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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.
2521f2c2 51 GCOV GCOV profiling is enabled.
1da177e4 52 HW Appropriate hardware is enabled.
1da177e4 53 IA-64 IA-64 architecture is enabled.
6146f0d5 54 IMA Integrity measurement architecture is enabled.
1da177e4 55 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 57 IPV6 IPv6 support is enabled.
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58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
84c08fd6 61 KGDB Kernel debugger support is enabled.
fef07aae 62 KVM Kernel Virtual Machine support is enabled.
11ef697b 63 LIBATA Libata driver is enabled
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64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
309e57df 72 MSI Message Signaled Interrupts (PCI).
c8facbb6 73 MTD MTD (Memory Technology Device) support is enabled.
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74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
734efb46 76 GENERIC_TIME The generic timeofday code is enabled.
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77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
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79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
7f785763 83 PCIE PCI Express support is enabled.
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84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
93 Documentation/scsi/.
20510f2f 94 SECURITY Different security models are enabled.
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95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
e523d93c 97 SH SuperH architecture is enabled.
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98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
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100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
f38f1d2a 102 FTRACE Function tracing enabled.
225a9be2 103 TPM TPM drivers are enabled.
1da177e4 104 TS Appropriate touchscreen support is enabled.
d4f373e5 105 UMS USB Mass Storage support is enabled.
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106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 113 X86-32 X86-32, aka i386 architecture is enabled.
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114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
71cced6e 116 Documentation/x86/x86_64/boot-options.txt .
c0115606 117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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118
119In addition, the following text indicates that the option:
120
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
124
125Parameters denoted with BOOT are actually interpreted by the boot
126loader, and have no meaning to the kernel directly.
127Do not modify the syntax of boot loader parameters without extreme
954a8b81 128need or coordination with <Documentation/x86/boot.txt>.
1da177e4 129
5558870b 130There are also arch-specific kernel-parameters not documented here.
71cced6e 131See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 132
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133Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134a trailing = on the name of any parameter states that that parameter will
135be entered as an environment variable, whereas its absence indicates that
136it will appear as a kernel argument readable via /proc/cmdline by programs
137running once the system is up.
138
9c4751fd 139The number of kernel parameters is not limited, but the length of the
140complete command line (parameters including spaces etc.) is limited to
141a fixed number of characters. This limit depends on the architecture
142and is between 256 and 4096 characters. It is defined in the file
143./include/asm/setup.h as COMMAND_LINE_SIZE.
144
145
6cececfc 146 acpi= [HW,ACPI,X86]
03d926f8 147 Advanced Configuration and Power Interface
68ca4069 148 Format: { force | off | strict | noirq | rsdt }
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149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
a9913044 152 strict -- Be less tolerant of platforms that are not
1da177e4 153 strictly ACPI specification compliant.
237889bf 154 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 155 copy_dsdt -- copy DSDT to memory
1da177e4 156
53471121 157 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 158
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159 acpi_apic_instance= [ACPI, IOAPIC]
160 Format: <int>
161 2: use 2nd APIC table, if available
162 1,0: use 1st APIC table
4e381a4f 163 default: 0
a1fdcc0d 164
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165 acpi_backlight= [HW,ACPI]
166 acpi_backlight=vendor
167 acpi_backlight=video
168 If set to vendor, prefer vendor specific driver
169 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
170 of the ACPI video.ko driver.
171
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172 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
173 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 174 Format: <int>
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175 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
176 debug output. Bits in debug_layer correspond to a
177 _COMPONENT in an ACPI source file, e.g.,
178 #define _COMPONENT ACPI_PCI_COMPONENT
179 Bits in debug_level correspond to a level in
180 ACPI_DEBUG_PRINT statements, e.g.,
181 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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182 The debug_level mask defaults to "info". See
183 Documentation/acpi/debug.txt for more information about
184 debug layers and levels.
a0d84a92 185
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186 Enable processor driver info messages:
187 acpi.debug_layer=0x20000000
188 Enable PCI/PCI interrupt routing info messages:
189 acpi.debug_layer=0x400000
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190 Enable AML "Debug" output, i.e., stores to the Debug
191 object while interpreting AML:
192 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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193 Enable all messages related to ACPI hardware:
194 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
195
196 Some values produce so much output that the system is
197 unusable. The "log_buf_len" parameter may be useful
198 if you need to capture more output.
f989106c 199
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200 acpi_display_output= [HW,ACPI]
201 acpi_display_output=vendor
202 acpi_display_output=video
203 See above.
204
205 acpi_irq_balance [HW,ACPI]
206 ACPI will balance active IRQs
207 default in APIC mode
208
209 acpi_irq_nobalance [HW,ACPI]
210 ACPI will not move active IRQs (default)
211 default in PIC mode
212
213 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
214 Format: <irq>,<irq>...
215
216 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
217 use by PCI
218 Format: <irq>,<irq>...
219
220 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
221
222 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
223 Format: To spoof as Windows 98: ="Microsoft Windows"
224
225 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
226 acpi_osi="string1" # add string1 -- only one string
227 acpi_osi="!string2" # remove built-in string2
228 acpi_osi= # disable all strings
229
6cececfc 230 acpi_pm_good [X86]
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231 Override the pmtimer bug detection: force the kernel
232 to assume that this machine's pmtimer latches its value
233 and always returns good values.
234
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235 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge | high | low }
237
238 acpi_serialize [HW,ACPI] force serialization of AML methods
239
240 acpi_skip_timer_override [HW,ACPI]
241 Recognize and ignore IRQ0/pin2 Interrupt Override.
242 For broken nForce2 BIOS resulting in XT-PIC timer.
243
244 acpi_sleep= [HW,ACPI] Sleep options
245 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
d7f0eea9 246 old_ordering, s4_nonvs, sci_force_enable }
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247 See Documentation/power/video.txt for information on
248 s3_bios and s3_mode.
249 s3_beep is for debugging; it makes the PC's speaker beep
250 as soon as the kernel's real-mode entry point is called.
251 s4_nohwsig prevents ACPI hardware signature from being
252 used during resume from hibernation.
253 old_ordering causes the ACPI 1.0 ordering of the _PTS
254 control method, with respect to putting devices into
255 low power states, to be enforced (the ACPI 2.0 ordering
256 of _PTS is used by default).
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257 nonvs prevents the kernel from saving/restoring the
258 ACPI NVS memory during suspend/hibernation and resume.
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259 sci_force_enable causes the kernel to set SCI_EN directly
260 on resume from S1/S3 (which is against the ACPI spec,
261 but some broken systems don't work without it).
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262
263 acpi_use_timer_override [HW,ACPI]
264 Use timer override. For some broken Nvidia NF5 boards
265 that require a timer override, but don't have HPET
266
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267 acpi_enforce_resources= [ACPI]
268 { strict | lax | no }
269 Check for resource conflicts between native drivers
270 and ACPI OperationRegions (SystemIO and SystemMemory
271 only). IO ports and memory declared in ACPI might be
272 used by the ACPI subsystem in arbitrary AML code and
273 can interfere with legacy drivers.
274 strict (default): access to resources claimed by ACPI
275 is denied; legacy drivers trying to access reserved
276 resources will fail to bind to device using them.
277 lax: access to resources claimed by ACPI is allowed;
278 legacy drivers trying to access reserved resources
279 will bind successfully but a warning message is logged.
280 no: ACPI OperationRegions are not marked as reserved,
281 no further checks are performed.
282
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283 ad1848= [HW,OSS]
284 Format: <io>,<irq>,<dma>,<dma2>,<type>
285
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286 add_efi_memmap [EFI; X86] Include EFI memory map in
287 kernel's map of available physical RAM.
288
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289 advansys= [HW,SCSI]
290 See header of drivers/scsi/advansys.c.
291
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292 aedsp16= [HW,OSS] Audio Excel DSP 16
293 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
294 See also header of sound/oss/aedsp16.c.
a9913044 295
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296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
301
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302 aha152x= [HW,SCSI]
303 See Documentation/scsi/aha152x.txt.
304
305 aha1542= [HW,SCSI]
306 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
307
308 aic7xxx= [HW,SCSI]
309 See Documentation/scsi/aic7xxx.txt.
310
311 aic79xx= [HW,SCSI]
312 See Documentation/scsi/aic79xx.txt.
313
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314 alignment= [KNL,ARM]
315 Allow the default userspace alignment fault handler
316 behaviour to be specified. Bit 0 enables warnings,
317 bit 1 enables fixups, and bit 2 sends a segfault.
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 fullflush - enable flushing of IO/TLB entries when
323 they are unmapped. Otherwise they are
324 flushed before they will be reused, which
325 is a lot of faster
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326 off - do not initialize any AMD IOMMU found in
327 the system
afa9fdc2 328
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329 amijoy.map= [HW,JOY] Amiga joystick support
330 Map of devices attached to JOY0DAT and JOY1DAT
331 Format: <a>,<b>
332 See also Documentation/kernel/input/joystick.txt
333
334 analog.map= [HW,JOY] Analog joystick and gamepad support
335 Specifies type or capabilities of an analog joystick
336 connected to one of 16 gameports
337 Format: <type1>,<type2>,..<type16>
338
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339 apc= [HW,SPARC]
340 Power management functions (SPARCstation-4/5 + deriv.)
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341 Format: noidle
342 Disable APC CPU standby support. SPARCstation-Fox does
343 not play well with APC CPU idle - disable it if you have
344 APC and your system crashes randomly.
345
ca1eda2d 346 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 347 Change the output verbosity whilst booting
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348 Format: { quiet (default) | verbose | debug }
349 Change the amount of debugging information output
350 when initialising the APIC and IO-APIC components.
a9913044 351
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352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
354
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355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
363
1da177e4 364 apm= [APM] Advanced Power Management
71f77055 365 See header of arch/x86/kernel/apm_32.c.
1da177e4 366
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367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
369
370 ataflop= [HW,M68k]
371
372 atarimouse= [HW,MOUSE] Atari Mouse
373
374 atascsi= [HW,SCSI] Atari SCSI
375
376 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
377 EzKey and similar keyboards
378
379 atkbd.reset= [HW] Reset keyboard during initialization
380
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381 atkbd.set= [HW] Select keyboard code set
382 Format: <int> (2 = AT (default), 3 = PS/2)
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383
384 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 keyboards
386
387 atkbd.softraw= [HW] Choose between synthetic and real raw mode
388 Format: <bool> (0 = real, 1 = synthetic (default))
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389
390 atkbd.softrepeat= [HW]
391 Use software keyboard repeat
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392
393 autotest [IA64]
394
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395 baycom_epp= [HW,AX25]
396 Format: <io>,<mode>
a9913044 397
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398 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
399 Format: <io>,<mode>
400 See header of drivers/net/hamradio/baycom_par.c.
401
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402 baycom_ser_fdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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404 Format: <io>,<irq>,<mode>[,<baud>]
405 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406
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407 baycom_ser_hdx= [HW,AX25]
408 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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409 Format: <io>,<irq>,<mode>
410 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411
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412 boot_delay= Milliseconds to delay each printk during boot.
413 Values larger than 10 seconds (10000) are changed to
414 no delay (0).
415 Format: integer
416
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417 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418
1da177e4 419 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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420 bttv.radio= Most important insmod options are available as
421 kernel args too.
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422 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
423 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
424
425 BusLogic= [HW,SCSI]
426 See drivers/scsi/BusLogic.c, comment before function
427 BusLogic_ParseDriverOptions().
428
429 c101= [NET] Moxa C101 synchronous serial card
430
cd4f0ef7 431 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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432 Sometimes CPU hardware bugs make them report the cache
433 size incorrectly. The kernel will attempt work arounds
434 to fix known problems, but for some CPUs it is not
435 possible to determine what the correct size should be.
436 This option provides an override for these situations.
437
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438 capability.disable=
439 [SECURITY] Disable capabilities. This would normally
440 be used only if an alternative security model is to be
441 configured. Potentially dangerous and should only be
442 used if you are entirely sure of the consequences.
443
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444 ccw_timeout_log [S390]
445 See Documentation/s390/CommonIO for details.
1da177e4 446
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447 cgroup_disable= [KNL] Disable a particular controller
448 Format: {name of the controller(s) to disable}
449 {Currently supported controllers - "memory"}
450
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451 checkreqprot [SELINUX] Set initial checkreqprot flag value.
452 Format: { "0" | "1" }
453 See security/selinux/Kconfig help text.
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454 0 -- check protection applied by kernel (includes
455 any implied execute protection).
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456 1 -- check protection requested by application.
457 Default value is set via a kernel config option.
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458 Value can be changed at runtime via
459 /selinux/checkreqprot.
460
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461 cio_ignore= [S390]
462 See Documentation/s390/CommonIO for details.
463
cd4f0ef7 464 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 465 [Deprecated]
3f6dee9b 466 Forces specified clocksource (if available) to be used
734efb46 467 when calculating gettimeofday(). If specified
3f6dee9b 468 clocksource is not available, it defaults to PIT.
