.TH CHRONYD 8 "December 04, 2009" chrony "System Administration" .SH NAME chronyd \- chrony background daemon .SH SYNOPSIS .B chronyd [\fIOPTIONS\fR] .SH DESCRIPTION \fIchrony\fR is a pair of programs for maintaining the accuracy of computer clocks. \fBchronyd\fR is a background daemon program that can be started at boot time. \fBchronyd\fR is a daemon which runs in background on the system. It obtains measurements (e.g. via the network) of the system's offset relative to other systems, and adjusts the system time accordingly. For isolated systems, the user can periodically enter the correct time by hand (using \fIchronyc\fR). In either case, \fBchronyd\fR determines the rate at which the computer gains or loses time, and compensates for this. .SH USAGE \fBchronyd\fR is usually started at boot-time and requires superuser privileges. If \fBchronyd\fR has been installed to its default location \fI/usr/local/sbin/chronyd\fR, starting it is simply a matter of entering the command: \fI/usr/local/sbin/chronyd\fR Information messages and warnings will be logged to syslog. .SH OPTIONS A summary of the options supported by \fBchronyd\fR is included below. .TP \fB\-P\fR \fIpriority\fR This option will select the SCHED_FIFO real-time scheduler at the specified priority (which must be between 0 and 100). This mode is supported only on Linux. .TP .B \-m This option will lock chronyd into RAM so that it will never be paged out. This mode is only supported on Linux. .TP .B \-d When run in this mode, the program will not detach itself from the terminal, and all messages will be sent to the terminal instead of to syslog. .TP \fB\-f\fR \fIconf-file\fR This option can be used to specify an alternate location for the configuration file (default \fI/etc/chrony.conf\fR). .TP .B \-r This option will reload sample histories for each of the servers being used. These histories are created by using the \fIdump\fR command in \fIchronyc\fR, or by setting the \fIdumponexit\fR directive in the configuration file. This option is useful if you want to stop and restart \fBchronyd\fR briefly for any reason, e.g. to install a new version. However, it only makes sense on systems where the kernel can maintain clock compensation whilst not under \fBchronyd\fR's control. The only version where this happens so far is Linux. On systems where this is not the case, e.g. Solaris and SunOS the option should not be used. .TP .B \-s This option will set the system clock from the computer's real-time clock. This is analogous to supplying the \fI-s\fR flag to the \fI/sbin/clock\fR program during the Linux boot sequence. Support for real-time clocks is limited at present - the criteria are described in the section on the \fIrtcfile\fR directive in the documentation supplied with the distribution. If \fBchronyd\fR cannot support the real time clock on your computer, this option cannot be used and a warning message will be logged to the syslog. If used in conjunction with the \fB-r\fR flag, \fBchronyd\fR will attempt to preserve the old samples after setting the system clock from the real time clock. This can be used to allow \fBchronyd\fR to perform long term averaging of the gain or loss rate across system reboots, and is useful for dial-up systems that are shut down when not in use. For this to work well, it relies on \fBchronyd\fR having been able to determine accurate statistics for the difference between the real time clock and system clock last time the computer was on. .TP \fB\-u\fR \fIuser\fR When this option is used, chronyd will drop root privileges to the specified user. So far, it works only on Linux when compiled with capabilities support. .TP .B \-v This option displays \fBchronyd\fR's version number to the terminal and exits .TP .B \-4 Resolve hostnames only to IPv4 addresses. .TP .B \-6 Resolve hostnames only to IPv6 addresses. .SH FILES \fI/etc/chrony.conf\fR .SH VERSION Version 1.24 .SH BUGS To report bugs, please visit \fIhttp://chrony.tuxfamily.org/\fR .SH "SEE ALSO" \fBchronyd\fR is documented in detail in the documentation supplied with the distribution (\fIchrony.txt\fR and \fIchrony.texi\fR) and is also available from \fIhttp://go.to/chrony\fR .BR chrony(1), .BR chronyc(1), .BR chrony.conf(5), .BR clock(8), .BR xntpd(8), .BR ntpd(8) .SH AUTHOR Richard Curnow This man-page was written by Jan Schaumann as part of "The Missing Man Pages Project". Please see \fIhttp://www.netmeister.org/misc/m2p2/index.html\fR for details. The complete chrony documentation is supplied in texinfo format.