ntp(1) General Commands Manual ntp(1)
Name
ntp - query a clock running the Network Time Protocol daemon, ntpd
Syntax
/usr/etc/ntp [ -v ][ -s ][ -f ] host1 | IPaddress1 ...
Description
The 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 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 When the 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 command then formats and prints the results on the standard output. You can specify hosts by
either host name or Internet address. The hosts that you specify must either exist in the file, or in the master database, if the database
is being served to your system by BIND/Hesiod or Yellow Pages. The default output shows the roundtrip delay of the NTP packet in seconds,
the estimated offset between the local time and remote time in seconds, and the date in format. See the reference page for more informa-
tion.
The and options can be used to reset the time of the local clock. Use with these options to initialize the system time prior to running
the daemon.
Options
-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, 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 option must be used with option. The local clock is not reset if the remote
host is unsynchronized.
Restrictions
Using the and options require that you be logged on as superuser.
Examples
The following is the default output to an query about a remote host with an internet address of 555.5.55.5:
# /usr/etc/ntp 555.5.55.5
555.5.55.5: delay:1.845207 offset:-0.358460 Mon Mar 20 08:05:44 1989
The following is the verbose output to an query about the same remote host:
# /usr/etc/ntp -v 555.5.55.5
Packet from: [555.5.55.5]
Leap 0, version 1, mode Server, poll 6, precision -10 stratum 1 (WWVB)
Synch Distance is 0000.1999 0.099991
Synch Dispersion is 0000.0000 0.000000
Reference Timestamp is a7bea6c3.88b40000 Tue Mar 7 14:06:43 1989
Originate Timestamp is a7bea6d7.d7e6e652 Tue Mar 7 14:07:03 1989
Receive Timestamp is a7bea6d7.cf1a0000 Tue Mar 7 14:07:03 1989
Transmit Timestamp is a7bea6d8.0ccc0000 Tue Mar 7 14:07:04 1989
Input Timestamp is a7bea6d8.1a77e5ea Tue Mar 7 14:07:04 1989
555.5.55.5: delay:0.019028 offset:-0.043890 Tue Mar 7 14:07:04 1989
The fields are interpreted as follows:
Packet from: [internet address]
The address of the remote host from which this NTP packet was received.
Leap n
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.
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 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 stan-
dard (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
Synch Dispersion is nn.nn nn.nn
The values reported are used internally by
The next five timestamps are given as NTP fixed-point values, in both hexadecimal and 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 remote 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 com-
mand line, the round-trip delay in seconds, and the offset between the two clocks in seconds (assuming symmetric round-trip times).
Diagnostics
The following error messages can be returned by NTP:
*Timeout*
hostname is not responding
May indicate that the daemon is not running on the remote host.
No such host: hostname
The daemon cannot resolve the specified host name in the file. Check that the host exists in the file, or that it
exists in the master database, if the database is being served to your system by BIND/Hesiod or Yellow Pages.
See Also
ctime(3), ntp.conf(5), ntpd(8), ntpdc(8)
RFC 1129--Internet time synchronization: The Network Time Protocol
Guide to System and Network Setup
Introduction to Networking and Distributed System Services
ntp(1)