Fetches current DHCPACKs from syslog and formats it into a BIND-friendly format. This script takes into account the current leases already placed in DNS. (Use case: replace computer hostnames with (first|last|nick)names for easy recognition). Room for update: read the dhcpd.leases file.

dhcpleases.sh

#!/bin/bash

date

grep dhcpd /var/log/syslog | grep hostname | grep -i dhcpack | grep 'xx.yy' | grep -v 'xx.yy.zz.1' | sed -e 's/\(.*\)DHCPACK on \(.*\) to \(.*\)\( \(.*\)\|\) via vlanUU$/\2 \3 \4/' | grep -v 'hostname' | sort -u > currdhcpleases.txt

rm forwarddns.zone 
rm reversedns.zone 

while read IPADDR MAC HOST
do
  GREP=`grep $IPADDR /etc/bind/somezonefile.zone`
	RET=$?
	KNOWNHOST=`echo $GREP | awk '{print $1};'`
	STRIPPEDHOST=`echo $HOST | sed -e 's/(\(.*\))/\1/'`
	STRIPPEDIP=`echo $IPADDR | cut -d '.' -f 4`
	if [[ "$RET" -eq "0" ]]; then
		# add forward dns
		echo -n "$KNOWNHOST" >> forwarddns.zone
		echo -ne "\t\t" >> forwarddns.zone
		NUMCHARS=`echo $KNOWNHOST | wc -c`
		if [[ "$NUMCHARS" -lt "9" ]]; then
			echo -ne "\t" >> forwarddns.zone
		fi 
		echo "IN A $IPADDR ; $MAC" >> forwarddns.zone
		# add reverse dns
		echo -e "$STRIPPEDIP\t\tIN PTR $KNOWNHOST.somezone." >> reversedns.zone
	else 
		# add unknown forward dns
		echo -e "$STRIPPEDHOST-new\t\tIN A $IPADDR ; $MAC" >> forwarddns.zone
		# add unknown reverse dns
		echo -e "$STRIPPEDIP\t\tIN PTR $STRIPPEDHOST-new.somezone." >> reversedns.zone
	fi
done <currdhcpleases.txt

#cat reversedns.zone | sort -u
echo "---"
cat forwarddns.zone | sort -uk4