How to Configure an NTP Server on AlmaLinux

Accurate timekeeping on servers is crucial for ensuring consistent logging, security protocols, and system operations. AlmaLinux, a robust and enterprise-grade Linux distribution, relies on Chrony as its default Network Time Protocol (NTP) implementation. This guide will walk you through configuring an NTP server on AlmaLinux step by step.

1. What is NTP, and Why is it Important?

Network Time Protocol (NTP) synchronizes system clocks over a network. Accurate time synchronization is essential for:

• Coordinating events across distributed systems.
• Avoiding issues with log timestamps.
• Maintaining secure communication protocols.

2. Prerequisites

Before you begin, ensure:

1. A fresh AlmaLinux installation with sudo privileges.
2. Firewall configuration is active and manageable.
3. The Chrony package is installed. Chrony is ideal for systems with intermittent connections due to its faster synchronization and better accuracy.

3. Steps to Configure an NTP Server

Step 1: Update Your System

Start by updating the system to ensure all packages are up to date:

sudo dnf update -y

Step 2: Install Chrony

Install Chrony, the default NTP daemon for AlmaLinux:

sudo dnf install chrony -y

Verify the installation:

chronyd -v

Step 3: Configure Chrony

Edit the Chrony configuration file to set up your NTP server:

sudo nano /etc/chrony.conf

Make the following changes:

• Comment out the default NTP pool by adding #:

  #pool 2.almalinux.pool.ntp.org iburst
  

• Add custom NTP servers near your location:

  server 0.pool.ntp.org iburst
  server 1.pool.ntp.org iburst
  server 2.pool.ntp.org iburst
  server 3.pool.ntp.org iburst
  

• Allow NTP requests from your local network:

  allow 192.168.1.0/24
  

• (Optional) Enable the server to act as a fallback source:

  local stratum 10
  

Save and exit the file.

Step 4: Start and Enable Chrony

Start the Chrony service and enable it to start on boot:

sudo systemctl start chronyd
sudo systemctl enable chronyd

Check the service status:

sudo systemctl status chronyd

Step 5: Adjust Firewall Settings

To allow NTP traffic through the firewall, open port 123/UDP:

sudo firewall-cmd --permanent --add-service=ntp
sudo firewall-cmd --reload

Step 6: Verify Configuration

Use Chrony commands to ensure your server is configured correctly:

1. View the active time sources:

   chronyc sources
   

2. Check synchronization status:

   chronyc tracking
   

4. Testing the NTP Server

To confirm that other systems can sync with your NTP server:

1. Set up a client system with Chrony installed.

2. Edit the client’s /etc/chrony.conf file, pointing it to your NTP server’s IP address:

   server <NTP-server-IP>
   

3. Restart the Chrony service:

   sudo systemctl restart chronyd
   

4. Verify time synchronization on the client:

   chronyc sources
   

5. Troubleshooting Tips

1. Chrony not starting:
   Check logs for details:

   journalctl -xe | grep chronyd
   

2. Firewall blocking traffic:
   Ensure port 123/UDP is open and correctly configured.

3. Clients not syncing:
   Verify the allow directive in the server’s Chrony configuration and confirm network connectivity.

Conclusion

Configuring an NTP server on AlmaLinux using Chrony is straightforward. With these steps, you can maintain precise time synchronization across your network, ensuring smooth operations and enhanced security. Whether you’re running a small network or an enterprise environment, this setup will provide the reliable timekeeping needed for modern systems.