Add read only flag to mount_gpt_image

mount_gpt_image.sh

 #!/bin/bash
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Helper script that mounts chromium os image from a device or directory
 # and creates mount points for /var and /usr/local (if in dev_mode).
 
 . "$(dirname "$0")/common.sh"
 
 # For functions related to gpt images.
 . "$(dirname "$0")/chromeos-common.sh"
 locate_gpt
 
 get_default_board
 
 # Flags.
 DEFINE_string board "$DEFAULT_BOARD" \
   "The board for which the image was built." b
+DEFINE_boolean read_only $FLAGS_FALSE \
+  "Mount in read only mode -- skips stateful items."
 DEFINE_boolean unmount $FLAGS_FALSE \
   "Unmount previously mounted dir." u
 DEFINE_string from "/dev/sdc" \
   "Directory containing image or device with image on it" f
 DEFINE_string image "chromiumos_image.bin"\
   "Name of the bin file if a directory is specified in the from flag" i
 DEFINE_string "rootfs_mountpt" "/tmp/m" "Mount point for rootfs" "r"
 DEFINE_string "stateful_mountpt" "/tmp/s" \
     "Mount point for stateful partition" "s"
 DEFINE_string "esp_mountpt" "" \
     "Mount point for esp partition" "e"
 DEFINE_boolean most_recent ${FLAGS_FALSE} "Use the most recent image dir" m
 
 # Parse flags
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 
 # Die on error
 set -e
 
 # Common unmounts for either a device or directory
 function unmount_image() {
   echo "Unmounting image from ${FLAGS_stateful_mountpt}" \
       "and ${FLAGS_rootfs_mountpt}"
   # Don't die on error to force cleanup
   set +e
   # Reset symlinks in /usr/local.
-  setup_symlinks_on_root "/usr/local" "/var" \
-    "${FLAGS_stateful_mountpt}"
-  fix_broken_symlinks "${FLAGS_rootfs_mountpt}"
+  if mount | grep "${FLAGS_rootfs_mountpt} (rw,bind)"; then
+    setup_symlinks_on_root "/usr/local" "/var" \
+      "${FLAGS_stateful_mountpt}"
+    fix_broken_symlinks "${FLAGS_rootfs_mountpt}"
+  fi
   sudo umount "${FLAGS_rootfs_mountpt}/usr/local"
   sudo umount "${FLAGS_rootfs_mountpt}/var"
   if [[ -n "${FLAGS_esp_mountpt}" ]]; then
     sudo umount -d "${FLAGS_esp_mountpt}"
   fi
   sudo umount -d "${FLAGS_stateful_mountpt}"
   sudo umount -d "${FLAGS_rootfs_mountpt}"
   set -e
 }
 
 function get_usb_partitions() {
-  sudo mount "${FLAGS_from}3" "${FLAGS_rootfs_mountpt}"
-  sudo mount "${FLAGS_from}1" "${FLAGS_stateful_mountpt}"
+  local ro_flag=""
+  [ ${FLAGS_read_only} -eq ${FLAGS_TRUE} ] && ro_flag="-o ro"
+
+  sudo mount ${ro_flag} "${FLAGS_from}3" "${FLAGS_rootfs_mountpt}"
+  sudo mount ${ro_flag} "${FLAGS_from}1" "${FLAGS_stateful_mountpt}"
   if [[ -n "${FLAGS_esp_mountpt}" ]]; then
-    sudo mount "${FLAGS_from}12" "${FLAGS_esp_mountpt}"
+    sudo mount ${ro_flag} "${FLAGS_from}12" "${FLAGS_esp_mountpt}"
   fi
 }
 
 function get_gpt_partitions() {
   local filename="${FLAGS_image}"
 
   # Mount the rootfs partition using a loopback device.
   local offset=$(partoffset "${FLAGS_from}/${filename}" 3)
-  sudo mount -o loop,offset=$(( offset * 512 )) "${FLAGS_from}/${filename}" \
-    "${FLAGS_rootfs_mountpt}"
+  local ro_flag=""
+  [ ${FLAGS_read_only} -eq ${FLAGS_TRUE} ] && ro_flag="-o ro"
+
+  sudo mount ${ro_flag} -o loop,offset=$(( offset * 512 )) \
+    "${FLAGS_from}/${filename}" "${FLAGS_rootfs_mountpt}"
 
   # Mount the stateful partition using a loopback device.
   offset=$(partoffset "${FLAGS_from}/${filename}" 1)
-  sudo mount -o loop,offset=$(( offset * 512 )) "${FLAGS_from}/${filename}" \
-    "${FLAGS_stateful_mountpt}"
+  sudo mount ${ro_flag} -o loop,offset=$(( offset * 512 )) \
+    "${FLAGS_from}/${filename}" "${FLAGS_stateful_mountpt}"
 
   # Mount the stateful partition using a loopback device.
   if [[ -n "${FLAGS_esp_mountpt}" ]]; then
     offset=$(partoffset "${FLAGS_from}/${filename}" 12)
-    sudo mount -o loop,offset=$(( offset * 512 )) "${FLAGS_from}/${filename}" \
-      "${FLAGS_esp_mountpt}"
+    sudo mount ${ro_flag} -o loop,offset=$(( offset * 512 )) \
+      "${FLAGS_from}/${filename}" "${FLAGS_esp_mountpt}"
   fi
 }
 
 # Mount a gpt based image.
 function mount_image() {
   mkdir -p "${FLAGS_rootfs_mountpt}"
   mkdir -p "${FLAGS_stateful_mountpt}"
   if [[ -n "${FLAGS_esp_mountpt}" ]]; then
     mkdir -p "${FLAGS_esp_mountpt}"
   fi
 
   # Get the partitions for the image / device.
   if [ -b ${FLAGS_from} ] ; then
     get_usb_partitions
   else
     get_gpt_partitions
   fi
 
   # Mount directories and setup symlinks.
   sudo mount --bind "${FLAGS_stateful_mountpt}/var" \
     "${FLAGS_rootfs_mountpt}/var"
   sudo mount --bind "${FLAGS_stateful_mountpt}/dev_image" \
     "${FLAGS_rootfs_mountpt}/usr/local"
   # Setup symlinks in /usr/local so you can emerge packages into /usr/local.
-  setup_symlinks_on_root "${FLAGS_stateful_mountpt}/dev_image" \
-    "${FLAGS_stateful_mountpt}/var" "${FLAGS_stateful_mountpt}"
+
+  if [ ${FLAGS_read_only} -eq ${FLAGS_FALSE} ]; then
+    setup_symlinks_on_root "${FLAGS_stateful_mountpt}/dev_image" \
+      "${FLAGS_stateful_mountpt}/var" "${FLAGS_stateful_mountpt}"
+  fi
   echo "Image specified by ${FLAGS_from} mounted at"\
     "${FLAGS_rootfs_mountpt} successfully."
 }
 
 # Find the last image built on the board.
 if [ ${FLAGS_most_recent} -eq ${FLAGS_TRUE} ] ; then
   IMAGES_DIR="${DEFAULT_BUILD_ROOT}/images/${FLAGS_board}"
   FLAGS_from="${IMAGES_DIR}/$(ls -t ${IMAGES_DIR} 2>&-| head -1)"
 fi
 
 # Turn path into an absolute path.
 FLAGS_from=`eval readlink -f ${FLAGS_from}`
 
 # Perform desired operation.
 if [ ${FLAGS_unmount} -eq ${FLAGS_TRUE} ] ; then
   unmount_image
 else
   mount_image
 fi