yocto-env.nix

A Nix flake that provides a reproducible, FHS-compatible build environment for the Yocto Project.

The flake exposes a single dev-shell that works against every currently supported Yocto release. Today that's:

Codename	Yocto	Released	Status
(master)	—	rolling	tracks current dev
wrynose	6.0	14 May 2026	LTS — until April 2030
scarthgap	5.0	29 April 2024	LTS — until April 2028
kirkstone	4.0	25 April 2022	LTS — ended April 2026

All four share the same UNINATIVE_MAXGLIBCVERSION regime, so one nixpkgs pin (currently nixos-unstable, glibc 2.42) keeps the FHS /lib/ld-linux-x86-64.so.2 compatible with each release's uninative tarball. See doc/uninative-glibc-caps.md for the full rationale.

When the cap regime shifts — a new release branches with a lower cap, or master bumps past what the current pin can satisfy — the flake's nixpkgs input is rolled forward in a new commit and the previous commit is tagged. Consumers needing the older shell check out the tag. We deliberately do not carry parallel per-codename shells; the historical overhead never paid off given that cap regimes change on a multi-year cadence.

Quick start

You can use the flake directly from GitHub without cloning it:

nix develop github:OSSystems/yocto-env.nix

If you have the repo checked out locally, nix develop works the same way against the working tree.

For an older Yocto release whose uninative cap predates the current nixpkgs pin, check out the tag captured before the most recent roll:

nix develop github:OSSystems/yocto-env.nix/<tag>

What the shell provides

The shell is an FHS bubblewrap environment (buildFHSEnvBubblewrap) preconfigured with the host tooling bitbake expects: gcc, gdb, git, git-lfs, gnumake, chrpath, cpio, diffstat, python3, rpcsvc-proto, util-linux, plus the usual compression/archive utilities and a Yocto-aware set of fetcher and testimage helpers.

The shell also wires the Nix toolchain into bitbake's hash-based caching: it exports BB_ENV_PASSTHROUGH_ADDITIONS with the NIX_*/dynamic-linker variables bitbake needs to forward to its subprocesses, and sets BBPOSTCONF to a generated conf snippet so those variables survive BB_BASEHASH_IGNORE_VARS.

A configured zsh (grml + fzf + eza) is launched as the interactive shell, with history persisted to ~/.history-yocto-env.

Repository layout

• flake.nix — minimal entry point; uses phaer/red-tape.
• lib/default.nix — exports mkYoctoEnv, the dev-shell builder.
• devshells/default.nix — the single devshell.
• doc/uninative-glibc-caps.md — supported set, refresh script, and tag-on-roll strategy.
• treefmt.nix + formatter.nix — formatter wiring (nix fmt).