Creating Debian packages in container

Overview

Container engines, in particular docker and podman, can be used for Debian packaging. Building inside a container avoids installing build dependencies on the host, ensures a clean and reproducible environment, and in case of podman allows to perform the build as unprivileged user.

Fork of docker-deb-builder, created by Tero Saarni.

Create build environment

The build environment is setup in advance by creating a container image to speed up builds. It only contains essential build dependencies, like gcc, thus one can be used to build different Debian packages. For each distribution a separate build environment needs to be created.

In this example the target is Ubuntu 22.04 and Debian sid, other distributions can be created by their respective Dockerfile:

docker build -t container-deb-builder:22.04 -f Dockerfile-ubuntu-22.04 .
podman build -t container-deb-builder:sid -f Dockerfile-Debian-sid-unstable .

The image name (container-deb-builder:22.04) is later used while building a Debian package.

Building packages

First download or git clone the source code of the package to build:

git clone ... ~/my-package-source

The source code should contain subdirectory called debian with at least a minimum set of packaging files: control, copyright, changelog and rules.

Run the build script to see its usage:

$ ./build -h
usage: build [options...] SOURCEDIR
Options:
  -i IMAGE     Name of the docker image (including tag) to use as package build environment.
  -c PROGRAM   Use a custom container engine.
  -o DIR       Destination directory to store packages to.
  -d DIR       Directory that contains other deb packages that need to be installed before build.
  -p profiles  Specify the profiles to build (e.g. nocheck). Takes a comma separated list.
  -C           Use ccache to cache compiled objects.
  -L           Run Lintian after a successful build.
  -B           Run blhc after a successful build.
  -t           Reset file modification timestamps to changelog entry.

To build Debian packages run following commands:

# create destination directory to store the build results
mkdir output

# build package from source directory
./build -i container-deb-builder:22.04 -o output ~/my-package-source

After a successful build the build results will be copied from the container into the output directory. The container itself is discarded.

Sometimes builds might require dependencies that cannot be installed with apt-get build-dep, e.g. when the required version of the dependency is not yet available. Those can be installed into the build environment by passing the option -d DIR, where DIR is a directory with *.deb files in it.

./build -i container-deb-builder:22.04 -o output -d dependencies ~/my-package-source

Native builds for foreign architectures

By default all packages are build for the architecture the host is running on. Docker and Podman however support running containers under a foreign architecture via QEMU. This emulation is quite slower than standard cross- compiling but enables native builds, which for example includes running tests.

First install the required system packages:

apt install binfmt-support qemu-user-static

Distinct images needs to be build for each architecture via the flag --platform, e.g. for arm64:

podman build -t container-deb-builder-arm64:sid -f Dockerfile-Debian-bookworm-12 --platform arm64 .

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Note:

Podman remembers the last architecture used for a local image, so be sure to specify the correct platform for further usage (especially if the name of the image is used multiple times).

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Building packages then works just by using the particular images.

Maintenance

The data for apt archives and ccache is stored in volumes. These volumes have the naming scheme cdebb__${ImageName}__(apt|ccache) and can be removed if the respective image does no longer exists or the disk space is needed.