Freeze. Thaw. Repeat.

This is a tech demo of CRIU and Docker integration, featuring tmux.

See it live in this ASCII video demo!

1. docker run -t -i --privileged --name critmux jpetazzo/critmux
2. Do stuff in tmux. Don't know what to do? Just type a few characters.
3. From another terminal, docker stop critmux. Container stops.
4. docker start critmux ; docker attach critmux. MIND. BLOWN.

Note: docker start -a doesn't quite work.

What the?

This container starts a little wrapper, which sets up a SIGTERM signal handler. Then it checks if there is some saved state in /state:

• if there is no saved state, we assume a clean start, setup a tmux session, and attach to it;
• if there is a saved state, it is restored it (it should be a tmux daemon process), then we attach to tmux.

The signal handler just sends a detach command to tmux; and the wrapper arranges for the state to be saved when tmux is detached. In other words, when detaching from tmux, or when sending SIGTERM, or when doing docker stop on the container, we end up saving its state.

Requirements

You need a fairly recent kernel. Debian's 3.14 works; some people reported that 3.13 didn't.

AUFS won't work.