Copying files from Docker container to host

Question

I\'m thinking of using Docker to build my dependencies on a Continuous Integration (CI) server, so that I don\'t have to install all the runtimes and libraries on the agents

Answer 1

Mount a "volume" and copy the artifacts into there:

mkdir artifacts
docker run -i -v ${PWD}/artifacts:/artifacts ubuntu:14.04 sh << COMMANDS
# ... build software here ...
cp  /artifacts
# ... copy more artifacts into `/artifacts` ...
COMMANDS

Then when the build finishes and the container is no longer running, it has already copied the artifacts from the build into the artifacts directory on the host.

Edit

Caveat: When you do this, you may run into problems with the user id of the docker user matching the user id of the current running user. That is, the files in /artifacts will be shown as owned by the user with the UID of the user used inside the docker container. A way around this may be to use the calling user's UID:

docker run -i -v ${PWD}:/working_dir -w /working_dir -u $(id -u) \
    ubuntu:14.04 sh << COMMANDS
# Since $(id -u) owns /working_dir, you should be okay running commands here
# and having them work. Then copy stuff into /working_dir/artifacts .
COMMANDS