Installing and Administering Internet Services

Chapter 7 217
Configuring NTP
Configuration
• Use NTP broadcasting where possible and practical in order to reduce
NTP traffic on subnets.
Configuration File
This section describes the statements that can be defined in the
/etc/ntp.conf configuration file. Configuration file statements are
described in the following subsections:
• “Configuring Relationships with Other Time Servers” on page 217
• “Configuring External Clocks” on page 219
• “Configuring a Driftfile” on page 220
• “Configuring Authentication” on page 221
• “Restricting Incoming NTP Packets” on page 223
Configuring Relationships with Other Time Servers
The roles of a time server are its relationships to other servers in the
synchronization subnet. In the configuration file, a role is defined with
one of four statements (peer, server, broadcast, and
broadcastclient):
peer host|IP_address specifies that the named host is to provide time
that the local host may synchronize to, and the local host is willing to
provide time to which the named host may be synchronized.
server host|IP_address specifies that the named host is to provide
time that the local host might synchronize to, but the local host does not
provide time to which the named host may be synchronized. (The local
host is a client of the named host.) In addition, server statements are
used to configure external clocks (radio clocks or local system clocks) for
stratum-1 servers. Refer to “Configuring External Clocks” on page 219
for more information.
broadcast host|broadcast_address specifies that the xntpd daemon in
the local host transmits broadcast NTP messages to a named address,
usually the broadcast address on your local network. (The local host is a
broadcaster.)
With the peer, server, or broadcast statement, you can also specify
one or more of the following options: