How to Install NTP Server On CentOS 8 /RHEL

In this tutorial we will learn:

  • How To Install NTP Server On CentOS 8 / CentOS 7 (CHRONY SUITE)
  • How to configure Chrony as NTP server

Introduction to the Chrony Suite

Chrony is an implementation of the Network Time Protocol (NTP). You can use Chrony:

to synchronize the system clock with NTP servers,
to synchronize the system clock with a reference clock, for example a GPS receiver,
to synchronize the system clock with a manual time input

chronyd can usually synchronize the clock faster and with better accuracy.
chronyd can work well in an environment where access to the time reference is intermittent, whereas ntpd needs regular polling of time reference to work well, also chronyd can perform well even when the network is congested for longer periods of time.

Install Chrony On CentOS 8 / CentOS 7 / RHEL

To install Chrony Suite execute DNF package manager:

# dnf install chrony

Example output:

Install Chrony On CentOS 8

After Chrony Suite successful install lets start Chrony and Enable Chrony NTP daemon to start after boot:

# systemctl start chronyd
# systemctl enable chronyd

To check Chrony status use:

# systemctl status chronyd

Configure Chrony as NTP server

By default, chronyd does not operate as an NTP server. So, we need to add an allow directive to the chrony.conf file in order for chronyd to open the server NTP port and respond to client requests.

Edit chrony.conf with any editor

# nano /etc/chrony.conf

Find out allow configuration directive and uncomment it. Then network address from which the clients are allowed to connect to the NTP server.

Configure Chrony as NTP server

Save and close config file, and then restart Chrony NTP daemon:

# systemctl start chronyd

If you want to Allow access to NTP server from multiple networks your chrony.conf ALLOW section should be like:

allow aaa.aaa.aaa.aaa/16
allow bbb.bbb.bbb.bbb/21
allow ccc.ccc.ccc.ccc/32

NTP Port Firewall Rule

Finlay don’t forget open NTP port on Linux firewall.

NTP protocol uses UDP port. So you need open UDP port 123 network address from which the clients are allowed to connect to the NTP server.

How To Check Chrony NTP Server

Check Chrony NTP server functionality

To check new installed NTP server functionality from client machine you can execute ntpdate command:

# ntpdate -u Your_ChronyNTP_Server

If everything is correct you will receive message like this:

26 Jun 00:03:16 ntpdate[15685]: adjust time server ntpserver.loc offset 0.005344 sec

Show the Chrony Server Current Time Sources

To check the Chrony NTP Server Current Time Sources run:

# chronyc sources

Example output:

Chrony NTP Server Time Sources

Congrats! We just learn How to Install NTP Server CentOS 8 /RHEL, Configure and test NTP server

   

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