CHRONY(1)							   User's Manual							 CHRONY(1)

NAME

       chrony - programs for keeping computer clocks accurate

SYNOPSIS

       chronyc [OPTIONS]

       chronyd [OPTIONS]

DESCRIPTION

       chrony  is a pair of programs for keeping computer clocks accurate.  chronyd is a background (daemon) program and chronyc is a command-line
       interface to it. Time reference sources for chronyd can be RFC1305 NTP servers, human (via keyboard and chronyc), or the  computer's  real-
       time  clock at boot time (Linux only). chronyd can determine the rate at which the computer gains or loses time and compensate for it while
       no external reference is present. Its use of NTP servers can be switched on and off (through  chronyc)  to  support  computers  with  dial-
       up/intermittent access to the Internet, and it can also act as an RFC1305-compatible NTP server.

USAGE

       chronyc	is  a command-line interface program which can be used to monitor chronyd's performance and to change various operating parameters
       whilst it is running.

       chronyd's main function is to obtain measurements of the true (UTC) time from one of several sources, and correct the system clock  accord-
       ingly.  It also works out the rate at which the system clock gains or loses time and uses this information to keep it accurate between mea-
       surements from the reference.

       The reference time can be derived from either Network Time Protocol  (NTP)  servers,  reference	clocks,  or  wristwatch-and-keyboard  (via
       chronyc).  The main source of information about the Network Time Protocol is http://www.eecis.udel.edu/~ntp.

       It is designed so that it can work on computers which only have intermittent access to reference sources, for example computers which use a
       dial-up account to access the Internet.	Of course, it will work on computers with permanent connections too.

       In addition, for Linux 2.0.x (for x >= 32) or 2.2 onwards, chronyd can monitor the system's real time clock performance, so the system  can
       maintain accurate time even across reboots.

       Typical accuracies available between 2 machines are

       On  an ethernet LAN : 100-200 microseconds, often much better On a V32bis dial-up modem connection : 10's of milliseconds (from one session
       to the next)

       With a good reference clock the accuracy can reach one microsecond.

       chronyd can also operate as an RFC1305-compatible NTP server and peer.

SEE ALSO

       chronyc(1), chrony(1)

       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								 December 04, 2009							 CHRONY(1)