The HDD's are not reporting any errors so this appears to me that something has corrupted. I haven't a clue what to do next. How can I get this system back up and running?
The server is only used as an rsync offsite backup drive. Reinstalling is an option but only as a last resort as the server is holding 1TB of backup data and to re-sync that it would take a month to do over our office connection.
You've experienced some filesystem corruption. From where you are, you can probably run
fsck -y /to kick off the process of filesystem repair, based on the image you attached. The
-yanswers yes to the questions the
fsckcommand will probably output. Try this first.