Clean Yosemite Install

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Level 1

15 points

Clean Yosemite Install

Hi All,

I have a new late 2014 iMac 1TB Fusion drive. Migration assistant went wonky because of the hard drive set up on my old MBP. Decided I'd like to just format this iMac and start fresh. I've reformatted hard drives before and done installs, just never on a fusion drive. I know to hop into recovery mode (cmd+option+r) and I know to hop into disc utility. However, when I get in there, I see Macintosh HD (this is the Logical Volume Group) and then underneath it, tabbed in, Macintosh HD (this is the Logical Partition). Here's where I'm lost and I haven't seen anything clear on the forums. Am I erasing the top level Macintosh HD, the logical volume group, or the second Macintosh HD, i.e. the logical partition. From here, I'm planning on just backing out to Recovery Mode and installing Yosemite through the internet.

Really, the only question here is which Macintosh HD do I erase? Thanks very much for the guidance.

iMac with Retina 5K display, OS X Yosemite (10.10.5)

Posted on Sep 2, 2016 4:48 PM

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Answer 1

Sep 2, 2016 5:08 PM in response to brjasp500

Here are the directions to format a fusion drive. Please read it over because it is not a trivial task like formatting a conventional disk drive.

http://blog.macsales.com/15617-creating-your-own-fusion-drive

Personally I would not reformat the Fusion Drive.

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Answer 2

brjasp500 Author

Level 1

15 points

Sep 2, 2016 5:02 PM in response to Allan Eckert

Thanks, Allan. I may be using the wrong terminology by saying reformat. I had read that it was possible to erase the drive and reinstall Yosemite without breaking the fusion. I actually spoke to Apple support early tonight and that gentleman told me to erase the logical partition, then reinstall. Rather than just go on one person's advice, I thought I'd ask here. Is it not possible to do this without following the instructions you've pointed to? Again, thank you for your time.

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Answer 3

Kappy

Level 10

362,017 points

Sep 2, 2016 5:05 PM in response to brjasp500

Here's the process:

Install Lion Through Yosemite from Scratch

Be sure you backup your files.

Restart the computer and after the chime press and hold down the COMMAND and R keys until the Apple logo appears. Wait for the Utility Menu to appear.
Select Disk Utility from the main menu and click on the Continue button.
After Disk Utility loads select the volume (this is the indented entry, usually Macintosh HD) from the side list. Click on the Erase tab in Disk Utility's main window.
Set the Format type to Mac OS Extended (Journaled.) Click on the Apply button
When the process has completed quit Disk Utility and return to the Utility Menu.
SelectReinstall OS X and click on the Continue button.

This will install the version of OS X you had installed.

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Answer 4

brjasp500 Author

Level 1

15 points

Sep 2, 2016 5:17 PM in response to Kappy

Thanks, Kappy. I'll give this a try.

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