61. Keeping time with ntp on debian

Set-up
NTP is used to accurately sync the clock on your computer and keep it current.

Install ntp if you haven't already
sudo apt-get install ntp ntpdate
the configuration file is in /etc/ntp.conf

You can have a look through the ntp.conf file and change the server lines to something closer to home if necessary -- you can find server pools for different regions here: http://www.pool.ntp.org/en/

If your clock is off by too much, syncing won't work, so you might want to do this to sync up the first time:

sudo service ntp stop
sudo ntpdate -u 0.pool.ntp.org

 8 Feb 16:28:42 ntpdate[10484]: step time server 121.0.0.41 offset -648.353916 sec

compare the output of date with e.g http://worldtimeserver.com

Now, start the ntp server again:

sudo service ntp start

Running your own local ntp server for your LAN

The NTP daemon will (presumably) run happily in the background and gradually adjust the time if it's off.

For a sub-LAN  you may want to sync e.g. the gateway to the ntp pool, then sync all the local computers to the gateway in order to cut down on traffic, like so.

Here's my version of that link:

server:

Here's /etc/ntp.conf on my server, which is seen as 192.168.1.1 by the local subnet (connected to inet on eth0 and subnet on eth1) . The last two lines were important to get it to work.

driftfile /var/lib/ntp/ntp.drift
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
server 0.oceania.pool.ntp.org
server 1.oceania.pool.ntp.org
server 2.oceania.pool.ntp.org
server 3.oceania.pool.ntp.org
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
restrict 127.0.0.1
restrict ::1
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
broadcast 192.168.1.255
server 127.127.1.0
fudge 127.127.1.0 stratum 10

sudo service ntp restart

and you're good to go

client:

/etc/ntp.conf

driftfile /var/lib/ntp/ntp.drift
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
server 192.168.1.1
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
restrict 127.0.0.1
restrict ::1
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
disable auth
broadcastclient

sudo service ntp restart

Checking if the client is connecting to the server.

me@kookaburra:~$ sudo service ntp stop
Stopping NTP server: ntpd.
me@kookaburra:~$ sudo ntpdate 192.168.1.1
 8 Feb 17:22:35 ntpdate[12846]: adjust time server 192.168.1.1 offset -0.008602 sec
me@kookaburra:~$ sudo service ntp start
Starting NTP server: ntpd.
me@kookaburra:~$ sudo ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 beryllium       LOCAL(0)        11 u    2   64    1    0.189   -7.332   0.000

(beryllium is the name of my 192.168.1.1 server.)