grub: support searching for boot by UUID

[jlebon]

This adds support for a boot_uuid dropin sitting alongside both the
BIOS and EFI GRUB configs to specify the UUID to scan for instead of
relying on labels.

Part of coreos/fedora-coreos-tracker#976.

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[bgilbert]

We should make sure to test this with petitboot; cc @coreos/multi-arch

[jlebon]

Just updated the commit message on this because it was referencing the old filename. @Prashanth684 Would you be able to test this on ppc64le? Reach out to me on chat and we can work through it together.

[jlebon]

Restarted CI! There's a new coreos-installer release in FCOS which can leverage this, so would be good to get this in soon.

[jlebon]

So to test this:

1. Build cosa with this patch plus this:

diff --cc src/create_disk.sh
index 567eb048a,567eb048a..c2778e541
--- a/src/create_disk.sh
+++ b/src/create_disk.sh
@@@ -321,8 -321,8 +321,10 @@@ els
      source ${config_directory}/boot_uuid
    fi
    if [ -n "${BOOT_UUID}" ]; then
++    echo "Searching boot device by UUID"
      search --fs-uuid "${BOOT_UUID}" --set prefix --no-floppy
    else
++    echo "Searching boot device by label"
      search --label boot --set prefix --no-floppy
    fi
  fi
diff --cc src/grub.cfg
index eada7d19d,eada7d19d..215271bf5
--- a/src/grub.cfg
+++ b/src/grub.cfg
@@@ -23,8 -23,8 +23,10 @@@ els
      source ${config_directory}/boot_uuid
    fi
    if [ -n "${BOOT_UUID}" ]; then
++    echo "Searching boot device by UUID"
      search --fs-uuid "${BOOT_UUID}" --set boot --no-floppy
    else
++    echo "Searching boot device by label"
      search --label boot --set boot --no-floppy
    fi
  fi

2. Build latest FCOS + coreos-boot-edit: run rdcore bind-boot fedora-coreos-config#1316, making sure that coreos-installer v0.11.0 gets pulled in
3. Run cosa run -c
4. Verify that the bootloader says "Searching boot device by label" on first boot.
5. Run reboot in the VM
6. Verify that the bootloader says "Searching boot device by UUID" on the subsequent boot.

[Prashanth684]

So to test this:

1. Build cosa with this patch plus this:

diff --cc src/create_disk.sh
index 567eb048a,567eb048a..c2778e541
--- a/src/create_disk.sh
+++ b/src/create_disk.sh
@@@ -321,8 -321,8 +321,10 @@@ els
      source ${config_directory}/boot_uuid
    fi
    if [ -n "${BOOT_UUID}" ]; then
++    echo "Searching boot device by UUID"
      search --fs-uuid "${BOOT_UUID}" --set prefix --no-floppy
    else
++    echo "Searching boot device by label"
      search --label boot --set prefix --no-floppy
    fi
  fi
diff --cc src/grub.cfg
index eada7d19d,eada7d19d..215271bf5
--- a/src/grub.cfg
+++ b/src/grub.cfg
@@@ -23,8 -23,8 +23,10 @@@ els
      source ${config_directory}/boot_uuid
    fi
    if [ -n "${BOOT_UUID}" ]; then
++    echo "Searching boot device by UUID"
      search --fs-uuid "${BOOT_UUID}" --set boot --no-floppy
    else
++    echo "Searching boot device by label"
      search --label boot --set boot --no-floppy
    fi
  fi

2. Build latest FCOS + coreos-boot-edit: run rdcore bind-boot fedora-coreos-config#1316, making sure that coreos-installer v0.11.0 gets pulled in
3. Run cosa run -c
4. Verify that the bootloader says "Searching boot device by label" on first boot.
5. Run reboot in the VM
6. Verify that the bootloader says "Searching boot device by UUID" on the subsequent boot.

tested on a p8 system and followed above steps and it works.

[jlebon]

Rebased for CI!