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 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 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 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: 37 38 ACPI ACPI support is enabled. 39 AGP AGP (Accelerated Graphics Port) is enabled. 40 ALSA ALSA sound support is enabled. 41 APIC APIC support is enabled. 42 APM Advanced Power Management support is enabled. 43 AVR32 AVR32 architecture is enabled. 44 AX25 Appropriate AX.25 support is enabled. 45 BLACKFIN Blackfin architecture is enabled. 46 DRM Direct Rendering Management support is enabled. 47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 48 EFI EFI Partitioning (GPT) is enabled 49 EIDE EIDE/ATAPI support is enabled. 50 FB The frame buffer device is enabled. 51 GCOV GCOV profiling is enabled. 52 HW Appropriate hardware is enabled. 53 IA-64 IA-64 architecture is enabled. 54 IMA Integrity measurement architecture is enabled. 55 IOSCHED More than one I/O scheduler is enabled. 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 57 ISAPNP ISA PnP code is enabled. 58 ISDN Appropriate ISDN support is enabled. 59 JOY Appropriate joystick support is enabled. 60 KVM Kernel Virtual Machine support is enabled. 61 LIBATA Libata driver is enabled 62 LP Printer support is enabled. 63 LOOP Loopback device support is enabled. 64 M68k M68k architecture is enabled. 65 These options have more detailed description inside of 66 Documentation/m68k/kernel-options.txt. 67 MCA MCA bus support is enabled. 68 MDA MDA console support is enabled. 69 MOUSE Appropriate mouse support is enabled. 70 MSI Message Signaled Interrupts (PCI). 71 MTD MTD (Memory Technology Device) support is enabled. 72 NET Appropriate network support is enabled. 73 NUMA NUMA support is enabled. 74 GENERIC_TIME The generic timeofday code is enabled. 75 NFS Appropriate NFS support is enabled. 76 OSS OSS sound support is enabled. 77 PV_OPS A paravirtualized kernel is enabled. 78 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 79 PARISC The PA-RISC architecture is enabled. 80 PCI PCI bus support is enabled. 81 PCIE PCI Express support is enabled. 82 PCMCIA The PCMCIA subsystem is enabled. 83 PNP Plug & Play support is enabled. 84 PPC PowerPC architecture is enabled. 85 PPT Parallel port support is enabled. 86 PS2 Appropriate PS/2 support is enabled. 87 RAM RAM disk support is enabled. 88 ROOTPLUG The example Root Plug LSM is enabled. 89 S390 S390 architecture is enabled. 90 SCSI Appropriate SCSI support is enabled. 91 A lot of drivers has their options described inside of 92 Documentation/scsi/. 93 SECURITY Different security models are enabled. 94 SELINUX SELinux support is enabled. 95 SERIAL Serial support is enabled. 96 SH SuperH architecture is enabled. 97 SMP The kernel is an SMP kernel. 98 SPARC Sparc architecture is enabled. 99 SWSUSP Software suspend (hibernation) is enabled. 100 SUSPEND System suspend states are enabled. 101 FTRACE Function tracing enabled. 102 TS Appropriate touchscreen support is enabled. 103 UMS USB Mass Storage support is enabled. 104 USB USB support is enabled. 105 USBHID USB Human Interface Device support is enabled. 106 V4L Video For Linux support is enabled. 107 VGA The VGA console has been enabled. 108 VT Virtual terminal support is enabled. 109 WDT Watchdog support is enabled. 110 XT IBM PC/XT MFM hard disk support is enabled. 111 X86-32 X86-32, aka i386 architecture is enabled. 112 X86-64 X86-64 architecture is enabled. 113 More X86-64 boot options can be found in 114 Documentation/x86/x86_64/boot-options.txt . 115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 116 117In addition, the following text indicates that the option: 118 119 BUGS= Relates to possible processor bugs on the said processor. 120 KNL Is a kernel start-up parameter. 121 BOOT Is a boot loader parameter. 122 123Parameters denoted with BOOT are actually interpreted by the boot 124loader, and have no meaning to the kernel directly. 125Do not modify the syntax of boot loader parameters without extreme 126need or coordination with <Documentation/x86/boot.txt>. 127 128There are also arch-specific kernel-parameters not documented here. 129See for example <Documentation/x86/x86_64/boot-options.txt>. 130 131Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 132a trailing = on the name of any parameter states that that parameter will 133be entered as an environment variable, whereas its absence indicates that 134it will appear as a kernel argument readable via /proc/cmdline by programs 135running once the system is up. 136 137The number of kernel parameters is not limited, but the length of the 138complete command line (parameters including spaces etc.) is limited to 139a fixed number of characters. This limit depends on the architecture 140and is between 256 and 4096 characters. It is defined in the file 141./include/asm/setup.h as COMMAND_LINE_SIZE. 142 143 144 acpi= [HW,ACPI,X86] 145 Advanced Configuration and Power Interface 146 Format: { force | off | ht | strict | noirq | rsdt } 147 force -- enable ACPI if default was off 148 off -- disable ACPI if default was on 149 noirq -- do not use ACPI for IRQ routing 150 ht -- run only enough ACPI to enable Hyper Threading 151 strict -- Be less tolerant of platforms that are not 152 strictly ACPI specification compliant. 153 rsdt -- prefer RSDT over (default) XSDT 154 155 See also Documentation/power/pm.txt, pci=noacpi 156 157 acpi_apic_instance= [ACPI, IOAPIC] 158 Format: <int> 159 2: use 2nd APIC table, if available 160 1,0: use 1st APIC table 161 default: 0 162 163 acpi_backlight= [HW,ACPI] 164 acpi_backlight=vendor 165 acpi_backlight=video 166 If set to vendor, prefer vendor specific driver 167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead 168 of the ACPI video.ko driver. 169 170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 172 Format: <int> 173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 174 debug output. Bits in debug_layer correspond to a 175 _COMPONENT in an ACPI source file, e.g., 176 #define _COMPONENT ACPI_PCI_COMPONENT 177 Bits in debug_level correspond to a level in 178 ACPI_DEBUG_PRINT statements, e.g., 179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 180 The debug_level mask defaults to "info". See 181 Documentation/acpi/debug.txt for more information about 182 debug layers and levels. 183 184 Enable processor driver info messages: 185 acpi.debug_layer=0x20000000 186 Enable PCI/PCI interrupt routing info messages: 187 acpi.debug_layer=0x400000 188 Enable AML "Debug" output, i.e., stores to the Debug 189 object while interpreting AML: 190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2 191 Enable all messages related to ACPI hardware: 192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 193 194 Some values produce so much output that the system is 195 unusable. The "log_buf_len" parameter may be useful 196 if you need to capture more output. 197 198 acpi_display_output= [HW,ACPI] 199 acpi_display_output=vendor 200 acpi_display_output=video 201 See above. 202 203 acpi_irq_balance [HW,ACPI] 204 ACPI will balance active IRQs 205 default in APIC mode 206 207 acpi_irq_nobalance [HW,ACPI] 208 ACPI will not move active IRQs (default) 209 default in PIC mode 210 211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 212 Format: <irq>,<irq>... 213 214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 215 use by PCI 216 Format: <irq>,<irq>... 217 218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 219 220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 221 Format: To spoof as Windows 98: ="Microsoft Windows" 222 223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 224 acpi_osi="string1" # add string1 -- only one string 225 acpi_osi="!string2" # remove built-in string2 226 acpi_osi= # disable all strings 227 228 acpi_pm_good [X86] 229 Override the pmtimer bug detection: force the kernel 230 to assume that this machine's pmtimer latches its value 231 and always returns good values. 232 233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 234 Format: { level | edge | high | low } 235 236 acpi_serialize [HW,ACPI] force serialization of AML methods 237 238 acpi_skip_timer_override [HW,ACPI] 239 Recognize and ignore IRQ0/pin2 Interrupt Override. 240 For broken nForce2 BIOS resulting in XT-PIC timer. 241 242 acpi_sleep= [HW,ACPI] Sleep options 243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 244 old_ordering, s4_nonvs } 245 See Documentation/power/video.txt for information on 246 s3_bios and s3_mode. 247 s3_beep is for debugging; it makes the PC's speaker beep 248 as soon as the kernel's real-mode entry point is called. 249 s4_nohwsig prevents ACPI hardware signature from being 250 used during resume from hibernation. 251 old_ordering causes the ACPI 1.0 ordering of the _PTS 252 control method, with respect to putting devices into 253 low power states, to be enforced (the ACPI 2.0 ordering 254 of _PTS is used by default). 255 s4_nonvs prevents the kernel from saving/restoring the 256 ACPI NVS memory during hibernation. 257 258 acpi_use_timer_override [HW,ACPI] 259 Use timer override. For some broken Nvidia NF5 boards 260 that require a timer override, but don't have HPET 261 262 acpi_enforce_resources= [ACPI] 263 { strict | lax | no } 264 Check for resource conflicts between native drivers 265 and ACPI OperationRegions (SystemIO and SystemMemory 266 only). IO ports and memory declared in ACPI might be 267 used by the ACPI subsystem in arbitrary AML code and 268 can interfere with legacy drivers. 269 strict (default): access to resources claimed by ACPI 270 is denied; legacy drivers trying to access reserved 271 resources will fail to bind to device using them. 272 lax: access to resources claimed by ACPI is allowed; 273 legacy drivers trying to access reserved resources 274 will bind successfully but a warning message is logged. 275 no: ACPI OperationRegions are not marked as reserved, 276 no further checks are performed. 277 278 ad1848= [HW,OSS] 279 Format: <io>,<irq>,<dma>,<dma2>,<type> 280 281 add_efi_memmap [EFI; X86] Include EFI memory map in 282 kernel's map of available physical RAM. 283 284 advansys= [HW,SCSI] 285 See header of drivers/scsi/advansys.c. 286 287 advwdt= [HW,WDT] Advantech WDT 288 Format: <iostart>,<iostop> 289 290 aedsp16= [HW,OSS] Audio Excel DSP 16 291 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 292 See also header of sound/oss/aedsp16.c. 293 294 agp= [AGP] 295 { off | try_unsupported } 296 off: disable AGP support 297 try_unsupported: try to drive unsupported chipsets 298 (may crash computer or cause data corruption) 299 300 aha152x= [HW,SCSI] 301 See Documentation/scsi/aha152x.txt. 302 303 aha1542= [HW,SCSI] 304 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 305 306 aic7xxx= [HW,SCSI] 307 See Documentation/scsi/aic7xxx.txt. 308 309 aic79xx= [HW,SCSI] 310 See Documentation/scsi/aic79xx.txt. 311 312 amd_iommu= [HW,X86-84] 313 Pass parameters to the AMD IOMMU driver in the system. 314 Possible values are: 315 isolate - enable device isolation (each device, as far 316 as possible, will get its own protection 317 domain) [default] 318 share - put every device behind one IOMMU into the 319 same protection domain 320 fullflush - enable flushing of IO/TLB entries when 321 they are unmapped. Otherwise they are 322 flushed before they will be reused, which 323 is a lot of faster 324 325 amijoy.map= [HW,JOY] Amiga joystick support 326 Map of devices attached to JOY0DAT and JOY1DAT 327 Format: <a>,<b> 328 See also Documentation/kernel/input/joystick.txt 329 330 analog.map= [HW,JOY] Analog joystick and gamepad support 331 Specifies type or capabilities of an analog joystick 332 connected to one of 16 gameports 333 Format: <type1>,<type2>,..<type16> 334 335 apc= [HW,SPARC] 336 Power management functions (SPARCstation-4/5 + deriv.) 337 Format: noidle 338 Disable APC CPU standby support. SPARCstation-Fox does 339 not play well with APC CPU idle - disable it if you have 340 APC and your system crashes randomly. 341 342 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 343 Change the output verbosity whilst booting 344 Format: { quiet (default) | verbose | debug } 345 Change the amount of debugging information output 346 when initialising the APIC and IO-APIC components. 347 348 apm= [APM] Advanced Power Management 349 See header of arch/x86/kernel/apm_32.c. 350 351 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 352 Format: <io>,<irq>,<nodeID> 353 354 ataflop= [HW,M68k] 355 356 atarimouse= [HW,MOUSE] Atari Mouse 357 358 atascsi= [HW,SCSI] Atari SCSI 359 360 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 361 EzKey and similar keyboards 362 363 atkbd.reset= [HW] Reset keyboard during initialization 364 365 atkbd.set= [HW] Select keyboard code set 366 Format: <int> (2 = AT (default), 3 = PS/2) 367 368 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 369 keyboards 370 371 atkbd.softraw= [HW] Choose between synthetic and real raw mode 372 Format: <bool> (0 = real, 1 = synthetic (default)) 373 374 atkbd.softrepeat= [HW] 375 Use software keyboard repeat 376 377 autotest [IA64] 378 379 baycom_epp= [HW,AX25] 380 Format: <io>,<mode> 381 382 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 383 Format: <io>,<mode> 384 See header of drivers/net/hamradio/baycom_par.c. 385 386 baycom_ser_fdx= [HW,AX25] 387 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 388 Format: <io>,<irq>,<mode>[,<baud>] 389 See header of drivers/net/hamradio/baycom_ser_fdx.c. 390 391 baycom_ser_hdx= [HW,AX25] 392 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 393 Format: <io>,<irq>,<mode> 394 See header of drivers/net/hamradio/baycom_ser_hdx.c. 395 396 boot_delay= Milliseconds to delay each printk during boot. 397 Values larger than 10 seconds (10000) are changed to 398 no delay (0). 399 Format: integer 400 401 bootmem_debug [KNL] Enable bootmem allocator debug messages. 402 403 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 404 bttv.radio= Most important insmod options are available as 405 kernel args too. 406 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 407 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 408 409 BusLogic= [HW,SCSI] 410 See drivers/scsi/BusLogic.c, comment before function 411 BusLogic_ParseDriverOptions(). 412 413 c101= [NET] Moxa C101 synchronous serial card 414 415 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 416 Sometimes CPU hardware bugs make them report the cache 417 size incorrectly. The kernel will attempt work arounds 418 to fix known problems, but for some CPUs it is not 419 possible to determine what the correct size should be. 420 This option provides an override for these situations. 421 422 capability.disable= 423 [SECURITY] Disable capabilities. This would normally 424 be used only if an alternative security model is to be 425 configured. Potentially dangerous and should only be 426 used if you are entirely sure of the consequences. 427 428 ccw_timeout_log [S390] 429 See Documentation/s390/CommonIO for details. 430 431 cgroup_disable= [KNL] Disable a particular controller 432 Format: {name of the controller(s) to disable} 433 {Currently supported controllers - "memory"} 434 435 checkreqprot [SELINUX] Set initial checkreqprot flag value. 436 Format: { "0" | "1" } 437 See security/selinux/Kconfig help text. 438 0 -- check protection applied by kernel (includes 439 any implied execute protection). 440 1 -- check protection requested by application. 441 Default value is set via a kernel config option. 442 Value can be changed at runtime via 443 /selinux/checkreqprot. 444 445 cio_ignore= [S390] 446 See Documentation/s390/CommonIO for details. 447 448 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 449 [Deprecated] 450 Forces specified clocksource (if available) to be used 451 when calculating gettimeofday(). If specified 452 clocksource is not available, it defaults to PIT. 453 Format: { pit | tsc | cyclone | pmtmr } 454 455 clocksource= [GENERIC_TIME] Override the default clocksource 456 Format: <string> 457 Override the default clocksource and use the clocksource 458 with the name specified. 459 Some clocksource names to choose from, depending on 460 the platform: 461 [all] jiffies (this is the base, fallback clocksource) 462 [ACPI] acpi_pm 463 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 464 pxa_timer,timer3,32k_counter,timer0_1 465 [AVR32] avr32 466 [X86-32] pit,hpet,tsc,vmi-timer; 467 scx200_hrt on Geode; cyclone on IBM x440 468 [MIPS] MIPS 469 [PARISC] cr16 470 [S390] tod 471 [SH] SuperH 472 [SPARC64] tick 473 [X86-64] hpet,tsc 474 475 clearcpuid=BITNUM [X86] 476 Disable CPUID feature X for the kernel. See 477 arch/x86/include/asm/cpufeature.h for the valid bit 478 numbers. Note the Linux specific bits are not necessarily 479 stable over kernel options, but the vendor specific 480 ones should be. 481 Also note that user programs calling CPUID directly 482 or using the feature without checking anything 483 will still see it. This just prevents it from 484 being used by the kernel or shown in /proc/cpuinfo. 485 Also note the kernel might malfunction if you disable 486 some critical bits. 487 488 cmo_free_hint= [PPC] Format: { yes | no } 489 Specify whether pages are marked as being inactive 490 when they are freed. This is used in CMO environments 491 to determine OS memory pressure for page stealing by 492 a hypervisor. 493 Default: yes 494 495 code_bytes [X86] How many bytes of object code to print 496 in an oops report. 497 Range: 0 - 8192 498 Default: 64 499 500 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 consoleblank= [KNL] The console blank (screen saver) timeout in 544 seconds. Defaults to 10*60 = 10mins. A value of 0 545 disables the blank timer. 546 547 coredump_filter= 548 [KNL] Change the default value for 549 /proc/<pid>/coredump_filter. 550 See also Documentation/filesystems/proc.txt. 551 552 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 553 Format: 554 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 555 556 crashkernel=nn[KMG]@ss[KMG] 557 [KNL] Reserve a chunk of physical memory to 558 hold a kernel to switch to with kexec on panic. 559 560 crashkernel=range1:size1[,range2:size2,...][@offset] 561 [KNL] Same as above, but depends on the memory 562 in the running system. The syntax of range is 563 start-[end] where start and end are both 564 a memory unit (amount[KMG]). See also 565 Documentation/kdump/kdump.txt for a example. 566 567 cs89x0_dma= [HW,NET] 568 Format: <dma> 569 570 cs89x0_media= [HW,NET] 571 Format: { rj45 | aui | bnc } 572 573 dasd= [HW,NET] 574 See header of drivers/s390/block/dasd_devmap.c. 575 576 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 577 (one device per port) 578 Format: <port#>,<type> 579 See also Documentation/input/joystick-parport.txt 580 581 debug [KNL] Enable kernel debugging (events log level). 582 583 debug_locks_verbose= 584 [KNL] verbose self-tests 585 Format=<0|1> 586 Print debugging info while doing the locking API 587 self-tests. 588 We default to 0 (no extra messages), setting it to 589 1 will print _a lot_ more information - normally 590 only useful to kernel developers. 591 592 debug_objects [KNL] Enable object debugging 593 594 no_debug_objects 595 [KNL] Disable object debugging 596 597 debugpat [X86] Enable PAT debugging 598 599 decnet.addr= [HW,NET] 600 Format: <area>[,<node>] 601 See also Documentation/networking/decnet.txt. 602 603 default_hugepagesz= 604 [same as hugepagesz=] The size of the default 605 HugeTLB page size. This is the size represented by 606 the legacy /proc/ hugepages APIs, used for SHM, and 607 default size when mounting hugetlbfs filesystems. 608 Defaults to the default architecture's huge page size 609 if not specified. 610 611 dhash_entries= [KNL] 612 Set number of hash buckets for dentry cache. 613 614 digi= [HW,SERIAL] 615 IO parameters + enable/disable command. 616 617 digiepca= [HW,SERIAL] 618 See drivers/char/README.epca and 619 Documentation/serial/digiepca.txt. 620 621 disable_mtrr_cleanup [X86] 622 The kernel tries to adjust MTRR layout from continuous 623 to discrete, to make X server driver able to add WB 624 entry later. This parameter disables that. 625 626 disable_mtrr_trim [X86, Intel and AMD only] 627 By default the kernel will trim any uncacheable 628 memory out of your available memory pool based on 629 MTRR settings. This parameter disables that behavior, 630 possibly causing your machine to run very slowly. 631 632 disable_timer_pin_1 [X86] 633 Disable PIN 1 of APIC timer 634 Can be useful to work around chipset bugs. 635 636 dmasound= [HW,OSS] Sound subsystem buffers 637 638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 639 this option disables the debugging code at boot. 640 641 dma_debug_entries=<number> 642 This option allows to tune the number of preallocated 643 entries for DMA-API debugging code. One entry is 644 required per DMA-API allocation. Use this if the 645 DMA-API debugging code disables itself because the 646 architectural default is too low. 647 648 dma_debug_driver=<driver_name> 649 With this option the DMA-API debugging driver 650 filter feature can be enabled at boot time. Just 651 pass the driver to filter for as the parameter. 652 The filter can be disabled or changed to another 653 driver later using sysfs. 654 655 dscc4.setup= [NET] 656 657 dtc3181e= [HW,SCSI] 658 659 dynamic_printk Enables pr_debug()/dev_dbg() calls if 660 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. 661 These can also be switched on/off via 662 <debugfs>/dynamic_printk/modules 663 664 earlycon= [KNL] Output early console device and options. 665 uart[8250],io,<addr>[,options] 666 uart[8250],mmio,<addr>[,options] 667 Start an early, polled-mode console on the 8250/16550 668 UART at the specified I/O port or MMIO address. 669 The options are the same as for ttyS, above. 670 671 earlyprintk= [X86,SH,BLACKFIN] 672 earlyprintk=vga 673 earlyprintk=serial[,ttySn[,baudrate]] 674 earlyprintk=ttySn[,baudrate] 675 earlyprintk=dbgp[debugController#] 676 677 Append ",keep" to not disable it when the real console 678 takes over. 679 680 Only vga or serial or usb debug port at a time. 681 682 Currently only ttyS0 and ttyS1 are supported. 683 684 Interaction with the standard serial driver is not 685 very good. 686 687 The VGA output is eventually overwritten by the real 688 console. 689 690 eata= [HW,SCSI] 691 692 edd= [EDD] 693 Format: {"off" | "on" | "skip[mbr]"} 694 695 eisa_irq_edge= [PARISC,HW] 696 See header of drivers/parisc/eisa.c. 697 698 elanfreq= [X86-32] 699 See comment before function elanfreq_setup() in 700 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 701 702 elevator= [IOSCHED] 703 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 704 See Documentation/block/as-iosched.txt and 705 Documentation/block/deadline-iosched.txt for details. 