
2955 window. The default value is 64 megabytes.
2958 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2959 Specifies alignment and device to reassign
2960 aligned memory resources.
2961 If <order of align> is not specified,
2962 PAGE_SIZE is used as alignment.
2963 PCI-PCI bridge can be specified, if resource
2964 windows need to be expanded.
2965 ecrc= Enable/disable PCIe ECRC (transaction layer
2966 end-to-end CRC checking).
2967 bios: Use BIOS/firmware settings. This is the
2971 hpiosize=nn[KMG] The fixed amount of bus space which is
2972 reserved for hotplug bridge's IO window.
2973 Default size is 256 bytes.
2974 hpmemsize=nn[KMG] The fixed amount of bus space which is
2975 reserved for hotplug bridge's memory window.
2976 Default size is 2 megabytes.
2977 realloc= Enable/disable reallocating PCI bridge resources
2978 if allocations done by BIOS are too small to
2979 accommodate resources required by all child
2981 off: Turn realloc off
2983 realloc same as realloc=on
2984 noari do not use PCIe ARI.
2985 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2986 only look for one device below a PCIe downstream
2989 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2992 force Enable ASPM even on devices that claim not to support it.
2993 WARNING: Forcing ASPM on may cause system lockups.
2995 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2996 nomsi Do not use MSI for PCI Express Native Hotplug (this
2997 makes all PCIe ports use INTx for hotplug services).
2999 pcie_ports= [PCIE] PCIe ports handling:
3000 auto Ask the BIOS whether or not to use native PCIe services
3001 associated with PCIe ports (PME, hot-plug, AER). Use
3002 them only if that is allowed by the BIOS.
3003 native Use native PCIe services associated with PCIe ports
3005 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3008 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3009 nomsi Do not use MSI for native PCIe PME signaling (this makes
3010 all PCIe root ports use INTx for all services).
3012 pcmv= [HW,PCMCIA] BadgePAD 4
3016 Keep all power-domains already enabled by bootloader on,
3017 even if no driver has claimed them. This is useful
3018 for debug and development, but should not be
3019 needed on a platform with proper driver support.
3022 See Documentation/blockdev/paride.txt.
3024 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3027 See arch/parisc/kernel/pdc_chassis.c
3029 percpu_alloc= Select which percpu first chunk allocator to use.
3030 Currently supported values are "embed" and "page".
3031 Archs may support subset or none of the selections.
3032 See comments in mm/percpu.c for details on each
3033 allocator. This parameter is primarily for debugging
3034 and performance comparison.
3037 See Documentation/blockdev/paride.txt.
3040 See Documentation/blockdev/paride.txt.
3042 pirq= [SMP,APIC] Manual mp-table setup
3043 See Documentation/x86/i386/IO-APIC.txt.
3045 plip= [PPT,NET] Parallel port network link
3046 Format: { parport<nr> | timid | 0 }
3047 See also Documentation/parport.txt.
3049 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3050 Override pmtimer IOPort with a hex value.
3054 Enable PNP debug messages (depends on the
3055 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3056 via /sys/module/pnp/parameters/debug. We always show
3057 current resource usage; turning this on also shows
3058 possible settings and some assignment information.
3064 { on | off | curr | res | no-curr | no-res }
3067 [ISAPNP] Exclude IRQs for the autoconfiguration
3070 [ISAPNP] Exclude DMAs for the autoconfiguration
3072 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3073 Ranges are in pairs (I/O port base and size).
3076 [ISAPNP] Exclude memory regions for the
3078 Ranges are in pairs (memory base and size).
3080 ports= [IP_VS_FTP] IPVS ftp helper module
3082 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3084 Format: <port>,<port>....
3086 ppc_strict_facility_enable
3087 [PPC] This option catches any kernel floating point,
3088 Altivec, VSX and SPE outside of regions specifically
3089 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3090 There is some performance impact when enabling this.
3092 print-fatal-signals=
3093 [KNL] debug: print fatal signals
3095 If enabled, warn about various signal handling
3096 related application anomalies: too many signals,
3097 too many POSIX.1 timers, fatal signals causing a
3100 If you hit the warning due to signal overflow,
3101 you might want to try "ulimit -i unlimited".
3105 printk.always_kmsg_dump=
3106 Trigger kmsg_dump for cases other than kernel oops or
3108 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3111 printk.time= Show timing data prefixed to each printk message line
3112 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3114 processor.max_cstate= [HW,ACPI]
3115 Limit processor to maximum C-state
3116 max_cstate=9 overrides any DMI blacklist limit.
3118 processor.nocst [HW,ACPI]
3119 Ignore the _CST method to determine C-states,
3120 instead using the legacy FADT method
3122 profile= [KNL] Enable kernel profiling via /proc/profile
3123 Format: [schedule,]<number>
3124 Param: "schedule" - profile schedule points.
3125 Param: <number> - step/bucket size as a power of 2 for
3126 statistical time based profiling.
3127 Param: "sleep" - profile D-state sleeping (millisecs).
3128 Requires CONFIG_SCHEDSTATS
3129 Param: "kvm" - profile VM exits.
3131 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3133 See Documentation/blockdev/ramdisk.txt.
3135 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3136 probe for; one of (bare|imps|exps|lifebook|any).
3137 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3139 psmouse.resetafter= [HW,MOUSE]
3140 Try to reset the device after so many bad packets
3143 [HW,MOUSE] Set desired mouse resolution, in dpi.
3144 psmouse.smartscroll=
3145 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3146 0 = disabled, 1 = enabled (default).
3148 pstore.backend= Specify the name of the pstore backend to use
3151 See Documentation/blockdev/paride.txt.
3154 [KNL] Number of legacy pty's. Overwrites compiled-in
3157 quiet [KNL] Disable most log messages
3162 See Documentation/md.txt.
3164 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3165 See Documentation/blockdev/ramdisk.txt.
