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
1486 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1487 0 disables intel_idle and fall back on acpi_idle.
1488 1 to 6 specify maximum depth of C-state.
1492 Do not enable intel_pstate as the default
1493 scaling driver for the supported processors
1495 Enable intel_pstate on systems that prohibit it by default
1496 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1497 instead of acpi-cpufreq may disable platform features, such
1498 as thermal controls and power capping, that rely on ACPI
1499 P-States information being indicated to OSPM and therefore
1500 should be used with caution. This option does not work with
1501 processors that aren't supported by the intel_pstate driver
1502 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1504 Do not enable hardware P state control (HWP)
1507 Only load intel_pstate on systems which support
1508 hardware P state control (HWP) if available.
1510 intremap= [X86-64, Intel-IOMMU]
1511 on enable Interrupt Remapping (default)
1512 off disable Interrupt Remapping
1513 nosid disable Source ID checking
1515 BIOS x2APIC opt-out request will be ignored
1517 iomem= Disable strict checking of access to MMIO memory
1518 strict regions from userspace.
1533 nobypass [PPC/POWERNV]
1534 Disable IOMMU bypass, using IOMMU for PCI devices.
1537 io7= [HW] IO7 for Marvel based alpha systems
1538 See comment before marvel_specify_io7 in
1539 arch/alpha/kernel/core_marvel.c.
1541 io_delay= [X86] I/O delay method
1543 Standard port 0x80 based delay
1545 Alternate port 0xed based delay (needed on some systems)
1547 Simple two microseconds delay
1552 See Documentation/filesystems/nfs/nfsroot.txt.
1555 When an interrupt is not handled search all handlers
1556 for it. Intended to get systems with badly broken
1560 When an interrupt is not handled search all handlers
1561 for it. Also check all handlers each timer
1562 interrupt. Intended to get systems with badly broken
1566 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1568 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1570 <cpu number>,...,<cpu number>
1572 <cpu number>-<cpu number>
1573 (must be a positive range in ascending order)
1575 <cpu number>,...,<cpu number>-<cpu number>
1577 This option can be used to specify one or more CPUs
1578 to isolate from the general SMP balancing and scheduling
1579 algorithms. You can move a process onto or off an
1580 "isolated" CPU via the CPU affinity syscalls or cpuset.
1581 <cpu number> begins at 0 and the maximum value is
1582 "number of CPUs in system - 1".
1584 This option is the preferred way to isolate CPUs. The
1585 alternative -- manually setting the CPU mask of all
1586 tasks in the system -- can cause problems and
1587 suboptimal load balancer performance.
1591 ivrs_ioapic [HW,X86_64]
1592 Provide an override to the IOAPIC-ID<->DEVICE-ID
1593 mapping provided in the IVRS ACPI table. For
1594 example, to map IOAPIC-ID decimal 10 to
1595 PCI device 00:14.0 write the parameter as:
1596 ivrs_ioapic[10]=00:14.0
1598 ivrs_hpet [HW,X86_64]
1599 Provide an override to the HPET-ID<->DEVICE-ID
1600 mapping provided in the IVRS ACPI table. For
1601 example, to map HPET-ID decimal 0 to
1602 PCI device 00:14.0 write the parameter as:
1603 ivrs_hpet[0]=00:14.0
1605 js= [HW,JOY] Analog joystick
1606 See Documentation/input/joystick.txt.
1609 Enable/disable kernel and module base offset ASLR
1610 (Address Space Layout Randomization) if built into
1611 the kernel. When CONFIG_HIBERNATION is selected,
1612 kASLR is disabled by default. When kASLR is enabled,
1613 hibernation will be disabled.
1617 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1618 specifies the amount of memory usable by the kernel
1619 for non-movable allocations. The requested amount is
1620 spread evenly throughout all nodes in the system. The
1621 remaining memory in each node is used for Movable
1622 pages. In the event, a node is too small to have both
1623 kernelcore and Movable pages, kernelcore pages will
1624 take priority and other nodes will have a larger number
1625 of Movable pages. The Movable zone is used for the
1626 allocation of pages that may be reclaimed or moved
1627 by the page migration subsystem. This means that
1628 HugeTLB pages may not be allocated from this zone.
1629 Note that allocations like PTEs-from-HighMem still
1630 use the HighMem zone if it exists, and the Normal
1631 zone if it does not.
1633 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1634 Format: <Controller#>[,poll interval]
1635 The controller # is the number of the ehci usb debug
1636 port as it is probed via PCI. The poll interval is
1637 optional and is the number seconds in between
1638 each poll cycle to the debug port in case you need
1639 the functionality for interrupting the kernel with
1640 gdb or control-c on the dbgp connection. When
1641 not using this parameter you use sysrq-g to break into
1642 the kernel debugger.
1644 kgdboc= [KGDB,HW] kgdb over consoles.
1645 Requires a tty driver that supports console polling,
1646 or a supported polling keyboard driver (non-usb).
1647 Serial only format: <serial_device>[,baud]
1648 keyboard only format: kbd
1649 keyboard and serial format: kbd,<serial_device>[,baud]
1650 Optional Kernel mode setting:
1651 kms, kbd format: kms,kbd
1652 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1654 kgdbwait [KGDB] Stop kernel execution and enter the
1655 kernel debugger at the earliest opportunity.
1657 kmac= [MIPS] korina ethernet MAC address.
1658 Configure the RouterBoard 532 series on-chip
1659 Ethernet adapter MAC address.
1661 kmemleak= [KNL] Boot-time kmemleak enable/disable
1662 Valid arguments: on, off
1664 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1667 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1668 Valid arguments: 0, 1, 2
1669 kmemcheck=0 (disabled)
1670 kmemcheck=1 (enabled)
1671 kmemcheck=2 (one-shot mode)
1672 Default: 2 (one-shot mode)
1674 kstack=N [X86] Print N words from the kernel stack
1677 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1678 Default is 0 (don't ignore, but inject #GP)
1680 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1684 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1685 Default is 1 (enabled)
1687 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1689 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1691 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1692 (virtualized MMU) support on capable Intel chips.
1693 Default is 1 (enabled)
1695 kvm-intel.emulate_invalid_guest_state=
1696 [KVM,Intel] Enable emulation of invalid guest states
1697 Default is 0 (disabled)
1699 kvm-intel.flexpriority=
1700 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1701 Default is 1 (enabled)
1704 [KVM,Intel] Enable VMX nesting (nVMX).
1705 Default is 0 (disabled)
1707 kvm-intel.unrestricted_guest=
1708 [KVM,Intel] Disable unrestricted guest feature
1709 (virtualized real and unpaged mode) on capable
1710 Intel chips. Default is 1 (enabled)
1712 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1713 feature (tagged TLBs) on capable Intel chips.
1714 Default is 1 (enabled)
1720 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1723 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1724 value for LAPIC timer one-shot implementation. Default
1725 back to the programmable timer unit in the LAPIC.
1727 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1730 libata.dma= [LIBATA] DMA control
1731 libata.dma=0 Disable all PATA and SATA DMA
1732 libata.dma=1 PATA and SATA Disk DMA only
1733 libata.dma=2 ATAPI (CDROM) DMA only
1734 libata.dma=4 Compact Flash DMA only
1735 Combinations also work, so libata.dma=3 enables DMA
1736 for disks and CDROMs, but not CFs.
1738 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1739 libata.ignore_hpa=0 keep BIOS limits (default)
1740 libata.ignore_hpa=1 ignore limits, using full disk
1742 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1746 libata.force= [LIBATA] Force configurations. The format is comma
1747 separated list of "[ID:]VAL" where ID is
1748 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1749 matching port, link or device. Basically, it matches
1750 the ATA ID string printed on console by libata. If
1751 the whole ID part is omitted, the last PORT and DEVICE
1752 values are used. If ID hasn't been specified yet, the
1753 configuration applies to all ports, links and devices.
1755 If only DEVICE is omitted, the parameter applies to
1756 the port and all links and devices behind it. DEVICE
1757 number of 0 either selects the first device or the
1758 first fan-out link behind PMP device. It does not
1759 select the host link. DEVICE number of 15 selects the
1760 host link and device attached to it.
1762 The VAL specifies the configuration to force. As long
1763 as there's no ambiguity shortcut notation is allowed.
1764 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1765 The following configurations can be forced.
1767 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1768 Any ID with matching PORT is used.
1770 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1772 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1773 udma[/][16,25,33,44,66,100,133] notation is also
1776 * [no]ncq: Turn on or off NCQ.
1778 * nohrst, nosrst, norst: suppress hard, soft
1781 * rstonce: only attempt one reset during
1782 hot-unplug link recovery
1784 * dump_id: dump IDENTIFY data.
1786 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1788 * disable: Disable this device.
1790 If there are multiple matching configurations changing
1791 the same attribute, the last one is used.
1793 memblock=debug [KNL] Enable memblock debug messages.
1795 load_ramdisk= [RAM] List of ramdisks to load from floppy
1796 See Documentation/blockdev/ramdisk.txt.
1798 lockd.nlm_grace_period=P [NFS] Assign grace period.
1801 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1804 lockd.nlm_timeout=T [NFS] Assign timeout value.
1807 lockd.nlm_udpport=M [NFS] Assign UDP port.
1810 locktorture.nreaders_stress= [KNL]
1811 Set the number of locking read-acquisition kthreads.
1812 Defaults to being automatically set based on the
1813 number of online CPUs.
1815 locktorture.nwriters_stress= [KNL]
1816 Set the number of locking write-acquisition kthreads.
1818 locktorture.onoff_holdoff= [KNL]
1819 Set time (s) after boot for CPU-hotplug testing.
1821 locktorture.onoff_interval= [KNL]
1822 Set time (s) between CPU-hotplug operations, or
1823 zero to disable CPU-hotplug testing.
1825 locktorture.shuffle_interval= [KNL]
1826 Set task-shuffle interval (jiffies). Shuffling
1827 tasks allows some CPUs to go into dyntick-idle
1828 mode during the locktorture test.
1830 locktorture.shutdown_secs= [KNL]
1831 Set time (s) after boot system shutdown. This
1832 is useful for hands-off automated testing.
1834 locktorture.stat_interval= [KNL]
1835 Time (s) between statistics printk()s.
1837 locktorture.stutter= [KNL]
1838 Time (s) to stutter testing, for example,
1839 specifying five seconds causes the test to run for
1840 five seconds, wait for five seconds, and so on.
