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NetBSD 6.1.5 - man page for timed (netbsd section 8)

TIMED(8)			   BSD System Manager's Manual				 TIMED(8)

NAME
     timed -- time server daemon

SYNOPSIS
     timed [-dMt] [-F host ...] [-G netgroup] [-i network | -n network]

DESCRIPTION
     The timed utility is a time server daemon which is normally invoked at boot time from the
     rc(8) file.  It synchronizes the host's time with the time of other machines, which are also
     running timed, in a local area network.  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 ICMP
     timestamp request message.

     The following options are available:

     -d      Enable debugging mode; do not detach from the terminal.

     -F host ...
	     Create a list of trusted hosts.  The timed utility will only accept trusted hosts as
	     masters.  If it finds an untrusted host claiming to be master, timed will suppress
	     incoming messages from that host and call for a new election.  This option implies
	     the -M option.  If this option is not specified, all hosts on the connected networks
	     are treated as trustworthy.

     -G netgroup
	     Specify a netgroup of trustworthy hosts, in addition to any masters specified with
	     the -M flag.  This option may only be specified once.

     -i network
	     Add network to the list of networks to ignore.  All other networks to which the
	     machine is directly connected are used by timed.  This option may be specified mul-
	     tiple times to add more than one network to the list.

     -M      Allow this host to become a timed master if necessary.

     -n network
	     Add network to the list of allowed networks.  All other networks to which the
	     machine is directly connected are ignored by timed.  This option may be specified
	     multiple times to add more than one network to the list.

     -t      Enable tracing of received messages and log to the file /var/log/timed.log.  Tracing
	     can be turned on or off while timed is running with the timedc(8) utility.

     The -n and -i flags are mutually exclusive and require as arguments real networks to which
     the host is connected (see networks(5)).  If neither flag is specified, timed will listen on
     all connected networks.

     A timed running without the -M nor -F flags will always remain a slave.  If the -F flag is
     not used, timed will treat all machines as trustworthy.

     The timed utility is based on a master-slave scheme.  When timed 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 adjtime(2) to
     perform the needed corrections on the host's clock.

     It also communicates with date(1) in order to set the date globally, and with timedc(8), a
     timed control utility.  If the machine running the master becomes unreachable, the slaves
     will elect a new master from among those slaves which are running with at least one of the
     -M and -F flags.

     At startup timed normally checks for a master time server on each network to which it is
     connected, except as modified by the -n and -i options described above.  It will request
     synchronization service from the first master server located.  If permitted by the -M or -F
     flags, it will provide synchronization service on any attached networks on which no trusted
     master server was detected.  Such a server propagates the time computed by the top-level
     master.  The timed utility will periodically check for the presence of a master on those
     networks for which it is operating as a slave.  If it finds that there are no trusted mas-
     ters on a network, it will begin the election process on that network.

     One way to synchronize a group of machines is to use ntpd(8) to synchronize the clock of one
     machine to a distant standard or a radio receiver and -F hostname to tell its timed to trust
     only itself.

     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.

     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 ini-
     tial time settings are often associated with ``multi-homed'' machines that looked for time
     masters on more than one network and eventually chose to become a slave on the other net-
     work.

WARNINGS
     Temporal chaos will result if two or more time daemons attempt to adjust the same clock.  If
     both timed and another time daemon are run on the same machine, ensure that the -F flag is
     used, so that timed never attempts to adjust the local clock.

     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 adminis-
     trative domain using the -F flag among all machines reached by a broadcast packet.  Failure
     to follow this rule is usually indicated by complaints concerning ``untrusted'' machines in
     the system log.

FILES
     /var/log/timed.log        tracing file for timed
     /var/log/timed.masterlog  log file for master timed

SEE ALSO
     date(1), adjtime(2), gettimeofday(2), icmp(4), netgroup(5), networks(5), ntpd(8), timedc(8)

     R. Gusella and S. Zatti, TSP: The Time Synchronization Protocol for UNIX 4.3BSD.

HISTORY
     The timed utility appeared in 4.3BSD.

BSD					   May 11, 1993 				      BSD


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