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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AX25 Appropriate AX.25 support is enabled.
38 BLACKFIN Blackfin architecture is enabled.
39 DRM Direct Rendering Management support is enabled.
40 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
41 EFI EFI Partitioning (GPT) is enabled
42 EIDE EIDE/ATAPI support is enabled.
43 FB The frame buffer device is enabled.
44 HW Appropriate hardware is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD (Memory Technology Device) support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel is enabled.
68 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCIE PCI Express support is enabled.
72 PCMCIA The PCMCIA subsystem is enabled.
73 PNP Plug & Play support is enabled.
74 PPC PowerPC architecture is enabled.
75 PPT Parallel port support is enabled.
76 PS2 Appropriate PS/2 support is enabled.
77 RAM RAM disk support is enabled.
78 S390 S390 architecture is enabled.
79 SCSI Appropriate SCSI support is enabled.
80 A lot of drivers has their options described inside of
81 Documentation/scsi/.
82 SELINUX SELinux support is enabled.
83 SERIAL Serial support is enabled.
84 SH SuperH architecture is enabled.
85 SMP The kernel is an SMP kernel.
86 SPARC Sparc architecture is enabled.
87 SWSUSP Software suspend is enabled.
88 TS Appropriate touchscreen support is enabled.
89 USB USB support is enabled.
90 USBHID USB Human Interface Device support is enabled.
91 V4L Video For Linux support is enabled.
92 VGA The VGA console has been enabled.
93 VT Virtual terminal support is enabled.
94 WDT Watchdog support is enabled.
95 XT IBM PC/XT MFM hard disk support is enabled.
96 X86-32 X86-32, aka i386 architecture is enabled.
97 X86-64 X86-64 architecture is enabled.
98 More X86-64 boot options can be found in
99 Documentation/x86_64/boot-options.txt .
101 In addition, the following text indicates that the option:
103 BUGS= Relates to possible processor bugs on the said processor.
104 KNL Is a kernel start-up parameter.
105 BOOT Is a boot loader parameter.
107 Parameters denoted with BOOT are actually interpreted by the boot
108 loader, and have no meaning to the kernel directly.
109 Do not modify the syntax of boot loader parameters without extreme
110 need or coordination with <Documentation/i386/boot.txt>.
112 There are also arch-specific kernel-parameters not documented here.
113 See for example <Documentation/x86_64/boot-options.txt>.
115 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
116 a trailing = on the name of any parameter states that that parameter will
117 be entered as an environment variable, whereas its absence indicates that
118 it will appear as a kernel argument readable via /proc/cmdline by programs
119 running once the system is up.
121 The number of kernel parameters is not limited, but the length of the
122 complete command line (parameters including spaces etc.) is limited to
123 a fixed number of characters. This limit depends on the architecture
124 and is between 256 and 4096 characters. It is defined in the file
125 ./include/asm/setup.h as COMMAND_LINE_SIZE.
128 acpi= [HW,ACPI,X86-64,i386]
129 Advanced Configuration and Power Interface
130 Format: { force | off | ht | strict | noirq }
131 force -- enable ACPI if default was off
132 off -- disable ACPI if default was on
133 noirq -- do not use ACPI for IRQ routing
134 ht -- run only enough ACPI to enable Hyper Threading
135 strict -- Be less tolerant of platforms that are not
136 strictly ACPI specification compliant.
138 See also Documentation/pm.txt, pci=noacpi
140 acpi_apic_instance= [ACPI, IOAPIC]
141 Format: <int>
142 2: use 2nd APIC table, if available
143 1,0: use 1st APIC table
144 default: 0
146 acpi_sleep= [HW,ACPI] Sleep options
147 Format: { s3_bios, s3_mode }
148 See Documentation/power/video.txt
150 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
151 Format: { level | edge | high | low }
153 acpi_irq_balance [HW,ACPI]
154 ACPI will balance active IRQs
155 default in APIC mode
157 acpi_irq_nobalance [HW,ACPI]
158 ACPI will not move active IRQs (default)
159 default in PIC mode
161 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
162 use by PCI
163 Format: <irq>,<irq>...
165 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
166 Format: <irq>,<irq>...
168 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
174 acpi_osi="string1" # add string1 -- only one string
175 acpi_osi="!string2" # remove built-in string2
176 acpi_osi= # disable all strings
178 acpi_serialize [HW,ACPI] force serialization of AML methods
180 acpi_skip_timer_override [HW,ACPI]
181 Recognize and ignore IRQ0/pin2 Interrupt Override.
182 For broken nForce2 BIOS resulting in XT-PIC timer.
183 acpi_use_timer_override [HW,ACPI}
184 Use timer override. For some broken Nvidia NF5 boards
185 that require a timer override, but don't have
186 HPET
188 acpi.debug_layer= [HW,ACPI]
189 Format: <int>
190 Each bit of the <int> indicates an ACPI debug layer,
191 1: enable, 0: disable. It is useful for boot time
192 debugging. After system has booted up, it can be set
193 via /sys/module/acpi/parameters/debug_layer.
194 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
195 Available bits (add the numbers together) to enable debug output
196 for specific parts of the ACPI subsystem:
197 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
198 0x10 namespace 0x20 parser 0x40 dispatcher
199 0x80 executer 0x100 resources 0x200 acpica debugger
200 0x400 os services 0x800 acpica disassembler.
201 The number can be in decimal or prefixed with 0x in hex.
202 Warning: Many of these options can produce a lot of
203 output and make your system unusable. Be very careful.
205 acpi.debug_level= [HW,ACPI]
206 Format: <int>
207 Each bit of the <int> indicates an ACPI debug level,
208 1: enable, 0: disable. It is useful for boot time
209 debugging. After system has booted up, it can be set
210 via /sys/module/acpi/parameters/debug_level.
211 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
212 Available bits (add the numbers together) to enable different
213 debug output levels of the ACPI subsystem:
214 0x01 error 0x02 warn 0x04 init 0x08 debug object
215 0x10 info 0x20 init names 0x40 parse 0x80 load
216 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
217 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
218 0x10000 resources 0x20000 user requests 0x40000 package.
219 The number can be in decimal or prefixed with 0x in hex.
220 Warning: Many of these options can produce a lot of
221 output and make your system unusable. Be very careful.
224 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
231 agp= [AGP]
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
247 ad1848= [HW,OSS]
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
250 advansys= [HW,SCSI]
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
260 aha152x= [HW,SCSI]
261 See Documentation/scsi/aha152x.txt.
263 aha1542= [HW,SCSI]
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
266 aic7xxx= [HW,SCSI]
267 See Documentation/scsi/aic7xxx.txt.
269 aic79xx= [HW,SCSI]
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
274 Format: <a>,<b>
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
282 apc= [HW,SPARC]
283 Power management functions (SPARCstation-4/5 + deriv.)
284 Format: noidle
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 applicom= [HW]
299 Format: <mem>,<irq>
301 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
302 Format: <io>,<irq>,<nodeID>
304 ataflop= [HW,M68k]
306 atarimouse= [HW,MOUSE] Atari Mouse
308 atascsi= [HW,SCSI] Atari SCSI
310 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
311 EzKey and similar keyboards
313 atkbd.reset= [HW] Reset keyboard during initialization
315 atkbd.set= [HW] Select keyboard code set
316 Format: <int> (2 = AT (default), 3 = PS/2)
318 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
319 keyboards
321 atkbd.softraw= [HW] Choose between synthetic and real raw mode
322 Format: <bool> (0 = real, 1 = synthetic (default))
324 atkbd.softrepeat= [HW]
325 Use software keyboard repeat
327 autotest [IA64]
329 baycom_epp= [HW,AX25]
330 Format: <io>,<mode>
332 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 Format: <io>,<mode>
334 See header of drivers/net/hamradio/baycom_par.c.
336 baycom_ser_fdx= [HW,AX25]
337 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
338 Format: <io>,<irq>,<mode>[,<baud>]
339 See header of drivers/net/hamradio/baycom_ser_fdx.c.
341 baycom_ser_hdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
343 Format: <io>,<irq>,<mode>
344 See header of drivers/net/hamradio/baycom_ser_hdx.c.
346 blkmtd_device= [HW,MTD]
347 blkmtd_erasesz=
348 blkmtd_ro=
349 blkmtd_bs=
350 blkmtd_count=
352 boot_delay= Milliseconds to delay each printk during boot.
