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 CMA Contiguous Memory Area support is enabled.
48 DRM Direct Rendering Management support is enabled.
49 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
50 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
51 EFI EFI Partitioning (GPT) is enabled
52 EIDE EIDE/ATAPI support is enabled.
53 EVM Extended Verification Module
54 FB The frame buffer device is enabled.
55 FTRACE Function tracing enabled.
56 GCOV GCOV profiling is enabled.
57 HW Appropriate hardware is enabled.
58 IA-64 IA-64 architecture is enabled.
59 IMA Integrity measurement architecture is enabled.
60 IOSCHED More than one I/O scheduler is enabled.
61 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
62 IPV6 IPv6 support is enabled.
63 ISAPNP ISA PnP code is enabled.
64 ISDN Appropriate ISDN support is enabled.
65 JOY Appropriate joystick support is enabled.
66 KGDB Kernel debugger support is enabled.
67 KVM Kernel Virtual Machine support is enabled.
68 LIBATA Libata driver is enabled
69 LP Printer support is enabled.
70 LOOP Loopback device support is enabled.
71 M68k M68k architecture is enabled.
72 These options have more detailed description inside of
73 Documentation/m68k/kernel-options.txt.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VMMIO Driver for memory mapped virtio devices is enabled.
114 VGA The VGA console has been enabled.
115 VT Virtual terminal support is enabled.
116 WDT Watchdog support is enabled.
117 XT IBM PC/XT MFM hard disk support is enabled.
118 X86-32 X86-32, aka i386 architecture is enabled.
119 X86-64 X86-64 architecture is enabled.
120 More X86-64 boot options can be found in
121 Documentation/x86/x86_64/boot-options.txt .
122 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
123 XEN Xen support is enabled
125 In addition, the following text indicates that the option:
127 BUGS= Relates to possible processor bugs on the said processor.
128 KNL Is a kernel start-up parameter.
129 BOOT Is a boot loader parameter.
131 Parameters denoted with BOOT are actually interpreted by the boot
132 loader, and have no meaning to the kernel directly.
133 Do not modify the syntax of boot loader parameters without extreme
134 need or coordination with <Documentation/x86/boot.txt>.
136 There are also arch-specific kernel-parameters not documented here.
137 See for example <Documentation/x86/x86_64/boot-options.txt>.
139 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
140 a trailing = on the name of any parameter states that that parameter will
141 be entered as an environment variable, whereas its absence indicates that
142 it will appear as a kernel argument readable via /proc/cmdline by programs
143 running once the system is up.
145 The number of kernel parameters is not limited, but the length of the
146 complete command line (parameters including spaces etc.) is limited to
147 a fixed number of characters. This limit depends on the architecture
148 and is between 256 and 4096 characters. It is defined in the file
149 ./include/asm/setup.h as COMMAND_LINE_SIZE.
151 Finally, the [KMG] suffix is commonly described after a number of kernel
152 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
153 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
154 bytes respectively. Such letter suffixes can also be entirely omitted.
158 Advanced Configuration and Power Interface
159 Format: { force | off | strict | noirq | rsdt }
160 force -- enable ACPI if default was off
161 off -- disable ACPI if default was on
162 noirq -- do not use ACPI for IRQ routing
163 strict -- Be less tolerant of platforms that are not
164 strictly ACPI specification compliant.
165 rsdt -- prefer RSDT over (default) XSDT
166 copy_dsdt -- copy DSDT to memory
168 See also Documentation/power/runtime_pm.txt, pci=noacpi
170 acpi_rsdp= [ACPI,EFI,KEXEC]
171 Pass the RSDP address to the kernel, mostly used
172 on machines running EFI runtime service to boot the
173 second kernel for kdump.
175 acpi_apic_instance= [ACPI, IOAPIC]
177 2: use 2nd APIC table, if available
178 1,0: use 1st APIC table
181 acpi_backlight= [HW,ACPI]
182 acpi_backlight=vendor
184 If set to vendor, prefer vendor specific driver
185 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
186 of the ACPI video.ko driver.
188 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
189 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
191 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
192 debug output. Bits in debug_layer correspond to a
193 _COMPONENT in an ACPI source file, e.g.,
194 #define _COMPONENT ACPI_PCI_COMPONENT
195 Bits in debug_level correspond to a level in
196 ACPI_DEBUG_PRINT statements, e.g.,
197 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
198 The debug_level mask defaults to "info". See
199 Documentation/acpi/debug.txt for more information about
200 debug layers and levels.
202 Enable processor driver info messages:
203 acpi.debug_layer=0x20000000
204 Enable PCI/PCI interrupt routing info messages:
205 acpi.debug_layer=0x400000
206 Enable AML "Debug" output, i.e., stores to the Debug
207 object while interpreting AML:
208 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
209 Enable all messages related to ACPI hardware:
210 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212 Some values produce so much output that the system is
213 unusable. The "log_buf_len" parameter may be useful
214 if you need to capture more output.
216 acpi_irq_balance [HW,ACPI]
217 ACPI will balance active IRQs
220 acpi_irq_nobalance [HW,ACPI]
221 ACPI will not move active IRQs (default)
224 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
225 Format: <irq>,<irq>...
227 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 Format: <irq>,<irq>...
231 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
234 Format: To spoof as Windows 98: ="Microsoft Windows"
236 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
237 acpi_osi="string1" # add string1 -- only one string
238 acpi_osi="!string2" # remove built-in string2
239 acpi_osi= # disable all strings
242 Override the pmtimer bug detection: force the kernel
243 to assume that this machine's pmtimer latches its value
244 and always returns good values.
246 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
247 Format: { level | edge | high | low }
249 acpi_serialize [HW,ACPI] force serialization of AML methods
251 acpi_skip_timer_override [HW,ACPI]
252 Recognize and ignore IRQ0/pin2 Interrupt Override.
253 For broken nForce2 BIOS resulting in XT-PIC timer.
255 acpi_sleep= [HW,ACPI] Sleep options
256 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
257 old_ordering, nonvs, sci_force_enable }
258 See Documentation/power/video.txt for information on
260 s3_beep is for debugging; it makes the PC's speaker beep
261 as soon as the kernel's real-mode entry point is called.
262 s4_nohwsig prevents ACPI hardware signature from being
263 used during resume from hibernation.
264 old_ordering causes the ACPI 1.0 ordering of the _PTS
265 control method, with respect to putting devices into
266 low power states, to be enforced (the ACPI 2.0 ordering
267 of _PTS is used by default).
268 nonvs prevents the kernel from saving/restoring the
269 ACPI NVS memory during suspend/hibernation and resume.
270 sci_force_enable causes the kernel to set SCI_EN directly
271 on resume from S1/S3 (which is against the ACPI spec,
272 but some broken systems don't work without it).
274 acpi_use_timer_override [HW,ACPI]
275 Use timer override. For some broken Nvidia NF5 boards
276 that require a timer override, but don't have HPET
278 acpi_enforce_resources= [ACPI]
279 { strict | lax | no }
280 Check for resource conflicts between native drivers
281 and ACPI OperationRegions (SystemIO and SystemMemory
282 only). IO ports and memory declared in ACPI might be
283 used by the ACPI subsystem in arbitrary AML code and
284 can interfere with legacy drivers.
285 strict (default): access to resources claimed by ACPI
286 is denied; legacy drivers trying to access reserved
287 resources will fail to bind to device using them.
288 lax: access to resources claimed by ACPI is allowed;
289 legacy drivers trying to access reserved resources
290 will bind successfully but a warning message is logged.
291 no: ACPI OperationRegions are not marked as reserved,
292 no further checks are performed.
294 add_efi_memmap [EFI; X86] Include EFI memory map in
295 kernel's map of available physical RAM.
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
304 See Documentation/sound/alsa/alsa-parameters.txt
307 Allow the default userspace alignment fault handler
308 behaviour to be specified. Bit 0 enables warnings,
309 bit 1 enables fixups, and bit 2 sends a segfault.
311 align_va_addr= [X86-64]
312 Align virtual addresses by clearing slice [14:12] when
313 allocating a VMA at process creation time. This option
314 gives you up to 3% performance improvement on AMD F15h
315 machines (where it is enabled by default) for a
316 CPU-intensive style benchmark, and it can vary highly in
317 a microbenchmark depending on workload and compiler.
319 32: only for 32-bit processes
320 64: only for 64-bit processes
321 on: enable for both 32- and 64-bit processes
322 off: disable for both 32- and 64-bit processes
324 amd_iommu= [HW,X86-64]
325 Pass parameters to the AMD IOMMU driver in the system.
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
331 off - do not initialize any AMD IOMMU found in
333 force_isolation - Force device isolation for all
334 devices. The IOMMU driver is not
335 allowed anymore to lift isolation
336 requirements as needed. This option
337 does not override iommu=pt
339 amd_iommu_dump= [HW,X86-64]
340 Enable AMD IOMMU driver option to dump the ACPI table
341 for AMD IOMMU. With this option enabled, AMD IOMMU
342 driver will print ACPI tables for AMD IOMMU during
343 IOMMU initialization.
345 amijoy.map= [HW,JOY] Amiga joystick support
346 Map of devices attached to JOY0DAT and JOY1DAT
348 See also Documentation/input/joystick.txt
350 analog.map= [HW,JOY] Analog joystick and gamepad support
351 Specifies type or capabilities of an analog joystick
352 connected to one of 16 gameports
353 Format: <type1>,<type2>,..<type16>
356 Power management functions (SPARCstation-4/5 + deriv.)
358 Disable APC CPU standby support. SPARCstation-Fox does
359 not play well with APC CPU idle - disable it if you have
360 APC and your system crashes randomly.
362 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
363 Change the output verbosity whilst booting
364 Format: { quiet (default) | verbose | debug }
365 Change the amount of debugging information output
366 when initialising the APIC and IO-APIC components.
369 See Documentation/networking/ipv6.txt.
371 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
372 Limit apic dumping. The parameter defines the maximal
373 number of local apics being dumped. Also it is possible
374 to set it to "all" by meaning -- no limit here.
375 Format: { 1 (default) | 2 | ... | all }.
376 The parameter valid if only apic=debug or
377 apic=verbose is specified.
378 Example: apic=debug show_lapic=all
380 apm= [APM] Advanced Power Management
381 See header of arch/x86/kernel/apm_32.c.
383 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
384 Format: <io>,<irq>,<nodeID>
388 atarimouse= [HW,MOUSE] Atari Mouse
390 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
391 EzKey and similar keyboards
393 atkbd.reset= [HW] Reset keyboard during initialization
395 atkbd.set= [HW] Select keyboard code set
396 Format: <int> (2 = AT (default), 3 = PS/2)
398 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
401 atkbd.softraw= [HW] Choose between synthetic and real raw mode
402 Format: <bool> (0 = real, 1 = synthetic (default))
404 atkbd.softrepeat= [HW]
405 Use software keyboard repeat
407 baycom_epp= [HW,AX25]
410 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
412 See header of drivers/net/hamradio/baycom_par.c.
414 baycom_ser_fdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
416 Format: <io>,<irq>,<mode>[,<baud>]
417 See header of drivers/net/hamradio/baycom_ser_fdx.c.
419 baycom_ser_hdx= [HW,AX25]
420 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
421 Format: <io>,<irq>,<mode>
422 See header of drivers/net/hamradio/baycom_ser_hdx.c.
424 boot_delay= Milliseconds to delay each printk during boot.
425 Values larger than 10 seconds (10000) are changed to
429 bootmem_debug [KNL] Enable bootmem allocator debug messages.
431 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
432 bttv.radio= Most important insmod options are available as
434 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
437 bulk_remove=off [PPC] This parameter disables the use of the pSeries
438 firmware feature for flushing multiple hpte entries
441 c101= [NET] Moxa C101 synchronous serial card
443 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
444 Sometimes CPU hardware bugs make them report the cache
445 size incorrectly. The kernel will attempt work arounds
446 to fix known problems, but for some CPUs it is not
447 possible to determine what the correct size should be.
448 This option provides an override for these situations.
450 ccw_timeout_log [S390]
451 See Documentation/s390/CommonIO for details.
453 cgroup_disable= [KNL] Disable a particular controller
454 Format: {name of the controller(s) to disable}
455 {Currently supported controllers - "memory"}
457 checkreqprot [SELINUX] Set initial checkreqprot flag value.
