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doc: update FAQ on improving accuracy

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Miroslav Lichvar
2023-12-05 13:54:44 +01:00
parent 89aa8fa342
commit 598b893e1d
1 changed files with 13 additions and 1 deletions
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doc/faq.adoc
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@@ -381,7 +381,7 @@ outliers corrupting the minimum delay. For example:
server ntp.local minpoll -7 maxpoll -7 filter 31 maxdelayquant 0.3 xleave server ntp.local minpoll -7 maxpoll -7 filter 31 maxdelayquant 0.3 xleave
---- ----
As an experimental feature added in version 4.2, `chronyd` supports an NTPv4 Since version 4.2, `chronyd` supports an NTPv4
extension field containing an additional timestamp to enable frequency transfer extension field containing an additional timestamp to enable frequency transfer
and significantly improve stability of synchronisation. It can be enabled by and significantly improve stability of synchronisation. It can be enabled by
the `extfield F323` option. For example: the `extfield F323` option. For example:
@@ -390,6 +390,18 @@ the `extfield F323` option. For example:
server ntp.local minpoll 0 maxpoll 0 xleave extfield F323 server ntp.local minpoll 0 maxpoll 0 xleave extfield F323
---- ----
Since version 4.5, `chronyd` can apply corrections from PTP one-step end-to-end
transparent clocks (e.g. network switches) to significantly improve accuracy of
synchronisation in local networks. It requires the PTP transport to be enabled
by the `ptpport` directive, HW timestamping, and the `extfield F324` option.
For example:
----
server ntp.local minpoll -4 maxpoll -4 xleave extfield F323 extfield F324 port 319
ptpport 319
hwtimestamp eth0 minpoll -4
----
=== Does `chronyd` have an ntpdate mode? === Does `chronyd` have an ntpdate mode?
Yes. With the `-q` option `chronyd` will set the system clock once and exit. Yes. With the `-q` option `chronyd` will set the system clock once and exit.