doc: convert FAQ to AsciiDoc and update it
It's now in a separate file again.
This commit is contained in:
Miroslav Lichvar
parent
d6aafa3f64
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chrony.texi.in
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chrony.texi.in
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@ -35,7 +35,6 @@ Copyright @copyright{} 2009-2014 Miroslav Lichvar
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* Installation:: How to compile and install the software
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* Installation:: How to compile and install the software
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* Typical scenarios:: How to configure the software for some common cases
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* Typical scenarios:: How to configure the software for some common cases
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* Usage reference:: Reference manual
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* Usage reference:: Reference manual
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* FAQ:: Answers to some common questions about chrony
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* GPL:: The GNU General Public License
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* GPL:: The GNU General Public License
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@end menu
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@end menu
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@c }}}
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@c }}}
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@ -4757,332 +4756,6 @@ command is issued.
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@c }}}
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@c }}}
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@c }}}
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@c }}}
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@c }}}
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@c }}}
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@c {{{ Ch:FAQ
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@node FAQ
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@chapter Frequently asked questions
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@c {{{ Chapter top
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@menu
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* Administrative issues::
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* Chrony compared to other programs::
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* Configuration issues::
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* Computer is not synchronising::
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* Issues with chronyc::
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* Real-time clock issues::
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* Microsoft Windows::
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* NTP-specific issues::
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* Linux-specific issues::
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* Solaris-specific issues::
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@end menu
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@c }}}
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@c {{{ S:Administrative issues
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@node Administrative issues
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@section Administrative issues
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@subsection Where can I get chrony source code?
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Tarballs are available via the @code{Download} link on the chrony web site.
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For the current development from the developers' version control system see the
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@code{Git} link on the web site.
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@subsection Are there any packaged versions of chrony?
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We are aware of packages for Arch, CentOS, Debian, Fedora, Gentoo, Mageia,
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OpenSuse, Slackware, Ubuntu, FreeBSD and NetBSD. We are not involved with how
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these are built or distributed.
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@subsection Where is the home page?
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It is currently at
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@uref{http://chrony.tuxfamily.org, http://chrony.tuxfamily.org}.
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@subsection Is there a mailing list?
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Yes, it's currently at @email{chrony-users@@chrony.tuxfamily.org}. There is a
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low-volume list called chrony-announce which is just for announcements of new
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releases or similar matters of high importance. You can join the lists by
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sending a message with the subject subscribe to
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@email{chrony-users-request@@chrony.tuxfamily.org} or
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@email{chrony-announce-request@@chrony.tuxfamily.org} respectively.
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For those who want to contribute to the development of chrony, there is a
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developers' mailing list. You can subscribe by sending mail with the subject
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subscribe to @email{chrony-dev-request@@chrony.tuxfamily.org}.
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@subsection What licence is applied to chrony?
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Starting from version 1.15, chrony is licensed under the GNU General Public
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License, Version 2. Versions prior to 1.15 were licensed under a custom
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BSD-like license.
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@c }}}
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@c {{{ S:Chrony compared to other programs
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@node Chrony compared to other programs
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@section Chrony compared to other programs
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@subsection How does chrony compare to ntpd?
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Chrony can usually synchronise the system clock faster and with better time
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accuracy, but it doesn't implement all NTP features, e.g. broadcast/multicast
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mode, or authentication based on public-key cryptography. For a more detailed
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comparison, see section @code{Comparison with ntpd} in the manual.
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If your computer connects to the 'net only for few minutes at a time, you turn
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your Linux computer off or suspend it frequently, the clock is not very stable
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(e.g. it is a virtual machine), or you want to use NTP on an isolated network
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with no hardware clocks in sight, chrony will probably work much better for
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you.
