I've always favored Clonezilla for free OS backup. I've used Mondo in the past, but I was not as impressed.
-It works well with Linux, but also works for Windows and others.
-It boots from a live CD, so it has no problems reading locked files and such.
-It automatically grabs the partition(s) data, the MBR, the partition layout, and more. It stores information about how to restore it all as metadata in a separate file.
-It automatically compresses everything of a noteworthy size into the format of your choice (standard and not-so-standard options are available, such as .tar.gz, .tar.7z, etc.).
-You can open most of the files it creates (including all the data from the OS) in standard tools like tar, gzip, and even things like winrar (although you'd also need to be able to read the formatting of the files within, if you're trying to do it in Windows).
-You can mount the image files it creates onto a directory of your choosing (in Linux/Unix), but you'll probably have to decompress them first.
Overall, it's just an excellent program. Also of note, it uses standard Linux utilities like BASH, tar, etc. to do everything, but instead of making you type a bunch of convoluted commands to make it happen, it just gives you some menu options and lets you say "go." (The included, built-in BASH scripts do all the work for you.) I often used this in professional computer repair work when I was manager at a computer store.
It's worth noting that this is best for backing-up something for long-term storage, or possible re-installation (which would be much faster than doing it from scratch, even if you didn't customize the OS settings much), but not as good if you intend to be accessing the files a lot once you back it all up. If you need to get into the files that you're going to be backing up, then I suggest using something like rsync, or a more automated rsync derivative like rdiff-backup (which has a GUI available called PyBackPack).
Last edited by DaneM; 04-24-2011 at 10:39 AM.