Booting drives

UEFI, the modern replacement for the BIOS, should make things much cleaner. Instead of relying on a Master Boot Record to point to a bootloader on a disk (you can’t fit a whole one in the 440 bytes provided), UEFI uses a FAT32 partition to store EFI images to do much the same thing. There should only ever be one such partition (even if you have multiple drives), and as OSes are installed they can add their own EFI images to this partition. Which OS to boot can be selected from the UEFI interface, so there should no longer be any issues with one OS depriving you of access to others, even if they’re located on the same drive.

When it first appeared, UEFI was much maligned, in part because it allows Secure Boot, which can restrict which OSes (or even kernels) can be booted. This is actually a good thing, as it can prevent rootkits and so on, and if you want to get your hands dirty you can even use it to only boot your own signed kernel images. But (unless you know where to turn it off) it can also prevent you booting a non-Windows OS. You’ll need to disable Secure Boot to boot the Pop!_OS ISO file, although some distros do support it. Unfortunately despite being an open standard (albeit a very complicated one) manufacturers sometimes produce buggy UEFI implementations that get as confused as the BIOSes they superseded. Fortunately, there are tools that can fix broken boots, such as Rescatux (www.supergrubdisk.org/rescatux/) – a whole distro dedicated to fixing things.