4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel=range1:size1[,range2:size2,...][@offset]
598 [KNL] Same as above, but depends on the memory
599 in the running system. The syntax of range is
600 start-[end] where start and end are both
601 a memory unit (amount[KMG]). See also
602 Documentation/kdump/kdump.txt for an example.
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
620 details. Deprecated, see dyndbg.
622 debug [KNL] Enable kernel debugging (events log level).
625 [KNL] verbose self-tests
627 Print debugging info while doing the locking API
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
672 Set number of hash buckets for dentry cache.
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
707 this option disables the debugging code at boot.
709 dma_debug_entries=<number>
710 This option allows to tune the number of preallocated
711 entries for DMA-API debugging code. One entry is
712 required per DMA-API allocation. Use this if the
713 DMA-API debugging code disables itself because the
714 architectural default is too low.
716 dma_debug_driver=<driver_name>
717 With this option the DMA-API debugging driver
718 filter feature can be enabled at boot time. Just
719 pass the driver to filter for as the parameter.
720 The filter can be disabled or changed to another
721 driver later using sysfs.
723 drm_kms_helper.edid_firmware=[<connector>:]<file>
724 Broken monitors, graphic adapters and KVMs may
725 send no or incorrect EDID data sets. This parameter
726 allows to specify an EDID data set in the
727 /lib/firmware directory that is used instead.
728 Generic built-in EDID data sets are used, if one of
729 edid/1024x768.bin, edid/1280x1024.bin,
730 edid/1680x1050.bin, or edid/1920x1080.bin is given
731 and no file with the same name exists. Details and
732 instructions how to build your own EDID data are
733 available in Documentation/EDID/HOWTO.txt. An EDID
734 data set will only be used for a particular connector,
735 if its name and a colon are prepended to the EDID
740 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
741 module.dyndbg[="val"]
742 Enable debug messages at boot time. See
743 Documentation/dynamic-debug-howto.txt for details.
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
757 earlyprintk=serial[,ttySn[,baudrate]]
758 earlyprintk=ttySn[,baudrate]
759 earlyprintk=dbgp[debugController#]
761 Append ",keep" to not disable it when the real console
764 Only vga or serial or usb debug port at a time.
766 Currently only ttyS0 and ttyS1 are supported.
768 Interaction with the standard serial driver is not
771 The VGA output is eventually overwritten by the real
774 ekgdboc= [X86,KGDB] Allow early kernel console debugging
777 This is designed to be used in conjunction with
778 the boot argument: earlyprintk=vga
781 Format: {"off" | "on" | "skip[mbr]"}
783 eisa_irq_edge= [PARISC,HW]
784 See header of drivers/parisc/eisa.c.
787 See comment before function elanfreq_setup() in
788 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
791 Format: {"cfq" | "deadline" | "noop"}
792 See Documentation/block/cfq-iosched.txt and
793 Documentation/block/deadline-iosched.txt for details.
795 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
796 Specifies physical address of start of kernel core
797 image elf header and optionally the size. Generally
798 kexec loader will pass this option to capture kernel.
799 See Documentation/kdump/kdump.txt for details.
801 enable_mtrr_cleanup [X86]
802 The kernel tries to adjust MTRR layout from continuous
803 to discrete, to make X server driver able to add WB
804 entry later. This parameter enables that.
806 enable_timer_pin_1 [X86]
807 Enable PIN 1 of APIC timer
808 Can be useful to work around chipset bugs
809 (in particular on some ATI chipsets).
810 The kernel tries to set a reasonable default.
812 enforcing [SELINUX] Set initial enforcing status.
814 See security/selinux/Kconfig help text.
815 0 -- permissive (log only, no denials).
816 1 -- enforcing (deny and log).
818 Value can be changed at runtime via /selinux/enforce.
821 Disable Error Record Serialization Table (ERST)
824 ether= [HW,NET] Ethernet cards parameters
825 This option is obsoleted by the "netdev=" option, which
826 has equivalent usage. See its documentation for details.
830 Permit 'security.evm' to be updated regardless of
831 current integrity status.
835 fail_make_request=[KNL]
836 General fault injection mechanism.
837 Format: <interval>,<probability>,<space>,<times>
838 See also Documentation/fault-injection/.
841 See Documentation/blockdev/floppy.txt.
843 force_pal_cache_flush
844 [IA-64] Avoid check_sal_cache_flush which may hang on
845 buggy SAL_CACHE_FLUSH implementations. Using this
846 parameter will force ia64_sal_cache_flush to call
847 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
850 [FTRACE] will set and start the specified tracer
851 as early as possible in order to facilitate early
854 ftrace_dump_on_oops[=orig_cpu]
855 [FTRACE] will dump the trace buffers on oops.
856 If no parameter is passed, ftrace will dump
857 buffers of all CPUs, but if you pass orig_cpu, it will
858 dump only the buffer of the CPU that triggered the
861 ftrace_filter=[function-list]
862 [FTRACE] Limit the functions traced by the function
863 tracer at boot up. function-list is a comma separated
864 list of functions. This list can be changed at run
865 time by the set_ftrace_filter file in the debugfs
868 ftrace_notrace=[function-list]
869 [FTRACE] Do not trace the functions specified in
870 function-list. This list can be changed at run time
871 by the set_ftrace_notrace file in the debugfs
874 ftrace_graph_filter=[function-list]
875 [FTRACE] Limit the top level callers functions traced
876 by the function graph tracer at boot up.
877 function-list is a comma separated list of functions
878 that can be changed at run time by the
879 set_graph_function file in the debugfs tracing directory.
882 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
883 support via parallel port (up to 5 devices per port)
884 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
885 See also Documentation/input/joystick-parport.txt
889 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
893 gcov_persist= [GCOV] When non-zero (default), profiling data for
894 kernel modules is saved and remains accessible via
895 debugfs, even when the module is unloaded/reloaded.
896 When zero, profiling data is discarded and associated
897 debugfs files are removed at module unload time.
899 gpt [EFI] Forces disk with valid GPT signature but
900 invalid Protective MBR to be treated as GPT.
902 grcan.enable0= [HW] Configuration of physical interface 0. Determines
903 the "Enable 0" bit of the configuration register.
906 grcan.enable1= [HW] Configuration of physical interface 1. Determines
907 the "Enable 0" bit of the configuration register.
910 grcan.select= [HW] Select which physical interface to use.
913 grcan.txsize= [HW] Sets the size of the tx buffer.
914 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
916 grcan.rxsize= [HW] Sets the size of the rx buffer.
917 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
920 hashdist= [KNL,NUMA] Large hashes allocated during boot
921 are distributed across NUMA nodes. Defaults on
922 for 64-bit NUMA, off otherwise.
923 Format: 0 | 1 (for off | on)
925 hcl= [IA-64] SGI's Hardware Graph compatibility layer
927 hd= [EIDE] (E)IDE hard drive subsystem geometry
928 Format: <cyl>,<head>,<sect>
931 Disable Hardware Error Source Table (HEST) support;
932 corresponding firmware-first mode error processing
933 logic will be disabled.
935 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
936 size of <nn>. This works even on boxes that have no
937 highmem otherwise. This also works to reduce highmem
938 size on bigger boxes.
940 highres= [KNL] Enable/disable high resolution timer mode.
941 Valid parameters: "on", "off"
945 See Documentation/isdn/README.HiSax.
949 hpet= [X86-32,HPET] option to control HPET usage
950 Format: { enable (default) | disable | force |
952 disable: disable HPET and use PIT instead
953 force: allow force enabled of undocumented chips (ICH4,
955 verbose: show contents of HPET registers during setup
957 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
958 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
959 On x86-64 and powerpc, this option can be specified
960 multiple times interleaved with hugepages= to reserve
961 huge pages of different sizes. Valid pages sizes on
962 x86-64 are 2M (when the CPU supports "pse") and 1G
963 (when the CPU supports the "pdpe1gb" cpuinfo flag)
964 Note that 1GB pages can only be allocated at boot time
965 using hugepages= and not freed afterwards.
967 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
968 terminal devices. Valid values: 0..8
969 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
970 If specified, z/VM IUCV HVC accepts connections
971 from listed z/VM user IDs only.
974 Do not unregister boot console at start. This is only
975 useful for debugging when something happens in the window
976 between unregistering the boot console and initializing
979 i2c_bus= [HW] Override the default board specific I2C bus speed
980 or register an additional I2C bus that is not
981 registered from board initialization code.
985 i8042.debug [HW] Toggle i8042 debug mode
986 i8042.direct [HW] Put keyboard port into non-translated mode
987 i8042.dumbkbd [HW] Pretend that controller can only read data from
988 keyboard and cannot control its state
989 (Don't attempt to blink the leds)
990 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
991 i8042.nokbd [HW] Don't check/create keyboard port
992 i8042.noloop [HW] Disable the AUX Loopback command while probing
994 i8042.nomux [HW] Don't check presence of an active multiplexing
996 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
998 i8042.notimeout [HW] Ignore timeout condition signalled by controller
999 i8042.reset [HW] Reset the controller during init and cleanup
1000 i8042.unlock [HW] Unlock (ignore) the keylock
1004 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1005 indicates that the driver is running on unsupported
1007 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1008 does not match list of supported models.
1010 [HW] Report power status in /proc/i8k
1011 (disabled by default)
1012 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1015 i915.invert_brightness=
1016 [DRM] Invert the sense of the variable that is used to
1017 set the brightness of the panel backlight. Normally a
1018 brightness value of 0 indicates backlight switched off,
1019 and the maximum of the brightness value sets the backlight
1020 to maximum brightness. If this parameter is set to 0
1021 (default) and the machine requires it, or this parameter
1022 is set to 1, a brightness value of 0 sets the backlight
1023 to maximum brightness, and the maximum of the brightness
1024 value switches the backlight off.
