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 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
475 apic_extnmi= [APIC,X86] External NMI delivery setting
476 Format: { bsp (default) | all | none }
477 bsp: External NMI is delivered only to CPU 0
478 all: External NMIs are broadcast to all CPUs as a
480 none: External NMI is masked for all CPUs. This is
481 useful so that a dump capture kernel won't be
485 See Documentation/networking/ipv6.txt.
487 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
488 Limit apic dumping. The parameter defines the maximal
489 number of local apics being dumped. Also it is possible
490 to set it to "all" by meaning -- no limit here.
491 Format: { 1 (default) | 2 | ... | all }.
492 The parameter valid if only apic=debug or
493 apic=verbose is specified.
494 Example: apic=debug show_lapic=all
496 apm= [APM] Advanced Power Management
497 See header of arch/x86/kernel/apm_32.c.
499 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
500 Format: <io>,<irq>,<nodeID>
504 atarimouse= [HW,MOUSE] Atari Mouse
506 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
507 EzKey and similar keyboards
509 atkbd.reset= [HW] Reset keyboard during initialization
511 atkbd.set= [HW] Select keyboard code set
512 Format: <int> (2 = AT (default), 3 = PS/2)
514 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
517 atkbd.softraw= [HW] Choose between synthetic and real raw mode
518 Format: <bool> (0 = real, 1 = synthetic (default))
520 atkbd.softrepeat= [HW]
521 Use software keyboard repeat
523 audit= [KNL] Enable the audit sub-system
524 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
525 0 - kernel audit is disabled and can not be enabled
526 until the next reboot
527 unset - kernel audit is initialized but disabled and
528 will be fully enabled by the userspace auditd.
529 1 - kernel audit is initialized and partially enabled,
530 storing at most audit_backlog_limit messages in
531 RAM until it is fully enabled by the userspace
535 audit_backlog_limit= [KNL] Set the audit queue size limit.
536 Format: <int> (must be >=0)
539 baycom_epp= [HW,AX25]
542 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
544 See header of drivers/net/hamradio/baycom_par.c.
546 baycom_ser_fdx= [HW,AX25]
547 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
548 Format: <io>,<irq>,<mode>[,<baud>]
549 See header of drivers/net/hamradio/baycom_ser_fdx.c.
551 baycom_ser_hdx= [HW,AX25]
552 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
553 Format: <io>,<irq>,<mode>
554 See header of drivers/net/hamradio/baycom_ser_hdx.c.
556 blkdevparts= Manual partition parsing of block device(s) for
557 embedded devices based on command line input.
558 See Documentation/block/cmdline-partition.txt
560 boot_delay= Milliseconds to delay each printk during boot.
561 Values larger than 10 seconds (10000) are changed to
565 bootmem_debug [KNL] Enable bootmem allocator debug messages.
567 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
568 bttv.radio= Most important insmod options are available as
570 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
573 bulk_remove=off [PPC] This parameter disables the use of the pSeries
574 firmware feature for flushing multiple hpte entries
577 c101= [NET] Moxa C101 synchronous serial card
579 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
580 Sometimes CPU hardware bugs make them report the cache
581 size incorrectly. The kernel will attempt work arounds
582 to fix known problems, but for some CPUs it is not
583 possible to determine what the correct size should be.
584 This option provides an override for these situations.
586 ca_keys= [KEYS] This parameter identifies a specific key(s) on
587 the system trusted keyring to be used for certificate
589 format: { id:<keyid> | builtin }
591 cca= [MIPS] Override the kernel pages' cache coherency
592 algorithm. Accepted values range from 0 to 7
593 inclusive. See arch/mips/include/asm/pgtable-bits.h
594 for platform specific values (SB1, Loongson3 and
597 ccw_timeout_log [S390]
598 See Documentation/s390/CommonIO for details.
600 cgroup_disable= [KNL] Disable a particular controller
601 Format: {name of the controller(s) to disable}
602 The effects of cgroup_disable=foo are:
603 - foo isn't auto-mounted if you mount all cgroups in
605 - foo isn't visible as an individually mountable
607 {Currently only "memory" controller deal with this and
608 cut the overhead, others just disable the usage. So
609 only cgroup_disable=memory is actually worthy}
611 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
613 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kernel memory accounting.
616 checkreqprot [SELINUX] Set initial checkreqprot flag value.
617 Format: { "0" | "1" }
618 See security/selinux/Kconfig help text.
619 0 -- check protection applied by kernel (includes
620 any implied execute protection).
621 1 -- check protection requested by application.
622 Default value is set via a kernel config option.
623 Value can be changed at runtime via
624 /selinux/checkreqprot.
627 See Documentation/s390/CommonIO for details.
630 Prevents the clock framework from automatically gating
631 clocks that have not been explicitly enabled by a Linux
632 device driver but are enabled in hardware at reset or
633 by the bootloader/firmware. Note that this does not
634 force such clocks to be always-on nor does it reserve
635 those clocks in any way. This parameter is useful for
636 debug and development, but should not be needed on a
637 platform with proper driver support. For more
638 information, see Documentation/clk.txt.
640 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
642 Forces specified clocksource (if available) to be used
643 when calculating gettimeofday(). If specified
644 clocksource is not available, it defaults to PIT.
645 Format: { pit | tsc | cyclone | pmtmr }
647 clocksource= Override the default clocksource
649 Override the default clocksource and use the clocksource
650 with the name specified.
651 Some clocksource names to choose from, depending on
653 [all] jiffies (this is the base, fallback clocksource)
655 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
656 pxa_timer,timer3,32k_counter,timer0_1
658 [X86-32] pit,hpet,tsc;
659 scx200_hrt on Geode; cyclone on IBM x440
667 clearcpuid=BITNUM [X86]
668 Disable CPUID feature X for the kernel. See
669 arch/x86/include/asm/cpufeatures.h for the valid bit
670 numbers. Note the Linux specific bits are not necessarily
671 stable over kernel options, but the vendor specific
673 Also note that user programs calling CPUID directly
674 or using the feature without checking anything
675 will still see it. This just prevents it from
676 being used by the kernel or shown in /proc/cpuinfo.
677 Also note the kernel might malfunction if you disable
680 cma=nn[MG]@[start[MG][-end[MG]]]
682 Sets the size of kernel global memory area for
683 contiguous memory allocations and optionally the
684 placement constraint by the physical address range of
685 memory allocations. A value of 0 disables CMA
686 altogether. For more information, see
687 include/linux/dma-contiguous.h
689 cmo_free_hint= [PPC] Format: { yes | no }
690 Specify whether pages are marked as being inactive
691 when they are freed. This is used in CMO environments
692 to determine OS memory pressure for page stealing by
696 coherent_pool=nn[KMG] [ARM,KNL]
697 Sets the size of memory pool for coherent, atomic dma
698 allocations, by default set to 256K.
700 code_bytes [X86] How many bytes of object code to print
705 com20020= [HW,NET] ARCnet - COM20020 chipset
707 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
709 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
713 ARCnet - COM90xx chipset (memory-mapped buffers)
714 Format: <io>[,<irq>[,<memstart>]]
716 condev= [HW,S390] console device
719 console= [KNL] Output console device and options.
721 tty<n> Use the virtual console device <n>.
725 Use the specified serial port. The options are of
726 the form "bbbbpnf", where "bbbb" is the baud rate,
727 "p" is parity ("n", "o", or "e"), "n" is number of
728 bits, and "f" is flow control ("r" for RTS or
729 omit it). Default is "9600n8".
731 See Documentation/serial-console.txt for more
733 Documentation/networking/netconsole.txt for an
736 uart[8250],io,<addr>[,options]
737 uart[8250],mmio,<addr>[,options]
738 uart[8250],mmio16,<addr>[,options]
739 uart[8250],mmio32,<addr>[,options]
740 uart[8250],0x<addr>[,options]
741 Start an early, polled-mode console on the 8250/16550
742 UART at the specified I/O port or MMIO address,
743 switching to the matching ttyS device later.
744 MMIO inter-register address stride is either 8-bit
745 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
746 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
747 to be equivalent to 'mmio'. 'options' are specified in
748 the same format described for ttyS above; if unspecified,
749 the h/w is not re-initialized.
751 hvc<n> Use the hypervisor console device <n>. This is for
752 both Xen and PowerPC hypervisors.
754 If the device connected to the port is not a TTY but a braille
755 device, prepend "brl," before the device type, for instance
757 For now, only VisioBraille is supported.
759 consoleblank= [KNL] The console blank (screen saver) timeout in
760 seconds. Defaults to 10*60 = 10mins. A value of 0
761 disables the blank timer.
764 [KNL] Change the default value for
765 /proc/<pid>/coredump_filter.
766 See also Documentation/filesystems/proc.txt.
768 cpuidle.off=1 [CPU_IDLE]
769 disable the cpuidle sub-system
772 [X86] Delay for N microsec between assert and de-assert
773 of APIC INIT to start processors. This delay occurs
774 on every CPU online, such as boot, and resume from suspend.
777 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
779 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
781 crashkernel=size[KMG][@offset[KMG]]
782 [KNL] Using kexec, Linux can switch to a 'crash kernel'
783 upon panic. This parameter reserves the physical
784 memory region [offset, offset + size] for that kernel
785 image. If '@offset' is omitted, then a suitable offset
786 is selected automatically. Check
787 Documentation/kdump/kdump.txt for further details.
789 crashkernel=range1:size1[,range2:size2,...][@offset]
790 [KNL] Same as above, but depends on the memory
791 in the running system. The syntax of range is
792 start-[end] where start and end are both
793 a memory unit (amount[KMG]). See also
794 Documentation/kdump/kdump.txt for an example.
796 crashkernel=size[KMG],high
797 [KNL, x86_64] range could be above 4G. Allow kernel
798 to allocate physical memory region from top, so could
799 be above 4G if system have more than 4G ram installed.
800 Otherwise memory region will be allocated below 4G, if
802 It will be ignored if crashkernel=X is specified.
803 crashkernel=size[KMG],low
804 [KNL, x86_64] range under 4G. When crashkernel=X,high
805 is passed, kernel could allocate physical memory region
806 above 4G, that cause second kernel crash on system
807 that require some amount of low memory, e.g. swiotlb
808 requires at least 64M+32K low memory, also enough extra
809 low memory is needed to make sure DMA buffers for 32-bit
810 devices won't run out. Kernel would try to allocate at
811 at least 256M below 4G automatically.
812 This one let user to specify own low range under 4G
813 for second kernel instead.
814 0: to disable low allocation.
815 It will be ignored when crashkernel=X,high is not used
816 or memory reserved is below 4G.
821 cs89x0_media= [HW,NET]
822 Format: { rj45 | aui | bnc }
825 See header of drivers/s390/block/dasd_devmap.c.
827 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
828 (one device per port)
829 Format: <port#>,<type>
830 See also Documentation/input/joystick-parport.txt
832 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
833 time. See Documentation/dynamic-debug-howto.txt for
834 details. Deprecated, see dyndbg.
836 debug [KNL] Enable kernel debugging (events log level).
839 [KNL] verbose self-tests
841 Print debugging info while doing the locking API
843 We default to 0 (no extra messages), setting it to
844 1 will print _a lot_ more information - normally
845 only useful to kernel developers.
847 debug_objects [KNL] Enable object debugging
850 [KNL] Disable object debugging
852 debug_guardpage_minorder=
853 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
854 parameter allows control of the order of pages that will
855 be intentionally kept free (and hence protected) by the
856 buddy allocator. Bigger value increase the probability
857 of catching random memory corruption, but reduce the
858 amount of memory for normal system use. The maximum
859 possible value is MAX_ORDER/2. Setting this parameter
860 to 1 or 2 should be enough to identify most random
861 memory corruption problems caused by bugs in kernel or
862 driver code when a CPU writes to (or reads from) a
863 random memory location. Note that there exists a class
864 of memory corruptions problems caused by buggy H/W or
865 F/W or by drivers badly programing DMA (basically when
866 memory is written at bus level and the CPU MMU is
867 bypassed) which are not detectable by
868 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
869 tracking down these problems.
872 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
873 parameter enables the feature at boot time. In
874 default, it is disabled. We can avoid allocating huge
875 chunk of memory for debug pagealloc if we don't enable
876 it at boot time and the system will work mostly same
877 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
878 on: enable the feature
880 debugpat [X86] Enable PAT debugging
882 decnet.addr= [HW,NET]
883 Format: <area>[,<node>]
884 See also Documentation/networking/decnet.txt.
887 [same as hugepagesz=] The size of the default
888 HugeTLB page size. This is the size represented by
889 the legacy /proc/ hugepages APIs, used for SHM, and
890 default size when mounting hugetlbfs filesystems.
891 Defaults to the default architecture's huge page size
895 Set number of hash buckets for dentry cache.
898 See Documentation/networking/ipv6.txt.
900 disable_cpu_apicid= [X86,APIC,SMP]
902 The number of initial APIC ID for the
903 corresponding CPU to be disabled at boot,
904 mostly used for the kdump 2nd kernel to
905 disable BSP to wake up multiple CPUs without
906 causing system reset or hang due to sending
909 disable_ddw [PPC/PSERIES]
910 Disable Dynamic DMA Window support. Use this if
911 to workaround buggy firmware.
914 See Documentation/networking/ipv6.txt.
916 disable_mtrr_cleanup [X86]
917 The kernel tries to adjust MTRR layout from continuous
918 to discrete, to make X server driver able to add WB
919 entry later. This parameter disables that.
921 disable_mtrr_trim [X86, Intel and AMD only]
922 By default the kernel will trim any uncacheable
923 memory out of your available memory pool based on
924 MTRR settings. This parameter disables that behavior,
925 possibly causing your machine to run very slowly.
927 disable_timer_pin_1 [X86]
928 Disable PIN 1 of APIC timer
929 Can be useful to work around chipset bugs.
931 dis_ucode_ldr [X86] Disable the microcode loader.
933 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
934 this option disables the debugging code at boot.
936 dma_debug_entries=<number>
937 This option allows to tune the number of preallocated
938 entries for DMA-API debugging code. One entry is
939 required per DMA-API allocation. Use this if the
940 DMA-API debugging code disables itself because the
941 architectural default is too low.
943 dma_debug_driver=<driver_name>
944 With this option the DMA-API debugging driver
945 filter feature can be enabled at boot time. Just
946 pass the driver to filter for as the parameter.
947 The filter can be disabled or changed to another
948 driver later using sysfs.
950 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
951 Broken monitors, graphic adapters, KVMs and EDIDless
952 panels may send no or incorrect EDID data sets.
953 This parameter allows to specify an EDID data sets
954 in the /lib/firmware directory that are used instead.
955 Generic built-in EDID data sets are used, if one of
956 edid/1024x768.bin, edid/1280x1024.bin,
957 edid/1680x1050.bin, or edid/1920x1080.bin is given
958 and no file with the same name exists. Details and
959 instructions how to build your own EDID data are
960 available in Documentation/EDID/HOWTO.txt. An EDID
961 data set will only be used for a particular connector,
962 if its name and a colon are prepended to the EDID
963 name. Each connector may use a unique EDID data
964 set by separating the files with a comma. An EDID
965 data set with no connector name will be used for
966 any connectors not explicitly specified.
970 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
971 module.dyndbg[="val"]
972 Enable debug messages at boot time. See
973 Documentation/dynamic-debug-howto.txt for details.
975 nompx [X86] Disables Intel Memory Protection Extensions.
976 See Documentation/x86/intel_mpx.txt for more
977 information about the feature.
979 nopku [X86] Disable Memory Protection Keys CPU feature found
983 on enable eager fpu restore
984 off disable eager fpu restore
985 auto selects the default scheme, which automatically
986 enables eagerfpu restore for xsaveopt.
988 module.async_probe [KNL]
989 Enable asynchronous probe on this module.
991 early_ioremap_debug [KNL]
992 Enable debug messages in early_ioremap support. This
993 is useful for tracking down temporary early mappings
994 which are not unmapped.
996 earlycon= [KNL] Output early console device and options.
998 When used with no options, the early console is
999 determined by the stdout-path property in device
1003 Start an early, polled-mode console on a cadence serial
1004 port at the specified address. The cadence serial port
1005 must already be setup and configured. Options are not
1008 uart[8250],io,<addr>[,options]
1009 uart[8250],mmio,<addr>[,options]
1010 uart[8250],mmio32,<addr>[,options]
1011 uart[8250],mmio32be,<addr>[,options]
1012 uart[8250],0x<addr>[,options]
1013 Start an early, polled-mode console on the 8250/16550
1014 UART at the specified I/O port or MMIO address.
1015 MMIO inter-register address stride is either 8-bit
1016 (mmio) or 32-bit (mmio32 or mmio32be).
1017 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1018 to be equivalent to 'mmio'. 'options' are specified
1019 in the same format described for "console=ttyS<n>"; if
1020 unspecified, the h/w is not initialized.
1024 Start an early, polled-mode console on a pl011 serial
1025 port at the specified address. The pl011 serial port
1026 must already be setup and configured. Options are not
1027 yet supported. If 'mmio32' is specified, then only
1028 the driver will use only 32-bit accessors to read/write
1029 the device registers.
1032 Start an early, polled-mode console on an msm serial
1033 port at the specified address. The serial port
1034 must already be setup and configured. Options are not
1037 msm_serial_dm,<addr>
1038 Start an early, polled-mode console on an msm serial
1039 dm port at the specified address. The serial port
1040 must already be setup and configured. Options are not
1043 smh Use ARM semihosting calls for early console.
1051 Use early console provided by serial driver available
1052 on Samsung SoCs, requires selecting proper type and
1053 a correct base address of the selected UART port. The
1054 serial port must already be setup and configured.
1055 Options are not yet supported.
1059 Use early console provided by Freescale LP UART driver
1060 found on Freescale Vybrid and QorIQ LS1021A processors.
1061 A valid base address must be provided, and the serial
1062 port must already be setup and configured.
1064 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1068 earlyprintk=serial[,ttySn[,baudrate]]
1069 earlyprintk=serial[,0x...[,baudrate]]
1070 earlyprintk=ttySn[,baudrate]
1071 earlyprintk=dbgp[debugController#]
1072 earlyprintk=pciserial,bus:device.function[,baudrate]
1074 earlyprintk is useful when the kernel crashes before
1075 the normal console is initialized. It is not enabled by
1076 default because it has some cosmetic problems.
1078 Append ",keep" to not disable it when the real console
1081 Only one of vga, efi, serial, or usb debug port can
1084 Currently only ttyS0 and ttyS1 may be specified by
1085 name. Other I/O ports may be explicitly specified
1086 on some architectures (x86 and arm at least) by
1087 replacing ttySn with an I/O port address, like this:
1088 earlyprintk=serial,0x1008,115200
1089 You can find the port for a given device in
1090 /proc/tty/driver/serial:
1091 2: uart:ST16650V2 port:00001008 irq:18 ...
1093 Interaction with the standard serial driver is not
1096 The VGA and EFI output is eventually overwritten by
1099 The xen output can only be used by Xen PV guests.
1101 edac_report= [HW,EDAC] Control how to report EDAC event
1102 Format: {"on" | "off" | "force"}
1103 on: enable EDAC to report H/W event. May be overridden
1104 by other higher priority error reporting module.
1105 off: disable H/W event reporting through EDAC.
1106 force: enforce the use of EDAC to report H/W event.
1109 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1112 This is designed to be used in conjunction with
1113 the boot argument: earlyprintk=vga
1116 Format: {"off" | "on" | "skip[mbr]"}
1119 Format: { "old_map", "nochunk", "noruntime", "debug" }
1120 old_map [X86-64]: switch to the old ioremap-based EFI
1121 runtime services mapping. 32-bit still uses this one by
1123 nochunk: disable reading files in "chunks" in the EFI
1124 boot stub, as chunking can cause problems with some
1125 firmware implementations.
1126 noruntime : disable EFI runtime services support
1127 debug: enable misc debug output
1129 efi_no_storage_paranoia [EFI; X86]
1130 Using this parameter you can use more than 50% of
1131 your efi variable storage. Use this parameter only if
1132 you are really sure that your UEFI does sane gc and
1133 fulfills the spec otherwise your board may brick.
1135 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1136 Add arbitrary attribute to specific memory range by
1137 updating original EFI memory map.
1138 Region of memory which aa attribute is added to is
1140 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1141 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1142 attribute is added to range 0x100000000-0x180000000 and
1143 0x10a0000000-0x1120000000.
1145 Using this parameter you can do debugging of EFI memmap
1146 related feature. For example, you can do debugging of
1147 Address Range Mirroring feature even if your box
1150 eisa_irq_edge= [PARISC,HW]
1151 See header of drivers/parisc/eisa.c.
1154 See comment before function elanfreq_setup() in
1155 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1158 Format: {"cfq" | "deadline" | "noop"}
1159 See Documentation/block/cfq-iosched.txt and
1160 Documentation/block/deadline-iosched.txt for details.
1162 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1163 Specifies physical address of start of kernel core
1164 image elf header and optionally the size. Generally
1165 kexec loader will pass this option to capture kernel.
1166 See Documentation/kdump/kdump.txt for details.
1168 enable_mtrr_cleanup [X86]
1169 The kernel tries to adjust MTRR layout from continuous
1170 to discrete, to make X server driver able to add WB
1171 entry later. This parameter enables that.
1173 enable_timer_pin_1 [X86]
1174 Enable PIN 1 of APIC timer
1175 Can be useful to work around chipset bugs
1176 (in particular on some ATI chipsets).
1177 The kernel tries to set a reasonable default.
1179 enforcing [SELINUX] Set initial enforcing status.
1181 See security/selinux/Kconfig help text.
1182 0 -- permissive (log only, no denials).
1183 1 -- enforcing (deny and log).
1185 Value can be changed at runtime via /selinux/enforce.
1188 Disable Error Record Serialization Table (ERST)
1191 ether= [HW,NET] Ethernet cards parameters
1192 This option is obsoleted by the "netdev=" option, which
1193 has equivalent usage. See its documentation for details.
1197 Permit 'security.evm' to be updated regardless of
1198 current integrity status.
1202 fail_make_request=[KNL]
1203 General fault injection mechanism.
1204 Format: <interval>,<probability>,<space>,<times>
1205 See also Documentation/fault-injection/.
1208 See Documentation/blockdev/floppy.txt.
1210 force_pal_cache_flush
1211 [IA-64] Avoid check_sal_cache_flush which may hang on
1212 buggy SAL_CACHE_FLUSH implementations. Using this
1213 parameter will force ia64_sal_cache_flush to call
1214 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1217 Forcefully enable Physical Address Extension (PAE).
1218 Many Pentium M systems disable PAE but may have a
1219 functionally usable PAE implementation.
1220 Warning: use of this parameter will taint the kernel
1221 and may cause unknown problems.
1224 [FTRACE] will set and start the specified tracer
1225 as early as possible in order to facilitate early
1228 ftrace_dump_on_oops[=orig_cpu]
1229 [FTRACE] will dump the trace buffers on oops.
1230 If no parameter is passed, ftrace will dump
1231 buffers of all CPUs, but if you pass orig_cpu, it will
1232 dump only the buffer of the CPU that triggered the
1235 ftrace_filter=[function-list]
1236 [FTRACE] Limit the functions traced by the function
1237 tracer at boot up. function-list is a comma separated
1238 list of functions. This list can be changed at run
1239 time by the set_ftrace_filter file in the debugfs
1242 ftrace_notrace=[function-list]
1243 [FTRACE] Do not trace the functions specified in
1244 function-list. This list can be changed at run time
1245 by the set_ftrace_notrace file in the debugfs
1248 ftrace_graph_filter=[function-list]
1249 [FTRACE] Limit the top level callers functions traced
1250 by the function graph tracer at boot up.
1251 function-list is a comma separated list of functions
1252 that can be changed at run time by the
1253 set_graph_function file in the debugfs tracing directory.
1255 ftrace_graph_notrace=[function-list]
1256 [FTRACE] Do not trace from the functions specified in
1257 function-list. This list is a comma separated list of
1258 functions that can be changed at run time by the
1259 set_graph_notrace file in the debugfs tracing directory.
1262 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1263 support via parallel port (up to 5 devices per port)
1264 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1265 See also Documentation/input/joystick-parport.txt
1269 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1273 gcov_persist= [GCOV] When non-zero (default), profiling data for
1274 kernel modules is saved and remains accessible via
1275 debugfs, even when the module is unloaded/reloaded.
1276 When zero, profiling data is discarded and associated
1277 debugfs files are removed at module unload time.
1279 gpt [EFI] Forces disk with valid GPT signature but
1280 invalid Protective MBR to be treated as GPT. If the
1281 primary GPT is corrupted, it enables the backup/alternate
1282 GPT to be used instead.
1284 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1285 the "Enable 0" bit of the configuration register.
1288 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1289 the "Enable 0" bit of the configuration register.
1292 grcan.select= [HW] Select which physical interface to use.
1295 grcan.txsize= [HW] Sets the size of the tx buffer.
1296 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1298 grcan.rxsize= [HW] Sets the size of the rx buffer.
1299 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1302 hardlockup_all_cpu_backtrace=
1303 [KNL] Should the hard-lockup detector generate
1304 backtraces on all cpus.
1307 hashdist= [KNL,NUMA] Large hashes allocated during boot
1308 are distributed across NUMA nodes. Defaults on
1309 for 64-bit NUMA, off otherwise.
1310 Format: 0 | 1 (for off | on)
1312 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1314 hd= [EIDE] (E)IDE hard drive subsystem geometry
1315 Format: <cyl>,<head>,<sect>
1318 Disable Hardware Error Source Table (HEST) support;
1319 corresponding firmware-first mode error processing
1320 logic will be disabled.
1322 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1323 size of <nn>. This works even on boxes that have no
1324 highmem otherwise. This also works to reduce highmem
1325 size on bigger boxes.
1327 highres= [KNL] Enable/disable high resolution timer mode.
1328 Valid parameters: "on", "off"
1332 See Documentation/isdn/README.HiSax.
1336 hpet= [X86-32,HPET] option to control HPET usage
1337 Format: { enable (default) | disable | force |
1339 disable: disable HPET and use PIT instead
1340 force: allow force enabled of undocumented chips (ICH4,
1342 verbose: show contents of HPET registers during setup
1344 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1345 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1347 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1348 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1349 On x86-64 and powerpc, this option can be specified
1350 multiple times interleaved with hugepages= to reserve
1351 huge pages of different sizes. Valid pages sizes on
1352 x86-64 are 2M (when the CPU supports "pse") and 1G
1353 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1355 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1356 terminal devices. Valid values: 0..8
1357 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1358 If specified, z/VM IUCV HVC accepts connections
1359 from listed z/VM user IDs only.
1361 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1362 hardware thread id mappings.
1363 Format: <cpu>:<hwthread>
1366 Do not unregister boot console at start. This is only
1367 useful for debugging when something happens in the window
1368 between unregistering the boot console and initializing
1371 i2c_bus= [HW] Override the default board specific I2C bus speed
1372 or register an additional I2C bus that is not
1373 registered from board initialization code.
1377 i8042.debug [HW] Toggle i8042 debug mode
1378 i8042.unmask_kbd_data
1379 [HW] Enable printing of interrupt data from the KBD port
1380 (disabled by default, and as a pre-condition
1381 requires that i8042.debug=1 be enabled)
1382 i8042.direct [HW] Put keyboard port into non-translated mode
1383 i8042.dumbkbd [HW] Pretend that controller can only read data from
1384 keyboard and cannot control its state
1385 (Don't attempt to blink the leds)
1386 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1387 i8042.nokbd [HW] Don't check/create keyboard port
1388 i8042.noloop [HW] Disable the AUX Loopback command while probing
1390 i8042.nomux [HW] Don't check presence of an active multiplexing
1392 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1394 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1395 i8042.reset [HW] Reset the controller during init and cleanup
1396 i8042.unlock [HW] Unlock (ignore) the keylock
1397 i8042.kbdreset [HW] Reset device connected to KBD port
1401 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1402 indicates that the driver is running on unsupported
1404 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1405 does not match list of supported models.
1407 [HW] Report power status in /proc/i8k
1408 (disabled by default)
1409 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1412 i915.invert_brightness=
1413 [DRM] Invert the sense of the variable that is used to
1414 set the brightness of the panel backlight. Normally a
1415 brightness value of 0 indicates backlight switched off,
1416 and the maximum of the brightness value sets the backlight
1417 to maximum brightness. If this parameter is set to 0
1418 (default) and the machine requires it, or this parameter
1419 is set to 1, a brightness value of 0 sets the backlight
1420 to maximum brightness, and the maximum of the brightness
1421 value switches the backlight off.
1422 -1 -- never invert brightness
1423 0 -- machine default
1424 1 -- force brightness inversion
1427 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1429 ide-core.nodma= [HW] (E)IDE subsystem
1430 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1431 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1432 .cdrom .chs .ignore_cable are additional options
1433 See Documentation/ide/ide.txt.
1435 ide-generic.probe-mask= [HW] (E)IDE subsystem
1437 Probe mask for legacy ISA IDE ports. Depending on
1438 platform up to 6 ports are supported, enabled by
1439 setting corresponding bits in the mask to 1. The
1440 default value is 0x0, which has a special meaning.
1441 On systems that have PCI, it triggers scanning the
1442 PCI bus for the first and the second port, which
1443 are then probed. On systems without PCI the value
1444 of 0x0 enables probing the two first ports as if it
1447 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1448 Claim all unknown PCI IDE storage controllers.
1451 Format: idle=poll, idle=halt, idle=nomwait
1452 Poll forces a polling idle loop that can slightly
1453 improve the performance of waking up a idle CPU, but
1454 will use a lot of power and make the system run hot.
1456 idle=halt: Halt is forced to be used for CPU idle.
