ntpdc.8   [plain text]

.\" $FreeBSD: src/usr.sbin/ntp/doc/ntpdc.8,v 1.11 2002/12/27 12:15:38 schweikh Exp $
.Dd January 7, 2000
.Nm ntpdc
.Nd special NTP query program
.Op Fl ilnps
.Op Fl c Ar command
.Op Ar host ...
utility is used to query the
.Xr ntpd 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
Extensive state and statistics information is available
through the
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
.Nm .
The following options are available:
.Bl -tag -width indent
.It Fl c Ar 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).
.Fl c
options may be given.
.It Fl i
to operate in interactive mode.
will be written to the standard output and commands read from the
standard input.
.It Fl l
Obtain a list of peers which are known to the server(s).
switch is equivalent to
.Ql -c listpeers .
.It Fl n
Output all host addresses in dotted-quad numeric format rather
than converting to the canonical host names.
.It Fl p
Print a list of the peers known to the server as well as a
summary of their state.
This is equivalent to
.Ql -c peers .
.It Fl 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
.Fl p
This is equivalent to
.Ql -c dmpeers .
If one or more request options are included on the command line
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,
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.
utility will prompt for
commands if the standard input is a terminal device.
utility 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.
utility makes
no attempt to retransmit requests, and will time requests out if
the remote host is not heard from within a suitable timeout
The operation of
are specific to the particular
implementation of the
.Xr ntpd 8
daemon and can be expected to
work only with this and maybe some previous versions of the daemon.
Requests from a remote
utility 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
Specifying a command line option other than
.Fl i
.Fl n
will cause the specified query (queries) to be sent to
the indicated host(s) immediately.
attempt to read interactive format commands from the standard
.Ss "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
.Ql \&> ,
followed by a file name, to the command line.
A number of interactive format commands are executed entirely
within the
utility itself and do not result in NTP
mode 7 requests being sent to a server.
These are described
.Bl -tag -width indent
.It Ic \&? Ar command_keyword
.It Ic help Ar command_keyword
.Ic \&?
will print a list of all the command
keywords known to this incarnation of
.Nm .
.Ic \&?
followed by a command keyword will print function and usage
information about the command.
This command is probably a better
source of information about
.Xr ntpq 8
than this manual
.It Ic delay Ar 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.
.It Ic host Ar hostname
Set the host to which future queries will be sent.
Hostname may
be either a host name or a numeric address.
.It Ic hostnames Op Cm yes | Cm no
.Cm yes
is specified, host names are printed in
information displays.
.Cm no
is specified, numeric
addresses are printed instead.
The default is
.Cm yes ,
modified using the command line
.Fl n
.It Ic keyid Ar keyid
This command allows the specification of a key number to be
used to authenticate configuration requests.
This must correspond
to a key number the server has been configured to use for this
.It Ic quit
.Nm .
.It Ic passwd
This command prompts you to type in a password (which will not
be echoed) which will be used to authenticate configuration
The password must correspond to the key configured for
use by the NTP server for this purpose if such requests are to be
.It Ic timeout Ar milliseconds
Specify a timeout period for responses to server queries.
default is about 8000 milliseconds.
Note that since
retries each query once after a timeout, the total waiting time for
a timeout will be twice the timeout value set.
.Ss "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
.Bl -tag -width indent
.It Ic 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.
.It Ic 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 ( 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.
The character in the left margin indicates the mode this peer
entry is operating in.
.Ql \&+
denotes symmetric active, a
.Ql \&-
indicates symmetric passive, a
.Ql \&=
means the
remote server is being polled in client mode, a
.Ql \&^
indicates that the server is broadcasting to this address, a
.Ql \&~
denotes that the remote peer is sending broadcasts and a
.Ql \&*
marks the peer the server is currently synchronizing
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
.Fn REFCLK "implementation_number" "parameter" .
.Ic hostnames
.Cm no
only IP-addresses
will be displayed.
.It Ic dmpeers
A slightly different peer summary list.
Identical to the output
of the
.Ic 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.
