Mounting EFS to CoreOS instances with the matching zone DNS endpoint automatically

coreos-efs-zone-aware

#cloud-config
write_files:
  - path: /etc/conf.d/nfs
    permissions: '0644'
    content: |
      OPTS_RPC_MOUNTD=""
coreos:
  units:
    - name: rpc-statd.service
      command: start
      enable: true
    - name: mnt-efs.mount
      content: |
        [Mount]
        What=AZ_ZONE.fs-[EFS-ID].efs.eu-west-1.amazonaws.com:/
        Where=/mnt/efs
        Type=nfs
    - name: efs-az.service
      command: start
      content: |
         [Unit]
         Description=mount EFS in this AZ
         [Service]
         Type=oneshot
         ExecStart=/bin/sh -c "AZ_ZONE=$(curl -L http://169.254.169.254/latest/meta-data/placement/availability-zone); sed -i \"s/AZ_ZONE/$AZ_ZONE/\" /etc/systemd/system/mnt-efs.mount; systemctl daemon-reload; systemctl restart mnt-efs.mount"