chapter06/shadow.xml

   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-ch6-sbu;</seg>
  35         <seg>&shadow-ch6-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
  58 find man -name Makefile.in -exec sed -i 's/groups\.1 / /'   {} \;
  59 find man -name Makefile.in -exec sed -i 's/getspnam\.3 / /' {} \;
  60 find 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 -i -e 's@#ENCRYPT_METHOD DES@ENCRYPT_METHOD SHA512@' \
  71        -e 's@/var/spool/mail@/var/mail@' etc/login.defs</userinput></screen>
  72
  73     <note>
  74       <para>If you chose to build Shadow with Cracklib support, run the following:</para>
  75
  76 <screen role="nodump"><userinput>sed -i 's@DICTPATH.*@DICTPATH\t/lib/cracklib/pw_dict@' etc/login.defs</userinput></screen>
  77     </note>
  78
  79     <para>Make a minor change to make the first group number generated
  80     by useradd 1000:</para>
  81
  82 <screen><userinput remap="pre">sed -i 's/1000/999/' etc/useradd</userinput></screen>
  83
  84     <para>Prepare Shadow for compilation:</para>
  85
  86 <screen><userinput remap="configure">./configure --sysconfdir=/etc --with-group-name-max-length=32</userinput></screen>
  87
  88     <variablelist>
  89       <title>The meaning of the configure option:</title>
  90
  91       <varlistentry>
  92         <term><parameter>--with-group-name-max-length=32</parameter></term>
  93         <listitem>
  94           <para>The maximum user name is 32 characters.  Make the maximum
  95           group name the same.</para>
  96         </listitem>
  97       </varlistentry>
  98
  99     </variablelist>
 100
 101     <para>Compile the package:</para>
 102
 103 <screen><userinput remap="make">make</userinput></screen>
 104
 105     <para>This package does not come with a test suite.</para>
 106
 107     <para>Install the package:</para>
 108
 109 <screen><userinput remap="install">make install</userinput></screen>
 110     <!--
 111     <para>Move a misplaced program to its proper location:</para>
 112
 113 <screen><userinput remap="install">mv -v /usr/bin/passwd /bin</userinput></screen>
 114     -->
 115
 116     <!-- <para>Move Shadow's libraries to more appropriate locations:</para>
 117
 118 <screen><userinput remap="install">mv -v /lib/libshadow.*a /usr/lib
 119 rm -v /lib/libshadow.so
 120 ln -sfv ../../lib/libshadow.so.0 /usr/lib/libshadow.so</userinput></screen> -->
 121
 122   </sect2>
 123
 124   <sect2 id="conf-shadow" role="configuration">
 125     <title>Configuring Shadow</title>
 126
 127     <indexterm zone="conf-shadow">
 128       <primary sortas="a-Shadow">Shadow</primary>
 129       <secondary>configuring</secondary>
 130     </indexterm>
 131
 132     <para>This package contains utilities to add, modify, and delete users and
 133     groups; set and change their passwords; and perform other administrative
 134     tasks. For a full explanation of what <emphasis>password shadowing</emphasis>
 135     means, see the <filename>doc/HOWTO</filename> file within the unpacked
 136     source tree. If using Shadow support, keep in mind that programs which need
 137     to verify passwords (display managers, FTP programs, pop3 daemons, etc.)
 138     must be Shadow-compliant. That is, they need to be able to work with
 139     shadowed passwords.</para>
 140
 141     <para>To enable shadowed passwords, run the following command:</para>
 142
 143 <screen><userinput>pwconv</userinput></screen>
 144
 145     <para>To enable shadowed group passwords, run:</para>
 146
 147 <screen><userinput>grpconv</userinput></screen>
 148
 149     <para>Shadow's stock configuration for the <command>useradd</command>
 150     utility has a few caveats that need some explanation. First, the default
 151     action for the <command>useradd</command> utility is to create the user and
 152     a group of the same name as the user. By default the user ID (UID) and
 153     group ID (GID) numbers will begin with 1000. This means if you don't pass
 154     parameters to <command>useradd</command>, each user will be a member of a
 155     unique group on the system. If this behavior is undesirable, you'll need
 156     to pass the <parameter>-g</parameter> parameter to
 157     <command>useradd</command>. The default parameters are stored in the
 158     <filename>/etc/default/useradd</filename> file. You may need to modify two
 159     parameters in this file to suit your particular needs.</para>
 160
 161     <variablelist>
 162       <title><filename>/etc/default/useradd</filename> Parameter Explanations</title>
 163
 164       <varlistentry>
 165         <term><parameter>GROUP=1000</parameter></term>
 166         <listitem>
 167           <para>This parameter sets the beginning of the group numbers used in
 168           the /etc/group file. You can modify it to anything you desire. Note
 169           that <command>useradd</command> will never reuse a UID or GID. If the
 170           number identified in this parameter is used, it will use the next
 171           available number after this. Note also that if you don't have a group
 172           1000 on your system the first time you use <command>useradd</command>
 173           without the <parameter>-g</parameter> parameter, you'll get a message
 174           displayed on the terminal that says:
 175           <computeroutput>useradd: unknown GID 1000</computeroutput>. You may
 176           disregard this message and group number 1000 will be used.</para>
 177         </listitem>
 178       </varlistentry>
 179       <varlistentry>
 180         <term><parameter>CREATE_MAIL_SPOOL=yes</parameter></term>
 181         <listitem>
 182           <para>This parameter causes <command>useradd</command> to create a
 183           mailbox file for the newly created user. <command>useradd</command>
 184           will make the group ownership of this file to the
 185           <systemitem class="groupname">mail</systemitem> group with 0660
 186           permissions. If you would prefer that these mailbox files are not
 187           created by <command>useradd</command>, issue the following
 188           command:</para>
 189
 190 <screen><userinput>sed -i 's/yes/no/' /etc/default/useradd</userinput></screen>
 191         </listitem>
 192       </varlistentry>
 193
 194     </variablelist>
 195
 196
 197   </sect2>
 198
 199   <sect2 role="configuration">
 200     <title>Setting the root password</title>
 201
 202     <para>Choose a password for user <emphasis>root</emphasis> and set it
 203     by running:</para>
 204
 205 <screen role="nodump"><userinput>passwd root</userinput></screen>
 206
 207   </sect2>
 208
 209   <sect2 id="contents-shadow" role="content">
 210     <title>Contents of Shadow</title>
 211
 212     <segmentedlist>
 213       <segtitle>Installed programs</segtitle>
 214       <segtitle>Installed directory</segtitle>
 215
 216       <seglistitem>
 217         <seg>chage, chfn, chgpasswd, chpasswd, chsh, expiry, faillog, gpasswd,
 218         groupadd, groupdel, groupmems, groupmod, grpck, grpconv, grpunconv,
 219         lastlog, login, logoutd, newgidmap, newgrp, newuidmap, newusers,
 220         nologin, passwd, pwck, pwconv, pwunconv, sg (link to newgrp), su,
 221         useradd, userdel, usermod, vigr (link to vipw), and vipw</seg>
 222         <seg>/etc/default</seg>
 223       </seglistitem>
 224     </segmentedlist>
 225
 226     <variablelist>
 227       <bridgehead renderas="sect3">Short Descriptions</bridgehead>
 228       <?dbfo list-presentation="list"?>
 229       <?dbhtml list-presentation="table"?>
 230
 231       <varlistentry id="chage">
 232         <term><command>chage</command></term>
 233         <listitem>
 234           <para>Used to change the maximum number of days between obligatory
 235           password changes</para>
 236           <indexterm zone="ch-system-shadow chage">
 237             <primary sortas="b-chage">chage</primary>
 238           </indexterm>
 239         </listitem>
 240       </varlistentry>
 241
 242       <varlistentry id="chfn">
 243         <term><command>chfn</command></term>
 244         <listitem>
 245           <para>Used to change a user's full name and other information</para>
 246           <indexterm zone="ch-system-shadow chfn">
 247             <primary sortas="b-chfn">chfn</primary>
 248           </indexterm>
 249         </listitem>
 250       </varlistentry>
 251
 252       <varlistentry id="chgpasswd">
 253         <term><command>chgpasswd</command></term>
 254         <listitem>
 255           <para>Used to update group passwords in batch mode</para>
 256           <indexterm zone="ch-system-shadow chgpasswd">
 257             <primary sortas="b-chgpasswd">chgpasswd</primary>
 258           </indexterm>
 259         </listitem>
 260       </varlistentry>
 261
 262       <varlistentry id="chpasswd">
 263         <term><command>chpasswd</command></term>
 264         <listitem>
 265           <para>Used to update user passwords in batch mode</para>
 266           <indexterm zone="ch-system-shadow chpasswd">
 267             <primary sortas="b-chpasswd">chpasswd</primary>
 268           </indexterm>
 269         </listitem>
 270       </varlistentry>
 271
 272       <varlistentry id="chsh">
 273         <term><command>chsh</command></term>
 274         <listitem>
 275           <para>Used to change a user's default login shell</para>
 276           <indexterm zone="ch-system-shadow chsh">
 277             <primary sortas="b-chsh">chsh</primary>
 278           </indexterm>
 279         </listitem>
 280       </varlistentry>
 281
 282       <varlistentry id="expiry">
 283         <term><command>expiry</command></term>
 284         <listitem>
 285           <para>Checks and enforces the current password expiration policy</para>
 286           <indexterm zone="ch-system-shadow expiry">
 287             <primary sortas="b-expiry">expiry</primary>
 288           </indexterm>
 289         </listitem>
 290       </varlistentry>
 291
 292       <varlistentry id="faillog">
 293         <term><command>faillog</command></term>
 294         <listitem>
 295           <para>Is used to examine the log of login failures, to set a maximum
 296           number of failures before an account is blocked, or to reset the
 297           failure count</para>
 298           <indexterm zone="ch-system-shadow faillog">
 299             <primary sortas="b-faillog">faillog</primary>
 300           </indexterm>
 301         </listitem>
 302       </varlistentry>
 303
 304       <varlistentry id="gpasswd">
 305         <term><command>gpasswd</command></term>
 306         <listitem>
 307           <para>Is used to add and delete members and administrators to
 308           groups</para>
 309           <indexterm zone="ch-system-shadow gpasswd">
 310             <primary sortas="b-gpasswd">gpasswd</primary>
 311           </indexterm>
 312         </listitem>
 313       </varlistentry>
 314
 315       <varlistentry id="groupadd">
 316         <term><command>groupadd</command></term>
 317         <listitem>
 318           <para>Creates a group with the given name</para>
 319           <indexterm zone="ch-system-shadow groupadd">
 320             <primary sortas="b-groupadd">groupadd</primary>
 321           </indexterm>
 322         </listitem>
 323       </varlistentry>
 324
 325       <varlistentry id="groupdel">
 326         <term><command>groupdel</command></term>
 327         <listitem>
 328           <para>Deletes the group with the given name</para>
 329           <indexterm zone="ch-system-shadow groupdel">
 330             <primary sortas="b-groupdel">groupdel</primary>
 331           </indexterm>
 332         </listitem>
 333       </varlistentry>
 334
 335       <varlistentry id="groupmems">
 336         <term><command>groupmems</command></term>
 337         <listitem>
 338           <para>Allows a user to administer his/her own group membership list
 339           without the requirement of super user privileges.</para>
 340           <indexterm zone="ch-system-shadow groupmems">
 341             <primary sortas="b-groupmems">groupmems</primary>
 342           </indexterm>
 343         </listitem>
 344       </varlistentry>
 345
 346       <varlistentry id="groupmod">
 347         <term><command>groupmod</command></term>
 348         <listitem>
 349           <para>Is used to modify the given group's name or GID</para>
 350           <indexterm zone="ch-system-shadow groupmod">
 351             <primary sortas="b-groupmod">groupmod</primary>
 352           </indexterm>
 353         </listitem>
 354       </varlistentry>
 355
 356       <varlistentry id="grpck">
 357         <term><command>grpck</command></term>
 358         <listitem>
 359           <para>Verifies the integrity of the group files
 360           <filename>/etc/group</filename> and
 361           <filename>/etc/gshadow</filename></para>
 362           <indexterm zone="ch-system-shadow grpck">
 363             <primary sortas="b-grpck">grpck</primary>
 364           </indexterm>
 365         </listitem>
 366       </varlistentry>
 367
 368       <varlistentry id="grpconv">
 369         <term><command>grpconv</command></term>
 370         <listitem>
 371           <para>Creates or updates the shadow group file from the normal
 372           group file</para>
 373           <indexterm zone="ch-system-shadow grpconv">
 374             <primary sortas="b-grpconv">grpconv</primary>
 375           </indexterm>
 376         </listitem>
 377       </varlistentry>
 378
 379       <varlistentry id="grpunconv">
 380         <term><command>grpunconv</command></term>
 381         <listitem>
 382           <para>Updates <filename>/etc/group</filename> from
 383           <filename>/etc/gshadow</filename> and then deletes the latter</para>
 384           <indexterm zone="ch-system-shadow grpunconv">
 385             <primary sortas="b-grpunconv">grpunconv</primary>
 386           </indexterm>
 387         </listitem>
 388       </varlistentry>
 389
 390       <varlistentry id="lastlog">
 391         <term><command>lastlog</command></term>
 392         <listitem>
 393           <para>Reports the most recent login of all users or of a
 394           given user</para>
 395           <indexterm zone="ch-system-shadow lastlog">
 396             <primary sortas="b-lastlog">lastlog</primary>
 397           </indexterm>
 398         </listitem>
 399       </varlistentry>
 400
 401       <varlistentry id="login">
 402         <term><command>login</command></term>
 403         <listitem>
 404           <para>Is used by the system to let users sign on</para>
 405           <indexterm zone="ch-system-shadow login">
 406             <primary sortas="b-login">login</primary>
 407           </indexterm>
 408         </listitem>
 409       </varlistentry>
 410
 411       <varlistentry id="logoutd">
 412         <term><command>logoutd</command></term>
 413         <listitem>
 414           <para>Is a daemon used to enforce restrictions on log-on time
 415           and ports</para>
 416           <indexterm zone="ch-system-shadow logoutd">
 417             <primary sortas="b-logoutd">logoutd</primary>
 418           </indexterm>
 419         </listitem>
 420       </varlistentry>
 421
 422       <varlistentry id="newgidmap">
 423         <term><command>newgidmap</command></term>
 424         <listitem>
 425           <para>Is used to set the gid mapping of a user namespace</para>
 426           <indexterm zone="ch-system-shadow newgidmap">
 427             <primary sortas="b-newgidmap">newgidmap</primary>
 428           </indexterm>
 429         </listitem>
 430       </varlistentry>
 431
 432       <varlistentry id="newgrp">
 433         <term><command>newgrp</command></term>
 434         <listitem>
 435           <para>Is used to change the current GID during a login session</para>
 436           <indexterm zone="ch-system-shadow newgrp">
 437             <primary sortas="b-newgrp">newgrp</primary>
 438           </indexterm>
 439         </listitem>
 440       </varlistentry>
 441
 442       <varlistentry id="newuidmap">
 443         <term><command>newuidmap</command></term>
 444         <listitem>
 445           <para>Is used to set the uid mapping of a user namespace</para>
 446           <indexterm zone="ch-system-shadow newuidmap">
 447             <primary sortas="b-newuidmap">newuidmap</primary>
 448           </indexterm>
 449         </listitem>
 450       </varlistentry>
 451
 452       <varlistentry id="newusers">
 453         <term><command>newusers</command></term>
 454         <listitem>
 455           <para>Is used to create or update an entire series of user
 456           accounts</para>
 457           <indexterm zone="ch-system-shadow newusers">
 458             <primary sortas="b-newusers">newusers</primary>
 459           </indexterm>
 460         </listitem>
 461       </varlistentry>
 462
 463       <varlistentry id="nologin">
 464         <term><command>nologin</command></term>
 465         <listitem>
 466           <para>Displays a message that an account is not available; it is designed
 467           to be used as the default shell for accounts that have been
 468           disabled</para>
 469           <indexterm zone="ch-system-shadow nologin">
 470             <primary sortas="b-nologin">nologin</primary>
 471           </indexterm>
 472         </listitem>
 473       </varlistentry>
 474
 475       <varlistentry id="passwd">
 476         <term><command>passwd</command></term>
