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 requires that 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/lib/gcc-lib/&lt;target&gt;/&lt;version&gt;/cpp. /lib/cpp
can either point at this binary, or at any other reference to 
this binary which exists in the filesystem. (For example, 
/usr/bin/cpp is also often used.)

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

/lib -- essential shared libraries and kernel modules
/lib/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>