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CHRONYD(8)                   System Administration                  CHRONYD(8)

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.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.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. The files are expected to be in the directory specified by
           the dumpdir 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 SIGSYS 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 try to make any adjustments of the clock. It will assume the
           clock is free running and still track its offset and frequency
           relative to the estimated true time. This option allows chronyd to
           run without the capability to adjust or set the system clock (e.g.
           in some containers) in order to operate as an NTP server. It is not
           recommended to run chronyd (with or without -x) when another
           process is controlling the system clock.
       -v
           With this option chronyd will print version number to the terminal
           and exit.
FILES
       /etc/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.

chrony 3.4                        2018-09-19                        CHRONYD(8)