From cd15b730f748e791af795fcc0632cd548dc8b91c Mon Sep 17 00:00:00 2001
From: Steve Langasek <steve.langasek@canonical.com>
Date: Thu, 28 Sep 2017 09:38:21 -0400
Subject: [PATCH] In a cloud environment, we can rely on the kernel being able
 to boot the root filesystem directly, without an initramfs; enable this when
 building minimized.

---
 live-build/ubuntu-cpc/functions               |  4 ++++
 .../ubuntu-cpc/hooks/032-disk-image.binary    | 23 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/live-build/ubuntu-cpc/functions b/live-build/ubuntu-cpc/functions
index 1cde487a..9e340149 100644
--- a/live-build/ubuntu-cpc/functions
+++ b/live-build/ubuntu-cpc/functions
@@ -273,6 +273,10 @@ replace_grub_root_with_label() {
     # Instead, we want grub to use the cloudimg-rootfs labelled disk
     CHROOT_ROOT="$1"
 
+    # If boot by partuuid has been requested, don't override.
+    if grep -q ^GRUB_FORCE_PARTUUID= $CHROOT_ROOT/etc/default/grub; then
+        return 0
+    fi
     sed -i -e "s,root=[^ ]\+,root=LABEL=cloudimg-rootfs," \
         "$CHROOT_ROOT/boot/grub/grub.cfg"
 }
diff --git a/live-build/ubuntu-cpc/hooks/032-disk-image.binary b/live-build/ubuntu-cpc/hooks/032-disk-image.binary
index 9c7d42ea..4e00649e 100755
--- a/live-build/ubuntu-cpc/hooks/032-disk-image.binary
+++ b/live-build/ubuntu-cpc/hooks/032-disk-image.binary
@@ -2,6 +2,8 @@
 
 . config/functions
 
+. /build/config/binary
+
 BOOTPART_START=
 BOOTPART_END=
 BOOT_MOUNTPOINT=
@@ -64,6 +66,8 @@ create_empty_partition "${disk_image}" "$ROOTPART" "$ROOTPART_START" -1 ext2 "$R
 
 mount_image "${disk_image}" "$ROOTPART"
 
+partuuid=$(blkid -s PARTUUID -o value "$rootfs_dev_mapper")
+
 # Copy the chroot in to the disk
 make_ext4_partition "${rootfs_dev_mapper}"
 mkdir mountpoint
@@ -111,6 +115,25 @@ if [ "${should_install_grub}" -eq 1 ]; then
         ${loop_device}
 
     rm mountpoint/tmp/device.map
+
+	if [ "$SUBPROJECT" = minimize ] && [ -n "$partuuid" ]; then
+		echo "partuuid found for root device; omitting initrd"
+		chroot mountpoint dpkg-divert --add \
+			--divert /usr/sbin/update-initramfs.divert-minimize \
+			--rename /usr/sbin/update-initramfs
+		cat > mountpoint/usr/sbin/update-initramfs <<'EOF'
+#! /bin/sh
+echo "initramfs disabled on this system.  To reenable, run:" >&2
+echo "  sudo rm -f /usr/sbin/update-initramfs" >&2
+echo "  sudo dpkg-divert --remove --rename /usr/sbin/update-initramfs" >&2
+exit 0
+EOF
+		chmod +x mountpoint/usr/sbin/update-initramfs
+		rm -f mountpoint/boot/initrd.img-*
+
+		echo "GRUB_FORCE_PARTUUID=$partuuid" >> mountpoint/etc/default/grub
+		chroot mountpoint update-grub
+	fi
 fi
 
 if [ "$ARCH" = "s390x" ]; then