iToph.com

I just upgraded to Leopard. I want to use Time Machine to back up my laptop, but the only hard drive I have with extra space is an external hard drive currently plugged into my Mac Mini.

My first problem is that I don't have an open partition of the right size. To solve this I have created a 50 GB disk image. I setup that disk image with no encryption and a format of "read/write disk image." It took a few hours to create this image.

Then I mounted this image on the Mini and shared it through AFP (Personal File Sharing). Then I mounted this shared drive on the laptop. I could not tell Time Machine to use this network share... it did not appear. The solution was to change a system preference via the command line:

defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

I heard about this technique here.

Then I told Time Machine to start backing up now. It failed with the error message: Time Machine Error The backup disk image could not be created. Eventually I found this thread. It advised me to:

1. Start Time Machine backup. Wait a little.
2. On the server, make a copy (cp -r) of the in-progress disk image.
3. Let Time Machine fail and delete the image.
4. Rename (mv) the copy created earlier to the same name of the deleted Time Machine sparsebundle image.

This worked!