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We've gotten enough questions that are related to building systems rather

Browse Source 
than anything about busybox that I'm deeming it a FAQ, and answering it.

I gave a quick swipe to a couple of other slightly stale questions along
the way.  The busybox 1.01 README has much more detailed versions of these
answers, that should probably be propogated to the 1.1 line and perhaps bits
of it transplanted to the FAQ?  (Or just have the README visible on the
web page someplace?)
This commit is contained in:
Rob Landley 2005-09-23 16:52:09 +00:00
parent 1eb645d8d7
commit 380ad123ac
1 changed files with 107 additions and 41 deletions
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docs/busybox.net/FAQ.html
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@ -8,6 +8,8 @@ about BusyBox. Some of the questions even have answers. If you
have additions to this FAQ document, we would love to add them,
<ol>
<li><a href="#getting_started">How can I get started using BusyBox?</a>
<li><a href="#build_system">How do I build a BusyBox-based system?</a>
<li><a href="#kernel">Which Linux kernel versions are supported?</a>
<li><a href="#arch">Which architectures does BusyBox run on?</a>
<li><a href="#libc">Which C libraries are supported?</a>
@ -15,7 +17,6 @@ have additions to this FAQ document, we would love to add them,
<li><a href="#bugs">I think I found a bug in BusyBox! What should I do?!</a>
<li><a href="#job_control">Why do I keep getting "sh: can't access tty; job control
turned off" errors? Why doesn't Control-C work within my shell?</a>
<li><a href="#getting_started">How can I get started using BusyBox?</a>
<li><a href="#demanding">I demand that you to add &lt;favorite feature&gt; right now! How come
you don't answer all my questions on the mailing list instantly? I demand
that you help me with all of my problems <em>Right Now</em>!</a>
@ -31,46 +32,132 @@ have additions to this FAQ document, we would love to add them,
</ol>
<hr />
<p>
<h2><a name="getting_started">How can I get started using BusyBox?</a></h2>
<p> If you just want to try out busybox without installing it, download the
tarball, extract it, run "make allyesconfig", and then run "make".
</p>
<p>
This will create a busybox binary with all features enabled. To try
out a busybox applet, type "./busybox [appletname] [options]", for
example "./busybox ls -l" or "./busybox cat LICENSE". Type "./busybox"
to see a command list, and "busybox appletname --help" to see a brief
usage message for a given applet.
</p>
<p>
BusyBox uses the name it was invoked under to determine which applet is
being invoked. (Try "mv busybox ls" and then "./ls -l".) Installing
busybox consists of creating symlinks (or hardlinks) to the busybox
binary for each applet in busybox, and making sure these symlinks are in
the shell's command $PATH. ("make install" creates these symlinks, and
"make install-hardlinks" creates hardlinks instead.) The special applet
name "busybox" (or with any optional suffix, such as "busybox-static")
uses the first argument to determine which applet to run, as shown above.
</p>
<p>
BusyBox also has a feature called the "standalone shell", where the busybox
shell runs any built-in applets before checking the command path. This
feature is also enabled by "make allyesconfig", and to try it out run
the command line "PATH= ./busybox ash". This will blank your command path
and run busybox as your command shell, so the only commands it can find
(without an explicit path such as /bin/ls) are the built-in busybox ones.
This is another good way to see what's built into busybox. (Note that the
standalone shell is dependent on the existence of /proc/self/exe, so before
using it in a chroot environment you must mount /proc.)
</p>
<p>
To build a smaller busybox binary, run "make menuconfig" and disable the
features you don't need. (Or run "make allnoconfig" and then use
menuconfig to add just the features you need. Don't forget to recompile
with "make" once you've finished configuring.)
</p>
<hr/>
<p/>
<h2><a name="build_system">How do I build a BusyBox-based system?</a></h2>
<p>
BusyBox is a package that replaces a dozen standard packages, but it is
not by itself a complete bootable system. Building an entire Linux
distribution from source is a bit beyond the scope of this FAQ, but it
understandably keeps cropping up on the mailing list, so here are some
pointers.
</p>
<p>
Start by learning how to strip a working system down to the bare essentials
needed to run one or two commands, so you know what it is you actually
need. An excellent practical place to do
this is the <a href="http://www.tldp.org/HOWTO/Bootdisk-HOWTO/">Linux
BootDisk Howto</a>, or for a more theoretical approach try
<a href="http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html">From
PowerUp to Bash Prompt</a>.
