On CentOS 9, setting up time synchronization is typically done using the **chronyd** service, which is the default time synchronization daemon. Here’s a step-by-step guide:
### 1. Install chrony (if not already installed)
“`bash
sudo dnf install chrony
“`
### 2. Enable and start the chronyd service
“`bash
sudo systemctl enable –now chronyd
“`
### 3. Verify service status
“`bash
sudo systemctl status chronyd
# Should show “active (running)”
“`
### 4. Configure NTP servers (optional)
Edit the configuration file:
“`bash
sudo vi /etc/chrony.conf
“`
Add/replace server lines (e.g., using Alibaba Cloud NTP servers):
“`conf
server ntp.aliyun.com iburst
server ntp1.aliyun.com iburst
“`
Save and exit (`:wq` in vi).
### 5. Restart chronyd to apply changes
“`bash
sudo systemctl restart chronyd
“`
### 6. Check synchronization status
“`bash
chronyc tracking
# Look for “Leap status” and “System time”
chronyc sources -v
# Shows all configured NTP sources
“`
### 7. Set the timezone
“`bash
# List available timezones:
timedatectl list-timezones
# Set timezone (e.g., Shanghai):
sudo timedatectl set-timezone Asia/Shanghai
“`
### 8. Enable NTP synchronization
“`bash
sudo timedatectl set-ntp yes
“`
### 9. Verify time configuration
“`bash
timedatectl
“`
Check that:
– `NTP service: active`
– `System clock synchronized: yes`
– Correct timezone shows
### 10. Force immediate synchronization (if needed)
“`bash
sudo chronyc -a makestep
“`
### Troubleshooting Tips:
1. **Firewall configuration** (allow NTP traffic):
“`bash
sudo firewall-cmd –add-service=ntp –permanent
sudo firewall-cmd –reload
“`
2. **Check detailed logs**:
“`bash
journalctl -u chronyd
“`
3. **Test connectivity to NTP servers**:
“`bash
chronyc -N server ntp.aliyun.com iburst
“`
4. **Reset chrony statistics** if needed:
“`bash
sudo chronyc -a online
“`
> **Note**: CentOS 9 uses chrony by default. For legacy systems, you could use `ntpd`, but chrony is recommended for better performance, especially on systems with intermittent network connections.