1<html><head><title>toybox FAQ</title> 2<!--#include file="header.html" --> 3 4<h1>Frequently Asked Questions</h1> 5 6<h2>General Questions</h2> 7 8<ul> 9<li><h2><a href="#why_toybox">Why toybox? (What was wrong with busybox?)</a></h2></li> 10<li><h2><a href="#capitalize">Do you capitalize toybox?</a></h2></li> 11<li><h2><a href="#support_horizon">Why a 7 year support horizon?</a></h2></li> 12<li><h2><a href="#releases">Why time based releases?</a></h2></li> 13<li><h2><a href="#code">Where do I start understanding the toybox source code?</a></h2></li> 14<li><h2><a href="#when">When were historical toybox versions released?</a></h2></li> 15<li><h2><a href="#bugs">Where do I report bugs?</a></h2></li> 16<li><h2><a href="#b_links">What are those /b/number links in the git log?</a></h2></li> 17<li><h2><a href="#opensource">What is the relationship between toybox and android?</a></h2></li> 18<li><h2><a href="#backporting">Will you backport fixes to old versions?</a></h2></li> 19<li><h2><a href="#dotslash">What's this ./ on the front of commands in your examples?</a></h2></li> 20 21</ul> 22 23<h2>Using toybox</h2> 24 25<ul> 26<!-- get binaries --> 27<li><h2><a href="#install">How do I install toybox?</h2></li> 28<li><h2><a href="#cross">How do I cross compile toybox?</h2></li> 29<li><h2><a href="#targets">What architectures does toybox support?</li> 30<li><h2><a href="#system">What part of Linux/Android does toybox provide?</h2></li> 31<li><h2><a href="#mkroot">How do I build a working Linux system with toybox?</a></h2></li> 32</ul> 33 34<hr /><h2><a name="why_toybox" />Q: "Why is there toybox? What was wrong with busybox?"</h2> 35 36<p>A: Toybox started back in 2006 when I (Rob Landley) 37<a href=https://lwn.net/Articles/202106/>handed off BusyBox maintainership</a> 38and <a href=http://landley.net/notes-2006.html#28-09-2006>started over from 39scratch</a> on a new codebase after a 40<a href=http://lists.busybox.net/pipermail/busybox/2006-September/058617.html>protracted licensing argument</a> took all the fun out of working on BusyBox.</p> 41 42<p>Toybox was just a personal project until it got 43<a href=http://landley.net/notes-2011.html#13-11-2011>relaunched</a> 44in November 2011 with a new goal to make Android 45<a href=http://landley.net/aboriginal/about.html#selfhost>self-hosting</a>. 46This involved me relicensing my own 47code, which made people who had never used or participated in the project 48<a href=https://lwn.net/Articles/478308/>loudly angry</a>. The switch came 49after a lot of thinking <a href=http://landley.net/talks/ohio-2013.txt>about 50licenses</a> and <a href=http://landley.net/notes-2011.html#21-03-2011>the 51transition to smartphones</a>, which led to a 52<a href=https://www.youtube.com/watch?v=SGmtP5Lg_t0>2013 talk</a> laying 53out a 54<a href=http://landley.net/talks/celf-2013.txt>strategy</a> 55to make Android self-hosting using toybox. This helped 56<a href=https://code.google.com/p/android/issues/detail?id=76861>bring 57it to Android's attention</a>, and they 58<a href=https://lwn.net/Articles/629362/>merged it</a> into Android M.</p> 59 60<p>The unfixable problem with busybox was licensing: BusyBox predates Android 61by almost a decade, but Android still doesn't ship with it because GPLv3 came 62out around the same time Android did and caused many people to throw 63out the GPLv2 baby with the GPLv3 bathwater. 64Android <a href=https://source.android.com/source/licenses.html>explicitly 65discourages</a> use of GPL and LGPL licenses in its products, and has gradually 66reimplemented historical GPL components (such as its bluetooth stack) under the 67Apache license. Apple's 68<a href=http://meta.ath0.com/2012/02/05/apples-great-gpl-purge/>less subtle</a> response was to freeze xcode at the last GPLv2 releases 69(GCC 4.2.1 with binutils 2.17) for over 5 years while sponsoring the 70development of new projects (clang/llvm/lld) to replace them, 71implementing a 72<a href=https://www.osnews.com/story/24572/apple-ditches-samba-in-favour-of-homegrown-replacement/>new SMB server</a> from scratch to 73<a href=https://archive.org/details/copyleftconf2020-allison>replace samba</a>, 74switching <a href=https://www.theverge.com/2019/6/4/18651872/apple-macos-catalina-zsh-bash-shell-replacement-features>bash with zsh</a>, and so on. 75Toybox itself exists because somebody in a legacy position 76just wouldn't shut up about GPLv3, otherwise I would probably 77still happily be maintaining BusyBox. (For more on how I wound 78up working on busybox in the first place, 79<a href=http://landley.net/aboriginal/history.html>see here</a>.)</p> 80 81<hr /><h2><a name="capitalize" />Q: Do you capitalize toybox?</h2> 82 83<p>A: Only at the start of a sentence. The command name is all lower case so 84it seems silly to capitalize the project name, but not capitalizing the 85start of sentences is awkward, so... compromise. (It is _not_ "ToyBox".)</p> 86 87<hr /><h2><a name="support_horizon">Q: Why a 7 year support horizon?</a></h2> 88 89<p>A: Our <a href=http://lists.busybox.net/pipermail/busybox/2006-September/058440.html>longstanding rule of thumb</a> is to try to run and build on 90hardware and distributions released up to 7 years ago, and feel ok dropping 91support for stuff older than that. (This is a little longer than Ubuntu's 92Long Term Support, but not by much.)</p> 93 94<p>My original theory was "4 to 5 of the 18-month cycles of moore's law should cover 95the vast majority of the installed base of PC hardware", loosely based on some 96research I did <a href=http://www.catb.org/esr/halloween/halloween9.html#id2867629>back in 2003</a> 97and <a href=http://catb.org/esr/writings/world-domination/world-domination-201.html#id248066>updated in 2006</a> 98which said that low end systems were 2 iterations of moore's 99law below the high end systems, and that another 2-3 iterations should cover 100the useful lifetime of most systems no longer being sold but still in use and 101potentially being upgraded to new software releases.