4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpi_force_32bit_fadt_addr
197 force FADT to use 32 bit addresses rather than the
198 64 bit X_* addresses. Some firmware have broken 64
199 bit addresses for force ACPI ignore these and use
200 the older legacy 32 bit addresses.
202 acpica_no_return_repair [HW, ACPI]
203 Disable AML predefined validation mechanism
204 This mechanism can repair the evaluation result to make
205 the return objects more ACPI specification compliant.
206 This option is useful for developers to identify the
207 root cause of an AML interpreter issue when the issue
208 has something to do with the repair mechanism.
210 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
211 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
213 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
214 debug output. Bits in debug_layer correspond to a
215 _COMPONENT in an ACPI source file, e.g.,
216 #define _COMPONENT ACPI_PCI_COMPONENT
217 Bits in debug_level correspond to a level in
218 ACPI_DEBUG_PRINT statements, e.g.,
219 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
220 The debug_level mask defaults to "info". See
221 Documentation/acpi/debug.txt for more information about
222 debug layers and levels.
224 Enable processor driver info messages:
225 acpi.debug_layer=0x20000000
226 Enable PCI/PCI interrupt routing info messages:
227 acpi.debug_layer=0x400000
228 Enable AML "Debug" output, i.e., stores to the Debug
229 object while interpreting AML:
230 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
231 Enable all messages related to ACPI hardware:
232 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
234 Some values produce so much output that the system is
235 unusable. The "log_buf_len" parameter may be useful
236 if you need to capture more output.
238 acpi_enforce_resources= [ACPI]
239 { strict | lax | no }
240 Check for resource conflicts between native drivers
241 and ACPI OperationRegions (SystemIO and SystemMemory
242 only). IO ports and memory declared in ACPI might be
243 used by the ACPI subsystem in arbitrary AML code and
244 can interfere with legacy drivers.
245 strict (default): access to resources claimed by ACPI
246 is denied; legacy drivers trying to access reserved
247 resources will fail to bind to device using them.
248 lax: access to resources claimed by ACPI is allowed;
249 legacy drivers trying to access reserved resources
250 will bind successfully but a warning message is logged.
251 no: ACPI OperationRegions are not marked as reserved,
252 no further checks are performed.
254 acpi_force_table_verification [HW,ACPI]
255 Enable table checksum verification during early stage.
256 By default, this is disabled due to x86 early mapping
259 acpi_irq_balance [HW,ACPI]
260 ACPI will balance active IRQs
263 acpi_irq_nobalance [HW,ACPI]
264 ACPI will not move active IRQs (default)
267 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
268 Format: <irq>,<irq>...
270 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
272 Format: <irq>,<irq>...
274 acpi_no_auto_serialize [HW,ACPI]
275 Disable auto-serialization of AML methods
276 AML control methods that contain the opcodes to create
277 named objects will be marked as "Serialized" by the
278 auto-serialization feature.
279 This feature is enabled by default.
280 This option allows to turn off the feature.
282 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
285 acpi_no_static_ssdt [HW,ACPI]
286 Disable installation of static SSDTs at early boot time
287 By default, SSDTs contained in the RSDT/XSDT will be
288 installed automatically and they will appear under
289 /sys/firmware/acpi/tables.
290 This option turns off this feature.
291 Note that specifying this option does not affect
292 dynamic table installation which will install SSDT
293 tables to /sys/firmware/acpi/tables/dynamic.
295 acpi_rsdp= [ACPI,EFI,KEXEC]
296 Pass the RSDP address to the kernel, mostly used
297 on machines running EFI runtime service to boot the
298 second kernel for kdump.
300 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
301 Format: To spoof as Windows 98: ="Microsoft Windows"
303 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
304 of 2 which is mandated by ACPI 6) as the supported ACPI
305 specification revision (when using this switch, it may
306 be necessary to carry out a cold reboot _twice_ in a
307 row to make it take effect on the platform firmware).
309 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
310 acpi_osi="string1" # add string1
311 acpi_osi="!string2" # remove string2
312 acpi_osi=!* # remove all strings
313 acpi_osi=! # disable all built-in OS vendor
315 acpi_osi= # disable all strings
317 'acpi_osi=!' can be used in combination with single or
318 multiple 'acpi_osi="string1"' to support specific OS
319 vendor string(s). Note that such command can only
320 affect the default state of the OS vendor strings, thus
321 it cannot affect the default state of the feature group
322 strings and the current state of the OS vendor strings,
323 specifying it multiple times through kernel command line
324 is meaningless. This command is useful when one do not
325 care about the state of the feature group strings which
326 should be controlled by the OSPM.
328 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
329 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
330 can make '_OSI("Windows 2000")' TRUE.
332 'acpi_osi=' cannot be used in combination with other
333 'acpi_osi=' command lines, the _OSI method will not
334 exist in the ACPI namespace. NOTE that such command can
335 only affect the _OSI support state, thus specifying it
336 multiple times through kernel command line is also
339 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
342 'acpi_osi=!*' can be used in combination with single or
343 multiple 'acpi_osi="string1"' to support specific
344 string(s). Note that such command can affect the
345 current state of both the OS vendor strings and the
346 feature group strings, thus specifying it multiple times
347 through kernel command line is meaningful. But it may
348 still not able to affect the final state of a string if
349 there are quirks related to this string. This command
350 is useful when one want to control the state of the
351 feature group strings to debug BIOS issues related to
354 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
355 '_OSI("Module Device")' FALSE.
356 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
357 '_OSI("Module Device")' TRUE.
358 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
360 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
362 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
363 they all will make '_OSI("Windows 2000")' TRUE.
366 Override the pmtimer bug detection: force the kernel
367 to assume that this machine's pmtimer latches its value
368 and always returns good values.
370 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
371 Format: { level | edge | high | low }
373 acpi_skip_timer_override [HW,ACPI]
374 Recognize and ignore IRQ0/pin2 Interrupt Override.
375 For broken nForce2 BIOS resulting in XT-PIC timer.
377 acpi_sleep= [HW,ACPI] Sleep options
378 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
379 old_ordering, nonvs, sci_force_enable }
380 See Documentation/power/video.txt for information on
382 s3_beep is for debugging; it makes the PC's speaker beep
383 as soon as the kernel's real-mode entry point is called.
384 s4_nohwsig prevents ACPI hardware signature from being
385 used during resume from hibernation.
386 old_ordering causes the ACPI 1.0 ordering of the _PTS
387 control method, with respect to putting devices into
388 low power states, to be enforced (the ACPI 2.0 ordering
389 of _PTS is used by default).
390 nonvs prevents the kernel from saving/restoring the
391 ACPI NVS memory during suspend/hibernation and resume.
392 sci_force_enable causes the kernel to set SCI_EN directly
393 on resume from S1/S3 (which is against the ACPI spec,
394 but some broken systems don't work without it).
396 acpi_use_timer_override [HW,ACPI]
397 Use timer override. For some broken Nvidia NF5 boards
398 that require a timer override, but don't have HPET
400 add_efi_memmap [EFI; X86] Include EFI memory map in
401 kernel's map of available physical RAM.
404 { off | try_unsupported }
405 off: disable AGP support
406 try_unsupported: try to drive unsupported chipsets
407 (may crash computer or cause data corruption)
410 See Documentation/sound/alsa/alsa-parameters.txt
413 Allow the default userspace alignment fault handler
414 behaviour to be specified. Bit 0 enables warnings,
415 bit 1 enables fixups, and bit 2 sends a segfault.
417 align_va_addr= [X86-64]
418 Align virtual addresses by clearing slice [14:12] when
419 allocating a VMA at process creation time. This option
420 gives you up to 3% performance improvement on AMD F15h
421 machines (where it is enabled by default) for a
422 CPU-intensive style benchmark, and it can vary highly in
423 a microbenchmark depending on workload and compiler.
425 32: only for 32-bit processes
426 64: only for 64-bit processes
427 on: enable for both 32- and 64-bit processes
428 off: disable for both 32- and 64-bit processes
430 alloc_snapshot [FTRACE]
431 Allocate the ftrace snapshot buffer on boot up when the
432 main buffer is allocated. This is handy if debugging
433 and you need to use tracing_snapshot() on boot up, and
434 do not want to use tracing_snapshot_alloc() as it needs
435 to be done where GFP_KERNEL allocations are allowed.
437 amd_iommu= [HW,X86-64]
438 Pass parameters to the AMD IOMMU driver in the system.
440 fullflush - enable flushing of IO/TLB entries when
441 they are unmapped. Otherwise they are
442 flushed before they will be reused, which
444 off - do not initialize any AMD IOMMU found in
446 force_isolation - Force device isolation for all
447 devices. The IOMMU driver is not
448 allowed anymore to lift isolation
449 requirements as needed. This option
450 does not override iommu=pt
452 amd_iommu_dump= [HW,X86-64]
453 Enable AMD IOMMU driver option to dump the ACPI table
454 for AMD IOMMU. With this option enabled, AMD IOMMU
455 driver will print ACPI tables for AMD IOMMU during
456 IOMMU initialization.
458 amijoy.map= [HW,JOY] Amiga joystick support
459 Map of devices attached to JOY0DAT and JOY1DAT
461 See also Documentation/input/joystick.txt
463 analog.map= [HW,JOY] Analog joystick and gamepad support
464 Specifies type or capabilities of an analog joystick
465 connected to one of 16 gameports
466 Format: <type1>,<type2>,..<type16>
469 Power management functions (SPARCstation-4/5 + deriv.)
471 Disable APC CPU standby support. SPARCstation-Fox does
472 not play well with APC CPU idle - disable it if you have
473 APC and your system crashes randomly.
475 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
476 Change the output verbosity whilst booting
477 Format: { quiet (default) | verbose | debug }
478 Change the amount of debugging information output
479 when initialising the APIC and IO-APIC components.
481 apic_extnmi= [APIC,X86] External NMI delivery setting
482 Format: { bsp (default) | all | none }
483 bsp: External NMI is delivered only to CPU 0
484 all: External NMIs are broadcast to all CPUs as a
486 none: External NMI is masked for all CPUs. This is
487 useful so that a dump capture kernel won't be
491 See Documentation/networking/ipv6.txt.
493 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
494 Limit apic dumping. The parameter defines the maximal
495 number of local apics being dumped. Also it is possible
496 to set it to "all" by meaning -- no limit here.
497 Format: { 1 (default) | 2 | ... | all }.
498 The parameter valid if only apic=debug or
499 apic=verbose is specified.
500 Example: apic=debug show_lapic=all
502 apm= [APM] Advanced Power Management
503 See header of arch/x86/kernel/apm_32.c.
505 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
506 Format: <io>,<irq>,<nodeID>
510 atarimouse= [HW,MOUSE] Atari Mouse
512 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
513 EzKey and similar keyboards
515 atkbd.reset= [HW] Reset keyboard during initialization
517 atkbd.set= [HW] Select keyboard code set
518 Format: <int> (2 = AT (default), 3 = PS/2)
520 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
523 atkbd.softraw= [HW] Choose between synthetic and real raw mode
524 Format: <bool> (0 = real, 1 = synthetic (default))
526 atkbd.softrepeat= [HW]
527 Use software keyboard repeat
529 audit= [KNL] Enable the audit sub-system
530 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
531 0 - kernel audit is disabled and can not be enabled
532 until the next reboot
533 unset - kernel audit is initialized but disabled and
534 will be fully enabled by the userspace auditd.
535 1 - kernel audit is initialized and partially enabled,
536 storing at most audit_backlog_limit messages in
537 RAM until it is fully enabled by the userspace
541 audit_backlog_limit= [KNL] Set the audit queue size limit.
542 Format: <int> (must be >=0)
545 baycom_epp= [HW,AX25]
548 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
550 See header of drivers/net/hamradio/baycom_par.c.
552 baycom_ser_fdx= [HW,AX25]
553 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
554 Format: <io>,<irq>,<mode>[,<baud>]
555 See header of drivers/net/hamradio/baycom_ser_fdx.c.
557 baycom_ser_hdx= [HW,AX25]
558 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
559 Format: <io>,<irq>,<mode>
560 See header of drivers/net/hamradio/baycom_ser_hdx.c.
562 blkdevparts= Manual partition parsing of block device(s) for
563 embedded devices based on command line input.
564 See Documentation/block/cmdline-partition.txt
566 boot_delay= Milliseconds to delay each printk during boot.
567 Values larger than 10 seconds (10000) are changed to
571 bootmem_debug [KNL] Enable bootmem allocator debug messages.
573 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
574 bttv.radio= Most important insmod options are available as
576 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
579 bulk_remove=off [PPC] This parameter disables the use of the pSeries
580 firmware feature for flushing multiple hpte entries
583 c101= [NET] Moxa C101 synchronous serial card
585 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
586 Sometimes CPU hardware bugs make them report the cache
587 size incorrectly. The kernel will attempt work arounds
588 to fix known problems, but for some CPUs it is not
589 possible to determine what the correct size should be.
590 This option provides an override for these situations.
592 ca_keys= [KEYS] This parameter identifies a specific key(s) on
593 the system trusted keyring to be used for certificate
595 format: { id:<keyid> | builtin }
597 cca= [MIPS] Override the kernel pages' cache coherency
598 algorithm. Accepted values range from 0 to 7
599 inclusive. See arch/mips/include/asm/pgtable-bits.h
600 for platform specific values (SB1, Loongson3 and
603 ccw_timeout_log [S390]
604 See Documentation/s390/CommonIO for details.
606 cgroup_disable= [KNL] Disable a particular controller
607 Format: {name of the controller(s) to disable}
608 The effects of cgroup_disable=foo are:
609 - foo isn't auto-mounted if you mount all cgroups in
611 - foo isn't visible as an individually mountable
613 {Currently only "memory" controller deal with this and
614 cut the overhead, others just disable the usage. So
615 only cgroup_disable=memory is actually worthy}
617 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
619 nosocket -- Disable socket memory accounting.
620 nokmem -- Disable kernel memory accounting.
622 checkreqprot [SELINUX] Set initial checkreqprot flag value.
623 Format: { "0" | "1" }
624 See security/selinux/Kconfig help text.
625 0 -- check protection applied by kernel (includes
626 any implied execute protection).
627 1 -- check protection requested by application.
628 Default value is set via a kernel config option.
629 Value can be changed at runtime via
630 /selinux/checkreqprot.
633 See Documentation/s390/CommonIO for details.
636 Prevents the clock framework from automatically gating
637 clocks that have not been explicitly enabled by a Linux
638 device driver but are enabled in hardware at reset or
639 by the bootloader/firmware. Note that this does not
640 force such clocks to be always-on nor does it reserve
641 those clocks in any way. This parameter is useful for
642 debug and development, but should not be needed on a
643 platform with proper driver support. For more
644 information, see Documentation/clk.txt.
646 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
648 Forces specified clocksource (if available) to be used
649 when calculating gettimeofday(). If specified
650 clocksource is not available, it defaults to PIT.
651 Format: { pit | tsc | cyclone | pmtmr }
653 clocksource= Override the default clocksource
655 Override the default clocksource and use the clocksource
656 with the name specified.
657 Some clocksource names to choose from, depending on
659 [all] jiffies (this is the base, fallback clocksource)
661 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
662 pxa_timer,timer3,32k_counter,timer0_1
664 [X86-32] pit,hpet,tsc;
665 scx200_hrt on Geode; cyclone on IBM x440
673 clearcpuid=BITNUM [X86]
674 Disable CPUID feature X for the kernel. See
675 arch/x86/include/asm/cpufeatures.h for the valid bit
676 numbers. Note the Linux specific bits are not necessarily
677 stable over kernel options, but the vendor specific
679 Also note that user programs calling CPUID directly
680 or using the feature without checking anything
681 will still see it. This just prevents it from
682 being used by the kernel or shown in /proc/cpuinfo.
683 Also note the kernel might malfunction if you disable
686 cma=nn[MG]@[start[MG][-end[MG]]]
688 Sets the size of kernel global memory area for
689 contiguous memory allocations and optionally the
690 placement constraint by the physical address range of
691 memory allocations. A value of 0 disables CMA
692 altogether. For more information, see
693 include/linux/dma-contiguous.h
695 cmo_free_hint= [PPC] Format: { yes | no }
696 Specify whether pages are marked as being inactive
697 when they are freed. This is used in CMO environments
698 to determine OS memory pressure for page stealing by
702 coherent_pool=nn[KMG] [ARM,KNL]
703 Sets the size of memory pool for coherent, atomic dma
704 allocations, by default set to 256K.
