From ddff3faba3d9d6461a28ef1369b388282775331d Mon Sep 17 00:00:00 2001
From: Gauthier Jolly <gauthier.jolly@canonical.com>
Date: Thu, 9 Oct 2025 12:14:32 +0200
Subject: [PATCH] cpc/UEFI: set the right partition type for the rootfs

To make our disk images more discoverable, we should use the correct
partition type for the root filesystem. This aligns with the
Discoverable Disk Image (DDI) specification developed by the UAPI
group[1] and makes our images more self-describing, e.g. with fdisk,
before:

Device         Start     End Sectors  Size Type
/dev/nbd0p1  2324480 7339998 5015519  2.4G Linux filesystem
...

and now after:

Device         Start     End Sectors  Size Type
/dev/nbd0p1  2324480 7339998 5015519  2.4G Linux root (x86-64)
...

[1] https://uapi-group.org/specifications/specs/discoverable_partitions_specification/
---
 live-build/functions                          | 40 +++++++++++++++++++
 .../hooks.d/base/disk-image-ppc64el.binary    |  4 +-
 .../hooks.d/base/disk-image-uefi.binary       |  7 +++-
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/live-build/functions b/live-build/functions
index a4b27bd0..4a2c57f7 100644
--- a/live-build/functions
+++ b/live-build/functions
@@ -1404,3 +1404,43 @@ EOF
 EOF
     fi
 }
+
+# Determine the appropriate partition type UUID for the root filesystem
+# based on the architecture.
+# Please see https://uapi-group.org/specifications/specs/discoverable_partitions_specification/
+# for where the GUIDs come from.
+gpt_root_partition_uuid() {
+    local ARCH="$1"
+
+    if [ -z "${ARCH:-}" ]; then
+        echo "usage: gpt_root_partition_uuid <arch>"
+        exit 1
+    fi
+
+    case "${ARCH}" in
+        "amd64")
+            ROOTFS_PARTITION_TYPE="4f68bce3-e8cd-4db1-96e7-fbcaf984b709"
+            ;;
+        "arm64")
+            ROOTFS_PARTITION_TYPE="b921b045-1df0-41c3-af44-4c6f280d3fae"
+            ;;
+        "armhf")
+            ROOTFS_PARTITION_TYPE="69dad710-2ce4-4e3c-b16c-21a1d49abed3"
+            ;;
+        "riscv64")
+            ROOTFS_PARTITION_TYPE="72ec70a6-cf74-40e6-bd49-4bda08e8f224"
+            ;;
+        "ppc64el")
+            ROOTFS_PARTITION_TYPE="c31c45e6-3f39-412e-80fb-4809c4980599"
+            ;;
+        "s390x")
+            ROOTFS_PARTITION_TYPE="5eead9a9-fe09-4a1e-a1d7-520d00531306"
+            ;;
+        *)
+            echo "Unsupported architecture: ${ARCH}"
+            exit 1
+            ;;
+    esac
+
+    echo "${ROOTFS_PARTITION_TYPE}"
+}
\ No newline at end of file
diff --git a/live-build/ubuntu-cpc/hooks.d/base/disk-image-ppc64el.binary b/live-build/ubuntu-cpc/hooks.d/base/disk-image-ppc64el.binary
index 50fe4522..701b8604 100755
--- a/live-build/ubuntu-cpc/hooks.d/base/disk-image-ppc64el.binary
+++ b/live-build/ubuntu-cpc/hooks.d/base/disk-image-ppc64el.binary
@@ -24,7 +24,9 @@ create_partitions() {
     sgdisk "${disk_image}" \
         --new=2::+8M \
         --new=1:
-    sgdisk "${disk_image}" -t 2:4100
+    sgdisk "${disk_image}" \
+        -t 2:4100 \
+        -t 1:"$(gpt_root_partition_uuid $ARCH)"
     sgdisk "${disk_image}" \
         --print
 }
diff --git a/live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary b/live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary
index fccccb99..cfe8ca3a 100755
--- a/live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary
+++ b/live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary
@@ -41,7 +41,8 @@ create_partitions() {
                    --typecode=15:ef00 \
                    --new=13::1G \
                    --typecode=13:ea00 \
-                   --new=1:
+                   --new=1: \
+                   --typecode=1:"$(gpt_root_partition_uuid $ARCH)"
             ;;
         riscv64)
             sgdisk "${disk_image}" \
@@ -51,6 +52,7 @@ create_partitions() {
                    --new=15::+106M \
                    --typecode=15:ef00 \
                    --new=1:: \
+                   --typecode=1:"$(gpt_root_partition_uuid $ARCH)" \
                    --attributes=1:set:2
             ;;
         amd64)
@@ -62,7 +64,8 @@ create_partitions() {
                    --new=1::
             sgdisk "${disk_image}" \
                    -t 14:ef02 \
-                   -t 15:ef00
+                   -t 15:ef00 \
+                   -t 1:"$(gpt_root_partition_uuid $ARCH)"
             ;;
     esac
     sgdisk "${disk_image}" \