source: chapter08/shadow.xml@ 6e18f2f

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Last change on this file since 6e18f2f was 3d92d63, checked in by Bruce Dubbs <bdubbs@…>, 4 years ago

Minor updates.

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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
8<sect1 id="ch-system-shadow" role="wrap">
9 <?dbhtml filename="shadow.html"?>
10
11 <sect1info condition="script">
12 <productname>shadow</productname>
13 <productnumber>&shadow-version;</productnumber>
14 <address>&shadow-url;</address>
15 </sect1info>
16
17 <title>Shadow-&shadow-version;</title>
18
19 <indexterm zone="ch-system-shadow">
20 <primary sortas="a-Shadow">Shadow</primary>
21 </indexterm>
22
23 <sect2 role="package">
24 <title/>
25
26 <para>The Shadow package contains programs for handling passwords in a secure
27 way.</para>
28
29 <segmentedlist>
30 <segtitle>&buildtime;</segtitle>
31 <segtitle>&diskspace;</segtitle>
32
33 <seglistitem>
34 <seg>&shadow-fin-sbu;</seg>
35 <seg>&shadow-fin-du;</seg>
36 </seglistitem>
37 </segmentedlist>
38
39 </sect2>
40
41 <sect2 role="installation">
42 <title>Installation of Shadow</title>
43
44 <note>
45 <para>If you would like to enforce the use of strong passwords, refer to
46 <ulink url="&blfs-book;postlfs/cracklib.html"/> for installing
47 CrackLib prior to building Shadow. Then add
48 <parameter>--with-libcrack</parameter> to the <command>configure</command>
49 command below.</para>
50 </note>
51
52 <para>Disable the installation of the <command>groups</command> program
53 and its man pages, as Coreutils provides a better version. Also,
54 prevent the installation of manual pages that were already installed in
55 <xref linkend="ch-system-man-pages"/>:</para>
56
57<screen><userinput remap="pre">sed -i 's/groups$(EXEEXT) //' src/Makefile.in
58find man -name Makefile.in -exec sed -i 's/groups\.1 / /' {} \;
59find man -name Makefile.in -exec sed -i 's/getspnam\.3 / /' {} \;
60find man -name Makefile.in -exec sed -i 's/passwd\.5 / /' {} \;</userinput></screen>
61
62 <para id="shadow-login_defs">Instead of using the default
63 <emphasis>crypt</emphasis> method, use the more secure
64 <emphasis>SHA-512</emphasis> method of password encryption, which also
65 allows passwords longer than 8 characters. It is also necessary to change
66 the obsolete <filename class="directory">/var/spool/mail</filename> location
67 for user mailboxes that Shadow uses by default to the <filename
68 class="directory">/var/mail</filename> location used currently:</para>
69
70<screen><userinput remap="pre">sed -e 's:#ENCRYPT_METHOD DES:ENCRYPT_METHOD SHA512:' \
71 -e 's:/var/spool/mail:/var/mail:' \
72 -i etc/login.defs</userinput></screen>
73
74 <note>
75 <para>If you chose to build Shadow with Cracklib support, run the following:</para>
76
77<screen role="nodump"><userinput>sed -i 's:DICTPATH.*:DICTPATH\t/lib/cracklib/pw_dict:' etc/login.defs</userinput></screen>
78 </note>
79
80 <para>Make a minor change to make the first group number generated
81 by useradd 1000:</para>
82
83<screen><userinput remap="pre">sed -i 's/1000/999/' etc/useradd</userinput></screen>
84
85 <para>Prepare Shadow for compilation:</para>
86
87<screen><userinput remap="configure">touch /usr/bin/passwd
88./configure --sysconfdir=/etc \
89 --with-group-name-max-length=32</userinput></screen>
90
91 <variablelist>
92 <title>The meaning of the configure option:</title>
93
94 <varlistentry>
95 <term><command>touch /usr/bin/passwd</command></term>
96 <listitem>
97 <para>The file <filename>/usr/bin/passwd</filename> needs
98 to exist because its location is harcoded in some programs, and
99 the default location if it does not exist is not right.</para>
100 </listitem>
101 </varlistentry>
102 <varlistentry>
103 <term><parameter>--with-group-name-max-length=32</parameter></term>
104 <listitem>
105 <para>The maximum user name is 32 characters. Make the maximum
106 group name the same.</para>
107 </listitem>
108 </varlistentry>
109
110 </variablelist>
111
112 <para>Compile the package:</para>
113
114<screen><userinput remap="make">make</userinput></screen>
115
116 <para>This package does not come with a test suite.</para>
117
118 <para>Install the package:</para>
119
120<screen><userinput remap="install">make install</userinput></screen>
121 <!--
122 <para>Move a misplaced program to its proper location:</para>
123
124<screen><userinput remap="install">mv -v /usr/bin/passwd /bin</userinput></screen>
125 -->
126
127 <!-- <para>Move Shadow's libraries to more appropriate locations:</para>
128
129<screen><userinput remap="install">mv -v /lib/libshadow.*a /usr/lib
130rm -v /lib/libshadow.so
131ln -sfv ../../lib/libshadow.so.0 /usr/lib/libshadow.so</userinput></screen> -->
132
133 </sect2>
134
135 <sect2 id="conf-shadow" role="configuration">
136 <title>Configuring Shadow</title>
137
138 <indexterm zone="conf-shadow">
139 <primary sortas="a-Shadow">Shadow</primary>
140 <secondary>configuring</secondary>
141 </indexterm>
142
143 <para>This package contains utilities to add, modify, and delete users and
144 groups; set and change their passwords; and perform other administrative
145 tasks. For a full explanation of what <emphasis>password shadowing</emphasis>
146 means, see the <filename>doc/HOWTO</filename> file within the unpacked
147 source tree. If using Shadow support, keep in mind that programs which need
148 to verify passwords (display managers, FTP programs, pop3 daemons, etc.)
149 must be Shadow-compliant. That is, they need to be able to work with
150 shadowed passwords.</para>
151
152 <para>To enable shadowed passwords, run the following command:</para>
153
154<screen><userinput>pwconv</userinput></screen>
155
156 <para>To enable shadowed group passwords, run:</para>
157
158<screen><userinput>grpconv</userinput></screen>
159
160 <para>Shadow's stock configuration for the <command>useradd</command>
161 utility has a few caveats that need some explanation. First, the default
162 action for the <command>useradd</command> utility is to create the user and
163 a group of the same name as the user. By default the user ID (UID) and
164 group ID (GID) numbers will begin with 1000. This means if you don't pass
165 parameters to <command>useradd</command>, each user will be a member of a
166 unique group on the system. If this behavior is undesirable, you'll need
167 to pass the <parameter>-g</parameter> parameter to
168 <command>useradd</command>. The default parameters are stored in the
169 <filename>/etc/default/useradd</filename> file. You may need to modify two
170 parameters in this file to suit your particular needs.</para>
171
172 <variablelist>
173 <title><filename>/etc/default/useradd</filename> Parameter Explanations</title>
174
175 <varlistentry>
176 <term><parameter>GROUP=1000</parameter></term>
177 <listitem>
178 <para>This parameter sets the beginning of the group numbers used in
179 the /etc/group file. You can modify it to anything you desire. Note
180 that <command>useradd</command> will never reuse a UID or GID. If the
181 number identified in this parameter is used, it will use the next
182 available number after this. Note also that if you don't have a group
183 1000 on your system the first time you use <command>useradd</command>
184 without the <parameter>-g</parameter> parameter, you'll get a message
185 displayed on the terminal that says:
186 <computeroutput>useradd: unknown GID 1000</computeroutput>. You may
187 disregard this message and group number 1000 will be used.</para>
188 </listitem>
189 </varlistentry>
190 <varlistentry>
191 <term><parameter>CREATE_MAIL_SPOOL=yes</parameter></term>
192 <listitem>
193 <para>This parameter causes <command>useradd</command> to create a
194 mailbox file for the newly created user. <command>useradd</command>
195 will make the group ownership of this file to the
196 <systemitem class="groupname">mail</systemitem> group with 0660
197 permissions. If you would prefer that these mailbox files are not
198 created by <command>useradd</command>, issue the following
199 command:</para>
200
201<screen><userinput>sed -i 's/yes/no/' /etc/default/useradd</userinput></screen>
202 </listitem>
203 </varlistentry>
204
205 </variablelist>
206
207
208 </sect2>
209
210 <sect2 role="configuration">
211 <title>Setting the root password</title>
212
213 <para>Choose a password for user <emphasis>root</emphasis> and set it
214 by running:</para>
215
216<screen role="nodump"><userinput>passwd root</userinput></screen>
217
218 </sect2>
219
220 <sect2 id="contents-shadow" role="content">
221 <title>Contents of Shadow</title>
222
223 <segmentedlist>
224 <segtitle>Installed programs</segtitle>
225 <segtitle>Installed directory</segtitle>
226
227 <seglistitem>
228 <seg>chage, chfn, chgpasswd, chpasswd, chsh, expiry, faillog, gpasswd,
229 groupadd, groupdel, groupmems, groupmod, grpck, grpconv, grpunconv,
230 lastlog, login, logoutd, newgidmap, newgrp, newuidmap, newusers,
231 nologin, passwd, pwck, pwconv, pwunconv, sg (link to newgrp), su,
232 useradd, userdel, usermod, vigr (link to vipw), and vipw</seg>
233 <seg>/etc/default</seg>
234 </seglistitem>
235 </segmentedlist>
236
237 <variablelist>
238 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
239 <?dbfo list-presentation="list"?>
240 <?dbhtml list-presentation="table"?>
241
242 <varlistentry id="chage">
243 <term><command>chage</command></term>
244 <listitem>
245 <para>Used to change the maximum number of days between obligatory
246 password changes</para>
247 <indexterm zone="ch-system-shadow chage">
248 <primary sortas="b-chage">chage</primary>
249 </indexterm>
250 </listitem>
251 </varlistentry>
252
253 <varlistentry id="chfn">
254 <term><command>chfn</command></term>
255 <listitem>
256 <para>Used to change a user's full name and other information</para>
257 <indexterm zone="ch-system-shadow chfn">
258 <primary sortas="b-chfn">chfn</primary>
259 </indexterm>
260 </listitem>
261 </varlistentry>
262
263 <varlistentry id="chgpasswd">
264 <term><command>chgpasswd</command></term>
265 <listitem>
266 <para>Used to update group passwords in batch mode</para>
267 <indexterm zone="ch-system-shadow chgpasswd">
268 <primary sortas="b-chgpasswd">chgpasswd</primary>
269 </indexterm>
270 </listitem>
271 </varlistentry>
272
273 <varlistentry id="chpasswd">
274 <term><command>chpasswd</command></term>
275 <listitem>
276 <para>Used to update user passwords in batch mode</para>
277 <indexterm zone="ch-system-shadow chpasswd">
278 <primary sortas="b-chpasswd">chpasswd</primary>
279 </indexterm>
280 </listitem>
281 </varlistentry>
282
283 <varlistentry id="chsh">
284 <term><command>chsh</command></term>
285 <listitem>
286 <para>Used to change a user's default login shell</para>
287 <indexterm zone="ch-system-shadow chsh">
288 <primary sortas="b-chsh">chsh</primary>
289 </indexterm>
290 </listitem>
291 </varlistentry>
292
293 <varlistentry id="expiry">
294 <term><command>expiry</command></term>
295 <listitem>
296 <para>Checks and enforces the current password expiration policy</para>
297 <indexterm zone="ch-system-shadow expiry">
298 <primary sortas="b-expiry">expiry</primary>
299 </indexterm>
300 </listitem>
301 </varlistentry>
302
303 <varlistentry id="faillog">
304 <term><command>faillog</command></term>
305 <listitem>
306 <para>Is used to examine the log of login failures, to set a maximum
307 number of failures before an account is blocked, or to reset the
308 failure count</para>
309 <indexterm zone="ch-system-shadow faillog">
310 <primary sortas="b-faillog">faillog</primary>
311 </indexterm>
312 </listitem>
313 </varlistentry>
314
315 <varlistentry id="gpasswd">
316 <term><command>gpasswd</command></term>
317 <listitem>
318 <para>Is used to add and delete members and administrators to
319 groups</para>
320 <indexterm zone="ch-system-shadow gpasswd">
321 <primary sortas="b-gpasswd">gpasswd</primary>
322 </indexterm>
323 </listitem>
324 </varlistentry>
325
326 <varlistentry id="groupadd">
327 <term><command>groupadd</command></term>
328 <listitem>
329 <para>Creates a group with the given name</para>
330 <indexterm zone="ch-system-shadow groupadd">
331 <primary sortas="b-groupadd">groupadd</primary>
332 </indexterm>
333 </listitem>
334 </varlistentry>
335
336 <varlistentry id="groupdel">
337 <term><command>groupdel</command></term>
338 <listitem>
339 <para>Deletes the group with the given name</para>
340 <indexterm zone="ch-system-shadow groupdel">
341 <primary sortas="b-groupdel">groupdel</primary>
