4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
450 [SECURITY] Disable capabilities. This would normally
451 be used only if an alternative security model is to be
452 configured. Potentially dangerous and should only be
453 used if you are entirely sure of the consequences.
455 ccw_timeout_log [S390]
456 See Documentation/s390/CommonIO for details.
458 cgroup_disable= [KNL] Disable a particular controller
459 Format: {name of the controller(s) to disable}
460 {Currently supported controllers - "memory"}
462 checkreqprot [SELINUX] Set initial checkreqprot flag value.
463 Format: { "0" | "1" }
464 See security/selinux/Kconfig help text.
465 0 -- check protection applied by kernel (includes
466 any implied execute protection).
467 1 -- check protection requested by application.
468 Default value is set via a kernel config option.
469 Value can be changed at runtime via
470 /selinux/checkreqprot.
473 See Documentation/s390/CommonIO for details.
475 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
477 Forces specified clocksource (if available) to be used
478 when calculating gettimeofday(). If specified
479 clocksource is not available, it defaults to PIT.
480 Format: { pit | tsc | cyclone | pmtmr }
482 clocksource= Override the default clocksource
484 Override the default clocksource and use the clocksource
485 with the name specified.
486 Some clocksource names to choose from, depending on
488 [all] jiffies (this is the base, fallback clocksource)
490 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
491 pxa_timer,timer3,32k_counter,timer0_1
493 [X86-32] pit,hpet,tsc;
494 scx200_hrt on Geode; cyclone on IBM x440
502 clearcpuid=BITNUM [X86]
503 Disable CPUID feature X for the kernel. See
504 arch/x86/include/asm/cpufeature.h for the valid bit
505 numbers. Note the Linux specific bits are not necessarily
506 stable over kernel options, but the vendor specific
508 Also note that user programs calling CPUID directly
509 or using the feature without checking anything
510 will still see it. This just prevents it from
511 being used by the kernel or shown in /proc/cpuinfo.
512 Also note the kernel might malfunction if you disable
516 Sets the size of kernel global memory area for contiguous
517 memory allocations. For more information, see
518 include/linux/dma-contiguous.h
520 cmo_free_hint= [PPC] Format: { yes | no }
521 Specify whether pages are marked as being inactive
522 when they are freed. This is used in CMO environments
523 to determine OS memory pressure for page stealing by
527 coherent_pool=nn[KMG] [ARM,KNL]
528 Sets the size of memory pool for coherent, atomic dma
529 allocations, by default set to 256K.
531 code_bytes [X86] How many bytes of object code to print
536 com20020= [HW,NET] ARCnet - COM20020 chipset
538 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
540 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
544 ARCnet - COM90xx chipset (memory-mapped buffers)
545 Format: <io>[,<irq>[,<memstart>]]
547 condev= [HW,S390] console device
550 console= [KNL] Output console device and options.
552 tty<n> Use the virtual console device <n>.
556 Use the specified serial port. The options are of
557 the form "bbbbpnf", where "bbbb" is the baud rate,
558 "p" is parity ("n", "o", or "e"), "n" is number of
559 bits, and "f" is flow control ("r" for RTS or
560 omit it). Default is "9600n8".
562 See Documentation/serial-console.txt for more
564 Documentation/networking/netconsole.txt for an
567 uart[8250],io,<addr>[,options]
568 uart[8250],mmio,<addr>[,options]
569 Start an early, polled-mode console on the 8250/16550
570 UART at the specified I/O port or MMIO address,
571 switching to the matching ttyS device later. The
572 options are the same as for ttyS, above.
574 If the device connected to the port is not a TTY but a braille
575 device, prepend "brl," before the device type, for instance
577 For now, only VisioBraille is supported.
579 consoleblank= [KNL] The console blank (screen saver) timeout in
580 seconds. Defaults to 10*60 = 10mins. A value of 0
581 disables the blank timer.
584 [KNL] Change the default value for
585 /proc/<pid>/coredump_filter.
586 See also Documentation/filesystems/proc.txt.
588 cpuidle.off=1 [CPU_IDLE]
589 disable the cpuidle sub-system
591 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
593 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
595 crashkernel=size[KMG][@offset[KMG]]
596 [KNL] Using kexec, Linux can switch to a 'crash kernel'
597 upon panic. This parameter reserves the physical
598 memory region [offset, offset + size] for that kernel
599 image. If '@offset' is omitted, then a suitable offset
600 is selected automatically. Check
601 Documentation/kdump/kdump.txt for further details.
603 crashkernel=range1:size1[,range2:size2,...][@offset]
604 [KNL] Same as above, but depends on the memory
605 in the running system. The syntax of range is
606 start-[end] where start and end are both
607 a memory unit (amount[KMG]). See also
608 Documentation/kdump/kdump.txt for an example.
613 cs89x0_media= [HW,NET]
614 Format: { rj45 | aui | bnc }
617 See header of drivers/s390/block/dasd_devmap.c.
619 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
620 (one device per port)
621 Format: <port#>,<type>
622 See also Documentation/input/joystick-parport.txt
624 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
625 time. See Documentation/dynamic-debug-howto.txt for
626 details. Deprecated, see dyndbg.
628 debug [KNL] Enable kernel debugging (events log level).
631 [KNL] verbose self-tests
633 Print debugging info while doing the locking API
635 We default to 0 (no extra messages), setting it to
636 1 will print _a lot_ more information - normally
637 only useful to kernel developers.
639 debug_objects [KNL] Enable object debugging
642 [KNL] Disable object debugging
644 debug_guardpage_minorder=
645 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
646 parameter allows control of the order of pages that will
647 be intentionally kept free (and hence protected) by the
648 buddy allocator. Bigger value increase the probability
649 of catching random memory corruption, but reduce the
650 amount of memory for normal system use. The maximum
651 possible value is MAX_ORDER/2. Setting this parameter
652 to 1 or 2 should be enough to identify most random
653 memory corruption problems caused by bugs in kernel or
654 driver code when a CPU writes to (or reads from) a
655 random memory location. Note that there exists a class
656 of memory corruptions problems caused by buggy H/W or
657 F/W or by drivers badly programing DMA (basically when
658 memory is written at bus level and the CPU MMU is
659 bypassed) which are not detectable by
660 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
661 tracking down these problems.
663 debugpat [X86] Enable PAT debugging
665 decnet.addr= [HW,NET]
666 Format: <area>[,<node>]
667 See also Documentation/networking/decnet.txt.
670 [same as hugepagesz=] The size of the default
671 HugeTLB page size. This is the size represented by
672 the legacy /proc/ hugepages APIs, used for SHM, and
673 default size when mounting hugetlbfs filesystems.
674 Defaults to the default architecture's huge page size
678 Set number of hash buckets for dentry cache.
681 IO parameters + enable/disable command.
683 digiepca= [HW,SERIAL]
684 See drivers/char/README.epca and
685 Documentation/serial/digiepca.txt.
688 See Documentation/networking/ipv6.txt.
690 disable_ddw [PPC/PSERIES]
691 Disable Dynamic DMA Window support. Use this if
692 to workaround buggy firmware.
695 See Documentation/networking/ipv6.txt.
697 disable_mtrr_cleanup [X86]
698 The kernel tries to adjust MTRR layout from continuous
699 to discrete, to make X server driver able to add WB
700 entry later. This parameter disables that.
702 disable_mtrr_trim [X86, Intel and AMD only]
703 By default the kernel will trim any uncacheable
704 memory out of your available memory pool based on
705 MTRR settings. This parameter disables that behavior,
706 possibly causing your machine to run very slowly.
708 disable_timer_pin_1 [X86]
709 Disable PIN 1 of APIC timer
710 Can be useful to work around chipset bugs.
712 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
713 this option disables the debugging code at boot.
715 dma_debug_entries=<number>
716 This option allows to tune the number of preallocated
717 entries for DMA-API debugging code. One entry is
718 required per DMA-API allocation. Use this if the
719 DMA-API debugging code disables itself because the
720 architectural default is too low.
722 dma_debug_driver=<driver_name>
723 With this option the DMA-API debugging driver
724 filter feature can be enabled at boot time. Just
725 pass the driver to filter for as the parameter.
726 The filter can be disabled or changed to another
727 driver later using sysfs.
729 drm_kms_helper.edid_firmware=[<connector>:]<file>
730 Broken monitors, graphic adapters and KVMs may
731 send no or incorrect EDID data sets. This parameter
732 allows to specify an EDID data set in the
733 /lib/firmware directory that is used instead.
734 Generic built-in EDID data sets are used, if one of
735 edid/1024x768.bin, edid/1280x1024.bin,
736 edid/1680x1050.bin, or edid/1920x1080.bin is given
737 and no file with the same name exists. Details and
738 instructions how to build your own EDID data are
739 available in Documentation/EDID/HOWTO.txt. An EDID
740 data set will only be used for a particular connector,
741 if its name and a colon are prepended to the EDID
746 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
747 module.dyndbg[="val"]
748 Enable debug messages at boot time. See
749 Documentation/dynamic-debug-howto.txt for details.
751 earlycon= [KNL] Output early console device and options.
752 uart[8250],io,<addr>[,options]
753 uart[8250],mmio,<addr>[,options]
754 uart[8250],mmio32,<addr>[,options]
755 Start an early, polled-mode console on the 8250/16550
756 UART at the specified I/O port or MMIO address.
757 MMIO inter-register address stride is either 8-bit
758 (mmio) or 32-bit (mmio32).
759 The options are the same as for ttyS, above.
761 earlyprintk= [X86,SH,BLACKFIN]
763 earlyprintk=serial[,ttySn[,baudrate]]
764 earlyprintk=ttySn[,baudrate]
765 earlyprintk=dbgp[debugController#]
767 Append ",keep" to not disable it when the real console
770 Only vga or serial or usb debug port at a time.
772 Currently only ttyS0 and ttyS1 are supported.
774 Interaction with the standard serial driver is not
777 The VGA output is eventually overwritten by the real
780 ekgdboc= [X86,KGDB] Allow early kernel console debugging
783 This is designed to be used in conjunction with
784 the boot argument: earlyprintk=vga
787 Format: {"off" | "on" | "skip[mbr]"}
789 eisa_irq_edge= [PARISC,HW]
790 See header of drivers/parisc/eisa.c.
793 See comment before function elanfreq_setup() in
794 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
797 Format: {"cfq" | "deadline" | "noop"}
798 See Documentation/block/cfq-iosched.txt and
799 Documentation/block/deadline-iosched.txt for details.
801 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
802 Specifies physical address of start of kernel core
803 image elf header and optionally the size. Generally
804 kexec loader will pass this option to capture kernel.
805 See Documentation/kdump/kdump.txt for details.
807 enable_mtrr_cleanup [X86]
808 The kernel tries to adjust MTRR layout from continuous
809 to discrete, to make X server driver able to add WB
810 entry later. This parameter enables that.
