post_install() {
  if [ ! -d '/var/lib/postgres' ]; then
    mkdir -p '/var/lib/postgres'
  fi
  if ! getent group postgres >/dev/null; then
    groupadd -g 88 postgres
  fi
  if ! getent passwd postgres >/dev/null; then
    useradd -c 'PostgreSQL user' -u 88 -g postgres -d '/var/lib/postgres' -s /bin/bash postgres
    passwd -l postgres >/dev/null
  fi
  if [ ! -d '/var/lib/postgres/data' ]; then
    mkdir -p '/var/lib/postgres/data'
    chown postgres:postgres '/var/lib/postgres/data'
  fi
  local datadir="/var/lib/postgres/data"
  echo "	==> requires datadir $datadir"
  echo "	==> run as user postgres: 'initdb -D $datadir'"

  postgres_shell=$(getent passwd postgres | cut -d: -f7)
  if [ "$postgres_shell" != '/bin/bash' ]; then
    chsh -s /bin/bash postgres &>/dev/null
  fi
}

post_upgrade() {
  post_install $1
}