aptly

Aptly is an open-source tool for managing Debian package repositories. It provides a comprehensive solution for creating, mirroring, publishing, and maintaining APT repositories, including offline and private repositories. Written in Go, aptly stores packages in a local content-addressable storage and can publish repositories and snapshots to HTTP(S) servers, filesystems, or cloud storage.

Key concepts in aptly are repositories, mirrors, and snapshots. A repository holds packages; a mirror is an upstream fetch task; a snapshot is a point-in-time copy for reproducibility. Publishing generates Release and InRelease metadata and exposes them at a URL. It supports GPG signing of metadata, multiple architectures, and filtering of included packages. The storage is content-addressable and uses copy-on-write semantics to make updates efficient. Aptly can publish to various backends, including local file servers and cloud storage such as S3 or Swift.

Typical workflow involves creating a mirror for a Debian or Ubuntu repository, updating to fetch new packages, creating a snapshot or publishing directly, and serving the result via a web host. Clients run apt-get update and point at the published URL, using GPG keys for verification.

Aptly is commonly used to operate private or mirrored repositories, enabling reproducible builds, controlled package selection, and bandwidth optimization. It provides a command-line interface and an API for automation, making it suitable for organizations that require deterministic repository states and flexible publishing options.