xntpdc(1M) xntpdc(1M)
NAME [Toc] [Back]
xntpdc - special NTP query program
SYNOPSIS [Toc] [Back]
xntpdc [ -dilnps ] [ -c command ] [ host ] [ ... ]
DESCRIPTION [Toc] [Back]
xntpdc is used to query the xntpd daemon about its current state and
to request changes in that state. The program may be run either in
interactive mode or controlled mode using command line arguments.
Extensive state and statistics information is available through the
xntpdc interface. In addition, nearly all the configuration options
which can be specified at start up using xntpd's configuration file
may also be specified at run time using xntpdc. 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 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. xntpdc will
prompt for commands if the standard input is a terminal device.
xntpdc 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. xntpdc makes no attempt to retransmit requests,
and will timeout requests if the remote host is not heard from within
a suitable timeout time.
The operation of xntpdc is specific to the particular implementation
of the xntpd daemon and can be expected to work only with this and
maybe some previous versions of the daemon. Requests from a remote
xntpdc program which affect the state of the local server must be
authenticated, which requires both the remote program and local server
to share a common key and key identifier.
COMMAND LINE OPTIONS [Toc] [Back]
Specifying a command line option other than -i or -n will cause the
specified query (or queries) to be sent to the indicated host(s)
immediately. Otherwise, xntpdc will attempt to read interactive format
commands from the standard input.
-c command The following command is interpreted as an interactive
format command and is added to the list of commands to
be executed on the specified host(s). Multiple -c
commands may be given.
-d Debugging information is printed.
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-i Force xntpdc 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 option is equivalent to -c listpeers
command. See "CONTROL MESSAGE COMMANDS" below.
-n Output all host addresses in dotted-quad numeric format
(xxx.xxx.xxx.xxx) rather than converting to the
canonical host names.
-p Print a list of peers known to the server as well as a
summary of their state. This is equivalent to -c peers
command. See "CONTROL MESSAGE COMMANDS" below.
-s Print a list of peers known to the server as well as a
summary of their state, but in a slightly different
format than the -p command. This is equivalent to -c
dmpeers command. See "CONTROL MESSAGE COMMANDS" below.
INTERACTIVE COMMANDS [Toc] [Back]
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. The output of individual
commands may be redirected or 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 described as follows:
? [command_keyword]
help [command_keyword]
A ? or help by itself will print a list of all
the command keywords. ntpq. A ? or help
followed by a command keyword (command_keyword)
will print function and usage information about
the command.
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.
host hostname Set the host to which future queries will be sent.
The hostname may be either a host name or a
numeric address.
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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 command.
keyid keyid This command allows the specification of a key
number to be used to authenticate configuration
requests. The keyid must correspond to a key
number that the server has been configured to use
for this purpose.
quit Exit xntpdc.
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 xntpdc retries each query once
after a timeout, the total waiting time for a
timeout will be twice the timeout value set.
CONTROL MESSAGE COMMANDS [Toc] [Back]
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.
listpeers Obtains and prints a brief list of the peers for
which the server is maintaining state. This list
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. In addition, the
character in the left margin indicates the mode
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this peer entry is operating in.
+ indicates symmetric active
- indicates symmetric passive
= indicates the remote server is being polled in
client mode
^ indicates the server is broadcasting to this
address
~ indicates the remote peer is sending
broadcasts
* indicates the peer that the server is
currently synchronizing to.
The contents of the host field may be a host name, an IP address,
a reference clock implementation name with its parameter or
REFCLK (implementation number, parameter). For hostnames no,
only IP addresses will be displayed.
dmpeers
A slightly different peer summary list. The output is
similar to that 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 period (.) indicates that this
peer was cast off in the falseticker detection. A plus (+)
indicates that the peer made it through. An asterisk (*)
denotes the peer that 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).
clockinfo 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 only if the kernel
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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-permillion
(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. multiline is the default.
sysinfo
Print a variety of system state variables, i.e., the state
related to the local server.
The system flags show various system flags, some of which
can be set and cleared by the enable and disable
configuration commands, respectively. The configurable flags
are the auth, bclient, monitor, pll, pps and stats flags.
Refer to (xntpd(1M)) for the description of these flags.
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.
memstats
Print statistics counters related to memory allocation code.
iostats
Print statistics counters maintained in the input-output
module.
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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.
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.
RUNTIME CONFIGURATION REQUESTS [Toc] [Back]
All requests which cause state changes in the server are authenticated
by the server using a configured NTP key. This facility is disabled if
the NTP key is not configured. 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 against 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.
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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 (encrypted) attached 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 synchronization if possible). The
preferred peer also determines the validity of the PPS
signal - if the preferred peer is suitable for
synchronization 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
using 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 [flag][...]
disable [flag][...]
These commands operate in the same way as the enable and
disable configuration file commands of xntpd. Described
below are the flags supported.
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auth Enables 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
enable.
bclient 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.
monitor Enables the monitoring facility. See the xntpdc
program and the monolist command for more
information. The default for this flag is enable.
pll Enables the server to adjust its local clock by
means of NTP. If disabled, 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. In this case,
the local clock driver is used. 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. The default
for this flag is disable.
stats Enables the statistics facility. The default for
this flag is enable.
restrict address mask flag [flag]
This command operates in the same way as the restrict
configuration file commands of xntpd.
unrestrict address mask flag [flag]
Unrestrict the matching entry from the restrict list.
delrestrict address mask [nttport]
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 xntpd
configuration file). This allows encryption keys to be
changed without restarting the server.
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trustkey [keyid][...]
untrustkey [keyid][...]
These commands operate in the same way as the trustedkey
and untrustkey configuration file commands of xntpd.
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.
AUTHOR [Toc] [Back]
xntpdc was developed by David L. Mills.
SEE ALSO [Toc] [Back]
xntpd(1M), ntpdate(1M), ntpq(1M).
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