Fixing system date out of sync in Debian —14 May 2013

I started using my old-ish Debian server again and realized the system date is off by 20 minutes…

The solution is to install ntpdate, which automatically synchronizes the clock at certain system events, for example when the network interface comes up.

To force synchronizing now, you can run ntpdate manually, but you must specify the NTP servers to use as reference on the command line, otherwise it will give you an error like this:

14 May 06:53:06 ntpdate[6505]: no servers can be used, exiting

An easier way is to run ntpdate-debian without arguments, which will use the NTP servers configured in /etc/default/ntpdate, which is a Debian-specific setup.