If the time on your workstation or server is not stable, strange errors might appear, such as:
$ tar zxvf /tmp/archive.tgz tar: my-file: time stamp 2019-03-28 14:04:45 is 0.042713488 s in the future
This can happen when your NTP daemon is not synchronized. This means it cannot reliably determine the current time.
First, make sure your NTP daemon is started:
$ sudo systemctl status ntpd ● ntpd.service - Network Time Service Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled) Active: active (running) since Thu 2019-03-28 17:13:10 CET; 16h ago Process: 33844 ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=0/SUCCESS) Main PID: 33845 (ntpd) Tasks: 1 Memory: 924.0K CGroup: /system.slice/ntpd.service └─33845 /usr/sbin/ntpd -u ntp:ntp -g
For your NTP daemon to be started, the state must be
Then, you can query its status with the
$ sudo ntpdc -c sysinfo system peer: www.almaprovence.fr system peer mode: client leap indicator: 00 stratum: 3 precision: -25 root distance: 0.00130 s root dispersion: 0.02950 s reference ID: [220.127.116.11] reference time: e0485cce.58fb4baf Fri, Mar 29 2019 9:58:54.347 system flags: auth ntp kernel stats jitter: 0.000259 s stability: 0.000 ppm broadcastdelay: 0.000000 s authdelay: 0.000000 s
In this output, you need to check the stratum.
The stratum tells you how far you are from the reference clock (the world
atomic clock). The closer you are,
the lower is the
stratum and the more stable your clock will be.
Usually, your stratum will be between 3 and 5. By convention, 16 means “unsynchronized”.
You can query the list of peers your NTP daemon is synchronized to with the
$ sudo ntpq -c peers remote refid st t when poll reach delay offset jitter ============================================================================== -stardust.ploup. 18.104.22.168 3 u 782 1024 377 4.272 -1.984 2.479 +server.bertold. 22.214.171.124 2 u 679 1024 377 4.235 -0.152 0.629 *www.almaprovenc 126.96.36.199 2 u 854 1024 377 0.321 -0.225 0.502 +ns.rail.eu.org 188.8.131.52 2 u 563 1024 377 0.455 0.413 0.630
Again, check the
st column (abbreviation for
stratum) and make sure your
peers have a correct stratum. As above, 16 means “unsynchronized”.
jitter column are also useful:
offsettells you how far away in time your peers are.
jittertells you how stable your peers are.
Last but not least, you can troubleshoot network issues with the
For the test to be meaningful, you need to shut down temporarily the NTP daemon:
sudo systemctl stop ntpd
Then, run the ntpdate command:
$ sudo ntpdate -q 0.rhel.pool.ntp.org server 184.108.40.206, stratum 2, offset -0.000393, delay 0.02974 server 220.127.116.11, stratum 2, offset 0.004071, delay 0.02733 server 18.104.22.168, stratum 2, offset -0.005378, delay 0.03003 server 22.214.171.124, stratum 2, offset 0.000207, delay 0.02658 29 Mar 10:45:09 ntpdate: adjust time server 126.96.36.199 offset 0.000207 sec
It is important to shut down the NTP daemon and run the
sudo in order for ntpdate to successfully bind to the NTP port,
ntpdate command fails, it is a strong indication that there is a network
issue between your host and the NTP peers.
After this step, do not forget to restart your NTP daemon:
sudo systemctl start ntpd