freebsd/usr.sbin/ntp/doc/ntpdc.8

.\"
.\" $FreeBSD$
.\"
.Dd January 7, 2000
.Dt NTPDC 8
.Os
.Sh NAME
.Nm ntpdc
.Nd special NTP query program
.Sh SYNOPSIS
.Nm ntpdc
.Op Fl ilnps
.Op Fl c Ar command
.Op Ar host ...
.Sh DESCRIPTION
.Nm
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 arguments.
Extensive state and statistics information is
available through the
.Nm
interface.
In addition, nearly all the configuration options which can
be specified at start up using
.Xr ntpd 8 Ns 's
configuration file may also be specified at run time using
.Nm Ns .
.Pp
If one or more request options is included on the command line when
.Nm
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
.Dq localhost
by default.
If no request options are given,
.Nm
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
.Dq localhost
when no other host is specified.
.Nm
will prompt for commands if the standard input is a terminal device.
.Pp
.Nm
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.
.Nm
makes no attempt to retransmit requests, and will time requests out if
the remote host is not heard from within a suitable timeout time.
.Pp
The operation of
.Nm
is 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
.Nm
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.
.Pp
Specifying a command line option other than
.Fl i
or
.Fl n
will cause the specified query (queries)
to be sent to the indicated host(s) immediately.
Otherwise,
.Nm
will attempt to read interactive format commands from the standard
input.
The following options are available:
.Bl -tag -width indent
.It Fl c Ar command
The
.Ar command
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
.Fl c
options may be given.
.It Fl i
Force
.Nm
to operate in interactive mode.
Prompts 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).
This switch is equivalent to
.Dq Li -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
.Dq Li -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
switch.
This is equivalent to
.Dq Li -c dmpeers .
.El
.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
.Qq > ,
followed by a
file name, to the command line.
.Pp
A number of interactive format commands are executed entirely within the
.Nm
program itself and do not result in
NTP mode 7 requests being sent to a server.
These are described following:
.Bl -tag -width indent
.It Ic ? Op Ar command_keyword
.It Ic help Op Ar command_keyword
A
.Ic ?
by itself will print a list of all the command keywords
known to this incarnation of
.Nm Ns .
A
.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
.Nm
than this manual page.
.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.
The
.Ar hostname
supplied
may be either a host name or a numeric
address.
.It Ic hostnames Ar yes | Ar no
If
.Ar yes
is specified, host names are printed in information
displays.
If
.Ar no
is given, numeric addresses are printed
instead.
The default is
.Ar yes
unless modified using the command line
.Fl n
switch.
.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 purpose.
.It Ic quit
Exit
.Nm Ns .
.It Ic 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.
.It Ic timeout Ar milliseconds
Specify a timeout period for responses to server queries.
The default
is about 5000 milliseconds.
Note that since
.Nm
retries each query once after a timeout, the total waiting time for a
timeout will be twice the timeout value set.
.El
.Ss Control Message Commands
Query commands result in
NTP mode 7 packets containing requests for
information being sent to the server.
These are
.Qq read-only
commands in that they make no modification of the server configuration
state.
.Bl -tag -width indent
.It Ic listpeers
Obtain and print 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.
.It Ic peers
Obtain 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
.Qq +
denotes symmetric
active, a
.Qq -
indicates symmetric passive, a
.Qq =
means
the remote server is being polled in client mode, a
.Qq ^
indicates that the server is broadcasting to this address, a
.Qq ~
denotes that the remote peer is sending broadcasts and a
.Qq *
marks the peer the server is currently synchronizing to.
.Pp
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
.Dq Li REFCLK(<implementation number>, <parameter>) .
On hostnames no
only IP addresses will be displayed.
.It Ic dmpeers
A slightly different peer summary list.
Identical to the output of the
.Em 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
.Qq \&.
indicates that this peer was cast off
in the falseticker detection, while a
.Qq +
indicates that the
peer made it through.
A
.Qq *
denotes the peer the server is
currently synchronizing with.
.It Xo Ic showpeer
.Ar peer_address
.Op Ar ...
.Xc
Show 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 Xo Ic pstats
.Ar peer_address
.Op Ar ...
.Xc
Show per-peer statistic counters associated with the specified peer(s).
.It Xo Ic clockinfo
.Ar clock_peer_address
.Op Ar ...
.Xc
Obtain and print information concerning a peer clock.
The 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 Ar oneline | Ar 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
.Qq offset
is the last offset given to the loop filter by the
packet processing code.
The
.Qq frequency
is the frequency error
of the local clock in parts-per-million (ppm).
The
.Qq time_const
controls the
.Qq stiffness
of the phase-lock loop and thus the speed at
which it can adapt to oscillator drift.
The
.Qq watchdog timer
value is the number of seconds which have elapsed since the last sample
offset was given to the loop filter.
The
.Ar oneline
and
.Ar multiline
options specify the format in which this information
is to be printed, with
.Ar multiline
as the default.
.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.
