Content-type: text/html Man page of ntp

ntp

Section: User Commands (1)
Index Return to Main Contents
 

NAME

ntp - 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 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.
 

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 seconds, 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 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.
 

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 remote host: # /usr/bin/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 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 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. 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. The values reported are used internally by the NTP daemon. 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. 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 seconds (assuming symmetric round-trip times).
 

SEE ALSO

ctime(3), ntp.conf(4), ntpdate(8), ntpdc(8), xntpd(8), xntpdc(8), ntpq(8)

Internet time synchronization: The Network Time Protocol (RFC 1129)

Network Administration


 

Index

NAME
SYNOPSIS
OPTIONS
DESCRIPTION
RESTRICTIONS
ERRORS
EXAMPLES
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 02:42:56 GMT, October 02, 2010