1457 In such case C2/C3 won't be used again.
1458 idle=nomwait: Disable mwait for CPU C-states
1460 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1461 Format: { strict | legacy | 2008 | relaxed }
1464 Choose which programs will be accepted for execution
1465 based on the IEEE 754 NaN encoding(s) supported by
1466 the FPU and the NaN encoding requested with the value
1467 of an ELF file header flag individually set by each
1468 binary. Hardware implementations are permitted to
1469 support either or both of the legacy and the 2008 NaN
1472 Available settings are as follows:
1473 strict accept binaries that request a NaN encoding
1474 supported by the FPU
1475 legacy only accept legacy-NaN binaries, if supported
1477 2008 only accept 2008-NaN binaries, if supported
1479 relaxed accept any binaries regardless of whether
1480 supported by the FPU
1482 The FPU emulator is always able to support both NaN
1483 encodings, so if no FPU hardware is present or it has
1484 been disabled with 'nofpu', then the settings of
1485 'legacy' and '2008' strap the emulator accordingly,
1486 'relaxed' straps the emulator for both legacy-NaN and
1487 2008-NaN, whereas 'strict' enables legacy-NaN only on
1488 legacy processors and both NaN encodings on MIPS32 or
1491 The setting for ABS.fmt/NEG.fmt instruction execution
1492 mode generally follows that for the NaN encoding,
1493 except where unsupported by hardware.
1495 ignore_loglevel [KNL]
1496 Ignore loglevel setting - this will print /all/
1497 kernel messages to the console. Useful for debugging.
1498 We also add it as printk module parameter, so users
1499 could change it dynamically, usually by
1500 /sys/module/printk/parameters/ignore_loglevel.
1503 Ignore RLIMIT_DATA setting for data mappings,
1504 print warning at first misuse. Can be changed via
1505 /sys/module/kernel/parameters/ignore_rlimit_data.
1507 ihash_entries= [KNL]
1508 Set number of hash buckets for inode cache.
1510 ima_appraise= [IMA] appraise integrity measurements
1511 Format: { "off" | "enforce" | "fix" | "log" }
1514 ima_appraise_tcb [IMA]
1515 The builtin appraise policy appraises all files
1519 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1523 The list of supported hash algorithms is defined
1524 in crypto/hash_info.h.
1527 The builtin measurement policy to load during IMA
1528 setup. Specyfing "tcb" as the value, measures all
1529 programs exec'd, files mmap'd for exec, and all files
1530 opened with the read mode bit set by either the
1531 effective uid (euid=0) or uid=0.
1534 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1535 Load a policy which meets the needs of the Trusted
1536 Computing Base. This means IMA will measure all
1537 programs exec'd, files mmap'd for exec, and all files
1538 opened for read by uid=0.
1541 Select one of defined IMA measurements template formats.
1542 Formats: { "ima" | "ima-ng" | "ima-sig" }
1546 [IMA] Define a custom template format.
1547 Format: { "field1|...|fieldN" }
1549 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1550 Format: <min_file_size>
1551 Set the minimal file size for using asynchronous hash.
1552 If left unspecified, ahash usage is disabled.
1554 ahash performance varies for different data sizes on
1555 different crypto accelerators. This option can be used
1556 to achieve the best performance for a particular HW.
1558 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1560 Set hashing buffer size. Default: 4k.
1562 ahash performance varies for different chunk sizes on
1563 different crypto accelerators. This option can be used
1564 to achieve best performance for particular HW.
1568 Run specified binary instead of /sbin/init as init
1571 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1572 for working out where the kernel is dying during
1575 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1576 initcall functions. Useful for debugging built-in
1577 modules and initcalls.
1579 initrd= [BOOT] Specify the location of the initial ramdisk
1581 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1584 int_pln_enable [x86] Enable power limit notification interrupt
1586 integrity_audit=[IMA]
1587 Format: { "0" | "1" }
1588 0 -- basic integrity auditing messages. (Default)
1589 1 -- additional integrity auditing messages.
1591 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1593 Enable intel iommu driver.
1595 Disable intel iommu driver.
1596 igfx_off [Default Off]
1597 By default, gfx is mapped as normal device. If a gfx
1598 device has a dedicated DMAR unit, the DMAR unit is
1599 bypassed by not enabling DMAR with this option. In
1600 this case, gfx device will use physical address for
1603 With this option iommu will not optimize to look
1604 for io virtual address below 32-bit forcing dual
1605 address cycle on pci bus for cards supporting greater
1606 than 32-bit addressing. The default is to look
1607 for translation below 32-bit and if not available
1608 then look in the higher range.
1609 strict [Default Off]
1610 With this option on every unmap_single operation will
1611 result in a hardware IOTLB flush operation as opposed
1612 to batching them for performance.
1613 sp_off [Default Off]
1614 By default, super page will be supported if Intel IOMMU
1615 has the capability. With this option, super page will
1617 ecs_off [Default Off]
1618 By default, extended context tables will be supported if
1619 the hardware advertises that it has support both for the
1620 extended tables themselves, and also PASID support. With
1621 this option set, extended tables will not be used even
1622 on hardware which claims to support them.
1624 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1625 0 disables intel_idle and fall back on acpi_idle.
1626 1 to 6 specify maximum depth of C-state.
1630 Do not enable intel_pstate as the default
1631 scaling driver for the supported processors
1633 Enable intel_pstate on systems that prohibit it by default
1634 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1635 instead of acpi-cpufreq may disable platform features, such
1636 as thermal controls and power capping, that rely on ACPI
1637 P-States information being indicated to OSPM and therefore
1638 should be used with caution. This option does not work with
1639 processors that aren't supported by the intel_pstate driver
1640 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1642 Do not enable hardware P state control (HWP)
1645 Only load intel_pstate on systems which support
1646 hardware P state control (HWP) if available.
1648 intremap= [X86-64, Intel-IOMMU]
1649 on enable Interrupt Remapping (default)
1650 off disable Interrupt Remapping
1651 nosid disable Source ID checking
1653 BIOS x2APIC opt-out request will be ignored
1654 nopost disable Interrupt Posting
1656 iomem= Disable strict checking of access to MMIO memory
1657 strict regions from userspace.
1672 nobypass [PPC/POWERNV]
1673 Disable IOMMU bypass, using IOMMU for PCI devices.
1676 io7= [HW] IO7 for Marvel based alpha systems
1677 See comment before marvel_specify_io7 in
1678 arch/alpha/kernel/core_marvel.c.
1680 io_delay= [X86] I/O delay method
1682 Standard port 0x80 based delay
1684 Alternate port 0xed based delay (needed on some systems)
1686 Simple two microseconds delay
1691 See Documentation/filesystems/nfs/nfsroot.txt.
1694 When an interrupt is not handled search all handlers
1695 for it. Intended to get systems with badly broken
1699 When an interrupt is not handled search all handlers
1700 for it. Also check all handlers each timer
1701 interrupt. Intended to get systems with badly broken
1705 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1707 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1709 <cpu number>,...,<cpu number>
1711 <cpu number>-<cpu number>
1712 (must be a positive range in ascending order)
1714 <cpu number>,...,<cpu number>-<cpu number>
1716 This option can be used to specify one or more CPUs
1717 to isolate from the general SMP balancing and scheduling
1718 algorithms. You can move a process onto or off an
1719 "isolated" CPU via the CPU affinity syscalls or cpuset.
1720 <cpu number> begins at 0 and the maximum value is
1721 "number of CPUs in system - 1".
1723 This option is the preferred way to isolate CPUs. The
1724 alternative -- manually setting the CPU mask of all
1725 tasks in the system -- can cause problems and
1726 suboptimal load balancer performance.
1730 ivrs_ioapic [HW,X86_64]
1731 Provide an override to the IOAPIC-ID<->DEVICE-ID
1732 mapping provided in the IVRS ACPI table. For
1733 example, to map IOAPIC-ID decimal 10 to
1734 PCI device 00:14.0 write the parameter as:
1735 ivrs_ioapic[10]=00:14.0
1737 ivrs_hpet [HW,X86_64]
1738 Provide an override to the HPET-ID<->DEVICE-ID
1739 mapping provided in the IVRS ACPI table. For
1740 example, to map HPET-ID decimal 0 to
1741 PCI device 00:14.0 write the parameter as:
1742 ivrs_hpet[0]=00:14.0
1744 js= [HW,JOY] Analog joystick
1745 See Documentation/input/joystick.txt.
1748 Enable/disable kernel and module base offset ASLR
1749 (Address Space Layout Randomization) if built into
1750 the kernel. When CONFIG_HIBERNATION is selected,
1751 kASLR is disabled by default. When kASLR is enabled,
1752 hibernation will be disabled.
1756 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1757 specifies the amount of memory usable by the kernel
1758 for non-movable allocations. The requested amount is
1759 spread evenly throughout all nodes in the system. The
1760 remaining memory in each node is used for Movable
1761 pages. In the event, a node is too small to have both
1762 kernelcore and Movable pages, kernelcore pages will
1763 take priority and other nodes will have a larger number
1764 of Movable pages. The Movable zone is used for the
1765 allocation of pages that may be reclaimed or moved
1766 by the page migration subsystem. This means that
1767 HugeTLB pages may not be allocated from this zone.
1768 Note that allocations like PTEs-from-HighMem still
1769 use the HighMem zone if it exists, and the Normal
1770 zone if it does not.
1772 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1773 Format: <Controller#>[,poll interval]
1774 The controller # is the number of the ehci usb debug
1775 port as it is probed via PCI. The poll interval is
1776 optional and is the number seconds in between
1777 each poll cycle to the debug port in case you need
1778 the functionality for interrupting the kernel with
1779 gdb or control-c on the dbgp connection. When
1780 not using this parameter you use sysrq-g to break into
1781 the kernel debugger.
1783 kgdboc= [KGDB,HW] kgdb over consoles.
1784 Requires a tty driver that supports console polling,
1785 or a supported polling keyboard driver (non-usb).
1786 Serial only format: <serial_device>[,baud]
1787 keyboard only format: kbd
1788 keyboard and serial format: kbd,<serial_device>[,baud]
1789 Optional Kernel mode setting:
1790 kms, kbd format: kms,kbd
1791 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1793 kgdbwait [KGDB] Stop kernel execution and enter the
1794 kernel debugger at the earliest opportunity.
1796 kmac= [MIPS] korina ethernet MAC address.
1797 Configure the RouterBoard 532 series on-chip
1798 Ethernet adapter MAC address.
1800 kmemleak= [KNL] Boot-time kmemleak enable/disable
1801 Valid arguments: on, off
1803 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1806 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1807 Valid arguments: 0, 1, 2
1808 kmemcheck=0 (disabled)
1809 kmemcheck=1 (enabled)
1810 kmemcheck=2 (one-shot mode)
1811 Default: 2 (one-shot mode)
1813 kstack=N [X86] Print N words from the kernel stack
1816 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1817 Default is 0 (don't ignore, but inject #GP)
1819 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1823 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1824 Default is 1 (enabled)
1826 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1828 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1830 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1831 (virtualized MMU) support on capable Intel chips.
1832 Default is 1 (enabled)
1834 kvm-intel.emulate_invalid_guest_state=
1835 [KVM,Intel] Enable emulation of invalid guest states
1836 Default is 0 (disabled)
1838 kvm-intel.flexpriority=
1839 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1840 Default is 1 (enabled)
1843 [KVM,Intel] Enable VMX nesting (nVMX).
1844 Default is 0 (disabled)
1846 kvm-intel.unrestricted_guest=
1847 [KVM,Intel] Disable unrestricted guest feature
1848 (virtualized real and unpaged mode) on capable
1849 Intel chips. Default is 1 (enabled)
1851 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1852 feature (tagged TLBs) on capable Intel chips.
1853 Default is 1 (enabled)
1859 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1862 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1863 value for LAPIC timer one-shot implementation. Default
1864 back to the programmable timer unit in the LAPIC.
1866 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1869 libata.dma= [LIBATA] DMA control
1870 libata.dma=0 Disable all PATA and SATA DMA
1871 libata.dma=1 PATA and SATA Disk DMA only
1872 libata.dma=2 ATAPI (CDROM) DMA only
1873 libata.dma=4 Compact Flash DMA only
1874 Combinations also work, so libata.dma=3 enables DMA
1875 for disks and CDROMs, but not CFs.
1877 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1878 libata.ignore_hpa=0 keep BIOS limits (default)
1879 libata.ignore_hpa=1 ignore limits, using full disk
1881 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1885 libata.force= [LIBATA] Force configurations. The format is comma
1886 separated list of "[ID:]VAL" where ID is
1887 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1888 matching port, link or device. Basically, it matches
1889 the ATA ID string printed on console by libata. If
1890 the whole ID part is omitted, the last PORT and DEVICE
1891 values are used. If ID hasn't been specified yet, the
1892 configuration applies to all ports, links and devices.
1894 If only DEVICE is omitted, the parameter applies to
1895 the port and all links and devices behind it. DEVICE
1896 number of 0 either selects the first device or the
1897 first fan-out link behind PMP device. It does not
1898 select the host link. DEVICE number of 15 selects the
1899 host link and device attached to it.
1901 The VAL specifies the configuration to force. As long
1902 as there's no ambiguity shortcut notation is allowed.
1903 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1904 The following configurations can be forced.
1906 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1907 Any ID with matching PORT is used.
1909 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1911 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1912 udma[/][16,25,33,44,66,100,133] notation is also
1915 * [no]ncq: Turn on or off NCQ.
1917 * [no]ncqtrim: Turn off queued DSM TRIM.
1919 * nohrst, nosrst, norst: suppress hard, soft
1922 * rstonce: only attempt one reset during
1923 hot-unplug link recovery
1925 * dump_id: dump IDENTIFY data.
1927 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1929 * disable: Disable this device.
1931 If there are multiple matching configurations changing
1932 the same attribute, the last one is used.
1934 memblock=debug [KNL] Enable memblock debug messages.
1936 load_ramdisk= [RAM] List of ramdisks to load from floppy
1937 See Documentation/blockdev/ramdisk.txt.
1939 lockd.nlm_grace_period=P [NFS] Assign grace period.
1942 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1945 lockd.nlm_timeout=T [NFS] Assign timeout value.
1948 lockd.nlm_udpport=M [NFS] Assign UDP port.
1951 locktorture.nreaders_stress= [KNL]
1952 Set the number of locking read-acquisition kthreads.
1953 Defaults to being automatically set based on the
1954 number of online CPUs.
1956 locktorture.nwriters_stress= [KNL]
1957 Set the number of locking write-acquisition kthreads.
1959 locktorture.onoff_holdoff= [KNL]
1960 Set time (s) after boot for CPU-hotplug testing.
1962 locktorture.onoff_interval= [KNL]
1963 Set time (s) between CPU-hotplug operations, or
1964 zero to disable CPU-hotplug testing.
1966 locktorture.shuffle_interval= [KNL]
1967 Set task-shuffle interval (jiffies). Shuffling
1968 tasks allows some CPUs to go into dyntick-idle
1969 mode during the locktorture test.
1971 locktorture.shutdown_secs= [KNL]
1972 Set time (s) after boot system shutdown. This
1973 is useful for hands-off automated testing.
1975 locktorture.stat_interval= [KNL]
1976 Time (s) between statistics printk()s.
1978 locktorture.stutter= [KNL]
1979 Time (s) to stutter testing, for example,
1980 specifying five seconds causes the test to run for
1981 five seconds, wait for five seconds, and so on.
1982 This tests the locking primitive's ability to
1983 transition abruptly to and from idle.
