cowbuilder

cowbuilder is a wrapper around pbuilder that creates and manages copy-on-write chroot environments for building Debian-derived packages. It leverages copy-on-write file systems to speed repeated builds by keeping a pristine base chroot and layering writable changes on top for each build.

Operation and design: cowbuilder builds by first creating a base chroot using debootstrap and then mounting a writable COW layer atop it. The result is a build environment that appears writable to the build process while keeping the underlying base untouched. When a build is finished, changes are contained to the COW layer and the base can be reused for subsequent builds, minimizing disk usage and setup time.

Usage and use case: Administrators create per-distribution and per-architecture environments and use the provided workflow to enter or run builds in those environments. It is typically used by Debian and Ubuntu package maintainers to isolate builds and improve reproducibility. The tool requires root access and a suitable COW-capable filesystem such as overlayfs or aufs; without a COW layer, the performance benefits are reduced and the environment may be less efficient to refresh.

Overview in packaging workflows: cowbuilder is part of the Debian/Ubuntu packaging toolbox and is designed to work with pbuilder and debootstrap to provide fast, repeatable build chroots. By minimizing the need to recreate full chroots for every build, it helps streamline package maintenance and testing in large repositories.

See also: pbuilder, debootstrap, chroot, copy-on-write, sbuild.