== Some plans for migrating my workstation from MBR booting to UEFI

Today [[I finally assembled
https://twitter.com/thatcks/status/951914892566695936]] the machine
that is to be [[my new office workstation WorkMachine2017]], although
I wasn't anywhere near brave enough to change over to using it on
a Friday. For the most part I expect the change over to be pretty
straightforward, because I'm just going to transplant all of my
current disks into it (and then I'll have to make sure the network
interface gets the right name, although [[I have a plan
https://twitter.com/thatcks/status/952033467214258177]]). However,
I want to switch my Fedora install from its current MBR based booting
to UEFI booting (probably with Secure Boot turned on), because it
seems pretty clear that UEFI booting is the way of the future ([[my
toe-stubbing not withstanding Fedora27SecureBootMistake]]).

My current set of [[SSD root disks SSDRootDilemma]] are partitioned
with GPT and have an [[EFI system partition
https://en.wikipedia.org/wiki/EFI_system_partition]], although the
partition is unused and unmounted; while I have a _/boot/efi_
directory with some stuff in it, that's part of _/boot_ and the
root filesystem. In order to switch over to UEFI booting, I think
I need to arrange for the EFI system partition to take over
_/boot/efi_, get populated with the necessary contents (whatever
they are), and then set up [[an UEFI boot entry or two
../tech/UEFIBootThings]]. But the devil is in the details.

Currently I have the machine set up with a Fedora 27 install on a
scratch disk, so I can run burnin tests and similar things. This
helpfully gives me a live Linux that I can poke around on and save
things from, although it also means that I have pre-existing UEFI
boot entries that are going to become invalid the moment I remove
the scratch disk.

So I think that what I want to do is something like this:

# Copy all of _/boot/efi_ from the current scratch install to an
  accessible place, so I can look at it easily in case I need to.
# Make sure that I have all of the necessary and relevant EFI
  packages installed on my machine. Based on the scratch install's
  package list, I'm definitely missing some (eg grub2-efi-x64), but
  I'm not sure if all of them are essential (eg mactel-boot). I
  might as well install everything, though.

  (It appears that all files in _/boot/efi_ on my scratch install
  are owned by RPMs, which is what I'd hope.)

# Turn off Secure Boot in the new machine's BIOS and enable MBR
  booting. My motto is 'one problem at a time', so I'd like to move
  my disks over to the new machine and sort out the inevitable
  problems without also having to wrangle the UEFI boot transition.

# Figure out the right magic way to format my existing EFI system
  partition in the EFI-proper way, because apparently I never did
  that. Naturally, [[Arch's wiki has good information
  https://wiki.archlinux.org/index.php/EFI_System_Partition#Format_the_partition]].
# Mount the EFI system partition somewhere, copy all of my current
  _/boot/efi_ to it, and shuffle things around so it becomes
  _/boot/efi_.
# Either copy my current _grub.cfg_ to _/boot/efi/EFI/fedora_ and
  edit it up or try to (re)generate a completely new one through
  some magic command. Probably I should start with what
  grub2-mkconfig produces when run from scratch and see how
  different it is from my current one (hopefully it can be persuaded
  to produce an EFI-based configuration even though my system was
  MBR booted).

# Set up a UEFI boot entry for Fedora on my EFI system partition.
  [[As I found out Fedora27SecureBootMistake]], this should boot
  _shimx64.efi_. I'm inclined to try to do this by modifying the
  existing 'Fedora' boot entry instead of deleting it and recreating
  it; in theory probably the only thing that needs to change is the
  partition GUID for the EFI system partition.

Assuming that I got everything right, at this point I should be
able to boot my machine through UEFI instead of through MBR booting.
I'm not sure if the motherboard's BIOS defaults to UEFI boot or if
I'll have to use the boot menu, but either way I can test it. If
the UEFI boot works I can turn on Secure Boot, at which point I
will be UEFI-only.

I think the most likely failure point is getting a working UEFI
_grub.cfg_. Grub2-mkconfig somehow knows whether or not you're using
UEFI (and there doesn't seem to be any command line option to control
this), plus my current _grub.cfg_ is fairly different from what the
Fedora 27 grub2-mkconfig generates in things like what grub2 modules
get loaded. Perhaps this is a good time to figure out and write
down what sort of changes I want to make to the stock grub2-mkconfig
result, or perhaps I should just abandon having a custom version
in general.

(I don't think my custom version is doing anything vital; it's just
got a look I'm used to. And I could test a non-custom version on
my current machine.)

I have [[two system SSDs SSDRootDilemma]], so I have an EFI system
partition on the second SSD as well. In the long run I should set
up an EFI boot environment on it as well, but that can definitely
wait until I have UEFI booting working in general. I'll also need
to worry about keeping at least _grub.cfg_ in sync between the two
copies. Or maybe I should just stick to having the basic EFI shell
and Grub2 boot environment present, and assume that if I have to
boot off the second SSD I'll need to glue things together by hand.

(My root filesystem is mirrored, but I obviously can't do that with
the EFI system partition. Yes, technically I might be able to get
away with it with [[the right choice of software RAID superblock
SoftwareRaidSuperblockFormats]], but no, I'm not even going to try
to go there.)