Erase External Hard Drive on Mac Terminal: A Comprehensive Guide

Are you looking to securely erase an external hard drive using your Mac terminal? This guide will walk you through the process, dispelling common misconceptions about data security and drive maintenance along the way.

It's no different than any other part of the drive as far as holding data, except neither the OS or you are allowed to touch it. When dealing with bad blocks or sectors on a drive, the firmware will attempt to move the data to a new location. It can't create more from out of nowhere – a drive has only as many sectors as it had when it shipped from the factory.

Sector replacement is often misused term that can be found online. For the typical user, even a single pass erase is sufficient for securing data. On the other hand, a seven-pass erase provides virtually unrecoverable security.

When you do a Secure Empty Trash on your Mac, the areas where data is stored are overwritten with random data seven times. Similarly, using Disk Utility to securely erase an entire rotating hard drive allows you to choose how many passes of overwriting data will occur.

It's essential to note that sector replacement has no relation to erasing data on a drive. Unlike solid-state drives (SSDs), it's unnecessary to write zeros and shorten the life of your SSD. In fact, operating an SSD full-time as a FileVault-encrypted drive and then reformatting it will effectively throw away the old encryption key, rendering sectors random bits.

SSDs employ wear leveling to avoid this issue, but zeroing out an entire SSD (or worse, using 7 or 35 pass random patterns) can significantly reduce its lifespan. Since SSDs have a limited number of writes per sector before physical wear occurs, it's unwise to declare something 'secure' when it isn't.

In conclusion, writing zeros on an SSD not only doesn't actually zero out data but also shortens the drive's life. If you're looking to erase an external drive, consider selecting one instead of your internal Apple SSD.

As for Disk Utility, it won't knowingly erase your boot drive, which is why you should avoid selecting it. Unfortunately, disk drives and SSDs make it challenging to perform a true guaranteed secure erase due to sector replacement on rotating devices and how SSDs handle data storage.

If you're looking to securely erase an external hard drive using Disk Utility, I'm afraid there isn't an obvious option to zero out the drive. However, by following this guide, you'll be better equipped to understand the complexities of drive maintenance and data security on your Mac.

Erase external hard drive mac terminal