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I have a LAN that is not connected to the internet, and I am trying to sychronize all the machines, Windows and Linux, to an NTP server. All I've been able to find is setting up an NTP client with an internet NTP server.

How can I setup my own Linux NTP server, or find good documentation on how?

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  • Try googling for "openntpd" (the server) and "ntpdate" (the client).
    – Cory J
    Commented Jun 10, 2010 at 19:16

2 Answers 2

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You're creating an island time zone. In effect you're creating a new Stratum 1 server for your network, and that can get tricky.

The fix for it is to use:

tos orphan

In your ntp.conf file. That tells NTP that your timezone is orphaned. But you need a new enough version (4.2.2) to use it. If you can't use, then use:

server 127.127.0.1
fudge 127.127.0.1 stratum 1

Also known as 'Undisciplined Local Clock'. Though I strongly recommend creating time pool, multiple servers who provide time mutually. It'll help slow down clock-drift.

server 127.127.0.1
peer 192.168.100.66
peer 192.168.100.69

And finally, if at all possible, using a GPS time-source is very well supported and will keep your time island close to true.

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  • 2
    According to support.ntp.org/bin/view/Support/OrphanMode 'tos orphan' requires an integer following to specify what time reference stratum server level must be unreachable before the ntpd process(es) switch to Orphan Mode. Placing just 'tos orphan' in the configuration file of a version 4.2.6 ntpd server gives an error like 'syntax error, unexpected T_EOC, expecting T_Integer'.
    – kbulgrien
    Commented Jul 28, 2014 at 17:47
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Depending on your distro, apt-get or yum install ntp should do the trick, than you just have to edit /etc/ntpd.conf to serve time.

http://www.ubuntugeek.com/network-time-protocol-ntp-server-and-clients-setup-in-ubuntu.html looks pretty in-depth.

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