lfs-book/chapter06/libcap.xml

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<sect1 id="ch-system-libcap" role="wrap">
  <?dbhtml filename="libcap.html"?>

  <sect1info condition="script">
    <productname>libcap</productname>
    <productnumber>&libcap-version;</productnumber>
    <address>&libcap-url;</address>
  </sect1info>

  <title>Libcap-&libcap-version;</title>

  <indexterm zone="ch-system-libcap">
    <primary sortas="a-Libcap">Libcap</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The Libcap package implements the user-space interfaces to the POSIX
    1003.1e capabilities available in Linux kernels. These capabilities are a
    partitioning of the all powerful root privilege into a set of distinct
    privileges.</para>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&libcap-ch6-sbu;</seg>
        <seg>&libcap-ch6-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

  <sect2 role="installation">
    <title>Installation of Libcap</title>

    <para>Prevent a static library from being installed:</para>

<screen><userinput remap="pre">sed -i '/install.*STALIBNAME/d' libcap/Makefile</userinput></screen>

    <para>Compile the package:</para>

<screen><userinput remap="make">make</userinput></screen>

    <para>This package does not come with a test suite.</para>

    <para>Install the package:</para>

<screen><userinput remap="install">make RAISE_SETFCAP=no lib=lib prefix=/usr install
chmod -v 755 /usr/lib/libcap.so</userinput></screen>

    <variablelist>
      <title>The meaning of the make option:</title>

      <varlistentry>
        <term><parameter>RAISE_SETFCAP=no</parameter></term>
        <listitem>
          <para>This parameter skips trying to use <command>setcap</command>
          on itself. This avoids an installation error if the kernel or file
          system does not support extended capabilities.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>lib=lib</parameter></term>
        <listitem>
          <para>This parameter installs the library in
          <filename>$prefix/lib</filename> rather than
          <filename>$prefix/lib64</filename> on x86_64. It has no effect on
          x86.</para>
        </listitem>
      </varlistentry>
 
    </variablelist>

    <para>The shared library needs to be moved to
    <filename class="directory">/lib</filename>, and as a result the
    <filename class="extension">.so</filename> file in
    <filename class="directory">/usr/lib</filename> will need to be recreated:</para>

<screen><userinput remap="install">mv -v /usr/lib/libcap.so.* /lib
ln -sfv ../../lib/$(readlink /usr/lib/libcap.so) /usr/lib/libcap.so</userinput></screen>

  </sect2>

  <sect2 id="contents-libcap" role="content">
    <title>Contents of Libcap</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>
      <segtitle>Installed library</segtitle>

      <seglistitem>
        <seg>capsh, getcap, getpcaps, and setcap</seg>
        <seg>libcap.so</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="capsh">
        <term><command>capsh</command></term>
        <listitem>
          <para>A shell wrapper to explore and constrain capability support</para>
          <indexterm zone="ch-system-libcap capsh">
            <primary sortas="b-capsh">capsh</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="getcap">
        <term><command>getcap</command></term>
        <listitem>
          <para>Examines file capabilities</para>
          <indexterm zone="ch-system-libcap getcap">
            <primary sortas="b-getcap">getcap</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="getpcaps">
        <term><command>getpcaps</command></term>
        <listitem>
          <para>Displays the capabilities on the queried process(es)</para>
          <indexterm zone="ch-system-libcap getpcaps">
            <primary sortas="b-getpcaps">getpcaps</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libcap">
        <term><filename class="libraryfile">libcap</filename></term>
        <listitem>
          <para>Contains the library functions for manipulating POSIX 1003.1e
          capabilities</para>
          <indexterm zone="ch-system-libcap libcap">
            <primary sortas="c-libcap">libcap</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="setcap">
        <term><command>setcap</command></term>
        <listitem>
          <para>Sets file capabilities</para>
          <indexterm zone="ch-system-libcap setcap">
            <primary sortas="b-setcap">setcap</primary>
          </indexterm>
        </listitem>
      </varlistentry>


    </variablelist>

  </sect2>

</sect1>