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

NAME
     timed - time server daemon

SYNOPSIS
     timed [-dtM] [-i network | -n network] [-F host ...]

DESCRIPTION
     The timed utility is a time server daemon which is normally invoked at
     boot time from the rc.network(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.

     -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 multiple times to add more
             than one network to the list.

     -F host ...
             -   Create a list of trusted hosts.
             -   Can take one or more parameters.
             -   timed 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.
             -   Use real host names (resolvable by RDNS) not aliases (eg in
                 named(8) parlance: use A names, not C names).
             -   Use full names eg time1.domain.com not time1.
             -   -F automatically includes the functionality of -M (so -M does
                 not need to asserted).
             -   If -F is not specified, all hosts on connected networks are
                 treated as trustworthy.

     -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 masters 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 initial 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
     network.

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 administrative 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), 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.

FreeBSD 11.0-PRERELEASE        February 11, 2008       FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | WARNINGS | FILES | SEE ALSO | HISTORY

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