353 Values larger than 10 seconds (10000) are changed to
354 no delay (0).
355 Format: integer
357 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
358 bttv.radio= Most important insmod options are available as
359 kernel args too.
360 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
361 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
363 BusLogic= [HW,SCSI]
364 See drivers/scsi/BusLogic.c, comment before function
365 BusLogic_ParseDriverOptions().
367 c101= [NET] Moxa C101 synchronous serial card
369 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
370 Sometimes CPU hardware bugs make them report the cache
371 size incorrectly. The kernel will attempt work arounds
372 to fix known problems, but for some CPUs it is not
373 possible to determine what the correct size should be.
374 This option provides an override for these situations.
376 chandev= [HW,NET] Generic channel device initialisation
378 checkreqprot [SELINUX] Set initial checkreqprot flag value.
379 Format: { "0" | "1" }
380 See security/selinux/Kconfig help text.
381 0 -- check protection applied by kernel (includes
382 any implied execute protection).
383 1 -- check protection requested by application.
384 Default value is set via a kernel config option.
385 Value can be changed at runtime via
386 /selinux/checkreqprot.
388 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
389 [Deprecated]
390 Forces specified clocksource (if available) to be used
391 when calculating gettimeofday(). If specified
392 clocksource is not available, it defaults to PIT.
393 Format: { pit | tsc | cyclone | pmtmr }
395 clocksource= [GENERIC_TIME] Override the default clocksource
396 Format: <string>
397 Override the default clocksource and use the clocksource
398 with the name specified.
399 Some clocksource names to choose from, depending on
400 the platform:
401 [all] jiffies (this is the base, fallback clocksource)
402 [ACPI] acpi_pm
403 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
404 pxa_timer,timer3,32k_counter,timer0_1
405 [AVR32] avr32
406 [X86-32] pit,hpet,tsc,vmi-timer;
407 scx200_hrt on Geode; cyclone on IBM x440
408 [MIPS] MIPS
409 [PARISC] cr16
410 [S390] tod
411 [SH] SuperH
412 [SPARC64] tick
413 [X86-64] hpet,tsc
415 code_bytes [IA32] How many bytes of object code to print in an
416 oops report.
417 Range: 0 - 8192
418 Default: 64
420 disable_8254_timer
421 enable_8254_timer
422 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
423 over the 8254 in addition to over the IO-APIC. The
424 kernel tries to set a sensible default.
426 hpet= [X86-32,HPET] option to disable HPET and use PIT.
427 Format: disable
429 com20020= [HW,NET] ARCnet - COM20020 chipset
430 Format:
431 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
433 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
434 Format: <io>[,<irq>]
436 com90xx= [HW,NET]
437 ARCnet - COM90xx chipset (memory-mapped buffers)
438 Format: <io>[,<irq>[,<memstart>]]
440 condev= [HW,S390] console device
441 conmode=
443 console= [KNL] Output console device and options.
445 tty<n> Use the virtual console device <n>.
447 ttyS<n>[,options]
448 ttyUSB0[,options]
449 Use the specified serial port. The options are of
450 the form "bbbbpnf", where "bbbb" is the baud rate,
451 "p" is parity ("n", "o", or "e"), "n" is number of
452 bits, and "f" is flow control ("r" for RTS or
453 omit it). Default is "9600n8".
455 See Documentation/serial-console.txt for more
456 information. See
457 Documentation/networking/netconsole.txt for an
458 alternative.
460 uart[8250],io,<addr>[,options]
461 uart[8250],mmio,<addr>[,options]
462 Start an early, polled-mode console on the 8250/16550
463 UART at the specified I/O port or MMIO address,
464 switching to the matching ttyS device later. The
465 options are the same as for ttyS, above.
467 earlycon= [KNL] Output early console device and options.
468 uart[8250],io,<addr>[,options]
469 uart[8250],mmio,<addr>[,options]
470 Start an early, polled-mode console on the 8250/16550
471 UART at the specified I/O port or MMIO address.
472 The options are the same as for ttyS, above.
474 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
475 Format:
476 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
478 crashkernel=nn[KMG]@ss[KMG]
479 [KNL] Reserve a chunk of physical memory to
480 hold a kernel to switch to with kexec on panic.
482 cs4232= [HW,OSS]
483 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
485 cs89x0_dma= [HW,NET]
486 Format: <dma>
488 cs89x0_media= [HW,NET]
489 Format: { rj45 | aui | bnc }
491 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
493 dasd= [HW,NET]
494 See header of drivers/s390/block/dasd_devmap.c.
496 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
497 (one device per port)
498 Format: <port#>,<type>
499 See also Documentation/input/joystick-parport.txt
501 debug [KNL] Enable kernel debugging (events log level).
503 debug_locks_verbose=
504 [KNL] verbose self-tests
505 Format=<0|1>
506 Print debugging info while doing the locking API
507 self-tests.
508 We default to 0 (no extra messages), setting it to
509 1 will print _a lot_ more information - normally
510 only useful to kernel developers.
512 decnet= [HW,NET]
513 Format: <area>[,<node>]
514 See also Documentation/networking/decnet.txt.
516 default_blu= [VT]
517 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
518 Change the default blue palette of the console.
519 This is a 16-member array composed of values
520 ranging from 0-255.
522 default_grn= [VT]
523 Format: <green0>,<green1>,<green2>,...,<green15>
524 Change the default green palette of the console.
525 This is a 16-member array composed of values
526 ranging from 0-255.
528 default_red= [VT]
529 Format: <red0>,<red1>,<red2>,...,<red15>
530 Change the default red palette of the console.
531 This is a 16-member array composed of values
532 ranging from 0-255.
534 default_utf8= [VT]
535 Format=<0|1>
536 Set system-wide default UTF-8 mode for all tty's.
537 Default is 0 and by setting to 1, it enables UTF-8
538 mode for all newly opened or allocated terminals.
540 dhash_entries= [KNL]
541 Set number of hash buckets for dentry cache.
543 digi= [HW,SERIAL]
544 IO parameters + enable/disable command.
546 digiepca= [HW,SERIAL]
547 See drivers/char/README.epca and
548 Documentation/digiepca.txt.
550 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
551 support available.
552 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
554 dmasound= [HW,OSS] Sound subsystem buffers
556 dscc4.setup= [NET]
558 dtc3181e= [HW,SCSI]
560 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
561 earlyprintk=vga
562 earlyprintk=serial[,ttySn[,baudrate]]
564 Append ",keep" to not disable it when the real console
565 takes over.
