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.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel_low=size[KMG]
598 [KNL, x86] parts under 4G.
600 crashkernel=range1:size1[,range2:size2,...][@offset]
601 [KNL] Same as above, but depends on the memory
602 in the running system. The syntax of range is
603 start-[end] where start and end are both
604 a memory unit (amount[KMG]). See also
605 Documentation/kdump/kdump.txt for an example.
610 cs89x0_media= [HW,NET]
611 Format: { rj45 | aui | bnc }
614 See header of drivers/s390/block/dasd_devmap.c.
616 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
617 (one device per port)
618 Format: <port#>,<type>
619 See also Documentation/input/joystick-parport.txt
621 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
622 time. See Documentation/dynamic-debug-howto.txt for
623 details. Deprecated, see dyndbg.
625 debug [KNL] Enable kernel debugging (events log level).
628 [KNL] verbose self-tests
630 Print debugging info while doing the locking API
632 We default to 0 (no extra messages), setting it to
633 1 will print _a lot_ more information - normally
634 only useful to kernel developers.
636 debug_objects [KNL] Enable object debugging
639 [KNL] Disable object debugging
641 debug_guardpage_minorder=
642 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
643 parameter allows control of the order of pages that will
644 be intentionally kept free (and hence protected) by the
645 buddy allocator. Bigger value increase the probability
646 of catching random memory corruption, but reduce the
647 amount of memory for normal system use. The maximum
648 possible value is MAX_ORDER/2. Setting this parameter
649 to 1 or 2 should be enough to identify most random
650 memory corruption problems caused by bugs in kernel or
651 driver code when a CPU writes to (or reads from) a
652 random memory location. Note that there exists a class
653 of memory corruptions problems caused by buggy H/W or
654 F/W or by drivers badly programing DMA (basically when
655 memory is written at bus level and the CPU MMU is
656 bypassed) which are not detectable by
657 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
658 tracking down these problems.
660 debugpat [X86] Enable PAT debugging
662 decnet.addr= [HW,NET]
663 Format: <area>[,<node>]
664 See also Documentation/networking/decnet.txt.
667 [same as hugepagesz=] The size of the default
668 HugeTLB page size. This is the size represented by
669 the legacy /proc/ hugepages APIs, used for SHM, and
670 default size when mounting hugetlbfs filesystems.
671 Defaults to the default architecture's huge page size
675 Set number of hash buckets for dentry cache.
678 IO parameters + enable/disable command.
680 digiepca= [HW,SERIAL]
681 See drivers/char/README.epca and
682 Documentation/serial/digiepca.txt.
685 See Documentation/networking/ipv6.txt.
687 disable_ddw [PPC/PSERIES]
688 Disable Dynamic DMA Window support. Use this if
689 to workaround buggy firmware.
692 See Documentation/networking/ipv6.txt.
694 disable_mtrr_cleanup [X86]
695 The kernel tries to adjust MTRR layout from continuous
696 to discrete, to make X server driver able to add WB
697 entry later. This parameter disables that.
699 disable_mtrr_trim [X86, Intel and AMD only]
700 By default the kernel will trim any uncacheable
701 memory out of your available memory pool based on
702 MTRR settings. This parameter disables that behavior,
703 possibly causing your machine to run very slowly.
705 disable_timer_pin_1 [X86]
706 Disable PIN 1 of APIC timer
707 Can be useful to work around chipset bugs.
709 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
710 this option disables the debugging code at boot.
712 dma_debug_entries=<number>
713 This option allows to tune the number of preallocated
714 entries for DMA-API debugging code. One entry is
715 required per DMA-API allocation. Use this if the
716 DMA-API debugging code disables itself because the
717 architectural default is too low.
719 dma_debug_driver=<driver_name>
720 With this option the DMA-API debugging driver
721 filter feature can be enabled at boot time. Just
722 pass the driver to filter for as the parameter.
723 The filter can be disabled or changed to another
724 driver later using sysfs.
726 drm_kms_helper.edid_firmware=[<connector>:]<file>
727 Broken monitors, graphic adapters and KVMs may
728 send no or incorrect EDID data sets. This parameter
729 allows to specify an EDID data set in the
730 /lib/firmware directory that is used instead.
731 Generic built-in EDID data sets are used, if one of
732 edid/1024x768.bin, edid/1280x1024.bin,
733 edid/1680x1050.bin, or edid/1920x1080.bin is given
734 and no file with the same name exists. Details and
735 instructions how to build your own EDID data are
736 available in Documentation/EDID/HOWTO.txt. An EDID
737 data set will only be used for a particular connector,
738 if its name and a colon are prepended to the EDID
743 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
744 module.dyndbg[="val"]
745 Enable debug messages at boot time. See
746 Documentation/dynamic-debug-howto.txt for details.
748 earlycon= [KNL] Output early console device and options.
749 uart[8250],io,<addr>[,options]
750 uart[8250],mmio,<addr>[,options]
751 uart[8250],mmio32,<addr>[,options]
752 Start an early, polled-mode console on the 8250/16550
753 UART at the specified I/O port or MMIO address.
754 MMIO inter-register address stride is either 8-bit
755 (mmio) or 32-bit (mmio32).
756 The options are the same as for ttyS, above.
758 earlyprintk= [X86,SH,BLACKFIN]
760 earlyprintk=serial[,ttySn[,baudrate]]
761 earlyprintk=ttySn[,baudrate]
762 earlyprintk=dbgp[debugController#]
764 Append ",keep" to not disable it when the real console
767 Only vga or serial or usb debug port at a time.
769 Currently only ttyS0 and ttyS1 are supported.
771 Interaction with the standard serial driver is not
774 The VGA output is eventually overwritten by the real
777 ekgdboc= [X86,KGDB] Allow early kernel console debugging
780 This is designed to be used in conjunction with
781 the boot argument: earlyprintk=vga
784 Format: {"off" | "on" | "skip[mbr]"}
786 eisa_irq_edge= [PARISC,HW]
787 See header of drivers/parisc/eisa.c.
790 See comment before function elanfreq_setup() in
791 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
794 Format: {"cfq" | "deadline" | "noop"}
795 See Documentation/block/cfq-iosched.txt and
796 Documentation/block/deadline-iosched.txt for details.
798 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
799 Specifies physical address of start of kernel core
800 image elf header and optionally the size. Generally
801 kexec loader will pass this option to capture kernel.
802 See Documentation/kdump/kdump.txt for details.
804 enable_mtrr_cleanup [X86]
805 The kernel tries to adjust MTRR layout from continuous
806 to discrete, to make X server driver able to add WB
807 entry later. This parameter enables that.
809 enable_timer_pin_1 [X86]
810 Enable PIN 1 of APIC timer
811 Can be useful to work around chipset bugs
812 (in particular on some ATI chipsets).
813 The kernel tries to set a reasonable default.
815 enforcing [SELINUX] Set initial enforcing status.
817 See security/selinux/Kconfig help text.
818 0 -- permissive (log only, no denials).
819 1 -- enforcing (deny and log).
821 Value can be changed at runtime via /selinux/enforce.
824 Disable Error Record Serialization Table (ERST)
827 ether= [HW,NET] Ethernet cards parameters
828 This option is obsoleted by the "netdev=" option, which
829 has equivalent usage. See its documentation for details.
833 Permit 'security.evm' to be updated regardless of
834 current integrity status.
838 fail_make_request=[KNL]
839 General fault injection mechanism.
840 Format: <interval>,<probability>,<space>,<times>
841 See also Documentation/fault-injection/.
844 See Documentation/blockdev/floppy.txt.
846 force_pal_cache_flush
847 [IA-64] Avoid check_sal_cache_flush which may hang on
848 buggy SAL_CACHE_FLUSH implementations. Using this
849 parameter will force ia64_sal_cache_flush to call
850 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
853 [FTRACE] will set and start the specified tracer
854 as early as possible in order to facilitate early
857 ftrace_dump_on_oops[=orig_cpu]
858 [FTRACE] will dump the trace buffers on oops.
859 If no parameter is passed, ftrace will dump
860 buffers of all CPUs, but if you pass orig_cpu, it will
861 dump only the buffer of the CPU that triggered the
864 ftrace_filter=[function-list]
865 [FTRACE] Limit the functions traced by the function
866 tracer at boot up. function-list is a comma separated
867 list of functions. This list can be changed at run
868 time by the set_ftrace_filter file in the debugfs
871 ftrace_notrace=[function-list]
872 [FTRACE] Do not trace the functions specified in
873 function-list. This list can be changed at run time
874 by the set_ftrace_notrace file in the debugfs
877 ftrace_graph_filter=[function-list]
878 [FTRACE] Limit the top level callers functions traced
879 by the function graph tracer at boot up.
880 function-list is a comma separated list of functions
881 that can be changed at run time by the
882 set_graph_function file in the debugfs tracing directory.
885 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
886 support via parallel port (up to 5 devices per port)
887 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
888 See also Documentation/input/joystick-parport.txt
892 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896 gcov_persist= [GCOV] When non-zero (default), profiling data for
897 kernel modules is saved and remains accessible via
898 debugfs, even when the module is unloaded/reloaded.
899 When zero, profiling data is discarded and associated
900 debugfs files are removed at module unload time.
902 gpt [EFI] Forces disk with valid GPT signature but
903 invalid Protective MBR to be treated as GPT.
905 grcan.enable0= [HW] Configuration of physical interface 0. Determines
906 the "Enable 0" bit of the configuration register.
909 grcan.enable1= [HW] Configuration of physical interface 1. Determines
910 the "Enable 0" bit of the configuration register.
913 grcan.select= [HW] Select which physical interface to use.
916 grcan.txsize= [HW] Sets the size of the tx buffer.
917 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
919 grcan.rxsize= [HW] Sets the size of the rx buffer.
920 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
923 hashdist= [KNL,NUMA] Large hashes allocated during boot
924 are distributed across NUMA nodes. Defaults on
925 for 64-bit NUMA, off otherwise.
926 Format: 0 | 1 (for off | on)
928 hcl= [IA-64] SGI's Hardware Graph compatibility layer
930 hd= [EIDE] (E)IDE hard drive subsystem geometry
931 Format: <cyl>,<head>,<sect>
934 Disable Hardware Error Source Table (HEST) support;
935 corresponding firmware-first mode error processing
936 logic will be disabled.
