Job orb


Skip to build

orb: check opam package reproducibility

This tool can check if an opam package build is reproductible (cf. It has two subcommands: build and rebuild.

The orb build conducts a build of an opam package, and collects the build result (and hashes thereof) and the build input (or build info), consisting of:

The orb rebuild takes this data as input and conducts a second build with the same environment, and compares that the hashes of the produced binaries are identical.

The orb build also has a command-line flag "--twice" to conduct a build and a rebuild directly afterwards. For debugging reproducibility, a "--keep-build" (useful with opam's "--keep-build-dir") option is provided that allows to compare intermediate build products as well.

Please have a look at "--diffoscope", "--out", "--switch-name", "--solver-timeout", "--date", and other command line parameters.

It is currently used as a payload of builder-worker to run the reproducible MirageOS unikernels infrastructure.

Binary packages for different platforms (Debian, Ubuntu, FreeBSD) are available at

Install & use

$ opam pin git+
$ orb build --twice --repos=default: cmdliner

Simple (and fast) failing and successful reproducible opam packages are in the reproducible-testing-repo.

Build 2021-11-24 15:47:58Z

Back to readme

Built on platform ubuntu-20.04

Build took 4min52s.

Execution result: exited 0.

Build info

Build artifacts

SHA256:ae4467bbeea1c300b37b1e6ce7319490a7d2db0d64c0d4e995fcdbb773912a68 (4.14MB)
SHA256:f301d2cafe93c27b1fe9adad5d011cfda2aa9e5a8ef38944b09882169cc92a53 (355B)
SHA256:ccaba82a2576e2eae424d2c7b3ab86b500bd529c33c9eb609414a66b1af5f887 (53.7kB)
SHA256:38f4404d2d458c9cfe5bf95b31f8b7b2c57b419cad5413217d10ec51ae7b92ce (4.48kB)

Reproduced by 14 builds

Comparisons with other builds on the same platform