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.
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
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
833 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
834 parameter enables the feature at boot time. In
835 default, it is disabled. We can avoid allocating huge
836 chunk of memory for debug pagealloc if we don't enable
837 it at boot time and the system will work mostly same
838 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
839 on: enable the feature
841 debugpat [X86] Enable PAT debugging
843 decnet.addr= [HW,NET]
844 Format: <area>[,<node>]
845 See also Documentation/networking/decnet.txt.
848 [same as hugepagesz=] The size of the default
849 HugeTLB page size. This is the size represented by
850 the legacy /proc/ hugepages APIs, used for SHM, and
851 default size when mounting hugetlbfs filesystems.
852 Defaults to the default architecture's huge page size
856 Set number of hash buckets for dentry cache.
859 See Documentation/networking/ipv6.txt.
861 disable_cpu_apicid= [X86,APIC,SMP]
863 The number of initial APIC ID for the
864 corresponding CPU to be disabled at boot,
865 mostly used for the kdump 2nd kernel to
866 disable BSP to wake up multiple CPUs without
867 causing system reset or hang due to sending
870 disable_ddw [PPC/PSERIES]
871 Disable Dynamic DMA Window support. Use this if
872 to workaround buggy firmware.
875 See Documentation/networking/ipv6.txt.
877 disable_mtrr_cleanup [X86]
878 The kernel tries to adjust MTRR layout from continuous
879 to discrete, to make X server driver able to add WB
880 entry later. This parameter disables that.
882 disable_mtrr_trim [X86, Intel and AMD only]
883 By default the kernel will trim any uncacheable
884 memory out of your available memory pool based on
885 MTRR settings. This parameter disables that behavior,
886 possibly causing your machine to run very slowly.
888 disable_timer_pin_1 [X86]
889 Disable PIN 1 of APIC timer
890 Can be useful to work around chipset bugs.
892 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
893 this option disables the debugging code at boot.
895 dma_debug_entries=<number>
896 This option allows to tune the number of preallocated
897 entries for DMA-API debugging code. One entry is
898 required per DMA-API allocation. Use this if the
899 DMA-API debugging code disables itself because the
900 architectural default is too low.
902 dma_debug_driver=<driver_name>
903 With this option the DMA-API debugging driver
904 filter feature can be enabled at boot time. Just
905 pass the driver to filter for as the parameter.
906 The filter can be disabled or changed to another
907 driver later using sysfs.
909 drm_kms_helper.edid_firmware=[<connector>:]<file>
910 Broken monitors, graphic adapters and KVMs may
911 send no or incorrect EDID data sets. This parameter
912 allows to specify an EDID data set in the
913 /lib/firmware directory that is used instead.
914 Generic built-in EDID data sets are used, if one of
915 edid/1024x768.bin, edid/1280x1024.bin,
916 edid/1680x1050.bin, or edid/1920x1080.bin is given
917 and no file with the same name exists. Details and
918 instructions how to build your own EDID data are
919 available in Documentation/EDID/HOWTO.txt. An EDID
920 data set will only be used for a particular connector,
921 if its name and a colon are prepended to the EDID
926 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
927 module.dyndbg[="val"]
928 Enable debug messages at boot time. See
929 Documentation/dynamic-debug-howto.txt for details.
931 early_ioremap_debug [KNL]
932 Enable debug messages in early_ioremap support. This
933 is useful for tracking down temporary early mappings
934 which are not unmapped.
936 earlycon= [KNL] Output early console device and options.
939 Start an early, polled-mode console on a cadence serial
940 port at the specified address. The cadence serial port
941 must already be setup and configured. Options are not
944 uart[8250],io,<addr>[,options]
945 uart[8250],mmio,<addr>[,options]
946 uart[8250],mmio32,<addr>[,options]
947 Start an early, polled-mode console on the 8250/16550
948 UART at the specified I/O port or MMIO address.
949 MMIO inter-register address stride is either 8-bit
950 (mmio) or 32-bit (mmio32).
951 The options are the same as for ttyS, above.
954 Start an early, polled-mode console on a pl011 serial
955 port at the specified address. The pl011 serial port
956 must already be setup and configured. Options are not
960 Start an early, polled-mode console on an msm serial
961 port at the specified address. The serial port
962 must already be setup and configured. Options are not
966 Start an early, polled-mode console on an msm serial
967 dm port at the specified address. The serial port
968 must already be setup and configured. Options are not
971 smh Use ARM semihosting calls for early console.
979 Use early console provided by serial driver available
980 on Samsung SoCs, requires selecting proper type and
981 a correct base address of the selected UART port. The
982 serial port must already be setup and configured.
983 Options are not yet supported.
985 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
989 earlyprintk=serial[,ttySn[,baudrate]]
990 earlyprintk=serial[,0x...[,baudrate]]
991 earlyprintk=ttySn[,baudrate]
992 earlyprintk=dbgp[debugController#]
994 earlyprintk is useful when the kernel crashes before
995 the normal console is initialized. It is not enabled by
996 default because it has some cosmetic problems.
998 Append ",keep" to not disable it when the real console
1001 Only one of vga, efi, serial, or usb debug port can
1004 Currently only ttyS0 and ttyS1 may be specified by
1005 name. Other I/O ports may be explicitly specified
1006 on some architectures (x86 and arm at least) by
1007 replacing ttySn with an I/O port address, like this:
1008 earlyprintk=serial,0x1008,115200
1009 You can find the port for a given device in
1010 /proc/tty/driver/serial:
1011 2: uart:ST16650V2 port:00001008 irq:18 ...
1013 Interaction with the standard serial driver is not
1016 The VGA and EFI output is eventually overwritten by
1019 The xen output can only be used by Xen PV guests.
1021 edac_report= [HW,EDAC] Control how to report EDAC event
1022 Format: {"on" | "off" | "force"}
1023 on: enable EDAC to report H/W event. May be overridden
1024 by other higher priority error reporting module.
1025 off: disable H/W event reporting through EDAC.
1026 force: enforce the use of EDAC to report H/W event.
1029 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1032 This is designed to be used in conjunction with
1033 the boot argument: earlyprintk=vga
1036 Format: {"off" | "on" | "skip[mbr]"}
1039 Format: { "old_map", "nochunk", "noruntime", "debug" }
1040 old_map [X86-64]: switch to the old ioremap-based EFI
1041 runtime services mapping. 32-bit still uses this one by
1043 nochunk: disable reading files in "chunks" in the EFI
1044 boot stub, as chunking can cause problems with some
1045 firmware implementations.
1046 noruntime : disable EFI runtime services support
1047 debug: enable misc debug output
1049 efi_no_storage_paranoia [EFI; X86]
1050 Using this parameter you can use more than 50% of
1051 your efi variable storage. Use this parameter only if
1052 you are really sure that your UEFI does sane gc and
1053 fulfills the spec otherwise your board may brick.
1055 eisa_irq_edge= [PARISC,HW]
1056 See header of drivers/parisc/eisa.c.
1059 See comment before function elanfreq_setup() in
1060 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1063 Format: {"cfq" | "deadline" | "noop"}
1064 See Documentation/block/cfq-iosched.txt and
1065 Documentation/block/deadline-iosched.txt for details.
1067 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1068 Specifies physical address of start of kernel core
1069 image elf header and optionally the size. Generally
1070 kexec loader will pass this option to capture kernel.
1071 See Documentation/kdump/kdump.txt for details.
1073 enable_mtrr_cleanup [X86]
1074 The kernel tries to adjust MTRR layout from continuous
1075 to discrete, to make X server driver able to add WB
1076 entry later. This parameter enables that.
1078 enable_timer_pin_1 [X86]
1079 Enable PIN 1 of APIC timer
1080 Can be useful to work around chipset bugs
1081 (in particular on some ATI chipsets).
1082 The kernel tries to set a reasonable default.
1084 enforcing [SELINUX] Set initial enforcing status.
1086 See security/selinux/Kconfig help text.
1087 0 -- permissive (log only, no denials).
1088 1 -- enforcing (deny and log).
1090 Value can be changed at runtime via /selinux/enforce.
1093 Disable Error Record Serialization Table (ERST)
1096 ether= [HW,NET] Ethernet cards parameters
1097 This option is obsoleted by the "netdev=" option, which
1098 has equivalent usage. See its documentation for details.
1102 Permit 'security.evm' to be updated regardless of
1103 current integrity status.
1107 fail_make_request=[KNL]
1108 General fault injection mechanism.
1109 Format: <interval>,<probability>,<space>,<times>
1110 See also Documentation/fault-injection/.
1113 See Documentation/blockdev/floppy.txt.
1115 force_pal_cache_flush
1116 [IA-64] Avoid check_sal_cache_flush which may hang on
1117 buggy SAL_CACHE_FLUSH implementations. Using this
1118 parameter will force ia64_sal_cache_flush to call
1119 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1122 Forcefully enable Physical Address Extension (PAE).
1123 Many Pentium M systems disable PAE but may have a
1124 functionally usable PAE implementation.
1125 Warning: use of this parameter will taint the kernel
1126 and may cause unknown problems.
1129 [FTRACE] will set and start the specified tracer
1130 as early as possible in order to facilitate early
1133 ftrace_dump_on_oops[=orig_cpu]
1134 [FTRACE] will dump the trace buffers on oops.
1135 If no parameter is passed, ftrace will dump
1136 buffers of all CPUs, but if you pass orig_cpu, it will
1137 dump only the buffer of the CPU that triggered the
1140 ftrace_filter=[function-list]
1141 [FTRACE] Limit the functions traced by the function
1142 tracer at boot up. function-list is a comma separated
1143 list of functions. This list can be changed at run
1144 time by the set_ftrace_filter file in the debugfs
1147 ftrace_notrace=[function-list]
1148 [FTRACE] Do not trace the functions specified in
1149 function-list. This list can be changed at run time
1150 by the set_ftrace_notrace file in the debugfs
1153 ftrace_graph_filter=[function-list]
1154 [FTRACE] Limit the top level callers functions traced
1155 by the function graph tracer at boot up.
1156 function-list is a comma separated list of functions
1157 that can be changed at run time by the
1158 set_graph_function file in the debugfs tracing directory.
1160 ftrace_graph_notrace=[function-list]
1161 [FTRACE] Do not trace from the functions specified in
1162 function-list. This list is a comma separated list of
1163 functions that can be changed at run time by the
1164 set_graph_notrace file in the debugfs tracing directory.
1167 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1168 support via parallel port (up to 5 devices per port)
1169 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1170 See also Documentation/input/joystick-parport.txt
1174 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1178 gcov_persist= [GCOV] When non-zero (default), profiling data for
1179 kernel modules is saved and remains accessible via
1180 debugfs, even when the module is unloaded/reloaded.
1181 When zero, profiling data is discarded and associated
1182 debugfs files are removed at module unload time.
1184 gpt [EFI] Forces disk with valid GPT signature but
1185 invalid Protective MBR to be treated as GPT. If the
1186 primary GPT is corrupted, it enables the backup/alternate
1187 GPT to be used instead.
1189 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1190 the "Enable 0" bit of the configuration register.
1193 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1194 the "Enable 0" bit of the configuration register.
1197 grcan.select= [HW] Select which physical interface to use.
1200 grcan.txsize= [HW] Sets the size of the tx buffer.
1201 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1203 grcan.rxsize= [HW] Sets the size of the rx buffer.
1204 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1207 hashdist= [KNL,NUMA] Large hashes allocated during boot
1208 are distributed across NUMA nodes. Defaults on
1209 for 64-bit NUMA, off otherwise.
1210 Format: 0 | 1 (for off | on)
1212 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1214 hd= [EIDE] (E)IDE hard drive subsystem geometry
1215 Format: <cyl>,<head>,<sect>
1218 Disable Hardware Error Source Table (HEST) support;
1219 corresponding firmware-first mode error processing
1220 logic will be disabled.
1222 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1223 size of <nn>. This works even on boxes that have no
1224 highmem otherwise. This also works to reduce highmem
1225 size on bigger boxes.
1227 highres= [KNL] Enable/disable high resolution timer mode.
1228 Valid parameters: "on", "off"
1232 See Documentation/isdn/README.HiSax.
1236 hpet= [X86-32,HPET] option to control HPET usage
1237 Format: { enable (default) | disable | force |
1239 disable: disable HPET and use PIT instead
1240 force: allow force enabled of undocumented chips (ICH4,
1242 verbose: show contents of HPET registers during setup
1244 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1245 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1247 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1248 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1249 On x86-64 and powerpc, this option can be specified
1250 multiple times interleaved with hugepages= to reserve
1251 huge pages of different sizes. Valid pages sizes on
1252 x86-64 are 2M (when the CPU supports "pse") and 1G
1253 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1255 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1256 terminal devices. Valid values: 0..8
1257 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1258 If specified, z/VM IUCV HVC accepts connections
1259 from listed z/VM user IDs only.
