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1 config DEFCONFIG_LIST
2 string
3 depends on !UML
4 option defconfig_list
5 default "/lib/modules/$UNAME_RELEASE/.config"
6 default "/etc/kernel-config"
7 default "/boot/config-$UNAME_RELEASE"
8 default "arch/$ARCH/defconfig"
10 menu "Code maturity level options"
12 config EXPERIMENTAL
13 bool "Prompt for development and/or incomplete code/drivers"
14 ---help---
15 Some of the various things that Linux supports (such as network
16 drivers, file systems, network protocols, etc.) can be in a state
17 of development where the functionality, stability, or the level of
18 testing is not yet high enough for general use. This is usually
19 known as the "alpha-test" phase among developers. If a feature is
20 currently in alpha-test, then the developers usually discourage
21 uninformed widespread use of this feature by the general public to
22 avoid "Why doesn't this work?" type mail messages. However, active
23 testing and use of these systems is welcomed. Just be aware that it
24 may not meet the normal level of reliability or it may fail to work
25 in some special cases. Detailed bug reports from people familiar
26 with the kernel internals are usually welcomed by the developers
27 (before submitting bug reports, please read the documents
28 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
29 <file:Documentation/BUG-HUNTING>, and
30 <file:Documentation/oops-tracing.txt> in the kernel source).
32 This option will also make obsoleted drivers available. These are
33 drivers that have been replaced by something else, and/or are
34 scheduled to be removed in a future kernel release.
36 Unless you intend to help test and develop a feature or driver that
37 falls into this category, or you have a situation that requires
38 using these features, you should probably say N here, which will
39 cause the configurator to present you with fewer choices. If
40 you say Y here, you will be offered the choice of using features or
41 drivers that are currently considered to be in the alpha-test phase.
43 config BROKEN
44 bool
46 config BROKEN_ON_SMP
47 bool
48 depends on BROKEN || !SMP
49 default y
51 config LOCK_KERNEL
52 bool
53 depends on SMP || PREEMPT
54 default y
56 config INIT_ENV_ARG_LIMIT
57 int
58 default 32 if !UML
59 default 128 if UML
60 help
61 Maximum of each of the number of arguments and environment
62 variables passed to init from the kernel command line.
64 endmenu
66 menu "General setup"
68 config LOCALVERSION
69 string "Local version - append to kernel release"
70 help
71 Append an extra string to the end of your kernel version.
72 This will show up when you type uname, for example.
73 The string you set here will be appended after the contents of
74 any files with a filename matching localversion* in your
75 object and source tree, in that order. Your total string can
76 be a maximum of 64 characters.
78 config LOCALVERSION_AUTO
79 bool "Automatically append version information to the version string"
80 default y
81 help
82 This will try to automatically determine if the current tree is a
83 release tree by looking for git tags that belong to the current
84 top of tree revision.
86 A string of the format -gxxxxxxxx will be added to the localversion
87 if a git-based tree is found. The string generated by this will be
88 appended after any matching localversion* files, and after the value
89 set in CONFIG_LOCALVERSION.
91 (The actual string used here is the first eight characters produced
92 by running the command:
94 $ git rev-parse --verify HEAD
96 which is done within the script "scripts/setlocalversion".)
98 config SWAP
99 bool "Support for paging of anonymous memory (swap)"
100 depends on MMU && BLOCK
101 default y
102 help
103 This option allows you to choose whether you want to have support
104 for so called swap devices or swap files in your kernel that are
105 used to provide more virtual memory than the actual RAM present
106 in your computer. If unsure say Y.
108 config SYSVIPC
109 bool "System V IPC"
110 ---help---
111 Inter Process Communication is a suite of library functions and
112 system calls which let processes (running programs) synchronize and
113 exchange information. It is generally considered to be a good thing,
114 and some programs won't run unless you say Y here. In particular, if
115 you want to run the DOS emulator dosemu under Linux (read the
116 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
117 you'll need to say Y here.
119 You can find documentation about IPC with "info ipc" and also in
120 section 6.4 of the Linux Programmer's Guide, available from
121 <http://www.tldp.org/guides.html>.
123 config IPC_NS
124 bool "IPC Namespaces"
125 depends on SYSVIPC
126 default n
127 help
128 Support ipc namespaces. This allows containers, i.e. virtual
129 environments, to use ipc namespaces to provide different ipc
130 objects for different servers. If unsure, say N.
132 config SYSVIPC_SYSCTL
133 bool
134 depends on SYSVIPC
135 depends on SYSCTL
136 default y
138 config POSIX_MQUEUE
139 bool "POSIX Message Queues"
140 depends on NET && EXPERIMENTAL
141 ---help---
142 POSIX variant of message queues is a part of IPC. In POSIX message
143 queues every message has a priority which decides about succession
144 of receiving it by a process. If you want to compile and run
145 programs written e.g. for Solaris with use of its POSIX message
146 queues (functions mq_*) say Y here.
148 POSIX message queues are visible as a filesystem called 'mqueue'
149 and can be mounted somewhere if you want to do filesystem
150 operations on message queues.
152 If unsure, say Y.
154 config BSD_PROCESS_ACCT
155 bool "BSD Process Accounting"
156 help
157 If you say Y here, a user level program will be able to instruct the
158 kernel (via a special system call) to write process accounting
159 information to a file: whenever a process exits, information about
160 that process will be appended to the file by the kernel. The
161 information includes things such as creation time, owning user,
162 command name, memory usage, controlling terminal etc. (the complete
163 list is in the struct acct in <file:include/linux/acct.h>). It is
164 up to the user level program to do useful things with this
165 information. This is generally a good idea, so say Y.
167 config BSD_PROCESS_ACCT_V3
168 bool "BSD Process Accounting version 3 file format"
169 depends on BSD_PROCESS_ACCT
170 default n
171 help
172 If you say Y here, the process accounting information is written
173 in a new file format that also logs the process IDs of each
174 process and it's parent. Note that this file format is incompatible
175 with previous v0/v1/v2 file formats, so you will need updated tools
176 for processing it. A preliminary version of these tools is available
177 at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
179 config TASKSTATS
180 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
181 depends on NET
182 default n
183 help
184 Export selected statistics for tasks/processes through the
185 generic netlink interface. Unlike BSD process accounting, the
186 statistics are available during the lifetime of tasks/processes as
187 responses to commands. Like BSD accounting, they are sent to user
188 space on task exit.
190 Say N if unsure.
192 config TASK_DELAY_ACCT
193 bool "Enable per-task delay accounting (EXPERIMENTAL)"
194 depends on TASKSTATS
195 help
196 Collect information on time spent by a task waiting for system
197 resources like cpu, synchronous block I/O completion and swapping
198 in pages. Such statistics can help in setting a task's priorities
199 relative to other tasks for cpu, io, rss limits etc.
201 Say N if unsure.
203 config TASK_XACCT
204 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
205 depends on TASKSTATS
206 help
207 Collect extended task accounting data and send the data
208 to userland for processing over the taskstats interface.
210 Say N if unsure.
212 config TASK_IO_ACCOUNTING
213 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
214 depends on TASK_XACCT
215 help
216 Collect information on the number of bytes of storage I/O which this
217 task has caused.
219 Say N if unsure.
221 config UTS_NS
222 bool "UTS Namespaces"
223 default n
224 help
225 Support uts namespaces. This allows containers, i.e.
226 vservers, to use uts namespaces to provide different
227 uts info for different servers. If unsure, say N.
229 config AUDIT
230 bool "Auditing support"
231 depends on NET
232 help
233 Enable auditing infrastructure that can be used with another
234 kernel subsystem, such as SELinux (which requires this for
235 logging of avc messages output). Does not do system-call
236 auditing without CONFIG_AUDITSYSCALL.
238 config AUDITSYSCALL
239 bool "Enable system-call auditing support"
240 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64)
241 default y if SECURITY_SELINUX
242 help
243 Enable low-overhead system-call auditing infrastructure that
244 can be used independently or with another kernel subsystem,
245 such as SELinux. To use audit's filesystem watch feature, please
246 ensure that INOTIFY is configured.
248 config IKCONFIG
249 tristate "Kernel .config support"
250 ---help---
251 This option enables the complete Linux kernel ".config" file
252 contents to be saved in the kernel. It provides documentation
253 of which kernel options are used in a running kernel or in an
254 on-disk kernel. This information can be extracted from the kernel
255 image file with the script scripts/extract-ikconfig and used as
256 input to rebuild the current kernel or to build another kernel.
257 It can also be extracted from a running kernel by reading
258 /proc/config.gz if enabled (below).
260 config IKCONFIG_PROC
261 bool "Enable access to .config through /proc/config.gz"
262 depends on IKCONFIG && PROC_FS
263 ---help---
264 This option enables access to the kernel configuration file
265 through /proc/config.gz.