</p> 102 103<p>That analysis missed <a href=http://landley.net/notes-2011.html#26-06-2011>industry 104changes</a> in the 1990's that stretched the gap 105from low end to high end from 2 cycles to 4 cycles, and ignored 106<a href=https://landley.net/notes-2010.html#09-10-2010>the switch</a> from PC to smartphone cutting off the R&D air supply of the 107laptop market. Meanwhile the Moore's Law <a href=https://en.wikipedia.org/wiki/Logistic_function>s-curve</a> started bending back down (as they 108<a href=https://en.wikipedia.org/wiki/Diffusion_of_innovations>always do</a>) 109back in 2000, and these days is pretty flat: the drive for faster clock 110speeds <a href=http://www.anandtech.com/show/613>stumbled</a> 111and <a href=http://www.pcworld.com/article/118603/article.html>died</a>, with 112the subsequent drive to go "wide" maxing out for most applications 113around 4x SMP with maybe 2 megabyte caches. These days the switch from exponential to 114linear growth in hardware capabilities is 115<a href=https://www.cnet.com/news/end-of-moores-law-its-not-just-about-physics/>common knowledge</a> and 116<a href=http://www.acm.org/articles/people-of-acm/2016/david-patterson>widely 117accepted</a>.</p> 118 119<p>But the 7 year rule of thumb stuck around anyway: if a kernel or libc 120feature is less than 7 years old, I try to have a build-time configure test 121for it to let the functionality cleanly drop out. I also keep old Ubuntu 122images around in VMs to perform the occasional defconfig build there to 123see what breaks. (I'm not perfect about this, but I accept bug reports.)</p> 124 125<hr /><h2><a name="releases" />Q: Why time based releases?</h2> 126<p>A: Toybox targets quarterly releases (a similar schedule to the Linux 127kernel) because Martin Michlmayr's excellent 128<a href=http://www.youtube.com/watch?v=IKsQsxubuAA>talk on the 129subject</a> was convincing. This is actually two questions, "why have 130releases" and "why schedule them".</p> 131 132<p>Releases provide synchronization points where the developers certify 133"it worked for me". Each release is a known version with predictable behavior, 134and right or wrong at least everyone should be seeing 135similar results so might be able to google an unexpected outcome. 136Releases focus end-user testing on specific versions 137where issues can be reproduced, diagnosed, and fixed. 138Releases also force the developers to do periodic tidying, packaging, 139documentation review, finish up partially implemented features languishing 140in their private trees, and give regular checkpoints to measure progress.</p> 141 142<p>Changes accumulate over time: different feature sets, data formats, 143control knobs... Toybox's switch from "ls -q" to "ls -b" as the default output 144format was not-a-bug-it's-a "design improvement", but the 145difference is academic if the change breaks somebody's script. 146Releases give you the option to schedule upgrades as maintenance, not to rock 147the boat just now, and use a known working release version until later.</p> 148 149<p>The counter-argument is that "continuous integration" 150can be made robust with sufficient automated testing. But like the 151<a href=https://web.archive.org/web/20131123071427/http://www.shirky.com/weblog/2013/11/healthcare-gov-and-the-gulf-between-planning-and-reality/>waterfall method</a>, this places insufficent 152emphasis on end-user feedback and learning from real world experience. 153Developer testing is either testing that the code does what the developers 154expect given known inputs running in an established environment, or it's 155regression testing against bugs previously found in the field. No plan 156survives contact with the enemy, and technology always breaks once it 157leaves the lab and encounters real world data and use cases in new 158runtime and build environments.</p> 159 160<p>The best way to give new users a reasonable first experience is to point 161them at specific stable versions where development quiesced and 162extra testing occurred. There will still be teething troubles, but multiple 163people experiencing the _same_ teething troubles can potentially 164help each other out.</p> 165 166<p>Releases on a schedule are better than releases "when it's ready" for 167the same reason a regularly scheduled bus beats one that leaves when it's 168"full enough": the schedule lets its users make plans. Even if the bus leaves 169empty you know when the next one arrives so missing this one isn't a disaster. 170and starting the engine to leave doesn't provoke a last-minute rush of nearby 171not-quite-ready passengers racing to catch it causing further delay and 172repeated start/stop cycles as it ALMOST leaves. 173(The video in the first paragraph goes into much greater detail.)</p> 174 175<hr /><h2><a name="code" />Q: Where do I start understanding the source code?</h2> 176 177<p>A: Toybox is written in C. There are longer writeups of the 178<a href=design.html>design ideas</a> and a <a href=code.html>code walkthrough</a>, 179and the <a href=about.html>about page</a> summarizes what we're trying to 180accomplish, but here's a quick start:</p> 181 182<p>Toybox uses the standard three stage configure/make/install 183<a href=code.html#building>build</a>, in this case "<b>make defconfig; 184make; make install</b>". Type "<b>make help</b>" to 185see available make targets.</p> 186 187<p><u>The configure stage</u> is copied from the Linux kernel (in the "kconfig" 188directory), and saves your selections in the file ".config" at the top 189level. The "<b>make defconfig</b>" target selects the 190maximum sane configuration (enabling all the commands and features that 191aren't unfinished, or only intended as examples, or debug code...) and is 192probably what you want. You can use "<b>make menuconfig</b>" to manually select 193specific commands to include, through an interactive menu (cursor up and 194down, enter to descend into a sub-menu, space to select an entry, ? to see 195an entry's help text, esc to exit). The menuconfig help text is the 196same as the command's "<b>--help</b>" output.</p> 197 198<p><u>The "make" stage</u> creates a toybox binary (which is stripped, look in 199generated/unstripped for the debug versions), and "<b>make install</b>" adds a bunch of 200symlinks to toybox under the various command names. Toybox determines which 201command to run based on the filename, or you can use the "toybox" name in which case the first 202argument is the command to run (ala "toybox ls -l").