[ntp:questions] Configuring dual refclock/PPS sources
John R. Ackermann N8UR
jra at febo.com
Thu Jan 15 15:11:58 UTC 2004
I have a pair of HP Z3801A GPS-disciplined oscillators that I've modified
to act (for ntpd's purposes) more-or-less like an HP 53503A "smart clock."
I have one of the units running pretty well using the following ntp.conf
pps /dev/pps0 assert hardpps
server 127.127.26.0 prefer ttl 1
fudge 127.127.26.0 time1 -0.966
fudge 127.127.22.0 refid GPS
I'm running ntpd version 4.1.1rc3 (from the FreeBSD 4.9 ports kit) so I
needed to use the "pps..." line to get the kernel discipline going. Also,
without the "ttl 1" option, the hpgps driver never kicked in; I have no
My question is how to configure for the second unit on the same machine,
which I have no reason to believe is any better or worse in timekeeping
performance than the first. Do I just duplicate these lines, changing the
address to unit 1?
In particular, the docs discourage having multiple servers tagged with the
"prefer" keyword, but how do I ensure that if the "prefer" unit fails, the
kernel discipline and PPS driver keep working from the remaining unit?
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