This Synology FAQ, while focused on how to get the data transported into the Synology via the GUI, is also applicable to Linux.
The pathnames will be different.
Instead of /volume1/Plex/Library/Application Support/Plex Media Server
the Linux path is /var/lib/plexmediaserver/Library/Application Support/Plex Media Server
Otherwise, the steps are the same until you get to permissions.
On Synology, you use the GUI.
On Linux, you use the command line.
