http://qr.ae/TUpklV
There's a few ways if you want to explore the container’s fs.
Start an interactive shell and cd/ls around: docker exec -it container bash
This requires a few things of the container though.
That there's some kind of shell and that you know the name of the shell.
That there's a ‘cd’ that or ‘ls’ command to explore with.
That the shell you enter as has access to read the directories and files.
A better way, is to docker commit the container. There will be a split second while the container is paused, but it will resume immediately after the commit.
Once it's committed, you can docker export it to a tarball and explore the file system from the host environment or another machine.
http://qr.ae/TUpklV