Docker Hub & Registries

Docker Registries

A registry is a storage and distribution system for Docker images.

Docker Hub

Docker Hub is the default public registry.

Authentication

# Login to Docker Hub
docker login

# Login with credentials
docker login -u USERNAME

# Logout
docker logout

# Login to other registries
docker login registry.example.com

Pulling Images

# Pull from Docker Hub
docker pull nginx
docker pull nginx:1.25-alpine

# Full format
docker pull docker.io/library/nginx:latest

# Pull from other registry
docker pull gcr.io/google-containers/nginx
docker pull ghcr.io/owner/image:tag

Pushing Images

# Tag for Docker Hub
docker tag myapp:1.0 username/myapp:1.0

# Push to Docker Hub
docker push username/myapp:1.0

# Tag for private registry
docker tag myapp:1.0 registry.example.com/myapp:1.0

# Push to private registry
docker push registry.example.com/myapp:1.0

Image Naming Convention

[REGISTRY/][NAMESPACE/]REPOSITORY[:TAG]

Examples:
nginx                           # Official image
username/myapp:1.0              # User image
gcr.io/project/myapp:latest     # Google Container Registry
ghcr.io/owner/image:tag         # GitHub Container Registry
registry.example.com/app:v1     # Private registry

Running Private Registry

# Run local registry
docker run -d -p 5000:5000 --name registry registry:2

# Tag and push to local registry
docker tag myapp:1.0 localhost:5000/myapp:1.0
docker push localhost:5000/myapp:1.0

# Pull from local registry
docker pull localhost:5000/myapp:1.0

Registry with Persistent Storage

# docker-compose.yml
services:
  registry:
    image: registry:2
    ports:
      - "5000:5000"
    volumes:
      - ./registry-data:/var/lib/registry
    environment:
      REGISTRY_STORAGE_DELETE_ENABLED: "true"

Image Tagging Strategies

# Multiple tags for same image
docker tag myapp:abc123 myapp:1.2.3
docker tag myapp:abc123 myapp:latest
docker push myapp:1.2.3
docker push myapp:latest

Searching Images

# Search Docker Hub
docker search nginx
docker search --limit 5 nginx

# Filter by stars
docker search --filter stars=100 nginx

# Filter official images
docker search --filter is-official=true nginx

Best Practices

1. Use specific tags - Avoid latest in production
2. Sign your images - Use Docker Content Trust
3. Scan for vulnerabilities - docker scout cves IMAGE
4. Use minimal base images - Alpine, distroless
5. Multi-arch images - Support multiple platforms