106 lines
4.1 KiB
Plaintext
106 lines
4.1 KiB
Plaintext
Building:
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=========
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The BusyBox build process is similar to the Linux kernel build:
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make menuconfig # This creates a file called ".config"
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make # This creates the "busybox" executable
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make install # or make PREFIX=/path/from/root install
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The full list of configuration and install options is available by typing:
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make help
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Quick Start:
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============
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The easy way to try out BusyBox for the first time, without having to install
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it, is to enable all features and then use "standalone shell" mode with a
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blank command $PATH:
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make allyesconfig
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make
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PATH= ./busybox ash
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Standalone shell mode causes busybox's built-in command shell to run
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any built-in busybox applets directly, without looking for external
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programs by that name. Supplying an empty command path (as above) means
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the only commands busybox can find are the built-in ones.
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(Note that the standalone shell requires the /proc directory to function.)
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Configuring Busybox:
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====================
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Busybox is optimized for size, but enabling the full set of functionality
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still results in a fairly large executable (more than 1 megabyte when
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statically linked). To save space, busybox can be configured with only the
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set of applets needed for each environment. The minimal configuration, with
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all applets disabled, produces a 4k executable. (It's useless, but very small.)
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The manual configurators "make config" and "make menuconfig" modify the
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existing configuration. Quick ways to get starting configurations include
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"make allyesconfig" (enables almost all options), "make allnoconfig" (disables
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all options), "make allbaseconfig" (enables all applets but disables all
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optional features), and "make defconfig" (reset to defaults).
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Configuring BusyBox produces a file ".config", which can be saved for future
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use.
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Installing Busybox:
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===================
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Busybox is a single executable that can behave like many different commands,
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and BusyBox uses the name it was invoked under to determine the desired
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behavior. (Try "mv busybox ls" and then "./ls -l".)
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Installing busybox consists of creating symlinks (or hardlinks) to the busybox
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binary for each applet enabled in busybox, and making sure these symlinks are
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in the shell's command $PATH. Running "make install" creates these symlinks,
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or "make install-hardlinks" creates hardlinks instead (useful on systems with
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a limited number of inodes). This install process uses the file
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"busybox.links" (created by make), which contains the list of enabled applets
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and the path at which to install them.
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Installing links to busybox is not always necessary. The special applet name
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"busybox" (or with any optional suffix, such as "busybox-static") uses the
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first argument to determine which applet to behave as, for example
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"./busybox cat LICENSE". (Running the busybox applet with no arguments gives
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a list of all enabled applets.) The standalone shell can also call busybox
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applets without links to busybox under other names in the filesystem. You can
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also configure a standaone install capability into the busybox base applet,
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and then install such links at runtime with one of "busybox --install" (for
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hardlinks) or "busybox --install -s" (for symlinks).
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Building out-of-tree:
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=====================
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By default, the BusyBox build puts its temporary files in the source tree.
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Building from a read-only source tree, or to building multiple
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configurations from the same source directory, requires the ability to
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put the temporary files somewhere else.
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To build out of tree, use the O=$BUILDPATH option during the configuration
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step, as in:
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make O=/some/empty/directory allyesconfig
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cd /some/empty/directory
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make
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make PREFIX=. install
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(Note, O= requires an absolute path.)
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Alternately, cd to the empty directory and do this instead:
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make top_srcdir=/path/to/source -f /path/to/source/Makefile allyesconfig
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make
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make install
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More Information:
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=================
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Se also the busybox FAQ, under the questions "How can I get started using
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BusyBox" and "How do I build a BusyBox-based system?" The BusyBox FAQ is
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available from http://www.busybox.net/FAQ.html or as the file
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docs/busybox.net/FAQ.html in this tarball.
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