267 config LOG_BUF_SHIFT
268 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
269 range 12 21
270 default 17 if S390 || LOCKDEP
271 default 16 if X86_NUMAQ || IA64
272 default 15 if SMP
273 default 14
274 help
275 Select kernel log buffer size as a power of 2.
276 Defaults and Examples:
277 17 => 128 KB for S/390
278 16 => 64 KB for x86 NUMAQ or IA-64
279 15 => 32 KB for SMP
280 14 => 16 KB for uniprocessor
281 13 => 8 KB
282 12 => 4 KB
284 config CPUSETS
285 bool "Cpuset support"
286 depends on SMP
287 help
288 This option will let you create and manage CPUSETs which
289 allow dynamically partitioning a system into sets of CPUs and
290 Memory Nodes and assigning tasks to run only within those sets.
291 This is primarily useful on large SMP or NUMA systems.
293 Say N if unsure.
295 config SYSFS_DEPRECATED
296 bool "Create deprecated sysfs files"
297 default y
298 help
299 This option creates deprecated symlinks such as the
300 "device"-link, the <subsystem>:<name>-link, and the
301 "bus"-link. It may also add deprecated key in the
302 uevent environment.
303 None of these features or values should be used today, as
304 they export driver core implementation details to userspace
305 or export properties which can't be kept stable across kernel
306 releases.
308 If enabled, this option will also move any device structures
309 that belong to a class, back into the /sys/class hierarchy, in
310 order to support older versions of udev.
312 If you are using a distro that was released in 2006 or later,
313 it should be safe to say N here.
315 config RELAY
316 bool "Kernel->user space relay support (formerly relayfs)"
317 help
318 This option enables support for relay interface support in
319 certain file systems (such as debugfs).
320 It is designed to provide an efficient mechanism for tools and
321 facilities to relay large amounts of data from kernel space to
322 user space.
324 If unsure, say N.
326 config BLK_DEV_INITRD
327 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
328 depends on BROKEN || !FRV
329 help
330 The initial RAM filesystem is a ramfs which is loaded by the
331 boot loader (loadlin or lilo) and that is mounted as root
332 before the normal boot procedure. It is typically used to
333 load modules needed to mount the "real" root file system,
334 etc. See <file:Documentation/initrd.txt> for details.
336 If RAM disk support (BLK_DEV_RAM) is also included, this
337 also enables initial RAM disk (initrd) support and adds
338 15 Kbytes (more on some other architectures) to the kernel size.
340 If unsure say Y.
342 if BLK_DEV_INITRD
344 source "usr/Kconfig"
346 endif
348 config CC_OPTIMIZE_FOR_SIZE
349 bool "Optimize for size (Look out for broken compilers!)"
350 default y
351 depends on ARM || H8300 || EXPERIMENTAL
352 help
353 Enabling this option will pass "-Os" instead of "-O2" to gcc
354 resulting in a smaller kernel.
356 WARNING: some versions of gcc may generate incorrect code with this
357 option. If problems are observed, a gcc upgrade may be needed.
359 If unsure, say N.
361 config SYSCTL
362 bool
364 menuconfig EMBEDDED
365 bool "Configure standard kernel features (for small systems)"
366 help
367 This option allows certain base kernel options and settings
368 to be disabled or tweaked. This is for specialized
369 environments which can tolerate a "non-standard" kernel.
370 Only use this if you really know what you are doing.
372 config UID16
373 bool "Enable 16-bit UID system calls" if EMBEDDED
374 depends on ARM || BFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
375 default y
376 help
377 This enables the legacy 16-bit UID syscall wrappers.
379 config SYSCTL_SYSCALL
380 bool "Sysctl syscall support" if EMBEDDED
381 default y
382 select SYSCTL
383 ---help---
384 sys_sysctl uses binary paths that have been found challenging
385 to properly maintain and use. The interface in /proc/sys
386 using paths with ascii names is now the primary path to this
387 information.
389 Almost nothing using the binary sysctl interface so if you are
390 trying to save some space it is probably safe to disable this,
391 making your kernel marginally smaller.
393 If unsure say Y here.
395 config KALLSYMS
396 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
397 default y
398 help
399 Say Y here to let the kernel print out symbolic crash information and
400 symbolic stack backtraces. This increases the size of the kernel
401 somewhat, as all symbols have to be loaded into the kernel image.
403 config KALLSYMS_ALL
404 bool "Include all symbols in kallsyms"
405 depends on DEBUG_KERNEL && KALLSYMS
406 help
407 Normally kallsyms only contains the symbols of functions, for nicer
408 OOPS messages. Some debuggers can use kallsyms for other
409 symbols too: say Y here to include all symbols, if you need them
410 and you don't care about adding 300k to the size of your kernel.
412 Say N.
414 config KALLSYMS_EXTRA_PASS
415 bool "Do an extra kallsyms pass"
416 depends on KALLSYMS
417 help
418 If kallsyms is not working correctly, the build will fail with
419 inconsistent kallsyms data. If that occurs, log a bug report and
420 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
421 Always say N here unless you find a bug in kallsyms, which must be
422 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
423 you wait for kallsyms to be fixed.
426 config HOTPLUG
427 bool "Support for hot-pluggable devices" if EMBEDDED
428 default y
429 help
430 This option is provided for the case where no hotplug or uevent
431 capabilities is wanted by the kernel. You should only consider
432 disabling this option for embedded systems that do not use modules, a
433 dynamic /dev tree, or dynamic device discovery. Just say Y.
435 config PRINTK
436 default y
437 bool "Enable support for printk" if EMBEDDED
438 help
439 This option enables normal printk support. Removing it
440 eliminates most of the message strings from the kernel image
441 and makes the kernel more or less silent. As this makes it
442 very difficult to diagnose system problems, saying N here is
443 strongly discouraged.
445 config BUG
446 bool "BUG() support" if EMBEDDED
447 default y
448 help
449 Disabling this option eliminates support for BUG and WARN, reducing
450 the size of your kernel image and potentially quietly ignoring
451 numerous fatal conditions. You should only consider disabling this
452 option for embedded systems with no facilities for reporting errors.
453 Just say Y.
455 config ELF_CORE
456 default y
457 bool "Enable ELF core dumps" if EMBEDDED
458 help
459 Enable support for generating core dumps. Disabling saves about 4k.
461 config BASE_FULL
462 default y
463 bool "Enable full-sized data structures for core" if EMBEDDED
464 help
465 Disabling this option reduces the size of miscellaneous core
466 kernel data structures. This saves memory on small machines,
467 but may reduce performance.
469 config FUTEX
470 bool "Enable futex support" if EMBEDDED
471 default y
472 select RT_MUTEXES
473 help
474 Disabling this option will cause the kernel to be built without
475 support for "fast userspace mutexes". The resulting kernel may not
476 run glibc-based applications correctly.
478 config ANON_INODES
479 bool "Enable anonymous inode source" if EMBEDDED
480 default y
481 help
482 Anonymous inode source for pseudo-files like epoll, signalfd,
483 timerfd and eventfd.
485 If unsure, say Y.
487 config EPOLL
488 bool "Enable eventpoll support" if EMBEDDED
489 default y
490 depends on ANON_INODES
491 help
492 Disabling this option will cause the kernel to be built without
493 support for epoll family of system calls.
495 config SIGNALFD
496 bool "Enable signalfd() system call" if EMBEDDED
497 depends on ANON_INODES
498 default y
499 help
500 Enable the signalfd() system call that allows to receive signals
501 on a file descriptor.
503 If unsure, say Y.
505 config TIMERFD
506 bool "Enable timerfd() system call" if EMBEDDED
507 depends on ANON_INODES
508 default y
509 help
510 Enable the timerfd() system call that allows to receive timer
511 events on a file descriptor.
513 If unsure, say Y.
515 config EVENTFD
516 bool "Enable eventfd() system call" if EMBEDDED
517 depends on ANON_INODES
518 default y
519 help
520 Enable the eventfd() system call that allows to receive both
521 kernel notification (ie. KAIO) or userspace notifications.
523 If unsure, say Y.
525 config SHMEM
526 bool "Use full shmem filesystem" if EMBEDDED
527 default y
528 depends on MMU
529 help
530 The shmem is an internal filesystem used to manage shared memory.
531 It is backed by swap and manages resource limits. It is also exported
532 to userspace as tmpfs if TMPFS is enabled. Disabling this
533 option replaces shmem and tmpfs with the much simpler ramfs code,
534 which may be appropriate on small systems without swap.
536 config VM_EVENT_COUNTERS
537 default y
538 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
539 help
540 VM event counters are needed for event counts to be shown.
541 This option allows the disabling of the VM event counters
542 on EMBEDDED systems. /proc/vmstat will only show page counts
543 if VM event counters are disabled.
545 config SLUB_DEBUG
546 default y
547 bool "Enable SLUB debugging support" if EMBEDDED
548 depends on SLUB
549 help
550 SLUB has extensive debug support features. Disabling these can
551 result in significant savings in code size. This also disables
552 SLUB sysfs support. /sys/slab will not exist and there will be
553 no support for cache validation etc.
555 choice
556 prompt "Choose SLAB allocator"
557 default SLAB
558 help
559 This option allows to select a slab allocator.
561 config SLAB
562 bool "SLAB"
563 help
564 The regular slab allocator that is established and known to work
565 well in all environments. It organizes cache hot objects in
566 per cpu and per node queues. SLAB is the default choice for
567 a slab allocator.
569 config SLUB
570 bool "SLUB (Unqueued Allocator)"
571 help
572 SLUB is a slab allocator that minimizes cache line usage
573 instead of managing queues of cached objects (SLAB approach).
574 Per cpu caching is realized using slabs of objects instead
575 of queues of objects. SLUB can use memory efficiently
576 and has enhanced diagnostics.
578 config SLOB
579 depends on EMBEDDED && !SPARSEMEM
580 bool "SLOB (Simple Allocator)"
581 help
582 SLOB replaces the SLAB allocator with a drastically simpler
583 allocator. SLOB is more space efficient than SLAB but does not
584 scale well (single lock for all operations) and is also highly
585 susceptible to fragmentation. SLUB can accomplish a higher object
586 density. It is usually better to use SLUB instead of SLOB.
588 endchoice
590 endmenu # General setup
592 config RT_MUTEXES
593 boolean
594 select PLIST
596 config TINY_SHMEM
597 default !SHMEM
598 bool
600 config BASE_SMALL
601 int
602 default 0 if BASE_FULL
603 default 1 if !BASE_FULL
605 menu "Loadable module support"
607 config MODULES
608 bool "Enable loadable module support"
609 help
610 Kernel modules are small pieces of compiled code which can
611 be inserted in the running kernel, rather than being
612 permanently built into the kernel. You use the "modprobe"
613 tool to add (and sometimes remove) them. If you say Y here,
614 many parts of the kernel can be built as modules (by
615 answering M instead of Y where indicated): this is most
616 useful for infrequently used options which are not required
617 for booting. For more information, see the man pages for
618 modprobe, lsmod, modinfo, insmod and rmmod.
620 If you say Y here, you will need to run "make
621 modules_install" to put the modules under /lib/modules/
622 where modprobe can find them (you may need to be root to do
623 this).
625 If unsure, say Y.
627 config MODULE_UNLOAD
628 bool "Module unloading"
629 depends on MODULES
630 help
631 Without this option you will not be able to unload any
632 modules (note that some modules may not be unloadable
633 anyway), which makes your kernel slightly smaller and
634 simpler. If unsure, say Y.
636 config MODULE_FORCE_UNLOAD
637 bool "Forced module unloading"
638 depends on MODULE_UNLOAD && EXPERIMENTAL
639 help
640 This option allows you to force a module to unload, even if the
641 kernel believes it is unsafe: the kernel will remove the module
642 without waiting for anyone to stop using it (using the -f option to
643 rmmod). This is mainly for kernel developers and desperate users.
644 If unsure, say N.
646 config MODVERSIONS
647 bool "Module versioning support"
648 depends on MODULES
649 help
650 Usually, you have to use modules compiled with your kernel.
651 Saying Y here makes it sometimes possible to use modules
652 compiled for different kernels, by adding enough information
653 to the modules to (hopefully) spot any changes which would
654 make them incompatible with the kernel you are running. If
655 unsure, say N.
657 config MODULE_SRCVERSION_ALL
658 bool "Source checksum for all modules"
659 depends on MODULES
660 help
661 Modules which contain a MODULE_VERSION get an extra "srcversion"
662 field inserted into their modinfo section, which contains a
663 sum of the source files which made it. This helps maintainers
664 see exactly which source was used to build a module (since
665 others sometimes change the module source without updating
666 the version). With this option, such a "srcversion" field
667 will be created for all modules. If unsure, say N.
669 config KMOD
670 bool "Automatic kernel module loading"
671 depends on MODULES
672 help
673 Normally when you have selected some parts of the kernel to
674 be created as kernel modules, you must load them (using the
675 "modprobe" command) before you can use them. If you say Y
676 here, some parts of the kernel will be able to load modules
677 automatically: when a part of the kernel needs a module, it
678 runs modprobe with the appropriate arguments, thereby
679 loading the module if it is available. If unsure, say Y.
681 config STOP_MACHINE
682 bool
683 default y
684 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
685 help
686 Need stop_machine() primitive.
687 endmenu
689 menu "Block layer"
690 source "block/Kconfig"
691 endmenu