HP-UX Reference (11i v2 03/08) - 1M System Administration Commands N-Z (vol 4)
x
xntpd(1M) xntpd(1M)
be installed elsewhere (see the -c conffile
command line option).
The file format is similar to other UNIX configuration files. Comments begin with a # character and
extend to the end of the line. Blank lines are ignored. Configuration commands consist of an initial key-
word followed by a list of arguments, some of which may be optional, separated by white space. Com-
mands may not be continued over multiple lines. Arguments may be host names, host addresses written
in numeric, dotted-quad form, integers, floating point numbers (when specifying times in seconds) and
text strings. Optional arguments are delimited by
[]
in the following descriptions, while alternatives
are separated by
|. The notation
[ ... ] means an optional, indefinite repetition of the last item
before the
[ ... ].
While there is a rich set of options available, the only required option is one or more server, peer or
broadcast commands described in the "Configuration Options" section. The examples in
/etc/ntp.conf.example
may also be helpful.
CONFIGURATION OPTIONS
The configuration commands are as described below:
peer address [ key key_id ][version
version_id ][ prefer ]
server address [ key key_id ][version
version_id ][ prefer ][mode mode ]
broadcast address [ key key_id ][version
version_id ][ttl ttl ]
The above three commands can be used to specify either the name or address of the time server and the
mode in which the time server should operate. The address can be either a DNS name or an IP address in
dotted-quad notation.
The
peer command specifies that the local server is to operate in symmetric active mode with the remote
server. In this mode, the local server can be synchronized to the remote server and, in addition, the
remote server can be synchronized by the local server. This is useful in a network of servers where,
depending on various failure scenarios, either the local or remote server may be the better source of time.
The
server command specifies that the local server is to operate in client mode with the specified
remote server. In this mode, the local server can be synchronized to the remote server, but the remote
server can never be synchronized to the local server. This is the most common operating mode (by far).
The
broadcast command specifies that the local server is to operate in broadcast mode, where the local
server sends periodic broadcast messages to a client population at the broadcast/multicast address
specified. Ordinarily, this specification applies only to the local server operating as a sender; for operation
as a broadcast client, see the broadcastclient
or multicastclient commands below. In this
mode, address is usually the broadcast address of (one of) the local network(s) or a multicast address
assigned to NTP. The address of 224.0.1.1 is assigned to NTP. This is presently the only address that
should be used. Note that the use of multicast features requires a multicast kernel.
OPTIONS
key key_id All packets sent to the address are to include authentication fields encrypted using the
specified key identifier, which is an unsigned 32 bit integer. The default is to not include
an encryption field.
version version_id
Specifies the version number to be used for outgoing NTP packets. Versions 1, 2, and 3
are the choices, with version 3 the default.
prefer Marks the server as preferred. All other things being equal, this host will be chosen for
synchronization among a set of correctly operating hosts.
ttl ttl This option is used only with broadcast mode. It specifies the ttl (time-to-live) to use on
multicast packets. Selection of the proper value, which defaults to 127, must be
co-ordinated with the network administrator(s).
broadcastclient
This command enables reception of broadcast server messages on any local interface.
Upon receiving a message for the first time, the broadcast client measures the nominal
server propagation delay using a brief client/server exchange with the server. Then, the
client enters the broadcastclient mode, in which it listens for and synchronizes to
succeeding broadcast messages. Note that, in order to avoid accidental or malicious disr-
uption in this mode, both the server and client should operate using symmetric-key or
public-key authentication.
HP-UX 11i Version 2: August 2003 − 2 − Hewlett-Packard Company Section 1M−−919