EFI Partition Mgmt | Wilders Security Forums

After I dodged the bullet from that Microsloth WinRE partition change in Jan2024, I’ve been watching my UEFI-GPT disk layout a little more carefully than usual.

All of a sudden, today, I noticed that I only have 1mB of space left in the DEFAULT 100mB EFI partition created from my July 2023 W10 build… I’ve never seen it that low, ever! Being a little concerned after the WinRE fiasco, I opted to extend my EFI partition by an additional 100mB… all went well.

I then decided to find out what the heck was taking up all that space in the EFI partition. LIVE Windows would not allow me to mount it for perusing/editing purposes (after all, it is an EFI partition and normal users shouldn’t be messing around in there).

I then loaded up my fav tool-based WinPE. It also would not let me mount it for the above purposes. I then used my fav partition tool and changed the ID of the EFI partition to Basic DATA Partition, after that, WinPE Windows would allow me to mount the partition.

Turns out it was full of BCD(<some sort of ID>).TM.blf and .regtrans-ms files… say What? I looked those up and basically they are BCD and REGISTRY change files for being able to revert changes, if necessary. They were dated from right after my build until a few days ago. Since I do mess with both my BCD and REGISTRY often, it appears there may be some limits to storing this stuff… I have no idea what happens if there’s not enough space to accomplish a Windows update of this partition and I don’t think I wanna find out (especially after the WinRE issue).

I then deleted all of those FileSets up to the beginning of 2024, unmounted the partition, reset the partition ID back to EFI and reBOOTed the System… all went well. Normally, on Legacy-MBR Systems, this info is managed either in the Microsoft System Reserved partition, if one exists, or in the OS partition itself. In both of those cases, those partitions are quite a bit larger than the UEFI-GPT required EFI partition (usually DEFAULTs to 100mB on a clean install) which would not offer the scare this scenario did.

My question is… do I mess around too much with my BCD and REGISTRY, or is there potential danger here with someone like me always tinkering? My expanded 200mB EFI partition should last me for a while, but does anyone know what happens when the EFI partition cannot accomplish a required Windows update?

I’ll be happy to listen to anyone with any knowlege or suggestion in this area.