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The original reason chrony was written was that ntpd (called xntpd at the
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time) could not to do anything sensible on a PC which was connected to
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the 'net only for about 5 minutes once or twice a day, mainly to
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upload/download email and news. The requirements were
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@itemize @bullet
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@item slew the time to correct it when going online and NTP servers become
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visible
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@item determine the rate at which the computer gains or loses time and use this
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information to keep it reasonably correct between connects to the 'net. This
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has to be done using a method that does not care about the intermittent
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availability of the references or the fact the computer is turned off between
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groups of measurements.
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@item maintain the time across reboots, by working out the error and drift rate
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of the computer's real-time clock and using this information to set the system
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clock correctly at boot up.
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@end itemize
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Also, when working with isolated networks with no true time references at all
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ntpd was found to give no help with managing the local clock's gain/loss rate
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on the NTP master node (which was set from watch). Some automated support was
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added to chrony to deal with this.
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@c }}}
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@c {{{ S:Configuration issues
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@node Configuration issues
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@section Configuration issues
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@subsection I have several computers on a LAN. Should be all clients of an external server?
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The best configuration is usually to make one computer the master, with the
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others as clients of it. Add a @code{local} directive to the master's
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chrony.conf file. This configuration will be better because
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@itemize @bullet
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@item the load on the external connection is less
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@item the load on the external NTP server(s) is less
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@item if your external connection goes down, the computers on the LAN will
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maintain a common time with each other.
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@end itemize
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@subsection Must I specify servers by IP address if DNS is not available on chronyd start?
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No. Starting from version 1.25, @code{chronyd} will keep trying to resolve the
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hostnames specified in the @code{server} and @code{peer} directives in
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increasing intervals until it succeeds. The @code{online} command can be
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issued from @code{chronyc} to try to resolve them immediately.
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@subsection How can I make chronyd more secure?
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If you don't need to serve time to NTP clients or peers, you can add
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@code{port 0} to the @file{chrony.conf} file to completely disable the NTP
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server functionality and prevent NTP requests from reaching @code{chronyd}.
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Starting from version 2.0, the NTP server port is open only when client access
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is allowed by the @code{allow} directive or command, an NTP peer is configured,
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or the @code{broadcast} directive is used.
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If you don't need to use @code{chronyc} remotely, you can add the following
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directives to the configuration file to bind the command sockets to the
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loopback interface. This is done by default since version 2.0.
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@example
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bindcmdaddress 127.0.0.1
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bindcmdaddress ::1
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@end example
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If you don't need to use @code{chronyc} at all, you can disable the command
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sockets by adding @code{cmdport 0} to the configuration file.
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On Linux, if @code{chronyd} is compiled with support for Linux capabilities
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(available in the libcap library), you can specify an unprivileged user with
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the `-u' option or @code{user} directive in the @file{chrony.conf} file to drop
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root privileges after start. The configure option @code{--with-user} can be
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used to drop the privileges by default.
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@subsection How can I improve the accuracy of the system clock with NTP sources?
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Select NTP servers that are well synchronised, stable and close to your network.
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It's better to use more than one server, three or four is usually recommended as
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the minimum, so @code{chronyd} can detect falsetickers and combine measurements
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from multiple sources.
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There are also useful options which can be set in the @code{server} directive,
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they are @code{minpoll}, @code{maxpoll}, @code{polltarget}, @code{maxdelay},
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@code{maxdelayratio} and @code{maxdelaydevratio}.
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The first three options set the minimum and maximum allowed polling interval,
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and how should be the actual interval adjusted in the specified range. Their
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default values are 6 (64 seconds) for @code{minpoll}, 10 (1024 seconds) for
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@code{maxpoll} and 6 (samples) for @code{polltarget}. The default values
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should be used for general servers on the internet. With your own NTP servers
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or if have permission to poll some servers more frequently, setting these
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options for shorter polling intervals may significantly improve the accuracy of
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the system clock.
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The optimal polling interval depends on many factors, including the ratio
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between the wander of the clock and the network jitter (sometimes expressed in
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NTP documents as the Allan intercept), the temperature sensitivity of the
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crystal oscillator and the maximum rate of change of the temperature.