1841 This tests the locking primitive's ability to
1842 transition abruptly to and from idle.
1844 locktorture.torture_runnable= [BOOT]
1845 Start locktorture running at boot time.
1847 locktorture.torture_type= [KNL]
1848 Specify the locking implementation to test.
1850 locktorture.verbose= [KNL]
1851 Enable additional printk() statements.
1853 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1856 loglevel= All Kernel Messages with a loglevel smaller than the
1857 console loglevel will be printed to the console. It can
1858 also be changed with klogd or other programs. The
1859 loglevels are defined as follows:
1861 0 (KERN_EMERG) system is unusable
1862 1 (KERN_ALERT) action must be taken immediately
1863 2 (KERN_CRIT) critical conditions
1864 3 (KERN_ERR) error conditions
1865 4 (KERN_WARNING) warning conditions
1866 5 (KERN_NOTICE) normal but significant condition
1867 6 (KERN_INFO) informational
1868 7 (KERN_DEBUG) debug-level messages
1870 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1871 in bytes. n must be a power of two and greater
1872 than the minimal size. The minimal size is defined
1873 by LOG_BUF_SHIFT kernel config parameter. There is
1874 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1875 that allows to increase the default size depending on
1876 the number of CPUs. See init/Kconfig for more details.
1878 logo.nologo [FB] Disables display of the built-in Linux logo.
1879 This may be used to provide more screen space for
1880 kernel log messages and is useful when debugging
1881 kernel boot problems.
1883 lp=0 [LP] Specify parallel ports to use, e.g,
1884 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1885 lp=reset first parallel port). 'lp=0' disables the
1886 lp=auto printer driver. 'lp=reset' (which can be
1887 specified in addition to the ports) causes
1888 attached printers to be reset. Using
1889 lp=port1,port2,... specifies the parallel ports
1890 to associate lp devices with, starting with
1891 lp0. A port specification may be 'none' to skip
1892 that lp device, or a parport name such as
1893 'parport0'. Specifying 'lp=auto' instead of a
1894 port specification list means that device IDs
1895 from each port should be examined, to see if
1896 an IEEE 1284-compliant printer is attached; if
1897 so, the driver will manage that printer.
1898 See also header of drivers/char/lp.c.
1901 Sets loops_per_jiffy to given constant, thus avoiding
1902 time-consuming boot-time autodetection (up to 250 ms per
1903 CPU). 0 enables autodetection (default). To determine
1904 the correct value for your kernel, boot with normal
1905 autodetection and see what value is printed. Note that
1906 on SMP systems the preset will be applied to all CPUs,
1907 which is likely to cause problems if your CPUs need
1908 significantly divergent settings. An incorrect value
1909 will cause delays in the kernel to be wrong, leading to
1910 unpredictable I/O errors and other breakage. Although
1911 unlikely, in the extreme case this might damage your
1915 Format: <io>,<irq>,<dma>
1917 machvec= [IA-64] Force the use of a particular machine-vector
1918 (machvec) in a generic kernel.
1919 Example: machvec=hpzx1_swiotlb
1921 machtype= [Loongson] Share the same kernel image file between different
1923 Example: machtype=lemote-yeeloong-2f-7inch
1925 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1926 than or equal to this physical address is ignored.
1928 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1929 should make use of. maxcpus=n : n >= 0 limits the
1930 kernel to using 'n' processors. n=0 is a special case,
1931 it is equivalent to "nosmp", which also disables
1934 max_loop= [LOOP] The number of loop block devices that get
1935 (loop.max_loop) unconditionally pre-created at init time. The default
1936 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1937 of statically allocating a predefined number, loop
1938 devices can be requested on-demand with the
1939 /dev/loop-control interface.
1941 mce [X86-32] Machine Check Exception
1943 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1945 md= [HW] RAID subsystems devices and level
1946 See Documentation/md.txt.
1949 Format: <first>,<last>
1950 Specifies range of consoles to be captured by the MDA.
1952 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1953 Amount of memory to be used when the kernel is not able
1954 to see the whole system memory or for test.
1955 [X86] Work as limiting max address. Use together
1956 with memmap= to avoid physical address space collisions.
1957 Without memmap= PCI devices could be placed at addresses
1958 belonging to unused RAM.
1960 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1964 [KNL,SH] Allow user to override the default size for
1965 per-device physically contiguous DMA buffers.
1967 memmap=exactmap [KNL,X86] Enable setting of an exact
1968 E820 memory map, as specified by the user.
1969 Such memmap=exactmap lines can be constructed based on
1970 BIOS output or other requirements. See the memmap=nn@ss
1973 memmap=nn[KMG]@ss[KMG]
1974 [KNL] Force usage of a specific region of memory.
1975 Region of memory to be used is from ss to ss+nn.
1977 memmap=nn[KMG]#ss[KMG]
1978 [KNL,ACPI] Mark specific memory as ACPI data.
1979 Region of memory to be marked is from ss to ss+nn.
1981 memmap=nn[KMG]$ss[KMG]
1982 [KNL,ACPI] Mark specific memory as reserved.
1983 Region of memory to be reserved is from ss to ss+nn.
1984 Example: Exclude memory from 0x18690000-0x1869ffff
1985 memmap=64K$0x18690000
1987 memmap=0x10000$0x18690000
1989 memmap=nn[KMG]!ss[KMG]
1990 [KNL,X86] Mark specific memory as protected.
1991 Region of memory to be used, from ss to ss+nn.
1992 The memory region may be marked as e820 type 12 (0xc)
1993 and is NVDIMM or ADR memory.
1995 memory_corruption_check=0/1 [X86]
1996 Some BIOSes seem to corrupt the first 64k of
1997 memory when doing things like suspend/resume.
1998 Setting this option will scan the memory
1999 looking for corruption. Enabling this will
2000 both detect corruption and prevent the kernel
2001 from using the memory being corrupted.
2002 However, its intended as a diagnostic tool; if
2003 repeatable BIOS-originated corruption always
2004 affects the same memory, you can use memmap=
2005 to prevent the kernel from using that memory.
2007 memory_corruption_check_size=size [X86]
2008 By default it checks for corruption in the low
2009 64k, making this memory unavailable for normal
2010 use. Use this parameter to scan for
2011 corruption in more or less memory.
2013 memory_corruption_check_period=seconds [X86]
2014 By default it checks for corruption every 60
2015 seconds. Use this parameter to check at some
2016 other rate. 0 disables periodic checking.
2018 memtest= [KNL,X86,ARM] Enable memtest
2020 default : 0 <disable>
2021 Specifies the number of memtest passes to be
2022 performed. Each pass selects another test
2023 pattern from a given set of patterns. Memtest
2024 fills the memory with this pattern, validates
2025 memory contents and reserves bad memory
2026 regions that are detected.
2028 meye.*= [HW] Set MotionEye Camera parameters
2029 See Documentation/video4linux/meye.txt.
2031 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2032 Multi-Function General Purpose Timers on AMD Geode
2035 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2036 the BIOS has incorrectly applied a workaround. TinyBIOS
2037 version 0.98 is known to be affected, 0.99 fixes the
2038 problem by letting the user disable the workaround.
2042 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2043 physical address is ignored.
2045 mini2440= [ARM,HW,KNL]
2046 Format:[0..2][b][c][t]
2048 MINI2440 configuration specification:
2049 0 - The attached screen is the 3.5" TFT
2050 1 - The attached screen is the 7" TFT
2051 2 - The VGA Shield is attached (1024x768)
2052 Leaving out the screen size parameter will not load
2053 the TFT driver, and the framebuffer will be left
2055 b - Enable backlight. The TFT backlight pin will be
2056 linked to the kernel VESA blanking code and a GPIO
2057 LED. This parameter is not necessary when using the
2059 c - Enable the s3c camera interface.
2060 t - Reserved for enabling touchscreen support. The
2061 touchscreen support is not enabled in the mainstream
2062 kernel as of 2.6.30, a preliminary port can be found
2063 in the "bleeding edge" mini2440 support kernel at
2064 http://repo.or.cz/w/linux-2.6/mini2440.git
2067 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2068 parameter allows control of the logging verbosity for
2069 the additional memory initialisation checks. A value
2070 of 0 disables mminit logging and a level of 4 will
2071 log everything. Information is printed at KERN_DEBUG
2072 so loglevel=8 may also need to be specified.
2075 [KNL] When CONFIG_MODULE_SIG is set, this means that
2076 modules without (valid) signatures will fail to load.
2077 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2078 is always true, so this option does nothing.
2081 [MOUSE] Maximum time between finger touching and
2082 leaving touchpad surface for touch to be considered
2083 a tap and be reported as a left button click (for
2084 touchpads working in absolute mode only).
2086 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2087 reporting absolute coordinates, such as tablets
2088 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2089 reporting absolute coordinates, such as tablets
2091 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2092 is similar to kernelcore except it specifies the
2093 amount of memory used for migratable allocations.
2094 If both kernelcore and movablecore is specified,
2095 then kernelcore will be at *least* the specified
2096 value but may be more. If movablecore on its own
2097 is specified, the administrator must be careful
2098 that the amount of memory usable for all allocations
2101 movable_node [KNL,X86] Boot-time switch to enable the effects
2102 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2104 MTD_Partition= [MTD]
2105 Format: <name>,<region-number>,<size>,<offset>
2107 MTD_Region= [MTD] Format:
2108 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2111 See drivers/mtd/cmdlinepart.c.
2113 multitce=off [PPC] This parameter disables the use of the pSeries
2114 firmware feature for updating multiple TCE entries
2117 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2119 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2121 boundary - index of last SLC block on Flex-OneNAND.
2122 The remaining blocks are configured as MLC blocks.
2123 lock - Configure if Flex-OneNAND boundary should be locked.
2124 Once locked, the boundary cannot be changed.
2125 1 indicates lock status, 0 indicates unlock status.
2128 ARM/S3C2412 JIVE boot control
2130 See arch/arm/mach-s3c2412/mach-jive.c
2132 mtouchusb.raw_coordinates=
2133 [HW] Make the MicroTouch USB driver use raw coordinates
2134 ('y', default) or cooked coordinates ('n')
2136 mtrr_chunk_size=nn[KMG] [X86]
2137 used for mtrr cleanup. It is largest continuous chunk
2138 that could hold holes aka. UC entries.
