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menu "Code maturity level options"
bool "Prompt for development and/or incomplete code/drivers"
Some of the various things that Linux supports (such as network
drivers, file systems, network protocols, etc.) can be in a state
of development where the functionality, stability, or the level of
testing is not yet high enough for general use. This is usually
known as the "alpha-test" phase among developers. If a feature is
currently in alpha-test, then the developers usually discourage
uninformed widespread use of this feature by the general public to
avoid "Why doesn't this work?" type mail messages. However, active
testing and use of these systems is welcomed. Just be aware that it
may not meet the normal level of reliability or it may fail to work
in some special cases. Detailed bug reports from people familiar
with the kernel internals are usually welcomed by the developers
(before submitting bug reports, please read the documents
<file:Documentation/BUG-HUNTING>, and
<file:Documentation/oops-tracing.txt> in the kernel source).
This option will also make obsoleted drivers available. These are
drivers that have been replaced by something else, and/or are
scheduled to be removed in a future kernel release.
Unless you intend to help test and develop a feature or driver that
falls into this category, or you have a situation that requires
using these features, you should probably say N here, which will
cause the configurator to present you with fewer choices. If
you say Y here, you will be offered the choice of using features or
drivers that are currently considered to be in the alpha-test phase.
config BROKEN
depends on BROKEN || !SMP
default y
depends on SMP || PREEMPT
default y
default 32 if !USERMODE
default 128 if USERMODE
Maximum of each of the number of arguments and environment
variables passed to init from the kernel command line.
menu "General setup"
string "Local version - append to kernel release"
Append an extra string to the end of your kernel version.
This will show up when you type uname, for example.
The string you set here will be appended after the contents of
any files with a filename matching localversion* in your
object and source tree, in that order. Your total string can
be a maximum of 64 characters.
bool "Automatically append version information to the version string"
default y
This will try to automatically determine if the current tree is a
release tree by looking for git tags that
belong to the current top of tree revision.
A string of the format -gxxxxxxxx will be added to the localversion
if a git based tree is found. The string generated by this will be
appended after any matching localversion* files, and after the value
Note: This requires Perl, and a git repository, but not necessarily
the git or cogito tools to be installed.
config SWAP
bool "Support for paging of anonymous memory (swap)"
depends on MMU
default y
This option allows you to choose whether you want to have support
for so called swap devices or swap files in your kernel that are
used to provide more virtual memory than the actual RAM present
in your computer. If unsure say Y.
config SYSVIPC
bool "System V IPC"
Inter Process Communication is a suite of library functions and
system calls which let processes (running programs) synchronize and
exchange information. It is generally considered to be a good thing,
and some programs won't run unless you say Y here. In particular, if
you want to run the DOS emulator dosemu under Linux (read the
DOSEMU-HOWTO, available from <>),
you'll need to say Y here.
You can find documentation about IPC with "info ipc" and also in
section 6.4 of the Linux Programmer's Guide, available from
bool "POSIX Message Queues"
depends on NET && EXPERIMENTAL
POSIX variant of message queues is a part of IPC. In POSIX message
queues every message has a priority which decides about succession
of receiving it by a process. If you want to compile and run
programs written e.g. for Solaris with use of its POSIX message
queues (functions mq_*) say Y here. To use this feature you will
also need mqueue library, available from
POSIX message queues are visible as a filesystem called 'mqueue'
and can be mounted somewhere if you want to do filesystem
operations on message queues.
If unsure, say Y.
bool "BSD Process Accounting"
If you say Y here, a user level program will be able to instruct the
kernel (via a special system call) to write process accounting
information to a file: whenever a process exits, information about
that process will be appended to the file by the kernel. The
information includes things such as creation time, owning user,
command name, memory usage, controlling terminal etc. (the complete
list is in the struct acct in <file:include/linux/acct.h>). It is
up to the user level program to do useful things with this
information. This is generally a good idea, so say Y.
bool "BSD Process Accounting version 3 file format"
default n
If you say Y here, the process accounting information is written
in a new file format that also logs the process IDs of each
process and it's parent. Note that this file format is incompatible
with previous v0/v1/v2 file formats, so you will need updated tools
for processing it. A preliminary version of these tools is available
at <>.
config SYSCTL
bool "Sysctl support"
The sysctl interface provides a means of dynamically changing
certain kernel parameters and variables on the fly without requiring
a recompile of the kernel or reboot of the system. The primary
interface consists of a system call, but if you say Y to "/proc
file system support", a tree of modifiable sysctl entries will be
generated beneath the /proc/sys directory. They are explained in the
files in <file:Documentation/sysctl/>. Note that enabling this
option will enlarge the kernel by at least 8 KB.
As it is generally a good thing, you should say Y here unless
building a kernel for install/rescue disks or your system is very
limited in memory.
config AUDIT
bool "Auditing support"
depends on NET
Enable auditing infrastructure that can be used with another
kernel subsystem, such as SELinux (which requires this for
logging of avc messages output). Does not do system-call
auditing without CONFIG_AUDITSYSCALL.
bool "Enable system-call auditing support"
depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64)
Enable low-overhead system-call auditing infrastructure that
can be used independently or with another kernel subsystem,
such as SELinux.
bool "Kernel .config support"
This option enables the complete Linux kernel ".config" file
contents to be saved in the kernel. It provides documentation
of which kernel options are used in a running kernel or in an
on-disk kernel. This information can be extracted from the kernel
image file with the script scripts/extract-ikconfig and used as
input to rebuild the current kernel or to build another kernel.
It can also be extracted from a running kernel by reading
/proc/config.gz if enabled (below).
bool "Enable access to .config through /proc/config.gz"
depends on IKCONFIG && PROC_FS
This option enables access to the kernel configuration file
through /proc/config.gz.
config CPUSETS
bool "Cpuset support"
depends on SMP
This option will let you create and manage CPUSETs which
allow dynamically partitioning a system into sets of CPUs and
Memory Nodes and assigning tasks to run only within those sets.
This is primarily useful on large SMP or NUMA systems.
Say N if unsure.
config RELAY
bool "Kernel->user space relay support (formerly relayfs)"
This option enables support for relay interface support in
certain file systems (such as debugfs).
It is designed to provide an efficient mechanism for tools and
facilities to relay large amounts of data from kernel space to
user space.
If unsure, say N.
source "usr/Kconfig"
config UID16
bool "Enable 16-bit UID system calls" if EMBEDDED
depends on ARM || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
default y
This enables the legacy 16-bit UID syscall wrappers.
config VM86
depends X86
default y
bool "Enable VM86 support" if EMBEDDED
This option is required by programs like DOSEMU to run 16-bit legacy
code on X86 processors. It also may be needed by software like
XFree86 to initialize some video cards via BIOS. Disabling this
option saves about 6k.
bool "Optimize for size (Look out for broken compilers!)"
default y
depends on ARM || H8300 || EXPERIMENTAL
Enabling this option will pass "-Os" instead of "-O2" to gcc
resulting in a smaller kernel.
WARNING: some versions of gcc may generate incorrect code with this
option. If problems are observed, a gcc upgrade may be needed.
If unsure, say N.
menuconfig EMBEDDED
bool "Configure standard kernel features (for small systems)"
This option allows certain base kernel options and settings
to be disabled or tweaked. This is for specialized
environments which can tolerate a "non-standard" kernel.
Only use this if you really know what you are doing.
bool "Load all symbols for debugging/kksymoops" if EMBEDDED
default y
Say Y here to let the kernel print out symbolic crash information and
symbolic stack backtraces. This increases the size of the kernel
somewhat, as all symbols have to be loaded into the kernel image.
bool "Include all symbols in kallsyms"
Normally kallsyms only contains the symbols of functions, for nicer
OOPS messages. Some debuggers can use kallsyms for other
symbols too: say Y here to include all symbols, if you need them
and you don't care about adding 300k to the size of your kernel.
Say N.
bool "Do an extra kallsyms pass"
depends on KALLSYMS
If kallsyms is not working correctly, the build will fail with
inconsistent kallsyms data. If that occurs, log a bug report and
turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
Always say N here unless you find a bug in kallsyms, which must be
reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
you wait for kallsyms to be fixed.
config HOTPLUG
bool "Support for hot-pluggable devices" if EMBEDDED
default y
This option is provided for the case where no hotplug or uevent
capabilities is wanted by the kernel. You should only consider
disabling this option for embedded systems that do not use modules, a
dynamic /dev tree, or dynamic device discovery. Just say Y.
config PRINTK
default y
bool "Enable support for printk" if EMBEDDED
This option enables normal printk support. Removing it
eliminates most of the message strings from the kernel image
and makes the kernel more or less silent. As this makes it
very difficult to diagnose system problems, saying N here is
strongly discouraged.
config BUG
bool "BUG() support" if EMBEDDED
default y
Disabling this option eliminates support for BUG and WARN, reducing
the size of your kernel image and potentially quietly ignoring
numerous fatal conditions. You should only consider disabling this
option for embedded systems with no facilities for reporting errors.
Just say Y.
config ELF_CORE
default y
bool "Enable ELF core dumps" if EMBEDDED
Enable support for generating core dumps. Disabling saves about 4k.
config BASE_FULL
default y
bool "Enable full-sized data structures for core" if EMBEDDED
Disabling this option reduces the size of miscellaneous core
kernel data structures. This saves memory on small machines,
but may reduce performance.
config FUTEX
bool "Enable futex support" if EMBEDDED
default y
Disabling this option will cause the kernel to be built without
support for "fast userspace mutexes". The resulting kernel may not
run glibc-based applications correctly.
config EPOLL
bool "Enable eventpoll support" if EMBEDDED
default y
Disabling this option will cause the kernel to be built without
support for epoll family of system calls.
config SHMEM
bool "Use full shmem filesystem" if EMBEDDED
default y
depends on MMU
The shmem is an internal filesystem used to manage shared memory.
It is backed by swap and manages resource limits. It is also exported
to userspace as tmpfs if TMPFS is enabled. Disabling this
option replaces shmem and tmpfs with the much simpler ramfs code,
which may be appropriate on small systems without swap.
config SLAB
default y
bool "Use full SLAB allocator" if EMBEDDED
Disabling this replaces the advanced SLAB allocator and
kmalloc support with the drastically simpler SLOB allocator.
SLOB is more space efficient but does not scale well and is
more susceptible to fragmentation.
endmenu # General setup
default !SHMEM
default 0 if BASE_FULL
default 1 if !BASE_FULL
config SLOB
default !SLAB
menu "Loadable module support"
config MODULES
bool "Enable loadable module support"
Kernel modules are small pieces of compiled code which can
be inserted in the running kernel, rather than being
permanently built into the kernel. You use the "modprobe"
tool to add (and sometimes remove) them. If you say Y here,
many parts of the kernel can be built as modules (by
answering M instead of Y where indicated): this is most
useful for infrequently used options which are not required
for booting. For more information, see the man pages for
modprobe, lsmod, modinfo, insmod and rmmod.
If you say Y here, you will need to run "make
modules_install" to put the modules under /lib/modules/
where modprobe can find them (you may need to be root to do
If unsure, say Y.
bool "Module unloading"
depends on MODULES
Without this option you will not be able to unload any
modules (note that some modules may not be unloadable
anyway), which makes your kernel slightly smaller and
simpler. If unsure, say Y.
bool "Forced module unloading"
This option allows you to force a module to unload, even if the
kernel believes it is unsafe: the kernel will remove the module
without waiting for anyone to stop using it (using the -f option to
rmmod). This is mainly for kernel developers and desperate users.
If unsure, say N.
bool "Module versioning support"
depends on MODULES
Usually, you have to use modules compiled with your kernel.
Saying Y here makes it sometimes possible to use modules
compiled for different kernels, by adding enough information
to the modules to (hopefully) spot any changes which would
make them incompatible with the kernel you are running. If
unsure, say N.
bool "Source checksum for all modules"
depends on MODULES
Modules which contain a MODULE_VERSION get an extra "srcversion"
field inserted into their modinfo section, which contains a
sum of the source files which made it. This helps maintainers
see exactly which source was used to build a module (since
others sometimes change the module source without updating
the version). With this option, such a "srcversion" field
will be created for all modules. If unsure, say N.
config KMOD
bool "Automatic kernel module loading"
depends on MODULES
Normally when you have selected some parts of the kernel to
be created as kernel modules, you must load them (using the
"modprobe" command) before you can use them. If you say Y
here, some parts of the kernel will be able to load modules
automatically: when a part of the kernel needs a module, it
runs modprobe with the appropriate arguments, thereby
loading the module if it is available. If unsure, say Y.
default y
Need stop_machine() primitive.
menu "Block layer"
source "block/Kconfig"