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doc: improve description of fallbackdrift directive

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Miroslav Lichvar 2018-03-27 13:08:01 +02:00
parent 94822d5156
commit 7848794222
1 changed files with 8 additions and 5 deletions
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doc/chrony.conf.adoc
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@ -771,9 +771,10 @@ driftfile @CHRONYVARDIR@/drift
[[fallbackdrift]]*fallbackdrift* _min-interval_ _max-interval_:: [[fallbackdrift]]*fallbackdrift* _min-interval_ _max-interval_::
Fallback drifts are long-term averages of the system clock drift calculated Fallback drifts are long-term averages of the system clock drift calculated
over exponentially increasing intervals. They are used when the clock is no over exponentially increasing intervals. They are used to avoid quickly
longer synchronised to avoid quickly drifting away from true time if there was drifting away from true time when the clock was not updated for a longer period
a short-term deviation in the drift before the synchronisation was lost. of time and there was a short-term deviation in the drift before the updates
stopped.
+ +
The directive specifies the minimum and maximum interval since the last clock The directive specifies the minimum and maximum interval since the last clock
update to switch between fallback drifts. They are defined as a power of 2 (in update to switch between fallback drifts. They are defined as a power of 2 (in
@ -785,8 +786,10 @@ fallbackdrift 16 19
+ +
In this example, the minimum interval is 16 (18 hours) and the maximum interval is In this example, the minimum interval is 16 (18 hours) and the maximum interval is
19 (6 days). The system clock frequency will be set to the first fallback 18 19 (6 days). The system clock frequency will be set to the first fallback 18
hours after last clock update, to the second after 36 hours, etc. This might be hours after last clock update, to the second after 36 hours, and so on. This
a good setting to cover daily and weekly temperature fluctuations. might be a good setting to cover frequency changes due to daily and weekly
temperature fluctuations. When the frequency is set to a fallback, the state of
the clock will change to '`Not synchronised`'.
+ +
By default (or if the specified maximum or minimum is 0), no fallbacks are used By default (or if the specified maximum or minimum is 0), no fallbacks are used
and the clock frequency changes only with new measurements from NTP sources, and the clock frequency changes only with new measurements from NTP sources,