xntpd(1M) xntpd(1M)
NAME
xntpd, in.xntpd - NTP daemon
SYNOPSIS
in.xntpd [-bdg] [-c conffile] [-f driftfile] [-l logfile] [-p pidfile]
[-r broadcastdelay]
DESCRIPTION
in.xntpd is a daemon process that administers the local time of a
Reliant UNIX system, possibly in conjunction with Internet standard
servers. in.xntpd is a complete implementation of the Network Time
Protocol (NTP) Version 3. NTP V3 is defined in RFC 1305. NTP V3 is
compatible with versions 1 and 2, defined in the RFCs 1059 and 1119.
in.xntpd executes all authorizations in fixed-point arithmetic. High-
precision timers can also be supported with the same accuracy.
Configuration parameters for in.xntpd are normally read from a confi-
guration file, usually /etc/ntp.conf, at system startup. If in.xntpd
is used as a broadcast client only, you can manage without the confi-
guration file. Internal variables and/or configuration parameters of
in.xntpd can be displayed or changed using the ntpq(1M) command.
The local in.xnptd can be configured in the modes "active/passive sym-
metric", "client/server", and "broadcast client/server" for remote
systems. A broadcast client automatically recognizes remote servers
and calculates time corrections based on the message propagation
delays between the server and the client. Broadcast clients can be
configured fully by means of parameters in the command line.
OPTIONS
-b in.xntpd is the broadcast client, i.e. it receives NTP broadcasts
and synchronizes the local time accordingly.
-c conffile
specifies the name of the configuration file (default value:
/etc/ntp.conf).
-d in.xntpd is started in test mode (debugging mode). This option
can be specified more than once resulting in more extensive test
messages.
-g in.xntpd always corrects the local system time based on a time-
stamp it has received. If this option is not specified, it is
only corrected if the deviation is not more then 1,000 seconds
greater than the timestamp it received.
-f driftfile
Specifies the name of the drift file (see below).
-l logfile
Specifies the name of the log file for syslog(3C) messages.
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-p pidfile
Specifies the name of the file in which in.xntpd stores its pro-
cess number.
-r broadcastdelay
in.xntpd normally equalizes message propagation delays between a
broadcast server and the client automatically. If this calibra-
tion fails, the value (in seconds) specified as the broadcast
delay is used instead.
CONFIGURATION PARAMETERS
The format of the in.xntpd configuration file is similar to other
Reliant UNIX configuration files. Comments are introduced by the #
character and apply until the line end. Blanks are ignored. Configura-
tion instructions consist of a keyword followed by a list of arguments
separated from each other by filter characters. An instruction may
only be one line in length. Optional arguments are included in subse-
quent instructions in [] and there is a | between arguments that can
be specified as alternatives.
peer hostaddress [version#] [prefer]
server hostaddress [version#] [prefer]
broadcast hostaddress [version#] [ttl#]
The computer addresses indicated by hostaddress must be speci-
fied in dot notation.
The peer command sets the local in.xntpd to the mode "active sym-
metric" for the NTP server on the hostaddress remote system. In
this mode, the servers can synchronize each other. This is useful
if each of the two servers could be the more reliable timer due
to different errors.
The server command sets the local in.xntpd to the "client mode"
for the specified server. In this mode, the local in.xntpd is
synchronized by the remote NTP server, but not the other way
around.
The broadcast command establishes the local in.xntpd as the
broadcast server. It transmits timestamps periodically to its
clients via the specified broadcast address. Broadcast client
operation is described under the broadcastclient command.
The version number for outgoing NTP packages can be set using the
version# argument. Possible values are 1, 2, and 3, the default
value is 3.
A partner can be marked as "preferred" using the prefer parameter
which means that otherwise equivalent candidates are selected for
synchronization.
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The ttl# argument can be used for a broadcast server. It speci-
fies the time to live of NTP broadcasts on the network in
seconds. The default value is 127.
broadcastclient
This instructs the local in.xntpd to synchronize the local system
time using incoming NTP broadcasts. A brief exchange of data with
the broadcast server is initiated upon receipt of the first
broadcast message to measure the message propagation delay, used
in calculating the local system time, to the server.
driftfile filename
This command names the file containing the accuracy deviation of
the local oscillator. This value is used to calculate a compensa-
tory value for the local variations and is only needed if the
local system time must be synchronized with greater accuracy. If
the driftfile does not exist or the driftfile command is missing,
a difference of 0 is presumed. Otherwise the deviation is speci-
fied as a floating-point value in multiples of 10^-6 (parts per
million, ppm).
enable bclient | pll
disable bclient | pll
These flags enable or disable options for in.xntpd. The bclient
flag assigns in.xntpd the role of a broadcast client (see above).
