1 Kernel Parameters 2 ~~~~~~~~~~~~~~~~~ 3 4The following is a consolidated list of the kernel parameters as implemented 5(mostly) by the __setup() macro and sorted into English Dictionary order 6(defined as ignoring all punctuation and sorting digits before letters in a 7case insensitive manner), and with descriptions where known. 8 9Module parameters for loadable modules are specified only as the 10parameter name with optional '=' and value as appropriate, such as: 11 12 modprobe usbcore blinkenlights=1 13 14Module parameters for modules that are built into the kernel image 15are specified on the kernel command line with the module name plus 16'.' plus parameter name, with '=' and value if appropriate, such as: 17 18 usbcore.blinkenlights=1 19 20This document may not be entirely up to date and comprehensive. The command 21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable 22module. Loadable modules, after being loaded into the running kernel, also 23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 24parameters may be changed at runtime by the command 25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 26 27The parameters listed below are only valid if certain kernel build options were 28enabled and if respective hardware is present. The text in square brackets at 29the beginning of each description states the restrictions within which a 30parameter is applicable: 31 32 ACPI ACPI support is enabled. 33 AGP AGP (Accelerated Graphics Port) is enabled. 34 ALSA ALSA sound support is enabled. 35 APIC APIC support is enabled. 36 APM Advanced Power Management support is enabled. 37 AVR32 AVR32 architecture is enabled. 38 AX25 Appropriate AX.25 support is enabled. 39 BLACKFIN Blackfin architecture is enabled. 40 DRM Direct Rendering Management support is enabled. 41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 42 EFI EFI Partitioning (GPT) is enabled 43 EIDE EIDE/ATAPI support is enabled. 44 FB The frame buffer device is enabled. 45 HW Appropriate hardware is enabled. 46 IA-64 IA-64 architecture is enabled. 47 IOSCHED More than one I/O scheduler is enabled. 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 49 ISAPNP ISA PnP code is enabled. 50 ISDN Appropriate ISDN support is enabled. 51 JOY Appropriate joystick support is enabled. 52 LIBATA Libata driver is enabled 53 LP Printer support is enabled. 54 LOOP Loopback device support is enabled. 55 M68k M68k architecture is enabled. 56 These options have more detailed description inside of 57 Documentation/m68k/kernel-options.txt. 58 MCA MCA bus support is enabled. 59 MDA MDA console support is enabled. 60 MOUSE Appropriate mouse support is enabled. 61 MSI Message Signaled Interrupts (PCI). 62 MTD MTD (Memory Technology Device) support is enabled. 63 NET Appropriate network support is enabled. 64 NUMA NUMA support is enabled. 65 GENERIC_TIME The generic timeofday code is enabled. 66 NFS Appropriate NFS support is enabled. 67 OSS OSS sound support is enabled. 68 PV_OPS A paravirtualized kernel is enabled. 69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 70 PARISC The PA-RISC architecture is enabled. 71 PCI PCI bus support is enabled. 72 PCIE PCI Express support is enabled. 73 PCMCIA The PCMCIA subsystem is enabled. 74 PNP Plug & Play support is enabled. 75 PPC PowerPC architecture is enabled. 76 PPT Parallel port support is enabled. 77 PS2 Appropriate PS/2 support is enabled. 78 RAM RAM disk support is enabled. 79 ROOTPLUG The example Root Plug LSM is enabled. 80 S390 S390 architecture is enabled. 81 SCSI Appropriate SCSI support is enabled. 82 A lot of drivers has their options described inside of 83 Documentation/scsi/. 84 SECURITY Different security models are enabled. 85 SELINUX SELinux support is enabled. 86 SERIAL Serial support is enabled. 87 SH SuperH architecture is enabled. 88 SMP The kernel is an SMP kernel. 89 SPARC Sparc architecture is enabled. 90 SWSUSP Software suspend (hibernation) is enabled. 91 SUSPEND System suspend states are enabled. 92 FTRACE Function tracing enabled. 93 TS Appropriate touchscreen support is enabled. 94 UMS USB Mass Storage support is enabled. 95 USB USB support is enabled. 96 USBHID USB Human Interface Device support is enabled. 97 V4L Video For Linux support is enabled. 98 VGA The VGA console has been enabled. 99 VT Virtual terminal support is enabled. 100 WDT Watchdog support is enabled. 101 XT IBM PC/XT MFM hard disk support is enabled. 102 X86-32 X86-32, aka i386 architecture is enabled. 103 X86-64 X86-64 architecture is enabled. 104 More X86-64 boot options can be found in 105 Documentation/x86/x86_64/boot-options.txt . 106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 107 108In addition, the following text indicates that the option: 109 110 BUGS= Relates to possible processor bugs on the said processor. 111 KNL Is a kernel start-up parameter. 112 BOOT Is a boot loader parameter. 113 114Parameters denoted with BOOT are actually interpreted by the boot 115loader, and have no meaning to the kernel directly. 116Do not modify the syntax of boot loader parameters without extreme 117need or coordination with <Documentation/x86/boot.txt>. 118 119There are also arch-specific kernel-parameters not documented here. 120See for example <Documentation/x86/x86_64/boot-options.txt>. 121 122Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 123a trailing = on the name of any parameter states that that parameter will 124be entered as an environment variable, whereas its absence indicates that 125it will appear as a kernel argument readable via /proc/cmdline by programs 126running once the system is up. 127 128The number of kernel parameters is not limited, but the length of the 129complete command line (parameters including spaces etc.) is limited to 130a fixed number of characters. This limit depends on the architecture 131and is between 256 and 4096 characters. It is defined in the file 132./include/asm/setup.h as COMMAND_LINE_SIZE. 133 134 135 acpi= [HW,ACPI,X86-64,i386] 136 Advanced Configuration and Power Interface 137 Format: { force | off | ht | strict | noirq | rsdt } 138 force -- enable ACPI if default was off 139 off -- disable ACPI if default was on 140 noirq -- do not use ACPI for IRQ routing 141 ht -- run only enough ACPI to enable Hyper Threading 142 strict -- Be less tolerant of platforms that are not 143 strictly ACPI specification compliant. 144 rsdt -- prefer RSDT over (default) XSDT 145 146 See also Documentation/power/pm.txt, pci=noacpi 147 148 acpi_apic_instance= [ACPI, IOAPIC] 149 Format: <int> 150 2: use 2nd APIC table, if available 151 1,0: use 1st APIC table 152 default: 0 153 154 acpi_sleep= [HW,ACPI] Sleep options 155 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 156 old_ordering, s4_nonvs } 157 See Documentation/power/video.txt for information on 158 s3_bios and s3_mode. 159 s3_beep is for debugging; it makes the PC's speaker beep 160 as soon as the kernel's real-mode entry point is called. 161 s4_nohwsig prevents ACPI hardware signature from being 162 used during resume from hibernation. 163 old_ordering causes the ACPI 1.0 ordering of the _PTS 164 control method, with respect to putting devices into 165 low power states, to be enforced (the ACPI 2.0 ordering 166 of _PTS is used by default). 167 s4_nonvs prevents the kernel from saving/restoring the 168 ACPI NVS memory during hibernation. 169 170 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 171 Format: { level | edge | high | low } 172 173 acpi_irq_balance [HW,ACPI] 174 ACPI will balance active IRQs 175 default in APIC mode 176 177 acpi_irq_nobalance [HW,ACPI] 178 ACPI will not move active IRQs (default) 179 default in PIC mode 180 181 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 182 use by PCI 183 Format: <irq>,<irq>... 184 185 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 186 Format: <irq>,<irq>... 187 188 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 189 190 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 191 Format: To spoof as Windows 98: ="Microsoft Windows" 192 193 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 194 acpi_osi="string1" # add string1 -- only one string 195 acpi_osi="!string2" # remove built-in string2 196 acpi_osi= # disable all strings 197 198 acpi_serialize [HW,ACPI] force serialization of AML methods 199 200 acpi_skip_timer_override [HW,ACPI] 201 Recognize and ignore IRQ0/pin2 Interrupt Override. 202 For broken nForce2 BIOS resulting in XT-PIC timer. 203 acpi_use_timer_override [HW,ACPI] 204 Use timer override. For some broken Nvidia NF5 boards 205 that require a timer override, but don't have 206 HPET 207 208 acpi_backlight= [HW,ACPI] 209 acpi_backlight=vendor 210 acpi_backlight=video 211 If set to vendor, prefer vendor specific driver 212 (e.g. thinkpad_acpi, sony_acpi, etc.) instead 213 of the ACPI video.ko driver. 214 215 acpi_display_output= [HW,ACPI] 216 acpi_display_output=vendor 217 acpi_display_output=video 218 See above. 219 220 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 221 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 222 Format: <int> 223 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 224 debug output. Bits in debug_layer correspond to a 225 _COMPONENT in an ACPI source file, e.g., 226 #define _COMPONENT ACPI_PCI_COMPONENT 227 Bits in debug_level correspond to a level in 228 ACPI_DEBUG_PRINT statements, e.g., 229 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 230 The debug_level mask defaults to "info". See 231 Documentation/acpi/debug.txt for more information about 232 debug layers and levels. 233 234 Enable processor driver info messages: 235 acpi.debug_layer=0x20000000 236 Enable PCI/PCI interrupt routing info messages: 237 acpi.debug_layer=0x400000 238 Enable AML "Debug" output, i.e., stores to the Debug 239 object while interpreting AML: 240 acpi.debug_layer=0xffffffff acpi.debug_level=0x2 241 Enable all messages related to ACPI hardware: 242 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 243 244 Some values produce so much output that the system is 245 unusable. The "log_buf_len" parameter may be useful 246 if you need to capture more output. 247 248 acpi.power_nocheck= [HW,ACPI] 249 Format: 1/0 enable/disable the check of power state. 250 On some bogus BIOS the _PSC object/_STA object of 251 power resource can't return the correct device power 252 state. In such case it is unneccessary to check its 253 power state again in power transition. 254 1 : disable the power state check 255 256 acpi_pm_good [X86-32,X86-64] 257 Override the pmtimer bug detection: force the kernel 258 to assume that this machine's pmtimer latches its value 259 and always returns good values. 