BusyBox - The Swiss Army Knife of Embedded Linux
busybox <applet> [arguments...] # or
<applet> [arguments...] # if symlinked
BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides minimalist replacements for most of the utilities you usually find in GNU coreutils, util-linux, etc. The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts.
BusyBox has been written with size-optimization and limited resources in mind. It is also extremely modular so you can easily include or exclude commands (or features) at compile time. This makes it easy to customize your embedded systems. To create a working system, just add /dev, /etc, and a Linux kernel. BusyBox provides a fairly complete POSIX environment for any small or embedded system.
BusyBox is extremely configurable. This allows you to include only the components you need, thereby reducing binary size. Run 'make config' or 'make menuconfig' to select the functionality that you wish to enable. Then run 'make' to compile BusyBox using your configuration.
After the compile has finished, you should use 'make install' to install BusyBox. This will install the 'bin/busybox' binary, in the target directory specified by CONFIG_PREFIX. CONFIG_PREFIX can be set when configuring BusyBox, or you can specify an alternative location at install time (i.e., with a command line like 'make CONFIG_PREFIX=/tmp/foo install'). If you enabled any applet installation scheme (either as symlinks or hardlinks), these will also be installed in the location pointed to by CONFIG_PREFIX.
BusyBox is a multi-call binary. A multi-call binary is an executable program that performs the same job as more than one utility program. That means there is just a single BusyBox binary, but that single binary acts like a large number of utilities. This allows BusyBox to be smaller since all the built-in utility programs (we call them applets) can share code for many common operations.
You can also invoke BusyBox by issuing a command as an argument on the command line. For example, entering
/bin/busybox ls
will also cause BusyBox to behave as 'ls'.
Of course, adding '/bin/busybox' into every command would be painful. So most people will invoke BusyBox using links to the BusyBox binary.
For example, entering
ln -s /bin/busybox ls
./ls
will cause BusyBox to behave as 'ls' (if the 'ls' command has been compiled into BusyBox). Generally speaking, you should never need to make all these links yourself, as the BusyBox build system will do this for you when you run the 'make install' command.
If you invoke BusyBox with no arguments, it will provide you with a list of the applets that have been compiled into your BusyBox binary.
Most BusyBox applets support the --help argument to provide a terse runtime description of their behavior. If the CONFIG_FEATURE_VERBOSE_USAGE option has been enabled, more detailed usage information will also be available.
Currently available applets include:
[, [[, ash, basename, cat, chmod, comm, cp, cttyhack, cut, date,
dirname, echo, egrep, expr, fgrep, grep, hush, ln, mkdir, mv,
readlink, rm, rmdir, sed, sh, sort, tee, test, touch, uniq, wc
ash [-/+OPTIONS] [-/+o OPT]... [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS]]
Unix shell interpreter
basename FILE [SUFFIX]
Strip directory path and .SUFFIX from FILE
cat [FILE]...
Concatenate FILEs and print them to stdout
chmod [-Rcvf] MODE[,MODE]... FILE...
Each MODE is one or more of the letters ugoa, one of the symbols +-= and one or more of the letters rwxst
-R Recurse
-c List changed files
-v List all files
-f Hide errors
comm [-123] FILE1 FILE2
Compare FILE1 with FILE2
-1 Suppress lines unique to FILE1
-2 Suppress lines unique to FILE2
-3 Suppress lines common to both files
cp [OPTIONS] SOURCE... DEST
Copy SOURCE(s) to DEST
-a Same as -dpR
-R,-r Recurse
-d,-P Preserve symlinks (default if -R)
-L Follow all symlinks
-H Follow symlinks on command line
-p Preserve file attributes if possible
-f Overwrite
-i Prompt before overwrite
-l,-s Create (sym)links
-u Copy only newer files
cttyhack [PROG ARGS]
Give PROG a controlling tty if possible. Example for /etc/inittab (for busybox init): ::respawn:/bin/cttyhack /bin/sh Giving controlling tty to shell running with PID 1: $ exec cttyhack sh Starting interactive shell from boot shell script:
setsid cttyhack sh
cut [OPTIONS] [FILE]...
Print selected fields from each input FILE to stdout
-b LIST Output only bytes from LIST
-c LIST Output only characters from LIST
-d CHAR Use CHAR instead of tab as the field delimiter
-s Output only the lines containing delimiter
-f N Print only these fields
-n Ignored
date [OPTIONS] [+FMT] [TIME]
Display time (using +FMT), or set time
[-s,--set] TIME Set time to TIME
-u,--utc Work in UTC (don't convert to local time)
-R,--rfc-2822 Output RFC-2822 compliant date string
-I[SPEC] Output ISO-8601 compliant date string
SPEC='date' (default) for date only,
'hours', 'minutes', or 'seconds' for date and
time to the indicated precision
-r,--reference FILE Display last modification time of FILE
-d,--date TIME Display TIME, not 'now'
-D FMT Use FMT for -d TIME conversion
Recognized TIME formats:
hh:mm[:ss]
[YYYY.]MM.DD-hh:mm[:ss]
YYYY-MM-DD hh:mm[:ss]
[[[[[YY]YY]MM]DD]hh]mm[.ss]
'date TIME' form accepts MMDDhhmm[[YY]YY][.ss] instead
dirname FILENAME
Strip non-directory suffix from FILENAME
echo [-neE] [ARG]...
Print the specified ARGs to stdout
-n Suppress trailing newline
-e Interpret backslash escapes (i.e., \t=tab)
-E Don't interpret backslash escapes (default)
expr EXPRESSION
Print the value of EXPRESSION to stdout
EXPRESSION may be:
ARG1 | ARG2 ARG1 if it is neither null nor 0, otherwise ARG2
ARG1 & ARG2 ARG1 if neither argument is null or 0, otherwise 0
ARG1 < ARG2 1 if ARG1 is less than ARG2, else 0. Similarly:
ARG1 <= ARG2
ARG1 = ARG2
ARG1 != ARG2
ARG1 >= ARG2
ARG1 > ARG2
ARG1 + ARG2 Sum of ARG1 and ARG2. Similarly:
ARG1 - ARG2
ARG1 * ARG2
ARG1 / ARG2
ARG1 % ARG2
STRING : REGEXP Anchored pattern match of REGEXP in STRING
match STRING REGEXP Same as STRING : REGEXP
substr STRING POS LENGTH Substring of STRING, POS counted from 1
index STRING CHARS Index in STRING where any CHARS is found, or 0
length STRING Length of STRING
quote TOKEN Interpret TOKEN as a string, even if
it is a keyword like 'match' or an
operator like '/'
(EXPRESSION) Value of EXPRESSION
Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and \) are not used, they return the number of characters matched or 0.
grep [-HhnlLoqvsriwFE] [-m N] [-A/B/C N] PATTERN/-e PATTERN.../-f FILE [FILE]...
Search for PATTERN in FILEs (or stdin)
-H Add 'filename:' prefix
-h Do not add 'filename:' prefix
-n Add 'line_no:' prefix
-l Show only names of files that match
-L Show only names of files that don't match
-c Show only count of matching lines
-o Show only the matching part of line
-q Quiet. Return 0 if PATTERN is found, 1 otherwise
-v Select non-matching lines
-s Suppress open and read errors
-r Recurse
-i Ignore case
-w Match whole words only
-x Match whole lines only
-F PATTERN is a literal (not regexp)
-E PATTERN is an extended regexp
-m N Match up to N times per file
-A N Print N lines of trailing context
-B N Print N lines of leading context
-C N Same as '-A N -B N'
-e PTRN Pattern to match
-f FILE Read pattern from file
hush [-nxl] [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS]]
Unix shell interpreter
ln [OPTIONS] TARGET... LINK|DIR
Create a link LINK or DIR/TARGET to the specified TARGET(s)
-s Make symlinks instead of hardlinks
-f Remove existing destinations
-n Don't dereference symlinks - treat like normal file
-b Make a backup of the target (if exists) before link operation
-S suf Use suffix instead of ~ when making backup files
-T 2nd arg must be a DIR
-v Verbose
mkdir [OPTIONS] DIRECTORY...
Create DIRECTORY
-m MODE Mode
-p No error if exists; make parent directories as needed
mv [-fin] SOURCE DEST or: mv [-fin] SOURCE... DIRECTORY
Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY
-f Don't prompt before overwriting
-i Interactive, prompt before overwrite
-n Don't overwrite an existing file
readlink [-fnv] FILE
Display the value of a symlink
-f Canonicalize by following all symlinks
-n Don't add newline
-v Verbose
rm [-irf] FILE...