706 code_bytes [X86] How many bytes of object code to print
711 com20020= [HW,NET] ARCnet - COM20020 chipset
713 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
715 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
719 ARCnet - COM90xx chipset (memory-mapped buffers)
720 Format: <io>[,<irq>[,<memstart>]]
722 condev= [HW,S390] console device
725 console= [KNL] Output console device and options.
727 tty<n> Use the virtual console device <n>.
731 Use the specified serial port. The options are of
732 the form "bbbbpnf", where "bbbb" is the baud rate,
733 "p" is parity ("n", "o", or "e"), "n" is number of
734 bits, and "f" is flow control ("r" for RTS or
735 omit it). Default is "9600n8".
737 See Documentation/serial-console.txt for more
739 Documentation/networking/netconsole.txt for an
742 uart[8250],io,<addr>[,options]
743 uart[8250],mmio,<addr>[,options]
744 uart[8250],mmio16,<addr>[,options]
745 uart[8250],mmio32,<addr>[,options]
746 uart[8250],0x<addr>[,options]
747 Start an early, polled-mode console on the 8250/16550
748 UART at the specified I/O port or MMIO address,
749 switching to the matching ttyS device later.
750 MMIO inter-register address stride is either 8-bit
751 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
752 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
753 to be equivalent to 'mmio'. 'options' are specified in
754 the same format described for ttyS above; if unspecified,
755 the h/w is not re-initialized.
757 hvc<n> Use the hypervisor console device <n>. This is for
758 both Xen and PowerPC hypervisors.
760 If the device connected to the port is not a TTY but a braille
761 device, prepend "brl," before the device type, for instance
763 For now, only VisioBraille is supported.
765 consoleblank= [KNL] The console blank (screen saver) timeout in
766 seconds. Defaults to 10*60 = 10mins. A value of 0
767 disables the blank timer.
770 [KNL] Change the default value for
771 /proc/<pid>/coredump_filter.
772 See also Documentation/filesystems/proc.txt.
774 cpuidle.off=1 [CPU_IDLE]
775 disable the cpuidle sub-system
778 [X86] Delay for N microsec between assert and de-assert
779 of APIC INIT to start processors. This delay occurs
780 on every CPU online, such as boot, and resume from suspend.
783 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
785 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
787 crashkernel=size[KMG][@offset[KMG]]
788 [KNL] Using kexec, Linux can switch to a 'crash kernel'
789 upon panic. This parameter reserves the physical
790 memory region [offset, offset + size] for that kernel
791 image. If '@offset' is omitted, then a suitable offset
792 is selected automatically. Check
793 Documentation/kdump/kdump.txt for further details.
795 crashkernel=range1:size1[,range2:size2,...][@offset]
796 [KNL] Same as above, but depends on the memory
797 in the running system. The syntax of range is
798 start-[end] where start and end are both
799 a memory unit (amount[KMG]). See also
800 Documentation/kdump/kdump.txt for an example.
802 crashkernel=size[KMG],high
803 [KNL, x86_64] range could be above 4G. Allow kernel
804 to allocate physical memory region from top, so could
805 be above 4G if system have more than 4G ram installed.
806 Otherwise memory region will be allocated below 4G, if
808 It will be ignored if crashkernel=X is specified.
809 crashkernel=size[KMG],low
810 [KNL, x86_64] range under 4G. When crashkernel=X,high
811 is passed, kernel could allocate physical memory region
812 above 4G, that cause second kernel crash on system
813 that require some amount of low memory, e.g. swiotlb
814 requires at least 64M+32K low memory, also enough extra
815 low memory is needed to make sure DMA buffers for 32-bit
816 devices won't run out. Kernel would try to allocate at
817 at least 256M below 4G automatically.
818 This one let user to specify own low range under 4G
819 for second kernel instead.
820 0: to disable low allocation.
821 It will be ignored when crashkernel=X,high is not used
822 or memory reserved is below 4G.
827 cs89x0_media= [HW,NET]
828 Format: { rj45 | aui | bnc }
831 See header of drivers/s390/block/dasd_devmap.c.
833 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
834 (one device per port)
835 Format: <port#>,<type>
836 See also Documentation/input/joystick-parport.txt
838 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
839 time. See Documentation/dynamic-debug-howto.txt for
840 details. Deprecated, see dyndbg.
842 debug [KNL] Enable kernel debugging (events log level).
845 [KNL] verbose self-tests
847 Print debugging info while doing the locking API
849 We default to 0 (no extra messages), setting it to
850 1 will print _a lot_ more information - normally
851 only useful to kernel developers.
853 debug_objects [KNL] Enable object debugging
856 [KNL] Disable object debugging
858 debug_guardpage_minorder=
859 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
860 parameter allows control of the order of pages that will
861 be intentionally kept free (and hence protected) by the
862 buddy allocator. Bigger value increase the probability
863 of catching random memory corruption, but reduce the
864 amount of memory for normal system use. The maximum
865 possible value is MAX_ORDER/2. Setting this parameter
866 to 1 or 2 should be enough to identify most random
867 memory corruption problems caused by bugs in kernel or
868 driver code when a CPU writes to (or reads from) a
869 random memory location. Note that there exists a class
870 of memory corruptions problems caused by buggy H/W or
871 F/W or by drivers badly programing DMA (basically when
872 memory is written at bus level and the CPU MMU is
873 bypassed) which are not detectable by
874 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
875 tracking down these problems.
878 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
879 parameter enables the feature at boot time. In
880 default, it is disabled. We can avoid allocating huge
881 chunk of memory for debug pagealloc if we don't enable
882 it at boot time and the system will work mostly same
883 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
884 on: enable the feature
886 debugpat [X86] Enable PAT debugging
888 decnet.addr= [HW,NET]
889 Format: <area>[,<node>]
890 See also Documentation/networking/decnet.txt.
893 [same as hugepagesz=] The size of the default
894 HugeTLB page size. This is the size represented by
895 the legacy /proc/ hugepages APIs, used for SHM, and
896 default size when mounting hugetlbfs filesystems.
897 Defaults to the default architecture's huge page size
901 Set number of hash buckets for dentry cache.
904 See Documentation/networking/ipv6.txt.
906 disable_cpu_apicid= [X86,APIC,SMP]
908 The number of initial APIC ID for the
909 corresponding CPU to be disabled at boot,
910 mostly used for the kdump 2nd kernel to
911 disable BSP to wake up multiple CPUs without
912 causing system reset or hang due to sending
915 disable_ddw [PPC/PSERIES]
916 Disable Dynamic DMA Window support. Use this if
917 to workaround buggy firmware.
920 See Documentation/networking/ipv6.txt.
922 disable_mtrr_cleanup [X86]
923 The kernel tries to adjust MTRR layout from continuous
924 to discrete, to make X server driver able to add WB
925 entry later. This parameter disables that.
927 disable_mtrr_trim [X86, Intel and AMD only]
928 By default the kernel will trim any uncacheable
929 memory out of your available memory pool based on
930 MTRR settings. This parameter disables that behavior,
931 possibly causing your machine to run very slowly.
933 disable_timer_pin_1 [X86]
934 Disable PIN 1 of APIC timer
935 Can be useful to work around chipset bugs.
937 dis_ucode_ldr [X86] Disable the microcode loader.
939 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
940 this option disables the debugging code at boot.
942 dma_debug_entries=<number>
943 This option allows to tune the number of preallocated
944 entries for DMA-API debugging code. One entry is
945 required per DMA-API allocation. Use this if the
946 DMA-API debugging code disables itself because the
947 architectural default is too low.
949 dma_debug_driver=<driver_name>
950 With this option the DMA-API debugging driver
951 filter feature can be enabled at boot time. Just
952 pass the driver to filter for as the parameter.
953 The filter can be disabled or changed to another
954 driver later using sysfs.
956 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
957 Broken monitors, graphic adapters, KVMs and EDIDless
958 panels may send no or incorrect EDID data sets.
959 This parameter allows to specify an EDID data sets
960 in the /lib/firmware directory that are used instead.
961 Generic built-in EDID data sets are used, if one of
962 edid/1024x768.bin, edid/1280x1024.bin,
963 edid/1680x1050.bin, or edid/1920x1080.bin is given
964 and no file with the same name exists. Details and
965 instructions how to build your own EDID data are
966 available in Documentation/EDID/HOWTO.txt. An EDID
967 data set will only be used for a particular connector,
968 if its name and a colon are prepended to the EDID
969 name. Each connector may use a unique EDID data
970 set by separating the files with a comma. An EDID
971 data set with no connector name will be used for
972 any connectors not explicitly specified.
976 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
977 module.dyndbg[="val"]
978 Enable debug messages at boot time. See
979 Documentation/dynamic-debug-howto.txt for details.
981 nompx [X86] Disables Intel Memory Protection Extensions.
982 See Documentation/x86/intel_mpx.txt for more
983 information about the feature.
986 on enable eager fpu restore
987 off disable eager fpu restore
988 auto selects the default scheme, which automatically
989 enables eagerfpu restore for xsaveopt.
991 module.async_probe [KNL]
992 Enable asynchronous probe on this module.
994 early_ioremap_debug [KNL]
995 Enable debug messages in early_ioremap support. This
996 is useful for tracking down temporary early mappings
997 which are not unmapped.
999 earlycon= [KNL] Output early console device and options.
1001 When used with no options, the early console is
1002 determined by the stdout-path property in device
1006 Start an early, polled-mode console on a cadence serial
1007 port at the specified address. The cadence serial port
1008 must already be setup and configured. Options are not
1011 uart[8250],io,<addr>[,options]
1012 uart[8250],mmio,<addr>[,options]
1013 uart[8250],mmio32,<addr>[,options]
1014 uart[8250],mmio32be,<addr>[,options]
1015 uart[8250],0x<addr>[,options]
1016 Start an early, polled-mode console on the 8250/16550
1017 UART at the specified I/O port or MMIO address.
1018 MMIO inter-register address stride is either 8-bit
1019 (mmio) or 32-bit (mmio32 or mmio32be).
1020 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1021 to be equivalent to 'mmio'. 'options' are specified
1022 in the same format described for "console=ttyS<n>"; if
1023 unspecified, the h/w is not initialized.
1027 Start an early, polled-mode console on a pl011 serial
1028 port at the specified address. The pl011 serial port
1029 must already be setup and configured. Options are not
1030 yet supported. If 'mmio32' is specified, then only
1031 the driver will use only 32-bit accessors to read/write
1032 the device registers.
1035 Start an early, polled-mode console on an msm serial
1036 port at the specified address. The serial port
1037 must already be setup and configured. Options are not
1040 msm_serial_dm,<addr>
1041 Start an early, polled-mode console on an msm serial
1042 dm port at the specified address. The serial port
1043 must already be setup and configured. Options are not
1046 smh Use ARM semihosting calls for early console.
1054 Use early console provided by serial driver available
1055 on Samsung SoCs, requires selecting proper type and
1056 a correct base address of the selected UART port. The
1057 serial port must already be setup and configured.
1058 Options are not yet supported.
1062 Use early console provided by Freescale LP UART driver
1063 found on Freescale Vybrid and QorIQ LS1021A processors.
1064 A valid base address must be provided, and the serial
1065 port must already be setup and configured.
1067 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1071 earlyprintk=serial[,ttySn[,baudrate]]
1072 earlyprintk=serial[,0x...[,baudrate]]
1073 earlyprintk=ttySn[,baudrate]
1074 earlyprintk=dbgp[debugController#]
1075 earlyprintk=pciserial,bus:device.function[,baudrate]
1077 earlyprintk is useful when the kernel crashes before
1078 the normal console is initialized. It is not enabled by
1079 default because it has some cosmetic problems.
1081 Append ",keep" to not disable it when the real console
1084 Only one of vga, efi, serial, or usb debug port can
1087 Currently only ttyS0 and ttyS1 may be specified by
1088 name. Other I/O ports may be explicitly specified
1089 on some architectures (x86 and arm at least) by
1090 replacing ttySn with an I/O port address, like this:
1091 earlyprintk=serial,0x1008,115200
1092 You can find the port for a given device in
1093 /proc/tty/driver/serial:
1094 2: uart:ST16650V2 port:00001008 irq:18 ...
1096 Interaction with the standard serial driver is not
1099 The VGA and EFI output is eventually overwritten by
1102 The xen output can only be used by Xen PV guests.
1104 edac_report= [HW,EDAC] Control how to report EDAC event
1105 Format: {"on" | "off" | "force"}
1106 on: enable EDAC to report H/W event. May be overridden
1107 by other higher priority error reporting module.
1108 off: disable H/W event reporting through EDAC.
1109 force: enforce the use of EDAC to report H/W event.
1112 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1115 This is designed to be used in conjunction with
1116 the boot argument: earlyprintk=vga
1119 Format: {"off" | "on" | "skip[mbr]"}
1122 Format: { "old_map", "nochunk", "noruntime", "debug" }
1123 old_map [X86-64]: switch to the old ioremap-based EFI
1124 runtime services mapping. 32-bit still uses this one by
1126 nochunk: disable reading files in "chunks" in the EFI
1127 boot stub, as chunking can cause problems with some
1128 firmware implementations.
1129 noruntime : disable EFI runtime services support
1130 debug: enable misc debug output
1132 efi_no_storage_paranoia [EFI; X86]
1133 Using this parameter you can use more than 50% of
1134 your efi variable storage. Use this parameter only if
1135 you are really sure that your UEFI does sane gc and
1136 fulfills the spec otherwise your board may brick.
1138 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1139 Add arbitrary attribute to specific memory range by
1140 updating original EFI memory map.
1141 Region of memory which aa attribute is added to is
1143 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1144 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1145 attribute is added to range 0x100000000-0x180000000 and
1146 0x10a0000000-0x1120000000.
1148 Using this parameter you can do debugging of EFI memmap
1149 related feature. For example, you can do debugging of
1150 Address Range Mirroring feature even if your box
1153 eisa_irq_edge= [PARISC,HW]
1154 See header of drivers/parisc/eisa.c.
1157 See comment before function elanfreq_setup() in
1158 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1161 Format: {"cfq" | "deadline" | "noop"}
1162 See Documentation/block/cfq-iosched.txt and
1163 Documentation/block/deadline-iosched.txt for details.
1165 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1166 Specifies physical address of start of kernel core
1167 image elf header and optionally the size. Generally
1168 kexec loader will pass this option to capture kernel.
1169 See Documentation/kdump/kdump.txt for details.
1171 enable_mtrr_cleanup [X86]
1172 The kernel tries to adjust MTRR layout from continuous
1173 to discrete, to make X server driver able to add WB
1174 entry later. This parameter enables that.
1176 enable_timer_pin_1 [X86]
1177 Enable PIN 1 of APIC timer
1178 Can be useful to work around chipset bugs
1179 (in particular on some ATI chipsets).
1180 The kernel tries to set a reasonable default.
1182 enforcing [SELINUX] Set initial enforcing status.
1184 See security/selinux/Kconfig help text.
1185 0 -- permissive (log only, no denials).
1186 1 -- enforcing (deny and log).
1188 Value can be changed at runtime via /selinux/enforce.
1191 Disable Error Record Serialization Table (ERST)
1194 ether= [HW,NET] Ethernet cards parameters
1195 This option is obsoleted by the "netdev=" option, which
1196 has equivalent usage. See its documentation for details.
1200 Permit 'security.evm' to be updated regardless of
1201 current integrity status.
1205 fail_make_request=[KNL]
1206 General fault injection mechanism.
1207 Format: <interval>,<probability>,<space>,<times>
1208 See also Documentation/fault-injection/.
1211 See Documentation/blockdev/floppy.txt.
1213 force_pal_cache_flush
1214 [IA-64] Avoid check_sal_cache_flush which may hang on
1215 buggy SAL_CACHE_FLUSH implementations. Using this
1216 parameter will force ia64_sal_cache_flush to call
1217 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1220 Forcefully enable Physical Address Extension (PAE).
1221 Many Pentium M systems disable PAE but may have a
1222 functionally usable PAE implementation.
1223 Warning: use of this parameter will taint the kernel
1224 and may cause unknown problems.
1227 [FTRACE] will set and start the specified tracer
1228 as early as possible in order to facilitate early
1231 ftrace_dump_on_oops[=orig_cpu]
1232 [FTRACE] will dump the trace buffers on oops.
1233 If no parameter is passed, ftrace will dump
1234 buffers of all CPUs, but if you pass orig_cpu, it will
1235 dump only the buffer of the CPU that triggered the
1238 ftrace_filter=[function-list]
1239 [FTRACE] Limit the functions traced by the function
1240 tracer at boot up. function-list is a comma separated
1241 list of functions. This list can be changed at run
1242 time by the set_ftrace_filter file in the debugfs
1245 ftrace_notrace=[function-list]
1246 [FTRACE] Do not trace the functions specified in
1247 function-list. This list can be changed at run time
1248 by the set_ftrace_notrace file in the debugfs
1251 ftrace_graph_filter=[function-list]
1252 [FTRACE] Limit the top level callers functions traced
1253 by the function graph tracer at boot up.
1254 function-list is a comma separated list of functions
1255 that can be changed at run time by the
1256 set_graph_function file in the debugfs tracing directory.
1258 ftrace_graph_notrace=[function-list]
1259 [FTRACE] Do not trace from the functions specified in
1260 function-list. This list is a comma separated list of
1261 functions that can be changed at run time by the
1262 set_graph_notrace file in the debugfs tracing directory.
1265 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1266 support via parallel port (up to 5 devices per port)
1267 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1268 See also Documentation/input/joystick-parport.txt
1272 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1276 gcov_persist= [GCOV] When non-zero (default), profiling data for
1277 kernel modules is saved and remains accessible via
1278 debugfs, even when the module is unloaded/reloaded.
1279 When zero, profiling data is discarded and associated
1280 debugfs files are removed at module unload time.
1282 gpt [EFI] Forces disk with valid GPT signature but
1283 invalid Protective MBR to be treated as GPT. If the
1284 primary GPT is corrupted, it enables the backup/alternate
1285 GPT to be used instead.
1287 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1288 the "Enable 0" bit of the configuration register.
1291 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1292 the "Enable 0" bit of the configuration register.
1295 grcan.select= [HW] Select which physical interface to use.
1298 grcan.txsize= [HW] Sets the size of the tx buffer.
1299 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1301 grcan.rxsize= [HW] Sets the size of the rx buffer.
1302 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1305 hardlockup_all_cpu_backtrace=
1306 [KNL] Should the hard-lockup detector generate
1307 backtraces on all cpus.
1310 hashdist= [KNL,NUMA] Large hashes allocated during boot
1311 are distributed across NUMA nodes. Defaults on
1312 for 64-bit NUMA, off otherwise.
1313 Format: 0 | 1 (for off | on)
1315 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1317 hd= [EIDE] (E)IDE hard drive subsystem geometry
1318 Format: <cyl>,<head>,<sect>
1321 Disable Hardware Error Source Table (HEST) support;
1322 corresponding firmware-first mode error processing
1323 logic will be disabled.
1325 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1326 size of <nn>. This works even on boxes that have no
1327 highmem otherwise. This also works to reduce highmem
1328 size on bigger boxes.
1330 highres= [KNL] Enable/disable high resolution timer mode.
1331 Valid parameters: "on", "off"
1335 See Documentation/isdn/README.HiSax.
1339 hpet= [X86-32,HPET] option to control HPET usage
1340 Format: { enable (default) | disable | force |
1342 disable: disable HPET and use PIT instead
1343 force: allow force enabled of undocumented chips (ICH4,
1345 verbose: show contents of HPET registers during setup
1347 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1348 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1350 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1351 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1352 On x86-64 and powerpc, this option can be specified
1353 multiple times interleaved with hugepages= to reserve
1354 huge pages of different sizes. Valid pages sizes on
1355 x86-64 are 2M (when the CPU supports "pse") and 1G
1356 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1358 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1359 terminal devices. Valid values: 0..8
1360 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1361 If specified, z/VM IUCV HVC accepts connections
1362 from listed z/VM user IDs only.
1364 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1365 hardware thread id mappings.
1366 Format: <cpu>:<hwthread>
1369 Do not unregister boot console at start. This is only
1370 useful for debugging when something happens in the window
1371 between unregistering the boot console and initializing
1374 i2c_bus= [HW] Override the default board specific I2C bus speed
1375 or register an additional I2C bus that is not
1376 registered from board initialization code.
1380 i8042.debug [HW] Toggle i8042 debug mode
1381 i8042.unmask_kbd_data
1382 [HW] Enable printing of interrupt data from the KBD port
1383 (disabled by default, and as a pre-condition
1384 requires that i8042.debug=1 be enabled)
1385 i8042.direct [HW] Put keyboard port into non-translated mode
1386 i8042.dumbkbd [HW] Pretend that controller can only read data from
1387 keyboard and cannot control its state
1388 (Don't attempt to blink the leds)
1389 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1390 i8042.nokbd [HW] Don't check/create keyboard port
1391 i8042.noloop [HW] Disable the AUX Loopback command while probing
1393 i8042.nomux [HW] Don't check presence of an active multiplexing
1395 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1397 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1398 i8042.reset [HW] Reset the controller during init and cleanup
1399 i8042.unlock [HW] Unlock (ignore) the keylock
1400 i8042.kbdreset [HW] Reset device connected to KBD port
1404 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1405 indicates that the driver is running on unsupported
1407 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1408 does not match list of supported models.
1410 [HW] Report power status in /proc/i8k
1411 (disabled by default)
1412 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1415 i915.invert_brightness=
1416 [DRM] Invert the sense of the variable that is used to
1417 set the brightness of the panel backlight. Normally a
1418 brightness value of 0 indicates backlight switched off,
1419 and the maximum of the brightness value sets the backlight
1420 to maximum brightness. If this parameter is set to 0
1421 (default) and the machine requires it, or this parameter
1422 is set to 1, a brightness value of 0 sets the backlight
1423 to maximum brightness, and the maximum of the brightness
1424 value switches the backlight off.
1425 -1 -- never invert brightness
1426 0 -- machine default
1427 1 -- force brightness inversion
1430 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1432 ide-core.nodma= [HW] (E)IDE subsystem
1433 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1434 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1435 .cdrom .chs .ignore_cable are additional options
1436 See Documentation/ide/ide.txt.
1438 ide-generic.probe-mask= [HW] (E)IDE subsystem
1440 Probe mask for legacy ISA IDE ports. Depending on
1441 platform up to 6 ports are supported, enabled by
1442 setting corresponding bits in the mask to 1. The
1443 default value is 0x0, which has a special meaning.
1444 On systems that have PCI, it triggers scanning the
1445 PCI bus for the first and the second port, which
1446 are then probed. On systems without PCI the value
1447 of 0x0 enables probing the two first ports as if it
1450 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1451 Claim all unknown PCI IDE storage controllers.
1454 Format: idle=poll, idle=halt, idle=nomwait
1455 Poll forces a polling idle loop that can slightly
1456 improve the performance of waking up a idle CPU, but
1457 will use a lot of power and make the system run hot.
1459 idle=halt: Halt is forced to be used for CPU idle.
1460 In such case C2/C3 won't be used again.
1461 idle=nomwait: Disable mwait for CPU C-states
1463 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1464 Format: { strict | legacy | 2008 | relaxed }
1467 Choose which programs will be accepted for execution
1468 based on the IEEE 754 NaN encoding(s) supported by
1469 the FPU and the NaN encoding requested with the value
1470 of an ELF file header flag individually set by each
1471 binary. Hardware implementations are permitted to
1472 support either or both of the legacy and the 2008 NaN
1475 Available settings are as follows:
1476 strict accept binaries that request a NaN encoding
1477 supported by the FPU
1478 legacy only accept legacy-NaN binaries, if supported
1480 2008 only accept 2008-NaN binaries, if supported
1482 relaxed accept any binaries regardless of whether
1483 supported by the FPU
1485 The FPU emulator is always able to support both NaN
1486 encodings, so if no FPU hardware is present or it has
1487 been disabled with 'nofpu', then the settings of
1488 'legacy' and '2008' strap the emulator accordingly,
1489 'relaxed' straps the emulator for both legacy-NaN and
1490 2008-NaN, whereas 'strict' enables legacy-NaN only on
1491 legacy processors and both NaN encodings on MIPS32 or
1494 The setting for ABS.fmt/NEG.fmt instruction execution
1495 mode generally follows that for the NaN encoding,
1496 except where unsupported by hardware.
1498 ignore_loglevel [KNL]
1499 Ignore loglevel setting - this will print /all/
1500 kernel messages to the console. Useful for debugging.
1501 We also add it as printk module parameter, so users
1502 could change it dynamically, usually by
1503 /sys/module/printk/parameters/ignore_loglevel.
1506 Ignore RLIMIT_DATA setting for data mappings,
1507 print warning at first misuse. Can be changed via
1508 /sys/module/kernel/parameters/ignore_rlimit_data.
1510 ihash_entries= [KNL]
1511 Set number of hash buckets for inode cache.
1513 ima_appraise= [IMA] appraise integrity measurements
1514 Format: { "off" | "enforce" | "fix" | "log" }
1517 ima_appraise_tcb [IMA]
1518 The builtin appraise policy appraises all files
1522 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1526 The list of supported hash algorithms is defined
1527 in crypto/hash_info.h.
1530 The builtin measurement policy to load during IMA
1531 setup. Specyfing "tcb" as the value, measures all
1532 programs exec'd, files mmap'd for exec, and all files
1533 opened with the read mode bit set by either the
1534 effective uid (euid=0) or uid=0.
1537 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1538 Load a policy which meets the needs of the Trusted
1539 Computing Base. This means IMA will measure all
1540 programs exec'd, files mmap'd for exec, and all files
1541 opened for read by uid=0.
1544 Select one of defined IMA measurements template formats.
1545 Formats: { "ima" | "ima-ng" | "ima-sig" }
1549 [IMA] Define a custom template format.
1550 Format: { "field1|...|fieldN" }
1552 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1553 Format: <min_file_size>
1554 Set the minimal file size for using asynchronous hash.
1555 If left unspecified, ahash usage is disabled.
1557 ahash performance varies for different data sizes on
1558 different crypto accelerators. This option can be used
1559 to achieve the best performance for a particular HW.
1561 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1563 Set hashing buffer size. Default: 4k.
1565 ahash performance varies for different chunk sizes on
1566 different crypto accelerators. This option can be used
1567 to achieve best performance for particular HW.
1571 Run specified binary instead of /sbin/init as init
1574 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1575 for working out where the kernel is dying during
1578 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1579 initcall functions. Useful for debugging built-in
1580 modules and initcalls.
1582 initrd= [BOOT] Specify the location of the initial ramdisk
1584 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1587 int_pln_enable [x86] Enable power limit notification interrupt
1589 integrity_audit=[IMA]
1590 Format: { "0" | "1" }
1591 0 -- basic integrity auditing messages. (Default)
1592 1 -- additional integrity auditing messages.
1594 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1596 Enable intel iommu driver.
1598 Disable intel iommu driver.
1599 igfx_off [Default Off]
1600 By default, gfx is mapped as normal device. If a gfx
1601 device has a dedicated DMAR unit, the DMAR unit is
1602 bypassed by not enabling DMAR with this option. In
1603 this case, gfx device will use physical address for
1606 With this option iommu will not optimize to look
1607 for io virtual address below 32-bit forcing dual
1608 address cycle on pci bus for cards supporting greater
1609 than 32-bit addressing. The default is to look
1610 for translation below 32-bit and if not available
1611 then look in the higher range.
1612 strict [Default Off]
1613 With this option on every unmap_single operation will
1614 result in a hardware IOTLB flush operation as opposed
1615 to batching them for performance.
1616 sp_off [Default Off]
1617 By default, super page will be supported if Intel IOMMU
1618 has the capability. With this option, super page will
1620 ecs_off [Default Off]
1621 By default, extended context tables will be supported if
1622 the hardware advertises that it has support both for the
1623 extended tables themselves, and also PASID support. With
1624 this option set, extended tables will not be used even
1625 on hardware which claims to support them.
1627 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1628 0 disables intel_idle and fall back on acpi_idle.
1629 1 to 6 specify maximum depth of C-state.
1633 Do not enable intel_pstate as the default
1634 scaling driver for the supported processors
1636 Enable intel_pstate on systems that prohibit it by default
1637 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1638 instead of acpi-cpufreq may disable platform features, such
1639 as thermal controls and power capping, that rely on ACPI
1640 P-States information being indicated to OSPM and therefore
1641 should be used with caution. This option does not work with
1642 processors that aren't supported by the intel_pstate driver
1643 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1645 Do not enable hardware P state control (HWP)
1648 Only load intel_pstate on systems which support
1649 hardware P state control (HWP) if available.
1651 intremap= [X86-64, Intel-IOMMU]
1652 on enable Interrupt Remapping (default)
1653 off disable Interrupt Remapping
1654 nosid disable Source ID checking
1656 BIOS x2APIC opt-out request will be ignored
1657 nopost disable Interrupt Posting
1659 iomem= Disable strict checking of access to MMIO memory
1660 strict regions from userspace.
1675 nobypass [PPC/POWERNV]
1676 Disable IOMMU bypass, using IOMMU for PCI devices.
1679 io7= [HW] IO7 for Marvel based alpha systems
1680 See comment before marvel_specify_io7 in
1681 arch/alpha/kernel/core_marvel.c.
1683 io_delay= [X86] I/O delay method
1685 Standard port 0x80 based delay
1687 Alternate port 0xed based delay (needed on some systems)
1689 Simple two microseconds delay
1694 See Documentation/filesystems/nfs/nfsroot.txt.
1696 irqaffinity= [SMP] Set the default irq affinity mask
1698 <cpu number>,...,<cpu number>
1700 <cpu number>-<cpu number>
1701 (must be a positive range in ascending order)
1703 <cpu number>,...,<cpu number>-<cpu number>
1706 When an interrupt is not handled search all handlers
1707 for it. Intended to get systems with badly broken
1711 When an interrupt is not handled search all handlers
1712 for it. Also check all handlers each timer
1713 interrupt. Intended to get systems with badly broken
1717 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1719 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1721 <cpu number>,...,<cpu number>
1723 <cpu number>-<cpu number>
1724 (must be a positive range in ascending order)
1726 <cpu number>,...,<cpu number>-<cpu number>
1728 This option can be used to specify one or more CPUs
1729 to isolate from the general SMP balancing and scheduling
1730 algorithms. You can move a process onto or off an
1731 "isolated" CPU via the CPU affinity syscalls or cpuset.
1732 <cpu number> begins at 0 and the maximum value is
1733 "number of CPUs in system - 1".
1735 This option is the preferred way to isolate CPUs. The
1736 alternative -- manually setting the CPU mask of all
1737 tasks in the system -- can cause problems and
1738 suboptimal load balancer performance.
1742 ivrs_ioapic [HW,X86_64]
1743 Provide an override to the IOAPIC-ID<->DEVICE-ID
1744 mapping provided in the IVRS ACPI table. For
1745 example, to map IOAPIC-ID decimal 10 to
1746 PCI device 00:14.0 write the parameter as:
1747 ivrs_ioapic[10]=00:14.0
1749 ivrs_hpet [HW,X86_64]
1750 Provide an override to the HPET-ID<->DEVICE-ID
1751 mapping provided in the IVRS ACPI table. For
1752 example, to map HPET-ID decimal 0 to
1753 PCI device 00:14.0 write the parameter as:
1754 ivrs_hpet[0]=00:14.0
1756 js= [HW,JOY] Analog joystick
1757 See Documentation/input/joystick.txt.
1760 Enable/disable kernel and module base offset ASLR
1761 (Address Space Layout Randomization) if built into
1762 the kernel. When CONFIG_HIBERNATION is selected,
1763 kASLR is disabled by default. When kASLR is enabled,
1764 hibernation will be disabled.
1768 kernelcore= [KNL,X86,IA-64,PPC]
1769 Format: nn[KMGTPE] | "mirror"
1771 specifies the amount of memory usable by the kernel
1772 for non-movable allocations. The requested amount is
1773 spread evenly throughout all nodes in the system. The
1774 remaining memory in each node is used for Movable
1775 pages. In the event, a node is too small to have both
1776 kernelcore and Movable pages, kernelcore pages will
1777 take priority and other nodes will have a larger number
1778 of Movable pages. The Movable zone is used for the
1779 allocation of pages that may be reclaimed or moved
1780 by the page migration subsystem. This means that
1781 HugeTLB pages may not be allocated from this zone.
1782 Note that allocations like PTEs-from-HighMem still
1783 use the HighMem zone if it exists, and the Normal
1784 zone if it does not.
1786 Instead of specifying the amount of memory (nn[KMGTPE]),
1787 you can specify "mirror" option. In case "mirror"
1788 option is specified, mirrored (reliable) memory is used
1789 for non-movable allocations and remaining memory is used
1790 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1791 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1794 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1795 Format: <Controller#>[,poll interval]
1796 The controller # is the number of the ehci usb debug
1797 port as it is probed via PCI. The poll interval is
1798 optional and is the number seconds in between
1799 each poll cycle to the debug port in case you need
1800 the functionality for interrupting the kernel with
1801 gdb or control-c on the dbgp connection. When
1802 not using this parameter you use sysrq-g to break into
1803 the kernel debugger.
