This tutorial will help you install and configure NTP server using Chrony onRHEL/CentOS/Alma/Rocky 9|8. NTP (Network Time Protocol) is a network protocol that allows for clock synchronization between computer systems. Chrony is a versatile implementation of the Network Time Protocol. It has two programs chronyand chronyd.
- chronyd is a daemon that can be started at boot time
chronycis a command-line interface program which can be used to monitorchronyd’s performance and to change various operating parameters whilst it is running.
Installing Chrony NTP Server
Set timezone. Replace Africa/Nairobi timezone with your correct value.
sudo timedatectl set-timezone Africa/NairobiChrony can be installed from package manager.
sudo yum -y install chronyAfter the installation, start and enable chronyd service.
sudo systemctl enable --now chronydThe service status should show running
$ systemctl status chronyd
systemctl status chronyd
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2024-07-31 15:12:00 EAT; 1s ago
Docs: man:chronyd(8)
man:chrony.conf(5)
Process: 15159 ExecStopPost=/usr/libexec/chrony-helper remove-daemon-state (code=exited, status=0/SUCCESS)
Process: 15170 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
Process: 15164 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 15168 (chronyd)
Tasks: 1 (limit: 48750)
Memory: 908.0K
CGroup: /system.slice/chronyd.service
└─15168 /usr/sbin/chronyd
Jul 31 15:12:00 rocky8.cloudspinx.com systemd[1]: chronyd.service: Succeeded.
Jul 31 15:12:00 rocky8.cloudspinx.com systemd[1]: Stopped NTP client/server.
Jul 31 15:12:00 rocky8.cloudspinx.com systemd[1]: Starting NTP client/server...
Jul 31 15:12:00 rocky8.cloudspinx.com chronyd[15168]: chronyd version 4.5 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP +SCFILTER +SIGND +ASYNCDNS +NTS +SECHASH +IPV6 +DEBUG)
Jul 31 15:12:00 rocky8.cloudspinx.com chronyd[15168]: Loaded 0 symmetric keys
Jul 31 15:12:00 rocky8.cloudspinx.com chronyd[15168]: Frequency -40.323 +/- 0.052 ppm read from /var/lib/chrony/drift
Jul 31 15:12:00 rocky8.cloudspinx.com chronyd[15168]: Using right/UTC timezone to obtain leap second data
Jul 31 15:12:00 rocky8.cloudspinx.com systemd[1]: Started NTP client/server.Configuring Chrony NTP Server
After the installation, you can make the changes on Chrony main configuration file /etc/chrony.conf
One main configuration change you can make is to set the time servers closest to you. Since I’m in Nairobi, I’ll set Africa NTP pool of servers.
sudo vi /etc/chrony.confAdd comment to the first pool line and add a list of NTP servers.
#pool 2.rocky.pool.ntp.org iburstYou can use Global NTP server and the system will try finding the closest available servers for you.
server pool.ntp.org iburstOptionally select pool based on your geographic location. See all zones in All Pool Servers.
- Asia
server 0.asia.pool.ntp.org iburst
server 1.asia.pool.ntp.org iburst
server 2.asia.pool.ntp.org iburst
server 3.asia.pool.ntp.org iburst- Africa
server 0.africa.pool.ntp.org iburst
server 1.africa.pool.ntp.org iburst
server 2.africa.pool.ntp.org iburst
server 3.africa.pool.ntp.org iburst- Europe
server 0.europe.pool.ntp.org iburst
server 1.europe.pool.ntp.org iburst
server 2.europe.pool.ntp.org iburst
server 3.europe.pool.ntp.org iburst- North America
server 0.north-america.pool.ntp.org iburst
server 1.north-america.pool.ntp.org iburst
server 2.north-america.pool.ntp.org iburst
server 3.north-america.pool.ntp.org iburst- South America
server 0.south-america.pool.ntp.org iburst
server 1.south-america.pool.ntp.org iburst
server 2.south-america.pool.ntp.org iburst
server 3.south-america.pool.ntp.org iburstSet NTP synchronization.
sudo timedatectl set-ntp trueRestart chronyd service after making the change.
sudo systemctl restart chronydYou can also specify IP addresses or network address block that is allowed to access your NTP server.
# Allow NTP client access from local network.
allow 192.168.25.0/24If you have active firewalld service, allow ntp port.
sudo firewall-cmd --add-service=ntp --permanent
sudo firewall-cmd --reloadCheck if NTP server is working.
$ sudo chronyc sources
210 Number of sources = 3
MS Name/IP address Stratum Poll Reach LastRx Last sample
^+ ntp.dts.mg 2 7 377 127 +2102us[+1979us] +/- 98ms
^* 196.9.24.88 2 7 377 2 -11ms[ -11ms] +/- 103ms
^+ jhb-ntp.mweb.co.za 3 7 377 132 -76us[ +158us] +/- 103msConfigure NTP Client to use our NTP server
Now that you have Chrony NTP Server installed and configured, you can configure NTP client.
Set timezone.
sudo timedatectl set-timezone Africa/NairobiInstall chrony and configure it as NTP client.
sudo yum -y install chronyEdit the configuration file to set NTP server to point your newly configured NTP server.
$ sudo vi /etc/chrony.conf
server 192.168.25.3Set NTP synchronization.
sudo timedatectl set-ntp trueStart and enable the service.
sudo systemctl enable --now chronydVerify the setting using the following command:
$ sudo chronyc sources
210 Number of sources = 3
MS Name/IP address Stratum Poll Reach LastRx Last sample
^+ 192.168.25.3 2 7 377 61 +12ms[ +12ms] +/- 100msThat’s all. You now have NTP server working on RHEL 8 server. See how you can use the timedatectl command to synchronize the system clock with NTP server.
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