Migrate Time Machine Backup from External Hard Drive to Airport Disk

Time capsule, a combination of hard drive and airport extreme is a sweet idea. The hard drive is server grade, meaning it is much less likely to fail. However, Time Capsule is expensive, and cannot be easily expanded or upgraded.

Luckily Apple made Airport Disk compatible with Time Machine since Mac OS X 10.5.2, although it is an unsupported feature. But anyone who is budget sensitive can enjoy wireless whole system backup.

The problem is, many people like me have been using Time Machine with external hard drive for a while now. We don’t want to lose our older backups. However, Apple has not provided us a tool to migrate our backups from these external hard drives to Time Capsule or Airport Extreme Base Station’s Airport Disk. We cannot simply copy these files to Airport Disk, because of hard links. And Apple uses folders to store backups when the hard drive is attached to the computer. But sparse bundle disk image is used on Time Capsule or Airport Disk.

I searched online and could not find a tutorial to solve this migration problem. After doing some research, I have solved this problem, so I am sharing my experience with you, with the following tutorial I believe is easy enough for anyone to do it.

First, you need another external hard drive, most likely. And this new hard drive is going to be used as Airport Disk. I have no problem with this because my older Time Machine backups are on a Firewire 800 drive, so I would rather keep it connected to my computer to store other data; Firewire 800 is FAST!!!

Second, attach both drives to your computer. Create a sparse bundle disk image on the new drive in the Terminal. For example, if your new drive is called “AirDisk”, do the following in the Terminal:

cd /Volume/AirDisk
hdiutil create -size 465g -fs HFS+J -type SPARSEBUNDLE -volname "Backup of Computer Name" Computer\ Name_eth0MACaddress.sparsebundle

Some explanation here. “-size 465g”, specify that this sparse bundle disk image will be 465GB big, but because it is sparse bundle, the actual size occupied will increase over time, so it won’t be 465 GB big immediately. You want to specify this number to be at least equal to the size of the drive you used for Time Machine backup, or it will fail at later stage.

‘-volname “Backup of Computer Name”‘, please replace “Computer Name” with your computer name. You can see it in “System Preferences>Sharing”.

Then you will specify the file name of the sparse bundle disk image. Please note, you will have to use “\ ” to indicate space in the next file name, the file name of the sparse bundle. And you will need to use “\'” to indicate “‘” in the file name also. For example, if the computer name is “Tom’s MacBook”, the file name should be “Tom\’s\ MacBook_eth0MACaddress.sparsebundle”. The last thing is to replace “eth0MACaddress” with your eth0 MAC address.

Find out your eth0 MAC address by going to System Preferences>Network. Choose Built-in Ethernet from the list on the left, then click “Advanced” at bottom right. Then choose “Ethernet” tab, and you will see the ethernet ID. Get rid of all the “:” and replace “eth0MACaddress” with this string. For example, if it says “00:1h:b2:88:24:76”, then use string “001hb2882476”.

Press enter and it will take a moment for this disk image to be created.

After it is finished, double click it to mount it. Then open Disk Utility and select this disk image from the list. Choose Restore tab on the right. Drag the old Time Machine disk to the “Source”, and drag this newly created disk volume called “Back up of Computer Name” to “Destination”. Click “Restore” button. It will take a while for this process to finish. So be patient.

After it is finished, the volume name of the newly created sparse bundle probably has changed. It doesn’t matter. If it is mounted, you can see a white disk on the desktop. Choose it, press enter, and change the name to “Backup of Computer Name”. You may want to keep it mounted, and allow Spotlight to completely index this disk before you attach it to your Airport Extreme.

Because disk images are always protected on Airport Extreme, as you can see through your Airport Utility, you don’t want Spotlight to index it over the air, because it will take forever to do so. And after Time Machine uses this disk image over the Air, you cannot use it any more by directly connect it to your computer because it is a secure disk. Well, maybe there is a way to mount this image after it has been used over the air, but I don’t know how.

So, after indexing is finished, attach this drive to your airport. From devices in Finder you can see the drive, and mount it. Then in System Preferences>Time Machine, choose this Airport Disk as the disk for use with Time Machine. And you are done. The first time back up may take a while. After it is done, Time Machine will recognize all your old backups.

That’s it, good luck migrating your old backups!

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