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 4.2.7p336 of ntpdc.
The program implements the SNTP protocol as defined by RFC 5905, the NTPv4 IETF specification.
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.
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>.
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. 4.2.7p336
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 Num 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
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.
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.
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).
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.
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.
This is the “numeric host addresses” option. Output all host addresses in dotted-quad numeric format rather than converting to the canonical host names.
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.
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.
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:
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>...<...>...</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:
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:
One of the following exit values will be returned:
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.
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 \&>, 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.
ntpdc.
A
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.
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.
ntpdc.
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.
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 \&~ denotes that the remote peer is sending broadcasts and a \&* marks the peer the server is currently synchronizing to.