How to reduce the docker image size which is already committed

Question

I know that the docker image is read-only. Therefore, deleting the file inside base-image within container does not change the size of docker. (result of docker ps -s)

I wanted to reduce image size, but it's already committed, and I can't reduce it. Because committed image is read-only. How can I delete the files inside the image? Or is there a way to commit image read-and-write mode instead of read-only?

Answer 1

The way to achieve it is creating a new image without the file.

After you have deleted the file(s) you want to inside the running container, run:

docker export <container id> -o <filename>

and

docker import <filename> <image name>

Doing it you will get a new image without those files.

To delete the files:

docker exec -ti <container id> /bin/bash

and delete the files