#MAC OS EFI BOOT HOW TO#
#MAC OS EFI BOOT INSTALL#
#MAC OS EFI BOOT UPDATE#
#MAC OS EFI BOOT FULL#

Make sure you have your disk and partition numbers the right way around or you may overwrite data:

#MAC OS EFI BOOT INSTALL#

If you have an external drive with a GPT partition table (OSX install stick should have it), you can clone that. As you can see, they recommend you clone an existing ESP rather than recreating the file system with newfs_msdos. The format of the EFI System Partition is documented by Apple here. This should sort out the partition itself, but as you've created an HFS partition in its place, you need to fix its format as well. Now re-add the EFI-partition with the correct layout and type gpt add -b 40 -i 1 -s 409600 -t C12A7328-F81F-11D2-BA4B-00A0C93EC93B disk0 To delete your wrong EFI-partition enter: gpt remove -i 1 disk0 To manipulate the GPT you have to unmount all mounted volumes on disk0 (first the CoreStorage volume, which has its own disk identifier disk2 but resides on disk0, then disk0): diskutil unmountDisk disk2 The partition with the index number 1 is the wrong formatted EFI-partition, the partition with index number 2 is your CoreStorage partition and the partition with index number 3 is your Recovery HD.

belong to the OS X Base System (your recovery system you booted to previously)Дisk0 is your main internal disk device containing the EFI-partition (dis0s1), the CoreStorage partition (disk0s2) and the Recovery HD (disk0s3).Дisk1 is a logical disk created by booting to the netboot image which contains a recovery system (OS X Base System = disk1s2) similar to the Recovery HD.Дisk2 is also a logical disk residing in disk0s2 and it contains the CoreStorage stack.Д®nter sudo gpt -r show disk0 Example listing: start size index contents The disk identifiers may be different then.ДЇirst you should get an overview of your disks and the partition layout:Д®nter diskutil list Example listing: /dev/disk0Дў: Apple_HFS OS X Base System *1.3 GB disk1s2

#MAC OS EFI BOOT FULL#

If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.ДЄlternatively you may start from a bootable installer thumb drive (Mavericks or Yosemite) or a thumb drive containing a full system (Mavericks or Yosemite). I recommend ethernet because it's more reliable.

On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot to a recovery netboot image which usually is loaded from an apple/akamai server.

#MAC OS EFI BOOT UPDATE#

The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated. Restart to Internet Recovery Mode by pressing alt cmd R at startup.

Detach any external drive (especially your external Time Machine backup drive).

Check all the warnings there before proceeding. I have copied some of the steps of the accepted answer.

#MAC OS EFI BOOT HOW TO#

Here is a similar question: How to fix broken EFI partition?. Since you have to modify your current start device you need to boot to Internet Recovery Mode or an external (thumb) drive.ДЄdditionally you need a valid EFI-partition or an image file of it. You can recreate the EFI System Partition (ESP) using the command-line tool gpt. If you want to start up your computer with this disk or include it in a RAID set, back up your data and partition this disk. This disk doesnвЂ™t contain an EFI system partition. I get the following error and cannot start Bootcamp after accidentally deleting the EFI-partition of my main drive.

Mac os efi boot