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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 DYNAMIC_DEBUG Build in debug messages and enable them at runtime 48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 49 EFI EFI Partitioning (GPT) is enabled 50 EIDE EIDE/ATAPI support is enabled. 51 FB The frame buffer device is enabled. 52 GCOV GCOV profiling is enabled. 53 HW Appropriate hardware is enabled. 54 IA-64 IA-64 architecture is enabled. 55 IMA Integrity measurement architecture is enabled. 56 IOSCHED More than one I/O scheduler is enabled. 57 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 58 IPV6 IPv6 support is enabled. 59 ISAPNP ISA PnP code is enabled. 60 ISDN Appropriate ISDN support is enabled. 61 JOY Appropriate joystick support is enabled. 62 KGDB Kernel debugger support is enabled. 63 KVM Kernel Virtual Machine support is enabled. 64 LIBATA Libata driver is enabled 65 LP Printer support is enabled. 66 LOOP Loopback device support is enabled. 67 M68k M68k architecture is enabled. 68 These options have more detailed description inside of 69 Documentation/m68k/kernel-options.txt. 70 MCA MCA bus support is enabled. 71 MDA MDA console support is enabled. 72 MOUSE Appropriate mouse support is enabled. 73 MSI Message Signaled Interrupts (PCI). 74 MTD MTD (Memory Technology Device) support is enabled. 75 NET Appropriate network support is enabled. 76 NUMA NUMA support is enabled. 77 NFS Appropriate NFS support is enabled. 78 OSS OSS sound support is enabled. 79 PV_OPS A paravirtualized kernel is enabled. 80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 81 PARISC The PA-RISC architecture is enabled. 82 PCI PCI bus support is enabled. 83 PCIE PCI Express support is enabled. 84 PCMCIA The PCMCIA subsystem is enabled. 85 PNP Plug & Play support is enabled. 86 PPC PowerPC architecture is enabled. 87 PPT Parallel port support is enabled. 88 PS2 Appropriate PS/2 support is enabled. 89 RAM RAM disk support is enabled. 90 S390 S390 architecture is enabled. 91 SCSI Appropriate SCSI support is enabled. 92 A lot of drivers have their options described inside 93 the Documentation/scsi/ sub-directory. 94 SECURITY Different security models are enabled. 95 SELINUX SELinux support is enabled. 96 APPARMOR AppArmor support is enabled. 97 SERIAL Serial support is enabled. 98 SH SuperH architecture is enabled. 99 SMP The kernel is an SMP kernel. 100 SPARC Sparc architecture is enabled. 101 SWSUSP Software suspend (hibernation) is enabled. 102 SUSPEND System suspend states are enabled. 103 FTRACE Function tracing enabled. 104 TPM TPM drivers are enabled. 105 TS Appropriate touchscreen support is enabled. 106 UMS USB Mass Storage support is enabled. 107 USB USB support is enabled. 108 USBHID USB Human Interface Device support is enabled. 109 V4L Video For Linux support is enabled. 110 VGA The VGA console has been enabled. 111 VT Virtual terminal support is enabled. 112 WDT Watchdog support is enabled. 113 XT IBM PC/XT MFM hard disk support is enabled. 114 X86-32 X86-32, aka i386 architecture is enabled. 115 X86-64 X86-64 architecture is enabled. 116 More X86-64 boot options can be found in 117 Documentation/x86/x86_64/boot-options.txt . 118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 119 XEN Xen support is enabled 120 121In addition, the following text indicates that the option: 122 123 BUGS= Relates to possible processor bugs on the said processor. 124 KNL Is a kernel start-up parameter. 125 BOOT Is a boot loader parameter. 126 127Parameters denoted with BOOT are actually interpreted by the boot 128loader, and have no meaning to the kernel directly. 129Do not modify the syntax of boot loader parameters without extreme 130need or coordination with <Documentation/x86/boot.txt>. 131 132There are also arch-specific kernel-parameters not documented here. 133See for example <Documentation/x86/x86_64/boot-options.txt>. 134 135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 136a trailing = on the name of any parameter states that that parameter will 137be entered as an environment variable, whereas its absence indicates that 138it will appear as a kernel argument readable via /proc/cmdline by programs 139running once the system is up. 140 141The number of kernel parameters is not limited, but the length of the 142complete command line (parameters including spaces etc.) is limited to 143a fixed number of characters. This limit depends on the architecture 144and is between 256 and 4096 characters. It is defined in the file 145./include/asm/setup.h as COMMAND_LINE_SIZE. 146 147Finally, the [KMG] suffix is commonly described after a number of kernel 148parameter values. These 'K', 'M', and 'G' letters represent the _binary_ 149multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30 150bytes respectively. Such letter suffixes can also be entirely omitted. 151 152 153 acpi= [HW,ACPI,X86] 154 Advanced Configuration and Power Interface 155 Format: { force | off | strict | noirq | rsdt } 156 force -- enable ACPI if default was off 157 off -- disable ACPI if default was on 158 noirq -- do not use ACPI for IRQ routing 159 strict -- Be less tolerant of platforms that are not 160 strictly ACPI specification compliant. 161 rsdt -- prefer RSDT over (default) XSDT 162 copy_dsdt -- copy DSDT to memory 163 164 See also Documentation/power/pm.txt, pci=noacpi 165 166 acpi_apic_instance= [ACPI, IOAPIC] 167 Format: <int> 168 2: use 2nd APIC table, if available 169 1,0: use 1st APIC table 170 default: 0 171 172 acpi_backlight= [HW,ACPI] 173 acpi_backlight=vendor 174 acpi_backlight=video 175 If set to vendor, prefer vendor specific driver 176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead 177 of the ACPI video.ko driver. 178 179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 181 Format: <int> 182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 183 debug output. Bits in debug_layer correspond to a 184 _COMPONENT in an ACPI source file, e.g., 185 #define _COMPONENT ACPI_PCI_COMPONENT 186 Bits in debug_level correspond to a level in 187 ACPI_DEBUG_PRINT statements, e.g., 188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 189 The debug_level mask defaults to "info". See 190 Documentation/acpi/debug.txt for more information about 191 debug layers and levels. 192 193 Enable processor driver info messages: 194 acpi.debug_layer=0x20000000 195 Enable PCI/PCI interrupt routing info messages: 196 acpi.debug_layer=0x400000 197 Enable AML "Debug" output, i.e., stores to the Debug 198 object while interpreting AML: 199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2 200 Enable all messages related to ACPI hardware: 201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 202 203 Some values produce so much output that the system is 204 unusable. The "log_buf_len" parameter may be useful 205 if you need to capture more output. 206 207 acpi_irq_balance [HW,ACPI] 208 ACPI will balance active IRQs 209 default in APIC mode 210 211 acpi_irq_nobalance [HW,ACPI] 212 ACPI will not move active IRQs (default) 213 default in PIC mode 214 215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 216 Format: <irq>,<irq>... 217 218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 219 use by PCI 220 Format: <irq>,<irq>... 221 222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 223 224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 225 Format: To spoof as Windows 98: ="Microsoft Windows" 226 227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 228 acpi_osi="string1" # add string1 -- only one string 229 acpi_osi="!string2" # remove built-in string2 230 acpi_osi= # disable all strings 231 232 acpi_pm_good [X86] 233 Override the pmtimer bug detection: force the kernel 234 to assume that this machine's pmtimer latches its value 235 and always returns good values. 236 237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 238 Format: { level | edge | high | low } 239 240 acpi_serialize [HW,ACPI] force serialization of AML methods 241 242 acpi_skip_timer_override [HW,ACPI] 243 Recognize and ignore IRQ0/pin2 Interrupt Override. 244 For broken nForce2 BIOS resulting in XT-PIC timer. 245 246 acpi_sleep= [HW,ACPI] Sleep options 247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 248 old_ordering, s4_nonvs, sci_force_enable } 249 See Documentation/power/video.txt for information on 250 s3_bios and s3_mode. 251 s3_beep is for debugging; it makes the PC's speaker beep 252 as soon as the kernel's real-mode entry point is called. 253 s4_nohwsig prevents ACPI hardware signature from being 254 used during resume from hibernation. 255 old_ordering causes the ACPI 1.0 ordering of the _PTS 256 control method, with respect to putting devices into 257 low power states, to be enforced (the ACPI 2.0 ordering 258 of _PTS is used by default). 259 nonvs prevents the kernel from saving/restoring the 260 ACPI NVS memory during suspend/hibernation and resume. 261 sci_force_enable causes the kernel to set SCI_EN directly 262 on resume from S1/S3 (which is against the ACPI spec, 263 but some broken systems don't work without it). 264 265 acpi_use_timer_override [HW,ACPI] 266 Use timer override. For some broken Nvidia NF5 boards 267 that require a timer override, but don't have HPET 268 269 acpi_enforce_resources= [ACPI] 270 { strict | lax | no } 271 Check for resource conflicts between native drivers 272 and ACPI OperationRegions (SystemIO and SystemMemory 273 only). IO ports and memory declared in ACPI might be 274 used by the ACPI subsystem in arbitrary AML code and 275 can interfere with legacy drivers. 276 strict (default): access to resources claimed by ACPI 277 is denied; legacy drivers trying to access reserved 278 resources will fail to bind to device using them. 279 lax: access to resources claimed by ACPI is allowed; 280 legacy drivers trying to access reserved resources 281 will bind successfully but a warning message is logged. 282 no: ACPI OperationRegions are not marked as reserved, 283 no further checks are performed. 284 285 add_efi_memmap [EFI; X86] Include EFI memory map in 286 kernel's map of available physical RAM. 287 288 agp= [AGP] 289 { off | try_unsupported } 290 off: disable AGP support 291 try_unsupported: try to drive unsupported chipsets 292 (may crash computer or cause data corruption) 293 294 ALSA [HW,ALSA] 295 See Documentation/sound/alsa/alsa-parameters.txt 296 297 alignment= [KNL,ARM] 298 Allow the default userspace alignment fault handler 299 behaviour to be specified. Bit 0 enables warnings, 300 bit 1 enables fixups, and bit 2 sends a segfault. 301 302 amd_iommu= [HW,X86-84] 303 Pass parameters to the AMD IOMMU driver in the system. 304 Possible values are: 305 fullflush - enable flushing of IO/TLB entries when 306 they are unmapped. Otherwise they are 307 flushed before they will be reused, which 308 is a lot of faster 309 off - do not initialize any AMD IOMMU found in 310 the system 311 312 amijoy.map= [HW,JOY] Amiga joystick support 313 Map of devices attached to JOY0DAT and JOY1DAT 314 Format: <a>,<b> 315 See also Documentation/kernel/input/joystick.txt 316 317 analog.map= [HW,JOY] Analog joystick and gamepad support 318 Specifies type or capabilities of an analog joystick 319 connected to one of 16 gameports 320 Format: <type1>,<type2>,..<type16> 321 322 apc= [HW,SPARC] 323 Power management functions (SPARCstation-4/5 + deriv.) 324 Format: noidle 325 Disable APC CPU standby support. SPARCstation-Fox does 326 not play well with APC CPU idle - disable it if you have 327 APC and your system crashes randomly. 328 329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 330 Change the output verbosity whilst booting 331 Format: { quiet (default) | verbose | debug } 332 Change the amount of debugging information output 333 when initialising the APIC and IO-APIC components. 334 335 autoconf= [IPV6] 336 See Documentation/networking/ipv6.txt. 337 338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 339 Limit apic dumping. The parameter defines the maximal 340 number of local apics being dumped. Also it is possible 341 to set it to "all" by meaning -- no limit here. 342 Format: { 1 (default) | 2 | ... | all }. 