drivers: power: report battery voltage in AOSP compatible format
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / kernel-parameters.txt
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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.
16290246 43 ARM ARM architecture is enabled.
e7ba176b 44 AVR32 AVR32 architecture is enabled.
1da177e4 45 AX25 Appropriate AX.25 support is enabled.
0ae53640 46 BLACKFIN Blackfin architecture is enabled.
1e435256 47 CLK Common clock infrastructure is enabled.
5c71d618 48 CMA Contiguous Memory Area support is enabled.
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49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
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51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
7102ebcd 54 EVM Extended Verification Module
1da177e4 55 FB The frame buffer device is enabled.
16290246 56 FTRACE Function tracing enabled.
2521f2c2 57 GCOV GCOV profiling is enabled.
1da177e4 58 HW Appropriate hardware is enabled.
1da177e4 59 IA-64 IA-64 architecture is enabled.
6146f0d5 60 IMA Integrity measurement architecture is enabled.
1da177e4 61 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 63 IPV6 IPv6 support is enabled.
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64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
84c08fd6 67 KGDB Kernel debugger support is enabled.
fef07aae 68 KVM Kernel Virtual Machine support is enabled.
11ef697b 69 LIBATA Libata driver is enabled
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70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
1da177e4 75 MDA MDA console support is enabled.
16290246 76 MIPS MIPS architecture is enabled.
1da177e4 77 MOUSE Appropriate mouse support is enabled.
309e57df 78 MSI Message Signaled Interrupts (PCI).
c8facbb6 79 MTD MTD (Memory Technology Device) support is enabled.
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80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
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84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
7f785763 88 PCIE PCI Express support is enabled.
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89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
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97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
20510f2f 99 SECURITY Different security models are enabled.
1da177e4 100 SELINUX SELinux support is enabled.
c1c124e9 101 APPARMOR AppArmor support is enabled.
1da177e4 102 SERIAL Serial support is enabled.
e523d93c 103 SH SuperH architecture is enabled.
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104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
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106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
225a9be2 108 TPM TPM drivers are enabled.
1da177e4 109 TS Appropriate touchscreen support is enabled.
d4f373e5 110 UMS USB Mass Storage support is enabled.
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111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
81a054ce 114 VMMIO Driver for memory mapped virtio devices is enabled.
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115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 119 X86-32 X86-32, aka i386 architecture is enabled.
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120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
71cced6e 122 Documentation/x86/x86_64/boot-options.txt .
16290246 123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
c1c5413a 124 XEN Xen support is enabled
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125
126In addition, the following text indicates that the option:
127
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
131
132Parameters denoted with BOOT are actually interpreted by the boot
133loader, and have no meaning to the kernel directly.
134Do not modify the syntax of boot loader parameters without extreme
954a8b81 135need or coordination with <Documentation/x86/boot.txt>.
1da177e4 136
5558870b 137There are also arch-specific kernel-parameters not documented here.
71cced6e 138See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 139
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140Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141a trailing = on the name of any parameter states that that parameter will
142be entered as an environment variable, whereas its absence indicates that
143it will appear as a kernel argument readable via /proc/cmdline by programs
144running once the system is up.
145
9c4751fd 146The number of kernel parameters is not limited, but the length of the
147complete command line (parameters including spaces etc.) is limited to
148a fixed number of characters. This limit depends on the architecture
149and is between 256 and 4096 characters. It is defined in the file
150./include/asm/setup.h as COMMAND_LINE_SIZE.
151
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152Finally, the [KMG] suffix is commonly described after a number of kernel
153parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155bytes respectively. Such letter suffixes can also be entirely omitted.
156
9c4751fd 157
6cececfc 158 acpi= [HW,ACPI,X86]
03d926f8 159 Advanced Configuration and Power Interface
68ca4069 160 Format: { force | off | strict | noirq | rsdt }
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161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
a9913044 164 strict -- Be less tolerant of platforms that are not
1da177e4 165 strictly ACPI specification compliant.
237889bf 166 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 167 copy_dsdt -- copy DSDT to memory
1da177e4 168
395cf969 169 See also Documentation/power/runtime_pm.txt, pci=noacpi
1da177e4 170
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171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
175
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176 acpi_apic_instance= [ACPI, IOAPIC]
177 Format: <int>
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
4e381a4f 180 default: 0
a1fdcc0d 181
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182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
184 acpi_backlight=video
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
188
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189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 191 Format: <int>
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192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
a0d84a92 202
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203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
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207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
f989106c 216
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217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
219 default in APIC mode
220
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
223 default in PIC mode
224
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
227
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
229 use by PCI
230 Format: <irq>,<irq>...
231
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
233
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
236
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1 -- only one string
239 acpi_osi="!string2" # remove built-in string2
240 acpi_osi= # disable all strings
241
6cececfc 242 acpi_pm_good [X86]
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243 Override the pmtimer bug detection: force the kernel
244 to assume that this machine's pmtimer latches its value
245 and always returns good values.
246
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247 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
248 Format: { level | edge | high | low }
249
250 acpi_serialize [HW,ACPI] force serialization of AML methods
251
252 acpi_skip_timer_override [HW,ACPI]
253 Recognize and ignore IRQ0/pin2 Interrupt Override.
254 For broken nForce2 BIOS resulting in XT-PIC timer.
255
256 acpi_sleep= [HW,ACPI] Sleep options
257 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
c3b0795c 258 old_ordering, nonvs, sci_force_enable }
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259 See Documentation/power/video.txt for information on
260 s3_bios and s3_mode.
261 s3_beep is for debugging; it makes the PC's speaker beep
262 as soon as the kernel's real-mode entry point is called.
263 s4_nohwsig prevents ACPI hardware signature from being
264 used during resume from hibernation.
265 old_ordering causes the ACPI 1.0 ordering of the _PTS
266 control method, with respect to putting devices into
267 low power states, to be enforced (the ACPI 2.0 ordering
268 of _PTS is used by default).
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269 nonvs prevents the kernel from saving/restoring the
270 ACPI NVS memory during suspend/hibernation and resume.
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271 sci_force_enable causes the kernel to set SCI_EN directly
272 on resume from S1/S3 (which is against the ACPI spec,
273 but some broken systems don't work without it).
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274
275 acpi_use_timer_override [HW,ACPI]
276 Use timer override. For some broken Nvidia NF5 boards
277 that require a timer override, but don't have HPET
278
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279 acpi_enforce_resources= [ACPI]
280 { strict | lax | no }
281 Check for resource conflicts between native drivers
282 and ACPI OperationRegions (SystemIO and SystemMemory
283 only). IO ports and memory declared in ACPI might be
284 used by the ACPI subsystem in arbitrary AML code and
285 can interfere with legacy drivers.
286 strict (default): access to resources claimed by ACPI
287 is denied; legacy drivers trying to access reserved
288 resources will fail to bind to device using them.
289 lax: access to resources claimed by ACPI is allowed;
290 legacy drivers trying to access reserved resources
291 will bind successfully but a warning message is logged.
292 no: ACPI OperationRegions are not marked as reserved,
293 no further checks are performed.
294
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295 add_efi_memmap [EFI; X86] Include EFI memory map in
296 kernel's map of available physical RAM.
297
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298 agp= [AGP]
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
303
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304 ALSA [HW,ALSA]
305 See Documentation/sound/alsa/alsa-parameters.txt
306
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307 alignment= [KNL,ARM]
308 Allow the default userspace alignment fault handler
309 behaviour to be specified. Bit 0 enables warnings,
310 bit 1 enables fixups, and bit 2 sends a segfault.
311
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312 align_va_addr= [X86-64]
313 Align virtual addresses by clearing slice [14:12] when
314 allocating a VMA at process creation time. This option
315 gives you up to 3% performance improvement on AMD F15h
316 machines (where it is enabled by default) for a
317 CPU-intensive style benchmark, and it can vary highly in
318 a microbenchmark depending on workload and compiler.
319
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320 32: only for 32-bit processes
321 64: only for 64-bit processes
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322 on: enable for both 32- and 64-bit processes
323 off: disable for both 32- and 64-bit processes
324
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325 alloc_snapshot [FTRACE]
326 Allocate the ftrace snapshot buffer on boot up when the
327 main buffer is allocated. This is handy if debugging
328 and you need to use tracing_snapshot() on boot up, and
329 do not want to use tracing_snapshot_alloc() as it needs
330 to be done where GFP_KERNEL allocations are allowed.
331
89e0b9a3 332 amd_iommu= [HW,X86-64]
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333 Pass parameters to the AMD IOMMU driver in the system.
334 Possible values are:
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335 fullflush - enable flushing of IO/TLB entries when
336 they are unmapped. Otherwise they are
337 flushed before they will be reused, which
338 is a lot of faster
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339 off - do not initialize any AMD IOMMU found in
340 the system
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341 force_isolation - Force device isolation for all
342 devices. The IOMMU driver is not
343 allowed anymore to lift isolation
344 requirements as needed. This option
345 does not override iommu=pt
afa9fdc2 346
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347 amd_iommu_dump= [HW,X86-64]
348 Enable AMD IOMMU driver option to dump the ACPI table
349 for AMD IOMMU. With this option enabled, AMD IOMMU
350 driver will print ACPI tables for AMD IOMMU during
351 IOMMU initialization.
352
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353 amijoy.map= [HW,JOY] Amiga joystick support
354 Map of devices attached to JOY0DAT and JOY1DAT
355 Format: <a>,<b>
395cf969 356 See also Documentation/input/joystick.txt
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357
358 analog.map= [HW,JOY] Analog joystick and gamepad support
359 Specifies type or capabilities of an analog joystick
360 connected to one of 16 gameports
361 Format: <type1>,<type2>,..<type16>
362
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363 apc= [HW,SPARC]
364 Power management functions (SPARCstation-4/5 + deriv.)
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365 Format: noidle
366 Disable APC CPU standby support. SPARCstation-Fox does
367 not play well with APC CPU idle - disable it if you have
368 APC and your system crashes randomly.
369
ca1eda2d 370 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 371 Change the output verbosity whilst booting
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372 Format: { quiet (default) | verbose | debug }
373 Change the amount of debugging information output
374 when initialising the APIC and IO-APIC components.
a9913044 375
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376 autoconf= [IPV6]
377 See Documentation/networking/ipv6.txt.
378
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379 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
380 Limit apic dumping. The parameter defines the maximal
381 number of local apics being dumped. Also it is possible
382 to set it to "all" by meaning -- no limit here.
383 Format: { 1 (default) | 2 | ... | all }.
384 The parameter valid if only apic=debug or
385 apic=verbose is specified.
386 Example: apic=debug show_lapic=all
387
1da177e4 388 apm= [APM] Advanced Power Management
71f77055 389 See header of arch/x86/kernel/apm_32.c.
1da177e4 390
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391 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
392 Format: <io>,<irq>,<nodeID>
393
394 ataflop= [HW,M68k]
395
396 atarimouse= [HW,MOUSE] Atari Mouse
397
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398 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
399 EzKey and similar keyboards
400
401 atkbd.reset= [HW] Reset keyboard during initialization
402
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403 atkbd.set= [HW] Select keyboard code set
404 Format: <int> (2 = AT (default), 3 = PS/2)
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405
406 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
407 keyboards
408
409 atkbd.softraw= [HW] Choose between synthetic and real raw mode
410 Format: <bool> (0 = real, 1 = synthetic (default))
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411
412 atkbd.softrepeat= [HW]
413 Use software keyboard repeat
1da177e4 414
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415 baycom_epp= [HW,AX25]
416 Format: <io>,<mode>
a9913044 417
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418 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
419 Format: <io>,<mode>
420 See header of drivers/net/hamradio/baycom_par.c.
421
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422 baycom_ser_fdx= [HW,AX25]
423 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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424 Format: <io>,<irq>,<mode>[,<baud>]
425 See header of drivers/net/hamradio/baycom_ser_fdx.c.
426
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427 baycom_ser_hdx= [HW,AX25]
428 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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429 Format: <io>,<irq>,<mode>
430 See header of drivers/net/hamradio/baycom_ser_hdx.c.
431
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432 boot_delay= Milliseconds to delay each printk during boot.
433 Values larger than 10 seconds (10000) are changed to
434 no delay (0).
435 Format: integer
436
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437 bootmem_debug [KNL] Enable bootmem allocator debug messages.
438
1da177e4 439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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440 bttv.radio= Most important insmod options are available as
441 kernel args too.
1da177e4 442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
395cf969 443 bttv.tuner=
1da177e4 444
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445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
447 at a time.
448
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449 c101= [NET] Moxa C101 synchronous serial card
450
cd4f0ef7 451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
457
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458 ccw_timeout_log [S390]
459 See Documentation/s390/CommonIO for details.
1da177e4 460
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461 cgroup_disable= [KNL] Disable a particular controller
462 Format: {name of the controller(s) to disable}
463 {Currently supported controllers - "memory"}
464
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465 checkreqprot [SELINUX] Set initial checkreqprot flag value.
466 Format: { "0" | "1" }
467 See security/selinux/Kconfig help text.
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468 0 -- check protection applied by kernel (includes
469 any implied execute protection).
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470 1 -- check protection requested by application.
471 Default value is set via a kernel config option.
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472 Value can be changed at runtime via
473 /selinux/checkreqprot.
474
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475 cio_ignore= [S390]
476 See Documentation/s390/CommonIO for details.
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477 clk_ignore_unused
478 [CLK]
479 Keep all clocks already enabled by bootloader on,
480 even if no driver has claimed them. This is useful
481 for debug and development, but should not be
482 needed on a platform with proper driver support.
483 For more information, see Documentation/clk.txt.
661ca0da 484
cd4f0ef7 485 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 486 [Deprecated]
3f6dee9b 487 Forces specified clocksource (if available) to be used
734efb46 488 when calculating gettimeofday(). If specified
3f6dee9b 489 clocksource is not available, it defaults to PIT.
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490 Format: { pit | tsc | cyclone | pmtmr }
491
592913ec 492 clocksource= Override the default clocksource
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493 Format: <string>
494 Override the default clocksource and use the clocksource
495 with the name specified.
496 Some clocksource names to choose from, depending on
497 the platform:
498 [all] jiffies (this is the base, fallback clocksource)
499 [ACPI] acpi_pm
500 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
501 pxa_timer,timer3,32k_counter,timer0_1
502 [AVR32] avr32
9863c90f 503 [X86-32] pit,hpet,tsc;
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504 scx200_hrt on Geode; cyclone on IBM x440
505 [MIPS] MIPS
506 [PARISC] cr16
507 [S390] tod
508 [SH] SuperH
509 [SPARC64] tick
510 [X86-64] hpet,tsc
511
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512 clearcpuid=BITNUM [X86]
513 Disable CPUID feature X for the kernel. See
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514 arch/x86/include/asm/cpufeature.h for the valid bit
515 numbers. Note the Linux specific bits are not necessarily
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516 stable over kernel options, but the vendor specific
517 ones should be.
518 Also note that user programs calling CPUID directly
519 or using the feature without checking anything
520 will still see it. This just prevents it from
521 being used by the kernel or shown in /proc/cpuinfo.
522 Also note the kernel might malfunction if you disable
523 some critical bits.
524
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525 cma=nn[MG] [ARM,KNL]
526 Sets the size of kernel global memory area for contiguous
527 memory allocations. For more information, see
528 include/linux/dma-contiguous.h
529
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530 cmo_free_hint= [PPC] Format: { yes | no }
531 Specify whether pages are marked as being inactive
532 when they are freed. This is used in CMO environments
533 to determine OS memory pressure for page stealing by
534 a hypervisor.
535 Default: yes
536
c7909509
MS
537 coherent_pool=nn[KMG] [ARM,KNL]
538 Sets the size of memory pool for coherent, atomic dma
e9da6e99 539 allocations, by default set to 256K.
c7909509 540
6cececfc 541 code_bytes [X86] How many bytes of object code to print
a25bd949 542 in an oops report.
86c41837
CE
543 Range: 0 - 8192
544 Default: 64
545
1da177e4 546 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
547 Format:
548 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
549
550 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
551 Format: <io>[,<irq>]
552
a9913044
RD
553 com90xx= [HW,NET]
554 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
555 Format: <io>[,<irq>[,<memstart>]]
556
557 condev= [HW,S390] console device
558 conmode=
a9913044 559
1da177e4
LT
560 console= [KNL] Output console device and options.
561
562 tty<n> Use the virtual console device <n>.
563
564 ttyS<n>[,options]
f1a1c2dc 565 ttyUSB0[,options]
1da177e4 566 Use the specified serial port. The options are of
f1a1c2dc
RD
567 the form "bbbbpnf", where "bbbb" is the baud rate,
568 "p" is parity ("n", "o", or "e"), "n" is number of
569 bits, and "f" is flow control ("r" for RTS or
570 omit it). Default is "9600n8".
571
572 See Documentation/serial-console.txt for more
573 information. See
574 Documentation/networking/netconsole.txt for an
575 alternative.
1da177e4 576
18a8bd94
YL
577 uart[8250],io,<addr>[,options]
578 uart[8250],mmio,<addr>[,options]
1da177e4
LT
579 Start an early, polled-mode console on the 8250/16550
580 UART at the specified I/O port or MMIO address,
581 switching to the matching ttyS device later. The
582 options are the same as for ttyS, above.
a2fd6419
KRW
583 hvc<n> Use the hypervisor console device <n>. This is for
584 both Xen and PowerPC hypervisors.
1da177e4 585
f7511d5f
ST
586 If the device connected to the port is not a TTY but a braille
587 device, prepend "brl," before the device type, for instance
588 console=brl,ttyS0
589 For now, only VisioBraille is supported.
590
f324edc8
DM
591 consoleblank= [KNL] The console blank (screen saver) timeout in
592 seconds. Defaults to 10*60 = 10mins. A value of 0
593 disables the blank timer.
594
4cb0e11b
HK
595 coredump_filter=
596 [KNL] Change the default value for
597 /proc/<pid>/coredump_filter.
598 See also Documentation/filesystems/proc.txt.
599
62027aea
LB
600 cpuidle.off=1 [CPU_IDLE]
601 disable the cpuidle sub-system
602
1da177e4 603 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
604 Format:
605 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 606
6f21e646
AD
607 crashkernel=size[KMG][@offset[KMG]]
608 [KNL] Using kexec, Linux can switch to a 'crash kernel'
609 upon panic. This parameter reserves the physical
610 memory region [offset, offset + size] for that kernel
611 image. If '@offset' is omitted, then a suitable offset
612 is selected automatically. Check
613 Documentation/kdump/kdump.txt for further details.
dc009d92 614
fb391599
BW
615 crashkernel=range1:size1[,range2:size2,...][@offset]
616 [KNL] Same as above, but depends on the memory
617 in the running system. The syntax of range is
618 start-[end] where start and end are both
619 a memory unit (amount[KMG]). See also
6f21e646 620 Documentation/kdump/kdump.txt for an example.
fb391599 621
adbc742b 622 crashkernel=size[KMG],high
55a20ee7
YL
623 [KNL, x86_64] range could be above 4G. Allow kernel
624 to allocate physical memory region from top, so could
625 be above 4G if system have more than 4G ram installed.
626 Otherwise memory region will be allocated below 4G, if
627 available.
628 It will be ignored if crashkernel=X is specified.
adbc742b
YL
629 crashkernel=size[KMG],low
630 [KNL, x86_64] range under 4G. When crashkernel=X,high
631 is passed, kernel could allocate physical memory region
c729de8f
YL
632 above 4G, that cause second kernel crash on system
633 that require some amount of low memory, e.g. swiotlb
634 requires at least 64M+32K low memory. Kernel would
635 try to allocate 72M below 4G automatically.
636 This one let user to specify own low range under 4G
637 for second kernel instead.
638 0: to disable low allocation.
adbc742b 639 It will be ignored when crashkernel=X,high is not used
55a20ee7 640 or memory reserved is below 4G.
c729de8f 641
1da177e4
LT
642 cs89x0_dma= [HW,NET]
643 Format: <dma>
644
645 cs89x0_media= [HW,NET]
646 Format: { rj45 | aui | bnc }
a9913044 647
a9913044 648 dasd= [HW,NET]
1da177e4
LT
649 See header of drivers/s390/block/dasd_devmap.c.
650
651 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
652 (one device per port)
653 Format: <port#>,<type>
654 See also Documentation/input/joystick-parport.txt
655
a648ec05
TR
656 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
657 time. See Documentation/dynamic-debug-howto.txt for
29e36c9f 658 details. Deprecated, see dyndbg.
a648ec05 659
1da177e4
LT
660 debug [KNL] Enable kernel debugging (events log level).
661
cae2ed9a
IM
662 debug_locks_verbose=
663 [KNL] verbose self-tests
664 Format=<0|1>
665 Print debugging info while doing the locking API
666 self-tests.
667 We default to 0 (no extra messages), setting it to
668 1 will print _a lot_ more information - normally
669 only useful to kernel developers.
670
3ac7fe5a
TG
671 debug_objects [KNL] Enable object debugging
672
3e8ebb5c
KM
673 no_debug_objects
674 [KNL] Disable object debugging
675
c0a32fc5
SG
676 debug_guardpage_minorder=
677 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
678 parameter allows control of the order of pages that will
679 be intentionally kept free (and hence protected) by the
680 buddy allocator. Bigger value increase the probability
681 of catching random memory corruption, but reduce the
682 amount of memory for normal system use. The maximum
683 possible value is MAX_ORDER/2. Setting this parameter
684 to 1 or 2 should be enough to identify most random
685 memory corruption problems caused by bugs in kernel or
686 driver code when a CPU writes to (or reads from) a
687 random memory location. Note that there exists a class
688 of memory corruptions problems caused by buggy H/W or
689 F/W or by drivers badly programing DMA (basically when
690 memory is written at bus level and the CPU MMU is
691 bypassed) which are not detectable by
692 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
693 tracking down these problems.
694
d3af01f1
TG
695 debugpat [X86] Enable PAT debugging
696
2d27a966 697 decnet.addr= [HW,NET]
1da177e4
LT
698 Format: <area>[,<node>]
699 See also Documentation/networking/decnet.txt.
700
0cb55ad2
RD
701 default_hugepagesz=
702 [same as hugepagesz=] The size of the default
703 HugeTLB page size. This is the size represented by
704 the legacy /proc/ hugepages APIs, used for SHM, and
705 default size when mounting hugetlbfs filesystems.
706 Defaults to the default architecture's huge page size
707 if not specified.
55ff9780 708
1da177e4
LT
709 dhash_entries= [KNL]
710 Set number of hash buckets for dentry cache.
a9913044 711
1da177e4
LT
712 digi= [HW,SERIAL]
713 IO parameters + enable/disable command.
714
715 digiepca= [HW,SERIAL]
716 See drivers/char/README.epca and
31c00fc1 717 Documentation/serial/digiepca.txt.
1da177e4 718
b0f83b28
BH
719 disable= [IPV6]
720 See Documentation/networking/ipv6.txt.
721
4e8b0cf4
NA
722 disable_ddw [PPC/PSERIES]
723 Disable Dynamic DMA Window support. Use this if
724 to workaround buggy firmware.
725
b0f83b28
BH
726 disable_ipv6= [IPV6]
727 See Documentation/networking/ipv6.txt.
728
95ffa243 729 disable_mtrr_cleanup [X86]
95ffa243
YL
730 The kernel tries to adjust MTRR layout from continuous
731 to discrete, to make X server driver able to add WB
0cb55ad2 732 entry later. This parameter disables that.
95ffa243 733
093af8d7 734 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
735 By default the kernel will trim any uncacheable
736 memory out of your available memory pool based on
737 MTRR settings. This parameter disables that behavior,
738 possibly causing your machine to run very slowly.
739
6cececfc 740 disable_timer_pin_1 [X86]
0cb55ad2
RD
741 Disable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs.
743
0cb55ad2
RD
744 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
745 this option disables the debugging code at boot.
746
747 dma_debug_entries=<number>
748 This option allows to tune the number of preallocated
749 entries for DMA-API debugging code. One entry is
750 required per DMA-API allocation. Use this if the
751 DMA-API debugging code disables itself because the
752 architectural default is too low.
753
1745de5e
JR
754 dma_debug_driver=<driver_name>
755 With this option the DMA-API debugging driver
756 filter feature can be enabled at boot time. Just
757 pass the driver to filter for as the parameter.
758 The filter can be disabled or changed to another
759 driver later using sysfs.
760
da0df92b
CE
761 drm_kms_helper.edid_firmware=[<connector>:]<file>
762 Broken monitors, graphic adapters and KVMs may
763 send no or incorrect EDID data sets. This parameter
764 allows to specify an EDID data set in the
765 /lib/firmware directory that is used instead.
766 Generic built-in EDID data sets are used, if one of
767 edid/1024x768.bin, edid/1280x1024.bin,
768 edid/1680x1050.bin, or edid/1920x1080.bin is given
769 and no file with the same name exists. Details and
770 instructions how to build your own EDID data are
771 available in Documentation/EDID/HOWTO.txt. An EDID
772 data set will only be used for a particular connector,
773 if its name and a colon are prepended to the EDID
774 name.
775
1da177e4
LT
776 dscc4.setup= [NET]
777
29e36c9f
JC
778 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
779 module.dyndbg[="val"]
780 Enable debug messages at boot time. See
781 Documentation/dynamic-debug-howto.txt for details.
782
0cb55ad2
RD
783 earlycon= [KNL] Output early console device and options.
784 uart[8250],io,<addr>[,options]
785 uart[8250],mmio,<addr>[,options]
1917ac76 786 uart[8250],mmio32,<addr>[,options]
0cb55ad2
RD
787 Start an early, polled-mode console on the 8250/16550
788 UART at the specified I/O port or MMIO address.
16290246
RD
789 MMIO inter-register address stride is either 8-bit
790 (mmio) or 32-bit (mmio32).
0cb55ad2
RD
791 The options are the same as for ttyS, above.
792
147ea091 793 earlyprintk= [X86,SH,BLACKFIN,ARM]
1da177e4 794 earlyprintk=vga
2482a92e 795 earlyprintk=xen
1da177e4 796 earlyprintk=serial[,ttySn[,baudrate]]
147ea091 797 earlyprintk=serial[,0x...[,baudrate]]
ea3acb19 798 earlyprintk=ttySn[,baudrate]
9780bc41 799 earlyprintk=dbgp[debugController#]
1da177e4 800
147ea091
DH
801 earlyprintk is useful when the kernel crashes before
802 the normal console is initialized. It is not enabled by
803 default because it has some cosmetic problems.
804
a9913044 805 Append ",keep" to not disable it when the real console
1da177e4
LT
806 takes over.
807
5c05917e 808 Only vga or serial or usb debug port at a time.
1da177e4 809
147ea091
DH
810 Currently only ttyS0 and ttyS1 may be specified by
811 name. Other I/O ports may be explicitly specified
812 on some architectures (x86 and arm at least) by
813 replacing ttySn with an I/O port address, like this:
814 earlyprintk=serial,0x1008,115200
815 You can find the port for a given device in
816 /proc/tty/driver/serial:
817 2: uart:ST16650V2 port:00001008 irq:18 ...
1da177e4
LT
818
819 Interaction with the standard serial driver is not
820 very good.
821
822 The VGA output is eventually overwritten by the real
823 console.
824
2482a92e
KRW
825 The xen output can only be used by Xen PV guests.
826
9731191f
JW
827 ekgdboc= [X86,KGDB] Allow early kernel console debugging
828 ekgdboc=kbd
829
25985edc 830 This is designed to be used in conjunction with
9731191f
JW
831 the boot argument: earlyprintk=vga
832
1da177e4 833 edd= [EDD]
8c4dd606 834 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 835
8c58bf3e
RW
836 efi_no_storage_paranoia [EFI; X86]
837 Using this parameter you can use more than 50% of
838 your efi variable storage. Use this parameter only if
839 you are really sure that your UEFI does sane gc and
840 fulfills the spec otherwise your board may brick.
841
1da177e4
LT
842 eisa_irq_edge= [PARISC,HW]
843 See header of drivers/parisc/eisa.c.
844
cd4f0ef7 845 elanfreq= [X86-32]
1da177e4 846 See comment before function elanfreq_setup() in
71f77055 847 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
848
849 elevator= [IOSCHED]
17a9e7bb 850 Format: {"cfq" | "deadline" | "noop"}
395cf969 851 See Documentation/block/cfq-iosched.txt and
a9913044
RD
852 Documentation/block/deadline-iosched.txt for details.
853
d3bf3795 854 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
a9913044 855 Specifies physical address of start of kernel core
d3bf3795
MH
856 image elf header and optionally the size. Generally
857 kexec loader will pass this option to capture kernel.
aac04b32 858 See Documentation/kdump/kdump.txt for details.
1da177e4 859
0cb55ad2
RD
860 enable_mtrr_cleanup [X86]
861 The kernel tries to adjust MTRR layout from continuous
862 to discrete, to make X server driver able to add WB
863 entry later. This parameter enables that.
864
ca1eda2d 865 enable_timer_pin_1 [X86]
0cb55ad2
RD
866 Enable PIN 1 of APIC timer
867 Can be useful to work around chipset bugs
868 (in particular on some ATI chipsets).
869 The kernel tries to set a reasonable default.
870
1da177e4
LT
871 enforcing [SELINUX] Set initial enforcing status.
872 Format: {"0" | "1"}
873 See security/selinux/Kconfig help text.
874 0 -- permissive (log only, no denials).
875 1 -- enforcing (deny and log).
876 Default value is 0.
877 Value can be changed at runtime via /selinux/enforce.
878
a08f82d0
HY
879 erst_disable [ACPI]
880 Disable Error Record Serialization Table (ERST)
881 support.
882
1da177e4
LT
883 ether= [HW,NET] Ethernet cards parameters
884 This option is obsoleted by the "netdev=" option, which
885 has equivalent usage. See its documentation for details.
886
7102ebcd
MZ
887 evm= [EVM]
888 Format: { "fix" }
889 Permit 'security.evm' to be updated regardless of
890 current integrity status.
891
de1ba09b
AM
892 failslab=
893 fail_page_alloc=
894 fail_make_request=[KNL]
895 General fault injection mechanism.
896 Format: <interval>,<probability>,<space>,<times>
395cf969 897 See also Documentation/fault-injection/.
de1ba09b 898
1da177e4 899 floppy= [HW]
31c00fc1 900 See Documentation/blockdev/floppy.txt.
1da177e4 901
f13ae30e
AC
902 force_pal_cache_flush
903 [IA-64] Avoid check_sal_cache_flush which may hang on
904 buggy SAL_CACHE_FLUSH implementations. Using this
905 parameter will force ia64_sal_cache_flush to call
906 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
907
d9e54076 908 ftrace=[tracer]
2af15d6a 909 [FTRACE] will set and start the specified tracer
d9e54076
PZ
910 as early as possible in order to facilitate early
911 boot debugging.
912
cecbca96 913 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 914 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
915 If no parameter is passed, ftrace will dump
916 buffers of all CPUs, but if you pass orig_cpu, it will
917 dump only the buffer of the CPU that triggered the
918 oops.
2af15d6a
SR
919
920 ftrace_filter=[function-list]
921 [FTRACE] Limit the functions traced by the function
922 tracer at boot up. function-list is a comma separated
923 list of functions. This list can be changed at run
924 time by the set_ftrace_filter file in the debugfs
16290246 925 tracing directory.
2af15d6a
SR
926
927 ftrace_notrace=[function-list]
928 [FTRACE] Do not trace the functions specified in
929 function-list. This list can be changed at run time
930 by the set_ftrace_notrace file in the debugfs
931 tracing directory.
d9e54076 932
369bc18f
SA
933 ftrace_graph_filter=[function-list]
934 [FTRACE] Limit the top level callers functions traced
935 by the function graph tracer at boot up.
936 function-list is a comma separated list of functions
937 that can be changed at run time by the
938 set_graph_function file in the debugfs tracing directory.
939
1da177e4
LT
940 gamecon.map[2|3]=
941 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
942 support via parallel port (up to 5 devices per port)
943 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
944 See also Documentation/input/joystick-parport.txt
945
946 gamma= [HW,DRM]
947
aaf23042
YL
948 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
949 Format: off | on
950 default: on
951
2521f2c2
PO
952 gcov_persist= [GCOV] When non-zero (default), profiling data for
953 kernel modules is saved and remains accessible via
954 debugfs, even when the module is unloaded/reloaded.
955 When zero, profiling data is discarded and associated
956 debugfs files are removed at module unload time.
957
d3926e19
TG
958 goldfish [X86] Enable the goldfish android emulator platform.
