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/usr/sbin/ntpdc [-46lpsidnv?!] [-c command] [-D debuglvl] [-< optfile] [-> optfile] [host] [...]
"-4" Force DNS resolution of following host names on the command line to the IPv4 namespace.
"-6" Force DNS resolution of following host names on the command line to the IPv6 namespace.
"-c command" The argument command is interpreted as an interactive 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 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 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.
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 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.
Note that in contexts where a host name is expected, a -4 qualifier preceding the host name forces DNS resolution to the IPv4 namespace, while a -6 qualifier forces DNS resolution to the IPv6 namespace.
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 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 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 from ntpdc to the host(s). This must correspond to a key number which the host/server has been configured to use for this purpose (server options: trustedkey, and requestkey). If authentication is not enabled on the host(s) for ntpdc commands, the command "keyid 0" should be given; otherwise the keyid of the next subsequent addpeer/addserver/broadcast command will be used.
"quit"
"exit" Exit ntpdc.
"debug [ no | more | less ]" With no parameter displays the current ntpdc debug level. The no flag turns off all debugging, while more and less increase and decrease the level respectively.
"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 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.
"version" Display the version of the ntpdc command.
"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 synchronization 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. 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)". If the "hostnames no" command has been given 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 [...]" 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).
"clockstat 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.
"kerninfo" Obtain and print kernel phase-lock loop operating parameters. This information is available if the host supports the ntp_adjtime system call.
"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. 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 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.
"sysstats" Print statistics counters maintained in the protocol module.
"ctlstats" Print statistics counters maintained in the control 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.
"ifstats" List interface statistics for interfaces used by ntpd for network communication.
"ifreload" Force rescan of current system interfaces. Outputs interface statistics for interfaces that could possibly change. Marks unchanged interfaces with ., added interfaces with + and deleted interfaces with -.
"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 in hand.
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 ] " "[ minpoll# | prefer | iburst | burst | minpoll N | maxpoll N [ dynamic ] [...] ]"
"addpeer peer_address [ prefer | iburst | burst | minpoll N" "| maxpoll N | keyid N | version N [...] ]" 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 keyid is nonzero, 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. If ntpdc's key number has not yet been set (e.g., by the keyid command), it will be set to this value. The version# can be 1 through 4 and defaults to 3. The remaining options are either a numeric value for minpoll# or literals prefer, iburst, burst, minpoll N, keyid N, version N, or maxpoll N (where N is a numeric value), and have the action as specified in the peer configuration file command of ntpd. See the server options page at file:///usr/share/doc/ntp/confopt.html for further information. Each flag (or its absence) replaces the previous setting. 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. The dynamic keyword allows association configuration even when no suitable network interface is found at configuration time. The dynamic interface update mechanism may complete the configuration when new interfaces appear (e.g. WLAN/PPP interfaces) at a later time and thus render the association operable.
"addserver peer_address [ keyid ] [ version ] [minpoll#" "| prefer | iburst | burst | minpoll N | maxpoll N [...] ]"
"addserver peer_address [ prefer | iburst | burst | minpoll N" "| maxpoll N | keyid N | version N [...] [ dynamic ] ]" Identical to the addpeer command, except that the operating mode is client.
"addrefclock clock_address [ mode [ prefer | burst | minpoll N" "| maxpoll N ...]]" Identical to the addpeer command, except that the address is a REFCLOCK designator and it configures a hardware refclock instead of a remote server.
"broadcast peer_address [ keyid ] [ version ] [ prefer ]" Identical to the addpeer command, except that the operating mode is broadcast. In this case a valid non-zero 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 [...]" 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 | calibrate | kernel | monitor | ntp | pps | stats]"
"disable [ auth | bclient | calibrate | kernel | monitor | ntp | pps | stats]" These commands operate in the same way as the enable and disable configuration file commands of ntpd. See the <a href="miscopt.html">Miscellaneous Options</a> page for further information.
"restrict address mask flag [ flag ]" This command operates in the same way as the restrict configuration 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.
"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 ntpd configuration file). This allows encryption keys to be changed without restarting the server.
"trustedkey keyid [...]"
"untrustedkey keyid [...]"
"controlkey keyid [...]"
"requestkey keyid [...]" These commands operate in the same way as the corresponding configuration file commands of ntpd.
"keytype md5" This command specifies the default keytype. Since the only type currently support is md5, this is a nop.
"authinfo" 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.
"preset [peer_address [...]]" Clear the statistics counters in various modules of the server with respect to the indicated peers.
NTPDC_<option-name> or NTPDC.aj The environmental presets take precedence (are processed later than) the configuration files. The option-name should be in all capital letters. For example, to set the --command option, you would set the NTPDC_COMMAND environment variable. The users home directory and the current directory are searched for a file named .ntprc.
ntpd(1M), ntpq(1M), ntprc(4), attributes(5)