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Index for Section 8 |
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Alphabetical listing for N |
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ntpdc(8)
NAME
ntpdc - monitor operation of the NTP daemon, ntpd
SYNOPSIS
/usr/bin/ntpdc [ -n ][ -v ] host1 | IPaddress1 ...
DESCRIPTION
The ntpdc command may be retired is a future release; use the xntpdc(8)
command instead.
The ntpdc command sends a query to the ntpd daemon running on each of the
hosts listed on the command line. The ntpd daemon on each responding host
sends information about the current calculated offset between its time and
the time of each of its NTP servers or peers. The ntpdc command formats
the information on the standard output.
The ntpdc program cannot be used to monitor the xntpd daemon. To monitor
the xntpd daemon, use either ntpq or xntpdc.
Note
You can specify hosts by either host name or Internet address. The hosts
that you specify must either exist in the /etc/hosts file, or in the master
hosts database, if the database is being served to your system by BIND or
Network Information Services (NIS).
The ntpdc command by default generates a terse, table-style report. If you
specify the -v option, the ntpdc command generates a verbose report.
FLAGS
-n Prints Internet addresses, instead of host names, of the servers or
peers. By default, the Internet addresses of the responding hosts and
the names of their servers or peers are printed.
-v Prints a verbose report for each of the servers or peers of the
responding host.
EXAMPLES
Terse Report:
The following is a typical terse report generated in response to the
command:
% /usr/bin/ntpdc 555.5.55.55
The host 555.5.55.55 is an NTP client, with the servers server1, server2,
and server3 specified in its /etc/ntp.conf file. The information returned
is about server1, server2, and server3.
Address Strat Poll Reach Delay Offset Disp
(rem) (lcl)
.server1 555.5.55.55 1 64 377 53.0 -65.0 5.0
*server2 555.5.55.55 1 256 377 155.0 -4.0 16.0
+server3 555.5.55.55 2 64 377 16.0 -61.0 3.0
The fields are interpreted as follows:
- , + , . or *
A minus sign (-), plus sign (+), or dot (.) indicates a pre-configured
peer (see the ntp.conf(4) reference page). The asterisk (*) indicates
which pre-configured peer (if any) is currently being used for
synchronization.
(rem)
The remote host name or Internet address of a peer or server of the
responding host.
(lcl)
The Internet address of the responding host that was specified on the
ntpdc command line.
Strat
The current operating stratum level of the peer or server. Since the
NTP hierarchy can change dynamically the stratum levels may change.
Lower stratum levels correspond to fewer hops to an accurate time
source, and do not necessarily correspond to higher accuracy.
Poll Current polling interval in seconds for this peer or server. Polling
intervals change dynamically.
Reach
Reachability in response to the last 8 polls (value of 8-bit shift
register). A value of 0377 indicates the remote system responded to
the last 8 polls.
Delay
The estimated round-trip delay in milliseconds for NTP message
exchanges between the responding host and this peer or server. Delay
is calculated from the previous 8 polls.
Offset
The estimated offset between the peer or server's time and the
responding host's time in milliseconds. This value is calculated from
the previous 8 polls.
Disp The current estimated value of dispersion in milliseconds for this
peer's offset/delay pair.
Dispersion is used by the ntpd daemon in the clock selection
algorithm. Increasing values of dispersion are associated with
decreasing quality of the estimate.
Verbose Report:
When the -v option is given, a verbose report for each of the servers or
peers of each of the hosts specified on the command line is generated.
The following is a typical verbose report generated in response to the
following command line:
% /usr/bin/ntpdc -v 111.11.111.11
Neighbor address 555.55.5.55 port:123 local address 111.11.1.11
Reach: 0377 stratum: 2, precision: -7
dispersion: 2.000000, flags: 1301, leap: 0
Reference clock ID: [22.22.2.22] timestamp: 7e5aa1a9.2add5d0b
hpoll: 10, ppoll: 10, timer: 1024, sent: 85 received: 90
Delay(ms) 20.00 20.00 28.00 29.00 20.00 39.00 29.00 28.00
Offset(ms) 5.00 6.00 5.00 -1.00 -2.00 0.00 3.00 5.00
delay: 20.000000 offset: 5.000000 dsp 2.000000
--------------------------------------------------------------------
The fields are interpreted as follows:
Neighbor address
The address and port number of one NTP server, followed by the
Internet address of the responding host (local address).
Reach:
Reachability in response to the last 8 polls (value of 8-bit shift
register). A value of 0377 indicates the remote system responded to
the last 8 polls.
stratum:
The current operating stratum level of the peer or server. Since the
NTP hierarchy can change dynamically the stratum levels may change.
Lower stratum levels correspond to fewer hops to an accurate time
source, and do not necessarily correspond to higher accuracy.
precision:
The precision of this clock, given in seconds as a power of 2. If
precision is equal to -7, that means that the precision is 2**-7, or
1/128 seconds. The ntpd daemon automatically determines the precision
of each clock based on the kernel variable HZ.
disp:
The current estimated value of dispersion in milliseconds for this
peer's offset/delay pair. Dispersion is used by the ntpd daemon in
the clock selection algorithm. Increasing values of dispersion are
associated with decreasing quality of the estimate.
flags: nn
The flags parameter is used by the ntpd daemon clock selection
process.
leap: flag
The leap second indicator. Non-zero if there is to be a leap second
inserted in the NTP timescale. The bits are set before 23:59 on the
day of insertion and reset after 00:00 on the following day.
Reference clock ID: address
If the NTP server is synchronized by a radio/satellite timecode
receiver, this field is WWV, WWVB, or GOES. If the NTP server is the
local reference clock, this field is LOCL. Finally, this field can be
the [internet_address] of the most accurate NTP server currently
serving the responding host.
timestamp: nn
The local time, in hex-timestamp format, when the local clock of the
server was last updated.
hpoll: n
The host poll interval which is the maximum interval between messages
transmitted to the server, in seconds as a power of 2. For example, a
value of 6 indicates an interval of 64 seconds.
ppoll: n
The peer poll interval which is the maximum interval between messages
sent by the server, in seconds as a power of 2. For example, a value
of 6 indicates an interval of 64 seconds.
timer: nn
The current poll rate in seconds.
sent: nn
The number of NTP packets sent to this server by the responding host.
received: nn
The number of NTP packets received from this server by the responding
host.
Delay and Offset
The round-trip delay and estimated clock offset for the last eight NTP
packet exchanges. If there are fewer than eight valid samples, the
delay field will be zero.
delay: est-delay offset: est-offset dsp: n
Estimated delay, offset, and dispersion calculated from the above 8
samples. See RFC 1129 for how to calculate the estimated delay,
offset, and dispersion.
ERRORS
host1: connection refused
Check whether the ntpd daemon is running on host1.
host2: unknown
The ntpdc command cannot resolve the host name host2. Check that host2
exists in the /etc/hosts file, or that it exists in the master hosts
database, if the database is being served by BIND or NIS.
If a server is listed in the host's /etc/ntp.conf file, but does not appear
in the ntpdc report, it is possible that the ntpd daemon on the responding
host can not resolve the server names in the /etc/ntp.conf file. Check
that the server exists in the responding host's /etc/hosts file or in the
master hosts database, if the database is being served to the responding
host by BIND or NIS.
RELATED INFORMATION
ntp(1), ntp.conf(4), ntpq(8), ntpsetup(8), xntpdc(8), xntpd(8)
RFC 1129-Internet Time Synchronization: the Network Time Protocol
Network Administration
Network and Communications Overview