1805 kgdboc= [KGDB,HW] kgdb over consoles.
1806 Requires a tty driver that supports console polling,
1807 or a supported polling keyboard driver (non-usb).
1808 Serial only format: <serial_device>[,baud]
1809 keyboard only format: kbd
1810 keyboard and serial format: kbd,<serial_device>[,baud]
1811 Optional Kernel mode setting:
1812 kms, kbd format: kms,kbd
1813 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1815 kgdbwait [KGDB] Stop kernel execution and enter the
1816 kernel debugger at the earliest opportunity.
1818 kmac= [MIPS] korina ethernet MAC address.
1819 Configure the RouterBoard 532 series on-chip
1820 Ethernet adapter MAC address.
1822 kmemleak= [KNL] Boot-time kmemleak enable/disable
1823 Valid arguments: on, off
1825 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1828 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1829 Valid arguments: 0, 1, 2
1830 kmemcheck=0 (disabled)
1831 kmemcheck=1 (enabled)
1832 kmemcheck=2 (one-shot mode)
1833 Default: 2 (one-shot mode)
1835 kstack=N [X86] Print N words from the kernel stack
1838 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1839 Default is 0 (don't ignore, but inject #GP)
1841 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1845 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1846 Default is 1 (enabled)
1848 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1850 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1852 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1853 (virtualized MMU) support on capable Intel chips.
1854 Default is 1 (enabled)
1856 kvm-intel.emulate_invalid_guest_state=
1857 [KVM,Intel] Enable emulation of invalid guest states
1858 Default is 0 (disabled)
1860 kvm-intel.flexpriority=
1861 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1862 Default is 1 (enabled)
1865 [KVM,Intel] Enable VMX nesting (nVMX).
1866 Default is 0 (disabled)
1868 kvm-intel.unrestricted_guest=
1869 [KVM,Intel] Disable unrestricted guest feature
1870 (virtualized real and unpaged mode) on capable
1871 Intel chips. Default is 1 (enabled)
1873 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1874 feature (tagged TLBs) on capable Intel chips.
1875 Default is 1 (enabled)
1881 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1884 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1885 value for LAPIC timer one-shot implementation. Default
1886 back to the programmable timer unit in the LAPIC.
1888 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1891 libata.dma= [LIBATA] DMA control
1892 libata.dma=0 Disable all PATA and SATA DMA
1893 libata.dma=1 PATA and SATA Disk DMA only
1894 libata.dma=2 ATAPI (CDROM) DMA only
1895 libata.dma=4 Compact Flash DMA only
1896 Combinations also work, so libata.dma=3 enables DMA
1897 for disks and CDROMs, but not CFs.
1899 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1900 libata.ignore_hpa=0 keep BIOS limits (default)
1901 libata.ignore_hpa=1 ignore limits, using full disk
1903 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1907 libata.force= [LIBATA] Force configurations. The format is comma
1908 separated list of "[ID:]VAL" where ID is
1909 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1910 matching port, link or device. Basically, it matches
1911 the ATA ID string printed on console by libata. If
1912 the whole ID part is omitted, the last PORT and DEVICE
1913 values are used. If ID hasn't been specified yet, the
1914 configuration applies to all ports, links and devices.
1916 If only DEVICE is omitted, the parameter applies to
1917 the port and all links and devices behind it. DEVICE
1918 number of 0 either selects the first device or the
1919 first fan-out link behind PMP device. It does not
1920 select the host link. DEVICE number of 15 selects the
1921 host link and device attached to it.
1923 The VAL specifies the configuration to force. As long
1924 as there's no ambiguity shortcut notation is allowed.
1925 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1926 The following configurations can be forced.
1928 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1929 Any ID with matching PORT is used.
1931 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1933 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1934 udma[/][16,25,33,44,66,100,133] notation is also
1937 * [no]ncq: Turn on or off NCQ.
1939 * [no]ncqtrim: Turn off queued DSM TRIM.
1941 * nohrst, nosrst, norst: suppress hard, soft
1944 * rstonce: only attempt one reset during
1945 hot-unplug link recovery
1947 * dump_id: dump IDENTIFY data.
1949 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1951 * disable: Disable this device.
1953 If there are multiple matching configurations changing
1954 the same attribute, the last one is used.
1956 memblock=debug [KNL] Enable memblock debug messages.
1958 load_ramdisk= [RAM] List of ramdisks to load from floppy
1959 See Documentation/blockdev/ramdisk.txt.
1961 lockd.nlm_grace_period=P [NFS] Assign grace period.
1964 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1967 lockd.nlm_timeout=T [NFS] Assign timeout value.
1970 lockd.nlm_udpport=M [NFS] Assign UDP port.
1973 locktorture.nreaders_stress= [KNL]
1974 Set the number of locking read-acquisition kthreads.
1975 Defaults to being automatically set based on the
1976 number of online CPUs.
1978 locktorture.nwriters_stress= [KNL]
1979 Set the number of locking write-acquisition kthreads.
1981 locktorture.onoff_holdoff= [KNL]
1982 Set time (s) after boot for CPU-hotplug testing.
1984 locktorture.onoff_interval= [KNL]
1985 Set time (s) between CPU-hotplug operations, or
1986 zero to disable CPU-hotplug testing.
1988 locktorture.shuffle_interval= [KNL]
1989 Set task-shuffle interval (jiffies). Shuffling
1990 tasks allows some CPUs to go into dyntick-idle
1991 mode during the locktorture test.
1993 locktorture.shutdown_secs= [KNL]
1994 Set time (s) after boot system shutdown. This
1995 is useful for hands-off automated testing.
1997 locktorture.stat_interval= [KNL]
1998 Time (s) between statistics printk()s.
2000 locktorture.stutter= [KNL]
2001 Time (s) to stutter testing, for example,
2002 specifying five seconds causes the test to run for
2003 five seconds, wait for five seconds, and so on.
2004 This tests the locking primitive's ability to
2005 transition abruptly to and from idle.
2007 locktorture.torture_runnable= [BOOT]
2008 Start locktorture running at boot time.
2010 locktorture.torture_type= [KNL]
2011 Specify the locking implementation to test.
2013 locktorture.verbose= [KNL]
2014 Enable additional printk() statements.
2016 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2019 loglevel= All Kernel Messages with a loglevel smaller than the
2020 console loglevel will be printed to the console. It can
2021 also be changed with klogd or other programs. The
2022 loglevels are defined as follows:
2024 0 (KERN_EMERG) system is unusable
2025 1 (KERN_ALERT) action must be taken immediately
2026 2 (KERN_CRIT) critical conditions
2027 3 (KERN_ERR) error conditions
2028 4 (KERN_WARNING) warning conditions
2029 5 (KERN_NOTICE) normal but significant condition
2030 6 (KERN_INFO) informational
2031 7 (KERN_DEBUG) debug-level messages
2033 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2034 in bytes. n must be a power of two and greater
2035 than the minimal size. The minimal size is defined
2036 by LOG_BUF_SHIFT kernel config parameter. There is
2037 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2038 that allows to increase the default size depending on
2039 the number of CPUs. See init/Kconfig for more details.
2041 logo.nologo [FB] Disables display of the built-in Linux logo.
2042 This may be used to provide more screen space for
2043 kernel log messages and is useful when debugging
2044 kernel boot problems.
2046 lp=0 [LP] Specify parallel ports to use, e.g,
2047 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2048 lp=reset first parallel port). 'lp=0' disables the
2049 lp=auto printer driver. 'lp=reset' (which can be
2050 specified in addition to the ports) causes
2051 attached printers to be reset. Using
2052 lp=port1,port2,... specifies the parallel ports
2053 to associate lp devices with, starting with
2054 lp0. A port specification may be 'none' to skip
2055 that lp device, or a parport name such as
2056 'parport0'. Specifying 'lp=auto' instead of a
2057 port specification list means that device IDs
2058 from each port should be examined, to see if
2059 an IEEE 1284-compliant printer is attached; if
2060 so, the driver will manage that printer.
2061 See also header of drivers/char/lp.c.
2064 Sets loops_per_jiffy to given constant, thus avoiding
2065 time-consuming boot-time autodetection (up to 250 ms per
2066 CPU). 0 enables autodetection (default). To determine
2067 the correct value for your kernel, boot with normal
2068 autodetection and see what value is printed. Note that
2069 on SMP systems the preset will be applied to all CPUs,
2070 which is likely to cause problems if your CPUs need
2071 significantly divergent settings. An incorrect value
2072 will cause delays in the kernel to be wrong, leading to
2073 unpredictable I/O errors and other breakage. Although
2074 unlikely, in the extreme case this might damage your
2078 Format: <io>,<irq>,<dma>
2080 machvec= [IA-64] Force the use of a particular machine-vector
2081 (machvec) in a generic kernel.
2082 Example: machvec=hpzx1_swiotlb
2084 machtype= [Loongson] Share the same kernel image file between different
2086 Example: machtype=lemote-yeeloong-2f-7inch
2088 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2089 than or equal to this physical address is ignored.
2091 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2092 should make use of. maxcpus=n : n >= 0 limits the
2093 kernel to using 'n' processors. n=0 is a special case,
2094 it is equivalent to "nosmp", which also disables
2097 max_loop= [LOOP] The number of loop block devices that get
2098 (loop.max_loop) unconditionally pre-created at init time. The default
2099 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2100 of statically allocating a predefined number, loop
2101 devices can be requested on-demand with the
2102 /dev/loop-control interface.
2104 mce [X86-32] Machine Check Exception
2106 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2108 md= [HW] RAID subsystems devices and level
2109 See Documentation/md.txt.
2112 Format: <first>,<last>
2113 Specifies range of consoles to be captured by the MDA.
2115 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2116 Amount of memory to be used when the kernel is not able
2117 to see the whole system memory or for test.
2118 [X86] Work as limiting max address. Use together
2119 with memmap= to avoid physical address space collisions.
2120 Without memmap= PCI devices could be placed at addresses
2121 belonging to unused RAM.
2123 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2127 [KNL,SH] Allow user to override the default size for
2128 per-device physically contiguous DMA buffers.
2130 memmap=exactmap [KNL,X86] Enable setting of an exact
2131 E820 memory map, as specified by the user.
2132 Such memmap=exactmap lines can be constructed based on
2133 BIOS output or other requirements. See the memmap=nn@ss
2136 memmap=nn[KMG]@ss[KMG]
2137 [KNL] Force usage of a specific region of memory.
2138 Region of memory to be used is from ss to ss+nn.
2140 memmap=nn[KMG]#ss[KMG]
2141 [KNL,ACPI] Mark specific memory as ACPI data.
2142 Region of memory to be marked is from ss to ss+nn.
2144 memmap=nn[KMG]$ss[KMG]
2145 [KNL,ACPI] Mark specific memory as reserved.
2146 Region of memory to be reserved is from ss to ss+nn.
2147 Example: Exclude memory from 0x18690000-0x1869ffff
2148 memmap=64K$0x18690000
2150 memmap=0x10000$0x18690000
2152 memmap=nn[KMG]!ss[KMG]
2153 [KNL,X86] Mark specific memory as protected.
2154 Region of memory to be used, from ss to ss+nn.
2155 The memory region may be marked as e820 type 12 (0xc)
2156 and is NVDIMM or ADR memory.
2158 memory_corruption_check=0/1 [X86]
2159 Some BIOSes seem to corrupt the first 64k of
2160 memory when doing things like suspend/resume.
2161 Setting this option will scan the memory
2162 looking for corruption. Enabling this will
2163 both detect corruption and prevent the kernel
2164 from using the memory being corrupted.
2165 However, its intended as a diagnostic tool; if
2166 repeatable BIOS-originated corruption always
2167 affects the same memory, you can use memmap=
2168 to prevent the kernel from using that memory.
2170 memory_corruption_check_size=size [X86]
2171 By default it checks for corruption in the low
2172 64k, making this memory unavailable for normal
2173 use. Use this parameter to scan for
2174 corruption in more or less memory.
2176 memory_corruption_check_period=seconds [X86]
2177 By default it checks for corruption every 60
2178 seconds. Use this parameter to check at some
2179 other rate. 0 disables periodic checking.
2181 memtest= [KNL,X86,ARM] Enable memtest
2183 default : 0 <disable>
2184 Specifies the number of memtest passes to be
2185 performed. Each pass selects another test
2186 pattern from a given set of patterns. Memtest
2187 fills the memory with this pattern, validates
2188 memory contents and reserves bad memory
2189 regions that are detected.
2191 meye.*= [HW] Set MotionEye Camera parameters
2192 See Documentation/video4linux/meye.txt.
2194 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2195 Multi-Function General Purpose Timers on AMD Geode
2198 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2199 the BIOS has incorrectly applied a workaround. TinyBIOS
2200 version 0.98 is known to be affected, 0.99 fixes the
2201 problem by letting the user disable the workaround.
2205 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2206 physical address is ignored.
2208 mini2440= [ARM,HW,KNL]
2209 Format:[0..2][b][c][t]
2211 MINI2440 configuration specification:
2212 0 - The attached screen is the 3.5" TFT
2213 1 - The attached screen is the 7" TFT
2214 2 - The VGA Shield is attached (1024x768)
2215 Leaving out the screen size parameter will not load
2216 the TFT driver, and the framebuffer will be left
2218 b - Enable backlight. The TFT backlight pin will be
2219 linked to the kernel VESA blanking code and a GPIO
2220 LED. This parameter is not necessary when using the
2222 c - Enable the s3c camera interface.
2223 t - Reserved for enabling touchscreen support. The
2224 touchscreen support is not enabled in the mainstream
2225 kernel as of 2.6.30, a preliminary port can be found
2226 in the "bleeding edge" mini2440 support kernel at
2227 http://repo.or.cz/w/linux-2.6/mini2440.git
2230 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2231 parameter allows control of the logging verbosity for
2232 the additional memory initialisation checks. A value
2233 of 0 disables mminit logging and a level of 4 will
2234 log everything. Information is printed at KERN_DEBUG
2235 so loglevel=8 may also need to be specified.
2238 [KNL] When CONFIG_MODULE_SIG is set, this means that
2239 modules without (valid) signatures will fail to load.
2240 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2241 is always true, so this option does nothing.
2244 [MOUSE] Maximum time between finger touching and
2245 leaving touchpad surface for touch to be considered
2246 a tap and be reported as a left button click (for
2247 touchpads working in absolute mode only).
2249 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2250 reporting absolute coordinates, such as tablets
2251 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2252 reporting absolute coordinates, such as tablets
2254 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2255 is similar to kernelcore except it specifies the
2256 amount of memory used for migratable allocations.
2257 If both kernelcore and movablecore is specified,
2258 then kernelcore will be at *least* the specified
2259 value but may be more. If movablecore on its own
2260 is specified, the administrator must be careful
2261 that the amount of memory usable for all allocations
2264 movable_node [KNL,X86] Boot-time switch to enable the effects
2265 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2267 MTD_Partition= [MTD]
2268 Format: <name>,<region-number>,<size>,<offset>
2270 MTD_Region= [MTD] Format:
2271 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2274 See drivers/mtd/cmdlinepart.c.
2276 multitce=off [PPC] This parameter disables the use of the pSeries
2277 firmware feature for updating multiple TCE entries
2280 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2282 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2284 boundary - index of last SLC block on Flex-OneNAND.
2285 The remaining blocks are configured as MLC blocks.
2286 lock - Configure if Flex-OneNAND boundary should be locked.
2287 Once locked, the boundary cannot be changed.
2288 1 indicates lock status, 0 indicates unlock status.
2291 ARM/S3C2412 JIVE boot control
2293 See arch/arm/mach-s3c2412/mach-jive.c
2295 mtouchusb.raw_coordinates=
2296 [HW] Make the MicroTouch USB driver use raw coordinates
2297 ('y', default) or cooked coordinates ('n')
2299 mtrr_chunk_size=nn[KMG] [X86]
2300 used for mtrr cleanup. It is largest continuous chunk
2301 that could hold holes aka. UC entries.
