ntpdc(8) - phpMan

ntpdc(8) System Manager's Manual ntpdc(8)

NAME
ntpdc - special NTP query program

SYNOPSIS
ntpdc [ -46dilnps ] [ -c command ] [ host ] [ ... ]

DESCRIPTION
ntpdc is used to query the ntpd 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 ntpdc
interface. In addition, nearly all the configuration options which can be specified at
startup using ntpd's configuration file may also be specified at run time using ntpdc.

If one or more request options are included on the command line when ntpdc 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, ntpdc
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. ntpdc will prompt for commands if the standard input is a termi-
nal device.

ntpdc 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. ntpdc makes no attempt to retransmit requests, and will time
requests out if the remote host is not heard from within a suitable timeout time.

The operation of ntpdc are specific to the particular implementation of the ntpd daemon
and can be expected to work only with this and maybe some previous versions of the daemon.
Requests from a remote ntpdc program which affect the state of the local server must be
authenticated, which requires both the remote program and local server share a common key
and key identifier.

Note that in contexts where a host name is expected, a -4 qualifier preceding the host
name forces DNS resolution to the IPv4 namespace, while a -6 qualifier forces DNS resolu-
tion to the IPv6 namespace.

COMMAND LINE OPTIONS
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, ntpdc will attempt
to read interactive format commands from the standard input.

-4 Force DNS resolution of following host names on the command line to the IPv4
namespace.

-6 Force DNS resolution of following host names on the command line to the IPv6
namespace.

-c command
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 Turn on debugging mode.

-i Force ntpdc to operate in interactive mode. Prompts will be written to the stan-
dard 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.

INTERACTIVE 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 ntpdc program
itself and do not result in NTP mode 7 requests being sent to a server. These are
described following.

? [ command_keyword ]

help [ command_keyword ]
A ? by itself will print a list of all the command keywords known to this incarna-
tion of ntpq. A ? followed by a command keyword will print function and usage
information about the command. This command is probably a better source of infor-
mation about ntpq than this manual page.

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.
Actually the server does not now require timestamps in authenticated requests, so
this command may be obsolete.

host hostname
Set the host to which future queries will be sent. Hostname may be either a host
name or a numeric address.

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 modi-
fied using the command line -n switch.

keyid keyid
This command allows the specification of a key number to be used to authenticate
configuration requests from ntpdc to the host(s). This must correspond to a key
number which the host/server has been configured to use for this purpose (server
options: trustedkey, and requestkey). If authentication is not enabled on the
host(s) for ntpdc commands, the command "keyid 0" should be given; otherwise the
keyid of the next subsequent addpeer/addserver/broadcast command will be used.

quit Exit ntpdc.

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 ntpdc retries each query once after a timeout,
the total waiting time for a timeout will be twice the timeout value set.

CONTROL MESSAGE 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 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, offset and dispersion of the peer, all
in seconds. 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 send-
ing broadcasts and a * 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 REF-
CLK(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 com-
mand, except for the character in the leftmost column. Characters only appear
beside peers which were included in the final stage of the clock selection algo-
rithm. 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 [...]
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 informa-
tion.

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 timekeep-
ing 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 off-
set 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 con-
trols 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 one-
line 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 specifi-
cation, 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.
These are the auth, bclient, monitor, pll, pps and stats flags. See the ntpd docu-
mentation for the meaning of these flags. There are two additional flags which are
read only, the kernel_pll and kernel_pps. These flags indicate the synchronization
status when the precision time kernel modifications are in use. The kernel_pll
indicates that the local clock is being disciplined by the kernel, while the ker-
nel_pps indicates the kernel discipline is provided by the PPS signal.

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 con-
figuration 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.

ifstats List interface statistics for interfaces used by ntpd for network communication.

ifreload
Force rescan of current system interfaces. Outputs interface statistics for inter-
faces that could possibly change. Marks unchanged interfaces with ., added inter-
faces with + and deleted interfaces with -.

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 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 ntpdc. This can
be done using the keyid and passwd commands, the latter of which will prompt at the termi-
nal 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 verifica-
tion 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 pass-
words 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 pro-
vide an adequate level of security.

The following commands all make authenticated requests.

addpeer peer_address [ prefer | iburst | burst | minpoll N | maxpoll N | keyidN | version
N [...] ]
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 keyid is nonzero, 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. If ntpdc's
key number has not yet been set (e.g., by the keyid command), it will be set to
this value. The version# can be 1 through 4 and defaults to 3. The remaining
options are either a numeric value for minpoll or literals prefer, iburst, burst,
minpoll N, keyid N, version N, or maxpoll N (where N is a numeric value), and
have the action as specified in the peer configuration file command of ntpd. See
the Server Options page for further information. Each flag (or its absence)
replaces the previous setting. 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. The dynamic keyword allows
association configuration even when no suitable network interface is found at con-
figuration time. The dynamic interface update mechanism may complete the configu-
ration when new interfaces appear (e.g. WLAN/PPP interfaces) at a later time and
thus render the association operable.

broadcast peer_address [ keyid ] [ version ] [ prefer ]
Identical to the addpeer command, except that the operating mode is broadcast. In
this case a valid non-zero 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 [...]
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 appropri-
ate, 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.

restrict address mask flag [ flag ]
This command operates in the same way as the restrict configuration file commands
of ntpd.

unrestrict address mask flag [ flag ]
Unrestrict the matching entry from the restrict list.

delrestrict address mask [ ntpport ]
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 ntpd
configuration file). This allows encryption keys to be changed without restarting
the server.

trustedkey keyid [...]

untrustedkey keyid [...]
These commands operate in the same way as the trustedkey and untrustedkey configu-
ration file commands of ntpd.

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 informa-
tion.

addtrap [ address ] [ port ] [ interface ]
Set a trap for asynchronous messages. See the source listing for further informa-
tion.

clrtrap [ address ] [ port ] [ interface]
Clear a trap for asynchronous messages. See the source listing for further infor-
mation.

reset Clear the statistics counters in various modules of the server. See the source
listing for further information.

BUGS
ntpdc 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.