4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_apic_instance= [ACPI, IOAPIC]
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 Format: <irq>,<irq>...
267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
272 This feature is enabled by default.
273 This option allows to turn off the feature.
275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
296 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
297 acpi_osi="string1" # add string1
298 acpi_osi="!string2" # remove string2
299 acpi_osi=!* # remove all strings
300 acpi_osi=! # disable all built-in OS vendor
302 acpi_osi= # disable all strings
304 'acpi_osi=!' can be used in combination with single or
305 multiple 'acpi_osi="string1"' to support specific OS
306 vendor string(s). Note that such command can only
307 affect the default state of the OS vendor strings, thus
308 it cannot affect the default state of the feature group
309 strings and the current state of the OS vendor strings,
310 specifying it multiple times through kernel command line
311 is meaningless. This command is useful when one do not
312 care about the state of the feature group strings which
313 should be controlled by the OSPM.
315 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
316 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
317 can make '_OSI("Windows 2000")' TRUE.
319 'acpi_osi=' cannot be used in combination with other
320 'acpi_osi=' command lines, the _OSI method will not
321 exist in the ACPI namespace. NOTE that such command can
322 only affect the _OSI support state, thus specifying it
323 multiple times through kernel command line is also
326 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
329 'acpi_osi=!*' can be used in combination with single or
330 multiple 'acpi_osi="string1"' to support specific
331 string(s). Note that such command can affect the
332 current state of both the OS vendor strings and the
333 feature group strings, thus specifying it multiple times
334 through kernel command line is meaningful. But it may
335 still not able to affect the final state of a string if
336 there are quirks related to this string. This command
337 is useful when one want to control the state of the
338 feature group strings to debug BIOS issues related to
341 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
342 '_OSI("Module Device")' FALSE.
343 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
344 '_OSI("Module Device")' TRUE.
345 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
347 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
349 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
350 they all will make '_OSI("Windows 2000")' TRUE.
353 Override the pmtimer bug detection: force the kernel
354 to assume that this machine's pmtimer latches its value
355 and always returns good values.
357 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
358 Format: { level | edge | high | low }
360 acpi_skip_timer_override [HW,ACPI]
361 Recognize and ignore IRQ0/pin2 Interrupt Override.
362 For broken nForce2 BIOS resulting in XT-PIC timer.
364 acpi_sleep= [HW,ACPI] Sleep options
365 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
366 old_ordering, nonvs, sci_force_enable }
367 See Documentation/power/video.txt for information on
369 s3_beep is for debugging; it makes the PC's speaker beep
370 as soon as the kernel's real-mode entry point is called.
371 s4_nohwsig prevents ACPI hardware signature from being
372 used during resume from hibernation.
373 old_ordering causes the ACPI 1.0 ordering of the _PTS
374 control method, with respect to putting devices into
375 low power states, to be enforced (the ACPI 2.0 ordering
376 of _PTS is used by default).
377 nonvs prevents the kernel from saving/restoring the
378 ACPI NVS memory during suspend/hibernation and resume.
379 sci_force_enable causes the kernel to set SCI_EN directly
380 on resume from S1/S3 (which is against the ACPI spec,
381 but some broken systems don't work without it).
383 acpi_use_timer_override [HW,ACPI]
384 Use timer override. For some broken Nvidia NF5 boards
385 that require a timer override, but don't have HPET
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
735 For now, only VisioBraille is supported.
737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
750 [X86] Delay for N microsec between assert and de-assert
751 of APIC INIT to start processors. This delay occurs
752 on every CPU online, such as boot, and resume from suspend.
755 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
757 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
759 crashkernel=size[KMG][@offset[KMG]]
760 [KNL] Using kexec, Linux can switch to a 'crash kernel'
761 upon panic. This parameter reserves the physical
762 memory region [offset, offset + size] for that kernel
763 image. If '@offset' is omitted, then a suitable offset
764 is selected automatically. Check
765 Documentation/kdump/kdump.txt for further details.
767 crashkernel=range1:size1[,range2:size2,...][@offset]
768 [KNL] Same as above, but depends on the memory
769 in the running system. The syntax of range is
770 start-[end] where start and end are both
771 a memory unit (amount[KMG]). See also
772 Documentation/kdump/kdump.txt for an example.
774 crashkernel=size[KMG],high
775 [KNL, x86_64] range could be above 4G. Allow kernel
776 to allocate physical memory region from top, so could
777 be above 4G if system have more than 4G ram installed.
778 Otherwise memory region will be allocated below 4G, if
780 It will be ignored if crashkernel=X is specified.
781 crashkernel=size[KMG],low
782 [KNL, x86_64] range under 4G. When crashkernel=X,high
783 is passed, kernel could allocate physical memory region
784 above 4G, that cause second kernel crash on system
785 that require some amount of low memory, e.g. swiotlb
786 requires at least 64M+32K low memory. Kernel would
787 try to allocate 72M below 4G automatically.
788 This one let user to specify own low range under 4G
789 for second kernel instead.
790 0: to disable low allocation.
791 It will be ignored when crashkernel=X,high is not used
792 or memory reserved is below 4G.
797 cs89x0_media= [HW,NET]
798 Format: { rj45 | aui | bnc }
801 See header of drivers/s390/block/dasd_devmap.c.
803 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
804 (one device per port)
805 Format: <port#>,<type>
806 See also Documentation/input/joystick-parport.txt
808 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
809 time. See Documentation/dynamic-debug-howto.txt for
810 details. Deprecated, see dyndbg.
812 debug [KNL] Enable kernel debugging (events log level).
815 [KNL] verbose self-tests
817 Print debugging info while doing the locking API
819 We default to 0 (no extra messages), setting it to
820 1 will print _a lot_ more information - normally
821 only useful to kernel developers.
823 debug_objects [KNL] Enable object debugging
826 [KNL] Disable object debugging
828 debug_guardpage_minorder=
829 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
830 parameter allows control of the order of pages that will
831 be intentionally kept free (and hence protected) by the
832 buddy allocator. Bigger value increase the probability
833 of catching random memory corruption, but reduce the
834 amount of memory for normal system use. The maximum
835 possible value is MAX_ORDER/2. Setting this parameter
836 to 1 or 2 should be enough to identify most random
837 memory corruption problems caused by bugs in kernel or
838 driver code when a CPU writes to (or reads from) a
839 random memory location. Note that there exists a class
840 of memory corruptions problems caused by buggy H/W or
841 F/W or by drivers badly programing DMA (basically when
842 memory is written at bus level and the CPU MMU is
843 bypassed) which are not detectable by
844 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
845 tracking down these problems.
848 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
849 parameter enables the feature at boot time. In
850 default, it is disabled. We can avoid allocating huge
851 chunk of memory for debug pagealloc if we don't enable
852 it at boot time and the system will work mostly same
853 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
854 on: enable the feature
856 debugpat [X86] Enable PAT debugging
858 decnet.addr= [HW,NET]
859 Format: <area>[,<node>]
860 See also Documentation/networking/decnet.txt.
863 [same as hugepagesz=] The size of the default
864 HugeTLB page size. This is the size represented by
865 the legacy /proc/ hugepages APIs, used for SHM, and
866 default size when mounting hugetlbfs filesystems.
867 Defaults to the default architecture's huge page size
871 Set number of hash buckets for dentry cache.
874 See Documentation/networking/ipv6.txt.
876 disable_cpu_apicid= [X86,APIC,SMP]
878 The number of initial APIC ID for the
879 corresponding CPU to be disabled at boot,
880 mostly used for the kdump 2nd kernel to
881 disable BSP to wake up multiple CPUs without
882 causing system reset or hang due to sending
885 disable_ddw [PPC/PSERIES]
886 Disable Dynamic DMA Window support. Use this if
887 to workaround buggy firmware.
890 See Documentation/networking/ipv6.txt.
892 disable_mtrr_cleanup [X86]
893 The kernel tries to adjust MTRR layout from continuous
894 to discrete, to make X server driver able to add WB
895 entry later. This parameter disables that.
897 disable_mtrr_trim [X86, Intel and AMD only]
898 By default the kernel will trim any uncacheable
899 memory out of your available memory pool based on
900 MTRR settings. This parameter disables that behavior,
901 possibly causing your machine to run very slowly.
903 disable_timer_pin_1 [X86]
904 Disable PIN 1 of APIC timer
905 Can be useful to work around chipset bugs.
907 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
908 this option disables the debugging code at boot.
910 dma_debug_entries=<number>
911 This option allows to tune the number of preallocated
912 entries for DMA-API debugging code. One entry is
913 required per DMA-API allocation. Use this if the
914 DMA-API debugging code disables itself because the
915 architectural default is too low.
917 dma_debug_driver=<driver_name>
918 With this option the DMA-API debugging driver
919 filter feature can be enabled at boot time. Just
920 pass the driver to filter for as the parameter.
921 The filter can be disabled or changed to another
922 driver later using sysfs.
924 drm_kms_helper.edid_firmware=[<connector>:]<file>
925 Broken monitors, graphic adapters and KVMs may
926 send no or incorrect EDID data sets. This parameter
927 allows to specify an EDID data set in the
928 /lib/firmware directory that is used instead.
929 Generic built-in EDID data sets are used, if one of
930 edid/1024x768.bin, edid/1280x1024.bin,
931 edid/1680x1050.bin, or edid/1920x1080.bin is given
932 and no file with the same name exists. Details and
933 instructions how to build your own EDID data are
934 available in Documentation/EDID/HOWTO.txt. An EDID
935 data set will only be used for a particular connector,
936 if its name and a colon are prepended to the EDID
941 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
942 module.dyndbg[="val"]
943 Enable debug messages at boot time. See
944 Documentation/dynamic-debug-howto.txt for details.
946 nompx [X86] Disables Intel Memory Protection Extensions.
947 See Documentation/x86/intel_mpx.txt for more
948 information about the feature.
951 on enable eager fpu restore
952 off disable eager fpu restore
953 auto selects the default scheme, which automatically
954 enables eagerfpu restore for xsaveopt.
956 early_ioremap_debug [KNL]
957 Enable debug messages in early_ioremap support. This
958 is useful for tracking down temporary early mappings
959 which are not unmapped.
961 earlycon= [KNL] Output early console device and options.
964 Start an early, polled-mode console on a cadence serial
965 port at the specified address. The cadence serial port
966 must already be setup and configured. Options are not
969 uart[8250],io,<addr>[,options]
970 uart[8250],mmio,<addr>[,options]
971 uart[8250],mmio32,<addr>[,options]
972 uart[8250],0x<addr>[,options]
973 Start an early, polled-mode console on the 8250/16550
974 UART at the specified I/O port or MMIO address.
975 MMIO inter-register address stride is either 8-bit
976 (mmio) or 32-bit (mmio32).
977 If none of [io|mmio|mmio32], <addr> is assumed to be
978 equivalent to 'mmio'. 'options' are specified in the
979 same format described for "console=ttyS<n>"; if
980 unspecified, the h/w is not initialized.
983 Start an early, polled-mode console on a pl011 serial
984 port at the specified address. The pl011 serial port
985 must already be setup and configured. Options are not
989 Start an early, polled-mode console on an msm serial
990 port at the specified address. The serial port
991 must already be setup and configured. Options are not
995 Start an early, polled-mode console on an msm serial
996 dm port at the specified address. The serial port
997 must already be setup and configured. Options are not
1000 smh Use ARM semihosting calls for early console.
1008 Use early console provided by serial driver available
1009 on Samsung SoCs, requires selecting proper type and
1010 a correct base address of the selected UART port. The
1011 serial port must already be setup and configured.
1012 Options are not yet supported.
1014 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1018 earlyprintk=serial[,ttySn[,baudrate]]
1019 earlyprintk=serial[,0x...[,baudrate]]
1020 earlyprintk=ttySn[,baudrate]
1021 earlyprintk=dbgp[debugController#]
1022 earlyprintk=pciserial,bus:device.function[,baudrate]
1024 earlyprintk is useful when the kernel crashes before
1025 the normal console is initialized. It is not enabled by
1026 default because it has some cosmetic problems.
1028 Append ",keep" to not disable it when the real console
1031 Only one of vga, efi, serial, or usb debug port can
1034 Currently only ttyS0 and ttyS1 may be specified by
1035 name. Other I/O ports may be explicitly specified
1036 on some architectures (x86 and arm at least) by
1037 replacing ttySn with an I/O port address, like this:
1038 earlyprintk=serial,0x1008,115200
1039 You can find the port for a given device in
1040 /proc/tty/driver/serial:
1041 2: uart:ST16650V2 port:00001008 irq:18 ...
1043 Interaction with the standard serial driver is not
1046 The VGA and EFI output is eventually overwritten by
1049 The xen output can only be used by Xen PV guests.
1051 edac_report= [HW,EDAC] Control how to report EDAC event
1052 Format: {"on" | "off" | "force"}
1053 on: enable EDAC to report H/W event. May be overridden
1054 by other higher priority error reporting module.
1055 off: disable H/W event reporting through EDAC.
1056 force: enforce the use of EDAC to report H/W event.
1059 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1062 This is designed to be used in conjunction with
1063 the boot argument: earlyprintk=vga
1066 Format: {"off" | "on" | "skip[mbr]"}
1069 Format: { "old_map", "nochunk", "noruntime", "debug" }
1070 old_map [X86-64]: switch to the old ioremap-based EFI
1071 runtime services mapping. 32-bit still uses this one by
1073 nochunk: disable reading files in "chunks" in the EFI
1074 boot stub, as chunking can cause problems with some
1075 firmware implementations.