812 enable_timer_pin_1 [X86]
813 Enable PIN 1 of APIC timer
814 Can be useful to work around chipset bugs
815 (in particular on some ATI chipsets).
816 The kernel tries to set a reasonable default.
818 enforcing [SELINUX] Set initial enforcing status.
820 See security/selinux/Kconfig help text.
821 0 -- permissive (log only, no denials).
822 1 -- enforcing (deny and log).
824 Value can be changed at runtime via /selinux/enforce.
827 Disable Error Record Serialization Table (ERST)
830 ether= [HW,NET] Ethernet cards parameters
831 This option is obsoleted by the "netdev=" option, which
832 has equivalent usage. See its documentation for details.
836 Permit 'security.evm' to be updated regardless of
837 current integrity status.
841 fail_make_request=[KNL]
842 General fault injection mechanism.
843 Format: <interval>,<probability>,<space>,<times>
844 See also Documentation/fault-injection/.
847 See Documentation/blockdev/floppy.txt.
849 force_pal_cache_flush
850 [IA-64] Avoid check_sal_cache_flush which may hang on
851 buggy SAL_CACHE_FLUSH implementations. Using this
852 parameter will force ia64_sal_cache_flush to call
853 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
856 [FTRACE] will set and start the specified tracer
857 as early as possible in order to facilitate early
860 ftrace_dump_on_oops[=orig_cpu]
861 [FTRACE] will dump the trace buffers on oops.
862 If no parameter is passed, ftrace will dump
863 buffers of all CPUs, but if you pass orig_cpu, it will
864 dump only the buffer of the CPU that triggered the
867 ftrace_filter=[function-list]
868 [FTRACE] Limit the functions traced by the function
869 tracer at boot up. function-list is a comma separated
870 list of functions. This list can be changed at run
871 time by the set_ftrace_filter file in the debugfs
874 ftrace_notrace=[function-list]
875 [FTRACE] Do not trace the functions specified in
876 function-list. This list can be changed at run time
877 by the set_ftrace_notrace file in the debugfs
880 ftrace_graph_filter=[function-list]
881 [FTRACE] Limit the top level callers functions traced
882 by the function graph tracer at boot up.
883 function-list is a comma separated list of functions
884 that can be changed at run time by the
885 set_graph_function file in the debugfs tracing directory.
888 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
889 support via parallel port (up to 5 devices per port)
890 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
891 See also Documentation/input/joystick-parport.txt
895 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
899 gcov_persist= [GCOV] When non-zero (default), profiling data for
900 kernel modules is saved and remains accessible via
901 debugfs, even when the module is unloaded/reloaded.
902 When zero, profiling data is discarded and associated
903 debugfs files are removed at module unload time.
905 gpt [EFI] Forces disk with valid GPT signature but
906 invalid Protective MBR to be treated as GPT.
908 grcan.enable0= [HW] Configuration of physical interface 0. Determines
909 the "Enable 0" bit of the configuration register.
912 grcan.enable1= [HW] Configuration of physical interface 1. Determines
913 the "Enable 0" bit of the configuration register.
916 grcan.select= [HW] Select which physical interface to use.
919 grcan.txsize= [HW] Sets the size of the tx buffer.
920 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
922 grcan.rxsize= [HW] Sets the size of the rx buffer.
923 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
926 hashdist= [KNL,NUMA] Large hashes allocated during boot
927 are distributed across NUMA nodes. Defaults on
928 for 64-bit NUMA, off otherwise.
929 Format: 0 | 1 (for off | on)
931 hcl= [IA-64] SGI's Hardware Graph compatibility layer
933 hd= [EIDE] (E)IDE hard drive subsystem geometry
934 Format: <cyl>,<head>,<sect>
937 Disable Hardware Error Source Table (HEST) support;
938 corresponding firmware-first mode error processing
939 logic will be disabled.
941 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
942 size of <nn>. This works even on boxes that have no
943 highmem otherwise. This also works to reduce highmem
944 size on bigger boxes.
946 highres= [KNL] Enable/disable high resolution timer mode.
947 Valid parameters: "on", "off"
951 See Documentation/isdn/README.HiSax.
955 hpet= [X86-32,HPET] option to control HPET usage
956 Format: { enable (default) | disable | force |
958 disable: disable HPET and use PIT instead
959 force: allow force enabled of undocumented chips (ICH4,
961 verbose: show contents of HPET registers during setup
963 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
964 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
965 On x86-64 and powerpc, this option can be specified
966 multiple times interleaved with hugepages= to reserve
967 huge pages of different sizes. Valid pages sizes on
968 x86-64 are 2M (when the CPU supports "pse") and 1G
969 (when the CPU supports the "pdpe1gb" cpuinfo flag)
970 Note that 1GB pages can only be allocated at boot time
971 using hugepages= and not freed afterwards.
973 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
974 terminal devices. Valid values: 0..8
975 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
976 If specified, z/VM IUCV HVC accepts connections
977 from listed z/VM user IDs only.
980 Do not unregister boot console at start. This is only
981 useful for debugging when something happens in the window
982 between unregistering the boot console and initializing
985 i2c_bus= [HW] Override the default board specific I2C bus speed
986 or register an additional I2C bus that is not
987 registered from board initialization code.
991 i8042.debug [HW] Toggle i8042 debug mode
992 i8042.direct [HW] Put keyboard port into non-translated mode
993 i8042.dumbkbd [HW] Pretend that controller can only read data from
994 keyboard and cannot control its state
995 (Don't attempt to blink the leds)
996 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
997 i8042.nokbd [HW] Don't check/create keyboard port
998 i8042.noloop [HW] Disable the AUX Loopback command while probing
1000 i8042.nomux [HW] Don't check presence of an active multiplexing
1002 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1004 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1005 i8042.reset [HW] Reset the controller during init and cleanup
1006 i8042.unlock [HW] Unlock (ignore) the keylock
1010 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1011 indicates that the driver is running on unsupported
1013 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1014 does not match list of supported models.
1016 [HW] Report power status in /proc/i8k
1017 (disabled by default)
1018 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1021 i915.invert_brightness=
1022 [DRM] Invert the sense of the variable that is used to
1023 set the brightness of the panel backlight. Normally a
1024 brightness value of 0 indicates backlight switched off,
1025 and the maximum of the brightness value sets the backlight
1026 to maximum brightness. If this parameter is set to 0
1027 (default) and the machine requires it, or this parameter
1028 is set to 1, a brightness value of 0 sets the backlight
1029 to maximum brightness, and the maximum of the brightness
1030 value switches the backlight off.
1031 -1 -- never invert brightness
1032 0 -- machine default
1033 1 -- force brightness inversion
1036 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1038 ide-core.nodma= [HW] (E)IDE subsystem
1039 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1040 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1041 .cdrom .chs .ignore_cable are additional options
1042 See Documentation/ide/ide.txt.
1044 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1045 Claim all unknown PCI IDE storage controllers.
1048 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1049 Poll forces a polling idle loop that can slightly
1050 improve the performance of waking up a idle CPU, but
1051 will use a lot of power and make the system run hot.
1053 idle=mwait: On systems which support MONITOR/MWAIT but
1054 the kernel chose to not use it because it doesn't save
1055 as much power as a normal idle loop, use the
1056 MONITOR/MWAIT idle loop anyways. Performance should be
1057 the same as idle=poll.
1058 idle=halt: Halt is forced to be used for CPU idle.
1059 In such case C2/C3 won't be used again.
1060 idle=nomwait: Disable mwait for CPU C-states
1062 ignore_loglevel [KNL]
1063 Ignore loglevel setting - this will print /all/
1064 kernel messages to the console. Useful for debugging.
1065 We also add it as printk module parameter, so users
1066 could change it dynamically, usually by
1067 /sys/module/printk/parameters/ignore_loglevel.
1069 ihash_entries= [KNL]
1070 Set number of hash buckets for inode cache.
1072 ima_appraise= [IMA] appraise integrity measurements
1073 Format: { "off" | "enforce" | "fix" }
1076 ima_appraise_tcb [IMA]
1077 The builtin appraise policy appraises all files
1081 Format: { "0" | "1" }
1082 0 -- integrity auditing messages. (Default)
1083 1 -- enable informational integrity auditing messages.
1086 Format: { "sha1" | "md5" }
1090 Load a policy which meets the needs of the Trusted
1091 Computing Base. This means IMA will measure all
1092 programs exec'd, files mmap'd for exec, and all files
1093 opened for read by uid=0.
1097 Run specified binary instead of /sbin/init as init
1100 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1101 for working out where the kernel is dying during
1104 initrd= [BOOT] Specify the location of the initial ramdisk
1106 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1109 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1111 Enable intel iommu driver.
1113 Disable intel iommu driver.
1114 igfx_off [Default Off]
1115 By default, gfx is mapped as normal device. If a gfx
1116 device has a dedicated DMAR unit, the DMAR unit is
1117 bypassed by not enabling DMAR with this option. In
1118 this case, gfx device will use physical address for
1121 With this option iommu will not optimize to look
1122 for io virtual address below 32-bit forcing dual
1123 address cycle on pci bus for cards supporting greater
1124 than 32-bit addressing. The default is to look
1125 for translation below 32-bit and if not available
1126 then look in the higher range.
1127 strict [Default Off]
1128 With this option on every unmap_single operation will
1129 result in a hardware IOTLB flush operation as opposed
1130 to batching them for performance.
1131 sp_off [Default Off]
1132 By default, super page will be supported if Intel IOMMU
1133 has the capability. With this option, super page will
1136 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1137 0 disables intel_idle and fall back on acpi_idle.
1138 1 to 6 specify maximum depth of C-state.
1140 intremap= [X86-64, Intel-IOMMU]
1141 on enable Interrupt Remapping (default)
1142 off disable Interrupt Remapping
1143 nosid disable Source ID checking
1145 BIOS x2APIC opt-out request will be ignored
1147 iomem= Disable strict checking of access to MMIO memory
1148 strict regions from userspace.
1165 io7= [HW] IO7 for Marvel based alpha systems
1166 See comment before marvel_specify_io7 in
1167 arch/alpha/kernel/core_marvel.c.
1169 io_delay= [X86] I/O delay method
1171 Standard port 0x80 based delay
1173 Alternate port 0xed based delay (needed on some systems)
1175 Simple two microseconds delay
1180 See Documentation/filesystems/nfs/nfsroot.txt.
1182 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1183 See comment before ip2_setup() in
1184 drivers/char/ip2/ip2base.c.
