NextcloudPi Alpine LXC login redirect loop after restoring from backup

[led7986]

Hi there everyone, I came across an issue recently which I thought should get a post here. I've been experimenting with different backup methods for my Alpine Nextcloud LXC and I discovered an issue after restoring a Proxmox container backup for either of the Nextcloud LXC types provided in the community scripts. Restoring a known working instance of Nextcloud would result in a login redirect loop in the Nextcloud WebUI with very little info in the log files about what's wrong.

In testing on Alpine Nextcloud LXC, I discovered that somewhere in the process of restoring the files from backup there's one directory which doesn't get restored. I don't know why it's not getting restored from the backup, maybe someone with more knowledge of how Proxmox LXC backups work can elaborate on a potential cause. To solve the login redirect loop all I have to do is create the directory /var/tmp/nextcloud and set nextcloud as the owner and root as group. The two command below are all that's needed. I have not tested the default NextcloudPi LXC for the same cause but it also is affected by the login redirect loop after restoring from backup.

mkdir /var/tmp/nextcloud
chown nextcloud:root /var/tmp/nextcloud

I'm not well versed in how PHP, Nginx and Nextcloud all work together in the Alpine instance but it looks like Nextcloud uses this directory for temporary session files. When those files can't be saved where expected, it was simply failing to load anything more than the login page making it look like a login loop. Nextcloud doesn't appear to be capable of creating the directory since all attempts to use OCC to repair things failed.

I'm unsure if this is limited to my configuration, possibly it is affecting others as well? I'm currently running Proxmox VE 8.2.7 and using the default settings when running the install script besides network setup.