XNTPDC(8)

NAME
xntpdc - query/control program for the Network Time Protocol daemon

SYNOPSIS
xntpdc [ -ilnps ] [ -c command ] [ host ] [ ... ]

DESCRIPTION
Xntpdc is used to query the xntpd(8) 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 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 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 time out time.

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

-c  The following argument 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 options may be given.

-i  Force xntpdc to operate in interactive mode. Prompts will be written to the standard output and commands read from the standard input.

-l  Obtain a list of peers which are known to the server(s). This switch is equivalent to "-c listpeers".

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

-p  Print a list of the peers known to the server as well as a summary of their state. This is equivalent to "-c peers".

-s  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 -p switch. This is equivalent to "-c dmpeers".

INTERNAL COMMANDS

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 the xntpdc program itself and do not result in NTP mode 7 requests being sent to a server. These are described following.

? [ command_keyword }

A "?" by itself will print a list of all the command keywords known to this incarnation of xntpdc. A "?" followed by a command keyword will print funcation and usage information about the command. This command is probably a better source of information about xntpdc than this manual page.

help [ command_keyword ]

A synonym for the ? command.

timeout millseconds

Specify a time out period for responses to server queries. The default is about 8000 milliseconds.

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. Hostname may be either a host name or a numeric (dotted quad) dmaddress.

keyid #

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.

passwd

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.

hostnames yes|no

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

quit

Exit xntpdc.

QUERY COMMANDS

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.

listpeers

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 candidates.

peers

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 "+" 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 parameter or "REFCLK(<implementation number>, <parameter>)". On "hostnames no" only IP-addresses will be displayed.

dmpeers

A slightly different peer summary list. Identical to the output 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 "." 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 [ addr2 ] [ addr3 ] [ addr4 ]

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 [ addr2 ] [ addr3 ] [ addr4 ]

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

clockinfo clock_peer_address [ addr2 ] [ addr3 ] [ addr4 ]

Obtain and print information concerning a peer clock. The values obtained provide information on the setting of fudge factors and other clock performance information.

kerninfo

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, with "multiline" as the default.

sysinfo

Print a variety of system state variables, i.e. state related to the local server. All except the last four lines are described in the NTP Version 3 specification, RFC 1305. The "system flags" show various system flags, some of which can be set and cleared by the "enable" and "disable" configuration commands, respectively. 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, while the "authdelay" shows the default authentication delay, as set by the "authdelay" configuration command.

sysstats

Print statistics counters maintained in the protocol module.

memstats

Print statistics counters related to memory allocation code.

iostats

Print statistics counters maintained in the input-output module.

timerstats

Print statistics counters maintained in the timer/event queue support code.

reslist

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 [ addr2 ] [ addr3 ] [ addr4 ]

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 in hand.

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 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 ]

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 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 "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 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# ]

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 a multicast address, a multicast-capable kernel is required.

unconfig peer_address [ addr2 ] [ addr3 ] [ addr4 ]

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 auth|bclient|pll|monitor|stats [ ... ]

Provides a way to enable various server options. Flags not mentioned are unaffected. The "auth" flag causes 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 disable (off). The "bclient" flag causes the server to listen for a message from a broadcast or multicast server, following which an association is automatically instantiated for that server. The default for this flag is disable (off). The "pll" flag enables the server to adjust its local clock, with default enable (on). If not set, 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. The "monitor" flag enables the monitoring facility (see elsewhere), with default disable (off). The "stats" flag enables statistics facility filegen (see description elsewhere.), with default enable (on).

disable auth|bclient|pll|monitor|stats [ ... ]

Provides a way to disable various server options. Flags not mentioned are unaffected. The flags presently available are described under the enable command.

restrict address mask flag [ flag ]

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
    Ignore all packets from hosts which match this entry. If this flag is specified neither queries nor time server polls will be responded to.

noquery
    Ignore all NTP mode 7 packets (i.e. information queries and configuration requests) from the source. Time service is not affected.

nomodify
    Ignore all NTP mode 7 packets which attempt to modify the state of the server (i.e. run time reconfiguration). Queries which return information are permitted.

notrap
    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.

lowpriotrap
    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.

noserve
    Ignore NTP packets whose mode is other than 7. In effect, time service is denied, though queries may still be permitted.

nopeer
    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.

notrust
    Treat these hosts normally in other respects, but never use them as synchronization sources.

limited
    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 "client_limit" hosts that have shown up at the server and that have been active during the last "client_limit_period" seconds are accepted. Requests from other clients from the same net are rejected. Only time request packets are taken into account. "Private", "control", and "broadcast" 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 xntpd. Thus, monitoring is active as long as there is a restriction entry with the "limited" flag. The default value for "client_limit" is 3. The default value for "client_limit_period" is 3600 seconds. Currently both variables are not runtime configurable.

ntpport
    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 "ntpport" and non-"ntpport" may be specified. The "ntpport" is considered more specific and is sorted later in the list.

unrestrict address mask flag [ flag ]

Remove the specified flag(s) from the restrict list entry indicated by the address and mask arguments.

delrestrict address mask [ ntpport ]

Delete the matching entry from the restrict list.

monitor yes|no

Enable or disable the monitoring facility. Note that a monitor no command followed by a monitor yes command is a good way of resetting the packet counts.

readkeys

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 [ keyid ] [ keyid ] [ keyid ]

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 a trusted key.

untrustkey keyid [ keyid ] [ keyid ] [ keyid ]

Removes one or more keys from the trusted key list.

authinfo

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

setprecision precision_value

Sets the precision which the server advertises to the specified value. This should be a negative integer in the range -4 through -20.

traps

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.

reset ...

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

SEE ALSO

xntpd(8)

HISTORY

Written by Dennis Ferguson at the University of Toronto.

BUGS

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.