How to clone a disk with Disk Utility for the Mac

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Cloning is the procedure by which you create a backup that is identical to a bootable system on an external drive. It also has been called mirroring a hard drive. With some software like Retrospect by EMC, you create a clone using a duplicate command and selecting the source and destination volume, once you make sure the permissions are set right. With Disk Utility the procedure of the permissions is similar, and will be outlined below. Note, with Mac OS X, backups which are bootable only include Firewire drives, and drives on an IDE bus recognizable by the system as a bootable drive. The purpose of making the drive bootable is that you can test the most basic function of the operating system in the clone to see if it will work as well as the original. If it does, chances are the clone is easily recoverable. The procedure outlined below can be done with Disk Utility in Mac OS X 10.4.2. It has not been tested with any other version. A reader of this article suggested it might be better to do this procedure by booting off the installer disk, which has Disk Utility in the Utilities menu of Tiger, and previous operating systems in the File menu. Booting from the installer disk is usually done with the startup manager: If you find something in the following procedure which could be edited, please sign the guestbook:

1. Create an admin user in Apple menu -> System Preferences -> Accounts with no Startup Items, and log into it.
2. Ensure that the destination drive you want to backup to is available on the desktop. Note, this drive can not have any data content you want to preserve, since this procedure overwrites the entire drive.
3. Open Disk Utility from your boot drive -> Applications folder -> Utilities folder.
4. Select the destination drive within Disk Utility, and click on Erase. From the Erase section, erase the hard disk.
5. Once that drive is erased, click on the dock or use command-tab (command is the Apple logo key) to make the Finder application active.
6. Select the erased drive, by clicking on it once, and ensure that the Ownership and Permissions are not ignored in the window which appears when you go to the File menu and select Get Info. Uncheck its checkbox if it is checked.
7. Switch back to Disk Utility and select the Restore section of Disk Utility.
8. Drag the destination drive from the Disk Utility left sidebar into the white field marked Destination.
9. Drag the Source drive from the left sidebar and put it in the white line marked Source.

1. Click on Restore. This procedure may take several hours. A 100 GB clone took 7 hours on Firewire 400 on an iMac G5 with 2 GB of RAM.

1. Go to Apple menu -> System Preferences -> Startup Disk. The clone should now appear in the startup disk list.
2. Select the clone from the Startup Disk listing, and click on restart.
3. If the clone appears in the upper right hand corner as an icon above the source, the clone was successful.