| 1 | Building:
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| 2 | =========
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| 3 |
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| 4 | The BusyBox build process is similar to the Linux kernel build:
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| 5 |
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| 6 | make menuconfig # This creates a file called ".config"
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| 7 | make # This creates the "busybox" executable
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| 8 | make install # or make CONFIG_PREFIX=/path/from/root install
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| 9 |
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| 10 | The full list of configuration and install options is available by typing:
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| 11 |
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| 12 | make help
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| 13 |
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| 14 | Quick Start:
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| 15 | ============
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| 16 |
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| 17 | The easy way to try out BusyBox for the first time, without having to install
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| 18 | it, is to enable all features and then use "standalone shell" mode with a
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| 19 | blank command $PATH.
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| 20 |
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| 21 | To enable all features, use "make defconfig", which produces the largest
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| 22 | general-purpose configuration. It's allyesconfig minus debugging options,
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| 23 | optional packaging choices, and a few special-purpose features requiring
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| 24 | extra configuration to use. Then enable "standalone shell" feature:
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| 25 |
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| 26 | make defconfig
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| 27 | make menuconfig
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| 28 | # select Busybox Settings
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| 29 | # then General Configuration
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| 30 | # then exec prefers applets
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| 31 | # exit back to top level menu
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| 32 | # select Shells
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| 33 | # then Standalone shell
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| 34 | # exit back to top level menu
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| 35 | # exit and save new configuration
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| 36 | # OR
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| 37 | # use these commands to modify .config directly:
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| 38 | sed -e 's/.*FEATURE_PREFER_APPLETS.*/CONFIG_FEATURE_PREFER_APPLETS=y/' -i .config
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| 39 | sed -e 's/.*FEATURE_SH_STANDALONE.*/CONFIG_FEATURE_SH_STANDALONE=y/' -i .config
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| 40 | make
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| 41 | PATH= ./busybox ash
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| 42 |
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| 43 | Standalone shell mode causes busybox's built-in command shell to run
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| 44 | any built-in busybox applets directly, without looking for external
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| 45 | programs by that name. Supplying an empty command path (as above) means
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| 46 | the only commands busybox can find are the built-in ones.
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| 47 |
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| 48 | Note that the standalone shell requires CONFIG_BUSYBOX_EXEC_PATH
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| 49 | to be set appropriately, depending on whether or not /proc/self/exe is
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| 50 | available. If you do not have /proc, then point that config option
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| 51 | to the location of your busybox binary, usually /bin/busybox.
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| 52 | Another solution is to patch the kernel (see
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| 53 | examples/linux-*_proc_self_exe.patch) to make exec("/proc/self/exe")
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| 54 | always work.
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| 55 |
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| 56 | Configuring Busybox:
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| 57 | ====================
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| 58 |
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| 59 | Busybox is optimized for size, but enabling the full set of functionality
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| 60 | still results in a fairly large executable -- more than 1 megabyte when
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| 61 | statically linked. To save space, busybox can be configured with only the
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| 62 | set of applets needed for each environment. The minimal configuration, with
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| 63 | all applets disabled, produces a 4k executable. (It's useless, but very small.)
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| 64 |
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| 65 | The manual configurator "make menuconfig" modifies the existing configuration.
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| 66 | (For systems without ncurses, try "make config" instead.) The two most
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| 67 | interesting starting configurations are "make allnoconfig" (to start with
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| 68 | everything disabled and add just what you need), and "make defconfig" (to
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| 69 | start with everything enabled and remove what you don't need). If menuconfig
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| 70 | is run without an existing configuration, make defconfig will run first to
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| 71 | create a known starting point.
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| 72 |
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| 73 | Other starting configurations (mostly used for testing purposes) include
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| 74 | "make allbareconfig" (enables all applets but disables all optional features),
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| 75 | "make allyesconfig" (enables absolutely everything including debug features),
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| 76 | and "make randconfig" (produce a random configuration). The configs/ directory
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| 77 | contains a number of additional configuration files ending in _defconfig which
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| 78 | are useful in specific cases. "make help" will list them.
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| 79 |
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| 80 | Configuring BusyBox produces a file ".config", which can be saved for future
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| 81 | use. Run "make oldconfig" to bring a .config file from an older version of
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| 82 | busybox up to date.
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| 83 |
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| 84 | Installing Busybox:
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| 85 | ===================
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| 86 |
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| 87 | Busybox is a single executable that can behave like many different commands,
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| 88 | and BusyBox uses the name it was invoked under to determine the desired
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| 89 | behavior. (Try "mv busybox ls" and then "./ls -l".)
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| 90 |
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| 91 | Installing busybox consists of creating symlinks (or hardlinks) to the busybox
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| 92 | binary for each applet enabled in busybox, and making sure these symlinks are
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| 93 | in the shell's command $PATH. Running "make install" creates these symlinks,
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| 94 | or "make install-hardlinks" creates hardlinks instead (useful on systems with
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| 95 | a limited number of inodes). This install process uses the file
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| 96 | "busybox.links" (created by make), which contains the list of enabled applets
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| 97 | and the path at which to install them.
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| 98 |
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| 99 | Installing links to busybox is not always necessary. The special applet name
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| 100 | "busybox" (or with any optional suffix, such as "busybox-static") uses the
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| 101 | first argument to determine which applet to behave as, for example
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| 102 | "./busybox cat LICENSE". (Running the busybox applet with no arguments gives
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| 103 | a list of all enabled applets.) The standalone shell can also call busybox
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| 104 | applets without links to busybox under other names in the filesystem. You can
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| 105 | also configure a standalone install capability into the busybox base applet,
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| 106 | and then install such links at runtime with one of "busybox --install" (for
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| 107 | hardlinks) or "busybox --install -s" (for symlinks).
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| 108 |
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| 109 | If you enabled the busybox shared library feature (libbusybox.so) and want
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| 110 | to run tests without installing, set your LD_LIBRARY_PATH accordingly when
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| 111 | running the executable:
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| 112 |
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| 113 | LD_LIBRARY_PATH=`pwd` ./busybox
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| 114 |
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| 115 | Building out-of-tree:
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| 116 | =====================
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| 117 |
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| 118 | By default, the BusyBox build puts its temporary files in the source tree.
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| 119 | Building from a read-only source tree, or building multiple configurations from
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| 120 | the same source directory, requires the ability to put the temporary files
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| 121 | somewhere else.
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| 122 |
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| 123 | To build out of tree, cd to an empty directory and configure busybox from there:
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| 124 |
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| 125 | make KBUILD_SRC=/path/to/source -f /path/to/source/Makefile defconfig
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| 126 | make
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| 127 | make install
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| 128 |
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| 129 | Alternately, use the O=$BUILDPATH option (with an absolute path) during the
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| 130 | configuration step, as in:
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| 131 |
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| 132 | make O=/some/empty/directory allyesconfig
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| 133 | cd /some/empty/directory
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| 134 | make
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| 135 | make CONFIG_PREFIX=. install
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| 136 |
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| 137 | More Information:
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| 138 | =================
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| 139 |
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| 140 | Se also the busybox FAQ, under the questions "How can I get started using
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| 141 | BusyBox" and "How do I build a BusyBox-based system?" The BusyBox FAQ is
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| 142 | available from http://www.busybox.net/FAQ.html
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