#!/usr/bin/ash

findmnt -Rruno TARGET /oldroot | awk '
BEGIN { i = 0 }
! /^\/(proc|dev|sys)/ {
  i++
  mounts[i] = $0
}
END {
  for (j = i; j > 0; j--) {
    print mounts[j]
  }
}
' | while read -r mount; do
  umount -l "$mount"
done

case $1 in
  poweroff|shutdown|halt)
    "$1" -f
    ;;
  *)
    type kexec >/dev/null && kexec -e
    reboot -f
    ;;
esac