Root/Documentation/kernel-parameters.txt

Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago.
By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing
1                          Kernel Parameters
2                          ~~~~~~~~~~~~~~~~~
3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12    modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18    usbcore.blinkenlights=1
19
20Hyphens (dashes) and underscores are equivalent in parameter names, so
21    log_buf_len=1M print-fatal-signals=1
22can also be entered as
23    log-buf-len=1M print_fatal_signals=1
24
25
26This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
33The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
37
38    ACPI ACPI support is enabled.
39    AGP AGP (Accelerated Graphics Port) is enabled.
40    ALSA ALSA sound support is enabled.
41    APIC APIC support is enabled.
42    APM Advanced Power Management support is enabled.
43    ARM ARM architecture is enabled.
44    AVR32 AVR32 architecture is enabled.
45    AX25 Appropriate AX.25 support is enabled.
46    BLACKFIN Blackfin architecture is enabled.
47    DRM Direct Rendering Management support is enabled.
48    DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49    EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50    EFI EFI Partitioning (GPT) is enabled
51    EIDE EIDE/ATAPI support is enabled.
52    EVM Extended Verification Module
53    FB The frame buffer device is enabled.
54    FTRACE Function tracing enabled.
55    GCOV GCOV profiling is enabled.
56    HW Appropriate hardware is enabled.
57    IA-64 IA-64 architecture is enabled.
58    IMA Integrity measurement architecture is enabled.
59    IOSCHED More than one I/O scheduler is enabled.
60    IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61    IPV6 IPv6 support is enabled.
62    ISAPNP ISA PnP code is enabled.
63    ISDN Appropriate ISDN support is enabled.
64    JOY Appropriate joystick support is enabled.
65    KGDB Kernel debugger support is enabled.
66    KVM Kernel Virtual Machine support is enabled.
67    LIBATA Libata driver is enabled
68    LP Printer support is enabled.
69    LOOP Loopback device support is enabled.
70    M68k M68k architecture is enabled.
71            These options have more detailed description inside of
72            Documentation/m68k/kernel-options.txt.
73    MDA MDA console support is enabled.
74    MIPS MIPS architecture is enabled.
75    MOUSE Appropriate mouse support is enabled.
76    MSI Message Signaled Interrupts (PCI).
77    MTD MTD (Memory Technology Device) support is enabled.
78    NET Appropriate network support is enabled.
79    NUMA NUMA support is enabled.
80    NFS Appropriate NFS support is enabled.
81    OSS OSS sound support is enabled.
82    PV_OPS A paravirtualized kernel is enabled.
83    PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84    PARISC The PA-RISC architecture is enabled.
85    PCI PCI bus support is enabled.
86    PCIE PCI Express support is enabled.
87    PCMCIA The PCMCIA subsystem is enabled.
88    PNP Plug & Play support is enabled.
89    PPC PowerPC architecture is enabled.
90    PPT Parallel port support is enabled.
91    PS2 Appropriate PS/2 support is enabled.
92    RAM RAM disk support is enabled.
93    S390 S390 architecture is enabled.
94    SCSI Appropriate SCSI support is enabled.
95            A lot of drivers have their options described inside
96            the Documentation/scsi/ sub-directory.
97    SECURITY Different security models are enabled.
98    SELINUX SELinux support is enabled.
99    APPARMOR AppArmor support is enabled.
100    SERIAL Serial support is enabled.
101    SH SuperH architecture is enabled.
102    SMP The kernel is an SMP kernel.
103    SPARC Sparc architecture is enabled.
104    SWSUSP Software suspend (hibernation) is enabled.
105    SUSPEND System suspend states are enabled.
106    TPM TPM drivers are enabled.
107    TS Appropriate touchscreen support is enabled.
108    UMS USB Mass Storage support is enabled.
109    USB USB support is enabled.
110    USBHID USB Human Interface Device support is enabled.
111    V4L Video For Linux support is enabled.
112    VMMIO Driver for memory mapped virtio devices is enabled.
113    VGA The VGA console has been enabled.
114    VT Virtual terminal support is enabled.
115    WDT Watchdog support is enabled.
116    XT IBM PC/XT MFM hard disk support is enabled.
117    X86-32 X86-32, aka i386 architecture is enabled.
118    X86-64 X86-64 architecture is enabled.
119            More X86-64 boot options can be found in
120            Documentation/x86/x86_64/boot-options.txt .
121    X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122    XEN Xen support is enabled
123
124In addition, the following text indicates that the option:
125
126    BUGS= Relates to possible processor bugs on the said processor.
127    KNL Is a kernel start-up parameter.
128    BOOT Is a boot loader parameter.
129
130Parameters denoted with BOOT are actually interpreted by the boot
131loader, and have no meaning to the kernel directly.
132Do not modify the syntax of boot loader parameters without extreme
133need or coordination with <Documentation/x86/boot.txt>.
134
135There are also arch-specific kernel-parameters not documented here.
136See for example <Documentation/x86/x86_64/boot-options.txt>.
137
138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139a trailing = on the name of any parameter states that that parameter will
140be entered as an environment variable, whereas its absence indicates that
141it will appear as a kernel argument readable via /proc/cmdline by programs
142running once the system is up.
143
144The number of kernel parameters is not limited, but the length of the
145complete command line (parameters including spaces etc.) is limited to
146a fixed number of characters. This limit depends on the architecture
147and is between 256 and 4096 characters. It is defined in the file
148./include/asm/setup.h as COMMAND_LINE_SIZE.
149
150Finally, the [KMG] suffix is commonly described after a number of kernel
151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153bytes respectively. Such letter suffixes can also be entirely omitted.
154
155
156    acpi= [HW,ACPI,X86]
157            Advanced Configuration and Power Interface
158            Format: { force | off | strict | noirq | rsdt }
159            force -- enable ACPI if default was off
160            off -- disable ACPI if default was on
161            noirq -- do not use ACPI for IRQ routing
162            strict -- Be less tolerant of platforms that are not
163                strictly ACPI specification compliant.
164            rsdt -- prefer RSDT over (default) XSDT
165            copy_dsdt -- copy DSDT to memory
166
167            See also Documentation/power/runtime_pm.txt, pci=noacpi
168
169    acpi_rsdp= [ACPI,EFI,KEXEC]
170            Pass the RSDP address to the kernel, mostly used
171            on machines running EFI runtime service to boot the
172            second kernel for kdump.
173
174    acpi_apic_instance= [ACPI, IOAPIC]
175            Format: <int>
176            2: use 2nd APIC table, if available
177            1,0: use 1st APIC table
178            default: 0
179
180    acpi_backlight= [HW,ACPI]
181            acpi_backlight=vendor
182            acpi_backlight=video
183            If set to vendor, prefer vendor specific driver
184            (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185            of the ACPI video.ko driver.
186
187    acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188    acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
189            Format: <int>
190            CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191            debug output. Bits in debug_layer correspond to a
192            _COMPONENT in an ACPI source file, e.g.,
193                #define _COMPONENT ACPI_PCI_COMPONENT
194            Bits in debug_level correspond to a level in
195            ACPI_DEBUG_PRINT statements, e.g.,
196                ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197            The debug_level mask defaults to "info". See
198            Documentation/acpi/debug.txt for more information about
199            debug layers and levels.
200
201            Enable processor driver info messages:
202                acpi.debug_layer=0x20000000
203            Enable PCI/PCI interrupt routing info messages:
204                acpi.debug_layer=0x400000
205            Enable AML "Debug" output, i.e., stores to the Debug
206            object while interpreting AML:
207                acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208            Enable all messages related to ACPI hardware:
209                acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
210
211            Some values produce so much output that the system is
212            unusable. The "log_buf_len" parameter may be useful
213            if you need to capture more output.
214
215    acpi_irq_balance [HW,ACPI]
216            ACPI will balance active IRQs
217            default in APIC mode
218
219    acpi_irq_nobalance [HW,ACPI]
220            ACPI will not move active IRQs (default)
221            default in PIC mode
222
223    acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224            Format: <irq>,<irq>...
225
226    acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
227            use by PCI
228            Format: <irq>,<irq>...
229
230    acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
231
232    acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233            Format: To spoof as Windows 98: ="Microsoft Windows"
234
235    acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236            acpi_osi="string1" # add string1 -- only one string
237            acpi_osi="!string2" # remove built-in string2
238            acpi_osi= # disable all strings
239
240    acpi_pm_good [X86]
241            Override the pmtimer bug detection: force the kernel
242            to assume that this machine's pmtimer latches its value
243            and always returns good values.
244
245    acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246            Format: { level | edge | high | low }
247
248    acpi_serialize [HW,ACPI] force serialization of AML methods
249
250    acpi_skip_timer_override [HW,ACPI]
251            Recognize and ignore IRQ0/pin2 Interrupt Override.
252            For broken nForce2 BIOS resulting in XT-PIC timer.
253
254    acpi_sleep= [HW,ACPI] Sleep options
255            Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256                  old_ordering, nonvs, sci_force_enable }
257            See Documentation/power/video.txt for information on
258            s3_bios and s3_mode.
259            s3_beep is for debugging; it makes the PC's speaker beep
260            as soon as the kernel's real-mode entry point is called.
261            s4_nohwsig prevents ACPI hardware signature from being
262            used during resume from hibernation.
263            old_ordering causes the ACPI 1.0 ordering of the _PTS
264            control method, with respect to putting devices into
265            low power states, to be enforced (the ACPI 2.0 ordering
266            of _PTS is used by default).
267            nonvs prevents the kernel from saving/restoring the
268            ACPI NVS memory during suspend/hibernation and resume.
269            sci_force_enable causes the kernel to set SCI_EN directly
270            on resume from S1/S3 (which is against the ACPI spec,
271            but some broken systems don't work without it).
272
273    acpi_use_timer_override [HW,ACPI]
274            Use timer override. For some broken Nvidia NF5 boards
275            that require a timer override, but don't have HPET
276
277    acpi_enforce_resources= [ACPI]
278            { strict | lax | no }
279            Check for resource conflicts between native drivers
280            and ACPI OperationRegions (SystemIO and SystemMemory
281            only). IO ports and memory declared in ACPI might be
282            used by the ACPI subsystem in arbitrary AML code and
283            can interfere with legacy drivers.
284            strict (default): access to resources claimed by ACPI
285            is denied; legacy drivers trying to access reserved
286            resources will fail to bind to device using them.
287            lax: access to resources claimed by ACPI is allowed;
288            legacy drivers trying to access reserved resources
289            will bind successfully but a warning message is logged.
290            no: ACPI OperationRegions are not marked as reserved,
291            no further checks are performed.
292
293    add_efi_memmap [EFI; X86] Include EFI memory map in
294            kernel's map of available physical RAM.
295
296    agp= [AGP]
297            { off | try_unsupported }
298            off: disable AGP support
299            try_unsupported: try to drive unsupported chipsets
300                (may crash computer or cause data corruption)
301
302    ALSA [HW,ALSA]
303            See Documentation/sound/alsa/alsa-parameters.txt
304
305    alignment= [KNL,ARM]
306            Allow the default userspace alignment fault handler
307            behaviour to be specified. Bit 0 enables warnings,
308            bit 1 enables fixups, and bit 2 sends a segfault.
309
310    align_va_addr= [X86-64]
311            Align virtual addresses by clearing slice [14:12] when
312            allocating a VMA at process creation time. This option
313            gives you up to 3% performance improvement on AMD F15h
314            machines (where it is enabled by default) for a
315            CPU-intensive style benchmark, and it can vary highly in
316            a microbenchmark depending on workload and compiler.
317
318            32: only for 32-bit processes
319            64: only for 64-bit processes
320            on: enable for both 32- and 64-bit processes
321            off: disable for both 32- and 64-bit processes
322
323    amd_iommu= [HW,X86-64]
324            Pass parameters to the AMD IOMMU driver in the system.
325            Possible values are:
326            fullflush - enable flushing of IO/TLB entries when
327                    they are unmapped. Otherwise they are
328                    flushed before they will be reused, which
329                    is a lot of faster
330            off - do not initialize any AMD IOMMU found in
331                    the system
332            force_isolation - Force device isolation for all
333                      devices. The IOMMU driver is not
334                      allowed anymore to lift isolation
335                      requirements as needed. This option
336                      does not override iommu=pt
337
338    amd_iommu_dump= [HW,X86-64]
339            Enable AMD IOMMU driver option to dump the ACPI table
340            for AMD IOMMU. With this option enabled, AMD IOMMU
341            driver will print ACPI tables for AMD IOMMU during
342            IOMMU initialization.
343
344    amijoy.map= [HW,JOY] Amiga joystick support
345            Map of devices attached to JOY0DAT and JOY1DAT
346            Format: <a>,<b>
347            See also Documentation/input/joystick.txt
348
349    analog.map= [HW,JOY] Analog joystick and gamepad support
350            Specifies type or capabilities of an analog joystick
351            connected to one of 16 gameports
352            Format: <type1>,<type2>,..<type16>
353
354    apc= [HW,SPARC]
355            Power management functions (SPARCstation-4/5 + deriv.)
356            Format: noidle
357            Disable APC CPU standby support. SPARCstation-Fox does
358            not play well with APC CPU idle - disable it if you have
359            APC and your system crashes randomly.
360
361    apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362            Change the output verbosity whilst booting
363            Format: { quiet (default) | verbose | debug }
364            Change the amount of debugging information output
365            when initialising the APIC and IO-APIC components.
366
367    autoconf= [IPV6]
368            See Documentation/networking/ipv6.txt.
369
370    show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371            Limit apic dumping. The parameter defines the maximal
372            number of local apics being dumped. Also it is possible
373            to set it to "all" by meaning -- no limit here.
374            Format: { 1 (default) | 2 | ... | all }.
375            The parameter valid if only apic=debug or
376            apic=verbose is specified.
377            Example: apic=debug show_lapic=all
378
379    apm= [APM] Advanced Power Management
380            See header of arch/x86/kernel/apm_32.c.
381
382    arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383            Format: <io>,<irq>,<nodeID>
384
385    ataflop= [HW,M68k]
386
387    atarimouse= [HW,MOUSE] Atari Mouse
388
389    atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390            EzKey and similar keyboards
391
392    atkbd.reset= [HW] Reset keyboard during initialization
393
394    atkbd.set= [HW] Select keyboard code set
395            Format: <int> (2 = AT (default), 3 = PS/2)
396
397    atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
398            keyboards
399
400    atkbd.softraw= [HW] Choose between synthetic and real raw mode
401            Format: <bool> (0 = real, 1 = synthetic (default))
402
403    atkbd.softrepeat= [HW]
404            Use software keyboard repeat
405
406    baycom_epp= [HW,AX25]
407            Format: <io>,<mode>
408
409    baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
410            Format: <io>,<mode>
411            See header of drivers/net/hamradio/baycom_par.c.
412
413    baycom_ser_fdx= [HW,AX25]
414            BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415            Format: <io>,<irq>,<mode>[,<baud>]
416            See header of drivers/net/hamradio/baycom_ser_fdx.c.
417
418    baycom_ser_hdx= [HW,AX25]
419            BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420            Format: <io>,<irq>,<mode>
421            See header of drivers/net/hamradio/baycom_ser_hdx.c.
422
423    boot_delay= Milliseconds to delay each printk during boot.
424            Values larger than 10 seconds (10000) are changed to
425            no delay (0).
426            Format: integer
427
428    bootmem_debug [KNL] Enable bootmem allocator debug messages.
429
430    bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431    bttv.radio= Most important insmod options are available as
432            kernel args too.
433    bttv.pll= See Documentation/video4linux/bttv/Insmod-options
434    bttv.tuner=
435
436    bulk_remove=off [PPC] This parameter disables the use of the pSeries
437            firmware feature for flushing multiple hpte entries
438            at a time.
439
440    c101= [NET] Moxa C101 synchronous serial card
441
442    cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443            Sometimes CPU hardware bugs make them report the cache
444            size incorrectly. The kernel will attempt work arounds
445            to fix known problems, but for some CPUs it is not
446            possible to determine what the correct size should be.
447            This option provides an override for these situations.
448
449    capability.disable=
450            [SECURITY] Disable capabilities. This would normally
451            be used only if an alternative security model is to be
452            configured. Potentially dangerous and should only be
453            used if you are entirely sure of the consequences.
454
455    ccw_timeout_log [S390]
456            See Documentation/s390/CommonIO for details.
457
458    cgroup_disable= [KNL] Disable a particular controller
459            Format: {name of the controller(s) to disable}
460                {Currently supported controllers - "memory"}
461
462    checkreqprot [SELINUX] Set initial checkreqprot flag value.
463            Format: { "0" | "1" }
464            See security/selinux/Kconfig help text.
465            0 -- check protection applied by kernel (includes
466                any implied execute protection).
467            1 -- check protection requested by application.
468            Default value is set via a kernel config option.
469            Value can be changed at runtime via
470                /selinux/checkreqprot.
471
472    cio_ignore= [S390]
473            See Documentation/s390/CommonIO for details.
474
475    clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
476            [Deprecated]
477            Forces specified clocksource (if available) to be used
478            when calculating gettimeofday(). If specified
479            clocksource is not available, it defaults to PIT.
480            Format: { pit | tsc | cyclone | pmtmr }
481
482    clocksource= Override the default clocksource
483            Format: <string>
484            Override the default clocksource and use the clocksource
485            with the name specified.
486            Some clocksource names to choose from, depending on
487            the platform:
488            [all] jiffies (this is the base, fallback clocksource)
489            [ACPI] acpi_pm
490            [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
491                pxa_timer,timer3,32k_counter,timer0_1
492            [AVR32] avr32
493            [X86-32] pit,hpet,tsc;
494                scx200_hrt on Geode; cyclone on IBM x440
495            [MIPS] MIPS
496            [PARISC] cr16
497            [S390] tod
498            [SH] SuperH
499            [SPARC64] tick
500            [X86-64] hpet,tsc
501
502    clearcpuid=BITNUM [X86]
503            Disable CPUID feature X for the kernel. See
504            arch/x86/include/asm/cpufeature.h for the valid bit
505            numbers. Note the Linux specific bits are not necessarily
506            stable over kernel options, but the vendor specific
507            ones should be.
508            Also note that user programs calling CPUID directly
509            or using the feature without checking anything
510            will still see it. This just prevents it from
511            being used by the kernel or shown in /proc/cpuinfo.
512            Also note the kernel might malfunction if you disable
513            some critical bits.
514
515    cma=nn[MG] [ARM,KNL]
516            Sets the size of kernel global memory area for contiguous
517            memory allocations. For more information, see
518            include/linux/dma-contiguous.h
519
520    cmo_free_hint= [PPC] Format: { yes | no }
521            Specify whether pages are marked as being inactive
522            when they are freed. This is used in CMO environments
523            to determine OS memory pressure for page stealing by
524            a hypervisor.
525            Default: yes
526
527    coherent_pool=nn[KMG] [ARM,KNL]
528            Sets the size of memory pool for coherent, atomic dma
529            allocations, by default set to 256K.
530
531    code_bytes [X86] How many bytes of object code to print
532            in an oops report.
533            Range: 0 - 8192
534            Default: 64
535
536    com20020= [HW,NET] ARCnet - COM20020 chipset
537            Format:
538            <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
539
540    com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
541            Format: <io>[,<irq>]
542
543    com90xx= [HW,NET]
544            ARCnet - COM90xx chipset (memory-mapped buffers)
545            Format: <io>[,<irq>[,<memstart>]]
546
547    condev= [HW,S390] console device
548    conmode=
549
550    console= [KNL] Output console device and options.
551
552        tty<n> Use the virtual console device <n>.
553
554        ttyS<n>[,options]
555        ttyUSB0[,options]
556            Use the specified serial port. The options are of
557            the form "bbbbpnf", where "bbbb" is the baud rate,
558            "p" is parity ("n", "o", or "e"), "n" is number of
559            bits, and "f" is flow control ("r" for RTS or
560            omit it). Default is "9600n8".
561
562            See Documentation/serial-console.txt for more
563            information. See
564            Documentation/networking/netconsole.txt for an
565            alternative.
566
567        uart[8250],io,<addr>[,options]
568        uart[8250],mmio,<addr>[,options]
569            Start an early, polled-mode console on the 8250/16550
570            UART at the specified I/O port or MMIO address,
571            switching to the matching ttyS device later. The
572            options are the same as for ttyS, above.
573
574                If the device connected to the port is not a TTY but a braille
575                device, prepend "brl," before the device type, for instance
576            console=brl,ttyS0
577        For now, only VisioBraille is supported.
578
579    consoleblank= [KNL] The console blank (screen saver) timeout in
580            seconds. Defaults to 10*60 = 10mins. A value of 0
581            disables the blank timer.
582
583    coredump_filter=
584            [KNL] Change the default value for
585            /proc/<pid>/coredump_filter.
586            See also Documentation/filesystems/proc.txt.
587
588    cpuidle.off=1 [CPU_IDLE]
589            disable the cpuidle sub-system
590
591    cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
592            Format:
593            <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
594
595    crashkernel=size[KMG][@offset[KMG]]
596            [KNL] Using kexec, Linux can switch to a 'crash kernel'
597            upon panic. This parameter reserves the physical
598            memory region [offset, offset + size] for that kernel
599            image. If '@offset' is omitted, then a suitable offset
600            is selected automatically. Check
601            Documentation/kdump/kdump.txt for further details.
602
603    crashkernel=range1:size1[,range2:size2,...][@offset]
604            [KNL] Same as above, but depends on the memory
605            in the running system. The syntax of range is
606            start-[end] where start and end are both
607            a memory unit (amount[KMG]). See also
608            Documentation/kdump/kdump.txt for an example.
609
610    cs89x0_dma= [HW,NET]
611            Format: <dma>
612
613    cs89x0_media= [HW,NET]
614            Format: { rj45 | aui | bnc }
615
616    dasd= [HW,NET]
617            See header of drivers/s390/block/dasd_devmap.c.
618
619    db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
620            (one device per port)
621            Format: <port#>,<type>
622            See also Documentation/input/joystick-parport.txt
623
624    ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
625            time. See Documentation/dynamic-debug-howto.txt for
626            details. Deprecated, see dyndbg.
627
628    debug [KNL] Enable kernel debugging (events log level).
629
630    debug_locks_verbose=
631            [KNL] verbose self-tests
632            Format=<0|1>
633            Print debugging info while doing the locking API
634            self-tests.
635            We default to 0 (no extra messages), setting it to
636            1 will print _a lot_ more information - normally
637            only useful to kernel developers.
638
639    debug_objects [KNL] Enable object debugging
640
641    no_debug_objects
642            [KNL] Disable object debugging
643
644    debug_guardpage_minorder=
645            [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
646            parameter allows control of the order of pages that will
647            be intentionally kept free (and hence protected) by the
648            buddy allocator. Bigger value increase the probability
649            of catching random memory corruption, but reduce the
650            amount of memory for normal system use. The maximum
651            possible value is MAX_ORDER/2. Setting this parameter
652            to 1 or 2 should be enough to identify most random
653            memory corruption problems caused by bugs in kernel or
654            driver code when a CPU writes to (or reads from) a
655            random memory location. Note that there exists a class
656            of memory corruptions problems caused by buggy H/W or
657            F/W or by drivers badly programing DMA (basically when
658            memory is written at bus level and the CPU MMU is
659            bypassed) which are not detectable by
660            CONFIG_DEBUG_PAGEALLOC, hence this option will not help
661            tracking down these problems.
662
663    debugpat [X86] Enable PAT debugging
664
665    decnet.addr= [HW,NET]
666            Format: <area>[,<node>]
667            See also Documentation/networking/decnet.txt.
668
669    default_hugepagesz=
670            [same as hugepagesz=] The size of the default
671            HugeTLB page size. This is the size represented by
672            the legacy /proc/ hugepages APIs, used for SHM, and
673            default size when mounting hugetlbfs filesystems.
674            Defaults to the default architecture's huge page size
675            if not specified.
676
677    dhash_entries= [KNL]
678            Set number of hash buckets for dentry cache.
679
680    digi= [HW,SERIAL]
681            IO parameters + enable/disable command.
682
683    digiepca= [HW,SERIAL]
684            See drivers/char/README.epca and
685            Documentation/serial/digiepca.txt.
686
687    disable= [IPV6]
688            See Documentation/networking/ipv6.txt.
689
690    disable_ddw [PPC/PSERIES]
691            Disable Dynamic DMA Window support. Use this if
692            to workaround buggy firmware.
693
694    disable_ipv6= [IPV6]
695            See Documentation/networking/ipv6.txt.
696
697    disable_mtrr_cleanup [X86]
698            The kernel tries to adjust MTRR layout from continuous
699            to discrete, to make X server driver able to add WB
700            entry later. This parameter disables that.
701
702    disable_mtrr_trim [X86, Intel and AMD only]
703            By default the kernel will trim any uncacheable
704            memory out of your available memory pool based on
705            MTRR settings. This parameter disables that behavior,
706            possibly causing your machine to run very slowly.
707
708    disable_timer_pin_1 [X86]
709            Disable PIN 1 of APIC timer
710            Can be useful to work around chipset bugs.
711
712    dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
713            this option disables the debugging code at boot.
714
715    dma_debug_entries=<number>
716            This option allows to tune the number of preallocated
717            entries for DMA-API debugging code. One entry is
718            required per DMA-API allocation. Use this if the
719            DMA-API debugging code disables itself because the
720            architectural default is too low.
721
722    dma_debug_driver=<driver_name>
723            With this option the DMA-API debugging driver
724            filter feature can be enabled at boot time. Just
725            pass the driver to filter for as the parameter.
726            The filter can be disabled or changed to another
727            driver later using sysfs.
728
729    drm_kms_helper.edid_firmware=[<connector>:]<file>
730            Broken monitors, graphic adapters and KVMs may
731            send no or incorrect EDID data sets. This parameter
732            allows to specify an EDID data set in the
733            /lib/firmware directory that is used instead.
734            Generic built-in EDID data sets are used, if one of
735            edid/1024x768.bin, edid/1280x1024.bin,
736            edid/1680x1050.bin, or edid/1920x1080.bin is given
737            and no file with the same name exists. Details and
738            instructions how to build your own EDID data are
739            available in Documentation/EDID/HOWTO.txt. An EDID
740            data set will only be used for a particular connector,
741            if its name and a colon are prepended to the EDID
742            name.
743
744    dscc4.setup= [NET]
745
746    dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
747    module.dyndbg[="val"]
748            Enable debug messages at boot time. See
749            Documentation/dynamic-debug-howto.txt for details.
750
751    earlycon= [KNL] Output early console device and options.
752        uart[8250],io,<addr>[,options]
753        uart[8250],mmio,<addr>[,options]
754        uart[8250],mmio32,<addr>[,options]
755            Start an early, polled-mode console on the 8250/16550
756            UART at the specified I/O port or MMIO address.
757            MMIO inter-register address stride is either 8-bit
758            (mmio) or 32-bit (mmio32).
759            The options are the same as for ttyS, above.
760
761    earlyprintk= [X86,SH,BLACKFIN]
762            earlyprintk=vga
763            earlyprintk=serial[,ttySn[,baudrate]]
764            earlyprintk=ttySn[,baudrate]
765            earlyprintk=dbgp[debugController#]
766
767            Append ",keep" to not disable it when the real console
768            takes over.
769
770            Only vga or serial or usb debug port at a time.
771
772            Currently only ttyS0 and ttyS1 are supported.
773
774            Interaction with the standard serial driver is not
775            very good.
776
777            The VGA output is eventually overwritten by the real
778            console.
779
780    ekgdboc= [X86,KGDB] Allow early kernel console debugging
781            ekgdboc=kbd
782
783            This is designed to be used in conjunction with
784            the boot argument: earlyprintk=vga
785
786    edd= [EDD]
787            Format: {"off" | "on" | "skip[mbr]"}
788
789    eisa_irq_edge= [PARISC,HW]
790            See header of drivers/parisc/eisa.c.
791
792    elanfreq= [X86-32]
793            See comment before function elanfreq_setup() in
794            arch/x86/kernel/cpu/cpufreq/elanfreq.c.