3168 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3169 the specified list of CPUs to be no-callback CPUs.
3170 Invocation of these CPUs' RCU callbacks will
3171 be offloaded to "rcuox/N" kthreads created for
3172 that purpose, where "x" is "b" for RCU-bh, "p"
3173 for RCU-preempt, and "s" for RCU-sched, and "N"
3174 is the CPU number. This reduces OS jitter on the
3175 offloaded CPUs, which can be useful for HPC and
3176 real-time workloads. It can also improve energy
3177 efficiency for asymmetric multiprocessors.
3180 Rather than requiring that offloaded CPUs
3181 (specified by rcu_nocbs= above) explicitly
3182 awaken the corresponding "rcuoN" kthreads,
3183 make these kthreads poll for callbacks.
3184 This improves the real-time response for the
3185 offloaded CPUs by relieving them of the need to
3186 wake up the corresponding kthread, but degrades
3187 energy efficiency by requiring that the kthreads
3188 periodically wake up to do the polling.
3190 rcutree.blimit= [KNL]
3191 Set maximum number of finished RCU callbacks to
3192 process in one batch.
3194 rcutree.dump_tree= [KNL]
3195 Dump the structure of the rcu_node combining tree
3196 out at early boot. This is used for diagnostic
3197 purposes, to verify correct tree setup.
3199 rcutree.gp_cleanup_delay= [KNL]
3200 Set the number of jiffies to delay each step of
3201 RCU grace-period cleanup. This only has effect
3202 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3204 rcutree.gp_init_delay= [KNL]
3205 Set the number of jiffies to delay each step of
3206 RCU grace-period initialization. This only has
3207 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3210 rcutree.gp_preinit_delay= [KNL]
3211 Set the number of jiffies to delay each step of
3212 RCU grace-period pre-initialization, that is,
3213 the propagation of recent CPU-hotplug changes up
3214 the rcu_node combining tree. This only has effect
3215 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3217 rcutree.rcu_fanout_exact= [KNL]
3218 Disable autobalancing of the rcu_node combining
3219 tree. This is used by rcutorture, and might
3220 possibly be useful for architectures having high
3221 cache-to-cache transfer latencies.
3223 rcutree.rcu_fanout_leaf= [KNL]
3224 Change the number of CPUs assigned to each
3225 leaf rcu_node structure. Useful for very
3226 large systems, which will choose the value 64,
3227 and for NUMA systems with large remote-access
3228 latencies, which will choose a value aligned
3229 with the appropriate hardware boundaries.
3231 rcutree.jiffies_till_sched_qs= [KNL]
3232 Set required age in jiffies for a
3233 given grace period before RCU starts
3234 soliciting quiescent-state help from
3235 rcu_note_context_switch().
3237 rcutree.jiffies_till_first_fqs= [KNL]
3238 Set delay from grace-period initialization to
3239 first attempt to force quiescent states.
3240 Units are jiffies, minimum value is zero,
3241 and maximum value is HZ.
3243 rcutree.jiffies_till_next_fqs= [KNL]
3244 Set delay between subsequent attempts to force
3245 quiescent states. Units are jiffies, minimum
3246 value is one, and maximum value is HZ.
3248 rcutree.kthread_prio= [KNL,BOOT]
3249 Set the SCHED_FIFO priority of the RCU per-CPU
3250 kthreads (rcuc/N). This value is also used for
3251 the priority of the RCU boost threads (rcub/N)
3252 and for the RCU grace-period kthreads (rcu_bh,
3253 rcu_preempt, and rcu_sched). If RCU_BOOST is
3254 set, valid values are 1-99 and the default is 1
3255 (the least-favored priority). Otherwise, when
3256 RCU_BOOST is not set, valid values are 0-99 and
3257 the default is zero (non-realtime operation).
3259 rcutree.rcu_nocb_leader_stride= [KNL]
3260 Set the number of NOCB kthread groups, which
3261 defaults to the square root of the number of
3262 CPUs. Larger numbers reduces the wakeup overhead
3263 on the per-CPU grace-period kthreads, but increases
3264 that same overhead on each group's leader.
3266 rcutree.qhimark= [KNL]
3267 Set threshold of queued RCU callbacks beyond which
3268 batch limiting is disabled.
3270 rcutree.qlowmark= [KNL]
3271 Set threshold of queued RCU callbacks below which
3272 batch limiting is re-enabled.
3274 rcutree.rcu_idle_gp_delay= [KNL]
3275 Set wakeup interval for idle CPUs that have
3276 RCU callbacks (RCU_FAST_NO_HZ=y).
3278 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3279 Set wakeup interval for idle CPUs that have
3280 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3281 Lazy RCU callbacks are those which RCU can
3282 prove do nothing more than free memory.
3284 rcutorture.cbflood_inter_holdoff= [KNL]
3285 Set holdoff time (jiffies) between successive
3286 callback-flood tests.
3288 rcutorture.cbflood_intra_holdoff= [KNL]
3289 Set holdoff time (jiffies) between successive
3290 bursts of callbacks within a given callback-flood
3293 rcutorture.cbflood_n_burst= [KNL]
3294 Set the number of bursts making up a given
3295 callback-flood test. Set this to zero to
3296 disable callback-flood testing.
3298 rcutorture.cbflood_n_per_burst= [KNL]
3299 Set the number of callbacks to be registered
3300 in a given burst of a callback-flood test.
