Nextcloud AIO Docker on Ubuntu Setup

I need assistance with my Nextcloud AIO and Docker setup on Ubuntu. The primary task is to mount an external hard drive within Docker for backup purposes. The backup will primarily include documents, files, and the entire system image.

Key Requirements:
- Mounting external hard drive in Docker
- Transferring data to hard drive
- Setting up automated backups
- Skills in Docker, Ubuntu and Nextcloud AIO are essential