Trying to erase my mac but keep getting error Couldn’t open device.: (-69877)

You must be booted to an external macOS installer such as in Recovery Mode (Command +R), Internet Recovery Mode (Command + Option + R), or from a bootable macOS USB installer. Even then, sometimes you will get an error attempting to erase the drive so make sure to immediately try to erase the drive again. I've seen some of our organization's Macs require two back to back attempts to erase the drive for some unknown reason. Depending on your Mac's setup, you may need to select the whole physical drive to erase instead of just erasing a single volume (Intel Macs only). Within Disk Utility you may need to click "View" and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility.

If you are still unsuccessful, then perhaps the drive is failing or perhaps the Mac is being managed by a school or business which is preventing modifications.

Greetings kelin1209,

I see you're looking to erase your Mac, but it continues to fail with an error so let's see how we can help.

For starters, let's make sure we're using the same steps as outlined via the following resource. We'll have both resources to view, but be sure you're checking out the steps that apply to the Mac that you have.

Use Disk Utility to erase an Intel-based Mac

Use Disk Utility to erase a Mac with Apple silicon

If you see that you are using the same steps and continue to get the error, let's try repairing the disk to see if that clears this up to be erased. For help with these steps, check out the following resource:

How to repair a Mac disk with Disk Utility

If repairing the disk doesn't allow you to then erase, Contact Apple Support for more in depth help.

Cheers!