SecureErase (Category 4 - DoE 3 - Pass Secure Erase) Macintosh HD - in Terminal app

"...never use these options for an SSD as SSDs don't work the same way as hard drives".

In that case, I've come to a dead-end.

Had I known that this particular drive was a critical point to mention from the start, this entire discussion would have ended substantially sooner.

Perhaps that could explain why I got the "Ownership of the affected disk is required." after entering my parameters.

These are the results from the (2) recently suggested parameters spacing (in recovery mode)::

[-bash-3.2# diskutil secureErase 4 /Volumes/Macintosh\HD

Could not find the disk /Volumes/MacintoshHD

[-bash-3.2# diskutil secureErase 4 "/Volumes/Macintosh HD"

A whole disk must be specified when doing secureErase without the

"freespace" option; if you need to wipe a single partition, you must

use diskutil zeroDisk or diskutil randomDisk but you will subsequently

need to reformat (newfs) the partition with "diskutil eraseVolume"

[-bash-3.2#

Thank you for your responses.

I will proceed with:

What to do before you sell, give away, or trade in your Mac - Apple Support.

I'm assuming that one of my parameters | commands that I entered (or perhaps the spacing) is causing the result I'm seeing"

Current parameters \ commands: diskutil secureErase 4/Volumes/Macintosh\ HD

Maybe "Volumes"?

Thank you for providing an alternative solution, John. Greatly appreciated.

However, since I've accomplished a level 4 Secure Erase equivalent on the Windows OS (many times in the past) with no problems whatsoever, I'm still focused on being able to accomplish this process on the Mac operating system.

I've had numerous phone conversations with Apple technical support team members.

The consistent response is "Apple does not provide support for Terminal".

I'm confident that it IS possible to perform a level 4 secure erase successfully on the MacOS.

In the meantime, I'll leave this post open (considering it unresolved as of this date) and continue my online research.

Thank you again to those who've responded to my post.

I agree with your assertion that high-level secure disk erasures require substantially longer processing times. My Windows OS secure erases were typically accomplished within a 24-hour timeframe. Since I have a few other computer systems available, the time it takes to do this task on my old Mac system is not an issue.

Thanks for your reply and for providing a link to and information about Knoppix, HWTech.

FYI: The hard drive was replaced in 2020.

I appreciate your suggestion, but I'm not comfortable with nor do I have even rudimentary Linux-based knowledge of booting from a Knoppix LInux USB stick without proper supervision.

If something were to happen during the process (possibly making the HD inoperable), that would put me in a far worse position than I'm currently in.

I continue to look for a solution that allows me to use Terminal as it is part of the MacOS.

Up to this point, the overwhelming consensus has been Terminal-avoidance, akin to the third rail of a subway line.

I hope to get a better understanding of why that is and if what I'm seeking can be accomplished successfully.

Thank you again, John.

Performing a level 0 may be adequate for the majority of end-users, but I'm not in that category.

You are correct in pointing out that I eventually intend to sell my iMac, but only after I complete a level 4 Secure Erase procedure on the hard drive.

I want to ensure I've taken the highest level of security available to thwart any attempts to tamper with the hard drive to extract data from it. The odds of that happening are probably highly unlikely, but I'm still going to move forward with the secure erase procedure using Terminal.

And, yes, I could just remove the hard drive and hammer it into oblivion, but that's not what I wish to do.

Thank you for your suggestion, Bob.

I'm going to assume that you've never had an opportunity to remove a hard drive from an iMac. It's a dreaded task even for the most tech-savvy Mac computer technician. I've had many opportunities to watch them do just that, and each time the struggle to open the iMac to access the hard drive was very apparent and eventually accomplished with tremendous difficulty. There was an equal struggle, again with much difficulty, in reassembling the iMac.

So (from my experience) this is definitely not a task for the uninitiated or, for that matter, any average mere mortal.

I have accomplished this same task many times with Windows-based PCs with no problems whatsoever. But getting into one of those systems only involved removing a few screws.

I stand corrected.

Glad to hear you've had positive and successful experiences with cracking open and accessing the iMac's internal components.

It's still not a task I want to perform.

I will move forward with finding someone who can guide me through a level 4 Secure Erase procedure.

When I find that individual and have accomplished the procedure, I will record the procedure here.

Thanks again, Bob and everyone else who took time out from their day to offer constructive suggestions.

It's always interesting to discover just how many ways any one problem can be solved especially when so many individuals can be reached to offer assistance.

Thank you, John.

I tried your suggestion of adding the space after the number 4 : diskutil secureErase 4 /Volumes/Macintosh\ HD

(Please note - this procedure WAS NOT carried out in RECOVERY MODE)

That resulted in the following statement: "Could not find the disk hd".