795
796    elevator= [IOSCHED]
797            Format: {"cfq" | "deadline" | "noop"}
798            See Documentation/block/cfq-iosched.txt and
799            Documentation/block/deadline-iosched.txt for details.
800
801    elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
802            Specifies physical address of start of kernel core
803            image elf header and optionally the size. Generally
804            kexec loader will pass this option to capture kernel.
805            See Documentation/kdump/kdump.txt for details.
806
807    enable_mtrr_cleanup [X86]
808            The kernel tries to adjust MTRR layout from continuous
809            to discrete, to make X server driver able to add WB
810            entry later. This parameter enables that.
811
812    enable_timer_pin_1 [X86]
813            Enable PIN 1 of APIC timer
814            Can be useful to work around chipset bugs
815            (in particular on some ATI chipsets).
816            The kernel tries to set a reasonable default.
817
818    enforcing [SELINUX] Set initial enforcing status.
819            Format: {"0" | "1"}
820            See security/selinux/Kconfig help text.
821            0 -- permissive (log only, no denials).
822            1 -- enforcing (deny and log).
823            Default value is 0.
824            Value can be changed at runtime via /selinux/enforce.
825
826    erst_disable [ACPI]
827            Disable Error Record Serialization Table (ERST)
828            support.
829
830    ether= [HW,NET] Ethernet cards parameters
831            This option is obsoleted by the "netdev=" option, which
832            has equivalent usage. See its documentation for details.
833
834    evm= [EVM]
835            Format: { "fix" }
836            Permit 'security.evm' to be updated regardless of
837            current integrity status.
838
839    failslab=
840    fail_page_alloc=
841    fail_make_request=[KNL]
842            General fault injection mechanism.
843            Format: <interval>,<probability>,<space>,<times>
844            See also Documentation/fault-injection/.
845
846    floppy= [HW]
847            See Documentation/blockdev/floppy.txt.
848
849    force_pal_cache_flush
850            [IA-64] Avoid check_sal_cache_flush which may hang on
851            buggy SAL_CACHE_FLUSH implementations. Using this
852            parameter will force ia64_sal_cache_flush to call
853            ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
854
855    ftrace=[tracer]
856            [FTRACE] will set and start the specified tracer
857            as early as possible in order to facilitate early
858            boot debugging.
859
860    ftrace_dump_on_oops[=orig_cpu]
861            [FTRACE] will dump the trace buffers on oops.
862            If no parameter is passed, ftrace will dump
863            buffers of all CPUs, but if you pass orig_cpu, it will
864            dump only the buffer of the CPU that triggered the
865            oops.
866
867    ftrace_filter=[function-list]
868            [FTRACE] Limit the functions traced by the function
869            tracer at boot up. function-list is a comma separated
870            list of functions. This list can be changed at run
871            time by the set_ftrace_filter file in the debugfs
872            tracing directory.
873
874    ftrace_notrace=[function-list]
875            [FTRACE] Do not trace the functions specified in
876            function-list. This list can be changed at run time
877            by the set_ftrace_notrace file in the debugfs
878            tracing directory.
879
880    ftrace_graph_filter=[function-list]
881            [FTRACE] Limit the top level callers functions traced
882            by the function graph tracer at boot up.
883            function-list is a comma separated list of functions
884            that can be changed at run time by the
885            set_graph_function file in the debugfs tracing directory.
886
887    gamecon.map[2|3]=
888            [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
889            support via parallel port (up to 5 devices per port)
890            Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
891            See also Documentation/input/joystick-parport.txt
892
893    gamma= [HW,DRM]
894
895    gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
896            Format: off | on
897            default: on
898
899    gcov_persist= [GCOV] When non-zero (default), profiling data for
900            kernel modules is saved and remains accessible via
901            debugfs, even when the module is unloaded/reloaded.
902            When zero, profiling data is discarded and associated
903            debugfs files are removed at module unload time.
904
905    gpt [EFI] Forces disk with valid GPT signature but
906            invalid Protective MBR to be treated as GPT.
907
908    hashdist= [KNL,NUMA] Large hashes allocated during boot
909            are distributed across NUMA nodes. Defaults on
910            for 64-bit NUMA, off otherwise.
911            Format: 0 | 1 (for off | on)
912
913    hcl= [IA-64] SGI's Hardware Graph compatibility layer
914
915    hd= [EIDE] (E)IDE hard drive subsystem geometry
916            Format: <cyl>,<head>,<sect>
917
918    hest_disable [ACPI]
919            Disable Hardware Error Source Table (HEST) support;
920            corresponding firmware-first mode error processing
921            logic will be disabled.
922
923    highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
924            size of <nn>. This works even on boxes that have no
925            highmem otherwise. This also works to reduce highmem
926            size on bigger boxes.
927
928    highres= [KNL] Enable/disable high resolution timer mode.
929            Valid parameters: "on", "off"
930            Default: "on"
931
932    hisax= [HW,ISDN]
933            See Documentation/isdn/README.HiSax.
934
935    hlt [BUGS=ARM,SH]
936
937    hpet= [X86-32,HPET] option to control HPET usage
938            Format: { enable (default) | disable | force |
939                verbose }
940            disable: disable HPET and use PIT instead
941            force: allow force enabled of undocumented chips (ICH4,
942                VIA, nVidia)
943            verbose: show contents of HPET registers during setup
944
945    hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
946    hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
947            On x86-64 and powerpc, this option can be specified
948            multiple times interleaved with hugepages= to reserve
949            huge pages of different sizes. Valid pages sizes on
950            x86-64 are 2M (when the CPU supports "pse") and 1G
951            (when the CPU supports the "pdpe1gb" cpuinfo flag)
952            Note that 1GB pages can only be allocated at boot time
953            using hugepages= and not freed afterwards.
954
955    hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
956                   terminal devices. Valid values: 0..8
957    hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
958                   If specified, z/VM IUCV HVC accepts connections
959                   from listed z/VM user IDs only.
960
961    keep_bootcon [KNL]
962            Do not unregister boot console at start. This is only
963            useful for debugging when something happens in the window
964            between unregistering the boot console and initializing
965            the real console.
966
967    i2c_bus= [HW] Override the default board specific I2C bus speed
968                 or register an additional I2C bus that is not
969                 registered from board initialization code.
970                 Format:
971                 <bus_id>,<clkrate>
972
973    i8042.debug [HW] Toggle i8042 debug mode
974    i8042.direct [HW] Put keyboard port into non-translated mode
975    i8042.dumbkbd [HW] Pretend that controller can only read data from
976                 keyboard and cannot control its state
977                 (Don't attempt to blink the leds)
978    i8042.noaux [HW] Don't check for auxiliary (== mouse) port
979    i8042.nokbd [HW] Don't check/create keyboard port
980    i8042.noloop [HW] Disable the AUX Loopback command while probing
981                 for the AUX port
982    i8042.nomux [HW] Don't check presence of an active multiplexing
983                 controller
984    i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
985                 controllers
986    i8042.notimeout [HW] Ignore timeout condition signalled by controller
987    i8042.reset [HW] Reset the controller during init and cleanup
988    i8042.unlock [HW] Unlock (ignore) the keylock
989
990    i810= [HW,DRM]
991
992    i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
993            indicates that the driver is running on unsupported
994            hardware.
995    i8k.force [HW] Activate i8k driver even if SMM BIOS signature
996            does not match list of supported models.
997    i8k.power_status
998            [HW] Report power status in /proc/i8k
999            (disabled by default)
1000    i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1001            capability is set.
1002
1003    i915.invert_brightness=
1004            [DRM] Invert the sense of the variable that is used to
1005            set the brightness of the panel backlight. Normally a
1006            brightness value of 0 indicates backlight switched off,
1007            and the maximum of the brightness value sets the backlight
1008            to maximum brightness. If this parameter is set to 0
1009            (default) and the machine requires it, or this parameter
1010            is set to 1, a brightness value of 0 sets the backlight
1011            to maximum brightness, and the maximum of the brightness
1012            value switches the backlight off.
1013            -1 -- never invert brightness
1014             0 -- machine default
1015             1 -- force brightness inversion
1016
1017    icn= [HW,ISDN]
1018            Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1019
1020    ide-core.nodma= [HW] (E)IDE subsystem
1021            Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1022            .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1023            .cdrom .chs .ignore_cable are additional options
1024            See Documentation/ide/ide.txt.
1025
1026    ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1027            Claim all unknown PCI IDE storage controllers.
1028
1029    idle= [X86]
1030            Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1031            Poll forces a polling idle loop that can slightly
1032            improve the performance of waking up a idle CPU, but
1033            will use a lot of power and make the system run hot.
1034            Not recommended.
1035            idle=mwait: On systems which support MONITOR/MWAIT but
1036            the kernel chose to not use it because it doesn't save
1037            as much power as a normal idle loop, use the
1038            MONITOR/MWAIT idle loop anyways. Performance should be
1039            the same as idle=poll.
1040            idle=halt: Halt is forced to be used for CPU idle.
1041            In such case C2/C3 won't be used again.
1042            idle=nomwait: Disable mwait for CPU C-states
1043
1044    ignore_loglevel [KNL]
1045            Ignore loglevel setting - this will print /all/
1046            kernel messages to the console. Useful for debugging.
1047            We also add it as printk module parameter, so users
1048            could change it dynamically, usually by
1049            /sys/module/printk/parameters/ignore_loglevel.
1050
1051    ihash_entries= [KNL]
1052            Set number of hash buckets for inode cache.
1053
1054    ima_audit= [IMA]
1055            Format: { "0" | "1" }
1056            0 -- integrity auditing messages. (Default)
1057            1 -- enable informational integrity auditing messages.
1058
1059    ima_hash= [IMA]
1060            Format: { "sha1" | "md5" }
1061            default: "sha1"
1062
1063    ima_tcb [IMA]
1064            Load a policy which meets the needs of the Trusted
1065            Computing Base. This means IMA will measure all
1066            programs exec'd, files mmap'd for exec, and all files
1067            opened for read by uid=0.
1068
1069    init= [KNL]
1070            Format: <full_path>
1071            Run specified binary instead of /sbin/init as init
1072            process.
1073
1074    initcall_debug [KNL] Trace initcalls as they are executed. Useful
1075            for working out where the kernel is dying during
1076            startup.
1077
1078    initrd= [BOOT] Specify the location of the initial ramdisk
1079
1080    inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1081            Format: <irq>
1082
1083    intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1084        on
1085            Enable intel iommu driver.
1086        off
1087            Disable intel iommu driver.
1088        igfx_off [Default Off]
1089            By default, gfx is mapped as normal device. If a gfx
1090            device has a dedicated DMAR unit, the DMAR unit is
1091            bypassed by not enabling DMAR with this option. In
1092            this case, gfx device will use physical address for
1093            DMA.
1094        forcedac [x86_64]
1095            With this option iommu will not optimize to look
1096            for io virtual address below 32-bit forcing dual
1097            address cycle on pci bus for cards supporting greater
1098            than 32-bit addressing. The default is to look
1099            for translation below 32-bit and if not available
1100            then look in the higher range.
1101        strict [Default Off]
1102            With this option on every unmap_single operation will
1103            result in a hardware IOTLB flush operation as opposed
1104            to batching them for performance.
1105        sp_off [Default Off]
1106            By default, super page will be supported if Intel IOMMU
1107            has the capability. With this option, super page will
1108            not be supported.
1109
1110    intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1111            0 disables intel_idle and fall back on acpi_idle.
1112            1 to 6 specify maximum depth of C-state.
1113
1114    intremap= [X86-64, Intel-IOMMU]
1115            on enable Interrupt Remapping (default)
1116            off disable Interrupt Remapping
1117            nosid disable Source ID checking
1118            no_x2apic_optout
1119                BIOS x2APIC opt-out request will be ignored
1120
1121    iomem= Disable strict checking of access to MMIO memory
1122        strict regions from userspace.
1123        relaxed
1124
1125    iommu= [x86]
1126        off
1127        force
1128        noforce
1129        biomerge
1130        panic
1131        nopanic
1132        merge
1133        nomerge
1134        forcesac
1135        soft
1136        pt [x86, IA-64]
1137
1138
1139    io7= [HW] IO7 for Marvel based alpha systems
1140            See comment before marvel_specify_io7 in
1141            arch/alpha/kernel/core_marvel.c.
1142
1143    io_delay= [X86] I/O delay method
1144        0x80
1145            Standard port 0x80 based delay
1146        0xed
1147            Alternate port 0xed based delay (needed on some systems)
1148        udelay
1149            Simple two microseconds delay
1150        none
1151            No delay
1152
1153    ip= [IP_PNP]
1154            See Documentation/filesystems/nfs/nfsroot.txt.
1155
1156    ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1157            See comment before ip2_setup() in
1158            drivers/char/ip2/ip2base.c.
1159
1160    irqfixup [HW]
1161            When an interrupt is not handled search all handlers
1162            for it. Intended to get systems with badly broken
1163            firmware running.
1164
1165    irqpoll [HW]
1166            When an interrupt is not handled search all handlers
1167            for it. Also check all handlers each timer
1168            interrupt. Intended to get systems with badly broken
1169            firmware running.
1170
1171    isapnp= [ISAPNP]
1172            Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1173
1174    isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1175            Format:
1176            <cpu number>,...,<cpu number>
1177            or
1178            <cpu number>-<cpu number>
1179            (must be a positive range in ascending order)
1180            or a mixture
1181            <cpu number>,...,<cpu number>-<cpu number>
1182
1183            This option can be used to specify one or more CPUs
1184            to isolate from the general SMP balancing and scheduling
1185            algorithms. You can move a process onto or off an
1186            "isolated" CPU via the CPU affinity syscalls or cpuset.
1187            <cpu number> begins at 0 and the maximum value is
1188            "number of CPUs in system - 1".
1189
1190            This option is the preferred way to isolate CPUs. The
1191            alternative -- manually setting the CPU mask of all
1192            tasks in the system -- can cause problems and
1193            suboptimal load balancer performance.