</p> 203 204<p><u>You can also build 205individual commands as standalone executables</u>, ala "make sed cat ls". 206The "make change" target builds all of them, as in "change for a $20".</p> 207 208<p><u>The main() function is in main.c</u> at the top level, 209along with setup plumbing and selecting which command to run this time. 210The function toybox_main() in the same file implements the "toybox" 211multiplexer command that lists and selects the other commands.</p> 212 213<p><u>The individual command implementations are under "toys"</u>, and are grouped 214into categories (mostly based on which standard they come from, posix, lsb, 215android...) The "pending" directory contains unfinished commands, and the 216"examples" directory contains example code that aren't really useful commands. 217Commands in those two directories 218are _not_ selected by defconfig. (Most of the files in the pending directory 219are third party submissions that have not yet undergone 220<a href=cleanup.html>proper code review</a>.)</p> 221 222<p><u>Common infrastructure shared between commands is under "lib"</u>. Most 223commands call lib/args.c to parse their command line arguments before calling 224the command's own main() function, which uses the option string in 225the command's NEWTOY() macro. This is similar to the libc function getopt(), 226but more powerful, and is documented at the top of lib/args.c. A NULL option 227string prevents this code from being called for that command.</p> 228 229<p><u>The build/install infrastructure is shell scripts under 230"scripts"</u> (starting with scripts/make.sh and scripts/install.sh). 231<u>These populate the "generated" directory</u> with headers 232created from other files, which are <a href=code.html#generated>described</a> 233in the code walkthrough. All the 234build's temporary files live under generated, including the .o files built 235from the .c files (in generated/obj). The "make clean" target deletes that 236directory. ("make distclean" also deletes your .config and deletes the 237kconfig binaries that process .config.)</p> 238 239<p><u>Each command's .c file contains all the information for that command</u>, so 240adding a command to toybox means adding a single file under "toys". 241Usually you <a href=code.html#adding>start a new command</a> by copying an 242existing command file to a new filename 243(toys/examples/hello.c, toys/examples/skeleton.c, toys/posix/cat.c, 244and toys/posix/true.c have all been used for this purpose) and then replacing 245all instances of its old name with the new name (which should match the 246new filename), and modifying the help text, argument string, and what the 247code does. You might have to "make distclean" before your new command 248shows up in defconfig or menuconfig.</p> 249 250<p><u>The toybox test suite lives in the "tests" directory</u>, and is 251driven by scripts/test.sh and scripts/runtest.sh. From the top 252level you can "make tests" to test everything, or "make test_sed" to test a 253single command's standalone version (which should behave identically, 254but that's why we test). You can set TEST_HOST=1 to test the host version 255instead of the toybox version (in theory they should work the same), 256and VERBOSE=all to see diffs of the expected and actual output for all 257failing tests. The default VERBOSE=fail stops at the first such failure.</p> 258 259<hr /><h2><a name="when" />Q: When were historical toybox versions released?</h2> 260 261<p>A: For vanilla releases, check the 262<a href=https://github.com/landley/toybox/tags>date on the commit tag</a> 263or <a href=https://landley.net/toybox/downloads/binaries/>the 264example binaries</a> against the output of "toybox --version". 265Between releases the --version 266information is in "git describe --tags" format with "tag-count-hash" showing the 267most recent commit tag, the number of commits since that tag, and 268the hash of the current commit.</p> 269 270<p>Android makes its own releases on its own 271<a href=https://en.wikipedia.org/wiki/Android_version_history>schedule</a> 272using its own version tags, but lists corresponding upstream toybox release 273versions <a href=https://android.googlesource.com/platform/system/core/+/master/shell_and_utilities/README.md>here</a>. For more detail you can look up 274<a href=https://android.googlesource.com/platform/external/toybox/+refs>AOSP's 275git tags</a>. (The <a href=https://source.android.com/setup/start>Android Open Source Project</a> is the "upstream" android vendors 276start form when making their own releases. Google's phones run AOSP versions 277verbatim, other vendors tend to take those releases as starting points to 278modify.)</p> 279 280<p>If you want to find the vanilla toybox commit corresponding to an AOSP 281toybox version, find the most recent commit in the android log that isn't from a 282@google or @android address and search for it in the vanilla commit log. 283(The timestamp should match but the hash will differ, 284because each git hash includes the previous 285git hash in the data used to generate it so all later commits have a different 286hash if any of the tree's history differs; yes Linus Torvalds published 3 years 287before Satoshi Nakamoto.) Once you've identified the vanilla commit's hash, 288"git describe --tags $HASH" in the vanilla tree should give you the --version 289info for that one.</p> 290 291<hr /><h2><a name="bugs" />Q: Where do I report bugs?</h2> 292 293<p>A: Ideally on the <a href=http://lists.landley.net/listinfo.cgi/toybox-landley.net>mailing list</a>, although <a href=mailto:rob@landley.net>emailing the 294maintainer</a> is a popular if slightly less reliable alternative. 295Issues submitted to <a href=https://github.com/landley/toybox>github</a> 296are generally dealt with less promptly, but mostly get done eventually. 297AOSP has its <a href=https://source.android.com/setup/contribute/report-bugs>own bug reporting mechanism</a> (although for toybox they usually forward them 298to the mailing list) and Android vendors usually forward them to AOSP which 299forwards them to the list.</p> 300 301<p>Note that if we can't reproduce a bug, we probably can't fix it. 302Not only does this mean providing enough information for us to see the 303behavior ourselves, but ideally doing so in a reasonably current version. 