4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpi_force_32bit_fadt_addr
197 force FADT to use 32 bit addresses rather than the
198 64 bit X_* addresses. Some firmware have broken 64
199 bit addresses for force ACPI ignore these and use
200 the older legacy 32 bit addresses.
202 acpica_no_return_repair [HW, ACPI]
203 Disable AML predefined validation mechanism
204 This mechanism can repair the evaluation result to make
205 the return objects more ACPI specification compliant.
206 This option is useful for developers to identify the
207 root cause of an AML interpreter issue when the issue
208 has something to do with the repair mechanism.
210 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
211 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
213 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
214 debug output. Bits in debug_layer correspond to a
215 _COMPONENT in an ACPI source file, e.g.,
216 #define _COMPONENT ACPI_PCI_COMPONENT
217 Bits in debug_level correspond to a level in
218 ACPI_DEBUG_PRINT statements, e.g.,
219 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
220 The debug_level mask defaults to "info". See
221 Documentation/acpi/debug.txt for more information about
222 debug layers and levels.
224 Enable processor driver info messages:
225 acpi.debug_layer=0x20000000
226 Enable PCI/PCI interrupt routing info messages:
227 acpi.debug_layer=0x400000
228 Enable AML "Debug" output, i.e., stores to the Debug
229 object while interpreting AML:
230 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
231 Enable all messages related to ACPI hardware:
232 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
234 Some values produce so much output that the system is
235 unusable. The "log_buf_len" parameter may be useful
236 if you need to capture more output.
238 acpi_enforce_resources= [ACPI]
239 { strict | lax | no }
240 Check for resource conflicts between native drivers
241 and ACPI OperationRegions (SystemIO and SystemMemory
242 only). IO ports and memory declared in ACPI might be
243 used by the ACPI subsystem in arbitrary AML code and
244 can interfere with legacy drivers.
245 strict (default): access to resources claimed by ACPI
246 is denied; legacy drivers trying to access reserved
247 resources will fail to bind to device using them.
248 lax: access to resources claimed by ACPI is allowed;
249 legacy drivers trying to access reserved resources
250 will bind successfully but a warning message is logged.
251 no: ACPI OperationRegions are not marked as reserved,
252 no further checks are performed.
254 acpi_force_table_verification [HW,ACPI]
255 Enable table checksum verification during early stage.
256 By default, this is disabled due to x86 early mapping
259 acpi_irq_balance [HW,ACPI]
260 ACPI will balance active IRQs
263 acpi_irq_nobalance [HW,ACPI]
264 ACPI will not move active IRQs (default)
267 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
268 Format: <irq>,<irq>...
270 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
272 Format: <irq>,<irq>...
274 acpi_no_auto_serialize [HW,ACPI]
275 Disable auto-serialization of AML methods
276 AML control methods that contain the opcodes to create
277 named objects will be marked as "Serialized" by the
278 auto-serialization feature.
279 This feature is enabled by default.
280 This option allows to turn off the feature.
282 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
285 acpi_no_static_ssdt [HW,ACPI]
286 Disable installation of static SSDTs at early boot time
287 By default, SSDTs contained in the RSDT/XSDT will be
288 installed automatically and they will appear under
289 /sys/firmware/acpi/tables.
290 This option turns off this feature.
291 Note that specifying this option does not affect
292 dynamic table installation which will install SSDT
293 tables to /sys/firmware/acpi/tables/dynamic.
295 acpi_rsdp= [ACPI,EFI,KEXEC]
296 Pass the RSDP address to the kernel, mostly used
297 on machines running EFI runtime service to boot the
298 second kernel for kdump.
300 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
301 Format: To spoof as Windows 98: ="Microsoft Windows"
303 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
304 of 2 which is mandated by ACPI 6) as the supported ACPI
305 specification revision (when using this switch, it may
306 be necessary to carry out a cold reboot _twice_ in a
307 row to make it take effect on the platform firmware).
309 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
310 acpi_osi="string1" # add string1
311 acpi_osi="!string2" # remove string2
312 acpi_osi=!* # remove all strings
313 acpi_osi=! # disable all built-in OS vendor
315 acpi_osi= # disable all strings
317 'acpi_osi=!' can be used in combination with single or
318 multiple 'acpi_osi="string1"' to support specific OS
319 vendor string(s). Note that such command can only
320 affect the default state of the OS vendor strings, thus
321 it cannot affect the default state of the feature group
322 strings and the current state of the OS vendor strings,
323 specifying it multiple times through kernel command line
324 is meaningless. This command is useful when one do not
325 care about the state of the feature group strings which
326 should be controlled by the OSPM.
328 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
329 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
330 can make '_OSI("Windows 2000")' TRUE.
332 'acpi_osi=' cannot be used in combination with other
333 'acpi_osi=' command lines, the _OSI method will not
334 exist in the ACPI namespace. NOTE that such command can
335 only affect the _OSI support state, thus specifying it
336 multiple times through kernel command line is also
339 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
342 'acpi_osi=!*' can be used in combination with single or
343 multiple 'acpi_osi="string1"' to support specific
344 string(s). Note that such command can affect the
345 current state of both the OS vendor strings and the
346 feature group strings, thus specifying it multiple times
347 through kernel command line is meaningful. But it may
348 still not able to affect the final state of a string if
349 there are quirks related to this string. This command
350 is useful when one want to control the state of the
351 feature group strings to debug BIOS issues related to
354 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
355 '_OSI("Module Device")' FALSE.
356 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
357 '_OSI("Module Device")' TRUE.
358 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
360 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
362 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
363 they all will make '_OSI("Windows 2000")' TRUE.
366 Override the pmtimer bug detection: force the kernel
367 to assume that this machine's pmtimer latches its value
368 and always returns good values.
370 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
371 Format: { level | edge | high | low }
373 acpi_skip_timer_override [HW,ACPI]
374 Recognize and ignore IRQ0/pin2 Interrupt Override.
375 For broken nForce2 BIOS resulting in XT-PIC timer.
377 acpi_sleep= [HW,ACPI] Sleep options
378 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
379 old_ordering, nonvs, sci_force_enable }
380 See Documentation/power/video.txt for information on
382 s3_beep is for debugging; it makes the PC's speaker beep
383 as soon as the kernel's real-mode entry point is called.
384 s4_nohwsig prevents ACPI hardware signature from being
385 used during resume from hibernation.
386 old_ordering causes the ACPI 1.0 ordering of the _PTS
387 control method, with respect to putting devices into
388 low power states, to be enforced (the ACPI 2.0 ordering
389 of _PTS is used by default).
390 nonvs prevents the kernel from saving/restoring the
391 ACPI NVS memory during suspend/hibernation and resume.
392 sci_force_enable causes the kernel to set SCI_EN directly
393 on resume from S1/S3 (which is against the ACPI spec,
394 but some broken systems don't work without it).
396 acpi_use_timer_override [HW,ACPI]
397 Use timer override. For some broken Nvidia NF5 boards
398 that require a timer override, but don't have HPET
400 add_efi_memmap [EFI; X86] Include EFI memory map in
401 kernel's map of available physical RAM.
404 { off | try_unsupported }
405 off: disable AGP support
406 try_unsupported: try to drive unsupported chipsets
407 (may crash computer or cause data corruption)
410 See Documentation/sound/alsa/alsa-parameters.txt
413 Allow the default userspace alignment fault handler
414 behaviour to be specified. Bit 0 enables warnings,
415 bit 1 enables fixups, and bit 2 sends a segfault.
417 align_va_addr= [X86-64]
418 Align virtual addresses by clearing slice [14:12] when
419 allocating a VMA at process creation time. This option
420 gives you up to 3% performance improvement on AMD F15h
421 machines (where it is enabled by default) for a
422 CPU-intensive style benchmark, and it can vary highly in
423 a microbenchmark depending on workload and compiler.
425 32: only for 32-bit processes
426 64: only for 64-bit processes
427 on: enable for both 32- and 64-bit processes
428 off: disable for both 32- and 64-bit processes
430 alloc_snapshot [FTRACE]
431 Allocate the ftrace snapshot buffer on boot up when the
432 main buffer is allocated. This is handy if debugging
433 and you need to use tracing_snapshot() on boot up, and
434 do not want to use tracing_snapshot_alloc() as it needs
435 to be done where GFP_KERNEL allocations are allowed.
437 amd_iommu= [HW,X86-64]
438 Pass parameters to the AMD IOMMU driver in the system.
440 fullflush - enable flushing of IO/TLB entries when
441 they are unmapped. Otherwise they are
442 flushed before they will be reused, which
444 off - do not initialize any AMD IOMMU found in
446 force_isolation - Force device isolation for all
447 devices. The IOMMU driver is not
448 allowed anymore to lift isolation
449 requirements as needed. This option
450 does not override iommu=pt
452 amd_iommu_dump= [HW,X86-64]
453 Enable AMD IOMMU driver option to dump the ACPI table
454 for AMD IOMMU. With this option enabled, AMD IOMMU
455 driver will print ACPI tables for AMD IOMMU during
456 IOMMU initialization.
458 amijoy.map= [HW,JOY] Amiga joystick support
459 Map of devices attached to JOY0DAT and JOY1DAT
461 See also Documentation/input/joystick.txt
463 analog.map= [HW,JOY] Analog joystick and gamepad support
464 Specifies type or capabilities of an analog joystick
465 connected to one of 16 gameports
466 Format: <type1>,<type2>,..<type16>
469 Power management functions (SPARCstation-4/5 + deriv.)
471 Disable APC CPU standby support. SPARCstation-Fox does
472 not play well with APC CPU idle - disable it if you have
473 APC and your system crashes randomly.
475 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
476 Change the output verbosity whilst booting
477 Format: { quiet (default) | verbose | debug }
478 Change the amount of debugging information output
479 when initialising the APIC and IO-APIC components.
481 apic_extnmi= [APIC,X86] External NMI delivery setting
482 Format: { bsp (default) | all | none }
483 bsp: External NMI is delivered only to CPU 0
484 all: External NMIs are broadcast to all CPUs as a
486 none: External NMI is masked for all CPUs. This is
487 useful so that a dump capture kernel won't be
491 See Documentation/networking/ipv6.txt.
493 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
494 Limit apic dumping. The parameter defines the maximal
495 number of local apics being dumped. Also it is possible
496 to set it to "all" by meaning -- no limit here.
497 Format: { 1 (default) | 2 | ... | all }.
498 The parameter valid if only apic=debug or
499 apic=verbose is specified.
500 Example: apic=debug show_lapic=all
502 apm= [APM] Advanced Power Management
503 See header of arch/x86/kernel/apm_32.c.
505 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
506 Format: <io>,<irq>,<nodeID>
510 atarimouse= [HW,MOUSE] Atari Mouse
512 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
513 EzKey and similar keyboards
515 atkbd.reset= [HW] Reset keyboard during initialization
517 atkbd.set= [HW] Select keyboard code set
518 Format: <int> (2 = AT (default), 3 = PS/2)
520 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
523 atkbd.softraw= [HW] Choose between synthetic and real raw mode
524 Format: <bool> (0 = real, 1 = synthetic (default))
526 atkbd.softrepeat= [HW]
527 Use software keyboard repeat
529 audit= [KNL] Enable the audit sub-system
530 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
531 0 - kernel audit is disabled and can not be enabled
532 until the next reboot
533 unset - kernel audit is initialized but disabled and
534 will be fully enabled by the userspace auditd.
535 1 - kernel audit is initialized and partially enabled,
536 storing at most audit_backlog_limit messages in
537 RAM until it is fully enabled by the userspace
541 audit_backlog_limit= [KNL] Set the audit queue size limit.
542 Format: <int> (must be >=0)
545 baycom_epp= [HW,AX25]
548 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
550 See header of drivers/net/hamradio/baycom_par.c.
552 baycom_ser_fdx= [HW,AX25]
553 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
554 Format: <io>,<irq>,<mode>[,<baud>]
555 See header of drivers/net/hamradio/baycom_ser_fdx.c.
557 baycom_ser_hdx= [HW,AX25]
558 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
559 Format: <io>,<irq>,<mode>
560 See header of drivers/net/hamradio/baycom_ser_hdx.c.
562 blkdevparts= Manual partition parsing of block device(s) for
563 embedded devices based on command line input.
564 See Documentation/block/cmdline-partition.txt
566 boot_delay= Milliseconds to delay each printk during boot.
567 Values larger than 10 seconds (10000) are changed to
571 bootmem_debug [KNL] Enable bootmem allocator debug messages.
573 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
574 bttv.radio= Most important insmod options are available as
576 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
579 bulk_remove=off [PPC] This parameter disables the use of the pSeries
580 firmware feature for flushing multiple hpte entries
583 c101= [NET] Moxa C101 synchronous serial card
585 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
586 Sometimes CPU hardware bugs make them report the cache
587 size incorrectly. The kernel will attempt work arounds
588 to fix known problems, but for some CPUs it is not
589 possible to determine what the correct size should be.
590 This option provides an override for these situations.
592 ca_keys= [KEYS] This parameter identifies a specific key(s) on
593 the system trusted keyring to be used for certificate
595 format: { id:<keyid> | builtin }
597 cca= [MIPS] Override the kernel pages' cache coherency
598 algorithm. Accepted values range from 0 to 7
599 inclusive. See arch/mips/include/asm/pgtable-bits.h
600 for platform specific values (SB1, Loongson3 and
603 ccw_timeout_log [S390]
604 See Documentation/s390/CommonIO for details.
606 cgroup_disable= [KNL] Disable a particular controller
607 Format: {name of the controller(s) to disable}
608 The effects of cgroup_disable=foo are:
609 - foo isn't auto-mounted if you mount all cgroups in
611 - foo isn't visible as an individually mountable
613 {Currently only "memory" controller deal with this and
614 cut the overhead, others just disable the usage. So
615 only cgroup_disable=memory is actually worthy}
617 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
618 Format: { controller[,controller...] | "all" }
619 Like cgroup_disable, but only applies to cgroup v1;
620 the blacklisted controllers remain available in cgroup2.
622 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
624 nosocket -- Disable socket memory accounting.
625 nokmem -- Disable kernel memory accounting.
627 checkreqprot [SELINUX] Set initial checkreqprot flag value.
628 Format: { "0" | "1" }
629 See security/selinux/Kconfig help text.
630 0 -- check protection applied by kernel (includes
631 any implied execute protection).
632 1 -- check protection requested by application.
633 Default value is set via a kernel config option.
634 Value can be changed at runtime via
635 /selinux/checkreqprot.
638 See Documentation/s390/CommonIO for details.
641 Prevents the clock framework from automatically gating
642 clocks that have not been explicitly enabled by a Linux
643 device driver but are enabled in hardware at reset or
644 by the bootloader/firmware. Note that this does not
645 force such clocks to be always-on nor does it reserve
646 those clocks in any way. This parameter is useful for
647 debug and development, but should not be needed on a
648 platform with proper driver support. For more
649 information, see Documentation/clk.txt.
651 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
653 Forces specified clocksource (if available) to be used
654 when calculating gettimeofday(). If specified
655 clocksource is not available, it defaults to PIT.
656 Format: { pit | tsc | cyclone | pmtmr }
658 clocksource= Override the default clocksource
660 Override the default clocksource and use the clocksource
661 with the name specified.
662 Some clocksource names to choose from, depending on
664 [all] jiffies (this is the base, fallback clocksource)
666 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
667 pxa_timer,timer3,32k_counter,timer0_1
669 [X86-32] pit,hpet,tsc;
670 scx200_hrt on Geode; cyclone on IBM x440
678 clearcpuid=BITNUM [X86]
679 Disable CPUID feature X for the kernel. See
680 arch/x86/include/asm/cpufeatures.h for the valid bit
681 numbers. Note the Linux specific bits are not necessarily
682 stable over kernel options, but the vendor specific
684 Also note that user programs calling CPUID directly
685 or using the feature without checking anything
686 will still see it. This just prevents it from
687 being used by the kernel or shown in /proc/cpuinfo.
688 Also note the kernel might malfunction if you disable
691 cma=nn[MG]@[start[MG][-end[MG]]]
693 Sets the size of kernel global memory area for
694 contiguous memory allocations and optionally the
695 placement constraint by the physical address range of
696 memory allocations. A value of 0 disables CMA
697 altogether. For more information, see
698 include/linux/dma-contiguous.h
700 cmo_free_hint= [PPC] Format: { yes | no }
701 Specify whether pages are marked as being inactive
702 when they are freed. This is used in CMO environments
703 to determine OS memory pressure for page stealing by
707 coherent_pool=nn[KMG] [ARM,KNL]
708 Sets the size of memory pool for coherent, atomic dma
709 allocations, by default set to 256K.
711 code_bytes [X86] How many bytes of object code to print
716 com20020= [HW,NET] ARCnet - COM20020 chipset
718 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
720 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
724 ARCnet - COM90xx chipset (memory-mapped buffers)
725 Format: <io>[,<irq>[,<memstart>]]
727 condev= [HW,S390] console device
730 console= [KNL] Output console device and options.
732 tty<n> Use the virtual console device <n>.
736 Use the specified serial port. The options are of
737 the form "bbbbpnf", where "bbbb" is the baud rate,
738 "p" is parity ("n", "o", or "e"), "n" is number of
739 bits, and "f" is flow control ("r" for RTS or
740 omit it). Default is "9600n8".
742 See Documentation/serial-console.txt for more
744 Documentation/networking/netconsole.txt for an
747 uart[8250],io,<addr>[,options]
748 uart[8250],mmio,<addr>[,options]
749 uart[8250],mmio16,<addr>[,options]
750 uart[8250],mmio32,<addr>[,options]
751 uart[8250],0x<addr>[,options]
752 Start an early, polled-mode console on the 8250/16550
753 UART at the specified I/O port or MMIO address,
754 switching to the matching ttyS device later.
755 MMIO inter-register address stride is either 8-bit
756 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
757 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
758 to be equivalent to 'mmio'. 'options' are specified in
759 the same format described for ttyS above; if unspecified,
760 the h/w is not re-initialized.
762 hvc<n> Use the hypervisor console device <n>. This is for
763 both Xen and PowerPC hypervisors.
765 If the device connected to the port is not a TTY but a braille
766 device, prepend "brl," before the device type, for instance
768 For now, only VisioBraille is supported.
770 consoleblank= [KNL] The console blank (screen saver) timeout in
771 seconds. Defaults to 10*60 = 10mins. A value of 0
772 disables the blank timer.
775 [KNL] Change the default value for
776 /proc/<pid>/coredump_filter.
777 See also Documentation/filesystems/proc.txt.
779 cpuidle.off=1 [CPU_IDLE]
780 disable the cpuidle sub-system
783 [X86] Delay for N microsec between assert and de-assert
784 of APIC INIT to start processors. This delay occurs
785 on every CPU online, such as boot, and resume from suspend.
788 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
790 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
792 crashkernel=size[KMG][@offset[KMG]]
793 [KNL] Using kexec, Linux can switch to a 'crash kernel'
794 upon panic. This parameter reserves the physical
795 memory region [offset, offset + size] for that kernel
796 image. If '@offset' is omitted, then a suitable offset
797 is selected automatically. Check
798 Documentation/kdump/kdump.txt for further details.
800 crashkernel=range1:size1[,range2:size2,...][@offset]
801 [KNL] Same as above, but depends on the memory
802 in the running system. The syntax of range is
803 start-[end] where start and end are both
804 a memory unit (amount[KMG]). See also
805 Documentation/kdump/kdump.txt for an example.
807 crashkernel=size[KMG],high
808 [KNL, x86_64] range could be above 4G. Allow kernel
809 to allocate physical memory region from top, so could
810 be above 4G if system have more than 4G ram installed.
811 Otherwise memory region will be allocated below 4G, if
813 It will be ignored if crashkernel=X is specified.
814 crashkernel=size[KMG],low
815 [KNL, x86_64] range under 4G. When crashkernel=X,high
816 is passed, kernel could allocate physical memory region
817 above 4G, that cause second kernel crash on system
818 that require some amount of low memory, e.g. swiotlb
819 requires at least 64M+32K low memory, also enough extra
820 low memory is needed to make sure DMA buffers for 32-bit
821 devices won't run out. Kernel would try to allocate at
822 at least 256M below 4G automatically.
823 This one let user to specify own low range under 4G
824 for second kernel instead.
825 0: to disable low allocation.
826 It will be ignored when crashkernel=X,high is not used
827 or memory reserved is below 4G.
832 cs89x0_media= [HW,NET]
833 Format: { rj45 | aui | bnc }
836 See header of drivers/s390/block/dasd_devmap.c.
838 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
839 (one device per port)
840 Format: <port#>,<type>
841 See also Documentation/input/joystick-parport.txt
843 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
844 time. See Documentation/dynamic-debug-howto.txt for
845 details. Deprecated, see dyndbg.
847 debug [KNL] Enable kernel debugging (events log level).
850 [KNL] verbose self-tests
852 Print debugging info while doing the locking API
854 We default to 0 (no extra messages), setting it to
855 1 will print _a lot_ more information - normally
856 only useful to kernel developers.
858 debug_objects [KNL] Enable object debugging
861 [KNL] Disable object debugging
863 debug_guardpage_minorder=
864 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
865 parameter allows control of the order of pages that will
866 be intentionally kept free (and hence protected) by the
867 buddy allocator. Bigger value increase the probability
868 of catching random memory corruption, but reduce the
869 amount of memory for normal system use. The maximum
870 possible value is MAX_ORDER/2. Setting this parameter
871 to 1 or 2 should be enough to identify most random
872 memory corruption problems caused by bugs in kernel or
873 driver code when a CPU writes to (or reads from) a
874 random memory location. Note that there exists a class
875 of memory corruptions problems caused by buggy H/W or
876 F/W or by drivers badly programing DMA (basically when
877 memory is written at bus level and the CPU MMU is
878 bypassed) which are not detectable by
879 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
880 tracking down these problems.
883 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
884 parameter enables the feature at boot time. In
885 default, it is disabled. We can avoid allocating huge
886 chunk of memory for debug pagealloc if we don't enable
887 it at boot time and the system will work mostly same
888 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
889 on: enable the feature
891 debugpat [X86] Enable PAT debugging
893 decnet.addr= [HW,NET]
894 Format: <area>[,<node>]
895 See also Documentation/networking/decnet.txt.
898 [same as hugepagesz=] The size of the default
899 HugeTLB page size. This is the size represented by
900 the legacy /proc/ hugepages APIs, used for SHM, and
901 default size when mounting hugetlbfs filesystems.
902 Defaults to the default architecture's huge page size
906 Set number of hash buckets for dentry cache.
909 See Documentation/networking/ipv6.txt.
911 disable_cpu_apicid= [X86,APIC,SMP]
913 The number of initial APIC ID for the
914 corresponding CPU to be disabled at boot,
915 mostly used for the kdump 2nd kernel to
916 disable BSP to wake up multiple CPUs without
917 causing system reset or hang due to sending
920 disable_ddw [PPC/PSERIES]
921 Disable Dynamic DMA Window support. Use this if
922 to workaround buggy firmware.
925 See Documentation/networking/ipv6.txt.
927 disable_mtrr_cleanup [X86]
928 The kernel tries to adjust MTRR layout from continuous
929 to discrete, to make X server driver able to add WB
930 entry later. This parameter disables that.
932 disable_mtrr_trim [X86, Intel and AMD only]
933 By default the kernel will trim any uncacheable
934 memory out of your available memory pool based on
935 MTRR settings. This parameter disables that behavior,
936 possibly causing your machine to run very slowly.
938 disable_timer_pin_1 [X86]
939 Disable PIN 1 of APIC timer
940 Can be useful to work around chipset bugs.
942 dis_ucode_ldr [X86] Disable the microcode loader.
944 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
945 this option disables the debugging code at boot.
947 dma_debug_entries=<number>
948 This option allows to tune the number of preallocated
949 entries for DMA-API debugging code. One entry is
950 required per DMA-API allocation. Use this if the
951 DMA-API debugging code disables itself because the
952 architectural default is too low.
954 dma_debug_driver=<driver_name>
955 With this option the DMA-API debugging driver
956 filter feature can be enabled at boot time. Just
957 pass the driver to filter for as the parameter.
958 The filter can be disabled or changed to another
959 driver later using sysfs.
961 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
962 Broken monitors, graphic adapters, KVMs and EDIDless
963 panels may send no or incorrect EDID data sets.
964 This parameter allows to specify an EDID data sets
965 in the /lib/firmware directory that are used instead.
966 Generic built-in EDID data sets are used, if one of
967 edid/1024x768.bin, edid/1280x1024.bin,
968 edid/1680x1050.bin, or edid/1920x1080.bin is given
969 and no file with the same name exists. Details and
970 instructions how to build your own EDID data are
971 available in Documentation/EDID/HOWTO.txt. An EDID
972 data set will only be used for a particular connector,
973 if its name and a colon are prepended to the EDID
974 name. Each connector may use a unique EDID data
975 set by separating the files with a comma. An EDID
976 data set with no connector name will be used for
977 any connectors not explicitly specified.
981 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
982 module.dyndbg[="val"]
983 Enable debug messages at boot time. See
984 Documentation/dynamic-debug-howto.txt for details.
986 nompx [X86] Disables Intel Memory Protection Extensions.
987 See Documentation/x86/intel_mpx.txt for more
988 information about the feature.
990 nopku [X86] Disable Memory Protection Keys CPU feature found
994 on enable eager fpu restore
995 off disable eager fpu restore
996 auto selects the default scheme, which automatically
997 enables eagerfpu restore for xsaveopt.
999 module.async_probe [KNL]
1000 Enable asynchronous probe on this module.
1002 early_ioremap_debug [KNL]
1003 Enable debug messages in early_ioremap support. This
1004 is useful for tracking down temporary early mappings
1005 which are not unmapped.
1007 earlycon= [KNL] Output early console device and options.
1009 When used with no options, the early console is
1010 determined by the stdout-path property in device
1014 Start an early, polled-mode console on a cadence serial
1015 port at the specified address. The cadence serial port
1016 must already be setup and configured. Options are not
1019 uart[8250],io,<addr>[,options]
1020 uart[8250],mmio,<addr>[,options]
1021 uart[8250],mmio32,<addr>[,options]
1022 uart[8250],mmio32be,<addr>[,options]
1023 uart[8250],0x<addr>[,options]
1024 Start an early, polled-mode console on the 8250/16550
1025 UART at the specified I/O port or MMIO address.
1026 MMIO inter-register address stride is either 8-bit
1027 (mmio) or 32-bit (mmio32 or mmio32be).
1028 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1029 to be equivalent to 'mmio'. 'options' are specified
1030 in the same format described for "console=ttyS<n>"; if
1031 unspecified, the h/w is not initialized.
1035 Start an early, polled-mode console on a pl011 serial
1036 port at the specified address. The pl011 serial port
1037 must already be setup and configured. Options are not
1038 yet supported. If 'mmio32' is specified, then only
1039 the driver will use only 32-bit accessors to read/write
1040 the device registers.
1043 Start an early, polled-mode console on an msm serial
1044 port at the specified address. The serial port
1045 must already be setup and configured. Options are not
1048 msm_serial_dm,<addr>
1049 Start an early, polled-mode console on an msm serial
1050 dm port at the specified address. The serial port
1051 must already be setup and configured. Options are not
1054 smh Use ARM semihosting calls for early console.
1062 Use early console provided by serial driver available
1063 on Samsung SoCs, requires selecting proper type and
1064 a correct base address of the selected UART port. The
1065 serial port must already be setup and configured.
1066 Options are not yet supported.
1070 Use early console provided by Freescale LP UART driver
1071 found on Freescale Vybrid and QorIQ LS1021A processors.
1072 A valid base address must be provided, and the serial
1073 port must already be setup and configured.
1075 armada3700_uart,<addr>
1076 Start an early, polled-mode console on the
1077 Armada 3700 serial port at the specified
1078 address. The serial port must already be setup
1079 and configured. Options are not yet supported.
1081 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1085 earlyprintk=serial[,ttySn[,baudrate]]
1086 earlyprintk=serial[,0x...[,baudrate]]
1087 earlyprintk=ttySn[,baudrate]
1088 earlyprintk=dbgp[debugController#]
1089 earlyprintk=pciserial,bus:device.function[,baudrate]
1091 earlyprintk is useful when the kernel crashes before
1092 the normal console is initialized. It is not enabled by
1093 default because it has some cosmetic problems.
1095 Append ",keep" to not disable it when the real console
1098 Only one of vga, efi, serial, or usb debug port can
1101 Currently only ttyS0 and ttyS1 may be specified by
1102 name. Other I/O ports may be explicitly specified
1103 on some architectures (x86 and arm at least) by
1104 replacing ttySn with an I/O port address, like this:
1105 earlyprintk=serial,0x1008,115200
1106 You can find the port for a given device in
1107 /proc/tty/driver/serial:
1108 2: uart:ST16650V2 port:00001008 irq:18 ...
1110 Interaction with the standard serial driver is not
1113 The VGA and EFI output is eventually overwritten by
1116 The xen output can only be used by Xen PV guests.
1118 edac_report= [HW,EDAC] Control how to report EDAC event
1119 Format: {"on" | "off" | "force"}
1120 on: enable EDAC to report H/W event. May be overridden
1121 by other higher priority error reporting module.
1122 off: disable H/W event reporting through EDAC.
1123 force: enforce the use of EDAC to report H/W event.
1126 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1129 This is designed to be used in conjunction with
1130 the boot argument: earlyprintk=vga
1133 Format: {"off" | "on" | "skip[mbr]"}
1136 Format: { "old_map", "nochunk", "noruntime", "debug" }
1137 old_map [X86-64]: switch to the old ioremap-based EFI
1138 runtime services mapping. 32-bit still uses this one by
1140 nochunk: disable reading files in "chunks" in the EFI
1141 boot stub, as chunking can cause problems with some
1142 firmware implementations.
1143 noruntime : disable EFI runtime services support
1144 debug: enable misc debug output
1146 efi_no_storage_paranoia [EFI; X86]
1147 Using this parameter you can use more than 50% of
1148 your efi variable storage. Use this parameter only if
1149 you are really sure that your UEFI does sane gc and
1150 fulfills the spec otherwise your board may brick.
1152 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1153 Add arbitrary attribute to specific memory range by
1154 updating original EFI memory map.
1155 Region of memory which aa attribute is added to is
1157 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1158 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1159 attribute is added to range 0x100000000-0x180000000 and
1160 0x10a0000000-0x1120000000.
1162 Using this parameter you can do debugging of EFI memmap
1163 related feature. For example, you can do debugging of
1164 Address Range Mirroring feature even if your box
1167 eisa_irq_edge= [PARISC,HW]
1168 See header of drivers/parisc/eisa.c.
1171 See comment before function elanfreq_setup() in
1172 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1175 Format: {"cfq" | "deadline" | "noop"}
1176 See Documentation/block/cfq-iosched.txt and
1177 Documentation/block/deadline-iosched.txt for details.
1179 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1180 Specifies physical address of start of kernel core
1181 image elf header and optionally the size. Generally
1182 kexec loader will pass this option to capture kernel.
1183 See Documentation/kdump/kdump.txt for details.
1185 enable_mtrr_cleanup [X86]
1186 The kernel tries to adjust MTRR layout from continuous
1187 to discrete, to make X server driver able to add WB
1188 entry later. This parameter enables that.
1190 enable_timer_pin_1 [X86]
1191 Enable PIN 1 of APIC timer
1192 Can be useful to work around chipset bugs
1193 (in particular on some ATI chipsets).
1194 The kernel tries to set a reasonable default.
1196 enforcing [SELINUX] Set initial enforcing status.
1198 See security/selinux/Kconfig help text.
1199 0 -- permissive (log only, no denials).
1200 1 -- enforcing (deny and log).
1202 Value can be changed at runtime via /selinux/enforce.
1205 Disable Error Record Serialization Table (ERST)
1208 ether= [HW,NET] Ethernet cards parameters
1209 This option is obsoleted by the "netdev=" option, which
1210 has equivalent usage. See its documentation for details.
1214 Permit 'security.evm' to be updated regardless of
1215 current integrity status.
1219 fail_make_request=[KNL]
1220 General fault injection mechanism.
1221 Format: <interval>,<probability>,<space>,<times>
1222 See also Documentation/fault-injection/.
1225 See Documentation/blockdev/floppy.txt.
1227 force_pal_cache_flush
1228 [IA-64] Avoid check_sal_cache_flush which may hang on
1229 buggy SAL_CACHE_FLUSH implementations. Using this
1230 parameter will force ia64_sal_cache_flush to call
1231 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1234 Forcefully enable Physical Address Extension (PAE).
1235 Many Pentium M systems disable PAE but may have a
1236 functionally usable PAE implementation.
1237 Warning: use of this parameter will taint the kernel
1238 and may cause unknown problems.
1241 [FTRACE] will set and start the specified tracer
1242 as early as possible in order to facilitate early
1245 ftrace_dump_on_oops[=orig_cpu]
1246 [FTRACE] will dump the trace buffers on oops.
1247 If no parameter is passed, ftrace will dump
1248 buffers of all CPUs, but if you pass orig_cpu, it will
1249 dump only the buffer of the CPU that triggered the
1252 ftrace_filter=[function-list]
1253 [FTRACE] Limit the functions traced by the function
1254 tracer at boot up. function-list is a comma separated
1255 list of functions. This list can be changed at run
1256 time by the set_ftrace_filter file in the debugfs
1259 ftrace_notrace=[function-list]
1260 [FTRACE] Do not trace the functions specified in
1261 function-list. This list can be changed at run time
1262 by the set_ftrace_notrace file in the debugfs
1265 ftrace_graph_filter=[function-list]
1266 [FTRACE] Limit the top level callers functions traced
1267 by the function graph tracer at boot up.
1268 function-list is a comma separated list of functions
1269 that can be changed at run time by the
1270 set_graph_function file in the debugfs tracing directory.
1272 ftrace_graph_notrace=[function-list]
1273 [FTRACE] Do not trace from the functions specified in
1274 function-list. This list is a comma separated list of
1275 functions that can be changed at run time by the
1276 set_graph_notrace file in the debugfs tracing directory.
1279 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1280 support via parallel port (up to 5 devices per port)
1281 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1282 See also Documentation/input/joystick-parport.txt
1286 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1290 gcov_persist= [GCOV] When non-zero (default), profiling data for
1291 kernel modules is saved and remains accessible via
1292 debugfs, even when the module is unloaded/reloaded.
1293 When zero, profiling data is discarded and associated
1294 debugfs files are removed at module unload time.
1296 gpt [EFI] Forces disk with valid GPT signature but
1297 invalid Protective MBR to be treated as GPT. If the
1298 primary GPT is corrupted, it enables the backup/alternate
1299 GPT to be used instead.
1301 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1302 the "Enable 0" bit of the configuration register.
1305 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1306 the "Enable 0" bit of the configuration register.
1309 grcan.select= [HW] Select which physical interface to use.
1312 grcan.txsize= [HW] Sets the size of the tx buffer.
1313 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1315 grcan.rxsize= [HW] Sets the size of the rx buffer.
1316 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1319 hardlockup_all_cpu_backtrace=
1320 [KNL] Should the hard-lockup detector generate
1321 backtraces on all cpus.
1324 hashdist= [KNL,NUMA] Large hashes allocated during boot
1325 are distributed across NUMA nodes. Defaults on
1326 for 64-bit NUMA, off otherwise.
1327 Format: 0 | 1 (for off | on)
1329 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1331 hd= [EIDE] (E)IDE hard drive subsystem geometry
1332 Format: <cyl>,<head>,<sect>
1335 Disable Hardware Error Source Table (HEST) support;
1336 corresponding firmware-first mode error processing
1337 logic will be disabled.
1339 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1340 size of <nn>. This works even on boxes that have no
1341 highmem otherwise. This also works to reduce highmem
1342 size on bigger boxes.
1344 highres= [KNL] Enable/disable high resolution timer mode.
1345 Valid parameters: "on", "off"
1349 See Documentation/isdn/README.HiSax.
1353 hpet= [X86-32,HPET] option to control HPET usage
1354 Format: { enable (default) | disable | force |
1356 disable: disable HPET and use PIT instead
1357 force: allow force enabled of undocumented chips (ICH4,
1359 verbose: show contents of HPET registers during setup
1361 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1362 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1364 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1365 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1366 On x86-64 and powerpc, this option can be specified
1367 multiple times interleaved with hugepages= to reserve
1368 huge pages of different sizes. Valid pages sizes on
1369 x86-64 are 2M (when the CPU supports "pse") and 1G
1370 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1372 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1373 terminal devices. Valid values: 0..8
1374 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1375 If specified, z/VM IUCV HVC accepts connections
1376 from listed z/VM user IDs only.
1378 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1379 hardware thread id mappings.
1380 Format: <cpu>:<hwthread>
1383 Do not unregister boot console at start. This is only
1384 useful for debugging when something happens in the window
1385 between unregistering the boot console and initializing
1388 i2c_bus= [HW] Override the default board specific I2C bus speed
1389 or register an additional I2C bus that is not
1390 registered from board initialization code.
1394 i8042.debug [HW] Toggle i8042 debug mode
1395 i8042.unmask_kbd_data
1396 [HW] Enable printing of interrupt data from the KBD port
1397 (disabled by default, and as a pre-condition
1398 requires that i8042.debug=1 be enabled)
1399 i8042.direct [HW] Put keyboard port into non-translated mode
1400 i8042.dumbkbd [HW] Pretend that controller can only read data from
1401 keyboard and cannot control its state
1402 (Don't attempt to blink the leds)
1403 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1404 i8042.nokbd [HW] Don't check/create keyboard port
1405 i8042.noloop [HW] Disable the AUX Loopback command while probing
1407 i8042.nomux [HW] Don't check presence of an active multiplexing
1409 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1411 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1412 i8042.reset [HW] Reset the controller during init, cleanup and
1413 suspend-to-ram transitions, only during s2r
1414 transitions, or never reset
1415 Format: { 1 | Y | y | 0 | N | n }
1416 1, Y, y: always reset controller
1417 0, N, n: don't ever reset controller
1418 Default: only on s2r transitions on x86; most other
1419 architectures force reset to be always executed
1420 i8042.unlock [HW] Unlock (ignore) the keylock
1421 i8042.kbdreset [HW] Reset device connected to KBD port
1425 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1426 indicates that the driver is running on unsupported
1428 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1429 does not match list of supported models.
1431 [HW] Report power status in /proc/i8k
1432 (disabled by default)
1433 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1436 i915.invert_brightness=
1437 [DRM] Invert the sense of the variable that is used to
1438 set the brightness of the panel backlight. Normally a
1439 brightness value of 0 indicates backlight switched off,
1440 and the maximum of the brightness value sets the backlight
1441 to maximum brightness. If this parameter is set to 0
1442 (default) and the machine requires it, or this parameter
1443 is set to 1, a brightness value of 0 sets the backlight
1444 to maximum brightness, and the maximum of the brightness
1445 value switches the backlight off.
1446 -1 -- never invert brightness
1447 0 -- machine default
1448 1 -- force brightness inversion
1451 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1453 ide-core.nodma= [HW] (E)IDE subsystem
1454 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1455 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1456 .cdrom .chs .ignore_cable are additional options
1457 See Documentation/ide/ide.txt.
1459 ide-generic.probe-mask= [HW] (E)IDE subsystem
1461 Probe mask for legacy ISA IDE ports. Depending on
1462 platform up to 6 ports are supported, enabled by
1463 setting corresponding bits in the mask to 1. The
1464 default value is 0x0, which has a special meaning.
1465 On systems that have PCI, it triggers scanning the
1466 PCI bus for the first and the second port, which
1467 are then probed. On systems without PCI the value
1468 of 0x0 enables probing the two first ports as if it
1471 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1472 Claim all unknown PCI IDE storage controllers.
1475 Format: idle=poll, idle=halt, idle=nomwait
1476 Poll forces a polling idle loop that can slightly
1477 improve the performance of waking up a idle CPU, but
1478 will use a lot of power and make the system run hot.
1480 idle=halt: Halt is forced to be used for CPU idle.
1481 In such case C2/C3 won't be used again.
1482 idle=nomwait: Disable mwait for CPU C-states
1484 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1485 Format: { strict | legacy | 2008 | relaxed }
1488 Choose which programs will be accepted for execution
1489 based on the IEEE 754 NaN encoding(s) supported by
1490 the FPU and the NaN encoding requested with the value
1491 of an ELF file header flag individually set by each
1492 binary. Hardware implementations are permitted to
1493 support either or both of the legacy and the 2008 NaN
1496 Available settings are as follows:
1497 strict accept binaries that request a NaN encoding
1498 supported by the FPU
1499 legacy only accept legacy-NaN binaries, if supported
1501 2008 only accept 2008-NaN binaries, if supported
1503 relaxed accept any binaries regardless of whether
1504 supported by the FPU
1506 The FPU emulator is always able to support both NaN
1507 encodings, so if no FPU hardware is present or it has
1508 been disabled with 'nofpu', then the settings of
1509 'legacy' and '2008' strap the emulator accordingly,
1510 'relaxed' straps the emulator for both legacy-NaN and
1511 2008-NaN, whereas 'strict' enables legacy-NaN only on
1512 legacy processors and both NaN encodings on MIPS32 or
1515 The setting for ABS.fmt/NEG.fmt instruction execution
1516 mode generally follows that for the NaN encoding,
1517 except where unsupported by hardware.
1519 ignore_loglevel [KNL]
1520 Ignore loglevel setting - this will print /all/
1521 kernel messages to the console. Useful for debugging.
1522 We also add it as printk module parameter, so users
1523 could change it dynamically, usually by
1524 /sys/module/printk/parameters/ignore_loglevel.
1527 Ignore RLIMIT_DATA setting for data mappings,
1528 print warning at first misuse. Can be changed via
1529 /sys/module/kernel/parameters/ignore_rlimit_data.
1531 ihash_entries= [KNL]
1532 Set number of hash buckets for inode cache.
1534 ima_appraise= [IMA] appraise integrity measurements
1535 Format: { "off" | "enforce" | "fix" | "log" }
1538 ima_appraise_tcb [IMA]
1539 The builtin appraise policy appraises all files
1543 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1547 The list of supported hash algorithms is defined
1548 in crypto/hash_info.h.
1551 The builtin measurement policy to load during IMA
1552 setup. Specyfing "tcb" as the value, measures all
1553 programs exec'd, files mmap'd for exec, and all files
1554 opened with the read mode bit set by either the
1555 effective uid (euid=0) or uid=0.
1558 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1559 Load a policy which meets the needs of the Trusted
1560 Computing Base. This means IMA will measure all
1561 programs exec'd, files mmap'd for exec, and all files
1562 opened for read by uid=0.
1565 Select one of defined IMA measurements template formats.
1566 Formats: { "ima" | "ima-ng" | "ima-sig" }
1570 [IMA] Define a custom template format.
1571 Format: { "field1|...|fieldN" }
1573 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1574 Format: <min_file_size>
1575 Set the minimal file size for using asynchronous hash.
1576 If left unspecified, ahash usage is disabled.
1578 ahash performance varies for different data sizes on
1579 different crypto accelerators. This option can be used
1580 to achieve the best performance for a particular HW.
1582 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1584 Set hashing buffer size. Default: 4k.
1586 ahash performance varies for different chunk sizes on
1587 different crypto accelerators. This option can be used
1588 to achieve best performance for particular HW.
1592 Run specified binary instead of /sbin/init as init
1595 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1596 for working out where the kernel is dying during
1599 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1600 initcall functions. Useful for debugging built-in
1601 modules and initcalls.
1603 initrd= [BOOT] Specify the location of the initial ramdisk
1605 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1608 int_pln_enable [x86] Enable power limit notification interrupt
1610 integrity_audit=[IMA]
1611 Format: { "0" | "1" }
1612 0 -- basic integrity auditing messages. (Default)
1613 1 -- additional integrity auditing messages.
1615 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1617 Enable intel iommu driver.
1619 Disable intel iommu driver.
1620 igfx_off [Default Off]
1621 By default, gfx is mapped as normal device. If a gfx
1622 device has a dedicated DMAR unit, the DMAR unit is
1623 bypassed by not enabling DMAR with this option. In
1624 this case, gfx device will use physical address for
1627 With this option iommu will not optimize to look
1628 for io virtual address below 32-bit forcing dual
1629 address cycle on pci bus for cards supporting greater
1630 than 32-bit addressing. The default is to look
1631 for translation below 32-bit and if not available
1632 then look in the higher range.
1633 strict [Default Off]
1634 With this option on every unmap_single operation will
1635 result in a hardware IOTLB flush operation as opposed
1636 to batching them for performance.
1637 sp_off [Default Off]
1638 By default, super page will be supported if Intel IOMMU
1639 has the capability. With this option, super page will
1641 ecs_off [Default Off]
1642 By default, extended context tables will be supported if
1643 the hardware advertises that it has support both for the
1644 extended tables themselves, and also PASID support. With
1645 this option set, extended tables will not be used even
1646 on hardware which claims to support them.
1648 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1649 0 disables intel_idle and fall back on acpi_idle.
1650 1 to 6 specify maximum depth of C-state.
1654 Do not enable intel_pstate as the default
1655 scaling driver for the supported processors
1657 Enable intel_pstate on systems that prohibit it by default
1658 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1659 instead of acpi-cpufreq may disable platform features, such
1660 as thermal controls and power capping, that rely on ACPI
1661 P-States information being indicated to OSPM and therefore
1662 should be used with caution. This option does not work with
1663 processors that aren't supported by the intel_pstate driver
1664 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1666 Do not enable hardware P state control (HWP)
1669 Only load intel_pstate on systems which support
1670 hardware P state control (HWP) if available.
1672 intremap= [X86-64, Intel-IOMMU]
1673 on enable Interrupt Remapping (default)
1674 off disable Interrupt Remapping
1675 nosid disable Source ID checking
1677 BIOS x2APIC opt-out request will be ignored
1678 nopost disable Interrupt Posting
1680 iomem= Disable strict checking of access to MMIO memory
1681 strict regions from userspace.
1696 nobypass [PPC/POWERNV]
1697 Disable IOMMU bypass, using IOMMU for PCI devices.
1700 io7= [HW] IO7 for Marvel based alpha systems
1701 See comment before marvel_specify_io7 in
1702 arch/alpha/kernel/core_marvel.c.
1704 io_delay= [X86] I/O delay method
1706 Standard port 0x80 based delay
1708 Alternate port 0xed based delay (needed on some systems)
1710 Simple two microseconds delay
1715 See Documentation/filesystems/nfs/nfsroot.txt.
1717 irqaffinity= [SMP] Set the default irq affinity mask
1719 <cpu number>,...,<cpu number>
1721 <cpu number>-<cpu number>
1722 (must be a positive range in ascending order)
1724 <cpu number>,...,<cpu number>-<cpu number>
1727 When an interrupt is not handled search all handlers
1728 for it. Intended to get systems with badly broken
1732 When an interrupt is not handled search all handlers
1733 for it. Also check all handlers each timer
1734 interrupt. Intended to get systems with badly broken
1738 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1740 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1742 <cpu number>,...,<cpu number>
1744 <cpu number>-<cpu number>
1745 (must be a positive range in ascending order)
1747 <cpu number>,...,<cpu number>-<cpu number>
1749 This option can be used to specify one or more CPUs
1750 to isolate from the general SMP balancing and scheduling
1751 algorithms. You can move a process onto or off an
1752 "isolated" CPU via the CPU affinity syscalls or cpuset.
1753 <cpu number> begins at 0 and the maximum value is
1754 "number of CPUs in system - 1".
1756 This option is the preferred way to isolate CPUs. The
1757 alternative -- manually setting the CPU mask of all
1758 tasks in the system -- can cause problems and
1759 suboptimal load balancer performance.
1763 ivrs_ioapic [HW,X86_64]
1764 Provide an override to the IOAPIC-ID<->DEVICE-ID
1765 mapping provided in the IVRS ACPI table. For
1766 example, to map IOAPIC-ID decimal 10 to
1767 PCI device 00:14.0 write the parameter as:
1768 ivrs_ioapic[10]=00:14.0
1770 ivrs_hpet [HW,X86_64]
1771 Provide an override to the HPET-ID<->DEVICE-ID
1772 mapping provided in the IVRS ACPI table. For
1773 example, to map HPET-ID decimal 0 to
1774 PCI device 00:14.0 write the parameter as:
1775 ivrs_hpet[0]=00:14.0
1777 js= [HW,JOY] Analog joystick
1778 See Documentation/input/joystick.txt.
1781 Enable/disable kernel and module base offset ASLR
1782 (Address Space Layout Randomization) if built into
1783 the kernel. When CONFIG_HIBERNATION is selected,
1784 kASLR is disabled by default. When kASLR is enabled,
1785 hibernation will be disabled.
1789 kernelcore= [KNL,X86,IA-64,PPC]
1790 Format: nn[KMGTPE] | "mirror"
1792 specifies the amount of memory usable by the kernel
1793 for non-movable allocations. The requested amount is
1794 spread evenly throughout all nodes in the system. The
1795 remaining memory in each node is used for Movable
1796 pages. In the event, a node is too small to have both
1797 kernelcore and Movable pages, kernelcore pages will
1798 take priority and other nodes will have a larger number
1799 of Movable pages. The Movable zone is used for the
1800 allocation of pages that may be reclaimed or moved
1801 by the page migration subsystem. This means that
1802 HugeTLB pages may not be allocated from this zone.
1803 Note that allocations like PTEs-from-HighMem still
1804 use the HighMem zone if it exists, and the Normal
1805 zone if it does not.
1807 Instead of specifying the amount of memory (nn[KMGTPE]),
1808 you can specify "mirror" option. In case "mirror"
1809 option is specified, mirrored (reliable) memory is used
1810 for non-movable allocations and remaining memory is used
1811 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1812 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1815 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1816 Format: <Controller#>[,poll interval]
1817 The controller # is the number of the ehci usb debug
1818 port as it is probed via PCI. The poll interval is
1819 optional and is the number seconds in between
1820 each poll cycle to the debug port in case you need
1821 the functionality for interrupting the kernel with
1822 gdb or control-c on the dbgp connection. When
1823 not using this parameter you use sysrq-g to break into
1824 the kernel debugger.
1826 kgdboc= [KGDB,HW] kgdb over consoles.
1827 Requires a tty driver that supports console polling,
1828 or a supported polling keyboard driver (non-usb).
1829 Serial only format: <serial_device>[,baud]
1830 keyboard only format: kbd
1831 keyboard and serial format: kbd,<serial_device>[,baud]
1832 Optional Kernel mode setting:
1833 kms, kbd format: kms,kbd
1834 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1836 kgdbwait [KGDB] Stop kernel execution and enter the
1837 kernel debugger at the earliest opportunity.
1839 kmac= [MIPS] korina ethernet MAC address.
1840 Configure the RouterBoard 532 series on-chip
1841 Ethernet adapter MAC address.
1843 kmemleak= [KNL] Boot-time kmemleak enable/disable
1844 Valid arguments: on, off
1846 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1849 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1850 Valid arguments: 0, 1, 2
1851 kmemcheck=0 (disabled)
1852 kmemcheck=1 (enabled)
1853 kmemcheck=2 (one-shot mode)
1854 Default: 2 (one-shot mode)
1856 kstack=N [X86] Print N words from the kernel stack
1859 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1860 Default is 0 (don't ignore, but inject #GP)
1862 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1866 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1867 Default is 1 (enabled)
1869 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1871 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1873 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1874 (virtualized MMU) support on capable Intel chips.
1875 Default is 1 (enabled)
1877 kvm-intel.emulate_invalid_guest_state=
1878 [KVM,Intel] Enable emulation of invalid guest states
1879 Default is 0 (disabled)
1881 kvm-intel.flexpriority=
1882 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1883 Default is 1 (enabled)
1886 [KVM,Intel] Enable VMX nesting (nVMX).
1887 Default is 0 (disabled)
1889 kvm-intel.unrestricted_guest=
1890 [KVM,Intel] Disable unrestricted guest feature
1891 (virtualized real and unpaged mode) on capable
1892 Intel chips. Default is 1 (enabled)
1894 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1895 feature (tagged TLBs) on capable Intel chips.
1896 Default is 1 (enabled)
1902 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1905 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1906 value for LAPIC timer one-shot implementation. Default
1907 back to the programmable timer unit in the LAPIC.
1909 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1912 libata.dma= [LIBATA] DMA control
1913 libata.dma=0 Disable all PATA and SATA DMA
1914 libata.dma=1 PATA and SATA Disk DMA only
1915 libata.dma=2 ATAPI (CDROM) DMA only
1916 libata.dma=4 Compact Flash DMA only
1917 Combinations also work, so libata.dma=3 enables DMA
1918 for disks and CDROMs, but not CFs.
1920 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1921 libata.ignore_hpa=0 keep BIOS limits (default)
1922 libata.ignore_hpa=1 ignore limits, using full disk
1924 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1928 libata.force= [LIBATA] Force configurations. The format is comma
1929 separated list of "[ID:]VAL" where ID is
1930 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1931 matching port, link or device. Basically, it matches
1932 the ATA ID string printed on console by libata. If
1933 the whole ID part is omitted, the last PORT and DEVICE
1934 values are used. If ID hasn't been specified yet, the
1935 configuration applies to all ports, links and devices.
1937 If only DEVICE is omitted, the parameter applies to
1938 the port and all links and devices behind it. DEVICE
1939 number of 0 either selects the first device or the
1940 first fan-out link behind PMP device. It does not
1941 select the host link. DEVICE number of 15 selects the
1942 host link and device attached to it.
1944 The VAL specifies the configuration to force. As long
1945 as there's no ambiguity shortcut notation is allowed.
1946 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1947 The following configurations can be forced.
1949 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1950 Any ID with matching PORT is used.
1952 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1954 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1955 udma[/][16,25,33,44,66,100,133] notation is also
1958 * [no]ncq: Turn on or off NCQ.
1960 * [no]ncqtrim: Turn off queued DSM TRIM.
1962 * nohrst, nosrst, norst: suppress hard, soft
1965 * rstonce: only attempt one reset during
1966 hot-unplug link recovery
1968 * dump_id: dump IDENTIFY data.
1970 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1972 * disable: Disable this device.
1974 If there are multiple matching configurations changing
1975 the same attribute, the last one is used.
1977 memblock=debug [KNL] Enable memblock debug messages.
1979 load_ramdisk= [RAM] List of ramdisks to load from floppy
1980 See Documentation/blockdev/ramdisk.txt.
1982 lockd.nlm_grace_period=P [NFS] Assign grace period.
1985 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1988 lockd.nlm_timeout=T [NFS] Assign timeout value.
1991 lockd.nlm_udpport=M [NFS] Assign UDP port.
1994 locktorture.nreaders_stress= [KNL]
1995 Set the number of locking read-acquisition kthreads.
1996 Defaults to being automatically set based on the
1997 number of online CPUs.
1999 locktorture.nwriters_stress= [KNL]
2000 Set the number of locking write-acquisition kthreads.
2002 locktorture.onoff_holdoff= [KNL]
2003 Set time (s) after boot for CPU-hotplug testing.
2005 locktorture.onoff_interval= [KNL]
2006 Set time (s) between CPU-hotplug operations, or
2007 zero to disable CPU-hotplug testing.
2009 locktorture.shuffle_interval= [KNL]
2010 Set task-shuffle interval (jiffies). Shuffling
2011 tasks allows some CPUs to go into dyntick-idle
2012 mode during the locktorture test.
2014 locktorture.shutdown_secs= [KNL]
2015 Set time (s) after boot system shutdown. This
2016 is useful for hands-off automated testing.
2018 locktorture.stat_interval= [KNL]
2019 Time (s) between statistics printk()s.
2021 locktorture.stutter= [KNL]
2022 Time (s) to stutter testing, for example,
2023 specifying five seconds causes the test to run for
2024 five seconds, wait for five seconds, and so on.
2025 This tests the locking primitive's ability to
2026 transition abruptly to and from idle.
2028 locktorture.torture_runnable= [BOOT]
2029 Start locktorture running at boot time.
2031 locktorture.torture_type= [KNL]
2032 Specify the locking implementation to test.
2034 locktorture.verbose= [KNL]
2035 Enable additional printk() statements.
2037 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2040 loglevel= All Kernel Messages with a loglevel smaller than the
2041 console loglevel will be printed to the console. It can
2042 also be changed with klogd or other programs. The
2043 loglevels are defined as follows:
2045 0 (KERN_EMERG) system is unusable
2046 1 (KERN_ALERT) action must be taken immediately
2047 2 (KERN_CRIT) critical conditions
2048 3 (KERN_ERR) error conditions
2049 4 (KERN_WARNING) warning conditions
2050 5 (KERN_NOTICE) normal but significant condition
2051 6 (KERN_INFO) informational
2052 7 (KERN_DEBUG) debug-level messages
2054 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2055 in bytes. n must be a power of two and greater
2056 than the minimal size. The minimal size is defined
2057 by LOG_BUF_SHIFT kernel config parameter. There is
2058 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2059 that allows to increase the default size depending on
2060 the number of CPUs. See init/Kconfig for more details.
2062 logo.nologo [FB] Disables display of the built-in Linux logo.
2063 This may be used to provide more screen space for
2064 kernel log messages and is useful when debugging
2065 kernel boot problems.
2067 lp=0 [LP] Specify parallel ports to use, e.g,
2068 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2069 lp=reset first parallel port). 'lp=0' disables the
2070 lp=auto printer driver. 'lp=reset' (which can be
2071 specified in addition to the ports) causes
2072 attached printers to be reset. Using
2073 lp=port1,port2,... specifies the parallel ports
2074 to associate lp devices with, starting with
2075 lp0. A port specification may be 'none' to skip
2076 that lp device, or a parport name such as
2077 'parport0'. Specifying 'lp=auto' instead of a
2078 port specification list means that device IDs
2079 from each port should be examined, to see if
2080 an IEEE 1284-compliant printer is attached; if
2081 so, the driver will manage that printer.
2082 See also header of drivers/char/lp.c.
2085 Sets loops_per_jiffy to given constant, thus avoiding
2086 time-consuming boot-time autodetection (up to 250 ms per
2087 CPU). 0 enables autodetection (default). To determine
2088 the correct value for your kernel, boot with normal
2089 autodetection and see what value is printed. Note that
2090 on SMP systems the preset will be applied to all CPUs,
2091 which is likely to cause problems if your CPUs need
2092 significantly divergent settings. An incorrect value
2093 will cause delays in the kernel to be wrong, leading to
2094 unpredictable I/O errors and other breakage. Although
2095 unlikely, in the extreme case this might damage your
2099 Format: <io>,<irq>,<dma>
2101 machvec= [IA-64] Force the use of a particular machine-vector
2102 (machvec) in a generic kernel.
2103 Example: machvec=hpzx1_swiotlb
2105 machtype= [Loongson] Share the same kernel image file between different
2107 Example: machtype=lemote-yeeloong-2f-7inch
2109 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2110 than or equal to this physical address is ignored.
2112 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2113 should make use of. maxcpus=n : n >= 0 limits the
2114 kernel to using 'n' processors. n=0 is a special case,
2115 it is equivalent to "nosmp", which also disables
2118 max_loop= [LOOP] The number of loop block devices that get
2119 (loop.max_loop) unconditionally pre-created at init time. The default
2120 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2121 of statically allocating a predefined number, loop
2122 devices can be requested on-demand with the
2123 /dev/loop-control interface.
2125 mce [X86-32] Machine Check Exception
2127 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2129 md= [HW] RAID subsystems devices and level
2130 See Documentation/md.txt.
2133 Format: <first>,<last>
2134 Specifies range of consoles to be captured by the MDA.
2136 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2137 Amount of memory to be used when the kernel is not able
2138 to see the whole system memory or for test.
2139 [X86] Work as limiting max address. Use together
2140 with memmap= to avoid physical address space collisions.
2141 Without memmap= PCI devices could be placed at addresses
2142 belonging to unused RAM.
2144 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2148 [KNL,SH] Allow user to override the default size for
2149 per-device physically contiguous DMA buffers.
2151 memmap=exactmap [KNL,X86] Enable setting of an exact
2152 E820 memory map, as specified by the user.
2153 Such memmap=exactmap lines can be constructed based on
2154 BIOS output or other requirements. See the memmap=nn@ss
2157 memmap=nn[KMG]@ss[KMG]
2158 [KNL] Force usage of a specific region of memory.
2159 Region of memory to be used is from ss to ss+nn.
2161 memmap=nn[KMG]#ss[KMG]
2162 [KNL,ACPI] Mark specific memory as ACPI data.
2163 Region of memory to be marked is from ss to ss+nn.
2165 memmap=nn[KMG]$ss[KMG]
2166 [KNL,ACPI] Mark specific memory as reserved.
2167 Region of memory to be reserved is from ss to ss+nn.
2168 Example: Exclude memory from 0x18690000-0x1869ffff
2169 memmap=64K$0x18690000
2171 memmap=0x10000$0x18690000
2173 memmap=nn[KMG]!ss[KMG]
2174 [KNL,X86] Mark specific memory as protected.
2175 Region of memory to be used, from ss to ss+nn.
2176 The memory region may be marked as e820 type 12 (0xc)
2177 and is NVDIMM or ADR memory.
2179 memory_corruption_check=0/1 [X86]
2180 Some BIOSes seem to corrupt the first 64k of
2181 memory when doing things like suspend/resume.
2182 Setting this option will scan the memory
2183 looking for corruption. Enabling this will
2184 both detect corruption and prevent the kernel
2185 from using the memory being corrupted.
2186 However, its intended as a diagnostic tool; if
2187 repeatable BIOS-originated corruption always
2188 affects the same memory, you can use memmap=
2189 to prevent the kernel from using that memory.
2191 memory_corruption_check_size=size [X86]
2192 By default it checks for corruption in the low
2193 64k, making this memory unavailable for normal
2194 use. Use this parameter to scan for
2195 corruption in more or less memory.
2197 memory_corruption_check_period=seconds [X86]
2198 By default it checks for corruption every 60
2199 seconds. Use this parameter to check at some
2200 other rate. 0 disables periodic checking.
2202 memtest= [KNL,X86,ARM] Enable memtest
2204 default : 0 <disable>
2205 Specifies the number of memtest passes to be
2206 performed. Each pass selects another test
2207 pattern from a given set of patterns. Memtest
2208 fills the memory with this pattern, validates
2209 memory contents and reserves bad memory
2210 regions that are detected.
2212 meye.*= [HW] Set MotionEye Camera parameters
2213 See Documentation/video4linux/meye.txt.
2215 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2216 Multi-Function General Purpose Timers on AMD Geode
2219 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2220 the BIOS has incorrectly applied a workaround. TinyBIOS
2221 version 0.98 is known to be affected, 0.99 fixes the
2222 problem by letting the user disable the workaround.
2226 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2227 physical address is ignored.
2229 mini2440= [ARM,HW,KNL]
2230 Format:[0..2][b][c][t]
2232 MINI2440 configuration specification:
2233 0 - The attached screen is the 3.5" TFT
2234 1 - The attached screen is the 7" TFT
2235 2 - The VGA Shield is attached (1024x768)
2236 Leaving out the screen size parameter will not load
2237 the TFT driver, and the framebuffer will be left
2239 b - Enable backlight. The TFT backlight pin will be
2240 linked to the kernel VESA blanking code and a GPIO
2241 LED. This parameter is not necessary when using the
2243 c - Enable the s3c camera interface.
2244 t - Reserved for enabling touchscreen support. The
2245 touchscreen support is not enabled in the mainstream
2246 kernel as of 2.6.30, a preliminary port can be found
2247 in the "bleeding edge" mini2440 support kernel at
2248 http://repo.or.cz/w/linux-2.6/mini2440.git
2251 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2252 parameter allows control of the logging verbosity for
2253 the additional memory initialisation checks. A value
2254 of 0 disables mminit logging and a level of 4 will
2255 log everything. Information is printed at KERN_DEBUG
2256 so loglevel=8 may also need to be specified.
2259 [KNL] When CONFIG_MODULE_SIG is set, this means that
2260 modules without (valid) signatures will fail to load.
2261 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2262 is always true, so this option does nothing.
2265 [MOUSE] Maximum time between finger touching and
2266 leaving touchpad surface for touch to be considered
2267 a tap and be reported as a left button click (for
2268 touchpads working in absolute mode only).
2270 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2271 reporting absolute coordinates, such as tablets
2272 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2273 reporting absolute coordinates, such as tablets
2275 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2276 is similar to kernelcore except it specifies the
2277 amount of memory used for migratable allocations.
2278 If both kernelcore and movablecore is specified,
2279 then kernelcore will be at *least* the specified
2280 value but may be more. If movablecore on its own
2281 is specified, the administrator must be careful
2282 that the amount of memory usable for all allocations
2285 movable_node [KNL,X86] Boot-time switch to enable the effects
2286 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2288 MTD_Partition= [MTD]
2289 Format: <name>,<region-number>,<size>,<offset>
2291 MTD_Region= [MTD] Format:
2292 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2295 See drivers/mtd/cmdlinepart.c.
2297 multitce=off [PPC] This parameter disables the use of the pSeries
2298 firmware feature for updating multiple TCE entries
2301 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2303 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2305 boundary - index of last SLC block on Flex-OneNAND.
2306 The remaining blocks are configured as MLC blocks.
2307 lock - Configure if Flex-OneNAND boundary should be locked.
2308 Once locked, the boundary cannot be changed.
2309 1 indicates lock status, 0 indicates unlock status.
2312 ARM/S3C2412 JIVE boot control
2314 See arch/arm/mach-s3c2412/mach-jive.c
2316 mtouchusb.raw_coordinates=
2317 [HW] Make the MicroTouch USB driver use raw coordinates
2318 ('y', default) or cooked coordinates ('n')
2320 mtrr_chunk_size=nn[KMG] [X86]
2321 used for mtrr cleanup. It is largest continuous chunk
2322 that could hold holes aka. UC entries.
2324 mtrr_gran_size=nn[KMG] [X86]
2325 Used for mtrr cleanup. It is granularity of mtrr block.
2327 Large value could prevent small alignment from
2330 mtrr_spare_reg_nr=n [X86]
2332 Range: 0,7 : spare reg number
2334 Used for mtrr cleanup. It is spare mtrr entries number.
2335 Set to 2 or more if your graphical card needs more.
2337 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2339 netdev= [NET] Network devices parameters
2340 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2341 Note that mem_start is often overloaded to mean
2342 something different and driver-specific.
2343 This usage is only documented in each driver source
2347 [NETFILTER] Enable connection tracking flow accounting
2348 0 to disable accounting
2349 1 to enable accounting
2352 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2353 See Documentation/filesystems/nfs/nfsroot.txt.
2355 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2356 See Documentation/filesystems/nfs/nfsroot.txt.
2358 nfsrootdebug [NFS] enable nfsroot debugging messages.
2359 See Documentation/filesystems/nfs/nfsroot.txt.
2361 nfs.callback_tcpport=
2362 [NFS] set the TCP port on which the NFSv4 callback
2363 channel should listen.
2366 [NFS] sets the pathname to the program which is used
2367 to update the NFS client cache entries.
2369 nfs.cache_getent_timeout=
2370 [NFS] sets the timeout after which an attempt to
2371 update a cache entry is deemed to have failed.
2373 nfs.idmap_cache_timeout=
2374 [NFS] set the maximum lifetime for idmapper cache
2378 [NFS] enable 64-bit inode numbers.
2379 If zero, the NFS client will fake up a 32-bit inode
2380 number for the readdir() and stat() syscalls instead
2381 of returning the full 64-bit number.
2382 The default is to return 64-bit inode numbers.
2384 nfs.max_session_slots=
2385 [NFSv4.1] Sets the maximum number of session slots
2386 the client will attempt to negotiate with the server.
2387 This limits the number of simultaneous RPC requests
2388 that the client can send to the NFSv4.1 server.
2389 Note that there is little point in setting this
2390 value higher than the max_tcp_slot_table_limit.
2392 nfs.nfs4_disable_idmapping=
2393 [NFSv4] When set to the default of '1', this option
2394 ensures that both the RPC level authentication
2395 scheme and the NFS level operations agree to use
2396 numeric uids/gids if the mount is using the
2397 'sec=sys' security flavour. In effect it is
2398 disabling idmapping, which can make migration from
2399 legacy NFSv2/v3 systems to NFSv4 easier.
2400 Servers that do not support this mode of operation
2401 will be autodetected by the client, and it will fall
2402 back to using the idmapper.
2403 To turn off this behaviour, set the value to '0'.
2405 [NFS4] Specify an additional fixed unique ident-
2406 ification string that NFSv4 clients can insert into
2407 their nfs_client_id4 string. This is typically a
2408 UUID that is generated at system install time.
2410 nfs.send_implementation_id =
2411 [NFSv4.1] Send client implementation identification
2412 information in exchange_id requests.
2413 If zero, no implementation identification information
2415 The default is to send the implementation identification
2418 nfs.recover_lost_locks =
2419 [NFSv4] Attempt to recover locks that were lost due
2420 to a lease timeout on the server. Please note that
2421 doing this risks data corruption, since there are
2422 no guarantees that the file will remain unchanged
2423 after the locks are lost.
2424 If you want to enable the kernel legacy behaviour of
2425 attempting to recover these locks, then set this
2427 The default parameter value of '0' causes the kernel
2428 not to attempt recovery of lost locks.
2430 nfs4.layoutstats_timer =
2431 [NFSv4.2] Change the rate at which the kernel sends
2432 layoutstats to the pNFS metadata server.
2434 Setting this to value to 0 causes the kernel to use
2435 whatever value is the default set by the layout
2436 driver. A non-zero value sets the minimum interval
2437 in seconds between layoutstats transmissions.
2439 nfsd.nfs4_disable_idmapping=
2440 [NFSv4] When set to the default of '1', the NFSv4
2441 server will return only numeric uids and gids to
2442 clients using auth_sys, and will accept numeric uids
2443 and gids from such clients. This is intended to ease
2444 migration from NFSv2/v3.
2446 objlayoutdriver.osd_login_prog=
2447 [NFS] [OBJLAYOUT] sets the pathname to the program which
2448 is used to automatically discover and login into new
2449 osd-targets. Please see:
2450 Documentation/filesystems/pnfs.txt for more explanations
2452 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2453 when a NMI is triggered.
2454 Format: [state][,regs][,debounce][,die]
2456 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2457 Format: [panic,][nopanic,][num]
2459 0 - turn hardlockup detector in nmi_watchdog off
2460 1 - turn hardlockup detector in nmi_watchdog on
2461 When panic is specified, panic when an NMI watchdog
2462 timeout occurs (or 'nopanic' to override the opposite
2463 default). To disable both hard and soft lockup detectors,
2464 please see 'nowatchdog'.
2465 This is useful when you use a panic=... timeout and
2466 need the box quickly up again.
2468 netpoll.carrier_timeout=
2469 [NET] Specifies amount of time (in seconds) that
2470 netpoll should wait for a carrier. By default netpoll
2473 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2474 emulation library even if a 387 maths coprocessor
2478 [HW] Never suspend the console
2479 Disable suspending of consoles during suspend and
2480 hibernate operations. Once disabled, debugging
2481 messages can reach various consoles while the rest
2482 of the system is being put to sleep (ie, while
2483 debugging driver suspend/resume hooks). This may
2484 not work reliably with all consoles, but is known
2485 to work with serial and VGA consoles.
2486 To facilitate more flexible debugging, we also add
2487 console_suspend, a printk module parameter to control
2488 it. Users could use console_suspend (usually
2489 /sys/module/printk/parameters/console_suspend) to
2490 turn on/off it dynamically.
2492 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2493 caches in the slab allocator. Saves per-node memory,
2494 but will impact performance.
2498 noapic [SMP,APIC] Tells the kernel to not make use of any
2499 IOAPICs that may be present in the system.
2501 noautogroup Disable scheduler automatic task group creation.
2503 nobats [PPC] Do not use BATs for mapping kernel lowmem
2504 on "Classic" PPC cores.
2508 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2510 nodelayacct [KNL] Disable per-task delay accounting
2512 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2514 nodsp [SH] Disable hardware DSP at boot time.
2516 noefi Disable EFI runtime services support.
2521 On X86-32 available only on PAE configured kernels.
2522 noexec=on: enable non-executable mappings (default)
2523 noexec=off: disable non-executable mappings
2526 Disable SMAP (Supervisor Mode Access Prevention)
2527 even if it is supported by processor.
2530 Disable SMEP (Supervisor Mode Execution Prevention)
2531 even if it is supported by processor.
2534 This affects only 32-bit executables.
2535 noexec32=on: enable non-executable mappings (default)
2536 read doesn't imply executable mappings
2537 noexec32=off: disable non-executable mappings
2538 read implies executable mappings
2540 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2542 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2543 register save and restore. The kernel will only save
2544 legacy floating-point registers on task switch.
2546 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2548 noxsave [BUGS=X86] Disables x86 extended register state save
2549 and restore using xsave. The kernel will fallback to
2550 enabling legacy floating-point and sse state.
2552 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2553 register states. The kernel will fall back to use
2554 xsave to save the states. By using this parameter,
2555 performance of saving the states is degraded because
2556 xsave doesn't support modified optimization while
2557 xsaveopt supports it on xsaveopt enabled systems.
2559 noxsaves [X86] Disables xsaves and xrstors used in saving and
2560 restoring x86 extended register state in compacted
2561 form of xsave area. The kernel will fall back to use
2562 xsaveopt and xrstor to save and restore the states
2563 in standard form of xsave area. By using this
2564 parameter, xsave area per process might occupy more
2565 memory on xsaves enabled systems.
2567 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2568 wfi(ARM) instruction doesn't work correctly and not to
2569 use it. This is also useful when using JTAG debugger.
2571 no_file_caps Tells the kernel not to honor file capabilities. The
2572 only way then for a file to be executed with privilege
2573 is to be setuid root or executed by root.
2575 nohalt [IA-64] Tells the kernel not to use the power saving
2576 function PAL_HALT_LIGHT when idle. This increases
2577 power-consumption. On the positive side, it reduces
2578 interrupt wake-up latency, which may improve performance
2579 in certain environments such as networked servers or
2582 nohibernate [HIBERNATION] Disable hibernation and resume.
2584 nohz= [KNL] Boottime enable/disable dynamic ticks
2585 Valid arguments: on, off
2588 nohz_full= [KNL,BOOT]
2589 In kernels built with CONFIG_NO_HZ_FULL=y, set
2590 the specified list of CPUs whose tick will be stopped
2591 whenever possible. The boot CPU will be forced outside
2592 the range to maintain the timekeeping.
2593 The CPUs in this range must also be included in the
2596 noiotrap [SH] Disables trapped I/O port accesses.
2598 noirqdebug [X86-32] Disables the code which attempts to detect and
2599 disable unhandled interrupt sources.
2601 no_timer_check [X86,APIC] Disables the code which tests for
2602 broken timer IRQ sources.
2604 noisapnp [ISAPNP] Disables ISA PnP code.
2606 noinitrd [RAM] Tells the kernel not to load any configured
2609 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2611 [Deprecated - use intremap=off]
2615 noinvpcid [X86] Disable the INVPCID cpu feature.
2617 nojitter [IA-64] Disables jitter checking for ITC timers.
2619 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2621 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2624 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2625 steal time is computed, but won't influence scheduler
2628 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2630 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2632 noltlbs [PPC] Do not use large page/tlb entries for kernel
2633 lowmem mapping on PPC40x and PPC8xx
2635 nomca [IA-64] Disable machine check abort handling
2637 nomce [X86-32] Disable Machine Check Exception
2639 nomfgpt [X86-32] Disable Multi-Function General Purpose
2640 Timer usage (for AMD Geode machines).
2642 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2643 shutdown the other cpus. Instead use the REBOOT_VECTOR
2646 nomodule Disable module load
2648 nopat [X86] Disable PAT (page attribute table extension of
2649 pagetables) support.
2651 norandmaps Don't use address space randomization. Equivalent to
2652 echo 0 > /proc/sys/kernel/randomize_va_space
2654 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2656 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2657 with UP alternatives
2659 nordrand [X86] Disable kernel use of the RDRAND and
2660 RDSEED instructions even if they are supported
2661 by the processor. RDRAND and RDSEED are still
2662 available to user space applications.
2664 noresume [SWSUSP] Disables resume and restores original swap
2667 no-scroll [VGA] Disables scrollback.
2668 This is required for the Braillex ib80-piezo Braille
2669 reader made by F.H. Papenmeier (Germany).
2673 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2675 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2676 and disable the IO APIC. legacy for "maxcpus=0".
2678 nosoftlockup [KNL] Disable the soft-lockup detector.
2680 nosync [HW,M68K] Disables sync negotiation for all devices.
2682 notsc [BUGS=X86-32] Disable Time Stamp Counter
2684 nowatchdog [KNL] Disable both lockup detectors, i.e.
2685 soft-lockup and NMI watchdog (hard-lockup).
2689 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2691 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2692 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2693 Some features depend on CPU0. Known dependencies are:
2694 1. Resume from suspend/hibernate depends on CPU0.
2695 Suspend/hibernate will fail if CPU0 is offline and you
2696 need to online CPU0 before suspend/hibernate.
2697 2. PIC interrupts also depend on CPU0. CPU0 can't be
2698 removed if a PIC interrupt is detected.
2699 It's said poweroff/reboot may depend on CPU0 on some
2700 machines although I haven't seen such issues so far
2701 after CPU0 is offline on a few tested machines.
2702 If the dependencies are under your control, you can
2703 turn on cpu0_hotplug.
2705 nptcg= [IA-64] Override max number of concurrent global TLB
2706 purges which is reported from either PAL_VM_SUMMARY or
2709 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2710 could support. nr_cpus=n : n >= 1 limits the kernel to
2711 supporting 'n' processors. Later in runtime you can not
2712 use hotplug cpu feature to put more cpu back to online.
2713 just like you compile the kernel NR_CPUS=n
2715 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2717 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2718 Allowed values are enable and disable
2720 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2721 one of ['zone', 'node', 'default'] can be specified
2722 This can be set from sysctl after boot.
2723 See Documentation/sysctl/vm.txt for details.
2725 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2726 See Documentation/debugging-via-ohci1394.txt for more
2729 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2730 Rather than timing out after 20 ms if an EC
2731 command is not properly ACKed, override the length
2732 of the timeout. We have interrupts disabled while
2733 waiting for the ACK, so if this is set too high
2734 interrupts *may* be lost!
2736 omap_mux= [OMAP] Override bootloader pin multiplexing.
2737 Format: <mux_mode0.mode_name=value>...
2738 For example, to override I2C bus2:
2739 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2741 oprofile.timer= [HW]
2742 Use timer interrupt instead of performance counters
2744 oprofile.cpu_type= Force an oprofile cpu type
2745 This might be useful if you have an older oprofile
2746 userland or if you want common events.
2747 Format: { arch_perfmon }
2748 arch_perfmon: [X86] Force use of architectural
2749 perfmon on Intel CPUs instead of the
2750 CPU specific event set.
2751 timer: [X86] Force use of architectural NMI
2752 timer mode (see also oprofile.timer
2753 for generic hr timer mode)
2754 [s390] Force legacy basic mode sampling
2755 (report cpu_type "timer")
2757 oops=panic Always panic on oopses. Default is to just kill the
2758 process, but there is a small probability of
2759 deadlocking the machine.
2760 This will also cause panics on machine check exceptions.
2761 Useful together with panic=30 to trigger a reboot.
2764 See Documentation/sound/oss/oss-parameters.txt
2766 page_owner= [KNL] Boot-time page_owner enabling option.
2767 Storage of the information about who allocated
2768 each page is disabled in default. With this switch,
2770 on: enable the feature
2772 page_poison= [KNL] Boot-time parameter changing the state of
2773 poisoning on the buddy allocator.
2774 off: turn off poisoning
2775 on: turn on poisoning
2777 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2778 timeout > 0: seconds before rebooting
2779 timeout = 0: wait forever
2780 timeout < 0: reboot immediately
2783 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2786 crash_kexec_post_notifiers
2787 Run kdump after running panic-notifiers and dumping
2788 kmsg. This only for the users who doubt kdump always
2789 succeeds in any situation.
2790 Note that this also increases risks of kdump failure,
2791 because some panic notifiers can make the crashed
2792 kernel more unstable.
2794 parkbd.port= [HW] Parallel port number the keyboard adapter is
2795 connected to, default is 0.
2797 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2798 0 for XT, 1 for AT (default is AT).
2801 parport= [HW,PPT] Specify parallel ports. 0 disables.
2802 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2803 Use 'auto' to force the driver to use any
2804 IRQ/DMA settings detected (the default is to
2805 ignore detected IRQ/DMA settings because of
2806 possible conflicts). You can specify the base
2807 address, IRQ, and DMA settings; IRQ and DMA
2808 should be numbers, or 'auto' (for using detected
2809 settings on that particular port), or 'nofifo'
2810 (to avoid using a FIFO even if it is detected).
2811 Parallel ports are assigned in the order they
2812 are specified on the command line, starting
2815 parport_init_mode= [HW,PPT]
2816 Configure VIA parallel port to operate in
2817 a specific mode. This is necessary on Pegasos
2818 computer where firmware has no options for setting
2819 up parallel port mode and sets it to spp.
2820 Currently this function knows 686a and 8231 chips.
2821 Format: [spp|ps2|epp|ecp|ecpepp]
2824 Halt all CPUs after the first oops has been printed for
2825 the specified number of seconds. This is to be used if
2826 your oopses keep scrolling off the screen.
2831 See header of drivers/block/paride/pcd.c.
2832 See also Documentation/blockdev/paride.txt.
2834 pci=option[,option...] [PCI] various PCI subsystem options:
2835 earlydump [X86] dump PCI config space before the kernel
2837 off [X86] don't probe for the PCI bus
2838 bios [X86-32] force use of PCI BIOS, don't access
2839 the hardware directly. Use this if your machine
2840 has a non-standard PCI host bridge.
2841 nobios [X86-32] disallow use of PCI BIOS, only direct
2842 hardware access methods are allowed. Use this
2843 if you experience crashes upon bootup and you
2844 suspect they are caused by the BIOS.
2845 conf1 [X86] Force use of PCI Configuration Access
2846 Mechanism 1 (config address in IO port 0xCF8,
2847 data in IO port 0xCFC, both 32-bit).
2848 conf2 [X86] Force use of PCI Configuration Access
2849 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2850 the function, IO port 0xCFA, also 8-bit, sets
2851 bus number. The config space is then accessed
2852 through ports 0xC000-0xCFFF).
2853 See http://wiki.osdev.org/PCI for more info
2854 on the configuration access mechanisms.
2855 noaer [PCIE] If the PCIEAER kernel config parameter is
2856 enabled, this kernel boot option can be used to
2857 disable the use of PCIE advanced error reporting.
2858 nodomains [PCI] Disable support for multiple PCI
2859 root domains (aka PCI segments, in ACPI-speak).
2860 nommconf [X86] Disable use of MMCONFIG for PCI
2862 check_enable_amd_mmconf [X86] check for and enable
2863 properly configured MMIO access to PCI
2864 config space on AMD family 10h CPU
2865 nomsi [MSI] If the PCI_MSI kernel config parameter is
2866 enabled, this kernel boot option can be used to
2867 disable the use of MSI interrupts system-wide.
2868 noioapicquirk [APIC] Disable all boot interrupt quirks.
2869 Safety option to keep boot IRQs enabled. This
2870 should never be necessary.
2871 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2872 primary IO-APIC for bridges that cannot disable
2873 boot IRQs. This fixes a source of spurious IRQs
2874 when the system masks IRQs.
2875 noioapicreroute [APIC] Disable workaround that uses the
2876 boot IRQ equivalent of an IRQ that connects to
2877 a chipset where boot IRQs cannot be disabled.
2878 The opposite of ioapicreroute.
2879 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2880 routing table. These calls are known to be buggy
2881 on several machines and they hang the machine
2882 when used, but on other computers it's the only
2883 way to get the interrupt routing table. Try
2884 this option if the kernel is unable to allocate
2885 IRQs or discover secondary PCI buses on your
2887 rom [X86] Assign address space to expansion ROMs.
2888 Use with caution as certain devices share
2889 address decoders between ROMs and other
2891 norom [X86] Do not assign address space to
2892 expansion ROMs that do not already have
2893 BIOS assigned address ranges.
2894 nobar [X86] Do not assign address space to the
2895 BARs that weren't assigned by the BIOS.
2896 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2897 assigned automatically to PCI devices. You can
2898 make the kernel exclude IRQs of your ISA cards
2900 pirqaddr=0xAAAAA [X86] Specify the physical address
2901 of the PIRQ table (normally generated
2902 by the BIOS) if it is outside the
2903 F0000h-100000h range.
2904 lastbus=N [X86] Scan all buses thru bus #N. Can be
2905 useful if the kernel is unable to find your
2906 secondary buses and you want to tell it
2907 explicitly which ones they are.
2908 assign-busses [X86] Always assign all PCI bus
2909 numbers ourselves, overriding
2910 whatever the firmware may have done.
2911 usepirqmask [X86] Honor the possible IRQ mask stored
2912 in the BIOS $PIR table. This is needed on
2913 some systems with broken BIOSes, notably
2914 some HP Pavilion N5400 and Omnibook XE3
2915 notebooks. This will have no effect if ACPI
2916 IRQ routing is enabled.
2917 noacpi [X86] Do not use ACPI for IRQ routing
2918 or for PCI scanning.
2919 use_crs [X86] Use PCI host bridge window information
2920 from ACPI. On BIOSes from 2008 or later, this
2921 is enabled by default. If you need to use this,
2922 please report a bug.
2923 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2924 If you need to use this, please report a bug.
2925 routeirq Do IRQ routing for all PCI devices.
2926 This is normally done in pci_enable_device(),
2927 so this option is a temporary workaround
2928 for broken drivers that don't call it.
2929 skip_isa_align [X86] do not align io start addr, so can
2930 handle more pci cards
2931 firmware [ARM] Do not re-enumerate the bus but instead
2932 just use the configuration from the
2933 bootloader. This is currently used on
2934 IXP2000 systems where the bus has to be
2935 configured a certain way for adjunct CPUs.
2936 noearly [X86] Don't do any early type 1 scanning.
2937 This might help on some broken boards which
2938 machine check when some devices' config space
2939 is read. But various workarounds are disabled
2940 and some IOMMU drivers will not work.
2941 bfsort Sort PCI devices into breadth-first order.
2942 This sorting is done to get a device
2943 order compatible with older (<= 2.4) kernels.
2944 nobfsort Don't sort PCI devices into breadth-first order.
2945 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2946 tuning and use the BIOS-configured MPS defaults.
2947 pcie_bus_safe Set every device's MPS to the largest value
2948 supported by all devices below the root complex.
2949 pcie_bus_perf Set device MPS to the largest allowable MPS
2950 based on its parent bus. Also set MRRS (Max
2951 Read Request Size) to the largest supported
2952 value (no larger than the MPS that the device
2953 or bus can support) for best performance.
2954 pcie_bus_peer2peer Set every device's MPS to 128B, which
2955 every device is guaranteed to support. This
2956 configuration allows peer-to-peer DMA between
2957 any pair of devices, possibly at the cost of
2958 reduced performance. This also guarantees
2959 that hot-added devices will work.
2960 cbiosize=nn[KMG] The fixed amount of bus space which is
2961 reserved for the CardBus bridge's IO window.
2962 The default value is 256 bytes.
2963 cbmemsize=nn[KMG] The fixed amount of bus space which is
2964 reserved for the CardBus bridge's memory
2965 window. The default value is 64 megabytes.
2968 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2969 Specifies alignment and device to reassign
2970 aligned memory resources.
2971 If <order of align> is not specified,
2972 PAGE_SIZE is used as alignment.
2973 PCI-PCI bridge can be specified, if resource
2974 windows need to be expanded.
2975 ecrc= Enable/disable PCIe ECRC (transaction layer
2976 end-to-end CRC checking).
2977 bios: Use BIOS/firmware settings. This is the
2981 hpiosize=nn[KMG] The fixed amount of bus space which is
2982 reserved for hotplug bridge's IO window.
2983 Default size is 256 bytes.
2984 hpmemsize=nn[KMG] The fixed amount of bus space which is
2985 reserved for hotplug bridge's memory window.
2986 Default size is 2 megabytes.
2987 realloc= Enable/disable reallocating PCI bridge resources
2988 if allocations done by BIOS are too small to
2989 accommodate resources required by all child
2991 off: Turn realloc off
2993 realloc same as realloc=on
2994 noari do not use PCIe ARI.
2995 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2996 only look for one device below a PCIe downstream
2999 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3002 force Enable ASPM even on devices that claim not to support it.
3003 WARNING: Forcing ASPM on may cause system lockups.
3005 pcie_hp= [PCIE] PCI Express Hotplug driver options:
3006 nomsi Do not use MSI for PCI Express Native Hotplug (this
3007 makes all PCIe ports use INTx for hotplug services).
3009 pcie_ports= [PCIE] PCIe ports handling:
3010 auto Ask the BIOS whether or not to use native PCIe services
3011 associated with PCIe ports (PME, hot-plug, AER). Use
3012 them only if that is allowed by the BIOS.
3013 native Use native PCIe services associated with PCIe ports
3015 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3018 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3019 nomsi Do not use MSI for native PCIe PME signaling (this makes
3020 all PCIe root ports use INTx for all services).
3022 pcmv= [HW,PCMCIA] BadgePAD 4
3026 Keep all power-domains already enabled by bootloader on,
3027 even if no driver has claimed them. This is useful
3028 for debug and development, but should not be
3029 needed on a platform with proper driver support.
3032 See Documentation/blockdev/paride.txt.
3034 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3037 See arch/parisc/kernel/pdc_chassis.c
3039 percpu_alloc= Select which percpu first chunk allocator to use.
3040 Currently supported values are "embed" and "page".
3041 Archs may support subset or none of the selections.
3042 See comments in mm/percpu.c for details on each
3043 allocator. This parameter is primarily for debugging
3044 and performance comparison.
3047 See Documentation/blockdev/paride.txt.
3050 See Documentation/blockdev/paride.txt.
3052 pirq= [SMP,APIC] Manual mp-table setup
3053 See Documentation/x86/i386/IO-APIC.txt.
3055 plip= [PPT,NET] Parallel port network link
3056 Format: { parport<nr> | timid | 0 }
3057 See also Documentation/parport.txt.
3059 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3060 Override pmtimer IOPort with a hex value.
3064 Enable PNP debug messages (depends on the
3065 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3066 via /sys/module/pnp/parameters/debug. We always show
3067 current resource usage; turning this on also shows
3068 possible settings and some assignment information.
3074 { on | off | curr | res | no-curr | no-res }
3077 [ISAPNP] Exclude IRQs for the autoconfiguration
3080 [ISAPNP] Exclude DMAs for the autoconfiguration
3082 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3083 Ranges are in pairs (I/O port base and size).
3086 [ISAPNP] Exclude memory regions for the
3088 Ranges are in pairs (memory base and size).
3090 ports= [IP_VS_FTP] IPVS ftp helper module
3092 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3094 Format: <port>,<port>....
3096 ppc_strict_facility_enable
3097 [PPC] This option catches any kernel floating point,
3098 Altivec, VSX and SPE outside of regions specifically
3099 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3100 There is some performance impact when enabling this.
3102 print-fatal-signals=
3103 [KNL] debug: print fatal signals
3105 If enabled, warn about various signal handling
3106 related application anomalies: too many signals,
3107 too many POSIX.1 timers, fatal signals causing a
3110 If you hit the warning due to signal overflow,
3111 you might want to try "ulimit -i unlimited".
3115 printk.always_kmsg_dump=
3116 Trigger kmsg_dump for cases other than kernel oops or
3118 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3121 printk.time= Show timing data prefixed to each printk message line
3122 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3124 processor.max_cstate= [HW,ACPI]
3125 Limit processor to maximum C-state
3126 max_cstate=9 overrides any DMI blacklist limit.
3128 processor.nocst [HW,ACPI]
3129 Ignore the _CST method to determine C-states,
3130 instead using the legacy FADT method
3132 profile= [KNL] Enable kernel profiling via /proc/profile
3133 Format: [schedule,]<number>
3134 Param: "schedule" - profile schedule points.
3135 Param: <number> - step/bucket size as a power of 2 for
3136 statistical time based profiling.
3137 Param: "sleep" - profile D-state sleeping (millisecs).
3138 Requires CONFIG_SCHEDSTATS
3139 Param: "kvm" - profile VM exits.
3141 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3143 See Documentation/blockdev/ramdisk.txt.
3145 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3146 probe for; one of (bare|imps|exps|lifebook|any).
3147 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3149 psmouse.resetafter= [HW,MOUSE]
3150 Try to reset the device after so many bad packets
3153 [HW,MOUSE] Set desired mouse resolution, in dpi.
3154 psmouse.smartscroll=
3155 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3156 0 = disabled, 1 = enabled (default).
3158 pstore.backend= Specify the name of the pstore backend to use
3161 See Documentation/blockdev/paride.txt.
3164 [KNL] Number of legacy pty's. Overwrites compiled-in
3167 quiet [KNL] Disable most log messages
3172 See Documentation/md.txt.
3174 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3175 See Documentation/blockdev/ramdisk.txt.
3178 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3179 the specified list of CPUs to be no-callback CPUs.
3180 Invocation of these CPUs' RCU callbacks will
3181 be offloaded to "rcuox/N" kthreads created for
3182 that purpose, where "x" is "b" for RCU-bh, "p"
3183 for RCU-preempt, and "s" for RCU-sched, and "N"
3184 is the CPU number. This reduces OS jitter on the
3185 offloaded CPUs, which can be useful for HPC and
3186 real-time workloads. It can also improve energy
3187 efficiency for asymmetric multiprocessors.
3190 Rather than requiring that offloaded CPUs
3191 (specified by rcu_nocbs= above) explicitly
3192 awaken the corresponding "rcuoN" kthreads,
3193 make these kthreads poll for callbacks.
3194 This improves the real-time response for the
3195 offloaded CPUs by relieving them of the need to
3196 wake up the corresponding kthread, but degrades
3197 energy efficiency by requiring that the kthreads
3198 periodically wake up to do the polling.
3200 rcutree.blimit= [KNL]
3201 Set maximum number of finished RCU callbacks to
3202 process in one batch.
3204 rcutree.dump_tree= [KNL]
3205 Dump the structure of the rcu_node combining tree
3206 out at early boot. This is used for diagnostic
3207 purposes, to verify correct tree setup.
3209 rcutree.gp_cleanup_delay= [KNL]
3210 Set the number of jiffies to delay each step of
3211 RCU grace-period cleanup. This only has effect
3212 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3214 rcutree.gp_init_delay= [KNL]
3215 Set the number of jiffies to delay each step of
3216 RCU grace-period initialization. This only has
3217 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3220 rcutree.gp_preinit_delay= [KNL]
3221 Set the number of jiffies to delay each step of
3222 RCU grace-period pre-initialization, that is,
3223 the propagation of recent CPU-hotplug changes up
3224 the rcu_node combining tree. This only has effect
3225 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3227 rcutree.rcu_fanout_exact= [KNL]
3228 Disable autobalancing of the rcu_node combining
3229 tree. This is used by rcutorture, and might
3230 possibly be useful for architectures having high
3231 cache-to-cache transfer latencies.
3233 rcutree.rcu_fanout_leaf= [KNL]
3234 Change the number of CPUs assigned to each
3235 leaf rcu_node structure. Useful for very
3236 large systems, which will choose the value 64,
3237 and for NUMA systems with large remote-access
3238 latencies, which will choose a value aligned
3239 with the appropriate hardware boundaries.
3241 rcutree.jiffies_till_sched_qs= [KNL]
3242 Set required age in jiffies for a
3243 given grace period before RCU starts
3244 soliciting quiescent-state help from
3245 rcu_note_context_switch().
3247 rcutree.jiffies_till_first_fqs= [KNL]
3248 Set delay from grace-period initialization to
3249 first attempt to force quiescent states.
3250 Units are jiffies, minimum value is zero,
3251 and maximum value is HZ.
3253 rcutree.jiffies_till_next_fqs= [KNL]
3254 Set delay between subsequent attempts to force
3255 quiescent states. Units are jiffies, minimum
3256 value is one, and maximum value is HZ.
3258 rcutree.kthread_prio= [KNL,BOOT]
3259 Set the SCHED_FIFO priority of the RCU per-CPU
3260 kthreads (rcuc/N). This value is also used for
3261 the priority of the RCU boost threads (rcub/N)
3262 and for the RCU grace-period kthreads (rcu_bh,
3263 rcu_preempt, and rcu_sched). If RCU_BOOST is
3264 set, valid values are 1-99 and the default is 1
3265 (the least-favored priority). Otherwise, when
3266 RCU_BOOST is not set, valid values are 0-99 and
3267 the default is zero (non-realtime operation).
3269 rcutree.rcu_nocb_leader_stride= [KNL]
3270 Set the number of NOCB kthread groups, which
3271 defaults to the square root of the number of
3272 CPUs. Larger numbers reduces the wakeup overhead
3273 on the per-CPU grace-period kthreads, but increases
3274 that same overhead on each group's leader.
3276 rcutree.qhimark= [KNL]
3277 Set threshold of queued RCU callbacks beyond which
3278 batch limiting is disabled.
3280 rcutree.qlowmark= [KNL]
3281 Set threshold of queued RCU callbacks below which
3282 batch limiting is re-enabled.
3284 rcutree.rcu_idle_gp_delay= [KNL]
3285 Set wakeup interval for idle CPUs that have
3286 RCU callbacks (RCU_FAST_NO_HZ=y).
3288 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3289 Set wakeup interval for idle CPUs that have
3290 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3291 Lazy RCU callbacks are those which RCU can
3292 prove do nothing more than free memory.
3294 rcutorture.cbflood_inter_holdoff= [KNL]
3295 Set holdoff time (jiffies) between successive
3296 callback-flood tests.
3298 rcutorture.cbflood_intra_holdoff= [KNL]
3299 Set holdoff time (jiffies) between successive
3300 bursts of callbacks within a given callback-flood
3303 rcutorture.cbflood_n_burst= [KNL]
3304 Set the number of bursts making up a given
3305 callback-flood test. Set this to zero to
3306 disable callback-flood testing.
3308 rcutorture.cbflood_n_per_burst= [KNL]
3309 Set the number of callbacks to be registered
3310 in a given burst of a callback-flood test.
3312 rcutorture.fqs_duration= [KNL]
3313 Set duration of force_quiescent_state bursts
3316 rcutorture.fqs_holdoff= [KNL]
3317 Set holdoff time within force_quiescent_state bursts
3320 rcutorture.fqs_stutter= [KNL]
3321 Set wait time between force_quiescent_state bursts
3324 rcutorture.gp_cond= [KNL]
3325 Use conditional/asynchronous update-side
3326 primitives, if available.
3328 rcutorture.gp_exp= [KNL]
3329 Use expedited update-side primitives, if available.
3331 rcutorture.gp_normal= [KNL]
3332 Use normal (non-expedited) asynchronous
3333 update-side primitives, if available.
3335 rcutorture.gp_sync= [KNL]
3336 Use normal (non-expedited) synchronous
3337 update-side primitives, if available. If all
3338 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3339 rcutorture.gp_normal=, and rcutorture.gp_sync=
3340 are zero, rcutorture acts as if is interpreted
3341 they are all non-zero.
3343 rcutorture.n_barrier_cbs= [KNL]
3344 Set callbacks/threads for rcu_barrier() testing.
3346 rcutorture.nfakewriters= [KNL]
3347 Set number of concurrent RCU writers. These just
3348 stress RCU, they don't participate in the actual
3349 test, hence the "fake".
3351 rcutorture.nreaders= [KNL]
3352 Set number of RCU readers. The value -1 selects
3353 N-1, where N is the number of CPUs. A value
3354 "n" less than -1 selects N-n-2, where N is again
3355 the number of CPUs. For example, -2 selects N
3356 (the number of CPUs), -3 selects N+1, and so on.
3358 rcutorture.object_debug= [KNL]
3359 Enable debug-object double-call_rcu() testing.
3361 rcutorture.onoff_holdoff= [KNL]
3362 Set time (s) after boot for CPU-hotplug testing.
3364 rcutorture.onoff_interval= [KNL]
3365 Set time (s) between CPU-hotplug operations, or
3366 zero to disable CPU-hotplug testing.
3368 rcutorture.shuffle_interval= [KNL]
3369 Set task-shuffle interval (s). Shuffling tasks
3370 allows some CPUs to go into dyntick-idle mode
3371 during the rcutorture test.
3373 rcutorture.shutdown_secs= [KNL]
3374 Set time (s) after boot system shutdown. This
3375 is useful for hands-off automated testing.
3377 rcutorture.stall_cpu= [KNL]
3378 Duration of CPU stall (s) to test RCU CPU stall
3379 warnings, zero to disable.
3381 rcutorture.stall_cpu_holdoff= [KNL]
3382 Time to wait (s) after boot before inducing stall.
3384 rcutorture.stat_interval= [KNL]
3385 Time (s) between statistics printk()s.
3387 rcutorture.stutter= [KNL]
3388 Time (s) to stutter testing, for example, specifying
3389 five seconds causes the test to run for five seconds,
3390 wait for five seconds, and so on. This tests RCU's
3391 ability to transition abruptly to and from idle.
3393 rcutorture.test_boost= [KNL]
3394 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3395 "Maybe" means test if the RCU implementation
3396 under test support RCU priority boosting.
3398 rcutorture.test_boost_duration= [KNL]
3399 Duration (s) of each individual boost test.
3401 rcutorture.test_boost_interval= [KNL]
3402 Interval (s) between each boost test.
3404 rcutorture.test_no_idle_hz= [KNL]
3405 Test RCU's dyntick-idle handling. See also the
3406 rcutorture.shuffle_interval parameter.
3408 rcutorture.torture_runnable= [BOOT]
3409 Start rcutorture running at boot time.
3411 rcutorture.torture_type= [KNL]
3412 Specify the RCU implementation to test.
3414 rcutorture.verbose= [KNL]
3415 Enable additional printk() statements.
3417 rcupdate.rcu_cpu_stall_suppress= [KNL]
3418 Suppress RCU CPU stall warning messages.
3420 rcupdate.rcu_cpu_stall_timeout= [KNL]
3421 Set timeout for RCU CPU stall warning messages.
3423 rcupdate.rcu_expedited= [KNL]
3424 Use expedited grace-period primitives, for
3425 example, synchronize_rcu_expedited() instead
3426 of synchronize_rcu(). This reduces latency,
3427 but can increase CPU utilization, degrade
3428 real-time latency, and degrade energy efficiency.
3429 No effect on CONFIG_TINY_RCU kernels.
3431 rcupdate.rcu_normal= [KNL]
3432 Use only normal grace-period primitives,
3433 for example, synchronize_rcu() instead of
3434 synchronize_rcu_expedited(). This improves
3435 real-time latency, CPU utilization, and
3436 energy efficiency, but can expose users to
3437 increased grace-period latency. This parameter
3438 overrides rcupdate.rcu_expedited. No effect on
3439 CONFIG_TINY_RCU kernels.
3441 rcupdate.rcu_normal_after_boot= [KNL]
3442 Once boot has completed (that is, after
3443 rcu_end_inkernel_boot() has been invoked), use
3444 only normal grace-period primitives. No effect
3445 on CONFIG_TINY_RCU kernels.
3447 rcupdate.rcu_task_stall_timeout= [KNL]
3448 Set timeout in jiffies for RCU task stall warning
3449 messages. Disable with a value less than or equal
3452 rcupdate.rcu_self_test= [KNL]
3453 Run the RCU early boot self tests
3455 rcupdate.rcu_self_test_bh= [KNL]
3456 Run the RCU bh early boot self tests
3458 rcupdate.rcu_self_test_sched= [KNL]
3459 Run the RCU sched early boot self tests
3463 Run specified binary instead of /init from the ramdisk,
3464 used for early userspace startup. See initrd.
3467 Format (x86 or x86_64):
3468 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3470 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3472 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3473 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3474 reboot_force is either force or not specified,
3475 reboot_cpu is s[mp]#### with #### being the processor
3476 to be used for rebooting.
3479 [KNL, SMP] Set scheduler's default relax_domain_level.
3480 See Documentation/cgroups/cpusets.txt.
3482 relative_sleep_states=
3483 [SUSPEND] Use sleep state labeling where the deepest
3484 state available other than hibernation is always "mem".
3485 Format: { "0" | "1" }
3486 0 -- Traditional sleep state labels.
3487 1 -- Relative sleep state labels.
3489 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3491 reservetop= [X86-32]
3493 Reserves a hole at the top of the kernel virtual
3498 Set the amount of memory to reserve for BIOS at
3499 the bottom of the address space.
3501 reset_devices [KNL] Force drivers to reset the underlying device
3502 during initialization.
3505 Specify the partition device for software suspend
3507 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3509 resume_offset= [SWSUSP]
3510 Specify the offset from the beginning of the partition
3511 given by "resume=" at which the swap header is located,
3512 in <PAGE_SIZE> units (needed only for swap files).
3513 See Documentation/power/swsusp-and-swap-files.txt
3515 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3516 read the resume files
3518 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3519 Useful for devices that are detected asynchronously
3520 (e.g. USB and MMC devices).
3522 hibernate= [HIBERNATION]
3523 noresume Don't check if there's a hibernation image
3524 present during boot.
3525 nocompress Don't compress/decompress hibernation images.
3526 no Disable hibernation and resume.
3528 retain_initrd [RAM] Keep initrd memory after extraction
3530 rfkill.default_state=
3531 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3532 etc. communication is blocked by default.
3535 rfkill.master_switch_mode=
3536 0 The "airplane mode" button does nothing.
3537 1 The "airplane mode" button toggles between everything
3538 blocked and the previous configuration.
3539 2 The "airplane mode" button toggles between everything
3540 blocked and everything unblocked.
3542 rhash_entries= [KNL,NET]
3543 Set number of hash buckets for route cache
3545 ro [KNL] Mount root device read-only on boot
3548 on Mark read-only kernel memory as read-only (default).
3549 off Leave read-only kernel memory writable for debugging.
3552 Enable the uart passthrough on the designated usb port
3553 on Rockchip SoCs. When active, the signals of the
3554 debug-uart get routed to the D+ and D- pins of the usb
3555 port and the regular usb controller gets disabled.
3557 root= [KNL] Root filesystem
3558 See name_to_dev_t comment in init/do_mounts.c.
3560 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3561 mount the root filesystem
3563 rootflags= [KNL] Set root filesystem mount option string
3565 rootfstype= [KNL] Set root filesystem type
3567 rootwait [KNL] Wait (indefinitely) for root device to show up.
3568 Useful for devices that are detected asynchronously
3569 (e.g. USB and MMC devices).
3571 rproc_mem=nn[KMG][@address]
3572 [KNL,ARM,CMA] Remoteproc physical memory block.
3573 Memory area to be used by remote processor image,
3576 rw [KNL] Mount root device read-write on boot
3578 S [KNL] Run init in single mode
3580 s390_iommu= [HW,S390]
3581 Set s390 IOTLB flushing mode
3583 With strict flushing every unmap operation will result in
3584 an IOTLB flush. Default is lazy flushing before reuse,
3588 See drivers/net/irda/sa1100_ir.c.
3590 sbni= [NET] Granch SBNI12 leased line adapter
3592 sched_debug [KNL] Enables verbose scheduler debug messages.
3594 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3595 Allowed values are enable and disable. This feature
3596 incurs a small amount of overhead in the scheduler
3597 but is useful for debugging and performance tuning.
3599 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3600 xtime_lock contention on larger systems, and/or RCU lock
3601 contention on all systems with CONFIG_MAXSMP set.
3602 Format: { "0" | "1" }
3603 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3605 Note: increases power consumption, thus should only be
3606 enabled if running jitter sensitive (HPC/RT) workloads.
3608 security= [SECURITY] Choose a security module to enable at boot.
3609 If this boot parameter is not specified, only the first
3610 security module asking for security registration will be
3611 loaded. An invalid security module name will be treated
3612 as if no module has been chosen.
3614 selinux= [SELINUX] Disable or enable SELinux at boot time.
3615 Format: { "0" | "1" }
3616 See security/selinux/Kconfig help text.
3619 Default value is set via kernel config option.
3620 If enabled at boot time, /selinux/disable can be used
3621 later to disable prior to initial policy load.
3623 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3624 Format: { "0" | "1" }
3625 See security/apparmor/Kconfig help text
3628 Default value is set via kernel config option.
3630 serialnumber [BUGS=X86-32]
3633 Maximal number of shapers.
3635 show_msr= [x86] show boot-time MSR settings
3636 Format: { <integer> }
3637 Show boot-time (BIOS-initialized) MSR settings.
3638 The parameter means the number of CPUs to show,
3639 for example 1 means boot CPU only.
3647 Disable merging of slabs with similar size. May be
3648 necessary if there is some reason to distinguish
3649 allocs to different slabs. Debug options disable
3650 merging on their own.
3651 For more information see Documentation/vm/slub.txt.
3653 slab_max_order= [MM, SLAB]
3654 Determines the maximum allowed order for slabs.
3655 A high setting may cause OOMs due to memory
3656 fragmentation. Defaults to 1 for systems with
3657 more than 32MB of RAM, 0 otherwise.
3659 slub_debug[=options[,slabs]] [MM, SLUB]
3660 Enabling slub_debug allows one to determine the
3661 culprit if slab objects become corrupted. Enabling
3662 slub_debug can create guard zones around objects and
3663 may poison objects when not in use. Also tracks the
3664 last alloc / free. For more information see
3665 Documentation/vm/slub.txt.
3667 slub_max_order= [MM, SLUB]
3668 Determines the maximum allowed order for slabs.
3669 A high setting may cause OOMs due to memory
3670 fragmentation. For more information see
3671 Documentation/vm/slub.txt.
3673 slub_min_objects= [MM, SLUB]
3674 The minimum number of objects per slab. SLUB will
3675 increase the slab order up to slub_max_order to
3676 generate a sufficiently large slab able to contain
3677 the number of objects indicated. The higher the number
3678 of objects the smaller the overhead of tracking slabs
3679 and the less frequently locks need to be acquired.
3680 For more information see Documentation/vm/slub.txt.
3682 slub_min_order= [MM, SLUB]
3683 Determines the minimum page order for slabs. Must be
3684 lower than slub_max_order.
3685 For more information see Documentation/vm/slub.txt.
3687 slub_nomerge [MM, SLUB]
3688 Same with slab_nomerge. This is supported for legacy.
3689 See slab_nomerge for more information.
3692 Format: <io1>[,<io2>[,...,<io8>]]
3694 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3695 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3696 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3697 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3698 smsc-ircc2.ircc_irq= [HW] IRQ line
3699 smsc-ircc2.ircc_dma= [HW] DMA channel
3700 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3701 0: Toshiba Satellite 1800 (GP data pin select)
3702 1: Fast pin select (default)
3706 [KNL] Should the soft-lockup detector generate panics.
3709 softlockup_all_cpu_backtrace=
3710 [KNL] Should the soft-lockup detector generate
3711 backtraces on all cpus.
3714 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3715 See Documentation/laptops/sonypi.txt
3717 spia_io_base= [HW,MTD]
3723 Enabled the stack tracer on boot up.
3725 stacktrace_filter=[function-list]
3726 [FTRACE] Limit the functions that the stack tracer
3727 will trace at boot up. function-list is a comma separated
3728 list of functions. This list can be changed at run
3729 time by the stack_trace_filter file in the debugfs
3730 tracing directory. Note, this enables stack tracing
3731 and the stacktrace above is not needed.
3735 Set the STI (builtin display/keyboard on the HP-PARISC
3736 machines) console (graphic card) which should be used
3737 as the initial boot-console.
3738 See also comment in drivers/video/console/sticore.c.
3741 See comment in drivers/video/console/sticore.c.
3744 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3746 sunrpc.min_resvport=
3747 sunrpc.max_resvport=
3749 SunRPC servers often require that client requests
3750 originate from a privileged port (i.e. a port in the
3751 range 0 < portnr < 1024).
3752 An administrator who wishes to reserve some of these
3753 ports for other uses may adjust the range that the
3754 kernel's sunrpc client considers to be privileged
3755 using these two parameters to set the minimum and
3756 maximum port values.
3760 Control how the NFS server code allocates CPUs to
3761 service thread pools. Depending on how many NICs
3762 you have and where their interrupts are bound, this
3763 option will affect which CPUs will do NFS serving.
3764 Note: this parameter cannot be changed while the
3765 NFS server is running.
3767 auto the server chooses an appropriate mode
3768 automatically using heuristics
3769 global a single global pool contains all CPUs
3770 percpu one pool for each CPU
3771 pernode one pool for each NUMA node (equivalent
3772 to global on non-NUMA machines)
3774 sunrpc.tcp_slot_table_entries=
3775 sunrpc.udp_slot_table_entries=
3777 Sets the upper limit on the number of simultaneous
3778 RPC calls that can be sent from the client to a
3779 server. Increasing these values may allow you to
3780 improve throughput, but will also increase the
3781 amount of memory reserved for use by the client.
3783 suspend.pm_test_delay=
3785 Sets the number of seconds to remain in a suspend test
3786 mode before resuming the system (see
3787 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3788 is set. Default value is 5.
3791 [KNL] Enable accounting of swap in memory resource
3792 controller if no parameter or 1 is given or disable
3793 it if 0 is given (See Documentation/cgroups/memory.txt)
3795 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3796 Format: { <int> | force }
3797 <int> -- Number of I/O TLB slabs
3798 force -- force using of bounce buffers even if they
3799 wouldn't be automatically used by the kernel
3803 sysfs.deprecated=0|1 [KNL]
3804 Enable/disable old style sysfs layout for old udev
3805 on older distributions. When this option is enabled
3806 very new udev will not work anymore. When this option
3807 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3808 in older udev will not work anymore.
3809 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3810 the kernel configuration.
3812 sysrq_always_enabled
3814 Ignore sysrq setting - this boot parameter will
3815 neutralize any effect of /proc/sys/kernel/sysrq.
3816 Useful for debugging.
3818 tcpmhash_entries= [KNL,NET]
3819 Set the number of tcp_metrics_hash slots.
3820 Default value is 8192 or 16384 depending on total
3821 ram pages. This is used to specify the TCP metrics
3822 cache size. See Documentation/networking/ip-sysctl.txt
3823 "tcp_no_metrics_save" section for more details.
3827 test_suspend= [SUSPEND][,N]
3828 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3829 standby suspend) or "freeze" (for suspend type freeze)
3830 as the system sleep state during system startup with
3831 the optional capability to repeat N number of times.
3832 The system is woken from this state using a
3833 wakeup-capable RTC alarm.
3835 thash_entries= [KNL,NET]
3836 Set number of hash buckets for TCP connection
3838 thermal.act= [HW,ACPI]
3839 -1: disable all active trip points in all thermal zones
3840 <degrees C>: override all lowest active trip points
3842 thermal.crt= [HW,ACPI]
3843 -1: disable all critical trip points in all thermal zones
3844 <degrees C>: override all critical trip points
3846 thermal.nocrt= [HW,ACPI]
3847 Set to disable actions on ACPI thermal zone
3848 critical and hot trip points.
3850 thermal.off= [HW,ACPI]
3851 1: disable ACPI thermal control
3853 thermal.psv= [HW,ACPI]
3854 -1: disable all passive trip points
3855 <degrees C>: override all passive trip points to this
3858 thermal.tzp= [HW,ACPI]
3859 Specify global default ACPI thermal zone polling rate
3860 <deci-seconds>: poll all this frequency
3861 0: no polling (default)
3864 Force threading of all interrupt handlers except those
3865 marked explicitly IRQF_NO_THREAD.
3868 Enable the Transcendent memory driver if built-in.
3870 tmem.cleancache=0|1 [KNL, XEN]
3871 Default is on (1). Disable the usage of the cleancache
3872 API to send anonymous pages to the hypervisor.
3874 tmem.frontswap=0|1 [KNL, XEN]
3875 Default is on (1). Disable the usage of the frontswap
3876 API to send swap pages to the hypervisor. If disabled
3877 the selfballooning and selfshrinking are force disabled.
3879 tmem.selfballooning=0|1 [KNL, XEN]
3880 Default is on (1). Disable the driving of swap pages
3883 tmem.selfshrinking=0|1 [KNL, XEN]
3884 Default is on (1). Partial swapoff that immediately
3885 transfers pages from Xen hypervisor back to the
3886 kernel based on different criteria.
3890 Specify if the kernel should make use of the cpu
3891 topology information if the hardware supports this.
3892 The scheduler will make use of this information and
3893 e.g. base its process migration decisions on it.
3896 topology_updates= [KNL, PPC, NUMA]
3898 Specify if the kernel should ignore (off)
3899 topology updates sent by the hypervisor to this
3904 tpm_suspend_pcr=[HW,TPM]
3905 Format: integer pcr id
3906 Specify that at suspend time, the tpm driver
3907 should extend the specified pcr with zeros,
3908 as a workaround for some chips which fail to
3909 flush the last written pcr on TPM_SaveState.
3910 This will guarantee that all the other pcrs
3913 trace_buf_size=nn[KMG]
3914 [FTRACE] will set tracing buffer size on each cpu.
3916 trace_event=[event-list]
3917 [FTRACE] Set and start specified trace events in order
3918 to facilitate early boot debugging.
3919 See also Documentation/trace/events.txt
3921 trace_options=[option-list]
3922 [FTRACE] Enable or disable tracer options at boot.
3923 The option-list is a comma delimited list of options
3924 that can be enabled or disabled just as if you were
3925 to echo the option name into
3927 /sys/kernel/debug/tracing/trace_options
3929 For example, to enable stacktrace option (to dump the
3930 stack trace of each event), add to the command line:
3932 trace_options=stacktrace
3934 See also Documentation/trace/ftrace.txt "trace options"
3938 Have the tracepoints sent to printk as well as the
3939 tracing ring buffer. This is useful for early boot up
3940 where the system hangs or reboots and does not give the
3941 option for reading the tracing buffer or performing a
3942 ftrace_dump_on_oops.
3944 To turn off having tracepoints sent to printk,
3945 echo 0 > /proc/sys/kernel/tracepoint_printk
3946 Note, echoing 1 into this file without the
3947 tracepoint_printk kernel cmdline option has no effect.
3951 Having tracepoints sent to printk() and activating high
3952 frequency tracepoints such as irq or sched, can cause
3953 the system to live lock.
3956 [FTRACE] enable this option to disable tracing when a
3957 warning is hit. This turns off "tracing_on". Tracing can
3958 be enabled again by echoing '1' into the "tracing_on"
3959 file located in /sys/kernel/debug/tracing/
3961 This option is useful, as it disables the trace before
3962 the WARNING dump is called, which prevents the trace to
3963 be filled with content caused by the warning output.
3965 This option can also be set at run time via the sysctl
3966 option: kernel/traceoff_on_warning
3968 transparent_hugepage=
3970 Format: [always|madvise|never]
3971 Can be used to control the default behavior of the system
3972 with respect to transparent hugepages.
3973 See Documentation/vm/transhuge.txt for more details.
3975 tsc= Disable clocksource stability checks for TSC.
3977 [x86] reliable: mark tsc clocksource as reliable, this
3978 disables clocksource verification at runtime, as well
3979 as the stability checks done at bootup. Used to enable
3980 high-resolution timer mode on older hardware, and in
3981 virtualized environment.
3982 [x86] noirqtime: Do not use TSC to do irq accounting.
3983 Used to run time disable IRQ_TIME_ACCOUNTING on any
3984 platforms where RDTSC is slow and this accounting
3987 turbografx.map[2|3]= [HW,JOY]
3988 TurboGraFX parallel port interface
3990 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3991 See also Documentation/input/joystick-parport.txt
3993 udbg-immortal [PPC] When debugging early kernel crashes that
3994 happen after console_init() and before a proper
3995 console driver takes over, this boot options might
3996 help "seeing" what's going on.
3998 uhash_entries= [KNL,NET]
3999 Set number of hash buckets for UDP/UDP-Lite connections
4002 [USB] Ignore overcurrent events (default N).
4003 Some badly-designed motherboards generate lots of
4004 bogus events, for ports that aren't wired to
4005 anything. Set this parameter to avoid log spamming.
4006 Note that genuine overcurrent events won't be
4010 [X86] Cause panic on unknown NMI.
4012 usbcore.authorized_default=
4013 [USB] Default USB device authorization:
4014 (default -1 = authorized except for wireless USB,
4015 0 = not authorized, 1 = authorized)
4017 usbcore.autosuspend=
4018 [USB] The autosuspend time delay (in seconds) used
4019 for newly-detected USB devices (default 2). This
4020 is the time required before an idle device will be
4021 autosuspended. Devices for which the delay is set
4022 to a negative value won't be autosuspended at all.
4024 usbcore.usbfs_snoop=
4025 [USB] Set to log all usbfs traffic (default 0 = off).
4027 usbcore.usbfs_snoop_max=
4028 [USB] Maximum number of bytes to snoop in each URB
4031 usbcore.blinkenlights=
4032 [USB] Set to cycle leds on hubs (default 0 = off).
4034 usbcore.old_scheme_first=
4035 [USB] Start with the old device initialization
4036 scheme (default 0 = off).
4038 usbcore.usbfs_memory_mb=
4039 [USB] Memory limit (in MB) for buffers allocated by
4040 usbfs (default = 16, 0 = max = 2047).
4042 usbcore.use_both_schemes=
4043 [USB] Try the other device initialization scheme
4044 if the first one fails (default 1 = enabled).
4046 usbcore.initial_descriptor_timeout=
4047 [USB] Specifies timeout for the initial 64-byte
4048 USB_REQ_GET_DESCRIPTOR request in milliseconds
4049 (default 5000 = 5.0 seconds).
4051 usbcore.nousb [USB] Disable the USB subsystem
4054 [USBHID] The interval which mice are to be polled at.
4056 usb-storage.delay_use=
4057 [UMS] The delay in seconds before a new device is
4058 scanned for Logical Units (default 1).
4061 [UMS] A list of quirks entries to supplement or
4062 override the built-in unusual_devs list. List
4063 entries are separated by commas. Each entry has
4064 the form VID:PID:Flags where VID and PID are Vendor
4065 and Product ID values (4-digit hex numbers) and
4066 Flags is a set of characters, each corresponding
4067 to a common usb-storage quirk flag as follows:
4068 a = SANE_SENSE (collect more than 18 bytes
4070 b = BAD_SENSE (don't collect more than 18
4071 bytes of sense data);
4072 c = FIX_CAPACITY (decrease the reported
4073 device capacity by one sector);
4074 d = NO_READ_DISC_INFO (don't use
4075 READ_DISC_INFO command);
4076 e = NO_READ_CAPACITY_16 (don't use
4077 READ_CAPACITY_16 command);
4078 f = NO_REPORT_OPCODES (don't use report opcodes
4080 g = MAX_SECTORS_240 (don't transfer more than
4081 240 sectors at a time, uas only);
4082 h = CAPACITY_HEURISTICS (decrease the
4083 reported device capacity by one
4084 sector if the number is odd);
4085 i = IGNORE_DEVICE (don't bind to this
4087 j = NO_REPORT_LUNS (don't use report luns
4089 l = NOT_LOCKABLE (don't try to lock and
4090 unlock ejectable media);
4091 m = MAX_SECTORS_64 (don't transfer more
4092 than 64 sectors = 32 KB at a time);
4093 n = INITIAL_READ10 (force a retry of the
4094 initial READ(10) command);
4095 o = CAPACITY_OK (accept the capacity
4096 reported by the device);
4097 p = WRITE_CACHE (the device cache is ON
4099 r = IGNORE_RESIDUE (the device reports
4100 bogus residue values);
4101 s = SINGLE_LUN (the device has only one
4103 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4104 commands, uas only);
4105 u = IGNORE_UAS (don't bind to the uas driver);
4106 w = NO_WP_DETECT (don't test whether the
4107 medium is write-protected).
4108 Example: quirks=0419:aaf5:rl,0421:0433:rc
4110 user_debug= [KNL,ARM]
4112 See arch/arm/Kconfig.debug help text.
4113 1 - undefined instruction events
4115 4 - invalid data aborts
4118 Example: user_debug=31
4121 [X86] Flags controlling user PTE allocations.
4123 nohigh = do not allocate PTE pages in
4124 HIGHMEM regardless of setting
4128 On X86_32, this is an alias for vdso32=. Otherwise:
4130 vdso=1: enable VDSO (the default)
4131 vdso=0: disable VDSO mapping
4133 vdso32= [X86] Control the 32-bit vDSO
4134 vdso32=1: enable 32-bit VDSO
4135 vdso32=0 or vdso32=2: disable 32-bit VDSO
4137 See the help text for CONFIG_COMPAT_VDSO for more
4138 details. If CONFIG_COMPAT_VDSO is set, the default is
4139 vdso32=0; otherwise, the default is vdso32=1.
4141 For compatibility with older kernels, vdso32=2 is an
4144 Try vdso32=0 if you encounter an error that says:
4145 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4148 vector=percpu: enable percpu vector domain
4150 video= [FB] Frame buffer configuration
4151 See Documentation/fb/modedb.txt.
4153 video.brightness_switch_enabled= [0,1]
4154 If set to 1, on receiving an ACPI notify event
4155 generated by hotkey, video driver will adjust brightness
4156 level and then send out the event to user space through
4157 the allocated input device; If set to 0, video driver
4158 will only send out the event without touching backlight
4163 [VMMIO] Memory mapped virtio (platform) device.
4165 <size>@<baseaddr>:<irq>[:<id>]
4167 <size> := size (can use standard suffixes
4169 <baseaddr> := physical base address
4170 <irq> := interrupt number (as passed to
4172 <id> := (optional) platform device id
4174 virtio_mmio.device=1K@0x100b0000:48:7
4176 Can be used multiple times for multiple devices.
4178 vga= [BOOT,X86-32] Select a particular video mode
4179 See Documentation/x86/boot.txt and
4180 Documentation/svga.txt.
4181 Use vga=ask for menu.
4182 This is actually a boot loader parameter; the value is
4183 passed to the kernel using a special protocol.
4185 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4186 size of <nn>. This can be used to increase the
4187 minimum size (128MB on x86). It can also be used to
4188 decrease the size and leave more room for directly
4191 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4194 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4197 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4201 Controls the behavior of vsyscalls (i.e. calls to
4202 fixed addresses of 0xffffffffff600x00 from legacy
4203 code). Most statically-linked binaries and older
4204 versions of glibc use these calls. Because these
4205 functions are at fixed addresses, they make nice
4206 targets for exploits that can control RIP.
4208 emulate [default] Vsyscalls turn into traps and are
4209 emulated reasonably safely.
4211 native Vsyscalls are native syscall instructions.
4212 This is a little bit faster than trapping
4213 and makes a few dynamic recompilers work
4214 better than they would in emulation mode.
4215 It also makes exploits much easier to write.
4217 none Vsyscalls don't work at all. This makes
4218 them quite hard to use for exploits but
4219 might break your system.
4221 vt.color= [VT] Default text color.
4222 Format: 0xYX, X = foreground, Y = background.
4223 Default: 0x07 = light gray on black.
4225 vt.cur_default= [VT] Default cursor shape.
4226 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4227 the parameters of the <Esc>[?A;B;Cc escape sequence;
4228 see VGA-softcursor.txt. Default: 2 = underline.
4230 vt.default_blu= [VT]
4231 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4232 Change the default blue palette of the console.
4233 This is a 16-member array composed of values
4236 vt.default_grn= [VT]
4237 Format: <green0>,<green1>,<green2>,...,<green15>
4238 Change the default green palette of the console.
4239 This is a 16-member array composed of values
4242 vt.default_red= [VT]
4243 Format: <red0>,<red1>,<red2>,...,<red15>
4244 Change the default red palette of the console.
4245 This is a 16-member array composed of values
4251 Set system-wide default UTF-8 mode for all tty's.
4252 Default is 1, i.e. UTF-8 mode is enabled for all
4253 newly opened terminals.
4255 vt.global_cursor_default=
4258 Set system-wide default for whether a cursor
4259 is shown on new VTs. Default is -1,
4260 i.e. cursors will be created by default unless
4261 overridden by individual drivers. 0 will hide
4262 cursors, 1 will display them.
4264 vt.italic= [VT] Default color for italic text; 0-15.
4267 vt.underline= [VT] Default color for underlined text; 0-15.
4270 watchdog timers [HW,WDT] For information on watchdog timers,
4271 see Documentation/watchdog/watchdog-parameters.txt
4272 or other driver-specific files in the
4273 Documentation/watchdog/ directory.
4275 workqueue.watchdog_thresh=
4276 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4277 warn stall conditions and dump internal state to
4278 help debugging. 0 disables workqueue stall
4279 detection; otherwise, it's the stall threshold
4280 duration in seconds. The default value is 30 and
4281 it can be updated at runtime by writing to the
4282 corresponding sysfs file.
4284 workqueue.disable_numa
4285 By default, all work items queued to unbound
4286 workqueues are affine to the NUMA nodes they're
4287 issued on, which results in better behavior in
4288 general. If NUMA affinity needs to be disabled for
4289 whatever reason, this option can be used. Note
4290 that this also can be controlled per-workqueue for
4291 workqueues visible under /sys/bus/workqueue/.
4293 workqueue.power_efficient
4294 Per-cpu workqueues are generally preferred because
4295 they show better performance thanks to cache
4296 locality; unfortunately, per-cpu workqueues tend to
4297 be more power hungry than unbound workqueues.
4299 Enabling this makes the per-cpu workqueues which
4300 were observed to contribute significantly to power
4301 consumption unbound, leading to measurably lower
4302 power usage at the cost of small performance
4305 The default value of this parameter is determined by
4306 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4308 workqueue.debug_force_rr_cpu
4309 Workqueue used to implicitly guarantee that work
4310 items queued without explicit CPU specified are put
4311 on the local CPU. This guarantee is no longer true
4312 and while local CPU is still preferred work items
4313 may be put on foreign CPUs. This debug option
4314 forces round-robin CPU selection to flush out
4315 usages which depend on the now broken guarantee.
4316 When enabled, memory and cache locality will be
4319 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4320 default x2apic cluster mode on platforms
4323 x86_intel_mid_timer= [X86-32,APBT]
4324 Choose timer option for x86 Intel MID platform.
4325 Two valid options are apbt timer only and lapic timer
4326 plus one apbt timer for broadcast timer.
4327 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4329 xen_512gb_limit [KNL,X86-64,XEN]
4330 Restricts the kernel running paravirtualized under Xen
4331 to use only up to 512 GB of RAM. The reason to do so is
4332 crash analysis tools and Xen tools for doing domain
4333 save/restore/migration must be enabled to handle larger
4336 xen_emul_unplug= [HW,X86,XEN]
4337 Unplug Xen emulated devices
4338 Format: [unplug0,][unplug1]
4339 ide-disks -- unplug primary master IDE devices
4340 aux-ide-disks -- unplug non-primary-master IDE devices
4341 nics -- unplug network devices
4342 all -- unplug all emulated devices (NICs and IDE disks)
4343 unnecessary -- unplugging emulated devices is
4344 unnecessary even if the host did not respond to
4346 never -- do not unplug even if version check succeeds
4348 xen_nopvspin [X86,XEN]
4349 Disables the ticketlock slowpath using Xen PV
4353 Disables the PV optimizations forcing the HVM guest to
4354 run as generic HVM guest with no PV drivers.
4356 xirc2ps_cs= [NET,PCMCIA]
4358 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4360 ______________________________________________________________________
4364 Add more DRM drivers.
projects / cascardo / linux.git / blob