cowbuilder

TLDR

Create a new cowbuilder environment

$ sudo cowbuilder --create --distribution [bookworm]

Update the cowbuilder environment

$ sudo cowbuilder --update

Build a package

$ sudo cowbuilder --build [package.dsc]

Login to the cowbuilder environment

$ sudo cowbuilder --login

Build for specific architecture

$ sudo cowbuilder --build --architecture [i386] [package.dsc]

Use specific base.cow location

$ sudo cowbuilder --basepath [/var/cache/pbuilder/base-bookworm.cow] --build [package.dsc]

SYNOPSIS

cowbuilder --create | --update | --build | --login [options]

cowbuilder is a wrapper around pbuilder that uses copy-on-write (COW) semantics for faster Debian package builds. Instead of creating a new chroot tarball for each build, it uses hard links to create a working copy, significantly reducing setup time.
The tool creates clean, reproducible build environments for Debian packages. Each build starts from a pristine base system, ensuring packages build correctly without hidden dependencies on the developer's system.
cowbuilder is commonly used for verifying package builds before upload to Debian archives, testing packages across different distributions, and CI/CD pipelines for Debian packaging.

PARAMETERS

--create

Create a new base.cow environment.

--update

Update packages in the cowbuilder environment.

--build dsc

Build a package from .dsc file.

--login

Start a shell in the chroot environment.

--distribution dist

Debian/Ubuntu distribution (bookworm, jammy, etc.).

--architecture arch

Target architecture (amd64, i386, arm64).

--basepath path

Path to base.cow directory.

--buildresult path

Directory for build results.

--mirror url

Package mirror URL.

--save-after-login

Save changes made during login session.

CAVEATS

Requires root privileges for chroot operations. The base.cow directory must be on a filesystem supporting hard links (not across filesystems). First build after update may be slower due to cache warming. COW benefits are lost if base.cow is on different filesystem than build directory.

HISTORY

cowbuilder was created as an enhancement to pbuilder (Personal Builder) by using COW filesystem techniques. Pbuilder itself was created by Junichi Uekawa in the early 2000s for building Debian packages in clean environments. Cowbuilder addressed pbuilder's main performance bottleneck: extracting the base tarball for each build.