SOLVED: Jellyfin update issue through Synology container

[TheDreadPirate]

You need to provide a VOLUME for Jellyfin to write /config and /cache to. Setting the environment variables to write to a specific folder is not the same thing. That just means that Docker will write the temporary file system to that directory. Keyword TEMPORARY file system. When you upgrade it will wipe out that folder and start over.

Once you provide the volume, you will also need to reset those environment variables to ensure Docker will write data in the correct structure.

Code:

JELLYFIN_DATA_DIR=/config
JELLYFIN_CACHE_DIR=/cache
JELLYFIN_CONFIG_DIR=/config/config
JELLYFIN_LOG_DIR=/config/log