260 261 agp= [AGP] 262 { off | try_unsupported } 263 off: disable AGP support 264 try_unsupported: try to drive unsupported chipsets 265 (may crash computer or cause data corruption) 266 267 enable_timer_pin_1 [i386,x86-64] 268 Enable PIN 1 of APIC timer 269 Can be useful to work around chipset bugs 270 (in particular on some ATI chipsets). 271 The kernel tries to set a reasonable default. 272 273 disable_timer_pin_1 [i386,x86-64] 274 Disable PIN 1 of APIC timer 275 Can be useful to work around chipset bugs. 276 277 ad1848= [HW,OSS] 278 Format: <io>,<irq>,<dma>,<dma2>,<type> 279 280 advansys= [HW,SCSI] 281 See header of drivers/scsi/advansys.c. 282 283 advwdt= [HW,WDT] Advantech WDT 284 Format: <iostart>,<iostop> 285 286 aedsp16= [HW,OSS] Audio Excel DSP 16 287 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 288 See also header of sound/oss/aedsp16.c. 289 290 aha152x= [HW,SCSI] 291 See Documentation/scsi/aha152x.txt. 292 293 aha1542= [HW,SCSI] 294 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 295 296 aic7xxx= [HW,SCSI] 297 See Documentation/scsi/aic7xxx.txt. 298 299 aic79xx= [HW,SCSI] 300 See Documentation/scsi/aic79xx.txt. 301 302 amd_iommu= [HW,X86-84] 303 Pass parameters to the AMD IOMMU driver in the system. 304 Possible values are: 305 isolate - enable device isolation (each device, as far 306 as possible, will get its own protection 307 domain) [default] 308 share - put every device behind one IOMMU into the 309 same protection domain 310 fullflush - enable flushing of IO/TLB entries when 311 they are unmapped. Otherwise they are 312 flushed before they will be reused, which 313 is a lot of faster 314 315 amd_iommu_size= [HW,X86-64] 316 Define the size of the aperture for the AMD IOMMU 317 driver. Possible values are: 318 '32M', '64M' (default), '128M', '256M', '512M', '1G' 319 320 amijoy.map= [HW,JOY] Amiga joystick support 321 Map of devices attached to JOY0DAT and JOY1DAT 322 Format: <a>,<b> 323 See also Documentation/kernel/input/joystick.txt 324 325 analog.map= [HW,JOY] Analog joystick and gamepad support 326 Specifies type or capabilities of an analog joystick 327 connected to one of 16 gameports 328 Format: <type1>,<type2>,..<type16> 329 330 apc= [HW,SPARC] 331 Power management functions (SPARCstation-4/5 + deriv.) 332 Format: noidle 333 Disable APC CPU standby support. SPARCstation-Fox does 334 not play well with APC CPU idle - disable it if you have 335 APC and your system crashes randomly. 336 337 apic= [APIC,i386] Advanced Programmable Interrupt Controller 338 Change the output verbosity whilst booting 339 Format: { quiet (default) | verbose | debug } 340 Change the amount of debugging information output 341 when initialising the APIC and IO-APIC components. 342 343 apm= [APM] Advanced Power Management 344 See header of arch/x86/kernel/apm_32.c. 345 346 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 347 Format: <io>,<irq>,<nodeID> 348 349 ataflop= [HW,M68k] 350 351 atarimouse= [HW,MOUSE] Atari Mouse 352 353 atascsi= [HW,SCSI] Atari SCSI 354 355 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 356 EzKey and similar keyboards 357 358 atkbd.reset= [HW] Reset keyboard during initialization 359 360 atkbd.set= [HW] Select keyboard code set 361 Format: <int> (2 = AT (default), 3 = PS/2) 362 363 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 364 keyboards 365 366 atkbd.softraw= [HW] Choose between synthetic and real raw mode 367 Format: <bool> (0 = real, 1 = synthetic (default)) 368 369 atkbd.softrepeat= [HW] 370 Use software keyboard repeat 371 372 autotest [IA64] 373 374 baycom_epp= [HW,AX25] 375 Format: <io>,<mode> 376 377 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 378 Format: <io>,<mode> 379 See header of drivers/net/hamradio/baycom_par.c. 380 381 baycom_ser_fdx= [HW,AX25] 382 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 383 Format: <io>,<irq>,<mode>[,<baud>] 384 See header of drivers/net/hamradio/baycom_ser_fdx.c. 385 386 baycom_ser_hdx= [HW,AX25] 387 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 388 Format: <io>,<irq>,<mode> 389 See header of drivers/net/hamradio/baycom_ser_hdx.c. 390 391 boot_delay= Milliseconds to delay each printk during boot. 392 Values larger than 10 seconds (10000) are changed to 393 no delay (0). 394 Format: integer 395 396 bootmem_debug [KNL] Enable bootmem allocator debug messages. 397 398 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 399 bttv.radio= Most important insmod options are available as 400 kernel args too. 401 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 402 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 403 404 BusLogic= [HW,SCSI] 405 See drivers/scsi/BusLogic.c, comment before function 406 BusLogic_ParseDriverOptions(). 407 408 c101= [NET] Moxa C101 synchronous serial card 409 410 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 411 Sometimes CPU hardware bugs make them report the cache 412 size incorrectly. The kernel will attempt work arounds 413 to fix known problems, but for some CPUs it is not 414 possible to determine what the correct size should be. 415 This option provides an override for these situations. 416 417 security= [SECURITY] Choose a security module to enable at boot. 418 If this boot parameter is not specified, only the first 419 security module asking for security registration will be 420 loaded. An invalid security module name will be treated 421 as if no module has been chosen. 422 423 capability.disable= 424 [SECURITY] Disable capabilities. This would normally 425 be used only if an alternative security model is to be 426 configured. Potentially dangerous and should only be 427 used if you are entirely sure of the consequences. 428 429 ccw_timeout_log [S390] 430 See Documentation/s390/CommonIO for details. 431 432 cgroup_disable= [KNL] Disable a particular controller 433 Format: {name of the controller(s) to disable} 434 {Currently supported controllers - "memory"} 435 436 checkreqprot [SELINUX] Set initial checkreqprot flag value. 437 Format: { "0" | "1" } 438 See security/selinux/Kconfig help text. 439 0 -- check protection applied by kernel (includes 440 any implied execute protection). 441 1 -- check protection requested by application. 442 Default value is set via a kernel config option. 443 Value can be changed at runtime via 444 /selinux/checkreqprot. 445 446 cio_ignore= [S390] 447 See Documentation/s390/CommonIO for details. 448 449 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 450 [Deprecated] 451 Forces specified clocksource (if available) to be used 452 when calculating gettimeofday(). If specified 453 clocksource is not available, it defaults to PIT. 454 Format: { pit | tsc | cyclone | pmtmr } 455 456 clocksource= [GENERIC_TIME] Override the default clocksource 457 Format: <string> 458 Override the default clocksource and use the clocksource 459 with the name specified. 460 Some clocksource names to choose from, depending on 461 the platform: 462 [all] jiffies (this is the base, fallback clocksource) 463 [ACPI] acpi_pm 464 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 465 pxa_timer,timer3,32k_counter,timer0_1 466 [AVR32] avr32 467 [X86-32] pit,hpet,tsc,vmi-timer; 468 scx200_hrt on Geode; cyclone on IBM x440 469 [MIPS] MIPS 470 [PARISC] cr16 471 [S390] tod 472 [SH] SuperH 473 [SPARC64] tick 474 [X86-64] hpet,tsc 475 476 clearcpuid=BITNUM [X86] 477 Disable CPUID feature X for the kernel. See 478 arch/x86/include/asm/cpufeature.h for the valid bit 479 numbers. Note the Linux specific bits are not necessarily 480 stable over kernel options, but the vendor specific 481 ones should be. 482 Also note that user programs calling CPUID directly 483 or using the feature without checking anything 484 will still see it. This just prevents it from 485 being used by the kernel or shown in /proc/cpuinfo. 486 Also note the kernel might malfunction if you disable 487 some critical bits. 488 489 code_bytes [IA32/X86_64] How many bytes of object code to print 490 in an oops report. 491 Range: 0 - 8192 492 Default: 64 493 494 hpet= [X86-32,HPET] option to control HPET usage 495 Format: { enable (default) | disable | force } 496 disable: disable HPET and use PIT instead 497 force: allow force enabled of undocumented chips (ICH4, 498 VIA, nVidia) 499 500 com20020= [HW,NET] ARCnet - COM20020 chipset 501 Format: 502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 503 504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 505 Format: <io>[,<irq>] 506 507 com90xx= [HW,NET] 508 ARCnet - COM90xx chipset (memory-mapped buffers) 509 Format: <io>[,<irq>[,<memstart>]] 510 511 condev= [HW,S390] console device 512 conmode= 513 514 console= [KNL] Output console device and options. 515 516 tty<n> Use the virtual console device <n>. 517 518 ttyS<n>[,options] 519 ttyUSB0[,options] 520 Use the specified serial port. The options are of 521 the form "bbbbpnf", where "bbbb" is the baud rate, 522 "p" is parity ("n", "o", or "e"), "n" is number of 523 bits, and "f" is flow control ("r" for RTS or 524 omit it). Default is "9600n8". 525 526 See Documentation/serial-console.txt for more 527 information. See 528 Documentation/networking/netconsole.txt for an 529 alternative. 530 531 uart[8250],io,<addr>[,options] 532 uart[8250],mmio,<addr>[,options] 533 Start an early, polled-mode console on the 8250/16550 534 UART at the specified I/O port or MMIO address, 535 switching to the matching ttyS device later. The 536 options are the same as for ttyS, above. 537 538 If the device connected to the port is not a TTY but a braille 539 device, prepend "brl," before the device type, for instance 540 console=brl,ttyS0 541 For now, only VisioBraille is supported. 542 543 earlycon= [KNL] Output early console device and options. 544 uart[8250],io,<addr>[,options] 545 uart[8250],mmio,<addr>[,options] 546 Start an early, polled-mode console on the 8250/16550 547 UART at the specified I/O port or MMIO address. 548 The options are the same as for ttyS, above. 549 550 no_console_suspend 551 [HW] Never suspend the console 552 Disable suspending of consoles during suspend and 553 hibernate operations. Once disabled, debugging 554 messages can reach various consoles while the rest 555 of the system is being put to sleep (ie, while 556 debugging driver suspend/resume hooks). This may 557 not work reliably with all consoles, but is known 558 to work with serial and VGA consoles. 559 560 coredump_filter= 561 [KNL] Change the default value for 562 /proc/<pid>/coredump_filter. 563 See also Documentation/filesystems/proc.txt. 564 565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 566 Format: 567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 568 569 crashkernel=nn[KMG]@ss[KMG] 570 [KNL] Reserve a chunk of physical memory to 571 hold a kernel to switch to with kexec on panic. 