Identify Your NTP Daemon
First, determine which NTP daemon your system uses:
root@server:~# systemctl list-units --type=service | grep -E "ntp|chrony|time"
chronyd.service loaded active running NTP client/server
systemd-timesyncd.service loaded active running Network Time Synchronization
| Daemon | Config File | Query Command |
|---|
| ntpd (classic) |
/etc/ntp.conf |
ntpq -p |
| chronyd |
/etc/chrony/chrony.conf or /etc/chrony.conf |
chronyc sources |
| systemd-timesyncd |
/etc/systemd/timesyncd.conf |
timedatectl timesync-status |
| W32Time (Windows) |
Registry / GPO |
w32tm /query /status |
Daemon Not Starting
Symptom: Service fails to start or immediately stops
The NTP service won't start, or starts and immediately crashes.
Check Service Status
root@server:~# systemctl status chronyd
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled)
Active: failed (Result: exit-code) since...
root@server:~# journalctl -xeu chronyd --no-pager | tail -50
Common Causes & Solutions
Cause 1: Configuration Syntax Error
root@server:~# chronyd -p
root@server:~# ntpd -n -d -c /etc/ntp.conf
Cause 2: Port 123 Already in Use
root@server:~# ss -ulnp | grep 123
UNCONN 0 0 *:123 *:* users:(("ntpd",pid=1234,fd=16))
root@server:~# systemctl stop ntpd
root@server:~# systemctl start chronyd
Cause 3: Permission Issues
root@server:~# ls -la /var/lib/chrony/drift
root@server:~# chown chrony:chrony /var/lib/chrony/drift
root@server:~# chown ntp:ntp /var/lib/ntp/drift
Cause 4: Multiple NTP Services Conflicting
root@server:~# systemctl disable --now systemd-timesyncd
root@server:~# systemctl disable --now ntpd
root@server:~# systemctl enable --now chronyd
Stratum 16 / No Sync Source
Symptom: System shows stratum 16 or "unsynchronised"
Stratum 16 means the NTP daemon has no valid time source. This is the "invalid/unknown" stratum level.
root@server:~# ntpq -c rv
...stratum=16, precision=-23...
root@server:~# chronyc tracking
Reference ID : 00000000 ()
Stratum : 0
...
Leap status : Not synchronised
Solutions
Check NTP Server Configuration
root@server:~# grep -E "^server|^pool" /etc/chrony/chrony.conf
pool 2.debian.pool.ntp.org iburst
server ntp.rdem-systems.com iburst prefer
Test Server Connectivity
root@server:~# chronyc sources -v
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^? ntp.rdem-systems.com 0 6 0 - +0ns[ +0ns] +/- 0ns
Force Initial Sync
root@server:~# chronyc makestep
root@server:~# systemctl stop ntpd
root@server:~# ntpdate -b pool.ntp.org
root@server:~# systemctl start ntpd
Stuck in .INIT State
Symptom: NTP shows .INIT for all servers
The refid column shows ".INIT." indicating the daemon hasn't completed initial synchronization.
root@server:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
0.pool.ntp.org .INIT. 16 p - 64 0 0.000 0.000 0.000
Common Causes
- System time too far off (>1000 seconds default panic threshold)
- Network issues preventing NTP queries
- DNS resolution failing
- Firewall blocking responses
Solution: Check DNS Resolution
root@server:~# host pool.ntp.org
pool.ntp.org has address 162.159.200.1
pool.ntp.org has address 162.159.200.123
root@server:~# echo "server 195.154.XXX.XXX iburst" >> /etc/ntp.conf
Solution: Fix Large Time Offset
root@server:~# ntpdate -q pool.ntp.org
server 162.159.200.1, stratum 3, offset -3600.123456...
root@server:~# systemctl stop ntpd
root@server:~# ntpdate -b pool.ntp.org
root@server:~# systemctl start ntpd
Wait Time
Initial synchronization can take 5-15 minutes depending on network conditions and polling intervals. Check the "reach" value - it should increase from 0 to 377 over time as queries succeed.
False Ticker Detection
Symptom: Server marked with 'x' (falseticker)
NTP has determined this server's time differs significantly from the majority of sources.
root@server:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
xntp1.example.com .GPS. 1 u 45 64 377 12.543 -250.284 1.023
*ntp2.example.com .PPS. 1 u 42 64 377 28.123 0.842 2.156
Understanding False Tickers
NTP uses a voting algorithm. If one server disagrees with the majority by more than a threshold, it's marked as a "false ticker" (x) and excluded from time calculations.
Solution 1: Add More Servers
With only 2 servers, NTP can't determine which is correct. Use at least 4 servers:
server ntp.rdem-systems.com iburst prefer
pool 0.pool.ntp.org iburst maxsources 2
pool 1.pool.ntp.org iburst maxsources 2
Solution 2: Verify Server Accuracy
root@server:~# ntpdate -q ntp1.example.com
root@server:~# ntpdate -q ntp2.example.com
Solution 3: Check GPS/PPS Source
If a GPS receiver is marked false ticker, check:
- GPS antenna signal strength
- Number of satellites locked (need 4+)
- PPS signal cable and configuration
Reach Value is 0
Symptom: Reach column shows 0 for all servers
No successful NTP queries have been received. The daemon cannot communicate with any server.
root@server:~# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
pool.ntp.org .POOL. 16 p - 64 0 0.000 0.000 0.000
Understanding Reach
Reach is an 8-bit octal register showing the last 8 query results. 377 (octal) = 11111111 (binary) = all 8 queries succeeded. 0 = no successful queries.
Diagnostic Steps
root@server:~# tcpdump -i any port 123 -c 10
root@server:~# iptables -L -n | grep 123
root@server:~# ntpdate -d pool.ntp.org 2>&1 | head -30
root@server:~# traceroute -U -p 123 pool.ntp.org
Common Fixes
- Open firewall:
ufw allow 123/udp
- Check DNS works:
host pool.ntp.org
- Use IP instead of hostname in config
- Restart daemon:
systemctl restart chronyd
- Wait - reach increases every poll interval
Chrony-Specific Issues
chronyc "506 Cannot talk to daemon"
Symptom: chronyc commands fail with connection error
Solution
root@server:~# systemctl status chronyd
root@server:~# grep cmdport /etc/chrony/chrony.conf
"makestep" Doesn't Work
Check makestep configuration
makestep 1 3 # Step if offset > 1s, first 3 updates
makestep 1 -1 # Step if offset > 1s, unlimited times
Slow Initial Sync
Speed up initial synchronization
server ntp.rdem-systems.com iburst
initstepslew 10 ntp.rdem-systems.com pool.ntp.org
Windows W32Time Issues
"The computer did not resync because no time data was available"
Solution
C:\> net stop w32time
C:\> w32tm /unregister
C:\> w32tm /register
C:\> net start w32time
C:\> w32tm /config /manualpeerlist:"pool-ntp.rdem-systems.com,0x8" /syncfromflags:manual /update
C:\> w32tm /resync /force
Domain Controller Time Issues
Configure PDC Emulator
C:\> w32tm /config /manualpeerlist:"pool-ntp.rdem-systems.com" /syncfromflags:manual /reliable:yes /update
C:\> net stop w32time && net start w32time
C:\> w32tm /resync
Hyper-V Time Sync Conflicts
Virtual Machine Warning
Hyper-V VMs have time sync integration services that can conflict with W32Time. Disable VM time sync if using external NTP:
PS C:\> Disable-VMIntegrationService -VMName "YourVM" -Name "Time Synchronization"
Verify Your Fix
After troubleshooting, test your NTP synchronization: