polarssl: disable SSLv3 support, fixes CVE-2014-3566 (POODLE)
[openwrt/openwrt.git] / docs / build.tex
1 One of the biggest challenges to getting started with embedded devices is that you
2 cannot just install a copy of Linux and expect to be able to compile a firmware.
3 Even if you did remember to install a compiler and every development tool offered,
4 you still would not have the basic set of tools needed to produce a firmware image.
5 The embedded device represents an entirely new hardware platform, which is
6 most of the time incompatible with the hardware on your development machine, so in a process called
7 cross compiling you need to produce a new compiler capable of generating code for
8 your embedded platform, and then use it to compile a basic Linux distribution to
9 run on your device.
10
11 The process of creating a cross compiler can be tricky, it is not something that is
12 regularly attempted and so there is a certain amount of mystery and black magic
13 associated with it. In many cases when you are dealing with embedded devices you will
14 be provided with a binary copy of a compiler and basic libraries rather than
15 instructions for creating your own -- it is a time saving step but at the same time
16 often means you will be using a rather dated set of tools. Likewise, it is also common
17 to be provided with a patched copy of the Linux kernel from the board or chip vendor,
18 but this is also dated and it can be difficult to spot exactly what has been
19 modified to make the kernel run on the embedded platform.
20
21 \subsection{Building an image}
22
23 OpenWrt takes a different approach to building a firmware; downloading, patching
24 and compiling everything from scratch, including the cross compiler. To put it
25 in simpler terms, OpenWrt does not contain any executables or even sources, it is an
26 automated system for downloading the sources, patching them to work with the given
27 platform and compiling them correctly for that platform. What this means is that
28 just by changing the template, you can change any step in the process.
29
30 As an example, if a new kernel is released, a simple change to one of the Makefiles
31 will download the latest kernel, patch it to run on the embedded platform and produce
32 a new firmware image -- there is no work to be done trying to track down an unmodified
33 copy of the existing kernel to see what changes had been made, the patches are
34 already provided and the process ends up almost completely transparent. This does not
35 just apply to the kernel, but to anything included with OpenWrt -- It is this one
36 simple understated concept which is what allows OpenWrt to stay on the bleeding edge
37 with the latest compilers, latest kernels and latest applications.
38
39 So let's take a look at OpenWrt and see how this all works.
40
41
42 \subsubsection{Download OpenWrt}
43
44 OpenWrt can be downloaded via subversion using the following command:
45
46 \begin{Verbatim}
47 $ svn checkout svn://svn.openwrt.org/openwrt/trunk openwrt-trunk
48 \end{Verbatim}
49
50 Additionally, there is a trac interface on \href{https://dev.openwrt.org/}{https://dev.openwrt.org/}
51 which can be used to monitor svn commits and browse the source repository.
52
53
54 \subsubsection{The directory structure}
55
56 There are four key directories in the base:
57
58 \begin{itemize}
59 \item \texttt{tools}
60 \item \texttt{toolchain}
61 \item \texttt{package}
62 \item \texttt{target}
63 \end{itemize}
64
65 \texttt{tools} and \texttt{toolchain} refer to common tools which will be
66 used to build the firmware image, the compiler, and the C library.
67 The result of this is three new directories, \texttt{build\_dir/host}, which is a temporary
68 directory for building the target independent tools, \texttt{build\_dir/toolchain-\textit{<arch>}*}
69 which is used for building the toolchain for a specific architecture, and
70 \texttt{staging\_dir/toolchain-\textit{<arch>}*} where the resulting toolchain is installed.
71 You will not need to do anything with the toolchain directory unless you intend to
72 add a new version of one of the components above.
73
74 \begin{itemize}
75 \item \texttt{build\_dir/host}
76 \item \texttt{build\_dir/toolchain-\textit{<arch>}*}
77 \end{itemize}
78
79 \texttt{package} is for exactly that -- packages. In an OpenWrt firmware, almost everything
80 is an \texttt{.ipk}, a software package which can be added to the firmware to provide new
81 features or removed to save space. Note that packages are also maintained outside of the main
82 trunk and can be obtained from subversion using the package feeds system:
83
84 \begin{Verbatim}
85 $ ./scripts/feeds update
86 \end{Verbatim}
87
88 Those packages can be used to extend the functionality of the build system and need to be
89 symlinked into the main trunk. Once you do that, the packages will show up in the menu for
90 configuration. You would do something like this:
91
92 \begin{Verbatim}
93 $ ./scripts/feeds search nmap
94 Search results in feed 'packages':
95 nmap Network exploration and/or security auditing utility
96
97 $ ./scripts/feeds install nmap
98 \end{Verbatim}
99
100 To include all packages, issue the following command:
101
102 \begin{Verbatim}
103 $ make package/symlinks
104 \end{Verbatim}
105
106 \texttt{target} refers to the embedded platform, this contains items which are specific to
107 a specific embedded platform. Of particular interest here is the "\texttt{target/linux}"
108 directory which is broken down by platform \textit{<arch>} and contains the patches to the
109 kernel, profile config, for a particular platform. There's also the "\texttt{target/image}" directory
110 which describes how to package a firmware for a specific platform.
111
112 Both the target and package steps will use the directory "\texttt{build\_dir/\textit{<arch>}}"
113 as a temporary directory for compiling. Additionally, anything downloaded by the toolchain,
114 target or package steps will be placed in the "\texttt{dl}" directory.
115
116 \begin{itemize}
117 \item \texttt{build\_dir/\textit{<arch>}}
118 \item \texttt{dl}
119 \end{itemize}
120
121 \subsubsection{Building OpenWrt}
122
123 While the OpenWrt build environment was intended mostly for developers, it also has to be
124 simple enough that an inexperienced end user can easily build his or her own customized firmware.
125
126 Running the command "\texttt{make menuconfig}" will bring up OpenWrt's configuration menu
127 screen, through this menu you can select which platform you're targeting, which versions of
128 the toolchain you want to use to build and what packages you want to install into the
129 firmware image. Note that it will also check to make sure you have the basic dependencies for it
130 to run correctly. If that fails, you will need to install some more tools in your local environment
131 before you can begin.
132
133 Similar to the linux kernel config, almost every option has three choices,
134 \texttt{y/m/n} which are represented as follows:
135
136 \begin{itemize}
137 \item{\texttt{<*>} (pressing y)} \\
138 This will be included in the firmware image
139 \item{\texttt{<M>} (pressing m)} \\
140 This will be compiled but not included (for later install)
141 \item{\texttt{< >} (pressing n)} \\
142 This will not be compiled
143 \end{itemize}
144
145 After you've finished with the menu configuration, exit and when prompted, save your
146 configuration changes.
147
148 If you want, you can also modify the kernel config for the selected target system.
149 simply run "\texttt{make kernel\_menuconfig}" and the build system will unpack the kernel sources
150 (if necessary), run menuconfig inside of the kernel tree, and then copy the kernel config
151 to \texttt{target/linux/\textit{<platform>}/config} so that it is preserved over
152 "\texttt{make clean}" calls.
153
154 To begin compiling the firmware, type "\texttt{make}". By default
155 OpenWrt will only display a high level overview of the compile process and not each individual
156 command.
157
158 \subsubsection{Example:}
159
160 \begin{Verbatim}
161 make[2] toolchain/install
162 make[3] -C toolchain install
163 make[2] target/compile
164 make[3] -C target compile
165 make[4] -C target/utils prepare
166
167 [...]
168 \end{Verbatim}
169
170 This makes it easier to monitor which step it's actually compiling and reduces the amount
171 of noise caused by the compile output. To see the full output, run the command
172 "\texttt{make V=99}".
173
174 During the build process, buildroot will download all sources to the "\texttt{dl}"
175 directory and will start patching and compiling them in the "\texttt{build\_dir/\textit{<arch>}}"
176 directory. When finished, the resulting firmware will be in the "\texttt{bin}" directory
177 and packages will be in the "\texttt{bin/packages}" directory.
178
179
180 \subsection{Creating packages}
181
182 One of the things that we've attempted to do with OpenWrt's template system is make it
183 incredibly easy to port software to OpenWrt. If you look at a typical package directory
184 in OpenWrt you'll find several things:
185
186 \begin{itemize}
187 \item \texttt{package/\textit{<name>}/Makefile}
188 \item \texttt{package/\textit{<name>}/patches}
189 \item \texttt{package/\textit{<name>}/files}
190 \end{itemize}
191
192 The patches directory is optional and typically contains bug fixes or optimizations to
193 reduce the size of the executable. The package makefile is the important item, provides
194 the steps actually needed to download and compile the package.
195
196 The files directory is also optional and typicall contains package specific startup scripts or default configuration files that can be used out of the box with OpenWrt.