1261 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1262 hardware thread id mappings.
1263 Format: <cpu>:<hwthread>
1266 Do not unregister boot console at start. This is only
1267 useful for debugging when something happens in the window
1268 between unregistering the boot console and initializing
1271 i2c_bus= [HW] Override the default board specific I2C bus speed
1272 or register an additional I2C bus that is not
1273 registered from board initialization code.
1277 i8042.debug [HW] Toggle i8042 debug mode
1278 i8042.direct [HW] Put keyboard port into non-translated mode
1279 i8042.dumbkbd [HW] Pretend that controller can only read data from
1280 keyboard and cannot control its state
1281 (Don't attempt to blink the leds)
1282 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1283 i8042.nokbd [HW] Don't check/create keyboard port
1284 i8042.noloop [HW] Disable the AUX Loopback command while probing
1286 i8042.nomux [HW] Don't check presence of an active multiplexing
1288 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1290 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1291 i8042.reset [HW] Reset the controller during init and cleanup
1292 i8042.unlock [HW] Unlock (ignore) the keylock
1293 i8042.kbdreset [HW] Reset device connected to KBD port
1297 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1298 indicates that the driver is running on unsupported
1300 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1301 does not match list of supported models.
1303 [HW] Report power status in /proc/i8k
1304 (disabled by default)
1305 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1308 i915.invert_brightness=
1309 [DRM] Invert the sense of the variable that is used to
1310 set the brightness of the panel backlight. Normally a
1311 brightness value of 0 indicates backlight switched off,
1312 and the maximum of the brightness value sets the backlight
1313 to maximum brightness. If this parameter is set to 0
1314 (default) and the machine requires it, or this parameter
1315 is set to 1, a brightness value of 0 sets the backlight
1316 to maximum brightness, and the maximum of the brightness
1317 value switches the backlight off.
1318 -1 -- never invert brightness
1319 0 -- machine default
1320 1 -- force brightness inversion
1323 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1325 ide-core.nodma= [HW] (E)IDE subsystem
1326 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1327 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1328 .cdrom .chs .ignore_cable are additional options
1329 See Documentation/ide/ide.txt.
1331 ide-generic.probe-mask= [HW] (E)IDE subsystem
1333 Probe mask for legacy ISA IDE ports. Depending on
1334 platform up to 6 ports are supported, enabled by
1335 setting corresponding bits in the mask to 1. The
1336 default value is 0x0, which has a special meaning.
1337 On systems that have PCI, it triggers scanning the
1338 PCI bus for the first and the second port, which
1339 are then probed. On systems without PCI the value
1340 of 0x0 enables probing the two first ports as if it
1343 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1344 Claim all unknown PCI IDE storage controllers.
1347 Format: idle=poll, idle=halt, idle=nomwait
1348 Poll forces a polling idle loop that can slightly
1349 improve the performance of waking up a idle CPU, but
1350 will use a lot of power and make the system run hot.
1352 idle=halt: Halt is forced to be used for CPU idle.
1353 In such case C2/C3 won't be used again.
1354 idle=nomwait: Disable mwait for CPU C-states
1356 ignore_loglevel [KNL]
1357 Ignore loglevel setting - this will print /all/
1358 kernel messages to the console. Useful for debugging.
1359 We also add it as printk module parameter, so users
1360 could change it dynamically, usually by
1361 /sys/module/printk/parameters/ignore_loglevel.
1363 ihash_entries= [KNL]
1364 Set number of hash buckets for inode cache.
1366 ima_appraise= [IMA] appraise integrity measurements
1367 Format: { "off" | "enforce" | "fix" | "log" }
1370 ima_appraise_tcb [IMA]
1371 The builtin appraise policy appraises all files
1375 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1379 The list of supported hash algorithms is defined
1380 in crypto/hash_info.h.
1383 Load a policy which meets the needs of the Trusted
1384 Computing Base. This means IMA will measure all
1385 programs exec'd, files mmap'd for exec, and all files
1386 opened for read by uid=0.
1389 Select one of defined IMA measurements template formats.
1390 Formats: { "ima" | "ima-ng" }
1394 [IMA] Define a custom template format.
1395 Format: { "field1|...|fieldN" }
1397 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1398 Format: <min_file_size>
1399 Set the minimal file size for using asynchronous hash.
1400 If left unspecified, ahash usage is disabled.
1402 ahash performance varies for different data sizes on
1403 different crypto accelerators. This option can be used
1404 to achieve the best performance for a particular HW.
1406 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1408 Set hashing buffer size. Default: 4k.
1410 ahash performance varies for different chunk sizes on
1411 different crypto accelerators. This option can be used
1412 to achieve best performance for particular HW.
1416 Run specified binary instead of /sbin/init as init
1419 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1420 for working out where the kernel is dying during
1423 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1424 initcall functions. Useful for debugging built-in
1425 modules and initcalls.
1427 initrd= [BOOT] Specify the location of the initial ramdisk
1429 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1432 int_pln_enable [x86] Enable power limit notification interrupt
1434 integrity_audit=[IMA]
1435 Format: { "0" | "1" }
1436 0 -- basic integrity auditing messages. (Default)
1437 1 -- additional integrity auditing messages.
1439 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1441 Enable intel iommu driver.
1443 Disable intel iommu driver.
1444 igfx_off [Default Off]
1445 By default, gfx is mapped as normal device. If a gfx
1446 device has a dedicated DMAR unit, the DMAR unit is
1447 bypassed by not enabling DMAR with this option. In
1448 this case, gfx device will use physical address for
1451 With this option iommu will not optimize to look
1452 for io virtual address below 32-bit forcing dual
1453 address cycle on pci bus for cards supporting greater
1454 than 32-bit addressing. The default is to look
1455 for translation below 32-bit and if not available
1456 then look in the higher range.
1457 strict [Default Off]
1458 With this option on every unmap_single operation will
1459 result in a hardware IOTLB flush operation as opposed
1460 to batching them for performance.
1461 sp_off [Default Off]
1462 By default, super page will be supported if Intel IOMMU
1463 has the capability. With this option, super page will
1466 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1467 0 disables intel_idle and fall back on acpi_idle.
1468 1 to 6 specify maximum depth of C-state.
1472 Do not enable intel_pstate as the default
1473 scaling driver for the supported processors
1475 Enable intel_pstate on systems that prohibit it by default
1476 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1477 instead of acpi-cpufreq may disable platform features, such
1478 as thermal controls and power capping, that rely on ACPI
1479 P-States information being indicated to OSPM and therefore
1480 should be used with caution. This option does not work with
1481 processors that aren't supported by the intel_pstate driver
1482 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1484 Do not enable hardware P state control (HWP)
1487 Only load intel_pstate on systems which support
1488 hardware P state control (HWP) if available.
1490 intremap= [X86-64, Intel-IOMMU]
1491 on enable Interrupt Remapping (default)
1492 off disable Interrupt Remapping
1493 nosid disable Source ID checking
1495 BIOS x2APIC opt-out request will be ignored
1497 iomem= Disable strict checking of access to MMIO memory
1498 strict regions from userspace.
1513 nobypass [PPC/POWERNV]
1514 Disable IOMMU bypass, using IOMMU for PCI devices.
1517 io7= [HW] IO7 for Marvel based alpha systems
1518 See comment before marvel_specify_io7 in
1519 arch/alpha/kernel/core_marvel.c.
1521 io_delay= [X86] I/O delay method
1523 Standard port 0x80 based delay
1525 Alternate port 0xed based delay (needed on some systems)
1527 Simple two microseconds delay
1532 See Documentation/filesystems/nfs/nfsroot.txt.
1535 When an interrupt is not handled search all handlers
1536 for it. Intended to get systems with badly broken
1540 When an interrupt is not handled search all handlers
1541 for it. Also check all handlers each timer
1542 interrupt. Intended to get systems with badly broken
1546 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1548 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1550 <cpu number>,...,<cpu number>
1552 <cpu number>-<cpu number>
1553 (must be a positive range in ascending order)
1555 <cpu number>,...,<cpu number>-<cpu number>
1557 This option can be used to specify one or more CPUs
1558 to isolate from the general SMP balancing and scheduling
1559 algorithms. You can move a process onto or off an
1560 "isolated" CPU via the CPU affinity syscalls or cpuset.
1561 <cpu number> begins at 0 and the maximum value is
1562 "number of CPUs in system - 1".
1564 This option is the preferred way to isolate CPUs. The
1565 alternative -- manually setting the CPU mask of all
1566 tasks in the system -- can cause problems and
1567 suboptimal load balancer performance.
1571 ivrs_ioapic [HW,X86_64]
1572 Provide an override to the IOAPIC-ID<->DEVICE-ID
1573 mapping provided in the IVRS ACPI table. For
1574 example, to map IOAPIC-ID decimal 10 to
1575 PCI device 00:14.0 write the parameter as:
1576 ivrs_ioapic[10]=00:14.0
1578 ivrs_hpet [HW,X86_64]
1579 Provide an override to the HPET-ID<->DEVICE-ID
1580 mapping provided in the IVRS ACPI table. For
1581 example, to map HPET-ID decimal 0 to
1582 PCI device 00:14.0 write the parameter as:
1583 ivrs_hpet[0]=00:14.0
1585 js= [HW,JOY] Analog joystick
1586 See Documentation/input/joystick.txt.
1589 Enable/disable kernel and module base offset ASLR
1590 (Address Space Layout Randomization) if built into
1591 the kernel. When CONFIG_HIBERNATION is selected,
1592 kASLR is disabled by default. When kASLR is enabled,
1593 hibernation will be disabled.
1597 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1598 specifies the amount of memory usable by the kernel
1599 for non-movable allocations. The requested amount is
1600 spread evenly throughout all nodes in the system. The
1601 remaining memory in each node is used for Movable
1602 pages. In the event, a node is too small to have both
1603 kernelcore and Movable pages, kernelcore pages will
1604 take priority and other nodes will have a larger number
1605 of Movable pages. The Movable zone is used for the
1606 allocation of pages that may be reclaimed or moved
1607 by the page migration subsystem. This means that
1608 HugeTLB pages may not be allocated from this zone.
1609 Note that allocations like PTEs-from-HighMem still
1610 use the HighMem zone if it exists, and the Normal
1611 zone if it does not.
1613 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1614 Format: <Controller#>[,poll interval]
1615 The controller # is the number of the ehci usb debug
1616 port as it is probed via PCI. The poll interval is
1617 optional and is the number seconds in between
1618 each poll cycle to the debug port in case you need
1619 the functionality for interrupting the kernel with
1620 gdb or control-c on the dbgp connection. When
1621 not using this parameter you use sysrq-g to break into
1622 the kernel debugger.
1624 kgdboc= [KGDB,HW] kgdb over consoles.
1625 Requires a tty driver that supports console polling,
1626 or a supported polling keyboard driver (non-usb).
1627 Serial only format: <serial_device>[,baud]
1628 keyboard only format: kbd
1629 keyboard and serial format: kbd,<serial_device>[,baud]
1630 Optional Kernel mode setting:
1631 kms, kbd format: kms,kbd
1632 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1634 kgdbwait [KGDB] Stop kernel execution and enter the
1635 kernel debugger at the earliest opportunity.
1637 kmac= [MIPS] korina ethernet MAC address.
1638 Configure the RouterBoard 532 series on-chip
1639 Ethernet adapter MAC address.
1641 kmemleak= [KNL] Boot-time kmemleak enable/disable
1642 Valid arguments: on, off
1644 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1647 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1648 Valid arguments: 0, 1, 2
1649 kmemcheck=0 (disabled)
1650 kmemcheck=1 (enabled)
1651 kmemcheck=2 (one-shot mode)
1652 Default: 2 (one-shot mode)
1654 kstack=N [X86] Print N words from the kernel stack
1657 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1658 Default is 0 (don't ignore, but inject #GP)
1660 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1664 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1665 Default is 1 (enabled)
1667 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1669 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1671 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1672 (virtualized MMU) support on capable Intel chips.
1673 Default is 1 (enabled)
1675 kvm-intel.emulate_invalid_guest_state=
1676 [KVM,Intel] Enable emulation of invalid guest states
1677 Default is 0 (disabled)
1679 kvm-intel.flexpriority=
1680 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1681 Default is 1 (enabled)
1684 [KVM,Intel] Enable VMX nesting (nVMX).