343 The parameter valid if only apic=debug or 344 apic=verbose is specified. 345 Example: apic=debug show_lapic=all 346 347 apm= [APM] Advanced Power Management 348 See header of arch/x86/kernel/apm_32.c. 349 350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 351 Format: <io>,<irq>,<nodeID> 352 353 ataflop= [HW,M68k] 354 355 atarimouse= [HW,MOUSE] Atari Mouse 356 357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 358 EzKey and similar keyboards 359 360 atkbd.reset= [HW] Reset keyboard during initialization 361 362 atkbd.set= [HW] Select keyboard code set 363 Format: <int> (2 = AT (default), 3 = PS/2) 364 365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 366 keyboards 367 368 atkbd.softraw= [HW] Choose between synthetic and real raw mode 369 Format: <bool> (0 = real, 1 = synthetic (default)) 370 371 atkbd.softrepeat= [HW] 372 Use software keyboard repeat 373 374 autotest [IA64] 375 376 baycom_epp= [HW,AX25] 377 Format: <io>,<mode> 378 379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 380 Format: <io>,<mode> 381 See header of drivers/net/hamradio/baycom_par.c. 382 383 baycom_ser_fdx= [HW,AX25] 384 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 385 Format: <io>,<irq>,<mode>[,<baud>] 386 See header of drivers/net/hamradio/baycom_ser_fdx.c. 387 388 baycom_ser_hdx= [HW,AX25] 389 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 390 Format: <io>,<irq>,<mode> 391 See header of drivers/net/hamradio/baycom_ser_hdx.c. 392 393 boot_delay= Milliseconds to delay each printk during boot. 394 Values larger than 10 seconds (10000) are changed to 395 no delay (0). 396 Format: integer 397 398 bootmem_debug [KNL] Enable bootmem allocator debug messages. 399 400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 401 bttv.radio= Most important insmod options are available as 402 kernel args too. 403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 405 406 bulk_remove=off [PPC] This parameter disables the use of the pSeries 407 firmware feature for flushing multiple hpte entries 408 at a time. 409 410 c101= [NET] Moxa C101 synchronous serial card 411 412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 413 Sometimes CPU hardware bugs make them report the cache 414 size incorrectly. The kernel will attempt work arounds 415 to fix known problems, but for some CPUs it is not 416 possible to determine what the correct size should be. 417 This option provides an override for these situations. 418 419 capability.disable= 420 [SECURITY] Disable capabilities. This would normally 421 be used only if an alternative security model is to be 422 configured. Potentially dangerous and should only be 423 used if you are entirely sure of the consequences. 424 425 ccw_timeout_log [S390] 426 See Documentation/s390/CommonIO for details. 427 428 cgroup_disable= [KNL] Disable a particular controller 429 Format: {name of the controller(s) to disable} 430 {Currently supported controllers - "memory"} 431 432 checkreqprot [SELINUX] Set initial checkreqprot flag value. 433 Format: { "0" | "1" } 434 See security/selinux/Kconfig help text. 435 0 -- check protection applied by kernel (includes 436 any implied execute protection). 437 1 -- check protection requested by application. 438 Default value is set via a kernel config option. 439 Value can be changed at runtime via 440 /selinux/checkreqprot. 441 442 cio_ignore= [S390] 443 See Documentation/s390/CommonIO for details. 444 445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 446 [Deprecated] 447 Forces specified clocksource (if available) to be used 448 when calculating gettimeofday(). If specified 449 clocksource is not available, it defaults to PIT. 450 Format: { pit | tsc | cyclone | pmtmr } 451 452 clocksource= Override the default clocksource 453 Format: <string> 454 Override the default clocksource and use the clocksource 455 with the name specified. 456 Some clocksource names to choose from, depending on 457 the platform: 458 [all] jiffies (this is the base, fallback clocksource) 459 [ACPI] acpi_pm 460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 461 pxa_timer,timer3,32k_counter,timer0_1 462 [AVR32] avr32 463 [X86-32] pit,hpet,tsc; 464 scx200_hrt on Geode; cyclone on IBM x440 465 [MIPS] MIPS 466 [PARISC] cr16 467 [S390] tod 468 [SH] SuperH 469 [SPARC64] tick 470 [X86-64] hpet,tsc 471 472 clearcpuid=BITNUM [X86] 473 Disable CPUID feature X for the kernel. See 474 arch/x86/include/asm/cpufeature.h for the valid bit 475 numbers. Note the Linux specific bits are not necessarily 476 stable over kernel options, but the vendor specific 477 ones should be. 478 Also note that user programs calling CPUID directly 479 or using the feature without checking anything 480 will still see it. This just prevents it from 481 being used by the kernel or shown in /proc/cpuinfo. 482 Also note the kernel might malfunction if you disable 483 some critical bits. 484 485 cmo_free_hint= [PPC] Format: { yes | no } 486 Specify whether pages are marked as being inactive 487 when they are freed. This is used in CMO environments 488 to determine OS memory pressure for page stealing by 489 a hypervisor. 490 Default: yes 491 492 code_bytes [X86] How many bytes of object code to print 493 in an oops report. 494 Range: 0 - 8192 495 Default: 64 496 497 com20020= [HW,NET] ARCnet - COM20020 chipset 498 Format: 499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 500 501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 502 Format: <io>[,<irq>] 503 504 com90xx= [HW,NET] 505 ARCnet - COM90xx chipset (memory-mapped buffers) 506 Format: <io>[,<irq>[,<memstart>]] 507 508 condev= [HW,S390] console device 509 conmode= 510 511 console= [KNL] Output console device and options. 512 513 tty<n> Use the virtual console device <n>. 514 515 ttyS<n>[,options] 516 ttyUSB0[,options] 517 Use the specified serial port. The options are of 518 the form "bbbbpnf", where "bbbb" is the baud rate, 519 "p" is parity ("n", "o", or "e"), "n" is number of 520 bits, and "f" is flow control ("r" for RTS or 521 omit it). Default is "9600n8". 522 523 See Documentation/serial-console.txt for more 524 information. See 525 Documentation/networking/netconsole.txt for an 526 alternative. 527 528 uart[8250],io,<addr>[,options] 529 uart[8250],mmio,<addr>[,options] 530 Start an early, polled-mode console on the 8250/16550 531 UART at the specified I/O port or MMIO address, 532 switching to the matching ttyS device later. The 533 options are the same as for ttyS, above. 534 535 If the device connected to the port is not a TTY but a braille 536 device, prepend "brl," before the device type, for instance 537 console=brl,ttyS0 538 For now, only VisioBraille is supported. 539 540 consoleblank= [KNL] The console blank (screen saver) timeout in 541 seconds. Defaults to 10*60 = 10mins. A value of 0 542 disables the blank timer. 543 544 coredump_filter= 545 [KNL] Change the default value for 546 /proc/<pid>/coredump_filter. 547 See also Documentation/filesystems/proc.txt. 548 549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 550 Format: 551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 552 553 crashkernel=size[KMG][@offset[KMG]] 554 [KNL] Using kexec, Linux can switch to a 'crash kernel' 555 upon panic. This parameter reserves the physical 556 memory region [offset, offset + size] for that kernel 557 image. If '@offset' is omitted, then a suitable offset 558 is selected automatically. Check 559 Documentation/kdump/kdump.txt for further details. 560 561 crashkernel=range1:size1[,range2:size2,...][@offset] 562 [KNL] Same as above, but depends on the memory 563 in the running system. The syntax of range is 564 start-[end] where start and end are both 565 a memory unit (amount[KMG]). See also 566 Documentation/kdump/kdump.txt for an example. 567 568 cs89x0_dma= [HW,NET] 569 Format: <dma> 570 571 cs89x0_media= [HW,NET] 572 Format: { rj45 | aui | bnc } 573 574 dasd= [HW,NET] 575 See header of drivers/s390/block/dasd_devmap.c. 576 577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 578 (one device per port) 579 Format: <port#>,<type> 580 See also Documentation/input/joystick-parport.txt 581 582 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot 583 time. See Documentation/dynamic-debug-howto.txt for 584 details. 585 586 debug [KNL] Enable kernel debugging (events log level). 587 588 debug_locks_verbose= 589 [KNL] verbose self-tests 590 Format=<0|1> 591 Print debugging info while doing the locking API 592 self-tests. 593 We default to 0 (no extra messages), setting it to 594 1 will print _a lot_ more information - normally 595 only useful to kernel developers. 596 597 debug_objects [KNL] Enable object debugging 598 599 no_debug_objects 600 [KNL] Disable object debugging 601 602 debugpat [X86] Enable PAT debugging 603 604 decnet.addr= [HW,NET] 605 Format: <area>[,<node>] 606 See also Documentation/networking/decnet.txt. 607 608 default_hugepagesz= 609 [same as hugepagesz=] The size of the default 610 HugeTLB page size. This is the size represented by 611 the legacy /proc/ hugepages APIs, used for SHM, and 612 default size when mounting hugetlbfs filesystems. 613 Defaults to the default architecture's huge page size 614 if not specified. 615 616 dhash_entries= [KNL] 617 Set number of hash buckets for dentry cache. 618 619 digi= [HW,SERIAL] 620 IO parameters + enable/disable command. 621 622 digiepca= [HW,SERIAL] 623 See drivers/char/README.epca and 624 Documentation/serial/digiepca.txt. 625 626 disable= [IPV6] 627 See Documentation/networking/ipv6.txt. 628 629 disable_ddw [PPC/PSERIES] 630 Disable Dynamic DMA Window support. Use this if 631 to workaround buggy firmware. 632 633 disable_ipv6= [IPV6] 634 See Documentation/networking/ipv6.txt. 635 636 disable_mtrr_cleanup [X86] 637 The kernel tries to adjust MTRR layout from continuous 638 to discrete, to make X server driver able to add WB 639 entry later. This parameter disables that. 640 641 disable_mtrr_trim [X86, Intel and AMD only] 642 By default the kernel will trim any uncacheable 643 memory out of your available memory pool based on 644 MTRR settings. This parameter disables that behavior, 645 possibly causing your machine to run very slowly. 646 647 disable_timer_pin_1 [X86] 648 Disable PIN 1 of APIC timer 649 Can be useful to work around chipset bugs. 650 651 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 652 this option disables the debugging code at boot. 653 654 dma_debug_entries=<number> 655 This option allows to tune the number of preallocated 656 entries for DMA-API debugging code. One entry is 657 required per DMA-API allocation. Use this if the 658 DMA-API debugging code disables itself because the 659 architectural default is too low. 660 661 dma_debug_driver=<driver_name> 662 With this option the DMA-API debugging driver 663 filter feature can be enabled at boot time. Just 664 pass the driver to filter for as the parameter. 665 The filter can be disabled or changed to another 666 driver later using sysfs. 667 668 dscc4.setup= [NET] 669 670 earlycon= [KNL] Output early console device and options. 671 uart[8250],io,<addr>[,options] 672 uart[8250],mmio,<addr>[,options] 673 uart[8250],mmio32,<addr>[,options] 674 Start an early, polled-mode console on the 8250/16550 675 UART at the specified I/O port or MMIO address. 676 MMIO inter-register address stride is either 8bit (mmio) 677 or 32bit (mmio32). 678 The options are the same as for ttyS, above. 679 680 earlyprintk= [X86,SH,BLACKFIN] 681 earlyprintk=vga 682 earlyprintk=serial[,ttySn[,baudrate]] 683 earlyprintk=ttySn[,baudrate] 684 earlyprintk=dbgp[debugController#] 685 686 Append ",keep" to not disable it when the real console 687 takes over. 688 689 Only vga or serial or usb debug port at a time. 690 691 Currently only ttyS0 and ttyS1 are supported. 692 693 Interaction with the standard serial driver is not 694 very good. 695 696 The VGA output is eventually overwritten by the real 697 console. 698 699 ekgdboc= [X86,KGDB] Allow early kernel console debugging 700 ekgdboc=kbd 701 702 This is designed to be used in conjunction with 703 the boot argument: earlyprintk=vga 704 705 edd= [EDD] 706 Format: {"off" | "on" | "skip[mbr]"} 707 708 eisa_irq_edge= [PARISC,HW] 709 See header of drivers/parisc/eisa.c. 710 711 elanfreq= [X86-32] 712 See comment before function elanfreq_setup() in 713 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 714 715 elevator= [IOSCHED] 716 Format: {"cfq" | "deadline" | "noop"} 717 See Documentation/block/as-iosched.txt and 718 Documentation/block/deadline-iosched.txt for details. 719 720 elfcorehdr= [IA64,PPC,SH,X86] 721 Specifies physical address of start of kernel core 722 image elf header. Generally kexec loader will 723 pass this option to capture kernel. 724 See Documentation/kdump/kdump.txt for details. 725 726 enable_mtrr_cleanup [X86] 727 The kernel tries to adjust MTRR layout from continuous 728 to discrete, to make X server driver able to add WB 729 entry later. This parameter enables that. 730 731 enable_timer_pin_1 [X86] 732 Enable PIN 1 of APIC timer 733 Can be useful to work around chipset bugs 734 (in particular on some ATI chipsets). 735 The kernel tries to set a reasonable default. 736 737 enforcing [SELINUX] Set initial enforcing status. 738 Format: {"0" | "1"} 739 See security/selinux/Kconfig help text. 740 0 -- permissive (log only, no denials). 741 1 -- enforcing (deny and log). 742 Default value is 0. 743 Value can be changed at runtime via /selinux/enforce. 744 745 erst_disable [ACPI] 746 Disable Error Record Serialization Table (ERST) 747 support. 748 749 ether= [HW,NET] Ethernet cards parameters 750 This option is obsoleted by the "netdev=" option, which 751 has equivalent usage. See its documentation for details. 752 753 failslab= 754 fail_page_alloc= 755 fail_make_request=[KNL] 756 General fault injection mechanism. 757 Format: <interval>,<probability>,<space>,<times> 758 See also /Documentation/fault-injection/. 759 760 floppy= [HW] 761 See Documentation/blockdev/floppy.txt. 762 763 force_pal_cache_flush 764 [IA-64] Avoid check_sal_cache_flush which may hang on 765 buggy SAL_CACHE_FLUSH implementations. Using this 766 parameter will force ia64_sal_cache_flush to call 767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 768 769 ftrace=[tracer] 770 [FTRACE] will set and start the specified tracer 771 as early as possible in order to facilitate early 772 boot debugging. 773 774 ftrace_dump_on_oops[=orig_cpu] 775 [FTRACE] will dump the trace buffers on oops. 776 If no parameter is passed, ftrace will dump 777 buffers of all CPUs, but if you pass orig_cpu, it will 778 dump only the buffer of the CPU that triggered the 779 oops. 780 781 ftrace_filter=[function-list] 782 [FTRACE] Limit the functions traced by the function 783 tracer at boot up. function-list is a comma separated 784 list of functions. This list can be changed at run 785 time by the set_ftrace_filter file in the debugfs 786 tracing directory. 787 788 ftrace_notrace=[function-list] 789 [FTRACE] Do not trace the functions specified in 790 function-list. This list can be changed at run time 791 by the set_ftrace_notrace file in the debugfs 792 tracing directory. 793 794 ftrace_graph_filter=[function-list] 795 [FTRACE] Limit the top level callers functions traced 796 by the function graph tracer at boot up. 797 function-list is a comma separated list of functions 798 that can be changed at run time by the 799 set_graph_function file in the debugfs tracing directory. 800 801 gamecon.map[2|3]= 802 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 803 support via parallel port (up to 5 devices per port) 804 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 805 See also Documentation/input/joystick-parport.txt 806 807 gamma= [HW,DRM] 808 809 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 810 Format: off | on 811 default: on 812 813 gcov_persist= [GCOV] When non-zero (default), profiling data for 814 kernel modules is saved and remains accessible via 815 debugfs, even when the module is unloaded/reloaded. 816 When zero, profiling data is discarded and associated 817 debugfs files are removed at module unload time. 818 819 gpt [EFI] Forces disk with valid GPT signature but 820 invalid Protective MBR to be treated as GPT. 821 822 hashdist= [KNL,NUMA] Large hashes allocated during boot 823 are distributed across NUMA nodes. Defaults on 824 for 64bit NUMA, off otherwise. 825 Format: 0 | 1 (for off | on) 826 827 hcl= [IA-64] SGI's Hardware Graph compatibility layer 828 829 hd= [EIDE] (E)IDE hard drive subsystem geometry 830 Format: <cyl>,<head>,<sect> 831 832 hest_disable [ACPI] 833 Disable Hardware Error Source Table (HEST) support; 834 corresponding firmware-first mode error processing 835 logic will be disabled. 836 837 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 838 size of <nn>. This works even on boxes that have no 839 highmem otherwise. This also works to reduce highmem 840 size on bigger boxes. 841 842 highres= [KNL] Enable/disable high resolution timer mode. 843 Valid parameters: "on", "off" 844 Default: "on" 845 846 hisax= [HW,ISDN] 847 See Documentation/isdn/README.HiSax. 848 849 hlt [BUGS=ARM,SH] 850 851 hpet= [X86-32,HPET] option to control HPET usage 852 Format: { enable (default) | disable | force | 853 verbose } 854 disable: disable HPET and use PIT instead 855 force: allow force enabled of undocumented chips (ICH4, 856 VIA, nVidia) 857 verbose: show contents of HPET registers during setup 858 859 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 860 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 861 On x86-64 and powerpc, this option can be specified 862 multiple times interleaved with hugepages= to reserve 863 huge pages of different sizes. Valid pages sizes on 864 x86-64 are 2M (when the CPU supports "pse") and 1G 865 (when the CPU supports the "pdpe1gb" cpuinfo flag) 866 Note that 1GB pages can only be allocated at boot time 867 using hugepages= and not freed afterwards. 868 869 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 870 terminal devices. Valid values: 0..8 871 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 872 If specified, z/VM IUCV HVC accepts connections 873 from listed z/VM user IDs only. 874 875 keep_bootcon [KNL] 876 Do not unregister boot console at start. This is only 877 useful for debugging when something happens in the window 878 between unregistering the boot console and initializing 879 the real console. 880 881 i2c_bus= [HW] Override the default board specific I2C bus speed 882 or register an additional I2C bus that is not 883 registered from board initialization code. 884 Format: 885 <bus_id>,<clkrate> 886 887 i8042.debug [HW] Toggle i8042 debug mode 888 i8042.direct [HW] Put keyboard port into non-translated mode 889 i8042.dumbkbd [HW] Pretend that controller can only read data from 890 keyboard and cannot control its state 891 (Don't attempt to blink the leds) 892 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 893 i8042.nokbd [HW] Don't check/create keyboard port 894 i8042.noloop [HW] Disable the AUX Loopback command while probing 895 for the AUX port 896 i8042.nomux [HW] Don't check presence of an active multiplexing 897 controller 898 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 899 controllers 900 i8042.notimeout [HW] Ignore timeout condition signalled by conroller 901 i8042.reset [HW] Reset the controller during init and cleanup 902 i8042.unlock [HW] Unlock (ignore) the keylock 903 904 i810= [HW,DRM] 905 906 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 907 indicates that the driver is running on unsupported 908 hardware. 909 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 910 does not match list of supported models. 911 i8k.power_status 912 [HW] Report power status in /proc/i8k 913 (disabled by default) 914 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 915 capability is set. 916 917 icn= [HW,ISDN] 918 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 919 920 ide-core.nodma= [HW] (E)IDE subsystem 921 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 922 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 923 .cdrom .chs .ignore_cable are additional options 924 See Documentation/ide/ide.txt. 925 926 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 927 Claim all unknown PCI IDE storage controllers. 928 929 idle= [X86] 930 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 931 Poll forces a polling idle loop that can slightly 932 improve the performance of waking up a idle CPU, but 933 will use a lot of power and make the system run hot. 934 Not recommended. 935 idle=mwait: On systems which support MONITOR/MWAIT but 936 the kernel chose to not use it because it doesn't save 937 as much power as a normal idle loop, use the 938 MONITOR/MWAIT idle loop anyways. Performance should be 939 the same as idle=poll. 940 idle=halt: Halt is forced to be used for CPU idle. 941 In such case C2/C3 won't be used again. 942 idle=nomwait: Disable mwait for CPU C-states 943 944 ignore_loglevel [KNL] 945 Ignore loglevel setting - this will print /all/ 946 kernel messages to the console. Useful for debugging. 947 948 ihash_entries= [KNL] 949 Set number of hash buckets for inode cache. 950 951 ima_audit= [IMA] 952 Format: { "0" | "1" } 953 0 -- integrity auditing messages. (Default) 954 1 -- enable informational integrity auditing messages. 955 956 ima_hash= [IMA] 957 Format: { "sha1" | "md5" } 958 default: "sha1" 959 960 ima_tcb [IMA] 961 Load a policy which meets the needs of the Trusted 962 Computing Base. This means IMA will measure all 963 programs exec'd, files mmap'd for exec, and all files 964 opened for read by uid=0. 965 966 init= [KNL] 967 Format: <full_path> 968 Run specified binary instead of /sbin/init as init 969 process. 970 971 initcall_debug [KNL] Trace initcalls as they are executed. Useful 972 for working out where the kernel is dying during 973 startup. 974 975 initrd= [BOOT] Specify the location of the initial ramdisk 976 977 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 978 Format: <irq> 979 980 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 981 on 982 Enable intel iommu driver. 983 off 984 Disable intel iommu driver. 985 igfx_off [Default Off] 986 By default, gfx is mapped as normal device. If a gfx 987 device has a dedicated DMAR unit, the DMAR unit is 988 bypassed by not enabling DMAR with this option. In 989 this case, gfx device will use physical address for 990 DMA. 991 forcedac [x86_64] 992 With this option iommu will not optimize to look 993 for io virtual address below 32 bit forcing dual 994 address cycle on pci bus for cards supporting greater 995 than 32 bit addressing. The default is to look 996 for translation below 32 bit and if not available 997 then look in the higher range. 998 strict [Default Off] 999 With this option on every unmap_single operation will 1000 result in a hardware IOTLB flush operation as opposed 1001 to batching them for performance. 1002 1003 intremap= [X86-64, Intel-IOMMU] 1004 Format: { on (default) | off | nosid } 1005 on enable Interrupt Remapping (default) 1006 off disable Interrupt Remapping 1007 nosid disable Source ID checking 1008 1009 inttest= [IA64] 1010 1011 iomem= Disable strict checking of access to MMIO memory 1012 strict regions from userspace. 1013 relaxed 1014 1015 iommu= [x86] 1016 off 1017 force 1018 noforce 1019 biomerge 1020 panic 1021 nopanic 1022 merge 1023 nomerge 1024 forcesac 1025 soft 1026 pt [x86, IA64] 1027 1028 io7= [HW] IO7 for Marvel based alpha systems 1029 See comment before marvel_specify_io7 in 1030 arch/alpha/kernel/core_marvel.c. 1031 1032 io_delay= [X86] I/O delay method 1033 0x80 1034 Standard port 0x80 based delay 1035 0xed 1036 Alternate port 0xed based delay (needed on some systems) 1037 udelay 1038 Simple two microseconds delay 1039 none 1040 No delay 1041 1042 ip= [IP_PNP] 1043 See Documentation/filesystems/nfs/nfsroot.txt. 1044 1045 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 1046 See comment before ip2_setup() in 1047 drivers/char/ip2/ip2base.c. 1048 1049 irqfixup [HW] 1050 When an interrupt is not handled search all handlers 1051 for it. Intended to get systems with badly broken 1052 firmware running. 1053 1054 irqpoll [HW] 1055 When an interrupt is not handled search all handlers 1056 for it. Also check all handlers each timer 1057 interrupt. Intended to get systems with badly broken 1058 firmware running. 