1025 -1 -- never invert brightness
1026 0 -- machine default
1027 1 -- force brightness inversion
1030 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1032 ide-core.nodma= [HW] (E)IDE subsystem
1033 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1034 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1035 .cdrom .chs .ignore_cable are additional options
1036 See Documentation/ide/ide.txt.
1038 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1039 Claim all unknown PCI IDE storage controllers.
1042 Format: idle=poll, idle=halt, idle=nomwait
1043 Poll forces a polling idle loop that can slightly
1044 improve the performance of waking up a idle CPU, but
1045 will use a lot of power and make the system run hot.
1047 idle=halt: Halt is forced to be used for CPU idle.
1048 In such case C2/C3 won't be used again.
1049 idle=nomwait: Disable mwait for CPU C-states
1051 ignore_loglevel [KNL]
1052 Ignore loglevel setting - this will print /all/
1053 kernel messages to the console. Useful for debugging.
1054 We also add it as printk module parameter, so users
1055 could change it dynamically, usually by
1056 /sys/module/printk/parameters/ignore_loglevel.
1058 ihash_entries= [KNL]
1059 Set number of hash buckets for inode cache.
1061 ima_appraise= [IMA] appraise integrity measurements
1062 Format: { "off" | "enforce" | "fix" }
1065 ima_appraise_tcb [IMA]
1066 The builtin appraise policy appraises all files
1070 Format: { "0" | "1" }
1071 0 -- integrity auditing messages. (Default)
1072 1 -- enable informational integrity auditing messages.
1075 Format: { "sha1" | "md5" }
1079 Load a policy which meets the needs of the Trusted
1080 Computing Base. This means IMA will measure all
1081 programs exec'd, files mmap'd for exec, and all files
1082 opened for read by uid=0.
1086 Run specified binary instead of /sbin/init as init
1089 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1090 for working out where the kernel is dying during
1093 initrd= [BOOT] Specify the location of the initial ramdisk
1095 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1098 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1100 Enable intel iommu driver.
1102 Disable intel iommu driver.
1103 igfx_off [Default Off]
1104 By default, gfx is mapped as normal device. If a gfx
1105 device has a dedicated DMAR unit, the DMAR unit is
1106 bypassed by not enabling DMAR with this option. In
1107 this case, gfx device will use physical address for
1110 With this option iommu will not optimize to look
1111 for io virtual address below 32-bit forcing dual
1112 address cycle on pci bus for cards supporting greater
1113 than 32-bit addressing. The default is to look
1114 for translation below 32-bit and if not available
1115 then look in the higher range.
1116 strict [Default Off]
1117 With this option on every unmap_single operation will
1118 result in a hardware IOTLB flush operation as opposed
1119 to batching them for performance.
1120 sp_off [Default Off]
1121 By default, super page will be supported if Intel IOMMU
1122 has the capability. With this option, super page will
1125 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1126 0 disables intel_idle and fall back on acpi_idle.
1127 1 to 6 specify maximum depth of C-state.
1131 Do not enable intel_pstate as the default
1132 scaling driver for the supported processors
1134 intremap= [X86-64, Intel-IOMMU]
1135 on enable Interrupt Remapping (default)
1136 off disable Interrupt Remapping
1137 nosid disable Source ID checking
1139 BIOS x2APIC opt-out request will be ignored
1141 iomem= Disable strict checking of access to MMIO memory
1142 strict regions from userspace.
1159 io7= [HW] IO7 for Marvel based alpha systems
1160 See comment before marvel_specify_io7 in
1161 arch/alpha/kernel/core_marvel.c.
1163 io_delay= [X86] I/O delay method
1165 Standard port 0x80 based delay
1167 Alternate port 0xed based delay (needed on some systems)
1169 Simple two microseconds delay
1174 See Documentation/filesystems/nfs/nfsroot.txt.
1176 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1177 See comment before ip2_setup() in
1178 drivers/char/ip2/ip2base.c.
1181 When an interrupt is not handled search all handlers
1182 for it. Intended to get systems with badly broken
1186 When an interrupt is not handled search all handlers
1187 for it. Also check all handlers each timer
1188 interrupt. Intended to get systems with badly broken
1192 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1194 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1196 <cpu number>,...,<cpu number>
1198 <cpu number>-<cpu number>
1199 (must be a positive range in ascending order)
1201 <cpu number>,...,<cpu number>-<cpu number>
1203 This option can be used to specify one or more CPUs
1204 to isolate from the general SMP balancing and scheduling
1205 algorithms. You can move a process onto or off an
1206 "isolated" CPU via the CPU affinity syscalls or cpuset.
1207 <cpu number> begins at 0 and the maximum value is
1208 "number of CPUs in system - 1".
1210 This option is the preferred way to isolate CPUs. The
1211 alternative -- manually setting the CPU mask of all
1212 tasks in the system -- can cause problems and
1213 suboptimal load balancer performance.
1217 js= [HW,JOY] Analog joystick
1218 See Documentation/input/joystick.txt.
1222 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1223 specifies the amount of memory usable by the kernel
1224 for non-movable allocations. The requested amount is
1225 spread evenly throughout all nodes in the system. The
1226 remaining memory in each node is used for Movable
1227 pages. In the event, a node is too small to have both
1228 kernelcore and Movable pages, kernelcore pages will
1229 take priority and other nodes will have a larger number
1230 of kernelcore pages. The Movable zone is used for the
1231 allocation of pages that may be reclaimed or moved
1232 by the page migration subsystem. This means that
1233 HugeTLB pages may not be allocated from this zone.
1234 Note that allocations like PTEs-from-HighMem still
1235 use the HighMem zone if it exists, and the Normal
1236 zone if it does not.
1238 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1239 Format: <Controller#>[,poll interval]
1240 The controller # is the number of the ehci usb debug
1241 port as it is probed via PCI. The poll interval is
1242 optional and is the number seconds in between
1243 each poll cycle to the debug port in case you need
1244 the functionality for interrupting the kernel with
1245 gdb or control-c on the dbgp connection. When
1246 not using this parameter you use sysrq-g to break into
1247 the kernel debugger.
1249 kgdboc= [KGDB,HW] kgdb over consoles.
1250 Requires a tty driver that supports console polling,
1251 or a supported polling keyboard driver (non-usb).
1252 Serial only format: <serial_device>[,baud]
1253 keyboard only format: kbd
1254 keyboard and serial format: kbd,<serial_device>[,baud]
1255 Optional Kernel mode setting:
1256 kms, kbd format: kms,kbd
1257 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1259 kgdbwait [KGDB] Stop kernel execution and enter the
1260 kernel debugger at the earliest opportunity.
1262 kmac= [MIPS] korina ethernet MAC address.
1263 Configure the RouterBoard 532 series on-chip
1264 Ethernet adapter MAC address.
1266 kmemleak= [KNL] Boot-time kmemleak enable/disable
1267 Valid arguments: on, off
1270 kstack=N [X86] Print N words from the kernel stack
1273 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1274 Default is 0 (don't ignore, but inject #GP)
1276 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1280 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1281 Default is 1 (enabled)
1283 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1285 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1287 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1288 (virtualized MMU) support on capable Intel chips.
1289 Default is 1 (enabled)
1291 kvm-intel.emulate_invalid_guest_state=
1292 [KVM,Intel] Enable emulation of invalid guest states
1293 Default is 0 (disabled)
1295 kvm-intel.flexpriority=
1296 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1297 Default is 1 (enabled)
1300 [KVM,Intel] Enable VMX nesting (nVMX).
1301 Default is 0 (disabled)
1303 kvm-intel.unrestricted_guest=
1304 [KVM,Intel] Disable unrestricted guest feature
1305 (virtualized real and unpaged mode) on capable
1306 Intel chips. Default is 1 (enabled)
1308 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1309 feature (tagged TLBs) on capable Intel chips.
1310 Default is 1 (enabled)
1316 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1319 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1320 value for LAPIC timer one-shot implementation. Default
1321 back to the programmable timer unit in the LAPIC.
1323 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1326 libata.dma= [LIBATA] DMA control
1327 libata.dma=0 Disable all PATA and SATA DMA
1328 libata.dma=1 PATA and SATA Disk DMA only
1329 libata.dma=2 ATAPI (CDROM) DMA only
1330 libata.dma=4 Compact Flash DMA only
1331 Combinations also work, so libata.dma=3 enables DMA
1332 for disks and CDROMs, but not CFs.
1334 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1335 libata.ignore_hpa=0 keep BIOS limits (default)
1336 libata.ignore_hpa=1 ignore limits, using full disk
1338 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1342 libata.force= [LIBATA] Force configurations. The format is comma
1343 separated list of "[ID:]VAL" where ID is
1344 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1345 matching port, link or device. Basically, it matches
1346 the ATA ID string printed on console by libata. If
1347 the whole ID part is omitted, the last PORT and DEVICE
1348 values are used. If ID hasn't been specified yet, the
1349 configuration applies to all ports, links and devices.
1351 If only DEVICE is omitted, the parameter applies to
1352 the port and all links and devices behind it. DEVICE
1353 number of 0 either selects the first device or the
1354 first fan-out link behind PMP device. It does not
1355 select the host link. DEVICE number of 15 selects the
1356 host link and device attached to it.
1358 The VAL specifies the configuration to force. As long
1359 as there's no ambiguity shortcut notation is allowed.
1360 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1361 The following configurations can be forced.
1363 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1364 Any ID with matching PORT is used.
1366 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1368 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1369 udma[/][16,25,33,44,66,100,133] notation is also
1372 * [no]ncq: Turn on or off NCQ.
1374 * nohrst, nosrst, norst: suppress hard, soft
1377 * rstonce: only attempt one reset during
1378 hot-unplug link recovery
1380 * dump_id: dump IDENTIFY data.
1382 If there are multiple matching configurations changing
1383 the same attribute, the last one is used.