2303 mtrr_gran_size=nn[KMG] [X86]
2304 Used for mtrr cleanup. It is granularity of mtrr block.
2306 Large value could prevent small alignment from
2309 mtrr_spare_reg_nr=n [X86]
2311 Range: 0,7 : spare reg number
2313 Used for mtrr cleanup. It is spare mtrr entries number.
2314 Set to 2 or more if your graphical card needs more.
2316 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2318 netdev= [NET] Network devices parameters
2319 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2320 Note that mem_start is often overloaded to mean
2321 something different and driver-specific.
2322 This usage is only documented in each driver source
2326 [NETFILTER] Enable connection tracking flow accounting
2327 0 to disable accounting
2328 1 to enable accounting
2331 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2332 See Documentation/filesystems/nfs/nfsroot.txt.
2334 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2335 See Documentation/filesystems/nfs/nfsroot.txt.
2337 nfsrootdebug [NFS] enable nfsroot debugging messages.
2338 See Documentation/filesystems/nfs/nfsroot.txt.
2340 nfs.callback_tcpport=
2341 [NFS] set the TCP port on which the NFSv4 callback
2342 channel should listen.
2345 [NFS] sets the pathname to the program which is used
2346 to update the NFS client cache entries.
2348 nfs.cache_getent_timeout=
2349 [NFS] sets the timeout after which an attempt to
2350 update a cache entry is deemed to have failed.
2352 nfs.idmap_cache_timeout=
2353 [NFS] set the maximum lifetime for idmapper cache
2357 [NFS] enable 64-bit inode numbers.
2358 If zero, the NFS client will fake up a 32-bit inode
2359 number for the readdir() and stat() syscalls instead
2360 of returning the full 64-bit number.
2361 The default is to return 64-bit inode numbers.
2363 nfs.max_session_slots=
2364 [NFSv4.1] Sets the maximum number of session slots
2365 the client will attempt to negotiate with the server.
2366 This limits the number of simultaneous RPC requests
2367 that the client can send to the NFSv4.1 server.
2368 Note that there is little point in setting this
2369 value higher than the max_tcp_slot_table_limit.
2371 nfs.nfs4_disable_idmapping=
2372 [NFSv4] When set to the default of '1', this option
2373 ensures that both the RPC level authentication
2374 scheme and the NFS level operations agree to use
2375 numeric uids/gids if the mount is using the
2376 'sec=sys' security flavour. In effect it is
2377 disabling idmapping, which can make migration from
2378 legacy NFSv2/v3 systems to NFSv4 easier.
2379 Servers that do not support this mode of operation
2380 will be autodetected by the client, and it will fall
2381 back to using the idmapper.
2382 To turn off this behaviour, set the value to '0'.
2384 [NFS4] Specify an additional fixed unique ident-
2385 ification string that NFSv4 clients can insert into
2386 their nfs_client_id4 string. This is typically a
2387 UUID that is generated at system install time.
2389 nfs.send_implementation_id =
2390 [NFSv4.1] Send client implementation identification
2391 information in exchange_id requests.
2392 If zero, no implementation identification information
2394 The default is to send the implementation identification
2397 nfs.recover_lost_locks =
2398 [NFSv4] Attempt to recover locks that were lost due
2399 to a lease timeout on the server. Please note that
2400 doing this risks data corruption, since there are
2401 no guarantees that the file will remain unchanged
2402 after the locks are lost.
2403 If you want to enable the kernel legacy behaviour of
2404 attempting to recover these locks, then set this
2406 The default parameter value of '0' causes the kernel
2407 not to attempt recovery of lost locks.
2409 nfs4.layoutstats_timer =
2410 [NFSv4.2] Change the rate at which the kernel sends
2411 layoutstats to the pNFS metadata server.
2413 Setting this to value to 0 causes the kernel to use
2414 whatever value is the default set by the layout
2415 driver. A non-zero value sets the minimum interval
2416 in seconds between layoutstats transmissions.
2418 nfsd.nfs4_disable_idmapping=
2419 [NFSv4] When set to the default of '1', the NFSv4
2420 server will return only numeric uids and gids to
2421 clients using auth_sys, and will accept numeric uids
2422 and gids from such clients. This is intended to ease
2423 migration from NFSv2/v3.
2425 objlayoutdriver.osd_login_prog=
2426 [NFS] [OBJLAYOUT] sets the pathname to the program which
2427 is used to automatically discover and login into new
2428 osd-targets. Please see:
2429 Documentation/filesystems/pnfs.txt for more explanations
2431 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2432 when a NMI is triggered.
2433 Format: [state][,regs][,debounce][,die]
2435 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2436 Format: [panic,][nopanic,][num]
2438 0 - turn hardlockup detector in nmi_watchdog off
2439 1 - turn hardlockup detector in nmi_watchdog on
2440 When panic is specified, panic when an NMI watchdog
2441 timeout occurs (or 'nopanic' to override the opposite
2442 default). To disable both hard and soft lockup detectors,
2443 please see 'nowatchdog'.
2444 This is useful when you use a panic=... timeout and
2445 need the box quickly up again.
2447 netpoll.carrier_timeout=
2448 [NET] Specifies amount of time (in seconds) that
2449 netpoll should wait for a carrier. By default netpoll
2452 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2453 emulation library even if a 387 maths coprocessor
2457 [HW] Never suspend the console
2458 Disable suspending of consoles during suspend and
2459 hibernate operations. Once disabled, debugging
2460 messages can reach various consoles while the rest
2461 of the system is being put to sleep (ie, while
2462 debugging driver suspend/resume hooks). This may
2463 not work reliably with all consoles, but is known
2464 to work with serial and VGA consoles.
2465 To facilitate more flexible debugging, we also add
2466 console_suspend, a printk module parameter to control
2467 it. Users could use console_suspend (usually
2468 /sys/module/printk/parameters/console_suspend) to
2469 turn on/off it dynamically.
2471 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2472 caches in the slab allocator. Saves per-node memory,
2473 but will impact performance.
2477 noapic [SMP,APIC] Tells the kernel to not make use of any
2478 IOAPICs that may be present in the system.
2480 noautogroup Disable scheduler automatic task group creation.
2482 nobats [PPC] Do not use BATs for mapping kernel lowmem
2483 on "Classic" PPC cores.
2487 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2489 nodelayacct [KNL] Disable per-task delay accounting
2491 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2493 nodsp [SH] Disable hardware DSP at boot time.
2495 noefi Disable EFI runtime services support.
2500 On X86-32 available only on PAE configured kernels.
2501 noexec=on: enable non-executable mappings (default)
2502 noexec=off: disable non-executable mappings
2505 Disable SMAP (Supervisor Mode Access Prevention)
2506 even if it is supported by processor.
2509 Disable SMEP (Supervisor Mode Execution Prevention)
2510 even if it is supported by processor.
2513 This affects only 32-bit executables.
2514 noexec32=on: enable non-executable mappings (default)
2515 read doesn't imply executable mappings
2516 noexec32=off: disable non-executable mappings
2517 read implies executable mappings
2519 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2521 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2522 register save and restore. The kernel will only save
2523 legacy floating-point registers on task switch.
2525 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2527 noxsave [BUGS=X86] Disables x86 extended register state save
2528 and restore using xsave. The kernel will fallback to
2529 enabling legacy floating-point and sse state.
2531 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2532 register states. The kernel will fall back to use
2533 xsave to save the states. By using this parameter,
2534 performance of saving the states is degraded because
2535 xsave doesn't support modified optimization while
2536 xsaveopt supports it on xsaveopt enabled systems.
2538 noxsaves [X86] Disables xsaves and xrstors used in saving and
2539 restoring x86 extended register state in compacted
2540 form of xsave area. The kernel will fall back to use
2541 xsaveopt and xrstor to save and restore the states
2542 in standard form of xsave area. By using this
2543 parameter, xsave area per process might occupy more
2544 memory on xsaves enabled systems.
2546 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2547 wfi(ARM) instruction doesn't work correctly and not to
2548 use it. This is also useful when using JTAG debugger.
2550 no_file_caps Tells the kernel not to honor file capabilities. The
2551 only way then for a file to be executed with privilege
2552 is to be setuid root or executed by root.
2554 nohalt [IA-64] Tells the kernel not to use the power saving
2555 function PAL_HALT_LIGHT when idle. This increases
2556 power-consumption. On the positive side, it reduces
2557 interrupt wake-up latency, which may improve performance
2558 in certain environments such as networked servers or
2561 nohibernate [HIBERNATION] Disable hibernation and resume.
2563 nohz= [KNL] Boottime enable/disable dynamic ticks
2564 Valid arguments: on, off
2567 nohz_full= [KNL,BOOT]
2568 In kernels built with CONFIG_NO_HZ_FULL=y, set
2569 the specified list of CPUs whose tick will be stopped
2570 whenever possible. The boot CPU will be forced outside
2571 the range to maintain the timekeeping.
2572 The CPUs in this range must also be included in the
2575 noiotrap [SH] Disables trapped I/O port accesses.
2577 noirqdebug [X86-32] Disables the code which attempts to detect and
2578 disable unhandled interrupt sources.
2580 no_timer_check [X86,APIC] Disables the code which tests for
2581 broken timer IRQ sources.
2583 noisapnp [ISAPNP] Disables ISA PnP code.
2585 noinitrd [RAM] Tells the kernel not to load any configured
2588 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2590 [Deprecated - use intremap=off]
2594 noinvpcid [X86] Disable the INVPCID cpu feature.
2596 nojitter [IA-64] Disables jitter checking for ITC timers.
2598 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2600 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2603 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2604 steal time is computed, but won't influence scheduler
2607 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2609 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2611 noltlbs [PPC] Do not use large page/tlb entries for kernel
2612 lowmem mapping on PPC40x.
2614 nomca [IA-64] Disable machine check abort handling
2616 nomce [X86-32] Disable Machine Check Exception
2618 nomfgpt [X86-32] Disable Multi-Function General Purpose
2619 Timer usage (for AMD Geode machines).
2621 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2622 shutdown the other cpus. Instead use the REBOOT_VECTOR
2625 nomodule Disable module load
2627 nopat [X86] Disable PAT (page attribute table extension of
2628 pagetables) support.
2630 norandmaps Don't use address space randomization. Equivalent to
2631 echo 0 > /proc/sys/kernel/randomize_va_space
2633 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2635 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2636 with UP alternatives
2638 nordrand [X86] Disable kernel use of the RDRAND and
2639 RDSEED instructions even if they are supported
2640 by the processor. RDRAND and RDSEED are still
2641 available to user space applications.
2643 noresume [SWSUSP] Disables resume and restores original swap
2646 no-scroll [VGA] Disables scrollback.
2647 This is required for the Braillex ib80-piezo Braille
2648 reader made by F.H. Papenmeier (Germany).
2652 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2654 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2655 and disable the IO APIC. legacy for "maxcpus=0".
2657 nosoftlockup [KNL] Disable the soft-lockup detector.
2659 nosync [HW,M68K] Disables sync negotiation for all devices.
2661 notsc [BUGS=X86-32] Disable Time Stamp Counter
2663 nowatchdog [KNL] Disable both lockup detectors, i.e.
2664 soft-lockup and NMI watchdog (hard-lockup).
2668 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2670 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2671 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2672 Some features depend on CPU0. Known dependencies are:
2673 1. Resume from suspend/hibernate depends on CPU0.
2674 Suspend/hibernate will fail if CPU0 is offline and you
2675 need to online CPU0 before suspend/hibernate.
2676 2. PIC interrupts also depend on CPU0. CPU0 can't be
2677 removed if a PIC interrupt is detected.
2678 It's said poweroff/reboot may depend on CPU0 on some
2679 machines although I haven't seen such issues so far
2680 after CPU0 is offline on a few tested machines.
2681 If the dependencies are under your control, you can
2682 turn on cpu0_hotplug.
2684 nptcg= [IA-64] Override max number of concurrent global TLB
2685 purges which is reported from either PAL_VM_SUMMARY or
2688 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2689 could support. nr_cpus=n : n >= 1 limits the kernel to
2690 supporting 'n' processors. Later in runtime you can not
2691 use hotplug cpu feature to put more cpu back to online.
2692 just like you compile the kernel NR_CPUS=n
2694 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2696 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2697 Allowed values are enable and disable
2699 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2700 one of ['zone', 'node', 'default'] can be specified
2701 This can be set from sysctl after boot.
2702 See Documentation/sysctl/vm.txt for details.
2704 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2705 See Documentation/debugging-via-ohci1394.txt for more
2708 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2709 Rather than timing out after 20 ms if an EC
2710 command is not properly ACKed, override the length
2711 of the timeout. We have interrupts disabled while
2712 waiting for the ACK, so if this is set too high
2713 interrupts *may* be lost!
2715 omap_mux= [OMAP] Override bootloader pin multiplexing.
2716 Format: <mux_mode0.mode_name=value>...
2717 For example, to override I2C bus2:
2718 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2720 oprofile.timer= [HW]
2721 Use timer interrupt instead of performance counters
2723 oprofile.cpu_type= Force an oprofile cpu type
2724 This might be useful if you have an older oprofile
2725 userland or if you want common events.
2726 Format: { arch_perfmon }
2727 arch_perfmon: [X86] Force use of architectural
2728 perfmon on Intel CPUs instead of the
2729 CPU specific event set.
2730 timer: [X86] Force use of architectural NMI
2731 timer mode (see also oprofile.timer
2732 for generic hr timer mode)
2733 [s390] Force legacy basic mode sampling
2734 (report cpu_type "timer")
2736 oops=panic Always panic on oopses. Default is to just kill the
2737 process, but there is a small probability of
2738 deadlocking the machine.
2739 This will also cause panics on machine check exceptions.
2740 Useful together with panic=30 to trigger a reboot.
2743 See Documentation/sound/oss/oss-parameters.txt
2745 page_owner= [KNL] Boot-time page_owner enabling option.
2746 Storage of the information about who allocated
2747 each page is disabled in default. With this switch,
2749 on: enable the feature
2751 page_poison= [KNL] Boot-time parameter changing the state of
2752 poisoning on the buddy allocator.
2753 off: turn off poisoning
2754 on: turn on poisoning
2756 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2757 timeout > 0: seconds before rebooting
2758 timeout = 0: wait forever
2759 timeout < 0: reboot immediately
2762 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2765 crash_kexec_post_notifiers
2766 Run kdump after running panic-notifiers and dumping
2767 kmsg. This only for the users who doubt kdump always
2768 succeeds in any situation.
2769 Note that this also increases risks of kdump failure,
2770 because some panic notifiers can make the crashed
2771 kernel more unstable.
2773 parkbd.port= [HW] Parallel port number the keyboard adapter is
2774 connected to, default is 0.
2776 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2777 0 for XT, 1 for AT (default is AT).
2780 parport= [HW,PPT] Specify parallel ports. 0 disables.
2781 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2782 Use 'auto' to force the driver to use any
2783 IRQ/DMA settings detected (the default is to
2784 ignore detected IRQ/DMA settings because of
2785 possible conflicts). You can specify the base
2786 address, IRQ, and DMA settings; IRQ and DMA
2787 should be numbers, or 'auto' (for using detected
2788 settings on that particular port), or 'nofifo'
2789 (to avoid using a FIFO even if it is detected).
2790 Parallel ports are assigned in the order they
2791 are specified on the command line, starting
2794 parport_init_mode= [HW,PPT]
2795 Configure VIA parallel port to operate in
2796 a specific mode. This is necessary on Pegasos
2797 computer where firmware has no options for setting
2798 up parallel port mode and sets it to spp.
2799 Currently this function knows 686a and 8231 chips.
2800 Format: [spp|ps2|epp|ecp|ecpepp]
2803 Halt all CPUs after the first oops has been printed for
2804 the specified number of seconds. This is to be used if
2805 your oopses keep scrolling off the screen.
2810 See header of drivers/block/paride/pcd.c.
2811 See also Documentation/blockdev/paride.txt.
2813 pci=option[,option...] [PCI] various PCI subsystem options:
2814 earlydump [X86] dump PCI config space before the kernel
2816 off [X86] don't probe for the PCI bus
2817 bios [X86-32] force use of PCI BIOS, don't access
2818 the hardware directly. Use this if your machine
2819 has a non-standard PCI host bridge.
2820 nobios [X86-32] disallow use of PCI BIOS, only direct
2821 hardware access methods are allowed. Use this
2822 if you experience crashes upon bootup and you
2823 suspect they are caused by the BIOS.
2824 conf1 [X86] Force use of PCI Configuration Access
2825 Mechanism 1 (config address in IO port 0xCF8,
2826 data in IO port 0xCFC, both 32-bit).
2827 conf2 [X86] Force use of PCI Configuration Access
2828 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2829 the function, IO port 0xCFA, also 8-bit, sets
2830 bus number. The config space is then accessed
2831 through ports 0xC000-0xCFFF).