938 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
939 size of <nn>. This works even on boxes that have no
940 highmem otherwise. This also works to reduce highmem
941 size on bigger boxes.
943 highres= [KNL] Enable/disable high resolution timer mode.
944 Valid parameters: "on", "off"
948 See Documentation/isdn/README.HiSax.
952 hpet= [X86-32,HPET] option to control HPET usage
953 Format: { enable (default) | disable | force |
955 disable: disable HPET and use PIT instead
956 force: allow force enabled of undocumented chips (ICH4,
958 verbose: show contents of HPET registers during setup
960 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
961 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
962 On x86-64 and powerpc, this option can be specified
963 multiple times interleaved with hugepages= to reserve
964 huge pages of different sizes. Valid pages sizes on
965 x86-64 are 2M (when the CPU supports "pse") and 1G
966 (when the CPU supports the "pdpe1gb" cpuinfo flag)
967 Note that 1GB pages can only be allocated at boot time
968 using hugepages= and not freed afterwards.
970 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
971 terminal devices. Valid values: 0..8
972 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
973 If specified, z/VM IUCV HVC accepts connections
974 from listed z/VM user IDs only.
977 Do not unregister boot console at start. This is only
978 useful for debugging when something happens in the window
979 between unregistering the boot console and initializing
982 i2c_bus= [HW] Override the default board specific I2C bus speed
983 or register an additional I2C bus that is not
984 registered from board initialization code.
988 i8042.debug [HW] Toggle i8042 debug mode
989 i8042.direct [HW] Put keyboard port into non-translated mode
990 i8042.dumbkbd [HW] Pretend that controller can only read data from
991 keyboard and cannot control its state
992 (Don't attempt to blink the leds)
993 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
994 i8042.nokbd [HW] Don't check/create keyboard port
995 i8042.noloop [HW] Disable the AUX Loopback command while probing
997 i8042.nomux [HW] Don't check presence of an active multiplexing
999 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1001 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1002 i8042.reset [HW] Reset the controller during init and cleanup
1003 i8042.unlock [HW] Unlock (ignore) the keylock
1007 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1008 indicates that the driver is running on unsupported
1010 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1011 does not match list of supported models.
1013 [HW] Report power status in /proc/i8k
1014 (disabled by default)
1015 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1018 i915.invert_brightness=
1019 [DRM] Invert the sense of the variable that is used to
1020 set the brightness of the panel backlight. Normally a
1021 brightness value of 0 indicates backlight switched off,
1022 and the maximum of the brightness value sets the backlight
1023 to maximum brightness. If this parameter is set to 0
1024 (default) and the machine requires it, or this parameter
1025 is set to 1, a brightness value of 0 sets the backlight
1026 to maximum brightness, and the maximum of the brightness
1027 value switches the backlight off.
1028 -1 -- never invert brightness
1029 0 -- machine default
1030 1 -- force brightness inversion
1033 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1035 ide-core.nodma= [HW] (E)IDE subsystem
1036 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1037 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1038 .cdrom .chs .ignore_cable are additional options
1039 See Documentation/ide/ide.txt.
1041 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1042 Claim all unknown PCI IDE storage controllers.
1045 Format: idle=poll, idle=halt, idle=nomwait
1046 Poll forces a polling idle loop that can slightly
1047 improve the performance of waking up a idle CPU, but
1048 will use a lot of power and make the system run hot.
1050 idle=halt: Halt is forced to be used for CPU idle.
1051 In such case C2/C3 won't be used again.
1052 idle=nomwait: Disable mwait for CPU C-states
1054 ignore_loglevel [KNL]
1055 Ignore loglevel setting - this will print /all/
1056 kernel messages to the console. Useful for debugging.
1057 We also add it as printk module parameter, so users
1058 could change it dynamically, usually by
1059 /sys/module/printk/parameters/ignore_loglevel.
1061 ihash_entries= [KNL]
1062 Set number of hash buckets for inode cache.
1064 ima_appraise= [IMA] appraise integrity measurements
1065 Format: { "off" | "enforce" | "fix" }
1068 ima_appraise_tcb [IMA]
1069 The builtin appraise policy appraises all files
1073 Format: { "0" | "1" }
1074 0 -- integrity auditing messages. (Default)
1075 1 -- enable informational integrity auditing messages.
1078 Format: { "sha1" | "md5" }
1082 Load a policy which meets the needs of the Trusted
1083 Computing Base. This means IMA will measure all
1084 programs exec'd, files mmap'd for exec, and all files
1085 opened for read by uid=0.
1089 Run specified binary instead of /sbin/init as init
1092 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1093 for working out where the kernel is dying during
1096 initrd= [BOOT] Specify the location of the initial ramdisk
1098 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1101 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1103 Enable intel iommu driver.
1105 Disable intel iommu driver.
1106 igfx_off [Default Off]
1107 By default, gfx is mapped as normal device. If a gfx
1108 device has a dedicated DMAR unit, the DMAR unit is
1109 bypassed by not enabling DMAR with this option. In
1110 this case, gfx device will use physical address for
1113 With this option iommu will not optimize to look
1114 for io virtual address below 32-bit forcing dual
1115 address cycle on pci bus for cards supporting greater
1116 than 32-bit addressing. The default is to look
1117 for translation below 32-bit and if not available
1118 then look in the higher range.
1119 strict [Default Off]
1120 With this option on every unmap_single operation will
1121 result in a hardware IOTLB flush operation as opposed
1122 to batching them for performance.
1123 sp_off [Default Off]
1124 By default, super page will be supported if Intel IOMMU
1125 has the capability. With this option, super page will
1128 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1129 0 disables intel_idle and fall back on acpi_idle.
1130 1 to 6 specify maximum depth of C-state.
1134 Do not enable intel_pstate as the default
1135 scaling driver for the supported processors
1137 intremap= [X86-64, Intel-IOMMU]
1138 on enable Interrupt Remapping (default)
1139 off disable Interrupt Remapping
1140 nosid disable Source ID checking
1142 BIOS x2APIC opt-out request will be ignored
1144 iomem= Disable strict checking of access to MMIO memory
1145 strict regions from userspace.
1162 io7= [HW] IO7 for Marvel based alpha systems
1163 See comment before marvel_specify_io7 in
1164 arch/alpha/kernel/core_marvel.c.
1166 io_delay= [X86] I/O delay method
1168 Standard port 0x80 based delay
1170 Alternate port 0xed based delay (needed on some systems)
1172 Simple two microseconds delay
1177 See Documentation/filesystems/nfs/nfsroot.txt.
1179 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1180 See comment before ip2_setup() in
1181 drivers/char/ip2/ip2base.c.
1184 When an interrupt is not handled search all handlers
1185 for it. Intended to get systems with badly broken
1189 When an interrupt is not handled search all handlers
1190 for it. Also check all handlers each timer
1191 interrupt. Intended to get systems with badly broken
1195 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1197 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1199 <cpu number>,...,<cpu number>
1201 <cpu number>-<cpu number>
1202 (must be a positive range in ascending order)
1204 <cpu number>,...,<cpu number>-<cpu number>
1206 This option can be used to specify one or more CPUs
1207 to isolate from the general SMP balancing and scheduling
1208 algorithms. You can move a process onto or off an
1209 "isolated" CPU via the CPU affinity syscalls or cpuset.
1210 <cpu number> begins at 0 and the maximum value is
1211 "number of CPUs in system - 1".
1213 This option is the preferred way to isolate CPUs. The
1214 alternative -- manually setting the CPU mask of all
1215 tasks in the system -- can cause problems and
1216 suboptimal load balancer performance.
1220 js= [HW,JOY] Analog joystick
1221 See Documentation/input/joystick.txt.
1225 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1226 specifies the amount of memory usable by the kernel
1227 for non-movable allocations. The requested amount is
1228 spread evenly throughout all nodes in the system. The
1229 remaining memory in each node is used for Movable
1230 pages. In the event, a node is too small to have both
1231 kernelcore and Movable pages, kernelcore pages will
1232 take priority and other nodes will have a larger number
1233 of kernelcore pages. The Movable zone is used for the
1234 allocation of pages that may be reclaimed or moved
1235 by the page migration subsystem. This means that
1236 HugeTLB pages may not be allocated from this zone.
1237 Note that allocations like PTEs-from-HighMem still
1238 use the HighMem zone if it exists, and the Normal
1239 zone if it does not.
1241 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1242 Format: <Controller#>[,poll interval]
1243 The controller # is the number of the ehci usb debug
1244 port as it is probed via PCI. The poll interval is
1245 optional and is the number seconds in between
1246 each poll cycle to the debug port in case you need
1247 the functionality for interrupting the kernel with
1248 gdb or control-c on the dbgp connection. When
1249 not using this parameter you use sysrq-g to break into
1250 the kernel debugger.
1252 kgdboc= [KGDB,HW] kgdb over consoles.
1253 Requires a tty driver that supports console polling,
1254 or a supported polling keyboard driver (non-usb).
1255 Serial only format: <serial_device>[,baud]
1256 keyboard only format: kbd
1257 keyboard and serial format: kbd,<serial_device>[,baud]
1258 Optional Kernel mode setting:
1259 kms, kbd format: kms,kbd
1260 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1262 kgdbwait [KGDB] Stop kernel execution and enter the
1263 kernel debugger at the earliest opportunity.
1265 kmac= [MIPS] korina ethernet MAC address.
1266 Configure the RouterBoard 532 series on-chip
1267 Ethernet adapter MAC address.
1269 kmemleak= [KNL] Boot-time kmemleak enable/disable
1270 Valid arguments: on, off
1273 kstack=N [X86] Print N words from the kernel stack
1276 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1277 Default is 0 (don't ignore, but inject #GP)
1279 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1283 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1284 Default is 1 (enabled)
1286 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1288 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1290 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1291 (virtualized MMU) support on capable Intel chips.
1292 Default is 1 (enabled)
1294 kvm-intel.emulate_invalid_guest_state=
1295 [KVM,Intel] Enable emulation of invalid guest states
1296 Default is 0 (disabled)
1298 kvm-intel.flexpriority=
1299 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1300 Default is 1 (enabled)
1303 [KVM,Intel] Enable VMX nesting (nVMX).
