How to install Mountain Lion as a second OS X with Yosemite
I need to install Mountain Lion with Yosemite at Macintosh HD creating a second partition -
is it really to do ?
MainStage, OS X Yosemite (10.10.3)
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You can't install an OS older than that which your computer came with.
If your computer came with Mountain Lion or earlier:
Restart with command - R held down and open Disk Utility.
Step 1 - select the top level hard drive.
Step 2 - select the Partition tab.
Step 3 - grab the //// to slide the partition up to make room for a new partition.
Step 4 - select the vacant space and hit the + sign.
Step 5- Mac OS Extended (Journaled) and add a name.
Step 5a, click and select GUID.
Then Apply.