Erich Blume
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## Summary - Merges `build-container.yaml` and `build-container-nix.yaml` into a single workflow - Detect job classifies each changed container by presence of `Dockerfile` and/or `default.nix` - Dockerfile containers build on `k8s` (indri) via Dagger; Nix containers build on `nix-container-builder` (ringtail) via nix-build + skopeo - Containers with both build files (alloy, nettest, ntfy) get built on both runners ## Test plan - [ ] Push a change to a Dockerfile-only container (e.g. grafana) — verify it builds on k8s only - [ ] Push a change to a nix-only container (e.g. jobsync) — verify it builds on nix-container-builder only - [ ] Push a change to a dual container (e.g. ntfy) — verify it builds on both runners - [ ] Test workflow_dispatch with a specific container name 🤖 Generated with [Claude Code](https://claude.com/claude-code) Reviewed-on: #306
150 lines
5.5 KiB
Markdown
150 lines
5.5 KiB
Markdown
---
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title: Build Container Image
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modified: 2026-02-24
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last-reviewed: 2026-02-15
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tags:
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- how-to
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- containers
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- ci
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---
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# Build a Container Image
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How to create a custom container image in BlumeOps, build it locally, and release it to the [[zot]] registry via the Forgejo CI pipeline.
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## Prerequisites
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- [Dagger CLI](https://docs.dagger.io/install) installed locally (for Dockerfile builds)
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- A `Dockerfile` and/or `default.nix` for the service
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## 1. Create the container directory
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Add build files under `containers/<name>/`:
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```
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containers/<name>/
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├── Dockerfile (built by Dagger on the k8s runner)
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├── default.nix (built by nix-build on the ringtail runner)
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└── (optional scripts, configs)
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```
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A container can have one or both build files. The directory name becomes the image name: `registry.ops.eblu.me/blumeops/<name>`.
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## 2. Build locally
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**Dockerfile** — test with Dagger:
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```bash
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dagger call build --src=. --container-name=<name>
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```
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**Nix** — test with Dagger (no local nix required):
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```bash
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dagger call build-nix --src=. --container-name=<name> export --path=./<name>.tar.gz
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```
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Or with nix-build directly (requires nix, e.g. on [[ringtail]]):
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```bash
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nix-build containers/<name>/default.nix -o result
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```
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## 3. Release
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Container builds trigger automatically when changes to `containers/<name>/` are merged to `main`. Both workflows fire and each skips if the relevant build file is absent.
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To trigger a manual build (e.g. from a branch or to rebuild at a specific commit):
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```bash
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mise run container-build-and-release <name>
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mise run container-build-and-release <name> --ref <commit-sha>
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```
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Use `--dry-run` to preview without dispatching.
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| Build file | Workflow | Runner | Registry tag |
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|------------|----------|--------|--------------|
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| `Dockerfile` | `build-container.yaml` | `k8s` (indri) | `:vX.Y.Z-<sha>` |
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| `default.nix` | `build-container-nix.yaml` | `nix-container-builder` ([[ringtail]]) | `:vX.Y.Z-<sha>-nix` |
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The version (`X.Y.Z`) is extracted from `ARG CONTAINER_APP_VERSION=` in the Dockerfile or `version = "..."` in `default.nix`. The SHA is the short (7-char) commit hash.
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Check available images and tags with:
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```bash
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mise run container-list
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```
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## 4. Update k8s manifests
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Change the image reference in `argocd/manifests/<service>/deployment.yaml`:
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```yaml
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image: registry.ops.eblu.me/blumeops/<name>:vX.Y.Z-abc1234
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```
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Then deploy per [[deploy-k8s-service]].
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### Squash-merge and container tags
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Container image tags include the git commit SHA they were built from (e.g. `v3.9.1-74029e1`). When a PR is squash-merged, the original branch commits are replaced by a single new commit on main — the SHA in the image tag no longer exists on main. After branch cleanup (30 days), the SHA becomes unreachable and the container loses source traceability.
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**The rule:** Production manifests must reference images built from a commit on main. After merging a PR that changed `containers/<name>/`:
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1. The merge to main automatically triggers a rebuild (the `build-container.yaml` / `build-container-nix.yaml` workflows fire on pushes to `main` that touch `containers/**`)
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2. Wait for the workflow to complete — check at `https://forge.eblu.me/eblume/blumeops/actions`
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3. Find the new main-SHA tag:
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```bash
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mise run container-list <name>
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```
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Tags marked `[main]` were built from a commit on main; tags marked `[branch]` are from PR branches
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4. Commit a C0 follow-up updating the manifest to use the `[main]` tag:
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```yaml
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image: registry.ops.eblu.me/blumeops/<name>:vX.Y.Z-<main-sha>
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```
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This follow-up C0 is expected and routine — it's the cost of squash-merge + SHA-tagged containers.
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## Common Patterns
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Existing containers demonstrate several build approaches:
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| Pattern | Example | Notes |
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|---------|---------|-------|
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| Alpine package install | [[#transmission]] | Simplest — install from apk |
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| Go from source | [[#miniflux]] | Clone upstream, `go build` |
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| Multi-stage with Node + Go | [[#navidrome]] | Separate UI and backend build stages |
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| Multi-stage Elixir | [[#teslamate]] | Elixir release with Node assets |
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| Runtime tarball download | [[#kiwix-serve]] | Download pre-built binary with arch detection |
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| Nix `dockerTools` | [[#ntfy-nix]] | `buildLayeredImage` with nix-built app |
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### transmission
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`containers/transmission/Dockerfile` — Installs transmission-daemon directly from Alpine packages. Good starting point for services available in apk.
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### miniflux
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`containers/miniflux/Dockerfile` — Two-stage Go build. Clones upstream at a pinned version tag, runs `make`, copies the binary into a minimal Alpine runtime.
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### navidrome
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`containers/navidrome/Dockerfile` — Three-stage build with separate Node.js UI compilation, Go backend build with CGO (taglib), and a minimal Alpine runtime with ffmpeg.
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### teslamate
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`containers/teslamate/Dockerfile` — Two-stage Elixir build with Node.js asset compilation. Uses Debian-based images due to Elixir/OTP dependencies.
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### kiwix-serve
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`containers/kiwix-serve/Dockerfile` — Downloads a pre-built binary from upstream, with architecture detection for cross-platform support.
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### ntfy (nix)
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`containers/ntfy/default.nix` — Builds ntfy from source using `buildGoModule` and packages it with `dockerTools.buildLayeredImage`. Runs alongside the existing Dockerfile; the nix variant is tagged `:version-nix` in the registry.
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## Related
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- [[deploy-k8s-service]] — Deploying the service that uses the image
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- [[create-release-artifact-workflow]] — Alternative: release non-container artifacts
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- [[dagger]] — Dagger CI reference
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