blumeops/docs/how-to/deployment/build-container-image.md

title	modified	last-reviewed	tags
Build Container Image	2026-02-24	2026-02-15	how-to containers ci

Build a Container Image

How to create a custom container image in BlumeOps, build it locally, and release it to the zot registry via the Forgejo CI pipeline.

Prerequisites

• Dagger CLI installed locally (for Dockerfile builds)
• A Dockerfile and/or default.nix for the service

1. Create the container directory

Add build files under containers/<name>/:

containers/<name>/
├── Dockerfile      (built by Dagger on the k8s runner)
├── default.nix     (built by nix-build on the ringtail runner)
└── (optional scripts, configs)

A container can have one or both build files. The directory name becomes the image name: registry.ops.eblu.me/blumeops/<name>.

2. Build locally

Dockerfile — test with Dagger:

dagger call build --src=. --container-name=<name>

Nix — test with Dagger (no local nix required):

dagger call build-nix --src=. --container-name=<name> export --path=./<name>.tar.gz

Or with nix-build directly (requires nix, e.g. on ringtail):

nix-build containers/<name>/default.nix -o result

3. Release

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.

To trigger a manual build (e.g. from a branch or to rebuild at a specific commit):

mise run container-build-and-release <name>
mise run container-build-and-release <name> --ref <commit-sha>

Use --dry-run to preview without dispatching.

Build file	Workflow	Runner	Registry tag
Dockerfile	build-container.yaml	k8s (indri)	:vX.Y.Z-<sha>
default.nix	build-container-nix.yaml	nix-container-builder (ringtail)	:vX.Y.Z-<sha>-nix

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.

Check available images and tags with:

mise run container-list

4. Update k8s manifests

Change the image reference in argocd/manifests/<service>/deployment.yaml:

image: registry.ops.eblu.me/blumeops/<name>:vX.Y.Z-abc1234

Then deploy per deploy-k8s-service.

Squash-merge and container tags

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.

The rule: Production manifests must reference images built from a commit on main. After merging a PR that changed containers/<name>/:

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/**)
2. Wait for the workflow to complete — check at https://forge.eblu.me/eblume/blumeops/actions
3. Find the new main-SHA tag:

   mise run container-list <name>
   

   Tags marked [main] were built from a commit on main; tags marked [branch] are from PR branches
4. Commit a C0 follow-up updating the manifest to use the [main] tag:

   image: registry.ops.eblu.me/blumeops/<name>:vX.Y.Z-<main-sha>
   

This follow-up C0 is expected and routine — it's the cost of squash-merge + SHA-tagged containers.

Common Patterns

Existing containers demonstrate several build approaches:

Pattern	Example	Notes
Alpine package install	#transmission	Simplest — install from apk
Go from source	#miniflux	Clone upstream, go build
Multi-stage with Node + Go	#navidrome	Separate UI and backend build stages
Multi-stage Elixir	#teslamate	Elixir release with Node assets
Runtime tarball download	#kiwix-serve	Download pre-built binary with arch detection
Nix dockerTools	#ntfy-nix	buildLayeredImage with nix-built app

transmission

containers/transmission/Dockerfile — Installs transmission-daemon directly from Alpine packages. Good starting point for services available in apk.

miniflux

containers/miniflux/Dockerfile — Two-stage Go build. Clones upstream at a pinned version tag, runs make, copies the binary into a minimal Alpine runtime.

navidrome

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.

teslamate

containers/teslamate/Dockerfile — Two-stage Elixir build with Node.js asset compilation. Uses Debian-based images due to Elixir/OTP dependencies.

kiwix-serve

containers/kiwix-serve/Dockerfile — Downloads a pre-built binary from upstream, with architecture detection for cross-platform support.

ntfy (nix)

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.

Related

• deploy-k8s-service — Deploying the service that uses the image
• create-release-artifact-workflow — Alternative: release non-container artifacts
• dagger — Dagger CI reference