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| author | Eric S. Raymond <esr@thyrsus.com> | 2013-10-28 14:32:23 -0400 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2013-10-28 22:48:40 -0400 |
| commit | 9a23b6a45cecae8be99c4d3fe2d69c76e0b194c3 (patch) | |
| tree | bbc330bdf55058736bd3bd1ef336f96488c9ba6e /www/gpsd-time-service-howto.txt | |
| parent | e4a396cdd3a843314188ed22f73ffcb47fa8f207 (diff) | |
| download | gpsd-9a23b6a45cecae8be99c4d3fe2d69c76e0b194c3.tar.gz | |
HOWTO markup fixes.
Diffstat (limited to 'www/gpsd-time-service-howto.txt')
| -rw-r--r-- | www/gpsd-time-service-howto.txt | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/www/gpsd-time-service-howto.txt b/www/gpsd-time-service-howto.txt index a92a87f9..d5caf619 100644 --- a/www/gpsd-time-service-howto.txt +++ b/www/gpsd-time-service-howto.txt @@ -771,6 +771,7 @@ A more detailed description of the output is available at In order to determine the correct GPS offset, do the following: +[start=1] 1. Add these lines to ntp.conf: ----------------------------------------------------------------------------- @@ -788,18 +789,27 @@ log statistics measurements tracking This enables logging of the peer server statistics. +[start=2] 2. Make sure the directory exists properly. For ntpd as root do: + +----------------------------------------------------------------------------- # mkdir -p /var/log/ntpstats # chown ntp:ntp /var/log/ntpstats +----------------------------------------------------------------------------- For chronyd as root do: + +----------------------------------------------------------------------------- # mkdir -p /var/log/chrony # chown root:root /var/log/chrony +----------------------------------------------------------------------------- +[start=3] 3. Start ntpd (or chronyd) and let it run for at least four hours. Periodically check progress with "ntpq -p" or "chronyc sources" and wait until change has settled out. +[start=4] 4. Calculate the average GPS offset using this script (a copy is included as contrib/ntpoffset in the GPSD distribution): @@ -812,6 +822,7 @@ awk ' This prints the average offset. +[start=5] 5. Adjust the "time1" value for unit 0 of your ntp.conf (the non-PPS channel) by subtracting the average offset from step 4. @@ -828,6 +839,7 @@ example: SHM 0 configured as: refclock SHM 0 poll 8 filter 1000 noselect +----------------------------------------------------------------------------- # chronyc sourcestats 210 Number of sources = 6 Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev @@ -841,6 +853,7 @@ ntp1.karneval.cz 17 10 89m 0.127 0.539 -4131us 574us In this case (Garmin 18x) the offset specified in the config for the SHM 0 source should be around 0.495. +----------------------------------------------------------------------------- == Providing public NTP service == |