Root/Documentation/kernel-parameters.txt

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    AVR32 AVR32 architecture is enabled.
44    AX25 Appropriate AX.25 support is enabled.
45    BLACKFIN Blackfin architecture is enabled.
46    DRM Direct Rendering Management support is enabled.
47    EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48    EFI EFI Partitioning (GPT) is enabled
49    EIDE EIDE/ATAPI support is enabled.
50    FB The frame buffer device is enabled.
51    GCOV GCOV profiling is enabled.
52    HW Appropriate hardware is enabled.
53    IA-64 IA-64 architecture is enabled.
54    IMA Integrity measurement architecture is enabled.
55    IOSCHED More than one I/O scheduler is enabled.
56    IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57    IPV6 IPv6 support is enabled.
58    ISAPNP ISA PnP code is enabled.
59    ISDN Appropriate ISDN support is enabled.
60    JOY Appropriate joystick support is enabled.
61    KVM Kernel Virtual Machine support is enabled.
62    LIBATA Libata driver is enabled
63    LP Printer support is enabled.
64    LOOP Loopback device support is enabled.
65    M68k M68k architecture is enabled.
66            These options have more detailed description inside of
67            Documentation/m68k/kernel-options.txt.
68    MCA MCA bus support is enabled.
69    MDA MDA console support is enabled.
70    MOUSE Appropriate mouse support is enabled.
71    MSI Message Signaled Interrupts (PCI).
72    MTD MTD (Memory Technology Device) support is enabled.
73    NET Appropriate network support is enabled.
74    NUMA NUMA support is enabled.
75    GENERIC_TIME The generic timeofday code is enabled.
76    NFS Appropriate NFS support is enabled.
77    OSS OSS sound support is enabled.
78    PV_OPS A paravirtualized kernel is enabled.
79    PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80    PARISC The PA-RISC architecture is enabled.
81    PCI PCI bus support is enabled.
82    PCIE PCI Express support is enabled.
83    PCMCIA The PCMCIA subsystem is enabled.
84    PNP Plug & Play support is enabled.
85    PPC PowerPC architecture is enabled.
86    PPT Parallel port support is enabled.
87    PS2 Appropriate PS/2 support is enabled.
88    RAM RAM disk support is enabled.
89    S390 S390 architecture is enabled.
90    SCSI Appropriate SCSI support is enabled.
91            A lot of drivers has their options described inside of
92            Documentation/scsi/.
93    SECURITY Different security models are enabled.
94    SELINUX SELinux support is enabled.
95    SERIAL Serial support is enabled.
96    SH SuperH architecture is enabled.
97    SMP The kernel is an SMP kernel.
98    SPARC Sparc architecture is enabled.
99    SWSUSP Software suspend (hibernation) is enabled.
100    SUSPEND System suspend states are enabled.
101    FTRACE Function tracing enabled.
102    TS Appropriate touchscreen support is enabled.
103    UMS USB Mass Storage support is enabled.
104    USB USB support is enabled.
105    USBHID USB Human Interface Device support is enabled.
106    V4L Video For Linux support is enabled.
107    VGA The VGA console has been enabled.
108    VT Virtual terminal support is enabled.
109    WDT Watchdog support is enabled.
110    XT IBM PC/XT MFM hard disk support is enabled.
111    X86-32 X86-32, aka i386 architecture is enabled.
112    X86-64 X86-64 architecture is enabled.
113            More X86-64 boot options can be found in
114            Documentation/x86/x86_64/boot-options.txt .
115    X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116
117In addition, the following text indicates that the option:
118
119    BUGS= Relates to possible processor bugs on the said processor.
120    KNL Is a kernel start-up parameter.
121    BOOT Is a boot loader parameter.
122
123Parameters denoted with BOOT are actually interpreted by the boot
124loader, and have no meaning to the kernel directly.
125Do not modify the syntax of boot loader parameters without extreme
126need or coordination with <Documentation/x86/boot.txt>.
127
128There are also arch-specific kernel-parameters not documented here.
129See for example <Documentation/x86/x86_64/boot-options.txt>.
130
131Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132a trailing = on the name of any parameter states that that parameter will
133be entered as an environment variable, whereas its absence indicates that
134it will appear as a kernel argument readable via /proc/cmdline by programs
135running once the system is up.
136
137The number of kernel parameters is not limited, but the length of the
138complete command line (parameters including spaces etc.) is limited to
139a fixed number of characters. This limit depends on the architecture
140and is between 256 and 4096 characters. It is defined in the file
141./include/asm/setup.h as COMMAND_LINE_SIZE.
142
143
144    acpi= [HW,ACPI,X86]
145            Advanced Configuration and Power Interface
146            Format: { force | off | ht | strict | noirq | rsdt }
147            force -- enable ACPI if default was off
148            off -- disable ACPI if default was on
149            noirq -- do not use ACPI for IRQ routing
150            ht -- run only enough ACPI to enable Hyper Threading
151            strict -- Be less tolerant of platforms that are not
152                strictly ACPI specification compliant.
153            rsdt -- prefer RSDT over (default) XSDT
154
155            See also Documentation/power/pm.txt, pci=noacpi
156
157    acpi_apic_instance= [ACPI, IOAPIC]
158            Format: <int>
159            2: use 2nd APIC table, if available
160            1,0: use 1st APIC table
161            default: 0
162
163    acpi_backlight= [HW,ACPI]
164            acpi_backlight=vendor
165            acpi_backlight=video
166            If set to vendor, prefer vendor specific driver
167            (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168            of the ACPI video.ko driver.
169
170    acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171    acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172            Format: <int>
173            CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174            debug output. Bits in debug_layer correspond to a
175            _COMPONENT in an ACPI source file, e.g.,
176                #define _COMPONENT ACPI_PCI_COMPONENT
177            Bits in debug_level correspond to a level in
178            ACPI_DEBUG_PRINT statements, e.g.,
179                ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180            The debug_level mask defaults to "info". See
181            Documentation/acpi/debug.txt for more information about
182            debug layers and levels.
183
184            Enable processor driver info messages:
185                acpi.debug_layer=0x20000000
186            Enable PCI/PCI interrupt routing info messages:
187                acpi.debug_layer=0x400000
188            Enable AML "Debug" output, i.e., stores to the Debug
189            object while interpreting AML:
190                acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191            Enable all messages related to ACPI hardware:
192                acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193
194            Some values produce so much output that the system is
195            unusable. The "log_buf_len" parameter may be useful
196            if you need to capture more output.
197
198    acpi_display_output= [HW,ACPI]
199            acpi_display_output=vendor
200            acpi_display_output=video
201            See above.
202
203    acpi_irq_balance [HW,ACPI]
204            ACPI will balance active IRQs
205            default in APIC mode
206
207    acpi_irq_nobalance [HW,ACPI]
208            ACPI will not move active IRQs (default)
209            default in PIC mode
210
211    acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212            Format: <irq>,<irq>...
213
214    acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215            use by PCI
216            Format: <irq>,<irq>...
217
218    acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219
220    acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221            Format: To spoof as Windows 98: ="Microsoft Windows"
222
223    acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224            acpi_osi="string1" # add string1 -- only one string
225            acpi_osi="!string2" # remove built-in string2
226            acpi_osi= # disable all strings
227
228    acpi_pm_good [X86]
229            Override the pmtimer bug detection: force the kernel
230            to assume that this machine's pmtimer latches its value
231            and always returns good values.
232
233    acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234            Format: { level | edge | high | low }
235
236    acpi_serialize [HW,ACPI] force serialization of AML methods
237
238    acpi_skip_timer_override [HW,ACPI]
239            Recognize and ignore IRQ0/pin2 Interrupt Override.
240            For broken nForce2 BIOS resulting in XT-PIC timer.
241
242    acpi_sleep= [HW,ACPI] Sleep options
243            Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244                  old_ordering, s4_nonvs, sci_force_enable }
245            See Documentation/power/video.txt for information on
246            s3_bios and s3_mode.
247            s3_beep is for debugging; it makes the PC's speaker beep
248            as soon as the kernel's real-mode entry point is called.
249            s4_nohwsig prevents ACPI hardware signature from being
250            used during resume from hibernation.
251            old_ordering causes the ACPI 1.0 ordering of the _PTS
252            control method, with respect to putting devices into
253            low power states, to be enforced (the ACPI 2.0 ordering
254            of _PTS is used by default).
255            s4_nonvs prevents the kernel from saving/restoring the
256            ACPI NVS memory during hibernation.
257            sci_force_enable causes the kernel to set SCI_EN directly
258            on resume from S1/S3 (which is against the ACPI spec,
259            but some broken systems don't work without it).
260
261    acpi_use_timer_override [HW,ACPI]
262            Use timer override. For some broken Nvidia NF5 boards
263            that require a timer override, but don't have HPET
264
265    acpi_enforce_resources= [ACPI]
266            { strict | lax | no }
267            Check for resource conflicts between native drivers
268            and ACPI OperationRegions (SystemIO and SystemMemory
269            only). IO ports and memory declared in ACPI might be
270            used by the ACPI subsystem in arbitrary AML code and
271            can interfere with legacy drivers.
272            strict (default): access to resources claimed by ACPI
273            is denied; legacy drivers trying to access reserved
274            resources will fail to bind to device using them.
275            lax: access to resources claimed by ACPI is allowed;
276            legacy drivers trying to access reserved resources
277            will bind successfully but a warning message is logged.
278            no: ACPI OperationRegions are not marked as reserved,
279            no further checks are performed.
280
281    ad1848= [HW,OSS]
282            Format: <io>,<irq>,<dma>,<dma2>,<type>
283
284    add_efi_memmap [EFI; X86] Include EFI memory map in
285            kernel's map of available physical RAM.
286
287    advansys= [HW,SCSI]
288            See header of drivers/scsi/advansys.c.
289
290    advwdt= [HW,WDT] Advantech WDT
291            Format: <iostart>,<iostop>
292
293    aedsp16= [HW,OSS] Audio Excel DSP 16
294            Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295            See also header of sound/oss/aedsp16.c.
296
297    agp= [AGP]
298            { off | try_unsupported }
299            off: disable AGP support
300            try_unsupported: try to drive unsupported chipsets
301                (may crash computer or cause data corruption)
302
303    aha152x= [HW,SCSI]
304            See Documentation/scsi/aha152x.txt.
305
306    aha1542= [HW,SCSI]
307            Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
308
309    aic7xxx= [HW,SCSI]
310            See Documentation/scsi/aic7xxx.txt.
311
312    aic79xx= [HW,SCSI]
313            See Documentation/scsi/aic79xx.txt.
314
315    alignment= [KNL,ARM]
316            Allow the default userspace alignment fault handler
317            behaviour to be specified. Bit 0 enables warnings,
318            bit 1 enables fixups, and bit 2 sends a segfault.
319
320    amd_iommu= [HW,X86-84]
321            Pass parameters to the AMD IOMMU driver in the system.
322            Possible values are:
323            fullflush - enable flushing of IO/TLB entries when
324                    they are unmapped. Otherwise they are
325                    flushed before they will be reused, which
326                    is a lot of faster
327
328    amijoy.map= [HW,JOY] Amiga joystick support
329            Map of devices attached to JOY0DAT and JOY1DAT
330            Format: <a>,<b>
331            See also Documentation/kernel/input/joystick.txt
332
333    analog.map= [HW,JOY] Analog joystick and gamepad support
334            Specifies type or capabilities of an analog joystick
335            connected to one of 16 gameports
336            Format: <type1>,<type2>,..<type16>
337
338    apc= [HW,SPARC]
339            Power management functions (SPARCstation-4/5 + deriv.)
340            Format: noidle
341            Disable APC CPU standby support. SPARCstation-Fox does
342            not play well with APC CPU idle - disable it if you have
343            APC and your system crashes randomly.
344
345    apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
346            Change the output verbosity whilst booting
347            Format: { quiet (default) | verbose | debug }
348            Change the amount of debugging information output
349            when initialising the APIC and IO-APIC components.
350
351    autoconf= [IPV6]
352            See Documentation/networking/ipv6.txt.
353
354    show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
355            Limit apic dumping. The parameter defines the maximal
356            number of local apics being dumped. Also it is possible
357            to set it to "all" by meaning -- no limit here.
358            Format: { 1 (default) | 2 | ... | all }.
359            The parameter valid if only apic=debug or
360            apic=verbose is specified.
361            Example: apic=debug show_lapic=all
362
363    apm= [APM] Advanced Power Management
364            See header of arch/x86/kernel/apm_32.c.
365
366    arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
367            Format: <io>,<irq>,<nodeID>
368
369    ataflop= [HW,M68k]
370
371    atarimouse= [HW,MOUSE] Atari Mouse
372
373    atascsi= [HW,SCSI] Atari SCSI
374
375    atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
376            EzKey and similar keyboards
377
378    atkbd.reset= [HW] Reset keyboard during initialization
379
380    atkbd.set= [HW] Select keyboard code set
381            Format: <int> (2 = AT (default), 3 = PS/2)
382
383    atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
384            keyboards
385
386    atkbd.softraw= [HW] Choose between synthetic and real raw mode
387            Format: <bool> (0 = real, 1 = synthetic (default))
388
389    atkbd.softrepeat= [HW]
390            Use software keyboard repeat
391
392    autotest [IA64]
393
394    baycom_epp= [HW,AX25]
395            Format: <io>,<mode>
396
397    baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
398            Format: <io>,<mode>
399            See header of drivers/net/hamradio/baycom_par.c.
400
401    baycom_ser_fdx= [HW,AX25]
402            BayCom Serial Port AX.25 Modem (Full Duplex Mode)
403            Format: <io>,<irq>,<mode>[,<baud>]
404            See header of drivers/net/hamradio/baycom_ser_fdx.c.
405
406    baycom_ser_hdx= [HW,AX25]
407            BayCom Serial Port AX.25 Modem (Half Duplex Mode)
408            Format: <io>,<irq>,<mode>
409            See header of drivers/net/hamradio/baycom_ser_hdx.c.
410
411    boot_delay= Milliseconds to delay each printk during boot.
412            Values larger than 10 seconds (10000) are changed to
413            no delay (0).
414            Format: integer
415
416    bootmem_debug [KNL] Enable bootmem allocator debug messages.
417
418    bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
419    bttv.radio= Most important insmod options are available as
420            kernel args too.
421    bttv.pll= See Documentation/video4linux/bttv/Insmod-options
422    bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
423
424    BusLogic= [HW,SCSI]
425            See drivers/scsi/BusLogic.c, comment before function
426            BusLogic_ParseDriverOptions().
427
428    c101= [NET] Moxa C101 synchronous serial card
429
430    cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
431            Sometimes CPU hardware bugs make them report the cache
432            size incorrectly. The kernel will attempt work arounds
433            to fix known problems, but for some CPUs it is not
434            possible to determine what the correct size should be.
435            This option provides an override for these situations.
436
437    capability.disable=
438            [SECURITY] Disable capabilities. This would normally
439            be used only if an alternative security model is to be
440            configured. Potentially dangerous and should only be
441            used if you are entirely sure of the consequences.
442
443    ccw_timeout_log [S390]
444            See Documentation/s390/CommonIO for details.
445
446    cgroup_disable= [KNL] Disable a particular controller
447            Format: {name of the controller(s) to disable}
448                {Currently supported controllers - "memory"}
449
450    checkreqprot [SELINUX] Set initial checkreqprot flag value.
451            Format: { "0" | "1" }
452            See security/selinux/Kconfig help text.
453            0 -- check protection applied by kernel (includes
454                any implied execute protection).
455            1 -- check protection requested by application.
456            Default value is set via a kernel config option.
457            Value can be changed at runtime via
458                /selinux/checkreqprot.
459
460    cio_ignore= [S390]
461            See Documentation/s390/CommonIO for details.
462
463    clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
464            [Deprecated]
465            Forces specified clocksource (if available) to be used
466            when calculating gettimeofday(). If specified
467            clocksource is not available, it defaults to PIT.
468            Format: { pit | tsc | cyclone | pmtmr }
469
470    clocksource= [GENERIC_TIME] Override the default clocksource
471            Format: <string>
472            Override the default clocksource and use the clocksource
473            with the name specified.
474            Some clocksource names to choose from, depending on
475            the platform:
476            [all] jiffies (this is the base, fallback clocksource)
477            [ACPI] acpi_pm
478            [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
479                pxa_timer,timer3,32k_counter,timer0_1
480            [AVR32] avr32
481            [X86-32] pit,hpet,tsc,vmi-timer;
482                scx200_hrt on Geode; cyclone on IBM x440
483            [MIPS] MIPS
484            [PARISC] cr16
485            [S390] tod
486            [SH] SuperH
487            [SPARC64] tick
488            [X86-64] hpet,tsc
489
490    clearcpuid=BITNUM [X86]
491            Disable CPUID feature X for the kernel. See
492            arch/x86/include/asm/cpufeature.h for the valid bit
493            numbers. Note the Linux specific bits are not necessarily
494            stable over kernel options, but the vendor specific
495            ones should be.
496            Also note that user programs calling CPUID directly
497            or using the feature without checking anything
498            will still see it. This just prevents it from
499            being used by the kernel or shown in /proc/cpuinfo.
500            Also note the kernel might malfunction if you disable
501            some critical bits.
502
503    cmo_free_hint= [PPC] Format: { yes | no }
504            Specify whether pages are marked as being inactive
505            when they are freed. This is used in CMO environments
506            to determine OS memory pressure for page stealing by
507            a hypervisor.
508            Default: yes
509
510    code_bytes [X86] How many bytes of object code to print
511            in an oops report.
512            Range: 0 - 8192
513            Default: 64
514
515    com20020= [HW,NET] ARCnet - COM20020 chipset
516            Format:
517            <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
518
519    com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
520            Format: <io>[,<irq>]
521
522    com90xx= [HW,NET]
523            ARCnet - COM90xx chipset (memory-mapped buffers)
524            Format: <io>[,<irq>[,<memstart>]]
525
526    condev= [HW,S390] console device
527    conmode=
528
529    console= [KNL] Output console device and options.
530
531        tty<n> Use the virtual console device <n>.
532
533        ttyS<n>[,options]
534        ttyUSB0[,options]
535            Use the specified serial port. The options are of
536            the form "bbbbpnf", where "bbbb" is the baud rate,
537            "p" is parity ("n", "o", or "e"), "n" is number of
538            bits, and "f" is flow control ("r" for RTS or
539            omit it). Default is "9600n8".
540
541            See Documentation/serial-console.txt for more
542            information. See
543            Documentation/networking/netconsole.txt for an
544            alternative.
545
546        uart[8250],io,<addr>[,options]
547        uart[8250],mmio,<addr>[,options]
548            Start an early, polled-mode console on the 8250/16550
549            UART at the specified I/O port or MMIO address,
550            switching to the matching ttyS device later. The
551            options are the same as for ttyS, above.
552
553                If the device connected to the port is not a TTY but a braille
554                device, prepend "brl," before the device type, for instance
555            console=brl,ttyS0
556        For now, only VisioBraille is supported.
557
558    consoleblank= [KNL] The console blank (screen saver) timeout in
559            seconds. Defaults to 10*60 = 10mins. A value of 0
560            disables the blank timer.
561
562    coredump_filter=
563            [KNL] Change the default value for
564            /proc/<pid>/coredump_filter.
565            See also Documentation/filesystems/proc.txt.
566
567    cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
568            Format:
569            <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
570
571    crashkernel=nn[KMG]@ss[KMG]
572            [KNL] Reserve a chunk of physical memory to
573            hold a kernel to switch to with kexec on panic.
574
575    crashkernel=range1:size1[,range2:size2,...][@offset]
576            [KNL] Same as above, but depends on the memory
577            in the running system. The syntax of range is
578            start-[end] where start and end are both
579            a memory unit (amount[KMG]). See also
580            Documentation/kdump/kdump.txt for a example.
581
582    cs89x0_dma= [HW,NET]
583            Format: <dma>
584
585    cs89x0_media= [HW,NET]
586            Format: { rj45 | aui | bnc }
587
588    dasd= [HW,NET]
589            See header of drivers/s390/block/dasd_devmap.c.
590
591    db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
592            (one device per port)
593            Format: <port#>,<type>
594            See also Documentation/input/joystick-parport.txt
595
596    debug [KNL] Enable kernel debugging (events log level).
597
598    debug_locks_verbose=
599            [KNL] verbose self-tests
600            Format=<0|1>
601            Print debugging info while doing the locking API
602            self-tests.
603            We default to 0 (no extra messages), setting it to
604            1 will print _a lot_ more information - normally
605            only useful to kernel developers.
606
607    debug_objects [KNL] Enable object debugging
608
609    no_debug_objects
610            [KNL] Disable object debugging
611
612    debugpat [X86] Enable PAT debugging
613
614    decnet.addr= [HW,NET]
615            Format: <area>[,<node>]
616            See also Documentation/networking/decnet.txt.
617
618    default_hugepagesz=
619            [same as hugepagesz=] The size of the default
620            HugeTLB page size. This is the size represented by
621            the legacy /proc/ hugepages APIs, used for SHM, and
622            default size when mounting hugetlbfs filesystems.
623            Defaults to the default architecture's huge page size
624            if not specified.
625
626    dhash_entries= [KNL]
627            Set number of hash buckets for dentry cache.
628
629    digi= [HW,SERIAL]
630            IO parameters + enable/disable command.
631
632    digiepca= [HW,SERIAL]
633            See drivers/char/README.epca and
634            Documentation/serial/digiepca.txt.
635
636    disable= [IPV6]
637            See Documentation/networking/ipv6.txt.
638
639    disable_ipv6= [IPV6]
640            See Documentation/networking/ipv6.txt.
641
642    disable_mtrr_cleanup [X86]
643            The kernel tries to adjust MTRR layout from continuous
644            to discrete, to make X server driver able to add WB
645            entry later. This parameter disables that.
646
647    disable_mtrr_trim [X86, Intel and AMD only]
648            By default the kernel will trim any uncacheable
649            memory out of your available memory pool based on
650            MTRR settings. This parameter disables that behavior,
651            possibly causing your machine to run very slowly.
652
653    disable_timer_pin_1 [X86]
654            Disable PIN 1 of APIC timer
655            Can be useful to work around chipset bugs.
656
657    dmasound= [HW,OSS] Sound subsystem buffers
658
659    dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660            this option disables the debugging code at boot.
661
662    dma_debug_entries=<number>
663            This option allows to tune the number of preallocated
664            entries for DMA-API debugging code. One entry is
665            required per DMA-API allocation. Use this if the
666            DMA-API debugging code disables itself because the
667            architectural default is too low.
668
669    dma_debug_driver=<driver_name>
670            With this option the DMA-API debugging driver
671            filter feature can be enabled at boot time. Just
672            pass the driver to filter for as the parameter.
673            The filter can be disabled or changed to another
674            driver later using sysfs.
675
676    dscc4.setup= [NET]
677
678    dtc3181e= [HW,SCSI]
679
680    dynamic_printk Enables pr_debug()/dev_dbg() calls if
681            CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
682            These can also be switched on/off via
683            <debugfs>/dynamic_printk/modules
684
685    earlycon= [KNL] Output early console device and options.
686        uart[8250],io,<addr>[,options]
687        uart[8250],mmio,<addr>[,options]
688            Start an early, polled-mode console on the 8250/16550
689            UART at the specified I/O port or MMIO address.
690            The options are the same as for ttyS, above.
691
692    earlyprintk= [X86,SH,BLACKFIN]
693            earlyprintk=vga
694            earlyprintk=serial[,ttySn[,baudrate]]
695            earlyprintk=ttySn[,baudrate]
696            earlyprintk=dbgp[debugController#]
697
698            Append ",keep" to not disable it when the real console
699            takes over.
700
701            Only vga or serial or usb debug port at a time.
702
703            Currently only ttyS0 and ttyS1 are supported.
704
705            Interaction with the standard serial driver is not
706            very good.
707
708            The VGA output is eventually overwritten by the real
709            console.
710
711    eata= [HW,SCSI]
712
713    edd= [EDD]
714            Format: {"off" | "on" | "skip[mbr]"}
715
716    eisa_irq_edge= [PARISC,HW]
717            See header of drivers/parisc/eisa.c.
718
719    elanfreq= [X86-32]
720            See comment before function elanfreq_setup() in
721            arch/x86/kernel/cpu/cpufreq/elanfreq.c.
722
723    elevator= [IOSCHED]
724            Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
725            See Documentation/block/as-iosched.txt and
726            Documentation/block/deadline-iosched.txt for details.
727
728    elfcorehdr= [IA64,PPC,SH,X86]
729            Specifies physical address of start of kernel core
730            image elf header. Generally kexec loader will
731            pass this option to capture kernel.
