ZFS doc fixes

[netatalk.git] / doc / manual / configuration.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter id="configuration">
  <title>Setting up Netatalk</title>

  <sect1>
    <title>File Services<indexterm>
        <primary>File Services</primary>

        <secondary>Netatalk's File Services</secondary>
      </indexterm></title>

    <para>Netatalk supplies AFP<indexterm>
        <primary>AFP</primary>

        <secondary>Apple Filing Protocol</secondary>
      </indexterm> services.</para>

    <sect2>
      <title>Setting up the AFP file server</title>

      <para>AFP (the Apple Filing Protocol) is the protocol Apple Macintoshes
      use for file services. The protocol has evolved over the years. The
      latest changes to the protocol, called "AFP 3.3", were added with the
      release of Snow Leopard<indexterm>
          <primary>Snow Leopard</primary>

          <secondary>Mac OS X 10.6</secondary>
        </indexterm> (Mac OS X 10.6).</para>

      <para>The afpd daemon offers the fileservices to Apple clients. The only
      configuration file is <filename>afp.conf</filename>. It uses a ini style
      configuration syntax.</para>

      <para>Mac OS X 10.5 (Leopard) added support for Time Machine backups
      over AFP. Two new functions ensure that backups are written to spinning
      disk, not just in the server's cache. Different host operating systems
      honour this cache flushing differently. To make a volume a Time Machine
      target use the volume option "<option>time machine =
      yes</option>".</para>

      <para>Starting with Netatalk 2.1 UNIX symlinks<indexterm>
          <primary>symlink</primary>

          <secondary>UNIX symlink</secondary>
        </indexterm> can be used on the server. Semantics are the same as for
      eg NFS, ie they are not resolved on the server side but instead it's
      completely up to the client to resolve them, resulting in links that
      point somewhere inside the clients filesystem view.</para>

      <sect3>
        <title>afp.conf</title>

        <para><filename>afp.conf</filename> is the configuration file used by
        afpd to determine the behaviour and configuration of the AFP file
        serverand the AFP volume that it provides.</para>

        <para>The <filename>afp.conf</filename> is divided into several
        sections:<variablelist>
            <varlistentry>
              <term>[Global]</term>

              <listitem>
                <para>The global section defines general server options</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>[Homes]</term>

              <listitem>
                <para>The homes section defines user home volumes</para>
              </listitem>
            </varlistentry>
          </variablelist>Any section not called <option>Global</option> or
        <option>Homes</option> is interpreted as an AFP volume.</para>

        <para>For sharing user homes by defining a <option>Homes</option>
        section you must specify the option <option>basedir regex</option>
        which can be a simple string with the path to the parent directory of
        all user homes or a regular expression.</para>

        <para>Example:</para>

        <para><programlisting>[Homes]
basedir regex = /home
</programlisting></para>

        <para>Now any user logging into the AFP server will have a user volume
        available whos path is <filename>/home/NAME</filename>.</para>

        <para>A more complex setup would be a server with a large amount of
        user homes which are split across eg two different
        filesystems:<itemizedlist>
            <listitem>
              <para>/RAID1/homes</para>
            </listitem>

            <listitem>
              <para>/RAID2/morehomes</para>
            </listitem>
          </itemizedlist>The following configuration is
        required:<programlisting>[Homes]
basedir regex = /RAID./.*homes
</programlisting></para>

        <para>If <option>basedir regex</option> contains symlink, set the
        canonicalized absolute path. When <filename>/home</filename> links to
        <filename>/usr/home</filename>: <programlisting>[Homes]
basedir regex = /usr/home</programlisting></para>

        <para>For a more detailed explanation of the available options, please
        refer to the <citerefentry>
            <refentrytitle>afp.conf</refentrytitle>

            <manvolnum>5</manvolnum>
          </citerefentry> man page.</para>
      </sect3>
    </sect2>

    <sect2 id="CNID-backends">
      <title>CNID<indexterm>
          <primary>CNID</primary>

          <secondary>Catalog Node ID</secondary>
        </indexterm> backends<indexterm>
          <primary>Backend</primary>

          <secondary>CNID backend</secondary>
        </indexterm></title>

      <para>Unlike other protocols like SMB or NFS, the AFP protocol mostly
      refers to files and directories by ID and not by a path (the IDs are
      also called CNID, that means Catalog Node ID). A typical AFP request
      uses a directory ID<indexterm>
          <primary>DID</primary>

          <secondary>Directory ID</secondary>
        </indexterm> and a filename, something like <phrase>"server, please
      open the file named 'Test' in the directory with id 167"</phrase>. For
      example "Aliases" on the Mac basically work by ID (with a fallback to
      the absolute path in more recent AFP clients. But this applies only to
      Finder, not to applications).</para>

      <para>Every file in an AFP volume has to have a unique file ID<indexterm>
          <primary>FID</primary>

          <secondary>File ID</secondary>
        </indexterm>, IDs must, according to the specs, never be reused, and
      IDs are 32 bit numbers (Directory IDs use the same ID pool). So, after
      ~4 billion files/folders have been written to an AFP volume, the ID pool
      is depleted and no new file can be written to the volume. No whining
      please :-)</para>

      <para>Netatalk needs to map IDs to files and folders in the host
      filesystem. To achieve this, several different CNID backends<indexterm>
          <primary>CNID backend</primary>
        </indexterm> are available and can be choosed by the <option>cnid
      scheme</option><indexterm>
          <primary>cnidscheme</primary>

          <secondary>specifying a CNID backend</secondary>
        </indexterm> option in the <citerefentry>
          <refentrytitle>afp.conf</refentrytitle>

          <manvolnum>5</manvolnum>
        </citerefentry> configuration file. A CNID backend is basically a
      database storing ID &lt;-&gt; name mappings.</para>

      <para>The CNID Databases are by default located in
      <filename>/var/netatalk/CNID</filename>.</para>

      <para>There is a command line utility called <command>dbd</command>
      available which can be used to verify, repair and rebuild the CNID
      database.</para>

      <note>
        <para>There are some CNID related things you should keep in mind when
        working with netatalk:</para>

        <itemizedlist>
          <listitem>
            <para>Don't nest volumes<indexterm>
                <primary>Nested volumes</primary>
              </indexterm>.</para>
          </listitem>

          <listitem>
            <para>CNID backends are databases, so they turn afpd into a file
            server/database mix.</para>
          </listitem>

          <listitem>
            <para>If there's no more space on the filesystem left, the
            database will get corrupted. You can work around this by either
            using the <option>vol dbpath</option> option and put the database
            files into another location or, if you use quotas, make sure the
            CNID database folder is owned by a user/group without a
            quota<indexterm>
                <primary>Quotas</primary>

                <secondary>Disk usage quotas</secondary>
              </indexterm>.</para>
          </listitem>

          <listitem>
            <para>Be careful with CNID databases for volumes that are mounted
            via NFS. That is a pretty audacious decision to make anyway, but
            putting a database there as well is really asking for trouble,
            i.e. database corruption. Use the <option>vol dbpath</option>
            directive to put the databases onto a local disk if you must use
            NFS<indexterm>
                <primary>NFS</primary>

                <secondary>Network File System</secondary>
              </indexterm> mounted volumes.</para>
          </listitem>
        </itemizedlist>
      </note>

      <sect3>
        <title>cdb<indexterm>
            <primary>CDB</primary>

            <secondary>"cdb" CNID backend</secondary>
          </indexterm></title>

        <para>The "concurrent database" backend is based on Berkeley DB. With
        this backend, several afpd daemons access the CNID database directly.
        Berkeley DB locking is used to synchronize access, if more than one
        afpd process is active for a volume. The drawback is, that the crash
        of a single afpd process might corrupt the database. cdb should only
        be used when sharing home directories for a larger number of users
        <emphasis>and</emphasis> it has been determined that a large number of
        <command>cnid_dbd</command> processes is problematic.</para>
      </sect3>

      <sect3>
        <title>dbd<indexterm>
            <primary>DBD</primary>

            <secondary>"dbd" CNID backend</secondary>
          </indexterm></title>

        <para>Access to the CNID database is restricted to the cnid_dbd daemon
        process. afpd processes communicate with the daemon for database reads
        and updates. The probability for database corruption is practically
        zero.</para>

        <para>This is the default backend since Netatalk 2.1.</para>
      </sect3>

      <sect3>
        <title>tdb<indexterm>
            <primary>tdb</primary>

            <secondary>"tdb" CNID backend</secondary>
          </indexterm></title>

        <para><abbrev>tdb</abbrev> is another persistent CNID database, it's
        Samba's <emphasis>Trivial Database</emphasis>. It could be used
        instead of <abbrev>cdb</abbrev> for user volumes.<important>
            <para>Only ever use it for volumes that are
            <emphasis>not</emphasis> shared and accessed by multiple clients
            at once !</para>
          </important>This backend is also used internally (as in-memory CNID
        database) as a fallback in case opening the primary database can't be
        opened, because <abbrev>tdb</abbrev> can work as in-memory database.
        This of course means upon restart the CNIDs are gone.</para>
      </sect3>

      <sect3>
        <title>last<indexterm>
            <primary>Last</primary>

            <secondary>"last" CNID backend</secondary>
          </indexterm></title>

        <para>The last backend is a in-memory tdb database. It is not
        persistent. Starting with netatalk 3.0, it becomes the <emphasis> read
        only mode</emphasis> automatically. This is useful e.g. for
        CD-ROMs.</para>
      </sect3>
    </sect2>

    <sect2 id="charsets">
      <title>Charsets<indexterm>
          <primary>Charset</primary>

          <secondary>character set</secondary>
        </indexterm>/Unicode<indexterm>
          <primary>Unicode</primary>
        </indexterm></title>

      <para></para>

      <sect3>
        <title>Why Unicode?</title>

        <para>Internally, computers don't know anything about characters and
        texts, they only know numbers. Therefore, each letter is assigned a
        number. A character set, often referred to as
        <emphasis>charset</emphasis> or
        <emphasis>codepage</emphasis><indexterm>
            <primary>Codepage</primary>
          </indexterm>, defines the mappings between numbers and
        letters.</para>

        <para>If two or more computer systems need to communicate with each
        other, the have to use the same character set. In the 1960s the
        ASCII<indexterm>
            <primary>ASCII</primary>

            <secondary>American Standard Code for Information
            Interchange</secondary>
          </indexterm> (American Standard Code for Information Interchange)
        character set was defined by the American Standards Association. The
        original form of ASCII represented 128 characters, more than enough to
        cover the English alphabet and numerals. Up to date, ASCII has been
        the normative character scheme used by computers.</para>

        <para>Later versions defined 256 characters to produce a more
        international fluency and to include some slightly esoteric graphical
        characters. Using this mode of encoding each character takes exactly
        one byte. Obviously, 256 characters still wasn't enough to map all the
        characters used in the various languages into one character
        set.</para>

        <para>As a result localized character sets were defined later, e.g the
        ISO-8859 character sets. Most operating system vendors introduced
        their own characters sets to satisfy their needs, e.g. IBM defined the
        <emphasis>codepage 437 (DOSLatinUS)</emphasis>, Apple introduced the
        <emphasis>MacRoman</emphasis><indexterm>
            <primary>MacRoman</primary>

            <secondary>MacRoman charset</secondary>
          </indexterm> codepage and so on. The characters that were assigned
        number larger than 127 were referred to as
        <emphasis>extended</emphasis> characters. These character sets
        conflict with another, as they use the same number for different
        characters, or vice versa.</para>

        <para>Almost all of those characters sets defined 256 characters,
        where the first 128 (0-127) character mappings are identical to ASCII.
        As a result, communication between systems using different codepages
        was effectively limited to the ASCII charset.</para>

        <para>To solve this problem new, larger character sets were defined.
        To make room for more character mappings, these character sets use at
        least 2 bytes to store a character. They are therefore referred to as
        <emphasis>multibyte</emphasis> character sets.</para>

        <para>One standardized multibyte charset encoding scheme is known as
        <ulink url="http://www.unicode.org/">unicode</ulink>. A big advantage
        of using a multibyte charset is that you only need one. There is no
        need to make sure two computers use the same charset when they are
        communicating.</para>
      </sect3>

      <sect3>
        <title>character sets used by Apple</title>

        <para>In the past, Apple clients used single-byte charsets to
        communicate over the network. Over the years Apple defined a number of
        codepages, western users will most likely be using the
        <emphasis>MacRoman</emphasis> codepage.</para>

        <para>Codepages defined by Apple include:</para>

        <itemizedlist>
          <listitem>
            <para>MacArabic, MacFarsi</para>
          </listitem>

          <listitem>
            <para>MacCentralEurope</para>
          </listitem>

          <listitem>
            <para>MacChineseSimple</para>
          </listitem>

          <listitem>
            <para>MacChineseTraditional</para>
          </listitem>

          <listitem>
            <para>MacCroation</para>
          </listitem>

          <listitem>
            <para>MacCyrillic</para>
          </listitem>

          <listitem>
            <para>MacDevanagari</para>
          </listitem>

          <listitem>
            <para>MacGreek</para>
          </listitem>

          <listitem>
            <para>MacHebrew</para>
          </listitem>

          <listitem>
            <para>MacIcelandic</para>
          </listitem>

          <listitem>
            <para>MacJapanese</para>
          </listitem>

          <listitem>
            <para>MacKorean</para>
          </listitem>

          <listitem>
            <para>MacRoman</para>
          </listitem>

          <listitem>
            <para>MacRomanian</para>
          </listitem>

          <listitem>
            <para>MacThai</para>
          </listitem>

          <listitem>
            <para>MacTurkish</para>
          </listitem>
        </itemizedlist>

        <para>Starting with Mac OS X and AFP3, <ulink
        url="http://www.utf-8.com/">UTF-8</ulink> is used. UTF-8 encodes
        Unicode characters in an ASCII compatible way, each Unicode character
        is encoded into 1-6 ASCII characters. UTF-8 is therefore not really a
        charset itself, it's an encoding of the Unicode charset.</para>

        <para>To complicate things, Unicode defines several <emphasis> <ulink
        url="http://www.unicode.org/reports/tr15/index.html">normalization</ulink>
        </emphasis> forms. While <ulink
        url="http://www.samba.org">samba</ulink><indexterm>
            <primary>Samba</primary>
          </indexterm> uses <emphasis>precomposed</emphasis><indexterm>
            <primary>Precomposed</primary>

            <secondary>Precomposed Unicode normalization</secondary>
          </indexterm> Unicode, which most Unix tools prefer as well, Apple
        decided to use the <emphasis>decomposed</emphasis><indexterm>
            <primary>Decomposed</primary>

            <secondary>Decomposed Unicode normalization</secondary>
          </indexterm> normalization.</para>

        <para>For example lets take the German character
        '<keycode>ä</keycode>'. Using the precomposed normalization, Unicode
        maps this character to 0xE4. In decomposed normalization, 'ä' is
        actually mapped to two characters, 0x61 and 0x308. 0x61 is the mapping
        for an 'a', 0x308 is the mapping for a <emphasis>COMBINING
        DIAERESIS</emphasis>.</para>

        <para>Netatalk refers to precomposed UTF-8 as
        <emphasis>UTF8</emphasis><indexterm>
            <primary>UTF8</primary>

            <secondary>Netatalk's precomposed UTF-8 encoding</secondary>
          </indexterm> and to decomposed UTF-8 as
        <emphasis>UTF8-MAC</emphasis><indexterm>
            <primary>UTF8-MAC</primary>

            <secondary>Netatalk's decomposed UTF-8 encoding</secondary>
          </indexterm>.</para>
      </sect3>

      <sect3>
        <title>afpd and character sets</title>

        <para>To support new AFP 3.x and older AFP 2.x clients at the same
        time, afpd needs to be able to convert between the various charsets
        used. AFP 3.x clients always use UTF8-MAC, AFP 2.x clients use one of
        the Apple codepages.</para>

        <para>At the time of this writing, netatalk supports the following
        Apple codepages:</para>

        <itemizedlist>
          <listitem>
            <para>MAC_CENTRALEUROPE</para>
          </listitem>

          <listitem>
            <para>MAC_CHINESE_SIMP</para>
          </listitem>

          <listitem>
            <para>MAC_CHINESE_TRAD</para>
          </listitem>

          <listitem>
            <para>MAC_CYRILLIC</para>
          </listitem>

          <listitem>
            <para>MAC_GREEK</para>
          </listitem>

          <listitem>
            <para>MAC_HEBREW</para>
          </listitem>

          <listitem>
            <para>MAC_JAPANESE</para>
          </listitem>

          <listitem>
            <para>MAC_KOREAN</para>
          </listitem>

          <listitem>
            <para>MAC_ROMAN</para>
          </listitem>

          <listitem>
            <para>MAC_TURKISH</para>
          </listitem>
        </itemizedlist>

        <para>afpd handles three different character set options:</para>

        <variablelist>
          <varlistentry>
            <term>unix charset<indexterm>
                <primary>unix charset</primary>

                <secondary>afpd's unix charset setting</secondary>
              </indexterm></term>

            <listitem>
              <para>This is the codepage used internally by your operating
              system. If not specified, it defaults to <option>UTF8</option>.
              If <option>LOCALE</option> is specified and your system support
              Unix locales, afpd tries to detect the codepage. afpd uses this
              codepage to read its configuration files, so you can use
              extended characters for volume names, login messages, etc. see
              <citerefentry>
                  <refentrytitle>afp.conf</refentrytitle>

                  <manvolnum>5</manvolnum>
                </citerefentry>.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term>mac charset<indexterm>
                <primary>mac charset</primary>

                <secondary>afpd's mac charset setting</secondary>
              </indexterm></term>

            <listitem>
              <para>As already mentioned, older Mac OS clients (up to AFP 2.2)
              use codepages to communicate with afpd. However, there is no
              support for negotiating the codepage used by the client in the
              AFP protocol. If not specified otherwise, afpd assumes the
              <emphasis>MacRoman</emphasis> codepage is used. In case you're
              clients use another codepage, e.g.
              <emphasis>MacCyrillic</emphasis>, you'll <emphasis
              role="bold">have</emphasis> to explicitly configure this. see
              <citerefentry>
                  <refentrytitle>afp.conf</refentrytitle>

                  <manvolnum>5</manvolnum>
                </citerefentry>.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term>vol charset<indexterm>
                <primary>vol charset</primary>

                <secondary>afpd's vol charset setting</secondary>
              </indexterm></term>

            <listitem>
              <para>This defines the charset afpd should use for filenames on
              disk. By default, it is the same as <option>unix
              charset</option>. If you have <ulink
              url="http://www.gnu.org/software/libiconv/">iconv</ulink><indexterm>
                  <primary>Iconv</primary>

                  <secondary>iconv encoding conversion engine</secondary>
                </indexterm> installed, you can use any iconv provided charset
              as well.</para>

              <para>afpd needs a way to preserve extended macintosh
              characters, or characters illegal in unix filenames, when saving
              files on a unix filesystem. Earlier versions used the the so
              called CAP encoding<indexterm>
                  <primary>CAP encoding</primary>

                  <secondary>CAP style character encoding</secondary>
                </indexterm>. An extended character (&gt;0x7F) would be
              converted to a :xx hex sequence, e.g. the Apple Logo (MacRoman:
              0xF0) was saved as :f0. Some special characters will be
              converted as to :xx notation as well. '/' will be encoded to
              :2f, if <option>usedots</option> was not specified, a leading
              dot '.' will be encoded as :2e.</para>

              <para>Even though this version now uses <option>UTF8</option> as
              the default encoding for filenames, '/' will be converted to
              ':'. For western users another useful setting could be
              <option>vol charset = ISO-8859-15</option>.</para>

              <para>If a character cannot be converted from the <option>mac
              charset</option> to the selected <option>vol charset</option>,
              afpd will save it as a CAP encoded character. For AFP3 clients,
              afpd will convert the UTF8 character to <option>mac
              charset</option> first. If this conversion fails, you'll receive
              a -50 error on the mac. <emphasis>Note</emphasis>: Whenever you
              can, please stick with the default UTF8 volume format. see
              <citerefentry>
                  <refentrytitle>afp.conf</refentrytitle>

                  <manvolnum>5</manvolnum>
                </citerefentry>.</para>
            </listitem>
          </varlistentry>
        </variablelist>
      </sect3>
    </sect2>

    <sect2 id="authentication">
      <title>Authentication<indexterm>
          <primary>Authentication</primary>

          <secondary>between AFP client and server</secondary>
        </indexterm></title>

      <sect3>
        <title>AFP authentication basics</title>

        <para>Apple chose a flexible model called "User Authentication
        Modules"<indexterm>
            <primary>UAM</primary>

            <secondary>User Authentication Module</secondary>
          </indexterm> (UAMs) for authentication purposes between AFP client
        and server. An AFP client initially connecting to an AFP server will
        ask for the list of UAMs which the server provides, and will choose
        the one with strongest encryption that the client supports.</para>

        <para>Several UAMs have been developed by Apple over the time, some by
        3rd-party developers.</para>
      </sect3>

      <sect3>
        <title>UAMs supported by Netatalk</title>

        <para>Netatalk supports the following ones by default:</para>

        <itemizedlist>
          <listitem>
            <para>"No User Authent"<indexterm>
                <primary>No User Authent</primary>

                <secondary>"No User Authent" UAM (guest access)</secondary>
              </indexterm> UAM (guest access without authentication)</para>
          </listitem>

          <listitem>
            <para>"Cleartxt Passwrd"<indexterm>
                <primary>Cleartxt Passwrd</primary>

                <secondary>"Cleartxt Passwrd" UAM</secondary>
              </indexterm> UAM (no password encryption)</para>
          </listitem>

          <listitem>
            <para>"Randnum exchange"<indexterm>
                <primary>Randnum exchange</primary>

                <secondary>"Randnum exchange" UAM</secondary>
              </indexterm>/"2-Way Randnum exchange"<indexterm>
                <primary>2-Way Randnum exchange</primary>

                <secondary>"2-Way Randnum exchange" UAM</secondary>
              </indexterm> UAMs (weak password encryption, separate password
            storage)</para>
          </listitem>

          <listitem>
            <para>"DHCAST128"<indexterm>
                <primary>DHCAST128</primary>

                <secondary>"DHCAST128" UAM</secondary>
              </indexterm> UAM (stronger password encryption)</para>
          </listitem>

          <listitem>
            <para>"DHX2"<indexterm>
                <primary>DHX2</primary>

                <secondary>"DHX2" UAM</secondary>
              </indexterm> UAM (successor of DHCAST128)</para>
          </listitem>
        </itemizedlist>

        <para>There exist other optional UAMs as well:</para>

        <itemizedlist>
          <listitem>
            <para>"PGPuam 1.0"<indexterm>
                <primary>PGPuam 1.0</primary>

                <secondary>"PGPuam 1.0" UAM</secondary>
              </indexterm><indexterm>
                <primary>uams_pgp.so</primary>

                <secondary>"PGPuam 1.0" UAM</secondary>
              </indexterm> UAM (PGP-based authentication for pre-Mac OS X
            clients. You'll also need the <ulink
            url="http://www.vmeng.com/vinnie/papers/pgpuam.html">PGPuam
            client</ulink> to let this work)</para>

            <para>You'll have to add <filename>"--enable-pgp-uam"</filename>
            to your configure switches to have this UAM available.</para>
          </listitem>

          <listitem>
            <para>"Kerberos IV"<indexterm>
                <primary>Kerberos IV</primary>

                <secondary>"Kerberos IV" UAM</secondary>
              </indexterm><indexterm>
                <primary>uams_krb4.so</primary>

                <secondary>"Kerberos IV" UAM</secondary>
              </indexterm>/"AFS Kerberos"<indexterm>
                <primary>AFS Kerberos</primary>

                <secondary>"AFS Kerberos" UAM (Kerberos IV)</secondary>
              </indexterm> UAMs (suitable to use <ulink
            url="http://web.mit.edu/macdev/KfM/Common/Documentation/faq.html">Kerberos
            v4 based authentication</ulink> and AFS file servers)</para>

            <para>Use <filename>"--enable-krb4-uam"</filename> at compile time
            to activate the build of this UAM.</para>
          </listitem>

          <listitem>
            <para>"Client Krb v2"<indexterm>
                <primary>Client Krb v2</primary>

                <secondary>"Client Krb v2" UAM (Kerberos V)</secondary>
              </indexterm> UAM (Kerberos V, suitable for "Single Sign On"
            Scenarios with OS X clients -- see below)</para>

            <para><filename>"--enable-krbV-uam"</filename> will provide you
            with the ability to use this UAM.</para>
          </listitem>
        </itemizedlist>

        <para>You can configure which UAMs should be activated by defining
        "<option>uam list</option>" in <option>Global</option> section.
        <command>afpd</command> will log which UAMs it's using and if problems
        occur while activating them in either
        <filename>netatalk.log</filename> or syslog at startup time.
        <citerefentry>
            <refentrytitle>asip-status.pl</refentrytitle>

            <manvolnum>1</manvolnum>
          </citerefentry> can be used to query the available UAMs of AFP
        servers as well.</para>

        <para>Having a specific UAM available at the server does not
        automatically mean that a client can use it. Client-side support is
        also necessary. For older Macintoshes running Mac OS &lt; X DHCAST128
        support exists since AppleShare client 3.8.x.</para>

        <para>On OS X, there exist some client-side techniques to make the
        AFP-client more verbose, so one can have a look what's happening while
        negotiating the UAMs to use. Compare with this <ulink
        url="http://article.gmane.org/gmane.network.netatalk.devel/7383/">hint</ulink>.</para>
      </sect3>

      <sect3>
        <title>Which UAMs to activate?</title>

        <para>It depends primarily on your needs and on the kind of Mac OS
        versions you have to support. Basically one should try to use
        DHCAST128 and DHX2 where possible because of its strength of password
        encryption.</para>

        <itemizedlist>
          <listitem>
            <para>Unless you really have to supply guest access to your
            server's volumes ensure that you disable "No User Authent" since
            it might lead accidentally to unauthorized access. In case you
            must enable guest access take care that you enforce this on a per
            volume base using the access controls.</para>
          </listitem>

          <listitem>
            <para>The "ClearTxt Passwrd" UAM is as bad as it sounds since
            passwords go unencrypted over the wire. Try to avoid it at both
            the server's side as well as on the client's. Note: If you want to
            provide Mac OS 8/9 clients with NetBoot-services then you need
            uams_cleartext.so since the AFP-client integrated into the Mac's
            firmware can only deal with this basic form of
            authentication.</para>
          </listitem>

          <listitem>
            <para>Since "Randnum exchange"/"2-Way Randnum exchange" uses only
            56 bit DES for encryption it should be avoided as well. Another
            disadvantage is the fact that the passwords have to be stored in
            cleartext on the server and that it doesn't integrate into both
            PAM scenarios or classic /etc/shadow (you have to administrate
            passwords separately by using the <citerefentry>
                <refentrytitle>afppasswd</refentrytitle>

                <manvolnum>1</manvolnum>
              </citerefentry> utility, if clients should use these
            UAMs)</para>
          </listitem>

          <listitem>
            <para>"DHCAST128" or "DHX2" should be a good compromise for most
            people since it combines stronger encryption with PAM
            integration.</para>
          </listitem>

          <listitem>
            <para>Using the Kerberos V<indexterm>
                <primary>Kerberos V</primary>

                <secondary>"Client Krb v2" UAM</secondary>
              </indexterm> ("Client Krb v2") UAM, it's possible to implement
            real single sign on scenarios using Kerberos tickets. The password
            is not sent over the network. Instead, the user password is used
            to decrypt a service ticket for the appleshare server. The service
            ticket contains an encryption key for the client and some
            encrypted data (which only the appleshare server can decrypt). The
            encrypted portion of the service ticket is sent to the server and
            used to authenticate the user. Because of the way that the afpd
            service principal detection is implemented, this authentication
            method is vulnerable to man-in-the-middle attacks.</para>
          </listitem>
        </itemizedlist>

        <para>For a more detailed overview over the technical implications of
        the different UAMs, please have a look at Apple's <ulink
        url="http://developer.apple.com/library/mac/#documentation/Networking/Conceptual/AFP/AFPSecurity/AFPSecurity.html#//apple_ref/doc/uid/TP40000854-CH232-SW1">File
        Server Security</ulink> pages.</para>
      </sect3>

      <sect3>
        <title>Using different authentication sources with specific
        UAMs</title>

        <para>Some UAMs provide the ability to use different authentication
        "backends", namely <filename>uams_cleartext.so</filename>,
        <filename>uams_dhx.so</filename> and
        <filename>uams_dhx2.so</filename>. They can use either classic Unix
        passwords from <filename>/etc/passwd</filename>
        (<filename>/etc/shadow</filename>) or PAM if the system supports that.
        <filename>uams_cleartext.so</filename> can be symlinked to either
        <filename>uams_passwd.so</filename> or
        <filename>uams_pam.so</filename>, <filename>uams_dhx.so</filename> to
        <filename>uams_dhx_passwd.so</filename> or
        <filename>uams_dhx_pam.so</filename> and
        <filename>uams_dhx2.so</filename> to
        <filename>uams_dhx2_passwd.so</filename> or
        <filename>uams_dhx2_pam.so</filename>.</para>

        <para>So, if it looks like this in Netatalk's UAMs folder (per default
        <filename>/etc/netatalk/uams/</filename>):<programlisting>uams_clrtxt.so -&gt; uams_pam.so
uams_dhx.so -&gt; uams_dhx_pam.so
uams_dhx2.so -&gt; uams_dhx2_pam.so</programlisting> then you're using PAM,
        otherwise classic Unix passwords. The main advantage of using PAM is
        that one can integrate Netatalk in centralized authentication
        scenarios, eg. via LDAP, NIS and the like. Please always keep in mind
        that the protection of your user's login credentials in such scenarios
        also depends on the strength of encryption that the UAM in question
        supplies. So think about eliminating weak UAMs like "ClearTxt Passwrd"
        and "Randnum exchange" completely from your network.</para>
      </sect3>

      <sect3>
        <title>Netatalk UAM overview table</title>

        <para>A small overview of the most common used UAMs.</para>

        <table orient="land">
          <title>Netatalk UAM overview</title>

          <tgroup align="center" cols="7">
            <colspec colname="col1" colnum="1" colwidth="0.5*" />

            <colspec colname="uam_guest" colnum="2" colwidth="1*" />

            <colspec colname="uam_clrtxt" colnum="3" colwidth="1*" />

            <colspec colname="uam_randnum" colnum="4" colwidth="1*" />

            <colspec colname="uam_dhx" colnum="5" colwidth="1*" />

            <colspec colname="uam_dhx2" colnum="6" colwidth="1*" />

            <colspec colname="uam_gss" colnum="7" colwidth="1*" />

            <tbody>
              <row>
                <entry align="center" rotate="0" valign="middle">UAM</entry>

                <entry>No User Authent<indexterm>
                    <primary>uams_guest.so</primary>

                    <secondary>"No User Authent" UAM (guest
                    access)</secondary>
                  </indexterm></entry>

                <entry>Cleartxt Passwrd<indexterm>
                    <primary>uams_cleartxt.so</primary>

                    <secondary>"Cleartxt Passwrd" UAM</secondary>
                  </indexterm></entry>

                <entry>(2-Way) Randnum exchange<indexterm>
                    <primary>uams_randnum.so</primary>

                    <secondary>"(2-Way) Randnum exchange" UAM</secondary>
                  </indexterm></entry>

                <entry>DHCAST128<indexterm>
                    <primary>uams_dhx.so</primary>

                    <secondary>"DHCAST128" UAM</secondary>
                  </indexterm></entry>

                <entry>DHX2<indexterm>
                    <primary>uams_dhx2.so</primary>

                    <secondary>"DHX2" UAM</secondary>
                  </indexterm></entry>

                <entry>Client Krb v2<indexterm>
                    <primary>uams_gss.so</primary>

                    <secondary>"Client Krb v2" UAM (Kerberos V)</secondary>
                  </indexterm></entry>
              </row>

              <row>
                <entry align="center" rotate="0" valign="middle">pssword
                length</entry>

                <entry>guest access</entry>

                <entry>max. 8 characters</entry>

                <entry>max. 8 characters</entry>

                <entry>max. 64 characters</entry>

                <entry>max. 256 characters</entry>

                <entry>Kerberos tickets</entry>
              </row>

              <row>
                <entry align="center" rotate="0" valign="middle">Client
                support</entry>

                <entry>built-in into all Mac OS versions</entry>

                <entry>built-in in all Mac OS versions except 10.0. Has to be
                activated explicitly in recent Mac OS X versions</entry>

                <entry>built-in into almost all Mac OS versions</entry>

                <entry>built-in since AppleShare client 3.8.4, available as a
                plug-in for 3.8.3, integrated in Mac OS X' AFP client</entry>

                <entry>built-in since Mac OS X 10.2</entry>

                <entry>built-in since Mac OS X 10.2</entry>
              </row>

              <row>
                <entry align="center" rotate="0"
                valign="middle">Encryption</entry>

                <entry>Enables guest access without authentication between
                client and server.</entry>

                <entry>Password will be sent in cleartext over the wire. Just
                as bad as it sounds, therefore avoid at all if possible (note:
                providing NetBoot services requires the ClearTxt UAM)</entry>

                <entry>8-byte random numbers are sent over the wire,
                comparable with DES, 56 bits. Vulnerable to offline dictionary
                attack. Requires passwords in clear on the server.</entry>

                <entry>Password will be encrypted with 128 bit SSL, user will
                be authenticated against the server but not vice versa.
                Therefor weak against man-in-the-middle attacks.</entry>

                <entry>Password will be encrypted using libgcrypt with CAST
                128 in CBC mode. User will be authenticated against the server
                but not vice versa. Therefor weak against man-in-the-middle
                attacks.</entry>

                <entry>Password is not sent over the network. Due to the
                service principal detection method, this authentication method
                is vulnerable to man-in-the-middle attacks.</entry>
              </row>

              <row>
                <entry align="center" rotate="0" valign="middle">Server
                support</entry>

                <entry align="center" valign="middle">uams_guest.so</entry>

                <entry align="center" valign="middle">uams_cleartxt.so</entry>

                <entry align="center" valign="middle">uams_randnum.so</entry>

                <entry align="center" valign="middle">uams_dhx.so</entry>

                <entry align="center" valign="middle">uams_dhx2.so</entry>

                <entry align="center" valign="middle">uams_gss.so</entry>
              </row>

              <row>
                <entry align="center" rotate="0" valign="middle">Password
                storage method</entry>

                <entry align="center" valign="middle">None</entry>

                <entry align="center" valign="middle">Either /etc/passwd
                (/etc/shadow) or PAM</entry>

                <entry align="center" valign="middle">Passwords stored in
                clear text in a separate text file</entry>

                <entry align="center" valign="middle">Either /etc/passwd
                (/etc/shadow) or PAM</entry>

                <entry align="center" valign="middle">Either /etc/passwd
                (/etc/shadow) or PAM</entry>

                <entry align="center" valign="middle">At the Kerberos Key
                Distribution Center*</entry>
              </row>
            </tbody>
          </tgroup>
        </table>

        <para>* Have a look at this <ulink
        url="http://cryptnet.net/fdp/admin/kerby-infra/en/kerby-infra.html">Kerberos
        overview</ulink></para>
      </sect3>

      <sect3 id="sshtunnel">
        <title>SSH tunneling</title>

        <para>Tunneling and all sort of VPN stuff has nothing to do with AFP
        authentication and UAMs in general. But since Apple introduced an
        option called "Allow Secure Connections Using SSH" and many people
        tend to confuse both things, we'll speak about that here too.</para>

        <sect4 id="manualsshtunnel">
          <title>Manually tunneling an AFP session</title>

          <para>This works since the first AFP servers that spoke "AFP over
          TCP" appeared in networks. One simply tunnels the remote server's
          AFP port to a local port different than 548 and connects locally to
          this port afterwards. On OS X this can be done by</para>

          <programlisting>ssh -l $USER $SERVER -L 10548:127.0.0.1:548 sleep 3000</programlisting>

          <para>After establishing the tunnel one will use
          <filename>"afp://127.0.0.1:10548"</filename> in the "Connect to
          server" dialog. All AFP traffic including the initial connection
          attempts will be sent encrypted over the wire since the local AFP
          client will connect to the Mac's local port 10548 which will be
          forwarded to the remote server's AFP port (we used the default 548)
          over SSH.</para>

          <para>These sorts of tunnels are an ideal solution if you've to
          access an AFP server providing weak authentications mechanisms
          through the Internet without having the ability to use a "real" VPN.
          Note that you can let <command>ssh</command> compress the data by
          using its "-C" switch and that the tunnel endpoints can be different
          from both AFP client and server (compare with the SSH documentation
          for details).</para>
        </sect4>

        <sect4 id="autosshtunnel">
          <title>Automatically establishing a tunneled AFP connection</title>

          <para>From Mac OS X 10.2 to 10.4, Apple added an "Allow Secure
          Connections Using SSH" checkbox to the "Connect to Server" dialog.
          The idea behind: When the server signals that it can be contacted by
          SSH then Mac OS X' AFP client tries to establish the tunnel and
          automagically sends all AFP traffic through it.</para>

          <para>But it took until the release of Mac OS X 10.3 that this
          feature worked the first time... partly. In case, the SSH tunnel
          can't be established the AFP client <emphasis
          role="strong">silently</emphasis> fell back to an unencrypted AFP
          connection attempt.</para>

          <para>Netatalk's afpd will report that it is capable of handling SSH
          tunneled AFP requests, when both "<option>advertise ssh</option>"
          and "<option>fqdn</option>" options are set in
          <option>Global</option> section (double check with <citerefentry>
              <refentrytitle>asip-status.pl</refentrytitle>

              <manvolnum>1</manvolnum>
            </citerefentry> after you restarted afpd when you made changes to
          the settings). But there are a couple of reasons why you don't want
          to use this option at all:</para>

          <itemizedlist>
            <listitem>
              <para>Tunneling TCP over TCP (as SSH does) is not the best idea.
              There exist better solutions like VPNs based on the IP
              layer.</para>
            </listitem>

            <listitem>
              <para>Since this SSH kludge isn't a normal UAM that integrates
              directly into the AFP authentication mechanisms but instead uses
              a single flag signalling clients whether they can <emphasis
              role="strong">try</emphasis> to establish a tunnel or not, it
              makes life harder to see what's happening when things go
              wrong.</para>
            </listitem>

            <listitem>
              <para>You cannot control which machines are logged on by
              Netatalk tools like a <command>macusers</command> since all
              connection attempts seem to be made from localhost.</para>
            </listitem>

            <listitem>
              <para>On the other side you've to limit access to afpd to
              localhost only (TCP wrappers) when you want to ensure that all
              AFP sessions are SSH encrypted or...</para>
            </listitem>

            <listitem>
              <para>...when you're using 10.2 - 10.3.3 then you get the
              opposite of what you'd expect: potentially unencrypted AFP
              communication (including logon credentials) on the network
              without a single notification that establishing the tunnel
              failed. Apple fixed that not until Mac OS X 10.3.4.</para>
            </listitem>

            <listitem>
              <para>Encrypting all AFP sessions via SSH can lead to a
              significantly higher load on the Netatalk server</para>
            </listitem>
          </itemizedlist>
        </sect4>
      </sect3>
    </sect2>

    <sect2 id="acls">
      <title>ACL Support<indexterm>
          <primary>ACLs</primary>
        </indexterm></title>

      <para>ACL support for AFP is implemented for ZFS ACLs on Solaris and
      derived platforms and for POSIX 1e ACLs on Linux.</para>

      <sect3>
        <title>Configuration</title>

        <para>For a basic mode of operation there's nothing to configure.
        Netatalk reads ACLs on the fly and calculates effective permissions
        which are then send to the AFP client via the so called
        UARights<indexterm>
            <primary>UARights</primary>
          </indexterm> permission bits. On a Mac, the Finder uses these bits
        to adjust permission in Finder windows. For example folder whos UNIX
        mode would only result in in read-only permissions for a user will not
        be displayed with a read-only icon and the user will be able to write
        to the folder given the folder has an ACL giving the user write
        access.</para>

        <para>By default, the effective permission of the authenticated user
        are only mapped to the mentioned UARights<indexterm>
            <primary>UARights</primary>
          </indexterm>permission structure, not the UNIX mode. You can adjust
        this behaviour with the configuration option <link
        linkend="map_acls">map acls</link>.</para>

        <para>However, neither in Finder "Get Info" windows nor in Terminal
        will you be able to see the ACLs, that's a result of how ACLs in OS X
        are designed. If you want to be able to display ACLs on the client,
        things get more involved as you must then setup both client and server
        to be part on a authentication domain (directory service, eg LDAP,
        OpenDirectory). The reason is, that in OS X ACLs are bound to UUIDs,
        not just uid's or gid's. Therefor afpd must be able to map every
        filesystem uid and gid to a UUID so that it can return the server side
        ACLs which are bound to UNIX uid and gid mapped to OS X UUIDs.</para>

        <para>Netatalk can query a directory server using LDAP queries. Either
        the directory server already provides an UUID attribute for user and
        groups (Active Directory, Open Directory) or you reuse an unused
        attribute (or add a new one) to you directory server (eg
        OpenLDAP).</para>

        <para>In detail:</para>

        <orderedlist>
          <listitem>
            <para>For Solaris/ZFS: ZFS Volumes</para>

            <para>You should configure a ZFS ACL know for any volume you want
            to use with Netatalk:</para>

            <screen>aclinherit = passthrough
aclmode = passthrough</screen>

            <para>For an explanation of what this knob does and how to apply
            it, check your hosts ZFS documentation (eg man zfs).</para>
          </listitem>

          <listitem>
            <para>Authentication Domain</para>

            <para>Your server and the clients must be part of a security
            association where identity data is coming from a common source.
            ACLs in Darwin are based on UUIDs and so is the ACL specification
            in AFP 3.2. Therefor your source of identity data has to provide
            an attribute for every user and group where a UUID is stored as a
            ASCII string. In other words:</para>

            <itemizedlist>
              <listitem>
                <para>you need an Open Directory Server or an LDAP server
                where you store UUIDs in some attribute</para>
              </listitem>

              <listitem>
                <para>your clients must be configured to use this
                server</para>
              </listitem>

              <listitem>
                <para>your server should be configured to use this server via
                nsswitch and PAM</para>
              </listitem>

              <listitem>
                <para>configure Netatalk via the special <link
                linkend="acl_options">LDAP options for ACLs</link> in <link
                linkend="afp.conf.5">afp.conf</link> so that Netatalk is able
                to retrieve the UUID for users and groups via LDAP search
                queries</para>
              </listitem>
            </itemizedlist>
          </listitem>
        </orderedlist>
      </sect3>

      <sect3>
        <title>OS X ACLs</title>

        <para>With Access Control Lists (ACLs) Mac OS X offers a powerful
        extension of the traditional UNIX permissions model. An ACL is an
        ordered list of Access Control Entries (ACEs) explicitly granting or
        denying a set of permissions to a given user or group.</para>

        <para>Unlike UNIX permissions, which are bound to user or group IDs,
        ACLs are tied to UUIDs. For this reason accessing an object's ACL
        requires server and client to use a common directory service which
        translates between UUIDs and user/group IDs.</para>

        <para>ACLs and UNIX permissions interact in a rather simple way. As
        ACLs are optional UNIX permissions act as a default mechanism for
        access control. Changing an objects's UNIX permissions will leave it's
        ACL intact and modifying an ACL will never change the object's UNIX
        permissions. While doing access checks, OS X first examines an
        object's ACL evaluating ACEs in order until all requested rights have
        been granted, a requested right has been explicitly denied by an ACE
        or the end of the list has been reached. In case there is no ACL or
        the permissions granted by the ACL are not sufficient to fulfill the
        request, OS X next evaluates the object's UNIX permissions. Therefore
        ACLs always have precedence over UNIX permissions.</para>
      </sect3>

      <sect3>
        <title>ZFS ACLs</title>

        <para>ZFS ACLs closely match OS X ACLs. Both offer mostly identical
        fine grained permissions and inheritance settings.</para>
      </sect3>

      <sect3>
        <title>POSIX ACLs</title>

        <sect4>
          <title>Overview</title>

          <para>Compared to OS X or NFSv4 ACLs, Posix ACLs represent a
          different, less versatile approach to overcome the limitations of
          the traditional UNIX permissions. Implementations are based on the
          withdrawn Posix 1003.1e standard.</para>

          <para>The standard defines two types of ACLs. Files and directories
          can have access ACLs which are consulted for access checks.
          Directories can also have default ACLs irrelevant to access checks.
          When a new object is created inside a directory with a default ACL,
          the default ACL is applied to the new object as it's access ACL.
          Subdirectories inherit default ACLs from their parent. There are no
          further mechanisms of inheritance control. </para>

          <para>Architectural differences between Posix ACLs and OS X ACLs
          especially involve:</para>

          <para><itemizedlist>
              <listitem>
                <para>No fine-granular permissions model. Like UNIX
                permissions Posix ACLs only differentiate between read, write
                and execute permissions.</para>
              </listitem>

              <listitem>
                <para>Entries within an ACL are unordered.</para>
              </listitem>

              <listitem>
                <para>Posix ACLs can only grant rights. There is no way to
                explicitly deny rights by an entry.</para>
              </listitem>

              <listitem>
                <para>UNIX permissions are integrated into an ACL as special
                entries.</para>
              </listitem>
            </itemizedlist></para>

          <para>Posix 1003.1e defines 6 different types of ACL entries. The
          first three types are used to integrate standard UNIX permissions.
          They form a minimal ACL, their presence is mandatory and only one
          entry of each type is allowed within an ACL.</para>

          <para><itemizedlist>
              <listitem>
                <para>ACL_USER_OBJ: the owner's access rights.</para>
              </listitem>

              <listitem>
                <para>ACL_GROUP_OBJ: the owning group's access rights.</para>
              </listitem>

              <listitem>
                <para>ACL_OTHER: everybody's access rights.</para>
              </listitem>
            </itemizedlist></para>

          <para>The remaining entry types expand the traditional permissions
          model:</para>

          <para><itemizedlist>
              <listitem>
                <para>ACL_USER: grants access rights to a certain user.</para>
              </listitem>

              <listitem>
                <para>ACL_GROUP: grants access rights to a certain
                group.</para>
              </listitem>

              <listitem>
                <para>ACL_MASK: limits the maximum access rights which can be
                granted by entries of type ACL_GROUP_OBJ, ACL_USER and
                ACL_GROUP. As the name suggests, this entry acts as a mask.
                Only one ACL_MASK entry is allowed per ACL. If an ACL contains
                ACL_USER or ACL_GROUP entries, an ACL_MASK entry must be
                present too, otherwise it is optional.</para>
              </listitem>
            </itemizedlist></para>

          <para>In order to maintain compatibility with applications not aware
          of ACLs, Posix 1003.1e changes the semantics of system calls and
          utilities which retrieve or manipulate an objects UNIX permissions.
          In case an object only has a minimal ACL, the group permissions bits
          of the UNIX permissions correspond to the value of the ACL_GROUP_OBJ
          entry.</para>

          <para>However, if the ACL also contains an ACL_MASK entry, the
          behavior of those system calls and utilities is different. The group
          permissions bits of the UNIX permissions correspond to the value of
          the ACL_MASK entry, i. e. calling "chmod g-w" will not only revoke
          write access for the group, but for all entities which have been
          granted write access by ACL_USER or ACL_GROUP entries.</para>
        </sect4>

        <sect4>
          <title>Mapping POSIX ACLs to OS X ACLs</title>

          <para>When a client wants to read an object's ACL, afpd maps it's
          Posix ACL onto an equivalent OS X ACL. Writing an object's ACL
          requires afpd to map an OS X ACL onto a Posix ACL. Due to
          architectural restrictions of Posix ACLs, it is usually impossible
          to find an exact mapping so that the result of the mapping process
          will be an approximation of the original ACL's semantic.</para>

          <para><itemizedlist>
              <listitem>
                <para>afpd silently discard entries which deny a set of
                permissions because they they can't be represented within the
                Posix architecture. </para>
              </listitem>

              <listitem>
                <para>As entries within Posix ACLs are unordered, it is
                impossible to preserve order.</para>
              </listitem>

              <listitem>
                <para>Inheritance control is subject to severe limitations as
                well:<itemizedlist>
                    <listitem>
                      <para>Entries with the only_inherit flag set will only
                      become part of the directory's default ACL.</para>
                    </listitem>

                    <listitem>
                      <para>Entries with at least one of the flags
                      file_inherit, directory_inherit or limit_inherit set,
                      will become part of the directory's access and default
                      ACL, but the restrictions they impose on inheritance
                      will be ignored.</para>
                    </listitem>
                  </itemizedlist></para>
              </listitem>

              <listitem>
                <para>The lack of a fine-granular permission model on the
                Posix side will normally result in an increase of granted
                permissions.</para>
              </listitem>
            </itemizedlist></para>

          <para>As OS X clients aren't aware of the Posix 1003.1e specific
          relationship between UNIX permissions and ACL_MASK, afpd does not
          expose this feature to the client to avoid compatibility issues and
          handles *unix permissions and ACLs the same way as Apple's reference
          implementation of AFP does. When an object's UNIX permissions are
          requested, afpd calculates proper group rights and returns the
          result together with the owner's and everybody's access rights to
          the caller via "permissions" and "ua_permissions" members of the
          FPUnixPrivs structure (see Apple Filing Protocol Reference, page
          181). Changing an object's permissions, afpd always updates
          ACL_USER_OBJ, ACL_GROUP_OBJ and ACL_OTHERS. If an ACL_MASK entry is
          present too, afpd recalculates it's value so that the new group
          rights become effective and existing entries of type ACL_USER or
          ACL_GROUP stay intact.</para>
        </sect4>
      </sect3>
    </sect2>

    <sect2 id="fce">
      <title>Filesystem Change Events<indexterm>
          <primary>FCE</primary>
        </indexterm></title>

      <para>Netatalk includes a nifty filesystem change event mechanism where
      afpd processes notfiy interested listeners about certain filesystem
      event by UDP network datagrams.</para>

      <para>For the format of the UDP packets and for an example C application
      that demonstrates how to use these in a listener, take a look at the
      Netatalk sourcefile <filename>bin/misc/fce.c</filename>.</para>

      <para>The currently supported FCE events are<itemizedlist>
          <listitem>
            <para>file modification (fmod)</para>
          </listitem>

          <listitem>
            <para>file deletion (fdel)</para>
          </listitem>

          <listitem>
            <para>directory deletion (ddel)</para>
          </listitem>

          <listitem>
            <para>file creation (fcre)</para>
          </listitem>

          <listitem>
            <para>directory deletion (ddel)</para>
          </listitem>
        </itemizedlist></para>

      <para>For details on the available simple configuration options take a
      look at <filename><link
      linkend="fceconf">afp.conf</link></filename>.</para>
    </sect2>
  </sect1>

  <sect1>
    <title>Starting and stopping Netatalk</title>

    <para>The Netatalk distribution comes with several operating system
    specific startup script templates that are tailored according to the
    options given to the "configure" script before compiling. Currently,
    templates are provided for RedHat (sysv style), RedHat (systemd style),
    SUSE (sysv style), SUSE (systemd style), Gentoo, NetBSD, Debian and
    Solaris. You can select to install the generated startup script(s)
    <indexterm>
        <primary>Startscript</primary>

        <secondary>startup script</secondary>
      </indexterm> by specifying a system type to "configure". To
    automatically install startup scripts give one of the available
    <option>--with-init-style</option> option to "configure".</para>

    <para>Since new releases of Linux distributions appear all the time and
    the startup procedure for the other systems mentioned above might change
    as well, it is probably a good idea to not blindly install a startup
    script but to look at it first to see if it will work on your system. If
    you use Netatalk as part of a fixed setup, like a Linux distribution, an
    RPM or a BSD package, things will probably have been arranged properly for
    you. The following therefore applies mostly for people who have compiled
    Netatalk themselves.</para>

    <para>The following daemon need to be started by whatever startup script
    mechanism is used:</para>

    <itemizedlist>
      <listitem>
        <para>netatalk<indexterm>
            <primary>netatalk</primary>
          </indexterm></para>
      </listitem>
    </itemizedlist>

    <para>Additionally, make sure that the configuration file
    <filename>afp.conf</filename> is in the right place.</para>
  </sect1>
</chapter>