I have recently discovered that my music directory and the micro sd card that's in my hand held media player (iBasso DX50) are not in sync, I don't have any idea how that could have happened. There are songs in both my music directory that are that are not on the sd card as well as a few songs that are on my sd card that are not in my music library. I've always used rsync either directly or through the program LuckBackup to keep everything in sync so again I don't know how this could have happened. Note that my music library is ext4 and my sd card is fat32. What should my rsync command look like to make both of these directories mirror each other with nothing deleted on either end? I know I could google this but it's my music library, I'm very carful with it and I would feel better with a human being holding my hand here. Also I haven't been using Linux as my primary OS for a while now, every since by SSD got corrupted :(

I think you've battled this before. My encounters with this has always been problems with filenames that are OK on the server but not allowed on FAT32. To sort this out I have to find a title that didn't sync and then see if some FAT32 rule was broken.

Also, it's possible that sync stops on the first failure. Nod to logs and MAX VERBOSITY at https://download.samba.org/pub/rsync/rsyncd.conf.html

Repeat, nod to all options about logging. Chain saws must be sharp, oiled and gassed up. You know what happened to Ash Williams.

Checking that site out now.

me@mothership ~ $ rsync -nrv --ignore-existing --exclude=.Trash-1000 --exclude=.audio_data /media/me/media-drive/music/ /media/me/MEDIA-SD/
sending incremental file list
Coldplay/A Rush Of Blood To The Head/01. Politik.flac
Coldplay/A Rush Of Blood To The Head/02. In My Place.flac
Coldplay/A Rush Of Blood To The Head/03. God Put A Smile Upon Your Face.flac
Coldplay/A Rush Of Blood To The Head/04. The Scientist.flac
Coldplay/A Rush Of Blood To The Head/05. Clocks.flac
Coldplay/A Rush Of Blood To The Head/06. Daylight.flac
Coldplay/A Rush Of Blood To The Head/07. Green Eyes.flac
Coldplay/A Rush Of Blood To The Head/08. Warning Sign.flac
Coldplay/A Rush Of Blood To The Head/09. A Whisper.flac
Coldplay/A Rush Of Blood To The Head/10. A Rush Of Blood To The Head.flac
Coldplay/A Rush Of Blood To The Head/11. Amsterdam.flac

sent 180,981 bytes  received 1,353 bytes  364,668.00 bytes/sec
total size is 41,185,457,595  speedup is 225,879.20 (DRY RUN)

This is the rsync command I am currently playing with. I wish rsync would give me better feedback than this. I would like to know how many files were copied and which files went from A to B as well as which files went from B to A. I am positive that the song clocks above was not on my sd card, I couldn't find it when I would look for in on my iBasso and I just validated that it is on in my music library and not on my sd card via the graphical search button on my file browser. I don't see anything bad standing out about the name.

Your command doesn't seem to have any log commands.

I think I figured it out with your help and yes, it was a naming issue. There was two different directories for the album on my computer, one named 'A Rush Of Blood To The Head' and the other named 'A Rush of Blood to the Head'. On ext4 this was fine but apparantly on the fat32 sd card they were considered to have the same name. Thanks for your help, got this figured out. :)

Glad it was a repeat of the same old thing. At least you didn't have to get out the chainsaw.