what is the /hda6 file, and how is it 91% full Got this email from cpanel Drive Critical: /hda6 (/tmp) is 91% full
You could also track down the space hogs with the "du" program. Just do.. cd /tmp du -sh * | less and go through each of them, clearing out the unnecessary files.
It is usually a good idea to not just remove everything in /tmp as it can remove PHP sessions (if they are stored there) and other things like mod_gzip cache files that are in use. I would second ub3r's recommendation to see what is taking up space.
Any session data that is being used can be recreated by whatever created it, it's true that you should probably look into it however deleting all the crap in tmp to restore service is also a good idea......