732            See Documentation/kdump/kdump.txt for details.
733
734    enable_mtrr_cleanup [X86]
735            The kernel tries to adjust MTRR layout from continuous
736            to discrete, to make X server driver able to add WB
737            entry later. This parameter enables that.
738
739    enable_timer_pin_1 [X86]
740            Enable PIN 1 of APIC timer
741            Can be useful to work around chipset bugs
742            (in particular on some ATI chipsets).
743            The kernel tries to set a reasonable default.
744
745    enforcing [SELINUX] Set initial enforcing status.
746            Format: {"0" | "1"}
747            See security/selinux/Kconfig help text.
748            0 -- permissive (log only, no denials).
749            1 -- enforcing (deny and log).
750            Default value is 0.
751            Value can be changed at runtime via /selinux/enforce.
752
753    ether= [HW,NET] Ethernet cards parameters
754            This option is obsoleted by the "netdev=" option, which
755            has equivalent usage. See its documentation for details.
756
757    eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
758            Format: <io>[,<irq>]
759
760    failslab=
761    fail_page_alloc=
762    fail_make_request=[KNL]
763            General fault injection mechanism.
764            Format: <interval>,<probability>,<space>,<times>
765            See also /Documentation/fault-injection/.
766
767    fd_mcs= [HW,SCSI]
768            See header of drivers/scsi/fd_mcs.c.
769
770    fdomain= [HW,SCSI]
771            See header of drivers/scsi/fdomain.c.
772
773    floppy= [HW]
774            See Documentation/blockdev/floppy.txt.
775
776    force_pal_cache_flush
777            [IA-64] Avoid check_sal_cache_flush which may hang on
778            buggy SAL_CACHE_FLUSH implementations. Using this
779            parameter will force ia64_sal_cache_flush to call
780            ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
781
782    ftrace=[tracer]
783            [FTRACE] will set and start the specified tracer
784            as early as possible in order to facilitate early
785            boot debugging.
786
787    ftrace_dump_on_oops
788            [FTRACE] will dump the trace buffers on oops.
789
790    ftrace_filter=[function-list]
791            [FTRACE] Limit the functions traced by the function
792            tracer at boot up. function-list is a comma separated
793            list of functions. This list can be changed at run
794            time by the set_ftrace_filter file in the debugfs
795            tracing directory.
796
797    ftrace_notrace=[function-list]
798            [FTRACE] Do not trace the functions specified in
799            function-list. This list can be changed at run time
800            by the set_ftrace_notrace file in the debugfs
801            tracing directory.
802
803    ftrace_graph_filter=[function-list]
804            [FTRACE] Limit the top level callers functions traced
805            by the function graph tracer at boot up.
806            function-list is a comma separated list of functions
807            that can be changed at run time by the
808            set_graph_function file in the debugfs tracing directory.
809
810    gamecon.map[2|3]=
811            [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
812            support via parallel port (up to 5 devices per port)
813            Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
814            See also Documentation/input/joystick-parport.txt
815
816    gamma= [HW,DRM]
817
818    gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
819            Format: off | on
820            default: on
821
822    gcov_persist= [GCOV] When non-zero (default), profiling data for
823            kernel modules is saved and remains accessible via
824            debugfs, even when the module is unloaded/reloaded.
825            When zero, profiling data is discarded and associated
826            debugfs files are removed at module unload time.
827
828    gdth= [HW,SCSI]
829            See header of drivers/scsi/gdth.c.
830
831    gpt [EFI] Forces disk with valid GPT signature but
832            invalid Protective MBR to be treated as GPT.
833
834    gvp11= [HW,SCSI]
835
836    hashdist= [KNL,NUMA] Large hashes allocated during boot
837            are distributed across NUMA nodes. Defaults on
838            for 64bit NUMA, off otherwise.
839            Format: 0 | 1 (for off | on)
840
841    hcl= [IA-64] SGI's Hardware Graph compatibility layer
842
843    hd= [EIDE] (E)IDE hard drive subsystem geometry
844            Format: <cyl>,<head>,<sect>
845
846    highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
847            size of <nn>. This works even on boxes that have no
848            highmem otherwise. This also works to reduce highmem
849            size on bigger boxes.
850
851    highres= [KNL] Enable/disable high resolution timer mode.
852            Valid parameters: "on", "off"
853            Default: "on"
854
855    hisax= [HW,ISDN]
856            See Documentation/isdn/README.HiSax.
857
858    hlt [BUGS=ARM,SH]
859
860    hpet= [X86-32,HPET] option to control HPET usage
861            Format: { enable (default) | disable | force |
862                verbose }
863            disable: disable HPET and use PIT instead
864            force: allow force enabled of undocumented chips (ICH4,
865                VIA, nVidia)
866            verbose: show contents of HPET registers during setup
867
868    hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
869    hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
870            On x86-64 and powerpc, this option can be specified
871            multiple times interleaved with hugepages= to reserve
872            huge pages of different sizes. Valid pages sizes on
873            x86-64 are 2M (when the CPU supports "pse") and 1G
874            (when the CPU supports the "pdpe1gb" cpuinfo flag)
875            Note that 1GB pages can only be allocated at boot time
876            using hugepages= and not freed afterwards.
877
878    hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
879                   terminal devices. Valid values: 0..8
880    hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
881                   If specified, z/VM IUCV HVC accepts connections
882                   from listed z/VM user IDs only.
883
884    i2c_bus= [HW] Override the default board specific I2C bus speed
885                 or register an additional I2C bus that is not
886                 registered from board initialization code.
887                 Format:
888                 <bus_id>,<clkrate>
889
890    i8042.debug [HW] Toggle i8042 debug mode
891    i8042.direct [HW] Put keyboard port into non-translated mode
892    i8042.dumbkbd [HW] Pretend that controller can only read data from
893                 keyboard and cannot control its state
894                 (Don't attempt to blink the leds)
895    i8042.noaux [HW] Don't check for auxiliary (== mouse) port
896    i8042.nokbd [HW] Don't check/create keyboard port
897    i8042.noloop [HW] Disable the AUX Loopback command while probing
898                 for the AUX port
899    i8042.nomux [HW] Don't check presence of an active multiplexing
900                 controller
901    i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
902                 controllers
903    i8042.panicblink=
904            [HW] Frequency with which keyboard LEDs should blink
905                 when kernel panics (default is 0.5 sec)
906    i8042.reset [HW] Reset the controller during init and cleanup
907    i8042.unlock [HW] Unlock (ignore) the keylock
908
909    i810= [HW,DRM]
910
911    i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
912            indicates that the driver is running on unsupported
913            hardware.
914    i8k.force [HW] Activate i8k driver even if SMM BIOS signature
915            does not match list of supported models.
916    i8k.power_status
917            [HW] Report power status in /proc/i8k
918            (disabled by default)
919    i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
920            capability is set.
921
922    ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
923            See Documentation/mca.txt.
924
925    icn= [HW,ISDN]
926            Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
927
928    ide-core.nodma= [HW] (E)IDE subsystem
929            Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
930            .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
931            .cdrom .chs .ignore_cable are additional options
932            See Documentation/ide/ide.txt.
933
934    ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
935            Claim all unknown PCI IDE storage controllers.
936
937    idle= [X86]
938            Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
939            Poll forces a polling idle loop that can slightly
940            improve the performance of waking up a idle CPU, but
941            will use a lot of power and make the system run hot.
942            Not recommended.
943            idle=mwait: On systems which support MONITOR/MWAIT but
944            the kernel chose to not use it because it doesn't save
945            as much power as a normal idle loop, use the
946            MONITOR/MWAIT idle loop anyways. Performance should be
947            the same as idle=poll.
948            idle=halt: Halt is forced to be used for CPU idle.
949            In such case C2/C3 won't be used again.
950            idle=nomwait: Disable mwait for CPU C-states
951
952    ignore_loglevel [KNL]
953            Ignore loglevel setting - this will print /all/
954            kernel messages to the console. Useful for debugging.
955
956    ihash_entries= [KNL]
957            Set number of hash buckets for inode cache.
958
959    ima_audit= [IMA]
960            Format: { "0" | "1" }
961            0 -- integrity auditing messages. (Default)
962            1 -- enable informational integrity auditing messages.
963
964    ima_hash= [IMA]
965            Format: { "sha1" | "md5" }
966            default: "sha1"
967
968    ima_tcb [IMA]
969            Load a policy which meets the needs of the Trusted
970            Computing Base. This means IMA will measure all
971            programs exec'd, files mmap'd for exec, and all files
972            opened for read by uid=0.
973
974    in2000= [HW,SCSI]
975            See header of drivers/scsi/in2000.c.
976
977    init= [KNL]
978            Format: <full_path>
979            Run specified binary instead of /sbin/init as init
980            process.
981
982    initcall_debug [KNL] Trace initcalls as they are executed. Useful
983            for working out where the kernel is dying during
984            startup.
985
986    initrd= [BOOT] Specify the location of the initial ramdisk
987
988    inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
989            Format: <irq>
990
991    intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
992        on
993            Enable intel iommu driver.
994        off
995            Disable intel iommu driver.
996        igfx_off [Default Off]
997            By default, gfx is mapped as normal device. If a gfx
998            device has a dedicated DMAR unit, the DMAR unit is
999            bypassed by not enabling DMAR with this option. In
1000            this case, gfx device will use physical address for
1001            DMA.
1002        forcedac [x86_64]
1003            With this option iommu will not optimize to look
1004            for io virtual address below 32 bit forcing dual
1005            address cycle on pci bus for cards supporting greater
1006            than 32 bit addressing. The default is to look
1007            for translation below 32 bit and if not available
1008            then look in the higher range.
1009        strict [Default Off]
1010            With this option on every unmap_single operation will
1011            result in a hardware IOTLB flush operation as opposed
1012            to batching them for performance.
1013
1014    inttest= [IA64]
1015
1016    iomem= Disable strict checking of access to MMIO memory
1017        strict regions from userspace.
1018        relaxed
1019
1020    iommu= [x86]
1021        off
1022        force
1023        noforce
1024        biomerge
1025        panic
1026        nopanic
1027        merge
1028        nomerge
1029        forcesac
1030        soft
1031        pt [x86, IA64]
1032
1033    io7= [HW] IO7 for Marvel based alpha systems
1034            See comment before marvel_specify_io7 in
1035            arch/alpha/kernel/core_marvel.c.
1036
1037    io_delay= [X86] I/O delay method
1038        0x80
1039            Standard port 0x80 based delay
1040        0xed
1041            Alternate port 0xed based delay (needed on some systems)
1042        udelay
1043            Simple two microseconds delay
1044        none
1045            No delay
1046
1047    ip= [IP_PNP]
1048            See Documentation/filesystems/nfs/nfsroot.txt.
1049
1050    ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1051            See comment before ip2_setup() in
1052            drivers/char/ip2/ip2base.c.
1053
1054    ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1055            See header of drivers/scsi/ips.c.
1056
1057    irqfixup [HW]
1058            When an interrupt is not handled search all handlers
1059            for it. Intended to get systems with badly broken
1060            firmware running.
1061
1062    irqpoll [HW]
1063            When an interrupt is not handled search all handlers
1064            for it. Also check all handlers each timer
1065            interrupt. Intended to get systems with badly broken
1066            firmware running.
1067
1068    isapnp= [ISAPNP]
1069            Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1070
1071    isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1072            Format:
1073            <cpu number>,...,<cpu number>
1074            or
1075            <cpu number>-<cpu number>
1076            (must be a positive range in ascending order)
1077            or a mixture
1078            <cpu number>,...,<cpu number>-<cpu number>
1079
1080            This option can be used to specify one or more CPUs
1081            to isolate from the general SMP balancing and scheduling
1082            algorithms. You can move a process onto or off an
1083            "isolated" CPU via the CPU affinity syscalls or cpuset.
1084            <cpu number> begins at 0 and the maximum value is
1085            "number of CPUs in system - 1".
1086
1087            This option is the preferred way to isolate CPUs. The
1088            alternative -- manually setting the CPU mask of all
1089            tasks in the system -- can cause problems and
1090            suboptimal load balancer performance.
1091
1092    iucv= [HW,NET]
1093
1094    js= [HW,JOY] Analog joystick
1095            See Documentation/input/joystick.txt.
1096
1097    keepinitrd [HW,ARM]
1098
1099    kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1100            specifies the amount of memory usable by the kernel
1101            for non-movable allocations. The requested amount is
1102            spread evenly throughout all nodes in the system. The
1103            remaining memory in each node is used for Movable
1104            pages. In the event, a node is too small to have both
1105            kernelcore and Movable pages, kernelcore pages will
1106            take priority and other nodes will have a larger number
1107            of kernelcore pages. The Movable zone is used for the
1108            allocation of pages that may be reclaimed or moved
1109            by the page migration subsystem. This means that
1110            HugeTLB pages may not be allocated from this zone.
1111            Note that allocations like PTEs-from-HighMem still
1112            use the HighMem zone if it exists, and the Normal
1113            zone if it does not.
