4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel_low=size[KMG]
598 [KNL, x86] parts under 4G.
600 crashkernel=range1:size1[,range2:size2,...][@offset]
601 [KNL] Same as above, but depends on the memory
602 in the running system. The syntax of range is
603 start-[end] where start and end are both
604 a memory unit (amount[KMG]). See also
605 Documentation/kdump/kdump.txt for an example.
610 cs89x0_media= [HW,NET]
611 Format: { rj45 | aui | bnc }
614 See header of drivers/s390/block/dasd_devmap.c.
616 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
617 (one device per port)
618 Format: <port#>,<type>
619 See also Documentation/input/joystick-parport.txt
621 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
622 time. See Documentation/dynamic-debug-howto.txt for
623 details. Deprecated, see dyndbg.
625 debug [KNL] Enable kernel debugging (events log level).
628 [KNL] verbose self-tests
630 Print debugging info while doing the locking API
632 We default to 0 (no extra messages), setting it to
633 1 will print _a lot_ more information - normally
634 only useful to kernel developers.
636 debug_objects [KNL] Enable object debugging
639 [KNL] Disable object debugging
641 debug_guardpage_minorder=
642 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
643 parameter allows control of the order of pages that will
644 be intentionally kept free (and hence protected) by the
645 buddy allocator. Bigger value increase the probability
646 of catching random memory corruption, but reduce the
647 amount of memory for normal system use. The maximum
648 possible value is MAX_ORDER/2. Setting this parameter
649 to 1 or 2 should be enough to identify most random
650 memory corruption problems caused by bugs in kernel or
651 driver code when a CPU writes to (or reads from) a
652 random memory location. Note that there exists a class
653 of memory corruptions problems caused by buggy H/W or
654 F/W or by drivers badly programing DMA (basically when
655 memory is written at bus level and the CPU MMU is
656 bypassed) which are not detectable by
657 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
658 tracking down these problems.
660 debugpat [X86] Enable PAT debugging
662 decnet.addr= [HW,NET]
663 Format: <area>[,<node>]
664 See also Documentation/networking/decnet.txt.
667 [same as hugepagesz=] The size of the default
668 HugeTLB page size. This is the size represented by
669 the legacy /proc/ hugepages APIs, used for SHM, and
670 default size when mounting hugetlbfs filesystems.
671 Defaults to the default architecture's huge page size
675 Set number of hash buckets for dentry cache.
678 IO parameters + enable/disable command.
680 digiepca= [HW,SERIAL]
681 See drivers/char/README.epca and
682 Documentation/serial/digiepca.txt.
685 See Documentation/networking/ipv6.txt.
687 disable_ddw [PPC/PSERIES]
688 Disable Dynamic DMA Window support. Use this if
689 to workaround buggy firmware.
692 See Documentation/networking/ipv6.txt.
694 disable_mtrr_cleanup [X86]
695 The kernel tries to adjust MTRR layout from continuous
696 to discrete, to make X server driver able to add WB
697 entry later. This parameter disables that.
699 disable_mtrr_trim [X86, Intel and AMD only]
700 By default the kernel will trim any uncacheable
701 memory out of your available memory pool based on
702 MTRR settings. This parameter disables that behavior,
703 possibly causing your machine to run very slowly.
705 disable_timer_pin_1 [X86]
706 Disable PIN 1 of APIC timer
707 Can be useful to work around chipset bugs.
709 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
710 this option disables the debugging code at boot.
712 dma_debug_entries=<number>
713 This option allows to tune the number of preallocated
714 entries for DMA-API debugging code. One entry is
715 required per DMA-API allocation. Use this if the
716 DMA-API debugging code disables itself because the
717 architectural default is too low.
719 dma_debug_driver=<driver_name>
720 With this option the DMA-API debugging driver
721 filter feature can be enabled at boot time. Just
722 pass the driver to filter for as the parameter.
723 The filter can be disabled or changed to another
724 driver later using sysfs.
726 drm_kms_helper.edid_firmware=[<connector>:]<file>
727 Broken monitors, graphic adapters and KVMs may
728 send no or incorrect EDID data sets. This parameter
729 allows to specify an EDID data set in the
730 /lib/firmware directory that is used instead.
731 Generic built-in EDID data sets are used, if one of
732 edid/1024x768.bin, edid/1280x1024.bin,
733 edid/1680x1050.bin, or edid/1920x1080.bin is given
734 and no file with the same name exists. Details and
735 instructions how to build your own EDID data are
736 available in Documentation/EDID/HOWTO.txt. An EDID
737 data set will only be used for a particular connector,
738 if its name and a colon are prepended to the EDID
743 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
744 module.dyndbg[="val"]
745 Enable debug messages at boot time. See
746 Documentation/dynamic-debug-howto.txt for details.
748 earlycon= [KNL] Output early console device and options.
749 uart[8250],io,<addr>[,options]
750 uart[8250],mmio,<addr>[,options]
751 uart[8250],mmio32,<addr>[,options]
752 Start an early, polled-mode console on the 8250/16550
753 UART at the specified I/O port or MMIO address.
754 MMIO inter-register address stride is either 8-bit
755 (mmio) or 32-bit (mmio32).
756 The options are the same as for ttyS, above.
758 earlyprintk= [X86,SH,BLACKFIN]
760 earlyprintk=serial[,ttySn[,baudrate]]
761 earlyprintk=ttySn[,baudrate]
762 earlyprintk=dbgp[debugController#]
764 Append ",keep" to not disable it when the real console
767 Only vga or serial or usb debug port at a time.
769 Currently only ttyS0 and ttyS1 are supported.
771 Interaction with the standard serial driver is not
774 The VGA output is eventually overwritten by the real
777 ekgdboc= [X86,KGDB] Allow early kernel console debugging
780 This is designed to be used in conjunction with
781 the boot argument: earlyprintk=vga
784 Format: {"off" | "on" | "skip[mbr]"}
786 eisa_irq_edge= [PARISC,HW]
787 See header of drivers/parisc/eisa.c.
790 See comment before function elanfreq_setup() in
791 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
794 Format: {"cfq" | "deadline" | "noop"}
795 See Documentation/block/cfq-iosched.txt and
796 Documentation/block/deadline-iosched.txt for details.
798 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
799 Specifies physical address of start of kernel core
800 image elf header and optionally the size. Generally
801 kexec loader will pass this option to capture kernel.
802 See Documentation/kdump/kdump.txt for details.
804 enable_mtrr_cleanup [X86]
805 The kernel tries to adjust MTRR layout from continuous
806 to discrete, to make X server driver able to add WB
807 entry later. This parameter enables that.
809 enable_timer_pin_1 [X86]
810 Enable PIN 1 of APIC timer
811 Can be useful to work around chipset bugs
812 (in particular on some ATI chipsets).
813 The kernel tries to set a reasonable default.
815 enforcing [SELINUX] Set initial enforcing status.
817 See security/selinux/Kconfig help text.
818 0 -- permissive (log only, no denials).
819 1 -- enforcing (deny and log).
821 Value can be changed at runtime via /selinux/enforce.
824 Disable Error Record Serialization Table (ERST)
827 ether= [HW,NET] Ethernet cards parameters
828 This option is obsoleted by the "netdev=" option, which
829 has equivalent usage. See its documentation for details.
833 Permit 'security.evm' to be updated regardless of
834 current integrity status.
838 fail_make_request=[KNL]
839 General fault injection mechanism.
840 Format: <interval>,<probability>,<space>,<times>
841 See also Documentation/fault-injection/.
844 See Documentation/blockdev/floppy.txt.
846 force_pal_cache_flush
847 [IA-64] Avoid check_sal_cache_flush which may hang on
848 buggy SAL_CACHE_FLUSH implementations. Using this
849 parameter will force ia64_sal_cache_flush to call
850 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
853 [FTRACE] will set and start the specified tracer
854 as early as possible in order to facilitate early
857 ftrace_dump_on_oops[=orig_cpu]
858 [FTRACE] will dump the trace buffers on oops.
859 If no parameter is passed, ftrace will dump
860 buffers of all CPUs, but if you pass orig_cpu, it will
861 dump only the buffer of the CPU that triggered the
864 ftrace_filter=[function-list]
865 [FTRACE] Limit the functions traced by the function
866 tracer at boot up. function-list is a comma separated
867 list of functions. This list can be changed at run
868 time by the set_ftrace_filter file in the debugfs
871 ftrace_notrace=[function-list]
872 [FTRACE] Do not trace the functions specified in
873 function-list. This list can be changed at run time
874 by the set_ftrace_notrace file in the debugfs
877 ftrace_graph_filter=[function-list]
878 [FTRACE] Limit the top level callers functions traced
879 by the function graph tracer at boot up.
880 function-list is a comma separated list of functions
881 that can be changed at run time by the
882 set_graph_function file in the debugfs tracing directory.
885 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
886 support via parallel port (up to 5 devices per port)
887 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
888 See also Documentation/input/joystick-parport.txt
892 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896 gcov_persist= [GCOV] When non-zero (default), profiling data for
897 kernel modules is saved and remains accessible via
898 debugfs, even when the module is unloaded/reloaded.
899 When zero, profiling data is discarded and associated
900 debugfs files are removed at module unload time.
902 gpt [EFI] Forces disk with valid GPT signature but
903 invalid Protective MBR to be treated as GPT.
905 grcan.enable0= [HW] Configuration of physical interface 0. Determines
906 the "Enable 0" bit of the configuration register.
909 grcan.enable1= [HW] Configuration of physical interface 1. Determines
910 the "Enable 0" bit of the configuration register.
913 grcan.select= [HW] Select which physical interface to use.
916 grcan.txsize= [HW] Sets the size of the tx buffer.
917 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
919 grcan.rxsize= [HW] Sets the size of the rx buffer.
920 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
923 hashdist= [KNL,NUMA] Large hashes allocated during boot
924 are distributed across NUMA nodes. Defaults on
925 for 64-bit NUMA, off otherwise.
926 Format: 0 | 1 (for off | on)
928 hcl= [IA-64] SGI's Hardware Graph compatibility layer
930 hd= [EIDE] (E)IDE hard drive subsystem geometry
931 Format: <cyl>,<head>,<sect>
934 Disable Hardware Error Source Table (HEST) support;
935 corresponding firmware-first mode error processing
936 logic will be disabled.
938 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
939 size of <nn>. This works even on boxes that have no
940 highmem otherwise. This also works to reduce highmem
941 size on bigger boxes.
943 highres= [KNL] Enable/disable high resolution timer mode.
