ntpdc: NTPD Control User's Manual


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ntpdc: NTPD Control User Manual

This document describes the use of the NTP Project's ntpdc program, that can be used to query a Network Time Protocol (NTP) server and display the time offset of the system clock relative to the server clock. Run as root, it can correct the system clock to this offset as well. It can be run as an interactive command or from a cron job.

This document applies to version 4.2.7p303 of ntpdc.

The program implements the SNTP protocol as defined by RFC 5905, the NTPv4 IETF specification.

Short Contents



Description

By default, ntpdc writes the local data and time (i.e., not UTC) to the standard output in the format:

     1996-10-15 20:17:25.123 (+0800) +4.567 +/- 0.089 secs

where YYYY-MM-DD HH:MM:SS.SUBSEC is the local date and time, (+0800) is the local timezone adjustment (so we would add 8 hours and 0 minutes to convert the reported local time to UTC), and the +4.567 +/- 0.089 secs indicates the time offset and error bound of the system clock relative to the server clock.



Invoking ntpdc

ntpdc is a utility program used to query ntpd(8) about its current state and to request changes in that state. It uses NTP mode 7 control message formats described in the source code. The program may be run either in interactive 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 specified at startup using ntpd's configuration file may also be specified at run time using ntpdc.

This section was generated by AutoGen, using the agtexi-cmd template and the option descriptions for the ntpdc program. This software is released under the NTP license, <http://ntp.org/license>.


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ntpdc help/usage (--help)

This is the automatically generated usage text for ntpdc.

The text printed is the same whether selected with the help option (--help) or the more-help option (--more-help). more-help will print the usage text by passing it through a pager program. more-help is disabled on platforms without a working fork(2) function. The PAGER environment variable is used to select the program, defaulting to more. Both will exit with a status code of 0.

ntpdc - vendor-specific NTPD control program - Ver. 4.2.7p303
USAGE:  ntpdc [ -<flag> [<val>] | --<name>[{=| }<val>] ]... [ host ...]
  Flg Arg Option-Name    Description
   -4 no  ipv4           Force IPv4 DNS name resolution
                                - prohibits these options:
                                ipv6
   -6 no  ipv6           Force IPv6 DNS name resolution
                                - prohibits these options:
                                ipv4
   -c Str command        run a command and exit
                                - may appear multiple times
   -d no  debug-level    Increase debug verbosity level
                                - may appear multiple times
   -D Str set-debug-level Set the debug verbosity level
                                - may appear multiple times
   -i no  interactive    Force ntpq to operate in interactive mode
                                - prohibits these options:
                                command
                                listpeers
                                peers
                                showpeers
   -l no  listpeers      Print a list of the peers
                                - prohibits these options:
                                command
   -n no  numeric        numeric host addresses
   -p no  peers          Print a list of the peers
                                - prohibits these options:
                                command
   -s no  showpeers      Show a list of the peers
                                - prohibits these options:
                                command
      opt version        Output version information and exit
   -? no  help           Display extended usage information and exit
   -! no  more-help      Extended usage information passed thru pager
   -> opt save-opts      Save the option state to a config file
   -< Str load-opts      Load options from a config file
                                - disabled as --no-load-opts
                                - may appear multiple times

Options are specified by doubled hyphens and their name or by a single
hyphen and the flag character.



The following option preset mechanisms are supported:
 - reading file $HOME/.ntprc
 - reading file ./.ntprc
 - examining environment variables named NTPDC_*

please send bug reports to:  http://bugs.ntp.org, bugs@ntp.org


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ipv4 option (-4)

This is the “force ipv4 dns name resolution” option.

This option has some usage constraints. It:

Force DNS resolution of following host names on the command line to the IPv4 namespace.


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ipv6 option (-6)

This is the “force ipv6 dns name resolution” option.

This option has some usage constraints. It:

Force DNS resolution of following host names on the command line to the IPv6 namespace.


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command option (-c)

This is the “run a command and exit” option. This option takes an argument string cmd.

This option has some usage constraints. It:

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).


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interactive option (-i)

This is the “force ntpq to operate in interactive mode” option.

This option has some usage constraints. It:

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


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listpeers option (-l)

This is the “print a list of the peers” option.

This option has some usage constraints. It:

Print a list of the peers known to the server as well as a summary of their state. This is equivalent to the 'listpeers' interactive command.


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numeric option (-n)

This is the “numeric host addresses” option. Output all host addresses in dotted-quad numeric format rather than converting to the canonical host names.


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peers option (-p)

This is the “print a list of the peers” option.

This option has some usage constraints. It:

Print a list of the peers known to the server as well as a summary of their state. This is equivalent to the 'peers' interactive command.


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showpeers option (-s)

This is the “show a list of the peers” option.

This option has some usage constraints. It:

Print a list of the peers known to the server as well as a summary of their state. This is equivalent to the 'dmpeers' interactive command.


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presetting/configuring ntpdc

Any option that is not marked as not presettable may be preset by loading values from configuration ("rc" or "ini") files, and values from environment variables named NTPDC and NTPDC_<OPTION_NAME>. <OPTION_NAME> must be one of the options listed above in upper case and segmented with underscores. The NTPDC variable will be tokenized and parsed like the command line. The remaining variables are tested for existence and their values are treated like option arguments.

libopts will search in 2 places for configuration files:

The environment variables HOME, and PWD are expanded and replaced when ntpdc runs. For any of these that are plain files, they are simply processed. For any that are directories, then a file named .ntprc is searched for within that directory and processed.

Configuration files may be in a wide variety of formats. The basic format is an option name followed by a value (argument) on the same line. Values may be separated from the option name with a colon, equal sign or simply white space. Values may be continued across multiple lines by escaping the newline with a backslash.

Multiple programs may also share the same initialization file. Common options are collected at the top, followed by program specific segments. The segments are separated by lines like:

    [NTPDC]

or by

    <?program ntpdc>

Do not mix these styles within one configuration file.

Compound values and carefully constructed string values may also be specified using XML syntax:

    <option-name>
       <sub-opt>...&lt;...&gt;...</sub-opt>
    </option-name>

yielding an option-name.sub-opt string value of

    "...<...>..."

AutoOpts does not track suboptions. You simply note that it is a hierarchicly valued option. AutoOpts does provide a means for searching the associated name/value pair list (see: optionFindValue).

The command line options relating to configuration and/or usage help are:

version (-)

Print the program version to standard out, optionally with licensing information, then exit 0. The optional argument specifies how much licensing detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. Only the first letter of the argument is examined:

version
Only print the version. This is the default.
copyright
Name the copyright usage licensing terms.
verbose
Print the full copyright usage licensing terms.


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ntpdc exit status

One of the following exit values will be returned:

0 (EXIT_SUCCESS)
Successful program execution.
1 (EXIT_FAILURE)
The operation failed or the command syntax was not valid.
66 (EX_NOINPUT)
A specified configuration file could not be loaded.
70 (EX_SOFTWARE)
libopts had an internal operational error. Please report it to autogen-users@lists.sourceforge.net. Thank you.


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ntpdc Usage

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. The ntpdc utility will prompt for commands if the standard input is a terminal device.

The ntpdc utility 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. The ntpdc utility 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(8) daemon and can be expected to work only with this and maybe some previous versions of the daemon. Requests from a remote ntpdc utility 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. 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, ntpdc will attempt to read interactive format commands from the standard input. .Ss "Interactive 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 .Ql \&> , followed by a file name, to the command line.

A number of interactive format commands are executed entirely within the ntpdc utility itself and do not result in NTP mode 7 requests being sent to a server. These are described following.

Ic
Ic
A .Sq Ic \&? will print a list of all the command keywords known to this incarnation of ntpdc. A .Sq Ic \&? 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(8) than this manual page.
Ic
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.
Ic
Set the host to which future queries will be sent. Hostname may be either a host name or a numeric address.
Ic
If .Cm yes is specified, host names are printed in information displays. If .Cm no is specified, numeric addresses are printed instead. The default is .Cm yes , unless modified using the command line -n switch.
Ic
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 purpose.
Ic
Exit ntpdc.
Ic
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.
Ic
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.

.Ss "Control Message 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.

Ic
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.
Ic
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 .Ql \&+ denotes symmetric active, a .Ql \&- indicates symmetric passive, a .Ql \&= means the remote server is being polled in client mode, a .Ql \&^ indicates that the server is broadcasting to this address, a .Ql \&~ denotes that the remote peer is sending broadcasts and a .Ql \&~ denotes that the remote peer is sending broadcasts and a .Ql \&* 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 .Fn REFCLK "implementation_number" "parameter" . On .Ic hostnames .Cm no only IP-addresses will be displayed.

Ic
A slightly different peer summary list. Identical to the output of the .Ic 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 .Ql \&. indicates that this peer was cast off in the falseticker detection, while a .Ql \&+ indicates that the peer made it through. A .Ql \&* denotes the peer the server is currently synchronizing with.
Ic
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.
Ic
Show per-peer statistic counters associated with the specified peer(s).
Ic
Obtain and print information concerning a peer clock. The values obtained provide information on the setting of fudge factors and other clock performance information.
Ic
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.
Ic
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 .Sq offset is the last offset given to the loop filter by the packet processing code. The .Sq frequency is the frequency error of the local clock in parts-per-million (ppm). The .Sq time_const controls the stiffness of the phase-lock loop and thus the speed at which it can adapt to oscillator drift. The .Sq watchdog timer value is the number of seconds which have elapsed since the last sample offset was given to the loop filter. The .Cm oneline and .Cm multiline options specify the format in which this information is to be printed, with .Cm multiline as the default.
Ic
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 .Sq system flags show various system flags, some of which can be set and cleared by the .Ic enable and .Ic disable configuration commands, respectively. These are the .Cm auth , .Cm bclient , .Cm monitor , .Cm pll , .Cm pps and .Cm stats flags. See the ntpd(8) documentation for the meaning of these flags. There are two additional flags which are read only, the .Cm kernel_pll and .Cm kernel_pps . These flags indicate the synchronization status when the precision time kernel modifications are in use. The .Sq kernel_pll indicates that the local clock is being disciplined by the kernel, while the .Sq kernel_pps indicates the kernel discipline is provided by the PPS signal.

The .Sq 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 .Va kern.clockrate.tick may be incorrect.

The .Sq broadcastdelay shows the default broadcast delay, as set by the .Ic broadcastdelay configuration command.

The .Sq authdelay shows the default authentication delay, as set by the .Ic authdelay configuration command.

Ic
Print statistics counters maintained in the protocol module.
Ic
Print statistics counters related to memory allocation code.
Ic
Print statistics counters maintained in the input-output module.
Ic
Print statistics counters maintained in the timer/event queue support code.
Ic
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.
Ic
Obtain and print traffic counts collected and maintained by the monitor facility. The version number should not normally need to be specified.
Ic
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.

.Ss "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 ntpdc. This can be done using the .Ic keyid and .Ic 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.

Xo
.Op Ar keyid .Op Ar version .Op Cm prefer .Xc 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 .Ar 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 .Ar version can be 1, 2 or 3 and defaults to 3. The .Cm 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.
Xo
.Op Ar keyid .Op Ar version .Op Cm prefer .Xc Identical to the addpeer command, except that the operating mode is client.
Xo
.Op Ar keyid .Op Ar version .Op Cm prefer .Xc Identical to the addpeer command, except that the operating mode is broadcast. In this case a valid key identifier and key are required. The .Ar 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.
Ic
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.
Xo
.Op Cm time1 .Op Cm time2 .Op Ar stratum .Op Ar refid .Xc This command provides a way to set certain data for a reference clock. See the source listing for further information.
Xo
.Oo .Cm auth | Cm bclient | .Cm calibrate | Cm kernel | .Cm monitor | Cm ntp | .Cm pps | Cm stats .Oc .Xc
Xo
.Oo .Cm auth | Cm bclient | .Cm calibrate | Cm kernel | .Cm monitor | Cm ntp | .Cm pps | Cm stats .Oc .Xc These commands operate in the same way as the .Ic enable and .Ic disable configuration file commands of ntpd(8).
Cm
Enables the server to synchronize with unconfigured peers only if the peer has been correctly authenticated using either public key or private key cryptography. The default for this flag is enable.
Cm
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.
Cm
Enables the calibrate feature for reference clocks. The default for this flag is disable.
Cm
Enables the kernel time discipline, if available. The default for this flag is enable if support is available, otherwise disable.
Cm
Enables the monitoring facility. See the ntpdc(8). program and the monlist command or further information. The default for this flag is enable.
Cm
Enables time and frequency discipline. In effect, this switch opens and closes the feedback loop, which is useful for testing. The default for this flag is enable.
Cm
Enables the pulse-per-second (PPS) signal when frequency and time is disciplined by the precision time kernel modifications. See the .Qq A Kernel Model for Precision Timekeeping (available as part of the HTML documentation provided in .Pa /usr/share/doc/ntp ) page for further information. The default for this flag is disable.
Cm
Enables the statistics facility. See the .Sx Monitoring Options section of ntp.conf(5) for further information. The default for this flag is disable.

.It Xo Ic restrict Ar address Ar mask .Ar flag Oo Ar ... Oc .Xc This command operates in the same way as the .Ic restrict configuration file commands of ntpd(8). .It Xo Ic unrestrict Ar address Ar mask .Ar flag Oo Ar ... Oc .Xc Unrestrict the matching entry from the restrict list. .It Xo Ic delrestrict Ar address Ar mask .Op Cm ntpport .Xc Delete the matching entry from the restrict list. .It Ic 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(8) configuration file). This allows encryption keys to be changed without restarting the server. .It Ic trustedkey Ar keyid Oo Ar ... Oc .It Ic untrustedkey Ar keyid Oo Ar ... Oc These commands operate in the same way as the .Ic trustedkey and .Ic untrustedkey configuration file commands of ntpd(8). .It Ic authinfo Returns information concerning the authentication module, including known keys and counts of encryptions and decryptions which have been done. .It Ic traps Display the traps set in the server. See the source listing for further information. .It Xo Ic addtrap Ar address .Op Ar port .Op Ar interface .Xc Set a trap for asynchronous messages. See the source listing for further information. .It Xo Ic clrtrap Ar address .Op Ar port .Op Ar interface .Xc Clear a trap for asynchronous messages. See the source listing for further information. .It Ic reset Clear the statistics counters in various modules of the server. See the source listing for further information.


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ntpdc See Also

ntp.conf(5), ntpd(8) .Rs .%A David L. Mills .%T Network Time Protocol (Version 3) .%O RFC1305 .Re


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ntpdc Authors

The formatting directives in this document came from FreeBSD.


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ntpdc Bugs

The ntpdc utility 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.

Please report bugs to http://bugs.ntp.org .



Usage

The simplest use of this program is as an unprivileged command to check the current time, offset, and error in the local clock. For example:

                        ntpdc ntpserver.somewhere
                   

With suitable privilege, it can be run as a command or in a cron job to reset the local clock from a reliable server, like the ntpdate and rdate commands. For example:

                        ntpdc -a ntpserver.somewhere