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469 Format: { pit | tsc | cyclone | pmtmr }
470
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471 clocksource= [GENERIC_TIME] Override the default clocksource
472 Format: <string>
473 Override the default clocksource and use the clocksource
474 with the name specified.
475 Some clocksource names to choose from, depending on
476 the platform:
477 [all] jiffies (this is the base, fallback clocksource)
478 [ACPI] acpi_pm
479 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
480 pxa_timer,timer3,32k_counter,timer0_1
481 [AVR32] avr32
cd4f0ef7 482 [X86-32] pit,hpet,tsc,vmi-timer;
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483 scx200_hrt on Geode; cyclone on IBM x440
484 [MIPS] MIPS
485 [PARISC] cr16
486 [S390] tod
487 [SH] SuperH
488 [SPARC64] tick
489 [X86-64] hpet,tsc
490
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491 clearcpuid=BITNUM [X86]
492 Disable CPUID feature X for the kernel. See
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493 arch/x86/include/asm/cpufeature.h for the valid bit
494 numbers. Note the Linux specific bits are not necessarily
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495 stable over kernel options, but the vendor specific
496 ones should be.
497 Also note that user programs calling CPUID directly
498 or using the feature without checking anything
499 will still see it. This just prevents it from
500 being used by the kernel or shown in /proc/cpuinfo.
501 Also note the kernel might malfunction if you disable
502 some critical bits.
503
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504 cmo_free_hint= [PPC] Format: { yes | no }
505 Specify whether pages are marked as being inactive
506 when they are freed. This is used in CMO environments
507 to determine OS memory pressure for page stealing by
508 a hypervisor.
509 Default: yes
510
6cececfc 511 code_bytes [X86] How many bytes of object code to print
a25bd949 512 in an oops report.
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513 Range: 0 - 8192
514 Default: 64
515
1da177e4 516 com20020= [HW,NET] ARCnet - COM20020 chipset
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517 Format:
518 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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519
520 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
521 Format: <io>[,<irq>]
522
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523 com90xx= [HW,NET]
524 ARCnet - COM90xx chipset (memory-mapped buffers)
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525 Format: <io>[,<irq>[,<memstart>]]
526
527 condev= [HW,S390] console device
528 conmode=
a9913044 529
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530 console= [KNL] Output console device and options.
531
532 tty<n> Use the virtual console device <n>.
533
534 ttyS<n>[,options]
f1a1c2dc 535 ttyUSB0[,options]
1da177e4 536 Use the specified serial port. The options are of
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RD
537 the form "bbbbpnf", where "bbbb" is the baud rate,
538 "p" is parity ("n", "o", or "e"), "n" is number of
539 bits, and "f" is flow control ("r" for RTS or
540 omit it). Default is "9600n8".
541
542 See Documentation/serial-console.txt for more
543 information. See
544 Documentation/networking/netconsole.txt for an
545 alternative.
1da177e4 546
18a8bd94
YL
547 uart[8250],io,<addr>[,options]
548 uart[8250],mmio,<addr>[,options]
1da177e4
LT
549 Start an early, polled-mode console on the 8250/16550
550 UART at the specified I/O port or MMIO address,
551 switching to the matching ttyS device later. The
552 options are the same as for ttyS, above.
553
f7511d5f
ST
554 If the device connected to the port is not a TTY but a braille
555 device, prepend "brl," before the device type, for instance
556 console=brl,ttyS0
557 For now, only VisioBraille is supported.
558
f324edc8
DM
559 consoleblank= [KNL] The console blank (screen saver) timeout in
560 seconds. Defaults to 10*60 = 10mins. A value of 0
561 disables the blank timer.
562
4cb0e11b
HK
563 coredump_filter=
564 [KNL] Change the default value for
565 /proc/<pid>/coredump_filter.
566 See also Documentation/filesystems/proc.txt.
567
1da177e4 568 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
569 Format:
570 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 571
dc009d92
EB
572 crashkernel=nn[KMG]@ss[KMG]
573 [KNL] Reserve a chunk of physical memory to
574 hold a kernel to switch to with kexec on panic.
575
fb391599
BW
576 crashkernel=range1:size1[,range2:size2,...][@offset]
577 [KNL] Same as above, but depends on the memory
578 in the running system. The syntax of range is
579 start-[end] where start and end are both
580 a memory unit (amount[KMG]). See also
581 Documentation/kdump/kdump.txt for a example.
582
1da177e4
LT
583 cs89x0_dma= [HW,NET]
584 Format: <dma>
585
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
a9913044 588
a9913044 589 dasd= [HW,NET]
1da177e4
LT
590 See header of drivers/s390/block/dasd_devmap.c.
591
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
596
597 debug [KNL] Enable kernel debugging (events log level).
598
cae2ed9a
IM
599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
607
3ac7fe5a
TG
608 debug_objects [KNL] Enable object debugging
609
3e8ebb5c
KM
610 no_debug_objects
611 [KNL] Disable object debugging
612
d3af01f1
TG
613 debugpat [X86] Enable PAT debugging
614
2d27a966 615 decnet.addr= [HW,NET]
1da177e4
LT
616 Format: <area>[,<node>]
617 See also Documentation/networking/decnet.txt.
618
0cb55ad2
RD
619 default_hugepagesz=
620 [same as hugepagesz=] The size of the default
621 HugeTLB page size. This is the size represented by
622 the legacy /proc/ hugepages APIs, used for SHM, and
623 default size when mounting hugetlbfs filesystems.
624 Defaults to the default architecture's huge page size
625 if not specified.
55ff9780 626
1da177e4
LT
627 dhash_entries= [KNL]
628 Set number of hash buckets for dentry cache.
a9913044 629
1da177e4
LT
630 digi= [HW,SERIAL]
631 IO parameters + enable/disable command.
632
633 digiepca= [HW,SERIAL]
634 See drivers/char/README.epca and
31c00fc1 635 Documentation/serial/digiepca.txt.
1da177e4 636
b0f83b28
BH
637 disable= [IPV6]
638 See Documentation/networking/ipv6.txt.
639
640 disable_ipv6= [IPV6]
641 See Documentation/networking/ipv6.txt.
642
95ffa243 643 disable_mtrr_cleanup [X86]
95ffa243
YL
644 The kernel tries to adjust MTRR layout from continuous
645 to discrete, to make X server driver able to add WB
0cb55ad2 646 entry later. This parameter disables that.
95ffa243 647
093af8d7 648 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
649 By default the kernel will trim any uncacheable
650 memory out of your available memory pool based on
651 MTRR settings. This parameter disables that behavior,
652 possibly causing your machine to run very slowly.
653
6cececfc 654 disable_timer_pin_1 [X86]
0cb55ad2
RD
655 Disable PIN 1 of APIC timer
656 Can be useful to work around chipset bugs.
657
1da177e4
LT
658 dmasound= [HW,OSS] Sound subsystem buffers
659
0cb55ad2
RD
660 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
661 this option disables the debugging code at boot.
662
663 dma_debug_entries=<number>
664 This option allows to tune the number of preallocated
665 entries for DMA-API debugging code. One entry is
666 required per DMA-API allocation. Use this if the
667 DMA-API debugging code disables itself because the
668 architectural default is too low.
669
1745de5e
JR
670 dma_debug_driver=<driver_name>
671 With this option the DMA-API debugging driver
672 filter feature can be enabled at boot time. Just
673 pass the driver to filter for as the parameter.
674 The filter can be disabled or changed to another
675 driver later using sysfs.
676
1da177e4
LT
677 dscc4.setup= [NET]
678
679 dtc3181e= [HW,SCSI]
680
0cb55ad2
RD
681 dynamic_printk Enables pr_debug()/dev_dbg() calls if
682 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
683 These can also be switched on/off via
684 <debugfs>/dynamic_printk/modules
685
686 earlycon= [KNL] Output early console device and options.
687 uart[8250],io,<addr>[,options]
688 uart[8250],mmio,<addr>[,options]
689 Start an early, polled-mode console on the 8250/16550
690 UART at the specified I/O port or MMIO address.
691 The options are the same as for ttyS, above.
692
6cececfc 693 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
694 earlyprintk=vga
695 earlyprintk=serial[,ttySn[,baudrate]]
ea3acb19 696 earlyprintk=ttySn[,baudrate]
9780bc41 697 earlyprintk=dbgp[debugController#]
1da177e4 698
a9913044 699 Append ",keep" to not disable it when the real console
1da177e4
LT
700 takes over.
701
5c05917e 702 Only vga or serial or usb debug port at a time.
1da177e4
LT
703
704 Currently only ttyS0 and ttyS1 are supported.
705
706 Interaction with the standard serial driver is not
707 very good.
708
709 The VGA output is eventually overwritten by the real
710 console.
711
9731191f
JW
712 ekgdboc= [X86,KGDB] Allow early kernel console debugging
713 ekgdboc=kbd
714
715 This is desgined to be used in conjunction with
716 the boot argument: earlyprintk=vga
717
1da177e4
LT
718 eata= [HW,SCSI]
719
1da177e4 720 edd= [EDD]
8c4dd606 721 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 722
1da177e4
LT
723 eisa_irq_edge= [PARISC,HW]
724 See header of drivers/parisc/eisa.c.
725
cd4f0ef7 726 elanfreq= [X86-32]
1da177e4 727 See comment before function elanfreq_setup() in
71f77055 728 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
729
730 elevator= [IOSCHED]
16ab3adf 731 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
732 See Documentation/block/as-iosched.txt and
733 Documentation/block/deadline-iosched.txt for details.
734
6cececfc 735 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 736 Specifies physical address of start of kernel core
aac04b32
VG
737 image elf header. Generally kexec loader will
738 pass this option to capture kernel.
739 See Documentation/kdump/kdump.txt for details.
1da177e4 740
0cb55ad2
RD
741 enable_mtrr_cleanup [X86]
742 The kernel tries to adjust MTRR layout from continuous
743 to discrete, to make X server driver able to add WB
744 entry later. This parameter enables that.
745
ca1eda2d 746 enable_timer_pin_1 [X86]
0cb55ad2
RD
747 Enable PIN 1 of APIC timer
748 Can be useful to work around chipset bugs
749 (in particular on some ATI chipsets).
750 The kernel tries to set a reasonable default.
751
1da177e4
LT
752 enforcing [SELINUX] Set initial enforcing status.
753 Format: {"0" | "1"}
754 See security/selinux/Kconfig help text.
755 0 -- permissive (log only, no denials).
756 1 -- enforcing (deny and log).
757 Default value is 0.
758 Value can be changed at runtime via /selinux/enforce.
759
a08f82d0
HY
760 erst_disable [ACPI]
761 Disable Error Record Serialization Table (ERST)
762 support.
763
1da177e4
LT
764 ether= [HW,NET] Ethernet cards parameters
765 This option is obsoleted by the "netdev=" option, which
766 has equivalent usage. See its documentation for details.
767
de1ba09b
AM
768 failslab=
769 fail_page_alloc=
770 fail_make_request=[KNL]
771 General fault injection mechanism.
772 Format: <interval>,<probability>,<space>,<times>
773 See also /Documentation/fault-injection/.
774
1da177e4
LT
775 fd_mcs= [HW,SCSI]
776 See header of drivers/scsi/fd_mcs.c.
777
778 fdomain= [HW,SCSI]
779 See header of drivers/scsi/fdomain.c.
780
781 floppy= [HW]
31c00fc1 782 See Documentation/blockdev/floppy.txt.
1da177e4 783
f13ae30e
AC
784 force_pal_cache_flush
785 [IA-64] Avoid check_sal_cache_flush which may hang on
786 buggy SAL_CACHE_FLUSH implementations. Using this
787 parameter will force ia64_sal_cache_flush to call
788 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
789
d9e54076 790 ftrace=[tracer]
2af15d6a 791 [FTRACE] will set and start the specified tracer
d9e54076
PZ
792 as early as possible in order to facilitate early
793 boot debugging.
794
cecbca96 795 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 796 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
797 If no parameter is passed, ftrace will dump
798 buffers of all CPUs, but if you pass orig_cpu, it will
799 dump only the buffer of the CPU that triggered the
800 oops.
2af15d6a
SR
801
802 ftrace_filter=[function-list]
803 [FTRACE] Limit the functions traced by the function
804 tracer at boot up. function-list is a comma separated
805 list of functions. This list can be changed at run
806 time by the set_ftrace_filter file in the debugfs
807 tracing directory.
808
809 ftrace_notrace=[function-list]
810 [FTRACE] Do not trace the functions specified in
811 function-list. This list can be changed at run time
812 by the set_ftrace_notrace file in the debugfs
813 tracing directory.
d9e54076 814
369bc18f
SA
815 ftrace_graph_filter=[function-list]
816 [FTRACE] Limit the top level callers functions traced
817 by the function graph tracer at boot up.
818 function-list is a comma separated list of functions
819 that can be changed at run time by the
820 set_graph_function file in the debugfs tracing directory.
