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CHRONYD(8)		     System Administration		    CHRONYD(8)

       chronyd - chrony	daemon

       chronyd [OPTION]... [DIRECTIVE]...

       chronyd is a daemon for synchronisation of the system clock. It can
       synchronise the clock with NTP servers, reference clocks	(e.g. a	GPS
       receiver), and manual input using wristwatch and	keyboard via chronyc.
       It can also operate as an NTPv4 (RFC 5905) server and peer to provide a
       time service to other computers in the network.

       If no configuration directives are specified on the command line,
       chronyd will read them from a configuration file. The compiled-in
       default location	of the file is /usr/local/etc/chrony.conf.

       Information messages and	warnings will be logged	to syslog.

	   With	this option hostnames will be resolved only to IPv4 addresses
	   and only IPv4 sockets will be created.

	   With	this option hostnames will be resolved only to IPv6 addresses
	   and only IPv6 sockets will be created.

       -f file
	   This	option can be used to specify an alternate location for	the
	   configuration file (default /usr/local/etc/chrony.conf).

	   When	run in this mode, the program will not detach itself from the

	   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.

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

	   This	option is similar to -q, but it	will only print	the offset
	   without any corrections of the clock.

	   This	option will try	to reload and then delete files	containing
	   sample histories for	each of	the servers and	reference clocks 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	should be used only on systems where the
	   kernel can maintain clock compensation whilst not under chronyd's
	   control (i.e. Linux,	FreeBSD, NetBSD	and Solaris).

	   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.

	   This	option will set	the system clock from the computer's real-time
	   clock (RTC) or to the last modification time	of the file specified
	   by the driftfile directive. Real-time clocks	are supported only on

	   If used in conjunction with the -r flag, chronyd will attempt to
	   preserve the	old samples after setting the system clock from	the
	   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 systems with intermittent	access to network 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 the last modification time of the	drift file is later than both
	   the current time and	the RTC	time, the system time will be set to
	   it to restore the time when chronyd was previously stopped. This is
	   useful on computers that have no RTC	or the RTC is broken (e.g. it
	   has no battery).

       -t timeout
	   This	option sets a timeout (in seconds) after which chronyd will
	   exit. If the	clock is not synchronised, it will exit	with a
	   non-zero status. This is useful with	the -q or -Q option to shorten
	   the maximum time waiting for	measurements, or with the -r option to
	   limit the time when chronyd is running, but still allow it to
	   adjust the frequency	of the system clock.

       -u user
	   This	option sets the	name of	the system user	to which chronyd will
	   switch after	start in order to drop root privileges.	It overrides
	   the user directive (default chronyd).

	   On Linux, chronyd needs to be compiled with support for the libcap
	   library. On macOS, FreeBSD, NetBSD and Solaris chronyd forks	into
	   two processes. The child process retains root privileges, but can
	   only	perform	a very limited range of	privileged system calls	on
	   behalf of the parent.

       -F level
	   This	option configures a system call	filter when chronyd is
	   compiled with support for the Linux secure computing	(seccomp)
	   facility. In	level 1	the process is killed when a forbidden system
	   call	is made, in level -1 the SYSSIG	signal is thrown instead and
	   in level 0 the filter is disabled (default 0).

	   It's	recommended to enable the filter only when it's	known to work
	   on the version of the system	where chrony is	installed as the
	   filter needs	to allow also system calls made	from libraries that
	   chronyd is using (e.g. libc)	and different versions or
	   implementations of the libraries may	make different system calls.
	   If the filter is missing some system	call, chronyd could be killed
	   even	in normal operation.

       -P priority
	   On Linux, this option will select the SCHED_FIFO real-time
	   scheduler at	the specified priority (which must be between 0	and
	   100). On macOS, this	option must have either	a value	of 0 (the
	   default) to disable the thread time constraint policy or 1 for the
	   policy to be	enabled. Other systems do not support this option.

	   This	option will lock chronyd into RAM so that it will never	be
	   paged out. This mode	is only	supported on Linux.

	   With	this option chronyd will print version number to the terminal
	   and exit.


       chronyc(1), chrony.conf(5)

       For instructions	on how to report bugs, please visit <https://>.

       chrony was written by Richard Curnow, Miroslav Lichvar, and others.

chrony 3.1			  2017-01-31			    CHRONYD(8)


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