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  • How to forcefully sync date and time using the NTP server in Linux


    The commands and steps to initiate a forceful sync with NTP server may vary based on the distribution you are using.

    By default if NTP service is running it will automatically sync the client's date and time from the NTP server based on the polling interval but what if you want to do a force sync immediately and cannot wait for the NTP client to sync it.



    On SuSE Enterprise Linux
    The current date and time on my node is
    # date
    Fri Dec  8 02:51:04 IST 2017

    My ntp service status
    # /etc/init.d/ntp status
         remote           refid      st t when poll reach   delay   offset  jitter
    ==============================================================================
     192.168.10.100    10.171.8.4       3 u    1   64    1    0.173  -593996   0.000
     10.40.130.1     .INIT.          16 u    -   64    0    0.000    0.000   0.000

    Checking for network time protocol daemon (NTPD):                       running

    So my ntp client is running, lets change the date and time of my node before doing a force sync
    # date --set "4 Dec 2017 10:00:00"
    Mon Dec  4 10:00:00 IST 2017

    My new date and time
    # date
    Mon Dec  4 10:00:02 IST 2017

    Time to do a force sync
    # /etc/init.d/ntp ntptimeset
    Time synchronized with 192.168.10.100

    So as you see it immediately sent a request to the NTP server and updated the localhost date and time details from the NTP server
    # date
    Thu Dec  7 10:23:35 IST 2017



    On Red Hat Enterprise Linux 7
    Unfortunately ntptimeset is not available in Red Hat Enterprise Linux so we have to try something else

    My existing date and time
    # date
    Thu Dec  7 10:25:03 IST 2017

    NTPD service status
    # systemctl status ntpd
    ● ntpd.service - Network Time Service
       Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled)
       Active: active (running) since Wed 2017-12-06 17:43:02 IST; 16h ago
      Process: 5957 ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=0/SUCCESS)
     Main PID: 5958 (ntpd)
       CGroup: /system.slice/ntpd.service
               └─5958 /usr/sbin/ntpd -u ntp:ntp -g

    Dec 06 17:43:02 Ban17-pgw01-a systemd[1]: Starting Network Time Service...
    Dec 06 17:43:02 Ban17-pgw01-a ntpd[5957]: ntpd 4.2.6p5@1.2349-o Wed Mar  1 09:00:51 UTC 2017 (1)
    Dec 06 17:43:02 Ban17-pgw01-a systemd[1]: Started Network Time Service.
    Dec 06 17:43:02 Ban17-pgw01-a ntpd[5958]: proto: precision = 0.038 usec
    Dec 06 17:43:02 Ban17-pgw01-a ntpd[5958]: 0.0.0.0 c01d 0d kern kernel time sync enabled

    Now lets change the date and time
    # date --set "4 Dec 2017 10:00:00"
    Mon Dec  4 10:00:00 IST 2017

    First stop the ntpd service
    # systemctl stop ntpd

    Next initiate a force sync from your NTP server using the below command
    # ntpdate 192.168.10.100
     7 Dec 10:27:36 ntpdate[6701]: step time server 192.168.10.100 offset 260769.003401 sec

    Now start the NTP service again
    # systemctl start ntpd

    Lastly validate if your localhost date and time is updated correctly
    # date
    Thu Dec  7 10:27:48 IST 2017

    IMPORTANT NOTE: If you do not wish to stop the ntp server for doing the sync then use "-u" with ntpdate
    -u      Direct  ntpdate  to  use  an unprivileged port for outgoing packets. This is most useful
            when behind a firewall that blocks incoming traffic to privileged ports, and you want to
            synchronize with hosts beyond the firewall. Note that the -d option always uses unprivi‐
            leged ports.

    Without '-u' and when NTPD service is running
    # ntpdate  0.in.pool.ntp.org
    10 Feb 17:34:48 ntpdate[2574]: the NTP socket is in use, exiting

    With '-u' and ntpd running in the background
    # ntpdate  -u 0.in.pool.ntp.org
    10 Feb 17:35:22 ntpdate[2575]: step time server 13.126.37.14 offset 1.335054 sec

    I hope the article was useful.

    Deepak Prasad

    is a techie and an author who is still trying to survive in this IT generation with very little knowledge he has on Linux/Unix, VMware, SAN Storage, Automation, networking etc

    You can follow him on Facebook or Google+


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    How to forcefully sync date and time using the NTP server in Linux How to forcefully sync date and time using the NTP server in Linux Reviewed by Deepak Prasad on Friday, December 08, 2017 Rating: 5

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