2832 See http://wiki.osdev.org/PCI for more info
2833 on the configuration access mechanisms.
2834 noaer [PCIE] If the PCIEAER kernel config parameter is
2835 enabled, this kernel boot option can be used to
2836 disable the use of PCIE advanced error reporting.
2837 nodomains [PCI] Disable support for multiple PCI
2838 root domains (aka PCI segments, in ACPI-speak).
2839 nommconf [X86] Disable use of MMCONFIG for PCI
2841 check_enable_amd_mmconf [X86] check for and enable
2842 properly configured MMIO access to PCI
2843 config space on AMD family 10h CPU
2844 nomsi [MSI] If the PCI_MSI kernel config parameter is
2845 enabled, this kernel boot option can be used to
2846 disable the use of MSI interrupts system-wide.
2847 noioapicquirk [APIC] Disable all boot interrupt quirks.
2848 Safety option to keep boot IRQs enabled. This
2849 should never be necessary.
2850 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2851 primary IO-APIC for bridges that cannot disable
2852 boot IRQs. This fixes a source of spurious IRQs
2853 when the system masks IRQs.
2854 noioapicreroute [APIC] Disable workaround that uses the
2855 boot IRQ equivalent of an IRQ that connects to
2856 a chipset where boot IRQs cannot be disabled.
2857 The opposite of ioapicreroute.
2858 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2859 routing table. These calls are known to be buggy
2860 on several machines and they hang the machine
2861 when used, but on other computers it's the only
2862 way to get the interrupt routing table. Try
2863 this option if the kernel is unable to allocate
2864 IRQs or discover secondary PCI buses on your
2866 rom [X86] Assign address space to expansion ROMs.
2867 Use with caution as certain devices share
2868 address decoders between ROMs and other
2870 norom [X86] Do not assign address space to
2871 expansion ROMs that do not already have
2872 BIOS assigned address ranges.
2873 nobar [X86] Do not assign address space to the
2874 BARs that weren't assigned by the BIOS.
2875 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2876 assigned automatically to PCI devices. You can
2877 make the kernel exclude IRQs of your ISA cards
2879 pirqaddr=0xAAAAA [X86] Specify the physical address
2880 of the PIRQ table (normally generated
2881 by the BIOS) if it is outside the
2882 F0000h-100000h range.
2883 lastbus=N [X86] Scan all buses thru bus #N. Can be
2884 useful if the kernel is unable to find your
2885 secondary buses and you want to tell it
2886 explicitly which ones they are.
2887 assign-busses [X86] Always assign all PCI bus
2888 numbers ourselves, overriding
2889 whatever the firmware may have done.
2890 usepirqmask [X86] Honor the possible IRQ mask stored
2891 in the BIOS $PIR table. This is needed on
2892 some systems with broken BIOSes, notably
2893 some HP Pavilion N5400 and Omnibook XE3
2894 notebooks. This will have no effect if ACPI
2895 IRQ routing is enabled.
2896 noacpi [X86] Do not use ACPI for IRQ routing
2897 or for PCI scanning.
2898 use_crs [X86] Use PCI host bridge window information
2899 from ACPI. On BIOSes from 2008 or later, this
2900 is enabled by default. If you need to use this,
2901 please report a bug.
2902 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2903 If you need to use this, please report a bug.
2904 routeirq Do IRQ routing for all PCI devices.
2905 This is normally done in pci_enable_device(),
2906 so this option is a temporary workaround
2907 for broken drivers that don't call it.
2908 skip_isa_align [X86] do not align io start addr, so can
2909 handle more pci cards
2910 firmware [ARM] Do not re-enumerate the bus but instead
2911 just use the configuration from the
2912 bootloader. This is currently used on
2913 IXP2000 systems where the bus has to be
2914 configured a certain way for adjunct CPUs.
2915 noearly [X86] Don't do any early type 1 scanning.
2916 This might help on some broken boards which
2917 machine check when some devices' config space
2918 is read. But various workarounds are disabled
2919 and some IOMMU drivers will not work.
2920 bfsort Sort PCI devices into breadth-first order.
2921 This sorting is done to get a device
2922 order compatible with older (<= 2.4) kernels.
2923 nobfsort Don't sort PCI devices into breadth-first order.
2924 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2925 tuning and use the BIOS-configured MPS defaults.
2926 pcie_bus_safe Set every device's MPS to the largest value
2927 supported by all devices below the root complex.
2928 pcie_bus_perf Set device MPS to the largest allowable MPS
2929 based on its parent bus. Also set MRRS (Max
2930 Read Request Size) to the largest supported
2931 value (no larger than the MPS that the device
2932 or bus can support) for best performance.
2933 pcie_bus_peer2peer Set every device's MPS to 128B, which
2934 every device is guaranteed to support. This
2935 configuration allows peer-to-peer DMA between
2936 any pair of devices, possibly at the cost of
2937 reduced performance. This also guarantees
2938 that hot-added devices will work.
2939 cbiosize=nn[KMG] The fixed amount of bus space which is
2940 reserved for the CardBus bridge's IO window.
2941 The default value is 256 bytes.
2942 cbmemsize=nn[KMG] The fixed amount of bus space which is
2943 reserved for the CardBus bridge's memory
2944 window. The default value is 64 megabytes.
2947 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2948 Specifies alignment and device to reassign
2949 aligned memory resources.
2950 If <order of align> is not specified,
2951 PAGE_SIZE is used as alignment.
2952 PCI-PCI bridge can be specified, if resource
2953 windows need to be expanded.
2954 ecrc= Enable/disable PCIe ECRC (transaction layer
2955 end-to-end CRC checking).
2956 bios: Use BIOS/firmware settings. This is the
2960 hpiosize=nn[KMG] The fixed amount of bus space which is
2961 reserved for hotplug bridge's IO window.
2962 Default size is 256 bytes.
2963 hpmemsize=nn[KMG] The fixed amount of bus space which is
2964 reserved for hotplug bridge's memory window.
2965 Default size is 2 megabytes.
2966 realloc= Enable/disable reallocating PCI bridge resources
2967 if allocations done by BIOS are too small to
2968 accommodate resources required by all child
2970 off: Turn realloc off
2972 realloc same as realloc=on
2973 noari do not use PCIe ARI.
2974 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2975 only look for one device below a PCIe downstream
2978 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2981 force Enable ASPM even on devices that claim not to support it.
2982 WARNING: Forcing ASPM on may cause system lockups.
2984 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2985 nomsi Do not use MSI for PCI Express Native Hotplug (this
2986 makes all PCIe ports use INTx for hotplug services).
2988 pcie_ports= [PCIE] PCIe ports handling:
2989 auto Ask the BIOS whether or not to use native PCIe services
2990 associated with PCIe ports (PME, hot-plug, AER). Use
2991 them only if that is allowed by the BIOS.
2992 native Use native PCIe services associated with PCIe ports
2994 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2997 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2998 nomsi Do not use MSI for native PCIe PME signaling (this makes
2999 all PCIe root ports use INTx for all services).
3001 pcmv= [HW,PCMCIA] BadgePAD 4
3005 Keep all power-domains already enabled by bootloader on,
3006 even if no driver has claimed them. This is useful
3007 for debug and development, but should not be
3008 needed on a platform with proper driver support.
3011 See Documentation/blockdev/paride.txt.
3013 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3016 See arch/parisc/kernel/pdc_chassis.c
3018 percpu_alloc= Select which percpu first chunk allocator to use.
3019 Currently supported values are "embed" and "page".
3020 Archs may support subset or none of the selections.
3021 See comments in mm/percpu.c for details on each
3022 allocator. This parameter is primarily for debugging
3023 and performance comparison.
3026 See Documentation/blockdev/paride.txt.
3029 See Documentation/blockdev/paride.txt.
3031 pirq= [SMP,APIC] Manual mp-table setup
3032 See Documentation/x86/i386/IO-APIC.txt.
3034 plip= [PPT,NET] Parallel port network link
3035 Format: { parport<nr> | timid | 0 }
3036 See also Documentation/parport.txt.
3038 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3039 Override pmtimer IOPort with a hex value.
3043 Enable PNP debug messages (depends on the
3044 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3045 via /sys/module/pnp/parameters/debug. We always show
3046 current resource usage; turning this on also shows
3047 possible settings and some assignment information.
3053 { on | off | curr | res | no-curr | no-res }
3056 [ISAPNP] Exclude IRQs for the autoconfiguration
3059 [ISAPNP] Exclude DMAs for the autoconfiguration
3061 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3062 Ranges are in pairs (I/O port base and size).
3065 [ISAPNP] Exclude memory regions for the
3067 Ranges are in pairs (memory base and size).
3069 ports= [IP_VS_FTP] IPVS ftp helper module
3071 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3073 Format: <port>,<port>....
3075 ppc_strict_facility_enable
3076 [PPC] This option catches any kernel floating point,
3077 Altivec, VSX and SPE outside of regions specifically
3078 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3079 There is some performance impact when enabling this.
3081 print-fatal-signals=
3082 [KNL] debug: print fatal signals
3084 If enabled, warn about various signal handling
3085 related application anomalies: too many signals,
3086 too many POSIX.1 timers, fatal signals causing a
3089 If you hit the warning due to signal overflow,
3090 you might want to try "ulimit -i unlimited".
3094 printk.always_kmsg_dump=
3095 Trigger kmsg_dump for cases other than kernel oops or
3097 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3100 printk.time= Show timing data prefixed to each printk message line
3101 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3103 processor.max_cstate= [HW,ACPI]
3104 Limit processor to maximum C-state
3105 max_cstate=9 overrides any DMI blacklist limit.
3107 processor.nocst [HW,ACPI]
3108 Ignore the _CST method to determine C-states,
3109 instead using the legacy FADT method
3111 profile= [KNL] Enable kernel profiling via /proc/profile
3112 Format: [schedule,]<number>
3113 Param: "schedule" - profile schedule points.
3114 Param: <number> - step/bucket size as a power of 2 for
3115 statistical time based profiling.
3116 Param: "sleep" - profile D-state sleeping (millisecs).
3117 Requires CONFIG_SCHEDSTATS
3118 Param: "kvm" - profile VM exits.
3120 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3122 See Documentation/blockdev/ramdisk.txt.
3124 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3125 probe for; one of (bare|imps|exps|lifebook|any).
3126 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3128 psmouse.resetafter= [HW,MOUSE]
3129 Try to reset the device after so many bad packets
3132 [HW,MOUSE] Set desired mouse resolution, in dpi.
3133 psmouse.smartscroll=
3134 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3135 0 = disabled, 1 = enabled (default).
3137 pstore.backend= Specify the name of the pstore backend to use
3140 See Documentation/blockdev/paride.txt.
3143 [KNL] Number of legacy pty's. Overwrites compiled-in
3146 quiet [KNL] Disable most log messages
3151 See Documentation/md.txt.
3153 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3154 See Documentation/blockdev/ramdisk.txt.
3157 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3158 the specified list of CPUs to be no-callback CPUs.
3159 Invocation of these CPUs' RCU callbacks will
3160 be offloaded to "rcuox/N" kthreads created for
3161 that purpose, where "x" is "b" for RCU-bh, "p"
3162 for RCU-preempt, and "s" for RCU-sched, and "N"
3163 is the CPU number. This reduces OS jitter on the
3164 offloaded CPUs, which can be useful for HPC and
3165 real-time workloads. It can also improve energy
3166 efficiency for asymmetric multiprocessors.
3169 Rather than requiring that offloaded CPUs
3170 (specified by rcu_nocbs= above) explicitly
3171 awaken the corresponding "rcuoN" kthreads,
3172 make these kthreads poll for callbacks.
3173 This improves the real-time response for the
3174 offloaded CPUs by relieving them of the need to
3175 wake up the corresponding kthread, but degrades
3176 energy efficiency by requiring that the kthreads
3177 periodically wake up to do the polling.
3179 rcutree.blimit= [KNL]
3180 Set maximum number of finished RCU callbacks to
3181 process in one batch.
3183 rcutree.dump_tree= [KNL]
3184 Dump the structure of the rcu_node combining tree
3185 out at early boot. This is used for diagnostic
3186 purposes, to verify correct tree setup.
3188 rcutree.gp_cleanup_delay= [KNL]
3189 Set the number of jiffies to delay each step of
3190 RCU grace-period cleanup. This only has effect
3191 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3193 rcutree.gp_init_delay= [KNL]
3194 Set the number of jiffies to delay each step of
3195 RCU grace-period initialization. This only has
3196 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3199 rcutree.gp_preinit_delay= [KNL]
3200 Set the number of jiffies to delay each step of
3201 RCU grace-period pre-initialization, that is,
3202 the propagation of recent CPU-hotplug changes up
3203 the rcu_node combining tree. This only has effect
3204 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3206 rcutree.rcu_fanout_exact= [KNL]
3207 Disable autobalancing of the rcu_node combining
3208 tree. This is used by rcutorture, and might
3209 possibly be useful for architectures having high
3210 cache-to-cache transfer latencies.
3212 rcutree.rcu_fanout_leaf= [KNL]
3213 Change the number of CPUs assigned to each
3214 leaf rcu_node structure. Useful for very
3215 large systems, which will choose the value 64,
3216 and for NUMA systems with large remote-access
3217 latencies, which will choose a value aligned
3218 with the appropriate hardware boundaries.
3220 rcutree.jiffies_till_sched_qs= [KNL]
3221 Set required age in jiffies for a
3222 given grace period before RCU starts
3223 soliciting quiescent-state help from
3224 rcu_note_context_switch().
3226 rcutree.jiffies_till_first_fqs= [KNL]
3227 Set delay from grace-period initialization to
3228 first attempt to force quiescent states.
3229 Units are jiffies, minimum value is zero,
3230 and maximum value is HZ.
3232 rcutree.jiffies_till_next_fqs= [KNL]
3233 Set delay between subsequent attempts to force
3234 quiescent states. Units are jiffies, minimum
3235 value is one, and maximum value is HZ.
3237 rcutree.kthread_prio= [KNL,BOOT]
3238 Set the SCHED_FIFO priority of the RCU per-CPU
3239 kthreads (rcuc/N). This value is also used for
3240 the priority of the RCU boost threads (rcub/N)
3241 and for the RCU grace-period kthreads (rcu_bh,
3242 rcu_preempt, and rcu_sched). If RCU_BOOST is
3243 set, valid values are 1-99 and the default is 1
3244 (the least-favored priority). Otherwise, when
3245 RCU_BOOST is not set, valid values are 0-99 and
3246 the default is zero (non-realtime operation).
3248 rcutree.rcu_nocb_leader_stride= [KNL]
3249 Set the number of NOCB kthread groups, which
3250 defaults to the square root of the number of
3251 CPUs. Larger numbers reduces the wakeup overhead
3252 on the per-CPU grace-period kthreads, but increases
3253 that same overhead on each group's leader.
3255 rcutree.qhimark= [KNL]
3256 Set threshold of queued RCU callbacks beyond which
3257 batch limiting is disabled.
3259 rcutree.qlowmark= [KNL]
3260 Set threshold of queued RCU callbacks below which
3261 batch limiting is re-enabled.
3263 rcutree.rcu_idle_gp_delay= [KNL]
3264 Set wakeup interval for idle CPUs that have
3265 RCU callbacks (RCU_FAST_NO_HZ=y).
3267 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3268 Set wakeup interval for idle CPUs that have
3269 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3270 Lazy RCU callbacks are those which RCU can
3271 prove do nothing more than free memory.
3273 rcutorture.cbflood_inter_holdoff= [KNL]
3274 Set holdoff time (jiffies) between successive
3275 callback-flood tests.
3277 rcutorture.cbflood_intra_holdoff= [KNL]
3278 Set holdoff time (jiffies) between successive
3279 bursts of callbacks within a given callback-flood
3282 rcutorture.cbflood_n_burst= [KNL]
3283 Set the number of bursts making up a given
3284 callback-flood test. Set this to zero to
3285 disable callback-flood testing.
3287 rcutorture.cbflood_n_per_burst= [KNL]
3288 Set the number of callbacks to be registered
3289 in a given burst of a callback-flood test.
3291 rcutorture.fqs_duration= [KNL]
3292 Set duration of force_quiescent_state bursts
3295 rcutorture.fqs_holdoff= [KNL]
3296 Set holdoff time within force_quiescent_state bursts
3299 rcutorture.fqs_stutter= [KNL]
3300 Set wait time between force_quiescent_state bursts
3303 rcutorture.gp_cond= [KNL]
3304 Use conditional/asynchronous update-side
3305 primitives, if available.
3307 rcutorture.gp_exp= [KNL]
3308 Use expedited update-side primitives, if available.
3310 rcutorture.gp_normal= [KNL]
3311 Use normal (non-expedited) asynchronous
3312 update-side primitives, if available.
3314 rcutorture.gp_sync= [KNL]
3315 Use normal (non-expedited) synchronous
3316 update-side primitives, if available. If all
3317 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3318 rcutorture.gp_normal=, and rcutorture.gp_sync=
3319 are zero, rcutorture acts as if is interpreted
3320 they are all non-zero.
3322 rcutorture.n_barrier_cbs= [KNL]
3323 Set callbacks/threads for rcu_barrier() testing.
3325 rcutorture.nfakewriters= [KNL]
3326 Set number of concurrent RCU writers. These just
3327 stress RCU, they don't participate in the actual
3328 test, hence the "fake".
3330 rcutorture.nreaders= [KNL]
3331 Set number of RCU readers. The value -1 selects
3332 N-1, where N is the number of CPUs. A value
3333 "n" less than -1 selects N-n-2, where N is again
3334 the number of CPUs. For example, -2 selects N
3335 (the number of CPUs), -3 selects N+1, and so on.
3337 rcutorture.object_debug= [KNL]
3338 Enable debug-object double-call_rcu() testing.
3340 rcutorture.onoff_holdoff= [KNL]
3341 Set time (s) after boot for CPU-hotplug testing.
3343 rcutorture.onoff_interval= [KNL]
3344 Set time (s) between CPU-hotplug operations, or
3345 zero to disable CPU-hotplug testing.
3347 rcutorture.shuffle_interval= [KNL]
3348 Set task-shuffle interval (s). Shuffling tasks
3349 allows some CPUs to go into dyntick-idle mode
3350 during the rcutorture test.
3352 rcutorture.shutdown_secs= [KNL]
3353 Set time (s) after boot system shutdown. This
3354 is useful for hands-off automated testing.
3356 rcutorture.stall_cpu= [KNL]
3357 Duration of CPU stall (s) to test RCU CPU stall
3358 warnings, zero to disable.
3360 rcutorture.stall_cpu_holdoff= [KNL]
3361 Time to wait (s) after boot before inducing stall.
3363 rcutorture.stat_interval= [KNL]
3364 Time (s) between statistics printk()s.
3366 rcutorture.stutter= [KNL]
3367 Time (s) to stutter testing, for example, specifying
3368 five seconds causes the test to run for five seconds,
3369 wait for five seconds, and so on. This tests RCU's
3370 ability to transition abruptly to and from idle.
3372 rcutorture.test_boost= [KNL]
3373 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3374 "Maybe" means test if the RCU implementation
3375 under test support RCU priority boosting.
3377 rcutorture.test_boost_duration= [KNL]
3378 Duration (s) of each individual boost test.
3380 rcutorture.test_boost_interval= [KNL]
3381 Interval (s) between each boost test.
3383 rcutorture.test_no_idle_hz= [KNL]
3384 Test RCU's dyntick-idle handling. See also the
3385 rcutorture.shuffle_interval parameter.
3387 rcutorture.torture_runnable= [BOOT]
3388 Start rcutorture running at boot time.
3390 rcutorture.torture_type= [KNL]
3391 Specify the RCU implementation to test.
3393 rcutorture.verbose= [KNL]
3394 Enable additional printk() statements.
3396 rcupdate.rcu_cpu_stall_suppress= [KNL]
3397 Suppress RCU CPU stall warning messages.
3399 rcupdate.rcu_cpu_stall_timeout= [KNL]
3400 Set timeout for RCU CPU stall warning messages.
3402 rcupdate.rcu_expedited= [KNL]
3403 Use expedited grace-period primitives, for
3404 example, synchronize_rcu_expedited() instead
3405 of synchronize_rcu(). This reduces latency,
3406 but can increase CPU utilization, degrade
3407 real-time latency, and degrade energy efficiency.
3408 No effect on CONFIG_TINY_RCU kernels.
3410 rcupdate.rcu_normal= [KNL]
3411 Use only normal grace-period primitives,
3412 for example, synchronize_rcu() instead of
3413 synchronize_rcu_expedited(). This improves
3414 real-time latency, CPU utilization, and
3415 energy efficiency, but can expose users to
3416 increased grace-period latency. This parameter
3417 overrides rcupdate.rcu_expedited. No effect on
3418 CONFIG_TINY_RCU kernels.
3420 rcupdate.rcu_normal_after_boot= [KNL]
3421 Once boot has completed (that is, after
3422 rcu_end_inkernel_boot() has been invoked), use
3423 only normal grace-period primitives. No effect
3424 on CONFIG_TINY_RCU kernels.
3426 rcupdate.rcu_task_stall_timeout= [KNL]
3427 Set timeout in jiffies for RCU task stall warning
3428 messages. Disable with a value less than or equal
3431 rcupdate.rcu_self_test= [KNL]
3432 Run the RCU early boot self tests
3434 rcupdate.rcu_self_test_bh= [KNL]
3435 Run the RCU bh early boot self tests
3437 rcupdate.rcu_self_test_sched= [KNL]
3438 Run the RCU sched early boot self tests
3442 Run specified binary instead of /init from the ramdisk,
3443 used for early userspace startup. See initrd.
3446 Format (x86 or x86_64):
3447 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3449 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3451 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3452 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3453 reboot_force is either force or not specified,
3454 reboot_cpu is s[mp]#### with #### being the processor
3455 to be used for rebooting.
3458 [KNL, SMP] Set scheduler's default relax_domain_level.
3459 See Documentation/cgroups/cpusets.txt.
3461 relative_sleep_states=
3462 [SUSPEND] Use sleep state labeling where the deepest
3463 state available other than hibernation is always "mem".
3464 Format: { "0" | "1" }
3465 0 -- Traditional sleep state labels.
3466 1 -- Relative sleep state labels.
3468 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3470 reservetop= [X86-32]
3472 Reserves a hole at the top of the kernel virtual
3477 Set the amount of memory to reserve for BIOS at
3478 the bottom of the address space.
3480 reset_devices [KNL] Force drivers to reset the underlying device
3481 during initialization.
3484 Specify the partition device for software suspend
3486 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3488 resume_offset= [SWSUSP]
3489 Specify the offset from the beginning of the partition
3490 given by "resume=" at which the swap header is located,
3491 in <PAGE_SIZE> units (needed only for swap files).
3492 See Documentation/power/swsusp-and-swap-files.txt
3494 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3495 read the resume files
3497 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3498 Useful for devices that are detected asynchronously
3499 (e.g. USB and MMC devices).
3501 hibernate= [HIBERNATION]
3502 noresume Don't check if there's a hibernation image
3503 present during boot.
3504 nocompress Don't compress/decompress hibernation images.
3505 no Disable hibernation and resume.
3507 retain_initrd [RAM] Keep initrd memory after extraction
3509 rfkill.default_state=
3510 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3511 etc. communication is blocked by default.
3514 rfkill.master_switch_mode=
3515 0 The "airplane mode" button does nothing.
3516 1 The "airplane mode" button toggles between everything
3517 blocked and the previous configuration.
3518 2 The "airplane mode" button toggles between everything
3519 blocked and everything unblocked.
3521 rhash_entries= [KNL,NET]
3522 Set number of hash buckets for route cache
3524 ro [KNL] Mount root device read-only on boot
3527 on Mark read-only kernel memory as read-only (default).
3528 off Leave read-only kernel memory writable for debugging.
3530 root= [KNL] Root filesystem
3531 See name_to_dev_t comment in init/do_mounts.c.
3533 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3534 mount the root filesystem
3536 rootflags= [KNL] Set root filesystem mount option string
3538 rootfstype= [KNL] Set root filesystem type
3540 rootwait [KNL] Wait (indefinitely) for root device to show up.
3541 Useful for devices that are detected asynchronously
3542 (e.g. USB and MMC devices).
3544 rproc_mem=nn[KMG][@address]
3545 [KNL,ARM,CMA] Remoteproc physical memory block.
3546 Memory area to be used by remote processor image,
3549 rw [KNL] Mount root device read-write on boot
3551 S [KNL] Run init in single mode
3553 s390_iommu= [HW,S390]
3554 Set s390 IOTLB flushing mode
3556 With strict flushing every unmap operation will result in
3557 an IOTLB flush. Default is lazy flushing before reuse,
3561 See drivers/net/irda/sa1100_ir.c.
3563 sbni= [NET] Granch SBNI12 leased line adapter
3565 sched_debug [KNL] Enables verbose scheduler debug messages.
3567 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3568 Allowed values are enable and disable. This feature
3569 incurs a small amount of overhead in the scheduler
3570 but is useful for debugging and performance tuning.
3572 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3573 xtime_lock contention on larger systems, and/or RCU lock
3574 contention on all systems with CONFIG_MAXSMP set.
3575 Format: { "0" | "1" }
3576 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3578 Note: increases power consumption, thus should only be
3579 enabled if running jitter sensitive (HPC/RT) workloads.
3581 security= [SECURITY] Choose a security module to enable at boot.
3582 If this boot parameter is not specified, only the first
3583 security module asking for security registration will be
3584 loaded. An invalid security module name will be treated
3585 as if no module has been chosen.
3587 selinux= [SELINUX] Disable or enable SELinux at boot time.
3588 Format: { "0" | "1" }
3589 See security/selinux/Kconfig help text.
3592 Default value is set via kernel config option.
3593 If enabled at boot time, /selinux/disable can be used
3594 later to disable prior to initial policy load.
3596 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3597 Format: { "0" | "1" }
3598 See security/apparmor/Kconfig help text
3601 Default value is set via kernel config option.
3603 serialnumber [BUGS=X86-32]
3606 Maximal number of shapers.
3608 show_msr= [x86] show boot-time MSR settings
3609 Format: { <integer> }
3610 Show boot-time (BIOS-initialized) MSR settings.
3611 The parameter means the number of CPUs to show,
3612 for example 1 means boot CPU only.
3620 Disable merging of slabs with similar size. May be
3621 necessary if there is some reason to distinguish
3622 allocs to different slabs. Debug options disable
3623 merging on their own.
3624 For more information see Documentation/vm/slub.txt.
3626 slab_max_order= [MM, SLAB]
3627 Determines the maximum allowed order for slabs.
3628 A high setting may cause OOMs due to memory
3629 fragmentation. Defaults to 1 for systems with
3630 more than 32MB of RAM, 0 otherwise.
3632 slub_debug[=options[,slabs]] [MM, SLUB]
3633 Enabling slub_debug allows one to determine the
3634 culprit if slab objects become corrupted. Enabling
3635 slub_debug can create guard zones around objects and
3636 may poison objects when not in use. Also tracks the
3637 last alloc / free. For more information see
3638 Documentation/vm/slub.txt.
3640 slub_max_order= [MM, SLUB]
3641 Determines the maximum allowed order for slabs.
3642 A high setting may cause OOMs due to memory
3643 fragmentation. For more information see
3644 Documentation/vm/slub.txt.
3646 slub_min_objects= [MM, SLUB]
3647 The minimum number of objects per slab. SLUB will
3648 increase the slab order up to slub_max_order to
3649 generate a sufficiently large slab able to contain
3650 the number of objects indicated. The higher the number
3651 of objects the smaller the overhead of tracking slabs
3652 and the less frequently locks need to be acquired.
3653 For more information see Documentation/vm/slub.txt.
3655 slub_min_order= [MM, SLUB]
3656 Determines the minimum page order for slabs. Must be
3657 lower than slub_max_order.
3658 For more information see Documentation/vm/slub.txt.
3660 slub_nomerge [MM, SLUB]
3661 Same with slab_nomerge. This is supported for legacy.
3662 See slab_nomerge for more information.
3665 Format: <io1>[,<io2>[,...,<io8>]]
3667 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3668 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3669 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3670 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3671 smsc-ircc2.ircc_irq= [HW] IRQ line
3672 smsc-ircc2.ircc_dma= [HW] DMA channel
3673 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3674 0: Toshiba Satellite 1800 (GP data pin select)
3675 1: Fast pin select (default)
3679 [KNL] Should the soft-lockup detector generate panics.
3682 softlockup_all_cpu_backtrace=
3683 [KNL] Should the soft-lockup detector generate
3684 backtraces on all cpus.
3687 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3688 See Documentation/laptops/sonypi.txt
3690 spia_io_base= [HW,MTD]
3696 Enabled the stack tracer on boot up.
3698 stacktrace_filter=[function-list]
3699 [FTRACE] Limit the functions that the stack tracer
3700 will trace at boot up. function-list is a comma separated
3701 list of functions. This list can be changed at run
3702 time by the stack_trace_filter file in the debugfs
3703 tracing directory. Note, this enables stack tracing
3704 and the stacktrace above is not needed.
3708 Set the STI (builtin display/keyboard on the HP-PARISC
3709 machines) console (graphic card) which should be used
3710 as the initial boot-console.
3711 See also comment in drivers/video/console/sticore.c.
3714 See comment in drivers/video/console/sticore.c.
3717 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3719 sunrpc.min_resvport=
3720 sunrpc.max_resvport=
3722 SunRPC servers often require that client requests
3723 originate from a privileged port (i.e. a port in the
3724 range 0 < portnr < 1024).
3725 An administrator who wishes to reserve some of these
3726 ports for other uses may adjust the range that the
3727 kernel's sunrpc client considers to be privileged
3728 using these two parameters to set the minimum and
3729 maximum port values.
3733 Control how the NFS server code allocates CPUs to
3734 service thread pools. Depending on how many NICs
3735 you have and where their interrupts are bound, this
3736 option will affect which CPUs will do NFS serving.
3737 Note: this parameter cannot be changed while the
3738 NFS server is running.
3740 auto the server chooses an appropriate mode
3741 automatically using heuristics
3742 global a single global pool contains all CPUs
3743 percpu one pool for each CPU
3744 pernode one pool for each NUMA node (equivalent
3745 to global on non-NUMA machines)
3747 sunrpc.tcp_slot_table_entries=
3748 sunrpc.udp_slot_table_entries=
3750 Sets the upper limit on the number of simultaneous
3751 RPC calls that can be sent from the client to a
3752 server. Increasing these values may allow you to
3753 improve throughput, but will also increase the
3754 amount of memory reserved for use by the client.
3756 suspend.pm_test_delay=
3758 Sets the number of seconds to remain in a suspend test
3759 mode before resuming the system (see
3760 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3761 is set. Default value is 5.
3764 [KNL] Enable accounting of swap in memory resource
3765 controller if no parameter or 1 is given or disable
3766 it if 0 is given (See Documentation/cgroups/memory.txt)
3768 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3769 Format: { <int> | force }
3770 <int> -- Number of I/O TLB slabs
3771 force -- force using of bounce buffers even if they
3772 wouldn't be automatically used by the kernel
3776 sysfs.deprecated=0|1 [KNL]
3777 Enable/disable old style sysfs layout for old udev
3778 on older distributions. When this option is enabled
3779 very new udev will not work anymore. When this option
3780 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3781 in older udev will not work anymore.
3782 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3783 the kernel configuration.
3785 sysrq_always_enabled
3787 Ignore sysrq setting - this boot parameter will
3788 neutralize any effect of /proc/sys/kernel/sysrq.
3789 Useful for debugging.
3791 tcpmhash_entries= [KNL,NET]
3792 Set the number of tcp_metrics_hash slots.
3793 Default value is 8192 or 16384 depending on total
3794 ram pages. This is used to specify the TCP metrics
3795 cache size. See Documentation/networking/ip-sysctl.txt
3796 "tcp_no_metrics_save" section for more details.
3800 test_suspend= [SUSPEND][,N]
3801 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3802 standby suspend) or "freeze" (for suspend type freeze)
3803 as the system sleep state during system startup with
3804 the optional capability to repeat N number of times.
3805 The system is woken from this state using a
3806 wakeup-capable RTC alarm.
3808 thash_entries= [KNL,NET]
3809 Set number of hash buckets for TCP connection
3811 thermal.act= [HW,ACPI]
3812 -1: disable all active trip points in all thermal zones
3813 <degrees C>: override all lowest active trip points
3815 thermal.crt= [HW,ACPI]
3816 -1: disable all critical trip points in all thermal zones
3817 <degrees C>: override all critical trip points
3819 thermal.nocrt= [HW,ACPI]
3820 Set to disable actions on ACPI thermal zone
3821 critical and hot trip points.
3823 thermal.off= [HW,ACPI]
3824 1: disable ACPI thermal control
3826 thermal.psv= [HW,ACPI]
3827 -1: disable all passive trip points
3828 <degrees C>: override all passive trip points to this
3831 thermal.tzp= [HW,ACPI]
3832 Specify global default ACPI thermal zone polling rate
3833 <deci-seconds>: poll all this frequency
3834 0: no polling (default)
3837 Force threading of all interrupt handlers except those
3838 marked explicitly IRQF_NO_THREAD.
3841 Enable the Transcendent memory driver if built-in.
3843 tmem.cleancache=0|1 [KNL, XEN]
3844 Default is on (1). Disable the usage of the cleancache
3845 API to send anonymous pages to the hypervisor.
3847 tmem.frontswap=0|1 [KNL, XEN]
3848 Default is on (1). Disable the usage of the frontswap
3849 API to send swap pages to the hypervisor. If disabled
3850 the selfballooning and selfshrinking are force disabled.
3852 tmem.selfballooning=0|1 [KNL, XEN]
3853 Default is on (1). Disable the driving of swap pages
3856 tmem.selfshrinking=0|1 [KNL, XEN]
3857 Default is on (1). Partial swapoff that immediately
3858 transfers pages from Xen hypervisor back to the
3859 kernel based on different criteria.
3863 Specify if the kernel should make use of the cpu
3864 topology information if the hardware supports this.
3865 The scheduler will make use of this information and
3866 e.g. base its process migration decisions on it.
3869 topology_updates= [KNL, PPC, NUMA]
3871 Specify if the kernel should ignore (off)
3872 topology updates sent by the hypervisor to this
3877 tpm_suspend_pcr=[HW,TPM]
3878 Format: integer pcr id
3879 Specify that at suspend time, the tpm driver
3880 should extend the specified pcr with zeros,
3881 as a workaround for some chips which fail to
3882 flush the last written pcr on TPM_SaveState.
3883 This will guarantee that all the other pcrs
3886 trace_buf_size=nn[KMG]
3887 [FTRACE] will set tracing buffer size on each cpu.
3889 trace_event=[event-list]
3890 [FTRACE] Set and start specified trace events in order
3891 to facilitate early boot debugging.
3892 See also Documentation/trace/events.txt
3894 trace_options=[option-list]
3895 [FTRACE] Enable or disable tracer options at boot.
3896 The option-list is a comma delimited list of options
3897 that can be enabled or disabled just as if you were
3898 to echo the option name into
3900 /sys/kernel/debug/tracing/trace_options
3902 For example, to enable stacktrace option (to dump the
3903 stack trace of each event), add to the command line:
3905 trace_options=stacktrace
3907 See also Documentation/trace/ftrace.txt "trace options"
3911 Have the tracepoints sent to printk as well as the
3912 tracing ring buffer. This is useful for early boot up
3913 where the system hangs or reboots and does not give the
3914 option for reading the tracing buffer or performing a
3915 ftrace_dump_on_oops.
3917 To turn off having tracepoints sent to printk,
3918 echo 0 > /proc/sys/kernel/tracepoint_printk
3919 Note, echoing 1 into this file without the
3920 tracepoint_printk kernel cmdline option has no effect.
3924 Having tracepoints sent to printk() and activating high
3925 frequency tracepoints such as irq or sched, can cause
3926 the system to live lock.
3929 [FTRACE] enable this option to disable tracing when a
3930 warning is hit. This turns off "tracing_on". Tracing can
3931 be enabled again by echoing '1' into the "tracing_on"
3932 file located in /sys/kernel/debug/tracing/
3934 This option is useful, as it disables the trace before
3935 the WARNING dump is called, which prevents the trace to
3936 be filled with content caused by the warning output.
3938 This option can also be set at run time via the sysctl
3939 option: kernel/traceoff_on_warning
3941 transparent_hugepage=
3943 Format: [always|madvise|never]
3944 Can be used to control the default behavior of the system
3945 with respect to transparent hugepages.
3946 See Documentation/vm/transhuge.txt for more details.
3948 tsc= Disable clocksource stability checks for TSC.
3950 [x86] reliable: mark tsc clocksource as reliable, this
3951 disables clocksource verification at runtime, as well
3952 as the stability checks done at bootup. Used to enable
3953 high-resolution timer mode on older hardware, and in
3954 virtualized environment.
3955 [x86] noirqtime: Do not use TSC to do irq accounting.
3956 Used to run time disable IRQ_TIME_ACCOUNTING on any
3957 platforms where RDTSC is slow and this accounting
3960 turbografx.map[2|3]= [HW,JOY]
3961 TurboGraFX parallel port interface
3963 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3964 See also Documentation/input/joystick-parport.txt
3966 udbg-immortal [PPC] When debugging early kernel crashes that
3967 happen after console_init() and before a proper
3968 console driver takes over, this boot options might
3969 help "seeing" what's going on.
3971 uhash_entries= [KNL,NET]
3972 Set number of hash buckets for UDP/UDP-Lite connections
3975 [USB] Ignore overcurrent events (default N).
3976 Some badly-designed motherboards generate lots of
3977 bogus events, for ports that aren't wired to
3978 anything. Set this parameter to avoid log spamming.
3979 Note that genuine overcurrent events won't be
3983 [X86] Cause panic on unknown NMI.
3985 usbcore.authorized_default=
3986 [USB] Default USB device authorization:
3987 (default -1 = authorized except for wireless USB,
3988 0 = not authorized, 1 = authorized)
3990 usbcore.autosuspend=
3991 [USB] The autosuspend time delay (in seconds) used
3992 for newly-detected USB devices (default 2). This
3993 is the time required before an idle device will be
3994 autosuspended. Devices for which the delay is set
3995 to a negative value won't be autosuspended at all.
3997 usbcore.usbfs_snoop=
3998 [USB] Set to log all usbfs traffic (default 0 = off).
4000 usbcore.usbfs_snoop_max=
4001 [USB] Maximum number of bytes to snoop in each URB
4004 usbcore.blinkenlights=
4005 [USB] Set to cycle leds on hubs (default 0 = off).
4007 usbcore.old_scheme_first=
4008 [USB] Start with the old device initialization
4009 scheme (default 0 = off).
4011 usbcore.usbfs_memory_mb=
4012 [USB] Memory limit (in MB) for buffers allocated by
4013 usbfs (default = 16, 0 = max = 2047).
4015 usbcore.use_both_schemes=
4016 [USB] Try the other device initialization scheme
4017 if the first one fails (default 1 = enabled).
4019 usbcore.initial_descriptor_timeout=
4020 [USB] Specifies timeout for the initial 64-byte
4021 USB_REQ_GET_DESCRIPTOR request in milliseconds
4022 (default 5000 = 5.0 seconds).
4024 usbcore.nousb [USB] Disable the USB subsystem
4027 [USBHID] The interval which mice are to be polled at.
4029 usb-storage.delay_use=
4030 [UMS] The delay in seconds before a new device is
4031 scanned for Logical Units (default 1).
4034 [UMS] A list of quirks entries to supplement or
4035 override the built-in unusual_devs list. List
4036 entries are separated by commas. Each entry has
4037 the form VID:PID:Flags where VID and PID are Vendor
4038 and Product ID values (4-digit hex numbers) and
4039 Flags is a set of characters, each corresponding
4040 to a common usb-storage quirk flag as follows:
4041 a = SANE_SENSE (collect more than 18 bytes
4043 b = BAD_SENSE (don't collect more than 18
4044 bytes of sense data);
4045 c = FIX_CAPACITY (decrease the reported
4046 device capacity by one sector);
4047 d = NO_READ_DISC_INFO (don't use
4048 READ_DISC_INFO command);
4049 e = NO_READ_CAPACITY_16 (don't use
4050 READ_CAPACITY_16 command);
4051 f = NO_REPORT_OPCODES (don't use report opcodes
4053 g = MAX_SECTORS_240 (don't transfer more than
4054 240 sectors at a time, uas only);
4055 h = CAPACITY_HEURISTICS (decrease the
4056 reported device capacity by one
4057 sector if the number is odd);
4058 i = IGNORE_DEVICE (don't bind to this
4060 l = NOT_LOCKABLE (don't try to lock and
4061 unlock ejectable media);
4062 m = MAX_SECTORS_64 (don't transfer more
4063 than 64 sectors = 32 KB at a time);
4064 n = INITIAL_READ10 (force a retry of the
4065 initial READ(10) command);
4066 o = CAPACITY_OK (accept the capacity
4067 reported by the device);
4068 p = WRITE_CACHE (the device cache is ON
4070 r = IGNORE_RESIDUE (the device reports
4071 bogus residue values);
4072 s = SINGLE_LUN (the device has only one
4074 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4075 commands, uas only);
4076 u = IGNORE_UAS (don't bind to the uas driver);
4077 w = NO_WP_DETECT (don't test whether the
4078 medium is write-protected).
4079 Example: quirks=0419:aaf5:rl,0421:0433:rc
4081 user_debug= [KNL,ARM]
4083 See arch/arm/Kconfig.debug help text.
4084 1 - undefined instruction events
4086 4 - invalid data aborts
4089 Example: user_debug=31
4092 [X86] Flags controlling user PTE allocations.
4094 nohigh = do not allocate PTE pages in
4095 HIGHMEM regardless of setting
4099 On X86_32, this is an alias for vdso32=. Otherwise:
4101 vdso=1: enable VDSO (the default)
4102 vdso=0: disable VDSO mapping
4104 vdso32= [X86] Control the 32-bit vDSO
4105 vdso32=1: enable 32-bit VDSO
4106 vdso32=0 or vdso32=2: disable 32-bit VDSO
4108 See the help text for CONFIG_COMPAT_VDSO for more
4109 details. If CONFIG_COMPAT_VDSO is set, the default is
4110 vdso32=0; otherwise, the default is vdso32=1.
4112 For compatibility with older kernels, vdso32=2 is an
4115 Try vdso32=0 if you encounter an error that says:
4116 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4119 vector=percpu: enable percpu vector domain
4121 video= [FB] Frame buffer configuration
4122 See Documentation/fb/modedb.txt.
4124 video.brightness_switch_enabled= [0,1]
4125 If set to 1, on receiving an ACPI notify event
4126 generated by hotkey, video driver will adjust brightness
4127 level and then send out the event to user space through
4128 the allocated input device; If set to 0, video driver
4129 will only send out the event without touching backlight
4134 [VMMIO] Memory mapped virtio (platform) device.
4136 <size>@<baseaddr>:<irq>[:<id>]
4138 <size> := size (can use standard suffixes
4140 <baseaddr> := physical base address
4141 <irq> := interrupt number (as passed to
4143 <id> := (optional) platform device id
4145 virtio_mmio.device=1K@0x100b0000:48:7
4147 Can be used multiple times for multiple devices.
4149 vga= [BOOT,X86-32] Select a particular video mode
4150 See Documentation/x86/boot.txt and
4151 Documentation/svga.txt.
4152 Use vga=ask for menu.
4153 This is actually a boot loader parameter; the value is
4154 passed to the kernel using a special protocol.
4156 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4157 size of <nn>. This can be used to increase the
4158 minimum size (128MB on x86). It can also be used to
4159 decrease the size and leave more room for directly
4162 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4165 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4168 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4172 Controls the behavior of vsyscalls (i.e. calls to
4173 fixed addresses of 0xffffffffff600x00 from legacy
4174 code). Most statically-linked binaries and older
4175 versions of glibc use these calls. Because these
4176 functions are at fixed addresses, they make nice
4177 targets for exploits that can control RIP.
4179 emulate [default] Vsyscalls turn into traps and are
4180 emulated reasonably safely.
4182 native Vsyscalls are native syscall instructions.
4183 This is a little bit faster than trapping
4184 and makes a few dynamic recompilers work
4185 better than they would in emulation mode.
4186 It also makes exploits much easier to write.
4188 none Vsyscalls don't work at all. This makes
4189 them quite hard to use for exploits but
4190 might break your system.
4192 vt.color= [VT] Default text color.
4193 Format: 0xYX, X = foreground, Y = background.
4194 Default: 0x07 = light gray on black.
4196 vt.cur_default= [VT] Default cursor shape.
4197 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4198 the parameters of the <Esc>[?A;B;Cc escape sequence;
4199 see VGA-softcursor.txt. Default: 2 = underline.
4201 vt.default_blu= [VT]
4202 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4203 Change the default blue palette of the console.
4204 This is a 16-member array composed of values
4207 vt.default_grn= [VT]
4208 Format: <green0>,<green1>,<green2>,...,<green15>
4209 Change the default green palette of the console.
4210 This is a 16-member array composed of values
4213 vt.default_red= [VT]
4214 Format: <red0>,<red1>,<red2>,...,<red15>
4215 Change the default red palette of the console.
4216 This is a 16-member array composed of values
4222 Set system-wide default UTF-8 mode for all tty's.
4223 Default is 1, i.e. UTF-8 mode is enabled for all
4224 newly opened terminals.
4226 vt.global_cursor_default=
4229 Set system-wide default for whether a cursor
4230 is shown on new VTs. Default is -1,
4231 i.e. cursors will be created by default unless
4232 overridden by individual drivers. 0 will hide
4233 cursors, 1 will display them.
4235 vt.italic= [VT] Default color for italic text; 0-15.
4238 vt.underline= [VT] Default color for underlined text; 0-15.
4241 watchdog timers [HW,WDT] For information on watchdog timers,
4242 see Documentation/watchdog/watchdog-parameters.txt
4243 or other driver-specific files in the
4244 Documentation/watchdog/ directory.
4246 workqueue.watchdog_thresh=
4247 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4248 warn stall conditions and dump internal state to
4249 help debugging. 0 disables workqueue stall
4250 detection; otherwise, it's the stall threshold
4251 duration in seconds. The default value is 30 and
4252 it can be updated at runtime by writing to the
4253 corresponding sysfs file.
4255 workqueue.disable_numa
4256 By default, all work items queued to unbound
4257 workqueues are affine to the NUMA nodes they're
4258 issued on, which results in better behavior in
4259 general. If NUMA affinity needs to be disabled for
4260 whatever reason, this option can be used. Note
4261 that this also can be controlled per-workqueue for
4262 workqueues visible under /sys/bus/workqueue/.
4264 workqueue.power_efficient
4265 Per-cpu workqueues are generally preferred because
4266 they show better performance thanks to cache
4267 locality; unfortunately, per-cpu workqueues tend to
4268 be more power hungry than unbound workqueues.
4270 Enabling this makes the per-cpu workqueues which
4271 were observed to contribute significantly to power
4272 consumption unbound, leading to measurably lower
4273 power usage at the cost of small performance
4276 The default value of this parameter is determined by
4277 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4279 workqueue.debug_force_rr_cpu
4280 Workqueue used to implicitly guarantee that work
4281 items queued without explicit CPU specified are put
4282 on the local CPU. This guarantee is no longer true
4283 and while local CPU is still preferred work items
4284 may be put on foreign CPUs. This debug option
4285 forces round-robin CPU selection to flush out
4286 usages which depend on the now broken guarantee.
4287 When enabled, memory and cache locality will be
4290 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4291 default x2apic cluster mode on platforms
4294 x86_intel_mid_timer= [X86-32,APBT]
4295 Choose timer option for x86 Intel MID platform.
4296 Two valid options are apbt timer only and lapic timer
4297 plus one apbt timer for broadcast timer.
4298 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4300 xen_512gb_limit [KNL,X86-64,XEN]
4301 Restricts the kernel running paravirtualized under Xen
4302 to use only up to 512 GB of RAM. The reason to do so is
4303 crash analysis tools and Xen tools for doing domain
4304 save/restore/migration must be enabled to handle larger
4307 xen_emul_unplug= [HW,X86,XEN]
4308 Unplug Xen emulated devices
4309 Format: [unplug0,][unplug1]
4310 ide-disks -- unplug primary master IDE devices
4311 aux-ide-disks -- unplug non-primary-master IDE devices
4312 nics -- unplug network devices
4313 all -- unplug all emulated devices (NICs and IDE disks)
4314 unnecessary -- unplugging emulated devices is
4315 unnecessary even if the host did not respond to
4317 never -- do not unplug even if version check succeeds
4319 xen_nopvspin [X86,XEN]
4320 Disables the ticketlock slowpath using Xen PV
4324 Disables the PV optimizations forcing the HVM guest to
4325 run as generic HVM guest with no PV drivers.
4327 xirc2ps_cs= [NET,PCMCIA]
4329 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4331 ______________________________________________________________________
4335 Add more DRM drivers.
projects / cascardo / linux.git / blob