3302 rcutorture.fqs_duration= [KNL]
3303 Set duration of force_quiescent_state bursts
3306 rcutorture.fqs_holdoff= [KNL]
3307 Set holdoff time within force_quiescent_state bursts
3310 rcutorture.fqs_stutter= [KNL]
3311 Set wait time between force_quiescent_state bursts
3314 rcutorture.gp_cond= [KNL]
3315 Use conditional/asynchronous update-side
3316 primitives, if available.
3318 rcutorture.gp_exp= [KNL]
3319 Use expedited update-side primitives, if available.
3321 rcutorture.gp_normal= [KNL]
3322 Use normal (non-expedited) asynchronous
3323 update-side primitives, if available.
3325 rcutorture.gp_sync= [KNL]
3326 Use normal (non-expedited) synchronous
3327 update-side primitives, if available. If all
3328 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3329 rcutorture.gp_normal=, and rcutorture.gp_sync=
3330 are zero, rcutorture acts as if is interpreted
3331 they are all non-zero.
3333 rcutorture.n_barrier_cbs= [KNL]
3334 Set callbacks/threads for rcu_barrier() testing.
3336 rcutorture.nfakewriters= [KNL]
3337 Set number of concurrent RCU writers. These just
3338 stress RCU, they don't participate in the actual
3339 test, hence the "fake".
3341 rcutorture.nreaders= [KNL]
3342 Set number of RCU readers. The value -1 selects
3343 N-1, where N is the number of CPUs. A value
3344 "n" less than -1 selects N-n-2, where N is again
3345 the number of CPUs. For example, -2 selects N
3346 (the number of CPUs), -3 selects N+1, and so on.
3348 rcutorture.object_debug= [KNL]
3349 Enable debug-object double-call_rcu() testing.
3351 rcutorture.onoff_holdoff= [KNL]
3352 Set time (s) after boot for CPU-hotplug testing.
3354 rcutorture.onoff_interval= [KNL]
3355 Set time (s) between CPU-hotplug operations, or
3356 zero to disable CPU-hotplug testing.
3358 rcutorture.shuffle_interval= [KNL]
3359 Set task-shuffle interval (s). Shuffling tasks
3360 allows some CPUs to go into dyntick-idle mode
3361 during the rcutorture test.
3363 rcutorture.shutdown_secs= [KNL]
3364 Set time (s) after boot system shutdown. This
3365 is useful for hands-off automated testing.
3367 rcutorture.stall_cpu= [KNL]
3368 Duration of CPU stall (s) to test RCU CPU stall
3369 warnings, zero to disable.
3371 rcutorture.stall_cpu_holdoff= [KNL]
3372 Time to wait (s) after boot before inducing stall.
3374 rcutorture.stat_interval= [KNL]
3375 Time (s) between statistics printk()s.
3377 rcutorture.stutter= [KNL]
3378 Time (s) to stutter testing, for example, specifying
3379 five seconds causes the test to run for five seconds,
3380 wait for five seconds, and so on. This tests RCU's
3381 ability to transition abruptly to and from idle.
3383 rcutorture.test_boost= [KNL]
3384 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3385 "Maybe" means test if the RCU implementation
3386 under test support RCU priority boosting.
3388 rcutorture.test_boost_duration= [KNL]
3389 Duration (s) of each individual boost test.
3391 rcutorture.test_boost_interval= [KNL]
3392 Interval (s) between each boost test.
3394 rcutorture.test_no_idle_hz= [KNL]
3395 Test RCU's dyntick-idle handling. See also the
3396 rcutorture.shuffle_interval parameter.
3398 rcutorture.torture_runnable= [BOOT]
3399 Start rcutorture running at boot time.
3401 rcutorture.torture_type= [KNL]
3402 Specify the RCU implementation to test.
3404 rcutorture.verbose= [KNL]
3405 Enable additional printk() statements.
3407 rcupdate.rcu_cpu_stall_suppress= [KNL]
3408 Suppress RCU CPU stall warning messages.
3410 rcupdate.rcu_cpu_stall_timeout= [KNL]
3411 Set timeout for RCU CPU stall warning messages.
3413 rcupdate.rcu_expedited= [KNL]
3414 Use expedited grace-period primitives, for
3415 example, synchronize_rcu_expedited() instead
3416 of synchronize_rcu(). This reduces latency,
3417 but can increase CPU utilization, degrade
3418 real-time latency, and degrade energy efficiency.
3419 No effect on CONFIG_TINY_RCU kernels.
3421 rcupdate.rcu_normal= [KNL]
3422 Use only normal grace-period primitives,
3423 for example, synchronize_rcu() instead of
3424 synchronize_rcu_expedited(). This improves
3425 real-time latency, CPU utilization, and
3426 energy efficiency, but can expose users to
3427 increased grace-period latency. This parameter
3428 overrides rcupdate.rcu_expedited. No effect on
3429 CONFIG_TINY_RCU kernels.
3431 rcupdate.rcu_normal_after_boot= [KNL]
3432 Once boot has completed (that is, after
3433 rcu_end_inkernel_boot() has been invoked), use
3434 only normal grace-period primitives. No effect
3435 on CONFIG_TINY_RCU kernels.
3437 rcupdate.rcu_task_stall_timeout= [KNL]
3438 Set timeout in jiffies for RCU task stall warning
3439 messages. Disable with a value less than or equal
3442 rcupdate.rcu_self_test= [KNL]
3443 Run the RCU early boot self tests
3445 rcupdate.rcu_self_test_bh= [KNL]
3446 Run the RCU bh early boot self tests
3448 rcupdate.rcu_self_test_sched= [KNL]
3449 Run the RCU sched early boot self tests
3453 Run specified binary instead of /init from the ramdisk,
3454 used for early userspace startup. See initrd.
3457 Format (x86 or x86_64):
3458 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3460 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3462 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3463 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3464 reboot_force is either force or not specified,
3465 reboot_cpu is s[mp]#### with #### being the processor
3466 to be used for rebooting.
