HOWTO: Set Up an NTP Server

[johnamcclintock]

Possibly a very stupid question but I'm going to ask it anyway:

Is it possible to set a Ubuntu machine up as an NTP server without it having any external clocks to reference to?

The reason I want to do this is that the machine itself has no Internet connectivity, typically, and is used to monitor Customer networks only so is intended to be secured and isolated from the Internet.

I assume this must be possible but wanted to ask first in case someone can very quickly answer for me.

Cheers,

John

[thug777]

http://ubuntuforums.org/showthread.php?t=579418

[johnamcclintock]

Thanks Thug. After some searching around I had figured this out. Unfortunately it's not helping me much as the Cisco switches I am trying to get to synchronise to my NTP server seem to not want to. They are seeing the stratum correctly (fudge+1) NTP server is directly connected into the switch in the NTP association but they are just refusing to use the server most of the time. On occasion, for no discernible reason, they will synch up but a reboot normally quickly fixes that. Most, most frustrating as if I install an NTP server on my Windows it work every time

[johnamcclintock]

Right, I have actually finally figured this out completely and the fault does not lie with the Ubuntu NTP server but rather with the switches. Even though the configuration guide claims that, if the switches are synchronised to an external time source they can provide time for other clients, this appears to be either a lie or there is an undocumented bug. Whenever I try to "serve" time from a switch to another switch for some reason the NTP server becomes unreachable to the original switch. This mean that the swtch become unsynchronised and thus no other switches will then synchronise to it! My fix, albeit not the cleanest ever, is to have all switches use the Linux server as the source for time (there is an IPSec tunnel between the network and the Linux machine hence it's not really a very nice solution!).
Now, my major problem seems to be that NTP on Ubuntu does not support authentication. Even the restrict part doesn't seem to stop the server sharing time with anything outside of the restrict list. Is there a definitive way to secure NTP, preferably by some sort of key exchange if possible?

Thanks,

John

[sirgad]

Just FYI: ntpd no longer reports synchronization in syslog, or anywhere else. This was relayed to me on the mailing list. Apparently, it was considered too "noisy". So, you should no longer use the "tail -f /var/log/syslog" command to look for entries of the type:

hostname ntpd[xxxx]: synchronized to x.x.x.x, stratum 2

to confirm synchronization.

S.

[rrbaps]

Hi,
I have connected my Ubuntu 11.04 system on a LAN. On the other machine(MC 2) we have Ubuntu 11.04. I wanna sync my computer to (MC 2) with atleast nanosecond precision. Can someone throw some light on it?

[bdalzell]

by the time we get to Xubuntu 12.04 ntpd seems to be absent from the archives.

however:

sudo aptitude install ntp

installed ntp and allowed me to set Applications>Settings>Time and Date

to the setting:

Keep synchronized with Internet servers

For what it is worth