ntp(1)ntp(1)NAMEntp - query a clock running a Network Time Protocol daemon, either ntpd
or xntpd
SYNOPSIS
/usr/bin/ntp [-v] [-s] [-f] host1 | IPaddress1 ...
OPTIONS
Specifies verbose output. The output shows the full contents of the
received NTP packets, plus the calculated offset and delay. 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. Forces set‐
ting 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.
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 stan‐
dard 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 sys‐
tem 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.
RESTRICTIONS
Using the -s and -f options require that you be logged on as superuser.
ERRORS
The following error messages can be returned by NTP: May indicate that
the NTP daemon is not running on the remote host. The NTP command can‐
not 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.
EXAMPLES
In the following examples, some output text lines may be broken. The
line end are marked with the backslash symbol (\) and the following
line is indented. Such text may appear as a single line on your termi‐
nal. 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 remote 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 Dis‐
persion 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: The address of the remote
host from which this NTP packet was received. 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. The NTP
protocol version. The NTP mode can be Server, Client, Symmetric
Passive, Symmetric Active, or Broadcast. See RFC 1129 for more
information on NTP modes. 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. The precision of the remote host's clock in sec‐
onds 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. The stratum of the clock in the NTP hierar‐
chy, 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. The
values reported are used internally by the NTP daemon. The val‐
ues 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. This specifies the last time the remote
host clock was adjusted. (remote time) This specifies when the
NTP request was transmitted by the local host to the remote
host. (local time) This specifies when the NTP request was
received at the remote host. (remote time) This specifies when
the NTP response was transmitted by the remote host. (remote
time) This specifies when the NTP response was received by the
local host. (local 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 between the two clocks in sec‐
onds (assuming symmetric round-trip times).
SEE ALSOctime(3), ntp.conf(4), ntpdate(8), xntpd(8), xntpdc(8), ntpq(8)
Internet time synchronization: The Network Time Protocol (RFC 1129)
Network Administration: Services
ntp(1)
