EFI partition deleted Solved

  1.    #1

    EFI partition deleted


    While installing a different OS. My EFI partition was wiped and set as unallocated space. I booted up a linux live cd and partitioned the unallocated space, formatting it back to FAT32. I was able to restore grub and boot into my linux distro. Now I want to restore windows' bootloader. I have a bootable usb with windows 10 on it.

    Can I just run
    Code:
    bcdboot X:\windows
    from the install media? Or are there other steps I need to take?

    Is there some GUI recovery type tool that will do it on the install media?
      My ComputerSystem Spec

  2. topgundcp's Avatar
    Posts : 2,443
    Ubuntu14.04x64 MintMate17x64 Win10Prox64
       #2

    Boot up Windows 10 from USB. Once booted, Press SHIFT + F10 to open admin command prompt.
    Type:
    diskpart
    select disk # -----> Where # is the disk number
    select partition # -----> Where # is partition number starting from 1 left to right
    set id=C12A7328-F81F-11D2-BA4B-00A0C93EC93B override ---> need to set id for the EFI System partition
    exit

    mountvol U: /s -----> Assign letter U to the EFI System partition
    bcdboot C:\windows /s U: /f UEFI ---> make sure the drive letter for Windows 10 is C, else change the letter appropriately.
    mountvol U: /d ---> unassign letter U
    reboot the PC.
      My ComputerSystem Spec

  3.    #3

    Okay, thank you. I will give that a try. Also, I appreciate you explaining what each step does.

    topgundcp said: View Post
    set id=C12A7328-F81F-11D2-BA4B-00A0C93EC93B override ---> need to set id for the EFI System partition
    Here, are we setting the UUID of the EFI partition? I don't want to change the UUID if possible as I will have to adjust it in my Linux Distros again.
      My ComputerSystem Spec

  4. topgundcp's Avatar
    Posts : 2,443
    Ubuntu14.04x64 MintMate17x64 Win10Prox64
       #4

    Format a partition as FAT32 will not be enough. You must set the id for Windows to recognize it as EFI System partition to boot from.
      My ComputerSystem Spec

  5.    #5

    topgundcp said: View Post
    Format a partition as FAT32 will not be enough. You must set the id for Windows to recognize it as EFI System partition to boot from.
    Right, I understand that part, but am I setting the UUID of the partition with that command? Is the UUID of the EFI partition C12A7328-F81F-11D2-BA4B-00A0C93EC93B on all windows installations?

    EDIT:

    Ah, I found the doc.

    So the ID for the EFI partition has to be
    C12A7328-F81F-11D2-BA4B-00A0C93EC93B for windows to recognize it?
      My ComputerSystem Spec

  6.    #6

    @topgundcp

    When I ran 'mountvol U: /s' the EFI partition was successfully mounted, so can I skip the 'set id' part since it seems the EFI partition is already recognized?
      My ComputerSystem Spec

  7.    #7

    I ran the commands as outlined above including the 'set id' part and I am now able to boot Windows. Thank you @topgundcp!
      My ComputerSystem Spec

  8. topgundcp's Avatar
    Posts : 2,443
    Ubuntu14.04x64 MintMate17x64 Win10Prox64
       #8

    You can find out if the partition is really set to the correct ID:
    Click image for larger version. 

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      My ComputerSystem Spec

  9.    #9

    Ah, I see, should have waited another 5 minutes haha. I had looked at the PARTUUID in gdisk in Linux and it didn't match, so I assume it needed to be set anyway.
      My ComputerSystem Spec


 

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