572 573 crashkernel=range1:size1[,range2:size2,...][@offset] 574 [KNL] Same as above, but depends on the memory 575 in the running system. The syntax of range is 576 start-[end] where start and end are both 577 a memory unit (amount[KMG]). See also 578 Documentation/kdump/kdump.txt for a example. 579 580 cs89x0_dma= [HW,NET] 581 Format: <dma> 582 583 cs89x0_media= [HW,NET] 584 Format: { rj45 | aui | bnc } 585 586 dasd= [HW,NET] 587 See header of drivers/s390/block/dasd_devmap.c. 588 589 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 590 (one device per port) 591 Format: <port#>,<type> 592 See also Documentation/input/joystick-parport.txt 593 594 debug [KNL] Enable kernel debugging (events log level). 595 596 debug_locks_verbose= 597 [KNL] verbose self-tests 598 Format=<0|1> 599 Print debugging info while doing the locking API 600 self-tests. 601 We default to 0 (no extra messages), setting it to 602 1 will print _a lot_ more information - normally 603 only useful to kernel developers. 604 605 debug_objects [KNL] Enable object debugging 606 607 debugpat [X86] Enable PAT debugging 608 609 decnet.addr= [HW,NET] 610 Format: <area>[,<node>] 611 See also Documentation/networking/decnet.txt. 612 613 vt.default_blu= [VT] 614 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 615 Change the default blue palette of the console. 616 This is a 16-member array composed of values 617 ranging from 0-255. 618 619 vt.default_grn= [VT] 620 Format: <green0>,<green1>,<green2>,...,<green15> 621 Change the default green palette of the console. 622 This is a 16-member array composed of values 623 ranging from 0-255. 624 625 vt.default_red= [VT] 626 Format: <red0>,<red1>,<red2>,...,<red15> 627 Change the default red palette of the console. 628 This is a 16-member array composed of values 629 ranging from 0-255. 630 631 vt.default_utf8= 632 [VT] 633 Format=<0|1> 634 Set system-wide default UTF-8 mode for all tty's. 635 Default is 1, i.e. UTF-8 mode is enabled for all 636 newly opened terminals. 637 638 dhash_entries= [KNL] 639 Set number of hash buckets for dentry cache. 640 641 digi= [HW,SERIAL] 642 IO parameters + enable/disable command. 643 644 digiepca= [HW,SERIAL] 645 See drivers/char/README.epca and 646 Documentation/serial/digiepca.txt. 647 648 disable_mtrr_cleanup [X86] 649 enable_mtrr_cleanup [X86] 650 The kernel tries to adjust MTRR layout from continuous 651 to discrete, to make X server driver able to add WB 652 entry later. This parameter enables/disables that. 653 654 mtrr_chunk_size=nn[KMG] [X86] 655 used for mtrr cleanup. It is largest continous chunk 656 that could hold holes aka. UC entries. 657 658 mtrr_gran_size=nn[KMG] [X86] 659 Used for mtrr cleanup. It is granularity of mtrr block. 660 Default is 1. 661 Large value could prevent small alignment from 662 using up MTRRs. 663 664 mtrr_spare_reg_nr=n [X86] 665 Format: <integer> 666 Range: 0,7 : spare reg number 667 Default : 1 668 Used for mtrr cleanup. It is spare mtrr entries number. 669 Set to 2 or more if your graphical card needs more. 670 671 disable_mtrr_trim [X86, Intel and AMD only] 672 By default the kernel will trim any uncacheable 673 memory out of your available memory pool based on 674 MTRR settings. This parameter disables that behavior, 675 possibly causing your machine to run very slowly. 676 677 dmasound= [HW,OSS] Sound subsystem buffers 678 679 dscc4.setup= [NET] 680 681 dtc3181e= [HW,SCSI] 682 683 earlyprintk= [X86-32,X86-64,SH,BLACKFIN] 684 earlyprintk=vga 685 earlyprintk=serial[,ttySn[,baudrate]] 686 earlyprintk=dbgp 687 688 Append ",keep" to not disable it when the real console 689 takes over. 690 691 Only vga or serial or usb debug port at a time. 692 693 Currently only ttyS0 and ttyS1 are supported. 694 695 Interaction with the standard serial driver is not 696 very good. 697 698 The VGA output is eventually overwritten by the real 699 console. 700 701 eata= [HW,SCSI] 702 703 edd= [EDD] 704 Format: {"off" | "on" | "skip[mbr]"} 705 706 eisa_irq_edge= [PARISC,HW] 707 See header of drivers/parisc/eisa.c. 708 709 elanfreq= [X86-32] 710 See comment before function elanfreq_setup() in 711 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 712 713 elevator= [IOSCHED] 714 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 715 See Documentation/block/as-iosched.txt and 716 Documentation/block/deadline-iosched.txt for details. 717 718 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64] 719 Specifies physical address of start of kernel core 720 image elf header. Generally kexec loader will 721 pass this option to capture kernel. 722 See Documentation/kdump/kdump.txt for details. 723 724 enforcing [SELINUX] Set initial enforcing status. 725 Format: {"0" | "1"} 726 See security/selinux/Kconfig help text. 727 0 -- permissive (log only, no denials). 728 1 -- enforcing (deny and log). 729 Default value is 0. 730 Value can be changed at runtime via /selinux/enforce. 731 732 ether= [HW,NET] Ethernet cards parameters 733 This option is obsoleted by the "netdev=" option, which 734 has equivalent usage. See its documentation for details. 735 736 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 737 Format: <io>[,<irq>] 738 739 failslab= 740 fail_page_alloc= 741 fail_make_request=[KNL] 742 General fault injection mechanism. 743 Format: <interval>,<probability>,<space>,<times> 744 See also /Documentation/fault-injection/. 745 746 fd_mcs= [HW,SCSI] 747 See header of drivers/scsi/fd_mcs.c. 748 749 fdomain= [HW,SCSI] 750 See header of drivers/scsi/fdomain.c. 751 752 floppy= [HW] 753 See Documentation/blockdev/floppy.txt. 754 755 force_pal_cache_flush 756 [IA-64] Avoid check_sal_cache_flush which may hang on 757 buggy SAL_CACHE_FLUSH implementations. Using this 758 parameter will force ia64_sal_cache_flush to call 759 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 760 761 ftrace=[tracer] 762 [ftrace] will set and start the specified tracer 763 as early as possible in order to facilitate early 764 boot debugging. 765 766 ftrace_dump_on_oops 767 [ftrace] will dump the trace buffers on oops. 768 769 gamecon.map[2|3]= 770 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 771 support via parallel port (up to 5 devices per port) 772 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 773 See also Documentation/input/joystick-parport.txt 774 775 gamma= [HW,DRM] 776 777 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 778 Format: off | on 779 default: on 780 781 gdth= [HW,SCSI] 782 See header of drivers/scsi/gdth.c. 783 784 gpt [EFI] Forces disk with valid GPT signature but 785 invalid Protective MBR to be treated as GPT. 786 787 gvp11= [HW,SCSI] 788 789 hashdist= [KNL,NUMA] Large hashes allocated during boot 790 are distributed across NUMA nodes. Defaults on 791 for IA-64, off otherwise. 792 Format: 0 | 1 (for off | on) 793 794 hcl= [IA-64] SGI's Hardware Graph compatibility layer 795 796 hd= [EIDE] (E)IDE hard drive subsystem geometry 797 Format: <cyl>,<head>,<sect> 798 799 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 800 size of <nn>. This works even on boxes that have no 801 highmem otherwise. This also works to reduce highmem 802 size on bigger boxes. 803 804 highres= [KNL] Enable/disable high resolution timer mode. 805 Valid parameters: "on", "off" 806 Default: "on" 807 808 hisax= [HW,ISDN] 809 See Documentation/isdn/README.HiSax. 810 811 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 812 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 813 On x86-64 and powerpc, this option can be specified 814 multiple times interleaved with hugepages= to reserve 815 huge pages of different sizes. Valid pages sizes on 816 x86-64 are 2M (when the CPU supports "pse") and 1G 817 (when the CPU supports the "pdpe1gb" cpuinfo flag) 818 Note that 1GB pages can only be allocated at boot time 819 using hugepages= and not freed afterwards. 820 default_hugepagesz= 821 [same as hugepagesz=] The size of the default 822 HugeTLB page size. This is the size represented by 823 the legacy /proc/ hugepages APIs, used for SHM, and 824 default size when mounting hugetlbfs filesystems. 825 Defaults to the default architecture's huge page size 826 if not specified. 827 828 hlt [BUGS=ARM,SH] 829 830 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 831 terminal devices. Valid values: 0..8 832 833 i8042.debug [HW] Toggle i8042 debug mode 834 i8042.direct [HW] Put keyboard port into non-translated mode 835 i8042.dumbkbd [HW] Pretend that controller can only read data from 836 keyboard and cannot control its state 837 (Don't attempt to blink the leds) 838 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 839 i8042.nokbd [HW] Don't check/create keyboard port 840 i8042.noloop [HW] Disable the AUX Loopback command while probing 841 for the AUX port 842 i8042.nomux [HW] Don't check presence of an active multiplexing 843 controller 844 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 845 controllers 846 i8042.panicblink= 847 [HW] Frequency with which keyboard LEDs should blink 848 when kernel panics (default is 0.5 sec) 849 i8042.reset [HW] Reset the controller during init and cleanup 850 i8042.unlock [HW] Unlock (ignore) the keylock 851 852 i810= [HW,DRM] 853 854 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 855 indicates that the driver is running on unsupported 856 hardware. 857 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 858 does not match list of supported models. 859 i8k.power_status 860 [HW] Report power status in /proc/i8k 861 (disabled by default) 862 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 863 capability is set. 864 865 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 866 See Documentation/mca.txt. 867 868 icn= [HW,ISDN] 869 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 870 871 ide-core.nodma= [HW] (E)IDE subsystem 872 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 873 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom 874 .chs .ignore_cable are additional options 875 See Documentation/ide/ide.txt. 876 877 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed 878 See Documentation/ide/ide.txt. 879 880 idle= [X86] 881 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 882 Poll forces a polling idle loop that can slightly 883 improve the performance of waking up a idle CPU, but 884 will use a lot of power and make the system run hot. 885 Not recommended. 886 idle=mwait: On systems which support MONITOR/MWAIT but 887 the kernel chose to not use it because it doesn't save 888 as much power as a normal idle loop, use the 889 MONITOR/MWAIT idle loop anyways. Performance should be 890 the same as idle=poll. 891 idle=halt: Halt is forced to be used for CPU idle. 892 In such case C2/C3 won't be used again. 893 idle=nomwait: Disable mwait for CPU C-states 894 895 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 896 Claim all unknown PCI IDE storage controllers. 897 898 ignore_loglevel [KNL] 899 Ignore loglevel setting - this will print /all/ 900 kernel messages to the console. Useful for debugging. 901 902 ihash_entries= [KNL] 903 Set number of hash buckets for inode cache. 904 905 in2000= [HW,SCSI] 906 See header of drivers/scsi/in2000.c. 907 908 init= [KNL] 909 Format: <full_path> 910 Run specified binary instead of /sbin/init as init 911 process. 912 913 initcall_debug [KNL] Trace initcalls as they are executed. Useful 914 for working out where the kernel is dying during 915 startup. 916 917 initrd= [BOOT] Specify the location of the initial ramdisk 918 919 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 920 Format: <irq> 921 922 inttest= [IA64] 923 924 iomem= Disable strict checking of access to MMIO memory 925 strict regions from userspace. 926 relaxed 927 928 iommu= [x86] 929 off 930 force 931 noforce 932 biomerge 933 panic 934 nopanic 935 merge 936 nomerge 937 forcesac 938 soft 939 940 941 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 942 on 943 Enable intel iommu driver. 944 off 945 Disable intel iommu driver. 946 igfx_off [Default Off] 947 By default, gfx is mapped as normal device. If a gfx 948 device has a dedicated DMAR unit, the DMAR unit is 949 bypassed by not enabling DMAR with this option. In 950 this case, gfx device will use physical address for 951 DMA. 952 forcedac [x86_64] 953 With this option iommu will not optimize to look 954 for io virtual address below 32 bit forcing dual 955 address cycle on pci bus for cards supporting greater 956 than 32 bit addressing. The default is to look 957 for translation below 32 bit and if not available 958 then look in the higher range. 959 strict [Default Off] 960 With this option on every unmap_single operation will 961 result in a hardware IOTLB flush operation as opposed 962 to batching them for performance. 963 964 io_delay= [X86-32,X86-64] I/O delay method 965 0x80 966 Standard port 0x80 based delay 967 0xed 968 Alternate port 0xed based delay (needed on some systems) 969 udelay 970 Simple two microseconds delay 971 none 972 No delay 973 974 io7= [HW] IO7 for Marvel based alpha systems 975 See comment before marvel_specify_io7 in 976 arch/alpha/kernel/core_marvel.c. 977 978 ip= [IP_PNP] 979 See Documentation/filesystems/nfsroot.txt. 980 981 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 982 See comment before ip2_setup() in 983 drivers/char/ip2/ip2base.c. 984 985 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 986 See header of drivers/scsi/ips.c. 987 988 ports= [IP_VS_FTP] IPVS ftp helper module 989 Default is 21. 990 Up to 8 (IP_VS_APP_MAX_PORTS) ports 991 may be specified. 992 Format: <port>,<port>.... 993 994 irqfixup [HW] 995 When an interrupt is not handled search all handlers 996 for it. Intended to get systems with badly broken 997 firmware running. 998 999 irqpoll [HW] 1000 When an interrupt is not handled search all handlers 1001 for it. Also check all handlers each timer 1002 interrupt. Intended to get systems with badly broken 1003 firmware running. 1004 1005 isapnp= [ISAPNP] 1006 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1007 1008 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1009 Format: 1010 <cpu number>,...,<cpu number> 1011 or 1012 <cpu number>-<cpu number> 1013 (must be a positive range in ascending order) 1014 or a mixture 1015 <cpu number>,...,<cpu number>-<cpu number> 1016 1017 This option can be used to specify one or more CPUs 1018 to isolate from the general SMP balancing and scheduling 1019 algorithms. You can move a process onto or off an 1020 "isolated" CPU via the CPU affinity syscalls or cpuset. 1021 <cpu number> begins at 0 and the maximum value is 1022 "number of CPUs in system - 1". 1023 1024 This option is the preferred way to isolate CPUs. The 1025 alternative -- manually setting the CPU mask of all 1026 tasks in the system -- can cause problems and 1027 suboptimal load balancer performance. 1028 1029 iucv= [HW,NET] 1030 1031 js= [HW,JOY] Analog joystick 1032 See Documentation/input/joystick.txt. 1033 1034 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 1035 specifies the amount of memory usable by the kernel 1036 for non-movable allocations. The requested amount is 1037 spread evenly throughout all nodes in the system. The 1038 remaining memory in each node is used for Movable 1039 pages. In the event, a node is too small to have both 1040 kernelcore and Movable pages, kernelcore pages will 1041 take priority and other nodes will have a larger number 1042 of kernelcore pages. The Movable zone is used for the 1043 allocation of pages that may be reclaimed or moved 1044 by the page migration subsystem. This means that 1045 HugeTLB pages may not be allocated from this zone. 1046 Note that allocations like PTEs-from-HighMem still 1047 use the HighMem zone if it exists, and the Normal 1048 zone if it does not. 1049 1050 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 1051 is similar to kernelcore except it specifies the 1052 amount of memory used for migratable allocations. 1053 If both kernelcore and movablecore is specified, 1054 then kernelcore will be at *least* the specified 1055 value but may be more. If movablecore on its own 1056 is specified, the administrator must be careful 1057 that the amount of memory usable for all allocations 1058 is not too small. 1059 1060 keepinitrd [HW,ARM] 1061 1062 kstack=N [X86-32,X86-64] Print N words from the kernel stack 1063 in oops dumps. 1064 1065 kgdboc= [HW] kgdb over consoles. 1066 Requires a tty driver that supports console polling. 1067 (only serial suported for now) 1068 Format: <serial_device>[,baud] 1069 1070 kmac= [MIPS] korina ethernet MAC address. 1071 Configure the RouterBoard 532 series on-chip 1072 Ethernet adapter MAC address. 1073 1074 l2cr= [PPC] 1075 1076 l3cr= [PPC] 1077 1078 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1079 disabled it. 1080 1081 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer 1082 in C2 power state. 1083 1084 libata.dma= [LIBATA] DMA control 1085 libata.dma=0 Disable all PATA and SATA DMA 1086 libata.dma=1 PATA and SATA Disk DMA only 1087 libata.dma=2 ATAPI (CDROM) DMA only 1088 libata.dma=4 Compact Flash DMA only 1089 Combinations also work, so libata.dma=3 enables DMA 1090 for disks and CDROMs, but not CFs. 1091 1092 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1093 when set. 1094 Format: <int> 1095 1096 libata.force= [LIBATA] Force configurations. The format is comma 1097 separated list of "[ID:]VAL" where ID is 1098 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1099 matching port, link or device. Basically, it matches 1100 the ATA ID string printed on console by libata. If 1101 the whole ID part is omitted, the last PORT and DEVICE 1102 values are used. If ID hasn't been specified yet, the 1103 configuration applies to all ports, links and devices. 1104 1105 If only DEVICE is omitted, the parameter applies to 1106 the port and all links and devices behind it. DEVICE 1107 number of 0 either selects the first device or the 1108 first fan-out link behind PMP device. It does not 1109 select the host link. DEVICE number of 15 selects the 1110 host link and device attached to it. 1111 1112 The VAL specifies the configuration to force. As long 1113 as there's no ambiguity shortcut notation is allowed. 1114 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1115 The following configurations can be forced. 1116 1117 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1118 Any ID with matching PORT is used. 1119 1120 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1121 1122 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1123 udma[/][16,25,33,44,66,100,133] notation is also 1124 allowed. 1125 1126 * [no]ncq: Turn on or off NCQ. 1127 1128 * nohrst, nosrst, norst: suppress hard, soft 1129 and both resets. 1130 1131 If there are multiple matching configurations changing 1132 the same attribute, the last one is used. 1133 1134 lmb=debug [KNL] Enable lmb debug messages. 1135 1136 load_ramdisk= [RAM] List of ramdisks to load from floppy 1137 See Documentation/blockdev/ramdisk.txt. 1138 1139 lockd.nlm_grace_period=P [NFS] Assign grace period. 1140 Format: <integer> 1141 1142 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1143 Format: <integer> 1144 1145 lockd.nlm_timeout=T [NFS] Assign timeout value. 1146 Format: <integer> 1147 1148 lockd.nlm_udpport=M [NFS] Assign UDP port. 1149 Format: <integer> 1150 1151 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1152 Format: <irq> 1153 1154 loglevel= All Kernel Messages with a loglevel smaller than the 1155 console loglevel will be printed to the console. It can 1156 also be changed with klogd or other programs. The 1157 loglevels are defined as follows: 1158 1159 0 (KERN_EMERG) system is unusable 1160 1 (KERN_ALERT) action must be taken immediately 1161 2 (KERN_CRIT) critical conditions 1162 3 (KERN_ERR) error conditions 1163 4 (KERN_WARNING) warning conditions 1164 5 (KERN_NOTICE) normal but significant condition 1165 6 (KERN_INFO) informational 1166 7 (KERN_DEBUG) debug-level messages 1167 1168 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1169 Format: { n | nk | nM } 1170 n must be a power of two. The default size 1171 is set in the kernel config file. 1172 1173 logo.nologo [FB] Disables display of the built-in Linux logo. 1174 This may be used to provide more screen space for 1175 kernel log messages and is useful when debugging 1176 kernel boot problems. 1177 1178 lp=0 [LP] Specify parallel ports to use, e.g, 1179 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1180 lp=reset first parallel port). 'lp=0' disables the 1181 lp=auto printer driver. 'lp=reset' (which can be 1182 specified in addition to the ports) causes 1183 attached printers to be reset. Using 1184 lp=port1,port2,... specifies the parallel ports 1185 to associate lp devices with, starting with 1186 lp0. A port specification may be 'none' to skip 1187 that lp device, or a parport name such as 1188 'parport0'. Specifying 'lp=auto' instead of a 1189 port specification list means that device IDs 1190 from each port should be examined, to see if 1191 an IEEE 1284-compliant printer is attached; if 1192 so, the driver will manage that printer. 1193 See also header of drivers/char/lp.c. 1194 1195 lpj=n [KNL] 1196 Sets loops_per_jiffy to given constant, thus avoiding 1197 time-consuming boot-time autodetection (up to 250 ms per 1198 CPU). 