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.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel=range1:size1[,range2:size2,...][@offset]
600 [KNL] Same as above, but depends on the memory
601 in the running system. The syntax of range is
602 start-[end] where start and end are both
603 a memory unit (amount[KMG]). See also
604 Documentation/kdump/kdump.txt for an example.
609 cs89x0_media= [HW,NET]
610 Format: { rj45 | aui | bnc }
613 See header of drivers/s390/block/dasd_devmap.c.
615 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
616 (one device per port)
617 Format: <port#>,<type>
618 See also Documentation/input/joystick-parport.txt
620 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
621 time. See Documentation/dynamic-debug-howto.txt for
622 details. Deprecated, see dyndbg.
624 debug [KNL] Enable kernel debugging (events log level).
627 [KNL] verbose self-tests
629 Print debugging info while doing the locking API
631 We default to 0 (no extra messages), setting it to
632 1 will print _a lot_ more information - normally
633 only useful to kernel developers.
635 debug_objects [KNL] Enable object debugging
638 [KNL] Disable object debugging
640 debug_guardpage_minorder=
641 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
642 parameter allows control of the order of pages that will
643 be intentionally kept free (and hence protected) by the
644 buddy allocator. Bigger value increase the probability
645 of catching random memory corruption, but reduce the
646 amount of memory for normal system use. The maximum
647 possible value is MAX_ORDER/2. Setting this parameter
648 to 1 or 2 should be enough to identify most random
649 memory corruption problems caused by bugs in kernel or
650 driver code when a CPU writes to (or reads from) a
651 random memory location. Note that there exists a class
652 of memory corruptions problems caused by buggy H/W or
653 F/W or by drivers badly programing DMA (basically when
654 memory is written at bus level and the CPU MMU is
655 bypassed) which are not detectable by
656 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
657 tracking down these problems.
659 debugpat [X86] Enable PAT debugging
661 decnet.addr= [HW,NET]
662 Format: <area>[,<node>]
663 See also Documentation/networking/decnet.txt.
666 [same as hugepagesz=] The size of the default
667 HugeTLB page size. This is the size represented by
668 the legacy /proc/ hugepages APIs, used for SHM, and
669 default size when mounting hugetlbfs filesystems.
670 Defaults to the default architecture's huge page size
674 Set number of hash buckets for dentry cache.
677 IO parameters + enable/disable command.
679 digiepca= [HW,SERIAL]
680 See drivers/char/README.epca and
681 Documentation/serial/digiepca.txt.
684 See Documentation/networking/ipv6.txt.
686 disable_ddw [PPC/PSERIES]
687 Disable Dynamic DMA Window support. Use this if
688 to workaround buggy firmware.
691 See Documentation/networking/ipv6.txt.
693 disable_mtrr_cleanup [X86]
694 The kernel tries to adjust MTRR layout from continuous
695 to discrete, to make X server driver able to add WB
696 entry later. This parameter disables that.
698 disable_mtrr_trim [X86, Intel and AMD only]
699 By default the kernel will trim any uncacheable
700 memory out of your available memory pool based on
701 MTRR settings. This parameter disables that behavior,
702 possibly causing your machine to run very slowly.
704 disable_timer_pin_1 [X86]
705 Disable PIN 1 of APIC timer
706 Can be useful to work around chipset bugs.
708 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
709 this option disables the debugging code at boot.
711 dma_debug_entries=<number>
712 This option allows to tune the number of preallocated
713 entries for DMA-API debugging code. One entry is
714 required per DMA-API allocation. Use this if the
715 DMA-API debugging code disables itself because the
716 architectural default is too low.
718 dma_debug_driver=<driver_name>
719 With this option the DMA-API debugging driver
720 filter feature can be enabled at boot time. Just
721 pass the driver to filter for as the parameter.
722 The filter can be disabled or changed to another
723 driver later using sysfs.
725 drm_kms_helper.edid_firmware=[<connector>:]<file>
726 Broken monitors, graphic adapters and KVMs may
727 send no or incorrect EDID data sets. This parameter
728 allows to specify an EDID data set in the
729 /lib/firmware directory that is used instead.
730 Generic built-in EDID data sets are used, if one of
731 edid/1024x768.bin, edid/1280x1024.bin,
732 edid/1680x1050.bin, or edid/1920x1080.bin is given
733 and no file with the same name exists. Details and
734 instructions how to build your own EDID data are
735 available in Documentation/EDID/HOWTO.txt. An EDID
736 data set will only be used for a particular connector,
737 if its name and a colon are prepended to the EDID
742 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
743 module.dyndbg[="val"]
744 Enable debug messages at boot time. See
745 Documentation/dynamic-debug-howto.txt for details.
747 earlycon= [KNL] Output early console device and options.
748 uart[8250],io,<addr>[,options]
749 uart[8250],mmio,<addr>[,options]
750 uart[8250],mmio32,<addr>[,options]
751 Start an early, polled-mode console on the 8250/16550
752 UART at the specified I/O port or MMIO address.
753 MMIO inter-register address stride is either 8-bit
754 (mmio) or 32-bit (mmio32).
755 The options are the same as for ttyS, above.
757 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 The xen output can only be used by Xen PV guests.
779 ekgdboc= [X86,KGDB] Allow early kernel console debugging
782 This is designed to be used in conjunction with
783 the boot argument: earlyprintk=vga
786 Format: {"off" | "on" | "skip[mbr]"}
788 eisa_irq_edge= [PARISC,HW]
789 See header of drivers/parisc/eisa.c.
792 See comment before function elanfreq_setup() in
793 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
796 Format: {"cfq" | "deadline" | "noop"}
797 See Documentation/block/cfq-iosched.txt and
798 Documentation/block/deadline-iosched.txt for details.
800 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
801 Specifies physical address of start of kernel core
802 image elf header and optionally the size. Generally
803 kexec loader will pass this option to capture kernel.
804 See Documentation/kdump/kdump.txt for details.
806 enable_mtrr_cleanup [X86]
807 The kernel tries to adjust MTRR layout from continuous
808 to discrete, to make X server driver able to add WB
809 entry later. This parameter enables that.
811 enable_timer_pin_1 [X86]
812 Enable PIN 1 of APIC timer
813 Can be useful to work around chipset bugs
814 (in particular on some ATI chipsets).
815 The kernel tries to set a reasonable default.
817 enforcing [SELINUX] Set initial enforcing status.
819 See security/selinux/Kconfig help text.
820 0 -- permissive (log only, no denials).
821 1 -- enforcing (deny and log).
823 Value can be changed at runtime via /selinux/enforce.
826 Disable Error Record Serialization Table (ERST)
829 ether= [HW,NET] Ethernet cards parameters
830 This option is obsoleted by the "netdev=" option, which
831 has equivalent usage. See its documentation for details.
835 Permit 'security.evm' to be updated regardless of
836 current integrity status.
840 fail_make_request=[KNL]
841 General fault injection mechanism.
842 Format: <interval>,<probability>,<space>,<times>
843 See also Documentation/fault-injection/.
846 See Documentation/blockdev/floppy.txt.
848 force_pal_cache_flush
849 [IA-64] Avoid check_sal_cache_flush which may hang on
850 buggy SAL_CACHE_FLUSH implementations. Using this
851 parameter will force ia64_sal_cache_flush to call
852 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
855 [FTRACE] will set and start the specified tracer
856 as early as possible in order to facilitate early
859 ftrace_dump_on_oops[=orig_cpu]
860 [FTRACE] will dump the trace buffers on oops.
861 If no parameter is passed, ftrace will dump
862 buffers of all CPUs, but if you pass orig_cpu, it will
863 dump only the buffer of the CPU that triggered the
866 ftrace_filter=[function-list]
867 [FTRACE] Limit the functions traced by the function
868 tracer at boot up. function-list is a comma separated
869 list of functions. This list can be changed at run
870 time by the set_ftrace_filter file in the debugfs
873 ftrace_notrace=[function-list]
874 [FTRACE] Do not trace the functions specified in
875 function-list. This list can be changed at run time
876 by the set_ftrace_notrace file in the debugfs
879 ftrace_graph_filter=[function-list]
880 [FTRACE] Limit the top level callers functions traced
881 by the function graph tracer at boot up.
882 function-list is a comma separated list of functions
883 that can be changed at run time by the
884 set_graph_function file in the debugfs tracing directory.
887 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
888 support via parallel port (up to 5 devices per port)
889 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
890 See also Documentation/input/joystick-parport.txt
894 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
898 gcov_persist= [GCOV] When non-zero (default), profiling data for
899 kernel modules is saved and remains accessible via
900 debugfs, even when the module is unloaded/reloaded.
901 When zero, profiling data is discarded and associated
902 debugfs files are removed at module unload time.
904 gpt [EFI] Forces disk with valid GPT signature but
905 invalid Protective MBR to be treated as GPT.
907 grcan.enable0= [HW] Configuration of physical interface 0. Determines
908 the "Enable 0" bit of the configuration register.
911 grcan.enable1= [HW] Configuration of physical interface 1. Determines
912 the "Enable 0" bit of the configuration register.
915 grcan.select= [HW] Select which physical interface to use.
918 grcan.txsize= [HW] Sets the size of the tx buffer.
919 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
921 grcan.rxsize= [HW] Sets the size of the rx buffer.
922 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
925 hashdist= [KNL,NUMA] Large hashes allocated during boot
926 are distributed across NUMA nodes. Defaults on
927 for 64-bit NUMA, off otherwise.
928 Format: 0 | 1 (for off | on)
930 hcl= [IA-64] SGI's Hardware Graph compatibility layer
932 hd= [EIDE] (E)IDE hard drive subsystem geometry
933 Format: <cyl>,<head>,<sect>
936 Disable Hardware Error Source Table (HEST) support;
937 corresponding firmware-first mode error processing
938 logic will be disabled.
940 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
941 size of <nn>. This works even on boxes that have no
942 highmem otherwise. This also works to reduce highmem
943 size on bigger boxes.
945 highres= [KNL] Enable/disable high resolution timer mode.
946 Valid parameters: "on", "off"
950 See Documentation/isdn/README.HiSax.
954 hpet= [X86-32,HPET] option to control HPET usage
955 Format: { enable (default) | disable | force |
957 disable: disable HPET and use PIT instead
958 force: allow force enabled of undocumented chips (ICH4,
960 verbose: show contents of HPET registers during setup
962 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
963 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
964 On x86-64 and powerpc, this option can be specified
965 multiple times interleaved with hugepages= to reserve
966 huge pages of different sizes. Valid pages sizes on
967 x86-64 are 2M (when the CPU supports "pse") and 1G
968 (when the CPU supports the "pdpe1gb" cpuinfo flag)
969 Note that 1GB pages can only be allocated at boot time
970 using hugepages= and not freed afterwards.
972 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
973 terminal devices. Valid values: 0..8
974 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
975 If specified, z/VM IUCV HVC accepts connections
976 from listed z/VM user IDs only.
979 Do not unregister boot console at start. This is only
980 useful for debugging when something happens in the window
981 between unregistering the boot console and initializing
984 i2c_bus= [HW] Override the default board specific I2C bus speed
985 or register an additional I2C bus that is not
986 registered from board initialization code.
990 i8042.debug [HW] Toggle i8042 debug mode
991 i8042.direct [HW] Put keyboard port into non-translated mode
992 i8042.dumbkbd [HW] Pretend that controller can only read data from
993 keyboard and cannot control its state
994 (Don't attempt to blink the leds)
995 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
996 i8042.nokbd [HW] Don't check/create keyboard port
997 i8042.noloop [HW] Disable the AUX Loopback command while probing
999 i8042.nomux [HW] Don't check presence of an active multiplexing
1001 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1003 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1004 i8042.reset [HW] Reset the controller during init and cleanup
1005 i8042.unlock [HW] Unlock (ignore) the keylock
1009 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1010 indicates that the driver is running on unsupported
1012 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1013 does not match list of supported models.
1015 [HW] Report power status in /proc/i8k
1016 (disabled by default)
1017 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1020 i915.invert_brightness=
1021 [DRM] Invert the sense of the variable that is used to
1022 set the brightness of the panel backlight. Normally a
1023 brightness value of 0 indicates backlight switched off,
1024 and the maximum of the brightness value sets the backlight
1025 to maximum brightness. If this parameter is set to 0
1026 (default) and the machine requires it, or this parameter
1027 is set to 1, a brightness value of 0 sets the backlight
1028 to maximum brightness, and the maximum of the brightness
1029 value switches the backlight off.
1030 -1 -- never invert brightness
1031 0 -- machine default
1032 1 -- force brightness inversion
1035 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1037 ide-core.nodma= [HW] (E)IDE subsystem
1038 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1039 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1040 .cdrom .chs .ignore_cable are additional options
1041 See Documentation/ide/ide.txt.
1043 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1044 Claim all unknown PCI IDE storage controllers.
1047 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1048 Poll forces a polling idle loop that can slightly
1049 improve the performance of waking up a idle CPU, but
1050 will use a lot of power and make the system run hot.
1052 idle=mwait: On systems which support MONITOR/MWAIT but
1053 the kernel chose to not use it because it doesn't save
1054 as much power as a normal idle loop, use the
1055 MONITOR/MWAIT idle loop anyways. Performance should be
1056 the same as idle=poll.
1057 idle=halt: Halt is forced to be used for CPU idle.
1058 In such case C2/C3 won't be used again.
1059 idle=nomwait: Disable mwait for CPU C-states
1061 ignore_loglevel [KNL]
1062 Ignore loglevel setting - this will print /all/
1063 kernel messages to the console. Useful for debugging.
1064 We also add it as printk module parameter, so users
1065 could change it dynamically, usually by
1066 /sys/module/printk/parameters/ignore_loglevel.
1068 ihash_entries= [KNL]
1069 Set number of hash buckets for inode cache.
1071 ima_appraise= [IMA] appraise integrity measurements
1072 Format: { "off" | "enforce" | "fix" }
1075 ima_appraise_tcb [IMA]
1076 The builtin appraise policy appraises all files
1080 Format: { "0" | "1" }
1081 0 -- integrity auditing messages. (Default)
1082 1 -- enable informational integrity auditing messages.
1085 Format: { "sha1" | "md5" }
1089 Load a policy which meets the needs of the Trusted
1090 Computing Base. This means IMA will measure all
1091 programs exec'd, files mmap'd for exec, and all files
1092 opened for read by uid=0.
1096 Run specified binary instead of /sbin/init as init
1099 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1100 for working out where the kernel is dying during
1103 initrd= [BOOT] Specify the location of the initial ramdisk
1105 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1108 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1110 Enable intel iommu driver.
1112 Disable intel iommu driver.
1113 igfx_off [Default Off]
1114 By default, gfx is mapped as normal device. If a gfx
1115 device has a dedicated DMAR unit, the DMAR unit is
1116 bypassed by not enabling DMAR with this option. In
1117 this case, gfx device will use physical address for
1120 With this option iommu will not optimize to look
1121 for io virtual address below 32-bit forcing dual
1122 address cycle on pci bus for cards supporting greater
1123 than 32-bit addressing. The default is to look
1124 for translation below 32-bit and if not available
1125 then look in the higher range.
1126 strict [Default Off]
1127 With this option on every unmap_single operation will
1128 result in a hardware IOTLB flush operation as opposed
1129 to batching them for performance.
1130 sp_off [Default Off]
1131 By default, super page will be supported if Intel IOMMU
1132 has the capability. With this option, super page will
1135 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1136 0 disables intel_idle and fall back on acpi_idle.
1137 1 to 6 specify maximum depth of C-state.
1139 intremap= [X86-64, Intel-IOMMU]
1140 on enable Interrupt Remapping (default)
1141 off disable Interrupt Remapping
1142 nosid disable Source ID checking
1144 BIOS x2APIC opt-out request will be ignored
1146 iomem= Disable strict checking of access to MMIO memory
1147 strict regions from userspace.
1164 io7= [HW] IO7 for Marvel based alpha systems
1165 See comment before marvel_specify_io7 in
1166 arch/alpha/kernel/core_marvel.c.
1168 io_delay= [X86] I/O delay method
1170 Standard port 0x80 based delay
1172 Alternate port 0xed based delay (needed on some systems)
1174 Simple two microseconds delay
1179 See Documentation/filesystems/nfs/nfsroot.txt.
1181 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1182 See comment before ip2_setup() in
1183 drivers/char/ip2/ip2base.c.
1186 When an interrupt is not handled search all handlers
1187 for it. Intended to get systems with badly broken
1191 When an interrupt is not handled search all handlers
1192 for it. Also check all handlers each timer
1193 interrupt. Intended to get systems with badly broken
1197 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1199 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1201 <cpu number>,...,<cpu number>
1203 <cpu number>-<cpu number>
1204 (must be a positive range in ascending order)
1206 <cpu number>,...,<cpu number>-<cpu number>
1208 This option can be used to specify one or more CPUs
1209 to isolate from the general SMP balancing and scheduling
1210 algorithms. You can move a process onto or off an
1211 "isolated" CPU via the CPU affinity syscalls or cpuset.
1212 <cpu number> begins at 0 and the maximum value is
1213 "number of CPUs in system - 1".
1215 This option is the preferred way to isolate CPUs. The
1216 alternative -- manually setting the CPU mask of all
1217 tasks in the system -- can cause problems and
1218 suboptimal load balancer performance.
1222 js= [HW,JOY] Analog joystick
1223 See Documentation/input/joystick.txt.
1227 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1228 specifies the amount of memory usable by the kernel
1229 for non-movable allocations. The requested amount is
1230 spread evenly throughout all nodes in the system. The
1231 remaining memory in each node is used for Movable
1232 pages. In the event, a node is too small to have both
1233 kernelcore and Movable pages, kernelcore pages will
1234 take priority and other nodes will have a larger number
1235 of kernelcore pages. The Movable zone is used for the
1236 allocation of pages that may be reclaimed or moved
1237 by the page migration subsystem. This means that
1238 HugeTLB pages may not be allocated from this zone.
1239 Note that allocations like PTEs-from-HighMem still
1240 use the HighMem zone if it exists, and the Normal
1241 zone if it does not.
1243 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1244 Format: <Controller#>[,poll interval]
1245 The controller # is the number of the ehci usb debug
1246 port as it is probed via PCI. The poll interval is
1247 optional and is the number seconds in between
1248 each poll cycle to the debug port in case you need
1249 the functionality for interrupting the kernel with
1250 gdb or control-c on the dbgp connection. When
1251 not using this parameter you use sysrq-g to break into
1252 the kernel debugger.
1254 kgdboc= [KGDB,HW] kgdb over consoles.
1255 Requires a tty driver that supports console polling,
1256 or a supported polling keyboard driver (non-usb).
1257 Serial only format: <serial_device>[,baud]
1258 keyboard only format: kbd
1259 keyboard and serial format: kbd,<serial_device>[,baud]
1260 Optional Kernel mode setting:
1261 kms, kbd format: kms,kbd
1262 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1264 kgdbwait [KGDB] Stop kernel execution and enter the
1265 kernel debugger at the earliest opportunity.
1267 kmac= [MIPS] korina ethernet MAC address.
1268 Configure the RouterBoard 532 series on-chip
1269 Ethernet adapter MAC address.
1271 kmemleak= [KNL] Boot-time kmemleak enable/disable
1272 Valid arguments: on, off
1275 kstack=N [X86] Print N words from the kernel stack
1278 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1279 Default is 0 (don't ignore, but inject #GP)
1281 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1285 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1286 Default is 1 (enabled)
1288 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1290 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1292 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1293 (virtualized MMU) support on capable Intel chips.
1294 Default is 1 (enabled)
1296 kvm-intel.emulate_invalid_guest_state=
1297 [KVM,Intel] Enable emulation of invalid guest states
1298 Default is 0 (disabled)
1300 kvm-intel.flexpriority=
1301 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1302 Default is 1 (enabled)
1305 [KVM,Intel] Enable VMX nesting (nVMX).
1306 Default is 0 (disabled)
1308 kvm-intel.unrestricted_guest=
1309 [KVM,Intel] Disable unrestricted guest feature
1310 (virtualized real and unpaged mode) on capable
1311 Intel chips. Default is 1 (enabled)
1313 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1314 feature (tagged TLBs) on capable Intel chips.
