Buck2 vs Open Build Service

Buck2 is a free build system from Meta for large-scale repositories that combine multiple programming languages. It uses Starlark rules, a dynamic dependency graph, and incremental actions to support extensible builds. Its language table lists prelude rules for C/C++, Erlang, Go, Haskell, Java, Kotlin, OCaml, Python, and Rust, though usability varies by language. Build actions can run remotely through services exposing Bazel's remote execution API; the project lists BuildBarn, BuildBuddy, EngFlow, and NativeLink as compatible with its distributed compilation support. Buck2 supports filesystem watching and can integrate with Meta's optional Eden virtual filesystem. Rules are hermetic by default and missing dependencies are errors, but local-only build steps are not sandboxed. The project describes Buck2 as early-stage and says it has no stable release tag; its latest binary tag changes with repository pushes. It warns that outside users may encounter rough edges, missing features, and missing toolchains. Source and binaries are available under MIT and Apache-2.0 licenses. The project directs users to GitHub for issue reports and offers a community Discord server.

Open Build Service (OBS) builds and distributes binary packages from source code in a consistent, reproducible way. Each package is built in a fresh jailed environment; when a build succeeds, OBS rebuilds packages that depend on it. The service can release packages, updates, add-ons, appliances, and complete distributions for different operating systems and hardware architectures. Documented package formats include RPM, DEB, and Arch, with recipes in formats such as spec, dsc, KIWI, and mkosi. Teams can use access controls, branches, merge requests, and submission reviews to coordinate work. GitHub.com and GitLab.com integrations are supported, as are self-hosted GitHub, GitLab, and Gitea instances when network connectivity works. The API gives clients and external services access to OBS resources, while the osc command-line client can edit sources and metadata, start builds, and gather results. OBS is GPL-licensed free software, available on a reference server for open-source developers or for installation on users’ own hardware or in a data center. The listed plan is free.