NAME
xntpdc - query/control program for the Network Time Protocol
daemon
SYNOPSIS
xntpdc [ -ilnps ] [ -c command ] [ host ] [ ... ]
DESCRIPTION
Xntpdc is used to query the xntpd(8) daemon about its
current state and to request changes in that state. 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. 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 compatable 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 time requests out if the remote host is not heard
from within a suitable time out time.
Command line options are described following. 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, xntpdc will attempt to read
interactive format commands from the standard input.
-c 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).
Multiple -c options may be given.
-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 switch is equivalent to "-c
listpeers".
-n Output all host addresses in dotted-quad numeric
format rather than converting to the canonical host
names.
-p Print a list of the peers known to the server as
well as a summary of their state. This is equivalent
to "-c peers".
-s Print 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 switch. This is
equivalent to "-c dmpeers".
INTERNAL 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 xntpdc program itself and do not result
in NTP mode 7 requests being sent to a server. These are
described following.
? [ command_keyword }
A "?" by itself will print a list of all the command
keywords known to this incarnation of xntpdc. A "?"
followed by a command keyword will print funcation and usage
information about the command. This command is probably a
better source of information about xntpdc than this manual
page.
help [ command_keyword ]
A synonym for the ? command.
timeout millseconds
Specify a time out period for responses to server queries.
The default is about 8000 milliseconds.
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. Hostname
may be either a host name or a numeric (dotted quad)
dmaddress.
keyid #
This command 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.
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.
hostnames yes|no
If "yes" is specified, host names are printed in information
displays. If "no" is given, numeric addresses are printed
instead. The default is "yes" unless modified using the
command line -n switch.
quit
Exit xntpdc.
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.
listpeers
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 synchonization 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 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 "*" marks the
peer the server is currently synchonizing 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.
dmpeers
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. 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 [ addr2 ] [ addr3 ] [ addr4 ]
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 [ addr2 ] [ addr3 ] [ addr4 ]
Show per-peer statistic counters associated with the
specified peer(s).
clockinfo clock_peer_address [ addr2 ] [ addr3 ] [ addr4 ]
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
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.
sysinfo
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. 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.
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.
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 [ addr2 ] [ addr3 ] [ addr4 ]
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 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 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.
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 synchronisation 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# ]
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 [ addr2 ] [ addr3 ] [ addr4 ]
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 auth|bclient|pll|monitor|stats [ ... ]
Provides a way to enable various server options. Flags not
mentioned are unaffected. The "auth" flag 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 flag is disable (off). The
"bclient" flag 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 flag is disable (off). The "pll" flag
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 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. The "monitor" flag enables the monitoring
facility (see elsewhere), with default disable (off). The
"stats" flag enables statistics facility filegen (see
description elsewhere.), with default enable (on).
disable auth|bclient|pll|monitor|stats [ ... ]
Provides a way to disable various server options. Flags not
mentioned are unaffected. The flags presently available are
described under the enable command.
restrict address mask flag [ flag ]
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
given in the following list:
ignore Ignore all packets from hosts which match this
entry. If this flag is specified neither queries
nor time server polls will be responded to.
noquery Ignore all NTP mode 7 packets (i.e. information
queries and configuration requests) from the
source. Time service is not affected.
nomodify Ignore all NTP mode 7 packets which attempt to
modify the state of the server (i.e. run time
reconfiguration). Queries which return information
are permitted.
notrap Decline 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.
lowpriotrap
Declare 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.
noserve Ignore NTP packets whose mode is other than 7. In
effect, time service is denied, though queries may
still be permitted.
nopeer Provide 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.
notrust Treat these hosts normally in other respects, but
never use them as synchronization sources.
limited 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.
ntpport 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.
unrestrict address mask flag [ flag ]
Remove the specified flag(s) from the restrict list entry
indicated by the address and mask arguments.
delrestrict address mask [ ntpport ]
Delete the matching entry from the restrict list.
monitor yes|no
Enable or disable the monitoring facility. Note that a
monitor no command followed by a monitor yes command is a
good way of resetting the packet counts.
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.
trustkey keyid [ keyid ] [ keyid ] [ keyid ]
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.
untrustkey keyid [ keyid ] [ keyid ] [ keyid ]
Removes one or more keys from the trusted key list.
authinfo
Returns information concerning the authentication module,
including known keys and counts of encryptions and
decryptions which have been done.
setprecision precision_value
Sets the precision which the server advertises to the
specified value. This should be a negative integer in the
range -4 through -20.
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 ALSO
xntpd(8)
HISTORY
Written by Dennis Ferguson at the University of Toronto.
BUGS
Xntpdc is a crude hack. Much of the information it shows is
deadly boring and could only be loved by its implementer.
The program 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.