NAME

       chronyd - chrony background daemon

SYNOPSIS

       chronyd [OPTIONS] [configuration commands]

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.

       If no configuration commands are specified on the command line, chronyd will read the commands  from  the
       configuration file (default /etc/chrony/chrony.conf).

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.  When chronyd was compiled with debugging support,
              this option can be used twice to print also debugging messages.

       -f conf-file
              This option can be used to specify an alternate  location  for  the  configuration  file  (default
              /etc/chrony/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 maintain clock compensation whilst not under chronyd's control.  The only version  where  this
              happens so far is Linux.  On other systems this 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
              conjunction 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/hwclock 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 documentation supplied with the distribution.

              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 (RTC).  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 RTC and system
              clock last time the computer was on.

              If chronyd doesn't support the RTC on your computer or there is no RTC installed, the system clock
              will be set with this option forward to the time of  the  last  modification  of  the  drift  file
              (specified  by the driftfile directive) to restore the system time at which chronyd was previously
              stopped.

       -u user
              This option sets the name of the user to which will chronyd switch  to  drop  root  privileges  if
              compiled with Linux capabilities support (default _chrony).

       -q     When  run  in this mode, chronyd will set the system clock once and exit.  It will not detach from
              the terminal.

       -Q     This option is similar to -q, but it will only print the offset and not correct the clock.

       -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/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).

       chronyc(1), chrony.conf(5), hwclock(8), ntpd(8)

       http://chrony.tuxfamily.org/

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 2.1.1                                        June 2015                                         CHRONYD(8)