944 Valid parameters: "on", "off"
948 See Documentation/isdn/README.HiSax.
952 hpet= [X86-32,HPET] option to control HPET usage
953 Format: { enable (default) | disable | force |
955 disable: disable HPET and use PIT instead
956 force: allow force enabled of undocumented chips (ICH4,
958 verbose: show contents of HPET registers during setup
960 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
961 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
962 On x86-64 and powerpc, this option can be specified
963 multiple times interleaved with hugepages= to reserve
964 huge pages of different sizes. Valid pages sizes on
965 x86-64 are 2M (when the CPU supports "pse") and 1G
966 (when the CPU supports the "pdpe1gb" cpuinfo flag)
967 Note that 1GB pages can only be allocated at boot time
968 using hugepages= and not freed afterwards.
970 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
971 terminal devices. Valid values: 0..8
972 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
973 If specified, z/VM IUCV HVC accepts connections
974 from listed z/VM user IDs only.
977 Do not unregister boot console at start. This is only
978 useful for debugging when something happens in the window
979 between unregistering the boot console and initializing
982 i2c_bus= [HW] Override the default board specific I2C bus speed
983 or register an additional I2C bus that is not
984 registered from board initialization code.
988 i8042.debug [HW] Toggle i8042 debug mode
989 i8042.direct [HW] Put keyboard port into non-translated mode
990 i8042.dumbkbd [HW] Pretend that controller can only read data from
991 keyboard and cannot control its state
992 (Don't attempt to blink the leds)
993 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
994 i8042.nokbd [HW] Don't check/create keyboard port
995 i8042.noloop [HW] Disable the AUX Loopback command while probing
997 i8042.nomux [HW] Don't check presence of an active multiplexing
999 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1001 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1002 i8042.reset [HW] Reset the controller during init and cleanup
1003 i8042.unlock [HW] Unlock (ignore) the keylock
1007 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1008 indicates that the driver is running on unsupported
1010 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1011 does not match list of supported models.
1013 [HW] Report power status in /proc/i8k
1014 (disabled by default)
1015 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1018 i915.invert_brightness=
1019 [DRM] Invert the sense of the variable that is used to
1020 set the brightness of the panel backlight. Normally a
1021 brightness value of 0 indicates backlight switched off,
1022 and the maximum of the brightness value sets the backlight
1023 to maximum brightness. If this parameter is set to 0
1024 (default) and the machine requires it, or this parameter
1025 is set to 1, a brightness value of 0 sets the backlight
1026 to maximum brightness, and the maximum of the brightness
1027 value switches the backlight off.
1028 -1 -- never invert brightness
1029 0 -- machine default
1030 1 -- force brightness inversion
1033 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1035 ide-core.nodma= [HW] (E)IDE subsystem
1036 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1037 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1038 .cdrom .chs .ignore_cable are additional options
1039 See Documentation/ide/ide.txt.
1041 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1042 Claim all unknown PCI IDE storage controllers.
1045 Format: idle=poll, idle=halt, idle=nomwait
1046 Poll forces a polling idle loop that can slightly
1047 improve the performance of waking up a idle CPU, but
1048 will use a lot of power and make the system run hot.
1050 idle=halt: Halt is forced to be used for CPU idle.
1051 In such case C2/C3 won't be used again.
1052 idle=nomwait: Disable mwait for CPU C-states
1054 ignore_loglevel [KNL]
1055 Ignore loglevel setting - this will print /all/
1056 kernel messages to the console. Useful for debugging.
1057 We also add it as printk module parameter, so users
1058 could change it dynamically, usually by
1059 /sys/module/printk/parameters/ignore_loglevel.
1061 ihash_entries= [KNL]
1062 Set number of hash buckets for inode cache.
1064 ima_appraise= [IMA] appraise integrity measurements
1065 Format: { "off" | "enforce" | "fix" }
1068 ima_appraise_tcb [IMA]
1069 The builtin appraise policy appraises all files
1073 Format: { "0" | "1" }
1074 0 -- integrity auditing messages. (Default)
1075 1 -- enable informational integrity auditing messages.
1078 Format: { "sha1" | "md5" }
1082 Load a policy which meets the needs of the Trusted
1083 Computing Base. This means IMA will measure all
1084 programs exec'd, files mmap'd for exec, and all files
1085 opened for read by uid=0.
1089 Run specified binary instead of /sbin/init as init
1092 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1093 for working out where the kernel is dying during
1096 initrd= [BOOT] Specify the location of the initial ramdisk
1098 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1101 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1103 Enable intel iommu driver.
1105 Disable intel iommu driver.
1106 igfx_off [Default Off]
1107 By default, gfx is mapped as normal device. If a gfx
1108 device has a dedicated DMAR unit, the DMAR unit is
1109 bypassed by not enabling DMAR with this option. In
1110 this case, gfx device will use physical address for
1113 With this option iommu will not optimize to look
1114 for io virtual address below 32-bit forcing dual
1115 address cycle on pci bus for cards supporting greater
1116 than 32-bit addressing. The default is to look
1117 for translation below 32-bit and if not available
1118 then look in the higher range.
1119 strict [Default Off]
1120 With this option on every unmap_single operation will
1121 result in a hardware IOTLB flush operation as opposed
1122 to batching them for performance.
1123 sp_off [Default Off]
1124 By default, super page will be supported if Intel IOMMU
1125 has the capability. With this option, super page will
1128 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1129 0 disables intel_idle and fall back on acpi_idle.
1130 1 to 6 specify maximum depth of C-state.
1134 Do not enable intel_pstate as the default
1135 scaling driver for the supported processors
1137 intremap= [X86-64, Intel-IOMMU]
1138 on enable Interrupt Remapping (default)
1139 off disable Interrupt Remapping
1140 nosid disable Source ID checking
1142 BIOS x2APIC opt-out request will be ignored
1144 iomem= Disable strict checking of access to MMIO memory
1145 strict regions from userspace.
1162 io7= [HW] IO7 for Marvel based alpha systems
1163 See comment before marvel_specify_io7 in
1164 arch/alpha/kernel/core_marvel.c.
1166 io_delay= [X86] I/O delay method
1168 Standard port 0x80 based delay
1170 Alternate port 0xed based delay (needed on some systems)
1172 Simple two microseconds delay
1177 See Documentation/filesystems/nfs/nfsroot.txt.
1179 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1180 See comment before ip2_setup() in
1181 drivers/char/ip2/ip2base.c.
1184 When an interrupt is not handled search all handlers
1185 for it. Intended to get systems with badly broken
1189 When an interrupt is not handled search all handlers
1190 for it. Also check all handlers each timer
1191 interrupt. Intended to get systems with badly broken
1195 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1197 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1199 <cpu number>,...,<cpu number>
1201 <cpu number>-<cpu number>
1202 (must be a positive range in ascending order)
1204 <cpu number>,...,<cpu number>-<cpu number>
1206 This option can be used to specify one or more CPUs
1207 to isolate from the general SMP balancing and scheduling
1208 algorithms. You can move a process onto or off an
1209 "isolated" CPU via the CPU affinity syscalls or cpuset.
1210 <cpu number> begins at 0 and the maximum value is
1211 "number of CPUs in system - 1".
1213 This option is the preferred way to isolate CPUs. The
1214 alternative -- manually setting the CPU mask of all
1215 tasks in the system -- can cause problems and
1216 suboptimal load balancer performance.
1220 js= [HW,JOY] Analog joystick
1221 See Documentation/input/joystick.txt.
1225 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1226 specifies the amount of memory usable by the kernel
1227 for non-movable allocations. The requested amount is
1228 spread evenly throughout all nodes in the system. The
1229 remaining memory in each node is used for Movable
1230 pages. In the event, a node is too small to have both
1231 kernelcore and Movable pages, kernelcore pages will
1232 take priority and other nodes will have a larger number
1233 of kernelcore pages. The Movable zone is used for the
1234 allocation of pages that may be reclaimed or moved
1235 by the page migration subsystem. This means that
1236 HugeTLB pages may not be allocated from this zone.
1237 Note that allocations like PTEs-from-HighMem still
1238 use the HighMem zone if it exists, and the Normal
1239 zone if it does not.
1241 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1242 Format: <Controller#>[,poll interval]
1243 The controller # is the number of the ehci usb debug
1244 port as it is probed via PCI. The poll interval is
1245 optional and is the number seconds in between
1246 each poll cycle to the debug port in case you need
1247 the functionality for interrupting the kernel with
1248 gdb or control-c on the dbgp connection. When
1249 not using this parameter you use sysrq-g to break into
1250 the kernel debugger.
1252 kgdboc= [KGDB,HW] kgdb over consoles.
1253 Requires a tty driver that supports console polling,
1254 or a supported polling keyboard driver (non-usb).
1255 Serial only format: <serial_device>[,baud]
1256 keyboard only format: kbd
1257 keyboard and serial format: kbd,<serial_device>[,baud]
1258 Optional Kernel mode setting:
1259 kms, kbd format: kms,kbd
1260 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1262 kgdbwait [KGDB] Stop kernel execution and enter the
1263 kernel debugger at the earliest opportunity.
1265 kmac= [MIPS] korina ethernet MAC address.
1266 Configure the RouterBoard 532 series on-chip
1267 Ethernet adapter MAC address.
1269 kmemleak= [KNL] Boot-time kmemleak enable/disable
1270 Valid arguments: on, off
1273 kstack=N [X86] Print N words from the kernel stack
1276 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1277 Default is 0 (don't ignore, but inject #GP)
1279 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1283 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1284 Default is 1 (enabled)
1286 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1288 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1290 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1291 (virtualized MMU) support on capable Intel chips.
1292 Default is 1 (enabled)
1294 kvm-intel.emulate_invalid_guest_state=
1295 [KVM,Intel] Enable emulation of invalid guest states
1296 Default is 0 (disabled)
1298 kvm-intel.flexpriority=
1299 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1300 Default is 1 (enabled)
1303 [KVM,Intel] Enable VMX nesting (nVMX).
1304 Default is 0 (disabled)
1306 kvm-intel.unrestricted_guest=
1307 [KVM,Intel] Disable unrestricted guest feature
1308 (virtualized real and unpaged mode) on capable
1309 Intel chips. Default is 1 (enabled)
1311 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1312 feature (tagged TLBs) on capable Intel chips.
1313 Default is 1 (enabled)
1319 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1322 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1323 value for LAPIC timer one-shot implementation. Default
1324 back to the programmable timer unit in the LAPIC.
