How can I repair the Windows 8 EFI Bootloader?

I've spent a lot of time trying to get my Windows 8 PC to boot again after cloning to a new SSD and try to summarise how I finally got it all working -

Firstly, boot from a UEFI Windows 8 recovery disk (CD/DVD/USB) - I found that the automated recovery process didn't find the correct Windows partition, nor when I managed to add it to BCD settings would it make it reliably bootable e.g. using BCDEDIT I got it to find and launch the Windows partition but it refused to cold boot or would not "keep" the settings after a 2nd reboot or power off.

Go into the Advanced options and run the Command Prompt.

Enter diskpart to use the DiskPart tool to ensure you have all the right partitions and to identify your EFI partition - the key thing here is that your EFI partition is formatted as FAT32:

DISKPART> sel disk 0

Disk 0 is now the selected disk.

DISKPART> list vol

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     E                       DVD-ROM         0 B  No Media
  Volume 1     C                NTFS   Partition    195 GB  Healthy    Boot
  Volume 2         WINRE        NTFS   Partition    400 MB  Healthy    Hidden
  Volume 3                      FAT32  Partition    260 MB  Healthy    System

Then assign a drive letter to the EFI partition:

DISKPART> sel vol 3

Volume 3 is the selected volume.

DISKPART> assign letter=b:

DiskPart successfully assigned the drive letter or mount point.

Exit DiskPart tool by entering exit and at the command prompt run the following:

cd /d b:\EFI\Microsoft\Boot\

bootrec /fixboot

Delete or rename the BCD file:

ren BCD BCD.bak

Use bcdboot.exe to recreate BCD store:

bcdboot c:\Windows /l en-gb /s b: /f ALL

The /f ALL parameter updates the BIOS settings including UEFI firmware/NVRAM, /l en-gb is to localise for UK/GB locale. The localisation defaults to US English, or use en-US.

Reboot and cross your fingers.

This gave me headaches. I was going in circles for a long while. There isn't a lot of reliable info about fixing UEFI/Windows 8 at the time of writing.

[EDIT]

To re-enable Hyper-V, I also had to run the following from an Administrator Command Prompt within Windows after rebooting:

bcdedit /set {default} hypervisorlaunchtype Auto
bcdedit /set {default} nx OptIn

The other answers are helpful but this is what I had to do to fix mine.

I had a 1.5 TB hard drive with Windows 7 installed on it. I then installed Windows 8 onto a 150 GB SSD I bought. The 1.5 TB hard drive failed and I could hear it making a noise, my computer would no longer start, saying "please insert system disk". I thought that the bootloader was missing as it must have been on the 1.5 TB disk. It turns out it was but the problem then was the guides I followed would not rebuild the bootloader or whatever it is called as i did not have an EFI partition on the smaller 150 GB disk (this may have existed on the failed disk), it only had 1 partition which filled the entire disk.

I did not want to lose all my data so I entered the Command Prompt by booting from my Windows 8 install USB drive (noting that you cannot boot the UEFI version of this if that appears, select to boot from the just the USB drive without the UEFI appearing before it).

Once in Command Prompt (see the other answers for instructions) you need to shrink the partition. To do this, enter the following commands, pressing Enter after each one:

diskpart

list disk

select disk 0

list partition

select partition 1

shrink desired=200 minimum=200

create partition efi

list partition

select partition 2

format fs=fat32

These commands will create the EFI partition. Double-check everything by typing list vol. You should see a 200 MB partition. You now need to assign it a letter. Do this by typing assign, then list vol again to see what letter has been assigned.

Now this is done you need to copy the boot files to this newly created partition:

bcdboot C:\Windows /l en-gb /s B: /f ALL

Note: you must replace C: with the drive letter of the partition that contains Windows, and B: with the letter assigned to the EFI partition you just created.

I also entered the following commands:

bootrec /fix

bootrec /fixmbr

These both came back successful, no idea if they really did anything but who cares. Windows is now fully recovered.


Okay, I've had time to put together a proper outline here. It's long, but it's pretty complete and should help you see what's going on.

First, one way this can happen:

  1. Your BIOS loses its settings.
  2. No problem, all that stuff's stored in the EFI partition.
  3. ...except for the SATA IDE vs AHCI setting, for obvious reasons.
  4. Were you using SATA-AHCI? You're probably using SATA-IDE now.
  5. Did you try to boot before you figured that out?
  6. If you did, it failed. Did you let Windows try to fix it?
  7. If you did, BLAM, it may very well have destroyed the Boot Configuration Database.
  8. Make sure you're using the correct SATA setting you were using last time.


Here's what you've probably done by now. IF ANY OF THIS DOES NOT MATCH, CAREFULLY EVALUATE WHETHER THIS IS IN FACT YOUR PROBLEM, and READ this for ideas but don't FOLLOW it without thinking first.

  1. You have HOPEFULLY ignored all the crap about fixing the Master Boot Record (MBR), partition table, partition flags, and other garbage that DOES NOT APPLY to an EFI boot scenario. AT ALL. At best, you would be able to completely rebuild a new, unrelated, NON-EFI boot solution. That might not be trivial, however, because:
  2. You have figured out that Windows is certain it does not have a Boot Configuration Database, but it is, unfortunately, either completely clueless or VERY certain about where it goes-- you can't quite tell which.
  3. You're aware that the boot store is normally (somewhere)\Boot\BCD and that the file is HIDDEN; view it using dir /a:hs.
  4. You've familiarized yourself a bit with BCDedit.exe and figured out that it will let you "mock up" a Boot Configuration Database in a staging file using /CreateStore (and please don't name it "BCD"), that you can explicitly use the staging file with the /Store option, that you can add a menu entry for the Windows Boot Manager using /Create {bootmgr}, and that you SHOULD be able to import it using /Import...
  5. ...but when you try to do this, you can't. You look into the /SysStore option, which sounds right, but you can't get it to use another store because it's "ambiguous". You have a hunch that it knows where the store is-- or should be-- but you can't find it.
  6. You've tried to use MountVol to mount the EFI partition, but it doesn't even show in the list, so you can't.


If ALL of that applies fairly closely to you, here is what MAY be going on:

  1. Windows can tell you're set up for EFI (you have booted the DVD via a UEFI boot, you have an EFI partition, etc.).
  2. It therefore knows WHERE TO LOOK for the BCD file-- however, it either somehow has the location wrong (not this problem, but similar) or the BCD has been deleted.
  3. Apparently, because it knows where it SHOULD be, this breaks /SysStore-- and actually, that's probably correct behavior, because otherwise you'd put it in the wrong place.
  4. As near as I can tell, MountVol deliberately hides the EFI partition (or is somehow incapable of noticing it). This prevents mounting the filesystem, which prevents finding the correct subdirectory, verifying that the database exists, etc.


So here, finally, is what you need to do about it. The good news is that it's probably a lot simpler than you're hoping by now.

  1. You do indeed have to mount the EFI partition.

    Actually, I have a hunch that's not strictly correct-- I strongly suspect the EFI partition is already mounted by some internal subsystem, which is why BCDedit gets cranky-- it doesn't see the database, but it knows where it should go. Whatever it does not have, however, is a drive letter. So-- what to do?

    Well...how far back do your DOS roots go? Do you remember the Assign command? Guess what.
  2. Start DiskPart.
  3. If you are not familiar with DiskPart, the way it basically works is a hierarchy of sets; you must select exactly one element at one level to proceed to the next. So, List Disk, and then Select Disk n where n is whatever's appropriate for you.
  4. Use List Partition and List Volume (note non-plural) to get some insight and identify your EFI partition.

    It is usually a 100MB FAT32 partition marked System. Keep in mind that your disk should be using a GPT partition table by now, so you may see quite a few partitions. Some of these are for emergency recovery-- fat lot of good they do for EFI problems, eh? Oh well.

    Notice that the EFI partition, and a few others, do not have drive letters. If you're so inclined, you can also view the GPT partition attributes, which may give you a few tangentially-related "Aha" moments as well.
  5. Select Partition n where n is the EFI partition. (I expect you could select the volume instead if you need to.)
  6. Assign. That's it. Don't specify a drive letter; just Assign.
  7. List Volume. You should now see a drive letter assigned to the EFI partition.
  8. Exit DiskPart.

    And now... a big fat warning. You will probably go directly to S: (or whatever you got from Assign) and notice a Boot partition. "AHA!" You will say. "There is no BCD file here!" First... remember that file is hidden. Second... dig around a bit more, and you will notice that while there is S:\EFI\Boot and also S:\EFI\Microsoft\Boot

    You need to check both of these for problems. S:\EFI\Boot is for the motherboard, and contains the Windows Boot LOADER (and possibly other things for other operating systems). This has this name because the motherboard has no idea if you're going to have Windows or not, and needs a fixed path that makes sense.
  9. Inspect S:\EFI\Boot. For Windows 7 Professional, 64-bit, you should see: bootx64.efi
    If you have installed an EFI shell (always a good idea), you might additionally see shellx64.efi.

    NOTE: Dual-boot Linux users using chainloader+1 WILL NOT see an extra entry here.
  10. Inspect S:\EFI\Microsoft\Boot using both dir and dir a:h. For Windows 7 Professional, 64-bit, you should see a bunch of language templates (en_US, etc.) and the following files: 
    bootmgr.efi
bootmgfw.efi
memtest.efi
BCD
BCD.Backup.001
BCD.Backup.002
    ...except that you probably don't see BCD, do you? But those backup files sure look tempting.
  11. Determine which backup file you want to use. Whatever recent changes it's missing are nowhere near as important as your ability to boot the system, so go for the one that's most intact. Probably you will see one large one and one fairly small one. The small one is already corrupt, and is an artifact of the failed repair process-- don't use it. If they're both large, use the older one. IN ANY CASE, make ADDITIONAL BACKUP COPIES OF THE BACKUPS somewhere else.
  12. Copy the backup you've decided to use to BCD.
  13. Exit the shell, shutdown cleanly, and reboot.
  14. Tell Windows to start NORMALLY. At this point, it should start.


Q: What if you don't HAVE a backup BCD?

A: Well, that really shouldn't happen. It likely means you're either in the wrong directory, support EFI but weren't actually using it, or somehow rebuilt your entire EFI partition without all of the required Windows materials (possible, especially when using multiple versions of Windows). In that case, you'll need to copy the EFI materials from the DVD, then either modify or rebuild the Boot Configuration Database using BCDedit.


Q: Can you give me an example of a scenario where BCDedit /SysStore can be used to do anything at all on an EFI system?

A: So far, no.

Anyway, hope this helps solve some problems for people, or at least gets them thinking. As a very important final point, please note that you can mount and inspect your EFI partition under Windows normally using the DiskPart: Assign technique above. You should do this at least once, to get a complete backup of your EFI partition, BEFORE you run into this kind of trouble. I recommend one backup into a subdirectory on your C: drive, and one on a USB flash drive.

Sorry that's so long-winded. I need to turn this into a proper article at some point, but there are so many people who are SO frustrated that I felt the need to document my experience as completely and rapidly as I could.

Tags:

Windows 7

Bootloader

Windows 8

Uefi

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