1304 Default is 0 (disabled)
1306 kvm-intel.unrestricted_guest=
1307 [KVM,Intel] Disable unrestricted guest feature
1308 (virtualized real and unpaged mode) on capable
1309 Intel chips. Default is 1 (enabled)
1311 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1312 feature (tagged TLBs) on capable Intel chips.
1313 Default is 1 (enabled)
1319 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1322 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1323 value for LAPIC timer one-shot implementation. Default
1324 back to the programmable timer unit in the LAPIC.
1326 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1329 libata.dma= [LIBATA] DMA control
1330 libata.dma=0 Disable all PATA and SATA DMA
1331 libata.dma=1 PATA and SATA Disk DMA only
1332 libata.dma=2 ATAPI (CDROM) DMA only
1333 libata.dma=4 Compact Flash DMA only
1334 Combinations also work, so libata.dma=3 enables DMA
1335 for disks and CDROMs, but not CFs.
1337 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1338 libata.ignore_hpa=0 keep BIOS limits (default)
1339 libata.ignore_hpa=1 ignore limits, using full disk
1341 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1345 libata.force= [LIBATA] Force configurations. The format is comma
1346 separated list of "[ID:]VAL" where ID is
1347 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1348 matching port, link or device. Basically, it matches
1349 the ATA ID string printed on console by libata. If
1350 the whole ID part is omitted, the last PORT and DEVICE
1351 values are used. If ID hasn't been specified yet, the
1352 configuration applies to all ports, links and devices.
1354 If only DEVICE is omitted, the parameter applies to
1355 the port and all links and devices behind it. DEVICE
1356 number of 0 either selects the first device or the
1357 first fan-out link behind PMP device. It does not
1358 select the host link. DEVICE number of 15 selects the
1359 host link and device attached to it.
1361 The VAL specifies the configuration to force. As long
1362 as there's no ambiguity shortcut notation is allowed.
1363 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1364 The following configurations can be forced.
1366 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1367 Any ID with matching PORT is used.
1369 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1371 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1372 udma[/][16,25,33,44,66,100,133] notation is also
1375 * [no]ncq: Turn on or off NCQ.
1377 * nohrst, nosrst, norst: suppress hard, soft
1380 * rstonce: only attempt one reset during
1381 hot-unplug link recovery
1383 * dump_id: dump IDENTIFY data.
1385 If there are multiple matching configurations changing
1386 the same attribute, the last one is used.
1388 memblock=debug [KNL] Enable memblock debug messages.
1390 load_ramdisk= [RAM] List of ramdisks to load from floppy
1391 See Documentation/blockdev/ramdisk.txt.
1393 lockd.nlm_grace_period=P [NFS] Assign grace period.
1396 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1399 lockd.nlm_timeout=T [NFS] Assign timeout value.
1402 lockd.nlm_udpport=M [NFS] Assign UDP port.
1405 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1408 loglevel= All Kernel Messages with a loglevel smaller than the
1409 console loglevel will be printed to the console. It can
1410 also be changed with klogd or other programs. The
1411 loglevels are defined as follows:
1413 0 (KERN_EMERG) system is unusable
1414 1 (KERN_ALERT) action must be taken immediately
1415 2 (KERN_CRIT) critical conditions
1416 3 (KERN_ERR) error conditions
1417 4 (KERN_WARNING) warning conditions
1418 5 (KERN_NOTICE) normal but significant condition
1419 6 (KERN_INFO) informational
1420 7 (KERN_DEBUG) debug-level messages
1422 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1423 in bytes. n must be a power of two. The default
1424 size is set in the kernel config file.
1426 logo.nologo [FB] Disables display of the built-in Linux logo.
1427 This may be used to provide more screen space for
1428 kernel log messages and is useful when debugging
1429 kernel boot problems.
1431 lp=0 [LP] Specify parallel ports to use, e.g,
1432 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1433 lp=reset first parallel port). 'lp=0' disables the
1434 lp=auto printer driver. 'lp=reset' (which can be
1435 specified in addition to the ports) causes
1436 attached printers to be reset. Using
1437 lp=port1,port2,... specifies the parallel ports
1438 to associate lp devices with, starting with
1439 lp0. A port specification may be 'none' to skip
1440 that lp device, or a parport name such as
1441 'parport0'. Specifying 'lp=auto' instead of a
1442 port specification list means that device IDs
1443 from each port should be examined, to see if
1444 an IEEE 1284-compliant printer is attached; if
1445 so, the driver will manage that printer.
1446 See also header of drivers/char/lp.c.
1449 Sets loops_per_jiffy to given constant, thus avoiding
1450 time-consuming boot-time autodetection (up to 250 ms per
1451 CPU). 0 enables autodetection (default). To determine
1452 the correct value for your kernel, boot with normal
1453 autodetection and see what value is printed. Note that
1454 on SMP systems the preset will be applied to all CPUs,
1455 which is likely to cause problems if your CPUs need
1456 significantly divergent settings. An incorrect value
1457 will cause delays in the kernel to be wrong, leading to
1458 unpredictable I/O errors and other breakage. Although
1459 unlikely, in the extreme case this might damage your
1463 Format: <io>,<irq>,<dma>
1465 machvec= [IA-64] Force the use of a particular machine-vector
1466 (machvec) in a generic kernel.
1467 Example: machvec=hpzx1_swiotlb
1469 machtype= [Loongson] Share the same kernel image file between different
1471 Example: machtype=lemote-yeeloong-2f-7inch
1473 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1474 than or equal to this physical address is ignored.
1476 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1477 should make use of. maxcpus=n : n >= 0 limits the
1478 kernel to using 'n' processors. n=0 is a special case,
1479 it is equivalent to "nosmp", which also disables
1482 max_loop= [LOOP] The number of loop block devices that get
1483 (loop.max_loop) unconditionally pre-created at init time. The default
1484 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1485 of statically allocating a predefined number, loop
1486 devices can be requested on-demand with the
1487 /dev/loop-control interface.
1489 mce [X86-32] Machine Check Exception
1491 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1493 md= [HW] RAID subsystems devices and level
1494 See Documentation/md.txt.
1497 Format: <first>,<last>
1498 Specifies range of consoles to be captured by the MDA.
1500 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1501 Amount of memory to be used when the kernel is not able
1502 to see the whole system memory or for test.
1503 [X86] Work as limiting max address. Use together
1504 with memmap= to avoid physical address space collisions.
1505 Without memmap= PCI devices could be placed at addresses
1506 belonging to unused RAM.
1508 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1512 [KNL,SH] Allow user to override the default size for
1513 per-device physically contiguous DMA buffers.
1515 memmap=exactmap [KNL,X86] Enable setting of an exact
1516 E820 memory map, as specified by the user.
1517 Such memmap=exactmap lines can be constructed based on
1518 BIOS output or other requirements. See the memmap=nn@ss
1521 memmap=nn[KMG]@ss[KMG]
1522 [KNL] Force usage of a specific region of memory
1523 Region of memory to be used, from ss to ss+nn.
1525 memmap=nn[KMG]#ss[KMG]
1526 [KNL,ACPI] Mark specific memory as ACPI data.
1527 Region of memory to be used, from ss to ss+nn.
1529 memmap=nn[KMG]$ss[KMG]
1530 [KNL,ACPI] Mark specific memory as reserved.
1531 Region of memory to be used, from ss to ss+nn.
1532 Example: Exclude memory from 0x18690000-0x1869ffff
1533 memmap=64K$0x18690000
1535 memmap=0x10000$0x18690000
1537 memory_corruption_check=0/1 [X86]
1538 Some BIOSes seem to corrupt the first 64k of
1539 memory when doing things like suspend/resume.
1540 Setting this option will scan the memory
1541 looking for corruption. Enabling this will
1542 both detect corruption and prevent the kernel
1543 from using the memory being corrupted.
1544 However, its intended as a diagnostic tool; if
1545 repeatable BIOS-originated corruption always
1546 affects the same memory, you can use memmap=
1547 to prevent the kernel from using that memory.
1549 memory_corruption_check_size=size [X86]
1550 By default it checks for corruption in the low
1551 64k, making this memory unavailable for normal
1552 use. Use this parameter to scan for
1553 corruption in more or less memory.
1555 memory_corruption_check_period=seconds [X86]
1556 By default it checks for corruption every 60
1557 seconds. Use this parameter to check at some
1558 other rate. 0 disables periodic checking.
1560 memtest= [KNL,X86] Enable memtest
1562 default : 0 <disable>
1563 Specifies the number of memtest passes to be
1564 performed. Each pass selects another test
1565 pattern from a given set of patterns. Memtest
1566 fills the memory with this pattern, validates
1567 memory contents and reserves bad memory
1568 regions that are detected.
1570 meye.*= [HW] Set MotionEye Camera parameters
1571 See Documentation/video4linux/meye.txt.
1573 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1574 Multi-Function General Purpose Timers on AMD Geode
1577 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1578 the BIOS has incorrectly applied a workaround. TinyBIOS
1579 version 0.98 is known to be affected, 0.99 fixes the
1580 problem by letting the user disable the workaround.
1584 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1585 physical address is ignored.
1587 mini2440= [ARM,HW,KNL]
1588 Format:[0..2][b][c][t]
1590 MINI2440 configuration specification:
1591 0 - The attached screen is the 3.5" TFT
1592 1 - The attached screen is the 7" TFT
1593 2 - The VGA Shield is attached (1024x768)
1594 Leaving out the screen size parameter will not load
1595 the TFT driver, and the framebuffer will be left
1597 b - Enable backlight. The TFT backlight pin will be
1598 linked to the kernel VESA blanking code and a GPIO
1599 LED. This parameter is not necessary when using the
1601 c - Enable the s3c camera interface.
1602 t - Reserved for enabling touchscreen support. The
1603 touchscreen support is not enabled in the mainstream
1604 kernel as of 2.6.30, a preliminary port can be found
1605 in the "bleeding edge" mini2440 support kernel at
1606 http://repo.or.cz/w/linux-2.6/mini2440.git
1609 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1610 parameter allows control of the logging verbosity for
1611 the additional memory initialisation checks. A value
1612 of 0 disables mminit logging and a level of 4 will
1613 log everything. Information is printed at KERN_DEBUG
1614 so loglevel=8 may also need to be specified.
