4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_rsdp= [ACPI,EFI,KEXEC]
183 Pass the RSDP address to the kernel, mostly used
184 on machines running EFI runtime service to boot the
185 second kernel for kdump.
187 acpi_apic_instance= [ACPI, IOAPIC]
189 2: use 2nd APIC table, if available
190 1,0: use 1st APIC table
193 acpi_backlight= [HW,ACPI]
194 acpi_backlight=vendor
196 If set to vendor, prefer vendor specific driver
197 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
198 of the ACPI video.ko driver.
200 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
201 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
203 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204 debug output. Bits in debug_layer correspond to a
205 _COMPONENT in an ACPI source file, e.g.,
206 #define _COMPONENT ACPI_PCI_COMPONENT
207 Bits in debug_level correspond to a level in
208 ACPI_DEBUG_PRINT statements, e.g.,
209 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
210 The debug_level mask defaults to "info". See
211 Documentation/acpi/debug.txt for more information about
212 debug layers and levels.
214 Enable processor driver info messages:
215 acpi.debug_layer=0x20000000
216 Enable PCI/PCI interrupt routing info messages:
217 acpi.debug_layer=0x400000
218 Enable AML "Debug" output, i.e., stores to the Debug
219 object while interpreting AML:
220 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
221 Enable all messages related to ACPI hardware:
222 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
224 Some values produce so much output that the system is
225 unusable. The "log_buf_len" parameter may be useful
226 if you need to capture more output.
228 acpi_force_table_verification [HW,ACPI]
229 Enable table checksum verification during early stage.
230 By default, this is disabled due to x86 early mapping
233 acpi_irq_balance [HW,ACPI]
234 ACPI will balance active IRQs
237 acpi_irq_nobalance [HW,ACPI]
238 ACPI will not move active IRQs (default)
241 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242 Format: <irq>,<irq>...
244 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
246 Format: <irq>,<irq>...
248 acpi_no_auto_serialize [HW,ACPI]
249 Disable auto-serialization of AML methods
250 AML control methods that contain the opcodes to create
251 named objects will be marked as "Serialized" by the
252 auto-serialization feature.
253 This feature is enabled by default.
254 This option allows to turn off the feature.
256 acpi_no_static_ssdt [HW,ACPI]
257 Disable installation of static SSDTs at early boot time
258 By default, SSDTs contained in the RSDT/XSDT will be
259 installed automatically and they will appear under
260 /sys/firmware/acpi/tables.
261 This option turns off this feature.
262 Note that specifying this option does not affect
263 dynamic table installation which will install SSDT
264 tables to /sys/firmware/acpi/tables/dynamic.
266 acpica_no_return_repair [HW, ACPI]
267 Disable AML predefined validation mechanism
268 This mechanism can repair the evaluation result to make
269 the return objects more ACPI specification compliant.
270 This option is useful for developers to identify the
271 root cause of an AML interpreter issue when the issue
272 has something to do with the repair mechanism.
274 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
275 Format: To spoof as Windows 98: ="Microsoft Windows"
277 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
278 acpi_osi="string1" # add string1
279 acpi_osi="!string2" # remove string2
280 acpi_osi=!* # remove all strings
281 acpi_osi=! # disable all built-in OS vendor
283 acpi_osi= # disable all strings
285 'acpi_osi=!' can be used in combination with single or
286 multiple 'acpi_osi="string1"' to support specific OS
287 vendor string(s). Note that such command can only
288 affect the default state of the OS vendor strings, thus
289 it cannot affect the default state of the feature group
290 strings and the current state of the OS vendor strings,
291 specifying it multiple times through kernel command line
292 is meaningless. This command is useful when one do not
293 care about the state of the feature group strings which
294 should be controlled by the OSPM.
296 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298 can make '_OSI("Windows 2000")' TRUE.
300 'acpi_osi=' cannot be used in combination with other
301 'acpi_osi=' command lines, the _OSI method will not
302 exist in the ACPI namespace. NOTE that such command can
303 only affect the _OSI support state, thus specifying it
304 multiple times through kernel command line is also
307 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
310 'acpi_osi=!*' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific
312 string(s). Note that such command can affect the
313 current state of both the OS vendor strings and the
314 feature group strings, thus specifying it multiple times
315 through kernel command line is meaningful. But it may
316 still not able to affect the final state of a string if
317 there are quirks related to this string. This command
318 is useful when one want to control the state of the
319 feature group strings to debug BIOS issues related to
322 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323 '_OSI("Module Device")' FALSE.
324 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325 '_OSI("Module Device")' TRUE.
326 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
328 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
330 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331 they all will make '_OSI("Windows 2000")' TRUE.
334 Override the pmtimer bug detection: force the kernel
335 to assume that this machine's pmtimer latches its value
336 and always returns good values.
338 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
339 Format: { level | edge | high | low }
341 acpi_skip_timer_override [HW,ACPI]
342 Recognize and ignore IRQ0/pin2 Interrupt Override.
343 For broken nForce2 BIOS resulting in XT-PIC timer.
345 acpi_sleep= [HW,ACPI] Sleep options
346 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
347 old_ordering, nonvs, sci_force_enable }
348 See Documentation/power/video.txt for information on
350 s3_beep is for debugging; it makes the PC's speaker beep
351 as soon as the kernel's real-mode entry point is called.
352 s4_nohwsig prevents ACPI hardware signature from being
353 used during resume from hibernation.
354 old_ordering causes the ACPI 1.0 ordering of the _PTS
355 control method, with respect to putting devices into
356 low power states, to be enforced (the ACPI 2.0 ordering
357 of _PTS is used by default).
358 nonvs prevents the kernel from saving/restoring the
359 ACPI NVS memory during suspend/hibernation and resume.
360 sci_force_enable causes the kernel to set SCI_EN directly
361 on resume from S1/S3 (which is against the ACPI spec,
362 but some broken systems don't work without it).
364 acpi_use_timer_override [HW,ACPI]
365 Use timer override. For some broken Nvidia NF5 boards
366 that require a timer override, but don't have HPET
368 acpi_enforce_resources= [ACPI]
369 { strict | lax | no }
370 Check for resource conflicts between native drivers
371 and ACPI OperationRegions (SystemIO and SystemMemory
372 only). IO ports and memory declared in ACPI might be
373 used by the ACPI subsystem in arbitrary AML code and
374 can interfere with legacy drivers.
375 strict (default): access to resources claimed by ACPI
376 is denied; legacy drivers trying to access reserved
377 resources will fail to bind to device using them.
378 lax: access to resources claimed by ACPI is allowed;
379 legacy drivers trying to access reserved resources
380 will bind successfully but a warning message is logged.
381 no: ACPI OperationRegions are not marked as reserved,
382 no further checks are performed.
384 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
735 For now, only VisioBraille is supported.
737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
749 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
751 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
753 crashkernel=size[KMG][@offset[KMG]]
754 [KNL] Using kexec, Linux can switch to a 'crash kernel'
755 upon panic. This parameter reserves the physical
756 memory region [offset, offset + size] for that kernel
757 image. If '@offset' is omitted, then a suitable offset
758 is selected automatically. Check
759 Documentation/kdump/kdump.txt for further details.
761 crashkernel=range1:size1[,range2:size2,...][@offset]
762 [KNL] Same as above, but depends on the memory
763 in the running system. The syntax of range is
764 start-[end] where start and end are both
765 a memory unit (amount[KMG]). See also
766 Documentation/kdump/kdump.txt for an example.
768 crashkernel=size[KMG],high
769 [KNL, x86_64] range could be above 4G. Allow kernel
770 to allocate physical memory region from top, so could
771 be above 4G if system have more than 4G ram installed.
772 Otherwise memory region will be allocated below 4G, if
774 It will be ignored if crashkernel=X is specified.
775 crashkernel=size[KMG],low
776 [KNL, x86_64] range under 4G. When crashkernel=X,high
777 is passed, kernel could allocate physical memory region
778 above 4G, that cause second kernel crash on system
779 that require some amount of low memory, e.g. swiotlb
780 requires at least 64M+32K low memory. Kernel would
781 try to allocate 72M below 4G automatically.
782 This one let user to specify own low range under 4G
783 for second kernel instead.
784 0: to disable low allocation.
785 It will be ignored when crashkernel=X,high is not used
786 or memory reserved is below 4G.
791 cs89x0_media= [HW,NET]
792 Format: { rj45 | aui | bnc }
795 See header of drivers/s390/block/dasd_devmap.c.
797 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
798 (one device per port)
799 Format: <port#>,<type>
800 See also Documentation/input/joystick-parport.txt
802 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
803 time. See Documentation/dynamic-debug-howto.txt for
804 details. Deprecated, see dyndbg.
806 debug [KNL] Enable kernel debugging (events log level).
809 [KNL] verbose self-tests
811 Print debugging info while doing the locking API
813 We default to 0 (no extra messages), setting it to
814 1 will print _a lot_ more information - normally
815 only useful to kernel developers.
817 debug_objects [KNL] Enable object debugging
820 [KNL] Disable object debugging
822 debug_guardpage_minorder=
823 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
824 parameter allows control of the order of pages that will
825 be intentionally kept free (and hence protected) by the
826 buddy allocator. Bigger value increase the probability
827 of catching random memory corruption, but reduce the
828 amount of memory for normal system use. The maximum
829 possible value is MAX_ORDER/2. Setting this parameter
830 to 1 or 2 should be enough to identify most random
831 memory corruption problems caused by bugs in kernel or
832 driver code when a CPU writes to (or reads from) a
833 random memory location. Note that there exists a class
834 of memory corruptions problems caused by buggy H/W or
835 F/W or by drivers badly programing DMA (basically when
836 memory is written at bus level and the CPU MMU is
837 bypassed) which are not detectable by
838 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
839 tracking down these problems.
842 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
843 parameter enables the feature at boot time. In
844 default, it is disabled. We can avoid allocating huge
845 chunk of memory for debug pagealloc if we don't enable
846 it at boot time and the system will work mostly same
847 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
848 on: enable the feature
850 debugpat [X86] Enable PAT debugging
852 decnet.addr= [HW,NET]
853 Format: <area>[,<node>]
854 See also Documentation/networking/decnet.txt.
857 [same as hugepagesz=] The size of the default
858 HugeTLB page size. This is the size represented by
859 the legacy /proc/ hugepages APIs, used for SHM, and
860 default size when mounting hugetlbfs filesystems.
861 Defaults to the default architecture's huge page size
865 Set number of hash buckets for dentry cache.
868 See Documentation/networking/ipv6.txt.
870 disable_cpu_apicid= [X86,APIC,SMP]
872 The number of initial APIC ID for the
873 corresponding CPU to be disabled at boot,
874 mostly used for the kdump 2nd kernel to
875 disable BSP to wake up multiple CPUs without
876 causing system reset or hang due to sending
879 disable_ddw [PPC/PSERIES]
880 Disable Dynamic DMA Window support. Use this if
881 to workaround buggy firmware.
884 See Documentation/networking/ipv6.txt.
886 disable_mtrr_cleanup [X86]
887 The kernel tries to adjust MTRR layout from continuous
888 to discrete, to make X server driver able to add WB
889 entry later. This parameter disables that.
891 disable_mtrr_trim [X86, Intel and AMD only]
892 By default the kernel will trim any uncacheable
893 memory out of your available memory pool based on
894 MTRR settings. This parameter disables that behavior,
895 possibly causing your machine to run very slowly.
897 disable_timer_pin_1 [X86]
898 Disable PIN 1 of APIC timer
899 Can be useful to work around chipset bugs.
901 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
902 this option disables the debugging code at boot.
904 dma_debug_entries=<number>
905 This option allows to tune the number of preallocated
906 entries for DMA-API debugging code. One entry is
907 required per DMA-API allocation. Use this if the
908 DMA-API debugging code disables itself because the
909 architectural default is too low.
911 dma_debug_driver=<driver_name>
912 With this option the DMA-API debugging driver
913 filter feature can be enabled at boot time. Just
914 pass the driver to filter for as the parameter.
915 The filter can be disabled or changed to another
916 driver later using sysfs.
918 drm_kms_helper.edid_firmware=[<connector>:]<file>
919 Broken monitors, graphic adapters and KVMs may
920 send no or incorrect EDID data sets. This parameter
921 allows to specify an EDID data set in the
922 /lib/firmware directory that is used instead.
923 Generic built-in EDID data sets are used, if one of
924 edid/1024x768.bin, edid/1280x1024.bin,
925 edid/1680x1050.bin, or edid/1920x1080.bin is given
926 and no file with the same name exists. Details and
927 instructions how to build your own EDID data are
928 available in Documentation/EDID/HOWTO.txt. An EDID
929 data set will only be used for a particular connector,
930 if its name and a colon are prepended to the EDID
935 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
936 module.dyndbg[="val"]
937 Enable debug messages at boot time. See
938 Documentation/dynamic-debug-howto.txt for details.
941 on enable eager fpu restore
942 off disable eager fpu restore
943 auto selects the default scheme, which automatically
944 enables eagerfpu restore for xsaveopt.
946 early_ioremap_debug [KNL]
947 Enable debug messages in early_ioremap support. This
948 is useful for tracking down temporary early mappings
949 which are not unmapped.
951 earlycon= [KNL] Output early console device and options.
954 Start an early, polled-mode console on a cadence serial
955 port at the specified address. The cadence serial port
956 must already be setup and configured. Options are not
959 uart[8250],io,<addr>[,options]
960 uart[8250],mmio,<addr>[,options]
961 uart[8250],mmio32,<addr>[,options]
962 uart[8250],mmio32be,<addr>[,options]
963 uart[8250],0x<addr>[,options]
964 Start an early, polled-mode console on the 8250/16550
965 UART at the specified I/O port or MMIO address.
966 MMIO inter-register address stride is either 8-bit
967 (mmio) or 32-bit (mmio32 or mmio32be).
