Busybox

•       A Linux system needs a basic set of programs to work

–       An init program

–       A shell

•       Various basic utilities for le manipulation and system configuration

•       In normal Linux systems, those programs are provided by different projects

–      coreutils, bash, grep, sed, tar, wget, modutils, etc. are all different projects

–      A lot of different components to integrate

–      Components not designed with embedded systems constraints in mind: they are not very configurable and have a wide range of features

•       Busybox is an alternative solution, extremely common on embedded systems

General purpose toolbox: Busybox

•       Rewrite of many useful Unix command line utilities

–      Integrated into a single project, which makes it easy to work with

–      Designed with embedded systems in mind: highly configurable, no unnecessary features

•       All the utilities are compiled into a single executable, /bin/busybox

–      Symbolic links to /bin/busybox are created for each application integrated into Busybox

•       http://www.busybox.net/

•       Although BusyBox does not support all the options provided by the commands it replaces, the subset it provides is sufficient for most typical uses

Configuring busybox

•       Get the latest stable sources from http://busybox.net

•       Congure BusyBox (creates a .config le):

–      make defconfig

                Good to begin with BusyBox. Congures BusyBox with all options for regular users.

•       make allnoconfig

–      Unselects all options. Good to congure only what you need.

•       make xconfig (graphical, needs the libqt3-mt-dev package) or make menuconfig (text)

–      Same conguration interfaces as the ones used by the Linux kernel (though older versions are used).

Compiling Busybox

•       Using “make menuconfig” command you can choose the commands to compile and the commands options and features that you need.

•       Set the cross-compiler prefix in the conguration interface:

–      BusyBox Settings -> Build Options -> Cross Compiler prefix

–      Example: arm-linux-

•       Set the installation directory in the conguration interface:

–      BusyBox Settings -> Installation Options -> BusyBox installation prefix

•       Add the cross-compiler path to the PATH environment variable:

–      export PATH=/usr/xtools/arm-unknown-linux-uclibcgnueabi/bin:$PATH

•       Compile BusyBox:

–      Make

–      Install it (this creates a Unix directory structure symbolic links to the busybox executable):

•       make install

Using busybox commands

•       To understand how best to use BusyBox, let's first take a look at the components installed on the target's root filesystem by BusyBox's build process. As observed there is  only one executable was installed, /bin/busybox.

•       This is the single binary with support for all the commands configured  This binary is never called directly, however. Instead, symbolic links bearing the original commands' names have been created to /bin/busybox. Such symbolic links have been created in all the directories in which the original commands would be found, including /bin, /sbin, /usr/bin, and /usr/sbin.

•       When you type a command during the system's normal operation, the busybox command is invoked via the symbolic link. In turn, busybox determines the actual command you were invoking using the name being used to run it. /bin/ls, for instance, points to /bin/busybox.

•       When you type ls, the busybox command is called and it determines that you were trying to use the ls command, because ls is the first argument on the command line

Busy box

•       Busy box provides all the required functionality while still remaining a very small-size application

•       BusyBox implements many commands. Here are a few:

•        ar, cat, chgrp, chmod, chown, chroot, cp, cpio, date, dd, df, dmesg, dos2unix, du, echo, env, expr, find, grep, gunzip, gzip, halt, id, ifconfig, init, insmod, kill, killall, ln, ls, lsmod, md5sum, mkdir, mknod, modprobe, more, mount, mv, ping, ps, pwd, reboot, renice, rm, rmdir, rmmod, route, rpm2cpio, sed, stty, swapon, sync, syslogd, tail, tar, telnet, tftp, touch, traceroute, umount, uname, uuencode, vi, wc, which, and whoami.

•       Although BusyBox does not support all the options provided by the commands it replaces, the subset it provides is sufficient for most typical uses.