title: SSH service broken after sshd_config was modified
body: <p>I modified the <code>sshd_config</code> but the ssh service became unavailable. How do I reset the config?</p>
  
  <p>Here is the log:</p>
  
  <pre><code>Jul 29 14:10:03 bye sshd[578]: /etc/ssh/sshd_config line 6: Badly formatted port number.
  Jul 29 14:10:03 bye systemd[1]: ssh.service: main process exited, code=exited, status=255/n/a
  Jul 29 14:10:03 bye systemd[1]: Unit ssh.service entered failed state.
  Jul 29 14:10:04 bye systemd[1]: ssh.service holdoff time over, scheduling restart.
  Jul 29 14:10:04 bye systemd[1]: Stopping OpenBSD Secure Shell server...
  Jul 29 14:10:04 bye systemd[1]: Starting Google Compute Engine VM initialization...
  Jul 29 14:10:04 bye systemd[1]: Started Google Compute Engine VM initialization.
  Jul 29 14:10:04 bye systemd[1]: Starting OpenBSD Secure Shell server...
  Jul 29 14:10:04 bye systemd[1]: Started OpenBSD Secure Shell server.
  Jul 29 14:10:04 bye sshd[582]: /etc/ssh/sshd_config line 6: Badly formatted port number.
  Jul 29 14:10:04 bye systemd[1]: ssh.service: main process exited, code=exited, status=255/n/a
  Jul 29 14:10:04 bye systemd[1]: Unit ssh.service entered failed state.
  Jul 29 14:10:04 bye systemd[1]: ssh.service holdoff time over, scheduling restart.
  </code></pre>