How to format an unreadable hard drive on Mac?

Posted by Katrina to Mac Data Recovery on August 31st, 2018

I have a 2TB external hard drive stored important files. Today, when trying to open one of working files, I received error message: "The disk is unreadable, do you want to initialize it now?" It seems that I should format the external hard drive before reusing it. Can anyone tell me how to format an unreadable hard drive on Mac?

Hard drive/external hard drive unreadable issue is often caused by virus attack, sudden power failure, unsafe ejection, improper operation, etc. In a word, it mainly results from corrupted file directory. If you are reminded: "the disk you inserted was not readable by this computer", this most effective solution is to format the unreadable hard drive on Mac. This passage will tell how to format an unreadable hard drive on Mac.

Recover data from unreadable hard drive before formatting

As formatting will erase all data on this hard drive, so please make a backup at first. If not, you can recover data from unreadable hard drive with free Mac hard drive recovery software, like iBoysoft Mac Data Recovery.

iBoysoft Mac Data Recovery can recover data from unreadable external hard drive, hard drive, USB flash drive, memory card, pen drive, etc. on macOS Mojave 10.14/High Sierra 10.13/Sierra 10.12/10.11/10.10/10.9/10.8/10.7.

Besides, iBoysoft Mac Data Recovery can also recover data from formatted drive, recover data from unmountable drive, recover data from corrupted drive, recover data from inaccessible drive, whatever is formatted with APFS, HFS+, HFS, exFAT, FAT32. It supports universal file types, including documents, photos, audios, videos, emails, etc.

Tutorial to recover data from unreadable hard drive with iBoysoft Mac Data Recovery

Step 1: Launch iBoysoft Mac Data Recovery and select the unreadable hard drive

Recover data from unreadable hard drive with iBoysoft Mac Data Recovery

Step 2: Choose "Deep Scan" on the bottom-left corner and click "Next" to scan lost data.

Step 3: Preview the searching results, choose files we need, and click "Recover" to get them back.

Step 4: Have a check to ensure we have got all lost data back.

How to format an unreadable hard drive on Mac?

After data recovery completes, you can format an unreadable hard drive with the following steps:

Method 1: Format unreadable hard drive with Disk Utility

Step 1: Go to Applications > Utilities and open Disk Utility.

Step 2: Select the unreadable hard drive you want to format from the left-side pane.

Step 3: Choose the option to "Erase" the disk at the center top of the window.

Step 4: Complete the related information (name, format, scheme), then click Erase.

Format an unreadable hard drive on Mac with Disk Utility

Step 4: Choose the option to "Erase" the disk at the center top of the window. Simply click on Erase and you'll have a newly formatted disk.

Method 2: Format unreadable hard drive with Terminal

Tips: When Disk Utility refuses to perform formatting for some reasons, Terminal enables you force erase disk Mac Terminal. But formatting unreadable hard drive with Terminal is suitable for experienced users. For common users, it's easy to result in bad aftermath when inputting wrong command line. So use it with caution.

Step 1: Opening Terminal from Applications > Utilities.

Step 2: Enter "diskutil list" into Terminal and you'll get a list of all mounted disks on your Mac.

Terminal disk list command

Step 3: Find the specific disk identifier of hard drive that you want to format and copy the identifier.

Step 4: Pick a name and a system format type. Then type in: Diskutil eraseDisk FILESYSTEM DISKNAME DISKIDENTIFIER.

For example, if the hard drive you want to erase has "/dev/disk3s1" as its identifier and you want to format it to Mac OS Extended Journaled (JHFS+) and name it as Empty. The syntax is going to look like this: Diskutil eraseDisk JHFS+ Empty/dev/disk3s1.

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