xntpdc - Monitor and control program for the Network Time
Protocol daemon
/usr/bin/xntpdc [-ilnps] [-c command] [host1 host2...]
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 specified 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.
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 interface.
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 xntpdc 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 communication 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 suitable time.
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 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 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 authentication. This is
used to enable (unreliable) server reconfiguration over
long delay network paths or between machines whose clocks
are unsynchronized. 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 specified, 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 command 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 correspond 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 [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. 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 information. Obtains and prints
packet count statistics from the control module. 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; multiline 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. 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 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, parameter). 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 specification. 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 commands,
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 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, while the authdelay
shows the default authentication delay, as set
by the authdelay configuration command. Prints a
number of stat counters maintained in the protocol
module. Prints counters maintained in the
timer/event queue support code. Prints the xntpdc
program version number.
Runtime Configuration Requests [Toc] [Back]
All requests that 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 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 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:
Adds a configured, 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 signal. 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 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. 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 unaffected. 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 authenticated 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 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. 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 possible 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 reconfiguration).
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 usually 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 partners.
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 broadcast packets are not
subject to client limitation and therefore are not contributing
to client count. History of clients is kept
using the monitoring 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.
***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.
Commands: ntpdate(8), ntpq(8), xntpd(8)
Files: ntp.conf(4)
xntpdc(8)
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