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