xntpdc(1M) xntpdc(1M)
NAME
xntpdc - query/control program for the Network Time Protocol
daemon
SYNOPSIS
xntpdc [-dilnps] [-c command] [host] [...]
DESCRIPTION
The xntpdc command queries the xntpd(1M) daemon about its
current state, and requests changes in that state.
USAGE
xntpdc 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 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 time
requests out if the remote host is not heard from within a
suitable time out time.
Options
Command line options are described below. Note that
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.
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-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.
-d Enable debugging.
-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 as
follows:
? [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 function and
usage information about the command. This command is
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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 address.
poll [#] [verbose]
Poll the current server in client mode. The first
argument is the number of times to poll (default is 1)
while the second argument may be given to obtain a more
detailed output of the results. This command is
currently just wishful thinking.
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.
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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 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 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 synchronizing to.
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.
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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).
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 actually the
frequency error, or drift, of your system's clock in the
units NTP uses for internal computations. Dividing this
number by 4096 should give you the actual drift rate.
The ``compliance'' is actually a long term average
offset and is used by NTP to control the gain of the
loop filter. The ``timer'' value is the number of
seconds which 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.
sysinfo
Print a variety of system state variables, i.e. state
related to the local server. Many of these values are
described in the NTP Version 2 specification, RFC 1119.
sysstats
Print a number of stat counters maintained in the
protocol module.
memstats
Print a number of counters related to the peer memory
allocation code.
iostats
Print counters maintained in the input-output module.
timerstats
Print counters maintained in the timer/event queue
support code.
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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
Obtain and print traffic counts collected and maintained
by the monitor facility.
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.
clkbug clock_peer_address [addr2] [addr3] [addr4]
Obtain debugging information for a clock peer. 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
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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#] [minpoll]
Add 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 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 or 2, and defaults to 2. If minpoll is specified
the polling interval for the association will remain
clamped at the minimum. The latter option is only
useful for testing. 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.
addserver peer_address [keyid] [version#] [minpoll]
Identical to the addpeer command except that polling is
done in client mode rather than symmetric active mode.
broadcast peer_address [keyid] [version#] [minpoll]
Identical to the addpeer command except that packets are
instead sent in broadcast mode. The peer_address
parameter will generally be a broadcast address on one
of your local networks.
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.
set bclient|auth [. . .]
Allows the setting of the broadcast client and/or
authenticate system flags. Setting the former causes
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the server to listen for broadcast NTP to synchronize to
broadcasts when appropriate. Setting the latter flag
causes the server to only synchronize with peers which
include an authentication field encrypted with one of
the local server's trusted keys.
clear bclient|auth [. . .]
Allows the broadcast client and/or authenticate system
flags to be cleared. Clearing the former causes
incoming broadcast NTP packets to be ignored. Clearing
the latter allows peers which have not included an
authentication field, or which have included one but
have encrypted it with an untrusted key, to be
considered synchronization candidates.
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 flag
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.
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.
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notrust
Treat these hosts normally in other respects, but
never use them as synchronization sources.
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.
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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.
setselect algorithm_number
Sets the selection weight algorithm to that indicated by
the specified number. This should be an integer value
between 1 and 5 inclusive. Algorithm 1 is that
specified in RFC 1119, the other 4 algorithms are
experimental and should be used with caution.
REFERENCES
xntpd(1M)
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