If I had a system that I booted in UEFI mode, I could tell you, but all of my hardware (even the ones running UEFI) boot OSs in BIOS mode.
Despite the fact that they're primarily a systemd distro, Arch Linux strongly recommends that you mount efivarfs in ro mode and remount rw when doing kernel upgrades.
GRUB2 seems to use efibootmgr to write stuff to EFI, and efibootmgr appears to lack a "detect if efivarfs is mounted ro and temporarily mount it rw" switch, so you have to do that manually too.
Gentoo's Genkernel-next doesn't seem to do anything at all with EFI.
Dracut (one of RedHat's initrd management tools) looks like it reads from efivarfs, but does not write to it. (But there's a lot of code in Dracut, so it's entirely possible I missed something.)
It's not entirely clear to me that you can't use BIOS boot with a GPT-formatted disk if your bootloader supports that sort of thing. It's also not clear to me whether or not chainloading from GRUB into Windows is supported with a BIOS/GPT partitioning scheme.
Regardless, it's a pity that the UEFI design committee apparently thought that requiring one to write data into the motherboard's persistent storage in order to boot into a OS was a reasonable thing to do.
> Despite the fact that they're primarily a systemd distro, Arch Linux strongly recommends that you mount efivarfs in ro mode and remount rw when doing kernel upgrades.
Why not leave it unmounted entirely, and only mount it when installing new boot entries?
A traditional BIOS or UEFI running in CSM requires an MBR formatted disk since the bootloader must be started from the first 512 bytes on disk. I have to boot ESXi on my ProLiant ML10 off a flash drive because my 3TB disk would become a 2TB disk otherwise.
Hybrid MBR is an extremely fragile and hackish technique to make crappy old firmware boot larger disks. In general I want my whole 3TB drive allocated to VM storage instead of partitioning it up so ESXi has somewhere to live, so just running that off an easily replaceable USB key is a lot simpler to maintain.
Despite the fact that they're primarily a systemd distro, Arch Linux strongly recommends that you mount efivarfs in ro mode and remount rw when doing kernel upgrades.
GRUB2 seems to use efibootmgr to write stuff to EFI, and efibootmgr appears to lack a "detect if efivarfs is mounted ro and temporarily mount it rw" switch, so you have to do that manually too.
Gentoo's Genkernel-next doesn't seem to do anything at all with EFI.
Dracut (one of RedHat's initrd management tools) looks like it reads from efivarfs, but does not write to it. (But there's a lot of code in Dracut, so it's entirely possible I missed something.)
It's not entirely clear to me that you can't use BIOS boot with a GPT-formatted disk if your bootloader supports that sort of thing. It's also not clear to me whether or not chainloading from GRUB into Windows is supported with a BIOS/GPT partitioning scheme.
Regardless, it's a pity that the UEFI design committee apparently thought that requiring one to write data into the motherboard's persistent storage in order to boot into a OS was a reasonable thing to do.