1187 When an interrupt is not handled search all handlers
1188 for it. Intended to get systems with badly broken
1192 When an interrupt is not handled search all handlers
1193 for it. Also check all handlers each timer
1194 interrupt. Intended to get systems with badly broken
1198 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1200 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1202 <cpu number>,...,<cpu number>
1204 <cpu number>-<cpu number>
1205 (must be a positive range in ascending order)
1207 <cpu number>,...,<cpu number>-<cpu number>
1209 This option can be used to specify one or more CPUs
1210 to isolate from the general SMP balancing and scheduling
1211 algorithms. You can move a process onto or off an
1212 "isolated" CPU via the CPU affinity syscalls or cpuset.
1213 <cpu number> begins at 0 and the maximum value is
1214 "number of CPUs in system - 1".
1216 This option is the preferred way to isolate CPUs. The
1217 alternative -- manually setting the CPU mask of all
1218 tasks in the system -- can cause problems and
1219 suboptimal load balancer performance.
1223 js= [HW,JOY] Analog joystick
1224 See Documentation/input/joystick.txt.
1228 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1229 specifies the amount of memory usable by the kernel
1230 for non-movable allocations. The requested amount is
1231 spread evenly throughout all nodes in the system. The
1232 remaining memory in each node is used for Movable
1233 pages. In the event, a node is too small to have both
1234 kernelcore and Movable pages, kernelcore pages will
1235 take priority and other nodes will have a larger number
1236 of kernelcore pages. The Movable zone is used for the
1237 allocation of pages that may be reclaimed or moved
1238 by the page migration subsystem. This means that
1239 HugeTLB pages may not be allocated from this zone.
1240 Note that allocations like PTEs-from-HighMem still
1241 use the HighMem zone if it exists, and the Normal
1242 zone if it does not.
1244 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1245 Format: <Controller#>[,poll interval]
1246 The controller # is the number of the ehci usb debug
1247 port as it is probed via PCI. The poll interval is
1248 optional and is the number seconds in between
1249 each poll cycle to the debug port in case you need
1250 the functionality for interrupting the kernel with
1251 gdb or control-c on the dbgp connection. When
1252 not using this parameter you use sysrq-g to break into
1253 the kernel debugger.
1255 kgdboc= [KGDB,HW] kgdb over consoles.
1256 Requires a tty driver that supports console polling,
1257 or a supported polling keyboard driver (non-usb).
1258 Serial only format: <serial_device>[,baud]
1259 keyboard only format: kbd
1260 keyboard and serial format: kbd,<serial_device>[,baud]
1261 Optional Kernel mode setting:
1262 kms, kbd format: kms,kbd
1263 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1265 kgdbwait [KGDB] Stop kernel execution and enter the
1266 kernel debugger at the earliest opportunity.
1268 kmac= [MIPS] korina ethernet MAC address.
1269 Configure the RouterBoard 532 series on-chip
1270 Ethernet adapter MAC address.
1272 kmemleak= [KNL] Boot-time kmemleak enable/disable
1273 Valid arguments: on, off
1276 kstack=N [X86] Print N words from the kernel stack
1279 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1280 Default is 0 (don't ignore, but inject #GP)
1282 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1286 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1287 Default is 1 (enabled)
1289 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1291 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1293 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1294 (virtualized MMU) support on capable Intel chips.
1295 Default is 1 (enabled)
1297 kvm-intel.emulate_invalid_guest_state=
1298 [KVM,Intel] Enable emulation of invalid guest states
1299 Default is 0 (disabled)
1301 kvm-intel.flexpriority=
1302 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1303 Default is 1 (enabled)
1306 [KVM,Intel] Enable VMX nesting (nVMX).
1307 Default is 0 (disabled)
1309 kvm-intel.unrestricted_guest=
1310 [KVM,Intel] Disable unrestricted guest feature
1311 (virtualized real and unpaged mode) on capable
1312 Intel chips. Default is 1 (enabled)
1314 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1315 feature (tagged TLBs) on capable Intel chips.
1316 Default is 1 (enabled)
1322 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1325 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1326 value for LAPIC timer one-shot implementation. Default
1327 back to the programmable timer unit in the LAPIC.
1329 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1332 libata.dma= [LIBATA] DMA control
1333 libata.dma=0 Disable all PATA and SATA DMA
1334 libata.dma=1 PATA and SATA Disk DMA only
1335 libata.dma=2 ATAPI (CDROM) DMA only
1336 libata.dma=4 Compact Flash DMA only
1337 Combinations also work, so libata.dma=3 enables DMA
1338 for disks and CDROMs, but not CFs.
1340 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1341 libata.ignore_hpa=0 keep BIOS limits (default)
1342 libata.ignore_hpa=1 ignore limits, using full disk
1344 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1348 libata.force= [LIBATA] Force configurations. The format is comma
1349 separated list of "[ID:]VAL" where ID is
1350 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1351 matching port, link or device. Basically, it matches
1352 the ATA ID string printed on console by libata. If
1353 the whole ID part is omitted, the last PORT and DEVICE
1354 values are used. If ID hasn't been specified yet, the
1355 configuration applies to all ports, links and devices.
1357 If only DEVICE is omitted, the parameter applies to
1358 the port and all links and devices behind it. DEVICE
1359 number of 0 either selects the first device or the
1360 first fan-out link behind PMP device. It does not
1361 select the host link. DEVICE number of 15 selects the
1362 host link and device attached to it.
1364 The VAL specifies the configuration to force. As long
1365 as there's no ambiguity shortcut notation is allowed.
1366 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1367 The following configurations can be forced.
1369 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1370 Any ID with matching PORT is used.
1372 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1374 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1375 udma[/][16,25,33,44,66,100,133] notation is also
1378 * [no]ncq: Turn on or off NCQ.
1380 * nohrst, nosrst, norst: suppress hard, soft
1383 * rstonce: only attempt one reset during
1384 hot-unplug link recovery
1386 * dump_id: dump IDENTIFY data.
1388 If there are multiple matching configurations changing
1389 the same attribute, the last one is used.
1391 memblock=debug [KNL] Enable memblock debug messages.
1393 load_ramdisk= [RAM] List of ramdisks to load from floppy
1394 See Documentation/blockdev/ramdisk.txt.
1396 lockd.nlm_grace_period=P [NFS] Assign grace period.
1399 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1402 lockd.nlm_timeout=T [NFS] Assign timeout value.
1405 lockd.nlm_udpport=M [NFS] Assign UDP port.
1408 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1411 loglevel= All Kernel Messages with a loglevel smaller than the
1412 console loglevel will be printed to the console. It can
1413 also be changed with klogd or other programs. The
1414 loglevels are defined as follows:
1416 0 (KERN_EMERG) system is unusable
1417 1 (KERN_ALERT) action must be taken immediately
1418 2 (KERN_CRIT) critical conditions
1419 3 (KERN_ERR) error conditions
1420 4 (KERN_WARNING) warning conditions
1421 5 (KERN_NOTICE) normal but significant condition
1422 6 (KERN_INFO) informational
1423 7 (KERN_DEBUG) debug-level messages
1425 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1426 in bytes. n must be a power of two. The default
1427 size is set in the kernel config file.
1429 logo.nologo [FB] Disables display of the built-in Linux logo.
1430 This may be used to provide more screen space for
1431 kernel log messages and is useful when debugging
1432 kernel boot problems.
1434 lp=0 [LP] Specify parallel ports to use, e.g,
1435 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1436 lp=reset first parallel port). 'lp=0' disables the
1437 lp=auto printer driver. 'lp=reset' (which can be
1438 specified in addition to the ports) causes
1439 attached printers to be reset. Using
1440 lp=port1,port2,... specifies the parallel ports
1441 to associate lp devices with, starting with
1442 lp0. A port specification may be 'none' to skip
1443 that lp device, or a parport name such as
1444 'parport0'. Specifying 'lp=auto' instead of a
1445 port specification list means that device IDs
1446 from each port should be examined, to see if
1447 an IEEE 1284-compliant printer is attached; if
1448 so, the driver will manage that printer.
1449 See also header of drivers/char/lp.c.
1452 Sets loops_per_jiffy to given constant, thus avoiding
1453 time-consuming boot-time autodetection (up to 250 ms per
1454 CPU). 0 enables autodetection (default). To determine
1455 the correct value for your kernel, boot with normal
1456 autodetection and see what value is printed. Note that
1457 on SMP systems the preset will be applied to all CPUs,
1458 which is likely to cause problems if your CPUs need
1459 significantly divergent settings. An incorrect value
1460 will cause delays in the kernel to be wrong, leading to
1461 unpredictable I/O errors and other breakage. Although
1462 unlikely, in the extreme case this might damage your
1466 Format: <io>,<irq>,<dma>
1468 machvec= [IA-64] Force the use of a particular machine-vector
1469 (machvec) in a generic kernel.
1470 Example: machvec=hpzx1_swiotlb
1472 machtype= [Loongson] Share the same kernel image file between different
1474 Example: machtype=lemote-yeeloong-2f-7inch
1476 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1477 than or equal to this physical address is ignored.
1479 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1480 should make use of. maxcpus=n : n >= 0 limits the
1481 kernel to using 'n' processors. n=0 is a special case,
1482 it is equivalent to "nosmp", which also disables
1485 max_loop= [LOOP] The number of loop block devices that get
1486 (loop.max_loop) unconditionally pre-created at init time. The default
1487 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1488 of statically allocating a predefined number, loop
1489 devices can be requested on-demand with the
1490 /dev/loop-control interface.
1492 mce [X86-32] Machine Check Exception
1494 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1496 md= [HW] RAID subsystems devices and level
1497 See Documentation/md.txt.
1500 Format: <first>,<last>
1501 Specifies range of consoles to be captured by the MDA.
1503 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1504 Amount of memory to be used when the kernel is not able
1505 to see the whole system memory or for test.
1506 [X86] Work as limiting max address. Use together
1507 with memmap= to avoid physical address space collisions.
1508 Without memmap= PCI devices could be placed at addresses
1509 belonging to unused RAM.
1511 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1515 [KNL,SH] Allow user to override the default size for
1516 per-device physically contiguous DMA buffers.
1518 memmap=exactmap [KNL,X86] Enable setting of an exact
1519 E820 memory map, as specified by the user.
1520 Such memmap=exactmap lines can be constructed based on
1521 BIOS output or other requirements. See the memmap=nn@ss
1524 memmap=nn[KMG]@ss[KMG]
1525 [KNL] Force usage of a specific region of memory
1526 Region of memory to be used, from ss to ss+nn.
1528 memmap=nn[KMG]#ss[KMG]
1529 [KNL,ACPI] Mark specific memory as ACPI data.
1530 Region of memory to be used, from ss to ss+nn.
1532 memmap=nn[KMG]$ss[KMG]
1533 [KNL,ACPI] Mark specific memory as reserved.