1685 Default is 0 (disabled)
1687 kvm-intel.unrestricted_guest=
1688 [KVM,Intel] Disable unrestricted guest feature
1689 (virtualized real and unpaged mode) on capable
1690 Intel chips. Default is 1 (enabled)
1692 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1693 feature (tagged TLBs) on capable Intel chips.
1694 Default is 1 (enabled)
1700 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1703 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1704 value for LAPIC timer one-shot implementation. Default
1705 back to the programmable timer unit in the LAPIC.
1707 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1710 libata.dma= [LIBATA] DMA control
1711 libata.dma=0 Disable all PATA and SATA DMA
1712 libata.dma=1 PATA and SATA Disk DMA only
1713 libata.dma=2 ATAPI (CDROM) DMA only
1714 libata.dma=4 Compact Flash DMA only
1715 Combinations also work, so libata.dma=3 enables DMA
1716 for disks and CDROMs, but not CFs.
1718 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1719 libata.ignore_hpa=0 keep BIOS limits (default)
1720 libata.ignore_hpa=1 ignore limits, using full disk
1722 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1726 libata.force= [LIBATA] Force configurations. The format is comma
1727 separated list of "[ID:]VAL" where ID is
1728 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1729 matching port, link or device. Basically, it matches
1730 the ATA ID string printed on console by libata. If
1731 the whole ID part is omitted, the last PORT and DEVICE
1732 values are used. If ID hasn't been specified yet, the
1733 configuration applies to all ports, links and devices.
1735 If only DEVICE is omitted, the parameter applies to
1736 the port and all links and devices behind it. DEVICE
1737 number of 0 either selects the first device or the
1738 first fan-out link behind PMP device. It does not
1739 select the host link. DEVICE number of 15 selects the
1740 host link and device attached to it.
1742 The VAL specifies the configuration to force. As long
1743 as there's no ambiguity shortcut notation is allowed.
1744 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1745 The following configurations can be forced.
1747 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1748 Any ID with matching PORT is used.
1750 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1752 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1753 udma[/][16,25,33,44,66,100,133] notation is also
1756 * [no]ncq: Turn on or off NCQ.
1758 * [no]ncqtrim: Turn off queued DSM TRIM.
1760 * nohrst, nosrst, norst: suppress hard, soft
1763 * rstonce: only attempt one reset during
1764 hot-unplug link recovery
1766 * dump_id: dump IDENTIFY data.
1768 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1770 * disable: Disable this device.
1772 If there are multiple matching configurations changing
1773 the same attribute, the last one is used.
1775 memblock=debug [KNL] Enable memblock debug messages.
1777 load_ramdisk= [RAM] List of ramdisks to load from floppy
1778 See Documentation/blockdev/ramdisk.txt.
1780 lockd.nlm_grace_period=P [NFS] Assign grace period.
1783 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1786 lockd.nlm_timeout=T [NFS] Assign timeout value.
1789 lockd.nlm_udpport=M [NFS] Assign UDP port.
1792 locktorture.nreaders_stress= [KNL]
1793 Set the number of locking read-acquisition kthreads.
1794 Defaults to being automatically set based on the
1795 number of online CPUs.
1797 locktorture.nwriters_stress= [KNL]
1798 Set the number of locking write-acquisition kthreads.
1800 locktorture.onoff_holdoff= [KNL]
1801 Set time (s) after boot for CPU-hotplug testing.
1803 locktorture.onoff_interval= [KNL]
1804 Set time (s) between CPU-hotplug operations, or
1805 zero to disable CPU-hotplug testing.
1807 locktorture.shuffle_interval= [KNL]
1808 Set task-shuffle interval (jiffies). Shuffling
1809 tasks allows some CPUs to go into dyntick-idle
1810 mode during the locktorture test.
1812 locktorture.shutdown_secs= [KNL]
1813 Set time (s) after boot system shutdown. This
1814 is useful for hands-off automated testing.
1816 locktorture.stat_interval= [KNL]
1817 Time (s) between statistics printk()s.
1819 locktorture.stutter= [KNL]
1820 Time (s) to stutter testing, for example,
1821 specifying five seconds causes the test to run for
1822 five seconds, wait for five seconds, and so on.
1823 This tests the locking primitive's ability to
1824 transition abruptly to and from idle.
1826 locktorture.torture_runnable= [BOOT]
1827 Start locktorture running at boot time.
1829 locktorture.torture_type= [KNL]
1830 Specify the locking implementation to test.
1832 locktorture.verbose= [KNL]
1833 Enable additional printk() statements.
1835 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1838 loglevel= All Kernel Messages with a loglevel smaller than the
1839 console loglevel will be printed to the console. It can
1840 also be changed with klogd or other programs. The
1841 loglevels are defined as follows:
1843 0 (KERN_EMERG) system is unusable
1844 1 (KERN_ALERT) action must be taken immediately
1845 2 (KERN_CRIT) critical conditions
1846 3 (KERN_ERR) error conditions
1847 4 (KERN_WARNING) warning conditions
1848 5 (KERN_NOTICE) normal but significant condition
1849 6 (KERN_INFO) informational
1850 7 (KERN_DEBUG) debug-level messages
1852 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1853 in bytes. n must be a power of two and greater
1854 than the minimal size. The minimal size is defined
1855 by LOG_BUF_SHIFT kernel config parameter. There is
1856 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1857 that allows to increase the default size depending on
1858 the number of CPUs. See init/Kconfig for more details.
1860 logo.nologo [FB] Disables display of the built-in Linux logo.
1861 This may be used to provide more screen space for
1862 kernel log messages and is useful when debugging
1863 kernel boot problems.
1865 lp=0 [LP] Specify parallel ports to use, e.g,
1866 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1867 lp=reset first parallel port). 'lp=0' disables the
1868 lp=auto printer driver. 'lp=reset' (which can be
1869 specified in addition to the ports) causes
1870 attached printers to be reset. Using
1871 lp=port1,port2,... specifies the parallel ports
1872 to associate lp devices with, starting with
1873 lp0. A port specification may be 'none' to skip
1874 that lp device, or a parport name such as
1875 'parport0'. Specifying 'lp=auto' instead of a
1876 port specification list means that device IDs
1877 from each port should be examined, to see if
1878 an IEEE 1284-compliant printer is attached; if
1879 so, the driver will manage that printer.
1880 See also header of drivers/char/lp.c.
1883 Sets loops_per_jiffy to given constant, thus avoiding
1884 time-consuming boot-time autodetection (up to 250 ms per
1885 CPU). 0 enables autodetection (default). To determine
1886 the correct value for your kernel, boot with normal
1887 autodetection and see what value is printed. Note that
1888 on SMP systems the preset will be applied to all CPUs,
1889 which is likely to cause problems if your CPUs need
1890 significantly divergent settings. An incorrect value
1891 will cause delays in the kernel to be wrong, leading to
1892 unpredictable I/O errors and other breakage. Although
1893 unlikely, in the extreme case this might damage your
1897 Format: <io>,<irq>,<dma>
1899 machvec= [IA-64] Force the use of a particular machine-vector
1900 (machvec) in a generic kernel.
1901 Example: machvec=hpzx1_swiotlb
1903 machtype= [Loongson] Share the same kernel image file between different
1905 Example: machtype=lemote-yeeloong-2f-7inch
1907 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1908 than or equal to this physical address is ignored.
1910 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1911 should make use of. maxcpus=n : n >= 0 limits the
1912 kernel to using 'n' processors. n=0 is a special case,
1913 it is equivalent to "nosmp", which also disables
1916 max_loop= [LOOP] The number of loop block devices that get
1917 (loop.max_loop) unconditionally pre-created at init time. The default
1918 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1919 of statically allocating a predefined number, loop
1920 devices can be requested on-demand with the
1921 /dev/loop-control interface.
1923 mce [X86-32] Machine Check Exception
1925 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1927 md= [HW] RAID subsystems devices and level
1928 See Documentation/md.txt.
1931 Format: <first>,<last>
1932 Specifies range of consoles to be captured by the MDA.
1934 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1935 Amount of memory to be used when the kernel is not able
1936 to see the whole system memory or for test.
1937 [X86] Work as limiting max address. Use together
1938 with memmap= to avoid physical address space collisions.
1939 Without memmap= PCI devices could be placed at addresses
1940 belonging to unused RAM.
1942 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1946 [KNL,SH] Allow user to override the default size for
1947 per-device physically contiguous DMA buffers.
1949 memmap=exactmap [KNL,X86] Enable setting of an exact
1950 E820 memory map, as specified by the user.
1951 Such memmap=exactmap lines can be constructed based on
1952 BIOS output or other requirements. See the memmap=nn@ss
1955 memmap=nn[KMG]@ss[KMG]
1956 [KNL] Force usage of a specific region of memory.
1957 Region of memory to be used is from ss to ss+nn.
1959 memmap=nn[KMG]#ss[KMG]
1960 [KNL,ACPI] Mark specific memory as ACPI data.
1961 Region of memory to be marked is from ss to ss+nn.
1963 memmap=nn[KMG]$ss[KMG]
1964 [KNL,ACPI] Mark specific memory as reserved.
1965 Region of memory to be reserved is from ss to ss+nn.
1966 Example: Exclude memory from 0x18690000-0x1869ffff
1967 memmap=64K$0x18690000
1969 memmap=0x10000$0x18690000
1971 memory_corruption_check=0/1 [X86]
1972 Some BIOSes seem to corrupt the first 64k of
1973 memory when doing things like suspend/resume.
1974 Setting this option will scan the memory
1975 looking for corruption. Enabling this will
1976 both detect corruption and prevent the kernel
1977 from using the memory being corrupted.
1978 However, its intended as a diagnostic tool; if
1979 repeatable BIOS-originated corruption always
1980 affects the same memory, you can use memmap=
1981 to prevent the kernel from using that memory.
1983 memory_corruption_check_size=size [X86]
1984 By default it checks for corruption in the low
1985 64k, making this memory unavailable for normal
1986 use. Use this parameter to scan for
1987 corruption in more or less memory.
1989 memory_corruption_check_period=seconds [X86]
1990 By default it checks for corruption every 60
1991 seconds. Use this parameter to check at some
1992 other rate. 0 disables periodic checking.
1994 memtest= [KNL,X86] Enable memtest
1996 default : 0 <disable>
1997 Specifies the number of memtest passes to be
1998 performed. Each pass selects another test
1999 pattern from a given set of patterns. Memtest
2000 fills the memory with this pattern, validates
2001 memory contents and reserves bad memory
2002 regions that are detected.
2004 meye.*= [HW] Set MotionEye Camera parameters
2005 See Documentation/video4linux/meye.txt.
2007 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2008 Multi-Function General Purpose Timers on AMD Geode
2011 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2012 the BIOS has incorrectly applied a workaround. TinyBIOS
2013 version 0.98 is known to be affected, 0.99 fixes the
2014 problem by letting the user disable the workaround.
2018 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2019 physical address is ignored.
2021 mini2440= [ARM,HW,KNL]
2022 Format:[0..2][b][c][t]
2024 MINI2440 configuration specification:
2025 0 - The attached screen is the 3.5" TFT
2026 1 - The attached screen is the 7" TFT
2027 2 - The VGA Shield is attached (1024x768)
2028 Leaving out the screen size parameter will not load
2029 the TFT driver, and the framebuffer will be left
2031 b - Enable backlight. The TFT backlight pin will be
2032 linked to the kernel VESA blanking code and a GPIO
2033 LED. This parameter is not necessary when using the
2035 c - Enable the s3c camera interface.
2036 t - Reserved for enabling touchscreen support. The
2037 touchscreen support is not enabled in the mainstream
2038 kernel as of 2.6.30, a preliminary port can be found
2039 in the "bleeding edge" mini2440 support kernel at
2040 http://repo.or.cz/w/linux-2.6/mini2440.git
2043 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2044 parameter allows control of the logging verbosity for
2045 the additional memory initialisation checks. A value
2046 of 0 disables mminit logging and a level of 4 will
2047 log everything. Information is printed at KERN_DEBUG
2048 so loglevel=8 may also need to be specified.
2051 [KNL] When CONFIG_MODULE_SIG is set, this means that
2052 modules without (valid) signatures will fail to load.
2053 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2054 is always true, so this option does nothing.
2057 [MOUSE] Maximum time between finger touching and
2058 leaving touchpad surface for touch to be considered
2059 a tap and be reported as a left button click (for
2060 touchpads working in absolute mode only).