304The older it is the greater the chance somebody else found and fixed it 305already, so the more out of date the version you're reporting a bug against 306the less effort we're going to put into reproducing the problem.</p> 307 308<hr /><h2><a name="b_links" />Q: What are those /b/number bug report 309links in the git log?</h2> 310 311<p>A: It's a Google thing. Replace /b/$NUMBER with 312https://issuetracker.google.com/$NUMBER to read it outside the googleplex.</p> 313 314<hr /><a name="opensource" /><h2>Q: What is the relationship between toybox and android?</h2> 315 316<p>A: The <a href=about.html>about page</a> tries to explain that, 317and Linux Weekly News has covered toybox's history a 318<a href=https://lwn.net/Articles/202106/>little</a> 319<a href=https://lwn.net/Articles/478308/>over</a> 320<a href=https://lwn.net/Articles/616272/>the</a> 321<a href=https://lwn.net/Articles/629362/>years</a>.</p> 322 323<p>Toybox is a traditional open source project created and maintained 324by hobbyist (volunteer) developers, originally for Linux but these days 325also running on Android, BSD, and MacOS. The project started in 2006 326and its original author (Rob Landley) 327continues to maintain the open source project.</p> 328 329<p>Android's base OS maintainer (Elliott Hughes, I.E. enh) 330<a href=https://github.com/landley/toybox/commit/69a9f257234a>ported</a> 331<a href=https://github.com/landley/toybox/commit/6a29bb1ebe62>toybox</a> 332to Android in 2014, merged it into Android M (Marshmallow), and remains 333Android's toybox maintainer. (He explained it in his own words in 334<a href=http://androidbackstage.blogspot.com/2016/07/episode-53-adb-on-adb.html>this podcast</a>, starting either 18 or 20 minutes in depending how 335much backstory you want.)</p> 336 337<p>Android's policy for toybox development is to push patches to the 338open source project (submitting them via the mailing list) then 339"git pull" the public tree into Android's tree. To avoid merge conflicts, Android's 340tree doesn't change any of the existing toybox files but instead adds <a href=https://android.googlesource.com/platform/external/toybox/+/refs/heads/master/Android.bp>parallel 341build infrastructure</a> off to one side. (Toybox uses a make wrapper around bash 342scripts, AOSP builds with soong/ninja instead and checks in a snapshot of the 343generated/ directory to avoid running kconfig each build). 344Android's changes to toybox going into the open source tree first 345and being pulled from there into Android keeps the two trees in 346sync, and makes sure each change undergoes full open source design review 347and discussion.</p> 348 349<p>Rob acknowledges Android is by far the largest userbase for the project, 350but develops on a standard 64-bit Linux+glibc distro while building embedded 35132-bit big-endian nommu musl systems requiring proper data alignment for work, 352and is not a Google employee so does not have access 353to the Google build cluster of powerful machines capable of running the full 354AOSP build in a reasonable amount of time. Rob is working to get android 355building under android (the list of toybox tools Android's build uses is 356<a href=https://android.googlesource.com/platform/prebuilts/build-tools/+/refs/heads/master/path/linux-x86/>here</a>, 357and what else it needs from its build environment is 358<a href=https://android.googlesource.com/platform/build/soong/+/refs/heads/master/ui/build/paths/config.go>here</a>), and he hopes someday to not only make a usable development 359environment out of it but also nudge the base OS towards a more granular 360package management system allowing you to upgrade things like toybox without 361a complete reinstall and reboot, plus the introduction of a "posix container" 362within which you can not only run builds, but selinux lets you run binaries 363you've just built). In the meantime, Rob tests static bionic 364builds via the Android NDK when he remembers, but has limited time to work 365on toybox because it's not his day job. (The products his company makes ship 366toybox and they do sponsor the project's development, but it's one of many 367responsibilities at work.)</p> 368 369<p>Elliott is the Android base OS maintainer, in which role he manages 370a team of engineers. He also has limited time for toybox, both because it's one 371of many packages he's responsible for (he maintains bionic, used to maintain 372dalvik...) and because he allowed himself to be promoted into management 373and thus spends less time coding than he does sitting in meetings where testers 374talk to security people about vendor issues.</p> 375 376<p>Android has many other coders and security people who submit the occasional 377toybox patch, but of the last 1000 commits at the <a href=https://github.com/landley/toybox/commit/88b34c4bd3f8>time 378of writing</a> this FAQ entry, Elliott submitted 276 and all other google.com 379or android.com addresses combined totaled 17. (Rob submitted 591, leaving 380116 from other sources, but for both Rob and Elliott there's a lot of "somebody 381else pointed out an issue, and then we wrote a patch". A lot of patches 382from both "Author:" lines thank someone else for the suggestion in the 383commit comment.)</p> 384 385<hr /><a name="backporting" /><h2>Q: Will you backport fixes to old versions?</h2> 386 387<p>A: Probably not. The easiest thing to do is get your issue fixed upstream 388in the current release, then get the newest version of the 389project built and running in the old environment.</p> 390 391<p>Backporting fixes generally isn't something open source projects run by 392volunteer developers do because the goal of the project's development community 393is to extend and improve the project. We're happy to respond to our users' 394needs, but if you're coming to the us for free tech support we're going 395to ask you to upgrade to a current version before we try to diagnose your 396problem.</p> 397 398<p>The volunteers are happy to fix any bugs you point out in the current 399versions because doing so helps everybody and makes the project better. We 400want to make the current version work for you. But diagnosing, debugging, and 401backporting fixes to old versions doesn't help anybody but you, so isn't 402something we do for free. The cost of volunteer tech support is using a 403reasonably current version of the project.</p> 404 405<p>If you're using an old version built with an old 406compiler on an old OS (kernel and libc), there's a fairly large chance 407whatever problem you're 408seeing already got fixed, and to get that fix all you have to do is upgrade 409to a newer version. Diagnosing a problem that wasn't our bug means we spent 410time that only helps you, without improving the project. 411If you don't at least _try_ a current version, you're asking us for free 412personalized tech support.</p> 413 414<p>Reproducing bugs in current versions also makes our job easier. 415The further back in time 416you are, the more work it is for us digging back in the history to figure 417out what we hadn't done yet in your version. If spot a problem in a git 418build pulled 3 days ago, it's obvious what changed and easy to fix or back out. 419If you ask about the current release version 3 months after it came out, 420we may have to think a while to remember what we did and there are a number of 421possible culprits, but it's still tractable. If you ask about 3 year old 422code, we have to reconstruct the history and the problem could be anything, 423there's a lot more ground to cover and we haven't seen it in a while.</p> 424 425<p>As a rule of thumb, volunteers will generally answer polite questions about 426a given version for about three years after its release before it's so old 427we don't remember the answer off the top of our head. And if you want us to 428put any _effort_ into tracking it down, we want you to put in a little effort 429of your own by confirming it's still a problem with the current version 430(I.E. we didn't fix it already). It's 431also hard for us to fix a problem of yours if we can't reproduce it because 432we don't have any systems running an environment that old.</p> 433 434<p>If you don't want to upgrade, you have the complete source code and thus 435the ability to fix it yourself, or can hire a consultant to do it for you. If 436you got your version from a vendor who still supports the older version, they 437can help you. But there are limits as to what volunteers will feel obliged to 438do for you.</p> 439 440<p>Commercial companies have different incentives. Your OS vendor, or 441hardware vendor for preinstalled systems, may have their own bug reporting 442mechanism and update channel providing backported fixes. And a paid consultant 443will happily set up a special environment just to reproduce your problem.</p> 444 445<hr /><h2><a name="install" />Q: How do I install toybox?</h2> 446 447<p>A: 448Multicall binaries like toybox behave differently based on the filename 449used to call them, so if you "mv toybox ls; ./ls -l" it acts like ls. Creating 450symlinks or hardlinks and adding them to the $PATH lets you run the 451commands normally by name, so that's probably what you want to do.</p> 452 453<p>If you already have a <a href=https://landley.net/toybox/downloads/binaries/>toybox binary</a> 454you can install a tree of command symlinks to 455<a href=http://git.musl-libc.org/cgit/musl/tree/include/paths.h>the 456standard path</a> 457locations (<b>export PATH=/bin:/usr/bin:/sbin:/usr/sbin</b>) by doing:</p> 458 459<blockquote><p><b>for i in $(/bin/toybox --long); do ln -s /bin/toybox $i; done</b></p></blockquote> 460 461<p>Or you can install all the symlinks in the same directory as the toybox binary 462(<b>export PATH="$PWD:$PATH"</b>) via:</p> 463 464<blockquote><p><b>for i in $(./toybox); do ln -s toybox $i; done</b></p></blockquote></p> 465 466<p>When building from source, use the "<b>make install</b>" and 467"<b>make install_flat</b>" 468targets with an appropriate <b>PREFIX=/target/path</b> either 469exported or on the make command line. When cross compiling, 470"<b>make list</b>" outputs the command names enabled by defconfig. 471For more information, see "<b>make help</b>".</p> 472 473<p>The command name "toybox" takes the second argument as the name of the 474command to run, so "./toybox ls -l" also behaves like ls. The "toybox" 475name is special in that it can have a suffix (toybox-i686 or toybox-1.2.3) 476and still be recognized, so you can have multiple versions of toybox in the 477same directory.</p> 478 479<p>When toybox doesn't recognize its 480filename as a command, it dereferences one 481level of symlink. So if your script needs "gsed" you can "ln -s sed gsed", 482then when you run "gsed" toybox knows how to be "sed".</p> 483 484<hr /><h2><a name="dotslash" />Q: What's this ./ on the front of commands in your examples?</h2> 485 486<p>A: When you don't give a path to a command's executable file, 487linux command shells search the directories listed in the $PATH envionment 488variable (in order), which usually doesn't include the current directory 489for security reasons. The 490magic name "." indicates the current directory (the same way ".." means 491the parent directory and starting with "/" means the root directory) 492so "./file" gives a path to the executable file, and thus runs a command 493out of the current directory where just typing "file" won't find it. 494For historical reasons PATH is colon-separated, and treats an 495empty entry (including leading/trailing colon) as "check the current 496directory", so if you WANT to add the current directory to PATH you 497can PATH="$PATH:" but doing so is a TERRIBLE idea.</p> 498 499<p>Toybox's shell (toysh) checks for built-in commands before looking at the 500$PATH (using the standard "bash builtin" logic just with lots more builtins), 501so "ls" doesn't have to exist in your filesystem for toybox to find it. When 502you give a path to a command the shell won't run the built-in version 503but will run the file at that location. (But the multiplexer command 504won't: "toybox /bin/ls" runs the built-in ls, you can't point it at an 505arbitrary file out of the filesystem and have it run that. You could 506"toybox nice /bin/ls" though.)</p> 507 508<hr /><h2><a name="standalone" />Q: How do I make individual/standalone toybox command binaries?