968 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
969 to be equivalent to 'mmio'. 'options' are specified
970 in the same format described for "console=ttyS<n>"; if
971 unspecified, the h/w is not initialized.
974 Start an early, polled-mode console on a pl011 serial
975 port at the specified address. The pl011 serial port
976 must already be setup and configured. Options are not
980 Start an early, polled-mode console on an msm serial
981 port at the specified address. The serial port
982 must already be setup and configured. Options are not
986 Start an early, polled-mode console on an msm serial
987 dm port at the specified address. The serial port
988 must already be setup and configured. Options are not
991 smh Use ARM semihosting calls for early console.
999 Use early console provided by serial driver available
1000 on Samsung SoCs, requires selecting proper type and
1001 a correct base address of the selected UART port. The
1002 serial port must already be setup and configured.
1003 Options are not yet supported.
1005 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1009 earlyprintk=serial[,ttySn[,baudrate]]
1010 earlyprintk=serial[,0x...[,baudrate]]
1011 earlyprintk=ttySn[,baudrate]
1012 earlyprintk=dbgp[debugController#]
1014 earlyprintk is useful when the kernel crashes before
1015 the normal console is initialized. It is not enabled by
1016 default because it has some cosmetic problems.
1018 Append ",keep" to not disable it when the real console
1021 Only one of vga, efi, serial, or usb debug port can
1024 Currently only ttyS0 and ttyS1 may be specified by
1025 name. Other I/O ports may be explicitly specified
1026 on some architectures (x86 and arm at least) by
1027 replacing ttySn with an I/O port address, like this:
1028 earlyprintk=serial,0x1008,115200
1029 You can find the port for a given device in
1030 /proc/tty/driver/serial:
1031 2: uart:ST16650V2 port:00001008 irq:18 ...
1033 Interaction with the standard serial driver is not
1036 The VGA and EFI output is eventually overwritten by
1039 The xen output can only be used by Xen PV guests.
1041 edac_report= [HW,EDAC] Control how to report EDAC event
1042 Format: {"on" | "off" | "force"}
1043 on: enable EDAC to report H/W event. May be overridden
1044 by other higher priority error reporting module.
1045 off: disable H/W event reporting through EDAC.
1046 force: enforce the use of EDAC to report H/W event.
1049 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1052 This is designed to be used in conjunction with
1053 the boot argument: earlyprintk=vga
1056 Format: {"off" | "on" | "skip[mbr]"}
1059 Format: { "old_map", "nochunk", "noruntime", "debug" }
1060 old_map [X86-64]: switch to the old ioremap-based EFI
1061 runtime services mapping. 32-bit still uses this one by
1063 nochunk: disable reading files in "chunks" in the EFI
1064 boot stub, as chunking can cause problems with some
1065 firmware implementations.
1066 noruntime : disable EFI runtime services support
1067 debug: enable misc debug output
1069 efi_no_storage_paranoia [EFI; X86]
1070 Using this parameter you can use more than 50% of
1071 your efi variable storage. Use this parameter only if
1072 you are really sure that your UEFI does sane gc and
1073 fulfills the spec otherwise your board may brick.
1075 eisa_irq_edge= [PARISC,HW]
1076 See header of drivers/parisc/eisa.c.
1079 See comment before function elanfreq_setup() in
1080 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1083 Format: {"cfq" | "deadline" | "noop"}
1084 See Documentation/block/cfq-iosched.txt and
1085 Documentation/block/deadline-iosched.txt for details.
1087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1088 Specifies physical address of start of kernel core
1089 image elf header and optionally the size. Generally
1090 kexec loader will pass this option to capture kernel.
1091 See Documentation/kdump/kdump.txt for details.
1093 enable_mtrr_cleanup [X86]
1094 The kernel tries to adjust MTRR layout from continuous
1095 to discrete, to make X server driver able to add WB
1096 entry later. This parameter enables that.
1098 enable_timer_pin_1 [X86]
1099 Enable PIN 1 of APIC timer
1100 Can be useful to work around chipset bugs
1101 (in particular on some ATI chipsets).
1102 The kernel tries to set a reasonable default.
1104 enforcing [SELINUX] Set initial enforcing status.
1106 See security/selinux/Kconfig help text.
1107 0 -- permissive (log only, no denials).
1108 1 -- enforcing (deny and log).
1110 Value can be changed at runtime via /selinux/enforce.
1113 Disable Error Record Serialization Table (ERST)
1116 ether= [HW,NET] Ethernet cards parameters
1117 This option is obsoleted by the "netdev=" option, which
1118 has equivalent usage. See its documentation for details.
1122 Permit 'security.evm' to be updated regardless of
1123 current integrity status.
1127 fail_make_request=[KNL]
1128 General fault injection mechanism.
1129 Format: <interval>,<probability>,<space>,<times>
1130 See also Documentation/fault-injection/.
1133 See Documentation/blockdev/floppy.txt.
1135 force_pal_cache_flush
1136 [IA-64] Avoid check_sal_cache_flush which may hang on
1137 buggy SAL_CACHE_FLUSH implementations. Using this
1138 parameter will force ia64_sal_cache_flush to call
1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1142 Forcefully enable Physical Address Extension (PAE).
1143 Many Pentium M systems disable PAE but may have a
1144 functionally usable PAE implementation.
1145 Warning: use of this parameter will taint the kernel
1146 and may cause unknown problems.
1149 [FTRACE] will set and start the specified tracer
1150 as early as possible in order to facilitate early
1153 ftrace_dump_on_oops[=orig_cpu]
1154 [FTRACE] will dump the trace buffers on oops.
1155 If no parameter is passed, ftrace will dump
1156 buffers of all CPUs, but if you pass orig_cpu, it will
1157 dump only the buffer of the CPU that triggered the
1160 ftrace_filter=[function-list]
1161 [FTRACE] Limit the functions traced by the function
1162 tracer at boot up. function-list is a comma separated
1163 list of functions. This list can be changed at run
1164 time by the set_ftrace_filter file in the debugfs
1167 ftrace_notrace=[function-list]
1168 [FTRACE] Do not trace the functions specified in
1169 function-list. This list can be changed at run time
1170 by the set_ftrace_notrace file in the debugfs
1173 ftrace_graph_filter=[function-list]
1174 [FTRACE] Limit the top level callers functions traced
1175 by the function graph tracer at boot up.
1176 function-list is a comma separated list of functions
1177 that can be changed at run time by the
1178 set_graph_function file in the debugfs tracing directory.
1180 ftrace_graph_notrace=[function-list]
1181 [FTRACE] Do not trace from the functions specified in
1182 function-list. This list is a comma separated list of
1183 functions that can be changed at run time by the
1184 set_graph_notrace file in the debugfs tracing directory.
1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1188 support via parallel port (up to 5 devices per port)
1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1190 See also Documentation/input/joystick-parport.txt
1194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1198 gcov_persist= [GCOV] When non-zero (default), profiling data for
1199 kernel modules is saved and remains accessible via
1200 debugfs, even when the module is unloaded/reloaded.
1201 When zero, profiling data is discarded and associated
1202 debugfs files are removed at module unload time.
1204 gpt [EFI] Forces disk with valid GPT signature but
1205 invalid Protective MBR to be treated as GPT. If the
1206 primary GPT is corrupted, it enables the backup/alternate
1207 GPT to be used instead.
1209 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1210 the "Enable 0" bit of the configuration register.
1213 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1214 the "Enable 0" bit of the configuration register.
1217 grcan.select= [HW] Select which physical interface to use.
1220 grcan.txsize= [HW] Sets the size of the tx buffer.
1221 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1223 grcan.rxsize= [HW] Sets the size of the rx buffer.
1224 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1227 hashdist= [KNL,NUMA] Large hashes allocated during boot
1228 are distributed across NUMA nodes. Defaults on
1229 for 64-bit NUMA, off otherwise.
1230 Format: 0 | 1 (for off | on)
1232 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1234 hd= [EIDE] (E)IDE hard drive subsystem geometry
1235 Format: <cyl>,<head>,<sect>
1238 Disable Hardware Error Source Table (HEST) support;
1239 corresponding firmware-first mode error processing
1240 logic will be disabled.
1242 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1243 size of <nn>. This works even on boxes that have no
1244 highmem otherwise. This also works to reduce highmem
1245 size on bigger boxes.
1247 highres= [KNL] Enable/disable high resolution timer mode.
1248 Valid parameters: "on", "off"
1252 See Documentation/isdn/README.HiSax.
1256 hpet= [X86-32,HPET] option to control HPET usage
1257 Format: { enable (default) | disable | force |
1259 disable: disable HPET and use PIT instead
1260 force: allow force enabled of undocumented chips (ICH4,
1262 verbose: show contents of HPET registers during setup
1264 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1265 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1267 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1268 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1269 On x86-64 and powerpc, this option can be specified
1270 multiple times interleaved with hugepages= to reserve
1271 huge pages of different sizes. Valid pages sizes on
1272 x86-64 are 2M (when the CPU supports "pse") and 1G
1273 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1275 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1276 terminal devices. Valid values: 0..8
1277 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1278 If specified, z/VM IUCV HVC accepts connections
1279 from listed z/VM user IDs only.
1281 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1282 hardware thread id mappings.
1283 Format: <cpu>:<hwthread>
1286 Do not unregister boot console at start. This is only
1287 useful for debugging when something happens in the window
1288 between unregistering the boot console and initializing
1291 i2c_bus= [HW] Override the default board specific I2C bus speed
1292 or register an additional I2C bus that is not
1293 registered from board initialization code.
1297 i8042.debug [HW] Toggle i8042 debug mode
1298 i8042.direct [HW] Put keyboard port into non-translated mode
1299 i8042.dumbkbd [HW] Pretend that controller can only read data from
1300 keyboard and cannot control its state
1301 (Don't attempt to blink the leds)
1302 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1303 i8042.nokbd [HW] Don't check/create keyboard port
1304 i8042.noloop [HW] Disable the AUX Loopback command while probing
1306 i8042.nomux [HW] Don't check presence of an active multiplexing
1308 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1310 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1311 i8042.reset [HW] Reset the controller during init and cleanup
1312 i8042.unlock [HW] Unlock (ignore) the keylock
1313 i8042.kbdreset [HW] Reset device connected to KBD port
1317 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1318 indicates that the driver is running on unsupported
1320 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1321 does not match list of supported models.
1323 [HW] Report power status in /proc/i8k
1324 (disabled by default)
1325 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1328 i915.invert_brightness=
1329 [DRM] Invert the sense of the variable that is used to
1330 set the brightness of the panel backlight. Normally a
1331 brightness value of 0 indicates backlight switched off,
1332 and the maximum of the brightness value sets the backlight
1333 to maximum brightness. If this parameter is set to 0
1334 (default) and the machine requires it, or this parameter
1335 is set to 1, a brightness value of 0 sets the backlight
1336 to maximum brightness, and the maximum of the brightness
1337 value switches the backlight off.
1338 -1 -- never invert brightness
1339 0 -- machine default
1340 1 -- force brightness inversion
1343 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1345 ide-core.nodma= [HW] (E)IDE subsystem
1346 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1347 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1348 .cdrom .chs .ignore_cable are additional options
1349 See Documentation/ide/ide.txt.
1351 ide-generic.probe-mask= [HW] (E)IDE subsystem
1353 Probe mask for legacy ISA IDE ports. Depending on
1354 platform up to 6 ports are supported, enabled by
1355 setting corresponding bits in the mask to 1. The
1356 default value is 0x0, which has a special meaning.
1357 On systems that have PCI, it triggers scanning the
1358 PCI bus for the first and the second port, which
1359 are then probed. On systems without PCI the value
1360 of 0x0 enables probing the two first ports as if it
1363 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1364 Claim all unknown PCI IDE storage controllers.
1367 Format: idle=poll, idle=halt, idle=nomwait
1368 Poll forces a polling idle loop that can slightly
1369 improve the performance of waking up a idle CPU, but
1370 will use a lot of power and make the system run hot.
1372 idle=halt: Halt is forced to be used for CPU idle.
1373 In such case C2/C3 won't be used again.
1374 idle=nomwait: Disable mwait for CPU C-states
1376 ignore_loglevel [KNL]
1377 Ignore loglevel setting - this will print /all/
1378 kernel messages to the console. Useful for debugging.
1379 We also add it as printk module parameter, so users
1380 could change it dynamically, usually by
1381 /sys/module/printk/parameters/ignore_loglevel.
1383 ihash_entries= [KNL]
1384 Set number of hash buckets for inode cache.
1386 ima_appraise= [IMA] appraise integrity measurements
1387 Format: { "off" | "enforce" | "fix" | "log" }
1390 ima_appraise_tcb [IMA]
1391 The builtin appraise policy appraises all files
1395 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1399 The list of supported hash algorithms is defined
1400 in crypto/hash_info.h.
1403 Load a policy which meets the needs of the Trusted
1404 Computing Base. This means IMA will measure all
1405 programs exec'd, files mmap'd for exec, and all files
1406 opened for read by uid=0.
1409 Select one of defined IMA measurements template formats.
1410 Formats: { "ima" | "ima-ng" }
1414 [IMA] Define a custom template format.
1415 Format: { "field1|...|fieldN" }
1417 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1418 Format: <min_file_size>
1419 Set the minimal file size for using asynchronous hash.
1420 If left unspecified, ahash usage is disabled.
1422 ahash performance varies for different data sizes on
1423 different crypto accelerators. This option can be used
1424 to achieve the best performance for a particular HW.
1426 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1428 Set hashing buffer size. Default: 4k.
1430 ahash performance varies for different chunk sizes on
1431 different crypto accelerators. This option can be used
1432 to achieve best performance for particular HW.
1436 Run specified binary instead of /sbin/init as init
1439 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1440 for working out where the kernel is dying during
1443 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1444 initcall functions. Useful for debugging built-in
1445 modules and initcalls.
