Usage at 100%

It's tough to tell without having access to your server. Just to clarify, this is shown as space used in the server itself, and not from your Linode Dashboard, right?

Try running:

cd /

sudo du -sh *

that will print out how much space is used in each directory, figure out from that what's using all your space. You can go down a directory and run the du command again to see what each subdir is using.

If you've brrn running the server for a while and it's reasonably high traffic, it's probably logs. Get logrotate setup to take care of that.