1617 [KNL] When CONFIG_MODULE_SIG is set, this means that
1618 modules without (valid) signatures will fail to load.
1619 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1620 is always true, so this option does nothing.
1623 [MOUSE] Maximum time between finger touching and
1624 leaving touchpad surface for touch to be considered
1625 a tap and be reported as a left button click (for
1626 touchpads working in absolute mode only).
1628 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1629 reporting absolute coordinates, such as tablets
1630 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1631 reporting absolute coordinates, such as tablets
1633 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1634 is similar to kernelcore except it specifies the
1635 amount of memory used for migratable allocations.
1636 If both kernelcore and movablecore is specified,
1637 then kernelcore will be at *least* the specified
1638 value but may be more. If movablecore on its own
1639 is specified, the administrator must be careful
1640 that the amount of memory usable for all allocations
1643 MTD_Partition= [MTD]
1644 Format: <name>,<region-number>,<size>,<offset>
1646 MTD_Region= [MTD] Format:
1647 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1650 See drivers/mtd/cmdlinepart.c.
1652 multitce=off [PPC] This parameter disables the use of the pSeries
1653 firmware feature for updating multiple TCE entries
1656 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1658 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1660 boundary - index of last SLC block on Flex-OneNAND.
1661 The remaining blocks are configured as MLC blocks.
1662 lock - Configure if Flex-OneNAND boundary should be locked.
1663 Once locked, the boundary cannot be changed.
1664 1 indicates lock status, 0 indicates unlock status.
1667 ARM/S3C2412 JIVE boot control
1669 See arch/arm/mach-s3c2412/mach-jive.c
1671 mtouchusb.raw_coordinates=
1672 [HW] Make the MicroTouch USB driver use raw coordinates
1673 ('y', default) or cooked coordinates ('n')
1675 mtrr_chunk_size=nn[KMG] [X86]
1676 used for mtrr cleanup. It is largest continuous chunk
1677 that could hold holes aka. UC entries.
1679 mtrr_gran_size=nn[KMG] [X86]
1680 Used for mtrr cleanup. It is granularity of mtrr block.
1682 Large value could prevent small alignment from
1685 mtrr_spare_reg_nr=n [X86]
1687 Range: 0,7 : spare reg number
1689 Used for mtrr cleanup. It is spare mtrr entries number.
1690 Set to 2 or more if your graphical card needs more.
1692 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1694 netdev= [NET] Network devices parameters
1695 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1696 Note that mem_start is often overloaded to mean
1697 something different and driver-specific.
1698 This usage is only documented in each driver source
1702 [NETFILTER] Enable connection tracking flow accounting
1703 0 to disable accounting
1704 1 to enable accounting
1707 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1708 See Documentation/filesystems/nfs/nfsroot.txt.
1710 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1711 See Documentation/filesystems/nfs/nfsroot.txt.
1713 nfsrootdebug [NFS] enable nfsroot debugging messages.
1714 See Documentation/filesystems/nfs/nfsroot.txt.
1716 nfs.callback_tcpport=
1717 [NFS] set the TCP port on which the NFSv4 callback
1718 channel should listen.
1721 [NFS] sets the pathname to the program which is used
1722 to update the NFS client cache entries.
1724 nfs.cache_getent_timeout=
1725 [NFS] sets the timeout after which an attempt to
1726 update a cache entry is deemed to have failed.
1728 nfs.idmap_cache_timeout=
1729 [NFS] set the maximum lifetime for idmapper cache
1733 [NFS] enable 64-bit inode numbers.
1734 If zero, the NFS client will fake up a 32-bit inode
1735 number for the readdir() and stat() syscalls instead
1736 of returning the full 64-bit number.
1737 The default is to return 64-bit inode numbers.
1739 nfs.max_session_slots=
1740 [NFSv4.1] Sets the maximum number of session slots
1741 the client will attempt to negotiate with the server.
1742 This limits the number of simultaneous RPC requests
1743 that the client can send to the NFSv4.1 server.
1744 Note that there is little point in setting this
1745 value higher than the max_tcp_slot_table_limit.
1747 nfs.nfs4_disable_idmapping=
1748 [NFSv4] When set to the default of '1', this option
1749 ensures that both the RPC level authentication
1750 scheme and the NFS level operations agree to use
1751 numeric uids/gids if the mount is using the
1752 'sec=sys' security flavour. In effect it is
1753 disabling idmapping, which can make migration from
1754 legacy NFSv2/v3 systems to NFSv4 easier.
1755 Servers that do not support this mode of operation
1756 will be autodetected by the client, and it will fall
1757 back to using the idmapper.
1758 To turn off this behaviour, set the value to '0'.
1760 [NFS4] Specify an additional fixed unique ident-
1761 ification string that NFSv4 clients can insert into
1762 their nfs_client_id4 string. This is typically a
1763 UUID that is generated at system install time.
1765 nfs.send_implementation_id =
1766 [NFSv4.1] Send client implementation identification
1767 information in exchange_id requests.
1768 If zero, no implementation identification information
1770 The default is to send the implementation identification
1773 nfsd.nfs4_disable_idmapping=
1774 [NFSv4] When set to the default of '1', the NFSv4
1775 server will return only numeric uids and gids to
1776 clients using auth_sys, and will accept numeric uids
1777 and gids from such clients. This is intended to ease
1778 migration from NFSv2/v3.
1780 objlayoutdriver.osd_login_prog=
1781 [NFS] [OBJLAYOUT] sets the pathname to the program which
1782 is used to automatically discover and login into new
1783 osd-targets. Please see:
1784 Documentation/filesystems/pnfs.txt for more explanations
1786 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1787 when a NMI is triggered.
1788 Format: [state][,regs][,debounce][,die]
1790 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1791 Format: [panic,][nopanic,][num]
1793 0 - turn nmi_watchdog off
1794 When panic is specified, panic when an NMI watchdog
1795 timeout occurs (or 'nopanic' to override the opposite
1797 This is useful when you use a panic=... timeout and
1798 need the box quickly up again.
1800 netpoll.carrier_timeout=
1801 [NET] Specifies amount of time (in seconds) that
1802 netpoll should wait for a carrier. By default netpoll
1805 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1806 emulation library even if a 387 maths coprocessor
1810 [HW] Never suspend the console
1811 Disable suspending of consoles during suspend and
1812 hibernate operations. Once disabled, debugging
1813 messages can reach various consoles while the rest
1814 of the system is being put to sleep (ie, while
1815 debugging driver suspend/resume hooks). This may
1816 not work reliably with all consoles, but is known
1817 to work with serial and VGA consoles.
1818 To facilitate more flexible debugging, we also add
1819 console_suspend, a printk module parameter to control
1820 it. Users could use console_suspend (usually
1821 /sys/module/printk/parameters/console_suspend) to
1822 turn on/off it dynamically.
1824 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1825 caches in the slab allocator. Saves per-node memory,
1826 but will impact performance.
1830 noapic [SMP,APIC] Tells the kernel to not make use of any
1831 IOAPICs that may be present in the system.
1833 noautogroup Disable scheduler automatic task group creation.
1835 nobats [PPC] Do not use BATs for mapping kernel lowmem
1836 on "Classic" PPC cores.
1840 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1842 nodelayacct [KNL] Disable per-task delay accounting
1844 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1846 nodsp [SH] Disable hardware DSP at boot time.
1848 noefi [X86] Disable EFI runtime services support.
1853 On X86-32 available only on PAE configured kernels.
1854 noexec=on: enable non-executable mappings (default)
1855 noexec=off: disable non-executable mappings
1858 Disable SMAP (Supervisor Mode Access Prevention)
1859 even if it is supported by processor.
1862 Disable SMEP (Supervisor Mode Execution Prevention)
1863 even if it is supported by processor.
1866 This affects only 32-bit executables.
1867 noexec32=on: enable non-executable mappings (default)
1868 read doesn't imply executable mappings
1869 noexec32=off: disable non-executable mappings
1870 read implies executable mappings
1872 nofpu [SH] Disable hardware FPU at boot time.
1874 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1875 register save and restore. The kernel will only save
1876 legacy floating-point registers on task switch.
1878 noxsave [BUGS=X86] Disables x86 extended register state save
1879 and restore using xsave. The kernel will fallback to
1880 enabling legacy floating-point and sse state.
1883 on enable eager fpu restore
1884 off disable eager fpu restore
1885 auto selects the default scheme, which automatically
1886 enables eagerfpu restore for xsaveopt.
1888 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1889 wfi(ARM) instruction doesn't work correctly and not to
1890 use it. This is also useful when using JTAG debugger.
1892 no_file_caps Tells the kernel not to honor file capabilities. The
1893 only way then for a file to be executed with privilege
1894 is to be setuid root or executed by root.
1896 nohalt [IA-64] Tells the kernel not to use the power saving
1897 function PAL_HALT_LIGHT when idle. This increases
1898 power-consumption. On the positive side, it reduces
1899 interrupt wake-up latency, which may improve performance
1900 in certain environments such as networked servers or
1903 nohz= [KNL] Boottime enable/disable dynamic ticks
1904 Valid arguments: on, off
1907 noiotrap [SH] Disables trapped I/O port accesses.
1909 noirqdebug [X86-32] Disables the code which attempts to detect and
1910 disable unhandled interrupt sources.
1912 no_timer_check [X86,APIC] Disables the code which tests for
1913 broken timer IRQ sources.
1915 noisapnp [ISAPNP] Disables ISA PnP code.
1917 noinitrd [RAM] Tells the kernel not to load any configured
1920 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1922 [Deprecated - use intremap=off]
1926 nojitter [IA-64] Disables jitter checking for ITC timers.
1928 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1930 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1933 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1934 steal time is computed, but won't influence scheduler
1937 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1939 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1941 noltlbs [PPC] Do not use large page/tlb entries for kernel
1942 lowmem mapping on PPC40x.
1944 nomca [IA-64] Disable machine check abort handling
1946 nomce [X86-32] Machine Check Exception
1948 nomfgpt [X86-32] Disable Multi-Function General Purpose
1949 Timer usage (for AMD Geode machines).
1951 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1952 shutdown the other cpus. Instead use the REBOOT_VECTOR
1955 nomodule Disable module load
1957 nopat [X86] Disable PAT (page attribute table extension of
1958 pagetables) support.
1960 norandmaps Don't use address space randomization. Equivalent to
1961 echo 0 > /proc/sys/kernel/randomize_va_space
1963 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1965 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1966 with UP alternatives
1968 noresidual [PPC] Don't use residual data on PReP machines.
1970 nordrand [X86] Disable the direct use of the RDRAND
1971 instruction even if it is supported by the
1972 processor. RDRAND is still available to user
1975 noresume [SWSUSP] Disables resume and restores original swap
1978 no-scroll [VGA] Disables scrollback.
1979 This is required for the Braillex ib80-piezo Braille
1980 reader made by F.H. Papenmeier (Germany).
1984 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1986 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1987 and disable the IO APIC. legacy for "maxcpus=0".
1989 nosoftlockup [KNL] Disable the soft-lockup detector.
1991 nosync [HW,M68K] Disables sync negotiation for all devices.
1993 notsc [BUGS=X86-32] Disable Time Stamp Counter
1995 nousb [USB] Disable the USB subsystem
1997 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2001 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2003 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2004 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2005 Some features depend on CPU0. Known dependencies are:
2006 1. Resume from suspend/hibernate depends on CPU0.
2007 Suspend/hibernate will fail if CPU0 is offline and you
2008 need to online CPU0 before suspend/hibernate.
2009 2. PIC interrupts also depend on CPU0. CPU0 can't be
2010 removed if a PIC interrupt is detected.
2011 It's said poweroff/reboot may depend on CPU0 on some
2012 machines although I haven't seen such issues so far
2013 after CPU0 is offline on a few tested machines.
2014 If the dependencies are under your control, you can
2015 turn on cpu0_hotplug.
2017 nptcg= [IA-64] Override max number of concurrent global TLB
2018 purges which is reported from either PAL_VM_SUMMARY or
2021 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2022 could support. nr_cpus=n : n >= 1 limits the kernel to
2023 supporting 'n' processors. Later in runtime you can not
2024 use hotplug cpu feature to put more cpu back to online.
2025 just like you compile the kernel NR_CPUS=n
2027 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2029 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2030 Allowed values are enable and disable
2032 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2033 one of ['zone', 'node', 'default'] can be specified
2034 This can be set from sysctl after boot.
2035 See Documentation/sysctl/vm.txt for details.
2037 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2038 See Documentation/debugging-via-ohci1394.txt for more
2041 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2042 Rather than timing out after 20 ms if an EC
2043 command is not properly ACKed, override the length
2044 of the timeout. We have interrupts disabled while
2045 waiting for the ACK, so if this is set too high
2046 interrupts *may* be lost!
2048 omap_mux= [OMAP] Override bootloader pin multiplexing.
2049 Format: <mux_mode0.mode_name=value>...
2050 For example, to override I2C bus2:
2051 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2053 oprofile.timer= [HW]
2054 Use timer interrupt instead of performance counters
2056 oprofile.cpu_type= Force an oprofile cpu type
2057 This might be useful if you have an older oprofile
2058 userland or if you want common events.
2059 Format: { arch_perfmon }
2060 arch_perfmon: [X86] Force use of architectural
2061 perfmon on Intel CPUs instead of the
2062 CPU specific event set.
2063 timer: [X86] Force use of architectural NMI
2064 timer mode (see also oprofile.timer
2065 for generic hr timer mode)
2066 [s390] Force legacy basic mode sampling
2067 (report cpu_type "timer")
2069 oops=panic Always panic on oopses. Default is to just kill the
2070 process, but there is a small probability of
2071 deadlocking the machine.
2072 This will also cause panics on machine check exceptions.
2073 Useful together with panic=30 to trigger a reboot.
2076 See Documentation/sound/oss/oss-parameters.txt
2078 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2079 timeout > 0: seconds before rebooting
2080 timeout = 0: wait forever
2081 timeout < 0: reboot immediately
2084 parkbd.port= [HW] Parallel port number the keyboard adapter is
2085 connected to, default is 0.
2087 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2088 0 for XT, 1 for AT (default is AT).
2091 parport= [HW,PPT] Specify parallel ports. 0 disables.
2092 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2093 Use 'auto' to force the driver to use any
2094 IRQ/DMA settings detected (the default is to
2095 ignore detected IRQ/DMA settings because of
2096 possible conflicts). You can specify the base
2097 address, IRQ, and DMA settings; IRQ and DMA
2098 should be numbers, or 'auto' (for using detected
2099 settings on that particular port), or 'nofifo'
2100 (to avoid using a FIFO even if it is detected).
2101 Parallel ports are assigned in the order they
2102 are specified on the command line, starting
2105 parport_init_mode= [HW,PPT]
2106 Configure VIA parallel port to operate in
2107 a specific mode. This is necessary on Pegasos
2108 computer where firmware has no options for setting
2109 up parallel port mode and sets it to spp.
2110 Currently this function knows 686a and 8231 chips.
2111 Format: [spp|ps2|epp|ecp|ecpepp]
2114 Halt all CPUs after the first oops has been printed for
2115 the specified number of seconds. This is to be used if
2116 your oopses keep scrolling off the screen.
2121 See header of drivers/block/paride/pcd.c.
2122 See also Documentation/blockdev/paride.txt.
2124 pci=option[,option...] [PCI] various PCI subsystem options:
2125 earlydump [X86] dump PCI config space before the kernel
2127 off [X86] don't probe for the PCI bus
2128 bios [X86-32] force use of PCI BIOS, don't access
2129 the hardware directly. Use this if your machine
2130 has a non-standard PCI host bridge.
2131 nobios [X86-32] disallow use of PCI BIOS, only direct
2132 hardware access methods are allowed. Use this
2133 if you experience crashes upon bootup and you
2134 suspect they are caused by the BIOS.
2135 conf1 [X86] Force use of PCI Configuration
2137 conf2 [X86] Force use of PCI Configuration
2139 noaer [PCIE] If the PCIEAER kernel config parameter is
2140 enabled, this kernel boot option can be used to
2141 disable the use of PCIE advanced error reporting.
2142 nodomains [PCI] Disable support for multiple PCI
2143 root domains (aka PCI segments, in ACPI-speak).
2144 nommconf [X86] Disable use of MMCONFIG for PCI
2146 check_enable_amd_mmconf [X86] check for and enable
2147 properly configured MMIO access to PCI
2148 config space on AMD family 10h CPU
2149 nomsi [MSI] If the PCI_MSI kernel config parameter is
2150 enabled, this kernel boot option can be used to
2151 disable the use of MSI interrupts system-wide.
2152 noioapicquirk [APIC] Disable all boot interrupt quirks.
2153 Safety option to keep boot IRQs enabled. This
2154 should never be necessary.
2155 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2156 primary IO-APIC for bridges that cannot disable
2157 boot IRQs. This fixes a source of spurious IRQs
2158 when the system masks IRQs.
2159 noioapicreroute [APIC] Disable workaround that uses the
2160 boot IRQ equivalent of an IRQ that connects to
2161 a chipset where boot IRQs cannot be disabled.
2162 The opposite of ioapicreroute.
2163 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2164 routing table. These calls are known to be buggy
2165 on several machines and they hang the machine
2166 when used, but on other computers it's the only
2167 way to get the interrupt routing table. Try
2168 this option if the kernel is unable to allocate
2169 IRQs or discover secondary PCI buses on your
2171 rom [X86] Assign address space to expansion ROMs.
2172 Use with caution as certain devices share
2173 address decoders between ROMs and other
2175 norom [X86] Do not assign address space to
2176 expansion ROMs that do not already have
2177 BIOS assigned address ranges.
2178 nobar [X86] Do not assign address space to the
2179 BARs that weren't assigned by the BIOS.
2180 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2181 assigned automatically to PCI devices. You can
2182 make the kernel exclude IRQs of your ISA cards
2184 pirqaddr=0xAAAAA [X86] Specify the physical address
2185 of the PIRQ table (normally generated
2186 by the BIOS) if it is outside the
2187 F0000h-100000h range.
2188 lastbus=N [X86] Scan all buses thru bus #N. Can be
2189 useful if the kernel is unable to find your
2190 secondary buses and you want to tell it
2191 explicitly which ones they are.
2192 assign-busses [X86] Always assign all PCI bus
2193 numbers ourselves, overriding
2194 whatever the firmware may have done.
2195 usepirqmask [X86] Honor the possible IRQ mask stored
2196 in the BIOS $PIR table. This is needed on
2197 some systems with broken BIOSes, notably
2198 some HP Pavilion N5400 and Omnibook XE3
2199 notebooks. This will have no effect if ACPI
2200 IRQ routing is enabled.
2201 noacpi [X86] Do not use ACPI for IRQ routing
2202 or for PCI scanning.
2203 use_crs [X86] Use PCI host bridge window information
2204 from ACPI. On BIOSes from 2008 or later, this
2205 is enabled by default. If you need to use this,
2206 please report a bug.
2207 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2208 If you need to use this, please report a bug.
2209 routeirq Do IRQ routing for all PCI devices.
2210 This is normally done in pci_enable_device(),
2211 so this option is a temporary workaround
2212 for broken drivers that don't call it.
2213 skip_isa_align [X86] do not align io start addr, so can
2214 handle more pci cards
2215 firmware [ARM] Do not re-enumerate the bus but instead
2216 just use the configuration from the
2217 bootloader. This is currently used on
2218 IXP2000 systems where the bus has to be
2219 configured a certain way for adjunct CPUs.
2220 noearly [X86] Don't do any early type 1 scanning.
2221 This might help on some broken boards which
2222 machine check when some devices' config space
2223 is read. But various workarounds are disabled
2224 and some IOMMU drivers will not work.
2225 bfsort Sort PCI devices into breadth-first order.
2226 This sorting is done to get a device
2227 order compatible with older (<= 2.4) kernels.
2228 nobfsort Don't sort PCI devices into breadth-first order.
2229 cbiosize=nn[KMG] The fixed amount of bus space which is
2230 reserved for the CardBus bridge's IO window.
