Recovery from attemted upgrade NC 16 -> NC 18


First of all, some discription of where I am and how I got there:
I had a Nextcloud instance running on,
and after the last pull and recreate of the container, stuff started to go sideways.

It stopped serving requests (internal server error, and I think it had a notice about maintenance mode). My decision was then to move to the official nextcloud docker image over at, and just pulled in the latest image.

I changed up the environment variables, container volume mappings and the paths in the config to match the new container image and gave it a go. Still no luck, still got internal server errors. The stdout of the container doesn’t contain any helpful logs regarding that, just apache access logs.

From what I could get to so far, the version listed in the config is, so I guess that’s the last version that I had working on my machine. The version i pulled in from docker hub was latest, so an 18 based version. I think it did some database migrations, because when I swap in a v16 or v17 NC container, it says that the data version for my nextcloud is 18.

My question now is, what can I recover from this, and how? I have that database (sadly no recent backups from before, because my automatic backups have broken and I haven’t gotten to fixing that yet), I have the config, I have the data folder. What I mostly want is to not loose the contacts stored on the server, I don’t think the database contains much else important stuff.