3469 [KNL, SMP] Set scheduler's default relax_domain_level.
3470 See Documentation/cgroups/cpusets.txt.
3472 relative_sleep_states=
3473 [SUSPEND] Use sleep state labeling where the deepest
3474 state available other than hibernation is always "mem".
3475 Format: { "0" | "1" }
3476 0 -- Traditional sleep state labels.
3477 1 -- Relative sleep state labels.
3479 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3481 reservetop= [X86-32]
3483 Reserves a hole at the top of the kernel virtual
3488 Set the amount of memory to reserve for BIOS at
3489 the bottom of the address space.
3491 reset_devices [KNL] Force drivers to reset the underlying device
3492 during initialization.
3495 Specify the partition device for software suspend
3497 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3499 resume_offset= [SWSUSP]
3500 Specify the offset from the beginning of the partition
3501 given by "resume=" at which the swap header is located,
3502 in <PAGE_SIZE> units (needed only for swap files).
3503 See Documentation/power/swsusp-and-swap-files.txt
3505 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3506 read the resume files
3508 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3509 Useful for devices that are detected asynchronously
3510 (e.g. USB and MMC devices).
3512 hibernate= [HIBERNATION]
3513 noresume Don't check if there's a hibernation image
3514 present during boot.
3515 nocompress Don't compress/decompress hibernation images.
3516 no Disable hibernation and resume.
3518 retain_initrd [RAM] Keep initrd memory after extraction
3520 rfkill.default_state=
3521 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3522 etc. communication is blocked by default.
3525 rfkill.master_switch_mode=
3526 0 The "airplane mode" button does nothing.
3527 1 The "airplane mode" button toggles between everything
3528 blocked and the previous configuration.
3529 2 The "airplane mode" button toggles between everything
3530 blocked and everything unblocked.
3532 rhash_entries= [KNL,NET]
3533 Set number of hash buckets for route cache
3535 ro [KNL] Mount root device read-only on boot
3538 on Mark read-only kernel memory as read-only (default).
3539 off Leave read-only kernel memory writable for debugging.
3542 Enable the uart passthrough on the designated usb port
3543 on Rockchip SoCs. When active, the signals of the
3544 debug-uart get routed to the D+ and D- pins of the usb
3545 port and the regular usb controller gets disabled.
3547 root= [KNL] Root filesystem
3548 See name_to_dev_t comment in init/do_mounts.c.
3550 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3551 mount the root filesystem
3553 rootflags= [KNL] Set root filesystem mount option string
3555 rootfstype= [KNL] Set root filesystem type
3557 rootwait [KNL] Wait (indefinitely) for root device to show up.
3558 Useful for devices that are detected asynchronously
3559 (e.g. USB and MMC devices).
3561 rproc_mem=nn[KMG][@address]
3562 [KNL,ARM,CMA] Remoteproc physical memory block.
3563 Memory area to be used by remote processor image,
3566 rw [KNL] Mount root device read-write on boot
3568 S [KNL] Run init in single mode
3570 s390_iommu= [HW,S390]
3571 Set s390 IOTLB flushing mode
3573 With strict flushing every unmap operation will result in
3574 an IOTLB flush. Default is lazy flushing before reuse,
3578 See drivers/net/irda/sa1100_ir.c.
3580 sbni= [NET] Granch SBNI12 leased line adapter
3582 sched_debug [KNL] Enables verbose scheduler debug messages.
3584 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3585 Allowed values are enable and disable. This feature
3586 incurs a small amount of overhead in the scheduler
3587 but is useful for debugging and performance tuning.
3589 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3590 xtime_lock contention on larger systems, and/or RCU lock
3591 contention on all systems with CONFIG_MAXSMP set.
3592 Format: { "0" | "1" }
3593 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3595 Note: increases power consumption, thus should only be
3596 enabled if running jitter sensitive (HPC/RT) workloads.
3598 security= [SECURITY] Choose a security module to enable at boot.
3599 If this boot parameter is not specified, only the first
3600 security module asking for security registration will be
3601 loaded. An invalid security module name will be treated
3602 as if no module has been chosen.
3604 selinux= [SELINUX] Disable or enable SELinux at boot time.
3605 Format: { "0" | "1" }
3606 See security/selinux/Kconfig help text.
3609 Default value is set via kernel config option.
3610 If enabled at boot time, /selinux/disable can be used
3611 later to disable prior to initial policy load.
3613 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3614 Format: { "0" | "1" }
3615 See security/apparmor/Kconfig help text
3618 Default value is set via kernel config option.
3620 serialnumber [BUGS=X86-32]
3623 Maximal number of shapers.
3625 show_msr= [x86] show boot-time MSR settings
3626 Format: { <integer> }
3627 Show boot-time (BIOS-initialized) MSR settings.
3628 The parameter means the number of CPUs to show,
3629 for example 1 means boot CPU only.
3637 Disable merging of slabs with similar size. May be
3638 necessary if there is some reason to distinguish
3639 allocs to different slabs. Debug options disable
3640 merging on their own.
3641 For more information see Documentation/vm/slub.txt.
3643 slab_max_order= [MM, SLAB]
3644 Determines the maximum allowed order for slabs.
3645 A high setting may cause OOMs due to memory
3646 fragmentation. Defaults to 1 for systems with
3647 more than 32MB of RAM, 0 otherwise.
