How to use Disk Utility to repair a disk on a Mac?

To repair a disk on a Mac using Disk Utility, restart in Recovery Mode by holding Command (⌘) R, select Disk Utility and click Continue. 1. Open Disk Utility from macOS Recovery for startup disks or from Applications > Utilities for external drives. 2. In Disk Utility, click View > Show All Devices, then select the volume (e.g., “Macintosh HD”), container, or physical drive needing repair. 3. Click the First Aid button and run the scan to detect and fix errors automatically, with success confirmed by a “disk was repaired successfully” message. 4. If First Aid fails, run it on the container and physical drive, restart and retry, or back up data and reformat the drive if necessary. Always back up data beforehand, use First Aid regularly on external drives, and if the startup disk is unrepairable, erase it and restore from a Time Machine backup.

To repair a disk on a Mac using Disk Utility, follow these steps. This built-in tool can help fix common disk issues, such as file system errors or startup problems.

1. Open Disk Utility in Recovery Mode

For the best results—especially when repairing the startup disk—you should use Disk Utility from macOS Recovery. This ensures the disk isn’t in use.

• Restart your Mac.
• Immediately hold down Command (⌘) R until you see the Apple logo or a spinning globe.
• Release the keys when you see the macOS Utilities window.
• Select Disk Utility and click Continue.

Note: If you're troubleshooting a non-startup disk (like an external drive), you can open Disk Utility from the Applications > Utilities folder while macOS is running.

2. Select the Correct Disk

In the Disk Utility window, you’ll see a list of drives and volumes on the left.

• Click View > Show All Devices (if not already selected). This shows the full hierarchy: physical drives, containers, and volumes.
• Select the volume you want to repair (usually named "Macintosh HD").
• For deeper issues, you may also need to select the container or physical drive above it.

3. Run First Aid

• With the correct disk or volume selected, click the First Aid button (shaped like a stethoscope).
• Click Run to begin the scan.

Disk Utility will check the file system for errors and attempt to repair them automatically.

• If repairs are successful, you’ll see a message like “The disk was repaired successfully.”
• If errors can’t be fixed, you may need to back up data and reformat the drive.

4. Handle Unrepairable Issues

If First Aid fails:

• Try running First Aid on the container and then the physical drive level.
• Restart and try again—sometimes a second pass catches lingering issues.
• If the disk still can’t be repaired, back up your data (if accessible) and consider erasing and reinstalling macOS.

Common tips:

• Always back up important data before attempting repairs.
• Use First Aid on external drives regularly to prevent corruption.
• If your Mac won’t start and Disk Utility can’t repair the disk, you may need to erase it and restore from a Time Machine backup.

Basically, Disk Utility’s First Aid is the go-to tool for most disk problems on Mac—and running it from Recovery Mode gives it the best chance to fix serious issues.

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