1194
1195    iucv= [HW,NET]
1196
1197    js= [HW,JOY] Analog joystick
1198            See Documentation/input/joystick.txt.
1199
1200    keepinitrd [HW,ARM]
1201
1202    kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1203            specifies the amount of memory usable by the kernel
1204            for non-movable allocations. The requested amount is
1205            spread evenly throughout all nodes in the system. The
1206            remaining memory in each node is used for Movable
1207            pages. In the event, a node is too small to have both
1208            kernelcore and Movable pages, kernelcore pages will
1209            take priority and other nodes will have a larger number
1210            of kernelcore pages. The Movable zone is used for the
1211            allocation of pages that may be reclaimed or moved
1212            by the page migration subsystem. This means that
1213            HugeTLB pages may not be allocated from this zone.
1214            Note that allocations like PTEs-from-HighMem still
1215            use the HighMem zone if it exists, and the Normal
1216            zone if it does not.
1217
1218    kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1219            Format: <Controller#>[,poll interval]
1220            The controller # is the number of the ehci usb debug
1221            port as it is probed via PCI. The poll interval is
1222            optional and is the number seconds in between
1223            each poll cycle to the debug port in case you need
1224            the functionality for interrupting the kernel with
1225            gdb or control-c on the dbgp connection. When
1226            not using this parameter you use sysrq-g to break into
1227            the kernel debugger.
1228
1229    kgdboc= [KGDB,HW] kgdb over consoles.
1230            Requires a tty driver that supports console polling,
1231            or a supported polling keyboard driver (non-usb).
1232             Serial only format: <serial_device>[,baud]
1233             keyboard only format: kbd
1234             keyboard and serial format: kbd,<serial_device>[,baud]
1235            Optional Kernel mode setting:
1236             kms, kbd format: kms,kbd
1237             kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1238
1239    kgdbwait [KGDB] Stop kernel execution and enter the
1240            kernel debugger at the earliest opportunity.
1241
1242    kmac= [MIPS] korina ethernet MAC address.
1243            Configure the RouterBoard 532 series on-chip
1244            Ethernet adapter MAC address.
1245
1246    kmemleak= [KNL] Boot-time kmemleak enable/disable
1247            Valid arguments: on, off
1248            Default: on
1249
1250    kstack=N [X86] Print N words from the kernel stack
1251            in oops dumps.
1252
1253    kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1254            Default is 0 (don't ignore, but inject #GP)
1255
1256    kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1257            KVM MMU at runtime.
1258            Default is 0 (off)
1259
1260    kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1261            Default is 1 (enabled)
1262
1263    kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1264            for all guests.
1265            Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1266
1267    kvm-intel.ept= [KVM,Intel] Disable extended page tables
1268            (virtualized MMU) support on capable Intel chips.
1269            Default is 1 (enabled)
1270
1271    kvm-intel.emulate_invalid_guest_state=
1272            [KVM,Intel] Enable emulation of invalid guest states
1273            Default is 0 (disabled)
1274
1275    kvm-intel.flexpriority=
1276            [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1277            Default is 1 (enabled)
1278
1279    kvm-intel.nested=
1280            [KVM,Intel] Enable VMX nesting (nVMX).
1281            Default is 0 (disabled)
1282
1283    kvm-intel.unrestricted_guest=
1284            [KVM,Intel] Disable unrestricted guest feature
1285            (virtualized real and unpaged mode) on capable
1286            Intel chips. Default is 1 (enabled)
1287
1288    kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1289            feature (tagged TLBs) on capable Intel chips.
1290            Default is 1 (enabled)
1291
1292    l2cr= [PPC]
1293
1294    l3cr= [PPC]
1295
1296    lapic [X86-32,APIC] Enable the local APIC even if BIOS
1297            disabled it.
1298
1299    lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1300            in C2 power state.
1301
1302    libata.dma= [LIBATA] DMA control
1303            libata.dma=0 Disable all PATA and SATA DMA
1304            libata.dma=1 PATA and SATA Disk DMA only
1305            libata.dma=2 ATAPI (CDROM) DMA only
1306            libata.dma=4 Compact Flash DMA only
1307            Combinations also work, so libata.dma=3 enables DMA
1308            for disks and CDROMs, but not CFs.
1309
1310    libata.ignore_hpa= [LIBATA] Ignore HPA limit
1311            libata.ignore_hpa=0 keep BIOS limits (default)
1312            libata.ignore_hpa=1 ignore limits, using full disk
1313
1314    libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1315            when set.
1316            Format: <int>
1317
1318    libata.force= [LIBATA] Force configurations. The format is comma
1319            separated list of "[ID:]VAL" where ID is
1320            PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1321            matching port, link or device. Basically, it matches
1322            the ATA ID string printed on console by libata. If
1323            the whole ID part is omitted, the last PORT and DEVICE
1324            values are used. If ID hasn't been specified yet, the
1325            configuration applies to all ports, links and devices.
1326
1327            If only DEVICE is omitted, the parameter applies to
1328            the port and all links and devices behind it. DEVICE
1329            number of 0 either selects the first device or the
1330            first fan-out link behind PMP device. It does not
1331            select the host link. DEVICE number of 15 selects the
1332            host link and device attached to it.
1333
1334            The VAL specifies the configuration to force. As long
1335            as there's no ambiguity shortcut notation is allowed.
1336            For example, both 1.5 and 1.5G would work for 1.5Gbps.
1337            The following configurations can be forced.
1338
1339            * Cable type: 40c, 80c, short40c, unk, ign or sata.
1340              Any ID with matching PORT is used.
1341
1342            * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1343
1344            * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1345              udma[/][16,25,33,44,66,100,133] notation is also
1346              allowed.
1347
1348            * [no]ncq: Turn on or off NCQ.
1349
1350            * nohrst, nosrst, norst: suppress hard, soft
1351                          and both resets.
1352
1353            * dump_id: dump IDENTIFY data.
1354
1355            If there are multiple matching configurations changing
1356            the same attribute, the last one is used.
1357
1358    memblock=debug [KNL] Enable memblock debug messages.
1359
1360    load_ramdisk= [RAM] List of ramdisks to load from floppy
1361            See Documentation/blockdev/ramdisk.txt.
1362
1363    lockd.nlm_grace_period=P [NFS] Assign grace period.
1364            Format: <integer>
1365
1366    lockd.nlm_tcpport=N [NFS] Assign TCP port.
1367            Format: <integer>
1368
1369    lockd.nlm_timeout=T [NFS] Assign timeout value.
1370            Format: <integer>
1371
1372    lockd.nlm_udpport=M [NFS] Assign UDP port.
1373            Format: <integer>
1374
1375    logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1376            Format: <irq>
1377
1378    loglevel= All Kernel Messages with a loglevel smaller than the
1379            console loglevel will be printed to the console. It can
1380            also be changed with klogd or other programs. The
1381            loglevels are defined as follows:
1382
1383            0 (KERN_EMERG) system is unusable
1384            1 (KERN_ALERT) action must be taken immediately
1385            2 (KERN_CRIT) critical conditions
1386            3 (KERN_ERR) error conditions
1387            4 (KERN_WARNING) warning conditions
1388            5 (KERN_NOTICE) normal but significant condition
1389            6 (KERN_INFO) informational
1390            7 (KERN_DEBUG) debug-level messages
1391
1392    log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1393            in bytes. n must be a power of two. The default
1394            size is set in the kernel config file.
1395
1396    logo.nologo [FB] Disables display of the built-in Linux logo.
1397            This may be used to provide more screen space for
1398            kernel log messages and is useful when debugging
1399            kernel boot problems.
1400
1401    lp=0 [LP] Specify parallel ports to use, e.g,
1402    lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1403    lp=reset first parallel port). 'lp=0' disables the
1404    lp=auto printer driver. 'lp=reset' (which can be
1405                specified in addition to the ports) causes
1406                attached printers to be reset. Using
1407                lp=port1,port2,... specifies the parallel ports
1408                to associate lp devices with, starting with
1409                lp0. A port specification may be 'none' to skip
1410                that lp device, or a parport name such as
1411                'parport0'. Specifying 'lp=auto' instead of a
1412                port specification list means that device IDs
1413                from each port should be examined, to see if
1414                an IEEE 1284-compliant printer is attached; if
1415                so, the driver will manage that printer.
1416                See also header of drivers/char/lp.c.
1417
1418    lpj=n [KNL]
1419            Sets loops_per_jiffy to given constant, thus avoiding
1420            time-consuming boot-time autodetection (up to 250 ms per
1421            CPU). 0 enables autodetection (default). To determine
1422            the correct value for your kernel, boot with normal
1423            autodetection and see what value is printed. Note that
1424            on SMP systems the preset will be applied to all CPUs,
1425            which is likely to cause problems if your CPUs need
1426            significantly divergent settings. An incorrect value
1427            will cause delays in the kernel to be wrong, leading to
1428            unpredictable I/O errors and other breakage. Although
1429            unlikely, in the extreme case this might damage your
1430            hardware.
1431
1432    ltpc= [NET]
1433            Format: <io>,<irq>,<dma>
1434
1435    machvec= [IA-64] Force the use of a particular machine-vector
1436            (machvec) in a generic kernel.
1437            Example: machvec=hpzx1_swiotlb
1438
1439    machtype= [Loongson] Share the same kernel image file between different
1440             yeeloong laptop.
1441            Example: machtype=lemote-yeeloong-2f-7inch
1442
1443    max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1444            than or equal to this physical address is ignored.
1445
1446    maxcpus= [SMP] Maximum number of processors that an SMP kernel
1447            should make use of. maxcpus=n : n >= 0 limits the
1448            kernel to using 'n' processors. n=0 is a special case,
1449            it is equivalent to "nosmp", which also disables
1450            the IO APIC.
1451
1452    max_loop= [LOOP] The number of loop block devices that get
1453    (loop.max_loop) unconditionally pre-created at init time. The default
1454            number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1455            of statically allocating a predefined number, loop
1456            devices can be requested on-demand with the
1457            /dev/loop-control interface.
1458
1459    mce [X86-32] Machine Check Exception
1460
1461    mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1462
1463    md= [HW] RAID subsystems devices and level
1464            See Documentation/md.txt.
1465
1466    mdacon= [MDA]
1467            Format: <first>,<last>
1468            Specifies range of consoles to be captured by the MDA.
1469
1470    mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1471            Amount of memory to be used when the kernel is not able
1472            to see the whole system memory or for test.
1473            [X86-32] Use together with memmap= to avoid physical
1474            address space collisions. Without memmap= PCI devices
1475            could be placed at addresses belonging to unused RAM.
1476
1477    mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1478            memory.
1479
1480    memchunk=nn[KMG]
1481            [KNL,SH] Allow user to override the default size for
1482            per-device physically contiguous DMA buffers.
1483
1484    memmap=exactmap [KNL,X86] Enable setting of an exact
1485            E820 memory map, as specified by the user.
1486            Such memmap=exactmap lines can be constructed based on
1487            BIOS output or other requirements. See the memmap=nn@ss
1488            option description.
1489
1490    memmap=nn[KMG]@ss[KMG]
1491            [KNL] Force usage of a specific region of memory
1492            Region of memory to be used, from ss to ss+nn.
1493
1494    memmap=nn[KMG]#ss[KMG]
1495            [KNL,ACPI] Mark specific memory as ACPI data.
1496            Region of memory to be used, from ss to ss+nn.
1497
1498    memmap=nn[KMG]$ss[KMG]
1499            [KNL,ACPI] Mark specific memory as reserved.
1500            Region of memory to be used, from ss to ss+nn.
1501            Example: Exclude memory from 0x18690000-0x1869ffff
1502                     memmap=64K$0x18690000
1503                     or
1504                     memmap=0x10000$0x18690000
1505
1506    memory_corruption_check=0/1 [X86]
1507            Some BIOSes seem to corrupt the first 64k of
1508            memory when doing things like suspend/resume.
1509            Setting this option will scan the memory
1510            looking for corruption. Enabling this will
1511            both detect corruption and prevent the kernel
1512            from using the memory being corrupted.
1513            However, its intended as a diagnostic tool; if
1514            repeatable BIOS-originated corruption always
1515            affects the same memory, you can use memmap=
1516            to prevent the kernel from using that memory.
1517
1518    memory_corruption_check_size=size [X86]
1519            By default it checks for corruption in the low
1520            64k, making this memory unavailable for normal
1521            use. Use this parameter to scan for
1522            corruption in more or less memory.
1523
1524    memory_corruption_check_period=seconds [X86]
1525            By default it checks for corruption every 60
1526            seconds. Use this parameter to check at some
1527            other rate. 0 disables periodic checking.
1528
1529    memtest= [KNL,X86] Enable memtest
1530            Format: <integer>
1531            default : 0 <disable>
1532            Specifies the number of memtest passes to be
1533            performed. Each pass selects another test
1534            pattern from a given set of patterns. Memtest
1535            fills the memory with this pattern, validates
1536            memory contents and reserves bad memory
1537            regions that are detected.
1538
1539    meye.*= [HW] Set MotionEye Camera parameters
1540            See Documentation/video4linux/meye.txt.
1541
1542    mfgpt_irq= [IA-32] Specify the IRQ to use for the
1543            Multi-Function General Purpose Timers on AMD Geode
1544            platforms.
1545
1546    mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1547            the BIOS has incorrectly applied a workaround. TinyBIOS
1548            version 0.98 is known to be affected, 0.99 fixes the
1549            problem by letting the user disable the workaround.
1550
1551    mga= [HW,DRM]
1552
1553    min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1554            physical address is ignored.
1555
1556    mini2440= [ARM,HW,KNL]
1557            Format:[0..2][b][c][t]
1558            Default: "0tb"
1559            MINI2440 configuration specification:
1560            0 - The attached screen is the 3.5" TFT
1561            1 - The attached screen is the 7" TFT
1562            2 - The VGA Shield is attached (1024x768)
1563            Leaving out the screen size parameter will not load
1564            the TFT driver, and the framebuffer will be left
1565            unconfigured.
1566            b - Enable backlight. The TFT backlight pin will be
1567            linked to the kernel VESA blanking code and a GPIO
1568            LED. This parameter is not necessary when using the
1569            VGA shield.
1570            c - Enable the s3c camera interface.