1985 locktorture.torture_runnable= [BOOT]
1986 Start locktorture running at boot time.
1988 locktorture.torture_type= [KNL]
1989 Specify the locking implementation to test.
1991 locktorture.verbose= [KNL]
1992 Enable additional printk() statements.
1994 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1997 loglevel= All Kernel Messages with a loglevel smaller than the
1998 console loglevel will be printed to the console. It can
1999 also be changed with klogd or other programs. The
2000 loglevels are defined as follows:
2002 0 (KERN_EMERG) system is unusable
2003 1 (KERN_ALERT) action must be taken immediately
2004 2 (KERN_CRIT) critical conditions
2005 3 (KERN_ERR) error conditions
2006 4 (KERN_WARNING) warning conditions
2007 5 (KERN_NOTICE) normal but significant condition
2008 6 (KERN_INFO) informational
2009 7 (KERN_DEBUG) debug-level messages
2011 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2012 in bytes. n must be a power of two and greater
2013 than the minimal size. The minimal size is defined
2014 by LOG_BUF_SHIFT kernel config parameter. There is
2015 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2016 that allows to increase the default size depending on
2017 the number of CPUs. See init/Kconfig for more details.
2019 logo.nologo [FB] Disables display of the built-in Linux logo.
2020 This may be used to provide more screen space for
2021 kernel log messages and is useful when debugging
2022 kernel boot problems.
2024 lp=0 [LP] Specify parallel ports to use, e.g,
2025 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2026 lp=reset first parallel port). 'lp=0' disables the
2027 lp=auto printer driver. 'lp=reset' (which can be
2028 specified in addition to the ports) causes
2029 attached printers to be reset. Using
2030 lp=port1,port2,... specifies the parallel ports
2031 to associate lp devices with, starting with
2032 lp0. A port specification may be 'none' to skip
2033 that lp device, or a parport name such as
2034 'parport0'. Specifying 'lp=auto' instead of a
2035 port specification list means that device IDs
2036 from each port should be examined, to see if
2037 an IEEE 1284-compliant printer is attached; if
2038 so, the driver will manage that printer.
2039 See also header of drivers/char/lp.c.
2042 Sets loops_per_jiffy to given constant, thus avoiding
2043 time-consuming boot-time autodetection (up to 250 ms per
2044 CPU). 0 enables autodetection (default). To determine
2045 the correct value for your kernel, boot with normal
2046 autodetection and see what value is printed. Note that
2047 on SMP systems the preset will be applied to all CPUs,
2048 which is likely to cause problems if your CPUs need
2049 significantly divergent settings. An incorrect value
2050 will cause delays in the kernel to be wrong, leading to
2051 unpredictable I/O errors and other breakage. Although
2052 unlikely, in the extreme case this might damage your
2056 Format: <io>,<irq>,<dma>
2058 machvec= [IA-64] Force the use of a particular machine-vector
2059 (machvec) in a generic kernel.
2060 Example: machvec=hpzx1_swiotlb
2062 machtype= [Loongson] Share the same kernel image file between different
2064 Example: machtype=lemote-yeeloong-2f-7inch
2066 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2067 than or equal to this physical address is ignored.
2069 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2070 should make use of. maxcpus=n : n >= 0 limits the
2071 kernel to using 'n' processors. n=0 is a special case,
2072 it is equivalent to "nosmp", which also disables
2075 max_loop= [LOOP] The number of loop block devices that get
2076 (loop.max_loop) unconditionally pre-created at init time. The default
2077 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2078 of statically allocating a predefined number, loop
2079 devices can be requested on-demand with the
2080 /dev/loop-control interface.
2082 mce [X86-32] Machine Check Exception
2084 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2086 md= [HW] RAID subsystems devices and level
2087 See Documentation/md.txt.
2090 Format: <first>,<last>
2091 Specifies range of consoles to be captured by the MDA.
2093 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2094 Amount of memory to be used when the kernel is not able
2095 to see the whole system memory or for test.
2096 [X86] Work as limiting max address. Use together
2097 with memmap= to avoid physical address space collisions.
2098 Without memmap= PCI devices could be placed at addresses
2099 belonging to unused RAM.
2101 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2105 [KNL,SH] Allow user to override the default size for
2106 per-device physically contiguous DMA buffers.
2108 memmap=exactmap [KNL,X86] Enable setting of an exact
2109 E820 memory map, as specified by the user.
2110 Such memmap=exactmap lines can be constructed based on
2111 BIOS output or other requirements. See the memmap=nn@ss
2114 memmap=nn[KMG]@ss[KMG]
2115 [KNL] Force usage of a specific region of memory.
2116 Region of memory to be used is from ss to ss+nn.
2118 memmap=nn[KMG]#ss[KMG]
2119 [KNL,ACPI] Mark specific memory as ACPI data.
2120 Region of memory to be marked is from ss to ss+nn.
2122 memmap=nn[KMG]$ss[KMG]
2123 [KNL,ACPI] Mark specific memory as reserved.
2124 Region of memory to be reserved is from ss to ss+nn.
2125 Example: Exclude memory from 0x18690000-0x1869ffff
2126 memmap=64K$0x18690000
2128 memmap=0x10000$0x18690000
2130 memmap=nn[KMG]!ss[KMG]
2131 [KNL,X86] Mark specific memory as protected.
2132 Region of memory to be used, from ss to ss+nn.
2133 The memory region may be marked as e820 type 12 (0xc)
2134 and is NVDIMM or ADR memory.
2136 memory_corruption_check=0/1 [X86]
2137 Some BIOSes seem to corrupt the first 64k of
2138 memory when doing things like suspend/resume.
2139 Setting this option will scan the memory
2140 looking for corruption. Enabling this will
2141 both detect corruption and prevent the kernel
2142 from using the memory being corrupted.
2143 However, its intended as a diagnostic tool; if
2144 repeatable BIOS-originated corruption always
2145 affects the same memory, you can use memmap=
2146 to prevent the kernel from using that memory.
2148 memory_corruption_check_size=size [X86]
2149 By default it checks for corruption in the low
2150 64k, making this memory unavailable for normal
2151 use. Use this parameter to scan for
2152 corruption in more or less memory.
2154 memory_corruption_check_period=seconds [X86]
2155 By default it checks for corruption every 60
2156 seconds. Use this parameter to check at some
2157 other rate. 0 disables periodic checking.
2159 memtest= [KNL,X86,ARM] Enable memtest
2161 default : 0 <disable>
2162 Specifies the number of memtest passes to be
2163 performed. Each pass selects another test
2164 pattern from a given set of patterns. Memtest
2165 fills the memory with this pattern, validates
2166 memory contents and reserves bad memory
2167 regions that are detected.
2169 meye.*= [HW] Set MotionEye Camera parameters
2170 See Documentation/video4linux/meye.txt.
2172 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2173 Multi-Function General Purpose Timers on AMD Geode
2176 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2177 the BIOS has incorrectly applied a workaround. TinyBIOS
2178 version 0.98 is known to be affected, 0.99 fixes the
2179 problem by letting the user disable the workaround.
2183 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2184 physical address is ignored.
2186 mini2440= [ARM,HW,KNL]
2187 Format:[0..2][b][c][t]
2189 MINI2440 configuration specification:
2190 0 - The attached screen is the 3.5" TFT
2191 1 - The attached screen is the 7" TFT
2192 2 - The VGA Shield is attached (1024x768)
2193 Leaving out the screen size parameter will not load
2194 the TFT driver, and the framebuffer will be left
2196 b - Enable backlight. The TFT backlight pin will be
2197 linked to the kernel VESA blanking code and a GPIO
2198 LED. This parameter is not necessary when using the
2200 c - Enable the s3c camera interface.
2201 t - Reserved for enabling touchscreen support. The
2202 touchscreen support is not enabled in the mainstream
2203 kernel as of 2.6.30, a preliminary port can be found
2204 in the "bleeding edge" mini2440 support kernel at
2205 http://repo.or.cz/w/linux-2.6/mini2440.git
2208 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2209 parameter allows control of the logging verbosity for
2210 the additional memory initialisation checks. A value
2211 of 0 disables mminit logging and a level of 4 will
2212 log everything. Information is printed at KERN_DEBUG
2213 so loglevel=8 may also need to be specified.
2216 [KNL] When CONFIG_MODULE_SIG is set, this means that
2217 modules without (valid) signatures will fail to load.
2218 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2219 is always true, so this option does nothing.
2222 [MOUSE] Maximum time between finger touching and
2223 leaving touchpad surface for touch to be considered
2224 a tap and be reported as a left button click (for
2225 touchpads working in absolute mode only).
2227 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2228 reporting absolute coordinates, such as tablets
2229 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2230 reporting absolute coordinates, such as tablets
2232 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2233 is similar to kernelcore except it specifies the
2234 amount of memory used for migratable allocations.
2235 If both kernelcore and movablecore is specified,
2236 then kernelcore will be at *least* the specified
2237 value but may be more. If movablecore on its own
2238 is specified, the administrator must be careful
2239 that the amount of memory usable for all allocations
2242 movable_node [KNL,X86] Boot-time switch to enable the effects
2243 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2245 MTD_Partition= [MTD]
2246 Format: <name>,<region-number>,<size>,<offset>
2248 MTD_Region= [MTD] Format:
2249 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2252 See drivers/mtd/cmdlinepart.c.
2254 multitce=off [PPC] This parameter disables the use of the pSeries
2255 firmware feature for updating multiple TCE entries
2258 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2260 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2262 boundary - index of last SLC block on Flex-OneNAND.
2263 The remaining blocks are configured as MLC blocks.
2264 lock - Configure if Flex-OneNAND boundary should be locked.
2265 Once locked, the boundary cannot be changed.
2266 1 indicates lock status, 0 indicates unlock status.
2269 ARM/S3C2412 JIVE boot control
2271 See arch/arm/mach-s3c2412/mach-jive.c
2273 mtouchusb.raw_coordinates=
2274 [HW] Make the MicroTouch USB driver use raw coordinates
2275 ('y', default) or cooked coordinates ('n')
2277 mtrr_chunk_size=nn[KMG] [X86]
2278 used for mtrr cleanup. It is largest continuous chunk
2279 that could hold holes aka. UC entries.
2281 mtrr_gran_size=nn[KMG] [X86]
2282 Used for mtrr cleanup. It is granularity of mtrr block.
2284 Large value could prevent small alignment from
2287 mtrr_spare_reg_nr=n [X86]
2289 Range: 0,7 : spare reg number
2291 Used for mtrr cleanup. It is spare mtrr entries number.
2292 Set to 2 or more if your graphical card needs more.
2294 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2296 netdev= [NET] Network devices parameters
2297 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2298 Note that mem_start is often overloaded to mean
2299 something different and driver-specific.
2300 This usage is only documented in each driver source
2304 [NETFILTER] Enable connection tracking flow accounting
2305 0 to disable accounting
2306 1 to enable accounting
2309 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2310 See Documentation/filesystems/nfs/nfsroot.txt.
2312 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2313 See Documentation/filesystems/nfs/nfsroot.txt.
2315 nfsrootdebug [NFS] enable nfsroot debugging messages.
2316 See Documentation/filesystems/nfs/nfsroot.txt.
2318 nfs.callback_tcpport=
2319 [NFS] set the TCP port on which the NFSv4 callback
2320 channel should listen.
2323 [NFS] sets the pathname to the program which is used
2324 to update the NFS client cache entries.
2326 nfs.cache_getent_timeout=
2327 [NFS] sets the timeout after which an attempt to
2328 update a cache entry is deemed to have failed.
2330 nfs.idmap_cache_timeout=
2331 [NFS] set the maximum lifetime for idmapper cache
2335 [NFS] enable 64-bit inode numbers.
2336 If zero, the NFS client will fake up a 32-bit inode
2337 number for the readdir() and stat() syscalls instead
2338 of returning the full 64-bit number.
2339 The default is to return 64-bit inode numbers.
2341 nfs.max_session_slots=
2342 [NFSv4.1] Sets the maximum number of session slots
2343 the client will attempt to negotiate with the server.
2344 This limits the number of simultaneous RPC requests
2345 that the client can send to the NFSv4.1 server.
2346 Note that there is little point in setting this
2347 value higher than the max_tcp_slot_table_limit.
2349 nfs.nfs4_disable_idmapping=
2350 [NFSv4] When set to the default of '1', this option
2351 ensures that both the RPC level authentication
2352 scheme and the NFS level operations agree to use
2353 numeric uids/gids if the mount is using the
2354 'sec=sys' security flavour. In effect it is
2355 disabling idmapping, which can make migration from
2356 legacy NFSv2/v3 systems to NFSv4 easier.
2357 Servers that do not support this mode of operation
2358 will be autodetected by the client, and it will fall
2359 back to using the idmapper.
2360 To turn off this behaviour, set the value to '0'.
2362 [NFS4] Specify an additional fixed unique ident-
2363 ification string that NFSv4 clients can insert into
2364 their nfs_client_id4 string. This is typically a
2365 UUID that is generated at system install time.
2367 nfs.send_implementation_id =
2368 [NFSv4.1] Send client implementation identification
2369 information in exchange_id requests.
2370 If zero, no implementation identification information
2372 The default is to send the implementation identification
2375 nfs.recover_lost_locks =
2376 [NFSv4] Attempt to recover locks that were lost due
2377 to a lease timeout on the server. Please note that
2378 doing this risks data corruption, since there are
2379 no guarantees that the file will remain unchanged
2380 after the locks are lost.
2381 If you want to enable the kernel legacy behaviour of
2382 attempting to recover these locks, then set this
2384 The default parameter value of '0' causes the kernel
2385 not to attempt recovery of lost locks.
2387 nfs4.layoutstats_timer =
2388 [NFSv4.2] Change the rate at which the kernel sends
2389 layoutstats to the pNFS metadata server.
2391 Setting this to value to 0 causes the kernel to use
2392 whatever value is the default set by the layout
2393 driver. A non-zero value sets the minimum interval
2394 in seconds between layoutstats transmissions.
2396 nfsd.nfs4_disable_idmapping=
2397 [NFSv4] When set to the default of '1', the NFSv4
2398 server will return only numeric uids and gids to
2399 clients using auth_sys, and will accept numeric uids
2400 and gids from such clients. This is intended to ease
2401 migration from NFSv2/v3.
2403 objlayoutdriver.osd_login_prog=
2404 [NFS] [OBJLAYOUT] sets the pathname to the program which
2405 is used to automatically discover and login into new
2406 osd-targets. Please see:
2407 Documentation/filesystems/pnfs.txt for more explanations
2409 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2410 when a NMI is triggered.
2411 Format: [state][,regs][,debounce][,die]
2413 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2414 Format: [panic,][nopanic,][num]
2416 0 - turn hardlockup detector in nmi_watchdog off
2417 1 - turn hardlockup detector in nmi_watchdog on
2418 When panic is specified, panic when an NMI watchdog
2419 timeout occurs (or 'nopanic' to override the opposite
2420 default). To disable both hard and soft lockup detectors,
2421 please see 'nowatchdog'.
2422 This is useful when you use a panic=... timeout and
2423 need the box quickly up again.
