LDP/LDP/guide/docbook/Linux-Filesystem-Hierarchy/lib.xml

<sect1 id="lib">
<title>/lib</title>

<para>
The /lib directory contains kernel modules and those shared library images (the C programming code library) needed to boot the system and run the commands in the root filesystem, ie. by binaries in /bin and /sbin. Libraries are readily identifiable through their filename extension of *.so. Windows equivalent to a shared library would be a DLL (dynamically linked library) file. They are essential for basic system functionality. Kernel modules (drivers) are in the subdirectory /lib/modules/'kernel-version'. To ensure proper module compilation you should ensure that /lib/modules/'kernel-version'/kernel/build points to /usr/src/'kernel-version' or ensure that the Makefile knows where the kernel source itself are located.
</para>

   <para>
    <variablelist>

     <varlistentry>
      <term>/lib/&apos;machine-architecture&apos;</term>
      <listitem>
       <para>Contains platform/architecture dependent libraries.</para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/iptables</term>
      <listitem>
       <para>iptables shared library files.</para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/kbd</term>
      <listitem>
       <para>Contains various keymaps.</para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/modules/&apos;kernel-version&apos;</term>
      <listitem>
       <para>The home of all the kernel modules. The organisation of 
       files here is reasonably clear so no requires no elaboration.
       </para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/modules/&apos;kernel-version&apos;/isapnpmap.dep</term>
      <listitem>
       <para>
       has details on ISA based cards, the modules that they 
       require and various other attributes.
       </para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/modules/&apos;kernel-version&apos;/modules.dep</term>
      <listitem>
       <para>
       lists all modules dependencies. This file can 
       be updated using the depmod command.
       </para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term>/lib/modules/&apos;kernel-version&apos;/pcimap</term>
      <listitem>
       <para>is the PCI equivalent of the 
       /lib/modules/'kernel-version'/isapnpmap.dep file.
       </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>/lib/modules/&apos;kernel-version&apos;/usbmap</term>
      <listitem>
       <para>is the USB equivalent of the 
       /lib/modules/'kernel-version'/isapnpmap.dep file.</para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>/lib/oss</term>
      <listitem>
       <para>
       All OSS (Open Sound System) files are installed 
       here by default.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>/lib/security</term>
      <listitem>
       <para>PAM library files.</para>
      </listitem>
     </varlistentry>

    </variablelist>
   </para>

<para>
<screen>
The FSSTND states that the /lib directory contains those shared library
images needed to boot the system and run the commands in the root filesystem,
ie. by binaries in /bin and /sbin.

Shared libraries that are only necessary for binaries in /usr (such as any 
X Window binaries) must not be in /lib. Only the shared libraries required
to run binaries in /bin and /sbin may be here. In particular, the library 
libm.so.* may also be placed in /usr/lib if it is not required by anything
in /bin or /sbin.

At least one of each of the following filename patterns are required (they 
may be files, or symbolic links):

libc.so.* The dynamically-linked C library (optional)
ld*       The execution time linker/loader (optional)

If a C preprocessor is installed, /lib/cpp must be a reference to it, for
historical reasons. The usual placement of this binary is /usr/bin/cpp.

The following directories, or symbolic links to directories, must be in 
/lib, if the corresponding subsystem is installed:

modules   Loadable kernel modules (optional)

/lib&lt;qual&gt; : Alternate format essential shared libraries (optional)

There may be one or more variants of the /lib directory on systems which
support more than one binary format requiring separate libraries.

This is commonly used for 64-bit or 32-bit support on systems which support
multiple binary formats, but require libraries of the same name. In this 
case, /lib32 and /lib64 might be the library directories, and /lib a symlink
to one of them.

If one or more of these directories exist, the requirements for their contents
are the same as the normal /lib directory, except that /lib&lt;qual&gt;/cpp is 
not required.

/lib&lt;qual&gt;/cpp is still permitted: this allows the case where /lib and 
/lib&lt;qual&gt; are the same (one is a symbolic link to the other).
</screen>
</para>

</sect1>