567 Only vga or serial at a time, not both.
569 Currently only ttyS0 and ttyS1 are supported.
571 Interaction with the standard serial driver is not
572 very good.
574 The VGA output is eventually overwritten by the real
575 console.
577 eata= [HW,SCSI]
579 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
580 Format: <int>
581 0: polling mode
582 non-0: interrupt mode (default)
584 eda= [HW,PS2]
586 edb= [HW,PS2]
588 edd= [EDD]
589 Format: {"of[f]" | "sk[ipmbr]"}
590 See comment in arch/i386/boot/edd.S
592 eicon= [HW,ISDN]
593 Format: <id>,<membase>,<irq>
595 eisa_irq_edge= [PARISC,HW]
596 See header of drivers/parisc/eisa.c.
598 elanfreq= [X86-32]
599 See comment before function elanfreq_setup() in
600 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
602 elevator= [IOSCHED]
603 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
604 See Documentation/block/as-iosched.txt and
605 Documentation/block/deadline-iosched.txt for details.
607 elfcorehdr= [X86-32, X86_64]
608 Specifies physical address of start of kernel core
609 image elf header. Generally kexec loader will
610 pass this option to capture kernel.
611 See Documentation/kdump/kdump.txt for details.
613 enforcing [SELINUX] Set initial enforcing status.
614 Format: {"0" | "1"}
615 See security/selinux/Kconfig help text.
616 0 -- permissive (log only, no denials).
617 1 -- enforcing (deny and log).
618 Default value is 0.
619 Value can be changed at runtime via /selinux/enforce.
621 es1371= [HW,OSS]
622 Format: <spdif>,[<nomix>,[<amplifier>]]
623 See also header of sound/oss/es1371.c.
625 ether= [HW,NET] Ethernet cards parameters
626 This option is obsoleted by the "netdev=" option, which
627 has equivalent usage. See its documentation for details.
629 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
630 Format: <io>[,<irq>]
632 failslab=
633 fail_page_alloc=
634 fail_make_request=[KNL]
635 General fault injection mechanism.
636 Format: <interval>,<probability>,<space>,<times>
637 See also /Documentation/fault-injection/.
639 fd_mcs= [HW,SCSI]
640 See header of drivers/scsi/fd_mcs.c.
642 fdomain= [HW,SCSI]
643 See header of drivers/scsi/fdomain.c.
645 floppy= [HW]
646 See Documentation/floppy.txt.
648 gamecon.map[2|3]=
649 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
650 support via parallel port (up to 5 devices per port)
651 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
652 See also Documentation/input/joystick-parport.txt
654 gamma= [HW,DRM]
656 gdth= [HW,SCSI]
657 See header of drivers/scsi/gdth.c.
659 gpt [EFI] Forces disk with valid GPT signature but
660 invalid Protective MBR to be treated as GPT.
662 gvp11= [HW,SCSI]
664 hashdist= [KNL,NUMA] Large hashes allocated during boot
665 are distributed across NUMA nodes. Defaults on
666 for IA-64, off otherwise.
667 Format: 0 | 1 (for off | on)
669 hcl= [IA-64] SGI's Hardware Graph compatibility layer
671 hd= [EIDE] (E)IDE hard drive subsystem geometry
672 Format: <cyl>,<head>,<sect>
674 hd?= [HW] (E)IDE subsystem
675 hd?lun= See Documentation/ide.txt.
677 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
678 size of <nn>. This works even on boxes that have no
679 highmem otherwise. This also works to reduce highmem
680 size on bigger boxes.
682 highres= [KNL] Enable/disable high resolution timer mode.
683 Valid parameters: "on", "off"
684 Default: "on"
686 hisax= [HW,ISDN]
687 See Documentation/isdn/README.HiSax.
689 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
691 i8042.direct [HW] Put keyboard port into non-translated mode
692 i8042.dumbkbd [HW] Pretend that controller can only read data from
693 keyboard and cannot control its state
694 (Don't attempt to blink the leds)
695 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
696 i8042.nokbd [HW] Don't check/create keyboard port
697 i8042.nomux [HW] Don't check presence of an active multiplexing
698 controller
699 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
700 controllers
701 i8042.panicblink=
702 [HW] Frequency with which keyboard LEDs should blink
703 when kernel panics (default is 0.5 sec)
704 i8042.reset [HW] Reset the controller during init and cleanup
705 i8042.unlock [HW] Unlock (ignore) the keylock
707 i810= [HW,DRM]
709 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
710 indicates that the driver is running on unsupported
711 hardware.
712 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
713 does not match list of supported models.
714 i8k.power_status
715 [HW] Report power status in /proc/i8k
716 (disabled by default)
717 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
718 capability is set.
720 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
721 See Documentation/mca.txt.
723 icn= [HW,ISDN]
724 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
726 ide= [HW] (E)IDE subsystem
727 Format: ide=nodma or ide=doubler or ide=reverse
728 See Documentation/ide.txt.
730 ide?= [HW] (E)IDE subsystem
731 Format: ide?=noprobe or chipset specific parameters.
732 See Documentation/ide.txt.
734 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
735 See Documentation/ide.txt.
737 idle= [X86]
738 Format: idle=poll or idle=mwait
739 Poll forces a polling idle loop that can slightly improves the performance
740 of waking up a idle CPU, but will use a lot of power and make the system
741 run hot. Not recommended.
742 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
743 to not use it because it doesn't save as much power as a normal idle
744 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
745 as idle=poll.
747 ignore_loglevel [KNL]
748 Ignore loglevel setting - this will print /all/
749 kernel messages to the console. Useful for debugging.
751 ihash_entries= [KNL]
752 Set number of hash buckets for inode cache.
754 in2000= [HW,SCSI]
755 See header of drivers/scsi/in2000.c.
757 init= [KNL]
758 Format: <full_path>
759 Run specified binary instead of /sbin/init as init
760 process.
762 initcall_debug [KNL] Trace initcalls as they are executed. Useful
763 for working out where the kernel is dying during
764 startup.
766 initrd= [BOOT] Specify the location of the initial ramdisk
768 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
769 Format: <irq>
771 inttest= [IA64]
773 io7= [HW] IO7 for Marvel based alpha systems
774 See comment before marvel_specify_io7 in
775 arch/alpha/kernel/core_marvel.c.
777 ip= [IP_PNP]
778 See Documentation/nfsroot.txt.
780 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
781 See comment before ip2_setup() in
782 drivers/char/ip2/ip2base.c.
784 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
785 See header of drivers/scsi/ips.c.
787 ports= [IP_VS_FTP] IPVS ftp helper module
788 Default is 21.
789 Up to 8 (IP_VS_APP_MAX_PORTS) ports
790 may be specified.
791 Format: <port>,<port>....
793 irqfixup [HW]
794 When an interrupt is not handled search all handlers
795 for it. Intended to get systems with badly broken
796 firmware running.
798 irqpoll [HW]
799 When an interrupt is not handled search all handlers
800 for it. Also check all handlers each timer
801 interrupt. Intended to get systems with badly broken
802 firmware running.
804 isapnp= [ISAPNP]
805 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
807 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
808 Format:
809 <cpu number>,...,<cpu number>
810 or
811 <cpu number>-<cpu number> (must be a positive range in ascending order)
812 or a mixture
813 <cpu number>,...,<cpu number>-<cpu number>
814 This option can be used to specify one or more CPUs
815 to isolate from the general SMP balancing and scheduling
816 algorithms. The only way to move a process onto or off
817 an "isolated" CPU is via the CPU affinity syscalls.