2425 netpoll.carrier_timeout=
2426 [NET] Specifies amount of time (in seconds) that
2427 netpoll should wait for a carrier. By default netpoll
2430 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2431 emulation library even if a 387 maths coprocessor
2435 [HW] Never suspend the console
2436 Disable suspending of consoles during suspend and
2437 hibernate operations. Once disabled, debugging
2438 messages can reach various consoles while the rest
2439 of the system is being put to sleep (ie, while
2440 debugging driver suspend/resume hooks). This may
2441 not work reliably with all consoles, but is known
2442 to work with serial and VGA consoles.
2443 To facilitate more flexible debugging, we also add
2444 console_suspend, a printk module parameter to control
2445 it. Users could use console_suspend (usually
2446 /sys/module/printk/parameters/console_suspend) to
2447 turn on/off it dynamically.
2449 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2450 caches in the slab allocator. Saves per-node memory,
2451 but will impact performance.
2455 noapic [SMP,APIC] Tells the kernel to not make use of any
2456 IOAPICs that may be present in the system.
2458 noautogroup Disable scheduler automatic task group creation.
2460 nobats [PPC] Do not use BATs for mapping kernel lowmem
2461 on "Classic" PPC cores.
2465 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2467 nodelayacct [KNL] Disable per-task delay accounting
2469 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2471 nodsp [SH] Disable hardware DSP at boot time.
2473 noefi Disable EFI runtime services support.
2478 On X86-32 available only on PAE configured kernels.
2479 noexec=on: enable non-executable mappings (default)
2480 noexec=off: disable non-executable mappings
2483 Disable SMAP (Supervisor Mode Access Prevention)
2484 even if it is supported by processor.
2487 Disable SMEP (Supervisor Mode Execution Prevention)
2488 even if it is supported by processor.
2491 This affects only 32-bit executables.
2492 noexec32=on: enable non-executable mappings (default)
2493 read doesn't imply executable mappings
2494 noexec32=off: disable non-executable mappings
2495 read implies executable mappings
2497 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2499 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2500 register save and restore. The kernel will only save
2501 legacy floating-point registers on task switch.
2503 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2505 noxsave [BUGS=X86] Disables x86 extended register state save
2506 and restore using xsave. The kernel will fallback to
2507 enabling legacy floating-point and sse state.
2509 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2510 register states. The kernel will fall back to use
2511 xsave to save the states. By using this parameter,
2512 performance of saving the states is degraded because
2513 xsave doesn't support modified optimization while
2514 xsaveopt supports it on xsaveopt enabled systems.
2516 noxsaves [X86] Disables xsaves and xrstors used in saving and
2517 restoring x86 extended register state in compacted
2518 form of xsave area. The kernel will fall back to use
2519 xsaveopt and xrstor to save and restore the states
2520 in standard form of xsave area. By using this
2521 parameter, xsave area per process might occupy more
2522 memory on xsaves enabled systems.
2524 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2525 wfi(ARM) instruction doesn't work correctly and not to
2526 use it. This is also useful when using JTAG debugger.
2528 no_file_caps Tells the kernel not to honor file capabilities. The
2529 only way then for a file to be executed with privilege
2530 is to be setuid root or executed by root.
2532 nohalt [IA-64] Tells the kernel not to use the power saving
2533 function PAL_HALT_LIGHT when idle. This increases
2534 power-consumption. On the positive side, it reduces
2535 interrupt wake-up latency, which may improve performance
2536 in certain environments such as networked servers or
2539 nohibernate [HIBERNATION] Disable hibernation and resume.
2541 nohz= [KNL] Boottime enable/disable dynamic ticks
2542 Valid arguments: on, off
2545 nohz_full= [KNL,BOOT]
2546 In kernels built with CONFIG_NO_HZ_FULL=y, set
2547 the specified list of CPUs whose tick will be stopped
2548 whenever possible. The boot CPU will be forced outside
2549 the range to maintain the timekeeping.
2550 The CPUs in this range must also be included in the
2553 noiotrap [SH] Disables trapped I/O port accesses.
2555 noirqdebug [X86-32] Disables the code which attempts to detect and
2556 disable unhandled interrupt sources.
2558 no_timer_check [X86,APIC] Disables the code which tests for
2559 broken timer IRQ sources.
2561 noisapnp [ISAPNP] Disables ISA PnP code.
2563 noinitrd [RAM] Tells the kernel not to load any configured
2566 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2568 [Deprecated - use intremap=off]
2572 noinvpcid [X86] Disable the INVPCID cpu feature.
2574 nojitter [IA-64] Disables jitter checking for ITC timers.
2576 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2578 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2581 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2582 steal time is computed, but won't influence scheduler
2585 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2587 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2589 noltlbs [PPC] Do not use large page/tlb entries for kernel
2590 lowmem mapping on PPC40x.
2592 nomca [IA-64] Disable machine check abort handling
2594 nomce [X86-32] Disable Machine Check Exception
2596 nomfgpt [X86-32] Disable Multi-Function General Purpose
2597 Timer usage (for AMD Geode machines).
2599 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2600 shutdown the other cpus. Instead use the REBOOT_VECTOR
2603 nomodule Disable module load
2605 nopat [X86] Disable PAT (page attribute table extension of
2606 pagetables) support.
2608 norandmaps Don't use address space randomization. Equivalent to
2609 echo 0 > /proc/sys/kernel/randomize_va_space
2611 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2613 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2614 with UP alternatives
2616 nordrand [X86] Disable kernel use of the RDRAND and
2617 RDSEED instructions even if they are supported
2618 by the processor. RDRAND and RDSEED are still
2619 available to user space applications.
2621 noresume [SWSUSP] Disables resume and restores original swap
2624 no-scroll [VGA] Disables scrollback.
2625 This is required for the Braillex ib80-piezo Braille
2626 reader made by F.H. Papenmeier (Germany).
2630 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2632 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2633 and disable the IO APIC. legacy for "maxcpus=0".
2635 nosoftlockup [KNL] Disable the soft-lockup detector.
2637 nosync [HW,M68K] Disables sync negotiation for all devices.
2639 notsc [BUGS=X86-32] Disable Time Stamp Counter
2641 nowatchdog [KNL] Disable both lockup detectors, i.e.
2642 soft-lockup and NMI watchdog (hard-lockup).
2646 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2648 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2649 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2650 Some features depend on CPU0. Known dependencies are:
2651 1. Resume from suspend/hibernate depends on CPU0.
2652 Suspend/hibernate will fail if CPU0 is offline and you
2653 need to online CPU0 before suspend/hibernate.
2654 2. PIC interrupts also depend on CPU0. CPU0 can't be
2655 removed if a PIC interrupt is detected.
2656 It's said poweroff/reboot may depend on CPU0 on some
2657 machines although I haven't seen such issues so far
2658 after CPU0 is offline on a few tested machines.
2659 If the dependencies are under your control, you can
2660 turn on cpu0_hotplug.
2662 nptcg= [IA-64] Override max number of concurrent global TLB
2663 purges which is reported from either PAL_VM_SUMMARY or
2666 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2667 could support. nr_cpus=n : n >= 1 limits the kernel to
2668 supporting 'n' processors. Later in runtime you can not
2669 use hotplug cpu feature to put more cpu back to online.
2670 just like you compile the kernel NR_CPUS=n
2672 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2674 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2675 Allowed values are enable and disable
2677 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2678 one of ['zone', 'node', 'default'] can be specified
2679 This can be set from sysctl after boot.
2680 See Documentation/sysctl/vm.txt for details.
2682 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2683 See Documentation/debugging-via-ohci1394.txt for more
2686 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2687 Rather than timing out after 20 ms if an EC
2688 command is not properly ACKed, override the length
2689 of the timeout. We have interrupts disabled while
2690 waiting for the ACK, so if this is set too high
2691 interrupts *may* be lost!
2693 omap_mux= [OMAP] Override bootloader pin multiplexing.
2694 Format: <mux_mode0.mode_name=value>...
2695 For example, to override I2C bus2:
2696 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2698 oprofile.timer= [HW]
2699 Use timer interrupt instead of performance counters
2701 oprofile.cpu_type= Force an oprofile cpu type
2702 This might be useful if you have an older oprofile
2703 userland or if you want common events.
2704 Format: { arch_perfmon }
2705 arch_perfmon: [X86] Force use of architectural
2706 perfmon on Intel CPUs instead of the
2707 CPU specific event set.
2708 timer: [X86] Force use of architectural NMI
2709 timer mode (see also oprofile.timer
2710 for generic hr timer mode)
2711 [s390] Force legacy basic mode sampling
2712 (report cpu_type "timer")
2714 oops=panic Always panic on oopses. Default is to just kill the
2715 process, but there is a small probability of
2716 deadlocking the machine.
2717 This will also cause panics on machine check exceptions.
2718 Useful together with panic=30 to trigger a reboot.
2721 See Documentation/sound/oss/oss-parameters.txt
2723 page_owner= [KNL] Boot-time page_owner enabling option.
2724 Storage of the information about who allocated
2725 each page is disabled in default. With this switch,
2727 on: enable the feature
2729 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2730 timeout > 0: seconds before rebooting
2731 timeout = 0: wait forever
2732 timeout < 0: reboot immediately
2735 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2738 crash_kexec_post_notifiers
2739 Run kdump after running panic-notifiers and dumping
2740 kmsg. This only for the users who doubt kdump always
2741 succeeds in any situation.
2742 Note that this also increases risks of kdump failure,
2743 because some panic notifiers can make the crashed
2744 kernel more unstable.
2746 parkbd.port= [HW] Parallel port number the keyboard adapter is
2747 connected to, default is 0.
2749 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2750 0 for XT, 1 for AT (default is AT).
2753 parport= [HW,PPT] Specify parallel ports. 0 disables.
2754 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2755 Use 'auto' to force the driver to use any
2756 IRQ/DMA settings detected (the default is to
2757 ignore detected IRQ/DMA settings because of
2758 possible conflicts). You can specify the base
2759 address, IRQ, and DMA settings; IRQ and DMA
2760 should be numbers, or 'auto' (for using detected
2761 settings on that particular port), or 'nofifo'
2762 (to avoid using a FIFO even if it is detected).
2763 Parallel ports are assigned in the order they
2764 are specified on the command line, starting
2767 parport_init_mode= [HW,PPT]
2768 Configure VIA parallel port to operate in
2769 a specific mode. This is necessary on Pegasos
2770 computer where firmware has no options for setting
2771 up parallel port mode and sets it to spp.
2772 Currently this function knows 686a and 8231 chips.
2773 Format: [spp|ps2|epp|ecp|ecpepp]
2776 Halt all CPUs after the first oops has been printed for
2777 the specified number of seconds. This is to be used if
2778 your oopses keep scrolling off the screen.
2783 See header of drivers/block/paride/pcd.c.
2784 See also Documentation/blockdev/paride.txt.
2786 pci=option[,option...] [PCI] various PCI subsystem options:
2787 earlydump [X86] dump PCI config space before the kernel
2789 off [X86] don't probe for the PCI bus
2790 bios [X86-32] force use of PCI BIOS, don't access
2791 the hardware directly. Use this if your machine
2792 has a non-standard PCI host bridge.
2793 nobios [X86-32] disallow use of PCI BIOS, only direct
2794 hardware access methods are allowed. Use this
2795 if you experience crashes upon bootup and you
2796 suspect they are caused by the BIOS.
2797 conf1 [X86] Force use of PCI Configuration Access
2798 Mechanism 1 (config address in IO port 0xCF8,
2799 data in IO port 0xCFC, both 32-bit).
2800 conf2 [X86] Force use of PCI Configuration Access
2801 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2802 the function, IO port 0xCFA, also 8-bit, sets
2803 bus number. The config space is then accessed
2804 through ports 0xC000-0xCFFF).
2805 See http://wiki.osdev.org/PCI for more info
2806 on the configuration access mechanisms.
2807 noaer [PCIE] If the PCIEAER kernel config parameter is
2808 enabled, this kernel boot option can be used to
2809 disable the use of PCIE advanced error reporting.
2810 nodomains [PCI] Disable support for multiple PCI
2811 root domains (aka PCI segments, in ACPI-speak).
2812 nommconf [X86] Disable use of MMCONFIG for PCI
2814 check_enable_amd_mmconf [X86] check for and enable
2815 properly configured MMIO access to PCI
2816 config space on AMD family 10h CPU
2817 nomsi [MSI] If the PCI_MSI kernel config parameter is
2818 enabled, this kernel boot option can be used to
2819 disable the use of MSI interrupts system-wide.
2820 noioapicquirk [APIC] Disable all boot interrupt quirks.
2821 Safety option to keep boot IRQs enabled. This
2822 should never be necessary.
2823 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2824 primary IO-APIC for bridges that cannot disable
2825 boot IRQs. This fixes a source of spurious IRQs
2826 when the system masks IRQs.
2827 noioapicreroute [APIC] Disable workaround that uses the
2828 boot IRQ equivalent of an IRQ that connects to
2829 a chipset where boot IRQs cannot be disabled.
2830 The opposite of ioapicreroute.
2831 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2832 routing table. These calls are known to be buggy
2833 on several machines and they hang the machine
2834 when used, but on other computers it's the only
2835 way to get the interrupt routing table. Try
2836 this option if the kernel is unable to allocate
2837 IRQs or discover secondary PCI buses on your
2839 rom [X86] Assign address space to expansion ROMs.
2840 Use with caution as certain devices share
2841 address decoders between ROMs and other
2843 norom [X86] Do not assign address space to
2844 expansion ROMs that do not already have
2845 BIOS assigned address ranges.
2846 nobar [X86] Do not assign address space to the
2847 BARs that weren't assigned by the BIOS.
2848 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2849 assigned automatically to PCI devices. You can
2850 make the kernel exclude IRQs of your ISA cards
2852 pirqaddr=0xAAAAA [X86] Specify the physical address
2853 of the PIRQ table (normally generated
2854 by the BIOS) if it is outside the
2855 F0000h-100000h range.
2856 lastbus=N [X86] Scan all buses thru bus #N. Can be
2857 useful if the kernel is unable to find your
2858 secondary buses and you want to tell it
2859 explicitly which ones they are.
2860 assign-busses [X86] Always assign all PCI bus
2861 numbers ourselves, overriding
2862 whatever the firmware may have done.
2863 usepirqmask [X86] Honor the possible IRQ mask stored
2864 in the BIOS $PIR table. This is needed on
2865 some systems with broken BIOSes, notably
2866 some HP Pavilion N5400 and Omnibook XE3
2867 notebooks. This will have no effect if ACPI
2868 IRQ routing is enabled.
2869 noacpi [X86] Do not use ACPI for IRQ routing
2870 or for PCI scanning.
2871 use_crs [X86] Use PCI host bridge window information
2872 from ACPI. On BIOSes from 2008 or later, this
2873 is enabled by default. If you need to use this,
2874 please report a bug.
2875 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2876 If you need to use this, please report a bug.
2877 routeirq Do IRQ routing for all PCI devices.
2878 This is normally done in pci_enable_device(),
2879 so this option is a temporary workaround
2880 for broken drivers that don't call it.
2881 skip_isa_align [X86] do not align io start addr, so can
2882 handle more pci cards
2883 firmware [ARM] Do not re-enumerate the bus but instead
2884 just use the configuration from the
2885 bootloader. This is currently used on
2886 IXP2000 systems where the bus has to be
2887 configured a certain way for adjunct CPUs.
