In case of either of the virtual servers, wiki:PuffinServer or wiki:PenguinServer locking up they can be rebooted via xen shell console access, Chris, Jim and Mark have access to this via their ssh keys:

ssh transition@xen1.webarch.net
xen-shell v1.9 - type 'help' for help.
xen-shell> list
You may control the following Xen instances:

        penguin.webarch.net
        puffin.webarch.net

(Use 'control' to take control of a particular instance.)
xen-shell> control penguin.webarch.net
Controlling: penguin.webarch.net
xen-shell> status
Guest : Running
xen-shell[penguin.webarch.net]> uptime
Host :  16:09:41 up 61 days,  1:44,  4 users,  load average: 0.09, 0.13, 0.09
Guest: 45 days 00:41:21
xen-shell[penguin.webarch.net]> help
xen-shell v1.9
The following commands are available within this shell:

Use of uninitialized value in sprintf at /usr/bin/xen-shell line 1603, <FIN> line 5.
    author - 
      boot - Boot the Xen guest.
   console - Gain access to a Xen guest via the serial console.
   control - Specify which Xen guest to control.
      exit - Exit the shell.
      help - Show general, or command-specific, help information.
      list - List Xen instances which you may control.
     pause - This will pause the Xen guest.
      quit - Exit this shell.
    reboot - Reboot the Xen guest.
    serial - Gain access to the Xen guest via the serial console.
  shutdown - Shutdown the Xen guest.
    status - Show the status of the Xen guest.
    sysreq - Send a 'sysreq' keystroke to the guest.
       top - Show system resource usage.
   unpause - This will unpause the Xen guest.
    uptime - Show the uptime information of your guest system and this host.
   version - Show the version of this shell, and of Xen.
    whoami - Show the user you're connected to the host system as.

For command-specific help run "help command".

xen-shell[penguin.webarch.net]> exit

For more on xen shell commands see ​http://www.xen-tools.org/software/xen-shell/commands.html