1315 Default is 1 (enabled)
1321 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1324 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1325 value for LAPIC timer one-shot implementation. Default
1326 back to the programmable timer unit in the LAPIC.
1328 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1331 libata.dma= [LIBATA] DMA control
1332 libata.dma=0 Disable all PATA and SATA DMA
1333 libata.dma=1 PATA and SATA Disk DMA only
1334 libata.dma=2 ATAPI (CDROM) DMA only
1335 libata.dma=4 Compact Flash DMA only
1336 Combinations also work, so libata.dma=3 enables DMA
1337 for disks and CDROMs, but not CFs.
1339 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1340 libata.ignore_hpa=0 keep BIOS limits (default)
1341 libata.ignore_hpa=1 ignore limits, using full disk
1343 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1347 libata.force= [LIBATA] Force configurations. The format is comma
1348 separated list of "[ID:]VAL" where ID is
1349 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1350 matching port, link or device. Basically, it matches
1351 the ATA ID string printed on console by libata. If
1352 the whole ID part is omitted, the last PORT and DEVICE
1353 values are used. If ID hasn't been specified yet, the
1354 configuration applies to all ports, links and devices.
1356 If only DEVICE is omitted, the parameter applies to
1357 the port and all links and devices behind it. DEVICE
1358 number of 0 either selects the first device or the
1359 first fan-out link behind PMP device. It does not
1360 select the host link. DEVICE number of 15 selects the
1361 host link and device attached to it.
1363 The VAL specifies the configuration to force. As long
1364 as there's no ambiguity shortcut notation is allowed.
1365 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1366 The following configurations can be forced.
1368 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1369 Any ID with matching PORT is used.
1371 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1373 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1374 udma[/][16,25,33,44,66,100,133] notation is also
1377 * [no]ncq: Turn on or off NCQ.
1379 * nohrst, nosrst, norst: suppress hard, soft
1382 * rstonce: only attempt one reset during
1383 hot-unplug link recovery
1385 * dump_id: dump IDENTIFY data.
1387 If there are multiple matching configurations changing
1388 the same attribute, the last one is used.
1390 memblock=debug [KNL] Enable memblock debug messages.
1392 load_ramdisk= [RAM] List of ramdisks to load from floppy
1393 See Documentation/blockdev/ramdisk.txt.
1395 lockd.nlm_grace_period=P [NFS] Assign grace period.
1398 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1401 lockd.nlm_timeout=T [NFS] Assign timeout value.
1404 lockd.nlm_udpport=M [NFS] Assign UDP port.
1407 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1410 loglevel= All Kernel Messages with a loglevel smaller than the
1411 console loglevel will be printed to the console. It can
1412 also be changed with klogd or other programs. The
1413 loglevels are defined as follows:
1415 0 (KERN_EMERG) system is unusable
1416 1 (KERN_ALERT) action must be taken immediately
1417 2 (KERN_CRIT) critical conditions
1418 3 (KERN_ERR) error conditions
1419 4 (KERN_WARNING) warning conditions
1420 5 (KERN_NOTICE) normal but significant condition
1421 6 (KERN_INFO) informational
1422 7 (KERN_DEBUG) debug-level messages
1424 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1425 in bytes. n must be a power of two. The default
1426 size is set in the kernel config file.
1428 logo.nologo [FB] Disables display of the built-in Linux logo.
1429 This may be used to provide more screen space for
1430 kernel log messages and is useful when debugging
1431 kernel boot problems.
1433 lp=0 [LP] Specify parallel ports to use, e.g,
1434 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1435 lp=reset first parallel port). 'lp=0' disables the
1436 lp=auto printer driver. 'lp=reset' (which can be
1437 specified in addition to the ports) causes
1438 attached printers to be reset. Using
1439 lp=port1,port2,... specifies the parallel ports
1440 to associate lp devices with, starting with
1441 lp0. A port specification may be 'none' to skip
1442 that lp device, or a parport name such as
1443 'parport0'. Specifying 'lp=auto' instead of a
1444 port specification list means that device IDs
1445 from each port should be examined, to see if
1446 an IEEE 1284-compliant printer is attached; if
1447 so, the driver will manage that printer.
1448 See also header of drivers/char/lp.c.
1451 Sets loops_per_jiffy to given constant, thus avoiding
1452 time-consuming boot-time autodetection (up to 250 ms per
1453 CPU). 0 enables autodetection (default). To determine
1454 the correct value for your kernel, boot with normal
1455 autodetection and see what value is printed. Note that
1456 on SMP systems the preset will be applied to all CPUs,
1457 which is likely to cause problems if your CPUs need
1458 significantly divergent settings. An incorrect value
1459 will cause delays in the kernel to be wrong, leading to
1460 unpredictable I/O errors and other breakage. Although
1461 unlikely, in the extreme case this might damage your
1465 Format: <io>,<irq>,<dma>
1467 machvec= [IA-64] Force the use of a particular machine-vector
1468 (machvec) in a generic kernel.
1469 Example: machvec=hpzx1_swiotlb
1471 machtype= [Loongson] Share the same kernel image file between different
1473 Example: machtype=lemote-yeeloong-2f-7inch
1475 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1476 than or equal to this physical address is ignored.
1478 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1479 should make use of. maxcpus=n : n >= 0 limits the
1480 kernel to using 'n' processors. n=0 is a special case,
1481 it is equivalent to "nosmp", which also disables
1484 max_loop= [LOOP] The number of loop block devices that get
1485 (loop.max_loop) unconditionally pre-created at init time. The default
1486 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1487 of statically allocating a predefined number, loop
1488 devices can be requested on-demand with the
1489 /dev/loop-control interface.
1491 mce [X86-32] Machine Check Exception
1493 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1495 md= [HW] RAID subsystems devices and level
1496 See Documentation/md.txt.
1499 Format: <first>,<last>
1500 Specifies range of consoles to be captured by the MDA.
1502 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1503 Amount of memory to be used when the kernel is not able
1504 to see the whole system memory or for test.
1505 [X86] Work as limiting max address. Use together
1506 with memmap= to avoid physical address space collisions.
1507 Without memmap= PCI devices could be placed at addresses
1508 belonging to unused RAM.
1510 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1514 [KNL,SH] Allow user to override the default size for
1515 per-device physically contiguous DMA buffers.
1517 memmap=exactmap [KNL,X86] Enable setting of an exact
1518 E820 memory map, as specified by the user.
1519 Such memmap=exactmap lines can be constructed based on
1520 BIOS output or other requirements. See the memmap=nn@ss
1523 memmap=nn[KMG]@ss[KMG]
1524 [KNL] Force usage of a specific region of memory
1525 Region of memory to be used, from ss to ss+nn.
1527 memmap=nn[KMG]#ss[KMG]
1528 [KNL,ACPI] Mark specific memory as ACPI data.
1529 Region of memory to be used, from ss to ss+nn.
1531 memmap=nn[KMG]$ss[KMG]
1532 [KNL,ACPI] Mark specific memory as reserved.
1533 Region of memory to be used, from ss to ss+nn.
1534 Example: Exclude memory from 0x18690000-0x1869ffff
1535 memmap=64K$0x18690000
1537 memmap=0x10000$0x18690000
1539 memory_corruption_check=0/1 [X86]
1540 Some BIOSes seem to corrupt the first 64k of
1541 memory when doing things like suspend/resume.
1542 Setting this option will scan the memory
1543 looking for corruption. Enabling this will
1544 both detect corruption and prevent the kernel
1545 from using the memory being corrupted.
1546 However, its intended as a diagnostic tool; if
1547 repeatable BIOS-originated corruption always
1548 affects the same memory, you can use memmap=
1549 to prevent the kernel from using that memory.
1551 memory_corruption_check_size=size [X86]
1552 By default it checks for corruption in the low
1553 64k, making this memory unavailable for normal
1554 use. Use this parameter to scan for
1555 corruption in more or less memory.
1557 memory_corruption_check_period=seconds [X86]
1558 By default it checks for corruption every 60
1559 seconds. Use this parameter to check at some
1560 other rate. 0 disables periodic checking.
1562 memtest= [KNL,X86] Enable memtest
1564 default : 0 <disable>
1565 Specifies the number of memtest passes to be
1566 performed. Each pass selects another test
1567 pattern from a given set of patterns. Memtest
1568 fills the memory with this pattern, validates
1569 memory contents and reserves bad memory
1570 regions that are detected.
1572 meye.*= [HW] Set MotionEye Camera parameters
1573 See Documentation/video4linux/meye.txt.
1575 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1576 Multi-Function General Purpose Timers on AMD Geode
1579 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1580 the BIOS has incorrectly applied a workaround. TinyBIOS
1581 version 0.98 is known to be affected, 0.99 fixes the
1582 problem by letting the user disable the workaround.
1586 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1587 physical address is ignored.
1589 mini2440= [ARM,HW,KNL]
1590 Format:[0..2][b][c][t]
1592 MINI2440 configuration specification:
1593 0 - The attached screen is the 3.5" TFT
1594 1 - The attached screen is the 7" TFT
1595 2 - The VGA Shield is attached (1024x768)
1596 Leaving out the screen size parameter will not load
1597 the TFT driver, and the framebuffer will be left
1599 b - Enable backlight. The TFT backlight pin will be
1600 linked to the kernel VESA blanking code and a GPIO
1601 LED. This parameter is not necessary when using the
1603 c - Enable the s3c camera interface.
1604 t - Reserved for enabling touchscreen support. The
1605 touchscreen support is not enabled in the mainstream
1606 kernel as of 2.6.30, a preliminary port can be found
1607 in the "bleeding edge" mini2440 support kernel at
1608 http://repo.or.cz/w/linux-2.6/mini2440.git
1611 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1612 parameter allows control of the logging verbosity for
1613 the additional memory initialisation checks. A value
1614 of 0 disables mminit logging and a level of 4 will
1615 log everything. Information is printed at KERN_DEBUG
1616 so loglevel=8 may also need to be specified.
1619 [KNL] When CONFIG_MODULE_SIG is set, this means that
1620 modules without (valid) signatures will fail to load.