1076 noruntime : disable EFI runtime services support
1077 debug: enable misc debug output
1079 efi_no_storage_paranoia [EFI; X86]
1080 Using this parameter you can use more than 50% of
1081 your efi variable storage. Use this parameter only if
1082 you are really sure that your UEFI does sane gc and
1083 fulfills the spec otherwise your board may brick.
1085 eisa_irq_edge= [PARISC,HW]
1086 See header of drivers/parisc/eisa.c.
1089 See comment before function elanfreq_setup() in
1090 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1093 Format: {"cfq" | "deadline" | "noop"}
1094 See Documentation/block/cfq-iosched.txt and
1095 Documentation/block/deadline-iosched.txt for details.
1097 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1098 Specifies physical address of start of kernel core
1099 image elf header and optionally the size. Generally
1100 kexec loader will pass this option to capture kernel.
1101 See Documentation/kdump/kdump.txt for details.
1103 enable_mtrr_cleanup [X86]
1104 The kernel tries to adjust MTRR layout from continuous
1105 to discrete, to make X server driver able to add WB
1106 entry later. This parameter enables that.
1108 enable_timer_pin_1 [X86]
1109 Enable PIN 1 of APIC timer
1110 Can be useful to work around chipset bugs
1111 (in particular on some ATI chipsets).
1112 The kernel tries to set a reasonable default.
1114 enforcing [SELINUX] Set initial enforcing status.
1116 See security/selinux/Kconfig help text.
1117 0 -- permissive (log only, no denials).
1118 1 -- enforcing (deny and log).
1120 Value can be changed at runtime via /selinux/enforce.
1123 Disable Error Record Serialization Table (ERST)
1126 ether= [HW,NET] Ethernet cards parameters
1127 This option is obsoleted by the "netdev=" option, which
1128 has equivalent usage. See its documentation for details.
1132 Permit 'security.evm' to be updated regardless of
1133 current integrity status.
1137 fail_make_request=[KNL]
1138 General fault injection mechanism.
1139 Format: <interval>,<probability>,<space>,<times>
1140 See also Documentation/fault-injection/.
1143 See Documentation/blockdev/floppy.txt.
1145 force_pal_cache_flush
1146 [IA-64] Avoid check_sal_cache_flush which may hang on
1147 buggy SAL_CACHE_FLUSH implementations. Using this
1148 parameter will force ia64_sal_cache_flush to call
1149 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1152 Forcefully enable Physical Address Extension (PAE).
1153 Many Pentium M systems disable PAE but may have a
1154 functionally usable PAE implementation.
1155 Warning: use of this parameter will taint the kernel
1156 and may cause unknown problems.
1159 [FTRACE] will set and start the specified tracer
1160 as early as possible in order to facilitate early
1163 ftrace_dump_on_oops[=orig_cpu]
1164 [FTRACE] will dump the trace buffers on oops.
1165 If no parameter is passed, ftrace will dump
1166 buffers of all CPUs, but if you pass orig_cpu, it will
1167 dump only the buffer of the CPU that triggered the
1170 ftrace_filter=[function-list]
1171 [FTRACE] Limit the functions traced by the function
1172 tracer at boot up. function-list is a comma separated
1173 list of functions. This list can be changed at run
1174 time by the set_ftrace_filter file in the debugfs
1177 ftrace_notrace=[function-list]
1178 [FTRACE] Do not trace the functions specified in
1179 function-list. This list can be changed at run time
1180 by the set_ftrace_notrace file in the debugfs
1183 ftrace_graph_filter=[function-list]
1184 [FTRACE] Limit the top level callers functions traced
1185 by the function graph tracer at boot up.
1186 function-list is a comma separated list of functions
1187 that can be changed at run time by the
1188 set_graph_function file in the debugfs tracing directory.
1190 ftrace_graph_notrace=[function-list]
1191 [FTRACE] Do not trace from the functions specified in
1192 function-list. This list is a comma separated list of
1193 functions that can be changed at run time by the
1194 set_graph_notrace file in the debugfs tracing directory.
1197 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1198 support via parallel port (up to 5 devices per port)
1199 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1200 See also Documentation/input/joystick-parport.txt
1204 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1208 gcov_persist= [GCOV] When non-zero (default), profiling data for
1209 kernel modules is saved and remains accessible via
1210 debugfs, even when the module is unloaded/reloaded.
1211 When zero, profiling data is discarded and associated
1212 debugfs files are removed at module unload time.
1214 gpt [EFI] Forces disk with valid GPT signature but
1215 invalid Protective MBR to be treated as GPT. If the
1216 primary GPT is corrupted, it enables the backup/alternate
1217 GPT to be used instead.
1219 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1220 the "Enable 0" bit of the configuration register.
1223 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1224 the "Enable 0" bit of the configuration register.
1227 grcan.select= [HW] Select which physical interface to use.
1230 grcan.txsize= [HW] Sets the size of the tx buffer.
1231 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1233 grcan.rxsize= [HW] Sets the size of the rx buffer.
1234 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1237 hashdist= [KNL,NUMA] Large hashes allocated during boot
1238 are distributed across NUMA nodes. Defaults on
1239 for 64-bit NUMA, off otherwise.
1240 Format: 0 | 1 (for off | on)
1242 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1244 hd= [EIDE] (E)IDE hard drive subsystem geometry
1245 Format: <cyl>,<head>,<sect>
1248 Disable Hardware Error Source Table (HEST) support;
1249 corresponding firmware-first mode error processing
1250 logic will be disabled.
1252 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1253 size of <nn>. This works even on boxes that have no
1254 highmem otherwise. This also works to reduce highmem
1255 size on bigger boxes.
1257 highres= [KNL] Enable/disable high resolution timer mode.
1258 Valid parameters: "on", "off"
1262 See Documentation/isdn/README.HiSax.
1266 hpet= [X86-32,HPET] option to control HPET usage
1267 Format: { enable (default) | disable | force |
1269 disable: disable HPET and use PIT instead
1270 force: allow force enabled of undocumented chips (ICH4,
1272 verbose: show contents of HPET registers during setup
1274 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1275 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1277 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1278 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1279 On x86-64 and powerpc, this option can be specified
1280 multiple times interleaved with hugepages= to reserve
1281 huge pages of different sizes. Valid pages sizes on
1282 x86-64 are 2M (when the CPU supports "pse") and 1G
1283 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1285 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1286 terminal devices. Valid values: 0..8
1287 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1288 If specified, z/VM IUCV HVC accepts connections
1289 from listed z/VM user IDs only.
1291 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1292 hardware thread id mappings.
1293 Format: <cpu>:<hwthread>
1296 Do not unregister boot console at start. This is only
1297 useful for debugging when something happens in the window
1298 between unregistering the boot console and initializing
1301 i2c_bus= [HW] Override the default board specific I2C bus speed
1302 or register an additional I2C bus that is not
1303 registered from board initialization code.
1307 i8042.debug [HW] Toggle i8042 debug mode
1308 i8042.direct [HW] Put keyboard port into non-translated mode
1309 i8042.dumbkbd [HW] Pretend that controller can only read data from
1310 keyboard and cannot control its state
1311 (Don't attempt to blink the leds)
1312 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1313 i8042.nokbd [HW] Don't check/create keyboard port
1314 i8042.noloop [HW] Disable the AUX Loopback command while probing
1316 i8042.nomux [HW] Don't check presence of an active multiplexing
1318 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1320 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1321 i8042.reset [HW] Reset the controller during init and cleanup
1322 i8042.unlock [HW] Unlock (ignore) the keylock
1323 i8042.kbdreset [HW] Reset device connected to KBD port
1327 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1328 indicates that the driver is running on unsupported
1330 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1331 does not match list of supported models.
1333 [HW] Report power status in /proc/i8k
1334 (disabled by default)
1335 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1338 i915.invert_brightness=
1339 [DRM] Invert the sense of the variable that is used to
1340 set the brightness of the panel backlight. Normally a
1341 brightness value of 0 indicates backlight switched off,
1342 and the maximum of the brightness value sets the backlight
1343 to maximum brightness. If this parameter is set to 0
1344 (default) and the machine requires it, or this parameter
1345 is set to 1, a brightness value of 0 sets the backlight
1346 to maximum brightness, and the maximum of the brightness
1347 value switches the backlight off.
1348 -1 -- never invert brightness
1349 0 -- machine default
1350 1 -- force brightness inversion
1353 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1355 ide-core.nodma= [HW] (E)IDE subsystem
1356 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1357 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1358 .cdrom .chs .ignore_cable are additional options
1359 See Documentation/ide/ide.txt.
1361 ide-generic.probe-mask= [HW] (E)IDE subsystem
1363 Probe mask for legacy ISA IDE ports. Depending on
1364 platform up to 6 ports are supported, enabled by
1365 setting corresponding bits in the mask to 1. The
1366 default value is 0x0, which has a special meaning.
1367 On systems that have PCI, it triggers scanning the
1368 PCI bus for the first and the second port, which
1369 are then probed. On systems without PCI the value
1370 of 0x0 enables probing the two first ports as if it
1373 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1374 Claim all unknown PCI IDE storage controllers.
1377 Format: idle=poll, idle=halt, idle=nomwait
1378 Poll forces a polling idle loop that can slightly
1379 improve the performance of waking up a idle CPU, but
1380 will use a lot of power and make the system run hot.
1382 idle=halt: Halt is forced to be used for CPU idle.
1383 In such case C2/C3 won't be used again.
1384 idle=nomwait: Disable mwait for CPU C-states
1386 ignore_loglevel [KNL]
1387 Ignore loglevel setting - this will print /all/
1388 kernel messages to the console. Useful for debugging.
1389 We also add it as printk module parameter, so users
1390 could change it dynamically, usually by
1391 /sys/module/printk/parameters/ignore_loglevel.
1393 ihash_entries= [KNL]
1394 Set number of hash buckets for inode cache.
1396 ima_appraise= [IMA] appraise integrity measurements
1397 Format: { "off" | "enforce" | "fix" | "log" }
1400 ima_appraise_tcb [IMA]
1401 The builtin appraise policy appraises all files
1405 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1409 The list of supported hash algorithms is defined
1410 in crypto/hash_info.h.
1413 Load a policy which meets the needs of the Trusted
1414 Computing Base. This means IMA will measure all
1415 programs exec'd, files mmap'd for exec, and all files
1416 opened for read by uid=0.
1419 Select one of defined IMA measurements template formats.
1420 Formats: { "ima" | "ima-ng" }
1424 [IMA] Define a custom template format.
1425 Format: { "field1|...|fieldN" }
1427 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1428 Format: <min_file_size>
1429 Set the minimal file size for using asynchronous hash.
1430 If left unspecified, ahash usage is disabled.
1432 ahash performance varies for different data sizes on
1433 different crypto accelerators. This option can be used
1434 to achieve the best performance for a particular HW.
1436 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1438 Set hashing buffer size. Default: 4k.
1440 ahash performance varies for different chunk sizes on
1441 different crypto accelerators. This option can be used
1442 to achieve best performance for particular HW.
1446 Run specified binary instead of /sbin/init as init
1449 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1450 for working out where the kernel is dying during
1453 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1454 initcall functions. Useful for debugging built-in
1455 modules and initcalls.
1457 initrd= [BOOT] Specify the location of the initial ramdisk
1459 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1462 int_pln_enable [x86] Enable power limit notification interrupt
1464 integrity_audit=[IMA]
1465 Format: { "0" | "1" }
1466 0 -- basic integrity auditing messages. (Default)
1467 1 -- additional integrity auditing messages.
1469 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1471 Enable intel iommu driver.
1473 Disable intel iommu driver.
1474 igfx_off [Default Off]
1475 By default, gfx is mapped as normal device. If a gfx
1476 device has a dedicated DMAR unit, the DMAR unit is
1477 bypassed by not enabling DMAR with this option. In
1478 this case, gfx device will use physical address for
1481 With this option iommu will not optimize to look
1482 for io virtual address below 32-bit forcing dual
1483 address cycle on pci bus for cards supporting greater
1484 than 32-bit addressing. The default is to look
1485 for translation below 32-bit and if not available
1486 then look in the higher range.
1487 strict [Default Off]
1488 With this option on every unmap_single operation will
1489 result in a hardware IOTLB flush operation as opposed
1490 to batching them for performance.
1491 sp_off [Default Off]
1492 By default, super page will be supported if Intel IOMMU
1493 has the capability. With this option, super page will
1495 ecs_off [Default Off]
1496 By default, extended context tables will be supported if
1497 the hardware advertises that it has support both for the
1498 extended tables themselves, and also PASID support. With
1499 this option set, extended tables will not be used even
1500 on hardware which claims to support them.
1502 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1503 0 disables intel_idle and fall back on acpi_idle.
1504 1 to 6 specify maximum depth of C-state.
1508 Do not enable intel_pstate as the default
1509 scaling driver for the supported processors
1511 Enable intel_pstate on systems that prohibit it by default
1512 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1513 instead of acpi-cpufreq may disable platform features, such
1514 as thermal controls and power capping, that rely on ACPI
1515 P-States information being indicated to OSPM and therefore
1516 should be used with caution. This option does not work with
1517 processors that aren't supported by the intel_pstate driver
1518 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1520 Do not enable hardware P state control (HWP)
1523 Only load intel_pstate on systems which support
1524 hardware P state control (HWP) if available.
1526 intremap= [X86-64, Intel-IOMMU]
1527 on enable Interrupt Remapping (default)
1528 off disable Interrupt Remapping
1529 nosid disable Source ID checking
1531 BIOS x2APIC opt-out request will be ignored
1533 iomem= Disable strict checking of access to MMIO memory
1534 strict regions from userspace.
1549 nobypass [PPC/POWERNV]
1550 Disable IOMMU bypass, using IOMMU for PCI devices.
1553 io7= [HW] IO7 for Marvel based alpha systems
1554 See comment before marvel_specify_io7 in
1555 arch/alpha/kernel/core_marvel.c.
1557 io_delay= [X86] I/O delay method
1559 Standard port 0x80 based delay
1561 Alternate port 0xed based delay (needed on some systems)
1563 Simple two microseconds delay
1568 See Documentation/filesystems/nfs/nfsroot.txt.
1571 When an interrupt is not handled search all handlers
1572 for it. Intended to get systems with badly broken
1576 When an interrupt is not handled search all handlers
1577 for it. Also check all handlers each timer
1578 interrupt. Intended to get systems with badly broken
1582 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1584 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1586 <cpu number>,...,<cpu number>
1588 <cpu number>-<cpu number>
1589 (must be a positive range in ascending order)
1591 <cpu number>,...,<cpu number>-<cpu number>
1593 This option can be used to specify one or more CPUs
1594 to isolate from the general SMP balancing and scheduling
1595 algorithms. You can move a process onto or off an
1596 "isolated" CPU via the CPU affinity syscalls or cpuset.
1597 <cpu number> begins at 0 and the maximum value is
1598 "number of CPUs in system - 1".
1600 This option is the preferred way to isolate CPUs. The
1601 alternative -- manually setting the CPU mask of all
1602 tasks in the system -- can cause problems and
1603 suboptimal load balancer performance.
1607 ivrs_ioapic [HW,X86_64]
1608 Provide an override to the IOAPIC-ID<->DEVICE-ID
1609 mapping provided in the IVRS ACPI table. For
1610 example, to map IOAPIC-ID decimal 10 to
1611 PCI device 00:14.0 write the parameter as:
1612 ivrs_ioapic[10]=00:14.0
1614 ivrs_hpet [HW,X86_64]
1615 Provide an override to the HPET-ID<->DEVICE-ID
1616 mapping provided in the IVRS ACPI table. For
1617 example, to map HPET-ID decimal 0 to
1618 PCI device 00:14.0 write the parameter as:
1619 ivrs_hpet[0]=00:14.0
1621 js= [HW,JOY] Analog joystick
1622 See Documentation/input/joystick.txt.
1625 Enable/disable kernel and module base offset ASLR
1626 (Address Space Layout Randomization) if built into
1627 the kernel. When CONFIG_HIBERNATION is selected,
1628 kASLR is disabled by default. When kASLR is enabled,
1629 hibernation will be disabled.
1633 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1634 specifies the amount of memory usable by the kernel
1635 for non-movable allocations. The requested amount is
1636 spread evenly throughout all nodes in the system. The
1637 remaining memory in each node is used for Movable
1638 pages. In the event, a node is too small to have both
1639 kernelcore and Movable pages, kernelcore pages will
1640 take priority and other nodes will have a larger number
1641 of Movable pages. The Movable zone is used for the
1642 allocation of pages that may be reclaimed or moved
1643 by the page migration subsystem. This means that
1644 HugeTLB pages may not be allocated from this zone.
1645 Note that allocations like PTEs-from-HighMem still
1646 use the HighMem zone if it exists, and the Normal
1647 zone if it does not.
1649 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1650 Format: <Controller#>[,poll interval]
1651 The controller # is the number of the ehci usb debug
1652 port as it is probed via PCI. The poll interval is
1653 optional and is the number seconds in between
1654 each poll cycle to the debug port in case you need
1655 the functionality for interrupting the kernel with
1656 gdb or control-c on the dbgp connection. When
1657 not using this parameter you use sysrq-g to break into
1658 the kernel debugger.
1660 kgdboc= [KGDB,HW] kgdb over consoles.
1661 Requires a tty driver that supports console polling,
1662 or a supported polling keyboard driver (non-usb).
1663 Serial only format: <serial_device>[,baud]
1664 keyboard only format: kbd
1665 keyboard and serial format: kbd,<serial_device>[,baud]
1666 Optional Kernel mode setting:
1667 kms, kbd format: kms,kbd
1668 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1670 kgdbwait [KGDB] Stop kernel execution and enter the
1671 kernel debugger at the earliest opportunity.
1673 kmac= [MIPS] korina ethernet MAC address.
1674 Configure the RouterBoard 532 series on-chip
1675 Ethernet adapter MAC address.
1677 kmemleak= [KNL] Boot-time kmemleak enable/disable
1678 Valid arguments: on, off
1680 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1683 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1684 Valid arguments: 0, 1, 2
1685 kmemcheck=0 (disabled)
1686 kmemcheck=1 (enabled)
1687 kmemcheck=2 (one-shot mode)
1688 Default: 2 (one-shot mode)
1690 kstack=N [X86] Print N words from the kernel stack
1693 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1694 Default is 0 (don't ignore, but inject #GP)
1696 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1700 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1701 Default is 1 (enabled)
1703 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1705 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1707 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1708 (virtualized MMU) support on capable Intel chips.
1709 Default is 1 (enabled)
1711 kvm-intel.emulate_invalid_guest_state=
1712 [KVM,Intel] Enable emulation of invalid guest states
1713 Default is 0 (disabled)
1715 kvm-intel.flexpriority=
1716 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1717 Default is 1 (enabled)
1720 [KVM,Intel] Enable VMX nesting (nVMX).
1721 Default is 0 (disabled)
1723 kvm-intel.unrestricted_guest=
1724 [KVM,Intel] Disable unrestricted guest feature
1725 (virtualized real and unpaged mode) on capable
1726 Intel chips. Default is 1 (enabled)
1728 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1729 feature (tagged TLBs) on capable Intel chips.
1730 Default is 1 (enabled)
1736 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1739 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1740 value for LAPIC timer one-shot implementation. Default
1741 back to the programmable timer unit in the LAPIC.
1743 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1746 libata.dma= [LIBATA] DMA control
1747 libata.dma=0 Disable all PATA and SATA DMA
1748 libata.dma=1 PATA and SATA Disk DMA only
1749 libata.dma=2 ATAPI (CDROM) DMA only
1750 libata.dma=4 Compact Flash DMA only
1751 Combinations also work, so libata.dma=3 enables DMA
1752 for disks and CDROMs, but not CFs.
1754 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1755 libata.ignore_hpa=0 keep BIOS limits (default)
1756 libata.ignore_hpa=1 ignore limits, using full disk
1758 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1762 libata.force= [LIBATA] Force configurations. The format is comma
1763 separated list of "[ID:]VAL" where ID is
1764 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1765 matching port, link or device. Basically, it matches
1766 the ATA ID string printed on console by libata. If
1767 the whole ID part is omitted, the last PORT and DEVICE
1768 values are used. If ID hasn't been specified yet, the
1769 configuration applies to all ports, links and devices.
1771 If only DEVICE is omitted, the parameter applies to
1772 the port and all links and devices behind it. DEVICE
1773 number of 0 either selects the first device or the
1774 first fan-out link behind PMP device. It does not
1775 select the host link. DEVICE number of 15 selects the
1776 host link and device attached to it.
1778 The VAL specifies the configuration to force. As long
1779 as there's no ambiguity shortcut notation is allowed.
1780 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1781 The following configurations can be forced.
1783 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1784 Any ID with matching PORT is used.
1786 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1788 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1789 udma[/][16,25,33,44,66,100,133] notation is also
1792 * [no]ncq: Turn on or off NCQ.
1794 * [no]ncqtrim: Turn off queued DSM TRIM.
1796 * nohrst, nosrst, norst: suppress hard, soft
1799 * rstonce: only attempt one reset during
1800 hot-unplug link recovery
1802 * dump_id: dump IDENTIFY data.
1804 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1806 * disable: Disable this device.
1808 If there are multiple matching configurations changing
1809 the same attribute, the last one is used.
1811 memblock=debug [KNL] Enable memblock debug messages.
1813 load_ramdisk= [RAM] List of ramdisks to load from floppy
1814 See Documentation/blockdev/ramdisk.txt.
1816 lockd.nlm_grace_period=P [NFS] Assign grace period.
1819 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1822 lockd.nlm_timeout=T [NFS] Assign timeout value.
1825 lockd.nlm_udpport=M [NFS] Assign UDP port.
1828 locktorture.nreaders_stress= [KNL]
1829 Set the number of locking read-acquisition kthreads.
1830 Defaults to being automatically set based on the
1831 number of online CPUs.
1833 locktorture.nwriters_stress= [KNL]
1834 Set the number of locking write-acquisition kthreads.
1836 locktorture.onoff_holdoff= [KNL]
1837 Set time (s) after boot for CPU-hotplug testing.
1839 locktorture.onoff_interval= [KNL]
1840 Set time (s) between CPU-hotplug operations, or
1841 zero to disable CPU-hotplug testing.
1843 locktorture.shuffle_interval= [KNL]
1844 Set task-shuffle interval (jiffies). Shuffling
1845 tasks allows some CPUs to go into dyntick-idle
1846 mode during the locktorture test.
1848 locktorture.shutdown_secs= [KNL]
1849 Set time (s) after boot system shutdown. This
1850 is useful for hands-off automated testing.
1852 locktorture.stat_interval= [KNL]
1853 Time (s) between statistics printk()s.
1855 locktorture.stutter= [KNL]
1856 Time (s) to stutter testing, for example,
1857 specifying five seconds causes the test to run for
1858 five seconds, wait for five seconds, and so on.
1859 This tests the locking primitive's ability to
1860 transition abruptly to and from idle.
1862 locktorture.torture_runnable= [BOOT]
1863 Start locktorture running at boot time.
1865 locktorture.torture_type= [KNL]
1866 Specify the locking implementation to test.
1868 locktorture.verbose= [KNL]
1869 Enable additional printk() statements.
1871 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1874 loglevel= All Kernel Messages with a loglevel smaller than the
1875 console loglevel will be printed to the console. It can
1876 also be changed with klogd or other programs. The
1877 loglevels are defined as follows:
1879 0 (KERN_EMERG) system is unusable
1880 1 (KERN_ALERT) action must be taken immediately
1881 2 (KERN_CRIT) critical conditions
1882 3 (KERN_ERR) error conditions
1883 4 (KERN_WARNING) warning conditions
1884 5 (KERN_NOTICE) normal but significant condition
1885 6 (KERN_INFO) informational
1886 7 (KERN_DEBUG) debug-level messages
1888 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1889 in bytes. n must be a power of two and greater
1890 than the minimal size. The minimal size is defined
1891 by LOG_BUF_SHIFT kernel config parameter. There is
1892 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1893 that allows to increase the default size depending on
1894 the number of CPUs. See init/Kconfig for more details.
1896 logo.nologo [FB] Disables display of the built-in Linux logo.
1897 This may be used to provide more screen space for
1898 kernel log messages and is useful when debugging
1899 kernel boot problems.
1901 lp=0 [LP] Specify parallel ports to use, e.g,
1902 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1903 lp=reset first parallel port). 'lp=0' disables the
1904 lp=auto printer driver. 'lp=reset' (which can be
1905 specified in addition to the ports) causes
1906 attached printers to be reset. Using
1907 lp=port1,port2,... specifies the parallel ports
1908 to associate lp devices with, starting with
1909 lp0. A port specification may be 'none' to skip
1910 that lp device, or a parport name such as
1911 'parport0'. Specifying 'lp=auto' instead of a
1912 port specification list means that device IDs
1913 from each port should be examined, to see if
1914 an IEEE 1284-compliant printer is attached; if
1915 so, the driver will manage that printer.
1916 See also header of drivers/char/lp.c.
1919 Sets loops_per_jiffy to given constant, thus avoiding
1920 time-consuming boot-time autodetection (up to 250 ms per
1921 CPU). 0 enables autodetection (default). To determine
1922 the correct value for your kernel, boot with normal
1923 autodetection and see what value is printed. Note that
1924 on SMP systems the preset will be applied to all CPUs,
1925 which is likely to cause problems if your CPUs need
1926 significantly divergent settings. An incorrect value
1927 will cause delays in the kernel to be wrong, leading to
1928 unpredictable I/O errors and other breakage. Although
1929 unlikely, in the extreme case this might damage your
1933 Format: <io>,<irq>,<dma>
1935 machvec= [IA-64] Force the use of a particular machine-vector
1936 (machvec) in a generic kernel.
1937 Example: machvec=hpzx1_swiotlb
1939 machtype= [Loongson] Share the same kernel image file between different
1941 Example: machtype=lemote-yeeloong-2f-7inch
1943 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1944 than or equal to this physical address is ignored.
1946 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1947 should make use of. maxcpus=n : n >= 0 limits the
1948 kernel to using 'n' processors. n=0 is a special case,
1949 it is equivalent to "nosmp", which also disables
1952 max_loop= [LOOP] The number of loop block devices that get
1953 (loop.max_loop) unconditionally pre-created at init time. The default
1954 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1955 of statically allocating a predefined number, loop
1956 devices can be requested on-demand with the
1957 /dev/loop-control interface.
1959 mce [X86-32] Machine Check Exception
1961 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1963 md= [HW] RAID subsystems devices and level
1964 See Documentation/md.txt.
1967 Format: <first>,<last>
1968 Specifies range of consoles to be captured by the MDA.
1970 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1971 Amount of memory to be used when the kernel is not able
1972 to see the whole system memory or for test.
1973 [X86] Work as limiting max address. Use together
1974 with memmap= to avoid physical address space collisions.
1975 Without memmap= PCI devices could be placed at addresses
1976 belonging to unused RAM.
1978 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1982 [KNL,SH] Allow user to override the default size for
1983 per-device physically contiguous DMA buffers.
1985 memmap=exactmap [KNL,X86] Enable setting of an exact
1986 E820 memory map, as specified by the user.
1987 Such memmap=exactmap lines can be constructed based on
1988 BIOS output or other requirements. See the memmap=nn@ss
1991 memmap=nn[KMG]@ss[KMG]
1992 [KNL] Force usage of a specific region of memory.
1993 Region of memory to be used is from ss to ss+nn.
1995 memmap=nn[KMG]#ss[KMG]
1996 [KNL,ACPI] Mark specific memory as ACPI data.
1997 Region of memory to be marked is from ss to ss+nn.
1999 memmap=nn[KMG]$ss[KMG]
2000 [KNL,ACPI] Mark specific memory as reserved.
2001 Region of memory to be reserved is from ss to ss+nn.
2002 Example: Exclude memory from 0x18690000-0x1869ffff
2003 memmap=64K$0x18690000
2005 memmap=0x10000$0x18690000
2007 memmap=nn[KMG]!ss[KMG]
2008 [KNL,X86] Mark specific memory as protected.
2009 Region of memory to be used, from ss to ss+nn.
2010 The memory region may be marked as e820 type 12 (0xc)
2011 and is NVDIMM or ADR memory.
2013 memory_corruption_check=0/1 [X86]
2014 Some BIOSes seem to corrupt the first 64k of
2015 memory when doing things like suspend/resume.
2016 Setting this option will scan the memory
2017 looking for corruption. Enabling this will
2018 both detect corruption and prevent the kernel
2019 from using the memory being corrupted.
2020 However, its intended as a diagnostic tool; if
2021 repeatable BIOS-originated corruption always
2022 affects the same memory, you can use memmap=
2023 to prevent the kernel from using that memory.
2025 memory_corruption_check_size=size [X86]
2026 By default it checks for corruption in the low
2027 64k, making this memory unavailable for normal
2028 use. Use this parameter to scan for
2029 corruption in more or less memory.
2031 memory_corruption_check_period=seconds [X86]
2032 By default it checks for corruption every 60
2033 seconds. Use this parameter to check at some
2034 other rate. 0 disables periodic checking.
2036 memtest= [KNL,X86,ARM] Enable memtest
2038 default : 0 <disable>
2039 Specifies the number of memtest passes to be
2040 performed. Each pass selects another test
2041 pattern from a given set of patterns. Memtest
2042 fills the memory with this pattern, validates
2043 memory contents and reserves bad memory
2044 regions that are detected.
2046 meye.*= [HW] Set MotionEye Camera parameters
2047 See Documentation/video4linux/meye.txt.
2049 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2050 Multi-Function General Purpose Timers on AMD Geode
2053 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2054 the BIOS has incorrectly applied a workaround. TinyBIOS
2055 version 0.98 is known to be affected, 0.99 fixes the
2056 problem by letting the user disable the workaround.
2060 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2061 physical address is ignored.
2063 mini2440= [ARM,HW,KNL]
2064 Format:[0..2][b][c][t]
2066 MINI2440 configuration specification:
2067 0 - The attached screen is the 3.5" TFT
2068 1 - The attached screen is the 7" TFT
2069 2 - The VGA Shield is attached (1024x768)
2070 Leaving out the screen size parameter will not load
2071 the TFT driver, and the framebuffer will be left
2073 b - Enable backlight. The TFT backlight pin will be
2074 linked to the kernel VESA blanking code and a GPIO
2075 LED. This parameter is not necessary when using the
2077 c - Enable the s3c camera interface.
2078 t - Reserved for enabling touchscreen support. The
2079 touchscreen support is not enabled in the mainstream
2080 kernel as of 2.6.30, a preliminary port can be found
2081 in the "bleeding edge" mini2440 support kernel at
2082 http://repo.or.cz/w/linux-2.6/mini2440.git
2085 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2086 parameter allows control of the logging verbosity for
2087 the additional memory initialisation checks. A value
2088 of 0 disables mminit logging and a level of 4 will
2089 log everything. Information is printed at KERN_DEBUG
2090 so loglevel=8 may also need to be specified.
2093 [KNL] When CONFIG_MODULE_SIG is set, this means that
2094 modules without (valid) signatures will fail to load.
2095 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2096 is always true, so this option does nothing.
2099 [MOUSE] Maximum time between finger touching and
2100 leaving touchpad surface for touch to be considered
2101 a tap and be reported as a left button click (for
2102 touchpads working in absolute mode only).
2104 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2105 reporting absolute coordinates, such as tablets
2106 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2107 reporting absolute coordinates, such as tablets
2109 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2110 is similar to kernelcore except it specifies the
2111 amount of memory used for migratable allocations.
2112 If both kernelcore and movablecore is specified,
2113 then kernelcore will be at *least* the specified
2114 value but may be more. If movablecore on its own
2115 is specified, the administrator must be careful
2116 that the amount of memory usable for all allocations
2119 movable_node [KNL,X86] Boot-time switch to enable the effects
2120 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2122 MTD_Partition= [MTD]
2123 Format: <name>,<region-number>,<size>,<offset>
2125 MTD_Region= [MTD] Format:
2126 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2129 See drivers/mtd/cmdlinepart.c.
2131 multitce=off [PPC] This parameter disables the use of the pSeries
2132 firmware feature for updating multiple TCE entries
2135 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2137 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2139 boundary - index of last SLC block on Flex-OneNAND.
2140 The remaining blocks are configured as MLC blocks.
2141 lock - Configure if Flex-OneNAND boundary should be locked.
2142 Once locked, the boundary cannot be changed.
2143 1 indicates lock status, 0 indicates unlock status.
2146 ARM/S3C2412 JIVE boot control
2148 See arch/arm/mach-s3c2412/mach-jive.c
2150 mtouchusb.raw_coordinates=
2151 [HW] Make the MicroTouch USB driver use raw coordinates
2152 ('y', default) or cooked coordinates ('n')
2154 mtrr_chunk_size=nn[KMG] [X86]
2155 used for mtrr cleanup. It is largest continuous chunk
2156 that could hold holes aka. UC entries.
2158 mtrr_gran_size=nn[KMG] [X86]
2159 Used for mtrr cleanup. It is granularity of mtrr block.
2161 Large value could prevent small alignment from
2164 mtrr_spare_reg_nr=n [X86]
2166 Range: 0,7 : spare reg number
2168 Used for mtrr cleanup. It is spare mtrr entries number.
2169 Set to 2 or more if your graphical card needs more.
2171 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2173 netdev= [NET] Network devices parameters
2174 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2175 Note that mem_start is often overloaded to mean
2176 something different and driver-specific.
2177 This usage is only documented in each driver source
2181 [NETFILTER] Enable connection tracking flow accounting
2182 0 to disable accounting
2183 1 to enable accounting
2186 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2187 See Documentation/filesystems/nfs/nfsroot.txt.
2189 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2190 See Documentation/filesystems/nfs/nfsroot.txt.
2192 nfsrootdebug [NFS] enable nfsroot debugging messages.
2193 See Documentation/filesystems/nfs/nfsroot.txt.
2195 nfs.callback_tcpport=
2196 [NFS] set the TCP port on which the NFSv4 callback
2197 channel should listen.
2200 [NFS] sets the pathname to the program which is used
2201 to update the NFS client cache entries.
2203 nfs.cache_getent_timeout=
2204 [NFS] sets the timeout after which an attempt to
2205 update a cache entry is deemed to have failed.
2207 nfs.idmap_cache_timeout=
2208 [NFS] set the maximum lifetime for idmapper cache
2212 [NFS] enable 64-bit inode numbers.
2213 If zero, the NFS client will fake up a 32-bit inode
2214 number for the readdir() and stat() syscalls instead
2215 of returning the full 64-bit number.
2216 The default is to return 64-bit inode numbers.
2218 nfs.max_session_slots=
2219 [NFSv4.1] Sets the maximum number of session slots
2220 the client will attempt to negotiate with the server.
2221 This limits the number of simultaneous RPC requests
2222 that the client can send to the NFSv4.1 server.
2223 Note that there is little point in setting this
2224 value higher than the max_tcp_slot_table_limit.
2226 nfs.nfs4_disable_idmapping=
2227 [NFSv4] When set to the default of '1', this option
2228 ensures that both the RPC level authentication
2229 scheme and the NFS level operations agree to use
2230 numeric uids/gids if the mount is using the
2231 'sec=sys' security flavour. In effect it is
2232 disabling idmapping, which can make migration from
2233 legacy NFSv2/v3 systems to NFSv4 easier.
2234 Servers that do not support this mode of operation
2235 will be autodetected by the client, and it will fall
2236 back to using the idmapper.
2237 To turn off this behaviour, set the value to '0'.
2239 [NFS4] Specify an additional fixed unique ident-
2240 ification string that NFSv4 clients can insert into
2241 their nfs_client_id4 string. This is typically a
2242 UUID that is generated at system install time.
2244 nfs.send_implementation_id =
2245 [NFSv4.1] Send client implementation identification
2246 information in exchange_id requests.
2247 If zero, no implementation identification information
2249 The default is to send the implementation identification
2252 nfs.recover_lost_locks =
2253 [NFSv4] Attempt to recover locks that were lost due
2254 to a lease timeout on the server. Please note that
2255 doing this risks data corruption, since there are
2256 no guarantees that the file will remain unchanged
2257 after the locks are lost.
2258 If you want to enable the kernel legacy behaviour of
2259 attempting to recover these locks, then set this
2261 The default parameter value of '0' causes the kernel
2262 not to attempt recovery of lost locks.
2264 nfsd.nfs4_disable_idmapping=
2265 [NFSv4] When set to the default of '1', the NFSv4
2266 server will return only numeric uids and gids to
2267 clients using auth_sys, and will accept numeric uids
2268 and gids from such clients. This is intended to ease
2269 migration from NFSv2/v3.
2271 objlayoutdriver.osd_login_prog=
2272 [NFS] [OBJLAYOUT] sets the pathname to the program which
2273 is used to automatically discover and login into new
2274 osd-targets. Please see:
2275 Documentation/filesystems/pnfs.txt for more explanations
2277 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2278 when a NMI is triggered.
2279 Format: [state][,regs][,debounce][,die]
2281 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2282 Format: [panic,][nopanic,][num]
2284 0 - turn nmi_watchdog off
2285 1 - turn nmi_watchdog on
2286 When panic is specified, panic when an NMI watchdog
2287 timeout occurs (or 'nopanic' to override the opposite
2289 This is useful when you use a panic=... timeout and
2290 need the box quickly up again.
2292 netpoll.carrier_timeout=
2293 [NET] Specifies amount of time (in seconds) that
2294 netpoll should wait for a carrier. By default netpoll
2297 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2298 emulation library even if a 387 maths coprocessor
2302 [HW] Never suspend the console
2303 Disable suspending of consoles during suspend and
2304 hibernate operations. Once disabled, debugging
2305 messages can reach various consoles while the rest
2306 of the system is being put to sleep (ie, while
2307 debugging driver suspend/resume hooks). This may
2308 not work reliably with all consoles, but is known
2309 to work with serial and VGA consoles.
2310 To facilitate more flexible debugging, we also add
2311 console_suspend, a printk module parameter to control
2312 it. Users could use console_suspend (usually
2313 /sys/module/printk/parameters/console_suspend) to
2314 turn on/off it dynamically.
2316 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2317 caches in the slab allocator. Saves per-node memory,
2318 but will impact performance.
2322 noapic [SMP,APIC] Tells the kernel to not make use of any
2323 IOAPICs that may be present in the system.
2325 noautogroup Disable scheduler automatic task group creation.
2327 nobats [PPC] Do not use BATs for mapping kernel lowmem
2328 on "Classic" PPC cores.
2332 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2334 nodelayacct [KNL] Disable per-task delay accounting
2336 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2338 nodsp [SH] Disable hardware DSP at boot time.
2340 noefi Disable EFI runtime services support.
2345 On X86-32 available only on PAE configured kernels.
2346 noexec=on: enable non-executable mappings (default)
2347 noexec=off: disable non-executable mappings
2350 Disable SMAP (Supervisor Mode Access Prevention)
2351 even if it is supported by processor.
2354 Disable SMEP (Supervisor Mode Execution Prevention)
2355 even if it is supported by processor.
2358 This affects only 32-bit executables.
2359 noexec32=on: enable non-executable mappings (default)
2360 read doesn't imply executable mappings
2361 noexec32=off: disable non-executable mappings
2362 read implies executable mappings
2364 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2366 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2367 register save and restore. The kernel will only save
2368 legacy floating-point registers on task switch.
2370 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2372 noxsave [BUGS=X86] Disables x86 extended register state save
2373 and restore using xsave. The kernel will fallback to
2374 enabling legacy floating-point and sse state.
2376 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2377 register states. The kernel will fall back to use
2378 xsave to save the states. By using this parameter,
2379 performance of saving the states is degraded because
2380 xsave doesn't support modified optimization while
2381 xsaveopt supports it on xsaveopt enabled systems.
2383 noxsaves [X86] Disables xsaves and xrstors used in saving and
2384 restoring x86 extended register state in compacted
2385 form of xsave area. The kernel will fall back to use
2386 xsaveopt and xrstor to save and restore the states
2387 in standard form of xsave area. By using this
2388 parameter, xsave area per process might occupy more
2389 memory on xsaves enabled systems.
2391 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2392 wfi(ARM) instruction doesn't work correctly and not to
2393 use it. This is also useful when using JTAG debugger.
2395 no_file_caps Tells the kernel not to honor file capabilities. The
2396 only way then for a file to be executed with privilege
2397 is to be setuid root or executed by root.
2399 nohalt [IA-64] Tells the kernel not to use the power saving
2400 function PAL_HALT_LIGHT when idle. This increases
2401 power-consumption. On the positive side, it reduces
2402 interrupt wake-up latency, which may improve performance
2403 in certain environments such as networked servers or
2406 nohibernate [HIBERNATION] Disable hibernation and resume.
2408 nohz= [KNL] Boottime enable/disable dynamic ticks
2409 Valid arguments: on, off
2412 nohz_full= [KNL,BOOT]
2413 In kernels built with CONFIG_NO_HZ_FULL=y, set
2414 the specified list of CPUs whose tick will be stopped
2415 whenever possible. The boot CPU will be forced outside
2416 the range to maintain the timekeeping.
2417 The CPUs in this range must also be included in the
2420 noiotrap [SH] Disables trapped I/O port accesses.
2422 noirqdebug [X86-32] Disables the code which attempts to detect and
2423 disable unhandled interrupt sources.
2425 no_timer_check [X86,APIC] Disables the code which tests for
2426 broken timer IRQ sources.
2428 noisapnp [ISAPNP] Disables ISA PnP code.
2430 noinitrd [RAM] Tells the kernel not to load any configured
2433 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2435 [Deprecated - use intremap=off]
2439 nojitter [IA-64] Disables jitter checking for ITC timers.
2441 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2443 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2446 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2447 steal time is computed, but won't influence scheduler
2450 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2452 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2454 noltlbs [PPC] Do not use large page/tlb entries for kernel
2455 lowmem mapping on PPC40x.
2457 nomca [IA-64] Disable machine check abort handling
2459 nomce [X86-32] Disable Machine Check Exception
2461 nomfgpt [X86-32] Disable Multi-Function General Purpose
2462 Timer usage (for AMD Geode machines).
2464 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2465 shutdown the other cpus. Instead use the REBOOT_VECTOR
2468 nomodule Disable module load
2470 nopat [X86] Disable PAT (page attribute table extension of
2471 pagetables) support.
2473 norandmaps Don't use address space randomization. Equivalent to
2474 echo 0 > /proc/sys/kernel/randomize_va_space
2476 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2478 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2479 with UP alternatives
2481 nordrand [X86] Disable kernel use of the RDRAND and
2482 RDSEED instructions even if they are supported
2483 by the processor. RDRAND and RDSEED are still
2484 available to user space applications.
2486 noresume [SWSUSP] Disables resume and restores original swap
2489 no-scroll [VGA] Disables scrollback.
2490 This is required for the Braillex ib80-piezo Braille
2491 reader made by F.H. Papenmeier (Germany).
2495 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2497 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2498 and disable the IO APIC. legacy for "maxcpus=0".
2500 nosoftlockup [KNL] Disable the soft-lockup detector.
2502 nosync [HW,M68K] Disables sync negotiation for all devices.
2504 notsc [BUGS=X86-32] Disable Time Stamp Counter
2506 nousb [USB] Disable the USB subsystem
2508 nowatchdog [KNL] Disable both lockup detectors, i.e.
2509 soft-lockup and NMI watchdog (hard-lockup).
2513 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2515 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2516 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2517 Some features depend on CPU0. Known dependencies are:
2518 1. Resume from suspend/hibernate depends on CPU0.
2519 Suspend/hibernate will fail if CPU0 is offline and you
2520 need to online CPU0 before suspend/hibernate.
2521 2. PIC interrupts also depend on CPU0. CPU0 can't be
2522 removed if a PIC interrupt is detected.
2523 It's said poweroff/reboot may depend on CPU0 on some
2524 machines although I haven't seen such issues so far
2525 after CPU0 is offline on a few tested machines.
2526 If the dependencies are under your control, you can
2527 turn on cpu0_hotplug.
2529 nptcg= [IA-64] Override max number of concurrent global TLB
2530 purges which is reported from either PAL_VM_SUMMARY or
2533 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2534 could support. nr_cpus=n : n >= 1 limits the kernel to
2535 supporting 'n' processors. Later in runtime you can not
2536 use hotplug cpu feature to put more cpu back to online.
2537 just like you compile the kernel NR_CPUS=n
2539 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2541 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2542 Allowed values are enable and disable
2544 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2545 one of ['zone', 'node', 'default'] can be specified
2546 This can be set from sysctl after boot.
2547 See Documentation/sysctl/vm.txt for details.
2549 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2550 See Documentation/debugging-via-ohci1394.txt for more
2553 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2554 Rather than timing out after 20 ms if an EC
2555 command is not properly ACKed, override the length
2556 of the timeout. We have interrupts disabled while
2557 waiting for the ACK, so if this is set too high
2558 interrupts *may* be lost!
2560 omap_mux= [OMAP] Override bootloader pin multiplexing.
2561 Format: <mux_mode0.mode_name=value>...
2562 For example, to override I2C bus2:
2563 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2565 oprofile.timer= [HW]
2566 Use timer interrupt instead of performance counters
2568 oprofile.cpu_type= Force an oprofile cpu type
2569 This might be useful if you have an older oprofile
2570 userland or if you want common events.
2571 Format: { arch_perfmon }
2572 arch_perfmon: [X86] Force use of architectural
2573 perfmon on Intel CPUs instead of the
2574 CPU specific event set.
2575 timer: [X86] Force use of architectural NMI
2576 timer mode (see also oprofile.timer
2577 for generic hr timer mode)
2578 [s390] Force legacy basic mode sampling
2579 (report cpu_type "timer")
2581 oops=panic Always panic on oopses. Default is to just kill the
2582 process, but there is a small probability of
2583 deadlocking the machine.
2584 This will also cause panics on machine check exceptions.
2585 Useful together with panic=30 to trigger a reboot.
2588 See Documentation/sound/oss/oss-parameters.txt
2590 page_owner= [KNL] Boot-time page_owner enabling option.
2591 Storage of the information about who allocated
2592 each page is disabled in default. With this switch,
2594 on: enable the feature
2596 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2597 timeout > 0: seconds before rebooting
2598 timeout = 0: wait forever
2599 timeout < 0: reboot immediately
2602 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2605 crash_kexec_post_notifiers
2606 Run kdump after running panic-notifiers and dumping
2607 kmsg. This only for the users who doubt kdump always
2608 succeeds in any situation.
2609 Note that this also increases risks of kdump failure,
2610 because some panic notifiers can make the crashed
2611 kernel more unstable.
2613 parkbd.port= [HW] Parallel port number the keyboard adapter is
2614 connected to, default is 0.
2616 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2617 0 for XT, 1 for AT (default is AT).
2620 parport= [HW,PPT] Specify parallel ports. 0 disables.
2621 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2622 Use 'auto' to force the driver to use any
2623 IRQ/DMA settings detected (the default is to
2624 ignore detected IRQ/DMA settings because of
2625 possible conflicts). You can specify the base
2626 address, IRQ, and DMA settings; IRQ and DMA
2627 should be numbers, or 'auto' (for using detected
2628 settings on that particular port), or 'nofifo'
2629 (to avoid using a FIFO even if it is detected).
2630 Parallel ports are assigned in the order they
2631 are specified on the command line, starting
2634 parport_init_mode= [HW,PPT]
2635 Configure VIA parallel port to operate in
2636 a specific mode. This is necessary on Pegasos
2637 computer where firmware has no options for setting
2638 up parallel port mode and sets it to spp.
2639 Currently this function knows 686a and 8231 chips.
2640 Format: [spp|ps2|epp|ecp|ecpepp]
2643 Halt all CPUs after the first oops has been printed for
2644 the specified number of seconds. This is to be used if
2645 your oopses keep scrolling off the screen.
2650 See header of drivers/block/paride/pcd.c.
2651 See also Documentation/blockdev/paride.txt.
2653 pci=option[,option...] [PCI] various PCI subsystem options:
2654 earlydump [X86] dump PCI config space before the kernel
2656 off [X86] don't probe for the PCI bus
2657 bios [X86-32] force use of PCI BIOS, don't access
2658 the hardware directly. Use this if your machine
2659 has a non-standard PCI host bridge.
2660 nobios [X86-32] disallow use of PCI BIOS, only direct
2661 hardware access methods are allowed. Use this
2662 if you experience crashes upon bootup and you
2663 suspect they are caused by the BIOS.
2664 conf1 [X86] Force use of PCI Configuration
2666 conf2 [X86] Force use of PCI Configuration
2668 noaer [PCIE] If the PCIEAER kernel config parameter is
2669 enabled, this kernel boot option can be used to
2670 disable the use of PCIE advanced error reporting.
2671 nodomains [PCI] Disable support for multiple PCI
2672 root domains (aka PCI segments, in ACPI-speak).
2673 nommconf [X86] Disable use of MMCONFIG for PCI
2675 check_enable_amd_mmconf [X86] check for and enable
2676 properly configured MMIO access to PCI
2677 config space on AMD family 10h CPU
2678 nomsi [MSI] If the PCI_MSI kernel config parameter is
2679 enabled, this kernel boot option can be used to
2680 disable the use of MSI interrupts system-wide.
2681 noioapicquirk [APIC] Disable all boot interrupt quirks.
2682 Safety option to keep boot IRQs enabled. This
2683 should never be necessary.
2684 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2685 primary IO-APIC for bridges that cannot disable
2686 boot IRQs. This fixes a source of spurious IRQs
2687 when the system masks IRQs.
2688 noioapicreroute [APIC] Disable workaround that uses the
2689 boot IRQ equivalent of an IRQ that connects to
2690 a chipset where boot IRQs cannot be disabled.
2691 The opposite of ioapicreroute.
2692 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2693 routing table. These calls are known to be buggy
2694 on several machines and they hang the machine
2695 when used, but on other computers it's the only
2696 way to get the interrupt routing table. Try
2697 this option if the kernel is unable to allocate
2698 IRQs or discover secondary PCI buses on your
2700 rom [X86] Assign address space to expansion ROMs.
2701 Use with caution as certain devices share
2702 address decoders between ROMs and other
2704 norom [X86] Do not assign address space to
2705 expansion ROMs that do not already have
2706 BIOS assigned address ranges.
2707 nobar [X86] Do not assign address space to the
2708 BARs that weren't assigned by the BIOS.
2709 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2710 assigned automatically to PCI devices. You can
2711 make the kernel exclude IRQs of your ISA cards
2713 pirqaddr=0xAAAAA [X86] Specify the physical address
2714 of the PIRQ table (normally generated
2715 by the BIOS) if it is outside the
2716 F0000h-100000h range.
2717 lastbus=N [X86] Scan all buses thru bus #N. Can be
2718 useful if the kernel is unable to find your
2719 secondary buses and you want to tell it
2720 explicitly which ones they are.
2721 assign-busses [X86] Always assign all PCI bus
2722 numbers ourselves, overriding
2723 whatever the firmware may have done.
2724 usepirqmask [X86] Honor the possible IRQ mask stored
2725 in the BIOS $PIR table. This is needed on
2726 some systems with broken BIOSes, notably
2727 some HP Pavilion N5400 and Omnibook XE3
2728 notebooks. This will have no effect if ACPI
2729 IRQ routing is enabled.
2730 noacpi [X86] Do not use ACPI for IRQ routing
2731 or for PCI scanning.
2732 use_crs [X86] Use PCI host bridge window information
2733 from ACPI. On BIOSes from 2008 or later, this
2734 is enabled by default. If you need to use this,
2735 please report a bug.
2736 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2737 If you need to use this, please report a bug.
2738 routeirq Do IRQ routing for all PCI devices.
2739 This is normally done in pci_enable_device(),
2740 so this option is a temporary workaround
2741 for broken drivers that don't call it.
2742 skip_isa_align [X86] do not align io start addr, so can
2743 handle more pci cards
2744 firmware [ARM] Do not re-enumerate the bus but instead
2745 just use the configuration from the
2746 bootloader. This is currently used on
2747 IXP2000 systems where the bus has to be
2748 configured a certain way for adjunct CPUs.
2749 noearly [X86] Don't do any early type 1 scanning.
2750 This might help on some broken boards which
2751 machine check when some devices' config space
2752 is read. But various workarounds are disabled
2753 and some IOMMU drivers will not work.
2754 bfsort Sort PCI devices into breadth-first order.
2755 This sorting is done to get a device
2756 order compatible with older (<= 2.4) kernels.
2757 nobfsort Don't sort PCI devices into breadth-first order.
2758 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2759 tuning and use the BIOS-configured MPS defaults.
2760 pcie_bus_safe Set every device's MPS to the largest value
2761 supported by all devices below the root complex.
2762 pcie_bus_perf Set device MPS to the largest allowable MPS
2763 based on its parent bus. Also set MRRS (Max
2764 Read Request Size) to the largest supported
2765 value (no larger than the MPS that the device
2766 or bus can support) for best performance.
2767 pcie_bus_peer2peer Set every device's MPS to 128B, which
2768 every device is guaranteed to support. This
2769 configuration allows peer-to-peer DMA between
2770 any pair of devices, possibly at the cost of
2771 reduced performance. This also guarantees
2772 that hot-added devices will work.
2773 cbiosize=nn[KMG] The fixed amount of bus space which is
2774 reserved for the CardBus bridge's IO window.
2775 The default value is 256 bytes.
2776 cbmemsize=nn[KMG] The fixed amount of bus space which is
2777 reserved for the CardBus bridge's memory
2778 window. The default value is 64 megabytes.
2781 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2782 Specifies alignment and device to reassign
2783 aligned memory resources.
2784 If <order of align> is not specified,
2785 PAGE_SIZE is used as alignment.
2786 PCI-PCI bridge can be specified, if resource
2787 windows need to be expanded.
2788 ecrc= Enable/disable PCIe ECRC (transaction layer
2789 end-to-end CRC checking).
2790 bios: Use BIOS/firmware settings. This is the
2794 hpiosize=nn[KMG] The fixed amount of bus space which is
2795 reserved for hotplug bridge's IO window.