2062 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2063 reporting absolute coordinates, such as tablets
2064 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2065 reporting absolute coordinates, such as tablets
2067 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2068 is similar to kernelcore except it specifies the
2069 amount of memory used for migratable allocations.
2070 If both kernelcore and movablecore is specified,
2071 then kernelcore will be at *least* the specified
2072 value but may be more. If movablecore on its own
2073 is specified, the administrator must be careful
2074 that the amount of memory usable for all allocations
2077 movable_node [KNL,X86] Boot-time switch to enable the effects
2078 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2080 MTD_Partition= [MTD]
2081 Format: <name>,<region-number>,<size>,<offset>
2083 MTD_Region= [MTD] Format:
2084 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2087 See drivers/mtd/cmdlinepart.c.
2089 multitce=off [PPC] This parameter disables the use of the pSeries
2090 firmware feature for updating multiple TCE entries
2093 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2095 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2097 boundary - index of last SLC block on Flex-OneNAND.
2098 The remaining blocks are configured as MLC blocks.
2099 lock - Configure if Flex-OneNAND boundary should be locked.
2100 Once locked, the boundary cannot be changed.
2101 1 indicates lock status, 0 indicates unlock status.
2104 ARM/S3C2412 JIVE boot control
2106 See arch/arm/mach-s3c2412/mach-jive.c
2108 mtouchusb.raw_coordinates=
2109 [HW] Make the MicroTouch USB driver use raw coordinates
2110 ('y', default) or cooked coordinates ('n')
2112 mtrr_chunk_size=nn[KMG] [X86]
2113 used for mtrr cleanup. It is largest continuous chunk
2114 that could hold holes aka. UC entries.
2116 mtrr_gran_size=nn[KMG] [X86]
2117 Used for mtrr cleanup. It is granularity of mtrr block.
2119 Large value could prevent small alignment from
2122 mtrr_spare_reg_nr=n [X86]
2124 Range: 0,7 : spare reg number
2126 Used for mtrr cleanup. It is spare mtrr entries number.
2127 Set to 2 or more if your graphical card needs more.
2129 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2131 netdev= [NET] Network devices parameters
2132 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2133 Note that mem_start is often overloaded to mean
2134 something different and driver-specific.
2135 This usage is only documented in each driver source
2139 [NETFILTER] Enable connection tracking flow accounting
2140 0 to disable accounting
2141 1 to enable accounting
2144 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2145 See Documentation/filesystems/nfs/nfsroot.txt.
2147 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2148 See Documentation/filesystems/nfs/nfsroot.txt.
2150 nfsrootdebug [NFS] enable nfsroot debugging messages.
2151 See Documentation/filesystems/nfs/nfsroot.txt.
2153 nfs.callback_tcpport=
2154 [NFS] set the TCP port on which the NFSv4 callback
2155 channel should listen.
2158 [NFS] sets the pathname to the program which is used
2159 to update the NFS client cache entries.
2161 nfs.cache_getent_timeout=
2162 [NFS] sets the timeout after which an attempt to
2163 update a cache entry is deemed to have failed.
2165 nfs.idmap_cache_timeout=
2166 [NFS] set the maximum lifetime for idmapper cache
2170 [NFS] enable 64-bit inode numbers.
2171 If zero, the NFS client will fake up a 32-bit inode
2172 number for the readdir() and stat() syscalls instead
2173 of returning the full 64-bit number.
2174 The default is to return 64-bit inode numbers.
2176 nfs.max_session_slots=
2177 [NFSv4.1] Sets the maximum number of session slots
2178 the client will attempt to negotiate with the server.
2179 This limits the number of simultaneous RPC requests
2180 that the client can send to the NFSv4.1 server.
2181 Note that there is little point in setting this
2182 value higher than the max_tcp_slot_table_limit.
2184 nfs.nfs4_disable_idmapping=
2185 [NFSv4] When set to the default of '1', this option
2186 ensures that both the RPC level authentication
2187 scheme and the NFS level operations agree to use
2188 numeric uids/gids if the mount is using the
2189 'sec=sys' security flavour. In effect it is
2190 disabling idmapping, which can make migration from
2191 legacy NFSv2/v3 systems to NFSv4 easier.
2192 Servers that do not support this mode of operation
2193 will be autodetected by the client, and it will fall
2194 back to using the idmapper.
2195 To turn off this behaviour, set the value to '0'.
2197 [NFS4] Specify an additional fixed unique ident-
2198 ification string that NFSv4 clients can insert into
2199 their nfs_client_id4 string. This is typically a
2200 UUID that is generated at system install time.
2202 nfs.send_implementation_id =
2203 [NFSv4.1] Send client implementation identification
2204 information in exchange_id requests.
2205 If zero, no implementation identification information
2207 The default is to send the implementation identification
2210 nfs.recover_lost_locks =
2211 [NFSv4] Attempt to recover locks that were lost due
2212 to a lease timeout on the server. Please note that
2213 doing this risks data corruption, since there are
2214 no guarantees that the file will remain unchanged
2215 after the locks are lost.
2216 If you want to enable the kernel legacy behaviour of
2217 attempting to recover these locks, then set this
2219 The default parameter value of '0' causes the kernel
2220 not to attempt recovery of lost locks.
2222 nfsd.nfs4_disable_idmapping=
2223 [NFSv4] When set to the default of '1', the NFSv4
2224 server will return only numeric uids and gids to
2225 clients using auth_sys, and will accept numeric uids
2226 and gids from such clients. This is intended to ease
2227 migration from NFSv2/v3.
2229 objlayoutdriver.osd_login_prog=
2230 [NFS] [OBJLAYOUT] sets the pathname to the program which
2231 is used to automatically discover and login into new
2232 osd-targets. Please see:
2233 Documentation/filesystems/pnfs.txt for more explanations
2235 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2236 when a NMI is triggered.
2237 Format: [state][,regs][,debounce][,die]
2239 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2240 Format: [panic,][nopanic,][num]
2242 0 - turn nmi_watchdog off
2243 When panic is specified, panic when an NMI watchdog
2244 timeout occurs (or 'nopanic' to override the opposite
2246 This is useful when you use a panic=... timeout and
2247 need the box quickly up again.
2249 netpoll.carrier_timeout=
2250 [NET] Specifies amount of time (in seconds) that
2251 netpoll should wait for a carrier. By default netpoll
2254 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2255 emulation library even if a 387 maths coprocessor
2259 [HW] Never suspend the console
2260 Disable suspending of consoles during suspend and
2261 hibernate operations. Once disabled, debugging
2262 messages can reach various consoles while the rest
2263 of the system is being put to sleep (ie, while
2264 debugging driver suspend/resume hooks). This may
2265 not work reliably with all consoles, but is known
2266 to work with serial and VGA consoles.
2267 To facilitate more flexible debugging, we also add
2268 console_suspend, a printk module parameter to control
2269 it. Users could use console_suspend (usually
2270 /sys/module/printk/parameters/console_suspend) to
2271 turn on/off it dynamically.
2273 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2274 caches in the slab allocator. Saves per-node memory,
2275 but will impact performance.
2279 noapic [SMP,APIC] Tells the kernel to not make use of any
2280 IOAPICs that may be present in the system.
2282 noautogroup Disable scheduler automatic task group creation.
2284 nobats [PPC] Do not use BATs for mapping kernel lowmem
2285 on "Classic" PPC cores.
2289 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2291 nodelayacct [KNL] Disable per-task delay accounting
2293 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2295 nodsp [SH] Disable hardware DSP at boot time.
2297 noefi Disable EFI runtime services support.
2302 On X86-32 available only on PAE configured kernels.
2303 noexec=on: enable non-executable mappings (default)
2304 noexec=off: disable non-executable mappings
2307 Disable SMAP (Supervisor Mode Access Prevention)
2308 even if it is supported by processor.
2311 Disable SMEP (Supervisor Mode Execution Prevention)
2312 even if it is supported by processor.
2315 This affects only 32-bit executables.
2316 noexec32=on: enable non-executable mappings (default)
2317 read doesn't imply executable mappings
2318 noexec32=off: disable non-executable mappings
2319 read implies executable mappings
2321 nofpu [SH] Disable hardware FPU at boot time.
2323 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2324 register save and restore. The kernel will only save
2325 legacy floating-point registers on task switch.
2327 noxsave [BUGS=X86] Disables x86 extended register state save
2328 and restore using xsave. The kernel will fallback to
2329 enabling legacy floating-point and sse state.
2331 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2332 register states. The kernel will fall back to use
2333 xsave to save the states. By using this parameter,
2334 performance of saving the states is degraded because
2335 xsave doesn't support modified optimization while
2336 xsaveopt supports it on xsaveopt enabled systems.
2338 noxsaves [X86] Disables xsaves and xrstors used in saving and
2339 restoring x86 extended register state in compacted
2340 form of xsave area. The kernel will fall back to use
2341 xsaveopt and xrstor to save and restore the states
2342 in standard form of xsave area. By using this
2343 parameter, xsave area per process might occupy more
2344 memory on xsaves enabled systems.
2347 on enable eager fpu restore
2348 off disable eager fpu restore
2349 auto selects the default scheme, which automatically
2350 enables eagerfpu restore for xsaveopt.
2352 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2353 wfi(ARM) instruction doesn't work correctly and not to
2354 use it. This is also useful when using JTAG debugger.
2356 no_file_caps Tells the kernel not to honor file capabilities. The
2357 only way then for a file to be executed with privilege
2358 is to be setuid root or executed by root.
2360 nohalt [IA-64] Tells the kernel not to use the power saving
2361 function PAL_HALT_LIGHT when idle. This increases
2362 power-consumption. On the positive side, it reduces
2363 interrupt wake-up latency, which may improve performance
2364 in certain environments such as networked servers or
2367 nohibernate [HIBERNATION] Disable hibernation and resume.
2369 nohz= [KNL] Boottime enable/disable dynamic ticks
2370 Valid arguments: on, off
2373 nohz_full= [KNL,BOOT]
2374 In kernels built with CONFIG_NO_HZ_FULL=y, set
2375 the specified list of CPUs whose tick will be stopped
2376 whenever possible. The boot CPU will be forced outside
2377 the range to maintain the timekeeping.
2378 The CPUs in this range must also be included in the
2381 noiotrap [SH] Disables trapped I/O port accesses.
2383 noirqdebug [X86-32] Disables the code which attempts to detect and
2384 disable unhandled interrupt sources.
2386 no_timer_check [X86,APIC] Disables the code which tests for
2387 broken timer IRQ sources.
2389 noisapnp [ISAPNP] Disables ISA PnP code.
2391 noinitrd [RAM] Tells the kernel not to load any configured
2394 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2396 [Deprecated - use intremap=off]
2400 nojitter [IA-64] Disables jitter checking for ITC timers.
2402 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2404 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2407 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2408 steal time is computed, but won't influence scheduler
2411 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2413 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2415 noltlbs [PPC] Do not use large page/tlb entries for kernel
2416 lowmem mapping on PPC40x.
2418 nomca [IA-64] Disable machine check abort handling
2420 nomce [X86-32] Machine Check Exception
2422 nomfgpt [X86-32] Disable Multi-Function General Purpose
2423 Timer usage (for AMD Geode machines).
2425 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2426 shutdown the other cpus. Instead use the REBOOT_VECTOR
2429 nomodule Disable module load
2431 nopat [X86] Disable PAT (page attribute table extension of
2432 pagetables) support.
2434 norandmaps Don't use address space randomization. Equivalent to
2435 echo 0 > /proc/sys/kernel/randomize_va_space
2437 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2439 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2440 with UP alternatives
2442 nordrand [X86] Disable kernel use of the RDRAND and
2443 RDSEED instructions even if they are supported
2444 by the processor. RDRAND and RDSEED are still
2445 available to user space applications.
2447 noresume [SWSUSP] Disables resume and restores original swap
2450 no-scroll [VGA] Disables scrollback.
2451 This is required for the Braillex ib80-piezo Braille
2452 reader made by F.H. Papenmeier (Germany).
2456 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2458 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2459 and disable the IO APIC. legacy for "maxcpus=0".
2461 nosoftlockup [KNL] Disable the soft-lockup detector.
2463 nosync [HW,M68K] Disables sync negotiation for all devices.
2465 notsc [BUGS=X86-32] Disable Time Stamp Counter
2467 nousb [USB] Disable the USB subsystem
2469 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2473 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2475 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2476 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2477 Some features depend on CPU0. Known dependencies are:
2478 1. Resume from suspend/hibernate depends on CPU0.
