Glossary

Container Registry

A container registry is a storage service for Docker images — analogous to npm registry for JavaScript or Packagist for PHP. It stores versioned images that servers pull during deployment.

How it is used

# Build the image
docker build -t myapp:1.2.0 .

# Tag for the registry
docker tag myapp:1.2.0 registry.example.com/myapp:1.2.0

# Push
docker push registry.example.com/myapp:1.2.0

# On the server
docker pull registry.example.com/myapp:1.2.0
docker run registry.example.com/myapp:1.2.0

Popular options

Docker Hub — public, free for public images
GitHub Container Registry (GHCR) — integrates with GitHub Actions
AWS ECR, Google Artifact Registry — cloud-native, integrated with clusters
Harbor — self-hosted, open-source

Tags and versioning

latest is dangerous in production: each pull may fetch a different image. Always pin to a specific tag or SHA digest.