1114
1115    kgdboc= [HW] kgdb over consoles.
1116            Requires a tty driver that supports console polling.
1117            (only serial supported for now)
1118            Format: <serial_device>[,baud]
1119
1120    kmac= [MIPS] korina ethernet MAC address.
1121            Configure the RouterBoard 532 series on-chip
1122            Ethernet adapter MAC address.
1123
1124    kmemleak= [KNL] Boot-time kmemleak enable/disable
1125            Valid arguments: on, off
1126            Default: on
1127
1128    kstack=N [X86] Print N words from the kernel stack
1129            in oops dumps.
1130
1131    kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1132            Default is 0 (don't ignore, but inject #GP)
1133
1134    kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1135            Default is 1 (enabled)
1136
1137    kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1138            Default is 0 (off)
1139
1140    kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1141            for all guests.
1142            Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1143
1144    kvm-intel.bypass_guest_pf=
1145            [KVM,Intel] Disables bypassing of guest page faults
1146            on Intel chips. Default is 1 (enabled)
1147
1148    kvm-intel.ept= [KVM,Intel] Disable extended page tables
1149            (virtualized MMU) support on capable Intel chips.
1150            Default is 1 (enabled)
1151
1152    kvm-intel.emulate_invalid_guest_state=
1153            [KVM,Intel] Enable emulation of invalid guest states
1154            Default is 0 (disabled)
1155
1156    kvm-intel.flexpriority=
1157            [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1158            Default is 1 (enabled)
1159
1160    kvm-intel.unrestricted_guest=
1161            [KVM,Intel] Disable unrestricted guest feature
1162            (virtualized real and unpaged mode) on capable
1163            Intel chips. Default is 1 (enabled)
1164
1165    kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1166            feature (tagged TLBs) on capable Intel chips.
1167            Default is 1 (enabled)
1168
1169    l2cr= [PPC]
1170
1171    l3cr= [PPC]
1172
1173    lapic [X86-32,APIC] Enable the local APIC even if BIOS
1174            disabled it.
1175
1176    lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1177            in C2 power state.
1178
1179    libata.dma= [LIBATA] DMA control
1180            libata.dma=0 Disable all PATA and SATA DMA
1181            libata.dma=1 PATA and SATA Disk DMA only
1182            libata.dma=2 ATAPI (CDROM) DMA only
1183            libata.dma=4 Compact Flash DMA only
1184            Combinations also work, so libata.dma=3 enables DMA
1185            for disks and CDROMs, but not CFs.
1186    
1187    libata.ignore_hpa= [LIBATA] Ignore HPA limit
1188            libata.ignore_hpa=0 keep BIOS limits (default)
1189            libata.ignore_hpa=1 ignore limits, using full disk
1190
1191    libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1192            when set.
1193            Format: <int>
1194
1195    libata.force= [LIBATA] Force configurations. The format is comma
1196            separated list of "[ID:]VAL" where ID is
1197            PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1198            matching port, link or device. Basically, it matches
1199            the ATA ID string printed on console by libata. If
1200            the whole ID part is omitted, the last PORT and DEVICE
1201            values are used. If ID hasn't been specified yet, the
1202            configuration applies to all ports, links and devices.
1203
1204            If only DEVICE is omitted, the parameter applies to
1205            the port and all links and devices behind it. DEVICE
1206            number of 0 either selects the first device or the
1207            first fan-out link behind PMP device. It does not
1208            select the host link. DEVICE number of 15 selects the
1209            host link and device attached to it.
1210
1211            The VAL specifies the configuration to force. As long
1212            as there's no ambiguity shortcut notation is allowed.
1213            For example, both 1.5 and 1.5G would work for 1.5Gbps.
1214            The following configurations can be forced.
1215
1216            * Cable type: 40c, 80c, short40c, unk, ign or sata.
1217              Any ID with matching PORT is used.
1218
1219            * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1220
1221            * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1222              udma[/][16,25,33,44,66,100,133] notation is also
1223              allowed.
1224
1225            * [no]ncq: Turn on or off NCQ.
1226
1227            * nohrst, nosrst, norst: suppress hard, soft
1228                          and both resets.
1229
1230            If there are multiple matching configurations changing
1231            the same attribute, the last one is used.
1232
1233    lmb=debug [KNL] Enable lmb debug messages.
1234
1235    load_ramdisk= [RAM] List of ramdisks to load from floppy
1236            See Documentation/blockdev/ramdisk.txt.
1237
1238    lockd.nlm_grace_period=P [NFS] Assign grace period.
1239            Format: <integer>
1240
1241    lockd.nlm_tcpport=N [NFS] Assign TCP port.
1242            Format: <integer>
1243
1244    lockd.nlm_timeout=T [NFS] Assign timeout value.
1245            Format: <integer>
1246
1247    lockd.nlm_udpport=M [NFS] Assign UDP port.
1248            Format: <integer>
1249
1250    logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1251            Format: <irq>
1252
1253    loglevel= All Kernel Messages with a loglevel smaller than the
1254            console loglevel will be printed to the console. It can
1255            also be changed with klogd or other programs. The
1256            loglevels are defined as follows:
1257
1258            0 (KERN_EMERG) system is unusable
1259            1 (KERN_ALERT) action must be taken immediately
1260            2 (KERN_CRIT) critical conditions
1261            3 (KERN_ERR) error conditions
1262            4 (KERN_WARNING) warning conditions
1263            5 (KERN_NOTICE) normal but significant condition
1264            6 (KERN_INFO) informational
1265            7 (KERN_DEBUG) debug-level messages
1266
1267    log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1268            Format: { n | nk | nM }
1269            n must be a power of two. The default size
1270            is set in the kernel config file.
1271
1272    logo.nologo [FB] Disables display of the built-in Linux logo.
1273            This may be used to provide more screen space for
1274            kernel log messages and is useful when debugging
1275            kernel boot problems.
1276
1277    lp=0 [LP] Specify parallel ports to use, e.g,
1278    lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1279    lp=reset first parallel port). 'lp=0' disables the
1280    lp=auto printer driver. 'lp=reset' (which can be
1281                specified in addition to the ports) causes
1282                attached printers to be reset. Using
1283                lp=port1,port2,... specifies the parallel ports
1284                to associate lp devices with, starting with
1285                lp0. A port specification may be 'none' to skip
1286                that lp device, or a parport name such as
1287                'parport0'. Specifying 'lp=auto' instead of a
1288                port specification list means that device IDs
1289                from each port should be examined, to see if
1290                an IEEE 1284-compliant printer is attached; if
1291                so, the driver will manage that printer.
1292                See also header of drivers/char/lp.c.
1293
1294    lpj=n [KNL]
1295            Sets loops_per_jiffy to given constant, thus avoiding
1296            time-consuming boot-time autodetection (up to 250 ms per
1297            CPU). 0 enables autodetection (default). To determine
1298            the correct value for your kernel, boot with normal
1299            autodetection and see what value is printed. Note that
1300            on SMP systems the preset will be applied to all CPUs,
1301            which is likely to cause problems if your CPUs need
1302            significantly divergent settings. An incorrect value
1303            will cause delays in the kernel to be wrong, leading to
1304            unpredictable I/O errors and other breakage. Although
1305            unlikely, in the extreme case this might damage your
1306            hardware.
1307
1308    ltpc= [NET]
1309            Format: <io>,<irq>,<dma>
1310
1311    mac5380= [HW,SCSI] Format:
1312            <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1313
1314    machvec= [IA64] Force the use of a particular machine-vector
1315            (machvec) in a generic kernel.
1316            Example: machvec=hpzx1_swiotlb
1317
1318    machtype= [Loongson] Share the same kernel image file between different
1319             yeeloong laptop.
1320            Example: machtype=lemote-yeeloong-2f-7inch
1321
1322    max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323            than or equal to this physical address is ignored.
1324
1325    maxcpus= [SMP] Maximum number of processors that an SMP kernel
1326            should make use of. maxcpus=n : n >= 0 limits the
1327            kernel to using 'n' processors. n=0 is a special case,
1328            it is equivalent to "nosmp", which also disables
1329            the IO APIC.
1330
1331    max_loop= [LOOP] Maximum number of loopback devices that can
1332            be mounted
1333            Format: <1-256>
1334
1335    max_luns= [SCSI] Maximum number of LUNs to probe.
1336            Should be between 1 and 2^32-1.
1337
1338    max_report_luns=
1339            [SCSI] Maximum number of LUNs received.
1340            Should be between 1 and 16384.
1341
1342    mcatest= [IA-64]
1343
1344    mce [X86-32] Machine Check Exception
1345
1346    mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1347
1348    md= [HW] RAID subsystems devices and level
1349            See Documentation/md.txt.
1350
1351    mdacon= [MDA]
1352            Format: <first>,<last>
1353            Specifies range of consoles to be captured by the MDA.
1354
1355    mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1356            Amount of memory to be used when the kernel is not able
1357            to see the whole system memory or for test.
1358            [X86-32] Use together with memmap= to avoid physical
1359            address space collisions. Without memmap= PCI devices
1360            could be placed at addresses belonging to unused RAM.
1361
1362    mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1363            memory.
1364
1365    memchunk=nn[KMG]
1366            [KNL,SH] Allow user to override the default size for
1367            per-device physically contiguous DMA buffers.
1368
1369    memmap=exactmap [KNL,X86] Enable setting of an exact
1370            E820 memory map, as specified by the user.
1371            Such memmap=exactmap lines can be constructed based on
1372            BIOS output or other requirements. See the memmap=nn@ss
1373            option description.
1374
1375    memmap=nn[KMG]@ss[KMG]
1376            [KNL] Force usage of a specific region of memory
1377            Region of memory to be used, from ss to ss+nn.
1378
1379    memmap=nn[KMG]#ss[KMG]
1380            [KNL,ACPI] Mark specific memory as ACPI data.
1381            Region of memory to be used, from ss to ss+nn.
1382
1383    memmap=nn[KMG]$ss[KMG]
1384            [KNL,ACPI] Mark specific memory as reserved.
1385            Region of memory to be used, from ss to ss+nn.
1386            Example: Exclude memory from 0x18690000-0x1869ffff
1387                     memmap=64K$0x18690000
1388                     or
1389                     memmap=0x10000$0x18690000
1390
1391    memory_corruption_check=0/1 [X86]
1392            Some BIOSes seem to corrupt the first 64k of
1393            memory when doing things like suspend/resume.
1394            Setting this option will scan the memory
1395            looking for corruption. Enabling this will
1396            both detect corruption and prevent the kernel
1397            from using the memory being corrupted.
1398            However, its intended as a diagnostic tool; if
1399            repeatable BIOS-originated corruption always
1400            affects the same memory, you can use memmap=
1401            to prevent the kernel from using that memory.
1402
1403    memory_corruption_check_size=size [X86]
1404            By default it checks for corruption in the low
1405            64k, making this memory unavailable for normal
1406            use. Use this parameter to scan for
1407            corruption in more or less memory.
1408
1409    memory_corruption_check_period=seconds [X86]
1410            By default it checks for corruption every 60
1411            seconds. Use this parameter to check at some
1412            other rate. 0 disables periodic checking.
1413
1414    memtest= [KNL,X86] Enable memtest
1415            Format: <integer>
1416            default : 0 <disable>
1417            Specifies the number of memtest passes to be
1418            performed. Each pass selects another test
1419            pattern from a given set of patterns. Memtest
1420            fills the memory with this pattern, validates
1421            memory contents and reserves bad memory
1422            regions that are detected.
1423
1424    meye.*= [HW] Set MotionEye Camera parameters
1425            See Documentation/video4linux/meye.txt.
1426
1427    mfgpt_irq= [IA-32] Specify the IRQ to use for the
1428            Multi-Function General Purpose Timers on AMD Geode
1429            platforms.
1430
1431    mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1432            the BIOS has incorrectly applied a workaround. TinyBIOS
1433            version 0.98 is known to be affected, 0.99 fixes the
1434            problem by letting the user disable the workaround.
1435
1436    mga= [HW,DRM]
1437
1438    min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1439            physical address is ignored.