 477         <listitem>
 478           <para>Is used to change the password for a user or group account</para>
 479           <indexterm zone="ch-system-shadow passwd">
 480             <primary sortas="b-passwd">passwd</primary>
 481           </indexterm>
 482         </listitem>
 483       </varlistentry>
 484
 485       <varlistentry id="pwck">
 486         <term><command>pwck</command></term>
 487         <listitem>
 488           <para>Verifies the integrity of the password files
 489           <filename>/etc/passwd</filename> and
 490           <filename>/etc/shadow</filename></para>
 491           <indexterm zone="ch-system-shadow pwck">
 492             <primary sortas="b-pwck">pwck</primary>
 493           </indexterm>
 494         </listitem>
 495       </varlistentry>
 496
 497       <varlistentry id="pwconv">
 498         <term><command>pwconv</command></term>
 499         <listitem>
 500           <para>Creates or updates the shadow password file from the normal
 501           password file</para>
 502           <indexterm zone="ch-system-shadow pwconv">
 503             <primary sortas="b-pwconv">pwconv</primary>
 504           </indexterm>
 505         </listitem>
 506       </varlistentry>
 507
 508       <varlistentry id="pwunconv">
 509         <term><command>pwunconv</command></term>
 510         <listitem>
 511           <para>Updates <filename>/etc/passwd</filename> from
 512           <filename>/etc/shadow</filename> and then deletes the latter</para>
 513           <indexterm zone="ch-system-shadow pwunconv">
 514             <primary sortas="b-pwunconv">pwunconv</primary>
 515           </indexterm>
 516         </listitem>
 517       </varlistentry>
 518
 519       <varlistentry id="sg">
 520         <term><command>sg</command></term>
 521         <listitem>
 522           <para>Executes a given command while the user's GID
 523           is set to that of the given group</para>
 524           <indexterm zone="ch-system-shadow sg">
 525             <primary sortas="b-sg">sg</primary>
 526           </indexterm>
 527         </listitem>
 528       </varlistentry>
 529
 530       <varlistentry id="su">
 531         <term><command>su</command></term>
 532         <listitem>
 533           <para>Runs a shell with substitute user and group IDs</para>
 534           <indexterm zone="ch-system-shadow su">
 535             <primary sortas="b-su">su</primary>
 536           </indexterm>
 537         </listitem>
 538       </varlistentry>
 539
 540       <varlistentry id="useradd">
 541         <term><command>useradd</command></term>
 542         <listitem>
 543           <para>Creates a new user with the given name, or updates the default
 544           new-user information</para>
 545           <indexterm zone="ch-system-shadow useradd">
 546             <primary sortas="b-useradd">useradd</primary>
 547           </indexterm>
 548         </listitem>
 549       </varlistentry>
 550
 551       <varlistentry id="userdel">
 552         <term><command>userdel</command></term>
 553         <listitem>
 554           <para>Deletes the given user account</para>
 555           <indexterm zone="ch-system-shadow userdel">
 556             <primary sortas="b-userdel">userdel</primary>
 557           </indexterm>
 558         </listitem>
 559       </varlistentry>
 560
 561       <varlistentry id="usermod">
 562         <term><command>usermod</command></term>
 563         <listitem>
 564           <para>Is used to modify the given user's login name, User
 565           Identification (UID), shell, initial group, home directory, etc.</para>
 566           <indexterm zone="ch-system-shadow usermod">
 567             <primary sortas="b-usermod">usermod</primary>
 568           </indexterm>
 569         </listitem>
 570       </varlistentry>
 571
 572       <varlistentry id="vigr">
 573         <term><command>vigr</command></term>
 574         <listitem>
 575           <para>Edits the <filename>/etc/group</filename> or
 576           <filename>/etc/gshadow</filename> files</para>
 577           <indexterm zone="ch-system-shadow vigr">
 578             <primary sortas="b-vigr">vigr</primary>
 579           </indexterm>
 580         </listitem>
 581       </varlistentry>
 582
 583       <varlistentry id="vipw">
 584         <term><command>vipw</command></term>
 585         <listitem>
 586           <para>Edits the <filename>/etc/passwd</filename> or
 587           <filename>/etc/shadow</filename> files</para>
 588           <indexterm zone="ch-system-shadow vipw">
 589             <primary sortas="b-vipw">vipw</primary>
 590           </indexterm>
 591         </listitem>
 592       </varlistentry>
 593
 594     </variablelist>
 595
 596   </sect2>
 597
 598 </sect1>