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    DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48    EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49    EFI EFI Partitioning (GPT) is enabled
50    EIDE EIDE/ATAPI support is enabled.
51    FB The frame buffer device is enabled.
52    GCOV GCOV profiling is enabled.
53    HW Appropriate hardware is enabled.
54    IA-64 IA-64 architecture is enabled.
55    IMA Integrity measurement architecture is enabled.
56    IOSCHED More than one I/O scheduler is enabled.
57    IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58    IPV6 IPv6 support is enabled.
59    ISAPNP ISA PnP code is enabled.
60    ISDN Appropriate ISDN support is enabled.
61    JOY Appropriate joystick support is enabled.
62    KGDB Kernel debugger support is enabled.
63    KVM Kernel Virtual Machine support is enabled.
64    LIBATA Libata driver is enabled
65    LP Printer support is enabled.
66    LOOP Loopback device support is enabled.
67    M68k M68k architecture is enabled.
68            These options have more detailed description inside of
69            Documentation/m68k/kernel-options.txt.
70    MCA MCA bus support is enabled.
71    MDA MDA console support is enabled.
72    MOUSE Appropriate mouse support is enabled.
73    MSI Message Signaled Interrupts (PCI).
74    MTD MTD (Memory Technology Device) support is enabled.
75    NET Appropriate network support is enabled.
76    NUMA NUMA support is enabled.
77    NFS Appropriate NFS support is enabled.
78    OSS OSS sound support is enabled.
79    PV_OPS A paravirtualized kernel is enabled.
80    PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81    PARISC The PA-RISC architecture is enabled.
82    PCI PCI bus support is enabled.
83    PCIE PCI Express support is enabled.
84    PCMCIA The PCMCIA subsystem is enabled.
85    PNP Plug & Play support is enabled.
86    PPC PowerPC architecture is enabled.
87    PPT Parallel port support is enabled.
88    PS2 Appropriate PS/2 support is enabled.
89    RAM RAM disk support is enabled.
90    S390 S390 architecture is enabled.
91    SCSI Appropriate SCSI support is enabled.
92            A lot of drivers have their options described inside
93            the Documentation/scsi/ sub-directory.
94    SECURITY Different security models are enabled.
95    SELINUX SELinux support is enabled.
96    APPARMOR AppArmor support is enabled.
97    SERIAL Serial support is enabled.
98    SH SuperH architecture is enabled.
99    SMP The kernel is an SMP kernel.
100    SPARC Sparc architecture is enabled.
101    SWSUSP Software suspend (hibernation) is enabled.
102    SUSPEND System suspend states are enabled.
103    FTRACE Function tracing enabled.
104    TPM TPM drivers are enabled.
105    TS Appropriate touchscreen support is enabled.
106    UMS USB Mass Storage support is enabled.
107    USB USB support is enabled.
108    USBHID USB Human Interface Device support is enabled.
109    V4L Video For Linux support is enabled.
110    VGA The VGA console has been enabled.
111    VT Virtual terminal support is enabled.
112    WDT Watchdog support is enabled.
113    XT IBM PC/XT MFM hard disk support is enabled.
114    X86-32 X86-32, aka i386 architecture is enabled.
115    X86-64 X86-64 architecture is enabled.
116            More X86-64 boot options can be found in
117            Documentation/x86/x86_64/boot-options.txt .
118    X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119    XEN Xen support is enabled
120
121In addition, the following text indicates that the option:
122
123    BUGS= Relates to possible processor bugs on the said processor.
124    KNL Is a kernel start-up parameter.
125    BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
130need or coordination with <Documentation/x86/boot.txt>.
131
132There are also arch-specific kernel-parameters not documented here.
133See for example <Documentation/x86/x86_64/boot-options.txt>.
134
135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
147Finally, the [KMG] suffix is commonly described after a number of kernel
148parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150bytes respectively. Such letter suffixes can also be entirely omitted.
151
152
153    acpi= [HW,ACPI,X86]
154            Advanced Configuration and Power Interface
155            Format: { force | off | strict | noirq | rsdt }
156            force -- enable ACPI if default was off
157            off -- disable ACPI if default was on
158            noirq -- do not use ACPI for IRQ routing
159            strict -- Be less tolerant of platforms that are not
160                strictly ACPI specification compliant.
161            rsdt -- prefer RSDT over (default) XSDT
162            copy_dsdt -- copy DSDT to memory
163
164            See also Documentation/power/pm.txt, pci=noacpi
165
166    acpi_apic_instance= [ACPI, IOAPIC]
167            Format: <int>
168            2: use 2nd APIC table, if available
169            1,0: use 1st APIC table
170            default: 0
171
172    acpi_backlight= [HW,ACPI]
173            acpi_backlight=vendor
174            acpi_backlight=video
175            If set to vendor, prefer vendor specific driver
176            (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177            of the ACPI video.ko driver.
178
179    acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180    acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
181            Format: <int>
182            CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183            debug output. Bits in debug_layer correspond to a
184            _COMPONENT in an ACPI source file, e.g.,
185                #define _COMPONENT ACPI_PCI_COMPONENT
186            Bits in debug_level correspond to a level in
187            ACPI_DEBUG_PRINT statements, e.g.,
188                ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
189            The debug_level mask defaults to "info". See
190            Documentation/acpi/debug.txt for more information about
191            debug layers and levels.
192
193            Enable processor driver info messages:
194                acpi.debug_layer=0x20000000
195            Enable PCI/PCI interrupt routing info messages:
196                acpi.debug_layer=0x400000
197            Enable AML "Debug" output, i.e., stores to the Debug
198            object while interpreting AML:
199                acpi.debug_layer=0xffffffff acpi.debug_level=0x2
200            Enable all messages related to ACPI hardware:
201                acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
202
203            Some values produce so much output that the system is
204            unusable. The "log_buf_len" parameter may be useful
205            if you need to capture more output.
206
207    acpi_irq_balance [HW,ACPI]
208            ACPI will balance active IRQs
209            default in APIC mode
210
211    acpi_irq_nobalance [HW,ACPI]
212            ACPI will not move active IRQs (default)
213            default in PIC mode
214
215    acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216            Format: <irq>,<irq>...
217
218    acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219            use by PCI
220            Format: <irq>,<irq>...
221
222    acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223
224    acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225            Format: To spoof as Windows 98: ="Microsoft Windows"
226
227    acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228            acpi_osi="string1" # add string1 -- only one string
229            acpi_osi="!string2" # remove built-in string2
230            acpi_osi= # disable all strings
231
232    acpi_pm_good [X86]
233            Override the pmtimer bug detection: force the kernel
234            to assume that this machine's pmtimer latches its value
235            and always returns good values.
236
237    acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238            Format: { level | edge | high | low }
239
240    acpi_serialize [HW,ACPI] force serialization of AML methods
241
242    acpi_skip_timer_override [HW,ACPI]
243            Recognize and ignore IRQ0/pin2 Interrupt Override.
244            For broken nForce2 BIOS resulting in XT-PIC timer.
245
246    acpi_sleep= [HW,ACPI] Sleep options
247            Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248                  old_ordering, s4_nonvs, sci_force_enable }
249            See Documentation/power/video.txt for information on
250            s3_bios and s3_mode.
251            s3_beep is for debugging; it makes the PC's speaker beep
252            as soon as the kernel's real-mode entry point is called.
253            s4_nohwsig prevents ACPI hardware signature from being
254            used during resume from hibernation.
255            old_ordering causes the ACPI 1.0 ordering of the _PTS
256            control method, with respect to putting devices into
257            low power states, to be enforced (the ACPI 2.0 ordering
258            of _PTS is used by default).
259            nonvs prevents the kernel from saving/restoring the
260            ACPI NVS memory during suspend/hibernation and resume.
261            sci_force_enable causes the kernel to set SCI_EN directly
262            on resume from S1/S3 (which is against the ACPI spec,
263            but some broken systems don't work without it).
264
265    acpi_use_timer_override [HW,ACPI]
266            Use timer override. For some broken Nvidia NF5 boards
267            that require a timer override, but don't have HPET
268
269    acpi_enforce_resources= [ACPI]
270            { strict | lax | no }
271            Check for resource conflicts between native drivers
272            and ACPI OperationRegions (SystemIO and SystemMemory
273            only). IO ports and memory declared in ACPI might be
274            used by the ACPI subsystem in arbitrary AML code and
275            can interfere with legacy drivers.
276            strict (default): access to resources claimed by ACPI
277            is denied; legacy drivers trying to access reserved
278            resources will fail to bind to device using them.
279            lax: access to resources claimed by ACPI is allowed;
280            legacy drivers trying to access reserved resources
281            will bind successfully but a warning message is logged.
282            no: ACPI OperationRegions are not marked as reserved,
283            no further checks are performed.
284
285    add_efi_memmap [EFI; X86] Include EFI memory map in
286            kernel's map of available physical RAM.
287
288    agp= [AGP]
289            { off | try_unsupported }
290            off: disable AGP support
291            try_unsupported: try to drive unsupported chipsets
292                (may crash computer or cause data corruption)
293
294    ALSA [HW,ALSA]
295            See Documentation/sound/alsa/alsa-parameters.txt
296
297    alignment= [KNL,ARM]
298            Allow the default userspace alignment fault handler
299            behaviour to be specified. Bit 0 enables warnings,
300            bit 1 enables fixups, and bit 2 sends a segfault.
301
302    amd_iommu= [HW,X86-84]
303            Pass parameters to the AMD IOMMU driver in the system.
304            Possible values are:
305            fullflush - enable flushing of IO/TLB entries when
306                    they are unmapped. Otherwise they are
307                    flushed before they will be reused, which
308                    is a lot of faster
309            off - do not initialize any AMD IOMMU found in
310                    the system
311
312    amijoy.map= [HW,JOY] Amiga joystick support
313            Map of devices attached to JOY0DAT and JOY1DAT
314            Format: <a>,<b>
315            See also Documentation/kernel/input/joystick.txt
316
317    analog.map= [HW,JOY] Analog joystick and gamepad support
318            Specifies type or capabilities of an analog joystick
319            connected to one of 16 gameports
320            Format: <type1>,<type2>,..<type16>
321
322    apc= [HW,SPARC]
323            Power management functions (SPARCstation-4/5 + deriv.)
324            Format: noidle
325            Disable APC CPU standby support. SPARCstation-Fox does
326            not play well with APC CPU idle - disable it if you have
327            APC and your system crashes randomly.
328
329    apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330            Change the output verbosity whilst booting
331            Format: { quiet (default) | verbose | debug }
332            Change the amount of debugging information output
333            when initialising the APIC and IO-APIC components.
334
335    autoconf= [IPV6]
336            See Documentation/networking/ipv6.txt.
337
338    show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339            Limit apic dumping. The parameter defines the maximal
340            number of local apics being dumped. Also it is possible
341            to set it to "all" by meaning -- no limit here.
342            Format: { 1 (default) | 2 | ... | all }.
343            The parameter valid if only apic=debug or
344            apic=verbose is specified.
345            Example: apic=debug show_lapic=all
346
347    apm= [APM] Advanced Power Management
348            See header of arch/x86/kernel/apm_32.c.
349
350    arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351            Format: <io>,<irq>,<nodeID>
352
353    ataflop= [HW,M68k]
354
355    atarimouse= [HW,MOUSE] Atari Mouse
356
357    atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358            EzKey and similar keyboards
359
360    atkbd.reset= [HW] Reset keyboard during initialization
361
362    atkbd.set= [HW] Select keyboard code set
363            Format: <int> (2 = AT (default), 3 = PS/2)
364
365    atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366            keyboards
367
368    atkbd.softraw= [HW] Choose between synthetic and real raw mode
369            Format: <bool> (0 = real, 1 = synthetic (default))
370
371    atkbd.softrepeat= [HW]
372            Use software keyboard repeat
373
374    autotest [IA64]
375
376    baycom_epp= [HW,AX25]
377            Format: <io>,<mode>
378
379    baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380            Format: <io>,<mode>
381            See header of drivers/net/hamradio/baycom_par.c.
382
383    baycom_ser_fdx= [HW,AX25]
384            BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385            Format: <io>,<irq>,<mode>[,<baud>]
386            See header of drivers/net/hamradio/baycom_ser_fdx.c.
387
388    baycom_ser_hdx= [HW,AX25]
389            BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390            Format: <io>,<irq>,<mode>
391            See header of drivers/net/hamradio/baycom_ser_hdx.c.
392
393    boot_delay= Milliseconds to delay each printk during boot.
