CHRONYD(8)						       System Administration							CHRONYD(8)

NAME

       chronyd - chrony background daemon

SYNOPSIS

       chronyd [OPTIONS]

DESCRIPTION

       chrony is a pair of programs for maintaining the accuracy of computer clocks. chronyd is a background daemon program that can be started at
       boot time.

       chronyd 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 chronyc).  In either case, chronyd determines the rate at which the computer gains or loses time, and compensates for this.

USAGE

       chronyd is usually started at boot-time and requires superuser privileges.

       If chronyd has been installed to its default location /usr/local/sbin/chronyd, starting it is simply a matter of entering the command:

       /usr/local/sbin/chronyd

       Information messages and warnings will be logged to syslog.

OPTIONS

       A summary of the options supported by chronyd is included below.

       -P priority
	      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.

       -m     This option will lock chronyd into RAM so that it will never be paged out.  This mode is only supported on Linux.

       -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.

       -f conf-file
	      This option can be used to specify an alternate location for the configuration file (default /etc/chrony.conf).

       -r     This option will reload sample histories for each of the servers being used.  These histories are created by using the dump  command
	      in chronyc, or by setting the dumponexit directive in the configuration file.  This option is useful if you want to stop and restart
	      chronyd briefly for any reason, e.g. to install a new version.  However, it only makes sense on systems where the kernel	can  main-
	      tain  clock compensation whilst not under chronyd'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.

       -s     This option will set the system clock from the computer's real-time clock.  This is analogous  to  supplying  the  -s  flag  to  the
	      /sbin/clock program during the Linux boot sequence.

	      Support for real-time clocks is limited at present - the criteria are described in the section on the rtcfile directive in the docu-
	      mentation supplied with the distribution.

	      If chronyd 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 -r flag, chronyd will attempt to preserve the old samples after setting the system clock from the
	      real time clock.	This can be used to allow chronyd 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 chronyd having been able
	      to determine accurate statistics for the difference between the real time clock and system clock last time the computer was on.

       -u user
	      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.

       -v     This option displays chronyd's version number to the terminal and exits

       -4     Resolve hostnames only to IPv4 addresses.

       -6     Resolve hostnames only to IPv6 addresses.

FILES

       /etc/chrony.conf

VERSION

       Version 1.24

BUGS

       To report bugs, please visit http://chrony.tuxfamily.org/

SEE ALSO

       chronyd is documented in detail in the documentation supplied with the distribution (chrony.txt and chrony.texi) and is also available from
       http://go.to/chrony

       chrony(1), chronyc(1), chrony.conf(5), clock(8), xntpd(8), ntpd(8)

AUTHOR

       Richard Curnow <rc@rc0.org.uk>

       This man-page was  written  by  Jan  Schaumann  <jschauma@netmeister.org>  as  part  of	"The  Missing  Man  Pages  Project".   Please  see
       http://www.netmeister.org/misc/m2p2/index.html for details.

       The complete chrony documentation is supplied in texinfo format.

chrony								 December 04, 2009							CHRONYD(8)