1440
1441    mini2440= [ARM,HW,KNL]
1442            Format:[0..2][b][c][t]
1443            Default: "0tb"
1444            MINI2440 configuration specification:
1445            0 - The attached screen is the 3.5" TFT
1446            1 - The attached screen is the 7" TFT
1447            2 - The VGA Shield is attached (1024x768)
1448            Leaving out the screen size parameter will not load
1449            the TFT driver, and the framebuffer will be left
1450            unconfigured.
1451            b - Enable backlight. The TFT backlight pin will be
1452            linked to the kernel VESA blanking code and a GPIO
1453            LED. This parameter is not necessary when using the
1454            VGA shield.
1455            c - Enable the s3c camera interface.
1456            t - Reserved for enabling touchscreen support. The
1457            touchscreen support is not enabled in the mainstream
1458            kernel as of 2.6.30, a preliminary port can be found
1459            in the "bleeding edge" mini2440 support kernel at
1460            http://repo.or.cz/w/linux-2.6/mini2440.git
1461
1462    mminit_loglevel=
1463            [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1464            parameter allows control of the logging verbosity for
1465            the additional memory initialisation checks. A value
1466            of 0 disables mminit logging and a level of 4 will
1467            log everything. Information is printed at KERN_DEBUG
1468            so loglevel=8 may also need to be specified.
1469
1470    mousedev.tap_time=
1471            [MOUSE] Maximum time between finger touching and
1472            leaving touchpad surface for touch to be considered
1473            a tap and be reported as a left button click (for
1474            touchpads working in absolute mode only).
1475            Format: <msecs>
1476    mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1477            reporting absolute coordinates, such as tablets
1478    mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1479            reporting absolute coordinates, such as tablets
1480
1481    movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1482            is similar to kernelcore except it specifies the
1483            amount of memory used for migratable allocations.
1484            If both kernelcore and movablecore is specified,
1485            then kernelcore will be at *least* the specified
1486            value but may be more. If movablecore on its own
1487            is specified, the administrator must be careful
1488            that the amount of memory usable for all allocations
1489            is not too small.
1490
1491    mpu401= [HW,OSS]
1492            Format: <io>,<irq>
1493
1494    MTD_Partition= [MTD]
1495            Format: <name>,<region-number>,<size>,<offset>
1496
1497    MTD_Region= [MTD] Format:
1498            <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1499
1500    mtdparts= [MTD]
1501            See drivers/mtd/cmdlinepart.c.
1502
1503    onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1504
1505            Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1506
1507            boundary - index of last SLC block on Flex-OneNAND.
1508                   The remaining blocks are configured as MLC blocks.
1509            lock - Configure if Flex-OneNAND boundary should be locked.
1510                   Once locked, the boundary cannot be changed.
1511                   1 indicates lock status, 0 indicates unlock status.
1512
1513    mtdset= [ARM]
1514            ARM/S3C2412 JIVE boot control
1515
1516            See arch/arm/mach-s3c2412/mach-jive.c
1517
1518    mtouchusb.raw_coordinates=
1519            [HW] Make the MicroTouch USB driver use raw coordinates
1520            ('y', default) or cooked coordinates ('n')
1521
1522    mtrr_chunk_size=nn[KMG] [X86]
1523            used for mtrr cleanup. It is largest continuous chunk
1524            that could hold holes aka. UC entries.
1525
1526    mtrr_gran_size=nn[KMG] [X86]
1527            Used for mtrr cleanup. It is granularity of mtrr block.
1528            Default is 1.
1529            Large value could prevent small alignment from
1530            using up MTRRs.
1531
1532    mtrr_spare_reg_nr=n [X86]
1533            Format: <integer>
1534            Range: 0,7 : spare reg number
1535            Default : 1
1536            Used for mtrr cleanup. It is spare mtrr entries number.
1537            Set to 2 or more if your graphical card needs more.
1538
1539    n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1540
1541    NCR_D700= [HW,SCSI]
1542            See header of drivers/scsi/NCR_D700.c.
1543
1544    ncr5380= [HW,SCSI]
1545
1546    ncr53c400= [HW,SCSI]
1547
1548    ncr53c400a= [HW,SCSI]
1549
1550    ncr53c406a= [HW,SCSI]
1551
1552    ncr53c8xx= [HW,SCSI]
1553
1554    netdev= [NET] Network devices parameters
1555            Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1556            Note that mem_start is often overloaded to mean
1557            something different and driver-specific.
1558            This usage is only documented in each driver source
1559            file if at all.
1560
1561    nf_conntrack.acct=
1562            [NETFILTER] Enable connection tracking flow accounting
1563            0 to disable accounting
1564            1 to enable accounting
1565            Default value depends on CONFIG_NF_CT_ACCT that is
1566            going to be removed in 2.6.29.
1567
1568    nfsaddrs= [NFS]
1569            See Documentation/filesystems/nfs/nfsroot.txt.
1570
1571    nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1572            See Documentation/filesystems/nfs/nfsroot.txt.
1573
1574    nfs.callback_tcpport=
1575            [NFS] set the TCP port on which the NFSv4 callback
1576            channel should listen.
1577
1578    nfs.cache_getent=
1579            [NFS] sets the pathname to the program which is used
1580            to update the NFS client cache entries.
1581
1582    nfs.cache_getent_timeout=
1583            [NFS] sets the timeout after which an attempt to
1584            update a cache entry is deemed to have failed.
1585
1586    nfs.idmap_cache_timeout=
1587            [NFS] set the maximum lifetime for idmapper cache
1588            entries.
1589
1590    nfs.enable_ino64=
1591            [NFS] enable 64-bit inode numbers.
1592            If zero, the NFS client will fake up a 32-bit inode
1593            number for the readdir() and stat() syscalls instead
1594            of returning the full 64-bit number.
1595            The default is to return 64-bit inode numbers.
1596
1597    nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1598            when a NMI is triggered.
1599            Format: [state][,regs][,debounce][,die]
1600
1601    nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1602            Format: [panic,][num]
1603            Valid num: 0,1,2
1604            0 - turn nmi_watchdog off
1605            1 - use the IO-APIC timer for the NMI watchdog
1606            2 - use the local APIC for the NMI watchdog using
1607            a performance counter. Note: This will use one
1608            performance counter and the local APIC's performance
1609            vector.
1610            When panic is specified, panic when an NMI watchdog
1611            timeout occurs.
1612            This is useful when you use a panic=... timeout and
1613            need the box quickly up again.
1614            Instead of 1 and 2 it is possible to use the following
1615            symbolic names: lapic and ioapic
1616            Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1617
1618    netpoll.carrier_timeout=
1619            [NET] Specifies amount of time (in seconds) that
1620            netpoll should wait for a carrier. By default netpoll
1621            waits 4 seconds.
1622
1623    no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1624            emulation library even if a 387 maths coprocessor
1625            is present.
1626
1627    no_console_suspend
1628            [HW] Never suspend the console
1629            Disable suspending of consoles during suspend and
1630            hibernate operations. Once disabled, debugging
1631            messages can reach various consoles while the rest
1632            of the system is being put to sleep (ie, while
1633            debugging driver suspend/resume hooks). This may
1634            not work reliably with all consoles, but is known
1635            to work with serial and VGA consoles.
1636
1637    noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1638            caches in the slab allocator. Saves per-node memory,
1639            but will impact performance.
1640
1641    noalign [KNL,ARM]
1642
1643    noapic [SMP,APIC] Tells the kernel to not make use of any
1644            IOAPICs that may be present in the system.
1645
1646    nobats [PPC] Do not use BATs for mapping kernel lowmem
1647            on "Classic" PPC cores.
1648
1649    nocache [ARM]
1650
1651    noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1652
1653    nodelayacct [KNL] Disable per-task delay accounting
1654
1655    nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1656
1657    nodsp [SH] Disable hardware DSP at boot time.
1658
1659    noefi [X86] Disable EFI runtime services support.
1660
1661    noexec [IA-64]
1662
1663    noexec [X86]
1664            On X86-32 available only on PAE configured kernels.
1665            noexec=on: enable non-executable mappings (default)
1666            noexec=off: disable non-executable mappings
1667
1668    noexec32 [X86-64]
1669            This affects only 32-bit executables.
1670            noexec32=on: enable non-executable mappings (default)
1671                read doesn't imply executable mappings
1672            noexec32=off: disable non-executable mappings
1673                read implies executable mappings
1674
1675    nofpu [SH] Disable hardware FPU at boot time.
1676
1677    nofxsr [BUGS=X86-32] Disables x86 floating point extended
1678            register save and restore. The kernel will only save
1679            legacy floating-point registers on task switch.
1680
1681    noxsave [BUGS=X86] Disables x86 extended register state save
1682            and restore using xsave. The kernel will fallback to
1683            enabling legacy floating-point and sse state.
1684
1685    nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1686            wfi(ARM) instruction doesn't work correctly and not to
1687            use it. This is also useful when using JTAG debugger.
1688
1689    no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1690            instruction doesn't work correctly and not to
1691            use it.
1692
1693    no_file_caps Tells the kernel not to honor file capabilities. The
1694            only way then for a file to be executed with privilege
1695            is to be setuid root or executed by root.
1696
1697    nohalt [IA-64] Tells the kernel not to use the power saving
1698            function PAL_HALT_LIGHT when idle. This increases
1699            power-consumption. On the positive side, it reduces
1700            interrupt wake-up latency, which may improve performance
1701            in certain environments such as networked servers or
1702            real-time systems.
1703
1704    nohz= [KNL] Boottime enable/disable dynamic ticks
1705            Valid arguments: on, off
1706            Default: on
1707
1708    noiotrap [SH] Disables trapped I/O port accesses.
1709
1710    noirqdebug [X86-32] Disables the code which attempts to detect and
1711            disable unhandled interrupt sources.
1712
1713    no_timer_check [X86,APIC] Disables the code which tests for
1714            broken timer IRQ sources.
1715
1716    noisapnp [ISAPNP] Disables ISA PnP code.
1717
1718    noinitrd [RAM] Tells the kernel not to load any configured
1719            initial RAM disk.
1720
1721    nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1722            remapping.
1723
1724    nointroute [IA-64]
1725
1726    nojitter [IA64] Disables jitter checking for ITC timers.
1727
1728    nolapic [X86-32,APIC] Do not enable or use the local APIC.
1729
1730    nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1731
1732    noltlbs [PPC] Do not use large page/tlb entries for kernel
1733            lowmem mapping on PPC40x.
1734
1735    nomca [IA-64] Disable machine check abort handling
1736
1737    nomce [X86-32] Machine Check Exception
1738
1739    nomfgpt [X86-32] Disable Multi-Function General Purpose
1740            Timer usage (for AMD Geode machines).
1741
1742    nopat [X86] Disable PAT (page attribute table extension of
1743            pagetables) support.
1744
1745    norandmaps Don't use address space randomization. Equivalent to
1746            echo 0 > /proc/sys/kernel/randomize_va_space
1747
1748    noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1749
1750    noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1751            with UP alternatives
1752
1753    noresidual [PPC] Don't use residual data on PReP machines.
1754
1755    noresume [SWSUSP] Disables resume and restores original swap
1756            space.
1757
1758    no-scroll [VGA] Disables scrollback.
1759            This is required for the Braillex ib80-piezo Braille
1760            reader made by F.H. Papenmeier (Germany).
1761
1762    nosbagart [IA-64]
1763
1764    nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1765
1766    nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1767            and disable the IO APIC. legacy for "maxcpus=0".
1768
1769    nosoftlockup [KNL] Disable the soft-lockup detector.
1770
1771    noswapaccount [KNL] Disable accounting of swap in memory resource
1772            controller. (See Documentation/cgroups/memory.txt)
1773
1774    nosync [HW,M68K] Disables sync negotiation for all devices.
1775
1776    notsc [BUGS=X86-32] Disable Time Stamp Counter
1777
1778    nousb [USB] Disable the USB subsystem
1779
1780    nowb [ARM]
1781
1782    nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1783
1784    nptcg= [IA64] Override max number of concurrent global TLB
1785            purges which is reported from either PAL_VM_SUMMARY or
1786            SAL PALO.
1787
1788    nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1789            could support. nr_cpus=n : n >= 1 limits the kernel to
1790            supporting 'n' processors. Later in runtime you can not
1791            use hotplug cpu feature to put more cpu back to online.
1792            just like you compile the kernel NR_CPUS=n
1793
1794    nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1795
1796    numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1797            one of ['zone', 'node', 'default'] can be specified
1798            This can be set from sysctl after boot.
1799            See Documentation/sysctl/vm.txt for details.
1800
1801    ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1802            See Documentation/debugging-via-ohci1394.txt for more
1803            info.