2796 Default size is 256 bytes.
2797 hpmemsize=nn[KMG] The fixed amount of bus space which is
2798 reserved for hotplug bridge's memory window.
2799 Default size is 2 megabytes.
2800 realloc= Enable/disable reallocating PCI bridge resources
2801 if allocations done by BIOS are too small to
2802 accommodate resources required by all child
2804 off: Turn realloc off
2806 realloc same as realloc=on
2807 noari do not use PCIe ARI.
2808 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2809 only look for one device below a PCIe downstream
2812 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2815 force Enable ASPM even on devices that claim not to support it.
2816 WARNING: Forcing ASPM on may cause system lockups.
2818 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2819 nomsi Do not use MSI for PCI Express Native Hotplug (this
2820 makes all PCIe ports use INTx for hotplug services).
2822 pcie_ports= [PCIE] PCIe ports handling:
2823 auto Ask the BIOS whether or not to use native PCIe services
2824 associated with PCIe ports (PME, hot-plug, AER). Use
2825 them only if that is allowed by the BIOS.
2826 native Use native PCIe services associated with PCIe ports
2828 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2831 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2832 nomsi Do not use MSI for native PCIe PME signaling (this makes
2833 all PCIe root ports use INTx for all services).
2835 pcmv= [HW,PCMCIA] BadgePAD 4
2839 Keep all power-domains already enabled by bootloader on,
2840 even if no driver has claimed them. This is useful
2841 for debug and development, but should not be
2842 needed on a platform with proper driver support.
2845 See Documentation/blockdev/paride.txt.
2847 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2850 See arch/parisc/kernel/pdc_chassis.c
2852 percpu_alloc= Select which percpu first chunk allocator to use.
2853 Currently supported values are "embed" and "page".
2854 Archs may support subset or none of the selections.
2855 See comments in mm/percpu.c for details on each
2856 allocator. This parameter is primarily for debugging
2857 and performance comparison.
2860 See Documentation/blockdev/paride.txt.
2863 See Documentation/blockdev/paride.txt.
2865 pirq= [SMP,APIC] Manual mp-table setup
2866 See Documentation/x86/i386/IO-APIC.txt.
2868 plip= [PPT,NET] Parallel port network link
2869 Format: { parport<nr> | timid | 0 }
2870 See also Documentation/parport.txt.
2872 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2873 Override pmtimer IOPort with a hex value.
2877 Enable PNP debug messages (depends on the
2878 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2879 via /sys/module/pnp/parameters/debug. We always show
2880 current resource usage; turning this on also shows
2881 possible settings and some assignment information.
2887 { on | off | curr | res | no-curr | no-res }
2890 [ISAPNP] Exclude IRQs for the autoconfiguration
2893 [ISAPNP] Exclude DMAs for the autoconfiguration
2895 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2896 Ranges are in pairs (I/O port base and size).
2899 [ISAPNP] Exclude memory regions for the
2901 Ranges are in pairs (memory base and size).
2903 ports= [IP_VS_FTP] IPVS ftp helper module
2905 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2907 Format: <port>,<port>....
2909 print-fatal-signals=
2910 [KNL] debug: print fatal signals
2912 If enabled, warn about various signal handling
2913 related application anomalies: too many signals,
2914 too many POSIX.1 timers, fatal signals causing a
2917 If you hit the warning due to signal overflow,
2918 you might want to try "ulimit -i unlimited".
2922 printk.always_kmsg_dump=
2923 Trigger kmsg_dump for cases other than kernel oops or
2925 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2928 printk.time= Show timing data prefixed to each printk message line
2929 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2931 processor.max_cstate= [HW,ACPI]
2932 Limit processor to maximum C-state
2933 max_cstate=9 overrides any DMI blacklist limit.
2935 processor.nocst [HW,ACPI]
2936 Ignore the _CST method to determine C-states,
2937 instead using the legacy FADT method
2939 profile= [KNL] Enable kernel profiling via /proc/profile
2940 Format: [schedule,]<number>
2941 Param: "schedule" - profile schedule points.
2942 Param: <number> - step/bucket size as a power of 2 for
2943 statistical time based profiling.
2944 Param: "sleep" - profile D-state sleeping (millisecs).
2945 Requires CONFIG_SCHEDSTATS
2946 Param: "kvm" - profile VM exits.
2948 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2950 See Documentation/blockdev/ramdisk.txt.
2952 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2953 probe for; one of (bare|imps|exps|lifebook|any).
2954 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2956 psmouse.resetafter= [HW,MOUSE]
2957 Try to reset the device after so many bad packets
2960 [HW,MOUSE] Set desired mouse resolution, in dpi.
2961 psmouse.smartscroll=
2962 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2963 0 = disabled, 1 = enabled (default).
2965 pstore.backend= Specify the name of the pstore backend to use
2968 See Documentation/blockdev/paride.txt.
2971 [KNL] Number of legacy pty's. Overwrites compiled-in
2974 quiet [KNL] Disable most log messages
2979 See Documentation/md.txt.
2981 ramdisk_blocksize= [RAM]
2982 See Documentation/blockdev/ramdisk.txt.
2984 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2985 See Documentation/blockdev/ramdisk.txt.
2988 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2989 the specified list of CPUs to be no-callback CPUs.
2990 Invocation of these CPUs' RCU callbacks will
2991 be offloaded to "rcuox/N" kthreads created for
2992 that purpose, where "x" is "b" for RCU-bh, "p"
2993 for RCU-preempt, and "s" for RCU-sched, and "N"
2994 is the CPU number. This reduces OS jitter on the
2995 offloaded CPUs, which can be useful for HPC and
2996 real-time workloads. It can also improve energy
2997 efficiency for asymmetric multiprocessors.
3000 Rather than requiring that offloaded CPUs
3001 (specified by rcu_nocbs= above) explicitly
3002 awaken the corresponding "rcuoN" kthreads,
3003 make these kthreads poll for callbacks.
3004 This improves the real-time response for the
3005 offloaded CPUs by relieving them of the need to
3006 wake up the corresponding kthread, but degrades
3007 energy efficiency by requiring that the kthreads
3008 periodically wake up to do the polling.
3010 rcutree.blimit= [KNL]
3011 Set maximum number of finished RCU callbacks to
3012 process in one batch.
3014 rcutree.dump_tree= [KNL]
3015 Dump the structure of the rcu_node combining tree
3016 out at early boot. This is used for diagnostic
3017 purposes, to verify correct tree setup.
3019 rcutree.gp_cleanup_delay= [KNL]
3020 Set the number of jiffies to delay each step of
3021 RCU grace-period cleanup. This only has effect
3022 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3024 rcutree.gp_init_delay= [KNL]
3025 Set the number of jiffies to delay each step of
3026 RCU grace-period initialization. This only has
3027 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3030 rcutree.gp_preinit_delay= [KNL]
3031 Set the number of jiffies to delay each step of
3032 RCU grace-period pre-initialization, that is,
3033 the propagation of recent CPU-hotplug changes up
3034 the rcu_node combining tree. This only has effect
3035 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3037 rcutree.rcu_fanout_exact= [KNL]
3038 Disable autobalancing of the rcu_node combining
3039 tree. This is used by rcutorture, and might
3040 possibly be useful for architectures having high
3041 cache-to-cache transfer latencies.
3043 rcutree.rcu_fanout_leaf= [KNL]
3044 Increase the number of CPUs assigned to each
3045 leaf rcu_node structure. Useful for very large
3048 rcutree.jiffies_till_sched_qs= [KNL]
3049 Set required age in jiffies for a
3050 given grace period before RCU starts
3051 soliciting quiescent-state help from
3052 rcu_note_context_switch().
3054 rcutree.jiffies_till_first_fqs= [KNL]
3055 Set delay from grace-period initialization to
3056 first attempt to force quiescent states.
3057 Units are jiffies, minimum value is zero,
3058 and maximum value is HZ.
3060 rcutree.jiffies_till_next_fqs= [KNL]
3061 Set delay between subsequent attempts to force
3062 quiescent states. Units are jiffies, minimum
3063 value is one, and maximum value is HZ.
3065 rcutree.kthread_prio= [KNL,BOOT]
3066 Set the SCHED_FIFO priority of the RCU per-CPU
3067 kthreads (rcuc/N). This value is also used for
3068 the priority of the RCU boost threads (rcub/N)
3069 and for the RCU grace-period kthreads (rcu_bh,
3070 rcu_preempt, and rcu_sched). If RCU_BOOST is
3071 set, valid values are 1-99 and the default is 1
3072 (the least-favored priority). Otherwise, when
3073 RCU_BOOST is not set, valid values are 0-99 and
3074 the default is zero (non-realtime operation).
3076 rcutree.rcu_nocb_leader_stride= [KNL]
3077 Set the number of NOCB kthread groups, which
3078 defaults to the square root of the number of
3079 CPUs. Larger numbers reduces the wakeup overhead
3080 on the per-CPU grace-period kthreads, but increases
3081 that same overhead on each group's leader.
3083 rcutree.qhimark= [KNL]
3084 Set threshold of queued RCU callbacks beyond which
3085 batch limiting is disabled.
3087 rcutree.qlowmark= [KNL]
3088 Set threshold of queued RCU callbacks below which
3089 batch limiting is re-enabled.
3091 rcutree.rcu_idle_gp_delay= [KNL]
3092 Set wakeup interval for idle CPUs that have
3093 RCU callbacks (RCU_FAST_NO_HZ=y).
3095 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3096 Set wakeup interval for idle CPUs that have
3097 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3098 Lazy RCU callbacks are those which RCU can
3099 prove do nothing more than free memory.
3101 rcutorture.cbflood_inter_holdoff= [KNL]
3102 Set holdoff time (jiffies) between successive
3103 callback-flood tests.
3105 rcutorture.cbflood_intra_holdoff= [KNL]
3106 Set holdoff time (jiffies) between successive
3107 bursts of callbacks within a given callback-flood
3110 rcutorture.cbflood_n_burst= [KNL]
3111 Set the number of bursts making up a given
3112 callback-flood test. Set this to zero to
3113 disable callback-flood testing.
3115 rcutorture.cbflood_n_per_burst= [KNL]
3116 Set the number of callbacks to be registered
3117 in a given burst of a callback-flood test.
3119 rcutorture.fqs_duration= [KNL]
3120 Set duration of force_quiescent_state bursts.
3122 rcutorture.fqs_holdoff= [KNL]
3123 Set holdoff time within force_quiescent_state bursts.
3125 rcutorture.fqs_stutter= [KNL]
3126 Set wait time between force_quiescent_state bursts.
3128 rcutorture.gp_exp= [KNL]
3129 Use expedited update-side primitives.
3131 rcutorture.gp_normal= [KNL]
3132 Use normal (non-expedited) update-side primitives.
3133 If both gp_exp and gp_normal are set, do both.
3134 If neither gp_exp nor gp_normal are set, still
3137 rcutorture.n_barrier_cbs= [KNL]
3138 Set callbacks/threads for rcu_barrier() testing.
3140 rcutorture.nfakewriters= [KNL]
3141 Set number of concurrent RCU writers. These just
3142 stress RCU, they don't participate in the actual
3143 test, hence the "fake".
3145 rcutorture.nreaders= [KNL]
3146 Set number of RCU readers. The value -1 selects
3147 N-1, where N is the number of CPUs. A value
3148 "n" less than -1 selects N-n-2, where N is again
3149 the number of CPUs. For example, -2 selects N
3150 (the number of CPUs), -3 selects N+1, and so on.
3152 rcutorture.object_debug= [KNL]
3153 Enable debug-object double-call_rcu() testing.
3155 rcutorture.onoff_holdoff= [KNL]
3156 Set time (s) after boot for CPU-hotplug testing.
3158 rcutorture.onoff_interval= [KNL]
3159 Set time (s) between CPU-hotplug operations, or
3160 zero to disable CPU-hotplug testing.
3162 rcutorture.torture_runnable= [BOOT]
3163 Start rcutorture running at boot time.
3165 rcutorture.shuffle_interval= [KNL]
3166 Set task-shuffle interval (s). Shuffling tasks
3167 allows some CPUs to go into dyntick-idle mode
3168 during the rcutorture test.
3170 rcutorture.shutdown_secs= [KNL]
3171 Set time (s) after boot system shutdown. This
3172 is useful for hands-off automated testing.
3174 rcutorture.stall_cpu= [KNL]
3175 Duration of CPU stall (s) to test RCU CPU stall
3176 warnings, zero to disable.
3178 rcutorture.stall_cpu_holdoff= [KNL]
3179 Time to wait (s) after boot before inducing stall.
3181 rcutorture.stat_interval= [KNL]
3182 Time (s) between statistics printk()s.
3184 rcutorture.stutter= [KNL]
3185 Time (s) to stutter testing, for example, specifying
3186 five seconds causes the test to run for five seconds,
3187 wait for five seconds, and so on. This tests RCU's
3188 ability to transition abruptly to and from idle.
3190 rcutorture.test_boost= [KNL]
3191 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3192 "Maybe" means test if the RCU implementation
3193 under test support RCU priority boosting.
3195 rcutorture.test_boost_duration= [KNL]
3196 Duration (s) of each individual boost test.
3198 rcutorture.test_boost_interval= [KNL]
3199 Interval (s) between each boost test.
3201 rcutorture.test_no_idle_hz= [KNL]
3202 Test RCU's dyntick-idle handling. See also the
3203 rcutorture.shuffle_interval parameter.
3205 rcutorture.torture_type= [KNL]
3206 Specify the RCU implementation to test.
3208 rcutorture.verbose= [KNL]
3209 Enable additional printk() statements.
3211 rcupdate.rcu_expedited= [KNL]
3212 Use expedited grace-period primitives, for
3213 example, synchronize_rcu_expedited() instead
3214 of synchronize_rcu(). This reduces latency,
3215 but can increase CPU utilization, degrade
3216 real-time latency, and degrade energy efficiency.
3218 rcupdate.rcu_cpu_stall_suppress= [KNL]
3219 Suppress RCU CPU stall warning messages.
3221 rcupdate.rcu_cpu_stall_timeout= [KNL]
3222 Set timeout for RCU CPU stall warning messages.
3224 rcupdate.rcu_task_stall_timeout= [KNL]
3225 Set timeout in jiffies for RCU task stall warning
3226 messages. Disable with a value less than or equal
3229 rcupdate.rcu_self_test= [KNL]
3230 Run the RCU early boot self tests
3232 rcupdate.rcu_self_test_bh= [KNL]
3233 Run the RCU bh early boot self tests
3235 rcupdate.rcu_self_test_sched= [KNL]
3236 Run the RCU sched early boot self tests
3240 Run specified binary instead of /init from the ramdisk,
3241 used for early userspace startup. See initrd.
3244 Format (x86 or x86_64):
3245 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3247 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3249 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3250 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3251 reboot_force is either force or not specified,
3252 reboot_cpu is s[mp]#### with #### being the processor
3253 to be used for rebooting.
3256 [KNL, SMP] Set scheduler's default relax_domain_level.
3257 See Documentation/cgroups/cpusets.txt.
3259 relative_sleep_states=
3260 [SUSPEND] Use sleep state labeling where the deepest
3261 state available other than hibernation is always "mem".
3262 Format: { "0" | "1" }
3263 0 -- Traditional sleep state labels.
3264 1 -- Relative sleep state labels.
3266 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3268 reservetop= [X86-32]
3270 Reserves a hole at the top of the kernel virtual
3275 Set the amount of memory to reserve for BIOS at
3276 the bottom of the address space.
3278 reset_devices [KNL] Force drivers to reset the underlying device
3279 during initialization.
3282 Specify the partition device for software suspend
3284 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3286 resume_offset= [SWSUSP]
3287 Specify the offset from the beginning of the partition
3288 given by "resume=" at which the swap header is located,
3289 in <PAGE_SIZE> units (needed only for swap files).
3290 See Documentation/power/swsusp-and-swap-files.txt
3292 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3293 read the resume files
3295 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3296 Useful for devices that are detected asynchronously
3297 (e.g. USB and MMC devices).
3299 hibernate= [HIBERNATION]
3300 noresume Don't check if there's a hibernation image
3301 present during boot.
3302 nocompress Don't compress/decompress hibernation images.
3303 no Disable hibernation and resume.
3305 retain_initrd [RAM] Keep initrd memory after extraction
3307 rfkill.default_state=
3308 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3309 etc. communication is blocked by default.
3312 rfkill.master_switch_mode=
3313 0 The "airplane mode" button does nothing.
3314 1 The "airplane mode" button toggles between everything
3315 blocked and the previous configuration.
3316 2 The "airplane mode" button toggles between everything
3317 blocked and everything unblocked.
3319 rhash_entries= [KNL,NET]
3320 Set number of hash buckets for route cache
3322 ro [KNL] Mount root device read-only on boot
3324 root= [KNL] Root filesystem
3325 See name_to_dev_t comment in init/do_mounts.c.
3327 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3328 mount the root filesystem
3330 rootflags= [KNL] Set root filesystem mount option string
3332 rootfstype= [KNL] Set root filesystem type
3334 rootwait [KNL] Wait (indefinitely) for root device to show up.
3335 Useful for devices that are detected asynchronously
3336 (e.g. USB and MMC devices).
3338 rproc_mem=nn[KMG][@address]
3339 [KNL,ARM,CMA] Remoteproc physical memory block.
3340 Memory area to be used by remote processor image,
3343 rw [KNL] Mount root device read-write on boot
3345 S [KNL] Run init in single mode
3347 s390_iommu= [HW,S390]
3348 Set s390 IOTLB flushing mode
3350 With strict flushing every unmap operation will result in
3351 an IOTLB flush. Default is lazy flushing before reuse,
3355 See drivers/net/irda/sa1100_ir.c.
3357 sbni= [NET] Granch SBNI12 leased line adapter
3359 sched_debug [KNL] Enables verbose scheduler debug messages.
3361 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3362 xtime_lock contention on larger systems, and/or RCU lock
3363 contention on all systems with CONFIG_MAXSMP set.
3364 Format: { "0" | "1" }
3365 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3367 Note: increases power consumption, thus should only be
3368 enabled if running jitter sensitive (HPC/RT) workloads.
3370 security= [SECURITY] Choose a security module to enable at boot.
3371 If this boot parameter is not specified, only the first
3372 security module asking for security registration will be
3373 loaded. An invalid security module name will be treated
3374 as if no module has been chosen.
3376 selinux= [SELINUX] Disable or enable SELinux at boot time.
3377 Format: { "0" | "1" }
3378 See security/selinux/Kconfig help text.
3381 Default value is set via kernel config option.
3382 If enabled at boot time, /selinux/disable can be used
3383 later to disable prior to initial policy load.
3385 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3386 Format: { "0" | "1" }
3387 See security/apparmor/Kconfig help text
3390 Default value is set via kernel config option.
3392 serialnumber [BUGS=X86-32]
3395 Maximal number of shapers.
3397 show_msr= [x86] show boot-time MSR settings
3398 Format: { <integer> }
3399 Show boot-time (BIOS-initialized) MSR settings.
3400 The parameter means the number of CPUs to show,
3401 for example 1 means boot CPU only.
3409 Disable merging of slabs with similar size. May be
3410 necessary if there is some reason to distinguish
3411 allocs to different slabs. Debug options disable
3412 merging on their own.
3413 For more information see Documentation/vm/slub.txt.
3415 slab_max_order= [MM, SLAB]
3416 Determines the maximum allowed order for slabs.
3417 A high setting may cause OOMs due to memory
3418 fragmentation. Defaults to 1 for systems with
3419 more than 32MB of RAM, 0 otherwise.
3421 slub_debug[=options[,slabs]] [MM, SLUB]
3422 Enabling slub_debug allows one to determine the
3423 culprit if slab objects become corrupted. Enabling
3424 slub_debug can create guard zones around objects and
3425 may poison objects when not in use. Also tracks the
3426 last alloc / free. For more information see
3427 Documentation/vm/slub.txt.
3429 slub_max_order= [MM, SLUB]
3430 Determines the maximum allowed order for slabs.
3431 A high setting may cause OOMs due to memory
3432 fragmentation. For more information see
3433 Documentation/vm/slub.txt.
3435 slub_min_objects= [MM, SLUB]
3436 The minimum number of objects per slab. SLUB will
3437 increase the slab order up to slub_max_order to
3438 generate a sufficiently large slab able to contain
3439 the number of objects indicated. The higher the number
3440 of objects the smaller the overhead of tracking slabs
3441 and the less frequently locks need to be acquired.
3442 For more information see Documentation/vm/slub.txt.
3444 slub_min_order= [MM, SLUB]
3445 Determines the minimum page order for slabs. Must be
3446 lower than slub_max_order.
3447 For more information see Documentation/vm/slub.txt.
3449 slub_nomerge [MM, SLUB]
3450 Same with slab_nomerge. This is supported for legacy.
3451 See slab_nomerge for more information.
3454 Format: <io1>[,<io2>[,...,<io8>]]
3456 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3457 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3458 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3459 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3460 smsc-ircc2.ircc_irq= [HW] IRQ line
3461 smsc-ircc2.ircc_dma= [HW] DMA channel
3462 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3463 0: Toshiba Satellite 1800 (GP data pin select)
3464 1: Fast pin select (default)
3468 [KNL] Should the soft-lockup detector generate panics.
3471 softlockup_all_cpu_backtrace=
3472 [KNL] Should the soft-lockup detector generate
3473 backtraces on all cpus.
3476 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3477 See Documentation/laptops/sonypi.txt
3479 spia_io_base= [HW,MTD]
3485 Enabled the stack tracer on boot up.
3487 stacktrace_filter=[function-list]
3488 [FTRACE] Limit the functions that the stack tracer
3489 will trace at boot up. function-list is a comma separated
3490 list of functions. This list can be changed at run
3491 time by the stack_trace_filter file in the debugfs
3492 tracing directory. Note, this enables stack tracing
3493 and the stacktrace above is not needed.
3497 Set the STI (builtin display/keyboard on the HP-PARISC
3498 machines) console (graphic card) which should be used
3499 as the initial boot-console.
3500 See also comment in drivers/video/console/sticore.c.
3503 See comment in drivers/video/console/sticore.c.
3506 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3508 sunrpc.min_resvport=
3509 sunrpc.max_resvport=
3511 SunRPC servers often require that client requests
3512 originate from a privileged port (i.e. a port in the
3513 range 0 < portnr < 1024).
3514 An administrator who wishes to reserve some of these
3515 ports for other uses may adjust the range that the
3516 kernel's sunrpc client considers to be privileged
3517 using these two parameters to set the minimum and
3518 maximum port values.
3522 Control how the NFS server code allocates CPUs to
3523 service thread pools. Depending on how many NICs
3524 you have and where their interrupts are bound, this
3525 option will affect which CPUs will do NFS serving.
3526 Note: this parameter cannot be changed while the
3527 NFS server is running.
3529 auto the server chooses an appropriate mode
3530 automatically using heuristics
3531 global a single global pool contains all CPUs
3532 percpu one pool for each CPU
3533 pernode one pool for each NUMA node (equivalent
3534 to global on non-NUMA machines)
3536 sunrpc.tcp_slot_table_entries=
3537 sunrpc.udp_slot_table_entries=
3539 Sets the upper limit on the number of simultaneous
3540 RPC calls that can be sent from the client to a
3541 server. Increasing these values may allow you to
3542 improve throughput, but will also increase the
3543 amount of memory reserved for use by the client.
3545 suspend.pm_test_delay=
3547 Sets the number of seconds to remain in a suspend test
3548 mode before resuming the system (see
3549 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3550 is set. Default value is 5.
3553 [KNL] Enable accounting of swap in memory resource
3554 controller if no parameter or 1 is given or disable
3555 it if 0 is given (See Documentation/cgroups/memory.txt)
3557 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3558 Format: { <int> | force }
3559 <int> -- Number of I/O TLB slabs
3560 force -- force using of bounce buffers even if they
3561 wouldn't be automatically used by the kernel
3565 sysfs.deprecated=0|1 [KNL]
3566 Enable/disable old style sysfs layout for old udev
3567 on older distributions. When this option is enabled
3568 very new udev will not work anymore. When this option
3569 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3570 in older udev will not work anymore.
3571 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3572 the kernel configuration.
3574 sysrq_always_enabled
3576 Ignore sysrq setting - this boot parameter will
3577 neutralize any effect of /proc/sys/kernel/sysrq.
3578 Useful for debugging.
3580 tcpmhash_entries= [KNL,NET]
3581 Set the number of tcp_metrics_hash slots.
3582 Default value is 8192 or 16384 depending on total
3583 ram pages. This is used to specify the TCP metrics
3584 cache size. See Documentation/networking/ip-sysctl.txt
3585 "tcp_no_metrics_save" section for more details.
3589 test_suspend= [SUSPEND][,N]
3590 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3591 standby suspend) or "freeze" (for suspend type freeze)
3592 as the system sleep state during system startup with
3593 the optional capability to repeat N number of times.
3594 The system is woken from this state using a
3595 wakeup-capable RTC alarm.
3597 thash_entries= [KNL,NET]
3598 Set number of hash buckets for TCP connection
3600 thermal.act= [HW,ACPI]
3601 -1: disable all active trip points in all thermal zones
3602 <degrees C>: override all lowest active trip points
3604 thermal.crt= [HW,ACPI]
3605 -1: disable all critical trip points in all thermal zones
3606 <degrees C>: override all critical trip points
3608 thermal.nocrt= [HW,ACPI]
3609 Set to disable actions on ACPI thermal zone
3610 critical and hot trip points.
3612 thermal.off= [HW,ACPI]
3613 1: disable ACPI thermal control
3615 thermal.psv= [HW,ACPI]
3616 -1: disable all passive trip points
3617 <degrees C>: override all passive trip points to this
3620 thermal.tzp= [HW,ACPI]
3621 Specify global default ACPI thermal zone polling rate
3622 <deci-seconds>: poll all this frequency
3623 0: no polling (default)
3626 Force threading of all interrupt handlers except those
3627 marked explicitly IRQF_NO_THREAD.
3630 Enable the Transcendent memory driver if built-in.
3632 tmem.cleancache=0|1 [KNL, XEN]
3633 Default is on (1). Disable the usage of the cleancache
3634 API to send anonymous pages to the hypervisor.
3636 tmem.frontswap=0|1 [KNL, XEN]
3637 Default is on (1). Disable the usage of the frontswap
3638 API to send swap pages to the hypervisor. If disabled
3639 the selfballooning and selfshrinking are force disabled.
3641 tmem.selfballooning=0|1 [KNL, XEN]
3642 Default is on (1). Disable the driving of swap pages
3645 tmem.selfshrinking=0|1 [KNL, XEN]
3646 Default is on (1). Partial swapoff that immediately
3647 transfers pages from Xen hypervisor back to the
3648 kernel based on different criteria.
3652 Specify if the kernel should make use of the cpu
3653 topology information if the hardware supports this.
3654 The scheduler will make use of this information and
3655 e.g. base its process migration decisions on it.
3658 topology_updates= [KNL, PPC, NUMA]
3660 Specify if the kernel should ignore (off)
3661 topology updates sent by the hypervisor to this
3666 tpm_suspend_pcr=[HW,TPM]
3667 Format: integer pcr id
3668 Specify that at suspend time, the tpm driver
3669 should extend the specified pcr with zeros,
3670 as a workaround for some chips which fail to
3671 flush the last written pcr on TPM_SaveState.
3672 This will guarantee that all the other pcrs
3675 trace_buf_size=nn[KMG]
3676 [FTRACE] will set tracing buffer size on each cpu.
3678 trace_event=[event-list]
3679 [FTRACE] Set and start specified trace events in order
3680 to facilitate early boot debugging.
3681 See also Documentation/trace/events.txt
3683 trace_options=[option-list]
3684 [FTRACE] Enable or disable tracer options at boot.
3685 The option-list is a comma delimited list of options
3686 that can be enabled or disabled just as if you were
3687 to echo the option name into
3689 /sys/kernel/debug/tracing/trace_options
3691 For example, to enable stacktrace option (to dump the
3692 stack trace of each event), add to the command line:
3694 trace_options=stacktrace
3696 See also Documentation/trace/ftrace.txt "trace options"
3700 Have the tracepoints sent to printk as well as the
3701 tracing ring buffer. This is useful for early boot up
3702 where the system hangs or reboots and does not give the
3703 option for reading the tracing buffer or performing a
3704 ftrace_dump_on_oops.
3706 To turn off having tracepoints sent to printk,
3707 echo 0 > /proc/sys/kernel/tracepoint_printk
3708 Note, echoing 1 into this file without the
3709 tracepoint_printk kernel cmdline option has no effect.
3713 Having tracepoints sent to printk() and activating high
3714 frequency tracepoints such as irq or sched, can cause
3715 the system to live lock.
3718 [FTRACE] enable this option to disable tracing when a
3719 warning is hit. This turns off "tracing_on". Tracing can
3720 be enabled again by echoing '1' into the "tracing_on"
3721 file located in /sys/kernel/debug/tracing/
3723 This option is useful, as it disables the trace before
3724 the WARNING dump is called, which prevents the trace to
3725 be filled with content caused by the warning output.
3727 This option can also be set at run time via the sysctl
3728 option: kernel/traceoff_on_warning
3730 transparent_hugepage=
3732 Format: [always|madvise|never]
3733 Can be used to control the default behavior of the system
3734 with respect to transparent hugepages.
3735 See Documentation/vm/transhuge.txt for more details.
3737 tsc= Disable clocksource stability checks for TSC.
3739 [x86] reliable: mark tsc clocksource as reliable, this
3740 disables clocksource verification at runtime, as well
3741 as the stability checks done at bootup. Used to enable
3742 high-resolution timer mode on older hardware, and in
3743 virtualized environment.
3744 [x86] noirqtime: Do not use TSC to do irq accounting.
3745 Used to run time disable IRQ_TIME_ACCOUNTING on any
3746 platforms where RDTSC is slow and this accounting
3749 turbografx.map[2|3]= [HW,JOY]
3750 TurboGraFX parallel port interface
3752 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3753 See also Documentation/input/joystick-parport.txt
3755 udbg-immortal [PPC] When debugging early kernel crashes that
3756 happen after console_init() and before a proper
3757 console driver takes over, this boot options might
3758 help "seeing" what's going on.
3760 uhash_entries= [KNL,NET]
3761 Set number of hash buckets for UDP/UDP-Lite connections
3764 [USB] Ignore overcurrent events (default N).
3765 Some badly-designed motherboards generate lots of
3766 bogus events, for ports that aren't wired to
3767 anything. Set this parameter to avoid log spamming.
3768 Note that genuine overcurrent events won't be
3772 [X86] Cause panic on unknown NMI.
3774 usbcore.authorized_default=
3775 [USB] Default USB device authorization:
3776 (default -1 = authorized except for wireless USB,
3777 0 = not authorized, 1 = authorized)
3779 usbcore.autosuspend=
3780 [USB] The autosuspend time delay (in seconds) used
3781 for newly-detected USB devices (default 2). This
3782 is the time required before an idle device will be
3783 autosuspended. Devices for which the delay is set
3784 to a negative value won't be autosuspended at all.
3786 usbcore.usbfs_snoop=
3787 [USB] Set to log all usbfs traffic (default 0 = off).
3789 usbcore.blinkenlights=
3790 [USB] Set to cycle leds on hubs (default 0 = off).
3792 usbcore.old_scheme_first=
3793 [USB] Start with the old device initialization
3794 scheme (default 0 = off).
3796 usbcore.usbfs_memory_mb=
3797 [USB] Memory limit (in MB) for buffers allocated by
3798 usbfs (default = 16, 0 = max = 2047).
3800 usbcore.use_both_schemes=
3801 [USB] Try the other device initialization scheme
3802 if the first one fails (default 1 = enabled).
3804 usbcore.initial_descriptor_timeout=
3805 [USB] Specifies timeout for the initial 64-byte
3806 USB_REQ_GET_DESCRIPTOR request in milliseconds
3807 (default 5000 = 5.0 seconds).
3810 [USBHID] The interval which mice are to be polled at.
3812 usb-storage.delay_use=
3813 [UMS] The delay in seconds before a new device is
3814 scanned for Logical Units (default 1).
3817 [UMS] A list of quirks entries to supplement or
3818 override the built-in unusual_devs list. List
3819 entries are separated by commas. Each entry has
3820 the form VID:PID:Flags where VID and PID are Vendor
3821 and Product ID values (4-digit hex numbers) and
3822 Flags is a set of characters, each corresponding
3823 to a common usb-storage quirk flag as follows:
3824 a = SANE_SENSE (collect more than 18 bytes
3826 b = BAD_SENSE (don't collect more than 18
3827 bytes of sense data);
3828 c = FIX_CAPACITY (decrease the reported
3829 device capacity by one sector);
3830 d = NO_READ_DISC_INFO (don't use
3831 READ_DISC_INFO command);
3832 e = NO_READ_CAPACITY_16 (don't use
3833 READ_CAPACITY_16 command);
3834 f = NO_REPORT_OPCODES (don't use report opcodes
3836 g = MAX_SECTORS_240 (don't transfer more than
3837 240 sectors at a time, uas only);
3838 h = CAPACITY_HEURISTICS (decrease the
3839 reported device capacity by one
3840 sector if the number is odd);
3841 i = IGNORE_DEVICE (don't bind to this
3843 l = NOT_LOCKABLE (don't try to lock and
3844 unlock ejectable media);
3845 m = MAX_SECTORS_64 (don't transfer more
3846 than 64 sectors = 32 KB at a time);
3847 n = INITIAL_READ10 (force a retry of the
3848 initial READ(10) command);
3849 o = CAPACITY_OK (accept the capacity
3850 reported by the device);
3851 p = WRITE_CACHE (the device cache is ON
3853 r = IGNORE_RESIDUE (the device reports
3854 bogus residue values);
3855 s = SINGLE_LUN (the device has only one
3857 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3858 commands, uas only);
3859 u = IGNORE_UAS (don't bind to the uas driver);
3860 w = NO_WP_DETECT (don't test whether the
3861 medium is write-protected).
3862 Example: quirks=0419:aaf5:rl,0421:0433:rc
3864 user_debug= [KNL,ARM]
3866 See arch/arm/Kconfig.debug help text.
3867 1 - undefined instruction events
3869 4 - invalid data aborts
3872 Example: user_debug=31
3875 [X86] Flags controlling user PTE allocations.
3877 nohigh = do not allocate PTE pages in
3878 HIGHMEM regardless of setting
3882 On X86_32, this is an alias for vdso32=. Otherwise:
3884 vdso=1: enable VDSO (the default)
3885 vdso=0: disable VDSO mapping
3887 vdso32= [X86] Control the 32-bit vDSO
3888 vdso32=1: enable 32-bit VDSO
3889 vdso32=0 or vdso32=2: disable 32-bit VDSO
3891 See the help text for CONFIG_COMPAT_VDSO for more
3892 details. If CONFIG_COMPAT_VDSO is set, the default is
3893 vdso32=0; otherwise, the default is vdso32=1.
3895 For compatibility with older kernels, vdso32=2 is an
3898 Try vdso32=0 if you encounter an error that says:
3899 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3902 vector=percpu: enable percpu vector domain
3904 video= [FB] Frame buffer configuration
3905 See Documentation/fb/modedb.txt.
3907 video.brightness_switch_enabled= [0,1]
3908 If set to 1, on receiving an ACPI notify event
3909 generated by hotkey, video driver will adjust brightness
3910 level and then send out the event to user space through
3911 the allocated input device; If set to 0, video driver
3912 will only send out the event without touching backlight
3917 [VMMIO] Memory mapped virtio (platform) device.
3919 <size>@<baseaddr>:<irq>[:<id>]
3921 <size> := size (can use standard suffixes
3923 <baseaddr> := physical base address
3924 <irq> := interrupt number (as passed to
3926 <id> := (optional) platform device id
3928 virtio_mmio.device=1K@0x100b0000:48:7
3930 Can be used multiple times for multiple devices.
3932 vga= [BOOT,X86-32] Select a particular video mode
3933 See Documentation/x86/boot.txt and
3934 Documentation/svga.txt.
3935 Use vga=ask for menu.
3936 This is actually a boot loader parameter; the value is
3937 passed to the kernel using a special protocol.
3939 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3940 size of <nn>. This can be used to increase the
3941 minimum size (128MB on x86). It can also be used to
3942 decrease the size and leave more room for directly
3945 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3948 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3951 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3955 Controls the behavior of vsyscalls (i.e. calls to
3956 fixed addresses of 0xffffffffff600x00 from legacy
3957 code). Most statically-linked binaries and older
3958 versions of glibc use these calls. Because these
3959 functions are at fixed addresses, they make nice
3960 targets for exploits that can control RIP.
3962 emulate [default] Vsyscalls turn into traps and are
3963 emulated reasonably safely.
3965 native Vsyscalls are native syscall instructions.
3966 This is a little bit faster than trapping
3967 and makes a few dynamic recompilers work
3968 better than they would in emulation mode.
3969 It also makes exploits much easier to write.
3971 none Vsyscalls don't work at all. This makes
3972 them quite hard to use for exploits but
3973 might break your system.
3975 vt.color= [VT] Default text color.
3976 Format: 0xYX, X = foreground, Y = background.
3977 Default: 0x07 = light gray on black.
3979 vt.cur_default= [VT] Default cursor shape.
3980 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3981 the parameters of the <Esc>[?A;B;Cc escape sequence;
3982 see VGA-softcursor.txt. Default: 2 = underline.
3984 vt.default_blu= [VT]
3985 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3986 Change the default blue palette of the console.
3987 This is a 16-member array composed of values
3990 vt.default_grn= [VT]
3991 Format: <green0>,<green1>,<green2>,...,<green15>
3992 Change the default green palette of the console.
3993 This is a 16-member array composed of values
3996 vt.default_red= [VT]
3997 Format: <red0>,<red1>,<red2>,...,<red15>
3998 Change the default red palette of the console.
3999 This is a 16-member array composed of values
4005 Set system-wide default UTF-8 mode for all tty's.
4006 Default is 1, i.e. UTF-8 mode is enabled for all
4007 newly opened terminals.
4009 vt.global_cursor_default=
4012 Set system-wide default for whether a cursor
4013 is shown on new VTs. Default is -1,
4014 i.e. cursors will be created by default unless
4015 overridden by individual drivers. 0 will hide
4016 cursors, 1 will display them.
4018 vt.italic= [VT] Default color for italic text; 0-15.
4021 vt.underline= [VT] Default color for underlined text; 0-15.
4024 watchdog timers [HW,WDT] For information on watchdog timers,
4025 see Documentation/watchdog/watchdog-parameters.txt
4026 or other driver-specific files in the
4027 Documentation/watchdog/ directory.
4029 workqueue.disable_numa
4030 By default, all work items queued to unbound
4031 workqueues are affine to the NUMA nodes they're
4032 issued on, which results in better behavior in
4033 general. If NUMA affinity needs to be disabled for
4034 whatever reason, this option can be used. Note
4035 that this also can be controlled per-workqueue for
4036 workqueues visible under /sys/bus/workqueue/.
4038 workqueue.power_efficient
4039 Per-cpu workqueues are generally preferred because
4040 they show better performance thanks to cache
4041 locality; unfortunately, per-cpu workqueues tend to
4042 be more power hungry than unbound workqueues.
4044 Enabling this makes the per-cpu workqueues which
4045 were observed to contribute significantly to power
4046 consumption unbound, leading to measurably lower
4047 power usage at the cost of small performance
4050 The default value of this parameter is determined by
4051 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4053 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4054 default x2apic cluster mode on platforms
4057 x86_intel_mid_timer= [X86-32,APBT]
4058 Choose timer option for x86 Intel MID platform.
4059 Two valid options are apbt timer only and lapic timer
4060 plus one apbt timer for broadcast timer.
4061 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4063 xen_emul_unplug= [HW,X86,XEN]
4064 Unplug Xen emulated devices
4065 Format: [unplug0,][unplug1]
4066 ide-disks -- unplug primary master IDE devices
4067 aux-ide-disks -- unplug non-primary-master IDE devices
4068 nics -- unplug network devices
4069 all -- unplug all emulated devices (NICs and IDE disks)
4070 unnecessary -- unplugging emulated devices is
4071 unnecessary even if the host did not respond to
4073 never -- do not unplug even if version check succeeds
4075 xen_nopvspin [X86,XEN]
4076 Disables the ticketlock slowpath using Xen PV
4080 Disables the PV optimizations forcing the HVM guest to
4081 run as generic HVM guest with no PV drivers.
4083 xirc2ps_cs= [NET,PCMCIA]
4085 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4087 ______________________________________________________________________
4091 Add more DRM drivers.
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