This script is now maintained on GitLab and no longer updated on this wiki.

I created this script as a simple reimplementation of a tool that I used in an old job. It allows you to easily update the serial number for a DNS zone in an automated fashion avoiding errors.

It's best used in conjunction with an $INCLUDE statement in the zone file referencing a separate SOA file, especially if multiple zones exist on your server. All that should be necessary to use it is to modify the SOA variable to point to your record or zone file and to ensure that the line that the serial number is on contains the string “Serial” as a comment (such as in the default zones that ship with BIND9 on Debian). You may need to modify the $SOA path depending on how you have configured your zone(s).

#!/bin/bash
#
# updatesoa.sh - a simple script to update BIND SOA serial numbers
#
# Copyright (c) 2011 Gabriel M. O'Brien
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
 
SOA=/etc/bind/SOA
 
[ -f $SOA ] || exit 65
 
oldsn=$( awk '/Serial/ { print $1 };' $SOA )
olddate=$( echo $oldsn | cut -b1-8 )
datestr=$( date +%Y%m%d )
 
# show current serial
printf 'Current DNS serial:\t%s\n' $oldsn
 
# if the date has changed reset the $inc to 00
if [ "$datestr" != "$olddate" ]; then
  inc=00
else
  # this strips the leading zero from the inc digits if present and increments
  inc=$( expr `echo $oldsn | rev | cut -b1-2 | rev` + 0 ) ; ((inc++))
fi
 
# if the increment is 99 then exit, the serial can not be more than 10 digits
if [ "$inc" == "100" ]; then
  echo "Current serial is 99, unable to increment automatically. Exiting."
  exit 1
fi
 
# now create the new serial
newsn=$( printf '%s%02d' $datestr $inc )
printf 'New DNS serial:\t\t%s\n' $newsn
 
# and update the SOA record
cp -f $SOA ${SOA}.old && \
  sed "s/${oldsn}/${newsn}/" ${SOA}.old > $SOA
printf 'SOA updated.\n'

If successful you will see something like this:

root@jupiter:/etc/bind# ./updatesoa.sh
Current DNS serial:     2015030807
New DNS serial:         2015030808
SOA updated.

Reminder: after this you will need to reload the zone!

Obvious error conditions are trapped in the script but it is probably far from foolproof.