0 enables autodetection (default). To determine 1199 the correct value for your kernel, boot with normal 1200 autodetection and see what value is printed. Note that 1201 on SMP systems the preset will be applied to all CPUs, 1202 which is likely to cause problems if your CPUs need 1203 significantly divergent settings. An incorrect value 1204 will cause delays in the kernel to be wrong, leading to 1205 unpredictable I/O errors and other breakage. Although 1206 unlikely, in the extreme case this might damage your 1207 hardware. 1208 1209 ltpc= [NET] 1210 Format: <io>,<irq>,<dma> 1211 1212 mac5380= [HW,SCSI] Format: 1213 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1214 1215 machvec= [IA64] Force the use of a particular machine-vector 1216 (machvec) in a generic kernel. 1217 Example: machvec=hpzx1_swiotlb 1218 1219 max_loop= [LOOP] Maximum number of loopback devices that can 1220 be mounted 1221 Format: <1-256> 1222 1223 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1224 should make use of. maxcpus=n : n >= 0 limits the 1225 kernel to using 'n' processors. n=0 is a special case, 1226 it is equivalent to "nosmp", which also disables 1227 the IO APIC. 1228 1229 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than 1230 or equal to this physical address is ignored. 1231 1232 max_luns= [SCSI] Maximum number of LUNs to probe. 1233 Should be between 1 and 2^32-1. 1234 1235 max_report_luns= 1236 [SCSI] Maximum number of LUNs received. 1237 Should be between 1 and 16384. 1238 1239 mcatest= [IA-64] 1240 1241 mce [X86-32] Machine Check Exception 1242 1243 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1244 1245 md= [HW] RAID subsystems devices and level 1246 See Documentation/md.txt. 1247 1248 mdacon= [MDA] 1249 Format: <first>,<last> 1250 Specifies range of consoles to be captured by the MDA. 1251 1252 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1253 Amount of memory to be used when the kernel is not able 1254 to see the whole system memory or for test. 1255 [X86-32] Use together with memmap= to avoid physical 1256 address space collisions. Without memmap= PCI devices 1257 could be placed at addresses belonging to unused RAM. 1258 1259 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1260 memory. 1261 1262 memchunk=nn[KMG] 1263 [KNL,SH] Allow user to override the default size for 1264 per-device physically contiguous DMA buffers. 1265 1266 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact 1267 E820 memory map, as specified by the user. 1268 Such memmap=exactmap lines can be constructed based on 1269 BIOS output or other requirements. See the memmap=nn@ss 1270 option description. 1271 1272 memmap=nn[KMG]@ss[KMG] 1273 [KNL] Force usage of a specific region of memory 1274 Region of memory to be used, from ss to ss+nn. 1275 1276 memmap=nn[KMG]#ss[KMG] 1277 [KNL,ACPI] Mark specific memory as ACPI data. 1278 Region of memory to be used, from ss to ss+nn. 1279 1280 memmap=nn[KMG]$ss[KMG] 1281 [KNL,ACPI] Mark specific memory as reserved. 1282 Region of memory to be used, from ss to ss+nn. 1283 Example: Exclude memory from 0x18690000-0x1869ffff 1284 memmap=64K$0x18690000 1285 or 1286 memmap=0x10000$0x18690000 1287 1288 memory_corruption_check=0/1 [X86] 1289 Some BIOSes seem to corrupt the first 64k of 1290 memory when doing things like suspend/resume. 1291 Setting this option will scan the memory 1292 looking for corruption. Enabling this will 1293 both detect corruption and prevent the kernel 1294 from using the memory being corrupted. 1295 However, its intended as a diagnostic tool; if 1296 repeatable BIOS-originated corruption always 1297 affects the same memory, you can use memmap= 1298 to prevent the kernel from using that memory. 1299 1300 memory_corruption_check_size=size [X86] 1301 By default it checks for corruption in the low 1302 64k, making this memory unavailable for normal 1303 use. Use this parameter to scan for 1304 corruption in more or less memory. 1305 1306 memory_corruption_check_period=seconds [X86] 1307 By default it checks for corruption every 60 1308 seconds. Use this parameter to check at some 1309 other rate. 0 disables periodic checking. 1310 1311 memtest= [KNL,X86] Enable memtest 1312 Format: <integer> 1313 range: 0,4 : pattern number 1314 default : 0 <disable> 1315 1316 meye.*= [HW] Set MotionEye Camera parameters 1317 See Documentation/video4linux/meye.txt. 1318 1319 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1320 Multi-Function General Purpose Timers on AMD Geode 1321 platforms. 1322 1323 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1324 the BIOS has incorrectly applied a workaround. TinyBIOS 1325 version 0.98 is known to be affected, 0.99 fixes the 1326 problem by letting the user disable the workaround. 1327 1328 mga= [HW,DRM] 1329 1330 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1331 physical address is ignored. 1332 1333 mminit_loglevel= 1334 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1335 parameter allows control of the logging verbosity for 1336 the additional memory initialisation checks. A value 1337 of 0 disables mminit logging and a level of 4 will 1338 log everything. Information is printed at KERN_DEBUG 1339 so loglevel=8 may also need to be specified. 1340 1341 mousedev.tap_time= 1342 [MOUSE] Maximum time between finger touching and 1343 leaving touchpad surface for touch to be considered 1344 a tap and be reported as a left button click (for 1345 touchpads working in absolute mode only). 1346 Format: <msecs> 1347 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1348 reporting absolute coordinates, such as tablets 1349 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1350 reporting absolute coordinates, such as tablets 1351 1352 mpu401= [HW,OSS] 1353 Format: <io>,<irq> 1354 1355 MTD_Partition= [MTD] 1356 Format: <name>,<region-number>,<size>,<offset> 1357 1358 MTD_Region= [MTD] Format: 1359 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1360 1361 mtdparts= [MTD] 1362 See drivers/mtd/cmdlinepart.c. 1363 1364 mtdset= [ARM] 1365 ARM/S3C2412 JIVE boot control 1366 1367 See arch/arm/mach-s3c2412/mach-jive.c 1368 1369 mtouchusb.raw_coordinates= 1370 [HW] Make the MicroTouch USB driver use raw coordinates 1371 ('y', default) or cooked coordinates ('n') 1372 1373 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1374 1375 NCR_D700= [HW,SCSI] 1376 See header of drivers/scsi/NCR_D700.c. 1377 1378 ncr5380= [HW,SCSI] 1379 1380 ncr53c400= [HW,SCSI] 1381 1382 ncr53c400a= [HW,SCSI] 1383 1384 ncr53c406a= [HW,SCSI] 1385 1386 ncr53c8xx= [HW,SCSI] 1387 1388 netdev= [NET] Network devices parameters 1389 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1390 Note that mem_start is often overloaded to mean 1391 something different and driver-specific. 1392 This usage is only documented in each driver source 1393 file if at all. 1394 1395 nf_conntrack.acct= 1396 [NETFILTER] Enable connection tracking flow accounting 1397 0 to disable accounting 1398 1 to enable accounting 1399 Default value depends on CONFIG_NF_CT_ACCT that is 1400 going to be removed in 2.6.29. 1401 1402 nfsaddrs= [NFS] 1403 See Documentation/filesystems/nfsroot.txt. 1404 1405 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1406 See Documentation/filesystems/nfsroot.txt. 1407 1408 nfs.callback_tcpport= 1409 [NFS] set the TCP port on which the NFSv4 callback 1410 channel should listen. 1411 1412 nfs.idmap_cache_timeout= 1413 [NFS] set the maximum lifetime for idmapper cache 1414 entries. 1415 1416 nfs.enable_ino64= 1417 [NFS] enable 64-bit inode numbers. 1418 If zero, the NFS client will fake up a 32-bit inode 1419 number for the readdir() and stat() syscalls instead 1420 of returning the full 64-bit number. 1421 The default is to return 64-bit inode numbers. 1422 1423 nmi_debug= [KNL,AVR32] Specify one or more actions to take 1424 when a NMI is triggered. 1425 Format: [state][,regs][,debounce][,die] 1426 1427 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels 1428 Format: [panic,][num] 1429 Valid num: 0,1,2 1430 0 - turn nmi_watchdog off 1431 1 - use the IO-APIC timer for the NMI watchdog 1432 2 - use the local APIC for the NMI watchdog using 1433 a performance counter. Note: This will use one performance 1434 counter and the local APIC's performance vector. 1435 When panic is specified panic when an NMI watchdog timeout occurs. 1436 This is useful when you use a panic=... timeout and need the box 1437 quickly up again. 1438 Instead of 1 and 2 it is possible to use the following 1439 symbolic names: lapic and ioapic 1440 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic 1441 1442 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1443 emulation library even if a 387 maths coprocessor 1444 is present. 1445 1446 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1447 caches in the slab allocator. Saves per-node memory, 1448 but will impact performance. 1449 1450 noalign [KNL,ARM] 1451 1452 noapic [SMP,APIC] Tells the kernel to not make use of any 1453 IOAPICs that may be present in the system. 1454 1455 nobats [PPC] Do not use BATs for mapping kernel lowmem 1456 on "Classic" PPC cores. 1457 1458 nocache [ARM] 1459 1460 nodelayacct [KNL] Disable per-task delay accounting 1461 1462 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1463 1464 nodsp [SH] Disable hardware DSP at boot time. 1465 1466 noefi [X86-32,X86-64] Disable EFI runtime services support. 1467 1468 noexec [IA-64] 1469 1470 noexec [X86-32,X86-64] 1471 On X86-32 available only on PAE configured kernels. 1472 noexec=on: enable non-executable mappings (default) 1473 noexec=off: disable non-executable mappings 1474 1475 noexec32 [X86-64] 1476 This affects only 32-bit executables. 1477 noexec32=on: enable non-executable mappings (default) 1478 read doesn't imply executable mappings 1479 noexec32=off: disable non-executable mappings 1480 read implies executable mappings 1481 1482 nofpu [SH] Disable hardware FPU at boot time. 1483 1484 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1485 register save and restore. The kernel will only save 1486 legacy floating-point registers on task switch. 1487 1488 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1489 1490 nohlt [BUGS=ARM,SH] 1491 1492 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1493 instruction doesn't work correctly and not to 1494 use it. 1495 1496 no_file_caps Tells the kernel not to honor file capabilities. The 1497 only way then for a file to be executed with privilege 1498 is to be setuid root or executed by root. 1499 1500 nohalt [IA-64] Tells the kernel not to use the power saving 1501 function PAL_HALT_LIGHT when idle. This increases 1502 power-consumption. On the positive side, it reduces 1503 interrupt wake-up latency, which may improve performance 1504 in certain environments such as networked servers or 1505 real-time systems. 1506 1507 nohz= [KNL] Boottime enable/disable dynamic ticks 1508 Valid arguments: on, off 1509 Default: on 1510 1511 noirqdebug [X86-32] Disables the code which attempts to detect and 1512 disable unhandled interrupt sources. 1513 1514 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for 1515 broken timer IRQ sources. 1516 1517 noisapnp [ISAPNP] Disables ISA PnP code. 1518 1519 noinitrd [RAM] Tells the kernel not to load any configured 1520 initial RAM disk. 1521 1522 nointroute [IA-64] 1523 1524 nojitter [IA64] Disables jitter checking for ITC timers. 1525 1526 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1527 1528 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1529 1530 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1531 1532 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 1533 default x2apic cluster mode on platforms 1534 supporting x2apic. 1535 1536 noltlbs [PPC] Do not use large page/tlb entries for kernel 1537 lowmem mapping on PPC40x. 1538 1539 nomca [IA-64] Disable machine check abort handling 1540 1541 nomce [X86-32] Machine Check Exception 1542 1543 nomfgpt [X86-32] Disable Multi-Function General Purpose 1544 Timer usage (for AMD Geode machines). 1545 1546 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1547 1548 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1549 with UP alternatives 1550 1551 noresidual [PPC] Don't use residual data on PReP machines. 1552 1553 noresume [SWSUSP] Disables resume and restores original swap 1554 space. 1555 1556 no-scroll [VGA] Disables scrollback. 1557 This is required for the Braillex ib80-piezo Braille 1558 reader made by F.H. Papenmeier (Germany). 1559 1560 nosbagart [IA-64] 1561 1562 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1563 1564 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1565 and disable the IO APIC. legacy for "maxcpus=0". 1566 1567 nosoftlockup [KNL] Disable the soft-lockup detector. 1568 1569 noswapaccount [KNL] Disable accounting of swap in memory resource 1570 controller. (See Documentation/controllers/memory.txt) 1571 1572 nosync [HW,M68K] Disables sync negotiation for all devices. 1573 1574 notsc [BUGS=X86-32] Disable Time Stamp Counter 1575 1576 nousb [USB] Disable the USB subsystem 1577 1578 nowb [ARM] 1579 1580 nptcg= [IA64] Override max number of concurrent global TLB 1581 purges which is reported from either PAL_VM_SUMMARY or 1582 SAL PALO. 1583 1584 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1585 one of ['zone', 'node', 'default'] can be specified 1586 This can be set from sysctl after boot. 1587 See Documentation/sysctl/vm.txt for details. 1588 1589 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1590 1591 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1592 See Documentation/debugging-via-ohci1394.txt for more 1593 info. 1594 1595 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1596 Rather than timing out after 20 ms if an EC 1597 command is not properly ACKed, override the length 1598 of the timeout. We have interrupts disabled while 1599 waiting for the ACK, so if this is set too high 1600 interrupts *may* be lost! 1601 1602 opl3= [HW,OSS] 1603 Format: <io> 1604 1605 oprofile.timer= [HW] 1606 Use timer interrupt instead of performance counters 1607 1608 osst= [HW,SCSI] SCSI Tape Driver 1609 Format: <buffer_size>,<write_threshold> 1610 See also Documentation/scsi/st.txt. 1611 1612 panic= [KNL] Kernel behaviour on panic 1613 Format: <timeout> 1614 1615 parkbd.port= [HW] Parallel port number the keyboard adapter is 1616 connected to, default is 0. 1617 Format: <parport#> 1618 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1619 0 for XT, 1 for AT (default is AT). 1620 Format: <mode> 1621 1622 parport= [HW,PPT] Specify parallel ports. 0 disables. 1623 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1624 Use 'auto' to force the driver to use any 1625 IRQ/DMA settings detected (the default is to 1626 ignore detected IRQ/DMA settings because of 1627 possible conflicts). You can specify the base 1628 address, IRQ, and DMA settings; IRQ and DMA 1629 should be numbers, or 'auto' (for using detected 1630 settings on that particular port), or 'nofifo' 1631 (to avoid using a FIFO even if it is detected). 1632 Parallel ports are assigned in the order they 1633 are specified on the command line, starting 1634 with parport0. 1635 1636 parport_init_mode= [HW,PPT] 1637 Configure VIA parallel port to operate in 1638 a specific mode. This is necessary on Pegasos 1639 computer where firmware has no options for setting 1640 up parallel port mode and sets it to spp. 1641 Currently this function knows 686a and 8231 chips. 1642 Format: [spp|ps2|epp|ecp|ecpepp] 1643 1644 pas2= [HW,OSS] Format: 1645 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1646 1647 pas16= [HW,SCSI] 1648 See header of drivers/scsi/pas16.c. 1649 1650 pause_on_oops= 1651 Halt all CPUs after the first oops has been printed for 1652 the specified number of seconds. This is to be used if 1653 your oopses keep scrolling off the screen. 1654 1655 pcbit= [HW,ISDN] 1656 1657 pcd. [PARIDE] 1658 See header of drivers/block/paride/pcd.c. 1659 See also Documentation/blockdev/paride.txt. 1660 1661 pci=option[,option...] [PCI] various PCI subsystem options: 1662 off [X86] don't probe for the PCI bus 1663 bios [X86-32] force use of PCI BIOS, don't access 1664 the hardware directly. Use this if your machine 1665 has a non-standard PCI host bridge. 1666 nobios [X86-32] disallow use of PCI BIOS, only direct 1667 hardware access methods are allowed. Use this 1668 if you experience crashes upon bootup and you 1669 suspect they are caused by the BIOS. 1670 conf1 [X86] Force use of PCI Configuration 1671 Mechanism 1. 1672 conf2 [X86] Force use of PCI Configuration 1673 Mechanism 2. 1674 noaer [PCIE] If the PCIEAER kernel config parameter is 1675 enabled, this kernel boot option can be used to 1676 disable the use of PCIE advanced error reporting. 1677 nodomains [PCI] Disable support for multiple PCI 1678 root domains (aka PCI segments, in ACPI-speak). 1679 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI 1680 Configuration 1681 nomsi [MSI] If the PCI_MSI kernel config parameter is 1682 enabled, this kernel boot option can be used to 1683 disable the use of MSI interrupts system-wide. 1684 noioapicquirk [APIC] Disable all boot interrupt quirks. 1685 Safety option to keep boot IRQs enabled. This 1686 should never be necessary. 1687 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1688 primary IO-APIC for bridges that cannot disable 1689 boot IRQs. This fixes a source of spurious IRQs 1690 when the system masks IRQs. 1691 noioapicreroute [APIC] Disable workaround that uses the 1692 boot IRQ equivalent of an IRQ that connects to 1693 a chipset where boot IRQs cannot be disabled. 1694 The opposite of ioapicreroute. 1695 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1696 routing table. These calls are known to be buggy 1697 on several machines and they hang the machine 1698 when used, but on other computers it's the only 1699 way to get the interrupt routing table. Try 1700 this option if the kernel is unable to allocate 1701 IRQs or discover secondary PCI buses on your 1702 motherboard. 1703 rom [X86] Assign address space to expansion ROMs. 1704 Use with caution as certain devices share 1705 address decoders between ROMs and other 1706 resources. 1707 norom [X86] Do not assign address space to 1708 expansion ROMs that do not already have 1709 BIOS assigned address ranges. 1710 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1711 assigned automatically to PCI devices. You can 1712 make the kernel exclude IRQs of your ISA cards 1713 this way. 1714 pirqaddr=0xAAAAA [X86] Specify the physical address 1715 of the PIRQ table (normally generated 1716 by the BIOS) if it is outside the 1717 F0000h-100000h range. 1718 lastbus=N [X86] Scan all buses thru bus #N. Can be 1719 useful if the kernel is unable to find your 1720 secondary buses and you want to tell it 1721 explicitly which ones they are. 1722 assign-busses [X86] Always assign all PCI bus 1723 numbers ourselves, overriding 1724 whatever the firmware may have done. 1725 usepirqmask [X86] Honor the possible IRQ mask stored 1726 in the BIOS $PIR table. This is needed on 1727 some systems with broken BIOSes, notably 1728 some HP Pavilion N5400 and Omnibook XE3 1729 notebooks. This will have no effect if ACPI 1730 IRQ routing is enabled. 1731 noacpi [X86] Do not use ACPI for IRQ routing 1732 or for PCI scanning. 1733 use_crs [X86] Use _CRS for PCI resource 1734 allocation. 1735 routeirq Do IRQ routing for all PCI devices. 1736 This is normally done in pci_enable_device(), 1737 so this option is a temporary workaround 1738 for broken drivers that don't call it. 1739 skip_isa_align [X86] do not align io start addr, so can 1740 handle more pci cards 1741 firmware [ARM] Do not re-enumerate the bus but instead 1742 just use the configuration from the 1743 bootloader. This is currently used on 1744 IXP2000 systems where the bus has to be 1745 configured a certain way for adjunct CPUs. 1746 noearly [X86] Don't do any early type 1 scanning. 1747 This might help on some broken boards which 1748 machine check when some devices' config space 1749 is read. But various workarounds are disabled 1750 and some IOMMU drivers will not work. 1751 bfsort Sort PCI devices into breadth-first order. 1752 This sorting is done to get a device 1753 order compatible with older (<= 2.4) kernels. 1754 nobfsort Don't sort PCI devices into breadth-first order. 1755 cbiosize=nn[KMG] The fixed amount of bus space which is 1756 reserved for the CardBus bridge's IO window. 1757 The default value is 256 bytes. 1758 cbmemsize=nn[KMG] The fixed amount of bus space which is 1759 reserved for the CardBus bridge's memory 1760 window. The default value is 64 megabytes. 1761 1762 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1763 Management. 1764 off Disable ASPM. 1765 force Enable ASPM even on devices that claim not to support it. 1766 WARNING: Forcing ASPM on may cause system lockups. 1767 1768 pcmv= [HW,PCMCIA] BadgePAD 4 1769 1770 pd. [PARIDE] 1771 See Documentation/blockdev/paride.txt. 1772 1773 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1774 boot time. 1775 Format: { 0 | 1 } 1776 See arch/parisc/kernel/pdc_chassis.c 1777 1778 pf. [PARIDE] 1779 See Documentation/blockdev/paride.txt. 1780 1781 pg. [PARIDE] 1782 See Documentation/blockdev/paride.txt. 1783 1784 pirq= [SMP,APIC] Manual mp-table setup 1785 See Documentation/x86/i386/IO-APIC.txt. 1786 1787 plip= [PPT,NET] Parallel port network link 1788 Format: { parport<nr> | timid | 0 } 1789 See also Documentation/parport.txt. 1790 1791 pmtmr= [X86] Manual setup of pmtmr I/O Port. 1792 Override pmtimer IOPort with a hex value. 1793 e.g. pmtmr=0x508 1794 1795 pnp.debug [PNP] 1796 Enable PNP debug messages. This depends on the 1797 CONFIG_PNP_DEBUG_MESSAGES option. 1798 1799 pnpacpi= [ACPI] 1800 { off } 1801 1802 pnpbios= [ISAPNP] 1803 { on | off | curr | res | no-curr | no-res } 1804 1805 pnp_reserve_irq= 1806 [ISAPNP] Exclude IRQs for the autoconfiguration 1807 1808 pnp_reserve_dma= 1809 [ISAPNP] Exclude DMAs for the autoconfiguration 1810 1811 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 1812 Ranges are in pairs (I/O port base and size). 1813 1814 pnp_reserve_mem= 1815 [ISAPNP] Exclude memory regions for the 1816 autoconfiguration. 1817 Ranges are in pairs (memory base and size). 1818 1819 dynamic_printk Enables pr_debug()/dev_dbg() calls if 1820 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. 1821 These can also be switched on/off via 1822 <debugfs>/dynamic_printk/modules 1823 1824 print-fatal-signals= 1825 [KNL] debug: print fatal signals 1826 print-fatal-signals=1: print segfault info to 1827 the kernel console. 1828 default: off. 1829 1830 printk.time= Show timing data prefixed to each printk message line 1831 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 1832 1833 profile= [KNL] Enable kernel profiling via /proc/profile 1834 Format: [schedule,]<number> 1835 Param: "schedule" - profile schedule points. 1836 Param: <number> - step/bucket size as a power of 2 for 1837 statistical time based profiling. 1838 Param: "sleep" - profile D-state sleeping (millisecs). 1839 Requires CONFIG_SCHEDSTATS 1840 Param: "kvm" - profile VM exits. 1841 1842 processor.max_cstate= [HW,ACPI] 1843 Limit processor to maximum C-state 1844 max_cstate=9 overrides any DMI blacklist limit. 1845 1846 processor.nocst [HW,ACPI] 1847 Ignore the _CST method to determine C-states, 1848 instead using the legacy FADT method 1849 1850 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 1851 before loading. 1852 See Documentation/blockdev/ramdisk.txt. 1853 1854 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 1855 probe for; one of (bare|imps|exps|lifebook|any). 1856 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 1857 per second. 1858 psmouse.resetafter= [HW,MOUSE] 1859 Try to reset the device after so many bad packets 1860 (0 = never). 1861 psmouse.resolution= 1862 [HW,MOUSE] Set desired mouse resolution, in dpi. 1863 psmouse.smartscroll= 1864 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 1865 0 = disabled, 1 = enabled (default). 1866 1867 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 1868 Format: 1869 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 1870 1871 pt. [PARIDE] 1872 See Documentation/blockdev/paride.txt. 1873 1874 pty.legacy_count= 1875 [KNL] Number of legacy pty's. Overwrites compiled-in 1876 default number. 1877 1878 quiet [KNL] Disable most log messages 1879 1880 r128= [HW,DRM] 1881 1882 raid= [HW,RAID] 1883 See Documentation/md.txt. 1884 1885 ramdisk_blocksize= [RAM] 1886 See Documentation/blockdev/ramdisk.txt. 1887 1888 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 1889 See Documentation/blockdev/ramdisk.txt. 1890 1891 rcupdate.blimit= [KNL,BOOT] 1892 Set maximum number of finished RCU callbacks to process 1893 in one batch. 1894 1895 rcupdate.qhimark= [KNL,BOOT] 1896 Set threshold of queued 1897 RCU callbacks over which batch limiting is disabled. 1898 1899 rcupdate.qlowmark= [KNL,BOOT] 1900 Set threshold of queued RCU callbacks below which 1901 batch limiting is re-enabled. 1902 1903 rdinit= [KNL] 1904 Format: <full_path> 1905 Run specified binary instead of /init from the ramdisk, 1906 used for early userspace startup. See initrd. 1907 1908 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 1909 Format: <reboot_mode>[,<reboot_mode2>[,...]] 1910 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 1911 1912 relax_domain_level= 1913 [KNL, SMP] Set scheduler's default relax_domain_level. 1914 See Documentation/cpusets.txt. 1915 1916 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 1917 1918 reservetop= [X86-32] 1919 Format: nn[KMG] 1920 Reserves a hole at the top of the kernel virtual 1921 address space. 1922 1923 reset_devices [KNL] Force drivers to reset the underlying device 1924 during initialization. 1925 1926 resume= [SWSUSP] 1927 Specify the partition device for software suspend 1928 1929 resume_offset= [SWSUSP] 1930 Specify the offset from the beginning of the partition 1931 given by "resume=" at which the swap header is located, 1932 in <PAGE_SIZE> units (needed only for swap files). 1933 See Documentation/power/swsusp-and-swap-files.txt 1934 1935 retain_initrd [RAM] Keep initrd memory after extraction 1936 1937 rhash_entries= [KNL,NET] 1938 Set number of hash buckets for route cache 1939 1940 riscom8= [HW,SERIAL] 1941 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 1942 1943 ro [KNL] Mount root device read-only on boot 1944 1945 root= [KNL] Root filesystem 1946 1947 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 1948 mount the root filesystem 1949 1950 rootflags= [KNL] Set root filesystem mount option string 1951 1952 rootfstype= [KNL] Set root filesystem type 1953 1954 rootwait [KNL] Wait (indefinitely) for root device to show up. 1955 Useful for devices that are detected asynchronously 1956 (e.g. USB and MMC devices). 1957 1958 root_plug.vendor_id= 1959 [ROOTPLUG] Override the default vendor ID 1960 1961 root_plug.product_id= 1962 [ROOTPLUG] Override the default product ID 1963 1964 root_plug.debug= 1965 [ROOTPLUG] Enable debugging output 1966 1967 rw [KNL] Mount root device read-write on boot 1968 1969 S [KNL] Run init in single mode 1970 1971 sa1100ir [NET] 1972 See drivers/net/irda/sa1100_ir.c. 1973 1974 sbni= [NET] Granch SBNI12 leased line adapter 1975 1976 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 1977 Format: <io>[,<timeout>[,<isapnp>]] 1978 1979 scsi_debug_*= [SCSI] 1980 See drivers/scsi/scsi_debug.c. 1981 1982 scsi_default_dev_flags= 1983 [SCSI] SCSI default device flags 1984 Format: <integer> 1985 1986 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 1987 Format: <vendor>:<model>:<flags> 1988 (flags are integer value) 1989 1990 scsi_logging_level= [SCSI] a bit mask of logging levels 1991 See drivers/scsi/scsi_logging.h for bits. Also 1992 settable via sysctl at dev.scsi.logging_level 1993 (/proc/sys/dev/scsi/logging_level). 1994 There is also a nice 'scsi_logging_level' script in the 1995 S390-tools package, available for download at 1996 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 1997 1998 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 1999 discovered. async scans them in kernel threads, 2000 allowing boot to proceed. none ignores them, expecting 2001 user space to do the scan. 2002 2003 selinux [SELINUX] Disable or enable SELinux at boot time. 2004 Format: { "0" | "1" } 2005 See security/selinux/Kconfig help text. 2006 0 -- disable. 2007 1 -- enable. 2008 Default value is set via kernel config option. 2009 If enabled at boot time, /selinux/disable can be used 2010 later to disable prior to initial policy load. 2011 2012 selinux_compat_net = 2013 [SELINUX] Set initial selinux_compat_net flag value. 2014 Format: { "0" | "1" } 2015 0 -- use new secmark-based packet controls 2016 1 -- use legacy packet controls 2017 Default value is 0 (preferred). 2018 Value can be changed at runtime via 2019 /selinux/compat_net. 2020 2021 serialnumber [BUGS=X86-32] 2022 2023 shapers= [NET] 2024 Maximal number of shapers. 2025 2026 show_msr= [x86] show boot-time MSR settings 2027 Format: { <integer> } 2028 Show boot-time (BIOS-initialized) MSR settings. 2029 The parameter means the number of CPUs to show, 2030 for example 1 means boot CPU only. 2031 2032 sim710= [SCSI,HW] 2033 See header of drivers/scsi/sim710.c. 2034 2035 simeth= [IA-64] 2036 simscsi= 2037 2038 slram= [HW,MTD] 2039 2040 slub_debug[=options[,slabs]] [MM, SLUB] 2041 Enabling slub_debug allows one to determine the 2042 culprit if slab objects become corrupted. Enabling 2043 slub_debug can create guard zones around objects and 2044 may poison objects when not in use. Also tracks the 2045 last alloc / free. For more information see 2046 Documentation/vm/slub.txt. 2047 2048 slub_max_order= [MM, SLUB] 2049 Determines the maximum allowed order for slabs. 2050 A high setting may cause OOMs due to memory 2051 fragmentation. For more information see 2052 Documentation/vm/slub.txt. 2053 2054 slub_min_objects= [MM, SLUB] 2055 The minimum number of objects per slab. SLUB will 2056 increase the slab order up to slub_max_order to 2057 generate a sufficiently large slab able to contain 2058 the number of objects indicated. The higher the number 2059 of objects the smaller the overhead of tracking slabs 2060 and the less frequently locks need to be acquired. 2061 For more information see Documentation/vm/slub.txt. 2062 2063 slub_min_order= [MM, SLUB] 2064 Determines the mininum page order for slabs. Must be 2065 lower than slub_max_order. 2066 For more information see Documentation/vm/slub.txt. 2067 2068 slub_nomerge [MM, SLUB] 2069 Disable merging of slabs with similar size. May be 2070 necessary if there is some reason to distinguish 2071 allocs to different slabs. Debug options disable 2072 merging on their own. 2073 For more information see Documentation/vm/slub.txt. 2074 2075 smart2= [HW] 2076 Format: <io1>[,<io2>[,...,<io8>]] 2077 2078 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2079 attempt to substitute SMP alternatives once at boot. 2080 2081 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2082 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2083 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2084 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2085 smsc-ircc2.ircc_irq= [HW] IRQ line 2086 smsc-ircc2.ircc_dma= [HW] DMA channel 2087 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2088 0: Toshiba Satellite 1800 (GP data pin select) 2089 1: Fast pin select (default) 2090 2: ATC IRMode 2091 2092 snd-ad1816a= [HW,ALSA] 2093 2094 snd-ad1848= [HW,ALSA] 2095 2096 snd-ali5451= [HW,ALSA] 2097 2098 snd-als100= [HW,ALSA] 2099 2100 snd-als4000= [HW,ALSA] 2101 2102 snd-azt2320= [HW,ALSA] 2103 2104 snd-cmi8330= [HW,ALSA] 2105 2106 snd-cmipci= [HW,ALSA] 2107 2108 snd-cs4231= [HW,ALSA] 2109 2110 snd-cs4232= [HW,ALSA] 2111 2112 snd-cs4236= [HW,ALSA] 2113 2114 snd-cs4281= [HW,ALSA] 2115 2116 snd-cs46xx= [HW,ALSA] 2117 2118 snd-dt019x= [HW,ALSA] 2119 2120 snd-dummy= [HW,ALSA] 2121 2122 snd-emu10k1= [HW,ALSA] 2123 2124 snd-ens1370= [HW,ALSA] 2125 2126 snd-ens1371= [HW,ALSA] 2127 2128 snd-es968= [HW,ALSA] 2129 2130 snd-es1688= [HW,ALSA] 2131 2132 snd-es18xx= [HW,ALSA] 2133 2134 snd-es1938= [HW,ALSA] 2135 2136 snd-es1968= [HW,ALSA] 2137 2138 snd-fm801= [HW,ALSA] 2139 2140 snd-gusclassic= [HW,ALSA] 2141 2142 snd-gusextreme= [HW,ALSA] 2143 2144 snd-gusmax= [HW,ALSA] 2145 2146 snd-hdsp= [HW,ALSA] 2147 2148 snd-ice1712= [HW,ALSA] 2149 2150 snd-intel8x0= [HW,ALSA] 2151 2152 snd-interwave= [HW,ALSA] 2153 2154 snd-interwave-stb= 2155 [HW,ALSA] 2156 2157 snd-korg1212= [HW,ALSA] 2158 2159 snd-maestro3= [HW,ALSA] 2160 2161 snd-mpu401= [HW,ALSA] 2162 2163 snd-mtpav= [HW,ALSA] 2164 2165 snd-nm256= [HW,ALSA] 2166 2167 snd-opl3sa2= [HW,ALSA] 2168 2169 snd-opti92x-ad1848= 2170 [HW,ALSA] 2171 2172 snd-opti92x-cs4231= 2173 [HW,ALSA] 2174 2175 snd-opti93x= [HW,ALSA] 2176 2177 snd-pmac= [HW,ALSA] 2178 2179 snd-rme32= [HW,ALSA] 2180 2181 snd-rme96= [HW,ALSA] 2182 2183 snd-rme9652= [HW,ALSA] 2184 2185 snd-sb8= [HW,ALSA] 2186 2187 snd-sb16= [HW,ALSA] 2188 2189 snd-sbawe= [HW,ALSA] 2190 2191 snd-serial= [HW,ALSA] 2192 2193 snd-sgalaxy= [HW,ALSA] 2194 2195 snd-sonicvibes= [HW,ALSA] 2196 2197 snd-sun-amd7930= 2198 [HW,ALSA] 2199 2200 snd-sun-cs4231= [HW,ALSA] 2201 2202 snd-trident= [HW,ALSA] 2203 2204 snd-usb-audio= [HW,ALSA,USB] 2205 2206 snd-via82xx= [HW,ALSA] 2207 2208 snd-virmidi= [HW,ALSA] 2209 2210 snd-wavefront= [HW,ALSA] 2211 2212 snd-ymfpci= [HW,ALSA] 2213 2214 softlockup_panic= 2215 [KNL] Should the soft-lockup detector generate panics. 2216 2217 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2218 See Documentation/sonypi.txt 2219 2220 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2221 See Documentation/serial/specialix.txt. 2222 2223 spia_io_base= [HW,MTD] 2224 spia_fio_base= 2225 spia_pedr= 2226 spia_peddr= 2227 2228 sscape= [HW,OSS] 2229 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2230 2231 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2232 See Documentation/scsi/st.txt. 2233 2234 stacktrace [FTRACE] 2235 Enabled the stack tracer on boot up. 2236 2237 sti= [PARISC,HW] 2238 Format: <num> 2239 Set the STI (builtin display/keyboard on the HP-PARISC 2240 machines) console (graphic card) which should be used 2241 as the initial boot-console. 2242 See also comment in drivers/video/console/sticore.c. 2243 2244 sti_font= [HW] 2245 See comment in drivers/video/console/sticore.c. 2246 2247 stifb= [HW] 2248 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2249 2250 sunrpc.pool_mode= 2251 [NFS] 2252 Control how the NFS server code allocates CPUs to 2253 service thread pools. Depending on how many NICs 2254 you have and where their interrupts are bound, this 2255 option will affect which CPUs will do NFS serving. 2256 Note: this parameter cannot be changed while the 2257 NFS server is running. 2258 2259 auto the server chooses an appropriate mode 2260 automatically using heuristics 2261 global a single global pool contains all CPUs 2262 percpu one pool for each CPU 2263 pernode one pool for each NUMA node (equivalent 2264 to global on non-NUMA machines) 2265 2266 swiotlb= [IA-64] Number of I/O TLB slabs 2267 2268 switches= [HW,M68k] 2269 2270 sym53c416= [HW,SCSI] 2271 See header of drivers/scsi/sym53c416.c. 2272 2273 sysrq_always_enabled 2274 [KNL] 2275 Ignore sysrq setting - this boot parameter will 2276 neutralize any effect of /proc/sys/kernel/sysrq. 2277 Useful for debugging. 2278 2279 t128= [HW,SCSI] 2280 See header of drivers/scsi/t128.c. 2281 2282 tdfx= [HW,DRM] 2283 2284 test_suspend= [SUSPEND] 2285 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2286 standby suspend) as the system sleep state to briefly 2287 enter during system startup. The system is woken from 2288 this state using a wakeup-capable RTC alarm. 2289 2290 thash_entries= [KNL,NET] 2291 Set number of hash buckets for TCP connection 2292 2293 thermal.act= [HW,ACPI] 2294 -1: disable all active trip points in all thermal zones 2295 <degrees C>: override all lowest active trip points 2296 2297 thermal.crt= [HW,ACPI] 2298 -1: disable all critical trip points in all thermal zones 2299 <degrees C>: override all critical trip points 2300 2301 thermal.nocrt= [HW,ACPI] 2302 Set to disable actions on ACPI thermal zone 2303 critical and hot trip points. 2304 2305 thermal.off= [HW,ACPI] 2306 1: disable ACPI thermal control 2307 2308 thermal.psv= [HW,ACPI] 2309 -1: disable all passive trip points 2310 <degrees C>: override all passive trip points to this 2311 value 2312 2313 thermal.tzp= [HW,ACPI] 2314 Specify global default ACPI thermal zone polling rate 2315 <deci-seconds>: poll all this frequency 2316 0: no polling (default) 2317 2318 tmscsim= [HW,SCSI] 2319 See comment before function dc390_setup() in 2320 drivers/scsi/tmscsim.c. 2321 2322 topology= [S390] 2323 Format: {off | on} 2324 Specify if the kernel should make use of the cpu 2325 topology informations if the hardware supports these. 2326 The scheduler will make use of these informations and 2327 e.g. base its process migration decisions on it. 2328 Default is off. 2329 2330 tp720= [HW,PS2] 2331 2332 trix= [HW,OSS] MediaTrix AudioTrix Pro 2333 Format: 2334 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2335 2336 tsc= Disable clocksource-must-verify flag for TSC. 2337 Format: <string> 2338 [x86] reliable: mark tsc clocksource as reliable, this 2339 disables clocksource verification at runtime. 2340 Used to enable high-resolution timer mode on older 2341 hardware, and in virtualized environment. 2342 2343 turbografx.map[2|3]= [HW,JOY] 2344 TurboGraFX parallel port interface 2345 Format: 2346 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2347 See also Documentation/input/joystick-parport.txt 2348 2349 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2350 See header of drivers/scsi/u14-34f.c. 2351 2352 uart401= [HW,OSS] 2353 Format: <io>,<irq> 2354 2355 uart6850= [HW,OSS] 2356 Format: <io>,<irq> 2357 2358 uhci-hcd.ignore_oc= 2359 [USB] Ignore overcurrent events (default N). 2360 Some badly-designed motherboards generate lots of 2361 bogus events, for ports that aren't wired to 2362 anything. Set this parameter to avoid log spamming. 2363 Note that genuine overcurrent events won't be 2364 reported either. 2365 2366 unknown_nmi_panic 2367 [X86-32,X86-64] 2368 Set unknown_nmi_panic=1 early on boot. 2369 2370 usbcore.autosuspend= 2371 [USB] The autosuspend time delay (in seconds) used 2372 for newly-detected USB devices (default 2). This 2373 is the time required before an idle device will be 2374 autosuspended. Devices for which the delay is set 2375 to a negative value won't be autosuspended at all. 2376 2377 usbcore.usbfs_snoop= 2378 [USB] Set to log all usbfs traffic (default 0 = off). 2379 2380 usbcore.blinkenlights= 2381 [USB] Set to cycle leds on hubs (default 0 = off). 2382 2383 usbcore.old_scheme_first= 2384 [USB] Start with the old device initialization 2385 scheme (default 0 = off). 2386 2387 usbcore.use_both_schemes= 2388 [USB] Try the other device initialization scheme 2389 if the first one fails (default 1 = enabled). 2390 2391 usbcore.initial_descriptor_timeout= 2392 [USB] Specifies timeout for the initial 64-byte 2393 USB_REQ_GET_DESCRIPTOR request in milliseconds 2394 (default 5000 = 5.0 seconds). 2395 2396 usbhid.mousepoll= 2397 [USBHID] The interval which mice are to be polled at. 2398 2399 usb-storage.delay_use= 2400 [UMS] The delay in seconds before a new device is 2401 scanned for Logical Units (default 5). 2402 2403 usb-storage.quirks= 2404 [UMS] A list of quirks entries to supplement or 2405 override the built-in unusual_devs list. List 2406 entries are separated by commas. Each entry has 2407 the form VID:PID:Flags where VID and PID are Vendor 2408 and Product ID values (4-digit hex numbers) and 2409 Flags is a set of characters, each corresponding 2410 to a common usb-storage quirk flag as follows: 2411 a = SANE_SENSE (collect more than 18 bytes 2412 of sense data); 2413 c = FIX_CAPACITY (decrease the reported 2414 device capacity by one sector); 2415 h = CAPACITY_HEURISTICS (decrease the 2416 reported device capacity by one 2417 sector if the number is odd); 2418 i = IGNORE_DEVICE (don't bind to this 2419 device); 2420 l = NOT_LOCKABLE (don't try to lock and 2421 unlock ejectable media); 2422 m = MAX_SECTORS_64 (don't transfer more 2423 than 64 sectors = 32 KB at a time); 2424 o = CAPACITY_OK (accept the capacity 2425 reported by the device); 2426 r = IGNORE_RESIDUE (the device reports 2427 bogus residue values); 2428 s = SINGLE_LUN (the device has only one 2429 Logical Unit); 2430 w = NO_WP_DETECT (don't test whether the 2431 medium is write-protected). 2432 Example: quirks=0419:aaf5:rl,0421:0433:rc 2433 2434 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in 2435 kernel's map of available physical RAM. 2436 2437 vdso= [X86-32,SH,x86-64] 2438 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2439 vdso=1: enable VDSO (default) 2440 vdso=0: disable VDSO mapping 2441 2442 vdso32= [X86-32,X86-64] 2443 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2444 vdso32=1: enable 32-bit VDSO (default) 2445 vdso32=0: disable 32-bit VDSO mapping 2446 2447 vector= [IA-64,SMP] 2448 vector=percpu: enable percpu vector domain 2449 2450 video= [FB] Frame buffer configuration 2451 See Documentation/fb/modedb.txt. 2452 2453 vga= [BOOT,X86-32] Select a particular video mode 2454 See Documentation/x86/boot.txt and 2455 Documentation/svga.txt. 2456 Use vga=ask for menu. 2457 This is actually a boot loader parameter; the value is 2458 passed to the kernel using a special protocol. 2459 2460 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2461 size of <nn>. This can be used to increase the 2462 minimum size (128MB on x86). It can also be used to 2463 decrease the size and leave more room for directly 2464 mapped kernel RAM. 2465 2466 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2467 Format: <command> 2468 2469 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2470 Format: <command> 2471 2472 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2473 Format: <command> 2474 2475 waveartist= [HW,OSS] 2476 Format: <io>,<irq>,<dma>,<dma2> 2477 2478 wd33c93= [HW,SCSI] 2479 See header of drivers/scsi/wd33c93.c. 2480 2481 wd7000= [HW,SCSI] 2482 See header of drivers/scsi/wd7000.c. 2483 2484 wdt= [WDT] Watchdog 2485 See Documentation/watchdog/wdt.txt. 2486 2487 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2488 xd_geo= See header of drivers/block/xd.c. 2489 2490 xirc2ps_cs= [NET,PCMCIA] 2491 Format: 2492 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2493 2494 norandmaps Don't use address space randomization. Equivalent to 2495 echo 0 > /proc/sys/kernel/randomize_va_space 2496 2497______________________________________________________________________ 2498 2499TODO: 2500 2501 Add documentation for ALSA options. 2502 Add more DRM drivers. 2503