fix(build_image): Configure legacy bootloaders to set root by UUID.

Make use of the new partition UUIDs for ROOT-A and ROOT-B in the root=
kernel parameters provided by the legacy (non-kexec) bootloaders. This
makes all of our images bootable as-is without having to pass them
through image_to_vm.sh. :-D

build_library/cgpt.py

@@ -485,6 +485,26 @@ def GetNum(options, image_type, layout_filename, label):
     return '-1'
 
 
+def GetUuid(options, image_type, layout_filename, label):
+  """Returns the unique partition UUID for a given label.
+
+  Note: Only useful if the UUID is specified in the config file, otherwise
+  the value returned unlikely to be what is actually used in the image.
+
+  Args:
+    options: Flags passed to the script
+    image_type: Type of image eg base/test/dev/prod
+    layout_filename: Path to partition configuration file
+    label: Label of the partition you want to read from
+  Returns:
+    String containing the requested UUID
+  """
+
+  partitions = GetPartitionTableFromConfig(options, layout_filename, image_type)
+  partition = GetPartitionByLabel(partitions, label)
+  return partition['uuid']
+
+
 def DoDebugOutput(options, image_type, layout_filename):
   """Prints out a human readable disk layout in on-disk order.
 
@@ -557,6 +577,10 @@ def main(argv):
       'usage': ['<image_type>', '<partition_config_file>', '<label>'],
       'func': GetNum,
     },
+    'readuuid': {
+      'usage': ['<image_type>', '<partition_config_file>', '<label>'],
+      'func': GetUuid,
+    },
     'debug': {
       'usage': ['<image_type>', '<partition_config_file>'],
       'func': DoDebugOutput,

build_library/create_legacy_bootloader_templates.sh

@@ -37,6 +37,9 @@ FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 switch_to_strict_mode
 
+# Useful for getting partition UUID values
+. "${BUILD_LIBRARY_DIR}/disk_layout_util.sh" || exit 1
+
 # Only let dm-verity block if rootfs verification is configured.
 # Also, set which device mapper correspondes to verity
 dev_wait=0
@@ -63,10 +66,11 @@ verity_common="${verity_common} dm_verity.dev_wait=${dev_wait}"
 # The templates are used by the installer to populate partition 12 with
 # the correct bootloader configuration.
 if [[ "${FLAGS_arch}" = "x86" || "${FLAGS_arch}" = "amd64"  ]]; then
-  # TODO: For some reason the /dev/disk/by-uuid is not being generated by udev
-  # in the initramfs. When we figure that out, switch to root=UUID=${UUID}.
   sudo mkdir -p ${FLAGS_to}
 
+  # Get partition UUIDs from the json config
+  ROOTA="PARTUUID=$(get_uuid base ROOT-A)"
+  ROOTB="PARTUUID=$(get_uuid base ROOT-B)"
 
   # Build configuration files for pygrub/pvgrub
   GRUB_DIR="${FLAGS_to}/boot/grub"
@@ -77,11 +81,11 @@ timeout         0
 
 title           CoreOS A
 root            (hd0,0)
-kernel          /syslinux/vmlinuz.A ${common_args} root=HDROOTA cros_legacy
+kernel          /syslinux/vmlinuz.A ${common_args} root=${ROOTA} cros_legacy
 
 title           CoreOS B
 root            (hd0,0)
-kernel          /syslinux/vmlinuz.B ${common_args} root=HDROOTB cros_legacy
+kernel          /syslinux/vmlinuz.B ${common_args} root=${ROOTB} cros_legacy
 EOF
   info "Emitted ${GRUB_DIR}/menu.lst.A"
 
@@ -91,7 +95,6 @@ EOF
   sudo sh -c "cat ${GRUB_DIR}/menu.lst.A >> ${GRUB_DIR}/menu.lst.B"
   info "Emitted ${GRUB_DIR}/menu.lst.B"
 
-  # HDROOTA will be replaced in image_to_vm.sh
   sudo cp ${GRUB_DIR}/menu.lst.A ${GRUB_DIR}/menu.lst
 
   # /boot/syslinux must be installed in partition 12 as /syslinux/.
@@ -126,7 +129,7 @@ EOF
 label coreos.A
   menu label coreos.A
   kernel vmlinuz.A
-  append ${common_args} root=HDROOTA i915.modeset=1 cros_legacy
+  append ${common_args} root=${ROOTA} i915.modeset=1 cros_legacy
 EOF
   info "Emitted ${SYSLINUX_DIR}/root.A.cfg"
 
@@ -134,7 +137,7 @@ EOF
 label coreos.B
   menu label coreos.B
   kernel vmlinuz.B
-  append ${common_args} root=HDROOTB i915.modeset=1 cros_legacy
+  append ${common_args} root=${ROOTB} i915.modeset=1 cros_legacy
 EOF
   info "Emitted ${SYSLINUX_DIR}/root.B.cfg"
 

build_library/disk_layout_util.sh

@@ -112,6 +112,14 @@ get_num() {
   cgpt_py readnum "${image_type}" "${DISK_LAYOUT_PATH}" ${label}
 }
 
+get_uuid() {
+  local image_type=$1
+  local label=$2
+  get_disk_layout_path
+
+  cgpt_py readuuid "${image_type}" "${DISK_LAYOUT_PATH}" ${label}
+}
+
 check_valid_layout() {
   local image_type=$1
   get_disk_layout_path

image_to_vm.sh

@@ -145,41 +145,6 @@ fi
 TEMP_PMBR="${TEMP_DIR}"/pmbr
 dd if="${SRC_IMAGE}" of="${TEMP_PMBR}" bs=512 count=1
 
-# Setup the bootloader configs to be correct for the image type
-TEMP_ESP_MNT=$(mktemp -d)
-cleanup() {
-  safe_umount "${TEMP_ESP_MNT}"
-  rmdir "${TEMP_ESP_MNT}"
-}
-trap cleanup INT TERM EXIT
-mkdir -p "${TEMP_ESP_MNT}"
-enable_rw_mount "${TEMP_ESP}"
-sudo mount -o loop "${TEMP_ESP}" "${TEMP_ESP_MNT}"
-
-SYSLINUX_DIR=${TEMP_ESP_MNT}/syslinux
-BOOT_DIR=${TEMP_ESP_MNT}/boot
-GRUB_DIR=${BOOT_DIR}/grub
-
-# Assume that if we are booting syslinux we are fully virtualized
-sudo sed -i -e "s%HDROOTA%/dev/sda${NUM_ROOTFS_A}%g" ${SYSLINUX_DIR}/root.A.cfg
-sudo sed -i -e "s%HDROOTB%/dev/sda${NUM_ROOTFS_B}%g" ${SYSLINUX_DIR}/root.B.cfg
-
-# Update the menu.lst to be right for xen pygrub/pv-grub or just guess for
-# everything else.
-if [ "${FLAGS_format}" = "xen" ]; then
-  sudo sed -i -e "s%HDROOTA%/dev/xvda${NUM_ROOTFS_A}%g" ${GRUB_DIR}/menu.lst
-  sudo sed -i -e "s%HDROOTB%/dev/xvda${NUM_ROOTFS_B}%g" ${GRUB_DIR}/menu.lst
-else
-  sudo sed -i -e "s%HDROOTA%/dev/sda${NUM_ROOTFS_A}%g" ${GRUB_DIR}/menu.lst
-  sudo sed -i -e "s%HDROOTB%/dev/sda${NUM_ROOTFS_B}%g" ${GRUB_DIR}/menu.lst
-fi
-
-cat ${GRUB_DIR}/menu.lst  ${SYSLINUX_DIR}/root.A.cfg
-
-# Unmount everything prior to building a final image
-trap - INT TERM EXIT
-cleanup
-
 # Set up a new partition table
 PARTITION_SCRIPT_PATH=$( tempfile )
 write_partition_script "${FLAGS_disk_layout}" "${PARTITION_SCRIPT_PATH}"