821
1da177e4
LT
822 gamecon.map[2|3]=
823 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
824 support via parallel port (up to 5 devices per port)
825 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
826 See also Documentation/input/joystick-parport.txt
827
828 gamma= [HW,DRM]
829
aaf23042
YL
830 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
831 Format: off | on
832 default: on
833
2521f2c2
PO
834 gcov_persist= [GCOV] When non-zero (default), profiling data for
835 kernel modules is saved and remains accessible via
836 debugfs, even when the module is unloaded/reloaded.
837 When zero, profiling data is discarded and associated
838 debugfs files are removed at module unload time.
839
1da177e4
LT
840 gdth= [HW,SCSI]
841 See header of drivers/scsi/gdth.c.
842
843 gpt [EFI] Forces disk with valid GPT signature but
844 invalid Protective MBR to be treated as GPT.
845
1da177e4
LT
846 gvp11= [HW,SCSI]
847
848 hashdist= [KNL,NUMA] Large hashes allocated during boot
849 are distributed across NUMA nodes. Defaults on
429aa0fc 850 for 64bit NUMA, off otherwise.
a9913044 851 Format: 0 | 1 (for off | on)
1da177e4
LT
852
853 hcl= [IA-64] SGI's Hardware Graph compatibility layer
854
855 hd= [EIDE] (E)IDE hard drive subsystem geometry
856 Format: <cyl>,<head>,<sect>
857
ea8c071c
HY
858 hest_disable [ACPI]
859 Disable Hardware Error Source Table (HEST) support;
860 corresponding firmware-first mode error processing
861 logic will be disabled.
862
1da177e4
LT
863 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
864 size of <nn>. This works even on boxes that have no
865 highmem otherwise. This also works to reduce highmem
866 size on bigger boxes.
867
54cdfdb4
TG
868 highres= [KNL] Enable/disable high resolution timer mode.
869 Valid parameters: "on", "off"
870 Default: "on"
871
1da177e4
LT
872 hisax= [HW,ISDN]
873 See Documentation/isdn/README.HiSax.
874
0cb55ad2
RD
875 hlt [BUGS=ARM,SH]
876
877 hpet= [X86-32,HPET] option to control HPET usage
878 Format: { enable (default) | disable | force |
879 verbose }
880 disable: disable HPET and use PIT instead
881 force: allow force enabled of undocumented chips (ICH4,
882 VIA, nVidia)
883 verbose: show contents of HPET registers during setup
884
b4718e62
AK
885 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
886 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
887 On x86-64 and powerpc, this option can be specified
888 multiple times interleaved with hugepages= to reserve
889 huge pages of different sizes. Valid pages sizes on
890 x86-64 are 2M (when the CPU supports "pse") and 1G
891 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
892 Note that 1GB pages can only be allocated at boot time
893 using hugepages= and not freed afterwards.
6902aa84 894
555d61d6
HB
895 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
896 terminal devices. Valid values: 0..8
431429ff
HB
897 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
898 If specified, z/VM IUCV HVC accepts connections
899 from listed z/VM user IDs only.
cef7125d 900
3a853fb9 901 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
902 or register an additional I2C bus that is not
903 registered from board initialization code.
3a853fb9
JN
904 Format:
905 <bus_id>,<clkrate>
906
36d95739 907 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 908 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
909 i8042.dumbkbd [HW] Pretend that controller can only read data from
910 keyboard and cannot control its state
1da177e4
LT
911 (Don't attempt to blink the leds)
912 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 913 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
914 i8042.noloop [HW] Disable the AUX Loopback command while probing
915 for the AUX port
1da177e4
LT
916 i8042.nomux [HW] Don't check presence of an active multiplexing
917 controller
918 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
919 controllers
920 i8042.panicblink=
921 [HW] Frequency with which keyboard LEDs should blink
922 when kernel panics (default is 0.5 sec)
923 i8042.reset [HW] Reset the controller during init and cleanup
924 i8042.unlock [HW] Unlock (ignore) the keylock
925
926 i810= [HW,DRM]
927
e70c9d5e
DT
928 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
929 indicates that the driver is running on unsupported
930 hardware.
1da177e4
LT
931 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
932 does not match list of supported models.
933 i8k.power_status
934 [HW] Report power status in /proc/i8k
935 (disabled by default)
936 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
937 capability is set.
938
939 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
940 See Documentation/mca.txt.
941
942 icn= [HW,ISDN]
943 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
944
0af80c04
DF
945 ide-core.nodma= [HW] (E)IDE subsystem
946 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
947 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
948 .cdrom .chs .ignore_cable are additional options
1c10e938 949 See Documentation/ide/ide.txt.
1da177e4 950
0cb55ad2
RD
951 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
952 Claim all unknown PCI IDE storage controllers.
953
f039b754 954 idle= [X86]
ada9cfdd
RD
955 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
956 Poll forces a polling idle loop that can slightly
957 improve the performance of waking up a idle CPU, but
958 will use a lot of power and make the system run hot.
959 Not recommended.
960 idle=mwait: On systems which support MONITOR/MWAIT but
961 the kernel chose to not use it because it doesn't save
962 as much power as a normal idle loop, use the
963 MONITOR/MWAIT idle loop anyways. Performance should be
964 the same as idle=poll.
965 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 966 In such case C2/C3 won't be used again.
ada9cfdd 967 idle=nomwait: Disable mwait for CPU C-states
a9913044 968
79290822
IM
969 ignore_loglevel [KNL]
970 Ignore loglevel setting - this will print /all/
971 kernel messages to the console. Useful for debugging.
972
1da177e4
LT
973 ihash_entries= [KNL]
974 Set number of hash buckets for inode cache.
975
3323eec9
MZ
976 ima_audit= [IMA]
977 Format: { "0" | "1" }
978 0 -- integrity auditing messages. (Default)
979 1 -- enable informational integrity auditing messages.
980
981 ima_hash= [IMA]
a9ed83a5 982 Format: { "sha1" | "md5" }
3323eec9
MZ
983 default: "sha1"
984
5789ba3b
EP
985 ima_tcb [IMA]
986 Load a policy which meets the needs of the Trusted
987 Computing Base. This means IMA will measure all
988 programs exec'd, files mmap'd for exec, and all files
989 opened for read by uid=0.
990
1da177e4
LT
991 in2000= [HW,SCSI]
992 See header of drivers/scsi/in2000.c.
993
994 init= [KNL]
995 Format: <full_path>
996 Run specified binary instead of /sbin/init as init
997 process.
998
999 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1000 for working out where the kernel is dying during
1001 startup.
1002
1003 initrd= [BOOT] Specify the location of the initial ramdisk
1004
1005 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1006 Format: <irq>
1007
ba395927 1008 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
1009 on
1010 Enable intel iommu driver.
ba395927
KA
1011 off
1012 Disable intel iommu driver.
1013 igfx_off [Default Off]
1014 By default, gfx is mapped as normal device. If a gfx
1015 device has a dedicated DMAR unit, the DMAR unit is
1016 bypassed by not enabling DMAR with this option. In
1017 this case, gfx device will use physical address for
1018 DMA.
7d3b03ce
KA
1019 forcedac [x86_64]
1020 With this option iommu will not optimize to look
1021 for io virtual address below 32 bit forcing dual
1022 address cycle on pci bus for cards supporting greater
1023 than 32 bit addressing. The default is to look
1024 for translation below 32 bit and if not available
1025 then look in the higher range.
5e0d2a6f 1026 strict [Default Off]
1027 With this option on every unmap_single operation will
1028 result in a hardware IOTLB flush operation as opposed
1029 to batching them for performance.
ba395927 1030
d1423d56
CW
1031 intremap= [X86-64, Intel-IOMMU]
1032 Format: { on (default) | off | nosid }
1033 on enable Interrupt Remapping (default)
1034 off disable Interrupt Remapping
1035 nosid disable Source ID checking
1036
0cb55ad2
RD
1037 inttest= [IA64]
1038
1039 iomem= Disable strict checking of access to MMIO memory
1040 strict regions from userspace.
1041 relaxed
1042
1043 iommu= [x86]
1044 off
1045 force
1046 noforce
1047 biomerge
1048 panic
1049 nopanic
1050 merge
1051 nomerge
1052 forcesac
1053 soft
4ed0d3e6 1054 pt [x86, IA64]
0cb55ad2
RD
1055
1056 io7= [HW] IO7 for Marvel based alpha systems
1057 See comment before marvel_specify_io7 in
1058 arch/alpha/kernel/core_marvel.c.
1059
6cececfc 1060 io_delay= [X86] I/O delay method
6e7c4025
IM
1061 0x80
1062 Standard port 0x80 based delay
1063 0xed
1064 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1065 udelay
6e7c4025
IM
1066 Simple two microseconds delay
1067 none
1068 No delay
b02aae9c 1069
1da177e4 1070 ip= [IP_PNP]
dc7a0816 1071 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1072
1073 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1074 See comment before ip2_setup() in
1075 drivers/char/ip2/ip2base.c.
1da177e4
LT
1076
1077 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1078 See header of drivers/scsi/ips.c.
1079
200803df
AC
1080 irqfixup [HW]
1081 When an interrupt is not handled search all handlers
1082 for it. Intended to get systems with badly broken
1083 firmware running.
1084
1085 irqpoll [HW]
1086 When an interrupt is not handled search all handlers
1087 for it. Also check all handlers each timer
1088 interrupt. Intended to get systems with badly broken
1089 firmware running.
1090
1da177e4 1091 isapnp= [ISAPNP]
a9913044 1092 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1093
1094 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1095 Format:
1096 <cpu number>,...,<cpu number>
1097 or
b225d44e
LZ
1098 <cpu number>-<cpu number>
1099 (must be a positive range in ascending order)
22f2e280
DF
1100 or a mixture
1101 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1102
1da177e4
LT
1103 This option can be used to specify one or more CPUs
1104 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1105 algorithms. You can move a process onto or off an
1106 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1107 <cpu number> begins at 0 and the maximum value is
1108 "number of CPUs in system - 1".
1109
1110 This option is the preferred way to isolate CPUs. The
a9913044
RD
1111 alternative -- manually setting the CPU mask of all
1112 tasks in the system -- can cause problems and
1113 suboptimal load balancer performance.
1da177e4 1114
a9913044 1115 iucv= [HW,NET]
1da177e4
LT
1116
1117 js= [HW,JOY] Analog joystick
1118 See Documentation/input/joystick.txt.
1119
0cb55ad2
RD
1120 keepinitrd [HW,ARM]
1121
6cececfc 1122 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1123 specifies the amount of memory usable by the kernel
1124 for non-movable allocations. The requested amount is
1125 spread evenly throughout all nodes in the system. The
1126 remaining memory in each node is used for Movable
1127 pages. In the event, a node is too small to have both
1128 kernelcore and Movable pages, kernelcore pages will
1129 take priority and other nodes will have a larger number
1130 of kernelcore pages. The Movable zone is used for the
1131 allocation of pages that may be reclaimed or moved
1132 by the page migration subsystem. This means that
1133 HugeTLB pages may not be allocated from this zone.
1134 Note that allocations like PTEs-from-HighMem still
1135 use the HighMem zone if it exists, and the Normal
1136 zone if it does not.
1137
4fe1da4e
JW
1138 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1139 Format: <Controller#>[,poll interval]
1140 The controller # is the number of the ehci usb debug
1141 port as it is probed via PCI. The poll interval is
1142 optional and is the number seconds in between
1143 each poll cycle to the debug port in case you need
1144 the functionality for interrupting the kernel with
1145 gdb or control-c on the dbgp connection. When
1146 not using this parameter you use sysrq-g to break into
1147 the kernel debugger.
1148
84c08fd6 1149 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1150 Requires a tty driver that supports console polling,
1151 or a supported polling keyboard driver (non-usb).
1152 Serial only format: <serial_device>[,baud]
1153 keyboard only format: kbd
1154 keyboard and serial format: kbd,<serial_device>[,baud]
6cdf6e06 1155
84c08fd6
JW
1156 kgdbwait [KGDB] Stop kernel execution and enter the
1157 kernel debugger at the earliest opportunity.
1158
9bed90c6
FF
1159 kmac= [MIPS] korina ethernet MAC address.
1160 Configure the RouterBoard 532 series on-chip
1161 Ethernet adapter MAC address.
1162
04f70336
CM
1163 kmemleak= [KNL] Boot-time kmemleak enable/disable
1164 Valid arguments: on, off
1165 Default: on
1166
6cececfc 1167 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1168 in oops dumps.
1169
fef07aae
AP
1170 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1171 Default is 0 (don't ignore, but inject #GP)
1172
1173 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1174 Default is 1 (enabled)
1175
1176 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1177 Default is 0 (off)
1178
1179 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1180 for all guests.
1181 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1182
1183 kvm-intel.bypass_guest_pf=
1184 [KVM,Intel] Disables bypassing of guest page faults
1185 on Intel chips. Default is 1 (enabled)
1186
1187 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1188 (virtualized MMU) support on capable Intel chips.
