[Bug 1396379] Re: installer uses first EFI system partition found even when directed otherwise

[Lord Enum]

So, I thought I'd take a quick look at this bug and why it's not been
fixed yet:

There's 3 parts to explore, Ubiquity itself, it's script to handle
installing grub (grub-installer) and grub-install itself.

Starting with grub-install itself, it does do something a little unexpected (to me at least) when installing to efi. When running grub-install /dev/sdb the variable that stores /dev/sdb internally is called install_device and when installing efi, that is ignored - as you can see in this code:
https://github.com/phil-opp/x86_64-grub/blob/54ad4ba67db8fd1e38068e49d3d94b88138046f8/util/grub-install.c#L1007 (<--- just the first version that came up in a search, but I assume it's the same in all grub-install.c versions)

So, grub-install relies on /boot or /boot/efi having the fat32 esp
partition mounted to it. Looking through the grub-installer it does not
do the mounting of /boot/efi itself - but it is correctly parsing the
grub partition selected in Ubiquity to grub-install (which grub-install
will not use (as explained above)). Ubiquity does the mounting - (it
creates /target when installing and then mounts the esp partition to
/target/boot/efi)

>From a quick look I believe Ubiquity creates the /boot/efi mount via writing a fstab into /target/etc as part of the install process. Long story short, I believe this is handled by 
https://git.launchpad.net/ubuntu/+source/ubiquity/tree/d-i/source/partman-efi/fstab.d/efi?h=applied/ubuntu/jammy
^ as you can see, this just searches for the first esp partition it can find, writes the fstab to mount it to /boot/efi and then finishes. Hence we get our problem that it's always the first esp partition that gets written to.

Because this is so convoluted, a fix is not immediately obvious. My own
fix is to modify grub-installer so that, just before running grub-
install, it checks if the destination is removable (i.e. a USB stick or
similar) and, if it is, adds the --removable + --no-nvram flag, unmounts
the /target/boot/efi Ubiquity set up and remounts it based on the boot
device that will be passed to grub-install. The modification to the
grub-installer script (located at /usr/shar/grub-installer) looks like:

if [ -n "$bootremovable" ]; then
   grub_install_params="$grub_install_params --removable --no-nvram"
   umount "$ROOT/boot/efi"
   bootdev_actual="$(fdisk -l | grep "$bootdev" | grep "EFI System" | cut -d' ' -f1)"
   mount "$bootdev_actual" "$ROOT/boot/efi"
fi

As this is my first ever attempt at writing anything in a shell script,
this is probably highly naive, but does work, should not have a negative
impact to other normal installs (as it only affects installing to
removables) and would stop anyone else from screwing up their Windows
partition when newbies think about trying out a Ubuntu based
distribution on a USB stick and find out, when they next reboot, that
instead of booting to Windows they get a grub prompt (typing exit in
that prompt does at least allow them to boot Windows - but still, not a
pleasant experience).

Attached is a diff that adds this against the version at:
https://git.launchpad.net/ubuntu/+source/ubiquity/plain/d-i/source/grub-
installer/grub-installer?h=applied/ubuntu/jammy


** Attachment added: "grub-installer-diff"
   https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1396379/+attachment/5597453/+files/grub-installer-diff

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https://bugs.launchpad.net/bugs/1396379

Title:
  installer uses first EFI system partition found even when directed
  otherwise

Status in grub-efi-amd64-signed package in Ubuntu:
  New
Status in ubiquity package in Ubuntu:
  Confirmed

Bug description:
  (k)ubuntu 14.04.1
  package version: 2.02~beta2-9ubuntu1

  i installed ubuntu on my external hard disk, where i also have a previously installed fedora system. i also have a windows
  (efi-booted) system in the internal hard disk.

  at install time via ubiquity i get all grub configuration files in the first EFI-labelled partition (i.e. /dev/sda2 in my case) instead of the one i selected (/dev/sdb1).
  later i changed my fstab mounting /boot/efi on /dev/sdb1 and tried to reinstall grub package (apt-get install --reinstall grub-efi-amd64); now all grub configuration files are in the rigt place, but booting from the external hard disk still shows the fedora grub installation, while selectin the internal hard disk from the bios menu shows a submenu listing ubuntu and windows.
  explicitly installing grub in the correct disk (grub-install /dev/sdb; grub-mkconfig -o /boot/efi/EFI/ubuntu/grub.cfg) has no effect, nor it has running efibootmgr (efibootmgr -c --disk /dev/sdb --part 1).

  expected results: grub shoud have been installed in the disk/partition i chose;
  actual results: ubuntu always chooses the first disk to install grub on.

  Note that this is not just about the dummy grub install location
  selector that is not used in EFI mode, but configuring one partition
  as do not use, and the other as ESP in the manual partitioning screen.

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