DeveloperWiki:Building in a clean chroot

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This article is part of the DeveloperWiki.


Building in a clean chroot prevents missing dependencies in packages, whether due to unwanted linking or packages missing in the depends array in the PKGBUILD. It also allows users to build a package for the stable repositories (core, extra, community) while having packages from [testing] installed.

Convenience Way

To quickly build a package in a chroot without any further tinkering, one can use the helper scripts from the devtools package.

These helper scripts should be called in the same directory where the PKGBUILD is, just like with makepkg. For instance, extra-i686-build automatically sets up chroot in /var/lib/archbuild, updates it, and builds a package for the extra repository. For multilib builds there is just multilib-build without an architecture.

Tip: Consult the table below for information on which script to use when building for a specific repository and architecture.
Note: [core] is omitted because those packages are required to go through [testing] first before landing in [core].
Target repository Architecture Build script to use
extra / community i686 extra-i686-build
extra / community x86_64 extra-x86_64-build
testing / community-testing i686 testing-i686-build
testing / community-testing x86_64 testing-x86_64-build
staging / community-staging i686 staging-i686-build
staging / community-staging x86_64 staging-x86_64-build
multilib x86_64 multilib-build
multilib-testing x86_64 multilib-testing-build
multilib-staging x86_64 multilib-staging-build

Classic Way

Setting Up A Chroot

The devtools package provides tools for creating and building within clean chroots. Install it if not done already:

pacman -S devtools

To make a clean chroot, create a directory in which the chroot will reside. For example, $HOME/chroot.

Now create the chroot:

mkdir $CHROOT
sudo mkarchroot $CHROOT/root base base-devel sudo
Note: One can also define the CHROOT variable in $HOME/.bashrc using the export command if the location is to be repeatedly used.

Edit $CHROOT/root/etc/makepkg.conf to set the packager name and any makeflags. Also adjust the mirror list in $CHROOT/root/etc/pacman.d/mirrorlist and enable [testing] in $CHROOT/root/etc/pacman.conf if desired.

Alternatively, provide a custompacman.conf and makepkg.conf with the following:

sudo mkarchroot -C <pacman.conf> -M <makepkg.conf> $CHROOT/root base base-devel sudo

It is recommended however users do not use custom pacman.conf and makepkg.conf during the initial creation of clean chroot to ensure no user-specific adjustments are made. Use with caution.

Building in the Chroot

Firstly, make sure the chroot is up to date with:

sudo mkarchroot -u $CHROOT/root

Then, to build a package in the chroot, run the following from the dir containing the PKGBUILD:

sudo makechrootpkg -c -r $CHROOT

A unionfs is used to maintain the clean chroot during building. All installed dependencies or makedepends and other changes made during building are done in $CHROOT/rw. Passing the -c flag to makechrootpkg ensures that this directory is cleaned before building starts.

Handling Major Rebuilds

The cleanest way to handle a major rebuild is to create a new chroot and build the first package (typically the package for which the rebuild is meant). Then create a local repo inside the new chroot. To do this:

sudo mkdir $CHROOT/root/repo
sudo chmod 0777 $CHROOT/root/repo

The chmod statement allows for the coping of package files and for the creation of the local repo as your user rather than root.

cp <package> $CHROOT/root/repo
cd $CHROOT/root/repo
repo-add local.db.tar.gz <package>

Then add the local repo to $CHROOT/root/etc/pacman.conf

Server = file:///repo

As long as you add only self built packages to this repo, you can add

SigLevel = TrustAll

and update the repo:

sudo mkarchroot -u $CHROOT/root

With every additional package rebuilt, copy the package to the local repo directory, add it to the repo database and update the chroot.

Alternate Rebuild Handling

The above directions will work fine, but they can dirty the "pristine" chroot that makechrootpkg tries to keep in check (that is the point of using unionfs - dirtying a separate 'rw' directory).

Using a custom repo

Follow the steps above to setup a local repo inside the chroot.

Build packages using:

sudo makechrootpkg -r $CHROOT -u

The -u will update the chroot before building (-Syu) but updates will be installed to the rw layer, maintaining a clean chroot.

Manual package installation

Packages can be installed manually to the rw layer of the chroot by using:

sudo makechrootpkg -r $CHROOT -I package-1.0-1-i686.pkg.tar.xz

Installation after building

Tell makechrootpkg to simply install a package to the rw layer of the chroot after building by passing the -i arg. Unrecognized args get passed to makepkg, so this calls `makepkg` with the -i arg.

sudo makechrootpkg -r $CHROOT -- -i