Installing and Configuring NTP Server on Ubuntu 22.04/Debian 11

13/07/2025

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Installing and Configuring NTP Server on Ubuntu 22.04/Debian 11

Ensuring Accurate Time Synchronization on Your Linux Servers

Accurate time is absolutely critical for modern computing systems. Without precise time synchronization, you can encounter a wide range of issues, from problematic log analysis and security vulnerabilities to failures in distributed applications and database inconsistencies. The Network Time Protocol (NTP) is the standard way to ensure all devices on your network agree on the correct time. While most systems can synchronize with external NTP servers, setting up your own internal NTP server offers benefits like reduced reliance on external networks, improved accuracy for internal clients, and greater control over your network’s time source.

This guide outlines the steps to install and configure an NTP server on common Linux distributions like Ubuntu and Debian, typically using the recommended chrony package.

Why Run an Internal NTP Server?

Centralized Control: You dictate the primary time source for your network.
Improved Performance: Clients synchronize with a local server, reducing latency and improving accuracy compared to synchronizing with distant external servers.
Reduced External Bandwidth: Only your server needs to synchronize externally, not every client.
Enhanced Security: You can restrict which clients can synchronize with your server.

Setting Up Your NTP Server with Chrony

chrony is a flexible and lightweight NTP client and server, often preferred over the older ntpd for its faster synchronization and better handling of intermittent network connectivity.

1. Install the chrony Package:

The first step is to install the necessary software. Open your server’s terminal and run the following command:

sudo apt update
sudo apt install chrony

This command updates your package list and then installs the chrony software. The service typically starts automatically after installation.

2. Configure Chrony:

The main configuration file for chrony is located at /etc/chrony/chrony.conf. You’ll need to edit this file to define your time sources and configure access for clients.

sudo nano /etc/chrony/chrony.conf

Inside the file, you’ll find lines starting with pool or server. These specify the upstream NTP servers your server will synchronize with. You can keep the defaults provided or replace them with servers closer to your location or known reliable public servers.

Key configuration options:

pool / server: Defines the upstream NTP servers.
```
pool ntp.ubuntu.com iburst maxsources 4
# or specific servers like:
# server 0.pool.ntp.org iburst
# server 1.pool.ntp.org iburst
```
Using iburst speeds up the initial synchronization. maxsources limits the number of sources used from a pool entry.
allow: Specifies which clients or networks are permitted to synchronize with this server. This is a crucial security step. By default, no clients might be allowed. You must add entries for your internal network(s).
```
allow 192.168.1.0/24
allow 10.0.0.0/8
```
Replace the example IP ranges with your actual internal network subnets. If you omit allow, only localhost can sync.
local stratum 10: If your server cannot reach any external sources (e.g., for an isolated network), this option allows it to act as an authoritative time source, albeit with a defined stratum level (lower is better, but 10 is typical for a server not synchronized to a hardware clock).

After making your changes, save and close the file.

3. Restart the Chrony Service:

For the configuration changes to take effect, you need to restart the chrony service:

sudo systemctl restart chrony

You can check the service status to ensure it’s running without errors:

sudo systemctl status chrony

4. Verify Synchronization Status:

chrony provides command-line tools to check its synchronization status and sources.

Check Tracking Status:
```
chronyc tracking
```
This command shows details about the synchronization status, including the reference ID, stratum, and estimated system time offset. Look for synchronized yes.
Check Configured Sources:
```
chronyc sources
```
This displays a list of the configured NTP sources and their status. The state indicator (^*, +, -, #, ?, x) shows the source’s quality and selection status. ^* indicates the currently selected source.
Check Source Statistics:
bash chronyc sourcestats
Provides more detailed statistics about the interaction with each source.

Security Considerations

Restricting access using the allow directive in /etc/chrony/chrony.conf is the most important security measure. Never leave your NTP server open to the entire internet unless you specifically intend to provide a public time service and have taken appropriate measures. Limit access only to the IP ranges or specific hosts that need to synchronize with your server.

Setting up your own NTP server provides a robust and reliable method for managing time across your network. By following these steps, you can ensure your servers and clients are always accurately synchronized, paving the way for smoother operations and easier troubleshooting.

Source: https://kifarunix.com/install-and-setup-ntp-server-on-ubuntu-22-04-debian-11/