NAME

       chronyd - chrony daemon

SYNOPSIS

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

DESCRIPTION

       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
       /etc/chrony/chrony.conf.

       Information messages and warnings will be logged to syslog.

OPTIONS

       -4
           With this option hostnames will be resolved only to IPv4 addresses and only IPv4
           sockets will be created.

       -6
           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 /etc/chrony/chrony.conf).

       -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 written to the terminal instead of syslog. When chronyd was compiled
           with debugging support, this option can be used twice to print also debugging
           messages.

       -l file
           This option specifies a file which should be used for logging instead of syslog or
           terminal.

       -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 the -q option, except it only prints the offset without
           making any corrections of the clock and it allows chronyd to be started without root
           privileges.

       -r
           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, Solaris, and macOS 10.13 or later).

       -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 (RTC) or to
           the last modification time of the file specified by the driftfile directive. Real-time
           clocks are supported only on Linux.

           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 _chrony).

           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.

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

       -x
           This option disables the control of the system clock. chronyd will not make any
           adjustments of the clock, but it will still track its offset and frequency relative to
           the estimated true time, and be able to operate as an NTP server. This allows chronyd
           to run without the capability to adjust or set the system clock (e.g. in some
           containers).

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

FILES

       /etc/chrony/chrony.conf

SEE ALSO

       chronyc(1), chrony.conf(5)

BUGS

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

AUTHORS

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