I have an iMac running Lion with a USB external drive attached for my Time Machine. The Time Machine is working great on this Mac. I just bought a Macbook Air and wanted to use the same Time Machine drive via the network, but I can't seem to get it to show up in the "Select Drive" setting in Time Machine on my MBA. Via many Google searches, the main instructions I found said to do the following: - Share the Time Machine drive on my iMac. So I went into Settings/Sharing and added my external drive to share and made sure it was set to Read/Write. - On my Macbook Air, I connected to my iMac using the account listed for Read/Write access. The external drive showed up and I double-clicked on it to mount it. The drive then showed up under "Devices" on my MBA and had the little Eject button next to it, so I know it was mounted. - Then I opened Time Machine on my MBA but the drive is not showing up. I'm not sure what I'm missing??? The only thing I read somewhere is that Lion made changes to the way Time Machine works and that it only supports AFP and not SMB? I don't really understand either of those, but the external drive is showing up via SMB, I believe. Is there any way for me to use this external drive on my iMac as my Time Machine drive on my MBA? Thanks!