1059 1060 isapnp= [ISAPNP] 1061 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1062 1063 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1064 Format: 1065 <cpu number>,...,<cpu number> 1066 or 1067 <cpu number>-<cpu number> 1068 (must be a positive range in ascending order) 1069 or a mixture 1070 <cpu number>,...,<cpu number>-<cpu number> 1071 1072 This option can be used to specify one or more CPUs 1073 to isolate from the general SMP balancing and scheduling 1074 algorithms. You can move a process onto or off an 1075 "isolated" CPU via the CPU affinity syscalls or cpuset. 1076 <cpu number> begins at 0 and the maximum value is 1077 "number of CPUs in system - 1". 1078 1079 This option is the preferred way to isolate CPUs. The 1080 alternative -- manually setting the CPU mask of all 1081 tasks in the system -- can cause problems and 1082 suboptimal load balancer performance. 1083 1084 iucv= [HW,NET] 1085 1086 js= [HW,JOY] Analog joystick 1087 See Documentation/input/joystick.txt. 1088 1089 keepinitrd [HW,ARM] 1090 1091 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1092 specifies the amount of memory usable by the kernel 1093 for non-movable allocations. The requested amount is 1094 spread evenly throughout all nodes in the system. The 1095 remaining memory in each node is used for Movable 1096 pages. In the event, a node is too small to have both 1097 kernelcore and Movable pages, kernelcore pages will 1098 take priority and other nodes will have a larger number 1099 of kernelcore pages. The Movable zone is used for the 1100 allocation of pages that may be reclaimed or moved 1101 by the page migration subsystem. This means that 1102 HugeTLB pages may not be allocated from this zone. 1103 Note that allocations like PTEs-from-HighMem still 1104 use the HighMem zone if it exists, and the Normal 1105 zone if it does not. 1106 1107 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 1108 Format: <Controller#>[,poll interval] 1109 The controller # is the number of the ehci usb debug 1110 port as it is probed via PCI. The poll interval is 1111 optional and is the number seconds in between 1112 each poll cycle to the debug port in case you need 1113 the functionality for interrupting the kernel with 1114 gdb or control-c on the dbgp connection. When 1115 not using this parameter you use sysrq-g to break into 1116 the kernel debugger. 1117 1118 kgdboc= [KGDB,HW] kgdb over consoles. 1119 Requires a tty driver that supports console polling, 1120 or a supported polling keyboard driver (non-usb). 1121 Serial only format: <serial_device>[,baud] 1122 keyboard only format: kbd 1123 keyboard and serial format: kbd,<serial_device>[,baud] 1124 Optional Kernel mode setting: 1125 kms, kbd format: kms,kbd 1126 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 1127 1128 kgdbwait [KGDB] Stop kernel execution and enter the 1129 kernel debugger at the earliest opportunity. 1130 1131 kmac= [MIPS] korina ethernet MAC address. 1132 Configure the RouterBoard 532 series on-chip 1133 Ethernet adapter MAC address. 1134 1135 kmemleak= [KNL] Boot-time kmemleak enable/disable 1136 Valid arguments: on, off 1137 Default: on 1138 1139 kstack=N [X86] Print N words from the kernel stack 1140 in oops dumps. 1141 1142 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1143 Default is 0 (don't ignore, but inject #GP) 1144 1145 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. 1146 Default is 1 (enabled) 1147 1148 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit 1149 KVM MMU at runtime. 1150 Default is 0 (off) 1151 1152 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1153 Default is 1 (enabled) 1154 1155 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1156 for all guests. 1157 Default is 1 (enabled) if in 64bit or 32bit-PAE mode 1158 1159 kvm-intel.bypass_guest_pf= 1160 [KVM,Intel] Disables bypassing of guest page faults 1161 on Intel chips. Default is 1 (enabled) 1162 1163 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1164 (virtualized MMU) support on capable Intel chips. 1165 Default is 1 (enabled) 1166 1167 kvm-intel.emulate_invalid_guest_state= 1168 [KVM,Intel] Enable emulation of invalid guest states 1169 Default is 0 (disabled) 1170 1171 kvm-intel.flexpriority= 1172 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1173 Default is 1 (enabled) 1174 1175 kvm-intel.unrestricted_guest= 1176 [KVM,Intel] Disable unrestricted guest feature 1177 (virtualized real and unpaged mode) on capable 1178 Intel chips. Default is 1 (enabled) 1179 1180 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1181 feature (tagged TLBs) on capable Intel chips. 1182 Default is 1 (enabled) 1183 1184 l2cr= [PPC] 1185 1186 l3cr= [PPC] 1187 1188 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1189 disabled it. 1190 1191 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1192 in C2 power state. 1193 1194 libata.dma= [LIBATA] DMA control 1195 libata.dma=0 Disable all PATA and SATA DMA 1196 libata.dma=1 PATA and SATA Disk DMA only 1197 libata.dma=2 ATAPI (CDROM) DMA only 1198 libata.dma=4 Compact Flash DMA only 1199 Combinations also work, so libata.dma=3 enables DMA 1200 for disks and CDROMs, but not CFs. 1201 1202 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1203 libata.ignore_hpa=0 keep BIOS limits (default) 1204 libata.ignore_hpa=1 ignore limits, using full disk 1205 1206 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1207 when set. 1208 Format: <int> 1209 1210 libata.force= [LIBATA] Force configurations. The format is comma 1211 separated list of "[ID:]VAL" where ID is 1212 PORT[.DEVICE]. PORT and DEVICE are decimal numbers 1213 matching port, link or device. Basically, it matches 1214 the ATA ID string printed on console by libata. If 1215 the whole ID part is omitted, the last PORT and DEVICE 1216 values are used. If ID hasn't been specified yet, the 1217 configuration applies to all ports, links and devices. 1218 1219 If only DEVICE is omitted, the parameter applies to 1220 the port and all links and devices behind it. DEVICE 1221 number of 0 either selects the first device or the 1222 first fan-out link behind PMP device. It does not 1223 select the host link. DEVICE number of 15 selects the 1224 host link and device attached to it. 1225 1226 The VAL specifies the configuration to force. As long 1227 as there's no ambiguity shortcut notation is allowed. 1228 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1229 The following configurations can be forced. 1230 1231 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1232 Any ID with matching PORT is used. 1233 1234 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1235 1236 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1237 udma[/][16,25,33,44,66,100,133] notation is also 1238 allowed. 1239 1240 * [no]ncq: Turn on or off NCQ. 1241 1242 * nohrst, nosrst, norst: suppress hard, soft 1243 and both resets. 1244 1245 * dump_id: dump IDENTIFY data. 1246 1247 If there are multiple matching configurations changing 1248 the same attribute, the last one is used. 1249 1250 memblock=debug [KNL] Enable memblock debug messages. 1251 1252 load_ramdisk= [RAM] List of ramdisks to load from floppy 1253 See Documentation/blockdev/ramdisk.txt. 1254 1255 lockd.nlm_grace_period=P [NFS] Assign grace period. 1256 Format: <integer> 1257 1258 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1259 Format: <integer> 1260 1261 lockd.nlm_timeout=T [NFS] Assign timeout value. 1262 Format: <integer> 1263 1264 lockd.nlm_udpport=M [NFS] Assign UDP port. 1265 Format: <integer> 1266 1267 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1268 Format: <irq> 1269 1270 loglevel= All Kernel Messages with a loglevel smaller than the 1271 console loglevel will be printed to the console. It can 1272 also be changed with klogd or other programs. The 1273 loglevels are defined as follows: 1274 1275 0 (KERN_EMERG) system is unusable 1276 1 (KERN_ALERT) action must be taken immediately 1277 2 (KERN_CRIT) critical conditions 1278 3 (KERN_ERR) error conditions 1279 4 (KERN_WARNING) warning conditions 1280 5 (KERN_NOTICE) normal but significant condition 1281 6 (KERN_INFO) informational 1282 7 (KERN_DEBUG) debug-level messages 1283 1284 log_buf_len=n[KMG] Sets the size of the printk ring buffer, 1285 in bytes. n must be a power of two. The default 1286 size is set in the kernel config file. 1287 1288 logo.nologo [FB] Disables display of the built-in Linux logo. 1289 This may be used to provide more screen space for 1290 kernel log messages and is useful when debugging 1291 kernel boot problems. 1292 1293 lp=0 [LP] Specify parallel ports to use, e.g, 1294 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1295 lp=reset first parallel port). 'lp=0' disables the 1296 lp=auto printer driver. 'lp=reset' (which can be 1297 specified in addition to the ports) causes 1298 attached printers to be reset. Using 1299 lp=port1,port2,... specifies the parallel ports 1300 to associate lp devices with, starting with 1301 lp0. A port specification may be 'none' to skip 1302 that lp device, or a parport name such as 1303 'parport0'. Specifying 'lp=auto' instead of a 1304 port specification list means that device IDs 1305 from each port should be examined, to see if 1306 an IEEE 1284-compliant printer is attached; if 1307 so, the driver will manage that printer. 1308 See also header of drivers/char/lp.c. 1309 1310 lpj=n [KNL] 1311 Sets loops_per_jiffy to given constant, thus avoiding 1312 time-consuming boot-time autodetection (up to 250 ms per 1313 CPU). 0 enables autodetection (default). To determine 1314 the correct value for your kernel, boot with normal 1315 autodetection and see what value is printed. Note that 1316 on SMP systems the preset will be applied to all CPUs, 1317 which is likely to cause problems if your CPUs need 1318 significantly divergent settings. An incorrect value 1319 will cause delays in the kernel to be wrong, leading to 1320 unpredictable I/O errors and other breakage. Although 1321 unlikely, in the extreme case this might damage your 1322 hardware. 1323 1324 ltpc= [NET] 1325 Format: <io>,<irq>,<dma> 1326 1327 machvec= [IA64] Force the use of a particular machine-vector 1328 (machvec) in a generic kernel. 1329 Example: machvec=hpzx1_swiotlb 1330 1331 machtype= [Loongson] Share the same kernel image file between different 1332 yeeloong laptop. 1333 Example: machtype=lemote-yeeloong-2f-7inch 1334 1335 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 1336 than or equal to this physical address is ignored. 1337 1338 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1339 should make use of. maxcpus=n : n >= 0 limits the 1340 kernel to using 'n' processors. n=0 is a special case, 1341 it is equivalent to "nosmp", which also disables 1342 the IO APIC. 1343 1344 max_loop= [LOOP] Maximum number of loopback devices that can 1345 be mounted 1346 Format: <1-256> 1347 1348 mcatest= [IA-64] 1349 1350 mce [X86-32] Machine Check Exception 1351 1352 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1353 1354 md= [HW] RAID subsystems devices and level 1355 See Documentation/md.txt. 1356 1357 mdacon= [MDA] 1358 Format: <first>,<last> 1359 Specifies range of consoles to be captured by the MDA. 1360 1361 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1362 Amount of memory to be used when the kernel is not able 1363 to see the whole system memory or for test. 1364 [X86-32] Use together with memmap= to avoid physical 1365 address space collisions. Without memmap= PCI devices 1366 could be placed at addresses belonging to unused RAM. 1367 1368 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1369 memory. 1370 1371 memchunk=nn[KMG] 1372 [KNL,SH] Allow user to override the default size for 1373 per-device physically contiguous DMA buffers. 1374 1375 memmap=exactmap [KNL,X86] Enable setting of an exact 1376 E820 memory map, as specified by the user. 1377 Such memmap=exactmap lines can be constructed based on 1378 BIOS output or other requirements. See the memmap=nn@ss 1379 option description. 1380 1381 memmap=nn[KMG]@ss[KMG] 1382 [KNL] Force usage of a specific region of memory 1383 Region of memory to be used, from ss to ss+nn. 1384 1385 memmap=nn[KMG]#ss[KMG] 1386 [KNL,ACPI] Mark specific memory as ACPI data. 1387 Region of memory to be used, from ss to ss+nn. 1388 1389 memmap=nn[KMG]$ss[KMG] 1390 [KNL,ACPI] Mark specific memory as reserved. 1391 Region of memory to be used, from ss to ss+nn. 1392 Example: Exclude memory from 0x18690000-0x1869ffff 1393 memmap=64K$0x18690000 1394 or 1395 memmap=0x10000$0x18690000 1396 1397 memory_corruption_check=0/1 [X86] 1398 Some BIOSes seem to corrupt the first 64k of 1399 memory when doing things like suspend/resume. 1400 Setting this option will scan the memory 1401 looking for corruption. Enabling this will 1402 both detect corruption and prevent the kernel 1403 from using the memory being corrupted. 1404 However, its intended as a diagnostic tool; if 1405 repeatable BIOS-originated corruption always 1406 affects the same memory, you can use memmap= 1407 to prevent the kernel from using that memory. 1408 1409 memory_corruption_check_size=size [X86] 1410 By default it checks for corruption in the low 1411 64k, making this memory unavailable for normal 1412 use. Use this parameter to scan for 1413 corruption in more or less memory. 1414 1415 memory_corruption_check_period=seconds [X86] 1416 By default it checks for corruption every 60 1417 seconds. Use this parameter to check at some 1418 other rate. 0 disables periodic checking. 1419 1420 memtest= [KNL,X86] Enable memtest 1421 Format: <integer> 1422 default : 0 <disable> 1423 Specifies the number of memtest passes to be 1424 performed. Each pass selects another test 1425 pattern from a given set of patterns. Memtest 1426 fills the memory with this pattern, validates 1427 memory contents and reserves bad memory 1428 regions that are detected. 1429 1430 meye.*= [HW] Set MotionEye Camera parameters 1431 See Documentation/video4linux/meye.txt. 1432 1433 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1434 Multi-Function General Purpose Timers on AMD Geode 1435 platforms. 1436 1437 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1438 the BIOS has incorrectly applied a workaround. TinyBIOS 1439 version 0.98 is known to be affected, 0.99 fixes the 1440 problem by letting the user disable the workaround. 1441 1442 mga= [HW,DRM] 1443 1444 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1445 physical address is ignored. 1446 1447 mini2440= [ARM,HW,KNL] 1448 Format:[0..2][b][c][t] 1449 Default: "0tb" 1450 MINI2440 configuration specification: 1451 0 - The attached screen is the 3.5" TFT 1452 1 - The attached screen is the 7" TFT 1453 2 - The VGA Shield is attached (1024x768) 1454 Leaving out the screen size parameter will not load 1455 the TFT driver, and the framebuffer will be left 1456 unconfigured. 1457 b - Enable backlight. The TFT backlight pin will be 1458 linked to the kernel VESA blanking code and a GPIO 1459 LED. This parameter is not necessary when using the 1460 VGA shield. 1461 c - Enable the s3c camera interface. 1462 t - Reserved for enabling touchscreen support. The 1463 touchscreen support is not enabled in the mainstream 1464 kernel as of 2.6.30, a preliminary port can be found 1465 in the "bleeding edge" mini2440 support kernel at 1466 http://repo.or.cz/w/linux-2.6/mini2440.git 1467 1468 mminit_loglevel= 1469 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1470 parameter allows control of the logging verbosity for 1471 the additional memory initialisation checks. A value 1472 of 0 disables mminit logging and a level of 4 will 1473 log everything. Information is printed at KERN_DEBUG 1474 so loglevel=8 may also need to be specified. 1475 1476 mousedev.tap_time= 1477 [MOUSE] Maximum time between finger touching and 1478 leaving touchpad surface for touch to be considered 1479 a tap and be reported as a left button click (for 1480 touchpads working in absolute mode only). 1481 Format: <msecs> 1482 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1483 reporting absolute coordinates, such as tablets 1484 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1485 reporting absolute coordinates, such as tablets 1486 1487 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1488 is similar to kernelcore except it specifies the 1489 amount of memory used for migratable allocations. 1490 If both kernelcore and movablecore is specified, 1491 then kernelcore will be at *least* the specified 1492 value but may be more. If movablecore on its own 1493 is specified, the administrator must be careful 1494 that the amount of memory usable for all allocations 1495 is not too small. 1496 1497 MTD_Partition= [MTD] 1498 Format: <name>,<region-number>,<size>,<offset> 1499 1500 MTD_Region= [MTD] Format: 1501 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1502 1503 mtdparts= [MTD] 1504 See drivers/mtd/cmdlinepart.c. 1505 1506 multitce=off [PPC] This parameter disables the use of the pSeries 1507 firmware feature for updating multiple TCE entries 1508 at a time. 1509 1510 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 1511 1512 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 1513 1514 boundary - index of last SLC block on Flex-OneNAND. 1515 The remaining blocks are configured as MLC blocks. 1516 lock - Configure if Flex-OneNAND boundary should be locked. 1517 Once locked, the boundary cannot be changed. 1518 1 indicates lock status, 0 indicates unlock status. 1519 1520 mtdset= [ARM] 1521 ARM/S3C2412 JIVE boot control 1522 1523 See arch/arm/mach-s3c2412/mach-jive.c 1524 1525 mtouchusb.raw_coordinates= 1526 [HW] Make the MicroTouch USB driver use raw coordinates 1527 ('y', default) or cooked coordinates ('n') 1528 1529 mtrr_chunk_size=nn[KMG] [X86] 1530 used for mtrr cleanup. It is largest continuous chunk 1531 that could hold holes aka. UC entries. 1532 1533 mtrr_gran_size=nn[KMG] [X86] 1534 Used for mtrr cleanup. It is granularity of mtrr block. 1535 Default is 1. 1536 Large value could prevent small alignment from 1537 using up MTRRs. 1538 1539 mtrr_spare_reg_nr=n [X86] 1540 Format: <integer> 1541 Range: 0,7 : spare reg number 1542 Default : 1 1543 Used for mtrr cleanup. It is spare mtrr entries number. 1544 Set to 2 or more if your graphical card needs more. 1545 1546 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1547 1548 netdev= [NET] Network devices parameters 1549 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1550 Note that mem_start is often overloaded to mean 1551 something different and driver-specific. 1552 This usage is only documented in each driver source 1553 file if at all. 1554 1555 nf_conntrack.acct= 1556 [NETFILTER] Enable connection tracking flow accounting 1557 0 to disable accounting 1558 1 to enable accounting 1559 Default value is 0. 1560 1561 nfsaddrs= [NFS] Deprecated. Use ip= instead. 1562 See Documentation/filesystems/nfs/nfsroot.txt. 1563 1564 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1565 See Documentation/filesystems/nfs/nfsroot.txt. 1566 1567 nfsrootdebug [NFS] enable nfsroot debugging messages. 1568 See Documentation/filesystems/nfs/nfsroot.txt. 1569 1570 nfs.callback_tcpport= 1571 [NFS] set the TCP port on which the NFSv4 callback 1572 channel should listen. 1573 1574 nfs.cache_getent= 1575 [NFS] sets the pathname to the program which is used 1576 to update the NFS client cache entries. 1577 1578 nfs.cache_getent_timeout= 1579 [NFS] sets the timeout after which an attempt to 1580 update a cache entry is deemed to have failed. 1581 1582 nfs.idmap_cache_timeout= 1583 [NFS] set the maximum lifetime for idmapper cache 1584 entries. 1585 1586 nfs.enable_ino64= 1587 [NFS] enable 64-bit inode numbers. 1588 If zero, the NFS client will fake up a 32-bit inode 1589 number for the readdir() and stat() syscalls instead 1590 of returning the full 64-bit number. 1591 The default is to return 64-bit inode numbers. 1592 1593 nfs.nfs4_disable_idmapping= 1594 [NFSv4] When set, this option disables the NFSv4 1595 idmapper on the client, but only if the mount 1596 is using the 'sec=sys' security flavour. This may 1597 make migration from legacy NFSv2/v3 systems easier 1598 provided that the server has the appropriate support. 1599 The default is to always enable NFSv4 idmapping. 1600 1601 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 1602 when a NMI is triggered. 1603 Format: [state][,regs][,debounce][,die] 1604 1605 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 1606 Format: [panic,][nopanic,][num] 1607 Valid num: 0 1608 0 - turn nmi_watchdog off 1609 When panic is specified, panic when an NMI watchdog 1610 timeout occurs (or 'nopanic' to override the opposite 1611 default). 1612 This is useful when you use a panic=... timeout and 1613 need the box quickly up again. 1614 1615 netpoll.carrier_timeout= 1616 [NET] Specifies amount of time (in seconds) that 1617 netpoll should wait for a carrier. By default netpoll 1618 waits 4 seconds. 1619 1620 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1621 emulation library even if a 387 maths coprocessor 1622 is present. 1623 1624 no_console_suspend 1625 [HW] Never suspend the console 1626 Disable suspending of consoles during suspend and 1627 hibernate operations. Once disabled, debugging 1628 messages can reach various consoles while the rest 1629 of the system is being put to sleep (ie, while 1630 debugging driver suspend/resume hooks). This may 1631 not work reliably with all consoles, but is known 1632 to work with serial and VGA consoles. 1633 1634 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1635 caches in the slab allocator. Saves per-node memory, 1636 but will impact performance. 1637 1638 noalign [KNL,ARM] 1639 1640 noapic [SMP,APIC] Tells the kernel to not make use of any 1641 IOAPICs that may be present in the system. 1642 1643 noautogroup Disable scheduler automatic task group creation. 1644 1645 nobats [PPC] Do not use BATs for mapping kernel lowmem 1646 on "Classic" PPC cores. 1647 1648 nocache [ARM] 1649 1650 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1651 1652 nodelayacct [KNL] Disable per-task delay accounting 1653 1654 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1655 1656 nodsp [SH] Disable hardware DSP at boot time. 1657 1658 noefi [X86] Disable EFI runtime services support. 1659 1660 noexec [IA-64] 1661 1662 noexec [X86] 1663 On X86-32 available only on PAE configured kernels. 1664 noexec=on: enable non-executable mappings (default) 1665 noexec=off: disable non-executable mappings 1666 1667 noexec32 [X86-64] 1668 This affects only 32-bit executables. 1669 noexec32=on: enable non-executable mappings (default) 1670 read doesn't imply executable mappings 1671 noexec32=off: disable non-executable mappings 1672 read implies executable mappings 1673 1674 nofpu [SH] Disable hardware FPU at boot time. 1675 1676 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1677 register save and restore. The kernel will only save 1678 legacy floating-point registers on task switch. 1679 1680 noxsave [BUGS=X86] Disables x86 extended register state save 1681 and restore using xsave. The kernel will fallback to 1682 enabling legacy floating-point and sse state. 1683 1684 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 1685 wfi(ARM) instruction doesn't work correctly and not to 1686 use it. This is also useful when using JTAG debugger. 1687 1688 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1689 instruction doesn't work correctly and not to 1690 use it. 1691 1692 no_file_caps Tells the kernel not to honor file capabilities. The 1693 only way then for a file to be executed with privilege 1694 is to be setuid root or executed by root. 1695 1696 nohalt [IA-64] Tells the kernel not to use the power saving 1697 function PAL_HALT_LIGHT when idle. This increases 1698 power-consumption. On the positive side, it reduces 1699 interrupt wake-up latency, which may improve performance 1700 in certain environments such as networked servers or 1701 real-time systems. 1702 1703 nohz= [KNL] Boottime enable/disable dynamic ticks 1704 Valid arguments: on, off 1705 Default: on 1706 1707 noiotrap [SH] Disables trapped I/O port accesses. 1708 1709 noirqdebug [X86-32] Disables the code which attempts to detect and 1710 disable unhandled interrupt sources. 1711 1712 no_timer_check [X86,APIC] Disables the code which tests for 1713 broken timer IRQ sources. 1714 1715 noisapnp [ISAPNP] Disables ISA PnP code. 1716 1717 noinitrd [RAM] Tells the kernel not to load any configured 1718 initial RAM disk. 1719 1720 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 1721 remapping. 1722 [Deprecated - use intremap=off] 1723 1724 nointroute [IA-64] 1725 1726 nojitter [IA64] Disables jitter checking for ITC timers. 1727 1728 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver 1729 1730 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page 1731 fault handling. 1732 1733 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1734 1735 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1736 1737 noltlbs [PPC] Do not use large page/tlb entries for kernel 1738 lowmem mapping on PPC40x. 1739 1740 nomca [IA-64] Disable machine check abort handling 1741 1742 nomce [X86-32] Machine Check Exception 1743 1744 nomfgpt [X86-32] Disable Multi-Function General Purpose 1745 Timer usage (for AMD Geode machines). 1746 1747 nopat [X86] Disable PAT (page attribute table extension of 1748 pagetables) support. 1749 1750 norandmaps Don't use address space randomization. Equivalent to 1751 echo 0 > /proc/sys/kernel/randomize_va_space 1752 1753 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops 1754 1755 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1756 with UP alternatives 1757 1758 noresidual [PPC] Don't use residual data on PReP machines. 1759 1760 noresume [SWSUSP] Disables resume and restores original swap 1761 space. 1762 1763 no-scroll [VGA] Disables scrollback. 1764 This is required for the Braillex ib80-piezo Braille 1765 reader made by F.H. Papenmeier (Germany). 1766 1767 nosbagart [IA-64] 1768 1769 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1770 1771 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1772 and disable the IO APIC. legacy for "maxcpus=0". 1773 1774 nosoftlockup [KNL] Disable the soft-lockup detector. 1775 1776 noswapaccount [KNL] Disable accounting of swap in memory resource 1777 controller. (See Documentation/cgroups/memory.txt) 1778 1779 nosync [HW,M68K] Disables sync negotiation for all devices. 1780 1781 notsc [BUGS=X86-32] Disable Time Stamp Counter 1782 1783 nousb [USB] Disable the USB subsystem 1784 1785 nowatchdog [KNL] Disable the lockup detector (NMI watchdog). 1786 1787 nowb [ARM] 1788 1789 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1790 1791 nptcg= [IA64] Override max number of concurrent global TLB 1792 purges which is reported from either PAL_VM_SUMMARY or 1793 SAL PALO. 1794 1795 nr_cpus= [SMP] Maximum number of processors that an SMP kernel 1796 could support. nr_cpus=n : n >= 1 limits the kernel to 1797 supporting 'n' processors. Later in runtime you can not 1798 use hotplug cpu feature to put more cpu back to online. 1799 just like you compile the kernel NR_CPUS=n 1800 1801 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1802 1803 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1804 one of ['zone', 'node', 'default'] can be specified 1805 This can be set from sysctl after boot. 1806 See Documentation/sysctl/vm.txt for details. 1807 1808 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1809 See Documentation/debugging-via-ohci1394.txt for more 1810 info. 1811 1812 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1813 Rather than timing out after 20 ms if an EC 1814 command is not properly ACKed, override the length 1815 of the timeout. We have interrupts disabled while 1816 waiting for the ACK, so if this is set too high 1817 interrupts *may* be lost! 1818 1819 omap_mux= [OMAP] Override bootloader pin multiplexing. 1820 Format: <mux_mode0.mode_name=value>... 1821 For example, to override I2C bus2: 1822 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 1823 1824 oprofile.timer= [HW] 1825 Use timer interrupt instead of performance counters 1826 1827 oprofile.cpu_type= Force an oprofile cpu type 1828 This might be useful if you have an older oprofile 1829 userland or if you want common events. 1830 Format: { arch_perfmon } 1831 arch_perfmon: [X86] Force use of architectural 1832 perfmon on Intel CPUs instead of the 1833 CPU specific event set. 1834 1835 oops=panic Always panic on oopses. Default is to just kill the 1836 process, but there is a small probability of 1837 deadlocking the machine. 1838 This will also cause panics on machine check exceptions. 1839 Useful together with panic=30 to trigger a reboot. 1840 1841 OSS [HW,OSS] 1842 See Documentation/sound/oss/oss-parameters.txt 1843 1844 panic= [KNL] Kernel behaviour on panic: delay <timeout> 1845 seconds before rebooting 1846 Format: <timeout> 1847 1848 parkbd.port= [HW] Parallel port number the keyboard adapter is 1849 connected to, default is 0. 1850 Format: <parport#> 1851 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1852 0 for XT, 1 for AT (default is AT). 1853 Format: <mode> 1854 1855 parport= [HW,PPT] Specify parallel ports. 0 disables. 1856 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1857 Use 'auto' to force the driver to use any 1858 IRQ/DMA settings detected (the default is to 1859 ignore detected IRQ/DMA settings because of 1860 possible conflicts). You can specify the base 1861 address, IRQ, and DMA settings; IRQ and DMA 1862 should be numbers, or 'auto' (for using detected 1863 settings on that particular port), or 'nofifo' 1864 (to avoid using a FIFO even if it is detected). 1865 Parallel ports are assigned in the order they 1866 are specified on the command line, starting 1867 with parport0. 1868 1869 parport_init_mode= [HW,PPT] 1870 Configure VIA parallel port to operate in 1871 a specific mode. This is necessary on Pegasos 1872 computer where firmware has no options for setting 1873 up parallel port mode and sets it to spp. 1874 Currently this function knows 686a and 8231 chips. 1875 Format: [spp|ps2|epp|ecp|ecpepp] 1876 1877 pause_on_oops= 1878 Halt all CPUs after the first oops has been printed for 1879 the specified number of seconds. This is to be used if 1880 your oopses keep scrolling off the screen. 1881 1882 pcbit= [HW,ISDN] 1883 1884 pcd. [PARIDE] 1885 See header of drivers/block/paride/pcd.c. 1886 See also Documentation/blockdev/paride.txt. 1887 1888 pci=option[,option...] [PCI] various PCI subsystem options: 1889 earlydump [X86] dump PCI config space before the kernel 1890 changes anything 1891 off [X86] don't probe for the PCI bus 1892 bios [X86-32] force use of PCI BIOS, don't access 1893 the hardware directly. Use this if your machine 1894 has a non-standard PCI host bridge. 1895 nobios [X86-32] disallow use of PCI BIOS, only direct 1896 hardware access methods are allowed. Use this 1897 if you experience crashes upon bootup and you 1898 suspect they are caused by the BIOS. 1899 conf1 [X86] Force use of PCI Configuration 1900 Mechanism 1. 1901 conf2 [X86] Force use of PCI Configuration 1902 Mechanism 2. 1903 noaer [PCIE] If the PCIEAER kernel config parameter is 1904 enabled, this kernel boot option can be used to 1905 disable the use of PCIE advanced error reporting. 1906 nodomains [PCI] Disable support for multiple PCI 1907 root domains (aka PCI segments, in ACPI-speak). 1908 nommconf [X86] Disable use of MMCONFIG for PCI 1909 Configuration 1910 check_enable_amd_mmconf [X86] check for and enable 1911 properly configured MMIO access to PCI 1912 config space on AMD family 10h CPU 1913 nomsi [MSI] If the PCI_MSI kernel config parameter is 1914 enabled, this kernel boot option can be used to 1915 disable the use of MSI interrupts system-wide. 1916 noioapicquirk [APIC] Disable all boot interrupt quirks. 1917 Safety option to keep boot IRQs enabled. This 1918 should never be necessary. 1919 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1920 primary IO-APIC for bridges that cannot disable 1921 boot IRQs. This fixes a source of spurious IRQs 1922 when the system masks IRQs. 1923 noioapicreroute [APIC] Disable workaround that uses the 1924 boot IRQ equivalent of an IRQ that connects to 1925 a chipset where boot IRQs cannot be disabled. 1926 The opposite of ioapicreroute. 1927 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1928 routing table. These calls are known to be buggy 1929 on several machines and they hang the machine 1930 when used, but on other computers it's the only 1931 way to get the interrupt routing table. Try 1932 this option if the kernel is unable to allocate 1933 IRQs or discover secondary PCI buses on your 1934 motherboard. 1935 rom [X86] Assign address space to expansion ROMs. 1936 Use with caution as certain devices share 1937 address decoders between ROMs and other 1938 resources. 1939 norom [X86] Do not assign address space to 1940 expansion ROMs that do not already have 1941 BIOS assigned address ranges. 1942 nobar [X86] Do not assign address space to the 1943 BARs that weren't assigned by the BIOS. 1944 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1945 assigned automatically to PCI devices. You can 1946 make the kernel exclude IRQs of your ISA cards 1947 this way. 1948 pirqaddr=0xAAAAA [X86] Specify the physical address 1949 of the PIRQ table (normally generated 1950 by the BIOS) if it is outside the 1951 F0000h-100000h range. 1952 lastbus=N [X86] Scan all buses thru bus #N. Can be 1953 useful if the kernel is unable to find your 1954 secondary buses and you want to tell it 1955 explicitly which ones they are. 1956 assign-busses [X86] Always assign all PCI bus 1957 numbers ourselves, overriding 1958 whatever the firmware may have done. 1959 usepirqmask [X86] Honor the possible IRQ mask stored 1960 in the BIOS $PIR table. This is needed on 1961 some systems with broken BIOSes, notably 1962 some HP Pavilion N5400 and Omnibook XE3 1963 notebooks. This will have no effect if ACPI 1964 IRQ routing is enabled. 1965 noacpi [X86] Do not use ACPI for IRQ routing 1966 or for PCI scanning. 1967 use_crs [X86] Use PCI host bridge window information 1968 from ACPI. On BIOSes from 2008 or later, this 1969 is enabled by default. If you need to use this, 1970 please report a bug. 1971 nocrs [X86] Ignore PCI host bridge windows from ACPI. 1972 If you need to use this, please report a bug. 1973 routeirq Do IRQ routing for all PCI devices. 1974 This is normally done in pci_enable_device(), 1975 so this option is a temporary workaround 1976 for broken drivers that don't call it. 1977 skip_isa_align [X86] do not align io start addr, so can 1978 handle more pci cards 1979 firmware [ARM] Do not re-enumerate the bus but instead 1980 just use the configuration from the 1981 bootloader. This is currently used on 1982 IXP2000 systems where the bus has to be 1983 configured a certain way for adjunct CPUs. 1984 noearly [X86] Don't do any early type 1 scanning. 1985 This might help on some broken boards which 1986 machine check when some devices' config space 1987 is read. But various workarounds are disabled 1988 and some IOMMU drivers will not work. 1989 bfsort Sort PCI devices into breadth-first order. 1990 This sorting is done to get a device 1991 order compatible with older (<= 2.4) kernels. 1992 nobfsort Don't sort PCI devices into breadth-first order. 1993 cbiosize=nn[KMG] The fixed amount of bus space which is 1994 reserved for the CardBus bridge's IO window. 1995 The default value is 256 bytes. 1996 cbmemsize=nn[KMG] The fixed amount of bus space which is 1997 reserved for the CardBus bridge's memory 1998 window. The default value is 64 megabytes. 1999 resource_alignment= 2000 Format: 2001 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] 2002 Specifies alignment and device to reassign 2003 aligned memory resources. 2004 If <order of align> is not specified, 2005 PAGE_SIZE is used as alignment. 2006 PCI-PCI bridge can be specified, if resource 2007 windows need to be expanded. 2008 ecrc= Enable/disable PCIe ECRC (transaction layer 2009 end-to-end CRC checking). 2010 bios: Use BIOS/firmware settings. This is the 2011 the default. 2012 off: Turn ECRC off 2013 on: Turn ECRC on. 2014 2015 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 2016 Management. 2017 off Disable ASPM. 2018 force Enable ASPM even on devices that claim not to support it. 2019 WARNING: Forcing ASPM on may cause system lockups. 2020 2021 pcie_ports= [PCIE] PCIe ports handling: 2022 auto Ask the BIOS whether or not to use native PCIe services 2023 associated with PCIe ports (PME, hot-plug, AER). Use 2024 them only if that is allowed by the BIOS. 2025 native Use native PCIe services associated with PCIe ports 2026 unconditionally. 2027 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe 2028 ports driver. 2029 2030 pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 2031 nomsi Do not use MSI for native PCIe PME signaling (this makes 2032 all PCIe root ports use INTx for all services). 2033 2034 pcmv= [HW,PCMCIA] BadgePAD 4 2035 2036 pd. [PARIDE] 2037 See Documentation/blockdev/paride.txt. 2038 2039 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 2040 boot time. 2041 Format: { 0 | 1 } 2042 See arch/parisc/kernel/pdc_chassis.c 2043 2044 percpu_alloc= Select which percpu first chunk allocator to use. 2045 Currently supported values are "embed" and "page". 2046 Archs may support subset or none of the selections. 2047 See comments in mm/percpu.c for details on each 2048 allocator. This parameter is primarily for debugging 2049 and performance comparison. 2050 2051 pf. [PARIDE] 2052 See Documentation/blockdev/paride.txt. 2053 2054 pg. [PARIDE] 2055 See Documentation/blockdev/paride.txt. 2056 2057 pirq= [SMP,APIC] Manual mp-table setup 2058 See Documentation/x86/i386/IO-APIC.txt. 2059 2060 plip= [PPT,NET] Parallel port network link 2061 Format: { parport<nr> | timid | 0 } 2062 See also Documentation/parport.txt. 2063 2064 pmtmr= [X86] Manual setup of pmtmr I/O Port. 2065 Override pmtimer IOPort with a hex value. 2066 e.g. pmtmr=0x508 2067 2068 pnp.debug [PNP] 2069 Enable PNP debug messages. This depends on the 2070 CONFIG_PNP_DEBUG_MESSAGES option. 2071 2072 pnpacpi= [ACPI] 2073 { off } 2074 2075 pnpbios= [ISAPNP] 2076 { on | off | curr | res | no-curr | no-res } 2077 2078 pnp_reserve_irq= 2079 [ISAPNP] Exclude IRQs for the autoconfiguration 2080 2081 pnp_reserve_dma= 2082 [ISAPNP] Exclude DMAs for the autoconfiguration 2083 2084 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 2085 Ranges are in pairs (I/O port base and size). 2086 2087 pnp_reserve_mem= 2088 [ISAPNP] Exclude memory regions for the 2089 autoconfiguration. 2090 Ranges are in pairs (memory base and size). 2091 2092 ports= [IP_VS_FTP] IPVS ftp helper module 2093 Default is 21. 2094 Up to 8 (IP_VS_APP_MAX_PORTS) ports 2095 may be specified. 2096 Format: <port>,<port>.... 2097 2098 print-fatal-signals= 2099 [KNL] debug: print fatal signals 2100 2101 If enabled, warn about various signal handling 2102 related application anomalies: too many signals, 2103 too many POSIX.1 timers, fatal signals causing a 2104 coredump - etc. 2105 2106 If you hit the warning due to signal overflow, 2107 you might want to try "ulimit -i unlimited". 2108 2109 default: off. 2110 2111 printk.time= Show timing data prefixed to each printk message line 2112 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 2113 2114 processor.max_cstate= [HW,ACPI] 2115 Limit processor to maximum C-state 2116 max_cstate=9 overrides any DMI blacklist limit. 2117 2118 processor.nocst [HW,ACPI] 2119 Ignore the _CST method to determine C-states, 2120 instead using the legacy FADT method 2121 2122 profile= [KNL] Enable kernel profiling via /proc/profile 2123 Format: [schedule,]<number> 2124 Param: "schedule" - profile schedule points. 2125 Param: <number> - step/bucket size as a power of 2 for 2126 statistical time based profiling. 2127 Param: "sleep" - profile D-state sleeping (millisecs). 2128 Requires CONFIG_SCHEDSTATS 2129 Param: "kvm" - profile VM exits. 2130 2131 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 2132 before loading. 2133 See Documentation/blockdev/ramdisk.txt. 2134 2135 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 2136 probe for; one of (bare|imps|exps|lifebook|any). 2137 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 2138 per second. 2139 psmouse.resetafter= [HW,MOUSE] 2140 Try to reset the device after so many bad packets 2141 (0 = never). 2142 psmouse.resolution= 2143 [HW,MOUSE] Set desired mouse resolution, in dpi. 2144 psmouse.smartscroll= 2145 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 2146 0 = disabled, 1 = enabled (default). 2147 2148 pt. [PARIDE] 2149 See Documentation/blockdev/paride.txt. 2150 2151 pty.legacy_count= 2152 [KNL] Number of legacy pty's. Overwrites compiled-in 2153 default number. 2154 2155 quiet [KNL] Disable most log messages 2156 2157 r128= [HW,DRM] 2158 2159 raid= [HW,RAID] 2160 See Documentation/md.txt. 2161 2162 ramdisk_blocksize= [RAM] 2163 See Documentation/blockdev/ramdisk.txt. 2164 2165 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 2166 See Documentation/blockdev/ramdisk.txt. 2167 2168 rcupdate.blimit= [KNL,BOOT] 2169 Set maximum number of finished RCU callbacks to process 2170 in one batch. 2171 2172 rcupdate.qhimark= [KNL,BOOT] 2173 Set threshold of queued 2174 RCU callbacks over which batch limiting is disabled. 2175 2176 rcupdate.qlowmark= [KNL,BOOT] 2177 Set threshold of queued RCU callbacks below which 2178 batch limiting is re-enabled. 2179 2180 rdinit= [KNL] 2181 Format: <full_path> 2182 Run specified binary instead of /init from the ramdisk, 2183 used for early userspace startup. See initrd. 2184 2185 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 2186 Format: <reboot_mode>[,<reboot_mode2>[,...]] 2187 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 2188 2189 relax_domain_level= 2190 [KNL, SMP] Set scheduler's default relax_domain_level. 2191 See Documentation/cgroups/cpusets.txt. 2192 2193 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 2194 2195 reservetop= [X86-32] 2196 Format: nn[KMG] 2197 Reserves a hole at the top of the kernel virtual 2198 address space. 2199 2200 reservelow= [X86] 2201 Format: nn[K] 2202 Set the amount of memory to reserve for BIOS at 2203 the bottom of the address space. 2204 2205 reset_devices [KNL] Force drivers to reset the underlying device 2206 during initialization. 2207 2208 resume= [SWSUSP] 2209 Specify the partition device for software suspend 2210 2211 resume_offset= [SWSUSP] 2212 Specify the offset from the beginning of the partition 2213 given by "resume=" at which the swap header is located, 2214 in <PAGE_SIZE> units (needed only for swap files). 2215 See Documentation/power/swsusp-and-swap-files.txt 2216 2217 hibernate= [HIBERNATION] 2218 noresume Don't check if there's a hibernation image 2219 present during boot. 2220 nocompress Don't compress/decompress hibernation images. 2221 2222 retain_initrd [RAM] Keep initrd memory after extraction 2223 2224 rhash_entries= [KNL,NET] 2225 Set number of hash buckets for route cache 2226 2227 riscom8= [HW,SERIAL] 2228 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 2229 2230 ro [KNL] Mount root device read-only on boot 2231 2232 root= [KNL] Root filesystem 2233 2234 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 2235 mount the root filesystem 2236 2237 rootflags= [KNL] Set root filesystem mount option string 2238 2239 rootfstype= [KNL] Set root filesystem type 2240 2241 rootwait [KNL] Wait (indefinitely) for root device to show up. 2242 Useful for devices that are detected asynchronously 2243 (e.g. USB and MMC devices). 2244 2245 rw [KNL] Mount root device read-write on boot 2246 2247 S [KNL] Run init in single mode 2248 2249 sa1100ir [NET] 2250 See drivers/net/irda/sa1100_ir.c. 2251 2252 sbni= [NET] Granch SBNI12 leased line adapter 2253 2254 sched_debug [KNL] Enables verbose scheduler debug messages. 2255 2256 security= [SECURITY] Choose a security module to enable at boot. 2257 If this boot parameter is not specified, only the first 2258 security module asking for security registration will be 2259 loaded. An invalid security module name will be treated 2260 as if no module has been chosen. 2261 2262 selinux= [SELINUX] Disable or enable SELinux at boot time. 2263 Format: { "0" | "1" } 2264 See security/selinux/Kconfig help text. 2265 0 -- disable. 2266 1 -- enable. 2267 Default value is set via kernel config option. 2268 If enabled at boot time, /selinux/disable can be used 2269 later to disable prior to initial policy load. 2270 2271 apparmor= [APPARMOR] Disable or enable AppArmor at boot time 2272 Format: { "0" | "1" } 2273 See security/apparmor/Kconfig help text 2274 0 -- disable. 2275 1 -- enable. 2276 Default value is set via kernel config option. 2277 2278 serialnumber [BUGS=X86-32] 2279 2280 shapers= [NET] 2281 Maximal number of shapers. 2282 2283 show_msr= [x86] show boot-time MSR settings 2284 Format: { <integer> } 2285 Show boot-time (BIOS-initialized) MSR settings. 2286 The parameter means the number of CPUs to show, 2287 for example 1 means boot CPU only. 2288 2289 simeth= [IA-64] 2290 simscsi= 2291 2292 slram= [HW,MTD] 2293 2294 slub_debug[=options[,slabs]] [MM, SLUB] 2295 Enabling slub_debug allows one to determine the 2296 culprit if slab objects become corrupted. Enabling 2297 slub_debug can create guard zones around objects and 2298 may poison objects when not in use. Also tracks the 2299 last alloc / free. For more information see 2300 Documentation/vm/slub.txt. 2301 2302 slub_max_order= [MM, SLUB] 2303 Determines the maximum allowed order for slabs. 2304 A high setting may cause OOMs due to memory 2305 fragmentation. For more information see 2306 Documentation/vm/slub.txt. 2307 2308 slub_min_objects= [MM, SLUB] 2309 The minimum number of objects per slab. SLUB will 2310 increase the slab order up to slub_max_order to 2311 generate a sufficiently large slab able to contain 2312 the number of objects indicated. The higher the number 2313 of objects the smaller the overhead of tracking slabs 2314 and the less frequently locks need to be acquired. 2315 For more information see Documentation/vm/slub.txt. 2316 2317 slub_min_order= [MM, SLUB] 2318 Determines the mininum page order for slabs. Must be 2319 lower than slub_max_order. 2320 For more information see Documentation/vm/slub.txt. 2321 2322 slub_nomerge [MM, SLUB] 2323 Disable merging of slabs with similar size. May be 2324 necessary if there is some reason to distinguish 2325 allocs to different slabs. Debug options disable 2326 merging on their own. 2327 For more information see Documentation/vm/slub.txt. 2328 2329 smart2= [HW] 2330 Format: <io1>[,<io2>[,...,<io8>]] 2331 2332 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2333 attempt to substitute SMP alternatives once at boot. 2334 2335 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2336 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2337 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2338 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2339 smsc-ircc2.ircc_irq= [HW] IRQ line 2340 smsc-ircc2.ircc_dma= [HW] DMA channel 2341 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2342 0: Toshiba Satellite 1800 (GP data pin select) 2343 1: Fast pin select (default) 2344 2: ATC IRMode 2345 2346 softlockup_panic= 2347 [KNL] Should the soft-lockup detector generate panics. 2348 Format: <integer> 2349 2350 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2351 See Documentation/sonypi.txt 2352 2353 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2354 See Documentation/serial/specialix.txt. 2355 2356 spia_io_base= [HW,MTD] 2357 spia_fio_base= 2358 spia_pedr= 2359 spia_peddr= 2360 2361 stacktrace [FTRACE] 2362 Enabled the stack tracer on boot up. 2363 2364 sti= [PARISC,HW] 2365 Format: <num> 2366 Set the STI (builtin display/keyboard on the HP-PARISC 2367 machines) console (graphic card) which should be used 2368 as the initial boot-console. 2369 See also comment in drivers/video/console/sticore.c. 2370 2371 sti_font= [HW] 2372 See comment in drivers/video/console/sticore.c. 2373 2374 stifb= [HW] 2375 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2376 2377 sunrpc.min_resvport= 2378 sunrpc.max_resvport= 2379 [NFS,SUNRPC] 2380 SunRPC servers often require that client requests 2381 originate from a privileged port (i.e. a port in the 2382 range 0 < portnr < 1024). 2383 An administrator who wishes to reserve some of these 2384 ports for other uses may adjust the range that the 2385 kernel's sunrpc client considers to be privileged 2386 using these two parameters to set the minimum and 2387 maximum port values. 2388 2389 sunrpc.pool_mode= 2390 [NFS] 2391 Control how the NFS server code allocates CPUs to 2392 service thread pools. Depending on how many NICs 2393 you have and where their interrupts are bound, this 2394 option will affect which CPUs will do NFS serving. 2395 Note: this parameter cannot be changed while the 2396 NFS server is running. 2397 2398 auto the server chooses an appropriate mode 2399 automatically using heuristics 2400 global a single global pool contains all CPUs 2401 percpu one pool for each CPU 2402 pernode one pool for each NUMA node (equivalent 2403 to global on non-NUMA machines) 2404 2405 sunrpc.tcp_slot_table_entries= 2406 sunrpc.udp_slot_table_entries= 2407 [NFS,SUNRPC] 2408 Sets the upper limit on the number of simultaneous 2409 RPC calls that can be sent from the client to a 2410 server. Increasing these values may allow you to 2411 improve throughput, but will also increase the 2412 amount of memory reserved for use by the client. 2413 2414 swapaccount[=0|1] 2415 [KNL] Enable accounting of swap in memory resource 2416 controller if no parameter or 1 is given or disable 2417 it if 0 is given (See Documentation/cgroups/memory.txt) 2418 2419 swiotlb= [IA-64] Number of I/O TLB slabs 2420 2421 switches= [HW,M68k] 2422 2423 sysfs.deprecated=0|1 [KNL] 2424 Enable/disable old style sysfs layout for old udev 2425 on older distributions. When this option is enabled 2426 very new udev will not work anymore. When this option 2427 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) 2428 in older udev will not work anymore. 2429 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in 2430 the kernel configuration. 2431 2432 sysrq_always_enabled 2433 [KNL] 2434 Ignore sysrq setting - this boot parameter will 2435 neutralize any effect of /proc/sys/kernel/sysrq. 2436 Useful for debugging. 2437 2438 tdfx= [HW,DRM] 2439 2440 test_suspend= [SUSPEND] 2441 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2442 standby suspend) as the system sleep state to briefly 2443 enter during system startup. The system is woken from 2444 this state using a wakeup-capable RTC alarm. 2445 2446 thash_entries= [KNL,NET] 2447 Set number of hash buckets for TCP connection 2448 2449 thermal.act= [HW,ACPI] 2450 -1: disable all active trip points in all thermal zones 2451 <degrees C>: override all lowest active trip points 2452 2453 thermal.crt= [HW,ACPI] 2454 -1: disable all critical trip points in all thermal zones 2455 <degrees C>: override all critical trip points 2456 2457 thermal.nocrt= [HW,ACPI] 2458 Set to disable actions on ACPI thermal zone 2459 critical and hot trip points. 2460 2461 thermal.off= [HW,ACPI] 2462 1: disable ACPI thermal control 2463 2464 thermal.psv= [HW,ACPI] 2465 -1: disable all passive trip points 2466 <degrees C>: override all passive trip points to this 2467 value 2468 2469 thermal.tzp= [HW,ACPI] 2470 Specify global default ACPI thermal zone polling rate 2471 <deci-seconds>: poll all this frequency 2472 0: no polling (default) 2473 2474 threadirqs [KNL] 2475 Force threading of all interrupt handlers except those 2476 marked explicitely IRQF_NO_THREAD. 2477 2478 topology= [S390] 2479 Format: {off | on} 2480 Specify if the kernel should make use of the cpu 2481 topology information if the hardware supports this. 2482 The scheduler will make use of this information and 2483 e.g. base its process migration decisions on it. 2484 Default is on. 2485 2486 tp720= [HW,PS2] 2487 2488 tpm_suspend_pcr=[HW,TPM] 2489 Format: integer pcr id 2490 Specify that at suspend time, the tpm driver 2491 should extend the specified pcr with zeros, 2492 as a workaround for some chips which fail to 2493 flush the last written pcr on TPM_SaveState. 2494 This will guarantee that all the other pcrs 2495 are saved. 2496 2497 trace_buf_size=nn[KMG] 2498 [FTRACE] will set tracing buffer size. 2499 2500 trace_event=[event-list] 2501 [FTRACE] Set and start specified trace events in order 2502 to facilitate early boot debugging. 2503 See also Documentation/trace/events.txt 2504 2505 tsc= Disable clocksource stability checks for TSC. 2506 Format: <string> 2507 [x86] reliable: mark tsc clocksource as reliable, this 2508 disables clocksource verification at runtime, as well 2509 as the stability checks done at bootup. Used to enable 2510 high-resolution timer mode on older hardware, and in 2511 virtualized environment. 2512 [x86] noirqtime: Do not use TSC to do irq accounting. 2513 Used to run time disable IRQ_TIME_ACCOUNTING on any 2514 platforms where RDTSC is slow and this accounting 2515 can add overhead. 2516 2517 turbografx.map[2|3]= [HW,JOY] 2518 TurboGraFX parallel port interface 2519 Format: 2520 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2521 See also Documentation/input/joystick-parport.txt 2522 2523 uhash_entries= [KNL,NET] 2524 Set number of hash buckets for UDP/UDP-Lite connections 2525 2526 uhci-hcd.ignore_oc= 2527 [USB] Ignore overcurrent events (default N). 2528 Some badly-designed motherboards generate lots of 2529 bogus events, for ports that aren't wired to 2530 anything. Set this parameter to avoid log spamming. 2531 Note that genuine overcurrent events won't be 2532 reported either. 2533 2534 unknown_nmi_panic 2535 [X86] Cause panic on unknown NMI. 2536 2537 usbcore.autosuspend= 2538 [USB] The autosuspend time delay (in seconds) used 2539 for newly-detected USB devices (default 2). This 2540 is the time required before an idle device will be 2541 autosuspended. Devices for which the delay is set 2542 to a negative value won't be autosuspended at all. 2543 2544 usbcore.usbfs_snoop= 2545 [USB] Set to log all usbfs traffic (default 0 = off). 2546 2547 usbcore.blinkenlights= 2548 [USB] Set to cycle leds on hubs (default 0 = off). 2549 2550 usbcore.old_scheme_first= 2551 [USB] Start with the old device initialization 2552 scheme (default 0 = off). 2553 2554 usbcore.use_both_schemes= 2555 [USB] Try the other device initialization scheme 2556 if the first one fails (default 1 = enabled). 2557 2558 usbcore.initial_descriptor_timeout= 2559 [USB] Specifies timeout for the initial 64-byte 2560 USB_REQ_GET_DESCRIPTOR request in milliseconds 2561 (default 5000 = 5.0 seconds). 2562 2563 usbhid.mousepoll= 2564 [USBHID] The interval which mice are to be polled at. 2565 2566 usb-storage.delay_use= 2567 [UMS] The delay in seconds before a new device is 2568 scanned for Logical Units (default 5). 2569 2570 usb-storage.quirks= 2571 [UMS] A list of quirks entries to supplement or 2572 override the built-in unusual_devs list. List 2573 entries are separated by commas. Each entry has 2574 the form VID:PID:Flags where VID and PID are Vendor 2575 and Product ID values (4-digit hex numbers) and 2576 Flags is a set of characters, each corresponding 2577 to a common usb-storage quirk flag as follows: 2578 a = SANE_SENSE (collect more than 18 bytes 2579 of sense data); 2580 b = BAD_SENSE (don't collect more than 18 2581 bytes of sense data); 2582 c = FIX_CAPACITY (decrease the reported 2583 device capacity by one sector); 2584 h = CAPACITY_HEURISTICS (decrease the 2585 reported device capacity by one 2586 sector if the number is odd); 2587 i = IGNORE_DEVICE (don't bind to this 2588 device); 2589 l = NOT_LOCKABLE (don't try to lock and 2590 unlock ejectable media); 2591 m = MAX_SECTORS_64 (don't transfer more 2592 than 64 sectors = 32 KB at a time); 2593 o = CAPACITY_OK (accept the capacity 2594 reported by the device); 2595 r = IGNORE_RESIDUE (the device reports 2596 bogus residue values); 2597 s = SINGLE_LUN (the device has only one 2598 Logical Unit); 2599 w = NO_WP_DETECT (don't test whether the 2600 medium is write-protected). 2601 Example: quirks=0419:aaf5:rl,0421:0433:rc 2602 2603 userpte= 2604 [X86] Flags controlling user PTE allocations. 2605 2606 nohigh = do not allocate PTE pages in 2607 HIGHMEM regardless of setting 2608 of CONFIG_HIGHPTE. 2609 2610 vdso= [X86,SH] 2611 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2612 vdso=1: enable VDSO (default) 2613 vdso=0: disable VDSO mapping 2614 2615 vdso32= [X86] 2616 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2617 vdso32=1: enable 32-bit VDSO (default) 2618 vdso32=0: disable 32-bit VDSO mapping 2619 2620 vector= [IA-64,SMP] 2621 vector=percpu: enable percpu vector domain 2622 2623 video= [FB] Frame buffer configuration 2624 See Documentation/fb/modedb.txt. 2625 2626 vga= [BOOT,X86-32] Select a particular video mode 2627 See Documentation/x86/boot.txt and 2628 Documentation/svga.txt. 2629 Use vga=ask for menu. 2630 This is actually a boot loader parameter; the value is 2631 passed to the kernel using a special protocol. 2632 2633 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2634 size of <nn>. This can be used to increase the 2635 minimum size (128MB on x86). It can also be used to 2636 decrease the size and leave more room for directly 2637 mapped kernel RAM. 2638 2639 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2640 Format: <command> 2641 2642 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2643 Format: <command> 2644 2645 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2646 Format: <command> 2647 2648 vt.cur_default= [VT] Default cursor shape. 2649 Format: 0xCCBBAA, where AA, BB, and CC are the same as 2650 the parameters of the <Esc>[?A;B;Cc escape sequence; 2651 see VGA-softcursor.txt. Default: 2 = underline. 2652 2653 vt.default_blu= [VT] 2654 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 2655 Change the default blue palette of the console. 2656 This is a 16-member array composed of values 2657 ranging from 0-255. 2658 2659 vt.default_grn= [VT] 2660 Format: <green0>,<green1>,<green2>,...,<green15> 2661 Change the default green palette of the console. 2662 This is a 16-member array composed of values 2663 ranging from 0-255. 2664 2665 vt.default_red= [VT] 2666 Format: <red0>,<red1>,<red2>,...,<red15> 2667 Change the default red palette of the console. 2668 This is a 16-member array composed of values 2669 ranging from 0-255. 2670 2671 vt.default_utf8= 2672 [VT] 2673 Format=<0|1> 2674 Set system-wide default UTF-8 mode for all tty's. 2675 Default is 1, i.e. UTF-8 mode is enabled for all 2676 newly opened terminals. 2677 2678 vt.global_cursor_default= 2679 [VT] 2680 Format=<-1|0|1> 2681 Set system-wide default for whether a cursor 2682 is shown on new VTs. Default is -1, 2683 i.e. cursors will be created by default unless 2684 overridden by individual drivers. 0 will hide 2685 cursors, 1 will display them. 2686 2687 watchdog timers [HW,WDT] For information on watchdog timers, 2688 see Documentation/watchdog/watchdog-parameters.txt 2689 or other driver-specific files in the 2690 Documentation/watchdog/ directory. 2691 2692 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 2693 default x2apic cluster mode on platforms 2694 supporting x2apic. 2695 2696 x86_mrst_timer= [X86-32,APBT] 2697 Choose timer option for x86 Moorestown MID platform. 2698 Two valid options are apbt timer only and lapic timer 2699 plus one apbt timer for broadcast timer. 2700 x86_mrst_timer=apbt_only | lapic_and_apbt 2701 2702 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2703 xd_geo= See header of drivers/block/xd.c. 2704 2705 xen_emul_unplug= [HW,X86,XEN] 2706 Unplug Xen emulated devices 2707 Format: [unplug0,][unplug1] 2708 ide-disks -- unplug primary master IDE devices 2709 aux-ide-disks -- unplug non-primary-master IDE devices 2710 nics -- unplug network devices 2711 all -- unplug all emulated devices (NICs and IDE disks) 2712 unnecessary -- unplugging emulated devices is 2713 unnecessary even if the host did not respond to 2714 the unplug protocol 2715 never -- do not unplug even if version check succeeds 2716 2717 xirc2ps_cs= [NET,PCMCIA] 2718 Format: 2719 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2720 2721______________________________________________________________________ 2722 2723TODO: 2724 2725 Add more DRM drivers.