1534 Region of memory to be used, from ss to ss+nn.
1535 Example: Exclude memory from 0x18690000-0x1869ffff
1536 memmap=64K$0x18690000
1538 memmap=0x10000$0x18690000
1540 memory_corruption_check=0/1 [X86]
1541 Some BIOSes seem to corrupt the first 64k of
1542 memory when doing things like suspend/resume.
1543 Setting this option will scan the memory
1544 looking for corruption. Enabling this will
1545 both detect corruption and prevent the kernel
1546 from using the memory being corrupted.
1547 However, its intended as a diagnostic tool; if
1548 repeatable BIOS-originated corruption always
1549 affects the same memory, you can use memmap=
1550 to prevent the kernel from using that memory.
1552 memory_corruption_check_size=size [X86]
1553 By default it checks for corruption in the low
1554 64k, making this memory unavailable for normal
1555 use. Use this parameter to scan for
1556 corruption in more or less memory.
1558 memory_corruption_check_period=seconds [X86]
1559 By default it checks for corruption every 60
1560 seconds. Use this parameter to check at some
1561 other rate. 0 disables periodic checking.
1563 memtest= [KNL,X86] Enable memtest
1565 default : 0 <disable>
1566 Specifies the number of memtest passes to be
1567 performed. Each pass selects another test
1568 pattern from a given set of patterns. Memtest
1569 fills the memory with this pattern, validates
1570 memory contents and reserves bad memory
1571 regions that are detected.
1573 meye.*= [HW] Set MotionEye Camera parameters
1574 See Documentation/video4linux/meye.txt.
1576 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1577 Multi-Function General Purpose Timers on AMD Geode
1580 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1581 the BIOS has incorrectly applied a workaround. TinyBIOS
1582 version 0.98 is known to be affected, 0.99 fixes the
1583 problem by letting the user disable the workaround.
1587 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1588 physical address is ignored.
1590 mini2440= [ARM,HW,KNL]
1591 Format:[0..2][b][c][t]
1593 MINI2440 configuration specification:
1594 0 - The attached screen is the 3.5" TFT
1595 1 - The attached screen is the 7" TFT
1596 2 - The VGA Shield is attached (1024x768)
1597 Leaving out the screen size parameter will not load
1598 the TFT driver, and the framebuffer will be left
1600 b - Enable backlight. The TFT backlight pin will be
1601 linked to the kernel VESA blanking code and a GPIO
1602 LED. This parameter is not necessary when using the
1604 c - Enable the s3c camera interface.
1605 t - Reserved for enabling touchscreen support. The
1606 touchscreen support is not enabled in the mainstream
1607 kernel as of 2.6.30, a preliminary port can be found
1608 in the "bleeding edge" mini2440 support kernel at
1609 http://repo.or.cz/w/linux-2.6/mini2440.git
1612 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1613 parameter allows control of the logging verbosity for
1614 the additional memory initialisation checks. A value
1615 of 0 disables mminit logging and a level of 4 will
1616 log everything. Information is printed at KERN_DEBUG
1617 so loglevel=8 may also need to be specified.
1620 [KNL] When CONFIG_MODULE_SIG is set, this means that
1621 modules without (valid) signatures will fail to load.
1622 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1623 is always true, so this option does nothing.
1626 [MOUSE] Maximum time between finger touching and
1627 leaving touchpad surface for touch to be considered
1628 a tap and be reported as a left button click (for
1629 touchpads working in absolute mode only).
1631 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1632 reporting absolute coordinates, such as tablets
1633 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1634 reporting absolute coordinates, such as tablets
1636 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1637 is similar to kernelcore except it specifies the
1638 amount of memory used for migratable allocations.
1639 If both kernelcore and movablecore is specified,
1640 then kernelcore will be at *least* the specified
1641 value but may be more. If movablecore on its own
1642 is specified, the administrator must be careful
1643 that the amount of memory usable for all allocations
1646 MTD_Partition= [MTD]
1647 Format: <name>,<region-number>,<size>,<offset>
1649 MTD_Region= [MTD] Format:
1650 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1653 See drivers/mtd/cmdlinepart.c.
1655 multitce=off [PPC] This parameter disables the use of the pSeries
1656 firmware feature for updating multiple TCE entries
1659 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1661 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1663 boundary - index of last SLC block on Flex-OneNAND.
1664 The remaining blocks are configured as MLC blocks.
1665 lock - Configure if Flex-OneNAND boundary should be locked.
1666 Once locked, the boundary cannot be changed.
1667 1 indicates lock status, 0 indicates unlock status.
1670 ARM/S3C2412 JIVE boot control
1672 See arch/arm/mach-s3c2412/mach-jive.c
1674 mtouchusb.raw_coordinates=
1675 [HW] Make the MicroTouch USB driver use raw coordinates
1676 ('y', default) or cooked coordinates ('n')
1678 mtrr_chunk_size=nn[KMG] [X86]
1679 used for mtrr cleanup. It is largest continuous chunk
1680 that could hold holes aka. UC entries.
1682 mtrr_gran_size=nn[KMG] [X86]
1683 Used for mtrr cleanup. It is granularity of mtrr block.
1685 Large value could prevent small alignment from
1688 mtrr_spare_reg_nr=n [X86]
1690 Range: 0,7 : spare reg number
1692 Used for mtrr cleanup. It is spare mtrr entries number.
1693 Set to 2 or more if your graphical card needs more.
1695 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1697 netdev= [NET] Network devices parameters
1698 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1699 Note that mem_start is often overloaded to mean
1700 something different and driver-specific.
1701 This usage is only documented in each driver source
1705 [NETFILTER] Enable connection tracking flow accounting
1706 0 to disable accounting
1707 1 to enable accounting
1710 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1711 See Documentation/filesystems/nfs/nfsroot.txt.
1713 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1714 See Documentation/filesystems/nfs/nfsroot.txt.
1716 nfsrootdebug [NFS] enable nfsroot debugging messages.
1717 See Documentation/filesystems/nfs/nfsroot.txt.
1719 nfs.callback_tcpport=
1720 [NFS] set the TCP port on which the NFSv4 callback
1721 channel should listen.
1724 [NFS] sets the pathname to the program which is used
1725 to update the NFS client cache entries.
1727 nfs.cache_getent_timeout=
1728 [NFS] sets the timeout after which an attempt to
1729 update a cache entry is deemed to have failed.
1731 nfs.idmap_cache_timeout=
1732 [NFS] set the maximum lifetime for idmapper cache
1736 [NFS] enable 64-bit inode numbers.
1737 If zero, the NFS client will fake up a 32-bit inode
1738 number for the readdir() and stat() syscalls instead
1739 of returning the full 64-bit number.
1740 The default is to return 64-bit inode numbers.
1742 nfs.max_session_slots=
1743 [NFSv4.1] Sets the maximum number of session slots
1744 the client will attempt to negotiate with the server.
1745 This limits the number of simultaneous RPC requests
1746 that the client can send to the NFSv4.1 server.
1747 Note that there is little point in setting this
1748 value higher than the max_tcp_slot_table_limit.
1750 nfs.nfs4_disable_idmapping=
1751 [NFSv4] When set to the default of '1', this option
1752 ensures that both the RPC level authentication
1753 scheme and the NFS level operations agree to use
1754 numeric uids/gids if the mount is using the
1755 'sec=sys' security flavour. In effect it is
1756 disabling idmapping, which can make migration from
1757 legacy NFSv2/v3 systems to NFSv4 easier.
1758 Servers that do not support this mode of operation
1759 will be autodetected by the client, and it will fall
1760 back to using the idmapper.
1761 To turn off this behaviour, set the value to '0'.
1763 [NFS4] Specify an additional fixed unique ident-
1764 ification string that NFSv4 clients can insert into
1765 their nfs_client_id4 string. This is typically a
1766 UUID that is generated at system install time.
1768 nfs.send_implementation_id =
1769 [NFSv4.1] Send client implementation identification
1770 information in exchange_id requests.
1771 If zero, no implementation identification information
1773 The default is to send the implementation identification
1776 nfsd.nfs4_disable_idmapping=
1777 [NFSv4] When set to the default of '1', the NFSv4
1778 server will return only numeric uids and gids to
1779 clients using auth_sys, and will accept numeric uids
1780 and gids from such clients. This is intended to ease
1781 migration from NFSv2/v3.
1783 objlayoutdriver.osd_login_prog=
1784 [NFS] [OBJLAYOUT] sets the pathname to the program which
1785 is used to automatically discover and login into new
1786 osd-targets. Please see:
1787 Documentation/filesystems/pnfs.txt for more explanations
1789 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1790 when a NMI is triggered.
1791 Format: [state][,regs][,debounce][,die]
1793 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1794 Format: [panic,][nopanic,][num]
1796 0 - turn nmi_watchdog off
1797 When panic is specified, panic when an NMI watchdog
1798 timeout occurs (or 'nopanic' to override the opposite
1800 This is useful when you use a panic=... timeout and
1801 need the box quickly up again.
1803 netpoll.carrier_timeout=
1804 [NET] Specifies amount of time (in seconds) that
1805 netpoll should wait for a carrier. By default netpoll
1808 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1809 emulation library even if a 387 maths coprocessor
1813 [HW] Never suspend the console
1814 Disable suspending of consoles during suspend and
1815 hibernate operations. Once disabled, debugging
1816 messages can reach various consoles while the rest
1817 of the system is being put to sleep (ie, while
1818 debugging driver suspend/resume hooks). This may
1819 not work reliably with all consoles, but is known
1820 to work with serial and VGA consoles.
1821 To facilitate more flexible debugging, we also add
1822 console_suspend, a printk module parameter to control
1823 it. Users could use console_suspend (usually
1824 /sys/module/printk/parameters/console_suspend) to
1825 turn on/off it dynamically.
1827 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1828 caches in the slab allocator. Saves per-node memory,
1829 but will impact performance.
1833 noapic [SMP,APIC] Tells the kernel to not make use of any
1834 IOAPICs that may be present in the system.
1836 noautogroup Disable scheduler automatic task group creation.
1838 nobats [PPC] Do not use BATs for mapping kernel lowmem
1839 on "Classic" PPC cores.
1843 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1845 nodelayacct [KNL] Disable per-task delay accounting
1847 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1849 nodsp [SH] Disable hardware DSP at boot time.
1851 noefi [X86] Disable EFI runtime services support.
1856 On X86-32 available only on PAE configured kernels.
1857 noexec=on: enable non-executable mappings (default)
1858 noexec=off: disable non-executable mappings
1861 Disable SMAP (Supervisor Mode Access Prevention)
1862 even if it is supported by processor.
1865 Disable SMEP (Supervisor Mode Execution Prevention)
1866 even if it is supported by processor.
1869 This affects only 32-bit executables.
1870 noexec32=on: enable non-executable mappings (default)
1871 read doesn't imply executable mappings
1872 noexec32=off: disable non-executable mappings
1873 read implies executable mappings
1875 nofpu [SH] Disable hardware FPU at boot time.
