Drive there. Go fast. It'll be fun. Plus, consulting clients like to pay for travel. Honest.
Anyway, it kind of doesn't matter what you set up. You are going to have to be on-site to tell them how to deal with it. There's tons of examples for how to set up backups with tar, and tons more for how to schedule tasks with cron. Those programs work the same way no matter what system they're using (well, they do now. tar used to have issues on OSX.)
The alternative is a commercial program like Retrospect, but you still have to be there to set it up properly. Never in the history of time has a consulting client been able to correctly install, schedule and maintain backups without the watchful eye of a clueful IT guy.
I'm dealing with a guy right now who refuses to accept the now-standard "Daily full backup on a large USB drive that you can take home" because he doesn't like the "take home" part. He won't use tapes since he's had disasters with two different tape backup systems (the tapes probably wore out since I doubt he had more than he needed to do his backup). He wants to back up 250GB of data from his $20,000 worth of servers over a 256k upstream cable connection to his 384k home DSL service to USB drives conveniently already attached to his home PC (the one his kids use. With Limewire pre-installed. And a screensaver from Freeze.com). He does not understand why a vein in my forehead starts throbbing every time we discuss this.
