64bit_issues.xml

<?xml version="1.0"?>
<!DOCTYPE chapter [
  <!ENTITY % entities SYSTEM "generic-entities.ent">
  %entities;
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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="cha-64bit">
 <title>32-Bit and 64-Bit Applications in a 64-Bit System Environment</title>
 <info>
  <meta name="description">Configure your 64-bit environment to run existing 32-bit applications without requiring additional ports</meta>
  <dm:docmanager xmlns:dm="urn:x-suse:ns:docmanager">
   <dm:bugtracker/>
   <dm:translation>yes</dm:translation>
  </dm:docmanager>
 <revhistory xml:id="rh-cha-64bit">
   <revision>
     <date>2026-04-09</date>
     <revdescription>
       <para/>
     </revdescription>
   </revision>
 </revhistory>
</info>
 <para>
  &productnamereg; is available for <phrase os="sles">several</phrase> 64-bit
  platforms. This does not necessarily mean that all the applications included
  have already been ported to 64-bit platforms. &productname; supports the use
  of 32-bit applications in a 64-bit system environment. This chapter offers a
  brief overview of how this support is implemented on 64-bit &productname;
  platforms.
 </para>
 <para>
  <phrase os="sles">&productname; for the 64-bit platforms IBM &ppc;, IBM
  &zseries; and &amd64;/&intel64;</phrase><phrase os="sled;osuse">&productname;
  for the 64-bit platforms &amd64;/&intel64;</phrase> is designed so that
  existing 32-bit applications run in the 64-bit environment
  <quote>out-of-the-box.</quote> <phrase os="sles">The corresponding 32-bit
  platforms are ppc for &power;, and x86 for &amd64;/&intel64;.</phrase> This
  support means that you can continue to use your preferred 32-bit applications
  without waiting for a corresponding 64-bit port to become available.<phrase os="sles"> The current &power; system runs most applications in 32-bit mode,
  but you can run 64-bit applications.</phrase>
 </para>


 <note>
  <title>No Support for Building 32-bit Applications</title>
  <para>
   &productname; does not support compiling 32-bit applications, it only offers
   runtime support for 32-bit binaries.
  </para>
 </note>


 <sect1 xml:id="sec-64bit-runt">
  <title>Runtime Support</title>

  <important>
   <title>Conflicts Between Application Versions</title>
   <para>
    If an application is available both for 32-bit and 64-bit environments,
    parallel installation of both versions is bound to lead to problems. In
    such cases, decide on one of the two versions and install and use this.
   </para>
   <para>
    An exception to this rule is PAM (pluggable authentication modules).
    &productname; uses PAM in the authentication process as a layer that
    mediates between user and application. On a 64-bit operating system that
    also runs 32-bit applications it is necessary to always install both
    versions of a PAM module.
   </para>
  </important>

  <para>
   To be executed correctly, every application requires a range of libraries.
   Unfortunately, the names for the 32-bit and 64-bit versions of these
   libraries are identical. They must be differentiated from each other in
   another way.
  </para>

  <para>
   To retain compatibility with the 32-bit version, the libraries are stored at
   the same place in the system as in the 32-bit environment. The 32-bit
   version of <filename>libc.so.6</filename> is located under
   <filename>/lib/libc.so.6</filename> in both the 32-bit and 64-bit
   environments.
  </para>

  <para>
   All 64-bit libraries and object files are located in directories called
   <filename>lib64</filename>. The 64-bit object files that you would normally
   expect to find under <filename>/lib</filename> and
   <filename>/usr/lib</filename> are now found under
   <filename>/lib64</filename> and <filename>/usr/lib64</filename>. This means
   that there is space for the 32-bit libraries under <filename>/lib</filename>
   and <filename>/usr/lib</filename>, so the file name for both versions can
   remain unchanged.
  </para>

  <para>
   Subdirectories of 32-bit <filename>/lib</filename> directories which contain
   data content that does not depend on the word size are not moved. This
   scheme conforms to LSB (Linux Standards Base) and FHS (File System Hierarchy
   Standard).
  </para>
 </sect1>
 <sect1 xml:id="sec-64bit-kernel">
  <title>Kernel Specifications</title>

  <para>
   The 64-bit kernels for &amd64;/&intel64;<phrase os="sles">, IBM &power; and
   IBM &zseries;</phrase> offer both a 64-bit and a 32-bit kernel ABI
   (application binary interface). The latter is identical with the ABI for the
   corresponding 32-bit kernel. This means that the 32-bit application can
   communicate with the 64-bit kernel in the same way as with the 32-bit
   kernel.
  </para>

  <para>
   The 32-bit emulation of system calls for a 64-bit kernel does not support
   all the APIs used by system programs. This depends on the platform. For this
   reason, few applications, like <command>lspci</command>, must be
   compiled<phrase os="sles"> on non-&power; platforms as 64-bit programs to
   function properly. On IBM &zseries;, not all ioctls are available in the
   32-bit kernel ABI</phrase>.
  </para>

  <para>
   A 64-bit kernel can only load 64-bit kernel modules that have been specially
   compiled for this kernel. It is not possible to use 32-bit kernel modules.
  </para>

  <tip>
   <title>Kernel-loadable Modules</title>
   <para>
    Some applications require separate kernel-loadable modules. If you intend
    to use such a 32-bit application in a 64-bit system environment, contact
    the provider of this application and &suse; to make sure that the 64-bit
    version of the kernel-loadable module and the 32-bit compiled version of
    the kernel API are available for this module.
   </para>
  </tip>
 </sect1>
</chapter>