Fix Disk Utility First Aid Failed on APFS Volume in macOS

Symptoms

When running Disk Utility's First Aid on an APFS volume, you may encounter one or more of the following:

• The process stops with a red error message: "First Aid failed"
• Error details mention "The volume /dev/diskXsY could not be verified completely"
• Error codes such as Error: -69845 (File system verify or repair failed) or Error: -69877 (Couldn't open device)
• The volume may appear unmounted or inaccessible in Finder
• Disk Utility may hang or become unresponsive

Root Causes

First Aid failures on APFS volumes are typically caused by:

• Active snapshots (e.g., Time Machine local snapshots) that prevent modification or repair
• File system corruption due to improper shutdown, power loss, or hardware issues
• Inconsistent metadata or damaged container structures
• Disk encryption conflicts (FileVault) when run from within the OS
• Third-party kernel extensions interfering with disk operations

Step-by-Step Fix

Prerequisites

• Back up important data if possible (see Prevention section)
• Ensure your Mac is plugged into power
• Close all open applications

Method 1: Repair via Terminal in Recovery Mode (Recommended)

1. Boot into Recovery Mode: Restart your Mac and hold Command (⌘) + R until the Apple logo appears.
2. Open Terminal: From the Utilities menu, select Terminal.
3. Identify the disk: Type diskutil list and press Enter. Note the identifier of your APFS volume (e.g., disk1s5).
4. Run fsck_apfs: Enter fsck_apfs -y /dev/diskXsY (replace diskXsY with your volume identifier). The -y flag automatically answers "yes" to repair prompts.
5. Allow repair: If errors are found, the tool will attempt to fix them. Wait for the process to complete (may take several minutes).
6. Verify success: Look for the message "The volume /dev/diskXsY appears to be OK" at the end. If errors remain, run fsck_apfs -y -l /dev/diskXsY (lowercase L) to attempt a more thorough repair.
7. Exit and restart: Type exit and then restart your Mac from the Apple menu.

Method 2: Delete Local Snapshots (If Snapshots Block Repair)

1. Boot into Recovery Mode as above.
2. Open Terminal and type tmutil listlocalsnapshots / to list snapshots.
3. Delete each snapshot with: tmutil deletelocalsnapshots /Volumes/YourVolumeName (use correct volume name).
4. After deletion, run First Aid again from Disk Utility or Terminal.

Method 3: Run First Aid in Safe Mode

1. Restart your Mac and hold Shift immediately after the startup chime.
2. Release when the login window appears (you may need to log in twice).
3. Open Disk Utility and run First Aid on the APFS volume.
4. Safe Mode loads only essential extensions and may bypass conflicts.

Alternative Fixes

• Use Disk Utility from Recovery Mode: Boot into Recovery (⌘+R) and run First Aid from there. This avoids OS-level locks.
• Check disk hardware: Use smartctl -a diskX (install smartmontools via Homebrew) or run Apple Diagnostics (hold D at startup) to rule out physical disk failure.
• Repair the container, not the volume: In Terminal, run diskutil repairDisk diskX (where X is the disk number, e.g., disk1) to fix the container structure.
• Third-party tools: Consider DiskWarrior or Drive Genius for advanced recovery if Apple tools fail.

Prevention

• Regular backups: Use Time Machine or other backup software to create frequent backups.
• Avoid improper shutdowns: Always shut down properly; force-restart only when necessary.
• Monitor disk health: Use Disk Utility's First Aid periodically (e.g., monthly) to catch issues early.
• Keep macOS updated: Apple releases APFS fixes in system updates.
• Disable unnecessary snapshots: If you don't use Time Machine, consider disabling local snapshots via tmutil disablelocal (use with caution).