After my media library grew to a certain size, my boot drive reached 100% capacity. This was due to all the metadata related to my media content. I decided I wanted to move that metadata onto the same storage that my media library is on.
I run my Plex server on Debian. My Plex files are at /var/lib/plexmediaserver/
1. Stop Plex
systemctl stop plexmediaserver.service2. Create the new Plex Media Server directory. I will be using my existing, mounted storage.
mkdir /mnt/Plex/PlexMediaServer3. Set the correct permissions for the new directory.
chown plex:plex /mnt/Plex/PlexMediaServer
chmod 755 /mnt/Plex/PlexMediaServer4. Copy files from original location to new location. Depending on how big your media library is - meaning, more metadata - this could take a while. I had ~50GB of metadata.
cp -r /var/lib/plexmediaserver /mnt/Plex/PlexMediaServer5. Create an entry in fstab to mount the relocated directory to /var/lib/plexmediaserver every time the server boots.
/mnt/PlexMedia/PlexMediaServer/plexmediaserver /var/lib/plexmediaserver none defaults,bind 0 0