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 * nohrst, nosrst, norst: suppress hard, soft
1761 * rstonce: only attempt one reset during
1762 hot-unplug link recovery
1764 * dump_id: dump IDENTIFY data.
1766 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1768 * disable: Disable this device.
1770 If there are multiple matching configurations changing
1771 the same attribute, the last one is used.
1773 memblock=debug [KNL] Enable memblock debug messages.
1775 load_ramdisk= [RAM] List of ramdisks to load from floppy
1776 See Documentation/blockdev/ramdisk.txt.
1778 lockd.nlm_grace_period=P [NFS] Assign grace period.
1781 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1784 lockd.nlm_timeout=T [NFS] Assign timeout value.
1787 lockd.nlm_udpport=M [NFS] Assign UDP port.
1790 locktorture.nreaders_stress= [KNL]
1791 Set the number of locking read-acquisition kthreads.
1792 Defaults to being automatically set based on the
1793 number of online CPUs.
1795 locktorture.nwriters_stress= [KNL]
1796 Set the number of locking write-acquisition kthreads.
1798 locktorture.onoff_holdoff= [KNL]
1799 Set time (s) after boot for CPU-hotplug testing.
1801 locktorture.onoff_interval= [KNL]
1802 Set time (s) between CPU-hotplug operations, or
1803 zero to disable CPU-hotplug testing.
1805 locktorture.shuffle_interval= [KNL]
1806 Set task-shuffle interval (jiffies). Shuffling
1807 tasks allows some CPUs to go into dyntick-idle
1808 mode during the locktorture test.
1810 locktorture.shutdown_secs= [KNL]
1811 Set time (s) after boot system shutdown. This
1812 is useful for hands-off automated testing.
1814 locktorture.stat_interval= [KNL]
1815 Time (s) between statistics printk()s.
1817 locktorture.stutter= [KNL]
1818 Time (s) to stutter testing, for example,
1819 specifying five seconds causes the test to run for
1820 five seconds, wait for five seconds, and so on.
1821 This tests the locking primitive's ability to
1822 transition abruptly to and from idle.
1824 locktorture.torture_runnable= [BOOT]
1825 Start locktorture running at boot time.
1827 locktorture.torture_type= [KNL]
1828 Specify the locking implementation to test.
1830 locktorture.verbose= [KNL]
1831 Enable additional printk() statements.
1833 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1836 loglevel= All Kernel Messages with a loglevel smaller than the
1837 console loglevel will be printed to the console. It can
1838 also be changed with klogd or other programs. The
1839 loglevels are defined as follows:
1841 0 (KERN_EMERG) system is unusable
1842 1 (KERN_ALERT) action must be taken immediately
1843 2 (KERN_CRIT) critical conditions
1844 3 (KERN_ERR) error conditions
1845 4 (KERN_WARNING) warning conditions
1846 5 (KERN_NOTICE) normal but significant condition
1847 6 (KERN_INFO) informational
1848 7 (KERN_DEBUG) debug-level messages
1850 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1851 in bytes. n must be a power of two and greater
1852 than the minimal size. The minimal size is defined
1853 by LOG_BUF_SHIFT kernel config parameter. There is
1854 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1855 that allows to increase the default size depending on
1856 the number of CPUs. See init/Kconfig for more details.
1858 logo.nologo [FB] Disables display of the built-in Linux logo.
1859 This may be used to provide more screen space for
1860 kernel log messages and is useful when debugging
1861 kernel boot problems.
1863 lp=0 [LP] Specify parallel ports to use, e.g,
1864 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1865 lp=reset first parallel port). 'lp=0' disables the
1866 lp=auto printer driver. 'lp=reset' (which can be
1867 specified in addition to the ports) causes
1868 attached printers to be reset. Using
1869 lp=port1,port2,... specifies the parallel ports
1870 to associate lp devices with, starting with
1871 lp0. A port specification may be 'none' to skip
1872 that lp device, or a parport name such as
1873 'parport0'. Specifying 'lp=auto' instead of a
1874 port specification list means that device IDs
1875 from each port should be examined, to see if
1876 an IEEE 1284-compliant printer is attached; if
1877 so, the driver will manage that printer.
1878 See also header of drivers/char/lp.c.
1881 Sets loops_per_jiffy to given constant, thus avoiding
1882 time-consuming boot-time autodetection (up to 250 ms per
1883 CPU). 0 enables autodetection (default). To determine
1884 the correct value for your kernel, boot with normal
1885 autodetection and see what value is printed. Note that
1886 on SMP systems the preset will be applied to all CPUs,
1887 which is likely to cause problems if your CPUs need
1888 significantly divergent settings. An incorrect value
1889 will cause delays in the kernel to be wrong, leading to
1890 unpredictable I/O errors and other breakage. Although
1891 unlikely, in the extreme case this might damage your
1895 Format: <io>,<irq>,<dma>
1897 machvec= [IA-64] Force the use of a particular machine-vector
1898 (machvec) in a generic kernel.
1899 Example: machvec=hpzx1_swiotlb
1901 machtype= [Loongson] Share the same kernel image file between different
1903 Example: machtype=lemote-yeeloong-2f-7inch
1905 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1906 than or equal to this physical address is ignored.
1908 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1909 should make use of. maxcpus=n : n >= 0 limits the
1910 kernel to using 'n' processors. n=0 is a special case,
1911 it is equivalent to "nosmp", which also disables
1914 max_loop= [LOOP] The number of loop block devices that get
1915 (loop.max_loop) unconditionally pre-created at init time. The default
1916 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1917 of statically allocating a predefined number, loop
1918 devices can be requested on-demand with the
1919 /dev/loop-control interface.
1921 mce [X86-32] Machine Check Exception
1923 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1925 md= [HW] RAID subsystems devices and level
1926 See Documentation/md.txt.
1929 Format: <first>,<last>
1930 Specifies range of consoles to be captured by the MDA.
1932 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1933 Amount of memory to be used when the kernel is not able
1934 to see the whole system memory or for test.
1935 [X86] Work as limiting max address. Use together
1936 with memmap= to avoid physical address space collisions.
1937 Without memmap= PCI devices could be placed at addresses
1938 belonging to unused RAM.
1940 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1944 [KNL,SH] Allow user to override the default size for
1945 per-device physically contiguous DMA buffers.
1947 memmap=exactmap [KNL,X86] Enable setting of an exact
1948 E820 memory map, as specified by the user.
1949 Such memmap=exactmap lines can be constructed based on
1950 BIOS output or other requirements. See the memmap=nn@ss
1953 memmap=nn[KMG]@ss[KMG]
1954 [KNL] Force usage of a specific region of memory.
1955 Region of memory to be used is from ss to ss+nn.
1957 memmap=nn[KMG]#ss[KMG]
1958 [KNL,ACPI] Mark specific memory as ACPI data.
1959 Region of memory to be marked is from ss to ss+nn.
1961 memmap=nn[KMG]$ss[KMG]
1962 [KNL,ACPI] Mark specific memory as reserved.
1963 Region of memory to be reserved is from ss to ss+nn.
1964 Example: Exclude memory from 0x18690000-0x1869ffff
1965 memmap=64K$0x18690000
1967 memmap=0x10000$0x18690000
1969 memory_corruption_check=0/1 [X86]
1970 Some BIOSes seem to corrupt the first 64k of
1971 memory when doing things like suspend/resume.
1972 Setting this option will scan the memory
1973 looking for corruption. Enabling this will
1974 both detect corruption and prevent the kernel
1975 from using the memory being corrupted.
1976 However, its intended as a diagnostic tool; if
1977 repeatable BIOS-originated corruption always
1978 affects the same memory, you can use memmap=
1979 to prevent the kernel from using that memory.
1981 memory_corruption_check_size=size [X86]
1982 By default it checks for corruption in the low
1983 64k, making this memory unavailable for normal
1984 use. Use this parameter to scan for
1985 corruption in more or less memory.
1987 memory_corruption_check_period=seconds [X86]
1988 By default it checks for corruption every 60
1989 seconds. Use this parameter to check at some
1990 other rate. 0 disables periodic checking.
1992 memtest= [KNL,X86] Enable memtest
1994 default : 0 <disable>
1995 Specifies the number of memtest passes to be
1996 performed. Each pass selects another test
1997 pattern from a given set of patterns. Memtest
1998 fills the memory with this pattern, validates
1999 memory contents and reserves bad memory
2000 regions that are detected.
2002 meye.*= [HW] Set MotionEye Camera parameters
2003 See Documentation/video4linux/meye.txt.
2005 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2006 Multi-Function General Purpose Timers on AMD Geode
2009 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2010 the BIOS has incorrectly applied a workaround. TinyBIOS
2011 version 0.98 is known to be affected, 0.99 fixes the
2012 problem by letting the user disable the workaround.
2016 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2017 physical address is ignored.
2019 mini2440= [ARM,HW,KNL]
2020 Format:[0..2][b][c][t]
2022 MINI2440 configuration specification:
2023 0 - The attached screen is the 3.5" TFT
2024 1 - The attached screen is the 7" TFT
2025 2 - The VGA Shield is attached (1024x768)
2026 Leaving out the screen size parameter will not load
2027 the TFT driver, and the framebuffer will be left
2029 b - Enable backlight. The TFT backlight pin will be
2030 linked to the kernel VESA blanking code and a GPIO
2031 LED. This parameter is not necessary when using the
2033 c - Enable the s3c camera interface.
