Exporting a Docker container with contents of mounted volume

Question

I am trying to export a docker container that uses a mounted local volume as its root, which I run with docker run --privileged -v /path/to/local/files:/root --name cse303dev -it cse303 to mount that local directory.

What is the best way of exporting the container AND all of the contents of that local mounted directory into a simple tar file of some sort? And then how would I easily re-import this container and run it so that I can see and use all of those files copied from the local machine that exported it? Is this possible?

Answer 1

You almost never "export" a container per se . Containers are generally intended to be freely destroyed and recreated.

In your case you already have the data you care about stored outside the container (in a bind-mounted folder, which is the easy case), so you can just copy that directory tree to wherever else and then run a new copy of the container there.

(cd /path/to/local/files; tar cvzf ~/local-files.tar.gz .)
scp local-files.tar.gz there:
ssh there

mkdir files
(cd files; tar xvzf ../local-files.tar.gz)
docker run -v $PWD/files:/root cse303

This is trickier if you're storing the data in a named volume. The Docker documentation describes how to back up the contents of a named volume and you'd have to go through that procedure.

Answer 2

If you want to export the entire contents of the container (including the mounted volumes, which might be a bad idea depending upon what you have mounted), then you want to run tar inside the container and pipe out the data to a file:

docker run --privileged -v /path/to/local/files:/root ${IMAGE_NAME} \
    tar -cf - -C / --exclude=proc --exclude=sys . | gzip > myfile.tgz

I would highly recommend excluding /proc and /sys (as in the above example) or you will likely encounter issues.