394            Values larger than 10 seconds (10000) are changed to
395            no delay (0).
396            Format: integer
397
398    bootmem_debug [KNL] Enable bootmem allocator debug messages.
399
400    bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401    bttv.radio= Most important insmod options are available as
402            kernel args too.
403    bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404    bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405
406    bulk_remove=off [PPC] This parameter disables the use of the pSeries
407            firmware feature for flushing multiple hpte entries
408            at a time.
409
410    c101= [NET] Moxa C101 synchronous serial card
411
412    cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413            Sometimes CPU hardware bugs make them report the cache
414            size incorrectly. The kernel will attempt work arounds
415            to fix known problems, but for some CPUs it is not
416            possible to determine what the correct size should be.
417            This option provides an override for these situations.
418
419    capability.disable=
420            [SECURITY] Disable capabilities. This would normally
421            be used only if an alternative security model is to be
422            configured. Potentially dangerous and should only be
423            used if you are entirely sure of the consequences.
424
425    ccw_timeout_log [S390]
426            See Documentation/s390/CommonIO for details.
427
428    cgroup_disable= [KNL] Disable a particular controller
429            Format: {name of the controller(s) to disable}
430                {Currently supported controllers - "memory"}
431
432    checkreqprot [SELINUX] Set initial checkreqprot flag value.
433            Format: { "0" | "1" }
434            See security/selinux/Kconfig help text.
435            0 -- check protection applied by kernel (includes
436                any implied execute protection).
437            1 -- check protection requested by application.
438            Default value is set via a kernel config option.
439            Value can be changed at runtime via
440                /selinux/checkreqprot.
441
442    cio_ignore= [S390]
443            See Documentation/s390/CommonIO for details.
444
445    clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
446            [Deprecated]
447            Forces specified clocksource (if available) to be used
448            when calculating gettimeofday(). If specified
449            clocksource is not available, it defaults to PIT.
450            Format: { pit | tsc | cyclone | pmtmr }
451
452    clocksource= Override the default clocksource
453            Format: <string>
454            Override the default clocksource and use the clocksource
455            with the name specified.
456            Some clocksource names to choose from, depending on
457            the platform:
458            [all] jiffies (this is the base, fallback clocksource)
459            [ACPI] acpi_pm
460            [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461                pxa_timer,timer3,32k_counter,timer0_1
462            [AVR32] avr32
463            [X86-32] pit,hpet,tsc;
464                scx200_hrt on Geode; cyclone on IBM x440
465            [MIPS] MIPS
466            [PARISC] cr16
467            [S390] tod
468            [SH] SuperH
469            [SPARC64] tick
470            [X86-64] hpet,tsc
471
472    clearcpuid=BITNUM [X86]
473            Disable CPUID feature X for the kernel. See
474            arch/x86/include/asm/cpufeature.h for the valid bit
475            numbers. Note the Linux specific bits are not necessarily
476            stable over kernel options, but the vendor specific
477            ones should be.
478            Also note that user programs calling CPUID directly
479            or using the feature without checking anything
480            will still see it. This just prevents it from
481            being used by the kernel or shown in /proc/cpuinfo.
482            Also note the kernel might malfunction if you disable
483            some critical bits.
484
485    cmo_free_hint= [PPC] Format: { yes | no }
486            Specify whether pages are marked as being inactive
487            when they are freed. This is used in CMO environments
488            to determine OS memory pressure for page stealing by
489            a hypervisor.
490            Default: yes
491
492    code_bytes [X86] How many bytes of object code to print
493            in an oops report.
494            Range: 0 - 8192
495            Default: 64
496
497    com20020= [HW,NET] ARCnet - COM20020 chipset
498            Format:
499            <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
500
501    com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502            Format: <io>[,<irq>]
503
504    com90xx= [HW,NET]
505            ARCnet - COM90xx chipset (memory-mapped buffers)
506            Format: <io>[,<irq>[,<memstart>]]
507
508    condev= [HW,S390] console device
509    conmode=
510
511    console= [KNL] Output console device and options.
512
513        tty<n> Use the virtual console device <n>.
514
515        ttyS<n>[,options]
516        ttyUSB0[,options]
517            Use the specified serial port. The options are of
518            the form "bbbbpnf", where "bbbb" is the baud rate,
519            "p" is parity ("n", "o", or "e"), "n" is number of
520            bits, and "f" is flow control ("r" for RTS or
521            omit it). Default is "9600n8".
522
523            See Documentation/serial-console.txt for more
524            information. See
525            Documentation/networking/netconsole.txt for an
526            alternative.
527
528        uart[8250],io,<addr>[,options]
529        uart[8250],mmio,<addr>[,options]
530            Start an early, polled-mode console on the 8250/16550
531            UART at the specified I/O port or MMIO address,
532            switching to the matching ttyS device later. The
533            options are the same as for ttyS, above.
534
535                If the device connected to the port is not a TTY but a braille
536                device, prepend "brl," before the device type, for instance
537            console=brl,ttyS0
538        For now, only VisioBraille is supported.
539
540    consoleblank= [KNL] The console blank (screen saver) timeout in
541            seconds. Defaults to 10*60 = 10mins. A value of 0
542            disables the blank timer.
543
544    coredump_filter=
545            [KNL] Change the default value for
546            /proc/<pid>/coredump_filter.
547            See also Documentation/filesystems/proc.txt.
548
549    cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
550            Format:
551            <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
552
553    crashkernel=size[KMG][@offset[KMG]]
554            [KNL] Using kexec, Linux can switch to a 'crash kernel'
555            upon panic. This parameter reserves the physical
556            memory region [offset, offset + size] for that kernel
557            image. If '@offset' is omitted, then a suitable offset
558            is selected automatically. Check
559            Documentation/kdump/kdump.txt for further details.
560
561    crashkernel=range1:size1[,range2:size2,...][@offset]
562            [KNL] Same as above, but depends on the memory
563            in the running system. The syntax of range is
564            start-[end] where start and end are both
565            a memory unit (amount[KMG]). See also
566            Documentation/kdump/kdump.txt for an example.
567
568    cs89x0_dma= [HW,NET]
569            Format: <dma>
570
571    cs89x0_media= [HW,NET]
572            Format: { rj45 | aui | bnc }
573
574    dasd= [HW,NET]
575            See header of drivers/s390/block/dasd_devmap.c.
576
577    db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578            (one device per port)
579            Format: <port#>,<type>
580            See also Documentation/input/joystick-parport.txt
581
582    ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
583            time. See Documentation/dynamic-debug-howto.txt for
584            details.
585
586    debug [KNL] Enable kernel debugging (events log level).
587
588    debug_locks_verbose=
589            [KNL] verbose self-tests
590            Format=<0|1>
591            Print debugging info while doing the locking API
592            self-tests.
593            We default to 0 (no extra messages), setting it to
594            1 will print _a lot_ more information - normally
595            only useful to kernel developers.
596
597    debug_objects [KNL] Enable object debugging
598
599    no_debug_objects
600            [KNL] Disable object debugging
601
602    debugpat [X86] Enable PAT debugging
603
604    decnet.addr= [HW,NET]
605            Format: <area>[,<node>]
606            See also Documentation/networking/decnet.txt.
607
608    default_hugepagesz=
609            [same as hugepagesz=] The size of the default
610            HugeTLB page size. This is the size represented by
611            the legacy /proc/ hugepages APIs, used for SHM, and
612            default size when mounting hugetlbfs filesystems.
613            Defaults to the default architecture's huge page size
614            if not specified.
615
616    dhash_entries= [KNL]
617            Set number of hash buckets for dentry cache.
618
619    digi= [HW,SERIAL]
620            IO parameters + enable/disable command.
621
622    digiepca= [HW,SERIAL]
623            See drivers/char/README.epca and
624            Documentation/serial/digiepca.txt.
625
626    disable= [IPV6]
627            See Documentation/networking/ipv6.txt.
628
629    disable_ipv6= [IPV6]
630            See Documentation/networking/ipv6.txt.
631
632    disable_mtrr_cleanup [X86]
633            The kernel tries to adjust MTRR layout from continuous
634            to discrete, to make X server driver able to add WB
635            entry later. This parameter disables that.
636
637    disable_mtrr_trim [X86, Intel and AMD only]
638            By default the kernel will trim any uncacheable
639            memory out of your available memory pool based on
640            MTRR settings. This parameter disables that behavior,
641            possibly causing your machine to run very slowly.
642
643    disable_timer_pin_1 [X86]
644            Disable PIN 1 of APIC timer
645            Can be useful to work around chipset bugs.
646
647    dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
648            this option disables the debugging code at boot.
649
650    dma_debug_entries=<number>
651            This option allows to tune the number of preallocated
652            entries for DMA-API debugging code. One entry is
653            required per DMA-API allocation. Use this if the
654            DMA-API debugging code disables itself because the
655            architectural default is too low.
656
657    dma_debug_driver=<driver_name>
658            With this option the DMA-API debugging driver
659            filter feature can be enabled at boot time. Just
660            pass the driver to filter for as the parameter.
661            The filter can be disabled or changed to another
662            driver later using sysfs.
663
664    dscc4.setup= [NET]
665
666    earlycon= [KNL] Output early console device and options.
667        uart[8250],io,<addr>[,options]
668        uart[8250],mmio,<addr>[,options]
669        uart[8250],mmio32,<addr>[,options]
670            Start an early, polled-mode console on the 8250/16550
671            UART at the specified I/O port or MMIO address.
672            MMIO inter-register address stride is either 8bit (mmio)
673                        or 32bit (mmio32).
674            The options are the same as for ttyS, above.
675
676    earlyprintk= [X86,SH,BLACKFIN]
677            earlyprintk=vga
678            earlyprintk=serial[,ttySn[,baudrate]]
679            earlyprintk=ttySn[,baudrate]
680            earlyprintk=dbgp[debugController#]
681
682            Append ",keep" to not disable it when the real console
683            takes over.
684
685            Only vga or serial or usb debug port at a time.
686
687            Currently only ttyS0 and ttyS1 are supported.
688
689            Interaction with the standard serial driver is not
690            very good.
691
692            The VGA output is eventually overwritten by the real
693            console.
694
695    ekgdboc= [X86,KGDB] Allow early kernel console debugging
696            ekgdboc=kbd
697
698            This is desgined to be used in conjunction with
699            the boot argument: earlyprintk=vga
700
701    edd= [EDD]
702            Format: {"off" | "on" | "skip[mbr]"}
703
704    eisa_irq_edge= [PARISC,HW]
705            See header of drivers/parisc/eisa.c.
706
707    elanfreq= [X86-32]
708            See comment before function elanfreq_setup() in
709            arch/x86/kernel/cpu/cpufreq/elanfreq.c.
710
711    elevator= [IOSCHED]
712            Format: {"cfq" | "deadline" | "noop"}
713            See Documentation/block/as-iosched.txt and
714            Documentation/block/deadline-iosched.txt for details.
715
716    elfcorehdr= [IA64,PPC,SH,X86]
717            Specifies physical address of start of kernel core
718            image elf header. Generally kexec loader will
719            pass this option to capture kernel.
720            See Documentation/kdump/kdump.txt for details.
721
722    enable_mtrr_cleanup [X86]
723            The kernel tries to adjust MTRR layout from continuous
724            to discrete, to make X server driver able to add WB
725            entry later. This parameter enables that.