2034 t - Reserved for enabling touchscreen support. The
2035 touchscreen support is not enabled in the mainstream
2036 kernel as of 2.6.30, a preliminary port can be found
2037 in the "bleeding edge" mini2440 support kernel at
2038 http://repo.or.cz/w/linux-2.6/mini2440.git
2041 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2042 parameter allows control of the logging verbosity for
2043 the additional memory initialisation checks. A value
2044 of 0 disables mminit logging and a level of 4 will
2045 log everything. Information is printed at KERN_DEBUG
2046 so loglevel=8 may also need to be specified.
2049 [KNL] When CONFIG_MODULE_SIG is set, this means that
2050 modules without (valid) signatures will fail to load.
2051 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2052 is always true, so this option does nothing.
2055 [MOUSE] Maximum time between finger touching and
2056 leaving touchpad surface for touch to be considered
2057 a tap and be reported as a left button click (for
2058 touchpads working in absolute mode only).
2060 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2061 reporting absolute coordinates, such as tablets
2062 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2063 reporting absolute coordinates, such as tablets
2065 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2066 is similar to kernelcore except it specifies the
2067 amount of memory used for migratable allocations.
2068 If both kernelcore and movablecore is specified,
2069 then kernelcore will be at *least* the specified
2070 value but may be more. If movablecore on its own
2071 is specified, the administrator must be careful
2072 that the amount of memory usable for all allocations
2075 movable_node [KNL,X86] Boot-time switch to enable the effects
2076 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2078 MTD_Partition= [MTD]
2079 Format: <name>,<region-number>,<size>,<offset>
2081 MTD_Region= [MTD] Format:
2082 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2085 See drivers/mtd/cmdlinepart.c.
2087 multitce=off [PPC] This parameter disables the use of the pSeries
2088 firmware feature for updating multiple TCE entries
2091 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2093 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2095 boundary - index of last SLC block on Flex-OneNAND.
2096 The remaining blocks are configured as MLC blocks.
2097 lock - Configure if Flex-OneNAND boundary should be locked.
2098 Once locked, the boundary cannot be changed.
2099 1 indicates lock status, 0 indicates unlock status.
2102 ARM/S3C2412 JIVE boot control
2104 See arch/arm/mach-s3c2412/mach-jive.c
2106 mtouchusb.raw_coordinates=
2107 [HW] Make the MicroTouch USB driver use raw coordinates
2108 ('y', default) or cooked coordinates ('n')
2110 mtrr_chunk_size=nn[KMG] [X86]
2111 used for mtrr cleanup. It is largest continuous chunk
2112 that could hold holes aka. UC entries.
2114 mtrr_gran_size=nn[KMG] [X86]
2115 Used for mtrr cleanup. It is granularity of mtrr block.
2117 Large value could prevent small alignment from
2120 mtrr_spare_reg_nr=n [X86]
2122 Range: 0,7 : spare reg number
2124 Used for mtrr cleanup. It is spare mtrr entries number.
2125 Set to 2 or more if your graphical card needs more.
2127 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2129 netdev= [NET] Network devices parameters
2130 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2131 Note that mem_start is often overloaded to mean
2132 something different and driver-specific.
2133 This usage is only documented in each driver source
2137 [NETFILTER] Enable connection tracking flow accounting
2138 0 to disable accounting
2139 1 to enable accounting
2142 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2143 See Documentation/filesystems/nfs/nfsroot.txt.
2145 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2146 See Documentation/filesystems/nfs/nfsroot.txt.
2148 nfsrootdebug [NFS] enable nfsroot debugging messages.
2149 See Documentation/filesystems/nfs/nfsroot.txt.
2151 nfs.callback_tcpport=
2152 [NFS] set the TCP port on which the NFSv4 callback
2153 channel should listen.
2156 [NFS] sets the pathname to the program which is used
2157 to update the NFS client cache entries.
2159 nfs.cache_getent_timeout=
2160 [NFS] sets the timeout after which an attempt to
2161 update a cache entry is deemed to have failed.
2163 nfs.idmap_cache_timeout=
2164 [NFS] set the maximum lifetime for idmapper cache
2168 [NFS] enable 64-bit inode numbers.
2169 If zero, the NFS client will fake up a 32-bit inode
2170 number for the readdir() and stat() syscalls instead
2171 of returning the full 64-bit number.
2172 The default is to return 64-bit inode numbers.
2174 nfs.max_session_slots=
2175 [NFSv4.1] Sets the maximum number of session slots
2176 the client will attempt to negotiate with the server.
2177 This limits the number of simultaneous RPC requests
2178 that the client can send to the NFSv4.1 server.
2179 Note that there is little point in setting this
2180 value higher than the max_tcp_slot_table_limit.
2182 nfs.nfs4_disable_idmapping=
2183 [NFSv4] When set to the default of '1', this option
2184 ensures that both the RPC level authentication
2185 scheme and the NFS level operations agree to use
2186 numeric uids/gids if the mount is using the
2187 'sec=sys' security flavour. In effect it is
2188 disabling idmapping, which can make migration from
2189 legacy NFSv2/v3 systems to NFSv4 easier.
2190 Servers that do not support this mode of operation
2191 will be autodetected by the client, and it will fall
2192 back to using the idmapper.
2193 To turn off this behaviour, set the value to '0'.
2195 [NFS4] Specify an additional fixed unique ident-
2196 ification string that NFSv4 clients can insert into
2197 their nfs_client_id4 string. This is typically a
2198 UUID that is generated at system install time.
2200 nfs.send_implementation_id =
2201 [NFSv4.1] Send client implementation identification
2202 information in exchange_id requests.
2203 If zero, no implementation identification information
2205 The default is to send the implementation identification
2208 nfs.recover_lost_locks =
2209 [NFSv4] Attempt to recover locks that were lost due
2210 to a lease timeout on the server. Please note that
2211 doing this risks data corruption, since there are
2212 no guarantees that the file will remain unchanged
2213 after the locks are lost.
2214 If you want to enable the kernel legacy behaviour of
2215 attempting to recover these locks, then set this
2217 The default parameter value of '0' causes the kernel
2218 not to attempt recovery of lost locks.
2220 nfsd.nfs4_disable_idmapping=
2221 [NFSv4] When set to the default of '1', the NFSv4
2222 server will return only numeric uids and gids to
2223 clients using auth_sys, and will accept numeric uids
2224 and gids from such clients. This is intended to ease
2225 migration from NFSv2/v3.
2227 objlayoutdriver.osd_login_prog=
2228 [NFS] [OBJLAYOUT] sets the pathname to the program which
2229 is used to automatically discover and login into new
2230 osd-targets. Please see:
2231 Documentation/filesystems/pnfs.txt for more explanations
2233 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2234 when a NMI is triggered.
2235 Format: [state][,regs][,debounce][,die]
2237 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2238 Format: [panic,][nopanic,][num]
2240 0 - turn nmi_watchdog off
2241 1 - turn nmi_watchdog on
2242 When panic is specified, panic when an NMI watchdog
2243 timeout occurs (or 'nopanic' to override the opposite
2245 This is useful when you use a panic=... timeout and
2246 need the box quickly up again.
2248 netpoll.carrier_timeout=
2249 [NET] Specifies amount of time (in seconds) that
2250 netpoll should wait for a carrier. By default netpoll
2253 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2254 emulation library even if a 387 maths coprocessor
2258 [HW] Never suspend the console
2259 Disable suspending of consoles during suspend and
2260 hibernate operations. Once disabled, debugging
2261 messages can reach various consoles while the rest
2262 of the system is being put to sleep (ie, while
2263 debugging driver suspend/resume hooks). This may
2264 not work reliably with all consoles, but is known
2265 to work with serial and VGA consoles.
2266 To facilitate more flexible debugging, we also add
2267 console_suspend, a printk module parameter to control
2268 it. Users could use console_suspend (usually
2269 /sys/module/printk/parameters/console_suspend) to
2270 turn on/off it dynamically.
2272 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2273 caches in the slab allocator. Saves per-node memory,
2274 but will impact performance.
2278 noapic [SMP,APIC] Tells the kernel to not make use of any
2279 IOAPICs that may be present in the system.
2281 noautogroup Disable scheduler automatic task group creation.
2283 nobats [PPC] Do not use BATs for mapping kernel lowmem
2284 on "Classic" PPC cores.
2288 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2290 nodelayacct [KNL] Disable per-task delay accounting
2292 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2294 nodsp [SH] Disable hardware DSP at boot time.
2296 noefi Disable EFI runtime services support.
2301 On X86-32 available only on PAE configured kernels.
2302 noexec=on: enable non-executable mappings (default)
2303 noexec=off: disable non-executable mappings
2306 Disable SMAP (Supervisor Mode Access Prevention)
2307 even if it is supported by processor.
2310 Disable SMEP (Supervisor Mode Execution Prevention)
2311 even if it is supported by processor.
2314 This affects only 32-bit executables.
2315 noexec32=on: enable non-executable mappings (default)
2316 read doesn't imply executable mappings
2317 noexec32=off: disable non-executable mappings
2318 read implies executable mappings
2320 nofpu [SH] Disable hardware FPU at boot time.
2322 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2323 register save and restore. The kernel will only save
2324 legacy floating-point registers on task switch.
2326 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2328 noxsave [BUGS=X86] Disables x86 extended register state save
2329 and restore using xsave. The kernel will fallback to
2330 enabling legacy floating-point and sse state.
2332 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2333 register states. The kernel will fall back to use
2334 xsave to save the states. By using this parameter,
2335 performance of saving the states is degraded because
2336 xsave doesn't support modified optimization while
2337 xsaveopt supports it on xsaveopt enabled systems.
2339 noxsaves [X86] Disables xsaves and xrstors used in saving and
2340 restoring x86 extended register state in compacted
2341 form of xsave area. The kernel will fall back to use
2342 xsaveopt and xrstor to save and restore the states
2343 in standard form of xsave area. By using this
2344 parameter, xsave area per process might occupy more
2345 memory on xsaves enabled systems.
2348 on enable eager fpu restore
2349 off disable eager fpu restore
2350 auto selects the default scheme, which automatically
2351 enables eagerfpu restore for xsaveopt.
2353 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2354 wfi(ARM) instruction doesn't work correctly and not to
2355 use it. This is also useful when using JTAG debugger.
2357 no_file_caps Tells the kernel not to honor file capabilities. The
2358 only way then for a file to be executed with privilege
2359 is to be setuid root or executed by root.
2361 nohalt [IA-64] Tells the kernel not to use the power saving
2362 function PAL_HALT_LIGHT when idle. This increases
2363 power-consumption. On the positive side, it reduces
2364 interrupt wake-up latency, which may improve performance
2365 in certain environments such as networked servers or
2368 nohibernate [HIBERNATION] Disable hibernation and resume.
2370 nohz= [KNL] Boottime enable/disable dynamic ticks
2371 Valid arguments: on, off
2374 nohz_full= [KNL,BOOT]
2375 In kernels built with CONFIG_NO_HZ_FULL=y, set
2376 the specified list of CPUs whose tick will be stopped
2377 whenever possible. The boot CPU will be forced outside
2378 the range to maintain the timekeeping.
2379 The CPUs in this range must also be included in the
2382 noiotrap [SH] Disables trapped I/O port accesses.
2384 noirqdebug [X86-32] Disables the code which attempts to detect and
2385 disable unhandled interrupt sources.
2387 no_timer_check [X86,APIC] Disables the code which tests for
2388 broken timer IRQ sources.
2390 noisapnp [ISAPNP] Disables ISA PnP code.
2392 noinitrd [RAM] Tells the kernel not to load any configured
2395 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2397 [Deprecated - use intremap=off]
2401 nojitter [IA-64] Disables jitter checking for ITC timers.
2403 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2405 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2408 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2409 steal time is computed, but won't influence scheduler
2412 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2414 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2416 noltlbs [PPC] Do not use large page/tlb entries for kernel
2417 lowmem mapping on PPC40x.
2419 nomca [IA-64] Disable machine check abort handling
2421 nomce [X86-32] Machine Check Exception
2423 nomfgpt [X86-32] Disable Multi-Function General Purpose
2424 Timer usage (for AMD Geode machines).
2426 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2427 shutdown the other cpus. Instead use the REBOOT_VECTOR
2430 nomodule Disable module load
2432 nopat [X86] Disable PAT (page attribute table extension of
2433 pagetables) support.
2435 norandmaps Don't use address space randomization. Equivalent to
2436 echo 0 > /proc/sys/kernel/randomize_va_space
2438 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2440 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2441 with UP alternatives
2443 nordrand [X86] Disable kernel use of the RDRAND and
2444 RDSEED instructions even if they are supported
2445 by the processor. RDRAND and RDSEED are still
2446 available to user space applications.
2448 noresume [SWSUSP] Disables resume and restores original swap
2451 no-scroll [VGA] Disables scrollback.
2452 This is required for the Braillex ib80-piezo Braille
2453 reader made by F.H. Papenmeier (Germany).
2457 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2459 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2460 and disable the IO APIC. legacy for "maxcpus=0".
2462 nosoftlockup [KNL] Disable the soft-lockup detector.
2464 nosync [HW,M68K] Disables sync negotiation for all devices.
2466 notsc [BUGS=X86-32] Disable Time Stamp Counter
2468 nousb [USB] Disable the USB subsystem
2470 nowatchdog [KNL] Disable both lockup detectors, i.e.
2471 soft-lockup and NMI watchdog (hard-lockup).
2475 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2477 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2478 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2479 Some features depend on CPU0. Known dependencies are:
2480 1. Resume from suspend/hibernate depends on CPU0.
2481 Suspend/hibernate will fail if CPU0 is offline and you
2482 need to online CPU0 before suspend/hibernate.
2483 2. PIC interrupts also depend on CPU0. CPU0 can't be
2484 removed if a PIC interrupt is detected.
2485 It's said poweroff/reboot may depend on CPU0 on some
2486 machines although I haven't seen such issues so far
2487 after CPU0 is offline on a few tested machines.
2488 If the dependencies are under your control, you can
2489 turn on cpu0_hotplug.
2491 nptcg= [IA-64] Override max number of concurrent global TLB
2492 purges which is reported from either PAL_VM_SUMMARY or
2495 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2496 could support. nr_cpus=n : n >= 1 limits the kernel to
2497 supporting 'n' processors. Later in runtime you can not
2498 use hotplug cpu feature to put more cpu back to online.
2499 just like you compile the kernel NR_CPUS=n
2501 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2503 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2504 Allowed values are enable and disable
2506 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2507 one of ['zone', 'node', 'default'] can be specified
2508 This can be set from sysctl after boot.
2509 See Documentation/sysctl/vm.txt for details.
2511 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2512 See Documentation/debugging-via-ohci1394.txt for more
2515 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2516 Rather than timing out after 20 ms if an EC
2517 command is not properly ACKed, override the length
2518 of the timeout. We have interrupts disabled while
2519 waiting for the ACK, so if this is set too high
2520 interrupts *may* be lost!
2522 omap_mux= [OMAP] Override bootloader pin multiplexing.
2523 Format: <mux_mode0.mode_name=value>...
2524 For example, to override I2C bus2:
2525 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2527 oprofile.timer= [HW]
2528 Use timer interrupt instead of performance counters
2530 oprofile.cpu_type= Force an oprofile cpu type
2531 This might be useful if you have an older oprofile
2532 userland or if you want common events.
2533 Format: { arch_perfmon }
2534 arch_perfmon: [X86] Force use of architectural
2535 perfmon on Intel CPUs instead of the
2536 CPU specific event set.
2537 timer: [X86] Force use of architectural NMI
2538 timer mode (see also oprofile.timer
2539 for generic hr timer mode)
2540 [s390] Force legacy basic mode sampling
2541 (report cpu_type "timer")
2543 oops=panic Always panic on oopses. Default is to just kill the
2544 process, but there is a small probability of
2545 deadlocking the machine.
2546 This will also cause panics on machine check exceptions.
2547 Useful together with panic=30 to trigger a reboot.
2550 See Documentation/sound/oss/oss-parameters.txt
2552 page_owner= [KNL] Boot-time page_owner enabling option.
2553 Storage of the information about who allocated
2554 each page is disabled in default. With this switch,
2556 on: enable the feature
2558 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2559 timeout > 0: seconds before rebooting
2560 timeout = 0: wait forever
2561 timeout < 0: reboot immediately
2564 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2567 crash_kexec_post_notifiers
2568 Run kdump after running panic-notifiers and dumping
2569 kmsg. This only for the users who doubt kdump always
2570 succeeds in any situation.
2571 Note that this also increases risks of kdump failure,
2572 because some panic notifiers can make the crashed
2573 kernel more unstable.
2575 parkbd.port= [HW] Parallel port number the keyboard adapter is
2576 connected to, default is 0.
2578 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2579 0 for XT, 1 for AT (default is AT).
2582 parport= [HW,PPT] Specify parallel ports. 0 disables.
2583 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2584 Use 'auto' to force the driver to use any
2585 IRQ/DMA settings detected (the default is to
2586 ignore detected IRQ/DMA settings because of
2587 possible conflicts). You can specify the base
2588 address, IRQ, and DMA settings; IRQ and DMA
2589 should be numbers, or 'auto' (for using detected
2590 settings on that particular port), or 'nofifo'
2591 (to avoid using a FIFO even if it is detected).
2592 Parallel ports are assigned in the order they
2593 are specified on the command line, starting
2596 parport_init_mode= [HW,PPT]
2597 Configure VIA parallel port to operate in
2598 a specific mode. This is necessary on Pegasos
2599 computer where firmware has no options for setting
2600 up parallel port mode and sets it to spp.
2601 Currently this function knows 686a and 8231 chips.
2602 Format: [spp|ps2|epp|ecp|ecpepp]
2605 Halt all CPUs after the first oops has been printed for
2606 the specified number of seconds. This is to be used if
2607 your oopses keep scrolling off the screen.
2612 See header of drivers/block/paride/pcd.c.
2613 See also Documentation/blockdev/paride.txt.
2615 pci=option[,option...] [PCI] various PCI subsystem options:
2616 earlydump [X86] dump PCI config space before the kernel
2618 off [X86] don't probe for the PCI bus
2619 bios [X86-32] force use of PCI BIOS, don't access
2620 the hardware directly. Use this if your machine
2621 has a non-standard PCI host bridge.
2622 nobios [X86-32] disallow use of PCI BIOS, only direct
2623 hardware access methods are allowed. Use this
2624 if you experience crashes upon bootup and you
2625 suspect they are caused by the BIOS.
2626 conf1 [X86] Force use of PCI Configuration
2628 conf2 [X86] Force use of PCI Configuration
2630 noaer [PCIE] If the PCIEAER kernel config parameter is
2631 enabled, this kernel boot option can be used to
2632 disable the use of PCIE advanced error reporting.
2633 nodomains [PCI] Disable support for multiple PCI
2634 root domains (aka PCI segments, in ACPI-speak).
2635 nommconf [X86] Disable use of MMCONFIG for PCI
2637 check_enable_amd_mmconf [X86] check for and enable
2638 properly configured MMIO access to PCI
2639 config space on AMD family 10h CPU
2640 nomsi [MSI] If the PCI_MSI kernel config parameter is
2641 enabled, this kernel boot option can be used to
2642 disable the use of MSI interrupts system-wide.
2643 noioapicquirk [APIC] Disable all boot interrupt quirks.
2644 Safety option to keep boot IRQs enabled. This
2645 should never be necessary.
2646 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2647 primary IO-APIC for bridges that cannot disable
2648 boot IRQs. This fixes a source of spurious IRQs
2649 when the system masks IRQs.
2650 noioapicreroute [APIC] Disable workaround that uses the
2651 boot IRQ equivalent of an IRQ that connects to
2652 a chipset where boot IRQs cannot be disabled.
2653 The opposite of ioapicreroute.
2654 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2655 routing table. These calls are known to be buggy
2656 on several machines and they hang the machine
2657 when used, but on other computers it's the only
2658 way to get the interrupt routing table. Try
2659 this option if the kernel is unable to allocate
2660 IRQs or discover secondary PCI buses on your
2662 rom [X86] Assign address space to expansion ROMs.
2663 Use with caution as certain devices share
2664 address decoders between ROMs and other
2666 norom [X86] Do not assign address space to
2667 expansion ROMs that do not already have
2668 BIOS assigned address ranges.
2669 nobar [X86] Do not assign address space to the
2670 BARs that weren't assigned by the BIOS.
2671 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2672 assigned automatically to PCI devices. You can
2673 make the kernel exclude IRQs of your ISA cards
2675 pirqaddr=0xAAAAA [X86] Specify the physical address
2676 of the PIRQ table (normally generated
2677 by the BIOS) if it is outside the
2678 F0000h-100000h range.
2679 lastbus=N [X86] Scan all buses thru bus #N. Can be
2680 useful if the kernel is unable to find your
2681 secondary buses and you want to tell it
2682 explicitly which ones they are.
2683 assign-busses [X86] Always assign all PCI bus
2684 numbers ourselves, overriding
2685 whatever the firmware may have done.
2686 usepirqmask [X86] Honor the possible IRQ mask stored
2687 in the BIOS $PIR table. This is needed on
2688 some systems with broken BIOSes, notably
2689 some HP Pavilion N5400 and Omnibook XE3
2690 notebooks. This will have no effect if ACPI
2691 IRQ routing is enabled.
2692 noacpi [X86] Do not use ACPI for IRQ routing
2693 or for PCI scanning.
2694 use_crs [X86] Use PCI host bridge window information
2695 from ACPI. On BIOSes from 2008 or later, this
2696 is enabled by default. If you need to use this,
2697 please report a bug.
2698 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2699 If you need to use this, please report a bug.
2700 routeirq Do IRQ routing for all PCI devices.
2701 This is normally done in pci_enable_device(),
2702 so this option is a temporary workaround
2703 for broken drivers that don't call it.
2704 skip_isa_align [X86] do not align io start addr, so can
2705 handle more pci cards
2706 firmware [ARM] Do not re-enumerate the bus but instead
2707 just use the configuration from the
2708 bootloader. This is currently used on
2709 IXP2000 systems where the bus has to be
2710 configured a certain way for adjunct CPUs.
2711 noearly [X86] Don't do any early type 1 scanning.
2712 This might help on some broken boards which
2713 machine check when some devices' config space
2714 is read. But various workarounds are disabled
2715 and some IOMMU drivers will not work.
2716 bfsort Sort PCI devices into breadth-first order.
2717 This sorting is done to get a device
2718 order compatible with older (<= 2.4) kernels.
2719 nobfsort Don't sort PCI devices into breadth-first order.
2720 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2721 tuning and use the BIOS-configured MPS defaults.
2722 pcie_bus_safe Set every device's MPS to the largest value
2723 supported by all devices below the root complex.
2724 pcie_bus_perf Set device MPS to the largest allowable MPS
2725 based on its parent bus. Also set MRRS (Max
2726 Read Request Size) to the largest supported
2727 value (no larger than the MPS that the device
2728 or bus can support) for best performance.
2729 pcie_bus_peer2peer Set every device's MPS to 128B, which
2730 every device is guaranteed to support. This
2731 configuration allows peer-to-peer DMA between
2732 any pair of devices, possibly at the cost of
2733 reduced performance. This also guarantees
2734 that hot-added devices will work.
2735 cbiosize=nn[KMG] The fixed amount of bus space which is
2736 reserved for the CardBus bridge's IO window.
2737 The default value is 256 bytes.
2738 cbmemsize=nn[KMG] The fixed amount of bus space which is
2739 reserved for the CardBus bridge's memory
2740 window. The default value is 64 megabytes.
2743 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2744 Specifies alignment and device to reassign
2745 aligned memory resources.
2746 If <order of align> is not specified,
2747 PAGE_SIZE is used as alignment.
2748 PCI-PCI bridge can be specified, if resource
2749 windows need to be expanded.
2750 ecrc= Enable/disable PCIe ECRC (transaction layer
2751 end-to-end CRC checking).
2752 bios: Use BIOS/firmware settings. This is the
2756 hpiosize=nn[KMG] The fixed amount of bus space which is
2757 reserved for hotplug bridge's IO window.
2758 Default size is 256 bytes.
2759 hpmemsize=nn[KMG] The fixed amount of bus space which is
2760 reserved for hotplug bridge's memory window.
2761 Default size is 2 megabytes.
2762 realloc= Enable/disable reallocating PCI bridge resources
2763 if allocations done by BIOS are too small to
2764 accommodate resources required by all child
2766 off: Turn realloc off
2768 realloc same as realloc=on
2769 noari do not use PCIe ARI.
2770 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2771 only look for one device below a PCIe downstream
2774 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2777 force Enable ASPM even on devices that claim not to support it.
2778 WARNING: Forcing ASPM on may cause system lockups.
2780 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2781 nomsi Do not use MSI for PCI Express Native Hotplug (this
2782 makes all PCIe ports use INTx for hotplug services).
2784 pcie_ports= [PCIE] PCIe ports handling:
2785 auto Ask the BIOS whether or not to use native PCIe services
2786 associated with PCIe ports (PME, hot-plug, AER). Use
2787 them only if that is allowed by the BIOS.
2788 native Use native PCIe services associated with PCIe ports
2790 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2793 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2794 nomsi Do not use MSI for native PCIe PME signaling (this makes
2795 all PCIe root ports use INTx for all services).
2797 pcmv= [HW,PCMCIA] BadgePAD 4
2801 Keep all power-domains already enabled by bootloader on,
2802 even if no driver has claimed them. This is useful
2803 for debug and development, but should not be
2804 needed on a platform with proper driver support.
2807 See Documentation/blockdev/paride.txt.
2809 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2812 See arch/parisc/kernel/pdc_chassis.c
2814 percpu_alloc= Select which percpu first chunk allocator to use.
2815 Currently supported values are "embed" and "page".
2816 Archs may support subset or none of the selections.
2817 See comments in mm/percpu.c for details on each
2818 allocator. This parameter is primarily for debugging
2819 and performance comparison.
2822 See Documentation/blockdev/paride.txt.
2825 See Documentation/blockdev/paride.txt.
2827 pirq= [SMP,APIC] Manual mp-table setup
2828 See Documentation/x86/i386/IO-APIC.txt.
2830 plip= [PPT,NET] Parallel port network link
2831 Format: { parport<nr> | timid | 0 }
2832 See also Documentation/parport.txt.
2834 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2835 Override pmtimer IOPort with a hex value.
2839 Enable PNP debug messages (depends on the
2840 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2841 via /sys/module/pnp/parameters/debug. We always show
2842 current resource usage; turning this on also shows
2843 possible settings and some assignment information.
2849 { on | off | curr | res | no-curr | no-res }
2852 [ISAPNP] Exclude IRQs for the autoconfiguration
2855 [ISAPNP] Exclude DMAs for the autoconfiguration
2857 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2858 Ranges are in pairs (I/O port base and size).