3649 slub_debug[=options[,slabs]] [MM, SLUB]
3650 Enabling slub_debug allows one to determine the
3651 culprit if slab objects become corrupted. Enabling
3652 slub_debug can create guard zones around objects and
3653 may poison objects when not in use. Also tracks the
3654 last alloc / free. For more information see
3655 Documentation/vm/slub.txt.
3657 slub_max_order= [MM, SLUB]
3658 Determines the maximum allowed order for slabs.
3659 A high setting may cause OOMs due to memory
3660 fragmentation. For more information see
3661 Documentation/vm/slub.txt.
3663 slub_min_objects= [MM, SLUB]
3664 The minimum number of objects per slab. SLUB will
3665 increase the slab order up to slub_max_order to
3666 generate a sufficiently large slab able to contain
3667 the number of objects indicated. The higher the number
3668 of objects the smaller the overhead of tracking slabs
3669 and the less frequently locks need to be acquired.
3670 For more information see Documentation/vm/slub.txt.
3672 slub_min_order= [MM, SLUB]
3673 Determines the minimum page order for slabs. Must be
3674 lower than slub_max_order.
3675 For more information see Documentation/vm/slub.txt.
3677 slub_nomerge [MM, SLUB]
3678 Same with slab_nomerge. This is supported for legacy.
3679 See slab_nomerge for more information.
3682 Format: <io1>[,<io2>[,...,<io8>]]
3684 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3685 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3686 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3687 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3688 smsc-ircc2.ircc_irq= [HW] IRQ line
3689 smsc-ircc2.ircc_dma= [HW] DMA channel
3690 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3691 0: Toshiba Satellite 1800 (GP data pin select)
3692 1: Fast pin select (default)
3696 [KNL] Should the soft-lockup detector generate panics.
3699 softlockup_all_cpu_backtrace=
3700 [KNL] Should the soft-lockup detector generate
3701 backtraces on all cpus.
3704 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3705 See Documentation/laptops/sonypi.txt
3707 spia_io_base= [HW,MTD]
3713 Enabled the stack tracer on boot up.
3715 stacktrace_filter=[function-list]
3716 [FTRACE] Limit the functions that the stack tracer
3717 will trace at boot up. function-list is a comma separated
3718 list of functions. This list can be changed at run
3719 time by the stack_trace_filter file in the debugfs
3720 tracing directory. Note, this enables stack tracing
3721 and the stacktrace above is not needed.
3725 Set the STI (builtin display/keyboard on the HP-PARISC
3726 machines) console (graphic card) which should be used
3727 as the initial boot-console.
3728 See also comment in drivers/video/console/sticore.c.
3731 See comment in drivers/video/console/sticore.c.
3734 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3736 sunrpc.min_resvport=
3737 sunrpc.max_resvport=
3739 SunRPC servers often require that client requests
3740 originate from a privileged port (i.e. a port in the
3741 range 0 < portnr < 1024).
3742 An administrator who wishes to reserve some of these
3743 ports for other uses may adjust the range that the
3744 kernel's sunrpc client considers to be privileged
3745 using these two parameters to set the minimum and
3746 maximum port values.
3750 Control how the NFS server code allocates CPUs to
3751 service thread pools. Depending on how many NICs
3752 you have and where their interrupts are bound, this
3753 option will affect which CPUs will do NFS serving.
3754 Note: this parameter cannot be changed while the
3755 NFS server is running.
3757 auto the server chooses an appropriate mode
3758 automatically using heuristics
3759 global a single global pool contains all CPUs
3760 percpu one pool for each CPU
3761 pernode one pool for each NUMA node (equivalent
3762 to global on non-NUMA machines)
3764 sunrpc.tcp_slot_table_entries=
3765 sunrpc.udp_slot_table_entries=
3767 Sets the upper limit on the number of simultaneous
3768 RPC calls that can be sent from the client to a
3769 server. Increasing these values may allow you to
3770 improve throughput, but will also increase the
3771 amount of memory reserved for use by the client.
3773 suspend.pm_test_delay=
3775 Sets the number of seconds to remain in a suspend test
3776 mode before resuming the system (see
3777 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3778 is set. Default value is 5.
3781 [KNL] Enable accounting of swap in memory resource
3782 controller if no parameter or 1 is given or disable
3783 it if 0 is given (See Documentation/cgroups/memory.txt)
3785 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3786 Format: { <int> | force }
3787 <int> -- Number of I/O TLB slabs
3788 force -- force using of bounce buffers even if they
3789 wouldn't be automatically used by the kernel
3793 sysfs.deprecated=0|1 [KNL]
3794 Enable/disable old style sysfs layout for old udev
3795 on older distributions. When this option is enabled
3796 very new udev will not work anymore. When this option
3797 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3798 in older udev will not work anymore.
3799 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3800 the kernel configuration.
3802 sysrq_always_enabled
3804 Ignore sysrq setting - this boot parameter will
3805 neutralize any effect of /proc/sys/kernel/sysrq.
3806 Useful for debugging.
3808 tcpmhash_entries= [KNL,NET]
3809 Set the number of tcp_metrics_hash slots.
3810 Default value is 8192 or 16384 depending on total
3811 ram pages. This is used to specify the TCP metrics
3812 cache size. See Documentation/networking/ip-sysctl.txt
3813 "tcp_no_metrics_save" section for more details.
3817 test_suspend= [SUSPEND][,N]
3818 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3819 standby suspend) or "freeze" (for suspend type freeze)
3820 as the system sleep state during system startup with
3821 the optional capability to repeat N number of times.
3822 The system is woken from this state using a
3823 wakeup-capable RTC alarm.
3825 thash_entries= [KNL,NET]
3826 Set number of hash buckets for TCP connection
3828 thermal.act= [HW,ACPI]
3829 -1: disable all active trip points in all thermal zones
3830 <degrees C>: override all lowest active trip points
3832 thermal.crt= [HW,ACPI]
3833 -1: disable all critical trip points in all thermal zones
3834 <degrees C>: override all critical trip points
3836 thermal.nocrt= [HW,ACPI]
3837 Set to disable actions on ACPI thermal zone
3838 critical and hot trip points.
