A Docker Registry is a centralized system for storing, managing, and distributing Docker images. These images are lightweight, standalone packages that contain everything needed to run a piece of software or code, runtime, libraries, and dependencies. The registry acts like a version-controlled warehouse where developers can push (upload) and pull (download) images as needed.
There are two main types of registries: public and private. Public registries like Docker Hub allow anyone to share and access images, while private registries offer more control and security, often used within organizations. Each registry is organized into repositories, and each repository can contain multiple versions (tags) of an image.
Registries are essential in CI/CD pipelines. After a successful build, an image is pushed to a registry, from where it can be pulled into staging or production environments. This ensures consistency across deployments and simplifies rollback if needed.
Docker registries also support features like access control, image scanning for vulnerabilities, and integration with authentication systems. You can even run your own registry using the official Docker image, giving you full control over your container distribution.
TYPES OF DOCKER REGISTRY-
1. Public Registries
These are open to everyone and typically host both official and community-contributed images.
- Docker Hub: The default and most widely used public registry.
- GitHub Container Registry: Integrated with GitHub repositories.
- Google Artifact Registry (formerly GCR): Public and private support with Google Cloud integration.
2. Private Registries
Used within organizations to store proprietary or sensitive images securely.
- Self-Hosted Docker Registry: Run using the official
registryimage (registry:2) on your own infrastructure. - Harbor: An open-source registry with advanced features like RBAC, image replication, and vulnerability scanning.
- JFrog Artifactory: Supports Docker and other artifact types with enterprise-grade features.
3. Cloud-Native Registries
Managed services offered by cloud providers, often tightly integrated with their ecosystems.
| REGISTRY | CLOUD PROVIDER | KEY FEATURES |
| Amazon Elastic Container Registry (ECR) | AWS | IAM integration, image scanning, lifecycle policies |
| Azure Container Registry (ACR) | AZURE | Active Directory support, geo-replication, content trust |
| Google Artifact Registry (GAR) | GOOGLE CLOUD | Multi-format support, vulnerability scanning, CI/CD integration |
SOME COMMONLY USED COMMANDS
| COMMAND | DESCRIPTION |
| docker login | Authenticate to a Docker registry (e.g., Docker Hub, private registry). |
| docker logout | Log out from a Docker registry. |
| docker tag <image> <registry>/<repo>:<tag> | Tag a local image for pushing to a registry. |
| docker push <registry>/<repo>:<tag> | Push a tagged image to a registry. |
| docker pull <registry>/<repo>:<tag> | Pull an image from a registry. |
| docker search <image> | Search for images on Docker Hub. |
| docker images | List all local images. |
| docker rmi <image> | Remove a local image. |
| docker save -o <file>.tar <image> | Save an image to a tar archive. |
| docker load -i <file>.tar | Load an image from a tar archive. |
| docker inspect <image> | View detailed metadata about an image. |
| docker registry (containerized) | Run a private registry using the registry:2 image. |
DIFFERENCE BETWEEN DOCKER HUB & PRIVATE REGISTERY
| ASPECT | DOCKER HUB | PRIVATE REGISTRY |
| ACCESSIBILITY | Public by default; supports private repos with limits on free plans | Fully controlled by the organization; access is restricted and customizable |
| HOSTING | Hosted by Docker Inc. (cloud-based) | Self-hosted or managed by cloud providers (e.g., AWS ECR, GCP Artifact Registry) |
| SECURITY | Basic access control; private repos require paid plans | Full control over authentication, authorization, and network access |
| CUSTOMIZATION | Limited customization | Highly customizable (e.g., Harbor supports RBAC, replication, vulnerability scans) |
| COST | Free tier available; paid plans for private repos and team features | May incur infrastructure or licensing costs depending on setup |
| PERFORMANCE | Subject to rate limits and shared infrastructure | Can be optimized for internal network speed and availability |
| USE CASE | Ideal for open-source projects, quick sharing, and public collaboration | Best for enterprise use, sensitive images, and compliance-heavy environments |
| INTEGRATION | Integrates with Docker CLI and CI/CD tools | Also integrates well, but may require additional setup depending on the platform |