What is "EFI Boot"?

Question

Level 1

13 points

What is "EFI Boot"?

HGI,

I am running 2 startup drives on my MacPro. One is Leopard 10.5.8 and the other is my new WD RE3 hard drive which was just set up with a clean install of Snow Leopard. At the moment SL is designated as my startup drive... but I find that if I hold down the option key on boot to select the start-up drive one drive icon is labeled LEOPARD and the other is labeled EFI BOOT and not its drive name Snow Leopard (which is how it shows on on the desktop.

Why is the Snow Leopard drive displaying as" EFI Boot"?

MacPro 2.66, Mac OS X (10.6), 6 GB ram.. iLife 08 /Aperture / CS3 / LightZone

Posted on Aug 31, 2009 12:24 AM

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Answer 1

hassiman Author

Level 1

13 points

Aug 31, 2009 9:03 AM in response to JavaSys

When I go in and look at that disk in SL disk utilies the the disk properties show it as being a GUID partition... Would it even be possible to install SL with a clean install if it were NOT a GUID disk partition?

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Answer 2

Aug 31, 2009 5:06 PM in response to hassiman

My Snow Leopard partition was showing OK in the option screen until I used Disk Warrior 4.2 to recreate the directories.

Now it shows as EFI boot, but it boots OK and seems to work OK. (I have not found anything failing yet).

Roberto

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Answer 3

Mini-Mac

Level 3

825 points

Sep 1, 2009 11:24 AM in response to Roberto Sepúlveda

I too had this issue come up after using DW 4.2, however I put my Snow Leopard DVD in the superdrive and restarting my computer, holding down the option key and selecting SL as the startup disk. Using disk utility I repaired my disk and and now there's no sign of EFI boot, it now says Macintosh HD. This is after restarting and holding down the option key.

Not sure why DW 4.2 is changing things but something is amok in that version.

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Answer 4

manilx

Level 1

1 points

Sep 25, 2009 1:48 AM in response to Mini-Mac

I also suddenly have this problem, on my MBP my internal HD shows up as EFI boot instead of as Macintosh HD as it used to be.
I don't know when this started but I used DW 4.2 on that drive.

I booted from a clone and used DiskUtility to repair the drive, no errors shown but this problem has not been fixed.

How can I fix this?

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Answer 5

manilx

Level 1

1 points

Sep 25, 2009 2:27 AM in response to manilx

Found the fix:

http://discussions.apple.com/thread.jspa?messageID=10290097#10290097

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Answer 6

JavaSys

Level 1

5 points

Aug 31, 2009 12:56 AM in response to hassiman

You are seeing "EFI boot" due to the partition format and structure of that disk.

You need to re-partition the disk and select "GUID Partition Table" in Disk Utility (options) when doing so.

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