2231 The default value is 256 bytes.
2232 cbmemsize=nn[KMG] The fixed amount of bus space which is
2233 reserved for the CardBus bridge's memory
2234 window. The default value is 64 megabytes.
2237 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2238 Specifies alignment and device to reassign
2239 aligned memory resources.
2240 If <order of align> is not specified,
2241 PAGE_SIZE is used as alignment.
2242 PCI-PCI bridge can be specified, if resource
2243 windows need to be expanded.
2244 ecrc= Enable/disable PCIe ECRC (transaction layer
2245 end-to-end CRC checking).
2246 bios: Use BIOS/firmware settings. This is the
2250 realloc= Enable/disable reallocating PCI bridge resources
2251 if allocations done by BIOS are too small to
2252 accommodate resources required by all child
2254 off: Turn realloc off
2256 realloc same as realloc=on
2257 noari do not use PCIe ARI.
2258 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2259 only look for one device below a PCIe downstream
2262 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2265 force Enable ASPM even on devices that claim not to support it.
2266 WARNING: Forcing ASPM on may cause system lockups.
2268 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2269 nomsi Do not use MSI for PCI Express Native Hotplug (this
2270 makes all PCIe ports use INTx for hotplug services).
2272 pcie_ports= [PCIE] PCIe ports handling:
2273 auto Ask the BIOS whether or not to use native PCIe services
2274 associated with PCIe ports (PME, hot-plug, AER). Use
2275 them only if that is allowed by the BIOS.
2276 native Use native PCIe services associated with PCIe ports
2278 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2281 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2282 nomsi Do not use MSI for native PCIe PME signaling (this makes
2283 all PCIe root ports use INTx for all services).
2285 pcmv= [HW,PCMCIA] BadgePAD 4
2288 See Documentation/blockdev/paride.txt.
2290 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2293 See arch/parisc/kernel/pdc_chassis.c
2295 percpu_alloc= Select which percpu first chunk allocator to use.
2296 Currently supported values are "embed" and "page".
2297 Archs may support subset or none of the selections.
2298 See comments in mm/percpu.c for details on each
2299 allocator. This parameter is primarily for debugging
2300 and performance comparison.
2303 See Documentation/blockdev/paride.txt.
2306 See Documentation/blockdev/paride.txt.
2308 pirq= [SMP,APIC] Manual mp-table setup
2309 See Documentation/x86/i386/IO-APIC.txt.
2311 plip= [PPT,NET] Parallel port network link
2312 Format: { parport<nr> | timid | 0 }
2313 See also Documentation/parport.txt.
2315 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2316 Override pmtimer IOPort with a hex value.
2320 Enable PNP debug messages (depends on the
2321 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2322 via /sys/module/pnp/parameters/debug. We always show
2323 current resource usage; turning this on also shows
2324 possible settings and some assignment information.
2330 { on | off | curr | res | no-curr | no-res }
2333 [ISAPNP] Exclude IRQs for the autoconfiguration
2336 [ISAPNP] Exclude DMAs for the autoconfiguration
2338 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2339 Ranges are in pairs (I/O port base and size).
2342 [ISAPNP] Exclude memory regions for the
2344 Ranges are in pairs (memory base and size).
2346 ports= [IP_VS_FTP] IPVS ftp helper module
2348 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2350 Format: <port>,<port>....
2352 print-fatal-signals=
2353 [KNL] debug: print fatal signals
2355 If enabled, warn about various signal handling
2356 related application anomalies: too many signals,
2357 too many POSIX.1 timers, fatal signals causing a
2360 If you hit the warning due to signal overflow,
2361 you might want to try "ulimit -i unlimited".
2365 printk.always_kmsg_dump=
2366 Trigger kmsg_dump for cases other than kernel oops or
2368 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2371 printk.time= Show timing data prefixed to each printk message line
2372 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2374 processor.max_cstate= [HW,ACPI]
2375 Limit processor to maximum C-state
2376 max_cstate=9 overrides any DMI blacklist limit.
2378 processor.nocst [HW,ACPI]
2379 Ignore the _CST method to determine C-states,
2380 instead using the legacy FADT method
2382 profile= [KNL] Enable kernel profiling via /proc/profile
2383 Format: [schedule,]<number>
2384 Param: "schedule" - profile schedule points.
2385 Param: <number> - step/bucket size as a power of 2 for
2386 statistical time based profiling.
2387 Param: "sleep" - profile D-state sleeping (millisecs).
2388 Requires CONFIG_SCHEDSTATS
2389 Param: "kvm" - profile VM exits.
2391 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2393 See Documentation/blockdev/ramdisk.txt.
2395 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2396 probe for; one of (bare|imps|exps|lifebook|any).
2397 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2399 psmouse.resetafter= [HW,MOUSE]
2400 Try to reset the device after so many bad packets
2403 [HW,MOUSE] Set desired mouse resolution, in dpi.
2404 psmouse.smartscroll=
2405 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2406 0 = disabled, 1 = enabled (default).
2408 pstore.backend= Specify the name of the pstore backend to use
2411 See Documentation/blockdev/paride.txt.
2414 [KNL] Number of legacy pty's. Overwrites compiled-in
2417 quiet [KNL] Disable most log messages
2422 See Documentation/md.txt.
2424 ramdisk_blocksize= [RAM]
2425 See Documentation/blockdev/ramdisk.txt.
2427 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2428 See Documentation/blockdev/ramdisk.txt.
2430 rcu_nocbs= [KNL,BOOT]
2431 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2432 the specified list of CPUs to be no-callback CPUs.
2433 Invocation of these CPUs' RCU callbacks will
2434 be offloaded to "rcuoN" kthreads created for
2435 that purpose. This reduces OS jitter on the
2436 offloaded CPUs, which can be useful for HPC and
2437 real-time workloads. It can also improve energy
2438 efficiency for asymmetric multiprocessors.
2440 rcu_nocb_poll [KNL,BOOT]
2441 Rather than requiring that offloaded CPUs
2442 (specified by rcu_nocbs= above) explicitly
2443 awaken the corresponding "rcuoN" kthreads,
2444 make these kthreads poll for callbacks.
2445 This improves the real-time response for the
2446 offloaded CPUs by relieving them of the need to
2447 wake up the corresponding kthread, but degrades
2448 energy efficiency by requiring that the kthreads
2449 periodically wake up to do the polling.
2451 rcutree.blimit= [KNL,BOOT]
2452 Set maximum number of finished RCU callbacks to process
2455 rcutree.fanout_leaf= [KNL,BOOT]
2456 Increase the number of CPUs assigned to each
2457 leaf rcu_node structure. Useful for very large
2460 rcutree.qhimark= [KNL,BOOT]
2461 Set threshold of queued
2462 RCU callbacks over which batch limiting is disabled.
2464 rcutree.qlowmark= [KNL,BOOT]
2465 Set threshold of queued RCU callbacks below which
2466 batch limiting is re-enabled.
2468 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2469 Suppress RCU CPU stall warning messages.
2471 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2472 Set timeout for RCU CPU stall warning messages.
2474 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2475 Set delay from grace-period initialization to
2476 first attempt to force quiescent states.
2477 Units are jiffies, minimum value is zero,
2478 and maximum value is HZ.
2480 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2481 Set delay between subsequent attempts to force
2482 quiescent states. Units are jiffies, minimum
2483 value is one, and maximum value is HZ.
2485 rcutorture.fqs_duration= [KNL,BOOT]
2486 Set duration of force_quiescent_state bursts.
2488 rcutorture.fqs_holdoff= [KNL,BOOT]
2489 Set holdoff time within force_quiescent_state bursts.
2491 rcutorture.fqs_stutter= [KNL,BOOT]
2492 Set wait time between force_quiescent_state bursts.
2494 rcutorture.irqreader= [KNL,BOOT]
2495 Test RCU readers from irq handlers.
2497 rcutorture.n_barrier_cbs= [KNL,BOOT]
2498 Set callbacks/threads for rcu_barrier() testing.
2500 rcutorture.nfakewriters= [KNL,BOOT]
2501 Set number of concurrent RCU writers. These just
2502 stress RCU, they don't participate in the actual
2503 test, hence the "fake".
2505 rcutorture.nreaders= [KNL,BOOT]
2506 Set number of RCU readers.
2508 rcutorture.onoff_holdoff= [KNL,BOOT]
2509 Set time (s) after boot for CPU-hotplug testing.
2511 rcutorture.onoff_interval= [KNL,BOOT]
2512 Set time (s) between CPU-hotplug operations, or
2513 zero to disable CPU-hotplug testing.
2515 rcutorture.shuffle_interval= [KNL,BOOT]
2516 Set task-shuffle interval (s). Shuffling tasks
2517 allows some CPUs to go into dyntick-idle mode
2518 during the rcutorture test.
2520 rcutorture.shutdown_secs= [KNL,BOOT]
2521 Set time (s) after boot system shutdown. This
2522 is useful for hands-off automated testing.
2524 rcutorture.stall_cpu= [KNL,BOOT]
2525 Duration of CPU stall (s) to test RCU CPU stall
2526 warnings, zero to disable.
2528 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2529 Time to wait (s) after boot before inducing stall.
2531 rcutorture.stat_interval= [KNL,BOOT]
2532 Time (s) between statistics printk()s.
2534 rcutorture.stutter= [KNL,BOOT]
2535 Time (s) to stutter testing, for example, specifying
2536 five seconds causes the test to run for five seconds,
2537 wait for five seconds, and so on. This tests RCU's
2538 ability to transition abruptly to and from idle.
2540 rcutorture.test_boost= [KNL,BOOT]
2541 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2542 "Maybe" means test if the RCU implementation
2543 under test support RCU priority boosting.
2545 rcutorture.test_boost_duration= [KNL,BOOT]
2546 Duration (s) of each individual boost test.
2548 rcutorture.test_boost_interval= [KNL,BOOT]
2549 Interval (s) between each boost test.
2551 rcutorture.test_no_idle_hz= [KNL,BOOT]
2552 Test RCU's dyntick-idle handling. See also the
2553 rcutorture.shuffle_interval parameter.
2555 rcutorture.torture_type= [KNL,BOOT]
2556 Specify the RCU implementation to test.
2558 rcutorture.verbose= [KNL,BOOT]
2559 Enable additional printk() statements.
2563 Run specified binary instead of /init from the ramdisk,
2564 used for early userspace startup. See initrd.
