xntpdc - Monitor and control program for the Network Time Protocol daemon
/usr/bin/xntpdc [-ilnps] [-c command] [host1 host2 ...]
Forces xntpdc to operate in interactive mode. Prompts will be written to the standard output and commands read from the standard input. Obtains a list of peers which are known to the server(s). This switch is equivalent to -c listpeers. Outputs all host addresses in dotted decimal notation rather than converting to the canonical host names. Prints a list of the peers known to the server as well as a summary of their state. This is equivalent to -c peers. Prints 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 option. This is equivalent to -c dmpeers. Interprets command as an interactive format command and adds it to the list of commands to be executed on the specified host(s). Multiple -c options may be given.
Specifying a command line option other than -i or -n sends the specified query (queries) to the indicated host(s) immediately; if no host is specified, localhost is the default. Otherwise, xntpdc attempts to read interactive format commands from the standard input.
The xntpdc program enables system managers to monitor and control the xntpd(8) daemon, and to make runtime configuration changes to xntpd running either locally or remotely. 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.
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 attempts 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. The xntpdc program prompts for commands if the standard input is a terminal device.
The xntpdc program uses NTP mode 7 packets to communicate with the NTP server, and can be used to query any compatible server on the network that permits it. Note: Since NTP uses the UDP protocol, this communication will be somewhat unreliable, especially over large network topologies. The xntpdc program makes no attempt to retransmit requests, and will time out if the remote host is not heard from within a suitable time.
Interactive format commands consist of a keyword followed by zero or more 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 commands are as follows:
A ? (question mark) by itself prints a list of all the command keywords known to this version of xntpdc. A ? followed by a command keyword prints function and usage information about the command. Specifies a time interval to be added to timestamps included in requests that require authentication. This is used to enable (unreliable) server reconfiguration over long delay network paths or between machines whose clocks are unsynchronized. A synonym for the ? command. Sets the host to which future queries will be sent. The hostname parameter may be either a host name or a numeric (dotted quad)address. If hostname is not specified, the current hostname is used. If yes is specified, prints host names in information displays. If no is given, prints numeric addresses instead. The default is yes unless modified using the command line -n option. 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. Prompts you to type in a password (which will not be echoed) that is 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. Exits xntpdc. Specifies a time out period for responses to server queries. The default is about 8000 milliseconds.
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 the state of the authentication code. Obtains debugging information for a clock peer. This information is provided only by some clock drivers, and is mostly unreadable without a copy of the driver source in hand. Obtains and prints clock status information. Obtains and prints packet count statistics from the control module. Sets or changes the debugging level. 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. The following characters are used: Indicates that this peer was cast off in the falseticker detection. Indicates that the peer made it through. Denotes the peer to which the server is currently synchronizing. Prints counters maintained in the input-output module. Obtains and prints kernel phase-lock loop operating parameters. This information is available only if the kernel has been specially modified for a precision timekeeping function. Obtains and prints current leap second 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 synchronization candidates. Prints 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, or drift, of your system's 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 that have elapsed since a new 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. Prints a number of counters related to the peer memory allocation code. Obtains and prints traffic counts collected and maintained by the monitor facility. The version number should not normally need to be specified. 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 current mode for this peer entry. The following characters are used: Denotes symmetric active. Indicates symmetric passive. Indicates the remote server is being polled in client mode. Indicates that the server is broadcasting to this address. Denotes that the remote peer is sending broadcasts. Marks the peer the server is currently synchronizing to.
All requests that 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 time stamp in the packet data, which is included in the computation of the authentication code. This time stamp 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: Adds a configured, symmetric active peer association with a peer at the given address. If the optional keyid is a nonzero integer, all outgoing packets to the remote server have an authentication field attached that is encrypted with this key. If the value is 0 (or not given), no authentication is done. The version# can be 1, 2, or 3; the default is 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. Adds a new server at address. 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. If minpoll is specified, the polling interval for the association will remain clamped at the minimum. Identical to the addpeer command except that operating mode is client. Sets a trap for asynchronous messages. Returns information concerning the authentication module, including known keys and counts of encryptions and decryptions which have been done. Identical to the addpeer command except that packets are instead sent in broadcast mode. 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. Clears a trap for asynchronous messages. Changes the authorization key identifier that the server uses to authenticate control messages to keyid. Deletes the matching entry from the restrict list. Provides a way to disable various server options. Flags not mentioned are unaffected. The flags presently available are described under the enable command. Provides a way to enable the following server options. Flags not mentioned are unaffected. 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). 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). 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. Enables the monitoring facility (see elsewhere), with default disable (off). Enables statistics facility filegen (see the filegen description), with default enable (on). This command provides a way to set certain data for a reference clock. Set the key type to use for authenticated requests. Enables or disables the monitoring facility. A monitor no command followed by a monitor yes command is a good way of resetting the packet counts. Resets the statistics counters associated with peers at the designated addresses. 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. Clears the statistics counters in various modules of the server. 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 as follows: Ignores all packets from hosts that match this entry. If this flag is specified neither queries nor time server polls will be responded to. Ignores all NTP mode 7 packets (information queries and configuration requests) from the source. Time service is not affected. Ignores all NTP mode 7 packets that attempt to modify the state of the server (run time reconfiguration). Queries that return information are permitted. Declines 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. Declares 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. Ignores NTP packets whose mode is other than 7. In effect, time service is denied, though queries may still be permitted. Provides 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. Treats these hosts normally in other respects, but never use them as synchronization sources. 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. 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. Sets the precision which the server advertises to the specified value. This should be a negative integer in the range -4 through -20. Displays the traps set in the server. 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. This command causes the configured bit to be removed from the specified peer(s). In many cases this causes 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. Removes the specified flag(s) from the restrict list entry indicated by the address and mask arguments. Removes one or more keys from the trusted key list.
The hostname is not in the local /etc/hosts file. Check that xntpd is running on the remote host being queried.
Commands: ntpdate(8), ntpq(8), ntpsetup(8), xntpd(8) delim off