1877 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1878 register save and restore. The kernel will only save
1879 legacy floating-point registers on task switch.
1881 noxsave [BUGS=X86] Disables x86 extended register state save
1882 and restore using xsave. The kernel will fallback to
1883 enabling legacy floating-point and sse state.
1886 on enable eager fpu restore
1887 off disable eager fpu restore
1888 auto selects the default scheme, which automatically
1889 enables eagerfpu restore for xsaveopt.
1891 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1892 wfi(ARM) instruction doesn't work correctly and not to
1893 use it. This is also useful when using JTAG debugger.
1895 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1896 instruction doesn't work correctly and not to
1899 no_file_caps Tells the kernel not to honor file capabilities. The
1900 only way then for a file to be executed with privilege
1901 is to be setuid root or executed by root.
1903 nohalt [IA-64] Tells the kernel not to use the power saving
1904 function PAL_HALT_LIGHT when idle. This increases
1905 power-consumption. On the positive side, it reduces
1906 interrupt wake-up latency, which may improve performance
1907 in certain environments such as networked servers or
1910 nohz= [KNL] Boottime enable/disable dynamic ticks
1911 Valid arguments: on, off
1914 noiotrap [SH] Disables trapped I/O port accesses.
1916 noirqdebug [X86-32] Disables the code which attempts to detect and
1917 disable unhandled interrupt sources.
1919 no_timer_check [X86,APIC] Disables the code which tests for
1920 broken timer IRQ sources.
1922 noisapnp [ISAPNP] Disables ISA PnP code.
1924 noinitrd [RAM] Tells the kernel not to load any configured
1927 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1929 [Deprecated - use intremap=off]
1933 nojitter [IA-64] Disables jitter checking for ITC timers.
1935 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1937 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1940 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1941 steal time is computed, but won't influence scheduler
1944 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1946 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1948 noltlbs [PPC] Do not use large page/tlb entries for kernel
1949 lowmem mapping on PPC40x.
1951 nomca [IA-64] Disable machine check abort handling
1953 nomce [X86-32] Machine Check Exception
1955 nomfgpt [X86-32] Disable Multi-Function General Purpose
1956 Timer usage (for AMD Geode machines).
1958 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1959 shutdown the other cpus. Instead use the REBOOT_VECTOR
1962 nomodule Disable module load
1964 nopat [X86] Disable PAT (page attribute table extension of
1965 pagetables) support.
1967 norandmaps Don't use address space randomization. Equivalent to
1968 echo 0 > /proc/sys/kernel/randomize_va_space
1970 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1972 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1973 with UP alternatives
1975 noresidual [PPC] Don't use residual data on PReP machines.
1977 nordrand [X86] Disable the direct use of the RDRAND
1978 instruction even if it is supported by the
1979 processor. RDRAND is still available to user
1982 noresume [SWSUSP] Disables resume and restores original swap
1985 no-scroll [VGA] Disables scrollback.
1986 This is required for the Braillex ib80-piezo Braille
1987 reader made by F.H. Papenmeier (Germany).
1991 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1993 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1994 and disable the IO APIC. legacy for "maxcpus=0".
1996 nosoftlockup [KNL] Disable the soft-lockup detector.
1998 nosync [HW,M68K] Disables sync negotiation for all devices.
2000 notsc [BUGS=X86-32] Disable Time Stamp Counter
2002 nousb [USB] Disable the USB subsystem
2004 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2008 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2010 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2011 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2012 Some features depend on CPU0. Known dependencies are:
2013 1. Resume from suspend/hibernate depends on CPU0.
2014 Suspend/hibernate will fail if CPU0 is offline and you
2015 need to online CPU0 before suspend/hibernate.
2016 2. PIC interrupts also depend on CPU0. CPU0 can't be
2017 removed if a PIC interrupt is detected.
2018 It's said poweroff/reboot may depend on CPU0 on some
2019 machines although I haven't seen such issues so far
2020 after CPU0 is offline on a few tested machines.
2021 If the dependencies are under your control, you can
2022 turn on cpu0_hotplug.
2024 nptcg= [IA-64] Override max number of concurrent global TLB
2025 purges which is reported from either PAL_VM_SUMMARY or
2028 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2029 could support. nr_cpus=n : n >= 1 limits the kernel to
2030 supporting 'n' processors. Later in runtime you can not
2031 use hotplug cpu feature to put more cpu back to online.
2032 just like you compile the kernel NR_CPUS=n
2034 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2036 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2037 Allowed values are enable and disable
2039 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2040 one of ['zone', 'node', 'default'] can be specified
2041 This can be set from sysctl after boot.
2042 See Documentation/sysctl/vm.txt for details.
2044 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2045 See Documentation/debugging-via-ohci1394.txt for more
2048 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2049 Rather than timing out after 20 ms if an EC
2050 command is not properly ACKed, override the length
2051 of the timeout. We have interrupts disabled while
2052 waiting for the ACK, so if this is set too high
2053 interrupts *may* be lost!
2055 omap_mux= [OMAP] Override bootloader pin multiplexing.
2056 Format: <mux_mode0.mode_name=value>...
2057 For example, to override I2C bus2:
2058 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2060 oprofile.timer= [HW]
2061 Use timer interrupt instead of performance counters
2063 oprofile.cpu_type= Force an oprofile cpu type
2064 This might be useful if you have an older oprofile
2065 userland or if you want common events.
2066 Format: { arch_perfmon }
2067 arch_perfmon: [X86] Force use of architectural
2068 perfmon on Intel CPUs instead of the
2069 CPU specific event set.
2070 timer: [X86] Force use of architectural NMI
2071 timer mode (see also oprofile.timer
2072 for generic hr timer mode)
2073 [s390] Force legacy basic mode sampling
2074 (report cpu_type "timer")
2076 oops=panic Always panic on oopses. Default is to just kill the
2077 process, but there is a small probability of
2078 deadlocking the machine.
2079 This will also cause panics on machine check exceptions.
2080 Useful together with panic=30 to trigger a reboot.
2083 See Documentation/sound/oss/oss-parameters.txt
2085 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2086 timeout > 0: seconds before rebooting
2087 timeout = 0: wait forever
2088 timeout < 0: reboot immediately
2091 parkbd.port= [HW] Parallel port number the keyboard adapter is
2092 connected to, default is 0.
2094 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2095 0 for XT, 1 for AT (default is AT).
2098 parport= [HW,PPT] Specify parallel ports. 0 disables.
2099 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2100 Use 'auto' to force the driver to use any
2101 IRQ/DMA settings detected (the default is to
2102 ignore detected IRQ/DMA settings because of
2103 possible conflicts). You can specify the base
2104 address, IRQ, and DMA settings; IRQ and DMA
2105 should be numbers, or 'auto' (for using detected
2106 settings on that particular port), or 'nofifo'
2107 (to avoid using a FIFO even if it is detected).
2108 Parallel ports are assigned in the order they
2109 are specified on the command line, starting
2112 parport_init_mode= [HW,PPT]
2113 Configure VIA parallel port to operate in
2114 a specific mode. This is necessary on Pegasos
2115 computer where firmware has no options for setting
2116 up parallel port mode and sets it to spp.
2117 Currently this function knows 686a and 8231 chips.
2118 Format: [spp|ps2|epp|ecp|ecpepp]
2121 Halt all CPUs after the first oops has been printed for
2122 the specified number of seconds. This is to be used if
2123 your oopses keep scrolling off the screen.
2128 See header of drivers/block/paride/pcd.c.
2129 See also Documentation/blockdev/paride.txt.
2131 pci=option[,option...] [PCI] various PCI subsystem options:
2132 earlydump [X86] dump PCI config space before the kernel
2134 off [X86] don't probe for the PCI bus
2135 bios [X86-32] force use of PCI BIOS, don't access
2136 the hardware directly. Use this if your machine
2137 has a non-standard PCI host bridge.
2138 nobios [X86-32] disallow use of PCI BIOS, only direct
2139 hardware access methods are allowed. Use this
2140 if you experience crashes upon bootup and you
2141 suspect they are caused by the BIOS.
2142 conf1 [X86] Force use of PCI Configuration
2144 conf2 [X86] Force use of PCI Configuration
2146 noaer [PCIE] If the PCIEAER kernel config parameter is
2147 enabled, this kernel boot option can be used to
2148 disable the use of PCIE advanced error reporting.
2149 nodomains [PCI] Disable support for multiple PCI
2150 root domains (aka PCI segments, in ACPI-speak).
2151 nommconf [X86] Disable use of MMCONFIG for PCI
2153 check_enable_amd_mmconf [X86] check for and enable
2154 properly configured MMIO access to PCI
2155 config space on AMD family 10h CPU
2156 nomsi [MSI] If the PCI_MSI kernel config parameter is
2157 enabled, this kernel boot option can be used to
2158 disable the use of MSI interrupts system-wide.
2159 noioapicquirk [APIC] Disable all boot interrupt quirks.
2160 Safety option to keep boot IRQs enabled. This
2161 should never be necessary.
2162 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2163 primary IO-APIC for bridges that cannot disable
2164 boot IRQs. This fixes a source of spurious IRQs
2165 when the system masks IRQs.
2166 noioapicreroute [APIC] Disable workaround that uses the
2167 boot IRQ equivalent of an IRQ that connects to
2168 a chipset where boot IRQs cannot be disabled.
2169 The opposite of ioapicreroute.
2170 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2171 routing table. These calls are known to be buggy
2172 on several machines and they hang the machine
2173 when used, but on other computers it's the only
2174 way to get the interrupt routing table. Try
2175 this option if the kernel is unable to allocate
2176 IRQs or discover secondary PCI buses on your
2178 rom [X86] Assign address space to expansion ROMs.
2179 Use with caution as certain devices share
2180 address decoders between ROMs and other
2182 norom [X86] Do not assign address space to
2183 expansion ROMs that do not already have
2184 BIOS assigned address ranges.
2185 nobar [X86] Do not assign address space to the
2186 BARs that weren't assigned by the BIOS.
2187 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2188 assigned automatically to PCI devices. You can
2189 make the kernel exclude IRQs of your ISA cards
2191 pirqaddr=0xAAAAA [X86] Specify the physical address
2192 of the PIRQ table (normally generated
2193 by the BIOS) if it is outside the
2194 F0000h-100000h range.
2195 lastbus=N [X86] Scan all buses thru bus #N. Can be
2196 useful if the kernel is unable to find your
2197 secondary buses and you want to tell it
2198 explicitly which ones they are.
2199 assign-busses [X86] Always assign all PCI bus
2200 numbers ourselves, overriding
2201 whatever the firmware may have done.
2202 usepirqmask [X86] Honor the possible IRQ mask stored
2203 in the BIOS $PIR table. This is needed on
2204 some systems with broken BIOSes, notably
2205 some HP Pavilion N5400 and Omnibook XE3
2206 notebooks. This will have no effect if ACPI
2207 IRQ routing is enabled.
2208 noacpi [X86] Do not use ACPI for IRQ routing
2209 or for PCI scanning.
2210 use_crs [X86] Use PCI host bridge window information
2211 from ACPI. On BIOSes from 2008 or later, this
2212 is enabled by default. If you need to use this,
2213 please report a bug.
2214 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2215 If you need to use this, please report a bug.
2216 routeirq Do IRQ routing for all PCI devices.
2217 This is normally done in pci_enable_device(),
2218 so this option is a temporary workaround
2219 for broken drivers that don't call it.
2220 skip_isa_align [X86] do not align io start addr, so can
2221 handle more pci cards
2222 firmware [ARM] Do not re-enumerate the bus but instead
2223 just use the configuration from the
2224 bootloader. This is currently used on
2225 IXP2000 systems where the bus has to be
2226 configured a certain way for adjunct CPUs.
2227 noearly [X86] Don't do any early type 1 scanning.
2228 This might help on some broken boards which
2229 machine check when some devices' config space
2230 is read. But various workarounds are disabled
2231 and some IOMMU drivers will not work.
2232 bfsort Sort PCI devices into breadth-first order.
2233 This sorting is done to get a device
2234 order compatible with older (<= 2.4) kernels.
2235 nobfsort Don't sort PCI devices into breadth-first order.
2236 cbiosize=nn[KMG] The fixed amount of bus space which is
2237 reserved for the CardBus bridge's IO window.
2238 The default value is 256 bytes.
2239 cbmemsize=nn[KMG] The fixed amount of bus space which is
2240 reserved for the CardBus bridge's memory
2241 window. The default value is 64 megabytes.
2244 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2245 Specifies alignment and device to reassign
2246 aligned memory resources.
2247 If <order of align> is not specified,
2248 PAGE_SIZE is used as alignment.
2249 PCI-PCI bridge can be specified, if resource
2250 windows need to be expanded.
2251 ecrc= Enable/disable PCIe ECRC (transaction layer
2252 end-to-end CRC checking).
2253 bios: Use BIOS/firmware settings. This is the
2257 realloc= Enable/disable reallocating PCI bridge resources
2258 if allocations done by BIOS are too small to
2259 accommodate resources required by all child
2261 off: Turn realloc off
2263 realloc same as realloc=on
2264 noari do not use PCIe ARI.
2265 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2266 only look for one device below a PCIe downstream
2269 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2272 force Enable ASPM even on devices that claim not to support it.
2273 WARNING: Forcing ASPM on may cause system lockups.
2275 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2276 nomsi Do not use MSI for PCI Express Native Hotplug (this
2277 makes all PCIe ports use INTx for hotplug services).
2279 pcie_ports= [PCIE] PCIe ports handling:
2280 auto Ask the BIOS whether or not to use native PCIe services
2281 associated with PCIe ports (PME, hot-plug, AER). Use
2282 them only if that is allowed by the BIOS.
2283 native Use native PCIe services associated with PCIe ports
2285 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2288 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2289 nomsi Do not use MSI for native PCIe PME signaling (this makes
2290 all PCIe root ports use INTx for all services).
2292 pcmv= [HW,PCMCIA] BadgePAD 4
2295 See Documentation/blockdev/paride.txt.
2297 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2300 See arch/parisc/kernel/pdc_chassis.c
2302 percpu_alloc= Select which percpu first chunk allocator to use.
2303 Currently supported values are "embed" and "page".
2304 Archs may support subset or none of the selections.
2305 See comments in mm/percpu.c for details on each
2306 allocator. This parameter is primarily for debugging
2307 and performance comparison.
2310 See Documentation/blockdev/paride.txt.
2313 See Documentation/blockdev/paride.txt.
2315 pirq= [SMP,APIC] Manual mp-table setup
2316 See Documentation/x86/i386/IO-APIC.txt.
2318 plip= [PPT,NET] Parallel port network link
2319 Format: { parport<nr> | timid | 0 }
2320 See also Documentation/parport.txt.
2322 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2323 Override pmtimer IOPort with a hex value.
2327 Enable PNP debug messages (depends on the
2328 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2329 via /sys/module/pnp/parameters/debug. We always show
2330 current resource usage; turning this on also shows
2331 possible settings and some assignment information.
2337 { on | off | curr | res | no-curr | no-res }
2340 [ISAPNP] Exclude IRQs for the autoconfiguration
2343 [ISAPNP] Exclude DMAs for the autoconfiguration
2345 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2346 Ranges are in pairs (I/O port base and size).
2349 [ISAPNP] Exclude memory regions for the
2351 Ranges are in pairs (memory base and size).
2353 ports= [IP_VS_FTP] IPVS ftp helper module
2355 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2357 Format: <port>,<port>....
2359 print-fatal-signals=
2360 [KNL] debug: print fatal signals
2362 If enabled, warn about various signal handling
2363 related application anomalies: too many signals,
2364 too many POSIX.1 timers, fatal signals causing a
2367 If you hit the warning due to signal overflow,
2368 you might want to try "ulimit -i unlimited".
2372 printk.always_kmsg_dump=
2373 Trigger kmsg_dump for cases other than kernel oops or
2375 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2378 printk.time= Show timing data prefixed to each printk message line
2379 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2381 processor.max_cstate= [HW,ACPI]
2382 Limit processor to maximum C-state
2383 max_cstate=9 overrides any DMI blacklist limit.
2385 processor.nocst [HW,ACPI]
2386 Ignore the _CST method to determine C-states,
2387 instead using the legacy FADT method
2389 profile= [KNL] Enable kernel profiling via /proc/profile
2390 Format: [schedule,]<number>
2391 Param: "schedule" - profile schedule points.
2392 Param: <number> - step/bucket size as a power of 2 for
2393 statistical time based profiling.
2394 Param: "sleep" - profile D-state sleeping (millisecs).
2395 Requires CONFIG_SCHEDSTATS
2396 Param: "kvm" - profile VM exits.
2398 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2400 See Documentation/blockdev/ramdisk.txt.
2402 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2403 probe for; one of (bare|imps|exps|lifebook|any).
2404 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2406 psmouse.resetafter= [HW,MOUSE]
2407 Try to reset the device after so many bad packets
2410 [HW,MOUSE] Set desired mouse resolution, in dpi.
2411 psmouse.smartscroll=
2412 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2413 0 = disabled, 1 = enabled (default).
2415 pstore.backend= Specify the name of the pstore backend to use
2418 See Documentation/blockdev/paride.txt.
2421 [KNL] Number of legacy pty's. Overwrites compiled-in
2424 quiet [KNL] Disable most log messages
2429 See Documentation/md.txt.
2431 ramdisk_blocksize= [RAM]
2432 See Documentation/blockdev/ramdisk.txt.
2434 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2435 See Documentation/blockdev/ramdisk.txt.
2437 rcu_nocbs= [KNL,BOOT]
2438 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2439 the specified list of CPUs to be no-callback CPUs.
2440 Invocation of these CPUs' RCU callbacks will
2441 be offloaded to "rcuoN" kthreads created for
2442 that purpose. This reduces OS jitter on the
2443 offloaded CPUs, which can be useful for HPC and
2444 real-time workloads. It can also improve energy
2445 efficiency for asymmetric multiprocessors.
2447 rcu_nocbs_poll [KNL,BOOT]
2448 Rather than requiring that offloaded CPUs
2449 (specified by rcu_nocbs= above) explicitly
2450 awaken the corresponding "rcuoN" kthreads,
2451 make these kthreads poll for callbacks.
2452 This improves the real-time response for the
2453 offloaded CPUs by relieving them of the need to
2454 wake up the corresponding kthread, but degrades
2455 energy efficiency by requiring that the kthreads
2456 periodically wake up to do the polling.
2458 rcutree.blimit= [KNL,BOOT]
2459 Set maximum number of finished RCU callbacks to process
2462 rcutree.fanout_leaf= [KNL,BOOT]
2463 Increase the number of CPUs assigned to each
2464 leaf rcu_node structure. Useful for very large
2467 rcutree.qhimark= [KNL,BOOT]
2468 Set threshold of queued
2469 RCU callbacks over which batch limiting is disabled.
2471 rcutree.qlowmark= [KNL,BOOT]
2472 Set threshold of queued RCU callbacks below which
2473 batch limiting is re-enabled.
2475 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2476 Suppress RCU CPU stall warning messages.
2478 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2479 Set timeout for RCU CPU stall warning messages.
2481 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2482 Set delay from grace-period initialization to
2483 first attempt to force quiescent states.
2484 Units are jiffies, minimum value is zero,
2485 and maximum value is HZ.
2487 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2488 Set delay between subsequent attempts to force
2489 quiescent states. Units are jiffies, minimum
2490 value is one, and maximum value is HZ.
2492 rcutorture.fqs_duration= [KNL,BOOT]
2493 Set duration of force_quiescent_state bursts.
2495 rcutorture.fqs_holdoff= [KNL,BOOT]
2496 Set holdoff time within force_quiescent_state bursts.
2498 rcutorture.fqs_stutter= [KNL,BOOT]
2499 Set wait time between force_quiescent_state bursts.
2501 rcutorture.irqreader= [KNL,BOOT]
2502 Test RCU readers from irq handlers.
2504 rcutorture.n_barrier_cbs= [KNL,BOOT]
2505 Set callbacks/threads for rcu_barrier() testing.
2507 rcutorture.nfakewriters= [KNL,BOOT]
2508 Set number of concurrent RCU writers. These just
2509 stress RCU, they don't participate in the actual
2510 test, hence the "fake".
2512 rcutorture.nreaders= [KNL,BOOT]
2513 Set number of RCU readers.
2515 rcutorture.onoff_holdoff= [KNL,BOOT]
2516 Set time (s) after boot for CPU-hotplug testing.
2518 rcutorture.onoff_interval= [KNL,BOOT]
2519 Set time (s) between CPU-hotplug operations, or
2520 zero to disable CPU-hotplug testing.
2522 rcutorture.shuffle_interval= [KNL,BOOT]
2523 Set task-shuffle interval (s). Shuffling tasks
2524 allows some CPUs to go into dyntick-idle mode
2525 during the rcutorture test.
2527 rcutorture.shutdown_secs= [KNL,BOOT]
2528 Set time (s) after boot system shutdown. This
2529 is useful for hands-off automated testing.
2531 rcutorture.stall_cpu= [KNL,BOOT]
2532 Duration of CPU stall (s) to test RCU CPU stall
2533 warnings, zero to disable.
2535 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2536 Time to wait (s) after boot before inducing stall.
