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Command: ntp | Section: 1 | Source: Digital UNIX | File: ntp.1.gz
ntp(1) General Commands Manual ntp(1)
NAME
ntp - query a clock running a Network Time Protocol daemon, either ntpd
or xntpd
SYNOPSIS
/usr/bin/ntp [ -v ][ -s ][ -f ] host1 | IPaddress1 ...
DESCRIPTION
The ntp command may be retired in a future release; use the ntpdate(8)
command instead.
The ntp command is used to determine the offset between the local clock
and a remote clock. It can also be used to set the local host's time
to a remote host's time. The ntp command sends an NTP packet to the
NTP daemon running on each of the remote hosts specified on the command
line. The remote hosts must be running either the ntpd daemon or xntpd
daemon. When the NTP daemon on the remote host receives the NTP
packet, it fills in the fields (as specified in RFC 1129), and sends
the packet back. The ntp command then formats and prints the results
on the standard output.
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 Service
(NIS).
The default output shows the roundtrip delay of the NTP packet in sec-
onds, the estimated offset between the local time and remote time in
seconds, and the date in ctime format. See the ctime(3) reference page
for more information.
The -s and -f options can be used to reset the time of the local clock.
FLAGS
-v Specifies verbose output. The output shows the full contents of
the received NTP packets, plus the calculated offset and delay.
-s Sets local clock to remote time. This only happens if the offset
between the local and remote time is less than 1000 seconds. The
local clock is not reset if the remote host is unsynchronized.
If you specify more than one host name on the command line, ntp
queries each host in order, waiting for each host to answer or
timeout before querying the next host. The local clock is set to
the time of the first remote host that responds.
-f Forces setting local clock regardless of offset. The -f option
must be used with -s option. The local clock is not reset if the
remote host is unsynchronized.
RESTRICTIONS
Using the -s and -f options require that you be logged on as superuser.
EXAMPLES
The following is the default output to an ntp query about a remote host
with an internet address of 555.5.55.5: # /usr/bin/ntp 555.5.55.5
555.5.55.5: delay:1.845207 offset:-0.358460 Mon Aug 20 08:05:44 1991
The following is the verbose output to an ntp query about the same re-
mote host: # /usr/bin/ntp -v 555.5.55.5
Packet from: [555.5.55.5] Leap 0, version 1, mode Server, poll 6, pre-
cision -10 stratum 1 (WWVB) Synch Distance is 0000.1999 0.099991 Synch
Dispersion is 0000.0000 0.000000 Reference Timestamp is
a7bea6c3.88b40000 Tue Aug 20 14:06:43 1991 Originate Timestamp is
a7bea6d7.d7e6e652 Tue Aug 20 14:07:03 1991 Receive Timestamp is
a7bea6d7.cf1a0000 Tue Aug 20 14:07:03 1991 Transmit Timestamp is
a7bea6d8.0ccc0000 Tue Aug 20 14:07:04 1991 Input Timestamp is
a7bea6d8.1a77e5ea Tue Aug 20 14:07:04 1991 555.5.55.5: delay:0.019028
offset:-0.043890 Tue Aug 20 14:07:04 1991
The fields are interpreted as follows:
Packet from: [internet address]
The address of the remote host from which this NTP packet was re-
ceived.
Leap n
The leap second indicator. Non-zero if there is to be a leap sec-
ond 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.
version n
The NTP protocol version.
mode type
The NTP mode can be Server, Client, Symmetric Passive, Symmetric
Active, or Broadcast. See RFC 1129 for more information on NTP
modes.
Poll x
The desired poll rate of the peer in seconds as a power of 2. For
example, if poll is equal to 6, that means that the poll rate is
one message exchanged every 2**6 seconds.
Precision x
The precision of the remote host's clock in seconds as a power of
2. For example, if precision is equal to -10, that means that the
precision is 2**-10. The NTP daemon sets this automatically.
Stratum n (source)
The stratum of the clock in the NTP hierarchy, along with the
source of the clock. The source is either the name of a reference
standard (such as WWVB or GOES), or the Internet address of the
clock that this clock references.
Synch Distance is nn.nn nn.nn
The values reported are used internally by the NTP daemon.
Synch Dispersion is nn.nn nn.nn
The values reported are used internally by the NTP daemon.
The next five timestamps are given as NTP fixed-point values, in both
hexadecimal and ctime. The timestamps are set either by this NTP
process, or by the remote host you are querying. These timestamps are
used by the local host to calculate delay and offset for this query.
Reference Timestamp is hex-timestamp ctime_string
This specifies the last time the remote host clock was adjusted.
(remote time)
Originate Timestamp is hex-timestamp ctime_string
This specifies when the NTP request was transmitted by the local
host to the remote host. (local time)
Receive Timestamp is hex-timestamp ctime_string
This specifies when the NTP request was received at the remote
host. (remote time)
Transmit Timestamp is hex-timestamp ctime_string
This specifies when the NTP response was transmitted by the re-
mote host. (remote time)
Input Timestamp is hex-timestamp ctime_string
This specifies when the NTP response was received by the local
host. (local time)
hostname: delay:time offset:time
This field summarizes the results of the query, giving the host
name or internet address of the responding clock specified in the
command line, the round-trip delay in seconds, and the offset be-
tween the two clocks in seconds (assuming symmetric round-trip
times).
ERRORS
The following error messages can be returned by NTP:
*Timeout*
hostname is not responding
May indicate that the NTP daemon is not running on
the remote host.
No such host: hostname
The NTP command cannot resolve the specified host
name in the /etc/hosts file. Check that the host
exists in the /etc/hosts file, or that it exists in
the master hosts database, if the database is being
served to your system by BIND or NIS.
RELATED INFORMATION
ctime(3), ntp.conf(4), ntpdate, ntpdc(8), xntpd(8), xntpdc(8), ntpq(8)
Internet time synchronization: The Network Time Protocol (RFC 1129)
Network Administration delim off
ntp(1)