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Fixing a Disk's Formatting for Bootability

The operating system has very specific requirements to be able to boot off of a disk. This document describes how to fix problems found when setting up a bootable backup, as described in Bootable Backup Script Template.

All of these operations take place using /Applications/Utilities/Disk Utility.app.

IMPORTANT: Repartitioning or reformatting permanently removes all information currently on the backup disk. Make sure you don't have anything you want to keep on the backup disk before continuing.

Fixing a disk’s partitioning and formatting:

To be bootable, a disk must be partitioned with a “GUID Partition Table” and the volume formatted as “Mac OS Extended (Journaled)”.

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