1447 initrd= [BOOT] Specify the location of the initial ramdisk
1449 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1452 int_pln_enable [x86] Enable power limit notification interrupt
1454 integrity_audit=[IMA]
1455 Format: { "0" | "1" }
1456 0 -- basic integrity auditing messages. (Default)
1457 1 -- additional integrity auditing messages.
1459 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1461 Enable intel iommu driver.
1463 Disable intel iommu driver.
1464 igfx_off [Default Off]
1465 By default, gfx is mapped as normal device. If a gfx
1466 device has a dedicated DMAR unit, the DMAR unit is
1467 bypassed by not enabling DMAR with this option. In
1468 this case, gfx device will use physical address for
1471 With this option iommu will not optimize to look
1472 for io virtual address below 32-bit forcing dual
1473 address cycle on pci bus for cards supporting greater
1474 than 32-bit addressing. The default is to look
1475 for translation below 32-bit and if not available
1476 then look in the higher range.
1477 strict [Default Off]
1478 With this option on every unmap_single operation will
1479 result in a hardware IOTLB flush operation as opposed
1480 to batching them for performance.
1481 sp_off [Default Off]
1482 By default, super page will be supported if Intel IOMMU
1483 has the capability. With this option, super page will
1485 ecs_off [Default Off]
1486 By default, extended context tables will be supported if
1487 the hardware advertises that it has support both for the
1488 extended tables themselves, and also PASID support. With
1489 this option set, extended tables will not be used even
1490 on hardware which claims to support them.
1492 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1493 0 disables intel_idle and fall back on acpi_idle.
1494 1 to 6 specify maximum depth of C-state.
1498 Do not enable intel_pstate as the default
1499 scaling driver for the supported processors
1501 Enable intel_pstate on systems that prohibit it by default
1502 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1503 instead of acpi-cpufreq may disable platform features, such
1504 as thermal controls and power capping, that rely on ACPI
1505 P-States information being indicated to OSPM and therefore
1506 should be used with caution. This option does not work with
1507 processors that aren't supported by the intel_pstate driver
1508 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1510 Do not enable hardware P state control (HWP)
1513 Only load intel_pstate on systems which support
1514 hardware P state control (HWP) if available.
1516 intremap= [X86-64, Intel-IOMMU]
1517 on enable Interrupt Remapping (default)
1518 off disable Interrupt Remapping
1519 nosid disable Source ID checking
1521 BIOS x2APIC opt-out request will be ignored
1523 iomem= Disable strict checking of access to MMIO memory
1524 strict regions from userspace.
1539 nobypass [PPC/POWERNV]
1540 Disable IOMMU bypass, using IOMMU for PCI devices.
1543 io7= [HW] IO7 for Marvel based alpha systems
1544 See comment before marvel_specify_io7 in
1545 arch/alpha/kernel/core_marvel.c.
1547 io_delay= [X86] I/O delay method
1549 Standard port 0x80 based delay
1551 Alternate port 0xed based delay (needed on some systems)
1553 Simple two microseconds delay
1558 See Documentation/filesystems/nfs/nfsroot.txt.
1561 When an interrupt is not handled search all handlers
1562 for it. Intended to get systems with badly broken
1566 When an interrupt is not handled search all handlers
1567 for it. Also check all handlers each timer
1568 interrupt. Intended to get systems with badly broken
1572 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1574 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1576 <cpu number>,...,<cpu number>
1578 <cpu number>-<cpu number>
1579 (must be a positive range in ascending order)
1581 <cpu number>,...,<cpu number>-<cpu number>
1583 This option can be used to specify one or more CPUs
1584 to isolate from the general SMP balancing and scheduling
1585 algorithms. You can move a process onto or off an
1586 "isolated" CPU via the CPU affinity syscalls or cpuset.
1587 <cpu number> begins at 0 and the maximum value is
1588 "number of CPUs in system - 1".
1590 This option is the preferred way to isolate CPUs. The
1591 alternative -- manually setting the CPU mask of all
1592 tasks in the system -- can cause problems and
1593 suboptimal load balancer performance.
1597 ivrs_ioapic [HW,X86_64]
1598 Provide an override to the IOAPIC-ID<->DEVICE-ID
1599 mapping provided in the IVRS ACPI table. For
1600 example, to map IOAPIC-ID decimal 10 to
1601 PCI device 00:14.0 write the parameter as:
1602 ivrs_ioapic[10]=00:14.0
1604 ivrs_hpet [HW,X86_64]
1605 Provide an override to the HPET-ID<->DEVICE-ID
1606 mapping provided in the IVRS ACPI table. For
1607 example, to map HPET-ID decimal 0 to
1608 PCI device 00:14.0 write the parameter as:
1609 ivrs_hpet[0]=00:14.0
1611 js= [HW,JOY] Analog joystick
1612 See Documentation/input/joystick.txt.
1615 Enable/disable kernel and module base offset ASLR
1616 (Address Space Layout Randomization) if built into
1617 the kernel. When CONFIG_HIBERNATION is selected,
1618 kASLR is disabled by default. When kASLR is enabled,
1619 hibernation will be disabled.
1623 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1624 specifies the amount of memory usable by the kernel
1625 for non-movable allocations. The requested amount is
1626 spread evenly throughout all nodes in the system. The
1627 remaining memory in each node is used for Movable
1628 pages. In the event, a node is too small to have both
1629 kernelcore and Movable pages, kernelcore pages will
1630 take priority and other nodes will have a larger number
1631 of Movable pages. The Movable zone is used for the
1632 allocation of pages that may be reclaimed or moved
1633 by the page migration subsystem. This means that
1634 HugeTLB pages may not be allocated from this zone.
1635 Note that allocations like PTEs-from-HighMem still
1636 use the HighMem zone if it exists, and the Normal
1637 zone if it does not.
1639 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1640 Format: <Controller#>[,poll interval]
1641 The controller # is the number of the ehci usb debug
1642 port as it is probed via PCI. The poll interval is
1643 optional and is the number seconds in between
1644 each poll cycle to the debug port in case you need
1645 the functionality for interrupting the kernel with
1646 gdb or control-c on the dbgp connection. When
1647 not using this parameter you use sysrq-g to break into
1648 the kernel debugger.
1650 kgdboc= [KGDB,HW] kgdb over consoles.
1651 Requires a tty driver that supports console polling,
1652 or a supported polling keyboard driver (non-usb).
1653 Serial only format: <serial_device>[,baud]
1654 keyboard only format: kbd
1655 keyboard and serial format: kbd,<serial_device>[,baud]
1656 Optional Kernel mode setting:
1657 kms, kbd format: kms,kbd
1658 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1660 kgdbwait [KGDB] Stop kernel execution and enter the
1661 kernel debugger at the earliest opportunity.
1663 kmac= [MIPS] korina ethernet MAC address.
1664 Configure the RouterBoard 532 series on-chip
1665 Ethernet adapter MAC address.
1667 kmemleak= [KNL] Boot-time kmemleak enable/disable
1668 Valid arguments: on, off
1670 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1673 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1674 Valid arguments: 0, 1, 2
1675 kmemcheck=0 (disabled)
1676 kmemcheck=1 (enabled)
1677 kmemcheck=2 (one-shot mode)
1678 Default: 2 (one-shot mode)
1680 kstack=N [X86] Print N words from the kernel stack
1683 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1684 Default is 0 (don't ignore, but inject #GP)
1686 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1690 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1691 Default is 1 (enabled)
1693 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1695 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1697 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1698 (virtualized MMU) support on capable Intel chips.
1699 Default is 1 (enabled)
1701 kvm-intel.emulate_invalid_guest_state=
1702 [KVM,Intel] Enable emulation of invalid guest states
1703 Default is 0 (disabled)
1705 kvm-intel.flexpriority=
1706 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1707 Default is 1 (enabled)
1710 [KVM,Intel] Enable VMX nesting (nVMX).
1711 Default is 0 (disabled)
1713 kvm-intel.unrestricted_guest=
1714 [KVM,Intel] Disable unrestricted guest feature
1715 (virtualized real and unpaged mode) on capable
1716 Intel chips. Default is 1 (enabled)
1718 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1719 feature (tagged TLBs) on capable Intel chips.
1720 Default is 1 (enabled)
1726 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1729 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1730 value for LAPIC timer one-shot implementation. Default
1731 back to the programmable timer unit in the LAPIC.
1733 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1736 libata.dma= [LIBATA] DMA control
1737 libata.dma=0 Disable all PATA and SATA DMA
1738 libata.dma=1 PATA and SATA Disk DMA only
1739 libata.dma=2 ATAPI (CDROM) DMA only
1740 libata.dma=4 Compact Flash DMA only
1741 Combinations also work, so libata.dma=3 enables DMA
1742 for disks and CDROMs, but not CFs.
1744 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1745 libata.ignore_hpa=0 keep BIOS limits (default)
1746 libata.ignore_hpa=1 ignore limits, using full disk
1748 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1752 libata.force= [LIBATA] Force configurations. The format is comma
1753 separated list of "[ID:]VAL" where ID is
1754 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1755 matching port, link or device. Basically, it matches
1756 the ATA ID string printed on console by libata. If
1757 the whole ID part is omitted, the last PORT and DEVICE
1758 values are used. If ID hasn't been specified yet, the
1759 configuration applies to all ports, links and devices.
1761 If only DEVICE is omitted, the parameter applies to
1762 the port and all links and devices behind it. DEVICE
1763 number of 0 either selects the first device or the
1764 first fan-out link behind PMP device. It does not
1765 select the host link. DEVICE number of 15 selects the
1766 host link and device attached to it.
1768 The VAL specifies the configuration to force. As long
1769 as there's no ambiguity shortcut notation is allowed.
1770 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1771 The following configurations can be forced.
1773 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1774 Any ID with matching PORT is used.
1776 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1778 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1779 udma[/][16,25,33,44,66,100,133] notation is also
1782 * [no]ncq: Turn on or off NCQ.
1784 * nohrst, nosrst, norst: suppress hard, soft
1787 * rstonce: only attempt one reset during
1788 hot-unplug link recovery
1790 * dump_id: dump IDENTIFY data.
1792 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1794 * disable: Disable this device.
1796 If there are multiple matching configurations changing
1797 the same attribute, the last one is used.
1799 memblock=debug [KNL] Enable memblock debug messages.
1801 load_ramdisk= [RAM] List of ramdisks to load from floppy
1802 See Documentation/blockdev/ramdisk.txt.
1804 lockd.nlm_grace_period=P [NFS] Assign grace period.
1807 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1810 lockd.nlm_timeout=T [NFS] Assign timeout value.
1813 lockd.nlm_udpport=M [NFS] Assign UDP port.
1816 locktorture.nreaders_stress= [KNL]
1817 Set the number of locking read-acquisition kthreads.
1818 Defaults to being automatically set based on the
1819 number of online CPUs.
1821 locktorture.nwriters_stress= [KNL]
1822 Set the number of locking write-acquisition kthreads.
1824 locktorture.onoff_holdoff= [KNL]
1825 Set time (s) after boot for CPU-hotplug testing.
1827 locktorture.onoff_interval= [KNL]
1828 Set time (s) between CPU-hotplug operations, or
1829 zero to disable CPU-hotplug testing.
1831 locktorture.shuffle_interval= [KNL]
1832 Set task-shuffle interval (jiffies). Shuffling
1833 tasks allows some CPUs to go into dyntick-idle
1834 mode during the locktorture test.
1836 locktorture.shutdown_secs= [KNL]
1837 Set time (s) after boot system shutdown. This
1838 is useful for hands-off automated testing.
1840 locktorture.stat_interval= [KNL]
1841 Time (s) between statistics printk()s.
1843 locktorture.stutter= [KNL]
1844 Time (s) to stutter testing, for example,
1845 specifying five seconds causes the test to run for
1846 five seconds, wait for five seconds, and so on.
1847 This tests the locking primitive's ability to
1848 transition abruptly to and from idle.
1850 locktorture.torture_runnable= [BOOT]
1851 Start locktorture running at boot time.
1853 locktorture.torture_type= [KNL]
1854 Specify the locking implementation to test.
1856 locktorture.verbose= [KNL]
1857 Enable additional printk() statements.
1859 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1862 loglevel= All Kernel Messages with a loglevel smaller than the
1863 console loglevel will be printed to the console. It can
1864 also be changed with klogd or other programs. The
1865 loglevels are defined as follows:
1867 0 (KERN_EMERG) system is unusable
1868 1 (KERN_ALERT) action must be taken immediately
1869 2 (KERN_CRIT) critical conditions
1870 3 (KERN_ERR) error conditions
1871 4 (KERN_WARNING) warning conditions
1872 5 (KERN_NOTICE) normal but significant condition
1873 6 (KERN_INFO) informational
1874 7 (KERN_DEBUG) debug-level messages
1876 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1877 in bytes. n must be a power of two and greater
1878 than the minimal size. The minimal size is defined
1879 by LOG_BUF_SHIFT kernel config parameter. There is
1880 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1881 that allows to increase the default size depending on
1882 the number of CPUs. See init/Kconfig for more details.
1884 logo.nologo [FB] Disables display of the built-in Linux logo.
1885 This may be used to provide more screen space for
1886 kernel log messages and is useful when debugging
1887 kernel boot problems.
1889 lp=0 [LP] Specify parallel ports to use, e.g,
1890 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1891 lp=reset first parallel port). 'lp=0' disables the
1892 lp=auto printer driver. 'lp=reset' (which can be
1893 specified in addition to the ports) causes
1894 attached printers to be reset. Using
1895 lp=port1,port2,... specifies the parallel ports
1896 to associate lp devices with, starting with
1897 lp0. A port specification may be 'none' to skip
1898 that lp device, or a parport name such as
1899 'parport0'. Specifying 'lp=auto' instead of a
1900 port specification list means that device IDs
1901 from each port should be examined, to see if
1902 an IEEE 1284-compliant printer is attached; if
1903 so, the driver will manage that printer.
1904 See also header of drivers/char/lp.c.
1907 Sets loops_per_jiffy to given constant, thus avoiding
1908 time-consuming boot-time autodetection (up to 250 ms per
1909 CPU). 0 enables autodetection (default). To determine
1910 the correct value for your kernel, boot with normal
1911 autodetection and see what value is printed. Note that
1912 on SMP systems the preset will be applied to all CPUs,
1913 which is likely to cause problems if your CPUs need
1914 significantly divergent settings. An incorrect value
1915 will cause delays in the kernel to be wrong, leading to
1916 unpredictable I/O errors and other breakage. Although
1917 unlikely, in the extreme case this might damage your
1921 Format: <io>,<irq>,<dma>
1923 machvec= [IA-64] Force the use of a particular machine-vector
1924 (machvec) in a generic kernel.
1925 Example: machvec=hpzx1_swiotlb
1927 machtype= [Loongson] Share the same kernel image file between different
1929 Example: machtype=lemote-yeeloong-2f-7inch
1931 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1932 than or equal to this physical address is ignored.
1934 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1935 should make use of. maxcpus=n : n >= 0 limits the
1936 kernel to using 'n' processors. n=0 is a special case,
1937 it is equivalent to "nosmp", which also disables
1940 max_loop= [LOOP] The number of loop block devices that get
1941 (loop.max_loop) unconditionally pre-created at init time. The default
1942 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1943 of statically allocating a predefined number, loop
1944 devices can be requested on-demand with the
1945 /dev/loop-control interface.
1947 mce [X86-32] Machine Check Exception
1949 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1951 md= [HW] RAID subsystems devices and level
1952 See Documentation/md.txt.
1955 Format: <first>,<last>
1956 Specifies range of consoles to be captured by the MDA.
1958 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1959 Amount of memory to be used when the kernel is not able
1960 to see the whole system memory or for test.
1961 [X86] Work as limiting max address. Use together
1962 with memmap= to avoid physical address space collisions.
1963 Without memmap= PCI devices could be placed at addresses
1964 belonging to unused RAM.
1966 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1970 [KNL,SH] Allow user to override the default size for
1971 per-device physically contiguous DMA buffers.
1973 memmap=exactmap [KNL,X86] Enable setting of an exact
1974 E820 memory map, as specified by the user.
1975 Such memmap=exactmap lines can be constructed based on
1976 BIOS output or other requirements. See the memmap=nn@ss
1979 memmap=nn[KMG]@ss[KMG]
1980 [KNL] Force usage of a specific region of memory.
1981 Region of memory to be used is from ss to ss+nn.
1983 memmap=nn[KMG]#ss[KMG]
1984 [KNL,ACPI] Mark specific memory as ACPI data.
1985 Region of memory to be marked is from ss to ss+nn.
1987 memmap=nn[KMG]$ss[KMG]
1988 [KNL,ACPI] Mark specific memory as reserved.
1989 Region of memory to be reserved is from ss to ss+nn.
1990 Example: Exclude memory from 0x18690000-0x1869ffff
1991 memmap=64K$0x18690000
1993 memmap=0x10000$0x18690000
1995 memmap=nn[KMG]!ss[KMG]
1996 [KNL,X86] Mark specific memory as protected.
1997 Region of memory to be used, from ss to ss+nn.
1998 The memory region may be marked as e820 type 12 (0xc)
1999 and is NVDIMM or ADR memory.
2001 memory_corruption_check=0/1 [X86]
2002 Some BIOSes seem to corrupt the first 64k of
2003 memory when doing things like suspend/resume.
2004 Setting this option will scan the memory
2005 looking for corruption. Enabling this will
2006 both detect corruption and prevent the kernel
2007 from using the memory being corrupted.
2008 However, its intended as a diagnostic tool; if
2009 repeatable BIOS-originated corruption always
2010 affects the same memory, you can use memmap=
2011 to prevent the kernel from using that memory.
2013 memory_corruption_check_size=size [X86]
2014 By default it checks for corruption in the low
2015 64k, making this memory unavailable for normal
2016 use. Use this parameter to scan for
2017 corruption in more or less memory.
2019 memory_corruption_check_period=seconds [X86]
2020 By default it checks for corruption every 60
2021 seconds. Use this parameter to check at some
2022 other rate. 0 disables periodic checking.
2024 memtest= [KNL,X86,ARM] Enable memtest
2026 default : 0 <disable>
2027 Specifies the number of memtest passes to be
2028 performed. Each pass selects another test
2029 pattern from a given set of patterns. Memtest
2030 fills the memory with this pattern, validates
2031 memory contents and reserves bad memory
2032 regions that are detected.
2034 meye.*= [HW] Set MotionEye Camera parameters
2035 See Documentation/video4linux/meye.txt.
2037 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2038 Multi-Function General Purpose Timers on AMD Geode
2041 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2042 the BIOS has incorrectly applied a workaround. TinyBIOS
2043 version 0.98 is known to be affected, 0.99 fixes the
2044 problem by letting the user disable the workaround.
2048 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2049 physical address is ignored.
2051 mini2440= [ARM,HW,KNL]
2052 Format:[0..2][b][c][t]
2054 MINI2440 configuration specification:
2055 0 - The attached screen is the 3.5" TFT
2056 1 - The attached screen is the 7" TFT
2057 2 - The VGA Shield is attached (1024x768)
2058 Leaving out the screen size parameter will not load
2059 the TFT driver, and the framebuffer will be left
2061 b - Enable backlight. The TFT backlight pin will be
2062 linked to the kernel VESA blanking code and a GPIO
2063 LED. This parameter is not necessary when using the
2065 c - Enable the s3c camera interface.
2066 t - Reserved for enabling touchscreen support. The
2067 touchscreen support is not enabled in the mainstream
2068 kernel as of 2.6.30, a preliminary port can be found
2069 in the "bleeding edge" mini2440 support kernel at
2070 http://repo.or.cz/w/linux-2.6/mini2440.git
2073 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2074 parameter allows control of the logging verbosity for
2075 the additional memory initialisation checks. A value
2076 of 0 disables mminit logging and a level of 4 will
2077 log everything. Information is printed at KERN_DEBUG
2078 so loglevel=8 may also need to be specified.
2081 [KNL] When CONFIG_MODULE_SIG is set, this means that
2082 modules without (valid) signatures will fail to load.
2083 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2084 is always true, so this option does nothing.
2087 [MOUSE] Maximum time between finger touching and
2088 leaving touchpad surface for touch to be considered
2089 a tap and be reported as a left button click (for
2090 touchpads working in absolute mode only).
2092 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2093 reporting absolute coordinates, such as tablets
2094 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2095 reporting absolute coordinates, such as tablets
2097 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2098 is similar to kernelcore except it specifies the
2099 amount of memory used for migratable allocations.
2100 If both kernelcore and movablecore is specified,
2101 then kernelcore will be at *least* the specified
2102 value but may be more. If movablecore on its own
2103 is specified, the administrator must be careful
2104 that the amount of memory usable for all allocations
2107 movable_node [KNL,X86] Boot-time switch to enable the effects
2108 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2110 MTD_Partition= [MTD]
2111 Format: <name>,<region-number>,<size>,<offset>
2113 MTD_Region= [MTD] Format:
2114 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2117 See drivers/mtd/cmdlinepart.c.
2119 multitce=off [PPC] This parameter disables the use of the pSeries
2120 firmware feature for updating multiple TCE entries
2123 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2125 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2127 boundary - index of last SLC block on Flex-OneNAND.
2128 The remaining blocks are configured as MLC blocks.
2129 lock - Configure if Flex-OneNAND boundary should be locked.
2130 Once locked, the boundary cannot be changed.
2131 1 indicates lock status, 0 indicates unlock status.
2134 ARM/S3C2412 JIVE boot control
2136 See arch/arm/mach-s3c2412/mach-jive.c
2138 mtouchusb.raw_coordinates=
2139 [HW] Make the MicroTouch USB driver use raw coordinates
2140 ('y', default) or cooked coordinates ('n')
2142 mtrr_chunk_size=nn[KMG] [X86]
2143 used for mtrr cleanup. It is largest continuous chunk
2144 that could hold holes aka. UC entries.
2146 mtrr_gran_size=nn[KMG] [X86]
2147 Used for mtrr cleanup. It is granularity of mtrr block.
2149 Large value could prevent small alignment from
2152 mtrr_spare_reg_nr=n [X86]
2154 Range: 0,7 : spare reg number
2156 Used for mtrr cleanup. It is spare mtrr entries number.
2157 Set to 2 or more if your graphical card needs more.
2159 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2161 netdev= [NET] Network devices parameters
2162 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2163 Note that mem_start is often overloaded to mean
2164 something different and driver-specific.
2165 This usage is only documented in each driver source
2169 [NETFILTER] Enable connection tracking flow accounting
2170 0 to disable accounting
2171 1 to enable accounting
2174 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2175 See Documentation/filesystems/nfs/nfsroot.txt.
2177 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2178 See Documentation/filesystems/nfs/nfsroot.txt.
2180 nfsrootdebug [NFS] enable nfsroot debugging messages.
2181 See Documentation/filesystems/nfs/nfsroot.txt.
2183 nfs.callback_tcpport=
2184 [NFS] set the TCP port on which the NFSv4 callback
2185 channel should listen.
2188 [NFS] sets the pathname to the program which is used
2189 to update the NFS client cache entries.
2191 nfs.cache_getent_timeout=
2192 [NFS] sets the timeout after which an attempt to
2193 update a cache entry is deemed to have failed.
2195 nfs.idmap_cache_timeout=
2196 [NFS] set the maximum lifetime for idmapper cache
2200 [NFS] enable 64-bit inode numbers.
2201 If zero, the NFS client will fake up a 32-bit inode
2202 number for the readdir() and stat() syscalls instead
2203 of returning the full 64-bit number.
2204 The default is to return 64-bit inode numbers.
2206 nfs.max_session_slots=
2207 [NFSv4.1] Sets the maximum number of session slots
2208 the client will attempt to negotiate with the server.
2209 This limits the number of simultaneous RPC requests
2210 that the client can send to the NFSv4.1 server.
2211 Note that there is little point in setting this
2212 value higher than the max_tcp_slot_table_limit.
2214 nfs.nfs4_disable_idmapping=
2215 [NFSv4] When set to the default of '1', this option
2216 ensures that both the RPC level authentication
2217 scheme and the NFS level operations agree to use
2218 numeric uids/gids if the mount is using the
2219 'sec=sys' security flavour. In effect it is
2220 disabling idmapping, which can make migration from
2221 legacy NFSv2/v3 systems to NFSv4 easier.
2222 Servers that do not support this mode of operation
2223 will be autodetected by the client, and it will fall
2224 back to using the idmapper.
2225 To turn off this behaviour, set the value to '0'.
2227 [NFS4] Specify an additional fixed unique ident-
2228 ification string that NFSv4 clients can insert into
2229 their nfs_client_id4 string. This is typically a
2230 UUID that is generated at system install time.
2232 nfs.send_implementation_id =
2233 [NFSv4.1] Send client implementation identification
2234 information in exchange_id requests.
2235 If zero, no implementation identification information
2237 The default is to send the implementation identification
2240 nfs.recover_lost_locks =
2241 [NFSv4] Attempt to recover locks that were lost due
2242 to a lease timeout on the server. Please note that
2243 doing this risks data corruption, since there are
2244 no guarantees that the file will remain unchanged
2245 after the locks are lost.
2246 If you want to enable the kernel legacy behaviour of
2247 attempting to recover these locks, then set this
2249 The default parameter value of '0' causes the kernel
2250 not to attempt recovery of lost locks.
2252 nfsd.nfs4_disable_idmapping=
2253 [NFSv4] When set to the default of '1', the NFSv4
2254 server will return only numeric uids and gids to
2255 clients using auth_sys, and will accept numeric uids
2256 and gids from such clients. This is intended to ease
2257 migration from NFSv2/v3.
2259 objlayoutdriver.osd_login_prog=
2260 [NFS] [OBJLAYOUT] sets the pathname to the program which
2261 is used to automatically discover and login into new
2262 osd-targets. Please see:
2263 Documentation/filesystems/pnfs.txt for more explanations
2265 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2266 when a NMI is triggered.
2267 Format: [state][,regs][,debounce][,die]
2269 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2270 Format: [panic,][nopanic,][num]
2272 0 - turn nmi_watchdog off
2273 1 - turn nmi_watchdog on
2274 When panic is specified, panic when an NMI watchdog
2275 timeout occurs (or 'nopanic' to override the opposite
2277 This is useful when you use a panic=... timeout and
2278 need the box quickly up again.
2280 netpoll.carrier_timeout=
2281 [NET] Specifies amount of time (in seconds) that
2282 netpoll should wait for a carrier. By default netpoll
2285 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2286 emulation library even if a 387 maths coprocessor
2290 [HW] Never suspend the console
2291 Disable suspending of consoles during suspend and
2292 hibernate operations. Once disabled, debugging
2293 messages can reach various consoles while the rest
2294 of the system is being put to sleep (ie, while
2295 debugging driver suspend/resume hooks). This may
2296 not work reliably with all consoles, but is known
2297 to work with serial and VGA consoles.
2298 To facilitate more flexible debugging, we also add
2299 console_suspend, a printk module parameter to control
2300 it. Users could use console_suspend (usually
2301 /sys/module/printk/parameters/console_suspend) to
2302 turn on/off it dynamically.
2304 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2305 caches in the slab allocator. Saves per-node memory,
2306 but will impact performance.
2310 noapic [SMP,APIC] Tells the kernel to not make use of any
2311 IOAPICs that may be present in the system.
2313 noautogroup Disable scheduler automatic task group creation.
2315 nobats [PPC] Do not use BATs for mapping kernel lowmem
2316 on "Classic" PPC cores.
2320 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2322 nodelayacct [KNL] Disable per-task delay accounting
2324 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2326 nodsp [SH] Disable hardware DSP at boot time.
2328 noefi Disable EFI runtime services support.