726
727    enable_timer_pin_1 [X86]
728            Enable PIN 1 of APIC timer
729            Can be useful to work around chipset bugs
730            (in particular on some ATI chipsets).
731            The kernel tries to set a reasonable default.
732
733    enforcing [SELINUX] Set initial enforcing status.
734            Format: {"0" | "1"}
735            See security/selinux/Kconfig help text.
736            0 -- permissive (log only, no denials).
737            1 -- enforcing (deny and log).
738            Default value is 0.
739            Value can be changed at runtime via /selinux/enforce.
740
741    erst_disable [ACPI]
742            Disable Error Record Serialization Table (ERST)
743            support.
744
745    ether= [HW,NET] Ethernet cards parameters
746            This option is obsoleted by the "netdev=" option, which
747            has equivalent usage. See its documentation for details.
748
749    failslab=
750    fail_page_alloc=
751    fail_make_request=[KNL]
752            General fault injection mechanism.
753            Format: <interval>,<probability>,<space>,<times>
754            See also /Documentation/fault-injection/.
755
756    floppy= [HW]
757            See Documentation/blockdev/floppy.txt.
758
759    force_pal_cache_flush
760            [IA-64] Avoid check_sal_cache_flush which may hang on
761            buggy SAL_CACHE_FLUSH implementations. Using this
762            parameter will force ia64_sal_cache_flush to call
763            ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
764
765    ftrace=[tracer]
766            [FTRACE] will set and start the specified tracer
767            as early as possible in order to facilitate early
768            boot debugging.
769
770    ftrace_dump_on_oops[=orig_cpu]
771            [FTRACE] will dump the trace buffers on oops.
772            If no parameter is passed, ftrace will dump
773            buffers of all CPUs, but if you pass orig_cpu, it will
774            dump only the buffer of the CPU that triggered the
775            oops.
776
777    ftrace_filter=[function-list]
778            [FTRACE] Limit the functions traced by the function
779            tracer at boot up. function-list is a comma separated
780            list of functions. This list can be changed at run
781            time by the set_ftrace_filter file in the debugfs
782            tracing directory.
783
784    ftrace_notrace=[function-list]
785            [FTRACE] Do not trace the functions specified in
786            function-list. This list can be changed at run time
787            by the set_ftrace_notrace file in the debugfs
788            tracing directory.
789
790    ftrace_graph_filter=[function-list]
791            [FTRACE] Limit the top level callers functions traced
792            by the function graph tracer at boot up.
793            function-list is a comma separated list of functions
794            that can be changed at run time by the
795            set_graph_function file in the debugfs tracing directory.
796
797    gamecon.map[2|3]=
798            [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
799            support via parallel port (up to 5 devices per port)
800            Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
801            See also Documentation/input/joystick-parport.txt
802
803    gamma= [HW,DRM]
804
805    gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
806            Format: off | on
807            default: on
808
809    gcov_persist= [GCOV] When non-zero (default), profiling data for
810            kernel modules is saved and remains accessible via
811            debugfs, even when the module is unloaded/reloaded.
812            When zero, profiling data is discarded and associated
813            debugfs files are removed at module unload time.
814
815    gpt [EFI] Forces disk with valid GPT signature but
816            invalid Protective MBR to be treated as GPT.
817
818    hashdist= [KNL,NUMA] Large hashes allocated during boot
819            are distributed across NUMA nodes. Defaults on
820            for 64bit NUMA, off otherwise.
821            Format: 0 | 1 (for off | on)
822
823    hcl= [IA-64] SGI's Hardware Graph compatibility layer
824
825    hd= [EIDE] (E)IDE hard drive subsystem geometry
826            Format: <cyl>,<head>,<sect>
827
828    hest_disable [ACPI]
829            Disable Hardware Error Source Table (HEST) support;
830            corresponding firmware-first mode error processing
831            logic will be disabled.
832
833    highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
834            size of <nn>. This works even on boxes that have no
835            highmem otherwise. This also works to reduce highmem
836            size on bigger boxes.
837
838    highres= [KNL] Enable/disable high resolution timer mode.
839            Valid parameters: "on", "off"
840            Default: "on"
841
842    hisax= [HW,ISDN]
843            See Documentation/isdn/README.HiSax.
844
845    hlt [BUGS=ARM,SH]
846
847    hpet= [X86-32,HPET] option to control HPET usage
848            Format: { enable (default) | disable | force |
849                verbose }
850            disable: disable HPET and use PIT instead
851            force: allow force enabled of undocumented chips (ICH4,
852                VIA, nVidia)
853            verbose: show contents of HPET registers during setup
854
855    hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
856    hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
857            On x86-64 and powerpc, this option can be specified
858            multiple times interleaved with hugepages= to reserve
859            huge pages of different sizes. Valid pages sizes on
860            x86-64 are 2M (when the CPU supports "pse") and 1G
861            (when the CPU supports the "pdpe1gb" cpuinfo flag)
862            Note that 1GB pages can only be allocated at boot time
863            using hugepages= and not freed afterwards.
864
865    hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
866                   terminal devices. Valid values: 0..8
867    hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
868                   If specified, z/VM IUCV HVC accepts connections
869                   from listed z/VM user IDs only.
870
871    i2c_bus= [HW] Override the default board specific I2C bus speed
872                 or register an additional I2C bus that is not
873                 registered from board initialization code.
874                 Format:
875                 <bus_id>,<clkrate>
876
877    i8042.debug [HW] Toggle i8042 debug mode
878    i8042.direct [HW] Put keyboard port into non-translated mode
879    i8042.dumbkbd [HW] Pretend that controller can only read data from
880                 keyboard and cannot control its state
881                 (Don't attempt to blink the leds)
882    i8042.noaux [HW] Don't check for auxiliary (== mouse) port
883    i8042.nokbd [HW] Don't check/create keyboard port
884    i8042.noloop [HW] Disable the AUX Loopback command while probing
885                 for the AUX port
886    i8042.nomux [HW] Don't check presence of an active multiplexing
887                 controller
888    i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
889                 controllers
890    i8042.notimeout [HW] Ignore timeout condition signalled by conroller
891    i8042.reset [HW] Reset the controller during init and cleanup
892    i8042.unlock [HW] Unlock (ignore) the keylock
893
894    i810= [HW,DRM]
895
896    i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
897            indicates that the driver is running on unsupported
898            hardware.
899    i8k.force [HW] Activate i8k driver even if SMM BIOS signature
900            does not match list of supported models.
901    i8k.power_status
902            [HW] Report power status in /proc/i8k
903            (disabled by default)
904    i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
905            capability is set.
906
907    icn= [HW,ISDN]
908            Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
909
910    ide-core.nodma= [HW] (E)IDE subsystem
911            Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
912            .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
913            .cdrom .chs .ignore_cable are additional options
914            See Documentation/ide/ide.txt.
915
916    ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
917            Claim all unknown PCI IDE storage controllers.
918
919    idle= [X86]
920            Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
921            Poll forces a polling idle loop that can slightly
922            improve the performance of waking up a idle CPU, but
923            will use a lot of power and make the system run hot.
924            Not recommended.
925            idle=mwait: On systems which support MONITOR/MWAIT but
926            the kernel chose to not use it because it doesn't save
927            as much power as a normal idle loop, use the
928            MONITOR/MWAIT idle loop anyways. Performance should be
929            the same as idle=poll.
930            idle=halt: Halt is forced to be used for CPU idle.
931            In such case C2/C3 won't be used again.
932            idle=nomwait: Disable mwait for CPU C-states
933
934    ignore_loglevel [KNL]
935            Ignore loglevel setting - this will print /all/
936            kernel messages to the console. Useful for debugging.
937
938    ihash_entries= [KNL]
939            Set number of hash buckets for inode cache.
940
941    ima_audit= [IMA]
942            Format: { "0" | "1" }
943            0 -- integrity auditing messages. (Default)
944            1 -- enable informational integrity auditing messages.
945
946    ima_hash= [IMA]
947            Format: { "sha1" | "md5" }
948            default: "sha1"
949
950    ima_tcb [IMA]
951            Load a policy which meets the needs of the Trusted
952            Computing Base. This means IMA will measure all
953            programs exec'd, files mmap'd for exec, and all files
954            opened for read by uid=0.
955
956    init= [KNL]
957            Format: <full_path>
958            Run specified binary instead of /sbin/init as init
959            process.
960
961    initcall_debug [KNL] Trace initcalls as they are executed. Useful
962            for working out where the kernel is dying during
963            startup.
964
965    initrd= [BOOT] Specify the location of the initial ramdisk
966
967    inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
968            Format: <irq>
969
970    intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
971        on
972            Enable intel iommu driver.
973        off
974            Disable intel iommu driver.
975        igfx_off [Default Off]
976            By default, gfx is mapped as normal device. If a gfx
977            device has a dedicated DMAR unit, the DMAR unit is
978            bypassed by not enabling DMAR with this option. In
979            this case, gfx device will use physical address for
980            DMA.
981        forcedac [x86_64]
982            With this option iommu will not optimize to look
983            for io virtual address below 32 bit forcing dual
984            address cycle on pci bus for cards supporting greater
985            than 32 bit addressing. The default is to look
986            for translation below 32 bit and if not available
987            then look in the higher range.
988        strict [Default Off]
989            With this option on every unmap_single operation will
990            result in a hardware IOTLB flush operation as opposed
991            to batching them for performance.
992
993    intremap= [X86-64, Intel-IOMMU]
994            Format: { on (default) | off | nosid }
995            on enable Interrupt Remapping (default)
996            off disable Interrupt Remapping
997            nosid disable Source ID checking
998
999    inttest= [IA64]
1000
1001    iomem= Disable strict checking of access to MMIO memory
1002        strict regions from userspace.
1003        relaxed
1004
1005    iommu= [x86]
1006        off
1007        force
1008        noforce
1009        biomerge
1010        panic
1011        nopanic
1012        merge
1013        nomerge
1014        forcesac
1015        soft
1016        pt [x86, IA64]
1017
1018    io7= [HW] IO7 for Marvel based alpha systems
1019            See comment before marvel_specify_io7 in
1020            arch/alpha/kernel/core_marvel.c.
1021
1022    io_delay= [X86] I/O delay method
1023        0x80
1024            Standard port 0x80 based delay
1025        0xed
1026            Alternate port 0xed based delay (needed on some systems)
1027        udelay
1028            Simple two microseconds delay
1029        none
1030            No delay
1031
1032    ip= [IP_PNP]
1033            See Documentation/filesystems/nfs/nfsroot.txt.
1034
1035    ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1036            See comment before ip2_setup() in
1037            drivers/char/ip2/ip2base.c.
1038
1039    irqfixup [HW]
1040            When an interrupt is not handled search all handlers
1041            for it. Intended to get systems with badly broken
1042            firmware running.
1043
1044    irqpoll [HW]
1045            When an interrupt is not handled search all handlers
1046            for it. Also check all handlers each timer
1047            interrupt. Intended to get systems with badly broken
1048            firmware running.
1049
1050    isapnp= [ISAPNP]
1051            Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1052
1053    isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1054            Format:
1055            <cpu number>,...,<cpu number>
1056            or
1057            <cpu number>-<cpu number>
1058            (must be a positive range in ascending order)
1059            or a mixture
1060            <cpu number>,...,<cpu number>-<cpu number>
1061
1062            This option can be used to specify one or more CPUs
1063            to isolate from the general SMP balancing and scheduling
1064            algorithms. You can move a process onto or off an
1065            "isolated" CPU via the CPU affinity syscalls or cpuset.
1066            <cpu number> begins at 0 and the maximum value is
1067            "number of CPUs in system - 1".
1068
1069            This option is the preferred way to isolate CPUs. The
1070            alternative -- manually setting the CPU mask of all
1071            tasks in the system -- can cause problems and
1072            suboptimal load balancer performance.