458 Format: { "0" | "1" }
459 See security/selinux/Kconfig help text.
460 0 -- check protection applied by kernel (includes
461 any implied execute protection).
462 1 -- check protection requested by application.
463 Default value is set via a kernel config option.
464 Value can be changed at runtime via
465 /selinux/checkreqprot.
468 See Documentation/s390/CommonIO for details.
470 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
472 Forces specified clocksource (if available) to be used
473 when calculating gettimeofday(). If specified
474 clocksource is not available, it defaults to PIT.
475 Format: { pit | tsc | cyclone | pmtmr }
477 clocksource= Override the default clocksource
479 Override the default clocksource and use the clocksource
480 with the name specified.
481 Some clocksource names to choose from, depending on
483 [all] jiffies (this is the base, fallback clocksource)
485 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
486 pxa_timer,timer3,32k_counter,timer0_1
488 [X86-32] pit,hpet,tsc;
489 scx200_hrt on Geode; cyclone on IBM x440
497 clearcpuid=BITNUM [X86]
498 Disable CPUID feature X for the kernel. See
499 arch/x86/include/asm/cpufeature.h for the valid bit
500 numbers. Note the Linux specific bits are not necessarily
501 stable over kernel options, but the vendor specific
503 Also note that user programs calling CPUID directly
504 or using the feature without checking anything
505 will still see it. This just prevents it from
506 being used by the kernel or shown in /proc/cpuinfo.
507 Also note the kernel might malfunction if you disable
511 Sets the size of kernel global memory area for contiguous
512 memory allocations. For more information, see
513 include/linux/dma-contiguous.h
515 cmo_free_hint= [PPC] Format: { yes | no }
516 Specify whether pages are marked as being inactive
517 when they are freed. This is used in CMO environments
518 to determine OS memory pressure for page stealing by
522 coherent_pool=nn[KMG] [ARM,KNL]
523 Sets the size of memory pool for coherent, atomic dma
524 allocations, by default set to 256K.
526 code_bytes [X86] How many bytes of object code to print
531 com20020= [HW,NET] ARCnet - COM20020 chipset
533 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
535 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
539 ARCnet - COM90xx chipset (memory-mapped buffers)
540 Format: <io>[,<irq>[,<memstart>]]
542 condev= [HW,S390] console device
545 console= [KNL] Output console device and options.
547 tty<n> Use the virtual console device <n>.
551 Use the specified serial port. The options are of
552 the form "bbbbpnf", where "bbbb" is the baud rate,
553 "p" is parity ("n", "o", or "e"), "n" is number of
554 bits, and "f" is flow control ("r" for RTS or
555 omit it). Default is "9600n8".
557 See Documentation/serial-console.txt for more
559 Documentation/networking/netconsole.txt for an
562 uart[8250],io,<addr>[,options]
563 uart[8250],mmio,<addr>[,options]
564 Start an early, polled-mode console on the 8250/16550
565 UART at the specified I/O port or MMIO address,
566 switching to the matching ttyS device later. The
567 options are the same as for ttyS, above.
568 hvc<n> Use the hypervisor console device <n>. This is for
569 both Xen and PowerPC hypervisors.
571 If the device connected to the port is not a TTY but a braille
572 device, prepend "brl," before the device type, for instance
574 For now, only VisioBraille is supported.
576 consoleblank= [KNL] The console blank (screen saver) timeout in
577 seconds. Defaults to 10*60 = 10mins. A value of 0
578 disables the blank timer.
581 [KNL] Change the default value for
582 /proc/<pid>/coredump_filter.
583 See also Documentation/filesystems/proc.txt.
585 cpuidle.off=1 [CPU_IDLE]
586 disable the cpuidle sub-system
588 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
590 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
592 crashkernel=size[KMG][@offset[KMG]]
593 [KNL] Using kexec, Linux can switch to a 'crash kernel'
594 upon panic. This parameter reserves the physical
595 memory region [offset, offset + size] for that kernel
596 image. If '@offset' is omitted, then a suitable offset
597 is selected automatically. Check
598 Documentation/kdump/kdump.txt for further details.
600 crashkernel_low=size[KMG]
601 [KNL, x86] parts under 4G.
603 crashkernel=range1:size1[,range2:size2,...][@offset]
604 [KNL] Same as above, but depends on the memory
605 in the running system. The syntax of range is
606 start-[end] where start and end are both
607 a memory unit (amount[KMG]). See also
608 Documentation/kdump/kdump.txt for an example.
613 cs89x0_media= [HW,NET]
614 Format: { rj45 | aui | bnc }
617 See header of drivers/s390/block/dasd_devmap.c.
619 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
620 (one device per port)
621 Format: <port#>,<type>
622 See also Documentation/input/joystick-parport.txt
624 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
625 time. See Documentation/dynamic-debug-howto.txt for
626 details. Deprecated, see dyndbg.
628 debug [KNL] Enable kernel debugging (events log level).
631 [KNL] verbose self-tests
633 Print debugging info while doing the locking API
635 We default to 0 (no extra messages), setting it to
636 1 will print _a lot_ more information - normally
637 only useful to kernel developers.
639 debug_objects [KNL] Enable object debugging
642 [KNL] Disable object debugging
644 debug_guardpage_minorder=
645 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
646 parameter allows control of the order of pages that will
647 be intentionally kept free (and hence protected) by the
648 buddy allocator. Bigger value increase the probability
649 of catching random memory corruption, but reduce the
650 amount of memory for normal system use. The maximum
651 possible value is MAX_ORDER/2. Setting this parameter
652 to 1 or 2 should be enough to identify most random
653 memory corruption problems caused by bugs in kernel or
654 driver code when a CPU writes to (or reads from) a
655 random memory location. Note that there exists a class
656 of memory corruptions problems caused by buggy H/W or
657 F/W or by drivers badly programing DMA (basically when
658 memory is written at bus level and the CPU MMU is
659 bypassed) which are not detectable by
660 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
661 tracking down these problems.
663 debugpat [X86] Enable PAT debugging
665 decnet.addr= [HW,NET]
666 Format: <area>[,<node>]
667 See also Documentation/networking/decnet.txt.
670 [same as hugepagesz=] The size of the default
671 HugeTLB page size. This is the size represented by
672 the legacy /proc/ hugepages APIs, used for SHM, and
673 default size when mounting hugetlbfs filesystems.
674 Defaults to the default architecture's huge page size
678 Set number of hash buckets for dentry cache.
681 IO parameters + enable/disable command.
683 digiepca= [HW,SERIAL]
684 See drivers/char/README.epca and
685 Documentation/serial/digiepca.txt.
688 See Documentation/networking/ipv6.txt.
690 disable_ddw [PPC/PSERIES]
691 Disable Dynamic DMA Window support. Use this if
692 to workaround buggy firmware.
695 See Documentation/networking/ipv6.txt.
697 disable_mtrr_cleanup [X86]
698 The kernel tries to adjust MTRR layout from continuous
699 to discrete, to make X server driver able to add WB
700 entry later. This parameter disables that.
702 disable_mtrr_trim [X86, Intel and AMD only]
703 By default the kernel will trim any uncacheable
704 memory out of your available memory pool based on
705 MTRR settings. This parameter disables that behavior,
706 possibly causing your machine to run very slowly.
708 disable_timer_pin_1 [X86]
709 Disable PIN 1 of APIC timer
710 Can be useful to work around chipset bugs.
712 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
713 this option disables the debugging code at boot.
715 dma_debug_entries=<number>
716 This option allows to tune the number of preallocated
717 entries for DMA-API debugging code. One entry is
718 required per DMA-API allocation. Use this if the
719 DMA-API debugging code disables itself because the
720 architectural default is too low.
722 dma_debug_driver=<driver_name>
723 With this option the DMA-API debugging driver
724 filter feature can be enabled at boot time. Just
725 pass the driver to filter for as the parameter.
726 The filter can be disabled or changed to another
727 driver later using sysfs.
729 drm_kms_helper.edid_firmware=[<connector>:]<file>
730 Broken monitors, graphic adapters and KVMs may
731 send no or incorrect EDID data sets. This parameter
732 allows to specify an EDID data set in the
733 /lib/firmware directory that is used instead.
734 Generic built-in EDID data sets are used, if one of
735 edid/1024x768.bin, edid/1280x1024.bin,
736 edid/1680x1050.bin, or edid/1920x1080.bin is given
737 and no file with the same name exists. Details and
738 instructions how to build your own EDID data are
739 available in Documentation/EDID/HOWTO.txt. An EDID
740 data set will only be used for a particular connector,
741 if its name and a colon are prepended to the EDID
746 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
747 module.dyndbg[="val"]
748 Enable debug messages at boot time. See
749 Documentation/dynamic-debug-howto.txt for details.
751 earlycon= [KNL] Output early console device and options.
752 uart[8250],io,<addr>[,options]
753 uart[8250],mmio,<addr>[,options]
754 uart[8250],mmio32,<addr>[,options]
755 Start an early, polled-mode console on the 8250/16550
756 UART at the specified I/O port or MMIO address.
757 MMIO inter-register address stride is either 8-bit
758 (mmio) or 32-bit (mmio32).
759 The options are the same as for ttyS, above.
761 earlyprintk= [X86,SH,BLACKFIN]
764 earlyprintk=serial[,ttySn[,baudrate]]
765 earlyprintk=ttySn[,baudrate]
766 earlyprintk=dbgp[debugController#]
768 Append ",keep" to not disable it when the real console
771 Only vga or serial or usb debug port at a time.
773 Currently only ttyS0 and ttyS1 are supported.
775 Interaction with the standard serial driver is not
778 The VGA output is eventually overwritten by the real
781 The xen output can only be used by Xen PV guests.
783 ekgdboc= [X86,KGDB] Allow early kernel console debugging
786 This is designed to be used in conjunction with
787 the boot argument: earlyprintk=vga
790 Format: {"off" | "on" | "skip[mbr]"}
792 eisa_irq_edge= [PARISC,HW]
793 See header of drivers/parisc/eisa.c.
796 See comment before function elanfreq_setup() in
797 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
800 Format: {"cfq" | "deadline" | "noop"}
801 See Documentation/block/cfq-iosched.txt and
802 Documentation/block/deadline-iosched.txt for details.
804 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
805 Specifies physical address of start of kernel core
806 image elf header and optionally the size. Generally
807 kexec loader will pass this option to capture kernel.
808 See Documentation/kdump/kdump.txt for details.
810 enable_mtrr_cleanup [X86]
811 The kernel tries to adjust MTRR layout from continuous
812 to discrete, to make X server driver able to add WB
813 entry later. This parameter enables that.
815 enable_timer_pin_1 [X86]
816 Enable PIN 1 of APIC timer
817 Can be useful to work around chipset bugs
818 (in particular on some ATI chipsets).
819 The kernel tries to set a reasonable default.
821 enforcing [SELINUX] Set initial enforcing status.
823 See security/selinux/Kconfig help text.
824 0 -- permissive (log only, no denials).
825 1 -- enforcing (deny and log).
827 Value can be changed at runtime via /selinux/enforce.
830 Disable Error Record Serialization Table (ERST)
833 ether= [HW,NET] Ethernet cards parameters
834 This option is obsoleted by the "netdev=" option, which
835 has equivalent usage. See its documentation for details.
839 Permit 'security.evm' to be updated regardless of
840 current integrity status.
844 fail_make_request=[KNL]
845 General fault injection mechanism.
846 Format: <interval>,<probability>,<space>,<times>
847 See also Documentation/fault-injection/.
850 See Documentation/blockdev/floppy.txt.
852 force_pal_cache_flush
853 [IA-64] Avoid check_sal_cache_flush which may hang on
854 buggy SAL_CACHE_FLUSH implementations. Using this
855 parameter will force ia64_sal_cache_flush to call
856 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
859 [FTRACE] will set and start the specified tracer
860 as early as possible in order to facilitate early
863 ftrace_dump_on_oops[=orig_cpu]
864 [FTRACE] will dump the trace buffers on oops.
865 If no parameter is passed, ftrace will dump
866 buffers of all CPUs, but if you pass orig_cpu, it will
867 dump only the buffer of the CPU that triggered the
870 ftrace_filter=[function-list]
871 [FTRACE] Limit the functions traced by the function
872 tracer at boot up. function-list is a comma separated
873 list of functions. This list can be changed at run
874 time by the set_ftrace_filter file in the debugfs
877 ftrace_notrace=[function-list]
878 [FTRACE] Do not trace the functions specified in
879 function-list. This list can be changed at run time
880 by the set_ftrace_notrace file in the debugfs
883 ftrace_graph_filter=[function-list]
884 [FTRACE] Limit the top level callers functions traced
885 by the function graph tracer at boot up.