2566 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2567 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2568 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2571 [KNL, SMP] Set scheduler's default relax_domain_level.
2572 See Documentation/cgroups/cpusets.txt.
2574 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2576 reservetop= [X86-32]
2578 Reserves a hole at the top of the kernel virtual
2583 Set the amount of memory to reserve for BIOS at
2584 the bottom of the address space.
2586 reset_devices [KNL] Force drivers to reset the underlying device
2587 during initialization.
2590 Specify the partition device for software suspend
2592 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2594 resume_offset= [SWSUSP]
2595 Specify the offset from the beginning of the partition
2596 given by "resume=" at which the swap header is located,
2597 in <PAGE_SIZE> units (needed only for swap files).
2598 See Documentation/power/swsusp-and-swap-files.txt
2600 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2601 read the resume files
2603 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2604 Useful for devices that are detected asynchronously
2605 (e.g. USB and MMC devices).
2607 hibernate= [HIBERNATION]
2608 noresume Don't check if there's a hibernation image
2609 present during boot.
2610 nocompress Don't compress/decompress hibernation images.
2612 retain_initrd [RAM] Keep initrd memory after extraction
2614 rhash_entries= [KNL,NET]
2615 Set number of hash buckets for route cache
2617 riscom8= [HW,SERIAL]
2618 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2620 ro [KNL] Mount root device read-only on boot
2622 root= [KNL] Root filesystem
2623 See name_to_dev_t comment in init/do_mounts.c.
2625 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2626 mount the root filesystem
2628 rootflags= [KNL] Set root filesystem mount option string
2630 rootfstype= [KNL] Set root filesystem type
2632 rootwait [KNL] Wait (indefinitely) for root device to show up.
2633 Useful for devices that are detected asynchronously
2634 (e.g. USB and MMC devices).
2636 rw [KNL] Mount root device read-write on boot
2638 S [KNL] Run init in single mode
2641 See drivers/net/irda/sa1100_ir.c.
2643 sbni= [NET] Granch SBNI12 leased line adapter
2645 sched_debug [KNL] Enables verbose scheduler debug messages.
2647 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2648 xtime_lock contention on larger systems, and/or RCU lock
2649 contention on all systems with CONFIG_MAXSMP set.
2650 Format: { "0" | "1" }
2651 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2653 Note: increases power consumption, thus should only be
2654 enabled if running jitter sensitive (HPC/RT) workloads.
2656 security= [SECURITY] Choose a security module to enable at boot.
2657 If this boot parameter is not specified, only the first
2658 security module asking for security registration will be
2659 loaded. An invalid security module name will be treated
2660 as if no module has been chosen.
2662 selinux= [SELINUX] Disable or enable SELinux at boot time.
2663 Format: { "0" | "1" }
2664 See security/selinux/Kconfig help text.
2667 Default value is set via kernel config option.
2668 If enabled at boot time, /selinux/disable can be used
2669 later to disable prior to initial policy load.
2671 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2672 Format: { "0" | "1" }
2673 See security/apparmor/Kconfig help text
2676 Default value is set via kernel config option.
2678 serialnumber [BUGS=X86-32]
2681 Maximal number of shapers.
2683 show_msr= [x86] show boot-time MSR settings
2684 Format: { <integer> }
2685 Show boot-time (BIOS-initialized) MSR settings.
2686 The parameter means the number of CPUs to show,
2687 for example 1 means boot CPU only.
2694 slab_max_order= [MM, SLAB]
2695 Determines the maximum allowed order for slabs.
2696 A high setting may cause OOMs due to memory
2697 fragmentation. Defaults to 1 for systems with
2698 more than 32MB of RAM, 0 otherwise.
2700 slub_debug[=options[,slabs]] [MM, SLUB]
2701 Enabling slub_debug allows one to determine the
2702 culprit if slab objects become corrupted. Enabling
2703 slub_debug can create guard zones around objects and
2704 may poison objects when not in use. Also tracks the
2705 last alloc / free. For more information see
2706 Documentation/vm/slub.txt.
2708 slub_max_order= [MM, SLUB]
2709 Determines the maximum allowed order for slabs.
2710 A high setting may cause OOMs due to memory
2711 fragmentation. For more information see
2712 Documentation/vm/slub.txt.
2714 slub_min_objects= [MM, SLUB]
2715 The minimum number of objects per slab. SLUB will
2716 increase the slab order up to slub_max_order to
2717 generate a sufficiently large slab able to contain
2718 the number of objects indicated. The higher the number
2719 of objects the smaller the overhead of tracking slabs
2720 and the less frequently locks need to be acquired.
2721 For more information see Documentation/vm/slub.txt.
2723 slub_min_order= [MM, SLUB]
2724 Determines the minimum page order for slabs. Must be
2725 lower than slub_max_order.
2726 For more information see Documentation/vm/slub.txt.
2728 slub_nomerge [MM, SLUB]
2729 Disable merging of slabs with similar size. May be
2730 necessary if there is some reason to distinguish
2731 allocs to different slabs. Debug options disable
2732 merging on their own.
2733 For more information see Documentation/vm/slub.txt.
2736 Format: <io1>[,<io2>[,...,<io8>]]
2738 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2739 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2740 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2741 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2742 smsc-ircc2.ircc_irq= [HW] IRQ line
2743 smsc-ircc2.ircc_dma= [HW] DMA channel
2744 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2745 0: Toshiba Satellite 1800 (GP data pin select)
2746 1: Fast pin select (default)
2750 [KNL] Should the soft-lockup detector generate panics.
2753 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2754 See Documentation/laptops/sonypi.txt
2756 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2757 See Documentation/serial/specialix.txt.
2759 spia_io_base= [HW,MTD]
2765 Enabled the stack tracer on boot up.
2767 stacktrace_filter=[function-list]
2768 [FTRACE] Limit the functions that the stack tracer
2769 will trace at boot up. function-list is a comma separated
2770 list of functions. This list can be changed at run
2771 time by the stack_trace_filter file in the debugfs
2772 tracing directory. Note, this enables stack tracing
2773 and the stacktrace above is not needed.
2777 Set the STI (builtin display/keyboard on the HP-PARISC
2778 machines) console (graphic card) which should be used
2779 as the initial boot-console.
2780 See also comment in drivers/video/console/sticore.c.
2783 See comment in drivers/video/console/sticore.c.
2786 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2788 sunrpc.min_resvport=
2789 sunrpc.max_resvport=
2791 SunRPC servers often require that client requests
2792 originate from a privileged port (i.e. a port in the
2793 range 0 < portnr < 1024).
2794 An administrator who wishes to reserve some of these
2795 ports for other uses may adjust the range that the
2796 kernel's sunrpc client considers to be privileged
2797 using these two parameters to set the minimum and
2798 maximum port values.
2802 Control how the NFS server code allocates CPUs to
2803 service thread pools. Depending on how many NICs
2804 you have and where their interrupts are bound, this
2805 option will affect which CPUs will do NFS serving.
2806 Note: this parameter cannot be changed while the
2807 NFS server is running.
2809 auto the server chooses an appropriate mode
2810 automatically using heuristics
2811 global a single global pool contains all CPUs
2812 percpu one pool for each CPU
2813 pernode one pool for each NUMA node (equivalent
2814 to global on non-NUMA machines)
2816 sunrpc.tcp_slot_table_entries=
2817 sunrpc.udp_slot_table_entries=
2819 Sets the upper limit on the number of simultaneous
2820 RPC calls that can be sent from the client to a
2821 server. Increasing these values may allow you to
2822 improve throughput, but will also increase the
2823 amount of memory reserved for use by the client.
2826 [KNL] Enable accounting of swap in memory resource
2827 controller if no parameter or 1 is given or disable
2828 it if 0 is given (See Documentation/cgroups/memory.txt)
2830 swiotlb= [IA-64] Number of I/O TLB slabs
2834 sysfs.deprecated=0|1 [KNL]
2835 Enable/disable old style sysfs layout for old udev
2836 on older distributions. When this option is enabled
2837 very new udev will not work anymore. When this option
2838 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2839 in older udev will not work anymore.
2840 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2841 the kernel configuration.
2843 sysrq_always_enabled
2845 Ignore sysrq setting - this boot parameter will
2846 neutralize any effect of /proc/sys/kernel/sysrq.
2847 Useful for debugging.
2851 test_suspend= [SUSPEND]
2852 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2853 standby suspend) as the system sleep state to briefly
2854 enter during system startup. The system is woken from
2855 this state using a wakeup-capable RTC alarm.
2857 thash_entries= [KNL,NET]
2858 Set number of hash buckets for TCP connection
2860 thermal.act= [HW,ACPI]
2861 -1: disable all active trip points in all thermal zones
2862 <degrees C>: override all lowest active trip points
2864 thermal.crt= [HW,ACPI]
2865 -1: disable all critical trip points in all thermal zones
2866 <degrees C>: override all critical trip points
2868 thermal.nocrt= [HW,ACPI]
2869 Set to disable actions on ACPI thermal zone
2870 critical and hot trip points.
2872 thermal.off= [HW,ACPI]
2873 1: disable ACPI thermal control
2875 thermal.psv= [HW,ACPI]
2876 -1: disable all passive trip points
2877 <degrees C>: override all passive trip points to this
2880 thermal.tzp= [HW,ACPI]
2881 Specify global default ACPI thermal zone polling rate
2882 <deci-seconds>: poll all this frequency
2883 0: no polling (default)
2886 Force threading of all interrupt handlers except those
2887 marked explicitly IRQF_NO_THREAD.
2891 Specify if the kernel should make use of the cpu
2892 topology information if the hardware supports this.
2893 The scheduler will make use of this information and
2894 e.g. base its process migration decisions on it.
2899 tpm_suspend_pcr=[HW,TPM]
2900 Format: integer pcr id
2901 Specify that at suspend time, the tpm driver
2902 should extend the specified pcr with zeros,
2903 as a workaround for some chips which fail to
2904 flush the last written pcr on TPM_SaveState.
2905 This will guarantee that all the other pcrs
2908 trace_buf_size=nn[KMG]
2909 [FTRACE] will set tracing buffer size.