1385 memblock=debug [KNL] Enable memblock debug messages.
1387 load_ramdisk= [RAM] List of ramdisks to load from floppy
1388 See Documentation/blockdev/ramdisk.txt.
1390 lockd.nlm_grace_period=P [NFS] Assign grace period.
1393 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1396 lockd.nlm_timeout=T [NFS] Assign timeout value.
1399 lockd.nlm_udpport=M [NFS] Assign UDP port.
1402 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1405 loglevel= All Kernel Messages with a loglevel smaller than the
1406 console loglevel will be printed to the console. It can
1407 also be changed with klogd or other programs. The
1408 loglevels are defined as follows:
1410 0 (KERN_EMERG) system is unusable
1411 1 (KERN_ALERT) action must be taken immediately
1412 2 (KERN_CRIT) critical conditions
1413 3 (KERN_ERR) error conditions
1414 4 (KERN_WARNING) warning conditions
1415 5 (KERN_NOTICE) normal but significant condition
1416 6 (KERN_INFO) informational
1417 7 (KERN_DEBUG) debug-level messages
1419 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1420 in bytes. n must be a power of two. The default
1421 size is set in the kernel config file.
1423 logo.nologo [FB] Disables display of the built-in Linux logo.
1424 This may be used to provide more screen space for
1425 kernel log messages and is useful when debugging
1426 kernel boot problems.
1428 lp=0 [LP] Specify parallel ports to use, e.g,
1429 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1430 lp=reset first parallel port). 'lp=0' disables the
1431 lp=auto printer driver. 'lp=reset' (which can be
1432 specified in addition to the ports) causes
1433 attached printers to be reset. Using
1434 lp=port1,port2,... specifies the parallel ports
1435 to associate lp devices with, starting with
1436 lp0. A port specification may be 'none' to skip
1437 that lp device, or a parport name such as
1438 'parport0'. Specifying 'lp=auto' instead of a
1439 port specification list means that device IDs
1440 from each port should be examined, to see if
1441 an IEEE 1284-compliant printer is attached; if
1442 so, the driver will manage that printer.
1443 See also header of drivers/char/lp.c.
1446 Sets loops_per_jiffy to given constant, thus avoiding
1447 time-consuming boot-time autodetection (up to 250 ms per
1448 CPU). 0 enables autodetection (default). To determine
1449 the correct value for your kernel, boot with normal
1450 autodetection and see what value is printed. Note that
1451 on SMP systems the preset will be applied to all CPUs,
1452 which is likely to cause problems if your CPUs need
1453 significantly divergent settings. An incorrect value
1454 will cause delays in the kernel to be wrong, leading to
1455 unpredictable I/O errors and other breakage. Although
1456 unlikely, in the extreme case this might damage your
1460 Format: <io>,<irq>,<dma>
1462 machvec= [IA-64] Force the use of a particular machine-vector
1463 (machvec) in a generic kernel.
1464 Example: machvec=hpzx1_swiotlb
1466 machtype= [Loongson] Share the same kernel image file between different
1468 Example: machtype=lemote-yeeloong-2f-7inch
1470 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1471 than or equal to this physical address is ignored.
1473 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1474 should make use of. maxcpus=n : n >= 0 limits the
1475 kernel to using 'n' processors. n=0 is a special case,
1476 it is equivalent to "nosmp", which also disables
1479 max_loop= [LOOP] The number of loop block devices that get
1480 (loop.max_loop) unconditionally pre-created at init time. The default
1481 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1482 of statically allocating a predefined number, loop
1483 devices can be requested on-demand with the
1484 /dev/loop-control interface.
1486 mce [X86-32] Machine Check Exception
1488 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1490 md= [HW] RAID subsystems devices and level
1491 See Documentation/md.txt.
1494 Format: <first>,<last>
1495 Specifies range of consoles to be captured by the MDA.
1497 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1498 Amount of memory to be used when the kernel is not able
1499 to see the whole system memory or for test.
1500 [X86] Work as limiting max address. Use together
1501 with memmap= to avoid physical address space collisions.
1502 Without memmap= PCI devices could be placed at addresses
1503 belonging to unused RAM.
1505 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1509 [KNL,SH] Allow user to override the default size for
1510 per-device physically contiguous DMA buffers.
1512 memmap=exactmap [KNL,X86] Enable setting of an exact
1513 E820 memory map, as specified by the user.
1514 Such memmap=exactmap lines can be constructed based on
1515 BIOS output or other requirements. See the memmap=nn@ss
1518 memmap=nn[KMG]@ss[KMG]
1519 [KNL] Force usage of a specific region of memory
1520 Region of memory to be used, from ss to ss+nn.
1522 memmap=nn[KMG]#ss[KMG]
1523 [KNL,ACPI] Mark specific memory as ACPI data.
1524 Region of memory to be used, from ss to ss+nn.
1526 memmap=nn[KMG]$ss[KMG]
1527 [KNL,ACPI] Mark specific memory as reserved.
1528 Region of memory to be used, from ss to ss+nn.
1529 Example: Exclude memory from 0x18690000-0x1869ffff
1530 memmap=64K$0x18690000
1532 memmap=0x10000$0x18690000
1534 memory_corruption_check=0/1 [X86]
1535 Some BIOSes seem to corrupt the first 64k of
1536 memory when doing things like suspend/resume.
1537 Setting this option will scan the memory
1538 looking for corruption. Enabling this will
1539 both detect corruption and prevent the kernel
1540 from using the memory being corrupted.
1541 However, its intended as a diagnostic tool; if
1542 repeatable BIOS-originated corruption always
1543 affects the same memory, you can use memmap=
1544 to prevent the kernel from using that memory.
1546 memory_corruption_check_size=size [X86]
1547 By default it checks for corruption in the low
1548 64k, making this memory unavailable for normal
1549 use. Use this parameter to scan for
1550 corruption in more or less memory.
1552 memory_corruption_check_period=seconds [X86]
1553 By default it checks for corruption every 60
1554 seconds. Use this parameter to check at some
1555 other rate. 0 disables periodic checking.
1557 memtest= [KNL,X86] Enable memtest
1559 default : 0 <disable>
1560 Specifies the number of memtest passes to be
1561 performed. Each pass selects another test
1562 pattern from a given set of patterns. Memtest
1563 fills the memory with this pattern, validates
1564 memory contents and reserves bad memory
1565 regions that are detected.
1567 meye.*= [HW] Set MotionEye Camera parameters
1568 See Documentation/video4linux/meye.txt.
1570 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1571 Multi-Function General Purpose Timers on AMD Geode
1574 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1575 the BIOS has incorrectly applied a workaround. TinyBIOS
1576 version 0.98 is known to be affected, 0.99 fixes the
1577 problem by letting the user disable the workaround.
1581 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1582 physical address is ignored.
1584 mini2440= [ARM,HW,KNL]
1585 Format:[0..2][b][c][t]
1587 MINI2440 configuration specification:
1588 0 - The attached screen is the 3.5" TFT
1589 1 - The attached screen is the 7" TFT
1590 2 - The VGA Shield is attached (1024x768)
1591 Leaving out the screen size parameter will not load
1592 the TFT driver, and the framebuffer will be left
1594 b - Enable backlight. The TFT backlight pin will be
1595 linked to the kernel VESA blanking code and a GPIO
1596 LED. This parameter is not necessary when using the
1598 c - Enable the s3c camera interface.
1599 t - Reserved for enabling touchscreen support. The
1600 touchscreen support is not enabled in the mainstream
1601 kernel as of 2.6.30, a preliminary port can be found
1602 in the "bleeding edge" mini2440 support kernel at
1603 http://repo.or.cz/w/linux-2.6/mini2440.git
1606 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1607 parameter allows control of the logging verbosity for
1608 the additional memory initialisation checks. A value
1609 of 0 disables mminit logging and a level of 4 will
1610 log everything. Information is printed at KERN_DEBUG
1611 so loglevel=8 may also need to be specified.
1614 [KNL] When CONFIG_MODULE_SIG is set, this means that
1615 modules without (valid) signatures will fail to load.
1616 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1617 is always true, so this option does nothing.
1620 [MOUSE] Maximum time between finger touching and
1621 leaving touchpad surface for touch to be considered
1622 a tap and be reported as a left button click (for
1623 touchpads working in absolute mode only).
1625 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1626 reporting absolute coordinates, such as tablets
1627 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1628 reporting absolute coordinates, such as tablets
1630 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1631 is similar to kernelcore except it specifies the
1632 amount of memory used for migratable allocations.
1633 If both kernelcore and movablecore is specified,
1634 then kernelcore will be at *least* the specified
1635 value but may be more. If movablecore on its own
1636 is specified, the administrator must be careful
1637 that the amount of memory usable for all allocations
1640 MTD_Partition= [MTD]
1641 Format: <name>,<region-number>,<size>,<offset>
1643 MTD_Region= [MTD] Format:
1644 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1647 See drivers/mtd/cmdlinepart.c.
1649 multitce=off [PPC] This parameter disables the use of the pSeries
1650 firmware feature for updating multiple TCE entries
1653 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1655 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1657 boundary - index of last SLC block on Flex-OneNAND.
1658 The remaining blocks are configured as MLC blocks.
1659 lock - Configure if Flex-OneNAND boundary should be locked.
1660 Once locked, the boundary cannot be changed.
1661 1 indicates lock status, 0 indicates unlock status.
1664 ARM/S3C2412 JIVE boot control
1666 See arch/arm/mach-s3c2412/mach-jive.c
1668 mtouchusb.raw_coordinates=
1669 [HW] Make the MicroTouch USB driver use raw coordinates
1670 ('y', default) or cooked coordinates ('n')
1672 mtrr_chunk_size=nn[KMG] [X86]
1673 used for mtrr cleanup. It is largest continuous chunk
1674 that could hold holes aka. UC entries.
