<sect1 id="intro">
 <title>Introduction</title>
  <sect2 id="what">
   <title>What is NFS?</title>
    <para>
      The Network File System (NFS) was developed to allow machines 
      to mount a disk partition on a remote machine as if it were on
      a local hard drive.   This allows for fast, seamless sharing of 
      files across a network.
    </para>
    <para>
      It also gives the potential for unwanted people to access your 
      hard drive over the network (and thereby possibly read your email 
      and delete all  your files as well as break into your system) if 
      you set it up incorrectly.  So please read the Security section of 
      this document carefully if you intend to implement an NFS setup.
    </para>
    <para>
      There are other systems that provide similar functionality to NFS.
      Samba (<ulink url="http://www.samba.org">http://www.samba.org</ulink>)
      provides file services to Windows clients.  The Andrew File
      System from IBM (<ulink url="http://www.transarc.com/Product/EFS/AFS/index.html">http://www.transarc.com/Product/EFS/AFS/index.html</ulink>), 
      recently open-sourced, provides a file sharing mechanism with some 
      additional security and performance features.  The Coda File System 
      (<ulink url="http://www.coda.cs.cmu.edu/">http://www.coda.cs.cmu.edu/</ulink>) is still in development as of this writing
      but is designed to work well with disconnected clients.  Many of the
      features of the Andrew and Coda file systems are slated for inclusion
      in the next version of NFS (Version 4) (<ulink url="http://www.nfsv4.org">http://www.nfsv4.org</ulink>).  The 
      advantage of NFS today is that it is mature, standard, well understood, 
      and supported robustly across a variety of platforms.
     </para>
  </sect2>
  <sect2 id="scope">
   <title>What is this HOWTO and what is it not?</title>
   <para>
     This HOWTO is intended as a complete, step-by-step guide to setting
     up NFS correctly and effectively.  Setting up NFS involves two steps,
     namely configuring the server and then configuring the client.  Each 
     of these steps is dealt with in order.  The document then offers     
     some tips for people with particular needs and hardware setups, as   
     well as security and troubleshooting advice.  
   </para>
   <para>
     This HOWTO is not a description of the guts and
     underlying structure of NFS.  For that you may wish to read
     <emphasis>Linux NFS and Automounter Administration</emphasis> by Erez Zadok (Sybex, 2001).  The classic NFS book, updated and still quite useful, is <emphasis>Managing NFS and NIS</emphasis> by Hal Stern, published by O'Reilly &
     Associates, Inc.  A much more advanced technical 
     description of NFS is available in <emphasis>NFS Illustrated</emphasis> by Brent Callaghan.
   </para>
   <para>
     This document is also not intended as a complete reference manual,
     and does not contain an exhaustive list of the features of Linux
     NFS.  For that, you can look at the man pages for <emphasis>nfs(5)</emphasis>, 
     <emphasis>exports(5)</emphasis>, <emphasis>mount(8)</emphasis>, <emphasis>fstab(5)</emphasis>, 
     <emphasis>nfsd(8)</emphasis>, <emphasis>lockd(8)</emphasis>, <emphasis>statd(8)</emphasis>, 
     <emphasis>rquotad(8)</emphasis>, and <emphasis>mountd(8)</emphasis>.
   </para>
   <para>
     It will also not cover PC-NFS, which is considered obsolete (users
     are encouraged to use Samba to share files with Windows machines) or NFS 
     Version 4, which is still in development.
   </para>
  </sect2>
  <sect2 id="knowprereq">
   <title>Knowledge Pre-Requisites</title>
   <para>
     You should know some basic things about TCP/IP networking before 
     reading this HOWTO; if you are in doubt, read the 
     <ulink url="http://www.linuxdoc.org/HOWTO/Networking-Overview-HOWTO.html">Networking-
     Overview-HOWTO</ulink>.
   </para>
  </sect2>
  <sect2 id="swprereq">
   <title>Software Pre-Requisites: Kernel Version and nfs-utils</title>
   <para>
     The difference between Version 2 NFS and version 3 NFS will be 
     explained later on; for now, you might simply take the suggestion 
     that you will need NFS Version 3 if you are installing a dedicated
     or high-volume file server.  NFS Version 2 should be fine for 
     casual use.
   </para>
   <para>
     NFS Version 2 has been around for quite some time now (at least 
     since the 1.2 kernel series) however you will need a kernel version
     of at least 2.2.18 if you wish to do any of the following:
    <itemizedlist>
     <listitem><para>Mix Linux NFS with other operating systems' NFS</para></listitem>
     <listitem><para>Use file locking reliably over NFS</para></listitem>
     <listitem><para>Use NFS Version 3.</para></listitem>
    </itemizedlist>
   </para>
   <para>
     There are also patches available for kernel versions above 2.2.14 
     that provide the above functionality.  Some of them can be downloaded
     from the Linux NFS homepage.  If your kernel version is 2.2.14-
     2.2.17 and you have the source code on hand, you can tell if these 
     patches have been added because NFS Version 3 server support will be 
     a configuration option.  However, unless you have some particular
     reason to use an older kernel, you should upgrade because many bugs
     have been fixed along the way.  Kernel 2.2.19 contains some additional
     locking improvements over 2.2.18.
   </para>
   <para>
     Version 3 functionality will also require the nfs-utils package of 
     at least version 0.1.6, and mount version 2.10m or newer.  However 
     because nfs-utils and mount are fully backwards compatible, and because 
     newer versions have lots of security and bug fixes, there is no good 
     reason not to install the newest nfs-utils and mount packages if you 
     are beginning an NFS setup.
   </para>
   <para>
     All 2.4 and higher kernels have full NFS Version 3 functionality.
   </para>
   <para>
     In all cases, if you are building your own kernel, you will need
     to select NFS and NFS Version 3 support at compile time.  Most
     (but not all) standard distributions come with kernels that support
     NFS version 3.
   </para>
   <para>
     Handling files larger than 2 GB will require a 2.4x kernel and a 
     2.2.x version of <application>glibc</application>.
   </para>
   <para>
     All kernels after 2.2.18 support NFS over TCP on the client side.
     As of this writing, server-side NFS over TCP only exists in a
     buggy form as an experimental option in the post-2.2.18 series;
     patches for 2.4 and 2.5 kernels have been introduced starting with
     2.4.17 and 2.5.6.  The patches are believed to be stable, though
     as of this writing they are relatively new and have not seen
     widespread use or integration into the mainstream 2.4 kernel.
   </para>
   <para>
     Because so many of the above functionalities were introduced in
     kernel version 2.2.18, this document was written to be consistent
     with kernels above this version (including 2.4.x).  If you have an
     older kernel, this document may not describe your NFS system
     correctly.
   </para>
   <para>
     As we write this document, NFS version 4 has only recently been
     finalized as a protocol, and no implementations are considered
     production-ready.  It will not be dealt with here.
   </para>
  </sect2>
  <sect2 id="furtherhelp">
  <title>Where to get help and further information</title>
  <para>
    As of November 2000, the Linux NFS homepage is at 
    <ulink url="http://nfs.sourceforge.net">http://nfs.sourceforge.net</ulink>.  Please check there for NFS related 
    mailing lists as well as the latest version of nfs-utils, NFS 
    kernel patches, and other NFS related packages.
   </para>
 
<para>
When you encounter a problem or have a question not covered in this
manual, the faq or the man pages, you should send a message to the nfs
mailing list (<email>nfs@lists.sourceforge.net</email>). To best help the developers
and other users help you assess your problem you should include:
</para>
<itemizedlist>
<listitem>
<para>
 the version of <application>nfs-utils</application> you are using
</para>
</listitem>
<listitem
<para>
 the version of the kernel and any non-stock applied kernels.
</para>
</listitem>
<listitem>
<para>
 the distribution of linux you are using
</para>
</listitem>
<listitem>
<para>
 the version(s) of other operating systems involved.
</para>
</listitem>
</itemizedlist>
<para>
It is also useful to know the networking configuration connecting the
hosts.
</para>
<para> 
If your problem involves the inability mount or export shares please
also include:
</para>
<itemizedlist>
<listitem>
<para>
 a copy of your <filename>/etc/exports</filename> file
</para>
</listitem>
<listitem>
<para>
 the output of <command>rpcinfo -p</command> <emphasis>localhost</emphasis> run on the server
</para>
</listitem>
<listitem>
<para>
 the output of <command>rpcinfo -p</command> <emphasis>servername</emphasis> run on the client
</para>
</listitem>
</itemizedlist>
<para>
Sending all of this information with a specific question, after reading
all the documentation, is the best way to ensure a helpful response from
the list.
</para>
 <para>
    You may also wish to look at the man pages for  <emphasis>nfs(5)</emphasis>, 
     <emphasis>exports(5)</emphasis>, <emphasis>mount(8)</emphasis>, <emphasis>fstab(5)</emphasis>, 
     <emphasis>nfsd(8)</emphasis>, <emphasis>lockd(8)</emphasis>, <emphasis>statd(8)</emphasis>, 
     <emphasis>rquotad(8)</emphasis>, and <emphasis>mountd(8)</emphasis>.
  </para>
 </sect2>
</sect1>

