backup

create the exclude file list:

sudo rsync -Pa / /media/youbackupdir --exclude=/media/* --exclude=/lib/* --exclude=/sys/* --exclude=/tmp/* --exclude=/proc/* --exclude=/mnt/* --exclude=/home/ye/.mozilla/* --exclude = ...

Also, you need to create a cron job to run every day.
find . -size +30M -print -exec ls -l {} \;

comm can be used to compare the difference between two files