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An example of the directive for an NTP server on the internet that you are
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allowed to poll frequently could be
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@example
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server foo.example.net minpoll 4 maxpoll 6 polltarget 16
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@end example
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An example using very short polling intervals for a server located in the
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same LAN could be
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@example
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server ntp.local minpoll 2 maxpoll 4 polltarget 30
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@end example
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The maxdelay options are useful to ignore measurements with larger delay (e.g.
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due to congestion in the network) and improve the stability of the
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synchronisation. The @code{maxdelaydevratio} option could be added to the
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example with local NTP server
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@example
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server ntp.local minpoll 2 maxpoll 4 polltarget 30 maxdelaydevratio 2
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@end example
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@c }}}
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@c {{{ S:Computer is not synchronising
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@node Computer is not synchronising
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@section Computer is not synchronising
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This is the most common problem. There are a number of reasons, see the
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following questions.
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@subsection Behind a firewall?
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If there is a firewall between you and the NTP server you're trying to use,
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the packets may be blocked. Try using a tool like wireshark or tcpdump to see
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if you're getting responses from the server. If you have an external modem,
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see if the receive light blinks straight after the transmit light (when the
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link is quiet apart from the NTP traffic.) Try adding @code{log measurements}
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to the @file{chrony.conf} file and look in the measurements.log file after
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chrony has been running for a short period. See if any measurements appear.
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@subsection Do you have a non-permanent (i.e. intermittent) Internet connection?
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Check that you're using chronyc's @code{online} and @code{offline} commands
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appropriately. Again, check in measurements.log to see if you're getting any
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data back from the server.
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@subsection In measurements.log, do the '7' and '8' flag columns always show zero?
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Do you have a @code{local stratum X} directive in the @file{chrony.conf} file? If X
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is lower than the stratum of the server you're trying to use, this situation
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will arise. You should always make X quite high (e.g. 10) in this directive.
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@c }}}
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@c {{{ S:Issues with chronyc
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@node Issues with chronyc
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@section Issues with chronyc
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@subsection I keep getting the error @code{506 Cannot talk to daemon}
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When accessing @code{chronyd} remotely, make sure that the @file{chrony.conf}
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file (on the computer where @code{chronyd} is running) has a @code{cmdallow}
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entry for the computer you are running @code{chronyc} on and an appropriate
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@code{bindcmdaddress} directive. This isn't necessary for localhost.
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Perhaps @code{chronyd} is not running. Try using the ps command (e.g. on
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Linux, 'ps -auxw') to see if it's running. Or try 'netstat -a' and see if the
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ports 123/udp and 323/udp are listening. If @code{chronyd} is not running, you
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may have a problem with the way you are trying to start it (e.g. at boot time).
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Perhaps you have a firewall set up in a way that blocks packets on port
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323/udp. You need to amend the firewall configuration in this case.
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@subsection Is the chronyc<->chronyd protocol documented anywhere?
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Only by the source code :-) See cmdmon.c (@code{chronyd} side) and client.c
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(@code{chronyc} side).
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@c }}}
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@c {{{ S:Real-time clock issues
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@node Real-time clock issues
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@section Real-time clock issues
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@subsection What is the real-time clock (RTC)?
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This is the clock which keeps the time even when your computer is turned off.
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It works with 1 second resolution. @code{chronyd} can monitor the rate at
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which the real-time clock gains or loses time, and compensate for it when you
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set the system time from it at the next reboot. See the documentation for
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details.
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@subsection I want to use chronyd's real-time clock support. Must I disable hwclock?
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The hwclock program is often set-up by default in the boot and shutdown scripts
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with many Linux installations. If you want to use chronyd's real-time clock
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support, the important thing is to disable hwclock in the shutdown procedure.
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If you don't, it will over-write the RTC with a new value, unknown to
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@code{chronyd}. At the next reboot, @code{chronyd} will compensate this (wrong)
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time with its estimate of how far the RTC has drifted whilst the power was off,
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giving a meaningless initial system time.
