1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
18 acpi_apic_instance= [ACPI, IOAPIC]
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
24 acpi_backlight= [HW,ACPI]
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
73 acpi_enforce_resources= [ACPI]
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
107 Format: <irq>,<irq>...
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
114 This facility can be used to prevent such uncontrolled
117 Support masking of GPEs numbered from 0x00 to 0x7f.
119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
124 This feature is enabled by default.
125 This option allows to turn off the feature.
127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
157 acpi_osi=!* # remove all strings
158 acpi_osi=! # disable all built-in OS vendor
160 acpi_osi=!! # enable all built-in OS vendor
162 acpi_osi= # disable all strings
164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
226 old_ordering, nonvs, sci_force_enable }
227 See Documentation/power/video.txt for information on
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
257 See Documentation/sound/alsa/alsa-parameters.txt
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
272 32: only for 32-bit processes
273 64: only for 64-bit processes
274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
284 amd_iommu= [HW,X86-64]
285 Pass parameters to the AMD IOMMU driver in the system.
287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
291 off - do not initialize any AMD IOMMU found in
293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
317 See also Documentation/input/joystick.txt
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
325 Power management functions (SPARCstation-4/5 + deriv.)
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
332 Change the output verbosity whilst booting
333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
347 See Documentation/networking/ipv6.txt.
349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
358 apm= [APM] Advanced Power Management
359 See header of arch/x86/kernel/apm_32.c.
361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
366 atarimouse= [HW,MOUSE] Atari Mouse
368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
371 atkbd.reset= [HW] Reset keyboard during initialization
373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
406 unset - Disable the BAU.
408 baycom_epp= [HW,AX25]
411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
413 See header of drivers/net/hamradio/baycom_par.c.
415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
437 Disable BERT OS support on buggy BIOSes.
439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
440 bttv.radio= Most important insmod options are available as
442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
449 c101= [NET] Moxa C101 synchronous serial card
451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
461 format: { id:<keyid> | builtin }
463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
477 - foo isn't visible as an individually mountable
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
490 nosocket -- Disable socket memory accounting.
491 nokmem -- Disable kernel memory accounting.
493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
500 Value can be changed at runtime via
501 /selinux/checkreqprot.
504 See Documentation/s390/CommonIO for details.
507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
519 Forces specified clocksource (if available) to be used
520 when calculating gettimeofday(). If specified
521 clocksource is not available, it defaults to PIT.
522 Format: { pit | tsc | cyclone | pmtmr }
524 clocksource= Override the default clocksource
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
530 [all] jiffies (this is the base, fallback clocksource)
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
535 [X86-32] pit,hpet,tsc;
536 scx200_hrt on Geode; cyclone on IBM x440
544 clocksource.arm_arch_timer.evtstrm=
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
552 clearcpuid=BITNUM [X86]
553 Disable CPUID feature X for the kernel. See
554 arch/x86/include/asm/cpufeatures.h for the valid bit
555 numbers. Note the Linux specific bits are not necessarily
556 stable over kernel options, but the vendor specific
558 Also note that user programs calling CPUID directly
559 or using the feature without checking anything
560 will still see it. This just prevents it from
561 being used by the kernel or shown in /proc/cpuinfo.
562 Also note the kernel might malfunction if you disable
565 cma=nn[MG]@[start[MG][-end[MG]]]
567 Sets the size of kernel global memory area for
568 contiguous memory allocations and optionally the
569 placement constraint by the physical address range of
570 memory allocations. A value of 0 disables CMA
571 altogether. For more information, see
572 include/linux/dma-contiguous.h
574 cmo_free_hint= [PPC] Format: { yes | no }
575 Specify whether pages are marked as being inactive
576 when they are freed. This is used in CMO environments
577 to determine OS memory pressure for page stealing by
581 coherent_pool=nn[KMG] [ARM,KNL]
582 Sets the size of memory pool for coherent, atomic dma
583 allocations, by default set to 256K.
585 code_bytes [X86] How many bytes of object code to print
590 com20020= [HW,NET] ARCnet - COM20020 chipset
592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
598 ARCnet - COM90xx chipset (memory-mapped buffers)
599 Format: <io>[,<irq>[,<memstart>]]
601 condev= [HW,S390] console device
604 console= [KNL] Output console device and options.
606 tty<n> Use the virtual console device <n>.
610 Use the specified serial port. The options are of
611 the form "bbbbpnf", where "bbbb" is the baud rate,
612 "p" is parity ("n", "o", or "e"), "n" is number of
613 bits, and "f" is flow control ("r" for RTS or
614 omit it). Default is "9600n8".
616 See Documentation/admin-guide/serial-console.rst for more
618 Documentation/networking/netconsole.txt for an
621 uart[8250],io,<addr>[,options]
622 uart[8250],mmio,<addr>[,options]
623 uart[8250],mmio16,<addr>[,options]
624 uart[8250],mmio32,<addr>[,options]
625 uart[8250],0x<addr>[,options]
626 Start an early, polled-mode console on the 8250/16550
627 UART at the specified I/O port or MMIO address,
628 switching to the matching ttyS device later.
629 MMIO inter-register address stride is either 8-bit
630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
632 to be equivalent to 'mmio'. 'options' are specified in
633 the same format described for ttyS above; if unspecified,
634 the h/w is not re-initialized.
636 hvc<n> Use the hypervisor console device <n>. This is for
637 both Xen and PowerPC hypervisors.
639 If the device connected to the port is not a TTY but a braille
640 device, prepend "brl," before the device type, for instance
642 For now, only VisioBraille is supported.
644 consoleblank= [KNL] The console blank (screen saver) timeout in
645 seconds. Defaults to 10*60 = 10mins. A value of 0
646 disables the blank timer.
649 [KNL] Change the default value for
650 /proc/<pid>/coredump_filter.
651 See also Documentation/filesystems/proc.txt.
653 cpuidle.off=1 [CPU_IDLE]
654 disable the cpuidle sub-system
657 [X86] Delay for N microsec between assert and de-assert
658 of APIC INIT to start processors. This delay occurs
659 on every CPU online, such as boot, and resume from suspend.
662 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
664 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
666 crashkernel=size[KMG][@offset[KMG]]
667 [KNL] Using kexec, Linux can switch to a 'crash kernel'
668 upon panic. This parameter reserves the physical
669 memory region [offset, offset + size] for that kernel
670 image. If '@offset' is omitted, then a suitable offset
671 is selected automatically. Check
672 Documentation/kdump/kdump.txt for further details.
674 crashkernel=range1:size1[,range2:size2,...][@offset]
675 [KNL] Same as above, but depends on the memory
676 in the running system. The syntax of range is
677 start-[end] where start and end are both
678 a memory unit (amount[KMG]). See also
679 Documentation/kdump/kdump.txt for an example.
681 crashkernel=size[KMG],high
682 [KNL, x86_64] range could be above 4G. Allow kernel
683 to allocate physical memory region from top, so could
684 be above 4G if system have more than 4G ram installed.
685 Otherwise memory region will be allocated below 4G, if
687 It will be ignored if crashkernel=X is specified.
688 crashkernel=size[KMG],low
689 [KNL, x86_64] range under 4G. When crashkernel=X,high
690 is passed, kernel could allocate physical memory region
691 above 4G, that cause second kernel crash on system
692 that require some amount of low memory, e.g. swiotlb
693 requires at least 64M+32K low memory, also enough extra
694 low memory is needed to make sure DMA buffers for 32-bit
695 devices won't run out. Kernel would try to allocate at
696 at least 256M below 4G automatically.
697 This one let user to specify own low range under 4G
698 for second kernel instead.
699 0: to disable low allocation.
700 It will be ignored when crashkernel=X,high is not used
701 or memory reserved is below 4G.
704 [KNL] Disable crypto self-tests
709 cs89x0_media= [HW,NET]
710 Format: { rj45 | aui | bnc }
713 See header of drivers/s390/block/dasd_devmap.c.
715 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
716 (one device per port)
717 Format: <port#>,<type>
718 See also Documentation/input/joystick-parport.txt
720 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
721 time. See Documentation/dynamic-debug-howto.txt for
722 details. Deprecated, see dyndbg.
724 debug [KNL] Enable kernel debugging (events log level).
727 [KNL] verbose self-tests
729 Print debugging info while doing the locking API
731 We default to 0 (no extra messages), setting it to
732 1 will print _a lot_ more information - normally
733 only useful to kernel developers.
735 debug_objects [KNL] Enable object debugging
738 [KNL] Disable object debugging
740 debug_guardpage_minorder=
741 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
742 parameter allows control of the order of pages that will
743 be intentionally kept free (and hence protected) by the
744 buddy allocator. Bigger value increase the probability
745 of catching random memory corruption, but reduce the
746 amount of memory for normal system use. The maximum
747 possible value is MAX_ORDER/2. Setting this parameter
748 to 1 or 2 should be enough to identify most random
749 memory corruption problems caused by bugs in kernel or
750 driver code when a CPU writes to (or reads from) a
751 random memory location. Note that there exists a class
752 of memory corruptions problems caused by buggy H/W or
753 F/W or by drivers badly programing DMA (basically when
754 memory is written at bus level and the CPU MMU is
755 bypassed) which are not detectable by
756 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
757 tracking down these problems.
760 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
761 parameter enables the feature at boot time. In
762 default, it is disabled. We can avoid allocating huge
763 chunk of memory for debug pagealloc if we don't enable
764 it at boot time and the system will work mostly same
765 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
766 on: enable the feature
768 debugpat [X86] Enable PAT debugging
770 decnet.addr= [HW,NET]
771 Format: <area>[,<node>]
772 See also Documentation/networking/decnet.txt.
775 [same as hugepagesz=] The size of the default
776 HugeTLB page size. This is the size represented by
777 the legacy /proc/ hugepages APIs, used for SHM, and
778 default size when mounting hugetlbfs filesystems.
779 Defaults to the default architecture's huge page size
783 Set number of hash buckets for dentry cache.
785 disable_1tb_segments [PPC]
786 Disables the use of 1TB hash page table segments. This
787 causes the kernel to fall back to 256MB segments which
788 can be useful when debugging issues that require an SLB
792 See Documentation/networking/ipv6.txt.
795 Disable RADIX MMU mode on POWER9
797 disable_cpu_apicid= [X86,APIC,SMP]
799 The number of initial APIC ID for the
800 corresponding CPU to be disabled at boot,
801 mostly used for the kdump 2nd kernel to
802 disable BSP to wake up multiple CPUs without
803 causing system reset or hang due to sending
806 disable_ddw [PPC/PSERIES]
807 Disable Dynamic DMA Window support. Use this if
808 to workaround buggy firmware.
811 See Documentation/networking/ipv6.txt.
813 disable_mtrr_cleanup [X86]
814 The kernel tries to adjust MTRR layout from continuous
815 to discrete, to make X server driver able to add WB
816 entry later. This parameter disables that.
818 disable_mtrr_trim [X86, Intel and AMD only]
819 By default the kernel will trim any uncacheable
820 memory out of your available memory pool based on
821 MTRR settings. This parameter disables that behavior,
822 possibly causing your machine to run very slowly.
824 disable_timer_pin_1 [X86]
825 Disable PIN 1 of APIC timer
826 Can be useful to work around chipset bugs.
828 dis_ucode_ldr [X86] Disable the microcode loader.
830 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
831 this option disables the debugging code at boot.
833 dma_debug_entries=<number>
834 This option allows to tune the number of preallocated
835 entries for DMA-API debugging code. One entry is
836 required per DMA-API allocation. Use this if the
837 DMA-API debugging code disables itself because the
838 architectural default is too low.
840 dma_debug_driver=<driver_name>
841 With this option the DMA-API debugging driver
842 filter feature can be enabled at boot time. Just
843 pass the driver to filter for as the parameter.
844 The filter can be disabled or changed to another
845 driver later using sysfs.
847 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
848 Broken monitors, graphic adapters, KVMs and EDIDless
849 panels may send no or incorrect EDID data sets.
850 This parameter allows to specify an EDID data sets
851 in the /lib/firmware directory that are used instead.
852 Generic built-in EDID data sets are used, if one of
853 edid/1024x768.bin, edid/1280x1024.bin,
854 edid/1680x1050.bin, or edid/1920x1080.bin is given
855 and no file with the same name exists. Details and
856 instructions how to build your own EDID data are
857 available in Documentation/EDID/HOWTO.txt. An EDID
858 data set will only be used for a particular connector,
859 if its name and a colon are prepended to the EDID
860 name. Each connector may use a unique EDID data
861 set by separating the files with a comma. An EDID
862 data set with no connector name will be used for
863 any connectors not explicitly specified.
867 dump_apple_properties [X86]
868 Dump name and content of EFI device properties on
869 x86 Macs. Useful for driver authors to determine
870 what data is available or for reverse-engineering.
872 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
873 module.dyndbg[="val"]
874 Enable debug messages at boot time. See
875 Documentation/dynamic-debug-howto.txt for details.
877 nompx [X86] Disables Intel Memory Protection Extensions.
878 See Documentation/x86/intel_mpx.txt for more
879 information about the feature.
881 nopku [X86] Disable Memory Protection Keys CPU feature found
884 module.async_probe [KNL]
885 Enable asynchronous probe on this module.
887 early_ioremap_debug [KNL]
888 Enable debug messages in early_ioremap support. This
889 is useful for tracking down temporary early mappings
890 which are not unmapped.
892 earlycon= [KNL] Output early console device and options.
894 When used with no options, the early console is
895 determined by the stdout-path property in device
898 cdns,<addr>[,options]
899 Start an early, polled-mode console on a Cadence
900 (xuartps) serial port at the specified address. Only
901 supported option is baud rate. If baud rate is not
902 specified, the serial port must already be setup and
905 uart[8250],io,<addr>[,options]
906 uart[8250],mmio,<addr>[,options]
907 uart[8250],mmio32,<addr>[,options]
908 uart[8250],mmio32be,<addr>[,options]
909 uart[8250],0x<addr>[,options]
910 Start an early, polled-mode console on the 8250/16550
911 UART at the specified I/O port or MMIO address.
912 MMIO inter-register address stride is either 8-bit
913 (mmio) or 32-bit (mmio32 or mmio32be).
914 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
915 to be equivalent to 'mmio'. 'options' are specified
916 in the same format described for "console=ttyS<n>"; if
917 unspecified, the h/w is not initialized.
921 Start an early, polled-mode console on a pl011 serial
922 port at the specified address. The pl011 serial port
923 must already be setup and configured. Options are not
924 yet supported. If 'mmio32' is specified, then only
925 the driver will use only 32-bit accessors to read/write
926 the device registers.
929 Start an early, polled-mode console on a meson serial
930 port at the specified address. The serial port must
931 already be setup and configured. Options are not yet
935 Start an early, polled-mode console on an msm serial
936 port at the specified address. The serial port
937 must already be setup and configured. Options are not
941 Start an early, polled-mode console on an msm serial
942 dm port at the specified address. The serial port
943 must already be setup and configured. Options are not
946 smh Use ARM semihosting calls for early console.
954 Use early console provided by serial driver available
955 on Samsung SoCs, requires selecting proper type and
956 a correct base address of the selected UART port. The
957 serial port must already be setup and configured.
958 Options are not yet supported.
961 Start an early, polled-mode console on a lantiq serial
962 (lqasc) port at the specified address. The serial port
963 must already be setup and configured. Options are not
968 Use early console provided by Freescale LP UART driver
969 found on Freescale Vybrid and QorIQ LS1021A processors.
970 A valid base address must be provided, and the serial
971 port must already be setup and configured.
973 armada3700_uart,<addr>
974 Start an early, polled-mode console on the
975 Armada 3700 serial port at the specified
976 address. The serial port must already be setup
977 and configured. Options are not yet supported.
979 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
984 earlyprintk=serial[,ttySn[,baudrate]]
985 earlyprintk=serial[,0x...[,baudrate]]
986 earlyprintk=ttySn[,baudrate]
987 earlyprintk=dbgp[debugController#]
988 earlyprintk=pciserial,bus:device.function[,baudrate]
990 earlyprintk is useful when the kernel crashes before
991 the normal console is initialized. It is not enabled by
992 default because it has some cosmetic problems.
994 Append ",keep" to not disable it when the real console
997 Only one of vga, efi, serial, or usb debug port can
1000 Currently only ttyS0 and ttyS1 may be specified by
1001 name. Other I/O ports may be explicitly specified
1002 on some architectures (x86 and arm at least) by
1003 replacing ttySn with an I/O port address, like this:
1004 earlyprintk=serial,0x1008,115200
1005 You can find the port for a given device in
1006 /proc/tty/driver/serial:
1007 2: uart:ST16650V2 port:00001008 irq:18 ...
1009 Interaction with the standard serial driver is not
1012 The VGA and EFI output is eventually overwritten by
1015 The xen output can only be used by Xen PV guests.
1017 The sclp output can only be used on s390.
1019 edac_report= [HW,EDAC] Control how to report EDAC event
1020 Format: {"on" | "off" | "force"}
1021 on: enable EDAC to report H/W event. May be overridden
1022 by other higher priority error reporting module.
1023 off: disable H/W event reporting through EDAC.
1024 force: enforce the use of EDAC to report H/W event.
1027 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1030 This is designed to be used in conjunction with
1031 the boot argument: earlyprintk=vga
1034 Format: {"off" | "on" | "skip[mbr]"}
1037 Format: { "old_map", "nochunk", "noruntime", "debug" }
1038 old_map [X86-64]: switch to the old ioremap-based EFI
1039 runtime services mapping. 32-bit still uses this one by
1041 nochunk: disable reading files in "chunks" in the EFI
1042 boot stub, as chunking can cause problems with some
1043 firmware implementations.
1044 noruntime : disable EFI runtime services support
1045 debug: enable misc debug output
1047 efi_no_storage_paranoia [EFI; X86]
1048 Using this parameter you can use more than 50% of
1049 your efi variable storage. Use this parameter only if
1050 you are really sure that your UEFI does sane gc and
1051 fulfills the spec otherwise your board may brick.
1053 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1054 Add arbitrary attribute to specific memory range by
1055 updating original EFI memory map.
1056 Region of memory which aa attribute is added to is
1058 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1059 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1060 attribute is added to range 0x100000000-0x180000000 and
1061 0x10a0000000-0x1120000000.
1063 Using this parameter you can do debugging of EFI memmap
1064 related feature. For example, you can do debugging of
1065 Address Range Mirroring feature even if your box
1068 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1069 that is to be dynamically loaded by Linux. If there are
1070 multiple variables with the same name but with different
1071 vendor GUIDs, all of them will be loaded. See
1072 Documentation/acpi/ssdt-overlays.txt for details.
1075 eisa_irq_edge= [PARISC,HW]
1076 See header of drivers/parisc/eisa.c.
1079 See comment before function elanfreq_setup() in
1080 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1083 Format: {"cfq" | "deadline" | "noop"}
1084 See Documentation/block/cfq-iosched.txt and
1085 Documentation/block/deadline-iosched.txt for details.
1087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1088 Specifies physical address of start of kernel core
1089 image elf header and optionally the size. Generally
1090 kexec loader will pass this option to capture kernel.
1091 See Documentation/kdump/kdump.txt for details.
1093 enable_mtrr_cleanup [X86]
1094 The kernel tries to adjust MTRR layout from continuous
1095 to discrete, to make X server driver able to add WB
1096 entry later. This parameter enables that.
1098 enable_timer_pin_1 [X86]
1099 Enable PIN 1 of APIC timer
1100 Can be useful to work around chipset bugs
1101 (in particular on some ATI chipsets).
1102 The kernel tries to set a reasonable default.
1104 enforcing [SELINUX] Set initial enforcing status.
1106 See security/selinux/Kconfig help text.
1107 0 -- permissive (log only, no denials).
1108 1 -- enforcing (deny and log).
1110 Value can be changed at runtime via /selinux/enforce.
1113 Disable Error Record Serialization Table (ERST)
1116 ether= [HW,NET] Ethernet cards parameters
1117 This option is obsoleted by the "netdev=" option, which
1118 has equivalent usage. See its documentation for details.
1122 Permit 'security.evm' to be updated regardless of
1123 current integrity status.
1127 fail_make_request=[KNL]
1128 General fault injection mechanism.
1129 Format: <interval>,<probability>,<space>,<times>
1130 See also Documentation/fault-injection/.
1133 See Documentation/blockdev/floppy.txt.
1135 force_pal_cache_flush
1136 [IA-64] Avoid check_sal_cache_flush which may hang on
1137 buggy SAL_CACHE_FLUSH implementations. Using this
1138 parameter will force ia64_sal_cache_flush to call
1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1142 Forcefully enable Physical Address Extension (PAE).
1143 Many Pentium M systems disable PAE but may have a
1144 functionally usable PAE implementation.
1145 Warning: use of this parameter will taint the kernel
1146 and may cause unknown problems.
1149 [FTRACE] will set and start the specified tracer
1150 as early as possible in order to facilitate early
1153 ftrace_dump_on_oops[=orig_cpu]
1154 [FTRACE] will dump the trace buffers on oops.
1155 If no parameter is passed, ftrace will dump
1156 buffers of all CPUs, but if you pass orig_cpu, it will
1157 dump only the buffer of the CPU that triggered the
1160 ftrace_filter=[function-list]
1161 [FTRACE] Limit the functions traced by the function
1162 tracer at boot up. function-list is a comma separated
1163 list of functions. This list can be changed at run
1164 time by the set_ftrace_filter file in the debugfs
1167 ftrace_notrace=[function-list]
1168 [FTRACE] Do not trace the functions specified in
1169 function-list. This list can be changed at run time
1170 by the set_ftrace_notrace file in the debugfs
1173 ftrace_graph_filter=[function-list]
1174 [FTRACE] Limit the top level callers functions traced
1175 by the function graph tracer at boot up.
1176 function-list is a comma separated list of functions
1177 that can be changed at run time by the
1178 set_graph_function file in the debugfs tracing directory.
1180 ftrace_graph_notrace=[function-list]
1181 [FTRACE] Do not trace from the functions specified in
1182 function-list. This list is a comma separated list of
1183 functions that can be changed at run time by the
1184 set_graph_notrace file in the debugfs tracing directory.
1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1188 support via parallel port (up to 5 devices per port)
1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1190 See also Documentation/input/joystick-parport.txt
1194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1198 gcov_persist= [GCOV] When non-zero (default), profiling data for
1199 kernel modules is saved and remains accessible via
1200 debugfs, even when the module is unloaded/reloaded.
1201 When zero, profiling data is discarded and associated
1202 debugfs files are removed at module unload time.
1204 goldfish [X86] Enable the goldfish android emulator platform.
1205 Don't use this when you are not running on the
1208 gpt [EFI] Forces disk with valid GPT signature but
1209 invalid Protective MBR to be treated as GPT. If the
1210 primary GPT is corrupted, it enables the backup/alternate
1211 GPT to be used instead.
1213 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1214 the "Enable 0" bit of the configuration register.
1217 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1218 the "Enable 0" bit of the configuration register.
1221 grcan.select= [HW] Select which physical interface to use.
1224 grcan.txsize= [HW] Sets the size of the tx buffer.
1225 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1227 grcan.rxsize= [HW] Sets the size of the rx buffer.
1228 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1231 gpio-mockup.gpio_mockup_ranges
1232 [HW] Sets the ranges of gpiochip of for this device.
1233 Format: <start1>,<end1>,<start2>,<end2>...
1235 hardlockup_all_cpu_backtrace=
1236 [KNL] Should the hard-lockup detector generate
1237 backtraces on all cpus.
1240 hashdist= [KNL,NUMA] Large hashes allocated during boot
1241 are distributed across NUMA nodes. Defaults on
1242 for 64-bit NUMA, off otherwise.
1243 Format: 0 | 1 (for off | on)
1245 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1247 hd= [EIDE] (E)IDE hard drive subsystem geometry
1248 Format: <cyl>,<head>,<sect>
1251 Disable Hardware Error Source Table (HEST) support;
1252 corresponding firmware-first mode error processing
1253 logic will be disabled.
1255 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1256 size of <nn>. This works even on boxes that have no
1257 highmem otherwise. This also works to reduce highmem
1258 size on bigger boxes.
1260 highres= [KNL] Enable/disable high resolution timer mode.
1261 Valid parameters: "on", "off"
1265 See Documentation/isdn/README.HiSax.
1269 hpet= [X86-32,HPET] option to control HPET usage
1270 Format: { enable (default) | disable | force |
1272 disable: disable HPET and use PIT instead
1273 force: allow force enabled of undocumented chips (ICH4,
1275 verbose: show contents of HPET registers during setup
1277 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1278 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1280 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1281 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1282 On x86-64 and powerpc, this option can be specified
1283 multiple times interleaved with hugepages= to reserve
1284 huge pages of different sizes. Valid pages sizes on
1285 x86-64 are 2M (when the CPU supports "pse") and 1G
1286 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1288 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1289 terminal devices. Valid values: 0..8
1290 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1291 If specified, z/VM IUCV HVC accepts connections
1292 from listed z/VM user IDs only.
1294 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1295 hardware thread id mappings.
1296 Format: <cpu>:<hwthread>
1299 Do not unregister boot console at start. This is only
1300 useful for debugging when something happens in the window
1301 between unregistering the boot console and initializing
1304 i2c_bus= [HW] Override the default board specific I2C bus speed
1305 or register an additional I2C bus that is not
1306 registered from board initialization code.
1310 i8042.debug [HW] Toggle i8042 debug mode
1311 i8042.unmask_kbd_data
1312 [HW] Enable printing of interrupt data from the KBD port
1313 (disabled by default, and as a pre-condition
1314 requires that i8042.debug=1 be enabled)
1315 i8042.direct [HW] Put keyboard port into non-translated mode
1316 i8042.dumbkbd [HW] Pretend that controller can only read data from
1317 keyboard and cannot control its state
1318 (Don't attempt to blink the leds)
1319 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1320 i8042.nokbd [HW] Don't check/create keyboard port
1321 i8042.noloop [HW] Disable the AUX Loopback command while probing
1323 i8042.nomux [HW] Don't check presence of an active multiplexing
1325 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1327 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1328 i8042.reset [HW] Reset the controller during init, cleanup and
1329 suspend-to-ram transitions, only during s2r
1330 transitions, or never reset
1331 Format: { 1 | Y | y | 0 | N | n }
1332 1, Y, y: always reset controller
1333 0, N, n: don't ever reset controller
1334 Default: only on s2r transitions on x86; most other
1335 architectures force reset to be always executed
1336 i8042.unlock [HW] Unlock (ignore) the keylock
1337 i8042.kbdreset [HW] Reset device connected to KBD port
1341 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1342 indicates that the driver is running on unsupported
1344 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1345 does not match list of supported models.
1347 [HW] Report power status in /proc/i8k
1348 (disabled by default)
1349 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1352 i915.invert_brightness=
1353 [DRM] Invert the sense of the variable that is used to
1354 set the brightness of the panel backlight. Normally a
1355 brightness value of 0 indicates backlight switched off,
1356 and the maximum of the brightness value sets the backlight
1357 to maximum brightness. If this parameter is set to 0
1358 (default) and the machine requires it, or this parameter
1359 is set to 1, a brightness value of 0 sets the backlight
1360 to maximum brightness, and the maximum of the brightness
1361 value switches the backlight off.
1362 -1 -- never invert brightness
1363 0 -- machine default
1364 1 -- force brightness inversion
1367 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1369 ide-core.nodma= [HW] (E)IDE subsystem
1370 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1371 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1372 .cdrom .chs .ignore_cable are additional options
1373 See Documentation/ide/ide.txt.
1375 ide-generic.probe-mask= [HW] (E)IDE subsystem
1377 Probe mask for legacy ISA IDE ports. Depending on
1378 platform up to 6 ports are supported, enabled by
1379 setting corresponding bits in the mask to 1. The
1380 default value is 0x0, which has a special meaning.
1381 On systems that have PCI, it triggers scanning the
1382 PCI bus for the first and the second port, which
1383 are then probed. On systems without PCI the value
1384 of 0x0 enables probing the two first ports as if it
1387 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1388 Claim all unknown PCI IDE storage controllers.
1391 Format: idle=poll, idle=halt, idle=nomwait
1392 Poll forces a polling idle loop that can slightly
1393 improve the performance of waking up a idle CPU, but
1394 will use a lot of power and make the system run hot.
1396 idle=halt: Halt is forced to be used for CPU idle.
1397 In such case C2/C3 won't be used again.
1398 idle=nomwait: Disable mwait for CPU C-states
1400 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1401 Format: { strict | legacy | 2008 | relaxed }
1404 Choose which programs will be accepted for execution
1405 based on the IEEE 754 NaN encoding(s) supported by
1406 the FPU and the NaN encoding requested with the value
1407 of an ELF file header flag individually set by each
1408 binary. Hardware implementations are permitted to
1409 support either or both of the legacy and the 2008 NaN
1412 Available settings are as follows:
1413 strict accept binaries that request a NaN encoding
1414 supported by the FPU
1415 legacy only accept legacy-NaN binaries, if supported
1417 2008 only accept 2008-NaN binaries, if supported
1419 relaxed accept any binaries regardless of whether
1420 supported by the FPU
1422 The FPU emulator is always able to support both NaN
1423 encodings, so if no FPU hardware is present or it has
1424 been disabled with 'nofpu', then the settings of
1425 'legacy' and '2008' strap the emulator accordingly,
1426 'relaxed' straps the emulator for both legacy-NaN and
1427 2008-NaN, whereas 'strict' enables legacy-NaN only on
1428 legacy processors and both NaN encodings on MIPS32 or
1431 The setting for ABS.fmt/NEG.fmt instruction execution
1432 mode generally follows that for the NaN encoding,
1433 except where unsupported by hardware.
1435 ignore_loglevel [KNL]
1436 Ignore loglevel setting - this will print /all/
1437 kernel messages to the console. Useful for debugging.
1438 We also add it as printk module parameter, so users
1439 could change it dynamically, usually by
1440 /sys/module/printk/parameters/ignore_loglevel.
1443 Ignore RLIMIT_DATA setting for data mappings,
1444 print warning at first misuse. Can be changed via
1445 /sys/module/kernel/parameters/ignore_rlimit_data.
1447 ihash_entries= [KNL]
1448 Set number of hash buckets for inode cache.
1450 ima_appraise= [IMA] appraise integrity measurements
1451 Format: { "off" | "enforce" | "fix" | "log" }
1454 ima_appraise_tcb [IMA]
1455 The builtin appraise policy appraises all files
1458 ima_canonical_fmt [IMA]
1459 Use the canonical format for the binary runtime
1460 measurements, instead of host native format.
1463 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1467 The list of supported hash algorithms is defined
1468 in crypto/hash_info.h.
1471 The builtin measurement policy to load during IMA
1472 setup. Specyfing "tcb" as the value, measures all
1473 programs exec'd, files mmap'd for exec, and all files
1474 opened with the read mode bit set by either the
1475 effective uid (euid=0) or uid=0.
1478 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1479 Load a policy which meets the needs of the Trusted
1480 Computing Base. This means IMA will measure all
1481 programs exec'd, files mmap'd for exec, and all files
1482 opened for read by uid=0.
1485 Select one of defined IMA measurements template formats.
1486 Formats: { "ima" | "ima-ng" | "ima-sig" }
1490 [IMA] Define a custom template format.
1491 Format: { "field1|...|fieldN" }
1493 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1494 Format: <min_file_size>
1495 Set the minimal file size for using asynchronous hash.
1496 If left unspecified, ahash usage is disabled.
1498 ahash performance varies for different data sizes on
1499 different crypto accelerators. This option can be used
1500 to achieve the best performance for a particular HW.
1502 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1504 Set hashing buffer size. Default: 4k.
1506 ahash performance varies for different chunk sizes on
1507 different crypto accelerators. This option can be used
1508 to achieve best performance for particular HW.
1512 Run specified binary instead of /sbin/init as init
1515 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1516 for working out where the kernel is dying during
1519 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1520 initcall functions. Useful for debugging built-in
1521 modules and initcalls.
1523 initrd= [BOOT] Specify the location of the initial ramdisk
1525 init_pkru= [x86] Specify the default memory protection keys rights
1526 register contents for all processes. 0x55555554 by
1527 default (disallow access to all but pkey 0). Can
1528 override in debugfs after boot.
1530 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1533 int_pln_enable [x86] Enable power limit notification interrupt
1535 integrity_audit=[IMA]
1536 Format: { "0" | "1" }
1537 0 -- basic integrity auditing messages. (Default)
1538 1 -- additional integrity auditing messages.
1540 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1542 Enable intel iommu driver.
1544 Disable intel iommu driver.
1545 igfx_off [Default Off]
1546 By default, gfx is mapped as normal device. If a gfx
1547 device has a dedicated DMAR unit, the DMAR unit is
1548 bypassed by not enabling DMAR with this option. In
1549 this case, gfx device will use physical address for
1552 With this option iommu will not optimize to look
1553 for io virtual address below 32-bit forcing dual
1554 address cycle on pci bus for cards supporting greater
1555 than 32-bit addressing. The default is to look
1556 for translation below 32-bit and if not available
1557 then look in the higher range.
1558 strict [Default Off]
1559 With this option on every unmap_single operation will
1560 result in a hardware IOTLB flush operation as opposed
1561 to batching them for performance.
1562 sp_off [Default Off]
1563 By default, super page will be supported if Intel IOMMU
1564 has the capability. With this option, super page will
1566 ecs_off [Default Off]
1567 By default, extended context tables will be supported if
1568 the hardware advertises that it has support both for the
1569 extended tables themselves, and also PASID support. With
1570 this option set, extended tables will not be used even
1571 on hardware which claims to support them.
1573 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1574 0 disables intel_idle and fall back on acpi_idle.
1575 1 to 9 specify maximum depth of C-state.
1579 Do not enable intel_pstate as the default
1580 scaling driver for the supported processors
1582 Use intel_pstate as a scaling driver, but configure it
1583 to work with generic cpufreq governors (instead of
1584 enabling its internal governor). This mode cannot be
1585 used along with the hardware-managed P-states (HWP)
1588 Enable intel_pstate on systems that prohibit it by default
1589 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1590 instead of acpi-cpufreq may disable platform features, such
1591 as thermal controls and power capping, that rely on ACPI
1592 P-States information being indicated to OSPM and therefore
1593 should be used with caution. This option does not work with
1594 processors that aren't supported by the intel_pstate driver
1595 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1597 Do not enable hardware P state control (HWP)
1600 Only load intel_pstate on systems which support
1601 hardware P state control (HWP) if available.
1603 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1604 Description Table, specifies preferred power management
1605 profile as "Enterprise Server" or "Performance Server",
1606 then this feature is turned on by default.
1608 Allow per-logical-CPU P-State performance control limits using
1609 cpufreq sysfs interface
1611 intremap= [X86-64, Intel-IOMMU]
1612 on enable Interrupt Remapping (default)
1613 off disable Interrupt Remapping
1614 nosid disable Source ID checking
1616 BIOS x2APIC opt-out request will be ignored
1617 nopost disable Interrupt Posting
1619 iomem= Disable strict checking of access to MMIO memory
1620 strict regions from userspace.
1635 nobypass [PPC/POWERNV]
1636 Disable IOMMU bypass, using IOMMU for PCI devices.
1639 io7= [HW] IO7 for Marvel based alpha systems
1640 See comment before marvel_specify_io7 in
1641 arch/alpha/kernel/core_marvel.c.
1643 io_delay= [X86] I/O delay method
1645 Standard port 0x80 based delay
1647 Alternate port 0xed based delay (needed on some systems)
1649 Simple two microseconds delay
1654 See Documentation/filesystems/nfs/nfsroot.txt.
1656 irqaffinity= [SMP] Set the default irq affinity mask
1657 The argument is a cpu list, as described above.
1660 When an interrupt is not handled search all handlers
1661 for it. Intended to get systems with badly broken
1665 When an interrupt is not handled search all handlers
1666 for it. Also check all handlers each timer
1667 interrupt. Intended to get systems with badly broken
1671 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1673 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1674 The argument is a cpu list, as described above.
1676 This option can be used to specify one or more CPUs
1677 to isolate from the general SMP balancing and scheduling
1678 algorithms. You can move a process onto or off an
1679 "isolated" CPU via the CPU affinity syscalls or cpuset.
1680 <cpu number> begins at 0 and the maximum value is
1681 "number of CPUs in system - 1".
1683 This option is the preferred way to isolate CPUs. The
1684 alternative -- manually setting the CPU mask of all
1685 tasks in the system -- can cause problems and
1686 suboptimal load balancer performance.
1690 ivrs_ioapic [HW,X86_64]
1691 Provide an override to the IOAPIC-ID<->DEVICE-ID
1692 mapping provided in the IVRS ACPI table. For
1693 example, to map IOAPIC-ID decimal 10 to
1694 PCI device 00:14.0 write the parameter as:
1695 ivrs_ioapic[10]=00:14.0
1697 ivrs_hpet [HW,X86_64]
1698 Provide an override to the HPET-ID<->DEVICE-ID
1699 mapping provided in the IVRS ACPI table. For
1700 example, to map HPET-ID decimal 0 to
1701 PCI device 00:14.0 write the parameter as:
1702 ivrs_hpet[0]=00:14.0
1704 ivrs_acpihid [HW,X86_64]
1705 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1706 mapping provided in the IVRS ACPI table. For
1707 example, to map UART-HID:UID AMD0020:0 to
1708 PCI device 00:14.5 write the parameter as:
1709 ivrs_acpihid[00:14.5]=AMD0020:0
1711 js= [HW,JOY] Analog joystick
1712 See Documentation/input/joystick.txt.
1715 When CONFIG_RANDOMIZE_BASE is set, this disables
1716 kernel and module base offset ASLR (Address Space
1717 Layout Randomization).
1721 kernelcore= [KNL,X86,IA-64,PPC]
1722 Format: nn[KMGTPE] | "mirror"
1724 specifies the amount of memory usable by the kernel
1725 for non-movable allocations. The requested amount is
1726 spread evenly throughout all nodes in the system. The
1727 remaining memory in each node is used for Movable
1728 pages. In the event, a node is too small to have both
1729 kernelcore and Movable pages, kernelcore pages will
1730 take priority and other nodes will have a larger number
1731 of Movable pages. The Movable zone is used for the
1732 allocation of pages that may be reclaimed or moved
1733 by the page migration subsystem. This means that
1734 HugeTLB pages may not be allocated from this zone.
1735 Note that allocations like PTEs-from-HighMem still
1736 use the HighMem zone if it exists, and the Normal
1737 zone if it does not.
1739 Instead of specifying the amount of memory (nn[KMGTPE]),
1740 you can specify "mirror" option. In case "mirror"
1741 option is specified, mirrored (reliable) memory is used
1742 for non-movable allocations and remaining memory is used
1743 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1744 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1747 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1748 Format: <Controller#>[,poll interval]
1749 The controller # is the number of the ehci usb debug
1750 port as it is probed via PCI. The poll interval is
1751 optional and is the number seconds in between
1752 each poll cycle to the debug port in case you need
1753 the functionality for interrupting the kernel with
1754 gdb or control-c on the dbgp connection. When
1755 not using this parameter you use sysrq-g to break into
1756 the kernel debugger.
1758 kgdboc= [KGDB,HW] kgdb over consoles.
1759 Requires a tty driver that supports console polling,
1760 or a supported polling keyboard driver (non-usb).
1761 Serial only format: <serial_device>[,baud]
1762 keyboard only format: kbd
1763 keyboard and serial format: kbd,<serial_device>[,baud]
1764 Optional Kernel mode setting:
1765 kms, kbd format: kms,kbd
1766 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1768 kgdbwait [KGDB] Stop kernel execution and enter the
1769 kernel debugger at the earliest opportunity.
1771 kmac= [MIPS] korina ethernet MAC address.
1772 Configure the RouterBoard 532 series on-chip
1773 Ethernet adapter MAC address.
1775 kmemleak= [KNL] Boot-time kmemleak enable/disable
1776 Valid arguments: on, off
1778 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1781 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1782 Valid arguments: 0, 1, 2
1783 kmemcheck=0 (disabled)
1784 kmemcheck=1 (enabled)
1785 kmemcheck=2 (one-shot mode)
1786 Default: 2 (one-shot mode)
1788 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1789 Default is 0 (don't ignore, but inject #GP)
1791 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1795 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1796 Default is 1 (enabled)
1798 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1800 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1802 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1803 (virtualized MMU) support on capable Intel chips.
1804 Default is 1 (enabled)
1806 kvm-intel.emulate_invalid_guest_state=
1807 [KVM,Intel] Enable emulation of invalid guest states
1808 Default is 0 (disabled)
1810 kvm-intel.flexpriority=
1811 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1812 Default is 1 (enabled)
1815 [KVM,Intel] Enable VMX nesting (nVMX).
1816 Default is 0 (disabled)
1818 kvm-intel.unrestricted_guest=
1819 [KVM,Intel] Disable unrestricted guest feature
1820 (virtualized real and unpaged mode) on capable
1821 Intel chips. Default is 1 (enabled)
1823 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1824 feature (tagged TLBs) on capable Intel chips.
1825 Default is 1 (enabled)
1831 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1834 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1835 value for LAPIC timer one-shot implementation. Default
1836 back to the programmable timer unit in the LAPIC.
1838 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1841 libata.dma= [LIBATA] DMA control
1842 libata.dma=0 Disable all PATA and SATA DMA
1843 libata.dma=1 PATA and SATA Disk DMA only
1844 libata.dma=2 ATAPI (CDROM) DMA only
1845 libata.dma=4 Compact Flash DMA only
1846 Combinations also work, so libata.dma=3 enables DMA
1847 for disks and CDROMs, but not CFs.
1849 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1850 libata.ignore_hpa=0 keep BIOS limits (default)
1851 libata.ignore_hpa=1 ignore limits, using full disk
1853 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1857 libata.force= [LIBATA] Force configurations. The format is comma
1858 separated list of "[ID:]VAL" where ID is
1859 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1860 matching port, link or device. Basically, it matches
1861 the ATA ID string printed on console by libata. If
1862 the whole ID part is omitted, the last PORT and DEVICE
1863 values are used. If ID hasn't been specified yet, the
1864 configuration applies to all ports, links and devices.
1866 If only DEVICE is omitted, the parameter applies to
1867 the port and all links and devices behind it. DEVICE
1868 number of 0 either selects the first device or the
1869 first fan-out link behind PMP device. It does not
1870 select the host link. DEVICE number of 15 selects the
1871 host link and device attached to it.
1873 The VAL specifies the configuration to force. As long
1874 as there's no ambiguity shortcut notation is allowed.
1875 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1876 The following configurations can be forced.
1878 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1879 Any ID with matching PORT is used.
1881 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1883 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1884 udma[/][16,25,33,44,66,100,133] notation is also
1887 * [no]ncq: Turn on or off NCQ.
1889 * [no]ncqtrim: Turn off queued DSM TRIM.
1891 * nohrst, nosrst, norst: suppress hard, soft
1894 * rstonce: only attempt one reset during
1895 hot-unplug link recovery
1897 * dump_id: dump IDENTIFY data.
1899 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1901 * disable: Disable this device.
1903 If there are multiple matching configurations changing
1904 the same attribute, the last one is used.
1906 memblock=debug [KNL] Enable memblock debug messages.
1908 load_ramdisk= [RAM] List of ramdisks to load from floppy
1909 See Documentation/blockdev/ramdisk.txt.
1911 lockd.nlm_grace_period=P [NFS] Assign grace period.
1914 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1917 lockd.nlm_timeout=T [NFS] Assign timeout value.
1920 lockd.nlm_udpport=M [NFS] Assign UDP port.
1923 locktorture.nreaders_stress= [KNL]
1924 Set the number of locking read-acquisition kthreads.
1925 Defaults to being automatically set based on the
1926 number of online CPUs.
1928 locktorture.nwriters_stress= [KNL]
1929 Set the number of locking write-acquisition kthreads.
1931 locktorture.onoff_holdoff= [KNL]
1932 Set time (s) after boot for CPU-hotplug testing.
1934 locktorture.onoff_interval= [KNL]
1935 Set time (s) between CPU-hotplug operations, or
1936 zero to disable CPU-hotplug testing.
1938 locktorture.shuffle_interval= [KNL]
1939 Set task-shuffle interval (jiffies). Shuffling
1940 tasks allows some CPUs to go into dyntick-idle
1941 mode during the locktorture test.
1943 locktorture.shutdown_secs= [KNL]
1944 Set time (s) after boot system shutdown. This
1945 is useful for hands-off automated testing.
1947 locktorture.stat_interval= [KNL]
1948 Time (s) between statistics printk()s.
1950 locktorture.stutter= [KNL]
1951 Time (s) to stutter testing, for example,
1952 specifying five seconds causes the test to run for
1953 five seconds, wait for five seconds, and so on.
1954 This tests the locking primitive's ability to
1955 transition abruptly to and from idle.
1957 locktorture.torture_runnable= [BOOT]
1958 Start locktorture running at boot time.
1960 locktorture.torture_type= [KNL]
1961 Specify the locking implementation to test.
1963 locktorture.verbose= [KNL]
1964 Enable additional printk() statements.
1966 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1969 loglevel= All Kernel Messages with a loglevel smaller than the
1970 console loglevel will be printed to the console. It can
1971 also be changed with klogd or other programs. The
1972 loglevels are defined as follows:
1974 0 (KERN_EMERG) system is unusable
1975 1 (KERN_ALERT) action must be taken immediately
1976 2 (KERN_CRIT) critical conditions
1977 3 (KERN_ERR) error conditions
1978 4 (KERN_WARNING) warning conditions
1979 5 (KERN_NOTICE) normal but significant condition
1980 6 (KERN_INFO) informational
1981 7 (KERN_DEBUG) debug-level messages
1983 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1984 in bytes. n must be a power of two and greater
1985 than the minimal size. The minimal size is defined
1986 by LOG_BUF_SHIFT kernel config parameter. There is
1987 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1988 that allows to increase the default size depending on
1989 the number of CPUs. See init/Kconfig for more details.
1991 logo.nologo [FB] Disables display of the built-in Linux logo.
1992 This may be used to provide more screen space for
1993 kernel log messages and is useful when debugging
1994 kernel boot problems.
1996 lp=0 [LP] Specify parallel ports to use, e.g,
1997 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1998 lp=reset first parallel port). 'lp=0' disables the
1999 lp=auto printer driver. 'lp=reset' (which can be
2000 specified in addition to the ports) causes
2001 attached printers to be reset. Using
2002 lp=port1,port2,... specifies the parallel ports
2003 to associate lp devices with, starting with
2004 lp0. A port specification may be 'none' to skip
2005 that lp device, or a parport name such as
2006 'parport0'. Specifying 'lp=auto' instead of a
2007 port specification list means that device IDs
2008 from each port should be examined, to see if
2009 an IEEE 1284-compliant printer is attached; if
2010 so, the driver will manage that printer.
2011 See also header of drivers/char/lp.c.
2014 Sets loops_per_jiffy to given constant, thus avoiding
2015 time-consuming boot-time autodetection (up to 250 ms per
2016 CPU). 0 enables autodetection (default). To determine
2017 the correct value for your kernel, boot with normal
2018 autodetection and see what value is printed. Note that
2019 on SMP systems the preset will be applied to all CPUs,
2020 which is likely to cause problems if your CPUs need
2021 significantly divergent settings. An incorrect value
2022 will cause delays in the kernel to be wrong, leading to
2023 unpredictable I/O errors and other breakage. Although
2024 unlikely, in the extreme case this might damage your
2028 Format: <io>,<irq>,<dma>
2030 machvec= [IA-64] Force the use of a particular machine-vector
2031 (machvec) in a generic kernel.
2032 Example: machvec=hpzx1_swiotlb
2034 machtype= [Loongson] Share the same kernel image file between different
2036 Example: machtype=lemote-yeeloong-2f-7inch
2038 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2039 than or equal to this physical address is ignored.
2041 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2042 will bring up during bootup. maxcpus=n : n >= 0 limits
2043 the kernel to bring up 'n' processors. Surely after
2044 bootup you can bring up the other plugged cpu by executing
2045 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2046 only takes effect during system bootup.
2047 While n=0 is a special case, it is equivalent to "nosmp",
2048 which also disables the IO APIC.
2050 max_loop= [LOOP] The number of loop block devices that get
2051 (loop.max_loop) unconditionally pre-created at init time. The default
2052 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2053 of statically allocating a predefined number, loop
2054 devices can be requested on-demand with the
2055 /dev/loop-control interface.
2057 mce [X86-32] Machine Check Exception
2059 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2061 md= [HW] RAID subsystems devices and level
2062 See Documentation/admin-guide/md.rst.
2065 Format: <first>,<last>
2066 Specifies range of consoles to be captured by the MDA.
2068 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2069 Amount of memory to be used when the kernel is not able
2070 to see the whole system memory or for test.
2071 [X86] Work as limiting max address. Use together
2072 with memmap= to avoid physical address space collisions.
2073 Without memmap= PCI devices could be placed at addresses
2074 belonging to unused RAM.
2076 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2080 [KNL,SH] Allow user to override the default size for
2081 per-device physically contiguous DMA buffers.
2083 memhp_default_state=online/offline
2084 [KNL] Set the initial state for the memory hotplug
2085 onlining policy. If not specified, the default value is
2086 set according to the
2087 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2089 See Documentation/memory-hotplug.txt.
2091 memmap=exactmap [KNL,X86] Enable setting of an exact
2092 E820 memory map, as specified by the user.
2093 Such memmap=exactmap lines can be constructed based on
2094 BIOS output or other requirements. See the memmap=nn@ss
2097 memmap=nn[KMG]@ss[KMG]
2098 [KNL] Force usage of a specific region of memory.
2099 Region of memory to be used is from ss to ss+nn.
2101 memmap=nn[KMG]#ss[KMG]
2102 [KNL,ACPI] Mark specific memory as ACPI data.
2103 Region of memory to be marked is from ss to ss+nn.
2105 memmap=nn[KMG]$ss[KMG]
2106 [KNL,ACPI] Mark specific memory as reserved.
2107 Region of memory to be reserved is from ss to ss+nn.
2108 Example: Exclude memory from 0x18690000-0x1869ffff
2109 memmap=64K$0x18690000
2111 memmap=0x10000$0x18690000
2113 memmap=nn[KMG]!ss[KMG]
2114 [KNL,X86] Mark specific memory as protected.
2115 Region of memory to be used, from ss to ss+nn.
2116 The memory region may be marked as e820 type 12 (0xc)
2117 and is NVDIMM or ADR memory.
2119 memory_corruption_check=0/1 [X86]
2120 Some BIOSes seem to corrupt the first 64k of
2121 memory when doing things like suspend/resume.
2122 Setting this option will scan the memory
2123 looking for corruption. Enabling this will
2124 both detect corruption and prevent the kernel
2125 from using the memory being corrupted.
2126 However, its intended as a diagnostic tool; if
2127 repeatable BIOS-originated corruption always
2128 affects the same memory, you can use memmap=
2129 to prevent the kernel from using that memory.
2131 memory_corruption_check_size=size [X86]
2132 By default it checks for corruption in the low
2133 64k, making this memory unavailable for normal
2134 use. Use this parameter to scan for
2135 corruption in more or less memory.
2137 memory_corruption_check_period=seconds [X86]
2138 By default it checks for corruption every 60
2139 seconds. Use this parameter to check at some
2140 other rate. 0 disables periodic checking.
2142 memtest= [KNL,X86,ARM] Enable memtest
2144 default : 0 <disable>
2145 Specifies the number of memtest passes to be
2146 performed. Each pass selects another test
2147 pattern from a given set of patterns. Memtest
2148 fills the memory with this pattern, validates
2149 memory contents and reserves bad memory
2150 regions that are detected.
2152 mem_sleep_default= [SUSPEND] Default system suspend mode:
2153 s2idle - Suspend-To-Idle
2154 shallow - Power-On Suspend or equivalent (if supported)
2155 deep - Suspend-To-RAM or equivalent (if supported)
2156 See Documentation/power/states.txt.
2158 meye.*= [HW] Set MotionEye Camera parameters
2159 See Documentation/video4linux/meye.txt.
2161 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2162 Multi-Function General Purpose Timers on AMD Geode
2165 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2166 the BIOS has incorrectly applied a workaround. TinyBIOS
2167 version 0.98 is known to be affected, 0.99 fixes the
2168 problem by letting the user disable the workaround.
2172 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2173 physical address is ignored.
2175 mini2440= [ARM,HW,KNL]
2176 Format:[0..2][b][c][t]
2178 MINI2440 configuration specification:
2179 0 - The attached screen is the 3.5" TFT
2180 1 - The attached screen is the 7" TFT
2181 2 - The VGA Shield is attached (1024x768)
2182 Leaving out the screen size parameter will not load
2183 the TFT driver, and the framebuffer will be left
2185 b - Enable backlight. The TFT backlight pin will be
2186 linked to the kernel VESA blanking code and a GPIO
2187 LED. This parameter is not necessary when using the
2189 c - Enable the s3c camera interface.
2190 t - Reserved for enabling touchscreen support. The
2191 touchscreen support is not enabled in the mainstream
2192 kernel as of 2.6.30, a preliminary port can be found
2193 in the "bleeding edge" mini2440 support kernel at
2194 http://repo.or.cz/w/linux-2.6/mini2440.git
2197 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2198 parameter allows control of the logging verbosity for
2199 the additional memory initialisation checks. A value
2200 of 0 disables mminit logging and a level of 4 will
2201 log everything. Information is printed at KERN_DEBUG
2202 so loglevel=8 may also need to be specified.
2205 [KNL] When CONFIG_MODULE_SIG is set, this means that
2206 modules without (valid) signatures will fail to load.
2207 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2208 is always true, so this option does nothing.
2210 module_blacklist= [KNL] Do not load a comma-separated list of
2211 modules. Useful for debugging problem modules.
2214 [MOUSE] Maximum time between finger touching and
2215 leaving touchpad surface for touch to be considered
2216 a tap and be reported as a left button click (for
2217 touchpads working in absolute mode only).
2219 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2220 reporting absolute coordinates, such as tablets
2221 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2222 reporting absolute coordinates, such as tablets
2224 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2225 is similar to kernelcore except it specifies the
2226 amount of memory used for migratable allocations.
2227 If both kernelcore and movablecore is specified,
2228 then kernelcore will be at *least* the specified
2229 value but may be more. If movablecore on its own
2230 is specified, the administrator must be careful
2231 that the amount of memory usable for all allocations
2234 movable_node [KNL] Boot-time switch to enable the effects
2235 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2237 MTD_Partition= [MTD]
2238 Format: <name>,<region-number>,<size>,<offset>
2240 MTD_Region= [MTD] Format:
2241 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2244 See drivers/mtd/cmdlinepart.c.
2246 multitce=off [PPC] This parameter disables the use of the pSeries
2247 firmware feature for updating multiple TCE entries
2250 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2252 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2254 boundary - index of last SLC block on Flex-OneNAND.
2255 The remaining blocks are configured as MLC blocks.
2256 lock - Configure if Flex-OneNAND boundary should be locked.
2257 Once locked, the boundary cannot be changed.
2258 1 indicates lock status, 0 indicates unlock status.
2261 ARM/S3C2412 JIVE boot control
2263 See arch/arm/mach-s3c2412/mach-jive.c
2265 mtouchusb.raw_coordinates=
2266 [HW] Make the MicroTouch USB driver use raw coordinates
2267 ('y', default) or cooked coordinates ('n')
2269 mtrr_chunk_size=nn[KMG] [X86]
2270 used for mtrr cleanup. It is largest continuous chunk
2271 that could hold holes aka. UC entries.
2273 mtrr_gran_size=nn[KMG] [X86]
2274 Used for mtrr cleanup. It is granularity of mtrr block.
2276 Large value could prevent small alignment from
2279 mtrr_spare_reg_nr=n [X86]
2281 Range: 0,7 : spare reg number
2283 Used for mtrr cleanup. It is spare mtrr entries number.
2284 Set to 2 or more if your graphical card needs more.
2286 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2288 netdev= [NET] Network devices parameters
2289 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2290 Note that mem_start is often overloaded to mean
2291 something different and driver-specific.
2292 This usage is only documented in each driver source
2296 [NETFILTER] Enable connection tracking flow accounting
2297 0 to disable accounting
2298 1 to enable accounting
2301 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2302 See Documentation/filesystems/nfs/nfsroot.txt.
2304 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2305 See Documentation/filesystems/nfs/nfsroot.txt.
2307 nfsrootdebug [NFS] enable nfsroot debugging messages.
2308 See Documentation/filesystems/nfs/nfsroot.txt.
2310 nfs.callback_nr_threads=
2311 [NFSv4] set the total number of threads that the
2312 NFS client will assign to service NFSv4 callback
2315 nfs.callback_tcpport=
2316 [NFS] set the TCP port on which the NFSv4 callback
2317 channel should listen.
2320 [NFS] sets the pathname to the program which is used
2321 to update the NFS client cache entries.
2323 nfs.cache_getent_timeout=
2324 [NFS] sets the timeout after which an attempt to
2325 update a cache entry is deemed to have failed.
2327 nfs.idmap_cache_timeout=
2328 [NFS] set the maximum lifetime for idmapper cache
2332 [NFS] enable 64-bit inode numbers.
2333 If zero, the NFS client will fake up a 32-bit inode
2334 number for the readdir() and stat() syscalls instead
2335 of returning the full 64-bit number.
2336 The default is to return 64-bit inode numbers.
2338 nfs.max_session_cb_slots=
2339 [NFSv4.1] Sets the maximum number of session
2340 slots the client will assign to the callback
2341 channel. This determines the maximum number of
2342 callbacks the client will process in parallel for
2343 a particular server.
2345 nfs.max_session_slots=
2346 [NFSv4.1] Sets the maximum number of session slots
2347 the client will attempt to negotiate with the server.
2348 This limits the number of simultaneous RPC requests
2349 that the client can send to the NFSv4.1 server.
2350 Note that there is little point in setting this
2351 value higher than the max_tcp_slot_table_limit.
2353 nfs.nfs4_disable_idmapping=
2354 [NFSv4] When set to the default of '1', this option
2355 ensures that both the RPC level authentication
2356 scheme and the NFS level operations agree to use
2357 numeric uids/gids if the mount is using the
2358 'sec=sys' security flavour. In effect it is
2359 disabling idmapping, which can make migration from
2360 legacy NFSv2/v3 systems to NFSv4 easier.
2361 Servers that do not support this mode of operation
2362 will be autodetected by the client, and it will fall
2363 back to using the idmapper.
2364 To turn off this behaviour, set the value to '0'.
2366 [NFS4] Specify an additional fixed unique ident-
2367 ification string that NFSv4 clients can insert into
2368 their nfs_client_id4 string. This is typically a
2369 UUID that is generated at system install time.
2371 nfs.send_implementation_id =
2372 [NFSv4.1] Send client implementation identification
2373 information in exchange_id requests.
2374 If zero, no implementation identification information
2376 The default is to send the implementation identification
2379 nfs.recover_lost_locks =
2380 [NFSv4] Attempt to recover locks that were lost due
2381 to a lease timeout on the server. Please note that
2382 doing this risks data corruption, since there are
2383 no guarantees that the file will remain unchanged
2384 after the locks are lost.
2385 If you want to enable the kernel legacy behaviour of
2386 attempting to recover these locks, then set this
2388 The default parameter value of '0' causes the kernel
2389 not to attempt recovery of lost locks.
2391 nfs4.layoutstats_timer =
2392 [NFSv4.2] Change the rate at which the kernel sends
2393 layoutstats to the pNFS metadata server.
2395 Setting this to value to 0 causes the kernel to use
2396 whatever value is the default set by the layout
2397 driver. A non-zero value sets the minimum interval
2398 in seconds between layoutstats transmissions.
2400 nfsd.nfs4_disable_idmapping=
2401 [NFSv4] When set to the default of '1', the NFSv4
2402 server will return only numeric uids and gids to
2403 clients using auth_sys, and will accept numeric uids
2404 and gids from such clients. This is intended to ease
2405 migration from NFSv2/v3.
2407 objlayoutdriver.osd_login_prog=
2408 [NFS] [OBJLAYOUT] sets the pathname to the program which
2409 is used to automatically discover and login into new
2410 osd-targets. Please see:
2411 Documentation/filesystems/pnfs.txt for more explanations
2413 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2414 when a NMI is triggered.
2415 Format: [state][,regs][,debounce][,die]
2417 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2418 Format: [panic,][nopanic,][num]
2420 0 - turn hardlockup detector in nmi_watchdog off
2421 1 - turn hardlockup detector in nmi_watchdog on
2422 When panic is specified, panic when an NMI watchdog
2423 timeout occurs (or 'nopanic' to override the opposite
2424 default). To disable both hard and soft lockup detectors,
2425 please see 'nowatchdog'.
2426 This is useful when you use a panic=... timeout and
2427 need the box quickly up again.
2429 netpoll.carrier_timeout=
2430 [NET] Specifies amount of time (in seconds) that
2431 netpoll should wait for a carrier. By default netpoll
2434 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2435 emulation library even if a 387 maths coprocessor
2439 [HW] Never suspend the console
2440 Disable suspending of consoles during suspend and
2441 hibernate operations. Once disabled, debugging
2442 messages can reach various consoles while the rest
2443 of the system is being put to sleep (ie, while
2444 debugging driver suspend/resume hooks). This may
2445 not work reliably with all consoles, but is known
2446 to work with serial and VGA consoles.
2447 To facilitate more flexible debugging, we also add
2448 console_suspend, a printk module parameter to control
2449 it. Users could use console_suspend (usually
2450 /sys/module/printk/parameters/console_suspend) to
2451 turn on/off it dynamically.
2453 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2454 caches in the slab allocator. Saves per-node memory,
2455 but will impact performance.
2459 noapic [SMP,APIC] Tells the kernel to not make use of any
2460 IOAPICs that may be present in the system.
2462 noautogroup Disable scheduler automatic task group creation.
2464 nobats [PPC] Do not use BATs for mapping kernel lowmem
2465 on "Classic" PPC cores.
2469 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2471 nodelayacct [KNL] Disable per-task delay accounting
2473 nodsp [SH] Disable hardware DSP at boot time.
2475 noefi Disable EFI runtime services support.
2480 On X86-32 available only on PAE configured kernels.
2481 noexec=on: enable non-executable mappings (default)
2482 noexec=off: disable non-executable mappings
2485 Disable SMAP (Supervisor Mode Access Prevention)
2486 even if it is supported by processor.
2489 Disable SMEP (Supervisor Mode Execution Prevention)
2490 even if it is supported by processor.
2493 This affects only 32-bit executables.
2494 noexec32=on: enable non-executable mappings (default)
2495 read doesn't imply executable mappings
2496 noexec32=off: disable non-executable mappings
2497 read implies executable mappings
2499 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2501 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2502 register save and restore. The kernel will only save
2503 legacy floating-point registers on task switch.
2505 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2507 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2508 Equivalent to smt=1.
2510 noxsave [BUGS=X86] Disables x86 extended register state save
2511 and restore using xsave. The kernel will fallback to
2512 enabling legacy floating-point and sse state.
2514 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2515 register states. The kernel will fall back to use
2516 xsave to save the states. By using this parameter,
2517 performance of saving the states is degraded because
2518 xsave doesn't support modified optimization while
2519 xsaveopt supports it on xsaveopt enabled systems.
2521 noxsaves [X86] Disables xsaves and xrstors used in saving and
2522 restoring x86 extended register state in compacted
2523 form of xsave area. The kernel will fall back to use
2524 xsaveopt and xrstor to save and restore the states
2525 in standard form of xsave area. By using this
2526 parameter, xsave area per process might occupy more
2527 memory on xsaves enabled systems.
2529 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2530 wfi(ARM) instruction doesn't work correctly and not to
2531 use it. This is also useful when using JTAG debugger.
2533 no_file_caps Tells the kernel not to honor file capabilities. The
2534 only way then for a file to be executed with privilege
2535 is to be setuid root or executed by root.
2537 nohalt [IA-64] Tells the kernel not to use the power saving
2538 function PAL_HALT_LIGHT when idle. This increases
2539 power-consumption. On the positive side, it reduces
2540 interrupt wake-up latency, which may improve performance
2541 in certain environments such as networked servers or
2544 nohibernate [HIBERNATION] Disable hibernation and resume.
2546 nohz= [KNL] Boottime enable/disable dynamic ticks
2547 Valid arguments: on, off
2550 nohz_full= [KNL,BOOT]
2551 The argument is a cpu list, as described above.
2552 In kernels built with CONFIG_NO_HZ_FULL=y, set
2553 the specified list of CPUs whose tick will be stopped
2554 whenever possible. The boot CPU will be forced outside
2555 the range to maintain the timekeeping.
2556 The CPUs in this range must also be included in the
2559 noiotrap [SH] Disables trapped I/O port accesses.
2561 noirqdebug [X86-32] Disables the code which attempts to detect and
2562 disable unhandled interrupt sources.
2564 no_timer_check [X86,APIC] Disables the code which tests for
2565 broken timer IRQ sources.
2567 noisapnp [ISAPNP] Disables ISA PnP code.
2569 noinitrd [RAM] Tells the kernel not to load any configured
2572 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2574 [Deprecated - use intremap=off]
2578 noinvpcid [X86] Disable the INVPCID cpu feature.
2580 nojitter [IA-64] Disables jitter checking for ITC timers.
2582 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2584 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2588 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2589 clock and use the default one.
2591 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2592 steal time is computed, but won't influence scheduler
2595 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2597 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2599 noltlbs [PPC] Do not use large page/tlb entries for kernel
2600 lowmem mapping on PPC40x and PPC8xx
2602 nomca [IA-64] Disable machine check abort handling
2604 nomce [X86-32] Disable Machine Check Exception
2606 nomfgpt [X86-32] Disable Multi-Function General Purpose
2607 Timer usage (for AMD Geode machines).
2609 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2610 shutdown the other cpus. Instead use the REBOOT_VECTOR
2613 nomodule Disable module load
2615 nopat [X86] Disable PAT (page attribute table extension of
2616 pagetables) support.
2618 norandmaps Don't use address space randomization. Equivalent to
2619 echo 0 > /proc/sys/kernel/randomize_va_space
2621 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2623 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2624 with UP alternatives
2626 nordrand [X86] Disable kernel use of the RDRAND and
2627 RDSEED instructions even if they are supported
2628 by the processor. RDRAND and RDSEED are still
2629 available to user space applications.
2631 noresume [SWSUSP] Disables resume and restores original swap
2634 no-scroll [VGA] Disables scrollback.
2635 This is required for the Braillex ib80-piezo Braille
2636 reader made by F.H. Papenmeier (Germany).
2640 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2642 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2643 and disable the IO APIC. legacy for "maxcpus=0".
2645 nosoftlockup [KNL] Disable the soft-lockup detector.
2647 nosync [HW,M68K] Disables sync negotiation for all devices.
2649 notsc [BUGS=X86-32] Disable Time Stamp Counter
2651 nowatchdog [KNL] Disable both lockup detectors, i.e.
2652 soft-lockup and NMI watchdog (hard-lockup).
2656 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2658 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2659 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2660 Some features depend on CPU0. Known dependencies are:
2661 1. Resume from suspend/hibernate depends on CPU0.
2662 Suspend/hibernate will fail if CPU0 is offline and you
2663 need to online CPU0 before suspend/hibernate.
2664 2. PIC interrupts also depend on CPU0. CPU0 can't be
2665 removed if a PIC interrupt is detected.
2666 It's said poweroff/reboot may depend on CPU0 on some
2667 machines although I haven't seen such issues so far
2668 after CPU0 is offline on a few tested machines.
2669 If the dependencies are under your control, you can
2670 turn on cpu0_hotplug.
2672 nptcg= [IA-64] Override max number of concurrent global TLB
2673 purges which is reported from either PAL_VM_SUMMARY or
2676 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2677 could support. nr_cpus=n : n >= 1 limits the kernel to
2678 support 'n' processors. It could be larger than the
2679 number of already plugged CPU during bootup, later in
2680 runtime you can physically add extra cpu until it reaches
2681 n. So during boot up some boot time memory for per-cpu
2682 variables need be pre-allocated for later physical cpu
2685 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2687 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2688 Allowed values are enable and disable
2690 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2691 one of ['zone', 'node', 'default'] can be specified
2692 This can be set from sysctl after boot.
2693 See Documentation/sysctl/vm.txt for details.
2695 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2696 See Documentation/debugging-via-ohci1394.txt for more
2699 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2700 Rather than timing out after 20 ms if an EC
2701 command is not properly ACKed, override the length
2702 of the timeout. We have interrupts disabled while
2703 waiting for the ACK, so if this is set too high
2704 interrupts *may* be lost!
2706 omap_mux= [OMAP] Override bootloader pin multiplexing.
2707 Format: <mux_mode0.mode_name=value>...
2708 For example, to override I2C bus2:
2709 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2711 oprofile.timer= [HW]
2712 Use timer interrupt instead of performance counters
2714 oprofile.cpu_type= Force an oprofile cpu type
2715 This might be useful if you have an older oprofile
2716 userland or if you want common events.
2717 Format: { arch_perfmon }
2718 arch_perfmon: [X86] Force use of architectural
2719 perfmon on Intel CPUs instead of the
2720 CPU specific event set.
2721 timer: [X86] Force use of architectural NMI
2722 timer mode (see also oprofile.timer
2723 for generic hr timer mode)
2725 oops=panic Always panic on oopses. Default is to just kill the
2726 process, but there is a small probability of
2727 deadlocking the machine.
2728 This will also cause panics on machine check exceptions.
2729 Useful together with panic=30 to trigger a reboot.
2732 See Documentation/sound/oss/oss-parameters.txt
2734 page_owner= [KNL] Boot-time page_owner enabling option.
2735 Storage of the information about who allocated
2736 each page is disabled in default. With this switch,
2738 on: enable the feature
2740 page_poison= [KNL] Boot-time parameter changing the state of
2741 poisoning on the buddy allocator.
2742 off: turn off poisoning
2743 on: turn on poisoning
2745 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2746 timeout > 0: seconds before rebooting
2747 timeout = 0: wait forever
2748 timeout < 0: reboot immediately
2751 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2754 crash_kexec_post_notifiers
2755 Run kdump after running panic-notifiers and dumping
2756 kmsg. This only for the users who doubt kdump always
2757 succeeds in any situation.
2758 Note that this also increases risks of kdump failure,
2759 because some panic notifiers can make the crashed
2760 kernel more unstable.
2762 parkbd.port= [HW] Parallel port number the keyboard adapter is
2763 connected to, default is 0.
2765 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2766 0 for XT, 1 for AT (default is AT).
2769 parport= [HW,PPT] Specify parallel ports. 0 disables.
2770 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2771 Use 'auto' to force the driver to use any
2772 IRQ/DMA settings detected (the default is to
2773 ignore detected IRQ/DMA settings because of
2774 possible conflicts). You can specify the base
2775 address, IRQ, and DMA settings; IRQ and DMA
2776 should be numbers, or 'auto' (for using detected
2777 settings on that particular port), or 'nofifo'
2778 (to avoid using a FIFO even if it is detected).
2779 Parallel ports are assigned in the order they
2780 are specified on the command line, starting
2783 parport_init_mode= [HW,PPT]
2784 Configure VIA parallel port to operate in
2785 a specific mode. This is necessary on Pegasos
2786 computer where firmware has no options for setting
2787 up parallel port mode and sets it to spp.
2788 Currently this function knows 686a and 8231 chips.
2789 Format: [spp|ps2|epp|ecp|ecpepp]
2792 Halt all CPUs after the first oops has been printed for
2793 the specified number of seconds. This is to be used if
2794 your oopses keep scrolling off the screen.
2799 See header of drivers/block/paride/pcd.c.
2800 See also Documentation/blockdev/paride.txt.
2802 pci=option[,option...] [PCI] various PCI subsystem options:
2803 earlydump [X86] dump PCI config space before the kernel
2805 off [X86] don't probe for the PCI bus
2806 bios [X86-32] force use of PCI BIOS, don't access
2807 the hardware directly. Use this if your machine
2808 has a non-standard PCI host bridge.
2809 nobios [X86-32] disallow use of PCI BIOS, only direct
2810 hardware access methods are allowed. Use this
2811 if you experience crashes upon bootup and you
2812 suspect they are caused by the BIOS.
2813 conf1 [X86] Force use of PCI Configuration Access
2814 Mechanism 1 (config address in IO port 0xCF8,
2815 data in IO port 0xCFC, both 32-bit).
2816 conf2 [X86] Force use of PCI Configuration Access
2817 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2818 the function, IO port 0xCFA, also 8-bit, sets
2819 bus number. The config space is then accessed
2820 through ports 0xC000-0xCFFF).
2821 See http://wiki.osdev.org/PCI for more info
2822 on the configuration access mechanisms.
2823 noaer [PCIE] If the PCIEAER kernel config parameter is
2824 enabled, this kernel boot option can be used to
2825 disable the use of PCIE advanced error reporting.
2826 nodomains [PCI] Disable support for multiple PCI
2827 root domains (aka PCI segments, in ACPI-speak).
2828 nommconf [X86] Disable use of MMCONFIG for PCI
2830 check_enable_amd_mmconf [X86] check for and enable
2831 properly configured MMIO access to PCI
2832 config space on AMD family 10h CPU
2833 nomsi [MSI] If the PCI_MSI kernel config parameter is
2834 enabled, this kernel boot option can be used to
2835 disable the use of MSI interrupts system-wide.
2836 noioapicquirk [APIC] Disable all boot interrupt quirks.
2837 Safety option to keep boot IRQs enabled. This
2838 should never be necessary.
2839 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2840 primary IO-APIC for bridges that cannot disable
2841 boot IRQs. This fixes a source of spurious IRQs
2842 when the system masks IRQs.
2843 noioapicreroute [APIC] Disable workaround that uses the
2844 boot IRQ equivalent of an IRQ that connects to
2845 a chipset where boot IRQs cannot be disabled.
2846 The opposite of ioapicreroute.
2847 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2848 routing table. These calls are known to be buggy
2849 on several machines and they hang the machine
2850 when used, but on other computers it's the only
2851 way to get the interrupt routing table. Try
2852 this option if the kernel is unable to allocate
2853 IRQs or discover secondary PCI buses on your
2855 rom [X86] Assign address space to expansion ROMs.
2856 Use with caution as certain devices share
2857 address decoders between ROMs and other
2859 norom [X86] Do not assign address space to
2860 expansion ROMs that do not already have
2861 BIOS assigned address ranges.
2862 nobar [X86] Do not assign address space to the
2863 BARs that weren't assigned by the BIOS.
2864 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2865 assigned automatically to PCI devices. You can
2866 make the kernel exclude IRQs of your ISA cards
2868 pirqaddr=0xAAAAA [X86] Specify the physical address
2869 of the PIRQ table (normally generated
2870 by the BIOS) if it is outside the
2871 F0000h-100000h range.
2872 lastbus=N [X86] Scan all buses thru bus #N. Can be
2873 useful if the kernel is unable to find your
2874 secondary buses and you want to tell it
2875 explicitly which ones they are.
2876 assign-busses [X86] Always assign all PCI bus
2877 numbers ourselves, overriding
2878 whatever the firmware may have done.
2879 usepirqmask [X86] Honor the possible IRQ mask stored
2880 in the BIOS $PIR table. This is needed on
2881 some systems with broken BIOSes, notably
2882 some HP Pavilion N5400 and Omnibook XE3
2883 notebooks. This will have no effect if ACPI
2884 IRQ routing is enabled.
2885 noacpi [X86] Do not use ACPI for IRQ routing
2886 or for PCI scanning.
2887 use_crs [X86] Use PCI host bridge window information
2888 from ACPI. On BIOSes from 2008 or later, this
2889 is enabled by default. If you need to use this,
2890 please report a bug.
2891 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2892 If you need to use this, please report a bug.
2893 routeirq Do IRQ routing for all PCI devices.
2894 This is normally done in pci_enable_device(),
2895 so this option is a temporary workaround
2896 for broken drivers that don't call it.
2897 skip_isa_align [X86] do not align io start addr, so can
2898 handle more pci cards
2899 noearly [X86] Don't do any early type 1 scanning.
2900 This might help on some broken boards which
2901 machine check when some devices' config space
2902 is read. But various workarounds are disabled
2903 and some IOMMU drivers will not work.
2904 bfsort Sort PCI devices into breadth-first order.
2905 This sorting is done to get a device
2906 order compatible with older (<= 2.4) kernels.
2907 nobfsort Don't sort PCI devices into breadth-first order.
2908 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2909 tuning and use the BIOS-configured MPS defaults.
2910 pcie_bus_safe Set every device's MPS to the largest value
2911 supported by all devices below the root complex.
2912 pcie_bus_perf Set device MPS to the largest allowable MPS
2913 based on its parent bus. Also set MRRS (Max
2914 Read Request Size) to the largest supported
2915 value (no larger than the MPS that the device
2916 or bus can support) for best performance.
2917 pcie_bus_peer2peer Set every device's MPS to 128B, which
2918 every device is guaranteed to support. This
2919 configuration allows peer-to-peer DMA between
2920 any pair of devices, possibly at the cost of
2921 reduced performance. This also guarantees
2922 that hot-added devices will work.
2923 cbiosize=nn[KMG] The fixed amount of bus space which is
2924 reserved for the CardBus bridge's IO window.
2925 The default value is 256 bytes.
2926 cbmemsize=nn[KMG] The fixed amount of bus space which is
2927 reserved for the CardBus bridge's memory
2928 window. The default value is 64 megabytes.
2931 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2932 [<order of align>@]pci:<vendor>:<device>\
2933 [:<subvendor>:<subdevice>][; ...]
2934 Specifies alignment and device to reassign
2935 aligned memory resources.
2936 If <order of align> is not specified,
2937 PAGE_SIZE is used as alignment.
2938 PCI-PCI bridge can be specified, if resource
2939 windows need to be expanded.
2940 To specify the alignment for several
2941 instances of a device, the PCI vendor,
2942 device, subvendor, and subdevice may be
2943 specified, e.g., 4096@pci:8086:9c22:103c:198f
2944 ecrc= Enable/disable PCIe ECRC (transaction layer
2945 end-to-end CRC checking).
2946 bios: Use BIOS/firmware settings. This is the
2950 hpiosize=nn[KMG] The fixed amount of bus space which is
2951 reserved for hotplug bridge's IO window.
2952 Default size is 256 bytes.
2953 hpmemsize=nn[KMG] The fixed amount of bus space which is
2954 reserved for hotplug bridge's memory window.
2955 Default size is 2 megabytes.
2956 hpbussize=nn The minimum amount of additional bus numbers
2957 reserved for buses below a hotplug bridge.
2959 realloc= Enable/disable reallocating PCI bridge resources
2960 if allocations done by BIOS are too small to
2961 accommodate resources required by all child
2963 off: Turn realloc off
2965 realloc same as realloc=on
2966 noari do not use PCIe ARI.
2967 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2968 only look for one device below a PCIe downstream
2971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2974 force Enable ASPM even on devices that claim not to support it.
2975 WARNING: Forcing ASPM on may cause system lockups.
2977 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2978 nomsi Do not use MSI for PCI Express Native Hotplug (this
2979 makes all PCIe ports use INTx for hotplug services).
2981 pcie_ports= [PCIE] PCIe ports handling:
2982 auto Ask the BIOS whether or not to use native PCIe services
2983 associated with PCIe ports (PME, hot-plug, AER). Use
2984 them only if that is allowed by the BIOS.
2985 native Use native PCIe services associated with PCIe ports
2987 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2990 pcie_port_pm= [PCIE] PCIe port power management handling:
2991 off Disable power management of all PCIe ports
2992 force Forcibly enable power management of all PCIe ports
2994 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2995 nomsi Do not use MSI for native PCIe PME signaling (this makes
2996 all PCIe root ports use INTx for all services).
2998 pcmv= [HW,PCMCIA] BadgePAD 4
3002 Keep all power-domains already enabled by bootloader on,
3003 even if no driver has claimed them. This is useful
3004 for debug and development, but should not be
3005 needed on a platform with proper driver support.
3008 See Documentation/blockdev/paride.txt.
3010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3013 See arch/parisc/kernel/pdc_chassis.c
3015 percpu_alloc= Select which percpu first chunk allocator to use.
3016 Currently supported values are "embed" and "page".
3017 Archs may support subset or none of the selections.
3018 See comments in mm/percpu.c for details on each
3019 allocator. This parameter is primarily for debugging
3020 and performance comparison.
3023 See Documentation/blockdev/paride.txt.
3026 See Documentation/blockdev/paride.txt.
3028 pirq= [SMP,APIC] Manual mp-table setup
3029 See Documentation/x86/i386/IO-APIC.txt.
3031 plip= [PPT,NET] Parallel port network link
3032 Format: { parport<nr> | timid | 0 }
3033 See also Documentation/parport.txt.
3035 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3036 Override pmtimer IOPort with a hex value.
3040 Enable PNP debug messages (depends on the
3041 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3042 via /sys/module/pnp/parameters/debug. We always show
3043 current resource usage; turning this on also shows
3044 possible settings and some assignment information.
3050 { on | off | curr | res | no-curr | no-res }
3053 [ISAPNP] Exclude IRQs for the autoconfiguration
3056 [ISAPNP] Exclude DMAs for the autoconfiguration
3058 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3059 Ranges are in pairs (I/O port base and size).
3062 [ISAPNP] Exclude memory regions for the
3064 Ranges are in pairs (memory base and size).
3066 ports= [IP_VS_FTP] IPVS ftp helper module
3068 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3070 Format: <port>,<port>....
3072 powersave=off [PPC] This option disables power saving features.
3073 It specifically disables cpuidle and sets the
3074 platform machine description specific power_save
3075 function to NULL. On Idle the CPU just reduces
3078 ppc_strict_facility_enable
3079 [PPC] This option catches any kernel floating point,
3080 Altivec, VSX and SPE outside of regions specifically
3081 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3082 There is some performance impact when enabling this.
3084 print-fatal-signals=
3085 [KNL] debug: print fatal signals
3087 If enabled, warn about various signal handling
3088 related application anomalies: too many signals,
3089 too many POSIX.1 timers, fatal signals causing a
3092 If you hit the warning due to signal overflow,
3093 you might want to try "ulimit -i unlimited".
3097 printk.always_kmsg_dump=
3098 Trigger kmsg_dump for cases other than kernel oops or
3100 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3103 printk.devkmsg={on,off,ratelimit}
3104 Control writing to /dev/kmsg.
3105 on - unlimited logging to /dev/kmsg from userspace
3106 off - logging to /dev/kmsg disabled
3107 ratelimit - ratelimit the logging
3110 printk.time= Show timing data prefixed to each printk message line
3111 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3113 processor.max_cstate= [HW,ACPI]
3114 Limit processor to maximum C-state
3115 max_cstate=9 overrides any DMI blacklist limit.
3117 processor.nocst [HW,ACPI]
3118 Ignore the _CST method to determine C-states,
3119 instead using the legacy FADT method
3121 profile= [KNL] Enable kernel profiling via /proc/profile
3122 Format: [schedule,]<number>
3123 Param: "schedule" - profile schedule points.
3124 Param: <number> - step/bucket size as a power of 2 for
3125 statistical time based profiling.
3126 Param: "sleep" - profile D-state sleeping (millisecs).
3127 Requires CONFIG_SCHEDSTATS
3128 Param: "kvm" - profile VM exits.
3130 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3132 See Documentation/blockdev/ramdisk.txt.
3134 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3135 probe for; one of (bare|imps|exps|lifebook|any).
3136 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3138 psmouse.resetafter= [HW,MOUSE]
3139 Try to reset the device after so many bad packets
3142 [HW,MOUSE] Set desired mouse resolution, in dpi.
3143 psmouse.smartscroll=
3144 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3145 0 = disabled, 1 = enabled (default).
3147 pstore.backend= Specify the name of the pstore backend to use
3150 See Documentation/blockdev/paride.txt.
3153 [KNL] Number of legacy pty's. Overwrites compiled-in
3156 quiet [KNL] Disable most log messages
3161 See Documentation/admin-guide/md.rst.
3163 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3164 See Documentation/blockdev/ramdisk.txt.
3167 The argument is a cpu list, as described above.
3169 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3170 the specified list of CPUs to be no-callback CPUs.
3171 Invocation of these CPUs' RCU callbacks will
3172 be offloaded to "rcuox/N" kthreads created for
3173 that purpose, where "x" is "b" for RCU-bh, "p"
3174 for RCU-preempt, and "s" for RCU-sched, and "N"
3175 is the CPU number. This reduces OS jitter on the
3176 offloaded CPUs, which can be useful for HPC and
3177 real-time workloads. It can also improve energy
3178 efficiency for asymmetric multiprocessors.
3181 Rather than requiring that offloaded CPUs
3182 (specified by rcu_nocbs= above) explicitly
3183 awaken the corresponding "rcuoN" kthreads,
3184 make these kthreads poll for callbacks.
3185 This improves the real-time response for the
3186 offloaded CPUs by relieving them of the need to
3187 wake up the corresponding kthread, but degrades
3188 energy efficiency by requiring that the kthreads
3189 periodically wake up to do the polling.
3191 rcutree.blimit= [KNL]
3192 Set maximum number of finished RCU callbacks to
3193 process in one batch.
3195 rcutree.dump_tree= [KNL]
3196 Dump the structure of the rcu_node combining tree
3197 out at early boot. This is used for diagnostic
3198 purposes, to verify correct tree setup.
3200 rcutree.gp_cleanup_delay= [KNL]
3201 Set the number of jiffies to delay each step of
3202 RCU grace-period cleanup. This only has effect
3203 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3205 rcutree.gp_init_delay= [KNL]
3206 Set the number of jiffies to delay each step of
3207 RCU grace-period initialization. This only has
3208 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3211 rcutree.gp_preinit_delay= [KNL]
3212 Set the number of jiffies to delay each step of
3213 RCU grace-period pre-initialization, that is,
3214 the propagation of recent CPU-hotplug changes up
3215 the rcu_node combining tree. This only has effect
3216 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3218 rcutree.rcu_fanout_exact= [KNL]
3219 Disable autobalancing of the rcu_node combining
3220 tree. This is used by rcutorture, and might
3221 possibly be useful for architectures having high
3222 cache-to-cache transfer latencies.
3224 rcutree.rcu_fanout_leaf= [KNL]
3225 Change the number of CPUs assigned to each
3226 leaf rcu_node structure. Useful for very
3227 large systems, which will choose the value 64,
3228 and for NUMA systems with large remote-access
3229 latencies, which will choose a value aligned
3230 with the appropriate hardware boundaries.
3232 rcutree.jiffies_till_sched_qs= [KNL]
3233 Set required age in jiffies for a
3234 given grace period before RCU starts
3235 soliciting quiescent-state help from
3236 rcu_note_context_switch().
3238 rcutree.jiffies_till_first_fqs= [KNL]
3239 Set delay from grace-period initialization to
3240 first attempt to force quiescent states.
3241 Units are jiffies, minimum value is zero,
3242 and maximum value is HZ.
3244 rcutree.jiffies_till_next_fqs= [KNL]
3245 Set delay between subsequent attempts to force
3246 quiescent states. Units are jiffies, minimum
3247 value is one, and maximum value is HZ.
3249 rcutree.kthread_prio= [KNL,BOOT]
3250 Set the SCHED_FIFO priority of the RCU per-CPU
3251 kthreads (rcuc/N). This value is also used for
3252 the priority of the RCU boost threads (rcub/N)
3253 and for the RCU grace-period kthreads (rcu_bh,
3254 rcu_preempt, and rcu_sched). If RCU_BOOST is
3255 set, valid values are 1-99 and the default is 1
3256 (the least-favored priority). Otherwise, when
3257 RCU_BOOST is not set, valid values are 0-99 and
3258 the default is zero (non-realtime operation).
3260 rcutree.rcu_nocb_leader_stride= [KNL]
3261 Set the number of NOCB kthread groups, which
3262 defaults to the square root of the number of
3263 CPUs. Larger numbers reduces the wakeup overhead
3264 on the per-CPU grace-period kthreads, but increases
3265 that same overhead on each group's leader.
3267 rcutree.qhimark= [KNL]
3268 Set threshold of queued RCU callbacks beyond which
3269 batch limiting is disabled.
3271 rcutree.qlowmark= [KNL]
3272 Set threshold of queued RCU callbacks below which
3273 batch limiting is re-enabled.
3275 rcutree.rcu_idle_gp_delay= [KNL]
3276 Set wakeup interval for idle CPUs that have
3277 RCU callbacks (RCU_FAST_NO_HZ=y).
3279 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3280 Set wakeup interval for idle CPUs that have
3281 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3282 Lazy RCU callbacks are those which RCU can
3283 prove do nothing more than free memory.
3285 rcutree.rcu_kick_kthreads= [KNL]
3286 Cause the grace-period kthread to get an extra
3287 wake_up() if it sleeps three times longer than
3288 it should at force-quiescent-state time.
3289 This wake_up() will be accompanied by a
3290 WARN_ONCE() splat and an ftrace_dump().
3292 rcuperf.gp_exp= [KNL]
3293 Measure performance of expedited synchronous
3294 grace-period primitives.
3296 rcuperf.holdoff= [KNL]
3297 Set test-start holdoff period. The purpose of
3298 this parameter is to delay the start of the
3299 test until boot completes in order to avoid
3302 rcuperf.nreaders= [KNL]
3303 Set number of RCU readers. The value -1 selects
3304 N, where N is the number of CPUs. A value
3305 "n" less than -1 selects N-n+1, where N is again
3306 the number of CPUs. For example, -2 selects N
3307 (the number of CPUs), -3 selects N+1, and so on.
3308 A value of "n" less than or equal to -N selects
3311 rcuperf.nwriters= [KNL]
3312 Set number of RCU writers. The values operate
3313 the same as for rcuperf.nreaders.
3314 N, where N is the number of CPUs
3316 rcuperf.perf_runnable= [BOOT]
3317 Start rcuperf running at boot time.
3319 rcuperf.shutdown= [KNL]
3320 Shut the system down after performance tests
3321 complete. This is useful for hands-off automated
3324 rcuperf.perf_type= [KNL]
3325 Specify the RCU implementation to test.
3327 rcuperf.verbose= [KNL]
3328 Enable additional printk() statements.
3330 rcutorture.cbflood_inter_holdoff= [KNL]
3331 Set holdoff time (jiffies) between successive
3332 callback-flood tests.
3334 rcutorture.cbflood_intra_holdoff= [KNL]
3335 Set holdoff time (jiffies) between successive
3336 bursts of callbacks within a given callback-flood
3339 rcutorture.cbflood_n_burst= [KNL]
3340 Set the number of bursts making up a given
3341 callback-flood test. Set this to zero to
3342 disable callback-flood testing.
3344 rcutorture.cbflood_n_per_burst= [KNL]
3345 Set the number of callbacks to be registered
3346 in a given burst of a callback-flood test.
3348 rcutorture.fqs_duration= [KNL]
3349 Set duration of force_quiescent_state bursts
3352 rcutorture.fqs_holdoff= [KNL]
3353 Set holdoff time within force_quiescent_state bursts
3356 rcutorture.fqs_stutter= [KNL]
3357 Set wait time between force_quiescent_state bursts
3360 rcutorture.gp_cond= [KNL]
3361 Use conditional/asynchronous update-side
3362 primitives, if available.
3364 rcutorture.gp_exp= [KNL]
3365 Use expedited update-side primitives, if available.
3367 rcutorture.gp_normal= [KNL]
3368 Use normal (non-expedited) asynchronous
3369 update-side primitives, if available.
3371 rcutorture.gp_sync= [KNL]
3372 Use normal (non-expedited) synchronous
3373 update-side primitives, if available. If all
3374 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3375 rcutorture.gp_normal=, and rcutorture.gp_sync=
3376 are zero, rcutorture acts as if is interpreted
3377 they are all non-zero.
3379 rcutorture.n_barrier_cbs= [KNL]
3380 Set callbacks/threads for rcu_barrier() testing.
3382 rcutorture.nfakewriters= [KNL]
3383 Set number of concurrent RCU writers. These just
3384 stress RCU, they don't participate in the actual
3385 test, hence the "fake".
3387 rcutorture.nreaders= [KNL]
3388 Set number of RCU readers. The value -1 selects
3389 N-1, where N is the number of CPUs. A value
3390 "n" less than -1 selects N-n-2, where N is again
3391 the number of CPUs. For example, -2 selects N
3392 (the number of CPUs), -3 selects N+1, and so on.
3394 rcutorture.object_debug= [KNL]
3395 Enable debug-object double-call_rcu() testing.
3397 rcutorture.onoff_holdoff= [KNL]
3398 Set time (s) after boot for CPU-hotplug testing.
3400 rcutorture.onoff_interval= [KNL]
3401 Set time (s) between CPU-hotplug operations, or
3402 zero to disable CPU-hotplug testing.
3404 rcutorture.shuffle_interval= [KNL]
3405 Set task-shuffle interval (s). Shuffling tasks
3406 allows some CPUs to go into dyntick-idle mode
3407 during the rcutorture test.
3409 rcutorture.shutdown_secs= [KNL]
3410 Set time (s) after boot system shutdown. This
3411 is useful for hands-off automated testing.
3413 rcutorture.stall_cpu= [KNL]
3414 Duration of CPU stall (s) to test RCU CPU stall
3415 warnings, zero to disable.
3417 rcutorture.stall_cpu_holdoff= [KNL]
3418 Time to wait (s) after boot before inducing stall.
3420 rcutorture.stat_interval= [KNL]
3421 Time (s) between statistics printk()s.
3423 rcutorture.stutter= [KNL]
3424 Time (s) to stutter testing, for example, specifying
3425 five seconds causes the test to run for five seconds,
3426 wait for five seconds, and so on. This tests RCU's
3427 ability to transition abruptly to and from idle.
3429 rcutorture.test_boost= [KNL]
3430 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3431 "Maybe" means test if the RCU implementation
3432 under test support RCU priority boosting.
3434 rcutorture.test_boost_duration= [KNL]
3435 Duration (s) of each individual boost test.
3437 rcutorture.test_boost_interval= [KNL]
3438 Interval (s) between each boost test.
3440 rcutorture.test_no_idle_hz= [KNL]
3441 Test RCU's dyntick-idle handling. See also the
3442 rcutorture.shuffle_interval parameter.
3444 rcutorture.torture_runnable= [BOOT]
3445 Start rcutorture running at boot time.
3447 rcutorture.torture_type= [KNL]
3448 Specify the RCU implementation to test.
3450 rcutorture.verbose= [KNL]
3451 Enable additional printk() statements.
3453 rcupdate.rcu_cpu_stall_suppress= [KNL]
3454 Suppress RCU CPU stall warning messages.
3456 rcupdate.rcu_cpu_stall_timeout= [KNL]
3457 Set timeout for RCU CPU stall warning messages.
3459 rcupdate.rcu_expedited= [KNL]
3460 Use expedited grace-period primitives, for
3461 example, synchronize_rcu_expedited() instead
3462 of synchronize_rcu(). This reduces latency,
3463 but can increase CPU utilization, degrade
3464 real-time latency, and degrade energy efficiency.
3465 No effect on CONFIG_TINY_RCU kernels.
3467 rcupdate.rcu_normal= [KNL]
3468 Use only normal grace-period primitives,
3469 for example, synchronize_rcu() instead of
3470 synchronize_rcu_expedited(). This improves
3471 real-time latency, CPU utilization, and
3472 energy efficiency, but can expose users to
3473 increased grace-period latency. This parameter
3474 overrides rcupdate.rcu_expedited. No effect on
3475 CONFIG_TINY_RCU kernels.
3477 rcupdate.rcu_normal_after_boot= [KNL]
3478 Once boot has completed (that is, after
3479 rcu_end_inkernel_boot() has been invoked), use
3480 only normal grace-period primitives. No effect
3481 on CONFIG_TINY_RCU kernels.
3483 rcupdate.rcu_task_stall_timeout= [KNL]
3484 Set timeout in jiffies for RCU task stall warning
3485 messages. Disable with a value less than or equal
3488 rcupdate.rcu_self_test= [KNL]
3489 Run the RCU early boot self tests
3491 rcupdate.rcu_self_test_bh= [KNL]
3492 Run the RCU bh early boot self tests
3494 rcupdate.rcu_self_test_sched= [KNL]
3495 Run the RCU sched early boot self tests
3499 Run specified binary instead of /init from the ramdisk,
3500 used for early userspace startup. See initrd.
3503 Format (x86 or x86_64):
3504 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3506 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3508 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3509 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3510 reboot_force is either force or not specified,
3511 reboot_cpu is s[mp]#### with #### being the processor
3512 to be used for rebooting.
3515 [KNL, SMP] Set scheduler's default relax_domain_level.
3516 See Documentation/cgroup-v1/cpusets.txt.
3518 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3520 reservetop= [X86-32]
3522 Reserves a hole at the top of the kernel virtual
3527 Set the amount of memory to reserve for BIOS at
3528 the bottom of the address space.
3530 reset_devices [KNL] Force drivers to reset the underlying device
3531 during initialization.
3534 Specify the partition device for software suspend
3536 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3538 resume_offset= [SWSUSP]
3539 Specify the offset from the beginning of the partition
3540 given by "resume=" at which the swap header is located,
3541 in <PAGE_SIZE> units (needed only for swap files).
3542 See Documentation/power/swsusp-and-swap-files.txt
3544 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3545 read the resume files
3547 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3548 Useful for devices that are detected asynchronously
3549 (e.g. USB and MMC devices).
3551 hibernate= [HIBERNATION]
3552 noresume Don't check if there's a hibernation image
3553 present during boot.
3554 nocompress Don't compress/decompress hibernation images.
3555 no Disable hibernation and resume.
3556 protect_image Turn on image protection during restoration
3557 (that will set all pages holding image data
3558 during restoration read-only).
3560 retain_initrd [RAM] Keep initrd memory after extraction
3562 rfkill.default_state=
3563 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3564 etc. communication is blocked by default.
3567 rfkill.master_switch_mode=
3568 0 The "airplane mode" button does nothing.
3569 1 The "airplane mode" button toggles between everything
3570 blocked and the previous configuration.
3571 2 The "airplane mode" button toggles between everything
3572 blocked and everything unblocked.
3574 rhash_entries= [KNL,NET]
3575 Set number of hash buckets for route cache
3578 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3581 ro [KNL] Mount root device read-only on boot
3584 on Mark read-only kernel memory as read-only (default).
3585 off Leave read-only kernel memory writable for debugging.
3588 Enable the uart passthrough on the designated usb port
3589 on Rockchip SoCs. When active, the signals of the
3590 debug-uart get routed to the D+ and D- pins of the usb
3591 port and the regular usb controller gets disabled.
3593 root= [KNL] Root filesystem
3594 See name_to_dev_t comment in init/do_mounts.c.
3596 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3597 mount the root filesystem
3599 rootflags= [KNL] Set root filesystem mount option string
3601 rootfstype= [KNL] Set root filesystem type
3603 rootwait [KNL] Wait (indefinitely) for root device to show up.
3604 Useful for devices that are detected asynchronously
3605 (e.g. USB and MMC devices).
3607 rproc_mem=nn[KMG][@address]
3608 [KNL,ARM,CMA] Remoteproc physical memory block.
3609 Memory area to be used by remote processor image,
3612 rw [KNL] Mount root device read-write on boot
3614 S [KNL] Run init in single mode
3616 s390_iommu= [HW,S390]
3617 Set s390 IOTLB flushing mode
3619 With strict flushing every unmap operation will result in
3620 an IOTLB flush. Default is lazy flushing before reuse,
3624 See drivers/net/irda/sa1100_ir.c.
3626 sbni= [NET] Granch SBNI12 leased line adapter
3628 sched_debug [KNL] Enables verbose scheduler debug messages.
3630 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3631 Allowed values are enable and disable. This feature
3632 incurs a small amount of overhead in the scheduler
3633 but is useful for debugging and performance tuning.
3635 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3636 xtime_lock contention on larger systems, and/or RCU lock
3637 contention on all systems with CONFIG_MAXSMP set.
3638 Format: { "0" | "1" }
3639 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3641 Note: increases power consumption, thus should only be
3642 enabled if running jitter sensitive (HPC/RT) workloads.
3644 security= [SECURITY] Choose a security module to enable at boot.
3645 If this boot parameter is not specified, only the first
3646 security module asking for security registration will be
3647 loaded. An invalid security module name will be treated
3648 as if no module has been chosen.
3650 selinux= [SELINUX] Disable or enable SELinux at boot time.
3651 Format: { "0" | "1" }
3652 See security/selinux/Kconfig help text.
3655 Default value is set via kernel config option.
3656 If enabled at boot time, /selinux/disable can be used
3657 later to disable prior to initial policy load.
3659 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3660 Format: { "0" | "1" }
3661 See security/apparmor/Kconfig help text
3664 Default value is set via kernel config option.
3666 serialnumber [BUGS=X86-32]
3669 Maximal number of shapers.
3677 Disable merging of slabs with similar size. May be
3678 necessary if there is some reason to distinguish
3679 allocs to different slabs. Debug options disable
3680 merging on their own.
3681 For more information see Documentation/vm/slub.txt.
3683 slab_max_order= [MM, SLAB]
3684 Determines the maximum allowed order for slabs.
3685 A high setting may cause OOMs due to memory
3686 fragmentation. Defaults to 1 for systems with
3687 more than 32MB of RAM, 0 otherwise.
3689 slub_debug[=options[,slabs]] [MM, SLUB]
3690 Enabling slub_debug allows one to determine the
3691 culprit if slab objects become corrupted. Enabling
3692 slub_debug can create guard zones around objects and
3693 may poison objects when not in use. Also tracks the
3694 last alloc / free. For more information see
3695 Documentation/vm/slub.txt.
3697 slub_memcg_sysfs= [MM, SLUB]
3698 Determines whether to enable sysfs directories for
3699 memory cgroup sub-caches. 1 to enable, 0 to disable.
3700 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3701 Enabling this can lead to a very high number of debug
3702 directories and files being created under
3705 slub_max_order= [MM, SLUB]
3706 Determines the maximum allowed order for slabs.
3707 A high setting may cause OOMs due to memory
3708 fragmentation. For more information see
3709 Documentation/vm/slub.txt.
3711 slub_min_objects= [MM, SLUB]
3712 The minimum number of objects per slab. SLUB will
3713 increase the slab order up to slub_max_order to
3714 generate a sufficiently large slab able to contain
3715 the number of objects indicated. The higher the number
3716 of objects the smaller the overhead of tracking slabs
3717 and the less frequently locks need to be acquired.
3718 For more information see Documentation/vm/slub.txt.
3720 slub_min_order= [MM, SLUB]
3721 Determines the minimum page order for slabs. Must be
3722 lower than slub_max_order.
3723 For more information see Documentation/vm/slub.txt.
3725 slub_nomerge [MM, SLUB]
3726 Same with slab_nomerge. This is supported for legacy.
3727 See slab_nomerge for more information.
3730 Format: <io1>[,<io2>[,...,<io8>]]
3732 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3733 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3734 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3735 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3736 smsc-ircc2.ircc_irq= [HW] IRQ line
3737 smsc-ircc2.ircc_dma= [HW] DMA channel
3738 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3739 0: Toshiba Satellite 1800 (GP data pin select)
3740 1: Fast pin select (default)
3743 smt [KNL,S390] Set the maximum number of threads (logical
3744 CPUs) to use per physical CPU on systems capable of
3745 symmetric multithreading (SMT). Will be capped to the
3746 actual hardware limit.
3748 Default: -1 (no limit)
3751 [KNL] Should the soft-lockup detector generate panics.
3754 softlockup_all_cpu_backtrace=
3755 [KNL] Should the soft-lockup detector generate
3756 backtraces on all cpus.
3759 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3760 See Documentation/laptops/sonypi.txt
3762 spia_io_base= [HW,MTD]
3768 Enabled the stack tracer on boot up.
3770 stacktrace_filter=[function-list]
3771 [FTRACE] Limit the functions that the stack tracer
3772 will trace at boot up. function-list is a comma separated
3773 list of functions. This list can be changed at run
3774 time by the stack_trace_filter file in the debugfs
3775 tracing directory. Note, this enables stack tracing
3776 and the stacktrace above is not needed.
3780 Set the STI (builtin display/keyboard on the HP-PARISC
3781 machines) console (graphic card) which should be used
3782 as the initial boot-console.
3783 See also comment in drivers/video/console/sticore.c.
3786 See comment in drivers/video/console/sticore.c.
3789 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3791 sunrpc.min_resvport=
3792 sunrpc.max_resvport=
3794 SunRPC servers often require that client requests
3795 originate from a privileged port (i.e. a port in the
3796 range 0 < portnr < 1024).
3797 An administrator who wishes to reserve some of these
3798 ports for other uses may adjust the range that the
3799 kernel's sunrpc client considers to be privileged
3800 using these two parameters to set the minimum and
3801 maximum port values.
3803 sunrpc.svc_rpc_per_connection_limit=
3805 Limit the number of requests that the server will
3806 process in parallel from a single connection.
3807 The default value is 0 (no limit).
3811 Control how the NFS server code allocates CPUs to
3812 service thread pools. Depending on how many NICs
3813 you have and where their interrupts are bound, this
3814 option will affect which CPUs will do NFS serving.
3815 Note: this parameter cannot be changed while the
3816 NFS server is running.
3818 auto the server chooses an appropriate mode
3819 automatically using heuristics
3820 global a single global pool contains all CPUs
3821 percpu one pool for each CPU
3822 pernode one pool for each NUMA node (equivalent
3823 to global on non-NUMA machines)
3825 sunrpc.tcp_slot_table_entries=
3826 sunrpc.udp_slot_table_entries=
3828 Sets the upper limit on the number of simultaneous
3829 RPC calls that can be sent from the client to a
3830 server. Increasing these values may allow you to
3831 improve throughput, but will also increase the
3832 amount of memory reserved for use by the client.
3834 suspend.pm_test_delay=
3836 Sets the number of seconds to remain in a suspend test
3837 mode before resuming the system (see
3838 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3839 is set. Default value is 5.
3842 [KNL] Enable accounting of swap in memory resource
3843 controller if no parameter or 1 is given or disable
3844 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3846 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3847 Format: { <int> | force | noforce }
3848 <int> -- Number of I/O TLB slabs
3849 force -- force using of bounce buffers even if they
3850 wouldn't be automatically used by the kernel
3851 noforce -- Never use bounce buffers (for debugging)
3855 sysfs.deprecated=0|1 [KNL]
3856 Enable/disable old style sysfs layout for old udev
3857 on older distributions. When this option is enabled
3858 very new udev will not work anymore. When this option
3859 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3860 in older udev will not work anymore.
3861 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3862 the kernel configuration.
3864 sysrq_always_enabled
3866 Ignore sysrq setting - this boot parameter will
3867 neutralize any effect of /proc/sys/kernel/sysrq.
3868 Useful for debugging.
3870 tcpmhash_entries= [KNL,NET]
3871 Set the number of tcp_metrics_hash slots.
3872 Default value is 8192 or 16384 depending on total
3873 ram pages. This is used to specify the TCP metrics
3874 cache size. See Documentation/networking/ip-sysctl.txt
3875 "tcp_no_metrics_save" section for more details.
3879 test_suspend= [SUSPEND][,N]
3880 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3881 standby suspend) or "freeze" (for suspend type freeze)
3882 as the system sleep state during system startup with
3883 the optional capability to repeat N number of times.
3884 The system is woken from this state using a
3885 wakeup-capable RTC alarm.
3887 thash_entries= [KNL,NET]
3888 Set number of hash buckets for TCP connection
3890 thermal.act= [HW,ACPI]
3891 -1: disable all active trip points in all thermal zones
3892 <degrees C>: override all lowest active trip points
3894 thermal.crt= [HW,ACPI]
3895 -1: disable all critical trip points in all thermal zones
3896 <degrees C>: override all critical trip points
3898 thermal.nocrt= [HW,ACPI]
3899 Set to disable actions on ACPI thermal zone
3900 critical and hot trip points.
3902 thermal.off= [HW,ACPI]
3903 1: disable ACPI thermal control
3905 thermal.psv= [HW,ACPI]
3906 -1: disable all passive trip points
3907 <degrees C>: override all passive trip points to this
3910 thermal.tzp= [HW,ACPI]
3911 Specify global default ACPI thermal zone polling rate
3912 <deci-seconds>: poll all this frequency
3913 0: no polling (default)
3916 Force threading of all interrupt handlers except those
3917 marked explicitly IRQF_NO_THREAD.
3920 Enable the Transcendent memory driver if built-in.
3922 tmem.cleancache=0|1 [KNL, XEN]
3923 Default is on (1). Disable the usage of the cleancache
3924 API to send anonymous pages to the hypervisor.
3926 tmem.frontswap=0|1 [KNL, XEN]
3927 Default is on (1). Disable the usage of the frontswap
3928 API to send swap pages to the hypervisor. If disabled
3929 the selfballooning and selfshrinking are force disabled.
3931 tmem.selfballooning=0|1 [KNL, XEN]
3932 Default is on (1). Disable the driving of swap pages
3935 tmem.selfshrinking=0|1 [KNL, XEN]
3936 Default is on (1). Partial swapoff that immediately
3937 transfers pages from Xen hypervisor back to the
3938 kernel based on different criteria.
3942 Specify if the kernel should make use of the cpu
3943 topology information if the hardware supports this.
3944 The scheduler will make use of this information and
3945 e.g. base its process migration decisions on it.
3948 topology_updates= [KNL, PPC, NUMA]
3950 Specify if the kernel should ignore (off)
3951 topology updates sent by the hypervisor to this
3956 tpm_suspend_pcr=[HW,TPM]
3957 Format: integer pcr id
3958 Specify that at suspend time, the tpm driver
3959 should extend the specified pcr with zeros,
3960 as a workaround for some chips which fail to
3961 flush the last written pcr on TPM_SaveState.
3962 This will guarantee that all the other pcrs
3965 trace_buf_size=nn[KMG]
3966 [FTRACE] will set tracing buffer size on each cpu.
3968 trace_event=[event-list]
3969 [FTRACE] Set and start specified trace events in order
3970 to facilitate early boot debugging. The event-list is a
3971 comma separated list of trace events to enable. See
3972 also Documentation/trace/events.txt
3974 trace_options=[option-list]
3975 [FTRACE] Enable or disable tracer options at boot.
3976 The option-list is a comma delimited list of options
3977 that can be enabled or disabled just as if you were
3978 to echo the option name into
3980 /sys/kernel/debug/tracing/trace_options
3982 For example, to enable stacktrace option (to dump the
3983 stack trace of each event), add to the command line:
3985 trace_options=stacktrace
3987 See also Documentation/trace/ftrace.txt "trace options"
3991 Have the tracepoints sent to printk as well as the
3992 tracing ring buffer. This is useful for early boot up
3993 where the system hangs or reboots and does not give the
3994 option for reading the tracing buffer or performing a
3995 ftrace_dump_on_oops.
3997 To turn off having tracepoints sent to printk,
3998 echo 0 > /proc/sys/kernel/tracepoint_printk
3999 Note, echoing 1 into this file without the
4000 tracepoint_printk kernel cmdline option has no effect.
4004 Having tracepoints sent to printk() and activating high
4005 frequency tracepoints such as irq or sched, can cause
4006 the system to live lock.
4009 [FTRACE] enable this option to disable tracing when a
4010 warning is hit. This turns off "tracing_on". Tracing can
4011 be enabled again by echoing '1' into the "tracing_on"
4012 file located in /sys/kernel/debug/tracing/
4014 This option is useful, as it disables the trace before
4015 the WARNING dump is called, which prevents the trace to
4016 be filled with content caused by the warning output.
4018 This option can also be set at run time via the sysctl
4019 option: kernel/traceoff_on_warning
4021 transparent_hugepage=
4023 Format: [always|madvise|never]
4024 Can be used to control the default behavior of the system
4025 with respect to transparent hugepages.
4026 See Documentation/vm/transhuge.txt for more details.
4028 tsc= Disable clocksource stability checks for TSC.
4030 [x86] reliable: mark tsc clocksource as reliable, this
4031 disables clocksource verification at runtime, as well
4032 as the stability checks done at bootup. Used to enable
4033 high-resolution timer mode on older hardware, and in
4034 virtualized environment.
4035 [x86] noirqtime: Do not use TSC to do irq accounting.
4036 Used to run time disable IRQ_TIME_ACCOUNTING on any
4037 platforms where RDTSC is slow and this accounting
4040 turbografx.map[2|3]= [HW,JOY]
4041 TurboGraFX parallel port interface
4043 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4044 See also Documentation/input/joystick-parport.txt
4046 udbg-immortal [PPC] When debugging early kernel crashes that
4047 happen after console_init() and before a proper
4048 console driver takes over, this boot options might
4049 help "seeing" what's going on.
4051 uhash_entries= [KNL,NET]
4052 Set number of hash buckets for UDP/UDP-Lite connections
4055 [USB] Ignore overcurrent events (default N).
4056 Some badly-designed motherboards generate lots of
4057 bogus events, for ports that aren't wired to
4058 anything. Set this parameter to avoid log spamming.
4059 Note that genuine overcurrent events won't be
4063 [X86] Cause panic on unknown NMI.
4065 usbcore.authorized_default=
4066 [USB] Default USB device authorization:
4067 (default -1 = authorized except for wireless USB,
4068 0 = not authorized, 1 = authorized)
4070 usbcore.autosuspend=
4071 [USB] The autosuspend time delay (in seconds) used
4072 for newly-detected USB devices (default 2). This
4073 is the time required before an idle device will be
4074 autosuspended. Devices for which the delay is set
4075 to a negative value won't be autosuspended at all.
4077 usbcore.usbfs_snoop=
4078 [USB] Set to log all usbfs traffic (default 0 = off).
4080 usbcore.usbfs_snoop_max=
4081 [USB] Maximum number of bytes to snoop in each URB
4084 usbcore.blinkenlights=
4085 [USB] Set to cycle leds on hubs (default 0 = off).
4087 usbcore.old_scheme_first=
4088 [USB] Start with the old device initialization
4089 scheme (default 0 = off).
4091 usbcore.usbfs_memory_mb=
4092 [USB] Memory limit (in MB) for buffers allocated by
4093 usbfs (default = 16, 0 = max = 2047).
4095 usbcore.use_both_schemes=
4096 [USB] Try the other device initialization scheme
4097 if the first one fails (default 1 = enabled).
4099 usbcore.initial_descriptor_timeout=
4100 [USB] Specifies timeout for the initial 64-byte
4101 USB_REQ_GET_DESCRIPTOR request in milliseconds
4102 (default 5000 = 5.0 seconds).
4104 usbcore.nousb [USB] Disable the USB subsystem
4107 [USBHID] The interval which mice are to be polled at.
4109 usb-storage.delay_use=
4110 [UMS] The delay in seconds before a new device is
4111 scanned for Logical Units (default 1).
4114 [UMS] A list of quirks entries to supplement or
4115 override the built-in unusual_devs list. List
4116 entries are separated by commas. Each entry has
4117 the form VID:PID:Flags where VID and PID are Vendor
4118 and Product ID values (4-digit hex numbers) and
4119 Flags is a set of characters, each corresponding
4120 to a common usb-storage quirk flag as follows:
4121 a = SANE_SENSE (collect more than 18 bytes
4123 b = BAD_SENSE (don't collect more than 18
4124 bytes of sense data);
4125 c = FIX_CAPACITY (decrease the reported
4126 device capacity by one sector);
4127 d = NO_READ_DISC_INFO (don't use
4128 READ_DISC_INFO command);
4129 e = NO_READ_CAPACITY_16 (don't use
4130 READ_CAPACITY_16 command);
4131 f = NO_REPORT_OPCODES (don't use report opcodes
4133 g = MAX_SECTORS_240 (don't transfer more than
4134 240 sectors at a time, uas only);
4135 h = CAPACITY_HEURISTICS (decrease the
4136 reported device capacity by one
4137 sector if the number is odd);
4138 i = IGNORE_DEVICE (don't bind to this
4140 j = NO_REPORT_LUNS (don't use report luns
4142 l = NOT_LOCKABLE (don't try to lock and
4143 unlock ejectable media);
4144 m = MAX_SECTORS_64 (don't transfer more
4145 than 64 sectors = 32 KB at a time);
4146 n = INITIAL_READ10 (force a retry of the
4147 initial READ(10) command);
4148 o = CAPACITY_OK (accept the capacity
4149 reported by the device);
4150 p = WRITE_CACHE (the device cache is ON
4152 r = IGNORE_RESIDUE (the device reports
4153 bogus residue values);
4154 s = SINGLE_LUN (the device has only one
4156 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4157 commands, uas only);
4158 u = IGNORE_UAS (don't bind to the uas driver);
4159 w = NO_WP_DETECT (don't test whether the
4160 medium is write-protected).
4161 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4162 even if the device claims no cache)
4163 Example: quirks=0419:aaf5:rl,0421:0433:rc
4165 user_debug= [KNL,ARM]
4167 See arch/arm/Kconfig.debug help text.
4168 1 - undefined instruction events
4170 4 - invalid data aborts
4173 Example: user_debug=31
4176 [X86] Flags controlling user PTE allocations.
4178 nohigh = do not allocate PTE pages in
4179 HIGHMEM regardless of setting
4183 On X86_32, this is an alias for vdso32=. Otherwise:
4185 vdso=1: enable VDSO (the default)
4186 vdso=0: disable VDSO mapping
4188 vdso32= [X86] Control the 32-bit vDSO
4189 vdso32=1: enable 32-bit VDSO
4190 vdso32=0 or vdso32=2: disable 32-bit VDSO
4192 See the help text for CONFIG_COMPAT_VDSO for more
4193 details. If CONFIG_COMPAT_VDSO is set, the default is
4194 vdso32=0; otherwise, the default is vdso32=1.
4196 For compatibility with older kernels, vdso32=2 is an
4199 Try vdso32=0 if you encounter an error that says:
4200 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4203 vector=percpu: enable percpu vector domain
4205 video= [FB] Frame buffer configuration
4206 See Documentation/fb/modedb.txt.
4208 video.brightness_switch_enabled= [0,1]
4209 If set to 1, on receiving an ACPI notify event
4210 generated by hotkey, video driver will adjust brightness
4211 level and then send out the event to user space through
4212 the allocated input device; If set to 0, video driver
4213 will only send out the event without touching backlight
4218 [VMMIO] Memory mapped virtio (platform) device.
4220 <size>@<baseaddr>:<irq>[:<id>]
4222 <size> := size (can use standard suffixes
4224 <baseaddr> := physical base address
4225 <irq> := interrupt number (as passed to
4227 <id> := (optional) platform device id
4229 virtio_mmio.device=1K@0x100b0000:48:7
4231 Can be used multiple times for multiple devices.
4233 vga= [BOOT,X86-32] Select a particular video mode
4234 See Documentation/x86/boot.txt and
4235 Documentation/svga.txt.
4236 Use vga=ask for menu.
4237 This is actually a boot loader parameter; the value is
4238 passed to the kernel using a special protocol.
4240 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4241 size of <nn>. This can be used to increase the
4242 minimum size (128MB on x86). It can also be used to
4243 decrease the size and leave more room for directly
4246 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4249 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4252 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4256 Controls the behavior of vsyscalls (i.e. calls to
4257 fixed addresses of 0xffffffffff600x00 from legacy
4258 code). Most statically-linked binaries and older
4259 versions of glibc use these calls. Because these
4260 functions are at fixed addresses, they make nice
4261 targets for exploits that can control RIP.
4263 emulate [default] Vsyscalls turn into traps and are
4264 emulated reasonably safely.
4266 native Vsyscalls are native syscall instructions.
4267 This is a little bit faster than trapping
4268 and makes a few dynamic recompilers work
4269 better than they would in emulation mode.
4270 It also makes exploits much easier to write.
4272 none Vsyscalls don't work at all. This makes
4273 them quite hard to use for exploits but
4274 might break your system.
4276 vt.color= [VT] Default text color.
4277 Format: 0xYX, X = foreground, Y = background.
4278 Default: 0x07 = light gray on black.
4280 vt.cur_default= [VT] Default cursor shape.
4281 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4282 the parameters of the <Esc>[?A;B;Cc escape sequence;
4283 see VGA-softcursor.txt. Default: 2 = underline.
4285 vt.default_blu= [VT]
4286 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4287 Change the default blue palette of the console.
4288 This is a 16-member array composed of values
4291 vt.default_grn= [VT]
4292 Format: <green0>,<green1>,<green2>,...,<green15>
4293 Change the default green palette of the console.
4294 This is a 16-member array composed of values
4297 vt.default_red= [VT]
4298 Format: <red0>,<red1>,<red2>,...,<red15>
4299 Change the default red palette of the console.
4300 This is a 16-member array composed of values
4306 Set system-wide default UTF-8 mode for all tty's.
4307 Default is 1, i.e. UTF-8 mode is enabled for all
4308 newly opened terminals.
4310 vt.global_cursor_default=
4313 Set system-wide default for whether a cursor
4314 is shown on new VTs. Default is -1,
4315 i.e. cursors will be created by default unless
4316 overridden by individual drivers. 0 will hide
4317 cursors, 1 will display them.
4319 vt.italic= [VT] Default color for italic text; 0-15.
4322 vt.underline= [VT] Default color for underlined text; 0-15.
4325 watchdog timers [HW,WDT] For information on watchdog timers,
4326 see Documentation/watchdog/watchdog-parameters.txt
4327 or other driver-specific files in the
4328 Documentation/watchdog/ directory.
4330 workqueue.watchdog_thresh=
4331 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4332 warn stall conditions and dump internal state to
4333 help debugging. 0 disables workqueue stall
4334 detection; otherwise, it's the stall threshold
4335 duration in seconds. The default value is 30 and
4336 it can be updated at runtime by writing to the
4337 corresponding sysfs file.
4339 workqueue.disable_numa
4340 By default, all work items queued to unbound
4341 workqueues are affine to the NUMA nodes they're
4342 issued on, which results in better behavior in
4343 general. If NUMA affinity needs to be disabled for
4344 whatever reason, this option can be used. Note
4345 that this also can be controlled per-workqueue for
4346 workqueues visible under /sys/bus/workqueue/.
4348 workqueue.power_efficient
4349 Per-cpu workqueues are generally preferred because
4350 they show better performance thanks to cache
4351 locality; unfortunately, per-cpu workqueues tend to
4352 be more power hungry than unbound workqueues.
4354 Enabling this makes the per-cpu workqueues which
4355 were observed to contribute significantly to power
4356 consumption unbound, leading to measurably lower
4357 power usage at the cost of small performance
4360 The default value of this parameter is determined by
4361 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4363 workqueue.debug_force_rr_cpu
4364 Workqueue used to implicitly guarantee that work
4365 items queued without explicit CPU specified are put
4366 on the local CPU. This guarantee is no longer true
4367 and while local CPU is still preferred work items
4368 may be put on foreign CPUs. This debug option
4369 forces round-robin CPU selection to flush out
4370 usages which depend on the now broken guarantee.
4371 When enabled, memory and cache locality will be
4374 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4375 default x2apic cluster mode on platforms
4378 x86_intel_mid_timer= [X86-32,APBT]
4379 Choose timer option for x86 Intel MID platform.
4380 Two valid options are apbt timer only and lapic timer
4381 plus one apbt timer for broadcast timer.
4382 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4384 xen_512gb_limit [KNL,X86-64,XEN]
4385 Restricts the kernel running paravirtualized under Xen
4386 to use only up to 512 GB of RAM. The reason to do so is
4387 crash analysis tools and Xen tools for doing domain
4388 save/restore/migration must be enabled to handle larger
4391 xen_emul_unplug= [HW,X86,XEN]
4392 Unplug Xen emulated devices
4393 Format: [unplug0,][unplug1]
4394 ide-disks -- unplug primary master IDE devices
4395 aux-ide-disks -- unplug non-primary-master IDE devices
4396 nics -- unplug network devices
4397 all -- unplug all emulated devices (NICs and IDE disks)
4398 unnecessary -- unplugging emulated devices is
4399 unnecessary even if the host did not respond to
4401 never -- do not unplug even if version check succeeds
4403 xen_nopvspin [X86,XEN]
4404 Disables the ticketlock slowpath using Xen PV
4408 Disables the PV optimizations forcing the HVM guest to
4409 run as generic HVM guest with no PV drivers.
4411 xirc2ps_cs= [NET,PCMCIA]
4413 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
git.samba.org / sfrench / cifs-2.6.git / blob