4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 ccw_timeout_log [S390]
575 See Documentation/s390/CommonIO for details.
577 cgroup_disable= [KNL] Disable a particular controller
578 Format: {name of the controller(s) to disable}
579 The effects of cgroup_disable=foo are:
580 - foo isn't auto-mounted if you mount all cgroups in
582 - foo isn't visible as an individually mountable
584 {Currently only "memory" controller deal with this and
585 cut the overhead, others just disable the usage. So
586 only cgroup_disable=memory is actually worthy}
588 checkreqprot [SELINUX] Set initial checkreqprot flag value.
589 Format: { "0" | "1" }
590 See security/selinux/Kconfig help text.
591 0 -- check protection applied by kernel (includes
592 any implied execute protection).
593 1 -- check protection requested by application.
594 Default value is set via a kernel config option.
595 Value can be changed at runtime via
596 /selinux/checkreqprot.
599 See Documentation/s390/CommonIO for details.
602 Keep all clocks already enabled by bootloader on,
603 even if no driver has claimed them. This is useful
604 for debug and development, but should not be
605 needed on a platform with proper driver support.
606 For more information, see Documentation/clk.txt.
608 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
610 Forces specified clocksource (if available) to be used
611 when calculating gettimeofday(). If specified
612 clocksource is not available, it defaults to PIT.
613 Format: { pit | tsc | cyclone | pmtmr }
615 clocksource= Override the default clocksource
617 Override the default clocksource and use the clocksource
618 with the name specified.
619 Some clocksource names to choose from, depending on
621 [all] jiffies (this is the base, fallback clocksource)
623 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
624 pxa_timer,timer3,32k_counter,timer0_1
626 [X86-32] pit,hpet,tsc;
627 scx200_hrt on Geode; cyclone on IBM x440
635 clearcpuid=BITNUM [X86]
636 Disable CPUID feature X for the kernel. See
637 arch/x86/include/asm/cpufeature.h for the valid bit
638 numbers. Note the Linux specific bits are not necessarily
639 stable over kernel options, but the vendor specific
641 Also note that user programs calling CPUID directly
642 or using the feature without checking anything
643 will still see it. This just prevents it from
644 being used by the kernel or shown in /proc/cpuinfo.
645 Also note the kernel might malfunction if you disable
648 cma=nn[MG]@[start[MG][-end[MG]]]
650 Sets the size of kernel global memory area for
651 contiguous memory allocations and optionally the
652 placement constraint by the physical address range of
653 memory allocations. For more information, see
654 include/linux/dma-contiguous.h
656 cmo_free_hint= [PPC] Format: { yes | no }
657 Specify whether pages are marked as being inactive
658 when they are freed. This is used in CMO environments
659 to determine OS memory pressure for page stealing by
663 coherent_pool=nn[KMG] [ARM,KNL]
664 Sets the size of memory pool for coherent, atomic dma
665 allocations, by default set to 256K.
667 code_bytes [X86] How many bytes of object code to print
672 com20020= [HW,NET] ARCnet - COM20020 chipset
674 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
676 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
680 ARCnet - COM90xx chipset (memory-mapped buffers)
681 Format: <io>[,<irq>[,<memstart>]]
683 condev= [HW,S390] console device
686 console= [KNL] Output console device and options.
688 tty<n> Use the virtual console device <n>.
692 Use the specified serial port. The options are of
693 the form "bbbbpnf", where "bbbb" is the baud rate,
694 "p" is parity ("n", "o", or "e"), "n" is number of
695 bits, and "f" is flow control ("r" for RTS or
696 omit it). Default is "9600n8".
698 See Documentation/serial-console.txt for more
700 Documentation/networking/netconsole.txt for an
703 uart[8250],io,<addr>[,options]
704 uart[8250],mmio,<addr>[,options]
705 Start an early, polled-mode console on the 8250/16550
706 UART at the specified I/O port or MMIO address,
707 switching to the matching ttyS device later. The
708 options are the same as for ttyS, above.
709 hvc<n> Use the hypervisor console device <n>. This is for
710 both Xen and PowerPC hypervisors.
712 If the device connected to the port is not a TTY but a braille
713 device, prepend "brl," before the device type, for instance
715 For now, only VisioBraille is supported.
717 consoleblank= [KNL] The console blank (screen saver) timeout in
718 seconds. Defaults to 10*60 = 10mins. A value of 0
719 disables the blank timer.
722 [KNL] Change the default value for
723 /proc/<pid>/coredump_filter.
724 See also Documentation/filesystems/proc.txt.
726 cpuidle.off=1 [CPU_IDLE]
727 disable the cpuidle sub-system
729 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
731 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
733 crashkernel=size[KMG][@offset[KMG]]
734 [KNL] Using kexec, Linux can switch to a 'crash kernel'
735 upon panic. This parameter reserves the physical
736 memory region [offset, offset + size] for that kernel
737 image. If '@offset' is omitted, then a suitable offset
738 is selected automatically. Check
739 Documentation/kdump/kdump.txt for further details.
741 crashkernel=range1:size1[,range2:size2,...][@offset]
742 [KNL] Same as above, but depends on the memory
743 in the running system. The syntax of range is
744 start-[end] where start and end are both
745 a memory unit (amount[KMG]). See also
746 Documentation/kdump/kdump.txt for an example.
748 crashkernel=size[KMG],high
749 [KNL, x86_64] range could be above 4G. Allow kernel
750 to allocate physical memory region from top, so could
751 be above 4G if system have more than 4G ram installed.
752 Otherwise memory region will be allocated below 4G, if
754 It will be ignored if crashkernel=X is specified.
755 crashkernel=size[KMG],low
756 [KNL, x86_64] range under 4G. When crashkernel=X,high
757 is passed, kernel could allocate physical memory region
758 above 4G, that cause second kernel crash on system
759 that require some amount of low memory, e.g. swiotlb
760 requires at least 64M+32K low memory. Kernel would
761 try to allocate 72M below 4G automatically.
762 This one let user to specify own low range under 4G
763 for second kernel instead.
764 0: to disable low allocation.
765 It will be ignored when crashkernel=X,high is not used
766 or memory reserved is below 4G.
771 cs89x0_media= [HW,NET]
772 Format: { rj45 | aui | bnc }
775 See header of drivers/s390/block/dasd_devmap.c.
777 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
778 (one device per port)
779 Format: <port#>,<type>
780 See also Documentation/input/joystick-parport.txt
782 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
783 time. See Documentation/dynamic-debug-howto.txt for
784 details. Deprecated, see dyndbg.
786 debug [KNL] Enable kernel debugging (events log level).
789 [KNL] verbose self-tests
791 Print debugging info while doing the locking API
793 We default to 0 (no extra messages), setting it to
794 1 will print _a lot_ more information - normally
795 only useful to kernel developers.
797 debug_objects [KNL] Enable object debugging
800 [KNL] Disable object debugging
802 debug_guardpage_minorder=
803 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
804 parameter allows control of the order of pages that will
805 be intentionally kept free (and hence protected) by the
806 buddy allocator. Bigger value increase the probability
807 of catching random memory corruption, but reduce the
808 amount of memory for normal system use. The maximum
809 possible value is MAX_ORDER/2. Setting this parameter
810 to 1 or 2 should be enough to identify most random
811 memory corruption problems caused by bugs in kernel or
812 driver code when a CPU writes to (or reads from) a
813 random memory location. Note that there exists a class
814 of memory corruptions problems caused by buggy H/W or
815 F/W or by drivers badly programing DMA (basically when
816 memory is written at bus level and the CPU MMU is
817 bypassed) which are not detectable by
818 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
819 tracking down these problems.
821 debugpat [X86] Enable PAT debugging
823 decnet.addr= [HW,NET]
824 Format: <area>[,<node>]
825 See also Documentation/networking/decnet.txt.
828 [same as hugepagesz=] The size of the default
829 HugeTLB page size. This is the size represented by
830 the legacy /proc/ hugepages APIs, used for SHM, and
831 default size when mounting hugetlbfs filesystems.
832 Defaults to the default architecture's huge page size
836 Set number of hash buckets for dentry cache.
839 See Documentation/networking/ipv6.txt.
841 disable_cpu_apicid= [X86,APIC,SMP]
843 The number of initial APIC ID for the
844 corresponding CPU to be disabled at boot,
845 mostly used for the kdump 2nd kernel to
846 disable BSP to wake up multiple CPUs without
847 causing system reset or hang due to sending
850 disable_ddw [PPC/PSERIES]
851 Disable Dynamic DMA Window support. Use this if
852 to workaround buggy firmware.
855 See Documentation/networking/ipv6.txt.
857 disable_mtrr_cleanup [X86]
858 The kernel tries to adjust MTRR layout from continuous
859 to discrete, to make X server driver able to add WB
860 entry later. This parameter disables that.
862 disable_mtrr_trim [X86, Intel and AMD only]
863 By default the kernel will trim any uncacheable
864 memory out of your available memory pool based on
865 MTRR settings. This parameter disables that behavior,
866 possibly causing your machine to run very slowly.
868 disable_timer_pin_1 [X86]
869 Disable PIN 1 of APIC timer
870 Can be useful to work around chipset bugs.
872 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
873 this option disables the debugging code at boot.
875 dma_debug_entries=<number>
876 This option allows to tune the number of preallocated
877 entries for DMA-API debugging code. One entry is
878 required per DMA-API allocation. Use this if the
879 DMA-API debugging code disables itself because the
880 architectural default is too low.
882 dma_debug_driver=<driver_name>
883 With this option the DMA-API debugging driver
884 filter feature can be enabled at boot time. Just
885 pass the driver to filter for as the parameter.
886 The filter can be disabled or changed to another
887 driver later using sysfs.
889 drm_kms_helper.edid_firmware=[<connector>:]<file>
890 Broken monitors, graphic adapters and KVMs may
891 send no or incorrect EDID data sets. This parameter
892 allows to specify an EDID data set in the
893 /lib/firmware directory that is used instead.
894 Generic built-in EDID data sets are used, if one of
895 edid/1024x768.bin, edid/1280x1024.bin,
896 edid/1680x1050.bin, or edid/1920x1080.bin is given
897 and no file with the same name exists. Details and
898 instructions how to build your own EDID data are
899 available in Documentation/EDID/HOWTO.txt. An EDID
900 data set will only be used for a particular connector,
901 if its name and a colon are prepended to the EDID
906 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
907 module.dyndbg[="val"]
908 Enable debug messages at boot time. See
909 Documentation/dynamic-debug-howto.txt for details.
911 early_ioremap_debug [KNL]
912 Enable debug messages in early_ioremap support. This
913 is useful for tracking down temporary early mappings
914 which are not unmapped.
916 earlycon= [KNL] Output early console device and options.
918 uart[8250],io,<addr>[,options]
919 uart[8250],mmio,<addr>[,options]
920 uart[8250],mmio32,<addr>[,options]
921 Start an early, polled-mode console on the 8250/16550
922 UART at the specified I/O port or MMIO address.
923 MMIO inter-register address stride is either 8-bit
924 (mmio) or 32-bit (mmio32).
925 The options are the same as for ttyS, above.
928 Start an early, polled-mode console on a pl011 serial
929 port at the specified address. The pl011 serial port
930 must already be setup and configured. Options are not
933 smh Use ARM semihosting calls for early console.
935 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
939 earlyprintk=serial[,ttySn[,baudrate]]
940 earlyprintk=serial[,0x...[,baudrate]]
941 earlyprintk=ttySn[,baudrate]
942 earlyprintk=dbgp[debugController#]
944 earlyprintk is useful when the kernel crashes before
945 the normal console is initialized. It is not enabled by
946 default because it has some cosmetic problems.
948 Append ",keep" to not disable it when the real console
951 Only one of vga, efi, serial, or usb debug port can
954 Currently only ttyS0 and ttyS1 may be specified by
955 name. Other I/O ports may be explicitly specified
956 on some architectures (x86 and arm at least) by
957 replacing ttySn with an I/O port address, like this:
958 earlyprintk=serial,0x1008,115200
959 You can find the port for a given device in
960 /proc/tty/driver/serial:
961 2: uart:ST16650V2 port:00001008 irq:18 ...
963 Interaction with the standard serial driver is not
966 The VGA and EFI output is eventually overwritten by
969 The xen output can only be used by Xen PV guests.
971 edac_report= [HW,EDAC] Control how to report EDAC event
972 Format: {"on" | "off" | "force"}
973 on: enable EDAC to report H/W event. May be overridden
974 by other higher priority error reporting module.
975 off: disable H/W event reporting through EDAC.
976 force: enforce the use of EDAC to report H/W event.
979 ekgdboc= [X86,KGDB] Allow early kernel console debugging
982 This is designed to be used in conjunction with
983 the boot argument: earlyprintk=vga
986 Format: {"off" | "on" | "skip[mbr]"}
989 Format: { "old_map" }
990 old_map [X86-64]: switch to the old ioremap-based EFI
991 runtime services mapping. 32-bit still uses this one by
994 efi_no_storage_paranoia [EFI; X86]
995 Using this parameter you can use more than 50% of
996 your efi variable storage. Use this parameter only if
997 you are really sure that your UEFI does sane gc and
998 fulfills the spec otherwise your board may brick.
1000 eisa_irq_edge= [PARISC,HW]
1001 See header of drivers/parisc/eisa.c.
1004 See comment before function elanfreq_setup() in
1005 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1008 Format: {"cfq" | "deadline" | "noop"}
1009 See Documentation/block/cfq-iosched.txt and
1010 Documentation/block/deadline-iosched.txt for details.
1012 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1013 Specifies physical address of start of kernel core
1014 image elf header and optionally the size. Generally
1015 kexec loader will pass this option to capture kernel.
1016 See Documentation/kdump/kdump.txt for details.
1018 enable_mtrr_cleanup [X86]
1019 The kernel tries to adjust MTRR layout from continuous
1020 to discrete, to make X server driver able to add WB
1021 entry later. This parameter enables that.
1023 enable_timer_pin_1 [X86]
1024 Enable PIN 1 of APIC timer
1025 Can be useful to work around chipset bugs
1026 (in particular on some ATI chipsets).
1027 The kernel tries to set a reasonable default.
1029 enforcing [SELINUX] Set initial enforcing status.
1031 See security/selinux/Kconfig help text.
1032 0 -- permissive (log only, no denials).
1033 1 -- enforcing (deny and log).
1035 Value can be changed at runtime via /selinux/enforce.
1038 Disable Error Record Serialization Table (ERST)
1041 ether= [HW,NET] Ethernet cards parameters
1042 This option is obsoleted by the "netdev=" option, which
1043 has equivalent usage. See its documentation for details.
1047 Permit 'security.evm' to be updated regardless of
1048 current integrity status.
1052 fail_make_request=[KNL]
1053 General fault injection mechanism.
1054 Format: <interval>,<probability>,<space>,<times>
1055 See also Documentation/fault-injection/.
1058 See Documentation/blockdev/floppy.txt.
1060 force_pal_cache_flush
1061 [IA-64] Avoid check_sal_cache_flush which may hang on
1062 buggy SAL_CACHE_FLUSH implementations. Using this
1063 parameter will force ia64_sal_cache_flush to call
1064 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1067 Forcefully enable Physical Address Extension (PAE).
1068 Many Pentium M systems disable PAE but may have a
1069 functionally usable PAE implementation.
1070 Warning: use of this parameter will taint the kernel
1071 and may cause unknown problems.
1074 [FTRACE] will set and start the specified tracer
1075 as early as possible in order to facilitate early
1078 ftrace_dump_on_oops[=orig_cpu]
1079 [FTRACE] will dump the trace buffers on oops.
1080 If no parameter is passed, ftrace will dump
1081 buffers of all CPUs, but if you pass orig_cpu, it will
1082 dump only the buffer of the CPU that triggered the
1085 ftrace_filter=[function-list]
1086 [FTRACE] Limit the functions traced by the function
1087 tracer at boot up. function-list is a comma separated
1088 list of functions. This list can be changed at run
1089 time by the set_ftrace_filter file in the debugfs
1092 ftrace_notrace=[function-list]
1093 [FTRACE] Do not trace the functions specified in
1094 function-list. This list can be changed at run time
1095 by the set_ftrace_notrace file in the debugfs
1098 ftrace_graph_filter=[function-list]
1099 [FTRACE] Limit the top level callers functions traced
1100 by the function graph tracer at boot up.
1101 function-list is a comma separated list of functions
1102 that can be changed at run time by the
1103 set_graph_function file in the debugfs tracing directory.
1106 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1107 support via parallel port (up to 5 devices per port)
1108 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1109 See also Documentation/input/joystick-parport.txt
1113 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1117 gcov_persist= [GCOV] When non-zero (default), profiling data for
1118 kernel modules is saved and remains accessible via
1119 debugfs, even when the module is unloaded/reloaded.
1120 When zero, profiling data is discarded and associated
1121 debugfs files are removed at module unload time.
1123 gpt [EFI] Forces disk with valid GPT signature but
1124 invalid Protective MBR to be treated as GPT. If the
1125 primary GPT is corrupted, it enables the backup/alternate
1126 GPT to be used instead.
1128 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1129 the "Enable 0" bit of the configuration register.
1132 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1133 the "Enable 0" bit of the configuration register.
1136 grcan.select= [HW] Select which physical interface to use.
1139 grcan.txsize= [HW] Sets the size of the tx buffer.
1140 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1142 grcan.rxsize= [HW] Sets the size of the rx buffer.
1143 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1146 hashdist= [KNL,NUMA] Large hashes allocated during boot
1147 are distributed across NUMA nodes. Defaults on
1148 for 64-bit NUMA, off otherwise.
1149 Format: 0 | 1 (for off | on)
1151 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1153 hd= [EIDE] (E)IDE hard drive subsystem geometry
1154 Format: <cyl>,<head>,<sect>
1157 Disable Hardware Error Source Table (HEST) support;
1158 corresponding firmware-first mode error processing
1159 logic will be disabled.
1161 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1162 size of <nn>. This works even on boxes that have no
1163 highmem otherwise. This also works to reduce highmem
1164 size on bigger boxes.
1166 highres= [KNL] Enable/disable high resolution timer mode.
1167 Valid parameters: "on", "off"
1171 See Documentation/isdn/README.HiSax.
1175 hpet= [X86-32,HPET] option to control HPET usage
1176 Format: { enable (default) | disable | force |
1178 disable: disable HPET and use PIT instead
1179 force: allow force enabled of undocumented chips (ICH4,
1181 verbose: show contents of HPET registers during setup
1183 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1184 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1186 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1187 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1188 On x86-64 and powerpc, this option can be specified
1189 multiple times interleaved with hugepages= to reserve
1190 huge pages of different sizes. Valid pages sizes on
1191 x86-64 are 2M (when the CPU supports "pse") and 1G
1192 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1193 Note that 1GB pages can only be allocated at boot time
1194 using hugepages= and not freed afterwards.
1196 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1197 terminal devices. Valid values: 0..8
1198 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1199 If specified, z/VM IUCV HVC accepts connections
1200 from listed z/VM user IDs only.
1202 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1203 hardware thread id mappings.
1204 Format: <cpu>:<hwthread>
1207 Do not unregister boot console at start. This is only
1208 useful for debugging when something happens in the window
1209 between unregistering the boot console and initializing
1212 i2c_bus= [HW] Override the default board specific I2C bus speed
1213 or register an additional I2C bus that is not
1214 registered from board initialization code.
1218 i8042.debug [HW] Toggle i8042 debug mode
1219 i8042.direct [HW] Put keyboard port into non-translated mode
1220 i8042.dumbkbd [HW] Pretend that controller can only read data from
1221 keyboard and cannot control its state
1222 (Don't attempt to blink the leds)
1223 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1224 i8042.nokbd [HW] Don't check/create keyboard port
1225 i8042.noloop [HW] Disable the AUX Loopback command while probing
1227 i8042.nomux [HW] Don't check presence of an active multiplexing
1229 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1231 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1232 i8042.reset [HW] Reset the controller during init and cleanup
1233 i8042.unlock [HW] Unlock (ignore) the keylock
1237 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1238 indicates that the driver is running on unsupported
1240 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1241 does not match list of supported models.
1243 [HW] Report power status in /proc/i8k
1244 (disabled by default)
1245 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1248 i915.invert_brightness=
1249 [DRM] Invert the sense of the variable that is used to
1250 set the brightness of the panel backlight. Normally a
1251 brightness value of 0 indicates backlight switched off,
1252 and the maximum of the brightness value sets the backlight
1253 to maximum brightness. If this parameter is set to 0
1254 (default) and the machine requires it, or this parameter
1255 is set to 1, a brightness value of 0 sets the backlight
1256 to maximum brightness, and the maximum of the brightness
1257 value switches the backlight off.
1258 -1 -- never invert brightness
1259 0 -- machine default
1260 1 -- force brightness inversion
1263 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1265 ide-core.nodma= [HW] (E)IDE subsystem
1266 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1267 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1268 .cdrom .chs .ignore_cable are additional options
1269 See Documentation/ide/ide.txt.
1271 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1272 Claim all unknown PCI IDE storage controllers.
1275 Format: idle=poll, idle=halt, idle=nomwait
1276 Poll forces a polling idle loop that can slightly
1277 improve the performance of waking up a idle CPU, but
1278 will use a lot of power and make the system run hot.
1280 idle=halt: Halt is forced to be used for CPU idle.
1281 In such case C2/C3 won't be used again.
1282 idle=nomwait: Disable mwait for CPU C-states
1284 ignore_loglevel [KNL]
1285 Ignore loglevel setting - this will print /all/
1286 kernel messages to the console. Useful for debugging.
1287 We also add it as printk module parameter, so users
1288 could change it dynamically, usually by
1289 /sys/module/printk/parameters/ignore_loglevel.
1291 ihash_entries= [KNL]
1292 Set number of hash buckets for inode cache.
1294 ima_appraise= [IMA] appraise integrity measurements
1295 Format: { "off" | "enforce" | "fix" }
1298 ima_appraise_tcb [IMA]
1299 The builtin appraise policy appraises all files
1303 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1307 The list of supported hash algorithms is defined
1308 in crypto/hash_info.h.
1311 Load a policy which meets the needs of the Trusted
1312 Computing Base. This means IMA will measure all
1313 programs exec'd, files mmap'd for exec, and all files
1314 opened for read by uid=0.
1317 Select one of defined IMA measurements template formats.
1318 Formats: { "ima" | "ima-ng" }
1321 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1322 Format: <min_file_size>
1323 Set the minimal file size for using asynchronous hash.
1324 If left unspecified, ahash usage is disabled.
1326 ahash performance varies for different data sizes on
1327 different crypto accelerators. This option can be used
1328 to achieve the best performance for a particular HW.
1330 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1332 Set hashing buffer size. Default: 4k.
1334 ahash performance varies for different chunk sizes on
1335 different crypto accelerators. This option can be used
1336 to achieve best performance for particular HW.
1340 Run specified binary instead of /sbin/init as init
1343 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1344 for working out where the kernel is dying during
1347 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1348 initcall functions. Useful for debugging built-in
1349 modules and initcalls.
1351 initrd= [BOOT] Specify the location of the initial ramdisk
1353 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1356 int_pln_enable [x86] Enable power limit notification interrupt
1358 integrity_audit=[IMA]
1359 Format: { "0" | "1" }
1360 0 -- basic integrity auditing messages. (Default)
1361 1 -- additional integrity auditing messages.
1363 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1365 Enable intel iommu driver.
1367 Disable intel iommu driver.
1368 igfx_off [Default Off]
1369 By default, gfx is mapped as normal device. If a gfx
1370 device has a dedicated DMAR unit, the DMAR unit is
1371 bypassed by not enabling DMAR with this option. In
1372 this case, gfx device will use physical address for
1375 With this option iommu will not optimize to look
1376 for io virtual address below 32-bit forcing dual
1377 address cycle on pci bus for cards supporting greater
1378 than 32-bit addressing. The default is to look
1379 for translation below 32-bit and if not available
1380 then look in the higher range.
1381 strict [Default Off]
1382 With this option on every unmap_single operation will
1383 result in a hardware IOTLB flush operation as opposed
1384 to batching them for performance.
1385 sp_off [Default Off]
1386 By default, super page will be supported if Intel IOMMU
1387 has the capability. With this option, super page will
1390 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1391 0 disables intel_idle and fall back on acpi_idle.
1392 1 to 6 specify maximum depth of C-state.
1396 Do not enable intel_pstate as the default
1397 scaling driver for the supported processors
1399 intremap= [X86-64, Intel-IOMMU]
1400 on enable Interrupt Remapping (default)
1401 off disable Interrupt Remapping
1402 nosid disable Source ID checking
1404 BIOS x2APIC opt-out request will be ignored
1406 iomem= Disable strict checking of access to MMIO memory
1407 strict regions from userspace.
1424 io7= [HW] IO7 for Marvel based alpha systems
1425 See comment before marvel_specify_io7 in
1426 arch/alpha/kernel/core_marvel.c.
1428 io_delay= [X86] I/O delay method
1430 Standard port 0x80 based delay
1432 Alternate port 0xed based delay (needed on some systems)
1434 Simple two microseconds delay
1439 See Documentation/filesystems/nfs/nfsroot.txt.
1441 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1442 See comment before ip2_setup() in
1443 drivers/char/ip2/ip2base.c.
1446 When an interrupt is not handled search all handlers
1447 for it. Intended to get systems with badly broken
1451 When an interrupt is not handled search all handlers
1452 for it. Also check all handlers each timer
1453 interrupt. Intended to get systems with badly broken
1457 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1459 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1461 <cpu number>,...,<cpu number>
1463 <cpu number>-<cpu number>
1464 (must be a positive range in ascending order)
1466 <cpu number>,...,<cpu number>-<cpu number>
1468 This option can be used to specify one or more CPUs
1469 to isolate from the general SMP balancing and scheduling
1470 algorithms. You can move a process onto or off an
1471 "isolated" CPU via the CPU affinity syscalls or cpuset.
1472 <cpu number> begins at 0 and the maximum value is
1473 "number of CPUs in system - 1".
1475 This option is the preferred way to isolate CPUs. The
1476 alternative -- manually setting the CPU mask of all
1477 tasks in the system -- can cause problems and
1478 suboptimal load balancer performance.
1482 ivrs_ioapic [HW,X86_64]
1483 Provide an override to the IOAPIC-ID<->DEVICE-ID
1484 mapping provided in the IVRS ACPI table. For
1485 example, to map IOAPIC-ID decimal 10 to
1486 PCI device 00:14.0 write the parameter as:
1487 ivrs_ioapic[10]=00:14.0
1489 ivrs_hpet [HW,X86_64]
1490 Provide an override to the HPET-ID<->DEVICE-ID
1491 mapping provided in the IVRS ACPI table. For
1492 example, to map HPET-ID decimal 0 to
1493 PCI device 00:14.0 write the parameter as:
1494 ivrs_hpet[0]=00:14.0
1496 js= [HW,JOY] Analog joystick
1497 See Documentation/input/joystick.txt.
1500 Enable/disable kernel and module base offset ASLR
1501 (Address Space Layout Randomization) if built into
1502 the kernel. When CONFIG_HIBERNATION is selected,
1503 kASLR is disabled by default. When kASLR is enabled,
1504 hibernation will be disabled.
1508 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1509 specifies the amount of memory usable by the kernel
1510 for non-movable allocations. The requested amount is
1511 spread evenly throughout all nodes in the system. The
1512 remaining memory in each node is used for Movable
1513 pages. In the event, a node is too small to have both
1514 kernelcore and Movable pages, kernelcore pages will
1515 take priority and other nodes will have a larger number
1516 of Movable pages. The Movable zone is used for the
1517 allocation of pages that may be reclaimed or moved
1518 by the page migration subsystem. This means that
1519 HugeTLB pages may not be allocated from this zone.
1520 Note that allocations like PTEs-from-HighMem still
1521 use the HighMem zone if it exists, and the Normal
1522 zone if it does not.
1524 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1525 Format: <Controller#>[,poll interval]
1526 The controller # is the number of the ehci usb debug
1527 port as it is probed via PCI. The poll interval is
1528 optional and is the number seconds in between
1529 each poll cycle to the debug port in case you need
1530 the functionality for interrupting the kernel with
1531 gdb or control-c on the dbgp connection. When
1532 not using this parameter you use sysrq-g to break into
1533 the kernel debugger.
1535 kgdboc= [KGDB,HW] kgdb over consoles.
1536 Requires a tty driver that supports console polling,
1537 or a supported polling keyboard driver (non-usb).
1538 Serial only format: <serial_device>[,baud]
1539 keyboard only format: kbd
1540 keyboard and serial format: kbd,<serial_device>[,baud]
1541 Optional Kernel mode setting:
1542 kms, kbd format: kms,kbd
1543 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1545 kgdbwait [KGDB] Stop kernel execution and enter the
1546 kernel debugger at the earliest opportunity.
1548 kmac= [MIPS] korina ethernet MAC address.
1549 Configure the RouterBoard 532 series on-chip
1550 Ethernet adapter MAC address.
1552 kmemleak= [KNL] Boot-time kmemleak enable/disable
1553 Valid arguments: on, off
1556 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1557 Valid arguments: 0, 1, 2
1558 kmemcheck=0 (disabled)
1559 kmemcheck=1 (enabled)
1560 kmemcheck=2 (one-shot mode)
1561 Default: 2 (one-shot mode)
1563 kstack=N [X86] Print N words from the kernel stack
1566 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1567 Default is 0 (don't ignore, but inject #GP)
1569 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1573 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1574 Default is 1 (enabled)
1576 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1578 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1580 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1581 (virtualized MMU) support on capable Intel chips.
1582 Default is 1 (enabled)
1584 kvm-intel.emulate_invalid_guest_state=
1585 [KVM,Intel] Enable emulation of invalid guest states
1586 Default is 0 (disabled)
1588 kvm-intel.flexpriority=
1589 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1590 Default is 1 (enabled)
1593 [KVM,Intel] Enable VMX nesting (nVMX).
1594 Default is 0 (disabled)
1596 kvm-intel.unrestricted_guest=
1597 [KVM,Intel] Disable unrestricted guest feature
1598 (virtualized real and unpaged mode) on capable
1599 Intel chips. Default is 1 (enabled)
1601 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1602 feature (tagged TLBs) on capable Intel chips.
1603 Default is 1 (enabled)
1609 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1612 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1613 value for LAPIC timer one-shot implementation. Default
1614 back to the programmable timer unit in the LAPIC.
1616 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1619 libata.dma= [LIBATA] DMA control
1620 libata.dma=0 Disable all PATA and SATA DMA
1621 libata.dma=1 PATA and SATA Disk DMA only
1622 libata.dma=2 ATAPI (CDROM) DMA only
1623 libata.dma=4 Compact Flash DMA only
1624 Combinations also work, so libata.dma=3 enables DMA
1625 for disks and CDROMs, but not CFs.
1627 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1628 libata.ignore_hpa=0 keep BIOS limits (default)
1629 libata.ignore_hpa=1 ignore limits, using full disk
1631 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1635 libata.force= [LIBATA] Force configurations. The format is comma
1636 separated list of "[ID:]VAL" where ID is
1637 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1638 matching port, link or device. Basically, it matches
1639 the ATA ID string printed on console by libata. If
1640 the whole ID part is omitted, the last PORT and DEVICE
1641 values are used. If ID hasn't been specified yet, the
1642 configuration applies to all ports, links and devices.
1644 If only DEVICE is omitted, the parameter applies to
1645 the port and all links and devices behind it. DEVICE
1646 number of 0 either selects the first device or the
1647 first fan-out link behind PMP device. It does not
1648 select the host link. DEVICE number of 15 selects the
1649 host link and device attached to it.
1651 The VAL specifies the configuration to force. As long
1652 as there's no ambiguity shortcut notation is allowed.
1653 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1654 The following configurations can be forced.
1656 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1657 Any ID with matching PORT is used.
1659 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1661 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1662 udma[/][16,25,33,44,66,100,133] notation is also
1665 * [no]ncq: Turn on or off NCQ.
1667 * nohrst, nosrst, norst: suppress hard, soft
1670 * rstonce: only attempt one reset during
1671 hot-unplug link recovery
1673 * dump_id: dump IDENTIFY data.
1675 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1677 * disable: Disable this device.
1679 If there are multiple matching configurations changing
1680 the same attribute, the last one is used.
1682 memblock=debug [KNL] Enable memblock debug messages.
1684 load_ramdisk= [RAM] List of ramdisks to load from floppy
1685 See Documentation/blockdev/ramdisk.txt.
1687 lockd.nlm_grace_period=P [NFS] Assign grace period.
1690 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1693 lockd.nlm_timeout=T [NFS] Assign timeout value.
1696 lockd.nlm_udpport=M [NFS] Assign UDP port.
1699 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1702 loglevel= All Kernel Messages with a loglevel smaller than the
1703 console loglevel will be printed to the console. It can
1704 also be changed with klogd or other programs. The
1705 loglevels are defined as follows:
1707 0 (KERN_EMERG) system is unusable
1708 1 (KERN_ALERT) action must be taken immediately
1709 2 (KERN_CRIT) critical conditions
1710 3 (KERN_ERR) error conditions
1711 4 (KERN_WARNING) warning conditions
1712 5 (KERN_NOTICE) normal but significant condition
1713 6 (KERN_INFO) informational
1714 7 (KERN_DEBUG) debug-level messages
1716 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1717 in bytes. n must be a power of two. The default
1718 size is set in the kernel config file.
1720 logo.nologo [FB] Disables display of the built-in Linux logo.
1721 This may be used to provide more screen space for
1722 kernel log messages and is useful when debugging
1723 kernel boot problems.
1725 lp=0 [LP] Specify parallel ports to use, e.g,
1726 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1727 lp=reset first parallel port). 'lp=0' disables the
1728 lp=auto printer driver. 'lp=reset' (which can be
1729 specified in addition to the ports) causes
1730 attached printers to be reset. Using
1731 lp=port1,port2,... specifies the parallel ports
1732 to associate lp devices with, starting with
1733 lp0. A port specification may be 'none' to skip
1734 that lp device, or a parport name such as
1735 'parport0'. Specifying 'lp=auto' instead of a
1736 port specification list means that device IDs
1737 from each port should be examined, to see if
1738 an IEEE 1284-compliant printer is attached; if
1739 so, the driver will manage that printer.
1740 See also header of drivers/char/lp.c.
1743 Sets loops_per_jiffy to given constant, thus avoiding
1744 time-consuming boot-time autodetection (up to 250 ms per
1745 CPU). 0 enables autodetection (default). To determine
1746 the correct value for your kernel, boot with normal
1747 autodetection and see what value is printed. Note that
1748 on SMP systems the preset will be applied to all CPUs,
1749 which is likely to cause problems if your CPUs need
1750 significantly divergent settings. An incorrect value
1751 will cause delays in the kernel to be wrong, leading to
1752 unpredictable I/O errors and other breakage. Although
1753 unlikely, in the extreme case this might damage your
1757 Format: <io>,<irq>,<dma>
1759 machvec= [IA-64] Force the use of a particular machine-vector
1760 (machvec) in a generic kernel.
1761 Example: machvec=hpzx1_swiotlb
1763 machtype= [Loongson] Share the same kernel image file between different
1765 Example: machtype=lemote-yeeloong-2f-7inch
1767 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1768 than or equal to this physical address is ignored.
1770 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1771 should make use of. maxcpus=n : n >= 0 limits the
1772 kernel to using 'n' processors. n=0 is a special case,
1773 it is equivalent to "nosmp", which also disables
1776 max_loop= [LOOP] The number of loop block devices that get
1777 (loop.max_loop) unconditionally pre-created at init time. The default
1778 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1779 of statically allocating a predefined number, loop
1780 devices can be requested on-demand with the
1781 /dev/loop-control interface.
1783 mce [X86-32] Machine Check Exception
1785 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1787 md= [HW] RAID subsystems devices and level
1788 See Documentation/md.txt.
1791 Format: <first>,<last>
1792 Specifies range of consoles to be captured by the MDA.
1794 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1795 Amount of memory to be used when the kernel is not able
1796 to see the whole system memory or for test.
1797 [X86] Work as limiting max address. Use together
1798 with memmap= to avoid physical address space collisions.
1799 Without memmap= PCI devices could be placed at addresses
1800 belonging to unused RAM.
1802 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1806 [KNL,SH] Allow user to override the default size for
1807 per-device physically contiguous DMA buffers.
1809 memmap=exactmap [KNL,X86] Enable setting of an exact
1810 E820 memory map, as specified by the user.
1811 Such memmap=exactmap lines can be constructed based on
1812 BIOS output or other requirements. See the memmap=nn@ss
1815 memmap=nn[KMG]@ss[KMG]
1816 [KNL] Force usage of a specific region of memory.
1817 Region of memory to be used is from ss to ss+nn.
1819 memmap=nn[KMG]#ss[KMG]
1820 [KNL,ACPI] Mark specific memory as ACPI data.
1821 Region of memory to be marked is from ss to ss+nn.
1823 memmap=nn[KMG]$ss[KMG]
1824 [KNL,ACPI] Mark specific memory as reserved.
1825 Region of memory to be reserved is from ss to ss+nn.
1826 Example: Exclude memory from 0x18690000-0x1869ffff
1827 memmap=64K$0x18690000
1829 memmap=0x10000$0x18690000
1831 memory_corruption_check=0/1 [X86]
1832 Some BIOSes seem to corrupt the first 64k of
1833 memory when doing things like suspend/resume.
1834 Setting this option will scan the memory
1835 looking for corruption. Enabling this will
1836 both detect corruption and prevent the kernel
1837 from using the memory being corrupted.
1838 However, its intended as a diagnostic tool; if
1839 repeatable BIOS-originated corruption always
1840 affects the same memory, you can use memmap=
1841 to prevent the kernel from using that memory.
1843 memory_corruption_check_size=size [X86]
1844 By default it checks for corruption in the low
1845 64k, making this memory unavailable for normal
1846 use. Use this parameter to scan for
1847 corruption in more or less memory.
1849 memory_corruption_check_period=seconds [X86]
1850 By default it checks for corruption every 60
1851 seconds. Use this parameter to check at some
1852 other rate. 0 disables periodic checking.
1854 memtest= [KNL,X86] Enable memtest
1856 default : 0 <disable>
1857 Specifies the number of memtest passes to be
1858 performed. Each pass selects another test
1859 pattern from a given set of patterns. Memtest
1860 fills the memory with this pattern, validates
1861 memory contents and reserves bad memory
1862 regions that are detected.
1864 meye.*= [HW] Set MotionEye Camera parameters
1865 See Documentation/video4linux/meye.txt.
1867 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1868 Multi-Function General Purpose Timers on AMD Geode
1871 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1872 the BIOS has incorrectly applied a workaround. TinyBIOS
1873 version 0.98 is known to be affected, 0.99 fixes the
1874 problem by letting the user disable the workaround.
1878 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1879 physical address is ignored.
1881 mini2440= [ARM,HW,KNL]
1882 Format:[0..2][b][c][t]
1884 MINI2440 configuration specification:
1885 0 - The attached screen is the 3.5" TFT
1886 1 - The attached screen is the 7" TFT
1887 2 - The VGA Shield is attached (1024x768)
1888 Leaving out the screen size parameter will not load
1889 the TFT driver, and the framebuffer will be left
1891 b - Enable backlight. The TFT backlight pin will be
1892 linked to the kernel VESA blanking code and a GPIO
1893 LED. This parameter is not necessary when using the
1895 c - Enable the s3c camera interface.
1896 t - Reserved for enabling touchscreen support. The
1897 touchscreen support is not enabled in the mainstream
1898 kernel as of 2.6.30, a preliminary port can be found
1899 in the "bleeding edge" mini2440 support kernel at
1900 http://repo.or.cz/w/linux-2.6/mini2440.git
1903 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1904 parameter allows control of the logging verbosity for
1905 the additional memory initialisation checks. A value
1906 of 0 disables mminit logging and a level of 4 will
1907 log everything. Information is printed at KERN_DEBUG
1908 so loglevel=8 may also need to be specified.
1911 [KNL] When CONFIG_MODULE_SIG is set, this means that
1912 modules without (valid) signatures will fail to load.
1913 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1914 is always true, so this option does nothing.
1917 [MOUSE] Maximum time between finger touching and
1918 leaving touchpad surface for touch to be considered
1919 a tap and be reported as a left button click (for
1920 touchpads working in absolute mode only).
1922 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1923 reporting absolute coordinates, such as tablets
1924 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1925 reporting absolute coordinates, such as tablets
1927 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1928 is similar to kernelcore except it specifies the
1929 amount of memory used for migratable allocations.
1930 If both kernelcore and movablecore is specified,
1931 then kernelcore will be at *least* the specified
1932 value but may be more. If movablecore on its own
1933 is specified, the administrator must be careful
1934 that the amount of memory usable for all allocations
1937 movable_node [KNL,X86] Boot-time switch to enable the effects
1938 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1940 MTD_Partition= [MTD]
1941 Format: <name>,<region-number>,<size>,<offset>
1943 MTD_Region= [MTD] Format:
1944 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1947 See drivers/mtd/cmdlinepart.c.
1949 multitce=off [PPC] This parameter disables the use of the pSeries
1950 firmware feature for updating multiple TCE entries
1953 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1955 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1957 boundary - index of last SLC block on Flex-OneNAND.
1958 The remaining blocks are configured as MLC blocks.
1959 lock - Configure if Flex-OneNAND boundary should be locked.
1960 Once locked, the boundary cannot be changed.
1961 1 indicates lock status, 0 indicates unlock status.
1964 ARM/S3C2412 JIVE boot control
1966 See arch/arm/mach-s3c2412/mach-jive.c
1968 mtouchusb.raw_coordinates=
1969 [HW] Make the MicroTouch USB driver use raw coordinates
1970 ('y', default) or cooked coordinates ('n')
1972 mtrr_chunk_size=nn[KMG] [X86]
1973 used for mtrr cleanup. It is largest continuous chunk
1974 that could hold holes aka. UC entries.
1976 mtrr_gran_size=nn[KMG] [X86]
1977 Used for mtrr cleanup. It is granularity of mtrr block.
1979 Large value could prevent small alignment from
1982 mtrr_spare_reg_nr=n [X86]
1984 Range: 0,7 : spare reg number
1986 Used for mtrr cleanup. It is spare mtrr entries number.
1987 Set to 2 or more if your graphical card needs more.
1989 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1991 netdev= [NET] Network devices parameters
1992 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1993 Note that mem_start is often overloaded to mean
1994 something different and driver-specific.
1995 This usage is only documented in each driver source
1999 [NETFILTER] Enable connection tracking flow accounting
2000 0 to disable accounting
2001 1 to enable accounting
2004 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2005 See Documentation/filesystems/nfs/nfsroot.txt.
2007 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2008 See Documentation/filesystems/nfs/nfsroot.txt.
2010 nfsrootdebug [NFS] enable nfsroot debugging messages.
2011 See Documentation/filesystems/nfs/nfsroot.txt.
2013 nfs.callback_tcpport=
2014 [NFS] set the TCP port on which the NFSv4 callback
2015 channel should listen.
2018 [NFS] sets the pathname to the program which is used
2019 to update the NFS client cache entries.
2021 nfs.cache_getent_timeout=
2022 [NFS] sets the timeout after which an attempt to
2023 update a cache entry is deemed to have failed.
2025 nfs.idmap_cache_timeout=
2026 [NFS] set the maximum lifetime for idmapper cache
2030 [NFS] enable 64-bit inode numbers.
2031 If zero, the NFS client will fake up a 32-bit inode
2032 number for the readdir() and stat() syscalls instead
2033 of returning the full 64-bit number.
2034 The default is to return 64-bit inode numbers.
2036 nfs.max_session_slots=
2037 [NFSv4.1] Sets the maximum number of session slots
2038 the client will attempt to negotiate with the server.
2039 This limits the number of simultaneous RPC requests
2040 that the client can send to the NFSv4.1 server.
2041 Note that there is little point in setting this
2042 value higher than the max_tcp_slot_table_limit.
2044 nfs.nfs4_disable_idmapping=
2045 [NFSv4] When set to the default of '1', this option
2046 ensures that both the RPC level authentication
2047 scheme and the NFS level operations agree to use
2048 numeric uids/gids if the mount is using the
2049 'sec=sys' security flavour. In effect it is
2050 disabling idmapping, which can make migration from
2051 legacy NFSv2/v3 systems to NFSv4 easier.
2052 Servers that do not support this mode of operation
2053 will be autodetected by the client, and it will fall
2054 back to using the idmapper.
2055 To turn off this behaviour, set the value to '0'.
2057 [NFS4] Specify an additional fixed unique ident-
2058 ification string that NFSv4 clients can insert into
2059 their nfs_client_id4 string. This is typically a
2060 UUID that is generated at system install time.
2062 nfs.send_implementation_id =
2063 [NFSv4.1] Send client implementation identification
2064 information in exchange_id requests.
2065 If zero, no implementation identification information
2067 The default is to send the implementation identification
2070 nfs.recover_lost_locks =
2071 [NFSv4] Attempt to recover locks that were lost due
2072 to a lease timeout on the server. Please note that
2073 doing this risks data corruption, since there are
2074 no guarantees that the file will remain unchanged
2075 after the locks are lost.
2076 If you want to enable the kernel legacy behaviour of
2077 attempting to recover these locks, then set this
2079 The default parameter value of '0' causes the kernel
2080 not to attempt recovery of lost locks.
2082 nfsd.nfs4_disable_idmapping=
2083 [NFSv4] When set to the default of '1', the NFSv4
2084 server will return only numeric uids and gids to
2085 clients using auth_sys, and will accept numeric uids
2086 and gids from such clients. This is intended to ease
2087 migration from NFSv2/v3.
2089 objlayoutdriver.osd_login_prog=
2090 [NFS] [OBJLAYOUT] sets the pathname to the program which
2091 is used to automatically discover and login into new
2092 osd-targets. Please see:
2093 Documentation/filesystems/pnfs.txt for more explanations
2095 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2096 when a NMI is triggered.
2097 Format: [state][,regs][,debounce][,die]
2099 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2100 Format: [panic,][nopanic,][num]
2102 0 - turn nmi_watchdog off
2103 When panic is specified, panic when an NMI watchdog
2104 timeout occurs (or 'nopanic' to override the opposite
2106 This is useful when you use a panic=... timeout and
2107 need the box quickly up again.
2109 netpoll.carrier_timeout=
2110 [NET] Specifies amount of time (in seconds) that
2111 netpoll should wait for a carrier. By default netpoll
2114 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2115 emulation library even if a 387 maths coprocessor
2119 [HW] Never suspend the console
2120 Disable suspending of consoles during suspend and
2121 hibernate operations. Once disabled, debugging
2122 messages can reach various consoles while the rest
2123 of the system is being put to sleep (ie, while
2124 debugging driver suspend/resume hooks). This may
2125 not work reliably with all consoles, but is known
2126 to work with serial and VGA consoles.
2127 To facilitate more flexible debugging, we also add
2128 console_suspend, a printk module parameter to control
2129 it. Users could use console_suspend (usually
2130 /sys/module/printk/parameters/console_suspend) to
2131 turn on/off it dynamically.
2133 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2134 caches in the slab allocator. Saves per-node memory,
2135 but will impact performance.
2139 noapic [SMP,APIC] Tells the kernel to not make use of any
2140 IOAPICs that may be present in the system.
2142 noautogroup Disable scheduler automatic task group creation.
2144 nobats [PPC] Do not use BATs for mapping kernel lowmem
2145 on "Classic" PPC cores.
2149 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2151 nodelayacct [KNL] Disable per-task delay accounting
2153 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2155 nodsp [SH] Disable hardware DSP at boot time.
2157 noefi [X86] Disable EFI runtime services support.
2162 On X86-32 available only on PAE configured kernels.
2163 noexec=on: enable non-executable mappings (default)
2164 noexec=off: disable non-executable mappings
2167 Disable SMAP (Supervisor Mode Access Prevention)
2168 even if it is supported by processor.
2171 Disable SMEP (Supervisor Mode Execution Prevention)
2172 even if it is supported by processor.
2175 This affects only 32-bit executables.
2176 noexec32=on: enable non-executable mappings (default)
2177 read doesn't imply executable mappings
2178 noexec32=off: disable non-executable mappings
2179 read implies executable mappings
2181 nofpu [SH] Disable hardware FPU at boot time.
2183 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2184 register save and restore. The kernel will only save
2185 legacy floating-point registers on task switch.
2187 noxsave [BUGS=X86] Disables x86 extended register state save
2188 and restore using xsave. The kernel will fallback to
2189 enabling legacy floating-point and sse state.
2192 on enable eager fpu restore
2193 off disable eager fpu restore
2194 auto selects the default scheme, which automatically
2195 enables eagerfpu restore for xsaveopt.
2197 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2198 wfi(ARM) instruction doesn't work correctly and not to
2199 use it. This is also useful when using JTAG debugger.
2201 no_file_caps Tells the kernel not to honor file capabilities. The
2202 only way then for a file to be executed with privilege
2203 is to be setuid root or executed by root.
2205 nohalt [IA-64] Tells the kernel not to use the power saving
2206 function PAL_HALT_LIGHT when idle. This increases
2207 power-consumption. On the positive side, it reduces
2208 interrupt wake-up latency, which may improve performance
2209 in certain environments such as networked servers or
2212 nohibernate [HIBERNATION] Disable hibernation and resume.
2214 nohz= [KNL] Boottime enable/disable dynamic ticks
2215 Valid arguments: on, off
2218 nohz_full= [KNL,BOOT]
2219 In kernels built with CONFIG_NO_HZ_FULL=y, set
2220 the specified list of CPUs whose tick will be stopped
2221 whenever possible. The boot CPU will be forced outside
2222 the range to maintain the timekeeping.
2223 The CPUs in this range must also be included in the
2226 noiotrap [SH] Disables trapped I/O port accesses.
2228 noirqdebug [X86-32] Disables the code which attempts to detect and
2229 disable unhandled interrupt sources.
2231 no_timer_check [X86,APIC] Disables the code which tests for
2232 broken timer IRQ sources.
2234 noisapnp [ISAPNP] Disables ISA PnP code.
2236 noinitrd [RAM] Tells the kernel not to load any configured
2239 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2241 [Deprecated - use intremap=off]
2245 nojitter [IA-64] Disables jitter checking for ITC timers.
2247 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2249 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2252 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2253 steal time is computed, but won't influence scheduler
2256 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2258 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2260 noltlbs [PPC] Do not use large page/tlb entries for kernel
2261 lowmem mapping on PPC40x.
2263 nomca [IA-64] Disable machine check abort handling
2265 nomce [X86-32] Machine Check Exception
2267 nomfgpt [X86-32] Disable Multi-Function General Purpose
2268 Timer usage (for AMD Geode machines).
2270 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2271 shutdown the other cpus. Instead use the REBOOT_VECTOR
2274 nomodule Disable module load
2276 nopat [X86] Disable PAT (page attribute table extension of
2277 pagetables) support.
2279 norandmaps Don't use address space randomization. Equivalent to
2280 echo 0 > /proc/sys/kernel/randomize_va_space
2282 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2284 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2285 with UP alternatives
2287 nordrand [X86] Disable kernel use of the RDRAND and
2288 RDSEED instructions even if they are supported
2289 by the processor. RDRAND and RDSEED are still
2290 available to user space applications.
2292 noresume [SWSUSP] Disables resume and restores original swap
2295 no-scroll [VGA] Disables scrollback.
2296 This is required for the Braillex ib80-piezo Braille
2297 reader made by F.H. Papenmeier (Germany).
2301 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2303 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2304 and disable the IO APIC. legacy for "maxcpus=0".
2306 nosoftlockup [KNL] Disable the soft-lockup detector.
2308 nosync [HW,M68K] Disables sync negotiation for all devices.
2310 notsc [BUGS=X86-32] Disable Time Stamp Counter
2312 nousb [USB] Disable the USB subsystem
2314 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2318 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2320 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2321 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2322 Some features depend on CPU0. Known dependencies are:
2323 1. Resume from suspend/hibernate depends on CPU0.
2324 Suspend/hibernate will fail if CPU0 is offline and you
2325 need to online CPU0 before suspend/hibernate.
2326 2. PIC interrupts also depend on CPU0. CPU0 can't be
2327 removed if a PIC interrupt is detected.
2328 It's said poweroff/reboot may depend on CPU0 on some
2329 machines although I haven't seen such issues so far
2330 after CPU0 is offline on a few tested machines.
2331 If the dependencies are under your control, you can
2332 turn on cpu0_hotplug.
2334 nptcg= [IA-64] Override max number of concurrent global TLB
2335 purges which is reported from either PAL_VM_SUMMARY or
2338 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2339 could support. nr_cpus=n : n >= 1 limits the kernel to
2340 supporting 'n' processors. Later in runtime you can not
2341 use hotplug cpu feature to put more cpu back to online.
2342 just like you compile the kernel NR_CPUS=n
2344 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2346 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2347 Allowed values are enable and disable
2349 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2350 one of ['zone', 'node', 'default'] can be specified
2351 This can be set from sysctl after boot.
2352 See Documentation/sysctl/vm.txt for details.
2354 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2355 See Documentation/debugging-via-ohci1394.txt for more
2358 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2359 Rather than timing out after 20 ms if an EC
2360 command is not properly ACKed, override the length
2361 of the timeout. We have interrupts disabled while
2362 waiting for the ACK, so if this is set too high
2363 interrupts *may* be lost!
2365 omap_mux= [OMAP] Override bootloader pin multiplexing.
2366 Format: <mux_mode0.mode_name=value>...
2367 For example, to override I2C bus2:
2368 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2370 oprofile.timer= [HW]
2371 Use timer interrupt instead of performance counters
2373 oprofile.cpu_type= Force an oprofile cpu type
2374 This might be useful if you have an older oprofile
2375 userland or if you want common events.
2376 Format: { arch_perfmon }
2377 arch_perfmon: [X86] Force use of architectural
2378 perfmon on Intel CPUs instead of the
2379 CPU specific event set.
2380 timer: [X86] Force use of architectural NMI
2381 timer mode (see also oprofile.timer
2382 for generic hr timer mode)
2383 [s390] Force legacy basic mode sampling
2384 (report cpu_type "timer")
2386 oops=panic Always panic on oopses. Default is to just kill the
2387 process, but there is a small probability of
2388 deadlocking the machine.
2389 This will also cause panics on machine check exceptions.
2390 Useful together with panic=30 to trigger a reboot.
2393 See Documentation/sound/oss/oss-parameters.txt
2395 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2396 timeout > 0: seconds before rebooting
2397 timeout = 0: wait forever
2398 timeout < 0: reboot immediately
2401 crash_kexec_post_notifiers
2402 Run kdump after running panic-notifiers and dumping
2403 kmsg. This only for the users who doubt kdump always
2404 succeeds in any situation.
2405 Note that this also increases risks of kdump failure,
2406 because some panic notifiers can make the crashed
2407 kernel more unstable.
2409 parkbd.port= [HW] Parallel port number the keyboard adapter is
2410 connected to, default is 0.
2412 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2413 0 for XT, 1 for AT (default is AT).
2416 parport= [HW,PPT] Specify parallel ports. 0 disables.
2417 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2418 Use 'auto' to force the driver to use any
2419 IRQ/DMA settings detected (the default is to
2420 ignore detected IRQ/DMA settings because of
2421 possible conflicts). You can specify the base
2422 address, IRQ, and DMA settings; IRQ and DMA
2423 should be numbers, or 'auto' (for using detected
2424 settings on that particular port), or 'nofifo'
2425 (to avoid using a FIFO even if it is detected).
2426 Parallel ports are assigned in the order they
2427 are specified on the command line, starting
2430 parport_init_mode= [HW,PPT]
2431 Configure VIA parallel port to operate in
2432 a specific mode. This is necessary on Pegasos
2433 computer where firmware has no options for setting
2434 up parallel port mode and sets it to spp.
2435 Currently this function knows 686a and 8231 chips.
2436 Format: [spp|ps2|epp|ecp|ecpepp]
2439 Halt all CPUs after the first oops has been printed for
2440 the specified number of seconds. This is to be used if
2441 your oopses keep scrolling off the screen.
2446 See header of drivers/block/paride/pcd.c.
2447 See also Documentation/blockdev/paride.txt.
2449 pci=option[,option...] [PCI] various PCI subsystem options:
2450 earlydump [X86] dump PCI config space before the kernel
2452 off [X86] don't probe for the PCI bus
2453 bios [X86-32] force use of PCI BIOS, don't access
2454 the hardware directly. Use this if your machine
2455 has a non-standard PCI host bridge.
2456 nobios [X86-32] disallow use of PCI BIOS, only direct
2457 hardware access methods are allowed. Use this
2458 if you experience crashes upon bootup and you
2459 suspect they are caused by the BIOS.
2460 conf1 [X86] Force use of PCI Configuration
2462 conf2 [X86] Force use of PCI Configuration
2464 noaer [PCIE] If the PCIEAER kernel config parameter is
2465 enabled, this kernel boot option can be used to
2466 disable the use of PCIE advanced error reporting.
2467 nodomains [PCI] Disable support for multiple PCI
2468 root domains (aka PCI segments, in ACPI-speak).
2469 nommconf [X86] Disable use of MMCONFIG for PCI
2471 check_enable_amd_mmconf [X86] check for and enable
2472 properly configured MMIO access to PCI
2473 config space on AMD family 10h CPU
2474 nomsi [MSI] If the PCI_MSI kernel config parameter is
2475 enabled, this kernel boot option can be used to
2476 disable the use of MSI interrupts system-wide.
2477 noioapicquirk [APIC] Disable all boot interrupt quirks.
2478 Safety option to keep boot IRQs enabled. This
2479 should never be necessary.
2480 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2481 primary IO-APIC for bridges that cannot disable
2482 boot IRQs. This fixes a source of spurious IRQs
2483 when the system masks IRQs.
2484 noioapicreroute [APIC] Disable workaround that uses the
2485 boot IRQ equivalent of an IRQ that connects to
2486 a chipset where boot IRQs cannot be disabled.
2487 The opposite of ioapicreroute.
2488 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2489 routing table. These calls are known to be buggy
2490 on several machines and they hang the machine
2491 when used, but on other computers it's the only
2492 way to get the interrupt routing table. Try
2493 this option if the kernel is unable to allocate
2494 IRQs or discover secondary PCI buses on your
2496 rom [X86] Assign address space to expansion ROMs.
2497 Use with caution as certain devices share
2498 address decoders between ROMs and other
2500 norom [X86] Do not assign address space to
2501 expansion ROMs that do not already have
2502 BIOS assigned address ranges.
2503 nobar [X86] Do not assign address space to the
2504 BARs that weren't assigned by the BIOS.
2505 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2506 assigned automatically to PCI devices. You can
2507 make the kernel exclude IRQs of your ISA cards
2509 pirqaddr=0xAAAAA [X86] Specify the physical address
2510 of the PIRQ table (normally generated
2511 by the BIOS) if it is outside the
2512 F0000h-100000h range.
2513 lastbus=N [X86] Scan all buses thru bus #N. Can be
2514 useful if the kernel is unable to find your
2515 secondary buses and you want to tell it
2516 explicitly which ones they are.
2517 assign-busses [X86] Always assign all PCI bus
2518 numbers ourselves, overriding
2519 whatever the firmware may have done.
2520 usepirqmask [X86] Honor the possible IRQ mask stored
2521 in the BIOS $PIR table. This is needed on
2522 some systems with broken BIOSes, notably
2523 some HP Pavilion N5400 and Omnibook XE3
2524 notebooks. This will have no effect if ACPI
2525 IRQ routing is enabled.
2526 noacpi [X86] Do not use ACPI for IRQ routing
2527 or for PCI scanning.
2528 use_crs [X86] Use PCI host bridge window information
2529 from ACPI. On BIOSes from 2008 or later, this
2530 is enabled by default. If you need to use this,
2531 please report a bug.
2532 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2533 If you need to use this, please report a bug.
2534 routeirq Do IRQ routing for all PCI devices.
2535 This is normally done in pci_enable_device(),
2536 so this option is a temporary workaround
2537 for broken drivers that don't call it.
2538 skip_isa_align [X86] do not align io start addr, so can
2539 handle more pci cards
2540 firmware [ARM] Do not re-enumerate the bus but instead
2541 just use the configuration from the
2542 bootloader. This is currently used on
2543 IXP2000 systems where the bus has to be
2544 configured a certain way for adjunct CPUs.
2545 noearly [X86] Don't do any early type 1 scanning.
2546 This might help on some broken boards which
2547 machine check when some devices' config space
2548 is read. But various workarounds are disabled
2549 and some IOMMU drivers will not work.
2550 bfsort Sort PCI devices into breadth-first order.
2551 This sorting is done to get a device
2552 order compatible with older (<= 2.4) kernels.
2553 nobfsort Don't sort PCI devices into breadth-first order.
2554 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2555 tuning and use the BIOS-configured MPS defaults.
2556 pcie_bus_safe Set every device's MPS to the largest value
2557 supported by all devices below the root complex.
2558 pcie_bus_perf Set device MPS to the largest allowable MPS
2559 based on its parent bus. Also set MRRS (Max
2560 Read Request Size) to the largest supported
2561 value (no larger than the MPS that the device
2562 or bus can support) for best performance.
2563 pcie_bus_peer2peer Set every device's MPS to 128B, which
2564 every device is guaranteed to support. This
2565 configuration allows peer-to-peer DMA between
2566 any pair of devices, possibly at the cost of
2567 reduced performance. This also guarantees
2568 that hot-added devices will work.
2569 cbiosize=nn[KMG] The fixed amount of bus space which is
2570 reserved for the CardBus bridge's IO window.
2571 The default value is 256 bytes.
2572 cbmemsize=nn[KMG] The fixed amount of bus space which is
2573 reserved for the CardBus bridge's memory
2574 window. The default value is 64 megabytes.
2577 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2578 Specifies alignment and device to reassign
2579 aligned memory resources.
2580 If <order of align> is not specified,
2581 PAGE_SIZE is used as alignment.
2582 PCI-PCI bridge can be specified, if resource
2583 windows need to be expanded.
2584 ecrc= Enable/disable PCIe ECRC (transaction layer
2585 end-to-end CRC checking).
2586 bios: Use BIOS/firmware settings. This is the
2590 hpiosize=nn[KMG] The fixed amount of bus space which is
2591 reserved for hotplug bridge's IO window.
2592 Default size is 256 bytes.
2593 hpmemsize=nn[KMG] The fixed amount of bus space which is
2594 reserved for hotplug bridge's memory window.
2595 Default size is 2 megabytes.
2596 realloc= Enable/disable reallocating PCI bridge resources
2597 if allocations done by BIOS are too small to
2598 accommodate resources required by all child
2600 off: Turn realloc off
2602 realloc same as realloc=on
2603 noari do not use PCIe ARI.
2604 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2605 only look for one device below a PCIe downstream
2608 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2611 force Enable ASPM even on devices that claim not to support it.
2612 WARNING: Forcing ASPM on may cause system lockups.
2614 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2615 nomsi Do not use MSI for PCI Express Native Hotplug (this
2616 makes all PCIe ports use INTx for hotplug services).
2618 pcie_ports= [PCIE] PCIe ports handling:
2619 auto Ask the BIOS whether or not to use native PCIe services
2620 associated with PCIe ports (PME, hot-plug, AER). Use
2621 them only if that is allowed by the BIOS.
2622 native Use native PCIe services associated with PCIe ports
2624 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2627 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2628 nomsi Do not use MSI for native PCIe PME signaling (this makes
2629 all PCIe root ports use INTx for all services).
2631 pcmv= [HW,PCMCIA] BadgePAD 4
2635 Keep all power-domains already enabled by bootloader on,
2636 even if no driver has claimed them. This is useful
2637 for debug and development, but should not be
2638 needed on a platform with proper driver support.
2641 See Documentation/blockdev/paride.txt.
2643 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2646 See arch/parisc/kernel/pdc_chassis.c
2648 percpu_alloc= Select which percpu first chunk allocator to use.
2649 Currently supported values are "embed" and "page".
2650 Archs may support subset or none of the selections.
2651 See comments in mm/percpu.c for details on each
2652 allocator. This parameter is primarily for debugging
2653 and performance comparison.
2656 See Documentation/blockdev/paride.txt.
2659 See Documentation/blockdev/paride.txt.
2661 pirq= [SMP,APIC] Manual mp-table setup
2662 See Documentation/x86/i386/IO-APIC.txt.
2664 plip= [PPT,NET] Parallel port network link
2665 Format: { parport<nr> | timid | 0 }
2666 See also Documentation/parport.txt.
2668 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2669 Override pmtimer IOPort with a hex value.
2673 Enable PNP debug messages (depends on the
2674 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2675 via /sys/module/pnp/parameters/debug. We always show
2676 current resource usage; turning this on also shows
2677 possible settings and some assignment information.
2683 { on | off | curr | res | no-curr | no-res }
2686 [ISAPNP] Exclude IRQs for the autoconfiguration
2689 [ISAPNP] Exclude DMAs for the autoconfiguration
2691 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2692 Ranges are in pairs (I/O port base and size).
2695 [ISAPNP] Exclude memory regions for the
2697 Ranges are in pairs (memory base and size).
2699 ports= [IP_VS_FTP] IPVS ftp helper module
2701 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2703 Format: <port>,<port>....
2705 print-fatal-signals=
2706 [KNL] debug: print fatal signals
2708 If enabled, warn about various signal handling
2709 related application anomalies: too many signals,
2710 too many POSIX.1 timers, fatal signals causing a
2713 If you hit the warning due to signal overflow,
2714 you might want to try "ulimit -i unlimited".
2718 printk.always_kmsg_dump=
2719 Trigger kmsg_dump for cases other than kernel oops or
2721 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2724 printk.time= Show timing data prefixed to each printk message line
2725 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2727 processor.max_cstate= [HW,ACPI]
2728 Limit processor to maximum C-state
2729 max_cstate=9 overrides any DMI blacklist limit.
2731 processor.nocst [HW,ACPI]
2732 Ignore the _CST method to determine C-states,
2733 instead using the legacy FADT method
2735 profile= [KNL] Enable kernel profiling via /proc/profile
2736 Format: [schedule,]<number>
2737 Param: "schedule" - profile schedule points.
2738 Param: <number> - step/bucket size as a power of 2 for
2739 statistical time based profiling.
2740 Param: "sleep" - profile D-state sleeping (millisecs).
2741 Requires CONFIG_SCHEDSTATS
2742 Param: "kvm" - profile VM exits.
2744 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2746 See Documentation/blockdev/ramdisk.txt.
2748 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2749 probe for; one of (bare|imps|exps|lifebook|any).
2750 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2752 psmouse.resetafter= [HW,MOUSE]
2753 Try to reset the device after so many bad packets
2756 [HW,MOUSE] Set desired mouse resolution, in dpi.
2757 psmouse.smartscroll=
2758 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2759 0 = disabled, 1 = enabled (default).
2761 pstore.backend= Specify the name of the pstore backend to use
2764 See Documentation/blockdev/paride.txt.
2767 [KNL] Number of legacy pty's. Overwrites compiled-in
2770 quiet [KNL] Disable most log messages
2775 See Documentation/md.txt.
2777 ramdisk_blocksize= [RAM]
2778 See Documentation/blockdev/ramdisk.txt.
2780 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2781 See Documentation/blockdev/ramdisk.txt.
2784 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2785 the specified list of CPUs to be no-callback CPUs.
2786 Invocation of these CPUs' RCU callbacks will
2787 be offloaded to "rcuox/N" kthreads created for
2788 that purpose, where "x" is "b" for RCU-bh, "p"
2789 for RCU-preempt, and "s" for RCU-sched, and "N"
2790 is the CPU number. This reduces OS jitter on the
2791 offloaded CPUs, which can be useful for HPC and
2792 real-time workloads. It can also improve energy
2793 efficiency for asymmetric multiprocessors.
2796 Rather than requiring that offloaded CPUs
2797 (specified by rcu_nocbs= above) explicitly
2798 awaken the corresponding "rcuoN" kthreads,
2799 make these kthreads poll for callbacks.
2800 This improves the real-time response for the
2801 offloaded CPUs by relieving them of the need to
2802 wake up the corresponding kthread, but degrades
2803 energy efficiency by requiring that the kthreads
2804 periodically wake up to do the polling.
2806 rcutree.blimit= [KNL]
2807 Set maximum number of finished RCU callbacks to
2808 process in one batch.
2810 rcutree.rcu_fanout_leaf= [KNL]
2811 Increase the number of CPUs assigned to each
2812 leaf rcu_node structure. Useful for very large
2815 rcutree.jiffies_till_first_fqs= [KNL]
2816 Set delay from grace-period initialization to
2817 first attempt to force quiescent states.
2818 Units are jiffies, minimum value is zero,
2819 and maximum value is HZ.
2821 rcutree.jiffies_till_next_fqs= [KNL]
2822 Set delay between subsequent attempts to force
2823 quiescent states. Units are jiffies, minimum
2824 value is one, and maximum value is HZ.
2826 rcutree.qhimark= [KNL]
2827 Set threshold of queued RCU callbacks beyond which
2828 batch limiting is disabled.
2830 rcutree.qlowmark= [KNL]
2831 Set threshold of queued RCU callbacks below which
2832 batch limiting is re-enabled.
2834 rcutree.rcu_idle_gp_delay= [KNL]
2835 Set wakeup interval for idle CPUs that have
2836 RCU callbacks (RCU_FAST_NO_HZ=y).
2838 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2839 Set wakeup interval for idle CPUs that have
2840 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2841 Lazy RCU callbacks are those which RCU can
2842 prove do nothing more than free memory.
2844 rcutorture.fqs_duration= [KNL]
2845 Set duration of force_quiescent_state bursts.
2847 rcutorture.fqs_holdoff= [KNL]
2848 Set holdoff time within force_quiescent_state bursts.
2850 rcutorture.fqs_stutter= [KNL]
2851 Set wait time between force_quiescent_state bursts.
2853 rcutorture.gp_exp= [KNL]
2854 Use expedited update-side primitives.
2856 rcutorture.gp_normal= [KNL]
2857 Use normal (non-expedited) update-side primitives.
2858 If both gp_exp and gp_normal are set, do both.
2859 If neither gp_exp nor gp_normal are set, still
2862 rcutorture.n_barrier_cbs= [KNL]
2863 Set callbacks/threads for rcu_barrier() testing.
2865 rcutorture.nfakewriters= [KNL]
2866 Set number of concurrent RCU writers. These just
2867 stress RCU, they don't participate in the actual
2868 test, hence the "fake".
2870 rcutorture.nreaders= [KNL]
2871 Set number of RCU readers.
2873 rcutorture.object_debug= [KNL]
2874 Enable debug-object double-call_rcu() testing.
2876 rcutorture.onoff_holdoff= [KNL]
2877 Set time (s) after boot for CPU-hotplug testing.
2879 rcutorture.onoff_interval= [KNL]
2880 Set time (s) between CPU-hotplug operations, or
2881 zero to disable CPU-hotplug testing.
2883 rcutorture.rcutorture_runnable= [BOOT]
2884 Start rcutorture running at boot time.
2886 rcutorture.shuffle_interval= [KNL]
2887 Set task-shuffle interval (s). Shuffling tasks
2888 allows some CPUs to go into dyntick-idle mode
2889 during the rcutorture test.
2891 rcutorture.shutdown_secs= [KNL]
2892 Set time (s) after boot system shutdown. This
2893 is useful for hands-off automated testing.
2895 rcutorture.stall_cpu= [KNL]
2896 Duration of CPU stall (s) to test RCU CPU stall
2897 warnings, zero to disable.
2899 rcutorture.stall_cpu_holdoff= [KNL]
2900 Time to wait (s) after boot before inducing stall.
2902 rcutorture.stat_interval= [KNL]
2903 Time (s) between statistics printk()s.
2905 rcutorture.stutter= [KNL]
2906 Time (s) to stutter testing, for example, specifying
2907 five seconds causes the test to run for five seconds,
2908 wait for five seconds, and so on. This tests RCU's
2909 ability to transition abruptly to and from idle.
2911 rcutorture.test_boost= [KNL]
2912 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2913 "Maybe" means test if the RCU implementation
2914 under test support RCU priority boosting.
2916 rcutorture.test_boost_duration= [KNL]
2917 Duration (s) of each individual boost test.
2919 rcutorture.test_boost_interval= [KNL]
2920 Interval (s) between each boost test.
2922 rcutorture.test_no_idle_hz= [KNL]
2923 Test RCU's dyntick-idle handling. See also the
2924 rcutorture.shuffle_interval parameter.
2926 rcutorture.torture_type= [KNL]
2927 Specify the RCU implementation to test.
2929 rcutorture.verbose= [KNL]
2930 Enable additional printk() statements.
2932 rcupdate.rcu_expedited= [KNL]
2933 Use expedited grace-period primitives, for
2934 example, synchronize_rcu_expedited() instead
2935 of synchronize_rcu(). This reduces latency,
2936 but can increase CPU utilization, degrade
2937 real-time latency, and degrade energy efficiency.
2939 rcupdate.rcu_cpu_stall_suppress= [KNL]
2940 Suppress RCU CPU stall warning messages.
2942 rcupdate.rcu_cpu_stall_timeout= [KNL]
2943 Set timeout for RCU CPU stall warning messages.
2947 Run specified binary instead of /init from the ramdisk,
2948 used for early userspace startup. See initrd.
2951 Format (x86 or x86_64):
2952 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2954 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2956 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2957 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2958 reboot_force is either force or not specified,
2959 reboot_cpu is s[mp]#### with #### being the processor
2960 to be used for rebooting.
2963 [KNL, SMP] Set scheduler's default relax_domain_level.
2964 See Documentation/cgroups/cpusets.txt.
2966 relative_sleep_states=
2967 [SUSPEND] Use sleep state labeling where the deepest
2968 state available other than hibernation is always "mem".
2969 Format: { "0" | "1" }
2970 0 -- Traditional sleep state labels.
2971 1 -- Relative sleep state labels.
2973 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2975 reservetop= [X86-32]
2977 Reserves a hole at the top of the kernel virtual
2982 Set the amount of memory to reserve for BIOS at
2983 the bottom of the address space.
2985 reset_devices [KNL] Force drivers to reset the underlying device
2986 during initialization.
2989 Specify the partition device for software suspend
2991 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2993 resume_offset= [SWSUSP]
2994 Specify the offset from the beginning of the partition
2995 given by "resume=" at which the swap header is located,
2996 in <PAGE_SIZE> units (needed only for swap files).
2997 See Documentation/power/swsusp-and-swap-files.txt
2999 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3000 read the resume files
3002 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3003 Useful for devices that are detected asynchronously
3004 (e.g. USB and MMC devices).
3006 hibernate= [HIBERNATION]
3007 noresume Don't check if there's a hibernation image
3008 present during boot.
3009 nocompress Don't compress/decompress hibernation images.
3010 no Disable hibernation and resume.
3012 retain_initrd [RAM] Keep initrd memory after extraction
3014 rhash_entries= [KNL,NET]
3015 Set number of hash buckets for route cache
3017 ro [KNL] Mount root device read-only on boot
3019 root= [KNL] Root filesystem
3020 See name_to_dev_t comment in init/do_mounts.c.
3022 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3023 mount the root filesystem
3025 rootflags= [KNL] Set root filesystem mount option string
3027 rootfstype= [KNL] Set root filesystem type
3029 rootwait [KNL] Wait (indefinitely) for root device to show up.
3030 Useful for devices that are detected asynchronously
3031 (e.g. USB and MMC devices).
3033 rproc_mem=nn[KMG][@address]
3034 [KNL,ARM,CMA] Remoteproc physical memory block.
3035 Memory area to be used by remote processor image,
3038 rw [KNL] Mount root device read-write on boot
3040 S [KNL] Run init in single mode
3043 See drivers/net/irda/sa1100_ir.c.
3045 sbni= [NET] Granch SBNI12 leased line adapter
3047 sched_debug [KNL] Enables verbose scheduler debug messages.
3049 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3050 xtime_lock contention on larger systems, and/or RCU lock
3051 contention on all systems with CONFIG_MAXSMP set.
3052 Format: { "0" | "1" }
3053 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3055 Note: increases power consumption, thus should only be
3056 enabled if running jitter sensitive (HPC/RT) workloads.
3058 security= [SECURITY] Choose a security module to enable at boot.
3059 If this boot parameter is not specified, only the first
3060 security module asking for security registration will be
3061 loaded. An invalid security module name will be treated
3062 as if no module has been chosen.
3064 selinux= [SELINUX] Disable or enable SELinux at boot time.
3065 Format: { "0" | "1" }
3066 See security/selinux/Kconfig help text.
3069 Default value is set via kernel config option.
3070 If enabled at boot time, /selinux/disable can be used
3071 later to disable prior to initial policy load.
3073 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3074 Format: { "0" | "1" }
3075 See security/apparmor/Kconfig help text
3078 Default value is set via kernel config option.
3080 serialnumber [BUGS=X86-32]
3083 Maximal number of shapers.
3085 show_msr= [x86] show boot-time MSR settings
3086 Format: { <integer> }
3087 Show boot-time (BIOS-initialized) MSR settings.
3088 The parameter means the number of CPUs to show,
3089 for example 1 means boot CPU only.
3096 slab_max_order= [MM, SLAB]
3097 Determines the maximum allowed order for slabs.
3098 A high setting may cause OOMs due to memory
3099 fragmentation. Defaults to 1 for systems with
3100 more than 32MB of RAM, 0 otherwise.
3102 slub_debug[=options[,slabs]] [MM, SLUB]
3103 Enabling slub_debug allows one to determine the
3104 culprit if slab objects become corrupted. Enabling
3105 slub_debug can create guard zones around objects and
3106 may poison objects when not in use. Also tracks the
3107 last alloc / free. For more information see
3108 Documentation/vm/slub.txt.
3110 slub_max_order= [MM, SLUB]
3111 Determines the maximum allowed order for slabs.
3112 A high setting may cause OOMs due to memory
3113 fragmentation. For more information see
3114 Documentation/vm/slub.txt.
3116 slub_min_objects= [MM, SLUB]
3117 The minimum number of objects per slab. SLUB will
3118 increase the slab order up to slub_max_order to
3119 generate a sufficiently large slab able to contain
3120 the number of objects indicated. The higher the number
3121 of objects the smaller the overhead of tracking slabs
3122 and the less frequently locks need to be acquired.
3123 For more information see Documentation/vm/slub.txt.
3125 slub_min_order= [MM, SLUB]
3126 Determines the minimum page order for slabs. Must be
3127 lower than slub_max_order.
3128 For more information see Documentation/vm/slub.txt.
3130 slub_nomerge [MM, SLUB]
3131 Disable merging of slabs with similar size. May be
3132 necessary if there is some reason to distinguish
3133 allocs to different slabs. Debug options disable
3134 merging on their own.
3135 For more information see Documentation/vm/slub.txt.
3138 Format: <io1>[,<io2>[,...,<io8>]]
3140 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3141 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3142 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3143 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3144 smsc-ircc2.ircc_irq= [HW] IRQ line
3145 smsc-ircc2.ircc_dma= [HW] DMA channel
3146 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3147 0: Toshiba Satellite 1800 (GP data pin select)
3148 1: Fast pin select (default)
3152 [KNL] Should the soft-lockup detector generate panics.
3155 softlockup_all_cpu_backtrace=
3156 [KNL] Should the soft-lockup detector generate
3157 backtraces on all cpus.
3160 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3161 See Documentation/laptops/sonypi.txt
3163 spia_io_base= [HW,MTD]
3169 Enabled the stack tracer on boot up.
3171 stacktrace_filter=[function-list]
3172 [FTRACE] Limit the functions that the stack tracer
3173 will trace at boot up. function-list is a comma separated
3174 list of functions. This list can be changed at run
3175 time by the stack_trace_filter file in the debugfs
3176 tracing directory. Note, this enables stack tracing
3177 and the stacktrace above is not needed.
3181 Set the STI (builtin display/keyboard on the HP-PARISC
3182 machines) console (graphic card) which should be used
3183 as the initial boot-console.
3184 See also comment in drivers/video/console/sticore.c.
3187 See comment in drivers/video/console/sticore.c.
3190 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3192 sunrpc.min_resvport=
3193 sunrpc.max_resvport=
3195 SunRPC servers often require that client requests
3196 originate from a privileged port (i.e. a port in the
3197 range 0 < portnr < 1024).
3198 An administrator who wishes to reserve some of these
3199 ports for other uses may adjust the range that the
3200 kernel's sunrpc client considers to be privileged
3201 using these two parameters to set the minimum and
3202 maximum port values.
3206 Control how the NFS server code allocates CPUs to
3207 service thread pools. Depending on how many NICs
3208 you have and where their interrupts are bound, this
3209 option will affect which CPUs will do NFS serving.
3210 Note: this parameter cannot be changed while the
3211 NFS server is running.
3213 auto the server chooses an appropriate mode
3214 automatically using heuristics
3215 global a single global pool contains all CPUs
3216 percpu one pool for each CPU
3217 pernode one pool for each NUMA node (equivalent
3218 to global on non-NUMA machines)
3220 sunrpc.tcp_slot_table_entries=
3221 sunrpc.udp_slot_table_entries=
3223 Sets the upper limit on the number of simultaneous
3224 RPC calls that can be sent from the client to a
3225 server. Increasing these values may allow you to
3226 improve throughput, but will also increase the
3227 amount of memory reserved for use by the client.
3230 [KNL] Enable accounting of swap in memory resource
3231 controller if no parameter or 1 is given or disable
3232 it if 0 is given (See Documentation/cgroups/memory.txt)
3234 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3235 Format: { <int> | force }
3236 <int> -- Number of I/O TLB slabs
3237 force -- force using of bounce buffers even if they
3238 wouldn't be automatically used by the kernel
3242 sysfs.deprecated=0|1 [KNL]
3243 Enable/disable old style sysfs layout for old udev
3244 on older distributions. When this option is enabled
3245 very new udev will not work anymore. When this option
3246 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3247 in older udev will not work anymore.
3248 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3249 the kernel configuration.
3251 sysrq_always_enabled
3253 Ignore sysrq setting - this boot parameter will
3254 neutralize any effect of /proc/sys/kernel/sysrq.
3255 Useful for debugging.
3259 test_suspend= [SUSPEND]
3260 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3261 standby suspend) as the system sleep state to briefly
3262 enter during system startup. The system is woken from
3263 this state using a wakeup-capable RTC alarm.
3265 thash_entries= [KNL,NET]
3266 Set number of hash buckets for TCP connection
3268 thermal.act= [HW,ACPI]
3269 -1: disable all active trip points in all thermal zones
3270 <degrees C>: override all lowest active trip points
3272 thermal.crt= [HW,ACPI]
3273 -1: disable all critical trip points in all thermal zones
3274 <degrees C>: override all critical trip points
3276 thermal.nocrt= [HW,ACPI]
3277 Set to disable actions on ACPI thermal zone
3278 critical and hot trip points.
3280 thermal.off= [HW,ACPI]
3281 1: disable ACPI thermal control
3283 thermal.psv= [HW,ACPI]
3284 -1: disable all passive trip points
3285 <degrees C>: override all passive trip points to this
3288 thermal.tzp= [HW,ACPI]
3289 Specify global default ACPI thermal zone polling rate
3290 <deci-seconds>: poll all this frequency
3291 0: no polling (default)
3294 Force threading of all interrupt handlers except those
3295 marked explicitly IRQF_NO_THREAD.
3298 Enable the Transcendent memory driver if built-in.
3300 tmem.cleancache=0|1 [KNL, XEN]
3301 Default is on (1). Disable the usage of the cleancache
3302 API to send anonymous pages to the hypervisor.
3304 tmem.frontswap=0|1 [KNL, XEN]
3305 Default is on (1). Disable the usage of the frontswap
3306 API to send swap pages to the hypervisor. If disabled
3307 the selfballooning and selfshrinking are force disabled.
3309 tmem.selfballooning=0|1 [KNL, XEN]
3310 Default is on (1). Disable the driving of swap pages
3313 tmem.selfshrinking=0|1 [KNL, XEN]
3314 Default is on (1). Partial swapoff that immediately
3315 transfers pages from Xen hypervisor back to the
3316 kernel based on different criteria.
3320 Specify if the kernel should make use of the cpu
3321 topology information if the hardware supports this.
3322 The scheduler will make use of this information and
3323 e.g. base its process migration decisions on it.
3328 tpm_suspend_pcr=[HW,TPM]
3329 Format: integer pcr id
3330 Specify that at suspend time, the tpm driver
3331 should extend the specified pcr with zeros,
3332 as a workaround for some chips which fail to
3333 flush the last written pcr on TPM_SaveState.
3334 This will guarantee that all the other pcrs
3337 trace_buf_size=nn[KMG]
3338 [FTRACE] will set tracing buffer size.
