So I am new to docker and still building my music library. Sometimes I import albums with no associated jpgs so I try to use the Import artwork function from within docker but the files that jriver finds on the internet never associate with the files on my NAS. What's best way to do this?
Probably a permission thing.
Check the permissions on your music files and what user the container runs MC as (defined by USER_ID and GROUP_ID variables, if you didnīt put anything its 1000). Whatever user it runs as probably only has read permissions on those files.
You can check your permissions either outside the container or inside the container with "ls -a <path to folder containing your media>" but you need the numeric user ids, names wonīt necessarily match outside and inside the container. To get the ID of a user use "id <username>".
The output should be something along those lines for ls
root@stuffs:/data/music/Jefferson Airplane/White Rabbit# ls -la
total 422693
drwxr-xr-x 2 app app 0 Aug 28 14:28 .
drwxr-xr-x 2 app app 0 Feb 13 2022 ..
-rwxr-xr-x 1 app app 34253407 Aug 28 14:28 '01 35 Of A Mile In 10 Seconds.flac'
-rwxr-xr-x 1 app app 31919237 Aug 28 14:28 "02 Don't Slip Away.flac"
-rwxr-xr-x 1 app app 37532001 Aug 28 14:28 '03 Get Together.flac'
-rwxr-xr-x 1 app app 39762786 Aug 28 14:28 "04 High Flyin' Bird.flac"
-rwxr-xr-x 1 app app 29871609 Aug 28 14:28 "05 It's No Secret.flac"
-rwxr-xr-x 1 app app 33860279 Aug 28 14:28 '06 My Best Friend.flac'
-rwxr-xr-x 1 app app 49209194 Aug 28 14:28 '07 Other Side Of Life.flac'
-rwxr-xr-x 1 app app 30919943 Aug 28 14:28 '08 Plastic Fantastic Lover.flac'
-rwxr-xr-x 1 app app 32982699 Aug 28 14:28 '09 Ride.flac'
-rwxr-xr-x 1 app app 32949209 Aug 28 14:28 '10 She Has Funny Cars.flac'
-rwxr-xr-x 1 app app 32499675 Aug 28 14:28 '11 Somebody To Love.flac'
-rwxr-xr-x 1 app app 25055109 Aug 28 14:28 '12 Today.flac'
-rwxr-xr-x 1 app app 21164515 Aug 28 14:28 '13 White Rabbit.flac'
It repeats rwx (read/write/execute) 3 times for user, group and others. The missing dashes are permissions that are not given. So in this case the user that owns the files has all permissions. The group only grants you read and execute. Further to the right the two "app" are the user and group that own the file. So if the first one did not say "app" there MC would be unable to write to that file.
If you conclude MC does not have write access to your media you can either change USER_ID and/or GROUP_ID environment variables set on container creation to one that has full access, or change permissions on the files.