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4 <h3>Frequently Asked Questions</h3>
6 This is a collection of some of the more frequently asked questions
7 about BusyBox. Some of the questions even have answers. If you
8 have additions to this FAQ document, we would love to add them,
11 <li><a href="#getting_started">How can I get started using BusyBox?</a>
12 <li><a href="#build_system">How do I build a BusyBox-based system?</a>
13 <li><a href="#init">Busybox init isn't working!</a>
14 <li><a href="#kernel">Which Linux kernel versions are supported?</a>
15 <li><a href="#arch">Which architectures does BusyBox run on?</a>
16 <li><a href="#libc">Which C libraries are supported?</a>
17 <li><a href="#commercial">Can I include BusyBox as part of the software on my device?</a>
18 <li><a href="#bugs">I think I found a bug in BusyBox! What should I do?!</a>
19 <li><a href="#job_control">Why do I keep getting "sh: can't access tty; job control
20 turned off" errors? Why doesn't Control-C work within my shell?</a>
21 <li><a href="#demanding">I demand that you to add <favorite feature> right now! How come
22 you don't answer all my questions on the mailing list instantly? I demand
23 that you help me with all of my problems <em>Right Now</em>!</a>
24 <li><a href="#helpme">I need help with BusyBox! What should I do?</a>
25 <li><a href="#contracts">I need you to add <favorite feature>! Are the BusyBox developers willing to
26 be paid in order to fix bugs or add in <favorite feature>? Are you willing to provide
27 support contracts?</a>
28 <li><a href="#external">Where can I find other small utilities since busybox does not include the features I want?</a></li>
29 <li><a href="#support">I think you guys are great and I want to help support your work!</a>
30 <li><a href="#optimize">I want to make busybox even smaller, how do I go about it?</a>
38 <h2><a name="getting_started">How can I get started using BusyBox?</a></h2>
39 <p> If you just want to try out busybox without installing it, download the
40 tarball, extract it, run "make allyesconfig", and then run "make".
43 This will create a busybox binary with all features enabled. To try
44 out a busybox applet, type "./busybox [appletname] [options]", for
45 example "./busybox ls -l" or "./busybox cat LICENSE". Type "./busybox"
46 to see a command list, and "busybox appletname --help" to see a brief
47 usage message for a given applet.
50 BusyBox uses the name it was invoked under to determine which applet is
51 being invoked. (Try "mv busybox ls" and then "./ls -l".) Installing
52 busybox consists of creating symlinks (or hardlinks) to the busybox
53 binary for each applet in busybox, and making sure these links are in
54 the shell's command $PATH. The special applet name "busybox" (or with
55 any optional suffix, such as "busybox-static") uses the first argument
56 to determine which applet to run, as shown above.
59 BusyBox also has a feature called the "standalone shell", where the busybox
60 shell runs any built-in applets before checking the command path. This
61 feature is also enabled by "make allyesconfig", and to try it out run
62 the command line "PATH= ./busybox ash". This will blank your command path
63 and run busybox as your command shell, so the only commands it can find
64 (without an explicit path such as /bin/ls) are the built-in busybox ones.
65 This is another good way to see what's built into busybox. (Note that the
66 standalone shell is dependent on the existence of /proc/self/exe, so before
67 using it in a chroot environment you must mount /proc.)
70 To build a smaller busybox binary, run "make menuconfig" and disable the
71 features you don't need. (Or run "make allnoconfig" and then use
72 menuconfig to add just the features you need. Don't forget to recompile
73 with "make" once you've finished configuring.)
77 <h2><a name="build_system">How do I build a BusyBox-based system?</a></h2>
79 BusyBox is a package that replaces a dozen standard packages, but it is
80 not by itself a complete bootable system. Building an entire Linux
81 distribution from source is a bit beyond the scope of this FAQ, but it
82 understandably keeps cropping up on the mailing list, so here are some
86 Start by learning how to strip a working system down to the bare essentials
87 needed to run one or two commands, so you know what it is you actually
88 need. An excellent practical place to do
89 this is the <a href="http://www.tldp.org/HOWTO/Bootdisk-HOWTO/">Linux
90 BootDisk Howto</a>, or for a more theoretical approach try
91 <a href="http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html">From
92 PowerUp to Bash Prompt</a>.
95 To learn how to build a working Linux system entirely from source code,
96 the place to go is the <a href="http://www.linuxfromscratch.org">Linux
97 From Scratch</a> project. They have an entire book of step-by-step
99 <a href="http://www.linuxfromscratch.org/lfs/view/stable/">read online</a>
101 <a href="http://www.linuxfromscratch.org/lfs/downloads/stable/">download</a>.