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There is no need to remove hwclock from the boot process, as long as
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@code{chronyd} is started after it has run.
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@subsection I just keep getting the '513 RTC driver not running' message
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For the real time clock support to work, you need the following three things
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@itemize @bullet
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@item a kernel that is supported (e.g. 2.2 onwards)
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@item enhanced RTC support compiled into the kernel
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@item an @code{rtcfile} directive in your chrony.conf file
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@end itemize
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@c }}}
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@c {{{ S:Microsoft Windows
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@node Microsoft Windows
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@section Microsoft Windows
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@subsection Does chrony support Windows?
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No. The @code{chronyc} program (the command-line client used for configuring
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@code{chronyd} while it is running) has been successfully built and run under
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Cygwin in the past. @code{chronyd} is not portable, because part of it is very
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system-dependent. It needs adapting to work with Windows' equivalent of the
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adjtimex() call, and it needs to be made to work as an NT service.
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@subsection Are there any plans to support Windows?
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We have no plans to do this. Anyone is welcome to pick this work up and
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contribute it back to the project.
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@c }}}
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@c {{{ S:NTP-specific issues
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@node NTP-specific issues
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@section NTP-specific issues
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@subsection Can chrony be driven from broadcast NTP servers?
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No, this NTP mode is not implemented yet.
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@subsection Can chronyd transmit broadcast NTP packets (e.g. to synchronise other computers on a private LAN)?
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Yes. Starting from version 1.17, chrony has this capability.
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@subsection Can chrony keep the system clock a fixed offset away from real time?
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This is not possible as the program currently stands.
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@subsection What happens if the network connection is dropped without using chronyc's 'offline' command first?
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In this case @code{chronyd} will keep trying to access the server(s) that it
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thinks are online. Eventually it will decide that they are unreachable and no
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longer consider itself synchronised to them. If you have other computers on
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your LAN accessing the computer that is affected this way, they too will become
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'unsynchronised', unless you have the 'local' directive set up on the master
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computer.
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The 'auto_offline' option to the 'server' entry in the chrony.conf file may be
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useful to avoid this situation.
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@c }}}
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@c {{{ S:Linux-specific issues
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@node Linux-specific issues
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@section Linux-specific issues
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@subsection I get "Could not open /dev/rtc, Device or resource busy" in my syslog file
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Some other program running on the system may be using the device.
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@c }}}
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@c {{{ S:Solaris-specific issues
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@node Solaris-specific issues
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@section Solaris-specific issues
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@subsection On Solaris 2.8, I get an error message about not being able to open kvm to change dosynctodr
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(The dosynctodr variable controls whether Solaris couples the equivalent of its
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BIOS clock into its system clock at regular intervals). The Solaris port of
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chrony was developed in the Solaris 2.5 era. Some aspect of the Solaris kernel
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has changed which prevents the same technique working. We no longer have root
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access to any Solaris machines to work on this, and we are reliant on somebody
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developing the patch and testing it.
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@c }}}
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@c }}}
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@c {{{ apx:GNU General Public License
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@c {{{ apx:GNU General Public License
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@node GPL
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@node GPL
|
||||||
@appendix GNU General Public License
|
@appendix GNU General Public License
|
||||||
|
|
|
||||||
273
doc/faq.adoc
Normal file
273
doc/faq.adoc
Normal file
|
|
@ -0,0 +1,273 @@
|
||||||
|
:toc:
|
||||||
|
:numbered:
|
||||||
|
|
||||||
|
Frequently Asked Questions
|
||||||
|
==========================
|
||||||
|
|
||||||
|
== Chrony compared to other programs
|
||||||
|
|
||||||
|
=== How does +chrony+ compare to +ntpd+?
|
||||||
|
|
||||||
|
+chrony+ can usually synchronise the system clock faster and with better time
|
||||||
|
accuracy, but it doesn't implement all NTP features, e.g. broadcast/multicast
|
||||||
|
mode, or authentication based on public-key cryptography. For a more detailed
|
||||||
|
comparison, see the http://chrony.tuxfamily.org/comparison.html[comparison
|
||||||
|
page] on the chrony website and section
|
||||||
|
http://chrony.tuxfamily.org/manual.html#Comparison-with-ntpd[Comparison with
|
||||||
|
ntpd] in the manual.
|
||||||
|
|
||||||
|
If your computer connects to the 'net only for few minutes at a time, you turn
|
||||||
|
your Linux computer off or suspend it frequently, the clock is not very stable
|
||||||
|
(e.g. it is a virtual machine), or you want to use NTP on an isolated network
|
||||||
|
with no hardware clocks in sight, +chrony+ will probably work much better for
|
||||||
|
you.
|
||||||
|
|
||||||
|
The original reason +chrony+ was written was that ntpd (called xntpd at the
|
||||||
|
time) could not to do anything sensible on a PC which was connected to the 'net
|
||||||
|
only for about 5 minutes once or twice a day, mainly to upload/download email
|
||||||
|
and news. The requirements were
|
||||||
|
|
||||||
|
* slew the time to correct it when going online and NTP servers
|
||||||
|
become visible
|
||||||
|
* determine the rate at which the computer gains or loses time and
|
||||||
|
use this information to keep it reasonably correct between connects
|
||||||
|
to the 'net. This has to be done using a method that does not care
|
||||||
|
about the intermittent availability of the references or the fact
|
||||||
|
the computer is turned off between groups of measurements.
|
||||||
|
* maintain the time across reboots, by working out the error and
|
||||||
|
drift rate of the computer's real-time clock and using this
|
||||||
|
information to set the system clock correctly at boot up.
|
||||||
|
|
||||||
|
Also, when working with isolated networks with no true time references at all
|
||||||
|
ntpd was found to give no help with managing the local clock's gain/loss rate
|
||||||
|
on the NTP master node (which was set from watch). Some automated support was
|
||||||
|
added to +chrony+ to deal with this.
|
||||||
|
|
||||||
|
== Configuration issues
|
||||||
|
|
||||||
|
=== I have several computers on a LAN. Should be all clients of an external server?
|
||||||
|
|
||||||
|
The best configuration is usually to make one computer the master, with
|
||||||
|
the others as clients of it. Add a +local+ directive to the master's
|
||||||
|
'chrony.conf' file. This configuration will be better because
|
||||||
|
|
||||||
|
* the load on the external connection is less
|
||||||
|
* the load on the external NTP server(s) is less
|
||||||
|
* if your external connection goes down, the computers on the LAN
|
||||||
|
will maintain a common time with each other.
|
||||||
|
|
||||||
|
=== Must I specify servers by IP address if DNS is not available on chronyd start?
|
||||||
|
|
||||||
|
No. Starting from version 1.25, +chronyd+ will keep trying to resolve
|
||||||
|
the hostnames specified in the +server+ and +peer+ directives in
|
||||||
|
increasing intervals until it succeeds. The +online+ command can be
|
||||||
|
issued from +chronyc+ to try to resolve them immediately.
|
||||||
|
|
||||||
|
=== How can I make chronyd more secure?
|
||||||
|
|
||||||
|
If you don't need to serve time to NTP clients or peers, you can add +port 0+
|
||||||
|
to the 'chrony.conf' file to completely disable the NTP server functionality
|
||||||
|
and prevent NTP requests from reaching +chronyd+. Starting from version 2.0,
|
||||||
|
the NTP server port is open only when client access is allowed by the +allow+
|
||||||
|
directive or command, an NTP peer is configured, or the +broadcast+ directive
|
||||||
|
is used.
|
||||||
|
|
||||||
|
If you don't need to use +chronyc+ remotely, you can add the following
|
||||||
|
directives to the configuration file to bind the command sockets to the
|
||||||
|
loopback interface. This is done by default since version 2.0.
