F21 on UEFI

[Chris Murphy]

I suggest booting live media with and without the legacy option
enabled, and compare dmesg from both boots. Check things like video
and trackpad support (if this is a laptop) and also the libata
messages for what linkage is made with the drive. This is highly
mixed, but on all of my EFI Macs, when I use the CSM-BIOS the SSD
falls back to a much slower IDE link whereas native EFI mode it uses a
SATA rev 3 link at full speed. This just really depends on the
compatibility support module being used by the firmware, it's not a
kernel thing.

Certainly in the short term it's fine to use the legacy option, but
I'd say better than even odds you'll eventually want to reinstall the
OS with the legacy option disabled. There is a way to do a conversion
but it's tricky and not exactly documented anywhere as far as I know.
MBR>GPT, create ~100-500 MB ESP somewhere, install efibootmgr, shim
and grub2-efi packages, update fstab, run grub2-mkconfig, change grub
symlink to point to new grub.cfg location so grubby can find it, run
dracut, and that ought to just about do it.


Chris Murphy