시간 동기화(크로니)

# Overall time status
timedatectl
 
# Confirm which service is handling sync
systemctl status chrony
 
# If Chrony is not installed and timesyncd is in use
timedatectl show-timesync

# A fresh 26.04 install usually has Chrony pre-installed and enabled
sudo apt update
sudo apt install chrony
 
# Enable and start immediately
sudo systemctl enable --now chrony

sudo nano /etc/chrony/chrony.conf

# Use the Ubuntu NTP pool (default)
pool ntp.ubuntu.com iburst maxsources 4

# Record the offset of the system clock vs. the hardware clock to speed up future sync
driftfile /var/lib/chrony/chrony.drift

# Step the clock in one go when the initial offset is large (first 3 updates)
makestep 1.0 3

sudo systemctl restart chrony

# View time sources and their status
chronyc sources -v
 
# View sync statistics (offset, jitter)
chronyc tracking
 
# View per-source measurement statistics
chronyc sourcestats
 
# Force an immediate step toward the server
sudo chronyc makestep
 
# Check whether the clock is synchronized
chronyc tracking | grep "Leap status"

# Allow LAN clients to query this host's time
allow 192.168.1.0/24

sudo systemctl restart chrony
 
# Open the NTP firewall port (UDP 123)
sudo ufw allow 123/udp