The
.Qq system flags
show various system flags, some of which can be set and cleared by the
.Ic enable
and
.Ic disable
configuration commands,
respectively.
These are the auth, bclient, monitor, pll, pps and stats flags,
as described below under the
.Ic enable
command in the
.Sx Runtime Configuration Requests
section.
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.
.Pp
The
.Qq 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
.Qq tick
may be incorrect.
.Pp
The
.Qq broadcastdelay
shows the default broadcast delay, as set by
the
.Qq broadcastdelay
configuration option, while the
.Qq authdelay
shows the default authentication delay, as set by
the
.Qq authdelay
configuration option.
.It Ic sysstats
Print statistics counters maintained in the protocol module.
.It Ic memstats
Print statistics counters related to memory allocation
code.
.It Ic iostats
Print statistics counters maintained in the input-output module.
.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 specified.
.It Xo Ic clkbug
.Ar clock_peer_address
.Op Ar ...
.Xc
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.
.El
.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 key).
The key number and the
corresponding key must also be made known to
.Nm Ns .
This can be done using the
.Ic keyid
and
.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.
.Pp
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.
.Pp
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 Ar prefer
.Xc
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.
If the value is 0 (or not given) no authentication will
be done.
The
.Ar version
can be 1, 2 or 3 and defaults to 3.
The
.Ar 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.
.It Xo Ic addserver
.Ar peer_address
.Op Ar keyid
.Op Ar version
.Op Ar prefer
.Xc
Identical to the
.Ic addpeer
command, except that the operating mode is client.
.It Xo Ic broadcast
.Ar peer_address
.Op Ar keyid
.Op Ar version
.Xc
Identical to the
.Ic addpeer
command, except that the operating mode is broadcast.
In this case a valid key identifier and key are required.
The
.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 required.
.It Xo Ic unconfig
.Ar peer_address
.Op Ar ...
.Xc
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 Ar time1
.Op Ar time2
.Op Ar stratum
.Op Ar refid
.Xc
This command provides a way to set certain data for a reference clock.
See the source listing for further information.
.It Xo Ic enable
.Ar flag
.Op Ar ...
.Xc
.It Xo Ic disable
.Ar flag
.Op Ar ...
.Xc
These commands operate in the same way as the
.Qq enable
and
.Qq disable
configuration file commands of
.Xr ntpd 8 .
Following is a description of the flags.
Note that only the auth, bclient, monitor, pll, pps and stats flags
can be set by
.Nm Ns ;
the pll_kernel and pps_kernel flags are read-only.
.Bl -tag -width indent
.It 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 bclient
Enables the server
to listen for a message from a broadcast or multicast server,
as in the
.Qq mutlicastclient
configuration option with default address.
The default for this flag is disable.
.It monitor
Enables the monitoring facility for the
.Ic monlist
command.
The default for this flag is enable.
.It 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
.Qo
Reference Clock Drivers
.Qc
page
(available as part of the HTML documentation
provided in
.Pa /usr/share/doc/ntp )
for further information.
The default for this flag is enable.
.It pps
Enables the pulse-per-second (PPS) signal
when frequency and time is disciplined
by the precision time kernel modifications.
See the
.Qo
A Kernel Model for Precision Timekeeping
.Qc
page
for further information.
The default for this flag is disable.
.It stats
Enables the statistics facility.
See the
.Qq Monitoring Support
section of the
.Xr ntp.conf 5
page
for further information.
The default for this flag is enable.
.It 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 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 pll_kernel flag.
.El
.It Xo Ic restrict
.Ar address
.Ar mask
.Ar flag
.Op Ar flag
.Xc
This command operates in the same was as the
.Qq restrict
configuration option of
.Xr ntpd 8 .
.It Xo Ic unrestrict
.Ar address
.Ar mask
.Ar flag
.Op Ar flag
.Xc
Unrestrict the matching entry from the restrict list.
.It Xo Ic delrestrict
.Ar address
.Ar mask
.Op Ar ntpport
.Xc
Delete the matching entry from the restrict list.
.It Ic readkeys
Cause 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).
This allows encryption keys to be changed without
restarting the server.
.It Xo Ic trustkey
.Ar keyid
.Op Ar ...
.Xc
.It Xo Ic untrustkey
.Ar keyid
.Op Ar ...
.Xc
These commands operate in the same way as the
.Qq trustedkey
and
.Qq untrustkey
configuration options 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
.Xc
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
.Xc
Clear a trap for asynchronous messages.
See the source listing for further information.
.It reset Ar counter Op Ar ...
Clear the statistics counters in various modules of the server.
See the source listing for further information.
.El
.Sh SEE ALSO
.Xr ntp.conf 5 ,
.Xr ntpd 8
.Rs
.%A David L. Mills
.%T Network Time Protocol (Version 3)
.%O RFC1305
.Re
.Sh HISTORY
Written by
.An Dennis Ferguson
at the University of Toronto.
.Sh BUGS
.Nm
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.