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doc: update FAQ

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Miroslav Lichvar 2016-11-28 16:42:31 +01:00
parent 6b3800cc94
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doc/faq.adoc
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@ -148,9 +148,14 @@ network. It's better to use more than one server, three or four is usually
recommended as the minimum, so `chronyd` can detect servers that serve false recommended as the minimum, so `chronyd` can detect servers that serve false
time and combine measurements from multiple sources. time and combine measurements from multiple sources.
If you have a network card with hardware timestamping supported on Linux, it
can be enabled by the *hwtimestamp* directive in the _chrony.conf_ file. It
should make local receive and transmit timestamps of NTP packets much more
accurate.
There are also useful options which can be set in the `server` directive, they There are also useful options which can be set in the `server` directive, they
are `minpoll`, `maxpoll`, `polltarget`, `maxdelay`, `maxdelayratio` and are `minpoll`, `maxpoll`, `polltarget`, `maxdelay`, `maxdelayratio`,
`maxdelaydevratio`. `maxdelaydevratio`, and `xleave`.
The first three options set the minimum and maximum allowed polling interval, The first three options set the minimum and maximum allowed polling interval,
and how should be the actual interval adjusted in the specified range. Their and how should be the actual interval adjusted in the specified range. Their
@ -189,6 +194,16 @@ with local NTP server
server ntp.local minpoll 2 maxpoll 4 polltarget 30 maxdelaydevratio 2 server ntp.local minpoll 2 maxpoll 4 polltarget 30 maxdelaydevratio 2
---- ----
If your server supports the interleaved mode, the `xleave` option should be
added to the `server` directive in order to receive server's more accurate
hardware or kernel transmit timestamps. When combined with local hardware
timestamping, a sub-microsecond accuracy may be possible. An example could be
----
server ntp.local minpoll 2 maxpoll 2 xleave
hwtimestamp eth0
----
=== What happened to the `commandkey` and `generatecommandkey` directives? === What happened to the `commandkey` and `generatecommandkey` directives?
They were removed in version 2.2. Authentication is no longer supported in the They were removed in version 2.2. Authentication is no longer supported in the
@ -376,7 +391,8 @@ to serve time to clients in the network which support the broadcast client mode
=== Can `chronyd` keep the system clock a fixed offset away from real time? === Can `chronyd` keep the system clock a fixed offset away from real time?
This is not possible as the program currently stands. Yes. Starting from version 3.0, an offset can be specified by the `offset`
option for all time sources in the _chrony.conf_ file.
=== What happens if the network connection is dropped without using ``chronyc``'s `offline` command first? === What happens if the network connection is dropped without using ``chronyc``'s `offline` command first?