by Emma Richardson.
This is what I run on my Debian server in terminal. It removes any file over 1 day old.
/path to backup folder(fill in with appropriate path)/* -mtime +1 -exec rm {} \;
Works beautifully - I have been fighting a hard drive that ran out of space for a few weeks now. Trying to get through to the end of semester before I move to a different server and so I run this every couple of days. I also sync my backup folder with an off-server location which helps.