You have probably heard the admonition to back up your startup disk before performing any system updates. That's an excellent idea, and something that I recommend often, but you may wonder just how to go about it.
The answer is: Any way you want, as long as you get it done. This guide will show you one of the many methods available for backing up a startup disk.
I'll use OS X's Disk Utility to perform the backup. It has two features that make it a good candidate for backing up a startup disk. First, it can produce a backup that is bootable, so you can use it as a startup disk in an emergency. And second, it's free. You already have it, because it's included with OS X.
What You Will Need
- Disk Utility, part of OS X and available at /Applications/Utilities/.
- An internal or external hard drive that's large enough to store the data on your current startup disk.
- A drive that doesn't contain any data you wish to keep. The method we will use will erase the destination drive during the backup process.
- Half an hour to two or more hours, depending on the size of the data you're backing up.
The destination hard drive can be an internal or external drive. If it's an external drive, there are two considerations that will determine whether the backup you create will be usable as an emergency startup drive.
- FireWire external drives can be used as startup disks on both PowerPC-based Macs and Intel-based Macs.
- USB external drives can be used as startup disks on Intel-based Macs, but not on PPC-based Macs.
- Thunderbolt external storage works fine as a startup drive for any Mac that includes a Thunderbolt port.
Even if your backup drive isn't usable as a startup disk, you can still use it to restore your original startup drive if needed; it will just require a few extra steps to restore the data.