1189 Default is 1 (enabled)
1190
1191 kvm-intel.emulate_invalid_guest_state=
1192 [KVM,Intel] Enable emulation of invalid guest states
1193 Default is 0 (disabled)
1194
1195 kvm-intel.flexpriority=
1196 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1197 Default is 1 (enabled)
1198
1199 kvm-intel.unrestricted_guest=
1200 [KVM,Intel] Disable unrestricted guest feature
1201 (virtualized real and unpaged mode) on capable
1202 Intel chips. Default is 1 (enabled)
1203
1204 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1205 feature (tagged TLBs) on capable Intel chips.
1206 Default is 1 (enabled)
1207
1da177e4
LT
1208 l2cr= [PPC]
1209
a78bfbfc
RB
1210 l3cr= [PPC]
1211
cd4f0ef7 1212 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1213 disabled it.
1da177e4 1214
6cececfc 1215 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1216 in C2 power state.
e585bef8 1217
fcb71f6f
FC
1218 libata.dma= [LIBATA] DMA control
1219 libata.dma=0 Disable all PATA and SATA DMA
1220 libata.dma=1 PATA and SATA Disk DMA only
1221 libata.dma=2 ATAPI (CDROM) DMA only
1222 libata.dma=4 Compact Flash DMA only
1223 Combinations also work, so libata.dma=3 enables DMA
1224 for disks and CDROMs, but not CFs.
20308871
MP
1225
1226 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1227 libata.ignore_hpa=0 keep BIOS limits (default)
1228 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1229
78e70c23
DJ
1230 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1231 when set.
1232 Format: <int>
1233
33267325
TH
1234 libata.force= [LIBATA] Force configurations. The format is comma
1235 separated list of "[ID:]VAL" where ID is
4c44f309 1236 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1237 matching port, link or device. Basically, it matches
1238 the ATA ID string printed on console by libata. If
1239 the whole ID part is omitted, the last PORT and DEVICE
1240 values are used. If ID hasn't been specified yet, the
1241 configuration applies to all ports, links and devices.
1242
1243 If only DEVICE is omitted, the parameter applies to
1244 the port and all links and devices behind it. DEVICE
1245 number of 0 either selects the first device or the
1246 first fan-out link behind PMP device. It does not
1247 select the host link. DEVICE number of 15 selects the
1248 host link and device attached to it.
1249
1250 The VAL specifies the configuration to force. As long
1251 as there's no ambiguity shortcut notation is allowed.
1252 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1253 The following configurations can be forced.
1254
1255 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1256 Any ID with matching PORT is used.
1257
1258 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1259
1260 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1261 udma[/][16,25,33,44,66,100,133] notation is also
1262 allowed.
1263
1264 * [no]ncq: Turn on or off NCQ.
1265
05944bdf
TH
1266 * nohrst, nosrst, norst: suppress hard, soft
1267 and both resets.
1268
43c9c591
TH
1269 * dump_id: dump IDENTIFY data.
1270
33267325
TH
1271 If there are multiple matching configurations changing
1272 the same attribute, the last one is used.
1273
95f72d1e 1274 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1275
1da177e4 1276 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1277 See Documentation/blockdev/ramdisk.txt.
1da177e4 1278
a6b25b67
RD
1279 lockd.nlm_grace_period=P [NFS] Assign grace period.
1280 Format: <integer>
1da177e4 1281
a6b25b67
RD
1282 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1283 Format: <integer>
1284
1285 lockd.nlm_timeout=T [NFS] Assign timeout value.
1286 Format: <integer>
1287
1288 lockd.nlm_udpport=M [NFS] Assign UDP port.
1289 Format: <integer>
1da177e4
LT
1290
1291 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1292 Format: <irq>
1293
1294 loglevel= All Kernel Messages with a loglevel smaller than the
1295 console loglevel will be printed to the console. It can
1296 also be changed with klogd or other programs. The
1297 loglevels are defined as follows:
1298
1299 0 (KERN_EMERG) system is unusable
1300 1 (KERN_ALERT) action must be taken immediately
1301 2 (KERN_CRIT) critical conditions
1302 3 (KERN_ERR) error conditions
1303 4 (KERN_WARNING) warning conditions
1304 5 (KERN_NOTICE) normal but significant condition
1305 6 (KERN_INFO) informational
1306 7 (KERN_DEBUG) debug-level messages
1307
1308 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1309 Format: { n | nk | nM }
1310 n must be a power of two. The default size
1311 is set in the kernel config file.
1da177e4 1312
accaa24c
RD
1313 logo.nologo [FB] Disables display of the built-in Linux logo.
1314 This may be used to provide more screen space for
1315 kernel log messages and is useful when debugging
1316 kernel boot problems.
1317
1da177e4
LT
1318 lp=0 [LP] Specify parallel ports to use, e.g,
1319 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1320 lp=reset first parallel port). 'lp=0' disables the
1321 lp=auto printer driver. 'lp=reset' (which can be
1322 specified in addition to the ports) causes
1323 attached printers to be reset. Using
1324 lp=port1,port2,... specifies the parallel ports
1325 to associate lp devices with, starting with
1326 lp0. A port specification may be 'none' to skip
1327 that lp device, or a parport name such as
1328 'parport0'. Specifying 'lp=auto' instead of a
1329 port specification list means that device IDs
1330 from each port should be examined, to see if
1331 an IEEE 1284-compliant printer is attached; if
1332 so, the driver will manage that printer.
1333 See also header of drivers/char/lp.c.
1334
1335 lpj=n [KNL]
1336 Sets loops_per_jiffy to given constant, thus avoiding
1337 time-consuming boot-time autodetection (up to 250 ms per
1338 CPU). 0 enables autodetection (default). To determine
1339 the correct value for your kernel, boot with normal
1340 autodetection and see what value is printed. Note that
1341 on SMP systems the preset will be applied to all CPUs,
1342 which is likely to cause problems if your CPUs need
1343 significantly divergent settings. An incorrect value
1344 will cause delays in the kernel to be wrong, leading to
1345 unpredictable I/O errors and other breakage. Although
1346 unlikely, in the extreme case this might damage your
1347 hardware.
1348
1349 ltpc= [NET]
1350 Format: <io>,<irq>,<dma>
1351
a9913044
RD
1352 mac5380= [HW,SCSI] Format:
1353 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1354
a9913044
RD
1355 machvec= [IA64] Force the use of a particular machine-vector
1356 (machvec) in a generic kernel.
1357 Example: machvec=hpzx1_swiotlb
1da177e4 1358
3209e70e
WZ
1359 machtype= [Loongson] Share the same kernel image file between different
1360 yeeloong laptop.
1361 Example: machtype=lemote-yeeloong-2f-7inch
1362
0cb55ad2
RD
1363 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1364 than or equal to this physical address is ignored.
1da177e4
LT
1365
1366 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1367 should make use of. maxcpus=n : n >= 0 limits the
1368 kernel to using 'n' processors. n=0 is a special case,
1369 it is equivalent to "nosmp", which also disables
1370 the IO APIC.
1da177e4 1371
0cb55ad2
RD
1372 max_loop= [LOOP] Maximum number of loopback devices that can
1373 be mounted
1374 Format: <1-256>
2b2c3750 1375
a9913044 1376 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1377 Should be between 1 and 2^32-1.
1378
1379 max_report_luns=
a9913044 1380 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1381 Should be between 1 and 16384.
1382
1da177e4
LT
1383 mcatest= [IA-64]
1384
cd4f0ef7 1385 mce [X86-32] Machine Check Exception
1da177e4 1386
71cced6e 1387 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1388
1da177e4
LT
1389 md= [HW] RAID subsystems devices and level
1390 See Documentation/md.txt.
a9913044 1391
1da177e4
LT
1392 mdacon= [MDA]
1393 Format: <first>,<last>
1394 Specifies range of consoles to be captured by the MDA.
a9913044 1395
1da177e4
LT
1396 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1397 Amount of memory to be used when the kernel is not able
1398 to see the whole system memory or for test.
cd4f0ef7 1399 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1400 address space collisions. Without memmap= PCI devices
1401 could be placed at addresses belonging to unused RAM.
1402
cd4f0ef7 1403 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1404 memory.
1405
6902aa84
PM
1406 memchunk=nn[KMG]
1407 [KNL,SH] Allow user to override the default size for
1408 per-device physically contiguous DMA buffers.
1409
6cececfc 1410 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1411 E820 memory map, as specified by the user.
1412 Such memmap=exactmap lines can be constructed based on
1413 BIOS output or other requirements. See the memmap=nn@ss
1414 option description.
1415
1416 memmap=nn[KMG]@ss[KMG]
1417 [KNL] Force usage of a specific region of memory
1418 Region of memory to be used, from ss to ss+nn.
1419
1420 memmap=nn[KMG]#ss[KMG]
1421 [KNL,ACPI] Mark specific memory as ACPI data.
1422 Region of memory to be used, from ss to ss+nn.
1423
1424 memmap=nn[KMG]$ss[KMG]
1425 [KNL,ACPI] Mark specific memory as reserved.
1426 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1427 Example: Exclude memory from 0x18690000-0x1869ffff
1428 memmap=64K$0x18690000
1429 or
1430 memmap=0x10000$0x18690000
1da177e4 1431
9f077871
JF
1432 memory_corruption_check=0/1 [X86]
1433 Some BIOSes seem to corrupt the first 64k of
1434 memory when doing things like suspend/resume.
1435 Setting this option will scan the memory
1436 looking for corruption. Enabling this will
1437 both detect corruption and prevent the kernel
1438 from using the memory being corrupted.
1439 However, its intended as a diagnostic tool; if
1440 repeatable BIOS-originated corruption always
1441 affects the same memory, you can use memmap=
1442 to prevent the kernel from using that memory.
1443
1444 memory_corruption_check_size=size [X86]
1445 By default it checks for corruption in the low
1446 64k, making this memory unavailable for normal
1447 use. Use this parameter to scan for
1448 corruption in more or less memory.
1449
1450 memory_corruption_check_period=seconds [X86]
1451 By default it checks for corruption every 60
1452 seconds. Use this parameter to check at some
1453 other rate. 0 disables periodic checking.
1454
caadbdce 1455 memtest= [KNL,X86] Enable memtest
c64df707 1456 Format: <integer>
c64df707 1457 default : 0 <disable>
9e5f6cf5
AH
1458 Specifies the number of memtest passes to be
1459 performed. Each pass selects another test
1460 pattern from a given set of patterns. Memtest
1461 fills the memory with this pattern, validates
1462 memory contents and reserves bad memory
1463 regions that are detected.
c64df707 1464
1da177e4
LT
1465 meye.*= [HW] Set MotionEye Camera parameters
1466 See Documentation/video4linux/meye.txt.
1467
8f36881b
AS
1468 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1469 Multi-Function General Purpose Timers on AMD Geode
1470 platforms.
1471
e6c4dc6c
WT
1472 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1473 the BIOS has incorrectly applied a workaround. TinyBIOS
1474 version 0.98 is known to be affected, 0.99 fixes the
1475 problem by letting the user disable the workaround.
1476
1da177e4
LT
1477 mga= [HW,DRM]
1478
1c207f95
RD
1479 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1480 physical address is ignored.
1481
39f45d7b
MP
1482 mini2440= [ARM,HW,KNL]
1483 Format:[0..2][b][c][t]
1484 Default: "0tb"
1485 MINI2440 configuration specification:
1486 0 - The attached screen is the 3.5" TFT
1487 1 - The attached screen is the 7" TFT
1488 2 - The VGA Shield is attached (1024x768)
1489 Leaving out the screen size parameter will not load
1490 the TFT driver, and the framebuffer will be left
1491 unconfigured.
1492 b - Enable backlight. The TFT backlight pin will be
1493 linked to the kernel VESA blanking code and a GPIO
1494 LED. This parameter is not necessary when using the
1495 VGA shield.
1496 c - Enable the s3c camera interface.
1497 t - Reserved for enabling touchscreen support. The
1498 touchscreen support is not enabled in the mainstream
1499 kernel as of 2.6.30, a preliminary port can be found
1500 in the "bleeding edge" mini2440 support kernel at
1501 http://repo.or.cz/w/linux-2.6/mini2440.git
1502
6b74ab97
MG
1503 mminit_loglevel=
1504 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1505 parameter allows control of the logging verbosity for
1506 the additional memory initialisation checks. A value
1507 of 0 disables mminit logging and a level of 4 will
1508 log everything. Information is printed at KERN_DEBUG
1509 so loglevel=8 may also need to be specified.
1510
1da177e4
LT
1511 mousedev.tap_time=
1512 [MOUSE] Maximum time between finger touching and
1513 leaving touchpad surface for touch to be considered
1514 a tap and be reported as a left button click (for
1515 touchpads working in absolute mode only).
1516 Format: <msecs>
1517 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1518 reporting absolute coordinates, such as tablets
1519 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1520 reporting absolute coordinates, such as tablets
1521
6cececfc 1522 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1523 is similar to kernelcore except it specifies the
1524 amount of memory used for migratable allocations.
1525 If both kernelcore and movablecore is specified,
1526 then kernelcore will be at *least* the specified
1527 value but may be more. If movablecore on its own
1528 is specified, the administrator must be careful
1529 that the amount of memory usable for all allocations
1530 is not too small.
