ntp(1) CLIX ntp(1)
NAME
ntp - Queries a Network Time Protocol (NTP) daemon
SYNOPSIS
ntp [-v] [-s] [-f] host ...
FLAGS
-v Displays verbose output, showing the full contents of received NTP
packets, plus calculated offset, displacement, and so on.
-s Sets the system time-of-day clock on the local host. The ntp command
uses the stime() function to set the clock. The clock is not changed
if the time offset is greater than 1000 seconds or if the clock on
the remote host is unsynchronized. You must be superuser to use this
flag.
-f Forces setting the system clock regardless of the offset. The -f
flag must be used with the -s flag. The clock is not changed if the
clock on the remote host is unsynchronized.
DESCRIPTION
The ntp command process is the Network Time Protocol (NTP) client. The
command sends a Network Time Protocol (NTP) packet to the NTP daemon
running on each of the specified hosts. The NTP daemon fills in fields of
the NTP packet as per RFC-1059 and sends the packet back. The ntp command
then formats and displays the results on stdout. A host can be specified
by its name or Internet address.
The default output shows the delay, offset, date, and time (in ctime
format) when the NTP daemon transmitted the packet.
Flags can reset the time of the local system clock.
NTP RESULTS
The default output for each host looks like the following:
128.8.10.1: delay:1.845207 offset:-0.358460 Mon Mar 20 08:05:44 1989
The verbose output for each host looks like the following:
Packet from: [128.8.10.1]
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
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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
umd1: delay:0.019028 offset:-0.043890 Tue Mar 7 14:07:04 1989
The various fields are interpreted as follows:
Packet from: address
The Internet address of the remote host the NTP daemon sending this
NTP packet resides on.
Leap n The leap second indicator. A value of 0 means there is no leap
second, 1 means a leap second is added to the last minute of the
current day, 2 means a leap second is subtracted from the last
minute of the current day, and 3 means the clock on the remote host
is unsynchronized.
version n
The version number of the NTP implementation on the remote host.
Currently, ntp exchanges NTP packets only with NTP daemons that
implement NTP version 1.
mode mode
The mode the remote NTP daemon is operating in toward the local
host.
poll exp
The minimum polling interval between messages sent by the peer,
specified in seconds as a power of two.
precision exp
The claimed precision of the clock, specified in seconds as a power
of two. For example, a clock derived from the power line frequency
(60 Hz) has a precision of 1/60 second (about 2^-6) and would be
indicated by a precision of -6.
stratum n (source)
The stratum of the clock in the NTP hierarchy, along with the
source of the clock, either the name of a reference standard (such
as WWVB or GOES) or the Internet address of the clock that
synchronized this clock.
The next two numbers are specified as 32-bit hexadecimal, fixed-point
values with a fraction point between bits 15 and 16, and as double values.
Synch Distance is fixed double
The estimated roundtrip delay to the primary synchronizing source,
in seconds.
Synch Dispersion is fixed double
The estimated dispersion to the primary synchronizing source, in
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ntp(1) CLIX ntp(1)
seconds.
The next five timestamps are specified as 64-bit hexadecimal, fixed-point
values with a fraction point between bits 31 and 32, and as a string in
ctime format. These timestamps are set either by this ntp command process
(local time), or by the remote NTP daemon (remote time).
Reference Timestamp is hex-timestamp ctime-string
The last time the clock on the remote host was adjusted (remote
time).
Originate Timestamp is hex-timestamp ctime-string
When the NTP request was transmitted by this ntp command process to
the NTP daemon (local time).
Receive Timestamp is hex-timestamp ctime-string
When the NTP request was received by the NTP daemon (remote time).
Transmit Timestamp is hex-timestamp ctime-string
When the NTP response was transmitted by the NTP daemon (remote
time).
Input Timestamp is hex-timestamp ctime-string
When the NTP response was received by this ntp command process
(local time).
hostname: delay:time offset:time ctime-string
The summary of the results of the query, giving the hostname of the
responding clock (from the command line), the round-trip delay in
seconds, the offset between the two clocks in seconds (assuming
symmetric roundtrip times), and a date and time value (in ctime
format) that is the delay value plus the transmit timestamp. The
delay and clock offset values are also calculated from the above
timestamps.
EXAMPLES
1. To display verbose output of the NTP packets sent from the hosts sam
and ss, enter:
ntp -v sam ss
2. To set the system time-of-day clock on the local host from the ntpd
daemon on host sam, enter:
ntp -s -f sam
The -f flag is used to change the clock regardless of the time offset.
FILES
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ntp(1) CLIX ntp(1)
/etc/resolv.conf
Domain Name System (DNS) client configuration file. DNS is the
preferred method for address resolution.
/etc/hosts
Configuration file mapping hostnames to Internet addresses.
DIAGNOSTICS
The ntp command displays the appropriate error message with the perror()
function. The condition where an error occurs is generally on connect,
read, and write operations.
EXIT VALUES
The ntp command exits with a value of 0 if successful. If unsuccessful,
it exits with a nonzero value.
RELATED INFORMATION
Commands: ntpd(8), ntpdc(1)
Functions: ctime(3), perror(3), stime(2)
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