Azure Windows VM Not Booting - BCD Files Missing

Hello Jon

Your VM is failing to boot due to missing or corrupted Boot Configuration Data (BCD) files (most commonly on the EFI System Partition for Generation 2 VMs, which is standard in Azure). The solution is to recreate the BCD store offline using the bcdboot command on the attached OS disk in your repair VM. This copies the necessary boot files directly from the Windows installation folder and rebuilds the BCD.

Link : https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/virtual-machines-windows-repair-boot-configuration-data

Steps to resolve perform these in your existing repair VM where the problematic OS disk is already attached as a data disk :

• Take a snapshot of the attached OS disk (if not already done) as a precaution.
• Open Command Prompt (run as Administrator).
• Double-check disk and volume numbers in every step—selecting the wrong disk could affect your repair VM. The attached OS disk is usually the one that is not the repair VM’s own system disk (confirm by size).

1.Identify the partitions on the attached OS disk:

diskpart
list disk
select disk <number of attached OS disk>
list volume

Windows volume: Look for the volume containing the \Windows folder (larger NTFS volume; note its drive letter, e.g., D:).

EFI System Partition: Small FAT32 volume (~100–500 MB), often without a drive letter and labeled “System” or similar. Note its volume number.

2.Assign a temporary drive letter to the EFI partition :

select volume <EFI volume number>
assign letter=S
exit

3.Check and repair the Windows volume file system :

chkdsk <Windows drive letter>: /f

4.Rebuild the BCD files :

bcdboot <Windows drive letter>:\Windows /s S: /f UEFI

Example: bcdboot D:\Windows /s S: /f UEFI Note: This works for Generation 2 (UEFI) VMs. If you have a rare Generation 1 (BIOS) VM, use /f BIOS and target the active boot partition instead.

5.Verify the new BCD :

bcdedit /store S:\EFI\Microsoft\Boot\BCD /enum

6.Repair the BCD references

bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {bootmgr} device partition=S:
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {bootmgr} integrityservices enable
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {default} device partition=<Windows drive letter>:
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {default} integrityservices enable
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {default} recoveryenabled Off
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {default} osdevice partition=<Windows drive letter>:
bcdedit /store S:\EFI\Microsoft\Boot\BCD /set {default} bootstatuspolicy IgnoreAllFailures

7.Remove the temporary EFI drive letter:

diskpart
select volume <EFI volume number or letter S>
remove letter=S
exit

Detach the repaired OS disk from the repair VM and re-attach it as the OS disk to the original VM (or use Azure’s az vm repair restore if you created the repair VM with Azure CLI commands).

Start the original VM and monitor boot diagnostics.

Link for BCDR concepts
https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/virtual-machines-windows-repair-boot-configuration-data

Link for offline repair
https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/os-bootmgr-missing

Automated repair
https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/repair-windows-vm-using-azure-virtual-machine-repair-commands

If the VM still fails to boot after these steps, or if you receive any specific error messages during execution , please reply with the exact output and we’ll investigate further options may include restoring from a verified snapshot or deeper disk analysis.

We’re here to help get your VM back online quickly. Let us know the results.

Thanks,
Manish.

Hello @Jon Faynleyb

I wanted to check if my last response made sense. I’d be glad to assist further or explain anything in more detail and please accept as Yes and upvote if the answer is helpful so that it can help others in the community.