2538 rcutorture.stat_interval= [KNL,BOOT]
2539 Time (s) between statistics printk()s.
2541 rcutorture.stutter= [KNL,BOOT]
2542 Time (s) to stutter testing, for example, specifying
2543 five seconds causes the test to run for five seconds,
2544 wait for five seconds, and so on. This tests RCU's
2545 ability to transition abruptly to and from idle.
2547 rcutorture.test_boost= [KNL,BOOT]
2548 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2549 "Maybe" means test if the RCU implementation
2550 under test support RCU priority boosting.
2552 rcutorture.test_boost_duration= [KNL,BOOT]
2553 Duration (s) of each individual boost test.
2555 rcutorture.test_boost_interval= [KNL,BOOT]
2556 Interval (s) between each boost test.
2558 rcutorture.test_no_idle_hz= [KNL,BOOT]
2559 Test RCU's dyntick-idle handling. See also the
2560 rcutorture.shuffle_interval parameter.
2562 rcutorture.torture_type= [KNL,BOOT]
2563 Specify the RCU implementation to test.
2565 rcutorture.verbose= [KNL,BOOT]
2566 Enable additional printk() statements.
2570 Run specified binary instead of /init from the ramdisk,
2571 used for early userspace startup. See initrd.
2573 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2574 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2575 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2578 [KNL, SMP] Set scheduler's default relax_domain_level.
2579 See Documentation/cgroups/cpusets.txt.
2581 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2583 reservetop= [X86-32]
2585 Reserves a hole at the top of the kernel virtual
2590 Set the amount of memory to reserve for BIOS at
2591 the bottom of the address space.
2593 reset_devices [KNL] Force drivers to reset the underlying device
2594 during initialization.
2597 Specify the partition device for software suspend
2599 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2601 resume_offset= [SWSUSP]
2602 Specify the offset from the beginning of the partition
2603 given by "resume=" at which the swap header is located,
2604 in <PAGE_SIZE> units (needed only for swap files).
2605 See Documentation/power/swsusp-and-swap-files.txt
2607 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2608 read the resume files
2610 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2611 Useful for devices that are detected asynchronously
2612 (e.g. USB and MMC devices).
2614 hibernate= [HIBERNATION]
2615 noresume Don't check if there's a hibernation image
2616 present during boot.
2617 nocompress Don't compress/decompress hibernation images.
2619 retain_initrd [RAM] Keep initrd memory after extraction
2621 rhash_entries= [KNL,NET]
2622 Set number of hash buckets for route cache
2624 riscom8= [HW,SERIAL]
2625 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2627 ro [KNL] Mount root device read-only on boot
2629 root= [KNL] Root filesystem
2630 See name_to_dev_t comment in init/do_mounts.c.
2632 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2633 mount the root filesystem
2635 rootflags= [KNL] Set root filesystem mount option string
2637 rootfstype= [KNL] Set root filesystem type
2639 rootwait [KNL] Wait (indefinitely) for root device to show up.
2640 Useful for devices that are detected asynchronously
2641 (e.g. USB and MMC devices).
2643 rw [KNL] Mount root device read-write on boot
2645 S [KNL] Run init in single mode
2648 See drivers/net/irda/sa1100_ir.c.
2650 sbni= [NET] Granch SBNI12 leased line adapter
2652 sched_debug [KNL] Enables verbose scheduler debug messages.
2654 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2655 xtime_lock contention on larger systems, and/or RCU lock
2656 contention on all systems with CONFIG_MAXSMP set.
2657 Format: { "0" | "1" }
2658 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2660 Note: increases power consumption, thus should only be
2661 enabled if running jitter sensitive (HPC/RT) workloads.
2663 security= [SECURITY] Choose a security module to enable at boot.
2664 If this boot parameter is not specified, only the first
2665 security module asking for security registration will be
2666 loaded. An invalid security module name will be treated
2667 as if no module has been chosen.
2669 selinux= [SELINUX] Disable or enable SELinux at boot time.
2670 Format: { "0" | "1" }
2671 See security/selinux/Kconfig help text.
2674 Default value is set via kernel config option.
2675 If enabled at boot time, /selinux/disable can be used
2676 later to disable prior to initial policy load.
2678 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2679 Format: { "0" | "1" }
2680 See security/apparmor/Kconfig help text
2683 Default value is set via kernel config option.
2685 serialnumber [BUGS=X86-32]
2688 Maximal number of shapers.
2690 show_msr= [x86] show boot-time MSR settings
2691 Format: { <integer> }
2692 Show boot-time (BIOS-initialized) MSR settings.
2693 The parameter means the number of CPUs to show,
2694 for example 1 means boot CPU only.
2701 slab_max_order= [MM, SLAB]
2702 Determines the maximum allowed order for slabs.
2703 A high setting may cause OOMs due to memory
2704 fragmentation. Defaults to 1 for systems with
2705 more than 32MB of RAM, 0 otherwise.
2707 slub_debug[=options[,slabs]] [MM, SLUB]
2708 Enabling slub_debug allows one to determine the
2709 culprit if slab objects become corrupted. Enabling
2710 slub_debug can create guard zones around objects and
2711 may poison objects when not in use. Also tracks the
2712 last alloc / free. For more information see
2713 Documentation/vm/slub.txt.
2715 slub_max_order= [MM, SLUB]
2716 Determines the maximum allowed order for slabs.
2717 A high setting may cause OOMs due to memory
2718 fragmentation. For more information see
2719 Documentation/vm/slub.txt.
2721 slub_min_objects= [MM, SLUB]
2722 The minimum number of objects per slab. SLUB will
2723 increase the slab order up to slub_max_order to
2724 generate a sufficiently large slab able to contain
2725 the number of objects indicated. The higher the number
2726 of objects the smaller the overhead of tracking slabs
2727 and the less frequently locks need to be acquired.
2728 For more information see Documentation/vm/slub.txt.
2730 slub_min_order= [MM, SLUB]
2731 Determines the minimum page order for slabs. Must be
2732 lower than slub_max_order.
2733 For more information see Documentation/vm/slub.txt.
2735 slub_nomerge [MM, SLUB]
2736 Disable merging of slabs with similar size. May be
2737 necessary if there is some reason to distinguish
2738 allocs to different slabs. Debug options disable
2739 merging on their own.
2740 For more information see Documentation/vm/slub.txt.
2743 Format: <io1>[,<io2>[,...,<io8>]]
2745 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2746 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2747 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2748 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2749 smsc-ircc2.ircc_irq= [HW] IRQ line
2750 smsc-ircc2.ircc_dma= [HW] DMA channel
2751 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2752 0: Toshiba Satellite 1800 (GP data pin select)
2753 1: Fast pin select (default)
2757 [KNL] Should the soft-lockup detector generate panics.
2760 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2761 See Documentation/laptops/sonypi.txt
2763 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2764 See Documentation/serial/specialix.txt.
2766 spia_io_base= [HW,MTD]
2772 Enabled the stack tracer on boot up.
2774 stacktrace_filter=[function-list]
2775 [FTRACE] Limit the functions that the stack tracer
2776 will trace at boot up. function-list is a comma separated
2777 list of functions. This list can be changed at run
2778 time by the stack_trace_filter file in the debugfs
2779 tracing directory. Note, this enables stack tracing
2780 and the stacktrace above is not needed.
2784 Set the STI (builtin display/keyboard on the HP-PARISC
2785 machines) console (graphic card) which should be used
2786 as the initial boot-console.
2787 See also comment in drivers/video/console/sticore.c.
2790 See comment in drivers/video/console/sticore.c.
2793 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2795 sunrpc.min_resvport=
2796 sunrpc.max_resvport=
2798 SunRPC servers often require that client requests
2799 originate from a privileged port (i.e. a port in the
2800 range 0 < portnr < 1024).
2801 An administrator who wishes to reserve some of these
2802 ports for other uses may adjust the range that the
2803 kernel's sunrpc client considers to be privileged
2804 using these two parameters to set the minimum and
2805 maximum port values.
2809 Control how the NFS server code allocates CPUs to
2810 service thread pools. Depending on how many NICs
2811 you have and where their interrupts are bound, this
2812 option will affect which CPUs will do NFS serving.
2813 Note: this parameter cannot be changed while the
2814 NFS server is running.
2816 auto the server chooses an appropriate mode
2817 automatically using heuristics
2818 global a single global pool contains all CPUs
2819 percpu one pool for each CPU
2820 pernode one pool for each NUMA node (equivalent
2821 to global on non-NUMA machines)
2823 sunrpc.tcp_slot_table_entries=
2824 sunrpc.udp_slot_table_entries=
2826 Sets the upper limit on the number of simultaneous
2827 RPC calls that can be sent from the client to a
2828 server. Increasing these values may allow you to
2829 improve throughput, but will also increase the
2830 amount of memory reserved for use by the client.
2833 [KNL] Enable accounting of swap in memory resource
2834 controller if no parameter or 1 is given or disable
2835 it if 0 is given (See Documentation/cgroups/memory.txt)
2837 swiotlb= [IA-64] Number of I/O TLB slabs
2841 sysfs.deprecated=0|1 [KNL]
2842 Enable/disable old style sysfs layout for old udev
2843 on older distributions. When this option is enabled
2844 very new udev will not work anymore. When this option
2845 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2846 in older udev will not work anymore.
2847 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2848 the kernel configuration.
2850 sysrq_always_enabled
2852 Ignore sysrq setting - this boot parameter will
2853 neutralize any effect of /proc/sys/kernel/sysrq.
2854 Useful for debugging.
2858 test_suspend= [SUSPEND]
2859 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2860 standby suspend) as the system sleep state to briefly
2861 enter during system startup. The system is woken from
2862 this state using a wakeup-capable RTC alarm.
2864 thash_entries= [KNL,NET]
2865 Set number of hash buckets for TCP connection
2867 thermal.act= [HW,ACPI]
2868 -1: disable all active trip points in all thermal zones
2869 <degrees C>: override all lowest active trip points
2871 thermal.crt= [HW,ACPI]
2872 -1: disable all critical trip points in all thermal zones
2873 <degrees C>: override all critical trip points
2875 thermal.nocrt= [HW,ACPI]
2876 Set to disable actions on ACPI thermal zone
2877 critical and hot trip points.
2879 thermal.off= [HW,ACPI]
2880 1: disable ACPI thermal control
2882 thermal.psv= [HW,ACPI]
2883 -1: disable all passive trip points
2884 <degrees C>: override all passive trip points to this
2887 thermal.tzp= [HW,ACPI]
2888 Specify global default ACPI thermal zone polling rate
2889 <deci-seconds>: poll all this frequency
2890 0: no polling (default)
2893 Force threading of all interrupt handlers except those
2894 marked explicitly IRQF_NO_THREAD.
