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nixos/docs/flake-lock-automation.md
2026-05-12 12:28:37 +10:00

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# flake.lock automation
This repository uses CI workflows to keep `flake.lock` up to date on a schedule and to verify that all declared NixOS hosts still evaluate after dependency updates.
## What this automation does
- A scheduled workflow runs `nix flake update` once per week.
- On GitHub, any resulting `flake.lock` change is proposed through a pull request.
- On Gitea, the workflow can commit and push `flake.lock` directly when PR automation is not configured.
- A separate CI workflow evaluates every configured host before merge:
- `nixos`
- `docker`
- `kuma`
- `server`
- `nix-cache`
- `nix-minimal`
## Why hosts should stop using `--upgrade-all`
`flake.lock` is the source of truth for pinned dependency versions in a flake-based workflow. Normal host rebuilds should consume the committed lock file instead of upgrading dependencies ad-hoc on each machine.
Recommended rebuild command:
```bash
sudo nixos-rebuild switch --flake git+https://gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git#$(hostname)
```
Using the committed lock file keeps all hosts aligned and makes updates auditable through CI and code review.
## Command differences
- `nix flake update`
- Updates flake input pins in `flake.lock`.
- Should be run in CI or in a dedicated update PR workflow.
- `nixos-rebuild --upgrade`
- Primarily for channel-based workflows; not the normal path for flake-pinned deployments.
- `nixos-rebuild --upgrade-all`
- Aggressively updates package sources and bypasses coordinated lock-file updates.
- Avoid for routine flake-based host rebuilds.
## nix-cache and remote builder fit
With `nix-cache` acting as a binary cache and remote builder, lock-file updates become safer and more reproducible:
- CI verifies host evaluations against the updated lock file.
- Builds can be performed once on the remote builder.
- Built artifacts can be served via `nix-cache` to other hosts, reducing rebuild time and drift.
## Token and secret handling
Do **not** commit access tokens into `flake.nix`, `flake.lock`, or any other tracked file.
If private source access is needed:
- configure tokens locally in `~/.config/nix/nix.conf` or equivalent machine-local config, or
- provide tokens through CI secrets/environment variables.
## GitHub Actions setup notes
- Ensure `GITHUB_TOKEN` has permission to create branches and pull requests (workflow sets `contents: write` and `pull-requests: write`).
- The update workflow uses `peter-evans/create-pull-request` with branch `chore/update-flake-lock`.
- The evaluation workflow runs on pull requests, pushes to `main`, and manual dispatch.
## Gitea Actions runner setup notes
- Ensure the runner image includes Git and can execute the Nix installer action.
- For direct push mode, grant workflow push permission to the repository.
- The workflow sets commit identity to:
- `user.name = gitea-actions`
- `user.email = gitea-actions@nix-cache.local`
- Commits are only created when `flake.lock` actually changes.