4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel=range1:size1[,range2:size2,...][@offset]
600 [KNL] Same as above, but depends on the memory
601 in the running system. The syntax of range is
602 start-[end] where start and end are both
603 a memory unit (amount[KMG]). See also
604 Documentation/kdump/kdump.txt for an example.
606 crashkernel_high=size[KMG]
607 [KNL, x86_64] range could be above 4G. Allow kernel
608 to allocate physical memory region from top, so could
609 be above 4G if system have more than 4G ram installed.
610 Otherwise memory region will be allocated below 4G, if
612 It will be ignored if crashkernel=X is specified.
613 crashkernel_low=size[KMG]
614 [KNL, x86_64] range under 4G. When crashkernel_high= is
615 passed, kernel could allocate physical memory region
616 above 4G, that cause second kernel crash on system
617 that require some amount of low memory, e.g. swiotlb
618 requires at least 64M+32K low memory. Kernel would
619 try to allocate 72M below 4G automatically.
620 This one let user to specify own low range under 4G
621 for second kernel instead.
622 0: to disable low allocation.
623 It will be ignored when crashkernel_high=X is not used
624 or memory reserved is below 4G.
629 cs89x0_media= [HW,NET]
630 Format: { rj45 | aui | bnc }
633 See header of drivers/s390/block/dasd_devmap.c.
635 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
636 (one device per port)
637 Format: <port#>,<type>
638 See also Documentation/input/joystick-parport.txt
640 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
641 time. See Documentation/dynamic-debug-howto.txt for
642 details. Deprecated, see dyndbg.
644 debug [KNL] Enable kernel debugging (events log level).
647 [KNL] verbose self-tests
649 Print debugging info while doing the locking API
651 We default to 0 (no extra messages), setting it to
652 1 will print _a lot_ more information - normally
653 only useful to kernel developers.
655 debug_objects [KNL] Enable object debugging
658 [KNL] Disable object debugging
660 debug_guardpage_minorder=
661 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
662 parameter allows control of the order of pages that will
663 be intentionally kept free (and hence protected) by the
664 buddy allocator. Bigger value increase the probability
665 of catching random memory corruption, but reduce the
666 amount of memory for normal system use. The maximum
667 possible value is MAX_ORDER/2. Setting this parameter
668 to 1 or 2 should be enough to identify most random
669 memory corruption problems caused by bugs in kernel or
670 driver code when a CPU writes to (or reads from) a
671 random memory location. Note that there exists a class
672 of memory corruptions problems caused by buggy H/W or
673 F/W or by drivers badly programing DMA (basically when
674 memory is written at bus level and the CPU MMU is
675 bypassed) which are not detectable by
676 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
677 tracking down these problems.
679 debugpat [X86] Enable PAT debugging
681 decnet.addr= [HW,NET]
682 Format: <area>[,<node>]
683 See also Documentation/networking/decnet.txt.
686 [same as hugepagesz=] The size of the default
687 HugeTLB page size. This is the size represented by
688 the legacy /proc/ hugepages APIs, used for SHM, and
689 default size when mounting hugetlbfs filesystems.
690 Defaults to the default architecture's huge page size
694 Set number of hash buckets for dentry cache.
697 IO parameters + enable/disable command.
699 digiepca= [HW,SERIAL]
700 See drivers/char/README.epca and
701 Documentation/serial/digiepca.txt.
704 See Documentation/networking/ipv6.txt.
706 disable_ddw [PPC/PSERIES]
707 Disable Dynamic DMA Window support. Use this if
708 to workaround buggy firmware.
711 See Documentation/networking/ipv6.txt.
713 disable_mtrr_cleanup [X86]
714 The kernel tries to adjust MTRR layout from continuous
715 to discrete, to make X server driver able to add WB
716 entry later. This parameter disables that.
718 disable_mtrr_trim [X86, Intel and AMD only]
719 By default the kernel will trim any uncacheable
720 memory out of your available memory pool based on
721 MTRR settings. This parameter disables that behavior,
722 possibly causing your machine to run very slowly.
724 disable_timer_pin_1 [X86]
725 Disable PIN 1 of APIC timer
726 Can be useful to work around chipset bugs.
728 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
729 this option disables the debugging code at boot.
731 dma_debug_entries=<number>
732 This option allows to tune the number of preallocated
733 entries for DMA-API debugging code. One entry is
734 required per DMA-API allocation. Use this if the
735 DMA-API debugging code disables itself because the
736 architectural default is too low.
738 dma_debug_driver=<driver_name>
739 With this option the DMA-API debugging driver
740 filter feature can be enabled at boot time. Just
741 pass the driver to filter for as the parameter.
742 The filter can be disabled or changed to another
743 driver later using sysfs.
745 drm_kms_helper.edid_firmware=[<connector>:]<file>
746 Broken monitors, graphic adapters and KVMs may
747 send no or incorrect EDID data sets. This parameter
748 allows to specify an EDID data set in the
749 /lib/firmware directory that is used instead.
750 Generic built-in EDID data sets are used, if one of
751 edid/1024x768.bin, edid/1280x1024.bin,
752 edid/1680x1050.bin, or edid/1920x1080.bin is given
753 and no file with the same name exists. Details and
754 instructions how to build your own EDID data are
755 available in Documentation/EDID/HOWTO.txt. An EDID
756 data set will only be used for a particular connector,
757 if its name and a colon are prepended to the EDID
762 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
763 module.dyndbg[="val"]
764 Enable debug messages at boot time. See
765 Documentation/dynamic-debug-howto.txt for details.
767 earlycon= [KNL] Output early console device and options.
768 uart[8250],io,<addr>[,options]
769 uart[8250],mmio,<addr>[,options]
770 uart[8250],mmio32,<addr>[,options]
771 Start an early, polled-mode console on the 8250/16550
772 UART at the specified I/O port or MMIO address.
773 MMIO inter-register address stride is either 8-bit
774 (mmio) or 32-bit (mmio32).
775 The options are the same as for ttyS, above.
777 earlyprintk= [X86,SH,BLACKFIN]
780 earlyprintk=serial[,ttySn[,baudrate]]
781 earlyprintk=ttySn[,baudrate]
782 earlyprintk=dbgp[debugController#]
784 Append ",keep" to not disable it when the real console
787 Only vga or serial or usb debug port at a time.
789 Currently only ttyS0 and ttyS1 are supported.
791 Interaction with the standard serial driver is not
794 The VGA output is eventually overwritten by the real
797 The xen output can only be used by Xen PV guests.
799 ekgdboc= [X86,KGDB] Allow early kernel console debugging
802 This is designed to be used in conjunction with
803 the boot argument: earlyprintk=vga
806 Format: {"off" | "on" | "skip[mbr]"}
808 eisa_irq_edge= [PARISC,HW]
809 See header of drivers/parisc/eisa.c.
812 See comment before function elanfreq_setup() in
813 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
816 Format: {"cfq" | "deadline" | "noop"}
817 See Documentation/block/cfq-iosched.txt and
818 Documentation/block/deadline-iosched.txt for details.
820 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
821 Specifies physical address of start of kernel core
822 image elf header and optionally the size. Generally
823 kexec loader will pass this option to capture kernel.
824 See Documentation/kdump/kdump.txt for details.
826 enable_mtrr_cleanup [X86]
827 The kernel tries to adjust MTRR layout from continuous
828 to discrete, to make X server driver able to add WB
829 entry later. This parameter enables that.
831 enable_timer_pin_1 [X86]
832 Enable PIN 1 of APIC timer
833 Can be useful to work around chipset bugs
834 (in particular on some ATI chipsets).
835 The kernel tries to set a reasonable default.
837 enforcing [SELINUX] Set initial enforcing status.
839 See security/selinux/Kconfig help text.
840 0 -- permissive (log only, no denials).
841 1 -- enforcing (deny and log).
843 Value can be changed at runtime via /selinux/enforce.
846 Disable Error Record Serialization Table (ERST)
849 ether= [HW,NET] Ethernet cards parameters
850 This option is obsoleted by the "netdev=" option, which
851 has equivalent usage. See its documentation for details.
855 Permit 'security.evm' to be updated regardless of
856 current integrity status.
860 fail_make_request=[KNL]
861 General fault injection mechanism.
862 Format: <interval>,<probability>,<space>,<times>
863 See also Documentation/fault-injection/.
866 See Documentation/blockdev/floppy.txt.
868 force_pal_cache_flush
869 [IA-64] Avoid check_sal_cache_flush which may hang on
870 buggy SAL_CACHE_FLUSH implementations. Using this
871 parameter will force ia64_sal_cache_flush to call
872 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
875 [FTRACE] will set and start the specified tracer
876 as early as possible in order to facilitate early
879 ftrace_dump_on_oops[=orig_cpu]
880 [FTRACE] will dump the trace buffers on oops.
881 If no parameter is passed, ftrace will dump
882 buffers of all CPUs, but if you pass orig_cpu, it will
883 dump only the buffer of the CPU that triggered the
886 ftrace_filter=[function-list]
887 [FTRACE] Limit the functions traced by the function
888 tracer at boot up. function-list is a comma separated
889 list of functions. This list can be changed at run
890 time by the set_ftrace_filter file in the debugfs
893 ftrace_notrace=[function-list]
894 [FTRACE] Do not trace the functions specified in
895 function-list. This list can be changed at run time
896 by the set_ftrace_notrace file in the debugfs
899 ftrace_graph_filter=[function-list]
900 [FTRACE] Limit the top level callers functions traced
901 by the function graph tracer at boot up.
902 function-list is a comma separated list of functions
903 that can be changed at run time by the
904 set_graph_function file in the debugfs tracing directory.
907 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
908 support via parallel port (up to 5 devices per port)
909 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
910 See also Documentation/input/joystick-parport.txt
914 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
918 gcov_persist= [GCOV] When non-zero (default), profiling data for
919 kernel modules is saved and remains accessible via
920 debugfs, even when the module is unloaded/reloaded.
921 When zero, profiling data is discarded and associated
922 debugfs files are removed at module unload time.
924 gpt [EFI] Forces disk with valid GPT signature but
925 invalid Protective MBR to be treated as GPT.
927 grcan.enable0= [HW] Configuration of physical interface 0. Determines
928 the "Enable 0" bit of the configuration register.
931 grcan.enable1= [HW] Configuration of physical interface 1. Determines
932 the "Enable 0" bit of the configuration register.
935 grcan.select= [HW] Select which physical interface to use.
