CONTENTS

SYNOPSIS

DESCRIPTION

The following options are available:

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.

SEE ALSO

HISTORY