This page describes what to do in case of an Icinga alert. For more information you could search the govuk-puppet repo for the source of the alert

Warning This document has not been updated for a while now. It may be out of date.

Last updated: 5 Apr 2022

ntp drift too high

The Network Time Protocol (NTP) daemon (ntpd) is responsible for keeping system time synchronised with standard time servers on the Internet.

The ntpd.drift file records the latest estimate of clock frequency error. If this value gets too high, this can be an indicator of large error between the system clock and the real time.

SSH to the affected machine, then run:

sudo service ntp stop
sudo ntpdate -B ntp.ubuntu.com
sudo service ntp start

Note

ntpdate -B will try to slew the time offset, which means continually adding/subtracting little bits of time until the clock is in sync. This is in contrast to a step change, where the clock’s time is just changed. Step changes can cause - for example - log timestamp inconsistencies.

According to the ntpdate man page, the slew can take hours to gradually take effect.

Additionally, the ntpdate functionality has been made available in the ntpd program. To resync an offset bigger than 1000, you can run sudo service ntp stop; sudo ntpd -gq; sudo service ntp start.