In this post, I will go over instructions on how to create a bootable USB flash drive containing the Mac OS X 10.10 Yosemite installer. I followed the instructions below to successfully create a bootable installer for Mac OS X 10.11 El Capitan, which is the last version to support the 2008 Core 2 Duo Macbook Pro. I needed to upgrade my sister’s 2008 Macbook Pro and found that the existing Mac OS X 10.6 Snow Leopard did not support the “createinstallmedia” tool I got a “Failed to start erase of disk due to error (-9999, 0)” error. Update 2: The instructions below will work to manually create a Mac OS X 10.11 El Capitan USB installation drive. Update: Go to Install macOS Sierra Using Bootable USB Flash Drive if you want to install macOS 10.12 Sierra instead.
