Which directories to exclude when backing system up with grsync?

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http://ubuntuforums.org – I have spent a lot of time setting up my Mythbox and I want to back it up in case of a hard drive failure or an update breaks something. Honestly if I had to start over I don't know if I could get it back the way it is now. I'm not afraid of the command line but I'm also far from a Linux wiz. Anyways, I was hoping to use grsync to backup my entire system. This way if anything at all goes wrong I can restore it to exactly the way it was before. I am going to exclude my recordings and videos so I can save disk space (my hard drive is 2 tb) and I don't really care if they end up being lost (Hardware)