Recently, I started hacking a TiVo HR10-250 that I've had for a million years unhacked.
Back when I first got it, there were dozens of threads of hundreds of messages in about 10 different forums you needed to read in order to hack the goofy thing. Everybody did their own thing, it was manual and a big pain.
Then came zipper (you can find all the details out at this link). It makes it very easy to hack the TiVos in general. However, there was just one problem. The ISO authoring tools it used were windows-based. Since I don't generally run on a Windows machine, this was a problem for me. So I tried to do the steps from the batch file by hand, and it didn't work out so well.
So I rewrote the batch file in a unix script running on FreeBSD. FreeBSD's iso extraction feature of tar made this process hassle free. I can build a new ISO image from an old one using only one port (mkisofs) and no privs are needed at any step. I thought about trying to teach tar how to create an iso image, but since mkisofs does such a good job, and there are *SO* many knobs and dials that need to be implemented to do that right, I just let mkisofs do its thing. I just can't get over how easy FreeBSD's tar made it to break apart the old bootable cd that does the hacking to add the zipper files. Kudos!
I've uploaded the script to the TiVo Community Forum thread about zipper if you are interested in looking into it.