Hi there,
I have recently stood up a NextCloud instance on my QNAP TS-451DeU-2G using its native container station by pulling down the nextcloud:latest image from dockerhub.
The setup process was relatively painless (once I figured correct MariaDB configuration settings) and was running flawlessly for at least 2 months, which allowed me to create a complete backup of my families phones, workstations, laptops etc… essentially 2 months were spent configuring the family device pool to sync with my new NAS and NextCloud instance… life was wonderful.
That was until the NAS seemed to crap out and required a re-start to become active again, the locally installed applications on the NAS seemed to restart without issue however the Nextcloud container, while configured to standup following a system reboot could not do so.
After some investigation it seemed that the portforwarding between the host and the container was not persisted.
This problem could only be addressed by creating a new container with the required portforwarding config… the issue here was that it initiated a new volume and a brand new instance of Nextcloud… which is not obviously what was intended.
Therefore my question is as follows, on the QNAP Container Station, how can i stand up a new container instance of NextCloud that can re-use the existing volumes (created during the previous setup ) so that I can continue to leverage the previously persisted media, backups etc that have been synced with NextCloud in its previous container incarnation?
Thanks in advance for any support, guidance, direction, wisdom bestowed 
Cheers,
dave