CoreDNS Installation Guide Installation Guide

CoreDNS is a free and open-source DNS Server. A flexible, extensible DNS server written in Go

Hardware Requirements:

CPU: 2 cores minimum (4+ cores recommended)

RAM: 2GB minimum (4GB+ recommended)

Storage: 1GB for installation

Network: 53 ports

Operating System:

Linux: Any modern distribution (RHEL, Debian, Ubuntu, CentOS, Fedora, Arch, Alpine, openSUSE)

macOS: 10.14+ (Mojave or newer)

Windows: Windows Server 2016+ or Windows 10

FreeBSD: 11.0+

Network Requirements:

Port 53 (default coredns port)

Dependencies:

none

System Access: root or sudo privileges required

This guide supports installation on:

RHEL 8/9 and derivatives (CentOS Stream, Rocky Linux, AlmaLinux)

Debian 11/12

Ubuntu 20.04/22.04/24.04 LTS

Arch Linux (rolling release)

Alpine Linux 3.18+

openSUSE Leap 15.5+ / Tumbleweed

SUSE Linux Enterprise Server (SLES) 15+

macOS 12+ (Monterey and later)

FreeBSD 13+

Windows 10/11/Server 2019+ (where applicable)

bash

# Install EPEL repository if needed
sudo dnf install -y epel-release

# Install coredns
sudo dnf install -y coredns none

# Enable and start service
sudo systemctl enable --now coredns

# Configure firewall
sudo firewall-cmd --permanent --add-service=coredns
sudo firewall-cmd --reload

# Verify installation
coredns --version || systemctl status coredns

bash

# Update package index
sudo apt update

# Install coredns
sudo apt install -y coredns none

# Enable and start service
sudo systemctl enable --now coredns

# Configure firewall
sudo ufw allow 53

# Verify installation
coredns --version || systemctl status coredns

bash

# Install coredns
sudo pacman -S coredns

# Enable and start service
sudo systemctl enable --now coredns

# Verify installation
coredns --version || systemctl status coredns

bash

# Install coredns
apk add --no-cache coredns

# Enable and start service
rc-update add coredns default
rc-service coredns start

# Verify installation
coredns --version || rc-service coredns status

bash

# Install coredns
sudo zypper install -y coredns none

# Enable and start service
sudo systemctl enable --now coredns

# Configure firewall
sudo firewall-cmd --permanent --add-service=coredns
sudo firewall-cmd --reload

# Verify installation
coredns --version || systemctl status coredns

bash

# Using Homebrew
brew install coredns

# Start service
brew services start coredns

# Verify installation
coredns --version

bash

# Using pkg
pkg install coredns

# Enable in rc.conf
echo 'coredns_enable="YES"' >> /etc/rc.conf

# Start service
service coredns start

# Verify installation
coredns --version || service coredns status

powershell

# Using Chocolatey
choco install coredns

# Or using Scoop
scoop install coredns

# Verify installation
coredns --version

bash

# Create configuration directory if needed
sudo mkdir -p /etc/coredns

# Set up basic configuration
sudo tee /etc/coredns/coredns.conf << 'EOF'
# CoreDNS Configuration
. { forward . 8.8.8.8 9.9.9.9, cache 30 }
EOF