The default value is off. The pll flag (default value: on)
enables updating of the local system time. This flag should only
be disabled if in.xntpd synchronizes other systems but the
system's own system time is to be set by other mechanisms.
PARAMETERS FOR ACCESS CONTROL
restrict address [mask numericmask] [flag] [...]
in.xntpd administers an access control list based on host
addresses and address masks. The sender address of received NTP
packages is first ANDed with the list entry mask and then com-
pared with the specified address. If both addresses match, the
access restrictions apply to the package received. The default
value for the mask argument is 255.255.255.255, i.e. the address
argument is interpreted as the address of an individual system.
The flag arguments define the access restrictions for systems
whose addresses are entered in the list in the manner described
above:
ignore
All NTP packages belonging to this system are ignored.
noquery
NTP packages belonging to this system are ignored if they
are mode 6 and 7 packages (status queries and configuration
jobs).
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nomodify
NTP packages belonging to this system are ignored if they
are mode 6 and 7 packages that change data on the local sys-
tem.
notrap
Trap messages for these systems based on special mode 6
packages are ignored.
lowpriotrap
Trap services for this system are classified as low prior-
ity. in.xntpd can administer up to 3 trap services and usu-
ally rejects jobs for further trap services. Low priority
services are, however, overwritten by new incoming jobs.
noserve
NTP packages belonging to this system are ignored if they
are not mode 6 and mode 7 packages. Status queries and con-
figuration jobs are allowed, therefore, but received time-
stamps are not noted.
nopeer
The local in.xntpd assumes a purely passive role for this
system in that only incoming synchronization jobs are
responded to.
notrust
The local in.xntpd does not undertake any synchronization
because of the existence of NTP packages for the system.
limited
These systems are subject to a limit with regard to the
number of active clients on the same network (in accordance
with the IP definition for Class A, B, and C). The default
for this is 3 and can be changed by the clientlimit command
(see below). Only clients whose timestamps are not longer
than a pre-defined inactivity time (default value: 3600
seconds) are considered active. The inactivity time can be
changed using the clientperiod command (see below).
ntpport
This is simply a modifier for an access restriction already
specified. It means that the restriction is only effective
if the sender's port number is the default UDP port for NTP
(123). restrict entries with the ignore and ntpport flags
are incorporated into the access control list for each net-
work address at startup so that in.xntpd does not synchron-
ize itself.
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clientlimit limit
This command defines the maximum number of clients in the same
network that the local in.xntpd may use as a server (default
value: 3).
clientperiod period
This command defines the inactivity time for limited clients in
seconds (default value: 3600). Any client that does not send a
timestamp to the in.xntpd within this time is no longer con-
sidered for limitation.
OTHER PARAMETERS
broadcastdelay seconds
in.xntpd normally equalizes message propagation delays between a
broadcast server and the client automatically using a separate
message protocol intended for this purpose. If this calibration
fails, a default value of 0.004 seconds is used if no other value
is specified via the broadcastdelay command.
trap hostaddress
This command configures a recipient for trap messages on the
specified system. Trap messages are transmitted by in.xntpd in
exceptional and error situations and logged by the recipient.
ADDRESSING TIMERS
In Reliant UNIX, only the system clock of the local system can be con-
figured as a timer. In principle, however, NTP also permits the confi-
guration of other timers, e.g. radio receivers for DCF77 signals.
Timers are addressed in the same way as partner systems. Pseudo IP
addresses of the form 127.127.t.u, which are invalid as normal IP
addresses, are used for this. t indicates the timer type, u is type-
specific. The system clock is specified using the pseudo IP address
127.127.1.0.
Timers are configured using the server command, where the address of
the timer must be entered as the system address. The version# argument
may not be specified, prefer, however, may. In contrast, the prefer
option must be specified in the configuration line for the system
clock in the case of broadcast servers which distribute the local sys-
tem time.
An alternative and more extensive command for the configuration of a
timer is the fudge command. The general format for this command is:
fudge 127.127.t.u [stratum int]
The stratum argument can be of importance for configuring the
local system clock. The stratum specifies how many stations
in.xntpd can use to request a highly accurate timestamp from an
external timer. Servers with the stratum 1 have direct access to
external time signals. Servers that receive their timestamp from
stratum 1 servers are stratum 2 servers, etc.
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The stratum is the main criterion by which in.xntpd selects one
server from a number of possible servers to be a client. Even the
local system clock is a "server" from the point of view of
in.xntpd. The default for its stratum is 3. By specifying a lower
or higher value for its stratum in the fudge command, it can be
given a higher or lower priority than other servers.
FILES
/etc/ntp.conf
default configuration filename
SEE ALSO
ntpdate(1M), ntpq(1M), ntptrace(1M).
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