BOOK/chapter08/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-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
  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 -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
 130 rm -v /lib/libshadow.so
 131 ln -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>