Master Docker Image Creation, Management, and Transfer: From Pull to Push

In most cases a Docker image is built on top of an existing base image (e.g., a minimal CentOS, Ubuntu, or Debian). Official base images are created manually by Docker Hub maintainers.

Docker Hub

Docker Hub is a cloud‑based registry service that links to code repositories, builds and tests images, stores manually pushed images, and integrates with Docker Cloud for deployment.

Image repository

Search and pull images from community or official libraries; manage private repositories

Automated builds triggered by source changes

Web UI and webhooks for post‑push actions

Organization support for team access control

GitHub and Bitbucket integration

Getting Docker Images

Use docker pull to retrieve an image from a remote registry.

docker pull (registry)[:(port)]/(namespace)/:(tag)

The registry provides the distribution service (default port 5000) and identifies the specific image.

Image Generation

Images can be created via:

Dockerfile

Commit from a running container

Docker Hub automated builds

Creating an Image from a Container

Use docker commit to snapshot a container as a new image.

docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]

Common options:

--author, -a : author information

-c, --change : apply Dockerfile instructions to the new image

-m, --message : commit message

-p, --pause : pause the container during commit (default true)

# docker pull busybox
# docker run --name bi -it busybox
/ # mkdir data
/ # echo 'nihao' > data/index.html
# docker commit -p bi
sha256:b726393438ac...
# docker tag b726393438ac luojialong123/v1
# docker push luojialong123/v1

After committing, the new image contains the added files. By default the container starts with sh, but you can set a custom entrypoint (e.g., /bin/httpd) when committing.

# docker inspect bi
"Cmd": ["sh"]
"Gateway": "172.17.0.1"
"IPAddress": "172.17.0.2"

Import and Export Images

Use docker save to export an image to a tar file and docker load to import it on another host.

# docker save -o busybox luojialong123/v1
# docker load -i busybox
Loaded image: luojialong123/v1:latest

This method avoids pushing to a registry when you only need to transfer an image between machines.

Additional Exercises

Search for images ( docker search centos), pull them, inspect, and run containers. The article also shows how to compile Apache httpd from source inside a CentOS container, create a custom startup script, commit the container as a new image, and run it with port mapping.