1531
1da177e4
LT
1532 mpu401= [HW,OSS]
1533 Format: <io>,<irq>
1534
1535 MTD_Partition= [MTD]
1536 Format: <name>,<region-number>,<size>,<offset>
1537
a9913044
RD
1538 MTD_Region= [MTD] Format:
1539 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1540
1541 mtdparts= [MTD]
c8facbb6 1542 See drivers/mtd/cmdlinepart.c.
1da177e4 1543
5988af23
RH
1544 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1545
1546 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1547
1548 boundary - index of last SLC block on Flex-OneNAND.
1549 The remaining blocks are configured as MLC blocks.
1550 lock - Configure if Flex-OneNAND boundary should be locked.
1551 Once locked, the boundary cannot be changed.
1552 1 indicates lock status, 0 indicates unlock status.
1553
9db829f4
BD
1554 mtdset= [ARM]
1555 ARM/S3C2412 JIVE boot control
1556
1557 See arch/arm/mach-s3c2412/mach-jive.c
1558
1da177e4 1559 mtouchusb.raw_coordinates=
a9913044
RD
1560 [HW] Make the MicroTouch USB driver use raw coordinates
1561 ('y', default) or cooked coordinates ('n')
1da177e4 1562
0cb55ad2 1563 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1564 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1565 that could hold holes aka. UC entries.
1566
1567 mtrr_gran_size=nn[KMG] [X86]
1568 Used for mtrr cleanup. It is granularity of mtrr block.
1569 Default is 1.
1570 Large value could prevent small alignment from
1571 using up MTRRs.
1572
1573 mtrr_spare_reg_nr=n [X86]
1574 Format: <integer>
1575 Range: 0,7 : spare reg number
1576 Default : 1
1577 Used for mtrr cleanup. It is spare mtrr entries number.
1578 Set to 2 or more if your graphical card needs more.
1579
1da177e4
LT
1580 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1581
1582 NCR_D700= [HW,SCSI]
1583 See header of drivers/scsi/NCR_D700.c.
1584
1585 ncr5380= [HW,SCSI]
1586
1587 ncr53c400= [HW,SCSI]
1588
1589 ncr53c400a= [HW,SCSI]
1590
1591 ncr53c406a= [HW,SCSI]
1592
1593 ncr53c8xx= [HW,SCSI]
1594
1595 netdev= [NET] Network devices parameters
1596 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1597 Note that mem_start is often overloaded to mean
1598 something different and driver-specific.
a9913044
RD
1599 This usage is only documented in each driver source
1600 file if at all.
1601
58401572
KPO
1602 nf_conntrack.acct=
1603 [NETFILTER] Enable connection tracking flow accounting
1604 0 to disable accounting
1605 1 to enable accounting
1606 Default value depends on CONFIG_NF_CT_ACCT that is
1607 going to be removed in 2.6.29.
1608
1da177e4 1609 nfsaddrs= [NFS]
dc7a0816 1610 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1611
1612 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1613 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1614
a72b4422
TM
1615 nfs.callback_tcpport=
1616 [NFS] set the TCP port on which the NFSv4 callback
1617 channel should listen.
1618
e571cbf1
TM
1619 nfs.cache_getent=
1620 [NFS] sets the pathname to the program which is used
1621 to update the NFS client cache entries.
1622
1623 nfs.cache_getent_timeout=
1624 [NFS] sets the timeout after which an attempt to
1625 update a cache entry is deemed to have failed.
1626
58df095b
TM
1627 nfs.idmap_cache_timeout=
1628 [NFS] set the maximum lifetime for idmapper cache
1629 entries.
1630
f43bf0be
TM
1631 nfs.enable_ino64=
1632 [NFS] enable 64-bit inode numbers.
1633 If zero, the NFS client will fake up a 32-bit inode
1634 number for the readdir() and stat() syscalls instead
1635 of returning the full 64-bit number.
1636 The default is to return 64-bit inode numbers.
1637
1e1030dc 1638 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1639 when a NMI is triggered.
1640 Format: [state][,regs][,debounce][,die]
1641
6cececfc 1642 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1643 Format: [panic,][num]
1644 Valid num: 0,1,2
1645 0 - turn nmi_watchdog off
1646 1 - use the IO-APIC timer for the NMI watchdog
1647 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1648 a performance counter. Note: This will use one
1649 performance counter and the local APIC's performance
1650 vector.
1651 When panic is specified, panic when an NMI watchdog
1652 timeout occurs.
1653 This is useful when you use a panic=... timeout and
1654 need the box quickly up again.
5b9a0e14
CG
1655 Instead of 1 and 2 it is possible to use the following
1656 symbolic names: lapic and ioapic
1657 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1658
bff38771
AV
1659 netpoll.carrier_timeout=
1660 [NET] Specifies amount of time (in seconds) that
1661 netpoll should wait for a carrier. By default netpoll
1662 waits 4 seconds.
1663
cd4f0ef7 1664 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1665 emulation library even if a 387 maths coprocessor
1666 is present.
1667
0cb55ad2
RD
1668 no_console_suspend
1669 [HW] Never suspend the console
1670 Disable suspending of consoles during suspend and
1671 hibernate operations. Once disabled, debugging
1672 messages can reach various consoles while the rest
1673 of the system is being put to sleep (ie, while
1674 debugging driver suspend/resume hooks). This may
1675 not work reliably with all consoles, but is known
1676 to work with serial and VGA consoles.
1677
c1aee215
CL
1678 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1679 caches in the slab allocator. Saves per-node memory,
1680 but will impact performance.
3395ee05 1681
a9913044
RD
1682 noalign [KNL,ARM]
1683
1da177e4
LT
1684 noapic [SMP,APIC] Tells the kernel to not make use of any
1685 IOAPICs that may be present in the system.
1686
1da177e4
LT
1687 nobats [PPC] Do not use BATs for mapping kernel lowmem
1688 on "Classic" PPC cores.
1689
1690 nocache [ARM]
a9913044 1691
0cb55ad2
RD
1692 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1693
163ecdff
SN
1694 nodelayacct [KNL] Disable per-task delay accounting
1695
1da177e4
LT
1696 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1697
6902aa84
PM
1698 nodsp [SH] Disable hardware DSP at boot time.
1699
6cececfc 1700 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1701
1da177e4
LT
1702 noexec [IA-64]
1703
6cececfc 1704 noexec [X86]
f5a1b191 1705 On X86-32 available only on PAE configured kernels.
1da177e4 1706 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1707 noexec=off: disable non-executable mappings
1708
1709 noexec32 [X86-64]
1710 This affects only 32-bit executables.
1711 noexec32=on: enable non-executable mappings (default)
1712 read doesn't imply executable mappings
1713 noexec32=off: disable non-executable mappings
1714 read implies executable mappings
1da177e4 1715
6902aa84
PM
1716 nofpu [SH] Disable hardware FPU at boot time.
1717
cd4f0ef7 1718 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1719 register save and restore. The kernel will only save
1720 legacy floating-point registers on task switch.
1da177e4 1721
0c752a93
SS
1722 noxsave [BUGS=X86] Disables x86 extended register state save
1723 and restore using xsave. The kernel will fallback to
1724 enabling legacy floating-point and sse state.
1725
01a24d2b
PZ
1726 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1727 wfi(ARM) instruction doesn't work correctly and not to
1728 use it. This is also useful when using JTAG debugger.
a9913044 1729
cd4f0ef7 1730 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1731 instruction doesn't work correctly and not to
1732 use it.
1733
1f29fae2
SH
1734 no_file_caps Tells the kernel not to honor file capabilities. The
1735 only way then for a file to be executed with privilege
1736 is to be setuid root or executed by root.
1737
1da177e4
LT
1738 nohalt [IA-64] Tells the kernel not to use the power saving
1739 function PAL_HALT_LIGHT when idle. This increases
1740 power-consumption. On the positive side, it reduces
1741 interrupt wake-up latency, which may improve performance
1742 in certain environments such as networked servers or
1743 real-time systems.
1744
79bf2bb3
TG
1745 nohz= [KNL] Boottime enable/disable dynamic ticks
1746 Valid arguments: on, off
1747 Default: on
1748
eeee7853
PM
1749 noiotrap [SH] Disables trapped I/O port accesses.
1750
cd4f0ef7 1751 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1752 disable unhandled interrupt sources.
1753
6cececfc 1754 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1755 broken timer IRQ sources.
1756
1da177e4
LT
1757 noisapnp [ISAPNP] Disables ISA PnP code.
1758
1759 noinitrd [RAM] Tells the kernel not to load any configured
1760 initial RAM disk.
1761
03ea8155
WH
1762 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1763 remapping.
d1423d56 1764 [Deprecated - use intremap=off]
03ea8155 1765
1da177e4
LT
1766 nointroute [IA-64]
1767
0aa366f3
TL
1768 nojitter [IA64] Disables jitter checking for ITC timers.
1769
cd4f0ef7 1770 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1771
cd4f0ef7 1772 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1773
1da177e4
LT
1774 noltlbs [PPC] Do not use large page/tlb entries for kernel
1775 lowmem mapping on PPC40x.
1776
312f1f01
H
1777 nomca [IA-64] Disable machine check abort handling
1778
cd4f0ef7 1779 nomce [X86-32] Machine Check Exception
abe37e5a 1780
83d7384f
AS
1781 nomfgpt [X86-32] Disable Multi-Function General Purpose
1782 Timer usage (for AMD Geode machines).
1783
016ddd9b
JK
1784 nopat [X86] Disable PAT (page attribute table extension of
1785 pagetables) support.
1786
0cb55ad2
RD
1787 norandmaps Don't use address space randomization. Equivalent to
1788 echo 0 > /proc/sys/kernel/randomize_va_space
1789
cd4f0ef7 1790 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1791
cd4f0ef7 1792 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1793 with UP alternatives
1794
1da177e4
LT
1795 noresidual [PPC] Don't use residual data on PReP machines.
1796
a9913044
RD
1797 noresume [SWSUSP] Disables resume and restores original swap
1798 space.
1799
1da177e4
LT
1800 no-scroll [VGA] Disables scrollback.
1801 This is required for the Braillex ib80-piezo Braille
1802 reader made by F.H. Papenmeier (Germany).
1803
1804 nosbagart [IA-64]
1805
cd4f0ef7 1806 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1807
61ec7567
LB
1808 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1809 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1810
97842216
DJ
1811 nosoftlockup [KNL] Disable the soft-lockup detector.
1812
c077719b 1813 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1814 controller. (See Documentation/cgroups/memory.txt)
c077719b 1815
1da177e4
LT
1816 nosync [HW,M68K] Disables sync negotiation for all devices.
1817
cd4f0ef7 1818 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1819
1820 nousb [USB] Disable the USB subsystem
1821
1822 nowb [ARM]
a9913044 1823
2b2fd87a
WH
1824 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1825
a6c75b86
FY
1826 nptcg= [IA64] Override max number of concurrent global TLB
1827 purges which is reported from either PAL_VM_SUMMARY or
1828 SAL PALO.
1829
2b633e3f
YL
1830 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1831 could support. nr_cpus=n : n >= 1 limits the kernel to
1832 supporting 'n' processors. Later in runtime you can not
1833 use hotplug cpu feature to put more cpu back to online.
1834 just like you compile the kernel NR_CPUS=n
1835
0cb55ad2
RD
1836 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1837
f0c0b2b8
KH
1838 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1839 one of ['zone', 'node', 'default'] can be specified
1840 This can be set from sysctl after boot.
1841 See Documentation/sysctl/vm.txt for details.
1842
7c4be253
RD
1843 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1844 See Documentation/debugging-via-ohci1394.txt for more
1845 info.
1846
3ef0e1f8
AS
1847 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1848 Rather than timing out after 20 ms if an EC
1849 command is not properly ACKed, override the length
1850 of the timeout. We have interrupts disabled while
1851 waiting for the ACK, so if this is set too high
1852 interrupts *may* be lost!
1853
15ac7afe
TL
1854 omap_mux= [OMAP] Override bootloader pin multiplexing.
1855 Format: <mux_mode0.mode_name=value>...
1856 For example, to override I2C bus2:
1857 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1858
1da177e4
LT
1859 opl3= [HW,OSS]
1860 Format: <io>
1861
1da177e4
LT
1862 oprofile.timer= [HW]
1863 Use timer interrupt instead of performance counters
1864
7e4e0bd5
RR
1865 oprofile.cpu_type= Force an oprofile cpu type
1866 This might be useful if you have an older oprofile
1867 userland or if you want common events.
8d7ff4f2
RR
1868 Format: { arch_perfmon }
1869 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
1870 perfmon on Intel CPUs instead of the
1871 CPU specific event set.
1dcdb5a9 1872
1da177e4
LT
1873 osst= [HW,SCSI] SCSI Tape Driver
1874 Format: <buffer_size>,<write_threshold>
1875 See also Documentation/scsi/st.txt.
1876
1877 panic= [KNL] Kernel behaviour on panic
1878 Format: <timeout>
1879
1880 parkbd.port= [HW] Parallel port number the keyboard adapter is
1881 connected to, default is 0.
