increment_zone_serial

#!/bin/bash

# Michael Vallaly (Mar '10) Ver 2.5
# from: <https://github.com/slaught/enki_cloud/blob/master/scripts/scripts/dns-increment>
#
# Modified by Jason Antman <jason@jasonantman.com>

# This script updates/increments the bind zone file serial number

SED_BIN="/bin/sed"
AWK_BIN="/usr/bin/awk"
DATE_BIN="/bin/date"
BC_BIN="/usr/bin/bc"
GREP_BIN="/bin/grep"

###########################################################################################

# Get the serial number from a bind zonefile
get_serial () {

  local target=$1

  # Grab the SOA DNS Zone Header
  SOA_HEADER=`cat $target |$SED_BIN 's/;.*$//' |$AWK_BIN '/^[A-Za-z0-9\-\.]*[\t \.\@]+IN[\t ]+SOA[\t ]+[A-Za-z0-9\-\. \t]+\(/,/\)/' |tr -d '\n' |awk '{print $7}'`

  # Get the currently set serial number
  echo "$SOA_HEADER" |tr -t '[:lower:]' '[:upper:]' |$GREP_BIN -E -e '[[:digit:]]{10}' -e '%SERIAL%'

}

# Check for required binaries
for req_bin in $AWK_BIN $SED_BIN $DATE_BIN $BC_BIN $GREP_BIN; do
  if [ ! -x "$req_bin" ]; then
    echo "Can't execute ${req_bin}! Aborting.."
    exit 1
  fi
done

# Check for needed commandline arguments
usage="$0 <zone_file>"
if [ $# -le 0 ]; then
  echo "$usage"
  exit 1
else
  FILE=`echo $1`
fi

if [ ! -e "${FILE}" ]; then
    echo "ERROR: file $FILE does not exist, exiting."
    exit 1
fi

# Generate todays base serial number
DATE_NOW=`$DATE_BIN +%Y%m%d`

# Current serial
OLD_SERIAL=`get_serial ${FILE}`

# Check that we got something back for a serial
if [ "${OLD_SERIAL}" == "" ]; then
  echo "Cannot find zone file ${FILE} serial number.. Exiting!"
  exit 1
fi

# Split up the serial
OLD_DATE=`echo $OLD_SERIAL |cut -c 1-8`
OLD_REV=`echo $OLD_SERIAL |cut -c 9-10`

if [ "${OLD_REV}x" == "x" ]; then
    OLD_REV=01
fi

# If the current date number is greater just use it
if [ "$(echo "$DATE_NOW > $OLD_DATE" |$BC_BIN)" -eq "1" ]; then
    NEW_SERIAL="${DATE_NOW}01"

# If we have the same date number increment the revsion number
elif [ "$(echo "$DATE_NOW == $OLD_DATE" |$BC_BIN)" -eq "1" ] ; then

    # Increment the revision number
    if [ "$(echo "$OLD_REV <= 98" |$BC_BIN)" -eq "1" ]; then
      NEW_REV=`printf "%02d\n" "$(echo "$OLD_REV + 1" |$BC_BIN)"`
      NEW_SERIAL="${DATE_NOW}${NEW_REV}"
    else
      echo "Too many revision for today wait till tomorrow.. Exiting!"
      exit 1
    fi

else
    echo "Current zonefile serial is in the future.. Time Skew? Exiting!"
    exit 1
fi

# Replace the serial # and install the new zonefile
$SED_BIN -e "s/${OLD_SERIAL}/${NEW_SERIAL}/" -i $FILE
replace_status=$?