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       chronyd - chrony background daemon


       chronyd [OPTIONS]


       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.


       chronyd  is  usually  started  at  boot-time  and  requires   superuser

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


       Information messages and warnings will be logged to syslog.


       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  maintain  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 documentation 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.




       Version 1.24


       To report bugs, please visit


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

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


       Richard Curnow <>

       This man-page was written by Jan Schaumann <> as
       part   of   "The   Missing   Man   Pages    Project".     Please    see for details.

       The complete chrony documentation is supplied in texinfo format.