System.IO.IOException: No space left on device

[TheDreadPirate]

Keep in mind that metadata and trickplays take up a lot of space, depending on the size of your library.

Posters, banners, actor images, chapter images, keyframes, extracted subtitles, trickplay images, etc., are all written to disk.

I have 270 movies, 4700 TV show episodes, 500 music videos, and 4100 songs. My jellyfin data directory and cache directory, combined, are just shy of 20GB.

Code:

chris@rat-trap:~$ du -sh /var/lib/jellyfin /var/cache/jellyfin
18G     /var/lib/jellyfin
1.9G    /var/cache/jellyfin

Depending on the size of your library and the options you enabled your jellyfin data directory could be larger. Than you have to take into consideration that your OS and all the installed applications take up space as well.

That doesn't take into consideration that, by default, jellyfin writes transcode files to /var. But this is configurable and can be on a separate disk.

100GB is probably a "safe" size for your root partition. 20GB is much too small.