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 a host editor? sshfs could probably do the job but since a running container is already some kind of host directory I wonder if there is a portable (between aufs, btrfs and device mapper) way to do that?

Accepted Answer

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.

How to edit Docker container files from the host?

Solution

Problem