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Does starting up NTPD daemon will automatically sync the client server with NTP server?
Our server is running 5 mins behind the current time when we checked the service was in stopped state so does just bringing up the service with perform the sync and correct the time drift or I need to manually run:
ntpdate -u <ntp server>
biz
Posted 2016-02-08T20:01:08.713
Reputation: 29
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This completely depends on the version of Linux you are using, but in general NTP syncing should be transparent and seamless; you should not have to manually kick off anything to get it running. That said, on older Ubuntu installs I did the following to force the system to rsync on a regular basis
First, create the following file in the cron daemon queue; I’m using Nano as an editor but feel free to use whatever plain text editor you prefer to us:
sudo nano /etc/cron.daily/ntpdate
And add this command to that file:
ntpdate -s -u ntp.ubuntu.com
Save and close that file and then make sure it has proper execute permissions like so:
sudo chmod 755 /etc/cron.daily/ntpdate
With that done, that ntupdate command will run daily behind the scenes without any additional user intervention.
JakeGould
Posted 2016-02-08T20:01:08.713
Reputation: 38 217
Is it safe to run ntpdate on a vm's which is holding SAP Application or Database ? I have seen many instance where correcting the time results in crashing the SAP instances.. – biz – 2016-02-08T20:18:38.493
@biz As you are behind the current time the application should be good. VMs should have their time synchronized to the containing server. Different containers have different mechanisms. This is where I would run
ntpd. The current NTP servers can be configured to slew time if you want to correct time slowly. – BillThor – 2016-02-09T00:49:13.460@BillThor So irrespective of behind/forward time is it safe to run ntpdate directly without bringing down the app/DB?Most of my servers are on OL5.5-6.x. Also can i configure a cronjob to run this on daily basis with slew argument? – biz – 2016-02-09T08:13:12.713
@biz
– BillThor – 2016-02-10T00:32:26.660ntpdis a deamon and should not need to be restarted. It is likely shutting down because your offset is outside the safe margins. Check http://serverfault.com/questions/671412/risk-of-starting-ntp-on-database-server/671489#671489 for some more details.Don't do it! ntpdate will jump the time - you don't want that with a production system. Configure/fix ntp and get that to slew the clock till its correct. That way you avoid any nasty jumps which might break something. – user3788685 – 2016-02-11T23:24:49.407