What is Docker Hub?

Learn that Docker Hub is a public registry.

What is Docker Hub?

A registry is the server where images are stored and shared. Docker Hub is the default public registry. If no registry is written in the image name, Docker Hub is assumed; if no user name is written, the official library repository is used:

nginx              = docker.io/library/nginx:latest
ali/api:1.0        = docker.io/ali/api:1.0
ghcr.io/ali/api    = GitHub Container Registry

For free accounts an hourly limit applies to anonymous pulls; logging in raises this limit.

Repositories and access

On Docker Hub each repository can be public or private. Anyone can pull from public repositories; only owners and team members can push. The tags in a repository can be seen in the web interface or with a script:

docker pull ali/api:1.0          # no login needed if public
docker search --limit 3 postgres # searching on Hub

Exercise Pull from different registries

Write two commands: pull nginx:alpine with Docker Hub's full name (docker.io/library/...); then pull the ghcr.io/ali/api:1.0 image from the GitHub registry.

Show example solution

docker pull docker.io/library/nginx:alpine
docker pull ghcr.io/ali/api:1.0

Test yourself

What is the full equivalent of the image name redis?
- docker.io/library/redis:latest
- redis.io/redis
- docker.io/redis/redis
- localhost/redis
Show answer

docker.io/library/redis:latest — The registry, namespace and tag are completed with defaults.

Pull the image by its full name.

docker pull ____/library/nginx:alpine

Show answer

docker pull docker.io/library/nginx:alpine

Match.

docker.io

Docker Hub
library/

Official image namespace
ghcr.io

GitHub registry
private depo

Only authorized pull

Next lesson: docker login

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