706 707 elfcorehdr= [IA64,PPC,SH,X86] 708 Specifies physical address of start of kernel core 709 image elf header. Generally kexec loader will 710 pass this option to capture kernel. 711 See Documentation/kdump/kdump.txt for details. 712 713 enable_mtrr_cleanup [X86] 714 The kernel tries to adjust MTRR layout from continuous 715 to discrete, to make X server driver able to add WB 716 entry later. This parameter enables that. 717 718 enable_timer_pin_1 [X86] 719 Enable PIN 1 of APIC timer 720 Can be useful to work around chipset bugs 721 (in particular on some ATI chipsets). 722 The kernel tries to set a reasonable default. 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 ftrace_filter=[function-list] 770 [FTRACE] Limit the functions traced by the function 771 tracer at boot up. function-list is a comma separated 772 list of functions. This list can be changed at run 773 time by the set_ftrace_filter file in the debugfs 774 tracing directory. 775 776 ftrace_notrace=[function-list] 777 [FTRACE] Do not trace the functions specified in 778 function-list. This list can be changed at run time 779 by the set_ftrace_notrace file in the debugfs 780 tracing directory. 781 782 gamecon.map[2|3]= 783 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 784 support via parallel port (up to 5 devices per port) 785 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 786 See also Documentation/input/joystick-parport.txt 787 788 gamma= [HW,DRM] 789 790 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 791 Format: off | on 792 default: on 793 794 gcov_persist= [GCOV] When non-zero (default), profiling data for 795 kernel modules is saved and remains accessible via 796 debugfs, even when the module is unloaded/reloaded. 797 When zero, profiling data is discarded and associated 798 debugfs files are removed at module unload time. 799 800 gdth= [HW,SCSI] 801 See header of drivers/scsi/gdth.c. 802 803 gpt [EFI] Forces disk with valid GPT signature but 804 invalid Protective MBR to be treated as GPT. 805 806 gvp11= [HW,SCSI] 807 808 hashdist= [KNL,NUMA] Large hashes allocated during boot 809 are distributed across NUMA nodes. Defaults on 810 for 64bit NUMA, off otherwise. 811 Format: 0 | 1 (for off | on) 812 813 hcl= [IA-64] SGI's Hardware Graph compatibility layer 814 815 hd= [EIDE] (E)IDE hard drive subsystem geometry 816 Format: <cyl>,<head>,<sect> 817 818 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 819 size of <nn>. This works even on boxes that have no 820 highmem otherwise. This also works to reduce highmem 821 size on bigger boxes. 822 823 highres= [KNL] Enable/disable high resolution timer mode. 824 Valid parameters: "on", "off" 825 Default: "on" 826 827 hisax= [HW,ISDN] 828 See Documentation/isdn/README.HiSax. 829 830 hlt [BUGS=ARM,SH] 831 832 hpet= [X86-32,HPET] option to control HPET usage 833 Format: { enable (default) | disable | force | 834 verbose } 835 disable: disable HPET and use PIT instead 836 force: allow force enabled of undocumented chips (ICH4, 837 VIA, nVidia) 838 verbose: show contents of HPET registers during setup 839 840 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 841 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 842 On x86-64 and powerpc, this option can be specified 843 multiple times interleaved with hugepages= to reserve 844 huge pages of different sizes. Valid pages sizes on 845 x86-64 are 2M (when the CPU supports "pse") and 1G 846 (when the CPU supports the "pdpe1gb" cpuinfo flag) 847 Note that 1GB pages can only be allocated at boot time 848 using hugepages= and not freed afterwards. 849 850 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 851 terminal devices. Valid values: 0..8 852 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 853 If specified, z/VM IUCV HVC accepts connections 854 from listed z/VM user IDs only. 855 856 i2c_bus= [HW] Override the default board specific I2C bus speed 857 or register an additional I2C bus that is not 858 registered from board initialization code. 859 Format: 860 <bus_id>,<clkrate> 861 862 i8042.debug [HW] Toggle i8042 debug mode 863 i8042.direct [HW] Put keyboard port into non-translated mode 864 i8042.dumbkbd [HW] Pretend that controller can only read data from 865 keyboard and cannot control its state 866 (Don't attempt to blink the leds) 867 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 868 i8042.nokbd [HW] Don't check/create keyboard port 869 i8042.noloop [HW] Disable the AUX Loopback command while probing 870 for the AUX port 871 i8042.nomux [HW] Don't check presence of an active multiplexing 872 controller 873 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 874 controllers 875 i8042.panicblink= 876 [HW] Frequency with which keyboard LEDs should blink 877 when kernel panics (default is 0.5 sec) 878 i8042.reset [HW] Reset the controller during init and cleanup 879 i8042.unlock [HW] Unlock (ignore) the keylock 880 881 i810= [HW,DRM] 882 883 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 884 indicates that the driver is running on unsupported 885 hardware. 886 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 887 does not match list of supported models. 888 i8k.power_status 889 [HW] Report power status in /proc/i8k 890 (disabled by default) 891 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 892 capability is set. 893 894 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 895 See Documentation/mca.txt. 896 897 icn= [HW,ISDN] 898 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 899 900 ide-core.nodma= [HW] (E)IDE subsystem 901 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 902 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 903 .cdrom .chs .ignore_cable are additional options 904 See Documentation/ide/ide.txt. 905 906 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 907 Claim all unknown PCI IDE storage controllers. 908 909 idle= [X86] 910 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 911 Poll forces a polling idle loop that can slightly 912 improve the performance of waking up a idle CPU, but 913 will use a lot of power and make the system run hot. 914 Not recommended. 915 idle=mwait: On systems which support MONITOR/MWAIT but 916 the kernel chose to not use it because it doesn't save 917 as much power as a normal idle loop, use the 918 MONITOR/MWAIT idle loop anyways. Performance should be 919 the same as idle=poll. 920 idle=halt: Halt is forced to be used for CPU idle. 921 In such case C2/C3 won't be used again. 922 idle=nomwait: Disable mwait for CPU C-states 923 924 ignore_loglevel [KNL] 925 Ignore loglevel setting - this will print /all/ 926 kernel messages to the console. Useful for debugging. 927 928 ihash_entries= [KNL] 929 Set number of hash buckets for inode cache. 930 931 ima_audit= [IMA] 932 Format: { "0" | "1" } 933 0 -- integrity auditing messages. (Default) 934 1 -- enable informational integrity auditing messages. 935 936 ima_hash= [IMA] 937 Format: { "sha1" | "md5" } 938 default: "sha1" 939 940 ima_tcb [IMA] 941 Load a policy which meets the needs of the Trusted 942 Computing Base. This means IMA will measure all 943 programs exec'd, files mmap'd for exec, and all files 944 opened for read by uid=0. 945 946 in2000= [HW,SCSI] 947 See header of drivers/scsi/in2000.c. 948 949 init= [KNL] 950 Format: <full_path> 951 Run specified binary instead of /sbin/init as init 952 process. 953 954 initcall_debug [KNL] Trace initcalls as they are executed. Useful 955 for working out where the kernel is dying during 956 startup. 957 958 initrd= [BOOT] Specify the location of the initial ramdisk 959 960 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 961 Format: <irq> 962 963 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 964 on 965 Enable intel iommu driver. 966 off 967 Disable intel iommu driver. 968 igfx_off [Default Off] 969 By default, gfx is mapped as normal device. If a gfx 970 device has a dedicated DMAR unit, the DMAR unit is 971 bypassed by not enabling DMAR with this option. In 972 this case, gfx device will use physical address for 973 DMA. 974 forcedac [x86_64] 975 With this option iommu will not optimize to look 976 for io virtual address below 32 bit forcing dual 977 address cycle on pci bus for cards supporting greater 978 than 32 bit addressing. The default is to look 979 for translation below 32 bit and if not available 980 then look in the higher range. 981 strict [Default Off] 982 With this option on every unmap_single operation will 983 result in a hardware IOTLB flush operation as opposed 984 to batching them for performance. 985 986 inttest= [IA64] 987 988 iomem= Disable strict checking of access to MMIO memory 989 strict regions from userspace. 990 relaxed 991 992 iommu= [x86] 993 off 994 force 995 noforce 996 biomerge 997 panic 998 nopanic 999 merge 1000 nomerge
1001 forcesac 1002 soft 1003 pt [x86, IA64] 1004 1005 io7= [HW] IO7 for Marvel based alpha systems 1006 See comment before marvel_specify_io7 in 1007 arch/alpha/kernel/core_marvel.c. 1008 1009 io_delay= [X86] I/O delay method 1010 0x80 1011 Standard port 0x80 based delay 1012 0xed 1013 Alternate port 0xed based delay (needed on some systems) 1014 udelay 1015 Simple two microseconds delay 1016 none 1017 No delay 1018 1019 ip= [IP_PNP] 1020 See Documentation/filesystems/nfsroot.txt. 1021 1022 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 1023 See comment before ip2_setup() in 1024 drivers/char/ip2/ip2base.c. 1025 1026 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 1027 See header of drivers/scsi/ips.c. 1028 1029 irqfixup [HW] 1030 When an interrupt is not handled search all handlers 1031 for it. Intended to get systems with badly broken 1032 firmware running. 1033 1034 irqpoll [HW] 1035 When an interrupt is not handled search all handlers 1036 for it. Also check all handlers each timer 1037 interrupt. Intended to get systems with badly broken 1038 firmware running. 1039 1040 isapnp= [ISAPNP] 1041 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1042 1043 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1044 Format: 1045 <cpu number>,...,<cpu number> 1046 or 1047 <cpu number>-<cpu number> 1048 (must be a positive range in ascending order) 1049 or a mixture 1050 <cpu number>,...,<cpu number>-<cpu number> 1051 1052 This option can be used to specify one or more CPUs 1053 to isolate from the general SMP balancing and scheduling 1054 algorithms. You can move a process onto or off an 1055 "isolated" CPU via the CPU affinity syscalls or cpuset. 1056 <cpu number> begins at 0 and the maximum value is 1057 "number of CPUs in system - 1". 1058 1059 This option is the preferred way to isolate CPUs. The 1060 alternative -- manually setting the CPU mask of all 1061 tasks in the system -- can cause problems and 1062 suboptimal load balancer performance. 1063 1064 iucv= [HW,NET] 1065 1066 js= [HW,JOY] Analog joystick 1067 See Documentation/input/joystick.txt. 1068 1069 keepinitrd [HW,ARM] 1070 1071 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1072 specifies the amount of memory usable by the kernel 1073 for non-movable allocations. The requested amount is 1074 spread evenly throughout all nodes in the system. The 1075 remaining memory in each node is used for Movable 1076 pages. In the event, a node is too small to have both 1077 kernelcore and Movable pages, kernelcore pages will 1078 take priority and other nodes will have a larger number 1079 of kernelcore pages. The Movable zone is used for the 1080 allocation of pages that may be reclaimed or moved 1081 by the page migration subsystem. This means that 1082 HugeTLB pages may not be allocated from this zone. 1083 Note that allocations like PTEs-from-HighMem still 1084 use the HighMem zone if it exists, and the Normal 1085 zone if it does not. 1086 1087 kgdboc= [HW] kgdb over consoles. 1088 Requires a tty driver that supports console polling. 1089 (only serial supported for now) 1090 Format: <serial_device>[,baud] 1091 1092 kmac= [MIPS] korina ethernet MAC address. 1093 Configure the RouterBoard 532 series on-chip 1094 Ethernet adapter MAC address. 1095 1096 kmemleak= [KNL] Boot-time kmemleak enable/disable 1097 Valid arguments: on, off 1098 Default: on 1099 1100 kstack=N [X86] Print N words from the kernel stack 1101 in oops dumps. 1102 1103 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1104 Default is 0 (don't ignore, but inject #GP) 1105 1106 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. 1107 Default is 1 (enabled) 1108 1109 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1110 Default is 0 (off) 1111 1112 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1113 for all guests. 1114 Default is 1 (enabled) if in 64bit or 32bit-PAE mode 1115 1116 kvm-intel.bypass_guest_pf= 1117 [KVM,Intel] Disables bypassing of guest page faults 1118 on Intel chips. Default is 1 (enabled) 1119 1120 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1121 (virtualized MMU) support on capable Intel chips. 1122 Default is 1 (enabled) 1123 1124 kvm-intel.emulate_invalid_guest_state= 1125 [KVM,Intel] Enable emulation of invalid guest states 1126 Default is 0 (disabled) 1127 1128 kvm-intel.flexpriority= 1129 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1130 Default is 1 (enabled) 1131 1132 kvm-intel.unrestricted_guest= 1133 [KVM,Intel] Disable unrestricted guest feature 1134 (virtualized real and unpaged mode) on capable 1135 Intel chips. Default is 1 (enabled) 1136 1137 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1138 feature (tagged TLBs) on capable Intel chips. 1139 Default is 1 (enabled) 1140 1141 l2cr= [PPC] 1142 1143 l3cr= [PPC] 1144 1145 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1146 disabled it. 1147 1148 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1149 in C2 power state. 1150 1151 libata.dma= [LIBATA] DMA control 1152 libata.dma=0 Disable all PATA and SATA DMA 1153 libata.dma=1 PATA and SATA Disk DMA only 1154 libata.dma=2 ATAPI (CDROM) DMA only 1155 libata.dma=4 Compact Flash DMA only 1156 Combinations also work, so libata.dma=3 enables DMA 1157 for disks and CDROMs, but not CFs. 1158 1159 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1160 libata.ignore_hpa=0 keep BIOS limits (default) 1161 libata.ignore_hpa=1 ignore limits, using full disk 1162 1163 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1164 when set. 1165 Format: <int> 1166 1167 libata.force= [LIBATA] Force configurations. The format is comma 1168 separated list of "[ID:]VAL" where ID is 1169 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1170 matching port, link or device. Basically, it matches 1171 the ATA ID string printed on console by libata. If 1172 the whole ID part is omitted, the last PORT and DEVICE 1173 values are used. If ID hasn't been specified yet, the 1174 configuration applies to all ports, links and devices. 1175 1176 If only DEVICE is omitted, the parameter applies to 1177 the port and all links and devices behind it. DEVICE 1178 number of 0 either selects the first device or the 1179 first fan-out link behind PMP device. It does not 1180 select the host link. DEVICE number of 15 selects the 1181 host link and device attached to it. 1182 1183 The VAL specifies the configuration to force. As long 1184 as there's no ambiguity shortcut notation is allowed. 1185 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1186 The following configurations can be forced. 1187 1188 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1189 Any ID with matching PORT is used. 1190 1191 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1192 1193 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1194 udma[/][16,25,33,44,66,100,133] notation is also 1195 allowed. 1196 1197 * [no]ncq: Turn on or off NCQ. 1198 1199 * nohrst, nosrst, norst: suppress hard, soft 1200 and both resets. 1201 1202 If there are multiple matching configurations changing 1203 the same attribute, the last one is used. 1204 1205 lmb=debug [KNL] Enable lmb debug messages. 1206 1207 load_ramdisk= [RAM] List of ramdisks to load from floppy 1208 See Documentation/blockdev/ramdisk.txt. 1209 1210 lockd.nlm_grace_period=P [NFS] Assign grace period. 1211 Format: <integer> 1212 1213 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1214 Format: <integer> 1215 1216 lockd.nlm_timeout=T [NFS] Assign timeout value. 1217 Format: <integer> 1218 1219 lockd.nlm_udpport=M [NFS] Assign UDP port. 1220 Format: <integer> 1221 1222 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1223 Format: <irq> 1224 1225 loglevel= All Kernel Messages with a loglevel smaller than the 1226 console loglevel will be printed to the console. It can 1227 also be changed with klogd or other programs. The 1228 loglevels are defined as follows: 1229 1230 0 (KERN_EMERG) system is unusable 1231 1 (KERN_ALERT) action must be taken immediately 1232 2 (KERN_CRIT) critical conditions 1233 3 (KERN_ERR) error conditions 1234 4 (KERN_WARNING) warning conditions 1235 5 (KERN_NOTICE) normal but significant condition 1236 6 (KERN_INFO) informational 1237 7 (KERN_DEBUG) debug-level messages 1238 1239 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1240 Format: { n | nk | nM } 1241 n must be a power of two. The default size 1242 is set in the kernel config file. 1243 1244 logo.nologo [FB] Disables display of the built-in Linux logo. 1245 This may be used to provide more screen space for 1246 kernel log messages and is useful when debugging 1247 kernel boot problems. 1248 1249 lp=0 [LP] Specify parallel ports to use, e.g, 1250 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1251 lp=reset first parallel port). 'lp=0' disables the 1252 lp=auto printer driver. 'lp=reset' (which can be 1253 specified in addition to the ports) causes 1254 attached printers to be reset. Using 1255 lp=port1,port2,... specifies the parallel ports 1256 to associate lp devices with, starting with 1257 lp0. A port specification may be 'none' to skip 1258 that lp device, or a parport name such as 1259 'parport0'. Specifying 'lp=auto' instead of a 1260 port specification list means that device IDs 1261 from each port should be examined, to see if 1262 an IEEE 1284-compliant printer is attached; if 1263 so, the driver will manage that printer. 1264 See also header of drivers/char/lp.c. 1265 1266 lpj=n [KNL] 1267 Sets loops_per_jiffy to given constant, thus avoiding 1268 time-consuming boot-time autodetection (up to 250 ms per 1269 CPU). 0 enables autodetection (default). To determine 1270 the correct value for your kernel, boot with normal 1271 autodetection and see what value is printed. Note that 1272 on SMP systems the preset will be applied to all CPUs, 1273 which is likely to cause problems if your CPUs need 1274 significantly divergent settings. An incorrect value 1275 will cause delays in the kernel to be wrong, leading to 1276 unpredictable I/O errors and other breakage. Although 1277 unlikely, in the extreme case this might damage your 1278 hardware. 1279 1280 ltpc= [NET] 1281 Format: <io>,<irq>,<dma> 1282 1283 mac5380= [HW,SCSI] Format: 1284 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1285 1286 machvec= [IA64] Force the use of a particular machine-vector 1287 (machvec) in a generic kernel. 1288 Example: machvec=hpzx1_swiotlb 1289 1290 machtype= [Loongson] Share the same kernel image file between different 1291 yeeloong laptop. 1292 Example: machtype=lemote-yeeloong-2f-7inch 1293 1294 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 1295 than or equal to this physical address is ignored. 1296 1297 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1298 should make use of. maxcpus=n : n >= 0 limits the 1299 kernel to using 'n' processors. n=0 is a special case, 1300 it is equivalent to "nosmp", which also disables 1301 the IO APIC. 1302 1303 max_loop= [LOOP] Maximum number of loopback devices that can 1304 be mounted 1305 Format: <1-256> 1306 1307 max_luns= [SCSI] Maximum number of LUNs to probe. 1308 Should be between 1 and 2^32-1. 1309 1310 max_report_luns= 1311 [SCSI] Maximum number of LUNs received. 1312 Should be between 1 and 16384. 1313 1314 mcatest= [IA-64] 1315 1316 mce [X86-32] Machine Check Exception 1317 1318 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1319 1320 md= [HW] RAID subsystems devices and level 1321 See Documentation/md.txt. 1322 1323 mdacon= [MDA] 1324 Format: <first>,<last> 1325 Specifies range of consoles to be captured by the MDA. 1326 1327 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1328 Amount of memory to be used when the kernel is not able 1329 to see the whole system memory or for test. 1330 [X86-32] Use together with memmap= to avoid physical 1331 address space collisions. Without memmap= PCI devices 1332 could be placed at addresses belonging to unused RAM. 1333 1334 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1335 memory. 1336 1337 memchunk=nn[KMG] 1338 [KNL,SH] Allow user to override the default size for 1339 per-device physically contiguous DMA buffers. 1340 1341 memmap=exactmap [KNL,X86] Enable setting of an exact 1342 E820 memory map, as specified by the user. 1343 Such memmap=exactmap lines can be constructed based on 1344 BIOS output or other requirements. See the memmap=nn@ss 1345 option description. 1346 1347 memmap=nn[KMG]@ss[KMG] 1348 [KNL] Force usage of a specific region of memory 1349 Region of memory to be used, from ss to ss+nn. 1350 1351 memmap=nn[KMG]#ss[KMG] 1352 [KNL,ACPI] Mark specific memory as ACPI data. 1353 Region of memory to be used, from ss to ss+nn. 1354 1355 memmap=nn[KMG]$ss[KMG] 1356 [KNL,ACPI] Mark specific memory as reserved. 1357 Region of memory to be used, from ss to ss+nn. 1358 Example: Exclude memory from 0x18690000-0x1869ffff 1359 memmap=64K$0x18690000 1360 or 1361 memmap=0x10000$0x18690000 1362 1363 memory_corruption_check=0/1 [X86] 1364 Some BIOSes seem to corrupt the first 64k of 1365 memory when doing things like suspend/resume. 1366 Setting this option will scan the memory 1367 looking for corruption. Enabling this will 1368 both detect corruption and prevent the kernel 1369 from using the memory being corrupted. 1370 However, its intended as a diagnostic tool; if 1371 repeatable BIOS-originated corruption always 1372 affects the same memory, you can use memmap= 1373 to prevent the kernel from using that memory. 1374 1375 memory_corruption_check_size=size [X86] 1376 By default it checks for corruption in the low 1377 64k, making this memory unavailable for normal 1378 use. Use this parameter to scan for 1379 corruption in more or less memory. 1380 1381 memory_corruption_check_period=seconds [X86] 1382 By default it checks for corruption every 60 1383 seconds. Use this parameter to check at some 1384 other rate. 0 disables periodic checking. 1385 1386 memtest= [KNL,X86] Enable memtest 1387 Format: <integer> 1388 default : 0 <disable> 1389 Specifies the number of memtest passes to be 1390 performed. Each pass selects another test 1391 pattern from a given set of patterns. Memtest 1392 fills the memory with this pattern, validates 1393 memory contents and reserves bad memory 1394 regions that are detected. 1395 1396 meye.*= [HW] Set MotionEye Camera parameters 1397 See Documentation/video4linux/meye.txt. 1398 1399 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1400 Multi-Function General Purpose Timers on AMD Geode 1401 platforms. 1402 1403 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1404 the BIOS has incorrectly applied a workaround. TinyBIOS 1405 version 0.98 is known to be affected, 0.99 fixes the 1406 problem by letting the user disable the workaround. 1407 1408 mga= [HW,DRM] 1409 1410 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1411 physical address is ignored. 1412 1413 mini2440= [ARM,HW,KNL] 1414 Format:[0..2][b][c][t] 1415 Default: "0tb" 1416 MINI2440 configuration specification: 1417 0 - The attached screen is the 3.5" TFT 1418 1 - The attached screen is the 7" TFT 1419 2 - The VGA Shield is attached (1024x768) 1420 Leaving out the screen size parameter will not load 1421 the TFT driver, and the framebuffer will be left 1422 unconfigured. 1423 b - Enable backlight. The TFT backlight pin will be 1424 linked to the kernel VESA blanking code and a GPIO 1425 LED. This parameter is not necessary when using the 1426 VGA shield. 1427 c - Enable the s3c camera interface. 1428 t - Reserved for enabling touchscreen support. The 1429 touchscreen support is not enabled in the mainstream 1430 kernel as of 2.6.30, a preliminary port can be found 1431 in the "bleeding edge" mini2440 support kernel at 1432 http://repo.or.cz/w/linux-2.6/mini2440.git 1433 1434 mminit_loglevel= 1435 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1436 parameter allows control of the logging verbosity for 1437 the additional memory initialisation checks. A value 1438 of 0 disables mminit logging and a level of 4 will 1439 log everything. Information is printed at KERN_DEBUG 1440 so loglevel=8 may also need to be specified. 1441 1442 mousedev.tap_time= 1443 [MOUSE] Maximum time between finger touching and 1444 leaving touchpad surface for touch to be considered 1445 a tap and be reported as a left button click (for 1446 touchpads working in absolute mode only). 1447 Format: <msecs> 1448 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1449 reporting absolute coordinates, such as tablets 1450 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1451 reporting absolute coordinates, such as tablets 1452 1453 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1454 is similar to kernelcore except it specifies the 1455 amount of memory used for migratable allocations. 1456 If both kernelcore and movablecore is specified, 1457 then kernelcore will be at *least* the specified 1458 value but may be more. If movablecore on its own 1459 is specified, the administrator must be careful 1460 that the amount of memory usable for all allocations 1461 is not too small. 1462 1463 mpu401= [HW,OSS] 1464 Format: <io>,<irq> 1465 1466 MTD_Partition= [MTD] 1467 Format: <name>,<region-number>,<size>,<offset> 1468 1469 MTD_Region= [MTD] Format: 1470 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1471 1472 mtdparts= [MTD] 1473 See drivers/mtd/cmdlinepart.c. 1474 1475 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 1476 1477 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 1478 1479 boundary - index of last SLC block on Flex-OneNAND. 1480 The remaining blocks are configured as MLC blocks. 1481 lock - Configure if Flex-OneNAND boundary should be locked. 1482 Once locked, the boundary cannot be changed. 1483 1 indicates lock status, 0 indicates unlock status. 1484 1485 mtdset= [ARM] 1486 ARM/S3C2412 JIVE boot control 1487 1488 See arch/arm/mach-s3c2412/mach-jive.c 1489 1490 mtouchusb.raw_coordinates= 1491 [HW] Make the MicroTouch USB driver use raw coordinates 1492 ('y', default) or cooked coordinates ('n') 1493 1494 mtrr_chunk_size=nn[KMG] [X86] 1495 used for mtrr cleanup. It is largest continuous chunk 1496 that could hold holes aka. UC entries. 1497 1498 mtrr_gran_size=nn[KMG] [X86] 1499 Used for mtrr cleanup. It is granularity of mtrr block. 1500 Default is 1. 1501 Large value could prevent small alignment from 1502 using up MTRRs. 1503 1504 mtrr_spare_reg_nr=n [X86] 1505 Format: <integer> 1506 Range: 0,7 : spare reg number 1507 Default : 1 1508 Used for mtrr cleanup. It is spare mtrr entries number. 1509 Set to 2 or more if your graphical card needs more. 1510 1511 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1512 1513 NCR_D700= [HW,SCSI] 1514 See header of drivers/scsi/NCR_D700.c. 1515 1516 ncr5380= [HW,SCSI] 1517 1518 ncr53c400= [HW,SCSI] 1519 1520 ncr53c400a= [HW,SCSI] 1521 1522 ncr53c406a= [HW,SCSI] 1523 1524 ncr53c8xx= [HW,SCSI] 1525 1526 netdev= [NET] Network devices parameters 1527 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1528 Note that mem_start is often overloaded to mean 1529 something different and driver-specific. 1530 This usage is only documented in each driver source 1531 file if at all. 1532 1533 nf_conntrack.acct= 1534 [NETFILTER] Enable connection tracking flow accounting 1535 0 to disable accounting 1536 1 to enable accounting 1537 Default value depends on CONFIG_NF_CT_ACCT that is 1538 going to be removed in 2.6.29. 1539 1540 nfsaddrs= [NFS] 1541 See Documentation/filesystems/nfsroot.txt. 1542 1543 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1544 See Documentation/filesystems/nfsroot.txt. 1545 1546 nfs.callback_tcpport= 1547 [NFS] set the TCP port on which the NFSv4 callback 1548 channel should listen. 1549 1550 nfs.cache_getent= 1551 [NFS] sets the pathname to the program which is used 1552 to update the NFS client cache entries. 1553 1554 nfs.cache_getent_timeout= 1555 [NFS] sets the timeout after which an attempt to 1556 update a cache entry is deemed to have failed. 1557 1558 nfs.idmap_cache_timeout= 1559 [NFS] set the maximum lifetime for idmapper cache 1560 entries. 1561 1562 nfs.enable_ino64= 1563 [NFS] enable 64-bit inode numbers. 1564 If zero, the NFS client will fake up a 32-bit inode 1565 number for the readdir() and stat() syscalls instead 1566 of returning the full 64-bit number. 1567 The default is to return 64-bit inode numbers. 1568 1569 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 1570 when a NMI is triggered. 1571 Format: [state][,regs][,debounce][,die] 1572 1573 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 1574 Format: [panic,][num] 1575 Valid num: 0,1,2 1576 0 - turn nmi_watchdog off 1577 1 - use the IO-APIC timer for the NMI watchdog 1578 2 - use the local APIC for the NMI watchdog using 1579 a performance counter. Note: This will use one 1580 performance counter and the local APIC's performance 1581 vector. 1582 When panic is specified, panic when an NMI watchdog 1583 timeout occurs. 1584 This is useful when you use a panic=... timeout and 1585 need the box quickly up again. 1586 Instead of 1 and 2 it is possible to use the following 1587 symbolic names: lapic and ioapic 1588 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic 1589 1590 netpoll.carrier_timeout= 1591 [NET] Specifies amount of time (in seconds) that 1592 netpoll should wait for a carrier. By default netpoll 1593 waits 4 seconds. 1594 1595 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1596 emulation library even if a 387 maths coprocessor 1597 is present. 1598 1599 no_console_suspend 1600 [HW] Never suspend the console 1601 Disable suspending of consoles during suspend and 1602 hibernate operations. Once disabled, debugging 1603 messages can reach various consoles while the rest 1604 of the system is being put to sleep (ie, while 1605 debugging driver suspend/resume hooks). This may 1606 not work reliably with all consoles, but is known 1607 to work with serial and VGA consoles. 1608 1609 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1610 caches in the slab allocator. Saves per-node memory, 1611 but will impact performance. 1612 1613 noalign [KNL,ARM] 1614 1615 noapic [SMP,APIC] Tells the kernel to not make use of any 1616 IOAPICs that may be present in the system. 1617 1618 nobats [PPC] Do not use BATs for mapping kernel lowmem 1619 on "Classic" PPC cores. 1620 1621 nocache [ARM] 1622 1623 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1624 1625 nodelayacct [KNL] Disable per-task delay accounting 1626 1627 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1628 1629 nodsp [SH] Disable hardware DSP at boot time. 1630 1631 noefi [X86] Disable EFI runtime services support. 1632 1633 noexec [IA-64] 1634 1635 noexec [X86] 1636 On X86-32 available only on PAE configured kernels. 1637 noexec=on: enable non-executable mappings (default) 1638 noexec=off: disable non-executable mappings 1639 1640 noexec32 [X86-64] 1641 This affects only 32-bit executables. 1642 noexec32=on: enable non-executable mappings (default) 1643 read doesn't imply executable mappings 1644 noexec32=off: disable non-executable mappings 1645 read implies executable mappings 1646 1647 nofpu [SH] Disable hardware FPU at boot time. 1648 1649 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1650 register save and restore. The kernel will only save 1651 legacy floating-point registers on task switch. 1652 1653 noxsave [BUGS=X86] Disables x86 extended register state save 1654 and restore using xsave. The kernel will fallback to 1655 enabling legacy floating-point and sse state. 1656 1657 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 1658 wfi(ARM) instruction doesn't work correctly and not to 1659 use it. This is also useful when using JTAG debugger. 1660 1661 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1662 instruction doesn't work correctly and not to 1663 use it. 1664 1665 no_file_caps Tells the kernel not to honor file capabilities. The 1666 only way then for a file to be executed with privilege 1667 is to be setuid root or executed by root. 1668 1669 nohalt [IA-64] Tells the kernel not to use the power saving 1670 function PAL_HALT_LIGHT when idle. This increases 1671 power-consumption. On the positive side, it reduces 1672 interrupt wake-up latency, which may improve performance 1673 in certain environments such as networked servers or 1674 real-time systems. 1675 1676 nohz= [KNL] Boottime enable/disable dynamic ticks 1677 Valid arguments: on, off 1678 Default: on 1679 1680 noiotrap [SH] Disables trapped I/O port accesses. 1681 1682 noirqdebug [X86-32] Disables the code which attempts to detect and 1683 disable unhandled interrupt sources. 1684 1685 no_timer_check [X86,APIC] Disables the code which tests for 1686 broken timer IRQ sources. 1687 1688 noisapnp [ISAPNP] Disables ISA PnP code. 1689 1690 noinitrd [RAM] Tells the kernel not to load any configured 1691 initial RAM disk. 1692 1693 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 1694 remapping. 1695 1696 nointroute [IA-64] 1697 1698 nojitter [IA64] Disables jitter checking for ITC timers. 1699 1700 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1701 1702 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1703 1704 noltlbs [PPC] Do not use large page/tlb entries for kernel 1705 lowmem mapping on PPC40x. 1706 1707 nomca [IA-64] Disable machine check abort handling 1708 1709 nomce [X86-32] Machine Check Exception 1710 1711 nomfgpt [X86-32] Disable Multi-Function General Purpose 1712 Timer usage (for AMD Geode machines). 1713 1714 norandmaps Don't use address space randomization. Equivalent to 1715 echo 0 > /proc/sys/kernel/randomize_va_space 1716 1717 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1718 1719 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1720 with UP alternatives 1721 1722 noresidual [PPC] Don't use residual data on PReP machines. 1723 1724 noresume [SWSUSP] Disables resume and restores original swap 1725 space. 1726 1727 no-scroll [VGA] Disables scrollback. 1728 This is required for the Braillex ib80-piezo Braille 1729 reader made by F.H. Papenmeier (Germany). 1730 1731 nosbagart [IA-64] 1732 1733 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1734 1735 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1736 and disable the IO APIC. legacy for "maxcpus=0". 1737 1738 nosoftlockup [KNL] Disable the soft-lockup detector. 1739 1740 noswapaccount [KNL] Disable accounting of swap in memory resource 1741 controller. (See Documentation/cgroups/memory.txt) 1742 1743 nosync [HW,M68K] Disables sync negotiation for all devices. 1744 1745 notsc [BUGS=X86-32] Disable Time Stamp Counter 1746 1747 nousb [USB] Disable the USB subsystem 1748 1749 nowb [ARM] 1750 1751 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1752 1753 nptcg= [IA64] Override max number of concurrent global TLB 1754 purges which is reported from either PAL_VM_SUMMARY or 1755 SAL PALO. 1756 1757 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1758 1759 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1760 one of ['zone', 'node', 'default'] can be specified 1761 This can be set from sysctl after boot. 1762 See Documentation/sysctl/vm.txt for details. 1763 1764 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1765 See Documentation/debugging-via-ohci1394.txt for more 1766 info. 1767 1768 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1769 Rather than timing out after 20 ms if an EC 1770 command is not properly ACKed, override the length 1771 of the timeout. We have interrupts disabled while 1772 waiting for the ACK, so if this is set too high 1773 interrupts *may* be lost! 1774 1775 opl3= [HW,OSS] 1776 Format: <io> 1777 1778 oprofile.timer= [HW] 1779 Use timer interrupt instead of performance counters 1780 1781 oprofile.cpu_type= Force an oprofile cpu type 1782 This might be useful if you have an older oprofile 1783 userland or if you want common events. 1784 Format: { arch_perfmon } 1785 arch_perfmon: [X86] Force use of architectural 1786 perfmon on Intel CPUs instead of the 1787 CPU specific event set. 1788 1789 osst= [HW,SCSI] SCSI Tape Driver 1790 Format: <buffer_size>,<write_threshold> 1791 See also Documentation/scsi/st.txt. 1792 1793 panic= [KNL] Kernel behaviour on panic 1794 Format: <timeout> 1795 1796 parkbd.port= [HW] Parallel port number the keyboard adapter is 1797 connected to, default is 0. 1798 Format: <parport#> 1799 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1800 0 for XT, 1 for AT (default is AT). 1801 Format: <mode> 1802 1803 parport= [HW,PPT] Specify parallel ports. 0 disables. 1804 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1805 Use 'auto' to force the driver to use any 1806 IRQ/DMA settings detected (the default is to 1807 ignore detected IRQ/DMA settings because of 1808 possible conflicts). You can specify the base 1809 address, IRQ, and DMA settings; IRQ and DMA 1810 should be numbers, or 'auto' (for using detected 1811 settings on that particular port), or 'nofifo' 1812 (to avoid using a FIFO even if it is detected). 1813 Parallel ports are assigned in the order they 1814 are specified on the command line, starting 1815 with parport0. 1816 1817 parport_init_mode= [HW,PPT] 1818 Configure VIA parallel port to operate in 1819 a specific mode. This is necessary on Pegasos 1820 computer where firmware has no options for setting 1821 up parallel port mode and sets it to spp. 1822 Currently this function knows 686a and 8231 chips. 1823 Format: [spp|ps2|epp|ecp|ecpepp] 1824 1825 pas2= [HW,OSS] Format: 1826 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1827 1828 pas16= [HW,SCSI] 1829 See header of drivers/scsi/pas16.c. 1830 1831 pause_on_oops= 1832 Halt all CPUs after the first oops has been printed for 1833 the specified number of seconds. This is to be used if 1834 your oopses keep scrolling off the screen. 1835 1836 pcbit= [HW,ISDN] 1837 1838 pcd. [PARIDE] 1839 See header of drivers/block/paride/pcd.c. 1840 See also Documentation/blockdev/paride.txt. 1841 1842 pci=option[,option...] [PCI] various PCI subsystem options: 1843 earlydump [X86] dump PCI config space before the kernel 1844 changes anything 1845 off [X86] don't probe for the PCI bus 1846 bios [X86-32] force use of PCI BIOS, don't access 1847 the hardware directly. Use this if your machine 1848 has a non-standard PCI host bridge. 1849 nobios [X86-32] disallow use of PCI BIOS, only direct 1850 hardware access methods are allowed. Use this 1851 if you experience crashes upon bootup and you 1852 suspect they are caused by the BIOS. 1853 conf1 [X86] Force use of PCI Configuration 1854 Mechanism 1. 1855 conf2 [X86] Force use of PCI Configuration 1856 Mechanism 2. 1857 noaer [PCIE] If the PCIEAER kernel config parameter is 1858 enabled, this kernel boot option can be used to 1859 disable the use of PCIE advanced error reporting. 1860 nodomains [PCI] Disable support for multiple PCI 1861 root domains (aka PCI segments, in ACPI-speak). 1862 nommconf [X86] Disable use of MMCONFIG for PCI 1863 Configuration 1864 check_enable_amd_mmconf [X86] check for and enable 1865 properly configured MMIO access to PCI 1866 config space on AMD family 10h CPU 1867 nomsi [MSI] If the PCI_MSI kernel config parameter is 1868 enabled, this kernel boot option can be used to 1869 disable the use of MSI interrupts system-wide. 1870 noioapicquirk [APIC] Disable all boot interrupt quirks. 1871 Safety option to keep boot IRQs enabled. This 1872 should never be necessary. 1873 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1874 primary IO-APIC for bridges that cannot disable 1875 boot IRQs. This fixes a source of spurious IRQs 1876 when the system masks IRQs. 1877 noioapicreroute [APIC] Disable workaround that uses the 1878 boot IRQ equivalent of an IRQ that connects to 1879 a chipset where boot IRQs cannot be disabled. 1880 The opposite of ioapicreroute. 1881 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1882 routing table. These calls are known to be buggy 1883 on several machines and they hang the machine 1884 when used, but on other computers it's the only 1885 way to get the interrupt routing table. Try 1886 this option if the kernel is unable to allocate 1887 IRQs or discover secondary PCI buses on your 1888 motherboard. 1889 rom [X86] Assign address space to expansion ROMs. 1890 Use with caution as certain devices share 1891 address decoders between ROMs and other 1892 resources. 1893 norom [X86] Do not assign address space to 1894 expansion ROMs that do not already have 1895 BIOS assigned address ranges. 1896 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1897 assigned automatically to PCI devices. You can 1898 make the kernel exclude IRQs of your ISA cards 1899 this way. 1900 pirqaddr=0xAAAAA [X86] Specify the physical address 1901 of the PIRQ table (normally generated 1902 by the BIOS) if it is outside the 1903 F0000h-100000h range. 1904 lastbus=N [X86] Scan all buses thru bus #N. Can be 1905 useful if the kernel is unable to find your 1906 secondary buses and you want to tell it 1907 explicitly which ones they are. 1908 assign-busses [X86] Always assign all PCI bus 1909 numbers ourselves, overriding 1910 whatever the firmware may have done. 1911 usepirqmask [X86] Honor the possible IRQ mask stored 1912 in the BIOS $PIR table. This is needed on 1913 some systems with broken BIOSes, notably 1914 some HP Pavilion N5400 and Omnibook XE3 1915 notebooks. This will have no effect if ACPI 1916 IRQ routing is enabled. 1917 noacpi [X86] Do not use ACPI for IRQ routing 1918 or for PCI scanning. 1919 use_crs [X86] Use _CRS for PCI resource 1920 allocation. 1921 routeirq Do IRQ routing for all PCI devices. 1922 This is normally done in pci_enable_device(), 1923 so this option is a temporary workaround 1924 for broken drivers that don't call it. 1925 skip_isa_align [X86] do not align io start addr, so can 1926 handle more pci cards 1927 firmware [ARM] Do not re-enumerate the bus but instead 1928 just use the configuration from the 1929 bootloader. This is currently used on 1930 IXP2000 systems where the bus has to be 1931 configured a certain way for adjunct CPUs. 1932 noearly [X86] Don't do any early type 1 scanning. 1933 This might help on some broken boards which 1934 machine check when some devices' config space 1935 is read. But various workarounds are disabled 1936 and some IOMMU drivers will not work. 1937 bfsort Sort PCI devices into breadth-first order. 1938 This sorting is done to get a device 1939 order compatible with older (<= 2.4) kernels. 1940 nobfsort Don't sort PCI devices into breadth-first order. 1941 cbiosize=nn[KMG] The fixed amount of bus space which is 1942 reserved for the CardBus bridge's IO window. 1943 The default value is 256 bytes. 1944 cbmemsize=nn[KMG] The fixed amount of bus space which is 1945 reserved for the CardBus bridge's memory 1946 window. The default value is 64 megabytes. 1947 resource_alignment= 1948 Format: 1949 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] 1950 Specifies alignment and device to reassign 1951 aligned memory resources. 1952 If <order of align> is not specified, 1953 PAGE_SIZE is used as alignment. 1954 PCI-PCI bridge can be specified, if resource 1955 windows need to be expanded. 1956 ecrc= Enable/disable PCIe ECRC (transaction layer 1957 end-to-end CRC checking). 1958 bios: Use BIOS/firmware settings. This is the 1959 the default. 1960 off: Turn ECRC off 1961 on: Turn ECRC on. 1962 1963 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1964 Management. 1965 off Disable ASPM. 1966 force Enable ASPM even on devices that claim not to support it. 1967 WARNING: Forcing ASPM on may cause system lockups. 1968 1969 pcmv= [HW,PCMCIA] BadgePAD 4 1970 1971 pd. [PARIDE] 1972 See Documentation/blockdev/paride.txt. 1973 1974 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1975 boot time. 1976 Format: { 0 | 1 } 1977 See arch/parisc/kernel/pdc_chassis.c 1978 1979 percpu_alloc= Select which percpu first chunk allocator to use. 1980 Currently supported values are "embed" and "page". 1981 Archs may support subset or none of the selections. 1982 See comments in mm/percpu.c for details on each 1983 allocator. This parameter is primarily for debugging 1984 and performance comparison. 1985 1986 pf. [PARIDE] 1987 See Documentation/blockdev/paride.txt. 1988 1989 pg. [PARIDE] 1990 See Documentation/blockdev/paride.txt. 1991 1992 pirq= [SMP,APIC] Manual mp-table setup 1993 See Documentation/x86/i386/IO-APIC.txt. 1994 1995 plip= [PPT,NET] Parallel port network link 1996 Format: { parport<nr> | timid | 0 } 1997 See also Documentation/parport.txt. 1998 1999 pmtmr= [X86] Manual setup of pmtmr I/O Port. 2000 Override pmtimer IOPort with a hex value.
2001 e.g. pmtmr=0x508 2002 2003 pnp.debug [PNP] 2004 Enable PNP debug messages. This depends on the 2005 CONFIG_PNP_DEBUG_MESSAGES option. 2006 2007 pnpacpi= [ACPI] 2008 { off } 2009 2010 pnpbios= [ISAPNP] 2011 { on | off | curr | res | no-curr | no-res } 2012 2013 pnp_reserve_irq= 2014 [ISAPNP] Exclude IRQs for the autoconfiguration 2015 2016 pnp_reserve_dma= 2017 [ISAPNP] Exclude DMAs for the autoconfiguration 2018 2019 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 2020 Ranges are in pairs (I/O port base and size). 2021 2022 pnp_reserve_mem= 2023 [ISAPNP] Exclude memory regions for the 2024 autoconfiguration. 2025 Ranges are in pairs (memory base and size). 2026 2027 ports= [IP_VS_FTP] IPVS ftp helper module 2028 Default is 21. 2029 Up to 8 (IP_VS_APP_MAX_PORTS) ports 2030 may be specified. 2031 Format: <port>,<port>.... 2032 2033 print-fatal-signals= 2034 [KNL] debug: print fatal signals 2035 print-fatal-signals=1: print segfault info to 2036 the kernel console. 2037 default: off. 2038 2039 printk.time= Show timing data prefixed to each printk message line 2040 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 2041 2042 processor.max_cstate= [HW,ACPI] 2043 Limit processor to maximum C-state 2044 max_cstate=9 overrides any DMI blacklist limit. 2045 2046 processor.nocst [HW,ACPI] 2047 Ignore the _CST method to determine C-states, 2048 instead using the legacy FADT method 2049 2050 profile= [KNL] Enable kernel profiling via /proc/profile 2051 Format: [schedule,]<number> 2052 Param: "schedule" - profile schedule points. 2053 Param: <number> - step/bucket size as a power of 2 for 2054 statistical time based profiling. 2055 Param: "sleep" - profile D-state sleeping (millisecs). 2056 Requires CONFIG_SCHEDSTATS 2057 Param: "kvm" - profile VM exits. 2058 2059 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 2060 before loading. 2061 See Documentation/blockdev/ramdisk.txt. 2062 2063 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 2064 probe for; one of (bare|imps|exps|lifebook|any). 2065 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 2066 per second. 2067 psmouse.resetafter= [HW,MOUSE] 2068 Try to reset the device after so many bad packets 2069 (0 = never). 2070 psmouse.resolution= 2071 [HW,MOUSE] Set desired mouse resolution, in dpi. 2072 psmouse.smartscroll= 2073 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 2074 0 = disabled, 1 = enabled (default). 2075 2076 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 2077 Format: 2078 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 2079 2080 pt. [PARIDE] 2081 See Documentation/blockdev/paride.txt. 2082 2083 pty.legacy_count= 2084 [KNL] Number of legacy pty's. Overwrites compiled-in 2085 default number. 2086 2087 quiet [KNL] Disable most log messages 2088 2089 r128= [HW,DRM] 2090 2091 raid= [HW,RAID] 2092 See Documentation/md.txt. 2093 2094 ramdisk_blocksize= [RAM] 2095 See Documentation/blockdev/ramdisk.txt. 2096 2097 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 2098 See Documentation/blockdev/ramdisk.txt. 2099 2100 rcupdate.blimit= [KNL,BOOT] 2101 Set maximum number of finished RCU callbacks to process 2102 in one batch. 2103 2104 rcupdate.qhimark= [KNL,BOOT] 2105 Set threshold of queued 2106 RCU callbacks over which batch limiting is disabled. 2107 2108 rcupdate.qlowmark= [KNL,BOOT] 2109 Set threshold of queued RCU callbacks below which 2110 batch limiting is re-enabled. 2111 2112 rdinit= [KNL] 2113 Format: <full_path> 2114 Run specified binary instead of /init from the ramdisk, 2115 used for early userspace startup. See initrd. 2116 2117 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 2118 Format: <reboot_mode>[,<reboot_mode2>[,...]] 2119 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 2120 2121 relax_domain_level= 2122 [KNL, SMP] Set scheduler's default relax_domain_level. 2123 See Documentation/cgroups/cpusets.txt. 2124 2125 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 2126 2127 reservetop= [X86-32] 2128 Format: nn[KMG] 2129 Reserves a hole at the top of the kernel virtual 2130 address space. 2131 2132 reset_devices [KNL] Force drivers to reset the underlying device 2133 during initialization. 2134 2135 resume= [SWSUSP] 2136 Specify the partition device for software suspend 2137 2138 resume_offset= [SWSUSP] 2139 Specify the offset from the beginning of the partition 2140 given by "resume=" at which the swap header is located, 2141 in <PAGE_SIZE> units (needed only for swap files). 2142 See Documentation/power/swsusp-and-swap-files.txt 2143 2144 retain_initrd [RAM] Keep initrd memory after extraction 2145 2146 rhash_entries= [KNL,NET] 2147 Set number of hash buckets for route cache 2148 2149 riscom8= [HW,SERIAL] 2150 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 2151 2152 ro [KNL] Mount root device read-only on boot 2153 2154 root= [KNL] Root filesystem 2155 2156 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 2157 mount the root filesystem 2158 2159 rootflags= [KNL] Set root filesystem mount option string 2160 2161 rootfstype= [KNL] Set root filesystem type 2162 2163 rootwait [KNL] Wait (indefinitely) for root device to show up. 2164 Useful for devices that are detected asynchronously 2165 (e.g. USB and MMC devices). 2166 2167 root_plug.vendor_id= 2168 [ROOTPLUG] Override the default vendor ID 2169 2170 root_plug.product_id= 2171 [ROOTPLUG] Override the default product ID 2172 2173 root_plug.debug= 2174 [ROOTPLUG] Enable debugging output 2175 2176 rw [KNL] Mount root device read-write on boot 2177 2178 S [KNL] Run init in single mode 2179 2180 sa1100ir [NET] 2181 See drivers/net/irda/sa1100_ir.c. 2182 2183 sbni= [NET] Granch SBNI12 leased line adapter 2184 2185 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 2186 Format: <io>[,<timeout>[,<isapnp>]] 2187 2188 scsi_debug_*= [SCSI] 2189 See drivers/scsi/scsi_debug.c. 2190 2191 scsi_default_dev_flags= 2192 [SCSI] SCSI default device flags 2193 Format: <integer> 2194 2195 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 2196 Format: <vendor>:<model>:<flags> 2197 (flags are integer value) 2198 2199 scsi_logging_level= [SCSI] a bit mask of logging levels 2200 See drivers/scsi/scsi_logging.h for bits. Also 2201 settable via sysctl at dev.scsi.logging_level 2202 (/proc/sys/dev/scsi/logging_level). 2203 There is also a nice 'scsi_logging_level' script in the 2204 S390-tools package, available for download at 2205 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 2206 2207 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 2208 discovered. async scans them in kernel threads, 2209 allowing boot to proceed. none ignores them, expecting 2210 user space to do the scan. 2211 2212 security= [SECURITY] Choose a security module to enable at boot. 2213 If this boot parameter is not specified, only the first 2214 security module asking for security registration will be 2215 loaded. An invalid security module name will be treated 2216 as if no module has been chosen. 2217 2218 selinux= [SELINUX] Disable or enable SELinux at boot time. 2219 Format: { "0" | "1" } 2220 See security/selinux/Kconfig help text. 2221 0 -- disable. 2222 1 -- enable. 2223 Default value is set via kernel config option. 2224 If enabled at boot time, /selinux/disable can be used 2225 later to disable prior to initial policy load. 2226 2227 serialnumber [BUGS=X86-32] 2228 2229 shapers= [NET] 2230 Maximal number of shapers. 2231 2232 show_msr= [x86] show boot-time MSR settings 2233 Format: { <integer> } 2234 Show boot-time (BIOS-initialized) MSR settings. 2235 The parameter means the number of CPUs to show, 2236 for example 1 means boot CPU only. 2237 2238 sim710= [SCSI,HW] 2239 See header of drivers/scsi/sim710.c. 2240 2241 simeth= [IA-64] 2242 simscsi= 2243 2244 slram= [HW,MTD] 2245 2246 slub_debug[=options[,slabs]] [MM, SLUB] 2247 Enabling slub_debug allows one to determine the 2248 culprit if slab objects become corrupted. Enabling 2249 slub_debug can create guard zones around objects and 2250 may poison objects when not in use. Also tracks the 2251 last alloc / free. For more information see 2252 Documentation/vm/slub.txt. 2253 2254 slub_max_order= [MM, SLUB] 2255 Determines the maximum allowed order for slabs. 2256 A high setting may cause OOMs due to memory 2257 fragmentation. For more information see 2258 Documentation/vm/slub.txt. 2259 2260 slub_min_objects= [MM, SLUB] 2261 The minimum number of objects per slab. SLUB will 2262 increase the slab order up to slub_max_order to 2263 generate a sufficiently large slab able to contain 2264 the number of objects indicated. The higher the number 2265 of objects the smaller the overhead of tracking slabs 2266 and the less frequently locks need to be acquired. 2267 For more information see Documentation/vm/slub.txt. 2268 2269 slub_min_order= [MM, SLUB] 2270 Determines the mininum page order for slabs. Must be 2271 lower than slub_max_order. 2272 For more information see Documentation/vm/slub.txt. 2273 2274 slub_nomerge [MM, SLUB] 2275 Disable merging of slabs with similar size. May be 2276 necessary if there is some reason to distinguish 2277 allocs to different slabs. Debug options disable 2278 merging on their own. 2279 For more information see Documentation/vm/slub.txt. 2280 2281 smart2= [HW] 2282 Format: <io1>[,<io2>[,...,<io8>]] 2283 2284 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2285 attempt to substitute SMP alternatives once at boot. 2286 2287 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2288 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2289 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2290 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2291 smsc-ircc2.ircc_irq= [HW] IRQ line 2292 smsc-ircc2.ircc_dma= [HW] DMA channel 2293 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2294 0: Toshiba Satellite 1800 (GP data pin select) 2295 1: Fast pin select (default) 2296 2: ATC IRMode 2297 2298 snd-ad1816a= [HW,ALSA] 2299 2300 snd-ad1848= [HW,ALSA] 2301 2302 snd-ali5451= [HW,ALSA] 2303 2304 snd-als100= [HW,ALSA] 2305 2306 snd-als4000= [HW,ALSA] 2307 2308 snd-azt2320= [HW,ALSA] 2309 2310 snd-cmi8330= [HW,ALSA] 2311 2312 snd-cmipci= [HW,ALSA] 2313 2314 snd-cs4231= [HW,ALSA] 2315 2316 snd-cs4232= [HW,ALSA] 2317 2318 snd-cs4236= [HW,ALSA] 2319 2320 snd-cs4281= [HW,ALSA] 2321 2322 snd-cs46xx= [HW,ALSA] 2323 2324 snd-dt019x= [HW,ALSA] 2325 2326 snd-dummy= [HW,ALSA] 2327 2328 snd-emu10k1= [HW,ALSA] 2329 2330 snd-ens1370= [HW,ALSA] 2331 2332 snd-ens1371= [HW,ALSA] 2333 2334 snd-es968= [HW,ALSA] 2335 2336 snd-es1688= [HW,ALSA] 2337 2338 snd-es18xx= [HW,ALSA] 2339 2340 snd-es1938= [HW,ALSA] 2341 2342 snd-es1968= [HW,ALSA] 2343 2344 snd-fm801= [HW,ALSA] 2345 2346 snd-gusclassic= [HW,ALSA] 2347 2348 snd-gusextreme= [HW,ALSA] 2349 2350 snd-gusmax= [HW,ALSA] 2351 2352 snd-hdsp= [HW,ALSA] 2353 2354 snd-ice1712= [HW,ALSA] 2355 2356 snd-intel8x0= [HW,ALSA] 2357 2358 snd-interwave= [HW,ALSA] 2359 2360 snd-interwave-stb= 2361 [HW,ALSA] 2362 2363 snd-korg1212= [HW,ALSA] 2364 2365 snd-maestro3= [HW,ALSA] 2366 2367 snd-mpu401= [HW,ALSA] 2368 2369 snd-mtpav= [HW,ALSA] 2370 2371 snd-nm256= [HW,ALSA] 2372 2373 snd-opl3sa2= [HW,ALSA] 2374 2375 snd-opti92x-ad1848= 2376 [HW,ALSA] 2377 2378 snd-opti92x-cs4231= 2379 [HW,ALSA] 2380 2381 snd-opti93x= [HW,ALSA] 2382 2383 snd-pmac= [HW,ALSA] 2384 2385 snd-rme32= [HW,ALSA] 2386 2387 snd-rme96= [HW,ALSA] 2388 2389 snd-rme9652= [HW,ALSA] 2390 2391 snd-sb8= [HW,ALSA] 2392 2393 snd-sb16= [HW,ALSA] 2394 2395 snd-sbawe= [HW,ALSA] 2396 2397 snd-serial= [HW,ALSA] 2398 2399 snd-sgalaxy= [HW,ALSA] 2400 2401 snd-sonicvibes= [HW,ALSA] 2402 2403 snd-sun-amd7930= 2404 [HW,ALSA] 2405 2406 snd-sun-cs4231= [HW,ALSA] 2407 2408 snd-trident= [HW,ALSA] 2409 2410 snd-usb-audio= [HW,ALSA,USB] 2411 2412 snd-via82xx= [HW,ALSA] 2413 2414 snd-virmidi= [HW,ALSA] 2415 2416 snd-wavefront= [HW,ALSA] 2417 2418 snd-ymfpci= [HW,ALSA] 2419 2420 softlockup_panic= 2421 [KNL] Should the soft-lockup detector generate panics. 2422 2423 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2424 See Documentation/sonypi.txt 2425 2426 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2427 See Documentation/serial/specialix.txt. 2428 2429 spia_io_base= [HW,MTD] 2430 spia_fio_base= 2431 spia_pedr= 2432 spia_peddr= 2433 2434 sscape= [HW,OSS] 2435 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2436 2437 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2438 See Documentation/scsi/st.txt. 2439 2440 stacktrace [FTRACE] 2441 Enabled the stack tracer on boot up. 2442 2443 sti= [PARISC,HW] 2444 Format: <num> 2445 Set the STI (builtin display/keyboard on the HP-PARISC 2446 machines) console (graphic card) which should be used 2447 as the initial boot-console. 2448 See also comment in drivers/video/console/sticore.c. 2449 2450 sti_font= [HW] 2451 See comment in drivers/video/console/sticore.c. 2452 2453 stifb= [HW] 2454 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2455 2456 sunrpc.min_resvport= 2457 sunrpc.max_resvport= 2458 [NFS,SUNRPC] 2459 SunRPC servers often require that client requests 2460 originate from a privileged port (i.e. a port in the 2461 range 0 < portnr < 1024). 2462 An administrator who wishes to reserve some of these 2463 ports for other uses may adjust the range that the 2464 kernel's sunrpc client considers to be privileged 2465 using these two parameters to set the minimum and 2466 maximum port values. 2467 2468 sunrpc.pool_mode= 2469 [NFS] 2470 Control how the NFS server code allocates CPUs to 2471 service thread pools. Depending on how many NICs 2472 you have and where their interrupts are bound, this 2473 option will affect which CPUs will do NFS serving. 2474 Note: this parameter cannot be changed while the 2475 NFS server is running. 2476 2477 auto the server chooses an appropriate mode 2478 automatically using heuristics 2479 global a single global pool contains all CPUs 2480 percpu one pool for each CPU 2481 pernode one pool for each NUMA node (equivalent 2482 to global on non-NUMA machines) 2483 2484 sunrpc.tcp_slot_table_entries= 2485 sunrpc.udp_slot_table_entries= 2486 [NFS,SUNRPC] 2487 Sets the upper limit on the number of simultaneous 2488 RPC calls that can be sent from the client to a 2489 server. Increasing these values may allow you to 2490 improve throughput, but will also increase the 2491 amount of memory reserved for use by the client. 2492 2493 swiotlb= [IA-64] Number of I/O TLB slabs 2494 2495 switches= [HW,M68k] 2496 2497 sym53c416= [HW,SCSI] 2498 See header of drivers/scsi/sym53c416.c. 2499 2500 sysrq_always_enabled 2501 [KNL] 2502 Ignore sysrq setting - this boot parameter will 2503 neutralize any effect of /proc/sys/kernel/sysrq. 2504 Useful for debugging. 2505 2506 t128= [HW,SCSI] 2507 See header of drivers/scsi/t128.c. 2508 2509 tdfx= [HW,DRM] 2510 2511 test_suspend= [SUSPEND] 2512 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2513 standby suspend) as the system sleep state to briefly 2514 enter during system startup. The system is woken from 2515 this state using a wakeup-capable RTC alarm. 2516 2517 thash_entries= [KNL,NET] 2518 Set number of hash buckets for TCP connection 2519 2520 thermal.act= [HW,ACPI] 2521 -1: disable all active trip points in all thermal zones 2522 <degrees C>: override all lowest active trip points 2523 2524 thermal.crt= [HW,ACPI] 2525 -1: disable all critical trip points in all thermal zones 2526 <degrees C>: override all critical trip points 2527 2528 thermal.nocrt= [HW,ACPI] 2529 Set to disable actions on ACPI thermal zone 2530 critical and hot trip points. 2531 2532 thermal.off= [HW,ACPI] 2533 1: disable ACPI thermal control 2534 2535 thermal.psv= [HW,ACPI] 2536 -1: disable all passive trip points 2537 <degrees C>: override all passive trip points to this 2538 value 2539 2540 thermal.tzp= [HW,ACPI] 2541 Specify global default ACPI thermal zone polling rate 2542 <deci-seconds>: poll all this frequency 2543 0: no polling (default) 2544 2545 tmscsim= [HW,SCSI] 2546 See comment before function dc390_setup() in 2547 drivers/scsi/tmscsim.c. 2548 2549 topology= [S390] 2550 Format: {off | on} 2551 Specify if the kernel should make use of the cpu 2552 topology informations if the hardware supports these. 2553 The scheduler will make use of these informations and 2554 e.g. base its process migration decisions on it. 2555 Default is off. 2556 2557 tp720= [HW,PS2] 2558 2559 trace_buf_size=nn[KMG] 2560 [FTRACE] will set tracing buffer size. 2561 2562 trace_event=[event-list] 2563 [FTRACE] Set and start specified trace events in order 2564 to facilitate early boot debugging. 2565 See also Documentation/trace/events.txt 2566 2567 trix= [HW,OSS] MediaTrix AudioTrix Pro 2568 Format: 2569 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2570 2571 tsc= Disable clocksource-must-verify flag for TSC. 2572 Format: <string> 2573 [x86] reliable: mark tsc clocksource as reliable, this 2574 disables clocksource verification at runtime. 2575 Used to enable high-resolution timer mode on older 2576 hardware, and in virtualized environment. 2577 2578 turbografx.map[2|3]= [HW,JOY] 2579 TurboGraFX parallel port interface 2580 Format: 2581 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2582 See also Documentation/input/joystick-parport.txt 2583 2584 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2585 See header of drivers/scsi/u14-34f.c. 2586 2587 uart401= [HW,OSS] 2588 Format: <io>,<irq> 2589 2590 uart6850= [HW,OSS] 2591 Format: <io>,<irq> 2592 2593 uhci-hcd.ignore_oc= 2594 [USB] Ignore overcurrent events (default N). 2595 Some badly-designed motherboards generate lots of 2596 bogus events, for ports that aren't wired to 2597 anything. Set this parameter to avoid log spamming. 2598 Note that genuine overcurrent events won't be 2599 reported either. 2600 2601 unknown_nmi_panic 2602 [X86] 2603 Set unknown_nmi_panic=1 early on boot. 2604 2605 usbcore.autosuspend= 2606 [USB] The autosuspend time delay (in seconds) used 2607 for newly-detected USB devices (default 2). This 2608 is the time required before an idle device will be 2609 autosuspended. Devices for which the delay is set 2610 to a negative value won't be autosuspended at all. 2611 2612 usbcore.usbfs_snoop= 2613 [USB] Set to log all usbfs traffic (default 0 = off). 2614 2615 usbcore.blinkenlights= 2616 [USB] Set to cycle leds on hubs (default 0 = off). 2617 2618 usbcore.old_scheme_first= 2619 [USB] Start with the old device initialization 2620 scheme (default 0 = off). 2621 2622 usbcore.use_both_schemes= 2623 [USB] Try the other device initialization scheme 2624 if the first one fails (default 1 = enabled). 2625 2626 usbcore.initial_descriptor_timeout= 2627 [USB] Specifies timeout for the initial 64-byte 2628 USB_REQ_GET_DESCRIPTOR request in milliseconds 2629 (default 5000 = 5.0 seconds). 2630 2631 usbhid.mousepoll= 2632 [USBHID] The interval which mice are to be polled at. 2633 2634 usb-storage.delay_use= 2635 [UMS] The delay in seconds before a new device is 2636 scanned for Logical Units (default 5). 2637 2638 usb-storage.quirks= 2639 [UMS] A list of quirks entries to supplement or 2640 override the built-in unusual_devs list. List 2641 entries are separated by commas. Each entry has 2642 the form VID:PID:Flags where VID and PID are Vendor 2643 and Product ID values (4-digit hex numbers) and 2644 Flags is a set of characters, each corresponding 2645 to a common usb-storage quirk flag as follows: 2646 a = SANE_SENSE (collect more than 18 bytes 2647 of sense data); 2648 c = FIX_CAPACITY (decrease the reported 2649 device capacity by one sector); 2650 h = CAPACITY_HEURISTICS (decrease the 2651 reported device capacity by one 2652 sector if the number is odd); 2653 i = IGNORE_DEVICE (don't bind to this 2654 device); 2655 l = NOT_LOCKABLE (don't try to lock and 2656 unlock ejectable media); 2657 m = MAX_SECTORS_64 (don't transfer more 2658 than 64 sectors = 32 KB at a time); 2659 o = CAPACITY_OK (accept the capacity 2660 reported by the device); 2661 r = IGNORE_RESIDUE (the device reports 2662 bogus residue values); 2663 s = SINGLE_LUN (the device has only one 2664 Logical Unit); 2665 w = NO_WP_DETECT (don't test whether the 2666 medium is write-protected). 2667 Example: quirks=0419:aaf5:rl,0421:0433:rc 2668 2669 vdso= [X86,SH] 2670 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2671 vdso=1: enable VDSO (default) 2672 vdso=0: disable VDSO mapping 2673 2674 vdso32= [X86] 2675 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2676 vdso32=1: enable 32-bit VDSO (default) 2677 vdso32=0: disable 32-bit VDSO mapping 2678 2679 vector= [IA-64,SMP] 2680 vector=percpu: enable percpu vector domain 2681 2682 video= [FB] Frame buffer configuration 2683 See Documentation/fb/modedb.txt. 2684 2685 vga= [BOOT,X86-32] Select a particular video mode 2686 See Documentation/x86/boot.txt and 2687 Documentation/svga.txt. 2688 Use vga=ask for menu. 2689 This is actually a boot loader parameter; the value is 2690 passed to the kernel using a special protocol. 2691 2692 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2693 size of <nn>. This can be used to increase the 2694 minimum size (128MB on x86). It can also be used to 2695 decrease the size and leave more room for directly 2696 mapped kernel RAM. 2697 2698 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2699 Format: <command> 2700 2701 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2702 Format: <command> 2703 2704 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2705 Format: <command> 2706 2707 vt.default_blu= [VT] 2708 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 2709 Change the default blue palette of the console. 2710 This is a 16-member array composed of values 2711 ranging from 0-255. 2712 2713 vt.default_grn= [VT] 2714 Format: <green0>,<green1>,<green2>,...,<green15> 2715 Change the default green palette of the console. 2716 This is a 16-member array composed of values 2717 ranging from 0-255. 2718 2719 vt.default_red= [VT] 2720 Format: <red0>,<red1>,<red2>,...,<red15> 2721 Change the default red palette of the console. 2722 This is a 16-member array composed of values 2723 ranging from 0-255. 2724 2725 vt.default_utf8= 2726 [VT] 2727 Format=<0|1> 2728 Set system-wide default UTF-8 mode for all tty's. 2729 Default is 1, i.e. UTF-8 mode is enabled for all 2730 newly opened terminals. 2731 2732 waveartist= [HW,OSS] 2733 Format: <io>,<irq>,<dma>,<dma2> 2734 2735 wd33c93= [HW,SCSI] 2736 See header of drivers/scsi/wd33c93.c. 2737 2738 wd7000= [HW,SCSI] 2739 See header of drivers/scsi/wd7000.c. 2740 2741 wdt= [WDT] Watchdog 2742 See Documentation/watchdog/wdt.txt. 2743 2744 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 2745 default x2apic cluster mode on platforms 2746 supporting x2apic. 2747 2748 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2749 xd_geo= See header of drivers/block/xd.c. 2750 2751 xirc2ps_cs= [NET,PCMCIA] 2752 Format: 2753 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2754 2755______________________________________________________________________ 2756 2757TODO: 2758 2759 Add documentation for ALSA options. 2760 Add more DRM drivers. 2761