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NAME    [Toc]    [Back]

     timed - time server daemon

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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.

     -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.  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

     -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
             /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

     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 an  NTP
daemon to
     synchronize  the  clock of one machine to a distant standard
or a radio receiver
 and -F hostname to tell its timed daemon 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    [Toc]    [Back]

     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
     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    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

     date(1),  adjtime(2), gettimeofday(2), icmp(4), netgroup(5),
     ntpd(8), rdate(8), timedc(8)

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

HISTORY    [Toc]    [Back]

     The timed utility appeared in 4.3BSD.

OpenBSD      3.6                           May      11,      1993
[ Back ]
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