938 grcan.txsize= [HW] Sets the size of the tx buffer.
939 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
941 grcan.rxsize= [HW] Sets the size of the rx buffer.
942 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
945 hashdist= [KNL,NUMA] Large hashes allocated during boot
946 are distributed across NUMA nodes. Defaults on
947 for 64-bit NUMA, off otherwise.
948 Format: 0 | 1 (for off | on)
950 hcl= [IA-64] SGI's Hardware Graph compatibility layer
952 hd= [EIDE] (E)IDE hard drive subsystem geometry
953 Format: <cyl>,<head>,<sect>
956 Disable Hardware Error Source Table (HEST) support;
957 corresponding firmware-first mode error processing
958 logic will be disabled.
960 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
961 size of <nn>. This works even on boxes that have no
962 highmem otherwise. This also works to reduce highmem
963 size on bigger boxes.
965 highres= [KNL] Enable/disable high resolution timer mode.
966 Valid parameters: "on", "off"
970 See Documentation/isdn/README.HiSax.
974 hpet= [X86-32,HPET] option to control HPET usage
975 Format: { enable (default) | disable | force |
977 disable: disable HPET and use PIT instead
978 force: allow force enabled of undocumented chips (ICH4,
980 verbose: show contents of HPET registers during setup
982 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
983 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
984 On x86-64 and powerpc, this option can be specified
985 multiple times interleaved with hugepages= to reserve
986 huge pages of different sizes. Valid pages sizes on
987 x86-64 are 2M (when the CPU supports "pse") and 1G
988 (when the CPU supports the "pdpe1gb" cpuinfo flag)
989 Note that 1GB pages can only be allocated at boot time
990 using hugepages= and not freed afterwards.
992 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
993 terminal devices. Valid values: 0..8
994 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
995 If specified, z/VM IUCV HVC accepts connections
996 from listed z/VM user IDs only.
998 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
999 hardware thread id mappings.
1000 Format: <cpu>:<hwthread>
1003 Do not unregister boot console at start. This is only
1004 useful for debugging when something happens in the window
1005 between unregistering the boot console and initializing
1008 i2c_bus= [HW] Override the default board specific I2C bus speed
1009 or register an additional I2C bus that is not
1010 registered from board initialization code.
1014 i8042.debug [HW] Toggle i8042 debug mode
1015 i8042.direct [HW] Put keyboard port into non-translated mode
1016 i8042.dumbkbd [HW] Pretend that controller can only read data from
1017 keyboard and cannot control its state
1018 (Don't attempt to blink the leds)
1019 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1020 i8042.nokbd [HW] Don't check/create keyboard port
1021 i8042.noloop [HW] Disable the AUX Loopback command while probing
1023 i8042.nomux [HW] Don't check presence of an active multiplexing
1025 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1027 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1028 i8042.reset [HW] Reset the controller during init and cleanup
1029 i8042.unlock [HW] Unlock (ignore) the keylock
1033 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1034 indicates that the driver is running on unsupported
1036 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1037 does not match list of supported models.
1039 [HW] Report power status in /proc/i8k
1040 (disabled by default)
1041 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1044 i915.invert_brightness=
1045 [DRM] Invert the sense of the variable that is used to
1046 set the brightness of the panel backlight. Normally a
1047 brightness value of 0 indicates backlight switched off,
1048 and the maximum of the brightness value sets the backlight
1049 to maximum brightness. If this parameter is set to 0
1050 (default) and the machine requires it, or this parameter
1051 is set to 1, a brightness value of 0 sets the backlight
1052 to maximum brightness, and the maximum of the brightness
1053 value switches the backlight off.
1054 -1 -- never invert brightness
1055 0 -- machine default
1056 1 -- force brightness inversion
1059 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1061 ide-core.nodma= [HW] (E)IDE subsystem
1062 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1063 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1064 .cdrom .chs .ignore_cable are additional options
1065 See Documentation/ide/ide.txt.
1067 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1068 Claim all unknown PCI IDE storage controllers.
1071 Format: idle=poll, idle=halt, idle=nomwait
1072 Poll forces a polling idle loop that can slightly
1073 improve the performance of waking up a idle CPU, but
1074 will use a lot of power and make the system run hot.
1076 idle=halt: Halt is forced to be used for CPU idle.
1077 In such case C2/C3 won't be used again.
1078 idle=nomwait: Disable mwait for CPU C-states
1080 ignore_loglevel [KNL]
1081 Ignore loglevel setting - this will print /all/
1082 kernel messages to the console. Useful for debugging.
1083 We also add it as printk module parameter, so users
1084 could change it dynamically, usually by
1085 /sys/module/printk/parameters/ignore_loglevel.
1087 ihash_entries= [KNL]
1088 Set number of hash buckets for inode cache.
1090 ima_appraise= [IMA] appraise integrity measurements
1091 Format: { "off" | "enforce" | "fix" }
1094 ima_appraise_tcb [IMA]
1095 The builtin appraise policy appraises all files
1099 Format: { "0" | "1" }
1100 0 -- integrity auditing messages. (Default)
1101 1 -- enable informational integrity auditing messages.
1104 Format: { "sha1" | "md5" }
1108 Load a policy which meets the needs of the Trusted
1109 Computing Base. This means IMA will measure all
1110 programs exec'd, files mmap'd for exec, and all files
1111 opened for read by uid=0.
1115 Run specified binary instead of /sbin/init as init
1118 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1119 for working out where the kernel is dying during
1122 initrd= [BOOT] Specify the location of the initial ramdisk
1124 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1127 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1129 Enable intel iommu driver.
1131 Disable intel iommu driver.
1132 igfx_off [Default Off]
1133 By default, gfx is mapped as normal device. If a gfx
1134 device has a dedicated DMAR unit, the DMAR unit is
1135 bypassed by not enabling DMAR with this option. In
1136 this case, gfx device will use physical address for
1139 With this option iommu will not optimize to look
1140 for io virtual address below 32-bit forcing dual
1141 address cycle on pci bus for cards supporting greater
1142 than 32-bit addressing. The default is to look
1143 for translation below 32-bit and if not available
1144 then look in the higher range.
1145 strict [Default Off]
1146 With this option on every unmap_single operation will
1147 result in a hardware IOTLB flush operation as opposed
1148 to batching them for performance.
1149 sp_off [Default Off]
1150 By default, super page will be supported if Intel IOMMU
1151 has the capability. With this option, super page will
1154 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1155 0 disables intel_idle and fall back on acpi_idle.
1156 1 to 6 specify maximum depth of C-state.
1160 Do not enable intel_pstate as the default
1161 scaling driver for the supported processors
1163 intremap= [X86-64, Intel-IOMMU]
1164 on enable Interrupt Remapping (default)
1165 off disable Interrupt Remapping
1166 nosid disable Source ID checking
1168 BIOS x2APIC opt-out request will be ignored
1170 iomem= Disable strict checking of access to MMIO memory
1171 strict regions from userspace.
1188 io7= [HW] IO7 for Marvel based alpha systems
1189 See comment before marvel_specify_io7 in
1190 arch/alpha/kernel/core_marvel.c.
1192 io_delay= [X86] I/O delay method
1194 Standard port 0x80 based delay
1196 Alternate port 0xed based delay (needed on some systems)
1198 Simple two microseconds delay
1203 See Documentation/filesystems/nfs/nfsroot.txt.
1205 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1206 See comment before ip2_setup() in
1207 drivers/char/ip2/ip2base.c.
1210 When an interrupt is not handled search all handlers
1211 for it. Intended to get systems with badly broken
1215 When an interrupt is not handled search all handlers
1216 for it. Also check all handlers each timer
1217 interrupt. Intended to get systems with badly broken
1221 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1223 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1225 <cpu number>,...,<cpu number>
1227 <cpu number>-<cpu number>
1228 (must be a positive range in ascending order)
1230 <cpu number>,...,<cpu number>-<cpu number>
1232 This option can be used to specify one or more CPUs
1233 to isolate from the general SMP balancing and scheduling
1234 algorithms. You can move a process onto or off an
1235 "isolated" CPU via the CPU affinity syscalls or cpuset.
1236 <cpu number> begins at 0 and the maximum value is
1237 "number of CPUs in system - 1".
1239 This option is the preferred way to isolate CPUs. The
1240 alternative -- manually setting the CPU mask of all
1241 tasks in the system -- can cause problems and
1242 suboptimal load balancer performance.
1246 js= [HW,JOY] Analog joystick
1247 See Documentation/input/joystick.txt.
1251 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1252 specifies the amount of memory usable by the kernel
1253 for non-movable allocations. The requested amount is
1254 spread evenly throughout all nodes in the system. The
1255 remaining memory in each node is used for Movable
1256 pages. In the event, a node is too small to have both
1257 kernelcore and Movable pages, kernelcore pages will
1258 take priority and other nodes will have a larger number
1259 of kernelcore pages. The Movable zone is used for the
1260 allocation of pages that may be reclaimed or moved
1261 by the page migration subsystem. This means that
1262 HugeTLB pages may not be allocated from this zone.
1263 Note that allocations like PTEs-from-HighMem still
1264 use the HighMem zone if it exists, and the Normal
1265 zone if it does not.
1267 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1268 Format: <Controller#>[,poll interval]
1269 The controller # is the number of the ehci usb debug
1270 port as it is probed via PCI. The poll interval is
1271 optional and is the number seconds in between
1272 each poll cycle to the debug port in case you need
1273 the functionality for interrupting the kernel with
1274 gdb or control-c on the dbgp connection. When
1275 not using this parameter you use sysrq-g to break into
1276 the kernel debugger.
1278 kgdboc= [KGDB,HW] kgdb over consoles.
1279 Requires a tty driver that supports console polling,
1280 or a supported polling keyboard driver (non-usb).
1281 Serial only format: <serial_device>[,baud]
1282 keyboard only format: kbd
1283 keyboard and serial format: kbd,<serial_device>[,baud]
1284 Optional Kernel mode setting:
1285 kms, kbd format: kms,kbd
1286 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1288 kgdbwait [KGDB] Stop kernel execution and enter the
1289 kernel debugger at the earliest opportunity.
1291 kmac= [MIPS] korina ethernet MAC address.
1292 Configure the RouterBoard 532 series on-chip
1293 Ethernet adapter MAC address.
1295 kmemleak= [KNL] Boot-time kmemleak enable/disable
1296 Valid arguments: on, off
1299 kstack=N [X86] Print N words from the kernel stack
1302 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1303 Default is 0 (don't ignore, but inject #GP)
1305 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1309 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1310 Default is 1 (enabled)
1312 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1314 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1316 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1317 (virtualized MMU) support on capable Intel chips.
1318 Default is 1 (enabled)
1320 kvm-intel.emulate_invalid_guest_state=
1321 [KVM,Intel] Enable emulation of invalid guest states
1322 Default is 0 (disabled)
1324 kvm-intel.flexpriority=
1325 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1326 Default is 1 (enabled)
1329 [KVM,Intel] Enable VMX nesting (nVMX).
1330 Default is 0 (disabled)
1332 kvm-intel.unrestricted_guest=
1333 [KVM,Intel] Disable unrestricted guest feature
1334 (virtualized real and unpaged mode) on capable
1335 Intel chips. Default is 1 (enabled)
1337 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1338 feature (tagged TLBs) on capable Intel chips.
1339 Default is 1 (enabled)
1345 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1348 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1349 value for LAPIC timer one-shot implementation. Default
1350 back to the programmable timer unit in the LAPIC.
1352 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1355 libata.dma= [LIBATA] DMA control
1356 libata.dma=0 Disable all PATA and SATA DMA
1357 libata.dma=1 PATA and SATA Disk DMA only
1358 libata.dma=2 ATAPI (CDROM) DMA only
1359 libata.dma=4 Compact Flash DMA only
1360 Combinations also work, so libata.dma=3 enables DMA
1361 for disks and CDROMs, but not CFs.
1363 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1364 libata.ignore_hpa=0 keep BIOS limits (default)
1365 libata.ignore_hpa=1 ignore limits, using full disk
1367 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1371 libata.force= [LIBATA] Force configurations. The format is comma
1372 separated list of "[ID:]VAL" where ID is
1373 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1374 matching port, link or device. Basically, it matches
1375 the ATA ID string printed on console by libata. If
1376 the whole ID part is omitted, the last PORT and DEVICE
1377 values are used. If ID hasn't been specified yet, the
1378 configuration applies to all ports, links and devices.
1380 If only DEVICE is omitted, the parameter applies to
1381 the port and all links and devices behind it. DEVICE
1382 number of 0 either selects the first device or the
1383 first fan-out link behind PMP device. It does not
1384 select the host link. DEVICE number of 15 selects the
1385 host link and device attached to it.
1387 The VAL specifies the configuration to force. As long
1388 as there's no ambiguity shortcut notation is allowed.
1389 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1390 The following configurations can be forced.
1392 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1393 Any ID with matching PORT is used.
1395 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1397 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1398 udma[/][16,25,33,44,66,100,133] notation is also
1401 * [no]ncq: Turn on or off NCQ.
1403 * nohrst, nosrst, norst: suppress hard, soft
1406 * rstonce: only attempt one reset during
1407 hot-unplug link recovery
1409 * dump_id: dump IDENTIFY data.
1411 If there are multiple matching configurations changing
1412 the same attribute, the last one is used.
1414 memblock=debug [KNL] Enable memblock debug messages.
1416 load_ramdisk= [RAM] List of ramdisks to load from floppy
1417 See Documentation/blockdev/ramdisk.txt.
1419 lockd.nlm_grace_period=P [NFS] Assign grace period.
1422 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1425 lockd.nlm_timeout=T [NFS] Assign timeout value.
1428 lockd.nlm_udpport=M [NFS] Assign UDP port.
1431 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1434 loglevel= All Kernel Messages with a loglevel smaller than the
1435 console loglevel will be printed to the console. It can
1436 also be changed with klogd or other programs. The
1437 loglevels are defined as follows:
1439 0 (KERN_EMERG) system is unusable
1440 1 (KERN_ALERT) action must be taken immediately
1441 2 (KERN_CRIT) critical conditions
1442 3 (KERN_ERR) error conditions
1443 4 (KERN_WARNING) warning conditions
1444 5 (KERN_NOTICE) normal but significant condition
1445 6 (KERN_INFO) informational
1446 7 (KERN_DEBUG) debug-level messages
1448 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1449 in bytes. n must be a power of two. The default
1450 size is set in the kernel config file.
1452 logo.nologo [FB] Disables display of the built-in Linux logo.
1453 This may be used to provide more screen space for
1454 kernel log messages and is useful when debugging
1455 kernel boot problems.
1457 lp=0 [LP] Specify parallel ports to use, e.g,
1458 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1459 lp=reset first parallel port). 'lp=0' disables the
1460 lp=auto printer driver. 'lp=reset' (which can be
1461 specified in addition to the ports) causes
1462 attached printers to be reset. Using
1463 lp=port1,port2,... specifies the parallel ports
1464 to associate lp devices with, starting with
1465 lp0. A port specification may be 'none' to skip
1466 that lp device, or a parport name such as
1467 'parport0'. Specifying 'lp=auto' instead of a
1468 port specification list means that device IDs
1469 from each port should be examined, to see if
1470 an IEEE 1284-compliant printer is attached; if
1471 so, the driver will manage that printer.
1472 See also header of drivers/char/lp.c.
1475 Sets loops_per_jiffy to given constant, thus avoiding
1476 time-consuming boot-time autodetection (up to 250 ms per
1477 CPU). 0 enables autodetection (default). To determine
1478 the correct value for your kernel, boot with normal
1479 autodetection and see what value is printed. Note that
1480 on SMP systems the preset will be applied to all CPUs,
1481 which is likely to cause problems if your CPUs need
1482 significantly divergent settings. An incorrect value
1483 will cause delays in the kernel to be wrong, leading to
1484 unpredictable I/O errors and other breakage. Although
1485 unlikely, in the extreme case this might damage your
1489 Format: <io>,<irq>,<dma>
1491 machvec= [IA-64] Force the use of a particular machine-vector
1492 (machvec) in a generic kernel.
1493 Example: machvec=hpzx1_swiotlb
1495 machtype= [Loongson] Share the same kernel image file between different
1497 Example: machtype=lemote-yeeloong-2f-7inch
1499 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1500 than or equal to this physical address is ignored.
1502 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1503 should make use of. maxcpus=n : n >= 0 limits the
1504 kernel to using 'n' processors. n=0 is a special case,
1505 it is equivalent to "nosmp", which also disables
1508 max_loop= [LOOP] The number of loop block devices that get
1509 (loop.max_loop) unconditionally pre-created at init time. The default
1510 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1511 of statically allocating a predefined number, loop
1512 devices can be requested on-demand with the
1513 /dev/loop-control interface.
1515 mce [X86-32] Machine Check Exception
1517 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1519 md= [HW] RAID subsystems devices and level
1520 See Documentation/md.txt.
1523 Format: <first>,<last>
1524 Specifies range of consoles to be captured by the MDA.
1526 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1527 Amount of memory to be used when the kernel is not able
1528 to see the whole system memory or for test.
1529 [X86] Work as limiting max address. Use together
1530 with memmap= to avoid physical address space collisions.
1531 Without memmap= PCI devices could be placed at addresses
1532 belonging to unused RAM.
1534 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1538 [KNL,SH] Allow user to override the default size for
1539 per-device physically contiguous DMA buffers.
1541 memmap=exactmap [KNL,X86] Enable setting of an exact
1542 E820 memory map, as specified by the user.
1543 Such memmap=exactmap lines can be constructed based on
1544 BIOS output or other requirements. See the memmap=nn@ss
1547 memmap=nn[KMG]@ss[KMG]
1548 [KNL] Force usage of a specific region of memory
1549 Region of memory to be used, from ss to ss+nn.
1551 memmap=nn[KMG]#ss[KMG]
1552 [KNL,ACPI] Mark specific memory as ACPI data.
1553 Region of memory to be used, from ss to ss+nn.
1555 memmap=nn[KMG]$ss[KMG]
1556 [KNL,ACPI] Mark specific memory as reserved.
1557 Region of memory to be used, from ss to ss+nn.
1558 Example: Exclude memory from 0x18690000-0x1869ffff
1559 memmap=64K$0x18690000
1561 memmap=0x10000$0x18690000
1563 memory_corruption_check=0/1 [X86]
1564 Some BIOSes seem to corrupt the first 64k of
1565 memory when doing things like suspend/resume.
1566 Setting this option will scan the memory
1567 looking for corruption. Enabling this will
1568 both detect corruption and prevent the kernel
1569 from using the memory being corrupted.
1570 However, its intended as a diagnostic tool; if
1571 repeatable BIOS-originated corruption always
1572 affects the same memory, you can use memmap=
1573 to prevent the kernel from using that memory.
1575 memory_corruption_check_size=size [X86]
1576 By default it checks for corruption in the low
1577 64k, making this memory unavailable for normal
1578 use. Use this parameter to scan for
1579 corruption in more or less memory.
1581 memory_corruption_check_period=seconds [X86]
1582 By default it checks for corruption every 60
1583 seconds. Use this parameter to check at some
1584 other rate. 0 disables periodic checking.
1586 memtest= [KNL,X86] Enable memtest
1588 default : 0 <disable>
1589 Specifies the number of memtest passes to be
1590 performed. Each pass selects another test
1591 pattern from a given set of patterns. Memtest
1592 fills the memory with this pattern, validates
1593 memory contents and reserves bad memory
1594 regions that are detected.
1596 meye.*= [HW] Set MotionEye Camera parameters
1597 See Documentation/video4linux/meye.txt.
1599 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1600 Multi-Function General Purpose Timers on AMD Geode
1603 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1604 the BIOS has incorrectly applied a workaround. TinyBIOS
1605 version 0.98 is known to be affected, 0.99 fixes the
1606 problem by letting the user disable the workaround.
1610 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1611 physical address is ignored.
1613 mini2440= [ARM,HW,KNL]
1614 Format:[0..2][b][c][t]
1616 MINI2440 configuration specification:
1617 0 - The attached screen is the 3.5" TFT
1618 1 - The attached screen is the 7" TFT
1619 2 - The VGA Shield is attached (1024x768)
1620 Leaving out the screen size parameter will not load
1621 the TFT driver, and the framebuffer will be left
1623 b - Enable backlight. The TFT backlight pin will be
1624 linked to the kernel VESA blanking code and a GPIO
1625 LED. This parameter is not necessary when using the
1627 c - Enable the s3c camera interface.