1882 Format: <parport#>
1883 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1884 0 for XT, 1 for AT (default is AT).
a9913044
RD
1885 Format: <mode>
1886
1887 parport= [HW,PPT] Specify parallel ports. 0 disables.
1888 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1889 Use 'auto' to force the driver to use any
1890 IRQ/DMA settings detected (the default is to
1891 ignore detected IRQ/DMA settings because of
1892 possible conflicts). You can specify the base
1893 address, IRQ, and DMA settings; IRQ and DMA
1894 should be numbers, or 'auto' (for using detected
1895 settings on that particular port), or 'nofifo'
1896 (to avoid using a FIFO even if it is detected).
1897 Parallel ports are assigned in the order they
1898 are specified on the command line, starting
1899 with parport0.
1900
1901 parport_init_mode= [HW,PPT]
1902 Configure VIA parallel port to operate in
1903 a specific mode. This is necessary on Pegasos
1904 computer where firmware has no options for setting
1905 up parallel port mode and sets it to spp.
1906 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1907 Format: [spp|ps2|epp|ecp|ecpepp]
1908
a9913044
RD
1909 pas2= [HW,OSS] Format:
1910 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1911
1da177e4
LT
1912 pas16= [HW,SCSI]
1913 See header of drivers/scsi/pas16.c.
1914
dd287796
AM
1915 pause_on_oops=
1916 Halt all CPUs after the first oops has been printed for
1917 the specified number of seconds. This is to be used if
1918 your oopses keep scrolling off the screen.
1919
1da177e4
LT
1920 pcbit= [HW,ISDN]
1921
1922 pcd. [PARIDE]
1923 See header of drivers/block/paride/pcd.c.
31c00fc1 1924 See also Documentation/blockdev/paride.txt.
1da177e4 1925
a9913044 1926 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1927 earlydump [X86] dump PCI config space before the kernel
1928 changes anything
c0115606 1929 off [X86] don't probe for the PCI bus
cd4f0ef7 1930 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1931 the hardware directly. Use this if your machine
1932 has a non-standard PCI host bridge.
cd4f0ef7 1933 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1934 hardware access methods are allowed. Use this
1935 if you experience crashes upon bootup and you
1936 suspect they are caused by the BIOS.
c0115606 1937 conf1 [X86] Force use of PCI Configuration
a9913044 1938 Mechanism 1.
c0115606 1939 conf2 [X86] Force use of PCI Configuration
a9913044 1940 Mechanism 2.
7f785763
RD
1941 noaer [PCIE] If the PCIEAER kernel config parameter is
1942 enabled, this kernel boot option can be used to
1943 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1944 nodomains [PCI] Disable support for multiple PCI
1945 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1946 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1947 Configuration
12983077
AH
1948 check_enable_amd_mmconf [X86] check for and enable
1949 properly configured MMIO access to PCI
1950 config space on AMD family 10h CPU
309e57df
MW
1951 nomsi [MSI] If the PCI_MSI kernel config parameter is
1952 enabled, this kernel boot option can be used to
1953 disable the use of MSI interrupts system-wide.
a9322f64
SA
1954 noioapicquirk [APIC] Disable all boot interrupt quirks.
1955 Safety option to keep boot IRQs enabled. This
1956 should never be necessary.
9197979b
SA
1957 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1958 primary IO-APIC for bridges that cannot disable
1959 boot IRQs. This fixes a source of spurious IRQs
1960 when the system masks IRQs.
41b9eb26
SA
1961 noioapicreroute [APIC] Disable workaround that uses the
1962 boot IRQ equivalent of an IRQ that connects to
1963 a chipset where boot IRQs cannot be disabled.
1964 The opposite of ioapicreroute.
cd4f0ef7 1965 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1966 routing table. These calls are known to be buggy
1967 on several machines and they hang the machine
1968 when used, but on other computers it's the only
1969 way to get the interrupt routing table. Try
1970 this option if the kernel is unable to allocate
1971 IRQs or discover secondary PCI buses on your
1972 motherboard.
c0115606 1973 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1974 Use with caution as certain devices share
1975 address decoders between ROMs and other
1976 resources.
c0115606 1977 norom [X86] Do not assign address space to
bb71ad88
GH
1978 expansion ROMs that do not already have
1979 BIOS assigned address ranges.
c0115606 1980 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1981 assigned automatically to PCI devices. You can
1982 make the kernel exclude IRQs of your ISA cards
1983 this way.
c0115606 1984 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1985 of the PIRQ table (normally generated
1986 by the BIOS) if it is outside the
1987 F0000h-100000h range.
c0115606 1988 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1989 useful if the kernel is unable to find your
1990 secondary buses and you want to tell it
1991 explicitly which ones they are.
c0115606 1992 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1993 numbers ourselves, overriding
1994 whatever the firmware may have done.
c0115606 1995 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1996 in the BIOS $PIR table. This is needed on
1997 some systems with broken BIOSes, notably
1998 some HP Pavilion N5400 and Omnibook XE3
1999 notebooks. This will have no effect if ACPI
2000 IRQ routing is enabled.
c0115606 2001 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 2002 or for PCI scanning.
7bc5e3f2
BH
2003 use_crs [X86] Use PCI host bridge window information
2004 from ACPI. On BIOSes from 2008 or later, this
2005 is enabled by default. If you need to use this,
2006 please report a bug.
2007 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2008 If you need to use this, please report a bug.
a9913044
RD
2009 routeirq Do IRQ routing for all PCI devices.
2010 This is normally done in pci_enable_device(),
2011 so this option is a temporary workaround
2012 for broken drivers that don't call it.
13a6ddb0
YL
2013 skip_isa_align [X86] do not align io start addr, so can
2014 handle more pci cards
a9913044
RD
2015 firmware [ARM] Do not re-enumerate the bus but instead
2016 just use the configuration from the
2017 bootloader. This is currently used on
2018 IXP2000 systems where the bus has to be
2019 configured a certain way for adjunct CPUs.
0637a70a
AK
2020 noearly [X86] Don't do any early type 1 scanning.
2021 This might help on some broken boards which
2022 machine check when some devices' config space
2023 is read. But various workarounds are disabled
2024 and some IOMMU drivers will not work.
6b4b78fe
MD
2025 bfsort Sort PCI devices into breadth-first order.
2026 This sorting is done to get a device
2027 order compatible with older (<= 2.4) kernels.
2028 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
2029 cbiosize=nn[KMG] The fixed amount of bus space which is
2030 reserved for the CardBus bridge's IO window.
2031 The default value is 256 bytes.
2032 cbmemsize=nn[KMG] The fixed amount of bus space which is
2033 reserved for the CardBus bridge's memory
2034 window. The default value is 64 megabytes.
32a9a682
YS
2035 resource_alignment=
2036 Format:
2037 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2038 Specifies alignment and device to reassign
2039 aligned memory resources.
2040 If <order of align> is not specified,
2041 PAGE_SIZE is used as alignment.
2042 PCI-PCI bridge can be specified, if resource
2043 windows need to be expanded.
43c16408
AP
2044 ecrc= Enable/disable PCIe ECRC (transaction layer
2045 end-to-end CRC checking).
2046 bios: Use BIOS/firmware settings. This is the
2047 the default.
2048 off: Turn ECRC off
2049 on: Turn ECRC on.
6b4b78fe 2050
e5665a45
CE
2051 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2052 Management.
2053 off Disable ASPM.
2054 force Enable ASPM even on devices that claim not to support it.
2055 WARNING: Forcing ASPM on may cause system lockups.
2056
c7f48656 2057 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
b27759f8
RW
2058 Format: {auto|force}[,nomsi]
2059 auto Use native PCIe PME signaling if the BIOS allows the
2060 kernel to control PCIe config registers of root ports.
c7f48656
RW
2061 force Use native PCIe PME signaling even if the BIOS refuses
2062 to allow the kernel to control the relevant PCIe config
2063 registers.
c39fae14
RW
2064 nomsi Do not use MSI for native PCIe PME signaling (this makes
2065 all PCIe root ports use INTx for everything).
c7f48656 2066
1da177e4
LT
2067 pcmv= [HW,PCMCIA] BadgePAD 4
2068
2069 pd. [PARIDE]
31c00fc1 2070 See Documentation/blockdev/paride.txt.
1da177e4
LT
2071
2072 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2073 boot time.
2074 Format: { 0 | 1 }
2075 See arch/parisc/kernel/pdc_chassis.c
2076
f58dc01b 2077 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2078 Currently supported values are "embed" and "page".
2079 Archs may support subset or none of the selections.
2080 See comments in mm/percpu.c for details on each
2081 allocator. This parameter is primarily for debugging
2082 and performance comparison.
fa8a7094 2083
1da177e4 2084 pf. [PARIDE]
31c00fc1 2085 See Documentation/blockdev/paride.txt.
1da177e4
LT
2086
2087 pg. [PARIDE]
31c00fc1 2088 See Documentation/blockdev/paride.txt.
1da177e4
LT
2089
2090 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2091 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2092
2093 plip= [PPT,NET] Parallel port network link
2094 Format: { parport<nr> | timid | 0 }
2095 See also Documentation/parport.txt.
2096
de32a243
TG
2097 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2098 Override pmtimer IOPort with a hex value.
2099 e.g. pmtmr=0x508
2100
97ef062b
BH
2101 pnp.debug [PNP]
2102 Enable PNP debug messages. This depends on the
2103 CONFIG_PNP_DEBUG_MESSAGES option.
2104
1da177e4
LT
2105 pnpacpi= [ACPI]
2106 { off }
2107
2108 pnpbios= [ISAPNP]
2109 { on | off | curr | res | no-curr | no-res }
2110
2111 pnp_reserve_irq=
2112 [ISAPNP] Exclude IRQs for the autoconfiguration
2113
2114 pnp_reserve_dma=
2115 [ISAPNP] Exclude DMAs for the autoconfiguration
2116
2117 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2118 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2119
2120 pnp_reserve_mem=
a9913044
RD
2121 [ISAPNP] Exclude memory regions for the
2122 autoconfiguration.
1da177e4
LT
2123 Ranges are in pairs (memory base and size).
2124
4af94f39
RD
2125 ports= [IP_VS_FTP] IPVS ftp helper module
2126 Default is 21.
2127 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2128 may be specified.
2129 Format: <port>,<port>....
2130
45807a1d
IM
2131 print-fatal-signals=
2132 [KNL] debug: print fatal signals
f84d49b2
NO
2133
2134 If enabled, warn about various signal handling
2135 related application anomalies: too many signals,
2136 too many POSIX.1 timers, fatal signals causing a
2137 coredump - etc.
2138
2139 If you hit the warning due to signal overflow,
2140 you might want to try "ulimit -i unlimited".
2141
45807a1d
IM
2142 default: off.
2143
e84845c4
RD
2144 printk.time= Show timing data prefixed to each printk message line
2145 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2146
0cb55ad2
RD
2147 processor.max_cstate= [HW,ACPI]
2148 Limit processor to maximum C-state
2149 max_cstate=9 overrides any DMI blacklist limit.
2150
2151 processor.nocst [HW,ACPI]
2152 Ignore the _CST method to determine C-states,
2153 instead using the legacy FADT method
2154
1da177e4 2155 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2156 Format: [schedule,]<number>
2157 Param: "schedule" - profile schedule points.
2158 Param: <number> - step/bucket size as a power of 2 for
2159 statistical time based profiling.
b3da2a73
MG
2160 Param: "sleep" - profile D-state sleeping (millisecs).
2161 Requires CONFIG_SCHEDSTATS
c0fe2e69 2162 Param: "kvm" - profile VM exits.
1da177e4 2163
1da177e4
LT
2164 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2165 before loading.
31c00fc1 2166 See Documentation/blockdev/ramdisk.txt.
1da177e4 2167
a9913044
RD
2168 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2169 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2170 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2171 per second.
a9913044
RD
2172 psmouse.resetafter= [HW,MOUSE]
2173 Try to reset the device after so many bad packets
1da177e4
LT
2174 (0 = never).
2175 psmouse.resolution=
2176 [HW,MOUSE] Set desired mouse resolution, in dpi.
2177 psmouse.smartscroll=
a9913044 2178 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2179 0 = disabled, 1 = enabled (default).
2180
2181 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
2182 Format:
2183 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
2184
2185 pt. [PARIDE]
31c00fc1 2186 See Documentation/blockdev/paride.txt.
1da177e4 2187
dc8c8587
KS
2188 pty.legacy_count=
2189 [KNL] Number of legacy pty's. Overwrites compiled-in
2190 default number.
2191
7d2c502f 2192 quiet [KNL] Disable most log messages
a9913044 2193
1da177e4
LT
2194 r128= [HW,DRM]
2195
2196 raid= [HW,RAID]
2197 See Documentation/md.txt.
2198
a9913044 2199 ramdisk_blocksize= [RAM]
31c00fc1 2200 See Documentation/blockdev/ramdisk.txt.
a9913044 2201
1da177e4 2202 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2203 See Documentation/blockdev/ramdisk.txt.
