--- /dev/null
+.\" Copyright (c) 1980, 1991 Regents of the University of California.
+.\" All rights reserved.
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+.\" notice, this list of conditions and the following disclaimer in the
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+.\" 3. All advertising materials mentioning features or use of this software
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+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
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+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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+.\"
+.\" @(#)timed.8 6.7 (Berkeley) 5/11/93
+.\"
+.Dd May 11, 1993
+.Dt TIMED 8
+.Os "Linux NetKit (0.17)"
+.Sh NAME
+.Nm timed
+.Nd time server daemon
+.Sh SYNOPSIS
+.Nm timed
+.Op Fl M
+.Op Fl t
+.Op Fl d
+.Op Fl i Ar network
+.Op Fl n Ar network
+.Op Fl F Ar host1 host2 ...
+.Sh DESCRIPTION
+This
+is a time server daemon and is normally invoked
+at boot time from the
+.Xr rc 8
+file.
+It synchronizes the host's time with the time of other
+machines in a local area network running
+.Nm timed 8 .
+These time servers will slow down the clocks of some machines
+and speed up the clocks of others to bring them to the average network time.
+The average network time is computed from measurements of clock differences
+using the
+.Tn ICMP
+timestamp request message.
+.Pp
+The service provided by
+.Nm timed
+is based on a master-slave
+scheme.
+When
+.Nm timed 8
+is started on a machine, it asks the master for the network time
+and sets the host's clock to that time.
+After that, it accepts synchronization messages periodically sent by
+the master and calls
+.Xr adjtime 2
+to perform the needed corrections on the host's clock.
+.Pp
+It also communicates with
+.Xr date 1
+in order to set the date globally,
+and with
+.Xr timedc 8 ,
+a timed control program.
+If the machine running the master crashes, then the slaves will elect
+a new master from among slaves running with the
+.Fl M
+flag.
+A
+.Nm timed
+running without the
+.Fl M
+or
+.Fl F
+flags will remain a slave.
+The
+.Fl t
+flag enables
+.Nm timed
+to trace the messages it receives in the
+file
+.Pa /var/log/timed.log .
+Tracing can be turned on or off by the program
+.Xr timedc 8 .
+The
+.Fl d
+flag is for debugging the daemon.
+It causes the program to not put itself into the background.
+Normally
+.Nm timed
+checks for a master time server on each network to which
+it is connected, except as modified by the options described below.
+It will request synchronization service from the first master server
+located.
+If permitted by the
+.Fl M
+flag, it will provide synchronization service on any attached networks
+on which no current master server was detected.
+Such a server propagates the time computed by the top-level master.
+The
+.Fl n
+flag, followed by the name of a network which the host is connected to
+(see
+.Xr networks 5 ) ,
+overrides the default choice of the
+network addresses made by the program.
+Each time the
+.Fl n
+flag appears, that network name is added to a list of valid networks.
+All other networks are ignored.
+The
+.Fl i
+flag, followed by the name of a network to which the host is connected
+(see
+.Xr networks 5 ) ,
+overrides the default choice of the network addresses made by the program.
+Each time the
+.Fl i
+flag appears, that network name is added to a list of networks to ignore.
+All other networks are used by the time daemon.
+The
+.Fl n
+and
+.Fl i
+flags are meaningless if used together.
+.Pp
+.Nm Timed
+checks for a master time server on each network to which
+it is connected, except as modified by the
+.Fl n
+and
+.Fl i
+options described above.
+If it finds masters on more than one network, it chooses one network
+on which to be a "slave," and then periodically checks the other
+networks to see if the masters there have disappeared.
+.Pp
+One way to synchronize a group of machines is to use an NTP daemon to
+synchronize the clock of one machine to a distant standard or a radio
+receiver and
+.Fl F Ar hostname
+to tell its timed daemon to trust only itself.
+.Pp
+Messages printed by the kernel on the system console occur with
+interrupts disabled.
+This means that the clock stops while they are printing.
+A machine with many disk or network hardware problems and consequent
+messages cannot keep good time by itself. Each message typically causes
+the clock to lose a dozen milliseconds. A time daemon can
+correct the result.
+.Pp
+Messages in the system log about machines that failed to respond
+usually indicate machines that crashed or were turned off.
+Complaints about machines that failed to respond to initial time
+settings are often associated with
+.Dq multi-homed
+machines that looked for time masters on more than one network and eventually
+chose to become slaves on other networks.
+.Sh WARNINGS
+If two or more time daemons, whether
+.Nm timed
+or
+.Xr ntp ,
+try to adjust the same clock, temporal chaos will result.
+If both
+.Nm
+and another time daemon are run on the same machine,
+ensure that the
+.Fl F
+flag is used, so that
+.Nm timed
+never attempts to adjust the local clock.
+.Pp
+The protocol is based on UDP/IP broadcasts. All machines within
+the range of a broadcast that are using the TSP protocol must cooperate.
+There cannot be more than a single administrative domain using the
+.Fl F
+flag among all machines reached by a broadcast packet.
+Failure to follow this rule is usually indicated by complaints concerning
+.Dq untrusted
+machines in the system log.
+.Sh FILES
+.Bl -tag -width /var/log/timed.masterlog -compact
+.It Pa /var/log/timed.log
+tracing file for timed
+.It Pa /var/log/timed.masterlog
+log file for master timed
+.El
+.Sh SEE ALSO
+.Xr date 1 ,
+.Xr adjtime 2 ,
+.Xr gettimeofday 2 ,
+.Xr icmp 4 ,
+.Xr timedc 8
+.Rs
+.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
+.%A R. Gusella
+.%A S. Zatti
+.Re
+.Sh HISTORY
+The
+.Nm
+daemon appeared in
+.Bx 4.3 .
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