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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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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
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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
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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
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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:
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37
38 ACPI ACPI support is enabled.
c99c108a 39 AGP AGP (Accelerated Graphics Port) is enabled.
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40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
e7ba176b 43 AVR32 AVR32 architecture is enabled.
1da177e4 44 AX25 Appropriate AX.25 support is enabled.
0ae53640 45 BLACKFIN Blackfin architecture is enabled.
a9913044 46 DRM Direct Rendering Management support is enabled.
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47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 HW Appropriate hardware is enabled.
1da177e4 52 IA-64 IA-64 architecture is enabled.
6146f0d5 53 IMA Integrity measurement architecture is enabled.
1da177e4 54 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
b9ce08c0 59 KMEMTRACE kmemtrace is enabled.
11ef697b 60 LIBATA Libata driver is enabled
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61 LP Printer support is enabled.
62 LOOP Loopback device support is enabled.
63 M68k M68k architecture is enabled.
64 These options have more detailed description inside of
65 Documentation/m68k/kernel-options.txt.
66 MCA MCA bus support is enabled.
67 MDA MDA console support is enabled.
68 MOUSE Appropriate mouse support is enabled.
309e57df 69 MSI Message Signaled Interrupts (PCI).
c8facbb6 70 MTD MTD (Memory Technology Device) support is enabled.
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71 NET Appropriate network support is enabled.
72 NUMA NUMA support is enabled.
734efb46 73 GENERIC_TIME The generic timeofday code is enabled.
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74 NFS Appropriate NFS support is enabled.
75 OSS OSS sound support is enabled.
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76 PV_OPS A paravirtualized kernel is enabled.
77 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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78 PARISC The PA-RISC architecture is enabled.
79 PCI PCI bus support is enabled.
7f785763 80 PCIE PCI Express support is enabled.
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81 PCMCIA The PCMCIA subsystem is enabled.
82 PNP Plug & Play support is enabled.
83 PPC PowerPC architecture is enabled.
84 PPT Parallel port support is enabled.
85 PS2 Appropriate PS/2 support is enabled.
86 RAM RAM disk support is enabled.
20510f2f 87 ROOTPLUG The example Root Plug LSM is enabled.
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88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
91 Documentation/scsi/.
20510f2f 92 SECURITY Different security models are enabled.
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93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
e523d93c 95 SH SuperH architecture is enabled.
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96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
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98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
f38f1d2a 100 FTRACE Function tracing enabled.
1da177e4 101 TS Appropriate touchscreen support is enabled.
d4f373e5 102 UMS USB Mass Storage support is enabled.
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103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 110 X86-32 X86-32, aka i386 architecture is enabled.
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111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
71cced6e 113 Documentation/x86/x86_64/boot-options.txt .
c0115606 114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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115
116In addition, the following text indicates that the option:
117
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
121
122Parameters denoted with BOOT are actually interpreted by the boot
123loader, and have no meaning to the kernel directly.
124Do not modify the syntax of boot loader parameters without extreme
954a8b81 125need or coordination with <Documentation/x86/boot.txt>.
1da177e4 126
5558870b 127There are also arch-specific kernel-parameters not documented here.
71cced6e 128See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 129
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130Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131a trailing = on the name of any parameter states that that parameter will
132be entered as an environment variable, whereas its absence indicates that
133it will appear as a kernel argument readable via /proc/cmdline by programs
134running once the system is up.
135
9c4751fd 136The number of kernel parameters is not limited, but the length of the
137complete command line (parameters including spaces etc.) is limited to
138a fixed number of characters. This limit depends on the architecture
139and is between 256 and 4096 characters. It is defined in the file
140./include/asm/setup.h as COMMAND_LINE_SIZE.
141
142
6cececfc 143 acpi= [HW,ACPI,X86]
03d926f8 144 Advanced Configuration and Power Interface
af23f573 145 Format: { force | off | ht | strict | noirq | rsdt }
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146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
a9913044 150 strict -- Be less tolerant of platforms that are not
1da177e4 151 strictly ACPI specification compliant.
237889bf 152 rsdt -- prefer RSDT over (default) XSDT
1da177e4 153
53471121 154 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 155
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156 acpi_apic_instance= [ACPI, IOAPIC]
157 Format: <int>
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
4e381a4f 160 default: 0
a1fdcc0d 161
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162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
164 acpi_backlight=video
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
168
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169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 171 Format: <int>
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172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
a0d84a92 182
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183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
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187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
192
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
f989106c 196
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197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
200 See above.
201
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
205
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
209
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
212
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
216
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
218
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
221
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
226
6cececfc 227 acpi_pm_good [X86]
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228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
231
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232 acpi.power_nocheck= [HW,ACPI]
233 Format: 1/0 enable/disable the check of power state.
234 On some bogus BIOS the _PSC object/_STA object of
235 power resource can't return the correct device power
236 state. In such case it is unneccessary to check its
237 power state again in power transition.
238 1 : disable the power state check
239
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240 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
241 Format: { level | edge | high | low }
242
243 acpi_serialize [HW,ACPI] force serialization of AML methods
244
245 acpi_skip_timer_override [HW,ACPI]
246 Recognize and ignore IRQ0/pin2 Interrupt Override.
247 For broken nForce2 BIOS resulting in XT-PIC timer.
248
249 acpi_sleep= [HW,ACPI] Sleep options
250 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
251 old_ordering, s4_nonvs }
252 See Documentation/power/video.txt for information on
253 s3_bios and s3_mode.
254 s3_beep is for debugging; it makes the PC's speaker beep
255 as soon as the kernel's real-mode entry point is called.
256 s4_nohwsig prevents ACPI hardware signature from being
257 used during resume from hibernation.
258 old_ordering causes the ACPI 1.0 ordering of the _PTS
259 control method, with respect to putting devices into
260 low power states, to be enforced (the ACPI 2.0 ordering
261 of _PTS is used by default).
262 s4_nonvs prevents the kernel from saving/restoring the
263 ACPI NVS memory during hibernation.
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
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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
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285 ad1848= [HW,OSS]
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
287
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288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
290
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291 advansys= [HW,SCSI]
292 See header of drivers/scsi/advansys.c.
293
294 advwdt= [HW,WDT] Advantech WDT
295 Format: <iostart>,<iostop>
296
297 aedsp16= [HW,OSS] Audio Excel DSP 16
298 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
299 See also header of sound/oss/aedsp16.c.
a9913044 300
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301 agp= [AGP]
302 { off | try_unsupported }
303 off: disable AGP support
304 try_unsupported: try to drive unsupported chipsets
305 (may crash computer or cause data corruption)
306
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307 aha152x= [HW,SCSI]
308 See Documentation/scsi/aha152x.txt.
309
310 aha1542= [HW,SCSI]
311 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
312
313 aic7xxx= [HW,SCSI]
314 See Documentation/scsi/aic7xxx.txt.
315
316 aic79xx= [HW,SCSI]
317 See Documentation/scsi/aic79xx.txt.
318
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319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
321 Possible values are:
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322 isolate - enable device isolation (each device, as far
323 as possible, will get its own protection
3ce1f93c 324 domain) [default]
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325 share - put every device behind one IOMMU into the
326 same protection domain
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327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
330 is a lot of faster
331
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332 amd_iommu_size= [HW,X86-64]
333 Define the size of the aperture for the AMD IOMMU
334 driver. Possible values are:
335 '32M', '64M' (default), '128M', '256M', '512M', '1G'
336
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337 amijoy.map= [HW,JOY] Amiga joystick support
338 Map of devices attached to JOY0DAT and JOY1DAT
339 Format: <a>,<b>
340 See also Documentation/kernel/input/joystick.txt
341
342 analog.map= [HW,JOY] Analog joystick and gamepad support
343 Specifies type or capabilities of an analog joystick
344 connected to one of 16 gameports
345 Format: <type1>,<type2>,..<type16>
346
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347 apc= [HW,SPARC]
348 Power management functions (SPARCstation-4/5 + deriv.)
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349 Format: noidle
350 Disable APC CPU standby support. SPARCstation-Fox does
351 not play well with APC CPU idle - disable it if you have
352 APC and your system crashes randomly.
353
ca1eda2d 354 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 355 Change the output verbosity whilst booting
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356 Format: { quiet (default) | verbose | debug }
357 Change the amount of debugging information output
358 when initialising the APIC and IO-APIC components.
a9913044 359
1da177e4 360 apm= [APM] Advanced Power Management
71f77055 361 See header of arch/x86/kernel/apm_32.c.
1da177e4 362
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363 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
364 Format: <io>,<irq>,<nodeID>
365
366 ataflop= [HW,M68k]
367
368 atarimouse= [HW,MOUSE] Atari Mouse
369
370 atascsi= [HW,SCSI] Atari SCSI
371
372 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
373 EzKey and similar keyboards
374
375 atkbd.reset= [HW] Reset keyboard during initialization
376
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377 atkbd.set= [HW] Select keyboard code set
378 Format: <int> (2 = AT (default), 3 = PS/2)
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379
380 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
381 keyboards
382
383 atkbd.softraw= [HW] Choose between synthetic and real raw mode
384 Format: <bool> (0 = real, 1 = synthetic (default))
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385
386 atkbd.softrepeat= [HW]
387 Use software keyboard repeat
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388
389 autotest [IA64]
390
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391 baycom_epp= [HW,AX25]
392 Format: <io>,<mode>
a9913044 393
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394 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
395 Format: <io>,<mode>
396 See header of drivers/net/hamradio/baycom_par.c.
397
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398 baycom_ser_fdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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400 Format: <io>,<irq>,<mode>[,<baud>]
401 See header of drivers/net/hamradio/baycom_ser_fdx.c.
402
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403 baycom_ser_hdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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405 Format: <io>,<irq>,<mode>
406 See header of drivers/net/hamradio/baycom_ser_hdx.c.
407
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408 boot_delay= Milliseconds to delay each printk during boot.
409 Values larger than 10 seconds (10000) are changed to
410 no delay (0).
411 Format: integer
412
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413 bootmem_debug [KNL] Enable bootmem allocator debug messages.
414
1da177e4 415 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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416 bttv.radio= Most important insmod options are available as
417 kernel args too.
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418 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
419 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
420
421 BusLogic= [HW,SCSI]
422 See drivers/scsi/BusLogic.c, comment before function
423 BusLogic_ParseDriverOptions().
424
425 c101= [NET] Moxa C101 synchronous serial card
426
cd4f0ef7 427 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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428 Sometimes CPU hardware bugs make them report the cache
429 size incorrectly. The kernel will attempt work arounds
430 to fix known problems, but for some CPUs it is not
431 possible to determine what the correct size should be.
432 This option provides an override for these situations.
433
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434 capability.disable=
435 [SECURITY] Disable capabilities. This would normally
436 be used only if an alternative security model is to be
437 configured. Potentially dangerous and should only be
438 used if you are entirely sure of the consequences.
439
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440 ccw_timeout_log [S390]
441 See Documentation/s390/CommonIO for details.
1da177e4 442
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443 cgroup_disable= [KNL] Disable a particular controller
444 Format: {name of the controller(s) to disable}
445 {Currently supported controllers - "memory"}
446
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447 checkreqprot [SELINUX] Set initial checkreqprot flag value.
448 Format: { "0" | "1" }
449 See security/selinux/Kconfig help text.
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450 0 -- check protection applied by kernel (includes
451 any implied execute protection).
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452 1 -- check protection requested by application.
453 Default value is set via a kernel config option.
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454 Value can be changed at runtime via
455 /selinux/checkreqprot.
456
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457 cio_ignore= [S390]
458 See Documentation/s390/CommonIO for details.
459
cd4f0ef7 460 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 461 [Deprecated]
3f6dee9b 462 Forces specified clocksource (if available) to be used
734efb46 463 when calculating gettimeofday(). If specified
3f6dee9b 464 clocksource is not available, it defaults to PIT.
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465 Format: { pit | tsc | cyclone | pmtmr }
466
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467 clocksource= [GENERIC_TIME] Override the default clocksource
468 Format: <string>
469 Override the default clocksource and use the clocksource
470 with the name specified.
471 Some clocksource names to choose from, depending on
472 the platform:
473 [all] jiffies (this is the base, fallback clocksource)
474 [ACPI] acpi_pm
475 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
476 pxa_timer,timer3,32k_counter,timer0_1
477 [AVR32] avr32
cd4f0ef7 478 [X86-32] pit,hpet,tsc,vmi-timer;
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479 scx200_hrt on Geode; cyclone on IBM x440
480 [MIPS] MIPS
481 [PARISC] cr16
482 [S390] tod
483 [SH] SuperH
484 [SPARC64] tick
485 [X86-64] hpet,tsc
486
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487 clearcpuid=BITNUM [X86]
488 Disable CPUID feature X for the kernel. See
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489 arch/x86/include/asm/cpufeature.h for the valid bit
490 numbers. Note the Linux specific bits are not necessarily
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491 stable over kernel options, but the vendor specific
492 ones should be.
493 Also note that user programs calling CPUID directly
494 or using the feature without checking anything
495 will still see it. This just prevents it from
496 being used by the kernel or shown in /proc/cpuinfo.
497 Also note the kernel might malfunction if you disable
498 some critical bits.
499
6cececfc 500 code_bytes [X86] How many bytes of object code to print
a25bd949 501 in an oops report.
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502 Range: 0 - 8192
503 Default: 64
504
1da177e4 505 com20020= [HW,NET] ARCnet - COM20020 chipset
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506 Format:
507 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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508
509 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 Format: <io>[,<irq>]
511
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512 com90xx= [HW,NET]
513 ARCnet - COM90xx chipset (memory-mapped buffers)
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514 Format: <io>[,<irq>[,<memstart>]]
515
516 condev= [HW,S390] console device
517 conmode=
a9913044 518
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519 console= [KNL] Output console device and options.
520
521 tty<n> Use the virtual console device <n>.
522
523 ttyS<n>[,options]
f1a1c2dc 524 ttyUSB0[,options]
1da177e4 525 Use the specified serial port. The options are of
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RD
526 the form "bbbbpnf", where "bbbb" is the baud rate,
527 "p" is parity ("n", "o", or "e"), "n" is number of
528 bits, and "f" is flow control ("r" for RTS or
529 omit it). Default is "9600n8".
530
531 See Documentation/serial-console.txt for more
532 information. See
533 Documentation/networking/netconsole.txt for an
534 alternative.
1da177e4 535
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536 uart[8250],io,<addr>[,options]
537 uart[8250],mmio,<addr>[,options]
1da177e4
LT
538 Start an early, polled-mode console on the 8250/16550
539 UART at the specified I/O port or MMIO address,
540 switching to the matching ttyS device later. The
541 options are the same as for ttyS, above.
542
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ST
543 If the device connected to the port is not a TTY but a braille
544 device, prepend "brl," before the device type, for instance
545 console=brl,ttyS0
546 For now, only VisioBraille is supported.
547
4cb0e11b
HK
548 coredump_filter=
549 [KNL] Change the default value for
550 /proc/<pid>/coredump_filter.
551 See also Documentation/filesystems/proc.txt.
552
1da177e4 553 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
554 Format:
555 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 556
dc009d92
EB
557 crashkernel=nn[KMG]@ss[KMG]
558 [KNL] Reserve a chunk of physical memory to
559 hold a kernel to switch to with kexec on panic.
560
fb391599
BW
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 a example.
567
1da177e4
LT
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
570
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
a9913044 573
a9913044 574 dasd= [HW,NET]
1da177e4
LT
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 debug [KNL] Enable kernel debugging (events log level).
583
cae2ed9a
IM
584 debug_locks_verbose=
585 [KNL] verbose self-tests
586 Format=<0|1>
587 Print debugging info while doing the locking API
588 self-tests.
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
592
3ac7fe5a
TG
593 debug_objects [KNL] Enable object debugging
594
3e8ebb5c
KM
595 no_debug_objects
596 [KNL] Disable object debugging
597
d3af01f1
TG
598 debugpat [X86] Enable PAT debugging
599
2d27a966 600 decnet.addr= [HW,NET]
1da177e4
LT
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
603
0cb55ad2
RD
604 default_hugepagesz=
605 [same as hugepagesz=] The size of the default
606 HugeTLB page size. This is the size represented by
607 the legacy /proc/ hugepages APIs, used for SHM, and
608 default size when mounting hugetlbfs filesystems.
609 Defaults to the default architecture's huge page size
610 if not specified.
55ff9780 611
1da177e4
LT
612 dhash_entries= [KNL]
613 Set number of hash buckets for dentry cache.
a9913044 614
1da177e4
LT
615 digi= [HW,SERIAL]
616 IO parameters + enable/disable command.
617
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
31c00fc1 620 Documentation/serial/digiepca.txt.
1da177e4 621
95ffa243 622 disable_mtrr_cleanup [X86]
95ffa243
YL
623 The kernel tries to adjust MTRR layout from continuous
624 to discrete, to make X server driver able to add WB
0cb55ad2 625 entry later. This parameter disables that.
95ffa243 626
093af8d7 627 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
628 By default the kernel will trim any uncacheable
629 memory out of your available memory pool based on
630 MTRR settings. This parameter disables that behavior,
631 possibly causing your machine to run very slowly.
632
6cececfc 633 disable_timer_pin_1 [X86]
0cb55ad2
RD
634 Disable PIN 1 of APIC timer
635 Can be useful to work around chipset bugs.
636
1da177e4
LT
637 dmasound= [HW,OSS] Sound subsystem buffers
638
0cb55ad2
RD
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
641
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
648
1da177e4
LT
649 dscc4.setup= [NET]
650
651 dtc3181e= [HW,SCSI]
652
0cb55ad2
RD
653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
657
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
661 Start an early, polled-mode console on the 8250/16550
662 UART at the specified I/O port or MMIO address.
663 The options are the same as for ttyS, above.
664
6cececfc 665 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
666 earlyprintk=vga
667 earlyprintk=serial[,ttySn[,baudrate]]
5c05917e 668 earlyprintk=dbgp
1da177e4 669
a9913044 670 Append ",keep" to not disable it when the real console
1da177e4
LT
671 takes over.
672
5c05917e 673 Only vga or serial or usb debug port at a time.
1da177e4
LT
674
675 Currently only ttyS0 and ttyS1 are supported.
676
677 Interaction with the standard serial driver is not
678 very good.
679
680 The VGA output is eventually overwritten by the real
681 console.
682
683 eata= [HW,SCSI]
684
1da177e4 685 edd= [EDD]
8c4dd606 686 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 687
1da177e4
LT
688 eisa_irq_edge= [PARISC,HW]
689 See header of drivers/parisc/eisa.c.
690
cd4f0ef7 691 elanfreq= [X86-32]
1da177e4 692 See comment before function elanfreq_setup() in
71f77055 693 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
694
695 elevator= [IOSCHED]
16ab3adf 696 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
697 See Documentation/block/as-iosched.txt and
698 Documentation/block/deadline-iosched.txt for details.
699
6cececfc 700 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 701 Specifies physical address of start of kernel core
aac04b32
VG
702 image elf header. Generally kexec loader will
703 pass this option to capture kernel.
704 See Documentation/kdump/kdump.txt for details.
1da177e4 705
0cb55ad2
RD
706 enable_mtrr_cleanup [X86]
707 The kernel tries to adjust MTRR layout from continuous
708 to discrete, to make X server driver able to add WB
709 entry later. This parameter enables that.
710
ca1eda2d 711 enable_timer_pin_1 [X86]
0cb55ad2
RD
712 Enable PIN 1 of APIC timer
713 Can be useful to work around chipset bugs
714 (in particular on some ATI chipsets).
715 The kernel tries to set a reasonable default.
716
1da177e4
LT
717 enforcing [SELINUX] Set initial enforcing status.
718 Format: {"0" | "1"}
719 See security/selinux/Kconfig help text.
720 0 -- permissive (log only, no denials).
721 1 -- enforcing (deny and log).
722 Default value is 0.
723 Value can be changed at runtime via /selinux/enforce.
724
1da177e4
LT
725 ether= [HW,NET] Ethernet cards parameters
726 This option is obsoleted by the "netdev=" option, which
727 has equivalent usage. See its documentation for details.
728
729 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
730 Format: <io>[,<irq>]
731
de1ba09b
AM
732 failslab=
733 fail_page_alloc=
734 fail_make_request=[KNL]
735 General fault injection mechanism.
736 Format: <interval>,<probability>,<space>,<times>
737 See also /Documentation/fault-injection/.
738
1da177e4
LT
739 fd_mcs= [HW,SCSI]
740 See header of drivers/scsi/fd_mcs.c.
741
742 fdomain= [HW,SCSI]
743 See header of drivers/scsi/fdomain.c.
744
745 floppy= [HW]
31c00fc1 746 See Documentation/blockdev/floppy.txt.
1da177e4 747
f13ae30e
AC
748 force_pal_cache_flush
749 [IA-64] Avoid check_sal_cache_flush which may hang on
750 buggy SAL_CACHE_FLUSH implementations. Using this
751 parameter will force ia64_sal_cache_flush to call
752 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
753
d9e54076
PZ
754 ftrace=[tracer]
755 [ftrace] will set and start the specified tracer
756 as early as possible in order to facilitate early
757 boot debugging.
758
759 ftrace_dump_on_oops
760 [ftrace] will dump the trace buffers on oops.
761
1da177e4
LT
762 gamecon.map[2|3]=
763 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
764 support via parallel port (up to 5 devices per port)
765 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
766 See also Documentation/input/joystick-parport.txt
767
768 gamma= [HW,DRM]
769
aaf23042
YL
770 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
771 Format: off | on
772 default: on
773
1da177e4
LT
774 gdth= [HW,SCSI]
775 See header of drivers/scsi/gdth.c.
776
777 gpt [EFI] Forces disk with valid GPT signature but
778 invalid Protective MBR to be treated as GPT.
779
1da177e4
LT
780 gvp11= [HW,SCSI]
781
782 hashdist= [KNL,NUMA] Large hashes allocated during boot
783 are distributed across NUMA nodes. Defaults on
429aa0fc 784 for 64bit NUMA, off otherwise.
a9913044 785 Format: 0 | 1 (for off | on)
1da177e4
LT
786
787 hcl= [IA-64] SGI's Hardware Graph compatibility layer
788
789 hd= [EIDE] (E)IDE hard drive subsystem geometry
790 Format: <cyl>,<head>,<sect>
791
1da177e4
LT
792 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
793 size of <nn>. This works even on boxes that have no
794 highmem otherwise. This also works to reduce highmem
795 size on bigger boxes.
796
54cdfdb4
TG
797 highres= [KNL] Enable/disable high resolution timer mode.
798 Valid parameters: "on", "off"
799 Default: "on"
800
1da177e4
LT
801 hisax= [HW,ISDN]
802 See Documentation/isdn/README.HiSax.
803
0cb55ad2
RD
804 hlt [BUGS=ARM,SH]
805
806 hpet= [X86-32,HPET] option to control HPET usage
807 Format: { enable (default) | disable | force |
808 verbose }
809 disable: disable HPET and use PIT instead
810 force: allow force enabled of undocumented chips (ICH4,
811 VIA, nVidia)
812 verbose: show contents of HPET registers during setup
813
b4718e62
AK
814 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
815 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
816 On x86-64 and powerpc, this option can be specified
817 multiple times interleaved with hugepages= to reserve
818 huge pages of different sizes. Valid pages sizes on
819 x86-64 are 2M (when the CPU supports "pse") and 1G
820 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
821 Note that 1GB pages can only be allocated at boot time
822 using hugepages= and not freed afterwards.
6902aa84 823
555d61d6
HB
824 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
825 terminal devices. Valid values: 0..8
431429ff
HB
826 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
827 If specified, z/VM IUCV HVC accepts connections
828 from listed z/VM user IDs only.
cef7125d 829
3a853fb9 830 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
831 or register an additional I2C bus that is not
832 registered from board initialization code.
3a853fb9
JN
833 Format:
834 <bus_id>,<clkrate>
835
36d95739 836 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 837 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
838 i8042.dumbkbd [HW] Pretend that controller can only read data from
839 keyboard and cannot control its state
1da177e4
LT
840 (Don't attempt to blink the leds)
841 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 842 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
843 i8042.noloop [HW] Disable the AUX Loopback command while probing
844 for the AUX port
1da177e4
LT
845 i8042.nomux [HW] Don't check presence of an active multiplexing
846 controller
847 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
848 controllers
849 i8042.panicblink=
850 [HW] Frequency with which keyboard LEDs should blink
851 when kernel panics (default is 0.5 sec)
852 i8042.reset [HW] Reset the controller during init and cleanup
853 i8042.unlock [HW] Unlock (ignore) the keylock
854
855 i810= [HW,DRM]
856
e70c9d5e
DT
857 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
858 indicates that the driver is running on unsupported
859 hardware.
1da177e4
LT
860 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
861 does not match list of supported models.
862 i8k.power_status
863 [HW] Report power status in /proc/i8k
864 (disabled by default)
865 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
866 capability is set.
867
868 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
869 See Documentation/mca.txt.
870
871 icn= [HW,ISDN]
872 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
873
0af80c04
DF
874 ide-core.nodma= [HW] (E)IDE subsystem
875 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
876 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
877 .chs .ignore_cable are additional options
1c10e938 878 See Documentation/ide/ide.txt.
1da177e4 879
1da177e4 880 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 881 See Documentation/ide/ide.txt.
1da177e4 882
0cb55ad2
RD
883 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
884 Claim all unknown PCI IDE storage controllers.
885
f039b754 886 idle= [X86]
ada9cfdd
RD
887 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
888 Poll forces a polling idle loop that can slightly
889 improve the performance of waking up a idle CPU, but
890 will use a lot of power and make the system run hot.
891 Not recommended.
892 idle=mwait: On systems which support MONITOR/MWAIT but
893 the kernel chose to not use it because it doesn't save
894 as much power as a normal idle loop, use the
895 MONITOR/MWAIT idle loop anyways. Performance should be
896 the same as idle=poll.
897 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 898 In such case C2/C3 won't be used again.
ada9cfdd 899 idle=nomwait: Disable mwait for CPU C-states
a9913044 900
79290822
IM
901 ignore_loglevel [KNL]
902 Ignore loglevel setting - this will print /all/
903 kernel messages to the console. Useful for debugging.
904
1da177e4
LT
905 ihash_entries= [KNL]
906 Set number of hash buckets for inode cache.
907
3323eec9
MZ
908 ima_audit= [IMA]
909 Format: { "0" | "1" }
910 0 -- integrity auditing messages. (Default)
911 1 -- enable informational integrity auditing messages.
912
913 ima_hash= [IMA]
914 Formt: { "sha1" | "md5" }
915 default: "sha1"
916
1da177e4
LT
917 in2000= [HW,SCSI]
918 See header of drivers/scsi/in2000.c.
919
920 init= [KNL]
921 Format: <full_path>
922 Run specified binary instead of /sbin/init as init
923 process.
924
925 initcall_debug [KNL] Trace initcalls as they are executed. Useful
926 for working out where the kernel is dying during
927 startup.
928
929 initrd= [BOOT] Specify the location of the initial ramdisk
930
931 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
932 Format: <irq>
933
ba395927 934 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
935 on
936 Enable intel iommu driver.
ba395927
KA
937 off
938 Disable intel iommu driver.
939 igfx_off [Default Off]
940 By default, gfx is mapped as normal device. If a gfx
941 device has a dedicated DMAR unit, the DMAR unit is
942 bypassed by not enabling DMAR with this option. In
943 this case, gfx device will use physical address for
944 DMA.
7d3b03ce
KA
945 forcedac [x86_64]
946 With this option iommu will not optimize to look
947 for io virtual address below 32 bit forcing dual
948 address cycle on pci bus for cards supporting greater
949 than 32 bit addressing. The default is to look
950 for translation below 32 bit and if not available
951 then look in the higher range.
5e0d2a6f 952 strict [Default Off]
953 With this option on every unmap_single operation will
954 result in a hardware IOTLB flush operation as opposed
955 to batching them for performance.
ba395927 956
0cb55ad2
RD
957 inttest= [IA64]
958
959 iomem= Disable strict checking of access to MMIO memory
960 strict regions from userspace.
961 relaxed
962
963 iommu= [x86]
964 off
965 force
966 noforce
967 biomerge
968 panic
969 nopanic
970 merge
971 nomerge
972 forcesac
973 soft
974
975 io7= [HW] IO7 for Marvel based alpha systems
976 See comment before marvel_specify_io7 in
977 arch/alpha/kernel/core_marvel.c.
978
6cececfc 979 io_delay= [X86] I/O delay method
6e7c4025
IM
980 0x80
981 Standard port 0x80 based delay
982 0xed
983 Alternate port 0xed based delay (needed on some systems)
b02aae9c 984 udelay
6e7c4025
IM
985 Simple two microseconds delay
986 none
987 No delay
b02aae9c 988
1da177e4 989 ip= [IP_PNP]
6ded55da 990 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
991
992 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
993 See comment before ip2_setup() in
994 drivers/char/ip2/ip2base.c.
1da177e4
LT
995
996 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
997 See header of drivers/scsi/ips.c.
998
200803df
AC
999 irqfixup [HW]
1000 When an interrupt is not handled search all handlers
1001 for it. Intended to get systems with badly broken
1002 firmware running.
1003
1004 irqpoll [HW]
1005 When an interrupt is not handled search all handlers
1006 for it. Also check all handlers each timer
1007 interrupt. Intended to get systems with badly broken
1008 firmware running.
1009
1da177e4 1010 isapnp= [ISAPNP]
a9913044 1011 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1012
1013 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1014 Format:
1015 <cpu number>,...,<cpu number>
1016 or
b225d44e
LZ
1017 <cpu number>-<cpu number>
1018 (must be a positive range in ascending order)
22f2e280
DF
1019 or a mixture
1020 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1021
1da177e4
LT
1022 This option can be used to specify one or more CPUs
1023 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1024 algorithms. You can move a process onto or off an
1025 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1026 <cpu number> begins at 0 and the maximum value is
1027 "number of CPUs in system - 1".
1028
1029 This option is the preferred way to isolate CPUs. The
a9913044
RD
1030 alternative -- manually setting the CPU mask of all
1031 tasks in the system -- can cause problems and
1032 suboptimal load balancer performance.
1da177e4 1033
a9913044 1034 iucv= [HW,NET]
1da177e4
LT
1035
1036 js= [HW,JOY] Analog joystick
1037 See Documentation/input/joystick.txt.
1038
0cb55ad2
RD
1039 keepinitrd [HW,ARM]
1040
6cececfc 1041 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1042 specifies the amount of memory usable by the kernel
1043 for non-movable allocations. The requested amount is
1044 spread evenly throughout all nodes in the system. The
1045 remaining memory in each node is used for Movable
1046 pages. In the event, a node is too small to have both
1047 kernelcore and Movable pages, kernelcore pages will
1048 take priority and other nodes will have a larger number
1049 of kernelcore pages. The Movable zone is used for the
1050 allocation of pages that may be reclaimed or moved
1051 by the page migration subsystem. This means that
1052 HugeTLB pages may not be allocated from this zone.
1053 Note that allocations like PTEs-from-HighMem still
1054 use the HighMem zone if it exists, and the Normal
1055 zone if it does not.
1056
b9ce08c0
EGM
1057 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1058 Controls whether kmemtrace is enabled
1059 at boot-time.
1060
1061 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1062 subbufs kmemtrace's relay channel has. Set this
1063 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1064 you experience buffer overruns.
1065
6cdf6e06
JW
1066 kgdboc= [HW] kgdb over consoles.
1067 Requires a tty driver that supports console polling.
1068 (only serial suported for now)
1069 Format: <serial_device>[,baud]
1070
9bed90c6
FF
1071 kmac= [MIPS] korina ethernet MAC address.
1072 Configure the RouterBoard 532 series on-chip
1073 Ethernet adapter MAC address.
1074
6cececfc 1075 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1076 in oops dumps.
1077
1da177e4
LT
1078 l2cr= [PPC]
1079
a78bfbfc
RB
1080 l3cr= [PPC]
1081
cd4f0ef7 1082 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1083 disabled it.
1da177e4 1084
6cececfc 1085 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1086 in C2 power state.
e585bef8 1087
fcb71f6f
FC
1088 libata.dma= [LIBATA] DMA control
1089 libata.dma=0 Disable all PATA and SATA DMA
1090 libata.dma=1 PATA and SATA Disk DMA only
1091 libata.dma=2 ATAPI (CDROM) DMA only
1092 libata.dma=4 Compact Flash DMA only
1093 Combinations also work, so libata.dma=3 enables DMA
1094 for disks and CDROMs, but not CFs.
1095
78e70c23
DJ
1096 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1097 when set.
1098 Format: <int>
1099
33267325
TH
1100 libata.force= [LIBATA] Force configurations. The format is comma
1101 separated list of "[ID:]VAL" where ID is
1102 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1103 matching port, link or device. Basically, it matches
1104 the ATA ID string printed on console by libata. If
1105 the whole ID part is omitted, the last PORT and DEVICE
1106 values are used. If ID hasn't been specified yet, the
1107 configuration applies to all ports, links and devices.
