Re: [LUG] NTP gibberish

[Simon Waters <Simon@xxxxxxxxxxxxxxxxxxxx>]

Neil Williams wrote:
> Does anyone understand NTP?

Understand is a bit strong I have used it on three large
networks to synchronise time, including machines that ran the
clock at a big manufacturing factory (Where staff got penalised
for being 5 minutes late, 10 minutes late etc so were very clock
conscious).

> The NTP documentation is complete garbage meant only for the Professor who
> wrote it, the NTP FAQ re-hashes the same jibberish about leap seconds UTC and
> falsetickers.

Is David a professor? He is always very helpful in my
experience, we corresponded when the NTP security scare was last
upon the world.

> I have NTP working - to a fashion - on the dial-up server. What I need is a
> simple command I can use on the CLIENT machines on the network to get that
> time from the server OFFLINE.

ntpdate servername

This will set the time, but it doesn't do it gradually like the
daemon process, so might break some client stuff. But it is good
for boot up scripts before you start apps.

> Right now I have to duplicate the entire ntp.conf file to each client and run
> ntptimeset -s or ntpd -q as root on each one whilst already connected to the
> internet. Why should I have to do this when the server already has the
> correct time, obtained using the same commands in /etc/ppp/ip-up.local?

I don't think you do, their ntp.conf should refer to local
servers only.

> So far, every attempt to get ntpd to just use the local server refuses:
> Found 1 servers, require 3 servers.

Okay the idea is you have a hierarchy (The levels are called
strata).

At the top are Atomic clocks and GPS based systems.

Machines at lower stratums use a selection of clocks at a higher
stratum. Maybe the code has got more paranoid as following the
recent GPS cock up, many sites clocks drifted through lack of
diversity in time sources!

Typically you define 3 servers at a lower strata than your ISP,
who form the basic onsite clocks and then others just use these
three as their servers. The three servers use the ISP time
servers as their "servers".

Clocks in the same strata can be "peers" to help maintain
accurate time, but I don't think people do that much now.

> Does anyone have a local LAN timeserver usable offline?
> message body to unsubscribe.

Offline?! No I'm not going back to that.... Never...

My ntp.conf for a single box syncing of Demon's time servers.

server ntp.demon.co.uk
server ntp1.demon.co.uk
server ntp2.demon.co.uk
server  127.127.1.0     # local clock
fudge   127.127.1.0 stratum 10
# Restrict access
restrict 0.0.0.0 ignore
driftfile /etc/ntp/drift
#multicastclient                        # listen on default
224.0.1.1
broadcastdelay  0.008
authenticate no
                  
I dare say the requirement for 3 time servers can be subverted
at the users own risk.

Most of the documentation can be ignored if your not after a
legally binding time (Such as used for Ambulance dispatch
recording in the USA), or atomic clock style precision.

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