886 function-list is a comma separated list of functions
887 that can be changed at run time by the
888 set_graph_function file in the debugfs tracing directory.
891 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
892 support via parallel port (up to 5 devices per port)
893 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
894 See also Documentation/input/joystick-parport.txt
898 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
902 gcov_persist= [GCOV] When non-zero (default), profiling data for
903 kernel modules is saved and remains accessible via
904 debugfs, even when the module is unloaded/reloaded.
905 When zero, profiling data is discarded and associated
906 debugfs files are removed at module unload time.
908 gpt [EFI] Forces disk with valid GPT signature but
909 invalid Protective MBR to be treated as GPT.
911 grcan.enable0= [HW] Configuration of physical interface 0. Determines
912 the "Enable 0" bit of the configuration register.
915 grcan.enable1= [HW] Configuration of physical interface 1. Determines
916 the "Enable 0" bit of the configuration register.
919 grcan.select= [HW] Select which physical interface to use.
922 grcan.txsize= [HW] Sets the size of the tx buffer.
923 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
925 grcan.rxsize= [HW] Sets the size of the rx buffer.
926 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
929 hashdist= [KNL,NUMA] Large hashes allocated during boot
930 are distributed across NUMA nodes. Defaults on
931 for 64-bit NUMA, off otherwise.
932 Format: 0 | 1 (for off | on)
934 hcl= [IA-64] SGI's Hardware Graph compatibility layer
936 hd= [EIDE] (E)IDE hard drive subsystem geometry
937 Format: <cyl>,<head>,<sect>
940 Disable Hardware Error Source Table (HEST) support;
941 corresponding firmware-first mode error processing
942 logic will be disabled.
944 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
945 size of <nn>. This works even on boxes that have no
946 highmem otherwise. This also works to reduce highmem
947 size on bigger boxes.
949 highres= [KNL] Enable/disable high resolution timer mode.
950 Valid parameters: "on", "off"
954 See Documentation/isdn/README.HiSax.
958 hpet= [X86-32,HPET] option to control HPET usage
959 Format: { enable (default) | disable | force |
961 disable: disable HPET and use PIT instead
962 force: allow force enabled of undocumented chips (ICH4,
964 verbose: show contents of HPET registers during setup
966 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
967 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
968 On x86-64 and powerpc, this option can be specified
969 multiple times interleaved with hugepages= to reserve
970 huge pages of different sizes. Valid pages sizes on
971 x86-64 are 2M (when the CPU supports "pse") and 1G
972 (when the CPU supports the "pdpe1gb" cpuinfo flag)
973 Note that 1GB pages can only be allocated at boot time
974 using hugepages= and not freed afterwards.
976 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
977 terminal devices. Valid values: 0..8
978 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
979 If specified, z/VM IUCV HVC accepts connections
980 from listed z/VM user IDs only.
982 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
983 hardware thread id mappings.
984 Format: <cpu>:<hwthread>
987 Do not unregister boot console at start. This is only
988 useful for debugging when something happens in the window
989 between unregistering the boot console and initializing
992 i2c_bus= [HW] Override the default board specific I2C bus speed
993 or register an additional I2C bus that is not
994 registered from board initialization code.
998 i8042.debug [HW] Toggle i8042 debug mode
999 i8042.direct [HW] Put keyboard port into non-translated mode
1000 i8042.dumbkbd [HW] Pretend that controller can only read data from
1001 keyboard and cannot control its state
1002 (Don't attempt to blink the leds)
1003 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1004 i8042.nokbd [HW] Don't check/create keyboard port
1005 i8042.noloop [HW] Disable the AUX Loopback command while probing
1007 i8042.nomux [HW] Don't check presence of an active multiplexing
1009 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1011 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1012 i8042.reset [HW] Reset the controller during init and cleanup
1013 i8042.unlock [HW] Unlock (ignore) the keylock
1017 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1018 indicates that the driver is running on unsupported
1020 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1021 does not match list of supported models.
1023 [HW] Report power status in /proc/i8k
1024 (disabled by default)
1025 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1028 i915.invert_brightness=
1029 [DRM] Invert the sense of the variable that is used to
1030 set the brightness of the panel backlight. Normally a
1031 brightness value of 0 indicates backlight switched off,
1032 and the maximum of the brightness value sets the backlight
1033 to maximum brightness. If this parameter is set to 0
1034 (default) and the machine requires it, or this parameter
1035 is set to 1, a brightness value of 0 sets the backlight
1036 to maximum brightness, and the maximum of the brightness
1037 value switches the backlight off.
1038 -1 -- never invert brightness
1039 0 -- machine default
1040 1 -- force brightness inversion
1043 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1045 ide-core.nodma= [HW] (E)IDE subsystem
1046 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1047 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1048 .cdrom .chs .ignore_cable are additional options
1049 See Documentation/ide/ide.txt.
1051 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1052 Claim all unknown PCI IDE storage controllers.
1055 Format: idle=poll, idle=halt, idle=nomwait
1056 Poll forces a polling idle loop that can slightly
1057 improve the performance of waking up a idle CPU, but
1058 will use a lot of power and make the system run hot.
1060 idle=halt: Halt is forced to be used for CPU idle.
1061 In such case C2/C3 won't be used again.
1062 idle=nomwait: Disable mwait for CPU C-states
1064 ignore_loglevel [KNL]
1065 Ignore loglevel setting - this will print /all/
1066 kernel messages to the console. Useful for debugging.
1067 We also add it as printk module parameter, so users
1068 could change it dynamically, usually by
1069 /sys/module/printk/parameters/ignore_loglevel.
1071 ihash_entries= [KNL]
1072 Set number of hash buckets for inode cache.
1074 ima_appraise= [IMA] appraise integrity measurements
1075 Format: { "off" | "enforce" | "fix" }
1078 ima_appraise_tcb [IMA]
1079 The builtin appraise policy appraises all files
1083 Format: { "0" | "1" }
1084 0 -- integrity auditing messages. (Default)
1085 1 -- enable informational integrity auditing messages.
1088 Format: { "sha1" | "md5" }
1092 Load a policy which meets the needs of the Trusted
1093 Computing Base. This means IMA will measure all
1094 programs exec'd, files mmap'd for exec, and all files
1095 opened for read by uid=0.
1099 Run specified binary instead of /sbin/init as init
1102 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1103 for working out where the kernel is dying during
1106 initrd= [BOOT] Specify the location of the initial ramdisk
1108 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1111 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1113 Enable intel iommu driver.
1115 Disable intel iommu driver.
1116 igfx_off [Default Off]
1117 By default, gfx is mapped as normal device. If a gfx
1118 device has a dedicated DMAR unit, the DMAR unit is
1119 bypassed by not enabling DMAR with this option. In
1120 this case, gfx device will use physical address for
1123 With this option iommu will not optimize to look
1124 for io virtual address below 32-bit forcing dual
1125 address cycle on pci bus for cards supporting greater
1126 than 32-bit addressing. The default is to look
1127 for translation below 32-bit and if not available
1128 then look in the higher range.
1129 strict [Default Off]
1130 With this option on every unmap_single operation will
1131 result in a hardware IOTLB flush operation as opposed
1132 to batching them for performance.
1133 sp_off [Default Off]
1134 By default, super page will be supported if Intel IOMMU
1135 has the capability. With this option, super page will
1138 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1139 0 disables intel_idle and fall back on acpi_idle.
1140 1 to 6 specify maximum depth of C-state.
1144 Do not enable intel_pstate as the default
1145 scaling driver for the supported processors
1147 intremap= [X86-64, Intel-IOMMU]
1148 on enable Interrupt Remapping (default)
1149 off disable Interrupt Remapping
1150 nosid disable Source ID checking
1152 BIOS x2APIC opt-out request will be ignored
1154 iomem= Disable strict checking of access to MMIO memory
1155 strict regions from userspace.
1172 io7= [HW] IO7 for Marvel based alpha systems
1173 See comment before marvel_specify_io7 in
1174 arch/alpha/kernel/core_marvel.c.
1176 io_delay= [X86] I/O delay method
1178 Standard port 0x80 based delay
1180 Alternate port 0xed based delay (needed on some systems)
1182 Simple two microseconds delay
1187 See Documentation/filesystems/nfs/nfsroot.txt.
1189 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1190 See comment before ip2_setup() in
1191 drivers/char/ip2/ip2base.c.
1194 When an interrupt is not handled search all handlers
1195 for it. Intended to get systems with badly broken
1199 When an interrupt is not handled search all handlers
1200 for it. Also check all handlers each timer
1201 interrupt. Intended to get systems with badly broken
1205 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1207 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1209 <cpu number>,...,<cpu number>
1211 <cpu number>-<cpu number>
1212 (must be a positive range in ascending order)
1214 <cpu number>,...,<cpu number>-<cpu number>
1216 This option can be used to specify one or more CPUs
1217 to isolate from the general SMP balancing and scheduling
1218 algorithms. You can move a process onto or off an
1219 "isolated" CPU via the CPU affinity syscalls or cpuset.
1220 <cpu number> begins at 0 and the maximum value is
1221 "number of CPUs in system - 1".
1223 This option is the preferred way to isolate CPUs. The
1224 alternative -- manually setting the CPU mask of all
1225 tasks in the system -- can cause problems and
1226 suboptimal load balancer performance.
1230 js= [HW,JOY] Analog joystick
1231 See Documentation/input/joystick.txt.
1235 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1236 specifies the amount of memory usable by the kernel
1237 for non-movable allocations. The requested amount is
1238 spread evenly throughout all nodes in the system. The
1239 remaining memory in each node is used for Movable
1240 pages. In the event, a node is too small to have both
1241 kernelcore and Movable pages, kernelcore pages will
1242 take priority and other nodes will have a larger number
1243 of kernelcore pages. The Movable zone is used for the
1244 allocation of pages that may be reclaimed or moved
1245 by the page migration subsystem. This means that
1246 HugeTLB pages may not be allocated from this zone.
1247 Note that allocations like PTEs-from-HighMem still
1248 use the HighMem zone if it exists, and the Normal
1249 zone if it does not.
1251 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1252 Format: <Controller#>[,poll interval]
1253 The controller # is the number of the ehci usb debug
1254 port as it is probed via PCI. The poll interval is
1255 optional and is the number seconds in between
1256 each poll cycle to the debug port in case you need
1257 the functionality for interrupting the kernel with
1258 gdb or control-c on the dbgp connection. When
1259 not using this parameter you use sysrq-g to break into
1260 the kernel debugger.
1262 kgdboc= [KGDB,HW] kgdb over consoles.
1263 Requires a tty driver that supports console polling,
1264 or a supported polling keyboard driver (non-usb).
1265 Serial only format: <serial_device>[,baud]
1266 keyboard only format: kbd
1267 keyboard and serial format: kbd,<serial_device>[,baud]
1268 Optional Kernel mode setting:
1269 kms, kbd format: kms,kbd
1270 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1272 kgdbwait [KGDB] Stop kernel execution and enter the
1273 kernel debugger at the earliest opportunity.
1275 kmac= [MIPS] korina ethernet MAC address.
1276 Configure the RouterBoard 532 series on-chip
1277 Ethernet adapter MAC address.
1279 kmemleak= [KNL] Boot-time kmemleak enable/disable
1280 Valid arguments: on, off
1283 kstack=N [X86] Print N words from the kernel stack
1286 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1287 Default is 0 (don't ignore, but inject #GP)
1289 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1293 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1294 Default is 1 (enabled)
1296 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1298 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1300 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1301 (virtualized MMU) support on capable Intel chips.
1302 Default is 1 (enabled)
1304 kvm-intel.emulate_invalid_guest_state=
1305 [KVM,Intel] Enable emulation of invalid guest states
1306 Default is 0 (disabled)
1308 kvm-intel.flexpriority=
1309 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1310 Default is 1 (enabled)
1313 [KVM,Intel] Enable VMX nesting (nVMX).
1314 Default is 0 (disabled)
1316 kvm-intel.unrestricted_guest=
1317 [KVM,Intel] Disable unrestricted guest feature
1318 (virtualized real and unpaged mode) on capable
1319 Intel chips. Default is 1 (enabled)
1321 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1322 feature (tagged TLBs) on capable Intel chips.
1323 Default is 1 (enabled)
1329 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1332 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1333 value for LAPIC timer one-shot implementation. Default
1334 back to the programmable timer unit in the LAPIC.
1336 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1339 libata.dma= [LIBATA] DMA control
1340 libata.dma=0 Disable all PATA and SATA DMA
1341 libata.dma=1 PATA and SATA Disk DMA only
1342 libata.dma=2 ATAPI (CDROM) DMA only
1343 libata.dma=4 Compact Flash DMA only
1344 Combinations also work, so libata.dma=3 enables DMA
1345 for disks and CDROMs, but not CFs.
1347 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1348 libata.ignore_hpa=0 keep BIOS limits (default)
1349 libata.ignore_hpa=1 ignore limits, using full disk
1351 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1355 libata.force= [LIBATA] Force configurations. The format is comma
1356 separated list of "[ID:]VAL" where ID is
1357 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1358 matching port, link or device. Basically, it matches
1359 the ATA ID string printed on console by libata. If
1360 the whole ID part is omitted, the last PORT and DEVICE
1361 values are used. If ID hasn't been specified yet, the
1362 configuration applies to all ports, links and devices.
1364 If only DEVICE is omitted, the parameter applies to
1365 the port and all links and devices behind it. DEVICE
1366 number of 0 either selects the first device or the
1367 first fan-out link behind PMP device. It does not
1368 select the host link. DEVICE number of 15 selects the
1369 host link and device attached to it.
1371 The VAL specifies the configuration to force. As long
1372 as there's no ambiguity shortcut notation is allowed.
1373 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1374 The following configurations can be forced.
1376 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1377 Any ID with matching PORT is used.
1379 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1381 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1382 udma[/][16,25,33,44,66,100,133] notation is also
1385 * [no]ncq: Turn on or off NCQ.
1387 * nohrst, nosrst, norst: suppress hard, soft
1390 * rstonce: only attempt one reset during
1391 hot-unplug link recovery
1393 * dump_id: dump IDENTIFY data.
1395 If there are multiple matching configurations changing
1396 the same attribute, the last one is used.
1398 memblock=debug [KNL] Enable memblock debug messages.
1400 load_ramdisk= [RAM] List of ramdisks to load from floppy
1401 See Documentation/blockdev/ramdisk.txt.
1403 lockd.nlm_grace_period=P [NFS] Assign grace period.
1406 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1409 lockd.nlm_timeout=T [NFS] Assign timeout value.
1412 lockd.nlm_udpport=M [NFS] Assign UDP port.
1415 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1418 loglevel= All Kernel Messages with a loglevel smaller than the
1419 console loglevel will be printed to the console. It can
1420 also be changed with klogd or other programs. The
1421 loglevels are defined as follows:
1423 0 (KERN_EMERG) system is unusable
1424 1 (KERN_ALERT) action must be taken immediately
1425 2 (KERN_CRIT) critical conditions
1426 3 (KERN_ERR) error conditions
1427 4 (KERN_WARNING) warning conditions
1428 5 (KERN_NOTICE) normal but significant condition
1429 6 (KERN_INFO) informational
1430 7 (KERN_DEBUG) debug-level messages
1432 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1433 in bytes. n must be a power of two. The default
1434 size is set in the kernel config file.
1436 logo.nologo [FB] Disables display of the built-in Linux logo.
1437 This may be used to provide more screen space for
1438 kernel log messages and is useful when debugging
1439 kernel boot problems.
1441 lp=0 [LP] Specify parallel ports to use, e.g,
1442 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1443 lp=reset first parallel port). 'lp=0' disables the
1444 lp=auto printer driver. 'lp=reset' (which can be
1445 specified in addition to the ports) causes
1446 attached printers to be reset. Using
1447 lp=port1,port2,... specifies the parallel ports
1448 to associate lp devices with, starting with
1449 lp0. A port specification may be 'none' to skip
1450 that lp device, or a parport name such as
1451 'parport0'. Specifying 'lp=auto' instead of a
1452 port specification list means that device IDs
1453 from each port should be examined, to see if
1454 an IEEE 1284-compliant printer is attached; if
1455 so, the driver will manage that printer.
1456 See also header of drivers/char/lp.c.
1459 Sets loops_per_jiffy to given constant, thus avoiding
1460 time-consuming boot-time autodetection (up to 250 ms per
1461 CPU). 0 enables autodetection (default). To determine
1462 the correct value for your kernel, boot with normal
1463 autodetection and see what value is printed. Note that
1464 on SMP systems the preset will be applied to all CPUs,
1465 which is likely to cause problems if your CPUs need
1466 significantly divergent settings. An incorrect value
1467 will cause delays in the kernel to be wrong, leading to
1468 unpredictable I/O errors and other breakage. Although
1469 unlikely, in the extreme case this might damage your
1473 Format: <io>,<irq>,<dma>
1475 machvec= [IA-64] Force the use of a particular machine-vector
1476 (machvec) in a generic kernel.
1477 Example: machvec=hpzx1_swiotlb
1479 machtype= [Loongson] Share the same kernel image file between different
1481 Example: machtype=lemote-yeeloong-2f-7inch
1483 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1484 than or equal to this physical address is ignored.
1486 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1487 should make use of. maxcpus=n : n >= 0 limits the
1488 kernel to using 'n' processors. n=0 is a special case,
1489 it is equivalent to "nosmp", which also disables
1492 max_loop= [LOOP] The number of loop block devices that get
1493 (loop.max_loop) unconditionally pre-created at init time. The default
1494 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1495 of statically allocating a predefined number, loop
1496 devices can be requested on-demand with the
1497 /dev/loop-control interface.
1499 mce [X86-32] Machine Check Exception
1501 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1503 md= [HW] RAID subsystems devices and level
1504 See Documentation/md.txt.
1507 Format: <first>,<last>
1508 Specifies range of consoles to be captured by the MDA.
1510 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1511 Amount of memory to be used when the kernel is not able
1512 to see the whole system memory or for test.
1513 [X86] Work as limiting max address. Use together
1514 with memmap= to avoid physical address space collisions.
1515 Without memmap= PCI devices could be placed at addresses
1516 belonging to unused RAM.
1518 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1522 [KNL,SH] Allow user to override the default size for
1523 per-device physically contiguous DMA buffers.
1525 memmap=exactmap [KNL,X86] Enable setting of an exact
1526 E820 memory map, as specified by the user.
1527 Such memmap=exactmap lines can be constructed based on
1528 BIOS output or other requirements. See the memmap=nn@ss
1531 memmap=nn[KMG]@ss[KMG]
1532 [KNL] Force usage of a specific region of memory
1533 Region of memory to be used, from ss to ss+nn.
1535 memmap=nn[KMG]#ss[KMG]
1536 [KNL,ACPI] Mark specific memory as ACPI data.
1537 Region of memory to be used, from ss to ss+nn.
1539 memmap=nn[KMG]$ss[KMG]
1540 [KNL,ACPI] Mark specific memory as reserved.
1541 Region of memory to be used, from ss to ss+nn.
1542 Example: Exclude memory from 0x18690000-0x1869ffff
1543 memmap=64K$0x18690000
1545 memmap=0x10000$0x18690000
1547 memory_corruption_check=0/1 [X86]
1548 Some BIOSes seem to corrupt the first 64k of
1549 memory when doing things like suspend/resume.
1550 Setting this option will scan the memory
1551 looking for corruption. Enabling this will
1552 both detect corruption and prevent the kernel
1553 from using the memory being corrupted.
1554 However, its intended as a diagnostic tool; if
1555 repeatable BIOS-originated corruption always
1556 affects the same memory, you can use memmap=
1557 to prevent the kernel from using that memory.
1559 memory_corruption_check_size=size [X86]
1560 By default it checks for corruption in the low
1561 64k, making this memory unavailable for normal
1562 use. Use this parameter to scan for
1563 corruption in more or less memory.
1565 memory_corruption_check_period=seconds [X86]
1566 By default it checks for corruption every 60
1567 seconds. Use this parameter to check at some
1568 other rate. 0 disables periodic checking.
1570 memtest= [KNL,X86] Enable memtest
1572 default : 0 <disable>
1573 Specifies the number of memtest passes to be
1574 performed. Each pass selects another test
1575 pattern from a given set of patterns. Memtest
1576 fills the memory with this pattern, validates
1577 memory contents and reserves bad memory
1578 regions that are detected.
1580 meye.*= [HW] Set MotionEye Camera parameters
1581 See Documentation/video4linux/meye.txt.
1583 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1584 Multi-Function General Purpose Timers on AMD Geode
1587 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1588 the BIOS has incorrectly applied a workaround. TinyBIOS
1589 version 0.98 is known to be affected, 0.99 fixes the
1590 problem by letting the user disable the workaround.
1594 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1595 physical address is ignored.
1597 mini2440= [ARM,HW,KNL]
1598 Format:[0..2][b][c][t]
1600 MINI2440 configuration specification:
1601 0 - The attached screen is the 3.5" TFT
1602 1 - The attached screen is the 7" TFT
1603 2 - The VGA Shield is attached (1024x768)
1604 Leaving out the screen size parameter will not load
1605 the TFT driver, and the framebuffer will be left
1607 b - Enable backlight. The TFT backlight pin will be
1608 linked to the kernel VESA blanking code and a GPIO
1609 LED. This parameter is not necessary when using the
1611 c - Enable the s3c camera interface.
1612 t - Reserved for enabling touchscreen support. The
1613 touchscreen support is not enabled in the mainstream
1614 kernel as of 2.6.30, a preliminary port can be found
1615 in the "bleeding edge" mini2440 support kernel at
1616 http://repo.or.cz/w/linux-2.6/mini2440.git
1619 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1620 parameter allows control of the logging verbosity for
1621 the additional memory initialisation checks. A value
1622 of 0 disables mminit logging and a level of 4 will
1623 log everything. Information is printed at KERN_DEBUG
1624 so loglevel=8 may also need to be specified.
1627 [KNL] When CONFIG_MODULE_SIG is set, this means that
1628 modules without (valid) signatures will fail to load.
1629 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1630 is always true, so this option does nothing.
1633 [MOUSE] Maximum time between finger touching and
1634 leaving touchpad surface for touch to be considered
1635 a tap and be reported as a left button click (for
1636 touchpads working in absolute mode only).
1638 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1639 reporting absolute coordinates, such as tablets
1640 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1641 reporting absolute coordinates, such as tablets
1643 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1644 is similar to kernelcore except it specifies the
1645 amount of memory used for migratable allocations.
1646 If both kernelcore and movablecore is specified,
1647 then kernelcore will be at *least* the specified
1648 value but may be more. If movablecore on its own
1649 is specified, the administrator must be careful
1650 that the amount of memory usable for all allocations
1653 MTD_Partition= [MTD]
1654 Format: <name>,<region-number>,<size>,<offset>
1656 MTD_Region= [MTD] Format:
1657 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1660 See drivers/mtd/cmdlinepart.c.
1662 multitce=off [PPC] This parameter disables the use of the pSeries
1663 firmware feature for updating multiple TCE entries
1666 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1668 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1670 boundary - index of last SLC block on Flex-OneNAND.
1671 The remaining blocks are configured as MLC blocks.
1672 lock - Configure if Flex-OneNAND boundary should be locked.
1673 Once locked, the boundary cannot be changed.
1674 1 indicates lock status, 0 indicates unlock status.
1677 ARM/S3C2412 JIVE boot control
1679 See arch/arm/mach-s3c2412/mach-jive.c
1681 mtouchusb.raw_coordinates=
1682 [HW] Make the MicroTouch USB driver use raw coordinates
1683 ('y', default) or cooked coordinates ('n')
1685 mtrr_chunk_size=nn[KMG] [X86]
1686 used for mtrr cleanup. It is largest continuous chunk
1687 that could hold holes aka. UC entries.
1689 mtrr_gran_size=nn[KMG] [X86]
1690 Used for mtrr cleanup. It is granularity of mtrr block.
1692 Large value could prevent small alignment from
1695 mtrr_spare_reg_nr=n [X86]
1697 Range: 0,7 : spare reg number
1699 Used for mtrr cleanup. It is spare mtrr entries number.
1700 Set to 2 or more if your graphical card needs more.
1702 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1704 netdev= [NET] Network devices parameters
1705 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1706 Note that mem_start is often overloaded to mean
1707 something different and driver-specific.
