If I may augment Peter’s reply;
Regarding making a backup of your PMS metadata, in Linux, the simplest and perfect backup you can make is
sudo sh
cd /var/lib/plexmediaserver
tar cf /where/to/save/backup/Library.tar ./Library
When complete, Library.tar will have the full backup image of your files.
Should you later need to restore it., you only need to stop PMS and do the following
sudo sh
cd /var/lib/plexmediaserver
rm -rf Library # remove anything which pre-exists
tar xf /path/to/saved/Librar.tar
chown -R plex:plex ./Library
Then start PMS.