Remove (unlink) FILEs
-i Always prompt before removing
-f Never prompt
-R,-r Recurse
rmdir [OPTIONS] DIRECTORY...
Remove DIRECTORY if it is empty
-p|--parents Include parents
--ignore-fail-on-non-empty
sed [-inrE] [-f FILE]... [-e CMD]... [FILE]... or: sed [-inrE] CMD [FILE]...
-e CMD Add CMD to sed commands to be executed
-f FILE Add FILE contents to sed commands to be executed
-i[SFX] Edit files in-place (otherwise sends to stdout)
Optionally back files up, appending SFX
-n Suppress automatic printing of pattern space
-r,-E Use extended regex syntax
If no -e or -f, the first non-option argument is the sed command string. Remaining arguments are input files (stdin if none).
sh [-/+OPTIONS] [-/+o OPT]... [-c 'SCRIPT' [ARG0 [ARGS]] / FILE [ARGS]]
Unix shell interpreter
sort [-nrugMcszbdfiokt] [-o FILE] [-k start[.offset][opts][,end[.offset][opts]] [-t CHAR] [FILE]...
Sort lines of text
-o FILE Output to FILE
-c Check whether input is sorted
-b Ignore leading blanks
-f Ignore case
-i Ignore unprintable characters
-d Dictionary order (blank or alphanumeric only)
-g General numerical sort
-M Sort month
-n Sort numbers
-t CHAR Field separator
-k N[,M] Sort by Nth field
-r Reverse sort order
-s Stable (don't sort ties alphabetically)
-u Suppress duplicate lines
-z Lines are terminated by NUL, not newline
tee [-ai] [FILE]...
Copy stdin to each FILE, and also to stdout
-a Append to the given FILEs, don't overwrite
-i Ignore interrupt signals (SIGINT)
touch [-c] [-d DATE] [-t DATE] [-r FILE] FILE...
Update the last-modified date on the given FILE[s]
-c Don't create files
-h Don't follow links
-d DT Date/time to use
-t DT Date/time to use
-r FILE Use FILE's date/time
uniq [-cdu][-f,s,w N] [INPUT [OUTPUT]]
Discard duplicate lines
-c Prefix lines by the number of occurrences
-d Only print duplicate lines
-u Only print unique lines
-f N Skip first N fields
-s N Skip first N chars (after any skipped fields)
-w N Compare N characters in line
wc [-cmlwL] [FILE]...
Count lines, words, and bytes for each FILE (or stdin)
-c Count bytes
-m Count characters
-l Count newlines
-w Count words
-L Print longest line length
GNU Libc (glibc) uses the Name Service Switch (NSS) to configure the behavior of the C library for the local environment, and to configure how it reads system data, such as passwords and group information. This is implemented using an /etc/nsswitch.conf configuration file, and using one or more of the /lib/libnss_* libraries. BusyBox tries to avoid using any libc calls that make use of NSS. Some applets however, such as login and su, will use libc functions that require NSS.
If you enable CONFIG_USE_BB_PWD_GRP, BusyBox will use internal functions to directly access the /etc/passwd, /etc/group, and /etc/shadow files without using NSS. This may allow you to run your system without the need for installing any of the NSS configuration files and libraries.
When used with glibc, the BusyBox 'networking' applets will similarly require that you install at least some of the glibc NSS stuff (in particular, /etc/nsswitch.conf, /lib/libnss_dns*, /lib/libnss_files*, and /lib/libresolv*).
Shameless Plug: As an alternative, one could use a C library such as uClibc. In addition to making your system significantly smaller, uClibc does not require the use of any NSS support files or libraries.
Denis Vlasenko <vda.linux@googlemail.com>
The following people have contributed code to BusyBox whether they know it or not. If you have written code included in BusyBox, you should probably be listed here so you can obtain your bit of eternal glory. If you should be listed here, or the description of what you have done needs more detail, or is incorrect, please send in an update.
Emanuele Aina <emanuele.aina@tiscali.it> run-parts
Erik Andersen <andersen@codepoet.org>
Tons of new stuff, major rewrite of most of the
core apps, tons of new apps as noted in header files.
Lots of tedious effort writing these boring docs that
nobody is going to actually read.
Laurence Anderson <l.d.anderson@warwick.ac.uk>
rpm2cpio, unzip, get_header_cpio, read_gz interface, rpm
Jeff Angielski <jeff@theptrgroup.com>
ftpput, ftpget
Edward Betts <edward@debian.org>
expr, hostid, logname, whoami
John Beppu <beppu@codepoet.org>
du, nslookup, sort
Brian Candler <B.Candler@pobox.com>
tiny-ls(ls)
Randolph Chung <tausq@debian.org>
fbset, ping, hostname
Dave Cinege <dcinege@psychosis.com>
more(v2), makedevs, dutmp, modularization, auto links file,
various fixes, Linux Router Project maintenance
Jordan Crouse <jordan@cosmicpenguin.net>
ipcalc
Magnus Damm <damm@opensource.se>
tftp client insmod powerpc support
Larry Doolittle <ldoolitt@recycle.lbl.gov>
pristine source directory compilation, lots of patches and fixes.
Glenn Engel <glenne@engel.org>
httpd
Gennady Feldman <gfeldman@gena01.com>
Sysklogd (single threaded syslogd, IPC Circular buffer support,
logread), various fixes.
Karl M. Hegbloom <karlheg@debian.org>
cp_mv.c, the test suite, various fixes to utility.c, &c.
Daniel Jacobowitz <dan@debian.org>
mktemp.c
Matt Kraai <kraai@alumni.cmu.edu>
documentation, bugfixes, test suite
Stephan Linz <linz@li-pro.net>
ipcalc, Red Hat equivalence
John Lombardo <john@deltanet.com>
tr
Glenn McGrath <bug1@iinet.net.au>
Common unarchiving code and unarchiving applets, ifupdown, ftpgetput,
nameif, sed, patch, fold, install, uudecode.
Various bugfixes, review and apply numerous patches.
Manuel Novoa III <mjn3@codepoet.org>
cat, head, mkfifo, mknod, rmdir, sleep, tee, tty, uniq, usleep, wc, yes,
mesg, vconfig, make_directory, parse_mode, dirname, mode_string,
get_last_path_component, simplify_path, and a number trivial libbb routines
also bug fixes, partial rewrites, and size optimizations in
ash, basename, cal, cmp, cp, df, du, echo, env, ln, logname, md5sum, mkdir,
mv, realpath, rm, sort, tail, touch, uname, watch, arith, human_readable,
interface, dutmp, ifconfig, route
Vladimir Oleynik <dzo@simtreas.ru>
cmdedit; xargs(current), httpd(current);
ports: ash, crond, fdisk, inetd, stty, traceroute, top;
locale, various fixes
and irreconcilable critic of everything not perfect.
Bruce Perens <bruce@pixar.com>
Original author of BusyBox in 1995, 1996. Some of his code can
still be found hiding here and there...
Tim Riker <Tim@Rikers.org>
bug fixes, member of fan club
Kent Robotti <robotti@metconnect.com>
reset, tons and tons of bug reports and patches.
Chip Rosenthal <chip@unicom.com>, <crosenth@covad.com>
wget - Contributed by permission of Covad Communications
Pavel Roskin <proski@gnu.org>
Lots of bugs fixes and patches.
Gyepi Sam <gyepi@praxis-sw.com>
Remote logging feature for syslogd
Linus Torvalds <torvalds@transmeta.com>
mkswap, fsck.minix, mkfs.minix
Mark Whitley <markw@codepoet.org>
grep, sed, cut, xargs(previous),
style-guide, new-applet-HOWTO, bug fixes, etc.
Charles P. Wright <cpwright@villagenet.com>
gzip, mini-netcat(nc)
Enrique Zanardi <ezanardi@ull.es>
tarcat (since removed), loadkmap, various fixes, Debian maintenance
Tito Ragusa <farmatito@tiscali.it>
devfsd and size optimizations in strings, openvt and deallocvt.
Paul Fox <pgf@foxharp.boston.ma.us>
vi editing mode for ash, various other patches/fixes
Roberto A. Foglietta <me@roberto.foglietta.name>
port: dnsd
Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
misc
Mike Frysinger <vapier@gentoo.org>
initial e2fsprogs, printenv, setarch, sum, misc
Jie Zhang <jie.zhang@analog.com>
fixed two bugs in msh and hush (exitcode of killed processes)