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MM Answers: How to erase the HDD / SSD from my Mac?

Today day of another edition of our column MM Answers!

The question of the day:

How to erase HDD / SSD from my Mac?

When we sell / donate a computer, it is essential to erase our data in order to make the Mac ready for its new owner.

Machines prior to chip T2

On Macs prior to the T2 chip (security chip that Apple has implemented on newer Macs), it is possible to use an external disk to boot the machine, including Disk Utility, Terminal, macOS Installer, etc.

In practice, the new chip makes storage encryption keys pass from Secure Enclave to the hardware encryption mechanism on the chip, causing the key never to leave the chip. In addition, T2 allows hardware verification of the operating system, kernel, startup, firmware, etc. Switching on kids, it is no longer possible to boot the system from an external disk.

And how to do disk erasing and installing macOS, then?

How to Erase Disk and System Installation

To do so, then follow these steps to enter macOS Recovery Mode:

Recovery Mode
  1. Restart the computer by holding down the R keys during the reboot;
  2. If you are not connected to the internet, choose a network from the Wi-Fi menu (at the top right of the screen)
  3. Wait until the start bar appears and release the keys (if you see a globe, it means your Mac is starting up). Internet Recovery Mode and the additional information needed to start Recovery Mode will be temporarily downloaded to your machine);
  4. When opening Recovery Mode, select Disk Utility and click Continue;
  5. Click on the Delete tab;
  6. Select the partition containing the start disk and not the HDD as a whole, which can count the Recovery Mode used in that process (in the "View" menu, click "Show All Devices");
  7. From the Format pop-up menu, choose the option corresponding to your system (for APFS format, type a name for your disk, such as Macintosh HD, and click Delete);
  8. After the disk has been erased, exit Disk Utility;
  9. Select Reinstall macOS and follow the onscreen instructions.
MacOS Mojave installer

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