Provided by: chrony_2.1.1-1_amd64 bug


       chronyd - chrony background daemon


       chronyd [OPTIONS] [configuration commands]


       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 privileges.

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


       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).


       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

              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

       -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.




       To report bugs, please visit


       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)


       Richard Curnow <>

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

       The complete chrony documentation is supplied in texinfo format.