MacBook Air and Time Machine setup

I have just bought a Macbook air, having bought an iMac about 2 months ago. I keep all my files (including iPhoto, iTunes, outlook and money dance data) on an external hard drive. The idea is that all I ever have to do when I go away is take my macbook air and my external hard drive with me, connect the two, and its like I've taken my iMac with all its data with me. When I come home, I simply plug my external hard drive back into the iMac, and I am working on updated files again.

I also have a second external hard drive. I will set that to be where Time Machine will back up my iMac files and settings.

So, my question. I have not yet started my Macbook, and I would like to initially set it up by using the iMac Time Machine backup, so that all my iMac settings and software etc is created in the same way on my macbook air. If all my files are on the the second external hard drive device, and that too is connected to my macbook air, how will time machine deal with 'installing' all the external hard drive backed up files that were originally backup up through the iMac, when the external hard drive is now connected to the Macbook air? i.e. it does not need to install them, as the hard drive would now be connected to the macbook air?

That's probably not well explained, but hopefully there is some sense in there somewhere

You're right it's a little convoluted since you say that you want to put the stuff from the iMac on the MB and then in the next breath say that it does not need to install them.

If you want the settings, apps and data to match the iMac, when you turn on the MBA for the first time it will ask if you want to restore from a backup. Say yes, pick your TM backup and it should install all the stuff from your iMac onto the MBA. I'm assuming here that you bought a MBA with enough drive space to do a restore from your iMac.

My question would be - are you backing up that drive that contains all your iTunes, iPhoto, etc. data?

Yes, well that is the intention.

The intention is, using Time Machine, to backup my Imac and the data in the 'active' external hard drive onto my 'stay-at-home' hard drive. Hopefully, once my MBA is setup, I will simply connect it to the 'active' hardrive whenever I need it, and I will have acces to all files as if I were on my Imac

I am not keeping any data files on my Imac, so the MBA, will not be required to store much at all, as it will operate using the 'active' external hard drive.

It's just the initial setup that confuses me, since, as Time Machine will have backed up my Imac settings and software and everything on my 'active' hard drive onto the 'stay-at-home' hard drive, when I go to setup my MBA, I really only want the settings and software from my Imac onto the MBA, as the files will already be on the 'active' hard drive, which the MBA will be able to access.

Hopefully, that makes sense. I am trying to achieve easy switching from my MBA to my Imac and back, as sometimes I might be away for a month, and operate on my MBA, but want to switch to my Imac when I am at home

Thanks for your help

In your particular situation, think I would consider moving your home folder to the external drive. This would mean never turning on either one of your Macs without that external drive attached to it. But, with only your OS & apps on each of your Macs - all your personal settings would then be on the external, both machines should act identically. It would also mean all of the data normally stored in your home folder (incl'g your personal settings) would automatically be written to the external without the need for you to be saving your data outside your home folder.

Maybe have a read of how to do this and check your experience with it on your iMac. I have not done this, but we have quite a few members now that are using this method on their Macs, particularly in combination with small SSD drives they use for the OS and applications and a separate drive for their home folder.

Here are a couple of tutorials - link - link. Might want to read a few before trying it out. And I would 'copy' vs 'move' my home folder initially - just in case - to make sure everything works ok, then you can delete the old home folder when you're confident everything is ok.

Maybe a couple will chime in that are doing this.