3840 thermal.off= [HW,ACPI]
3841 1: disable ACPI thermal control
3843 thermal.psv= [HW,ACPI]
3844 -1: disable all passive trip points
3845 <degrees C>: override all passive trip points to this
3848 thermal.tzp= [HW,ACPI]
3849 Specify global default ACPI thermal zone polling rate
3850 <deci-seconds>: poll all this frequency
3851 0: no polling (default)
3854 Force threading of all interrupt handlers except those
3855 marked explicitly IRQF_NO_THREAD.
3858 Enable the Transcendent memory driver if built-in.
3860 tmem.cleancache=0|1 [KNL, XEN]
3861 Default is on (1). Disable the usage of the cleancache
3862 API to send anonymous pages to the hypervisor.
3864 tmem.frontswap=0|1 [KNL, XEN]
3865 Default is on (1). Disable the usage of the frontswap
3866 API to send swap pages to the hypervisor. If disabled
3867 the selfballooning and selfshrinking are force disabled.
3869 tmem.selfballooning=0|1 [KNL, XEN]
3870 Default is on (1). Disable the driving of swap pages
3873 tmem.selfshrinking=0|1 [KNL, XEN]
3874 Default is on (1). Partial swapoff that immediately
3875 transfers pages from Xen hypervisor back to the
3876 kernel based on different criteria.
3880 Specify if the kernel should make use of the cpu
3881 topology information if the hardware supports this.
3882 The scheduler will make use of this information and
3883 e.g. base its process migration decisions on it.
3886 topology_updates= [KNL, PPC, NUMA]
3888 Specify if the kernel should ignore (off)
3889 topology updates sent by the hypervisor to this
3894 tpm_suspend_pcr=[HW,TPM]
3895 Format: integer pcr id
3896 Specify that at suspend time, the tpm driver
3897 should extend the specified pcr with zeros,
3898 as a workaround for some chips which fail to
3899 flush the last written pcr on TPM_SaveState.
3900 This will guarantee that all the other pcrs
3903 trace_buf_size=nn[KMG]
3904 [FTRACE] will set tracing buffer size on each cpu.
3906 trace_event=[event-list]
3907 [FTRACE] Set and start specified trace events in order
3908 to facilitate early boot debugging.
3909 See also Documentation/trace/events.txt
3911 trace_options=[option-list]
3912 [FTRACE] Enable or disable tracer options at boot.
3913 The option-list is a comma delimited list of options
3914 that can be enabled or disabled just as if you were
3915 to echo the option name into
3917 /sys/kernel/debug/tracing/trace_options
3919 For example, to enable stacktrace option (to dump the
3920 stack trace of each event), add to the command line:
3922 trace_options=stacktrace
3924 See also Documentation/trace/ftrace.txt "trace options"
3928 Have the tracepoints sent to printk as well as the
3929 tracing ring buffer. This is useful for early boot up
3930 where the system hangs or reboots and does not give the
3931 option for reading the tracing buffer or performing a
3932 ftrace_dump_on_oops.
3934 To turn off having tracepoints sent to printk,
3935 echo 0 > /proc/sys/kernel/tracepoint_printk
3936 Note, echoing 1 into this file without the
3937 tracepoint_printk kernel cmdline option has no effect.
3941 Having tracepoints sent to printk() and activating high
3942 frequency tracepoints such as irq or sched, can cause
3943 the system to live lock.
3946 [FTRACE] enable this option to disable tracing when a
3947 warning is hit. This turns off "tracing_on". Tracing can
3948 be enabled again by echoing '1' into the "tracing_on"
3949 file located in /sys/kernel/debug/tracing/
3951 This option is useful, as it disables the trace before
3952 the WARNING dump is called, which prevents the trace to
3953 be filled with content caused by the warning output.
3955 This option can also be set at run time via the sysctl
3956 option: kernel/traceoff_on_warning
3958 transparent_hugepage=
3960 Format: [always|madvise|never]
3961 Can be used to control the default behavior of the system
3962 with respect to transparent hugepages.
3963 See Documentation/vm/transhuge.txt for more details.
3965 tsc= Disable clocksource stability checks for TSC.
3967 [x86] reliable: mark tsc clocksource as reliable, this
3968 disables clocksource verification at runtime, as well
3969 as the stability checks done at bootup. Used to enable
3970 high-resolution timer mode on older hardware, and in
3971 virtualized environment.
3972 [x86] noirqtime: Do not use TSC to do irq accounting.
3973 Used to run time disable IRQ_TIME_ACCOUNTING on any
3974 platforms where RDTSC is slow and this accounting
3977 turbografx.map[2|3]= [HW,JOY]
3978 TurboGraFX parallel port interface
3980 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3981 See also Documentation/input/joystick-parport.txt
3983 udbg-immortal [PPC] When debugging early kernel crashes that
3984 happen after console_init() and before a proper
3985 console driver takes over, this boot options might
3986 help "seeing" what's going on.
3988 uhash_entries= [KNL,NET]
3989 Set number of hash buckets for UDP/UDP-Lite connections
3992 [USB] Ignore overcurrent events (default N).
3993 Some badly-designed motherboards generate lots of
3994 bogus events, for ports that aren't wired to
3995 anything. Set this parameter to avoid log spamming.
3996 Note that genuine overcurrent events won't be
4000 [X86] Cause panic on unknown NMI.