1108
1109 If only DEVICE is omitted, the parameter applies to
1110 the port and all links and devices behind it. DEVICE
1111 number of 0 either selects the first device or the
1112 first fan-out link behind PMP device. It does not
1113 select the host link. DEVICE number of 15 selects the
1114 host link and device attached to it.
1115
1116 The VAL specifies the configuration to force. As long
1117 as there's no ambiguity shortcut notation is allowed.
1118 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1119 The following configurations can be forced.
1120
1121 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1122 Any ID with matching PORT is used.
1123
1124 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1125
1126 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1127 udma[/][16,25,33,44,66,100,133] notation is also
1128 allowed.
1129
1130 * [no]ncq: Turn on or off NCQ.
1131
05944bdf
TH
1132 * nohrst, nosrst, norst: suppress hard, soft
1133 and both resets.
1134
33267325
TH
1135 If there are multiple matching configurations changing
1136 the same attribute, the last one is used.
1137
7c4be253
RD
1138 lmb=debug [KNL] Enable lmb debug messages.
1139
1da177e4 1140 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1141 See Documentation/blockdev/ramdisk.txt.
1da177e4 1142
a6b25b67
RD
1143 lockd.nlm_grace_period=P [NFS] Assign grace period.
1144 Format: <integer>
1da177e4 1145
a6b25b67
RD
1146 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1147 Format: <integer>
1148
1149 lockd.nlm_timeout=T [NFS] Assign timeout value.
1150 Format: <integer>
1151
1152 lockd.nlm_udpport=M [NFS] Assign UDP port.
1153 Format: <integer>
1da177e4
LT
1154
1155 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1156 Format: <irq>
1157
1158 loglevel= All Kernel Messages with a loglevel smaller than the
1159 console loglevel will be printed to the console. It can
1160 also be changed with klogd or other programs. The
1161 loglevels are defined as follows:
1162
1163 0 (KERN_EMERG) system is unusable
1164 1 (KERN_ALERT) action must be taken immediately
1165 2 (KERN_CRIT) critical conditions
1166 3 (KERN_ERR) error conditions
1167 4 (KERN_WARNING) warning conditions
1168 5 (KERN_NOTICE) normal but significant condition
1169 6 (KERN_INFO) informational
1170 7 (KERN_DEBUG) debug-level messages
1171
1172 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1173 Format: { n | nk | nM }
1174 n must be a power of two. The default size
1175 is set in the kernel config file.
1da177e4 1176
accaa24c
RD
1177 logo.nologo [FB] Disables display of the built-in Linux logo.
1178 This may be used to provide more screen space for
1179 kernel log messages and is useful when debugging
1180 kernel boot problems.
1181
1da177e4
LT
1182 lp=0 [LP] Specify parallel ports to use, e.g,
1183 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1184 lp=reset first parallel port). 'lp=0' disables the
1185 lp=auto printer driver. 'lp=reset' (which can be
1186 specified in addition to the ports) causes
1187 attached printers to be reset. Using
1188 lp=port1,port2,... specifies the parallel ports
1189 to associate lp devices with, starting with
1190 lp0. A port specification may be 'none' to skip
1191 that lp device, or a parport name such as
1192 'parport0'. Specifying 'lp=auto' instead of a
1193 port specification list means that device IDs
1194 from each port should be examined, to see if
1195 an IEEE 1284-compliant printer is attached; if
1196 so, the driver will manage that printer.
1197 See also header of drivers/char/lp.c.
1198
1199 lpj=n [KNL]
1200 Sets loops_per_jiffy to given constant, thus avoiding
1201 time-consuming boot-time autodetection (up to 250 ms per
1202 CPU). 0 enables autodetection (default). To determine
1203 the correct value for your kernel, boot with normal
1204 autodetection and see what value is printed. Note that
1205 on SMP systems the preset will be applied to all CPUs,
1206 which is likely to cause problems if your CPUs need
1207 significantly divergent settings. An incorrect value
1208 will cause delays in the kernel to be wrong, leading to
1209 unpredictable I/O errors and other breakage. Although
1210 unlikely, in the extreme case this might damage your
1211 hardware.
1212
1213 ltpc= [NET]
1214 Format: <io>,<irq>,<dma>
1215
a9913044
RD
1216 mac5380= [HW,SCSI] Format:
1217 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1218
a9913044
RD
1219 machvec= [IA64] Force the use of a particular machine-vector
1220 (machvec) in a generic kernel.
1221 Example: machvec=hpzx1_swiotlb
1da177e4 1222
0cb55ad2
RD
1223 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1224 than or equal to this physical address is ignored.
1da177e4
LT
1225
1226 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1227 should make use of. maxcpus=n : n >= 0 limits the
1228 kernel to using 'n' processors. n=0 is a special case,
1229 it is equivalent to "nosmp", which also disables
1230 the IO APIC.
1da177e4 1231
0cb55ad2
RD
1232 max_loop= [LOOP] Maximum number of loopback devices that can
1233 be mounted
1234 Format: <1-256>
2b2c3750 1235
a9913044 1236 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1237 Should be between 1 and 2^32-1.
1238
1239 max_report_luns=
a9913044 1240 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1241 Should be between 1 and 16384.
1242
1da177e4
LT
1243 mcatest= [IA-64]
1244
cd4f0ef7 1245 mce [X86-32] Machine Check Exception
1da177e4 1246
71cced6e 1247 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1248
1da177e4
LT
1249 md= [HW] RAID subsystems devices and level
1250 See Documentation/md.txt.
a9913044 1251
1da177e4
LT
1252 mdacon= [MDA]
1253 Format: <first>,<last>
1254 Specifies range of consoles to be captured by the MDA.
a9913044 1255
1da177e4
LT
1256 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1257 Amount of memory to be used when the kernel is not able
1258 to see the whole system memory or for test.
cd4f0ef7 1259 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1260 address space collisions. Without memmap= PCI devices
1261 could be placed at addresses belonging to unused RAM.
1262
cd4f0ef7 1263 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1264 memory.
1265
6902aa84
PM
1266 memchunk=nn[KMG]
1267 [KNL,SH] Allow user to override the default size for
1268 per-device physically contiguous DMA buffers.
1269
6cececfc 1270 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1271 E820 memory map, as specified by the user.
1272 Such memmap=exactmap lines can be constructed based on
1273 BIOS output or other requirements. See the memmap=nn@ss
1274 option description.
1275
1276 memmap=nn[KMG]@ss[KMG]
1277 [KNL] Force usage of a specific region of memory
1278 Region of memory to be used, from ss to ss+nn.
1279
1280 memmap=nn[KMG]#ss[KMG]
1281 [KNL,ACPI] Mark specific memory as ACPI data.
1282 Region of memory to be used, from ss to ss+nn.
1283
1284 memmap=nn[KMG]$ss[KMG]
1285 [KNL,ACPI] Mark specific memory as reserved.
1286 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1287 Example: Exclude memory from 0x18690000-0x1869ffff
1288 memmap=64K$0x18690000
1289 or
1290 memmap=0x10000$0x18690000
1da177e4 1291
9f077871
JF
1292 memory_corruption_check=0/1 [X86]
1293 Some BIOSes seem to corrupt the first 64k of
1294 memory when doing things like suspend/resume.
1295 Setting this option will scan the memory
1296 looking for corruption. Enabling this will
1297 both detect corruption and prevent the kernel
1298 from using the memory being corrupted.
1299 However, its intended as a diagnostic tool; if
1300 repeatable BIOS-originated corruption always
1301 affects the same memory, you can use memmap=
1302 to prevent the kernel from using that memory.
1303
1304 memory_corruption_check_size=size [X86]
1305 By default it checks for corruption in the low
1306 64k, making this memory unavailable for normal
1307 use. Use this parameter to scan for
1308 corruption in more or less memory.
1309
1310 memory_corruption_check_period=seconds [X86]
1311 By default it checks for corruption every 60
1312 seconds. Use this parameter to check at some
1313 other rate. 0 disables periodic checking.
1314
caadbdce 1315 memtest= [KNL,X86] Enable memtest
c64df707 1316 Format: <integer>
c64df707 1317 default : 0 <disable>
9e5f6cf5
AH
1318 Specifies the number of memtest passes to be
1319 performed. Each pass selects another test
1320 pattern from a given set of patterns. Memtest
1321 fills the memory with this pattern, validates
1322 memory contents and reserves bad memory
1323 regions that are detected.
c64df707 1324
1da177e4
LT
1325 meye.*= [HW] Set MotionEye Camera parameters
1326 See Documentation/video4linux/meye.txt.
1327
8f36881b
AS
1328 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1329 Multi-Function General Purpose Timers on AMD Geode
1330 platforms.
1331
e6c4dc6c
WT
1332 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1333 the BIOS has incorrectly applied a workaround. TinyBIOS
1334 version 0.98 is known to be affected, 0.99 fixes the
1335 problem by letting the user disable the workaround.
1336
1da177e4
LT
1337 mga= [HW,DRM]
1338
1c207f95
RD
1339 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1340 physical address is ignored.
1341
6b74ab97
MG
1342 mminit_loglevel=
1343 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1344 parameter allows control of the logging verbosity for
1345 the additional memory initialisation checks. A value
1346 of 0 disables mminit logging and a level of 4 will
1347 log everything. Information is printed at KERN_DEBUG
1348 so loglevel=8 may also need to be specified.
1349
1da177e4
LT
1350 mousedev.tap_time=
1351 [MOUSE] Maximum time between finger touching and
1352 leaving touchpad surface for touch to be considered
1353 a tap and be reported as a left button click (for
1354 touchpads working in absolute mode only).
1355 Format: <msecs>
1356 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1357 reporting absolute coordinates, such as tablets
1358 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1359 reporting absolute coordinates, such as tablets
1360
6cececfc 1361 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1362 is similar to kernelcore except it specifies the
1363 amount of memory used for migratable allocations.
1364 If both kernelcore and movablecore is specified,
1365 then kernelcore will be at *least* the specified
1366 value but may be more. If movablecore on its own
1367 is specified, the administrator must be careful
1368 that the amount of memory usable for all allocations
1369 is not too small.
1370
1da177e4
LT
1371 mpu401= [HW,OSS]
1372 Format: <io>,<irq>
1373
1374 MTD_Partition= [MTD]
1375 Format: <name>,<region-number>,<size>,<offset>
1376
a9913044
RD
1377 MTD_Region= [MTD] Format:
1378 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1379
1380 mtdparts= [MTD]
c8facbb6 1381 See drivers/mtd/cmdlinepart.c.
1da177e4 1382
9db829f4
BD
1383 mtdset= [ARM]
1384 ARM/S3C2412 JIVE boot control
1385
1386 See arch/arm/mach-s3c2412/mach-jive.c
1387
1da177e4 1388 mtouchusb.raw_coordinates=
a9913044
RD
1389 [HW] Make the MicroTouch USB driver use raw coordinates
1390 ('y', default) or cooked coordinates ('n')
1da177e4 1391
0cb55ad2
RD
1392 mtrr_chunk_size=nn[KMG] [X86]
1393 used for mtrr cleanup. It is largest continous chunk
1394 that could hold holes aka. UC entries.
1395
1396 mtrr_gran_size=nn[KMG] [X86]
1397 Used for mtrr cleanup. It is granularity of mtrr block.
1398 Default is 1.
1399 Large value could prevent small alignment from
1400 using up MTRRs.
1401
1402 mtrr_spare_reg_nr=n [X86]
1403 Format: <integer>
1404 Range: 0,7 : spare reg number
1405 Default : 1
1406 Used for mtrr cleanup. It is spare mtrr entries number.
1407 Set to 2 or more if your graphical card needs more.
1408
1da177e4
LT
1409 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1410
1411 NCR_D700= [HW,SCSI]
1412 See header of drivers/scsi/NCR_D700.c.
1413
1414 ncr5380= [HW,SCSI]
1415
1416 ncr53c400= [HW,SCSI]
1417
1418 ncr53c400a= [HW,SCSI]
1419
1420 ncr53c406a= [HW,SCSI]
1421
1422 ncr53c8xx= [HW,SCSI]
1423
1424 netdev= [NET] Network devices parameters
1425 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1426 Note that mem_start is often overloaded to mean
1427 something different and driver-specific.
a9913044
RD
1428 This usage is only documented in each driver source
1429 file if at all.
1430
58401572
KPO
1431 nf_conntrack.acct=
1432 [NETFILTER] Enable connection tracking flow accounting
1433 0 to disable accounting
1434 1 to enable accounting
1435 Default value depends on CONFIG_NF_CT_ACCT that is
1436 going to be removed in 2.6.29.
1437
1da177e4 1438 nfsaddrs= [NFS]
6ded55da 1439 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1440
1441 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1442 See Documentation/filesystems/nfsroot.txt.
1da177e4 1443
a72b4422
TM
1444 nfs.callback_tcpport=
1445 [NFS] set the TCP port on which the NFSv4 callback
1446 channel should listen.
1447
58df095b
TM
1448 nfs.idmap_cache_timeout=
1449 [NFS] set the maximum lifetime for idmapper cache
1450 entries.
1451
f43bf0be
TM
1452 nfs.enable_ino64=
1453 [NFS] enable 64-bit inode numbers.
1454 If zero, the NFS client will fake up a 32-bit inode
1455 number for the readdir() and stat() syscalls instead
1456 of returning the full 64-bit number.
1457 The default is to return 64-bit inode numbers.
1458
e7ba176b
HS
1459 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1460 when a NMI is triggered.
1461 Format: [state][,regs][,debounce][,die]
1462
6cececfc 1463 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1464 Format: [panic,][num]
1465 Valid num: 0,1,2
1466 0 - turn nmi_watchdog off
1467 1 - use the IO-APIC timer for the NMI watchdog
1468 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1469 a performance counter. Note: This will use one
1470 performance counter and the local APIC's performance
1471 vector.
1472 When panic is specified, panic when an NMI watchdog
1473 timeout occurs.
1474 This is useful when you use a panic=... timeout and
1475 need the box quickly up again.
5b9a0e14
CG
1476 Instead of 1 and 2 it is possible to use the following
1477 symbolic names: lapic and ioapic
1478 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1479
cd4f0ef7 1480 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1481 emulation library even if a 387 maths coprocessor
1482 is present.
1483
0cb55ad2
RD
1484 no_console_suspend
1485 [HW] Never suspend the console
1486 Disable suspending of consoles during suspend and
1487 hibernate operations. Once disabled, debugging
1488 messages can reach various consoles while the rest
1489 of the system is being put to sleep (ie, while
1490 debugging driver suspend/resume hooks). This may
1491 not work reliably with all consoles, but is known
1492 to work with serial and VGA consoles.
1493
c1aee215
CL
1494 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1495 caches in the slab allocator. Saves per-node memory,
1496 but will impact performance.
3395ee05 1497
a9913044
RD
1498 noalign [KNL,ARM]
1499
1da177e4
LT
1500 noapic [SMP,APIC] Tells the kernel to not make use of any
1501 IOAPICs that may be present in the system.
1502
1da177e4
LT
1503 nobats [PPC] Do not use BATs for mapping kernel lowmem
1504 on "Classic" PPC cores.
1505
1506 nocache [ARM]
a9913044 1507
0cb55ad2
RD
1508 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1509
163ecdff
SN
1510 nodelayacct [KNL] Disable per-task delay accounting
1511
1da177e4
LT
1512 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1513
6902aa84
PM
1514 nodsp [SH] Disable hardware DSP at boot time.
1515
6cececfc 1516 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1517
1da177e4
LT
1518 noexec [IA-64]
1519
6cececfc 1520 noexec [X86]
f5a1b191 1521 On X86-32 available only on PAE configured kernels.
1da177e4 1522 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1523 noexec=off: disable non-executable mappings
1524
1525 noexec32 [X86-64]
1526 This affects only 32-bit executables.
1527 noexec32=on: enable non-executable mappings (default)
1528 read doesn't imply executable mappings
1529 noexec32=off: disable non-executable mappings
1530 read implies executable mappings
1da177e4 1531
6902aa84
PM
1532 nofpu [SH] Disable hardware FPU at boot time.
1533
cd4f0ef7 1534 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1535 register save and restore. The kernel will only save
1536 legacy floating-point registers on task switch.
1da177e4 1537
0c752a93
SS
1538 noxsave [BUGS=X86] Disables x86 extended register state save
1539 and restore using xsave. The kernel will fallback to
1540 enabling legacy floating-point and sse state.
1541
01a24d2b
PZ
1542 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1543 wfi(ARM) instruction doesn't work correctly and not to
1544 use it. This is also useful when using JTAG debugger.
a9913044 1545
cd4f0ef7 1546 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1547 instruction doesn't work correctly and not to
1548 use it.
1549
1f29fae2
SH
1550 no_file_caps Tells the kernel not to honor file capabilities. The
1551 only way then for a file to be executed with privilege
1552 is to be setuid root or executed by root.
1553
1da177e4
LT
1554 nohalt [IA-64] Tells the kernel not to use the power saving
1555 function PAL_HALT_LIGHT when idle. This increases
1556 power-consumption. On the positive side, it reduces
1557 interrupt wake-up latency, which may improve performance
1558 in certain environments such as networked servers or
1559 real-time systems.
1560
79bf2bb3
TG
1561 nohz= [KNL] Boottime enable/disable dynamic ticks
1562 Valid arguments: on, off
1563 Default: on
1564
eeee7853
PM
1565 noiotrap [SH] Disables trapped I/O port accesses.
1566
cd4f0ef7 1567 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1568 disable unhandled interrupt sources.
1569
6cececfc 1570 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1571 broken timer IRQ sources.
1572
1da177e4
LT
1573 noisapnp [ISAPNP] Disables ISA PnP code.
1574
1575 noinitrd [RAM] Tells the kernel not to load any configured
1576 initial RAM disk.
1577
1578 nointroute [IA-64]
1579
0aa366f3
TL
1580 nojitter [IA64] Disables jitter checking for ITC timers.
1581
cd4f0ef7 1582 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1583
cd4f0ef7 1584 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1585
1da177e4
LT
1586 noltlbs [PPC] Do not use large page/tlb entries for kernel
1587 lowmem mapping on PPC40x.
1588
312f1f01
H
1589 nomca [IA-64] Disable machine check abort handling
1590
cd4f0ef7 1591 nomce [X86-32] Machine Check Exception
abe37e5a 1592
83d7384f
AS
1593 nomfgpt [X86-32] Disable Multi-Function General Purpose
1594 Timer usage (for AMD Geode machines).
1595
0cb55ad2
RD
1596 norandmaps Don't use address space randomization. Equivalent to
1597 echo 0 > /proc/sys/kernel/randomize_va_space
1598
cd4f0ef7 1599 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1600
cd4f0ef7 1601 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1602 with UP alternatives
1603
1da177e4
LT
1604 noresidual [PPC] Don't use residual data on PReP machines.
1605
a9913044
RD
1606 noresume [SWSUSP] Disables resume and restores original swap
1607 space.
1608
1da177e4
LT
1609 no-scroll [VGA] Disables scrollback.
1610 This is required for the Braillex ib80-piezo Braille
1611 reader made by F.H. Papenmeier (Germany).
1612
1613 nosbagart [IA-64]
1614
cd4f0ef7 1615 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1616
61ec7567
LB
1617 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1618 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1619
97842216
DJ
1620 nosoftlockup [KNL] Disable the soft-lockup detector.
1621
c077719b 1622 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1623 controller. (See Documentation/cgroups/memory.txt)
c077719b 1624
1da177e4
LT
1625 nosync [HW,M68K] Disables sync negotiation for all devices.
1626
cd4f0ef7 1627 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1628
1629 nousb [USB] Disable the USB subsystem
1630
1631 nowb [ARM]
a9913044 1632
8b5b94e4
WH
1633 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1634
a6c75b86
FY
1635 nptcg= [IA64] Override max number of concurrent global TLB
1636 purges which is reported from either PAL_VM_SUMMARY or
1637 SAL PALO.
1638
0cb55ad2
RD
1639 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1640
f0c0b2b8
KH
1641 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1642 one of ['zone', 'node', 'default'] can be specified
1643 This can be set from sysctl after boot.
1644 See Documentation/sysctl/vm.txt for details.
1645
7c4be253
RD
1646 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1647 See Documentation/debugging-via-ohci1394.txt for more
1648 info.
1649
3ef0e1f8
AS
1650 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1651 Rather than timing out after 20 ms if an EC
1652 command is not properly ACKed, override the length
1653 of the timeout. We have interrupts disabled while
1654 waiting for the ACK, so if this is set too high
1655 interrupts *may* be lost!
1656
1da177e4
LT
1657 opl3= [HW,OSS]
1658 Format: <io>
1659
1da177e4
LT
1660 oprofile.timer= [HW]
1661 Use timer interrupt instead of performance counters
1662
1da177e4
LT
1663 osst= [HW,SCSI] SCSI Tape Driver
1664 Format: <buffer_size>,<write_threshold>
1665 See also Documentation/scsi/st.txt.
1666
1667 panic= [KNL] Kernel behaviour on panic
1668 Format: <timeout>
1669
1670 parkbd.port= [HW] Parallel port number the keyboard adapter is
1671 connected to, default is 0.
1672 Format: <parport#>
1673 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1674 0 for XT, 1 for AT (default is AT).
a9913044
RD
1675 Format: <mode>
1676
1677 parport= [HW,PPT] Specify parallel ports. 0 disables.
1678 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1679 Use 'auto' to force the driver to use any
1680 IRQ/DMA settings detected (the default is to
1681 ignore detected IRQ/DMA settings because of
1682 possible conflicts). You can specify the base
1683 address, IRQ, and DMA settings; IRQ and DMA
1684 should be numbers, or 'auto' (for using detected
1685 settings on that particular port), or 'nofifo'
1686 (to avoid using a FIFO even if it is detected).
1687 Parallel ports are assigned in the order they
1688 are specified on the command line, starting
1689 with parport0.
1690
1691 parport_init_mode= [HW,PPT]
1692 Configure VIA parallel port to operate in
1693 a specific mode. This is necessary on Pegasos
1694 computer where firmware has no options for setting
1695 up parallel port mode and sets it to spp.
1696 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1697 Format: [spp|ps2|epp|ecp|ecpepp]
1698
a9913044
RD
1699 pas2= [HW,OSS] Format:
1700 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1701
1da177e4
LT
1702 pas16= [HW,SCSI]
1703 See header of drivers/scsi/pas16.c.
1704
dd287796
AM
1705 pause_on_oops=
1706 Halt all CPUs after the first oops has been printed for
1707 the specified number of seconds. This is to be used if
1708 your oopses keep scrolling off the screen.
1709
1da177e4
LT
1710 pcbit= [HW,ISDN]
1711
1712 pcd. [PARIDE]
1713 See header of drivers/block/paride/pcd.c.
31c00fc1 1714 See also Documentation/blockdev/paride.txt.
1da177e4 1715
a9913044 1716 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1717 earlydump [X86] dump PCI config space before the kernel
1718 changes anything
c0115606 1719 off [X86] don't probe for the PCI bus
cd4f0ef7 1720 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1721 the hardware directly. Use this if your machine
1722 has a non-standard PCI host bridge.
cd4f0ef7 1723 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1724 hardware access methods are allowed. Use this
1725 if you experience crashes upon bootup and you
1726 suspect they are caused by the BIOS.
c0115606 1727 conf1 [X86] Force use of PCI Configuration
a9913044 1728 Mechanism 1.
c0115606 1729 conf2 [X86] Force use of PCI Configuration
a9913044 1730 Mechanism 2.
7f785763
RD
1731 noaer [PCIE] If the PCIEAER kernel config parameter is
1732 enabled, this kernel boot option can be used to
1733 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1734 nodomains [PCI] Disable support for multiple PCI
1735 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1736 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1737 Configuration
309e57df
MW
1738 nomsi [MSI] If the PCI_MSI kernel config parameter is
1739 enabled, this kernel boot option can be used to
1740 disable the use of MSI interrupts system-wide.
a9322f64
SA
1741 noioapicquirk [APIC] Disable all boot interrupt quirks.
1742 Safety option to keep boot IRQs enabled. This
1743 should never be necessary.
9197979b
SA
1744 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1745 primary IO-APIC for bridges that cannot disable
1746 boot IRQs. This fixes a source of spurious IRQs
1747 when the system masks IRQs.
41b9eb26
SA
1748 noioapicreroute [APIC] Disable workaround that uses the
1749 boot IRQ equivalent of an IRQ that connects to
1750 a chipset where boot IRQs cannot be disabled.
1751 The opposite of ioapicreroute.
cd4f0ef7 1752 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1753 routing table. These calls are known to be buggy
1754 on several machines and they hang the machine
1755 when used, but on other computers it's the only
1756 way to get the interrupt routing table. Try
1757 this option if the kernel is unable to allocate
1758 IRQs or discover secondary PCI buses on your
1759 motherboard.
c0115606 1760 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1761 Use with caution as certain devices share
1762 address decoders between ROMs and other
1763 resources.
c0115606 1764 norom [X86] Do not assign address space to
bb71ad88
GH
1765 expansion ROMs that do not already have
1766 BIOS assigned address ranges.
c0115606 1767 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1768 assigned automatically to PCI devices. You can
1769 make the kernel exclude IRQs of your ISA cards
1770 this way.
c0115606 1771 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1772 of the PIRQ table (normally generated
1773 by the BIOS) if it is outside the
1774 F0000h-100000h range.
c0115606 1775 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1776 useful if the kernel is unable to find your
1777 secondary buses and you want to tell it
1778 explicitly which ones they are.
c0115606 1779 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1780 numbers ourselves, overriding
1781 whatever the firmware may have done.
c0115606 1782 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1783 in the BIOS $PIR table. This is needed on
1784 some systems with broken BIOSes, notably
1785 some HP Pavilion N5400 and Omnibook XE3
1786 notebooks. This will have no effect if ACPI
1787 IRQ routing is enabled.
c0115606 1788 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1789 or for PCI scanning.
9e9f46c4 1790 nocrs [X86] Don't use _CRS for PCI resource
62f420f8 1791 allocation.
a9913044
RD
1792 routeirq Do IRQ routing for all PCI devices.
1793 This is normally done in pci_enable_device(),
1794 so this option is a temporary workaround
1795 for broken drivers that don't call it.
13a6ddb0
YL
1796 skip_isa_align [X86] do not align io start addr, so can
1797 handle more pci cards
a9913044
RD
1798 firmware [ARM] Do not re-enumerate the bus but instead
1799 just use the configuration from the
1800 bootloader. This is currently used on
1801 IXP2000 systems where the bus has to be
1802 configured a certain way for adjunct CPUs.
0637a70a
AK
1803 noearly [X86] Don't do any early type 1 scanning.
1804 This might help on some broken boards which
1805 machine check when some devices' config space
1806 is read. But various workarounds are disabled
1807 and some IOMMU drivers will not work.
6b4b78fe
MD
1808 bfsort Sort PCI devices into breadth-first order.
1809 This sorting is done to get a device
1810 order compatible with older (<= 2.4) kernels.
1811 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1812 cbiosize=nn[KMG] The fixed amount of bus space which is
1813 reserved for the CardBus bridge's IO window.
1814 The default value is 256 bytes.
1815 cbmemsize=nn[KMG] The fixed amount of bus space which is
1816 reserved for the CardBus bridge's memory
1817 window. The default value is 64 megabytes.
32a9a682
YS
1818 resource_alignment=
1819 Format:
1820 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1821 Specifies alignment and device to reassign
1822 aligned memory resources.
1823 If <order of align> is not specified,
1824 PAGE_SIZE is used as alignment.
1825 PCI-PCI bridge can be specified, if resource
1826 windows need to be expanded.
6b4b78fe 1827
e5665a45
CE
1828 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1829 Management.
1830 off Disable ASPM.
1831 force Enable ASPM even on devices that claim not to support it.
1832 WARNING: Forcing ASPM on may cause system lockups.
1833
1da177e4
LT
1834 pcmv= [HW,PCMCIA] BadgePAD 4
1835
1836 pd. [PARIDE]
31c00fc1 1837 See Documentation/blockdev/paride.txt.
1da177e4
LT
1838
1839 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1840 boot time.
1841 Format: { 0 | 1 }
1842 See arch/parisc/kernel/pdc_chassis.c
1843
1844 pf. [PARIDE]
31c00fc1 1845 See Documentation/blockdev/paride.txt.
1da177e4
LT
1846
1847 pg. [PARIDE]
31c00fc1 1848 See Documentation/blockdev/paride.txt.
1da177e4
LT
1849
1850 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 1851 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
1852
1853 plip= [PPT,NET] Parallel port network link
1854 Format: { parport<nr> | timid | 0 }
1855 See also Documentation/parport.txt.
1856
de32a243
TG
1857 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1858 Override pmtimer IOPort with a hex value.
1859 e.g. pmtmr=0x508
1860
97ef062b
BH
1861 pnp.debug [PNP]
1862 Enable PNP debug messages. This depends on the
1863 CONFIG_PNP_DEBUG_MESSAGES option.
1864
1da177e4
LT
1865 pnpacpi= [ACPI]
1866 { off }
1867
1868 pnpbios= [ISAPNP]
1869 { on | off | curr | res | no-curr | no-res }
1870
1871 pnp_reserve_irq=
1872 [ISAPNP] Exclude IRQs for the autoconfiguration
1873
1874 pnp_reserve_dma=
1875 [ISAPNP] Exclude DMAs for the autoconfiguration
1876
1877 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1878 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1879
1880 pnp_reserve_mem=
a9913044
RD
1881 [ISAPNP] Exclude memory regions for the
1882 autoconfiguration.
1da177e4
LT
1883 Ranges are in pairs (memory base and size).
1884
4af94f39
RD
1885 ports= [IP_VS_FTP] IPVS ftp helper module
1886 Default is 21.
1887 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1888 may be specified.
1889 Format: <port>,<port>....
1890
45807a1d
IM
1891 print-fatal-signals=
1892 [KNL] debug: print fatal signals
1893 print-fatal-signals=1: print segfault info to
1894 the kernel console.
1895 default: off.
1896
e84845c4
RD
1897 printk.time= Show timing data prefixed to each printk message line
1898 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1899
0cb55ad2
RD
1900 processor.max_cstate= [HW,ACPI]
1901 Limit processor to maximum C-state
1902 max_cstate=9 overrides any DMI blacklist limit.
1903
1904 processor.nocst [HW,ACPI]
1905 Ignore the _CST method to determine C-states,
1906 instead using the legacy FADT method
1907
1da177e4 1908 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1909 Format: [schedule,]<number>
1910 Param: "schedule" - profile schedule points.
1911 Param: <number> - step/bucket size as a power of 2 for
1912 statistical time based profiling.
b3da2a73
MG
1913 Param: "sleep" - profile D-state sleeping (millisecs).
1914 Requires CONFIG_SCHEDSTATS
c0fe2e69 1915 Param: "kvm" - profile VM exits.
1da177e4 1916
1da177e4
LT
1917 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1918 before loading.
31c00fc1 1919 See Documentation/blockdev/ramdisk.txt.
1da177e4 1920
a9913044
RD
1921 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1922 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1923 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1924 per second.
a9913044
RD
1925 psmouse.resetafter= [HW,MOUSE]
1926 Try to reset the device after so many bad packets
1da177e4
LT
1927 (0 = never).
1928 psmouse.resolution=
1929 [HW,MOUSE] Set desired mouse resolution, in dpi.
1930 psmouse.smartscroll=
a9913044 1931 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1932 0 = disabled, 1 = enabled (default).
1933
1934 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1935 Format:
1936 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1937
1938 pt. [PARIDE]
31c00fc1 1939 See Documentation/blockdev/paride.txt.
1da177e4 1940
dc8c8587
KS
1941 pty.legacy_count=
1942 [KNL] Number of legacy pty's. Overwrites compiled-in
1943 default number.
1944
7d2c502f 1945 quiet [KNL] Disable most log messages
a9913044 1946
1da177e4
LT
1947 r128= [HW,DRM]
1948
1949 raid= [HW,RAID]
1950 See Documentation/md.txt.
1951
a9913044 1952 ramdisk_blocksize= [RAM]
31c00fc1 1953 See Documentation/blockdev/ramdisk.txt.
a9913044 1954
1da177e4 1955 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 1956 See Documentation/blockdev/ramdisk.txt.
1da177e4 1957
24aaef8d
RD
1958 rcupdate.blimit= [KNL,BOOT]
1959 Set maximum number of finished RCU callbacks to process
1960 in one batch.
21a1ea9e 1961
24aaef8d
RD
1962 rcupdate.qhimark= [KNL,BOOT]
1963 Set threshold of queued
21a1ea9e
DS
1964 RCU callbacks over which batch limiting is disabled.
1965
24aaef8d
RD
1966 rcupdate.qlowmark= [KNL,BOOT]
1967 Set threshold of queued RCU callbacks below which
1968 batch limiting is re-enabled.
21a1ea9e 1969
ffdfc409
OJ
1970 rdinit= [KNL]
1971 Format: <full_path>
1972 Run specified binary instead of /init from the ramdisk,
1973 used for early userspace startup. See initrd.
1974
cd4f0ef7 1975 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1976 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 1977 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1978
46b6d94e
PJ
1979 relax_domain_level=
1980 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 1981 See Documentation/cgroups/cpusets.txt.
46b6d94e 1982
1da177e4
LT
1983 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1984
cd4f0ef7 1985 reservetop= [X86-32]
461a9aff
ZA
1986 Format: nn[KMG]
1987 Reserves a hole at the top of the kernel virtual
1988 address space.
1989
7e96287d
VG
1990 reset_devices [KNL] Force drivers to reset the underlying device
1991 during initialization.
1992
a9913044
RD
1993 resume= [SWSUSP]
1994 Specify the partition device for software suspend
1da177e4 1995
ecbd0da1
RW
1996 resume_offset= [SWSUSP]
1997 Specify the offset from the beginning of the partition
1998 given by "resume=" at which the swap header is located,
1999 in <PAGE_SIZE> units (needed only for swap files).
2000 See Documentation/power/swsusp-and-swap-files.txt
2001
0a7b35cb
MN
2002 retain_initrd [RAM] Keep initrd memory after extraction
2003
1da177e4
LT
2004 rhash_entries= [KNL,NET]
2005 Set number of hash buckets for route cache
2006
2007 riscom8= [HW,SERIAL]
2008 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2009
2010 ro [KNL] Mount root device read-only on boot
2011
2012 root= [KNL] Root filesystem
2013
2014 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2015 mount the root filesystem
2016
2017 rootflags= [KNL] Set root filesystem mount option string
2018
2019 rootfstype= [KNL] Set root filesystem type
2020
cc1ed754
PO
2021 rootwait [KNL] Wait (indefinitely) for root device to show up.
2022 Useful for devices that are detected asynchronously
2023 (e.g. USB and MMC devices).
2024
20510f2f
JM
2025 root_plug.vendor_id=
2026 [ROOTPLUG] Override the default vendor ID
2027
2028 root_plug.product_id=
2029 [ROOTPLUG] Override the default product ID
2030
2031 root_plug.debug=
2032 [ROOTPLUG] Enable debugging output
2033
1da177e4
LT
2034 rw [KNL] Mount root device read-write on boot
2035
2036 S [KNL] Run init in single mode
2037
2038 sa1100ir [NET]
2039 See drivers/net/irda/sa1100_ir.c.
2040
1da177e4 2041 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2042
1da177e4
LT
2043 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2044 Format: <io>[,<timeout>[,<isapnp>]]
2045
2046 scsi_debug_*= [SCSI]
2047 See drivers/scsi/scsi_debug.c.
2048
2049 scsi_default_dev_flags=
2050 [SCSI] SCSI default device flags
2051 Format: <integer>
2052
2053 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2054 Format: <vendor>:<model>:<flags>
2055 (flags are integer value)
2056
6af6632a
RD
2057 scsi_logging_level= [SCSI] a bit mask of logging levels
2058 See drivers/scsi/scsi_logging.h for bits. Also
2059 settable via sysctl at dev.scsi.logging_level
2060 (/proc/sys/dev/scsi/logging_level).
2061 There is also a nice 'scsi_logging_level' script in the
2062 S390-tools package, available for download at
2063 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 2064
3e082a91
MW
2065 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2066 discovered. async scans them in kernel threads,
2067 allowing boot to proceed. none ignores them, expecting
2068 user space to do the scan.
2069
0cb55ad2
RD
2070 security= [SECURITY] Choose a security module to enable at boot.
2071 If this boot parameter is not specified, only the first
2072 security module asking for security registration will be
2073 loaded. An invalid security module name will be treated
2074 as if no module has been chosen.
2075
2076 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2077 Format: { "0" | "1" }
2078 See security/selinux/Kconfig help text.
2079 0 -- disable.
2080 1 -- enable.
2081 Default value is set via kernel config option.
2082 If enabled at boot time, /selinux/disable can be used
2083 later to disable prior to initial policy load.
2084
cd4f0ef7 2085 serialnumber [BUGS=X86-32]
1da177e4 2086
1da177e4
LT
2087 shapers= [NET]
2088 Maximal number of shapers.
a9913044 2089
b05f78f5
YL
2090 show_msr= [x86] show boot-time MSR settings
2091 Format: { <integer> }
2092 Show boot-time (BIOS-initialized) MSR settings.
2093 The parameter means the number of CPUs to show,
2094 for example 1 means boot CPU only.
2095
1da177e4
LT
2096 sim710= [SCSI,HW]
2097 See header of drivers/scsi/sim710.c.
2098
2099 simeth= [IA-64]
2100 simscsi=
a9913044 2101
1da177e4
LT
2102 slram= [HW,MTD]
2103
f0630fff
CL
2104 slub_debug[=options[,slabs]] [MM, SLUB]
2105 Enabling slub_debug allows one to determine the
2106 culprit if slab objects become corrupted. Enabling
2107 slub_debug can create guard zones around objects and
2108 may poison objects when not in use. Also tracks the
2109 last alloc / free. For more information see
2110 Documentation/vm/slub.txt.
c1aee215
CL
2111
2112 slub_max_order= [MM, SLUB]
f0630fff
CL
2113 Determines the maximum allowed order for slabs.
2114 A high setting may cause OOMs due to memory
2115 fragmentation. For more information see
2116 Documentation/vm/slub.txt.
c1aee215
CL
2117
2118 slub_min_objects= [MM, SLUB]
f0630fff
CL
2119 The minimum number of objects per slab. SLUB will
2120 increase the slab order up to slub_max_order to
2121 generate a sufficiently large slab able to contain
2122 the number of objects indicated. The higher the number
2123 of objects the smaller the overhead of tracking slabs
2124 and the less frequently locks need to be acquired.
c1aee215
CL
2125 For more information see Documentation/vm/slub.txt.
2126
2127 slub_min_order= [MM, SLUB]
2128 Determines the mininum page order for slabs. Must be
f0630fff 2129 lower than slub_max_order.
c1aee215
CL
2130 For more information see Documentation/vm/slub.txt.
2131
2132 slub_nomerge [MM, SLUB]
f0630fff 2133 Disable merging of slabs with similar size. May be
c1aee215 2134 necessary if there is some reason to distinguish
f0630fff
CL
2135 allocs to different slabs. Debug options disable
2136 merging on their own.
c1aee215
CL
2137 For more information see Documentation/vm/slub.txt.
2138
1da177e4
LT
2139 smart2= [HW]
2140 Format: <io1>[,<io2>[,...,<io8>]]
2141
cd4f0ef7 2142 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2143 attempt to substitute SMP alternatives once at boot.
2144
d0d4f69b
BH
2145 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2146 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2147 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2148 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2149 smsc-ircc2.ircc_irq= [HW] IRQ line
2150 smsc-ircc2.ircc_dma= [HW] DMA channel
2151 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2152 0: Toshiba Satellite 1800 (GP data pin select)
2153 1: Fast pin select (default)
2154 2: ATC IRMode
2155
1da177e4
LT
2156 snd-ad1816a= [HW,ALSA]
2157
2158 snd-ad1848= [HW,ALSA]
2159
2160 snd-ali5451= [HW,ALSA]
2161
2162 snd-als100= [HW,ALSA]
2163
2164 snd-als4000= [HW,ALSA]
2165
2166 snd-azt2320= [HW,ALSA]
2167
2168 snd-cmi8330= [HW,ALSA]
2169
2170 snd-cmipci= [HW,ALSA]
2171
2172 snd-cs4231= [HW,ALSA]
2173
2174 snd-cs4232= [HW,ALSA]
2175
2176 snd-cs4236= [HW,ALSA]
2177
2178 snd-cs4281= [HW,ALSA]
2179
2180 snd-cs46xx= [HW,ALSA]
2181
2182 snd-dt019x= [HW,ALSA]
2183
2184 snd-dummy= [HW,ALSA]
2185
2186 snd-emu10k1= [HW,ALSA]
2187
2188 snd-ens1370= [HW,ALSA]
2189
2190 snd-ens1371= [HW,ALSA]
2191
2192 snd-es968= [HW,ALSA]
2193
2194 snd-es1688= [HW,ALSA]
2195
2196 snd-es18xx= [HW,ALSA]
2197
2198 snd-es1938= [HW,ALSA]
2199
2200 snd-es1968= [HW,ALSA]
2201
2202 snd-fm801= [HW,ALSA]
2203
2204 snd-gusclassic= [HW,ALSA]
2205
2206 snd-gusextreme= [HW,ALSA]
2207
2208 snd-gusmax= [HW,ALSA]
2209
2210 snd-hdsp= [HW,ALSA]
2211
2212 snd-ice1712= [HW,ALSA]
2213
2214 snd-intel8x0= [HW,ALSA]
2215
2216 snd-interwave= [HW,ALSA]
2217
2218 snd-interwave-stb=
2219 [HW,ALSA]
2220
2221 snd-korg1212= [HW,ALSA]
2222
2223 snd-maestro3= [HW,ALSA]
2224
2225 snd-mpu401= [HW,ALSA]
2226
2227 snd-mtpav= [HW,ALSA]
2228
2229 snd-nm256= [HW,ALSA]
2230
2231 snd-opl3sa2= [HW,ALSA]
2232
2233 snd-opti92x-ad1848=
2234 [HW,ALSA]
2235
2236 snd-opti92x-cs4231=
2237 [HW,ALSA]
2238
2239 snd-opti93x= [HW,ALSA]
2240
2241 snd-pmac= [HW,ALSA]
2242
2243 snd-rme32= [HW,ALSA]
2244
2245 snd-rme96= [HW,ALSA]
2246
2247 snd-rme9652= [HW,ALSA]
2248
2249 snd-sb8= [HW,ALSA]
2250
2251 snd-sb16= [HW,ALSA]
2252
2253 snd-sbawe= [HW,ALSA]
2254
2255 snd-serial= [HW,ALSA]
2256
2257 snd-sgalaxy= [HW,ALSA]
2258
2259 snd-sonicvibes= [HW,ALSA]
2260
2261 snd-sun-amd7930=
2262 [HW,ALSA]
2263
2264 snd-sun-cs4231= [HW,ALSA]
2265
2266 snd-trident= [HW,ALSA]
2267
2268 snd-usb-audio= [HW,ALSA,USB]
2269
2270 snd-via82xx= [HW,ALSA]
2271
2272 snd-virmidi= [HW,ALSA]
2273
2274 snd-wavefront= [HW,ALSA]
2275
2276 snd-ymfpci= [HW,ALSA]
a9913044 2277
9c44bc03
IM
2278 softlockup_panic=
2279 [KNL] Should the soft-lockup detector generate panics.
2280
1da177e4
LT
2281 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2282 See Documentation/sonypi.txt
2283
2284 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2285 See Documentation/serial/specialix.txt.
1da177e4
LT
2286
2287 spia_io_base= [HW,MTD]
2288 spia_fio_base=
2289 spia_pedr=
2290 spia_peddr=
2291
2292 sscape= [HW,OSS]
2293 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2294
1da177e4
LT
2295 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2296 See Documentation/scsi/st.txt.
2297
f38f1d2a
SR
2298 stacktrace [FTRACE]
2299 Enabled the stack tracer on boot up.
2300
1da177e4
LT
2301 sti= [PARISC,HW]
2302 Format: <num>
2303 Set the STI (builtin display/keyboard on the HP-PARISC
2304 machines) console (graphic card) which should be used
2305 as the initial boot-console.
2306 See also comment in drivers/video/console/sticore.c.
2307
2308 sti_font= [HW]
2309 See comment in drivers/video/console/sticore.c.
2310
2311 stifb= [HW]
2312 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2313
42a7fc4a
GB
2314 sunrpc.pool_mode=
2315 [NFS]
2316 Control how the NFS server code allocates CPUs to
2317 service thread pools. Depending on how many NICs
2318 you have and where their interrupts are bound, this
2319 option will affect which CPUs will do NFS serving.
2320 Note: this parameter cannot be changed while the
2321 NFS server is running.
2322
2323 auto the server chooses an appropriate mode
2324 automatically using heuristics
2325 global a single global pool contains all CPUs
2326 percpu one pool for each CPU
2327 pernode one pool for each NUMA node (equivalent
2328 to global on non-NUMA machines)
2329
1da177e4 2330 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2331
1da177e4
LT
2332 switches= [HW,M68k]
2333
2334 sym53c416= [HW,SCSI]
2335 See header of drivers/scsi/sym53c416.c.
2336
5d6f647f
IM
2337 sysrq_always_enabled
2338 [KNL]
2339 Ignore sysrq setting - this boot parameter will
2340 neutralize any effect of /proc/sys/kernel/sysrq.
2341 Useful for debugging.
2342
1da177e4
LT
2343 t128= [HW,SCSI]
2344 See header of drivers/scsi/t128.c.
2345
2346 tdfx= [HW,DRM]
2347
77437fd4
DB
2348 test_suspend= [SUSPEND]
2349 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2350 standby suspend) as the system sleep state to briefly
2351 enter during system startup. The system is woken from
2352 this state using a wakeup-capable RTC alarm.
2353
1da177e4
LT
2354 thash_entries= [KNL,NET]
2355 Set number of hash buckets for TCP connection
2356
f8707ec9
LB
2357 thermal.act= [HW,ACPI]
2358 -1: disable all active trip points in all thermal zones
2359 <degrees C>: override all lowest active trip points
2360
c52a7419
LB
2361 thermal.crt= [HW,ACPI]
2362 -1: disable all critical trip points in all thermal zones
22a94d79 2363 <degrees C>: override all critical trip points
c52a7419 2364
f5487145
LB
2365 thermal.nocrt= [HW,ACPI]
2366 Set to disable actions on ACPI thermal zone
2367 critical and hot trip points.
2368
72b33ef8
LB
2369 thermal.off= [HW,ACPI]
2370 1: disable ACPI thermal control
2371
a70cdc52
LB
2372 thermal.psv= [HW,ACPI]
2373 -1: disable all passive trip points
ada9cfdd
RD
2374 <degrees C>: override all passive trip points to this
2375 value
a70cdc52 2376
730ff34d
LB
2377 thermal.tzp= [HW,ACPI]
2378 Specify global default ACPI thermal zone polling rate
2379 <deci-seconds>: poll all this frequency
2380 0: no polling (default)
2381
1da177e4
LT
2382 tmscsim= [HW,SCSI]
2383 See comment before function dc390_setup() in
2384 drivers/scsi/tmscsim.c.
2385
2b1a61f0
HC
2386 topology= [S390]
2387 Format: {off | on}
2388 Specify if the kernel should make use of the cpu
2389 topology informations if the hardware supports these.
2390 The scheduler will make use of these informations and
2391 e.g. base its process migration decisions on it.
2392 Default is off.
2393
1da177e4
LT
2394 tp720= [HW,PS2]
2395
631595fb
KM
2396 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2397
1da177e4 2398 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2399 Format:
2400 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2401
395628ef
AK
2402 tsc= Disable clocksource-must-verify flag for TSC.
2403 Format: <string>
2404 [x86] reliable: mark tsc clocksource as reliable, this
2405 disables clocksource verification at runtime.
2406 Used to enable high-resolution timer mode on older
2407 hardware, and in virtualized environment.
2408
a9913044
RD
2409 turbografx.map[2|3]= [HW,JOY]
2410 TurboGraFX parallel port interface
2411 Format:
2412 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2413 See also Documentation/input/joystick-parport.txt
2414
2415 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2416 See header of drivers/scsi/u14-34f.c.
2417
2418 uart401= [HW,OSS]
2419 Format: <io>,<irq>
2420
2421 uart6850= [HW,OSS]
2422 Format: <io>,<irq>
2423
5f8364b7
AS
2424 uhci-hcd.ignore_oc=
2425 [USB] Ignore overcurrent events (default N).
2426 Some badly-designed motherboards generate lots of
2427 bogus events, for ports that aren't wired to
2428 anything. Set this parameter to avoid log spamming.
2429 Note that genuine overcurrent events won't be
2430 reported either.
2431
e3a61b0a 2432 unknown_nmi_panic
6cececfc 2433 [X86]
e3a61b0a
SA
2434 Set unknown_nmi_panic=1 early on boot.
2435
b5e795f8
AS
2436 usbcore.autosuspend=
2437 [USB] The autosuspend time delay (in seconds) used
2438 for newly-detected USB devices (default 2). This
2439 is the time required before an idle device will be
2440 autosuspended. Devices for which the delay is set
eaafbc3a 2441 to a negative value won't be autosuspended at all.
b5e795f8 2442
fd7c519d
JK
2443 usbcore.usbfs_snoop=
2444 [USB] Set to log all usbfs traffic (default 0 = off).
2445
2446 usbcore.blinkenlights=
2447 [USB] Set to cycle leds on hubs (default 0 = off).
2448
2449 usbcore.old_scheme_first=
2450 [USB] Start with the old device initialization
2451 scheme (default 0 = off).
2452
2453 usbcore.use_both_schemes=
2454 [USB] Try the other device initialization scheme
2455 if the first one fails (default 1 = enabled).
2456
2457 usbcore.initial_descriptor_timeout=
2458 [USB] Specifies timeout for the initial 64-byte
2459 USB_REQ_GET_DESCRIPTOR request in milliseconds
2460 (default 5000 = 5.0 seconds).
2461
1da177e4
LT
2462 usbhid.mousepoll=
2463 [USBHID] The interval which mice are to be polled at.
a9913044 2464
d4f373e5
AS
2465 usb-storage.delay_use=
2466 [UMS] The delay in seconds before a new device is
2467 scanned for Logical Units (default 5).
2468
2469 usb-storage.quirks=
2470 [UMS] A list of quirks entries to supplement or
2471 override the built-in unusual_devs list. List
2472 entries are separated by commas. Each entry has
2473 the form VID:PID:Flags where VID and PID are Vendor
2474 and Product ID values (4-digit hex numbers) and
2475 Flags is a set of characters, each corresponding
2476 to a common usb-storage quirk flag as follows:
c838ea46
AS
2477 a = SANE_SENSE (collect more than 18 bytes
2478 of sense data);
d4f373e5
AS
2479 c = FIX_CAPACITY (decrease the reported
2480 device capacity by one sector);
c838ea46
AS
2481 h = CAPACITY_HEURISTICS (decrease the
2482 reported device capacity by one
2483 sector if the number is odd);
d4f373e5
AS
2484 i = IGNORE_DEVICE (don't bind to this
2485 device);
2486 l = NOT_LOCKABLE (don't try to lock and
2487 unlock ejectable media);
2488 m = MAX_SECTORS_64 (don't transfer more
2489 than 64 sectors = 32 KB at a time);
c838ea46
AS
2490 o = CAPACITY_OK (accept the capacity
2491 reported by the device);
d4f373e5
AS
2492 r = IGNORE_RESIDUE (the device reports
2493 bogus residue values);
2494 s = SINGLE_LUN (the device has only one
2495 Logical Unit);
2496 w = NO_WP_DETECT (don't test whether the
2497 medium is write-protected).
2498 Example: quirks=0419:aaf5:rl,0421:0433:rc
2499
6cececfc 2500 vdso= [X86,SH]
1dbf527c 2501 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2502 vdso=1: enable VDSO (default)
2503 vdso=0: disable VDSO mapping
2504
6cececfc 2505 vdso32= [X86]
af65d648
RM
2506 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2507 vdso32=1: enable 32-bit VDSO (default)
2508 vdso32=0: disable 32-bit VDSO mapping
2509
d080d397
YI
2510 vector= [IA-64,SMP]
2511 vector=percpu: enable percpu vector domain
2512
1da177e4
LT
2513 video= [FB] Frame buffer configuration
2514 See Documentation/fb/modedb.txt.
2515
cd4f0ef7 2516 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2517 See Documentation/x86/boot.txt and
a9913044 2518 Documentation/svga.txt.
1da177e4
LT
2519 Use vga=ask for menu.
2520 This is actually a boot loader parameter; the value is
2521 passed to the kernel using a special protocol.
2522
a9913044 2523 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2524 size of <nn>. This can be used to increase the
2525 minimum size (128MB on x86). It can also be used to
2526 decrease the size and leave more room for directly
2527 mapped kernel RAM.
2528
585c3047
PO
2529 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2530 Format: <command>
1da177e4 2531
585c3047
PO
2532 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2533 Format: <command>
2534
2535 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2536 Format: <command>
a9913044 2537
0cb55ad2
RD
2538 vt.default_blu= [VT]
2539 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2540 Change the default blue palette of the console.
2541 This is a 16-member array composed of values
2542 ranging from 0-255.
2543
2544 vt.default_grn= [VT]
2545 Format: <green0>,<green1>,<green2>,...,<green15>
2546 Change the default green palette of the console.
2547 This is a 16-member array composed of values
2548 ranging from 0-255.
2549
2550 vt.default_red= [VT]
2551 Format: <red0>,<red1>,<red2>,...,<red15>
2552 Change the default red palette of the console.
2553 This is a 16-member array composed of values
2554 ranging from 0-255.
2555
2556 vt.default_utf8=
2557 [VT]
2558 Format=<0|1>
2559 Set system-wide default UTF-8 mode for all tty's.
2560 Default is 1, i.e. UTF-8 mode is enabled for all
2561 newly opened terminals.
2562
1da177e4
LT
2563 waveartist= [HW,OSS]
2564 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2565
1da177e4
LT
2566 wd33c93= [HW,SCSI]
2567 See header of drivers/scsi/wd33c93.c.
2568
2569 wd7000= [HW,SCSI]
2570 See header of drivers/scsi/wd7000.c.
2571
2572 wdt= [WDT] Watchdog
8dfe9c21 2573 See Documentation/watchdog/wdt.txt.
1da177e4 2574
0cb55ad2
RD
2575 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2576 default x2apic cluster mode on platforms
2577 supporting x2apic.
2578
1da177e4
LT
2579 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2580 xd_geo= See header of drivers/block/xd.c.
2581
2582 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2583 Format:
2584 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2585
a9913044 2586______________________________________________________________________
1da177e4
LT
2587
2588TODO:
2589
2590 Add documentation for ALSA options.
2591 Add more DRM drivers.