|
||||||
|
|
||||||
|
----
|
||||||
|
bindcmdaddress 127.0.0.1
|
||||||
|
bindcmdaddress ::1
|
||||||
|
----
|
||||||
|
|
||||||
|
If you don't need to use +chronyc+ at all, you can disable the command sockets
|
||||||
|
by adding +cmdport 0+ to the configuration file.
|
||||||
|
|
||||||
|
On Linux, if +chronyd+ is compiled with support for Linux capabilities
|
||||||
|
(available in the libcap library), you can specify an unprivileged user with
|
||||||
|
the +-u+ option or +user+ directive in the 'chrony.conf' file to drop root
|
||||||
|
privileges after start. The configure option +--with-user+ can be used to drop
|
||||||
|
the privileges by default.
|
||||||
|
|
||||||
|
=== How can I improve the accuracy of the system clock with NTP sources?
|
||||||
|
|
||||||
|
Select NTP servers that are well synchronised, stable and close to your
|
||||||
|
network. It's better to use more than one server, three or four is usually
|
||||||
|
recommended as the minimum, so +chronyd+ can detect falsetickers and combine
|
||||||
|
measurements from multiple sources.
|
||||||
|
|
||||||
|
There are also useful options which can be set in the +server+ directive, they
|
||||||
|
are +minpoll+, +maxpoll+, +polltarget+, +maxdelay+, +maxdelayratio+ and
|
||||||
|
+maxdelaydevratio+.
|
||||||
|
|
||||||
|
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
|
||||||
|
default values are 6 (64 seconds) for +minpoll+, 10 (1024 seconds) for
|
||||||
|
+maxpoll+ and 6 (samples) for +polltarget+. The default values should be used
|
||||||
|
for general servers on the internet. With your own NTP servers or if have
|
||||||
|
permission to poll some servers more frequently, setting these options for
|
||||||
|
shorter polling intervals may significantly improve the accuracy of the system
|
||||||
|
clock.
|
||||||
|
|
||||||
|
The optimal polling interval depends on many factors, including the ratio
|
||||||
|
between the wander of the clock and the network jitter (sometimes expressed in
|
||||||
|
NTP documents as the Allan intercept), the temperature sensitivity of the
|
||||||
|
crystal oscillator and the maximum rate of change of the temperature.
|
||||||
|
|
||||||
|
An example of the directive for an NTP server on the internet that you are
|
||||||
|
allowed to poll frequently could be
|
||||||
|
|
||||||
|
----
|
||||||
|
server foo.example.net minpoll 4 maxpoll 6 polltarget 16
|
||||||
|
----
|
||||||
|
|
||||||
|
An example using very short polling intervals for a server located in the same
|
||||||
|
LAN could be
|
||||||
|
|
||||||
|
----
|
||||||
|
server ntp.local minpoll 2 maxpoll 4 polltarget 30
|
||||||
|
----
|
||||||
|
|
||||||
|
The maxdelay options are useful to ignore measurements with larger delay (e.g.
|
||||||
|
due to congestion in the network) and improve the stability of the
|
||||||
|
synchronisation. The +maxdelaydevratio+ option could be added to the example
|
||||||
|
with local NTP server
|
||||||
|
|
||||||
|
----
|
||||||
|
server ntp.local minpoll 2 maxpoll 4 polltarget 30 maxdelaydevratio 2
|
||||||
|
----
|
||||||
|
|
||||||
|
== Computer is not synchronising
|
||||||
|
|
||||||
|
This is the most common problem. There are a number of reasons, see the
|
||||||
|
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 +chrony+ has
|
||||||
|
been running for a short period. See if any measurements appear.
|
||||||
|
|
||||||
|
=== Are NTP servers specified with the +offline+ option?
|
||||||
|
|
||||||
|
Check that you're using +chronyc+\'s +online+ and +offline+ commands
|
||||||
|
appropriately. Again, check in 'measurements.log' to see if you're getting any
|
||||||
|
data back from the server.