4002 usbcore.authorized_default=
4003 [USB] Default USB device authorization:
4004 (default -1 = authorized except for wireless USB,
4005 0 = not authorized, 1 = authorized)
4007 usbcore.autosuspend=
4008 [USB] The autosuspend time delay (in seconds) used
4009 for newly-detected USB devices (default 2). This
4010 is the time required before an idle device will be
4011 autosuspended. Devices for which the delay is set
4012 to a negative value won't be autosuspended at all.
4014 usbcore.usbfs_snoop=
4015 [USB] Set to log all usbfs traffic (default 0 = off).
4017 usbcore.usbfs_snoop_max=
4018 [USB] Maximum number of bytes to snoop in each URB
4021 usbcore.blinkenlights=
4022 [USB] Set to cycle leds on hubs (default 0 = off).
4024 usbcore.old_scheme_first=
4025 [USB] Start with the old device initialization
4026 scheme (default 0 = off).
4028 usbcore.usbfs_memory_mb=
4029 [USB] Memory limit (in MB) for buffers allocated by
4030 usbfs (default = 16, 0 = max = 2047).
4032 usbcore.use_both_schemes=
4033 [USB] Try the other device initialization scheme
4034 if the first one fails (default 1 = enabled).
4036 usbcore.initial_descriptor_timeout=
4037 [USB] Specifies timeout for the initial 64-byte
4038 USB_REQ_GET_DESCRIPTOR request in milliseconds
4039 (default 5000 = 5.0 seconds).
4041 usbcore.nousb [USB] Disable the USB subsystem
4044 [USBHID] The interval which mice are to be polled at.
4046 usb-storage.delay_use=
4047 [UMS] The delay in seconds before a new device is
4048 scanned for Logical Units (default 1).
4051 [UMS] A list of quirks entries to supplement or
4052 override the built-in unusual_devs list. List
4053 entries are separated by commas. Each entry has
4054 the form VID:PID:Flags where VID and PID are Vendor
4055 and Product ID values (4-digit hex numbers) and
4056 Flags is a set of characters, each corresponding
4057 to a common usb-storage quirk flag as follows:
4058 a = SANE_SENSE (collect more than 18 bytes
4060 b = BAD_SENSE (don't collect more than 18
4061 bytes of sense data);
4062 c = FIX_CAPACITY (decrease the reported
4063 device capacity by one sector);
4064 d = NO_READ_DISC_INFO (don't use
4065 READ_DISC_INFO command);
4066 e = NO_READ_CAPACITY_16 (don't use
4067 READ_CAPACITY_16 command);
4068 f = NO_REPORT_OPCODES (don't use report opcodes
4070 g = MAX_SECTORS_240 (don't transfer more than
4071 240 sectors at a time, uas only);
4072 h = CAPACITY_HEURISTICS (decrease the
4073 reported device capacity by one
4074 sector if the number is odd);
4075 i = IGNORE_DEVICE (don't bind to this
4077 l = NOT_LOCKABLE (don't try to lock and
4078 unlock ejectable media);
4079 m = MAX_SECTORS_64 (don't transfer more
4080 than 64 sectors = 32 KB at a time);
4081 n = INITIAL_READ10 (force a retry of the
4082 initial READ(10) command);
4083 o = CAPACITY_OK (accept the capacity
4084 reported by the device);
4085 p = WRITE_CACHE (the device cache is ON
4087 r = IGNORE_RESIDUE (the device reports
4088 bogus residue values);
4089 s = SINGLE_LUN (the device has only one
4091 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4092 commands, uas only);
4093 u = IGNORE_UAS (don't bind to the uas driver);
4094 w = NO_WP_DETECT (don't test whether the
4095 medium is write-protected).
4096 Example: quirks=0419:aaf5:rl,0421:0433:rc
4098 user_debug= [KNL,ARM]
4100 See arch/arm/Kconfig.debug help text.
4101 1 - undefined instruction events
4103 4 - invalid data aborts
4106 Example: user_debug=31
4109 [X86] Flags controlling user PTE allocations.
4111 nohigh = do not allocate PTE pages in
4112 HIGHMEM regardless of setting
4116 On X86_32, this is an alias for vdso32=. Otherwise:
4118 vdso=1: enable VDSO (the default)
4119 vdso=0: disable VDSO mapping
4121 vdso32= [X86] Control the 32-bit vDSO
4122 vdso32=1: enable 32-bit VDSO
4123 vdso32=0 or vdso32=2: disable 32-bit VDSO
4125 See the help text for CONFIG_COMPAT_VDSO for more
4126 details. If CONFIG_COMPAT_VDSO is set, the default is
4127 vdso32=0; otherwise, the default is vdso32=1.
4129 For compatibility with older kernels, vdso32=2 is an
4132 Try vdso32=0 if you encounter an error that says:
4133 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4136 vector=percpu: enable percpu vector domain
4138 video= [FB] Frame buffer configuration
4139 See Documentation/fb/modedb.txt.
4141 video.brightness_switch_enabled= [0,1]
4142 If set to 1, on receiving an ACPI notify event
4143 generated by hotkey, video driver will adjust brightness
4144 level and then send out the event to user space through
4145 the allocated input device; If set to 0, video driver
4146 will only send out the event without touching backlight
4151 [VMMIO] Memory mapped virtio (platform) device.
4153 <size>@<baseaddr>:<irq>[:<id>]
4155 <size> := size (can use standard suffixes
4157 <baseaddr> := physical base address
4158 <irq> := interrupt number (as passed to
4160 <id> := (optional) platform device id
4162 virtio_mmio.device=1K@0x100b0000:48:7
4164 Can be used multiple times for multiple devices.
4166 vga= [BOOT,X86-32] Select a particular video mode
4167 See Documentation/x86/boot.txt and
4168 Documentation/svga.txt.
4169 Use vga=ask for menu.
4170 This is actually a boot loader parameter; the value is
4171 passed to the kernel using a special protocol.