</p>
<p>
To learn how to build a working Linux system entirely from source code,
the place to go is the <a href="http://www.linuxfromscratch.org">Linux
From Scratch</a> project. They have an entire book of step-by-step
instructions you can
<a href="http://www.linuxfromscratch.org/lfs/view/stable/">read online</a>
or
<a href="http://www.linuxfromscratch.org/lfs/downloads/stable/">download</a>.
Be sure to check out the other sections of their main page, including
Beyond Linux From Scratch, Hardened Linux From Scratch, their Hints
directory, and their LiveCD project. (They also have mailing lists which
are better sources of answers to Linux-system building questions than
the busybox list.)
</p>
<p>
If you want an automated yet customizable system builder which produces
a BusyBox and uClibc based system, try
<a href="http://buildroot.uclibc.org">buildroot</a>, which is
another project by the maintainer of the uClibc and BusyBox projects
(Erik Andersen). Download the tarball, extract it, unset CC, make.
For more instructions, see the website.
</p>
<hr />
<p>
<h2><a name="kernel">Which Linux kernel versions are supported?</a></h2>
<p>
Full functionality requires Linux 2.2.x or better. A large fraction of the
Full functionality requires Linux 2.4.x or better. (Earlier versions may
still work, but are no longer regularly tested.) A large fraction of the
code should run on just about anything. While the current code is fairly
Linux specific, it should be fairly easy to port the majority of the code
to support, say, FreeBSD or Solaris, or Mac OS X, or even Windows (if you
are into that sort of thing).
</p>
<hr />
<p>
<h2><a name="arch">Which architectures does BusyBox run on?</a></h2>
<p>
BusyBox in general will build on any architecture supported by gcc.
Kernel module loading for 2.2 and 2.4 Linux kernels is currently
Kernel module loading for 2.4 Linux kernels is currently
limited to ARM, CRIS, H8/300, x86, ia64, x86_64, m68k, MIPS, PowerPC,
S390, SH3/4/5, Sparc, v850e, and x86_64 for 2.4.x kernels.
</p>
<p>
With 2.6.x kernels, module loading support should work on all architectures.
</p>
<hr />
<p>
<h2><a name="libc">Which C libraries are supported?</a></h2>
<p>
uClibc and glibc are supported. People have been looking at newlib and
dietlibc, but they are currently considered unsupported, untested, or
worse. Linux-libc5 is no longer supported. If you require a small C
library, you should probably use uClibc.
On Linux, BusyBox releases are tested against uClibc (0.9.27 or later) and
glibc (2.2 or later). Both should provide full functionality with busybox,
and if you find a bug we want to hear about it.
</p>
</p>
Linux-libc5 is no longer maintained (and has no known advantages over
uClibc), dietlibc is known to have numerous unfixed bugs, and klibc is
missing too many features to build BusyBox. If you require a small C
library for Linux, the busybox developers recommend uClibc.
</p>
<p>
Some BusyBox applets have been built and run under a combination
of newlib and libgloss (see
<a href="http://www.busybox.net/lists/busybox/2005-March/013759.html">this thread</a>).
This is still experimental, but may be supported in a future release.
</p>
<hr />
<p>
<h2><a name="commercial">Can I include BusyBox as part of the software on my device?</a></h2>
@ -133,27 +220,6 @@ have additions to this FAQ document, we would love to add them,
run your shell on a real console...
<hr />
<p>
<h2><a name="getting_started">How can I get started using BusyBox?</a></h2>
<p>
An easy method to build your own basic BusyBox based system, is to
follow these simple steps:
<ul>
<li> Point your web browser <a href="http://buildroot.uclibc.org/">here</a>
<li> Download a copy of buildroot
<li> Unpack the tarball on your Linux system somewhere
<li> run 'make' and configure things to taste.
<li> run 'unset CC'. Some Linux systems (i.e. Gentoo) set 'CC'
in the system environment which messes up cross compiles.
<li> run 'make'
<li> go have lunch, drink a pop, call a friend, play a video game, etc
till it finishes downloading software and compiling things.
<li> You should now have a shiny new BusyBox based system.
</ul>
<hr />
<p>
<h2><a name="demanding">I demand that you to add &lt;favorite feature&gt; right now! How come