Fix Windows BCD registry for common boot problems.
When you move your Windows installation to another partition or another hard disk (or SSD or NVMe), it is amazingly hard to get Windows booting again from the new disk or partition.
The reason is the byzantine construct with a BCD registry where Windows stores partition and disk UUIDs to identify the locations to read files to be booted from. This makes moving really harder than it needs to be:
- By using partition and disk UUIDs rather the filesystem UUIDs (which grub normally does), a 1:1 copy of a partition is not good enough to make Windows find it. You need to adjust the BCD.
- As BCD is a binary registry format, adjusting it is hard.
fix_boot_bcd.py BCDFILE analyzes the BCD file and searches for the
partition and disk UUIDs and checks whether these are consistent and
existing on your system. Wrong Disk UUIDs for existing parititions
UUIDs are just corrected. For non-existing parttion UUIDS, you get offered
a selection of the existing partitions and the BCD is then adjusted
according to your choices. (A backup file is created if any changes are made.)
With option -n, it does not do any changes but just lists the boot
entries and reports problems. With option -o, you can force the
script to consider partition UUIDs as invalid and ask for replacement.
You would typically run this as root on Linux with /boot/efi/Boot/BCD
for the Windows Boot Manager and with /boot/efi/EFI/Microsoft/Boot/BCD
for Windows Boot and /boot/efi/EFI/Microsoft/Recovery/BCD for
Windows Recovery Boot. (The path assumes that your EFI boot partition
is mounted at /boot/efi which is typically the case on Linux machines.)
For image files, you can use kpartx to setup device-mapper and loopback
mappings and the script will then happily process BCD entries referring
to disk and partition UUIDs from the image.
Note that it requires the reged binary (from the chntpw package)
to read and change the Windows registry entries.
To access registries, there is a little ORM-like translation tool in
class registry_dict.RegDict which behaves like a dictionary with
additional read() and write() methods that do the registry reading,
writing and translation into python data structures.
Feel free to reuse it.
Notes: The registry_dict.py helper is under Apache-2.0 license, while
the fix script fix_boot_bcd.py uses the CC-BY-SA-4.0 license. So do
not create proprietary tools nor remove credits to me from the latter.
Please note that despite all care and creating a BCD.bak backup file,
this script may damage your BCD file and render your system unbootable.
You have been warned, please use at your own risk!
This tool was inspired by Moondarker with his instructions which I found from lupoDharkael who made me aware of the original source.