I accidentally erased OS in disk utility and now I can't erase the HD

Question

Level 1

7 points

I accidentally erased OS in disk utility and now I can't erase the HD

Hey there hoping you can help. Soooo I didn't follow instructions properly when I was in disk utility to erase my hard drive (to do a factory reset) and accidentally erased the operating system underneath the hard drive (on the left hand side of menu). So I thought I would try to erase the hard drive after that but comes up with error. So then I went back to utilities menu and tried to "reinstall macOS" but then the hard drive is greyed out and says it's locked. I also tried partitioning the drive, no idea if that is even an option to fix it but it says it's too small. See images if I need more explanation, although now after I deleted the OS it now says "OS X Base System".

I have googled and can't find anything, looks like no one has done anything as dumb as this ;)

Posted on Sep 28, 2017 7:12 AM

Reply

Answer 1

Top-ranking reply

Popchezque Author

Level 1

7 points

Oct 2, 2017 2:31 AM in response to Popchezque

Success!

Thank you to everyone for their help, but nothing was working - probably due to my failure to understand! I did some more researching, I tried these steps below - not sure which parts made it work but I thought I would add it to this thread in case anyone is here trying to find the answer to the same question:

I gave up trying to erase the HD and reinstall OS in the Mac OS Utility because neither of those worked. I also had tried getting a bootable copy of OS on a USB and that didn't work either. However I was able to restore from time machine back up so I did that. However when that was done, I still had no luck doing either erase or reinstall.

Next I turned off spotlight by using terminal command (instructions I found on the internet) and then also turned off time machine.

Then I went back to the utility, it still didn't let me erase the HD, but it did let me "reinstall OS" so I did that. Then when that was done I went back into the utility and it finally let me do the HD erase. So then I did "reinstall OS" again and now I'm sorted!

As I said, by no means is this expert advice but a combination of these things finally got it to work. I'm sure there must be a quicker way ;)

Reply

Answer 2

Courcoul

Level 6

18,732 points

Sep 28, 2017 12:39 PM in response to Popchezque

Won't work since you can't erase the drive you booted from. The Recovery Partition is after all a part of that drive. After ensuring the Mac has Internet connectivity, start up in Internet Recovery Mode so it boots from Apple's servers and the drive is fully accessible. Hold down Option Command R prior to startup chime. Will take awhile depending on your connectivity speed.

Reply

Answer 3

Popchezque Author

Level 1

7 points

Oct 2, 2017 3:21 AM in response to Lexiepex

Thanks for help Lexiepex, at that stage no, it wasn't working, I tried to reinstall OS but it kept giving me an error message so that's when I had to do time machine because everything else was giving me error messages. It wasn't until I loaded the time machine and then switch off spotlight/time machine was I then able to do the reinstall OS.

Reply

Answer 4

SeaPapp

Level 7

26,492 points

Sep 29, 2017 3:24 AM in response to Popchezque

How to install macOS - Apple Support

Reply

Answer 5

Lexiepex

Level 6

14,108 points

Sep 30, 2017 2:08 AM in response to Popchezque

You can not format the disk from which you started the mac.

Your first picture shows "child count 3": this means that you have 3 "partitions" (as should be):

1. the EFI partition, this is in Fat and has about 250MB size

2. the Recovery Partition, this is your recovery partition, size 650MB

3. and the OS (Startup) Partition, this is the "startup" disk, size 128GB (in your case).

pay attention to the sizes!

The recovery partition and the efi partition are still OK, not accessable (and correctly so) from another partition.

So you should start in the Recovery partition ( start while holding the CM+R keys), it is slow, when you see the menu, choose DiskUtility from the Utilities menu.

In disk utilities select your start partition and see what size is used:

- if "normal" click the FirstAid tab (select the text, so you see what it is doing) let it repair, when necessary twice or thrice.

- If empty, re-install OS, you have to have an internet connection because your existing OS will be downloaded and installed.

Reply

Answer 6

Eric Root

Level 10

685,483 points

Sep 29, 2017 5:26 PM in response to Popchezque

If your computer came with DVD disks, boot off the disk, and use Disk Utility to erase the hard drive. Then reinstall the OS and upgrade from there.

Reply

Answer 7

Lexiepex

Level 6

14,108 points

Oct 2, 2017 2:52 AM in response to Popchezque

so basically you did this:

"

So you should start in the Recovery partition ( start while holding the CM+R keys), it is slow, when you see the menu, choose DiskUtility from the Utilities menu.

In disk utilities select your start partition and see what size is used:

- if "normal" click the FirstAid tab (select the text, so you see what it is doing) let it repair, when necessary twice or thrice.

- If empty, re-install OS, you have to have an internet connection because your existing OS will be downloaded and installed.

"

as far as I understand you.

Reply

Answer 8

Popchezque Author

Level 1

7 points

Sep 28, 2017 4:46 PM in response to Courcoul

Thanks for your help, it's desperately needed :) ok so I had no idea about the Internet recovery mode, so I read you enter it by cmd + opt + R at start up but it keeps taking me to disk utility. So is my laptop too old for internet recovery? So then what do I do?

I

did look at "reinstall macOS" again just to see what would happen and this time it's come up with two drives: "OS X Base System" and "Recovery HD", the recovery is still locked and when I clicked on OS Base it says it's not formatted as Mac OS ext... "use disk utility to enable journaling or reformat the disk".

Sorry if I'm painful, but my husband is not good at this stuff, I might as well ask a sack of potatoes for help ;)

Reply

Answer 9

Popchezque Author

Level 1

7 points

Sep 29, 2017 6:08 PM in response to Eric Root

Going off your idea, I suppose you would suggest putting it on a USB and boot from that? I will give it a go, but let me know if I'm wasting my time or if I'm going to blow up my laptop doing that haha ;)

Reply