Type sudo mkdir /boot/efi to create the standard mount point for the EFI System Partition (ESP). Type sudo mount /dev/sda1 /boot/efi to mount the ESP at /boot/efi. (Change /dev/sda1 if your ESP has an unusual partition number.) You can use gdisk to check the ESP's number, if you like. Type ls /boot/efi.

A small utility that mounts a EFI partition on the selected hard drive or usb flash drive This is a simple wrapper for the terminal diskutil +some buttons What's New in Version 1.2.3 See changelog Released March 26, 2016. Boot macOS, Windows, and Linux in UEFI or legacy mode on Mac or PC with UEFI or BIOS firmware Boot using UEFI firmware directly or CloverEFI UEFI firmware emulation Customizable GUI including themes, icons, fonts, background images, animations, and mouse pointers. Theme manager and theme repository at http://sourceforge.net/p/cloverefiboot/themes/. EFI Mounter v3 MacMan’s version of Koen2X’s EFI Mounter v3. Modified to use the diskutil command and sMacMan’s version of Koen2X’s EFI Mounter v2. Modified to use the diskutil command and supports running on systems with up to 10 disks attached. Command Line EFI Mounter is a minimalist Mac OS X application that offers you the possibility to visualize all the volumes connected to your computer and mount any of the included EFI partitions.

So: how important is that partition?

A EFI partition is created when a drive (HDD, SSD, or flash) is partitioned as GUID. The EFI partition holds information specific to that system's hardware and includes drivers for the boot up process .. so, yes, it's pretty important.

Assuming I need it, how do I get it back?

See if any of the following articles can help answer that question:

EFI Files: The UEFI Boot Loader - Lifewire
Fixing a Broken EFI Partition on Mac - OSXDaily

I think you will find that using Recovery Mode to re-install macOS will be the easiest way to repair the corrupted/missing EFI partition in the long run.

How to reinstall macOS - Apple Support
Installing or reinstalling OS X in Recovery Mode - iDB
Use the Recovery HD Volume to Reinstall or Troubleshoot OS X - Lifewire

Aug 7, 2018 4:04 AM

by Rod Smith, rodsmith@rodsbooks.com

Originally written: 1/2011; Last Web page update: 6/17/2013 (last major update: 5/4/2012)

I'm a technical writer and consultant specializing in Linuxtechnologies. This Web page is provided free of charge and with no annoyingoutside ads; however, I did take time to prepare it, and Web hosting doescost money. If you find this Web page useful, please consider making asmall donation to help keep this site up and running. Thanks!

Donate $1.00

Donate $2.50

Donate $5.00

Donate $10.00

Donate another value

Note: This page is written using a rather elderly 32-bit Mac Mini as a reference, and using Ubuntu 12.04 as a reference. Developments in the last year have rendered certain of the procedures on this page sub-optimal. I've tried to point these out, but I haven't fully researched better replacements, and I lack the modern hardware on which to test some of the better methods on more recent 64-bit Macs. Thus, you may need to deviate from these instructions on modern computers.

The Problem

When installing Ubuntu Linux on an Intel-based Macintosh, most peoplefollow any of several guides available on the Internet, such as thisUbuntu document. Most of these guides, however, rely on features of theMacintosh that are intended to enable it to boot Windows. In particular,these guides typically end up creating a configuration that boots Linuxusing its Compatibility Support Module (CSM), which provides BIOSemulation on the Mac. In this mode, the Mac sets up a Basic Input OutputSystem (BIOS) layer that the OS can use, rather than rely on the ExtensibleFirmware Interface (EFI) that OS X uses to run on the computer. BIOSemulation is expedient, and it's the only way that most versions of Windowscan boot directly on a Mac, but it's got several drawbacks:

Longer boot times—BIOS emulation is widely regarded as slowing the boot process. I've not tested this effect myself, so I'm not sure how significant it is.
Reduced graphics card flexibility—On some models with multiple graphics chipsets, you can't select which chipset to use in BIOS mode, but you can in EFI mode. My own Mac isn't one of the affected models, so I can't comment further on this issue.
Use of a hybrid MBR—Intel-based Macs use the GUID Partition Table (GPT) rather than the more common Master Boot Record (MBR) partitioning system. Windows, however, can't boot from GPT disks on BIOS-based computers (which it thinks a Mac is thanks to Apple's BIOS emulation). Therefore, Apple uses an ugly and dangerous hack known as a hybrid MBR, in which a GPT data structure known as the protective MBR is altered to make the disk look like an MBR disk to Windows. The trouble is that hybrid MBRs frequently cause problems. In fact, even the Ubuntu installer often gets it wrong; it tries to be helpful by creating a hybrid MBR, but depending on your partition layout, it can create a partition table that the popular libparted-based partitioning tools won't touch.

As far as I can tell, BIOS emulation mode only works when a hybrid MBRis present on the hard disk or when a BIOS-bootable optical disk isinserted in the optical drive. Thus, you can't use BIOS emulation mode witha conventional GPT disk unless you plan to use a bootable optical disc toboot Linux.

Ubuntu can use the BIOS emulation and hybrid MBR that enable Windows toboot on Macs, but it doesn't need to! If you don't use thesefeatures, you won't see their problems. Hybrid MBRs, in particular, are aBad Idea (with a capital B and a capital I). I've seen numerous problemsreported at the Ubuntu Forums relatedto Ubuntu installations on Macs with hybrid MBRs, and more problems withsimilar configurations elsewhere. See my hybrid MBR Web pagefor a technical description of what they are and what can go wrong withthem. In short, they can get out of sync, cause confusion about whichpartition is which, and become damaged in frustrating ways. Whenever Ithink I've heard of every possible problem with hybrid MBRs, I stumbleacross a new one. You're better off without one, if that'spossible—and it is, if you dual-boot OS X and Linux but notWindows.

The trouble is that Ubuntu doesn't support installing to a Mac in EFImode, at least not as of version 12.04. (Some sources claim that this nowworks on some later versions, but I haven't tested this claim—indeed,I lack the hardware to do so!) The normal 64-bit discs can boot on PCs ineither BIOS mode or (if the PC supports it) UEFI mode (UEFI being,essentially, EFI 2.x). These discs reportedly do not boot on Macs(although I suspect they might with the help of rEFIt or rEFInd). The 32-bit Ubuntuinstallation discs lack EFI support. Ubuntu has also released 64-bit discimages for Macs. Ironically, these boot only in BIOS mode! Therefore, torid your computer of the dangerous hybrid MBR, you'll need to jump throughsome hoops. An alternative to all of this is to run Ubuntu in a virtualenvironment, such as VirtualBox.This can be a good solution in some cases, but it doesn't give Linux directaccess to the hardware and you'll lose some speed.

Some Caveats

Although my opinion is that Intel-based Macs are best booted using EFIand a GPT with a protective MBR rather than a hybrid MBR, there aredrawbacks to doing it this way. These include:

No Windows—As noted earlier, Windows relies heavily on BIOS emulation to boot on a Mac; therefore, if you want to triple-boot OS X, Linux, and Windows, you'll need a hybrid MBR to boot Windows. (You might, however, consider dual-booting OS X and Linux and run Windows in a virtual machine such as VirtualBox. This will eliminate the need for BIOS emulation and hybrid MBRs.) In theory, you could triple-boot with a hybrid MBR but still use EFI mode to boot Linux. I've not tested this, and the benefits are greatly reduced since you've still got the hybrid MBR on your hard disk.
Limited nVidia driver support—The biggest caveat to booting Linux in EFI mode on Macs is that some Linux video drivers, particularly for nVidia chipsets, don't work well when you boot in EFI mode. Thus, if you've got a Mac with an nVidia video chipset, you'll need to use the less capable fbdev drivers rather than the faster nVidia drivers. My own first-generation Intel Mac Mini uses an Intel video chipset and is not affected by this problem, so it doesn't bother me, but it could be a deal-breaker for you. I've seen some suggestions that these problems are less seri

Efi Mounter For Mac