Why do Windows 10/11 feature updates recreate the Boot Configuration Database (BCD)?


BadAnalysis

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Hello folks,

I have a multiboot twin Windows 11 system. I've configured everthing so that both installations don't interfere with one another and I moved the EFI partition to a dedicated SSD to keep it partitioned away from anything else. For some reason, Every time there is a major update, Windows rewrite the entire BCD and ruins it. Does anybody know why this happens? It is immensely frustrating.

Thanks.
 
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Winsanity

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When Windows does a major upgrade it goes through a process of moving OS files around between partitions and boots from different locations during the reboot phases of the upgrade process, so it may end up touching the BCD store several times before it's done. Unfortunately Windows is infamously inconsiderate of multi-boot use cases so it has a unpleasant tendency to break other installed bootloader's. I've attached a diagram of the upgrade phases that shows how often it touches the BCD/boot entries, but there's more info about it here if you're interested: Windows 10 upgrade issues troubleshooting - Windows Client
 

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cereberus

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Hello folks,

I have a multiboot twin Windows 11 system. I've configured everthing so that both installations don't interfere with one another and I moved the EFI partition to a dedicated SSD to keep it partitioned away from anything else. For some reason, Every time there is a major update, Windows rewrite the entire BCD and ruins it. Does anybody know why this happens? It is immensely frustrating.

Thanks.
Yeah - this is a PITA and different to previous version W10. I have 7 Windows OSs (6 in native booting vhdx files), with Host OS being default.

Every time one of those upgrades, it sets that version to default and screws up menu order. When you reboot, it then boots into upgraded version and finishes off the upgrade.

Under W10, it did not do this but you had to manually select the OS from the boot menu. This was fine!

What intellectually challenged dipstick from MS decided it was ok to change the default OS and order just so it would automatically finish upgrade?

I tried just restoring the efi partition, which keeps resets boot menu, but unfortunately, the boot entry for the upgraded OS is no longer valid.

I use Easybcd to fix things now. Once in a while, you get a "phantom" windows boot manager entry which msconfig or easybcd do not see.
After a lot of faffing around, I found bootice could see it and you could delete it from there.

I actually tend to do the vhdx upgrades the way we used to do them via Hyper-V, as then it does not touch bcd on Host OS.
That is no good in your case as your second OS is a direct installation,

If you only use one version now and then, you could consider cloning it to a vhdx file, creating a boot entry, the upgrading via Hyper-V but that assumes you are running Pro.
 

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cereberus

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When Windows does a major upgrade it goes through a process of moving OS files around between partitions and boots from different locations during the reboot phases of the upgrade process, so it may end up touching the BCD store several times before it's done. Unfortunately Windows is infamously inconsiderate of multi-boot use cases so it has a unpleasant tendency to break other installed bootloader's. I've attached a diagram of the upgrade phases that shows how often it touches the BCD/boot entries, but there's more info about it here if you're interested: Windows 10 upgrade issues troubleshooting - Windows Client
The issue is that the behaviour of how the upgrades affect the bcd has changed between W10 and W11, and definitely a change for the worse.
 

My Computer

System One

  • OS
    Windows 10 Pro + others in VHDs
    Computer type
    Laptop
    Manufacturer/Model
    ASUS Vivobook 14
    CPU
    I7
    Motherboard
    Yep, Laptop has one.
    Memory
    16 GB
    Graphics Card(s)
    Integrated Intel Iris XE
    Sound Card
    Realtek built in
    Monitor(s) Displays
    N/A
    Screen Resolution
    1920x1080
    Hard Drives
    1 TB Optane NVME SSD, 1 TB NVME SSD
    PSU
    Yep, got one
    Case
    Yep, got one
    Cooling
    Stella Artois
    Keyboard
    Built in
    Mouse
    Bluetooth , wired
    Internet Speed
    72 Mb/s :-(
    Browser
    Edge mostly
    Antivirus
    Defender
    Other Info
    TPM 2.0

BadAnalysis

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Thanks. First and last time I try that.
 

My Computer

System One

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    Other Info
    Changes every few days :)

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