1621 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1622 is always true, so this option does nothing.
1625 [MOUSE] Maximum time between finger touching and
1626 leaving touchpad surface for touch to be considered
1627 a tap and be reported as a left button click (for
1628 touchpads working in absolute mode only).
1630 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1631 reporting absolute coordinates, such as tablets
1632 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1633 reporting absolute coordinates, such as tablets
1635 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1636 is similar to kernelcore except it specifies the
1637 amount of memory used for migratable allocations.
1638 If both kernelcore and movablecore is specified,
1639 then kernelcore will be at *least* the specified
1640 value but may be more. If movablecore on its own
1641 is specified, the administrator must be careful
1642 that the amount of memory usable for all allocations
1645 MTD_Partition= [MTD]
1646 Format: <name>,<region-number>,<size>,<offset>
1648 MTD_Region= [MTD] Format:
1649 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1652 See drivers/mtd/cmdlinepart.c.
1654 multitce=off [PPC] This parameter disables the use of the pSeries
1655 firmware feature for updating multiple TCE entries
1658 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1660 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1662 boundary - index of last SLC block on Flex-OneNAND.
1663 The remaining blocks are configured as MLC blocks.
1664 lock - Configure if Flex-OneNAND boundary should be locked.
1665 Once locked, the boundary cannot be changed.
1666 1 indicates lock status, 0 indicates unlock status.
1669 ARM/S3C2412 JIVE boot control
1671 See arch/arm/mach-s3c2412/mach-jive.c
1673 mtouchusb.raw_coordinates=
1674 [HW] Make the MicroTouch USB driver use raw coordinates
1675 ('y', default) or cooked coordinates ('n')
1677 mtrr_chunk_size=nn[KMG] [X86]
1678 used for mtrr cleanup. It is largest continuous chunk
1679 that could hold holes aka. UC entries.
1681 mtrr_gran_size=nn[KMG] [X86]
1682 Used for mtrr cleanup. It is granularity of mtrr block.
1684 Large value could prevent small alignment from
1687 mtrr_spare_reg_nr=n [X86]
1689 Range: 0,7 : spare reg number
1691 Used for mtrr cleanup. It is spare mtrr entries number.
1692 Set to 2 or more if your graphical card needs more.
1694 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1696 netdev= [NET] Network devices parameters
1697 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1698 Note that mem_start is often overloaded to mean
1699 something different and driver-specific.
1700 This usage is only documented in each driver source
1704 [NETFILTER] Enable connection tracking flow accounting
1705 0 to disable accounting
1706 1 to enable accounting
1709 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1710 See Documentation/filesystems/nfs/nfsroot.txt.
1712 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1713 See Documentation/filesystems/nfs/nfsroot.txt.
1715 nfsrootdebug [NFS] enable nfsroot debugging messages.
1716 See Documentation/filesystems/nfs/nfsroot.txt.
1718 nfs.callback_tcpport=
1719 [NFS] set the TCP port on which the NFSv4 callback
1720 channel should listen.
1723 [NFS] sets the pathname to the program which is used
1724 to update the NFS client cache entries.
1726 nfs.cache_getent_timeout=
1727 [NFS] sets the timeout after which an attempt to
1728 update a cache entry is deemed to have failed.
1730 nfs.idmap_cache_timeout=
1731 [NFS] set the maximum lifetime for idmapper cache
1735 [NFS] enable 64-bit inode numbers.
1736 If zero, the NFS client will fake up a 32-bit inode
1737 number for the readdir() and stat() syscalls instead
1738 of returning the full 64-bit number.
1739 The default is to return 64-bit inode numbers.
1741 nfs.max_session_slots=
1742 [NFSv4.1] Sets the maximum number of session slots
1743 the client will attempt to negotiate with the server.
1744 This limits the number of simultaneous RPC requests
1745 that the client can send to the NFSv4.1 server.
1746 Note that there is little point in setting this
1747 value higher than the max_tcp_slot_table_limit.
1749 nfs.nfs4_disable_idmapping=
1750 [NFSv4] When set to the default of '1', this option
1751 ensures that both the RPC level authentication
1752 scheme and the NFS level operations agree to use
1753 numeric uids/gids if the mount is using the
1754 'sec=sys' security flavour. In effect it is
1755 disabling idmapping, which can make migration from
1756 legacy NFSv2/v3 systems to NFSv4 easier.
1757 Servers that do not support this mode of operation
1758 will be autodetected by the client, and it will fall
1759 back to using the idmapper.
1760 To turn off this behaviour, set the value to '0'.
1762 [NFS4] Specify an additional fixed unique ident-
1763 ification string that NFSv4 clients can insert into
1764 their nfs_client_id4 string. This is typically a
1765 UUID that is generated at system install time.
1767 nfs.send_implementation_id =
1768 [NFSv4.1] Send client implementation identification
1769 information in exchange_id requests.
1770 If zero, no implementation identification information
1772 The default is to send the implementation identification
1775 nfsd.nfs4_disable_idmapping=
1776 [NFSv4] When set to the default of '1', the NFSv4
1777 server will return only numeric uids and gids to
1778 clients using auth_sys, and will accept numeric uids
1779 and gids from such clients. This is intended to ease
1780 migration from NFSv2/v3.
1782 objlayoutdriver.osd_login_prog=
1783 [NFS] [OBJLAYOUT] sets the pathname to the program which
1784 is used to automatically discover and login into new
1785 osd-targets. Please see:
1786 Documentation/filesystems/pnfs.txt for more explanations
1788 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1789 when a NMI is triggered.
1790 Format: [state][,regs][,debounce][,die]
1792 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1793 Format: [panic,][nopanic,][num]
1795 0 - turn nmi_watchdog off
1796 When panic is specified, panic when an NMI watchdog
1797 timeout occurs (or 'nopanic' to override the opposite
1799 This is useful when you use a panic=... timeout and
1800 need the box quickly up again.
1802 netpoll.carrier_timeout=
1803 [NET] Specifies amount of time (in seconds) that
1804 netpoll should wait for a carrier. By default netpoll
1807 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1808 emulation library even if a 387 maths coprocessor
1812 [HW] Never suspend the console
1813 Disable suspending of consoles during suspend and
1814 hibernate operations. Once disabled, debugging
1815 messages can reach various consoles while the rest
1816 of the system is being put to sleep (ie, while
1817 debugging driver suspend/resume hooks). This may
1818 not work reliably with all consoles, but is known
1819 to work with serial and VGA consoles.
1820 To facilitate more flexible debugging, we also add
1821 console_suspend, a printk module parameter to control
1822 it. Users could use console_suspend (usually
1823 /sys/module/printk/parameters/console_suspend) to
1824 turn on/off it dynamically.
1826 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1827 caches in the slab allocator. Saves per-node memory,
1828 but will impact performance.
1832 noapic [SMP,APIC] Tells the kernel to not make use of any
1833 IOAPICs that may be present in the system.
1835 noautogroup Disable scheduler automatic task group creation.
1837 nobats [PPC] Do not use BATs for mapping kernel lowmem
1838 on "Classic" PPC cores.
1842 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1844 nodelayacct [KNL] Disable per-task delay accounting
1846 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1848 nodsp [SH] Disable hardware DSP at boot time.
1850 noefi [X86] Disable EFI runtime services support.
1855 On X86-32 available only on PAE configured kernels.
1856 noexec=on: enable non-executable mappings (default)
1857 noexec=off: disable non-executable mappings
1860 Disable SMAP (Supervisor Mode Access Prevention)
1861 even if it is supported by processor.
1864 Disable SMEP (Supervisor Mode Execution Prevention)
1865 even if it is supported by processor.
1868 This affects only 32-bit executables.
1869 noexec32=on: enable non-executable mappings (default)
1870 read doesn't imply executable mappings
1871 noexec32=off: disable non-executable mappings
1872 read implies executable mappings
1874 nofpu [SH] Disable hardware FPU at boot time.
1876 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1877 register save and restore. The kernel will only save
1878 legacy floating-point registers on task switch.
1880 noxsave [BUGS=X86] Disables x86 extended register state save
1881 and restore using xsave. The kernel will fallback to
1882 enabling legacy floating-point and sse state.
1885 on enable eager fpu restore
1886 off disable eager fpu restore
1887 auto selects the default scheme, which automatically
1888 enables eagerfpu restore for xsaveopt.
1890 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1891 wfi(ARM) instruction doesn't work correctly and not to
1892 use it. This is also useful when using JTAG debugger.
1894 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1895 instruction doesn't work correctly and not to
1898 no_file_caps Tells the kernel not to honor file capabilities. The
1899 only way then for a file to be executed with privilege
1900 is to be setuid root or executed by root.
1902 nohalt [IA-64] Tells the kernel not to use the power saving
1903 function PAL_HALT_LIGHT when idle. This increases
1904 power-consumption. On the positive side, it reduces
1905 interrupt wake-up latency, which may improve performance
1906 in certain environments such as networked servers or
1909 nohz= [KNL] Boottime enable/disable dynamic ticks
1910 Valid arguments: on, off
1913 noiotrap [SH] Disables trapped I/O port accesses.
1915 noirqdebug [X86-32] Disables the code which attempts to detect and
1916 disable unhandled interrupt sources.
1918 no_timer_check [X86,APIC] Disables the code which tests for
1919 broken timer IRQ sources.
1921 noisapnp [ISAPNP] Disables ISA PnP code.
1923 noinitrd [RAM] Tells the kernel not to load any configured
1926 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1928 [Deprecated - use intremap=off]
1932 nojitter [IA-64] Disables jitter checking for ITC timers.
1934 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1936 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1939 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1940 steal time is computed, but won't influence scheduler
1943 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1945 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1947 noltlbs [PPC] Do not use large page/tlb entries for kernel
1948 lowmem mapping on PPC40x.
1950 nomca [IA-64] Disable machine check abort handling
1952 nomce [X86-32] Machine Check Exception
1954 nomfgpt [X86-32] Disable Multi-Function General Purpose
1955 Timer usage (for AMD Geode machines).
1957 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1958 shutdown the other cpus. Instead use the REBOOT_VECTOR
1961 nomodule Disable module load
1963 nopat [X86] Disable PAT (page attribute table extension of
1964 pagetables) support.
