# Arch Build System

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Related articles

- Arch packaging standards
- Arch User Repository
- Creating packages
- Kernel Compilation with ABS
- makepkg
- Official repositories
- pacman
- PKGBUILD
- Patching in ABS

The Arch build system 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 .pkg.tar.zst packages.

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` or `make install clean` within the port's directory.

ABS is a similar concept. A part of ABS is a SVN repository and an equivalent Git repository. The repository contains a directory corresponding to each package available in Arch Linux. The directories of the repository contain a PKGBUILD file (and sometimes other files), and do not contain the software source nor binary. By issuing makepkg inside a directory, the software sources are downloaded, the software is compiled, and then packaged within the build directory. Then you can use pacman to install the package.

## Overview

This article or section needs expansion.

Reason: Clarify which components are actually part of the ABS. (Discuss in Talk:Arch Build System#)

'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:

Repository tree
  The directory structure containing files needed to build all official packages but not the packages themselves nor the source files of the software. It is available in svn and git repositories. See the section #Repository tree for more information.

PKGBUILD
  A Bash script that contains the URL of the source code along with the compilation and packaging instructions.

makepkg
  A shell command tool which reads the PKGBUILDs, automatically downloads and compiles the sources and creates a .pkg.tar* according to the `PKGEXT` array in `makepkg.conf`. You may also use makepkg to make your own custom packages from the AUR or third-party sources. See Creating packages for more information.

pacman
  pacman is completely separate, but is necessarily invoked either by makepkg or manually, to install and remove the built packages and for fetching dependencies.

AUR
  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 which is simply a bare git repository, the AUR exists as a polished website interface with various interactive features. 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.

Warning: Official PKGBUILDs assume that packages are built in a clean chroot. Building software on a dirty build system may fail or cause unexpected behaviour at runtime, because if the build system detects dependencies dynamically, the result depends on what packages are available on the build system.

### Repository tree

The core, extra, and testing official repositories are in the packages repository for checkout. The community and multilib repositories are in the community repository.

Each package has its own subdirectory. Within it there are `repos` and `trunk` directories. `repos` is further broken down by repository name (e.g., core) and architecture. PKGBUILDs and files found in `repos` are used in official builds. Files found in `trunk` are used by developers in preparation before being copied to `repos`.

For example, the tree for acl looks like this:

    acl
    acl/repos
    acl/repos/core-x86_64
    acl/repos/core-x86_64/PKGBUILD
    acl/trunk
    acl/trunk/PKGBUILD

The source code for the package is not present in the ABS directory. Instead, the `PKGBUILD` contains a URL that will download the source code when the package is built.

## Use cases

ABS automates certain tasks related to compilation from source. Its use cases are:

- Any use case that requires you to compile or recompile a package.
- 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 (e.g. enabling or disabling options, patching).
- Rebuild your entire system using your compiler flags, "à la FreeBSD".
- Cleanly build and install your own custom kernel (see Kernel compilation).
- Get kernel modules working with a 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.

## Usage

### Retrieve PKGBUILD source

To retrieve the PKGBUILD required to build a certain package from source, you can either use SVN or a Git-based approach using the asp package which is a thin wrapper around the svntogit repositories. In the following, the svn-based method as well as the git-based method are described.

#### Retrieve PKGBUILD source using Git

As a precondition, install the asp package. Asp is a tool to retrieve the build source files for Arch Linux packages using the Git interface. Also see the Arch Linux BBS forum thread [1].

To clone the svntogit-repository for a specific package, use:

    $ asp checkout pkgname

This will clone the git repository for the given package into a directory named like the package.

To update the cloned git repository, run `asp update` followed by `git pull` inside the git repository.

Furthermore, you can use all other git commands to checkout an older version of the package or to track custom changes. For more information on git usage, see the git page.

If you just want to copy a snapshot of the current PKGBUILD for a specific package, use:

    $ asp export pkgname

#### Retrieve PKGBUILD source using SVN

##### Prerequisites

Install the subversion package.

##### Checkout a repository

Warning: Do not download the whole repository; only follow the instructions below. The entire SVN repository is huge. Not only will it take an obscene amount of disk space, but it will also tax the archlinux.org server for you to download it. If you abuse this service, your address may be blocked. Never use the public SVN for any sort of scripting.

To checkout the core, extra, and testing official repositories:

    $ svn checkout --depth=empty svn://svn.archlinux.org/packages

To checkout the community and multilib repositories:

    $ svn checkout --depth=empty svn://svn.archlinux.org/community

In both cases, it simply creates an empty directory, but it does know that it is an svn checkout.

##### Checkout a package

In the directory containing the svn repository you checked out (i.e., packages or community), do:

    $ svn update package-name

This will pull the package you requested into your checkout. From now on, any time you svn update at the top level, this will be updated as well.

If you specify a package that does not exist, svn will not warn you. It will just print something like "At revision 115847", without creating any files. If that happens:

- check your spelling of the package name
- check that the package has not been moved to another repository (i.e. from community to the main repository)
- check https://archlinux.org/packages to see if the package is built from another base package (for example, python-tensorflow is built from the tensorflow PKGBUILD)

Tip: To checkout an older version of a package, see #Checkout an older version of a package.

You should periodically update all of your checked out packages if you wish to perform rebuilds on more recent revisions of the repositories. To do so, do:

    $ svn update

##### Checkout an older version of a package

Within the svn repository you checked out as described in #Checkout a repository (i.e. "packages" or "community"), first examine the log:

    $ svn log package-name

Find out the revision you want by examining the history, then specify the revision you wish to checkout. For example, to checkout revision `r1729` you would do:

    $ svn update -r1729 package-name

This will update an existing working copy of package-name to the chosen revision.

You can also specify a date. If no revision on that day exists, svn will grab the most recent package before that time. The following example checks out the revision from 2009-03-03:

    $ svn update -r'{20090303}' package-name

It is possible to checkout packages at versions before they were moved to another repository as well; check the logs thoroughly for the date they were moved or the last revision number.

### Build package

Configure makepkg for building packages from the PKGBUILDs you have checked out, as explained in makepkg#Configuration.

Then, copy the directory containing the PKGBUILD you wish to modify to a new location. Make the desired modifications there and use makepkg there as described in makepkg#Usage to create and install the new package.

## Tips and tricks

### Preserve modified packages

Updating the system with pacman will replace a modified package from ABS with the package of the same name from the official repositories. See the following instructions for how to avoid this.

Insert a group array into the PKGBUILD, and add the package to a group called `modified`.

    PKGBUILD

    groups=('modified')

Add this group to the section `IgnoreGroup` in `/etc/pacman.conf`.

    /etc/pacman.conf

    IgnoreGroup = modified

If new versions are available in the official repositories during a system update, pacman prints a note that it is skipping this update because it is in the IgnoreGroup section. At this point the modified package should be rebuilt from ABS to avoid partial upgrades.

## Other tools

- pbget - retrieve PKGBUILDs for individual packages directly from the web interface. Includes AUR support.

Categories:

- About Arch
- Package development
- Package management

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