User:ZyMOS/Howto configure the linux kernel/init

User:ZyMOS/Howto configure the linux kernel / init

Code maturity level options

 * Option: EXPERIMENTAL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 , , , , and  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 These are drivers that have been replaced by something else, and/or are scheduled to be removed in a future kernel release.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.


 * Option: CLEAN_COMPILE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Select only drivers expected to compile cleanly" if EXPERIMENTAL
 * default y
 * Select this option if you don't even want to see the option to configure known-broken drivers.
 * If unsure, say Y


 * Option: BROKEN
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * depends on !CLEAN_COMPILE
 * default y


 * Option: BROKEN_ON_SMP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * depends on BROKEN || !SMP
 * default y


 * Option: LOCK_KERNEL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * depends on SMP || PREEMPT
 * default y


 * Option: INIT_ENV_ARG_LIMIT
 * Kernel Versions: 2.6.15.6 ...


 * 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.

General setup
"Local version - append to kernel release"
 * Option: LOCALVERSION
 * Kernel Versions: 2.6.15.6 ...
 * 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.


 * Option: LOCALVERSION_AUTO
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 set in CONFIG_LOCALVERSION
 * Note: This requires Perl, and a git repository, but not necessarily the git or cogito tools to be installed.


 * Option: SWAP
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 socalled 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.


 * Option: SYSVIPC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "System V IPC"
 * depends on MMU
 * 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 .


 * Option: POSIX_MQUEUE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: BSD_PROCESS_ACCT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 ).  It is up to the user level program to do useful things with this information.  This is generally a good idea, so say Y.


 * Option: BSD_PROCESS_ACCT_V3
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "BSD Process Accounting version 3 file format"
 * depends on BSD_PROCESS_ACCT
 * 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 .


 * Option: SYSCTL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 .  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.


 * Option: AUDIT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Auditing support"
 * depends on NET
 * default y if SECURITY_SELINUX
 * 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.


 * Option: AUDITSYSCALL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Enable system-call auditing support"
 * depends on AUDIT && (X86 || PPC || PPC64 || ARCH_S390 || IA64 || UML || SPARC64)
 * default y if SECURITY_SELINUX
 * Enable low-overhead system-call auditing infrastructure that can be used independently or with another kernel subsystem, such as SELinux.


 * Option: HOTPLUG
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Support for hot-pluggable devices" if !ARCH_S390
 * default ARCH_S390
 * This option is provided for the case where no in-kernel-tree modules require HOTPLUG functionality, but a module built outside the kernel tree does. Such modules require Y here.


 * Option: KOBJECT_UEVENT
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Kernel Userspace Events" if EMBEDDED
 * depends on NET
 * default y
 * This option enables the kernel userspace event layer, which is a simple mechanism for kernel-to-user communication over a netlink socket. The goal of the kernel userspace events layer is to provide a simple and efficient events system, that notifies userspace about kobject state changes. This will enable applications to just listen for events instead of polling system devices and files. Hotplug events (kobject addition and removal) are also available on the netlink socket in addition to the execution of /sbin/hotplug if CONFIG_HOTPLUG is enabled.
 * Say Y, unless you are building a system requiring minimal memory consumption.


 * Option: IKCONFIG
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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).


 * Option: IKCONFIG_PROC
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: CPUSETS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: User:ZyMOS/Howto configure the linux kernel/usr


 * Option: CC_OPTIMIZE_FOR_SIZE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.

EMBEDDED
 * (on/off) "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.


 * Option: KALLSYMS
 * Kernel Versions: 2.6.15.6 ...bool "Load all symbols for debugging/kksymoops" if EMBEDDEDdefault yhelp 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.


 * Option: KALLSYMS_ALL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Include all symbols in kallsyms"
 * depends on DEBUG_KERNEL && 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.


 * Option: KALLSYMS_EXTRA_PASS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: PRINTK
 * Kernel Versions: 2.6.15.6 ...
 * default y
 * (on/off) "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.


 * Option: BUG
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: BASE_FULL
 * Kernel Versions: 2.6.15.6 ...
 * default y
 * (on/off) "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.


 * Option: FUTEX
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: EPOLL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: SHMEM
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.

"Function alignment" if EMBEDDED
 * Option: CC_ALIGN_FUNCTIONS
 * Kernel Versions: 2.6.15.6 ...
 * default 0
 * Align the start of functions to the next power-of-two greater than n, skipping up to n bytes. For instance, 32 aligns functions to the next 32-byte boundary, but 24 would align to the next 32-byte boundary only if this can be done by skipping 23 bytes or less. Zero means use compiler's default.

"Label alignment" if EMBEDDED
 * Option: CC_ALIGN_LABELS
 * Kernel Versions: 2.6.15.6 ...
 * default 0
 * Align all branch targets to a power-of-two boundary, skipping up to n bytes like ALIGN_FUNCTIONS. This option can easily make code slower, because it must insert dummy operations for when the branch target is reached in the usual flow of the code. Zero means use compiler's default.

"Loop alignment" if EMBEDDED
 * Option: CC_ALIGN_LOOPS
 * Kernel Versions: 2.6.15.6 ...
 * default 0
 * Align loops to a power-of-two boundary, skipping up to n bytes. Zero means use compiler's default.

"Jump alignment" if EMBEDDED
 * Option: CC_ALIGN_JUMPS
 * Kernel Versions: 2.6.15.6 ...
 * default 0
 * Align branch targets to a power-of-two boundary, for branch targets where the targets can only be reached by jumping, skipping up to n bytes like ALIGN_FUNCTIONS. In this case, no dummy operations need be executed. Zero means use compiler's default.


 * General setup


 * Option: TINY_SHMEM
 * Kernel Versions: 2.6.15.6 ...
 * default !SHMEM
 * (on/off)


 * Option: BASE_SMALL
 * Kernel Versions: 2.6.15.6 ...


 * default 0 if BASE_FULL
 * default 1 if !BASE_FULL

Loadable module support

 * Option: MODULES
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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 this).
 * If unsure, say Y.


 * Option: MODULE_UNLOAD
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: MODULE_FORCE_UNLOAD
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Forced module unloading"
 * depends on MODULE_UNLOAD && EXPERIMENTAL
 * 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.


 * Option: OBSOLETE_MODPARM
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * default y
 * depends on MODULES
 * You need this option to use module parameters on modules which have not been converted to the new module parameter system yet. If unsure, say Y.


 * Option: MODVERSIONS
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "Module versioning support (EXPERIMENTAL)"
 * depends on MODULES && EXPERIMENTAL
 * 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.


 * Option: MODULE_SRCVERSION_ALL
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: KMOD
 * Kernel Versions: 2.6.15.6 ...
 * (on/off) "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.


 * Option: STOP_MACHINE
 * Kernel Versions: 2.6.15.6 ...
 * (on/off)
 * default y
 * depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 * Need stop_machine primitive.

Block layer

 * Option: User:ZyMOS/Howto configure the linux kernel/block