1571            t - Reserved for enabling touchscreen support. The
1572            touchscreen support is not enabled in the mainstream
1573            kernel as of 2.6.30, a preliminary port can be found
1574            in the "bleeding edge" mini2440 support kernel at
1575            http://repo.or.cz/w/linux-2.6/mini2440.git
1576
1577    mminit_loglevel=
1578            [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1579            parameter allows control of the logging verbosity for
1580            the additional memory initialisation checks. A value
1581            of 0 disables mminit logging and a level of 4 will
1582            log everything. Information is printed at KERN_DEBUG
1583            so loglevel=8 may also need to be specified.
1584
1585    mousedev.tap_time=
1586            [MOUSE] Maximum time between finger touching and
1587            leaving touchpad surface for touch to be considered
1588            a tap and be reported as a left button click (for
1589            touchpads working in absolute mode only).
1590            Format: <msecs>
1591    mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1592            reporting absolute coordinates, such as tablets
1593    mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1594            reporting absolute coordinates, such as tablets
1595
1596    movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1597            is similar to kernelcore except it specifies the
1598            amount of memory used for migratable allocations.
1599            If both kernelcore and movablecore is specified,
1600            then kernelcore will be at *least* the specified
1601            value but may be more. If movablecore on its own
1602            is specified, the administrator must be careful
1603            that the amount of memory usable for all allocations
1604            is not too small.
1605
1606    MTD_Partition= [MTD]
1607            Format: <name>,<region-number>,<size>,<offset>
1608
1609    MTD_Region= [MTD] Format:
1610            <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1611
1612    mtdparts= [MTD]
1613            See drivers/mtd/cmdlinepart.c.
1614
1615    multitce=off [PPC] This parameter disables the use of the pSeries
1616            firmware feature for updating multiple TCE entries
1617            at a time.
1618
1619    onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1620
1621            Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1622
1623            boundary - index of last SLC block on Flex-OneNAND.
1624                   The remaining blocks are configured as MLC blocks.
1625            lock - Configure if Flex-OneNAND boundary should be locked.
1626                   Once locked, the boundary cannot be changed.
1627                   1 indicates lock status, 0 indicates unlock status.
1628
1629    mtdset= [ARM]
1630            ARM/S3C2412 JIVE boot control
1631
1632            See arch/arm/mach-s3c2412/mach-jive.c
1633
1634    mtouchusb.raw_coordinates=
1635            [HW] Make the MicroTouch USB driver use raw coordinates
1636            ('y', default) or cooked coordinates ('n')
1637
1638    mtrr_chunk_size=nn[KMG] [X86]
1639            used for mtrr cleanup. It is largest continuous chunk
1640            that could hold holes aka. UC entries.
1641
1642    mtrr_gran_size=nn[KMG] [X86]
1643            Used for mtrr cleanup. It is granularity of mtrr block.
1644            Default is 1.
1645            Large value could prevent small alignment from
1646            using up MTRRs.
1647
1648    mtrr_spare_reg_nr=n [X86]
1649            Format: <integer>
1650            Range: 0,7 : spare reg number
1651            Default : 1
1652            Used for mtrr cleanup. It is spare mtrr entries number.
1653            Set to 2 or more if your graphical card needs more.
1654
1655    n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1656
1657    netdev= [NET] Network devices parameters
1658            Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1659            Note that mem_start is often overloaded to mean
1660            something different and driver-specific.
1661            This usage is only documented in each driver source
1662            file if at all.
1663
1664    nf_conntrack.acct=
1665            [NETFILTER] Enable connection tracking flow accounting
1666            0 to disable accounting
1667            1 to enable accounting
1668            Default value is 0.
1669
1670    nfsaddrs= [NFS] Deprecated. Use ip= instead.
1671            See Documentation/filesystems/nfs/nfsroot.txt.
1672
1673    nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1674            See Documentation/filesystems/nfs/nfsroot.txt.
1675
1676    nfsrootdebug [NFS] enable nfsroot debugging messages.
1677            See Documentation/filesystems/nfs/nfsroot.txt.
1678
1679    nfs.callback_tcpport=
1680            [NFS] set the TCP port on which the NFSv4 callback
1681            channel should listen.
1682
1683    nfs.cache_getent=
1684            [NFS] sets the pathname to the program which is used
1685            to update the NFS client cache entries.
1686
1687    nfs.cache_getent_timeout=
1688            [NFS] sets the timeout after which an attempt to
1689            update a cache entry is deemed to have failed.
1690
1691    nfs.idmap_cache_timeout=
1692            [NFS] set the maximum lifetime for idmapper cache
1693            entries.
1694
1695    nfs.enable_ino64=
1696            [NFS] enable 64-bit inode numbers.
1697            If zero, the NFS client will fake up a 32-bit inode
1698            number for the readdir() and stat() syscalls instead
1699            of returning the full 64-bit number.
1700            The default is to return 64-bit inode numbers.
1701
1702    nfs.max_session_slots=
1703            [NFSv4.1] Sets the maximum number of session slots
1704            the client will attempt to negotiate with the server.
1705            This limits the number of simultaneous RPC requests
1706            that the client can send to the NFSv4.1 server.
1707            Note that there is little point in setting this
1708            value higher than the max_tcp_slot_table_limit.
1709
1710    nfs.nfs4_disable_idmapping=
1711            [NFSv4] When set to the default of '1', this option
1712            ensures that both the RPC level authentication
1713            scheme and the NFS level operations agree to use
1714            numeric uids/gids if the mount is using the
1715            'sec=sys' security flavour. In effect it is
1716            disabling idmapping, which can make migration from
1717            legacy NFSv2/v3 systems to NFSv4 easier.
1718            Servers that do not support this mode of operation
1719            will be autodetected by the client, and it will fall
1720            back to using the idmapper.
1721            To turn off this behaviour, set the value to '0'.
1722
1723    nfs.send_implementation_id =
1724            [NFSv4.1] Send client implementation identification
1725            information in exchange_id requests.
1726            If zero, no implementation identification information
1727            will be sent.
1728            The default is to send the implementation identification
1729            information.
1730
1731    nfsd.nfs4_disable_idmapping=
1732            [NFSv4] When set to the default of '1', the NFSv4
1733            server will return only numeric uids and gids to
1734            clients using auth_sys, and will accept numeric uids
1735            and gids from such clients. This is intended to ease
1736            migration from NFSv2/v3.
1737
1738    objlayoutdriver.osd_login_prog=
1739            [NFS] [OBJLAYOUT] sets the pathname to the program which
1740            is used to automatically discover and login into new
1741            osd-targets. Please see:
1742            Documentation/filesystems/pnfs.txt for more explanations
1743
1744    nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1745            when a NMI is triggered.
1746            Format: [state][,regs][,debounce][,die]
1747
1748    nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1749            Format: [panic,][nopanic,][num]
1750            Valid num: 0
1751            0 - turn nmi_watchdog off
1752            When panic is specified, panic when an NMI watchdog
1753            timeout occurs (or 'nopanic' to override the opposite
1754            default).
1755            This is useful when you use a panic=... timeout and
1756            need the box quickly up again.
1757
1758    netpoll.carrier_timeout=
1759            [NET] Specifies amount of time (in seconds) that
1760            netpoll should wait for a carrier. By default netpoll
1761            waits 4 seconds.
1762
1763    no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1764            emulation library even if a 387 maths coprocessor
1765            is present.
1766
1767    no_console_suspend
1768            [HW] Never suspend the console
1769            Disable suspending of consoles during suspend and
1770            hibernate operations. Once disabled, debugging
1771            messages can reach various consoles while the rest
1772            of the system is being put to sleep (ie, while
1773            debugging driver suspend/resume hooks). This may
1774            not work reliably with all consoles, but is known
1775            to work with serial and VGA consoles.
1776            To facilitate more flexible debugging, we also add
1777            console_suspend, a printk module parameter to control
1778            it. Users could use console_suspend (usually
1779            /sys/module/printk/parameters/console_suspend) to
1780            turn on/off it dynamically.
1781
1782    noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1783            caches in the slab allocator. Saves per-node memory,
1784            but will impact performance.
1785
1786    noalign [KNL,ARM]
1787
1788    noapic [SMP,APIC] Tells the kernel to not make use of any
1789            IOAPICs that may be present in the system.
1790
1791    noautogroup Disable scheduler automatic task group creation.
1792
1793    nobats [PPC] Do not use BATs for mapping kernel lowmem
1794            on "Classic" PPC cores.
1795
1796    nocache [ARM]
1797
1798    noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1799
1800    nodelayacct [KNL] Disable per-task delay accounting
1801
1802    nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1803
1804    nodsp [SH] Disable hardware DSP at boot time.
1805
1806    noefi [X86] Disable EFI runtime services support.
1807
1808    noexec [IA-64]
1809
1810    noexec [X86]
1811            On X86-32 available only on PAE configured kernels.
1812            noexec=on: enable non-executable mappings (default)
1813            noexec=off: disable non-executable mappings
1814
1815    nosmep [X86]
1816            Disable SMEP (Supervisor Mode Execution Protection)
1817            even if it is supported by processor.
1818
1819    noexec32 [X86-64]
1820            This affects only 32-bit executables.
1821            noexec32=on: enable non-executable mappings (default)
1822                read doesn't imply executable mappings
1823            noexec32=off: disable non-executable mappings
1824                read implies executable mappings
1825
1826    nofpu [SH] Disable hardware FPU at boot time.
1827
1828    nofxsr [BUGS=X86-32] Disables x86 floating point extended
1829            register save and restore. The kernel will only save
1830            legacy floating-point registers on task switch.
1831
1832    noxsave [BUGS=X86] Disables x86 extended register state save
1833            and restore using xsave. The kernel will fallback to
1834            enabling legacy floating-point and sse state.
1835
1836    nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1837            wfi(ARM) instruction doesn't work correctly and not to
1838            use it. This is also useful when using JTAG debugger.
1839
1840    no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1841            instruction doesn't work correctly and not to
1842            use it.
1843
1844    no_file_caps Tells the kernel not to honor file capabilities. The
1845            only way then for a file to be executed with privilege
1846            is to be setuid root or executed by root.
1847
1848    nohalt [IA-64] Tells the kernel not to use the power saving
1849            function PAL_HALT_LIGHT when idle. This increases
1850            power-consumption. On the positive side, it reduces
1851            interrupt wake-up latency, which may improve performance
1852            in certain environments such as networked servers or
1853            real-time systems.
1854
1855    nohz= [KNL] Boottime enable/disable dynamic ticks
1856            Valid arguments: on, off
1857            Default: on
1858
1859    noiotrap [SH] Disables trapped I/O port accesses.
1860
1861    noirqdebug [X86-32] Disables the code which attempts to detect and
1862            disable unhandled interrupt sources.
1863
1864    no_timer_check [X86,APIC] Disables the code which tests for
1865            broken timer IRQ sources.
1866
1867    noisapnp [ISAPNP] Disables ISA PnP code.
1868
1869    noinitrd [RAM] Tells the kernel not to load any configured
1870            initial RAM disk.
1871
1872    nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1873            remapping.
1874            [Deprecated - use intremap=off]
1875
1876    nointroute [IA-64]
1877
1878    nojitter [IA-64] Disables jitter checking for ITC timers.
1879
1880    no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1881
1882    no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1883            fault handling.
1884
1885    no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1886            steal time is computed, but won't influence scheduler
1887            behaviour
1888
1889    nolapic [X86-32,APIC] Do not enable or use the local APIC.
1890
1891    nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1892
1893    noltlbs [PPC] Do not use large page/tlb entries for kernel
1894            lowmem mapping on PPC40x.
1895
1896    nomca [IA-64] Disable machine check abort handling
1897
1898    nomce [X86-32] Machine Check Exception
1899
1900    nomfgpt [X86-32] Disable Multi-Function General Purpose
1901            Timer usage (for AMD Geode machines).
1902
1903    nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1904            shutdown the other cpus. Instead use the REBOOT_VECTOR
1905            irq.
1906
1907    nomodule Disable module load
1908
1909    nopat [X86] Disable PAT (page attribute table extension of
1910            pagetables) support.
1911
1912    norandmaps Don't use address space randomization. Equivalent to
1913            echo 0 > /proc/sys/kernel/randomize_va_space
1914
1915    noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1916
1917    noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1918            with UP alternatives
1919
1920    noresidual [PPC] Don't use residual data on PReP machines.
1921
1922    nordrand [X86] Disable the direct use of the RDRAND
1923            instruction even if it is supported by the
1924            processor. RDRAND is still available to user
1925            space applications.
1926
1927    noresume [SWSUSP] Disables resume and restores original swap
1928            space.
1929
1930    no-scroll [VGA] Disables scrollback.
1931            This is required for the Braillex ib80-piezo Braille
1932            reader made by F.H. Papenmeier (Germany).
1933
1934    nosbagart [IA-64]
1935
1936    nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1937
1938    nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1939            and disable the IO APIC. legacy for "maxcpus=0".
1940
1941    nosoftlockup [KNL] Disable the soft-lockup detector.
1942
1943    nosync [HW,M68K] Disables sync negotiation for all devices.
1944
1945    notsc [BUGS=X86-32] Disable Time Stamp Counter
1946
1947    nousb [USB] Disable the USB subsystem
1948
1949    nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1950
1951    nowb [ARM]
1952
1953    nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1954
1955    nptcg= [IA-64] Override max number of concurrent global TLB
1956            purges which is reported from either PAL_VM_SUMMARY or
1957            SAL PALO.
1958
1959    nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1960            could support. nr_cpus=n : n >= 1 limits the kernel to
1961            supporting 'n' processors. Later in runtime you can not
1962            use hotplug cpu feature to put more cpu back to online.
1963            just like you compile the kernel NR_CPUS=n
1964
1965    nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1966
1967    numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1968            one of ['zone', 'node', 'default'] can be specified
1969            This can be set from sysctl after boot.
1970            See Documentation/sysctl/vm.txt for details.
1971
1972    ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1973            See Documentation/debugging-via-ohci1394.txt for more
1974            info.
1975
1976    olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1977            Rather than timing out after 20 ms if an EC
1978            command is not properly ACKed, override the length
1979            of the timeout. We have interrupts disabled while
1980            waiting for the ACK, so if this is set too high
1981            interrupts *may* be lost!
1982
1983    omap_mux= [OMAP] Override bootloader pin multiplexing.
1984            Format: <mux_mode0.mode_name=value>...
1985            For example, to override I2C bus2:
1986            omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1987
1988    oprofile.timer= [HW]
1989            Use timer interrupt instead of performance counters
1990
1991    oprofile.cpu_type= Force an oprofile cpu type
1992            This might be useful if you have an older oprofile
1993            userland or if you want common events.
1994            Format: { arch_perfmon }
1995            arch_perfmon: [X86] Force use of architectural
1996                perfmon on Intel CPUs instead of the
1997                CPU specific event set.
1998            timer: [X86] Force use of architectural NMI
1999                timer mode (see also oprofile.timer
2000                for generic hr timer mode)
2001                [s390] Force legacy basic mode sampling
2002                                (report cpu_type "timer")
2003
2004    oops=panic Always panic on oopses. Default is to just kill the
2005            process, but there is a small probability of
2006            deadlocking the machine.
2007            This will also cause panics on machine check exceptions.
2008            Useful together with panic=30 to trigger a reboot.
2009
2010    OSS [HW,OSS]
2011            See Documentation/sound/oss/oss-parameters.txt
2012
2013    panic= [KNL] Kernel behaviour on panic: delay <timeout>
2014            timeout > 0: seconds before rebooting
2015            timeout = 0: wait forever
2016            timeout < 0: reboot immediately
2017            Format: <timeout>
2018
2019    parkbd.port= [HW] Parallel port number the keyboard adapter is
2020            connected to, default is 0.
2021            Format: <parport#>
2022    parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2023            0 for XT, 1 for AT (default is AT).
2024            Format: <mode>
2025
2026    parport= [HW,PPT] Specify parallel ports. 0 disables.
2027            Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2028            Use 'auto' to force the driver to use any
2029            IRQ/DMA settings detected (the default is to
2030            ignore detected IRQ/DMA settings because of
2031            possible conflicts). You can specify the base
2032            address, IRQ, and DMA settings; IRQ and DMA
2033            should be numbers, or 'auto' (for using detected
2034            settings on that particular port), or 'nofifo'
2035            (to avoid using a FIFO even if it is detected).
2036            Parallel ports are assigned in the order they
2037            are specified on the command line, starting
2038            with parport0.
2039
2040    parport_init_mode= [HW,PPT]
2041            Configure VIA parallel port to operate in
2042            a specific mode. This is necessary on Pegasos
2043            computer where firmware has no options for setting
2044            up parallel port mode and sets it to spp.
2045            Currently this function knows 686a and 8231 chips.
2046            Format: [spp|ps2|epp|ecp|ecpepp]
2047
2048    pause_on_oops=
2049            Halt all CPUs after the first oops has been printed for
2050            the specified number of seconds. This is to be used if
2051            your oopses keep scrolling off the screen.
2052
2053    pcbit= [HW,ISDN]
2054
2055    pcd. [PARIDE]
2056            See header of drivers/block/paride/pcd.c.
2057            See also Documentation/blockdev/paride.txt.
2058
2059    pci=option[,option...] [PCI] various PCI subsystem options:
2060        earlydump [X86] dump PCI config space before the kernel
2061                    changes anything
2062        off [X86] don't probe for the PCI bus
2063        bios [X86-32] force use of PCI BIOS, don't access
2064                the hardware directly. Use this if your machine
2065                has a non-standard PCI host bridge.
2066        nobios [X86-32] disallow use of PCI BIOS, only direct
2067                hardware access methods are allowed. Use this
2068                if you experience crashes upon bootup and you
2069                suspect they are caused by the BIOS.
2070        conf1 [X86] Force use of PCI Configuration
2071                Mechanism 1.
2072        conf2 [X86] Force use of PCI Configuration
2073                Mechanism 2.
2074        noaer [PCIE] If the PCIEAER kernel config parameter is
2075                enabled, this kernel boot option can be used to
2076                disable the use of PCIE advanced error reporting.
2077        nodomains [PCI] Disable support for multiple PCI
2078                root domains (aka PCI segments, in ACPI-speak).
2079        nommconf [X86] Disable use of MMCONFIG for PCI
2080                Configuration
2081        check_enable_amd_mmconf [X86] check for and enable
2082                properly configured MMIO access to PCI
2083                config space on AMD family 10h CPU
2084        nomsi [MSI] If the PCI_MSI kernel config parameter is
2085                enabled, this kernel boot option can be used to
2086                disable the use of MSI interrupts system-wide.
2087        noioapicquirk [APIC] Disable all boot interrupt quirks.
2088                Safety option to keep boot IRQs enabled. This
2089                should never be necessary.
2090        ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2091                primary IO-APIC for bridges that cannot disable
2092                boot IRQs. This fixes a source of spurious IRQs
2093                when the system masks IRQs.
2094        noioapicreroute [APIC] Disable workaround that uses the
2095                boot IRQ equivalent of an IRQ that connects to
2096                a chipset where boot IRQs cannot be disabled.
2097                The opposite of ioapicreroute.
2098        biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2099                routing table. These calls are known to be buggy
2100                on several machines and they hang the machine
2101                when used, but on other computers it's the only
2102                way to get the interrupt routing table. Try
2103                this option if the kernel is unable to allocate
2104                IRQs or discover secondary PCI buses on your
2105                motherboard.
2106        rom [X86] Assign address space to expansion ROMs.
2107                Use with caution as certain devices share
2108                address decoders between ROMs and other
2109                resources.
2110        norom [X86] Do not assign address space to
2111                expansion ROMs that do not already have
2112                BIOS assigned address ranges.
2113        nobar [X86] Do not assign address space to the
2114                BARs that weren't assigned by the BIOS.
2115        irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2116                assigned automatically to PCI devices. You can
2117                make the kernel exclude IRQs of your ISA cards
2118                this way.
2119        pirqaddr=0xAAAAA [X86] Specify the physical address
2120                of the PIRQ table (normally generated
2121                by the BIOS) if it is outside the
2122                F0000h-100000h range.
2123        lastbus=N [X86] Scan all buses thru bus #N. Can be
2124                useful if the kernel is unable to find your
2125                secondary buses and you want to tell it
2126                explicitly which ones they are.
2127        assign-busses [X86] Always assign all PCI bus
2128                numbers ourselves, overriding
2129                whatever the firmware may have done.
2130        usepirqmask [X86] Honor the possible IRQ mask stored
2131                in the BIOS $PIR table. This is needed on
2132                some systems with broken BIOSes, notably
2133                some HP Pavilion N5400 and Omnibook XE3
2134                notebooks. This will have no effect if ACPI
2135                IRQ routing is enabled.
2136        noacpi [X86] Do not use ACPI for IRQ routing
2137                or for PCI scanning.
2138        use_crs [X86] Use PCI host bridge window information
2139                from ACPI. On BIOSes from 2008 or later, this
2140                is enabled by default. If you need to use this,
2141                please report a bug.
2142        nocrs [X86] Ignore PCI host bridge windows from ACPI.
2143                    If you need to use this, please report a bug.
2144        routeirq Do IRQ routing for all PCI devices.
2145                This is normally done in pci_enable_device(),
2146                so this option is a temporary workaround
2147                for broken drivers that don't call it.
2148        skip_isa_align [X86] do not align io start addr, so can
2149                handle more pci cards
2150        firmware [ARM] Do not re-enumerate the bus but instead
2151                just use the configuration from the
2152                bootloader. This is currently used on
2153                IXP2000 systems where the bus has to be
2154                configured a certain way for adjunct CPUs.
2155        noearly [X86] Don't do any early type 1 scanning.
2156                This might help on some broken boards which
2157                machine check when some devices' config space
2158                is read. But various workarounds are disabled
2159                and some IOMMU drivers will not work.
2160        bfsort Sort PCI devices into breadth-first order.
2161                This sorting is done to get a device
2162                order compatible with older (<= 2.4) kernels.
2163        nobfsort Don't sort PCI devices into breadth-first order.
2164        cbiosize=nn[KMG] The fixed amount of bus space which is
2165                reserved for the CardBus bridge's IO window.
2166                The default value is 256 bytes.
2167        cbmemsize=nn[KMG] The fixed amount of bus space which is
2168                reserved for the CardBus bridge's memory
2169                window. The default value is 64 megabytes.
2170        resource_alignment=
2171                Format:
2172                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2173                Specifies alignment and device to reassign
2174                aligned memory resources.
2175                If <order of align> is not specified,
2176                PAGE_SIZE is used as alignment.
2177                PCI-PCI bridge can be specified, if resource
2178                windows need to be expanded.
2179        ecrc= Enable/disable PCIe ECRC (transaction layer
2180                end-to-end CRC checking).
2181                bios: Use BIOS/firmware settings. This is the
2182                the default.
2183                off: Turn ECRC off
2184                on: Turn ECRC on.
2185        realloc= Enable/disable reallocating PCI bridge resources
2186                if allocations done by BIOS are too small to
2187                accommodate resources required by all child
2188                devices.
2189                off: Turn realloc off
2190                on: Turn realloc on
2191        realloc same as realloc=on
2192        noari do not use PCIe ARI.
2193        pcie_scan_all Scan all possible PCIe devices. Otherwise we
2194                only look for one device below a PCIe downstream
2195                port.
2196
2197    pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2198            Management.
2199        off Disable ASPM.
2200        force Enable ASPM even on devices that claim not to support it.
2201            WARNING: Forcing ASPM on may cause system lockups.
2202
2203    pcie_hp= [PCIE] PCI Express Hotplug driver options:
2204        nomsi Do not use MSI for PCI Express Native Hotplug (this
2205            makes all PCIe ports use INTx for hotplug services).
2206
2207    pcie_ports= [PCIE] PCIe ports handling:
2208        auto Ask the BIOS whether or not to use native PCIe services
2209            associated with PCIe ports (PME, hot-plug, AER). Use
2210            them only if that is allowed by the BIOS.
2211        native Use native PCIe services associated with PCIe ports
2212            unconditionally.
2213        compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2214            ports driver.
2215
2216    pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2217        nomsi Do not use MSI for native PCIe PME signaling (this makes
2218            all PCIe root ports use INTx for all services).
2219
2220    pcmv= [HW,PCMCIA] BadgePAD 4
2221
2222    pd. [PARIDE]
2223            See Documentation/blockdev/paride.txt.
2224
2225    pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2226            boot time.
2227            Format: { 0 | 1 }
2228            See arch/parisc/kernel/pdc_chassis.c
2229
2230    percpu_alloc= Select which percpu first chunk allocator to use.
2231            Currently supported values are "embed" and "page".
2232            Archs may support subset or none of the selections.
2233            See comments in mm/percpu.c for details on each
2234            allocator. This parameter is primarily for debugging
2235            and performance comparison.
2236
2237    pf. [PARIDE]
2238            See Documentation/blockdev/paride.txt.
2239
2240    pg. [PARIDE]
2241            See Documentation/blockdev/paride.txt.
2242
2243    pirq= [SMP,APIC] Manual mp-table setup
2244            See Documentation/x86/i386/IO-APIC.txt.
2245
2246    plip= [PPT,NET] Parallel port network link
2247            Format: { parport<nr> | timid | 0 }
2248            See also Documentation/parport.txt.
2249
2250    pmtmr= [X86] Manual setup of pmtmr I/O Port.
2251            Override pmtimer IOPort with a hex value.
2252            e.g. pmtmr=0x508
2253
2254    pnp.debug=1 [PNP]
2255            Enable PNP debug messages (depends on the
2256            CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2257            via /sys/module/pnp/parameters/debug. We always show
2258            current resource usage; turning this on also shows
2259            possible settings and some assignment information.
2260
2261    pnpacpi= [ACPI]
2262            { off }
2263
2264    pnpbios= [ISAPNP]
2265            { on | off | curr | res | no-curr | no-res }
2266
2267    pnp_reserve_irq=
2268            [ISAPNP] Exclude IRQs for the autoconfiguration
2269
2270    pnp_reserve_dma=
2271            [ISAPNP] Exclude DMAs for the autoconfiguration
2272
2273    pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2274            Ranges are in pairs (I/O port base and size).
2275
2276    pnp_reserve_mem=
2277            [ISAPNP] Exclude memory regions for the
2278            autoconfiguration.
2279            Ranges are in pairs (memory base and size).
2280
2281    ports= [IP_VS_FTP] IPVS ftp helper module
2282            Default is 21.
2283            Up to 8 (IP_VS_APP_MAX_PORTS) ports
2284            may be specified.
2285            Format: <port>,<port>....
2286
2287    print-fatal-signals=
2288            [KNL] debug: print fatal signals
2289
2290            If enabled, warn about various signal handling
2291            related application anomalies: too many signals,
2292            too many POSIX.1 timers, fatal signals causing a
2293            coredump - etc.
2294
2295            If you hit the warning due to signal overflow,
2296            you might want to try "ulimit -i unlimited".
2297
2298            default: off.
2299
2300    printk.always_kmsg_dump=
2301            Trigger kmsg_dump for cases other than kernel oops or
2302            panics
2303            Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2304            default: disabled
2305
2306    printk.time= Show timing data prefixed to each printk message line
2307            Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2308
2309    processor.max_cstate= [HW,ACPI]
2310            Limit processor to maximum C-state
2311            max_cstate=9 overrides any DMI blacklist limit.
2312
2313    processor.nocst [HW,ACPI]
2314            Ignore the _CST method to determine C-states,
2315            instead using the legacy FADT method
2316
2317    profile= [KNL] Enable kernel profiling via /proc/profile
2318            Format: [schedule,]<number>
2319            Param: "schedule" - profile schedule points.
2320            Param: <number> - step/bucket size as a power of 2 for
2321                statistical time based profiling.
2322            Param: "sleep" - profile D-state sleeping (millisecs).
2323                Requires CONFIG_SCHEDSTATS
2324            Param: "kvm" - profile VM exits.
2325
2326    prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2327            before loading.
2328            See Documentation/blockdev/ramdisk.txt.
2329
2330    psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2331            probe for; one of (bare|imps|exps|lifebook|any).
2332    psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2333            per second.
2334    psmouse.resetafter= [HW,MOUSE]
2335            Try to reset the device after so many bad packets
2336            (0 = never).
2337    psmouse.resolution=
2338            [HW,MOUSE] Set desired mouse resolution, in dpi.
2339    psmouse.smartscroll=
2340            [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2341            0 = disabled, 1 = enabled (default).
2342
2343    pstore.backend= Specify the name of the pstore backend to use
2344
2345    pt. [PARIDE]
2346            See Documentation/blockdev/paride.txt.
2347
2348    pty.legacy_count=
2349            [KNL] Number of legacy pty's. Overwrites compiled-in
2350            default number.
2351
2352    quiet [KNL] Disable most log messages
2353
2354    r128= [HW,DRM]
2355
2356    raid= [HW,RAID]
2357            See Documentation/md.txt.
2358
2359    ramdisk_blocksize= [RAM]
2360            See Documentation/blockdev/ramdisk.txt.
2361
2362    ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2363            See Documentation/blockdev/ramdisk.txt.
2364
2365    rcutree.blimit= [KNL,BOOT]
2366            Set maximum number of finished RCU callbacks to process
2367            in one batch.
2368
2369    rcutree.fanout_leaf= [KNL,BOOT]
2370            Increase the number of CPUs assigned to each
2371            leaf rcu_node structure. Useful for very large
2372            systems.
2373
2374    rcutree.qhimark= [KNL,BOOT]
2375            Set threshold of queued
2376            RCU callbacks over which batch limiting is disabled.
2377
2378    rcutree.qlowmark= [KNL,BOOT]
2379            Set threshold of queued RCU callbacks below which
2380            batch limiting is re-enabled.
2381
2382    rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2383            Suppress RCU CPU stall warning messages.
2384
2385    rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2386            Set timeout for RCU CPU stall warning messages.
2387
2388    rcutorture.fqs_duration= [KNL,BOOT]
2389            Set duration of force_quiescent_state bursts.
2390
2391    rcutorture.fqs_holdoff= [KNL,BOOT]
2392            Set holdoff time within force_quiescent_state bursts.
2393
2394    rcutorture.fqs_stutter= [KNL,BOOT]
2395            Set wait time between force_quiescent_state bursts.
2396
2397    rcutorture.irqreader= [KNL,BOOT]
2398            Test RCU readers from irq handlers.
2399
2400    rcutorture.n_barrier_cbs= [KNL,BOOT]
2401            Set callbacks/threads for rcu_barrier() testing.
2402
2403    rcutorture.nfakewriters= [KNL,BOOT]
2404            Set number of concurrent RCU writers. These just
2405            stress RCU, they don't participate in the actual
2406            test, hence the "fake".
2407
2408    rcutorture.nreaders= [KNL,BOOT]
2409            Set number of RCU readers.
2410
2411    rcutorture.onoff_holdoff= [KNL,BOOT]
2412            Set time (s) after boot for CPU-hotplug testing.
2413
2414    rcutorture.onoff_interval= [KNL,BOOT]
2415            Set time (s) between CPU-hotplug operations, or
2416            zero to disable CPU-hotplug testing.
2417
2418    rcutorture.shuffle_interval= [KNL,BOOT]
2419            Set task-shuffle interval (s). Shuffling tasks
2420            allows some CPUs to go into dyntick-idle mode
2421            during the rcutorture test.
2422
2423    rcutorture.shutdown_secs= [KNL,BOOT]
2424            Set time (s) after boot system shutdown. This
2425            is useful for hands-off automated testing.
2426
2427    rcutorture.stall_cpu= [KNL,BOOT]
2428            Duration of CPU stall (s) to test RCU CPU stall
2429            warnings, zero to disable.
2430
2431    rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2432            Time to wait (s) after boot before inducing stall.
2433
2434    rcutorture.stat_interval= [KNL,BOOT]
2435            Time (s) between statistics printk()s.
2436
2437    rcutorture.stutter= [KNL,BOOT]
2438            Time (s) to stutter testing, for example, specifying
2439            five seconds causes the test to run for five seconds,
2440            wait for five seconds, and so on. This tests RCU's
2441            ability to transition abruptly to and from idle.
2442
2443    rcutorture.test_boost= [KNL,BOOT]
2444            Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2445            "Maybe" means test if the RCU implementation
2446            under test support RCU priority boosting.
2447
2448    rcutorture.test_boost_duration= [KNL,BOOT]
2449            Duration (s) of each individual boost test.
2450
2451    rcutorture.test_boost_interval= [KNL,BOOT]
2452            Interval (s) between each boost test.
2453
2454    rcutorture.test_no_idle_hz= [KNL,BOOT]
2455            Test RCU's dyntick-idle handling. See also the
2456            rcutorture.shuffle_interval parameter.
2457
2458    rcutorture.torture_type= [KNL,BOOT]
2459            Specify the RCU implementation to test.
2460
2461    rcutorture.verbose= [KNL,BOOT]
2462            Enable additional printk() statements.
2463
2464    rdinit= [KNL]
2465            Format: <full_path>
2466            Run specified binary instead of /init from the ramdisk,
2467            used for early userspace startup. See initrd.
2468
2469    reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2470            Format: <reboot_mode>[,<reboot_mode2>[,...]]
2471            See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2472
2473    relax_domain_level=
2474            [KNL, SMP] Set scheduler's default relax_domain_level.
2475            See Documentation/cgroups/cpusets.txt.
2476
2477    reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2478
2479    reservetop= [X86-32]
2480            Format: nn[KMG]
2481            Reserves a hole at the top of the kernel virtual
2482            address space.
2483
2484    reservelow= [X86]
2485            Format: nn[K]
2486            Set the amount of memory to reserve for BIOS at
2487            the bottom of the address space.
2488
2489    reset_devices [KNL] Force drivers to reset the underlying device
2490            during initialization.
2491
2492    resume= [SWSUSP]
2493            Specify the partition device for software suspend
2494            Format:
2495            {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2496
2497    resume_offset= [SWSUSP]
2498            Specify the offset from the beginning of the partition
2499            given by "resume=" at which the swap header is located,
2500            in <PAGE_SIZE> units (needed only for swap files).
2501            See Documentation/power/swsusp-and-swap-files.txt
2502
2503    resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2504            read the resume files
2505
2506    resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2507            Useful for devices that are detected asynchronously
2508            (e.g. USB and MMC devices).
2509
2510    hibernate= [HIBERNATION]
2511        noresume Don't check if there's a hibernation image
2512                present during boot.
2513        nocompress Don't compress/decompress hibernation images.
2514
2515    retain_initrd [RAM] Keep initrd memory after extraction
2516
2517    rhash_entries= [KNL,NET]
2518            Set number of hash buckets for route cache
2519
2520    riscom8= [HW,SERIAL]
2521            Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2522
2523    ro [KNL] Mount root device read-only on boot
2524
2525    root= [KNL] Root filesystem
2526            See name_to_dev_t comment in init/do_mounts.c.
2527
2528    rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2529            mount the root filesystem
2530
2531    rootflags= [KNL] Set root filesystem mount option string
2532
2533    rootfstype= [KNL] Set root filesystem type
2534
2535    rootwait [KNL] Wait (indefinitely) for root device to show up.
2536            Useful for devices that are detected asynchronously
2537            (e.g. USB and MMC devices).
2538
2539    rw [KNL] Mount root device read-write on boot
2540
2541    S [KNL] Run init in single mode
2542
2543    sa1100ir [NET]
2544            See drivers/net/irda/sa1100_ir.c.
2545
2546    sbni= [NET] Granch SBNI12 leased line adapter
2547
2548    sched_debug [KNL] Enables verbose scheduler debug messages.
2549
2550    skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2551            xtime_lock contention on larger systems, and/or RCU lock
2552            contention on all systems with CONFIG_MAXSMP set.
2553            Format: { "0" | "1" }
2554            0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2555            1 -- enable.
2556            Note: increases power consumption, thus should only be
2557            enabled if running jitter sensitive (HPC/RT) workloads.
2558
2559    security= [SECURITY] Choose a security module to enable at boot.
2560            If this boot parameter is not specified, only the first
2561            security module asking for security registration will be
2562            loaded. An invalid security module name will be treated
2563            as if no module has been chosen.
2564
2565    selinux= [SELINUX] Disable or enable SELinux at boot time.
2566            Format: { "0" | "1" }
2567            See security/selinux/Kconfig help text.
2568            0 -- disable.
2569            1 -- enable.
2570            Default value is set via kernel config option.
2571            If enabled at boot time, /selinux/disable can be used
2572            later to disable prior to initial policy load.
2573
2574    apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2575            Format: { "0" | "1" }
2576            See security/apparmor/Kconfig help text
2577            0 -- disable.
2578            1 -- enable.
2579            Default value is set via kernel config option.
2580
2581    serialnumber [BUGS=X86-32]
2582
2583    shapers= [NET]
2584            Maximal number of shapers.
2585
2586    show_msr= [x86] show boot-time MSR settings
2587            Format: { <integer> }
2588            Show boot-time (BIOS-initialized) MSR settings.
2589            The parameter means the number of CPUs to show,
2590            for example 1 means boot CPU only.
2591
2592    simeth= [IA-64]
2593    simscsi=
2594
2595    slram= [HW,MTD]
2596
2597    slab_max_order= [MM, SLAB]
2598            Determines the maximum allowed order for slabs.
2599            A high setting may cause OOMs due to memory
2600            fragmentation. Defaults to 1 for systems with
2601            more than 32MB of RAM, 0 otherwise.
2602
2603    slub_debug[=options[,slabs]] [MM, SLUB]
2604            Enabling slub_debug allows one to determine the
2605            culprit if slab objects become corrupted. Enabling
2606            slub_debug can create guard zones around objects and
2607            may poison objects when not in use. Also tracks the
2608            last alloc / free. For more information see
2609            Documentation/vm/slub.txt.
2610
2611    slub_max_order= [MM, SLUB]
2612            Determines the maximum allowed order for slabs.
2613            A high setting may cause OOMs due to memory
2614            fragmentation. For more information see
2615            Documentation/vm/slub.txt.
2616
2617    slub_min_objects= [MM, SLUB]
2618            The minimum number of objects per slab. SLUB will
2619            increase the slab order up to slub_max_order to
2620            generate a sufficiently large slab able to contain
2621            the number of objects indicated. The higher the number
2622            of objects the smaller the overhead of tracking slabs
2623            and the less frequently locks need to be acquired.
2624            For more information see Documentation/vm/slub.txt.
2625
2626    slub_min_order= [MM, SLUB]
2627            Determines the minimum page order for slabs. Must be
2628            lower than slub_max_order.
2629            For more information see Documentation/vm/slub.txt.
2630
2631    slub_nomerge [MM, SLUB]
2632            Disable merging of slabs with similar size. May be
2633            necessary if there is some reason to distinguish
2634            allocs to different slabs. Debug options disable
2635            merging on their own.
2636            For more information see Documentation/vm/slub.txt.
2637
2638    smart2= [HW]
2639            Format: <io1>[,<io2>[,...,<io8>]]
2640
2641    smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2642            attempt to substitute SMP alternatives once at boot.
2643
2644    smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2645    smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2646    smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2647    smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2648    smsc-ircc2.ircc_irq= [HW] IRQ line
2649    smsc-ircc2.ircc_dma= [HW] DMA channel
2650    smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2651                0: Toshiba Satellite 1800 (GP data pin select)
2652                1: Fast pin select (default)
2653                2: ATC IRMode
2654
2655    softlockup_panic=
2656            [KNL] Should the soft-lockup detector generate panics.
2657            Format: <integer>
2658
2659    sonypi.*= [HW] Sony Programmable I/O Control Device driver
2660            See Documentation/laptops/sonypi.txt
2661
2662    specialix= [HW,SERIAL] Specialix multi-serial port adapter
2663            See Documentation/serial/specialix.txt.
2664
2665    spia_io_base= [HW,MTD]
2666    spia_fio_base=
2667    spia_pedr=
2668    spia_peddr=
2669
2670    stacktrace [FTRACE]
2671            Enabled the stack tracer on boot up.
2672
2673    stacktrace_filter=[function-list]
2674            [FTRACE] Limit the functions that the stack tracer
2675            will trace at boot up. function-list is a comma separated
2676            list of functions. This list can be changed at run
2677            time by the stack_trace_filter file in the debugfs
2678            tracing directory. Note, this enables stack tracing
2679            and the stacktrace above is not needed.
2680
2681    sti= [PARISC,HW]
2682            Format: <num>
2683            Set the STI (builtin display/keyboard on the HP-PARISC
2684            machines) console (graphic card) which should be used
2685            as the initial boot-console.
2686            See also comment in drivers/video/console/sticore.c.
2687
2688    sti_font= [HW]
2689            See comment in drivers/video/console/sticore.c.
2690
2691    stifb= [HW]
2692            Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2693
2694    sunrpc.min_resvport=
2695    sunrpc.max_resvport=
2696            [NFS,SUNRPC]
2697            SunRPC servers often require that client requests
2698            originate from a privileged port (i.e. a port in the
2699            range 0 < portnr < 1024).
2700            An administrator who wishes to reserve some of these
2701            ports for other uses may adjust the range that the
2702            kernel's sunrpc client considers to be privileged
2703            using these two parameters to set the minimum and
2704            maximum port values.
2705
2706    sunrpc.pool_mode=
2707            [NFS]
2708            Control how the NFS server code allocates CPUs to
2709            service thread pools. Depending on how many NICs
2710            you have and where their interrupts are bound, this
2711            option will affect which CPUs will do NFS serving.
2712            Note: this parameter cannot be changed while the
2713            NFS server is running.
2714
2715            auto the server chooses an appropriate mode
2716                    automatically using heuristics
2717            global a single global pool contains all CPUs
2718            percpu one pool for each CPU
2719            pernode one pool for each NUMA node (equivalent
2720                    to global on non-NUMA machines)
2721
2722    sunrpc.tcp_slot_table_entries=
2723    sunrpc.udp_slot_table_entries=
2724            [NFS,SUNRPC]
2725            Sets the upper limit on the number of simultaneous
2726            RPC calls that can be sent from the client to a
2727            server. Increasing these values may allow you to
2728            improve throughput, but will also increase the
2729            amount of memory reserved for use by the client.
2730
2731    swapaccount[=0|1]
2732            [KNL] Enable accounting of swap in memory resource
2733            controller if no parameter or 1 is given or disable
2734            it if 0 is given (See Documentation/cgroups/memory.txt)
2735
2736    swiotlb= [IA-64] Number of I/O TLB slabs
2737
2738    switches= [HW,M68k]
2739
2740    sysfs.deprecated=0|1 [KNL]
2741            Enable/disable old style sysfs layout for old udev
2742            on older distributions. When this option is enabled
2743            very new udev will not work anymore. When this option
2744            is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2745            in older udev will not work anymore.
2746            Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2747            the kernel configuration.
2748
2749    sysrq_always_enabled
2750            [KNL]
2751            Ignore sysrq setting - this boot parameter will
2752            neutralize any effect of /proc/sys/kernel/sysrq.
2753            Useful for debugging.
2754
2755    tdfx= [HW,DRM]
2756
2757    test_suspend= [SUSPEND]
2758            Specify "mem" (for Suspend-to-RAM) or "standby" (for
2759            standby suspend) as the system sleep state to briefly
2760            enter during system startup. The system is woken from
2761            this state using a wakeup-capable RTC alarm.
2762
2763    thash_entries= [KNL,NET]
2764            Set number of hash buckets for TCP connection
2765
2766    thermal.act= [HW,ACPI]
2767            -1: disable all active trip points in all thermal zones
2768            <degrees C>: override all lowest active trip points
2769
2770    thermal.crt= [HW,ACPI]
2771            -1: disable all critical trip points in all thermal zones
2772            <degrees C>: override all critical trip points
2773
2774    thermal.nocrt= [HW,ACPI]
2775            Set to disable actions on ACPI thermal zone
2776            critical and hot trip points.
2777
2778    thermal.off= [HW,ACPI]
2779            1: disable ACPI thermal control
2780
2781    thermal.psv= [HW,ACPI]
2782            -1: disable all passive trip points
2783            <degrees C>: override all passive trip points to this
2784            value
2785
2786    thermal.tzp= [HW,ACPI]
2787            Specify global default ACPI thermal zone polling rate
2788            <deci-seconds>: poll all this frequency
2789            0: no polling (default)
2790
2791    threadirqs [KNL]
2792            Force threading of all interrupt handlers except those
2793            marked explicitly IRQF_NO_THREAD.
2794
2795    topology= [S390]
2796            Format: {off | on}
2797            Specify if the kernel should make use of the cpu
2798            topology information if the hardware supports this.
2799            The scheduler will make use of this information and
2800            e.g. base its process migration decisions on it.
2801            Default is on.
2802
2803    tp720= [HW,PS2]
2804
2805    tpm_suspend_pcr=[HW,TPM]
2806            Format: integer pcr id
2807            Specify that at suspend time, the tpm driver
2808            should extend the specified pcr with zeros,
2809            as a workaround for some chips which fail to
2810            flush the last written pcr on TPM_SaveState.
2811            This will guarantee that all the other pcrs
2812            are saved.
2813
2814    trace_buf_size=nn[KMG]
2815            [FTRACE] will set tracing buffer size.
2816
2817    trace_event=[event-list]
2818            [FTRACE] Set and start specified trace events in order
2819            to facilitate early boot debugging.
2820            See also Documentation/trace/events.txt
2821
2822    transparent_hugepage=
2823            [KNL]
2824            Format: [always|madvise|never]
2825            Can be used to control the default behavior of the system
2826            with respect to transparent hugepages.
2827            See Documentation/vm/transhuge.txt for more details.
2828
2829    tsc= Disable clocksource stability checks for TSC.
2830            Format: <string>
2831            [x86] reliable: mark tsc clocksource as reliable, this
2832            disables clocksource verification at runtime, as well
2833            as the stability checks done at bootup. Used to enable
2834            high-resolution timer mode on older hardware, and in
2835            virtualized environment.
2836            [x86] noirqtime: Do not use TSC to do irq accounting.
2837            Used to run time disable IRQ_TIME_ACCOUNTING on any
2838            platforms where RDTSC is slow and this accounting
2839            can add overhead.
2840
2841    turbografx.map[2|3]= [HW,JOY]
2842            TurboGraFX parallel port interface
2843            Format:
2844            <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2845            See also Documentation/input/joystick-parport.txt
2846
2847    udbg-immortal [PPC] When debugging early kernel crashes that
2848            happen after console_init() and before a proper
2849            console driver takes over, this boot options might
2850            help "seeing" what's going on.
2851
2852    uhash_entries= [KNL,NET]
2853            Set number of hash buckets for UDP/UDP-Lite connections
2854
2855    uhci-hcd.ignore_oc=
2856            [USB] Ignore overcurrent events (default N).
2857            Some badly-designed motherboards generate lots of
2858            bogus events, for ports that aren't wired to
2859            anything. Set this parameter to avoid log spamming.
2860            Note that genuine overcurrent events won't be
2861            reported either.
2862
2863    unknown_nmi_panic
2864            [X86] Cause panic on unknown NMI.
2865
2866    usbcore.authorized_default=
2867            [USB] Default USB device authorization:
2868            (default -1 = authorized except for wireless USB,
2869            0 = not authorized, 1 = authorized)
2870
2871    usbcore.autosuspend=
2872            [USB] The autosuspend time delay (in seconds) used
2873            for newly-detected USB devices (default 2). This
2874            is the time required before an idle device will be
2875            autosuspended. Devices for which the delay is set
2876            to a negative value won't be autosuspended at all.
2877
2878    usbcore.usbfs_snoop=
2879            [USB] Set to log all usbfs traffic (default 0 = off).
2880
2881    usbcore.blinkenlights=
2882            [USB] Set to cycle leds on hubs (default 0 = off).
2883
2884    usbcore.old_scheme_first=
2885            [USB] Start with the old device initialization
2886            scheme (default 0 = off).
2887
2888    usbcore.usbfs_memory_mb=
2889            [USB] Memory limit (in MB) for buffers allocated by
2890            usbfs (default = 16, 0 = max = 2047).
2891
2892    usbcore.use_both_schemes=
2893            [USB] Try the other device initialization scheme
2894            if the first one fails (default 1 = enabled).
2895
2896    usbcore.initial_descriptor_timeout=
2897            [USB] Specifies timeout for the initial 64-byte
2898                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2899            (default 5000 = 5.0 seconds).
2900
2901    usbhid.mousepoll=
2902            [USBHID] The interval which mice are to be polled at.
2903
2904    usb-storage.delay_use=
2905            [UMS] The delay in seconds before a new device is
2906            scanned for Logical Units (default 5).
2907
2908    usb-storage.quirks=
2909            [UMS] A list of quirks entries to supplement or
2910            override the built-in unusual_devs list. List
2911            entries are separated by commas. Each entry has
2912            the form VID:PID:Flags where VID and PID are Vendor
2913            and Product ID values (4-digit hex numbers) and
2914            Flags is a set of characters, each corresponding
2915            to a common usb-storage quirk flag as follows:
2916                a = SANE_SENSE (collect more than 18 bytes
2917                    of sense data);
2918                b = BAD_SENSE (don't collect more than 18
2919                    bytes of sense data);
2920                c = FIX_CAPACITY (decrease the reported
2921                    device capacity by one sector);
2922                d = NO_READ_DISC_INFO (don't use
2923                    READ_DISC_INFO command);
2924                e = NO_READ_CAPACITY_16 (don't use
2925                    READ_CAPACITY_16 command);
2926                h = CAPACITY_HEURISTICS (decrease the
2927                    reported device capacity by one
2928                    sector if the number is odd);
2929                i = IGNORE_DEVICE (don't bind to this
2930                    device);
2931                l = NOT_LOCKABLE (don't try to lock and
2932                    unlock ejectable media);
2933                m = MAX_SECTORS_64 (don't transfer more
2934                    than 64 sectors = 32 KB at a time);
2935                n = INITIAL_READ10 (force a retry of the
2936                    initial READ(10) command);
2937                o = CAPACITY_OK (accept the capacity
2938                    reported by the device);
2939                p = WRITE_CACHE (the device cache is ON
2940                    by default);
2941                r = IGNORE_RESIDUE (the device reports
2942                    bogus residue values);
2943                s = SINGLE_LUN (the device has only one
2944                    Logical Unit);
2945                w = NO_WP_DETECT (don't test whether the
2946                    medium is write-protected).
2947            Example: quirks=0419:aaf5:rl,0421:0433:rc
2948
2949    user_debug= [KNL,ARM]
2950            Format: <int>
2951            See arch/arm/Kconfig.debug help text.
2952                 1 - undefined instruction events
2953                 2 - system calls
2954                 4 - invalid data aborts
2955                 8 - SIGSEGV faults
2956                16 - SIGBUS faults
2957            Example: user_debug=31
2958
2959    userpte=
2960            [X86] Flags controlling user PTE allocations.
2961
2962                nohigh = do not allocate PTE pages in
2963                    HIGHMEM regardless of setting
2964                    of CONFIG_HIGHPTE.
2965
2966    vdso= [X86,SH]
2967            vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2968            vdso=1: enable VDSO (default)
2969            vdso=0: disable VDSO mapping
2970
2971    vdso32= [X86]
2972            vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2973            vdso32=1: enable 32-bit VDSO (default)
2974            vdso32=0: disable 32-bit VDSO mapping
2975
2976    vector= [IA-64,SMP]
2977            vector=percpu: enable percpu vector domain
2978
2979    video= [FB] Frame buffer configuration
2980            See Documentation/fb/modedb.txt.
2981
2982    virtio_mmio.device=
2983            [VMMIO] Memory mapped virtio (platform) device.
2984
2985                <size>@<baseaddr>:<irq>[:<id>]
2986            where:
2987                <size> := size (can use standard suffixes
2988                        like K, M and G)
2989                <baseaddr> := physical base address
2990                <irq> := interrupt number (as passed to
2991                        request_irq())
2992                <id> := (optional) platform device id
2993            example:
2994                virtio_mmio.device=1K@0x100b0000:48:7
2995
2996            Can be used multiple times for multiple devices.
2997
2998    vga= [BOOT,X86-32] Select a particular video mode
2999            See Documentation/x86/boot.txt and
3000            Documentation/svga.txt.
3001            Use vga=ask for menu.
3002            This is actually a boot loader parameter; the value is
3003            passed to the kernel using a special protocol.
3004
3005    vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3006            size of <nn>. This can be used to increase the
3007            minimum size (128MB on x86). It can also be used to
3008            decrease the size and leave more room for directly
3009            mapped kernel RAM.
3010
3011    vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3012            Format: <command>
3013
3014    vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3015            Format: <command>
3016
3017    vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3018            Format: <command>
3019
3020    vsyscall= [X86-64]
3021            Controls the behavior of vsyscalls (i.e. calls to
3022            fixed addresses of 0xffffffffff600x00 from legacy
3023            code). Most statically-linked binaries and older
3024            versions of glibc use these calls. Because these
3025            functions are at fixed addresses, they make nice
3026            targets for exploits that can control RIP.
3027
3028            emulate [default] Vsyscalls turn into traps and are
3029                        emulated reasonably safely.
3030
3031            native Vsyscalls are native syscall instructions.
3032                        This is a little bit faster than trapping
3033                        and makes a few dynamic recompilers work
3034                        better than they would in emulation mode.
3035                        It also makes exploits much easier to write.
3036
3037            none Vsyscalls don't work at all. This makes
3038                        them quite hard to use for exploits but
3039                        might break your system.
3040
3041    vt.cur_default= [VT] Default cursor shape.
3042            Format: 0xCCBBAA, where AA, BB, and CC are the same as
3043            the parameters of the <Esc>[?A;B;Cc escape sequence;
3044            see VGA-softcursor.txt. Default: 2 = underline.
3045
3046    vt.default_blu= [VT]
3047            Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3048            Change the default blue palette of the console.
3049            This is a 16-member array composed of values
3050            ranging from 0-255.
3051
3052    vt.default_grn= [VT]
3053            Format: <green0>,<green1>,<green2>,...,<green15>
3054            Change the default green palette of the console.
3055            This is a 16-member array composed of values
3056            ranging from 0-255.
3057
3058    vt.default_red= [VT]
3059            Format: <red0>,<red1>,<red2>,...,<red15>
3060            Change the default red palette of the console.
3061            This is a 16-member array composed of values
3062            ranging from 0-255.
3063
3064    vt.default_utf8=
3065            [VT]
3066            Format=<0|1>
3067            Set system-wide default UTF-8 mode for all tty's.
3068            Default is 1, i.e. UTF-8 mode is enabled for all
3069            newly opened terminals.
3070
3071    vt.global_cursor_default=
3072            [VT]
3073            Format=<-1|0|1>
3074            Set system-wide default for whether a cursor
3075            is shown on new VTs. Default is -1,
3076            i.e. cursors will be created by default unless
3077            overridden by individual drivers. 0 will hide
3078            cursors, 1 will display them.
3079
3080    watchdog timers [HW,WDT] For information on watchdog timers,
3081            see Documentation/watchdog/watchdog-parameters.txt
3082            or other driver-specific files in the
3083            Documentation/watchdog/ directory.
3084
3085    x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3086            default x2apic cluster mode on platforms
3087            supporting x2apic.
3088
3089    x86_mrst_timer= [X86-32,APBT]
3090            Choose timer option for x86 Moorestown MID platform.
3091            Two valid options are apbt timer only and lapic timer
3092            plus one apbt timer for broadcast timer.
3093            x86_mrst_timer=apbt_only | lapic_and_apbt
3094
3095    xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3096    xd_geo= See header of drivers/block/xd.c.
3097
3098    xen_emul_unplug= [HW,X86,XEN]
3099            Unplug Xen emulated devices
3100            Format: [unplug0,][unplug1]
3101            ide-disks -- unplug primary master IDE devices
3102            aux-ide-disks -- unplug non-primary-master IDE devices
3103            nics -- unplug network devices
3104            all -- unplug all emulated devices (NICs and IDE disks)
3105            unnecessary -- unplugging emulated devices is
3106                unnecessary even if the host did not respond to
3107                the unplug protocol
3108            never -- do not unplug even if version check succeeds
3109
3110    xirc2ps_cs= [NET,PCMCIA]
3111            Format:
3112            <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3113
3114______________________________________________________________________
3115
3116TODO:
3117
3118    Add more DRM drivers.
3119

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