openafs/doc/xml/UserGuide/auusg005.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter id="HDRWQ20">
  <title>Using OpenAFS</title>

  <para>This chapter explains how to perform four basic AFS tasks: logging in and authenticating with AFS, ending an AFS session,
  accessing the AFS filespace, and changing your password.</para>

  <sect1 id="HDRWQ21">
    <title>Logging in and Authenticating with AFS</title>

    <para>To access the AFS filespace as an authenticated user, you must both log into an AFS client machine's local (UNIX) file
    system and authenticate with AFS. When you log in, you establish your local system identity. When you authenticate, you prove
    your identity to AFS and obtain a token, which your Cache Manager uses to prove your authenticated status to the AFS server
    processes it contacts on your behalf. Users who are not authenticated (who do not have a token) have limited access to AFS
    directories and files.</para>

    <sect2 id="HDRWQ22">
      <title>Logging In</title>

      <indexterm><primary>logging in</primary></indexterm>

      <indexterm><primary>login utility</primary></indexterm>

      <indexterm><primary>commands</primary><secondary>login</secondary></indexterm>

      <para>On machines that use AFS enabled PAM modules with their login utility, you log in and authenticate in one step. On machines that do not use
      an AFS enabled PAM modules, you log in and authenticate in separate steps. To determine which type of login configuration your
      machine uses, you can check for AFS tokens after logging in, or ask your system administrator, who can also tell you about any
      differences between your login procedure and the two methods described here.</para>
    </sect2>

    <sect2 id="Header_33">
      <title>To Log In Using an AFS enabled PAM module</title>

      <para>Provide your username at the <computeroutput>login:</computeroutput> prompt that appears when you establish a new
      connection to a machine. Then provide your password at the <computeroutput>Password:</computeroutput> prompt as shown in the
      following example. (Your password does not echo visibly on the screen.)</para>

      <programlisting>
   login: <replaceable>username</replaceable>
   Password: <replaceable>password</replaceable>
      </programlisting>

      <para>If you are not sure which type of login utility is running on your machine, it is best to issue the <emphasis
      role="bold">tokens</emphasis> command to check if you are authenticated; for instructions, see <link linkend="HDRWQ30">To
      Display Your Tokens</link>. If you do not have tokens, issue the <emphasis role="bold">kinit/aklog</emphasis> command pair as described in
      <link linkend="HDRWQ29">To Authenticate with AFS</link>.</para>
    </sect2>

    <sect2 id="HDRWQ23">
      <title>To Log In Using a Two-Step Login Procedure</title>

      <para>If your machine does not use AFS enabled PAM modules, you must perform a two-step procedure:

      <orderedlist>
        <listitem>
          <para>Log in to your client machine's local file system by providing a user name and password at the <emphasis
          role="bold">login</emphasis> program's prompts.</para>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">kinit</emphasis> command to authenticate with kerberos and
		  obtain a ticket granting ticket ( or TGT).

		<programlisting>
   % <emphasis role="bold">kinit</emphasis>
   Password: <replaceable>your_Kerberos_password</replaceable>
                </programlisting></para>
        </listitem>
        <listitem>
	          <para>Issue the <emphasis role="bold">aklog</emphasis> command to obtain an AFS token using your TGT.
       <programlisting>

   % <emphasis role="bold">aklog</emphasis>

	</programlisting>
        </para>
	<para>On systems with an AFS enabled kinit program, the kinit program can be configured to run the aklog
              program for you by default, but running it again has no negative side effects.</para>

	</listitem>
      </orderedlist>
      </para>
      <note>
        <para>If your machine uses a two-step login procedure, you can choose to use different passwords for logging in and
        authenticating.</para>
      </note>
    </sect2>

    <sect2 id="HDRWQ24">
      <title>Authenticating with AFS</title>

      <para>To work most effectively in the AFS filespace, you must authenticate with AFS. When you do, your Cache Manager is given
      a token as proof of your authenticated status. It uses your token when requesting services from AFS servers, which accept the
      token as proof of your authenticated status. If you do not have a token, AFS servers consider you to be the <emphasis
      role="bold">anonymous</emphasis> user and your access to AFS filespace is limited: you have only the ACL permissions granted
      to the <emphasis role="bold">system:anyuser</emphasis> group. <indexterm><primary>authentication</primary><secondary>tokens as proof</secondary></indexterm> <indexterm><primary>tokens</primary><secondary>as proof of authentication</secondary></indexterm> <indexterm><primary>Cache Manager</primary><secondary>tokens, use of</secondary></indexterm></para>

      <para>You can obtain new tokens (reauthenticate) at any time, even after using an AFS enabled login utility, which logs you
      in and authenticates you in one step. Issue the <emphasis role="bold">aklog</emphasis> command as described in <link
      linkend="HDRWQ29">To Authenticate with AFS</link>. If your kerberos TGT has expired, you will also need to use the <emphasis role="bold">kinit</emphasis> command.</para>

      <sect3 id="HDRWQ25">
        <title>Protecting Your Tokens with a PAG</title>

        <para>To make your access to AFS as secure as possible, it is best to associate your tokens with a unique identification
        number called a <emphasis>PAG</emphasis> (for <emphasis>process authentication group</emphasis>).
		<indexterm><primary>PAG</primary></indexterm>
        <indexterm><primary>process authentication group (PAG)</primary></indexterm>
		<indexterm><primary>setpag argument to klog command</primary></indexterm>
		AFS enabled login utilities automatically create a PAG and associate the new
        token with it. To create a PAG when you use the two-step login procedure, include the <emphasis role="bold">aklog</emphasis>
        command's <emphasis role="bold">-setpag</emphasis> flag. If you do not use this flag, your tokens are associated with your
        UNIX UID number instead. This type of association has two potential drawbacks:

        <itemizedlist>
          <listitem>
            <para>Anyone who can assume your local UNIX identity can use your tokens. The local superuser <emphasis
            role="bold">root</emphasis> can always use the UNIX <emphasis role="bold">su</emphasis> command to assume your UNIX UID,
            even without knowing your password.</para>
          </listitem>

          <listitem>
            <para>In some environments, certain programs cannot use your tokens even when it is appropriate for them to do so. For
            example, printing commands such as <emphasis role="bold">lp</emphasis> or <emphasis role="bold">lpr</emphasis> possibly
            cannot access the files you want to print, because they cannot use your tokens.</para>
          </listitem>
        </itemizedlist>
</para>
      </sect3>

      <sect3 id="HDRWQ26">
        <title>Obtaining Tokens For Foreign Cells</title>

        <indexterm><primary>authentication</primary><secondary>in a foreign cell</secondary></indexterm>

        <para>A token is valid only in one cell (the cell whose AFS authentication service issued it). The AFS server processes in
        any other cell consider you to be the <emphasis role="bold">anonymous</emphasis> user unless you have an account in the cell
        and authenticate with its AFS authentication service.</para>

        <para>To obtain tokens in a foreign cell, you must first obtain a kerberos TGT for the realm used to authenticate for that cell.
		Unfortunately, while AFS tokens have support for multi-realm credentials, most kerberos implementations don't handle this as
		gracefully. You can control where kerberos stores it's credentials by using the ENV variable <emphasis role="bold">KRB5CCNAME</emphasis>.
		If you want to get a token for a foreign cell, without destroying the kerberos credentials of your current session, you
		need to follow this sequence of commands.
	<programlisting>

   env KRB5CCNAME=/tmp/test.ticket kinit user@REMOTE.REALM
   env KRB5CCNAME=/tmp/test.ticket aklog -c remote.realm -k REMOTE.REALM

	</programlisting>
		It's probably a good idea to remove the TGT from the remote realm after doing this. For kerberos implementations that don't use
		file based ticket caches ( Mac OS X, Windows), you will need to use the graphic kerberos ticket manager included in the OS to
		switch kerberos identities.
	    You can have tokens for your home cell and one or more foreign cells at the same
        time.</para>
      </sect3>

      <sect3 id="HDRWQ27">
        <title>The One-Token-Per-Cell Rule</title>

        <para>You can have only one token per cell for each PAG you have obtained on a client machine. If you already have a token
        for a particular cell and issue the <emphasis role="bold">aklog</emphasis> command, the new token overwrites the existing
        one. Getting a new token is useful if your current token is almost expired but you want to continue accessing AFS files. For
        a discussion of token expiration, see <link linkend="HDRWQ28">Token Lifetime</link>.</para>

        <para>To obtain a second token for the same cell, you need to run a process in a different PAG. OpenAFS provides the <emphasis role="bold">pagsh</emphasis> command to start a new shell in with a different PAG. You will then need to authenticate as described in <link
	      linkend="HDRWQ29">To Authenticate with AFS</link>.
	      </para>
      </sect3>

      <sect3 id="Header_39">
        <title>Obtaining Tokens as Another User</title>

        <indexterm><primary>authentication</primary><secondary>as another user</secondary></indexterm>

        <para>You can authenticate as another username if you know the associated password. (It is, of course, unethical to use
        someone else's tokens without permission.) If you use the <emphasis role="bold">kinit</emphasis> and
		<emphasis role="bold">aklog</emphasis>  commands to authenticate as
        another Kerberos username and obtain an AFS token, you retain your own local (UNIX) identity, but the AFS
		server processes recognize you as the other user. The new token replaces any token you already have for the
		relevant cell (for the reason described in <link
        linkend="HDRWQ27">The One-Token-Per-Cell Rule</link>).</para>
      </sect3>

      <sect3 id="HDRWQ28">
        <title>Token Lifetime</title>

        <indexterm><primary>tokens</primary><secondary>lifetime</secondary></indexterm>

        <indexterm><primary>lifetime of tokens</primary></indexterm>

        <para>Tokens and Kerberos TGT's have a limited lifetime. To determine when your tokens expire, issue the <emphasis
        role="bold">tokens</emphasis> command as described in <link linkend="HDRWQ30">To Display Your Tokens</link>. If you are ever
        unable to access AFS in a way that you normally can, issuing the <emphasis role="bold">tokens</emphasis> command tells you
        whether an expired token is a possible reason.</para>

        <para>Your cell's kerberos administrators set the default lifetime of your kerberos TGT. The AFS authentication service never grants a token
        lifetime longer than the current TGT lifetime, but you can request a TGT with a shorter lifetime. See the <emphasis
        role="bold">kinit</emphasis> man page on your system to learn how to use
        its <emphasis role="bold">-lifetime</emphasis> argument for this purpose.</para>
      </sect3>

    </sect2>

    <sect2 id="HDRWQ29">
      <title>To Authenticate with AFS</title>

      <indexterm><primary>aklog command</primary></indexterm>
      <indexterm><primary>kinit command</primary></indexterm>
      <indexterm><primary>commands</primary><secondary>aklog</secondary></indexterm>
     <indexterm><primary>commands</primary><secondary>kinit</secondary></indexterm>
      <indexterm><primary>tokens</primary><secondary>getting</secondary></indexterm>

      <para>If your machine is not using an AFS enabled login utility, you must authenticate after login by issuing the <emphasis
      role="bold">kinit</emphasis> command and then use <emphasis role="bold">aklog</emphasis> to obtain a token. You can also
      issue these commands at any time to obtain a token with a later expiration
      date than your current token.</para>

      <programlisting>
   % <emphasis role="bold">kinit</emphasis> [<emphasis role="bold">userid@KRB5.REALM</emphasis>]
   Password: <replaceable>your_kerberos_password</replaceable>
</programlisting>

      <para>where

      <variablelist>
        <varlistentry>
          <term><emphasis role="bold">userid@KRB5.REALM</emphasis></term>

          <listitem>
            <para>is the kerberos userid and realm that you want to get a TGT from. If the machine is properly configured
				for your local cell and realm, you should not need to specify the kerberos identity.</para>
          </listitem>
        </varlistentry>

      </variablelist>
      </para>

      <para>Your password does not echo visibly appear on the screen. When the command shell prompt returns,
      you have a kerberos TGT. You then need to use the <emphasis role="bold">aklog</emphasis> command to
      obtain an AFS token.</para>

	  <programlisting>
   % <emphasis role="bold">aklog</emphasis> [<emphasis role="bold">-cell afs.cell.name</emphasis>]  [<emphasis role="bold">-k KRB5.REALM</emphasis>]
          </programlisting>

      <para>where

      <variablelist>
        <varlistentry>
          <term><emphasis role="bold">KRB5.REALM</emphasis></term>

          <listitem>
            <para>is the kerberos realm used to authenticate the AFS cell.</para>
          </listitem>
        </varlistentry>

	<varlistentry>
	  <term><emphasis role="bold">afs.cell.name</emphasis></term>

	  <listitem>
	    <para>is the AFS cell for which you want a token.</para>
	  </listitem>
	</varlistentry>

      </variablelist>
      </para>

      <para>You can use the <emphasis role="bold">tokens</emphasis> command to verify that you are authenticated,
      as described in the following section.</para>

      <note xml:id="note.a.note.on.kerberos.realms.and.afs.cellnames">
          <title>A Note on Kerberos Realms and AFS Cellnames</title>
          <para>These are two things that are often the same, but each has it's own distinct rules.
          By convention, kerberos realms are always in UPPER CASE and afs cellnames are in lower case.
          Thus username@KRB5.REALM is the kerberos identity used for the AFS cell krb5.realm. There is
          no restriction that the cell and realm names must match, but most sites are set up that way
          to avoid confusion. In a well configured system you should never need worry about this until
          you need to access remote realms/cells.</para>
      </note>

    </sect2>

    <sect2 id="HDRWQ30">
      <title>To Display Your Tokens</title>

      <indexterm><primary>checking</primary><secondary>tokens</secondary></indexterm>

      <indexterm><primary>commands</primary><secondary>tokens</secondary></indexterm>

      <indexterm><primary>tokens</primary><secondary>command</secondary></indexterm>

      <indexterm><primary>tokens</primary><secondary>displaying</secondary></indexterm>

      <indexterm><primary>displaying</primary><secondary>tokens</secondary></indexterm>

      <para>Use the <emphasis role="bold">tokens</emphasis> command to display your tokens.</para>

      <programlisting>
   % <emphasis role="bold">tokens</emphasis>
</programlisting>

      <para>The following output indicates that you have no tokens:</para>

      <programlisting>
   Tokens held by the Cache Manager:
       --End of list--
</programlisting>

      <para>If you have one or more tokens, the output looks something like the following example, in which the tokens for AFS UID
      1022 in the <emphasis role="bold">abc.com</emphasis> cell expire on August 3 at 2:35 p.m. The tokens for AFS UID 9554 in the
      <emphasis role="bold">stateu.edu</emphasis> cell expire on August 4 at 1:02 a.m.</para>

      <programlisting>
   Tokens held by the Cache Manager:
   User's (AFS ID 1022) tokens for afs@abc.com [Expires Aug   3 14:35]
   User's (AFS ID 9554) tokens for afs@stateu.edu [Expires Aug   4  1:02]
      --End of list--
</programlisting>
    </sect2>

    <sect2 id="Header_44">
      <title>Example: Authenticating in the Local Cell</title>

      <indexterm><primary>examples</primary><secondary>authenticating</secondary></indexterm>

      <para>Suppose that user <emphasis role="bold">terry</emphasis> cannot save a file. He uses the <emphasis
      role="bold">tokens</emphasis> command and finds that his tokens have expired. He reauthenticates in his local cell under his
      current identity by issuing the following commands:</para>

      <programlisting>
   % <emphasis role="bold">kinit</emphasis>
   Password:  <replaceable>terry's_password</replaceable>
   % <emphasis role="bold">aklog</emphasis>

</programlisting>

      <para>The he issues the <emphasis role="bold">tokens</emphasis> command to make sure he is authenticated.</para>

      <programlisting>
   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
   User's (AFS ID 4562) tokens for afs@abc.com [Expires Jun 22 14:35]
      --End of list--
</programlisting>
    </sect2>

    <sect2 id="Header_45">
      <title>Example: Authenticating as a Another User</title>

      <indexterm><primary>examples</primary><secondary>authenticating as another user</secondary></indexterm>

      <para>Now <emphasis role="bold">terry</emphasis> authenticates in his local cell as another user, <emphasis
      role="bold">pat</emphasis>. The new token replaces <emphasis role="bold">terry</emphasis>'s existing token, because the Cache
      Manager can store only one token per cell per login session on a machine.</para>

      <programlisting>
   % <emphasis role="bold">kinit pat</emphasis>
   Password: <replaceable>pat's_password</replaceable>
   % <emphasis role="bold">aklog</emphasis>
   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
   User's (AFS ID 4278) tokens for afs@abc.com [Expires Jun 23 9:46]
      --End of list--
</programlisting>
    </sect2>

    <sect2 id="Header_46">
      <title>Example: Authenticating in a Foreign Cell</title>

      <indexterm><primary>examples</primary><secondary>authenticating in a foreign cell</secondary></indexterm>

      <para>Now <emphasis role="bold">terry</emphasis> authenticates in the <emphasis role="bold">stateu.edu</emphasis> cell where
      his account is called <emphasis role="bold">ts09</emphasis>.</para>

      <programlisting>
   % <emphasis role="bold">env KRB5CCNAME=/tmp/temp.tgt kinit ts09@STATEU.EDU</emphasis>
	Password: <replaceable>ts09's_password</replaceable>
   % <emphasis role="bold">env KRB5CCNAME=/tmp/temp.tgt aklog  ts09 -cell stateu.edu</emphasis>

   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
   User's (AFS ID 4562) tokens for afs@abc.com [Expires Jun 22 14:35]
   User's (AFS ID 8346) tokens for afs@stateu.edu [Expires Jun 23  1:02]
       --End of list--
</programlisting>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ33">
    <title>Exiting an AFS Session</title>

    <indexterm><primary>tokens</primary><secondary>destroying</secondary></indexterm>

    <indexterm><primary>unauthenticating</primary></indexterm>

    <indexterm><primary>exiting an AFS session</primary></indexterm>

    <indexterm><primary>logging out</primary></indexterm>

    <indexterm><primary>quitting an AFS session</primary></indexterm>

    <para>Because logging in and authenticating with AFS are distinct operations, you must both logout and unauthenticate (issue the
    <emphasis role="bold">unlog</emphasis> command to discard your tokens) when exiting an AFS session. Simply logging out does not
    necessarily destroy your tokens.</para>

    <para>You can use the <emphasis role="bold">unlog</emphasis> command any time you want to unauthenticate, not just when logging
    out. For instance, it is a good practice to unauthenticate before leaving your machine unattended, to prevent other users from
    using your tokens during your absence. When you return to your machine, issue the <emphasis role="bold">aklog</emphasis> command
    to reauthenticate, as described in <link linkend="HDRWQ29">To Authenticate with AFS</link>.</para>

    <para>Do not issue the <emphasis role="bold">unlog</emphasis> command when you are running jobs that take a long time to
    complete, even if you are logging out. Such processes must have a token during the entire time they need authenticated access to
    AFS.</para>

    <para>If you have tokens from multiple cells and want to discard only some of them, include the <emphasis
    role="bold">unlog</emphasis> command's <emphasis role="bold">-cell</emphasis> argument.</para>

    <sect2 id="Header_50">
      <title>To Discard Tokens</title>

      <indexterm><primary>commands</primary><secondary>unlog</secondary></indexterm>

      <indexterm><primary>unlog command</primary></indexterm>

      <para>Issue the <emphasis role="bold">unlog</emphasis> command to discard your tokens:</para>

      <programlisting>
   % <emphasis role="bold">unlog -cell</emphasis>  &lt;<replaceable>cell name</replaceable>&gt;<superscript>+</superscript>
</programlisting>

      <para>Omit the <emphasis role="bold">-cell</emphasis> argument to discard all of your tokens, or use it to name each cell for
      which to discard tokens. It is best to provide the full name of each cell (such as <emphasis role="bold">stateu.edu</emphasis>
      or <emphasis role="bold">abc.com</emphasis>).</para>

      <para>You can issue the <emphasis role="bold">tokens</emphasis> command to verify that your tokens were destroyed, as in the
      following example.</para>

      <programlisting>
   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
      --End of list--
</programlisting>
    </sect2>

    <sect2 id="Header_51">
      <title>Example: Unauthenticating from a Specific Cell</title>

      <indexterm><primary>examples</primary><secondary>unauthenticating from selected cells</secondary></indexterm>

      <para>In the following example, a user has tokens in both the <emphasis role="bold">accounting</emphasis> and <emphasis
      role="bold">marketing</emphasis> cells at her company. She discards the token for the <emphasis
      role="bold">acctg.abc.com</emphasis> cell but keeps the token for the <emphasis role="bold">mktg.abc.com</emphasis>
      cell.</para>

      <programlisting>
   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
   User's (AFS ID 35) tokens for afs@acctg.abc.com [Expires Nov 10 22:30]
   User's (AFS ID 674) tokens for afs@mktg.abc.com [Expires Nov 10 18:44]
      --End of list--
   % <emphasis role="bold">unlog -cell acctg.abc.com</emphasis>
   % <emphasis role="bold">tokens</emphasis>
   Tokens held by the Cache Manager:
   User's (AFS ID 674) tokens for afs@mktg.abc.com [Expires Nov 10 18:44]
      --End of list--
</programlisting>
    </sect2>

    <sect2 id="Header_52">
      <title>To Log Out</title>

      <para>After you have unauthenticated, log out by issuing the command appropriate for your machine type, which is possibly one
      of the following.</para>

      <programlisting>
   % <emphasis role="bold">logout</emphasis>
</programlisting>

      <para>or</para>

      <programlisting>
   % <emphasis role="bold">exit</emphasis>
</programlisting>

      <para>or</para>

      <programlisting>
   % &lt;<emphasis role="bold">Ctrl-d</emphasis>&gt;
</programlisting>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ34">
    <title>Accessing the AFS Filespace</title>

    <indexterm><primary>files</primary><secondary>accessing AFS</secondary></indexterm>

    <indexterm><primary>directories</primary><secondary>accessing AFS</secondary></indexterm>

    <para>While you are logged in and authenticated, you can access files in AFS just as you do in the UNIX file system. The only
    difference is that you can access potentially many more files. Just as in the UNIX file system, you can only access those files
    for which you have permission. AFS uses access control lists (ACLs) to control access, as described in <link
    linkend="HDRWQ44">Protecting Your Directories and Files</link>.</para>

    <sect2 id="Header_54">
      <title>AFS Pathnames</title>

      <indexterm><primary>pathnames</primary></indexterm>

      <para>AFS pathnames look very similar to UNIX file system names. The main difference is that every AFS pathname begins with
      the AFS root directory, which is called <emphasis role="bold">/afs</emphasis> by convention. Having <emphasis
      role="bold">/afs</emphasis> at the top of every AFS cell's filespace links together their filespaces into a global filespace.
      <indexterm><primary>AFS</primary><secondary>accessing filespace</secondary></indexterm> <indexterm><primary>access to AFS filespace</primary><secondary>format of pathnames</secondary></indexterm> <indexterm><primary>afs (/afs) directory</primary><secondary>as root of AFS filespace</secondary></indexterm> <indexterm><primary>format of AFS pathnames</primary></indexterm></para>

      <para><emphasis role="bold">Note for Windows users:</emphasis> Windows uses a backslash (&nbsp;<emphasis
      role="bold">\</emphasis>&nbsp;) rather than a forward slash (&nbsp;<emphasis role="bold">/</emphasis>&nbsp;) to separate the
      elements in a pathname. Otherwise, your access to AFS filespace is much the same as for users working on UNIX machines.</para>

      <para>The second element in AFS pathnames is generally a cell's name. For example, the ABC Corporation cell is called
      <emphasis role="bold">abc.com</emphasis> and the pathname of every file in its filespace begins with the string <emphasis
      role="bold">/afs/abc.com</emphasis>. Some cells also create a directory at the second level with a shortened name (such as
      <emphasis role="bold">abc</emphasis> for <emphasis role="bold">abc.com</emphasis> or <emphasis role="bold">stateu</emphasis>
      for <emphasis role="bold">stateu.edu</emphasis>), to reduce the amount of typing necessary. Your system administrator can tell
      you if your cell's filespace includes shortened names like this. The rest of the pathname depends on how the cell's
      administrators organized its filespace.</para>

      <para>To access directories and files in AFS you must both specify the correct pathname and have the required permissions on
      the ACL that protects the directory and the files in it.</para>
    </sect2>

    <sect2 id="Header_55">
      <title>Example: Displaying the Contents of Another User's Directory</title>

      <para>The user <emphasis role="bold">terry</emphasis> wants to look for a file belonging to another user, <emphasis
      role="bold">pat</emphasis>. He issues the <emphasis role="bold">ls</emphasis> command on the appropriate pathname.</para>

      <programlisting>
   % <emphasis role="bold">ls /afs/abc.com/usr/pat/public</emphasis>
   doc/                    directions/
   guide/                  jokes/
   library/
</programlisting>
    </sect2>

    <sect2 id="HDRWQ35">
      <title>Accessing Foreign Cells</title>

      <indexterm><primary>foreign cells</primary><secondary>accessing</secondary></indexterm>

      <indexterm><primary>system:anyuser group</primary><secondary>controlling access by foreign users</secondary></indexterm>

      <para>You can access files not only in your own cell, but in any AFS cell that you can reach via the network, regardless of
      geographical location. There are two additional requirements:

      <itemizedlist>
        <listitem>
          <para>Your Cache Manager's list of foreign cells must include the cell you want to access. Only the local superuser
          <emphasis role="bold">root</emphasis> can edit the list of cells, but anyone can display it. See <link
          linkend="HDRWQ42">Determining Access to Foreign Cells</link>.</para>
        </listitem>

        <listitem>
          <para>The ACL on the directory that houses the file, and on every parent directory in the pathname, must grant you the
          necessary permissions. The simplest way for the directory's owner to extend permission to foreign users is to put an entry
          for the <emphasis role="bold">system:anyuser</emphasis> group on the ACL.</para>

          <para>The alternative is for the foreign cell's administrator to create an account for you, essentially making you a local
          user in the cell. The directory's owner creates an ACL entry for you as for any other local user. To authenticate in the
          foreign cell, issue the <emphasis role="bold">aklog</emphasis> command with the <emphasis role="bold">-cell</emphasis>
          argument.</para>
        </listitem>
      </itemizedlist>
      </para>

      <para>For further discussion of directory and file protection, see <link linkend="HDRWQ44">Protecting Your Directories and
      Files</link>.</para>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ36">
    <title>Changing Your Password</title>

    <para>In cells that use an AFS and kerberos enabled login utility, the password is the same for both logging in and authenticating with AFS.
    In this case, generally you use a single command, <emphasis role="bold">kpasswd</emphasis>, to change the password. But this may vary from system to system, if in doubt contact your local system administrator.</para>

    <para>If your machine does not use an AFS and kerberos enabled login utility, there are separate passwords for logging into the local file
    system and authenticating with AFS. (The two passwords can be the same or different, at your discretion.) In this case, use the
    <emphasis role="bold">kpasswd</emphasis> command to change your Kerberos password and the UNIX <emphasis
    role="bold">passwd</emphasis> command to change your UNIX password.</para>

  </sect1>
</chapter>