efsaz.sh

#!/bin/bash
#
# efsaz         Set availability zone for EFS mounts in fstab
#
# chkconfig: 345 24 74
# description:  Replaces the availability zone for EFS mount points in fstab \
#               with the proper value for the current instance, which it gets \
#               from instance metadata. This script must run before the \
#               netfs script, which mounts network filesystems. It is useful \
#               in autoscaling groups, where the instance starting might \
#               be in a different AZ than the one the image was built from. \
#               DEPENDS ON curl BEING INSTALLED ON THE SYSTEM. Adjust if needed.
### BEGIN INIT INFO
# Short-Description: Set AZ for EFS mounts in fstab
# Description: Set AZ for EFS mounts in fstab
### END INIT INFO

# Uncommenting this line along with echo_success and echo_failure lines below
# on RHEL-like Linus distributions offers some pretty printing
#. /etc/init.d/functions

case "$1" in
  start)
    echo -n "Updating EFS AZ in fstab"
    # the region defined here will be replaced with the current AZ
    region="eu-west"
    efs_server={{ tal_efs_server }}
    if [[ $efs_server != *amazonaws.com* ]]; then
        # the server name is probably wrong. exit, rather than being sorry
        #echo_failure
        exit 1
    fi
    az=`curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone`
    if [[ $? -ne 0 ]]; then
        #echo_failure
        exit 2
    fi
    # 'sed -i' doesn't exist on BSD and it's not safe
    fstab_new=`cat /etc/fstab | \
        sed s/^${region}-..\.${efs_server}/${az}\.${efs_server}/`
    cp /etc/fstab /tmp/fstab.efsaz.bak
    echo "$fstab_new" > /etc/fstab
    if [[ $? -eq 0 ]]; then
        #echo_success
        #echo
        exit 0
    else
        #echo_failure
        #echo
        exit 3
    fi
  *)
    # anything else besides start will do nothing. maybe we could output
    # the relevant contents of fstab on status or something, but it's not
    # worth the effort
esac