Add an option to specify an alternative NIC for image_to_live.sh

host/image_to_live.sh

 #!/bin/bash
 
 # Copyright (c) 2009-2010 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.
 
 # Script to update an image onto a live running ChromiumOS instance.
 . $(dirname "$(readlink -f "$0")")/outside_chroot_common.sh ||
   SCRIPT_ROOT=/usr/lib/crosutils
 
 . "${SCRIPT_ROOT}/common.sh" ||
   (echo "Unable to load common.sh" && false) ||
   exit 1
 
 . "${SCRIPT_ROOT}/remote_access.sh" || die "Unable to load remote_access.sh"
 
 # Flags to control image_to_live.
 DEFINE_boolean ignore_hostname ${FLAGS_TRUE} \
   "Ignore existing AU hostname on running instance use this hostname."
 DEFINE_boolean ignore_version ${FLAGS_TRUE} \
   "Ignore existing version on running instance and always update."
+DEFINE_string netdev "eth0" \
+  "The network device to use for figuring out hostname. \
+   This is useful on hosts with multiple NICs."
 DEFINE_string server_log "dev_server.log" \
   "Path to log for the devserver."
 DEFINE_boolean update "${FLAGS_TRUE}" \
   "Perform update of root partition."
 DEFINE_boolean update_known_hosts ${FLAGS_FALSE} \
   "Update your known_hosts with the new remote instance's key."
 DEFINE_string update_log "update_engine.log" \
   "Path to log for the update_engine."
 DEFINE_string update_url "" "Full url of an update image."
 DEFINE_boolean verify ${FLAGS_TRUE} "Verify image on device after update."
@@ skipping 53 matching lines @@
 # some targets may have dns resolution issues trying to contact back
 # to us.
 function get_hostname {
   local hostname
   # Try to parse ifconfig for ip address. Use sudo, because not all distros
   # allow a common user to call ifconfig.
   # TODO(zbehan): What if target is not connected via eth0? Update over wifi?
   # Dedicated usb NIC? Perhaps this detection should be done in the target,
   # which will get the return address in one way or another. Or maybe we should
   # just open a ssh tunnel and use localhost.
-  hostname=$(/sbin/ifconfig eth0 |
+  hostname=$(/sbin/ifconfig ${FLAGS_netdev} |
       grep 'inet addr' |
       cut -f2 -d':' |
       cut -f1 -d' ')
 
   # Fallback to $HOSTNAME if that failed
   [ -z "${hostname}" ] && hostname=${HOSTNAME}
 
   echo ${hostname}
 }
 
@@ skipping 314 matching lines @@
     local release_description=$(echo ${REMOTE_OUT} | cut -d '=' -f 2)
     info "Update was successful and rebooted to $release_description"
   fi
 
   print_time_elapsed
 
   exit 0
 }
 
 main $@