Installing NTP (time synchronisation)
19 May 2005
- Set timezone (optional)
- create symbolical link from
/usr/share/zoneinfo/... to /etc/localtime:
ln -sf /usr/share/zoneinfo/Europe/Brussels /etc/localtime
- Set UTC mode (optional)
- if your hardware clock runs in UTC (Universal Coordinated Time) mode, add
UTC=true
to the /etc/sysconfig/clock file
- Make sure
ntpd is not running
- Use
service ntpd stop to stop it.
- Choose the NTP server you will get your time from
- it can be an internal server that has the NTP service open for clients, or an public NTP server. To be sure, use 2 servers. To check if you can access it, run
ntpdate timeserver.ntp.ch
- Edit the
/etc/ntp.conf file
- Rename the current file to
ntp.bak.conf and make a small new one:
restrict default ignore<br />
server timeserver.ntp.ch # Swiss time<br />
server ntp.ucsd.edu # Univ of California, San Diego<br />
restrict timeserver.ntp.ch mask 255.255.255.255 nomodify notrap noquery<br />
restrict ntp.ucsd.edu mask 255.255.255.255 nomodify notrap noquery<br />
server 127.127.1.0 # local clock<br />
fudge 127.127.1.0 stratum 10 #so it only takes over if the rest fails<br />
restrict 127.0.0.1 driftfile /etc/ntp/drift broadcastdelay 0.008 authenticate no
- Set your system clock right
- Run the following command a couple of times:
ntpdate -u timeserver.ntp.ch # or whatever server you want to use
You will see the initial diffence in time go away afer the 2nd or 3rd time.
- Set hardware clock
/sbin/hwclock --systohc- Run the
ntpd daemon
service ntpd start- Add
ntpd to the services started at boot time
chkconfig ntpd on- Check the NTP results
ntpd -p
will show you what the difference is between your clock and that of the servers you added. You are looking for lines like
<br />
remote refid st t when poll reach delay offset jitter<br />
==========================================================================<br />
LOCAL LOCAL 10 l 30 64 377 0.000 0.000 0.004 *<br />
192.168.246.107 192.168.246.88 3 u 41 128 177 0.313 5.598 0.345
and not lines like
<br />
remote refid st t when poll reach delay offset jitter<br />
==========================================================================<br />
192.168.246.126 LOCAL 11 u 37 128 375 0.204 6082.02 6069.84
Jitter is too high!
