source: networking/netprogs/ntp.xml@ 3d8d0049

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4 <!ENTITY % general-entities SYSTEM "../../general.ent">
5 %general-entities;
6
7 <!ENTITY ntp-download-http "https://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-&ntp-version;.tar.gz">
8 <!ENTITY ntp-download-ftp " ">
9 <!ENTITY ntp-md5sum "e1e6b23d2fc75cced41801dbcd6c2561">
10 <!ENTITY ntp-size "6.7 MB">
11 <!ENTITY ntp-buildsize "108 MB (with tests)">
12 <!ENTITY ntp-time "0.4 SBU (Using parallelism=4; with tests)">
13]>
14
15<sect1 id="ntp" xreflabel="ntp-&ntp-version;">
16 <?dbhtml filename="ntp.html"?>
17
18 <sect1info>
19 <date>$Date$</date>
20 </sect1info>
21
22 <title>ntp-&ntp-version;</title>
23
24 <indexterm zone="ntp">
25 <primary sortas="a-ntp">ntp</primary>
26 </indexterm>
27
28 <sect2 role="package">
29 <title>Introduction to ntp</title>
30
31 <para>
32 The <application>ntp</application> package contains a client and server
33 to keep the time synchronized between various computers over
34 a network. This package is the official reference implementation of the
35 NTP protocol.
36 </para>
37
38 &lfs110a_checked;
39
40 <bridgehead renderas="sect3">Package Information</bridgehead>
41 <itemizedlist spacing="compact">
42 <listitem>
43 <para>
44 Download (HTTP): <ulink url="&ntp-download-http;"/>
45 </para>
46 </listitem>
47 <listitem>
48 <para>
49 Download (FTP): <ulink url="&ntp-download-ftp;"/>
50 </para>
51 </listitem>
52 <listitem>
53 <para>
54 Download MD5 sum: &ntp-md5sum;
55 </para>
56 </listitem>
57 <listitem>
58 <para>
59 Download size: &ntp-size;
60 </para>
61 </listitem>
62 <listitem>
63 <para>
64 Estimated disk space required: &ntp-buildsize;
65 </para>
66 </listitem>
67 <listitem>
68 <para>
69 Estimated build time: &ntp-time;
70 </para>
71 </listitem>
72 </itemizedlist>
73
74 <bridgehead renderas="sect3">ntp Dependencies</bridgehead>
75
76 <bridgehead renderas="sect4">Required</bridgehead>
77 <para role="required">
78 <xref linkend="perl-io-socket-ssl"/>
79 </para>
80
81<!-- Tested 4.2.8p11 with neither wget nor lynx on system: Not required.
82 <bridgehead renderas="sect4">Recommended</bridgehead>
83 <para role="recommended">
84 <xref role="runtime" linkend="wget"/> (runtime, for
85 <command>update-leap</command>)
86<!- - The download code for update-leap uses the File::Fetch perl module,
87 which may use wget, or lynx, or some core perl modules, so maybe move
88 to optional - ->
89 </para>
90-->
91 <bridgehead renderas="sect4">Optional</bridgehead>
92 <para role="optional">
93 <xref linkend="libcap-pam"/>,
94 <xref linkend="libevent"/>,
95 <ulink url="http://www.thrysoee.dk/editline/">libedit</ulink>, and
96 <ulink url="https://www.gnu.org/software/autogen/">libopts from AutoGen</ulink>
97 </para>
98
99 <para condition="html" role="usernotes">User Notes:
100 <ulink url="&blfs-wiki;/ntp"/></para>
101
102 </sect2>
103
104 <sect2 role="installation">
105 <title>Installation of ntp</title>
106
107 <para>
108 There should be a dedicated user and group to take control
109 of the <command>ntpd</command> daemon after it is
110 started. Issue the following commands as the
111 <systemitem class="username">root</systemitem> user:
112 </para>
113
114<screen role="root"><userinput>groupadd -g 87 ntp &amp;&amp;
115useradd -c "Network Time Protocol" -d /var/lib/ntp -u 87 \
116 -g ntp -s /bin/false ntp</userinput></screen>
117
118<!-- At least one of the issues has been reported upstream. The next para
119 is valid for 4.8.2p10 -->
120 <para>
121 The <command>update-leap</command> command needs to be fixed in order
122 to run properly:
123 </para>
124
125<screen><userinput>sed -e 's/"(\\S+)"/"?([^\\s"]+)"?/' \
126 -i scripts/update-leap/update-leap.in</userinput></screen>
127
128 <para>
129 Now fix an issue introduced with glibc-2.34:
130 </para>
131
132<screen><userinput>sed -e 's/#ifndef __sun/#if !defined(__sun) \&amp;\&amp; !defined(__GLIBC__)/' \
133 -i libntp/work_thread.c</userinput></screen>
134
135 <para>
136 Install <application>ntp</application> by running
137 the following commands:
138 </para>
139
140<screen><userinput>./configure --prefix=/usr \
141 --bindir=/usr/sbin \
142 --sysconfdir=/etc \
143 --enable-linuxcaps \
144 --with-lineeditlibs=readline \
145 --docdir=/usr/share/doc/ntp-&ntp-version; &amp;&amp;
146make</userinput></screen>
147
148 <para>
149 To test the results, issue: <command>make check</command>.
150 </para>
151
152 <para>
153 Now, as the <systemitem class="username">root</systemitem> user:
154 </para>
155
156<screen role="root"><userinput>make install &amp;&amp;
157install -v -o ntp -g ntp -d /var/lib/ntp</userinput></screen>
158
159 </sect2>
160
161 <sect2 role="commands">
162 <title>Command Explanations</title>
163
164 <para>
165 <envar>CFLAGS="-O2 -g -fPIC"</envar>: This environment variable
166 is necessary to generate Position Independent Code needed for
167 use in the package libraries.
168 </para>
169
170 <para>
171 <parameter>--bindir=/usr/sbin</parameter>: This parameter places
172 the administrative programs in <filename
173 class="directory">/usr/sbin</filename>.
174 </para>
175
176 <para>
177 <parameter>--enable-linuxcaps</parameter>: ntpd is run as user
178 ntp, so use Linux capabilities for non-root clock control.
179 </para>
180
181 <para>
182 <parameter>--with-lineeditlibs=readline</parameter>: This switch
183 enables <application>Readline</application> support for
184 <command>ntpdc</command> and <command>ntpq</command> programs. If omitted,
185 <application>libedit</application> will be used if installed, otherwise no
186 readline capabilites will be compiled.
187 </para>
188
189 </sect2>
190
191 <sect2 role="configuration">
192 <title>Configuring ntp</title>
193
194 <sect3 id="ntp-config">
195 <title>Config Files</title>
196
197 <para>
198 <filename>/etc/ntp.conf</filename>
199 </para>
200
201 <indexterm zone="ntp ntp-config">
202 <primary sortas="e-etc-ntp.conf">/etc/ntp.conf</primary>
203 </indexterm>
204
205 </sect3>
206
207 <sect3>
208 <title>Configuration Information</title>
209
210 <para>
211 The following configuration file first defines various ntp
212 servers with open access from different continents. Second, it
213 creates a drift file where <command>ntpd</command> stores the
214 frequency offset and a pid file to store the
215 <command>ntpd</command> process ID. Third, it defines the location
216 for the leap-second definition file
217 <filename>/etc/ntp.leapseconds</filename>, that the
218 <command>update-leap</command> script checks and updates, when
219 necessary. This script can be run as a cron job and the
220 <application>ntp</application> developers recommend a frequency of
221 about three weeks for the updates. Since the documentation included
222 with the package is sparse, visit the ntp website at
223 <ulink url="http://www.ntp.org/"/> and
224 <ulink url="http://www.pool.ntp.org/"/> for more information.
225 </para>
226
227<screen role="root"><userinput>cat &gt; /etc/ntp.conf &lt;&lt; "EOF"
228<literal># Asia
229server 0.asia.pool.ntp.org
230
231# Australia
232server 0.oceania.pool.ntp.org
233
234# Europe
235server 0.europe.pool.ntp.org
236
237# North America
238server 0.north-america.pool.ntp.org
239
240# South America
241server 2.south-america.pool.ntp.org
242
243driftfile /var/lib/ntp/ntp.drift
244pidfile /run/ntpd.pid
245
246leapfile /var/lib/ntp/ntp.leapseconds</literal>
247EOF</userinput></screen>
248
249 <para>
250 You may wish to add a <quote>Security session</quote>. For
251 explanations, see <ulink url=
252 "https://www.eecis.udel.edu/~mills/ntp/html/accopt.html#restrict"/>.
253 </para>
254
255<screen role="root"><userinput>cat &gt;&gt; /etc/ntp.conf &lt;&lt; "EOF"
256<literal># Security session
257restrict default limited kod nomodify notrap nopeer noquery
258restrict -6 default limited kod nomodify notrap nopeer noquery
259
260restrict 127.0.0.1
261restrict ::1</literal>
262EOF</userinput></screen>
263
264 </sect3>
265
266 <sect3 id="ntp-init">
267 <title>Synchronizing the Time</title>
268
269 <para>
270 There are two options. Option one is to run <command>ntpd</command>
271 continuously and allow it to synchronize the time in a gradual manner.
272 The other option is to run <command>ntpd</command> periodically (using
273 cron) and update the time each time <command>ntpd</command> is
274 scheduled.
275 </para>
276
277 <para>
278 If you choose Option one, then install the
279 <phrase revision="sysv"><filename>/etc/rc.d/init.d/ntp</filename>
280 init script</phrase>
281 <phrase revision="systemd"><filename>ntpd.service</filename>
282 unit</phrase>
283 included in the
284 <xref linkend="bootscripts" revision="sysv"/>
285 <xref linkend="systemd-units" revision="systemd"/> package.
286 </para>
287
288 <indexterm zone="ntp ntp-init" revision="sysv">
289 <primary sortas="f-ntp">ntp</primary>
290 </indexterm>
291
292 <indexterm zone="ntp ntp-init" revision="systemd">
293 <primary sortas="f-ntpd">ntpd.service</primary>
294 </indexterm>
295
296<screen role="root"><userinput>make install-ntpd</userinput></screen>
297
298 <para>
299 If you prefer to run <command>ntpd</command> periodically, add the
300 following command to <systemitem class="username">root</systemitem>'s
301 <filename>crontab</filename>:
302 </para>
303
304<screen><literal>ntpd -q</literal></screen>
305
306 <para revision="sysv">
307 Execute the following command if you would like to set the hardware
308 clock to the current system time at shutdown and reboot:
309 </para>
310
311<screen role="root" revision="sysv"><userinput>ln -v -sf ../init.d/setclock /etc/rc.d/rc0.d/K46setclock &amp;&amp;
312ln -v -sf ../init.d/setclock /etc/rc.d/rc6.d/K46setclock</userinput></screen>
313
314 <para revision="sysv">
315 The other way around is already set up by LFS.
316 </para>
317
318 </sect3>
319
320 </sect2>
321
322 <sect2 role="content">
323 <title>Contents</title>
324
325 <segmentedlist>
326 <segtitle>Installed Programs</segtitle>
327 <segtitle>Installed Libraries</segtitle>
328 <segtitle>Installed Directories</segtitle>
329
330 <seglistitem>
331 <seg>calc_tickadj, ntp-keygen, ntp-wait, ntpd, ntpdate, ntpdc, ntpq,
332 ntptime, ntptrace, sntp, tickadj and update-leap</seg>
333 <seg>None</seg>
334 <seg>/usr/share/ntp,
335 /usr/share/doc/ntp-4.2.8 and
336 /var/lib/ntp</seg>
337 </seglistitem>
338 </segmentedlist>
339
340 <variablelist>
341 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
342 <?dbfo list-presentation="list"?>
343 <?dbhtml list-presentation="table"?>
344
345 <varlistentry id="calc_tickadj">
346 <term><command>calc_tickadj</command></term>
347 <listitem>
348 <para>
349 calculates optimal value for tick given ntp drift file
350 </para>
351 <indexterm zone="ntp calc_tickadj">
352 <primary sortas="b-calc_tickadj">calc_tickadj</primary>
353 </indexterm>
354 </listitem>
355 </varlistentry>
356
357 <varlistentry id="ntp-keygen">
358 <term><command>ntp-keygen</command></term>
359 <listitem>
360 <para>
361 generates cryptographic data files used by the NTPv4 authentication
362 and identification schemes
363 </para>
364 <indexterm zone="ntp ntp-keygen">
365 <primary sortas="b-ntp-keygen">ntp-keygen</primary>
366 </indexterm>
367 </listitem>
368 </varlistentry>
369
370 <varlistentry id="ntp-wait">
