DeveloperWiki:Building in a Clean Chroot

From ArchWiki
Revision as of 13:03, 8 December 2009 by Pjmattal (talk | contribs)
Jump to: navigation, search


This article is part of the DeveloperWiki.


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


Building with chroots requires aufs2. You will need to install the aufs2 and aufs2-util packages before you get started.

Setting Up A Chroot

The devtools package provides tools for creating and building within clean chroots. To make a clean chroot, firstly create the directory you want it to reside in. For the purposes of this article this will be called <chrootdir>. The create your chroot using

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

The -C and -M flags are optional, but it is recommended to provide these with clean pacman.conf and makepkg.conf files (directly from the pacman package) during first creation of clean chroot to ensure lack of user specific adjustments.

Edit the <chrootdir>/root/etc/makepkg.conf file to set the packager name and any makeflags. Also adjust the mirror list in <chrootdir>/root/etc/pacman.d/mirrorlist and enable [testing] in <chrootdir>/root/etc/pacman.conf if wanted.

Building in the Chroot

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

sudo mkarchroot -u <chrootdir>/root

Then, to build a package in your chroot run

sudo makechrootpkg -c -r <chrootdir>

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 <chrootdir>/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 your first package (typically the package you are doing the rebuild for). Then create a local repo in you chroot. To do this:

sudo mkdir <chrootdir>/root/repo
sudo chmod 777 <chrootdir>/root/repo

The chmod statement allows you to copy package files and create the local repo as your user rather than root.

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

Then add the local repo to <chrootdir>/root/etc/pacman.conf

Server = file:///repo

and update your repo

sudo mkarchroot -u <chrootdir>/root

With every additional package rebuilt, copy the package to the local repo directory, add it to the repo database and update your 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 <chrootdir> -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 <chrootdir> -I package-1.0-1-i686.pkg.tar.gz

Installation after building

You can 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 <chrootdir> -- -i