197
198 Looking at one of the package makefiles, you'd hardly recognize it as a makefile.
199 Through what can only be described as blatant disregard and abuse of the traditional
200 make format, the makefile has been transformed into an object oriented template which
201 simplifies the entire ordeal.
202
203 Here for example, is \texttt{package/bridge/Makefile}:
204
205 \begin{Verbatim}[frame=single,numbers=left]
206
207 include $(TOPDIR)/rules.mk
208
209 PKG_NAME:=bridge
210 PKG_VERSION:=1.0.6
211 PKG_RELEASE:=1
212
213 PKG_SOURCE:=bridge-utils-$(PKG_VERSION).tar.gz
214 PKG_SOURCE_URL:=@SF/bridge
215 PKG_MD5SUM:=9b7dc52656f5cbec846a7ba3299f73bd
216 PKG_CAT:=zcat
217
218 PKG_BUILD_DIR:=$(BUILD_DIR)/bridge-utils-$(PKG_VERSION)
219
220 include $(INCLUDE_DIR)/package.mk
221
222 define Package/bridge
223 SECTION:=net
224 CATEGORY:=Base system
225 TITLE:=Ethernet bridging configuration utility
226 URL:=http://bridge.sourceforge.net/
227 endef
228
229 define Package/bridge/description
230 Manage ethernet bridging:
231 a way to connect networks together to form a larger network.
232 endef
233
234 define Build/Configure
235 $(call Build/Configure/Default, \
236 --with-linux-headers="$(LINUX_DIR)" \
237 )
238 endef
239
240 define Package/bridge/install
241 $(INSTALL_DIR) $(1)/usr/sbin
242 $(INSTALL_BIN) $(PKG_BUILD_DIR)/brctl/brctl $(1)/usr/sbin/
243 endef
244
245 $(eval $(call BuildPackage,bridge))
246 \end{Verbatim}
247
248 As you can see, there's not much work to be done; everything is hidden in other makefiles
249 and abstracted to the point where you only need to specify a few variables.
250
251 \begin{itemize}
252 \item \texttt{PKG\_NAME} \\
253 The name of the package, as seen via menuconfig and ipkg
254 \item \texttt{PKG\_VERSION} \\
255 The upstream version number that we are downloading
256 \item \texttt{PKG\_RELEASE} \\
257 The version of this package Makefile
258 \item \texttt{PKG\_SOURCE} \\
259 The filename of the original sources
260 \item \texttt{PKG\_SOURCE\_URL} \\
261 Where to download the sources from (no trailing slash), you can add multiple download sources by separating them with a \\ and a carriage return.
262 \item \texttt{PKG\_MD5SUM} \\
263 A checksum to validate the download
264 \item \texttt{PKG\_CAT} \\
265 How to decompress the sources (zcat, bzcat, unzip)
266 \item \texttt{PKG\_BUILD\_DIR} \\
267 Where to compile the package
268 \end{itemize}
269
270 The \texttt{PKG\_*} variables define where to download the package from;
271 \texttt{@SF} is a special keyword for downloading packages from sourceforge. There is also
272 another keyword of \texttt{@GNU} for grabbing GNU source releases. If any of the above mentionned download source fails, the OpenWrt mirrors will be used as source.
273
274 The md5sum (if present) is used to verify the package was downloaded correctly and
275 \texttt{PKG\_BUILD\_DIR} defines where to find the package after the sources are
276 uncompressed into \texttt{\$(BUILD\_DIR)}.
277
278 At the bottom of the file is where the real magic happens, "BuildPackage" is a macro
279 set up by the earlier include statements. BuildPackage only takes one argument directly --
280 the name of the package to be built, in this case "\texttt{bridge}". All other information
281 is taken from the define blocks. This is a way of providing a level of verbosity, it's
282 inherently clear what the contents of the \texttt{description} template in
283 \texttt{Package/bridge} is, which wouldn't be the case if we passed this information
284 directly as the Nth argument to \texttt{BuildPackage}.
285
286 \texttt{BuildPackage} uses the following defines:
287
288 \textbf{\texttt{Package/\textit{<name>}}:} \\
289 \texttt{\textit{<name>}} matches the argument passed to buildroot, this describes
290 the package the menuconfig and ipkg entries. Within \texttt{Package/\textit{<name>}}
291 you can define the following variables:
292
293 \begin{itemize}
294 \item \texttt{SECTION} \\
295 The section of package (currently unused)
296 \item \texttt{CATEGORY} \\
297 Which menu it appears in menuconfig: Network, Sound, Utilities, Multimedia ...
298 \item \texttt{TITLE} \\
299 A short description of the package
300 \item \texttt{URL} \\
301 Where to find the original software
302 \item \texttt{MAINTAINER} (optional) \\
303 Who to contact concerning the package
304 \item \texttt{DEPENDS} (optional) \\
305 Which packages must be built/installed before this package. To reference a dependency defined in the
306 same Makefile, use \textit{<dependency name>}. If defined as an external package, use
307 \textit{+<dependency name>}. For a kernel version dependency use: \textit{@LINUX\_2\_<minor version>}
308 \item \texttt{BUILDONLY} (optional) \\
309 Set this option to 1 if you do NOT want your package to appear in menuconfig.
310 This is useful for packages which are only used as build dependencies.
311 \end{itemize}
312
313 \textbf{\texttt{Package/\textit{<name>}/conffiles} (optional):} \\
314 A list of config files installed by this package, one file per line.
315
316 \textbf{\texttt{Build/Prepare} (optional):} \\
317 A set of commands to unpack and patch the sources. You may safely leave this
318 undefined.
319
320 \textbf{\texttt{Build/Configure} (optional):} \\
321 You can leave this undefined if the source doesn't use configure or has a
322 normal config script, otherwise you can put your own commands here or use
323 "\texttt{\$(call Build/Configure/Default,\textit{<first list of arguments, second list>})}" as above to
324 pass in additional arguments for a standard configure script. The first list of arguments will be passed
325 to the configure script like that: \texttt{--arg 1} \texttt{--arg 2}. The second list contains arguments that should be
326 defined before running the configure script such as autoconf or compiler specific variables.
327
328 To make it easier to modify the configure command line, you can either extend or completely override the following variables:
329 \begin{itemize}
330 \item \texttt{CONFIGURE\_ARGS} \\
331 Contains all command line arguments (format: \texttt{--arg 1} \texttt{--arg 2})
332 \item \texttt{CONFIGURE\_VARS} \\
333 Contains all environment variables that are passed to ./configure (format: \texttt{NAME="value"})
334 \end{itemize}
335
336 \textbf{\texttt{Build/Compile} (optional):} \\
337 How to compile the source; in most cases you should leave this undefined.
338
339 As with \texttt{Build/Configure} there are two variables that allow you to override
340 the make command line environment variables and flags:
341 \begin{itemize}
342 \item \texttt{MAKE\_FLAGS} \\
343 Contains all command line arguments (typically variable overrides like \texttt{NAME="value"}
344 \item \texttt{MAKE\_VARS} \\
345 Contains all environment variables that are passed to the make command
346 \end{itemize}
347
348 \textbf{\texttt{Build/InstallDev} (optional):} \\
349 If your package provides a library that needs to be made available to other packages,
350 you can use the \texttt{Build/InstallDev} template to copy it into the staging directory
351 which is used to collect all files that other packages might depend on at build time.
352 When it is called by the build system, two parameters are passed to it. \texttt{\$(1)} points to
353 the regular staging dir, typically \texttt{staging\_dir/\textit{ARCH}}, while \texttt{\$(2)} points
354 to \texttt{staging\_dir/host}. The host staging dir is only used for binaries, which are
355 to be executed or linked against on the host and its \texttt{bin/} subdirectory is included
356 in the \texttt{PATH} which is passed down to the build system processes.
357 Please use \texttt{\$(1)} and \texttt{\$(2)} here instead of the build system variables
358 \texttt{\$(STAGING\_DIR)} and \texttt{\$(STAGING\_DIR\_HOST)}, because the build system behavior
359 when staging libraries might change in the future to include automatic uninstallation.
360
361 \textbf{\texttt{Package/\textit{<name>}/install}:} \\
362 A set of commands to copy files out of the compiled source and into the ipkg
363 which is represented by the \texttt{\$(1)} directory. Note that there are currently
364 4 defined install macros:
365 \begin{itemize}
366 \item \texttt{INSTALL\_DIR} \\
367 install -d -m0755
368 \item \texttt{INSTALL\_BIN} \\
369 install -m0755
370 \item \texttt{INSTALL\_DATA} \\
371 install -m0644
372 \item \texttt{INSTALL\_CONF} \\
373 install -m0600
374 \end{itemize}
375
376 The reason that some of the defines are prefixed by "\texttt{Package/\textit{<name>}}"
377 and others are simply "\texttt{Build}" is because of the possibility of generating
378 multiple packages from a single source. OpenWrt works under the assumption of one
379 source per package Makefile, but you can split that source into as many packages as
380 desired. Since you only need to compile the sources once, there's one global set of
381 "\texttt{Build}" defines, but you can add as many "Package/<name>" defines as you want
382 by adding extra calls to \texttt{BuildPackage} -- see the dropbear package for an example.
383
384 After you have created your \texttt{package/\textit{<name>}/Makefile}, the new package
385 will automatically show in the menu the next time you run "make menuconfig" and if selected
386 will be built automatically the next time "\texttt{make}" is run.
387
388 \subsection{Creating binary packages}
389
390 You might want to create binary packages and include them in the resulting images as packages.
391 To do so, you can use the following template, which basically sets to nothing the Configure and
392 Compile templates.
393
394 \begin{Verbatim}[frame=single,numbers=left]
395
396 include $(TOPDIR)/rules.mk
397
398 PKG_NAME:=binpkg
399 PKG_VERSION:=1.0
400 PKG_RELEASE:=1
401
402 PKG_SOURCE:=binpkg-$(PKG_VERSION).tar.gz
403 PKG_SOURCE_URL:=http://server
404 PKG_MD5SUM:=9b7dc52656f5cbec846a7ba3299f73bd
405 PKG_CAT:=zcat
406
407 include $(INCLUDE_DIR)/package.mk
408
409 define Package/binpkg
410 SECTION:=net
411 CATEGORY:=Network
412 TITLE:=Binary package
413 endef
414
415 define Package/bridge/description
416 Binary package
417 endef
418
419 define Build/Configure
420 endef
421
422 define Build/Compile
423 endef
424
425 define Package/bridge/install
426 $(INSTALL_DIR) $(1)/usr/sbin
427 $(INSTALL_BIN) $(PKG_BUILD_DIR)/* $(1)/usr/sbin/
428 endef
429
430 $(eval $(call BuildPackage,bridge))
431 \end{Verbatim}
432
433 Provided that the tarball which contains the binaries reflects the final
434 directory layout (/usr, /lib ...), it becomes very easy to get your package
435 look like one build from sources.
436
437 Note that using the same technique, you can easily create binary pcakages
438 for your proprietary kernel modules as well.
439
440 \subsection{Creating kernel modules packages}
441
442 The OpenWrt distribution makes the distinction between two kind of kernel modules, those coming along with the mainline kernel, and the others available as a separate project. We will see later that a common template is used for both of them.
443
444 For kernel modules that are part of the mainline kernel source, the makefiles are located in \textit{package/kernel/modules/*.mk} and they appear under the section "Kernel modules"
445
446 For external kernel modules, you can add them to the build system just like if they were software packages by defining a KernelPackage section in the package makefile.
447
448 Here for instance the Makefile for the I2C subsytem kernel modules :
449
450 \begin{Verbatim}[frame=single,numbers=left]
451
452 I2CMENU:=I2C Bus
453
454 define KernelPackage/i2c-core
455 TITLE:=I2C support
456 DESCRIPTION:=Kernel modules for i2c support
457 SUBMENU:=$(I2CMENU)
458 KCONFIG:=CONFIG_I2C_CORE CONFIG_I2C_DEV
459 FILES:=$(MODULES_DIR)/kernel/drivers/i2c/*.$(LINUX_KMOD_SUFFIX)
460 AUTOLOAD:=$(call AutoLoad,50,i2c-core i2c-dev)
461 endef
462 $(eval $(call KernelPackage,i2c-core))
463 \end{Verbatim}
464
465 To group kernel modules under a common description in menuconfig, you might want to define a \textit{<description>MENU} variable on top of the kernel modules makefile.
466
467 \begin{itemize}
468 \item \texttt{TITLE} \\
469 The name of the module as seen via menuconfig
470 \item \texttt{DESCRIPTION} \\
471 The description as seen via help in menuconfig
472 \item \texttt{SUBMENU} \\
473 The sub menu under which this package will be seen
474 \item \texttt{KCONFIG} \\
475 Kernel configuration option dependency. For external modules, remove it.
476 \item \texttt{FILES} \\
477 Files you want to inlude to this kernel module package, separate with spaces.
478 \item \texttt{AUTOLOAD} \\
479 Modules that will be loaded automatically on boot, the order you write them is the order they would be loaded.
480 \end{itemize}
481
482 After you have created your \texttt{package/kernel/modules/\textit{<name>}.mk}, the new kernel modules package
483 will automatically show in the menu under "Kernel modules" next time you run "make menuconfig" and if selected
484 will be built automatically the next time "\texttt{make}" is run.
485
486 \subsection{Conventions}
487
488 There are a couple conventions to follow regarding packages:
489
490 \begin{itemize}
491 \item \texttt{files}
492 \begin{enumerate}
493 \item configuration files follow the convention \\
494 \texttt{\textit{<name>}.conf}
495 \item init files follow the convention \\
496 \texttt{\textit{<name>}.init}
497 \end{enumerate}
498 \item \texttt{patches}
499 \begin{enumerate}
500 \item patches are numerically prefixed and named related to what they do
501 \end{enumerate}
502 \end{itemize}
503
504 \subsection{Troubleshooting}
505
506 If you find your package doesn't show up in menuconfig, try the following command to
507 see if you get the correct description:
508
509 \begin{Verbatim}
510 TOPDIR=$PWD make -C package/<name> DUMP=1 V=99
511 \end{Verbatim}
512
513 If you're just having trouble getting your package to compile, there's a few
514 shortcuts you can take. Instead of waiting for make to get to your package, you can
515 run one of the following:
516
517 \begin{itemize}
518 \item \texttt{make package/\textit{<name>}/clean V=99}
519 \item \texttt{make package/\textit{<name>}/install V=99}
520 \end{itemize}
521
522 Another nice trick is that if the source directory under \texttt{build\_dir/\textit{<arch>}}
523 is newer than the package directory, it won't clobber it by unpacking the sources again.
524 If you were working on a patch you could simply edit the sources under the
525 \texttt{build\_dir/\textit{<arch>}/\textit{<source>}} directory and run the install command above,
526 when satisfied, copy the patched sources elsewhere and diff them with the unpatched
527 sources. A warning though - if you go modify anything under \texttt{package/\textit{<name>}}
528 it will remove the old sources and unpack a fresh copy.
529
530 Other useful targets include:
531
532 \begin{itemize}
533 \item \texttt{make package/\textit{<name>}/prepare V=99}
534 \item \texttt{make package/\textit{<name>}/compile V=99}
535 \item \texttt{make package/\textit{<name>}/configure V=99}
536 \end{itemize}
537
538
539 \subsection{Using build environments}
540 OpenWrt provides a means of building images for multiple configurations
541 which can use multiple targets in one single checkout. These \emph{environments}
542 store a copy of the .config file generated by \texttt{make menuconfig} and the contents
543 of the \texttt{./files} folder.
544 The script \texttt{./scripts/env} is used to manage these environments, it uses
545 \texttt{git} (which needs to be installed on your system) as backend for version control.
546
547 The command
548 \begin{Verbatim}
549 ./scripts/env help
550 \end{Verbatim}
551 produces a short help text with a list of commands.
552
553 To create a new environment named \texttt{current}, run the following command
554 \begin{Verbatim}
555 ./scripts/env new current
556 \end{Verbatim}
557 This will move your \texttt{.config} file and \texttt{./files} (if it exists) to
558 the \texttt{env/} subdirectory and create symlinks in the base folder.
559
560 After running make menuconfig or changing things in files/, your current state will
561 differ from what has been saved before. To show these changes, use:
562 \begin{Verbatim}
563 ./scripts/env diff
564 \end{Verbatim}
565
566 If you want to save these changes, run:
567 \begin{Verbatim}
568 ./scripts/env save
569 \end{Verbatim}
570 If you want to revert your changes to the previously saved copy, run:
571 \begin{Verbatim}
572 ./scripts/env revert
573 \end{Verbatim}
574
575 If you want, you can now create a second environment using the \texttt{new} command.
576 It will ask you whether you want to make it a clone of the current environment (e.g.
577 for minor changes) or if you want to start with a clean version (e.g. for selecting
578 a new target).
579
580 To switch to a different environment (e.g. \texttt{test1}), use:
581 \begin{Verbatim}
582 ./scripts/env switch test1
583 \end{Verbatim}
584
585 To rename the current branch to a new name (e.g. \texttt{test2}), use:
586 \begin{Verbatim}
587 ./scripts/env rename test2
588 \end{Verbatim}
589
590 If you want to get rid of environment switching and keep everything in the base directory
591 again, use:
592 \begin{Verbatim}
593 ./scripts/env clear
594 \end{Verbatim}