first-boot

#! /bin/bash
# Copyright 2013 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Run initialization code the first time this image boots on a given instance.

declare -r INSTANCE_FILE=${PREFIX}/var/lib/google/vm-instance-id
declare -r LOCK_FILE=${INSTANCE_FILE}.lock

mkdir -p ${PREFIX}/var/lib/google/
mkdir -p ${PREFIX}/var/lib/google/per-instance

function log() {
  if [[ -x ${PREFIX}/usr/bin/logger ]]; then
    echo $* | ${PREFIX}/usr/bin/logger -t first-boot -p auth.info
  else
    echo $* >&2
  fi
}

function get_instance_id() {
  # Do not retry to get the metadata value on failures.
  MDS_TRIES=1 ${PREFIX}/usr/share/google/get_metadata_value instance-id 2>/dev/null
}

# Output the instance id.
# Returns 1 if the instance id hasn't changed, 0 if it has.
function update_instanceid_on_disk() {
  local readonly instanceid=$1

  if [[ "${instanceid}" == "" ]]; then
    # Cannot determine instance id.  Either we're not running on a Compute VM,
    # or networking hasn't started up yet, etc.
    exit 1
  fi

  if [[ "${instanceid}" != "unknown-instance" &&
        "${instanceid}" == "$(cat ${INSTANCE_FILE} 2>/dev/null)" ]]; then
    # Instance id is same as on disk.
    exit 1
  fi

  # We are booting this instance for the first time.
  echo ${instanceid} > ${INSTANCE_FILE}
  exit 0
}

# This uses a subshell, opens LOCK_FILE on FD 200, locks it, and then
# checks whether the instance has changed.
function sync_new_instance_check() {
  local instanceid=$(get_instance_id)
  (flock 200; update_instanceid_on_disk ${instanceid}) 200> ${LOCK_FILE}
  return $?
}

sync_new_instance_check
if [[ $? != 0 ]]; then
  # The instance hasn't changed.  Just exit.
  exit 0
fi

#####################################################################
# If the instance hasn't changed, we have now exited this script.
# Since the instance changed, we have to do a bunch of work.
#####################################################################

log "Running first-boot"

declare -r INSTANCE_ID=$(cat ${INSTANCE_FILE})

# Regenerate host keys for ssh.
if [[ -x ${PREFIX}/usr/share/google/regenerate-host-keys ]]; then
  ${PREFIX}/usr/share/google/regenerate-host-keys
fi

# Make a per-instance data directory.
mkdir -p ${PREFIX}/var/lib/google/per-instance/${INSTANCE_ID}

# Run system updates.
if [[ -f ${PREFIX}/etc/lsb-release ]]; then
  # Update packages for apt-get.
  if [[ -x ${PREFIX}/usr/bin/apt-get ]]; then
    ${PREFIX}/usr/bin/apt-get -q -y --force-yes update
  fi
fi