</h2> 509 510<p>After running the configure step (generally "make defconfig") 511you can "make list" to see available command names you can use as build 512targets to build just that command 513(ala "make sed"). Commands built this way do not contain a multiplexer and 514don't care what the command filename is.</p> 515 516<p>The "make change" target (as in change for a $20) builds every command 517standalone (in the "change" subdirectory). Note that this is collectively 518about 10 times as large as the multiplexer version, both in disk space and 519runtime memory. (Even more when statically linked.)</p> 520 521<hr /><h2><a name="cross" />Q: How do I cross compile toybox?</h2> 522 523<p>A: You need a compiler "toolchain" capable of producing binaries that 524run on your target. A toolchain is an 525integrated suite of compiler, assembler, and linker, plus the standard 526headers and 527libraries necessary to build C programs. (And a few miscellaneous binaries like 528nm and objdump that display info about <a href=https://en.wikipedia.org/wiki/Executable_and_Linkable_Format>ELF files</a>.)</p> 529 530<p>Toybox supports the standard $CROSS_COMPILE prefix environnment variable, 531same as the Linux kernel build uses. This is used to prefix all the tools 532(target-cc, target-ld, target-strip) during the build, meaning the prefix 533usually ends with a "-" that's easy to forget but kind of important 534("target-cc" and "targetcc" are not the same name).</p> 535 536<p>You can either provide a 537full path in the CROSS_COMPILE string, or add the appropriate bin directory 538to your $PATH. I.E:</p> 539 540<blockquote> 541<b><p>make LDFLAGS=--static CROSS_COMPILE=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin/m68k-linux-musl- distclean defconfig toybox</p></b> 542</blockquote> 543 544<p>Is equivalent to:</p> 545 546<blockquote><b><p> 547export "PATH=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin:$PATH"<br /> 548LDFLAGS=--static CROSS_COMPILE=m68k-linux-musl- make distclean defconfig toybox 549</p></b></blockquote> 550 551<p>(Both of those examples use static linking so you can install just 552the single file to target, or test them with "qemu-m68k toybox". Feel free 553to dynamically link instead if you prefer, mkroot offers a "dynamic" 554add-on to copy the compiler's shared libraries into the new root 555filesystem.)</p> 556 557<p>Toybox's <a href=#mkroot>system builder</a> can use a simpler $CROSS 558variable to specify the target(s) to build for if you've installed 559<a href=#cross2>compatible</a> cross compilers under the "ccc" directory. 560Behind the scenes this uses wildcard expansion to set $CROSS_COMPILER to 561an appropriate path/prefix-.</p> 562 563<hr /><h2><a name="targets">Q: What architectures does toybox support?</h2> 564 565<p>Toybox runs on 64 bit and 32 bit processors, little endian and big endian, 566tries to respect alignment, and will enable nommu support when fork() is 567unavailable (or when TOYBOX_FORCE_NOMMU is enabled in the config to 568work around broken nommu toolchains), but otherwise tries to be 569processor agnostic (although some commands such as strace can't avoid 570a processor-specific if/else staircase.).</p> 571 572<P>Several commands (such as ps/top) are unavoidably full of Linux assumptions. 573Some subset of the commands have been made to run on BSD and MacOS X, and 574lib/portability.* and scripts/genconfig.sh exist to catch some known 575variations.</p> 576</p> 577 578<p>Each release gets tested against two compilers (llvm, gcc), three C 579libraries (bionic, musl, glibc), and a half-dozen different processor 580types, in the following combinations:</p> 581 582<a name="cross1" /> 583<p><a href="#cross1">1) gcc+glibc = host toolchain</a></p> 584 585<p>Most Linux distros come with that as a host compiler, which is used by 586default when you build normally 587(<b>make distclean defconfig toybox</b>, or <b>make menuconfig</b> followed 588by <b>make</b>).</p> 589 590<p>You can use LDFLAGS=--static if you want static binaries, but static 591glibc is hugely inefficient ("hello world" is 810k on x86-64) and throws a 592zillion linker warnings because one of its previous maintainers 593<a href=https://www.akkadia.org/drepper/no_static_linking.html>was insane</a> 594(which meant at the time he refused to fix 595<a href=https://elinux.org/images/2/2d/ELC2010-gc-sections_Denys_Vlasenko.pdf>obvious bugs</a>), plus it uses dlopen() at runtime to implement basic things like 596<a href=https://stackoverflow.com/questions/15165306/compile-a-static-binary-which-code-there-a-function-gethostbyname>DNS lookup</a> (which is almost impossible 597to support properly from a static binary because you wind up with two 598instances of malloc() managing two heaps which corrupt as soon as a malloc() 599from one is free()d into the other, although glibc added 600<a href=https://stackoverflow.com/questions/14289488/use-dlsym-on-a-static-binary>improper support</a> which still requires the shared libraries to be 601installed on the system alongside the static binary: 602<a href=https://www.youtube.com/watch?v=Ih-3vK2qLls>in brief, avoid</a>). 603These days glibc is <a href=https://blog.aurel32.net/175>maintained 604by a committee</a> instead of a single 605maintainer, if that's an improvement. (As with Windows and 606Cobol, most people just try to get on with their lives.)</p> 607 608<a name="cross2" /> 609<p><a href="#cross2">2) gcc+musl = musl-cross-make</a></p> 610 611<p>These cross compilers are built from the 612<a href=http://musl.libc.org/>musl-libc</a> maintainer's 613<a href=https://github.com/richfelker/musl-cross-make>musl-cross-make</a> 614project, built by running toybox's <a href=https://github.com/landley/toybox/blob/master/scripts/mcm-buildall.sh>scripts/mcm-buildall.sh</a> in that directory, 615and then symlink the resulting "ccc" subdirectory into toybox where 616"make root CROSS=" can find them, ala:</p> 617 618<blockquote><b><pre> 619cd ~ 620git clone https://github.com/landley/toybox 621git clone https://github.com/richfelker/musl-cross-make 622cd musl-cross-make 623../toybox/scripts/mcm-buildall.sh # this takes a while 624ln -s $(realpath ccc) ../toybox/ccc 625</pre></b></blockquote> 626 627<p>Since this takes a long time to run, and builds lots of targets 628(cross and native), we've uploaded 629<a href=downloads/binaries/toolchains/latest>the resulting binaries</a> 630so you can wget and extract a tarball or two instead of 631compiling them all yourself. (See the README in that directory for details. 632Yes there's a big source tarball in there for license compliance reasons.)</p> 633 634<p>Instead of CROSS= you can also specify a CROSS_COMPILE= prefix 635in the same format the Linux kernel build uses. You can either provide a 636full path in the CROSS_COMPILE string, or add the appropriate bin directory 637to your $PATH. I.E:</p> 638 639<blockquote> 640<b><p>make LDFLAGS=--static CROSS_COMPILE=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin/m68k-linux-musl- distclean defconfig toybox</p></b> 641</blockquote> 642 643<p>Is equivalent to:</p> 644 645<blockquote><b><p> 646export "PATH=~/musl-cross-make/ccc/m68k-linux-musl-cross/bin:$PATH"<br /> 647LDFLAGS=--static make distclean defconfig toybox CROSS=m68k-linux-musl- 648</p></b></blockquote> 649 650<p>Note: these examples use static linking because a dynamic musl binary 651won't run on your host unless you install musl's libc.so into the system 652libraries (which is an accident waiting to happen adding a second C library 653to most glibc linux distribution) or play with $LD_LIBRARY_PATH. 654(The <a href=https://github.com/landley/toybox/blob/master/scripts/root/dynamic>dynamic</a> package 655in mkroot copies the shared libraries out of the toolchain to create a dynamic 656linking environment in the root filesystem, but it's not nearly as well 657tested.)</p> 658 659<a name="cross3" /> 660<p><a href="#cross3">3) llvm+bionic = Android NDK</a></p> 661 662<p>The <a href=https://developer.android.com/ndk/downloads>Android 663Native Development Kit</a> provides an llvm toolchain with the bionic 664libc used by Android. To turn it into something toybox can use, you 665just have to add an appropriately prefixed "cc" symlink to the other 666prefixed tools, ala:</p> 667 668<blockquote><b><pre> 669unzip android-ndk-r21b-linux-x86_64.zip 670cd android-ndk-21b/toolchains/llvm/prebuilt/linux-x86_64/bin 671ln -s x86_64-linux-android29-clang x86_64-linux-android-cc 672PATH="$PWD:$PATH" 673cd ~/toybox 674make distclean 675make LDFLAGS=--static CROSS_COMPILE=x86_64-linux-android- defconfig toybox 676</pre></b></blockquote> 677 678<p>Again, you need to static link unless you want to install bionic on your 679host. Binaries statically linked against bionic are almost as big as with 680glibc, but at least it doesn't have the dlopen() issues. (You still can't 681sanely use dlopen() from a static binary, but bionic doesn't use dlopen() 682internally to implement basic features.)</p> 683 684<p>Note: although the resulting toybox will run in a standard 685Linux system, even "hello world" 686statically linked against bionic segfaults before calling main() 687when /dev/null isn't present. This presents mkroot with a chicken and 688egg problem for both chroot and qemu cases, because mkroot's init script 689has to mount devtmpfs on /dev to provide /dev/null before the shell binary 690can run mkroot's init script. 691Since mkroot runs as a normal user, we can't "mknod dev/null" at build 692time to create a "null" device in the filesystem we're packaging up so 693initramfs doesn't start with an empty /dev, and the 694<a href=https://lkml.org/lkml/2016/6/22/686>kernel</a> 695<a href=https://lkml.org/lkml/2017/5/14/180>developers</a> 696<a href=https://lkml.org/lkml/2017/9/13/651>repeatedly</a> 697<a href=https://lkml.org/lkml/2020/5/14/1584>rejected</a> a patch to 698make the Linux kernel honor DEVTMPFS_MOUNT in initramfs. Teaching toybox 699cpio to accept synthetic filesystem metadata, 700presumably in <a href=https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt>get_init_cpio</a> format, remains a todo item.</p> 701 702<hr /><h2><a name="system" />Q: What part of Linux/Android does toybox provide?</h2> 703 704<p>A: 705Toybox is one of three packages (linux, libc, command line) which together provide a bootable unix-style command line operating system. 706Toybox provides the "command line" part, with a 707<a href=https://en.wikipedia.org/wiki/Bash_(Unix_shell)>bash</a> compatible 708<a href=https://en.wikipedia.org/wiki/Unix_shell>command line interpreter</a> 709and over two hundred <a href=https://landley.net/toybox/help.html>commands</a> 710to call from it, as documented in 711<a href=https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/>posix</a>, 712the <a href=https://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/cmdbehav.html>Linux Standard Base</a>, and the 713<a href=https://man7.org/linux/man-pages/dir_section_1.html>Linux Manual 714Pages</a>.</p> 715 716<p>Toybox is not by itself a complete operating system, it's a set of standard command line utilities that run in an operating system. 717Booting a simple system to a shell prompt requires a kernel to drive the hardware (such as Linux, or BSD with a Linux emulation layer), programs for the system to run (such as toybox's commands), and a C library ("libc") to connect them together.</p> 718 719<p>Toybox has a policy of requiring no external dependencies other than the 720kernel and C library (at least for defconfig builds). You can optionally enable support for 721additional libraries in menuconfig (such as openssl, zlib, or selinux), 722but toybox either provides its own built-in versions of such functionality 723(which the libraries provide larger, more complex, often assembly optimized 724alternatives to), or allows things like selinux support to cleanly drop 725out.</p> 726 727<p>Static linking (with the --static option) copies library contents 728into the resulting binary, creating larger but more portable programs which 729can run even if they're the only file in the filesystem. Otherwise, 730the "dynamically" linked programs require each shared library file to be 731present on the target system, either copied out of the toolchain or built 732again from source (with potential version skew if they don't match the toolchain 733versions exactly), plus a dynamic linker executable installed at a specific 734absolute path. See the 735<a href=https://www.man7.org/linux/man-pages/man1/ldd.1.html>ldd</a>, 736<a href=https://www.man7.org/linux/man-pages/man8/ld.so.8.html>ld.so</a>, 737and <a href=https://www.man7.org/linux/man-pages/man7/libc.7.html>libc</a> 738man pages for details.</p> 739 740<p>Most embedded systems will add another package to the kernel/libc/cmdline 741above containing the dedicated "application" that the embedded system exists to 742run, plus any other packages that application depends on. 743Build systems add a native version of the toolchain packages so 744they can compile additional software on the resulting system. Desktop systems 745add a GUI and additional application packages like web browsers 746and video players. A linux distro like Debian adds hundreds of packages. 747Android adds around a thousand.</p> 748 749<p>But all of these systems conceptually sit on a common three-package 750"kernel/libc/cmdline" base (often inefficiently implemented and broken up 751into more packages), and toybox aims to provide a simple, reproducible, 752auditable version of the cmdline portion of that base.</p> 753 754<hr /><h2><a name="mkroot" />Q: How do you build a working Linux system with toybox?</h2> 755 756<p>A: Toybox has a built-in <a href=https://github.com/landley/toybox/blob/master/scripts/mkroot.sh>system builder</a>, with the Makefile target "<b>make 757root</b>". To enter the resulting root filesystem, "<b>sudo chroot 758root/host/fs /init</b>". Type "exit" to get back out.</p> 759 760<p>You can cross compile simple three package (toybox+libc+linux) 761systems configured to boot to a shell prompt under the emulator 762<a href=https://qemu.org>qemu</a> 763by specifying a target type with CROSS= 764(or by setting CROSS_COMPILE= to a <a href=#cross>cross compiler</a> prefix with optional absolute 765path), and pointing the build at a Linux kernel source directory, ala:</p> 766 767<blockquote><p><b>make root CROSS=sh4 LINUX=~/linux</b></p></blockquote> 768 769<p>Then you can <b>cd root/sh4; ./qemu-sh4.sh</b> to launch the emulator. 770(You'll need the appropriate qemu-system-* emulator binary installed.) 771Type "exit" when done and it should shut down the emulator on the way out, 772similar to exiting the chroot version. (Except this is more like you ssh'd 773to a remote machine: the emulator created its own CPU with its own memory 774and I/O devices, and booted a kernel in it.)</p> 775 776<p>The build finds the <a href=#system>three packages</a> needed to produce 777this system because 1) you're in a toybox source directory, 2) your cross 778compiler has a libc built into it, 3) you tell it where to find a Linux kernel 779source directory with LINUX= on the command line. If you don't say LINUX=, 780it skips that part of the build and just produces a root filesystem directory 781ala the first example in this FAQ answer.</p> 782 783<p>The CROSS= shortcut expects a "ccc" symlink in the toybox source directory 784pointing at a directory full of cross compilers. The ones I test this with are built from the musl-libc 785maintainer's 786<a href=https://github.com/richfelker/musl-cross-make>musl-cross-make</a> 787project, built by running toybox's scripts/mcm-buildall.sh in that directory, 788and then symlink the resulting "ccc" subdirectory into toybox where CROSS= 789can find them:</p> 790 791<blockquote><b><pre> 792cd ~ 793git clone https://github.com/landley/toybox 794git clone https://github.com/richfelker/musl-cross-make 795cd musl-cross-make 796../toybox/scripts/mcm-buildall.sh # this takes a while 797ln -s $(realpath ccc) ../toybox/ccc 798</pre></b></blockquote> 799 800<p>If you don't want to do that, you can download <a href=http://mkroot.musl.cc/latest/>prebuilt binary versions</a> from Zach van Rijn's site and 801just extract them into a "ccc" subdirectory under the toybox source.</p> 802 803<p>Once you've installed the cross compilers, "<b>make root CROSS=help</b>" 804should list all the available cross compilers it recognizes under ccc, 805something like:</p> 806 807<blockquote><b><p> 808aarch64 armv4l armv5l armv7l armv7m armv7r i486 i686 m68k microblaze mips mips64 mipsel powerpc powerpc64 powerpc64le s390x sh2eb sh4 x32 x86_64 809</p></b></blockquote> 810 811<p>(A long time ago I 812<a href=http://landley.net/aboriginal/architectures.html>tried to explain</a> 813what some of these architectures were.)</p> 814 815<p>You can build all the targets at once, and can add additonal packages 816to the build, by calling the script directly and listing packages on 817the command line:</p> 818 819<blockquote> 820<p><b>scripts/mkroot.sh CROSS=all LINUX=~/linux dropbear</b></p> 821</blockquote> 822 823<p>An example package build script (building the dropbear ssh server, adding a 824port forward from 127.0.0.1:2222 to the qemu command line, and providing a 825ssh2dropbear.sh convenience script to the output directory) is provided 826in the scripts/root directory. If you add your own scripts elsewhere, just 827give a path to them on the command line. (No, I'm not merging more package build 828scripts, I <a href=https://speakerdeck.com/landley/developing-for-non-x86-targets-using-qemu?slide=78>learned that lesson</a> long ago. But if you 829want to write your own, feel free.)</p> 830 831<p>(Note: currently mkroot.sh cheats. If you don't have a .config it'll 832make defconfig and add CONFIG_SH and CONFIG_ROUTE to it, because the new 833root filesystem kinda needs those commands to function properly. If you already 834have a .config that 835_doesn't_ have CONFIG_SH in it, you won't get a shell prompt or be able to run 836the init script without a shell. This is currently a problem because sh 837and route are still in pending and thus not in defconfig, so "make root" 838cheats and adds them. I'm working on it. tl;dr if make root doesn't work 839"rm .config" and run it again, and all this should be fixed up in future when 840those two commands are promoted out of pending so "make defconfig" would have 841what you need anyway. It's designed to let yout tweak your config, which is 842why it uses the .config that's there when there is one, but the default is 843currently wrong because it's not quite finished yet. All this should be 844cleaned up in a future release, before 1.0.)</p> 845 846 847 848<!--#include file="footer.html" --> 849