Migrated to new Lion, how to share Time-Machine? I just got a new MacBook Pro since I was due for a new machine and needed Lion for the new Xcode. I also got an Apple TV with the idea of centralizing all the digital media in my house by hosting it on my old Snow-Leopard MacBook Pro using iTunes. 

I set up the new machine using my USB drive's Time-Machine partition and fixed up a few odds and ends and am now happily using Lion there. But I want to use the USB drive on the old machine as a Time-Machine drive for both machines. 

But the new Lion machine doesn't see the shared drive from the old machine and I don't want to swap the drive around, I just want it to work as a backup when I connect to my home network. I've spent the afternoon reading articles on how to do this for various flavors of OSX but none of them address my configuration and now I feel over-saturated with information.

So, my questions are: First, can I do this? Second, where can I find good documentation on setting this up? I'm fairly technical and am not afraid of getting deep into the details if it will give me a painless way to do backups and I've grown to like the simplicity of Time-Machine. (Plus I use VCS systems for all the critical files in my day to day work).

Thanks!
No. Most technically minded people have stopped trying to hack together AFP as Apple have changed the code to tighten up and only show legitimate sources not connected as direct attach storage.

Apple provides two products that let Mac Clients see a hard drive as a Time Machine backup when they are not connected DAS but instead NAS (network attached storage) which facilitates the sharing of one drive with multiple macs simultaneously and without reconnecting cables:


TimeCapsule - only the internal drive is supported for Time Machine.
OS X Server - can mark any share point as being available for Time Machine use.


Yes, anything is possible in software given enough money, time or ingenuity, but for reasons I can only presume is enough smart people breaking TimeMachine and blaming Apple for lost data when using DIY Time Machine targets, this has been tightened up in Lion to preclude any easy solution that is documented at present on the internet from working.