How to fix greyed out 'Erase' option for disk image in recovery mode?

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How to fix greyed out 'Erase' option for disk image in recovery mode?

I'm having a bit of an issue erasing my disk image in recovery mode.

When I am logged in to my account and go to my Disk Utility, it only shows my Internal SSD drive. When I go into recovery mode, Disk Utility shows an External disk image. I wanted to erase this disk image, however the 'Erase' option is greyed out, so it doesn't give me the option.

Do I need to change permissions somewhere to do this?

Kind regards,

sharedev

MacBook Pro (Retina, 13-inch,Early 2015), macOS Sierra (10.12.6), null

Posted on Oct 12, 2017 9:53 AM

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Answer 1

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keg55

Level 6

11,755 points

Oct 12, 2017 6:06 PM in response to sharedev

Your USB boot drive is also an OS X Base System which is an external "Recovery HD" versus your internal Recovery HD. When you boot from this drive you're going to the OS X or macOS Utilities Menu. So again, you can't delete it because you're booted into it. It's just like when you boot into your Macintosh HD. You can't erase it or unmount it because you're booted into it.

You don't need to be concerned about the OS X Base System. It's there for a reason and is not to be messed with. Think of it as a minimal operating system with tools to help you repair disks, restore your system, reinstall your operating system along with other tools.

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Answer 2

keg55

Level 6

11,755 points

Oct 12, 2017 10:48 AM in response to sharedev

If this 'disk image' is OS X Base System or something like that underneath Apple Disk Image, it's your Recovery HD and you can't erase it because you're booted into it.

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Answer 3

keg55

Level 6

11,755 points

Oct 13, 2017 4:22 AM in response to sharedev

Again, don't worry about what the Apple Disk Image or OS X Base System entries do. They just show you that you are booted into a Recovery system - minimal OS.

What are you trying to do?

There is a Security Options button when you Erase button a volume. If all you're doing is erasing your Macintosh HD so you can install/reinstall an operating system, erasing the volume is all you need to do.

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Answer 4

sharedev Author

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Oct 12, 2017 6:25 PM in response to keg55

Thanks! I didn't know that about the Base System.

There is an Apple Disk Image that the Base System appears to be sitting in, however, that I believe is the disk image for the whole OS? In the tutorials I've been looking at, this disk image is 'secure erased', but just like the Base System that appears to sit inside of it, the erase button is greyed out (even when booting from USB like before).

I had already erased the HD, but it never gave me the option to secure erase it, so I assume that option will be found in the disk image itself?

Sorry, this is the first time I've had to do this!

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Answer 5

sharedev Author

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Oct 13, 2017 1:27 PM in response to keg55

But isn't the disk image a compressed version of the hard drive? Meaning that nothing is truly cleaned securely until it's wiped?

When I tried erasing my SDD securely it never showed any secure options, and the erase took all of about 5 seconds unfortunately.

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Answer 6

keg55

Level 6

11,755 points

Oct 13, 2017 3:18 PM in response to sharedev

I don't know how you tried to do a secure erase. But you really shouldn't do anymore than an erase on an SSD drive. Doing a zero write to an SSD is not recommended due to the wear it can put on the drive.

You can do whatever you want to your Mac. But I don't believe you need to do any more than an erase if you're reinstalling your OS. And I don't know what you're trying to do after an erase.

Personally, I have never done any more than an erase on an internal drive (SSD or HDD) before reinstalling the operating system on Mac that I was selling or giving away. Apple doesn't mention anything about a secure erase in their support link for what to do before you sell or give away your Mac. So, Apple doesn't think it's necessary either. Item #7 of that link discusses erasing the drive.

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Answer 7

sharedev Author

Level 1

11 points

Oct 12, 2017 4:04 PM in response to keg55

Thanks for your answer.

I created a bootable usb drive, booted from that instead, but when I go to my Disk Utility in Recovery mode, I still can't unmount my 'Base System' or erase it because it says it is still in use.

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