2333 On X86-32 available only on PAE configured kernels.
2334 noexec=on: enable non-executable mappings (default)
2335 noexec=off: disable non-executable mappings
2338 Disable SMAP (Supervisor Mode Access Prevention)
2339 even if it is supported by processor.
2342 Disable SMEP (Supervisor Mode Execution Prevention)
2343 even if it is supported by processor.
2346 This affects only 32-bit executables.
2347 noexec32=on: enable non-executable mappings (default)
2348 read doesn't imply executable mappings
2349 noexec32=off: disable non-executable mappings
2350 read implies executable mappings
2352 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2354 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2355 register save and restore. The kernel will only save
2356 legacy floating-point registers on task switch.
2358 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2360 noxsave [BUGS=X86] Disables x86 extended register state save
2361 and restore using xsave. The kernel will fallback to
2362 enabling legacy floating-point and sse state.
2364 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2365 register states. The kernel will fall back to use
2366 xsave to save the states. By using this parameter,
2367 performance of saving the states is degraded because
2368 xsave doesn't support modified optimization while
2369 xsaveopt supports it on xsaveopt enabled systems.
2371 noxsaves [X86] Disables xsaves and xrstors used in saving and
2372 restoring x86 extended register state in compacted
2373 form of xsave area. The kernel will fall back to use
2374 xsaveopt and xrstor to save and restore the states
2375 in standard form of xsave area. By using this
2376 parameter, xsave area per process might occupy more
2377 memory on xsaves enabled systems.
2379 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2380 wfi(ARM) instruction doesn't work correctly and not to
2381 use it. This is also useful when using JTAG debugger.
2383 no_file_caps Tells the kernel not to honor file capabilities. The
2384 only way then for a file to be executed with privilege
2385 is to be setuid root or executed by root.
2387 nohalt [IA-64] Tells the kernel not to use the power saving
2388 function PAL_HALT_LIGHT when idle. This increases
2389 power-consumption. On the positive side, it reduces
2390 interrupt wake-up latency, which may improve performance
2391 in certain environments such as networked servers or
2394 nohibernate [HIBERNATION] Disable hibernation and resume.
2396 nohz= [KNL] Boottime enable/disable dynamic ticks
2397 Valid arguments: on, off
2400 nohz_full= [KNL,BOOT]
2401 In kernels built with CONFIG_NO_HZ_FULL=y, set
2402 the specified list of CPUs whose tick will be stopped
2403 whenever possible. The boot CPU will be forced outside
2404 the range to maintain the timekeeping.
2405 The CPUs in this range must also be included in the
2408 noiotrap [SH] Disables trapped I/O port accesses.
2410 noirqdebug [X86-32] Disables the code which attempts to detect and
2411 disable unhandled interrupt sources.
2413 no_timer_check [X86,APIC] Disables the code which tests for
2414 broken timer IRQ sources.
2416 noisapnp [ISAPNP] Disables ISA PnP code.
2418 noinitrd [RAM] Tells the kernel not to load any configured
2421 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2423 [Deprecated - use intremap=off]
2427 nojitter [IA-64] Disables jitter checking for ITC timers.
2429 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2431 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2434 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2435 steal time is computed, but won't influence scheduler
2438 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2440 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2442 noltlbs [PPC] Do not use large page/tlb entries for kernel
2443 lowmem mapping on PPC40x.
2445 nomca [IA-64] Disable machine check abort handling
2447 nomce [X86-32] Machine Check Exception
2449 nomfgpt [X86-32] Disable Multi-Function General Purpose
2450 Timer usage (for AMD Geode machines).
2452 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2453 shutdown the other cpus. Instead use the REBOOT_VECTOR
2456 nomodule Disable module load
2458 nopat [X86] Disable PAT (page attribute table extension of
2459 pagetables) support.
2461 norandmaps Don't use address space randomization. Equivalent to
2462 echo 0 > /proc/sys/kernel/randomize_va_space
2464 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2466 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2467 with UP alternatives
2469 nordrand [X86] Disable kernel use of the RDRAND and
2470 RDSEED instructions even if they are supported
2471 by the processor. RDRAND and RDSEED are still
2472 available to user space applications.
2474 noresume [SWSUSP] Disables resume and restores original swap
2477 no-scroll [VGA] Disables scrollback.
2478 This is required for the Braillex ib80-piezo Braille
2479 reader made by F.H. Papenmeier (Germany).
2483 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2485 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2486 and disable the IO APIC. legacy for "maxcpus=0".
2488 nosoftlockup [KNL] Disable the soft-lockup detector.
2490 nosync [HW,M68K] Disables sync negotiation for all devices.
2492 notsc [BUGS=X86-32] Disable Time Stamp Counter
2494 nousb [USB] Disable the USB subsystem
2496 nowatchdog [KNL] Disable both lockup detectors, i.e.
2497 soft-lockup and NMI watchdog (hard-lockup).
2501 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2503 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2504 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2505 Some features depend on CPU0. Known dependencies are:
2506 1. Resume from suspend/hibernate depends on CPU0.
2507 Suspend/hibernate will fail if CPU0 is offline and you
2508 need to online CPU0 before suspend/hibernate.
2509 2. PIC interrupts also depend on CPU0. CPU0 can't be
2510 removed if a PIC interrupt is detected.
2511 It's said poweroff/reboot may depend on CPU0 on some
2512 machines although I haven't seen such issues so far
2513 after CPU0 is offline on a few tested machines.
2514 If the dependencies are under your control, you can
2515 turn on cpu0_hotplug.
2517 nptcg= [IA-64] Override max number of concurrent global TLB
2518 purges which is reported from either PAL_VM_SUMMARY or
2521 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2522 could support. nr_cpus=n : n >= 1 limits the kernel to
2523 supporting 'n' processors. Later in runtime you can not
2524 use hotplug cpu feature to put more cpu back to online.
2525 just like you compile the kernel NR_CPUS=n
2527 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2529 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2530 Allowed values are enable and disable
2532 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2533 one of ['zone', 'node', 'default'] can be specified
2534 This can be set from sysctl after boot.
2535 See Documentation/sysctl/vm.txt for details.
2537 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2538 See Documentation/debugging-via-ohci1394.txt for more
2541 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2542 Rather than timing out after 20 ms if an EC
2543 command is not properly ACKed, override the length
2544 of the timeout. We have interrupts disabled while
2545 waiting for the ACK, so if this is set too high
2546 interrupts *may* be lost!
2548 omap_mux= [OMAP] Override bootloader pin multiplexing.
2549 Format: <mux_mode0.mode_name=value>...
2550 For example, to override I2C bus2:
2551 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2553 oprofile.timer= [HW]
2554 Use timer interrupt instead of performance counters
2556 oprofile.cpu_type= Force an oprofile cpu type
2557 This might be useful if you have an older oprofile
2558 userland or if you want common events.
2559 Format: { arch_perfmon }
2560 arch_perfmon: [X86] Force use of architectural
2561 perfmon on Intel CPUs instead of the
2562 CPU specific event set.
2563 timer: [X86] Force use of architectural NMI
2564 timer mode (see also oprofile.timer
2565 for generic hr timer mode)
2566 [s390] Force legacy basic mode sampling
2567 (report cpu_type "timer")
2569 oops=panic Always panic on oopses. Default is to just kill the
2570 process, but there is a small probability of
2571 deadlocking the machine.
2572 This will also cause panics on machine check exceptions.
2573 Useful together with panic=30 to trigger a reboot.
2576 See Documentation/sound/oss/oss-parameters.txt
2578 page_owner= [KNL] Boot-time page_owner enabling option.
2579 Storage of the information about who allocated
2580 each page is disabled in default. With this switch,
2582 on: enable the feature
2584 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2585 timeout > 0: seconds before rebooting
2586 timeout = 0: wait forever
2587 timeout < 0: reboot immediately
2590 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2593 crash_kexec_post_notifiers
2594 Run kdump after running panic-notifiers and dumping
2595 kmsg. This only for the users who doubt kdump always
2596 succeeds in any situation.
2597 Note that this also increases risks of kdump failure,
2598 because some panic notifiers can make the crashed
2599 kernel more unstable.
2601 parkbd.port= [HW] Parallel port number the keyboard adapter is
2602 connected to, default is 0.
2604 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2605 0 for XT, 1 for AT (default is AT).
2608 parport= [HW,PPT] Specify parallel ports. 0 disables.
2609 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2610 Use 'auto' to force the driver to use any
2611 IRQ/DMA settings detected (the default is to
2612 ignore detected IRQ/DMA settings because of
2613 possible conflicts). You can specify the base
2614 address, IRQ, and DMA settings; IRQ and DMA
2615 should be numbers, or 'auto' (for using detected
2616 settings on that particular port), or 'nofifo'
2617 (to avoid using a FIFO even if it is detected).
2618 Parallel ports are assigned in the order they
2619 are specified on the command line, starting
2622 parport_init_mode= [HW,PPT]
2623 Configure VIA parallel port to operate in
2624 a specific mode. This is necessary on Pegasos
2625 computer where firmware has no options for setting
2626 up parallel port mode and sets it to spp.
2627 Currently this function knows 686a and 8231 chips.
2628 Format: [spp|ps2|epp|ecp|ecpepp]
2631 Halt all CPUs after the first oops has been printed for
2632 the specified number of seconds. This is to be used if
2633 your oopses keep scrolling off the screen.
2638 See header of drivers/block/paride/pcd.c.
2639 See also Documentation/blockdev/paride.txt.
2641 pci=option[,option...] [PCI] various PCI subsystem options:
2642 earlydump [X86] dump PCI config space before the kernel
2644 off [X86] don't probe for the PCI bus
2645 bios [X86-32] force use of PCI BIOS, don't access
2646 the hardware directly. Use this if your machine
2647 has a non-standard PCI host bridge.
2648 nobios [X86-32] disallow use of PCI BIOS, only direct
2649 hardware access methods are allowed. Use this
2650 if you experience crashes upon bootup and you
2651 suspect they are caused by the BIOS.
2652 conf1 [X86] Force use of PCI Configuration
2654 conf2 [X86] Force use of PCI Configuration
2656 noaer [PCIE] If the PCIEAER kernel config parameter is
2657 enabled, this kernel boot option can be used to
2658 disable the use of PCIE advanced error reporting.
2659 nodomains [PCI] Disable support for multiple PCI
2660 root domains (aka PCI segments, in ACPI-speak).
2661 nommconf [X86] Disable use of MMCONFIG for PCI
2663 check_enable_amd_mmconf [X86] check for and enable
2664 properly configured MMIO access to PCI
2665 config space on AMD family 10h CPU
2666 nomsi [MSI] If the PCI_MSI kernel config parameter is
2667 enabled, this kernel boot option can be used to
2668 disable the use of MSI interrupts system-wide.
2669 noioapicquirk [APIC] Disable all boot interrupt quirks.
2670 Safety option to keep boot IRQs enabled. This
2671 should never be necessary.
2672 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2673 primary IO-APIC for bridges that cannot disable
2674 boot IRQs. This fixes a source of spurious IRQs
2675 when the system masks IRQs.
2676 noioapicreroute [APIC] Disable workaround that uses the
2677 boot IRQ equivalent of an IRQ that connects to
2678 a chipset where boot IRQs cannot be disabled.
2679 The opposite of ioapicreroute.
2680 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2681 routing table. These calls are known to be buggy
2682 on several machines and they hang the machine
2683 when used, but on other computers it's the only
2684 way to get the interrupt routing table. Try
2685 this option if the kernel is unable to allocate
2686 IRQs or discover secondary PCI buses on your
2688 rom [X86] Assign address space to expansion ROMs.
2689 Use with caution as certain devices share
2690 address decoders between ROMs and other
2692 norom [X86] Do not assign address space to
2693 expansion ROMs that do not already have
2694 BIOS assigned address ranges.
2695 nobar [X86] Do not assign address space to the
2696 BARs that weren't assigned by the BIOS.
2697 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2698 assigned automatically to PCI devices. You can
2699 make the kernel exclude IRQs of your ISA cards
2701 pirqaddr=0xAAAAA [X86] Specify the physical address
2702 of the PIRQ table (normally generated
2703 by the BIOS) if it is outside the
2704 F0000h-100000h range.
2705 lastbus=N [X86] Scan all buses thru bus #N. Can be
2706 useful if the kernel is unable to find your
2707 secondary buses and you want to tell it
2708 explicitly which ones they are.
2709 assign-busses [X86] Always assign all PCI bus
2710 numbers ourselves, overriding
2711 whatever the firmware may have done.
2712 usepirqmask [X86] Honor the possible IRQ mask stored
2713 in the BIOS $PIR table. This is needed on
2714 some systems with broken BIOSes, notably
2715 some HP Pavilion N5400 and Omnibook XE3
2716 notebooks. This will have no effect if ACPI
2717 IRQ routing is enabled.
2718 noacpi [X86] Do not use ACPI for IRQ routing
2719 or for PCI scanning.
2720 use_crs [X86] Use PCI host bridge window information
2721 from ACPI. On BIOSes from 2008 or later, this
2722 is enabled by default. If you need to use this,
2723 please report a bug.
2724 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2725 If you need to use this, please report a bug.
2726 routeirq Do IRQ routing for all PCI devices.
2727 This is normally done in pci_enable_device(),
2728 so this option is a temporary workaround
2729 for broken drivers that don't call it.
2730 skip_isa_align [X86] do not align io start addr, so can
2731 handle more pci cards
2732 firmware [ARM] Do not re-enumerate the bus but instead
2733 just use the configuration from the
2734 bootloader. This is currently used on
2735 IXP2000 systems where the bus has to be
2736 configured a certain way for adjunct CPUs.
2737 noearly [X86] Don't do any early type 1 scanning.
2738 This might help on some broken boards which
2739 machine check when some devices' config space
2740 is read. But various workarounds are disabled
2741 and some IOMMU drivers will not work.
2742 bfsort Sort PCI devices into breadth-first order.
