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