DeveloperWiki:Building in a Clean Chroot

Introduction

This article is part of the DeveloperWiki.

Why

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.

$ mkdir ~/chroot

Define the CHROOT variable:

# CHROOT=$HOME/chroot

Now create the chroot (the sub directory root is required because the $CHROOT directory will get other sub directories for clean working copies):

# mkarchroot $CHROOT/root base-devel

Note: One can also define the CHROOT variable in $HOME/.bashrc using the export command if the location is to be repeatedly used.

Edit ~/.makepkg.conf to set the packager name and any makeflags. Also adjust the mirrorlist in $CHROOT/root/etc/pacman.d/mirrorlist and enable the testing repository in $CHROOT/root/etc/pacman.conf, if desired.

Custom pacman.conf

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

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

Warning: Using a custom pacman.conf or makepkg.conf during the initial creation of clean chroot can result in unintended custom adjustments to the chroot environment. Use with caution.

Building in the Chroot

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

# arch-nspawn $CHROOT/root pacman -Syu

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

# makechrootpkg -c -r $CHROOT

Passing the -c flag to makechrootpkg ensures that the working chroot (named $CHROOT/$USERNAME) is cleaned before building starts.

Manual package installation

Packages can be installed manually to the working chroot by using:

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

If done from a directory that contains a PKGBUILD, the package will then be built. Avoid being in such a directory if you want to just install the package.

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.

# makechrootpkg -r $CHROOT -- -i

Handling Major Rebuilds

The cleanest way to handle a major rebuild is to use the [staging] repositories. Build the first package against [extra] and push it to [staging]. Then rebuild all following packages against [staging] and push them there.

If you can't use [staging], you can build against custom packages using a command like this:

# extra-x86_64-build -- -I ~/packages/foobar/foobar-2-1-any.pkg.tar.xz

You can specify more than one package to be installed using multiple -I arguments.

A simpler, but dirtier way to handle a major rebuild is to install all built packages in the chroot, never cleaning it. Build the first package using:

# extra-x86_64-build

And build all following packages using:

# makechrootpkg -n -r /var/lib/archbuild/extra-x86_64

Running namcap (the -n argument) implies installing the package in the chroot. *-build also does this by default.