1676 mtrr_gran_size=nn[KMG] [X86]
1677 Used for mtrr cleanup. It is granularity of mtrr block.
1679 Large value could prevent small alignment from
1682 mtrr_spare_reg_nr=n [X86]
1684 Range: 0,7 : spare reg number
1686 Used for mtrr cleanup. It is spare mtrr entries number.
1687 Set to 2 or more if your graphical card needs more.
1689 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1691 netdev= [NET] Network devices parameters
1692 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1693 Note that mem_start is often overloaded to mean
1694 something different and driver-specific.
1695 This usage is only documented in each driver source
1699 [NETFILTER] Enable connection tracking flow accounting
1700 0 to disable accounting
1701 1 to enable accounting
1704 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1705 See Documentation/filesystems/nfs/nfsroot.txt.
1707 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1708 See Documentation/filesystems/nfs/nfsroot.txt.
1710 nfsrootdebug [NFS] enable nfsroot debugging messages.
1711 See Documentation/filesystems/nfs/nfsroot.txt.
1713 nfs.callback_tcpport=
1714 [NFS] set the TCP port on which the NFSv4 callback
1715 channel should listen.
1718 [NFS] sets the pathname to the program which is used
1719 to update the NFS client cache entries.
1721 nfs.cache_getent_timeout=
1722 [NFS] sets the timeout after which an attempt to
1723 update a cache entry is deemed to have failed.
1725 nfs.idmap_cache_timeout=
1726 [NFS] set the maximum lifetime for idmapper cache
1730 [NFS] enable 64-bit inode numbers.
1731 If zero, the NFS client will fake up a 32-bit inode
1732 number for the readdir() and stat() syscalls instead
1733 of returning the full 64-bit number.
1734 The default is to return 64-bit inode numbers.
1736 nfs.max_session_slots=
1737 [NFSv4.1] Sets the maximum number of session slots
1738 the client will attempt to negotiate with the server.
1739 This limits the number of simultaneous RPC requests
1740 that the client can send to the NFSv4.1 server.
1741 Note that there is little point in setting this
1742 value higher than the max_tcp_slot_table_limit.
1744 nfs.nfs4_disable_idmapping=
1745 [NFSv4] When set to the default of '1', this option
1746 ensures that both the RPC level authentication
1747 scheme and the NFS level operations agree to use
1748 numeric uids/gids if the mount is using the
1749 'sec=sys' security flavour. In effect it is
1750 disabling idmapping, which can make migration from
1751 legacy NFSv2/v3 systems to NFSv4 easier.
1752 Servers that do not support this mode of operation
1753 will be autodetected by the client, and it will fall
1754 back to using the idmapper.
1755 To turn off this behaviour, set the value to '0'.
1757 [NFS4] Specify an additional fixed unique ident-
1758 ification string that NFSv4 clients can insert into
1759 their nfs_client_id4 string. This is typically a
1760 UUID that is generated at system install time.
1762 nfs.send_implementation_id =
1763 [NFSv4.1] Send client implementation identification
1764 information in exchange_id requests.
1765 If zero, no implementation identification information
1767 The default is to send the implementation identification
1770 nfsd.nfs4_disable_idmapping=
1771 [NFSv4] When set to the default of '1', the NFSv4
1772 server will return only numeric uids and gids to
1773 clients using auth_sys, and will accept numeric uids
1774 and gids from such clients. This is intended to ease
1775 migration from NFSv2/v3.
1777 objlayoutdriver.osd_login_prog=
1778 [NFS] [OBJLAYOUT] sets the pathname to the program which
1779 is used to automatically discover and login into new
1780 osd-targets. Please see:
1781 Documentation/filesystems/pnfs.txt for more explanations
1783 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1784 when a NMI is triggered.
1785 Format: [state][,regs][,debounce][,die]
1787 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1788 Format: [panic,][nopanic,][num]
1790 0 - turn nmi_watchdog off
1791 When panic is specified, panic when an NMI watchdog
1792 timeout occurs (or 'nopanic' to override the opposite
1794 This is useful when you use a panic=... timeout and
1795 need the box quickly up again.
1797 netpoll.carrier_timeout=
1798 [NET] Specifies amount of time (in seconds) that
1799 netpoll should wait for a carrier. By default netpoll
1802 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1803 emulation library even if a 387 maths coprocessor
1807 [HW] Never suspend the console
1808 Disable suspending of consoles during suspend and
1809 hibernate operations. Once disabled, debugging
1810 messages can reach various consoles while the rest
1811 of the system is being put to sleep (ie, while
1812 debugging driver suspend/resume hooks). This may
1813 not work reliably with all consoles, but is known
1814 to work with serial and VGA consoles.
1815 To facilitate more flexible debugging, we also add
1816 console_suspend, a printk module parameter to control
1817 it. Users could use console_suspend (usually
1818 /sys/module/printk/parameters/console_suspend) to
1819 turn on/off it dynamically.
1821 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1822 caches in the slab allocator. Saves per-node memory,
1823 but will impact performance.
1827 noapic [SMP,APIC] Tells the kernel to not make use of any
1828 IOAPICs that may be present in the system.
1830 noautogroup Disable scheduler automatic task group creation.
1832 nobats [PPC] Do not use BATs for mapping kernel lowmem
1833 on "Classic" PPC cores.
1837 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1839 nodelayacct [KNL] Disable per-task delay accounting
1841 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1843 nodsp [SH] Disable hardware DSP at boot time.
1845 noefi [X86] Disable EFI runtime services support.
1850 On X86-32 available only on PAE configured kernels.
1851 noexec=on: enable non-executable mappings (default)
1852 noexec=off: disable non-executable mappings
1855 Disable SMAP (Supervisor Mode Access Prevention)
1856 even if it is supported by processor.
1859 Disable SMEP (Supervisor Mode Execution Prevention)
1860 even if it is supported by processor.
1863 This affects only 32-bit executables.
1864 noexec32=on: enable non-executable mappings (default)
1865 read doesn't imply executable mappings
1866 noexec32=off: disable non-executable mappings
1867 read implies executable mappings
1869 nofpu [SH] Disable hardware FPU at boot time.
1871 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1872 register save and restore. The kernel will only save
1873 legacy floating-point registers on task switch.
1875 noxsave [BUGS=X86] Disables x86 extended register state save
1876 and restore using xsave. The kernel will fallback to
1877 enabling legacy floating-point and sse state.
1880 on enable eager fpu restore
1881 off disable eager fpu restore
1882 auto selects the default scheme, which automatically
1883 enables eagerfpu restore for xsaveopt.
1885 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1886 wfi(ARM) instruction doesn't work correctly and not to
1887 use it. This is also useful when using JTAG debugger.
1889 no_file_caps Tells the kernel not to honor file capabilities. The
1890 only way then for a file to be executed with privilege
1891 is to be setuid root or executed by root.
1893 nohalt [IA-64] Tells the kernel not to use the power saving
1894 function PAL_HALT_LIGHT when idle. This increases
1895 power-consumption. On the positive side, it reduces
1896 interrupt wake-up latency, which may improve performance
1897 in certain environments such as networked servers or
1900 nohz= [KNL] Boottime enable/disable dynamic ticks
1901 Valid arguments: on, off
1904 noiotrap [SH] Disables trapped I/O port accesses.
1906 noirqdebug [X86-32] Disables the code which attempts to detect and
1907 disable unhandled interrupt sources.
1909 no_timer_check [X86,APIC] Disables the code which tests for
1910 broken timer IRQ sources.
1912 noisapnp [ISAPNP] Disables ISA PnP code.
1914 noinitrd [RAM] Tells the kernel not to load any configured
1917 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1919 [Deprecated - use intremap=off]
1923 nojitter [IA-64] Disables jitter checking for ITC timers.
1925 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1927 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1930 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1931 steal time is computed, but won't influence scheduler
1934 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1936 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1938 noltlbs [PPC] Do not use large page/tlb entries for kernel
1939 lowmem mapping on PPC40x.
1941 nomca [IA-64] Disable machine check abort handling
1943 nomce [X86-32] Machine Check Exception
1945 nomfgpt [X86-32] Disable Multi-Function General Purpose
1946 Timer usage (for AMD Geode machines).
1948 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1949 shutdown the other cpus. Instead use the REBOOT_VECTOR
1952 nomodule Disable module load
1954 nopat [X86] Disable PAT (page attribute table extension of
1955 pagetables) support.
1957 norandmaps Don't use address space randomization. Equivalent to
1958 echo 0 > /proc/sys/kernel/randomize_va_space
1960 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1962 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1963 with UP alternatives
1965 noresidual [PPC] Don't use residual data on PReP machines.
1967 nordrand [X86] Disable the direct use of the RDRAND
1968 instruction even if it is supported by the
1969 processor. RDRAND is still available to user
1972 noresume [SWSUSP] Disables resume and restores original swap
1975 no-scroll [VGA] Disables scrollback.
1976 This is required for the Braillex ib80-piezo Braille
1977 reader made by F.H. Papenmeier (Germany).
1981 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1983 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1984 and disable the IO APIC. legacy for "maxcpus=0".
1986 nosoftlockup [KNL] Disable the soft-lockup detector.
1988 nosync [HW,M68K] Disables sync negotiation for all devices.
1990 notsc [BUGS=X86-32] Disable Time Stamp Counter
1992 nousb [USB] Disable the USB subsystem
1994 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1998 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2000 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2001 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2002 Some features depend on CPU0. Known dependencies are:
2003 1. Resume from suspend/hibernate depends on CPU0.
2004 Suspend/hibernate will fail if CPU0 is offline and you
2005 need to online CPU0 before suspend/hibernate.
2006 2. PIC interrupts also depend on CPU0. CPU0 can't be
2007 removed if a PIC interrupt is detected.
2008 It's said poweroff/reboot may depend on CPU0 on some
2009 machines although I haven't seen such issues so far
2010 after CPU0 is offline on a few tested machines.
2011 If the dependencies are under your control, you can
2012 turn on cpu0_hotplug.
2014 nptcg= [IA-64] Override max number of concurrent global TLB
2015 purges which is reported from either PAL_VM_SUMMARY or
2018 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2019 could support. nr_cpus=n : n >= 1 limits the kernel to
2020 supporting 'n' processors. Later in runtime you can not
2021 use hotplug cpu feature to put more cpu back to online.
2022 just like you compile the kernel NR_CPUS=n
2024 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2026 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2027 Allowed values are enable and disable
2029 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2030 one of ['zone', 'node', 'default'] can be specified
2031 This can be set from sysctl after boot.
2032 See Documentation/sysctl/vm.txt for details.
2034 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2035 See Documentation/debugging-via-ohci1394.txt for more
2038 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2039 Rather than timing out after 20 ms if an EC
2040 command is not properly ACKed, override the length
2041 of the timeout. We have interrupts disabled while
2042 waiting for the ACK, so if this is set too high
2043 interrupts *may* be lost!
2045 omap_mux= [OMAP] Override bootloader pin multiplexing.
2046 Format: <mux_mode0.mode_name=value>...
2047 For example, to override I2C bus2:
2048 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2050 oprofile.timer= [HW]
2051 Use timer interrupt instead of performance counters
2053 oprofile.cpu_type= Force an oprofile cpu type
2054 This might be useful if you have an older oprofile
2055 userland or if you want common events.
2056 Format: { arch_perfmon }
2057 arch_perfmon: [X86] Force use of architectural
2058 perfmon on Intel CPUs instead of the
2059 CPU specific event set.
2060 timer: [X86] Force use of architectural NMI
2061 timer mode (see also oprofile.timer
2062 for generic hr timer mode)
2063 [s390] Force legacy basic mode sampling
2064 (report cpu_type "timer")
2066 oops=panic Always panic on oopses. Default is to just kill the
2067 process, but there is a small probability of
2068 deadlocking the machine.
2069 This will also cause panics on machine check exceptions.
2070 Useful together with panic=30 to trigger a reboot.
2073 See Documentation/sound/oss/oss-parameters.txt
2075 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2076 timeout > 0: seconds before rebooting
2077 timeout = 0: wait forever
2078 timeout < 0: reboot immediately
2081 parkbd.port= [HW] Parallel port number the keyboard adapter is
2082 connected to, default is 0.
2084 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2085 0 for XT, 1 for AT (default is AT).
2088 parport= [HW,PPT] Specify parallel ports. 0 disables.
2089 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2090 Use 'auto' to force the driver to use any
2091 IRQ/DMA settings detected (the default is to
2092 ignore detected IRQ/DMA settings because of
2093 possible conflicts). You can specify the base
2094 address, IRQ, and DMA settings; IRQ and DMA
2095 should be numbers, or 'auto' (for using detected
2096 settings on that particular port), or 'nofifo'
2097 (to avoid using a FIFO even if it is detected).
2098 Parallel ports are assigned in the order they
2099 are specified on the command line, starting
2102 parport_init_mode= [HW,PPT]
2103 Configure VIA parallel port to operate in
2104 a specific mode. This is necessary on Pegasos
2105 computer where firmware has no options for setting
2106 up parallel port mode and sets it to spp.
2107 Currently this function knows 686a and 8231 chips.
2108 Format: [spp|ps2|epp|ecp|ecpepp]
2111 Halt all CPUs after the first oops has been printed for
2112 the specified number of seconds. This is to be used if
2113 your oopses keep scrolling off the screen.
2118 See header of drivers/block/paride/pcd.c.
2119 See also Documentation/blockdev/paride.txt.
2121 pci=option[,option...] [PCI] various PCI subsystem options:
2122 earlydump [X86] dump PCI config space before the kernel
2124 off [X86] don't probe for the PCI bus
2125 bios [X86-32] force use of PCI BIOS, don't access
2126 the hardware directly. Use this if your machine
2127 has a non-standard PCI host bridge.
2128 nobios [X86-32] disallow use of PCI BIOS, only direct
2129 hardware access methods are allowed. Use this
2130 if you experience crashes upon bootup and you
2131 suspect they are caused by the BIOS.
2132 conf1 [X86] Force use of PCI Configuration
2134 conf2 [X86] Force use of PCI Configuration
2136 noaer [PCIE] If the PCIEAER kernel config parameter is
2137 enabled, this kernel boot option can be used to
2138 disable the use of PCIE advanced error reporting.
2139 nodomains [PCI] Disable support for multiple PCI
2140 root domains (aka PCI segments, in ACPI-speak).
2141 nommconf [X86] Disable use of MMCONFIG for PCI
2143 check_enable_amd_mmconf [X86] check for and enable
2144 properly configured MMIO access to PCI
2145 config space on AMD family 10h CPU
2146 nomsi [MSI] If the PCI_MSI kernel config parameter is
2147 enabled, this kernel boot option can be used to
2148 disable the use of MSI interrupts system-wide.
2149 noioapicquirk [APIC] Disable all boot interrupt quirks.
2150 Safety option to keep boot IRQs enabled. This
2151 should never be necessary.
2152 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2153 primary IO-APIC for bridges that cannot disable
2154 boot IRQs. This fixes a source of spurious IRQs
2155 when the system masks IRQs.
2156 noioapicreroute [APIC] Disable workaround that uses the
2157 boot IRQ equivalent of an IRQ that connects to
2158 a chipset where boot IRQs cannot be disabled.
2159 The opposite of ioapicreroute.
2160 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2161 routing table. These calls are known to be buggy
2162 on several machines and they hang the machine
2163 when used, but on other computers it's the only
2164 way to get the interrupt routing table. Try
2165 this option if the kernel is unable to allocate
2166 IRQs or discover secondary PCI buses on your
2168 rom [X86] Assign address space to expansion ROMs.
2169 Use with caution as certain devices share
2170 address decoders between ROMs and other
2172 norom [X86] Do not assign address space to
2173 expansion ROMs that do not already have
2174 BIOS assigned address ranges.
2175 nobar [X86] Do not assign address space to the
2176 BARs that weren't assigned by the BIOS.
2177 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2178 assigned automatically to PCI devices. You can
2179 make the kernel exclude IRQs of your ISA cards
2181 pirqaddr=0xAAAAA [X86] Specify the physical address
2182 of the PIRQ table (normally generated
2183 by the BIOS) if it is outside the
2184 F0000h-100000h range.
2185 lastbus=N [X86] Scan all buses thru bus #N. Can be
2186 useful if the kernel is unable to find your
2187 secondary buses and you want to tell it
2188 explicitly which ones they are.
2189 assign-busses [X86] Always assign all PCI bus
2190 numbers ourselves, overriding
2191 whatever the firmware may have done.
2192 usepirqmask [X86] Honor the possible IRQ mask stored
2193 in the BIOS $PIR table. This is needed on
2194 some systems with broken BIOSes, notably
2195 some HP Pavilion N5400 and Omnibook XE3
2196 notebooks. This will have no effect if ACPI
2197 IRQ routing is enabled.
2198 noacpi [X86] Do not use ACPI for IRQ routing
2199 or for PCI scanning.
2200 use_crs [X86] Use PCI host bridge window information
2201 from ACPI. On BIOSes from 2008 or later, this
2202 is enabled by default. If you need to use this,
2203 please report a bug.
2204 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2205 If you need to use this, please report a bug.
2206 routeirq Do IRQ routing for all PCI devices.
2207 This is normally done in pci_enable_device(),
2208 so this option is a temporary workaround
2209 for broken drivers that don't call it.
2210 skip_isa_align [X86] do not align io start addr, so can
2211 handle more pci cards
2212 firmware [ARM] Do not re-enumerate the bus but instead
2213 just use the configuration from the
2214 bootloader. This is currently used on
2215 IXP2000 systems where the bus has to be
2216 configured a certain way for adjunct CPUs.
2217 noearly [X86] Don't do any early type 1 scanning.
2218 This might help on some broken boards which
2219 machine check when some devices' config space
2220 is read. But various workarounds are disabled
2221 and some IOMMU drivers will not work.
2222 bfsort Sort PCI devices into breadth-first order.
2223 This sorting is done to get a device
2224 order compatible with older (<= 2.4) kernels.
2225 nobfsort Don't sort PCI devices into breadth-first order.
2226 cbiosize=nn[KMG] The fixed amount of bus space which is
2227 reserved for the CardBus bridge's IO window.
2228 The default value is 256 bytes.
2229 cbmemsize=nn[KMG] The fixed amount of bus space which is
2230 reserved for the CardBus bridge's memory
2231 window. The default value is 64 megabytes.
2234 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2235 Specifies alignment and device to reassign
2236 aligned memory resources.
2237 If <order of align> is not specified,
2238 PAGE_SIZE is used as alignment.
2239 PCI-PCI bridge can be specified, if resource
2240 windows need to be expanded.
2241 ecrc= Enable/disable PCIe ECRC (transaction layer
2242 end-to-end CRC checking).
2243 bios: Use BIOS/firmware settings. This is the
2247 realloc= Enable/disable reallocating PCI bridge resources
2248 if allocations done by BIOS are too small to
2249 accommodate resources required by all child
2251 off: Turn realloc off
2253 realloc same as realloc=on
2254 noari do not use PCIe ARI.
2255 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2256 only look for one device below a PCIe downstream
2259 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2262 force Enable ASPM even on devices that claim not to support it.
2263 WARNING: Forcing ASPM on may cause system lockups.
2265 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2266 nomsi Do not use MSI for PCI Express Native Hotplug (this
2267 makes all PCIe ports use INTx for hotplug services).
2269 pcie_ports= [PCIE] PCIe ports handling:
2270 auto Ask the BIOS whether or not to use native PCIe services
2271 associated with PCIe ports (PME, hot-plug, AER). Use
2272 them only if that is allowed by the BIOS.
2273 native Use native PCIe services associated with PCIe ports
2275 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2278 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2279 nomsi Do not use MSI for native PCIe PME signaling (this makes
2280 all PCIe root ports use INTx for all services).
2282 pcmv= [HW,PCMCIA] BadgePAD 4
2285 See Documentation/blockdev/paride.txt.
2287 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2290 See arch/parisc/kernel/pdc_chassis.c
2292 percpu_alloc= Select which percpu first chunk allocator to use.
2293 Currently supported values are "embed" and "page".
2294 Archs may support subset or none of the selections.
2295 See comments in mm/percpu.c for details on each
2296 allocator. This parameter is primarily for debugging
2297 and performance comparison.
2300 See Documentation/blockdev/paride.txt.
2303 See Documentation/blockdev/paride.txt.
2305 pirq= [SMP,APIC] Manual mp-table setup
2306 See Documentation/x86/i386/IO-APIC.txt.
2308 plip= [PPT,NET] Parallel port network link
2309 Format: { parport<nr> | timid | 0 }
2310 See also Documentation/parport.txt.
2312 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2313 Override pmtimer IOPort with a hex value.
2317 Enable PNP debug messages (depends on the
2318 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2319 via /sys/module/pnp/parameters/debug. We always show
2320 current resource usage; turning this on also shows
2321 possible settings and some assignment information.
2327 { on | off | curr | res | no-curr | no-res }
2330 [ISAPNP] Exclude IRQs for the autoconfiguration
2333 [ISAPNP] Exclude DMAs for the autoconfiguration
2335 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2336 Ranges are in pairs (I/O port base and size).
2339 [ISAPNP] Exclude memory regions for the
2341 Ranges are in pairs (memory base and size).
2343 ports= [IP_VS_FTP] IPVS ftp helper module
2345 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2347 Format: <port>,<port>....
2349 print-fatal-signals=
2350 [KNL] debug: print fatal signals
2352 If enabled, warn about various signal handling
2353 related application anomalies: too many signals,
2354 too many POSIX.1 timers, fatal signals causing a
2357 If you hit the warning due to signal overflow,
2358 you might want to try "ulimit -i unlimited".
2362 printk.always_kmsg_dump=
2363 Trigger kmsg_dump for cases other than kernel oops or
2365 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2368 printk.time= Show timing data prefixed to each printk message line
2369 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2371 processor.max_cstate= [HW,ACPI]
2372 Limit processor to maximum C-state
2373 max_cstate=9 overrides any DMI blacklist limit.
2375 processor.nocst [HW,ACPI]
2376 Ignore the _CST method to determine C-states,
2377 instead using the legacy FADT method
2379 profile= [KNL] Enable kernel profiling via /proc/profile
2380 Format: [schedule,]<number>
2381 Param: "schedule" - profile schedule points.
2382 Param: <number> - step/bucket size as a power of 2 for
2383 statistical time based profiling.
2384 Param: "sleep" - profile D-state sleeping (millisecs).
2385 Requires CONFIG_SCHEDSTATS
2386 Param: "kvm" - profile VM exits.
2388 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2390 See Documentation/blockdev/ramdisk.txt.
2392 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2393 probe for; one of (bare|imps|exps|lifebook|any).
2394 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2396 psmouse.resetafter= [HW,MOUSE]
2397 Try to reset the device after so many bad packets
2400 [HW,MOUSE] Set desired mouse resolution, in dpi.
2401 psmouse.smartscroll=
2402 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2403 0 = disabled, 1 = enabled (default).
2405 pstore.backend= Specify the name of the pstore backend to use
2408 See Documentation/blockdev/paride.txt.
2411 [KNL] Number of legacy pty's. Overwrites compiled-in
2414 quiet [KNL] Disable most log messages
2419 See Documentation/md.txt.
2421 ramdisk_blocksize= [RAM]
2422 See Documentation/blockdev/ramdisk.txt.
2424 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2425 See Documentation/blockdev/ramdisk.txt.
2427 rcu_nocbs= [KNL,BOOT]
2428 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2429 the specified list of CPUs to be no-callback CPUs.
2430 Invocation of these CPUs' RCU callbacks will
2431 be offloaded to "rcuoN" kthreads created for
2432 that purpose. This reduces OS jitter on the
2433 offloaded CPUs, which can be useful for HPC and
2434 real-time workloads. It can also improve energy
2435 efficiency for asymmetric multiprocessors.
2437 rcu_nocb_poll [KNL,BOOT]
2438 Rather than requiring that offloaded CPUs
2439 (specified by rcu_nocbs= above) explicitly
2440 awaken the corresponding "rcuoN" kthreads,
2441 make these kthreads poll for callbacks.
2442 This improves the real-time response for the
2443 offloaded CPUs by relieving them of the need to
2444 wake up the corresponding kthread, but degrades
2445 energy efficiency by requiring that the kthreads
2446 periodically wake up to do the polling.
2448 rcutree.blimit= [KNL,BOOT]
2449 Set maximum number of finished RCU callbacks to process
2452 rcutree.fanout_leaf= [KNL,BOOT]
2453 Increase the number of CPUs assigned to each
2454 leaf rcu_node structure. Useful for very large
2457 rcutree.qhimark= [KNL,BOOT]
2458 Set threshold of queued
2459 RCU callbacks over which batch limiting is disabled.
2461 rcutree.qlowmark= [KNL,BOOT]
2462 Set threshold of queued RCU callbacks below which
2463 batch limiting is re-enabled.
2465 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2466 Suppress RCU CPU stall warning messages.
2468 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2469 Set timeout for RCU CPU stall warning messages.
2471 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2472 Set delay from grace-period initialization to
2473 first attempt to force quiescent states.
2474 Units are jiffies, minimum value is zero,
2475 and maximum value is HZ.
2477 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2478 Set delay between subsequent attempts to force
2479 quiescent states. Units are jiffies, minimum
2480 value is one, and maximum value is HZ.
2482 rcutorture.fqs_duration= [KNL,BOOT]
2483 Set duration of force_quiescent_state bursts.
2485 rcutorture.fqs_holdoff= [KNL,BOOT]
2486 Set holdoff time within force_quiescent_state bursts.
2488 rcutorture.fqs_stutter= [KNL,BOOT]
2489 Set wait time between force_quiescent_state bursts.
2491 rcutorture.irqreader= [KNL,BOOT]
2492 Test RCU readers from irq handlers.
2494 rcutorture.n_barrier_cbs= [KNL,BOOT]
2495 Set callbacks/threads for rcu_barrier() testing.
2497 rcutorture.nfakewriters= [KNL,BOOT]
2498 Set number of concurrent RCU writers. These just
2499 stress RCU, they don't participate in the actual
2500 test, hence the "fake".
2502 rcutorture.nreaders= [KNL,BOOT]
2503 Set number of RCU readers.
2505 rcutorture.onoff_holdoff= [KNL,BOOT]
2506 Set time (s) after boot for CPU-hotplug testing.
2508 rcutorture.onoff_interval= [KNL,BOOT]
2509 Set time (s) between CPU-hotplug operations, or
2510 zero to disable CPU-hotplug testing.
2512 rcutorture.shuffle_interval= [KNL,BOOT]
2513 Set task-shuffle interval (s). Shuffling tasks
2514 allows some CPUs to go into dyntick-idle mode
2515 during the rcutorture test.
2517 rcutorture.shutdown_secs= [KNL,BOOT]
2518 Set time (s) after boot system shutdown. This
2519 is useful for hands-off automated testing.
2521 rcutorture.stall_cpu= [KNL,BOOT]
2522 Duration of CPU stall (s) to test RCU CPU stall
2523 warnings, zero to disable.
2525 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2526 Time to wait (s) after boot before inducing stall.
2528 rcutorture.stat_interval= [KNL,BOOT]
2529 Time (s) between statistics printk()s.
2531 rcutorture.stutter= [KNL,BOOT]
2532 Time (s) to stutter testing, for example, specifying
2533 five seconds causes the test to run for five seconds,
2534 wait for five seconds, and so on. This tests RCU's
2535 ability to transition abruptly to and from idle.
2537 rcutorture.test_boost= [KNL,BOOT]
2538 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2539 "Maybe" means test if the RCU implementation
2540 under test support RCU priority boosting.
2542 rcutorture.test_boost_duration= [KNL,BOOT]
2543 Duration (s) of each individual boost test.
2545 rcutorture.test_boost_interval= [KNL,BOOT]
2546 Interval (s) between each boost test.
2548 rcutorture.test_no_idle_hz= [KNL,BOOT]
2549 Test RCU's dyntick-idle handling. See also the
2550 rcutorture.shuffle_interval parameter.
2552 rcutorture.torture_type= [KNL,BOOT]
2553 Specify the RCU implementation to test.
2555 rcutorture.verbose= [KNL,BOOT]
2556 Enable additional printk() statements.
2560 Run specified binary instead of /init from the ramdisk,
2561 used for early userspace startup. See initrd.
2563 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2564 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2565 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2568 [KNL, SMP] Set scheduler's default relax_domain_level.
2569 See Documentation/cgroups/cpusets.txt.
2571 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2573 reservetop= [X86-32]
2575 Reserves a hole at the top of the kernel virtual
2580 Set the amount of memory to reserve for BIOS at
2581 the bottom of the address space.
2583 reset_devices [KNL] Force drivers to reset the underlying device
2584 during initialization.
2587 Specify the partition device for software suspend
2589 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2591 resume_offset= [SWSUSP]
2592 Specify the offset from the beginning of the partition
2593 given by "resume=" at which the swap header is located,
2594 in <PAGE_SIZE> units (needed only for swap files).
2595 See Documentation/power/swsusp-and-swap-files.txt
2597 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2598 read the resume files
2600 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2601 Useful for devices that are detected asynchronously
2602 (e.g. USB and MMC devices).
2604 hibernate= [HIBERNATION]
2605 noresume Don't check if there's a hibernation image
2606 present during boot.
2607 nocompress Don't compress/decompress hibernation images.
2609 retain_initrd [RAM] Keep initrd memory after extraction
2611 rhash_entries= [KNL,NET]
2612 Set number of hash buckets for route cache
2614 riscom8= [HW,SERIAL]
2615 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2617 ro [KNL] Mount root device read-only on boot
2619 root= [KNL] Root filesystem
2620 See name_to_dev_t comment in init/do_mounts.c.
2622 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2623 mount the root filesystem
2625 rootflags= [KNL] Set root filesystem mount option string
2627 rootfstype= [KNL] Set root filesystem type
2629 rootwait [KNL] Wait (indefinitely) for root device to show up.
2630 Useful for devices that are detected asynchronously
2631 (e.g. USB and MMC devices).
2633 rw [KNL] Mount root device read-write on boot
2635 S [KNL] Run init in single mode
2638 See drivers/net/irda/sa1100_ir.c.
2640 sbni= [NET] Granch SBNI12 leased line adapter
2642 sched_debug [KNL] Enables verbose scheduler debug messages.
2644 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2645 xtime_lock contention on larger systems, and/or RCU lock
2646 contention on all systems with CONFIG_MAXSMP set.
2647 Format: { "0" | "1" }
2648 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2650 Note: increases power consumption, thus should only be
2651 enabled if running jitter sensitive (HPC/RT) workloads.
2653 security= [SECURITY] Choose a security module to enable at boot.
2654 If this boot parameter is not specified, only the first
2655 security module asking for security registration will be
2656 loaded. An invalid security module name will be treated
2657 as if no module has been chosen.
2659 selinux= [SELINUX] Disable or enable SELinux at boot time.
2660 Format: { "0" | "1" }
2661 See security/selinux/Kconfig help text.
2664 Default value is set via kernel config option.
2665 If enabled at boot time, /selinux/disable can be used
2666 later to disable prior to initial policy load.
2668 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2669 Format: { "0" | "1" }
2670 See security/apparmor/Kconfig help text
2673 Default value is set via kernel config option.
2675 serialnumber [BUGS=X86-32]
2678 Maximal number of shapers.
2680 show_msr= [x86] show boot-time MSR settings
2681 Format: { <integer> }
2682 Show boot-time (BIOS-initialized) MSR settings.
2683 The parameter means the number of CPUs to show,
2684 for example 1 means boot CPU only.
2691 slab_max_order= [MM, SLAB]
2692 Determines the maximum allowed order for slabs.
2693 A high setting may cause OOMs due to memory
2694 fragmentation. Defaults to 1 for systems with
2695 more than 32MB of RAM, 0 otherwise.
2697 slub_debug[=options[,slabs]] [MM, SLUB]
2698 Enabling slub_debug allows one to determine the
2699 culprit if slab objects become corrupted. Enabling
2700 slub_debug can create guard zones around objects and
2701 may poison objects when not in use. Also tracks the
2702 last alloc / free. For more information see
2703 Documentation/vm/slub.txt.
2705 slub_max_order= [MM, SLUB]
2706 Determines the maximum allowed order for slabs.
2707 A high setting may cause OOMs due to memory
2708 fragmentation. For more information see
2709 Documentation/vm/slub.txt.
2711 slub_min_objects= [MM, SLUB]
2712 The minimum number of objects per slab. SLUB will
2713 increase the slab order up to slub_max_order to
2714 generate a sufficiently large slab able to contain
2715 the number of objects indicated. The higher the number
2716 of objects the smaller the overhead of tracking slabs
2717 and the less frequently locks need to be acquired.
2718 For more information see Documentation/vm/slub.txt.
2720 slub_min_order= [MM, SLUB]
2721 Determines the minimum page order for slabs. Must be
2722 lower than slub_max_order.
2723 For more information see Documentation/vm/slub.txt.
2725 slub_nomerge [MM, SLUB]
2726 Disable merging of slabs with similar size. May be
2727 necessary if there is some reason to distinguish
2728 allocs to different slabs. Debug options disable
2729 merging on their own.
2730 For more information see Documentation/vm/slub.txt.
2733 Format: <io1>[,<io2>[,...,<io8>]]
2735 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2736 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2737 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2738 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2739 smsc-ircc2.ircc_irq= [HW] IRQ line
2740 smsc-ircc2.ircc_dma= [HW] DMA channel
2741 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2742 0: Toshiba Satellite 1800 (GP data pin select)
2743 1: Fast pin select (default)
2747 [KNL] Should the soft-lockup detector generate panics.
2750 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2751 See Documentation/laptops/sonypi.txt
2753 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2754 See Documentation/serial/specialix.txt.
2756 spia_io_base= [HW,MTD]
2762 Enabled the stack tracer on boot up.
2764 stacktrace_filter=[function-list]
2765 [FTRACE] Limit the functions that the stack tracer
2766 will trace at boot up. function-list is a comma separated
2767 list of functions. This list can be changed at run
2768 time by the stack_trace_filter file in the debugfs
2769 tracing directory. Note, this enables stack tracing
2770 and the stacktrace above is not needed.
2774 Set the STI (builtin display/keyboard on the HP-PARISC
2775 machines) console (graphic card) which should be used
2776 as the initial boot-console.
2777 See also comment in drivers/video/console/sticore.c.
2780 See comment in drivers/video/console/sticore.c.
2783 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2785 sunrpc.min_resvport=
2786 sunrpc.max_resvport=
2788 SunRPC servers often require that client requests
2789 originate from a privileged port (i.e. a port in the
2790 range 0 < portnr < 1024).
2791 An administrator who wishes to reserve some of these
2792 ports for other uses may adjust the range that the
2793 kernel's sunrpc client considers to be privileged
2794 using these two parameters to set the minimum and
2795 maximum port values.
2799 Control how the NFS server code allocates CPUs to
2800 service thread pools. Depending on how many NICs
2801 you have and where their interrupts are bound, this
2802 option will affect which CPUs will do NFS serving.
2803 Note: this parameter cannot be changed while the
2804 NFS server is running.
2806 auto the server chooses an appropriate mode
2807 automatically using heuristics
2808 global a single global pool contains all CPUs
2809 percpu one pool for each CPU
2810 pernode one pool for each NUMA node (equivalent
2811 to global on non-NUMA machines)
2813 sunrpc.tcp_slot_table_entries=
2814 sunrpc.udp_slot_table_entries=
2816 Sets the upper limit on the number of simultaneous
2817 RPC calls that can be sent from the client to a
2818 server. Increasing these values may allow you to
2819 improve throughput, but will also increase the
2820 amount of memory reserved for use by the client.
2823 [KNL] Enable accounting of swap in memory resource
2824 controller if no parameter or 1 is given or disable
2825 it if 0 is given (See Documentation/cgroups/memory.txt)
2827 swiotlb= [IA-64] Number of I/O TLB slabs
2831 sysfs.deprecated=0|1 [KNL]
2832 Enable/disable old style sysfs layout for old udev
2833 on older distributions. When this option is enabled
2834 very new udev will not work anymore. When this option
2835 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2836 in older udev will not work anymore.
2837 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2838 the kernel configuration.
2840 sysrq_always_enabled
2842 Ignore sysrq setting - this boot parameter will
2843 neutralize any effect of /proc/sys/kernel/sysrq.
2844 Useful for debugging.
2848 test_suspend= [SUSPEND]
2849 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2850 standby suspend) as the system sleep state to briefly
2851 enter during system startup. The system is woken from
2852 this state using a wakeup-capable RTC alarm.
2854 thash_entries= [KNL,NET]
2855 Set number of hash buckets for TCP connection
2857 thermal.act= [HW,ACPI]
2858 -1: disable all active trip points in all thermal zones
2859 <degrees C>: override all lowest active trip points
2861 thermal.crt= [HW,ACPI]
2862 -1: disable all critical trip points in all thermal zones
2863 <degrees C>: override all critical trip points
2865 thermal.nocrt= [HW,ACPI]
2866 Set to disable actions on ACPI thermal zone
2867 critical and hot trip points.
2869 thermal.off= [HW,ACPI]
2870 1: disable ACPI thermal control
2872 thermal.psv= [HW,ACPI]
2873 -1: disable all passive trip points
2874 <degrees C>: override all passive trip points to this
2877 thermal.tzp= [HW,ACPI]
2878 Specify global default ACPI thermal zone polling rate
2879 <deci-seconds>: poll all this frequency
2880 0: no polling (default)
2883 Force threading of all interrupt handlers except those
2884 marked explicitly IRQF_NO_THREAD.
2888 Specify if the kernel should make use of the cpu
2889 topology information if the hardware supports this.
2890 The scheduler will make use of this information and
2891 e.g. base its process migration decisions on it.
2896 tpm_suspend_pcr=[HW,TPM]
2897 Format: integer pcr id
2898 Specify that at suspend time, the tpm driver
2899 should extend the specified pcr with zeros,
2900 as a workaround for some chips which fail to
2901 flush the last written pcr on TPM_SaveState.
2902 This will guarantee that all the other pcrs
2905 trace_buf_size=nn[KMG]
2906 [FTRACE] will set tracing buffer size.
2908 trace_event=[event-list]
2909 [FTRACE] Set and start specified trace events in order
2910 to facilitate early boot debugging.
2911 See also Documentation/trace/events.txt
2913 trace_options=[option-list]
2914 [FTRACE] Enable or disable tracer options at boot.
2915 The option-list is a comma delimited list of options
2916 that can be enabled or disabled just as if you were
2917 to echo the option name into
2919 /sys/kernel/debug/tracing/trace_options
2921 For example, to enable stacktrace option (to dump the
2922 stack trace of each event), add to the command line:
2924 trace_options=stacktrace
2926 See also Documentation/trace/ftrace.txt "trace options"
2929 transparent_hugepage=
2931 Format: [always|madvise|never]
2932 Can be used to control the default behavior of the system
2933 with respect to transparent hugepages.
2934 See Documentation/vm/transhuge.txt for more details.
2936 tsc= Disable clocksource stability checks for TSC.
2938 [x86] reliable: mark tsc clocksource as reliable, this
2939 disables clocksource verification at runtime, as well
2940 as the stability checks done at bootup. Used to enable
2941 high-resolution timer mode on older hardware, and in
2942 virtualized environment.
2943 [x86] noirqtime: Do not use TSC to do irq accounting.
2944 Used to run time disable IRQ_TIME_ACCOUNTING on any
2945 platforms where RDTSC is slow and this accounting
2948 turbografx.map[2|3]= [HW,JOY]
2949 TurboGraFX parallel port interface
2951 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2952 See also Documentation/input/joystick-parport.txt
2954 udbg-immortal [PPC] When debugging early kernel crashes that
2955 happen after console_init() and before a proper
2956 console driver takes over, this boot options might
2957 help "seeing" what's going on.
2959 uhash_entries= [KNL,NET]
2960 Set number of hash buckets for UDP/UDP-Lite connections
2963 [USB] Ignore overcurrent events (default N).
2964 Some badly-designed motherboards generate lots of
2965 bogus events, for ports that aren't wired to
2966 anything. Set this parameter to avoid log spamming.
2967 Note that genuine overcurrent events won't be
2971 [X86] Cause panic on unknown NMI.
2973 usbcore.authorized_default=
2974 [USB] Default USB device authorization:
2975 (default -1 = authorized except for wireless USB,
2976 0 = not authorized, 1 = authorized)
2978 usbcore.autosuspend=
2979 [USB] The autosuspend time delay (in seconds) used
2980 for newly-detected USB devices (default 2). This
2981 is the time required before an idle device will be
2982 autosuspended. Devices for which the delay is set
2983 to a negative value won't be autosuspended at all.
2985 usbcore.usbfs_snoop=
2986 [USB] Set to log all usbfs traffic (default 0 = off).
2988 usbcore.blinkenlights=
2989 [USB] Set to cycle leds on hubs (default 0 = off).
2991 usbcore.old_scheme_first=
2992 [USB] Start with the old device initialization
2993 scheme (default 0 = off).
2995 usbcore.usbfs_memory_mb=
2996 [USB] Memory limit (in MB) for buffers allocated by
2997 usbfs (default = 16, 0 = max = 2047).
2999 usbcore.use_both_schemes=
3000 [USB] Try the other device initialization scheme
3001 if the first one fails (default 1 = enabled).
3003 usbcore.initial_descriptor_timeout=
3004 [USB] Specifies timeout for the initial 64-byte
3005 USB_REQ_GET_DESCRIPTOR request in milliseconds
3006 (default 5000 = 5.0 seconds).
3009 [USBHID] The interval which mice are to be polled at.
3011 usb-storage.delay_use=
3012 [UMS] The delay in seconds before a new device is
3013 scanned for Logical Units (default 5).
3016 [UMS] A list of quirks entries to supplement or
3017 override the built-in unusual_devs list. List
3018 entries are separated by commas. Each entry has
3019 the form VID:PID:Flags where VID and PID are Vendor
3020 and Product ID values (4-digit hex numbers) and
3021 Flags is a set of characters, each corresponding
3022 to a common usb-storage quirk flag as follows:
3023 a = SANE_SENSE (collect more than 18 bytes
3025 b = BAD_SENSE (don't collect more than 18
3026 bytes of sense data);
3027 c = FIX_CAPACITY (decrease the reported
3028 device capacity by one sector);
3029 d = NO_READ_DISC_INFO (don't use
3030 READ_DISC_INFO command);
3031 e = NO_READ_CAPACITY_16 (don't use
3032 READ_CAPACITY_16 command);
3033 h = CAPACITY_HEURISTICS (decrease the
3034 reported device capacity by one
3035 sector if the number is odd);
3036 i = IGNORE_DEVICE (don't bind to this
3038 l = NOT_LOCKABLE (don't try to lock and
3039 unlock ejectable media);
3040 m = MAX_SECTORS_64 (don't transfer more
3041 than 64 sectors = 32 KB at a time);
3042 n = INITIAL_READ10 (force a retry of the
3043 initial READ(10) command);
3044 o = CAPACITY_OK (accept the capacity
3045 reported by the device);
3046 p = WRITE_CACHE (the device cache is ON
3048 r = IGNORE_RESIDUE (the device reports
3049 bogus residue values);
3050 s = SINGLE_LUN (the device has only one
3052 w = NO_WP_DETECT (don't test whether the
3053 medium is write-protected).
3054 Example: quirks=0419:aaf5:rl,0421:0433:rc
3056 user_debug= [KNL,ARM]
3058 See arch/arm/Kconfig.debug help text.
3059 1 - undefined instruction events
3061 4 - invalid data aborts
3064 Example: user_debug=31
3067 [X86] Flags controlling user PTE allocations.
3069 nohigh = do not allocate PTE pages in
3070 HIGHMEM regardless of setting
3074 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3075 vdso=1: enable VDSO (default)
3076 vdso=0: disable VDSO mapping
3079 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3080 vdso32=1: enable 32-bit VDSO (default)
3081 vdso32=0: disable 32-bit VDSO mapping
3084 vector=percpu: enable percpu vector domain
3086 video= [FB] Frame buffer configuration
3087 See Documentation/fb/modedb.txt.
3090 [VMMIO] Memory mapped virtio (platform) device.
3092 <size>@<baseaddr>:<irq>[:<id>]
3094 <size> := size (can use standard suffixes
3096 <baseaddr> := physical base address
3097 <irq> := interrupt number (as passed to
3099 <id> := (optional) platform device id
3101 virtio_mmio.device=1K@0x100b0000:48:7
3103 Can be used multiple times for multiple devices.
3105 vga= [BOOT,X86-32] Select a particular video mode
3106 See Documentation/x86/boot.txt and
3107 Documentation/svga.txt.
3108 Use vga=ask for menu.
3109 This is actually a boot loader parameter; the value is
3110 passed to the kernel using a special protocol.
3112 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3113 size of <nn>. This can be used to increase the
3114 minimum size (128MB on x86). It can also be used to
3115 decrease the size and leave more room for directly
3118 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3121 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3124 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3128 Controls the behavior of vsyscalls (i.e. calls to
3129 fixed addresses of 0xffffffffff600x00 from legacy
3130 code). Most statically-linked binaries and older
3131 versions of glibc use these calls. Because these
3132 functions are at fixed addresses, they make nice
3133 targets for exploits that can control RIP.
3135 emulate [default] Vsyscalls turn into traps and are
3136 emulated reasonably safely.
3138 native Vsyscalls are native syscall instructions.
3139 This is a little bit faster than trapping
3140 and makes a few dynamic recompilers work
3141 better than they would in emulation mode.
3142 It also makes exploits much easier to write.
3144 none Vsyscalls don't work at all. This makes
3145 them quite hard to use for exploits but
3146 might break your system.
3148 vt.cur_default= [VT] Default cursor shape.
3149 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3150 the parameters of the <Esc>[?A;B;Cc escape sequence;
3151 see VGA-softcursor.txt. Default: 2 = underline.
3153 vt.default_blu= [VT]
3154 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3155 Change the default blue palette of the console.
3156 This is a 16-member array composed of values
3159 vt.default_grn= [VT]
3160 Format: <green0>,<green1>,<green2>,...,<green15>
3161 Change the default green palette of the console.
3162 This is a 16-member array composed of values
3165 vt.default_red= [VT]
3166 Format: <red0>,<red1>,<red2>,...,<red15>
3167 Change the default red palette of the console.
3168 This is a 16-member array composed of values
3174 Set system-wide default UTF-8 mode for all tty's.
3175 Default is 1, i.e. UTF-8 mode is enabled for all
3176 newly opened terminals.
3178 vt.global_cursor_default=
3181 Set system-wide default for whether a cursor
3182 is shown on new VTs. Default is -1,
3183 i.e. cursors will be created by default unless
3184 overridden by individual drivers. 0 will hide
3185 cursors, 1 will display them.
3187 watchdog timers [HW,WDT] For information on watchdog timers,
3188 see Documentation/watchdog/watchdog-parameters.txt
3189 or other driver-specific files in the
3190 Documentation/watchdog/ directory.
3192 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3193 default x2apic cluster mode on platforms
3196 x86_mrst_timer= [X86-32,APBT]
3197 Choose timer option for x86 Moorestown MID platform.
3198 Two valid options are apbt timer only and lapic timer
3199 plus one apbt timer for broadcast timer.
3200 x86_mrst_timer=apbt_only | lapic_and_apbt
3202 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3203 xd_geo= See header of drivers/block/xd.c.
3205 xen_emul_unplug= [HW,X86,XEN]
3206 Unplug Xen emulated devices
3207 Format: [unplug0,][unplug1]
3208 ide-disks -- unplug primary master IDE devices
3209 aux-ide-disks -- unplug non-primary-master IDE devices
3210 nics -- unplug network devices
3211 all -- unplug all emulated devices (NICs and IDE disks)
3212 unnecessary -- unplugging emulated devices is
3213 unnecessary even if the host did not respond to
3215 never -- do not unplug even if version check succeeds
3217 xirc2ps_cs= [NET,PCMCIA]
3219 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3221 ______________________________________________________________________
3225 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob