Disk Utility Still Can’t Check and Repair APFS Volumes and Containers Published on November 19, 2021 by hoakley on The Eclectic Light Company --- Overview Disk Utility's critical function of checking and repairing disks has been problematic since APFS was introduced. A persistent bug prevents Disk Utility from unmounting APFS volumes or containers, which is necessary for disk repair. This issue worsened with macOS Monterey 12.0.1, rendering some disks completely uncheckable and unrepairable through Disk Utility. --- Key Issues with Disk Utility and APFS Unmount Failure: Disk Utility relies on fsckapfs for repairs but must first unmount the volume/container. Unmounting often fails due to a bug. Confusing Error Messages: Earlier macOS versions (Catalina, Big Sur) issued confusing warnings that recommended backing up data unnecessarily. Mounting Status Ambiguity: Despite appearing unmounted, APFS containers often remain mounted at the system level, blocking repair operations. No Impact on HFS+: The problem appears isolated to APFS volumes and containers, not HFS+ volumes. --- Explanation of Repair Process Disk Utility’s First Aid uses the fsckapfs command with options: -y to automatically repair errors. -n to check without repairing. -S to exclude snapshots during checks. Unmounting volumes or containers is mandatory before running these commands properly, but Disk Utility fails at this step. --- Workarounds Using Recovery Mode Boot into macOS Recovery. Run Disk Utility from Recovery where unmounting issues are less problematic. Preferred for boot volumes (System/Data). Using Terminal Commands Identify the device name for the APFS container or volume (e.g., /dev/disk7s2 for a volume, /dev/disk7 for a container). Unmount the volume/container using Disk Utility's GUI or Terminal (diskutil unmount). Run fsckapfs in Terminal: Remount the volume/container with Disk Utility or diskutil mount. For encrypted volumes: Use diskutil apfs unlockVolume /dev/disk7s2 -nomount to unlock without mounting. --- Best Practices According to Apple Check and repair volumes within a container first. Then check the container. Finally, check the entire disk. This is the opposite of previous community advice. --- Community Feedback Highlights The unmounting bug has persisted inconsistently for years. Some users recommend regularly running Disk Utility in Recovery mode. Third-party tools struggle due to lack of API access; building reliable replacements is complex. Symptoms include slow or failed unmounts, especially with external APFS-formatted drives. Some reports of phantom disk space and snapshot-related mounting issues. Experts stress the importance of preventing data corruption by safely ejecting drives. APFS doesn't require frequent checking like HFS+; the filesystem design reduces corruption chances. Users discuss issues with snapshots causing errors and the need for manual unmounting via Terminal. --- Conclusion Apple’s Disk Utility still cannot reliably check and repair APFS volumes and containers due to a long-standing unmounting bug. Users are advised to: Use Recovery Mode for disk repairs when possible. Employ the Terminal fsckapfs command for manual checks and repairs. Manually unmount volumes or containers before repair. Be vigilant in safely ejecting drives to prevent data loss. While challenging, these workarounds allow continued maintenance until Apple addresses the bug. --- Additional resources and detailed commentary are available on The Eclectic Light Company blog along with community discussions.