For the most part, this guide: https://www.uxora.com/other/virtualization/55-install-xpenology-dsm-6-2-x-on-proxmox can be followed, but some tweaks have to be made before starting.


How to activate Active Backup features

Note: Must change admin user password to something without any special characters.

Visit the URLs in order:

https://synology.unixfy.net/webapi/auth.cgi?api=SYNO.API.Auth&method=Login&version=1&account=yourusername&passwd=yourpassword
https://synology.unixfy.net/webapi/entry.cgi?api=SYNO.ActiveBackup.Activation&method=set&version=1&activated=true&serial_number="yoursn"

https://synology.unixfy.net/webapi/entry.cgi?api=SYNO.ActiveBackup.Activation&method=get&version=1