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doc: improve answer in FAQ for firewall issue

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Miroslav Lichvar 2016-05-23 09:00:42 +02:00
parent 91cbebb629
commit 962ca91574
1 changed files with 18 additions and 7 deletions
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doc/faq.adoc
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@ -205,13 +205,24 @@ following questions.
=== Behind a firewall?
If there is a firewall between you and the NTP server you're trying to use, the
packets may be blocked. Try using a tool like `wireshark` or `tcpdump` to see if
you're getting responses from the server. If you have an external modem, see
if the receive light blinks straight after the transmit light (when the link is
quiet apart from the NTP traffic). Try adding `log measurements` to the
_chrony.conf_ file and look in the _measurements.log_ file after `chronyd` has
been running for a short period. See if any measurements appear.
Check the `Reach` value printed by the ``chronyc``'s `sources` command. If it's
zero, it means `chronyd` did not get any valid responses from the NTP server
you are trying to use. If there is a firewall between you and the server, the
packets may be blocked. Try using a tool like `wireshark` or `tcpdump` to see
if you're getting any responses from the server.
When `chronyd` is receiving responses from the servers, the output of the
`sources` command issued few minutes after `chronyd` start might look like
this:
----
210 Number of sources = 3
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^* foo.example.net 2 6 377 34 +484us[ -157us] +/- 30ms
^- bar.example.net 2 6 377 34 +33ms[ +32ms] +/- 47ms
^+ baz.example.net 3 6 377 35 -1397us[-2033us] +/- 60ms
----
=== Are NTP servers specified with the `offline` option?