Ubuntu DNS Stub Listener #Disable

During setting up PiHole, it requires to listen on DNS (53/TCP, 53/UDP) on the host. Ubuntu version that I am running on (20.04) by default listens on port 53 because it runs as DNS Stub Listener.

PiHole will give errors about Binding error

To disable Ubuntu running as DNS Stub Listener, do the followings:

> sudo vi /etc/systemd/resolved.conf 

un-comment #DNSStubListener=yes 
change it to DNSStubListener=no

> sudo service systemd-resolved restart
> sudo systemctl disable systemd-resolved.service
> sudo systemctl stop systemd-resolved
> sudo mv /etc/resolv.conf /etc/resolv.conf.old
> sudo shutdown -h now -r

GoDaddy DNS Update Using API

I recently need to update my DNS entry which is hosted in GoDaddy. GoDaddy supports API call to update DNS entries, which is amazing!!

You need to generate the API key and secret.

create the file below and cronjob it!

#!/bin/bash

domain="domain.tld"
type="A"
name="@"
ttl="3600"
port="1"
weight="1"
key="my-api-key"
secret="my-api-secret"

headers="Authorization: sso-key $key:$secret"
echo "Headers = " $headers

result=$(curl -X GET -H "$headers" "https://api.godaddy.com/v1/domains/$domain/records/$type/$name")
echo "Result = " $result

dnsIP=$(echo $result | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b")
echo "DNS IP = " $dnsIP

ret=$(curl -s GET "http://ipinfo.io/json")
currentIP=$(echo $ret | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b")
echo "Current IP = " $currentIP

if [ $dnsIP != $currentIP ];
then
        echo "IP's are not equal, updating record"
        curl -X PUT "https://api.godaddy.com/v1/domains/$domain/records/$type/$name" \
                -H "accept: application/json" \
                -H "Content-Type: application/json" \
                -H "$headers" \
                -d "[ { \"data\": \"$currentIP\", \"port\": $port, \"priority\": 0, \"protocol\": \"string\", \"service\": \"string\", \"ttl\": $ttl, \"weight\": $weight } ]"
fi

if [ $dnsIP = $currentIP ];
then
        echo "IP's are equal, no update required"
fi

BIND DDNS

OK, So I have a requirement to host one of my domains internally. The reason for this is because I would like to be able to learn more about BIND9 as well as having flexibility to do Dynamic DNS.

I spawned a VM and install Ubuntu on it. During the installation, I selected DNS server as part of the feature to be installed.

Here are the steps I took to set it up:

Step #1 - Edit /etc/bind/named.conf.local

key "domain.com.au." {

        algorithm hmac-md5;

        secret "w81WcwhateverhereGnCQ==";

};

zone "domain.com.au" {

        type master;

        allow-update { key "domain.com.au."; };

        journal "/var/cache/bind/db.domain.com.au.jnl";

        file "/etc/bind/master/db.domain.com.au";

};

The key section is used for the automatic update using nsupdate tool which is part of BIND installation package. the secret value is generated by using the following:

dnssec-keygen -a HMAC-MD5 -b 128 -n HOST domain.com.au

This tool generates 2 files = .key and .private

open the .key file and copy the key, e.g. w81WcwhateverhereGnCQ==, and put it in the key section above. 

Note: That is NOT my KEY -

Then you need to save the .private file and keep is safe to be used later with nsupdate

The zone section is where my DNS zone is configured

Step #2 - Create Zone File

Create a master folder within /etc/bind

Copy /etc/bind/db.local to /etc/bind/master/db.domain.com.au

Change permission on the folder

chown -R bind:bind /etc/bind/master

chmod 775 -R /etc/bind/master

Step #3 - Edit /etc/bind/master/db.domain.com.au

Edit the file and adjust the content to suit your need

Restart the BIND process:

sudo /etc/init.d/bind9 restart

Have a look the syslog file to make sure everything is OK

tail -f /var/log/syslog

Step #4 - Create Dynamic DNS Script File

Create ddns.sh file with the following content:

#!/bin/bash

# This script fetches the current external IP Address, writes out an nsupdate file

# Then performs an nsupdate to our remote server of choice

# This script should be placed on a 10 minute crontab

WGET=$(which wget)

ECHO=$(which echo)

NSUPDATE=$(which nsupdate)

IP_FILE="/home/ddns/ip"

IP=$($WGET -q -O - checkip.dyndns.org|sed -e 's/.*Current IP Address: //' -e 's/<.*$//')

IS_UPDATE="no"

if [ -f $IP_FILE ]

then

        #Get file content

        IP_OLD=$(<$IP_FILE)

        $ECHO "File IP exists with the content: $IP_OLD"

        $ECHO "Old IP: $IP_OLD"

        if [ "$IP_OLD" == "$IP" ]

        then

                $ECHO "IP is not changing: $IP"

        else

                $ECHO "IP changes. OLD IP: $IP_OLD, NEW IP: $IP"

                $ECHO "$IP" > $IP_FILE

                IS_UPDATE="yes"

        fi

else

        $ECHO "File IP does not exist, creating one..."

        IS_UPDATE="yes"

        $ECHO "$IP" > $IP_FILE

fi

$ECHO "server bind.domain.com.au" > /tmp/nsupdate

$ECHO "debug yes" >> /tmp/nsupdate

$ECHO "zone domain.com.au." >> /tmp/nsupdate

$ECHO "update delete domain.com.au A" >> /tmp/nsupdate

$ECHO "update add domain.com.au 600 A $IP" >> /tmp/nsupdate

$ECHO "update delete www.domain.com.au A" >> /tmp/nsupdate

$ECHO "update add www.domain.com.au 600 A $IP" >> /tmp/nsupdate

$ECHO "send" >> /tmp/nsupdate

$ECHO "Is Update: $IS_UPDATE"

if [ "$IS_UPDATE" == "yes" ]

then

        $NSUPDATE -k /home/ddns/Kdomain.com.au.+157+05161.private -v /tmp/nsupdate 2>&1

        $ECHO "Updating..."

fi

The script does the following:

• Get the Public IP address from checkip.dyndns.org
• Check whether or not the IP has changed from the previous pooling. This is done by storing the IP to a file and compare it on the next query
• If the IP has changed, run nsupdate

Notice the .private key is used here.

Then you can do cronjob to run ddns.sh regularly

DNS IP to localhost

While I am doing this coding of DNS server and using my development machine to debug the program, I need to somehow configure my Windows 7 client's DNS setting to point to itself as the DNS server (e.g. 127.0.0.1).

Surprisingly, Windows 7 rejects the setting when you put 127.0.0.1 as the DNS IP address of your network connection.

Found the following Powershell to change it easily

$wmi = Get-WmiObject win32_networkadapterconfiguration -filter "ipenabled = 'true'"
$wmi.SetDNSServerSearchOrder("127.0.0.1")

Active Directory DNS Waiting for Initial Replication

When you boot the 1st domain controller within the environment which has more than 1 DC, by default the DC is waiting for initial inbound replication from the other DC. But because this is the first DC you boot, this is going to take a while

To avoid this, add the following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters
Value name: Repl Perform Initial Synchronizations
Value type: REG_DWORD
Value data: 0

Add Reboot!
Do not use this method in the producation environment