818 <cpu number> begins at 0 and the maximum value is
819 "number of CPUs in system - 1".
821 This option is the preferred way to isolate CPUs. The
822 alternative -- manually setting the CPU mask of all
823 tasks in the system -- can cause problems and
824 suboptimal load balancer performance.
826 iucv= [HW,NET]
828 js= [HW,JOY] Analog joystick
829 See Documentation/input/joystick.txt.
831 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
832 specifies the amount of memory usable by the kernel
833 for non-movable allocations. The requested amount is
834 spread evenly throughout all nodes in the system. The
835 remaining memory in each node is used for Movable
836 pages. In the event, a node is too small to have both
837 kernelcore and Movable pages, kernelcore pages will
838 take priority and other nodes will have a larger number
839 of kernelcore pages. The Movable zone is used for the
840 allocation of pages that may be reclaimed or moved
841 by the page migration subsystem. This means that
842 HugeTLB pages may not be allocated from this zone.
843 Note that allocations like PTEs-from-HighMem still
844 use the HighMem zone if it exists, and the Normal
845 zone if it does not.
847 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
848 is similar to kernelcore except it specifies the
849 amount of memory used for migratable allocations.
850 If both kernelcore and movablecore is specified,
851 then kernelcore will be at *least* the specified
852 value but may be more. If movablecore on its own
853 is specified, the administrator must be careful
854 that the amount of memory usable for all allocations
855 is not too small.
857 keepinitrd [HW,ARM]
859 kstack=N [X86-32,X86-64] Print N words from the kernel stack
860 in oops dumps.
862 l2cr= [PPC]
864 lapic [X86-32,APIC] Enable the local APIC even if BIOS
865 disabled it.
867 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
868 C2 power state.
870 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
871 Format: addr:<io>,irq:<irq>
873 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
874 when set.
875 Format: <int>
877 load_ramdisk= [RAM] List of ramdisks to load from floppy
878 See Documentation/ramdisk.txt.
880 lockd.nlm_grace_period=P [NFS] Assign grace period.
881 Format: <integer>
883 lockd.nlm_tcpport=N [NFS] Assign TCP port.
884 Format: <integer>
886 lockd.nlm_timeout=T [NFS] Assign timeout value.
887 Format: <integer>
889 lockd.nlm_udpport=M [NFS] Assign UDP port.
890 Format: <integer>
892 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
893 Format: <irq>
895 loglevel= All Kernel Messages with a loglevel smaller than the
896 console loglevel will be printed to the console. It can
897 also be changed with klogd or other programs. The
898 loglevels are defined as follows:
900 0 (KERN_EMERG) system is unusable
901 1 (KERN_ALERT) action must be taken immediately
902 2 (KERN_CRIT) critical conditions
903 3 (KERN_ERR) error conditions
904 4 (KERN_WARNING) warning conditions
905 5 (KERN_NOTICE) normal but significant condition
906 6 (KERN_INFO) informational
907 7 (KERN_DEBUG) debug-level messages
909 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
910 Format: { n | nk | nM }
911 n must be a power of two. The default size
912 is set in the kernel config file.
914 logo.nologo [FB] Disables display of the built-in Linux logo.
915 This may be used to provide more screen space for
916 kernel log messages and is useful when debugging
917 kernel boot problems.
919 lp=0 [LP] Specify parallel ports to use, e.g,
920 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
921 lp=reset first parallel port). 'lp=0' disables the
922 lp=auto printer driver. 'lp=reset' (which can be
923 specified in addition to the ports) causes
924 attached printers to be reset. Using
925 lp=port1,port2,... specifies the parallel ports
926 to associate lp devices with, starting with
927 lp0. A port specification may be 'none' to skip
928 that lp device, or a parport name such as
929 'parport0'. Specifying 'lp=auto' instead of a
930 port specification list means that device IDs
931 from each port should be examined, to see if
932 an IEEE 1284-compliant printer is attached; if
933 so, the driver will manage that printer.
934 See also header of drivers/char/lp.c.
936 lpj=n [KNL]
937 Sets loops_per_jiffy to given constant, thus avoiding
938 time-consuming boot-time autodetection (up to 250 ms per
939 CPU). 0 enables autodetection (default). To determine
940 the correct value for your kernel, boot with normal
941 autodetection and see what value is printed. Note that
942 on SMP systems the preset will be applied to all CPUs,
943 which is likely to cause problems if your CPUs need
944 significantly divergent settings. An incorrect value
945 will cause delays in the kernel to be wrong, leading to
946 unpredictable I/O errors and other breakage. Although
947 unlikely, in the extreme case this might damage your
948 hardware.
950 ltpc= [NET]
951 Format: <io>,<irq>,<dma>
953 mac5380= [HW,SCSI] Format:
954 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
956 mac53c9x= [HW,SCSI] Format:
957 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
959 machvec= [IA64] Force the use of a particular machine-vector
960 (machvec) in a generic kernel.
961 Example: machvec=hpzx1_swiotlb
963 max_loop= [LOOP] Maximum number of loopback devices that can
964 be mounted
965 Format: <1-256>
967 maxcpus= [SMP] Maximum number of processors that an SMP kernel
968 should make use of. maxcpus=n : n >= 0 limits the
969 kernel to using 'n' processors. n=0 is a special case,
970 it is equivalent to "nosmp", which also disables
971 the IO APIC.
973 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
974 equal to this physical address is ignored.
976 max_luns= [SCSI] Maximum number of LUNs to probe.
977 Should be between 1 and 2^32-1.
979 max_report_luns=
980 [SCSI] Maximum number of LUNs received.
981 Should be between 1 and 16384.
983 mca-pentium [BUGS=X86-32]
985 mcatest= [IA-64]
987 mce [X86-32] Machine Check Exception
989 md= [HW] RAID subsystems devices and level
990 See Documentation/md.txt.
992 mdacon= [MDA]
993 Format: <first>,<last>
994 Specifies range of consoles to be captured by the MDA.
996 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
997 Amount of memory to be used when the kernel is not able
998 to see the whole system memory or for test.
999 [X86-32] Use together with memmap= to avoid physical
1000 address space collisions. Without memmap= PCI devices
1001 could be placed at addresses belonging to unused RAM.
1003 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1004 memory.
1006 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1007 E820 memory map, as specified by the user.
1008 Such memmap=exactmap lines can be constructed based on
1009 BIOS output or other requirements. See the memmap=nn@ss
1010 option description.
1012 memmap=nn[KMG]@ss[KMG]
1013 [KNL] Force usage of a specific region of memory
1014 Region of memory to be used, from ss to ss+nn.
1016 memmap=nn[KMG]#ss[KMG]
1017 [KNL,ACPI] Mark specific memory as ACPI data.
1018 Region of memory to be used, from ss to ss+nn.
1020 memmap=nn[KMG]$ss[KMG]
1021 [KNL,ACPI] Mark specific memory as reserved.
1022 Region of memory to be used, from ss to ss+nn.
1024 meye.*= [HW] Set MotionEye Camera parameters
1025 See Documentation/video4linux/meye.txt.
1027 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1028 Multi-Function General Purpose Timers on AMD Geode
1029 platforms.
1031 mga= [HW,DRM]
1033 mousedev.tap_time=
1034 [MOUSE] Maximum time between finger touching and
1035 leaving touchpad surface for touch to be considered
1036 a tap and be reported as a left button click (for
1037 touchpads working in absolute mode only).