1628 t - Reserved for enabling touchscreen support. The
1629 touchscreen support is not enabled in the mainstream
1630 kernel as of 2.6.30, a preliminary port can be found
1631 in the "bleeding edge" mini2440 support kernel at
1632 http://repo.or.cz/w/linux-2.6/mini2440.git
1635 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1636 parameter allows control of the logging verbosity for
1637 the additional memory initialisation checks. A value
1638 of 0 disables mminit logging and a level of 4 will
1639 log everything. Information is printed at KERN_DEBUG
1640 so loglevel=8 may also need to be specified.
1643 [KNL] When CONFIG_MODULE_SIG is set, this means that
1644 modules without (valid) signatures will fail to load.
1645 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1646 is always true, so this option does nothing.
1649 [MOUSE] Maximum time between finger touching and
1650 leaving touchpad surface for touch to be considered
1651 a tap and be reported as a left button click (for
1652 touchpads working in absolute mode only).
1654 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1655 reporting absolute coordinates, such as tablets
1656 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1657 reporting absolute coordinates, such as tablets
1659 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1660 is similar to kernelcore except it specifies the
1661 amount of memory used for migratable allocations.
1662 If both kernelcore and movablecore is specified,
1663 then kernelcore will be at *least* the specified
1664 value but may be more. If movablecore on its own
1665 is specified, the administrator must be careful
1666 that the amount of memory usable for all allocations
1669 MTD_Partition= [MTD]
1670 Format: <name>,<region-number>,<size>,<offset>
1672 MTD_Region= [MTD] Format:
1673 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1676 See drivers/mtd/cmdlinepart.c.
1678 multitce=off [PPC] This parameter disables the use of the pSeries
1679 firmware feature for updating multiple TCE entries
1682 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1684 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1686 boundary - index of last SLC block on Flex-OneNAND.
1687 The remaining blocks are configured as MLC blocks.
1688 lock - Configure if Flex-OneNAND boundary should be locked.
1689 Once locked, the boundary cannot be changed.
1690 1 indicates lock status, 0 indicates unlock status.
1693 ARM/S3C2412 JIVE boot control
1695 See arch/arm/mach-s3c2412/mach-jive.c
1697 mtouchusb.raw_coordinates=
1698 [HW] Make the MicroTouch USB driver use raw coordinates
1699 ('y', default) or cooked coordinates ('n')
1701 mtrr_chunk_size=nn[KMG] [X86]
1702 used for mtrr cleanup. It is largest continuous chunk
1703 that could hold holes aka. UC entries.
1705 mtrr_gran_size=nn[KMG] [X86]
1706 Used for mtrr cleanup. It is granularity of mtrr block.
1708 Large value could prevent small alignment from
1711 mtrr_spare_reg_nr=n [X86]
1713 Range: 0,7 : spare reg number
1715 Used for mtrr cleanup. It is spare mtrr entries number.
1716 Set to 2 or more if your graphical card needs more.
1718 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1720 netdev= [NET] Network devices parameters
1721 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1722 Note that mem_start is often overloaded to mean
1723 something different and driver-specific.
1724 This usage is only documented in each driver source
1728 [NETFILTER] Enable connection tracking flow accounting
1729 0 to disable accounting
1730 1 to enable accounting
1733 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1734 See Documentation/filesystems/nfs/nfsroot.txt.
1736 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1737 See Documentation/filesystems/nfs/nfsroot.txt.
1739 nfsrootdebug [NFS] enable nfsroot debugging messages.
1740 See Documentation/filesystems/nfs/nfsroot.txt.
1742 nfs.callback_tcpport=
1743 [NFS] set the TCP port on which the NFSv4 callback
1744 channel should listen.
1747 [NFS] sets the pathname to the program which is used
1748 to update the NFS client cache entries.
1750 nfs.cache_getent_timeout=
1751 [NFS] sets the timeout after which an attempt to
1752 update a cache entry is deemed to have failed.
1754 nfs.idmap_cache_timeout=
1755 [NFS] set the maximum lifetime for idmapper cache
1759 [NFS] enable 64-bit inode numbers.
1760 If zero, the NFS client will fake up a 32-bit inode
1761 number for the readdir() and stat() syscalls instead
1762 of returning the full 64-bit number.
1763 The default is to return 64-bit inode numbers.
1765 nfs.max_session_slots=
1766 [NFSv4.1] Sets the maximum number of session slots
1767 the client will attempt to negotiate with the server.
1768 This limits the number of simultaneous RPC requests
1769 that the client can send to the NFSv4.1 server.
1770 Note that there is little point in setting this
1771 value higher than the max_tcp_slot_table_limit.
1773 nfs.nfs4_disable_idmapping=
1774 [NFSv4] When set to the default of '1', this option
1775 ensures that both the RPC level authentication
1776 scheme and the NFS level operations agree to use
1777 numeric uids/gids if the mount is using the
1778 'sec=sys' security flavour. In effect it is
1779 disabling idmapping, which can make migration from
1780 legacy NFSv2/v3 systems to NFSv4 easier.
1781 Servers that do not support this mode of operation
1782 will be autodetected by the client, and it will fall
1783 back to using the idmapper.
1784 To turn off this behaviour, set the value to '0'.
1786 [NFS4] Specify an additional fixed unique ident-
1787 ification string that NFSv4 clients can insert into
1788 their nfs_client_id4 string. This is typically a
1789 UUID that is generated at system install time.
1791 nfs.send_implementation_id =
1792 [NFSv4.1] Send client implementation identification
1793 information in exchange_id requests.
1794 If zero, no implementation identification information
1796 The default is to send the implementation identification
1799 nfsd.nfs4_disable_idmapping=
1800 [NFSv4] When set to the default of '1', the NFSv4
1801 server will return only numeric uids and gids to
1802 clients using auth_sys, and will accept numeric uids
1803 and gids from such clients. This is intended to ease
1804 migration from NFSv2/v3.
1806 objlayoutdriver.osd_login_prog=
1807 [NFS] [OBJLAYOUT] sets the pathname to the program which
1808 is used to automatically discover and login into new
1809 osd-targets. Please see:
1810 Documentation/filesystems/pnfs.txt for more explanations
1812 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1813 when a NMI is triggered.
1814 Format: [state][,regs][,debounce][,die]
1816 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1817 Format: [panic,][nopanic,][num]
1819 0 - turn nmi_watchdog off
1820 When panic is specified, panic when an NMI watchdog
1821 timeout occurs (or 'nopanic' to override the opposite
1823 This is useful when you use a panic=... timeout and
1824 need the box quickly up again.
1826 netpoll.carrier_timeout=
1827 [NET] Specifies amount of time (in seconds) that
1828 netpoll should wait for a carrier. By default netpoll
1831 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1832 emulation library even if a 387 maths coprocessor
1836 [HW] Never suspend the console
1837 Disable suspending of consoles during suspend and
1838 hibernate operations. Once disabled, debugging
1839 messages can reach various consoles while the rest
1840 of the system is being put to sleep (ie, while
1841 debugging driver suspend/resume hooks). This may
1842 not work reliably with all consoles, but is known
1843 to work with serial and VGA consoles.
1844 To facilitate more flexible debugging, we also add
1845 console_suspend, a printk module parameter to control
1846 it. Users could use console_suspend (usually
1847 /sys/module/printk/parameters/console_suspend) to
1848 turn on/off it dynamically.
1850 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1851 caches in the slab allocator. Saves per-node memory,
1852 but will impact performance.
1856 noapic [SMP,APIC] Tells the kernel to not make use of any
1857 IOAPICs that may be present in the system.
1859 noautogroup Disable scheduler automatic task group creation.
1861 nobats [PPC] Do not use BATs for mapping kernel lowmem
1862 on "Classic" PPC cores.
1866 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1868 nodelayacct [KNL] Disable per-task delay accounting
1870 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1872 nodsp [SH] Disable hardware DSP at boot time.
1874 noefi [X86] Disable EFI runtime services support.
1879 On X86-32 available only on PAE configured kernels.
1880 noexec=on: enable non-executable mappings (default)
1881 noexec=off: disable non-executable mappings
1884 Disable SMAP (Supervisor Mode Access Prevention)
1885 even if it is supported by processor.
1888 Disable SMEP (Supervisor Mode Execution Prevention)
1889 even if it is supported by processor.
1892 This affects only 32-bit executables.
1893 noexec32=on: enable non-executable mappings (default)
1894 read doesn't imply executable mappings
1895 noexec32=off: disable non-executable mappings
1896 read implies executable mappings
1898 nofpu [SH] Disable hardware FPU at boot time.
1900 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1901 register save and restore. The kernel will only save
1902 legacy floating-point registers on task switch.
1904 noxsave [BUGS=X86] Disables x86 extended register state save
1905 and restore using xsave. The kernel will fallback to
1906 enabling legacy floating-point and sse state.
1909 on enable eager fpu restore
1910 off disable eager fpu restore
1911 auto selects the default scheme, which automatically
1912 enables eagerfpu restore for xsaveopt.
1914 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1915 wfi(ARM) instruction doesn't work correctly and not to
1916 use it. This is also useful when using JTAG debugger.
1918 no_file_caps Tells the kernel not to honor file capabilities. The
1919 only way then for a file to be executed with privilege
1920 is to be setuid root or executed by root.
1922 nohalt [IA-64] Tells the kernel not to use the power saving
1923 function PAL_HALT_LIGHT when idle. This increases
1924 power-consumption. On the positive side, it reduces
1925 interrupt wake-up latency, which may improve performance
1926 in certain environments such as networked servers or
1929 nohz= [KNL] Boottime enable/disable dynamic ticks
1930 Valid arguments: on, off
1933 noiotrap [SH] Disables trapped I/O port accesses.
1935 noirqdebug [X86-32] Disables the code which attempts to detect and
1936 disable unhandled interrupt sources.
1938 no_timer_check [X86,APIC] Disables the code which tests for
1939 broken timer IRQ sources.
1941 noisapnp [ISAPNP] Disables ISA PnP code.
1943 noinitrd [RAM] Tells the kernel not to load any configured
1946 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1948 [Deprecated - use intremap=off]
1952 nojitter [IA-64] Disables jitter checking for ITC timers.
1954 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1956 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1959 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1960 steal time is computed, but won't influence scheduler
1963 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1965 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1967 noltlbs [PPC] Do not use large page/tlb entries for kernel
1968 lowmem mapping on PPC40x.
1970 nomca [IA-64] Disable machine check abort handling
1972 nomce [X86-32] Machine Check Exception
1974 nomfgpt [X86-32] Disable Multi-Function General Purpose
1975 Timer usage (for AMD Geode machines).
1977 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1978 shutdown the other cpus. Instead use the REBOOT_VECTOR
1981 nomodule Disable module load
1983 nopat [X86] Disable PAT (page attribute table extension of
1984 pagetables) support.
1986 norandmaps Don't use address space randomization. Equivalent to
1987 echo 0 > /proc/sys/kernel/randomize_va_space
1989 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1991 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1992 with UP alternatives
1994 noresidual [PPC] Don't use residual data on PReP machines.
1996 nordrand [X86] Disable the direct use of the RDRAND
1997 instruction even if it is supported by the
1998 processor. RDRAND is still available to user
2001 noresume [SWSUSP] Disables resume and restores original swap
2004 no-scroll [VGA] Disables scrollback.
2005 This is required for the Braillex ib80-piezo Braille
2006 reader made by F.H. Papenmeier (Germany).
2010 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2012 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2013 and disable the IO APIC. legacy for "maxcpus=0".
2015 nosoftlockup [KNL] Disable the soft-lockup detector.
2017 nosync [HW,M68K] Disables sync negotiation for all devices.
2019 notsc [BUGS=X86-32] Disable Time Stamp Counter
2021 nousb [USB] Disable the USB subsystem
2023 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2027 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2029 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2030 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2031 Some features depend on CPU0. Known dependencies are:
2032 1. Resume from suspend/hibernate depends on CPU0.
2033 Suspend/hibernate will fail if CPU0 is offline and you
2034 need to online CPU0 before suspend/hibernate.
2035 2. PIC interrupts also depend on CPU0. CPU0 can't be
2036 removed if a PIC interrupt is detected.
2037 It's said poweroff/reboot may depend on CPU0 on some
2038 machines although I haven't seen such issues so far
2039 after CPU0 is offline on a few tested machines.
2040 If the dependencies are under your control, you can
2041 turn on cpu0_hotplug.
2043 nptcg= [IA-64] Override max number of concurrent global TLB
2044 purges which is reported from either PAL_VM_SUMMARY or
2047 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2048 could support. nr_cpus=n : n >= 1 limits the kernel to
2049 supporting 'n' processors. Later in runtime you can not
2050 use hotplug cpu feature to put more cpu back to online.
2051 just like you compile the kernel NR_CPUS=n
2053 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2055 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2056 Allowed values are enable and disable
2058 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2059 one of ['zone', 'node', 'default'] can be specified
2060 This can be set from sysctl after boot.
2061 See Documentation/sysctl/vm.txt for details.
2063 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2064 See Documentation/debugging-via-ohci1394.txt for more
2067 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2068 Rather than timing out after 20 ms if an EC
2069 command is not properly ACKed, override the length
2070 of the timeout. We have interrupts disabled while
2071 waiting for the ACK, so if this is set too high
2072 interrupts *may* be lost!
2074 omap_mux= [OMAP] Override bootloader pin multiplexing.
2075 Format: <mux_mode0.mode_name=value>...
2076 For example, to override I2C bus2:
2077 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2079 oprofile.timer= [HW]
2080 Use timer interrupt instead of performance counters
2082 oprofile.cpu_type= Force an oprofile cpu type
2083 This might be useful if you have an older oprofile
2084 userland or if you want common events.
2085 Format: { arch_perfmon }
2086 arch_perfmon: [X86] Force use of architectural
2087 perfmon on Intel CPUs instead of the
2088 CPU specific event set.
2089 timer: [X86] Force use of architectural NMI
2090 timer mode (see also oprofile.timer
2091 for generic hr timer mode)
2092 [s390] Force legacy basic mode sampling
2093 (report cpu_type "timer")
2095 oops=panic Always panic on oopses. Default is to just kill the
2096 process, but there is a small probability of
2097 deadlocking the machine.
2098 This will also cause panics on machine check exceptions.
2099 Useful together with panic=30 to trigger a reboot.
2102 See Documentation/sound/oss/oss-parameters.txt
2104 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2105 timeout > 0: seconds before rebooting
2106 timeout = 0: wait forever
2107 timeout < 0: reboot immediately
2110 parkbd.port= [HW] Parallel port number the keyboard adapter is
2111 connected to, default is 0.
2113 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2114 0 for XT, 1 for AT (default is AT).
2117 parport= [HW,PPT] Specify parallel ports. 0 disables.
2118 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2119 Use 'auto' to force the driver to use any
2120 IRQ/DMA settings detected (the default is to
2121 ignore detected IRQ/DMA settings because of
2122 possible conflicts). You can specify the base
2123 address, IRQ, and DMA settings; IRQ and DMA
2124 should be numbers, or 'auto' (for using detected
2125 settings on that particular port), or 'nofifo'
2126 (to avoid using a FIFO even if it is detected).
2127 Parallel ports are assigned in the order they
2128 are specified on the command line, starting
2131 parport_init_mode= [HW,PPT]
2132 Configure VIA parallel port to operate in
2133 a specific mode. This is necessary on Pegasos
2134 computer where firmware has no options for setting
2135 up parallel port mode and sets it to spp.
2136 Currently this function knows 686a and 8231 chips.
2137 Format: [spp|ps2|epp|ecp|ecpepp]
2140 Halt all CPUs after the first oops has been printed for
2141 the specified number of seconds. This is to be used if
2142 your oopses keep scrolling off the screen.
2147 See header of drivers/block/paride/pcd.c.
2148 See also Documentation/blockdev/paride.txt.
2150 pci=option[,option...] [PCI] various PCI subsystem options:
2151 earlydump [X86] dump PCI config space before the kernel
2153 off [X86] don't probe for the PCI bus
2154 bios [X86-32] force use of PCI BIOS, don't access
2155 the hardware directly. Use this if your machine
2156 has a non-standard PCI host bridge.
2157 nobios [X86-32] disallow use of PCI BIOS, only direct
2158 hardware access methods are allowed. Use this
2159 if you experience crashes upon bootup and you
2160 suspect they are caused by the BIOS.
2161 conf1 [X86] Force use of PCI Configuration
2163 conf2 [X86] Force use of PCI Configuration
2165 noaer [PCIE] If the PCIEAER kernel config parameter is
2166 enabled, this kernel boot option can be used to
2167 disable the use of PCIE advanced error reporting.
2168 nodomains [PCI] Disable support for multiple PCI
2169 root domains (aka PCI segments, in ACPI-speak).
2170 nommconf [X86] Disable use of MMCONFIG for PCI
2172 check_enable_amd_mmconf [X86] check for and enable
2173 properly configured MMIO access to PCI
2174 config space on AMD family 10h CPU
2175 nomsi [MSI] If the PCI_MSI kernel config parameter is
2176 enabled, this kernel boot option can be used to
2177 disable the use of MSI interrupts system-wide.
2178 noioapicquirk [APIC] Disable all boot interrupt quirks.
2179 Safety option to keep boot IRQs enabled. This
2180 should never be necessary.
2181 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2182 primary IO-APIC for bridges that cannot disable
2183 boot IRQs. This fixes a source of spurious IRQs
2184 when the system masks IRQs.
2185 noioapicreroute [APIC] Disable workaround that uses the
2186 boot IRQ equivalent of an IRQ that connects to
2187 a chipset where boot IRQs cannot be disabled.
2188 The opposite of ioapicreroute.
2189 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2190 routing table. These calls are known to be buggy
2191 on several machines and they hang the machine
2192 when used, but on other computers it's the only
2193 way to get the interrupt routing table. Try
2194 this option if the kernel is unable to allocate
2195 IRQs or discover secondary PCI buses on your
2197 rom [X86] Assign address space to expansion ROMs.
2198 Use with caution as certain devices share
2199 address decoders between ROMs and other
2201 norom [X86] Do not assign address space to
2202 expansion ROMs that do not already have
2203 BIOS assigned address ranges.
2204 nobar [X86] Do not assign address space to the
2205 BARs that weren't assigned by the BIOS.
2206 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2207 assigned automatically to PCI devices. You can
2208 make the kernel exclude IRQs of your ISA cards
2210 pirqaddr=0xAAAAA [X86] Specify the physical address
2211 of the PIRQ table (normally generated
2212 by the BIOS) if it is outside the
2213 F0000h-100000h range.
2214 lastbus=N [X86] Scan all buses thru bus #N. Can be
2215 useful if the kernel is unable to find your
2216 secondary buses and you want to tell it
2217 explicitly which ones they are.
2218 assign-busses [X86] Always assign all PCI bus
2219 numbers ourselves, overriding
2220 whatever the firmware may have done.
2221 usepirqmask [X86] Honor the possible IRQ mask stored
2222 in the BIOS $PIR table. This is needed on
2223 some systems with broken BIOSes, notably
2224 some HP Pavilion N5400 and Omnibook XE3
2225 notebooks. This will have no effect if ACPI
2226 IRQ routing is enabled.
2227 noacpi [X86] Do not use ACPI for IRQ routing
2228 or for PCI scanning.
2229 use_crs [X86] Use PCI host bridge window information
2230 from ACPI. On BIOSes from 2008 or later, this
2231 is enabled by default. If you need to use this,
2232 please report a bug.
2233 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2234 If you need to use this, please report a bug.
2235 routeirq Do IRQ routing for all PCI devices.
2236 This is normally done in pci_enable_device(),
2237 so this option is a temporary workaround
2238 for broken drivers that don't call it.
2239 skip_isa_align [X86] do not align io start addr, so can
2240 handle more pci cards
2241 firmware [ARM] Do not re-enumerate the bus but instead
2242 just use the configuration from the
2243 bootloader. This is currently used on
2244 IXP2000 systems where the bus has to be
2245 configured a certain way for adjunct CPUs.
2246 noearly [X86] Don't do any early type 1 scanning.
2247 This might help on some broken boards which
2248 machine check when some devices' config space
2249 is read. But various workarounds are disabled
2250 and some IOMMU drivers will not work.
2251 bfsort Sort PCI devices into breadth-first order.
2252 This sorting is done to get a device
2253 order compatible with older (<= 2.4) kernels.
2254 nobfsort Don't sort PCI devices into breadth-first order.
2255 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2256 tuning and use the BIOS-configured MPS defaults.
2257 pcie_bus_safe Set every device's MPS to the largest value
2258 supported by all devices below the root complex.
2259 pcie_bus_perf Set device MPS to the largest allowable MPS
2260 based on its parent bus. Also set MRRS (Max
2261 Read Request Size) to the largest supported
2262 value (no larger than the MPS that the device
2263 or bus can support) for best performance.
2264 pcie_bus_peer2peer Set every device's MPS to 128B, which
2265 every device is guaranteed to support. This
2266 configuration allows peer-to-peer DMA between
2267 any pair of devices, possibly at the cost of
2268 reduced performance. This also guarantees
2269 that hot-added devices will work.
2270 cbiosize=nn[KMG] The fixed amount of bus space which is
2271 reserved for the CardBus bridge's IO window.
2272 The default value is 256 bytes.
2273 cbmemsize=nn[KMG] The fixed amount of bus space which is
2274 reserved for the CardBus bridge's memory
2275 window. The default value is 64 megabytes.
2278 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2279 Specifies alignment and device to reassign
2280 aligned memory resources.
2281 If <order of align> is not specified,
2282 PAGE_SIZE is used as alignment.
2283 PCI-PCI bridge can be specified, if resource
2284 windows need to be expanded.
2285 ecrc= Enable/disable PCIe ECRC (transaction layer
2286 end-to-end CRC checking).
2287 bios: Use BIOS/firmware settings. This is the
2291 hpiosize=nn[KMG] The fixed amount of bus space which is
2292 reserved for hotplug bridge's IO window.
2293 Default size is 256 bytes.
2294 hpmemsize=nn[KMG] The fixed amount of bus space which is
2295 reserved for hotplug bridge's memory window.
2296 Default size is 2 megabytes.
2297 realloc= Enable/disable reallocating PCI bridge resources
2298 if allocations done by BIOS are too small to
2299 accommodate resources required by all child
2301 off: Turn realloc off
2303 realloc same as realloc=on
2304 noari do not use PCIe ARI.
2305 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2306 only look for one device below a PCIe downstream
2309 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2312 force Enable ASPM even on devices that claim not to support it.
2313 WARNING: Forcing ASPM on may cause system lockups.
2315 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2316 nomsi Do not use MSI for PCI Express Native Hotplug (this
2317 makes all PCIe ports use INTx for hotplug services).
2319 pcie_ports= [PCIE] PCIe ports handling:
2320 auto Ask the BIOS whether or not to use native PCIe services
2321 associated with PCIe ports (PME, hot-plug, AER). Use
2322 them only if that is allowed by the BIOS.
2323 native Use native PCIe services associated with PCIe ports
2325 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2328 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2329 nomsi Do not use MSI for native PCIe PME signaling (this makes
2330 all PCIe root ports use INTx for all services).
2332 pcmv= [HW,PCMCIA] BadgePAD 4
2335 See Documentation/blockdev/paride.txt.
2337 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2340 See arch/parisc/kernel/pdc_chassis.c
2342 percpu_alloc= Select which percpu first chunk allocator to use.
2343 Currently supported values are "embed" and "page".
2344 Archs may support subset or none of the selections.
2345 See comments in mm/percpu.c for details on each
2346 allocator. This parameter is primarily for debugging
2347 and performance comparison.
2350 See Documentation/blockdev/paride.txt.
2353 See Documentation/blockdev/paride.txt.
2355 pirq= [SMP,APIC] Manual mp-table setup
2356 See Documentation/x86/i386/IO-APIC.txt.
2358 plip= [PPT,NET] Parallel port network link
2359 Format: { parport<nr> | timid | 0 }
2360 See also Documentation/parport.txt.
2362 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2363 Override pmtimer IOPort with a hex value.
2367 Enable PNP debug messages (depends on the
2368 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2369 via /sys/module/pnp/parameters/debug. We always show
2370 current resource usage; turning this on also shows
2371 possible settings and some assignment information.
2377 { on | off | curr | res | no-curr | no-res }
2380 [ISAPNP] Exclude IRQs for the autoconfiguration
2383 [ISAPNP] Exclude DMAs for the autoconfiguration
2385 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2386 Ranges are in pairs (I/O port base and size).
2389 [ISAPNP] Exclude memory regions for the
2391 Ranges are in pairs (memory base and size).
2393 ports= [IP_VS_FTP] IPVS ftp helper module
2395 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2397 Format: <port>,<port>....
2399 print-fatal-signals=
2400 [KNL] debug: print fatal signals
2402 If enabled, warn about various signal handling
2403 related application anomalies: too many signals,
2404 too many POSIX.1 timers, fatal signals causing a
2407 If you hit the warning due to signal overflow,
2408 you might want to try "ulimit -i unlimited".
2412 printk.always_kmsg_dump=
2413 Trigger kmsg_dump for cases other than kernel oops or
2415 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2418 printk.time= Show timing data prefixed to each printk message line
2419 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2421 processor.max_cstate= [HW,ACPI]
2422 Limit processor to maximum C-state
2423 max_cstate=9 overrides any DMI blacklist limit.
2425 processor.nocst [HW,ACPI]
2426 Ignore the _CST method to determine C-states,
2427 instead using the legacy FADT method
2429 profile= [KNL] Enable kernel profiling via /proc/profile
2430 Format: [schedule,]<number>
2431 Param: "schedule" - profile schedule points.
2432 Param: <number> - step/bucket size as a power of 2 for
2433 statistical time based profiling.
2434 Param: "sleep" - profile D-state sleeping (millisecs).
2435 Requires CONFIG_SCHEDSTATS
2436 Param: "kvm" - profile VM exits.
2438 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2440 See Documentation/blockdev/ramdisk.txt.
2442 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2443 probe for; one of (bare|imps|exps|lifebook|any).
2444 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2446 psmouse.resetafter= [HW,MOUSE]
2447 Try to reset the device after so many bad packets
2450 [HW,MOUSE] Set desired mouse resolution, in dpi.
2451 psmouse.smartscroll=
2452 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2453 0 = disabled, 1 = enabled (default).
2455 pstore.backend= Specify the name of the pstore backend to use
2458 See Documentation/blockdev/paride.txt.
2461 [KNL] Number of legacy pty's. Overwrites compiled-in
2464 quiet [KNL] Disable most log messages
2469 See Documentation/md.txt.
2471 ramdisk_blocksize= [RAM]
2472 See Documentation/blockdev/ramdisk.txt.
2474 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2475 See Documentation/blockdev/ramdisk.txt.
2477 rcu_nocbs= [KNL,BOOT]
2478 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2479 the specified list of CPUs to be no-callback CPUs.
2480 Invocation of these CPUs' RCU callbacks will
2481 be offloaded to "rcuoN" kthreads created for
2482 that purpose. This reduces OS jitter on the
2483 offloaded CPUs, which can be useful for HPC and
2484 real-time workloads. It can also improve energy
2485 efficiency for asymmetric multiprocessors.
2487 rcu_nocb_poll [KNL,BOOT]
2488 Rather than requiring that offloaded CPUs
2489 (specified by rcu_nocbs= above) explicitly
2490 awaken the corresponding "rcuoN" kthreads,
2491 make these kthreads poll for callbacks.
2492 This improves the real-time response for the
2493 offloaded CPUs by relieving them of the need to
2494 wake up the corresponding kthread, but degrades
2495 energy efficiency by requiring that the kthreads
2496 periodically wake up to do the polling.
2498 rcutree.blimit= [KNL,BOOT]
2499 Set maximum number of finished RCU callbacks to process
2502 rcutree.fanout_leaf= [KNL,BOOT]
2503 Increase the number of CPUs assigned to each
2504 leaf rcu_node structure. Useful for very large
2507 rcutree.qhimark= [KNL,BOOT]
2508 Set threshold of queued
2509 RCU callbacks over which batch limiting is disabled.
2511 rcutree.qlowmark= [KNL,BOOT]
2512 Set threshold of queued RCU callbacks below which
2513 batch limiting is re-enabled.
2515 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2516 Suppress RCU CPU stall warning messages.
2518 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2519 Set timeout for RCU CPU stall warning messages.
2521 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2522 Set delay from grace-period initialization to
2523 first attempt to force quiescent states.
2524 Units are jiffies, minimum value is zero,
2525 and maximum value is HZ.
2527 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2528 Set delay between subsequent attempts to force
2529 quiescent states. Units are jiffies, minimum
2530 value is one, and maximum value is HZ.
2532 rcutorture.fqs_duration= [KNL,BOOT]
2533 Set duration of force_quiescent_state bursts.
2535 rcutorture.fqs_holdoff= [KNL,BOOT]
2536 Set holdoff time within force_quiescent_state bursts.
2538 rcutorture.fqs_stutter= [KNL,BOOT]
2539 Set wait time between force_quiescent_state bursts.
2541 rcutorture.irqreader= [KNL,BOOT]
2542 Test RCU readers from irq handlers.
2544 rcutorture.n_barrier_cbs= [KNL,BOOT]
2545 Set callbacks/threads for rcu_barrier() testing.
2547 rcutorture.nfakewriters= [KNL,BOOT]
2548 Set number of concurrent RCU writers. These just
2549 stress RCU, they don't participate in the actual
2550 test, hence the "fake".
2552 rcutorture.nreaders= [KNL,BOOT]
2553 Set number of RCU readers.
2555 rcutorture.onoff_holdoff= [KNL,BOOT]
2556 Set time (s) after boot for CPU-hotplug testing.
2558 rcutorture.onoff_interval= [KNL,BOOT]
2559 Set time (s) between CPU-hotplug operations, or
2560 zero to disable CPU-hotplug testing.
2562 rcutorture.shuffle_interval= [KNL,BOOT]
2563 Set task-shuffle interval (s). Shuffling tasks
2564 allows some CPUs to go into dyntick-idle mode
2565 during the rcutorture test.
2567 rcutorture.shutdown_secs= [KNL,BOOT]
2568 Set time (s) after boot system shutdown. This
2569 is useful for hands-off automated testing.
2571 rcutorture.stall_cpu= [KNL,BOOT]
2572 Duration of CPU stall (s) to test RCU CPU stall
2573 warnings, zero to disable.
2575 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2576 Time to wait (s) after boot before inducing stall.
2578 rcutorture.stat_interval= [KNL,BOOT]
2579 Time (s) between statistics printk()s.
2581 rcutorture.stutter= [KNL,BOOT]
2582 Time (s) to stutter testing, for example, specifying
2583 five seconds causes the test to run for five seconds,
2584 wait for five seconds, and so on. This tests RCU's
2585 ability to transition abruptly to and from idle.
2587 rcutorture.test_boost= [KNL,BOOT]
2588 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2589 "Maybe" means test if the RCU implementation
2590 under test support RCU priority boosting.
2592 rcutorture.test_boost_duration= [KNL,BOOT]
2593 Duration (s) of each individual boost test.
2595 rcutorture.test_boost_interval= [KNL,BOOT]
2596 Interval (s) between each boost test.
2598 rcutorture.test_no_idle_hz= [KNL,BOOT]
2599 Test RCU's dyntick-idle handling. See also the
2600 rcutorture.shuffle_interval parameter.
2602 rcutorture.torture_type= [KNL,BOOT]
2603 Specify the RCU implementation to test.
2605 rcutorture.verbose= [KNL,BOOT]
2606 Enable additional printk() statements.
2610 Run specified binary instead of /init from the ramdisk,
2611 used for early userspace startup. See initrd.
2613 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2614 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2615 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2618 [KNL, SMP] Set scheduler's default relax_domain_level.
2619 See Documentation/cgroups/cpusets.txt.
2621 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2623 reservetop= [X86-32]
2625 Reserves a hole at the top of the kernel virtual
2630 Set the amount of memory to reserve for BIOS at
2631 the bottom of the address space.
2633 reset_devices [KNL] Force drivers to reset the underlying device
2634 during initialization.
2637 Specify the partition device for software suspend
2639 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2641 resume_offset= [SWSUSP]
2642 Specify the offset from the beginning of the partition
2643 given by "resume=" at which the swap header is located,
2644 in <PAGE_SIZE> units (needed only for swap files).
2645 See Documentation/power/swsusp-and-swap-files.txt
2647 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2648 read the resume files
2650 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2651 Useful for devices that are detected asynchronously
2652 (e.g. USB and MMC devices).
2654 hibernate= [HIBERNATION]
2655 noresume Don't check if there's a hibernation image
2656 present during boot.
2657 nocompress Don't compress/decompress hibernation images.
2659 retain_initrd [RAM] Keep initrd memory after extraction
2661 rhash_entries= [KNL,NET]
2662 Set number of hash buckets for route cache
2664 riscom8= [HW,SERIAL]
2665 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2667 ro [KNL] Mount root device read-only on boot
2669 root= [KNL] Root filesystem
2670 See name_to_dev_t comment in init/do_mounts.c.
2672 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2673 mount the root filesystem
2675 rootflags= [KNL] Set root filesystem mount option string
2677 rootfstype= [KNL] Set root filesystem type
2679 rootwait [KNL] Wait (indefinitely) for root device to show up.
2680 Useful for devices that are detected asynchronously
2681 (e.g. USB and MMC devices).
2683 rw [KNL] Mount root device read-write on boot
2685 S [KNL] Run init in single mode
2688 See drivers/net/irda/sa1100_ir.c.
2690 sbni= [NET] Granch SBNI12 leased line adapter
2692 sched_debug [KNL] Enables verbose scheduler debug messages.
2694 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2695 xtime_lock contention on larger systems, and/or RCU lock
2696 contention on all systems with CONFIG_MAXSMP set.
2697 Format: { "0" | "1" }
2698 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2700 Note: increases power consumption, thus should only be
2701 enabled if running jitter sensitive (HPC/RT) workloads.
2703 security= [SECURITY] Choose a security module to enable at boot.
2704 If this boot parameter is not specified, only the first
2705 security module asking for security registration will be
2706 loaded. An invalid security module name will be treated
2707 as if no module has been chosen.
2709 selinux= [SELINUX] Disable or enable SELinux at boot time.
2710 Format: { "0" | "1" }
2711 See security/selinux/Kconfig help text.
2714 Default value is set via kernel config option.
2715 If enabled at boot time, /selinux/disable can be used
2716 later to disable prior to initial policy load.
2718 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2719 Format: { "0" | "1" }
2720 See security/apparmor/Kconfig help text
2723 Default value is set via kernel config option.
2725 serialnumber [BUGS=X86-32]
2728 Maximal number of shapers.
2730 show_msr= [x86] show boot-time MSR settings
2731 Format: { <integer> }
2732 Show boot-time (BIOS-initialized) MSR settings.
2733 The parameter means the number of CPUs to show,
2734 for example 1 means boot CPU only.
2741 slab_max_order= [MM, SLAB]
2742 Determines the maximum allowed order for slabs.
2743 A high setting may cause OOMs due to memory
2744 fragmentation. Defaults to 1 for systems with
2745 more than 32MB of RAM, 0 otherwise.
2747 slub_debug[=options[,slabs]] [MM, SLUB]
2748 Enabling slub_debug allows one to determine the
2749 culprit if slab objects become corrupted. Enabling
2750 slub_debug can create guard zones around objects and
2751 may poison objects when not in use. Also tracks the
2752 last alloc / free. For more information see
2753 Documentation/vm/slub.txt.
2755 slub_max_order= [MM, SLUB]
2756 Determines the maximum allowed order for slabs.
2757 A high setting may cause OOMs due to memory
2758 fragmentation. For more information see
2759 Documentation/vm/slub.txt.
2761 slub_min_objects= [MM, SLUB]
2762 The minimum number of objects per slab. SLUB will
2763 increase the slab order up to slub_max_order to
2764 generate a sufficiently large slab able to contain
2765 the number of objects indicated. The higher the number
2766 of objects the smaller the overhead of tracking slabs
2767 and the less frequently locks need to be acquired.
2768 For more information see Documentation/vm/slub.txt.
2770 slub_min_order= [MM, SLUB]
2771 Determines the minimum page order for slabs. Must be
2772 lower than slub_max_order.
2773 For more information see Documentation/vm/slub.txt.
2775 slub_nomerge [MM, SLUB]
2776 Disable merging of slabs with similar size. May be
2777 necessary if there is some reason to distinguish
2778 allocs to different slabs. Debug options disable
2779 merging on their own.
2780 For more information see Documentation/vm/slub.txt.
2783 Format: <io1>[,<io2>[,...,<io8>]]
2785 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2786 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2787 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2788 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2789 smsc-ircc2.ircc_irq= [HW] IRQ line
2790 smsc-ircc2.ircc_dma= [HW] DMA channel
2791 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2792 0: Toshiba Satellite 1800 (GP data pin select)
2793 1: Fast pin select (default)
2797 [KNL] Should the soft-lockup detector generate panics.
2800 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2801 See Documentation/laptops/sonypi.txt
2803 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2804 See Documentation/serial/specialix.txt.
2806 spia_io_base= [HW,MTD]
2812 Enabled the stack tracer on boot up.
2814 stacktrace_filter=[function-list]
2815 [FTRACE] Limit the functions that the stack tracer
2816 will trace at boot up. function-list is a comma separated
2817 list of functions. This list can be changed at run
2818 time by the stack_trace_filter file in the debugfs
2819 tracing directory. Note, this enables stack tracing
2820 and the stacktrace above is not needed.
2824 Set the STI (builtin display/keyboard on the HP-PARISC
2825 machines) console (graphic card) which should be used
2826 as the initial boot-console.
2827 See also comment in drivers/video/console/sticore.c.
2830 See comment in drivers/video/console/sticore.c.
2833 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2835 sunrpc.min_resvport=
2836 sunrpc.max_resvport=
2838 SunRPC servers often require that client requests
2839 originate from a privileged port (i.e. a port in the
2840 range 0 < portnr < 1024).
2841 An administrator who wishes to reserve some of these
2842 ports for other uses may adjust the range that the
2843 kernel's sunrpc client considers to be privileged
2844 using these two parameters to set the minimum and
2845 maximum port values.
2849 Control how the NFS server code allocates CPUs to
2850 service thread pools. Depending on how many NICs
2851 you have and where their interrupts are bound, this
2852 option will affect which CPUs will do NFS serving.
2853 Note: this parameter cannot be changed while the
2854 NFS server is running.
2856 auto the server chooses an appropriate mode
2857 automatically using heuristics
2858 global a single global pool contains all CPUs
2859 percpu one pool for each CPU
2860 pernode one pool for each NUMA node (equivalent
2861 to global on non-NUMA machines)
2863 sunrpc.tcp_slot_table_entries=
2864 sunrpc.udp_slot_table_entries=
2866 Sets the upper limit on the number of simultaneous
2867 RPC calls that can be sent from the client to a
2868 server. Increasing these values may allow you to
2869 improve throughput, but will also increase the
2870 amount of memory reserved for use by the client.
2873 [KNL] Enable accounting of swap in memory resource
2874 controller if no parameter or 1 is given or disable
2875 it if 0 is given (See Documentation/cgroups/memory.txt)
2877 swiotlb= [IA-64] Number of I/O TLB slabs
2881 sysfs.deprecated=0|1 [KNL]
2882 Enable/disable old style sysfs layout for old udev
2883 on older distributions. When this option is enabled
2884 very new udev will not work anymore. When this option
2885 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2886 in older udev will not work anymore.
2887 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2888 the kernel configuration.
2890 sysrq_always_enabled
2892 Ignore sysrq setting - this boot parameter will
2893 neutralize any effect of /proc/sys/kernel/sysrq.
2894 Useful for debugging.
2898 test_suspend= [SUSPEND]
2899 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2900 standby suspend) as the system sleep state to briefly
2901 enter during system startup. The system is woken from
2902 this state using a wakeup-capable RTC alarm.
2904 thash_entries= [KNL,NET]
2905 Set number of hash buckets for TCP connection
2907 thermal.act= [HW,ACPI]
2908 -1: disable all active trip points in all thermal zones
2909 <degrees C>: override all lowest active trip points
2911 thermal.crt= [HW,ACPI]
2912 -1: disable all critical trip points in all thermal zones
2913 <degrees C>: override all critical trip points
2915 thermal.nocrt= [HW,ACPI]
2916 Set to disable actions on ACPI thermal zone
2917 critical and hot trip points.
2919 thermal.off= [HW,ACPI]
2920 1: disable ACPI thermal control
2922 thermal.psv= [HW,ACPI]
2923 -1: disable all passive trip points
2924 <degrees C>: override all passive trip points to this
2927 thermal.tzp= [HW,ACPI]
2928 Specify global default ACPI thermal zone polling rate
2929 <deci-seconds>: poll all this frequency
2930 0: no polling (default)
2933 Force threading of all interrupt handlers except those
2934 marked explicitly IRQF_NO_THREAD.
2938 Specify if the kernel should make use of the cpu
2939 topology information if the hardware supports this.
2940 The scheduler will make use of this information and
2941 e.g. base its process migration decisions on it.
2946 tpm_suspend_pcr=[HW,TPM]
2947 Format: integer pcr id
2948 Specify that at suspend time, the tpm driver
2949 should extend the specified pcr with zeros,
2950 as a workaround for some chips which fail to
2951 flush the last written pcr on TPM_SaveState.
2952 This will guarantee that all the other pcrs
2955 trace_buf_size=nn[KMG]
2956 [FTRACE] will set tracing buffer size.
2958 trace_event=[event-list]
2959 [FTRACE] Set and start specified trace events in order
2960 to facilitate early boot debugging.
2961 See also Documentation/trace/events.txt
2963 trace_options=[option-list]
2964 [FTRACE] Enable or disable tracer options at boot.
2965 The option-list is a comma delimited list of options
2966 that can be enabled or disabled just as if you were
2967 to echo the option name into
2969 /sys/kernel/debug/tracing/trace_options
2971 For example, to enable stacktrace option (to dump the
2972 stack trace of each event), add to the command line:
2974 trace_options=stacktrace
2976 See also Documentation/trace/ftrace.txt "trace options"
2979 transparent_hugepage=
2981 Format: [always|madvise|never]
2982 Can be used to control the default behavior of the system
2983 with respect to transparent hugepages.
2984 See Documentation/vm/transhuge.txt for more details.
2986 tsc= Disable clocksource stability checks for TSC.
2988 [x86] reliable: mark tsc clocksource as reliable, this
2989 disables clocksource verification at runtime, as well
2990 as the stability checks done at bootup. Used to enable
2991 high-resolution timer mode on older hardware, and in
2992 virtualized environment.
2993 [x86] noirqtime: Do not use TSC to do irq accounting.
2994 Used to run time disable IRQ_TIME_ACCOUNTING on any
2995 platforms where RDTSC is slow and this accounting
2998 turbografx.map[2|3]= [HW,JOY]
2999 TurboGraFX parallel port interface
3001 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3002 See also Documentation/input/joystick-parport.txt
3004 udbg-immortal [PPC] When debugging early kernel crashes that
3005 happen after console_init() and before a proper
3006 console driver takes over, this boot options might
3007 help "seeing" what's going on.
3009 uhash_entries= [KNL,NET]
3010 Set number of hash buckets for UDP/UDP-Lite connections
3013 [USB] Ignore overcurrent events (default N).
3014 Some badly-designed motherboards generate lots of
3015 bogus events, for ports that aren't wired to
3016 anything. Set this parameter to avoid log spamming.
3017 Note that genuine overcurrent events won't be
3021 [X86] Cause panic on unknown NMI.
3023 usbcore.authorized_default=
3024 [USB] Default USB device authorization:
3025 (default -1 = authorized except for wireless USB,
3026 0 = not authorized, 1 = authorized)
3028 usbcore.autosuspend=
3029 [USB] The autosuspend time delay (in seconds) used
3030 for newly-detected USB devices (default 2). This
3031 is the time required before an idle device will be
3032 autosuspended. Devices for which the delay is set
3033 to a negative value won't be autosuspended at all.
3035 usbcore.usbfs_snoop=
3036 [USB] Set to log all usbfs traffic (default 0 = off).
3038 usbcore.blinkenlights=
3039 [USB] Set to cycle leds on hubs (default 0 = off).
3041 usbcore.old_scheme_first=
3042 [USB] Start with the old device initialization
3043 scheme (default 0 = off).
3045 usbcore.usbfs_memory_mb=
3046 [USB] Memory limit (in MB) for buffers allocated by
3047 usbfs (default = 16, 0 = max = 2047).
3049 usbcore.use_both_schemes=
3050 [USB] Try the other device initialization scheme
3051 if the first one fails (default 1 = enabled).
3053 usbcore.initial_descriptor_timeout=
3054 [USB] Specifies timeout for the initial 64-byte
3055 USB_REQ_GET_DESCRIPTOR request in milliseconds
3056 (default 5000 = 5.0 seconds).
3059 [USBHID] The interval which mice are to be polled at.
3061 usb-storage.delay_use=
3062 [UMS] The delay in seconds before a new device is
3063 scanned for Logical Units (default 5).
3066 [UMS] A list of quirks entries to supplement or
3067 override the built-in unusual_devs list. List
3068 entries are separated by commas. Each entry has
3069 the form VID:PID:Flags where VID and PID are Vendor
3070 and Product ID values (4-digit hex numbers) and
3071 Flags is a set of characters, each corresponding
3072 to a common usb-storage quirk flag as follows:
3073 a = SANE_SENSE (collect more than 18 bytes
3075 b = BAD_SENSE (don't collect more than 18
3076 bytes of sense data);
3077 c = FIX_CAPACITY (decrease the reported
3078 device capacity by one sector);
3079 d = NO_READ_DISC_INFO (don't use
3080 READ_DISC_INFO command);
3081 e = NO_READ_CAPACITY_16 (don't use
3082 READ_CAPACITY_16 command);
3083 h = CAPACITY_HEURISTICS (decrease the
3084 reported device capacity by one
3085 sector if the number is odd);
3086 i = IGNORE_DEVICE (don't bind to this
3088 l = NOT_LOCKABLE (don't try to lock and
3089 unlock ejectable media);
3090 m = MAX_SECTORS_64 (don't transfer more
3091 than 64 sectors = 32 KB at a time);
3092 n = INITIAL_READ10 (force a retry of the
3093 initial READ(10) command);
3094 o = CAPACITY_OK (accept the capacity
3095 reported by the device);
3096 p = WRITE_CACHE (the device cache is ON
3098 r = IGNORE_RESIDUE (the device reports
3099 bogus residue values);
3100 s = SINGLE_LUN (the device has only one
3102 w = NO_WP_DETECT (don't test whether the
3103 medium is write-protected).
3104 Example: quirks=0419:aaf5:rl,0421:0433:rc
3106 user_debug= [KNL,ARM]
3108 See arch/arm/Kconfig.debug help text.
3109 1 - undefined instruction events
3111 4 - invalid data aborts
3114 Example: user_debug=31
3117 [X86] Flags controlling user PTE allocations.
3119 nohigh = do not allocate PTE pages in
3120 HIGHMEM regardless of setting
3124 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3125 vdso=1: enable VDSO (default)
3126 vdso=0: disable VDSO mapping
3129 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3130 vdso32=1: enable 32-bit VDSO (default)
3131 vdso32=0: disable 32-bit VDSO mapping
3134 vector=percpu: enable percpu vector domain
3136 video= [FB] Frame buffer configuration
3137 See Documentation/fb/modedb.txt.
3140 [VMMIO] Memory mapped virtio (platform) device.
3142 <size>@<baseaddr>:<irq>[:<id>]
3144 <size> := size (can use standard suffixes
3146 <baseaddr> := physical base address
3147 <irq> := interrupt number (as passed to
3149 <id> := (optional) platform device id
3151 virtio_mmio.device=1K@0x100b0000:48:7
3153 Can be used multiple times for multiple devices.
3155 vga= [BOOT,X86-32] Select a particular video mode
3156 See Documentation/x86/boot.txt and
3157 Documentation/svga.txt.
3158 Use vga=ask for menu.
3159 This is actually a boot loader parameter; the value is
3160 passed to the kernel using a special protocol.
3162 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3163 size of <nn>. This can be used to increase the
3164 minimum size (128MB on x86). It can also be used to
3165 decrease the size and leave more room for directly
3168 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3171 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3174 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3178 Controls the behavior of vsyscalls (i.e. calls to
3179 fixed addresses of 0xffffffffff600x00 from legacy
3180 code). Most statically-linked binaries and older
3181 versions of glibc use these calls. Because these
3182 functions are at fixed addresses, they make nice
3183 targets for exploits that can control RIP.
3185 emulate [default] Vsyscalls turn into traps and are
3186 emulated reasonably safely.
3188 native Vsyscalls are native syscall instructions.
3189 This is a little bit faster than trapping
3190 and makes a few dynamic recompilers work
3191 better than they would in emulation mode.
3192 It also makes exploits much easier to write.
3194 none Vsyscalls don't work at all. This makes
3195 them quite hard to use for exploits but
3196 might break your system.
3198 vt.cur_default= [VT] Default cursor shape.
3199 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3200 the parameters of the <Esc>[?A;B;Cc escape sequence;
3201 see VGA-softcursor.txt. Default: 2 = underline.
3203 vt.default_blu= [VT]
3204 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3205 Change the default blue palette of the console.
3206 This is a 16-member array composed of values
3209 vt.default_grn= [VT]
3210 Format: <green0>,<green1>,<green2>,...,<green15>
3211 Change the default green palette of the console.
3212 This is a 16-member array composed of values
3215 vt.default_red= [VT]
3216 Format: <red0>,<red1>,<red2>,...,<red15>
3217 Change the default red palette of the console.
3218 This is a 16-member array composed of values
3224 Set system-wide default UTF-8 mode for all tty's.
3225 Default is 1, i.e. UTF-8 mode is enabled for all
3226 newly opened terminals.
3228 vt.global_cursor_default=
3231 Set system-wide default for whether a cursor
3232 is shown on new VTs. Default is -1,
3233 i.e. cursors will be created by default unless
3234 overridden by individual drivers. 0 will hide
3235 cursors, 1 will display them.
3237 watchdog timers [HW,WDT] For information on watchdog timers,
3238 see Documentation/watchdog/watchdog-parameters.txt
3239 or other driver-specific files in the
3240 Documentation/watchdog/ directory.
3242 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3243 default x2apic cluster mode on platforms
3246 x86_mrst_timer= [X86-32,APBT]
3247 Choose timer option for x86 Moorestown MID platform.
3248 Two valid options are apbt timer only and lapic timer
3249 plus one apbt timer for broadcast timer.
3250 x86_mrst_timer=apbt_only | lapic_and_apbt
3252 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3253 xd_geo= See header of drivers/block/xd.c.
3255 xen_emul_unplug= [HW,X86,XEN]
3256 Unplug Xen emulated devices
3257 Format: [unplug0,][unplug1]
3258 ide-disks -- unplug primary master IDE devices
3259 aux-ide-disks -- unplug non-primary-master IDE devices
3260 nics -- unplug network devices
3261 all -- unplug all emulated devices (NICs and IDE disks)
3262 unnecessary -- unplugging emulated devices is
3263 unnecessary even if the host did not respond to
3265 never -- do not unplug even if version check succeeds
3267 xirc2ps_cs= [NET,PCMCIA]
3269 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3271 ______________________________________________________________________
3275 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob