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Alex Spinov
Alex Spinov

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Buildah Has a Free API — Build OCI Container Images Without Docker

#docker #containers #api #devops

Buildah builds OCI-compatible container images without requiring a Docker daemon. It's rootless, daemonless, and perfect for CI/CD pipelines where you can't run Docker-in-Docker.

Free, open source, by Red Hat. Used in OpenShift, Tekton, and GitHub Actions.

Why Use Buildah?

  • No daemon — doesn't need Docker daemon running
  • Rootless — build images as non-root user
  • Dockerfile compatible — use existing Dockerfiles
  • Fine-grained control — build images step by step with CLI
  • OCI standard — produces images compatible with Docker, Podman, K8s
  • CI/CD friendly — no Docker-in-Docker needed

Quick Setup

1. Install 

# Ubuntu/Debian
sudo apt install buildah

# Fedora/RHEL
sudo dnf install buildah

# macOS (via Podman machine)
brew install podman
podman machine init && podman machine start
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2. Build from Dockerfile 

# Same as docker build
buildah build -t my-app:v1 .

# With build args
buildah build --build-arg NODE_ENV=production -t my-app:prod .

# Multi-stage builds work too
buildah build -f Dockerfile.multi -t my-app:slim .
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3. Build Step by Step 

# Create a container from base image
container=$(buildah from ubuntu:22.04)

# Run commands inside
buildah run $container -- apt-get update
buildah run $container -- apt-get install -y python3 python3-pip
buildah run $container -- pip3 install requests beautifulsoup4

# Copy files
buildah copy $container ./scraper.py /app/scraper.py

# Set working directory and entrypoint
buildah config --workingdir /app $container
buildah config --entrypoint '["python3", "scraper.py"]' $container
buildah config --label maintainer="spinov001@gmail.com" $container

# Commit to image
buildah commit $container my-scraper:latest

# Push to registry
buildah push my-scraper:latest docker://ghcr.io/my-org/my-scraper:latest
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4. Rootless Builds 

# No sudo needed!
buildah build -t my-app .
buildah images
buildah push my-app docker://registry.example.com/my-app:latest
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5. Inspect Images 

# List images
buildah images

# Inspect image
buildah inspect my-app:latest | jq '{created: .Docker.created, layers: (.Docker.rootfs.diff_ids | length), config: .Docker.config.Cmd}'

# List containers (working containers)
buildah containers

# Remove image
buildah rmi my-app:latest
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CI/CD Example (GitHub Actions) 

name: Build with Buildah
on: push
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4
    - name: Build image
      run: |
        buildah build -t my-app:${{ github.sha }} .
    - name: Push to GHCR
      run: |
        buildah login -u ${{ github.actor }} -p ${{ secrets.GITHUB_TOKEN }} ghcr.io
        buildah push my-app:${{ github.sha }} docker://ghcr.io/${{ github.repository }}:${{ github.sha }}
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Python Automation 

import subprocess
import json

def buildah_cmd(*args):
    result = subprocess.run(["buildah"] + list(args), capture_output=True, text=True)
    return result.stdout.strip()

# List images
images = buildah_cmd("images", "--json")
for img in json.loads(images):
    print(f"Image: {img['names'][0] if img['names'] else 'unnamed'} | Size: {img['size']}")

# Build
buildah_cmd("build", "-t", "my-app:latest", ".")
print("Build complete!")
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Buildah vs Docker Build

Feature Buildah Docker
Daemon required No Yes
Rootless Yes Partial
Dockerfile support Yes Yes
Step-by-step build Yes No
OCI compatible Yes Yes
CI/CD friendly Excellent Needs DinD

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