2479 Suspend/hibernate will fail if CPU0 is offline and you
2480 need to online CPU0 before suspend/hibernate.
2481 2. PIC interrupts also depend on CPU0. CPU0 can't be
2482 removed if a PIC interrupt is detected.
2483 It's said poweroff/reboot may depend on CPU0 on some
2484 machines although I haven't seen such issues so far
2485 after CPU0 is offline on a few tested machines.
2486 If the dependencies are under your control, you can
2487 turn on cpu0_hotplug.
2489 nptcg= [IA-64] Override max number of concurrent global TLB
2490 purges which is reported from either PAL_VM_SUMMARY or
2493 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2494 could support. nr_cpus=n : n >= 1 limits the kernel to
2495 supporting 'n' processors. Later in runtime you can not
2496 use hotplug cpu feature to put more cpu back to online.
2497 just like you compile the kernel NR_CPUS=n
2499 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2501 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2502 Allowed values are enable and disable
2504 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2505 one of ['zone', 'node', 'default'] can be specified
2506 This can be set from sysctl after boot.
2507 See Documentation/sysctl/vm.txt for details.
2509 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2510 See Documentation/debugging-via-ohci1394.txt for more
2513 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2514 Rather than timing out after 20 ms if an EC
2515 command is not properly ACKed, override the length
2516 of the timeout. We have interrupts disabled while
2517 waiting for the ACK, so if this is set too high
2518 interrupts *may* be lost!
2520 omap_mux= [OMAP] Override bootloader pin multiplexing.
2521 Format: <mux_mode0.mode_name=value>...
2522 For example, to override I2C bus2:
2523 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2525 oprofile.timer= [HW]
2526 Use timer interrupt instead of performance counters
2528 oprofile.cpu_type= Force an oprofile cpu type
2529 This might be useful if you have an older oprofile
2530 userland or if you want common events.
2531 Format: { arch_perfmon }
2532 arch_perfmon: [X86] Force use of architectural
2533 perfmon on Intel CPUs instead of the
2534 CPU specific event set.
2535 timer: [X86] Force use of architectural NMI
2536 timer mode (see also oprofile.timer
2537 for generic hr timer mode)
2538 [s390] Force legacy basic mode sampling
2539 (report cpu_type "timer")
2541 oops=panic Always panic on oopses. Default is to just kill the
2542 process, but there is a small probability of
2543 deadlocking the machine.
2544 This will also cause panics on machine check exceptions.
2545 Useful together with panic=30 to trigger a reboot.
2548 See Documentation/sound/oss/oss-parameters.txt
2550 page_owner= [KNL] Boot-time page_owner enabling option.
2551 Storage of the information about who allocated
2552 each page is disabled in default. With this switch,
2554 on: enable the feature
2556 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2557 timeout > 0: seconds before rebooting
2558 timeout = 0: wait forever
2559 timeout < 0: reboot immediately
2562 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2565 crash_kexec_post_notifiers
2566 Run kdump after running panic-notifiers and dumping
2567 kmsg. This only for the users who doubt kdump always
2568 succeeds in any situation.
2569 Note that this also increases risks of kdump failure,
2570 because some panic notifiers can make the crashed
2571 kernel more unstable.
2573 parkbd.port= [HW] Parallel port number the keyboard adapter is
2574 connected to, default is 0.
2576 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2577 0 for XT, 1 for AT (default is AT).
2580 parport= [HW,PPT] Specify parallel ports. 0 disables.
2581 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2582 Use 'auto' to force the driver to use any
2583 IRQ/DMA settings detected (the default is to
2584 ignore detected IRQ/DMA settings because of
2585 possible conflicts). You can specify the base
2586 address, IRQ, and DMA settings; IRQ and DMA
2587 should be numbers, or 'auto' (for using detected
2588 settings on that particular port), or 'nofifo'
2589 (to avoid using a FIFO even if it is detected).
2590 Parallel ports are assigned in the order they
2591 are specified on the command line, starting
2594 parport_init_mode= [HW,PPT]
2595 Configure VIA parallel port to operate in
2596 a specific mode. This is necessary on Pegasos
2597 computer where firmware has no options for setting
2598 up parallel port mode and sets it to spp.
2599 Currently this function knows 686a and 8231 chips.
2600 Format: [spp|ps2|epp|ecp|ecpepp]
2603 Halt all CPUs after the first oops has been printed for
2604 the specified number of seconds. This is to be used if
2605 your oopses keep scrolling off the screen.
2610 See header of drivers/block/paride/pcd.c.
2611 See also Documentation/blockdev/paride.txt.
2613 pci=option[,option...] [PCI] various PCI subsystem options:
2614 earlydump [X86] dump PCI config space before the kernel
2616 off [X86] don't probe for the PCI bus
2617 bios [X86-32] force use of PCI BIOS, don't access
2618 the hardware directly. Use this if your machine
2619 has a non-standard PCI host bridge.
2620 nobios [X86-32] disallow use of PCI BIOS, only direct
2621 hardware access methods are allowed. Use this
2622 if you experience crashes upon bootup and you
2623 suspect they are caused by the BIOS.
2624 conf1 [X86] Force use of PCI Configuration
2626 conf2 [X86] Force use of PCI Configuration
2628 noaer [PCIE] If the PCIEAER kernel config parameter is
2629 enabled, this kernel boot option can be used to
2630 disable the use of PCIE advanced error reporting.
2631 nodomains [PCI] Disable support for multiple PCI
2632 root domains (aka PCI segments, in ACPI-speak).
2633 nommconf [X86] Disable use of MMCONFIG for PCI
2635 check_enable_amd_mmconf [X86] check for and enable
2636 properly configured MMIO access to PCI
2637 config space on AMD family 10h CPU
2638 nomsi [MSI] If the PCI_MSI kernel config parameter is
2639 enabled, this kernel boot option can be used to
2640 disable the use of MSI interrupts system-wide.
2641 noioapicquirk [APIC] Disable all boot interrupt quirks.
2642 Safety option to keep boot IRQs enabled. This
2643 should never be necessary.
2644 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2645 primary IO-APIC for bridges that cannot disable
2646 boot IRQs. This fixes a source of spurious IRQs
2647 when the system masks IRQs.
2648 noioapicreroute [APIC] Disable workaround that uses the
2649 boot IRQ equivalent of an IRQ that connects to
2650 a chipset where boot IRQs cannot be disabled.
2651 The opposite of ioapicreroute.
2652 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2653 routing table. These calls are known to be buggy
2654 on several machines and they hang the machine
2655 when used, but on other computers it's the only
2656 way to get the interrupt routing table. Try
2657 this option if the kernel is unable to allocate
2658 IRQs or discover secondary PCI buses on your
2660 rom [X86] Assign address space to expansion ROMs.
2661 Use with caution as certain devices share
2662 address decoders between ROMs and other
2664 norom [X86] Do not assign address space to
2665 expansion ROMs that do not already have
2666 BIOS assigned address ranges.
2667 nobar [X86] Do not assign address space to the
2668 BARs that weren't assigned by the BIOS.
2669 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2670 assigned automatically to PCI devices. You can
2671 make the kernel exclude IRQs of your ISA cards
2673 pirqaddr=0xAAAAA [X86] Specify the physical address
2674 of the PIRQ table (normally generated
2675 by the BIOS) if it is outside the
2676 F0000h-100000h range.
2677 lastbus=N [X86] Scan all buses thru bus #N. Can be
2678 useful if the kernel is unable to find your
2679 secondary buses and you want to tell it
2680 explicitly which ones they are.
2681 assign-busses [X86] Always assign all PCI bus
2682 numbers ourselves, overriding
2683 whatever the firmware may have done.
2684 usepirqmask [X86] Honor the possible IRQ mask stored
2685 in the BIOS $PIR table. This is needed on
2686 some systems with broken BIOSes, notably
2687 some HP Pavilion N5400 and Omnibook XE3
2688 notebooks. This will have no effect if ACPI
2689 IRQ routing is enabled.
2690 noacpi [X86] Do not use ACPI for IRQ routing
2691 or for PCI scanning.
2692 use_crs [X86] Use PCI host bridge window information
2693 from ACPI. On BIOSes from 2008 or later, this
2694 is enabled by default. If you need to use this,
2695 please report a bug.
2696 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2697 If you need to use this, please report a bug.
2698 routeirq Do IRQ routing for all PCI devices.
2699 This is normally done in pci_enable_device(),
2700 so this option is a temporary workaround
2701 for broken drivers that don't call it.
2702 skip_isa_align [X86] do not align io start addr, so can
2703 handle more pci cards
2704 firmware [ARM] Do not re-enumerate the bus but instead
2705 just use the configuration from the
2706 bootloader. This is currently used on
2707 IXP2000 systems where the bus has to be
2708 configured a certain way for adjunct CPUs.
2709 noearly [X86] Don't do any early type 1 scanning.
2710 This might help on some broken boards which
2711 machine check when some devices' config space
2712 is read. But various workarounds are disabled
2713 and some IOMMU drivers will not work.
2714 bfsort Sort PCI devices into breadth-first order.
2715 This sorting is done to get a device
2716 order compatible with older (<= 2.4) kernels.
2717 nobfsort Don't sort PCI devices into breadth-first order.
2718 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2719 tuning and use the BIOS-configured MPS defaults.
2720 pcie_bus_safe Set every device's MPS to the largest value
2721 supported by all devices below the root complex.
2722 pcie_bus_perf Set device MPS to the largest allowable MPS
2723 based on its parent bus. Also set MRRS (Max
2724 Read Request Size) to the largest supported
2725 value (no larger than the MPS that the device
2726 or bus can support) for best performance.
2727 pcie_bus_peer2peer Set every device's MPS to 128B, which
2728 every device is guaranteed to support. This
2729 configuration allows peer-to-peer DMA between
2730 any pair of devices, possibly at the cost of
2731 reduced performance. This also guarantees
2732 that hot-added devices will work.
2733 cbiosize=nn[KMG] The fixed amount of bus space which is
2734 reserved for the CardBus bridge's IO window.
2735 The default value is 256 bytes.
2736 cbmemsize=nn[KMG] The fixed amount of bus space which is
2737 reserved for the CardBus bridge's memory
2738 window. The default value is 64 megabytes.
2741 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2742 Specifies alignment and device to reassign
2743 aligned memory resources.
2744 If <order of align> is not specified,
2745 PAGE_SIZE is used as alignment.
2746 PCI-PCI bridge can be specified, if resource
2747 windows need to be expanded.
2748 ecrc= Enable/disable PCIe ECRC (transaction layer
2749 end-to-end CRC checking).
2750 bios: Use BIOS/firmware settings. This is the
2754 hpiosize=nn[KMG] The fixed amount of bus space which is
2755 reserved for hotplug bridge's IO window.
2756 Default size is 256 bytes.
2757 hpmemsize=nn[KMG] The fixed amount of bus space which is
2758 reserved for hotplug bridge's memory window.
2759 Default size is 2 megabytes.
2760 realloc= Enable/disable reallocating PCI bridge resources
2761 if allocations done by BIOS are too small to
2762 accommodate resources required by all child
2764 off: Turn realloc off
2766 realloc same as realloc=on
2767 noari do not use PCIe ARI.
2768 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2769 only look for one device below a PCIe downstream
2772 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2775 force Enable ASPM even on devices that claim not to support it.
2776 WARNING: Forcing ASPM on may cause system lockups.
2778 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2779 nomsi Do not use MSI for PCI Express Native Hotplug (this
2780 makes all PCIe ports use INTx for hotplug services).
2782 pcie_ports= [PCIE] PCIe ports handling:
2783 auto Ask the BIOS whether or not to use native PCIe services
2784 associated with PCIe ports (PME, hot-plug, AER). Use
2785 them only if that is allowed by the BIOS.
2786 native Use native PCIe services associated with PCIe ports
2788 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2791 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2792 nomsi Do not use MSI for native PCIe PME signaling (this makes
2793 all PCIe root ports use INTx for all services).
2795 pcmv= [HW,PCMCIA] BadgePAD 4
2799 Keep all power-domains already enabled by bootloader on,
2800 even if no driver has claimed them. This is useful
2801 for debug and development, but should not be
2802 needed on a platform with proper driver support.
2805 See Documentation/blockdev/paride.txt.
2807 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2810 See arch/parisc/kernel/pdc_chassis.c
2812 percpu_alloc= Select which percpu first chunk allocator to use.
2813 Currently supported values are "embed" and "page".
2814 Archs may support subset or none of the selections.
2815 See comments in mm/percpu.c for details on each
2816 allocator. This parameter is primarily for debugging
2817 and performance comparison.
