When you boot up your Mac, it immediately searches for the startup drive – that is to say, the drive that contains the operating system (the System folder). This is typically your hard drive although some people have several start up external drives available. A friend of mine has a few of them, each with a different version of the Mac Operating System. More advanced users might use a separate startup drive for program testing.

One of my backup routines involves making a clone of my hard drive and every now and then, just to ensure that the backup is working correctly, I’ll change my startup drive to boot from my external clone. It’s always a good idea to verify your physical backups regularly.

Quick Guide: Select a Startup Disk

1. Click  and then click System Preferences.
2. Click Startup Disk
    
3. Select the drive you want to use for your Startup Disk
   
4. Click Restart

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