''' Set up \*(-- to give an unbreakable dash;
''' string Tr holds user defined translation string.
''' Greek uppercase omega is used as a dummy character.
.if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
xntpdc - query/control program for the Network Time Protocol daemon
daemon about its current state and to request changes in that state. The
program may be run either in interactive mode or controlled using
command line arguments. Extensive state and statistics information is
interface. In addition, nearly all the configuration options which can
be specified at start up using
configuration file may also be specified at run time using
If one or more request options is included on the command line when
is executed, each of the requests will be sent to the NTP servers running
on each of the hosts given as command line arguments, or on
by default. If no request options are given,
will attempt to read commands from the standard input and execute these
on the NTP server running on the first host given on the command line, again
when no other host is specified.
will prompt for commands if the standard input is a terminal device.
uses NTP mode 7 packets to communicate with the NTP server, and hence
can be used to query any compatable server on the network which permits
it. Note that since NTP is a UDP protocol this communication will be
somewhat unreliable, especially over large distances in terms of network
makes no attempt to retransmit requests, and will time requests out if
the remote host is not heard from within a suitable time out time.
Command line options are described following. Specifying a command
will cause the specified query (queries) to be sent to the indicated
host(s) immediately. Otherwise,
will attempt to read interactive format commands from the standard input.
The following argument is interpreted as an interactive format command
and is added to the list of commands to be executed on the specified
to operate in interactive mode. Prompts will be written to the
standard output and commands read from the standard input.
Obtain a list of peers which are known to the server(s). This switch
is equivalent to \*(L"-c listpeers\*(R".
Output all host addresses in dotted\-quad numeric format rather than
converting to the canonical host names.
Print a list of the peers known to the server as well as a summary
of their state. This is equivalent to \*(L"-c peers\*(R".
Print a list of the peers known to the server as well as a summary
of their state, but in a slightly different format than the
switch. This is equivalent to \*(L"-c dmpeers\*(R".
Interactive format commands consist of a keyword followed by zero
to four arguments. Only enough characters of the full keyword to
uniquely identify the command need be typed. The output of a command
is normally sent to the standard output, but optionally the output of
individual commands may be sent to a file by appending a \*(L">\*(R",
followed by a file name, to the command line.
A number of interactive format commands are executed entirely within the
program itself and do not result in NTP mode 7 requests being sent
to a server. These are described following.
A \*(L"?\*(R" by itself will print a list of all the command keywords
known to this incarnation of
A \*(L"?\*(R" followed by a command keyword will print funcation and
usage information about the command. This command is probably a better
source of information about
Specify a time out period for responses to server queries. The default
is about 8000 milliseconds.
Specify a time interval to be added to timestamps included in requests
which require authentication. This is used to enable (unreliable) server
reconfiguration over long delay network paths or between machines whose
clocks are unsynchronized.
Set the host to which future queries will be sent.
may be either a host name or a numeric
Poll the current server in client mode. The first argument is the
number of times to poll (default is 1) while the second argument may
be given to obtain a more detailed output of the results. This command
is currently just wishful thinking.
This command allows the specification of a key number to be used to
authenticate configuration requests. This must correspond to the
key number the server has been configured to use for this purpose.
This command prompts you to type in a password (which will not be
echoed) which will be used to authenticate configuration requests. The
password must correspond to the key configured for use by the NTP
server for this purpose if such requests are to be successful.
If \*(L"yes\*(R" is specified, host names are printed in information
displays. If \*(L"no\*(R" is given, numeric addresses are printed
instead. The default is \*(L"yes\*(R" unless modified using the command
Query commands result in NTP mode 7 packets containing requests for
information being sent to the server. These are \*(L"read\-only\*(R"
commands in that they make no modification of the server configuration
Obtains and prints a brief list of the peers for which the
server is maintaining state. These should include all configured
peer associations as well as those peers whose stratum is such that
they are considered by the server to be possible future synchonization
Obtains a list of peers for which the server is maintaining state, along
with a summary of that state. Summary information includes the address
of the remote peer, the local interface address (0.0.0.0 if a local address
has yet to be determined), the stratum of the remote peer (a stratum of
16 indicates the remote peer is unsynchronized), the polling interval,
in seconds, the reachability
register, in octal, and the current estimated delay, offset and dispersion
of the peer, all in seconds. In addition, the character in the left
margin indicates the mode this peer entry is operating in. A
\*(L"+\*(R" denotes symmetric active, a \*(L"-\*(R" indicates symmetric
passive, a \*(L"=\*(R" means the remote server is being polled in
client mode, a \*(L"^\*(R" indicates that the server is broadcasting
to this address, a \*(L"~\*(R" denotes that the remote peer is sending
broadcasts and a \*(L"*\*(R" marks the peer the server is currently
The contents of the host field may be one of four forms. It may be a host name,
an IP address, a reference clock implementation name with its parameter or
\*(L"REFCLK(<implementation number>, <parameter>)\*(R". On \*(L"hostnames no\*(R"
only IP\-addresses will be displayed.
A slightly different peer summary list. Identical to the output of the
command except for the character in the leftmost column. Characters
only appear beside peers which were included in the final stage of
the clock selection algorithm. A \*(L".\*(R" indicates that this
peer was cast off in the falseticker detection, while a \*(L"+\*(R"
indicates that the peer made it through. A \*(L"*\*(R" denotes the
peer the server is currently synchronizing with.
Shows a detailed display of the current peer variables for one or more
peers. Most of these values are described in the NTP Version 2
Show per\-peer statistic counters associated with the specified peer(s).
Print the values of selected loop filter variables. The loop filter is
the part of NTP which deals with adjusting the local system clock. The
\*(L"offset\*(R" is the last offset given to the loop filter by the
packet processing code. The \*(L"frequency\*(R" is actually the
frequency error, or drift, of your system's clock in the units NTP
uses for internal computations. Dividing this number by 4096 should
give you the actual drift rate. The \*(L"compliance\*(R" is actually
a long term average offset and is used by NTP to control the gain of
the loop filter. The \*(L"timer\*(R" value is the number of seconds
which have elapsed since a new sample offset was given to the loop
filter. The \*(L"oneline\*(R" and \*(L"multiline\*(R" options specify
the format in which this information is to be printed. \*(L"multiline\*(R"
Print a variety of system state variables, i.e. state related to the
local server. Many of these values are described in the NTP Version 2
Print a number of stat counters maintained in the protocol module.
Print a number of counters related to the peer memory allocation
Print counters maintained in the input\-output module.
Print counters maintained in the timer/event queue support code.
Obtain and print the server's restriction list. This list is (usually)
printed in sorted order and may help to understand how the restrictions
Obtain and print traffic counts collected and maintained by the
Obtain and print information concerning a peer clock. The values
obtained provide information on the setting of fudge factors and
other clock performance information.
Obtain debugging information for a clock peer. This information is
provided only by some clock drivers and is mostly undecodable without
a copy of the driver source in hand.
Obtain and print kernel phase-lock loop operating parameters. This
information is available only if the kernel has been specially modified
for a precision timekeeping function.
.SH RUNTIME CONFIGURATION REQUESTS
All requests which cause state changes in the server are authenticated
by the server using a configured NTP key (the facility can also be
the server by not configuring a key). The key number and the corresponding
key must also be made known to
This can be done using the
commands, the latter of which will prompt at the
terminal for a password to use
as the encryption key. You will also be prompted automatically for
both the key number and password the
first time a command which would result in an authenticated request
to the server is given. Authentication not only provides verification
that the requester has permission to make such changes, but also gives
an extra degree of protection again transmission errors.
Authenticated requests always include a timestamp in the packet data, which
is included in the computation of the authentication code. This timestamp
is compared by the server to its receive time stamp. If they differ
by more than a small amount the request is rejected. This is done for
two reasons. First, it makes simple replay attacks on the server, by someone
who might be able to overhear traffic on your LAN, much more difficult.
Second, it makes it more difficult to request configuration changes
to your server from topologically remote hosts. While the reconfiguration
facility will work well with a server on the local host, and may work
adequately between time\-synchronized hosts on the same LAN, it will
work very poorly for more distant hosts. As such, if reasonable passwords
are chosen, care is taken in the distribution and protection of keys and
appropriate source address restrictions are applied, the
run time reconfiguration facility should provide an adequate level of
The following commands all make authenticated requests.
Add a configured, symmetric active peer association with a peer at the
given address. If the optional \*(L"keyid\*(R" is a nonzero integer
all outgoing packets to the remote server will
have an authentication field attached encrypted with this key. If the
value is 0 (or not given) no authentication will be done. The
\*(L"version#\*(R" can be 1 or 2, and defaults to 2. If \*(L"minpoll\*(R"
is specified the polling interval for the association will remain
clamped at the minimum. The latter option is only useful for testing.
Note that an existing association with the same peer may be deleted
when this command is executed, or may simply be converted to conform to
the new configuration, as appropriate. The prefer keyword indicates
a preferred peer (and thus will be used primarily for clock synchronisation
if possible). The preferred peer also determines the validity of the PPS
signal - if the preferred peer is suitable for synchronisation so is the
command except that polling is done in client mode rather than
command except that packets are instead sent in broadcast mode. The
\*(L"peer_address\*(R" parameter will generally be a broadcast address
on one of your local networks.
This command causes the configured bit to be removed from the specified
peer(s). In many cases this will cause the peer association to be
deleted. When appropriate, however, the association may persist in
an unconfigured mode if the remote peer is willing to continue on in
.B set bclient|mclient|auth
Allows the setting of the broadcast/multicast client and/or authenticate
system flags. Setting bclient causes the server to listen for broadcast
NTP to to synchronize to broadcasts when appropriate. Setting mclient
causes the same thing, but using multicast facilities, when available.
Setting auth causes the server to only synchronize with peers which
include an authentication field encrypted with one of the local server's
Allows the broadcast/multicast client and/or authenticate system flags to be
cleared. Clearing bclient causes incoming broadcast and multicast NTP packets
to be ignored. Clearing auth allows peers which have not included
an authentication field, or which have included one but have encrypted
it with an untrusted key, to be considered synchronization candidates.
Causes flag(s) to be added to an existing restrict list entry, or adds
a new entry to the list with the specified flag(s). The possible choices
for the flags arguments are given in the following list:
Ignore all packets from hosts which match this entry. If this flag
is specified neither queries nor time server polls will be responded
Ignore all NTP mode 7 packets (i.e. information queries and configuration
requests) from the source. Time service is not affected.
Ignore all NTP mode 7 packets which attempt to modify the state of the
server (i.e. run time reconfiguration). Queries which return information
Decline to provide mode 6 control message trap service to matching
hosts. The trap service is a subsystem of the mode 6 control message
protocol which is intended for use by remote event logging programs.
Declare traps set by matching hosts to be low priority. The number
of traps a server can maintain is limited (the current limit is 3).
Traps are usually assigned on a first come, first served basis, with
later trap requestors being denied service. This flag modifies the
assignment algorithm by allowing low priority traps to be overridden
by later requests for normal priority traps.
Ignore NTP packets whose mode is other than 7. In effect, time service is
denied, though queries may still be permitted.
Provide stateless time service to polling hosts, but do not allocate peer
memory resources to these hosts even if they otherwise might be considered
useful as future synchronization partners.
Treat these hosts normally in other respects, but never use them as
These hosts are subject to limitation of number of clients from the
same net. Net in this context refers to the IP notion of net (class A,
class B, class C, etc.). Only the first \*(L"client_limit\*(R" hosts
that have shown up at the server and that have been active during the
last \*(L"client_limit_period\*(R" seconds are accepted. Requests from
other clients from the same net are rejected. Only time request
packets are taken into account. \*(L"Private\*(R", \*(L"control\*(R",
and \*(L"broadcast\*(R" packets are not subject to client limitation
and therefore are not contributing to client count. History of clients
is kept using the monitoring capability of
Thus, monitoring is active as long as there is a restriction entry
with the \*(L"limited\*(R" flag. The default value for
\*(L"client_limit\*(R" is 3. The default value for
\*(L"client_limit_period\*(R" is 3600 seconds. Currently both
variables are not runtime configurable.
This is actually a match algorithm modifier, rather than a restriction
flag. Its presence causes the restriction entry to be matched only if
the source port in the packet is the standard NTP UDP port (123). Both
\*(L"ntpport\*(R" and non\-\*(L"ntpport\*(R" may be specified. The
\*(L"ntpport\*(R" is considered more specific and is sorted later in the
Remove the specified flag(s) from the restrict list entry indicated
Delete the matching entry from the restrict list.
Enable or disable the monitoring facility. Note that a
command is a good way of resetting the packet counts.
Causes the current set of authentication keys to be purged and a
new set to be obtained by rereading the keys file (which must have
configuration file). This allows encryption keys to be changed without
Adds one or more keys to the trusted key list. When authentication
is enabled, peers whose time is to be trusted must be authenticated using
Removes one or more keys from the trusted key list.
Returns information concerning the authentication module, including
known keys and counts of encryptions and decryptions which have been
Sets the precision which the server advertises to the specified value. This
should be a negative integer in the range -4 through -20.
Written by Dennis Ferguson at the University of Toronto.
is a crude hack. Much of the information it shows is deadly boring
and could only be loved by its implementer. The program was designed
so that new (and temporary) features were easy to hack in, at great
expense to the program's ease of use. Despite this, the program
projects / unix-history / blob