2743 This sorting is done to get a device
2744 order compatible with older (<= 2.4) kernels.
2745 nobfsort Don't sort PCI devices into breadth-first order.
2746 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2747 tuning and use the BIOS-configured MPS defaults.
2748 pcie_bus_safe Set every device's MPS to the largest value
2749 supported by all devices below the root complex.
2750 pcie_bus_perf Set device MPS to the largest allowable MPS
2751 based on its parent bus. Also set MRRS (Max
2752 Read Request Size) to the largest supported
2753 value (no larger than the MPS that the device
2754 or bus can support) for best performance.
2755 pcie_bus_peer2peer Set every device's MPS to 128B, which
2756 every device is guaranteed to support. This
2757 configuration allows peer-to-peer DMA between
2758 any pair of devices, possibly at the cost of
2759 reduced performance. This also guarantees
2760 that hot-added devices will work.
2761 cbiosize=nn[KMG] The fixed amount of bus space which is
2762 reserved for the CardBus bridge's IO window.
2763 The default value is 256 bytes.
2764 cbmemsize=nn[KMG] The fixed amount of bus space which is
2765 reserved for the CardBus bridge's memory
2766 window. The default value is 64 megabytes.
2769 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2770 Specifies alignment and device to reassign
2771 aligned memory resources.
2772 If <order of align> is not specified,
2773 PAGE_SIZE is used as alignment.
2774 PCI-PCI bridge can be specified, if resource
2775 windows need to be expanded.
2776 ecrc= Enable/disable PCIe ECRC (transaction layer
2777 end-to-end CRC checking).
2778 bios: Use BIOS/firmware settings. This is the
2782 hpiosize=nn[KMG] The fixed amount of bus space which is
2783 reserved for hotplug bridge's IO window.
2784 Default size is 256 bytes.
2785 hpmemsize=nn[KMG] The fixed amount of bus space which is
2786 reserved for hotplug bridge's memory window.
2787 Default size is 2 megabytes.
2788 realloc= Enable/disable reallocating PCI bridge resources
2789 if allocations done by BIOS are too small to
2790 accommodate resources required by all child
2792 off: Turn realloc off
2794 realloc same as realloc=on
2795 noari do not use PCIe ARI.
2796 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2797 only look for one device below a PCIe downstream
2800 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2803 force Enable ASPM even on devices that claim not to support it.
2804 WARNING: Forcing ASPM on may cause system lockups.
2806 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2807 nomsi Do not use MSI for PCI Express Native Hotplug (this
2808 makes all PCIe ports use INTx for hotplug services).
2810 pcie_ports= [PCIE] PCIe ports handling:
2811 auto Ask the BIOS whether or not to use native PCIe services
2812 associated with PCIe ports (PME, hot-plug, AER). Use
2813 them only if that is allowed by the BIOS.
2814 native Use native PCIe services associated with PCIe ports
2816 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2819 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2820 nomsi Do not use MSI for native PCIe PME signaling (this makes
2821 all PCIe root ports use INTx for all services).
2823 pcmv= [HW,PCMCIA] BadgePAD 4
2827 Keep all power-domains already enabled by bootloader on,
2828 even if no driver has claimed them. This is useful
2829 for debug and development, but should not be
2830 needed on a platform with proper driver support.
2833 See Documentation/blockdev/paride.txt.
2835 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2838 See arch/parisc/kernel/pdc_chassis.c
2840 percpu_alloc= Select which percpu first chunk allocator to use.
2841 Currently supported values are "embed" and "page".
2842 Archs may support subset or none of the selections.
2843 See comments in mm/percpu.c for details on each
2844 allocator. This parameter is primarily for debugging
2845 and performance comparison.
2848 See Documentation/blockdev/paride.txt.
2851 See Documentation/blockdev/paride.txt.
2853 pirq= [SMP,APIC] Manual mp-table setup
2854 See Documentation/x86/i386/IO-APIC.txt.
2856 plip= [PPT,NET] Parallel port network link
2857 Format: { parport<nr> | timid | 0 }
2858 See also Documentation/parport.txt.
2860 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2861 Override pmtimer IOPort with a hex value.
2865 Enable PNP debug messages (depends on the
2866 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2867 via /sys/module/pnp/parameters/debug. We always show
2868 current resource usage; turning this on also shows
2869 possible settings and some assignment information.
2875 { on | off | curr | res | no-curr | no-res }
2878 [ISAPNP] Exclude IRQs for the autoconfiguration
2881 [ISAPNP] Exclude DMAs for the autoconfiguration
2883 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2884 Ranges are in pairs (I/O port base and size).
2887 [ISAPNP] Exclude memory regions for the
2889 Ranges are in pairs (memory base and size).
2891 ports= [IP_VS_FTP] IPVS ftp helper module
2893 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2895 Format: <port>,<port>....
2897 print-fatal-signals=
2898 [KNL] debug: print fatal signals
2900 If enabled, warn about various signal handling
2901 related application anomalies: too many signals,
2902 too many POSIX.1 timers, fatal signals causing a
2905 If you hit the warning due to signal overflow,
2906 you might want to try "ulimit -i unlimited".
2910 printk.always_kmsg_dump=
2911 Trigger kmsg_dump for cases other than kernel oops or
2913 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2916 printk.time= Show timing data prefixed to each printk message line
2917 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2919 processor.max_cstate= [HW,ACPI]
2920 Limit processor to maximum C-state
2921 max_cstate=9 overrides any DMI blacklist limit.
2923 processor.nocst [HW,ACPI]
2924 Ignore the _CST method to determine C-states,
2925 instead using the legacy FADT method
2927 profile= [KNL] Enable kernel profiling via /proc/profile
2928 Format: [schedule,]<number>
2929 Param: "schedule" - profile schedule points.
2930 Param: <number> - step/bucket size as a power of 2 for
2931 statistical time based profiling.
2932 Param: "sleep" - profile D-state sleeping (millisecs).
2933 Requires CONFIG_SCHEDSTATS
2934 Param: "kvm" - profile VM exits.
2936 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2938 See Documentation/blockdev/ramdisk.txt.
2940 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2941 probe for; one of (bare|imps|exps|lifebook|any).
2942 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2944 psmouse.resetafter= [HW,MOUSE]
2945 Try to reset the device after so many bad packets
2948 [HW,MOUSE] Set desired mouse resolution, in dpi.
2949 psmouse.smartscroll=
2950 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2951 0 = disabled, 1 = enabled (default).
2953 pstore.backend= Specify the name of the pstore backend to use
2956 See Documentation/blockdev/paride.txt.
2959 [KNL] Number of legacy pty's. Overwrites compiled-in
2962 quiet [KNL] Disable most log messages
2967 See Documentation/md.txt.
2969 ramdisk_blocksize= [RAM]
2970 See Documentation/blockdev/ramdisk.txt.
2972 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2973 See Documentation/blockdev/ramdisk.txt.
2976 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2977 the specified list of CPUs to be no-callback CPUs.
2978 Invocation of these CPUs' RCU callbacks will
2979 be offloaded to "rcuox/N" kthreads created for
2980 that purpose, where "x" is "b" for RCU-bh, "p"
2981 for RCU-preempt, and "s" for RCU-sched, and "N"
2982 is the CPU number. This reduces OS jitter on the
2983 offloaded CPUs, which can be useful for HPC and
2984 real-time workloads. It can also improve energy
2985 efficiency for asymmetric multiprocessors.
2988 Rather than requiring that offloaded CPUs
2989 (specified by rcu_nocbs= above) explicitly
2990 awaken the corresponding "rcuoN" kthreads,
2991 make these kthreads poll for callbacks.
2992 This improves the real-time response for the
2993 offloaded CPUs by relieving them of the need to
2994 wake up the corresponding kthread, but degrades
2995 energy efficiency by requiring that the kthreads
2996 periodically wake up to do the polling.
2998 rcutree.blimit= [KNL]
2999 Set maximum number of finished RCU callbacks to
3000 process in one batch.
3002 rcutree.gp_init_delay= [KNL]
3003 Set the number of jiffies to delay each step of
3004 RCU grace-period initialization. This only has
3005 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3008 rcutree.rcu_fanout_leaf= [KNL]
3009 Increase the number of CPUs assigned to each
3010 leaf rcu_node structure. Useful for very large
3013 rcutree.jiffies_till_sched_qs= [KNL]
3014 Set required age in jiffies for a
3015 given grace period before RCU starts
3016 soliciting quiescent-state help from
3017 rcu_note_context_switch().
3019 rcutree.jiffies_till_first_fqs= [KNL]
3020 Set delay from grace-period initialization to
3021 first attempt to force quiescent states.
3022 Units are jiffies, minimum value is zero,
3023 and maximum value is HZ.
3025 rcutree.jiffies_till_next_fqs= [KNL]
3026 Set delay between subsequent attempts to force
3027 quiescent states. Units are jiffies, minimum
3028 value is one, and maximum value is HZ.
3030 rcutree.kthread_prio= [KNL,BOOT]
3031 Set the SCHED_FIFO priority of the RCU per-CPU
3032 kthreads (rcuc/N). This value is also used for
3033 the priority of the RCU boost threads (rcub/N)
3034 and for the RCU grace-period kthreads (rcu_bh,
3035 rcu_preempt, and rcu_sched). If RCU_BOOST is
3036 set, valid values are 1-99 and the default is 1
3037 (the least-favored priority). Otherwise, when
3038 RCU_BOOST is not set, valid values are 0-99 and
3039 the default is zero (non-realtime operation).
3041 rcutree.rcu_nocb_leader_stride= [KNL]
3042 Set the number of NOCB kthread groups, which
3043 defaults to the square root of the number of
3044 CPUs. Larger numbers reduces the wakeup overhead
3045 on the per-CPU grace-period kthreads, but increases
3046 that same overhead on each group's leader.
3048 rcutree.qhimark= [KNL]
3049 Set threshold of queued RCU callbacks beyond which
3050 batch limiting is disabled.
3052 rcutree.qlowmark= [KNL]
3053 Set threshold of queued RCU callbacks below which
3054 batch limiting is re-enabled.
3056 rcutree.rcu_idle_gp_delay= [KNL]
3057 Set wakeup interval for idle CPUs that have
3058 RCU callbacks (RCU_FAST_NO_HZ=y).
3060 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3061 Set wakeup interval for idle CPUs that have
3062 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3063 Lazy RCU callbacks are those which RCU can
3064 prove do nothing more than free memory.
3066 rcutorture.cbflood_inter_holdoff= [KNL]
3067 Set holdoff time (jiffies) between successive
3068 callback-flood tests.
3070 rcutorture.cbflood_intra_holdoff= [KNL]
3071 Set holdoff time (jiffies) between successive
3072 bursts of callbacks within a given callback-flood
3075 rcutorture.cbflood_n_burst= [KNL]
3076 Set the number of bursts making up a given
3077 callback-flood test. Set this to zero to
3078 disable callback-flood testing.
3080 rcutorture.cbflood_n_per_burst= [KNL]
3081 Set the number of callbacks to be registered
3082 in a given burst of a callback-flood test.
3084 rcutorture.fqs_duration= [KNL]
3085 Set duration of force_quiescent_state bursts.
3087 rcutorture.fqs_holdoff= [KNL]
3088 Set holdoff time within force_quiescent_state bursts.
3090 rcutorture.fqs_stutter= [KNL]
3091 Set wait time between force_quiescent_state bursts.
3093 rcutorture.gp_exp= [KNL]
3094 Use expedited update-side primitives.
3096 rcutorture.gp_normal= [KNL]
3097 Use normal (non-expedited) update-side primitives.
3098 If both gp_exp and gp_normal are set, do both.
3099 If neither gp_exp nor gp_normal are set, still
3102 rcutorture.n_barrier_cbs= [KNL]
3103 Set callbacks/threads for rcu_barrier() testing.
3105 rcutorture.nfakewriters= [KNL]
3106 Set number of concurrent RCU writers. These just
3107 stress RCU, they don't participate in the actual
3108 test, hence the "fake".
3110 rcutorture.nreaders= [KNL]
3111 Set number of RCU readers.
3113 rcutorture.object_debug= [KNL]
3114 Enable debug-object double-call_rcu() testing.
3116 rcutorture.onoff_holdoff= [KNL]
3117 Set time (s) after boot for CPU-hotplug testing.
3119 rcutorture.onoff_interval= [KNL]
3120 Set time (s) between CPU-hotplug operations, or
3121 zero to disable CPU-hotplug testing.
3123 rcutorture.torture_runnable= [BOOT]
3124 Start rcutorture running at boot time.
3126 rcutorture.shuffle_interval= [KNL]
3127 Set task-shuffle interval (s). Shuffling tasks
3128 allows some CPUs to go into dyntick-idle mode
3129 during the rcutorture test.
3131 rcutorture.shutdown_secs= [KNL]
3132 Set time (s) after boot system shutdown. This
3133 is useful for hands-off automated testing.
3135 rcutorture.stall_cpu= [KNL]
3136 Duration of CPU stall (s) to test RCU CPU stall
3137 warnings, zero to disable.
3139 rcutorture.stall_cpu_holdoff= [KNL]
3140 Time to wait (s) after boot before inducing stall.
3142 rcutorture.stat_interval= [KNL]
3143 Time (s) between statistics printk()s.
3145 rcutorture.stutter= [KNL]
3146 Time (s) to stutter testing, for example, specifying
3147 five seconds causes the test to run for five seconds,
3148 wait for five seconds, and so on. This tests RCU's
3149 ability to transition abruptly to and from idle.
3151 rcutorture.test_boost= [KNL]
3152 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3153 "Maybe" means test if the RCU implementation
3154 under test support RCU priority boosting.
3156 rcutorture.test_boost_duration= [KNL]
3157 Duration (s) of each individual boost test.
3159 rcutorture.test_boost_interval= [KNL]
3160 Interval (s) between each boost test.
3162 rcutorture.test_no_idle_hz= [KNL]
3163 Test RCU's dyntick-idle handling. See also the
3164 rcutorture.shuffle_interval parameter.