1804
1805    olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1806            Rather than timing out after 20 ms if an EC
1807            command is not properly ACKed, override the length
1808            of the timeout. We have interrupts disabled while
1809            waiting for the ACK, so if this is set too high
1810            interrupts *may* be lost!
1811
1812    omap_mux= [OMAP] Override bootloader pin multiplexing.
1813            Format: <mux_mode0.mode_name=value>...
1814            For example, to override I2C bus2:
1815            omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1816
1817    opl3= [HW,OSS]
1818            Format: <io>
1819
1820    oprofile.timer= [HW]
1821            Use timer interrupt instead of performance counters
1822
1823    oprofile.cpu_type= Force an oprofile cpu type
1824            This might be useful if you have an older oprofile
1825            userland or if you want common events.
1826            Format: { arch_perfmon }
1827            arch_perfmon: [X86] Force use of architectural
1828                perfmon on Intel CPUs instead of the
1829                CPU specific event set.
1830
1831    osst= [HW,SCSI] SCSI Tape Driver
1832            Format: <buffer_size>,<write_threshold>
1833            See also Documentation/scsi/st.txt.
1834
1835    panic= [KNL] Kernel behaviour on panic
1836            Format: <timeout>
1837
1838    parkbd.port= [HW] Parallel port number the keyboard adapter is
1839            connected to, default is 0.
1840            Format: <parport#>
1841    parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1842            0 for XT, 1 for AT (default is AT).
1843            Format: <mode>
1844
1845    parport= [HW,PPT] Specify parallel ports. 0 disables.
1846            Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1847            Use 'auto' to force the driver to use any
1848            IRQ/DMA settings detected (the default is to
1849            ignore detected IRQ/DMA settings because of
1850            possible conflicts). You can specify the base
1851            address, IRQ, and DMA settings; IRQ and DMA
1852            should be numbers, or 'auto' (for using detected
1853            settings on that particular port), or 'nofifo'
1854            (to avoid using a FIFO even if it is detected).
1855            Parallel ports are assigned in the order they
1856            are specified on the command line, starting
1857            with parport0.
1858
1859    parport_init_mode= [HW,PPT]
1860            Configure VIA parallel port to operate in
1861            a specific mode. This is necessary on Pegasos
1862            computer where firmware has no options for setting
1863            up parallel port mode and sets it to spp.
1864            Currently this function knows 686a and 8231 chips.
1865            Format: [spp|ps2|epp|ecp|ecpepp]
1866
1867    pas2= [HW,OSS] Format:
1868            <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1869
1870    pas16= [HW,SCSI]
1871            See header of drivers/scsi/pas16.c.
1872
1873    pause_on_oops=
1874            Halt all CPUs after the first oops has been printed for
1875            the specified number of seconds. This is to be used if
1876            your oopses keep scrolling off the screen.
1877
1878    pcbit= [HW,ISDN]
1879
1880    pcd. [PARIDE]
1881            See header of drivers/block/paride/pcd.c.
1882            See also Documentation/blockdev/paride.txt.
1883
1884    pci=option[,option...] [PCI] various PCI subsystem options:
1885        earlydump [X86] dump PCI config space before the kernel
1886                    changes anything
1887        off [X86] don't probe for the PCI bus
1888        bios [X86-32] force use of PCI BIOS, don't access
1889                the hardware directly. Use this if your machine
1890                has a non-standard PCI host bridge.
1891        nobios [X86-32] disallow use of PCI BIOS, only direct
1892                hardware access methods are allowed. Use this
1893                if you experience crashes upon bootup and you
1894                suspect they are caused by the BIOS.
1895        conf1 [X86] Force use of PCI Configuration
1896                Mechanism 1.
1897        conf2 [X86] Force use of PCI Configuration
1898                Mechanism 2.
1899        noaer [PCIE] If the PCIEAER kernel config parameter is
1900                enabled, this kernel boot option can be used to
1901                disable the use of PCIE advanced error reporting.
1902        nodomains [PCI] Disable support for multiple PCI
1903                root domains (aka PCI segments, in ACPI-speak).
1904        nommconf [X86] Disable use of MMCONFIG for PCI
1905                Configuration
1906        check_enable_amd_mmconf [X86] check for and enable
1907                properly configured MMIO access to PCI
1908                config space on AMD family 10h CPU
1909        nomsi [MSI] If the PCI_MSI kernel config parameter is
1910                enabled, this kernel boot option can be used to
1911                disable the use of MSI interrupts system-wide.
1912        noioapicquirk [APIC] Disable all boot interrupt quirks.
1913                Safety option to keep boot IRQs enabled. This
1914                should never be necessary.
1915        ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1916                primary IO-APIC for bridges that cannot disable
1917                boot IRQs. This fixes a source of spurious IRQs
1918                when the system masks IRQs.
1919        noioapicreroute [APIC] Disable workaround that uses the
1920                boot IRQ equivalent of an IRQ that connects to
1921                a chipset where boot IRQs cannot be disabled.
1922                The opposite of ioapicreroute.
1923        biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1924                routing table. These calls are known to be buggy
1925                on several machines and they hang the machine
1926                when used, but on other computers it's the only
1927                way to get the interrupt routing table. Try
1928                this option if the kernel is unable to allocate
1929                IRQs or discover secondary PCI buses on your
1930                motherboard.
1931        rom [X86] Assign address space to expansion ROMs.
1932                Use with caution as certain devices share
1933                address decoders between ROMs and other
1934                resources.
1935        norom [X86] Do not assign address space to
1936                expansion ROMs that do not already have
1937                BIOS assigned address ranges.
1938        irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1939                assigned automatically to PCI devices. You can
1940                make the kernel exclude IRQs of your ISA cards
1941                this way.
1942        pirqaddr=0xAAAAA [X86] Specify the physical address
1943                of the PIRQ table (normally generated
1944                by the BIOS) if it is outside the
1945                F0000h-100000h range.
1946        lastbus=N [X86] Scan all buses thru bus #N. Can be
1947                useful if the kernel is unable to find your
1948                secondary buses and you want to tell it
1949                explicitly which ones they are.
1950        assign-busses [X86] Always assign all PCI bus
1951                numbers ourselves, overriding
1952                whatever the firmware may have done.
1953        usepirqmask [X86] Honor the possible IRQ mask stored
1954                in the BIOS $PIR table. This is needed on
1955                some systems with broken BIOSes, notably
1956                some HP Pavilion N5400 and Omnibook XE3
1957                notebooks. This will have no effect if ACPI
1958                IRQ routing is enabled.
1959        noacpi [X86] Do not use ACPI for IRQ routing
1960                or for PCI scanning.
1961        use_crs [X86] Use PCI host bridge window information
1962                from ACPI. On BIOSes from 2008 or later, this
1963                is enabled by default. If you need to use this,
1964                please report a bug.
1965        nocrs [X86] Ignore PCI host bridge windows from ACPI.
1966                    If you need to use this, please report a bug.
1967        routeirq Do IRQ routing for all PCI devices.
1968                This is normally done in pci_enable_device(),
1969                so this option is a temporary workaround
1970                for broken drivers that don't call it.
1971        skip_isa_align [X86] do not align io start addr, so can
1972                handle more pci cards
1973        firmware [ARM] Do not re-enumerate the bus but instead
1974                just use the configuration from the
1975                bootloader. This is currently used on
1976                IXP2000 systems where the bus has to be
1977                configured a certain way for adjunct CPUs.
1978        noearly [X86] Don't do any early type 1 scanning.
1979                This might help on some broken boards which
1980                machine check when some devices' config space
1981                is read. But various workarounds are disabled
1982                and some IOMMU drivers will not work.
1983        bfsort Sort PCI devices into breadth-first order.
1984                This sorting is done to get a device
1985                order compatible with older (<= 2.4) kernels.
1986        nobfsort Don't sort PCI devices into breadth-first order.
1987        cbiosize=nn[KMG] The fixed amount of bus space which is
1988                reserved for the CardBus bridge's IO window.
1989                The default value is 256 bytes.
1990        cbmemsize=nn[KMG] The fixed amount of bus space which is
1991                reserved for the CardBus bridge's memory
1992                window. The default value is 64 megabytes.
1993        resource_alignment=
1994                Format:
1995                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1996                Specifies alignment and device to reassign
1997                aligned memory resources.
1998                If <order of align> is not specified,
1999                PAGE_SIZE is used as alignment.
2000                PCI-PCI bridge can be specified, if resource
2001                windows need to be expanded.
2002        ecrc= Enable/disable PCIe ECRC (transaction layer
2003                end-to-end CRC checking).
2004                bios: Use BIOS/firmware settings. This is the
2005                the default.
2006                off: Turn ECRC off
2007                on: Turn ECRC on.
2008
2009    pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2010            Management.
2011        off Disable ASPM.
2012        force Enable ASPM even on devices that claim not to support it.
2013            WARNING: Forcing ASPM on may cause system lockups.
2014
2015    pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2016        off Do not use native PCIe PME signaling.
2017        force Use native PCIe PME signaling even if the BIOS refuses
2018            to allow the kernel to control the relevant PCIe config
2019            registers.
2020        nomsi Do not use MSI for native PCIe PME signaling (this makes
2021            all PCIe root ports use INTx for everything).
2022
2023    pcmv= [HW,PCMCIA] BadgePAD 4
2024
2025    pd. [PARIDE]
2026            See Documentation/blockdev/paride.txt.
2027
2028    pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2029            boot time.
2030            Format: { 0 | 1 }
2031            See arch/parisc/kernel/pdc_chassis.c
2032
2033    percpu_alloc= Select which percpu first chunk allocator to use.
2034            Currently supported values are "embed" and "page".
2035            Archs may support subset or none of the selections.
2036            See comments in mm/percpu.c for details on each
2037            allocator. This parameter is primarily for debugging
2038            and performance comparison.
2039
2040    pf. [PARIDE]
2041            See Documentation/blockdev/paride.txt.
2042
2043    pg. [PARIDE]
2044            See Documentation/blockdev/paride.txt.
2045
2046    pirq= [SMP,APIC] Manual mp-table setup
2047            See Documentation/x86/i386/IO-APIC.txt.
2048
2049    plip= [PPT,NET] Parallel port network link
2050            Format: { parport<nr> | timid | 0 }
2051            See also Documentation/parport.txt.
2052
2053    pmtmr= [X86] Manual setup of pmtmr I/O Port.
2054            Override pmtimer IOPort with a hex value.
2055            e.g. pmtmr=0x508
2056
2057    pnp.debug [PNP]
2058            Enable PNP debug messages. This depends on the
2059            CONFIG_PNP_DEBUG_MESSAGES option.
2060
2061    pnpacpi= [ACPI]
2062            { off }
2063
2064    pnpbios= [ISAPNP]
2065            { on | off | curr | res | no-curr | no-res }
2066
2067    pnp_reserve_irq=
2068            [ISAPNP] Exclude IRQs for the autoconfiguration
2069
2070    pnp_reserve_dma=
2071            [ISAPNP] Exclude DMAs for the autoconfiguration
2072
2073    pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2074            Ranges are in pairs (I/O port base and size).
2075
2076    pnp_reserve_mem=
2077            [ISAPNP] Exclude memory regions for the
2078            autoconfiguration.
2079            Ranges are in pairs (memory base and size).
2080
2081    ports= [IP_VS_FTP] IPVS ftp helper module
2082            Default is 21.
2083            Up to 8 (IP_VS_APP_MAX_PORTS) ports
2084            may be specified.
2085            Format: <port>,<port>....
2086
2087    print-fatal-signals=
2088            [KNL] debug: print fatal signals
2089
2090            If enabled, warn about various signal handling
2091            related application anomalies: too many signals,
2092            too many POSIX.1 timers, fatal signals causing a
2093            coredump - etc.
2094
2095            If you hit the warning due to signal overflow,
2096            you might want to try "ulimit -i unlimited".
2097
2098            default: off.
2099
2100    printk.time= Show timing data prefixed to each printk message line
2101            Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2102
2103    processor.max_cstate= [HW,ACPI]
2104            Limit processor to maximum C-state
2105            max_cstate=9 overrides any DMI blacklist limit.
2106
2107    processor.nocst [HW,ACPI]
2108            Ignore the _CST method to determine C-states,
2109            instead using the legacy FADT method
2110
2111    profile= [KNL] Enable kernel profiling via /proc/profile
2112            Format: [schedule,]<number>
2113            Param: "schedule" - profile schedule points.
2114            Param: <number> - step/bucket size as a power of 2 for
2115                statistical time based profiling.
