Containers

Alpine- and ASDF-Powered Development Containers
Lightweight Docker images built on Alpine Linux and ASDF, designed to streamline tool installation, multi-architecture support (amd64/arm64), and consistent development environments.

• Build Docker images for different tools and environments (e.g., asdf) across both amd64 and arm64 platforms.
• Automatically tag versioned builds based on upstream dependencies (e.g., Alpine, ASDF versions).
• Push to Docker Hub (docker.io/dmascot/<image>:<version> and :latest).
• Track build metadata to prevent redundant builds.
• Cleanly separate CI and local build workflows.

📂 Directory Structure

.
├── build.sh                      # Central logic for all image builds used by both CI and local build
├── local_build.sh                # Local builder script;builds one image locally
├── common.sh                     # Shared shell functions and helpers
├── build-info.json               # Metadata for last-known build versions (CI)
├── local-build-info.json         # Metadata for last-known local builds (not committed to the repository)

├── images/
│   └── asdf/
│   │   ├── Dockerfile
│   │   ├── build.sh                # Image-specific version logic
│   │   └── asdf_helper.sh          # Script added to container image
│   └── <image_name>/
│       ├── Dockerfile
│       ├── build.sh                # Image-specific version logic
│       └── <image specific script> # Script added to container image

🛠 Usage

✅ Local Build

./local_build.sh <image-name> [--dry-run]

To enable debug printing:

DEBUG="true" ./local_build.sh <image-name> [--dry-run]

✅ CI Builds

GitHub Actions uses .github/workflows/_build-and-push.yml to build and push multi-arch images only if versions have changed. It uses build-info.json as metadata to track this.

➕ Adding a New Image

1. Create a new folder under images/, e.g. images/mytool/
2. Add a Dockerfile with your image definition
3. Create a build.sh file with the following structure.Ensure the function name is the same (i.e. build_image_data) and that its output is a JSON string like this:

{ 
  "IMAGE_DATA": {
    "BUILD_VERSION": "v1.0",
    "TOOL_VERSION": "v0.1"
  },
  "BUILD_ARGS": ["KEY1=VAL1","KEY2=VAL2",..]
}

Below is a simple example script:

    #!/bin/bash
    set -euo pipefail

    build_image_data() {
    local context_path="$1"

    # Example version detection
    local BUILD_VERSION="1.0.0"
    local TOOL_VERSION="0.0.2"

    jq -n \
        --arg build_version "$BUILD_VERSION" \
        --arg tool_version "$TOOL_VERSION" \
        --argjson build_args "$(jq -n --arg ar1 "TOOL_VERSION=$tool_version" '[ $ar1 ]')" \
        '{
          IMAGE_DATA: {
            BUILD_VERSION: $build_version,
            TOOL_VERSION: $tool_version,
          },
          BUILD_ARGS: $build_args
        }' 

1. Ensure BUILD_VERSION is present in the file, if not you will see an error.
2. BUILD_ARGS are optional and are limited to --build-arg only. They cannot be used to pass other Docker build options

🤝 Contributing

Pull requests are welcome! Please follow the pattern used in images/asdf, and test your changes locally before submitting.

📦 Docker Hub

Images are published to: https://hub.docker.com/u/dmascot

Improvements

• Run a vulnerability scan
• Support force build (i.e. rebuild even if build-info.json marks it as built)
• Manage additional Docker build options if needed (i.e., beyond --build-arg)