On the Digital Ocean droplet, using Ubuntu 16.04.4, after installing ISPConfig, through this shellscript (https://github.com/servisys/ispconfig_setup) and giving the command poweroff, to create the snapshot, the syste...
You may want to spin up a Debian system instead of Ubuntu.
As per the github page:
For now it is tested and developed only on Debian systems.
Maybe it works well also on Ubuntu systems.