|A detailed description of the package building process. Covers package creation and testing.|
|VCS PKGBUILD Guidelines|
This article aims to assist users creating their own packages using the Arch Linux "ports-like" build system. It covers creation of a PKGBUILD – a package build description file sourced by makepkg to create a binary package from source. If already in possession of a PKGBUILD, see makepkg.
- 1 Overview
- 2 Preparation
- 3 Creating a PKGBUILD
- 4 Testing the PKGBUILD and package
- 5 Summary
- 6 See Also
- 7 Acknowledgement
Packages in Arch Linux are built using the makepkg utility and the information stored in a PKGBUILD file. When makepkg is run, it searches for a PKGBUILD in the current directory and follows the instructions therein to either compile or otherwise acquire the required files to be packaged within a package file (pkgname.pkg.tar.xz). The resulting package contains binary files and installation instructions; readily installed with pacman.
An Arch package is no more than a tar archive compressed using xz, or 'tarball', which contains:
- The binary files to install
- .PKGINFO: contains all the metadata needed by pacman to deal with packages, dependencies, etc.
- .INSTALL: an optional file used to execute commands after the install/upgrade/remove stage. (This file is present only if specified in the PKGBUILD.)
- .Changelog: an optional file kept by the package maintainer documenting the changes of the package. (It is not present in all packages.)
2.1 Prerequisite software
First ensure that the necessary tools are installed. The package group base-devel should be sufficient; it includes make and additional tools needed for compiling from source.
# pacman -S base-devel
- Checks if package dependencies are installed.
- Downloads the source file(s) from the specified server(s).
- Unpacks the source file(s).
- Compiles the software and installs it under a fakeroot environment.
- Strips symbols from binaries and libraries.
- Generates the package meta file which is included with each package.
- Compress the fakeroot environment into a package file.
- Stores the package file in the configured destination directory, which is the present working directory by default.
2.2 Download and test the installation
Download the source tarball of the software you want to package, extract it, and follow the author's steps to install the program. Make a note of all commands and/or steps needed to compile and install it. You will be repeating those same commands in the PKGBUILD file.
Most software authors stick to the 3-step build cycle:
./configure make make install
This is a good time to make sure the program is working correctly.
3 Creating a PKGBUILD
When you run makepkg, it will look for a PKGBUILD file in the present working directory. If a PKGBUILD file is found it will download the software's source code and compile it according to the instructions specified in the PKGBUILD file. The instructions must be fully interpretable by the Bash shell. After successful completion, the resulting binaries and metadata of the package, i.e. package version and dependencies, are packed in a pkgname.pkg.tar.xz package file that can be installed with pacman -U <package file>.
To begin with a new package, you should first create an empty working directory, (preferably ~/abs/pkgname), change into that directory, and create a PKGBUILD file. You can either copy the prototype PKGBUILD /usr/share/pacman/PKGBUILD.proto to your working directory or copy a PKGBUILD from a similar package. The latter may be useful if you only need to change a few options.
3.1 Defining PKGBUILD variables
Example PKGBUILDs are located in /usr/share/pacman/.
makepkg defines three variables that you should use as part of the build and install process:
- This contains the absolute path to the directory where the PKGBUILD file is located. This variable used to be used in combination with /src or /pkg postfixes, but the use of srcdir and pkgdir variables is the modern method. $startdir/src is not guaranteed to be the same as $srcdir, and likewise for $pkgdir. Use of this variable is deprecated and strongly discouraged.
- This points to the directory where makepkg extracts or copies all source files.
- This points to the directory where makepkg bundles the installed package, which becomes the root directory of your built package.
3.2 The build() function
Now you need to implement the build() function in the PKGBUILD file. This function uses common shell commands in Bash_%28Unix_shell%29 Bash syntax to automatically compile software and create a pkg directory to install the software to. This allows makepkg to package files without having to sift through your filesystem.
The first step in the build() function is to change into the directory created by uncompressing the source tarball. In most common cases the first command will look like this:
Now, you need to list the same commands you used when you manually compiled the software. The build() function in essence automates everything you did by hand and compiles the software in the fakeroot build environment. If the software you are packaging uses a configure script, it is good practice to use --prefix=/usr when building packages for pacman. A lot of software installs files relative to the /usr/local directory, which should only be done if you are manually building from source. All Arch Linux packages should use the /usr directory. As seen in the /usr/share/pacman/PKGBUILD.proto file, the next two lines often look like this:
./configure --prefix=/usr make
3.3 The check() function
Place for calls to make check and similar testing routines. Users who don't need it (and occasionally maintainer who can not fix package for this to pass) can disable !check in PKGBUILD/makepkg options.
3.4 The package() function
The final step is to put the compiled files in a directory where makepkg can retrieve them to create a package. This by default is the pkg directory — a simple fakeroot environment. The pkg directory replicates the hierarchy of the root file system of the software's installation paths. If you have to manually place files under the root of your filesystem, you should install them in the pkg directory under the same directory structure. For example, if you want to install a file to /usr/bin, it should instead be placed under $pkgdir/usr/bin. Very few install procedures require the user to copy dozens of files manually. Instead, for most software, calling make install will do so. The final line should look like the following in order to correctly install the software in the pkg directory:
make DESTDIR="$pkgdir" install
In some odd cases, the software expects to be run from a single directory. In such cases, it is wise to simply copy these to $pkgdir/opt.
More often than not, the installation process of the software will create any sub-directories below the pkg directory. If it does not, however, makepkg will generate a lot of errors and you will need to manually create sub-directories by adding the appropriate mkdir -p commands in the build() function before the installation procedure is run.
In old packages, there was no package() function. So, putting compiled files was done at the end of the build() function. If package() is not present, build() runs via fakeroot. If package() is present, build() runs as the user calling makepkg, package() runs via fakeroot.
makepkg --repackage runs only the package() function, so it creates a *.pkg.* file without compiling the package. This may save time e.g. if you just have changed the depends variable of the package.
3.5 Additional guidelines
Please read Arch Packaging Standards thoroughly for best practices and additional considerations.
4 Testing the PKGBUILD and package
As you are writing the build() function, you will want to test your changes frequently to ensure there are no bugs. You can do this using the makepkg command in the directory containing the PKGBUILD file. With a properly formatted PKGBUILD, makepkg will create a package; with a broken or unfinished PKGBUILD, it will raise an error.
If makepkg finishes successfully, it will place a file named pkgname-pkgver.pkg.tar.xz in your working directory. This package can be installed with the pacman -U command. However, just because a package file was built does not imply that it is fully functional. It might conceivably contain only the directory and no files whatsoever if, for example, a prefix was specified improperly. You can use pacman's query functions to display a list of files contained in the package and the dependencies it requires with pacman -Qlp [package file] and pacman -Qip [package file] respectively.
If the package looks sane, then you are done! However, if you plan on releasing the PKGBUILD file, it is imperative that you check and double-check the contents of the depends array.
Also ensure that the package binaries actually run flawlessly! It is annoying to release a package that contains all necessary files, but crashes because of some obscure configuration option that does not quite work well with the rest of the system. If you are only going to compile packages for your own system, though, you do not need to worry too much about this quality assurance step, as you are the only person suffering from mistakes, after all.
4.1 Checking package sanity
After testing package functionality check it for errors using namcap:
$ namcap PKGBUILD $ namcap <package file name>.pkg.tar.xz
- Check PKGBUILD contents for common errors and package file hierarchy for unnecessary/misplaced files
- Scan all ELF files in package using ldd, automatically reporting which packages with required shared libraries are missing from depends and which can be omitted as transitive dependencies
- Heuristically search for missing and redundant dependencies
and much more. Get into the habit of checking your packages with namcap to avoid fixing simplest mistakes after package submission.
- Download the source tarball of the software you want to package.
- Try compiling the package and installing it into an arbitrary directory.
- Copy over the prototype /usr/share/pacman/PKGBUILD.proto and rename it to PKGBUILD in a temporary working directory -- preferably ~/abs/.
- Edit the PKGBUILD according to the needs of your package.
- Run makepkg and see whether the resulting package is built correctly.
- If not, repeat the last two steps.
- Before you can automate the package building process, you should have done it manually at least once unless you know exactly what you are doing in advance, in which case you would not be reading this in the first place. Unfortunately, although a good bunch of program authors stick to the 3-step build cycle of "./configure; make; make install", this is not always the case, and things can get real ugly if you have to apply patches to make everything work at all. Rule of thumb: If you cannot get the program to compile from the source tarball, and make it install itself to a defined, temporary subdirectory, you do not even need to try packaging it. There is not any magic pixie dust in makepkg that makes source problems go away.
- In a few cases, the packages are not even available as source and you have to use something like sh installer.run to get it to work. You will have to do quite a bit of research (read READMEs, INSTALL instructions, man pages, perhaps ebuilds from Gentoo or other package installers, possibly even the MAKEFILEs or source code) to get it working. In some really bad cases, you have to edit the source files to get it to work at all. However, makepkg needs to be completely autonomous, with no user input. Therefore if you need to edit the makefiles, you may have to bundle a custom patch with the PKGBUILD and install it from inside the build() function, or you might have to issue some sed commands from inside the build() function.