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diff --git a/doc/chronyd.adoc b/doc/chronyd.adoc new file mode 100644 index 0000000..d3b78a4 --- /dev/null +++ b/doc/chronyd.adoc @@ -0,0 +1,186 @@ +// This file is part of chrony +// +// Copyright (C) Richard P. Curnow 1997-2003 +// Copyright (C) Miroslav Lichvar 2009-2017 +// +// This program is free software; you can redistribute it and/or modify +// it under the terms of version 2 of the GNU General Public License as +// published by the Free Software Foundation. +// +// This program is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. +// +// You should have received a copy of the GNU General Public License along +// with this program; if not, write to the Free Software Foundation, Inc., +// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + += chronyd(8) +:doctype: manpage +:man manual: System Administration +:man source: chrony @CHRONY_VERSION@ + +== 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 _@SYSCONFDIR@/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 _@SYSCONFDIR@/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 +<<chrony.conf.adoc#dumpdir,*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 <<chrony.conf.adoc#initstepslew,*initstepslew*>> +directive and the <<chrony.conf.adoc#makestep,*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 +<<chrony.conf.adoc#driftfile,*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 +<<chrony.conf.adoc#user,*user*>> directive (default _@DEFAULT_USER@_). ++ +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 + +_@SYSCONFDIR@/chrony.conf_ + +== SEE ALSO + +<<chronyc.adoc#,*chronyc(1)*>>, <<chrony.conf.adoc#,*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. |