https://www.howtoforge.com/tutorial/perfect-server-debian-8-jessie-apache-bind-dovecot-ispconfig-3/2/
https://www.howtoforge.com/tutorial/perfect-server-debian-8-jessie-apache-bind-dovecot-ispconfig-3/3/
===
Backup entire ispconfig 3 and restore
https://www.howtoforge.com/community/threads/ispconfig-3-move-to-another-server.41643/#post-295412
https://www.howtoforge.com/community/threads/what-to-backup-ispconfig-and-need-to-know-how.41595/