/usr/lib/fai/fai-vol_id is in fai-setup-storage 3.4.8ubuntu5.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | #! /bin/bash
# Copyright (c) 2009 by Michael Tautschnig <mt@debian.org>
udev_vol_id="/lib/udev/vol_id"
udev_blkid="/sbin/blkid"
get_uuid() {
  if [ -z $udev_vol_id ] ; then
    $udev_blkid -s UUID -o value $1
    exit $?
  fi
  /lib/udev/vol_id -u $1
  exit $?
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
get_label() {
  if [ -z $udev_vol_id ] ; then
    $udev_blkid -s LABEL -o value $1
    exit $?
  fi
  /lib/udev/vol_id -L $1
  exitcode=$?
  if [ $exitcode -eq 0 -o $exitcode -eq 3 ] ; then
    exitcode=0
  fi
  exit $exitcode
}
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# main program
if [ -e $udev_blkid ] ; then
  udev_vol_id=""
else
  if [ ! -e $udev_vol_id ] ; then
    "Neither udev vol_id nor blkid found!"
    exit 1
  fi
fi
while getopts ul opt ; do
      case "$opt" in
        u) shift ; get_uuid $1 ;;
        l) shift ; get_label $1 ;;
      esac
done
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