1. I have too much money to spend for a spare hard drive to clone my Mac hard drive.
2. I want to have a bootable external hard drive, installing on an external USB hard drive is not possible.
3. I want to upgrade my Mac’s hard drive, and I don’t want to do the installations and setup all over again

Obviously number 3 is my answer. I acquired a bigger capacity hard drive to upgrade my current 120GB hard drive in my MacBook. After some Googling around, I found an answer.

There is an Apple utility program called Apple restore or asr located in /usr/sbin. Connect your external USB hard drive and format it using Disk Utility. Open the Terminal in Applications -> Utilities. Type the following command line into the Terminal to copy your hard drive over your external drive.

% sudo asr -source /Volumes/OSX BOOT VOLUME NAME/ -target /Volumes/TARGET VOLUME NAME/

Replace “OSX BOOT VOLUME NAME” and “TARGET VOLUME NAME” with actual volume names. asr will take quite some time to copy the contents of hard drive to external hard drive. Get a cuppa, pop in your iPod earphone and relax.

When asr completes the execution, it will print a message:

asr: did not copy blessed information to target, which may have missing or out-of-date blessed folder information.

Then, bless your target drive with this:

% sudo bless -folder /Volumes/TARGET VOLUME NAME/System/Library/CoreServices

Now, the hard drive is bootable. Restart your Mac and hold down “option” key. A screen will appear allowing to choose which volume to boot from.