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  <H1 ALIGN="CENTER">Apache Server Frequently Asked Questions</H1>

  <P>

  $Revision: 1.63.2.13 $ ($Date: 1997/07/31 08:57:21 $)

  $Revision: 1.63.2.14 $ ($Date: 1997/08/03 08:47:57 $)

  </P>

  <P>

  The latest version of this FAQ is always available from the main

   <LI><A HREF="#linux-shmget">When I run it under Linux I get "shmget:

    function not found", what should I do?</A>

   </LI>

   <LI><A HREF="#authauthoritative">Why does my authentification give

   <LI><A HREF="#authauthoritative">Why does my authentication give

    me a server error?</A>

   <LI><A HREF="#auth-on-same-machine">Do I have to keep the (mSQL)

    authentification information on the same machine?</A>

    authentication information on the same machine?</A>

   </LI>

   <LI><A HREF="#msql-slow">Why is my mSQL authentification terribly slow?</A>

   <LI><A HREF="#msql-slow">Why is my mSQL authentication terribly slow?</A>

   </LI>

   <LI><A HREF="#rewrite-more-config">Where can I find mod_rewrite rulesets

    which already solve particular URL-related problems?</A>

  This is generally only necessary when you are calling external

  programs from your script that send output to stdout, or if there will

  be a long delay between the time the headers are sent and the actual

  content starts being emitted.  To maximise performance, you should

  content starts being emitted.  To maximize performance, you should

  turn buffer-flushing back <EM>off</EM> (with <CODE>$| = 0</CODE> or the

  equivalent) after the statements that send the headers, as displayed

  above.

      <STRONG>Can I increase <SAMP>FD_SETSIZE</SAMP> on FreeBSD?</STRONG>

     </A>

  <P>

  On versions of FreeBSD older than 2.2 <SAMP>FD_SETSIZE</SAMP>, which

  limits the number of open files on the system, is controlled by a

  kernel option and is limited to 256.  You can set this value using a

  line such as the following in your kernel configuration file:

  On versions of FreeBSD before 3.0, the <SAMP>FD_SETSIZE</SAMP> define 

  defaults to 256.  This means that you will have trouble usefully using

  more than 256 file descriptors in Apache.  This can be increased, but

  doing so can be tricky.

  If you are using a version prior to 2.2, you need to recompile your

  kernel with a larger FD_SETSIZE.  This can be done by adding a 

  line such as:

  </P>

  <DL>

   <DD><CODE>options FD_SETSIZE <EM>nnn</EM></CODE>

   </DD>

  </DL>

  <P>

  This can restrict the number of

  virtual hosts you can use, especially if they all use different log

  files.  Increasing this limit (and recompiling Apache) is not enough,

  as it is on some platforms (such as Solaris), as you also will have

  to recompile <SAMP>libc</SAMP> with the changed setting.

  To your kernel config file.  Starting at version 2.2, this is no

  longer necessary.

  </P>

  <P>

  With FreeBSD 2.2 and later, you <EM>can</EM> increase the setting of

  <SAMP>FD_SETSIZE</SAMP> at Apache compilation time by adding

  &quot;<SAMP>-DFD_SETSIZE=<EM>nnn</EM></SAMP>&quot; to the

  <SAMP>EXTRA_CFLAGS</SAMP> line in your <SAMP>Configuration</SAMP>

  file.

  If you are using a version of 2.1-stable from after 1997/03/10 or

  2.2 or 3.0-current from before 1997/06/28, there is a limit in

  the resolver library that prevents it from using more file descriptors

  than what FD_SETSIZE is set to when libc is compiled.  To increase

  this, you have to recompile libc with a higher FD_SETSIZE.

  </P>

  <P>

  On FreeBSD 3.0 the default is 1024, so the problem is lessened still

  more, and may not require any intervention at all.

  In FreeBSD 3.0, the default FD_SETSIZE has been increased to

  1024 and the above limitation in the resolver library

  has been removed.

  </P>

  <P>

  After you deal with the appropriate changes above, you can increase 

  the setting of <SAMP>FD_SETSIZE</SAMP> at Apache compilation time 

  by adding &quot;<SAMP>-DFD_SETSIZE=<EM>nnn</EM></SAMP>&quot; to the

  <SAMP>EXTRA_CFLAGS</SAMP> line in your <SAMP>Configuration</SAMP>

  file.

  </P>

  <HR>

 </LI>

     </A>

  <P>

  This is a normal message and nothing about which to be alarmed.  It simply

  means that the client cancelled the connection before it had been

  means that the client canceled the connection before it had been

  completely set up - such as by the end-user pressing the "Stop"

  button.  People's patience being what it is, sites with response-time

  problems or slow network links may experiences this more than

  <HR>

 </LI>

 <LI><A NAME="authauthoritative">

      <STRONG>Why does my authentification give me a server error?</STRONG>

      <STRONG>Why does my authentication give me a server error?</STRONG>

     </A>

  <P>

  Under normal circumstances, the Apache access control modules will

  pass unrecognized user IDs on to the next access control module in

  line.  Only if the user ID is recognized and the password is validated

  (or not) will it give the usual success or "authentification

  (or not) will it give the usual success or "authentication

  failed" messages.

  </P>

  <P>

  <SAMP>mod_auth_mysql</SAMP>, <SAMP>mod_auth_anon</SAMP> or

  <SAMP>mod_auth_cookie</SAMP> modules on their own.  These are by

  default <STRONG>not</STRONG> authoritative, and this will pass the

  buck on to the (non-existent) next authentification module when the

  buck on to the (non-existent) next authentication module when the

  user ID is not in their respective database.  Just add the appropriate

  '<SAMP><EM>XXX</EM>Authoritative yes</SAMP>' line to the configuration.

  </P>

  <HR>

 </LI>

 <LI><A NAME="auth-on-same-machine">

      <STRONG>Do I have to keep the (mSQL) authentification information

      <STRONG>Do I have to keep the (mSQL) authentication information

      on the same machine?</STRONG>

     </A>

  <P>

  Some organizations feel very strongly about keeping the authentification

  Some organizations feel very strongly about keeping the authentication

  information on a different machine than the webserver. With the

  <SAMP>mod_auth_msql</SAMP>, <SAMP>mod_auth_mysql</SAMP>, and other SQL

  modules connecting to (R)DBMses this is quite possible. Just configure

  <HR>

 </LI>

 <LI><A NAME="msql-slow">

      <STRONG>Why is my mSQL authentification terribly slow?</STRONG>

      <STRONG>Why is my mSQL authentication terribly slow?</STRONG>

     </A>

  <P>

  You have probably configured the Host by specificing a FQHN,

  You have probably configured the Host by specifying a FQHN,

  and thus the libmsql will use a full blown tcp/ip socket to talk to

  the database, rather than a fast internal device.  The

  <SAMP>libmsql</SAMP>, the mSQL FAQ, and the <SAMP>mod_auth_msql</SAMP>

  <A

      HREF="http://www.heise.de/ix/artikel/9612149/"

  >http://www.heise.de/ix/artikel/9612149/</A>,

  the english (translated) version can be found at 

  the English (translated) version can be found at 

  <A

      HREF="http://www.heise.de/ix/artikel/E/9612149/"

  >http://www.heise.de/ix/artikel/E/9612149/</A>.