2861 [ISAPNP] Exclude memory regions for the
2863 Ranges are in pairs (memory base and size).
2865 ports= [IP_VS_FTP] IPVS ftp helper module
2867 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2869 Format: <port>,<port>....
2871 print-fatal-signals=
2872 [KNL] debug: print fatal signals
2874 If enabled, warn about various signal handling
2875 related application anomalies: too many signals,
2876 too many POSIX.1 timers, fatal signals causing a
2879 If you hit the warning due to signal overflow,
2880 you might want to try "ulimit -i unlimited".
2884 printk.always_kmsg_dump=
2885 Trigger kmsg_dump for cases other than kernel oops or
2887 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2890 printk.time= Show timing data prefixed to each printk message line
2891 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2893 processor.max_cstate= [HW,ACPI]
2894 Limit processor to maximum C-state
2895 max_cstate=9 overrides any DMI blacklist limit.
2897 processor.nocst [HW,ACPI]
2898 Ignore the _CST method to determine C-states,
2899 instead using the legacy FADT method
2901 profile= [KNL] Enable kernel profiling via /proc/profile
2902 Format: [schedule,]<number>
2903 Param: "schedule" - profile schedule points.
2904 Param: <number> - step/bucket size as a power of 2 for
2905 statistical time based profiling.
2906 Param: "sleep" - profile D-state sleeping (millisecs).
2907 Requires CONFIG_SCHEDSTATS
2908 Param: "kvm" - profile VM exits.
2910 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2912 See Documentation/blockdev/ramdisk.txt.
2914 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2915 probe for; one of (bare|imps|exps|lifebook|any).
2916 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2918 psmouse.resetafter= [HW,MOUSE]
2919 Try to reset the device after so many bad packets
2922 [HW,MOUSE] Set desired mouse resolution, in dpi.
2923 psmouse.smartscroll=
2924 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2925 0 = disabled, 1 = enabled (default).
2927 pstore.backend= Specify the name of the pstore backend to use
2930 See Documentation/blockdev/paride.txt.
2933 [KNL] Number of legacy pty's. Overwrites compiled-in
2936 quiet [KNL] Disable most log messages
2941 See Documentation/md.txt.
2943 ramdisk_blocksize= [RAM]
2944 See Documentation/blockdev/ramdisk.txt.
2946 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2947 See Documentation/blockdev/ramdisk.txt.
2950 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2951 the specified list of CPUs to be no-callback CPUs.
2952 Invocation of these CPUs' RCU callbacks will
2953 be offloaded to "rcuox/N" kthreads created for
2954 that purpose, where "x" is "b" for RCU-bh, "p"
2955 for RCU-preempt, and "s" for RCU-sched, and "N"
2956 is the CPU number. This reduces OS jitter on the
2957 offloaded CPUs, which can be useful for HPC and
2958 real-time workloads. It can also improve energy
2959 efficiency for asymmetric multiprocessors.
2962 Rather than requiring that offloaded CPUs
2963 (specified by rcu_nocbs= above) explicitly
2964 awaken the corresponding "rcuoN" kthreads,
2965 make these kthreads poll for callbacks.
2966 This improves the real-time response for the
2967 offloaded CPUs by relieving them of the need to
2968 wake up the corresponding kthread, but degrades
2969 energy efficiency by requiring that the kthreads
2970 periodically wake up to do the polling.
2972 rcutree.blimit= [KNL]
2973 Set maximum number of finished RCU callbacks to
2974 process in one batch.
2976 rcutree.rcu_fanout_leaf= [KNL]
2977 Increase the number of CPUs assigned to each
2978 leaf rcu_node structure. Useful for very large
2981 rcutree.jiffies_till_sched_qs= [KNL]
2982 Set required age in jiffies for a
2983 given grace period before RCU starts
2984 soliciting quiescent-state help from
2985 rcu_note_context_switch().
2987 rcutree.jiffies_till_first_fqs= [KNL]
2988 Set delay from grace-period initialization to
2989 first attempt to force quiescent states.
2990 Units are jiffies, minimum value is zero,
2991 and maximum value is HZ.
2993 rcutree.jiffies_till_next_fqs= [KNL]
2994 Set delay between subsequent attempts to force
2995 quiescent states. Units are jiffies, minimum
2996 value is one, and maximum value is HZ.
2998 rcutree.kthread_prio= [KNL,BOOT]
2999 Set the SCHED_FIFO priority of the RCU
3000 per-CPU kthreads (rcuc/N). This value is also
3001 used for the priority of the RCU boost threads
3002 (rcub/N). Valid values are 1-99 and the default
3003 is 1 (the least-favored priority).
3005 rcutree.rcu_nocb_leader_stride= [KNL]
3006 Set the number of NOCB kthread groups, which
3007 defaults to the square root of the number of
3008 CPUs. Larger numbers reduces the wakeup overhead
3009 on the per-CPU grace-period kthreads, but increases
3010 that same overhead on each group's leader.
3012 rcutree.qhimark= [KNL]
3013 Set threshold of queued RCU callbacks beyond which
3014 batch limiting is disabled.
3016 rcutree.qlowmark= [KNL]
3017 Set threshold of queued RCU callbacks below which
3018 batch limiting is re-enabled.
3020 rcutree.rcu_idle_gp_delay= [KNL]
3021 Set wakeup interval for idle CPUs that have
3022 RCU callbacks (RCU_FAST_NO_HZ=y).
3024 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3025 Set wakeup interval for idle CPUs that have
3026 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3027 Lazy RCU callbacks are those which RCU can
3028 prove do nothing more than free memory.
3030 rcutorture.cbflood_inter_holdoff= [KNL]
3031 Set holdoff time (jiffies) between successive
3032 callback-flood tests.
3034 rcutorture.cbflood_intra_holdoff= [KNL]
3035 Set holdoff time (jiffies) between successive
3036 bursts of callbacks within a given callback-flood
3039 rcutorture.cbflood_n_burst= [KNL]
3040 Set the number of bursts making up a given
3041 callback-flood test. Set this to zero to
3042 disable callback-flood testing.
3044 rcutorture.cbflood_n_per_burst= [KNL]
3045 Set the number of callbacks to be registered
3046 in a given burst of a callback-flood test.
3048 rcutorture.fqs_duration= [KNL]
3049 Set duration of force_quiescent_state bursts.
3051 rcutorture.fqs_holdoff= [KNL]
3052 Set holdoff time within force_quiescent_state bursts.
3054 rcutorture.fqs_stutter= [KNL]
3055 Set wait time between force_quiescent_state bursts.
3057 rcutorture.gp_exp= [KNL]
3058 Use expedited update-side primitives.
3060 rcutorture.gp_normal= [KNL]
3061 Use normal (non-expedited) update-side primitives.
3062 If both gp_exp and gp_normal are set, do both.
3063 If neither gp_exp nor gp_normal are set, still
3066 rcutorture.n_barrier_cbs= [KNL]
3067 Set callbacks/threads for rcu_barrier() testing.
3069 rcutorture.nfakewriters= [KNL]
3070 Set number of concurrent RCU writers. These just
3071 stress RCU, they don't participate in the actual
3072 test, hence the "fake".
3074 rcutorture.nreaders= [KNL]
3075 Set number of RCU readers.
3077 rcutorture.object_debug= [KNL]
3078 Enable debug-object double-call_rcu() testing.
3080 rcutorture.onoff_holdoff= [KNL]
3081 Set time (s) after boot for CPU-hotplug testing.
3083 rcutorture.onoff_interval= [KNL]
3084 Set time (s) between CPU-hotplug operations, or
3085 zero to disable CPU-hotplug testing.
3087 rcutorture.torture_runnable= [BOOT]
3088 Start rcutorture running at boot time.
3090 rcutorture.shuffle_interval= [KNL]
3091 Set task-shuffle interval (s). Shuffling tasks
3092 allows some CPUs to go into dyntick-idle mode
3093 during the rcutorture test.
3095 rcutorture.shutdown_secs= [KNL]
3096 Set time (s) after boot system shutdown. This
3097 is useful for hands-off automated testing.
3099 rcutorture.stall_cpu= [KNL]
3100 Duration of CPU stall (s) to test RCU CPU stall
3101 warnings, zero to disable.
3103 rcutorture.stall_cpu_holdoff= [KNL]
3104 Time to wait (s) after boot before inducing stall.
3106 rcutorture.stat_interval= [KNL]
3107 Time (s) between statistics printk()s.
3109 rcutorture.stutter= [KNL]
3110 Time (s) to stutter testing, for example, specifying
3111 five seconds causes the test to run for five seconds,
3112 wait for five seconds, and so on. This tests RCU's
3113 ability to transition abruptly to and from idle.
3115 rcutorture.test_boost= [KNL]
3116 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3117 "Maybe" means test if the RCU implementation
3118 under test support RCU priority boosting.
3120 rcutorture.test_boost_duration= [KNL]
3121 Duration (s) of each individual boost test.
3123 rcutorture.test_boost_interval= [KNL]
3124 Interval (s) between each boost test.
3126 rcutorture.test_no_idle_hz= [KNL]
3127 Test RCU's dyntick-idle handling. See also the
3128 rcutorture.shuffle_interval parameter.
