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NTPDC(8)                  BSD System Manager's Manual                 NTPDC(8)

     ntpdc -- special NTP query program

     ntpdc [-ilnps] [-c command] [-host] [-...]

     ntpdc is used to query the ntpd daemon about its current state and to
     request changes in that state. The program may be run either in interac-
     tive mode or controlled using command line arguments. Extensive state and
     statistics information is available through the ntpdc interface. In addi-
     tion, nearly all the configuration options which can be specified at
     start up using ntpd's configuration file may also be specified at run
     time using ntpdc

     If one or more request options is included on the command line when ntpdc
     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, ntpdc will attempt to read com-
     mands from the standard input and execute these on the NTP server running
     on the first host given on the command line, again defaulting to local-
     host when no other host is specified.  ntpdc will prompt for commands if
     the standard input is a terminal device.

     ntpdc 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 net-
     work topology.  ntpdc 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 ntpdc are specific to the particular implementation of
     the ntpd daemon and can be expected to work only with this and maybe some
     previous versions of the daemon. Requests from a remote ntpdc 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 -i or -n will cause the spec-
     ified query (queries) to be sent to the indicated host(s) immediately.
     Otherwise, ntpdc will attempt to read interactive format commands from
     the standard input.

     -c command
             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 ntpdc to operate in interactive mode. Prompts will be writ-
             ten to the standard output and commands read from the standard

     -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 sum-
             mary of their state. This is equivalent to -c -peers

     -s      Print a list of the peers known to the server as well as a sum-
             mary of their state, but in a slightly different format than the
             -p switch. This is equivalent to -c -dmpeers

     Interactive format commands consist of a keyword followed by zero to four
     arguments. Only enough characters of the full keyword to uniquely iden-
     tify 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
     ntpdc 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]
             A ? by itself will print a list of all the command keywords known
             to this incarnation of ntpq.  A ? followed by a command keyword
             will print function and usage information about the command. This
             command is probably a better source of information about ntpq
             than this manual page.

     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. Actually the
             server does not now require timestamps in authenticated requests,
             so this command may be obsolete.

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

     hostnames [yes | no]
             If yes is specified, host names are printed in information dis-
             plays.  If no is specified, numeric addresses are printed
             instead. The default is yes, unless modified using the command
             line -n switch.

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

     quit    Exit ntpdc

     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

     timeout milliseconds
             Specify a timeout period for responses to server queries. The
             default is about 8000 milliseconds. Note that since ntpdc 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. 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 synchro-
             nization 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 ( 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
             synchronizing 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.

             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 . indi-
             cates 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 [...]
             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

     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 spe-
             cially modified for a precision timekeeping function.

     loopinfo [oneline | multiline]
             Print the values of selected loop filter variables. The loop fil-
             ter is the part of NTP which deals with adjusting the local sys-
             tem 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.

             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. These are the auth, bclient, monitor, pll, pps and
             stats flags.  See the ntpd documentation for the meaning of these
             flags. There are two additional flags which are read only, the
             kernel_pll and kernel_pps the precision time kernel modifications
             are in use. The kernel_pll indicates that the local clock is
             being disciplined by the kernel, while the kernel_pps indicates
             the kernel discipline is provided by the PPS signal.  The
             stability is the residual frequency error remaining after the
             system frequency correction is applied and is intended for main-
             tenance 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 configura-
             tion 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

     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 informa-
     tion is provided only by some clock drivers and is mostly undecodable
     without a copy of the driver source in hand.

     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 corre-
     sponding 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 dif-
     ficult.  Second, it makes it more difficult to request configuration
     changes to your server from topologically remote hosts. While the recon-
     figuration 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 secu-

     The following commands all make authenticated requests.

     addpeer peer_address [keyid] [version] [prefer]
             Add a configured peer association at the given address and oper-
             ating 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 synchroni-
             sation 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 a multicast address, a multicast-capable kernel is

     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 associ-
             ation 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 ntpd.  Following is a description
             of the flags. Note that only the auth, bclient, monitor pll, pps
             and stats flags can be set by ntpdc ; the pll_kernel and
             pps_kernel flags are read-only.

             auth    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 broad-
                     cast or multicast server, as in the multicastclient com-
                     mand with default address.  The default for this flag is

                     Enables the monitoring facility. See the ntpdc program
                     and the monlist command or further information. The
                     default for this flag is enable.

             pll     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 syn-
                     chronization to other clients.  In this case, the local
                     clock driver is used. See the Reference Clock Drivers
                     page in /usr/share/doc/html/ntp/refclock.htm for further
                     information. The default for this flag is enable.

             pps     Enables the pulse-per-second (PPS) signal when frequency
                     and time is disciplined by the precision time kernel mod-
                     ifications. See the A Kernel Model for Precision
                     Timekeeping page in /usr/share/doc/html/ntp/kern.htm for
                     further information.  The default for this flag is dis-

             stats   Enables the statistics facility. See the Monitoring
                     Options page in /usr/share/doc/html/ntp/monopt.htm for
                     further information. The default for this flag is enable.

                     When the precision time kernel modifications are
                     installed, this indicates the kernel controls the clock
                     discipline; otherwise, the daemon controls the clock dis-

                     When the precision time kernel modifications are
                     installed and a pulse-per-second (PPS) signal is avail-
                     able, this indicates the PPS signal controls the clock
                     discipline; otherwise, the daemon or kernel controls the
                     clock discipline, as indicated by the pll_kernel flag.

     restrict address mask flag [flag]
             This command operates in the same way as the restrict configura-
             tion file commands of ntpd

     unrestrict address mask flag [flag]
             Unrestrict the matching entry from the restrict list.

     delrestrict address mask [ntpport]
             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 ntpd 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 ntpd

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

     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.

     David L. Mills (millsATudel.edu)

     ntpdc 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

BSD                             March 29, 2000                             BSD