Docker commit method

In this guide, you’ll learn how to create a Docker image from a running container using docker container commit. This technique can be useful for rapid prototyping or debugging changes without writing a Dockerfile. For production-grade images, you should still prefer the Dockerfile approach to ensure repeatability and version control.

Overview

Typically, custom images are built with a Dockerfile:

docker build -t myapp:latest .

Alternatively, you can:

1. Launch a container from a base image (e.g., httpd).
2. Modify files or install packages inside the container.
3. Commit the container’s state as a new image.

When to Use docker commit

Step-by-Step Example

1. Run an httpd container in detached mode

   docker run -d --name httpd httpd
   

2. Enter the container and update the default web page

   docker exec -it httpd bash
   root@container:/# cat > /usr/local/apache2/htdocs/index.html <<EOF
   Welcome to my custom web application
   EOF
   root@container:/# exit
   

3. Commit the container state to a new image

   docker container commit -a "Ravi" httpd customhttpd
   

4. Verify the new image

   docker image ls
   REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
   customhttpd   latest    adac0f56a7df   5 seconds ago   138MB
   httpd         latest    417af7dc28bc   8 days ago      138MB
   

Comparison: Dockerfile vs. docker commit

References

• Dockerfile reference
• docker container commit
• docker exec documentation
• Docker image management