You can try mounting that volume and then use the tmutil command to tell Time Machine where do you want backups to go to. Just make sure that nobody else is using the sparsebundle from the network
Stepwise:
- Mount the
.sparsebundle disk image
- Open Terminal
In the Terminal command line, type:
sudo tmutil setdestination /Volumes/{mounted-disk-image}
Be sure to replace {mounted-disk-image} above to the drive's mount point name.
- Open the Time Machine menu and force-start a backup.
Watch the contents of the Backups.backupdb folder in the disk image as Time Machine runs and ensure that it is creating your new backup set.
Note that you'll need Lion for this. Enter the command man tmutil in the Terminal for more information.
I think I can get you started, but using terminal commands, which you said you'd prefer to avoid. Apologies, but it might give you a starting point. All of the following you could put in a bash script and run as a login item.
You'll need to first share out the target drive(s) (MyBook in the examples below) using file sharing (System Preferences > Sharing > check the File Sharing box, add the drives you need and set appropriate permissions - I just use Everyone to keep it simple).
You can mount a remote machine and/or its associated drives using mount like so:
Make a directory as the mount point (obviously call test whatever you want):
mkdir /Volumes/test
Now mount the remote drive. I'm assuming this is already connected to your iMac and appears when you connect to your iMac using Finder:
mount -t afp afp://<your mac's name>/<drive name to mount> /Volumes/test
On my remote Mac Mini, to connect to my MyBook attached to it via USB, that would be:
mount -t afp afp://bobs-mac-mini/MyBook /Volumes/test
If you need to authenticate (I got error -5000 when trying to mount my home folder), you can also do this using
mount -t afp afp://<username>:<password>@<your mac's name>/<drive name to mount> /Volumes/test
However, the password would unfortunately have to be in the clear. So again, this might be:
mount -t afp afp://binarybob:password123@bobs-mac-mini/MyBook /Volumes/test
You can also connect to your home folder using the above method, just by replacing MyBook with the name of your home folder.
The drive you mounted should now appear in the finder and you should be able to use it like any other locally mounted drive. When you're finished, you can do:
umount /Volumes/test
to remove it. BTW, if you're not an administrator, you might need to add sudo in front of each command and type an administrator password.
Best Answer
You can set up your iMac as a fully functioning time machine server by purchasing the OSX Lion Server from the Mac App Store.
This provides you with an official method free from hacks to allow you to backup individual machines such as macbooks etc to a single target machine. I backup my Macbook Air to my iMac in this way. For extra safety, I occassionally clone off this backup volume in the iMac to an external disk and store it out of the house.