You should also back up /etc since this often contains any modifications you may have made during the installation process.
I do: Every system file (under /; don't forget, for example, /boot/grub/menu.lst) modified is stored under RCS. A nightly cron job e-mails me about files still checked out. A weekly cron job gathers the RCS directories and stores them on a back-up system. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]