2820 See Documentation/blockdev/paride.txt.
2823 See Documentation/blockdev/paride.txt.
2825 pirq= [SMP,APIC] Manual mp-table setup
2826 See Documentation/x86/i386/IO-APIC.txt.
2828 plip= [PPT,NET] Parallel port network link
2829 Format: { parport<nr> | timid | 0 }
2830 See also Documentation/parport.txt.
2832 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2833 Override pmtimer IOPort with a hex value.
2837 Enable PNP debug messages (depends on the
2838 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2839 via /sys/module/pnp/parameters/debug. We always show
2840 current resource usage; turning this on also shows
2841 possible settings and some assignment information.
2847 { on | off | curr | res | no-curr | no-res }
2850 [ISAPNP] Exclude IRQs for the autoconfiguration
2853 [ISAPNP] Exclude DMAs for the autoconfiguration
2855 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2856 Ranges are in pairs (I/O port base and size).
2859 [ISAPNP] Exclude memory regions for the
2861 Ranges are in pairs (memory base and size).
2863 ports= [IP_VS_FTP] IPVS ftp helper module
2865 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2867 Format: <port>,<port>....
2869 print-fatal-signals=
2870 [KNL] debug: print fatal signals
2872 If enabled, warn about various signal handling
2873 related application anomalies: too many signals,
2874 too many POSIX.1 timers, fatal signals causing a
2877 If you hit the warning due to signal overflow,
2878 you might want to try "ulimit -i unlimited".
2882 printk.always_kmsg_dump=
2883 Trigger kmsg_dump for cases other than kernel oops or
2885 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2888 printk.time= Show timing data prefixed to each printk message line
2889 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2891 processor.max_cstate= [HW,ACPI]
2892 Limit processor to maximum C-state
2893 max_cstate=9 overrides any DMI blacklist limit.
2895 processor.nocst [HW,ACPI]
2896 Ignore the _CST method to determine C-states,
2897 instead using the legacy FADT method
2899 profile= [KNL] Enable kernel profiling via /proc/profile
2900 Format: [schedule,]<number>
2901 Param: "schedule" - profile schedule points.
2902 Param: <number> - step/bucket size as a power of 2 for
2903 statistical time based profiling.
2904 Param: "sleep" - profile D-state sleeping (millisecs).
2905 Requires CONFIG_SCHEDSTATS
2906 Param: "kvm" - profile VM exits.
2908 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2910 See Documentation/blockdev/ramdisk.txt.
2912 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2913 probe for; one of (bare|imps|exps|lifebook|any).
2914 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2916 psmouse.resetafter= [HW,MOUSE]
2917 Try to reset the device after so many bad packets
2920 [HW,MOUSE] Set desired mouse resolution, in dpi.
2921 psmouse.smartscroll=
2922 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2923 0 = disabled, 1 = enabled (default).
2925 pstore.backend= Specify the name of the pstore backend to use
2928 See Documentation/blockdev/paride.txt.
2931 [KNL] Number of legacy pty's. Overwrites compiled-in
2934 quiet [KNL] Disable most log messages
2939 See Documentation/md.txt.
2941 ramdisk_blocksize= [RAM]
2942 See Documentation/blockdev/ramdisk.txt.
2944 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2945 See Documentation/blockdev/ramdisk.txt.
2948 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2949 the specified list of CPUs to be no-callback CPUs.
2950 Invocation of these CPUs' RCU callbacks will
2951 be offloaded to "rcuox/N" kthreads created for
2952 that purpose, where "x" is "b" for RCU-bh, "p"
2953 for RCU-preempt, and "s" for RCU-sched, and "N"
2954 is the CPU number. This reduces OS jitter on the
2955 offloaded CPUs, which can be useful for HPC and
2956 real-time workloads. It can also improve energy
2957 efficiency for asymmetric multiprocessors.
2960 Rather than requiring that offloaded CPUs
2961 (specified by rcu_nocbs= above) explicitly
2962 awaken the corresponding "rcuoN" kthreads,
2963 make these kthreads poll for callbacks.
2964 This improves the real-time response for the
2965 offloaded CPUs by relieving them of the need to
2966 wake up the corresponding kthread, but degrades
2967 energy efficiency by requiring that the kthreads
2968 periodically wake up to do the polling.
2970 rcutree.blimit= [KNL]
2971 Set maximum number of finished RCU callbacks to
2972 process in one batch.
2974 rcutree.rcu_fanout_leaf= [KNL]
2975 Increase the number of CPUs assigned to each
2976 leaf rcu_node structure. Useful for very large
2979 rcutree.jiffies_till_sched_qs= [KNL]
2980 Set required age in jiffies for a
2981 given grace period before RCU starts
2982 soliciting quiescent-state help from
2983 rcu_note_context_switch().
2985 rcutree.jiffies_till_first_fqs= [KNL]
2986 Set delay from grace-period initialization to
2987 first attempt to force quiescent states.
2988 Units are jiffies, minimum value is zero,
2989 and maximum value is HZ.
2991 rcutree.jiffies_till_next_fqs= [KNL]
2992 Set delay between subsequent attempts to force
2993 quiescent states. Units are jiffies, minimum
2994 value is one, and maximum value is HZ.
2996 rcutree.kthread_prio= [KNL,BOOT]
2997 Set the SCHED_FIFO priority of the RCU
2998 per-CPU kthreads (rcuc/N). This value is also
2999 used for the priority of the RCU boost threads
3000 (rcub/N). Valid values are 1-99 and the default
3001 is 1 (the least-favored priority).
3003 rcutree.rcu_nocb_leader_stride= [KNL]
3004 Set the number of NOCB kthread groups, which
3005 defaults to the square root of the number of
3006 CPUs. Larger numbers reduces the wakeup overhead
3007 on the per-CPU grace-period kthreads, but increases
3008 that same overhead on each group's leader.
3010 rcutree.qhimark= [KNL]
3011 Set threshold of queued RCU callbacks beyond which
3012 batch limiting is disabled.
3014 rcutree.qlowmark= [KNL]
3015 Set threshold of queued RCU callbacks below which
3016 batch limiting is re-enabled.
3018 rcutree.rcu_idle_gp_delay= [KNL]
3019 Set wakeup interval for idle CPUs that have
3020 RCU callbacks (RCU_FAST_NO_HZ=y).
3022 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3023 Set wakeup interval for idle CPUs that have
3024 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3025 Lazy RCU callbacks are those which RCU can
3026 prove do nothing more than free memory.
3028 rcutorture.cbflood_inter_holdoff= [KNL]
3029 Set holdoff time (jiffies) between successive
3030 callback-flood tests.
3032 rcutorture.cbflood_intra_holdoff= [KNL]
3033 Set holdoff time (jiffies) between successive
3034 bursts of callbacks within a given callback-flood
3037 rcutorture.cbflood_n_burst= [KNL]
3038 Set the number of bursts making up a given
3039 callback-flood test. Set this to zero to
3040 disable callback-flood testing.
3042 rcutorture.cbflood_n_per_burst= [KNL]
3043 Set the number of callbacks to be registered
3044 in a given burst of a callback-flood test.
3046 rcutorture.fqs_duration= [KNL]
3047 Set duration of force_quiescent_state bursts.
3049 rcutorture.fqs_holdoff= [KNL]
3050 Set holdoff time within force_quiescent_state bursts.
3052 rcutorture.fqs_stutter= [KNL]
3053 Set wait time between force_quiescent_state bursts.
3055 rcutorture.gp_exp= [KNL]
3056 Use expedited update-side primitives.
3058 rcutorture.gp_normal= [KNL]
3059 Use normal (non-expedited) update-side primitives.
3060 If both gp_exp and gp_normal are set, do both.
3061 If neither gp_exp nor gp_normal are set, still
3064 rcutorture.n_barrier_cbs= [KNL]
3065 Set callbacks/threads for rcu_barrier() testing.
3067 rcutorture.nfakewriters= [KNL]
3068 Set number of concurrent RCU writers. These just
3069 stress RCU, they don't participate in the actual
3070 test, hence the "fake".
3072 rcutorture.nreaders= [KNL]
3073 Set number of RCU readers.
3075 rcutorture.object_debug= [KNL]
3076 Enable debug-object double-call_rcu() testing.
3078 rcutorture.onoff_holdoff= [KNL]
3079 Set time (s) after boot for CPU-hotplug testing.
3081 rcutorture.onoff_interval= [KNL]
3082 Set time (s) between CPU-hotplug operations, or
3083 zero to disable CPU-hotplug testing.
3085 rcutorture.torture_runnable= [BOOT]
3086 Start rcutorture running at boot time.
3088 rcutorture.shuffle_interval= [KNL]
3089 Set task-shuffle interval (s). Shuffling tasks
3090 allows some CPUs to go into dyntick-idle mode
3091 during the rcutorture test.
3093 rcutorture.shutdown_secs= [KNL]
3094 Set time (s) after boot system shutdown. This
3095 is useful for hands-off automated testing.
3097 rcutorture.stall_cpu= [KNL]
3098 Duration of CPU stall (s) to test RCU CPU stall
3099 warnings, zero to disable.
3101 rcutorture.stall_cpu_holdoff= [KNL]
3102 Time to wait (s) after boot before inducing stall.
3104 rcutorture.stat_interval= [KNL]
3105 Time (s) between statistics printk()s.
3107 rcutorture.stutter= [KNL]
3108 Time (s) to stutter testing, for example, specifying
3109 five seconds causes the test to run for five seconds,
3110 wait for five seconds, and so on. This tests RCU's
3111 ability to transition abruptly to and from idle.
3113 rcutorture.test_boost= [KNL]
3114 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3115 "Maybe" means test if the RCU implementation
3116 under test support RCU priority boosting.
3118 rcutorture.test_boost_duration= [KNL]
3119 Duration (s) of each individual boost test.
3121 rcutorture.test_boost_interval= [KNL]
3122 Interval (s) between each boost test.
3124 rcutorture.test_no_idle_hz= [KNL]
3125 Test RCU's dyntick-idle handling. See also the
3126 rcutorture.shuffle_interval parameter.
3128 rcutorture.torture_type= [KNL]
3129 Specify the RCU implementation to test.
3131 rcutorture.verbose= [KNL]
3132 Enable additional printk() statements.
3134 rcupdate.rcu_expedited= [KNL]
3135 Use expedited grace-period primitives, for
3136 example, synchronize_rcu_expedited() instead
3137 of synchronize_rcu(). This reduces latency,
3138 but can increase CPU utilization, degrade
3139 real-time latency, and degrade energy efficiency.
3141 rcupdate.rcu_cpu_stall_suppress= [KNL]
3142 Suppress RCU CPU stall warning messages.
3144 rcupdate.rcu_cpu_stall_timeout= [KNL]
3145 Set timeout for RCU CPU stall warning messages.
3147 rcupdate.rcu_task_stall_timeout= [KNL]
3148 Set timeout in jiffies for RCU task stall warning
3149 messages. Disable with a value less than or equal
3152 rcupdate.rcu_self_test= [KNL]
3153 Run the RCU early boot self tests
3155 rcupdate.rcu_self_test_bh= [KNL]
3156 Run the RCU bh early boot self tests
3158 rcupdate.rcu_self_test_sched= [KNL]
3159 Run the RCU sched early boot self tests
3163 Run specified binary instead of /init from the ramdisk,
3164 used for early userspace startup. See initrd.
3167 Format (x86 or x86_64):
3168 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3170 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3172 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3173 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3174 reboot_force is either force or not specified,
3175 reboot_cpu is s[mp]#### with #### being the processor
3176 to be used for rebooting.
3179 [KNL, SMP] Set scheduler's default relax_domain_level.
3180 See Documentation/cgroups/cpusets.txt.
3182 relative_sleep_states=
3183 [SUSPEND] Use sleep state labeling where the deepest
3184 state available other than hibernation is always "mem".
3185 Format: { "0" | "1" }
3186 0 -- Traditional sleep state labels.
3187 1 -- Relative sleep state labels.
3189 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3191 reservetop= [X86-32]
3193 Reserves a hole at the top of the kernel virtual
3198 Set the amount of memory to reserve for BIOS at
3199 the bottom of the address space.
3201 reset_devices [KNL] Force drivers to reset the underlying device
3202 during initialization.
3205 Specify the partition device for software suspend
3207 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3209 resume_offset= [SWSUSP]
3210 Specify the offset from the beginning of the partition
3211 given by "resume=" at which the swap header is located,
3212 in <PAGE_SIZE> units (needed only for swap files).
