xntpdc
- special NTP query program
xntpdc [ -ilnps ] [ -c command ] [ host ] [ ...
]
xntpdc
is used to query the xntpd
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 timeout time.
The operation of xntpdc
are specific to the particular
implementation of the xntpd
daemon and can be expected to
work only with this and maybe some previous versions of the daemon.
Requests from a remote xntpdc
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.
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 command
-i
xntpdc
to operate in interactive mode. Prompts
will be written to the standard output and commands read from the
standard input.
-l
-c listpeers
.
-n
-p
-c peers
.
-s
-c dmpeers
.
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 ]
helpl [ command_keyword ]
?
by itself will print a list of all the command
keywords known to this incarnation of ntpq
. 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 ntpq
than this manual page.
delay milliseconds
host hostname
hostnames [ yes | no ]
yes
is specified, host names are printed in
information displays. If no
is specified, numeric addresses
are printed instead. The default is yes
, unless modified
using the command line -n
switch.
keyid keyid
quit
xntpdc
.
passwd
timeout millseconds
xntpdc
retries each query once after a timeout, the total waiting time for a
timeout will be twice the timeout value set.
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
peers
+
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
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 [...]
pstats peer_address [...]
clockinfo clock_peer_address [...]
kerninfo
loopinfo [ oneline | multiline ]
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
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
xntpd
documentation 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 kernel_pps
indicates the kernel discipline is provided by the PPS signal.
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.
broadcastdelay
shows the default broadcast
delay, as set by the broadcastdelay
configuration command.
authdelay
shows the default authentication
delay, as set by the authdelay
configuration command.
sysstats
memstats
iostats
timerstats
reslist
monlist [ version ]
clkbug clock_peer_address [...]
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 ]
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 ]
broadcast peer_address [ keyid ] [
version ] [ prefer ]
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 [...]
fudge peer_address [ time1 ] [ time2 ]
[ stratum ] [ refid ]
enable [ flag ] [ ... ]
disable [ flag ] [ ... ]
enable
and disable
configuration file commands of
xntpd
.
restrict address mask flag [ flag
]
restrict
configuration file commands of xntpd
.
unrestrict address mask flag [ flag
]
delrestrict address mask [ ntpport ]
readkeys
xntpd
configuration file). This allows
encryption keys to be changed without restarting the server.
trustkey keyid [...]
untrustkey keyid [...]
trustedkey
and untrustkey
configuration file
commands of xntpd
.
authinfo
traps
addtrap [ address [ port ] [ interface
]
clrtrap [ address [ port ] [
interface]
reset
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.