The problem and solution

I want to automatically distribute my DNS to two locations on a DirectAdmin server that only has one IP address. The issue is that DirectAdmin only syncs DNS records with DirectAdmin servers, so it will cost more to buy the cheapest DirectAdmin license, which costs at least $5, and a minimum of 4GB VPS, which raises the price. Therefore, I decided to write a script that can accomplish this on a cheap 1GB VPS from Netcup. In this thorough tutorial, we’ll go over how to fix any discrepancies between local and remote nameservers and synchronize DNS zones between DirectAdmin (ns1) and BIND (ns2) servers.

in my case ns1 directadmin nameserver is located in the USA, and ns2 server is located in Germany.

Table of Contents

1. Introduction
2. Setting Up SSH Key Authentication
3. Creating the DNS Sync Script
4. Configuring BIND on ns2
5. Troubleshooting Common Issues
6. Conclusion

1. Introduction

DNS synchronization ensures that changes made in one DNS server are automatically reflected in another. This is particularly important when managing domains across multiple servers. In this scenario, we have a DirectAdmin server (ns1) and a BIND-only server (ns2). Our goal is to sync DNS records from ns1 to ns2, ensuring both servers are always up-to-date.

2. Setting Up SSH Key Authentication

To securely transfer DNS zone files between servers, we need to set up SSH key authentication. This eliminates the need for password prompts during automated tasks.

Step 1: Generate an SSH Key on ns1

ssh-keygen -t ed25519 -N "" -f ~/.ssh/ns2-sync

Step 2: Copy the Public Key to ns2

ssh-copy-id -i ~/.ssh/ns2-sync.pub root@2.2.2.2

in above mentioned command 2.2.2.2 is the ip of your ns2 or secondary dns server

Step 3: Test Password-less Login

ssh -i /root/.ssh/ns2-sync root@ns2 "echo 'SSH works!'"

3. Creating the DNS Sync Script

We’ll create a script (dns-sync.sh) that automates the synchronization process.

Step 1: Create the Script File

nano /usr/local/bin/dns-sync.sh

Step 2: Add the Following Content

#!/bin/bash

# Configuration
REMOTE_USER="root"
# this is the remote server ip or secondary server ip
REMOTE_HOST="2.2.2.2" 
LOCAL_ZONE_DIR="/var/named"
REMOTE_ZONE_DIR="/var/lib/bind/domains"
REMOTE_CONF_DIR="/etc/bind/zones"
SSH_CMD="ssh -i /root/.ssh/ns2-sync ${REMOTE_USER}@${REMOTE_HOST}"
RSYNC_OPTS=(-avz --delete -e "ssh -i /root/.ssh/ns2-sync")

# Create temporary directory for config generation
TMP_DIR=$(mktemp -d)
trap 'rm -rf $TMP_DIR' EXIT

# Generate BIND zone configurations
for zone_file in ${LOCAL_ZONE_DIR}/*.db; do
    domain=$(basename "${zone_file%.db}")
    cat <<EOF > "${TMP_DIR}/${domain}.conf"
zone "${domain}" {
    type master;
    file "${REMOTE_ZONE_DIR}/${domain}.db";
};
EOF
done

# Sync zone files and configurations
rsync "${RSYNC_OPTS[@]}" ${LOCAL_ZONE_DIR}/*.db ${REMOTE_HOST}:${REMOTE_ZONE_DIR}/
rsync "${RSYNC_OPTS[@]}" ${TMP_DIR}/*.conf ${REMOTE_HOST}:${REMOTE_CONF_DIR}/

# Fix permissions and reload BIND
${SSH_CMD} -T << 'EOF'  # Added -T flag
chown -R bind:bind /var/lib/bind/domains
chmod 644 /var/lib/bind/domains/*.db
systemctl reload bind9
EOF

Step 3: Make the Script Executable

chmod +x /usr/local/bin/dns-sync.sh

4. Configuring BIND on ns2

Step 1: Create Required Directories

mkdir -p /var/lib/bind/domains
mkdir -p /etc/bind/zones
chown -R bind:bind /var/lib/bind/domains
chmod 755 /var/lib/bind/domains
chmod 755 /etc/bind/zones

Step 2: Update BIND Configuration

Add the following line to /etc/bind/named.conf.local:

include "/etc/bind/zones/*.conf";

5. Troubleshooting Common Issues

Issue: Local NS List Does Not Match Parent NS List

Ensure the NS records in your DNS zone file match those registered with your domain registrar.

6. Conclusion

By following this guide, you’ve successfully synchronized DNS zones between DirectAdmin and BIND, ensuring seamless domain management. Regularly syncing DNS records helps maintain website availability and email functionality. If you encounter any issues, refer to the troubleshooting section for assistance.

Happy DNS managing! 🚀

If you do not have bind installed on NS2 server then Installing BIND on ns2 here is the instructions

Installing BIND on ns2

Below are the detailed steps to install BIND on your ns2 server, along with the necessary commands. This will ensure that your ns2 server is properly set up to handle DNS requests and synchronize with your DirectAdmin server (ns1).

sudo apt update && sudo apt upgrade -y

sudo apt install bind9 -y

systemctl status bind9

sudo nano /etc/bind/named.conf.options

include "/etc/bind/zones/*.conf";

sudo nano /etc/bind/named.conf.local

sudo mkdir -p /var/lib/bind/domains
sudo mkdir -p /etc/bind/zones
sudo chown -R bind:bind /var/lib/bind/domains
sudo chmod 755 /var/lib/bind/domains
sudo chmod 755 /etc/bind/zones

named-checkconf

sudo systemctl restart bind9

sudo systemctl enable bind9

sudo ufw allow 53/tcp
sudo ufw allow 53/udp
sudo ufw reload

Summary of Commands

Here’s a summary of the commands you need to run to install and configure BIND on your ns2 server:

# Update system
sudo apt update && sudo apt upgrade -y

# Install BIND9
sudo apt install bind9 -y

# Check BIND status
systemctl status bind9

# Edit named.conf.options (optional)
sudo nano /etc/bind/named.conf.options

# Edit named.conf.local
sudo nano /etc/bind/named.conf.local
# Add: include "/etc/bind/zones/*.conf";

# Create zone directories
sudo mkdir -p /var/lib/bind/domains
sudo mkdir -p /etc/bind/zones
sudo chown -R bind:bind /var/lib/bind/domains
sudo chmod 755 /var/lib/bind/domains
sudo chmod 755 /etc/bind/zones

# Test configuration
named-checkconf

# Restart BIND
sudo systemctl restart bind9

# Enable BIND on boot
sudo systemctl enable bind9

# Allow DNS traffic through firewall
sudo ufw allow 53/tcp
sudo ufw allow 53/udp
sudo ufw reload

By following these steps, you’ll have BIND installed and configured on your ns2 server, ready to synchronize DNS records with your DirectAdmin server (ns1).

Setup Cron on a directadmin server to sync dns records

Scheduling DNS Sync Script with Cron

To ensure your DNS records are automatically synchronized between DirectAdmin (ns1) and BIND (ns2), you can schedule the `dns-sync.sh` script to run at regular intervals using a cron job. Follow these steps to set up the cron job:

crontab -e

* * * * * command_to_be_executed
- - - - -
| | | | |
| | | | +-- Year              (range: 1900-3000)
| | | +---- Month             (range: 1-12)
| | +------ Day of the Month  (range: 1-31)
| +-------- Hour              (range: 0-23)
+---------- Minute            (range: 0-59)

0 * * * * /usr/local/bin/dns-sync.sh >> /var/log/dns-sync.log 2>&1

*/15 * * * * /usr/local/bin/dns-sync.sh >> /var/log/dns-sync.log 2>&1

0 0 * * * /usr/local/bin/dns-sync.sh >> /var/log/dns-sync.log 2>&1

crontab -l

tail -f /var/log/dns-sync.log

Summary

By following these steps, you can easily schedule the `dns-sync.sh` script to run automatically at the desired interval using a cron job. This ensures that your DNS records are always up-to-date and synchronized between your DirectAdmin server (ns1) and BIND server (ns2).