3213 See Documentation/power/swsusp-and-swap-files.txt
3215 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3216 read the resume files
3218 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3219 Useful for devices that are detected asynchronously
3220 (e.g. USB and MMC devices).
3222 hibernate= [HIBERNATION]
3223 noresume Don't check if there's a hibernation image
3224 present during boot.
3225 nocompress Don't compress/decompress hibernation images.
3226 no Disable hibernation and resume.
3228 retain_initrd [RAM] Keep initrd memory after extraction
3230 rfkill.default_state=
3231 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3232 etc. communication is blocked by default.
3235 rfkill.master_switch_mode=
3236 0 The "airplane mode" button does nothing.
3237 1 The "airplane mode" button toggles between everything
3238 blocked and the previous configuration.
3239 2 The "airplane mode" button toggles between everything
3240 blocked and everything unblocked.
3242 rhash_entries= [KNL,NET]
3243 Set number of hash buckets for route cache
3245 ro [KNL] Mount root device read-only on boot
3247 root= [KNL] Root filesystem
3248 See name_to_dev_t comment in init/do_mounts.c.
3250 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3251 mount the root filesystem
3253 rootflags= [KNL] Set root filesystem mount option string
3255 rootfstype= [KNL] Set root filesystem type
3257 rootwait [KNL] Wait (indefinitely) for root device to show up.
3258 Useful for devices that are detected asynchronously
3259 (e.g. USB and MMC devices).
3261 rproc_mem=nn[KMG][@address]
3262 [KNL,ARM,CMA] Remoteproc physical memory block.
3263 Memory area to be used by remote processor image,
3266 rw [KNL] Mount root device read-write on boot
3268 S [KNL] Run init in single mode
3270 s390_iommu= [HW,S390]
3271 Set s390 IOTLB flushing mode
3273 With strict flushing every unmap operation will result in
3274 an IOTLB flush. Default is lazy flushing before reuse,
3278 See drivers/net/irda/sa1100_ir.c.
3280 sbni= [NET] Granch SBNI12 leased line adapter
3282 sched_debug [KNL] Enables verbose scheduler debug messages.
3284 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3285 xtime_lock contention on larger systems, and/or RCU lock
3286 contention on all systems with CONFIG_MAXSMP set.
3287 Format: { "0" | "1" }
3288 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3290 Note: increases power consumption, thus should only be
3291 enabled if running jitter sensitive (HPC/RT) workloads.
3293 security= [SECURITY] Choose a security module to enable at boot.
3294 If this boot parameter is not specified, only the first
3295 security module asking for security registration will be
3296 loaded. An invalid security module name will be treated
3297 as if no module has been chosen.
3299 selinux= [SELINUX] Disable or enable SELinux at boot time.
3300 Format: { "0" | "1" }
3301 See security/selinux/Kconfig help text.
3304 Default value is set via kernel config option.
3305 If enabled at boot time, /selinux/disable can be used
3306 later to disable prior to initial policy load.
3308 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3309 Format: { "0" | "1" }
3310 See security/apparmor/Kconfig help text
3313 Default value is set via kernel config option.
3315 serialnumber [BUGS=X86-32]
3318 Maximal number of shapers.
3320 show_msr= [x86] show boot-time MSR settings
3321 Format: { <integer> }
3322 Show boot-time (BIOS-initialized) MSR settings.
3323 The parameter means the number of CPUs to show,
3324 for example 1 means boot CPU only.
3332 Disable merging of slabs with similar size. May be
3333 necessary if there is some reason to distinguish
3334 allocs to different slabs. Debug options disable
3335 merging on their own.
3336 For more information see Documentation/vm/slub.txt.
3338 slab_max_order= [MM, SLAB]
3339 Determines the maximum allowed order for slabs.
3340 A high setting may cause OOMs due to memory
3341 fragmentation. Defaults to 1 for systems with
3342 more than 32MB of RAM, 0 otherwise.
3344 slub_debug[=options[,slabs]] [MM, SLUB]
3345 Enabling slub_debug allows one to determine the
3346 culprit if slab objects become corrupted. Enabling
3347 slub_debug can create guard zones around objects and
3348 may poison objects when not in use. Also tracks the
3349 last alloc / free. For more information see
3350 Documentation/vm/slub.txt.
3352 slub_max_order= [MM, SLUB]
3353 Determines the maximum allowed order for slabs.
3354 A high setting may cause OOMs due to memory
3355 fragmentation. For more information see
3356 Documentation/vm/slub.txt.
3358 slub_min_objects= [MM, SLUB]
3359 The minimum number of objects per slab. SLUB will
3360 increase the slab order up to slub_max_order to
3361 generate a sufficiently large slab able to contain
3362 the number of objects indicated. The higher the number
3363 of objects the smaller the overhead of tracking slabs
3364 and the less frequently locks need to be acquired.
3365 For more information see Documentation/vm/slub.txt.
3367 slub_min_order= [MM, SLUB]
3368 Determines the minimum page order for slabs. Must be
3369 lower than slub_max_order.
3370 For more information see Documentation/vm/slub.txt.
3372 slub_nomerge [MM, SLUB]
3373 Same with slab_nomerge. This is supported for legacy.
3374 See slab_nomerge for more information.
3377 Format: <io1>[,<io2>[,...,<io8>]]
3379 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3380 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3381 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3382 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3383 smsc-ircc2.ircc_irq= [HW] IRQ line
3384 smsc-ircc2.ircc_dma= [HW] DMA channel
3385 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3386 0: Toshiba Satellite 1800 (GP data pin select)
3387 1: Fast pin select (default)
3391 [KNL] Should the soft-lockup detector generate panics.
3394 softlockup_all_cpu_backtrace=
3395 [KNL] Should the soft-lockup detector generate
3396 backtraces on all cpus.
3399 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3400 See Documentation/laptops/sonypi.txt
3402 spia_io_base= [HW,MTD]
3408 Enabled the stack tracer on boot up.
3410 stacktrace_filter=[function-list]
3411 [FTRACE] Limit the functions that the stack tracer
3412 will trace at boot up. function-list is a comma separated
3413 list of functions. This list can be changed at run
3414 time by the stack_trace_filter file in the debugfs
3415 tracing directory. Note, this enables stack tracing
3416 and the stacktrace above is not needed.
3420 Set the STI (builtin display/keyboard on the HP-PARISC
3421 machines) console (graphic card) which should be used
3422 as the initial boot-console.
3423 See also comment in drivers/video/console/sticore.c.
3426 See comment in drivers/video/console/sticore.c.
3429 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3431 sunrpc.min_resvport=
3432 sunrpc.max_resvport=
3434 SunRPC servers often require that client requests
3435 originate from a privileged port (i.e. a port in the
3436 range 0 < portnr < 1024).
3437 An administrator who wishes to reserve some of these
3438 ports for other uses may adjust the range that the
3439 kernel's sunrpc client considers to be privileged
3440 using these two parameters to set the minimum and
3441 maximum port values.
3445 Control how the NFS server code allocates CPUs to
3446 service thread pools. Depending on how many NICs
3447 you have and where their interrupts are bound, this
3448 option will affect which CPUs will do NFS serving.
3449 Note: this parameter cannot be changed while the
3450 NFS server is running.
3452 auto the server chooses an appropriate mode
3453 automatically using heuristics
3454 global a single global pool contains all CPUs
3455 percpu one pool for each CPU
3456 pernode one pool for each NUMA node (equivalent
3457 to global on non-NUMA machines)
3459 sunrpc.tcp_slot_table_entries=
3460 sunrpc.udp_slot_table_entries=
3462 Sets the upper limit on the number of simultaneous
3463 RPC calls that can be sent from the client to a
3464 server. Increasing these values may allow you to
3465 improve throughput, but will also increase the
3466 amount of memory reserved for use by the client.
3469 [KNL] Enable accounting of swap in memory resource
3470 controller if no parameter or 1 is given or disable
3471 it if 0 is given (See Documentation/cgroups/memory.txt)
3473 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3474 Format: { <int> | force }
3475 <int> -- Number of I/O TLB slabs
3476 force -- force using of bounce buffers even if they
3477 wouldn't be automatically used by the kernel
3481 sysfs.deprecated=0|1 [KNL]
3482 Enable/disable old style sysfs layout for old udev
3483 on older distributions. When this option is enabled
3484 very new udev will not work anymore. When this option
3485 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3486 in older udev will not work anymore.
3487 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3488 the kernel configuration.
3490 sysrq_always_enabled
3492 Ignore sysrq setting - this boot parameter will
3493 neutralize any effect of /proc/sys/kernel/sysrq.
3494 Useful for debugging.
3496 tcpmhash_entries= [KNL,NET]
3497 Set the number of tcp_metrics_hash slots.
3498 Default value is 8192 or 16384 depending on total
3499 ram pages. This is used to specify the TCP metrics
3500 cache size. See Documentation/networking/ip-sysctl.txt
3501 "tcp_no_metrics_save" section for more details.
3505 test_suspend= [SUSPEND][,N]
3506 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3507 standby suspend) or "freeze" (for suspend type freeze)
3508 as the system sleep state during system startup with
3509 the optional capability to repeat N number of times.
3510 The system is woken from this state using a
3511 wakeup-capable RTC alarm.
3513 thash_entries= [KNL,NET]
3514 Set number of hash buckets for TCP connection
3516 thermal.act= [HW,ACPI]
3517 -1: disable all active trip points in all thermal zones
3518 <degrees C>: override all lowest active trip points
3520 thermal.crt= [HW,ACPI]
3521 -1: disable all critical trip points in all thermal zones
3522 <degrees C>: override all critical trip points
3524 thermal.nocrt= [HW,ACPI]
3525 Set to disable actions on ACPI thermal zone
3526 critical and hot trip points.
3528 thermal.off= [HW,ACPI]
3529 1: disable ACPI thermal control
3531 thermal.psv= [HW,ACPI]
3532 -1: disable all passive trip points
3533 <degrees C>: override all passive trip points to this
3536 thermal.tzp= [HW,ACPI]
3537 Specify global default ACPI thermal zone polling rate
3538 <deci-seconds>: poll all this frequency
3539 0: no polling (default)
3542 Force threading of all interrupt handlers except those
3543 marked explicitly IRQF_NO_THREAD.
3546 Enable the Transcendent memory driver if built-in.
3548 tmem.cleancache=0|1 [KNL, XEN]
3549 Default is on (1). Disable the usage of the cleancache
3550 API to send anonymous pages to the hypervisor.
3552 tmem.frontswap=0|1 [KNL, XEN]
3553 Default is on (1). Disable the usage of the frontswap
3554 API to send swap pages to the hypervisor. If disabled
3555 the selfballooning and selfshrinking are force disabled.
3557 tmem.selfballooning=0|1 [KNL, XEN]
3558 Default is on (1). Disable the driving of swap pages
3561 tmem.selfshrinking=0|1 [KNL, XEN]
3562 Default is on (1). Partial swapoff that immediately
3563 transfers pages from Xen hypervisor back to the
3564 kernel based on different criteria.
3568 Specify if the kernel should make use of the cpu
3569 topology information if the hardware supports this.
3570 The scheduler will make use of this information and
3571 e.g. base its process migration decisions on it.
3574 topology_updates= [KNL, PPC, NUMA]
3576 Specify if the kernel should ignore (off)
3577 topology updates sent by the hypervisor to this
3582 tpm_suspend_pcr=[HW,TPM]
3583 Format: integer pcr id
3584 Specify that at suspend time, the tpm driver
3585 should extend the specified pcr with zeros,
3586 as a workaround for some chips which fail to
3587 flush the last written pcr on TPM_SaveState.
3588 This will guarantee that all the other pcrs
3591 trace_buf_size=nn[KMG]
3592 [FTRACE] will set tracing buffer size on each cpu.
3594 trace_event=[event-list]
3595 [FTRACE] Set and start specified trace events in order
3596 to facilitate early boot debugging.
3597 See also Documentation/trace/events.txt
3599 trace_options=[option-list]
3600 [FTRACE] Enable or disable tracer options at boot.
3601 The option-list is a comma delimited list of options
3602 that can be enabled or disabled just as if you were
3603 to echo the option name into
3605 /sys/kernel/debug/tracing/trace_options
3607 For example, to enable stacktrace option (to dump the
3608 stack trace of each event), add to the command line:
3610 trace_options=stacktrace
3612 See also Documentation/trace/ftrace.txt "trace options"
3616 Have the tracepoints sent to printk as well as the
3617 tracing ring buffer. This is useful for early boot up
3618 where the system hangs or reboots and does not give the
3619 option for reading the tracing buffer or performing a
3620 ftrace_dump_on_oops.
