Chrony is the default NTP client for CentOS 8 or higher.

Installation[edit | edit source]

# yum install chrony
# systemctl enable chronyd

If using Chrony as a NTP server, adjust the firewall rules to allow incoming NTP traffic.

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

Configuration[edit | edit source]

The main configuration file is at /etc/chrony.conf.

NTP servers can be defined with Server or pool. Eg:

server 136.159.2.1
pool 2.centos.pool.ntp.org iburst

If using Chrony as a NTP server, define which subnets have access with the Allow x.x.x.x/yy directive.

Restart the chronyd service to apply.

# systemctl restart chronyd

Usage[edit | edit source]

Check the status of the NTP sources and peers:

# chronyc sources
210 Number of sources = 4
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^+ 173.0.48.220.reverse.wow>     2   6   177    54    -19ms[  -19ms] +/-   79ms
^+ time.cloudflare.com           3   6   177    54    +11ms[  +11ms] +/-   44ms
^* voipmonitor.wci.com           2   6   177    55  +7058us[+1670us] +/-   29ms
^+ 144.172.126.201               2   6   177    54  +6575us[+6575us] +/-   22ms

# chronyc clients
Hostname                      NTP   Drop Int IntL Last     Cmd   Drop Int  Last
===============================================================================
localhost                       0      0   -   -     -       1      0   -   229
localhost                       0      0   -   -     -       1      0   -   229