The Network Time Protocol or NTP is essential for synchronizing system clocks across your environment. Having a reliable and accurate time service is not only important for many different applications but for logging and auditing as well. In RHEL 8, Chrony is used for implementing NTP. In Part 1, we will review setting this service up as a client and look at the basic functionality of the chronyc command to interact with the chrony daemon, chronyd.

Client Setup

Install the Chrony package

# dnf install chrony

Enable and start the chrony daemon

# systemctl enable chronyd
# systemctl start chronyd

Verify NTP is working by using the chronyc command to display the current time sources. You can use the -v verbose flag to display a description for each column

# chronyc sources
210 Number of sources = 4
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^+ voipmonitor.wci.com           2   6    17     1  -2428us[-3365us] +/-   85ms
^* clock.trit.net                2   6    17     1   -362us[-1299us] +/-   94ms
^- radio-sunshine.org            2   6    17     1  -5644us[-5644us] +/-  177ms
^* time.cloudflare.com          2   6    17     0    +12ms[  +12ms] +/-  205ms

As you can see, Chrony is already configured to a pool of NTP sources. This is enabled by default within the configuration file /etc/chrony.conf.

# grep ^server /etc/chrony.conf
server 0.rhel.pool.ntp.org
server 1.rhel.pool.ntp.org
server 2.rhel.pool.ntp.org
server 3.rhel.pool.ntp.org

Add your own NTP Server

Edit the /etc/chrony.conf configuration file to add your own local time server. You can specify the ip or dns name. (See Part 2 for Server setup)

# vi /etc/chrony.conf
server t1.networklogician.com

Restart the Chrony daemon and verify the new source

# systemctl restart chronyd

# chronyc sources
210 Number of sources = 5
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^? t1.networklogician.com      1   6     1    27  -3350us[-1785us] +/-   53ms
^- voipmonitor.wci.com           2   6    17    21  +2542us[+2542us] +/-   68ms
^- clock.trit.net                3   6    17    22  -6294us[-9084us] +/-  147ms
^+ radio-sunshine.org            2   6    17    21  -3355us[-6145us] +/-   75ms
^* time.cloudflare.com           3   6    17    21  +1421us[-1369us] +/-   36ms

Other monitoring options that are useful to keep in mind when using the chronyc command are – rtcdata, smoothing, sources, sourcestats and tracking. You can review the manpage for a complete list or run help from the interactive terminal you get by running chronyc without options.

# chronyc

chronyc> help

In Part 2, we will cover the steps to setup the Chrony server and some of the main configuration options available within /etc/chrony.conf.