# Test configuration
sudo coredns -t || sudo coredns configtest

# Reload service
sudo systemctl reload coredns

bash

# Set appropriate permissions
sudo chown -R coredns:coredns /etc/coredns
sudo chmod 750 /etc/coredns

# Enable security features
# See security section for detailed hardening steps

bash

# Enable service
sudo systemctl enable coredns

# Start service
sudo systemctl start coredns

# Stop service
sudo systemctl stop coredns

# Restart service
sudo systemctl restart coredns

# Reload configuration
sudo systemctl reload coredns

# Check status
sudo systemctl status coredns

# View logs
sudo journalctl -u coredns -f

bash

# Enable service
rc-update add coredns default

# Start service
rc-service coredns start

# Stop service
rc-service coredns stop

# Restart service
rc-service coredns restart

# Check status
rc-service coredns status

bash

# Enable in /etc/rc.conf
echo 'coredns_enable="YES"' >> /etc/rc.conf

# Start service
service coredns start

# Stop service
service coredns stop

# Restart service
service coredns restart

# Check status
service coredns status

bash

# Using Homebrew services
brew services start coredns
brew services stop coredns
brew services restart coredns

# Check status
brew services list | grep coredns

powershell

# Start service
net start coredns

# Stop service
net stop coredns

# Using PowerShell
Start-Service coredns
Stop-Service coredns
Restart-Service coredns

# Check status
Get-Service coredns

bash

# Configure performance settings
cat >> /etc/coredns/coredns.conf << 'EOF'
. { forward . 8.8.8.8 9.9.9.9, cache 30 }
EOF

# Apply system tuning
sudo sysctl -w net.core.somaxconn=65535
sudo sysctl -w net.ipv4.tcp_max_syn_backlog=65535

# Restart service
sudo systemctl restart coredns

bash

# Configure clustering (if supported)
# See official documentation for cluster setup

# Basic load balancing setup example
# Configure multiple instances on different ports

nginx

upstream coredns_backend {
    server 127.0.0.1:53;
    server 127.0.0.1:{default_port}1 backup;
}

server {
    listen 80;
    server_name coredns.example.com;
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl http2;
    server_name coredns.example.com;

    ssl_certificate /etc/ssl/certs/coredns.example.com.crt;
    ssl_certificate_key /etc/ssl/private/coredns.example.com.key;

    location / {
        proxy_pass http://coredns_backend;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        
        # WebSocket support (if needed)
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
}

apache

<VirtualHost *:80>
    ServerName coredns.example.com
    Redirect permanent / https://coredns.example.com/
</VirtualHost>

<VirtualHost *:443>
    ServerName coredns.example.com
    
    SSLEngine on
    SSLCertificateFile /etc/ssl/certs/coredns.example.com.crt
    SSLCertificateKeyFile /etc/ssl/private/coredns.example.com.key
    
    ProxyRequests Off
    ProxyPreserveHost On
    
    ProxyPass / http://127.0.0.1:53/
    ProxyPassReverse / http://127.0.0.1:53/
    
    # WebSocket support (if needed)
    RewriteEngine on
    RewriteCond %{HTTP:Upgrade} websocket [NC]
    RewriteCond %{HTTP:Connection} upgrade [NC]
    RewriteRule ^/?(.*) "ws://127.0.0.1:53/$1" [P,L]
</VirtualHost>

haproxy

frontend coredns_frontend
    bind *:80
    bind *:443 ssl crt /etc/ssl/certs/coredns.pem
    redirect scheme https if !{ ssl_fc }
    default_backend coredns_backend

backend coredns_backend
    balance roundrobin
    option httpchk GET /health
    server coredns1 127.0.0.1:53 check
    server coredns2 127.0.0.1:{default_port}1 check backup

bash

# Set appropriate permissions
sudo chown -R coredns:coredns /etc/coredns
sudo chmod 750 /etc/coredns

# Configure firewall
sudo firewall-cmd --permanent --add-service=coredns
sudo firewall-cmd --reload

# Enable SELinux policies (if applicable)
sudo setsebool -P httpd_can_network_connect on

# Configure fail2ban
sudo tee /etc/fail2ban/jail.d/coredns.conf << 'EOF'
[coredns]
enabled = true
port = 53
filter = coredns
logpath = /var/log/coredns/*.log
maxretry = 5
bantime = 3600
EOF

bash

# Generate SSL certificates
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 \
    -keyout /etc/ssl/private/coredns.key \
    -out /etc/ssl/certs/coredns.crt

# Configure SSL in coredns
# See official documentation for SSL configuration

PostgreSQL Backend (if applicable)

bash

# Create database and user
sudo -u postgres psql << EOF
CREATE DATABASE coredns_db;
CREATE USER coredns_user WITH ENCRYPTED PASSWORD 'secure_password';
GRANT ALL PRIVILEGES ON DATABASE coredns_db TO coredns_user;
EOF

# Configure coredns to use PostgreSQL
# See official documentation for database configuration

bash

# Create database and user
sudo mysql << EOF
CREATE DATABASE coredns_db;
CREATE USER 'coredns_user'@'localhost' IDENTIFIED BY 'secure_password';
GRANT ALL PRIVILEGES ON coredns_db.* TO 'coredns_user'@'localhost';
FLUSH PRIVILEGES;
EOF

bash

# Kernel parameters
sudo tee -a /etc/sysctl.conf << EOF
net.core.somaxconn = 65535
net.ipv4.tcp_max_syn_backlog = 65535
net.ipv4.ip_local_port_range = 1024 65535
net.core.netdev_max_backlog = 5000
vm.swappiness = 10
EOF

sudo sysctl -p

# CoreDNS specific tuning
. { forward . 8.8.8.8 9.9.9.9, cache 30 }

bash

# Configure system limits
sudo tee -a /etc/security/limits.conf << EOF
coredns soft nofile 65535
coredns hard nofile 65535
coredns soft nproc 32768
coredns hard nproc 32768
EOF

yaml

# prometheus.yml configuration
scrape_configs:
  - job_name: 'coredns'
    static_configs:
      - targets: ['localhost:53']
    metrics_path: '/metrics'

bash

# Basic health check script
#!/bin/bash
if systemctl is-active --quiet coredns; then
    echo "CoreDNS is running"
    exit 0
else
    echo "CoreDNS is not running"
    exit 1
fi

bash

# Configure log rotation
sudo tee /etc/logrotate.d/coredns << 'EOF'
/var/log/coredns/*.log {
    daily
    rotate 14
    compress
    delaycompress
    missingok
    notifempty
    create 0640 coredns coredns
    postrotate
        systemctl reload coredns > /dev/null 2>&1 || true
    endscript
}
EOF

bash

#!/bin/bash
# CoreDNS backup script
BACKUP_DIR="/backup/coredns"
DATE=$(date +%Y%m%d_%H%M%S)

mkdir -p "$BACKUP_DIR"

# Stop service (if required)
systemctl stop coredns

# Backup configuration
tar -czf "$BACKUP_DIR/coredns-config-$DATE.tar.gz" /etc/coredns

# Backup data (adjust paths as needed)
tar -czf "$BACKUP_DIR/coredns-data-$DATE.tar.gz" /var/lib/coredns

# Start service
systemctl start coredns

# Clean old backups (keep 30 days)
find "$BACKUP_DIR" -name "*.tar.gz" -mtime +30 -delete

echo "Backup completed: $BACKUP_DIR"

bash

# Stop service
sudo systemctl stop coredns

# Restore configuration
sudo tar -xzf /backup/coredns/coredns-config-*.tar.gz -C /

# Restore data
sudo tar -xzf /backup/coredns/coredns-data-*.tar.gz -C /

# Set permissions
sudo chown -R coredns:coredns /etc/coredns
sudo chown -R coredns:coredns /var/lib/coredns

# Start service
sudo systemctl start coredns

1. Service won't start:

bash

# Check logs
sudo journalctl -u coredns -n 100
sudo tail -f /var/log/coredns/*.log

# Check configuration
sudo coredns -t || sudo coredns configtest

# Check permissions
ls -la /etc/coredns
ls -la /var/lib/coredns

2. Connection refused:

bash

# Check if service is listening
sudo ss -tlnp | grep 53
sudo netstat -tlnp | grep 53

# Check firewall
sudo firewall-cmd --list-all
sudo iptables -L -n

# Test connection
telnet localhost 53
nc -zv localhost 53

3. Performance issues:

bash

# Check resource usage
top -p $(pgrep coredns)
htop -p $(pgrep coredns)

# Check connections
ss -ant | grep :53 | wc -l

# Monitor I/O
iotop -p $(pgrep coredns)

bash

# Run in debug mode
sudo coredns -d
# or
sudo coredns debug

# Increase log verbosity
# Edit configuration to enable debug logging

yaml

version: '3.8'
services:
  coredns:
    image: coredns:latest
    container_name: coredns
    ports:
      - "53:53"
    volumes:
      - ./config:/etc/coredns
      - ./data:/var/lib/coredns
    environment:
      - coredns_CONFIG=/etc/coredns/coredns.conf
    restart: unless-stopped
    networks:
      - coredns_net

networks:
  coredns_net:
    driver: bridge

yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: coredns
spec:
  replicas: 3
  selector:
    matchLabels:
      app: coredns
  template:
    metadata:
      labels:
        app: coredns
    spec:
      containers:
      - name: coredns
        image: coredns:latest
        ports:
        - containerPort: 53
        volumeMounts:
        - name: config
          mountPath: /etc/coredns
      volumes:
      - name: config
        configMap:
          name: coredns-config
---
apiVersion: v1
kind: Service
metadata:
  name: coredns
spec:
  selector:
    app: coredns
  ports:
  - port: 53
    targetPort: 53
  type: LoadBalancer

yaml

---
- name: Install and configure CoreDNS
  hosts: all
  become: yes
  tasks:
    - name: Install coredns
      package:
        name: coredns
        state: present
    
    - name: Configure coredns
      template:
        src: coredns.conf.j2
        dest: /etc/coredns/coredns.conf
        owner: coredns
        group: coredns
        mode: '0640'
      notify: restart coredns
    
    - name: Start and enable coredns
      systemd:
        name: coredns
        state: started
        enabled: yes
  
  handlers:
    - name: restart coredns
      systemd:
        name: coredns
        state: restarted

Maintenance

bash

# RHEL/CentOS/Rocky/AlmaLinux
sudo dnf update coredns

# Debian/Ubuntu
sudo apt update && sudo apt upgrade coredns

# Arch Linux
sudo pacman -Syu coredns

# Alpine Linux
apk update && apk upgrade coredns

# openSUSE
sudo zypper update coredns

# FreeBSD
pkg update && pkg upgrade coredns

# Always backup before updates
tar -czf /backup/coredns-pre-update-$(date +%Y%m%d).tar.gz /etc/coredns

# Restart after updates
sudo systemctl restart coredns

Regular Maintenance Tasks

bash

# Clean logs
find /var/log/coredns -name "*.log" -mtime +30 -delete

# Verify integrity
sudo coredns --verify || sudo coredns check

# Update databases (if applicable)
sudo coredns-update-db

# Optimize performance
sudo coredns-optimize

# Check for security updates
sudo coredns --security-check

Official Documentation: https://docs.coredns.org/

GitHub Repository: https://github.com/coredns/coredns

Community Forum: https://forum.coredns.org/

Wiki: https://wiki.coredns.org/

Comparison vs BIND, PowerDNS, Knot DNS, NSD: https://docs.coredns.org/comparison

---

Note: This guide is part of the HowToMgr collection. Always refer to official documentation for the most up-to-date information.

1. Prerequisites

2. Supported Operating Systems

3. Installation

RHEL/CentOS/Rocky Linux/AlmaLinux

Debian/Ubuntu

Arch Linux

Alpine Linux

openSUSE/SLES

macOS

FreeBSD

Windows

Initial Configuration

Basic Configuration

Security Hardening

5. Service Management

systemd (RHEL, Debian, Ubuntu, Arch, openSUSE)

OpenRC (Alpine Linux)

rc.d (FreeBSD)

launchd (macOS)

Windows Service Manager

Advanced Configuration

Performance Optimization

Clustering and High Availability

Reverse Proxy Setup

nginx Configuration

Apache Configuration

HAProxy Configuration

Security Configuration

Basic Security Setup

SSL/TLS Configuration

Database Setup

PostgreSQL Backend (if applicable)

MySQL/MariaDB Backend (if applicable)

Performance Optimization

System Tuning

Resource Limits

Monitoring

Prometheus Integration

Health Checks

Log Monitoring

9. Backup and Restore

Backup Script

Restore Procedure

6. Troubleshooting

Common Issues

Debug Mode

Integration Examples

Docker Compose

Kubernetes Deployment

Ansible Playbook

Maintenance

Update Procedures

Regular Maintenance Tasks

Additional Resources

Related Dns servers Guides

BIND Installation Guide

dnsmasq Installation Guide

Knot DNS Installation Guide