2116            Param: "sleep" - profile D-state sleeping (millisecs).
2117                Requires CONFIG_SCHEDSTATS
2118            Param: "kvm" - profile VM exits.
2119
2120    prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2121            before loading.
2122            See Documentation/blockdev/ramdisk.txt.
2123
2124    psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2125            probe for; one of (bare|imps|exps|lifebook|any).
2126    psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2127            per second.
2128    psmouse.resetafter= [HW,MOUSE]
2129            Try to reset the device after so many bad packets
2130            (0 = never).
2131    psmouse.resolution=
2132            [HW,MOUSE] Set desired mouse resolution, in dpi.
2133    psmouse.smartscroll=
2134            [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2135            0 = disabled, 1 = enabled (default).
2136
2137    pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2138            Format:
2139            <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2140
2141    pt. [PARIDE]
2142            See Documentation/blockdev/paride.txt.
2143
2144    pty.legacy_count=
2145            [KNL] Number of legacy pty's. Overwrites compiled-in
2146            default number.
2147
2148    quiet [KNL] Disable most log messages
2149
2150    r128= [HW,DRM]
2151
2152    raid= [HW,RAID]
2153            See Documentation/md.txt.
2154
2155    ramdisk_blocksize= [RAM]
2156            See Documentation/blockdev/ramdisk.txt.
2157
2158    ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2159            See Documentation/blockdev/ramdisk.txt.
2160
2161    rcupdate.blimit= [KNL,BOOT]
2162            Set maximum number of finished RCU callbacks to process
2163            in one batch.
2164
2165    rcupdate.qhimark= [KNL,BOOT]
2166            Set threshold of queued
2167            RCU callbacks over which batch limiting is disabled.
2168
2169    rcupdate.qlowmark= [KNL,BOOT]
2170            Set threshold of queued RCU callbacks below which
2171            batch limiting is re-enabled.
2172
2173    rdinit= [KNL]
2174            Format: <full_path>
2175            Run specified binary instead of /init from the ramdisk,
2176            used for early userspace startup. See initrd.
2177
2178    reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2179            Format: <reboot_mode>[,<reboot_mode2>[,...]]
2180            See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2181
2182    relax_domain_level=
2183            [KNL, SMP] Set scheduler's default relax_domain_level.
2184            See Documentation/cgroups/cpusets.txt.
2185
2186    reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2187
2188    reservetop= [X86-32]
2189            Format: nn[KMG]
2190            Reserves a hole at the top of the kernel virtual
2191            address space.
2192
2193    reset_devices [KNL] Force drivers to reset the underlying device
2194            during initialization.
2195
2196    resume= [SWSUSP]
2197            Specify the partition device for software suspend
2198
2199    resume_offset= [SWSUSP]
2200            Specify the offset from the beginning of the partition
2201            given by "resume=" at which the swap header is located,
2202            in <PAGE_SIZE> units (needed only for swap files).
2203            See Documentation/power/swsusp-and-swap-files.txt
2204
2205    retain_initrd [RAM] Keep initrd memory after extraction
2206
2207    rhash_entries= [KNL,NET]
2208            Set number of hash buckets for route cache
2209
2210    riscom8= [HW,SERIAL]
2211            Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2212
2213    ro [KNL] Mount root device read-only on boot
2214
2215    root= [KNL] Root filesystem
2216
2217    rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2218            mount the root filesystem
2219
2220    rootflags= [KNL] Set root filesystem mount option string
2221
2222    rootfstype= [KNL] Set root filesystem type
2223
2224    rootwait [KNL] Wait (indefinitely) for root device to show up.
2225            Useful for devices that are detected asynchronously
2226            (e.g. USB and MMC devices).
2227
2228    rw [KNL] Mount root device read-write on boot
2229
2230    S [KNL] Run init in single mode
2231
2232    sa1100ir [NET]
2233            See drivers/net/irda/sa1100_ir.c.
2234
2235    sbni= [NET] Granch SBNI12 leased line adapter
2236
2237    sched_debug [KNL] Enables verbose scheduler debug messages.
2238
2239    sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2240            Format: <io>[,<timeout>[,<isapnp>]]
2241
2242    scsi_debug_*= [SCSI]
2243            See drivers/scsi/scsi_debug.c.
2244
2245    scsi_default_dev_flags=
2246            [SCSI] SCSI default device flags
2247            Format: <integer>
2248
2249    scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2250            Format: <vendor>:<model>:<flags>
2251            (flags are integer value)
2252
2253    scsi_logging_level= [SCSI] a bit mask of logging levels
2254            See drivers/scsi/scsi_logging.h for bits. Also
2255            settable via sysctl at dev.scsi.logging_level
2256            (/proc/sys/dev/scsi/logging_level).
2257            There is also a nice 'scsi_logging_level' script in the
2258            S390-tools package, available for download at
2259            http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2260
2261    scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2262            discovered. async scans them in kernel threads,
2263            allowing boot to proceed. none ignores them, expecting
2264            user space to do the scan.
2265
2266    security= [SECURITY] Choose a security module to enable at boot.
2267            If this boot parameter is not specified, only the first
2268            security module asking for security registration will be
2269            loaded. An invalid security module name will be treated
2270            as if no module has been chosen.
2271
2272    selinux= [SELINUX] Disable or enable SELinux at boot time.
2273            Format: { "0" | "1" }
2274            See security/selinux/Kconfig help text.
2275            0 -- disable.
2276            1 -- enable.
2277            Default value is set via kernel config option.
2278            If enabled at boot time, /selinux/disable can be used
2279            later to disable prior to initial policy load.
2280
2281    serialnumber [BUGS=X86-32]
2282
2283    shapers= [NET]
2284            Maximal number of shapers.
2285
2286    show_msr= [x86] show boot-time MSR settings
2287            Format: { <integer> }
2288            Show boot-time (BIOS-initialized) MSR settings.
2289            The parameter means the number of CPUs to show,
2290            for example 1 means boot CPU only.
2291
2292    sim710= [SCSI,HW]
2293            See header of drivers/scsi/sim710.c.
2294
2295    simeth= [IA-64]
2296    simscsi=
2297
2298    slram= [HW,MTD]
2299
2300    slub_debug[=options[,slabs]] [MM, SLUB]
2301            Enabling slub_debug allows one to determine the
2302            culprit if slab objects become corrupted. Enabling
2303            slub_debug can create guard zones around objects and
2304            may poison objects when not in use. Also tracks the
2305            last alloc / free. For more information see
2306            Documentation/vm/slub.txt.
2307
2308    slub_max_order= [MM, SLUB]
2309            Determines the maximum allowed order for slabs.
2310            A high setting may cause OOMs due to memory
2311            fragmentation. For more information see
2312            Documentation/vm/slub.txt.
2313
2314    slub_min_objects= [MM, SLUB]
2315            The minimum number of objects per slab. SLUB will
2316            increase the slab order up to slub_max_order to
2317            generate a sufficiently large slab able to contain
2318            the number of objects indicated. The higher the number
2319            of objects the smaller the overhead of tracking slabs
2320            and the less frequently locks need to be acquired.
2321            For more information see Documentation/vm/slub.txt.
2322
2323    slub_min_order= [MM, SLUB]
2324            Determines the mininum page order for slabs. Must be
2325            lower than slub_max_order.
2326            For more information see Documentation/vm/slub.txt.
2327
2328    slub_nomerge [MM, SLUB]
2329            Disable merging of slabs with similar size. May be
2330            necessary if there is some reason to distinguish
2331            allocs to different slabs. Debug options disable
2332            merging on their own.
2333            For more information see Documentation/vm/slub.txt.
2334
2335    smart2= [HW]
2336            Format: <io1>[,<io2>[,...,<io8>]]
2337
2338    smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2339            attempt to substitute SMP alternatives once at boot.
2340
2341    smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2342    smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2343    smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2344    smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2345    smsc-ircc2.ircc_irq= [HW] IRQ line
2346    smsc-ircc2.ircc_dma= [HW] DMA channel
2347    smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2348                0: Toshiba Satellite 1800 (GP data pin select)
2349                1: Fast pin select (default)
2350                2: ATC IRMode
2351
2352    snd-ad1816a= [HW,ALSA]
2353
2354    snd-ad1848= [HW,ALSA]
2355
2356    snd-ali5451= [HW,ALSA]
2357
2358    snd-als100= [HW,ALSA]
2359
2360    snd-als4000= [HW,ALSA]
2361
2362    snd-azt2320= [HW,ALSA]
2363
2364    snd-cmi8330= [HW,ALSA]
2365
2366    snd-cmipci= [HW,ALSA]
2367
2368    snd-cs4231= [HW,ALSA]
2369
2370    snd-cs4232= [HW,ALSA]
2371
2372    snd-cs4236= [HW,ALSA]
2373
2374    snd-cs4281= [HW,ALSA]
2375
2376    snd-cs46xx= [HW,ALSA]
2377
2378    snd-dt019x= [HW,ALSA]
2379
2380    snd-dummy= [HW,ALSA]
2381
2382    snd-emu10k1= [HW,ALSA]
2383
2384    snd-ens1370= [HW,ALSA]
2385
2386    snd-ens1371= [HW,ALSA]
2387
2388    snd-es968= [HW,ALSA]
2389
2390    snd-es1688= [HW,ALSA]
2391
2392    snd-es18xx= [HW,ALSA]
2393
2394    snd-es1938= [HW,ALSA]
2395
2396    snd-es1968= [HW,ALSA]
2397
2398    snd-fm801= [HW,ALSA]
2399
2400    snd-gusclassic= [HW,ALSA]
2401
2402    snd-gusextreme= [HW,ALSA]
2403
2404    snd-gusmax= [HW,ALSA]
2405
2406    snd-hdsp= [HW,ALSA]
2407
2408    snd-ice1712= [HW,ALSA]
2409
2410    snd-intel8x0= [HW,ALSA]
2411
2412    snd-interwave= [HW,ALSA]
2413
2414    snd-interwave-stb=
2415            [HW,ALSA]
2416
2417    snd-korg1212= [HW,ALSA]
2418
2419    snd-maestro3= [HW,ALSA]
2420
2421    snd-mpu401= [HW,ALSA]
2422
2423    snd-mtpav= [HW,ALSA]
2424
2425    snd-nm256= [HW,ALSA]
2426
2427    snd-opl3sa2= [HW,ALSA]
2428
2429    snd-opti92x-ad1848=
2430            [HW,ALSA]
2431
2432    snd-opti92x-cs4231=
2433            [HW,ALSA]
2434
2435    snd-opti93x= [HW,ALSA]
2436
2437    snd-pmac= [HW,ALSA]
2438
2439    snd-rme32= [HW,ALSA]
2440
2441    snd-rme96= [HW,ALSA]
2442
2443    snd-rme9652= [HW,ALSA]
2444
2445    snd-sb8= [HW,ALSA]
2446
2447    snd-sb16= [HW,ALSA]
2448
2449    snd-sbawe= [HW,ALSA]
2450
2451    snd-serial= [HW,ALSA]
2452
2453    snd-sgalaxy= [HW,ALSA]
2454
2455    snd-sonicvibes= [HW,ALSA]
2456
2457    snd-sun-amd7930=
2458            [HW,ALSA]
2459
2460    snd-sun-cs4231= [HW,ALSA]
2461
2462    snd-trident= [HW,ALSA]
2463
2464    snd-usb-audio= [HW,ALSA,USB]
2465
2466    snd-via82xx= [HW,ALSA]
2467
2468    snd-virmidi= [HW,ALSA]
2469
2470    snd-wavefront= [HW,ALSA]
2471
2472    snd-ymfpci= [HW,ALSA]
2473
2474    softlockup_panic=
2475            [KNL] Should the soft-lockup detector generate panics.
2476
2477    sonypi.*= [HW] Sony Programmable I/O Control Device driver
2478            See Documentation/sonypi.txt
2479
2480    specialix= [HW,SERIAL] Specialix multi-serial port adapter
2481            See Documentation/serial/specialix.txt.
2482
2483    spia_io_base= [HW,MTD]
2484    spia_fio_base=
2485    spia_pedr=
2486    spia_peddr=
2487
2488    sscape= [HW,OSS]
2489            Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2490
2491    st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2492            See Documentation/scsi/st.txt.
