el capitan - The OS X Installation couldn't be completed
I get the above error while trying to upgrade my 2010 MacBook Pro from Yosemite. I've been attempting for more than 10 hours. Spoken to an advisor over the phone 3 times. Have tried installing through recovery mode. Still nothing. I didn't back up before. So don't really want to attempt a clean install.
MacBook Pro, OS X El Capitan (10.11)