102 Be sure to check out the other sections of their main page, including
103 Beyond Linux From Scratch, Hardened Linux From Scratch, their Hints
104 directory, and their LiveCD project. (They also have mailing lists which
105 are better sources of answers to Linux-system building questions than
109 If you want an automated yet customizable system builder which produces
110 a BusyBox and uClibc based system, try
111 <a href="http://buildroot.uclibc.org">buildroot</a>, which is
112 another project by the maintainer of the uClibc (Erik Andersen).
113 Download the tarball, extract it, unset CC, make.
114 For more instructions, see the website.
119 <h2><a name="init">Busybox init isn't working!</a></h2>
121 Build a statically linked version of the following "hello world" program
122 with your cross compiler toolchain.
125 #include <stdio.h>
127 int main(int argc, char *argv)
129 printf("Hello world!\n");
135 Now try to boot your device with an "init=" argument pointing to your
136 hello world program. Did you see the hello world message? Until you
137 do, don't bother messing with busybox init.
141 Once you've got it working statically linked, try getting it to work
142 dynamically linked. Then read the FAQ entry before this one.
147 <h2><a name="kernel">Which Linux kernel versions are supported?</a></h2>
149 Full functionality requires Linux 2.4.x or better. (Earlier versions may
150 still work, but are no longer regularly tested.) A large fraction of the
151 code should run on just about anything. While the current code is fairly
152 Linux specific, it should be fairly easy to port the majority of the code
153 to support, say, FreeBSD or Solaris, or Mac OS X, or even Windows (if you
154 are into that sort of thing).
158 <h2><a name="arch">Which architectures does BusyBox run on?</a></h2>
160 BusyBox in general will build on any architecture supported by gcc.
161 Kernel module loading for 2.4 Linux kernels is currently
162 limited to ARM, CRIS, H8/300, x86, ia64, x86_64, m68k, MIPS, PowerPC,
163 S390, SH3/4/5, Sparc, v850e, and x86_64 for 2.4.x kernels.
166 With 2.6.x kernels, module loading support should work on all architectures.
170 <h2><a name="libc">Which C libraries are supported?</a></h2>
172 On Linux, BusyBox releases are tested against uClibc (0.9.27 or later) and
173 glibc (2.2 or later). Both should provide full functionality with busybox,
174 and if you find a bug we want to hear about it.
177 Linux-libc5 is no longer maintained (and has no known advantages over
178 uClibc), dietlibc is known to have numerous unfixed bugs, and klibc is
179 missing too many features to build BusyBox. If you require a small C
180 library for Linux, the busybox developers recommend uClibc.
183 Some BusyBox applets have been built and run under a combination
184 of newlib and libgloss (see
185 <a href="http://www.busybox.net/lists/busybox/2005-March/013759.html">this thread</a>).
186 This is still experimental, but may be supported in a future release.
190 <h2><a name="commercial">Can I include BusyBox as part of the software on my device?</a></h2>
192 Yes. As long as you <a href="http://busybox.net/license.html">fully comply
193 with the generous terms of the GPL BusyBox license</a> you can ship BusyBox
194 as part of the software on your device.
197 <a href="#support">Please consider sharing some of the money you make.</a>
202 <h2><a name="bugs">I think I found a bug in BusyBox! What should I do?</a></h2>
208 If you simply need help with using or configuring BusyBox, please submit a
209 detailed description of your problem to the BusyBox mailing list at <a
210 href="mailto:busybox@mail.busybox.net"> busybox@mail.busybox.net</a>.
211 Please do not send email to individual developers asking
212 for private help unless you are planning on paying for consulting services.
213 When we answer questions on the BusyBox mailing list, it helps everyone,
214 while private answers help only you...
218 The developers of BusyBox are busy people, and have only so much they can
219 keep in their brains at a time. As a result, bug reports sometimes get
220 lost when posted to the mailing list. To prevent your bug report from
221 getting lost, if you find a bug in BusyBox, please use the <a
222 href="http://bugs.busybox.net/">BusyBox Bug and Patch Tracking System</a>
223 to submit a detailed bug report.
227 The same also applies to patches... Regardless of whether your patch is a
228 bug fix or adds shiney new features, please post your patch to the <a
229 href="http://bugs.busybox.net/">BusyBox Bug and Patch Tracking System</a>
230 to make certain it is properly considered.
235 <h2><a name="job_control">Why do I keep getting "sh: can't access tty; job control
236 turned off" errors? Why doesn't Control-C work within my shell?</a></h2>
239 Job control will be turned off since your shell can not obtain a controlling
240 terminal. This typically happens when you run your shell on /dev/console.
241 The kernel will not provide a controlling terminal on the /dev/console
242 device. Your should run your shell on a normal tty such as tty1 or ttyS0
243 and everything will work perfectly. If you <em>REALLY</em> want your shell
244 to run on /dev/console, then you can hack your kernel (if you are into that
245 sortof thing) by changing drivers/char/tty_io.c to change the lines where
246 it sets "noctty = 1;" to instead set it to "0". I recommend you instead
247 run your shell on a real console...
252 <h2><a name="demanding">I demand that you to add <favorite feature> right now! How come
253 you don't answer all my questions on the mailing list instantly? I demand
254 that you help me with all of my problems <em>Right Now</em>!</a></h2>
257 You have not paid us a single cent and yet you still have the product of
258 many years of our work. We are not your slaves! We work on BusyBox
259 because we find it useful and interesting. If you go off flaming us, we
265 <h2><a name="helpme">I need help with BusyBox! What should I do?</a></h2>
268 If you find that you need help with BusyBox, you can ask for help on the
269 BusyBox mailing list at busybox@mail.busybox.net. In addition to the BusyBox
270 mailing list, Erik (andersee), Manuel (mjn3), Rob (landley) and others are
271 known to hang out on the uClibc IRC channel: #uclibc on irc.freenode.net.
272 (Daily logs of that IRC channel, going back to 2002, are available
273 <a href="http://ibot.Rikers.org/%23uclibc/">here</a>.)
277 <b>Please do not send private email to Rob, Erik, Manuel, or the other
278 BusyBox contributors asking for private help unless you are planning on
279 paying for consulting services.</b>
283 When we answer questions on the BusyBox mailing list, it helps everyone
284 since people with similar problems in the future will be able to get help
285 by searching the mailing list archives. Private help is reserved as a paid
286 service. If you need to use private communication, or if you are serious
287 about getting timely assistance with BusyBox, you should seriously consider
288 paying for consulting services.
296 <h2><a name="contracts">I need you to add <favorite feature>! Are the BusyBox
297 developers willing to be paid in order to fix bugs or add in <favorite feature>?
298 Are you willing to provide support contracts?</a></h2>
301 Sure! Now you have our attention! What you should do is contact <a
302 href="mailto:andersen@codepoet.org">Erik Andersen</a> of <a
303 href="http://codepoet-consulting.com/">CodePoet Consulting</a> to bid
304 on your project. If Erik is too busy to personally add your feature, there
305 are many other active BusyBox contributors who will almost certainly be able
306 to help you out. Erik can contact them privately, and may even let you to
307 post your request for services on the mailing list.
312 <h2><a name="external">Where can I find other small utilities since busybox
313 does not include the features I want?</a></h2>
315 We maintain such a <a href="tinyutils.html">list</a> on this site!
320 <h2><a name="support">I think you guys are great and I want to help support your work!</a></h2>
323 Wow, that would be great! If you would like to make a donation to help
324 support BusyBox, and/or request features, you can click here:
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339 If you prefer to contact Erik directly to make a donation, donate hardware,
340 request support, etc, you can contact
341 <a href="http://codepoet-consulting.com/">CodePoet Consulting</a> here.
342 CodePoet Consulting can accept both Visa and MasterCard for those that do
347 <h2><a name="optimize">I want to make busybox even smaller, how do I go about it?</a></h2>
349 To conserve bytes it's good to know where they're being used, and the
350 size of the final executable isn't always a reliable indicator of
351 the size of the components (since various structures are rounded up,
352 so a small change may not even be visible by itself, but many small
356 The busybox Makefile can generate a report of how much space is actually
357 being used by each function and variable. Run "<b>make sizes</b>" (preferably
358 with CONFIG_DEBUG off) to get a list of symbols and the amount of
359 space allocated for each one, sorted by size.
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