2140 mtrr_gran_size=nn[KMG] [X86]
2141 Used for mtrr cleanup. It is granularity of mtrr block.
2143 Large value could prevent small alignment from
2146 mtrr_spare_reg_nr=n [X86]
2148 Range: 0,7 : spare reg number
2150 Used for mtrr cleanup. It is spare mtrr entries number.
2151 Set to 2 or more if your graphical card needs more.
2153 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2155 netdev= [NET] Network devices parameters
2156 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2157 Note that mem_start is often overloaded to mean
2158 something different and driver-specific.
2159 This usage is only documented in each driver source
2163 [NETFILTER] Enable connection tracking flow accounting
2164 0 to disable accounting
2165 1 to enable accounting
2168 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2169 See Documentation/filesystems/nfs/nfsroot.txt.
2171 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2172 See Documentation/filesystems/nfs/nfsroot.txt.
2174 nfsrootdebug [NFS] enable nfsroot debugging messages.
2175 See Documentation/filesystems/nfs/nfsroot.txt.
2177 nfs.callback_tcpport=
2178 [NFS] set the TCP port on which the NFSv4 callback
2179 channel should listen.
2182 [NFS] sets the pathname to the program which is used
2183 to update the NFS client cache entries.
2185 nfs.cache_getent_timeout=
2186 [NFS] sets the timeout after which an attempt to
2187 update a cache entry is deemed to have failed.
2189 nfs.idmap_cache_timeout=
2190 [NFS] set the maximum lifetime for idmapper cache
2194 [NFS] enable 64-bit inode numbers.
2195 If zero, the NFS client will fake up a 32-bit inode
2196 number for the readdir() and stat() syscalls instead
2197 of returning the full 64-bit number.
2198 The default is to return 64-bit inode numbers.
2200 nfs.max_session_slots=
2201 [NFSv4.1] Sets the maximum number of session slots
2202 the client will attempt to negotiate with the server.
2203 This limits the number of simultaneous RPC requests
2204 that the client can send to the NFSv4.1 server.
2205 Note that there is little point in setting this
2206 value higher than the max_tcp_slot_table_limit.
2208 nfs.nfs4_disable_idmapping=
2209 [NFSv4] When set to the default of '1', this option
2210 ensures that both the RPC level authentication
2211 scheme and the NFS level operations agree to use
2212 numeric uids/gids if the mount is using the
2213 'sec=sys' security flavour. In effect it is
2214 disabling idmapping, which can make migration from
2215 legacy NFSv2/v3 systems to NFSv4 easier.
2216 Servers that do not support this mode of operation
2217 will be autodetected by the client, and it will fall
2218 back to using the idmapper.
2219 To turn off this behaviour, set the value to '0'.
2221 [NFS4] Specify an additional fixed unique ident-
2222 ification string that NFSv4 clients can insert into
2223 their nfs_client_id4 string. This is typically a
2224 UUID that is generated at system install time.
2226 nfs.send_implementation_id =
2227 [NFSv4.1] Send client implementation identification
2228 information in exchange_id requests.
2229 If zero, no implementation identification information
2231 The default is to send the implementation identification
2234 nfs.recover_lost_locks =
2235 [NFSv4] Attempt to recover locks that were lost due
2236 to a lease timeout on the server. Please note that
2237 doing this risks data corruption, since there are
2238 no guarantees that the file will remain unchanged
2239 after the locks are lost.
2240 If you want to enable the kernel legacy behaviour of
2241 attempting to recover these locks, then set this
2243 The default parameter value of '0' causes the kernel
2244 not to attempt recovery of lost locks.
2246 nfsd.nfs4_disable_idmapping=
2247 [NFSv4] When set to the default of '1', the NFSv4
2248 server will return only numeric uids and gids to
2249 clients using auth_sys, and will accept numeric uids
2250 and gids from such clients. This is intended to ease
2251 migration from NFSv2/v3.
2253 objlayoutdriver.osd_login_prog=
2254 [NFS] [OBJLAYOUT] sets the pathname to the program which
2255 is used to automatically discover and login into new
2256 osd-targets. Please see:
2257 Documentation/filesystems/pnfs.txt for more explanations
2259 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2260 when a NMI is triggered.
2261 Format: [state][,regs][,debounce][,die]
2263 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2264 Format: [panic,][nopanic,][num]
2266 0 - turn nmi_watchdog off
2267 1 - turn nmi_watchdog on
2268 When panic is specified, panic when an NMI watchdog
2269 timeout occurs (or 'nopanic' to override the opposite
2271 This is useful when you use a panic=... timeout and
2272 need the box quickly up again.
2274 netpoll.carrier_timeout=
2275 [NET] Specifies amount of time (in seconds) that
2276 netpoll should wait for a carrier. By default netpoll
2279 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2280 emulation library even if a 387 maths coprocessor
2284 [HW] Never suspend the console
2285 Disable suspending of consoles during suspend and
2286 hibernate operations. Once disabled, debugging
2287 messages can reach various consoles while the rest
2288 of the system is being put to sleep (ie, while
2289 debugging driver suspend/resume hooks). This may
2290 not work reliably with all consoles, but is known
2291 to work with serial and VGA consoles.
2292 To facilitate more flexible debugging, we also add
2293 console_suspend, a printk module parameter to control
2294 it. Users could use console_suspend (usually
2295 /sys/module/printk/parameters/console_suspend) to
2296 turn on/off it dynamically.
2298 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2299 caches in the slab allocator. Saves per-node memory,
2300 but will impact performance.
2304 noapic [SMP,APIC] Tells the kernel to not make use of any
2305 IOAPICs that may be present in the system.
2307 noautogroup Disable scheduler automatic task group creation.
2309 nobats [PPC] Do not use BATs for mapping kernel lowmem
2310 on "Classic" PPC cores.
2314 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2316 nodelayacct [KNL] Disable per-task delay accounting
2318 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2320 nodsp [SH] Disable hardware DSP at boot time.
2322 noefi Disable EFI runtime services support.
2327 On X86-32 available only on PAE configured kernels.
2328 noexec=on: enable non-executable mappings (default)
2329 noexec=off: disable non-executable mappings
2332 Disable SMAP (Supervisor Mode Access Prevention)
2333 even if it is supported by processor.
2336 Disable SMEP (Supervisor Mode Execution Prevention)
2337 even if it is supported by processor.
2340 This affects only 32-bit executables.
2341 noexec32=on: enable non-executable mappings (default)
2342 read doesn't imply executable mappings
2343 noexec32=off: disable non-executable mappings
2344 read implies executable mappings
2346 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2348 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2349 register save and restore. The kernel will only save
2350 legacy floating-point registers on task switch.
2352 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2354 noxsave [BUGS=X86] Disables x86 extended register state save
2355 and restore using xsave. The kernel will fallback to
2356 enabling legacy floating-point and sse state.
2358 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2359 register states. The kernel will fall back to use
2360 xsave to save the states. By using this parameter,
2361 performance of saving the states is degraded because
2362 xsave doesn't support modified optimization while
2363 xsaveopt supports it on xsaveopt enabled systems.
2365 noxsaves [X86] Disables xsaves and xrstors used in saving and
2366 restoring x86 extended register state in compacted
2367 form of xsave area. The kernel will fall back to use
2368 xsaveopt and xrstor to save and restore the states
2369 in standard form of xsave area. By using this
2370 parameter, xsave area per process might occupy more
2371 memory on xsaves enabled systems.
2373 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2374 wfi(ARM) instruction doesn't work correctly and not to
2375 use it. This is also useful when using JTAG debugger.
2377 no_file_caps Tells the kernel not to honor file capabilities. The
2378 only way then for a file to be executed with privilege
2379 is to be setuid root or executed by root.
2381 nohalt [IA-64] Tells the kernel not to use the power saving
2382 function PAL_HALT_LIGHT when idle. This increases
2383 power-consumption. On the positive side, it reduces
2384 interrupt wake-up latency, which may improve performance
2385 in certain environments such as networked servers or
2388 nohibernate [HIBERNATION] Disable hibernation and resume.
2390 nohz= [KNL] Boottime enable/disable dynamic ticks
2391 Valid arguments: on, off
2394 nohz_full= [KNL,BOOT]
2395 In kernels built with CONFIG_NO_HZ_FULL=y, set
2396 the specified list of CPUs whose tick will be stopped
2397 whenever possible. The boot CPU will be forced outside
2398 the range to maintain the timekeeping.
2399 The CPUs in this range must also be included in the
2402 noiotrap [SH] Disables trapped I/O port accesses.
2404 noirqdebug [X86-32] Disables the code which attempts to detect and
2405 disable unhandled interrupt sources.
2407 no_timer_check [X86,APIC] Disables the code which tests for
2408 broken timer IRQ sources.
2410 noisapnp [ISAPNP] Disables ISA PnP code.
2412 noinitrd [RAM] Tells the kernel not to load any configured
2415 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2417 [Deprecated - use intremap=off]
2421 nojitter [IA-64] Disables jitter checking for ITC timers.
2423 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2425 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2428 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2429 steal time is computed, but won't influence scheduler
2432 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2434 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2436 noltlbs [PPC] Do not use large page/tlb entries for kernel
2437 lowmem mapping on PPC40x.
2439 nomca [IA-64] Disable machine check abort handling
2441 nomce [X86-32] Machine Check Exception
2443 nomfgpt [X86-32] Disable Multi-Function General Purpose
2444 Timer usage (for AMD Geode machines).
2446 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2447 shutdown the other cpus. Instead use the REBOOT_VECTOR
2450 nomodule Disable module load
2452 nopat [X86] Disable PAT (page attribute table extension of
2453 pagetables) support.
2455 norandmaps Don't use address space randomization. Equivalent to
2456 echo 0 > /proc/sys/kernel/randomize_va_space
2458 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2460 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2461 with UP alternatives
2463 nordrand [X86] Disable kernel use of the RDRAND and
2464 RDSEED instructions even if they are supported
2465 by the processor. RDRAND and RDSEED are still
2466 available to user space applications.
2468 noresume [SWSUSP] Disables resume and restores original swap
2471 no-scroll [VGA] Disables scrollback.
2472 This is required for the Braillex ib80-piezo Braille
2473 reader made by F.H. Papenmeier (Germany).
2477 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2479 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2480 and disable the IO APIC. legacy for "maxcpus=0".