342 </indexterm>
343 </listitem>
344 </varlistentry>
345
346 <varlistentry id="groupmems">
347 <term><command>groupmems</command></term>
348 <listitem>
349 <para>Allows a user to administer his/her own group membership list
350 without the requirement of super user privileges.</para>
351 <indexterm zone="ch-system-shadow groupmems">
352 <primary sortas="b-groupmems">groupmems</primary>
353 </indexterm>
354 </listitem>
355 </varlistentry>
356
357 <varlistentry id="groupmod">
358 <term><command>groupmod</command></term>
359 <listitem>
360 <para>Is used to modify the given group's name or GID</para>
361 <indexterm zone="ch-system-shadow groupmod">
362 <primary sortas="b-groupmod">groupmod</primary>
363 </indexterm>
364 </listitem>
365 </varlistentry>
366
367 <varlistentry id="grpck">
368 <term><command>grpck</command></term>
369 <listitem>
370 <para>Verifies the integrity of the group files
371 <filename>/etc/group</filename> and
372 <filename>/etc/gshadow</filename></para>
373 <indexterm zone="ch-system-shadow grpck">
374 <primary sortas="b-grpck">grpck</primary>
375 </indexterm>
376 </listitem>
377 </varlistentry>
378
379 <varlistentry id="grpconv">
380 <term><command>grpconv</command></term>
381 <listitem>
382 <para>Creates or updates the shadow group file from the normal
383 group file</para>
384 <indexterm zone="ch-system-shadow grpconv">
385 <primary sortas="b-grpconv">grpconv</primary>
386 </indexterm>
387 </listitem>
388 </varlistentry>
389
390 <varlistentry id="grpunconv">
391 <term><command>grpunconv</command></term>
392 <listitem>
393 <para>Updates <filename>/etc/group</filename> from
394 <filename>/etc/gshadow</filename> and then deletes the latter</para>
395 <indexterm zone="ch-system-shadow grpunconv">
396 <primary sortas="b-grpunconv">grpunconv</primary>
397 </indexterm>
398 </listitem>
399 </varlistentry>
400
401 <varlistentry id="lastlog">
402 <term><command>lastlog</command></term>
403 <listitem>
404 <para>Reports the most recent login of all users or of a
405 given user</para>
406 <indexterm zone="ch-system-shadow lastlog">
407 <primary sortas="b-lastlog">lastlog</primary>
408 </indexterm>
409 </listitem>
410 </varlistentry>
411
412 <varlistentry id="login">
413 <term><command>login</command></term>
414 <listitem>
415 <para>Is used by the system to let users sign on</para>
416 <indexterm zone="ch-system-shadow login">
417 <primary sortas="b-login">login</primary>
418 </indexterm>
419 </listitem>
420 </varlistentry>
421
422 <varlistentry id="logoutd">
423 <term><command>logoutd</command></term>
424 <listitem>
425 <para>Is a daemon used to enforce restrictions on log-on time
426 and ports</para>
427 <indexterm zone="ch-system-shadow logoutd">
428 <primary sortas="b-logoutd">logoutd</primary>
429 </indexterm>
430 </listitem>
431 </varlistentry>
432
433 <varlistentry id="newgidmap">
434 <term><command>newgidmap</command></term>
435 <listitem>
436 <para>Is used to set the gid mapping of a user namespace</para>
437 <indexterm zone="ch-system-shadow newgidmap">
438 <primary sortas="b-newgidmap">newgidmap</primary>
439 </indexterm>
440 </listitem>
441 </varlistentry>
442
443 <varlistentry id="newgrp">
444 <term><command>newgrp</command></term>
445 <listitem>
446 <para>Is used to change the current GID during a login session</para>
447 <indexterm zone="ch-system-shadow newgrp">
448 <primary sortas="b-newgrp">newgrp</primary>
449 </indexterm>
450 </listitem>
451 </varlistentry>
452
453 <varlistentry id="newuidmap">
454 <term><command>newuidmap</command></term>
455 <listitem>
456 <para>Is used to set the uid mapping of a user namespace</para>
457 <indexterm zone="ch-system-shadow newuidmap">
458 <primary sortas="b-newuidmap">newuidmap</primary>
459 </indexterm>
460 </listitem>
461 </varlistentry>
462
463 <varlistentry id="newusers">
464 <term><command>newusers</command></term>
465 <listitem>
466 <para>Is used to create or update an entire series of user
467 accounts</para>
468 <indexterm zone="ch-system-shadow newusers">
469 <primary sortas="b-newusers">newusers</primary>
470 </indexterm>
471 </listitem>
472 </varlistentry>
473
474 <varlistentry id="nologin">
475 <term><command>nologin</command></term>