3130 rcutorture.torture_type= [KNL]
3131 Specify the RCU implementation to test.
3133 rcutorture.verbose= [KNL]
3134 Enable additional printk() statements.
3136 rcupdate.rcu_expedited= [KNL]
3137 Use expedited grace-period primitives, for
3138 example, synchronize_rcu_expedited() instead
3139 of synchronize_rcu(). This reduces latency,
3140 but can increase CPU utilization, degrade
3141 real-time latency, and degrade energy efficiency.
3143 rcupdate.rcu_cpu_stall_suppress= [KNL]
3144 Suppress RCU CPU stall warning messages.
3146 rcupdate.rcu_cpu_stall_timeout= [KNL]
3147 Set timeout for RCU CPU stall warning messages.
3149 rcupdate.rcu_task_stall_timeout= [KNL]
3150 Set timeout in jiffies for RCU task stall warning
3151 messages. Disable with a value less than or equal
3154 rcupdate.rcu_self_test= [KNL]
3155 Run the RCU early boot self tests
3157 rcupdate.rcu_self_test_bh= [KNL]
3158 Run the RCU bh early boot self tests
3160 rcupdate.rcu_self_test_sched= [KNL]
3161 Run the RCU sched early boot self tests
3165 Run specified binary instead of /init from the ramdisk,
3166 used for early userspace startup. See initrd.
3169 Format (x86 or x86_64):
3170 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3172 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3174 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3175 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3176 reboot_force is either force or not specified,
3177 reboot_cpu is s[mp]#### with #### being the processor
3178 to be used for rebooting.
3181 [KNL, SMP] Set scheduler's default relax_domain_level.
3182 See Documentation/cgroups/cpusets.txt.
3184 relative_sleep_states=
3185 [SUSPEND] Use sleep state labeling where the deepest
3186 state available other than hibernation is always "mem".
3187 Format: { "0" | "1" }
3188 0 -- Traditional sleep state labels.
3189 1 -- Relative sleep state labels.
3191 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3193 reservetop= [X86-32]
3195 Reserves a hole at the top of the kernel virtual
3200 Set the amount of memory to reserve for BIOS at
3201 the bottom of the address space.
3203 reset_devices [KNL] Force drivers to reset the underlying device
3204 during initialization.
3207 Specify the partition device for software suspend
3209 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3211 resume_offset= [SWSUSP]
3212 Specify the offset from the beginning of the partition
3213 given by "resume=" at which the swap header is located,
3214 in <PAGE_SIZE> units (needed only for swap files).
3215 See Documentation/power/swsusp-and-swap-files.txt
3217 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3218 read the resume files
3220 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3221 Useful for devices that are detected asynchronously
3222 (e.g. USB and MMC devices).
3224 hibernate= [HIBERNATION]
3225 noresume Don't check if there's a hibernation image
3226 present during boot.
3227 nocompress Don't compress/decompress hibernation images.
3228 no Disable hibernation and resume.
3230 retain_initrd [RAM] Keep initrd memory after extraction
3232 rfkill.default_state=
3233 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3234 etc. communication is blocked by default.
3237 rfkill.master_switch_mode=
3238 0 The "airplane mode" button does nothing.
3239 1 The "airplane mode" button toggles between everything
3240 blocked and the previous configuration.
3241 2 The "airplane mode" button toggles between everything
3242 blocked and everything unblocked.
3244 rhash_entries= [KNL,NET]
3245 Set number of hash buckets for route cache
3247 ro [KNL] Mount root device read-only on boot
3249 root= [KNL] Root filesystem
3250 See name_to_dev_t comment in init/do_mounts.c.
3252 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3253 mount the root filesystem
3255 rootflags= [KNL] Set root filesystem mount option string
3257 rootfstype= [KNL] Set root filesystem type
3259 rootwait [KNL] Wait (indefinitely) for root device to show up.
3260 Useful for devices that are detected asynchronously
3261 (e.g. USB and MMC devices).
3263 rproc_mem=nn[KMG][@address]
3264 [KNL,ARM,CMA] Remoteproc physical memory block.
3265 Memory area to be used by remote processor image,
3268 rw [KNL] Mount root device read-write on boot
3270 S [KNL] Run init in single mode
3272 s390_iommu= [HW,S390]
3273 Set s390 IOTLB flushing mode
3275 With strict flushing every unmap operation will result in
3276 an IOTLB flush. Default is lazy flushing before reuse,
3280 See drivers/net/irda/sa1100_ir.c.
3282 sbni= [NET] Granch SBNI12 leased line adapter
3284 sched_debug [KNL] Enables verbose scheduler debug messages.
3286 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3287 xtime_lock contention on larger systems, and/or RCU lock
3288 contention on all systems with CONFIG_MAXSMP set.
3289 Format: { "0" | "1" }
3290 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3292 Note: increases power consumption, thus should only be
3293 enabled if running jitter sensitive (HPC/RT) workloads.
3295 security= [SECURITY] Choose a security module to enable at boot.
3296 If this boot parameter is not specified, only the first
3297 security module asking for security registration will be
3298 loaded. An invalid security module name will be treated
3299 as if no module has been chosen.
3301 selinux= [SELINUX] Disable or enable SELinux at boot time.
3302 Format: { "0" | "1" }
3303 See security/selinux/Kconfig help text.
3306 Default value is set via kernel config option.
3307 If enabled at boot time, /selinux/disable can be used
3308 later to disable prior to initial policy load.
3310 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3311 Format: { "0" | "1" }
3312 See security/apparmor/Kconfig help text
3315 Default value is set via kernel config option.
3317 serialnumber [BUGS=X86-32]
3320 Maximal number of shapers.
3322 show_msr= [x86] show boot-time MSR settings
3323 Format: { <integer> }
3324 Show boot-time (BIOS-initialized) MSR settings.
3325 The parameter means the number of CPUs to show,
3326 for example 1 means boot CPU only.
3334 Disable merging of slabs with similar size. May be
3335 necessary if there is some reason to distinguish
3336 allocs to different slabs. Debug options disable
3337 merging on their own.
3338 For more information see Documentation/vm/slub.txt.
3340 slab_max_order= [MM, SLAB]
3341 Determines the maximum allowed order for slabs.
3342 A high setting may cause OOMs due to memory
3343 fragmentation. Defaults to 1 for systems with
3344 more than 32MB of RAM, 0 otherwise.
3346 slub_debug[=options[,slabs]] [MM, SLUB]
3347 Enabling slub_debug allows one to determine the
3348 culprit if slab objects become corrupted. Enabling
3349 slub_debug can create guard zones around objects and
3350 may poison objects when not in use. Also tracks the
3351 last alloc / free. For more information see
3352 Documentation/vm/slub.txt.
3354 slub_max_order= [MM, SLUB]
3355 Determines the maximum allowed order for slabs.
3356 A high setting may cause OOMs due to memory
3357 fragmentation. For more information see
3358 Documentation/vm/slub.txt.
3360 slub_min_objects= [MM, SLUB]
3361 The minimum number of objects per slab. SLUB will
3362 increase the slab order up to slub_max_order to
3363 generate a sufficiently large slab able to contain
3364 the number of objects indicated. The higher the number
3365 of objects the smaller the overhead of tracking slabs
3366 and the less frequently locks need to be acquired.
3367 For more information see Documentation/vm/slub.txt.
3369 slub_min_order= [MM, SLUB]
3370 Determines the minimum page order for slabs. Must be
3371 lower than slub_max_order.
3372 For more information see Documentation/vm/slub.txt.
3374 slub_nomerge [MM, SLUB]
3375 Same with slab_nomerge. This is supported for legacy.
3376 See slab_nomerge for more information.
3379 Format: <io1>[,<io2>[,...,<io8>]]
3381 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3382 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3383 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3384 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3385 smsc-ircc2.ircc_irq= [HW] IRQ line
3386 smsc-ircc2.ircc_dma= [HW] DMA channel
3387 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3388 0: Toshiba Satellite 1800 (GP data pin select)
3389 1: Fast pin select (default)
3393 [KNL] Should the soft-lockup detector generate panics.
3396 softlockup_all_cpu_backtrace=
3397 [KNL] Should the soft-lockup detector generate
3398 backtraces on all cpus.
3401 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3402 See Documentation/laptops/sonypi.txt
3404 spia_io_base= [HW,MTD]
3410 Enabled the stack tracer on boot up.
3412 stacktrace_filter=[function-list]
3413 [FTRACE] Limit the functions that the stack tracer
3414 will trace at boot up. function-list is a comma separated
3415 list of functions. This list can be changed at run
3416 time by the stack_trace_filter file in the debugfs
3417 tracing directory. Note, this enables stack tracing
3418 and the stacktrace above is not needed.
3422 Set the STI (builtin display/keyboard on the HP-PARISC
3423 machines) console (graphic card) which should be used
3424 as the initial boot-console.
3425 See also comment in drivers/video/console/sticore.c.
3428 See comment in drivers/video/console/sticore.c.
3431 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3433 sunrpc.min_resvport=
3434 sunrpc.max_resvport=
3436 SunRPC servers often require that client requests
3437 originate from a privileged port (i.e. a port in the
3438 range 0 < portnr < 1024).
3439 An administrator who wishes to reserve some of these
3440 ports for other uses may adjust the range that the
3441 kernel's sunrpc client considers to be privileged
3442 using these two parameters to set the minimum and
3443 maximum port values.