1073
1074    iucv= [HW,NET]
1075
1076    js= [HW,JOY] Analog joystick
1077            See Documentation/input/joystick.txt.
1078
1079    keepinitrd [HW,ARM]
1080
1081    kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1082            specifies the amount of memory usable by the kernel
1083            for non-movable allocations. The requested amount is
1084            spread evenly throughout all nodes in the system. The
1085            remaining memory in each node is used for Movable
1086            pages. In the event, a node is too small to have both
1087            kernelcore and Movable pages, kernelcore pages will
1088            take priority and other nodes will have a larger number
1089            of kernelcore pages. The Movable zone is used for the
1090            allocation of pages that may be reclaimed or moved
1091            by the page migration subsystem. This means that
1092            HugeTLB pages may not be allocated from this zone.
1093            Note that allocations like PTEs-from-HighMem still
1094            use the HighMem zone if it exists, and the Normal
1095            zone if it does not.
1096
1097    kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1098            Format: <Controller#>[,poll interval]
1099            The controller # is the number of the ehci usb debug
1100            port as it is probed via PCI. The poll interval is
1101            optional and is the number seconds in between
1102            each poll cycle to the debug port in case you need
1103            the functionality for interrupting the kernel with
1104            gdb or control-c on the dbgp connection. When
1105            not using this parameter you use sysrq-g to break into
1106            the kernel debugger.
1107
1108    kgdboc= [KGDB,HW] kgdb over consoles.
1109            Requires a tty driver that supports console polling,
1110            or a supported polling keyboard driver (non-usb).
1111             Serial only format: <serial_device>[,baud]
1112             keyboard only format: kbd
1113             keyboard and serial format: kbd,<serial_device>[,baud]
1114            Optional Kernel mode setting:
1115             kms, kbd format: kms,kbd
1116             kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1117
1118    kgdbwait [KGDB] Stop kernel execution and enter the
1119            kernel debugger at the earliest opportunity.
1120
1121    kmac= [MIPS] korina ethernet MAC address.
1122            Configure the RouterBoard 532 series on-chip
1123            Ethernet adapter MAC address.
1124
1125    kmemleak= [KNL] Boot-time kmemleak enable/disable
1126            Valid arguments: on, off
1127            Default: on
1128
1129    kstack=N [X86] Print N words from the kernel stack
1130            in oops dumps.
1131
1132    kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133            Default is 0 (don't ignore, but inject #GP)
1134
1135    kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136            Default is 1 (enabled)
1137
1138    kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1139            KVM MMU at runtime.
1140            Default is 0 (off)
1141
1142    kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1143            Default is 1 (enabled)
1144
1145    kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1146            for all guests.
1147            Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1148
1149    kvm-intel.bypass_guest_pf=
1150            [KVM,Intel] Disables bypassing of guest page faults
1151            on Intel chips. Default is 1 (enabled)
1152
1153    kvm-intel.ept= [KVM,Intel] Disable extended page tables
1154            (virtualized MMU) support on capable Intel chips.
1155            Default is 1 (enabled)
1156
1157    kvm-intel.emulate_invalid_guest_state=
1158            [KVM,Intel] Enable emulation of invalid guest states
1159            Default is 0 (disabled)
1160
1161    kvm-intel.flexpriority=
1162            [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1163            Default is 1 (enabled)
1164
1165    kvm-intel.unrestricted_guest=
1166            [KVM,Intel] Disable unrestricted guest feature
1167            (virtualized real and unpaged mode) on capable
1168            Intel chips. Default is 1 (enabled)
1169
1170    kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1171            feature (tagged TLBs) on capable Intel chips.
1172            Default is 1 (enabled)
1173
1174    l2cr= [PPC]
1175
1176    l3cr= [PPC]
1177
1178    lapic [X86-32,APIC] Enable the local APIC even if BIOS
1179            disabled it.
1180
1181    lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1182            in C2 power state.
1183
1184    libata.dma= [LIBATA] DMA control
1185            libata.dma=0 Disable all PATA and SATA DMA
1186            libata.dma=1 PATA and SATA Disk DMA only
1187            libata.dma=2 ATAPI (CDROM) DMA only
1188            libata.dma=4 Compact Flash DMA only
1189            Combinations also work, so libata.dma=3 enables DMA
1190            for disks and CDROMs, but not CFs.
1191    
1192    libata.ignore_hpa= [LIBATA] Ignore HPA limit
1193            libata.ignore_hpa=0 keep BIOS limits (default)
1194            libata.ignore_hpa=1 ignore limits, using full disk
1195
1196    libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1197            when set.
1198            Format: <int>
1199
1200    libata.force= [LIBATA] Force configurations. The format is comma
1201            separated list of "[ID:]VAL" where ID is
1202            PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1203            matching port, link or device. Basically, it matches
1204            the ATA ID string printed on console by libata. If
1205            the whole ID part is omitted, the last PORT and DEVICE
1206            values are used. If ID hasn't been specified yet, the
1207            configuration applies to all ports, links and devices.
1208
1209            If only DEVICE is omitted, the parameter applies to
1210            the port and all links and devices behind it. DEVICE
1211            number of 0 either selects the first device or the
1212            first fan-out link behind PMP device. It does not
1213            select the host link. DEVICE number of 15 selects the
1214            host link and device attached to it.
1215
1216            The VAL specifies the configuration to force. As long
1217            as there's no ambiguity shortcut notation is allowed.
1218            For example, both 1.5 and 1.5G would work for 1.5Gbps.
1219            The following configurations can be forced.
1220
1221            * Cable type: 40c, 80c, short40c, unk, ign or sata.
1222              Any ID with matching PORT is used.
1223
1224            * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1225
1226            * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1227              udma[/][16,25,33,44,66,100,133] notation is also
1228              allowed.
1229
1230            * [no]ncq: Turn on or off NCQ.
1231
1232            * nohrst, nosrst, norst: suppress hard, soft
1233                          and both resets.
1234
1235            * dump_id: dump IDENTIFY data.
1236
1237            If there are multiple matching configurations changing
1238            the same attribute, the last one is used.
1239
1240    memblock=debug [KNL] Enable memblock debug messages.
1241
1242    load_ramdisk= [RAM] List of ramdisks to load from floppy
1243            See Documentation/blockdev/ramdisk.txt.
1244
1245    lockd.nlm_grace_period=P [NFS] Assign grace period.
1246            Format: <integer>
1247
1248    lockd.nlm_tcpport=N [NFS] Assign TCP port.
1249            Format: <integer>
1250
1251    lockd.nlm_timeout=T [NFS] Assign timeout value.
1252            Format: <integer>
1253
1254    lockd.nlm_udpport=M [NFS] Assign UDP port.
1255            Format: <integer>
1256
1257    logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1258            Format: <irq>
1259
1260    loglevel= All Kernel Messages with a loglevel smaller than the
1261            console loglevel will be printed to the console. It can
1262            also be changed with klogd or other programs. The
1263            loglevels are defined as follows:
1264
1265            0 (KERN_EMERG) system is unusable
1266            1 (KERN_ALERT) action must be taken immediately
1267            2 (KERN_CRIT) critical conditions
1268            3 (KERN_ERR) error conditions
1269            4 (KERN_WARNING) warning conditions
1270            5 (KERN_NOTICE) normal but significant condition
1271            6 (KERN_INFO) informational
1272            7 (KERN_DEBUG) debug-level messages
1273
1274    log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1275            in bytes. n must be a power of two. The default
1276            size is set in the kernel config file.
1277
1278    logo.nologo [FB] Disables display of the built-in Linux logo.
1279            This may be used to provide more screen space for
1280            kernel log messages and is useful when debugging
1281            kernel boot problems.
1282
1283    lp=0 [LP] Specify parallel ports to use, e.g,
1284    lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1285    lp=reset first parallel port). 'lp=0' disables the
1286    lp=auto printer driver. 'lp=reset' (which can be
1287                specified in addition to the ports) causes
1288                attached printers to be reset. Using
1289                lp=port1,port2,... specifies the parallel ports
1290                to associate lp devices with, starting with
1291                lp0. A port specification may be 'none' to skip
1292                that lp device, or a parport name such as
1293                'parport0'. Specifying 'lp=auto' instead of a
1294                port specification list means that device IDs
1295                from each port should be examined, to see if
1296                an IEEE 1284-compliant printer is attached; if
1297                so, the driver will manage that printer.
1298                See also header of drivers/char/lp.c.
1299
1300    lpj=n [KNL]
1301            Sets loops_per_jiffy to given constant, thus avoiding
1302            time-consuming boot-time autodetection (up to 250 ms per
1303            CPU). 0 enables autodetection (default). To determine
1304            the correct value for your kernel, boot with normal
1305            autodetection and see what value is printed. Note that
1306            on SMP systems the preset will be applied to all CPUs,
1307            which is likely to cause problems if your CPUs need
1308            significantly divergent settings. An incorrect value
1309            will cause delays in the kernel to be wrong, leading to
1310            unpredictable I/O errors and other breakage. Although
1311            unlikely, in the extreme case this might damage your
1312            hardware.
1313
1314    ltpc= [NET]
1315            Format: <io>,<irq>,<dma>
1316
1317    machvec= [IA64] Force the use of a particular machine-vector
1318            (machvec) in a generic kernel.
1319            Example: machvec=hpzx1_swiotlb
1320
1321    machtype= [Loongson] Share the same kernel image file between different
1322             yeeloong laptop.
1323            Example: machtype=lemote-yeeloong-2f-7inch
1324
1325    max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1326            than or equal to this physical address is ignored.
1327
1328    maxcpus= [SMP] Maximum number of processors that an SMP kernel
1329            should make use of. maxcpus=n : n >= 0 limits the
1330            kernel to using 'n' processors. n=0 is a special case,
1331            it is equivalent to "nosmp", which also disables
1332            the IO APIC.
1333
1334    max_loop= [LOOP] Maximum number of loopback devices that can
1335            be mounted
1336            Format: <1-256>
1337
1338    mcatest= [IA-64]
1339
1340    mce [X86-32] Machine Check Exception
1341
1342    mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1343
1344    md= [HW] RAID subsystems devices and level
1345            See Documentation/md.txt.
1346
1347    mdacon= [MDA]
1348            Format: <first>,<last>
1349            Specifies range of consoles to be captured by the MDA.
1350
1351    mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1352            Amount of memory to be used when the kernel is not able
1353            to see the whole system memory or for test.
1354            [X86-32] Use together with memmap= to avoid physical
1355            address space collisions. Without memmap= PCI devices
1356            could be placed at addresses belonging to unused RAM.
1357
1358    mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1359            memory.
1360
1361    memchunk=nn[KMG]
1362            [KNL,SH] Allow user to override the default size for
1363            per-device physically contiguous DMA buffers.
1364
1365    memmap=exactmap [KNL,X86] Enable setting of an exact
1366            E820 memory map, as specified by the user.
1367            Such memmap=exactmap lines can be constructed based on
1368            BIOS output or other requirements. See the memmap=nn@ss
1369            option description.
1370
1371    memmap=nn[KMG]@ss[KMG]
1372            [KNL] Force usage of a specific region of memory
1373            Region of memory to be used, from ss to ss+nn.
1374
1375    memmap=nn[KMG]#ss[KMG]
1376            [KNL,ACPI] Mark specific memory as ACPI data.
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 reserved.
1381            Region of memory to be used, from ss to ss+nn.
1382            Example: Exclude memory from 0x18690000-0x1869ffff
1383                     memmap=64K$0x18690000
1384                     or
1385                     memmap=0x10000$0x18690000
1386
1387    memory_corruption_check=0/1 [X86]
1388            Some BIOSes seem to corrupt the first 64k of
1389            memory when doing things like suspend/resume.
1390            Setting this option will scan the memory
1391            looking for corruption. Enabling this will
1392            both detect corruption and prevent the kernel
1393            from using the memory being corrupted.
1394            However, its intended as a diagnostic tool; if
1395            repeatable BIOS-originated corruption always
1396            affects the same memory, you can use memmap=
1397            to prevent the kernel from using that memory.
