doc/xml/AdminGuide/auagd020.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <chapter id="HDRWQ562">
   3   <title>Managing Access Control Lists</title>
   4
   5   <para>To control access to a directory and all of the files in it, AFS associates an <emphasis>access control list</emphasis>
   6   (<emphasis>ACL</emphasis>) with it, rather than the mode bits that the UNIX file system (UFS) associates with individual files or
   7   directories. AFS ACLs provide more refined access control because there are seven access permissions rather than UFS's three, and
   8   there is room for approximately 20 user or group entries on an ACL, rather than just the three UFS entries (<emphasis
   9   role="bold">owner</emphasis>, <emphasis role="bold">group</emphasis>, and <emphasis role="bold">other</emphasis>).</para>
  10
  11   <sect1 id="HDRWQ563">
  12     <title>Summary of Instructions</title>
  13
  14     <para>This chapter explains how to perform the following tasks by using the indicated commands:</para>
  15
  16     <informaltable frame="none">
  17       <tgroup cols="2">
  18         <colspec colwidth="57*" />
  19
  20         <colspec colwidth="43*" />
  21
  22         <tbody>
  23           <row>
  24             <entry>Examine access control list</entry>
  25
  26             <entry><emphasis role="bold">fs listacl</emphasis></entry>
  27           </row>
  28
  29           <row>
  30             <entry>Edit ACL's normal permissions section</entry>
  31
  32             <entry><emphasis role="bold">fs setacl</emphasis></entry>
  33           </row>
  34
  35           <row>
  36             <entry>Edit ACL's negative permissions section</entry>
  37
  38             <entry><emphasis role="bold">fs setacl</emphasis> with <emphasis role="bold">-negative</emphasis> flag</entry>
  39           </row>
  40
  41           <row>
  42             <entry>Replace an ACL</entry>
  43
  44             <entry><emphasis role="bold">fs setacl</emphasis> with <emphasis role="bold">-clear</emphasis> flag</entry>
  45           </row>
  46
  47           <row>
  48             <entry>Copy an ACL</entry>
  49
  50             <entry><emphasis role="bold">fs copyacl</emphasis></entry>
  51           </row>
  52
  53           <row>
  54             <entry>Remove obsolete AFS UIDs</entry>
  55
  56             <entry><emphasis role="bold">fs cleanacl</emphasis></entry>
  57           </row>
  58         </tbody>
  59       </tgroup>
  60     </informaltable>
  61   </sect1>
  62
  63   <sect1 id="HDRWQ565">
  64     <title>Protecting Data in AFS</title>
  65
  66     <indexterm>
  67       <primary>protection of file data</primary>
  68
  69       <secondary>see also: <emphasis>ACL</emphasis></secondary>
  70     </indexterm>
  71
  72     <indexterm>
  73       <primary>protection of file data</primary>
  74
  75       <secondary>AFS compared to UFS<emphasis>ACL</emphasis></secondary>
  76     </indexterm>
  77
  78     <para>This section describes the main differences between the AFS and UFS file protection systems, discusses the implications of
  79     directory-level protections, and describes the seven access permissions.</para>
  80
  81     <sect2 id="HDRWQ566">
  82       <title>Differences Between UFS and AFS Data Protection</title>
  83
  84       <indexterm>
  85         <primary>UFS</primary>
  86
  87         <secondary>file protection compared to AFS</secondary>
  88       </indexterm>
  89
  90       <indexterm>
  91         <primary>protection of file data</primary>
  92
  93         <secondary>AFS compared to UFS<emphasis>ACL</emphasis></secondary>
  94       </indexterm>
  95
  96       <indexterm>
  97         <primary>ACL</primary>
  98
  99         <secondary>compared to UNIX protection</secondary>
 100       </indexterm>
 101
 102       <para>The UFS mode bits data protection system and the AFS ACL system differ in the following ways: <itemizedlist>
 103           <listitem>
 104             <para>Protection at the file level (UFS) versus the directory level (AFS)</para>
 105
 106             <para>UFS associates a set of nine mode bits with each file element, three (<emphasis role="bold">rwx</emphasis>) for
 107             each of the element's owner, owning group, and all other users. A similar set of mode bits on the file's directory
 108             applies to the file only in an oblique way.</para>
 109
 110             <para>An AFS ACL instead protects all files in a directory in the same way. If a certain file is more sensitive than
 111             others, store it in a directory with a more restrictive ACL.</para>
 112
 113             <para>Defining access at the directory level has important consequences: <indexterm>
 114                 <primary>directory-level data protection</primary>
 115
 116                 <secondary>implications</secondary>
 117               </indexterm> <itemizedlist>
 118                 <listitem>
 119                   <para>The permissions on a directory's ACL apply to all of the files in the directory. When you move a file to a
 120                   different directory, you effectively change the access permissions that apply to it to those on its new
 121                   directory's ACL. Changing a directory's ACL changes the protection on all the files in it.</para>
 122                 </listitem>
 123
 124                 <listitem>
 125                   <para>When you create a subdirectory, its initial ACL is created as a copy of its parent directory's ACL. You can
 126                   then change the subdirectory's ACL independently. However, the parent directory's ACL continues to control access
 127                   to the subdirectory in the following way: the parent directory's ACL must grant the <emphasis
 128                   role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>) permission to a user (or a group the user
 129                   belongs to) in order for the user to access the subdirectory at all.</para>
 130
 131                   <para>In general, then, it is best to assign fairly liberal access permissions to high-level directories
 132                   (including user home directories). In particular, it often makes sense to grant at least the <emphasis
 133                   role="bold">l</emphasis> permission to the <emphasis role="bold">system:anyuser</emphasis> or <emphasis
 134                   role="bold">system:authuser</emphasis> group on high-level directories. For further discussion, see <link
 135                   linkend="HDRWQ571">Using Groups on ACLs</link>.</para>
 136                 </listitem>
 137               </itemizedlist></para>
 138           </listitem>
 139
 140           <listitem>
 141             <para>How the mode bits are interpreted</para>
 142
 143             <para>Mode bits are the only file-protection system in UFS. AFS allows you to set the UNIX mode bits on a file in
 144             addition to the ACL on its directory, but it interprets them differently. See <link linkend="HDRWQ580">How AFS
 145             Interprets the UNIX Mode Bits</link>.</para>
 146           </listitem>
 147
 148           <listitem>
 149             <para>Three access permissions (UFS) versus seven (AFS)</para>
 150
 151             <para>UFS defines three access permissions in the form of mode bits: <emphasis role="bold">r</emphasis> (<emphasis
 152             role="bold">read</emphasis>), <emphasis role="bold">w</emphasis> (<emphasis role="bold">write</emphasis>), and <emphasis
 153             role="bold">x</emphasis> (<emphasis role="bold">execute</emphasis>). AFS defines seven permissions, which makes access
 154             control more precise. For detailed descriptions, see <link linkend="HDRWQ567">The AFS ACL Permissions</link>.
 155             <simplelist>
 156                 <member><emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>)</member>
 157
 158                 <member><emphasis role="bold">d</emphasis> (<emphasis role="bold">delete</emphasis>)</member>
 159
 160                 <member><emphasis role="bold">i</emphasis> (<emphasis role="bold">insert</emphasis>)</member>
 161
 162                 <member><emphasis role="bold">k</emphasis> (<emphasis role="bold">lock</emphasis>)</member>
 163
 164                 <member><emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>)</member>
 165
 166                 <member><emphasis role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>)</member>
 167
 168                 <member><emphasis role="bold">w</emphasis> (<emphasis role="bold">write</emphasis>)</member>
 169               </simplelist></para>
 170           </listitem>
 171
 172           <listitem>
 173             <para>Three defined users and groups (UFS) versus many (AFS)</para>
 174
 175             <para>UFS controls access for one user and two groups by providing a set of mode bits for each: the user who owns the
 176             file or directory, a single defined group, and everyone who has an account on the system.</para>
 177
 178             <para>AFS, in contrast, allows you to place many entries (individual users or groups) on an ACL, granting a different
 179             set of access permissions to each one. The number of possible entries is about 20, and depends on how much space each
 180             entry occupies in the memory allocated for the ACL itself.</para>
 181
 182             <para>AFS defines two system groups, <emphasis role="bold">system:anyuser</emphasis> and <emphasis
 183             role="bold">system:authuser</emphasis>, which represent all users and all authenticated users, respectively; for further
 184             discussion, see <link linkend="HDRWQ571">Using Groups on ACLs</link>. In addition, users can define their own groups in
 185             the Protection Database, consisting of individual users or machine IP addresses. Users who have the <emphasis
 186             role="bold">a</emphasis> permission on an ACL can create entries for the system groups as well as groups defined by
 187             themselves or other users. For information on defining groups, see <link linkend="HDRWQ531">Administering the Protection
 188             Database</link>.</para>
 189
 190             <para>When a user requests access to a file or directory, the File Server sums together all of the permissions that the
 191             relevant ACL extends to the user and to groups to which the user belongs. Placing group entries on ACLs therefore can
 192             control access for many more users than the ACL can accommodate as individual entries.</para>
 193           </listitem>
 194         </itemizedlist></para>
 195     </sect2>
 196
 197     <sect2 id="HDRWQ567">
 198       <title>The AFS ACL Permissions</title>
 199
 200       <indexterm>
 201         <primary>access</primary>
 202
 203         <secondary>permissions on ACL (see entries: <emphasis>permissions on ACL</emphasis>, <emphasis>ACL</emphasis>)</secondary>
 204       </indexterm>
 205
 206       <indexterm>
 207         <primary>permissions on ACL</primary>
 208
 209         <secondary>defined</secondary>
 210       </indexterm>
 211
 212       <indexterm>
 213         <primary>ACL</primary>
 214
 215         <secondary>permissions defined</secondary>
 216       </indexterm>
 217
 218       <para>Functionally, the seven standard ACL permissions fall into two groups: one that applies to the directory itself and one
 219       that applies to the files it contains.</para>
 220
 221       <sect3 id="HDRWQ568">
 222         <title>The Four Directory Permissions</title>
 223
 224         <para>The four permissions in this group are meaningful with respect to the directory itself. For example, the <emphasis
 225         role="bold">i</emphasis> (<emphasis role="bold">insert</emphasis>) permission does not control addition of data to a file,
 226         but rather creation of a new file or subdirectory. <variablelist>
 227             <varlistentry>
 228               <term><emphasis role="bold">The l (lookup) permission</emphasis></term>
 229
 230               <listitem>
 231                 <para>This permission functions as something of a gate keeper for access to the directory and its files, because a
 232                 user must have it in order to exercise any other permissions. In particular, a user must have this permission to
 233                 access anything in the directory's subdirectories, even if the ACL on a subdirectory grants extensive permissions.
 234                 <indexterm>
 235                     <primary>lookup ACL permission</primary>
 236
 237                     <secondary></secondary>
 238
 239                     <see>l ACL permission</see>
 240                   </indexterm> <indexterm>
 241                     <primary>l ACL permission</primary>
 242                   </indexterm></para>
 243
 244                 <para>This permission enables a user to issue the following commands: <itemizedlist>
 245                     <listitem>
 246                       <para>The <emphasis role="bold">ls</emphasis> command to list the names of the files and subdirectories in the
 247                       directory</para>
 248                     </listitem>
 249
 250                     <listitem>
 251                       <para>The <emphasis role="bold">ls -ld</emphasis> command to obtain complete status information for the
 252                       directory element itself</para>
 253                     </listitem>
 254
 255                     <listitem>
 256                       <para>The <emphasis role="bold">fs listacl</emphasis> command to examine the directory's ACL</para>
 257                     </listitem>
 258                   </itemizedlist></para>
 259
 260                 <para>This permission does not enable a user to read the contents of a file in the directory, to issue the <emphasis
 261                 role="bold">ls -l</emphasis> command on a file in the directory, or to issue the <emphasis role="bold">fs
 262                 listacl</emphasis> command with the filename as the <emphasis role="bold">-path</emphasis> argument. Those
 263                 operations require the <emphasis role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>) permission which
 264                 is described in <link linkend="HDRWQ569">The Three File Permissions</link>.</para>
 265
 266                 <para>Similarly, this permission does not enable a user to issue the <emphasis role="bold">ls</emphasis>, <emphasis
 267                 role="bold">ls -l</emphasis>, <emphasis role="bold">ls -ld</emphasis>, or <emphasis role="bold">fs
 268                 listacl</emphasis> commands against a subdirectory of the directory. Those operations require the <emphasis
 269                 role="bold">l</emphasis> permission on the ACL of the subdirectory itself.</para>
 270               </listitem>
 271             </varlistentry>
 272
 273             <varlistentry>
 274               <term><emphasis role="bold">The i (insert) permission</emphasis></term>
 275
 276               <listitem>
 277                 <para>This permission enables a user to add new files to the directory, either by creating or copying, and to create
 278                 new subdirectories. It does not extend into any subdirectories, which are protected by their own ACLs. <indexterm>
 279                     <primary>insert ACL permission</primary>
 280
 281                     <secondary></secondary>
 282
 283                     <see>i ACL permission</see>
 284                   </indexterm> <indexterm>
 285                     <primary>i ACL permission</primary>
 286                   </indexterm></para>
 287               </listitem>
 288             </varlistentry>
 289
 290             <varlistentry>
 291               <term><emphasis role="bold">The d (delete) permission</emphasis></term>
 292
 293               <listitem>
 294                 <para>This permission enables a user to remove files and subdirectories from the directory or move them into other
 295                 directories (assuming that the user has the <emphasis role="bold">i</emphasis> permission on the ACL of the other
 296                 directories). <indexterm>
 297                     <primary>delete ACL permission</primary>
 298
 299                     <secondary></secondary>
 300
 301                     <see>d ACL permission</see>
 302                   </indexterm> <indexterm>
 303                     <primary>d ACL permission</primary>
 304                   </indexterm></para>
 305               </listitem>
 306             </varlistentry>
 307
 308             <varlistentry>
 309               <term><emphasis role="bold">The a (administer) permission</emphasis></term>
 310
 311               <listitem>
 312                 <para>This permission enables a user to change the directory's ACL. Members of the
 313                     <emphasis role="bold">system:administrators</emphasis> group implicitly have
 314                   this permission on every directory (that is, even if that group does not appear on
 315                   the ACL). Similarly, the owner of a volume root directory implicitly has this
 316                   permission on its ACL and those of all directories within the volume. <indexterm>
 317                     <primary>administer ACL permission</primary>
 318                     <secondary/>
 319                     <see>a ACL permission</see>
 320                   </indexterm>
 321                   <indexterm>
 322                     <primary>a ACL permission</primary>
 323                   </indexterm><indexterm>
 324                     <primary>implicit ACL permissions</primary>
 325                   </indexterm></para>
 326               </listitem>
 327             </varlistentry>
 328           </variablelist></para>
 329       </sect3>
 330
 331       <sect3 id="HDRWQ569">
 332         <title>The Three File Permissions</title>
 333
 334         <para>The three permissions in this group are meaningful with respect to files in a directory, rather than the directory
 335         itself or its subdirectories. <variablelist>
 336             <varlistentry>
 337               <term><emphasis role="bold">The r (read) permission</emphasis></term>
 338
 339               <listitem>
 340                 <para>This permission enables a user to read the contents of files in the directory and to issue the <emphasis
 341                 role="bold">ls -l</emphasis> command to stat the file elements. <indexterm>
 342                     <primary>read</primary>
 343
 344                     <secondary>ACL permission</secondary>
 345
 346                     <see>r ACL permission)</see>
 347                   </indexterm> <indexterm>
 348                     <primary>r ACL permission</primary>
 349                   </indexterm></para>
 350               </listitem>
 351             </varlistentry>
 352
 353             <varlistentry>
 354               <term><emphasis role="bold">The w (write) permission</emphasis></term>
 355
 356               <listitem>
 357                 <para>This permission enables a user to modify the contents of files in the directory and to issue the <emphasis
 358                 role="bold">chmod</emphasis> command to change their UNIX mode bits. <indexterm>
 359                     <primary>write</primary>
 360
 361                     <secondary>ACL permission</secondary>
 362
 363                     <see>write ACL permission</see>
 364                   </indexterm> <indexterm>
 365                     <primary>w ACL permission</primary>
 366                   </indexterm></para>
 367               </listitem>
 368             </varlistentry>
 369
 370             <varlistentry>
 371               <term><emphasis role="bold">The k (lock) permission</emphasis></term>
 372
 373               <listitem>
 374                 <para>This permission enables the user to run programs that issue system calls to lock files in the directory.
 375                 <indexterm>
 376                     <primary>lock ACL permission</primary>
 377
 378                     <secondary></secondary>
 379
 380                     <see>k ACL permission</see>
 381                   </indexterm> <indexterm>
 382                     <primary>k ACL permission</primary>
 383                   </indexterm></para>
 384               </listitem>
 385             </varlistentry>
 386           </variablelist></para>
 387       </sect3>
 388
 389       <sect3 id="Header_635">
 390         <title>The Eight Auxiliary Permissions</title>
 391
 392         <indexterm>
 393           <primary>undefined ACL permissions</primary>
 394         </indexterm>
 395
 396         <indexterm>
 397           <primary>auxiliary ACL permissions</primary>
 398         </indexterm>
 399
 400         <indexterm>
 401           <primary>ACL</primary>
 402
 403           <secondary>auxiliary permissions</secondary>
 404         </indexterm>
 405
 406         <para>AFS provides eight additional permissions that do not have a defined meaning, denoted by the uppercase letters
 407         <emphasis role="bold">A</emphasis>, <emphasis role="bold">B</emphasis>, <emphasis role="bold">C</emphasis>, <emphasis
 408         role="bold">D</emphasis>, <emphasis role="bold">E</emphasis>, <emphasis role="bold">F</emphasis>, <emphasis
 409         role="bold">G</emphasis>, and <emphasis role="bold">H</emphasis>.</para>
 410
 411         <para>You can write application programs that assign a meaning to one or more of the permissions, and then place them on
 412         ACLs to control file access by those programs. For example, you can modify a print program to recognize and interpret the
 413         permissions, and then place them on directories that house files that the program accesses. Use the <emphasis role="bold">fs
 414         listacl</emphasis> and <emphasis role="bold">fs setacl</emphasis> commands to display and set the auxiliary permissions on
 415         ACLs just like the standard seven.</para>
 416       </sect3>
 417
 418       <sect3 id="Header_636">
 419         <title>Shorthand Notation for Sets of Permissions</title>
 420
 421         <indexterm>
 422           <primary>ACL</primary>
 423
 424           <secondary>shorthand notation for grouping permissions</secondary>
 425         </indexterm>
 426
 427         <indexterm>
 428           <primary>shorthand notation</primary>
 429
 430           <secondary>ACL permissions</secondary>
 431         </indexterm>
 432
 433         <para>You can combine the seven permissions in any way in an ACL entry, but certain combinations are more useful than
 434         others. Four of the more common combinations have corresponding shorthand forms. When using the <emphasis role="bold">fs
 435         setacl</emphasis> command to define ACL entries, you can provide either one or more of the individual letters that represent
 436         the permissions, or one of the following shorthand forms: <variablelist>
 437             <indexterm>
 438               <primary>all shorthand for ACL permissions</primary>
 439             </indexterm>
 440
 441             <varlistentry>
 442               <term><emphasis role="bold">all</emphasis></term>
 443
 444               <listitem>
 445                 <para>Represents all seven standard permissions (<emphasis role="bold">rlidwka</emphasis>). <indexterm>
 446                     <primary>none shorthand for ACL permissions</primary>
 447                   </indexterm></para>
 448               </listitem>
 449             </varlistentry>
 450
 451             <varlistentry>
 452               <term><emphasis role="bold">none</emphasis></term>
 453
 454               <listitem>
 455                 <para>Removes the entry from the ACL, leaving the user or group with no permissions. <indexterm>
 456                     <primary>read</primary>
 457
 458                     <secondary>shorthand for ACL permissions</secondary>
 459                   </indexterm></para>
 460               </listitem>
 461             </varlistentry>
 462
 463             <varlistentry>
 464               <term><emphasis role="bold">read</emphasis></term>
 465
 466               <listitem>
 467                 <para>Represents the <emphasis role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>) and <emphasis
 468                 role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>) permissions. <indexterm>
 469                     <primary>write</primary>
 470
 471                     <secondary>shorthand for ACL permissions</secondary>
 472                   </indexterm></para>
 473               </listitem>
 474             </varlistentry>
 475
 476             <varlistentry>
 477               <term><emphasis role="bold">write</emphasis></term>
 478
 479               <listitem>
 480                 <para>Represents all permissions except <emphasis role="bold">a</emphasis> (<emphasis
 481                 role="bold">administer</emphasis>): <emphasis role="bold">rlidwk</emphasis>.</para>
 482               </listitem>
 483             </varlistentry>
 484           </variablelist></para>
 485       </sect3>
 486     </sect2>
 487
 488     <sect2 id="HDRWQ570">
 489       <title>Using Normal and Negative Permissions</title>
 490
 491       <indexterm>
 492         <primary>ACL</primary>
 493
 494         <secondary>normal vs. negative permissions</secondary>
 495       </indexterm>
 496
 497       <indexterm>
 498         <primary>normal ACL permissions</primary>
 499
 500         <secondary>defined</secondary>
 501       </indexterm>
 502
 503       <indexterm>
 504         <primary>negative ACL permissions</primary>
 505
 506         <secondary>defined</secondary>
 507       </indexterm>
 508
 509       <para>ACLs enable you both to grant and to deny access to a directory and the files in it. To grant access, use the <emphasis
 510       role="bold">fs setacl</emphasis> command to create an ACL entry that associates a set of permissions with a user or group, as
 511       described in <link linkend="HDRWQ573">Setting ACL Entries</link>. When you use the <emphasis role="bold">fs listacl</emphasis>
 512       command to display an ACL (as described in <link linkend="HDRWQ572">Displaying ACLs</link>), such entries appear underneath
 513       the following header, which uses the term <emphasis>rights</emphasis> to refer to permissions:</para>
 514
 515       <programlisting>
 516    Normal rights
 517 </programlisting>
 518
 519       <para>There are two ways to deny access: <orderedlist>
 520           <listitem>
 521             <para>The recommended method is simply to omit an entry for the user or group from the ACL, or to omit the appropriate
 522             permissions from the entry. Use the <emphasis role="bold">fs setacl</emphasis> command to remove or edit an existing
 523             entry, using the instructions in <link linkend="HDRWQ574">To add, remove, or edit normal ACL permissions</link>. In most
 524             circumstances, this method is enough to prevent access of certain kinds or by certain users. You must take care,
 525             however, not to grant the undesired permissions to any groups to which such users belong.</para>
 526           </listitem>
 527
 528           <listitem>
 529             <para>The more explicit method for denying access is to use the <emphasis role="bold">-negative</emphasis> flag to the
 530             <emphasis role="bold">fs setacl</emphasis> command to create an entry that associates <emphasis>negative
 531             permissions</emphasis> with the user or group; for instructions, see <link linkend="HDRWQ575">To add, remove, or edit
 532             negative ACL permissions</link>. The output from the <emphasis role="bold">fs listacl</emphasis> command lists negative
 533             entries underneath the following header: <programlisting>
 534    Negative rights
 535 </programlisting></para>
 536
 537             <para>When determining what type of access to grant to a user, the File Server first compiles a set of permissions by
 538             examining all of the entries in the <computeroutput>Normal rights</computeroutput> section of the ACL. It then subtracts
 539             any permissions associated with the user (or with groups to which the user belongs) on the <computeroutput>Negative
 540             rights</computeroutput> section of the ACL. Therefore, negative permissions always cancel out normal permissions.</para>
 541
 542             <para>Using negative permissions reverses the usual semantics of the <emphasis role="bold">fs setacl</emphasis> command,
 543             introducing the potential for confusion. In particular, combining the <emphasis role="bold">none</emphasis> shorthand
 544             and the <emphasis role="bold">-negative</emphasis> flag constitutes a double negative: by removing an entry from the
 545             <computeroutput>Negative rights</computeroutput> section of the ACL, you enable a user once again to obtain permissions
 546             via entries in the <computeroutput>Normal rights</computeroutput> section. Combining the <emphasis
 547             role="bold">all</emphasis> shorthand with the <emphasis role="bold">-negative</emphasis> flag explicitly denies all
 548             permissions.</para>
 549
 550             <para>Note also that it is pointless to create an entry in the <computeroutput>Negative rights</computeroutput> section
 551             if an entry in the <computeroutput>Normal rights</computeroutput> section grants the denied permissions to the <emphasis
 552             role="bold">system:anyuser</emphasis> group. In this case, users can obtain the permissions simply by using the
 553             <emphasis role="bold">unlog</emphasis> command to discard their tokens. When they do so, the File Server recognizes them
 554             as the <emphasis role="bold">anonymous</emphasis> user, who belongs to the <emphasis
 555             role="bold">system:anyuser</emphasis> group but does not match the entries on the <computeroutput>Negative
 556             rights</computeroutput> section of the ACL.</para>
 557           </listitem>
 558         </orderedlist></para>
 559     </sect2>
 560
 561     <sect2 id="HDRWQ571">
 562       <title>Using Groups on ACLs</title>
 563
 564       <indexterm>
 565         <primary>group</primary>
 566
 567         <secondary>ACL entry, usefulness of</secondary>
 568       </indexterm>
 569
 570       <indexterm>
 571         <primary>ACL</primary>
 572
 573         <secondary>group entries, usefulness</secondary>
 574       </indexterm>
 575
 576       <para>As previously mentioned, placing a group entry on an ACL enables you to control access for many users at once. You can
 577       grant a new user access to many files and directories simply by adding the user to a group that appears on the relevant ACLs.
 578       You can also create groups of machines, in which case any user logged on to the machine obtains the access that is granted to
 579       the group. On directories where they have the <emphasis role="bold">a</emphasis> permission on the ACL, users can define their
 580       own groups and can create ACL entries for any groups, not just groups that they create or own themselves. For instructions on
 581       creating groups of users or machines, and a discussion of the most effective ways to use different types of groups, see <link
 582       linkend="HDRWQ531">Administering the Protection Database</link>. <indexterm>
 583           <primary>system groups</primary>
 584
 585           <secondary>using on ACLs</secondary>
 586         </indexterm> <indexterm>
 587           <primary>group</primary>
 588
 589           <secondary>system-defined on ACLs</secondary>
 590         </indexterm> <indexterm>
 591           <primary>ACL</primary>
 592
 593           <secondary>system groups on</secondary>
 594         </indexterm> <indexterm>
 595           <primary>system:anyuser group</primary>
 596
 597           <secondary>using on ACLs</secondary>
 598         </indexterm> <indexterm>
 599           <primary>system:authuser group</primary>
 600
 601           <secondary>using on ACLs</secondary>
 602         </indexterm></para>
 603
 604       <para>AFS also defines the following two system groups, which can be very useful on ACLs because they potentially represent a
 605       large group of people. For more information about these groups, see <link linkend="HDRWQ535">The System Groups</link>.
 606       <variablelist>
 607           <varlistentry>
 608             <term><emphasis role="bold">system:anyuser</emphasis></term>
 609
 610             <listitem>
 611               <para>Includes anyone who can access the cell's file tree, including users who have logged in as the local superuser
 612               <emphasis role="bold">root</emphasis>, have connected to a local machine from somewhere outside the cell, and AFS
 613               users who belong to a foreign cell. This group includes users who do not have tokens that are valid for the local AFS
 614               servers; the servers recognize them as the user <emphasis role="bold">anonymous</emphasis>.</para>
 615
 616               <para>Note that creating an ACL entry for this group is the only way to extend access to AFS users from foreign cells,
 617               unless you create local authentication accounts for them. <indexterm>
 618                   <primary>ACL</primary>
 619
 620                   <secondary>foreign users on</secondary>
 621                 </indexterm></para>
 622             </listitem>
 623           </varlistentry>
 624
 625           <varlistentry>
 626             <term><emphasis role="bold">system:authuser</emphasis></term>
 627
 628             <listitem>
 629               <para>Includes all users who have a valid AFS token obtained from the local cell's authentication service.</para>
 630             </listitem>
 631           </varlistentry>
 632         </variablelist></para>
 633
 634       <para>It is particularly useful to grant the <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>)
 635       permission to the <emphasis role="bold">system:anyuser</emphasis> group on the ACL of most directories in the file system,
 636       especially at the upper levels. This permission enables users only to learn the names of files and subdirectories in a
 637       directory, but without it they cannot traverse their way through the directories in the path to a target file.</para>
 638
 639       <para>A slightly more restrictive alternative is to grant the <emphasis role="bold">l</emphasis> permission to the <emphasis
 640       role="bold">system:authuser</emphasis> group. If that is still not restrictive enough, you can grant the <emphasis
 641       role="bold">l</emphasis> to specific users or groups, which cannot exceed about 20 in number on a given ACL.</para>
 642
 643       <para>Another reason to grant certain permissions to the <emphasis role="bold">system:anyuser</emphasis> group is to enable
 644       the correct operation of processes that provide services such as printing and mail delivery. For example, in addition to the
 645       <emphasis role="bold">l</emphasis> permission, a print process possibly needs the <emphasis role="bold">r</emphasis>
 646       (<emphasis role="bold">read</emphasis>) permission in order to access the contents of files, and a mail delivery process
 647       possibly requires the <emphasis role="bold">i</emphasis> (<emphasis role="bold">insert</emphasis>) permission to deliver new
 648       pieces of mail.</para>
 649
 650       <para>The ACL on the root directory of every newly created volume grants all permissions to the <emphasis
 651       role="bold">system:administrators</emphasis> group. You can remove this entry if you wish, but members of the <emphasis
 652       role="bold">system:administrators</emphasis> group always implicitly have the <emphasis role="bold">a</emphasis> (<emphasis
 653       role="bold">administer</emphasis>), and by default also the <emphasis role="bold">l</emphasis>, permission on every
 654       directory's ACL. The <emphasis role="bold">a</emphasis> permission enables them to grant themselves other permissions
 655       explicitly when necessary. To learn about changing this default set of permissions, see <link linkend="HDRWQ586">Administering
 656       the system:administrators Group</link>.</para>
 657     </sect2>
 658   </sect1>
 659
 660   <sect1 id="HDRWQ572">
 661     <title>Displaying ACLs</title>
 662
 663     <indexterm>
 664       <primary>ACL</primary>
 665
 666       <secondary>displaying</secondary>
 667     </indexterm>
 668
 669     <indexterm>
 670       <primary>displaying</primary>
 671
 672       <secondary>ACL entries</secondary>
 673     </indexterm>
 674
 675     <para>To display the ACL associated with a file, directory or symbolic link, issue the <emphasis role="bold">fs
 676     listacl</emphasis> command. The output for a symbolic link displays the ACL that applies to its target file or directory, rather
 677     than the ACL on the directory that houses the symbolic link.</para>
 678
 679     <para><emphasis role="bold">Note for AFS/DFS Migration Toolkit users:</emphasis> If the machine on which you issue the <emphasis
 680     role="bold">fs listacl</emphasis> command is configured to access a DCE cell's DFS filespace via the AFS/DFS Migration Toolkit,
 681     you can use the command to display the ACL on DFS files and directories. To display a DFS directory's Initial Container and
 682     Initial Object ACL instead of the regular one, include the <emphasis role="bold">fs listacl</emphasis> command's <emphasis
 683     role="bold">-id</emphasis> or <emphasis role="bold">-if</emphasis> flag. For instructions, see the <emphasis>OpenAFS/DFS
 684     Migration Toolkit Administration Guide and Reference</emphasis>. The <emphasis role="bold">fs</emphasis> command interpreter
 685     ignores the <emphasis role="bold">-id</emphasis> and <emphasis role="bold">-if</emphasis> flags if you include them when
 686     displaying an AFS ACL. <indexterm>
 687         <primary>fs commands</primary>
 688
 689         <secondary>listacl</secondary>
 690       </indexterm><indexterm>
 691         <primary>commands</primary>
 692
 693         <secondary>fs listacl</secondary>
 694       </indexterm></para>
 695
 696     <sect2 id="Header_640">
 697       <title>To display an ACL</title>
 698
 699       <orderedlist>
 700         <listitem>
 701           <para>Issue the <emphasis role="bold">fs listacl</emphasis> command. <programlisting>
 702    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;+]
 703 </programlisting></para>
 704
 705           <para>where</para>
 706
 707           <variablelist>
 708             <varlistentry>
 709               <term><emphasis role="bold">la</emphasis></term>
 710
 711               <listitem>
 712                 <para>Is an acceptable alias for <emphasis role="bold">listacl</emphasis> (and <emphasis
 713                 role="bold">lista</emphasis> is the shortest acceptable abbreviation).</para>
 714               </listitem>
 715             </varlistentry>
 716
 717             <varlistentry>
 718               <term><emphasis role="bold">dir/file path</emphasis></term>
 719
 720               <listitem>
 721                 <para>Names one or more files or directories for which to display the ACL. For files, the output displays the ACL
 722                 for its directory. If you omit this argument, the output is for the current working directory. Partial pathnames are
 723                 interpreted relative to the current working directory. You can also use the following notation on its own or as part
 724                 of a pathname: <variablelist>
 725                     <varlistentry>
 726                       <term><emphasis role="bold">.</emphasis></term>
 727
 728                       <listitem>
 729                         <para>(A single period). Specifies the current working directory.</para>
 730                       </listitem>
 731                     </varlistentry>
 732
 733                     <varlistentry>
 734                       <term><emphasis role="bold">..</emphasis></term>
 735
 736                       <listitem>
 737                         <para>(Two periods). Specifies the current working directory's parent directory.</para>
 738                       </listitem>
 739                     </varlistentry>
 740
 741                     <varlistentry>
 742                       <term><emphasis role="bold">*</emphasis></term>
 743
 744                       <listitem>
 745                         <para>(The asterisk). Specifies each file and subdirectory in the current working directory. The ACL
 746                         displayed for a file is always the same as for its directory, but the ACL for each subdirectory can
 747                         differ.</para>
 748                       </listitem>
 749                     </varlistentry>
 750                   </variablelist></para>
 751               </listitem>
 752             </varlistentry>
 753           </variablelist>
 754         </listitem>
 755       </orderedlist>
 756
 757       <para>The following error message indicates that you do not have the permissions needed to display an ACL. To specify a
 758       directory name as the dir/file path argument, you must have the <emphasis role="bold">l</emphasis> (<emphasis
 759       role="bold">lookup</emphasis>) permission on the ACL. To specify a filename, you must also have the <emphasis
 760       role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>) permission on its directory's ACL.</para>
 761
 762       <programlisting>
 763    fs: You don't have the required access permissions on 'dir/file path'
 764 </programlisting>
 765
 766       <para>Members of the <emphasis role="bold">system:administrators</emphasis> group and the directory's owner (as reported by
 767       the <emphasis role="bold">ls -ld</emphasis> command) implicitly have the <emphasis role="bold">a</emphasis> (<emphasis
 768       role="bold">administer</emphasis>) permission on every directory's ACL, and can use the <emphasis role="bold">fs
 769       setacl</emphasis> command to grant themselves the required permissions; for instructions, see <link linkend="HDRWQ573">Setting
 770       ACL Entries</link>.</para>
 771
 772       <para>The output for each file or directory specified as dir/file path begins with the following header to identify it:</para>
 773
 774       <programlisting>
 775    Access list for  dir/file path is
 776 </programlisting>
 777
 778       <para>The <computeroutput>Normal rights</computeroutput> header appears on the next line, followed by lines that each pair a
 779       user or group name and a set of permissions. The permissions appear as the single letters defined in <link
 780       linkend="HDRWQ567">The AFS ACL Permissions</link>, and always in the order <emphasis role="bold">rlidwka</emphasis>. If there
 781       are any negative permissions, the <computeroutput>Negative rights</computeroutput> header appears next, followed by pairs of
 782       negative permissions.</para>
 783
 784       <para>The following example displays the ACL on user <emphasis role="bold">terry</emphasis>'s home directory in the Example
 785       Corporation cell:</para>
 786
 787       <programlisting>
 788    % <emphasis role="bold">fs la /afs/example.com/usr/terry</emphasis>
 789    Access list for /afs/example.com/usr/terry is
 790    Normal permissions:
 791       system:authuser rl
 792       pat rlw
 793       terry rlidwka
 794    Negative permissions:
 795       terry:other-dept rl
 796       jones rl
 797 </programlisting>
 798
 799       <para>where <emphasis role="bold">pat</emphasis>, <emphasis role="bold">terry</emphasis>, and <emphasis
 800       role="bold">jones</emphasis> are individual users, <emphasis role="bold">system:authuser</emphasis> is a system group, and
 801       <emphasis role="bold">terry:other-dept</emphasis> is a group that <emphasis role="bold">terry</emphasis> owns. The list of
 802       normal permissions grants all permissions to <emphasis role="bold">terry</emphasis>, the <emphasis role="bold">r</emphasis>
 803       (<emphasis role="bold">read</emphasis>), <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>), and
 804       <emphasis role="bold">w</emphasis> (<emphasis role="bold">write</emphasis>) permissions to <emphasis
 805       role="bold">pat</emphasis>, and the <emphasis role="bold">r</emphasis> and <emphasis role="bold">l</emphasis> permissions to
 806       the members of the <emphasis role="bold">system:authuser</emphasis> group.</para>
 807
 808       <para>The list of negative permissions denies the <emphasis role="bold">r</emphasis> and <emphasis role="bold">l</emphasis>
 809       permissions to <emphasis role="bold">jones</emphasis> and the members of the <emphasis role="bold">terry:other-dept</emphasis>
 810       group. These entries effectively prevent them from accessing <emphasis role="bold">terry</emphasis>'s home directory in any
 811       way, because they cancel out the <emphasis role="bold">r</emphasis> and <emphasis role="bold">l</emphasis> permissions
 812       extended to the <emphasis role="bold">system:authuser</emphasis> group, which is the only entry on the <computeroutput>Normal
 813       rights</computeroutput> section of the ACL that possibly applies to them.</para>
 814     </sect2>
 815   </sect1>
 816
 817   <sect1 id="HDRWQ573">
 818     <title>Setting ACL Entries</title>
 819
 820     <indexterm>
 821       <primary>ACL</primary>
 822
 823       <secondary>setting entries</secondary>
 824     </indexterm>
 825
 826     <indexterm>
 827       <primary>ACL</primary>
 828
 829       <secondary>editing entries</secondary>
 830     </indexterm>
 831
 832     <indexterm>
 833       <primary>ACL</primary>
 834
 835       <secondary>adding entries</secondary>
 836     </indexterm>
 837
 838     <indexterm>
 839       <primary>ACL</primary>
 840
 841       <secondary>removing entries</secondary>
 842     </indexterm>
 843
 844     <indexterm>
 845       <primary>changing</primary>
 846
 847       <secondary>ACL entries</secondary>
 848     </indexterm>
 849
 850     <indexterm>
 851       <primary>setting</primary>
 852
 853       <secondary>ACL entries</secondary>
 854     </indexterm>
 855
 856     <indexterm>
 857       <primary>granting</primary>
 858
 859       <secondary>file access by setting ACL</secondary>
 860     </indexterm>
 861
 862     <indexterm>
 863       <primary>creating</primary>
 864
 865       <secondary>ACL entry</secondary>
 866     </indexterm>
 867
 868     <indexterm>
 869       <primary>adding</primary>
 870
 871       <secondary>ACL entry</secondary>
 872
 873       <tertiary>normal permissions</tertiary>
 874     </indexterm>
 875
 876     <indexterm>
 877       <primary>removing</primary>
 878
 879       <secondary>ACL entry</secondary>
 880     </indexterm>
 881
 882     <para>To add, remove, or edit ACL entries, use the <emphasis role="bold">fs setacl</emphasis> command. By default, the command
 883     manipulates entries on the normal permissions section of the ACL. To manipulate entries on the negative permissions section,
 884     include the <emphasis role="bold">-negative</emphasis> flag.</para>
 885
 886     <para>You must have the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission on an ACL to
 887     edit it. The owner of a directory (as reported by the <emphasis role="bold">ls -ld</emphasis>) command and members of the
 888     <emphasis role="bold">system:administrators</emphasis> group always implicitly have it on every ACL. By default, members of the
 889     <emphasis role="bold">system:administrators</emphasis> group also implicitly have the <emphasis role="bold">l</emphasis>
 890     (<emphasis role="bold">lookup</emphasis>) permission.</para>
 891
 892     <para><emphasis role="bold">Note for AFS/DFS Migration Toolkit users:</emphasis> If the machine on which you issue the <emphasis
 893     role="bold">fs setacl</emphasis> command is configured to access a DCE cell's DFS filespace via the AFS/DFS Migration Toolkit,
 894     you can use the command to set the ACL on DFS files and directories. To set a DFS directory's Initial Container and Initial
 895     Object ACL instead of the regular one, include the <emphasis role="bold">fs setacl</emphasis> command's <emphasis
 896     role="bold">-id</emphasis> or <emphasis role="bold">-if</emphasis> flag. For instructions, see the <emphasis>OpenAFS/DFS
 897     Migration Toolkit Administration Guide and Reference</emphasis>. The <emphasis role="bold">fs</emphasis> command interpreter
 898     ignores the <emphasis role="bold">-id</emphasis> and <emphasis role="bold">-if</emphasis> flags if you include them when setting
 899     an AFS ACL. <indexterm>
 900         <primary>fs commands</primary>
 901
 902         <secondary>setacl</secondary>
 903       </indexterm><indexterm>
 904         <primary>commands</primary>
 905
 906         <secondary>fs setacl</secondary>
 907       </indexterm></para>
 908
 909     <sect2 id="HDRWQ574">
 910       <title>To add, remove, or edit normal ACL permissions</title>
 911
 912       <orderedlist>
 913         <listitem>
 914           <para>Verify that you have the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission
 915           on each directory for which you are editing the ACL. If necessary, issue the <emphasis role="bold">fs listacl</emphasis>
 916           command, which is fully described in <link linkend="HDRWQ572">Displaying ACLs</link>. <programlisting>
 917    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;]
 918 </programlisting></para>
 919         </listitem>
 920
 921         <listitem>
 922           <para>Issue the <emphasis role="bold">fs setacl</emphasis> command to edit entries in the normal permissions section of
 923           the ACL. To remove an entry, specify the <emphasis role="bold">none</emphasis> shorthand as the permissions. If an ACL
 924           entry already exists, the permissions you specify completely replace those in the existing entry. <programlisting>
 925    % <emphasis role="bold">fs setacl  -dir</emphasis> &lt;<replaceable>directory</replaceable>&gt;+ <emphasis role="bold">-acl</emphasis> &lt;<replaceable>access list entries</replaceable>&gt;+
 926 </programlisting></para>
 927
 928           <para>where</para>
 929
 930           <variablelist>
 931             <varlistentry>
 932               <term><emphasis role="bold">sa</emphasis></term>
 933
 934               <listitem>
 935                 <para>Is an acceptable alias for <emphasis role="bold">setacl</emphasis> (and <emphasis role="bold">seta</emphasis>
 936                 is the shortest acceptable abbreviation).</para>
 937               </listitem>
 938             </varlistentry>
 939
 940             <varlistentry>
 941               <term><emphasis role="bold">-dir</emphasis></term>
 942
 943               <listitem>
 944                 <para>Names one or more directories to which to apply the ACL entries defined by the <emphasis
 945                 role="bold">-acl</emphasis> argument. Partial pathnames are interpreted relative to the current working
 946                 directory.</para>
 947
 948                 <para>Specify the read/write path to each directory, to avoid the failure that results when you attempt to change a
 949                 read-only volume. By convention, you indicate the read/write path by placing a period before the cell name at the
 950                 pathname's second level (for example, <emphasis role="bold">/afs/.example.com</emphasis>). For further discussion of the
 951                 concept of read/write and read-only paths through the filespace, see <link linkend="HDRWQ209">The Rules of Mount
 952                 Point Traversal</link>.</para>
 953
 954                 <para>You can also use the following notation on its own or as part of a pathname:</para>
 955
 956                 <variablelist>
 957                   <varlistentry>
 958                     <term><emphasis role="bold">.</emphasis></term>
 959
 960                     <listitem>
 961                       <para>(A single period). If used by itself, sets the ACL on the current working directory.</para>
 962                     </listitem>
 963                   </varlistentry>
 964
 965                   <varlistentry>
 966                     <term><emphasis role="bold">..</emphasis></term>
 967
 968                     <listitem>
 969                       <para>(Two periods). If used by itself, sets the ACL on the current working directory's parent
 970                       directory.</para>
 971                     </listitem>
 972                   </varlistentry>
 973
 974                   <varlistentry>
 975                     <term><emphasis role="bold">*</emphasis></term>
 976
 977                     <listitem>
 978                       <para>(The asterisk). Sets the ACL on each of the subdirectories in the current working directory. You must
 979                       precede it with the <emphasis role="bold">-dir</emphasis> switch, since it potentially designates multiple
 980                       directories. The <emphasis role="bold">fs</emphasis> command interpreter generates the following error message
 981                       for each file in the directory: <programlisting>
 982    fs: 'filename': Not a directory
 983 </programlisting></para>
 984                     </listitem>
 985                   </varlistentry>
 986                 </variablelist>
 987
 988                 <para>If you specify only one directory or file name, you can omit the <emphasis role="bold">-dir</emphasis> and
 989                 <emphasis role="bold">-acl</emphasis> switches.</para>
 990               </listitem>
 991             </varlistentry>
 992
 993             <varlistentry>
 994               <term><emphasis role="bold">-acl</emphasis></term>
 995
 996               <listitem>
 997                 <para>Specifies one or more ACL entries, each of which pairs a user or group name and a set of permissions. Separate
 998                 the pairs, and the two parts of each pair, with one or more spaces.</para>
 999
1000                 <para>To define the permissions, provide either:</para>
1001
1002                 <itemizedlist>
1003                   <listitem>
1004                     <para>One or more of the letters that represent the standard or auxiliary permissions (<emphasis
1005                     role="bold">rlidwka</emphasis> and <emphasis role="bold">ABCDEFGH</emphasis>), in any order</para>
1006                   </listitem>
1007
1008                   <listitem>
1009                     <para>One of the four shorthand notations: <itemizedlist>
1010                         <listitem>
1011                           <para><emphasis role="bold">all</emphasis> (equals <emphasis role="bold">rlidwka</emphasis>)</para>
1012                         </listitem>
1013
1014                         <listitem>
1015                           <para><emphasis role="bold">none</emphasis> (removes the entry)</para>
1016                         </listitem>
1017
1018                         <listitem>
1019                           <para><emphasis role="bold">read</emphasis> (equals <emphasis role="bold">rl</emphasis>)</para>
1020                         </listitem>
1021
1022                         <listitem>
1023                           <para><emphasis role="bold">write</emphasis> (equals <emphasis role="bold">rlidwk</emphasis>)</para>
1024                         </listitem>
1025                       </itemizedlist></para>
1026                   </listitem>
1027                 </itemizedlist>
1028
1029                 <para>For a more detailed description of the permissions and shorthand notations, see <link linkend="HDRWQ567">The
1030                 AFS ACL Permissions</link>.</para>
1031
1032                 <para>On a single command line, you can combine user and group entries. You can also use individual letters in some
1033                 pairs and the shorthand notations in other pairs, but cannot combine letters and shorthand notation within a single
1034                 pair.</para>
1035               </listitem>
1036             </varlistentry>
1037           </variablelist>
1038         </listitem>
1039       </orderedlist>
1040
1041       <para>Either of the following examples grants user <emphasis role="bold">pat</emphasis> the <emphasis role="bold">r</emphasis>
1042       (<emphasis role="bold">read</emphasis>) and <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>)
1043       permissions on the ACL of the <emphasis role="bold">notes</emphasis> subdirectory in the issuer's home directory. They
1044       illustrate how it is possible to omit the <emphasis role="bold">-dir</emphasis> and <emphasis role="bold">-acl</emphasis>
1045       switches when you name only one directory.</para>
1046
1047       <programlisting>
1048    % <emphasis role="bold">fs sa ~/notes pat rl</emphasis>
1049    % <emphasis role="bold">fs sa ~/notes pat read</emphasis>
1050 </programlisting>
1051
1052       <para>The following example edits the ACL for the current working directory. It removes the entry for the <emphasis
1053       role="bold">system:anyuser</emphasis> group, and adds two entries: one grants all permissions except <emphasis
1054       role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) to the members of the <emphasis
1055       role="bold">terry:colleagues</emphasis> group and the other grants the <emphasis role="bold">r</emphasis> (<emphasis
1056       role="bold">read</emphasis>) and <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>) permissions to
1057       the <emphasis role="bold">system:authuser</emphasis> group. The command appears on two lines here only for legibility.</para>
1058
1059       <programlisting>
1060    % <emphasis role="bold">fs  sa  -dir . -acl  system:anyuser  none  terry:colleagues  write  \
1061            system:authuser  rl</emphasis>
1062 </programlisting>
1063
1064       <indexterm>
1065         <primary>fs commands</primary>
1066
1067         <secondary>setacl</secondary>
1068
1069         <tertiary>with -negative flag</tertiary>
1070       </indexterm>
1071
1072       <indexterm>
1073         <primary>commands</primary>
1074
1075         <secondary>fs setacl</secondary>
1076
1077         <tertiary>with -negative flag</tertiary>
1078       </indexterm>
1079
1080       <indexterm>
1081         <primary>creating</primary>
1082
1083         <secondary>ACL entry in negative permissions section</secondary>
1084       </indexterm>
1085
1086       <indexterm>
1087         <primary>adding</primary>
1088
1089         <secondary>ACL entry</secondary>
1090
1091         <tertiary>negative permissions</tertiary>
1092       </indexterm>
1093
1094       <indexterm>
1095         <primary>denying</primary>
1096
1097         <secondary>file access with negative ACL entry</secondary>
1098       </indexterm>
1099     </sect2>
1100
1101     <sect2 id="HDRWQ575">
1102       <title>To add, remove, or edit negative ACL permissions</title>
1103
1104       <orderedlist>
1105         <listitem>
1106           <para>Verify that you have the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission
1107           on each directory for which you are editing the ACL. If necessary, issue the <emphasis role="bold">fs listacl</emphasis>
1108           command, which is fully described in <link linkend="HDRWQ572">Displaying ACLs</link>. <programlisting>
1109    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;]
1110 </programlisting></para>
1111         </listitem>
1112
1113         <listitem>
1114           <para>Issue the <emphasis role="bold">fs setacl</emphasis> command with the <emphasis role="bold">-negative</emphasis>
1115           flag to edit entries in the negative permissions section of the ACL. To remove an entry, specify the <emphasis
1116           role="bold">none</emphasis> shorthand as the permissions. If an ACL entry already exists for a user or group, the
1117           permissions you specify completely replace those in the existing entry. <programlisting>
1118    % <emphasis role="bold">fs setacl -dir</emphasis> &lt;<replaceable>directory</replaceable>&gt;+ <emphasis role="bold">-acl</emphasis> &lt;<replaceable>access list entries</replaceable>&gt;+  <emphasis
1119                 role="bold">-negative</emphasis>
1120 </programlisting></para>
1121
1122           <para>where</para>
1123
1124           <variablelist>
1125             <varlistentry>
1126               <term><emphasis role="bold">sa</emphasis></term>
1127
1128               <listitem>
1129                 <para>Is an acceptable alias for <emphasis role="bold">setacl</emphasis> (and <emphasis role="bold">seta</emphasis>
1130                 is the shortest acceptable abbreviation).</para>
1131               </listitem>
1132             </varlistentry>
1133
1134             <varlistentry>
1135               <term><emphasis role="bold">-dir</emphasis></term>
1136
1137               <listitem>
1138                 <para>Names one or more directories to which to apply the negative ACL entries defined by the <emphasis
1139                 role="bold">-acl</emphasis> argument. Specify the read/write path to each directory, to avoid the failure that
1140                 results when you attempt to change a read-only volume. For a detailed description of acceptable values, see <link
1141                 linkend="HDRWQ574">To add, remove, or edit normal ACL permissions</link>.</para>
1142               </listitem>
1143             </varlistentry>
1144
1145             <varlistentry>
1146               <term><emphasis role="bold">-acl</emphasis></term>
1147
1148               <listitem>
1149                 <para>Specifies one or more ACL entries, each of which pairs a user or group name and a set of permissions. Separate
1150                 the pairs, and the two parts of each pair, with one or more spaces. For a detailed description of acceptable values,
1151                 see <link linkend="HDRWQ574">To add, remove, or edit normal ACL permissions</link>. Keep in mind that the usual
1152                 meaning of each permission is reversed.</para>
1153               </listitem>
1154             </varlistentry>
1155
1156             <varlistentry>
1157               <term><emphasis role="bold">-negative</emphasis></term>
1158
1159               <listitem>
1160                 <para>Places the entries defined by the <emphasis role="bold">-acl</emphasis> argument on the negative permissions
1161                 section of the ACL for each directory named by the <emphasis role="bold">-dir</emphasis> argument.</para>
1162               </listitem>
1163             </varlistentry>
1164           </variablelist>
1165         </listitem>
1166       </orderedlist>
1167
1168       <para>The following example denies user <emphasis role="bold">pat</emphasis> the <emphasis role="bold">w</emphasis> (<emphasis
1169       role="bold">write</emphasis>) and <emphasis role="bold">d</emphasis> (<emphasis role="bold">delete</emphasis>) permissions for
1170       the <emphasis role="bold">project</emphasis> subdirectory of the current working directory.</para>
1171
1172       <programlisting>
1173    % <emphasis role="bold">fs sa project pat wd -neg</emphasis>
1174 </programlisting>
1175     </sect2>
1176   </sect1>
1177
1178   <sect1 id="HDRWQ576">
1179     <title>Completely Replacing an ACL</title>
1180
1181     <indexterm>
1182       <primary>ACL</primary>
1183
1184       <secondary>replacing all entries</secondary>
1185     </indexterm>
1186
1187     <indexterm>
1188       <primary>ACL</primary>
1189
1190       <secondary>clearing</secondary>
1191     </indexterm>
1192
1193     <indexterm>
1194       <primary>replacing</primary>
1195
1196       <secondary>all entries on ACL</secondary>
1197     </indexterm>
1198
1199     <indexterm>
1200       <primary>erasing</primary>
1201
1202       <secondary>all ACL entries</secondary>
1203     </indexterm>
1204
1205     <indexterm>
1206       <primary>clearing</primary>
1207
1208       <secondary>all ACL entries</secondary>
1209     </indexterm>
1210
1211     <indexterm>
1212       <primary>removing</primary>
1213
1214       <secondary>all ACL entries</secondary>
1215     </indexterm>
1216
1217     <para>It is sometimes simplest to clear an ACL completely before defining new permissions on it, for instance if the mix of
1218     normal and negative permissions makes it difficult to understand how their interaction affects a user's access to the directory.
1219     To clear an ACL completely while you define new entries, include the <emphasis role="bold">-clear</emphasis> flag on the
1220     <emphasis role="bold">fs setacl</emphasis> command. When you include this flag, you can create entries on either the normal
1221     permissions or the negative permissions section of the ACL, but not on both at once.</para>
1222
1223     <para>Remember to create an entry that grants appropriate permissions to the directory's owner. The owner implicitly has the
1224     <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission required to replace a deleted entry,
1225     but the effects of a missing ACL entry (particularly the lack of the <emphasis role="bold">lookup</emphasis> permission) can be
1226     so confusing that it becomes difficult for the owner to realize that the missing entry is causing the problems. <indexterm>
1227         <primary>fs commands</primary>
1228
1229         <secondary>setacl</secondary>
1230
1231         <tertiary>with -clear flag</tertiary>
1232       </indexterm> <indexterm>
1233         <primary>commands</primary>
1234
1235         <secondary>fs setacl</secondary>
1236
1237         <tertiary>with -clear flag</tertiary>
1238       </indexterm></para>
1239
1240     <sect2 id="Header_645">
1241       <title>To replace an ACL completely</title>
1242
1243       <orderedlist>
1244         <listitem>
1245           <para>Verify that you have the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission
1246           on each directory for which you are editing the ACL. If necessary, issue the <emphasis role="bold">fs listacl</emphasis>
1247           command, which is fully described in <link linkend="HDRWQ572">Displaying ACLs</link>. <programlisting>
1248    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;]
1249 </programlisting></para>
1250         </listitem>
1251
1252         <listitem>
1253           <para>Issue the <emphasis role="bold">fs setacl</emphasis> command with the <emphasis role="bold">-clear</emphasis> flag
1254           to clear the ACL completely before setting either normal or negative permissions. Because you need to grant the owner of
1255           the directory all permissions, it is better in most cases to set normal permissions at this point. <programlisting>
1256    % <emphasis role="bold">fs setacl -dir</emphasis> &lt;<replaceable>directory</replaceable>&gt;+ <emphasis role="bold">-acl</emphasis> &lt;<replaceable>access list entries</replaceable>&gt;+ <emphasis
1257                 role="bold">-clear</emphasis>  \
1258                [<emphasis role="bold">-negative</emphasis>]
1259 </programlisting></para>
1260
1261           <para>where</para>
1262
1263           <variablelist>
1264             <varlistentry>
1265               <term><emphasis role="bold">sa</emphasis></term>
1266
1267               <listitem>
1268                 <para>Is an acceptable alias for <emphasis role="bold">setacl</emphasis> (and <emphasis role="bold">seta</emphasis>
1269                 is the shortest acceptable abbreviation).</para>
1270               </listitem>
1271             </varlistentry>
1272
1273             <varlistentry>
1274               <term><emphasis role="bold">-dir</emphasis></term>
1275
1276               <listitem>
1277                 <para>Names one or more directories to which to apply the negative ACL entries defined by the <emphasis
1278                 role="bold">-acl</emphasis> argument. Specify the read/write path to each directory, to avoid the failure that
1279                 results when you attempt to change a read-only volume. For a detailed description of acceptable values, see <link
1280                 linkend="HDRWQ574">To add, remove, or edit normal ACL permissions</link>.</para>
1281               </listitem>
1282             </varlistentry>
1283
1284             <varlistentry>
1285               <term><emphasis role="bold">-acl</emphasis></term>
1286
1287               <listitem>
1288                 <para>Specifies one or more ACL entries, each of which pairs a user or group name and a set of permissions. Separate
1289                 the pairs, and the two parts of each pair, with one or more spaces. Remember to grant all permissions to the owner
1290                 of the directory. For a detailed description of acceptable values, see <link linkend="HDRWQ574">To add, remove, or
1291                 edit normal ACL permissions</link>.</para>
1292               </listitem>
1293             </varlistentry>
1294
1295             <varlistentry>
1296               <term><emphasis role="bold">-clear</emphasis></term>
1297
1298               <listitem>
1299                 <para>Removes all entries from each ACL before creating the entries indicated by the <emphasis
1300                 role="bold">-acl</emphasis> argument.</para>
1301               </listitem>
1302             </varlistentry>
1303
1304             <varlistentry>
1305               <term><emphasis role="bold">-negative</emphasis></term>
1306
1307               <listitem>
1308                 <para>Places the entries defined by the <emphasis role="bold">-acl</emphasis> argument on the negative permissions
1309                 section of each ACL.</para>
1310               </listitem>
1311             </varlistentry>
1312           </variablelist>
1313         </listitem>
1314       </orderedlist>
1315     </sect2>
1316   </sect1>
1317
1318   <sect1 id="HDRWQ577">
1319     <title>Copying ACLs Between Directories</title>
1320
1321     <indexterm>
1322       <primary>ACL</primary>
1323
1324       <secondary>copying between directories</secondary>
1325     </indexterm>
1326
1327     <indexterm>
1328       <primary>creating</primary>
1329
1330       <secondary>ACL as copy of another</secondary>
1331     </indexterm>
1332
1333     <indexterm>
1334       <primary>copying</primary>
1335
1336       <secondary>ACL between directories</secondary>
1337     </indexterm>
1338
1339     <para>The <emphasis role="bold">fs copyacl</emphasis> command copies a source directory's ACL to one or more destination
1340     directories. It does not affect the source ACL at all, but changes each destination ACL as follows: <itemizedlist>
1341         <listitem>
1342           <para>If an entry on the source ACL does not exist on the destination ACL, the command copies it to the destination
1343           ACL.</para>
1344         </listitem>
1345
1346         <listitem>
1347           <para>If an entry on the destination ACL does not also exist on the source ACL, the command does not remove it unless you
1348           include the <emphasis role="bold">-clear</emphasis> flag to overwrite the destination ACL completely.</para>
1349         </listitem>
1350
1351         <listitem>
1352           <para>If an entry is on both ACLs, the command changes the permissions on the destination ACL entry to match the source
1353           ACL entry.</para>
1354         </listitem>
1355       </itemizedlist></para>
1356
1357     <para><emphasis role="bold">Note for AFS/DFS Migration Toolkit users:</emphasis> If the machine is configured to enable AFS
1358     users to access a DCE cell's DFS filespace via the AFS/DFS Migration Toolkit, then you can use the <emphasis role="bold">fs
1359     copyacl</emphasis> command to copy ACLs between DFS files and directories also. The command includes <emphasis
1360     role="bold">-id</emphasis> and <emphasis role="bold">-if</emphasis> flags for altering a DFS directory's Initial Container and
1361     Initial Object ACLs as well as its regular ACL; see the <emphasis>OpenAFS/DFS Migration Toolkit Administration Guide and
1362     Reference</emphasis>. You cannot copy ACLs between AFS and DFS directories, because they use different ACL formats. The
1363     <emphasis role="bold">fs</emphasis> command interpreter ignores the <emphasis role="bold">-id</emphasis> and <emphasis
1364     role="bold">-if</emphasis> flags if you include them when copying AFS ACLs. <indexterm>
1365         <primary>fs commands</primary>
1366
1367         <secondary>copyacl</secondary>
1368       </indexterm><indexterm>
1369         <primary>commands</primary>
1370
1371         <secondary>fs copyacl</secondary>
1372       </indexterm></para>
1373
1374     <sect2 id="Header_647">
1375       <title>To copy an ACL between directories</title>
1376
1377       <orderedlist>
1378         <listitem>
1379           <para>Verify that you have the <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>) permission on
1380           the source ACL and the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission on each
1381           destination ACL. To identify the source directory by naming a file in it, you must also have the <emphasis
1382           role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>) permission on the source ACL. If necessary, issue the
1383           <emphasis role="bold">fs listacl</emphasis> command, which is fully described in <link linkend="HDRWQ572">Displaying
1384           ACLs</link>. <programlisting>
1385    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;]
1386 </programlisting></para>
1387         </listitem>
1388
1389         <listitem>
1390           <para>Issue the <emphasis role="bold">fs copyacl</emphasis> command to copy a source ACL to the ACL
1391           on one or more destination directories. (The command appears here on two lines only for legibility.) <programlisting>
1392    % <emphasis role="bold">fs copyacl -fromdir</emphasis> &lt;<replaceable>source directory</replaceable>&gt; <emphasis role="bold">-todir</emphasis> &lt;<replaceable>destination directory</replaceable>&gt;+  \
1393                 [<emphasis role="bold">-clear</emphasis>]
1394 </programlisting></para>
1395
1396           <para>where</para>
1397
1398           <variablelist>
1399             <varlistentry>
1400               <term><emphasis role="bold">co</emphasis></term>
1401
1402               <listitem>
1403                 <para>Is the shortest acceptable abbreviation for <emphasis role="bold">copyacl</emphasis>.</para>
1404               </listitem>
1405             </varlistentry>
1406
1407             <varlistentry>
1408               <term><emphasis role="bold">-fromdir</emphasis></term>
1409
1410               <listitem>
1411                 <para>Names the source directory from which to copy the ACL. Partial pathnames are interpreted relative to the
1412                 current working directory. If this argument names a file, the ACL is copied from its directory.</para>
1413               </listitem>
1414             </varlistentry>
1415
1416             <varlistentry>
1417               <term><emphasis role="bold">-todir</emphasis></term>
1418
1419               <listitem>
1420                 <para>Names each destination directory to which to copy the source ACL. Partial pathnames are interpreted relative
1421                 to the current working directory. Filenames are not acceptable.</para>
1422
1423                 <para>Specify the read/write path to each directory, to avoid the failure that results when you attempt to change a
1424                 read-only volume. By convention, you indicate the read/write path by placing a period before the cell name at the
1425                 pathname's second level (for example, <emphasis role="bold">/afs/.example.com</emphasis>). For further discussion of the
1426                 concept of read/write and read-only paths through the filespace, see <link linkend="HDRWQ209">The Rules of Mount
1427                 Point Traversal</link>.</para>
1428               </listitem>
1429             </varlistentry>
1430
1431             <varlistentry>
1432               <term><emphasis role="bold">-clear</emphasis></term>
1433
1434               <listitem>
1435                 <para>Completely overwrites each destination directory's ACL with the source ACL.</para>
1436               </listitem>
1437             </varlistentry>
1438           </variablelist>
1439         </listitem>
1440       </orderedlist>
1441
1442       <para>The following example copies the ACL from the current working directory's <emphasis role="bold">notes</emphasis>
1443       subdirectory to the <emphasis role="bold">plans</emphasis> subdirectory. The issuer does not include the <emphasis
1444       role="bold">-clear</emphasis> flag, so the entry for user <emphasis role="bold">pat</emphasis> remains on the <emphasis
1445       role="bold">plans</emphasis> directory's ACL although there is no corresponding entry on the <emphasis
1446       role="bold">notes</emphasis> directory's ACL.</para>
1447
1448       <programlisting>
1449    % <emphasis role="bold">fs la notes plans</emphasis>
1450    Access list for notes is
1451    Normal permissions:
1452       terry rlidwka
1453       smith rl
1454       jones rl
1455    Access list for plans is
1456    Normal permissions:
1457       terry rlidwk
1458       pat rlidwk
1459    % <emphasis role="bold">fs copyacl notes plans</emphasis>
1460    % <emphasis role="bold">fs la notes plans</emphasis>
1461    Access list for notes is
1462    Normal permissions:
1463       terry rlidwka
1464       smith rl
1465       jones rl
1466    Access list for plans is
1467    Normal permissions:
1468       terry rlidwka
1469       pat rlidwk
1470       smith rl
1471       jones rl
1472 </programlisting>
1473
1474       <indexterm>
1475         <primary>ACL</primary>
1476
1477         <secondary>removing obsolete AFS IDs</secondary>
1478       </indexterm>
1479
1480       <indexterm>
1481         <primary>removing</primary>
1482
1483         <secondary>obsolete AFS IDs from ACL</secondary>
1484       </indexterm>
1485
1486       <indexterm>
1487         <primary>AFS UID</primary>
1488
1489         <secondary>removing obsolete from ACL</secondary>
1490       </indexterm>
1491
1492       <indexterm>
1493         <primary>AFS GID</primary>
1494
1495         <secondary>removing obsolete from ACL</secondary>
1496       </indexterm>
1497
1498       <indexterm>
1499         <primary>ACL</primary>
1500
1501         <secondary>cleaning</secondary>
1502       </indexterm>
1503     </sect2>
1504   </sect1>
1505
1506   <sect1 id="HDRWQ579">
1507     <title>Removing Obsolete AFS IDs from ACLs</title>
1508
1509     <para>When you remove a user or group entry from the Protection Database, the <emphasis role="bold">fs listacl</emphasis>
1510     command displays the user's AFS UID (or group's AFS GID) in ACL entries, rather than the name. In the following example, user
1511     <emphasis role="bold">terry</emphasis> has an ACL entry for the group <emphasis role="bold">terry:friends</emphasis> (AFS GID
1512     -567) on her home directory in the Example Corporation cell, and then removes the group from the Protection Database.</para>
1513
1514     <programlisting>
1515    % <emphasis role="bold">fs listacl /afs/example.com/usr/terry</emphasis>
1516    Access list for /afs/example.com/usr/terry is
1517    Normal permissions:
1518      terry:friends rlik
1519      system:anyuser l
1520      terry rlidwka
1521    % <emphasis role="bold">pts delete terry:friends</emphasis>
1522    % <emphasis role="bold">fs listacl /afs/example.com/usr/terry</emphasis>
1523    Access list for /afs/example.com/usr/terry is
1524    Normal permissions:
1525      -567 rlik
1526      system:anyuser l
1527      terry rlidwka
1528 </programlisting>
1529
1530     <para>Leaving AFS IDs on ACLs serves no function, because the ID no longer corresponds to an active user or group. Furthermore,
1531     if the ID is ever assigned to a new user or group, then the new possessor of the ID gains access that the owner of the directory
1532     actually intended for the previous possessor. (Reusing AFS IDs is not recommended precisely for this reason.)</para>
1533
1534     <para>To remove obsolete AFS UIDs from ACLs, use the <emphasis role="bold">fs cleanacl</emphasis> command. <indexterm>
1535         <primary>commands</primary>
1536
1537         <secondary>fs cleanacl</secondary>
1538       </indexterm> <indexterm>
1539         <primary>fs commands</primary>
1540
1541         <secondary>cleanacl</secondary>
1542       </indexterm></para>
1543
1544     <sect2 id="Header_649">
1545       <title>To clean obsolete AFS IDs from an ACL</title>
1546
1547       <orderedlist>
1548         <listitem>
1549           <para>Verify that you have the <emphasis role="bold">a</emphasis> (<emphasis role="bold">administer</emphasis>) permission
1550           on each directory for which you are cleaning the ACL. If necessary, issue the <emphasis role="bold">fs listacl</emphasis>
1551           command, which is fully described in <link linkend="HDRWQ572">Displaying ACLs</link>. <programlisting>
1552    % <emphasis role="bold">fs listacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;]
1553 </programlisting></para>
1554         </listitem>
1555
1556         <listitem>
1557           <para>Issue the <emphasis role="bold">fs cleanacl</emphasis> command to remove entries for obsolete AFS IDs.
1558           <programlisting>
1559    % <emphasis role="bold">fs cleanacl</emphasis> [&lt;<replaceable>dir/file path</replaceable>&gt;+]
1560 </programlisting></para>
1561
1562           <para>where</para>
1563
1564           <variablelist>
1565             <varlistentry>
1566               <term><emphasis role="bold">cl</emphasis></term>
1567
1568               <listitem>
1569                 <para>Is the shortest acceptable abbreviation of <emphasis role="bold">cleanacl</emphasis>.</para>
1570               </listitem>
1571             </varlistentry>
1572
1573             <varlistentry>
1574               <term><emphasis role="bold">dir/file path</emphasis></term>
1575
1576               <listitem>
1577                 <para>Names each directory for which to clean the ACL. If this argument names a file, its directory's ACL is
1578                 cleaned. Omit this argument to clean the current working directory's ACL.</para>
1579
1580                 <para>Specify the read/write path to each directory, to avoid the failure that results when you attempt to change a
1581                 read-only volume. By convention, you indicate the read/write path by placing a period before the cell name at the
1582                 pathname's second level (for example, <emphasis role="bold">/afs/.example.com</emphasis>). For further discussion of the
1583                 concept of read/write and read-only paths through the filespace, see <link linkend="HDRWQ209">The Rules of Mount
1584                 Point Traversal</link>.</para>
1585
1586                 <para>You can also use the following notation on its own or as part of a pathname:</para>
1587
1588                 <variablelist>
1589                   <varlistentry>
1590                     <term><emphasis role="bold">.</emphasis></term>
1591
1592                     <listitem>
1593                       <para>(A single period). If used by itself, cleans the current working directory's ACL.</para>
1594                     </listitem>
1595                   </varlistentry>
1596
1597                   <varlistentry>
1598                     <term><emphasis role="bold">..</emphasis></term>
1599
1600                     <listitem>
1601                       <para>(Two periods). If used by itself, cleans the ACL on the current working directory's parent
1602                       directory.</para>
1603                     </listitem>
1604                   </varlistentry>
1605
1606                   <varlistentry>
1607                     <term><emphasis role="bold">*</emphasis></term>
1608
1609                     <listitem>
1610                       <para>(The asterisk). Cleans the ACL of each of the subdirectories in the current working directory. However,
1611                       if you use the asterisk and there are obsolete AFS IDs on any directory's ACL, the following error message
1612                       appears for every file in the directory: <programlisting>
1613    fs: 'filename': Not a directory
1614 </programlisting></para>
1615                     </listitem>
1616                   </varlistentry>
1617                 </variablelist>
1618               </listitem>
1619             </varlistentry>
1620           </variablelist>
1621         </listitem>
1622       </orderedlist>
1623
1624       <para>If there are obsolete AFS IDs on a directory, the command interpreter displays its cleaned ACL under the following
1625       header.</para>
1626
1627       <programlisting>
1628    Access list for directory is now
1629 </programlisting>
1630
1631       <para>If a directory's ACL has no obsolete AFS IDs on it, the following message appears for each.</para>
1632
1633       <programlisting>
1634    Access list for directory is fine.
1635 </programlisting>
1636     </sect2>
1637   </sect1>
1638
1639   <sect1 id="HDRWQ580">
1640     <title>How AFS Interprets the UNIX Mode Bits</title>
1641
1642     <indexterm>
1643       <primary>UNIX</primary>
1644
1645       <secondary>mode bits, interpretation in AFS</secondary>
1646     </indexterm>
1647
1648     <indexterm>
1649       <primary>UFS</primary>
1650
1651       <secondary>mode bits, interpretation in AFS</secondary>
1652     </indexterm>
1653
1654     <indexterm>
1655       <primary>mode bits (UNIX)</primary>
1656
1657       <secondary>interpretation in AFS</secondary>
1658     </indexterm>
1659
1660     <para>Although AFS uses ACLs to protect file data rather than the mode bits that UFS uses, it does not ignore the mode bits
1661     entirely. When you issue the <emphasis role="bold">chmod</emphasis> command on an AFS file or directory, AFS changes the bits
1662     appropriately. To change a file's mode bits, you must have the AFS <emphasis role="bold">w</emphasis> (<emphasis
1663     role="bold">write</emphasis>) permission on the ACL of the file's directory. To change a directory's mode bits, you must have
1664     the <emphasis role="bold">d</emphasis> (<emphasis role="bold">delete</emphasis>), <emphasis role="bold">i</emphasis> (<emphasis
1665     role="bold">insert</emphasis>), and <emphasis role="bold">l</emphasis> (<emphasis role="bold">lookup</emphasis>) permissions on
1666     its ACL.</para>
1667
1668     <para>AFS also uses the UNIX mode bits as follows:</para>
1669
1670     <itemizedlist>
1671       <listitem>
1672         <para>It uses the initial bit to determine the element's type. This is the bit that appears first in the output from the
1673         <emphasis role="bold">ls -l</emphasis> command and shows the hyphen (<emphasis role="bold">-</emphasis>) for a file or the
1674         letter <emphasis role="bold">d</emphasis> for a directory.</para>
1675       </listitem>
1676
1677       <listitem>
1678         <para>It does not use any of the mode bits on a directory.</para>
1679       </listitem>
1680
1681       <listitem>
1682         <para>For a file, the first (owner) set of bits interacts with the ACL entries that apply to the file in the following way:
1683         <itemizedlist>
1684             <listitem>
1685               <para>If the first <emphasis role="bold">r</emphasis> mode bit is not set, no one (including the owner) can read the
1686               file, no matter what permissions they have on the ACL. If the bit is set, users also need the <emphasis
1687               role="bold">r</emphasis> (<emphasis role="bold">read</emphasis>) and <emphasis role="bold">l</emphasis> permissions on
1688               the ACL of the file's directory to read the file.</para>
1689             </listitem>
1690
1691             <listitem>
1692               <para>If the first <emphasis role="bold">w</emphasis> mode bit is not set, no one (including the owner) can modify the
1693               file. If the <emphasis role="bold">w</emphasis> bit is set, users also need the <emphasis role="bold">w</emphasis> and
1694               <emphasis role="bold">l</emphasis> permissions on the ACL of the file's directory to modify the file.</para>
1695             </listitem>
1696
1697             <listitem>
1698               <para>There is no ACL permission directly corresponding to the <emphasis role="bold">x</emphasis> mode bit, but to
1699               execute a file stored in AFS, the user must also have the <emphasis role="bold">r</emphasis> and <emphasis
1700               role="bold">l</emphasis> permissions on the ACL of the file's directory.</para>
1701             </listitem>
1702           </itemizedlist></para>
1703       </listitem>
1704     </itemizedlist>
1705   </sect1>
1706 </chapter>