2888 noearly [X86] Don't do any early type 1 scanning.
2889 This might help on some broken boards which
2890 machine check when some devices' config space
2891 is read. But various workarounds are disabled
2892 and some IOMMU drivers will not work.
2893 bfsort Sort PCI devices into breadth-first order.
2894 This sorting is done to get a device
2895 order compatible with older (<= 2.4) kernels.
2896 nobfsort Don't sort PCI devices into breadth-first order.
2897 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2898 tuning and use the BIOS-configured MPS defaults.
2899 pcie_bus_safe Set every device's MPS to the largest value
2900 supported by all devices below the root complex.
2901 pcie_bus_perf Set device MPS to the largest allowable MPS
2902 based on its parent bus. Also set MRRS (Max
2903 Read Request Size) to the largest supported
2904 value (no larger than the MPS that the device
2905 or bus can support) for best performance.
2906 pcie_bus_peer2peer Set every device's MPS to 128B, which
2907 every device is guaranteed to support. This
2908 configuration allows peer-to-peer DMA between
2909 any pair of devices, possibly at the cost of
2910 reduced performance. This also guarantees
2911 that hot-added devices will work.
2912 cbiosize=nn[KMG] The fixed amount of bus space which is
2913 reserved for the CardBus bridge's IO window.
2914 The default value is 256 bytes.
2915 cbmemsize=nn[KMG] The fixed amount of bus space which is
2916 reserved for the CardBus bridge's memory
2917 window. The default value is 64 megabytes.
2920 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2921 Specifies alignment and device to reassign
2922 aligned memory resources.
2923 If <order of align> is not specified,
2924 PAGE_SIZE is used as alignment.
2925 PCI-PCI bridge can be specified, if resource
2926 windows need to be expanded.
2927 ecrc= Enable/disable PCIe ECRC (transaction layer
2928 end-to-end CRC checking).
2929 bios: Use BIOS/firmware settings. This is the
2933 hpiosize=nn[KMG] The fixed amount of bus space which is
2934 reserved for hotplug bridge's IO window.
2935 Default size is 256 bytes.
2936 hpmemsize=nn[KMG] The fixed amount of bus space which is
2937 reserved for hotplug bridge's memory window.
2938 Default size is 2 megabytes.
2939 realloc= Enable/disable reallocating PCI bridge resources
2940 if allocations done by BIOS are too small to
2941 accommodate resources required by all child
2943 off: Turn realloc off
2945 realloc same as realloc=on
2946 noari do not use PCIe ARI.
2947 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2948 only look for one device below a PCIe downstream
2951 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2954 force Enable ASPM even on devices that claim not to support it.
2955 WARNING: Forcing ASPM on may cause system lockups.
2957 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2958 nomsi Do not use MSI for PCI Express Native Hotplug (this
2959 makes all PCIe ports use INTx for hotplug services).
2961 pcie_ports= [PCIE] PCIe ports handling:
2962 auto Ask the BIOS whether or not to use native PCIe services
2963 associated with PCIe ports (PME, hot-plug, AER). Use
2964 them only if that is allowed by the BIOS.
2965 native Use native PCIe services associated with PCIe ports
2967 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2970 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2971 nomsi Do not use MSI for native PCIe PME signaling (this makes
2972 all PCIe root ports use INTx for all services).
2974 pcmv= [HW,PCMCIA] BadgePAD 4
2978 Keep all power-domains already enabled by bootloader on,
2979 even if no driver has claimed them. This is useful
2980 for debug and development, but should not be
2981 needed on a platform with proper driver support.
2984 See Documentation/blockdev/paride.txt.
2986 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2989 See arch/parisc/kernel/pdc_chassis.c
2991 percpu_alloc= Select which percpu first chunk allocator to use.
2992 Currently supported values are "embed" and "page".
2993 Archs may support subset or none of the selections.
2994 See comments in mm/percpu.c for details on each
2995 allocator. This parameter is primarily for debugging
2996 and performance comparison.
2999 See Documentation/blockdev/paride.txt.
3002 See Documentation/blockdev/paride.txt.
3004 pirq= [SMP,APIC] Manual mp-table setup
3005 See Documentation/x86/i386/IO-APIC.txt.
3007 plip= [PPT,NET] Parallel port network link
3008 Format: { parport<nr> | timid | 0 }
3009 See also Documentation/parport.txt.
3011 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3012 Override pmtimer IOPort with a hex value.
3016 Enable PNP debug messages (depends on the
3017 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3018 via /sys/module/pnp/parameters/debug. We always show
3019 current resource usage; turning this on also shows
3020 possible settings and some assignment information.
3026 { on | off | curr | res | no-curr | no-res }
3029 [ISAPNP] Exclude IRQs for the autoconfiguration
3032 [ISAPNP] Exclude DMAs for the autoconfiguration
3034 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3035 Ranges are in pairs (I/O port base and size).
3038 [ISAPNP] Exclude memory regions for the
3040 Ranges are in pairs (memory base and size).
3042 ports= [IP_VS_FTP] IPVS ftp helper module
3044 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3046 Format: <port>,<port>....
3048 ppc_strict_facility_enable
3049 [PPC] This option catches any kernel floating point,
3050 Altivec, VSX and SPE outside of regions specifically
3051 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3052 There is some performance impact when enabling this.
3054 print-fatal-signals=
3055 [KNL] debug: print fatal signals
3057 If enabled, warn about various signal handling
3058 related application anomalies: too many signals,
3059 too many POSIX.1 timers, fatal signals causing a
3062 If you hit the warning due to signal overflow,
3063 you might want to try "ulimit -i unlimited".
3067 printk.always_kmsg_dump=
3068 Trigger kmsg_dump for cases other than kernel oops or
3070 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3073 printk.time= Show timing data prefixed to each printk message line
3074 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3076 processor.max_cstate= [HW,ACPI]
3077 Limit processor to maximum C-state
3078 max_cstate=9 overrides any DMI blacklist limit.
3080 processor.nocst [HW,ACPI]
3081 Ignore the _CST method to determine C-states,
3082 instead using the legacy FADT method
3084 profile= [KNL] Enable kernel profiling via /proc/profile
3085 Format: [schedule,]<number>
3086 Param: "schedule" - profile schedule points.
3087 Param: <number> - step/bucket size as a power of 2 for
3088 statistical time based profiling.
3089 Param: "sleep" - profile D-state sleeping (millisecs).
3090 Requires CONFIG_SCHEDSTATS
3091 Param: "kvm" - profile VM exits.
3093 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3095 See Documentation/blockdev/ramdisk.txt.
3097 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3098 probe for; one of (bare|imps|exps|lifebook|any).
3099 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3101 psmouse.resetafter= [HW,MOUSE]
3102 Try to reset the device after so many bad packets
3105 [HW,MOUSE] Set desired mouse resolution, in dpi.
3106 psmouse.smartscroll=
3107 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3108 0 = disabled, 1 = enabled (default).
3110 pstore.backend= Specify the name of the pstore backend to use
3113 See Documentation/blockdev/paride.txt.
3116 [KNL] Number of legacy pty's. Overwrites compiled-in
3119 quiet [KNL] Disable most log messages
3124 See Documentation/md.txt.
3126 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3127 See Documentation/blockdev/ramdisk.txt.
3130 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3131 the specified list of CPUs to be no-callback CPUs.
3132 Invocation of these CPUs' RCU callbacks will
3133 be offloaded to "rcuox/N" kthreads created for
3134 that purpose, where "x" is "b" for RCU-bh, "p"
3135 for RCU-preempt, and "s" for RCU-sched, and "N"
3136 is the CPU number. This reduces OS jitter on the
3137 offloaded CPUs, which can be useful for HPC and
3138 real-time workloads. It can also improve energy
3139 efficiency for asymmetric multiprocessors.
3142 Rather than requiring that offloaded CPUs
3143 (specified by rcu_nocbs= above) explicitly
3144 awaken the corresponding "rcuoN" kthreads,
3145 make these kthreads poll for callbacks.
3146 This improves the real-time response for the
3147 offloaded CPUs by relieving them of the need to
3148 wake up the corresponding kthread, but degrades
3149 energy efficiency by requiring that the kthreads
3150 periodically wake up to do the polling.
3152 rcutree.blimit= [KNL]
3153 Set maximum number of finished RCU callbacks to
3154 process in one batch.
3156 rcutree.dump_tree= [KNL]
3157 Dump the structure of the rcu_node combining tree
3158 out at early boot. This is used for diagnostic
3159 purposes, to verify correct tree setup.
3161 rcutree.gp_cleanup_delay= [KNL]
3162 Set the number of jiffies to delay each step of
3163 RCU grace-period cleanup. This only has effect
3164 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3166 rcutree.gp_init_delay= [KNL]
3167 Set the number of jiffies to delay each step of
3168 RCU grace-period initialization. This only has
3169 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3172 rcutree.gp_preinit_delay= [KNL]
3173 Set the number of jiffies to delay each step of
3174 RCU grace-period pre-initialization, that is,
3175 the propagation of recent CPU-hotplug changes up
3176 the rcu_node combining tree. This only has effect
3177 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3179 rcutree.rcu_fanout_exact= [KNL]
3180 Disable autobalancing of the rcu_node combining
3181 tree. This is used by rcutorture, and might
3182 possibly be useful for architectures having high
3183 cache-to-cache transfer latencies.
3185 rcutree.rcu_fanout_leaf= [KNL]
3186 Change the number of CPUs assigned to each
3187 leaf rcu_node structure. Useful for very
3188 large systems, which will choose the value 64,
3189 and for NUMA systems with large remote-access
3190 latencies, which will choose a value aligned
3191 with the appropriate hardware boundaries.
3193 rcutree.jiffies_till_sched_qs= [KNL]
3194 Set required age in jiffies for a
3195 given grace period before RCU starts
3196 soliciting quiescent-state help from
3197 rcu_note_context_switch().
3199 rcutree.jiffies_till_first_fqs= [KNL]
3200 Set delay from grace-period initialization to
3201 first attempt to force quiescent states.
3202 Units are jiffies, minimum value is zero,
3203 and maximum value is HZ.
3205 rcutree.jiffies_till_next_fqs= [KNL]
3206 Set delay between subsequent attempts to force
3207 quiescent states. Units are jiffies, minimum
3208 value is one, and maximum value is HZ.
3210 rcutree.kthread_prio= [KNL,BOOT]
3211 Set the SCHED_FIFO priority of the RCU per-CPU
3212 kthreads (rcuc/N). This value is also used for
3213 the priority of the RCU boost threads (rcub/N)
3214 and for the RCU grace-period kthreads (rcu_bh,
3215 rcu_preempt, and rcu_sched). If RCU_BOOST is
3216 set, valid values are 1-99 and the default is 1
3217 (the least-favored priority). Otherwise, when
3218 RCU_BOOST is not set, valid values are 0-99 and
3219 the default is zero (non-realtime operation).
3221 rcutree.rcu_nocb_leader_stride= [KNL]
3222 Set the number of NOCB kthread groups, which
3223 defaults to the square root of the number of
3224 CPUs. Larger numbers reduces the wakeup overhead
3225 on the per-CPU grace-period kthreads, but increases
3226 that same overhead on each group's leader.
3228 rcutree.qhimark= [KNL]
3229 Set threshold of queued RCU callbacks beyond which
3230 batch limiting is disabled.
3232 rcutree.qlowmark= [KNL]
3233 Set threshold of queued RCU callbacks below which
3234 batch limiting is re-enabled.
3236 rcutree.rcu_idle_gp_delay= [KNL]
3237 Set wakeup interval for idle CPUs that have
3238 RCU callbacks (RCU_FAST_NO_HZ=y).
3240 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3241 Set wakeup interval for idle CPUs that have
3242 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3243 Lazy RCU callbacks are those which RCU can
3244 prove do nothing more than free memory.
3246 rcutorture.cbflood_inter_holdoff= [KNL]
3247 Set holdoff time (jiffies) between successive
3248 callback-flood tests.
3250 rcutorture.cbflood_intra_holdoff= [KNL]
3251 Set holdoff time (jiffies) between successive
3252 bursts of callbacks within a given callback-flood
3255 rcutorture.cbflood_n_burst= [KNL]
3256 Set the number of bursts making up a given
3257 callback-flood test. Set this to zero to
3258 disable callback-flood testing.
3260 rcutorture.cbflood_n_per_burst= [KNL]
3261 Set the number of callbacks to be registered
3262 in a given burst of a callback-flood test.
3264 rcutorture.fqs_duration= [KNL]
3265 Set duration of force_quiescent_state bursts
3268 rcutorture.fqs_holdoff= [KNL]
3269 Set holdoff time within force_quiescent_state bursts
3272 rcutorture.fqs_stutter= [KNL]
3273 Set wait time between force_quiescent_state bursts
3276 rcutorture.gp_cond= [KNL]
3277 Use conditional/asynchronous update-side
3278 primitives, if available.
3280 rcutorture.gp_exp= [KNL]
3281 Use expedited update-side primitives, if available.
3283 rcutorture.gp_normal= [KNL]
3284 Use normal (non-expedited) asynchronous
3285 update-side primitives, if available.
3287 rcutorture.gp_sync= [KNL]
3288 Use normal (non-expedited) synchronous
3289 update-side primitives, if available. If all
3290 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3291 rcutorture.gp_normal=, and rcutorture.gp_sync=
3292 are zero, rcutorture acts as if is interpreted
3293 they are all non-zero.
3295 rcutorture.n_barrier_cbs= [KNL]
3296 Set callbacks/threads for rcu_barrier() testing.
3298 rcutorture.nfakewriters= [KNL]
3299 Set number of concurrent RCU writers. These just
3300 stress RCU, they don't participate in the actual
3301 test, hence the "fake".
3303 rcutorture.nreaders= [KNL]
3304 Set number of RCU readers. The value -1 selects
3305 N-1, where N is the number of CPUs. A value
3306 "n" less than -1 selects N-n-2, where N is again
3307 the number of CPUs. For example, -2 selects N
3308 (the number of CPUs), -3 selects N+1, and so on.
3310 rcutorture.object_debug= [KNL]
3311 Enable debug-object double-call_rcu() testing.
3313 rcutorture.onoff_holdoff= [KNL]
3314 Set time (s) after boot for CPU-hotplug testing.
3316 rcutorture.onoff_interval= [KNL]
3317 Set time (s) between CPU-hotplug operations, or
3318 zero to disable CPU-hotplug testing.
3320 rcutorture.shuffle_interval= [KNL]
3321 Set task-shuffle interval (s). Shuffling tasks
3322 allows some CPUs to go into dyntick-idle mode
3323 during the rcutorture test.
3325 rcutorture.shutdown_secs= [KNL]
3326 Set time (s) after boot system shutdown. This
3327 is useful for hands-off automated testing.
3329 rcutorture.stall_cpu= [KNL]
3330 Duration of CPU stall (s) to test RCU CPU stall
3331 warnings, zero to disable.
3333 rcutorture.stall_cpu_holdoff= [KNL]
3334 Time to wait (s) after boot before inducing stall.
3336 rcutorture.stat_interval= [KNL]
3337 Time (s) between statistics printk()s.
3339 rcutorture.stutter= [KNL]
3340 Time (s) to stutter testing, for example, specifying
3341 five seconds causes the test to run for five seconds,
3342 wait for five seconds, and so on. This tests RCU's
3343 ability to transition abruptly to and from idle.
