Resolved Help Needed: Can't erase iMac Drive for fresh install

[VideoBeagle]

I'm trying to do a complete fresh install of Mavericks on my iMac 2012.
It has the "1tb fusion drive"

I can not get the drive to erase, no matter what I do.

I boot into a installer flash drive, and use disk utility to erase the drive...it starts unmounting...crashes and reboots.
I boot into a USB drive with an OS on it, same thing.

I try to just unmount it, and it says it's busy and to stop any thing using the drive...though there's nothing..
Googling suggested killing spotlight...tried it, didn't help.

I try to use diskutil unmountDisk force "/Volumes/Macintosh Drive" and terminal crashes.

Can't Repartion the drive to try in that direction... all options there are greyed out.

Can anyone suggest a solution?

 

[VideoBeagle]

Basic hardware test comes out fine.. been running the extended test, which is taking a while.

 

[DeltaMac]

Do you have File Vault turned on?
You will need to turn File Vault off first, then you will be able to delete the CoreStorage logical volume group.
Looks like you know how to use the terminal to do that.

 

[VideoBeagle]

I don't use file vault...but maybe it's on on the full usb install? (was just a blank drive I installed maverciks on to test something some time ago).
I'll kill the extened test and give it a try.

 

[VideoBeagle]

Nope...filevault is off

 

[VideoBeagle]

Now I get to "removing logical volume from logical group" ...and it crashes on that.

 

[DeltaMac]

Try a different method in the terminal - -
http://apple.stackexchange.com/ques...sh-hd-to-its-original-partition-configuration
Scroll down about 2/3 of that page, to a post that begins with a
WARNING: ONLY FOLLOW THESE INSTRUCTIONS IF YOU HAVE EITHER: etc, etc.
That should be your relevant instructions. Easy to follow, and you do have to type in the correct UUID for your Logical Volume Group.

DO NOT leave any external drives attached, until you have everything formatted, and the new system installed.
This shouldn't really be an issue, but I like less possibility of confusion during erase and reinstall. (I have made bad mistakes by moving too quickly, and choosing to erase my backup drive, when the main drive was already blank, too )
So, keep your task it simple!

 

[AppleNewton]

Try clicking on the actual partition and not the volume of the hard drive, it would be the indented Macintosh HD, just click Erase on that and then restore the OS.

 

[DeltaMac]

Try clicking on the actual partition and not the volume of the hard drive, it would be the indented Macintosh HD, just click Erase on that and then restore the OS.

That won't work until you can actually see the partition. The Logical Volume Group doesn't show the drive itself, only "virtual" partitions. You have to remove the CoreStorage volume on that fusion drive, which will revert the partitions to show the actual SSD and HDD drives.

 

[VideoBeagle]

Try a different method in the terminal - -
http://apple.stackexchange.com/ques...sh-hd-to-its-original-partition-configuration

Thanks I'll check that out.

Try clicking on the actual partition and not the volume of the hard drive, it would be the indented Macintosh HD, just click Erase on that and then restore the OS.

What part of "use disk utility to erase the drive...it starts unmounting...crashes and reboots." did you not understand?

 

[VideoBeagle]

Try a different method in the terminal - -
http://apple.stackexchange.com/ques...sh-hd-to-its-original-partition-configuration
Scroll down about 2/3 of that page, to a post that begins with a
WARNING: ONLY FOLLOW THESE INSTRUCTIONS IF YOU HAVE EITHER: etc, etc.
That should be your relevant instructions. Easy to follow, and you do have to type in the correct UUID for your Logical Volume Group.

Worked perfectly. Removed all externals, followed the instructions and it worked.
I plugged my Mavericks install flash drive back in, booted to it, and going to proceed with a reinstall!

 

[VideoBeagle]

And as an annoying post mortem, looking in my thread history, I see I went thru this a year ago, give or take a few days