1da177e4 2204
24aaef8d
RD
2205 rcupdate.blimit= [KNL,BOOT]
2206 Set maximum number of finished RCU callbacks to process
2207 in one batch.
21a1ea9e 2208
24aaef8d
RD
2209 rcupdate.qhimark= [KNL,BOOT]
2210 Set threshold of queued
21a1ea9e
DS
2211 RCU callbacks over which batch limiting is disabled.
2212
24aaef8d
RD
2213 rcupdate.qlowmark= [KNL,BOOT]
2214 Set threshold of queued RCU callbacks below which
2215 batch limiting is re-enabled.
21a1ea9e 2216
ffdfc409
OJ
2217 rdinit= [KNL]
2218 Format: <full_path>
2219 Run specified binary instead of /init from the ramdisk,
2220 used for early userspace startup. See initrd.
2221
cd4f0ef7 2222 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2223 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2224 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2225
46b6d94e
PJ
2226 relax_domain_level=
2227 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2228 See Documentation/cgroups/cpusets.txt.
46b6d94e 2229
1da177e4
LT
2230 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2231
cd4f0ef7 2232 reservetop= [X86-32]
461a9aff
ZA
2233 Format: nn[KMG]
2234 Reserves a hole at the top of the kernel virtual
2235 address space.
2236
7e96287d
VG
2237 reset_devices [KNL] Force drivers to reset the underlying device
2238 during initialization.
2239
a9913044
RD
2240 resume= [SWSUSP]
2241 Specify the partition device for software suspend
1da177e4 2242
ecbd0da1
RW
2243 resume_offset= [SWSUSP]
2244 Specify the offset from the beginning of the partition
2245 given by "resume=" at which the swap header is located,
2246 in <PAGE_SIZE> units (needed only for swap files).
2247 See Documentation/power/swsusp-and-swap-files.txt
2248
0a7b35cb
MN
2249 retain_initrd [RAM] Keep initrd memory after extraction
2250
1da177e4
LT
2251 rhash_entries= [KNL,NET]
2252 Set number of hash buckets for route cache
2253
2254 riscom8= [HW,SERIAL]
2255 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2256
2257 ro [KNL] Mount root device read-only on boot
2258
2259 root= [KNL] Root filesystem
2260
2261 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2262 mount the root filesystem
2263
2264 rootflags= [KNL] Set root filesystem mount option string
2265
2266 rootfstype= [KNL] Set root filesystem type
2267
cc1ed754
PO
2268 rootwait [KNL] Wait (indefinitely) for root device to show up.
2269 Useful for devices that are detected asynchronously
2270 (e.g. USB and MMC devices).
2271
1da177e4
LT
2272 rw [KNL] Mount root device read-write on boot
2273
2274 S [KNL] Run init in single mode
2275
2276 sa1100ir [NET]
2277 See drivers/net/irda/sa1100_ir.c.
2278
1da177e4 2279 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2280
f6630114
MT
2281 sched_debug [KNL] Enables verbose scheduler debug messages.
2282
1da177e4
LT
2283 scsi_debug_*= [SCSI]
2284 See drivers/scsi/scsi_debug.c.
2285
2286 scsi_default_dev_flags=
2287 [SCSI] SCSI default device flags
2288 Format: <integer>
2289
2290 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2291 Format: <vendor>:<model>:<flags>
2292 (flags are integer value)
2293
6af6632a
RD
2294 scsi_logging_level= [SCSI] a bit mask of logging levels
2295 See drivers/scsi/scsi_logging.h for bits. Also
2296 settable via sysctl at dev.scsi.logging_level
2297 (/proc/sys/dev/scsi/logging_level).
2298 There is also a nice 'scsi_logging_level' script in the
2299 S390-tools package, available for download at
2300 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 2301
3e082a91
MW
2302 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2303 discovered. async scans them in kernel threads,
2304 allowing boot to proceed. none ignores them, expecting
2305 user space to do the scan.
2306
0cb55ad2
RD
2307 security= [SECURITY] Choose a security module to enable at boot.
2308 If this boot parameter is not specified, only the first
2309 security module asking for security registration will be
2310 loaded. An invalid security module name will be treated
2311 as if no module has been chosen.
2312
2313 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2314 Format: { "0" | "1" }
2315 See security/selinux/Kconfig help text.
2316 0 -- disable.
2317 1 -- enable.
2318 Default value is set via kernel config option.
2319 If enabled at boot time, /selinux/disable can be used
2320 later to disable prior to initial policy load.
2321
cd4f0ef7 2322 serialnumber [BUGS=X86-32]
1da177e4 2323
1da177e4
LT
2324 shapers= [NET]
2325 Maximal number of shapers.
a9913044 2326
b05f78f5
YL
2327 show_msr= [x86] show boot-time MSR settings
2328 Format: { <integer> }
2329 Show boot-time (BIOS-initialized) MSR settings.
2330 The parameter means the number of CPUs to show,
2331 for example 1 means boot CPU only.
2332
1da177e4
LT
2333 sim710= [SCSI,HW]
2334 See header of drivers/scsi/sim710.c.
2335
2336 simeth= [IA-64]
2337 simscsi=
a9913044 2338
1da177e4
LT
2339 slram= [HW,MTD]
2340
f0630fff
CL
2341 slub_debug[=options[,slabs]] [MM, SLUB]
2342 Enabling slub_debug allows one to determine the
2343 culprit if slab objects become corrupted. Enabling
2344 slub_debug can create guard zones around objects and
2345 may poison objects when not in use. Also tracks the
2346 last alloc / free. For more information see
2347 Documentation/vm/slub.txt.
c1aee215
CL
2348
2349 slub_max_order= [MM, SLUB]
f0630fff
CL
2350 Determines the maximum allowed order for slabs.
2351 A high setting may cause OOMs due to memory
2352 fragmentation. For more information see
2353 Documentation/vm/slub.txt.
c1aee215
CL
2354
2355 slub_min_objects= [MM, SLUB]
f0630fff
CL
2356 The minimum number of objects per slab. SLUB will
2357 increase the slab order up to slub_max_order to
2358 generate a sufficiently large slab able to contain
2359 the number of objects indicated. The higher the number
2360 of objects the smaller the overhead of tracking slabs
2361 and the less frequently locks need to be acquired.
c1aee215
CL
2362 For more information see Documentation/vm/slub.txt.
2363
2364 slub_min_order= [MM, SLUB]
2365 Determines the mininum page order for slabs. Must be
f0630fff 2366 lower than slub_max_order.
c1aee215
CL
2367 For more information see Documentation/vm/slub.txt.
2368
2369 slub_nomerge [MM, SLUB]
f0630fff 2370 Disable merging of slabs with similar size. May be
c1aee215 2371 necessary if there is some reason to distinguish
f0630fff
CL
2372 allocs to different slabs. Debug options disable
2373 merging on their own.
c1aee215
CL
2374 For more information see Documentation/vm/slub.txt.
2375
1da177e4
LT
2376 smart2= [HW]
2377 Format: <io1>[,<io2>[,...,<io8>]]
2378
cd4f0ef7 2379 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2380 attempt to substitute SMP alternatives once at boot.
2381
d0d4f69b
BH
2382 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2383 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2384 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2385 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2386 smsc-ircc2.ircc_irq= [HW] IRQ line
2387 smsc-ircc2.ircc_dma= [HW] DMA channel
2388 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2389 0: Toshiba Satellite 1800 (GP data pin select)
2390 1: Fast pin select (default)
2391 2: ATC IRMode
2392
1da177e4
LT
2393 snd-ad1816a= [HW,ALSA]
2394
2395 snd-ad1848= [HW,ALSA]
2396
2397 snd-ali5451= [HW,ALSA]
2398
2399 snd-als100= [HW,ALSA]
2400
2401 snd-als4000= [HW,ALSA]
2402
2403 snd-azt2320= [HW,ALSA]
2404
2405 snd-cmi8330= [HW,ALSA]
2406
2407 snd-cmipci= [HW,ALSA]
2408
2409 snd-cs4231= [HW,ALSA]
2410
2411 snd-cs4232= [HW,ALSA]
2412
2413 snd-cs4236= [HW,ALSA]
2414
2415 snd-cs4281= [HW,ALSA]
2416
2417 snd-cs46xx= [HW,ALSA]
2418
2419 snd-dt019x= [HW,ALSA]
2420
2421 snd-dummy= [HW,ALSA]
2422
2423 snd-emu10k1= [HW,ALSA]
2424
2425 snd-ens1370= [HW,ALSA]
2426
2427 snd-ens1371= [HW,ALSA]
2428
2429 snd-es968= [HW,ALSA]
2430
2431 snd-es1688= [HW,ALSA]
2432
2433 snd-es18xx= [HW,ALSA]
2434
2435 snd-es1938= [HW,ALSA]
2436
2437 snd-es1968= [HW,ALSA]
2438
2439 snd-fm801= [HW,ALSA]
2440
2441 snd-gusclassic= [HW,ALSA]
2442
2443 snd-gusextreme= [HW,ALSA]
2444
2445 snd-gusmax= [HW,ALSA]
2446
2447 snd-hdsp= [HW,ALSA]
2448
2449 snd-ice1712= [HW,ALSA]
2450
2451 snd-intel8x0= [HW,ALSA]
2452
2453 snd-interwave= [HW,ALSA]
2454
2455 snd-interwave-stb=
2456 [HW,ALSA]
2457
2458 snd-korg1212= [HW,ALSA]
2459
2460 snd-maestro3= [HW,ALSA]
2461
2462 snd-mpu401= [HW,ALSA]
2463
2464 snd-mtpav= [HW,ALSA]
2465
2466 snd-nm256= [HW,ALSA]
2467
2468 snd-opl3sa2= [HW,ALSA]
2469
2470 snd-opti92x-ad1848=
2471 [HW,ALSA]
2472
2473 snd-opti92x-cs4231=
2474 [HW,ALSA]
2475
2476 snd-opti93x= [HW,ALSA]
2477
2478 snd-pmac= [HW,ALSA]
2479
2480 snd-rme32= [HW,ALSA]
2481
2482 snd-rme96= [HW,ALSA]
2483
2484 snd-rme9652= [HW,ALSA]
2485
2486 snd-sb8= [HW,ALSA]
2487
2488 snd-sb16= [HW,ALSA]
2489
2490 snd-sbawe= [HW,ALSA]
2491
2492 snd-serial= [HW,ALSA]
2493
2494 snd-sgalaxy= [HW,ALSA]
2495
2496 snd-sonicvibes= [HW,ALSA]
2497
2498 snd-sun-amd7930=
2499 [HW,ALSA]
2500
2501 snd-sun-cs4231= [HW,ALSA]
2502
2503 snd-trident= [HW,ALSA]
2504
2505 snd-usb-audio= [HW,ALSA,USB]
2506
2507 snd-via82xx= [HW,ALSA]
2508
2509 snd-virmidi= [HW,ALSA]
2510
2511 snd-wavefront= [HW,ALSA]
2512
2513 snd-ymfpci= [HW,ALSA]
a9913044 2514
9c44bc03
IM
2515 softlockup_panic=
2516 [KNL] Should the soft-lockup detector generate panics.
2517
1da177e4
LT
2518 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2519 See Documentation/sonypi.txt
2520
2521 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2522 See Documentation/serial/specialix.txt.
1da177e4
LT
2523
2524 spia_io_base= [HW,MTD]
2525 spia_fio_base=
2526 spia_pedr=
2527 spia_peddr=
2528
2529 sscape= [HW,OSS]
2530 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2531
1da177e4
LT
2532 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2533 See Documentation/scsi/st.txt.
2534
f38f1d2a
SR
2535 stacktrace [FTRACE]
2536 Enabled the stack tracer on boot up.
2537
1da177e4
LT
2538 sti= [PARISC,HW]
2539 Format: <num>
2540 Set the STI (builtin display/keyboard on the HP-PARISC
2541 machines) console (graphic card) which should be used
2542 as the initial boot-console.
2543 See also comment in drivers/video/console/sticore.c.
2544
2545 sti_font= [HW]
2546 See comment in drivers/video/console/sticore.c.
2547
2548 stifb= [HW]
2549 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2550
cbf11071
TM
2551 sunrpc.min_resvport=
2552 sunrpc.max_resvport=
2553 [NFS,SUNRPC]
2554 SunRPC servers often require that client requests
2555 originate from a privileged port (i.e. a port in the
2556 range 0 < portnr < 1024).
2557 An administrator who wishes to reserve some of these
2558 ports for other uses may adjust the range that the
2559 kernel's sunrpc client considers to be privileged
2560 using these two parameters to set the minimum and
2561 maximum port values.
2562
42a7fc4a
GB
2563 sunrpc.pool_mode=
2564 [NFS]
2565 Control how the NFS server code allocates CPUs to
2566 service thread pools. Depending on how many NICs
2567 you have and where their interrupts are bound, this
2568 option will affect which CPUs will do NFS serving.
2569 Note: this parameter cannot be changed while the
2570 NFS server is running.
2571
2572 auto the server chooses an appropriate mode
2573 automatically using heuristics
2574 global a single global pool contains all CPUs
2575 percpu one pool for each CPU
2576 pernode one pool for each NUMA node (equivalent
2577 to global on non-NUMA machines)
2578
cbf11071
TM
2579 sunrpc.tcp_slot_table_entries=
2580 sunrpc.udp_slot_table_entries=
2581 [NFS,SUNRPC]
2582 Sets the upper limit on the number of simultaneous
2583 RPC calls that can be sent from the client to a
2584 server. Increasing these values may allow you to
2585 improve throughput, but will also increase the
2586 amount of memory reserved for use by the client.
2587
1da177e4 2588 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2589
1da177e4
LT
2590 switches= [HW,M68k]
2591
2592 sym53c416= [HW,SCSI]
2593 See header of drivers/scsi/sym53c416.c.
2594
5d6f647f
IM
2595 sysrq_always_enabled
2596 [KNL]
2597 Ignore sysrq setting - this boot parameter will
2598 neutralize any effect of /proc/sys/kernel/sysrq.
2599 Useful for debugging.
2600
1da177e4
LT
2601 t128= [HW,SCSI]
2602 See header of drivers/scsi/t128.c.
2603
2604 tdfx= [HW,DRM]
2605
77437fd4
DB
2606 test_suspend= [SUSPEND]
2607 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2608 standby suspend) as the system sleep state to briefly
2609 enter during system startup. The system is woken from
2610 this state using a wakeup-capable RTC alarm.
2611
1da177e4
LT
2612 thash_entries= [KNL,NET]
2613 Set number of hash buckets for TCP connection
2614
f8707ec9
LB
2615 thermal.act= [HW,ACPI]
2616 -1: disable all active trip points in all thermal zones
2617 <degrees C>: override all lowest active trip points
2618
c52a7419
LB
2619 thermal.crt= [HW,ACPI]
2620 -1: disable all critical trip points in all thermal zones
22a94d79 2621 <degrees C>: override all critical trip points
c52a7419 2622
f5487145
LB
2623 thermal.nocrt= [HW,ACPI]
2624 Set to disable actions on ACPI thermal zone
2625 critical and hot trip points.
2626
72b33ef8
LB
2627 thermal.off= [HW,ACPI]
2628 1: disable ACPI thermal control
2629
a70cdc52
LB
2630 thermal.psv= [HW,ACPI]
2631 -1: disable all passive trip points
ada9cfdd
RD
2632 <degrees C>: override all passive trip points to this
2633 value
a70cdc52 2634
730ff34d
LB
2635 thermal.tzp= [HW,ACPI]
2636 Specify global default ACPI thermal zone polling rate
2637 <deci-seconds>: poll all this frequency
2638 0: no polling (default)
2639
1da177e4
LT
2640 tmscsim= [HW,SCSI]
2641 See comment before function dc390_setup() in
2642 drivers/scsi/tmscsim.c.
2643
2b1a61f0
HC
2644 topology= [S390]
2645 Format: {off | on}
2646 Specify if the kernel should make use of the cpu
2647 topology informations if the hardware supports these.
2648 The scheduler will make use of these informations and
2649 e.g. base its process migration decisions on it.
2650 Default is off.
2651
1da177e4
LT
2652 tp720= [HW,PS2]
2653
225a9be2
RA
2654 tpm_suspend_pcr=[HW,TPM]
2655 Format: integer pcr id
2656 Specify that at suspend time, the tpm driver
2657 should extend the specified pcr with zeros,
2658 as a workaround for some chips which fail to
2659 flush the last written pcr on TPM_SaveState.
2660 This will guarantee that all the other pcrs
2661 are saved.
2662
9d612bef
LZ
2663 trace_buf_size=nn[KMG]
2664 [FTRACE] will set tracing buffer size.
631595fb 2665
020e5f85
LZ
2666 trace_event=[event-list]
2667 [FTRACE] Set and start specified trace events in order
2668 to facilitate early boot debugging.
2669 See also Documentation/trace/events.txt
2670
1da177e4 2671 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2672 Format:
2673 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2674
395628ef
AK
2675 tsc= Disable clocksource-must-verify flag for TSC.
2676 Format: <string>
2677 [x86] reliable: mark tsc clocksource as reliable, this
2678 disables clocksource verification at runtime.
2679 Used to enable high-resolution timer mode on older
2680 hardware, and in virtualized environment.
2681
a9913044
RD
2682 turbografx.map[2|3]= [HW,JOY]
2683 TurboGraFX parallel port interface
2684 Format:
2685 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2686 See also Documentation/input/joystick-parport.txt
2687
2688 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2689 See header of drivers/scsi/u14-34f.c.
2690
2691 uart401= [HW,OSS]
2692 Format: <io>,<irq>
2693
2694 uart6850= [HW,OSS]
2695 Format: <io>,<irq>
2696
f86dcc5a
ED
2697 uhash_entries= [KNL,NET]
2698 Set number of hash buckets for UDP/UDP-Lite connections
2699
5f8364b7
AS
2700 uhci-hcd.ignore_oc=
2701 [USB] Ignore overcurrent events (default N).
2702 Some badly-designed motherboards generate lots of
2703 bogus events, for ports that aren't wired to
2704 anything. Set this parameter to avoid log spamming.
2705 Note that genuine overcurrent events won't be
2706 reported either.
2707
e3a61b0a 2708 unknown_nmi_panic
6cececfc 2709 [X86]
e3a61b0a
SA
2710 Set unknown_nmi_panic=1 early on boot.
2711
b5e795f8
AS
2712 usbcore.autosuspend=
2713 [USB] The autosuspend time delay (in seconds) used
2714 for newly-detected USB devices (default 2). This
2715 is the time required before an idle device will be
2716 autosuspended. Devices for which the delay is set
eaafbc3a 2717 to a negative value won't be autosuspended at all.
b5e795f8 2718
fd7c519d
JK
2719 usbcore.usbfs_snoop=
2720 [USB] Set to log all usbfs traffic (default 0 = off).
2721
2722 usbcore.blinkenlights=
2723 [USB] Set to cycle leds on hubs (default 0 = off).
2724
2725 usbcore.old_scheme_first=
2726 [USB] Start with the old device initialization
2727 scheme (default 0 = off).
2728
2729 usbcore.use_both_schemes=
2730 [USB] Try the other device initialization scheme
2731 if the first one fails (default 1 = enabled).
2732
2733 usbcore.initial_descriptor_timeout=
2734 [USB] Specifies timeout for the initial 64-byte
2735 USB_REQ_GET_DESCRIPTOR request in milliseconds
2736 (default 5000 = 5.0 seconds).
2737
1da177e4
LT
2738 usbhid.mousepoll=
2739 [USBHID] The interval which mice are to be polled at.
a9913044 2740
d4f373e5
AS
2741 usb-storage.delay_use=
2742 [UMS] The delay in seconds before a new device is
2743 scanned for Logical Units (default 5).
2744
2745 usb-storage.quirks=
2746 [UMS] A list of quirks entries to supplement or
2747 override the built-in unusual_devs list. List
2748 entries are separated by commas. Each entry has
2749 the form VID:PID:Flags where VID and PID are Vendor
2750 and Product ID values (4-digit hex numbers) and
2751 Flags is a set of characters, each corresponding
2752 to a common usb-storage quirk flag as follows:
c838ea46
AS
2753 a = SANE_SENSE (collect more than 18 bytes
2754 of sense data);
a0bb1081
AS
2755 b = BAD_SENSE (don't collect more than 18
2756 bytes of sense data);
d4f373e5
AS
2757 c = FIX_CAPACITY (decrease the reported
2758 device capacity by one sector);
c838ea46
AS
2759 h = CAPACITY_HEURISTICS (decrease the
2760 reported device capacity by one
2761 sector if the number is odd);
d4f373e5
AS
2762 i = IGNORE_DEVICE (don't bind to this
2763 device);
2764 l = NOT_LOCKABLE (don't try to lock and
2765 unlock ejectable media);
2766 m = MAX_SECTORS_64 (don't transfer more
2767 than 64 sectors = 32 KB at a time);
c838ea46
AS
2768 o = CAPACITY_OK (accept the capacity
2769 reported by the device);
d4f373e5
AS
2770 r = IGNORE_RESIDUE (the device reports
2771 bogus residue values);
2772 s = SINGLE_LUN (the device has only one
2773 Logical Unit);
2774 w = NO_WP_DETECT (don't test whether the
2775 medium is write-protected).
2776 Example: quirks=0419:aaf5:rl,0421:0433:rc
2777
14315592
IC
2778 userpte=
2779 [X86] Flags controlling user PTE allocations.
2780
2781 nohigh = do not allocate PTE pages in
2782 HIGHMEM regardless of setting
2783 of CONFIG_HIGHPTE.
2784
6cececfc 2785 vdso= [X86,SH]
1dbf527c 2786 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2787 vdso=1: enable VDSO (default)
2788 vdso=0: disable VDSO mapping
2789
6cececfc 2790 vdso32= [X86]
af65d648
RM
2791 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2792 vdso32=1: enable 32-bit VDSO (default)
2793 vdso32=0: disable 32-bit VDSO mapping
2794
d080d397
YI
2795 vector= [IA-64,SMP]
2796 vector=percpu: enable percpu vector domain
2797
1da177e4
LT
2798 video= [FB] Frame buffer configuration
2799 See Documentation/fb/modedb.txt.
2800
cd4f0ef7 2801 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2802 See Documentation/x86/boot.txt and
a9913044 2803 Documentation/svga.txt.
1da177e4
LT
2804 Use vga=ask for menu.
2805 This is actually a boot loader parameter; the value is
2806 passed to the kernel using a special protocol.
2807
a9913044 2808 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2809 size of <nn>. This can be used to increase the
2810 minimum size (128MB on x86). It can also be used to
2811 decrease the size and leave more room for directly
2812 mapped kernel RAM.
2813
585c3047
PO
2814 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2815 Format: <command>
1da177e4 2816
585c3047
PO
2817 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2818 Format: <command>
2819
2820 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2821 Format: <command>
a9913044 2822
9ea9a886
CL
2823 vt.cur_default= [VT] Default cursor shape.
2824 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2825 the parameters of the <Esc>[?A;B;Cc escape sequence;
2826 see VGA-softcursor.txt. Default: 2 = underline.
2827
0cb55ad2
RD
2828 vt.default_blu= [VT]
2829 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2830 Change the default blue palette of the console.
2831 This is a 16-member array composed of values
2832 ranging from 0-255.
2833
2834 vt.default_grn= [VT]
2835 Format: <green0>,<green1>,<green2>,...,<green15>
2836 Change the default green palette of the console.
2837 This is a 16-member array composed of values
2838 ranging from 0-255.
2839
2840 vt.default_red= [VT]
2841 Format: <red0>,<red1>,<red2>,...,<red15>
2842 Change the default red palette of the console.
2843 This is a 16-member array composed of values
2844 ranging from 0-255.
2845
2846 vt.default_utf8=
2847 [VT]
2848 Format=<0|1>
2849 Set system-wide default UTF-8 mode for all tty's.
2850 Default is 1, i.e. UTF-8 mode is enabled for all
2851 newly opened terminals.
2852
f6c06b68
MG
2853 vt.global_cursor_default=
2854 [VT]
2855 Format=<-1|0|1>
2856 Set system-wide default for whether a cursor
2857 is shown on new VTs. Default is -1,
2858 i.e. cursors will be created by default unless
2859 overridden by individual drivers. 0 will hide
2860 cursors, 1 will display them.
2861
1da177e4
LT
2862 waveartist= [HW,OSS]
2863 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2864
1da177e4
LT
2865 wd33c93= [HW,SCSI]
2866 See header of drivers/scsi/wd33c93.c.
2867
2868 wd7000= [HW,SCSI]
2869 See header of drivers/scsi/wd7000.c.
2870
4724ba57
RD
2871 watchdog timers [HW,WDT] For information on watchdog timers,
2872 see Documentation/watchdog/watchdog-parameters.txt
2873 or other driver-specific files in the
2874 Documentation/watchdog/ directory.
1da177e4 2875
0cb55ad2
RD
2876 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2877 default x2apic cluster mode on platforms
2878 supporting x2apic.
2879
bb24c471
JP
2880 x86_mrst_timer= [X86-32,APBT]
2881 Choose timer option for x86 Moorestown MID platform.
2882 Two valid options are apbt timer only and lapic timer
2883 plus one apbt timer for broadcast timer.
2884 x86_mrst_timer=apbt_only | lapic_and_apbt
2885
1da177e4
LT
2886 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2887 xd_geo= See header of drivers/block/xd.c.
2888
2889 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2890 Format:
2891 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2892
a9913044 2893______________________________________________________________________
1da177e4
LT
2894
2895TODO:
2896
2897 Add documentation for ALSA options.
2898 Add more DRM drivers.