1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
<HTML
><HEAD
><TITLE
>NTP - Network Time Protocol</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
REL="HOME"
TITLE="The Linux System Administrator's Guide"
HREF="index.html"><LINK
REL="UP"
TITLE="Keeping Time"
HREF="c2762.html"><LINK
REL="PREVIOUS"
TITLE="When the clock is wrong"
HREF="x2846.html"><LINK
REL="NEXT"
TITLE="Basic NTP configuration"
HREF="x2869.html"></HEAD
><BODY
CLASS="sect1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>The Linux System Administrator's Guide: </TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="x2846.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 13. Keeping Time</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x2869.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="AEN2859"
></A
>13.5. NTP - Network Time Protocol</H1
><P
> A networked computer (even if just over a modem) can
check its own clock automatically by comparing it to the time
on another computer known to keep accurate time. Network Time
Protocol (or NTP) does exactly that. It is a method of verifying
and correcting your computer's time by synchronizing it with a
another system. With NTP your system's time can be maintained
to within milliseconds of Coordinated Universal Time.
<A
NAME="AEN2862"
HREF="#FTN.AEN2862"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
>
</P
><P
> For more casual Linux users, this is just a nice luxury.
At my home all our clocks are set based upon what my Linux system
says the time is. For larger organizations this "luxury" can
become essential. Being able to search log files for events based
upon time can make life a lot easier and take a lot of the "guess work"
out of debugging.
</P
><P
> Another example of how important NTP can be is with a SAN.
Some SAN's require NTP be configured and running properly to allow
for proper synchronization over filesystem usage, and proper
timestamp control. Some SANs (and some applications) can become
confused when dealing with files that have timestamps that are in
the future.
</P
><P
> Most Linux distributions come with a NTP package of some kind,
either a .deb or .rpm package. You can use that to install NTP, or you
can download the source files from <A
HREF="http://www.ntp.org/downloads.html"
TARGET="_top"
> http://www.ntp.org/downloads.html</A
> and compile it yourself. Either way,
the basic configuration is the same.</P
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN2862"
HREF="x2859.html#AEN2862"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>Visit <A
HREF="http://www.time.gov/about.html/"
TARGET="_top"
> http://www.time.gov/about.html</A
> for more info.</P
></TD
></TR
></TABLE
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="x2846.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="x2869.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>When the clock is wrong</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c2762.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Basic NTP configuration</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
|
