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/bashset -euo pipefail
build_image_data() {
local context_path="$1"# Example version detectionlocal BUILD_VERSION="1.0.0"local TOOL_VERSION="0.0.2"
jq -n \
--arg build_version "$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)