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xntpdc- special NTP query program
xntpdc [ -ilnps ] [ -c command ] [ host ] [ ...
xntpdc is used to query the
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
available through the
xntpdc interface. In addition, nearly
all the configuration options which can be specified at start up using
xntpd's configuration file may also be specified at run time using
If one or more request options is included on the command line when
xntpdc 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 localhost by default. If no request options are given,
xntpdc 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 defaulting to localhost when no other
host is specified.
xntpdc will prompt for commands if the
standard input is a terminal device.
xntpdc 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 topology.
xntpdc makes no
attempt to retransmit requests, and will time requests out if the remote
host is not heard from within a suitable timeout time.
The operation of
xntpdc are specific to the particular
implementation of the
xntpd daemon and can be expected to
work only with this and maybe some previous versions of the daemon.
Requests from a remote
xntpdc program which affect the
state of the local server must be authenticated, which requires both the
remote program and local server share a common key and key identifier.
Specifying a command line option other than
-n will cause the specified query (queries) to be sent to
the indicated host(s) immediately. Otherwise,
attempt to read interactive format commands from the standard input.
xntpdcto operate in interactive mode. Prompts will be written to the standard output and commands read from the standard input.
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
followed by a file name, to the command line.
A number of interactive format commands are executed entirely within
xntpdc program itself and do not result in NTP mode 7
requests being sent to a server. These are described following.
? [ command_keyword ]
helpl [ command_keyword ]
?by itself will print a list of all the command keywords known to this incarnation of
?followed by a command keyword will print funcation and usage information about the command. This command is probably a better source of information about
ntpqthan this manual page.
hostnames [ yes | no ]
yesis specified, host names are printed in information displays. If
nois specified, numeric addresses are printed instead. The default is
yes, unless modified using the command line
xntpdcretries each query once after a timeout, the total waiting time for a timeout will be twice the timeout value set.
Query commands result in NTP mode 7 packets containing requests for information being sent to the server. These are read-only commands in that they make no modification of the server configuration state.
+denotes symmetric active, a
-indicates symmetric passive, a
=means the remote server is being polled in client mode, a
^indicates that the server is broadcasting to this address, a
~denotes that the remote peer is sending broadcasts and a
*marks the peer the server is currently synchonizing to.
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
hostnames no only IP-addresses
will be displayed.
peerscommand, 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
.indicates that this peer was cast off in the falseticker detection, while a
+indicates that the peer made it through. A
*denotes the peer the server is currently synchronizing with.
showpeer peer_address [...]
pstats peer_address [...]
clockinfo clock_peer_address [...]
loopinfo [ oneline | multiline ]
offsetis the last offset given to the loop filter by the packet processing code. The
frequencyis the frequency error of the local clock in parts-per-million (ppm). The
time_constcontrols the stiffness of the phase-lock loop and thus the speed at which it can adapt to oscillator drift. The
watchdog timervalue is the number of seconds which have elapsed since the last sample offset was given to the loop filter. The
multilineoptions specify the format in which this information is to be printed, with
multilineas the default.
system flagsshow various system flags, some of which can be set and cleared by the
disableconfiguration commands, respectively. These are the
statsflags. See the
xntpddocumentation for the meaning of these flags. There are two additional flags which are read only, the
kernel_pps. These flags indicate the synchronization status when the precision time kernel modifications are in use. The
kernel_pllindicates that the local clock is being disciplined by the kernel, while the kernel_pps indicates the kernel discipline is provided by the PPS signal.
stabilityis the residual frequency error remaining after the system frequency correction is applied and is intended for maintenance and debugging. In most architectures, this value will initially decrease from as high as 500 ppm to a nominal value in the range .01 to 0.1 ppm. If it remains high for some time after starting the daemon, something may be wrong with the local clock, or the value of the kernel variable
tickmay be incorrect.
broadcastdelayshows the default broadcast delay, as set by the
authdelayshows the default authentication delay, as set by the
monlist [ version ]
clkbug clock_peer_address [...]
All requests which cause state changes in the server are authenticated by the server using a configured NTP key (the facility can also be disabled by the server by not configuring a key). The key number and the corresponding key must also be made known to xtnpdc. This can be done using the keyid and passwd 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 security.
The following commands all make authenticated requests.
addpeer peer_address [ keyid ] [ version ] [ prefer ]
keyidis 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
version#can be 1, 2 or 3 and defaults to 3. The
preferkeyword 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 PPS signal.
addserver peer_address [ keyid ] [ version ] [ prefer ]
broadcast peer_address [ keyid ] [ version ] [ prefer ]
peer_addressparameter can be the broadcast address of the local network or a multicast group address assigned to NTP. If a multicast address, a multicast-capable kernel is required.
unconfig peer_address [...]
fudge peer_address [ time1 ] [ time2 ] [ stratum ] [ refid ]
enable [ flag ] [ ... ]
disable [ flag ] [ ... ]
disableconfiguration file commands of
xntpd. Following is a description of the flags. Note that only the
statsflags can be set by
pps_kernelflags are read-only.
multicastclientcommand with default address. The default for this flag is disable.
xntpdcprogram and the
monlistcommand or further information. The default for this flag is enable.
restrict address mask flag [ flag ]
restrictconfiguration file commands of
unrestrict address mask flag [ flag ]
delrestrict address mask [ ntpport ]
xntpdconfiguration file). This allows encryption keys to be changed without restarting the server.
trustkey keyid [...]
untrustkey keyid [...]
untrustkeyconfiguration file commands of
addtrap [ address [ port ] [ interface ]
clrtrap [ address [ port ] [ interface]
xntpdc 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
is occasionally useful.