https://www.howtoforge.com/tutorial/perfect-server-debian-8-jessie-apache-bind-dovecot-ispconfig-3/

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/

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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/