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/sbin/chronyd, starting it is simply a matter of entering the command:

       /usr/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.

       -n     When run in this mode, the program will not detach itself from the terminal.

       -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.

       -R     When this option is used, the initstepslew directive and the makestep directive used with a positive limit  will	be  ignored.  This
	      option is useful when restarting chronyd and can be used in conjuction with the -r option.

       -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 and create only IPv4 sockets.

       -6     Resolve hostnames only to IPv6 addresses and create only IPv6 sockets.

FILES

       /etc/chrony.conf

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), hwclock(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 1.29.1							   January 2014 							CHRONYD(8)