Force systemd timesyncd to sync time with NTP server immediately

Solution 1:

Without installing any more packages... Turn NTP off, manually set the time to be close enough, turn NTP back on:

Set NTP Service inactive

$ timedatectl set-ntp false

Set the time manually

Get the approximate LOCAL time from the wall clock, your phone, the Internet. It doesn't need to be perfect because we'll turn ntp back on in a moment...

$ sudo timedatectl set-time "2019-06-22 13:41:00"

Set NTP service active

$ sudo timedatectl set-ntp true

Wait.

Wait a few minutes. If the response in timedatectl does not change then you have networking issues.

john@mybox:~$ timedatectl
               Local time: Sat 2019-06-22 13:49:53 AEST
           Universal time: Sat 2019-06-22 03:49:53 UTC
                 RTC time: Sat 2019-06-22 03:49:54
                Time zone: Australia/Sydney (AEST, +1000)
System clock synchronized: no
              NTP service: active
          RTC in local TZ: no

The "System clock synchronized: no" will turn to "yes" when it has adjusted enough to be considered 'in sync'. Something like:

john@mybox:~$ timedatectl 
               Local time: Wed 2020-07-22 09:50:32 AEST  
           Universal time: Tue 2020-07-21 23:50:32 UTC   
                 RTC time: Tue 2020-07-21 23:50:32       
                Time zone: Australia/Sydney (AEST, +1000)
System clock synchronized: yes                           
              NTP service: active                        
          RTC in local TZ: no  

and

john@mybox:~$ timedatectl timesync-status
       Server: 91.189.91.157 (ntp.ubuntu.com)  
Poll interval: 1min 4s (min: 32s; max 34min 8s)
         Leap: normal                          
      Version: 4                               
      Stratum: 2                               
    Reference: 8CCBCC4D                        
    Precision: 1us (-24)                       
Root distance: 64.781ms (max: 5s)              
       Offset: -88.040ms                       
        Delay: 754.084ms                       
       Jitter: 78.200ms                        
  Packet count: 8                               
     Frequency: -187.812ppm  

Trouble shooting

$ cat /etc/systemd/timesyncd.conf
[Time]
NTP=pool.ntp.org

$ timedatectl timesync-status
       Server: 13.210.208.89 (au.pool.ntp.org)
Poll interval: 8min 32s (min: 32s; max 34min 8s)
 Packet count: 0

$ grep systemd-timesyncd /var/log/syslog | tail
Jun 22 14:13:09 meebox systemd-timesyncd[8333]: Timed out waiting for reply from 103.214.220.220:123 (au.pool.ntp.org).

My ntp packets were being blocked by the corporate firewall.

Solution 2:

To use an actual NTP implementation, you need to install and configure one, chrony or maybe ntpd. Do so if you require any monitoring of time performance. I will assume chrony.

Add iburst to your pool or server lines in your config to speed up the initial few packets. It still may take a couple minutes to stabilize, be patient.

chronyc tracking will show the current offset. Have an idea of what your requirements are, one second accuracy can easily tolerate tens of milliseconds offset.

chronyc makestep will make the current adjustment immediately. Not necessary usually.

---

timesyncd is an SNTP client that can set the time, but not discipline it gradually and continuously, nor filter remote NTP server based on quality. (It also cannot talk to time hardware or PTP, only NTP protocol.) A little better than repeated ntpdate, by which I mean not very good clock. Personally, I replace it on most servers.

About the only way to set the time with timesyncd is manually: timedatectl set-time "2019-01-15 00:40:16". It does not have robust means to discipline and monitor the clock. Basic NTP stats via timedatectl timesync-status are a relatively new thing, I don't think that option is available in Red Hat 7 or Ubuntu 18.04.

systemd defines "syncronized" to be if NTP was ever used to tell Linux to adjust the clock. Specifically, if kernel discipline call adjtimex() returned without error, and not the initial state. See the source code, systemd/src/basic/time-util.c.