1326 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1329 libata.dma= [LIBATA] DMA control
1330 libata.dma=0 Disable all PATA and SATA DMA
1331 libata.dma=1 PATA and SATA Disk DMA only
1332 libata.dma=2 ATAPI (CDROM) DMA only
1333 libata.dma=4 Compact Flash DMA only
1334 Combinations also work, so libata.dma=3 enables DMA
1335 for disks and CDROMs, but not CFs.
1337 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1338 libata.ignore_hpa=0 keep BIOS limits (default)
1339 libata.ignore_hpa=1 ignore limits, using full disk
1341 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1345 libata.force= [LIBATA] Force configurations. The format is comma
1346 separated list of "[ID:]VAL" where ID is
1347 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1348 matching port, link or device. Basically, it matches
1349 the ATA ID string printed on console by libata. If
1350 the whole ID part is omitted, the last PORT and DEVICE
1351 values are used. If ID hasn't been specified yet, the
1352 configuration applies to all ports, links and devices.
1354 If only DEVICE is omitted, the parameter applies to
1355 the port and all links and devices behind it. DEVICE
1356 number of 0 either selects the first device or the
1357 first fan-out link behind PMP device. It does not
1358 select the host link. DEVICE number of 15 selects the
1359 host link and device attached to it.
1361 The VAL specifies the configuration to force. As long
1362 as there's no ambiguity shortcut notation is allowed.
1363 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1364 The following configurations can be forced.
1366 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1367 Any ID with matching PORT is used.
1369 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1371 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1372 udma[/][16,25,33,44,66,100,133] notation is also
1375 * [no]ncq: Turn on or off NCQ.
1377 * nohrst, nosrst, norst: suppress hard, soft
1380 * rstonce: only attempt one reset during
1381 hot-unplug link recovery
1383 * dump_id: dump IDENTIFY data.
1385 If there are multiple matching configurations changing
1386 the same attribute, the last one is used.
1388 memblock=debug [KNL] Enable memblock debug messages.
1390 load_ramdisk= [RAM] List of ramdisks to load from floppy
1391 See Documentation/blockdev/ramdisk.txt.
1393 lockd.nlm_grace_period=P [NFS] Assign grace period.
1396 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1399 lockd.nlm_timeout=T [NFS] Assign timeout value.
1402 lockd.nlm_udpport=M [NFS] Assign UDP port.
1405 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1408 loglevel= All Kernel Messages with a loglevel smaller than the
1409 console loglevel will be printed to the console. It can
1410 also be changed with klogd or other programs. The
1411 loglevels are defined as follows:
1413 0 (KERN_EMERG) system is unusable
1414 1 (KERN_ALERT) action must be taken immediately
1415 2 (KERN_CRIT) critical conditions
1416 3 (KERN_ERR) error conditions
1417 4 (KERN_WARNING) warning conditions
1418 5 (KERN_NOTICE) normal but significant condition
1419 6 (KERN_INFO) informational
1420 7 (KERN_DEBUG) debug-level messages
1422 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1423 in bytes. n must be a power of two. The default
1424 size is set in the kernel config file.
1426 logo.nologo [FB] Disables display of the built-in Linux logo.
1427 This may be used to provide more screen space for
1428 kernel log messages and is useful when debugging
1429 kernel boot problems.
1431 lp=0 [LP] Specify parallel ports to use, e.g,
1432 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1433 lp=reset first parallel port). 'lp=0' disables the
1434 lp=auto printer driver. 'lp=reset' (which can be
1435 specified in addition to the ports) causes
1436 attached printers to be reset. Using
1437 lp=port1,port2,... specifies the parallel ports
1438 to associate lp devices with, starting with
1439 lp0. A port specification may be 'none' to skip
1440 that lp device, or a parport name such as
1441 'parport0'. Specifying 'lp=auto' instead of a
1442 port specification list means that device IDs
1443 from each port should be examined, to see if
1444 an IEEE 1284-compliant printer is attached; if
1445 so, the driver will manage that printer.
1446 See also header of drivers/char/lp.c.
1449 Sets loops_per_jiffy to given constant, thus avoiding
1450 time-consuming boot-time autodetection (up to 250 ms per
1451 CPU). 0 enables autodetection (default). To determine
1452 the correct value for your kernel, boot with normal
1453 autodetection and see what value is printed. Note that
1454 on SMP systems the preset will be applied to all CPUs,
1455 which is likely to cause problems if your CPUs need
1456 significantly divergent settings. An incorrect value
1457 will cause delays in the kernel to be wrong, leading to
1458 unpredictable I/O errors and other breakage. Although
1459 unlikely, in the extreme case this might damage your
1463 Format: <io>,<irq>,<dma>
1465 machvec= [IA-64] Force the use of a particular machine-vector
1466 (machvec) in a generic kernel.
1467 Example: machvec=hpzx1_swiotlb
1469 machtype= [Loongson] Share the same kernel image file between different
1471 Example: machtype=lemote-yeeloong-2f-7inch
1473 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1474 than or equal to this physical address is ignored.
1476 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1477 should make use of. maxcpus=n : n >= 0 limits the
1478 kernel to using 'n' processors. n=0 is a special case,
1479 it is equivalent to "nosmp", which also disables
1482 max_loop= [LOOP] The number of loop block devices that get
1483 (loop.max_loop) unconditionally pre-created at init time. The default
1484 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1485 of statically allocating a predefined number, loop
1486 devices can be requested on-demand with the
1487 /dev/loop-control interface.
1489 mce [X86-32] Machine Check Exception
1491 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1493 md= [HW] RAID subsystems devices and level
1494 See Documentation/md.txt.
1497 Format: <first>,<last>
1498 Specifies range of consoles to be captured by the MDA.
1500 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1501 Amount of memory to be used when the kernel is not able
1502 to see the whole system memory or for test.
1503 [X86] Work as limiting max address. Use together
1504 with memmap= to avoid physical address space collisions.
1505 Without memmap= PCI devices could be placed at addresses
1506 belonging to unused RAM.
1508 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1512 [KNL,SH] Allow user to override the default size for
1513 per-device physically contiguous DMA buffers.
1515 memmap=exactmap [KNL,X86] Enable setting of an exact
1516 E820 memory map, as specified by the user.
1517 Such memmap=exactmap lines can be constructed based on
1518 BIOS output or other requirements. See the memmap=nn@ss
1521 memmap=nn[KMG]@ss[KMG]
1522 [KNL] Force usage of a specific region of memory
1523 Region of memory to be used, from ss to ss+nn.
1525 memmap=nn[KMG]#ss[KMG]
1526 [KNL,ACPI] Mark specific memory as ACPI data.
1527 Region of memory to be used, from ss to ss+nn.
1529 memmap=nn[KMG]$ss[KMG]
1530 [KNL,ACPI] Mark specific memory as reserved.
1531 Region of memory to be used, from ss to ss+nn.
1532 Example: Exclude memory from 0x18690000-0x1869ffff
1533 memmap=64K$0x18690000
1535 memmap=0x10000$0x18690000
1537 memory_corruption_check=0/1 [X86]
1538 Some BIOSes seem to corrupt the first 64k of
1539 memory when doing things like suspend/resume.
1540 Setting this option will scan the memory
1541 looking for corruption. Enabling this will
1542 both detect corruption and prevent the kernel
1543 from using the memory being corrupted.
1544 However, its intended as a diagnostic tool; if
1545 repeatable BIOS-originated corruption always
1546 affects the same memory, you can use memmap=
1547 to prevent the kernel from using that memory.
1549 memory_corruption_check_size=size [X86]
1550 By default it checks for corruption in the low
1551 64k, making this memory unavailable for normal
1552 use. Use this parameter to scan for
1553 corruption in more or less memory.
1555 memory_corruption_check_period=seconds [X86]
1556 By default it checks for corruption every 60
1557 seconds. Use this parameter to check at some
1558 other rate. 0 disables periodic checking.
1560 memtest= [KNL,X86] Enable memtest
1562 default : 0 <disable>
1563 Specifies the number of memtest passes to be
1564 performed. Each pass selects another test
1565 pattern from a given set of patterns. Memtest
1566 fills the memory with this pattern, validates
1567 memory contents and reserves bad memory
1568 regions that are detected.
1570 meye.*= [HW] Set MotionEye Camera parameters
1571 See Documentation/video4linux/meye.txt.
1573 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1574 Multi-Function General Purpose Timers on AMD Geode
1577 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1578 the BIOS has incorrectly applied a workaround. TinyBIOS
1579 version 0.98 is known to be affected, 0.99 fixes the
1580 problem by letting the user disable the workaround.
1584 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1585 physical address is ignored.
1587 mini2440= [ARM,HW,KNL]
1588 Format:[0..2][b][c][t]
1590 MINI2440 configuration specification:
1591 0 - The attached screen is the 3.5" TFT
1592 1 - The attached screen is the 7" TFT
1593 2 - The VGA Shield is attached (1024x768)
1594 Leaving out the screen size parameter will not load
1595 the TFT driver, and the framebuffer will be left
1597 b - Enable backlight. The TFT backlight pin will be
1598 linked to the kernel VESA blanking code and a GPIO
1599 LED. This parameter is not necessary when using the
1601 c - Enable the s3c camera interface.
1602 t - Reserved for enabling touchscreen support. The
1603 touchscreen support is not enabled in the mainstream
1604 kernel as of 2.6.30, a preliminary port can be found
1605 in the "bleeding edge" mini2440 support kernel at
1606 http://repo.or.cz/w/linux-2.6/mini2440.git
1609 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1610 parameter allows control of the logging verbosity for
1611 the additional memory initialisation checks. A value
1612 of 0 disables mminit logging and a level of 4 will
1613 log everything. Information is printed at KERN_DEBUG
1614 so loglevel=8 may also need to be specified.
1617 [KNL] When CONFIG_MODULE_SIG is set, this means that
1618 modules without (valid) signatures will fail to load.
1619 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1620 is always true, so this option does nothing.
1623 [MOUSE] Maximum time between finger touching and
1624 leaving touchpad surface for touch to be considered
1625 a tap and be reported as a left button click (for
1626 touchpads working in absolute mode only).
1628 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1629 reporting absolute coordinates, such as tablets
1630 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1631 reporting absolute coordinates, such as tablets
1633 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1634 is similar to kernelcore except it specifies the
1635 amount of memory used for migratable allocations.
1636 If both kernelcore and movablecore is specified,
1637 then kernelcore will be at *least* the specified
1638 value but may be more. If movablecore on its own
1639 is specified, the administrator must be careful
1640 that the amount of memory usable for all allocations
1644 [KNL,X86,IA-64,PPC] This parameter is similar to
1645 memmap except it specifies the memory map of
1647 This option inform the kernel to use Hot Pluggable bit
1648 in flags from SRAT from ACPI BIOS to determine which
1649 memory devices could be hotplugged. The corresponding
1650 memory ranges will be set as ZONE_MOVABLE.
1651 NOTE: Whatever node the kernel resides in will always
1654 movablemem_map=nn[KMG]@ss[KMG]
1655 [KNL,X86,IA-64,PPC] This parameter is similar to
1656 memmap except it specifies the memory map of
1658 If user specifies memory ranges, the info in SRAT will
1659 be ingored. And it works like the following:
1660 - If more ranges are all within one node, then from
1661 lowest ss to the end of the node will be ZONE_MOVABLE.
1662 - If a range is within a node, then from ss to the end
1663 of the node will be ZONE_MOVABLE.
1664 - If a range covers two or more nodes, then from ss to
1665 the end of the 1st node will be ZONE_MOVABLE, and all
1666 the rest nodes will only have ZONE_MOVABLE.
1667 If memmap is specified at the same time, the
1668 movablemem_map will be limited within the memmap
1669 areas. If kernelcore or movablecore is also specified,
1670 movablemem_map will have higher priority to be
1671 satisfied. So the administrator should be careful that
1672 the amount of movablemem_map areas are not too large.
1673 Otherwise kernel won't have enough memory to start.
1674 NOTE: We don't stop users specifying the node the
1675 kernel resides in as hotpluggable so that this
1676 option can be used as a workaround of firmware
1679 MTD_Partition= [MTD]
1680 Format: <name>,<region-number>,<size>,<offset>
1682 MTD_Region= [MTD] Format:
1683 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1686 See drivers/mtd/cmdlinepart.c.
1688 multitce=off [PPC] This parameter disables the use of the pSeries
1689 firmware feature for updating multiple TCE entries
1692 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1694 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1696 boundary - index of last SLC block on Flex-OneNAND.
1697 The remaining blocks are configured as MLC blocks.
1698 lock - Configure if Flex-OneNAND boundary should be locked.
1699 Once locked, the boundary cannot be changed.
1700 1 indicates lock status, 0 indicates unlock status.
1703 ARM/S3C2412 JIVE boot control
1705 See arch/arm/mach-s3c2412/mach-jive.c
1707 mtouchusb.raw_coordinates=
1708 [HW] Make the MicroTouch USB driver use raw coordinates
1709 ('y', default) or cooked coordinates ('n')
1711 mtrr_chunk_size=nn[KMG] [X86]
1712 used for mtrr cleanup. It is largest continuous chunk
1713 that could hold holes aka. UC entries.
1715 mtrr_gran_size=nn[KMG] [X86]
1716 Used for mtrr cleanup. It is granularity of mtrr block.
1718 Large value could prevent small alignment from
1721 mtrr_spare_reg_nr=n [X86]
1723 Range: 0,7 : spare reg number
1725 Used for mtrr cleanup. It is spare mtrr entries number.
1726 Set to 2 or more if your graphical card needs more.
1728 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1730 netdev= [NET] Network devices parameters
1731 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1732 Note that mem_start is often overloaded to mean
1733 something different and driver-specific.
1734 This usage is only documented in each driver source
1738 [NETFILTER] Enable connection tracking flow accounting
1739 0 to disable accounting
1740 1 to enable accounting
1743 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1744 See Documentation/filesystems/nfs/nfsroot.txt.
1746 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1747 See Documentation/filesystems/nfs/nfsroot.txt.
1749 nfsrootdebug [NFS] enable nfsroot debugging messages.
1750 See Documentation/filesystems/nfs/nfsroot.txt.
1752 nfs.callback_tcpport=
1753 [NFS] set the TCP port on which the NFSv4 callback
1754 channel should listen.
1757 [NFS] sets the pathname to the program which is used
1758 to update the NFS client cache entries.
1760 nfs.cache_getent_timeout=
1761 [NFS] sets the timeout after which an attempt to
1762 update a cache entry is deemed to have failed.
1764 nfs.idmap_cache_timeout=
1765 [NFS] set the maximum lifetime for idmapper cache
1769 [NFS] enable 64-bit inode numbers.
1770 If zero, the NFS client will fake up a 32-bit inode
1771 number for the readdir() and stat() syscalls instead
1772 of returning the full 64-bit number.
1773 The default is to return 64-bit inode numbers.
1775 nfs.max_session_slots=
1776 [NFSv4.1] Sets the maximum number of session slots
1777 the client will attempt to negotiate with the server.
1778 This limits the number of simultaneous RPC requests
1779 that the client can send to the NFSv4.1 server.
1780 Note that there is little point in setting this
1781 value higher than the max_tcp_slot_table_limit.
1783 nfs.nfs4_disable_idmapping=
1784 [NFSv4] When set to the default of '1', this option
1785 ensures that both the RPC level authentication
1786 scheme and the NFS level operations agree to use
1787 numeric uids/gids if the mount is using the
1788 'sec=sys' security flavour. In effect it is
1789 disabling idmapping, which can make migration from
1790 legacy NFSv2/v3 systems to NFSv4 easier.
1791 Servers that do not support this mode of operation
1792 will be autodetected by the client, and it will fall
1793 back to using the idmapper.
1794 To turn off this behaviour, set the value to '0'.
1796 [NFS4] Specify an additional fixed unique ident-
1797 ification string that NFSv4 clients can insert into
1798 their nfs_client_id4 string. This is typically a
1799 UUID that is generated at system install time.
1801 nfs.send_implementation_id =
1802 [NFSv4.1] Send client implementation identification
1803 information in exchange_id requests.
1804 If zero, no implementation identification information
1806 The default is to send the implementation identification
1809 nfsd.nfs4_disable_idmapping=
1810 [NFSv4] When set to the default of '1', the NFSv4
1811 server will return only numeric uids and gids to
1812 clients using auth_sys, and will accept numeric uids
1813 and gids from such clients. This is intended to ease
1814 migration from NFSv2/v3.
1816 objlayoutdriver.osd_login_prog=
1817 [NFS] [OBJLAYOUT] sets the pathname to the program which
1818 is used to automatically discover and login into new
1819 osd-targets. Please see:
1820 Documentation/filesystems/pnfs.txt for more explanations
1822 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1823 when a NMI is triggered.
1824 Format: [state][,regs][,debounce][,die]
1826 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1827 Format: [panic,][nopanic,][num]
1829 0 - turn nmi_watchdog off
1830 When panic is specified, panic when an NMI watchdog
1831 timeout occurs (or 'nopanic' to override the opposite
1833 This is useful when you use a panic=... timeout and
1834 need the box quickly up again.
1836 netpoll.carrier_timeout=
1837 [NET] Specifies amount of time (in seconds) that
1838 netpoll should wait for a carrier. By default netpoll
1841 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1842 emulation library even if a 387 maths coprocessor
1846 [HW] Never suspend the console
1847 Disable suspending of consoles during suspend and
1848 hibernate operations. Once disabled, debugging
1849 messages can reach various consoles while the rest
1850 of the system is being put to sleep (ie, while
1851 debugging driver suspend/resume hooks). This may
1852 not work reliably with all consoles, but is known
1853 to work with serial and VGA consoles.
1854 To facilitate more flexible debugging, we also add
1855 console_suspend, a printk module parameter to control
1856 it. Users could use console_suspend (usually
1857 /sys/module/printk/parameters/console_suspend) to
1858 turn on/off it dynamically.
1860 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1861 caches in the slab allocator. Saves per-node memory,
1862 but will impact performance.
1866 noapic [SMP,APIC] Tells the kernel to not make use of any
1867 IOAPICs that may be present in the system.
1869 noautogroup Disable scheduler automatic task group creation.
1871 nobats [PPC] Do not use BATs for mapping kernel lowmem
1872 on "Classic" PPC cores.
1876 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1878 nodelayacct [KNL] Disable per-task delay accounting
1880 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1882 nodsp [SH] Disable hardware DSP at boot time.
1884 noefi [X86] Disable EFI runtime services support.
1889 On X86-32 available only on PAE configured kernels.
1890 noexec=on: enable non-executable mappings (default)
1891 noexec=off: disable non-executable mappings
1894 Disable SMAP (Supervisor Mode Access Prevention)
1895 even if it is supported by processor.
1898 Disable SMEP (Supervisor Mode Execution Prevention)
1899 even if it is supported by processor.
1902 This affects only 32-bit executables.
1903 noexec32=on: enable non-executable mappings (default)
1904 read doesn't imply executable mappings
1905 noexec32=off: disable non-executable mappings
1906 read implies executable mappings
1908 nofpu [SH] Disable hardware FPU at boot time.
1910 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1911 register save and restore. The kernel will only save
1912 legacy floating-point registers on task switch.
1914 noxsave [BUGS=X86] Disables x86 extended register state save
1915 and restore using xsave. The kernel will fallback to
1916 enabling legacy floating-point and sse state.
1919 on enable eager fpu restore
1920 off disable eager fpu restore
1921 auto selects the default scheme, which automatically
1922 enables eagerfpu restore for xsaveopt.
1924 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1925 wfi(ARM) instruction doesn't work correctly and not to
1926 use it. This is also useful when using JTAG debugger.
1928 no_file_caps Tells the kernel not to honor file capabilities. The
1929 only way then for a file to be executed with privilege
1930 is to be setuid root or executed by root.
1932 nohalt [IA-64] Tells the kernel not to use the power saving
1933 function PAL_HALT_LIGHT when idle. This increases
1934 power-consumption. On the positive side, it reduces
1935 interrupt wake-up latency, which may improve performance
1936 in certain environments such as networked servers or
1939 nohz= [KNL] Boottime enable/disable dynamic ticks
1940 Valid arguments: on, off
1943 noiotrap [SH] Disables trapped I/O port accesses.
1945 noirqdebug [X86-32] Disables the code which attempts to detect and
1946 disable unhandled interrupt sources.
1948 no_timer_check [X86,APIC] Disables the code which tests for
1949 broken timer IRQ sources.
1951 noisapnp [ISAPNP] Disables ISA PnP code.
1953 noinitrd [RAM] Tells the kernel not to load any configured
1956 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1958 [Deprecated - use intremap=off]
1962 nojitter [IA-64] Disables jitter checking for ITC timers.
1964 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1966 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1969 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1970 steal time is computed, but won't influence scheduler
1973 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1975 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1977 noltlbs [PPC] Do not use large page/tlb entries for kernel
1978 lowmem mapping on PPC40x.