3166 rcutorture.torture_type= [KNL]
3167 Specify the RCU implementation to test.
3169 rcutorture.verbose= [KNL]
3170 Enable additional printk() statements.
3172 rcupdate.rcu_expedited= [KNL]
3173 Use expedited grace-period primitives, for
3174 example, synchronize_rcu_expedited() instead
3175 of synchronize_rcu(). This reduces latency,
3176 but can increase CPU utilization, degrade
3177 real-time latency, and degrade energy efficiency.
3179 rcupdate.rcu_cpu_stall_suppress= [KNL]
3180 Suppress RCU CPU stall warning messages.
3182 rcupdate.rcu_cpu_stall_timeout= [KNL]
3183 Set timeout for RCU CPU stall warning messages.
3185 rcupdate.rcu_task_stall_timeout= [KNL]
3186 Set timeout in jiffies for RCU task stall warning
3187 messages. Disable with a value less than or equal
3190 rcupdate.rcu_self_test= [KNL]
3191 Run the RCU early boot self tests
3193 rcupdate.rcu_self_test_bh= [KNL]
3194 Run the RCU bh early boot self tests
3196 rcupdate.rcu_self_test_sched= [KNL]
3197 Run the RCU sched early boot self tests
3201 Run specified binary instead of /init from the ramdisk,
3202 used for early userspace startup. See initrd.
3205 Format (x86 or x86_64):
3206 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3208 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3210 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3211 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3212 reboot_force is either force or not specified,
3213 reboot_cpu is s[mp]#### with #### being the processor
3214 to be used for rebooting.
3217 [KNL, SMP] Set scheduler's default relax_domain_level.
3218 See Documentation/cgroups/cpusets.txt.
3220 relative_sleep_states=
3221 [SUSPEND] Use sleep state labeling where the deepest
3222 state available other than hibernation is always "mem".
3223 Format: { "0" | "1" }
3224 0 -- Traditional sleep state labels.
3225 1 -- Relative sleep state labels.
3227 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3229 reservetop= [X86-32]
3231 Reserves a hole at the top of the kernel virtual
3236 Set the amount of memory to reserve for BIOS at
3237 the bottom of the address space.
3239 reset_devices [KNL] Force drivers to reset the underlying device
3240 during initialization.
3243 Specify the partition device for software suspend
3245 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3247 resume_offset= [SWSUSP]
3248 Specify the offset from the beginning of the partition
3249 given by "resume=" at which the swap header is located,
3250 in <PAGE_SIZE> units (needed only for swap files).
3251 See Documentation/power/swsusp-and-swap-files.txt
3253 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3254 read the resume files
3256 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3257 Useful for devices that are detected asynchronously
3258 (e.g. USB and MMC devices).
3260 hibernate= [HIBERNATION]
3261 noresume Don't check if there's a hibernation image
3262 present during boot.
3263 nocompress Don't compress/decompress hibernation images.
3264 no Disable hibernation and resume.
3266 retain_initrd [RAM] Keep initrd memory after extraction
3268 rfkill.default_state=
3269 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3270 etc. communication is blocked by default.
3273 rfkill.master_switch_mode=
3274 0 The "airplane mode" button does nothing.
3275 1 The "airplane mode" button toggles between everything
3276 blocked and the previous configuration.
3277 2 The "airplane mode" button toggles between everything
3278 blocked and everything unblocked.
3280 rhash_entries= [KNL,NET]
3281 Set number of hash buckets for route cache
3283 ro [KNL] Mount root device read-only on boot
3285 root= [KNL] Root filesystem
3286 See name_to_dev_t comment in init/do_mounts.c.
3288 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3289 mount the root filesystem
3291 rootflags= [KNL] Set root filesystem mount option string
3293 rootfstype= [KNL] Set root filesystem type
3295 rootwait [KNL] Wait (indefinitely) for root device to show up.
3296 Useful for devices that are detected asynchronously
3297 (e.g. USB and MMC devices).
3299 rproc_mem=nn[KMG][@address]
3300 [KNL,ARM,CMA] Remoteproc physical memory block.
3301 Memory area to be used by remote processor image,
3304 rw [KNL] Mount root device read-write on boot
3306 S [KNL] Run init in single mode
3308 s390_iommu= [HW,S390]
3309 Set s390 IOTLB flushing mode
3311 With strict flushing every unmap operation will result in
3312 an IOTLB flush. Default is lazy flushing before reuse,
3316 See drivers/net/irda/sa1100_ir.c.
3318 sbni= [NET] Granch SBNI12 leased line adapter
3320 sched_debug [KNL] Enables verbose scheduler debug messages.
3322 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3323 xtime_lock contention on larger systems, and/or RCU lock
3324 contention on all systems with CONFIG_MAXSMP set.
3325 Format: { "0" | "1" }
3326 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3328 Note: increases power consumption, thus should only be
3329 enabled if running jitter sensitive (HPC/RT) workloads.
3331 security= [SECURITY] Choose a security module to enable at boot.
3332 If this boot parameter is not specified, only the first
3333 security module asking for security registration will be
3334 loaded. An invalid security module name will be treated
3335 as if no module has been chosen.
3337 selinux= [SELINUX] Disable or enable SELinux at boot time.
3338 Format: { "0" | "1" }
3339 See security/selinux/Kconfig help text.
3342 Default value is set via kernel config option.
3343 If enabled at boot time, /selinux/disable can be used
3344 later to disable prior to initial policy load.
3346 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3347 Format: { "0" | "1" }
3348 See security/apparmor/Kconfig help text
3351 Default value is set via kernel config option.
3353 serialnumber [BUGS=X86-32]
3356 Maximal number of shapers.
3358 show_msr= [x86] show boot-time MSR settings
3359 Format: { <integer> }
3360 Show boot-time (BIOS-initialized) MSR settings.
3361 The parameter means the number of CPUs to show,
3362 for example 1 means boot CPU only.
3370 Disable merging of slabs with similar size. May be
3371 necessary if there is some reason to distinguish
3372 allocs to different slabs. Debug options disable
3373 merging on their own.
3374 For more information see Documentation/vm/slub.txt.
3376 slab_max_order= [MM, SLAB]
3377 Determines the maximum allowed order for slabs.
3378 A high setting may cause OOMs due to memory
3379 fragmentation. Defaults to 1 for systems with
3380 more than 32MB of RAM, 0 otherwise.
3382 slub_debug[=options[,slabs]] [MM, SLUB]
3383 Enabling slub_debug allows one to determine the
3384 culprit if slab objects become corrupted. Enabling
3385 slub_debug can create guard zones around objects and
3386 may poison objects when not in use. Also tracks the
3387 last alloc / free. For more information see
3388 Documentation/vm/slub.txt.
3390 slub_max_order= [MM, SLUB]
3391 Determines the maximum allowed order for slabs.
3392 A high setting may cause OOMs due to memory
3393 fragmentation. For more information see
3394 Documentation/vm/slub.txt.
3396 slub_min_objects= [MM, SLUB]
3397 The minimum number of objects per slab. SLUB will
3398 increase the slab order up to slub_max_order to
3399 generate a sufficiently large slab able to contain
3400 the number of objects indicated. The higher the number
3401 of objects the smaller the overhead of tracking slabs
3402 and the less frequently locks need to be acquired.
3403 For more information see Documentation/vm/slub.txt.
3405 slub_min_order= [MM, SLUB]
3406 Determines the minimum page order for slabs. Must be
3407 lower than slub_max_order.
3408 For more information see Documentation/vm/slub.txt.
3410 slub_nomerge [MM, SLUB]
3411 Same with slab_nomerge. This is supported for legacy.
3412 See slab_nomerge for more information.
3415 Format: <io1>[,<io2>[,...,<io8>]]
3417 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3418 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3419 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3420 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3421 smsc-ircc2.ircc_irq= [HW] IRQ line
3422 smsc-ircc2.ircc_dma= [HW] DMA channel
3423 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3424 0: Toshiba Satellite 1800 (GP data pin select)
3425 1: Fast pin select (default)
3429 [KNL] Should the soft-lockup detector generate panics.
3432 softlockup_all_cpu_backtrace=
3433 [KNL] Should the soft-lockup detector generate
3434 backtraces on all cpus.
3437 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3438 See Documentation/laptops/sonypi.txt
3440 spia_io_base= [HW,MTD]
3446 Enabled the stack tracer on boot up.
3448 stacktrace_filter=[function-list]
3449 [FTRACE] Limit the functions that the stack tracer
3450 will trace at boot up. function-list is a comma separated
3451 list of functions. This list can be changed at run
3452 time by the stack_trace_filter file in the debugfs
3453 tracing directory. Note, this enables stack tracing
3454 and the stacktrace above is not needed.
3458 Set the STI (builtin display/keyboard on the HP-PARISC
3459 machines) console (graphic card) which should be used
3460 as the initial boot-console.
3461 See also comment in drivers/video/console/sticore.c.
3464 See comment in drivers/video/console/sticore.c.
3467 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3469 sunrpc.min_resvport=
3470 sunrpc.max_resvport=
3472 SunRPC servers often require that client requests
3473 originate from a privileged port (i.e. a port in the
3474 range 0 < portnr < 1024).
3475 An administrator who wishes to reserve some of these
3476 ports for other uses may adjust the range that the
3477 kernel's sunrpc client considers to be privileged
3478 using these two parameters to set the minimum and
3479 maximum port values.
3483 Control how the NFS server code allocates CPUs to
3484 service thread pools. Depending on how many NICs
3485 you have and where their interrupts are bound, this
3486 option will affect which CPUs will do NFS serving.
3487 Note: this parameter cannot be changed while the
3488 NFS server is running.
3490 auto the server chooses an appropriate mode
3491 automatically using heuristics
3492 global a single global pool contains all CPUs
3493 percpu one pool for each CPU
3494 pernode one pool for each NUMA node (equivalent
3495 to global on non-NUMA machines)
3497 sunrpc.tcp_slot_table_entries=
3498 sunrpc.udp_slot_table_entries=
3500 Sets the upper limit on the number of simultaneous
3501 RPC calls that can be sent from the client to a
3502 server. Increasing these values may allow you to
3503 improve throughput, but will also increase the
3504 amount of memory reserved for use by the client.
3506 suspend.pm_test_delay=
3508 Sets the number of seconds to remain in a suspend test
3509 mode before resuming the system (see
3510 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3511 is set. Default value is 5.
3514 [KNL] Enable accounting of swap in memory resource
3515 controller if no parameter or 1 is given or disable
3516 it if 0 is given (See Documentation/cgroups/memory.txt)
3518 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3519 Format: { <int> | force }
3520 <int> -- Number of I/O TLB slabs
3521 force -- force using of bounce buffers even if they
3522 wouldn't be automatically used by the kernel
3526 sysfs.deprecated=0|1 [KNL]
3527 Enable/disable old style sysfs layout for old udev
3528 on older distributions. When this option is enabled
3529 very new udev will not work anymore. When this option
3530 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3531 in older udev will not work anymore.
3532 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3533 the kernel configuration.
3535 sysrq_always_enabled
3537 Ignore sysrq setting - this boot parameter will
3538 neutralize any effect of /proc/sys/kernel/sysrq.
3539 Useful for debugging.
3541 tcpmhash_entries= [KNL,NET]
3542 Set the number of tcp_metrics_hash slots.
3543 Default value is 8192 or 16384 depending on total
3544 ram pages. This is used to specify the TCP metrics
3545 cache size. See Documentation/networking/ip-sysctl.txt
3546 "tcp_no_metrics_save" section for more details.
3550 test_suspend= [SUSPEND][,N]
3551 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3552 standby suspend) or "freeze" (for suspend type freeze)
3553 as the system sleep state during system startup with
3554 the optional capability to repeat N number of times.
3555 The system is woken from this state using a
3556 wakeup-capable RTC alarm.
3558 thash_entries= [KNL,NET]
3559 Set number of hash buckets for TCP connection
3561 thermal.act= [HW,ACPI]
3562 -1: disable all active trip points in all thermal zones
3563 <degrees C>: override all lowest active trip points
3565 thermal.crt= [HW,ACPI]
3566 -1: disable all critical trip points in all thermal zones
3567 <degrees C>: override all critical trip points
3569 thermal.nocrt= [HW,ACPI]
3570 Set to disable actions on ACPI thermal zone
3571 critical and hot trip points.
3573 thermal.off= [HW,ACPI]
3574 1: disable ACPI thermal control
3576 thermal.psv= [HW,ACPI]
3577 -1: disable all passive trip points
3578 <degrees C>: override all passive trip points to this
3581 thermal.tzp= [HW,ACPI]
3582 Specify global default ACPI thermal zone polling rate
3583 <deci-seconds>: poll all this frequency
3584 0: no polling (default)
3587 Force threading of all interrupt handlers except those
3588 marked explicitly IRQF_NO_THREAD.
3591 Enable the Transcendent memory driver if built-in.
3593 tmem.cleancache=0|1 [KNL, XEN]
3594 Default is on (1). Disable the usage of the cleancache
3595 API to send anonymous pages to the hypervisor.
3597 tmem.frontswap=0|1 [KNL, XEN]
3598 Default is on (1). Disable the usage of the frontswap
3599 API to send swap pages to the hypervisor. If disabled
3600 the selfballooning and selfshrinking are force disabled.
3602 tmem.selfballooning=0|1 [KNL, XEN]
3603 Default is on (1). Disable the driving of swap pages
3606 tmem.selfshrinking=0|1 [KNL, XEN]
3607 Default is on (1). Partial swapoff that immediately
3608 transfers pages from Xen hypervisor back to the
3609 kernel based on different criteria.
3613 Specify if the kernel should make use of the cpu
3614 topology information if the hardware supports this.
3615 The scheduler will make use of this information and
3616 e.g. base its process migration decisions on it.