959 Don't use this when you are not running on the
960 android emulator
961
1da177e4
LT
962 gpt [EFI] Forces disk with valid GPT signature but
963 invalid Protective MBR to be treated as GPT.
964
6cec9b07
AL
965 grcan.enable0= [HW] Configuration of physical interface 0. Determines
966 the "Enable 0" bit of the configuration register.
967 Format: 0 | 1
968 Default: 0
969 grcan.enable1= [HW] Configuration of physical interface 1. Determines
970 the "Enable 0" bit of the configuration register.
971 Format: 0 | 1
972 Default: 0
973 grcan.select= [HW] Select which physical interface to use.
974 Format: 0 | 1
975 Default: 0
976 grcan.txsize= [HW] Sets the size of the tx buffer.
977 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
978 Default: 1024
979 grcan.rxsize= [HW] Sets the size of the rx buffer.
980 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
981 Default: 1024
982
1da177e4
LT
983 hashdist= [KNL,NUMA] Large hashes allocated during boot
984 are distributed across NUMA nodes. Defaults on
16290246 985 for 64-bit NUMA, off otherwise.
a9913044 986 Format: 0 | 1 (for off | on)
1da177e4
LT
987
988 hcl= [IA-64] SGI's Hardware Graph compatibility layer
989
990 hd= [EIDE] (E)IDE hard drive subsystem geometry
991 Format: <cyl>,<head>,<sect>
992
ea8c071c
HY
993 hest_disable [ACPI]
994 Disable Hardware Error Source Table (HEST) support;
995 corresponding firmware-first mode error processing
996 logic will be disabled.
997
1da177e4
LT
998 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
999 size of <nn>. This works even on boxes that have no
1000 highmem otherwise. This also works to reduce highmem
1001 size on bigger boxes.
1002
54cdfdb4
TG
1003 highres= [KNL] Enable/disable high resolution timer mode.
1004 Valid parameters: "on", "off"
1005 Default: "on"
1006
1da177e4
LT
1007 hisax= [HW,ISDN]
1008 See Documentation/isdn/README.HiSax.
1009
0cb55ad2
RD
1010 hlt [BUGS=ARM,SH]
1011
1012 hpet= [X86-32,HPET] option to control HPET usage
1013 Format: { enable (default) | disable | force |
1014 verbose }
1015 disable: disable HPET and use PIT instead
1016 force: allow force enabled of undocumented chips (ICH4,
1017 VIA, nVidia)
1018 verbose: show contents of HPET registers during setup
1019
b4718e62
AK
1020 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1021 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
1022 On x86-64 and powerpc, this option can be specified
1023 multiple times interleaved with hugepages= to reserve
1024 huge pages of different sizes. Valid pages sizes on
1025 x86-64 are 2M (when the CPU supports "pse") and 1G
1026 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
1027 Note that 1GB pages can only be allocated at boot time
1028 using hugepages= and not freed afterwards.
6902aa84 1029
555d61d6
HB
1030 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1031 terminal devices. Valid values: 0..8
431429ff
HB
1032 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1033 If specified, z/VM IUCV HVC accepts connections
1034 from listed z/VM user IDs only.
cef7125d 1035
fdabf525
JH
1036 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1037 hardware thread id mappings.
1038 Format: <cpu>:<hwthread>
1039
7bf69395
FDN
1040 keep_bootcon [KNL]
1041 Do not unregister boot console at start. This is only
1042 useful for debugging when something happens in the window
1043 between unregistering the boot console and initializing
1044 the real console.
1045
3a853fb9 1046 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
1047 or register an additional I2C bus that is not
1048 registered from board initialization code.
3a853fb9
JN
1049 Format:
1050 <bus_id>,<clkrate>
1051
36d95739 1052 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 1053 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
1054 i8042.dumbkbd [HW] Pretend that controller can only read data from
1055 keyboard and cannot control its state
1da177e4
LT
1056 (Don't attempt to blink the leds)
1057 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 1058 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
1059 i8042.noloop [HW] Disable the AUX Loopback command while probing
1060 for the AUX port
1da177e4
LT
1061 i8042.nomux [HW] Don't check presence of an active multiplexing
1062 controller
1063 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1064 controllers
24775d65 1065 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1da177e4
LT
1066 i8042.reset [HW] Reset the controller during init and cleanup
1067 i8042.unlock [HW] Unlock (ignore) the keylock
bdf5d033 1068 i8042.kbdreset [HW] Reset device connected to KBD port
1da177e4
LT
1069
1070 i810= [HW,DRM]
1071
e70c9d5e
DT
1072 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1073 indicates that the driver is running on unsupported
1074 hardware.
1da177e4
LT
1075 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1076 does not match list of supported models.
1077 i8k.power_status
1078 [HW] Report power status in /proc/i8k
1079 (disabled by default)
1080 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1081 capability is set.
1082
4dca20ef 1083 i915.invert_brightness=
7bd90909
CE
1084 [DRM] Invert the sense of the variable that is used to
1085 set the brightness of the panel backlight. Normally a
4dca20ef
CE
1086 brightness value of 0 indicates backlight switched off,
1087 and the maximum of the brightness value sets the backlight
1088 to maximum brightness. If this parameter is set to 0
1089 (default) and the machine requires it, or this parameter
1090 is set to 1, a brightness value of 0 sets the backlight
1091 to maximum brightness, and the maximum of the brightness
1092 value switches the backlight off.
1093 -1 -- never invert brightness
1094 0 -- machine default
1095 1 -- force brightness inversion
7bd90909 1096
1da177e4
LT
1097 icn= [HW,ISDN]
1098 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1099
0af80c04
DF
1100 ide-core.nodma= [HW] (E)IDE subsystem
1101 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
1102 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1103 .cdrom .chs .ignore_cable are additional options
1c10e938 1104 See Documentation/ide/ide.txt.
1da177e4 1105
0cb55ad2
RD
1106 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1107 Claim all unknown PCI IDE storage controllers.
1108
f039b754 1109 idle= [X86]
69fb3676 1110 Format: idle=poll, idle=halt, idle=nomwait
ada9cfdd
RD
1111 Poll forces a polling idle loop that can slightly
1112 improve the performance of waking up a idle CPU, but
1113 will use a lot of power and make the system run hot.
1114 Not recommended.
ada9cfdd 1115 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 1116 In such case C2/C3 won't be used again.
ada9cfdd 1117 idle=nomwait: Disable mwait for CPU C-states
a9913044 1118
79290822
IM
1119 ignore_loglevel [KNL]
1120 Ignore loglevel setting - this will print /all/
1121 kernel messages to the console. Useful for debugging.
0eca6b7c
YZ
1122 We also add it as printk module parameter, so users
1123 could change it dynamically, usually by
1124 /sys/module/printk/parameters/ignore_loglevel.
79290822 1125
1da177e4
LT
1126 ihash_entries= [KNL]
1127 Set number of hash buckets for inode cache.
1128
2fe5d6de
MZ
1129 ima_appraise= [IMA] appraise integrity measurements
1130 Format: { "off" | "enforce" | "fix" }
1131 default: "enforce"
1132
07f6a794
MZ
1133 ima_appraise_tcb [IMA]
1134 The builtin appraise policy appraises all files
1135 owned by uid=0.
1136
3323eec9
MZ
1137 ima_audit= [IMA]
1138 Format: { "0" | "1" }
1139 0 -- integrity auditing messages. (Default)
1140 1 -- enable informational integrity auditing messages.
1141
1142 ima_hash= [IMA]
a9ed83a5 1143 Format: { "sha1" | "md5" }
3323eec9
MZ
1144 default: "sha1"
1145
5789ba3b
EP
1146 ima_tcb [IMA]
1147 Load a policy which meets the needs of the Trusted
1148 Computing Base. This means IMA will measure all
1149 programs exec'd, files mmap'd for exec, and all files
1150 opened for read by uid=0.
1151
1da177e4
LT
1152 init= [KNL]
1153 Format: <full_path>
1154 Run specified binary instead of /sbin/init as init
1155 process.
1156
1157 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1158 for working out where the kernel is dying during
1159 startup.
1160
1161 initrd= [BOOT] Specify the location of the initial ramdisk
1162
1163 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1164 Format: <irq>
1165
ba395927 1166 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
1167 on
1168 Enable intel iommu driver.
ba395927
KA
1169 off
1170 Disable intel iommu driver.
1171 igfx_off [Default Off]
1172 By default, gfx is mapped as normal device. If a gfx
1173 device has a dedicated DMAR unit, the DMAR unit is
1174 bypassed by not enabling DMAR with this option. In
1175 this case, gfx device will use physical address for
1176 DMA.
7d3b03ce
KA
1177 forcedac [x86_64]
1178 With this option iommu will not optimize to look
16290246 1179 for io virtual address below 32-bit forcing dual
7d3b03ce 1180 address cycle on pci bus for cards supporting greater
16290246
RD
1181 than 32-bit addressing. The default is to look
1182 for translation below 32-bit and if not available
7d3b03ce 1183 then look in the higher range.
5e0d2a6f 1184 strict [Default Off]
1185 With this option on every unmap_single operation will
1186 result in a hardware IOTLB flush operation as opposed
1187 to batching them for performance.
6dd9a7c7
YS
1188 sp_off [Default Off]
1189 By default, super page will be supported if Intel IOMMU
1190 has the capability. With this option, super page will
1191 not be supported.
2e92c7ad
MI
1192
1193 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1194 0 disables intel_idle and fall back on acpi_idle.
1195 1 to 6 specify maximum depth of C-state.
1196
6be26498
DB
1197 intel_pstate= [X86]
1198 disable
1199 Do not enable intel_pstate as the default
1200 scaling driver for the supported processors
1201
d1423d56 1202 intremap= [X86-64, Intel-IOMMU]
d1423d56
CW
1203 on enable Interrupt Remapping (default)
1204 off disable Interrupt Remapping
1205 nosid disable Source ID checking
41750d31
SS
1206 no_x2apic_optout
1207 BIOS x2APIC opt-out request will be ignored
d1423d56 1208
0cb55ad2
RD
1209 iomem= Disable strict checking of access to MMIO memory
1210 strict regions from userspace.
1211 relaxed
1212
1213 iommu= [x86]
1214 off
1215 force
1216 noforce
1217 biomerge
1218 panic
1219 nopanic
1220 merge
1221 nomerge
1222 forcesac
1223 soft
bcb71abe 1224 pt [x86, IA-64]
bcb71abe 1225
0cb55ad2
RD
1226
1227 io7= [HW] IO7 for Marvel based alpha systems
1228 See comment before marvel_specify_io7 in
1229 arch/alpha/kernel/core_marvel.c.
1230
6cececfc 1231 io_delay= [X86] I/O delay method
6e7c4025
IM
1232 0x80
1233 Standard port 0x80 based delay
1234 0xed
1235 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1236 udelay
6e7c4025
IM
1237 Simple two microseconds delay
1238 none
1239 No delay
b02aae9c 1240
1da177e4 1241 ip= [IP_PNP]
dc7a0816 1242 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1243
1244 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1245 See comment before ip2_setup() in
1246 drivers/char/ip2/ip2base.c.
1da177e4 1247
200803df
AC
1248 irqfixup [HW]
1249 When an interrupt is not handled search all handlers
1250 for it. Intended to get systems with badly broken
1251 firmware running.
1252
1253 irqpoll [HW]
1254 When an interrupt is not handled search all handlers
1255 for it. Also check all handlers each timer
1256 interrupt. Intended to get systems with badly broken
1257 firmware running.
1258
1da177e4 1259 isapnp= [ISAPNP]
a9913044 1260 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1261
1262 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1263 Format:
1264 <cpu number>,...,<cpu number>
1265 or
b225d44e
LZ
1266 <cpu number>-<cpu number>
1267 (must be a positive range in ascending order)
22f2e280
DF
1268 or a mixture
1269 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1270
1da177e4
LT
1271 This option can be used to specify one or more CPUs
1272 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1273 algorithms. You can move a process onto or off an
1274 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1275 <cpu number> begins at 0 and the maximum value is
1276 "number of CPUs in system - 1".
1277
1278 This option is the preferred way to isolate CPUs. The
a9913044
RD
1279 alternative -- manually setting the CPU mask of all
1280 tasks in the system -- can cause problems and
1281 suboptimal load balancer performance.
1da177e4 1282
a9913044 1283 iucv= [HW,NET]
1da177e4 1284
7d8bfa26
JR
1285 ivrs_ioapic [HW,X86_64]
1286 Provide an override to the IOAPIC-ID<->DEVICE-ID
1287 mapping provided in the IVRS ACPI table. For
1288 example, to map IOAPIC-ID decimal 10 to
1289 PCI device 00:14.0 write the parameter as:
1290 ivrs_ioapic[10]=00:14.0
1291
1292 ivrs_hpet [HW,X86_64]
1293 Provide an override to the HPET-ID<->DEVICE-ID
1294 mapping provided in the IVRS ACPI table. For
1295 example, to map HPET-ID decimal 0 to
1296 PCI device 00:14.0 write the parameter as:
1297 ivrs_hpet[0]=00:14.0
1298
1da177e4
LT
1299 js= [HW,JOY] Analog joystick
1300 See Documentation/input/joystick.txt.
1301
0cb55ad2
RD
1302 keepinitrd [HW,ARM]
1303
6cececfc 1304 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1305 specifies the amount of memory usable by the kernel
1306 for non-movable allocations. The requested amount is
1307 spread evenly throughout all nodes in the system. The
1308 remaining memory in each node is used for Movable
1309 pages. In the event, a node is too small to have both
1310 kernelcore and Movable pages, kernelcore pages will
1311 take priority and other nodes will have a larger number
1312 of kernelcore pages. The Movable zone is used for the
1313 allocation of pages that may be reclaimed or moved
1314 by the page migration subsystem. This means that
1315 HugeTLB pages may not be allocated from this zone.
1316 Note that allocations like PTEs-from-HighMem still
1317 use the HighMem zone if it exists, and the Normal
1318 zone if it does not.
1319
4fe1da4e
JW
1320 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1321 Format: <Controller#>[,poll interval]
1322 The controller # is the number of the ehci usb debug
1323 port as it is probed via PCI. The poll interval is
1324 optional and is the number seconds in between
1325 each poll cycle to the debug port in case you need
1326 the functionality for interrupting the kernel with
1327 gdb or control-c on the dbgp connection. When
1328 not using this parameter you use sysrq-g to break into
1329 the kernel debugger.
1330
84c08fd6 1331 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1332 Requires a tty driver that supports console polling,
1333 or a supported polling keyboard driver (non-usb).
65b5ac14
JW
1334 Serial only format: <serial_device>[,baud]
1335 keyboard only format: kbd
1336 keyboard and serial format: kbd,<serial_device>[,baud]
1337 Optional Kernel mode setting:
1338 kms, kbd format: kms,kbd
1339 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
6cdf6e06 1340
84c08fd6
JW
1341 kgdbwait [KGDB] Stop kernel execution and enter the
1342 kernel debugger at the earliest opportunity.
1343
9bed90c6
FF
1344 kmac= [MIPS] korina ethernet MAC address.
1345 Configure the RouterBoard 532 series on-chip
1346 Ethernet adapter MAC address.
1347
04f70336
CM
1348 kmemleak= [KNL] Boot-time kmemleak enable/disable
1349 Valid arguments: on, off
1350 Default: on
1351
6cececfc 1352 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1353 in oops dumps.
1354
fef07aae
AP
1355 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1356 Default is 0 (don't ignore, but inject #GP)
1357
a182d873
XG
1358 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1359 KVM MMU at runtime.
fef07aae
AP
1360 Default is 0 (off)
1361
fef07aae 1362 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
8475f94a 1363 Default is 1 (enabled)
fef07aae
AP
1364
1365 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1366 for all guests.
16290246 1367 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
fef07aae 1368
fef07aae
AP
1369 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1370 (virtualized MMU) support on capable Intel chips.
1371 Default is 1 (enabled)
1372
1373 kvm-intel.emulate_invalid_guest_state=
1374 [KVM,Intel] Enable emulation of invalid guest states
1375 Default is 0 (disabled)
1376
1377 kvm-intel.flexpriority=
1378 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1379 Default is 1 (enabled)
1380
e1a72ae2
SL
1381 kvm-intel.nested=
1382 [KVM,Intel] Enable VMX nesting (nVMX).
