Debian is broken. I installed X2Go and FreeNX and then I needed to reboot but couldn’t because the shutdown program was not installed. I installed that, rebooted, but somehow the virtual machine was corrupted beyond restoration. I’m recovering from a backup but it will take some more work to get everything back to current so this machine may be down overnight. Please use Ubuntu or Mint if you need a Debian-based machine in the meantime.