1038 Format: <msecs>
1039 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1040 reporting absolute coordinates, such as tablets
1041 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1042 reporting absolute coordinates, such as tablets
1044 mpu401= [HW,OSS]
1045 Format: <io>,<irq>
1047 MTD_Partition= [MTD]
1048 Format: <name>,<region-number>,<size>,<offset>
1050 MTD_Region= [MTD] Format:
1051 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1053 mtdparts= [MTD]
1054 See drivers/mtd/cmdlinepart.c.
1056 mtouchusb.raw_coordinates=
1057 [HW] Make the MicroTouch USB driver use raw coordinates
1058 ('y', default) or cooked coordinates ('n')
1060 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1062 NCR_D700= [HW,SCSI]
1063 See header of drivers/scsi/NCR_D700.c.
1065 ncr5380= [HW,SCSI]
1067 ncr53c400= [HW,SCSI]
1069 ncr53c400a= [HW,SCSI]
1071 ncr53c406a= [HW,SCSI]
1073 ncr53c8xx= [HW,SCSI]
1075 netdev= [NET] Network devices parameters
1076 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1077 Note that mem_start is often overloaded to mean
1078 something different and driver-specific.
1079 This usage is only documented in each driver source
1080 file if at all.
1082 nfsaddrs= [NFS]
1083 See Documentation/nfsroot.txt.
1085 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1086 See Documentation/nfsroot.txt.
1088 nfs.callback_tcpport=
1089 [NFS] set the TCP port on which the NFSv4 callback
1090 channel should listen.
1092 nfs.idmap_cache_timeout=
1093 [NFS] set the maximum lifetime for idmapper cache
1094 entries.
1096 nfs.enable_ino64=
1097 [NFS] enable 64-bit inode numbers.
1098 If zero, the NFS client will fake up a 32-bit inode
1099 number for the readdir() and stat() syscalls instead
1100 of returning the full 64-bit number.
1101 The default is to return 64-bit inode numbers.
1103 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1105 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1106 emulation library even if a 387 maths coprocessor
1107 is present.
1109 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1110 caches in the slab allocator. Saves per-node memory,
1111 but will impact performance.
1113 noalign [KNL,ARM]
1115 noapic [SMP,APIC] Tells the kernel to not make use of any
1116 IOAPICs that may be present in the system.
1118 noasync [HW,M68K] Disables async and sync negotiation for
1119 all devices.
1121 nobats [PPC] Do not use BATs for mapping kernel lowmem
1122 on "Classic" PPC cores.
1124 nocache [ARM]
1126 nodelayacct [KNL] Disable per-task delay accounting
1128 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1130 noexec [IA-64]
1132 noexec [X86-32,X86-64]
1133 noexec=on: enable non-executable mappings (default)
1134 noexec=off: disable nn-executable mappings
1136 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1137 register save and restore. The kernel will only save
1138 legacy floating-point registers on task switch.
1140 nohlt [BUGS=ARM]
1142 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1143 instruction doesn't work correctly and not to
1144 use it.
1146 nohalt [IA-64] Tells the kernel not to use the power saving
1147 function PAL_HALT_LIGHT when idle. This increases
1148 power-consumption. On the positive side, it reduces
1149 interrupt wake-up latency, which may improve performance
1150 in certain environments such as networked servers or
1151 real-time systems.
1153 nohz= [KNL] Boottime enable/disable dynamic ticks
1154 Valid arguments: on, off
1155 Default: on
1157 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1159 noirqdebug [X86-32] Disables the code which attempts to detect and
1160 disable unhandled interrupt sources.
1162 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1163 broken timer IRQ sources.
1165 noisapnp [ISAPNP] Disables ISA PnP code.
1167 noinitrd [RAM] Tells the kernel not to load any configured
1168 initial RAM disk.
1170 nointroute [IA-64]
1172 nojitter [IA64] Disables jitter checking for ITC timers.
1174 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1176 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1178 noltlbs [PPC] Do not use large page/tlb entries for kernel
1179 lowmem mapping on PPC40x.
1181 nomca [IA-64] Disable machine check abort handling
1183 nomce [X86-32] Machine Check Exception
1185 nomfgpt [X86-32] Disable Multi-Function General Purpose
1186 Timer usage (for AMD Geode machines).
1188 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1190 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1191 with UP alternatives
1193 noresidual [PPC] Don't use residual data on PReP machines.
1195 noresume [SWSUSP] Disables resume and restores original swap
1196 space.
1198 no-scroll [VGA] Disables scrollback.
1199 This is required for the Braillex ib80-piezo Braille
1200 reader made by F.H. Papenmeier (Germany).
1202 nosbagart [IA-64]
1204 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1206 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1207 and disable the IO APIC. legacy for "maxcpus=0".
1209 nosoftlockup [KNL] Disable the soft-lockup detector.
1211 nosync [HW,M68K] Disables sync negotiation for all devices.
1213 notsc [BUGS=X86-32] Disable Time Stamp Counter
1215 nousb [USB] Disable the USB subsystem
1217 nowb [ARM]
1219 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1220 one of ['zone', 'node', 'default'] can be specified
1221 This can be set from sysctl after boot.
1222 See Documentation/sysctl/vm.txt for details.
1224 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1226 opl3= [HW,OSS]
1227 Format: <io>
1229 oprofile.timer= [HW]
1230 Use timer interrupt instead of performance counters
1232 osst= [HW,SCSI] SCSI Tape Driver
1233 Format: <buffer_size>,<write_threshold>
1234 See also Documentation/scsi/st.txt.
1236 panic= [KNL] Kernel behaviour on panic
1237 Format: <timeout>
1239 parkbd.port= [HW] Parallel port number the keyboard adapter is
1240 connected to, default is 0.
1241 Format: <parport#>
1242 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1243 0 for XT, 1 for AT (default is AT).
1244 Format: <mode>
1246 parport= [HW,PPT] Specify parallel ports. 0 disables.
1247 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1248 Use 'auto' to force the driver to use any
1249 IRQ/DMA settings detected (the default is to
1250 ignore detected IRQ/DMA settings because of
1251 possible conflicts). You can specify the base
1252 address, IRQ, and DMA settings; IRQ and DMA
1253 should be numbers, or 'auto' (for using detected
1254 settings on that particular port), or 'nofifo'
1255 (to avoid using a FIFO even if it is detected).
1256 Parallel ports are assigned in the order they
1257 are specified on the command line, starting
1258 with parport0.
1260 parport_init_mode= [HW,PPT]
1261 Configure VIA parallel port to operate in
1262 a specific mode. This is necessary on Pegasos
1263 computer where firmware has no options for setting
1264 up parallel port mode and sets it to spp.
1265 Currently this function knows 686a and 8231 chips.
1266 Format: [spp|ps2|epp|ecp|ecpepp]
1268 pas2= [HW,OSS] Format:
1269 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1271 pas16= [HW,SCSI]
1272 See header of drivers/scsi/pas16.c.
1274 pause_on_oops=
1275 Halt all CPUs after the first oops has been printed for
1276 the specified number of seconds. This is to be used if
1277 your oopses keep scrolling off the screen.
1279 pcbit= [HW,ISDN]
1281 pcd. [PARIDE]
1282 See header of drivers/block/paride/pcd.c.
1283 See also Documentation/paride.txt.
1285 pci=option[,option...] [PCI] various PCI subsystem options:
1286 off [X86-32] don't probe for the PCI bus
1287 bios [X86-32] force use of PCI BIOS, don't access
1288 the hardware directly. Use this if your machine
1289 has a non-standard PCI host bridge.
1290 nobios [X86-32] disallow use of PCI BIOS, only direct
1291 hardware access methods are allowed. Use this
1292 if you experience crashes upon bootup and you
1293 suspect they are caused by the BIOS.
1294 conf1 [X86-32] Force use of PCI Configuration
1295 Mechanism 1.
1296 conf2 [X86-32] Force use of PCI Configuration
1297 Mechanism 2.
1298 noaer [PCIE] If the PCIEAER kernel config parameter is
1299 enabled, this kernel boot option can be used to
1300 disable the use of PCIE advanced error reporting.
1301 nodomains [PCI] Disable support for multiple PCI
1302 root domains (aka PCI segments, in ACPI-speak).
1303 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1304 Configuration
1305 nomsi [MSI] If the PCI_MSI kernel config parameter is
1306 enabled, this kernel boot option can be used to
1307 disable the use of MSI interrupts system-wide.
1308 nosort [X86-32] Don't sort PCI devices according to
1309 order given by the PCI BIOS. This sorting is
1310 done to get a device order compatible with
1311 older kernels.
1312 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1313 routing table. These calls are known to be buggy
1314 on several machines and they hang the machine
1315 when used, but on other computers it's the only
1316 way to get the interrupt routing table. Try
1317 this option if the kernel is unable to allocate
1318 IRQs or discover secondary PCI buses on your
1319 motherboard.
1320 rom [X86-32] Assign address space to expansion ROMs.
1321 Use with caution as certain devices share
1322 address decoders between ROMs and other
1323 resources.
1324 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1325 assigned automatically to PCI devices. You can
1326 make the kernel exclude IRQs of your ISA cards
1327 this way.
1328 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1329 of the PIRQ table (normally generated
1330 by the BIOS) if it is outside the
1331 F0000h-100000h range.
1332 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1333 useful if the kernel is unable to find your
1334 secondary buses and you want to tell it
1335 explicitly which ones they are.
1336 assign-busses [X86-32] Always assign all PCI bus
1337 numbers ourselves, overriding
1338 whatever the firmware may have done.
1339 usepirqmask [X86-32] Honor the possible IRQ mask stored
1340 in the BIOS $PIR table. This is needed on
1341 some systems with broken BIOSes, notably
1342 some HP Pavilion N5400 and Omnibook XE3
1343 notebooks. This will have no effect if ACPI
1344 IRQ routing is enabled.
1345 noacpi [X86-32] Do not use ACPI for IRQ routing
1346 or for PCI scanning.
1347 use_crs [X86-32] Use _CRS for PCI resource
1348 allocation.
1349 routeirq Do IRQ routing for all PCI devices.
1350 This is normally done in pci_enable_device(),
1351 so this option is a temporary workaround
1352 for broken drivers that don't call it.
1353 firmware [ARM] Do not re-enumerate the bus but instead
1354 just use the configuration from the
1355 bootloader. This is currently used on
1356 IXP2000 systems where the bus has to be
1357 configured a certain way for adjunct CPUs.
1358 noearly [X86] Don't do any early type 1 scanning.
1359 This might help on some broken boards which
1360 machine check when some devices' config space
1361 is read. But various workarounds are disabled
1362 and some IOMMU drivers will not work.
1363 bfsort Sort PCI devices into breadth-first order.
1364 This sorting is done to get a device
1365 order compatible with older (<= 2.4) kernels.
1366 nobfsort Don't sort PCI devices into breadth-first order.
1367 cbiosize=nn[KMG] The fixed amount of bus space which is
1368 reserved for the CardBus bridge's IO window.
1369 The default value is 256 bytes.
1370 cbmemsize=nn[KMG] The fixed amount of bus space which is
1371 reserved for the CardBus bridge's memory
1372 window. The default value is 64 megabytes.
1374 pcmv= [HW,PCMCIA] BadgePAD 4
1376 pd. [PARIDE]
1377 See Documentation/paride.txt.
1379 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1380 boot time.
1381 Format: { 0 | 1 }
1382 See arch/parisc/kernel/pdc_chassis.c
1384 pf. [PARIDE]
1385 See Documentation/paride.txt.
1387 pg. [PARIDE]
1388 See Documentation/paride.txt.
1390 pirq= [SMP,APIC] Manual mp-table setup
1391 See Documentation/i386/IO-APIC.txt.
1393 plip= [PPT,NET] Parallel port network link
1394 Format: { parport<nr> | timid | 0 }
1395 See also Documentation/parport.txt.
1397 pnpacpi= [ACPI]
1398 { off }
1400 pnpbios= [ISAPNP]
1401 { on | off | curr | res | no-curr | no-res }
1403 pnp_reserve_irq=
1404 [ISAPNP] Exclude IRQs for the autoconfiguration
1406 pnp_reserve_dma=
1407 [ISAPNP] Exclude DMAs for the autoconfiguration
1409 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1410 Ranges are in pairs (I/O port base and size).
1412 pnp_reserve_mem=
1413 [ISAPNP] Exclude memory regions for the
1414 autoconfiguration.
1415 Ranges are in pairs (memory base and size).
1417 print-fatal-signals=
1418 [KNL] debug: print fatal signals
1419 print-fatal-signals=1: print segfault info to
1420 the kernel console.
1421 default: off.
1423 printk.time= Show timing data prefixed to each printk message line
1424 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1426 profile= [KNL] Enable kernel profiling via /proc/profile
1427 Format: [schedule,]<number>
1428 Param: "schedule" - profile schedule points.
1429 Param: <number> - step/bucket size as a power of 2 for
1430 statistical time based profiling.
1431 Param: "sleep" - profile D-state sleeping (millisecs)
1433 processor.max_cstate= [HW,ACPI]
1434 Limit processor to maximum C-state
1435 max_cstate=9 overrides any DMI blacklist limit.
1437 processor.nocst [HW,ACPI]
1438 Ignore the _CST method to determine C-states,
1439 instead using the legacy FADT method
1441 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1442 before loading.
1443 See Documentation/ramdisk.txt.
1445 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1446 probe for; one of (bare|imps|exps|lifebook|any).
1447 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1448 per second.
1449 psmouse.resetafter= [HW,MOUSE]
1450 Try to reset the device after so many bad packets
1451 (0 = never).
1452 psmouse.resolution=
1453 [HW,MOUSE] Set desired mouse resolution, in dpi.
1454 psmouse.smartscroll=
1455 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1456 0 = disabled, 1 = enabled (default).
1458 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1459 Format:
1460 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1462 pt. [PARIDE]
1463 See Documentation/paride.txt.
1465 pty.legacy_count=
1466 [KNL] Number of legacy pty's. Overwrites compiled-in
1467 default number.
1469 quiet [KNL] Disable most log messages
1471 r128= [HW,DRM]
1473 raid= [HW,RAID]
1474 See Documentation/md.txt.
1476 ramdisk_blocksize= [RAM]
1477 See Documentation/ramdisk.txt.
1479 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1480 See Documentation/ramdisk.txt.
1482 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1483 RCU callbacks to process in one batch.
1485 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1486 RCU callbacks over which batch limiting is disabled.
1488 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1489 RCU callbacks below which batch limiting is re-enabled.
1491 rdinit= [KNL]
1492 Format: <full_path>
1493 Run specified binary instead of /init from the ramdisk,
1494 used for early userspace startup. See initrd.
1496 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1497 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1498 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1500 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1502 reservetop= [X86-32]
1503 Format: nn[KMG]
1504 Reserves a hole at the top of the kernel virtual
1505 address space.
1507 reset_devices [KNL] Force drivers to reset the underlying device
1508 during initialization.
1510 resume= [SWSUSP]
1511 Specify the partition device for software suspend
1513 resume_offset= [SWSUSP]
1514 Specify the offset from the beginning of the partition
1515 given by "resume=" at which the swap header is located,
1516 in <PAGE_SIZE> units (needed only for swap files).
1517 See Documentation/power/swsusp-and-swap-files.txt
1519 retain_initrd [RAM] Keep initrd memory after extraction
1521 rhash_entries= [KNL,NET]
1522 Set number of hash buckets for route cache
1524 riscom8= [HW,SERIAL]
1525 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1527 ro [KNL] Mount root device read-only on boot
1529 root= [KNL] Root filesystem
1531 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1532 mount the root filesystem
1534 rootflags= [KNL] Set root filesystem mount option string
1536 rootfstype= [KNL] Set root filesystem type
1538 rootwait [KNL] Wait (indefinitely) for root device to show up.
1539 Useful for devices that are detected asynchronously
1540 (e.g. USB and MMC devices).
1542 rw [KNL] Mount root device read-write on boot
1544 S [KNL] Run init in single mode
1546 sa1100ir [NET]
1547 See drivers/net/irda/sa1100_ir.c.
1549 sb= [HW,OSS]
1550 Format: <io>,<irq>,<dma>,<dma2>
1552 sbni= [NET] Granch SBNI12 leased line adapter
1554 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1555 Format: <io>[,<timeout>[,<isapnp>]]
1557 scsi_debug_*= [SCSI]
1558 See drivers/scsi/scsi_debug.c.
1560 scsi_default_dev_flags=
1561 [SCSI] SCSI default device flags
1562 Format: <integer>
1564 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1565 Format: <vendor>:<model>:<flags>
1566 (flags are integer value)
1568 scsi_logging= [SCSI]
1570 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1571 discovered. async scans them in kernel threads,
1572 allowing boot to proceed. none ignores them, expecting
1573 user space to do the scan.
1575 selinux [SELINUX] Disable or enable SELinux at boot time.
1576 Format: { "0" | "1" }
1577 See security/selinux/Kconfig help text.
1578 0 -- disable.
1579 1 -- enable.
1580 Default value is set via kernel config option.
1581 If enabled at boot time, /selinux/disable can be used
1582 later to disable prior to initial policy load.
1584 selinux_compat_net =
1585 [SELINUX] Set initial selinux_compat_net flag value.
1586 Format: { "0" | "1" }
1587 0 -- use new secmark-based packet controls
1588 1 -- use legacy packet controls
1589 Default value is 0 (preferred).
1590 Value can be changed at runtime via
1591 /selinux/compat_net.
1593 serialnumber [BUGS=X86-32]
1595 sg_def_reserved_size= [SCSI]
1597 shapers= [NET]
1598 Maximal number of shapers.
1600 sim710= [SCSI,HW]
1601 See header of drivers/scsi/sim710.c.
1603 simeth= [IA-64]
1604 simscsi=
1606 slram= [HW,MTD]
1608 slub_debug[=options[,slabs]] [MM, SLUB]
1609 Enabling slub_debug allows one to determine the
1610 culprit if slab objects become corrupted. Enabling
1611 slub_debug can create guard zones around objects and
1612 may poison objects when not in use. Also tracks the
1613 last alloc / free. For more information see
1614 Documentation/vm/slub.txt.
1616 slub_max_order= [MM, SLUB]
1617 Determines the maximum allowed order for slabs.
1618 A high setting may cause OOMs due to memory
1619 fragmentation. For more information see
1620 Documentation/vm/slub.txt.
1622 slub_min_objects= [MM, SLUB]
1623 The minimum number of objects per slab. SLUB will
1624 increase the slab order up to slub_max_order to
1625 generate a sufficiently large slab able to contain
1626 the number of objects indicated. The higher the number
1627 of objects the smaller the overhead of tracking slabs
1628 and the less frequently locks need to be acquired.
1629 For more information see Documentation/vm/slub.txt.
1631 slub_min_order= [MM, SLUB]
1632 Determines the mininum page order for slabs. Must be
1633 lower than slub_max_order.
1634 For more information see Documentation/vm/slub.txt.
1636 slub_nomerge [MM, SLUB]
1637 Disable merging of slabs with similar size. May be
1638 necessary if there is some reason to distinguish
1639 allocs to different slabs. Debug options disable
1640 merging on their own.
1641 For more information see Documentation/vm/slub.txt.
1643 smart2= [HW]
1644 Format: <io1>[,<io2>[,...,<io8>]]
1646 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1647 attempt to substitute SMP alternatives once at boot.
1649 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1650 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1651 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1652 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1653 smsc-ircc2.ircc_irq= [HW] IRQ line
1654 smsc-ircc2.ircc_dma= [HW] DMA channel
1655 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1656 0: Toshiba Satellite 1800 (GP data pin select)
1657 1: Fast pin select (default)
1658 2: ATC IRMode
1660 snd-ad1816a= [HW,ALSA]
1662 snd-ad1848= [HW,ALSA]
1664 snd-ali5451= [HW,ALSA]
1666 snd-als100= [HW,ALSA]
1668 snd-als4000= [HW,ALSA]
1670 snd-azt2320= [HW,ALSA]
1672 snd-cmi8330= [HW,ALSA]
1674 snd-cmipci= [HW,ALSA]
1676 snd-cs4231= [HW,ALSA]
1678 snd-cs4232= [HW,ALSA]
1680 snd-cs4236= [HW,ALSA]
1682 snd-cs4281= [HW,ALSA]
1684 snd-cs46xx= [HW,ALSA]
1686 snd-dt019x= [HW,ALSA]
1688 snd-dummy= [HW,ALSA]
1690 snd-emu10k1= [HW,ALSA]
1692 snd-ens1370= [HW,ALSA]
1694 snd-ens1371= [HW,ALSA]
1696 snd-es968= [HW,ALSA]
1698 snd-es1688= [HW,ALSA]
1700 snd-es18xx= [HW,ALSA]
1702 snd-es1938= [HW,ALSA]
1704 snd-es1968= [HW,ALSA]
1706 snd-fm801= [HW,ALSA]
1708 snd-gusclassic= [HW,ALSA]
1710 snd-gusextreme= [HW,ALSA]
1712 snd-gusmax= [HW,ALSA]
1714 snd-hdsp= [HW,ALSA]
1716 snd-ice1712= [HW,ALSA]
1718 snd-intel8x0= [HW,ALSA]
1720 snd-interwave= [HW,ALSA]
1722 snd-interwave-stb=
1723 [HW,ALSA]
1725 snd-korg1212= [HW,ALSA]
1727 snd-maestro3= [HW,ALSA]
1729 snd-mpu401= [HW,ALSA]
1731 snd-mtpav= [HW,ALSA]
1733 snd-nm256= [HW,ALSA]
1735 snd-opl3sa2= [HW,ALSA]
1737 snd-opti92x-ad1848=
1738 [HW,ALSA]
1740 snd-opti92x-cs4231=
1741 [HW,ALSA]
1743 snd-opti93x= [HW,ALSA]
1745 snd-pmac= [HW,ALSA]
1747 snd-rme32= [HW,ALSA]
1749 snd-rme96= [HW,ALSA]
1751 snd-rme9652= [HW,ALSA]
1753 snd-sb8= [HW,ALSA]
1755 snd-sb16= [HW,ALSA]
1757 snd-sbawe= [HW,ALSA]
1759 snd-serial= [HW,ALSA]
1761 snd-sgalaxy= [HW,ALSA]
1763 snd-sonicvibes= [HW,ALSA]
1765 snd-sun-amd7930=
1766 [HW,ALSA]
1768 snd-sun-cs4231= [HW,ALSA]
1770 snd-trident= [HW,ALSA]
1772 snd-usb-audio= [HW,ALSA,USB]
1774 snd-via82xx= [HW,ALSA]
1776 snd-virmidi= [HW,ALSA]
1778 snd-wavefront= [HW,ALSA]
1780 snd-ymfpci= [HW,ALSA]
1782 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1783 See Documentation/sonypi.txt
1785 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1786 See Documentation/specialix.txt.
1788 spia_io_base= [HW,MTD]
1789 spia_fio_base=
1790 spia_pedr=
1791 spia_peddr=
1793 sscape= [HW,OSS]
1794 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1796 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1797 See Documentation/scsi/st.txt.
1799 st0x= [HW,SCSI]
1800 See header of drivers/scsi/seagate.c.
1802 sti= [PARISC,HW]
1803 Format: <num>
1804 Set the STI (builtin display/keyboard on the HP-PARISC
1805 machines) console (graphic card) which should be used
1806 as the initial boot-console.
1807 See also comment in drivers/video/console/sticore.c.
1809 sti_font= [HW]
1810 See comment in drivers/video/console/sticore.c.
1812 stifb= [HW]
1813 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1815 sunrpc.pool_mode=
1816 [NFS]
1817 Control how the NFS server code allocates CPUs to
1818 service thread pools. Depending on how many NICs
1819 you have and where their interrupts are bound, this
1820 option will affect which CPUs will do NFS serving.
1821 Note: this parameter cannot be changed while the
1822 NFS server is running.
1824 auto the server chooses an appropriate mode
1825 automatically using heuristics
1826 global a single global pool contains all CPUs
1827 percpu one pool for each CPU
1828 pernode one pool for each NUMA node (equivalent
1829 to global on non-NUMA machines)
1831 swiotlb= [IA-64] Number of I/O TLB slabs
1833 switches= [HW,M68k]
1835 sym53c416= [HW,SCSI]
1836 See header of drivers/scsi/sym53c416.c.
1838 sysrq_always_enabled
1839 [KNL]
1840 Ignore sysrq setting - this boot parameter will
1841 neutralize any effect of /proc/sys/kernel/sysrq.
1842 Useful for debugging.
1844 t128= [HW,SCSI]
1845 See header of drivers/scsi/t128.c.
1847 tdfx= [HW,DRM]
1849 thash_entries= [KNL,NET]
1850 Set number of hash buckets for TCP connection
1852 thermal.act= [HW,ACPI]
1853 -1: disable all active trip points in all thermal zones
1854 <degrees C>: override all lowest active trip points
1856 thermal.crt= [HW,ACPI]
1857 -1: disable all critical trip points in all thermal zones
1858 <degrees C>: lower all critical trip points
1860 thermal.nocrt= [HW,ACPI]
1861 Set to disable actions on ACPI thermal zone
1862 critical and hot trip points.
1864 thermal.off= [HW,ACPI]
1865 1: disable ACPI thermal control
1867 thermal.psv= [HW,ACPI]
1868 -1: disable all passive trip points
1869 <degrees C>: override all passive trip points to this value
1871 thermal.tzp= [HW,ACPI]
1872 Specify global default ACPI thermal zone polling rate
1873 <deci-seconds>: poll all this frequency
1874 0: no polling (default)
1876 time Show timing data prefixed to each printk message line
1877 [deprecated, see 'printk.time']
1879 tipar.timeout= [HW,PPT]
1880 Set communications timeout in tenths of a second
1881 (default 15).
1883 tipar.delay= [HW,PPT]
1884 Set inter-bit delay in microseconds (default 10).
1886 tmc8xx= [HW,SCSI]
1887 See header of drivers/scsi/seagate.c.
1889 tmscsim= [HW,SCSI]
1890 See comment before function dc390_setup() in
1891 drivers/scsi/tmscsim.c.
1893 tp720= [HW,PS2]
1895 trix= [HW,OSS] MediaTrix AudioTrix Pro
1896 Format:
1897 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1899 turbografx.map[2|3]= [HW,JOY]
1900 TurboGraFX parallel port interface
1901 Format:
1902 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1903 See also Documentation/input/joystick-parport.txt
1905 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1906 See header of drivers/scsi/u14-34f.c.
1908 uart401= [HW,OSS]
1909 Format: <io>,<irq>
1911 uart6850= [HW,OSS]
1912 Format: <io>,<irq>
1914 uhci-hcd.ignore_oc=
1915 [USB] Ignore overcurrent events (default N).
1916 Some badly-designed motherboards generate lots of
1917 bogus events, for ports that aren't wired to
1918 anything. Set this parameter to avoid log spamming.
1919 Note that genuine overcurrent events won't be
1920 reported either.
1922 usbcore.autosuspend=
1923 [USB] The autosuspend time delay (in seconds) used
1924 for newly-detected USB devices (default 2). This
1925 is the time required before an idle device will be
1926 autosuspended. Devices for which the delay is set
1927 to a negative value won't be autosuspended at all.
1929 usbhid.mousepoll=
1930 [USBHID] The interval which mice are to be polled at.
1932 vdso= [X86-32,SH,x86-64]
1933 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1934 vdso=1: enable VDSO (default)
1935 vdso=0: disable VDSO mapping
1937 vector= [IA-64,SMP]
1938 vector=percpu: enable percpu vector domain
1940 video= [FB] Frame buffer configuration
1941 See Documentation/fb/modedb.txt.
1943 vga= [BOOT,X86-32] Select a particular video mode
1944 See Documentation/i386/boot.txt and
1945 Documentation/svga.txt.
1946 Use vga=ask for menu.
1947 This is actually a boot loader parameter; the value is
1948 passed to the kernel using a special protocol.
1950 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1951 size of <nn>. This can be used to increase the
1952 minimum size (128MB on x86). It can also be used to
1953 decrease the size and leave more room for directly
1954 mapped kernel RAM.
1956 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1957 Format: <command>
1959 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1960 Format: <command>
1962 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1963 Format: <command>
1965 waveartist= [HW,OSS]
1966 Format: <io>,<irq>,<dma>,<dma2>
1968 wd33c93= [HW,SCSI]
1969 See header of drivers/scsi/wd33c93.c.
1971 wd7000= [HW,SCSI]
1972 See header of drivers/scsi/wd7000.c.
1974 wdt= [WDT] Watchdog
1975 See Documentation/watchdog/wdt.txt.
1977 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1978 xd_geo= See header of drivers/block/xd.c.
1980 xirc2ps_cs= [NET,PCMCIA]
1981 Format:
1982 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1984 norandmaps Don't use address space randomization
1985 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1987 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1988 This is useful to get more information why
1989 you got a "dwarf2 unwinder stuck"
1991 ______________________________________________________________________
1993 TODO:
1995 Add documentation for ALSA options.
1996 Add more DRM drivers.