How To Repair Digital Clock Drift

		GNU/Linux Desktop Survival Guide past Graham Williams

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Some organization clocks practise non run all that accurately. Some hints on dealing with clock problems can be constitute in the Clock mini HOWTO at http://world wide web.tldp.org/HOWTO/Clock.html, but the hwclock and adjtimex manual pages tend to be an easier read!

Be warned though, the Debian proposition is not to dabble with hwclock . Information technology is highly recommended that you install the ntp-simple bundle (to run a daemon that checks regularly to keep your clock in sync) and/or ntpdate (to update your clock at each boot or to manually run a command to update your clock) to keep your clock accurate. These are discussed in more particular beneath.

If you install both ntp-uncomplicated and ntpdate and you manually fix up cron to run ntpdate every 60 minutes then you will probably receive e-mail every hr to tell you that ntpdate can't go the ntp socket (considering the ntpd daemon from ntp-elementary is probably using information technology!):

          half-dozen Oct 09:08:02 ntpdate[23856]: the NTP socket is in use, exiting

Just install one of them!

Using NTP

The Network Time Protocol (NTP) daemon provided by the ntp-simple package is by far the easiest mode to manage the accuracy of your clock, particularly if you are continued to the internet (fifty-fifty if but intermittently).

The ntp-elementary daemon (ntpd) effectively sets the clock by speeding it up or slowing it downwardly depending on its natural migrate so that it gets in sync and stays there. This avoids a "sudden daze" to the system with a dramatic change to the time, although more often than not the system tin can handle information technology.

The primary configuration required is to identify an NTP server. Look at the lists at http://www.eecis.udel.edu/~ntp/, for example.

After running ntpd for a little while your clock will be ready to an accurate fourth dimension and volition maintain an accurate time. However, if the amount of difference is too great then ntpd will non modify the clock. Later on setting up ntp-simple you can install ntpdate and on install (and reboot) the clock will be updated to the correct time co-ordinate to the server you have called for ntp-simple.

With ntp-simple installed on one of your hosts, Velox (36.52) for example, on the local network you lot can now use Velox (36.52) as a ntp server simply by installing ntp on each machine and pointing them to Velox (36.52) as the server.

ntpdate

If you only accept irregular admission to the Cyberspace then ntpdate is useful. The package provides the ntpdate command to query an NTP server and to update your clock. You can do this manually as you run across fit with:

          $ ntpdate ntp.togaware.com

The advantage is that you will not take regular net transmissions as with the NTP server. This could save you up to 4MB per day. This could also be washed as a cron task, for example.

For irregular access through a modem using PPP though, a adept idea is to create a script file in /etc/ppp/ip-upwards.d called ntpdate containing:

#!/bin/sh  #invoke ntpdate to set fourth dimension from system clock if [ -x /usr/sbin/ntpdate ]; and then         /usr/sbin/ntpdate -s -t 5 ntp.togaware.com         /sbin/hwclock --systohc fi

Brand sure the script is executable:

          # chmod a+rx /etc/ppp/ip-up.d/ntpdate

And then each time you connect the local clock volition be synchronised with the NTP server.

Subsections

- Using NTP
- ntpdate

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