1980 nomca [IA-64] Disable machine check abort handling
1982 nomce [X86-32] Machine Check Exception
1984 nomfgpt [X86-32] Disable Multi-Function General Purpose
1985 Timer usage (for AMD Geode machines).
1987 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1988 shutdown the other cpus. Instead use the REBOOT_VECTOR
1991 nomodule Disable module load
1993 nopat [X86] Disable PAT (page attribute table extension of
1994 pagetables) support.
1996 norandmaps Don't use address space randomization. Equivalent to
1997 echo 0 > /proc/sys/kernel/randomize_va_space
1999 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2001 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2002 with UP alternatives
2004 noresidual [PPC] Don't use residual data on PReP machines.
2006 nordrand [X86] Disable the direct use of the RDRAND
2007 instruction even if it is supported by the
2008 processor. RDRAND is still available to user
2011 noresume [SWSUSP] Disables resume and restores original swap
2014 no-scroll [VGA] Disables scrollback.
2015 This is required for the Braillex ib80-piezo Braille
2016 reader made by F.H. Papenmeier (Germany).
2020 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2022 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2023 and disable the IO APIC. legacy for "maxcpus=0".
2025 nosoftlockup [KNL] Disable the soft-lockup detector.
2027 nosync [HW,M68K] Disables sync negotiation for all devices.
2029 notsc [BUGS=X86-32] Disable Time Stamp Counter
2031 nousb [USB] Disable the USB subsystem
2033 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2037 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2039 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2040 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2041 Some features depend on CPU0. Known dependencies are:
2042 1. Resume from suspend/hibernate depends on CPU0.
2043 Suspend/hibernate will fail if CPU0 is offline and you
2044 need to online CPU0 before suspend/hibernate.
2045 2. PIC interrupts also depend on CPU0. CPU0 can't be
2046 removed if a PIC interrupt is detected.
2047 It's said poweroff/reboot may depend on CPU0 on some
2048 machines although I haven't seen such issues so far
2049 after CPU0 is offline on a few tested machines.
2050 If the dependencies are under your control, you can
2051 turn on cpu0_hotplug.
2053 nptcg= [IA-64] Override max number of concurrent global TLB
2054 purges which is reported from either PAL_VM_SUMMARY or
2057 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2058 could support. nr_cpus=n : n >= 1 limits the kernel to
2059 supporting 'n' processors. Later in runtime you can not
2060 use hotplug cpu feature to put more cpu back to online.
2061 just like you compile the kernel NR_CPUS=n
2063 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2065 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2066 Allowed values are enable and disable
2068 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2069 one of ['zone', 'node', 'default'] can be specified
2070 This can be set from sysctl after boot.
2071 See Documentation/sysctl/vm.txt for details.
2073 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2074 See Documentation/debugging-via-ohci1394.txt for more
2077 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2078 Rather than timing out after 20 ms if an EC
2079 command is not properly ACKed, override the length
2080 of the timeout. We have interrupts disabled while
2081 waiting for the ACK, so if this is set too high
2082 interrupts *may* be lost!
2084 omap_mux= [OMAP] Override bootloader pin multiplexing.
2085 Format: <mux_mode0.mode_name=value>...
2086 For example, to override I2C bus2:
2087 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2089 oprofile.timer= [HW]
2090 Use timer interrupt instead of performance counters
2092 oprofile.cpu_type= Force an oprofile cpu type
2093 This might be useful if you have an older oprofile
2094 userland or if you want common events.
2095 Format: { arch_perfmon }
2096 arch_perfmon: [X86] Force use of architectural
2097 perfmon on Intel CPUs instead of the
2098 CPU specific event set.
2099 timer: [X86] Force use of architectural NMI
2100 timer mode (see also oprofile.timer
2101 for generic hr timer mode)
2102 [s390] Force legacy basic mode sampling
2103 (report cpu_type "timer")
2105 oops=panic Always panic on oopses. Default is to just kill the
2106 process, but there is a small probability of
2107 deadlocking the machine.
2108 This will also cause panics on machine check exceptions.
2109 Useful together with panic=30 to trigger a reboot.
2112 See Documentation/sound/oss/oss-parameters.txt
2114 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2115 timeout > 0: seconds before rebooting
2116 timeout = 0: wait forever
2117 timeout < 0: reboot immediately
2120 parkbd.port= [HW] Parallel port number the keyboard adapter is
2121 connected to, default is 0.
2123 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2124 0 for XT, 1 for AT (default is AT).
2127 parport= [HW,PPT] Specify parallel ports. 0 disables.
2128 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2129 Use 'auto' to force the driver to use any
2130 IRQ/DMA settings detected (the default is to
2131 ignore detected IRQ/DMA settings because of
2132 possible conflicts). You can specify the base
2133 address, IRQ, and DMA settings; IRQ and DMA
2134 should be numbers, or 'auto' (for using detected
2135 settings on that particular port), or 'nofifo'
2136 (to avoid using a FIFO even if it is detected).
2137 Parallel ports are assigned in the order they
2138 are specified on the command line, starting
2141 parport_init_mode= [HW,PPT]
2142 Configure VIA parallel port to operate in
2143 a specific mode. This is necessary on Pegasos
2144 computer where firmware has no options for setting
2145 up parallel port mode and sets it to spp.
2146 Currently this function knows 686a and 8231 chips.
2147 Format: [spp|ps2|epp|ecp|ecpepp]
2150 Halt all CPUs after the first oops has been printed for
2151 the specified number of seconds. This is to be used if
2152 your oopses keep scrolling off the screen.
2157 See header of drivers/block/paride/pcd.c.
2158 See also Documentation/blockdev/paride.txt.
2160 pci=option[,option...] [PCI] various PCI subsystem options:
2161 earlydump [X86] dump PCI config space before the kernel
2163 off [X86] don't probe for the PCI bus
2164 bios [X86-32] force use of PCI BIOS, don't access
2165 the hardware directly. Use this if your machine
2166 has a non-standard PCI host bridge.
2167 nobios [X86-32] disallow use of PCI BIOS, only direct
2168 hardware access methods are allowed. Use this
2169 if you experience crashes upon bootup and you
2170 suspect they are caused by the BIOS.
2171 conf1 [X86] Force use of PCI Configuration
2173 conf2 [X86] Force use of PCI Configuration
2175 noaer [PCIE] If the PCIEAER kernel config parameter is
2176 enabled, this kernel boot option can be used to
2177 disable the use of PCIE advanced error reporting.
2178 nodomains [PCI] Disable support for multiple PCI
2179 root domains (aka PCI segments, in ACPI-speak).
2180 nommconf [X86] Disable use of MMCONFIG for PCI
2182 check_enable_amd_mmconf [X86] check for and enable
2183 properly configured MMIO access to PCI
2184 config space on AMD family 10h CPU
2185 nomsi [MSI] If the PCI_MSI kernel config parameter is
2186 enabled, this kernel boot option can be used to
2187 disable the use of MSI interrupts system-wide.
2188 noioapicquirk [APIC] Disable all boot interrupt quirks.
2189 Safety option to keep boot IRQs enabled. This
2190 should never be necessary.
2191 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2192 primary IO-APIC for bridges that cannot disable
2193 boot IRQs. This fixes a source of spurious IRQs
2194 when the system masks IRQs.
2195 noioapicreroute [APIC] Disable workaround that uses the
2196 boot IRQ equivalent of an IRQ that connects to
2197 a chipset where boot IRQs cannot be disabled.
2198 The opposite of ioapicreroute.
2199 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2200 routing table. These calls are known to be buggy
2201 on several machines and they hang the machine
2202 when used, but on other computers it's the only
2203 way to get the interrupt routing table. Try
2204 this option if the kernel is unable to allocate
2205 IRQs or discover secondary PCI buses on your
2207 rom [X86] Assign address space to expansion ROMs.
2208 Use with caution as certain devices share
2209 address decoders between ROMs and other
2211 norom [X86] Do not assign address space to
2212 expansion ROMs that do not already have
2213 BIOS assigned address ranges.
2214 nobar [X86] Do not assign address space to the
2215 BARs that weren't assigned by the BIOS.
2216 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2217 assigned automatically to PCI devices. You can
2218 make the kernel exclude IRQs of your ISA cards
2220 pirqaddr=0xAAAAA [X86] Specify the physical address
2221 of the PIRQ table (normally generated
2222 by the BIOS) if it is outside the
2223 F0000h-100000h range.
2224 lastbus=N [X86] Scan all buses thru bus #N. Can be
2225 useful if the kernel is unable to find your
2226 secondary buses and you want to tell it
2227 explicitly which ones they are.
2228 assign-busses [X86] Always assign all PCI bus
2229 numbers ourselves, overriding
2230 whatever the firmware may have done.
2231 usepirqmask [X86] Honor the possible IRQ mask stored
2232 in the BIOS $PIR table. This is needed on
2233 some systems with broken BIOSes, notably
2234 some HP Pavilion N5400 and Omnibook XE3
2235 notebooks. This will have no effect if ACPI
2236 IRQ routing is enabled.
2237 noacpi [X86] Do not use ACPI for IRQ routing
2238 or for PCI scanning.
2239 use_crs [X86] Use PCI host bridge window information
2240 from ACPI. On BIOSes from 2008 or later, this
2241 is enabled by default. If you need to use this,
2242 please report a bug.
2243 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2244 If you need to use this, please report a bug.
2245 routeirq Do IRQ routing for all PCI devices.
2246 This is normally done in pci_enable_device(),
2247 so this option is a temporary workaround
2248 for broken drivers that don't call it.
2249 skip_isa_align [X86] do not align io start addr, so can
2250 handle more pci cards
2251 firmware [ARM] Do not re-enumerate the bus but instead
2252 just use the configuration from the
2253 bootloader. This is currently used on
2254 IXP2000 systems where the bus has to be
2255 configured a certain way for adjunct CPUs.
2256 noearly [X86] Don't do any early type 1 scanning.
2257 This might help on some broken boards which
2258 machine check when some devices' config space
2259 is read. But various workarounds are disabled
2260 and some IOMMU drivers will not work.
2261 bfsort Sort PCI devices into breadth-first order.
2262 This sorting is done to get a device
2263 order compatible with older (<= 2.4) kernels.
2264 nobfsort Don't sort PCI devices into breadth-first order.
2265 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2266 tuning and use the BIOS-configured MPS defaults.
2267 pcie_bus_safe Set every device's MPS to the largest value
2268 supported by all devices below the root complex.
