I wanted to move my nixOS installation to a bigger SSD. After copying over the data, and creating a UEFI boot entry, it didn't show up in the boot menu. After rebooting I found the entry changed to: VenHw(99e275e7-75a0-4b37-a2e6-c5385e6c00cb) This seems to be the indication for a broken entry. In my case, the contents of the EFI partition weren't right, but this also comes up, after I disconnected the original drive UEFI systems can be programmed via the nvram.