SSH Container

A simple container which runs SSH upon startup.

It will persist SSH host keys in /srv/ssh/ - thus allowing the container to have a persistent SSH "identity" across startups.

Note that this container does not set up any users.

If the environment variable ROOT_AUTHORIZED_KEY is set, this will be added to /root/.ssh/authorized_keys.

It does make some minor tweaks to the Debian default SSH configuration to enforce that root can only login using a key (password authentication is not allowed) - see 10-ssh-container.conf for details.

The container's ENTRYPOINT (technically /ssh-setup) will generate keys as needed (and persist them to /srv/ssh/) and start a SSH daemon before launching the given command. If no command is given, it will default to /bin/bash.

Ports

The container will expose an SSH server on port 22.

Volumes

To persist across container restarts: mount a persistent volume on /srv/ssh.

Health Check

The container provides a simple health check with the command /ssh-healthcheck.

Building on This

If you build a container based on this image, be sure to do exactly one of:

• Do not override the Dockerfile ENTRYPOINT, thus leaving the ENTRYPOINT from this container in effect.

• Early in your entrypoint script: make a call to /ssh-setup. Be sure to to handle a non-zero exit code from ssh-setup correctly - e.g.:

   #!/bin/sh
   set -e
   /ssh-setup
   # Do your own stuff here
  

  It is also recommended that you provide your setup script (e.g. named /mycontainer-setup) and make it available for users who want to build on top of your container - probably with instructions similar to this in your own README.md file.

• Make your Dockerfile ENTRYPOINT a call to /ssh-entrypoint giving the path to your own entrypoint (and any parameters it needs) as parameters - e.g.:

   # Dockerfile
   ...
   COPY mycontainer-entrypoint /mycontainer-entrypoint
   ENTRYPOINT ["/ssh-entrypoint", "/mycontainer-entrypoint", "foo", "bar"]
   ...
  

Also: be sure to invoke /ssh-healthcheck as part of your own healthcheck.