ntpdc(1) User Commands ntpdc(1)
ntpdc - vendor-specific NTPD control program
ntpdc [-flags] [-flag [value]] [--option-name[[=| ]value]] [ host ...]
ntpdc is deprecated. Please use ntpq(1) instead - it can do everything ntpdc used to do, and it does so using a much more sane interface.
ntpdc is a utility program used to query ntpd(1) 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 argu-
ments. 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.
Force IPv4 DNS name resolution. This option must not appear in combination with any of the following options: ipv6.
Force DNS resolution of following host names on the command line to the IPv4 namespace.
Force IPv6 DNS name resolution. This option must not appear in combination with any of the following options: ipv4.
Force DNS resolution of following host names on the command line to the IPv6 namespace.
-c cmd, --command=cmd
run a command and exit. This option may appear an unlimited number of times.
The following argument is interpreted as an interactive format command and is added to the list of commands to be executed on the
Increase debug verbosity level. This option may appear an unlimited number of times.
-D number, --set-debug-level=number
Set the debug verbosity level. This option may appear an unlimited number of times. This option takes an integer number as its
Force ntpq to operate in interactive mode. This option must not appear in combination with any of the following options: command,
listpeers, peers, showpeers.
Force ntpq to operate in interactive mode. Prompts will be written to the standard output and commands read from the standard
Print a list of the peers. This option must not appear in combination with any of the following options: command.
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
numeric host addresses.
Output all host addresses in dotted-quad numeric format rather than converting to the canonical host names.
Print a list of the peers. This option must not appear in combination with any of the following options: command.
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
Show a list of the peers. This option must not appear in combination with any of the following options: command.
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
Display usage information and exit.
Pass the extended usage information through a pager.
-> [cfgfile], --save-opts [=cfgfile]
Save the option state to cfgfile. The default is the last configuration file listed in the OPTION PRESETS section, below. The com-
mand will exit after updating the config file.
-< cfgfile, --load-opts=cfgfile, --no-load-opts
Load options from cfgfile. The no-load-opts form will disable the loading of earlier config/rc/ini files. --no-load-opts is han-
dled early, out of order.
Output version of program and exit. The default mode is `v', a simple version. The `c' mode will print copyright information and
`n' will print the full copyright notice.
Any option that is not marked as not presettable may be preset by loading values from configuration ("RC" or ".INI") file(s) and values
from environment variables named:
NTPDC_<option-name> or NTPDC
The environmental presets take precedence (are processed later than) the configuration files. The homerc files are "$HOME", and ".". If
any of these are directories, then the file .ntprc is searched for within those directories.
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
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 dis-
tances 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(1) 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 com-
mands from the standard input.
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 utility itself and do not result in NTP mode 7 requests
being sent to a server. These are described following.
A '?' will print a list of all the command keywords known to this incarnation of ntpdc. 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(1) than
this manual page.
Specify a time interval to be added to timestamps included in requests which require authentication. This is used to enable (unre-
liable) 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.
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.
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.
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.
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.
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.
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 synchroniza-
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 '-' indi-
cates symmetric passive, a '=' means the remote server is being polled in client mode, a '^' indicates that the server is broadcast-
ing to this address, a '~' denotes that the remote peer is sending broadcasts and 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() 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 col-
umn. 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
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.
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.
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.
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(1) 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 synchro-
nization 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 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 kern.clockrate.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.
Print statistics counters maintained in the input-output module.
Print statistics counters maintained in the timer/event queue support code.
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.
Obtain and print traffic counts collected and maintained by the monitor facility. The version number should not normally need to be
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.
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 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 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-syn-
chronized 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] [prefer]
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 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 synchronisa-
tion 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 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 con-
tinue 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(1).
auth Enables the server to synchronize with unconfigured peers only if the peer has been correctly authenticated using either pub-
lic key or private key cryptography. The default for this flag is enable.
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.
Enables the calibrate feature for reference clocks. The default for this flag is disable.
kernel Enables the kernel time discipline, if available. The default for this flag is enable if support is available, otherwise
Enables the monitoring facility. See the documentation here about the monlist command or further information. The default
for this flag is enable.
ntp Enables time and frequency discipline. In effect, this switch opens and closes the feedback loop, which is useful for test-
ing. 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 Timekeeping" (available as part of the HTML documentation provided in
/usr/share/doc/ntp) page for further information. The default for this flag is disable.
stats Enables the statistics facility. See the Monitoring Options section of ntp.conf(5) for further information. The default for
this flag is disable.
restrict address mask flag [...]
This command operates in the same way as the restrict configuration file commands of ntpd(1).
unrestrict address mask 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(1) configuration file). This allows encryption keys to be changed without restarting the server.
trustedkey keyid [...]
untrustedkey keyid [...]
These commands operate in the same way as the trustedkey and untrustedkey configuration file commands of ntpd(1).
Returns information concerning the authentication module, including known keys and counts of encryptions and decryptions which have
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.
See OPTION PRESETS for configuration environment variables.
See OPTION PRESETS for configuration files.
One of the following exit values will be returned:
Successful program execution.
The operation failed or the command syntax was not valid.
A specified configuration file could not be loaded.
libopts had an internal operational error. Please report it to email@example.com. Thank you.
ntp.conf(5), ntpd(1) David L. Mills, Network Time Protocol (Version 3), RFC1305
The formatting directives in this document came from FreeBSD.
Copyright (C) 1992-2017 The University of Delaware and Network Time Foundation all rights reserved. This program is released under the
terms of the NTP license, <http://ntp.org/license>.
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 pro-
gram 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 .
Please send bug reports to: http://bugs.ntp.org, firstname.lastname@example.org
This manual page was AutoGen-erated from the ntpdc option definitions.
4.2.8p13 20 Feb 2019 ntpdc(1)