|
||||||
|
|
||||||
|
== Issues with +chronyc+
|
||||||
|
|
||||||
|
=== I keep getting the error +506 Cannot talk to daemon+
|
||||||
|
|
||||||
|
When accessing +chronyd+ remotely, make sure that the 'chrony.conf' file (on
|
||||||
|
the computer where +chronyd+ is running) has a 'cmdallow' entry for the
|
||||||
|
computer you are running +chronyc+ on and an appropriate 'bindcmdaddress'
|
||||||
|
directive. This isn't necessary for localhost.
|
||||||
|
|
||||||
|
Perhaps +chronyd+ is not running. Try using the +ps+ command (e.g. on Linux,
|
||||||
|
+ps -auxw+) to see if it's running. Or try +netstat -a+ and see if the ports
|
||||||
|
123/udp and 323/udp are listening. If +chronyd+ is not running, you may have a
|
||||||
|
problem with the way you are trying to start it (e.g. at boot time).
|
||||||
|
|
||||||
|
Perhaps you have a firewall set up in a way that blocks packets on port
|
||||||
|
323/udp. You need to amend the firewall configuration in this case.
|
||||||
|
|
||||||
|
=== Is the +chronyc+ / +chronyd+ protocol documented anywhere?
|
||||||
|
|
||||||
|
Only by the source code :-) See 'cmdmon.c' (+chronyd+ side) and 'client.c'
|
||||||
|
(+chronyc+ side).
|
||||||
|
|
||||||
|
== Real-time clock issues
|
||||||
|
|
||||||
|
=== What is the real-time clock (RTC)?
|
||||||
|
|
||||||
|
This is the clock which keeps the time even when your computer is turned off.
|
||||||
|
It works with 1 second resolution. +chronyd+ can monitor the rate at which the
|
||||||
|
real-time clock gains or loses time, and compensate for it when you set the
|
||||||
|
system time from it at the next reboot. See the documentation for details.
|
||||||
|
|
||||||
|
=== I want to use +chronyd+'s real-time clock support. Must I disable hwclock?
|
||||||
|
|
||||||
|
The hwclock program is often set-up by default in the boot and shutdown scripts
|
||||||
|
with many Linux installations. If you want to use +chronyd+'s real-time clock
|
||||||
|
support, the important thing is to disable hwclock in the shutdown procedure.
|
||||||
|
If you don't, it will over-write the RTC with a new value, unknown to
|
||||||
|
+chronyd+. At the next reboot, +chronyd+ will compensate this (wrong) time
|
||||||
|
with its estimate of how far the RTC has drifted whilst the power was off,
|
||||||
|
giving a meaningless initial system time.
|
||||||
|
|
||||||
|
There is no need to remove hwclock from the boot process, as long as +chronyd+
|
||||||
|
is started after it has run.
|
||||||
|
|
||||||
|
=== I just keep getting the +513 RTC driver not running+ message
|
||||||
|
|
||||||
|
For the real time clock support to work, you need the following three
|
||||||
|
things
|
||||||
|
|
||||||
|
* a kernel that is supported (e.g. 2.2 onwards)
|
||||||
|
* enhanced RTC support compiled into the kernel
|
||||||
|
* an +rtcfile+ directive in your 'chrony.conf' file
|
||||||
|
|
||||||
|
== Microsoft Windows
|
||||||
|
|
||||||
|
=== Does +chrony+ support Windows?
|
||||||
|
|
||||||
|
No. The +chronyc+ program (the command-line client used for configuring
|
||||||
|
+chronyd+ while it is running) has been successfully built and run under
|
||||||
|
Cygwin in the past. +chronyd+ is not portable, because part of it is
|
||||||
|
very system-dependent. It needs adapting to work with Windows'
|
||||||
|
equivalent of the adjtimex() call, and it needs to be made to work as a
|
||||||
|
service.
|
||||||
|
|
||||||
|
=== Are there any plans to support Windows?
