Advanced Docker Image Construction with Bash
On current versions of Docker, you can’t mount volumes during image construction. This poses an issue for me as I don’t want to replicate gigabytes of data already existing on my disk when it won’t appear on the final build. Therefore, instead of building an image with a traditional Dockerfile, we’re going to use a bash script on a running base image container and export the filesystem to create the image from.
So first run the base image with the mounts that you want
docker run -v /mnt:/mnt -td --name containername baseimage /bin/bash
Then copy whatever
setup script you have and execute it on the running container
docker cp setup containername:/setup docker exec -it containername /setup
Once the setup script finalizes, we can export the container filesystem into a file called
docker export --output="image.tar" containername
Once we’ve exported the filesystem, we can get rid of the existing container
docker stop containername && docker rm containername
Now create a
Dockerfile with the following:
FROM scratch ADD image.tar / CMD ["bin/bash"]
Now you can create the image by building the Dockerfile
docker build -t finalimagename .