1708 This usage is only documented in each driver source
1712 [NETFILTER] Enable connection tracking flow accounting
1713 0 to disable accounting
1714 1 to enable accounting
1717 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1718 See Documentation/filesystems/nfs/nfsroot.txt.
1720 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1721 See Documentation/filesystems/nfs/nfsroot.txt.
1723 nfsrootdebug [NFS] enable nfsroot debugging messages.
1724 See Documentation/filesystems/nfs/nfsroot.txt.
1726 nfs.callback_tcpport=
1727 [NFS] set the TCP port on which the NFSv4 callback
1728 channel should listen.
1731 [NFS] sets the pathname to the program which is used
1732 to update the NFS client cache entries.
1734 nfs.cache_getent_timeout=
1735 [NFS] sets the timeout after which an attempt to
1736 update a cache entry is deemed to have failed.
1738 nfs.idmap_cache_timeout=
1739 [NFS] set the maximum lifetime for idmapper cache
1743 [NFS] enable 64-bit inode numbers.
1744 If zero, the NFS client will fake up a 32-bit inode
1745 number for the readdir() and stat() syscalls instead
1746 of returning the full 64-bit number.
1747 The default is to return 64-bit inode numbers.
1749 nfs.max_session_slots=
1750 [NFSv4.1] Sets the maximum number of session slots
1751 the client will attempt to negotiate with the server.
1752 This limits the number of simultaneous RPC requests
1753 that the client can send to the NFSv4.1 server.
1754 Note that there is little point in setting this
1755 value higher than the max_tcp_slot_table_limit.
1757 nfs.nfs4_disable_idmapping=
1758 [NFSv4] When set to the default of '1', this option
1759 ensures that both the RPC level authentication
1760 scheme and the NFS level operations agree to use
1761 numeric uids/gids if the mount is using the
1762 'sec=sys' security flavour. In effect it is
1763 disabling idmapping, which can make migration from
1764 legacy NFSv2/v3 systems to NFSv4 easier.
1765 Servers that do not support this mode of operation
1766 will be autodetected by the client, and it will fall
1767 back to using the idmapper.
1768 To turn off this behaviour, set the value to '0'.
1770 [NFS4] Specify an additional fixed unique ident-
1771 ification string that NFSv4 clients can insert into
1772 their nfs_client_id4 string. This is typically a
1773 UUID that is generated at system install time.
1775 nfs.send_implementation_id =
1776 [NFSv4.1] Send client implementation identification
1777 information in exchange_id requests.
1778 If zero, no implementation identification information
1780 The default is to send the implementation identification
1783 nfsd.nfs4_disable_idmapping=
1784 [NFSv4] When set to the default of '1', the NFSv4
1785 server will return only numeric uids and gids to
1786 clients using auth_sys, and will accept numeric uids
1787 and gids from such clients. This is intended to ease
1788 migration from NFSv2/v3.
1790 objlayoutdriver.osd_login_prog=
1791 [NFS] [OBJLAYOUT] sets the pathname to the program which
1792 is used to automatically discover and login into new
1793 osd-targets. Please see:
1794 Documentation/filesystems/pnfs.txt for more explanations
1796 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1797 when a NMI is triggered.
1798 Format: [state][,regs][,debounce][,die]
1800 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1801 Format: [panic,][nopanic,][num]
1803 0 - turn nmi_watchdog off
1804 When panic is specified, panic when an NMI watchdog
1805 timeout occurs (or 'nopanic' to override the opposite
1807 This is useful when you use a panic=... timeout and
1808 need the box quickly up again.
1810 netpoll.carrier_timeout=
1811 [NET] Specifies amount of time (in seconds) that
1812 netpoll should wait for a carrier. By default netpoll
1815 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1816 emulation library even if a 387 maths coprocessor
1820 [HW] Never suspend the console
1821 Disable suspending of consoles during suspend and
1822 hibernate operations. Once disabled, debugging
1823 messages can reach various consoles while the rest
1824 of the system is being put to sleep (ie, while
1825 debugging driver suspend/resume hooks). This may
1826 not work reliably with all consoles, but is known
1827 to work with serial and VGA consoles.
1828 To facilitate more flexible debugging, we also add
1829 console_suspend, a printk module parameter to control
1830 it. Users could use console_suspend (usually
1831 /sys/module/printk/parameters/console_suspend) to
1832 turn on/off it dynamically.
1834 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1835 caches in the slab allocator. Saves per-node memory,
1836 but will impact performance.
1840 noapic [SMP,APIC] Tells the kernel to not make use of any
1841 IOAPICs that may be present in the system.
1843 noautogroup Disable scheduler automatic task group creation.
1845 nobats [PPC] Do not use BATs for mapping kernel lowmem
1846 on "Classic" PPC cores.
1850 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1852 nodelayacct [KNL] Disable per-task delay accounting
1854 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1856 nodsp [SH] Disable hardware DSP at boot time.
1858 noefi [X86] Disable EFI runtime services support.
1863 On X86-32 available only on PAE configured kernels.
1864 noexec=on: enable non-executable mappings (default)
1865 noexec=off: disable non-executable mappings
1868 Disable SMAP (Supervisor Mode Access Prevention)
1869 even if it is supported by processor.
1872 Disable SMEP (Supervisor Mode Execution Prevention)
1873 even if it is supported by processor.
1876 This affects only 32-bit executables.
1877 noexec32=on: enable non-executable mappings (default)
1878 read doesn't imply executable mappings
1879 noexec32=off: disable non-executable mappings
1880 read implies executable mappings
1882 nofpu [SH] Disable hardware FPU at boot time.
1884 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1885 register save and restore. The kernel will only save
1886 legacy floating-point registers on task switch.
1888 noxsave [BUGS=X86] Disables x86 extended register state save
1889 and restore using xsave. The kernel will fallback to
1890 enabling legacy floating-point and sse state.
1893 on enable eager fpu restore
1894 off disable eager fpu restore
1895 auto selects the default scheme, which automatically
1896 enables eagerfpu restore for xsaveopt.
1898 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1899 wfi(ARM) instruction doesn't work correctly and not to
1900 use it. This is also useful when using JTAG debugger.
1902 no_file_caps Tells the kernel not to honor file capabilities. The
1903 only way then for a file to be executed with privilege
1904 is to be setuid root or executed by root.
1906 nohalt [IA-64] Tells the kernel not to use the power saving
1907 function PAL_HALT_LIGHT when idle. This increases
1908 power-consumption. On the positive side, it reduces
1909 interrupt wake-up latency, which may improve performance
1910 in certain environments such as networked servers or
1913 nohz= [KNL] Boottime enable/disable dynamic ticks
1914 Valid arguments: on, off
1917 noiotrap [SH] Disables trapped I/O port accesses.
1919 noirqdebug [X86-32] Disables the code which attempts to detect and
1920 disable unhandled interrupt sources.
1922 no_timer_check [X86,APIC] Disables the code which tests for
1923 broken timer IRQ sources.
1925 noisapnp [ISAPNP] Disables ISA PnP code.
1927 noinitrd [RAM] Tells the kernel not to load any configured
1930 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1932 [Deprecated - use intremap=off]
1936 nojitter [IA-64] Disables jitter checking for ITC timers.
1938 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1940 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1943 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1944 steal time is computed, but won't influence scheduler
1947 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1949 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1951 noltlbs [PPC] Do not use large page/tlb entries for kernel
1952 lowmem mapping on PPC40x.
1954 nomca [IA-64] Disable machine check abort handling
1956 nomce [X86-32] Machine Check Exception
1958 nomfgpt [X86-32] Disable Multi-Function General Purpose
1959 Timer usage (for AMD Geode machines).
1961 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1962 shutdown the other cpus. Instead use the REBOOT_VECTOR
1965 nomodule Disable module load
1967 nopat [X86] Disable PAT (page attribute table extension of
1968 pagetables) support.
1970 norandmaps Don't use address space randomization. Equivalent to
1971 echo 0 > /proc/sys/kernel/randomize_va_space
1973 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1975 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1976 with UP alternatives
1978 noresidual [PPC] Don't use residual data on PReP machines.
1980 nordrand [X86] Disable the direct use of the RDRAND
1981 instruction even if it is supported by the
1982 processor. RDRAND is still available to user
1985 noresume [SWSUSP] Disables resume and restores original swap
1988 no-scroll [VGA] Disables scrollback.
1989 This is required for the Braillex ib80-piezo Braille
1990 reader made by F.H. Papenmeier (Germany).
1994 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1996 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1997 and disable the IO APIC. legacy for "maxcpus=0".
1999 nosoftlockup [KNL] Disable the soft-lockup detector.
2001 nosync [HW,M68K] Disables sync negotiation for all devices.
2003 notsc [BUGS=X86-32] Disable Time Stamp Counter
2005 nousb [USB] Disable the USB subsystem
2007 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2011 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2013 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2014 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2015 Some features depend on CPU0. Known dependencies are:
2016 1. Resume from suspend/hibernate depends on CPU0.
2017 Suspend/hibernate will fail if CPU0 is offline and you
2018 need to online CPU0 before suspend/hibernate.
2019 2. PIC interrupts also depend on CPU0. CPU0 can't be
2020 removed if a PIC interrupt is detected.
2021 It's said poweroff/reboot may depend on CPU0 on some
2022 machines although I haven't seen such issues so far
2023 after CPU0 is offline on a few tested machines.
2024 If the dependencies are under your control, you can
2025 turn on cpu0_hotplug.
2027 nptcg= [IA-64] Override max number of concurrent global TLB
2028 purges which is reported from either PAL_VM_SUMMARY or
2031 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2032 could support. nr_cpus=n : n >= 1 limits the kernel to
2033 supporting 'n' processors. Later in runtime you can not
2034 use hotplug cpu feature to put more cpu back to online.
2035 just like you compile the kernel NR_CPUS=n
2037 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2039 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2040 Allowed values are enable and disable
2042 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2043 one of ['zone', 'node', 'default'] can be specified
2044 This can be set from sysctl after boot.
2045 See Documentation/sysctl/vm.txt for details.
2047 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2048 See Documentation/debugging-via-ohci1394.txt for more
2051 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2052 Rather than timing out after 20 ms if an EC
2053 command is not properly ACKed, override the length
2054 of the timeout. We have interrupts disabled while
2055 waiting for the ACK, so if this is set too high
2056 interrupts *may* be lost!
2058 omap_mux= [OMAP] Override bootloader pin multiplexing.
2059 Format: <mux_mode0.mode_name=value>...
2060 For example, to override I2C bus2:
2061 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2063 oprofile.timer= [HW]
2064 Use timer interrupt instead of performance counters
2066 oprofile.cpu_type= Force an oprofile cpu type
2067 This might be useful if you have an older oprofile
2068 userland or if you want common events.
2069 Format: { arch_perfmon }
2070 arch_perfmon: [X86] Force use of architectural
2071 perfmon on Intel CPUs instead of the
2072 CPU specific event set.
2073 timer: [X86] Force use of architectural NMI
2074 timer mode (see also oprofile.timer
2075 for generic hr timer mode)
2076 [s390] Force legacy basic mode sampling
2077 (report cpu_type "timer")
2079 oops=panic Always panic on oopses. Default is to just kill the
2080 process, but there is a small probability of
2081 deadlocking the machine.
2082 This will also cause panics on machine check exceptions.
2083 Useful together with panic=30 to trigger a reboot.
2086 See Documentation/sound/oss/oss-parameters.txt
2088 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2089 timeout > 0: seconds before rebooting
2090 timeout = 0: wait forever
2091 timeout < 0: reboot immediately
2094 parkbd.port= [HW] Parallel port number the keyboard adapter is
2095 connected to, default is 0.
2097 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2098 0 for XT, 1 for AT (default is AT).
2101 parport= [HW,PPT] Specify parallel ports. 0 disables.
2102 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2103 Use 'auto' to force the driver to use any
2104 IRQ/DMA settings detected (the default is to
2105 ignore detected IRQ/DMA settings because of
2106 possible conflicts). You can specify the base
2107 address, IRQ, and DMA settings; IRQ and DMA
2108 should be numbers, or 'auto' (for using detected
2109 settings on that particular port), or 'nofifo'
2110 (to avoid using a FIFO even if it is detected).
