How to edit Docker container files from the host?

Question

Now that I found a way to expose host files to the container (-v option) I would like to do kind of the opposite:

How can I edit files from a running container with

Answer 1

Whilst it is possible, and the other answers explain how, you should avoid editing files in the Union File System if you can.

Your definition of volumes isn't quite right - it's more about bypassing the Union File System than exposing files on the host. For example, if I do:

$ docker run --name="test" -v /volume-test debian echo "test"

The directory /volume-test inside the container will not be part of the Union File System and instead will exist somewhere on the host. I haven't specified where on the host, as I may not care - I'm not exposing host files, just creating a directory that is shareable between containers and the host. You can find out exactly where it is on the host with:

$ docker inspect -f "{{.Volumes}}" test
map[/volume_test:/var/lib/docker/vfs/dir/b7fff1922e25f0df949e650dfa885dbc304d9d213f703250cf5857446d104895]

If you really need to just make a quick edit to a file to test something, either use docker exec to get a shell in the container and edit directly, or use docker cp to copy the file out, edit on the host and copy back in.