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 continuously, 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 illumos. Closely related systems may work too. Any other system will likely require a porting exercise. 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-project.org/ 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 the NTPv3 (RFC 1305) and NTPv4 (RFC 5905) specification. The source code of the xntpd/ntpd implementation written by Dennis Fergusson, Lars Mathiesen, David Mills, and others has been used to check the details of the protocol. The following people have provided patches and other major contributions to chrony: Lonnie Abelbeck Benny Lyne Amorsen Andrew Bishop Vincent Blut Luca Boccassi Stephan I. Boettcher David Bohman Goswin Brederlow Leigh Brown Erik Bryer Jonathan Cameron Bryan Christianson Juliusz Chroboczek Dan Drown Kamil Dudka Christian Ehrhardt Paul Elliott Robert Fairley Stefan R. Filipek Andy Fiddaman Mike Fleetwood Rob Gill Alexander Gretencord Andrew Griffiths Walter Haidinger Juergen Hannken-Illjes John Hasler Tjalling Hattink Liam Hatton Holger Hoffstätte Jachym Holecek Håkan Johansson Jim Knoble Antti Jrvinen Uwe Kleine-König Eric Lammerts Stefan Lucke Victor Lum Kevin Lyda Paul Menzel Vladimir Michl Victor Moroz Kalle Olavi Niemitalo Patrick Oppenlander Frank Otto Denny Page Rupesh Patel Chris Perl Gautier PHILIPPON Andreas Piesk Mike Ryan Baruch Siach Josef 'Jeff' Sipek Foster Snowhill Andreas Steinmetz NAKAMURA Takumi Timo Teras Bill Unruh Luke Valenta Stephen Wadeley Bernhard Weiss Wolfgang Weisselberg Bernhard M. Wiedemann Joachim Wiedorn Ralf Wildenhues Ulrich Windl Michael Witten Doug Woodward Thomas Zajic Many other people have contributed bug reports and suggestions. We are sorry we cannot identify all of you individually.