2111 Parallel ports are assigned in the order they
2112 are specified on the command line, starting
2115 parport_init_mode= [HW,PPT]
2116 Configure VIA parallel port to operate in
2117 a specific mode. This is necessary on Pegasos
2118 computer where firmware has no options for setting
2119 up parallel port mode and sets it to spp.
2120 Currently this function knows 686a and 8231 chips.
2121 Format: [spp|ps2|epp|ecp|ecpepp]
2124 Halt all CPUs after the first oops has been printed for
2125 the specified number of seconds. This is to be used if
2126 your oopses keep scrolling off the screen.
2131 See header of drivers/block/paride/pcd.c.
2132 See also Documentation/blockdev/paride.txt.
2134 pci=option[,option...] [PCI] various PCI subsystem options:
2135 earlydump [X86] dump PCI config space before the kernel
2137 off [X86] don't probe for the PCI bus
2138 bios [X86-32] force use of PCI BIOS, don't access
2139 the hardware directly. Use this if your machine
2140 has a non-standard PCI host bridge.
2141 nobios [X86-32] disallow use of PCI BIOS, only direct
2142 hardware access methods are allowed. Use this
2143 if you experience crashes upon bootup and you
2144 suspect they are caused by the BIOS.
2145 conf1 [X86] Force use of PCI Configuration
2147 conf2 [X86] Force use of PCI Configuration
2149 noaer [PCIE] If the PCIEAER kernel config parameter is
2150 enabled, this kernel boot option can be used to
2151 disable the use of PCIE advanced error reporting.
2152 nodomains [PCI] Disable support for multiple PCI
2153 root domains (aka PCI segments, in ACPI-speak).
2154 nommconf [X86] Disable use of MMCONFIG for PCI
2156 check_enable_amd_mmconf [X86] check for and enable
2157 properly configured MMIO access to PCI
2158 config space on AMD family 10h CPU
2159 nomsi [MSI] If the PCI_MSI kernel config parameter is
2160 enabled, this kernel boot option can be used to
2161 disable the use of MSI interrupts system-wide.
2162 noioapicquirk [APIC] Disable all boot interrupt quirks.
2163 Safety option to keep boot IRQs enabled. This
2164 should never be necessary.
2165 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2166 primary IO-APIC for bridges that cannot disable
2167 boot IRQs. This fixes a source of spurious IRQs
2168 when the system masks IRQs.
2169 noioapicreroute [APIC] Disable workaround that uses the
2170 boot IRQ equivalent of an IRQ that connects to
2171 a chipset where boot IRQs cannot be disabled.
2172 The opposite of ioapicreroute.
2173 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2174 routing table. These calls are known to be buggy
2175 on several machines and they hang the machine
2176 when used, but on other computers it's the only
2177 way to get the interrupt routing table. Try
2178 this option if the kernel is unable to allocate
2179 IRQs or discover secondary PCI buses on your
2181 rom [X86] Assign address space to expansion ROMs.
2182 Use with caution as certain devices share
2183 address decoders between ROMs and other
2185 norom [X86] Do not assign address space to
2186 expansion ROMs that do not already have
2187 BIOS assigned address ranges.
2188 nobar [X86] Do not assign address space to the
2189 BARs that weren't assigned by the BIOS.
2190 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2191 assigned automatically to PCI devices. You can
2192 make the kernel exclude IRQs of your ISA cards
2194 pirqaddr=0xAAAAA [X86] Specify the physical address
2195 of the PIRQ table (normally generated
2196 by the BIOS) if it is outside the
2197 F0000h-100000h range.
2198 lastbus=N [X86] Scan all buses thru bus #N. Can be
2199 useful if the kernel is unable to find your
2200 secondary buses and you want to tell it
2201 explicitly which ones they are.
2202 assign-busses [X86] Always assign all PCI bus
2203 numbers ourselves, overriding
2204 whatever the firmware may have done.
2205 usepirqmask [X86] Honor the possible IRQ mask stored
2206 in the BIOS $PIR table. This is needed on
2207 some systems with broken BIOSes, notably
2208 some HP Pavilion N5400 and Omnibook XE3
2209 notebooks. This will have no effect if ACPI
2210 IRQ routing is enabled.
2211 noacpi [X86] Do not use ACPI for IRQ routing
2212 or for PCI scanning.
2213 use_crs [X86] Use PCI host bridge window information
2214 from ACPI. On BIOSes from 2008 or later, this
2215 is enabled by default. If you need to use this,
2216 please report a bug.
2217 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2218 If you need to use this, please report a bug.
2219 routeirq Do IRQ routing for all PCI devices.
2220 This is normally done in pci_enable_device(),
2221 so this option is a temporary workaround
2222 for broken drivers that don't call it.
2223 skip_isa_align [X86] do not align io start addr, so can
2224 handle more pci cards
2225 firmware [ARM] Do not re-enumerate the bus but instead
2226 just use the configuration from the
2227 bootloader. This is currently used on
2228 IXP2000 systems where the bus has to be
2229 configured a certain way for adjunct CPUs.
2230 noearly [X86] Don't do any early type 1 scanning.
2231 This might help on some broken boards which
2232 machine check when some devices' config space
2233 is read. But various workarounds are disabled
2234 and some IOMMU drivers will not work.
2235 bfsort Sort PCI devices into breadth-first order.
2236 This sorting is done to get a device
2237 order compatible with older (<= 2.4) kernels.
2238 nobfsort Don't sort PCI devices into breadth-first order.
2239 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2240 tuning and use the BIOS-configured MPS defaults.
2241 pcie_bus_safe Set every device's MPS to the largest value
2242 supported by all devices below the root complex.
2243 pcie_bus_perf Set device MPS to the largest allowable MPS
2244 based on its parent bus. Also set MRRS (Max
2245 Read Request Size) to the largest supported
2246 value (no larger than the MPS that the device
2247 or bus can support) for best performance.
2248 pcie_bus_peer2peer Set every device's MPS to 128B, which
2249 every device is guaranteed to support. This
2250 configuration allows peer-to-peer DMA between
2251 any pair of devices, possibly at the cost of
2252 reduced performance. This also guarantees
2253 that hot-added devices will work.
2254 cbiosize=nn[KMG] The fixed amount of bus space which is
2255 reserved for the CardBus bridge's IO window.
2256 The default value is 256 bytes.
2257 cbmemsize=nn[KMG] The fixed amount of bus space which is
2258 reserved for the CardBus bridge's memory
2259 window. The default value is 64 megabytes.
2262 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2263 Specifies alignment and device to reassign
2264 aligned memory resources.
2265 If <order of align> is not specified,
2266 PAGE_SIZE is used as alignment.
2267 PCI-PCI bridge can be specified, if resource
2268 windows need to be expanded.
2269 ecrc= Enable/disable PCIe ECRC (transaction layer
2270 end-to-end CRC checking).
2271 bios: Use BIOS/firmware settings. This is the
2275 hpiosize=nn[KMG] The fixed amount of bus space which is
2276 reserved for hotplug bridge's IO window.
2277 Default size is 256 bytes.
2278 hpmemsize=nn[KMG] The fixed amount of bus space which is
2279 reserved for hotplug bridge's memory window.
2280 Default size is 2 megabytes.
2281 realloc= Enable/disable reallocating PCI bridge resources
2282 if allocations done by BIOS are too small to
2283 accommodate resources required by all child
2285 off: Turn realloc off
2287 realloc same as realloc=on
2288 noari do not use PCIe ARI.
2289 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2290 only look for one device below a PCIe downstream
2293 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2296 force Enable ASPM even on devices that claim not to support it.
2297 WARNING: Forcing ASPM on may cause system lockups.
2299 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2300 nomsi Do not use MSI for PCI Express Native Hotplug (this
2301 makes all PCIe ports use INTx for hotplug services).
2303 pcie_ports= [PCIE] PCIe ports handling:
2304 auto Ask the BIOS whether or not to use native PCIe services
2305 associated with PCIe ports (PME, hot-plug, AER). Use
2306 them only if that is allowed by the BIOS.
2307 native Use native PCIe services associated with PCIe ports
2309 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2312 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2313 nomsi Do not use MSI for native PCIe PME signaling (this makes
2314 all PCIe root ports use INTx for all services).
2316 pcmv= [HW,PCMCIA] BadgePAD 4
2319 See Documentation/blockdev/paride.txt.
2321 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2324 See arch/parisc/kernel/pdc_chassis.c
2326 percpu_alloc= Select which percpu first chunk allocator to use.
2327 Currently supported values are "embed" and "page".
2328 Archs may support subset or none of the selections.
2329 See comments in mm/percpu.c for details on each
2330 allocator. This parameter is primarily for debugging
2331 and performance comparison.
2334 See Documentation/blockdev/paride.txt.
2337 See Documentation/blockdev/paride.txt.
2339 pirq= [SMP,APIC] Manual mp-table setup
2340 See Documentation/x86/i386/IO-APIC.txt.
2342 plip= [PPT,NET] Parallel port network link
2343 Format: { parport<nr> | timid | 0 }
2344 See also Documentation/parport.txt.
2346 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2347 Override pmtimer IOPort with a hex value.
2351 Enable PNP debug messages (depends on the
2352 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2353 via /sys/module/pnp/parameters/debug. We always show
2354 current resource usage; turning this on also shows
2355 possible settings and some assignment information.
2361 { on | off | curr | res | no-curr | no-res }
2364 [ISAPNP] Exclude IRQs for the autoconfiguration
2367 [ISAPNP] Exclude DMAs for the autoconfiguration
2369 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2370 Ranges are in pairs (I/O port base and size).
2373 [ISAPNP] Exclude memory regions for the
2375 Ranges are in pairs (memory base and size).
2377 ports= [IP_VS_FTP] IPVS ftp helper module
2379 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2381 Format: <port>,<port>....
2383 print-fatal-signals=
2384 [KNL] debug: print fatal signals
2386 If enabled, warn about various signal handling
2387 related application anomalies: too many signals,
2388 too many POSIX.1 timers, fatal signals causing a
2391 If you hit the warning due to signal overflow,
2392 you might want to try "ulimit -i unlimited".
2396 printk.always_kmsg_dump=
2397 Trigger kmsg_dump for cases other than kernel oops or
2399 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2402 printk.time= Show timing data prefixed to each printk message line
2403 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2405 processor.max_cstate= [HW,ACPI]
2406 Limit processor to maximum C-state
2407 max_cstate=9 overrides any DMI blacklist limit.
2409 processor.nocst [HW,ACPI]
2410 Ignore the _CST method to determine C-states,
2411 instead using the legacy FADT method
2413 profile= [KNL] Enable kernel profiling via /proc/profile
2414 Format: [schedule,]<number>
2415 Param: "schedule" - profile schedule points.
2416 Param: <number> - step/bucket size as a power of 2 for
2417 statistical time based profiling.
2418 Param: "sleep" - profile D-state sleeping (millisecs).
2419 Requires CONFIG_SCHEDSTATS
2420 Param: "kvm" - profile VM exits.
2422 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2424 See Documentation/blockdev/ramdisk.txt.
2426 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2427 probe for; one of (bare|imps|exps|lifebook|any).
2428 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2430 psmouse.resetafter= [HW,MOUSE]
2431 Try to reset the device after so many bad packets
2434 [HW,MOUSE] Set desired mouse resolution, in dpi.
2435 psmouse.smartscroll=
2436 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2437 0 = disabled, 1 = enabled (default).
2439 pstore.backend= Specify the name of the pstore backend to use
2442 See Documentation/blockdev/paride.txt.
2445 [KNL] Number of legacy pty's. Overwrites compiled-in
2448 quiet [KNL] Disable most log messages
2453 See Documentation/md.txt.
2455 ramdisk_blocksize= [RAM]
2456 See Documentation/blockdev/ramdisk.txt.
2458 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2459 See Documentation/blockdev/ramdisk.txt.
2461 rcu_nocbs= [KNL,BOOT]
2462 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2463 the specified list of CPUs to be no-callback CPUs.
2464 Invocation of these CPUs' RCU callbacks will
2465 be offloaded to "rcuoN" kthreads created for
2466 that purpose. This reduces OS jitter on the
2467 offloaded CPUs, which can be useful for HPC and
2468 real-time workloads. It can also improve energy
2469 efficiency for asymmetric multiprocessors.
