A utility for updating /etc/lsb-release values.

BUG=5581
TEST=updated an image, updated a device, verified /etc/lsb-release

Review URL: http://codereview.chromium.org/3145008

scripts/image_signing/common.sh

@@ -6,6 +6,7 @@
 
 # Determine script directory
 SCRIPT_DIR=$(dirname $0)
+PROG=$(basename $0)
 GPT=cgpt
 
 # Read GPT table to find the starting location of a specific partition.

scripts/image_signing/set_lsb_release.sh

@@ -0,0 +1,56 @@
+#!/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.
+
+# Customizes a Chrome OS release image by setting /etc/lsb-release values.
+
+# Usage: ./set_lsb_release.sh <image.bin> [<key> <value>]
+#
+# If executed with key/value parameters, sets <key>=<value> in
+# /etc/lsb-release and then dumps /etc/lsb-release to stdout. If
+# executed with no key/value, dumps /etc/lsb-release to stdout. Note
+# that the order of the keyvals in /etc/lsb-release may not be
+# preserved.
+
+# Load common constants and variables.
+. "$(dirname "$0")/common.sh"
+
+set_lsb_release_keyval() {
+  local rootfs=$1
+  local key=$2
+  local value=$3
+  echo "Setting '$key' to '$value'..."
+  local temp_lsb_release="$rootfs/etc/temp-lsb-release"
+  echo "$key=$value" | sudo tee "$temp_lsb_release" > /dev/null
+  grep -Ev "^$key=" "$rootfs/etc/lsb-release" \
+    | sudo tee -a "$temp_lsb_release" > /dev/null
+  sudo mv -f "$temp_lsb_release" "$rootfs/etc/lsb-release"
+}
+
+main() {
+  set -e
+
+  local image=$1
+  local key=$2
+  local value=$3
+  if [ $# -ne 1 ] && [ $# -ne 3 ]; then
+    echo "Usage: $PROG <image.bin> [<key> <value>]"
+    exit 1
+  fi
+
+  local rootfs=$(mktemp -d)
+  mount_image_partition "$image" 3 "$rootfs"
+  trap "sudo umount -d $rootfs; rm -rf $rootfs" EXIT
+  if [ -n "$key" ]; then
+    set_lsb_release_keyval "$rootfs" "$key" "$value"
+    touch "$image"  # Updates the image modification time.
+  fi
+  echo ===
+  cat "$rootfs/etc/lsb-release"
+  echo ===
+  echo Done.
+}
+
+main $@