3622 To turn off having tracepoints sent to printk,
3623 echo 0 > /proc/sys/kernel/tracepoint_printk
3624 Note, echoing 1 into this file without the
3625 tracepoint_printk kernel cmdline option has no effect.
3629 Having tracepoints sent to printk() and activating high
3630 frequency tracepoints such as irq or sched, can cause
3631 the system to live lock.
3634 [FTRACE] enable this option to disable tracing when a
3635 warning is hit. This turns off "tracing_on". Tracing can
3636 be enabled again by echoing '1' into the "tracing_on"
3637 file located in /sys/kernel/debug/tracing/
3639 This option is useful, as it disables the trace before
3640 the WARNING dump is called, which prevents the trace to
3641 be filled with content caused by the warning output.
3643 This option can also be set at run time via the sysctl
3644 option: kernel/traceoff_on_warning
3646 transparent_hugepage=
3648 Format: [always|madvise|never]
3649 Can be used to control the default behavior of the system
3650 with respect to transparent hugepages.
3651 See Documentation/vm/transhuge.txt for more details.
3653 tsc= Disable clocksource stability checks for TSC.
3655 [x86] reliable: mark tsc clocksource as reliable, this
3656 disables clocksource verification at runtime, as well
3657 as the stability checks done at bootup. Used to enable
3658 high-resolution timer mode on older hardware, and in
3659 virtualized environment.
3660 [x86] noirqtime: Do not use TSC to do irq accounting.
3661 Used to run time disable IRQ_TIME_ACCOUNTING on any
3662 platforms where RDTSC is slow and this accounting
3665 turbografx.map[2|3]= [HW,JOY]
3666 TurboGraFX parallel port interface
3668 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3669 See also Documentation/input/joystick-parport.txt
3671 udbg-immortal [PPC] When debugging early kernel crashes that
3672 happen after console_init() and before a proper
3673 console driver takes over, this boot options might
3674 help "seeing" what's going on.
3676 uhash_entries= [KNL,NET]
3677 Set number of hash buckets for UDP/UDP-Lite connections
3680 [USB] Ignore overcurrent events (default N).
3681 Some badly-designed motherboards generate lots of
3682 bogus events, for ports that aren't wired to
3683 anything. Set this parameter to avoid log spamming.
3684 Note that genuine overcurrent events won't be
3688 [X86] Cause panic on unknown NMI.
3690 usbcore.authorized_default=
3691 [USB] Default USB device authorization:
3692 (default -1 = authorized except for wireless USB,
3693 0 = not authorized, 1 = authorized)
3695 usbcore.autosuspend=
3696 [USB] The autosuspend time delay (in seconds) used
3697 for newly-detected USB devices (default 2). This
3698 is the time required before an idle device will be
3699 autosuspended. Devices for which the delay is set
3700 to a negative value won't be autosuspended at all.
3702 usbcore.usbfs_snoop=
3703 [USB] Set to log all usbfs traffic (default 0 = off).
3705 usbcore.blinkenlights=
3706 [USB] Set to cycle leds on hubs (default 0 = off).
3708 usbcore.old_scheme_first=
3709 [USB] Start with the old device initialization
3710 scheme (default 0 = off).
3712 usbcore.usbfs_memory_mb=
3713 [USB] Memory limit (in MB) for buffers allocated by
3714 usbfs (default = 16, 0 = max = 2047).
3716 usbcore.use_both_schemes=
3717 [USB] Try the other device initialization scheme
3718 if the first one fails (default 1 = enabled).
3720 usbcore.initial_descriptor_timeout=
3721 [USB] Specifies timeout for the initial 64-byte
3722 USB_REQ_GET_DESCRIPTOR request in milliseconds
3723 (default 5000 = 5.0 seconds).
3726 [USBHID] The interval which mice are to be polled at.
3728 usb-storage.delay_use=
3729 [UMS] The delay in seconds before a new device is
3730 scanned for Logical Units (default 1).
3733 [UMS] A list of quirks entries to supplement or
3734 override the built-in unusual_devs list. List
3735 entries are separated by commas. Each entry has
3736 the form VID:PID:Flags where VID and PID are Vendor
3737 and Product ID values (4-digit hex numbers) and
3738 Flags is a set of characters, each corresponding
3739 to a common usb-storage quirk flag as follows:
3740 a = SANE_SENSE (collect more than 18 bytes
3742 b = BAD_SENSE (don't collect more than 18
3743 bytes of sense data);
3744 c = FIX_CAPACITY (decrease the reported
3745 device capacity by one sector);
3746 d = NO_READ_DISC_INFO (don't use
3747 READ_DISC_INFO command);
3748 e = NO_READ_CAPACITY_16 (don't use
3749 READ_CAPACITY_16 command);
3750 f = NO_REPORT_OPCODES (don't use report opcodes
3752 h = CAPACITY_HEURISTICS (decrease the
3753 reported device capacity by one
3754 sector if the number is odd);
3755 i = IGNORE_DEVICE (don't bind to this
3757 l = NOT_LOCKABLE (don't try to lock and
3758 unlock ejectable media);
3759 m = MAX_SECTORS_64 (don't transfer more
3760 than 64 sectors = 32 KB at a time);
3761 n = INITIAL_READ10 (force a retry of the
3762 initial READ(10) command);
3763 o = CAPACITY_OK (accept the capacity
3764 reported by the device);
3765 p = WRITE_CACHE (the device cache is ON
3767 r = IGNORE_RESIDUE (the device reports
3768 bogus residue values);
3769 s = SINGLE_LUN (the device has only one
3771 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3772 commands, uas only);
3773 u = IGNORE_UAS (don't bind to the uas driver);
3774 w = NO_WP_DETECT (don't test whether the
3775 medium is write-protected).
3776 Example: quirks=0419:aaf5:rl,0421:0433:rc
3778 user_debug= [KNL,ARM]
3780 See arch/arm/Kconfig.debug help text.
3781 1 - undefined instruction events
3783 4 - invalid data aborts
3786 Example: user_debug=31
3789 [X86] Flags controlling user PTE allocations.
3791 nohigh = do not allocate PTE pages in
3792 HIGHMEM regardless of setting
3796 On X86_32, this is an alias for vdso32=. Otherwise:
3798 vdso=1: enable VDSO (the default)
3799 vdso=0: disable VDSO mapping
3801 vdso32= [X86] Control the 32-bit vDSO
3802 vdso32=1: enable 32-bit VDSO
3803 vdso32=0 or vdso32=2: disable 32-bit VDSO
3805 See the help text for CONFIG_COMPAT_VDSO for more
3806 details. If CONFIG_COMPAT_VDSO is set, the default is
3807 vdso32=0; otherwise, the default is vdso32=1.
3809 For compatibility with older kernels, vdso32=2 is an
3812 Try vdso32=0 if you encounter an error that says:
3813 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3816 vector=percpu: enable percpu vector domain
3818 video= [FB] Frame buffer configuration
3819 See Documentation/fb/modedb.txt.
3821 video.brightness_switch_enabled= [0,1]
3822 If set to 1, on receiving an ACPI notify event
3823 generated by hotkey, video driver will adjust brightness
3824 level and then send out the event to user space through
3825 the allocated input device; If set to 0, video driver
3826 will only send out the event without touching backlight
3831 [VMMIO] Memory mapped virtio (platform) device.
3833 <size>@<baseaddr>:<irq>[:<id>]
3835 <size> := size (can use standard suffixes
3837 <baseaddr> := physical base address
3838 <irq> := interrupt number (as passed to
3840 <id> := (optional) platform device id
3842 virtio_mmio.device=1K@0x100b0000:48:7
3844 Can be used multiple times for multiple devices.
3846 vga= [BOOT,X86-32] Select a particular video mode
3847 See Documentation/x86/boot.txt and
3848 Documentation/svga.txt.
3849 Use vga=ask for menu.
3850 This is actually a boot loader parameter; the value is
3851 passed to the kernel using a special protocol.
3853 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3854 size of <nn>. This can be used to increase the
3855 minimum size (128MB on x86). It can also be used to
3856 decrease the size and leave more room for directly
3859 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3862 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3865 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3869 Controls the behavior of vsyscalls (i.e. calls to
3870 fixed addresses of 0xffffffffff600x00 from legacy
3871 code). Most statically-linked binaries and older
3872 versions of glibc use these calls. Because these
3873 functions are at fixed addresses, they make nice
3874 targets for exploits that can control RIP.
3876 emulate [default] Vsyscalls turn into traps and are
3877 emulated reasonably safely.
3879 native Vsyscalls are native syscall instructions.
3880 This is a little bit faster than trapping
3881 and makes a few dynamic recompilers work
3882 better than they would in emulation mode.
3883 It also makes exploits much easier to write.
3885 none Vsyscalls don't work at all. This makes
3886 them quite hard to use for exploits but
3887 might break your system.
3889 vt.color= [VT] Default text color.
3890 Format: 0xYX, X = foreground, Y = background.
3891 Default: 0x07 = light gray on black.
3893 vt.cur_default= [VT] Default cursor shape.
3894 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3895 the parameters of the <Esc>[?A;B;Cc escape sequence;
3896 see VGA-softcursor.txt. Default: 2 = underline.
3898 vt.default_blu= [VT]
3899 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3900 Change the default blue palette of the console.
3901 This is a 16-member array composed of values
3904 vt.default_grn= [VT]
3905 Format: <green0>,<green1>,<green2>,...,<green15>
3906 Change the default green palette of the console.
3907 This is a 16-member array composed of values
3910 vt.default_red= [VT]
3911 Format: <red0>,<red1>,<red2>,...,<red15>
3912 Change the default red palette of the console.
3913 This is a 16-member array composed of values
3919 Set system-wide default UTF-8 mode for all tty's.
3920 Default is 1, i.e. UTF-8 mode is enabled for all
3921 newly opened terminals.
3923 vt.global_cursor_default=
3926 Set system-wide default for whether a cursor
3927 is shown on new VTs. Default is -1,
3928 i.e. cursors will be created by default unless
3929 overridden by individual drivers. 0 will hide
3930 cursors, 1 will display them.
3932 vt.italic= [VT] Default color for italic text; 0-15.
3935 vt.underline= [VT] Default color for underlined text; 0-15.
3938 watchdog timers [HW,WDT] For information on watchdog timers,
3939 see Documentation/watchdog/watchdog-parameters.txt
3940 or other driver-specific files in the
3941 Documentation/watchdog/ directory.
3943 workqueue.disable_numa
3944 By default, all work items queued to unbound
3945 workqueues are affine to the NUMA nodes they're
3946 issued on, which results in better behavior in
3947 general. If NUMA affinity needs to be disabled for
3948 whatever reason, this option can be used. Note
3949 that this also can be controlled per-workqueue for
3950 workqueues visible under /sys/bus/workqueue/.
3952 workqueue.power_efficient
3953 Per-cpu workqueues are generally preferred because
3954 they show better performance thanks to cache
3955 locality; unfortunately, per-cpu workqueues tend to
3956 be more power hungry than unbound workqueues.
3958 Enabling this makes the per-cpu workqueues which
3959 were observed to contribute significantly to power
3960 consumption unbound, leading to measurably lower
3961 power usage at the cost of small performance
3964 The default value of this parameter is determined by
3965 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3967 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3968 default x2apic cluster mode on platforms
3971 x86_intel_mid_timer= [X86-32,APBT]
3972 Choose timer option for x86 Intel MID platform.
3973 Two valid options are apbt timer only and lapic timer
3974 plus one apbt timer for broadcast timer.
3975 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3977 xen_emul_unplug= [HW,X86,XEN]
3978 Unplug Xen emulated devices
3979 Format: [unplug0,][unplug1]
3980 ide-disks -- unplug primary master IDE devices
3981 aux-ide-disks -- unplug non-primary-master IDE devices
3982 nics -- unplug network devices
3983 all -- unplug all emulated devices (NICs and IDE disks)
3984 unnecessary -- unplugging emulated devices is
3985 unnecessary even if the host did not respond to
3987 never -- do not unplug even if version check succeeds
3989 xen_nopvspin [X86,XEN]
3990 Disables the ticketlock slowpath using Xen PV
3994 Disables the PV optimizations forcing the HVM guest to
3995 run as generic HVM guest with no PV drivers.
3997 xirc2ps_cs= [NET,PCMCIA]
3999 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4001 ______________________________________________________________________
4005 Add more DRM drivers.
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