Use Time Machine with a Network Drive (NAS)
Part 2

I’ve been having some trouble with my NAS device that led me to delete the directory I use for my Time Machine backups. As a result, I created a new directory and set up Time Machine to use it as I detailed in my previous post. Unfortunately, it didn’t work. Time Machine gave me an error saying “The backup disk image could not be created.”

Obviously something has changed since I first started using Time Machine with my NAS. I’m currently running OS X 10.5.4, so I’m assuming one of the updates “broke” this for me. I did some research and found a solution.

What I had to do was create the backup disk image locally, and then copy it to the NAS. Since the Time Machine error message indicated that creating the backup disk image was the problem (and presumable the only problem), this should fix things. Well, at least for now. If this much broke as the result of a software update, a future update my break it further. Anyway, I want to continue using my NAS for Time Machine backups as long as I can.

The name of the backup disk image file is a combination of the machine name and the MAC address of the machine being backed up, plus “sparsebundle”. The name of my iMac is “the-bronze” (Joss Whedon fans will understand). I went to System Preferences / Network to find the MAC address of my ethernet port, labeled below as “Ethernet ID.” There are numerous other ways to find the MAC address, but this seemed like the easiest way to me.

So the name of my backup disk image needs to be “the-bronze_0017f2de3895.sparsebundle.” To create that file, I opened a Terminal window and used hdiutil, an Apple command line program for working with disk images. Note that hdiutil is on my system by default – I haven’t installed anything special.

the-bronze:~ ron$ hdiutil create -fs HFS+J -volname "Backup of the-bronze" the-bronze_0017f2de3895.sparsebundle
hdiutil: create: WARNING: size unspecified and no other options imply a size
created: /Users/ron/the-bronze_0017f2de3895.sparsebundle
the-bronze:~ ron$

I copied the resulting file to my NAS, set up Time Machine as described in my previous post, and… it worked!