2471 rcu_nocb_poll [KNL,BOOT]
2472 Rather than requiring that offloaded CPUs
2473 (specified by rcu_nocbs= above) explicitly
2474 awaken the corresponding "rcuoN" kthreads,
2475 make these kthreads poll for callbacks.
2476 This improves the real-time response for the
2477 offloaded CPUs by relieving them of the need to
2478 wake up the corresponding kthread, but degrades
2479 energy efficiency by requiring that the kthreads
2480 periodically wake up to do the polling.
2482 rcutree.blimit= [KNL,BOOT]
2483 Set maximum number of finished RCU callbacks to process
2486 rcutree.fanout_leaf= [KNL,BOOT]
2487 Increase the number of CPUs assigned to each
2488 leaf rcu_node structure. Useful for very large
2491 rcutree.qhimark= [KNL,BOOT]
2492 Set threshold of queued
2493 RCU callbacks over which batch limiting is disabled.
2495 rcutree.qlowmark= [KNL,BOOT]
2496 Set threshold of queued RCU callbacks below which
2497 batch limiting is re-enabled.
2499 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2500 Suppress RCU CPU stall warning messages.
2502 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2503 Set timeout for RCU CPU stall warning messages.
2505 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2506 Set delay from grace-period initialization to
2507 first attempt to force quiescent states.
2508 Units are jiffies, minimum value is zero,
2509 and maximum value is HZ.
2511 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2512 Set delay between subsequent attempts to force
2513 quiescent states. Units are jiffies, minimum
2514 value is one, and maximum value is HZ.
2516 rcutorture.fqs_duration= [KNL,BOOT]
2517 Set duration of force_quiescent_state bursts.
2519 rcutorture.fqs_holdoff= [KNL,BOOT]
2520 Set holdoff time within force_quiescent_state bursts.
2522 rcutorture.fqs_stutter= [KNL,BOOT]
2523 Set wait time between force_quiescent_state bursts.
2525 rcutorture.irqreader= [KNL,BOOT]
2526 Test RCU readers from irq handlers.
2528 rcutorture.n_barrier_cbs= [KNL,BOOT]
2529 Set callbacks/threads for rcu_barrier() testing.
2531 rcutorture.nfakewriters= [KNL,BOOT]
2532 Set number of concurrent RCU writers. These just
2533 stress RCU, they don't participate in the actual
2534 test, hence the "fake".
2536 rcutorture.nreaders= [KNL,BOOT]
2537 Set number of RCU readers.
2539 rcutorture.onoff_holdoff= [KNL,BOOT]
2540 Set time (s) after boot for CPU-hotplug testing.
2542 rcutorture.onoff_interval= [KNL,BOOT]
2543 Set time (s) between CPU-hotplug operations, or
2544 zero to disable CPU-hotplug testing.
2546 rcutorture.shuffle_interval= [KNL,BOOT]
2547 Set task-shuffle interval (s). Shuffling tasks
2548 allows some CPUs to go into dyntick-idle mode
2549 during the rcutorture test.
2551 rcutorture.shutdown_secs= [KNL,BOOT]
2552 Set time (s) after boot system shutdown. This
2553 is useful for hands-off automated testing.
2555 rcutorture.stall_cpu= [KNL,BOOT]
2556 Duration of CPU stall (s) to test RCU CPU stall
2557 warnings, zero to disable.
2559 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2560 Time to wait (s) after boot before inducing stall.
2562 rcutorture.stat_interval= [KNL,BOOT]
2563 Time (s) between statistics printk()s.
2565 rcutorture.stutter= [KNL,BOOT]
2566 Time (s) to stutter testing, for example, specifying
2567 five seconds causes the test to run for five seconds,
2568 wait for five seconds, and so on. This tests RCU's
2569 ability to transition abruptly to and from idle.
2571 rcutorture.test_boost= [KNL,BOOT]
2572 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2573 "Maybe" means test if the RCU implementation
2574 under test support RCU priority boosting.
2576 rcutorture.test_boost_duration= [KNL,BOOT]
2577 Duration (s) of each individual boost test.
2579 rcutorture.test_boost_interval= [KNL,BOOT]
2580 Interval (s) between each boost test.
2582 rcutorture.test_no_idle_hz= [KNL,BOOT]
2583 Test RCU's dyntick-idle handling. See also the
2584 rcutorture.shuffle_interval parameter.
2586 rcutorture.torture_type= [KNL,BOOT]
2587 Specify the RCU implementation to test.
2589 rcutorture.verbose= [KNL,BOOT]
2590 Enable additional printk() statements.
2594 Run specified binary instead of /init from the ramdisk,
2595 used for early userspace startup. See initrd.
2597 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2598 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2599 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2602 [KNL, SMP] Set scheduler's default relax_domain_level.
2603 See Documentation/cgroups/cpusets.txt.
2605 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2607 reservetop= [X86-32]
2609 Reserves a hole at the top of the kernel virtual
2614 Set the amount of memory to reserve for BIOS at
2615 the bottom of the address space.
2617 reset_devices [KNL] Force drivers to reset the underlying device
2618 during initialization.
2621 Specify the partition device for software suspend
2623 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2625 resume_offset= [SWSUSP]
2626 Specify the offset from the beginning of the partition
2627 given by "resume=" at which the swap header is located,
2628 in <PAGE_SIZE> units (needed only for swap files).
2629 See Documentation/power/swsusp-and-swap-files.txt
2631 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2632 read the resume files
2634 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2635 Useful for devices that are detected asynchronously
2636 (e.g. USB and MMC devices).
2638 hibernate= [HIBERNATION]
2639 noresume Don't check if there's a hibernation image
2640 present during boot.
2641 nocompress Don't compress/decompress hibernation images.
2643 retain_initrd [RAM] Keep initrd memory after extraction
2645 rhash_entries= [KNL,NET]
2646 Set number of hash buckets for route cache
2648 riscom8= [HW,SERIAL]
2649 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2651 ro [KNL] Mount root device read-only on boot
2653 root= [KNL] Root filesystem
2654 See name_to_dev_t comment in init/do_mounts.c.
2656 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2657 mount the root filesystem
2659 rootflags= [KNL] Set root filesystem mount option string
2661 rootfstype= [KNL] Set root filesystem type
2663 rootwait [KNL] Wait (indefinitely) for root device to show up.
2664 Useful for devices that are detected asynchronously
2665 (e.g. USB and MMC devices).
2667 rproc_mem=nn[KMG][@address]
2668 [KNL,ARM,CMA] Remoteproc physical memory block.
2669 Memory area to be used by remote processor image,
2672 rw [KNL] Mount root device read-write on boot
2674 S [KNL] Run init in single mode
2677 See drivers/net/irda/sa1100_ir.c.
2679 sbni= [NET] Granch SBNI12 leased line adapter
2681 sched_debug [KNL] Enables verbose scheduler debug messages.
2683 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2684 xtime_lock contention on larger systems, and/or RCU lock
2685 contention on all systems with CONFIG_MAXSMP set.
2686 Format: { "0" | "1" }
2687 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2689 Note: increases power consumption, thus should only be
2690 enabled if running jitter sensitive (HPC/RT) workloads.
2692 security= [SECURITY] Choose a security module to enable at boot.
2693 If this boot parameter is not specified, only the first
2694 security module asking for security registration will be
2695 loaded. An invalid security module name will be treated
2696 as if no module has been chosen.
2698 selinux= [SELINUX] Disable or enable SELinux at boot time.
2699 Format: { "0" | "1" }
2700 See security/selinux/Kconfig help text.
2703 Default value is set via kernel config option.
2704 If enabled at boot time, /selinux/disable can be used
2705 later to disable prior to initial policy load.
2707 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2708 Format: { "0" | "1" }
2709 See security/apparmor/Kconfig help text
2712 Default value is set via kernel config option.
2714 serialnumber [BUGS=X86-32]
2717 Maximal number of shapers.
2719 show_msr= [x86] show boot-time MSR settings
2720 Format: { <integer> }
2721 Show boot-time (BIOS-initialized) MSR settings.
2722 The parameter means the number of CPUs to show,
2723 for example 1 means boot CPU only.
2730 slab_max_order= [MM, SLAB]
2731 Determines the maximum allowed order for slabs.
2732 A high setting may cause OOMs due to memory
2733 fragmentation. Defaults to 1 for systems with
2734 more than 32MB of RAM, 0 otherwise.
2736 slub_debug[=options[,slabs]] [MM, SLUB]
2737 Enabling slub_debug allows one to determine the
2738 culprit if slab objects become corrupted. Enabling
2739 slub_debug can create guard zones around objects and
2740 may poison objects when not in use. Also tracks the
2741 last alloc / free. For more information see
2742 Documentation/vm/slub.txt.
2744 slub_max_order= [MM, SLUB]
2745 Determines the maximum allowed order for slabs.
2746 A high setting may cause OOMs due to memory
2747 fragmentation. For more information see
2748 Documentation/vm/slub.txt.
2750 slub_min_objects= [MM, SLUB]
2751 The minimum number of objects per slab. SLUB will
2752 increase the slab order up to slub_max_order to
2753 generate a sufficiently large slab able to contain
2754 the number of objects indicated. The higher the number
2755 of objects the smaller the overhead of tracking slabs
2756 and the less frequently locks need to be acquired.
2757 For more information see Documentation/vm/slub.txt.
2759 slub_min_order= [MM, SLUB]
2760 Determines the minimum page order for slabs. Must be
2761 lower than slub_max_order.
2762 For more information see Documentation/vm/slub.txt.
2764 slub_nomerge [MM, SLUB]
2765 Disable merging of slabs with similar size. May be
2766 necessary if there is some reason to distinguish
2767 allocs to different slabs. Debug options disable
2768 merging on their own.
2769 For more information see Documentation/vm/slub.txt.
2772 Format: <io1>[,<io2>[,...,<io8>]]
2774 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2775 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2776 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2777 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2778 smsc-ircc2.ircc_irq= [HW] IRQ line
2779 smsc-ircc2.ircc_dma= [HW] DMA channel
2780 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2781 0: Toshiba Satellite 1800 (GP data pin select)
2782 1: Fast pin select (default)
2786 [KNL] Should the soft-lockup detector generate panics.
2789 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2790 See Documentation/laptops/sonypi.txt
2792 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2793 See Documentation/serial/specialix.txt.
2795 spia_io_base= [HW,MTD]
2801 Enabled the stack tracer on boot up.
2803 stacktrace_filter=[function-list]
2804 [FTRACE] Limit the functions that the stack tracer
2805 will trace at boot up. function-list is a comma separated
2806 list of functions. This list can be changed at run
2807 time by the stack_trace_filter file in the debugfs
2808 tracing directory. Note, this enables stack tracing
2809 and the stacktrace above is not needed.
2813 Set the STI (builtin display/keyboard on the HP-PARISC
2814 machines) console (graphic card) which should be used
2815 as the initial boot-console.
2816 See also comment in drivers/video/console/sticore.c.
2819 See comment in drivers/video/console/sticore.c.
2822 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2824 sunrpc.min_resvport=
2825 sunrpc.max_resvport=
2827 SunRPC servers often require that client requests
2828 originate from a privileged port (i.e. a port in the
2829 range 0 < portnr < 1024).
2830 An administrator who wishes to reserve some of these
2831 ports for other uses may adjust the range that the
2832 kernel's sunrpc client considers to be privileged
2833 using these two parameters to set the minimum and
2834 maximum port values.
2838 Control how the NFS server code allocates CPUs to
2839 service thread pools. Depending on how many NICs
2840 you have and where their interrupts are bound, this
2841 option will affect which CPUs will do NFS serving.
2842 Note: this parameter cannot be changed while the
2843 NFS server is running.
2845 auto the server chooses an appropriate mode
2846 automatically using heuristics
2847 global a single global pool contains all CPUs
2848 percpu one pool for each CPU
2849 pernode one pool for each NUMA node (equivalent
2850 to global on non-NUMA machines)
2852 sunrpc.tcp_slot_table_entries=
2853 sunrpc.udp_slot_table_entries=
2855 Sets the upper limit on the number of simultaneous
2856 RPC calls that can be sent from the client to a
2857 server. Increasing these values may allow you to
2858 improve throughput, but will also increase the
2859 amount of memory reserved for use by the client.