3619 topology_updates= [KNL, PPC, NUMA]
3621 Specify if the kernel should ignore (off)
3622 topology updates sent by the hypervisor to this
3627 tpm_suspend_pcr=[HW,TPM]
3628 Format: integer pcr id
3629 Specify that at suspend time, the tpm driver
3630 should extend the specified pcr with zeros,
3631 as a workaround for some chips which fail to
3632 flush the last written pcr on TPM_SaveState.
3633 This will guarantee that all the other pcrs
3636 trace_buf_size=nn[KMG]
3637 [FTRACE] will set tracing buffer size on each cpu.
3639 trace_event=[event-list]
3640 [FTRACE] Set and start specified trace events in order
3641 to facilitate early boot debugging.
3642 See also Documentation/trace/events.txt
3644 trace_options=[option-list]
3645 [FTRACE] Enable or disable tracer options at boot.
3646 The option-list is a comma delimited list of options
3647 that can be enabled or disabled just as if you were
3648 to echo the option name into
3650 /sys/kernel/debug/tracing/trace_options
3652 For example, to enable stacktrace option (to dump the
3653 stack trace of each event), add to the command line:
3655 trace_options=stacktrace
3657 See also Documentation/trace/ftrace.txt "trace options"
3661 Have the tracepoints sent to printk as well as the
3662 tracing ring buffer. This is useful for early boot up
3663 where the system hangs or reboots and does not give the
3664 option for reading the tracing buffer or performing a
3665 ftrace_dump_on_oops.
3667 To turn off having tracepoints sent to printk,
3668 echo 0 > /proc/sys/kernel/tracepoint_printk
3669 Note, echoing 1 into this file without the
3670 tracepoint_printk kernel cmdline option has no effect.
3674 Having tracepoints sent to printk() and activating high
3675 frequency tracepoints such as irq or sched, can cause
3676 the system to live lock.
3679 [FTRACE] enable this option to disable tracing when a
3680 warning is hit. This turns off "tracing_on". Tracing can
3681 be enabled again by echoing '1' into the "tracing_on"
3682 file located in /sys/kernel/debug/tracing/
3684 This option is useful, as it disables the trace before
3685 the WARNING dump is called, which prevents the trace to
3686 be filled with content caused by the warning output.
3688 This option can also be set at run time via the sysctl
3689 option: kernel/traceoff_on_warning
3691 transparent_hugepage=
3693 Format: [always|madvise|never]
3694 Can be used to control the default behavior of the system
3695 with respect to transparent hugepages.
3696 See Documentation/vm/transhuge.txt for more details.
3698 tsc= Disable clocksource stability checks for TSC.
3700 [x86] reliable: mark tsc clocksource as reliable, this
3701 disables clocksource verification at runtime, as well
3702 as the stability checks done at bootup. Used to enable
3703 high-resolution timer mode on older hardware, and in
3704 virtualized environment.
3705 [x86] noirqtime: Do not use TSC to do irq accounting.
3706 Used to run time disable IRQ_TIME_ACCOUNTING on any
3707 platforms where RDTSC is slow and this accounting
3710 turbografx.map[2|3]= [HW,JOY]
3711 TurboGraFX parallel port interface
3713 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3714 See also Documentation/input/joystick-parport.txt
3716 udbg-immortal [PPC] When debugging early kernel crashes that
3717 happen after console_init() and before a proper
3718 console driver takes over, this boot options might
3719 help "seeing" what's going on.
3721 uhash_entries= [KNL,NET]
3722 Set number of hash buckets for UDP/UDP-Lite connections
3725 [USB] Ignore overcurrent events (default N).
3726 Some badly-designed motherboards generate lots of
3727 bogus events, for ports that aren't wired to
3728 anything. Set this parameter to avoid log spamming.
3729 Note that genuine overcurrent events won't be
3733 [X86] Cause panic on unknown NMI.
3735 usbcore.authorized_default=
3736 [USB] Default USB device authorization:
3737 (default -1 = authorized except for wireless USB,
3738 0 = not authorized, 1 = authorized)
3740 usbcore.autosuspend=
3741 [USB] The autosuspend time delay (in seconds) used
3742 for newly-detected USB devices (default 2). This
3743 is the time required before an idle device will be
3744 autosuspended. Devices for which the delay is set
3745 to a negative value won't be autosuspended at all.
3747 usbcore.usbfs_snoop=
3748 [USB] Set to log all usbfs traffic (default 0 = off).
3750 usbcore.blinkenlights=
3751 [USB] Set to cycle leds on hubs (default 0 = off).
3753 usbcore.old_scheme_first=
3754 [USB] Start with the old device initialization
3755 scheme (default 0 = off).
3757 usbcore.usbfs_memory_mb=
3758 [USB] Memory limit (in MB) for buffers allocated by
3759 usbfs (default = 16, 0 = max = 2047).
3761 usbcore.use_both_schemes=
3762 [USB] Try the other device initialization scheme
3763 if the first one fails (default 1 = enabled).
3765 usbcore.initial_descriptor_timeout=
3766 [USB] Specifies timeout for the initial 64-byte
3767 USB_REQ_GET_DESCRIPTOR request in milliseconds
3768 (default 5000 = 5.0 seconds).
3771 [USBHID] The interval which mice are to be polled at.
3773 usb-storage.delay_use=
3774 [UMS] The delay in seconds before a new device is
3775 scanned for Logical Units (default 1).
3778 [UMS] A list of quirks entries to supplement or
3779 override the built-in unusual_devs list. List
3780 entries are separated by commas. Each entry has
3781 the form VID:PID:Flags where VID and PID are Vendor
3782 and Product ID values (4-digit hex numbers) and
3783 Flags is a set of characters, each corresponding
3784 to a common usb-storage quirk flag as follows:
3785 a = SANE_SENSE (collect more than 18 bytes
3787 b = BAD_SENSE (don't collect more than 18
3788 bytes of sense data);
3789 c = FIX_CAPACITY (decrease the reported
3790 device capacity by one sector);
3791 d = NO_READ_DISC_INFO (don't use
3792 READ_DISC_INFO command);
3793 e = NO_READ_CAPACITY_16 (don't use
3794 READ_CAPACITY_16 command);
3795 f = NO_REPORT_OPCODES (don't use report opcodes
3797 g = MAX_SECTORS_240 (don't transfer more than
3798 240 sectors at a time, uas only);
3799 h = CAPACITY_HEURISTICS (decrease the
3800 reported device capacity by one
3801 sector if the number is odd);
3802 i = IGNORE_DEVICE (don't bind to this
3804 l = NOT_LOCKABLE (don't try to lock and
3805 unlock ejectable media);
3806 m = MAX_SECTORS_64 (don't transfer more
3807 than 64 sectors = 32 KB at a time);
3808 n = INITIAL_READ10 (force a retry of the
3809 initial READ(10) command);
3810 o = CAPACITY_OK (accept the capacity
3811 reported by the device);
3812 p = WRITE_CACHE (the device cache is ON
3814 r = IGNORE_RESIDUE (the device reports
3815 bogus residue values);
3816 s = SINGLE_LUN (the device has only one
3818 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3819 commands, uas only);
3820 u = IGNORE_UAS (don't bind to the uas driver);
3821 w = NO_WP_DETECT (don't test whether the
3822 medium is write-protected).
3823 Example: quirks=0419:aaf5:rl,0421:0433:rc
3825 user_debug= [KNL,ARM]
3827 See arch/arm/Kconfig.debug help text.
3828 1 - undefined instruction events
3830 4 - invalid data aborts
3833 Example: user_debug=31
3836 [X86] Flags controlling user PTE allocations.
3838 nohigh = do not allocate PTE pages in
3839 HIGHMEM regardless of setting
3843 On X86_32, this is an alias for vdso32=. Otherwise:
3845 vdso=1: enable VDSO (the default)
3846 vdso=0: disable VDSO mapping
3848 vdso32= [X86] Control the 32-bit vDSO
3849 vdso32=1: enable 32-bit VDSO
3850 vdso32=0 or vdso32=2: disable 32-bit VDSO
3852 See the help text for CONFIG_COMPAT_VDSO for more
3853 details. If CONFIG_COMPAT_VDSO is set, the default is
3854 vdso32=0; otherwise, the default is vdso32=1.
3856 For compatibility with older kernels, vdso32=2 is an
3859 Try vdso32=0 if you encounter an error that says:
3860 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3863 vector=percpu: enable percpu vector domain
3865 video= [FB] Frame buffer configuration
3866 See Documentation/fb/modedb.txt.
3868 video.brightness_switch_enabled= [0,1]
3869 If set to 1, on receiving an ACPI notify event
3870 generated by hotkey, video driver will adjust brightness
3871 level and then send out the event to user space through
3872 the allocated input device; If set to 0, video driver
3873 will only send out the event without touching backlight
3878 [VMMIO] Memory mapped virtio (platform) device.
3880 <size>@<baseaddr>:<irq>[:<id>]
3882 <size> := size (can use standard suffixes
3884 <baseaddr> := physical base address
3885 <irq> := interrupt number (as passed to
3887 <id> := (optional) platform device id
3889 virtio_mmio.device=1K@0x100b0000:48:7
3891 Can be used multiple times for multiple devices.
3893 vga= [BOOT,X86-32] Select a particular video mode
3894 See Documentation/x86/boot.txt and
3895 Documentation/svga.txt.
3896 Use vga=ask for menu.
3897 This is actually a boot loader parameter; the value is
3898 passed to the kernel using a special protocol.
3900 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3901 size of <nn>. This can be used to increase the
3902 minimum size (128MB on x86). It can also be used to
3903 decrease the size and leave more room for directly
3906 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3909 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3912 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3916 Controls the behavior of vsyscalls (i.e. calls to
3917 fixed addresses of 0xffffffffff600x00 from legacy
3918 code). Most statically-linked binaries and older
3919 versions of glibc use these calls. Because these
3920 functions are at fixed addresses, they make nice
3921 targets for exploits that can control RIP.
3923 emulate [default] Vsyscalls turn into traps and are
3924 emulated reasonably safely.
3926 native Vsyscalls are native syscall instructions.
3927 This is a little bit faster than trapping
3928 and makes a few dynamic recompilers work
3929 better than they would in emulation mode.
3930 It also makes exploits much easier to write.
3932 none Vsyscalls don't work at all. This makes
3933 them quite hard to use for exploits but
3934 might break your system.
3936 vt.color= [VT] Default text color.
3937 Format: 0xYX, X = foreground, Y = background.
3938 Default: 0x07 = light gray on black.
3940 vt.cur_default= [VT] Default cursor shape.
3941 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3942 the parameters of the <Esc>[?A;B;Cc escape sequence;
3943 see VGA-softcursor.txt. Default: 2 = underline.
3945 vt.default_blu= [VT]
3946 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3947 Change the default blue palette of the console.
3948 This is a 16-member array composed of values
3951 vt.default_grn= [VT]
3952 Format: <green0>,<green1>,<green2>,...,<green15>
3953 Change the default green palette of the console.
3954 This is a 16-member array composed of values
3957 vt.default_red= [VT]
3958 Format: <red0>,<red1>,<red2>,...,<red15>
3959 Change the default red palette of the console.
3960 This is a 16-member array composed of values
3966 Set system-wide default UTF-8 mode for all tty's.
3967 Default is 1, i.e. UTF-8 mode is enabled for all
3968 newly opened terminals.
3970 vt.global_cursor_default=
3973 Set system-wide default for whether a cursor
3974 is shown on new VTs. Default is -1,
3975 i.e. cursors will be created by default unless
3976 overridden by individual drivers. 0 will hide
3977 cursors, 1 will display them.
3979 vt.italic= [VT] Default color for italic text; 0-15.
3982 vt.underline= [VT] Default color for underlined text; 0-15.
3985 watchdog timers [HW,WDT] For information on watchdog timers,
3986 see Documentation/watchdog/watchdog-parameters.txt
3987 or other driver-specific files in the
3988 Documentation/watchdog/ directory.
3990 workqueue.disable_numa
3991 By default, all work items queued to unbound
3992 workqueues are affine to the NUMA nodes they're
3993 issued on, which results in better behavior in
3994 general. If NUMA affinity needs to be disabled for
3995 whatever reason, this option can be used. Note
3996 that this also can be controlled per-workqueue for
3997 workqueues visible under /sys/bus/workqueue/.
3999 workqueue.power_efficient
4000 Per-cpu workqueues are generally preferred because
4001 they show better performance thanks to cache
4002 locality; unfortunately, per-cpu workqueues tend to
4003 be more power hungry than unbound workqueues.
4005 Enabling this makes the per-cpu workqueues which
4006 were observed to contribute significantly to power
4007 consumption unbound, leading to measurably lower
4008 power usage at the cost of small performance
4011 The default value of this parameter is determined by
4012 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4014 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4015 default x2apic cluster mode on platforms
4018 x86_intel_mid_timer= [X86-32,APBT]
4019 Choose timer option for x86 Intel MID platform.
4020 Two valid options are apbt timer only and lapic timer
4021 plus one apbt timer for broadcast timer.
4022 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4024 xen_emul_unplug= [HW,X86,XEN]
4025 Unplug Xen emulated devices
4026 Format: [unplug0,][unplug1]
4027 ide-disks -- unplug primary master IDE devices
4028 aux-ide-disks -- unplug non-primary-master IDE devices
4029 nics -- unplug network devices
4030 all -- unplug all emulated devices (NICs and IDE disks)
4031 unnecessary -- unplugging emulated devices is
4032 unnecessary even if the host did not respond to
4034 never -- do not unplug even if version check succeeds
4036 xen_nopvspin [X86,XEN]
4037 Disables the ticketlock slowpath using Xen PV
4041 Disables the PV optimizations forcing the HVM guest to
4042 run as generic HVM guest with no PV drivers.
4044 xirc2ps_cs= [NET,PCMCIA]
4046 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4048 ______________________________________________________________________
4052 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob