Before proceeding further, you should understand that EFI-mode booting is not about booting partitions; it's about booting files. This fact doesn't alter the mechanics of day-to-day booting, but it's critical for debugging boot problems and doing manual boot loader and boot manager installations. In BIOS, boot loaders reside in the Master Boot Record (MBR; that is, the first sector) of the hard disk and in the first sector (sometimes called the Partition Boot Record, or PBR) of partitions. Thus, it's sensible to talk about "booting a partition" or something similar, on a BIOS-based computer. Under EFI, though, boot loaders are stored in ordinary files on a FAT partition called the EFI System Partition (ESP). (On Macs, boot loaders can also reside on various HFS+ volumes.) Thus, "booting a partition" is pretty much meaningless under EFI. (One partial exception relates to the fallback filename, which is EFI\BOOT\bootx64.efi on AMD64 systems; this filename is booted if no other registered boot loader can be found. It's most often used on removable media to make them bootable.) If you think your EFI-based computer, such as a Mac, is "booting a partition," you're likely to go on a wild goose chase when trying to debug boot problems. That said, I don't think your problem is fundamentally about the boot process, although it could be there's a tie-in somewhere....
For your specific problem, I have three suggestions:
- Re-install rEFInd from OS X. Chances are your initial installation lacked an EFI filesystem driver for ext4fs (or whatever filesystem holds your Linux kernel). Re-installing now, after Ubuntu has been installed, should cause the
refind-install script to set up the ext4fs driver, which will enable rEFInd to boot the Linux kernel directly. This may work better than going through GRUB. Note, however, that if you're using a filesystem other than ext4fs, you should instead install the appropriate filesystem driver manually. (See this page of the rEFInd documentation for details.)
- See this question and its answers for information on "black screen" problems. These problems were rampant about two years ago, but have become much less common today. Causes were varied, so you may need to try multiple solutions.
- Instead of installing the 2.5-year-old 14.04, install the 16.04.1 or 16.10 version of Ubuntu. These distributions include newer software and so may work around the problem you're encountering. (Of course, the 14.04.5 you're using includes updates to some critical components, such as the kernel; but it's still behind the times on other software, which might be the cause of your black-screen problem.)
Model Name: MacBook Pro Model Identifier: MacBookPro10,1 Processor Name: Intel Core i7 Processor Speed: 2.3 GHz Number of Processors: 1 Total Number of Cores: 4 L2 Cache (per Core): 256 KB L3 Cache: 6 MB Memory: 8 GB Boot ROM Version: MBP101.00EE.B0A SMC Version (system): 2.3f36 Serial Number (system): C02HX34KDKQ1 Hardware UUID: 967B66AF-E613-51C7-A120-EB009EAFA11F
– Mystery121 Oct 12 '16 at 12:55