|
||||||
|
|
||||||
|
We have no plans to do this. Anyone is welcome to pick this work up and
|
||||||
|
contribute it back to the project.
|
||||||
|
|
||||||
|
== NTP-specific issues
|
||||||
|
|
||||||
|
=== Can +chrony+ be driven from broadcast NTP servers?
|
||||||
|
|
||||||
|
No, this NTP mode is not implemented yet.
|
||||||
|
|
||||||
|
=== Can chronyd transmit broadcast NTP packets (e.g. to synchronise other computers on a private LAN)?
|
||||||
|
|
||||||
|
Yes. Starting from version 1.17, +chrony+ has this capability.
|
||||||
|
|
||||||
|
=== Can +chrony+ keep the system clock a fixed offset away from real time?
|
||||||
|
|
||||||
|
This is not possible as the program currently stands.
|
||||||
|
|
||||||
|
=== What happens if the network connection is dropped without using +chronyc+'s +offline+ command first?
|
||||||
|
|
||||||
|
+chronyd+ will keep trying to access the server(s) that it thinks are online.
|
||||||
|
When the network is connected again, it will take some time (on average half of
|
||||||
|
the current polling interval) before new measurements are made and the clock is
|
||||||
|
corrected. If the servers were set to offline and the +online+ command was
|
||||||
|
issued when the network was connected, +chronyd+ would make new measurements
|
||||||
|
immediately.
|
||||||
|
|
||||||
|
The +auto_offline+ option to the +server+ entry in the 'chrony.conf' file may
|
||||||
|
be useful to switch the servers to the offline state automatically.
|
||||||
|
|
||||||
|
== Linux-specific issues
|
||||||
|
|
||||||
|
=== I get +Could not open /dev/rtc, Device or resource busy+ in my syslog file
|
||||||
|
|
||||||
|
Some other program running on the system may be using the device.
|
||||||
|
|
||||||
|
== Solaris-specific issues
|
||||||
|
|
||||||
|
=== I get an error message about not being able to open kvm to change dosynctodr
|
||||||
|
|
||||||
|
(The dosynctodr variable controls whether Solaris couples the equivalent
|
||||||
|
of its BIOS clock into its system clock at regular intervals). The
|
||||||
|
Solaris port of +chrony+ was developed in the Solaris 2.5 era. Some
|
||||||
|
aspect of the Solaris kernel has changed which prevents the same
|
||||||
|
technique working. We no longer have root access to any Solaris
|
||||||
|
machines to work on this, and we are reliant on somebody developing the
|
||||||
|
patch and testing it.
|
||||||
12
make_release
12
make_release
|
|
@ -59,15 +59,9 @@ if [ $(wc -l < INSTALL) -gt 100 -o $(wc -l < INSTALL) -lt 85 ]; then
|
||||||
exit 3
|
exit 3
|
||||||
fi
|
fi
|
||||||
|
|
||||||
awk '/^[1-9] Frequently asked questions$/{p=1}
|
a2x --lynx -f text doc/faq.adoc || exit 1
|
||||||
/^Appendix A GNU General Public License$/{exit}; p' chrony.txt | \
|
mv doc/faq.text FAQ
|
||||||
tail -n +4 | sed 's/^[1-9]\.\([1-9]\)/\1/' | sed 's/^----/--/' | \
|
rm -rf doc
|
||||||
sed 's/^====/==/' > FAQ
|
|
||||||
|
|
||||||
if [ $(wc -l < FAQ) -gt 400 -o $(wc -l < FAQ) -lt 200 ]; then
|
|
||||||
echo "FAQ generated incorrectly?"
|
|
||||||
exit 3
|
|
||||||
fi
|
|
||||||
|
|
||||||
rm -f config.h config.log make_release .gitignore
|
rm -f config.h config.log make_release .gitignore
|
||||||
|
|
||||||
|
|
|
||||||
Loading…
Reference in a new issue