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Thread: Questions about EFI, firmware, booting, and the possibility of bricking a macbook

  1. #1

    Member Since
    Feb 08, 2011
    Questions about EFI, firmware, booting, and the possibility of bricking a macbook
    I am using a 2007 macbook. I had been running a triple-boot using the refit bootloader, and it was working just fine. I purchased a bigger hard drive for it - a 750gb seagate momentus - and am in the process of re-installing everything on it from scratch. Refit didn't work when I installed it and upon doing some research via google, it appears that there is an issue with refit not working with newer/bigger hard drives. I came across one person who said that when he had this problem, he installed refit on the hidden EFI partition instead of the OS X partition, and that it worked then. Now, this made little sense to me, 'cause whether it's the EFI partition or the OS X partition, it's the same physical disk, and if refit has a problem with these bigger hard drives, then I don't see why installing it on a different partition should make a difference, unless the difference has to do with the EFI partition being FAT32 instead of HFS+. Regardless, I wanted to give it a shot, but I need to understand more about the EFI boot process first, because I want to avoid getting into a situation where the machine won't boot at all.

    According to what I read, in order to install refit on the EFI partition, I would have to not only bless it, but I'd have to use this -setboot parameter, which as I understand it, tells the firmware to boot the machine from the blessed file/folder on the EFI partition rather than the blessed file/folder on the OS X partition. I have also read the OS X uses the EFI partition when it performs firmware updates, and that it might get rid of the refit folder should such a firmware update take place. And so the fear is, the refit folder on the EFI partition is blessed, it somehow disappears because of a firmware update, and the next time I try to boot, I get a grey screen because the firmware is still set to boot from the EFI partition, but it can't find the refit folder and it won't be able to boot from anywhere else. So, my questions are:

    1. Is it possible that I could get into a situation where because the machine can't find any bootloader, I can't boot at all, not from any partition on the hd, not from os x dvd, not from usb, not from anywhere? Is that a possibility?

    2. If it is a possibility, then wouldn't the only solutions be to either find a way to set the firmware to boot from the OS X partition again, or to find a way to copy the refit folder back to the EFI partition?

    3. Also, if #1 is a possibility, then how did the macbook boot (from os x dvd) in the first place when the hard drive was completely blank and newly installed in the machine, and there's no bootloader file to point to? I don't really understand EFI as much as I want to.

    I basically just want to know if installing refit on the EFI partition would in any way open my macbook up to getting bricked. I normally wouldn't even want to use the EFI partition at all, but I want to use refit, and apparently there's an issue with it and bigger hard drives, and someone said it would work if installed on the EFI partition. I haven't done anything yet, I just want to know what the risks are and how big they are so I can decide if it's worth it to try.

    Ok, I realize that's a lot of information, I'm sorry for not being more concise, but any assistance is appreciated.

  2. #2

    Member Since
    Feb 08, 2011
    Anyone? I could really use some help...

  3. #3

    chscag's Avatar
    Member Since
    Jan 23, 2008
    Keller, Texas
    Your questions are probably beyond the scope of what advice these forums can provide and much too complex to try to answer without more research.

    The only reason I'm replying is that I'm familiar with rEFIt having used it several times for dual boot scenarios. Personally, if it were me, I would not attempt to place rEFIt on the EFI partition. As you may already know, the partition is very small to begin with (200 MB) and is used for firmware updates. I doubt your 2007 MacBook will ever need a firmware update but there is always a possibility that you could "brick" the machine in the process of placing rEFIt on the EFI partition.

    I wasn't aware that rEFIt had a problem with larger hard drives. Where did you get that information from? And have you been in contact with the rEFIt developers to make sure that is the case?

    Sorry I can't be of more help on this. My advice is to try to get in touch with the rEFIt folks and see if they can offer any help. I understand that rEFIt is an open source project and the developers are part timers, but you never know.

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