3345 rcutorture.test_boost= [KNL]
3346 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3347 "Maybe" means test if the RCU implementation
3348 under test support RCU priority boosting.
3350 rcutorture.test_boost_duration= [KNL]
3351 Duration (s) of each individual boost test.
3353 rcutorture.test_boost_interval= [KNL]
3354 Interval (s) between each boost test.
3356 rcutorture.test_no_idle_hz= [KNL]
3357 Test RCU's dyntick-idle handling. See also the
3358 rcutorture.shuffle_interval parameter.
3360 rcutorture.torture_runnable= [BOOT]
3361 Start rcutorture running at boot time.
3363 rcutorture.torture_type= [KNL]
3364 Specify the RCU implementation to test.
3366 rcutorture.verbose= [KNL]
3367 Enable additional printk() statements.
3369 rcupdate.rcu_cpu_stall_suppress= [KNL]
3370 Suppress RCU CPU stall warning messages.
3372 rcupdate.rcu_cpu_stall_timeout= [KNL]
3373 Set timeout for RCU CPU stall warning messages.
3375 rcupdate.rcu_expedited= [KNL]
3376 Use expedited grace-period primitives, for
3377 example, synchronize_rcu_expedited() instead
3378 of synchronize_rcu(). This reduces latency,
3379 but can increase CPU utilization, degrade
3380 real-time latency, and degrade energy efficiency.
3381 No effect on CONFIG_TINY_RCU kernels.
3383 rcupdate.rcu_normal= [KNL]
3384 Use only normal grace-period primitives,
3385 for example, synchronize_rcu() instead of
3386 synchronize_rcu_expedited(). This improves
3387 real-time latency, CPU utilization, and
3388 energy efficiency, but can expose users to
3389 increased grace-period latency. This parameter
3390 overrides rcupdate.rcu_expedited. No effect on
3391 CONFIG_TINY_RCU kernels.
3393 rcupdate.rcu_normal_after_boot= [KNL]
3394 Once boot has completed (that is, after
3395 rcu_end_inkernel_boot() has been invoked), use
3396 only normal grace-period primitives. No effect
3397 on CONFIG_TINY_RCU kernels.
3399 rcupdate.rcu_task_stall_timeout= [KNL]
3400 Set timeout in jiffies for RCU task stall warning
3401 messages. Disable with a value less than or equal
3404 rcupdate.rcu_self_test= [KNL]
3405 Run the RCU early boot self tests
3407 rcupdate.rcu_self_test_bh= [KNL]
3408 Run the RCU bh early boot self tests
3410 rcupdate.rcu_self_test_sched= [KNL]
3411 Run the RCU sched early boot self tests
3415 Run specified binary instead of /init from the ramdisk,
3416 used for early userspace startup. See initrd.
3419 Format (x86 or x86_64):
3420 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3422 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3424 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3425 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3426 reboot_force is either force or not specified,
3427 reboot_cpu is s[mp]#### with #### being the processor
3428 to be used for rebooting.
3431 [KNL, SMP] Set scheduler's default relax_domain_level.
3432 See Documentation/cgroups/cpusets.txt.
3434 relative_sleep_states=
3435 [SUSPEND] Use sleep state labeling where the deepest
3436 state available other than hibernation is always "mem".
3437 Format: { "0" | "1" }
3438 0 -- Traditional sleep state labels.
3439 1 -- Relative sleep state labels.
3441 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3443 reservetop= [X86-32]
3445 Reserves a hole at the top of the kernel virtual
3450 Set the amount of memory to reserve for BIOS at
3451 the bottom of the address space.
3453 reset_devices [KNL] Force drivers to reset the underlying device
3454 during initialization.
3457 Specify the partition device for software suspend
3459 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3461 resume_offset= [SWSUSP]
3462 Specify the offset from the beginning of the partition
3463 given by "resume=" at which the swap header is located,
3464 in <PAGE_SIZE> units (needed only for swap files).
3465 See Documentation/power/swsusp-and-swap-files.txt
3467 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3468 read the resume files
3470 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3471 Useful for devices that are detected asynchronously
3472 (e.g. USB and MMC devices).
3474 hibernate= [HIBERNATION]
3475 noresume Don't check if there's a hibernation image
3476 present during boot.
3477 nocompress Don't compress/decompress hibernation images.
3478 no Disable hibernation and resume.
3480 retain_initrd [RAM] Keep initrd memory after extraction
3482 rfkill.default_state=
3483 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3484 etc. communication is blocked by default.
3487 rfkill.master_switch_mode=
3488 0 The "airplane mode" button does nothing.
3489 1 The "airplane mode" button toggles between everything
3490 blocked and the previous configuration.
3491 2 The "airplane mode" button toggles between everything
3492 blocked and everything unblocked.
3494 rhash_entries= [KNL,NET]
3495 Set number of hash buckets for route cache
3497 ro [KNL] Mount root device read-only on boot
3499 root= [KNL] Root filesystem
3500 See name_to_dev_t comment in init/do_mounts.c.
3502 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3503 mount the root filesystem
3505 rootflags= [KNL] Set root filesystem mount option string
3507 rootfstype= [KNL] Set root filesystem type
3509 rootwait [KNL] Wait (indefinitely) for root device to show up.
3510 Useful for devices that are detected asynchronously
3511 (e.g. USB and MMC devices).
3513 rproc_mem=nn[KMG][@address]
3514 [KNL,ARM,CMA] Remoteproc physical memory block.
3515 Memory area to be used by remote processor image,
3518 rw [KNL] Mount root device read-write on boot
3520 S [KNL] Run init in single mode
3522 s390_iommu= [HW,S390]
3523 Set s390 IOTLB flushing mode
3525 With strict flushing every unmap operation will result in
3526 an IOTLB flush. Default is lazy flushing before reuse,
3530 See drivers/net/irda/sa1100_ir.c.
3532 sbni= [NET] Granch SBNI12 leased line adapter
3534 sched_debug [KNL] Enables verbose scheduler debug messages.
3536 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3537 xtime_lock contention on larger systems, and/or RCU lock
3538 contention on all systems with CONFIG_MAXSMP set.
3539 Format: { "0" | "1" }
3540 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3542 Note: increases power consumption, thus should only be
3543 enabled if running jitter sensitive (HPC/RT) workloads.
3545 security= [SECURITY] Choose a security module to enable at boot.
3546 If this boot parameter is not specified, only the first
3547 security module asking for security registration will be
3548 loaded. An invalid security module name will be treated
3549 as if no module has been chosen.
3551 selinux= [SELINUX] Disable or enable SELinux at boot time.
3552 Format: { "0" | "1" }
3553 See security/selinux/Kconfig help text.
3556 Default value is set via kernel config option.
3557 If enabled at boot time, /selinux/disable can be used
3558 later to disable prior to initial policy load.
3560 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3561 Format: { "0" | "1" }
3562 See security/apparmor/Kconfig help text
3565 Default value is set via kernel config option.
3567 serialnumber [BUGS=X86-32]
3570 Maximal number of shapers.
3572 show_msr= [x86] show boot-time MSR settings
3573 Format: { <integer> }
3574 Show boot-time (BIOS-initialized) MSR settings.
3575 The parameter means the number of CPUs to show,
3576 for example 1 means boot CPU only.
3584 Disable merging of slabs with similar size. May be
3585 necessary if there is some reason to distinguish
3586 allocs to different slabs. Debug options disable
3587 merging on their own.
3588 For more information see Documentation/vm/slub.txt.
3590 slab_max_order= [MM, SLAB]
3591 Determines the maximum allowed order for slabs.
3592 A high setting may cause OOMs due to memory
3593 fragmentation. Defaults to 1 for systems with
3594 more than 32MB of RAM, 0 otherwise.
3596 slub_debug[=options[,slabs]] [MM, SLUB]
3597 Enabling slub_debug allows one to determine the
3598 culprit if slab objects become corrupted. Enabling
3599 slub_debug can create guard zones around objects and
3600 may poison objects when not in use. Also tracks the
3601 last alloc / free. For more information see
3602 Documentation/vm/slub.txt.
3604 slub_max_order= [MM, SLUB]
3605 Determines the maximum allowed order for slabs.
3606 A high setting may cause OOMs due to memory
3607 fragmentation. For more information see
3608 Documentation/vm/slub.txt.
3610 slub_min_objects= [MM, SLUB]
3611 The minimum number of objects per slab. SLUB will
3612 increase the slab order up to slub_max_order to
3613 generate a sufficiently large slab able to contain
3614 the number of objects indicated. The higher the number
3615 of objects the smaller the overhead of tracking slabs
3616 and the less frequently locks need to be acquired.
3617 For more information see Documentation/vm/slub.txt.
3619 slub_min_order= [MM, SLUB]
3620 Determines the minimum page order for slabs. Must be
3621 lower than slub_max_order.
3622 For more information see Documentation/vm/slub.txt.
3624 slub_nomerge [MM, SLUB]
3625 Same with slab_nomerge. This is supported for legacy.
3626 See slab_nomerge for more information.
3629 Format: <io1>[,<io2>[,...,<io8>]]
3631 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3632 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3633 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3634 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3635 smsc-ircc2.ircc_irq= [HW] IRQ line
3636 smsc-ircc2.ircc_dma= [HW] DMA channel
3637 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3638 0: Toshiba Satellite 1800 (GP data pin select)
3639 1: Fast pin select (default)
3643 [KNL] Should the soft-lockup detector generate panics.
3646 softlockup_all_cpu_backtrace=
3647 [KNL] Should the soft-lockup detector generate
3648 backtraces on all cpus.
3651 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3652 See Documentation/laptops/sonypi.txt
3654 spia_io_base= [HW,MTD]
3660 Enabled the stack tracer on boot up.
3662 stacktrace_filter=[function-list]
3663 [FTRACE] Limit the functions that the stack tracer
3664 will trace at boot up. function-list is a comma separated
3665 list of functions. This list can be changed at run
3666 time by the stack_trace_filter file in the debugfs
3667 tracing directory. Note, this enables stack tracing
3668 and the stacktrace above is not needed.
3672 Set the STI (builtin display/keyboard on the HP-PARISC
3673 machines) console (graphic card) which should be used
3674 as the initial boot-console.
3675 See also comment in drivers/video/console/sticore.c.
3678 See comment in drivers/video/console/sticore.c.
3681 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3683 sunrpc.min_resvport=
3684 sunrpc.max_resvport=
3686 SunRPC servers often require that client requests
3687 originate from a privileged port (i.e. a port in the
3688 range 0 < portnr < 1024).
3689 An administrator who wishes to reserve some of these
3690 ports for other uses may adjust the range that the
3691 kernel's sunrpc client considers to be privileged
3692 using these two parameters to set the minimum and
3693 maximum port values.
3697 Control how the NFS server code allocates CPUs to
3698 service thread pools. Depending on how many NICs
3699 you have and where their interrupts are bound, this
3700 option will affect which CPUs will do NFS serving.
3701 Note: this parameter cannot be changed while the
3702 NFS server is running.
3704 auto the server chooses an appropriate mode
3705 automatically using heuristics
3706 global a single global pool contains all CPUs
3707 percpu one pool for each CPU
3708 pernode one pool for each NUMA node (equivalent
3709 to global on non-NUMA machines)
3711 sunrpc.tcp_slot_table_entries=
3712 sunrpc.udp_slot_table_entries=
3714 Sets the upper limit on the number of simultaneous
3715 RPC calls that can be sent from the client to a
3716 server. Increasing these values may allow you to
3717 improve throughput, but will also increase the
3718 amount of memory reserved for use by the client.
3720 suspend.pm_test_delay=
3722 Sets the number of seconds to remain in a suspend test
3723 mode before resuming the system (see
3724 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3725 is set. Default value is 5.
3728 [KNL] Enable accounting of swap in memory resource
3729 controller if no parameter or 1 is given or disable
3730 it if 0 is given (See Documentation/cgroups/memory.txt)
3732 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3733 Format: { <int> | force }
3734 <int> -- Number of I/O TLB slabs
3735 force -- force using of bounce buffers even if they
3736 wouldn't be automatically used by the kernel
3740 sysfs.deprecated=0|1 [KNL]
3741 Enable/disable old style sysfs layout for old udev
3742 on older distributions. When this option is enabled
3743 very new udev will not work anymore. When this option
3744 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3745 in older udev will not work anymore.
3746 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3747 the kernel configuration.
3749 sysrq_always_enabled
3751 Ignore sysrq setting - this boot parameter will
3752 neutralize any effect of /proc/sys/kernel/sysrq.
3753 Useful for debugging.
3755 tcpmhash_entries= [KNL,NET]
3756 Set the number of tcp_metrics_hash slots.
3757 Default value is 8192 or 16384 depending on total
3758 ram pages. This is used to specify the TCP metrics
3759 cache size. See Documentation/networking/ip-sysctl.txt
3760 "tcp_no_metrics_save" section for more details.
3764 test_suspend= [SUSPEND][,N]
3765 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3766 standby suspend) or "freeze" (for suspend type freeze)
3767 as the system sleep state during system startup with
3768 the optional capability to repeat N number of times.
3769 The system is woken from this state using a
3770 wakeup-capable RTC alarm.
3772 thash_entries= [KNL,NET]
3773 Set number of hash buckets for TCP connection
3775 thermal.act= [HW,ACPI]
3776 -1: disable all active trip points in all thermal zones
3777 <degrees C>: override all lowest active trip points
3779 thermal.crt= [HW,ACPI]
3780 -1: disable all critical trip points in all thermal zones
3781 <degrees C>: override all critical trip points
3783 thermal.nocrt= [HW,ACPI]
3784 Set to disable actions on ACPI thermal zone
3785 critical and hot trip points.
3787 thermal.off= [HW,ACPI]
3788 1: disable ACPI thermal control
3790 thermal.psv= [HW,ACPI]
3791 -1: disable all passive trip points
3792 <degrees C>: override all passive trip points to this
3795 thermal.tzp= [HW,ACPI]
3796 Specify global default ACPI thermal zone polling rate
3797 <deci-seconds>: poll all this frequency
3798 0: no polling (default)
3801 Force threading of all interrupt handlers except those
3802 marked explicitly IRQF_NO_THREAD.
3805 Enable the Transcendent memory driver if built-in.
3807 tmem.cleancache=0|1 [KNL, XEN]
3808 Default is on (1). Disable the usage of the cleancache
3809 API to send anonymous pages to the hypervisor.
3811 tmem.frontswap=0|1 [KNL, XEN]
3812 Default is on (1). Disable the usage of the frontswap
3813 API to send swap pages to the hypervisor. If disabled
3814 the selfballooning and selfshrinking are force disabled.
3816 tmem.selfballooning=0|1 [KNL, XEN]
3817 Default is on (1). Disable the driving of swap pages
3820 tmem.selfshrinking=0|1 [KNL, XEN]
3821 Default is on (1). Partial swapoff that immediately
3822 transfers pages from Xen hypervisor back to the
3823 kernel based on different criteria.
3827 Specify if the kernel should make use of the cpu
3828 topology information if the hardware supports this.