1398
1399    memory_corruption_check_size=size [X86]
1400            By default it checks for corruption in the low
1401            64k, making this memory unavailable for normal
1402            use. Use this parameter to scan for
1403            corruption in more or less memory.
1404
1405    memory_corruption_check_period=seconds [X86]
1406            By default it checks for corruption every 60
1407            seconds. Use this parameter to check at some
1408            other rate. 0 disables periodic checking.
1409
1410    memtest= [KNL,X86] Enable memtest
1411            Format: <integer>
1412            default : 0 <disable>
1413            Specifies the number of memtest passes to be
1414            performed. Each pass selects another test
1415            pattern from a given set of patterns. Memtest
1416            fills the memory with this pattern, validates
1417            memory contents and reserves bad memory
1418            regions that are detected.
1419
1420    meye.*= [HW] Set MotionEye Camera parameters
1421            See Documentation/video4linux/meye.txt.
1422
1423    mfgpt_irq= [IA-32] Specify the IRQ to use for the
1424            Multi-Function General Purpose Timers on AMD Geode
1425            platforms.
1426
1427    mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1428            the BIOS has incorrectly applied a workaround. TinyBIOS
1429            version 0.98 is known to be affected, 0.99 fixes the
1430            problem by letting the user disable the workaround.
1431
1432    mga= [HW,DRM]
1433
1434    min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1435            physical address is ignored.
1436
1437    mini2440= [ARM,HW,KNL]
1438            Format:[0..2][b][c][t]
1439            Default: "0tb"
1440            MINI2440 configuration specification:
1441            0 - The attached screen is the 3.5" TFT
1442            1 - The attached screen is the 7" TFT
1443            2 - The VGA Shield is attached (1024x768)
1444            Leaving out the screen size parameter will not load
1445            the TFT driver, and the framebuffer will be left
1446            unconfigured.
1447            b - Enable backlight. The TFT backlight pin will be
1448            linked to the kernel VESA blanking code and a GPIO
1449            LED. This parameter is not necessary when using the
1450            VGA shield.
1451            c - Enable the s3c camera interface.
1452            t - Reserved for enabling touchscreen support. The
1453            touchscreen support is not enabled in the mainstream
1454            kernel as of 2.6.30, a preliminary port can be found
1455            in the "bleeding edge" mini2440 support kernel at
1456            http://repo.or.cz/w/linux-2.6/mini2440.git
1457
1458    mminit_loglevel=
1459            [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1460            parameter allows control of the logging verbosity for
1461            the additional memory initialisation checks. A value
1462            of 0 disables mminit logging and a level of 4 will
1463            log everything. Information is printed at KERN_DEBUG
1464            so loglevel=8 may also need to be specified.
1465
1466    mousedev.tap_time=
1467            [MOUSE] Maximum time between finger touching and
1468            leaving touchpad surface for touch to be considered
1469            a tap and be reported as a left button click (for
1470            touchpads working in absolute mode only).
1471            Format: <msecs>
1472    mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1473            reporting absolute coordinates, such as tablets
1474    mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1475            reporting absolute coordinates, such as tablets
1476
1477    movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1478            is similar to kernelcore except it specifies the
1479            amount of memory used for migratable allocations.
1480            If both kernelcore and movablecore is specified,
1481            then kernelcore will be at *least* the specified
1482            value but may be more. If movablecore on its own
1483            is specified, the administrator must be careful
1484            that the amount of memory usable for all allocations
1485            is not too small.
1486
1487    MTD_Partition= [MTD]
1488            Format: <name>,<region-number>,<size>,<offset>
1489
1490    MTD_Region= [MTD] Format:
1491            <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1492
1493    mtdparts= [MTD]
1494            See drivers/mtd/cmdlinepart.c.
1495
1496    multitce=off [PPC] This parameter disables the use of the pSeries
1497            firmware feature for updating multiple TCE entries
1498            at a time.
1499
1500    onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1501
1502            Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1503
1504            boundary - index of last SLC block on Flex-OneNAND.
1505                   The remaining blocks are configured as MLC blocks.
1506            lock - Configure if Flex-OneNAND boundary should be locked.
1507                   Once locked, the boundary cannot be changed.
1508                   1 indicates lock status, 0 indicates unlock status.
1509
1510    mtdset= [ARM]
1511            ARM/S3C2412 JIVE boot control
1512
1513            See arch/arm/mach-s3c2412/mach-jive.c
1514
1515    mtouchusb.raw_coordinates=
1516            [HW] Make the MicroTouch USB driver use raw coordinates
1517            ('y', default) or cooked coordinates ('n')
1518
1519    mtrr_chunk_size=nn[KMG] [X86]
1520            used for mtrr cleanup. It is largest continuous chunk
1521            that could hold holes aka. UC entries.
1522
1523    mtrr_gran_size=nn[KMG] [X86]
1524            Used for mtrr cleanup. It is granularity of mtrr block.
1525            Default is 1.
1526            Large value could prevent small alignment from
1527            using up MTRRs.
1528
1529    mtrr_spare_reg_nr=n [X86]
1530            Format: <integer>
1531            Range: 0,7 : spare reg number
1532            Default : 1
1533            Used for mtrr cleanup. It is spare mtrr entries number.
1534            Set to 2 or more if your graphical card needs more.
1535
1536    n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1537
1538    netdev= [NET] Network devices parameters
1539            Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1540            Note that mem_start is often overloaded to mean
1541            something different and driver-specific.
1542            This usage is only documented in each driver source
1543            file if at all.
1544
1545    nf_conntrack.acct=
1546            [NETFILTER] Enable connection tracking flow accounting
1547            0 to disable accounting
1548            1 to enable accounting
1549            Default value is 0.
1550
1551    nfsaddrs= [NFS] Deprecated. Use ip= instead.
1552            See Documentation/filesystems/nfs/nfsroot.txt.
1553
1554    nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1555            See Documentation/filesystems/nfs/nfsroot.txt.
1556
1557    nfsrootdebug [NFS] enable nfsroot debugging messages.
1558            See Documentation/filesystems/nfs/nfsroot.txt.
1559
1560    nfs.callback_tcpport=
1561            [NFS] set the TCP port on which the NFSv4 callback
1562            channel should listen.
1563
1564    nfs.cache_getent=
1565            [NFS] sets the pathname to the program which is used
1566            to update the NFS client cache entries.
1567
1568    nfs.cache_getent_timeout=
1569            [NFS] sets the timeout after which an attempt to
1570            update a cache entry is deemed to have failed.
1571
1572    nfs.idmap_cache_timeout=
1573            [NFS] set the maximum lifetime for idmapper cache
1574            entries.
1575
1576    nfs.enable_ino64=
1577            [NFS] enable 64-bit inode numbers.
1578            If zero, the NFS client will fake up a 32-bit inode
1579            number for the readdir() and stat() syscalls instead
1580            of returning the full 64-bit number.
1581            The default is to return 64-bit inode numbers.
1582
1583    nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1584            when a NMI is triggered.
1585            Format: [state][,regs][,debounce][,die]
1586
1587    nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1588            Format: [panic,][num]
1589            Valid num: 0
1590            0 - turn nmi_watchdog off
1591            When panic is specified, panic when an NMI watchdog
1592            timeout occurs.
1593            This is useful when you use a panic=... timeout and
1594            need the box quickly up again.
1595
1596    netpoll.carrier_timeout=
1597            [NET] Specifies amount of time (in seconds) that
1598            netpoll should wait for a carrier. By default netpoll
1599            waits 4 seconds.
1600
1601    no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1602            emulation library even if a 387 maths coprocessor
1603            is present.
1604
1605    no_console_suspend
1606            [HW] Never suspend the console
1607            Disable suspending of consoles during suspend and
1608            hibernate operations. Once disabled, debugging
1609            messages can reach various consoles while the rest
1610            of the system is being put to sleep (ie, while
1611            debugging driver suspend/resume hooks). This may
1612            not work reliably with all consoles, but is known
1613            to work with serial and VGA consoles.
1614
1615    noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1616            caches in the slab allocator. Saves per-node memory,
1617            but will impact performance.
1618
1619    noalign [KNL,ARM]
1620
1621    noapic [SMP,APIC] Tells the kernel to not make use of any
1622            IOAPICs that may be present in the system.
1623
1624    noautogroup Disable scheduler automatic task group creation.
1625
1626    nobats [PPC] Do not use BATs for mapping kernel lowmem
1627            on "Classic" PPC cores.
1628
1629    nocache [ARM]
1630
1631    noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1632
1633    nodelayacct [KNL] Disable per-task delay accounting
1634
1635    nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1636
1637    nodsp [SH] Disable hardware DSP at boot time.
1638
1639    noefi [X86] Disable EFI runtime services support.
1640
1641    noexec [IA-64]
1642
1643    noexec [X86]
1644            On X86-32 available only on PAE configured kernels.
1645            noexec=on: enable non-executable mappings (default)
1646            noexec=off: disable non-executable mappings
1647
1648    noexec32 [X86-64]
1649            This affects only 32-bit executables.
1650            noexec32=on: enable non-executable mappings (default)
1651                read doesn't imply executable mappings
1652            noexec32=off: disable non-executable mappings
1653                read implies executable mappings
1654
1655    nofpu [SH] Disable hardware FPU at boot time.
1656
1657    nofxsr [BUGS=X86-32] Disables x86 floating point extended
1658            register save and restore. The kernel will only save
1659            legacy floating-point registers on task switch.
1660
1661    noxsave [BUGS=X86] Disables x86 extended register state save
1662            and restore using xsave. The kernel will fallback to
1663            enabling legacy floating-point and sse state.
1664
1665    nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1666            wfi(ARM) instruction doesn't work correctly and not to
1667            use it. This is also useful when using JTAG debugger.
1668
1669    no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1670            instruction doesn't work correctly and not to
1671            use it.
1672
1673    no_file_caps Tells the kernel not to honor file capabilities. The
1674            only way then for a file to be executed with privilege
1675            is to be setuid root or executed by root.
1676
1677    nohalt [IA-64] Tells the kernel not to use the power saving
1678            function PAL_HALT_LIGHT when idle. This increases
1679            power-consumption. On the positive side, it reduces
1680            interrupt wake-up latency, which may improve performance
1681            in certain environments such as networked servers or
1682            real-time systems.
1683
1684    nohz= [KNL] Boottime enable/disable dynamic ticks
1685            Valid arguments: on, off
1686            Default: on
1687
1688    noiotrap [SH] Disables trapped I/O port accesses.
1689
1690    noirqdebug [X86-32] Disables the code which attempts to detect and
1691            disable unhandled interrupt sources.
1692
1693    no_timer_check [X86,APIC] Disables the code which tests for
1694            broken timer IRQ sources.
1695
1696    noisapnp [ISAPNP] Disables ISA PnP code.
1697
1698    noinitrd [RAM] Tells the kernel not to load any configured
1699            initial RAM disk.
1700
1701    nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1702            remapping.
1703            [Deprecated - use intremap=off]
1704
1705    nointroute [IA-64]
1706
1707    nojitter [IA64] Disables jitter checking for ITC timers.
1708
1709    no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1710
1711    no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1712            fault handling.
1713
1714    nolapic [X86-32,APIC] Do not enable or use the local APIC.
1715
1716    nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1717
1718    noltlbs [PPC] Do not use large page/tlb entries for kernel
1719            lowmem mapping on PPC40x.
1720
1721    nomca [IA-64] Disable machine check abort handling
1722
1723    nomce [X86-32] Machine Check Exception
1724
1725    nomfgpt [X86-32] Disable Multi-Function General Purpose
1726            Timer usage (for AMD Geode machines).
1727
1728    nopat [X86] Disable PAT (page attribute table extension of
1729            pagetables) support.