2269 pcie_bus_perf Set device MPS to the largest allowable MPS
2270 based on its parent bus. Also set MRRS (Max
2271 Read Request Size) to the largest supported
2272 value (no larger than the MPS that the device
2273 or bus can support) for best performance.
2274 pcie_bus_peer2peer Set every device's MPS to 128B, which
2275 every device is guaranteed to support. This
2276 configuration allows peer-to-peer DMA between
2277 any pair of devices, possibly at the cost of
2278 reduced performance. This also guarantees
2279 that hot-added devices will work.
2280 cbiosize=nn[KMG] The fixed amount of bus space which is
2281 reserved for the CardBus bridge's IO window.
2282 The default value is 256 bytes.
2283 cbmemsize=nn[KMG] The fixed amount of bus space which is
2284 reserved for the CardBus bridge's memory
2285 window. The default value is 64 megabytes.
2288 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2289 Specifies alignment and device to reassign
2290 aligned memory resources.
2291 If <order of align> is not specified,
2292 PAGE_SIZE is used as alignment.
2293 PCI-PCI bridge can be specified, if resource
2294 windows need to be expanded.
2295 ecrc= Enable/disable PCIe ECRC (transaction layer
2296 end-to-end CRC checking).
2297 bios: Use BIOS/firmware settings. This is the
2301 hpiosize=nn[KMG] The fixed amount of bus space which is
2302 reserved for hotplug bridge's IO window.
2303 Default size is 256 bytes.
2304 hpmemsize=nn[KMG] The fixed amount of bus space which is
2305 reserved for hotplug bridge's memory window.
2306 Default size is 2 megabytes.
2307 realloc= Enable/disable reallocating PCI bridge resources
2308 if allocations done by BIOS are too small to
2309 accommodate resources required by all child
2311 off: Turn realloc off
2313 realloc same as realloc=on
2314 noari do not use PCIe ARI.
2315 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2316 only look for one device below a PCIe downstream
2319 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2322 force Enable ASPM even on devices that claim not to support it.
2323 WARNING: Forcing ASPM on may cause system lockups.
2325 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2326 nomsi Do not use MSI for PCI Express Native Hotplug (this
2327 makes all PCIe ports use INTx for hotplug services).
2329 pcie_ports= [PCIE] PCIe ports handling:
2330 auto Ask the BIOS whether or not to use native PCIe services
2331 associated with PCIe ports (PME, hot-plug, AER). Use
2332 them only if that is allowed by the BIOS.
2333 native Use native PCIe services associated with PCIe ports
2335 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2338 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2339 nomsi Do not use MSI for native PCIe PME signaling (this makes
2340 all PCIe root ports use INTx for all services).
2342 pcmv= [HW,PCMCIA] BadgePAD 4
2345 See Documentation/blockdev/paride.txt.
2347 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2350 See arch/parisc/kernel/pdc_chassis.c
2352 percpu_alloc= Select which percpu first chunk allocator to use.
2353 Currently supported values are "embed" and "page".
2354 Archs may support subset or none of the selections.
2355 See comments in mm/percpu.c for details on each
2356 allocator. This parameter is primarily for debugging
2357 and performance comparison.
2360 See Documentation/blockdev/paride.txt.
2363 See Documentation/blockdev/paride.txt.
2365 pirq= [SMP,APIC] Manual mp-table setup
2366 See Documentation/x86/i386/IO-APIC.txt.
2368 plip= [PPT,NET] Parallel port network link
2369 Format: { parport<nr> | timid | 0 }
2370 See also Documentation/parport.txt.
2372 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2373 Override pmtimer IOPort with a hex value.
2377 Enable PNP debug messages (depends on the
2378 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2379 via /sys/module/pnp/parameters/debug. We always show
2380 current resource usage; turning this on also shows
2381 possible settings and some assignment information.
2387 { on | off | curr | res | no-curr | no-res }
2390 [ISAPNP] Exclude IRQs for the autoconfiguration
2393 [ISAPNP] Exclude DMAs for the autoconfiguration
2395 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2396 Ranges are in pairs (I/O port base and size).
2399 [ISAPNP] Exclude memory regions for the
2401 Ranges are in pairs (memory base and size).
2403 ports= [IP_VS_FTP] IPVS ftp helper module
2405 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2407 Format: <port>,<port>....
2409 print-fatal-signals=
2410 [KNL] debug: print fatal signals
2412 If enabled, warn about various signal handling
2413 related application anomalies: too many signals,
2414 too many POSIX.1 timers, fatal signals causing a
2417 If you hit the warning due to signal overflow,
2418 you might want to try "ulimit -i unlimited".
2422 printk.always_kmsg_dump=
2423 Trigger kmsg_dump for cases other than kernel oops or
2425 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2428 printk.time= Show timing data prefixed to each printk message line
2429 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2431 processor.max_cstate= [HW,ACPI]
2432 Limit processor to maximum C-state
2433 max_cstate=9 overrides any DMI blacklist limit.
2435 processor.nocst [HW,ACPI]
2436 Ignore the _CST method to determine C-states,
2437 instead using the legacy FADT method
2439 profile= [KNL] Enable kernel profiling via /proc/profile
2440 Format: [schedule,]<number>
2441 Param: "schedule" - profile schedule points.
2442 Param: <number> - step/bucket size as a power of 2 for
2443 statistical time based profiling.
2444 Param: "sleep" - profile D-state sleeping (millisecs).
2445 Requires CONFIG_SCHEDSTATS
2446 Param: "kvm" - profile VM exits.
2448 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2450 See Documentation/blockdev/ramdisk.txt.
2452 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2453 probe for; one of (bare|imps|exps|lifebook|any).
2454 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2456 psmouse.resetafter= [HW,MOUSE]
2457 Try to reset the device after so many bad packets
2460 [HW,MOUSE] Set desired mouse resolution, in dpi.
2461 psmouse.smartscroll=
2462 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2463 0 = disabled, 1 = enabled (default).
2465 pstore.backend= Specify the name of the pstore backend to use
2468 See Documentation/blockdev/paride.txt.
2471 [KNL] Number of legacy pty's. Overwrites compiled-in
2474 quiet [KNL] Disable most log messages
2479 See Documentation/md.txt.
2481 ramdisk_blocksize= [RAM]
2482 See Documentation/blockdev/ramdisk.txt.
2484 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2485 See Documentation/blockdev/ramdisk.txt.
2487 rcu_nocbs= [KNL,BOOT]
2488 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2489 the specified list of CPUs to be no-callback CPUs.
2490 Invocation of these CPUs' RCU callbacks will
2491 be offloaded to "rcuoN" kthreads created for
2492 that purpose. This reduces OS jitter on the
2493 offloaded CPUs, which can be useful for HPC and
2494 real-time workloads. It can also improve energy
2495 efficiency for asymmetric multiprocessors.
2497 rcu_nocb_poll [KNL,BOOT]
2498 Rather than requiring that offloaded CPUs
2499 (specified by rcu_nocbs= above) explicitly
2500 awaken the corresponding "rcuoN" kthreads,
2501 make these kthreads poll for callbacks.
2502 This improves the real-time response for the
2503 offloaded CPUs by relieving them of the need to
2504 wake up the corresponding kthread, but degrades
2505 energy efficiency by requiring that the kthreads
2506 periodically wake up to do the polling.
2508 rcutree.blimit= [KNL,BOOT]
2509 Set maximum number of finished RCU callbacks to process
2512 rcutree.fanout_leaf= [KNL,BOOT]
2513 Increase the number of CPUs assigned to each
2514 leaf rcu_node structure. Useful for very large
2517 rcutree.qhimark= [KNL,BOOT]
2518 Set threshold of queued
2519 RCU callbacks over which batch limiting is disabled.
2521 rcutree.qlowmark= [KNL,BOOT]
2522 Set threshold of queued RCU callbacks below which
2523 batch limiting is re-enabled.
2525 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2526 Suppress RCU CPU stall warning messages.
2528 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2529 Set timeout for RCU CPU stall warning messages.
2531 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2532 Set delay from grace-period initialization to
2533 first attempt to force quiescent states.
2534 Units are jiffies, minimum value is zero,
2535 and maximum value is HZ.
2537 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2538 Set delay between subsequent attempts to force
2539 quiescent states. Units are jiffies, minimum
2540 value is one, and maximum value is HZ.
2542 rcutorture.fqs_duration= [KNL,BOOT]
2543 Set duration of force_quiescent_state bursts.
2545 rcutorture.fqs_holdoff= [KNL,BOOT]
2546 Set holdoff time within force_quiescent_state bursts.
2548 rcutorture.fqs_stutter= [KNL,BOOT]
2549 Set wait time between force_quiescent_state bursts.
2551 rcutorture.irqreader= [KNL,BOOT]
2552 Test RCU readers from irq handlers.
2554 rcutorture.n_barrier_cbs= [KNL,BOOT]
2555 Set callbacks/threads for rcu_barrier() testing.
2557 rcutorture.nfakewriters= [KNL,BOOT]
2558 Set number of concurrent RCU writers. These just
2559 stress RCU, they don't participate in the actual
2560 test, hence the "fake".
2562 rcutorture.nreaders= [KNL,BOOT]
2563 Set number of RCU readers.
2565 rcutorture.onoff_holdoff= [KNL,BOOT]
2566 Set time (s) after boot for CPU-hotplug testing.
2568 rcutorture.onoff_interval= [KNL,BOOT]
2569 Set time (s) between CPU-hotplug operations, or
2570 zero to disable CPU-hotplug testing.
2572 rcutorture.shuffle_interval= [KNL,BOOT]
2573 Set task-shuffle interval (s). Shuffling tasks
2574 allows some CPUs to go into dyntick-idle mode
2575 during the rcutorture test.
2577 rcutorture.shutdown_secs= [KNL,BOOT]
2578 Set time (s) after boot system shutdown. This
2579 is useful for hands-off automated testing.
2581 rcutorture.stall_cpu= [KNL,BOOT]
2582 Duration of CPU stall (s) to test RCU CPU stall
2583 warnings, zero to disable.
2585 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2586 Time to wait (s) after boot before inducing stall.
2588 rcutorture.stat_interval= [KNL,BOOT]
2589 Time (s) between statistics printk()s.
2591 rcutorture.stutter= [KNL,BOOT]
2592 Time (s) to stutter testing, for example, specifying
2593 five seconds causes the test to run for five seconds,
2594 wait for five seconds, and so on. This tests RCU's
2595 ability to transition abruptly to and from idle.
2597 rcutorture.test_boost= [KNL,BOOT]
2598 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2599 "Maybe" means test if the RCU implementation
2600 under test support RCU priority boosting.
2602 rcutorture.test_boost_duration= [KNL,BOOT]
2603 Duration (s) of each individual boost test.
2605 rcutorture.test_boost_interval= [KNL,BOOT]
2606 Interval (s) between each boost test.
2608 rcutorture.test_no_idle_hz= [KNL,BOOT]
2609 Test RCU's dyntick-idle handling. See also the
2610 rcutorture.shuffle_interval parameter.
2612 rcutorture.torture_type= [KNL,BOOT]
2613 Specify the RCU implementation to test.
2615 rcutorture.verbose= [KNL,BOOT]
2616 Enable additional printk() statements.
2620 Run specified binary instead of /init from the ramdisk,
2621 used for early userspace startup. See initrd.
2623 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2624 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2625 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2628 [KNL, SMP] Set scheduler's default relax_domain_level.
2629 See Documentation/cgroups/cpusets.txt.
2631 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2633 reservetop= [X86-32]
2635 Reserves a hole at the top of the kernel virtual
2640 Set the amount of memory to reserve for BIOS at
2641 the bottom of the address space.
2643 reset_devices [KNL] Force drivers to reset the underlying device
2644 during initialization.
2647 Specify the partition device for software suspend
2649 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2651 resume_offset= [SWSUSP]
2652 Specify the offset from the beginning of the partition
2653 given by "resume=" at which the swap header is located,
2654 in <PAGE_SIZE> units (needed only for swap files).
2655 See Documentation/power/swsusp-and-swap-files.txt
2657 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2658 read the resume files
2660 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2661 Useful for devices that are detected asynchronously
2662 (e.g. USB and MMC devices).
2664 hibernate= [HIBERNATION]
2665 noresume Don't check if there's a hibernation image
2666 present during boot.
2667 nocompress Don't compress/decompress hibernation images.
2669 retain_initrd [RAM] Keep initrd memory after extraction
2671 rhash_entries= [KNL,NET]
2672 Set number of hash buckets for route cache
2674 riscom8= [HW,SERIAL]
2675 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2677 ro [KNL] Mount root device read-only on boot
2679 root= [KNL] Root filesystem
2680 See name_to_dev_t comment in init/do_mounts.c.
2682 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2683 mount the root filesystem
2685 rootflags= [KNL] Set root filesystem mount option string
2687 rootfstype= [KNL] Set root filesystem type
2689 rootwait [KNL] Wait (indefinitely) for root device to show up.
2690 Useful for devices that are detected asynchronously
2691 (e.g. USB and MMC devices).
2693 rw [KNL] Mount root device read-write on boot
2695 S [KNL] Run init in single mode
2698 See drivers/net/irda/sa1100_ir.c.
2700 sbni= [NET] Granch SBNI12 leased line adapter
2702 sched_debug [KNL] Enables verbose scheduler debug messages.
2704 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2705 xtime_lock contention on larger systems, and/or RCU lock
2706 contention on all systems with CONFIG_MAXSMP set.
2707 Format: { "0" | "1" }
2708 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2710 Note: increases power consumption, thus should only be
2711 enabled if running jitter sensitive (HPC/RT) workloads.
2713 security= [SECURITY] Choose a security module to enable at boot.
2714 If this boot parameter is not specified, only the first
2715 security module asking for security registration will be
2716 loaded. An invalid security module name will be treated
2717 as if no module has been chosen.
2719 selinux= [SELINUX] Disable or enable SELinux at boot time.
2720 Format: { "0" | "1" }
2721 See security/selinux/Kconfig help text.
2724 Default value is set via kernel config option.
2725 If enabled at boot time, /selinux/disable can be used
2726 later to disable prior to initial policy load.
2728 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2729 Format: { "0" | "1" }
2730 See security/apparmor/Kconfig help text
2733 Default value is set via kernel config option.
2735 serialnumber [BUGS=X86-32]
2738 Maximal number of shapers.
2740 show_msr= [x86] show boot-time MSR settings
2741 Format: { <integer> }
2742 Show boot-time (BIOS-initialized) MSR settings.
2743 The parameter means the number of CPUs to show,
2744 for example 1 means boot CPU only.
2751 slab_max_order= [MM, SLAB]
2752 Determines the maximum allowed order for slabs.
2753 A high setting may cause OOMs due to memory
2754 fragmentation. Defaults to 1 for systems with
2755 more than 32MB of RAM, 0 otherwise.
2757 slub_debug[=options[,slabs]] [MM, SLUB]
2758 Enabling slub_debug allows one to determine the
2759 culprit if slab objects become corrupted. Enabling
2760 slub_debug can create guard zones around objects and
2761 may poison objects when not in use. Also tracks the
2762 last alloc / free. For more information see
2763 Documentation/vm/slub.txt.
2765 slub_max_order= [MM, SLUB]
2766 Determines the maximum allowed order for slabs.
2767 A high setting may cause OOMs due to memory
2768 fragmentation. For more information see
2769 Documentation/vm/slub.txt.
2771 slub_min_objects= [MM, SLUB]
2772 The minimum number of objects per slab. SLUB will
2773 increase the slab order up to slub_max_order to
2774 generate a sufficiently large slab able to contain
2775 the number of objects indicated. The higher the number
2776 of objects the smaller the overhead of tracking slabs
2777 and the less frequently locks need to be acquired.
2778 For more information see Documentation/vm/slub.txt.
2780 slub_min_order= [MM, SLUB]
2781 Determines the minimum page order for slabs. Must be
2782 lower than slub_max_order.
2783 For more information see Documentation/vm/slub.txt.
2785 slub_nomerge [MM, SLUB]
2786 Disable merging of slabs with similar size. May be
2787 necessary if there is some reason to distinguish
2788 allocs to different slabs. Debug options disable
2789 merging on their own.
2790 For more information see Documentation/vm/slub.txt.
2793 Format: <io1>[,<io2>[,...,<io8>]]
2795 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2796 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2797 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2798 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2799 smsc-ircc2.ircc_irq= [HW] IRQ line
2800 smsc-ircc2.ircc_dma= [HW] DMA channel
2801 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2802 0: Toshiba Satellite 1800 (GP data pin select)
2803 1: Fast pin select (default)
2807 [KNL] Should the soft-lockup detector generate panics.
2810 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2811 See Documentation/laptops/sonypi.txt
2813 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2814 See Documentation/serial/specialix.txt.
2816 spia_io_base= [HW,MTD]
2822 Enabled the stack tracer on boot up.
2824 stacktrace_filter=[function-list]
2825 [FTRACE] Limit the functions that the stack tracer
2826 will trace at boot up. function-list is a comma separated
2827 list of functions. This list can be changed at run
2828 time by the stack_trace_filter file in the debugfs
2829 tracing directory. Note, this enables stack tracing
2830 and the stacktrace above is not needed.
2834 Set the STI (builtin display/keyboard on the HP-PARISC
2835 machines) console (graphic card) which should be used
2836 as the initial boot-console.
2837 See also comment in drivers/video/console/sticore.c.
2840 See comment in drivers/video/console/sticore.c.
2843 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2845 sunrpc.min_resvport=
2846 sunrpc.max_resvport=
2848 SunRPC servers often require that client requests
2849 originate from a privileged port (i.e. a port in the
2850 range 0 < portnr < 1024).
2851 An administrator who wishes to reserve some of these
2852 ports for other uses may adjust the range that the
2853 kernel's sunrpc client considers to be privileged
2854 using these two parameters to set the minimum and
2855 maximum port values.
2859 Control how the NFS server code allocates CPUs to
2860 service thread pools. Depending on how many NICs
2861 you have and where their interrupts are bound, this
2862 option will affect which CPUs will do NFS serving.
2863 Note: this parameter cannot be changed while the
2864 NFS server is running.
2866 auto the server chooses an appropriate mode
2867 automatically using heuristics
2868 global a single global pool contains all CPUs
2869 percpu one pool for each CPU
2870 pernode one pool for each NUMA node (equivalent
2871 to global on non-NUMA machines)
2873 sunrpc.tcp_slot_table_entries=
2874 sunrpc.udp_slot_table_entries=
2876 Sets the upper limit on the number of simultaneous
2877 RPC calls that can be sent from the client to a
2878 server. Increasing these values may allow you to
2879 improve throughput, but will also increase the
2880 amount of memory reserved for use by the client.
2883 [KNL] Enable accounting of swap in memory resource
2884 controller if no parameter or 1 is given or disable
2885 it if 0 is given (See Documentation/cgroups/memory.txt)
2887 swiotlb= [IA-64] Number of I/O TLB slabs
2891 sysfs.deprecated=0|1 [KNL]
2892 Enable/disable old style sysfs layout for old udev
2893 on older distributions. When this option is enabled
2894 very new udev will not work anymore. When this option
2895 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2896 in older udev will not work anymore.
2897 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2898 the kernel configuration.
2900 sysrq_always_enabled
2902 Ignore sysrq setting - this boot parameter will
2903 neutralize any effect of /proc/sys/kernel/sysrq.
2904 Useful for debugging.
2908 test_suspend= [SUSPEND]
2909 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2910 standby suspend) as the system sleep state to briefly
2911 enter during system startup. The system is woken from
2912 this state using a wakeup-capable RTC alarm.
2914 thash_entries= [KNL,NET]
2915 Set number of hash buckets for TCP connection
2917 thermal.act= [HW,ACPI]
2918 -1: disable all active trip points in all thermal zones
2919 <degrees C>: override all lowest active trip points
2921 thermal.crt= [HW,ACPI]
2922 -1: disable all critical trip points in all thermal zones
2923 <degrees C>: override all critical trip points
2925 thermal.nocrt= [HW,ACPI]
2926 Set to disable actions on ACPI thermal zone
2927 critical and hot trip points.
2929 thermal.off= [HW,ACPI]
2930 1: disable ACPI thermal control
2932 thermal.psv= [HW,ACPI]
2933 -1: disable all passive trip points
2934 <degrees C>: override all passive trip points to this
2937 thermal.tzp= [HW,ACPI]
2938 Specify global default ACPI thermal zone polling rate
2939 <deci-seconds>: poll all this frequency
2940 0: no polling (default)
2943 Force threading of all interrupt handlers except those
2944 marked explicitly IRQF_NO_THREAD.
2948 Specify if the kernel should make use of the cpu
2949 topology information if the hardware supports this.
2950 The scheduler will make use of this information and
2951 e.g. base its process migration decisions on it.
2956 tpm_suspend_pcr=[HW,TPM]
2957 Format: integer pcr id
2958 Specify that at suspend time, the tpm driver
2959 should extend the specified pcr with zeros,
2960 as a workaround for some chips which fail to
2961 flush the last written pcr on TPM_SaveState.
2962 This will guarantee that all the other pcrs
2965 trace_buf_size=nn[KMG]
2966 [FTRACE] will set tracing buffer size.
2968 trace_event=[event-list]
2969 [FTRACE] Set and start specified trace events in order
2970 to facilitate early boot debugging.
2971 See also Documentation/trace/events.txt
2973 trace_options=[option-list]
2974 [FTRACE] Enable or disable tracer options at boot.
2975 The option-list is a comma delimited list of options
2976 that can be enabled or disabled just as if you were
2977 to echo the option name into
2979 /sys/kernel/debug/tracing/trace_options
2981 For example, to enable stacktrace option (to dump the
2982 stack trace of each event), add to the command line:
2984 trace_options=stacktrace
2986 See also Documentation/trace/ftrace.txt "trace options"
2989 transparent_hugepage=
2991 Format: [always|madvise|never]
2992 Can be used to control the default behavior of the system
2993 with respect to transparent hugepages.
2994 See Documentation/vm/transhuge.txt for more details.
2996 tsc= Disable clocksource stability checks for TSC.
2998 [x86] reliable: mark tsc clocksource as reliable, this
2999 disables clocksource verification at runtime, as well
3000 as the stability checks done at bootup. Used to enable
3001 high-resolution timer mode on older hardware, and in
3002 virtualized environment.
3003 [x86] noirqtime: Do not use TSC to do irq accounting.
3004 Used to run time disable IRQ_TIME_ACCOUNTING on any
3005 platforms where RDTSC is slow and this accounting
3008 turbografx.map[2|3]= [HW,JOY]
3009 TurboGraFX parallel port interface
3011 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3012 See also Documentation/input/joystick-parport.txt
3014 udbg-immortal [PPC] When debugging early kernel crashes that
3015 happen after console_init() and before a proper
3016 console driver takes over, this boot options might
3017 help "seeing" what's going on.
3019 uhash_entries= [KNL,NET]
3020 Set number of hash buckets for UDP/UDP-Lite connections
3023 [USB] Ignore overcurrent events (default N).
3024 Some badly-designed motherboards generate lots of
3025 bogus events, for ports that aren't wired to
3026 anything. Set this parameter to avoid log spamming.
3027 Note that genuine overcurrent events won't be
3031 [X86] Cause panic on unknown NMI.
3033 usbcore.authorized_default=
3034 [USB] Default USB device authorization:
3035 (default -1 = authorized except for wireless USB,
3036 0 = not authorized, 1 = authorized)
3038 usbcore.autosuspend=
3039 [USB] The autosuspend time delay (in seconds) used
3040 for newly-detected USB devices (default 2). This
3041 is the time required before an idle device will be
3042 autosuspended. Devices for which the delay is set
3043 to a negative value won't be autosuspended at all.
3045 usbcore.usbfs_snoop=
3046 [USB] Set to log all usbfs traffic (default 0 = off).
3048 usbcore.blinkenlights=
3049 [USB] Set to cycle leds on hubs (default 0 = off).
3051 usbcore.old_scheme_first=
3052 [USB] Start with the old device initialization
3053 scheme (default 0 = off).
3055 usbcore.usbfs_memory_mb=
3056 [USB] Memory limit (in MB) for buffers allocated by
3057 usbfs (default = 16, 0 = max = 2047).
3059 usbcore.use_both_schemes=
3060 [USB] Try the other device initialization scheme
3061 if the first one fails (default 1 = enabled).
3063 usbcore.initial_descriptor_timeout=
3064 [USB] Specifies timeout for the initial 64-byte
3065 USB_REQ_GET_DESCRIPTOR request in milliseconds
3066 (default 5000 = 5.0 seconds).
3069 [USBHID] The interval which mice are to be polled at.
3071 usb-storage.delay_use=
3072 [UMS] The delay in seconds before a new device is
3073 scanned for Logical Units (default 5).
3076 [UMS] A list of quirks entries to supplement or
3077 override the built-in unusual_devs list. List
3078 entries are separated by commas. Each entry has
3079 the form VID:PID:Flags where VID and PID are Vendor
3080 and Product ID values (4-digit hex numbers) and
3081 Flags is a set of characters, each corresponding
3082 to a common usb-storage quirk flag as follows:
3083 a = SANE_SENSE (collect more than 18 bytes
3085 b = BAD_SENSE (don't collect more than 18
3086 bytes of sense data);
3087 c = FIX_CAPACITY (decrease the reported
3088 device capacity by one sector);
3089 d = NO_READ_DISC_INFO (don't use
3090 READ_DISC_INFO command);
3091 e = NO_READ_CAPACITY_16 (don't use
3092 READ_CAPACITY_16 command);
3093 h = CAPACITY_HEURISTICS (decrease the
3094 reported device capacity by one
3095 sector if the number is odd);
3096 i = IGNORE_DEVICE (don't bind to this
3098 l = NOT_LOCKABLE (don't try to lock and
3099 unlock ejectable media);
3100 m = MAX_SECTORS_64 (don't transfer more
3101 than 64 sectors = 32 KB at a time);
3102 n = INITIAL_READ10 (force a retry of the
3103 initial READ(10) command);
3104 o = CAPACITY_OK (accept the capacity
3105 reported by the device);
3106 p = WRITE_CACHE (the device cache is ON
3108 r = IGNORE_RESIDUE (the device reports
3109 bogus residue values);
3110 s = SINGLE_LUN (the device has only one
3112 w = NO_WP_DETECT (don't test whether the
3113 medium is write-protected).
3114 Example: quirks=0419:aaf5:rl,0421:0433:rc
3116 user_debug= [KNL,ARM]
3118 See arch/arm/Kconfig.debug help text.
3119 1 - undefined instruction events
3121 4 - invalid data aborts
3124 Example: user_debug=31
3127 [X86] Flags controlling user PTE allocations.
3129 nohigh = do not allocate PTE pages in
3130 HIGHMEM regardless of setting
3134 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3135 vdso=1: enable VDSO (default)
3136 vdso=0: disable VDSO mapping
3139 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3140 vdso32=1: enable 32-bit VDSO (default)
3141 vdso32=0: disable 32-bit VDSO mapping
3144 vector=percpu: enable percpu vector domain
3146 video= [FB] Frame buffer configuration
3147 See Documentation/fb/modedb.txt.
3150 [VMMIO] Memory mapped virtio (platform) device.
3152 <size>@<baseaddr>:<irq>[:<id>]
3154 <size> := size (can use standard suffixes
3156 <baseaddr> := physical base address
3157 <irq> := interrupt number (as passed to
3159 <id> := (optional) platform device id
3161 virtio_mmio.device=1K@0x100b0000:48:7
3163 Can be used multiple times for multiple devices.
3165 vga= [BOOT,X86-32] Select a particular video mode
3166 See Documentation/x86/boot.txt and
3167 Documentation/svga.txt.
3168 Use vga=ask for menu.
3169 This is actually a boot loader parameter; the value is
3170 passed to the kernel using a special protocol.
3172 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3173 size of <nn>. This can be used to increase the
3174 minimum size (128MB on x86). It can also be used to
3175 decrease the size and leave more room for directly
3178 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3181 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3184 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3188 Controls the behavior of vsyscalls (i.e. calls to
3189 fixed addresses of 0xffffffffff600x00 from legacy
3190 code). Most statically-linked binaries and older
3191 versions of glibc use these calls. Because these
3192 functions are at fixed addresses, they make nice
3193 targets for exploits that can control RIP.
3195 emulate [default] Vsyscalls turn into traps and are
3196 emulated reasonably safely.
3198 native Vsyscalls are native syscall instructions.
3199 This is a little bit faster than trapping
3200 and makes a few dynamic recompilers work
3201 better than they would in emulation mode.
3202 It also makes exploits much easier to write.
3204 none Vsyscalls don't work at all. This makes
3205 them quite hard to use for exploits but
3206 might break your system.
3208 vt.cur_default= [VT] Default cursor shape.
3209 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3210 the parameters of the <Esc>[?A;B;Cc escape sequence;
3211 see VGA-softcursor.txt. Default: 2 = underline.
3213 vt.default_blu= [VT]
3214 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3215 Change the default blue palette of the console.
3216 This is a 16-member array composed of values
3219 vt.default_grn= [VT]
3220 Format: <green0>,<green1>,<green2>,...,<green15>
3221 Change the default green palette of the console.
3222 This is a 16-member array composed of values
3225 vt.default_red= [VT]
3226 Format: <red0>,<red1>,<red2>,...,<red15>
3227 Change the default red palette of the console.
3228 This is a 16-member array composed of values
3234 Set system-wide default UTF-8 mode for all tty's.
3235 Default is 1, i.e. UTF-8 mode is enabled for all
3236 newly opened terminals.
3238 vt.global_cursor_default=
3241 Set system-wide default for whether a cursor
3242 is shown on new VTs. Default is -1,
3243 i.e. cursors will be created by default unless
3244 overridden by individual drivers. 0 will hide
3245 cursors, 1 will display them.
3247 watchdog timers [HW,WDT] For information on watchdog timers,
3248 see Documentation/watchdog/watchdog-parameters.txt
3249 or other driver-specific files in the
3250 Documentation/watchdog/ directory.
3252 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3253 default x2apic cluster mode on platforms
3256 x86_mrst_timer= [X86-32,APBT]
3257 Choose timer option for x86 Moorestown MID platform.
3258 Two valid options are apbt timer only and lapic timer
3259 plus one apbt timer for broadcast timer.
3260 x86_mrst_timer=apbt_only | lapic_and_apbt
3262 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3263 xd_geo= See header of drivers/block/xd.c.
3265 xen_emul_unplug= [HW,X86,XEN]
3266 Unplug Xen emulated devices
3267 Format: [unplug0,][unplug1]
3268 ide-disks -- unplug primary master IDE devices
3269 aux-ide-disks -- unplug non-primary-master IDE devices
3270 nics -- unplug network devices
3271 all -- unplug all emulated devices (NICs and IDE disks)
3272 unnecessary -- unplugging emulated devices is
3273 unnecessary even if the host did not respond to
3275 never -- do not unplug even if version check succeeds
3277 xirc2ps_cs= [NET,PCMCIA]
3279 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3281 ______________________________________________________________________
3285 Add more DRM drivers.
projects / GitHub / mt8127 / android_kernel_alcatel_ttab.git / blob