2482 nosoftlockup [KNL] Disable the soft-lockup detector.
2484 nosync [HW,M68K] Disables sync negotiation for all devices.
2486 notsc [BUGS=X86-32] Disable Time Stamp Counter
2488 nousb [USB] Disable the USB subsystem
2490 nowatchdog [KNL] Disable both lockup detectors, i.e.
2491 soft-lockup and NMI watchdog (hard-lockup).
2495 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2497 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2498 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2499 Some features depend on CPU0. Known dependencies are:
2500 1. Resume from suspend/hibernate depends on CPU0.
2501 Suspend/hibernate will fail if CPU0 is offline and you
2502 need to online CPU0 before suspend/hibernate.
2503 2. PIC interrupts also depend on CPU0. CPU0 can't be
2504 removed if a PIC interrupt is detected.
2505 It's said poweroff/reboot may depend on CPU0 on some
2506 machines although I haven't seen such issues so far
2507 after CPU0 is offline on a few tested machines.
2508 If the dependencies are under your control, you can
2509 turn on cpu0_hotplug.
2511 nptcg= [IA-64] Override max number of concurrent global TLB
2512 purges which is reported from either PAL_VM_SUMMARY or
2515 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2516 could support. nr_cpus=n : n >= 1 limits the kernel to
2517 supporting 'n' processors. Later in runtime you can not
2518 use hotplug cpu feature to put more cpu back to online.
2519 just like you compile the kernel NR_CPUS=n
2521 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2523 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2524 Allowed values are enable and disable
2526 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2527 one of ['zone', 'node', 'default'] can be specified
2528 This can be set from sysctl after boot.
2529 See Documentation/sysctl/vm.txt for details.
2531 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2532 See Documentation/debugging-via-ohci1394.txt for more
2535 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2536 Rather than timing out after 20 ms if an EC
2537 command is not properly ACKed, override the length
2538 of the timeout. We have interrupts disabled while
2539 waiting for the ACK, so if this is set too high
2540 interrupts *may* be lost!
2542 omap_mux= [OMAP] Override bootloader pin multiplexing.
2543 Format: <mux_mode0.mode_name=value>...
2544 For example, to override I2C bus2:
2545 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2547 oprofile.timer= [HW]
2548 Use timer interrupt instead of performance counters
2550 oprofile.cpu_type= Force an oprofile cpu type
2551 This might be useful if you have an older oprofile
2552 userland or if you want common events.
2553 Format: { arch_perfmon }
2554 arch_perfmon: [X86] Force use of architectural
2555 perfmon on Intel CPUs instead of the
2556 CPU specific event set.
2557 timer: [X86] Force use of architectural NMI
2558 timer mode (see also oprofile.timer
2559 for generic hr timer mode)
2560 [s390] Force legacy basic mode sampling
2561 (report cpu_type "timer")
2563 oops=panic Always panic on oopses. Default is to just kill the
2564 process, but there is a small probability of
2565 deadlocking the machine.
2566 This will also cause panics on machine check exceptions.
2567 Useful together with panic=30 to trigger a reboot.
2570 See Documentation/sound/oss/oss-parameters.txt
2572 page_owner= [KNL] Boot-time page_owner enabling option.
2573 Storage of the information about who allocated
2574 each page is disabled in default. With this switch,
2576 on: enable the feature
2578 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2579 timeout > 0: seconds before rebooting
2580 timeout = 0: wait forever
2581 timeout < 0: reboot immediately
2584 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2587 crash_kexec_post_notifiers
2588 Run kdump after running panic-notifiers and dumping
2589 kmsg. This only for the users who doubt kdump always
2590 succeeds in any situation.
2591 Note that this also increases risks of kdump failure,
2592 because some panic notifiers can make the crashed
2593 kernel more unstable.
2595 parkbd.port= [HW] Parallel port number the keyboard adapter is
2596 connected to, default is 0.
2598 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2599 0 for XT, 1 for AT (default is AT).
2602 parport= [HW,PPT] Specify parallel ports. 0 disables.
2603 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2604 Use 'auto' to force the driver to use any
2605 IRQ/DMA settings detected (the default is to
2606 ignore detected IRQ/DMA settings because of
2607 possible conflicts). You can specify the base
2608 address, IRQ, and DMA settings; IRQ and DMA
2609 should be numbers, or 'auto' (for using detected
2610 settings on that particular port), or 'nofifo'
2611 (to avoid using a FIFO even if it is detected).
2612 Parallel ports are assigned in the order they
2613 are specified on the command line, starting
2616 parport_init_mode= [HW,PPT]
2617 Configure VIA parallel port to operate in
2618 a specific mode. This is necessary on Pegasos
2619 computer where firmware has no options for setting
2620 up parallel port mode and sets it to spp.
2621 Currently this function knows 686a and 8231 chips.
2622 Format: [spp|ps2|epp|ecp|ecpepp]
2625 Halt all CPUs after the first oops has been printed for
2626 the specified number of seconds. This is to be used if
2627 your oopses keep scrolling off the screen.
2632 See header of drivers/block/paride/pcd.c.
2633 See also Documentation/blockdev/paride.txt.
2635 pci=option[,option...] [PCI] various PCI subsystem options:
2636 earlydump [X86] dump PCI config space before the kernel
2638 off [X86] don't probe for the PCI bus
2639 bios [X86-32] force use of PCI BIOS, don't access
2640 the hardware directly. Use this if your machine
2641 has a non-standard PCI host bridge.
2642 nobios [X86-32] disallow use of PCI BIOS, only direct
2643 hardware access methods are allowed. Use this
2644 if you experience crashes upon bootup and you
2645 suspect they are caused by the BIOS.
2646 conf1 [X86] Force use of PCI Configuration
2648 conf2 [X86] Force use of PCI Configuration
2650 noaer [PCIE] If the PCIEAER kernel config parameter is
2651 enabled, this kernel boot option can be used to
2652 disable the use of PCIE advanced error reporting.
2653 nodomains [PCI] Disable support for multiple PCI
2654 root domains (aka PCI segments, in ACPI-speak).
2655 nommconf [X86] Disable use of MMCONFIG for PCI
2657 check_enable_amd_mmconf [X86] check for and enable
2658 properly configured MMIO access to PCI
2659 config space on AMD family 10h CPU
2660 nomsi [MSI] If the PCI_MSI kernel config parameter is
2661 enabled, this kernel boot option can be used to
2662 disable the use of MSI interrupts system-wide.
2663 noioapicquirk [APIC] Disable all boot interrupt quirks.
2664 Safety option to keep boot IRQs enabled. This
2665 should never be necessary.
2666 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2667 primary IO-APIC for bridges that cannot disable
2668 boot IRQs. This fixes a source of spurious IRQs
2669 when the system masks IRQs.
2670 noioapicreroute [APIC] Disable workaround that uses the
2671 boot IRQ equivalent of an IRQ that connects to
2672 a chipset where boot IRQs cannot be disabled.
2673 The opposite of ioapicreroute.
2674 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2675 routing table. These calls are known to be buggy
2676 on several machines and they hang the machine
2677 when used, but on other computers it's the only
2678 way to get the interrupt routing table. Try
2679 this option if the kernel is unable to allocate
2680 IRQs or discover secondary PCI buses on your
2682 rom [X86] Assign address space to expansion ROMs.
2683 Use with caution as certain devices share
2684 address decoders between ROMs and other
2686 norom [X86] Do not assign address space to
2687 expansion ROMs that do not already have
2688 BIOS assigned address ranges.
2689 nobar [X86] Do not assign address space to the
2690 BARs that weren't assigned by the BIOS.
2691 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2692 assigned automatically to PCI devices. You can
2693 make the kernel exclude IRQs of your ISA cards
2695 pirqaddr=0xAAAAA [X86] Specify the physical address
2696 of the PIRQ table (normally generated
2697 by the BIOS) if it is outside the
2698 F0000h-100000h range.
2699 lastbus=N [X86] Scan all buses thru bus #N. Can be
2700 useful if the kernel is unable to find your
2701 secondary buses and you want to tell it
2702 explicitly which ones they are.
2703 assign-busses [X86] Always assign all PCI bus
2704 numbers ourselves, overriding
2705 whatever the firmware may have done.
2706 usepirqmask [X86] Honor the possible IRQ mask stored
2707 in the BIOS $PIR table. This is needed on
2708 some systems with broken BIOSes, notably
2709 some HP Pavilion N5400 and Omnibook XE3
2710 notebooks. This will have no effect if ACPI
2711 IRQ routing is enabled.
2712 noacpi [X86] Do not use ACPI for IRQ routing
2713 or for PCI scanning.
2714 use_crs [X86] Use PCI host bridge window information
2715 from ACPI. On BIOSes from 2008 or later, this
2716 is enabled by default. If you need to use this,
2717 please report a bug.
2718 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2719 If you need to use this, please report a bug.
2720 routeirq Do IRQ routing for all PCI devices.
2721 This is normally done in pci_enable_device(),
2722 so this option is a temporary workaround
2723 for broken drivers that don't call it.
2724 skip_isa_align [X86] do not align io start addr, so can
2725 handle more pci cards
2726 firmware [ARM] Do not re-enumerate the bus but instead
2727 just use the configuration from the
2728 bootloader. This is currently used on
2729 IXP2000 systems where the bus has to be
2730 configured a certain way for adjunct CPUs.
2731 noearly [X86] Don't do any early type 1 scanning.
2732 This might help on some broken boards which
2733 machine check when some devices' config space
2734 is read. But various workarounds are disabled
2735 and some IOMMU drivers will not work.
2736 bfsort Sort PCI devices into breadth-first order.
2737 This sorting is done to get a device
2738 order compatible with older (<= 2.4) kernels.
2739 nobfsort Don't sort PCI devices into breadth-first order.
2740 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2741 tuning and use the BIOS-configured MPS defaults.
2742 pcie_bus_safe Set every device's MPS to the largest value
2743 supported by all devices below the root complex.
2744 pcie_bus_perf Set device MPS to the largest allowable MPS
2745 based on its parent bus. Also set MRRS (Max
2746 Read Request Size) to the largest supported
2747 value (no larger than the MPS that the device
2748 or bus can support) for best performance.
2749 pcie_bus_peer2peer Set every device's MPS to 128B, which
2750 every device is guaranteed to support. This
2751 configuration allows peer-to-peer DMA between
2752 any pair of devices, possibly at the cost of
2753 reduced performance. This also guarantees
2754 that hot-added devices will work.
2755 cbiosize=nn[KMG] The fixed amount of bus space which is
2756 reserved for the CardBus bridge's IO window.
2757 The default value is 256 bytes.
2758 cbmemsize=nn[KMG] The fixed amount of bus space which is
2759 reserved for the CardBus bridge's memory
2760 window. The default value is 64 megabytes.
2763 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2764 Specifies alignment and device to reassign
2765 aligned memory resources.
2766 If <order of align> is not specified,
2767 PAGE_SIZE is used as alignment.
2768 PCI-PCI bridge can be specified, if resource
2769 windows need to be expanded.
2770 ecrc= Enable/disable PCIe ECRC (transaction layer
2771 end-to-end CRC checking).
2772 bios: Use BIOS/firmware settings. This is the
2776 hpiosize=nn[KMG] The fixed amount of bus space which is
2777 reserved for hotplug bridge's IO window.
2778 Default size is 256 bytes.
2779 hpmemsize=nn[KMG] The fixed amount of bus space which is
2780 reserved for hotplug bridge's memory window.
2781 Default size is 2 megabytes.
2782 realloc= Enable/disable reallocating PCI bridge resources
2783 if allocations done by BIOS are too small to
2784 accommodate resources required by all child
2786 off: Turn realloc off
2788 realloc same as realloc=on
2789 noari do not use PCIe ARI.
2790 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2791 only look for one device below a PCIe downstream
2794 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2797 force Enable ASPM even on devices that claim not to support it.
2798 WARNING: Forcing ASPM on may cause system lockups.
2800 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2801 nomsi Do not use MSI for PCI Express Native Hotplug (this
2802 makes all PCIe ports use INTx for hotplug services).
2804 pcie_ports= [PCIE] PCIe ports handling:
2805 auto Ask the BIOS whether or not to use native PCIe services
2806 associated with PCIe ports (PME, hot-plug, AER). Use
2807 them only if that is allowed by the BIOS.
2808 native Use native PCIe services associated with PCIe ports
2810 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2813 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2814 nomsi Do not use MSI for native PCIe PME signaling (this makes
2815 all PCIe root ports use INTx for all services).
2817 pcmv= [HW,PCMCIA] BadgePAD 4
2821 Keep all power-domains already enabled by bootloader on,
2822 even if no driver has claimed them. This is useful
2823 for debug and development, but should not be
2824 needed on a platform with proper driver support.
2827 See Documentation/blockdev/paride.txt.
2829 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2832 See arch/parisc/kernel/pdc_chassis.c
2834 percpu_alloc= Select which percpu first chunk allocator to use.
2835 Currently supported values are "embed" and "page".
2836 Archs may support subset or none of the selections.
2837 See comments in mm/percpu.c for details on each
2838 allocator. This parameter is primarily for debugging
2839 and performance comparison.
2842 See Documentation/blockdev/paride.txt.
2845 See Documentation/blockdev/paride.txt.
2847 pirq= [SMP,APIC] Manual mp-table setup
2848 See Documentation/x86/i386/IO-APIC.txt.
2850 plip= [PPT,NET] Parallel port network link
2851 Format: { parport<nr> | timid | 0 }
2852 See also Documentation/parport.txt.
2854 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2855 Override pmtimer IOPort with a hex value.
2859 Enable PNP debug messages (depends on the
2860 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2861 via /sys/module/pnp/parameters/debug. We always show
2862 current resource usage; turning this on also shows
2863 possible settings and some assignment information.
2869 { on | off | curr | res | no-curr | no-res }
2872 [ISAPNP] Exclude IRQs for the autoconfiguration
2875 [ISAPNP] Exclude DMAs for the autoconfiguration
2877 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2878 Ranges are in pairs (I/O port base and size).
2881 [ISAPNP] Exclude memory regions for the
2883 Ranges are in pairs (memory base and size).
2885 ports= [IP_VS_FTP] IPVS ftp helper module
2887 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2889 Format: <port>,<port>....
2891 print-fatal-signals=
2892 [KNL] debug: print fatal signals
2894 If enabled, warn about various signal handling
2895 related application anomalies: too many signals,
2896 too many POSIX.1 timers, fatal signals causing a
2899 If you hit the warning due to signal overflow,
2900 you might want to try "ulimit -i unlimited".
2904 printk.always_kmsg_dump=
2905 Trigger kmsg_dump for cases other than kernel oops or
2907 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2910 printk.time= Show timing data prefixed to each printk message line
2911 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2913 processor.max_cstate= [HW,ACPI]
2914 Limit processor to maximum C-state
2915 max_cstate=9 overrides any DMI blacklist limit.
2917 processor.nocst [HW,ACPI]
2918 Ignore the _CST method to determine C-states,
2919 instead using the legacy FADT method
2921 profile= [KNL] Enable kernel profiling via /proc/profile
2922 Format: [schedule,]<number>
2923 Param: "schedule" - profile schedule points.
2924 Param: <number> - step/bucket size as a power of 2 for
2925 statistical time based profiling.
2926 Param: "sleep" - profile D-state sleeping (millisecs).
2927 Requires CONFIG_SCHEDSTATS
2928 Param: "kvm" - profile VM exits.
2930 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2932 See Documentation/blockdev/ramdisk.txt.
2934 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2935 probe for; one of (bare|imps|exps|lifebook|any).
2936 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2938 psmouse.resetafter= [HW,MOUSE]
2939 Try to reset the device after so many bad packets
2942 [HW,MOUSE] Set desired mouse resolution, in dpi.
2943 psmouse.smartscroll=
2944 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2945 0 = disabled, 1 = enabled (default).
2947 pstore.backend= Specify the name of the pstore backend to use
2950 See Documentation/blockdev/paride.txt.
2953 [KNL] Number of legacy pty's. Overwrites compiled-in
2956 quiet [KNL] Disable most log messages
2961 See Documentation/md.txt.
2963 ramdisk_blocksize= [RAM]
2964 See Documentation/blockdev/ramdisk.txt.
2966 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2967 See Documentation/blockdev/ramdisk.txt.
2970 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2971 the specified list of CPUs to be no-callback CPUs.
2972 Invocation of these CPUs' RCU callbacks will
2973 be offloaded to "rcuox/N" kthreads created for
2974 that purpose, where "x" is "b" for RCU-bh, "p"
2975 for RCU-preempt, and "s" for RCU-sched, and "N"
2976 is the CPU number. This reduces OS jitter on the
2977 offloaded CPUs, which can be useful for HPC and
2978 real-time workloads. It can also improve energy
2979 efficiency for asymmetric multiprocessors.
2982 Rather than requiring that offloaded CPUs
2983 (specified by rcu_nocbs= above) explicitly
2984 awaken the corresponding "rcuoN" kthreads,
2985 make these kthreads poll for callbacks.
2986 This improves the real-time response for the
2987 offloaded CPUs by relieving them of the need to
2988 wake up the corresponding kthread, but degrades
2989 energy efficiency by requiring that the kthreads
2990 periodically wake up to do the polling.
2992 rcutree.blimit= [KNL]
2993 Set maximum number of finished RCU callbacks to
2994 process in one batch.
2996 rcutree.gp_init_delay= [KNL]
2997 Set the number of jiffies to delay each step of
2998 RCU grace-period initialization. This only has
2999 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3002 rcutree.rcu_fanout_leaf= [KNL]
3003 Increase the number of CPUs assigned to each
3004 leaf rcu_node structure. Useful for very large
3007 rcutree.jiffies_till_sched_qs= [KNL]
3008 Set required age in jiffies for a
3009 given grace period before RCU starts
3010 soliciting quiescent-state help from
3011 rcu_note_context_switch().
3013 rcutree.jiffies_till_first_fqs= [KNL]
3014 Set delay from grace-period initialization to
3015 first attempt to force quiescent states.
3016 Units are jiffies, minimum value is zero,
3017 and maximum value is HZ.
3019 rcutree.jiffies_till_next_fqs= [KNL]
3020 Set delay between subsequent attempts to force
3021 quiescent states. Units are jiffies, minimum
3022 value is one, and maximum value is HZ.
3024 rcutree.kthread_prio= [KNL,BOOT]
3025 Set the SCHED_FIFO priority of the RCU per-CPU
3026 kthreads (rcuc/N). This value is also used for
3027 the priority of the RCU boost threads (rcub/N)
3028 and for the RCU grace-period kthreads (rcu_bh,
3029 rcu_preempt, and rcu_sched). If RCU_BOOST is
3030 set, valid values are 1-99 and the default is 1
3031 (the least-favored priority). Otherwise, when
3032 RCU_BOOST is not set, valid values are 0-99 and
3033 the default is zero (non-realtime operation).
3035 rcutree.rcu_nocb_leader_stride= [KNL]
3036 Set the number of NOCB kthread groups, which
3037 defaults to the square root of the number of
3038 CPUs. Larger numbers reduces the wakeup overhead
3039 on the per-CPU grace-period kthreads, but increases
3040 that same overhead on each group's leader.
3042 rcutree.qhimark= [KNL]
3043 Set threshold of queued RCU callbacks beyond which
3044 batch limiting is disabled.
3046 rcutree.qlowmark= [KNL]
3047 Set threshold of queued RCU callbacks below which
3048 batch limiting is re-enabled.
3050 rcutree.rcu_idle_gp_delay= [KNL]
3051 Set wakeup interval for idle CPUs that have
3052 RCU callbacks (RCU_FAST_NO_HZ=y).
3054 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3055 Set wakeup interval for idle CPUs that have
3056 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3057 Lazy RCU callbacks are those which RCU can
3058 prove do nothing more than free memory.
3060 rcutorture.cbflood_inter_holdoff= [KNL]
3061 Set holdoff time (jiffies) between successive
3062 callback-flood tests.
3064 rcutorture.cbflood_intra_holdoff= [KNL]
3065 Set holdoff time (jiffies) between successive
3066 bursts of callbacks within a given callback-flood
3069 rcutorture.cbflood_n_burst= [KNL]
3070 Set the number of bursts making up a given
3071 callback-flood test. Set this to zero to
3072 disable callback-flood testing.
3074 rcutorture.cbflood_n_per_burst= [KNL]
3075 Set the number of callbacks to be registered
3076 in a given burst of a callback-flood test.
3078 rcutorture.fqs_duration= [KNL]
3079 Set duration of force_quiescent_state bursts.
3081 rcutorture.fqs_holdoff= [KNL]
3082 Set holdoff time within force_quiescent_state bursts.
3084 rcutorture.fqs_stutter= [KNL]
3085 Set wait time between force_quiescent_state bursts.
3087 rcutorture.gp_exp= [KNL]
3088 Use expedited update-side primitives.
3090 rcutorture.gp_normal= [KNL]
3091 Use normal (non-expedited) update-side primitives.
3092 If both gp_exp and gp_normal are set, do both.
3093 If neither gp_exp nor gp_normal are set, still
3096 rcutorture.n_barrier_cbs= [KNL]
3097 Set callbacks/threads for rcu_barrier() testing.
3099 rcutorture.nfakewriters= [KNL]
3100 Set number of concurrent RCU writers. These just
3101 stress RCU, they don't participate in the actual
3102 test, hence the "fake".
3104 rcutorture.nreaders= [KNL]
3105 Set number of RCU readers.
3107 rcutorture.object_debug= [KNL]
3108 Enable debug-object double-call_rcu() testing.
3110 rcutorture.onoff_holdoff= [KNL]
3111 Set time (s) after boot for CPU-hotplug testing.
3113 rcutorture.onoff_interval= [KNL]
3114 Set time (s) between CPU-hotplug operations, or
3115 zero to disable CPU-hotplug testing.
3117 rcutorture.torture_runnable= [BOOT]
3118 Start rcutorture running at boot time.
3120 rcutorture.shuffle_interval= [KNL]
3121 Set task-shuffle interval (s). Shuffling tasks
3122 allows some CPUs to go into dyntick-idle mode
3123 during the rcutorture test.
3125 rcutorture.shutdown_secs= [KNL]
3126 Set time (s) after boot system shutdown. This
3127 is useful for hands-off automated testing.
3129 rcutorture.stall_cpu= [KNL]
3130 Duration of CPU stall (s) to test RCU CPU stall
3131 warnings, zero to disable.
3133 rcutorture.stall_cpu_holdoff= [KNL]
3134 Time to wait (s) after boot before inducing stall.
3136 rcutorture.stat_interval= [KNL]
3137 Time (s) between statistics printk()s.
3139 rcutorture.stutter= [KNL]
3140 Time (s) to stutter testing, for example, specifying
3141 five seconds causes the test to run for five seconds,
3142 wait for five seconds, and so on. This tests RCU's
3143 ability to transition abruptly to and from idle.
3145 rcutorture.test_boost= [KNL]
3146 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3147 "Maybe" means test if the RCU implementation
3148 under test support RCU priority boosting.
3150 rcutorture.test_boost_duration= [KNL]
3151 Duration (s) of each individual boost test.
3153 rcutorture.test_boost_interval= [KNL]
3154 Interval (s) between each boost test.
3156 rcutorture.test_no_idle_hz= [KNL]
3157 Test RCU's dyntick-idle handling. See also the
3158 rcutorture.shuffle_interval parameter.
3160 rcutorture.torture_type= [KNL]
3161 Specify the RCU implementation to test.
3163 rcutorture.verbose= [KNL]
3164 Enable additional printk() statements.
3166 rcupdate.rcu_expedited= [KNL]
3167 Use expedited grace-period primitives, for
3168 example, synchronize_rcu_expedited() instead
3169 of synchronize_rcu(). This reduces latency,
3170 but can increase CPU utilization, degrade
3171 real-time latency, and degrade energy efficiency.
3173 rcupdate.rcu_cpu_stall_suppress= [KNL]
3174 Suppress RCU CPU stall warning messages.
3176 rcupdate.rcu_cpu_stall_timeout= [KNL]
3177 Set timeout for RCU CPU stall warning messages.
3179 rcupdate.rcu_task_stall_timeout= [KNL]
3180 Set timeout in jiffies for RCU task stall warning
3181 messages. Disable with a value less than or equal
3184 rcupdate.rcu_self_test= [KNL]
3185 Run the RCU early boot self tests
3187 rcupdate.rcu_self_test_bh= [KNL]
3188 Run the RCU bh early boot self tests
3190 rcupdate.rcu_self_test_sched= [KNL]
3191 Run the RCU sched early boot self tests
3195 Run specified binary instead of /init from the ramdisk,
3196 used for early userspace startup. See initrd.
3199 Format (x86 or x86_64):
3200 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3202 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3204 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3205 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3206 reboot_force is either force or not specified,
3207 reboot_cpu is s[mp]#### with #### being the processor
3208 to be used for rebooting.
3211 [KNL, SMP] Set scheduler's default relax_domain_level.
3212 See Documentation/cgroups/cpusets.txt.
3214 relative_sleep_states=
3215 [SUSPEND] Use sleep state labeling where the deepest
3216 state available other than hibernation is always "mem".
3217 Format: { "0" | "1" }
3218 0 -- Traditional sleep state labels.
3219 1 -- Relative sleep state labels.
3221 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3223 reservetop= [X86-32]
3225 Reserves a hole at the top of the kernel virtual
3230 Set the amount of memory to reserve for BIOS at
3231 the bottom of the address space.
3233 reset_devices [KNL] Force drivers to reset the underlying device
3234 during initialization.
3237 Specify the partition device for software suspend
3239 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3241 resume_offset= [SWSUSP]
3242 Specify the offset from the beginning of the partition
3243 given by "resume=" at which the swap header is located,
3244 in <PAGE_SIZE> units (needed only for swap files).
3245 See Documentation/power/swsusp-and-swap-files.txt
3247 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3248 read the resume files
3250 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3251 Useful for devices that are detected asynchronously
3252 (e.g. USB and MMC devices).
3254 hibernate= [HIBERNATION]
3255 noresume Don't check if there's a hibernation image
3256 present during boot.
3257 nocompress Don't compress/decompress hibernation images.
3258 no Disable hibernation and resume.
3260 retain_initrd [RAM] Keep initrd memory after extraction
3262 rfkill.default_state=
3263 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3264 etc. communication is blocked by default.
3267 rfkill.master_switch_mode=
3268 0 The "airplane mode" button does nothing.
3269 1 The "airplane mode" button toggles between everything
3270 blocked and the previous configuration.
3271 2 The "airplane mode" button toggles between everything
3272 blocked and everything unblocked.
3274 rhash_entries= [KNL,NET]
3275 Set number of hash buckets for route cache
3277 ro [KNL] Mount root device read-only on boot
3279 root= [KNL] Root filesystem
3280 See name_to_dev_t comment in init/do_mounts.c.
3282 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3283 mount the root filesystem
3285 rootflags= [KNL] Set root filesystem mount option string
3287 rootfstype= [KNL] Set root filesystem type
3289 rootwait [KNL] Wait (indefinitely) for root device to show up.
3290 Useful for devices that are detected asynchronously
3291 (e.g. USB and MMC devices).
3293 rproc_mem=nn[KMG][@address]
3294 [KNL,ARM,CMA] Remoteproc physical memory block.
3295 Memory area to be used by remote processor image,
3298 rw [KNL] Mount root device read-write on boot
3300 S [KNL] Run init in single mode
3302 s390_iommu= [HW,S390]
3303 Set s390 IOTLB flushing mode
3305 With strict flushing every unmap operation will result in
3306 an IOTLB flush. Default is lazy flushing before reuse,
3310 See drivers/net/irda/sa1100_ir.c.
3312 sbni= [NET] Granch SBNI12 leased line adapter
3314 sched_debug [KNL] Enables verbose scheduler debug messages.
3316 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3317 xtime_lock contention on larger systems, and/or RCU lock
3318 contention on all systems with CONFIG_MAXSMP set.
3319 Format: { "0" | "1" }
3320 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3322 Note: increases power consumption, thus should only be
3323 enabled if running jitter sensitive (HPC/RT) workloads.
3325 security= [SECURITY] Choose a security module to enable at boot.
3326 If this boot parameter is not specified, only the first
3327 security module asking for security registration will be
3328 loaded. An invalid security module name will be treated
3329 as if no module has been chosen.
3331 selinux= [SELINUX] Disable or enable SELinux at boot time.
3332 Format: { "0" | "1" }
3333 See security/selinux/Kconfig help text.
3336 Default value is set via kernel config option.
3337 If enabled at boot time, /selinux/disable can be used
3338 later to disable prior to initial policy load.
3340 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3341 Format: { "0" | "1" }
3342 See security/apparmor/Kconfig help text
3345 Default value is set via kernel config option.
3347 serialnumber [BUGS=X86-32]
3350 Maximal number of shapers.
3352 show_msr= [x86] show boot-time MSR settings
3353 Format: { <integer> }
3354 Show boot-time (BIOS-initialized) MSR settings.
3355 The parameter means the number of CPUs to show,
3356 for example 1 means boot CPU only.
3364 Disable merging of slabs with similar size. May be
3365 necessary if there is some reason to distinguish
3366 allocs to different slabs. Debug options disable
3367 merging on their own.
3368 For more information see Documentation/vm/slub.txt.
3370 slab_max_order= [MM, SLAB]
3371 Determines the maximum allowed order for slabs.
3372 A high setting may cause OOMs due to memory
3373 fragmentation. Defaults to 1 for systems with
3374 more than 32MB of RAM, 0 otherwise.
3376 slub_debug[=options[,slabs]] [MM, SLUB]
3377 Enabling slub_debug allows one to determine the
3378 culprit if slab objects become corrupted. Enabling
3379 slub_debug can create guard zones around objects and
3380 may poison objects when not in use. Also tracks the
3381 last alloc / free. For more information see
3382 Documentation/vm/slub.txt.
3384 slub_max_order= [MM, SLUB]
3385 Determines the maximum allowed order for slabs.
3386 A high setting may cause OOMs due to memory
3387 fragmentation. For more information see
3388 Documentation/vm/slub.txt.
3390 slub_min_objects= [MM, SLUB]
3391 The minimum number of objects per slab. SLUB will
3392 increase the slab order up to slub_max_order to
3393 generate a sufficiently large slab able to contain
3394 the number of objects indicated. The higher the number
3395 of objects the smaller the overhead of tracking slabs
3396 and the less frequently locks need to be acquired.
3397 For more information see Documentation/vm/slub.txt.
3399 slub_min_order= [MM, SLUB]
3400 Determines the minimum page order for slabs. Must be
3401 lower than slub_max_order.
3402 For more information see Documentation/vm/slub.txt.
3404 slub_nomerge [MM, SLUB]
3405 Same with slab_nomerge. This is supported for legacy.
3406 See slab_nomerge for more information.
3409 Format: <io1>[,<io2>[,...,<io8>]]
3411 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3412 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3413 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3414 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3415 smsc-ircc2.ircc_irq= [HW] IRQ line
3416 smsc-ircc2.ircc_dma= [HW] DMA channel
3417 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3418 0: Toshiba Satellite 1800 (GP data pin select)
3419 1: Fast pin select (default)
3423 [KNL] Should the soft-lockup detector generate panics.
3426 softlockup_all_cpu_backtrace=
3427 [KNL] Should the soft-lockup detector generate
3428 backtraces on all cpus.
3431 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3432 See Documentation/laptops/sonypi.txt
3434 spia_io_base= [HW,MTD]
3440 Enabled the stack tracer on boot up.
3442 stacktrace_filter=[function-list]
3443 [FTRACE] Limit the functions that the stack tracer
3444 will trace at boot up. function-list is a comma separated
3445 list of functions. This list can be changed at run
3446 time by the stack_trace_filter file in the debugfs
3447 tracing directory. Note, this enables stack tracing
3448 and the stacktrace above is not needed.
3452 Set the STI (builtin display/keyboard on the HP-PARISC
3453 machines) console (graphic card) which should be used
3454 as the initial boot-console.
3455 See also comment in drivers/video/console/sticore.c.
3458 See comment in drivers/video/console/sticore.c.
3461 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3463 sunrpc.min_resvport=
3464 sunrpc.max_resvport=
3466 SunRPC servers often require that client requests
3467 originate from a privileged port (i.e. a port in the
3468 range 0 < portnr < 1024).
3469 An administrator who wishes to reserve some of these
3470 ports for other uses may adjust the range that the
3471 kernel's sunrpc client considers to be privileged
3472 using these two parameters to set the minimum and
3473 maximum port values.
3477 Control how the NFS server code allocates CPUs to
3478 service thread pools. Depending on how many NICs
3479 you have and where their interrupts are bound, this
3480 option will affect which CPUs will do NFS serving.
3481 Note: this parameter cannot be changed while the
3482 NFS server is running.
3484 auto the server chooses an appropriate mode
3485 automatically using heuristics
3486 global a single global pool contains all CPUs
3487 percpu one pool for each CPU
3488 pernode one pool for each NUMA node (equivalent
3489 to global on non-NUMA machines)
3491 sunrpc.tcp_slot_table_entries=
3492 sunrpc.udp_slot_table_entries=
3494 Sets the upper limit on the number of simultaneous
3495 RPC calls that can be sent from the client to a
3496 server. Increasing these values may allow you to
3497 improve throughput, but will also increase the
3498 amount of memory reserved for use by the client.
3500 suspend.pm_test_delay=
3502 Sets the number of seconds to remain in a suspend test
3503 mode before resuming the system (see
3504 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3505 is set. Default value is 5.
3508 [KNL] Enable accounting of swap in memory resource
3509 controller if no parameter or 1 is given or disable
3510 it if 0 is given (See Documentation/cgroups/memory.txt)
3512 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3513 Format: { <int> | force }
3514 <int> -- Number of I/O TLB slabs
3515 force -- force using of bounce buffers even if they
3516 wouldn't be automatically used by the kernel
3520 sysfs.deprecated=0|1 [KNL]
3521 Enable/disable old style sysfs layout for old udev
3522 on older distributions. When this option is enabled
3523 very new udev will not work anymore. When this option
3524 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3525 in older udev will not work anymore.
3526 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3527 the kernel configuration.
3529 sysrq_always_enabled
3531 Ignore sysrq setting - this boot parameter will
3532 neutralize any effect of /proc/sys/kernel/sysrq.
3533 Useful for debugging.
3535 tcpmhash_entries= [KNL,NET]
3536 Set the number of tcp_metrics_hash slots.
3537 Default value is 8192 or 16384 depending on total
3538 ram pages. This is used to specify the TCP metrics
3539 cache size. See Documentation/networking/ip-sysctl.txt
3540 "tcp_no_metrics_save" section for more details.
3544 test_suspend= [SUSPEND][,N]
3545 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3546 standby suspend) or "freeze" (for suspend type freeze)
3547 as the system sleep state during system startup with
3548 the optional capability to repeat N number of times.
3549 The system is woken from this state using a
3550 wakeup-capable RTC alarm.
3552 thash_entries= [KNL,NET]
3553 Set number of hash buckets for TCP connection
3555 thermal.act= [HW,ACPI]
3556 -1: disable all active trip points in all thermal zones
3557 <degrees C>: override all lowest active trip points
3559 thermal.crt= [HW,ACPI]
3560 -1: disable all critical trip points in all thermal zones
3561 <degrees C>: override all critical trip points
3563 thermal.nocrt= [HW,ACPI]
3564 Set to disable actions on ACPI thermal zone
3565 critical and hot trip points.
3567 thermal.off= [HW,ACPI]
3568 1: disable ACPI thermal control
3570 thermal.psv= [HW,ACPI]
3571 -1: disable all passive trip points
3572 <degrees C>: override all passive trip points to this
3575 thermal.tzp= [HW,ACPI]
3576 Specify global default ACPI thermal zone polling rate
3577 <deci-seconds>: poll all this frequency
3578 0: no polling (default)
3581 Force threading of all interrupt handlers except those
3582 marked explicitly IRQF_NO_THREAD.
3585 Enable the Transcendent memory driver if built-in.
3587 tmem.cleancache=0|1 [KNL, XEN]
3588 Default is on (1). Disable the usage of the cleancache
3589 API to send anonymous pages to the hypervisor.
3591 tmem.frontswap=0|1 [KNL, XEN]
3592 Default is on (1). Disable the usage of the frontswap
3593 API to send swap pages to the hypervisor. If disabled
3594 the selfballooning and selfshrinking are force disabled.
3596 tmem.selfballooning=0|1 [KNL, XEN]
3597 Default is on (1). Disable the driving of swap pages
3600 tmem.selfshrinking=0|1 [KNL, XEN]
3601 Default is on (1). Partial swapoff that immediately
3602 transfers pages from Xen hypervisor back to the
3603 kernel based on different criteria.
3607 Specify if the kernel should make use of the cpu
3608 topology information if the hardware supports this.
3609 The scheduler will make use of this information and
3610 e.g. base its process migration decisions on it.
3613 topology_updates= [KNL, PPC, NUMA]
3615 Specify if the kernel should ignore (off)
3616 topology updates sent by the hypervisor to this
3621 tpm_suspend_pcr=[HW,TPM]
3622 Format: integer pcr id
3623 Specify that at suspend time, the tpm driver
3624 should extend the specified pcr with zeros,
3625 as a workaround for some chips which fail to
3626 flush the last written pcr on TPM_SaveState.
3627 This will guarantee that all the other pcrs
3630 trace_buf_size=nn[KMG]
3631 [FTRACE] will set tracing buffer size on each cpu.
3633 trace_event=[event-list]
3634 [FTRACE] Set and start specified trace events in order
3635 to facilitate early boot debugging.
3636 See also Documentation/trace/events.txt
3638 trace_options=[option-list]
3639 [FTRACE] Enable or disable tracer options at boot.
3640 The option-list is a comma delimited list of options
3641 that can be enabled or disabled just as if you were
3642 to echo the option name into
3644 /sys/kernel/debug/tracing/trace_options
3646 For example, to enable stacktrace option (to dump the
3647 stack trace of each event), add to the command line:
3649 trace_options=stacktrace
3651 See also Documentation/trace/ftrace.txt "trace options"
3655 Have the tracepoints sent to printk as well as the
3656 tracing ring buffer. This is useful for early boot up
3657 where the system hangs or reboots and does not give the
3658 option for reading the tracing buffer or performing a
3659 ftrace_dump_on_oops.
3661 To turn off having tracepoints sent to printk,
3662 echo 0 > /proc/sys/kernel/tracepoint_printk
3663 Note, echoing 1 into this file without the
3664 tracepoint_printk kernel cmdline option has no effect.
3668 Having tracepoints sent to printk() and activating high
3669 frequency tracepoints such as irq or sched, can cause
3670 the system to live lock.
3673 [FTRACE] enable this option to disable tracing when a
3674 warning is hit. This turns off "tracing_on". Tracing can
3675 be enabled again by echoing '1' into the "tracing_on"
3676 file located in /sys/kernel/debug/tracing/
3678 This option is useful, as it disables the trace before
3679 the WARNING dump is called, which prevents the trace to
3680 be filled with content caused by the warning output.
3682 This option can also be set at run time via the sysctl
3683 option: kernel/traceoff_on_warning
3685 transparent_hugepage=
3687 Format: [always|madvise|never]
3688 Can be used to control the default behavior of the system
3689 with respect to transparent hugepages.
3690 See Documentation/vm/transhuge.txt for more details.
3692 tsc= Disable clocksource stability checks for TSC.
3694 [x86] reliable: mark tsc clocksource as reliable, this
3695 disables clocksource verification at runtime, as well
3696 as the stability checks done at bootup. Used to enable
3697 high-resolution timer mode on older hardware, and in
3698 virtualized environment.
3699 [x86] noirqtime: Do not use TSC to do irq accounting.
3700 Used to run time disable IRQ_TIME_ACCOUNTING on any
3701 platforms where RDTSC is slow and this accounting
3704 turbografx.map[2|3]= [HW,JOY]
3705 TurboGraFX parallel port interface
3707 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3708 See also Documentation/input/joystick-parport.txt
3710 udbg-immortal [PPC] When debugging early kernel crashes that
3711 happen after console_init() and before a proper
3712 console driver takes over, this boot options might
3713 help "seeing" what's going on.
3715 uhash_entries= [KNL,NET]
3716 Set number of hash buckets for UDP/UDP-Lite connections
3719 [USB] Ignore overcurrent events (default N).
3720 Some badly-designed motherboards generate lots of
3721 bogus events, for ports that aren't wired to
3722 anything. Set this parameter to avoid log spamming.