.Ql \&.
indicates that this peer was cast off in the falseticker
detection, while a
.Ql \&+
indicates that the peer made it
.Ql \&*
denotes the peer the server is currently
synchronizing with.
.It Ic showpeer Ar 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.
.It Ic pstats Ar peer_address ...
Show per-peer statistic counters associated with the specified
.It Ic clockinfo Ar clock_peer_address ...
Obtain and print information concerning a peer clock.
values obtained provide information on the setting of fudge factors
and other clock performance information.
.It Ic 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.
.It Ic loopinfo Op Cm oneline | Cm 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.
.Sq offset
is the last offset given to the
loop filter by the packet processing code.
.Sq frequency
is the frequency error of the local clock in parts-per-million
.Sq time_const
controls the stiffness of the
phase-lock loop and thus the speed at which it can adapt to
oscillator drift.
.Sq watchdog timer
value is the number
of seconds which have elapsed since the last sample offset was
given to the loop filter.
.Cm oneline
.Cm multiline
options specify the format in which this
information is to be printed, with
.Cm multiline
as the
.It Ic 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.
.Sq system flags
show various system flags, some of
which can be set and cleared by the
.Ic enable
.Ic disable
configuration commands, respectively.
These are
.Cm auth  ,
.Cm bclient ,
.Cm monitor ,
.Cm pll ,
.Cm pps
.Cm stats
See the
.Xr ntpd 8
documentation for the meaning of these flags.
are two additional flags which are read only, the
.Cm kernel_pll
.Cm kernel_pps .
These flags indicate
the synchronization status when the precision time kernel
modifications are in use.
.Sq kernel_pll
indicates that
the local clock is being disciplined by the kernel, while the
.Sq kernel_pps
indicates the kernel discipline is provided by the PPS
.Sq 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
.Va kern.clockrate.tick
may be
.Sq broadcastdelay
shows the default broadcast delay,
as set by the
.Ic broadcastdelay
configuration command.
.Sq authdelay
shows the default authentication delay,
as set by the
.Ic authdelay
configuration command.
.It Ic sysstats
Print statistics counters maintained in the protocol
.It Ic memstats
Print statistics counters related to memory allocation
.It Ic iostats
Print statistics counters maintained in the input-output
.It Ic timerstats
Print statistics counters maintained in the timer/event queue
support code.
.It Ic 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.
.It Ic monlist Op Ar version
Obtain and print traffic counts collected and maintained by the
monitor facility.
The version number should not normally need to be
.It Ic clkbug Ar clock_peer_address ...
Obtain debugging information for a reference clock driver.
information is provided only by some clock drivers and is mostly
undecodable without a copy of the driver source in hand.
.Ss "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
The key number and the corresponding key must also be made
known to
.Nm .
This can be done using the
.Ic keyid
.Ic 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
This timestamp is compared by the server to its receive time
If they differ by more than a small amount the request is
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.
.Bl -tag -width indent
.It Xo Ic addpeer Ar peer_address
.Op Ar keyid
.Op Ar version
.Op Cm 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
.Ar keyid
is a
nonzero integer, all outgoing packets to the remote server will
have an authentication field attached encrypted with this key.
the value is 0 (or not given) no authentication will be done.
.Ar version
can be 1, 2 or 3 and defaults to 3.
.Cm prefer
keyword indicates a preferred peer (and thus will
be used primarily for clock synchronisation if possible).
preferred peer also determines the validity of the PPS signal - if
the preferred peer is suitable for synchronisation so is the PPS
.It Xo Ic addserver Ar peer_address
.Op Ar keyid
.Op Ar version
.Op Cm prefer
Identical to the addpeer command, except that the operating
mode is client.
.It Xo Ic broadcast Ar peer_address
.Op Ar keyid
.Op Ar version
.Op Cm prefer
Identical to the addpeer command, except that the operating
mode is broadcast.
In this case a valid key identifier and key are
.Ar 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
.It Ic unconfig Ar 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 appropriate, however, the
association may persist in an unconfigured mode if the remote peer
is willing to continue on in this fashion.
.It Xo Ic fudge Ar peer_address
.Op Cm time1
.Op Cm time2
.Op Ar stratum
.Op Ar refid
This command provides a way to set certain data for a reference
See the source listing for further information.
.It Ic enable Ar flag ...
.It Ic disable Ar flag ...
These commands operate in the same way as the
.Ic enable
.Ic disable
configuration file commands of
.Xr ntpd 8  .
Following is a description of the flags.
Note that only the
.Cm auth  ,
.Cm bclient ,
.Cm monitor ,
.Cm pll ,
.Cm pps
.Cm stats
flags can be set by
.Nm ;
.Cm pll_kernel
.Cm pps_kernel
flags are
.Bl -tag -width indent
.It Cm auth
Enables 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 enable.
.It Cm bclient
Enables the server to listen for a message from a broadcast or
multicast server, as in the
.Ic multicastclient
command with
default address.
The default for this flag is disable.
.It Cm monitor
Enables the monitoring facility.
See the
.Ic monlist
command for further information.
default for this flag is enable.
.It Cm pll
Enables the server to adjust its local clock by means of NTP.
If disabled, 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.
In this case, the local
clock driver is used.
See the
.Qq "Reference Clock Drivers"
(available as part of the HTML documentation
provided in
.Pa /usr/share/doc/ntp )
page for further information.
The default for
this flag is enable.
.It Cm pps
Enables the pulse-per-second (PPS) signal when frequency and
time is disciplined by the precision time kernel modifications.
.Qq "A Kernel Model for Precision Timekeeping"
page for further information.
The default for this flag is
.It Cm stats
Enables the statistics facility.
See the
.Sx Monitoring Options
of the
.Xr ntp.conf 5
page for further information.
The default for this flag is enable.
.It Cm pll_kernel
When the precision time kernel modifications are installed,
this indicates the kernel controls the clock discipline; otherwise,
the daemon controls the clock discipline.
.It Cm pps_kernel
When the precision time kernel modifications are installed and
a pulse-per-second (PPS) signal is available, this indicates the
PPS signal controls the clock discipline; otherwise, the daemon or
kernel controls the clock discipline, as indicated by the
.Cm pll_kernel
.It Xo Ic restrict Ar address Ar mask
.Ar flag ...
This command operates in the same way as the
.Ic restrict
configuration file commands of
.Xr ntpd 8  .
.It Xo Ic unrestrict Ar address Ar mask
.Ar flag ...
Unrestrict the matching entry from the restrict list.
.It Xo Ic delrestrict Ar address Ar mask
.Op Cm ntpport
Delete the matching entry from the restrict list.
.It Ic 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
.Xr ntpd 8
configuration file).
allows encryption keys to be changed without restarting the
.It Ic trustedkey Ar keyid ...
.It Ic untrustedkey Ar keyid ...
These commands operate in the same way as the
.Ic trustedkey
.Ic untrustedkey
configuration file
commands of
.Xr ntpd 8  .
.It Ic authinfo
Returns information concerning the authentication module,
including known keys and counts of encryptions and decryptions
which have been done.
.It Ic traps
Display the traps set in the server.
See the source listing for
further information.
.It Xo Ic addtrap Ar address
.Op Ar port
.Op Ar interface
Set a trap for asynchronous messages.
See the source listing
for further information.
.It Xo Ic clrtrap Ar address
.Op Ar port
.Op Ar interface
Clear a trap for asynchronous messages.
See the source listing
for further information.
.It Ic reset
Clear the statistics counters in various modules of the server.
See the source listing for further information.
.Xr ntp.conf 5 ,
.Xr ntpd 8
.%A David L. Mills
.%T Network Time Protocol (Version 3)
.%O RFC1305
utility is a crude hack.
Much of the information it shows is
deadly boring and could only be loved by its implementer.
program was designed so that new (and temporary) features were easy
to hack in, at great expense to the program's ease of use.
this, the program is occasionally useful.