4173 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4174 size of <nn>. This can be used to increase the
4175 minimum size (128MB on x86). It can also be used to
4176 decrease the size and leave more room for directly
4179 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4182 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4185 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4189 Controls the behavior of vsyscalls (i.e. calls to
4190 fixed addresses of 0xffffffffff600x00 from legacy
4191 code). Most statically-linked binaries and older
4192 versions of glibc use these calls. Because these
4193 functions are at fixed addresses, they make nice
4194 targets for exploits that can control RIP.
4196 emulate [default] Vsyscalls turn into traps and are
4197 emulated reasonably safely.
4199 native Vsyscalls are native syscall instructions.
4200 This is a little bit faster than trapping
4201 and makes a few dynamic recompilers work
4202 better than they would in emulation mode.
4203 It also makes exploits much easier to write.
4205 none Vsyscalls don't work at all. This makes
4206 them quite hard to use for exploits but
4207 might break your system.
4209 vt.color= [VT] Default text color.
4210 Format: 0xYX, X = foreground, Y = background.
4211 Default: 0x07 = light gray on black.
4213 vt.cur_default= [VT] Default cursor shape.
4214 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4215 the parameters of the <Esc>[?A;B;Cc escape sequence;
4216 see VGA-softcursor.txt. Default: 2 = underline.
4218 vt.default_blu= [VT]
4219 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4220 Change the default blue palette of the console.
4221 This is a 16-member array composed of values
4224 vt.default_grn= [VT]
4225 Format: <green0>,<green1>,<green2>,...,<green15>
4226 Change the default green palette of the console.
4227 This is a 16-member array composed of values
4230 vt.default_red= [VT]
4231 Format: <red0>,<red1>,<red2>,...,<red15>
4232 Change the default red palette of the console.
4233 This is a 16-member array composed of values
4239 Set system-wide default UTF-8 mode for all tty's.
4240 Default is 1, i.e. UTF-8 mode is enabled for all
4241 newly opened terminals.
4243 vt.global_cursor_default=
4246 Set system-wide default for whether a cursor
4247 is shown on new VTs. Default is -1,
4248 i.e. cursors will be created by default unless
4249 overridden by individual drivers. 0 will hide
4250 cursors, 1 will display them.
4252 vt.italic= [VT] Default color for italic text; 0-15.
4255 vt.underline= [VT] Default color for underlined text; 0-15.
4258 watchdog timers [HW,WDT] For information on watchdog timers,
4259 see Documentation/watchdog/watchdog-parameters.txt
4260 or other driver-specific files in the
4261 Documentation/watchdog/ directory.
4263 workqueue.watchdog_thresh=
4264 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4265 warn stall conditions and dump internal state to
4266 help debugging. 0 disables workqueue stall
4267 detection; otherwise, it's the stall threshold
4268 duration in seconds. The default value is 30 and
4269 it can be updated at runtime by writing to the
4270 corresponding sysfs file.
4272 workqueue.disable_numa
4273 By default, all work items queued to unbound
4274 workqueues are affine to the NUMA nodes they're
4275 issued on, which results in better behavior in
4276 general. If NUMA affinity needs to be disabled for
4277 whatever reason, this option can be used. Note
4278 that this also can be controlled per-workqueue for
4279 workqueues visible under /sys/bus/workqueue/.
4281 workqueue.power_efficient
4282 Per-cpu workqueues are generally preferred because
4283 they show better performance thanks to cache
4284 locality; unfortunately, per-cpu workqueues tend to
4285 be more power hungry than unbound workqueues.
4287 Enabling this makes the per-cpu workqueues which
4288 were observed to contribute significantly to power
4289 consumption unbound, leading to measurably lower
4290 power usage at the cost of small performance
4293 The default value of this parameter is determined by
4294 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4296 workqueue.debug_force_rr_cpu
4297 Workqueue used to implicitly guarantee that work
4298 items queued without explicit CPU specified are put
4299 on the local CPU. This guarantee is no longer true
4300 and while local CPU is still preferred work items
4301 may be put on foreign CPUs. This debug option
4302 forces round-robin CPU selection to flush out
4303 usages which depend on the now broken guarantee.
4304 When enabled, memory and cache locality will be
4307 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4308 default x2apic cluster mode on platforms
4311 x86_intel_mid_timer= [X86-32,APBT]
4312 Choose timer option for x86 Intel MID platform.
4313 Two valid options are apbt timer only and lapic timer
4314 plus one apbt timer for broadcast timer.
4315 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4317 xen_512gb_limit [KNL,X86-64,XEN]
4318 Restricts the kernel running paravirtualized under Xen
4319 to use only up to 512 GB of RAM. The reason to do so is
4320 crash analysis tools and Xen tools for doing domain
4321 save/restore/migration must be enabled to handle larger
4324 xen_emul_unplug= [HW,X86,XEN]
4325 Unplug Xen emulated devices
4326 Format: [unplug0,][unplug1]
4327 ide-disks -- unplug primary master IDE devices
4328 aux-ide-disks -- unplug non-primary-master IDE devices
4329 nics -- unplug network devices
4330 all -- unplug all emulated devices (NICs and IDE disks)
4331 unnecessary -- unplugging emulated devices is
4332 unnecessary even if the host did not respond to
4334 never -- do not unplug even if version check succeeds
4336 xen_nopvspin [X86,XEN]
4337 Disables the ticketlock slowpath using Xen PV
4341 Disables the PV optimizations forcing the HVM guest to
4342 run as generic HVM guest with no PV drivers.
4344 xirc2ps_cs= [NET,PCMCIA]
4346 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4348 ______________________________________________________________________
4352 Add more DRM drivers.
projects / cascardo / linux.git / blob