3723 Note that genuine overcurrent events won't be
3727 [X86] Cause panic on unknown NMI.
3729 usbcore.authorized_default=
3730 [USB] Default USB device authorization:
3731 (default -1 = authorized except for wireless USB,
3732 0 = not authorized, 1 = authorized)
3734 usbcore.autosuspend=
3735 [USB] The autosuspend time delay (in seconds) used
3736 for newly-detected USB devices (default 2). This
3737 is the time required before an idle device will be
3738 autosuspended. Devices for which the delay is set
3739 to a negative value won't be autosuspended at all.
3741 usbcore.usbfs_snoop=
3742 [USB] Set to log all usbfs traffic (default 0 = off).
3744 usbcore.blinkenlights=
3745 [USB] Set to cycle leds on hubs (default 0 = off).
3747 usbcore.old_scheme_first=
3748 [USB] Start with the old device initialization
3749 scheme (default 0 = off).
3751 usbcore.usbfs_memory_mb=
3752 [USB] Memory limit (in MB) for buffers allocated by
3753 usbfs (default = 16, 0 = max = 2047).
3755 usbcore.use_both_schemes=
3756 [USB] Try the other device initialization scheme
3757 if the first one fails (default 1 = enabled).
3759 usbcore.initial_descriptor_timeout=
3760 [USB] Specifies timeout for the initial 64-byte
3761 USB_REQ_GET_DESCRIPTOR request in milliseconds
3762 (default 5000 = 5.0 seconds).
3765 [USBHID] The interval which mice are to be polled at.
3767 usb-storage.delay_use=
3768 [UMS] The delay in seconds before a new device is
3769 scanned for Logical Units (default 1).
3772 [UMS] A list of quirks entries to supplement or
3773 override the built-in unusual_devs list. List
3774 entries are separated by commas. Each entry has
3775 the form VID:PID:Flags where VID and PID are Vendor
3776 and Product ID values (4-digit hex numbers) and
3777 Flags is a set of characters, each corresponding
3778 to a common usb-storage quirk flag as follows:
3779 a = SANE_SENSE (collect more than 18 bytes
3781 b = BAD_SENSE (don't collect more than 18
3782 bytes of sense data);
3783 c = FIX_CAPACITY (decrease the reported
3784 device capacity by one sector);
3785 d = NO_READ_DISC_INFO (don't use
3786 READ_DISC_INFO command);
3787 e = NO_READ_CAPACITY_16 (don't use
3788 READ_CAPACITY_16 command);
3789 f = NO_REPORT_OPCODES (don't use report opcodes
3791 g = MAX_SECTORS_240 (don't transfer more than
3792 240 sectors at a time, uas only);
3793 h = CAPACITY_HEURISTICS (decrease the
3794 reported device capacity by one
3795 sector if the number is odd);
3796 i = IGNORE_DEVICE (don't bind to this
3798 l = NOT_LOCKABLE (don't try to lock and
3799 unlock ejectable media);
3800 m = MAX_SECTORS_64 (don't transfer more
3801 than 64 sectors = 32 KB at a time);
3802 n = INITIAL_READ10 (force a retry of the
3803 initial READ(10) command);
3804 o = CAPACITY_OK (accept the capacity
3805 reported by the device);
3806 p = WRITE_CACHE (the device cache is ON
3808 r = IGNORE_RESIDUE (the device reports
3809 bogus residue values);
3810 s = SINGLE_LUN (the device has only one
3812 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3813 commands, uas only);
3814 u = IGNORE_UAS (don't bind to the uas driver);
3815 w = NO_WP_DETECT (don't test whether the
3816 medium is write-protected).
3817 Example: quirks=0419:aaf5:rl,0421:0433:rc
3819 user_debug= [KNL,ARM]
3821 See arch/arm/Kconfig.debug help text.
3822 1 - undefined instruction events
3824 4 - invalid data aborts
3827 Example: user_debug=31
3830 [X86] Flags controlling user PTE allocations.
3832 nohigh = do not allocate PTE pages in
3833 HIGHMEM regardless of setting
3837 On X86_32, this is an alias for vdso32=. Otherwise:
3839 vdso=1: enable VDSO (the default)
3840 vdso=0: disable VDSO mapping
3842 vdso32= [X86] Control the 32-bit vDSO
3843 vdso32=1: enable 32-bit VDSO
3844 vdso32=0 or vdso32=2: disable 32-bit VDSO
3846 See the help text for CONFIG_COMPAT_VDSO for more
3847 details. If CONFIG_COMPAT_VDSO is set, the default is
3848 vdso32=0; otherwise, the default is vdso32=1.
3850 For compatibility with older kernels, vdso32=2 is an
3853 Try vdso32=0 if you encounter an error that says:
3854 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3857 vector=percpu: enable percpu vector domain
3859 video= [FB] Frame buffer configuration
3860 See Documentation/fb/modedb.txt.
3862 video.brightness_switch_enabled= [0,1]
3863 If set to 1, on receiving an ACPI notify event
3864 generated by hotkey, video driver will adjust brightness
3865 level and then send out the event to user space through
3866 the allocated input device; If set to 0, video driver
3867 will only send out the event without touching backlight
3872 [VMMIO] Memory mapped virtio (platform) device.
3874 <size>@<baseaddr>:<irq>[:<id>]
3876 <size> := size (can use standard suffixes
3878 <baseaddr> := physical base address
3879 <irq> := interrupt number (as passed to
3881 <id> := (optional) platform device id
3883 virtio_mmio.device=1K@0x100b0000:48:7
3885 Can be used multiple times for multiple devices.
3887 vga= [BOOT,X86-32] Select a particular video mode
3888 See Documentation/x86/boot.txt and
3889 Documentation/svga.txt.
3890 Use vga=ask for menu.
3891 This is actually a boot loader parameter; the value is
3892 passed to the kernel using a special protocol.
3894 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3895 size of <nn>. This can be used to increase the
3896 minimum size (128MB on x86). It can also be used to
3897 decrease the size and leave more room for directly
3900 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3903 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3906 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3910 Controls the behavior of vsyscalls (i.e. calls to
3911 fixed addresses of 0xffffffffff600x00 from legacy
3912 code). Most statically-linked binaries and older
3913 versions of glibc use these calls. Because these
3914 functions are at fixed addresses, they make nice
3915 targets for exploits that can control RIP.
3917 emulate [default] Vsyscalls turn into traps and are
3918 emulated reasonably safely.
3920 native Vsyscalls are native syscall instructions.
3921 This is a little bit faster than trapping
3922 and makes a few dynamic recompilers work
3923 better than they would in emulation mode.
3924 It also makes exploits much easier to write.
3926 none Vsyscalls don't work at all. This makes
3927 them quite hard to use for exploits but
3928 might break your system.
3930 vt.color= [VT] Default text color.
3931 Format: 0xYX, X = foreground, Y = background.
3932 Default: 0x07 = light gray on black.
3934 vt.cur_default= [VT] Default cursor shape.
3935 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3936 the parameters of the <Esc>[?A;B;Cc escape sequence;
3937 see VGA-softcursor.txt. Default: 2 = underline.
3939 vt.default_blu= [VT]
3940 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3941 Change the default blue palette of the console.
3942 This is a 16-member array composed of values
3945 vt.default_grn= [VT]
3946 Format: <green0>,<green1>,<green2>,...,<green15>
3947 Change the default green palette of the console.
3948 This is a 16-member array composed of values
3951 vt.default_red= [VT]
3952 Format: <red0>,<red1>,<red2>,...,<red15>
3953 Change the default red palette of the console.
3954 This is a 16-member array composed of values
3960 Set system-wide default UTF-8 mode for all tty's.
3961 Default is 1, i.e. UTF-8 mode is enabled for all
3962 newly opened terminals.
3964 vt.global_cursor_default=
3967 Set system-wide default for whether a cursor
3968 is shown on new VTs. Default is -1,
3969 i.e. cursors will be created by default unless
3970 overridden by individual drivers. 0 will hide
3971 cursors, 1 will display them.
3973 vt.italic= [VT] Default color for italic text; 0-15.
3976 vt.underline= [VT] Default color for underlined text; 0-15.
3979 watchdog timers [HW,WDT] For information on watchdog timers,
3980 see Documentation/watchdog/watchdog-parameters.txt
3981 or other driver-specific files in the
3982 Documentation/watchdog/ directory.
3984 workqueue.disable_numa
3985 By default, all work items queued to unbound
3986 workqueues are affine to the NUMA nodes they're
3987 issued on, which results in better behavior in
3988 general. If NUMA affinity needs to be disabled for
3989 whatever reason, this option can be used. Note
3990 that this also can be controlled per-workqueue for
3991 workqueues visible under /sys/bus/workqueue/.
3993 workqueue.power_efficient
3994 Per-cpu workqueues are generally preferred because
3995 they show better performance thanks to cache
3996 locality; unfortunately, per-cpu workqueues tend to
3997 be more power hungry than unbound workqueues.
3999 Enabling this makes the per-cpu workqueues which
4000 were observed to contribute significantly to power
4001 consumption unbound, leading to measurably lower
4002 power usage at the cost of small performance
4005 The default value of this parameter is determined by
4006 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4008 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4009 default x2apic cluster mode on platforms
4012 x86_intel_mid_timer= [X86-32,APBT]
4013 Choose timer option for x86 Intel MID platform.
4014 Two valid options are apbt timer only and lapic timer
4015 plus one apbt timer for broadcast timer.
4016 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4018 xen_emul_unplug= [HW,X86,XEN]
4019 Unplug Xen emulated devices
4020 Format: [unplug0,][unplug1]
4021 ide-disks -- unplug primary master IDE devices
4022 aux-ide-disks -- unplug non-primary-master IDE devices
4023 nics -- unplug network devices
4024 all -- unplug all emulated devices (NICs and IDE disks)
4025 unnecessary -- unplugging emulated devices is
4026 unnecessary even if the host did not respond to
4028 never -- do not unplug even if version check succeeds
4030 xen_nopvspin [X86,XEN]
4031 Disables the ticketlock slowpath using Xen PV
4035 Disables the PV optimizations forcing the HVM guest to
4036 run as generic HVM guest with no PV drivers.
4038 xirc2ps_cs= [NET,PCMCIA]
4040 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4042 ______________________________________________________________________
4046 Add more DRM drivers.
projects / karo-tx-linux.git / blob