3340 trace_event=[event-list]
3341 [FTRACE] Set and start specified trace events in order
3342 to facilitate early boot debugging.
3343 See also Documentation/trace/events.txt
3345 trace_options=[option-list]
3346 [FTRACE] Enable or disable tracer options at boot.
3347 The option-list is a comma delimited list of options
3348 that can be enabled or disabled just as if you were
3349 to echo the option name into
3351 /sys/kernel/debug/tracing/trace_options
3353 For example, to enable stacktrace option (to dump the
3354 stack trace of each event), add to the command line:
3356 trace_options=stacktrace
3358 See also Documentation/trace/ftrace.txt "trace options"
3362 [FTRACE] enable this option to disable tracing when a
3363 warning is hit. This turns off "tracing_on". Tracing can
3364 be enabled again by echoing '1' into the "tracing_on"
3365 file located in /sys/kernel/debug/tracing/
3367 This option is useful, as it disables the trace before
3368 the WARNING dump is called, which prevents the trace to
3369 be filled with content caused by the warning output.
3371 This option can also be set at run time via the sysctl
3372 option: kernel/traceoff_on_warning
3374 transparent_hugepage=
3376 Format: [always|madvise|never]
3377 Can be used to control the default behavior of the system
3378 with respect to transparent hugepages.
3379 See Documentation/vm/transhuge.txt for more details.
3381 tsc= Disable clocksource stability checks for TSC.
3383 [x86] reliable: mark tsc clocksource as reliable, this
3384 disables clocksource verification at runtime, as well
3385 as the stability checks done at bootup. Used to enable
3386 high-resolution timer mode on older hardware, and in
3387 virtualized environment.
3388 [x86] noirqtime: Do not use TSC to do irq accounting.
3389 Used to run time disable IRQ_TIME_ACCOUNTING on any
3390 platforms where RDTSC is slow and this accounting
3393 turbografx.map[2|3]= [HW,JOY]
3394 TurboGraFX parallel port interface
3396 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3397 See also Documentation/input/joystick-parport.txt
3399 udbg-immortal [PPC] When debugging early kernel crashes that
3400 happen after console_init() and before a proper
3401 console driver takes over, this boot options might
3402 help "seeing" what's going on.
3404 uhash_entries= [KNL,NET]
3405 Set number of hash buckets for UDP/UDP-Lite connections
3408 [USB] Ignore overcurrent events (default N).
3409 Some badly-designed motherboards generate lots of
3410 bogus events, for ports that aren't wired to
3411 anything. Set this parameter to avoid log spamming.
3412 Note that genuine overcurrent events won't be
3416 [X86] Cause panic on unknown NMI.
3418 usbcore.authorized_default=
3419 [USB] Default USB device authorization:
3420 (default -1 = authorized except for wireless USB,
3421 0 = not authorized, 1 = authorized)
3423 usbcore.autosuspend=
3424 [USB] The autosuspend time delay (in seconds) used
3425 for newly-detected USB devices (default 2). This
3426 is the time required before an idle device will be
3427 autosuspended. Devices for which the delay is set
3428 to a negative value won't be autosuspended at all.
3430 usbcore.usbfs_snoop=
3431 [USB] Set to log all usbfs traffic (default 0 = off).
3433 usbcore.blinkenlights=
3434 [USB] Set to cycle leds on hubs (default 0 = off).
3436 usbcore.old_scheme_first=
3437 [USB] Start with the old device initialization
3438 scheme (default 0 = off).
3440 usbcore.usbfs_memory_mb=
3441 [USB] Memory limit (in MB) for buffers allocated by
3442 usbfs (default = 16, 0 = max = 2047).
3444 usbcore.use_both_schemes=
3445 [USB] Try the other device initialization scheme
3446 if the first one fails (default 1 = enabled).
3448 usbcore.initial_descriptor_timeout=
3449 [USB] Specifies timeout for the initial 64-byte
3450 USB_REQ_GET_DESCRIPTOR request in milliseconds
3451 (default 5000 = 5.0 seconds).
3454 [USBHID] The interval which mice are to be polled at.
3456 usb-storage.delay_use=
3457 [UMS] The delay in seconds before a new device is
3458 scanned for Logical Units (default 5).
3461 [UMS] A list of quirks entries to supplement or
3462 override the built-in unusual_devs list. List
3463 entries are separated by commas. Each entry has
3464 the form VID:PID:Flags where VID and PID are Vendor
3465 and Product ID values (4-digit hex numbers) and
3466 Flags is a set of characters, each corresponding
3467 to a common usb-storage quirk flag as follows:
3468 a = SANE_SENSE (collect more than 18 bytes
3470 b = BAD_SENSE (don't collect more than 18
3471 bytes of sense data);
3472 c = FIX_CAPACITY (decrease the reported
3473 device capacity by one sector);
3474 d = NO_READ_DISC_INFO (don't use
3475 READ_DISC_INFO command);
3476 e = NO_READ_CAPACITY_16 (don't use
3477 READ_CAPACITY_16 command);
3478 h = CAPACITY_HEURISTICS (decrease the
3479 reported device capacity by one
3480 sector if the number is odd);
3481 i = IGNORE_DEVICE (don't bind to this
3483 l = NOT_LOCKABLE (don't try to lock and
3484 unlock ejectable media);
3485 m = MAX_SECTORS_64 (don't transfer more
3486 than 64 sectors = 32 KB at a time);
3487 n = INITIAL_READ10 (force a retry of the
3488 initial READ(10) command);
3489 o = CAPACITY_OK (accept the capacity
3490 reported by the device);
3491 p = WRITE_CACHE (the device cache is ON
3493 r = IGNORE_RESIDUE (the device reports
3494 bogus residue values);
3495 s = SINGLE_LUN (the device has only one
3497 w = NO_WP_DETECT (don't test whether the
3498 medium is write-protected).
3499 Example: quirks=0419:aaf5:rl,0421:0433:rc
3501 user_debug= [KNL,ARM]
3503 See arch/arm/Kconfig.debug help text.
3504 1 - undefined instruction events
3506 4 - invalid data aborts
3509 Example: user_debug=31
3512 [X86] Flags controlling user PTE allocations.
3514 nohigh = do not allocate PTE pages in
3515 HIGHMEM regardless of setting
3519 On X86_32, this is an alias for vdso32=. Otherwise:
3521 vdso=1: enable VDSO (the default)
3522 vdso=0: disable VDSO mapping
3524 vdso32= [X86] Control the 32-bit vDSO
3525 vdso32=1: enable 32-bit VDSO
3526 vdso32=0 or vdso32=2: disable 32-bit VDSO
3528 See the help text for CONFIG_COMPAT_VDSO for more
3529 details. If CONFIG_COMPAT_VDSO is set, the default is
3530 vdso32=0; otherwise, the default is vdso32=1.
3532 For compatibility with older kernels, vdso32=2 is an
3535 Try vdso32=0 if you encounter an error that says:
3536 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3539 vector=percpu: enable percpu vector domain
3541 video= [FB] Frame buffer configuration
3542 See Documentation/fb/modedb.txt.
3544 video.brightness_switch_enabled= [0,1]
3545 If set to 1, on receiving an ACPI notify event
3546 generated by hotkey, video driver will adjust brightness
3547 level and then send out the event to user space through
3548 the allocated input device; If set to 0, video driver
3549 will only send out the event without touching backlight
3554 [VMMIO] Memory mapped virtio (platform) device.
3556 <size>@<baseaddr>:<irq>[:<id>]
3558 <size> := size (can use standard suffixes
3560 <baseaddr> := physical base address
3561 <irq> := interrupt number (as passed to
3563 <id> := (optional) platform device id
3565 virtio_mmio.device=1K@0x100b0000:48:7
3567 Can be used multiple times for multiple devices.
3569 vga= [BOOT,X86-32] Select a particular video mode
3570 See Documentation/x86/boot.txt and
3571 Documentation/svga.txt.
3572 Use vga=ask for menu.
3573 This is actually a boot loader parameter; the value is
3574 passed to the kernel using a special protocol.
3576 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3577 size of <nn>. This can be used to increase the
3578 minimum size (128MB on x86). It can also be used to
3579 decrease the size and leave more room for directly
3582 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3585 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3588 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3592 Controls the behavior of vsyscalls (i.e. calls to
3593 fixed addresses of 0xffffffffff600x00 from legacy
3594 code). Most statically-linked binaries and older
3595 versions of glibc use these calls. Because these
3596 functions are at fixed addresses, they make nice
3597 targets for exploits that can control RIP.
3599 emulate [default] Vsyscalls turn into traps and are
3600 emulated reasonably safely.
3602 native Vsyscalls are native syscall instructions.
3603 This is a little bit faster than trapping
3604 and makes a few dynamic recompilers work
3605 better than they would in emulation mode.
3606 It also makes exploits much easier to write.
3608 none Vsyscalls don't work at all. This makes
3609 them quite hard to use for exploits but
3610 might break your system.
3612 vt.color= [VT] Default text color.
3613 Format: 0xYX, X = foreground, Y = background.
3614 Default: 0x07 = light gray on black.
3616 vt.cur_default= [VT] Default cursor shape.
3617 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3618 the parameters of the <Esc>[?A;B;Cc escape sequence;
3619 see VGA-softcursor.txt. Default: 2 = underline.
3621 vt.default_blu= [VT]
3622 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3623 Change the default blue palette of the console.
3624 This is a 16-member array composed of values
3627 vt.default_grn= [VT]
3628 Format: <green0>,<green1>,<green2>,...,<green15>
3629 Change the default green palette of the console.
3630 This is a 16-member array composed of values
3633 vt.default_red= [VT]
3634 Format: <red0>,<red1>,<red2>,...,<red15>
3635 Change the default red palette of the console.
3636 This is a 16-member array composed of values
3642 Set system-wide default UTF-8 mode for all tty's.
3643 Default is 1, i.e. UTF-8 mode is enabled for all
3644 newly opened terminals.
3646 vt.global_cursor_default=
3649 Set system-wide default for whether a cursor
3650 is shown on new VTs. Default is -1,
3651 i.e. cursors will be created by default unless
3652 overridden by individual drivers. 0 will hide
3653 cursors, 1 will display them.
3655 vt.italic= [VT] Default color for italic text; 0-15.
3658 vt.underline= [VT] Default color for underlined text; 0-15.
3661 watchdog timers [HW,WDT] For information on watchdog timers,
3662 see Documentation/watchdog/watchdog-parameters.txt
3663 or other driver-specific files in the
3664 Documentation/watchdog/ directory.
3666 workqueue.disable_numa
3667 By default, all work items queued to unbound
3668 workqueues are affine to the NUMA nodes they're
3669 issued on, which results in better behavior in
3670 general. If NUMA affinity needs to be disabled for
3671 whatever reason, this option can be used. Note
3672 that this also can be controlled per-workqueue for
3673 workqueues visible under /sys/bus/workqueue/.
3675 workqueue.power_efficient
3676 Per-cpu workqueues are generally preferred because
3677 they show better performance thanks to cache
3678 locality; unfortunately, per-cpu workqueues tend to
3679 be more power hungry than unbound workqueues.
3681 Enabling this makes the per-cpu workqueues which
3682 were observed to contribute significantly to power
3683 consumption unbound, leading to measurably lower
3684 power usage at the cost of small performance
3687 The default value of this parameter is determined by
3688 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3690 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3691 default x2apic cluster mode on platforms
3694 x86_intel_mid_timer= [X86-32,APBT]
3695 Choose timer option for x86 Intel MID platform.
3696 Two valid options are apbt timer only and lapic timer
3697 plus one apbt timer for broadcast timer.
3698 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3700 xen_emul_unplug= [HW,X86,XEN]
3701 Unplug Xen emulated devices
3702 Format: [unplug0,][unplug1]
3703 ide-disks -- unplug primary master IDE devices
3704 aux-ide-disks -- unplug non-primary-master IDE devices
3705 nics -- unplug network devices
3706 all -- unplug all emulated devices (NICs and IDE disks)
3707 unnecessary -- unplugging emulated devices is
3708 unnecessary even if the host did not respond to
3710 never -- do not unplug even if version check succeeds
3712 xen_nopvspin [X86,XEN]
3713 Disables the ticketlock slowpath using Xen PV
3716 xirc2ps_cs= [NET,PCMCIA]
3718 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3720 ______________________________________________________________________
3724 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob