How to recover data from external hard drive on Mac

Mac's that come with SSDs have limited storage. For instance, my MacBook Air has only 256GB of hard drive space. As a result, I keep most of my files on external hard drives and USB pen drives. However, it is not uncommon when Mac's don't read these external disks or the drives become unmountable or corrupted. Let's see how you can recover data from external drives even when your Mac is unable to read the drive.

Basic cable and hub check

Repair Disk with Disk Utility - First Aid

• Go to Disk Utilities using Finder
• Select the disk you want to repair from the left sidebar
• Click on the First Aid icon which will start a scan on that volume to scan for errors and then repairs all the errors found on the volume, if necessary. While First Aid runs, it will create a lock on the disk. It means that you won't be able to use any other application while First Aid runs. However, it won't take much time for the scan to run.

Use a tool to recover files from a corrupted, unmountable or formatted external disk

• Install a free tool like iBoysoft free Mac Data recovery on your Mac. This tool can do all types of data recovery on its free version except for APFS data recovery, which if an ideal use case for us since we are recovering data on an external disk.
• Connect your disk to Mac and choose the Initialize... option that appears. Launch iBoysoft Data Recovery. It will ask for your Admin password since it needs to be able to make changes on your hard drive.
• Select the hard disk from the list of disks that appears on the UI of the tool and click on Scan.

• The tool will start reading the attached disk and will categorize the found files into different folders depending on the file type like Images, Videos, Emails, Documents, Audios, etc. Wait for the Scan to complete

• Once the scan is complete, you can choose the copy the recovered files to your Mac hard drive or another external drive connect to your Mac.

Repair external hard drive using FSCK

• Each filesystem is identified by a unique ID called the identifier of that disk. We need this in addition to the device node to be able to run FSCK on your hard drive.
• To get this number, make sure your disk is attached to the Mac. Open the Mac Terminal and run

  diskutil list

  followed by the enter button.
• You will see all the currently connected drives. This list will include both the mounted and unmounted drives.
• Note down the device identifier. It will look something like this

  /dev/disk1

  and is usually present on the leftmost side of the command result.
• Since fsck needs to scan for all memory locations, it needs unhindered access to the storage. For this, the tool cannot be run when your Mac is ON in the normal mode. You need to restart in the basic command line mode. To do this, restart your Mac and when it starts it boot-up sequence, hold down "Command + S" button.
• Release the buttons when you see the command line interface appearing on the screen. Some text will print on the screen which you can ignore. When it stops, you should be able to see

  root#

• Now, you can run fsck on the externally connected drive by using the command

  /sbin/fsck_hfs -fy /dev/disk3

  when the part "/dev/disk3" needs to be replaced by the disk identifier you have noted down before.
• When the check is complete, it will print a text "OK" after which you can restart your Mac by typing "reboot" and pressing enter button.

Wrap up