2911 trace_event=[event-list]
2912 [FTRACE] Set and start specified trace events in order
2913 to facilitate early boot debugging.
2914 See also Documentation/trace/events.txt
2916 trace_options=[option-list]
2917 [FTRACE] Enable or disable tracer options at boot.
2918 The option-list is a comma delimited list of options
2919 that can be enabled or disabled just as if you were
2920 to echo the option name into
2922 /sys/kernel/debug/tracing/trace_options
2924 For example, to enable stacktrace option (to dump the
2925 stack trace of each event), add to the command line:
2927 trace_options=stacktrace
2929 See also Documentation/trace/ftrace.txt "trace options"
2932 transparent_hugepage=
2934 Format: [always|madvise|never]
2935 Can be used to control the default behavior of the system
2936 with respect to transparent hugepages.
2937 See Documentation/vm/transhuge.txt for more details.
2939 tsc= Disable clocksource stability checks for TSC.
2941 [x86] reliable: mark tsc clocksource as reliable, this
2942 disables clocksource verification at runtime, as well
2943 as the stability checks done at bootup. Used to enable
2944 high-resolution timer mode on older hardware, and in
2945 virtualized environment.
2946 [x86] noirqtime: Do not use TSC to do irq accounting.
2947 Used to run time disable IRQ_TIME_ACCOUNTING on any
2948 platforms where RDTSC is slow and this accounting
2951 turbografx.map[2|3]= [HW,JOY]
2952 TurboGraFX parallel port interface
2954 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2955 See also Documentation/input/joystick-parport.txt
2957 udbg-immortal [PPC] When debugging early kernel crashes that
2958 happen after console_init() and before a proper
2959 console driver takes over, this boot options might
2960 help "seeing" what's going on.
2962 uhash_entries= [KNL,NET]
2963 Set number of hash buckets for UDP/UDP-Lite connections
2966 [USB] Ignore overcurrent events (default N).
2967 Some badly-designed motherboards generate lots of
2968 bogus events, for ports that aren't wired to
2969 anything. Set this parameter to avoid log spamming.
2970 Note that genuine overcurrent events won't be
2974 [X86] Cause panic on unknown NMI.
2976 usbcore.authorized_default=
2977 [USB] Default USB device authorization:
2978 (default -1 = authorized except for wireless USB,
2979 0 = not authorized, 1 = authorized)
2981 usbcore.autosuspend=
2982 [USB] The autosuspend time delay (in seconds) used
2983 for newly-detected USB devices (default 2). This
2984 is the time required before an idle device will be
2985 autosuspended. Devices for which the delay is set
2986 to a negative value won't be autosuspended at all.
2988 usbcore.usbfs_snoop=
2989 [USB] Set to log all usbfs traffic (default 0 = off).
2991 usbcore.blinkenlights=
2992 [USB] Set to cycle leds on hubs (default 0 = off).
2994 usbcore.old_scheme_first=
2995 [USB] Start with the old device initialization
2996 scheme (default 0 = off).
2998 usbcore.usbfs_memory_mb=
2999 [USB] Memory limit (in MB) for buffers allocated by
3000 usbfs (default = 16, 0 = max = 2047).
3002 usbcore.use_both_schemes=
3003 [USB] Try the other device initialization scheme
3004 if the first one fails (default 1 = enabled).
3006 usbcore.initial_descriptor_timeout=
3007 [USB] Specifies timeout for the initial 64-byte
3008 USB_REQ_GET_DESCRIPTOR request in milliseconds
3009 (default 5000 = 5.0 seconds).
3012 [USBHID] The interval which mice are to be polled at.
3014 usb-storage.delay_use=
3015 [UMS] The delay in seconds before a new device is
3016 scanned for Logical Units (default 5).
3019 [UMS] A list of quirks entries to supplement or
3020 override the built-in unusual_devs list. List
3021 entries are separated by commas. Each entry has
3022 the form VID:PID:Flags where VID and PID are Vendor
3023 and Product ID values (4-digit hex numbers) and
3024 Flags is a set of characters, each corresponding
3025 to a common usb-storage quirk flag as follows:
3026 a = SANE_SENSE (collect more than 18 bytes
3028 b = BAD_SENSE (don't collect more than 18
3029 bytes of sense data);
3030 c = FIX_CAPACITY (decrease the reported
3031 device capacity by one sector);
3032 d = NO_READ_DISC_INFO (don't use
3033 READ_DISC_INFO command);
3034 e = NO_READ_CAPACITY_16 (don't use
3035 READ_CAPACITY_16 command);
3036 h = CAPACITY_HEURISTICS (decrease the
3037 reported device capacity by one
3038 sector if the number is odd);
3039 i = IGNORE_DEVICE (don't bind to this
3041 l = NOT_LOCKABLE (don't try to lock and
3042 unlock ejectable media);
3043 m = MAX_SECTORS_64 (don't transfer more
3044 than 64 sectors = 32 KB at a time);
3045 n = INITIAL_READ10 (force a retry of the
3046 initial READ(10) command);
3047 o = CAPACITY_OK (accept the capacity
3048 reported by the device);
3049 p = WRITE_CACHE (the device cache is ON
3051 r = IGNORE_RESIDUE (the device reports
3052 bogus residue values);
3053 s = SINGLE_LUN (the device has only one
3055 w = NO_WP_DETECT (don't test whether the
3056 medium is write-protected).
3057 Example: quirks=0419:aaf5:rl,0421:0433:rc
3059 user_debug= [KNL,ARM]
3061 See arch/arm/Kconfig.debug help text.
3062 1 - undefined instruction events
3064 4 - invalid data aborts
3067 Example: user_debug=31
3070 [X86] Flags controlling user PTE allocations.
3072 nohigh = do not allocate PTE pages in
3073 HIGHMEM regardless of setting
3077 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3078 vdso=1: enable VDSO (default)
3079 vdso=0: disable VDSO mapping
3082 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3083 vdso32=1: enable 32-bit VDSO (default)
3084 vdso32=0: disable 32-bit VDSO mapping
3087 vector=percpu: enable percpu vector domain
3089 video= [FB] Frame buffer configuration
3090 See Documentation/fb/modedb.txt.
3093 [VMMIO] Memory mapped virtio (platform) device.
3095 <size>@<baseaddr>:<irq>[:<id>]
3097 <size> := size (can use standard suffixes
3099 <baseaddr> := physical base address
3100 <irq> := interrupt number (as passed to
3102 <id> := (optional) platform device id
3104 virtio_mmio.device=1K@0x100b0000:48:7
3106 Can be used multiple times for multiple devices.
3108 vga= [BOOT,X86-32] Select a particular video mode
3109 See Documentation/x86/boot.txt and
3110 Documentation/svga.txt.
3111 Use vga=ask for menu.
3112 This is actually a boot loader parameter; the value is
3113 passed to the kernel using a special protocol.
3115 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3116 size of <nn>. This can be used to increase the
3117 minimum size (128MB on x86). It can also be used to
3118 decrease the size and leave more room for directly
3121 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3124 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3127 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3131 Controls the behavior of vsyscalls (i.e. calls to
3132 fixed addresses of 0xffffffffff600x00 from legacy
3133 code). Most statically-linked binaries and older
3134 versions of glibc use these calls. Because these
3135 functions are at fixed addresses, they make nice
3136 targets for exploits that can control RIP.
3138 emulate [default] Vsyscalls turn into traps and are
3139 emulated reasonably safely.
3141 native Vsyscalls are native syscall instructions.
3142 This is a little bit faster than trapping
3143 and makes a few dynamic recompilers work
3144 better than they would in emulation mode.
3145 It also makes exploits much easier to write.
3147 none Vsyscalls don't work at all. This makes
3148 them quite hard to use for exploits but
3149 might break your system.
3151 vt.cur_default= [VT] Default cursor shape.
3152 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3153 the parameters of the <Esc>[?A;B;Cc escape sequence;
3154 see VGA-softcursor.txt. Default: 2 = underline.
3156 vt.default_blu= [VT]
3157 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3158 Change the default blue palette of the console.
3159 This is a 16-member array composed of values
3162 vt.default_grn= [VT]
3163 Format: <green0>,<green1>,<green2>,...,<green15>
3164 Change the default green palette of the console.
3165 This is a 16-member array composed of values
3168 vt.default_red= [VT]
3169 Format: <red0>,<red1>,<red2>,...,<red15>
3170 Change the default red palette of the console.
3171 This is a 16-member array composed of values
3177 Set system-wide default UTF-8 mode for all tty's.
3178 Default is 1, i.e. UTF-8 mode is enabled for all
3179 newly opened terminals.
3181 vt.global_cursor_default=
3184 Set system-wide default for whether a cursor
3185 is shown on new VTs. Default is -1,
3186 i.e. cursors will be created by default unless
3187 overridden by individual drivers. 0 will hide
3188 cursors, 1 will display them.
3190 watchdog timers [HW,WDT] For information on watchdog timers,
3191 see Documentation/watchdog/watchdog-parameters.txt
3192 or other driver-specific files in the
3193 Documentation/watchdog/ directory.
3195 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3196 default x2apic cluster mode on platforms
3199 x86_mrst_timer= [X86-32,APBT]
3200 Choose timer option for x86 Moorestown MID platform.
3201 Two valid options are apbt timer only and lapic timer
3202 plus one apbt timer for broadcast timer.
3203 x86_mrst_timer=apbt_only | lapic_and_apbt
3205 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3206 xd_geo= See header of drivers/block/xd.c.
3208 xen_emul_unplug= [HW,X86,XEN]
3209 Unplug Xen emulated devices
3210 Format: [unplug0,][unplug1]
3211 ide-disks -- unplug primary master IDE devices
3212 aux-ide-disks -- unplug non-primary-master IDE devices
3213 nics -- unplug network devices
3214 all -- unplug all emulated devices (NICs and IDE disks)
3215 unnecessary -- unplugging emulated devices is
3216 unnecessary even if the host did not respond to
3218 never -- do not unplug even if version check succeeds
3220 xirc2ps_cs= [NET,PCMCIA]
3222 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3224 ______________________________________________________________________
3228 Add more DRM drivers.
projects / mirror_ubuntu-jammy-kernel.git / blob