DNS A record and PTR record delete - linux

Question

I have a duplicate in DNS record when adding new instance. My goal is to use "nsupdate" to be able to delete A record by IP if new instance IP is found. This is what I did. However, it didn't delete any duplicate when ran this script. what will be the best walk around?
domain=${domainname}
nodename=(hostname | awk -F. '{print $1}')
local_ip=$(ifconfig eth0 | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1')
nslookup ${local_ip} | grep SERVFAIL
if [[ $? < 0 ]] ; then
echo "Record already exists"
echo -e "update ${local_ip} IN A"
else
echo "creating forward Record: ${codename}.${domain}"
echo -e "update add ${nodename}.${domain} 3600 A ${local_ip}\nsend" | nsupdate -g
fi

Answer 1

It looks like you have several problems
Grep will not return a value less than 0, so your code to do your update will never run. Even if it did run, you're not echoing that command to nsupdate, so your record still wouldn't be changed. Also, there are several typos in your code
domain=${domainname}
nodename=(hostname | awk -F. '{print $1}')
local_ip=$(ifconfig eth0 | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1')
if nslookup ${local_ip} | grep SERVFAIL; then
echo "creating forward Record: ${nodename}.${domain}"
echo -e "update add ${nodename}.${domain} 3600 A ${local_ip}\nsend" | nsupdate -g
else
echo "Record already exists"
echo -e "update ${local_ip} IN A" | nsupdate -g
fi
I've never used nsupdate personally, but i'm assuming that you meant to send your update command to it in the same fashion as your 'add'.