Chrony is the recommended Network Time Protocol (NTP) implementation for modern Linux distributions. Chrony synchronizes the system clock with configured NTP servers using UDP port 123.

Important Notes

• Use at least two NTP servers whenever possible.
• Internal enterprise NTP servers should be preferred over public NTP servers.
• Ensure UDP port 123 is permitted between clients and NTP servers.
• All LDAP providers, consumers, proxy servers, and authentication systems should synchronize to the same NTP source.
• Time synchronization is critical for TLS certificate validation, Kerberos authentication, log correlation, monitoring, and replication troubleshooting.

Set the Timezone

Display the current timezone configuration:

timedatectl

List available timezones:

timedatectl list-timezones

Example:

timedatectl list-timezones | grep New_York

Set the timezone:

sudo timedatectl set-timezone America/New_York

Verify the change:

timedatectl

Output:

Local time: Tue 2026-06-01 09:30:15 EDT
Universal time: Tue 2026-06-01 13:30:15 UTC
RTC time: Tue 2026-06-01 13:30:15
Time zone: America/New_York (EDT, -0400)
System clock synchronized: yes
NTP service: active

Install Chrony

RHEL, Rocky Linux, AlmaLinux, CentOS Stream

sudo dnf install chrony -y

Debian and Ubuntu

sudo apt update
sudo apt install chrony -y

SUSE Linux Enterprise Server (SLES)

sudo zypper install chrony

Enable and Start the Chrony Service

RHEL, Rocky Linux, AlmaLinux, CentOS Stream, SLES

sudo systemctl enable --now chronyd

Verify service status:

sudo systemctl status chronyd

Output:

● chronyd.service - NTP client/server
   Loaded: loaded
   Active: active (running)

Debian and Ubuntu

sudo systemctl enable --now chrony

Verify service status:

sudo systemctl status chrony

Output:

● chrony.service - chrony, an NTP client/server
   Loaded: loaded
   Active: active (running)

Configure NTP Servers

RHEL, Rocky Linux, AlmaLinux, CentOS Stream, SLES

Edit:

sudo vi /etc/chrony.conf

Debian and Ubuntu

Edit:

sudo vi /etc/chrony/chrony.conf

Example configuration:

server ntp1.company.com iburst
server ntp2.company.com iburst

Or use public NTP pool servers:

server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst
server 2.pool.ntp.org iburst
server 3.pool.ntp.org iburst

Restart Chrony after making changes:

RHEL/Rocky/SLES:

sudo systemctl restart chronyd

Debian/Ubuntu:

sudo systemctl restart chrony

Verify Time Synchronization

Display synchronization status:

chronyc tracking

Example output:

Reference ID    : C0A80101
Stratum         : 2
System time     : synchronized
Last offset     : 0.000123 seconds

Display configured NTP sources:

chronyc sources -v

Example output:

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^* ntp1.company.com              2   6   377     42   +15us[ +20us] +/- 1ms
^+ ntp2.company.com              2   6   377     44   +18us[ +23us] +/- 2ms

Verify synchronization using systemd:

timedatectl

Output:

System clock synchronized: yes
NTP service: active

Force an Immediate Time Correction

If the server has significant clock drift:

sudo chronyc makestep

Verify synchronization:

chronyc tracking

Troubleshooting

Check Chrony Service Status

RHEL/Rocky/SLES:

systemctl status chronyd

Debian/Ubuntu:

systemctl status chrony

Check NTP Sources

chronyc sources -v

Check Synchronization Status

chronyc tracking

Review Logs

RHEL/Rocky/SLES:

journalctl -u chronyd

Debian/Ubuntu:

journalctl -u chrony

Verify Network Connectivity

Chrony communicates using UDP port 123.

Verify DNS resolution:

host ntp1.company.com

Verify firewall and network connectivity to configured NTP servers.