xntpdc(8)xntpdc(8)NAMExntpdc - Monitor and control program for the Network Time Protocol dae‐
mon
SYNOPSIS
/usr/bin/xntpdc [-ilnps] [-c command] [host1 host2...]
OPTIONS
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 speci‐
fied 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.
DESCRIPTION
Note
The latest versions of the xntpdc command and xntpd daemon, delivered
with NTP Version 4, are incompatible with previous versions of NTP. If
you use the latest xntpdc command to collect information from an older
xntpd daemon, or an older xntpdc command to collect information from
the latest xntpd daemon, you will receive inconsistent results.
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 inter‐
face.
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 xnt‐
pdc 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 communi‐
cation 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 suit‐
able time.
COMMANDS
Interactive Commands
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 nor‐
mally sent to the standard output, but optionally the output of indi‐
vidual 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 authentica‐
tion. This is used to enable (unreliable) server reconfiguration over
long delay network paths or between machines whose clocks are unsyn‐
chronized. 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 speci‐
fied, 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 com‐
mand 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 corre‐
spond 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
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 informa‐
tion. Obtains and prints packet count statistics from the control mod‐
ule. 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; multi‐
line 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. Sum‐
mary information includes the address of the remote peer, the local
interface address (0.0.0.0 if a local address has yet to be deter‐
mined), 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, off‐
set and dispersion of the peer, all in seconds. In addition, the char‐
acter 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.
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(implementation number, parame‐
ter). On hostnames no only, IP-addresses will be displayed.
Shows per-peer statistic counters associated with the specified
peer(s). Obtains and prints the server's restriction list.
This list is (usually) printed in sorted order and may help to
understand how the restrictions are applied. 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 specifi‐
cation. Prints a variety of system state variables, that is the
state related to the local server. Many of these values are
described in the NTP Version 3 specification, RFC 1305. The
system options show various system options, some of which can be
set and cleared by the enable and disable configuration com‐
mands, respectively. The stability is the residual frequency
error remaining after the system frequency correction is applied
and is intended for maintenance and debugging. In most architec‐
tures, 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 configura‐
tion command, while the authdelay shows the default authentica‐
tion delay, as set by the authdelay configuration command.
Prints a number of stat counters maintained in the protocol mod‐
ule. Prints counters maintained in the timer/event queue sup‐
port code. Prints the xntpdc program version number.
Runtime Configuration Requests
All requests that cause state changes in the server are authenticated
by the server using a configured NTP key (the facility can also be dis‐
abled 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 con‐
figuration 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 distri‐
bution and protection of keys and appropriate source address restric‐
tions are applied, the run time reconfiguration facility should provide
an adequate level of security.
The following commands all make authenticated requests: Adds a config‐
ured, 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 sig‐
nal. 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 identi‐
fier and key are required. The peer_address parameter can be the broad‐
cast 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. Options not mentioned are unaf‐
fected. The options presently available are described under the enable
command. Provides a way to enable the following server options.
Options not mentioned are unaffected. Causes the server to synchronize
with unconfigured peers only if the peer has been correctly authenti‐
cated using a trusted key and key identifier. The default for this
option 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 option
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 option 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 authenti‐
cation 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 possi‐
ble 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 recon‐
figuration). 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 usu‐
ally 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 part‐
ners. 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 broad‐
cast packets are not subject to client limitation and therefore are not
contributing to client count. History of clients is kept using the mon‐
itoring 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.
ERRORS
***Can't find host hostname
Explanation:
The hostname is not in the local /etc/hosts file. hostname:
timed out, nothing received ***Request timed out
Explanation:
Check that xntpd is running on the remote host being queried.
SEE ALSO
Commands: ntpdate(8), ntpq(8), xntpd(8)
Files: ntp.conf(4)xntpdc(8)
