ntp.1

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 1 代码 · 共 214 行

.TH ntp 1
.SH Name
ntp \- query a clock running the Network Time Protocol daemon, ntpd
.SH Syntax
.B /usr/etc/ntp 
[
.B \-v
][
.B \-s
][
.B \-f
]
.I host1 \fR|\fP IPaddress1 ...
.SH Description
.NXR "ntp command"
The 
.PN 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 
.PN ntp
command sends an NTP packet to the NTP daemon,
.PN ntpd ,
running on each of the remote hosts specified on the command line.  
The remote hosts must be running 
.PN ntpd .
When the 
.PN ntpd
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 
.PN ntp
command then formats and prints
the results on the standard output. 
.NT
You can specify hosts by either host name or Internet
address.  The hosts that you specify must either exist
in the
.PN /etc/hosts
file, or in the master
.PN hosts
database, if the database is being served to your
system by BIND/Hesiod or Yellow Pages.
.NE
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 
.PN ctime 
format.  See the 
.MS ctime 3
reference page for more information.
.PP
The
.PN \-s
and
.PN \-f
options can be used to reset the time of the local clock.  
Use
.PN ntp
with these options to initialize the system time prior to running the
.PN ntpd
daemon.  
.SH Options
.IP \-v 5
Specifies verbose output.  The output shows the full contents of the 
received NTP packets, plus the calculated offset and delay.
.IP \-s 5
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.  
.IP
If you specify more than one host name on the command line, 
.PN 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.
.IP \-f 5
Forces setting local clock regardless of offset.  The
.PN \-f 
option must be used with 
.PN \-s 
option.  The local clock is not reset if the remote
host is unsynchronized.
.SH Restrictions
Using the 
.PN \-s
and 
.PN \-f
options require that you be logged on as superuser.
.SH Examples
The following is the default output to an
.PN ntp
query about a remote host with an internet address of 555.5.55.5:
.NXR "ntp command" "sample output"
.EX
# \f(CB/usr/etc/ntp 555.5.55.5\f(CW

555.5.55.5: delay:1.845207 offset:-0.358460  Mon Mar 20 08:05:44 1989
.EE
.PP
The following is the verbose output to an 
.PN ntp 
query about the same remote host:
.EX
# \f(CB/usr/etc/ntp \-v 555.5.55.5\f(CW

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
.EE
.PP
The fields are interpreted as follows:
.IP "Packet from: [\fIinternet address\fP]" 5
The address of the remote host from which this NTP packet was received.
.IP "Leap \fIn\fP" 5
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.
.IP "version \fIn\fP"
The NTP protocol version.
.IP "mode \fItype\fP"
The NTP mode can be Server, Client, Symmetric Passive,
Symmetric Active, or Broadcast. See RFC 1129 for more information
on NTP modes.
.IP "Poll \fIx\fP" 5
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.
.IP "Precision \fIx\fP" 5
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 
.PN ntpd
daemon sets this automatically.
.IP "Stratum \fIn\fP (\fIsource\fP)" 5
The stratum of the clock in the NTP hierarchy, along with
the source of the clock.  The \fIsource\fP is either the name of a reference
standard (such as WWVB or GOES), or the Internet address of
the clock that this clock references.
.IP "Synch Distance is \fInn.nn nn.nn\fP" 5
The values reported are used internally by 
.PN ntpd .
.IP "Synch Dispersion is \fInn.nn nn.nn\fP" 5
The values reported are used internally by
.PN ntpd .
.PP
The next five timestamps are given as NTP fixed-point values, in
both hexadecimal and 
.PN 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.
.IP "Reference Timestamp is \fIhex-timestamp ctime_string\fP"
This specifies the last time the remote host clock was adjusted.
(remote time)
.IP "Originate Timestamp is \fIhex-timestamp ctime_string\fP"
This specifies when the NTP request was transmitted by the
local host to the remote host. (local time)
.IP "Receive Timestamp is \fIhex-timestamp ctime_string\fP"
This specifies when the NTP request was received at the remote
host.  (remote time)
.IP "Transmit Timestamp is \fIhex-timestamp ctime_string\fP"
This specifies when the NTP response was transmitted by the 
remote host.  (remote time)
.IP "Input Timestamp is \fIhex-timestamp ctime_string\fP" 5
This specifies when the NTP response was received by the local host.
(local time)
.IP "\fIhostname\fP: delay:\fItime\fP offset:\fItime\fP" 5
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).  
.SH Diagnostics
The following error messages can be returned by NTP:
.TP 20
\f(CW*Timeout*\fP
.TP 20
\fIhostname\fP \f(CWis not responding\fP
May indicate that the 
.PN ntpd
daemon is not running on the remote host.
.TP 20
\f(CWNo such host: \fIhostname\fP
The
.PN ntpd
daemon cannot resolve the specified host name
in the
.PN /etc/hosts
file.  Check that the host
exists in the
.PN /etc/hosts
file, or that it exists in the master
.PN hosts
database, if the database is being served to your system
by BIND/Hesiod or Yellow Pages.
.SH See Also
ctime(3), ntp.conf(5), ntpd(8), ntpdc(8)
.br
\fIRFC 1129\(emInternet time synchronization:  The Network Time Protocol\fP
.br
\fIGuide to System and Network Setup\fP
.br
\fIIntroduction to Networking and Distributed System Services\fP