ntpdc(1)                                                              ntpdc(1)


       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  inter-
       active mode or controlled using command line arguments. Extensive state
       and statistics information is available through the  ntpdc   interface.
       In  addition,  nearly all the configuration options which can be speci-
       fied at startup using ntpd’s configuration file may also  be  specified
       at run time using ntpdc .

       If  one  or  more request options are 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 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.  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 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.  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
       specified query (queries) to be sent to the indicated  host(s)  immedi-
       ately.  Otherwise,  ntpdc  will attempt to read interactive format com-
       mands 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 exe-
               cuted on the specified host(s).  Multiple  -c  options  may  be

       -i      Force  ntpdc   to  operate in interactive mode. Prompts will be
               written to the standard output and commands read from the stan-
               dard 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 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
       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 ntpdc  program itself and do not result  in  NTP  mode  7  requests
       being sent to a server. These are described following.

       ? [     command_keyword  ]

               help  [  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 funcation and usage
               information about the command. This command is probably a  bet-
               ter 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  unsynchro-
               nized.  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
               displays. 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 cor-
               respond to a key number the server has been configured  to  use
               for this purpose.

       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 successful.

       timeout millseconds  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  config-
               ured  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 ( 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  sec-
               onds,  the  reachability  register,  in  octal, and the current
               estimated delay, offset and dispersion of the peer, all in sec-
               onds.  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  dis-

       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 .  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.

               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 associ-
               ated with the specified peer(s).

               clock_peer_address  [...]  Obtain and  print  information  con-
               cerning  a  peer clock. The values obtained provide information
               on the setting of fudge factors  and  other  clock  performance

               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
               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 fre-
               quency 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 fil-
               ter. The oneline  and multiline  options specify the format  in
               which this information is to be printed, with multiline  as the

       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  com-
               mands,  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  .  These  flags
               indicate  the  synchronization  status  when 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
               afterthe 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 nom-
               inal  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.

       iostats Print statistics counters maintained in the  input-output  mod-

               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  main-
               tained  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 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 dis-
       abled  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 con-
       figuration 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  ade-
       quate level of security.

       The following commands all make authenticated requests.

       addpeer peer_address  [ keyid  ] [ version  ] [ prefer  ] Add a config-
               ured 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 authentica-
               tion 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  indi-
               cates  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.

               peer_address  [ keyid  ] [ version  ] [ prefer  ] Identical  to
               the  addpeer command, except that the operating mode is client.

               peer_address  [ keyid  ] [ version  ] [ prefer  ] Identical  to
               the  addpeer  command, except that the operating mode is broad-
               cast. 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.

               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
               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

       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.

       bclient 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.

       monitor 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 synchronization to other clients. In  this
               case,  the  local clock driver is used. See the Reference Clock
               Drivers page 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 modifications.
               See  the  A Kernel Model for Precision Timekeepingpage for fur-
               ther information. The default for this flag is disable.

       stats   Enables the statistics facility.  See  the  Monitoring  Options
               page  for  further  information.  The  default for this flag is

               When the precision time  kernel  modifications  are  installed,
               this indicates the kernel controls the clock discipline; other-
               wise, the daemon controls the clock discipline.

               When the precision time kernel modifications are installed  and
               a  pulse-per-second  (PPS)  signal is available, 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.

               address mask flag  [ flag  ] This command operates in the  same
               way as the restrict configuration file commands of ntpd .

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

               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

               keyid  [...]

               keyid   [...]   These  commands  operate in the same way as the
               trustedkey  and untrustedkey  configuration  file  commands  of
               ntpd .

               Returns   information  concerning  the  authentication  module,
               including 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.


       ntpdc  is a crude hack. Much of the information it shows is deadly bor-
       ing 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.


       Primary source of documentation: /usr/share/doc/ntp-*/ntpdc.html


       David L. Mills <mills@udel.edu>

ntp 4.1.1b-r5                                                         ntpdc(1)

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