2493
2494    stacktrace [FTRACE]
2495            Enabled the stack tracer on boot up.
2496
2497    sti= [PARISC,HW]
2498            Format: <num>
2499            Set the STI (builtin display/keyboard on the HP-PARISC
2500            machines) console (graphic card) which should be used
2501            as the initial boot-console.
2502            See also comment in drivers/video/console/sticore.c.
2503
2504    sti_font= [HW]
2505            See comment in drivers/video/console/sticore.c.
2506
2507    stifb= [HW]
2508            Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2509
2510    sunrpc.min_resvport=
2511    sunrpc.max_resvport=
2512            [NFS,SUNRPC]
2513            SunRPC servers often require that client requests
2514            originate from a privileged port (i.e. a port in the
2515            range 0 < portnr < 1024).
2516            An administrator who wishes to reserve some of these
2517            ports for other uses may adjust the range that the
2518            kernel's sunrpc client considers to be privileged
2519            using these two parameters to set the minimum and
2520            maximum port values.
2521
2522    sunrpc.pool_mode=
2523            [NFS]
2524            Control how the NFS server code allocates CPUs to
2525            service thread pools. Depending on how many NICs
2526            you have and where their interrupts are bound, this
2527            option will affect which CPUs will do NFS serving.
2528            Note: this parameter cannot be changed while the
2529            NFS server is running.
2530
2531            auto the server chooses an appropriate mode
2532                    automatically using heuristics
2533            global a single global pool contains all CPUs
2534            percpu one pool for each CPU
2535            pernode one pool for each NUMA node (equivalent
2536                    to global on non-NUMA machines)
2537
2538    sunrpc.tcp_slot_table_entries=
2539    sunrpc.udp_slot_table_entries=
2540            [NFS,SUNRPC]
2541            Sets the upper limit on the number of simultaneous
2542            RPC calls that can be sent from the client to a
2543            server. Increasing these values may allow you to
2544            improve throughput, but will also increase the
2545            amount of memory reserved for use by the client.
2546
2547    swiotlb= [IA-64] Number of I/O TLB slabs
2548
2549    switches= [HW,M68k]
2550
2551    sym53c416= [HW,SCSI]
2552            See header of drivers/scsi/sym53c416.c.
2553
2554    sysrq_always_enabled
2555            [KNL]
2556            Ignore sysrq setting - this boot parameter will
2557            neutralize any effect of /proc/sys/kernel/sysrq.
2558            Useful for debugging.
2559
2560    t128= [HW,SCSI]
2561            See header of drivers/scsi/t128.c.
2562
2563    tdfx= [HW,DRM]
2564
2565    test_suspend= [SUSPEND]
2566            Specify "mem" (for Suspend-to-RAM) or "standby" (for
2567            standby suspend) as the system sleep state to briefly
2568            enter during system startup. The system is woken from
2569            this state using a wakeup-capable RTC alarm.
2570
2571    thash_entries= [KNL,NET]
2572            Set number of hash buckets for TCP connection
2573
2574    thermal.act= [HW,ACPI]
2575            -1: disable all active trip points in all thermal zones
2576            <degrees C>: override all lowest active trip points
2577
2578    thermal.crt= [HW,ACPI]
2579            -1: disable all critical trip points in all thermal zones
2580            <degrees C>: override all critical trip points
2581
2582    thermal.nocrt= [HW,ACPI]
2583            Set to disable actions on ACPI thermal zone
2584            critical and hot trip points.
2585
2586    thermal.off= [HW,ACPI]
2587            1: disable ACPI thermal control
2588
2589    thermal.psv= [HW,ACPI]
2590            -1: disable all passive trip points
2591            <degrees C>: override all passive trip points to this
2592            value
2593
2594    thermal.tzp= [HW,ACPI]
2595            Specify global default ACPI thermal zone polling rate
2596            <deci-seconds>: poll all this frequency
2597            0: no polling (default)
2598
2599    tmscsim= [HW,SCSI]
2600            See comment before function dc390_setup() in
2601            drivers/scsi/tmscsim.c.
2602
2603    topology= [S390]
2604            Format: {off | on}
2605            Specify if the kernel should make use of the cpu
2606            topology informations if the hardware supports these.
2607            The scheduler will make use of these informations and
2608            e.g. base its process migration decisions on it.
2609            Default is off.
2610
2611    tp720= [HW,PS2]
2612
2613    trace_buf_size=nn[KMG]
2614            [FTRACE] will set tracing buffer size.
2615
2616    trace_event=[event-list]
2617            [FTRACE] Set and start specified trace events in order
2618            to facilitate early boot debugging.
2619            See also Documentation/trace/events.txt
2620
2621    trix= [HW,OSS] MediaTrix AudioTrix Pro
2622            Format:
2623            <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2624
2625    tsc= Disable clocksource-must-verify flag for TSC.
2626            Format: <string>
2627            [x86] reliable: mark tsc clocksource as reliable, this
2628            disables clocksource verification at runtime.
2629            Used to enable high-resolution timer mode on older
2630            hardware, and in virtualized environment.
2631
2632    turbografx.map[2|3]= [HW,JOY]
2633            TurboGraFX parallel port interface
2634            Format:
2635            <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2636            See also Documentation/input/joystick-parport.txt
2637
2638    u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2639            See header of drivers/scsi/u14-34f.c.
2640
2641    uart401= [HW,OSS]
2642            Format: <io>,<irq>
2643
2644    uart6850= [HW,OSS]
2645            Format: <io>,<irq>
2646
2647    uhash_entries= [KNL,NET]
2648            Set number of hash buckets for UDP/UDP-Lite connections
2649
2650    uhci-hcd.ignore_oc=
2651            [USB] Ignore overcurrent events (default N).
2652            Some badly-designed motherboards generate lots of
2653            bogus events, for ports that aren't wired to
2654            anything. Set this parameter to avoid log spamming.
2655            Note that genuine overcurrent events won't be
2656            reported either.
2657
2658    unknown_nmi_panic
2659            [X86]
2660            Set unknown_nmi_panic=1 early on boot.
2661
2662    usbcore.autosuspend=
2663            [USB] The autosuspend time delay (in seconds) used
2664            for newly-detected USB devices (default 2). This
2665            is the time required before an idle device will be
2666            autosuspended. Devices for which the delay is set
2667            to a negative value won't be autosuspended at all.
2668
2669    usbcore.usbfs_snoop=
2670            [USB] Set to log all usbfs traffic (default 0 = off).
2671
2672    usbcore.blinkenlights=
2673            [USB] Set to cycle leds on hubs (default 0 = off).
2674
2675    usbcore.old_scheme_first=
2676            [USB] Start with the old device initialization
2677            scheme (default 0 = off).
2678
2679    usbcore.use_both_schemes=
2680            [USB] Try the other device initialization scheme
2681            if the first one fails (default 1 = enabled).
2682
2683    usbcore.initial_descriptor_timeout=
2684            [USB] Specifies timeout for the initial 64-byte
2685                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2686            (default 5000 = 5.0 seconds).
2687
2688    usbhid.mousepoll=
2689            [USBHID] The interval which mice are to be polled at.
2690
2691    usb-storage.delay_use=
2692            [UMS] The delay in seconds before a new device is
2693            scanned for Logical Units (default 5).
2694
2695    usb-storage.quirks=
2696            [UMS] A list of quirks entries to supplement or
2697            override the built-in unusual_devs list. List
2698            entries are separated by commas. Each entry has
2699            the form VID:PID:Flags where VID and PID are Vendor
2700            and Product ID values (4-digit hex numbers) and
2701            Flags is a set of characters, each corresponding
2702            to a common usb-storage quirk flag as follows:
2703                a = SANE_SENSE (collect more than 18 bytes
2704                    of sense data);
2705                b = BAD_SENSE (don't collect more than 18
2706                    bytes of sense data);
2707                c = FIX_CAPACITY (decrease the reported
2708                    device capacity by one sector);
2709                h = CAPACITY_HEURISTICS (decrease the
2710                    reported device capacity by one
2711                    sector if the number is odd);
2712                i = IGNORE_DEVICE (don't bind to this
2713                    device);
2714                l = NOT_LOCKABLE (don't try to lock and
2715                    unlock ejectable media);
2716                m = MAX_SECTORS_64 (don't transfer more
2717                    than 64 sectors = 32 KB at a time);
2718                o = CAPACITY_OK (accept the capacity
2719                    reported by the device);
2720                r = IGNORE_RESIDUE (the device reports
2721                    bogus residue values);
2722                s = SINGLE_LUN (the device has only one
2723                    Logical Unit);
2724                w = NO_WP_DETECT (don't test whether the
2725                    medium is write-protected).
2726            Example: quirks=0419:aaf5:rl,0421:0433:rc
2727
2728    userpte=
2729            [X86] Flags controlling user PTE allocations.
2730
2731                nohigh = do not allocate PTE pages in
2732                    HIGHMEM regardless of setting
2733                    of CONFIG_HIGHPTE.
2734
2735    vdso= [X86,SH]
2736            vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2737            vdso=1: enable VDSO (default)
2738            vdso=0: disable VDSO mapping
2739
2740    vdso32= [X86]
2741            vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2742            vdso32=1: enable 32-bit VDSO (default)
2743            vdso32=0: disable 32-bit VDSO mapping
2744
2745    vector= [IA-64,SMP]
2746            vector=percpu: enable percpu vector domain
2747
2748    video= [FB] Frame buffer configuration
2749            See Documentation/fb/modedb.txt.
2750
2751    vga= [BOOT,X86-32] Select a particular video mode
2752            See Documentation/x86/boot.txt and
2753            Documentation/svga.txt.
2754            Use vga=ask for menu.
2755            This is actually a boot loader parameter; the value is
2756            passed to the kernel using a special protocol.
2757
2758    vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2759            size of <nn>. This can be used to increase the
2760            minimum size (128MB on x86). It can also be used to
2761            decrease the size and leave more room for directly
2762            mapped kernel RAM.
2763
2764    vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2765            Format: <command>
2766
2767    vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2768            Format: <command>
2769
2770    vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2771            Format: <command>
2772
2773    vt.cur_default= [VT] Default cursor shape.
2774            Format: 0xCCBBAA, where AA, BB, and CC are the same as
2775            the parameters of the <Esc>[?A;B;Cc escape sequence;
2776            see VGA-softcursor.txt. Default: 2 = underline.
2777
2778    vt.default_blu= [VT]
2779            Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2780            Change the default blue palette of the console.
2781            This is a 16-member array composed of values
2782            ranging from 0-255.
2783
2784    vt.default_grn= [VT]
2785            Format: <green0>,<green1>,<green2>,...,<green15>
2786            Change the default green palette of the console.
2787            This is a 16-member array composed of values
2788            ranging from 0-255.
2789
2790    vt.default_red= [VT]
2791            Format: <red0>,<red1>,<red2>,...,<red15>
2792            Change the default red palette of the console.
2793            This is a 16-member array composed of values
2794            ranging from 0-255.
2795
2796    vt.default_utf8=
2797            [VT]
2798            Format=<0|1>
2799            Set system-wide default UTF-8 mode for all tty's.
2800            Default is 1, i.e. UTF-8 mode is enabled for all
2801            newly opened terminals.
2802
2803    vt.global_cursor_default=
2804            [VT]
2805            Format=<-1|0|1>
2806            Set system-wide default for whether a cursor
2807            is shown on new VTs. Default is -1,
2808            i.e. cursors will be created by default unless
2809            overridden by individual drivers. 0 will hide
2810            cursors, 1 will display them.
2811
2812    waveartist= [HW,OSS]
2813            Format: <io>,<irq>,<dma>,<dma2>
2814
2815    wd33c93= [HW,SCSI]
2816            See header of drivers/scsi/wd33c93.c.
2817
2818    wd7000= [HW,SCSI]
2819            See header of drivers/scsi/wd7000.c.
2820
2821    wdt= [WDT] Watchdog
2822            See Documentation/watchdog/wdt.txt.
2823
2824    x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2825            default x2apic cluster mode on platforms
2826            supporting x2apic.
2827
2828    x86_mrst_timer= [X86-32,APBT]
2829            Choose timer option for x86 Moorestown MID platform.
2830            Two valid options are apbt timer only and lapic timer
2831            plus one apbt timer for broadcast timer.
2832            x86_mrst_timer=apbt_only | lapic_and_apbt
2833
2834    xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2835    xd_geo= See header of drivers/block/xd.c.
2836
2837    xirc2ps_cs= [NET,PCMCIA]
2838            Format:
2839            <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2840
2841______________________________________________________________________
2842
2843TODO:
2844
2845    Add documentation for ALSA options.
2846    Add more DRM drivers.
2847

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