Arch Build System
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This article provides an overview of the Arch Build System along with a walkthrough for beginners. It is not a complete reference guide! For a quick and simple introduction to the ABS, see the ABS FAQ. If you need more information, please reference the man pages.
- 1 What is the Arch Build System?
- 2 Why would I want to use ABS?
- 3 Walkthrough
What is the Arch Build System?
The Arch Build System, ABS for short, is a ports-like system for building and packaging software from source code. While pacman is the specialized Arch tool for binary package management (including packages built with the ABS), ABS is a collection of tools for compiling source into installable
What is a ports-like system?
Ports is a system used by *BSD to automate the process of building software from source code. The system uses a port to download, unpack, patch, compile, and install the given software. A port is merely a small directory on the user's computer, named after the corresponding software to be installed, that contains a few files with the instructions for building and installing the software from source. This makes installing software as simple as typing
make install clean within the port's directory.
ABS is a similar concept
ABS is made up of a directory tree (the ABS tree) residing under
/var/abs. This tree contains many subdirectories, each within a category and each named by their respective package. This tree represents (but does not contain) all official Arch software, retrievable through the SVN system. You may refer to each package-named subdirectory as an 'ABS', much the way one would refer to a 'port'. These ABS (or subdirectories) do not contain the software package nor the source but rather a PKGBUILD file (and sometimes other files). A PKGBUILD is a simple BASH build script -- a text file containing the compilation and packaging instructions as well as the URL of the appropriate source tarball to be downloaded. (The most important component of ABS are PKGBUILDs.) By issuing the ABS makepkg command, the software is first compiled and then packaged within the build directory before being installed. Now you may use pacman, the Arch Linux package manager, to install, upgrade, and remove your new package.
'ABS' may be used as an umbrella term since it includes and relies on several other components; therefore, though not technically accurate, 'ABS' can refer to the following tools as a complete toolkit:
- ABS tree
- The ABS directory structure; an SVN hierarchy under
/var/abs/on your (local) machine. It contains many subdirectories, named for all available official Arch Linux software from repositories specified in
/etc/abs.conf, but not the packages themselves. The tree is created after installing the package with pacman and subsequently running the
- A Bash script that contains the URL of the source code along with the compilation and packaging instructions.
- ABS shell command tool which reads the PKGBUILDs, automatically downloads and compiles the sources and creates a
.pkg.tar.xz, according to the
- pacman is completely separate, but is necessarily invoked either by makepkg or manually, to install and remove the built packages and for fetching dependencies.
- The Arch User Repository is separate from ABS but AUR (unsupported) PKGBUILDs are built using makepkg to compile and package up software. In contrast to the ABS tree on your local machine, the AUR exists as a website interface. It contains many thousands of user-contributed PKGBUILDs for software which is unavailable as an official Arch package. If you need to build a package outside the official Arch tree, chances are it is in the AUR.
Why would I want to use ABS?
The Arch Build System is used to:
- Compile or recompile a package, for any reason
- Make and install new packages from source of software for which no packages are yet available (see Creating Packages)
- Customize existing packages to fit your needs (enabling or disabling options, patching)
- Rebuild your entire system using your compiler flags, "a la FreeBSD" (e.g. with pacbuilder)
- Cleanly build and install your own custom kernel (see Kernel Compilation)
- Get kernel modules working with your custom kernel
- Easily compile and install a newer, older, beta, or development version of an Arch package by editing the version number in the PKGBUILD
ABS is not necessary to use Arch Linux, but it is useful for automating certain tasks of source compilation.
With the ABS tree in place, an Arch user has all available Arch software at their fingertips to compile from source, automatically package as a
.pkg.tar.xz, and finally, install with pacman.
Install the pacman. Running
abs as root creates the ABS tree by synchronizing with the Arch Linux server. If you wanted to build a package from source you would copy the build files (usually residing under
/var/abs/<repo>/<pkgname>) to a build directory, navigate to that directory, edit the PKGBUILD (if desired/necessary) and do makepkg. According to instructions in the PKGBUILD, makepkg will download the appropriate source tarball, unpack it, patch if desired, compile according to
CFLAGS specified in
makepkg.conf, and finally compress the built files into a package with the extension
.pkg.tar.xz. PKGBUILDs may be customized to suit your unique configuration needs, or for applying patches. Installing is as easy as doing
pacman -U <.pkg.tar.xz file>. Package removal is also handled by pacman.
Set the PACKAGER variable in /etc/makepkg.conf
Setting the PACKAGER variable in
/etc/makepkg.conf is an optional but highly recommended step. It allows a "flag" to quickly identify which packages have been built and/or installed by YOU, not the official maintainer! This is easily accomplished using expac available from the community repo:
$ grep myname /etc/makepkg.conf PACKAGER="myname <email@example.com>
$ expac "%n %p" | grep "myname" | column -t binutils myname gcc myname gcc-libs myname glibc myname tar myname
To use the ABS, you first need to install official repositories.from the
This will grab the abs-sync scripts, various build scipts, and rsync (as a dependency, if you do not already have it).
Before you can actually build anything, however, you will also need to grab basic compiling tools. These are handily collected in the package group base-devel. This group can be installed with:
# pacman -S base-devel
As root, edit
/etc/abs.conf to include your desired repositories.
! in front of the appropriate repositories. For example:
REPOS=(core extra community !testing)
Download the ABS tree
As root, run:
Your ABS tree is now created under
/var/abs. Note the appropriate branches of the ABS tree now exist and correspond to the ones you specified in
The abs command should be run periodically to keep in sync with the official repositories. Individual ABS package files can also be downloaded with:
# abs <repository>/<package>
/etc/makepkg.conf specifies global environment variables and compiler flags which you may wish to edit if you are using an SMP system, or to specify other desired optimizations. The default settings are for i686 and x86_64 optimizations which will work fine for those architectures on single-CPU systems. (The defaults will work on SMP machines, but will only use one core/CPU when compiling -- see makepkg.conf.)
The ABS tree
When you run
abs for the first time, it synchronizes the ABS tree on the Arch Linux server to your computer. The ABS tree is an SVN directory hierarchy located under
/var/abs and looks like this:
| -- core/ | || -- base/ | || || -- acl/ | || || || -- PKGBUILD | || || -- attr/ | || || || -- PKGBUILD | || || -- ... | || -- devel/ | || || -- abs/ | || || || -- PKGBUILD | || || -- autoconf/ | || || || -- PKGBUILD | || || -- ... | || -- ... | -- extra/ | || -- daemons/ | || || -- acpid/ | || || || -- PKGBUILD | || || || -- ... | || || -- apache/ | || || || -- ... | || || -- ... | || -- ... | -- community/ | || -- ...
The ABS tree has exactly the same structure as the package database:
- First-level: Category directories
- Second-level: Package name directories
- Third level: PKGBUILD (contains information needed to build a package) and other related files (patches, other files needed for building the package)
The source code for the package is not present in the ABS directory. Instead, the PKGBUILD file contains a URL that will download the source code when the package is built.
Create a build directory
It is recommended to create a build directory where the actual compiling will take place; you should never modify the ABS tree by building within it, as data will be lost (overwritten) on each ABS update. It is good practice to use your home directory, though some Arch users prefer to create a 'local' directory under
/var/abs/, owned by a normal user.
Create your build directory. e.g.:
$ mkdir -p $HOME/abs
Copy the ABS from the tree (
/var/abs/branch/category/pkgname) to the build directory,
Traditional method of compiling software, without ABS
If you are not familiar with manually compiling software from source, you should know that most packages (but not all) can be built from source in this traditional way:
- Download source tarball from remote server, using web browser, ftp, wget or alternate method.
- Decompress the source file:
$ tar -xzf foo-0.99.tar.gz
$ tar -xjf foo-0.99.tar.bz2
- Enter the directory:
$ cd foo-0.99
- Configure the package. Generally, there is a script called
configurein the source directory that is used to configure the package (add or remove support for things, choose the install destination, etc.) and check that your computer has all the software needed by the package. It can be run by:
$ ./configure [option]
You should first try the help to better understand how it works:
$ ./configure --help
--prefix option is not passed to the script, most scripts will use
/usr/local as the install path, but others will use
/usr. For the sake of consistency, it is generally advised to pass the
--prefix=/usr/local option. It is good practice to install personal programs in
/usr/local, and to have the ones being managed by the distro in
/usr. This ensures personal program versions can coexist with those being managed by the distro's package manager -- in Arch's case, pacman.
$ ./configure --prefix=/usr/local
- Compile the sources:
# make install
- Removal would be accomplished by entering the source directory and running:
# make uninstall
However, you should always read the
INSTALL file to know how the package should be built and installed! Not all packages use the
configure; make; make install system!
The build function, the ABS way
ABS is an elegant tool which allows for powerful assistance and customization for the build process and creates a pacman-trackable package file for installation. The ABS method involves copying an ABS from the tree to a build directory, and doing makepkg. In our example, we will build the slim display manager package.
Copy the slim ABS from the ABS tree to a build directory:
$ cp -r /var/abs/extra/slim/ ~/abs
Navigate to the build directory:
$ cd ~/abs/slim
Modify the PKGBUILD to add or remove support for components, to patch or to change package versions, etc. (optional):
$ nano PKGBUILD
Run makepkg as normal user (with
-s switch to install with automatic dependency handling):
$ makepkg -s
Install as root:
# pacman -U slim-1.3.0-2-i686.pkg.tar.xz
That's it. You have just built slim from source and cleanly installed it to your system with pacman. Package removal is also handled by pacman -- (
pacman -R slim).
Essentially, the same steps are being executed as described in the traditional method (generally including the
./configure, make, make install steps) but the software is installed into a fake root environment. (A fake root is simply a subdirectory within the build directory that functions and behaves as the system's root directory. In conjunction with the fakeroot program, makepkg creates a fake root directory, and installs the compiled binaries and associated files into it, with root as owner.) The fake root, or subdirectory tree containing the compiled software, is then compressed into an archive with the extension
.pkg.tar.xz, or a package. When invoked, pacman then extracts the package (installs it) into the system's real root directory (
The ABS method adds a level of convenience and automation, while still maintaining complete transparency and control of the build and installation functions by including them in the PKGBUILD.