1383 Default is 0 (disabled)
1384
fef07aae
AP
1385 kvm-intel.unrestricted_guest=
1386 [KVM,Intel] Disable unrestricted guest feature
1387 (virtualized real and unpaged mode) on capable
1388 Intel chips. Default is 1 (enabled)
1389
1390 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1391 feature (tagged TLBs) on capable Intel chips.
1392 Default is 1 (enabled)
1393
1da177e4
LT
1394 l2cr= [PPC]
1395
a78bfbfc
RB
1396 l3cr= [PPC]
1397
cd4f0ef7 1398 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1399 disabled it.
1da177e4 1400
279f1461
SS
1401 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1402 value for LAPIC timer one-shot implementation. Default
1403 back to the programmable timer unit in the LAPIC.
1404
6cececfc 1405 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1406 in C2 power state.
e585bef8 1407
fcb71f6f
FC
1408 libata.dma= [LIBATA] DMA control
1409 libata.dma=0 Disable all PATA and SATA DMA
1410 libata.dma=1 PATA and SATA Disk DMA only
1411 libata.dma=2 ATAPI (CDROM) DMA only
16290246 1412 libata.dma=4 Compact Flash DMA only
fcb71f6f
FC
1413 Combinations also work, so libata.dma=3 enables DMA
1414 for disks and CDROMs, but not CFs.
16290246 1415
20308871
MP
1416 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1417 libata.ignore_hpa=0 keep BIOS limits (default)
1418 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1419
78e70c23
DJ
1420 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1421 when set.
1422 Format: <int>
1423
33267325
TH
1424 libata.force= [LIBATA] Force configurations. The format is comma
1425 separated list of "[ID:]VAL" where ID is
4c44f309 1426 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1427 matching port, link or device. Basically, it matches
1428 the ATA ID string printed on console by libata. If
1429 the whole ID part is omitted, the last PORT and DEVICE
1430 values are used. If ID hasn't been specified yet, the
1431 configuration applies to all ports, links and devices.
1432
1433 If only DEVICE is omitted, the parameter applies to
1434 the port and all links and devices behind it. DEVICE
1435 number of 0 either selects the first device or the
1436 first fan-out link behind PMP device. It does not
1437 select the host link. DEVICE number of 15 selects the
1438 host link and device attached to it.
1439
1440 The VAL specifies the configuration to force. As long
1441 as there's no ambiguity shortcut notation is allowed.
1442 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1443 The following configurations can be forced.
1444
1445 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1446 Any ID with matching PORT is used.
1447
1448 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1449
1450 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1451 udma[/][16,25,33,44,66,100,133] notation is also
1452 allowed.
1453
1454 * [no]ncq: Turn on or off NCQ.
1455
05944bdf
TH
1456 * nohrst, nosrst, norst: suppress hard, soft
1457 and both resets.
1458
ca6d43b0
DW
1459 * rstonce: only attempt one reset during
1460 hot-unplug link recovery
1461
43c9c591
TH
1462 * dump_id: dump IDENTIFY data.
1463
3d097b15
VP
1464 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1465
1dc58ce4
RJ
1466 * disable: Disable this device.
1467
33267325
TH
1468 If there are multiple matching configurations changing
1469 the same attribute, the last one is used.
1470
95f72d1e 1471 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1472
1da177e4 1473 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1474 See Documentation/blockdev/ramdisk.txt.
1da177e4 1475
a6b25b67
RD
1476 lockd.nlm_grace_period=P [NFS] Assign grace period.
1477 Format: <integer>
1da177e4 1478
a6b25b67
RD
1479 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1480 Format: <integer>
1481
1482 lockd.nlm_timeout=T [NFS] Assign timeout value.
1483 Format: <integer>
1484
1485 lockd.nlm_udpport=M [NFS] Assign UDP port.
1486 Format: <integer>
1da177e4
LT
1487
1488 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1489 Format: <irq>
1490
1491 loglevel= All Kernel Messages with a loglevel smaller than the
1492 console loglevel will be printed to the console. It can
1493 also be changed with klogd or other programs. The
1494 loglevels are defined as follows:
1495
1496 0 (KERN_EMERG) system is unusable
1497 1 (KERN_ALERT) action must be taken immediately
1498 2 (KERN_CRIT) critical conditions
1499 3 (KERN_ERR) error conditions
1500 4 (KERN_WARNING) warning conditions
1501 5 (KERN_NOTICE) normal but significant condition
1502 6 (KERN_INFO) informational
1503 7 (KERN_DEBUG) debug-level messages
1504
c756d08a
RD
1505 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1506 in bytes. n must be a power of two. The default
1507 size is set in the kernel config file.
1da177e4 1508
accaa24c
RD
1509 logo.nologo [FB] Disables display of the built-in Linux logo.
1510 This may be used to provide more screen space for
1511 kernel log messages and is useful when debugging
1512 kernel boot problems.
1513
1da177e4
LT
1514 lp=0 [LP] Specify parallel ports to use, e.g,
1515 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1516 lp=reset first parallel port). 'lp=0' disables the
1517 lp=auto printer driver. 'lp=reset' (which can be
1518 specified in addition to the ports) causes
1519 attached printers to be reset. Using
1520 lp=port1,port2,... specifies the parallel ports
1521 to associate lp devices with, starting with
1522 lp0. A port specification may be 'none' to skip
1523 that lp device, or a parport name such as
1524 'parport0'. Specifying 'lp=auto' instead of a
1525 port specification list means that device IDs
1526 from each port should be examined, to see if
1527 an IEEE 1284-compliant printer is attached; if
1528 so, the driver will manage that printer.
1529 See also header of drivers/char/lp.c.
1530
1531 lpj=n [KNL]
1532 Sets loops_per_jiffy to given constant, thus avoiding
1533 time-consuming boot-time autodetection (up to 250 ms per
1534 CPU). 0 enables autodetection (default). To determine
1535 the correct value for your kernel, boot with normal
1536 autodetection and see what value is printed. Note that
1537 on SMP systems the preset will be applied to all CPUs,
1538 which is likely to cause problems if your CPUs need
1539 significantly divergent settings. An incorrect value
1540 will cause delays in the kernel to be wrong, leading to
1541 unpredictable I/O errors and other breakage. Although
1542 unlikely, in the extreme case this might damage your
1543 hardware.
1544
1545 ltpc= [NET]
1546 Format: <io>,<irq>,<dma>
1547
16290246 1548 machvec= [IA-64] Force the use of a particular machine-vector
a9913044
RD
1549 (machvec) in a generic kernel.
1550 Example: machvec=hpzx1_swiotlb
1da177e4 1551
3209e70e
WZ
1552 machtype= [Loongson] Share the same kernel image file between different
1553 yeeloong laptop.
1554 Example: machtype=lemote-yeeloong-2f-7inch
1555
0cb55ad2
RD
1556 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1557 than or equal to this physical address is ignored.
1da177e4
LT
1558
1559 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1560 should make use of. maxcpus=n : n >= 0 limits the
1561 kernel to using 'n' processors. n=0 is a special case,
1562 it is equivalent to "nosmp", which also disables
1563 the IO APIC.
1da177e4 1564
d134b00b
KS
1565 max_loop= [LOOP] The number of loop block devices that get
1566 (loop.max_loop) unconditionally pre-created at init time. The default
1567 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1568 of statically allocating a predefined number, loop
1569 devices can be requested on-demand with the
1570 /dev/loop-control interface.
2b2c3750 1571
cd4f0ef7 1572 mce [X86-32] Machine Check Exception
1da177e4 1573
71cced6e 1574 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1575
1da177e4
LT
1576 md= [HW] RAID subsystems devices and level
1577 See Documentation/md.txt.
a9913044 1578
1da177e4
LT
1579 mdacon= [MDA]
1580 Format: <first>,<last>
1581 Specifies range of consoles to be captured by the MDA.
a9913044 1582
1da177e4
LT
1583 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1584 Amount of memory to be used when the kernel is not able
1585 to see the whole system memory or for test.
fbb97d87
WC
1586 [X86] Work as limiting max address. Use together
1587 with memmap= to avoid physical address space collisions.
1588 Without memmap= PCI devices could be placed at addresses
1589 belonging to unused RAM.
1da177e4 1590
cd4f0ef7 1591 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1592 memory.
1593
6902aa84
PM
1594 memchunk=nn[KMG]
1595 [KNL,SH] Allow user to override the default size for
1596 per-device physically contiguous DMA buffers.
1597
6cececfc 1598 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1599 E820 memory map, as specified by the user.
1600 Such memmap=exactmap lines can be constructed based on
1601 BIOS output or other requirements. See the memmap=nn@ss
1602 option description.
1603
1604 memmap=nn[KMG]@ss[KMG]
1605 [KNL] Force usage of a specific region of memory
1606 Region of memory to be used, from ss to ss+nn.
1607
1608 memmap=nn[KMG]#ss[KMG]
1609 [KNL,ACPI] Mark specific memory as ACPI data.
1610 Region of memory to be used, from ss to ss+nn.
1611
1612 memmap=nn[KMG]$ss[KMG]
1613 [KNL,ACPI] Mark specific memory as reserved.
1614 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1615 Example: Exclude memory from 0x18690000-0x1869ffff
1616 memmap=64K$0x18690000
1617 or
1618 memmap=0x10000$0x18690000
1da177e4 1619
9f077871
JF
1620 memory_corruption_check=0/1 [X86]
1621 Some BIOSes seem to corrupt the first 64k of
1622 memory when doing things like suspend/resume.
1623 Setting this option will scan the memory
1624 looking for corruption. Enabling this will
1625 both detect corruption and prevent the kernel
1626 from using the memory being corrupted.
1627 However, its intended as a diagnostic tool; if
1628 repeatable BIOS-originated corruption always
1629 affects the same memory, you can use memmap=
1630 to prevent the kernel from using that memory.
1631
1632 memory_corruption_check_size=size [X86]
1633 By default it checks for corruption in the low
1634 64k, making this memory unavailable for normal
1635 use. Use this parameter to scan for
1636 corruption in more or less memory.
1637
1638 memory_corruption_check_period=seconds [X86]
1639 By default it checks for corruption every 60
1640 seconds. Use this parameter to check at some
1641 other rate. 0 disables periodic checking.
1642
caadbdce 1643 memtest= [KNL,X86] Enable memtest
c64df707 1644 Format: <integer>
c64df707 1645 default : 0 <disable>
9e5f6cf5
AH
1646 Specifies the number of memtest passes to be
1647 performed. Each pass selects another test
1648 pattern from a given set of patterns. Memtest
1649 fills the memory with this pattern, validates
1650 memory contents and reserves bad memory
1651 regions that are detected.
c64df707 1652
1da177e4
LT
1653 meye.*= [HW] Set MotionEye Camera parameters
1654 See Documentation/video4linux/meye.txt.
1655
8f36881b
AS
1656 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1657 Multi-Function General Purpose Timers on AMD Geode
1658 platforms.
1659
e6c4dc6c
WT
1660 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1661 the BIOS has incorrectly applied a workaround. TinyBIOS
1662 version 0.98 is known to be affected, 0.99 fixes the
1663 problem by letting the user disable the workaround.
1664
1da177e4
LT
1665 mga= [HW,DRM]
1666
1c207f95
RD
1667 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1668 physical address is ignored.
1669
39f45d7b
MP
1670 mini2440= [ARM,HW,KNL]
1671 Format:[0..2][b][c][t]
1672 Default: "0tb"
1673 MINI2440 configuration specification:
1674 0 - The attached screen is the 3.5" TFT
1675 1 - The attached screen is the 7" TFT
1676 2 - The VGA Shield is attached (1024x768)
1677 Leaving out the screen size parameter will not load
1678 the TFT driver, and the framebuffer will be left
1679 unconfigured.
1680 b - Enable backlight. The TFT backlight pin will be
1681 linked to the kernel VESA blanking code and a GPIO
1682 LED. This parameter is not necessary when using the
1683 VGA shield.
1684 c - Enable the s3c camera interface.
1685 t - Reserved for enabling touchscreen support. The
1686 touchscreen support is not enabled in the mainstream
1687 kernel as of 2.6.30, a preliminary port can be found
1688 in the "bleeding edge" mini2440 support kernel at
1689 http://repo.or.cz/w/linux-2.6/mini2440.git
1690
6b74ab97
MG
1691 mminit_loglevel=
1692 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1693 parameter allows control of the logging verbosity for
1694 the additional memory initialisation checks. A value
1695 of 0 disables mminit logging and a level of 4 will
1696 log everything. Information is printed at KERN_DEBUG
1697 so loglevel=8 may also need to be specified.
1698
106a4ee2
RR
1699 module.sig_enforce
1700 [KNL] When CONFIG_MODULE_SIG is set, this means that
1701 modules without (valid) signatures will fail to load.
2a039be7 1702 Note that if CONFIG_MODULE_SIG_FORCE is set, that
106a4ee2
RR
1703 is always true, so this option does nothing.
1704
1da177e4
LT
1705 mousedev.tap_time=
1706 [MOUSE] Maximum time between finger touching and
1707 leaving touchpad surface for touch to be considered
1708 a tap and be reported as a left button click (for
1709 touchpads working in absolute mode only).
1710 Format: <msecs>
1711 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1712 reporting absolute coordinates, such as tablets
1713 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1714 reporting absolute coordinates, such as tablets
1715
6cececfc 1716 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1717 is similar to kernelcore except it specifies the
1718 amount of memory used for migratable allocations.
1719 If both kernelcore and movablecore is specified,
1720 then kernelcore will be at *least* the specified
1721 value but may be more. If movablecore on its own
1722 is specified, the administrator must be careful
1723 that the amount of memory usable for all allocations
1724 is not too small.
1725
1da177e4
LT
1726 MTD_Partition= [MTD]
1727 Format: <name>,<region-number>,<size>,<offset>
1728
a9913044
RD
1729 MTD_Region= [MTD] Format:
1730 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1731
1732 mtdparts= [MTD]
c8facbb6 1733 See drivers/mtd/cmdlinepart.c.
1da177e4 1734
4e89a2d8
WS
1735 multitce=off [PPC] This parameter disables the use of the pSeries
1736 firmware feature for updating multiple TCE entries
1737 at a time.
1738
5988af23
RH
1739 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1740
1741 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1742
1743 boundary - index of last SLC block on Flex-OneNAND.
1744 The remaining blocks are configured as MLC blocks.
1745 lock - Configure if Flex-OneNAND boundary should be locked.
1746 Once locked, the boundary cannot be changed.
1747 1 indicates lock status, 0 indicates unlock status.
1748
9db829f4
BD
1749 mtdset= [ARM]
1750 ARM/S3C2412 JIVE boot control
1751
1752 See arch/arm/mach-s3c2412/mach-jive.c
1753
1da177e4 1754 mtouchusb.raw_coordinates=
a9913044
RD
1755 [HW] Make the MicroTouch USB driver use raw coordinates
1756 ('y', default) or cooked coordinates ('n')
1da177e4 1757
0cb55ad2 1758 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1759 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1760 that could hold holes aka. UC entries.
1761
1762 mtrr_gran_size=nn[KMG] [X86]
1763 Used for mtrr cleanup. It is granularity of mtrr block.
1764 Default is 1.
1765 Large value could prevent small alignment from
1766 using up MTRRs.
1767
1768 mtrr_spare_reg_nr=n [X86]
1769 Format: <integer>
1770 Range: 0,7 : spare reg number
1771 Default : 1
1772 Used for mtrr cleanup. It is spare mtrr entries number.
1773 Set to 2 or more if your graphical card needs more.
1774
1da177e4
LT
1775 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1776
1da177e4
LT
1777 netdev= [NET] Network devices parameters
1778 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1779 Note that mem_start is often overloaded to mean
1780 something different and driver-specific.
a9913044
RD
1781 This usage is only documented in each driver source
1782 file if at all.
1783
58401572
KPO
1784 nf_conntrack.acct=
1785 [NETFILTER] Enable connection tracking flow accounting
1786 0 to disable accounting
1787 1 to enable accounting
d70a011d 1788 Default value is 0.
58401572 1789
306a0753 1790 nfsaddrs= [NFS] Deprecated. Use ip= instead.
dc7a0816 1791 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1792
1793 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1794 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1795
306a0753
CL
1796 nfsrootdebug [NFS] enable nfsroot debugging messages.
1797 See Documentation/filesystems/nfs/nfsroot.txt.
1798
a72b4422
TM
1799 nfs.callback_tcpport=
1800 [NFS] set the TCP port on which the NFSv4 callback
1801 channel should listen.
1802
e571cbf1
TM
1803 nfs.cache_getent=
1804 [NFS] sets the pathname to the program which is used
1805 to update the NFS client cache entries.
1806
1807 nfs.cache_getent_timeout=
1808 [NFS] sets the timeout after which an attempt to
1809 update a cache entry is deemed to have failed.
1810
58df095b
TM
1811 nfs.idmap_cache_timeout=
1812 [NFS] set the maximum lifetime for idmapper cache
1813 entries.
1814
f43bf0be
TM
1815 nfs.enable_ino64=
1816 [NFS] enable 64-bit inode numbers.
1817 If zero, the NFS client will fake up a 32-bit inode
1818 number for the readdir() and stat() syscalls instead
1819 of returning the full 64-bit number.
1820 The default is to return 64-bit inode numbers.
1821
ef159e91
TM
1822 nfs.max_session_slots=
1823 [NFSv4.1] Sets the maximum number of session slots
1824 the client will attempt to negotiate with the server.
1825 This limits the number of simultaneous RPC requests
1826 that the client can send to the NFSv4.1 server.
1827 Note that there is little point in setting this
1828 value higher than the max_tcp_slot_table_limit.
1829
b064eca2 1830 nfs.nfs4_disable_idmapping=
074b1d12
TM
1831 [NFSv4] When set to the default of '1', this option
1832 ensures that both the RPC level authentication
1833 scheme and the NFS level operations agree to use
1834 numeric uids/gids if the mount is using the
1835 'sec=sys' security flavour. In effect it is
1836 disabling idmapping, which can make migration from
1837 legacy NFSv2/v3 systems to NFSv4 easier.
1838 Servers that do not support this mode of operation
1839 will be autodetected by the client, and it will fall
1840 back to using the idmapper.
1841 To turn off this behaviour, set the value to '0'.
6f2ea7f2
CL
1842 nfs.nfs4_unique_id=
1843 [NFS4] Specify an additional fixed unique ident-
1844 ification string that NFSv4 clients can insert into
1845 their nfs_client_id4 string. This is typically a
1846 UUID that is generated at system install time.
b064eca2 1847
db8ac8ba
WAA
1848 nfs.send_implementation_id =
1849 [NFSv4.1] Send client implementation identification
1850 information in exchange_id requests.
1851 If zero, no implementation identification information
1852 will be sent.
1853 The default is to send the implementation identification
1854 information.
1855
e9541ce8
BF
1856 nfsd.nfs4_disable_idmapping=
1857 [NFSv4] When set to the default of '1', the NFSv4
1858 server will return only numeric uids and gids to
1859 clients using auth_sys, and will accept numeric uids
1860 and gids from such clients. This is intended to ease
1861 migration from NFSv2/v3.
db8ac8ba 1862
18d98f6c
SB
1863 objlayoutdriver.osd_login_prog=
1864 [NFS] [OBJLAYOUT] sets the pathname to the program which
1865 is used to automatically discover and login into new
1866 osd-targets. Please see:
1867 Documentation/filesystems/pnfs.txt for more explanations
1868
1e1030dc 1869 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1870 when a NMI is triggered.
1871 Format: [state][,regs][,debounce][,die]
1872
6cececfc 1873 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
fef2c9bc 1874 Format: [panic,][nopanic,][num]
5dc30558 1875 Valid num: 0
5b9a0e14 1876 0 - turn nmi_watchdog off
0cb55ad2 1877 When panic is specified, panic when an NMI watchdog
fef2c9bc
DZ
1878 timeout occurs (or 'nopanic' to override the opposite
1879 default).
0cb55ad2
RD
1880 This is useful when you use a panic=... timeout and
1881 need the box quickly up again.
1da177e4 1882
bff38771
AV
1883 netpoll.carrier_timeout=
1884 [NET] Specifies amount of time (in seconds) that
1885 netpoll should wait for a carrier. By default netpoll
1886 waits 4 seconds.
1887
cd4f0ef7 1888 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1889 emulation library even if a 387 maths coprocessor
1890 is present.
1891
0cb55ad2
RD
1892 no_console_suspend
1893 [HW] Never suspend the console
1894 Disable suspending of consoles during suspend and
1895 hibernate operations. Once disabled, debugging
1896 messages can reach various consoles while the rest
1897 of the system is being put to sleep (ie, while
1898 debugging driver suspend/resume hooks). This may
1899 not work reliably with all consoles, but is known
1900 to work with serial and VGA consoles.
134620f7
YZ
1901 To facilitate more flexible debugging, we also add
1902 console_suspend, a printk module parameter to control
1903 it. Users could use console_suspend (usually
1904 /sys/module/printk/parameters/console_suspend) to
1905 turn on/off it dynamically.
0cb55ad2 1906
c1aee215
CL
1907 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1908 caches in the slab allocator. Saves per-node memory,
1909 but will impact performance.
3395ee05 1910
a9913044
RD
1911 noalign [KNL,ARM]
1912
1da177e4
LT
1913 noapic [SMP,APIC] Tells the kernel to not make use of any
1914 IOAPICs that may be present in the system.
1915
5091faa4
MG
1916 noautogroup Disable scheduler automatic task group creation.
1917
1da177e4
LT
1918 nobats [PPC] Do not use BATs for mapping kernel lowmem
1919 on "Classic" PPC cores.
1920
1921 nocache [ARM]
a9913044 1922
0cb55ad2
RD
1923 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1924
163ecdff
SN
1925 nodelayacct [KNL] Disable per-task delay accounting
1926
1da177e4
LT
1927 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1928
6902aa84
PM
1929 nodsp [SH] Disable hardware DSP at boot time.
1930
6cececfc 1931 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1932
1da177e4
LT
1933 noexec [IA-64]
1934
6cececfc 1935 noexec [X86]
f5a1b191 1936 On X86-32 available only on PAE configured kernels.
1da177e4 1937 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1938 noexec=off: disable non-executable mappings
1939
52b6179a
PA
1940 nosmap [X86]
1941 Disable SMAP (Supervisor Mode Access Prevention)
1942 even if it is supported by processor.
1943
de5397ad 1944 nosmep [X86]
52b6179a 1945 Disable SMEP (Supervisor Mode Execution Prevention)
de5397ad
FY
1946 even if it is supported by processor.
1947
f5a1b191
JS
1948 noexec32 [X86-64]
1949 This affects only 32-bit executables.
1950 noexec32=on: enable non-executable mappings (default)
1951 read doesn't imply executable mappings
1952 noexec32=off: disable non-executable mappings
1953 read implies executable mappings
1da177e4 1954
6902aa84
PM
1955 nofpu [SH] Disable hardware FPU at boot time.
1956
cd4f0ef7 1957 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1958 register save and restore. The kernel will only save
1959 legacy floating-point registers on task switch.
1da177e4 1960
0c752a93
SS
1961 noxsave [BUGS=X86] Disables x86 extended register state save
1962 and restore using xsave. The kernel will fallback to
1963 enabling legacy floating-point and sse state.
1964
5d2bd700 1965 eagerfpu= [X86]
e0022981 1966 on enable eager fpu restore
5d2bd700 1967 off disable eager fpu restore
e0022981
SS
1968 auto selects the default scheme, which automatically
1969 enables eagerfpu restore for xsaveopt.
5d2bd700 1970
01a24d2b
PZ
1971 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1972 wfi(ARM) instruction doesn't work correctly and not to
1973 use it. This is also useful when using JTAG debugger.
a9913044 1974
1f29fae2
SH
1975 no_file_caps Tells the kernel not to honor file capabilities. The
1976 only way then for a file to be executed with privilege
1977 is to be setuid root or executed by root.
1978
1da177e4
LT
1979 nohalt [IA-64] Tells the kernel not to use the power saving
1980 function PAL_HALT_LIGHT when idle. This increases
1981 power-consumption. On the positive side, it reduces
1982 interrupt wake-up latency, which may improve performance
1983 in certain environments such as networked servers or
1984 real-time systems.
1985
79bf2bb3
TG
1986 nohz= [KNL] Boottime enable/disable dynamic ticks
1987 Valid arguments: on, off
1988 Default: on
1989
c5bfece2
FW
1990 nohz_full= [KNL,BOOT]
1991 In kernels built with CONFIG_NO_HZ_FULL=y, set
a831881b 1992 the specified list of CPUs whose tick will be stopped
0453b435
FW
1993 whenever possible. The boot CPU will be forced outside
1994 the range to maintain the timekeeping.
d1e43fa5
FW
1995 The CPUs in this range must also be included in the
1996 rcu_nocbs= set.
a831881b 1997
eeee7853
PM
1998 noiotrap [SH] Disables trapped I/O port accesses.
1999
cd4f0ef7 2000 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
2001 disable unhandled interrupt sources.
2002
6cececfc 2003 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
2004 broken timer IRQ sources.
2005
1da177e4
LT
2006 noisapnp [ISAPNP] Disables ISA PnP code.
2007
2008 noinitrd [RAM] Tells the kernel not to load any configured
2009 initial RAM disk.
2010
03ea8155
WH
2011 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2012 remapping.
d1423d56 2013 [Deprecated - use intremap=off]
03ea8155 2014
1da177e4
LT
2015 nointroute [IA-64]
2016
16290246 2017 nojitter [IA-64] Disables jitter checking for ITC timers.
0aa366f3 2018
9cf4c4fc
JK
2019 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2020
fd10cde9
GN
2021 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2022 fault handling.
2023
d910f5c1
GC
2024 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2025 steal time is computed, but won't influence scheduler
2026 behaviour
2027
cd4f0ef7 2028 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 2029
cd4f0ef7 2030 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 2031
1da177e4
LT
2032 noltlbs [PPC] Do not use large page/tlb entries for kernel
2033 lowmem mapping on PPC40x.
2034
312f1f01
H
2035 nomca [IA-64] Disable machine check abort handling
2036
cd4f0ef7 2037 nomce [X86-32] Machine Check Exception
abe37e5a 2038
83d7384f
AS
2039 nomfgpt [X86-32] Disable Multi-Function General Purpose
2040 Timer usage (for AMD Geode machines).
2041
bda62633
DZ
2042 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2043 shutdown the other cpus. Instead use the REBOOT_VECTOR
2044 irq.
2045
02608bef
DY
2046 nomodule Disable module load
2047
016ddd9b
JK
2048 nopat [X86] Disable PAT (page attribute table extension of
2049 pagetables) support.
2050
0cb55ad2
RD
2051 norandmaps Don't use address space randomization. Equivalent to
2052 echo 0 > /proc/sys/kernel/randomize_va_space
2053
bbff2168 2054 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
959b4fdf 2055
cd4f0ef7 2056 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
2057 with UP alternatives
2058
49d859d7
PA
2059 nordrand [X86] Disable the direct use of the RDRAND
2060 instruction even if it is supported by the
2061 processor. RDRAND is still available to user
2062 space applications.
2063
a9913044
RD
2064 noresume [SWSUSP] Disables resume and restores original swap
2065 space.
2066
1da177e4
LT
2067 no-scroll [VGA] Disables scrollback.
2068 This is required for the Braillex ib80-piezo Braille
2069 reader made by F.H. Papenmeier (Germany).
2070
2071 nosbagart [IA-64]
2072
cd4f0ef7 2073 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 2074
61ec7567
LB
2075 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2076 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 2077
97842216
DJ
2078 nosoftlockup [KNL] Disable the soft-lockup detector.
2079
1da177e4
LT
2080 nosync [HW,M68K] Disables sync negotiation for all devices.
2081
cd4f0ef7 2082 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
2083
2084 nousb [USB] Disable the USB subsystem
2085
55142374 2086 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
58687acb 2087
1da177e4 2088 nowb [ARM]
a9913044 2089
2b2fd87a
WH
2090 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2091
f78cff48
FY
2092 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2093 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2094 Some features depend on CPU0. Known dependencies are:
2095 1. Resume from suspend/hibernate depends on CPU0.
2096 Suspend/hibernate will fail if CPU0 is offline and you
2097 need to online CPU0 before suspend/hibernate.
2098 2. PIC interrupts also depend on CPU0. CPU0 can't be
2099 removed if a PIC interrupt is detected.
2100 It's said poweroff/reboot may depend on CPU0 on some
2101 machines although I haven't seen such issues so far
2102 after CPU0 is offline on a few tested machines.
2103 If the dependencies are under your control, you can
2104 turn on cpu0_hotplug.
2105
16290246 2106 nptcg= [IA-64] Override max number of concurrent global TLB
a6c75b86
FY
2107 purges which is reported from either PAL_VM_SUMMARY or
2108 SAL PALO.
2109
2b633e3f
YL
2110 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2111 could support. nr_cpus=n : n >= 1 limits the kernel to
2112 supporting 'n' processors. Later in runtime you can not
2113 use hotplug cpu feature to put more cpu back to online.
2114 just like you compile the kernel NR_CPUS=n
2115
0cb55ad2
RD
2116 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2117
1a687c2e
MG
2118 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2119 Allowed values are enable and disable
2120
f0c0b2b8
KH
2121 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2122 one of ['zone', 'node', 'default'] can be specified
2123 This can be set from sysctl after boot.
2124 See Documentation/sysctl/vm.txt for details.
2125
7c4be253
RD
2126 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2127 See Documentation/debugging-via-ohci1394.txt for more
2128 info.
2129
3ef0e1f8
AS
2130 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2131 Rather than timing out after 20 ms if an EC
2132 command is not properly ACKed, override the length
2133 of the timeout. We have interrupts disabled while
2134 waiting for the ACK, so if this is set too high
2135 interrupts *may* be lost!
2136
15ac7afe
TL
2137 omap_mux= [OMAP] Override bootloader pin multiplexing.
2138 Format: <mux_mode0.mode_name=value>...
2139 For example, to override I2C bus2:
2140 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2141
1da177e4
LT
2142 oprofile.timer= [HW]
2143 Use timer interrupt instead of performance counters
2144
7e4e0bd5
RR
2145 oprofile.cpu_type= Force an oprofile cpu type
2146 This might be useful if you have an older oprofile
2147 userland or if you want common events.
8d7ff4f2
RR
2148 Format: { arch_perfmon }
2149 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
2150 perfmon on Intel CPUs instead of the
2151 CPU specific event set.
159a80b2
RR
2152 timer: [X86] Force use of architectural NMI
2153 timer mode (see also oprofile.timer
2154 for generic hr timer mode)
dd3c4670
AK
2155 [s390] Force legacy basic mode sampling
2156 (report cpu_type "timer")
1dcdb5a9 2157
44a4dcf7
RD
2158 oops=panic Always panic on oopses. Default is to just kill the
2159 process, but there is a small probability of
2160 deadlocking the machine.
d404ab0a
OH
2161 This will also cause panics on machine check exceptions.
2162 Useful together with panic=30 to trigger a reboot.
2163
bcfde334
RD
2164 OSS [HW,OSS]
2165 See Documentation/sound/oss/oss-parameters.txt
2166
44a4dcf7 2167 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4302fbc8
HD
2168 timeout > 0: seconds before rebooting
2169 timeout = 0: wait forever
2170 timeout < 0: reboot immediately
1da177e4
LT
2171 Format: <timeout>
2172
2173 parkbd.port= [HW] Parallel port number the keyboard adapter is
2174 connected to, default is 0.
2175 Format: <parport#>
2176 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2177 0 for XT, 1 for AT (default is AT).
a9913044
RD
2178 Format: <mode>
2179
2180 parport= [HW,PPT] Specify parallel ports. 0 disables.
2181 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2182 Use 'auto' to force the driver to use any
2183 IRQ/DMA settings detected (the default is to
2184 ignore detected IRQ/DMA settings because of
2185 possible conflicts). You can specify the base
2186 address, IRQ, and DMA settings; IRQ and DMA
2187 should be numbers, or 'auto' (for using detected
2188 settings on that particular port), or 'nofifo'
2189 (to avoid using a FIFO even if it is detected).
2190 Parallel ports are assigned in the order they
2191 are specified on the command line, starting
2192 with parport0.
2193
2194 parport_init_mode= [HW,PPT]
2195 Configure VIA parallel port to operate in
2196 a specific mode. This is necessary on Pegasos
2197 computer where firmware has no options for setting
2198 up parallel port mode and sets it to spp.
2199 Currently this function knows 686a and 8231 chips.
1da177e4
LT
2200 Format: [spp|ps2|epp|ecp|ecpepp]
2201
dd287796
AM
2202 pause_on_oops=
2203 Halt all CPUs after the first oops has been printed for
2204 the specified number of seconds. This is to be used if
2205 your oopses keep scrolling off the screen.
2206
1da177e4
LT
2207 pcbit= [HW,ISDN]
2208
2209 pcd. [PARIDE]
2210 See header of drivers/block/paride/pcd.c.
31c00fc1 2211 See also Documentation/blockdev/paride.txt.
1da177e4 2212
a9913044 2213 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
2214 earlydump [X86] dump PCI config space before the kernel
2215 changes anything
c0115606 2216 off [X86] don't probe for the PCI bus
cd4f0ef7 2217 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
2218 the hardware directly. Use this if your machine
2219 has a non-standard PCI host bridge.
cd4f0ef7 2220 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
2221 hardware access methods are allowed. Use this
2222 if you experience crashes upon bootup and you
2223 suspect they are caused by the BIOS.
c0115606 2224 conf1 [X86] Force use of PCI Configuration
a9913044 2225 Mechanism 1.
c0115606 2226 conf2 [X86] Force use of PCI Configuration
a9913044 2227 Mechanism 2.
7f785763
RD
2228 noaer [PCIE] If the PCIEAER kernel config parameter is
2229 enabled, this kernel boot option can be used to
2230 disable the use of PCIE advanced error reporting.
32a2eea7
JG
2231 nodomains [PCI] Disable support for multiple PCI
2232 root domains (aka PCI segments, in ACPI-speak).
6cececfc 2233 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 2234 Configuration
12983077
AH
2235 check_enable_amd_mmconf [X86] check for and enable
2236 properly configured MMIO access to PCI
2237 config space on AMD family 10h CPU
309e57df
MW
2238 nomsi [MSI] If the PCI_MSI kernel config parameter is
2239 enabled, this kernel boot option can be used to
2240 disable the use of MSI interrupts system-wide.
a9322f64
SA
2241 noioapicquirk [APIC] Disable all boot interrupt quirks.
2242 Safety option to keep boot IRQs enabled. This
2243 should never be necessary.
9197979b
SA
2244 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2245 primary IO-APIC for bridges that cannot disable
2246 boot IRQs. This fixes a source of spurious IRQs
2247 when the system masks IRQs.
41b9eb26
SA
2248 noioapicreroute [APIC] Disable workaround that uses the
2249 boot IRQ equivalent of an IRQ that connects to
2250 a chipset where boot IRQs cannot be disabled.
2251 The opposite of ioapicreroute.
cd4f0ef7 2252 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
2253 routing table. These calls are known to be buggy
2254 on several machines and they hang the machine
2255 when used, but on other computers it's the only
2256 way to get the interrupt routing table. Try
2257 this option if the kernel is unable to allocate
2258 IRQs or discover secondary PCI buses on your
2259 motherboard.
c0115606 2260 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
2261 Use with caution as certain devices share
2262 address decoders between ROMs and other
2263 resources.
c0115606 2264 norom [X86] Do not assign address space to
bb71ad88
GH
2265 expansion ROMs that do not already have
2266 BIOS assigned address ranges.
7bd1c365
MH
2267 nobar [X86] Do not assign address space to the
2268 BARs that weren't assigned by the BIOS.
c0115606 2269 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
2270 assigned automatically to PCI devices. You can
2271 make the kernel exclude IRQs of your ISA cards
2272 this way.
c0115606 2273 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
2274 of the PIRQ table (normally generated
2275 by the BIOS) if it is outside the
2276 F0000h-100000h range.
c0115606 2277 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
2278 useful if the kernel is unable to find your
2279 secondary buses and you want to tell it
2280 explicitly which ones they are.
c0115606 2281 assign-busses [X86] Always assign all PCI bus
a9913044
RD
2282 numbers ourselves, overriding
2283 whatever the firmware may have done.
c0115606 2284 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
2285 in the BIOS $PIR table. This is needed on
2286 some systems with broken BIOSes, notably
2287 some HP Pavilion N5400 and Omnibook XE3
2288 notebooks. This will have no effect if ACPI
2289 IRQ routing is enabled.
c0115606 2290 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 2291 or for PCI scanning.
7bc5e3f2
BH
2292 use_crs [X86] Use PCI host bridge window information
2293 from ACPI. On BIOSes from 2008 or later, this
2294 is enabled by default. If you need to use this,
2295 please report a bug.
2296 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2297 If you need to use this, please report a bug.
a9913044
RD
2298 routeirq Do IRQ routing for all PCI devices.
2299 This is normally done in pci_enable_device(),
2300 so this option is a temporary workaround
2301 for broken drivers that don't call it.
13a6ddb0
YL
2302 skip_isa_align [X86] do not align io start addr, so can
2303 handle more pci cards
a9913044
RD
2304 firmware [ARM] Do not re-enumerate the bus but instead
2305 just use the configuration from the
2306 bootloader. This is currently used on
2307 IXP2000 systems where the bus has to be
2308 configured a certain way for adjunct CPUs.
0637a70a
AK
2309 noearly [X86] Don't do any early type 1 scanning.
2310 This might help on some broken boards which
2311 machine check when some devices' config space
2312 is read. But various workarounds are disabled
2313 and some IOMMU drivers will not work.
6b4b78fe
MD
2314 bfsort Sort PCI devices into breadth-first order.
2315 This sorting is done to get a device
2316 order compatible with older (<= 2.4) kernels.
2317 nobfsort Don't sort PCI devices into breadth-first order.
fa238712
YW
2318 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2319 tuning and use the BIOS-configured MPS defaults.
2320 pcie_bus_safe Set every device's MPS to the largest value
2321 supported by all devices below the root complex.
2322 pcie_bus_perf Set device MPS to the largest allowable MPS
2323 based on its parent bus. Also set MRRS (Max
2324 Read Request Size) to the largest supported
2325 value (no larger than the MPS that the device
2326 or bus can support) for best performance.
2327 pcie_bus_peer2peer Set every device's MPS to 128B, which
2328 every device is guaranteed to support. This
2329 configuration allows peer-to-peer DMA between
2330 any pair of devices, possibly at the cost of
2331 reduced performance. This also guarantees
2332 that hot-added devices will work.
4516a618
AN
2333 cbiosize=nn[KMG] The fixed amount of bus space which is
2334 reserved for the CardBus bridge's IO window.
2335 The default value is 256 bytes.
2336 cbmemsize=nn[KMG] The fixed amount of bus space which is
2337 reserved for the CardBus bridge's memory
2338 window. The default value is 64 megabytes.
32a9a682
YS
2339 resource_alignment=
2340 Format:
2341 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2342 Specifies alignment and device to reassign
2343 aligned memory resources.
2344 If <order of align> is not specified,
2345 PAGE_SIZE is used as alignment.
2346 PCI-PCI bridge can be specified, if resource
2347 windows need to be expanded.
43c16408
AP
2348 ecrc= Enable/disable PCIe ECRC (transaction layer
2349 end-to-end CRC checking).
2350 bios: Use BIOS/firmware settings. This is the
2351 the default.
2352 off: Turn ECRC off
2353 on: Turn ECRC on.
8c8803c5
YW
2354 hpiosize=nn[KMG] The fixed amount of bus space which is
2355 reserved for hotplug bridge's IO window.
2356 Default size is 256 bytes.
2357 hpmemsize=nn[KMG] The fixed amount of bus space which is
2358 reserved for hotplug bridge's memory window.
2359 Default size is 2 megabytes.
b55438fd
YL
2360 realloc= Enable/disable reallocating PCI bridge resources
2361 if allocations done by BIOS are too small to
2362 accommodate resources required by all child
2363 devices.
2364 off: Turn realloc off
2365 on: Turn realloc on
2366 realloc same as realloc=on
6748dcc2 2367 noari do not use PCIe ARI.
284f5f9d
BH
2368 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2369 only look for one device below a PCIe downstream
2370 port.
6b4b78fe 2371
e5665a45
CE
2372 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2373 Management.
2374 off Disable ASPM.
2375 force Enable ASPM even on devices that claim not to support it.
2376 WARNING: Forcing ASPM on may cause system lockups.
2377
7570a333
MT
2378 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2379 nomsi Do not use MSI for PCI Express Native Hotplug (this
2380 makes all PCIe ports use INTx for hotplug services).
2381
79dd9182 2382 pcie_ports= [PCIE] PCIe ports handling:
28eb5f27
RW
2383 auto Ask the BIOS whether or not to use native PCIe services
2384 associated with PCIe ports (PME, hot-plug, AER). Use
2385 them only if that is allowed by the BIOS.
2386 native Use native PCIe services associated with PCIe ports
2387 unconditionally.
79dd9182
RW
2388 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2389 ports driver.
2390
c7f48656 2391 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
c39fae14 2392 nomsi Do not use MSI for native PCIe PME signaling (this makes
28eb5f27 2393 all PCIe root ports use INTx for all services).
c7f48656 2394
1da177e4
LT
2395 pcmv= [HW,PCMCIA] BadgePAD 4
2396
2397 pd. [PARIDE]
31c00fc1 2398 See Documentation/blockdev/paride.txt.
1da177e4
LT
2399
2400 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2401 boot time.
2402 Format: { 0 | 1 }
2403 See arch/parisc/kernel/pdc_chassis.c
2404
f58dc01b 2405 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2406 Currently supported values are "embed" and "page".
2407 Archs may support subset or none of the selections.
2408 See comments in mm/percpu.c for details on each
2409 allocator. This parameter is primarily for debugging
2410 and performance comparison.
fa8a7094 2411
1da177e4 2412 pf. [PARIDE]
31c00fc1 2413 See Documentation/blockdev/paride.txt.
1da177e4
LT
2414
2415 pg. [PARIDE]
31c00fc1 2416 See Documentation/blockdev/paride.txt.
1da177e4
LT
2417
2418 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2419 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2420
2421 plip= [PPT,NET] Parallel port network link
2422 Format: { parport<nr> | timid | 0 }
2423 See also Documentation/parport.txt.
2424
16290246 2425 pmtmr= [X86] Manual setup of pmtmr I/O Port.
de32a243
TG
2426 Override pmtimer IOPort with a hex value.
2427 e.g. pmtmr=0x508
2428
96242116
BH
2429 pnp.debug=1 [PNP]
2430 Enable PNP debug messages (depends on the
2431 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2432 via /sys/module/pnp/parameters/debug. We always show
2433 current resource usage; turning this on also shows
2434 possible settings and some assignment information.
97ef062b 2435
1da177e4
LT
2436 pnpacpi= [ACPI]
2437 { off }
2438
2439 pnpbios= [ISAPNP]
2440 { on | off | curr | res | no-curr | no-res }
2441
2442 pnp_reserve_irq=
2443 [ISAPNP] Exclude IRQs for the autoconfiguration
2444
2445 pnp_reserve_dma=
2446 [ISAPNP] Exclude DMAs for the autoconfiguration
2447
2448 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2449 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2450
2451 pnp_reserve_mem=
a9913044
RD
2452 [ISAPNP] Exclude memory regions for the
2453 autoconfiguration.
1da177e4
LT
2454 Ranges are in pairs (memory base and size).
2455
4af94f39
RD
2456 ports= [IP_VS_FTP] IPVS ftp helper module
2457 Default is 21.
2458 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2459 may be specified.
2460 Format: <port>,<port>....
2461
45807a1d
IM
2462 print-fatal-signals=
2463 [KNL] debug: print fatal signals
f84d49b2
NO
2464
2465 If enabled, warn about various signal handling
2466 related application anomalies: too many signals,
2467 too many POSIX.1 timers, fatal signals causing a
2468 coredump - etc.
2469
2470 If you hit the warning due to signal overflow,
2471 you might want to try "ulimit -i unlimited".
2472
45807a1d
IM
2473 default: off.
2474
c22ab332
MG
2475 printk.always_kmsg_dump=
2476 Trigger kmsg_dump for cases other than kernel oops or
2477 panics
2478 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2479 default: disabled
2480
e84845c4
RD
2481 printk.time= Show timing data prefixed to each printk message line
2482 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2483
0cb55ad2
RD
2484 processor.max_cstate= [HW,ACPI]
2485 Limit processor to maximum C-state
2486 max_cstate=9 overrides any DMI blacklist limit.
2487
2488 processor.nocst [HW,ACPI]
2489 Ignore the _CST method to determine C-states,
2490 instead using the legacy FADT method
2491
1da177e4 2492 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2493 Format: [schedule,]<number>
2494 Param: "schedule" - profile schedule points.
2495 Param: <number> - step/bucket size as a power of 2 for
2496 statistical time based profiling.
b3da2a73
MG
2497 Param: "sleep" - profile D-state sleeping (millisecs).
2498 Requires CONFIG_SCHEDSTATS
c0fe2e69 2499 Param: "kvm" - profile VM exits.
1da177e4 2500
1da177e4
LT
2501 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2502 before loading.
31c00fc1 2503 See Documentation/blockdev/ramdisk.txt.
1da177e4 2504
a9913044
RD
2505 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2506 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2507 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2508 per second.
a9913044
RD
2509 psmouse.resetafter= [HW,MOUSE]
2510 Try to reset the device after so many bad packets
1da177e4
LT
2511 (0 = never).
2512 psmouse.resolution=
2513 [HW,MOUSE] Set desired mouse resolution, in dpi.
2514 psmouse.smartscroll=
a9913044 2515 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2516 0 = disabled, 1 = enabled (default).
2517
dee28e72
MG
2518 pstore.backend= Specify the name of the pstore backend to use
2519
1da177e4 2520 pt. [PARIDE]
31c00fc1 2521 See Documentation/blockdev/paride.txt.
1da177e4 2522
dc8c8587
KS
2523 pty.legacy_count=
2524 [KNL] Number of legacy pty's. Overwrites compiled-in
2525 default number.
2526
7d2c502f 2527 quiet [KNL] Disable most log messages
a9913044 2528
1da177e4
LT
2529 r128= [HW,DRM]
2530
2531 raid= [HW,RAID]
2532 See Documentation/md.txt.
2533
a9913044 2534 ramdisk_blocksize= [RAM]
31c00fc1 2535 See Documentation/blockdev/ramdisk.txt.
a9913044 2536
1da177e4 2537 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2538 See Documentation/blockdev/ramdisk.txt.
1da177e4 2539
3fbfbf7a
PM
2540 rcu_nocbs= [KNL,BOOT]
2541 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2542 the specified list of CPUs to be no-callback CPUs.
2543 Invocation of these CPUs' RCU callbacks will
a4889858
PM
2544 be offloaded to "rcuox/N" kthreads created for
2545 that purpose, where "x" is "b" for RCU-bh, "p"
2546 for RCU-preempt, and "s" for RCU-sched, and "N"
2547 is the CPU number. This reduces OS jitter on the
3fbfbf7a 2548 offloaded CPUs, which can be useful for HPC and
a4889858 2549
3fbfbf7a
PM
2550 real-time workloads. It can also improve energy
2551 efficiency for asymmetric multiprocessors.
2552
1b0048a4 2553 rcu_nocb_poll [KNL,BOOT]
3fbfbf7a
PM
2554 Rather than requiring that offloaded CPUs
2555 (specified by rcu_nocbs= above) explicitly
2556 awaken the corresponding "rcuoN" kthreads,
2557 make these kthreads poll for callbacks.
2558 This improves the real-time response for the
2559 offloaded CPUs by relieving them of the need to
2560 wake up the corresponding kthread, but degrades
2561 energy efficiency by requiring that the kthreads
2562 periodically wake up to do the polling.
2563
dabb8aa9 2564 rcutree.blimit= [KNL,BOOT]
24aaef8d
RD
2565 Set maximum number of finished RCU callbacks to process
2566 in one batch.
21a1ea9e 2567
f885b7f2
PM
2568 rcutree.fanout_leaf= [KNL,BOOT]
2569 Increase the number of CPUs assigned to each
2570 leaf rcu_node structure. Useful for very large
2571 systems.
2572
c0f4dfd4
PM
2573 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2574 Set delay from grace-period initialization to
2575 first attempt to force quiescent states.
2576 Units are jiffies, minimum value is zero,
2577 and maximum value is HZ.
2578
2579 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2580 Set delay between subsequent attempts to force
2581 quiescent states. Units are jiffies, minimum
2582 value is one, and maximum value is HZ.
2583
dabb8aa9 2584 rcutree.qhimark= [KNL,BOOT]
24aaef8d 2585 Set threshold of queued
21a1ea9e
DS
2586 RCU callbacks over which batch limiting is disabled.
2587
dabb8aa9 2588 rcutree.qlowmark= [KNL,BOOT]
24aaef8d
RD
2589 Set threshold of queued RCU callbacks below which
2590 batch limiting is re-enabled.
21a1ea9e 2591
dabb8aa9
PM
2592 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2593 Suppress RCU CPU stall warning messages.
2594
2595 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2596 Set timeout for RCU CPU stall warning messages.
2597
c0f4dfd4
PM
2598 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2599 Set wakeup interval for idle CPUs that have
2600 RCU callbacks (RCU_FAST_NO_HZ=y).
d40011f6 2601
c0f4dfd4
PM
2602 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2603 Set wakeup interval for idle CPUs that have
2604 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2605 Lazy RCU callbacks are those which RCU can
2606 prove do nothing more than free memory.
d40011f6 2607
dabb8aa9
PM
2608 rcutorture.fqs_duration= [KNL,BOOT]
2609 Set duration of force_quiescent_state bursts.
2610
2611 rcutorture.fqs_holdoff= [KNL,BOOT]
2612 Set holdoff time within force_quiescent_state bursts.
2613
2614 rcutorture.fqs_stutter= [KNL,BOOT]
2615 Set wait time between force_quiescent_state bursts.
2616
2617 rcutorture.irqreader= [KNL,BOOT]
2618 Test RCU readers from irq handlers.
2619
2620 rcutorture.n_barrier_cbs= [KNL,BOOT]
2621 Set callbacks/threads for rcu_barrier() testing.
2622
2623 rcutorture.nfakewriters= [KNL,BOOT]
2624 Set number of concurrent RCU writers. These just
2625 stress RCU, they don't participate in the actual
2626 test, hence the "fake".
2627
2628 rcutorture.nreaders= [KNL,BOOT]
2629 Set number of RCU readers.
2630
2631 rcutorture.onoff_holdoff= [KNL,BOOT]
2632 Set time (s) after boot for CPU-hotplug testing.
2633
2634 rcutorture.onoff_interval= [KNL,BOOT]
2635 Set time (s) between CPU-hotplug operations, or
2636 zero to disable CPU-hotplug testing.
2637
2638 rcutorture.shuffle_interval= [KNL,BOOT]
2639 Set task-shuffle interval (s). Shuffling tasks
2640 allows some CPUs to go into dyntick-idle mode
2641 during the rcutorture test.
2642
2643 rcutorture.shutdown_secs= [KNL,BOOT]
2644 Set time (s) after boot system shutdown. This
2645 is useful for hands-off automated testing.
2646
2647 rcutorture.stall_cpu= [KNL,BOOT]
2648 Duration of CPU stall (s) to test RCU CPU stall
2649 warnings, zero to disable.
2650
2651 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2652 Time to wait (s) after boot before inducing stall.
2653
2654 rcutorture.stat_interval= [KNL,BOOT]
2655 Time (s) between statistics printk()s.
2656
2657 rcutorture.stutter= [KNL,BOOT]
2658 Time (s) to stutter testing, for example, specifying
2659 five seconds causes the test to run for five seconds,
2660 wait for five seconds, and so on. This tests RCU's
2661 ability to transition abruptly to and from idle.
2662
2663 rcutorture.test_boost= [KNL,BOOT]
2664 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2665 "Maybe" means test if the RCU implementation
2666 under test support RCU priority boosting.
2667
2668 rcutorture.test_boost_duration= [KNL,BOOT]
2669 Duration (s) of each individual boost test.
2670
2671 rcutorture.test_boost_interval= [KNL,BOOT]
2672 Interval (s) between each boost test.
2673
2674 rcutorture.test_no_idle_hz= [KNL,BOOT]
2675 Test RCU's dyntick-idle handling. See also the
2676 rcutorture.shuffle_interval parameter.
2677
2678 rcutorture.torture_type= [KNL,BOOT]
2679 Specify the RCU implementation to test.
2680
2681 rcutorture.verbose= [KNL,BOOT]
2682 Enable additional printk() statements.
2683
ffdfc409
OJ
2684 rdinit= [KNL]
2685 Format: <full_path>
2686 Run specified binary instead of /init from the ramdisk,
2687 used for early userspace startup. See initrd.
2688
cd4f0ef7 2689 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2690 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2691 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2692
46b6d94e
PJ
2693 relax_domain_level=
2694 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2695 See Documentation/cgroups/cpusets.txt.
46b6d94e 2696
1da177e4
LT
2697 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2698
cd4f0ef7 2699 reservetop= [X86-32]
461a9aff
ZA
2700 Format: nn[KMG]
2701 Reserves a hole at the top of the kernel virtual
2702 address space.
2703
9ea77bdb
PA
2704 reservelow= [X86]
2705 Format: nn[K]
2706 Set the amount of memory to reserve for BIOS at
2707 the bottom of the address space.
2708
7e96287d
VG
2709 reset_devices [KNL] Force drivers to reset the underlying device
2710 during initialization.
2711
a9913044
RD
2712 resume= [SWSUSP]
2713 Specify the partition device for software suspend
2df83fa4
MB
2714 Format:
2715 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
1da177e4 2716
ecbd0da1
RW
2717 resume_offset= [SWSUSP]
2718 Specify the offset from the beginning of the partition
2719 given by "resume=" at which the swap header is located,
2720 in <PAGE_SIZE> units (needed only for swap files).
2721 See Documentation/power/swsusp-and-swap-files.txt
2722
f126f733
BS
2723 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2724 read the resume files
2725
6f8d7022
BS
2726 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2727 Useful for devices that are detected asynchronously
2728 (e.g. USB and MMC devices).
2729
f996fc96
BS
2730 hibernate= [HIBERNATION]
2731 noresume Don't check if there's a hibernation image
2732 present during boot.
2733 nocompress Don't compress/decompress hibernation images.
2734
0a7b35cb
MN
2735 retain_initrd [RAM] Keep initrd memory after extraction
2736
1da177e4
LT
2737 rhash_entries= [KNL,NET]
2738 Set number of hash buckets for route cache
2739
2740 riscom8= [HW,SERIAL]
2741 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2742
2743 ro [KNL] Mount root device read-only on boot
2744
2745 root= [KNL] Root filesystem
f2d34fd9 2746 See name_to_dev_t comment in init/do_mounts.c.
1da177e4
LT
2747
2748 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2749 mount the root filesystem
2750
2751 rootflags= [KNL] Set root filesystem mount option string
2752
2753 rootfstype= [KNL] Set root filesystem type
2754
cc1ed754
PO
2755 rootwait [KNL] Wait (indefinitely) for root device to show up.
2756 Useful for devices that are detected asynchronously
2757 (e.g. USB and MMC devices).
2758
5c71d618
RT
2759 rproc_mem=nn[KMG][@address]
2760 [KNL,ARM,CMA] Remoteproc physical memory block.
2761 Memory area to be used by remote processor image,
2762 managed by CMA.
2763
1da177e4
LT
2764 rw [KNL] Mount root device read-write on boot
2765
2766 S [KNL] Run init in single mode
2767
2768 sa1100ir [NET]
2769 See drivers/net/irda/sa1100_ir.c.
2770
1da177e4 2771 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2772
f6630114
MT
2773 sched_debug [KNL] Enables verbose scheduler debug messages.
2774
5307c955
MG
2775 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2776 xtime_lock contention on larger systems, and/or RCU lock
2777 contention on all systems with CONFIG_MAXSMP set.
2778 Format: { "0" | "1" }
2779 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2780 1 -- enable.
2781 Note: increases power consumption, thus should only be
2782 enabled if running jitter sensitive (HPC/RT) workloads.
2783
0cb55ad2
RD
2784 security= [SECURITY] Choose a security module to enable at boot.
2785 If this boot parameter is not specified, only the first
2786 security module asking for security registration will be
2787 loaded. An invalid security module name will be treated
2788 as if no module has been chosen.
2789
2790 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2791 Format: { "0" | "1" }
2792 See security/selinux/Kconfig help text.
2793 0 -- disable.
2794 1 -- enable.
2795 Default value is set via kernel config option.
2796 If enabled at boot time, /selinux/disable can be used
2797 later to disable prior to initial policy load.
2798
c1c124e9
JJ
2799 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2800 Format: { "0" | "1" }
2801 See security/apparmor/Kconfig help text
2802 0 -- disable.
2803 1 -- enable.
2804 Default value is set via kernel config option.
2805
cd4f0ef7 2806 serialnumber [BUGS=X86-32]
1da177e4 2807
1da177e4
LT
2808 shapers= [NET]
2809 Maximal number of shapers.
a9913044 2810
b05f78f5
YL
2811 show_msr= [x86] show boot-time MSR settings
2812 Format: { <integer> }
2813 Show boot-time (BIOS-initialized) MSR settings.
2814 The parameter means the number of CPUs to show,
2815 for example 1 means boot CPU only.
2816
1da177e4
LT
2817 simeth= [IA-64]
2818 simscsi=
a9913044 2819
1da177e4
LT
2820 slram= [HW,MTD]
2821
3df1cccd
DR
2822 slab_max_order= [MM, SLAB]
2823 Determines the maximum allowed order for slabs.
2824 A high setting may cause OOMs due to memory
2825 fragmentation. Defaults to 1 for systems with
2826 more than 32MB of RAM, 0 otherwise.
2827
f0630fff
CL
2828 slub_debug[=options[,slabs]] [MM, SLUB]
2829 Enabling slub_debug allows one to determine the
2830 culprit if slab objects become corrupted. Enabling
2831 slub_debug can create guard zones around objects and
2832 may poison objects when not in use. Also tracks the
2833 last alloc / free. For more information see
2834 Documentation/vm/slub.txt.
c1aee215
CL
2835
2836 slub_max_order= [MM, SLUB]
f0630fff
CL
2837 Determines the maximum allowed order for slabs.
2838 A high setting may cause OOMs due to memory
2839 fragmentation. For more information see
2840 Documentation/vm/slub.txt.
c1aee215
CL
2841
2842 slub_min_objects= [MM, SLUB]
f0630fff
CL
2843 The minimum number of objects per slab. SLUB will
2844 increase the slab order up to slub_max_order to
2845 generate a sufficiently large slab able to contain
2846 the number of objects indicated. The higher the number
2847 of objects the smaller the overhead of tracking slabs
2848 and the less frequently locks need to be acquired.
c1aee215
CL
2849 For more information see Documentation/vm/slub.txt.
2850
2851 slub_min_order= [MM, SLUB]
24775d65 2852 Determines the minimum page order for slabs. Must be
f0630fff 2853 lower than slub_max_order.
c1aee215
CL
2854 For more information see Documentation/vm/slub.txt.
2855
2856 slub_nomerge [MM, SLUB]
f0630fff 2857 Disable merging of slabs with similar size. May be
c1aee215 2858 necessary if there is some reason to distinguish
f0630fff
CL
2859 allocs to different slabs. Debug options disable
2860 merging on their own.
c1aee215
CL
2861 For more information see Documentation/vm/slub.txt.
2862
1da177e4
LT
2863 smart2= [HW]
2864 Format: <io1>[,<io2>[,...,<io8>]]
2865
d0d4f69b
BH
2866 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2867 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2868 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2869 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2870 smsc-ircc2.ircc_irq= [HW] IRQ line
2871 smsc-ircc2.ircc_dma= [HW] DMA channel
2872 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2873 0: Toshiba Satellite 1800 (GP data pin select)
2874 1: Fast pin select (default)
2875 2: ATC IRMode
2876
9c44bc03
IM
2877 softlockup_panic=
2878 [KNL] Should the soft-lockup detector generate panics.
44a4dcf7 2879 Format: <integer>
9c44bc03 2880
1da177e4 2881 sonypi.*= [HW] Sony Programmable I/O Control Device driver
395cf969 2882 See Documentation/laptops/sonypi.txt
1da177e4
LT
2883
2884 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2885 See Documentation/serial/specialix.txt.
1da177e4
LT
2886
2887 spia_io_base= [HW,MTD]
2888 spia_fio_base=
2889 spia_pedr=
2890 spia_peddr=
2891
1ad9a25d
HD
2892 stack_guard_gap= [MM]
2893 override the default stack gap protection. The value
2894 is in page units and it defines how many pages prior
2895 to (for stacks growing down) resp. after (for stacks
2896 growing up) the main stack are reserved for no other
2897 mapping. Default value is 256 pages.
2898
f38f1d2a
SR
2899 stacktrace [FTRACE]
2900 Enabled the stack tracer on boot up.
2901
762e1207
SR
2902 stacktrace_filter=[function-list]
2903 [FTRACE] Limit the functions that the stack tracer
2904 will trace at boot up. function-list is a comma separated
2905 list of functions. This list can be changed at run
2906 time by the stack_trace_filter file in the debugfs
2907 tracing directory. Note, this enables stack tracing
2908 and the stacktrace above is not needed.
2909
1da177e4
LT
2910 sti= [PARISC,HW]
2911 Format: <num>
2912 Set the STI (builtin display/keyboard on the HP-PARISC
2913 machines) console (graphic card) which should be used
2914 as the initial boot-console.
2915 See also comment in drivers/video/console/sticore.c.
2916
2917 sti_font= [HW]
2918 See comment in drivers/video/console/sticore.c.
2919
2920 stifb= [HW]
2921 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2922
cbf11071
TM
2923 sunrpc.min_resvport=
2924 sunrpc.max_resvport=
2925 [NFS,SUNRPC]
2926 SunRPC servers often require that client requests
2927 originate from a privileged port (i.e. a port in the
2928 range 0 < portnr < 1024).
2929 An administrator who wishes to reserve some of these
2930 ports for other uses may adjust the range that the
2931 kernel's sunrpc client considers to be privileged
2932 using these two parameters to set the minimum and
2933 maximum port values.
2934
42a7fc4a
GB
2935 sunrpc.pool_mode=
2936 [NFS]
2937 Control how the NFS server code allocates CPUs to
2938 service thread pools. Depending on how many NICs
2939 you have and where their interrupts are bound, this
2940 option will affect which CPUs will do NFS serving.
2941 Note: this parameter cannot be changed while the
2942 NFS server is running.
2943
2944 auto the server chooses an appropriate mode
2945 automatically using heuristics
2946 global a single global pool contains all CPUs
2947 percpu one pool for each CPU
2948 pernode one pool for each NUMA node (equivalent
2949 to global on non-NUMA machines)
2950
cbf11071
TM
2951 sunrpc.tcp_slot_table_entries=
2952 sunrpc.udp_slot_table_entries=
2953 [NFS,SUNRPC]
2954 Sets the upper limit on the number of simultaneous
2955 RPC calls that can be sent from the client to a
2956 server. Increasing these values may allow you to
2957 improve throughput, but will also increase the
2958 amount of memory reserved for use by the client.
2959
a42c390c
MH
2960 swapaccount[=0|1]
2961 [KNL] Enable accounting of swap in memory resource
2962 controller if no parameter or 1 is given or disable
2963 it if 0 is given (See Documentation/cgroups/memory.txt)
2964
1da177e4 2965 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2966
1da177e4
LT
2967 switches= [HW,M68k]
2968
e52eec13
AK
2969 sysfs.deprecated=0|1 [KNL]
2970 Enable/disable old style sysfs layout for old udev
2971 on older distributions. When this option is enabled
2972 very new udev will not work anymore. When this option
2973 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2974 in older udev will not work anymore.
2975 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2976 the kernel configuration.
2977
5d6f647f
IM
2978 sysrq_always_enabled
2979 [KNL]
2980 Ignore sysrq setting - this boot parameter will
2981 neutralize any effect of /proc/sys/kernel/sysrq.
2982 Useful for debugging.
2983
1da177e4
LT
2984 tdfx= [HW,DRM]
2985
77437fd4
DB
2986 test_suspend= [SUSPEND]
2987 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2988 standby suspend) as the system sleep state to briefly
2989 enter during system startup. The system is woken from
2990 this state using a wakeup-capable RTC alarm.
2991
1da177e4
LT
2992 thash_entries= [KNL,NET]
2993 Set number of hash buckets for TCP connection
2994
f8707ec9
LB
2995 thermal.act= [HW,ACPI]
2996 -1: disable all active trip points in all thermal zones
2997 <degrees C>: override all lowest active trip points
2998
c52a7419
LB
2999 thermal.crt= [HW,ACPI]
3000 -1: disable all critical trip points in all thermal zones
22a94d79 3001 <degrees C>: override all critical trip points
c52a7419 3002
f5487145
LB
3003 thermal.nocrt= [HW,ACPI]
3004 Set to disable actions on ACPI thermal zone
3005 critical and hot trip points.
3006
72b33ef8
LB
3007 thermal.off= [HW,ACPI]
3008 1: disable ACPI thermal control
3009
a70cdc52
LB
3010 thermal.psv= [HW,ACPI]
3011 -1: disable all passive trip points
ada9cfdd
RD
3012 <degrees C>: override all passive trip points to this
3013 value
a70cdc52 3014
730ff34d
LB
3015 thermal.tzp= [HW,ACPI]
3016 Specify global default ACPI thermal zone polling rate
3017 <deci-seconds>: poll all this frequency
3018 0: no polling (default)
3019
8d32a307
TG
3020 threadirqs [KNL]
3021 Force threading of all interrupt handlers except those
24775d65 3022 marked explicitly IRQF_NO_THREAD.
8d32a307 3023
2ca62b04
KRW
3024 tmem [KNL,XEN]
3025 Enable the Transcendent memory driver if built-in.
3026
3027 tmem.cleancache=0|1 [KNL, XEN]
3028 Default is on (1). Disable the usage of the cleancache
3029 API to send anonymous pages to the hypervisor.
3030
3031 tmem.frontswap=0|1 [KNL, XEN]
3032 Default is on (1). Disable the usage of the frontswap
37d46e15
KRW
3033 API to send swap pages to the hypervisor. If disabled
3034 the selfballooning and selfshrinking are force disabled.
2ca62b04
KRW
3035
3036 tmem.selfballooning=0|1 [KNL, XEN]
3037 Default is on (1). Disable the driving of swap pages
3038 to the hypervisor.
3039
3040 tmem.selfshrinking=0|1 [KNL, XEN]
3041 Default is on (1). Partial swapoff that immediately
3042 transfers pages from Xen hypervisor back to the
3043 kernel based on different criteria.
3044
2b1a61f0
HC
3045 topology= [S390]
3046 Format: {off | on}
3047 Specify if the kernel should make use of the cpu
f65e51d7
SL
3048 topology information if the hardware supports this.
3049 The scheduler will make use of this information and
2b1a61f0 3050 e.g. base its process migration decisions on it.
c9af3fa9 3051 Default is on.
2b1a61f0 3052
1da177e4
LT
3053 tp720= [HW,PS2]
3054
225a9be2
RA
3055 tpm_suspend_pcr=[HW,TPM]
3056 Format: integer pcr id
3057 Specify that at suspend time, the tpm driver
3058 should extend the specified pcr with zeros,
3059 as a workaround for some chips which fail to
3060 flush the last written pcr on TPM_SaveState.
3061 This will guarantee that all the other pcrs
3062 are saved.
3063
9d612bef
LZ
3064 trace_buf_size=nn[KMG]
3065 [FTRACE] will set tracing buffer size.
631595fb 3066
020e5f85
LZ
3067 trace_event=[event-list]
3068 [FTRACE] Set and start specified trace events in order
3069 to facilitate early boot debugging.
3070 See also Documentation/trace/events.txt
3071
7bcfaf54
SR
3072 trace_options=[option-list]
3073 [FTRACE] Enable or disable tracer options at boot.
3074 The option-list is a comma delimited list of options
3075 that can be enabled or disabled just as if you were
3076 to echo the option name into
3077
3078 /sys/kernel/debug/tracing/trace_options
3079
3080 For example, to enable stacktrace option (to dump the
3081 stack trace of each event), add to the command line:
3082
3083 trace_options=stacktrace
3084
3085 See also Documentation/trace/ftrace.txt "trace options"
3086 section.
3087
fcf4d821
JK
3088 transparent_hugepage=
3089 [KNL]
3090 Format: [always|madvise|never]
3091 Can be used to control the default behavior of the system
3092 with respect to transparent hugepages.
3093 See Documentation/vm/transhuge.txt for more details.
3094
d3b8f889 3095 tsc= Disable clocksource stability checks for TSC.
395628ef
AK
3096 Format: <string>
3097 [x86] reliable: mark tsc clocksource as reliable, this
d3b8f889
JS
3098 disables clocksource verification at runtime, as well
3099 as the stability checks done at bootup. Used to enable
3100 high-resolution timer mode on older hardware, and in
3101 virtualized environment.
e82b8e4e
VP
3102 [x86] noirqtime: Do not use TSC to do irq accounting.
3103 Used to run time disable IRQ_TIME_ACCOUNTING on any
3104 platforms where RDTSC is slow and this accounting
3105 can add overhead.
395628ef 3106
a9913044
RD
3107 turbografx.map[2|3]= [HW,JOY]
3108 TurboGraFX parallel port interface
3109 Format:
3110 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
3111 See also Documentation/input/joystick-parport.txt
3112
b6935f8c
CK
3113 udbg-immortal [PPC] When debugging early kernel crashes that
3114 happen after console_init() and before a proper
3115 console driver takes over, this boot options might
3116 help "seeing" what's going on.
3117
f86dcc5a
ED
3118 uhash_entries= [KNL,NET]
3119 Set number of hash buckets for UDP/UDP-Lite connections
3120
5f8364b7
AS
3121 uhci-hcd.ignore_oc=
3122 [USB] Ignore overcurrent events (default N).
3123 Some badly-designed motherboards generate lots of
3124 bogus events, for ports that aren't wired to
3125 anything. Set this parameter to avoid log spamming.
3126 Note that genuine overcurrent events won't be
3127 reported either.
3128
e3a61b0a 3129 unknown_nmi_panic
44a4dcf7 3130 [X86] Cause panic on unknown NMI.
e3a61b0a 3131
c4fc2342
CDH
3132 usbcore.authorized_default=
3133 [USB] Default USB device authorization:
3134 (default -1 = authorized except for wireless USB,
3135 0 = not authorized, 1 = authorized)
3136
b5e795f8
AS
3137 usbcore.autosuspend=
3138 [USB] The autosuspend time delay (in seconds) used
3139 for newly-detected USB devices (default 2). This
3140 is the time required before an idle device will be
3141 autosuspended. Devices for which the delay is set
eaafbc3a 3142 to a negative value won't be autosuspended at all.
b5e795f8 3143
fd7c519d
JK
3144 usbcore.usbfs_snoop=
3145 [USB] Set to log all usbfs traffic (default 0 = off).
3146
3147 usbcore.blinkenlights=
3148 [USB] Set to cycle leds on hubs (default 0 = off).
3149
3150 usbcore.old_scheme_first=
3151 [USB] Start with the old device initialization
3152 scheme (default 0 = off).
3153
3f5eb8d5
AS
3154 usbcore.usbfs_memory_mb=
3155 [USB] Memory limit (in MB) for buffers allocated by
3156 usbfs (default = 16, 0 = max = 2047).
3157
fd7c519d
JK
3158 usbcore.use_both_schemes=
3159 [USB] Try the other device initialization scheme
3160 if the first one fails (default 1 = enabled).
3161
3162 usbcore.initial_descriptor_timeout=
3163 [USB] Specifies timeout for the initial 64-byte
3164 USB_REQ_GET_DESCRIPTOR request in milliseconds
3165 (default 5000 = 5.0 seconds).
3166
1da177e4
LT
3167 usbhid.mousepoll=
3168 [USBHID] The interval which mice are to be polled at.
a9913044 3169
d4f373e5
AS
3170 usb-storage.delay_use=
3171 [UMS] The delay in seconds before a new device is
3172 scanned for Logical Units (default 5).
3173
3174 usb-storage.quirks=
3175 [UMS] A list of quirks entries to supplement or
3176 override the built-in unusual_devs list. List
3177 entries are separated by commas. Each entry has
3178 the form VID:PID:Flags where VID and PID are Vendor
3179 and Product ID values (4-digit hex numbers) and
3180 Flags is a set of characters, each corresponding
3181 to a common usb-storage quirk flag as follows:
c838ea46
AS
3182 a = SANE_SENSE (collect more than 18 bytes
3183 of sense data);
a0bb1081
AS
3184 b = BAD_SENSE (don't collect more than 18
3185 bytes of sense data);
d4f373e5
AS
3186 c = FIX_CAPACITY (decrease the reported
3187 device capacity by one sector);
5116901d
KR
3188 d = NO_READ_DISC_INFO (don't use
3189 READ_DISC_INFO command);
3190 e = NO_READ_CAPACITY_16 (don't use
3191 READ_CAPACITY_16 command);
c838ea46
AS
3192 h = CAPACITY_HEURISTICS (decrease the
3193 reported device capacity by one
3194 sector if the number is odd);
d4f373e5
AS
3195 i = IGNORE_DEVICE (don't bind to this
3196 device);
3197 l = NOT_LOCKABLE (don't try to lock and
3198 unlock ejectable media);
3199 m = MAX_SECTORS_64 (don't transfer more
3200 than 64 sectors = 32 KB at a time);
21c13a4f
AS
3201 n = INITIAL_READ10 (force a retry of the
3202 initial READ(10) command);
c838ea46
AS
3203 o = CAPACITY_OK (accept the capacity
3204 reported by the device);
eaa05dfc
NJ
3205 p = WRITE_CACHE (the device cache is ON
3206 by default);
d4f373e5
AS
3207 r = IGNORE_RESIDUE (the device reports
3208 bogus residue values);
3209 s = SINGLE_LUN (the device has only one
3210 Logical Unit);
3211 w = NO_WP_DETECT (don't test whether the
3212 medium is write-protected).
3213 Example: quirks=0419:aaf5:rl,0421:0433:rc
3214
ac1667db
SB
3215 user_debug= [KNL,ARM]
3216 Format: <int>
3217 See arch/arm/Kconfig.debug help text.
3218 1 - undefined instruction events
3219 2 - system calls
3220 4 - invalid data aborts
3221 8 - SIGSEGV faults
3222 16 - SIGBUS faults
3223 Example: user_debug=31
3224
14315592
IC
3225 userpte=
3226 [X86] Flags controlling user PTE allocations.
3227
3228 nohigh = do not allocate PTE pages in
3229 HIGHMEM regardless of setting
3230 of CONFIG_HIGHPTE.
3231
6fa3eb70
S
3232 uuid_debug= (Boolean) whether to enable debugging of TuxOnIce's
3233 uuid support.
3234
6cececfc 3235 vdso= [X86,SH]
1dbf527c 3236 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
3237 vdso=1: enable VDSO (default)
3238 vdso=0: disable VDSO mapping
3239
6cececfc 3240 vdso32= [X86]
af65d648
RM
3241 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3242 vdso32=1: enable 32-bit VDSO (default)
3243 vdso32=0: disable 32-bit VDSO mapping
3244
d080d397
YI
3245 vector= [IA-64,SMP]
3246 vector=percpu: enable percpu vector domain
3247
1da177e4
LT
3248 video= [FB] Frame buffer configuration
3249 See Documentation/fb/modedb.txt.
3250
81a054ce
PM
3251 virtio_mmio.device=
3252 [VMMIO] Memory mapped virtio (platform) device.
3253
3254 <size>@<baseaddr>:<irq>[:<id>]
3255 where:
3256 <size> := size (can use standard suffixes
3257 like K, M and G)
3258 <baseaddr> := physical base address
3259 <irq> := interrupt number (as passed to
3260 request_irq())
3261 <id> := (optional) platform device id
3262 example:
3263 virtio_mmio.device=1K@0x100b0000:48:7
3264
3265 Can be used multiple times for multiple devices.
3266
cd4f0ef7 3267 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 3268 See Documentation/x86/boot.txt and
a9913044 3269 Documentation/svga.txt.
1da177e4
LT
3270 Use vga=ask for menu.
3271 This is actually a boot loader parameter; the value is
3272 passed to the kernel using a special protocol.
3273
a9913044 3274 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
3275 size of <nn>. This can be used to increase the
3276 minimum size (128MB on x86). It can also be used to
3277 decrease the size and leave more room for directly
3278 mapped kernel RAM.
3279
585c3047
PO
3280 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3281 Format: <command>
1da177e4 3282
585c3047
PO
3283 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3284 Format: <command>
3285
3286 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3287 Format: <command>
a9913044 3288
3ae36655
AL
3289 vsyscall= [X86-64]
3290 Controls the behavior of vsyscalls (i.e. calls to
3291 fixed addresses of 0xffffffffff600x00 from legacy
3292 code). Most statically-linked binaries and older
3293 versions of glibc use these calls. Because these
3294 functions are at fixed addresses, they make nice
3295 targets for exploits that can control RIP.
3296
2e57ae05
AL
3297 emulate [default] Vsyscalls turn into traps and are
3298 emulated reasonably safely.
3ae36655 3299
2e57ae05 3300 native Vsyscalls are native syscall instructions.
3ae36655
AL
3301 This is a little bit faster than trapping
3302 and makes a few dynamic recompilers work
3303 better than they would in emulation mode.
3304 It also makes exploits much easier to write.
3305
3306 none Vsyscalls don't work at all. This makes
3307 them quite hard to use for exploits but
3308 might break your system.
3309
9ea9a886
CL
3310 vt.cur_default= [VT] Default cursor shape.
3311 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3312 the parameters of the <Esc>[?A;B;Cc escape sequence;
3313 see VGA-softcursor.txt. Default: 2 = underline.
3314
0cb55ad2
RD
3315 vt.default_blu= [VT]
3316 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3317 Change the default blue palette of the console.
3318 This is a 16-member array composed of values
3319 ranging from 0-255.
3320
3321 vt.default_grn= [VT]
3322 Format: <green0>,<green1>,<green2>,...,<green15>
3323 Change the default green palette of the console.
3324 This is a 16-member array composed of values
3325 ranging from 0-255.
3326
3327 vt.default_red= [VT]
3328 Format: <red0>,<red1>,<red2>,...,<red15>
3329 Change the default red palette of the console.
3330 This is a 16-member array composed of values
3331 ranging from 0-255.
3332
3333 vt.default_utf8=
3334 [VT]
3335 Format=<0|1>
3336 Set system-wide default UTF-8 mode for all tty's.
3337 Default is 1, i.e. UTF-8 mode is enabled for all
3338 newly opened terminals.
3339
f6c06b68
MG
3340 vt.global_cursor_default=
3341 [VT]
3342 Format=<-1|0|1>
3343 Set system-wide default for whether a cursor
3344 is shown on new VTs. Default is -1,
3345 i.e. cursors will be created by default unless
3346 overridden by individual drivers. 0 will hide
3347 cursors, 1 will display them.
3348
4724ba57
RD
3349 watchdog timers [HW,WDT] For information on watchdog timers,
3350 see Documentation/watchdog/watchdog-parameters.txt
3351 or other driver-specific files in the
3352 Documentation/watchdog/ directory.
1da177e4 3353
d55262c4
TH
3354 workqueue.disable_numa
3355 By default, all work items queued to unbound
3356 workqueues are affine to the NUMA nodes they're
3357 issued on, which results in better behavior in
3358 general. If NUMA affinity needs to be disabled for
3359 whatever reason, this option can be used. Note
3360 that this also can be controlled per-workqueue for
3361 workqueues visible under /sys/bus/workqueue/.
3362
0cb55ad2
RD
3363 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3364 default x2apic cluster mode on platforms
3365 supporting x2apic.
3366
bb24c471
JP
3367 x86_mrst_timer= [X86-32,APBT]
3368 Choose timer option for x86 Moorestown MID platform.
3369 Two valid options are apbt timer only and lapic timer
3370 plus one apbt timer for broadcast timer.
3371 x86_mrst_timer=apbt_only | lapic_and_apbt
3372
c1c5413a
SS
3373 xen_emul_unplug= [HW,X86,XEN]
3374 Unplug Xen emulated devices
3375 Format: [unplug0,][unplug1]
3376 ide-disks -- unplug primary master IDE devices
3377 aux-ide-disks -- unplug non-primary-master IDE devices
3378 nics -- unplug network devices
3379 all -- unplug all emulated devices (NICs and IDE disks)
1dc7ce99
IC
3380 unnecessary -- unplugging emulated devices is
3381 unnecessary even if the host did not respond to
3382 the unplug protocol
c93a4dfb 3383 never -- do not unplug even if version check succeeds
c1c5413a 3384
1da177e4 3385 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
3386 Format:
3387 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 3388
a9913044 3389______________________________________________________________________
1da177e4
LT
3390
3391TODO:
3392
1da177e4 3393 Add more DRM drivers.