Format a Drive to Boot Intel Macs
TMO Quick Tip - Format a Drive to Boot Intel Macs
by , 7:30 AM EDT, August 16th, 2006
Formatting an external drive to use as a boot volume for Intel-based Macs is easy to do, but if you miss one crucial step, your efforts will be wasted. Apple's new Macs require the GUID Partition Table (GPT) scheme for bootable disks instead of the older Apple Partition Map (APM). The problem is that Disk Utility formats external drives with APM by default.
Here's how to format a drive with GPT:
- Launch Disk Utility. It's in Applications/Utilities/Disk Utility.
- Choose the drive you want to format from the drive list on the left. Be sure to select the drive's description instead of its name.
- Click the Partition tab. If you don't see the Partition tab, you selected the drive's name. Click on the description just above the drive name to reveal the Partition tab.
- Click the Options button.
- Select GUID Partition Table.
- Click OK.
- Click Partition.
![]() Be sure to select your drive's description before clicking Options. |
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![]() Choose GUID to make your drive bootable. |
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This is necessary only if you plan on using an external drive as a startup disk, and it works with FireWire and USB 2.0 drives. You don't need to worry about this with internal drives, either. GUID is the default selection when you format drives installed inside your Mac.
if you have ideas for Mac related tips that you think other TMO readers might find helpful.
Observer Comments
Wed Aug 16, 2006 9:15 am Subject: My External Drives Are Bootable -- No GUID Actions Taken
I have two external drives with two partitions on one drive and four partitions on the other. All of the partitions are bootable. When I created the partitions I didn't do anything special as regards the GUID stuff. The partitions are all the target destinations of scheduled SuperDuper! backups.
Wed Aug 16, 2006 12:40 pm Subject: I did the same thing, but...
Wed Aug 23, 2006 6:24 pm Subject: Does not work with USB 2.0
You can not use the GUID partition scheme on a USB 2.0 drive, only thru Firewire just got trying using Disk Utility and Ipartition all came back as input/output error email me if you do have a work around, just dropped $60 for a ministack, now I should have gotten the V2 and paid a extra $20 for firewire
If I format a 300 GB drive that already has two partitions, will I loose data on the other partition?
Please email me ASAP if you know.
Thanks
Howie
howiej1@sbcglobal.net
Comments are currently closed. Please email the author instead.
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