1966 norandmaps Don't use address space randomization. Equivalent to
1967 echo 0 > /proc/sys/kernel/randomize_va_space
1969 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1971 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1972 with UP alternatives
1974 noresidual [PPC] Don't use residual data on PReP machines.
1976 nordrand [X86] Disable the direct use of the RDRAND
1977 instruction even if it is supported by the
1978 processor. RDRAND is still available to user
1981 noresume [SWSUSP] Disables resume and restores original swap
1984 no-scroll [VGA] Disables scrollback.
1985 This is required for the Braillex ib80-piezo Braille
1986 reader made by F.H. Papenmeier (Germany).
1990 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1992 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1993 and disable the IO APIC. legacy for "maxcpus=0".
1995 nosoftlockup [KNL] Disable the soft-lockup detector.
1997 nosync [HW,M68K] Disables sync negotiation for all devices.
1999 notsc [BUGS=X86-32] Disable Time Stamp Counter
2001 nousb [USB] Disable the USB subsystem
2003 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2007 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2009 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2010 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2011 Some features depend on CPU0. Known dependencies are:
2012 1. Resume from suspend/hibernate depends on CPU0.
2013 Suspend/hibernate will fail if CPU0 is offline and you
2014 need to online CPU0 before suspend/hibernate.
2015 2. PIC interrupts also depend on CPU0. CPU0 can't be
2016 removed if a PIC interrupt is detected.
2017 It's said poweroff/reboot may depend on CPU0 on some
2018 machines although I haven't seen such issues so far
2019 after CPU0 is offline on a few tested machines.
2020 If the dependencies are under your control, you can
2021 turn on cpu0_hotplug.
2023 nptcg= [IA-64] Override max number of concurrent global TLB
2024 purges which is reported from either PAL_VM_SUMMARY or
2027 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2028 could support. nr_cpus=n : n >= 1 limits the kernel to
2029 supporting 'n' processors. Later in runtime you can not
2030 use hotplug cpu feature to put more cpu back to online.
2031 just like you compile the kernel NR_CPUS=n
2033 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2035 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2036 Allowed values are enable and disable
2038 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2039 one of ['zone', 'node', 'default'] can be specified
2040 This can be set from sysctl after boot.
2041 See Documentation/sysctl/vm.txt for details.
2043 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2044 See Documentation/debugging-via-ohci1394.txt for more
2047 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2048 Rather than timing out after 20 ms if an EC
2049 command is not properly ACKed, override the length
2050 of the timeout. We have interrupts disabled while
2051 waiting for the ACK, so if this is set too high
2052 interrupts *may* be lost!
2054 omap_mux= [OMAP] Override bootloader pin multiplexing.
2055 Format: <mux_mode0.mode_name=value>...
2056 For example, to override I2C bus2:
2057 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2059 oprofile.timer= [HW]
2060 Use timer interrupt instead of performance counters
2062 oprofile.cpu_type= Force an oprofile cpu type
2063 This might be useful if you have an older oprofile
2064 userland or if you want common events.
2065 Format: { arch_perfmon }
2066 arch_perfmon: [X86] Force use of architectural
2067 perfmon on Intel CPUs instead of the
2068 CPU specific event set.
2069 timer: [X86] Force use of architectural NMI
2070 timer mode (see also oprofile.timer
2071 for generic hr timer mode)
2072 [s390] Force legacy basic mode sampling
2073 (report cpu_type "timer")
2075 oops=panic Always panic on oopses. Default is to just kill the
2076 process, but there is a small probability of
2077 deadlocking the machine.
2078 This will also cause panics on machine check exceptions.
2079 Useful together with panic=30 to trigger a reboot.
2082 See Documentation/sound/oss/oss-parameters.txt
2084 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2085 timeout > 0: seconds before rebooting
2086 timeout = 0: wait forever
2087 timeout < 0: reboot immediately
2090 parkbd.port= [HW] Parallel port number the keyboard adapter is
2091 connected to, default is 0.
2093 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2094 0 for XT, 1 for AT (default is AT).
2097 parport= [HW,PPT] Specify parallel ports. 0 disables.
2098 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2099 Use 'auto' to force the driver to use any
2100 IRQ/DMA settings detected (the default is to
2101 ignore detected IRQ/DMA settings because of
2102 possible conflicts). You can specify the base
2103 address, IRQ, and DMA settings; IRQ and DMA
2104 should be numbers, or 'auto' (for using detected
2105 settings on that particular port), or 'nofifo'
2106 (to avoid using a FIFO even if it is detected).
2107 Parallel ports are assigned in the order they
2108 are specified on the command line, starting
2111 parport_init_mode= [HW,PPT]
2112 Configure VIA parallel port to operate in
2113 a specific mode. This is necessary on Pegasos
2114 computer where firmware has no options for setting
2115 up parallel port mode and sets it to spp.
2116 Currently this function knows 686a and 8231 chips.
2117 Format: [spp|ps2|epp|ecp|ecpepp]
2120 Halt all CPUs after the first oops has been printed for
2121 the specified number of seconds. This is to be used if
2122 your oopses keep scrolling off the screen.
2127 See header of drivers/block/paride/pcd.c.
2128 See also Documentation/blockdev/paride.txt.
2130 pci=option[,option...] [PCI] various PCI subsystem options:
2131 earlydump [X86] dump PCI config space before the kernel
2133 off [X86] don't probe for the PCI bus
2134 bios [X86-32] force use of PCI BIOS, don't access
2135 the hardware directly. Use this if your machine
2136 has a non-standard PCI host bridge.
2137 nobios [X86-32] disallow use of PCI BIOS, only direct
2138 hardware access methods are allowed. Use this
2139 if you experience crashes upon bootup and you
2140 suspect they are caused by the BIOS.
2141 conf1 [X86] Force use of PCI Configuration
2143 conf2 [X86] Force use of PCI Configuration
2145 noaer [PCIE] If the PCIEAER kernel config parameter is
2146 enabled, this kernel boot option can be used to
2147 disable the use of PCIE advanced error reporting.
2148 nodomains [PCI] Disable support for multiple PCI
2149 root domains (aka PCI segments, in ACPI-speak).
2150 nommconf [X86] Disable use of MMCONFIG for PCI
2152 check_enable_amd_mmconf [X86] check for and enable
2153 properly configured MMIO access to PCI
2154 config space on AMD family 10h CPU
2155 nomsi [MSI] If the PCI_MSI kernel config parameter is
2156 enabled, this kernel boot option can be used to
2157 disable the use of MSI interrupts system-wide.
2158 noioapicquirk [APIC] Disable all boot interrupt quirks.
2159 Safety option to keep boot IRQs enabled. This
2160 should never be necessary.
2161 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2162 primary IO-APIC for bridges that cannot disable
2163 boot IRQs. This fixes a source of spurious IRQs
2164 when the system masks IRQs.
2165 noioapicreroute [APIC] Disable workaround that uses the
2166 boot IRQ equivalent of an IRQ that connects to
2167 a chipset where boot IRQs cannot be disabled.
2168 The opposite of ioapicreroute.
2169 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2170 routing table. These calls are known to be buggy
2171 on several machines and they hang the machine
2172 when used, but on other computers it's the only
2173 way to get the interrupt routing table. Try
2174 this option if the kernel is unable to allocate
2175 IRQs or discover secondary PCI buses on your
2177 rom [X86] Assign address space to expansion ROMs.
2178 Use with caution as certain devices share
2179 address decoders between ROMs and other
2181 norom [X86] Do not assign address space to
2182 expansion ROMs that do not already have
2183 BIOS assigned address ranges.
2184 nobar [X86] Do not assign address space to the
2185 BARs that weren't assigned by the BIOS.
2186 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2187 assigned automatically to PCI devices. You can
2188 make the kernel exclude IRQs of your ISA cards
2190 pirqaddr=0xAAAAA [X86] Specify the physical address
2191 of the PIRQ table (normally generated
2192 by the BIOS) if it is outside the
2193 F0000h-100000h range.
2194 lastbus=N [X86] Scan all buses thru bus #N. Can be
2195 useful if the kernel is unable to find your
2196 secondary buses and you want to tell it
2197 explicitly which ones they are.
2198 assign-busses [X86] Always assign all PCI bus
2199 numbers ourselves, overriding
2200 whatever the firmware may have done.
2201 usepirqmask [X86] Honor the possible IRQ mask stored
2202 in the BIOS $PIR table. This is needed on
2203 some systems with broken BIOSes, notably
2204 some HP Pavilion N5400 and Omnibook XE3
2205 notebooks. This will have no effect if ACPI
2206 IRQ routing is enabled.
2207 noacpi [X86] Do not use ACPI for IRQ routing
2208 or for PCI scanning.
2209 use_crs [X86] Use PCI host bridge window information
2210 from ACPI. On BIOSes from 2008 or later, this
2211 is enabled by default. If you need to use this,
2212 please report a bug.
2213 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2214 If you need to use this, please report a bug.
2215 routeirq Do IRQ routing for all PCI devices.
2216 This is normally done in pci_enable_device(),
2217 so this option is a temporary workaround
2218 for broken drivers that don't call it.
2219 skip_isa_align [X86] do not align io start addr, so can
2220 handle more pci cards
2221 firmware [ARM] Do not re-enumerate the bus but instead
2222 just use the configuration from the
2223 bootloader. This is currently used on
2224 IXP2000 systems where the bus has to be
2225 configured a certain way for adjunct CPUs.
2226 noearly [X86] Don't do any early type 1 scanning.
2227 This might help on some broken boards which
2228 machine check when some devices' config space
2229 is read. But various workarounds are disabled
2230 and some IOMMU drivers will not work.
2231 bfsort Sort PCI devices into breadth-first order.
2232 This sorting is done to get a device
2233 order compatible with older (<= 2.4) kernels.
2234 nobfsort Don't sort PCI devices into breadth-first order.
2235 cbiosize=nn[KMG] The fixed amount of bus space which is
2236 reserved for the CardBus bridge's IO window.
2237 The default value is 256 bytes.
2238 cbmemsize=nn[KMG] The fixed amount of bus space which is
2239 reserved for the CardBus bridge's memory
2240 window. The default value is 64 megabytes.
2243 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2244 Specifies alignment and device to reassign
2245 aligned memory resources.
2246 If <order of align> is not specified,
2247 PAGE_SIZE is used as alignment.
2248 PCI-PCI bridge can be specified, if resource
2249 windows need to be expanded.
2250 ecrc= Enable/disable PCIe ECRC (transaction layer
2251 end-to-end CRC checking).
2252 bios: Use BIOS/firmware settings. This is the
2256 realloc= Enable/disable reallocating PCI bridge resources
2257 if allocations done by BIOS are too small to
2258 accommodate resources required by all child
2260 off: Turn realloc off
2262 realloc same as realloc=on
2263 noari do not use PCIe ARI.
2264 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2265 only look for one device below a PCIe downstream
2268 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2271 force Enable ASPM even on devices that claim not to support it.
2272 WARNING: Forcing ASPM on may cause system lockups.
2274 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2275 nomsi Do not use MSI for PCI Express Native Hotplug (this
2276 makes all PCIe ports use INTx for hotplug services).
2278 pcie_ports= [PCIE] PCIe ports handling:
2279 auto Ask the BIOS whether or not to use native PCIe services
2280 associated with PCIe ports (PME, hot-plug, AER). Use
2281 them only if that is allowed by the BIOS.
2282 native Use native PCIe services associated with PCIe ports
2284 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2287 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2288 nomsi Do not use MSI for native PCIe PME signaling (this makes
2289 all PCIe root ports use INTx for all services).
2291 pcmv= [HW,PCMCIA] BadgePAD 4
2294 See Documentation/blockdev/paride.txt.
2296 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2299 See arch/parisc/kernel/pdc_chassis.c
2301 percpu_alloc= Select which percpu first chunk allocator to use.
2302 Currently supported values are "embed" and "page".
2303 Archs may support subset or none of the selections.
2304 See comments in mm/percpu.c for details on each
2305 allocator. This parameter is primarily for debugging
2306 and performance comparison.
2309 See Documentation/blockdev/paride.txt.
2312 See Documentation/blockdev/paride.txt.
2314 pirq= [SMP,APIC] Manual mp-table setup
2315 See Documentation/x86/i386/IO-APIC.txt.
2317 plip= [PPT,NET] Parallel port network link
2318 Format: { parport<nr> | timid | 0 }
2319 See also Documentation/parport.txt.
2321 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2322 Override pmtimer IOPort with a hex value.
2326 Enable PNP debug messages (depends on the
2327 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2328 via /sys/module/pnp/parameters/debug. We always show
2329 current resource usage; turning this on also shows
2330 possible settings and some assignment information.
2336 { on | off | curr | res | no-curr | no-res }
2339 [ISAPNP] Exclude IRQs for the autoconfiguration
2342 [ISAPNP] Exclude DMAs for the autoconfiguration
2344 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2345 Ranges are in pairs (I/O port base and size).
2348 [ISAPNP] Exclude memory regions for the
2350 Ranges are in pairs (memory base and size).
2352 ports= [IP_VS_FTP] IPVS ftp helper module
2354 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2356 Format: <port>,<port>....
2358 print-fatal-signals=
2359 [KNL] debug: print fatal signals
2361 If enabled, warn about various signal handling
2362 related application anomalies: too many signals,
2363 too many POSIX.1 timers, fatal signals causing a
2366 If you hit the warning due to signal overflow,
2367 you might want to try "ulimit -i unlimited".
2371 printk.always_kmsg_dump=
2372 Trigger kmsg_dump for cases other than kernel oops or
2374 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2377 printk.time= Show timing data prefixed to each printk message line
2378 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2380 processor.max_cstate= [HW,ACPI]
2381 Limit processor to maximum C-state
2382 max_cstate=9 overrides any DMI blacklist limit.
2384 processor.nocst [HW,ACPI]
2385 Ignore the _CST method to determine C-states,
2386 instead using the legacy FADT method
2388 profile= [KNL] Enable kernel profiling via /proc/profile
2389 Format: [schedule,]<number>
2390 Param: "schedule" - profile schedule points.
2391 Param: <number> - step/bucket size as a power of 2 for
2392 statistical time based profiling.
2393 Param: "sleep" - profile D-state sleeping (millisecs).
2394 Requires CONFIG_SCHEDSTATS
2395 Param: "kvm" - profile VM exits.
2397 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2399 See Documentation/blockdev/ramdisk.txt.
2401 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2402 probe for; one of (bare|imps|exps|lifebook|any).
2403 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2405 psmouse.resetafter= [HW,MOUSE]
2406 Try to reset the device after so many bad packets
2409 [HW,MOUSE] Set desired mouse resolution, in dpi.
2410 psmouse.smartscroll=
2411 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2412 0 = disabled, 1 = enabled (default).
2414 pstore.backend= Specify the name of the pstore backend to use
2417 See Documentation/blockdev/paride.txt.
2420 [KNL] Number of legacy pty's. Overwrites compiled-in
2423 quiet [KNL] Disable most log messages
2428 See Documentation/md.txt.
2430 ramdisk_blocksize= [RAM]
2431 See Documentation/blockdev/ramdisk.txt.
2433 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2434 See Documentation/blockdev/ramdisk.txt.
2436 rcu_nocbs= [KNL,BOOT]
2437 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2438 the specified list of CPUs to be no-callback CPUs.
2439 Invocation of these CPUs' RCU callbacks will
2440 be offloaded to "rcuoN" kthreads created for
2441 that purpose. This reduces OS jitter on the
2442 offloaded CPUs, which can be useful for HPC and
2443 real-time workloads. It can also improve energy
2444 efficiency for asymmetric multiprocessors.
2446 rcu_nocb_poll [KNL,BOOT]
2447 Rather than requiring that offloaded CPUs
2448 (specified by rcu_nocbs= above) explicitly
2449 awaken the corresponding "rcuoN" kthreads,
2450 make these kthreads poll for callbacks.
2451 This improves the real-time response for the
2452 offloaded CPUs by relieving them of the need to
2453 wake up the corresponding kthread, but degrades
2454 energy efficiency by requiring that the kthreads
2455 periodically wake up to do the polling.
2457 rcutree.blimit= [KNL,BOOT]
2458 Set maximum number of finished RCU callbacks to process
2461 rcutree.fanout_leaf= [KNL,BOOT]
2462 Increase the number of CPUs assigned to each
2463 leaf rcu_node structure. Useful for very large
2466 rcutree.qhimark= [KNL,BOOT]
2467 Set threshold of queued
2468 RCU callbacks over which batch limiting is disabled.
2470 rcutree.qlowmark= [KNL,BOOT]
2471 Set threshold of queued RCU callbacks below which
2472 batch limiting is re-enabled.
2474 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2475 Suppress RCU CPU stall warning messages.
2477 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2478 Set timeout for RCU CPU stall warning messages.
2480 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2481 Set delay from grace-period initialization to
2482 first attempt to force quiescent states.
2483 Units are jiffies, minimum value is zero,
2484 and maximum value is HZ.
2486 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2487 Set delay between subsequent attempts to force
2488 quiescent states. Units are jiffies, minimum
2489 value is one, and maximum value is HZ.
2491 rcutorture.fqs_duration= [KNL,BOOT]
2492 Set duration of force_quiescent_state bursts.
2494 rcutorture.fqs_holdoff= [KNL,BOOT]
2495 Set holdoff time within force_quiescent_state bursts.
2497 rcutorture.fqs_stutter= [KNL,BOOT]
2498 Set wait time between force_quiescent_state bursts.
2500 rcutorture.irqreader= [KNL,BOOT]
2501 Test RCU readers from irq handlers.
2503 rcutorture.n_barrier_cbs= [KNL,BOOT]
2504 Set callbacks/threads for rcu_barrier() testing.
2506 rcutorture.nfakewriters= [KNL,BOOT]
2507 Set number of concurrent RCU writers. These just
2508 stress RCU, they don't participate in the actual
2509 test, hence the "fake".
2511 rcutorture.nreaders= [KNL,BOOT]
2512 Set number of RCU readers.
2514 rcutorture.onoff_holdoff= [KNL,BOOT]
2515 Set time (s) after boot for CPU-hotplug testing.
2517 rcutorture.onoff_interval= [KNL,BOOT]
2518 Set time (s) between CPU-hotplug operations, or
2519 zero to disable CPU-hotplug testing.
2521 rcutorture.shuffle_interval= [KNL,BOOT]
2522 Set task-shuffle interval (s). Shuffling tasks
2523 allows some CPUs to go into dyntick-idle mode
2524 during the rcutorture test.
2526 rcutorture.shutdown_secs= [KNL,BOOT]
2527 Set time (s) after boot system shutdown. This
2528 is useful for hands-off automated testing.
2530 rcutorture.stall_cpu= [KNL,BOOT]
2531 Duration of CPU stall (s) to test RCU CPU stall
2532 warnings, zero to disable.
2534 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2535 Time to wait (s) after boot before inducing stall.
2537 rcutorture.stat_interval= [KNL,BOOT]
2538 Time (s) between statistics printk()s.
2540 rcutorture.stutter= [KNL,BOOT]
2541 Time (s) to stutter testing, for example, specifying
2542 five seconds causes the test to run for five seconds,
2543 wait for five seconds, and so on. This tests RCU's
2544 ability to transition abruptly to and from idle.
2546 rcutorture.test_boost= [KNL,BOOT]
2547 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2548 "Maybe" means test if the RCU implementation
2549 under test support RCU priority boosting.
2551 rcutorture.test_boost_duration= [KNL,BOOT]
2552 Duration (s) of each individual boost test.
2554 rcutorture.test_boost_interval= [KNL,BOOT]
2555 Interval (s) between each boost test.
2557 rcutorture.test_no_idle_hz= [KNL,BOOT]
2558 Test RCU's dyntick-idle handling. See also the
2559 rcutorture.shuffle_interval parameter.
2561 rcutorture.torture_type= [KNL,BOOT]
2562 Specify the RCU implementation to test.
2564 rcutorture.verbose= [KNL,BOOT]
2565 Enable additional printk() statements.
2569 Run specified binary instead of /init from the ramdisk,
2570 used for early userspace startup. See initrd.
2572 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2573 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2574 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2577 [KNL, SMP] Set scheduler's default relax_domain_level.
2578 See Documentation/cgroups/cpusets.txt.
2580 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2582 reservetop= [X86-32]
2584 Reserves a hole at the top of the kernel virtual
2589 Set the amount of memory to reserve for BIOS at
2590 the bottom of the address space.
2592 reset_devices [KNL] Force drivers to reset the underlying device
2593 during initialization.
2596 Specify the partition device for software suspend
2598 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2600 resume_offset= [SWSUSP]
2601 Specify the offset from the beginning of the partition
2602 given by "resume=" at which the swap header is located,
2603 in <PAGE_SIZE> units (needed only for swap files).
2604 See Documentation/power/swsusp-and-swap-files.txt
2606 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2607 read the resume files
2609 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2610 Useful for devices that are detected asynchronously
2611 (e.g. USB and MMC devices).
2613 hibernate= [HIBERNATION]
2614 noresume Don't check if there's a hibernation image
2615 present during boot.
2616 nocompress Don't compress/decompress hibernation images.
2618 retain_initrd [RAM] Keep initrd memory after extraction
2620 rhash_entries= [KNL,NET]
2621 Set number of hash buckets for route cache
2623 riscom8= [HW,SERIAL]
2624 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2626 ro [KNL] Mount root device read-only on boot
2628 root= [KNL] Root filesystem
2629 See name_to_dev_t comment in init/do_mounts.c.
2631 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2632 mount the root filesystem
2634 rootflags= [KNL] Set root filesystem mount option string
2636 rootfstype= [KNL] Set root filesystem type
2638 rootwait [KNL] Wait (indefinitely) for root device to show up.
2639 Useful for devices that are detected asynchronously
2640 (e.g. USB and MMC devices).
2642 rw [KNL] Mount root device read-write on boot
2644 S [KNL] Run init in single mode
2647 See drivers/net/irda/sa1100_ir.c.
2649 sbni= [NET] Granch SBNI12 leased line adapter
2651 sched_debug [KNL] Enables verbose scheduler debug messages.
2653 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2654 xtime_lock contention on larger systems, and/or RCU lock
2655 contention on all systems with CONFIG_MAXSMP set.
2656 Format: { "0" | "1" }
2657 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2659 Note: increases power consumption, thus should only be
2660 enabled if running jitter sensitive (HPC/RT) workloads.
2662 security= [SECURITY] Choose a security module to enable at boot.
2663 If this boot parameter is not specified, only the first
2664 security module asking for security registration will be
2665 loaded. An invalid security module name will be treated
2666 as if no module has been chosen.
2668 selinux= [SELINUX] Disable or enable SELinux at boot time.
2669 Format: { "0" | "1" }
2670 See security/selinux/Kconfig help text.
2673 Default value is set via kernel config option.
2674 If enabled at boot time, /selinux/disable can be used
2675 later to disable prior to initial policy load.
2677 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2678 Format: { "0" | "1" }
2679 See security/apparmor/Kconfig help text
2682 Default value is set via kernel config option.
2684 serialnumber [BUGS=X86-32]
2687 Maximal number of shapers.
2689 show_msr= [x86] show boot-time MSR settings
2690 Format: { <integer> }
2691 Show boot-time (BIOS-initialized) MSR settings.
2692 The parameter means the number of CPUs to show,
2693 for example 1 means boot CPU only.
2700 slab_max_order= [MM, SLAB]
2701 Determines the maximum allowed order for slabs.
2702 A high setting may cause OOMs due to memory
2703 fragmentation. Defaults to 1 for systems with
2704 more than 32MB of RAM, 0 otherwise.
2706 slub_debug[=options[,slabs]] [MM, SLUB]
2707 Enabling slub_debug allows one to determine the
2708 culprit if slab objects become corrupted. Enabling
2709 slub_debug can create guard zones around objects and
2710 may poison objects when not in use. Also tracks the
2711 last alloc / free. For more information see
2712 Documentation/vm/slub.txt.
2714 slub_max_order= [MM, SLUB]
2715 Determines the maximum allowed order for slabs.
2716 A high setting may cause OOMs due to memory
2717 fragmentation. For more information see
2718 Documentation/vm/slub.txt.
2720 slub_min_objects= [MM, SLUB]
2721 The minimum number of objects per slab. SLUB will
2722 increase the slab order up to slub_max_order to
2723 generate a sufficiently large slab able to contain
2724 the number of objects indicated. The higher the number
2725 of objects the smaller the overhead of tracking slabs
2726 and the less frequently locks need to be acquired.
2727 For more information see Documentation/vm/slub.txt.
2729 slub_min_order= [MM, SLUB]
2730 Determines the minimum page order for slabs. Must be
2731 lower than slub_max_order.
2732 For more information see Documentation/vm/slub.txt.
2734 slub_nomerge [MM, SLUB]
2735 Disable merging of slabs with similar size. May be
2736 necessary if there is some reason to distinguish
2737 allocs to different slabs. Debug options disable
2738 merging on their own.
2739 For more information see Documentation/vm/slub.txt.
2742 Format: <io1>[,<io2>[,...,<io8>]]
2744 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2745 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2746 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2747 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2748 smsc-ircc2.ircc_irq= [HW] IRQ line
2749 smsc-ircc2.ircc_dma= [HW] DMA channel
2750 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2751 0: Toshiba Satellite 1800 (GP data pin select)
2752 1: Fast pin select (default)
2756 [KNL] Should the soft-lockup detector generate panics.
2759 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2760 See Documentation/laptops/sonypi.txt
2762 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2763 See Documentation/serial/specialix.txt.
2765 spia_io_base= [HW,MTD]
2771 Enabled the stack tracer on boot up.
2773 stacktrace_filter=[function-list]
2774 [FTRACE] Limit the functions that the stack tracer
2775 will trace at boot up. function-list is a comma separated
2776 list of functions. This list can be changed at run
2777 time by the stack_trace_filter file in the debugfs
2778 tracing directory. Note, this enables stack tracing
2779 and the stacktrace above is not needed.
2783 Set the STI (builtin display/keyboard on the HP-PARISC
2784 machines) console (graphic card) which should be used
2785 as the initial boot-console.
2786 See also comment in drivers/video/console/sticore.c.
2789 See comment in drivers/video/console/sticore.c.
2792 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2794 sunrpc.min_resvport=
2795 sunrpc.max_resvport=
2797 SunRPC servers often require that client requests
2798 originate from a privileged port (i.e. a port in the
2799 range 0 < portnr < 1024).
2800 An administrator who wishes to reserve some of these
2801 ports for other uses may adjust the range that the
2802 kernel's sunrpc client considers to be privileged
2803 using these two parameters to set the minimum and
2804 maximum port values.
2808 Control how the NFS server code allocates CPUs to
2809 service thread pools. Depending on how many NICs
2810 you have and where their interrupts are bound, this
2811 option will affect which CPUs will do NFS serving.
2812 Note: this parameter cannot be changed while the
2813 NFS server is running.
2815 auto the server chooses an appropriate mode
2816 automatically using heuristics
2817 global a single global pool contains all CPUs
2818 percpu one pool for each CPU
2819 pernode one pool for each NUMA node (equivalent
2820 to global on non-NUMA machines)
2822 sunrpc.tcp_slot_table_entries=
2823 sunrpc.udp_slot_table_entries=
2825 Sets the upper limit on the number of simultaneous
2826 RPC calls that can be sent from the client to a
2827 server. Increasing these values may allow you to
2828 improve throughput, but will also increase the
2829 amount of memory reserved for use by the client.
2832 [KNL] Enable accounting of swap in memory resource
2833 controller if no parameter or 1 is given or disable
2834 it if 0 is given (See Documentation/cgroups/memory.txt)
2836 swiotlb= [IA-64] Number of I/O TLB slabs
2840 sysfs.deprecated=0|1 [KNL]
2841 Enable/disable old style sysfs layout for old udev
2842 on older distributions. When this option is enabled
2843 very new udev will not work anymore. When this option
2844 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2845 in older udev will not work anymore.
2846 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2847 the kernel configuration.
2849 sysrq_always_enabled
2851 Ignore sysrq setting - this boot parameter will
2852 neutralize any effect of /proc/sys/kernel/sysrq.
2853 Useful for debugging.
2857 test_suspend= [SUSPEND]
2858 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2859 standby suspend) as the system sleep state to briefly
2860 enter during system startup. The system is woken from
2861 this state using a wakeup-capable RTC alarm.
2863 thash_entries= [KNL,NET]
2864 Set number of hash buckets for TCP connection
2866 thermal.act= [HW,ACPI]
2867 -1: disable all active trip points in all thermal zones
2868 <degrees C>: override all lowest active trip points
2870 thermal.crt= [HW,ACPI]
2871 -1: disable all critical trip points in all thermal zones
2872 <degrees C>: override all critical trip points
2874 thermal.nocrt= [HW,ACPI]
2875 Set to disable actions on ACPI thermal zone
2876 critical and hot trip points.
2878 thermal.off= [HW,ACPI]
2879 1: disable ACPI thermal control
2881 thermal.psv= [HW,ACPI]
2882 -1: disable all passive trip points
2883 <degrees C>: override all passive trip points to this
2886 thermal.tzp= [HW,ACPI]
2887 Specify global default ACPI thermal zone polling rate
2888 <deci-seconds>: poll all this frequency
2889 0: no polling (default)
2892 Force threading of all interrupt handlers except those
2893 marked explicitly IRQF_NO_THREAD.
2897 Specify if the kernel should make use of the cpu
2898 topology information if the hardware supports this.
2899 The scheduler will make use of this information and
2900 e.g. base its process migration decisions on it.
2905 tpm_suspend_pcr=[HW,TPM]
2906 Format: integer pcr id
2907 Specify that at suspend time, the tpm driver
2908 should extend the specified pcr with zeros,
2909 as a workaround for some chips which fail to
2910 flush the last written pcr on TPM_SaveState.
2911 This will guarantee that all the other pcrs
2914 trace_buf_size=nn[KMG]
2915 [FTRACE] will set tracing buffer size.
2917 trace_event=[event-list]
2918 [FTRACE] Set and start specified trace events in order
2919 to facilitate early boot debugging.
2920 See also Documentation/trace/events.txt
2922 trace_options=[option-list]
2923 [FTRACE] Enable or disable tracer options at boot.
2924 The option-list is a comma delimited list of options
2925 that can be enabled or disabled just as if you were
2926 to echo the option name into
2928 /sys/kernel/debug/tracing/trace_options
2930 For example, to enable stacktrace option (to dump the
2931 stack trace of each event), add to the command line:
2933 trace_options=stacktrace
2935 See also Documentation/trace/ftrace.txt "trace options"
2938 transparent_hugepage=
2940 Format: [always|madvise|never]
2941 Can be used to control the default behavior of the system
2942 with respect to transparent hugepages.
2943 See Documentation/vm/transhuge.txt for more details.
2945 tsc= Disable clocksource stability checks for TSC.
2947 [x86] reliable: mark tsc clocksource as reliable, this
2948 disables clocksource verification at runtime, as well
2949 as the stability checks done at bootup. Used to enable
2950 high-resolution timer mode on older hardware, and in
2951 virtualized environment.
2952 [x86] noirqtime: Do not use TSC to do irq accounting.
2953 Used to run time disable IRQ_TIME_ACCOUNTING on any
2954 platforms where RDTSC is slow and this accounting
2957 turbografx.map[2|3]= [HW,JOY]
2958 TurboGraFX parallel port interface
2960 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2961 See also Documentation/input/joystick-parport.txt
2963 udbg-immortal [PPC] When debugging early kernel crashes that
2964 happen after console_init() and before a proper
2965 console driver takes over, this boot options might
2966 help "seeing" what's going on.
2968 uhash_entries= [KNL,NET]
2969 Set number of hash buckets for UDP/UDP-Lite connections
2972 [USB] Ignore overcurrent events (default N).
2973 Some badly-designed motherboards generate lots of
2974 bogus events, for ports that aren't wired to
2975 anything. Set this parameter to avoid log spamming.
2976 Note that genuine overcurrent events won't be
2980 [X86] Cause panic on unknown NMI.
2982 usbcore.authorized_default=
2983 [USB] Default USB device authorization:
2984 (default -1 = authorized except for wireless USB,
2985 0 = not authorized, 1 = authorized)
2987 usbcore.autosuspend=
2988 [USB] The autosuspend time delay (in seconds) used
2989 for newly-detected USB devices (default 2). This
2990 is the time required before an idle device will be
2991 autosuspended. Devices for which the delay is set
2992 to a negative value won't be autosuspended at all.
2994 usbcore.usbfs_snoop=
2995 [USB] Set to log all usbfs traffic (default 0 = off).
2997 usbcore.blinkenlights=
2998 [USB] Set to cycle leds on hubs (default 0 = off).
3000 usbcore.old_scheme_first=
3001 [USB] Start with the old device initialization
3002 scheme (default 0 = off).
3004 usbcore.usbfs_memory_mb=
3005 [USB] Memory limit (in MB) for buffers allocated by
3006 usbfs (default = 16, 0 = max = 2047).
3008 usbcore.use_both_schemes=
3009 [USB] Try the other device initialization scheme
3010 if the first one fails (default 1 = enabled).
3012 usbcore.initial_descriptor_timeout=
3013 [USB] Specifies timeout for the initial 64-byte
3014 USB_REQ_GET_DESCRIPTOR request in milliseconds
3015 (default 5000 = 5.0 seconds).
3018 [USBHID] The interval which mice are to be polled at.
3020 usb-storage.delay_use=
3021 [UMS] The delay in seconds before a new device is
3022 scanned for Logical Units (default 5).
3025 [UMS] A list of quirks entries to supplement or
3026 override the built-in unusual_devs list. List
3027 entries are separated by commas. Each entry has
3028 the form VID:PID:Flags where VID and PID are Vendor
3029 and Product ID values (4-digit hex numbers) and
3030 Flags is a set of characters, each corresponding
3031 to a common usb-storage quirk flag as follows:
3032 a = SANE_SENSE (collect more than 18 bytes
3034 b = BAD_SENSE (don't collect more than 18
3035 bytes of sense data);
3036 c = FIX_CAPACITY (decrease the reported
3037 device capacity by one sector);
3038 d = NO_READ_DISC_INFO (don't use
3039 READ_DISC_INFO command);
3040 e = NO_READ_CAPACITY_16 (don't use
3041 READ_CAPACITY_16 command);
3042 h = CAPACITY_HEURISTICS (decrease the
3043 reported device capacity by one
3044 sector if the number is odd);
3045 i = IGNORE_DEVICE (don't bind to this
3047 l = NOT_LOCKABLE (don't try to lock and
3048 unlock ejectable media);
3049 m = MAX_SECTORS_64 (don't transfer more
3050 than 64 sectors = 32 KB at a time);
3051 n = INITIAL_READ10 (force a retry of the
3052 initial READ(10) command);
3053 o = CAPACITY_OK (accept the capacity
3054 reported by the device);
3055 p = WRITE_CACHE (the device cache is ON
3057 r = IGNORE_RESIDUE (the device reports
3058 bogus residue values);
3059 s = SINGLE_LUN (the device has only one
3061 w = NO_WP_DETECT (don't test whether the
3062 medium is write-protected).
3063 Example: quirks=0419:aaf5:rl,0421:0433:rc
3065 user_debug= [KNL,ARM]
3067 See arch/arm/Kconfig.debug help text.
3068 1 - undefined instruction events
3070 4 - invalid data aborts
3073 Example: user_debug=31
3076 [X86] Flags controlling user PTE allocations.
3078 nohigh = do not allocate PTE pages in
3079 HIGHMEM regardless of setting
3083 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3084 vdso=1: enable VDSO (default)
3085 vdso=0: disable VDSO mapping
3088 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3089 vdso32=1: enable 32-bit VDSO (default)
3090 vdso32=0: disable 32-bit VDSO mapping
3093 vector=percpu: enable percpu vector domain
3095 video= [FB] Frame buffer configuration
3096 See Documentation/fb/modedb.txt.
3099 [VMMIO] Memory mapped virtio (platform) device.
3101 <size>@<baseaddr>:<irq>[:<id>]
3103 <size> := size (can use standard suffixes
3105 <baseaddr> := physical base address
3106 <irq> := interrupt number (as passed to
3108 <id> := (optional) platform device id
3110 virtio_mmio.device=1K@0x100b0000:48:7
3112 Can be used multiple times for multiple devices.
3114 vga= [BOOT,X86-32] Select a particular video mode
3115 See Documentation/x86/boot.txt and
3116 Documentation/svga.txt.
3117 Use vga=ask for menu.
3118 This is actually a boot loader parameter; the value is
3119 passed to the kernel using a special protocol.
3121 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3122 size of <nn>. This can be used to increase the
3123 minimum size (128MB on x86). It can also be used to
3124 decrease the size and leave more room for directly
3127 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3130 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3133 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3137 Controls the behavior of vsyscalls (i.e. calls to
3138 fixed addresses of 0xffffffffff600x00 from legacy
3139 code). Most statically-linked binaries and older
3140 versions of glibc use these calls. Because these
3141 functions are at fixed addresses, they make nice
3142 targets for exploits that can control RIP.
3144 emulate [default] Vsyscalls turn into traps and are
3145 emulated reasonably safely.
3147 native Vsyscalls are native syscall instructions.
3148 This is a little bit faster than trapping
3149 and makes a few dynamic recompilers work
3150 better than they would in emulation mode.
3151 It also makes exploits much easier to write.
3153 none Vsyscalls don't work at all. This makes
3154 them quite hard to use for exploits but
3155 might break your system.
3157 vt.cur_default= [VT] Default cursor shape.
3158 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3159 the parameters of the <Esc>[?A;B;Cc escape sequence;
3160 see VGA-softcursor.txt. Default: 2 = underline.
3162 vt.default_blu= [VT]
3163 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3164 Change the default blue palette of the console.
3165 This is a 16-member array composed of values
3168 vt.default_grn= [VT]
3169 Format: <green0>,<green1>,<green2>,...,<green15>
3170 Change the default green palette of the console.
3171 This is a 16-member array composed of values
3174 vt.default_red= [VT]
3175 Format: <red0>,<red1>,<red2>,...,<red15>
3176 Change the default red palette of the console.
3177 This is a 16-member array composed of values
3183 Set system-wide default UTF-8 mode for all tty's.
3184 Default is 1, i.e. UTF-8 mode is enabled for all
3185 newly opened terminals.
3187 vt.global_cursor_default=
3190 Set system-wide default for whether a cursor
3191 is shown on new VTs. Default is -1,
3192 i.e. cursors will be created by default unless
3193 overridden by individual drivers. 0 will hide
3194 cursors, 1 will display them.
3196 watchdog timers [HW,WDT] For information on watchdog timers,
3197 see Documentation/watchdog/watchdog-parameters.txt
3198 or other driver-specific files in the
3199 Documentation/watchdog/ directory.
3201 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3202 default x2apic cluster mode on platforms
3205 x86_mrst_timer= [X86-32,APBT]
3206 Choose timer option for x86 Moorestown MID platform.
3207 Two valid options are apbt timer only and lapic timer
3208 plus one apbt timer for broadcast timer.
3209 x86_mrst_timer=apbt_only | lapic_and_apbt
3211 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3212 xd_geo= See header of drivers/block/xd.c.
3214 xen_emul_unplug= [HW,X86,XEN]
3215 Unplug Xen emulated devices
3216 Format: [unplug0,][unplug1]
3217 ide-disks -- unplug primary master IDE devices
3218 aux-ide-disks -- unplug non-primary-master IDE devices
3219 nics -- unplug network devices
3220 all -- unplug all emulated devices (NICs and IDE disks)
3221 unnecessary -- unplugging emulated devices is
3222 unnecessary even if the host did not respond to
3224 never -- do not unplug even if version check succeeds
3226 xirc2ps_cs= [NET,PCMCIA]
3228 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3230 ______________________________________________________________________
3234 Add more DRM drivers.
projects / mirror_ubuntu-jammy-kernel.git / blob