476 <listitem>
477 <para>Displays a message that an account is not available; it is designed
478 to be used as the default shell for accounts that have been
479 disabled</para>
480 <indexterm zone="ch-system-shadow nologin">
481 <primary sortas="b-nologin">nologin</primary>
482 </indexterm>
483 </listitem>
484 </varlistentry>
485
486 <varlistentry id="passwd">
487 <term><command>passwd</command></term>
488 <listitem>
489 <para>Is used to change the password for a user or group account</para>
490 <indexterm zone="ch-system-shadow passwd">
491 <primary sortas="b-passwd">passwd</primary>
492 </indexterm>
493 </listitem>
494 </varlistentry>
495
496 <varlistentry id="pwck">
497 <term><command>pwck</command></term>
498 <listitem>
499 <para>Verifies the integrity of the password files
500 <filename>/etc/passwd</filename> and
501 <filename>/etc/shadow</filename></para>
502 <indexterm zone="ch-system-shadow pwck">
503 <primary sortas="b-pwck">pwck</primary>
504 </indexterm>
505 </listitem>
506 </varlistentry>
507
508 <varlistentry id="pwconv">
509 <term><command>pwconv</command></term>
510 <listitem>
511 <para>Creates or updates the shadow password file from the normal
512 password file</para>
513 <indexterm zone="ch-system-shadow pwconv">
514 <primary sortas="b-pwconv">pwconv</primary>
515 </indexterm>
516 </listitem>
517 </varlistentry>
518
519 <varlistentry id="pwunconv">
520 <term><command>pwunconv</command></term>
521 <listitem>
522 <para>Updates <filename>/etc/passwd</filename> from
523 <filename>/etc/shadow</filename> and then deletes the latter</para>
524 <indexterm zone="ch-system-shadow pwunconv">
525 <primary sortas="b-pwunconv">pwunconv</primary>
526 </indexterm>
527 </listitem>
528 </varlistentry>
529
530 <varlistentry id="sg">
531 <term><command>sg</command></term>
532 <listitem>
533 <para>Executes a given command while the user's GID
534 is set to that of the given group</para>
535 <indexterm zone="ch-system-shadow sg">
536 <primary sortas="b-sg">sg</primary>
537 </indexterm>
538 </listitem>
539 </varlistentry>
540
541 <varlistentry id="su">
542 <term><command>su</command></term>
543 <listitem>
544 <para>Runs a shell with substitute user and group IDs</para>
545 <indexterm zone="ch-system-shadow su">
546 <primary sortas="b-su">su</primary>
547 </indexterm>
548 </listitem>
549 </varlistentry>
550
551 <varlistentry id="useradd">
552 <term><command>useradd</command></term>
553 <listitem>
554 <para>Creates a new user with the given name, or updates the default
555 new-user information</para>
556 <indexterm zone="ch-system-shadow useradd">
557 <primary sortas="b-useradd">useradd</primary>
558 </indexterm>
559 </listitem>
560 </varlistentry>
561
562 <varlistentry id="userdel">
563 <term><command>userdel</command></term>
564 <listitem>
565 <para>Deletes the given user account</para>
566 <indexterm zone="ch-system-shadow userdel">
567 <primary sortas="b-userdel">userdel</primary>
568 </indexterm>
569 </listitem>
570 </varlistentry>
571
572 <varlistentry id="usermod">
573 <term><command>usermod</command></term>
574 <listitem>
575 <para>Is used to modify the given user's login name, User
576 Identification (UID), shell, initial group, home directory, etc.</para>
577 <indexterm zone="ch-system-shadow usermod">
578 <primary sortas="b-usermod">usermod</primary>
579 </indexterm>
580 </listitem>
581 </varlistentry>
582
583 <varlistentry id="vigr">
584 <term><command>vigr</command></term>
585 <listitem>
586 <para>Edits the <filename>/etc/group</filename> or
587 <filename>/etc/gshadow</filename> files</para>
588 <indexterm zone="ch-system-shadow vigr">
589 <primary sortas="b-vigr">vigr</primary>
590 </indexterm>
591 </listitem>
592 </varlistentry>
593
594 <varlistentry id="vipw">
595 <term><command>vipw</command></term>
596 <listitem>
597 <para>Edits the <filename>/etc/passwd</filename> or
598 <filename>/etc/shadow</filename> files</para>
599 <indexterm zone="ch-system-shadow vipw">
600 <primary sortas="b-vipw">vipw</primary>
601 </indexterm>
602 </listitem>
603 </varlistentry>
604
605 </variablelist>
606
607 </sect2>
608
609</sect1>
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