Repair Mac External Hard Drive without Disk Utility

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Summary: In this blog, we’ll share a variety of alternative methods to repair your Mac external hard drive in case Disk Utility fails to fix the drive.

Download the free-to-try Mac data recovery tool to recover data from an external hard drive.


Table of Content

1. Use FSCK Command in Terminal to Repair External Hard Drive
2. Use FSCK Command in Single-User Mode to Fix External Drive
3. Recover Inaccessible Data Using Mac Data Recovery Software

Disk Utility is a useful storage drive management software that allows you to perform the external hard drive repair task with ease by using First Aid. But sometimes, Disk Utility’s First Aid fails to repair your external hard drive and the drive’s data remains inaccessible. Don’t worry, you can use alternative methods to repair your Mac external hard drive in case Disk Utility doesn’t work. Also, you can recover data from a corrupt external drive on Mac.

But before learning the repair and recovery methods, know why a Mac external hard drive turns inaccessible, appreciate the Mac file system and its importance, and learn the reasons that lead to file system corruption.

Why Mac External Hard Drive Turns Inaccessible?

At times, an unexpected event corrupts the partition table, EFI partition, or APFS/HFS file system of the Mac external storage drive. This logical damage of the external hard drive makes the drive and its stored data inaccessible on Mac.

Mac File System and Its Importance

Your Mac external hard drive contains reserved space for GUID Partition Table, EFI System Partition, and APFS Container. The APFS container comprises Container superblock, Checkpoint area, Space manager area, and storage for objects and file data. The container can have multiple volumes with their file systems. The Mac’s file system allows storage and retrieval of data to and from the storage drive.

Reasons for File System Corruption

The following situations may damage the storage drive’s file system, which may not get fixed with Disk Utility’s First Aid feature:

  • An application may write into the file system thereby causing corruption on the disk.
  • If the block containing the file system of the drive turns bad, then the storage drive fails.
  • A malware on Mac may write on the file system space, thus crippling drive access.

Few reasons for corruption of legacy file-system formatted storage drive are as follows:

  • A macOS crash or abrupt power cut results in non-syncing of information to the file system, which results in its corruption.
  • The sudden removal of an external storage drive without proper un-mounting may result in an incomplete write operation and corruption.
  • If the external storage drive does not un-mount due to running programs that are accessing the drive, forced ejection can corrupt its file system.

The next sections describe numerous methods to repair Mac storage drive without Disk Utility.

1. Use FSCK Command in Terminal to Repair External Hard Drive

When Disk Utility’s First Aid can’t fix the file system corruption issue on your Mac external hard drive, run the fsck (file system consistency check) command in the macOS Terminal.

Steps to repair Mac external hard drive by using Terminal are as follows:

  1. Go to Finder > Applications > Utilities > Terminal.
  2. In the Terminal window, type df –h and hit Return. Note down the file system identifier of the external hard drive, say /dev/disk4s1.
  3. Type unmount /dev/disk4s1 and hit Return. This command unmounts the external drive.
  4. Type fsck_hfs -y /dev/disk4s1 and hit Return. The fsck_hfs verifies and repairs hfs containers and volumes. If the external storage drive is in the apfs format, use fsck_apfs instead of fsck_hfs. The parameter -y repairs any damage that is found.
  5. If you receive the message “File system was modified”, re-run the above fsck command.
  6. Use the fsck command again until it says, “The volume appears to be OK.”

Also Read: List of Top 5 Mac Hard Disk Drive Repair Software

2. Use FSCK Command in Single-User Mode to Fix External Drive

Use the fsck command in the single-user mode to repair the file system corruption issue on your Mac external hard drive.

Steps to repair Mac external hard drive by using single-user mode are as follows:

  1. Start or restart your Mac then promptly press and hold Command + S keys.
  2. Release the keys once you see white text. Your Mac boots into single-user mode.
  3. On the prompt, type fsck_hfs –y /dev/disk4s1 and hit Return.
  4. Check the message provided by the fsck command. Rerun fsck command till you get OK.
  5. Reboot your Mac and this time don’t press any key to boot your Mac normally.

3. Recover Inaccessible Data Using Mac Data Recovery Software

When none of the above methods succeed to repair the external hard drive, use a Mac data recovery software to recover the inaccessible data from the drive whose file system, EFI partition, or partition table is lost, deleted, or damaged.

Steps to recover data from a corrupt Mac external drive are as follows:

Free download the *trial version of Stellar Data Recovery Professional for Mac.

  • Install the software in the Applications folder on your Mac.
  • Launch the software. Toggle on the file types to customize the scan. Click Next.
  • Select the corrupt external hard drive then click Scan.
  • Preview the scanned items to check their integrity. Select all those files that are required.
  • Click Recover then click Browse to specify the save location. Click Save.
  • View the recovered files from the recovery location.

*The trial software allows you to scan and preview files, but you need to activate it to save the recoverable files. The software has a 30-day money-back guarantee, so activate with confidence.

Once you recover your data, use Disk Utility to erase the external hard drive, and recreate a new file system. Restore the recovered data to the newly formatted external hard drive.

Precautions and Best Practices

The following precautions and best practices will lessen the chances of file system corruption:

  • Always unmount your external hard drive safely.
  • Do not eject or pull the cable of the drive abruptly.
  • Don’t transfer files or manage external disk when your Mac is low in battery.
  • Back up your external hard drive data.


When Disk Utility’s First Aid can’t repair an external hard drive, use file system consistency check (fsck) command in Terminal or Single-User Mode to fix file system corruption issue. Corruption in the file system makes the stored data inaccessible, so follow the precautions and best practices to mitigate it.

The fsck method is risky and can result in data loss, so back up the external hard drive before performing the steps. If you can’t back up the data or want a safer solution, use Stellar Data Recovery Professional for Mac to scan and recover data from the corrupt external hard drive. Later, erase the drive and restore data to the drive.