Windows Server 2012R2 Upgrade Rolls Back

Question

Hello, everyone…. I have a sticky upgrade mess that I just inherited.  I’m not the original server builder nor maintainer, they’re long gone.  I just took it over.  Problem is, we’re in a Unix shop and I’m a Unix expert, not a Windows expert.  Dozens of servers, only two of them are Windows, so I’m hoping for some help and advice…

 

It’s my understanding that this box originally started life as NT351 and was migrated forward over the years to NT4, 2k, 2k3, 2008 and finally 2012R2.  Yes, very old.  It’s an SMB server with the sole job of sharing files and currently hosts hundreds of millions of files.  No applications.  I’ve been tasking with upgrading to newer Windows.

 

It’s a VM hosted on ESX, 8 CPU cores, 64GB and plenty of hard drive space.  Because of the nature of the workload, I’m only afforded a few hours on Friday and Saturday night for upgrades.  Yes, I have VM snapshots so when I break it I can roll back but taking the server down for a complete reinstall and moving the data isn’t an option as they won’t give me the time.

 

I’ve tried rolling up to 2016, 2019, 2022 and now 2025.  Every flavor looks like it’s going to go smoothly and rolls through copying files and multiple reboots then finally comes to a rolling back upgrade message and reboots back to 2012R2.  When I login I met with a screen that says, “The installation failed in the SECOND_BOOT phase with an error during BOOT operation.”  It points me to a MS article that is of no help.

 

The disks are GPT and TPM is available.  I don’t know what’s going on but I’m also not a deep enough Windows users even know where to look.  Yes, I’ve googled it and even asked the AI’s but still not getting anywhere.

 

I realize this is an old unsupported version but, can anyone offer any kinds of insights as to where I might look to figure this out.  I’m at a complete loss here and would appreciate any and all help I can get!

 

Thank you in advance!

 

-brian