I successfully installed Elementary OS (Loki) on a MBP 15"(MacBookPro8,2) alongside OSX 10.7 and another installation of Sierra. On startup I would get a screen with the 3 options,for each os. All worked fine. I have been using Elementary for two weeks with lots of specific installs and customization,browser bookmarks, etc. I had to switch computers and moved the same hard disk to a 13" MBP (MacBookPro9,2). Usually macs will start up right away without (major) issues when swapping hd. But to my surprise the grub with the 3 selections does not show on startup but only gray screen that stays indefinitely. I am able to use the "option" key on start up and then select and successfully boot one of the two OSX but if I choose the EFI icon(its the only other option other then the recovery ones) - which is the Elementary install I imagine, the computer freezes. Is there a way I can fix this and get the grub startup up screen as it was before on the MBP 15"? I have not changed anything to the disk so this is quite puzzling and frustrating since I really need to get back to Elementary where I have work projects and files - OSX's cannot mount the Elementary partitions. Any help greatly appreciated but to clarify - at this point I would prefer to stay away yet from rEFInd solutions/suggestions but find a way to get the elementary grub to show back as it was if possible.