Hello there. End of 2014 I bought a external SSD drive to use this as my Systemdrive (via thunderbolt). I installed OSX successful and worked happy the last 12 month on my iMac mid2011. Today I bought me a brand new iMac 5k, but if I want to boot OSX from my external Thunderbolt-SSD I just see nothing as a black screen and a white sign meaning "not allowed". On an Apple-Page I read this means that the iMac couldn't find a valid system folder. So what happend here and is it possible to make my external OSX run on my new iMac? A year ago I thought I'm smart because of the idea I could work on every Mac simply plugin my Thunderbold-SSD-Drive... xD Hope for helpful hints.