This is the README for chrony. What is chrony? =============== chrony is a versatile implementation of the Network Time Protocol (NTP). It can synchronise the system clock with NTP servers, reference clocks (e.g. GPS receiver), and manual input using wristwatch and keyboard. It can also operate as an NTPv4 (RFC 5905) server and peer to provide a time service to other computers in the network. It is designed to perform well in a wide range of conditions, including intermittent network connections, heavily congested networks, changing temperatures (ordinary computer clocks are sensitive to temperature), and systems that do not run continuosly, or run on a virtual machine. Typical accuracy between two machines synchronised over the Internet is within a few milliseconds; on a LAN, accuracy is typically in tens of microseconds. With hardware timestamping, or a hardware reference clock, sub-microsecond accuracy may be possible. Two programs are included in chrony, chronyd is a daemon that can be started at boot time and chronyc is a command-line interface program which can be used to monitor chronyd's performance and to change various operating parameters whilst it is running. What will chrony run on? ======================== The software is known to work on Linux, FreeBSD, NetBSD, macOS and Solaris. Closely related systems may work too. Any other system will likely require a porting exercise. You would need to start from one of the existing system-specific drivers and look into the quirks of certain system calls and the kernel on your target system. How do I set it up? =================== The file INSTALL gives instructions. On supported systems the compilation process should be automatic. You will need a C compiler, e.g. gcc or clang. What documentation is there? ============================ The distribution includes manual pages and a document containing Frequently Asked Questions (FAQ). The documentation is also available on the chrony web pages, accessible through the URL https://chrony.tuxfamily.org/ Where are new versions announced? ================================= There is a low volume mailing list where new versions and other important news relating to chrony is announced. You can join this list by sending mail with the subject "subscribe" to chrony-announce-request@chrony.tuxfamily.org These messages will be copied to chrony-users (see below). How can I get support for chrony? and where can I discuss new features, possible bugs etc? ======================================================== There are 3 mailing lists relating to chrony. chrony-announce was mentioned above. chrony-users is a users' discussion list, e.g. for general questions and answers about using chrony. chrony-dev is a more technical list, e.g. for discussing how new features should be implemented, exchange of information between developers etc. To subscribe to either of these lists, send a message with the subject "subscribe" to chrony-users-request@chrony.tuxfamily.org or chrony-dev-request@chrony.tuxfamily.org as applicable. When you are reporting a bug, please send us all the information you can. Unfortunately, chrony has proven to be one of those programs where it is very difficult to reproduce bugs in a different environment. So we may have to interact with you quite a lot to obtain enough extra logging and tracing to pin-point the problem in some cases. Please be patient and plan for this! License ======= chrony is distributed under the GNU General Public License version 2. Authors ======= Richard P. Curnow Miroslav Lichvar Acknowledgements ================ In writing the chronyd program, extensive use has been made of RFC 1305 and RFC 5905, written by David Mills. The source code of the NTP reference implementation has been used to check the details of the protocol. The following people have provided patches and other major contributions to the program : Lonnie Abelbeck Benny Lyne Amorsen Andrew Bishop Vincent Blut Stephan I. Boettcher Goswin Brederlow Leigh Brown Erik Bryer Jonathan Cameron Bryan Christianson Juliusz Chroboczek Christian Ehrhardt Paul Elliott Stefan R. Filipek Mike Fleetwood Alexander Gretencord Andrew Griffiths Walter Haidinger Juergen Hannken-Illjes John Hasler Tjalling Hattink Liam Hatton Jachym Holecek Håkan Johansson Jim Knoble Antti Jrvinen Eric Lammerts Stefan Lucke Victor Lum Kevin Lyda Paul Menzel Vladimir Michl Victor Moroz Kalle Olavi Niemitalo Frank Otto Denny Page Chris Perl Gautier PHILIPPON Andreas Piesk Andreas Steinmetz NAKAMURA Takumi Timo Teras Bill Unruh Stephen Wadeley Bernhard Weiss Wolfgang Weisselberg Bernhard M. Wiedemann Joachim Wiedorn Ralf Wildenhues Ulrich Windl Doug Woodward Thomas Zajic Many other people have contributed bug reports and suggestions. We are sorry we cannot identify all of you individually.