3829 The scheduler will make use of this information and
3830 e.g. base its process migration decisions on it.
3833 topology_updates= [KNL, PPC, NUMA]
3835 Specify if the kernel should ignore (off)
3836 topology updates sent by the hypervisor to this
3841 tpm_suspend_pcr=[HW,TPM]
3842 Format: integer pcr id
3843 Specify that at suspend time, the tpm driver
3844 should extend the specified pcr with zeros,
3845 as a workaround for some chips which fail to
3846 flush the last written pcr on TPM_SaveState.
3847 This will guarantee that all the other pcrs
3850 trace_buf_size=nn[KMG]
3851 [FTRACE] will set tracing buffer size on each cpu.
3853 trace_event=[event-list]
3854 [FTRACE] Set and start specified trace events in order
3855 to facilitate early boot debugging.
3856 See also Documentation/trace/events.txt
3858 trace_options=[option-list]
3859 [FTRACE] Enable or disable tracer options at boot.
3860 The option-list is a comma delimited list of options
3861 that can be enabled or disabled just as if you were
3862 to echo the option name into
3864 /sys/kernel/debug/tracing/trace_options
3866 For example, to enable stacktrace option (to dump the
3867 stack trace of each event), add to the command line:
3869 trace_options=stacktrace
3871 See also Documentation/trace/ftrace.txt "trace options"
3875 Have the tracepoints sent to printk as well as the
3876 tracing ring buffer. This is useful for early boot up
3877 where the system hangs or reboots and does not give the
3878 option for reading the tracing buffer or performing a
3879 ftrace_dump_on_oops.
3881 To turn off having tracepoints sent to printk,
3882 echo 0 > /proc/sys/kernel/tracepoint_printk
3883 Note, echoing 1 into this file without the
3884 tracepoint_printk kernel cmdline option has no effect.
3888 Having tracepoints sent to printk() and activating high
3889 frequency tracepoints such as irq or sched, can cause
3890 the system to live lock.
3893 [FTRACE] enable this option to disable tracing when a
3894 warning is hit. This turns off "tracing_on". Tracing can
3895 be enabled again by echoing '1' into the "tracing_on"
3896 file located in /sys/kernel/debug/tracing/
3898 This option is useful, as it disables the trace before
3899 the WARNING dump is called, which prevents the trace to
3900 be filled with content caused by the warning output.
3902 This option can also be set at run time via the sysctl
3903 option: kernel/traceoff_on_warning
3905 transparent_hugepage=
3907 Format: [always|madvise|never]
3908 Can be used to control the default behavior of the system
3909 with respect to transparent hugepages.
3910 See Documentation/vm/transhuge.txt for more details.
3912 tsc= Disable clocksource stability checks for TSC.
3914 [x86] reliable: mark tsc clocksource as reliable, this
3915 disables clocksource verification at runtime, as well
3916 as the stability checks done at bootup. Used to enable
3917 high-resolution timer mode on older hardware, and in
3918 virtualized environment.
3919 [x86] noirqtime: Do not use TSC to do irq accounting.
3920 Used to run time disable IRQ_TIME_ACCOUNTING on any
3921 platforms where RDTSC is slow and this accounting
3924 turbografx.map[2|3]= [HW,JOY]
3925 TurboGraFX parallel port interface
3927 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3928 See also Documentation/input/joystick-parport.txt
3930 udbg-immortal [PPC] When debugging early kernel crashes that
3931 happen after console_init() and before a proper
3932 console driver takes over, this boot options might
3933 help "seeing" what's going on.
3935 uhash_entries= [KNL,NET]
3936 Set number of hash buckets for UDP/UDP-Lite connections
3939 [USB] Ignore overcurrent events (default N).
3940 Some badly-designed motherboards generate lots of
3941 bogus events, for ports that aren't wired to
3942 anything. Set this parameter to avoid log spamming.
3943 Note that genuine overcurrent events won't be
3947 [X86] Cause panic on unknown NMI.
3949 usbcore.authorized_default=
3950 [USB] Default USB device authorization:
3951 (default -1 = authorized except for wireless USB,
3952 0 = not authorized, 1 = authorized)
3954 usbcore.autosuspend=
3955 [USB] The autosuspend time delay (in seconds) used
3956 for newly-detected USB devices (default 2). This
3957 is the time required before an idle device will be
3958 autosuspended. Devices for which the delay is set
3959 to a negative value won't be autosuspended at all.
3961 usbcore.usbfs_snoop=
3962 [USB] Set to log all usbfs traffic (default 0 = off).
3964 usbcore.usbfs_snoop_max=
3965 [USB] Maximum number of bytes to snoop in each URB
3968 usbcore.blinkenlights=
3969 [USB] Set to cycle leds on hubs (default 0 = off).
3971 usbcore.old_scheme_first=
3972 [USB] Start with the old device initialization
3973 scheme (default 0 = off).
3975 usbcore.usbfs_memory_mb=
3976 [USB] Memory limit (in MB) for buffers allocated by
3977 usbfs (default = 16, 0 = max = 2047).
3979 usbcore.use_both_schemes=
3980 [USB] Try the other device initialization scheme
3981 if the first one fails (default 1 = enabled).
3983 usbcore.initial_descriptor_timeout=
3984 [USB] Specifies timeout for the initial 64-byte
3985 USB_REQ_GET_DESCRIPTOR request in milliseconds
3986 (default 5000 = 5.0 seconds).
3988 usbcore.nousb [USB] Disable the USB subsystem
3991 [USBHID] The interval which mice are to be polled at.
3993 usb-storage.delay_use=
3994 [UMS] The delay in seconds before a new device is
3995 scanned for Logical Units (default 1).
3998 [UMS] A list of quirks entries to supplement or
3999 override the built-in unusual_devs list. List
4000 entries are separated by commas. Each entry has
4001 the form VID:PID:Flags where VID and PID are Vendor
4002 and Product ID values (4-digit hex numbers) and
4003 Flags is a set of characters, each corresponding
4004 to a common usb-storage quirk flag as follows:
4005 a = SANE_SENSE (collect more than 18 bytes
4007 b = BAD_SENSE (don't collect more than 18
4008 bytes of sense data);
4009 c = FIX_CAPACITY (decrease the reported
4010 device capacity by one sector);
4011 d = NO_READ_DISC_INFO (don't use
4012 READ_DISC_INFO command);
4013 e = NO_READ_CAPACITY_16 (don't use
4014 READ_CAPACITY_16 command);
4015 f = NO_REPORT_OPCODES (don't use report opcodes
4017 g = MAX_SECTORS_240 (don't transfer more than
4018 240 sectors at a time, uas only);
4019 h = CAPACITY_HEURISTICS (decrease the
4020 reported device capacity by one
4021 sector if the number is odd);
4022 i = IGNORE_DEVICE (don't bind to this
4024 l = NOT_LOCKABLE (don't try to lock and
4025 unlock ejectable media);
4026 m = MAX_SECTORS_64 (don't transfer more
4027 than 64 sectors = 32 KB at a time);
4028 n = INITIAL_READ10 (force a retry of the
4029 initial READ(10) command);
4030 o = CAPACITY_OK (accept the capacity
4031 reported by the device);
4032 p = WRITE_CACHE (the device cache is ON
4034 r = IGNORE_RESIDUE (the device reports
4035 bogus residue values);
4036 s = SINGLE_LUN (the device has only one
4038 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4039 commands, uas only);
4040 u = IGNORE_UAS (don't bind to the uas driver);
4041 w = NO_WP_DETECT (don't test whether the
4042 medium is write-protected).
4043 Example: quirks=0419:aaf5:rl,0421:0433:rc
4045 user_debug= [KNL,ARM]
4047 See arch/arm/Kconfig.debug help text.
4048 1 - undefined instruction events
4050 4 - invalid data aborts
4053 Example: user_debug=31
4056 [X86] Flags controlling user PTE allocations.
4058 nohigh = do not allocate PTE pages in
4059 HIGHMEM regardless of setting
4063 On X86_32, this is an alias for vdso32=. Otherwise:
4065 vdso=1: enable VDSO (the default)
4066 vdso=0: disable VDSO mapping
4068 vdso32= [X86] Control the 32-bit vDSO
4069 vdso32=1: enable 32-bit VDSO
4070 vdso32=0 or vdso32=2: disable 32-bit VDSO
4072 See the help text for CONFIG_COMPAT_VDSO for more
4073 details. If CONFIG_COMPAT_VDSO is set, the default is
4074 vdso32=0; otherwise, the default is vdso32=1.
4076 For compatibility with older kernels, vdso32=2 is an
4079 Try vdso32=0 if you encounter an error that says:
4080 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4083 vector=percpu: enable percpu vector domain
4085 video= [FB] Frame buffer configuration
4086 See Documentation/fb/modedb.txt.
4088 video.brightness_switch_enabled= [0,1]
4089 If set to 1, on receiving an ACPI notify event
4090 generated by hotkey, video driver will adjust brightness
4091 level and then send out the event to user space through
4092 the allocated input device; If set to 0, video driver
4093 will only send out the event without touching backlight
4098 [VMMIO] Memory mapped virtio (platform) device.
4100 <size>@<baseaddr>:<irq>[:<id>]
4102 <size> := size (can use standard suffixes
4104 <baseaddr> := physical base address
4105 <irq> := interrupt number (as passed to
4107 <id> := (optional) platform device id
4109 virtio_mmio.device=1K@0x100b0000:48:7
4111 Can be used multiple times for multiple devices.
4113 vga= [BOOT,X86-32] Select a particular video mode
4114 See Documentation/x86/boot.txt and
4115 Documentation/svga.txt.
4116 Use vga=ask for menu.
4117 This is actually a boot loader parameter; the value is
4118 passed to the kernel using a special protocol.
4120 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4121 size of <nn>. This can be used to increase the
4122 minimum size (128MB on x86). It can also be used to
4123 decrease the size and leave more room for directly
4126 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4129 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4132 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4136 Controls the behavior of vsyscalls (i.e. calls to
4137 fixed addresses of 0xffffffffff600x00 from legacy
4138 code). Most statically-linked binaries and older
4139 versions of glibc use these calls. Because these
4140 functions are at fixed addresses, they make nice
4141 targets for exploits that can control RIP.
4143 emulate [default] Vsyscalls turn into traps and are
4144 emulated reasonably safely.
4146 native Vsyscalls are native syscall instructions.
4147 This is a little bit faster than trapping
4148 and makes a few dynamic recompilers work
4149 better than they would in emulation mode.
4150 It also makes exploits much easier to write.
4152 none Vsyscalls don't work at all. This makes
4153 them quite hard to use for exploits but
4154 might break your system.
4156 vt.color= [VT] Default text color.
4157 Format: 0xYX, X = foreground, Y = background.
4158 Default: 0x07 = light gray on black.
4160 vt.cur_default= [VT] Default cursor shape.
4161 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4162 the parameters of the <Esc>[?A;B;Cc escape sequence;
4163 see VGA-softcursor.txt. Default: 2 = underline.
4165 vt.default_blu= [VT]
4166 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4167 Change the default blue palette of the console.
4168 This is a 16-member array composed of values
4171 vt.default_grn= [VT]
4172 Format: <green0>,<green1>,<green2>,...,<green15>
4173 Change the default green palette of the console.
4174 This is a 16-member array composed of values
4177 vt.default_red= [VT]
4178 Format: <red0>,<red1>,<red2>,...,<red15>
4179 Change the default red palette of the console.
4180 This is a 16-member array composed of values
4186 Set system-wide default UTF-8 mode for all tty's.
4187 Default is 1, i.e. UTF-8 mode is enabled for all
4188 newly opened terminals.
4190 vt.global_cursor_default=
4193 Set system-wide default for whether a cursor
4194 is shown on new VTs. Default is -1,
4195 i.e. cursors will be created by default unless
4196 overridden by individual drivers. 0 will hide
4197 cursors, 1 will display them.
4199 vt.italic= [VT] Default color for italic text; 0-15.
4202 vt.underline= [VT] Default color for underlined text; 0-15.
4205 watchdog timers [HW,WDT] For information on watchdog timers,
4206 see Documentation/watchdog/watchdog-parameters.txt
4207 or other driver-specific files in the
4208 Documentation/watchdog/ directory.
4210 workqueue.watchdog_thresh=
4211 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4212 warn stall conditions and dump internal state to
4213 help debugging. 0 disables workqueue stall
4214 detection; otherwise, it's the stall threshold
4215 duration in seconds. The default value is 30 and
4216 it can be updated at runtime by writing to the
4217 corresponding sysfs file.
4219 workqueue.disable_numa
4220 By default, all work items queued to unbound
4221 workqueues are affine to the NUMA nodes they're
4222 issued on, which results in better behavior in
4223 general. If NUMA affinity needs to be disabled for
4224 whatever reason, this option can be used. Note
4225 that this also can be controlled per-workqueue for
4226 workqueues visible under /sys/bus/workqueue/.
4228 workqueue.power_efficient
4229 Per-cpu workqueues are generally preferred because
4230 they show better performance thanks to cache
4231 locality; unfortunately, per-cpu workqueues tend to
4232 be more power hungry than unbound workqueues.
4234 Enabling this makes the per-cpu workqueues which
4235 were observed to contribute significantly to power
4236 consumption unbound, leading to measurably lower
4237 power usage at the cost of small performance
4240 The default value of this parameter is determined by
4241 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4243 workqueue.debug_force_rr_cpu
4244 Workqueue used to implicitly guarantee that work
4245 items queued without explicit CPU specified are put
4246 on the local CPU. This guarantee is no longer true
4247 and while local CPU is still preferred work items
4248 may be put on foreign CPUs. This debug option
4249 forces round-robin CPU selection to flush out
4250 usages which depend on the now broken guarantee.
4251 When enabled, memory and cache locality will be
4254 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4255 default x2apic cluster mode on platforms
4258 x86_intel_mid_timer= [X86-32,APBT]
4259 Choose timer option for x86 Intel MID platform.
4260 Two valid options are apbt timer only and lapic timer
4261 plus one apbt timer for broadcast timer.
4262 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4264 xen_512gb_limit [KNL,X86-64,XEN]
4265 Restricts the kernel running paravirtualized under Xen
4266 to use only up to 512 GB of RAM. The reason to do so is
4267 crash analysis tools and Xen tools for doing domain
4268 save/restore/migration must be enabled to handle larger
4271 xen_emul_unplug= [HW,X86,XEN]
4272 Unplug Xen emulated devices
4273 Format: [unplug0,][unplug1]
4274 ide-disks -- unplug primary master IDE devices
4275 aux-ide-disks -- unplug non-primary-master IDE devices
4276 nics -- unplug network devices
4277 all -- unplug all emulated devices (NICs and IDE disks)
4278 unnecessary -- unplugging emulated devices is
4279 unnecessary even if the host did not respond to
4281 never -- do not unplug even if version check succeeds
4283 xen_nopvspin [X86,XEN]
4284 Disables the ticketlock slowpath using Xen PV
4288 Disables the PV optimizations forcing the HVM guest to
4289 run as generic HVM guest with no PV drivers.
4291 xirc2ps_cs= [NET,PCMCIA]
4293 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4295 ______________________________________________________________________
4299 Add more DRM drivers.
projects / cascardo / linux.git / blob