371 <term><command>ntp-wait</command></term>
372 <listitem>
373 <para>
374 is useful at boot time, to delay the boot sequence until
375 <command>ntpd</command> has set the time
376 </para>
377 <indexterm zone="ntp ntp-wait">
378 <primary sortas="b-ntp-wait">ntp-wait</primary>
379 </indexterm>
380 </listitem>
381 </varlistentry>
382
383 <varlistentry id="ntpd">
384 <term><command>ntpd</command></term>
385 <listitem>
386 <para>
387 is a ntp daemon that runs in the background and keeps
388 the date and time synchronized based on response from configured
389 ntp servers. It also functions as a ntp server
390 </para>
391 <indexterm zone="ntp ntpd">
392 <primary sortas="b-ntpd">ntpd</primary>
393 </indexterm>
394 </listitem>
395 </varlistentry>
396
397 <varlistentry id="ntpdate">
398 <term><command>ntpdate</command></term>
399 <listitem>
400 <para>
401 is a client program that sets the date and time based on
402 the response from an ntp server. This command is deprecated
403 </para>
404 <indexterm zone="ntp ntpdate">
405 <primary sortas="b-ntpdate">ntpdate</primary>
406 </indexterm>
407 </listitem>
408 </varlistentry>
409
410 <varlistentry id="ntpdc">
411 <term><command>ntpdc</command></term>
412 <listitem>
413 <para>
414 is used to query the ntp daemon about its current state
415 and to request changes in that state
416 </para>
417 <indexterm zone="ntp ntpdc">
418 <primary sortas="b-ntpdc">ntpdc</primary>
419 </indexterm>
420 </listitem>
421 </varlistentry>
422
423 <varlistentry id="ntpq">
424 <term><command>ntpq</command></term>
425 <listitem>
426 <para>
427 is a utility program used to monitor <command>ntpd</command>
428 operations and determine performance
429 </para>
430 <indexterm zone="ntp ntpq">
431 <primary sortas="b-ntpq">ntpq</primary>
432 </indexterm>
433 </listitem>
434 </varlistentry>
435
436 <varlistentry id="ntptime">
437 <term><command>ntptime</command></term>
438 <listitem>
439 <para>
440 reads and displays time-related kernel variables
441 </para>
442 <indexterm zone="ntp ntptime">
443 <primary sortas="b-ntptime">ntptime</primary>
444 </indexterm>
445 </listitem>
446 </varlistentry>
447
448 <varlistentry id="ntptrace">
449 <term><command>ntptrace</command></term>
450 <listitem>
451 <para>
452 traces a chain of ntp servers back to the primary source
453 </para>
454 <indexterm zone="ntp ntptrace">
455 <primary sortas="b-ntptrace">ntptrace</primary>
456 </indexterm>
457 </listitem>
458 </varlistentry>
459
460 <varlistentry id="sntp">
461 <term><command>sntp</command></term>
462 <listitem>
463 <para>
464 is a Simple Network Time Protocol (SNTP) client
465 </para>
466 <indexterm zone="ntp sntp">
467 <primary sortas="b-sntp">sntp</primary>
468 </indexterm>
469 </listitem>
470 </varlistentry>
471
472 <varlistentry id="tickadj">
473 <term><command>tickadj</command></term>
474 <listitem>
475 <para>
476 reads, and optionally modifies, several timekeeping-related
477 variables in older kernels that do not have support for precision
478 timekeeping
479 </para>
480 <indexterm zone="ntp tickadj">
481 <primary sortas="b-tickadj">tickadj</primary>
482 </indexterm>
483 </listitem>
484 </varlistentry>
485
486 <varlistentry id="update-leap">
487 <term><command>update-leap</command></term>
488 <listitem>
489 <para>
490 is a script to verify and, if necessary, update the leap-second
491 definition file
492 </para>
493 <indexterm zone="ntp update-leap">
494 <primary sortas="b-update-leap">update-leap</primary>
495 </indexterm>
496 </listitem>
497 </varlistentry>
498
499 </variablelist>
500
501 </sect2>
502
503</sect1>
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