2898 Specify if the kernel should make use of the cpu
2899 topology information if the hardware supports this.
2900 The scheduler will make use of this information and
2901 e.g. base its process migration decisions on it.
2906 tpm_suspend_pcr=[HW,TPM]
2907 Format: integer pcr id
2908 Specify that at suspend time, the tpm driver
2909 should extend the specified pcr with zeros,
2910 as a workaround for some chips which fail to
2911 flush the last written pcr on TPM_SaveState.
2912 This will guarantee that all the other pcrs
2915 trace_buf_size=nn[KMG]
2916 [FTRACE] will set tracing buffer size.
2918 trace_event=[event-list]
2919 [FTRACE] Set and start specified trace events in order
2920 to facilitate early boot debugging.
2921 See also Documentation/trace/events.txt
2923 trace_options=[option-list]
2924 [FTRACE] Enable or disable tracer options at boot.
2925 The option-list is a comma delimited list of options
2926 that can be enabled or disabled just as if you were
2927 to echo the option name into
2929 /sys/kernel/debug/tracing/trace_options
2931 For example, to enable stacktrace option (to dump the
2932 stack trace of each event), add to the command line:
2934 trace_options=stacktrace
2936 See also Documentation/trace/ftrace.txt "trace options"
2939 transparent_hugepage=
2941 Format: [always|madvise|never]
2942 Can be used to control the default behavior of the system
2943 with respect to transparent hugepages.
2944 See Documentation/vm/transhuge.txt for more details.
2946 tsc= Disable clocksource stability checks for TSC.
2948 [x86] reliable: mark tsc clocksource as reliable, this
2949 disables clocksource verification at runtime, as well
2950 as the stability checks done at bootup. Used to enable
2951 high-resolution timer mode on older hardware, and in
2952 virtualized environment.
2953 [x86] noirqtime: Do not use TSC to do irq accounting.
2954 Used to run time disable IRQ_TIME_ACCOUNTING on any
2955 platforms where RDTSC is slow and this accounting
2958 turbografx.map[2|3]= [HW,JOY]
2959 TurboGraFX parallel port interface
2961 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2962 See also Documentation/input/joystick-parport.txt
2964 udbg-immortal [PPC] When debugging early kernel crashes that
2965 happen after console_init() and before a proper
2966 console driver takes over, this boot options might
2967 help "seeing" what's going on.
2969 uhash_entries= [KNL,NET]
2970 Set number of hash buckets for UDP/UDP-Lite connections
2973 [USB] Ignore overcurrent events (default N).
2974 Some badly-designed motherboards generate lots of
2975 bogus events, for ports that aren't wired to
2976 anything. Set this parameter to avoid log spamming.
2977 Note that genuine overcurrent events won't be
2981 [X86] Cause panic on unknown NMI.
2983 usbcore.authorized_default=
2984 [USB] Default USB device authorization:
2985 (default -1 = authorized except for wireless USB,
2986 0 = not authorized, 1 = authorized)
2988 usbcore.autosuspend=
2989 [USB] The autosuspend time delay (in seconds) used
2990 for newly-detected USB devices (default 2). This
2991 is the time required before an idle device will be
2992 autosuspended. Devices for which the delay is set
2993 to a negative value won't be autosuspended at all.
2995 usbcore.usbfs_snoop=
2996 [USB] Set to log all usbfs traffic (default 0 = off).
2998 usbcore.blinkenlights=
2999 [USB] Set to cycle leds on hubs (default 0 = off).
3001 usbcore.old_scheme_first=
3002 [USB] Start with the old device initialization
3003 scheme (default 0 = off).
3005 usbcore.usbfs_memory_mb=
3006 [USB] Memory limit (in MB) for buffers allocated by
3007 usbfs (default = 16, 0 = max = 2047).
3009 usbcore.use_both_schemes=
3010 [USB] Try the other device initialization scheme
3011 if the first one fails (default 1 = enabled).
3013 usbcore.initial_descriptor_timeout=
3014 [USB] Specifies timeout for the initial 64-byte
3015 USB_REQ_GET_DESCRIPTOR request in milliseconds
3016 (default 5000 = 5.0 seconds).
3019 [USBHID] The interval which mice are to be polled at.
3021 usb-storage.delay_use=
3022 [UMS] The delay in seconds before a new device is
3023 scanned for Logical Units (default 5).
3026 [UMS] A list of quirks entries to supplement or
3027 override the built-in unusual_devs list. List
3028 entries are separated by commas. Each entry has
3029 the form VID:PID:Flags where VID and PID are Vendor
3030 and Product ID values (4-digit hex numbers) and
3031 Flags is a set of characters, each corresponding
3032 to a common usb-storage quirk flag as follows:
3033 a = SANE_SENSE (collect more than 18 bytes
3035 b = BAD_SENSE (don't collect more than 18
3036 bytes of sense data);
3037 c = FIX_CAPACITY (decrease the reported
3038 device capacity by one sector);
3039 d = NO_READ_DISC_INFO (don't use
3040 READ_DISC_INFO command);
3041 e = NO_READ_CAPACITY_16 (don't use
3042 READ_CAPACITY_16 command);
3043 h = CAPACITY_HEURISTICS (decrease the
3044 reported device capacity by one
3045 sector if the number is odd);
3046 i = IGNORE_DEVICE (don't bind to this
3048 l = NOT_LOCKABLE (don't try to lock and
3049 unlock ejectable media);
3050 m = MAX_SECTORS_64 (don't transfer more
3051 than 64 sectors = 32 KB at a time);
3052 n = INITIAL_READ10 (force a retry of the
3053 initial READ(10) command);
3054 o = CAPACITY_OK (accept the capacity
3055 reported by the device);
3056 p = WRITE_CACHE (the device cache is ON
3058 r = IGNORE_RESIDUE (the device reports
3059 bogus residue values);
3060 s = SINGLE_LUN (the device has only one
3062 w = NO_WP_DETECT (don't test whether the
3063 medium is write-protected).
3064 Example: quirks=0419:aaf5:rl,0421:0433:rc
3066 user_debug= [KNL,ARM]
3068 See arch/arm/Kconfig.debug help text.
3069 1 - undefined instruction events
3071 4 - invalid data aborts
3074 Example: user_debug=31
3077 [X86] Flags controlling user PTE allocations.
3079 nohigh = do not allocate PTE pages in
3080 HIGHMEM regardless of setting
3084 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3085 vdso=1: enable VDSO (default)
3086 vdso=0: disable VDSO mapping
3089 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3090 vdso32=1: enable 32-bit VDSO (default)
3091 vdso32=0: disable 32-bit VDSO mapping
3094 vector=percpu: enable percpu vector domain
3096 video= [FB] Frame buffer configuration
3097 See Documentation/fb/modedb.txt.
3100 [VMMIO] Memory mapped virtio (platform) device.
3102 <size>@<baseaddr>:<irq>[:<id>]
3104 <size> := size (can use standard suffixes
3106 <baseaddr> := physical base address
3107 <irq> := interrupt number (as passed to
3109 <id> := (optional) platform device id
3111 virtio_mmio.device=1K@0x100b0000:48:7
3113 Can be used multiple times for multiple devices.
3115 vga= [BOOT,X86-32] Select a particular video mode
3116 See Documentation/x86/boot.txt and
3117 Documentation/svga.txt.
3118 Use vga=ask for menu.
3119 This is actually a boot loader parameter; the value is
3120 passed to the kernel using a special protocol.
3122 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3123 size of <nn>. This can be used to increase the
3124 minimum size (128MB on x86). It can also be used to
3125 decrease the size and leave more room for directly
3128 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3131 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3134 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3138 Controls the behavior of vsyscalls (i.e. calls to
3139 fixed addresses of 0xffffffffff600x00 from legacy
3140 code). Most statically-linked binaries and older
3141 versions of glibc use these calls. Because these
3142 functions are at fixed addresses, they make nice
3143 targets for exploits that can control RIP.
3145 emulate [default] Vsyscalls turn into traps and are
3146 emulated reasonably safely.
3148 native Vsyscalls are native syscall instructions.
3149 This is a little bit faster than trapping
3150 and makes a few dynamic recompilers work
3151 better than they would in emulation mode.
3152 It also makes exploits much easier to write.
3154 none Vsyscalls don't work at all. This makes
3155 them quite hard to use for exploits but
3156 might break your system.
3158 vt.cur_default= [VT] Default cursor shape.
3159 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3160 the parameters of the <Esc>[?A;B;Cc escape sequence;
3161 see VGA-softcursor.txt. Default: 2 = underline.
3163 vt.default_blu= [VT]
3164 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3165 Change the default blue palette of the console.
3166 This is a 16-member array composed of values
3169 vt.default_grn= [VT]
3170 Format: <green0>,<green1>,<green2>,...,<green15>
3171 Change the default green palette of the console.
3172 This is a 16-member array composed of values
3175 vt.default_red= [VT]
3176 Format: <red0>,<red1>,<red2>,...,<red15>
3177 Change the default red palette of the console.
3178 This is a 16-member array composed of values
3184 Set system-wide default UTF-8 mode for all tty's.
3185 Default is 1, i.e. UTF-8 mode is enabled for all
3186 newly opened terminals.
3188 vt.global_cursor_default=
3191 Set system-wide default for whether a cursor
3192 is shown on new VTs. Default is -1,
3193 i.e. cursors will be created by default unless
3194 overridden by individual drivers. 0 will hide
3195 cursors, 1 will display them.
3197 watchdog timers [HW,WDT] For information on watchdog timers,
3198 see Documentation/watchdog/watchdog-parameters.txt
3199 or other driver-specific files in the
3200 Documentation/watchdog/ directory.
3202 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3203 default x2apic cluster mode on platforms
3206 x86_mrst_timer= [X86-32,APBT]
3207 Choose timer option for x86 Moorestown MID platform.
3208 Two valid options are apbt timer only and lapic timer
3209 plus one apbt timer for broadcast timer.
3210 x86_mrst_timer=apbt_only | lapic_and_apbt
3212 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3213 xd_geo= See header of drivers/block/xd.c.
3215 xen_emul_unplug= [HW,X86,XEN]
3216 Unplug Xen emulated devices
3217 Format: [unplug0,][unplug1]
3218 ide-disks -- unplug primary master IDE devices
3219 aux-ide-disks -- unplug non-primary-master IDE devices
3220 nics -- unplug network devices
3221 all -- unplug all emulated devices (NICs and IDE disks)
3222 unnecessary -- unplugging emulated devices is
3223 unnecessary even if the host did not respond to
3225 never -- do not unplug even if version check succeeds
3227 xirc2ps_cs= [NET,PCMCIA]
3229 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3231 ______________________________________________________________________
3235 Add more DRM drivers.
projects / mirror_ubuntu-zesty-kernel.git / blob