3447 Control how the NFS server code allocates CPUs to
3448 service thread pools. Depending on how many NICs
3449 you have and where their interrupts are bound, this
3450 option will affect which CPUs will do NFS serving.
3451 Note: this parameter cannot be changed while the
3452 NFS server is running.
3454 auto the server chooses an appropriate mode
3455 automatically using heuristics
3456 global a single global pool contains all CPUs
3457 percpu one pool for each CPU
3458 pernode one pool for each NUMA node (equivalent
3459 to global on non-NUMA machines)
3461 sunrpc.tcp_slot_table_entries=
3462 sunrpc.udp_slot_table_entries=
3464 Sets the upper limit on the number of simultaneous
3465 RPC calls that can be sent from the client to a
3466 server. Increasing these values may allow you to
3467 improve throughput, but will also increase the
3468 amount of memory reserved for use by the client.
3471 [KNL] Enable accounting of swap in memory resource
3472 controller if no parameter or 1 is given or disable
3473 it if 0 is given (See Documentation/cgroups/memory.txt)
3475 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3476 Format: { <int> | force }
3477 <int> -- Number of I/O TLB slabs
3478 force -- force using of bounce buffers even if they
3479 wouldn't be automatically used by the kernel
3483 sysfs.deprecated=0|1 [KNL]
3484 Enable/disable old style sysfs layout for old udev
3485 on older distributions. When this option is enabled
3486 very new udev will not work anymore. When this option
3487 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3488 in older udev will not work anymore.
3489 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3490 the kernel configuration.
3492 sysrq_always_enabled
3494 Ignore sysrq setting - this boot parameter will
3495 neutralize any effect of /proc/sys/kernel/sysrq.
3496 Useful for debugging.
3498 tcpmhash_entries= [KNL,NET]
3499 Set the number of tcp_metrics_hash slots.
3500 Default value is 8192 or 16384 depending on total
3501 ram pages. This is used to specify the TCP metrics
3502 cache size. See Documentation/networking/ip-sysctl.txt
3503 "tcp_no_metrics_save" section for more details.
3507 test_suspend= [SUSPEND][,N]
3508 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3509 standby suspend) or "freeze" (for suspend type freeze)
3510 as the system sleep state during system startup with
3511 the optional capability to repeat N number of times.
3512 The system is woken from this state using a
3513 wakeup-capable RTC alarm.
3515 thash_entries= [KNL,NET]
3516 Set number of hash buckets for TCP connection
3518 thermal.act= [HW,ACPI]
3519 -1: disable all active trip points in all thermal zones
3520 <degrees C>: override all lowest active trip points
3522 thermal.crt= [HW,ACPI]
3523 -1: disable all critical trip points in all thermal zones
3524 <degrees C>: override all critical trip points
3526 thermal.nocrt= [HW,ACPI]
3527 Set to disable actions on ACPI thermal zone
3528 critical and hot trip points.
3530 thermal.off= [HW,ACPI]
3531 1: disable ACPI thermal control
3533 thermal.psv= [HW,ACPI]
3534 -1: disable all passive trip points
3535 <degrees C>: override all passive trip points to this
3538 thermal.tzp= [HW,ACPI]
3539 Specify global default ACPI thermal zone polling rate
3540 <deci-seconds>: poll all this frequency
3541 0: no polling (default)
3544 Force threading of all interrupt handlers except those
3545 marked explicitly IRQF_NO_THREAD.
3548 Enable the Transcendent memory driver if built-in.
3550 tmem.cleancache=0|1 [KNL, XEN]
3551 Default is on (1). Disable the usage of the cleancache
3552 API to send anonymous pages to the hypervisor.
3554 tmem.frontswap=0|1 [KNL, XEN]
3555 Default is on (1). Disable the usage of the frontswap
3556 API to send swap pages to the hypervisor. If disabled
3557 the selfballooning and selfshrinking are force disabled.
3559 tmem.selfballooning=0|1 [KNL, XEN]
3560 Default is on (1). Disable the driving of swap pages
3563 tmem.selfshrinking=0|1 [KNL, XEN]
3564 Default is on (1). Partial swapoff that immediately
3565 transfers pages from Xen hypervisor back to the
3566 kernel based on different criteria.
3570 Specify if the kernel should make use of the cpu
3571 topology information if the hardware supports this.
3572 The scheduler will make use of this information and
3573 e.g. base its process migration decisions on it.
3576 topology_updates= [KNL, PPC, NUMA]
3578 Specify if the kernel should ignore (off)
3579 topology updates sent by the hypervisor to this
3584 tpm_suspend_pcr=[HW,TPM]
3585 Format: integer pcr id
3586 Specify that at suspend time, the tpm driver
3587 should extend the specified pcr with zeros,
3588 as a workaround for some chips which fail to
3589 flush the last written pcr on TPM_SaveState.
3590 This will guarantee that all the other pcrs
3593 trace_buf_size=nn[KMG]
3594 [FTRACE] will set tracing buffer size on each cpu.
3596 trace_event=[event-list]
3597 [FTRACE] Set and start specified trace events in order
3598 to facilitate early boot debugging.
3599 See also Documentation/trace/events.txt
3601 trace_options=[option-list]
3602 [FTRACE] Enable or disable tracer options at boot.
3603 The option-list is a comma delimited list of options
3604 that can be enabled or disabled just as if you were
3605 to echo the option name into
3607 /sys/kernel/debug/tracing/trace_options
3609 For example, to enable stacktrace option (to dump the
3610 stack trace of each event), add to the command line:
3612 trace_options=stacktrace
3614 See also Documentation/trace/ftrace.txt "trace options"
3618 Have the tracepoints sent to printk as well as the
3619 tracing ring buffer. This is useful for early boot up
3620 where the system hangs or reboots and does not give the
3621 option for reading the tracing buffer or performing a
3622 ftrace_dump_on_oops.
3624 To turn off having tracepoints sent to printk,
3625 echo 0 > /proc/sys/kernel/tracepoint_printk
3626 Note, echoing 1 into this file without the
3627 tracepoint_printk kernel cmdline option has no effect.
3631 Having tracepoints sent to printk() and activating high
3632 frequency tracepoints such as irq or sched, can cause
3633 the system to live lock.
3636 [FTRACE] enable this option to disable tracing when a
3637 warning is hit. This turns off "tracing_on". Tracing can
3638 be enabled again by echoing '1' into the "tracing_on"
3639 file located in /sys/kernel/debug/tracing/
3641 This option is useful, as it disables the trace before
3642 the WARNING dump is called, which prevents the trace to
3643 be filled with content caused by the warning output.
3645 This option can also be set at run time via the sysctl
3646 option: kernel/traceoff_on_warning
3648 transparent_hugepage=
3650 Format: [always|madvise|never]
3651 Can be used to control the default behavior of the system
3652 with respect to transparent hugepages.
3653 See Documentation/vm/transhuge.txt for more details.
3655 tsc= Disable clocksource stability checks for TSC.
3657 [x86] reliable: mark tsc clocksource as reliable, this
3658 disables clocksource verification at runtime, as well
3659 as the stability checks done at bootup. Used to enable
3660 high-resolution timer mode on older hardware, and in
3661 virtualized environment.
3662 [x86] noirqtime: Do not use TSC to do irq accounting.
3663 Used to run time disable IRQ_TIME_ACCOUNTING on any
3664 platforms where RDTSC is slow and this accounting
3667 turbografx.map[2|3]= [HW,JOY]
3668 TurboGraFX parallel port interface
3670 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3671 See also Documentation/input/joystick-parport.txt
3673 udbg-immortal [PPC] When debugging early kernel crashes that
3674 happen after console_init() and before a proper
3675 console driver takes over, this boot options might
3676 help "seeing" what's going on.
3678 uhash_entries= [KNL,NET]
3679 Set number of hash buckets for UDP/UDP-Lite connections
3682 [USB] Ignore overcurrent events (default N).
3683 Some badly-designed motherboards generate lots of
3684 bogus events, for ports that aren't wired to
3685 anything. Set this parameter to avoid log spamming.
3686 Note that genuine overcurrent events won't be
3690 [X86] Cause panic on unknown NMI.
3692 usbcore.authorized_default=
3693 [USB] Default USB device authorization:
3694 (default -1 = authorized except for wireless USB,
3695 0 = not authorized, 1 = authorized)
3697 usbcore.autosuspend=
3698 [USB] The autosuspend time delay (in seconds) used
3699 for newly-detected USB devices (default 2). This
3700 is the time required before an idle device will be
3701 autosuspended. Devices for which the delay is set
3702 to a negative value won't be autosuspended at all.
3704 usbcore.usbfs_snoop=
3705 [USB] Set to log all usbfs traffic (default 0 = off).
3707 usbcore.blinkenlights=
3708 [USB] Set to cycle leds on hubs (default 0 = off).
3710 usbcore.old_scheme_first=
3711 [USB] Start with the old device initialization
3712 scheme (default 0 = off).
3714 usbcore.usbfs_memory_mb=
3715 [USB] Memory limit (in MB) for buffers allocated by
3716 usbfs (default = 16, 0 = max = 2047).
3718 usbcore.use_both_schemes=
3719 [USB] Try the other device initialization scheme
3720 if the first one fails (default 1 = enabled).
3722 usbcore.initial_descriptor_timeout=
3723 [USB] Specifies timeout for the initial 64-byte
3724 USB_REQ_GET_DESCRIPTOR request in milliseconds
3725 (default 5000 = 5.0 seconds).
3728 [USBHID] The interval which mice are to be polled at.
3730 usb-storage.delay_use=
3731 [UMS] The delay in seconds before a new device is
3732 scanned for Logical Units (default 1).
3735 [UMS] A list of quirks entries to supplement or
3736 override the built-in unusual_devs list. List
3737 entries are separated by commas. Each entry has
3738 the form VID:PID:Flags where VID and PID are Vendor
3739 and Product ID values (4-digit hex numbers) and
3740 Flags is a set of characters, each corresponding
3741 to a common usb-storage quirk flag as follows:
3742 a = SANE_SENSE (collect more than 18 bytes
3744 b = BAD_SENSE (don't collect more than 18
3745 bytes of sense data);
3746 c = FIX_CAPACITY (decrease the reported
3747 device capacity by one sector);
3748 d = NO_READ_DISC_INFO (don't use
3749 READ_DISC_INFO command);
3750 e = NO_READ_CAPACITY_16 (don't use
3751 READ_CAPACITY_16 command);
3752 f = NO_REPORT_OPCODES (don't use report opcodes
3754 h = CAPACITY_HEURISTICS (decrease the
3755 reported device capacity by one
3756 sector if the number is odd);
3757 i = IGNORE_DEVICE (don't bind to this
3759 l = NOT_LOCKABLE (don't try to lock and
3760 unlock ejectable media);
3761 m = MAX_SECTORS_64 (don't transfer more
3762 than 64 sectors = 32 KB at a time);
3763 n = INITIAL_READ10 (force a retry of the
3764 initial READ(10) command);
3765 o = CAPACITY_OK (accept the capacity
3766 reported by the device);
3767 p = WRITE_CACHE (the device cache is ON
3769 r = IGNORE_RESIDUE (the device reports
3770 bogus residue values);
3771 s = SINGLE_LUN (the device has only one
3773 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3774 commands, uas only);
3775 u = IGNORE_UAS (don't bind to the uas driver);
3776 w = NO_WP_DETECT (don't test whether the
3777 medium is write-protected).
3778 Example: quirks=0419:aaf5:rl,0421:0433:rc
3780 user_debug= [KNL,ARM]
3782 See arch/arm/Kconfig.debug help text.
3783 1 - undefined instruction events
3785 4 - invalid data aborts
3788 Example: user_debug=31
3791 [X86] Flags controlling user PTE allocations.
3793 nohigh = do not allocate PTE pages in
3794 HIGHMEM regardless of setting
3798 On X86_32, this is an alias for vdso32=. Otherwise:
3800 vdso=1: enable VDSO (the default)
3801 vdso=0: disable VDSO mapping
3803 vdso32= [X86] Control the 32-bit vDSO
3804 vdso32=1: enable 32-bit VDSO
3805 vdso32=0 or vdso32=2: disable 32-bit VDSO
3807 See the help text for CONFIG_COMPAT_VDSO for more
3808 details. If CONFIG_COMPAT_VDSO is set, the default is
3809 vdso32=0; otherwise, the default is vdso32=1.
3811 For compatibility with older kernels, vdso32=2 is an
3814 Try vdso32=0 if you encounter an error that says:
3815 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3818 vector=percpu: enable percpu vector domain
3820 video= [FB] Frame buffer configuration
3821 See Documentation/fb/modedb.txt.
3823 video.brightness_switch_enabled= [0,1]
3824 If set to 1, on receiving an ACPI notify event
3825 generated by hotkey, video driver will adjust brightness
3826 level and then send out the event to user space through
3827 the allocated input device; If set to 0, video driver
3828 will only send out the event without touching backlight
3833 [VMMIO] Memory mapped virtio (platform) device.
3835 <size>@<baseaddr>:<irq>[:<id>]
3837 <size> := size (can use standard suffixes
3839 <baseaddr> := physical base address
3840 <irq> := interrupt number (as passed to
3842 <id> := (optional) platform device id
3844 virtio_mmio.device=1K@0x100b0000:48:7
3846 Can be used multiple times for multiple devices.
3848 vga= [BOOT,X86-32] Select a particular video mode
3849 See Documentation/x86/boot.txt and
3850 Documentation/svga.txt.
3851 Use vga=ask for menu.
3852 This is actually a boot loader parameter; the value is
3853 passed to the kernel using a special protocol.
3855 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3856 size of <nn>. This can be used to increase the
3857 minimum size (128MB on x86). It can also be used to
3858 decrease the size and leave more room for directly
3861 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3864 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3867 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3871 Controls the behavior of vsyscalls (i.e. calls to
3872 fixed addresses of 0xffffffffff600x00 from legacy
3873 code). Most statically-linked binaries and older
3874 versions of glibc use these calls. Because these
3875 functions are at fixed addresses, they make nice
3876 targets for exploits that can control RIP.
3878 emulate [default] Vsyscalls turn into traps and are
3879 emulated reasonably safely.
3881 native Vsyscalls are native syscall instructions.
3882 This is a little bit faster than trapping
3883 and makes a few dynamic recompilers work
3884 better than they would in emulation mode.
3885 It also makes exploits much easier to write.
3887 none Vsyscalls don't work at all. This makes
3888 them quite hard to use for exploits but
3889 might break your system.
3891 vt.color= [VT] Default text color.
3892 Format: 0xYX, X = foreground, Y = background.
3893 Default: 0x07 = light gray on black.
3895 vt.cur_default= [VT] Default cursor shape.
3896 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3897 the parameters of the <Esc>[?A;B;Cc escape sequence;
3898 see VGA-softcursor.txt. Default: 2 = underline.
3900 vt.default_blu= [VT]
3901 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3902 Change the default blue palette of the console.
3903 This is a 16-member array composed of values
3906 vt.default_grn= [VT]
3907 Format: <green0>,<green1>,<green2>,...,<green15>
3908 Change the default green palette of the console.
3909 This is a 16-member array composed of values
3912 vt.default_red= [VT]
3913 Format: <red0>,<red1>,<red2>,...,<red15>
3914 Change the default red palette of the console.
3915 This is a 16-member array composed of values
3921 Set system-wide default UTF-8 mode for all tty's.
3922 Default is 1, i.e. UTF-8 mode is enabled for all
3923 newly opened terminals.
3925 vt.global_cursor_default=
3928 Set system-wide default for whether a cursor
3929 is shown on new VTs. Default is -1,
3930 i.e. cursors will be created by default unless
3931 overridden by individual drivers. 0 will hide
3932 cursors, 1 will display them.
3934 vt.italic= [VT] Default color for italic text; 0-15.
3937 vt.underline= [VT] Default color for underlined text; 0-15.
3940 watchdog timers [HW,WDT] For information on watchdog timers,
3941 see Documentation/watchdog/watchdog-parameters.txt
3942 or other driver-specific files in the
3943 Documentation/watchdog/ directory.
3945 workqueue.disable_numa
3946 By default, all work items queued to unbound
3947 workqueues are affine to the NUMA nodes they're
3948 issued on, which results in better behavior in
3949 general. If NUMA affinity needs to be disabled for
3950 whatever reason, this option can be used. Note
3951 that this also can be controlled per-workqueue for
3952 workqueues visible under /sys/bus/workqueue/.
3954 workqueue.power_efficient
3955 Per-cpu workqueues are generally preferred because
3956 they show better performance thanks to cache
3957 locality; unfortunately, per-cpu workqueues tend to
3958 be more power hungry than unbound workqueues.
3960 Enabling this makes the per-cpu workqueues which
3961 were observed to contribute significantly to power
3962 consumption unbound, leading to measurably lower
3963 power usage at the cost of small performance
3966 The default value of this parameter is determined by
3967 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3969 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3970 default x2apic cluster mode on platforms
3973 x86_intel_mid_timer= [X86-32,APBT]
3974 Choose timer option for x86 Intel MID platform.
3975 Two valid options are apbt timer only and lapic timer
3976 plus one apbt timer for broadcast timer.
3977 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3979 xen_emul_unplug= [HW,X86,XEN]
3980 Unplug Xen emulated devices
3981 Format: [unplug0,][unplug1]
3982 ide-disks -- unplug primary master IDE devices
3983 aux-ide-disks -- unplug non-primary-master IDE devices
3984 nics -- unplug network devices
3985 all -- unplug all emulated devices (NICs and IDE disks)
3986 unnecessary -- unplugging emulated devices is
3987 unnecessary even if the host did not respond to
3989 never -- do not unplug even if version check succeeds
3991 xen_nopvspin [X86,XEN]
3992 Disables the ticketlock slowpath using Xen PV
3996 Disables the PV optimizations forcing the HVM guest to
3997 run as generic HVM guest with no PV drivers.
3999 xirc2ps_cs= [NET,PCMCIA]
4001 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4003 ______________________________________________________________________
4007 Add more DRM drivers.
projects / cascardo / linux.git / blob