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HP-UX 11i Version 3: February 2007

Technical documentation

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xntpdc — special NTP query program


xntpdc [ -dilnps ] [ -c command ] [ host ] [ ... ]


xntpdc is used to query the xntpd daemon about its current state and to request changes in that state. The program may be run either in interactive mode or controlled mode 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 xntpdc. 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 compatible 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 timeout requests if the remote host is not heard from within a suitable timeout time.

The operation of xntpdc is 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 to share a common key and key identifier.


Specifying a command line option other than -i or -n will cause the specified query (or queries) to be sent to the indicated host(s) immediately. Otherwise, xntpdc will attempt to read interactive format commands from the standard input.

-c command

The following command is interpreted as an interactive format command and is added to the list of commands to be executed on the specified host(s). Multiple -c commands may be given.


Debugging information is printed.


Force xntpdc 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 option is equivalent to -c listpeers command. See "CONTROL MESSAGE COMMANDS" below.


Output all host addresses in dotted-quad numeric format (xxx.xxx.xxx.xxx) rather than converting to the canonical host names.


Print a list of peers known to the server as well as a summary of their state. This is equivalent to -c peers command. See "CONTROL MESSAGE COMMANDS" below.


Print a list of peers known to the server as well as a summary of their state, but in a slightly different format than the -p command. This is equivalent to -c dmpeers command. See "CONTROL MESSAGE COMMANDS" below.


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. The output of individual commands may be redirected or 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 the xntpdc program itself and do not result in NTP mode 7 requests being sent to a server. These commands are described as follows:

? [command_keyword]

help [command_keyword]

A ? or help by itself will print a list of all the command keywords. ntpq. A ? or help followed by a command keyword (command_keyword) will print function and usage information about the command.

delay 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.

host hostname

Set the host to which future queries will be sent. The hostname may be either a host name or a numeric address.

hostnames [yes|no]

If yes is specified, host names are printed in information displays. If no is specified, numeric addresses are printed instead. The default is yes, unless modified using the command line -n command.

keyid keyid

This command allows the specification of a key number to be used to authenticate configuration requests. The keyid must correspond to a key number that the server has been configured to use for this purpose.


Exit xntpdc.


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.

timeout milliseconds

Specify a timeout period for responses to server queries. The default is about 8000 milliseconds. Note that since xntpdc retries 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.


Obtains and prints a brief list of the peers for which the server is maintaining state. This list 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 synchronization candidates.


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 ( 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.


indicates symmetric active


indicates symmetric passive


indicates the remote server is being polled in client mode


indicates the server is broadcasting to this address


indicates the remote peer is sending broadcasts


indicates the peer that the server is currently synchronizing to.

The contents of the host field may be a host name, an IP address, a reference clock implementation name with its parameter or REFCLK (implementation number, parameter). For hostnames no, only IP addresses will be displayed.


A slightly different peer summary list. The output is similar to that of the peers 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 period (.) indicates that this peer was cast off in the falseticker detection. A plus (+) indicates that the peer made it through. An asterisk (*) denotes the peer that the server is currently synchronizing with.

showpeer peer_address [ ... ]

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 specification.

pstats peer_address [ ... ]

Show per-peer statistic counters associated with the specified peer(s).

clockinfo clock_peer_address [ ... ]

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 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.

loopinfo [oneline|multiline]

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 offset is the last offset given to the loop filter by the packet processing code. The frequency is the frequency error of the local clock in parts-per-million (ppm). The time_const controls the stiffness of the phase-lock loop and thus the speed at which it can adapt to oscillator drift. The watchdog timer value is the number of seconds which have elapsed since the last sample offset was given to the loop filter. The oneline and multiline options specify the format in which this information is to be printed. multiline is the default.


Print a variety of system state variables, i.e., the state related to the local server.

The system flags show various system flags, some of which can be set and cleared by the enable and disable configuration commands, respectively. The configurable flags are the auth, bclient, monitor, pll, pps and stats flags. Refer to xntpd(1M) for the description of these flags.

The stability is 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 tick may be incorrect.

The broadcastdelay shows the default broadcast delay, as set by the broadcastdelay configuration command.

The authdelay shows the default authentication delay, as set by the authdelay configuration command.


Print statistics counters maintained in the protocol module.


Print statistics counters related to memory allocation code.


Print statistics counters maintained in the input-output module.


Print statistics 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 are applied.

monlist [version]

Obtain and print traffic counts collected and maintained by the monitor facility. The version number should not normally need to be specified.

clkbug clock_peer_address[...]

Obtain debugging information for a reference clock driver. This information is provided only by some clock drivers and is mostly undecodable without a copy of the driver source.


All requests which cause state changes in the server are authenticated by the server using a configured NTP key. This facility is disabled if the NTP key is not configured. 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 against 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]

Add a configured peer association at the given address and operating in symmetric active mode. 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. If the optional keyid is a nonzero integer, all outgoing packets to the remote server will have an authentication field (encrypted) attached 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 prefer keyword indicates a preferred peer (and thus will be used primarily for clock synchronization if possible). The preferred peer also determines the validity of the PPS signal - if the preferred peer is suitable for synchronization so is the PPS signal.

addserver peer_address [keyid][version][prefer]

Identical to the addpeer command, except that the operating mode is client.

broadcast peer_address [keyid][version][prefer]

Identical to the addpeer command, except that the operating mode is broadcast. In this case a valid key identifier and key are required. The peer_address parameter can be the broadcast address of the local network or a multicast group address assigned to NTP. If using a multicast address, a multicast-capable kernel is required.

unconfig peer_address [...]

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 this fashion.

fudge peer_address [time1][time2][stratum][refid]

This command provides a way to set certain data for a reference clock. See the source listing for further information.

enable [flag][...]

disable [flag][...]

These commands operate in the same way as the enable and disable configuration file commands of xntpd. Described below are the flags supported.


Enables the server to synchronize with unconfigured peers only if the peer has been correctly authenticated using a trusted key and key identifier. The default for this flag is enable.


Enables the server to listen for a message from a broadcast or multicast server, as in the multicastclient command with default address. The default for this flag is disable.


Enables the monitoring facility. See the xntpdc program and the monolist command for more information. The default for this flag is enable.


Enables the server to adjust its local clock by means of NTP. If disabled, the local clock free-runs at its intrinsic time and frequency offset. This flag is useful in case the local clock is controlled by some other device or protocol and NTP is used only to provide synchronization to other clients. In this case, the local clock driver is used. The default for this flag is enable.


Enables the pulse-per-second (PPS) signal when frequency and time is disciplined by the precision time kernel modifications. The default for this flag is disable.


Enables the statistics facility. The default for this flag is enable.

restrict address mask flag [flag]

This command operates in the same way as the restrict configuration file commands of xntpd.

unrestrict address mask flag [flag]

Unrestrict the matching entry from the restrict list.

delrestrict address mask [nttport]

Delete the matching entry from the restrict list.


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 been specified in the xntpd configuration file). This allows encryption keys to be changed without restarting the server.

trustkey [keyid][...]

untrustkey [keyid][...]

These commands operate in the same way as the trustedkey and untrustkey configuration file commands of xntpd.


Returns information concerning the authentication module, including known keys and counts of encryptions and decryptions which have been done.


Display the traps set in the server. See the source listing for further information.

addtrap [address][port][interface]

Set a trap for asynchronous messages. See the source listing for further information.

clrtrap [address][port][interface]

Clear a trap for asynchronous messages. See the source listing for further information.


Clear the statistics counters in various modules of the server. See the source listing for further information.


xntpdc was developed by David L. Mills.

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