1730
1731    norandmaps Don't use address space randomization. Equivalent to
1732            echo 0 > /proc/sys/kernel/randomize_va_space
1733
1734    noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1735
1736    noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1737            with UP alternatives
1738
1739    noresidual [PPC] Don't use residual data on PReP machines.
1740
1741    noresume [SWSUSP] Disables resume and restores original swap
1742            space.
1743
1744    no-scroll [VGA] Disables scrollback.
1745            This is required for the Braillex ib80-piezo Braille
1746            reader made by F.H. Papenmeier (Germany).
1747
1748    nosbagart [IA-64]
1749
1750    nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1751
1752    nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1753            and disable the IO APIC. legacy for "maxcpus=0".
1754
1755    nosoftlockup [KNL] Disable the soft-lockup detector.
1756
1757    noswapaccount [KNL] Disable accounting of swap in memory resource
1758            controller. (See Documentation/cgroups/memory.txt)
1759
1760    nosync [HW,M68K] Disables sync negotiation for all devices.
1761
1762    notsc [BUGS=X86-32] Disable Time Stamp Counter
1763
1764    nousb [USB] Disable the USB subsystem
1765
1766    nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1767
1768    nowb [ARM]
1769
1770    nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1771
1772    nptcg= [IA64] Override max number of concurrent global TLB
1773            purges which is reported from either PAL_VM_SUMMARY or
1774            SAL PALO.
1775
1776    nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1777            could support. nr_cpus=n : n >= 1 limits the kernel to
1778            supporting 'n' processors. Later in runtime you can not
1779            use hotplug cpu feature to put more cpu back to online.
1780            just like you compile the kernel NR_CPUS=n
1781
1782    nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1783
1784    numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1785            one of ['zone', 'node', 'default'] can be specified
1786            This can be set from sysctl after boot.
1787            See Documentation/sysctl/vm.txt for details.
1788
1789    ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1790            See Documentation/debugging-via-ohci1394.txt for more
1791            info.
1792
1793    olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1794            Rather than timing out after 20 ms if an EC
1795            command is not properly ACKed, override the length
1796            of the timeout. We have interrupts disabled while
1797            waiting for the ACK, so if this is set too high
1798            interrupts *may* be lost!
1799
1800    omap_mux= [OMAP] Override bootloader pin multiplexing.
1801            Format: <mux_mode0.mode_name=value>...
1802            For example, to override I2C bus2:
1803            omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1804
1805    oprofile.timer= [HW]
1806            Use timer interrupt instead of performance counters
1807
1808    oprofile.cpu_type= Force an oprofile cpu type
1809            This might be useful if you have an older oprofile
1810            userland or if you want common events.
1811            Format: { arch_perfmon }
1812            arch_perfmon: [X86] Force use of architectural
1813                perfmon on Intel CPUs instead of the
1814                CPU specific event set.
1815
1816    OSS [HW,OSS]
1817            See Documentation/sound/oss/oss-parameters.txt
1818
1819    panic= [KNL] Kernel behaviour on panic
1820            Format: <timeout>
1821
1822    parkbd.port= [HW] Parallel port number the keyboard adapter is
1823            connected to, default is 0.
1824            Format: <parport#>
1825    parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1826            0 for XT, 1 for AT (default is AT).
1827            Format: <mode>
1828
1829    parport= [HW,PPT] Specify parallel ports. 0 disables.
1830            Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1831            Use 'auto' to force the driver to use any
1832            IRQ/DMA settings detected (the default is to
1833            ignore detected IRQ/DMA settings because of
1834            possible conflicts). You can specify the base
1835            address, IRQ, and DMA settings; IRQ and DMA
1836            should be numbers, or 'auto' (for using detected
1837            settings on that particular port), or 'nofifo'
1838            (to avoid using a FIFO even if it is detected).
1839            Parallel ports are assigned in the order they
1840            are specified on the command line, starting
1841            with parport0.
1842
1843    parport_init_mode= [HW,PPT]
1844            Configure VIA parallel port to operate in
1845            a specific mode. This is necessary on Pegasos
1846            computer where firmware has no options for setting
1847            up parallel port mode and sets it to spp.
1848            Currently this function knows 686a and 8231 chips.
1849            Format: [spp|ps2|epp|ecp|ecpepp]
1850
1851    pause_on_oops=
1852            Halt all CPUs after the first oops has been printed for
1853            the specified number of seconds. This is to be used if
1854            your oopses keep scrolling off the screen.
1855
1856    pcbit= [HW,ISDN]
1857
1858    pcd. [PARIDE]
1859            See header of drivers/block/paride/pcd.c.
1860            See also Documentation/blockdev/paride.txt.
1861
1862    pci=option[,option...] [PCI] various PCI subsystem options:
1863        earlydump [X86] dump PCI config space before the kernel
1864                    changes anything
1865        off [X86] don't probe for the PCI bus
1866        bios [X86-32] force use of PCI BIOS, don't access
1867                the hardware directly. Use this if your machine
1868                has a non-standard PCI host bridge.
1869        nobios [X86-32] disallow use of PCI BIOS, only direct
1870                hardware access methods are allowed. Use this
1871                if you experience crashes upon bootup and you
1872                suspect they are caused by the BIOS.
1873        conf1 [X86] Force use of PCI Configuration
1874                Mechanism 1.
1875        conf2 [X86] Force use of PCI Configuration
1876                Mechanism 2.
1877        noaer [PCIE] If the PCIEAER kernel config parameter is
1878                enabled, this kernel boot option can be used to
1879                disable the use of PCIE advanced error reporting.
1880        nodomains [PCI] Disable support for multiple PCI
1881                root domains (aka PCI segments, in ACPI-speak).
1882        nommconf [X86] Disable use of MMCONFIG for PCI
1883                Configuration
1884        check_enable_amd_mmconf [X86] check for and enable
1885                properly configured MMIO access to PCI
1886                config space on AMD family 10h CPU
1887        nomsi [MSI] If the PCI_MSI kernel config parameter is
1888                enabled, this kernel boot option can be used to
1889                disable the use of MSI interrupts system-wide.
1890        noioapicquirk [APIC] Disable all boot interrupt quirks.
1891                Safety option to keep boot IRQs enabled. This
1892                should never be necessary.
1893        ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1894                primary IO-APIC for bridges that cannot disable
1895                boot IRQs. This fixes a source of spurious IRQs
1896                when the system masks IRQs.
1897        noioapicreroute [APIC] Disable workaround that uses the
1898                boot IRQ equivalent of an IRQ that connects to
1899                a chipset where boot IRQs cannot be disabled.
1900                The opposite of ioapicreroute.
1901        biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1902                routing table. These calls are known to be buggy
1903                on several machines and they hang the machine
1904                when used, but on other computers it's the only
1905                way to get the interrupt routing table. Try
1906                this option if the kernel is unable to allocate
1907                IRQs or discover secondary PCI buses on your
1908                motherboard.
1909        rom [X86] Assign address space to expansion ROMs.
1910                Use with caution as certain devices share
1911                address decoders between ROMs and other
1912                resources.
1913        norom [X86] Do not assign address space to
1914                expansion ROMs that do not already have
1915                BIOS assigned address ranges.
1916        nobar [X86] Do not assign address space to the
1917                BARs that weren't assigned by the BIOS.
1918        irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1919                assigned automatically to PCI devices. You can
1920                make the kernel exclude IRQs of your ISA cards
1921                this way.
1922        pirqaddr=0xAAAAA [X86] Specify the physical address
1923                of the PIRQ table (normally generated
1924                by the BIOS) if it is outside the
1925                F0000h-100000h range.
1926        lastbus=N [X86] Scan all buses thru bus #N. Can be
1927                useful if the kernel is unable to find your
1928                secondary buses and you want to tell it
1929                explicitly which ones they are.
1930        assign-busses [X86] Always assign all PCI bus
1931                numbers ourselves, overriding
1932                whatever the firmware may have done.
1933        usepirqmask [X86] Honor the possible IRQ mask stored
1934                in the BIOS $PIR table. This is needed on
1935                some systems with broken BIOSes, notably
1936                some HP Pavilion N5400 and Omnibook XE3
1937                notebooks. This will have no effect if ACPI
1938                IRQ routing is enabled.
1939        noacpi [X86] Do not use ACPI for IRQ routing
1940                or for PCI scanning.
1941        use_crs [X86] Use PCI host bridge window information
1942                from ACPI. On BIOSes from 2008 or later, this
1943                is enabled by default. If you need to use this,
1944                please report a bug.
1945        nocrs [X86] Ignore PCI host bridge windows from ACPI.
1946                    If you need to use this, please report a bug.
1947        routeirq Do IRQ routing for all PCI devices.
1948                This is normally done in pci_enable_device(),
1949                so this option is a temporary workaround
1950                for broken drivers that don't call it.
1951        skip_isa_align [X86] do not align io start addr, so can
1952                handle more pci cards
1953        firmware [ARM] Do not re-enumerate the bus but instead
1954                just use the configuration from the
1955                bootloader. This is currently used on
1956                IXP2000 systems where the bus has to be
1957                configured a certain way for adjunct CPUs.
1958        noearly [X86] Don't do any early type 1 scanning.
1959                This might help on some broken boards which
1960                machine check when some devices' config space
1961                is read. But various workarounds are disabled
1962                and some IOMMU drivers will not work.
1963        bfsort Sort PCI devices into breadth-first order.
1964                This sorting is done to get a device
1965                order compatible with older (<= 2.4) kernels.
1966        nobfsort Don't sort PCI devices into breadth-first order.
1967        cbiosize=nn[KMG] The fixed amount of bus space which is
1968                reserved for the CardBus bridge's IO window.
1969                The default value is 256 bytes.
1970        cbmemsize=nn[KMG] The fixed amount of bus space which is
1971                reserved for the CardBus bridge's memory
1972                window. The default value is 64 megabytes.
1973        resource_alignment=
1974                Format:
1975                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1976                Specifies alignment and device to reassign
1977                aligned memory resources.
1978                If <order of align> is not specified,
1979                PAGE_SIZE is used as alignment.
1980                PCI-PCI bridge can be specified, if resource
1981                windows need to be expanded.
1982        ecrc= Enable/disable PCIe ECRC (transaction layer
1983                end-to-end CRC checking).
1984                bios: Use BIOS/firmware settings. This is the
1985                the default.
1986                off: Turn ECRC off
1987                on: Turn ECRC on.
1988
1989    pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1990            Management.
1991        off Disable ASPM.
1992        force Enable ASPM even on devices that claim not to support it.
1993            WARNING: Forcing ASPM on may cause system lockups.
1994
1995    pcie_ports= [PCIE] PCIe ports handling:
1996        auto Ask the BIOS whether or not to use native PCIe services
1997            associated with PCIe ports (PME, hot-plug, AER). Use
1998            them only if that is allowed by the BIOS.
1999        native Use native PCIe services associated with PCIe ports
2000            unconditionally.
2001        compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2002            ports driver.
2003
2004    pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2005        nomsi Do not use MSI for native PCIe PME signaling (this makes
2006            all PCIe root ports use INTx for all services).
2007
2008    pcmv= [HW,PCMCIA] BadgePAD 4
2009
2010    pd. [PARIDE]
2011            See Documentation/blockdev/paride.txt.
2012
2013    pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2014            boot time.
2015            Format: { 0 | 1 }
2016            See arch/parisc/kernel/pdc_chassis.c
2017
2018    percpu_alloc= Select which percpu first chunk allocator to use.
2019            Currently supported values are "embed" and "page".
2020            Archs may support subset or none of the selections.
2021            See comments in mm/percpu.c for details on each
2022            allocator. This parameter is primarily for debugging
2023            and performance comparison.
2024
2025    pf. [PARIDE]
2026            See Documentation/blockdev/paride.txt.
2027
2028    pg. [PARIDE]
2029            See Documentation/blockdev/paride.txt.
2030
2031    pirq= [SMP,APIC] Manual mp-table setup
2032            See Documentation/x86/i386/IO-APIC.txt.
2033
2034    plip= [PPT,NET] Parallel port network link
2035            Format: { parport<nr> | timid | 0 }
2036            See also Documentation/parport.txt.
2037
2038    pmtmr= [X86] Manual setup of pmtmr I/O Port.
2039            Override pmtimer IOPort with a hex value.
2040            e.g. pmtmr=0x508
2041
2042    pnp.debug [PNP]
2043            Enable PNP debug messages. This depends on the
2044            CONFIG_PNP_DEBUG_MESSAGES option.
2045
2046    pnpacpi= [ACPI]
2047            { off }
2048
2049    pnpbios= [ISAPNP]
2050            { on | off | curr | res | no-curr | no-res }
2051
2052    pnp_reserve_irq=
2053            [ISAPNP] Exclude IRQs for the autoconfiguration
2054
2055    pnp_reserve_dma=
2056            [ISAPNP] Exclude DMAs for the autoconfiguration
2057
2058    pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2059            Ranges are in pairs (I/O port base and size).
2060
2061    pnp_reserve_mem=
2062            [ISAPNP] Exclude memory regions for the
2063            autoconfiguration.
2064            Ranges are in pairs (memory base and size).
2065
2066    ports= [IP_VS_FTP] IPVS ftp helper module
2067            Default is 21.
2068            Up to 8 (IP_VS_APP_MAX_PORTS) ports
2069            may be specified.
2070            Format: <port>,<port>....
2071
2072    print-fatal-signals=
2073            [KNL] debug: print fatal signals
2074
2075            If enabled, warn about various signal handling
2076            related application anomalies: too many signals,
2077            too many POSIX.1 timers, fatal signals causing a
2078            coredump - etc.
2079
2080            If you hit the warning due to signal overflow,
2081            you might want to try "ulimit -i unlimited".
2082
2083            default: off.
2084
2085    printk.time= Show timing data prefixed to each printk message line
2086            Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2087
2088    processor.max_cstate= [HW,ACPI]
2089            Limit processor to maximum C-state
2090            max_cstate=9 overrides any DMI blacklist limit.
2091
2092    processor.nocst [HW,ACPI]
2093            Ignore the _CST method to determine C-states,
2094            instead using the legacy FADT method
2095
2096    profile= [KNL] Enable kernel profiling via /proc/profile
2097            Format: [schedule,]<number>
2098            Param: "schedule" - profile schedule points.
2099            Param: <number> - step/bucket size as a power of 2 for
2100                statistical time based profiling.
2101            Param: "sleep" - profile D-state sleeping (millisecs).
2102                Requires CONFIG_SCHEDSTATS
2103            Param: "kvm" - profile VM exits.
2104
2105    prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2106            before loading.
2107            See Documentation/blockdev/ramdisk.txt.
2108
2109    psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2110            probe for; one of (bare|imps|exps|lifebook|any).
2111    psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2112            per second.
2113    psmouse.resetafter= [HW,MOUSE]
2114            Try to reset the device after so many bad packets
2115            (0 = never).
2116    psmouse.resolution=
2117            [HW,MOUSE] Set desired mouse resolution, in dpi.
2118    psmouse.smartscroll=
2119            [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2120            0 = disabled, 1 = enabled (default).
2121
2122    pt. [PARIDE]
2123            See Documentation/blockdev/paride.txt.
2124
2125    pty.legacy_count=
2126            [KNL] Number of legacy pty's. Overwrites compiled-in
2127            default number.
2128
2129    quiet [KNL] Disable most log messages
2130
2131    r128= [HW,DRM]
2132
2133    raid= [HW,RAID]
2134            See Documentation/md.txt.
2135
2136    ramdisk_blocksize= [RAM]
2137            See Documentation/blockdev/ramdisk.txt.
2138
2139    ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2140            See Documentation/blockdev/ramdisk.txt.
2141
2142    rcupdate.blimit= [KNL,BOOT]
2143            Set maximum number of finished RCU callbacks to process
2144            in one batch.
2145
2146    rcupdate.qhimark= [KNL,BOOT]
2147            Set threshold of queued
2148            RCU callbacks over which batch limiting is disabled.
2149
2150    rcupdate.qlowmark= [KNL,BOOT]
2151            Set threshold of queued RCU callbacks below which
2152            batch limiting is re-enabled.
2153
2154    rdinit= [KNL]
2155            Format: <full_path>
2156            Run specified binary instead of /init from the ramdisk,
2157            used for early userspace startup. See initrd.
2158
2159    reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2160            Format: <reboot_mode>[,<reboot_mode2>[,...]]
2161            See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2162
2163    relax_domain_level=
2164            [KNL, SMP] Set scheduler's default relax_domain_level.
2165            See Documentation/cgroups/cpusets.txt.
2166
2167    reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2168
2169    reservetop= [X86-32]
2170            Format: nn[KMG]
2171            Reserves a hole at the top of the kernel virtual
2172            address space.
2173
2174    reservelow= [X86]
2175            Format: nn[K]
2176            Set the amount of memory to reserve for BIOS at
2177            the bottom of the address space.
2178
2179    reset_devices [KNL] Force drivers to reset the underlying device
2180            during initialization.
2181
2182    resume= [SWSUSP]
2183            Specify the partition device for software suspend
2184
2185    resume_offset= [SWSUSP]
2186            Specify the offset from the beginning of the partition
2187            given by "resume=" at which the swap header is located,
2188            in <PAGE_SIZE> units (needed only for swap files).
2189            See Documentation/power/swsusp-and-swap-files.txt
2190
2191    hibernate= [HIBERNATION]
2192        noresume Don't check if there's a hibernation image
2193                present during boot.
2194        nocompress Don't compress/decompress hibernation images.
2195
2196    retain_initrd [RAM] Keep initrd memory after extraction
2197
2198    rhash_entries= [KNL,NET]
2199            Set number of hash buckets for route cache
2200
2201    riscom8= [HW,SERIAL]
2202            Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2203
2204    ro [KNL] Mount root device read-only on boot
2205
2206    root= [KNL] Root filesystem
2207
2208    rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2209            mount the root filesystem
2210
2211    rootflags= [KNL] Set root filesystem mount option string
2212
2213    rootfstype= [KNL] Set root filesystem type
2214
2215    rootwait [KNL] Wait (indefinitely) for root device to show up.
2216            Useful for devices that are detected asynchronously
2217            (e.g. USB and MMC devices).
2218
2219    rw [KNL] Mount root device read-write on boot
2220
2221    S [KNL] Run init in single mode
2222
2223    sa1100ir [NET]
2224            See drivers/net/irda/sa1100_ir.c.
2225
2226    sbni= [NET] Granch SBNI12 leased line adapter
2227
2228    sched_debug [KNL] Enables verbose scheduler debug messages.
2229
2230    security= [SECURITY] Choose a security module to enable at boot.
2231            If this boot parameter is not specified, only the first
2232            security module asking for security registration will be
2233            loaded. An invalid security module name will be treated
2234            as if no module has been chosen.
2235
2236    selinux= [SELINUX] Disable or enable SELinux at boot time.
2237            Format: { "0" | "1" }
2238            See security/selinux/Kconfig help text.
2239            0 -- disable.
2240            1 -- enable.
2241            Default value is set via kernel config option.
2242            If enabled at boot time, /selinux/disable can be used
2243            later to disable prior to initial policy load.
2244
2245    apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2246            Format: { "0" | "1" }
2247            See security/apparmor/Kconfig help text
2248            0 -- disable.
2249            1 -- enable.
2250            Default value is set via kernel config option.
2251
2252    serialnumber [BUGS=X86-32]
2253
2254    shapers= [NET]
2255            Maximal number of shapers.
2256
2257    show_msr= [x86] show boot-time MSR settings
2258            Format: { <integer> }
2259            Show boot-time (BIOS-initialized) MSR settings.
2260            The parameter means the number of CPUs to show,
2261            for example 1 means boot CPU only.
2262
2263    simeth= [IA-64]
2264    simscsi=
2265
2266    slram= [HW,MTD]
2267
2268    slub_debug[=options[,slabs]] [MM, SLUB]
2269            Enabling slub_debug allows one to determine the
2270            culprit if slab objects become corrupted. Enabling
2271            slub_debug can create guard zones around objects and
2272            may poison objects when not in use. Also tracks the
2273            last alloc / free. For more information see
2274            Documentation/vm/slub.txt.
2275
2276    slub_max_order= [MM, SLUB]
2277            Determines the maximum allowed order for slabs.
2278            A high setting may cause OOMs due to memory
2279            fragmentation. For more information see
2280            Documentation/vm/slub.txt.
2281
2282    slub_min_objects= [MM, SLUB]
2283            The minimum number of objects per slab. SLUB will
2284            increase the slab order up to slub_max_order to
2285            generate a sufficiently large slab able to contain
2286            the number of objects indicated. The higher the number
2287            of objects the smaller the overhead of tracking slabs
2288            and the less frequently locks need to be acquired.
2289            For more information see Documentation/vm/slub.txt.
2290
2291    slub_min_order= [MM, SLUB]
2292            Determines the mininum page order for slabs. Must be
2293            lower than slub_max_order.
2294            For more information see Documentation/vm/slub.txt.
2295
2296    slub_nomerge [MM, SLUB]
2297            Disable merging of slabs with similar size. May be
2298            necessary if there is some reason to distinguish
2299            allocs to different slabs. Debug options disable
2300            merging on their own.
2301            For more information see Documentation/vm/slub.txt.
2302
2303    smart2= [HW]
2304            Format: <io1>[,<io2>[,...,<io8>]]
2305
2306    smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2307            attempt to substitute SMP alternatives once at boot.
2308
2309    smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2310    smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2311    smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2312    smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2313    smsc-ircc2.ircc_irq= [HW] IRQ line
2314    smsc-ircc2.ircc_dma= [HW] DMA channel
2315    smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2316                0: Toshiba Satellite 1800 (GP data pin select)
2317                1: Fast pin select (default)
2318                2: ATC IRMode
2319
2320    softlockup_panic=
2321            [KNL] Should the soft-lockup detector generate panics.
2322
2323    sonypi.*= [HW] Sony Programmable I/O Control Device driver
2324            See Documentation/sonypi.txt
2325
2326    specialix= [HW,SERIAL] Specialix multi-serial port adapter
2327            See Documentation/serial/specialix.txt.
2328
2329    spia_io_base= [HW,MTD]
2330    spia_fio_base=
2331    spia_pedr=
2332    spia_peddr=
2333
2334    stacktrace [FTRACE]
2335            Enabled the stack tracer on boot up.
2336
2337    sti= [PARISC,HW]
2338            Format: <num>
2339            Set the STI (builtin display/keyboard on the HP-PARISC
2340            machines) console (graphic card) which should be used
2341            as the initial boot-console.
2342            See also comment in drivers/video/console/sticore.c.
2343
2344    sti_font= [HW]
2345            See comment in drivers/video/console/sticore.c.
2346
2347    stifb= [HW]
2348            Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2349
2350    sunrpc.min_resvport=
2351    sunrpc.max_resvport=
2352            [NFS,SUNRPC]
2353            SunRPC servers often require that client requests
2354            originate from a privileged port (i.e. a port in the
2355            range 0 < portnr < 1024).
2356            An administrator who wishes to reserve some of these
2357            ports for other uses may adjust the range that the
2358            kernel's sunrpc client considers to be privileged
2359            using these two parameters to set the minimum and
2360            maximum port values.
2361
2362    sunrpc.pool_mode=
2363            [NFS]
2364            Control how the NFS server code allocates CPUs to
2365            service thread pools. Depending on how many NICs
2366            you have and where their interrupts are bound, this
2367            option will affect which CPUs will do NFS serving.
2368            Note: this parameter cannot be changed while the
2369            NFS server is running.
2370
2371            auto the server chooses an appropriate mode
2372                    automatically using heuristics
2373            global a single global pool contains all CPUs
2374            percpu one pool for each CPU
2375            pernode one pool for each NUMA node (equivalent
2376                    to global on non-NUMA machines)
2377
2378    sunrpc.tcp_slot_table_entries=
2379    sunrpc.udp_slot_table_entries=
2380            [NFS,SUNRPC]
2381            Sets the upper limit on the number of simultaneous
2382            RPC calls that can be sent from the client to a
2383            server. Increasing these values may allow you to
2384            improve throughput, but will also increase the
2385            amount of memory reserved for use by the client.
2386
2387    swapaccount[=0|1]
2388            [KNL] Enable accounting of swap in memory resource
2389            controller if no parameter or 1 is given or disable
2390            it if 0 is given (See Documentation/cgroups/memory.txt)
2391
2392    swiotlb= [IA-64] Number of I/O TLB slabs
2393
2394    switches= [HW,M68k]
2395
2396    sysfs.deprecated=0|1 [KNL]
2397            Enable/disable old style sysfs layout for old udev
2398            on older distributions. When this option is enabled
2399            very new udev will not work anymore. When this option
2400            is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2401            in older udev will not work anymore.
2402            Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2403            the kernel configuration.
2404
2405    sysrq_always_enabled
2406            [KNL]
2407            Ignore sysrq setting - this boot parameter will
2408            neutralize any effect of /proc/sys/kernel/sysrq.
2409            Useful for debugging.
2410
2411    tdfx= [HW,DRM]
2412
2413    test_suspend= [SUSPEND]
2414            Specify "mem" (for Suspend-to-RAM) or "standby" (for
2415            standby suspend) as the system sleep state to briefly
2416            enter during system startup. The system is woken from
2417            this state using a wakeup-capable RTC alarm.
2418
2419    thash_entries= [KNL,NET]
2420            Set number of hash buckets for TCP connection
2421
2422    thermal.act= [HW,ACPI]
2423            -1: disable all active trip points in all thermal zones
2424            <degrees C>: override all lowest active trip points
2425
2426    thermal.crt= [HW,ACPI]
2427            -1: disable all critical trip points in all thermal zones
2428            <degrees C>: override all critical trip points
2429
2430    thermal.nocrt= [HW,ACPI]
2431            Set to disable actions on ACPI thermal zone
2432            critical and hot trip points.
2433
2434    thermal.off= [HW,ACPI]
2435            1: disable ACPI thermal control
2436
2437    thermal.psv= [HW,ACPI]
2438            -1: disable all passive trip points
2439            <degrees C>: override all passive trip points to this
2440            value
2441
2442    thermal.tzp= [HW,ACPI]
2443            Specify global default ACPI thermal zone polling rate
2444            <deci-seconds>: poll all this frequency
2445            0: no polling (default)
2446
2447    topology= [S390]
2448            Format: {off | on}
2449            Specify if the kernel should make use of the cpu
2450            topology informations if the hardware supports these.
2451            The scheduler will make use of these informations and
2452            e.g. base its process migration decisions on it.
2453            Default is on.
2454
2455    tp720= [HW,PS2]
2456
2457    tpm_suspend_pcr=[HW,TPM]
2458            Format: integer pcr id
2459            Specify that at suspend time, the tpm driver
2460            should extend the specified pcr with zeros,
2461            as a workaround for some chips which fail to
2462            flush the last written pcr on TPM_SaveState.
2463            This will guarantee that all the other pcrs
2464            are saved.
2465
2466    trace_buf_size=nn[KMG]
2467            [FTRACE] will set tracing buffer size.
2468
2469    trace_event=[event-list]
2470            [FTRACE] Set and start specified trace events in order
2471            to facilitate early boot debugging.
2472            See also Documentation/trace/events.txt
2473
2474    tsc= Disable clocksource stability checks for TSC.
2475            Format: <string>
2476            [x86] reliable: mark tsc clocksource as reliable, this
2477            disables clocksource verification at runtime, as well
2478            as the stability checks done at bootup. Used to enable
2479            high-resolution timer mode on older hardware, and in
2480            virtualized environment.
2481            [x86] noirqtime: Do not use TSC to do irq accounting.
2482            Used to run time disable IRQ_TIME_ACCOUNTING on any
2483            platforms where RDTSC is slow and this accounting
2484            can add overhead.
2485
2486    turbografx.map[2|3]= [HW,JOY]
2487            TurboGraFX parallel port interface
2488            Format:
2489            <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2490            See also Documentation/input/joystick-parport.txt
2491
2492    uhash_entries= [KNL,NET]
2493            Set number of hash buckets for UDP/UDP-Lite connections
2494
2495    uhci-hcd.ignore_oc=
2496            [USB] Ignore overcurrent events (default N).
2497            Some badly-designed motherboards generate lots of
2498            bogus events, for ports that aren't wired to
2499            anything. Set this parameter to avoid log spamming.
2500            Note that genuine overcurrent events won't be
2501            reported either.
2502
2503    unknown_nmi_panic
2504            [X86]
2505            Set unknown_nmi_panic=1 early on boot.
2506
2507    usbcore.autosuspend=
2508            [USB] The autosuspend time delay (in seconds) used
2509            for newly-detected USB devices (default 2). This
2510            is the time required before an idle device will be
2511            autosuspended. Devices for which the delay is set
2512            to a negative value won't be autosuspended at all.
2513
2514    usbcore.usbfs_snoop=
2515            [USB] Set to log all usbfs traffic (default 0 = off).
2516
2517    usbcore.blinkenlights=
2518            [USB] Set to cycle leds on hubs (default 0 = off).
2519
2520    usbcore.old_scheme_first=
2521            [USB] Start with the old device initialization
2522            scheme (default 0 = off).
2523
2524    usbcore.use_both_schemes=
2525            [USB] Try the other device initialization scheme
2526            if the first one fails (default 1 = enabled).
2527
2528    usbcore.initial_descriptor_timeout=
2529            [USB] Specifies timeout for the initial 64-byte
2530                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2531            (default 5000 = 5.0 seconds).
2532
2533    usbhid.mousepoll=
2534            [USBHID] The interval which mice are to be polled at.
2535
2536    usb-storage.delay_use=
2537            [UMS] The delay in seconds before a new device is
2538            scanned for Logical Units (default 5).
2539
2540    usb-storage.quirks=
2541            [UMS] A list of quirks entries to supplement or
2542            override the built-in unusual_devs list. List
2543            entries are separated by commas. Each entry has
2544            the form VID:PID:Flags where VID and PID are Vendor
2545            and Product ID values (4-digit hex numbers) and
2546            Flags is a set of characters, each corresponding
2547            to a common usb-storage quirk flag as follows:
2548                a = SANE_SENSE (collect more than 18 bytes
2549                    of sense data);
2550                b = BAD_SENSE (don't collect more than 18
2551                    bytes of sense data);
2552                c = FIX_CAPACITY (decrease the reported
2553                    device capacity by one sector);
2554                h = CAPACITY_HEURISTICS (decrease the
2555                    reported device capacity by one
2556                    sector if the number is odd);
2557                i = IGNORE_DEVICE (don't bind to this
2558                    device);
2559                l = NOT_LOCKABLE (don't try to lock and
2560                    unlock ejectable media);
2561                m = MAX_SECTORS_64 (don't transfer more
2562                    than 64 sectors = 32 KB at a time);
2563                o = CAPACITY_OK (accept the capacity
2564                    reported by the device);
2565                r = IGNORE_RESIDUE (the device reports
2566                    bogus residue values);
2567                s = SINGLE_LUN (the device has only one
2568                    Logical Unit);
2569                w = NO_WP_DETECT (don't test whether the
2570                    medium is write-protected).
2571            Example: quirks=0419:aaf5:rl,0421:0433:rc
2572
2573    userpte=
2574            [X86] Flags controlling user PTE allocations.
2575
2576                nohigh = do not allocate PTE pages in
2577                    HIGHMEM regardless of setting
2578                    of CONFIG_HIGHPTE.
2579
2580    vdso= [X86,SH]
2581            vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2582            vdso=1: enable VDSO (default)
2583            vdso=0: disable VDSO mapping
2584
2585    vdso32= [X86]
2586            vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2587            vdso32=1: enable 32-bit VDSO (default)
2588            vdso32=0: disable 32-bit VDSO mapping
2589
2590    vector= [IA-64,SMP]
2591            vector=percpu: enable percpu vector domain
2592
2593    video= [FB] Frame buffer configuration
2594            See Documentation/fb/modedb.txt.
2595
2596    vga= [BOOT,X86-32] Select a particular video mode
2597            See Documentation/x86/boot.txt and
2598            Documentation/svga.txt.
2599            Use vga=ask for menu.
2600            This is actually a boot loader parameter; the value is
2601            passed to the kernel using a special protocol.
2602
2603    vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2604            size of <nn>. This can be used to increase the
2605            minimum size (128MB on x86). It can also be used to
2606            decrease the size and leave more room for directly
2607            mapped kernel RAM.
2608
2609    vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2610            Format: <command>
2611
2612    vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2613            Format: <command>
2614
2615    vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2616            Format: <command>
2617
2618    vt.cur_default= [VT] Default cursor shape.
2619            Format: 0xCCBBAA, where AA, BB, and CC are the same as
2620            the parameters of the <Esc>[?A;B;Cc escape sequence;
2621            see VGA-softcursor.txt. Default: 2 = underline.
2622
2623    vt.default_blu= [VT]
2624            Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2625            Change the default blue palette of the console.
2626            This is a 16-member array composed of values
2627            ranging from 0-255.
2628
2629    vt.default_grn= [VT]
2630            Format: <green0>,<green1>,<green2>,...,<green15>
2631            Change the default green palette of the console.
2632            This is a 16-member array composed of values
2633            ranging from 0-255.
2634
2635    vt.default_red= [VT]
2636            Format: <red0>,<red1>,<red2>,...,<red15>
2637            Change the default red palette of the console.
2638            This is a 16-member array composed of values
2639            ranging from 0-255.
2640
2641    vt.default_utf8=
2642            [VT]
2643            Format=<0|1>
2644            Set system-wide default UTF-8 mode for all tty's.
2645            Default is 1, i.e. UTF-8 mode is enabled for all
2646            newly opened terminals.
2647
2648    vt.global_cursor_default=
2649            [VT]
2650            Format=<-1|0|1>
2651            Set system-wide default for whether a cursor
2652            is shown on new VTs. Default is -1,
2653            i.e. cursors will be created by default unless
2654            overridden by individual drivers. 0 will hide
2655            cursors, 1 will display them.
2656
2657    watchdog timers [HW,WDT] For information on watchdog timers,
2658            see Documentation/watchdog/watchdog-parameters.txt
2659            or other driver-specific files in the
2660            Documentation/watchdog/ directory.
2661
2662    x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2663            default x2apic cluster mode on platforms
2664            supporting x2apic.
2665
2666    x86_mrst_timer= [X86-32,APBT]
2667            Choose timer option for x86 Moorestown MID platform.
2668            Two valid options are apbt timer only and lapic timer
2669            plus one apbt timer for broadcast timer.
2670            x86_mrst_timer=apbt_only | lapic_and_apbt
2671
2672    xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2673    xd_geo= See header of drivers/block/xd.c.
2674
2675    xen_emul_unplug= [HW,X86,XEN]
2676            Unplug Xen emulated devices
2677            Format: [unplug0,][unplug1]
2678            ide-disks -- unplug primary master IDE devices
2679            aux-ide-disks -- unplug non-primary-master IDE devices
2680            nics -- unplug network devices
2681            all -- unplug all emulated devices (NICs and IDE disks)
2682            unnecessary -- unplugging emulated devices is
2683                unnecessary even if the host did not respond to
2684                the unplug protocol
2685            never -- do not unplug even if version check succeeds
2686
2687    xirc2ps_cs= [NET,PCMCIA]
2688            Format:
2689            <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2690
2691______________________________________________________________________
2692
2693TODO:
2694
2695    Add more DRM drivers.
2696

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