Nathan Campos

Today as I was ready to get some work done on the machine I regard as the
ultimate laptop, a MacBook Air 13-inch from 2017 [1], I rebooted into rEFInd [2]
and chose my Windows partition, only to be greeted by this lovely message:

Starting bootmgfw.efi
Using load options ''
BlInitializeLibrary failed 0xc00000bb

Since it has been quite a long time since I booted into Windows, and since then
I had also installed Debian 12 on this machine, I thought that maybe it messed
with the Windows Boot Manager, which is very unlikely, but I was getting
desperate and just wanted things to work, so I tried booting into GRUB and chose
the Windows Boot Manager from there. This time the machine simply hang with no
error on GRUB's wallpaper.

With nothing else to try I decided to give up and search for the problem. The
search quickly wielded a promising result straight from Microsoft, titled "Error
(BlInitializeLibrary failed XXX) when you install or start an operating system
on a 64-bit UEFI-based computer" [3], which in its cause section describes the
problem as follows:

This problem occurs because the boot firmware on the computer generates lots
of memory fragmentation.

Right below this explanation they also give the worlds best advice ever on how
to fix it. In the section entitled workaround, this is what they expect you to
do to fix it:

We recommend that you do not let boot firmware create large amounts of
fragmentation. Large memory fragmentation degrades the overall startup
performance and causes problems.

It's literally the "have you tried not having problems" joke, but on the
official Microsoft documentation!

Eventually, after going to the second page of search results, since the first
page is always filled with SEO garbage and that amazing Microsoft KB article, I
was able to find a helpful StackExchange answer that pointed me in the right
direction [4].

This problem is apparently caused by a corrupted MBR partition on a GPT system,
something I never heard of before, I always thought GPT completely replaced the
MBR boot sector, but I guess I was wrong.

First thing to do was disable Mac OS X's System Integrity Protection (SIP) [5],
which protects you from doing dumb things with the root filesystem. Then I had
to download the amazing GPT fdisk [6] from the same guy that made rEFInd.

Upon opening GPT fdisk I was greeted with the following output:

$ sudo gdisk /dev/disk0
GPT fdisk (gdisk) version 1.0.10

Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help):

I guess I had an MBR boot sector after all, which may have been corrupted along
my triple boot adventures, so as per the StackExchange answer, I had to convert
the hybrid MBR partition table into a protective MBR. In order to do this I had
to execute the following "commands" in this order:

  1. 'x' to enter expert mode.
  2. 'n' to create a new protective MBR.
  3. 'w' to write the changes to disk.

The logs of my entire interaction with the program were as follows:

GPT fdisk (gdisk) version 1.0.10

Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): p
Disk /dev/disk0: 1000215216 sectors, 476.9 GiB
Sector size (logical): 512 bytes
Disk identifier (GUID): 2634FCB6-2B0F-4AA2-9418-B000BF96F5AB
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 1000215182
Partitions will be aligned on 8-sector boundaries
Total free space is 885 sectors (442.5 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              40          409639   200.0 MiB   EF00  EFI System Partition
   2          409640       607832063   289.6 GiB   AF0A
   3       607832064       920332063   149.0 GiB   0700
   4       920332288       998215679   37.1 GiB    8300
   5       998215680      1000214527   976.0 MiB   8200

Command (? for help): x

Expert command (? for help): n

Expert command (? for help): o

Disk size is 1000215216 sectors (476.9 GiB)
MBR disk identifier: 0x00000000
MBR partitions:

Number  Boot  Start Sector   End Sector   Status      Code
   1                     1   1000215215   primary     0xEE

Expert command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/disk0.
Warning: Devices opened with shared lock will not have their
partition table automatically reloaded!
Warning: The kernel may continue to use old or deleted partitions.
You should reboot or remove the drive.
The operation has completed successfully.

After this entire ordeal, and a reboot, I was finally able to boot back into
Windows. Although it was quite a stressful and time consuming task, I learned
a lot more about GPT through this adventure, and if this were to happen again,
I now know exactly what to do.


[1]: https://everymac.com/systems/apple/macbook-air/specs/macbook-air-core-i5-1.8-13-2017-specs.html
[2]: https://www.rodsbooks.com/refind/
[3]: https://learn.microsoft.com/en-us/troubleshoot/windows-client/setup-upgrade-and-drivers/blinitializelibrary-failed-start-os-on-64-bit-uefi-based-computer
[4]: https://apple.stackexchange.com/a/325875
[5]: https://developer.apple.com/documentation/security/disabling-and-enabling-system-integrity-protection
[6]: https://www.rodsbooks.com/gdisk/