2862 [KNL] Enable accounting of swap in memory resource
2863 controller if no parameter or 1 is given or disable
2864 it if 0 is given (See Documentation/cgroups/memory.txt)
2866 swiotlb= [IA-64] Number of I/O TLB slabs
2870 sysfs.deprecated=0|1 [KNL]
2871 Enable/disable old style sysfs layout for old udev
2872 on older distributions. When this option is enabled
2873 very new udev will not work anymore. When this option
2874 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2875 in older udev will not work anymore.
2876 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2877 the kernel configuration.
2879 sysrq_always_enabled
2881 Ignore sysrq setting - this boot parameter will
2882 neutralize any effect of /proc/sys/kernel/sysrq.
2883 Useful for debugging.
2887 test_suspend= [SUSPEND]
2888 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2889 standby suspend) as the system sleep state to briefly
2890 enter during system startup. The system is woken from
2891 this state using a wakeup-capable RTC alarm.
2893 thash_entries= [KNL,NET]
2894 Set number of hash buckets for TCP connection
2896 thermal.act= [HW,ACPI]
2897 -1: disable all active trip points in all thermal zones
2898 <degrees C>: override all lowest active trip points
2900 thermal.crt= [HW,ACPI]
2901 -1: disable all critical trip points in all thermal zones
2902 <degrees C>: override all critical trip points
2904 thermal.nocrt= [HW,ACPI]
2905 Set to disable actions on ACPI thermal zone
2906 critical and hot trip points.
2908 thermal.off= [HW,ACPI]
2909 1: disable ACPI thermal control
2911 thermal.psv= [HW,ACPI]
2912 -1: disable all passive trip points
2913 <degrees C>: override all passive trip points to this
2916 thermal.tzp= [HW,ACPI]
2917 Specify global default ACPI thermal zone polling rate
2918 <deci-seconds>: poll all this frequency
2919 0: no polling (default)
2922 Force threading of all interrupt handlers except those
2923 marked explicitly IRQF_NO_THREAD.
2927 Specify if the kernel should make use of the cpu
2928 topology information if the hardware supports this.
2929 The scheduler will make use of this information and
2930 e.g. base its process migration decisions on it.
2935 tpm_suspend_pcr=[HW,TPM]
2936 Format: integer pcr id
2937 Specify that at suspend time, the tpm driver
2938 should extend the specified pcr with zeros,
2939 as a workaround for some chips which fail to
2940 flush the last written pcr on TPM_SaveState.
2941 This will guarantee that all the other pcrs
2944 trace_buf_size=nn[KMG]
2945 [FTRACE] will set tracing buffer size.
2947 trace_event=[event-list]
2948 [FTRACE] Set and start specified trace events in order
2949 to facilitate early boot debugging.
2950 See also Documentation/trace/events.txt
2952 trace_options=[option-list]
2953 [FTRACE] Enable or disable tracer options at boot.
2954 The option-list is a comma delimited list of options
2955 that can be enabled or disabled just as if you were
2956 to echo the option name into
2958 /sys/kernel/debug/tracing/trace_options
2960 For example, to enable stacktrace option (to dump the
2961 stack trace of each event), add to the command line:
2963 trace_options=stacktrace
2965 See also Documentation/trace/ftrace.txt "trace options"
2968 transparent_hugepage=
2970 Format: [always|madvise|never]
2971 Can be used to control the default behavior of the system
2972 with respect to transparent hugepages.
2973 See Documentation/vm/transhuge.txt for more details.
2975 tsc= Disable clocksource stability checks for TSC.
2977 [x86] reliable: mark tsc clocksource as reliable, this
2978 disables clocksource verification at runtime, as well
2979 as the stability checks done at bootup. Used to enable
2980 high-resolution timer mode on older hardware, and in
2981 virtualized environment.
2982 [x86] noirqtime: Do not use TSC to do irq accounting.
2983 Used to run time disable IRQ_TIME_ACCOUNTING on any
2984 platforms where RDTSC is slow and this accounting
2987 turbografx.map[2|3]= [HW,JOY]
2988 TurboGraFX parallel port interface
2990 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2991 See also Documentation/input/joystick-parport.txt
2993 udbg-immortal [PPC] When debugging early kernel crashes that
2994 happen after console_init() and before a proper
2995 console driver takes over, this boot options might
2996 help "seeing" what's going on.
2998 uhash_entries= [KNL,NET]
2999 Set number of hash buckets for UDP/UDP-Lite connections
3002 [USB] Ignore overcurrent events (default N).
3003 Some badly-designed motherboards generate lots of
3004 bogus events, for ports that aren't wired to
3005 anything. Set this parameter to avoid log spamming.
3006 Note that genuine overcurrent events won't be
3010 [X86] Cause panic on unknown NMI.
3012 usbcore.authorized_default=
3013 [USB] Default USB device authorization:
3014 (default -1 = authorized except for wireless USB,
3015 0 = not authorized, 1 = authorized)
3017 usbcore.autosuspend=
3018 [USB] The autosuspend time delay (in seconds) used
3019 for newly-detected USB devices (default 2). This
3020 is the time required before an idle device will be
3021 autosuspended. Devices for which the delay is set
3022 to a negative value won't be autosuspended at all.
3024 usbcore.usbfs_snoop=
3025 [USB] Set to log all usbfs traffic (default 0 = off).
3027 usbcore.blinkenlights=
3028 [USB] Set to cycle leds on hubs (default 0 = off).
3030 usbcore.old_scheme_first=
3031 [USB] Start with the old device initialization
3032 scheme (default 0 = off).
3034 usbcore.usbfs_memory_mb=
3035 [USB] Memory limit (in MB) for buffers allocated by
3036 usbfs (default = 16, 0 = max = 2047).
3038 usbcore.use_both_schemes=
3039 [USB] Try the other device initialization scheme
3040 if the first one fails (default 1 = enabled).
3042 usbcore.initial_descriptor_timeout=
3043 [USB] Specifies timeout for the initial 64-byte
3044 USB_REQ_GET_DESCRIPTOR request in milliseconds
3045 (default 5000 = 5.0 seconds).
3048 [USBHID] The interval which mice are to be polled at.
3050 usb-storage.delay_use=
3051 [UMS] The delay in seconds before a new device is
3052 scanned for Logical Units (default 5).
3055 [UMS] A list of quirks entries to supplement or
3056 override the built-in unusual_devs list. List
3057 entries are separated by commas. Each entry has
3058 the form VID:PID:Flags where VID and PID are Vendor
3059 and Product ID values (4-digit hex numbers) and
3060 Flags is a set of characters, each corresponding
3061 to a common usb-storage quirk flag as follows:
3062 a = SANE_SENSE (collect more than 18 bytes
3064 b = BAD_SENSE (don't collect more than 18
3065 bytes of sense data);
3066 c = FIX_CAPACITY (decrease the reported
3067 device capacity by one sector);
3068 d = NO_READ_DISC_INFO (don't use
3069 READ_DISC_INFO command);
3070 e = NO_READ_CAPACITY_16 (don't use
3071 READ_CAPACITY_16 command);
3072 h = CAPACITY_HEURISTICS (decrease the
3073 reported device capacity by one
3074 sector if the number is odd);
3075 i = IGNORE_DEVICE (don't bind to this
3077 l = NOT_LOCKABLE (don't try to lock and
3078 unlock ejectable media);
3079 m = MAX_SECTORS_64 (don't transfer more
3080 than 64 sectors = 32 KB at a time);
3081 n = INITIAL_READ10 (force a retry of the
3082 initial READ(10) command);
3083 o = CAPACITY_OK (accept the capacity
3084 reported by the device);
3085 p = WRITE_CACHE (the device cache is ON
3087 r = IGNORE_RESIDUE (the device reports
3088 bogus residue values);
3089 s = SINGLE_LUN (the device has only one
3091 w = NO_WP_DETECT (don't test whether the
3092 medium is write-protected).
3093 Example: quirks=0419:aaf5:rl,0421:0433:rc
3095 user_debug= [KNL,ARM]
3097 See arch/arm/Kconfig.debug help text.
3098 1 - undefined instruction events
3100 4 - invalid data aborts
3103 Example: user_debug=31
3106 [X86] Flags controlling user PTE allocations.
3108 nohigh = do not allocate PTE pages in
3109 HIGHMEM regardless of setting
3113 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3114 vdso=1: enable VDSO (default)
3115 vdso=0: disable VDSO mapping
3118 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3119 vdso32=1: enable 32-bit VDSO (default)
3120 vdso32=0: disable 32-bit VDSO mapping
3123 vector=percpu: enable percpu vector domain
3125 video= [FB] Frame buffer configuration
3126 See Documentation/fb/modedb.txt.
3129 [VMMIO] Memory mapped virtio (platform) device.
3131 <size>@<baseaddr>:<irq>[:<id>]
3133 <size> := size (can use standard suffixes
3135 <baseaddr> := physical base address
3136 <irq> := interrupt number (as passed to
3138 <id> := (optional) platform device id
3140 virtio_mmio.device=1K@0x100b0000:48:7
3142 Can be used multiple times for multiple devices.
3144 vga= [BOOT,X86-32] Select a particular video mode
3145 See Documentation/x86/boot.txt and
3146 Documentation/svga.txt.
3147 Use vga=ask for menu.
3148 This is actually a boot loader parameter; the value is
3149 passed to the kernel using a special protocol.
3151 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3152 size of <nn>. This can be used to increase the
3153 minimum size (128MB on x86). It can also be used to
3154 decrease the size and leave more room for directly
3157 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3160 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3163 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3167 Controls the behavior of vsyscalls (i.e. calls to
3168 fixed addresses of 0xffffffffff600x00 from legacy
3169 code). Most statically-linked binaries and older
3170 versions of glibc use these calls. Because these
3171 functions are at fixed addresses, they make nice
3172 targets for exploits that can control RIP.
3174 emulate [default] Vsyscalls turn into traps and are
3175 emulated reasonably safely.
3177 native Vsyscalls are native syscall instructions.
3178 This is a little bit faster than trapping
3179 and makes a few dynamic recompilers work
3180 better than they would in emulation mode.
3181 It also makes exploits much easier to write.
3183 none Vsyscalls don't work at all. This makes
3184 them quite hard to use for exploits but
3185 might break your system.
3187 vt.cur_default= [VT] Default cursor shape.
3188 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3189 the parameters of the <Esc>[?A;B;Cc escape sequence;
3190 see VGA-softcursor.txt. Default: 2 = underline.
3192 vt.default_blu= [VT]
3193 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3194 Change the default blue palette of the console.
3195 This is a 16-member array composed of values
3198 vt.default_grn= [VT]
3199 Format: <green0>,<green1>,<green2>,...,<green15>
3200 Change the default green palette of the console.
3201 This is a 16-member array composed of values
3204 vt.default_red= [VT]
3205 Format: <red0>,<red1>,<red2>,...,<red15>
3206 Change the default red palette of the console.
3207 This is a 16-member array composed of values
3213 Set system-wide default UTF-8 mode for all tty's.
3214 Default is 1, i.e. UTF-8 mode is enabled for all
3215 newly opened terminals.
3217 vt.global_cursor_default=
3220 Set system-wide default for whether a cursor
3221 is shown on new VTs. Default is -1,
3222 i.e. cursors will be created by default unless
3223 overridden by individual drivers. 0 will hide
3224 cursors, 1 will display them.
3226 watchdog timers [HW,WDT] For information on watchdog timers,
3227 see Documentation/watchdog/watchdog-parameters.txt
3228 or other driver-specific files in the
3229 Documentation/watchdog/ directory.
3231 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3232 default x2apic cluster mode on platforms
3235 x86_mrst_timer= [X86-32,APBT]
3236 Choose timer option for x86 Moorestown MID platform.
3237 Two valid options are apbt timer only and lapic timer
3238 plus one apbt timer for broadcast timer.
3239 x86_mrst_timer=apbt_only | lapic_and_apbt
3241 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3242 xd_geo= See header of drivers/block/xd.c.
3244 xen_emul_unplug= [HW,X86,XEN]
3245 Unplug Xen emulated devices
3246 Format: [unplug0,][unplug1]
3247 ide-disks -- unplug primary master IDE devices
3248 aux-ide-disks -- unplug non-primary-master IDE devices
3249 nics -- unplug network devices
3250 all -- unplug all emulated devices (NICs and IDE disks)
3251 unnecessary -- unplugging emulated devices is
3252 unnecessary even if the host did not respond to
3254 never -- do not unplug even if version check succeeds
3256 xirc2ps_cs= [NET,PCMCIA]
3258 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3260 ______________________________________________________________________
3264 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob