Deleted EFI!

Discussion in 'macOS' started by wdw_, Jul 15, 2011.

  1. wdw_ macrumors regular


    Aug 18, 2002
    I didn't know what it was. I thought it had been created when I installed Lion DP4 on a separate partition, like the recovery partition..anyway, I went to delete Lion and it's partitions and I deleted EFI with it, only now realizing my stupid mistake.

    I found an article on how to make a new one, but it's from 2006 and the numbers he's citing don't match up with my system. Here's the article:

    He says my boot HD should start at block 409640 but it starts at 409636. Small difference. But then he refers to the bootHD as rdisk0 and mine is rdisk1. Is this normal?

    I'm really more of a GUI guy, but I can follow instructions. If someone knows how to do this, please....HELP ME!!!! thx.
  2. maflynn Moderator


    Staff Member

    May 3, 2009
    If you're data is backed up, why not create a single GUID partition in Disk Utility to reload OSX on. I've added/deleted and modified EFI partitions before if I wanted to get it back to factory fresh conditions, thats what I did.

    You'll need to boot off your OSX install disk to do that but it should work

    btw, deleting something you didn't know what it was is perhaps not the smartest approach to computers ;)
  3. wdw_ thread starter macrumors regular


    Aug 18, 2002
    Well I've made and deleted partitions before. But I guess it's been a while as I wasn't aware of the EFI partition. And yeah, I didn't know what it was, but I thought it was part of Lion, which I was deleting at the time. I've just gone back down to one partition so many times over the years, it didn't seem unnatural.

    I don't know how I didn't know about the EFI parition....well.. wait. I did get my HDD replaced after it crashed last year. I think it used to be a different partition map scheme. It used to be APM. But when the repair people put in a new one they probably formatted it with with GUID, which I also wasn't aware of. That must be why I've never seen that EFI partition.

    Anyway, I thought about reformatting last night before I posted, but most of my data isn't backed up. The stuff I wouldn't want to lose is backed up, but I have music and movies (which I could find again) but take up a lot of space. And I don't want to trash em.

    I maybe have enough HDDs around here to evacuate if I must, but I'd really like to just remake the EFI partition. Seems like it's possible and not too hard. I just need a little help with that article and the problems I had with it, or some other way of remaking the EFI partition.

    Thanks for your help, but reformatting is my last resort.
  4. wdw_ thread starter macrumors regular


    Aug 18, 2002
    Well, if anyone comes here looking for an answer, I managed to make a new EFI partition using iPartition. I installed the latest version on another mac, rebooted my iMac into target disk mode and of course connected the two via firewire, and made a new, 200mb, EFI formatted partition at the beginning of the disk. It's a as good as new, and Lion installed fine.

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