Chapter 3 Using Dynamic Modules
Table of Contents
Dynamic modules provide a means of allowing developers and third parties to extend the capabilities of the Secure Web Server. When properly configured in the server configuration file, these modules will be loaded into the Web server at startup time. As the Secure Web Server is powered by Apache, modules conforming to the Apache DSO API can be use with the Secure Web Server.
The Secure Web Server can be customized using dynamic modules provided from Apache and other sources. For a complete list of the Secure Web Server 1.3 modules (DSO and integrated), see Appendix A. See Appendix B for a complete list of the Secure Web Server 2.0 modules.
The Secure Web Server integrates many Apache modules and provides many other modules as dynamic shared objects (DSO). The DSO modules are not integrated because they are not usually part of the default configuration of an Apache server. Section : Standard Modules Provided as DSO Modules lists the standard Apache modules provided as DSO modules. Section : Nonstandard Modules Provided as DSO Modules lists nonstandard DSO modules provided in the Secure Web Server kit. (Nonstandard DSO modules are modules not from the Apache Foundation.)
Administrators can build Apache modules for use with the Secure Web Server. The standard Apache apxs utility (/usr/internet/httpd/bin/apxs or /usr/opt/hpapache2/bin/apxs) is provided with the Secure Web Server to assist you during compilation and installation of the Apache modules.
Instructions for compiling modules using the apxs utility are usually included with the source code for that particular module. Instructions can also be found in the standard Apache documentation on the Web: http://www.apache.org.
Standard Apache documentation is also included with the Secure Web Server in the IAEAPDOCxxxsubset, installed in /usr/internet/httpd/apdocs. Standard Apache 2.0 documentation is installed in /usr/hpapache2/manual.
The Secure Web Server provides several standard Apache modules as DSO modules. These are modules that are included in source form as part of the Apache Version 1.3 source distributions and Apache Version 2.0 source distribution. Although there are many modules that are included in the distributions, many of them are not included in the default server configuration. The optional modules are provided in the form of DSO modules so they can be activated if needed. Table A-2 lists and describes the modules for the Secure Web Server 1.3. Table B-2 lists and describes the modules for the Secure Web Server 2.0.
Usually, an Apache DSO module will not perform any useful function until the module-specific configuration directives activate the module's functionality. The module-specific documentation explains the module configuration directives. For Apache DSO modules provided with the Secure Web Server, refer to either the Apache documentation provided with the Secure Web Server kit, or the documentation available on the Apache Web site:
If the ClearModule directive is present, it signals the server that the list of loaded modules needs to be reordered. The ClearModule directive begins the process by clearing the internal list of modules, thus providing the configuration file with a complete list of all modules (integrated and DSO). Each module is readded to the module list with an AddModule directive (Section : Using the AddModule Directive).
The AddModule directive is used by the Web server to build a list of modules in order of precedence. The directive is only needed if the ClearModule directive is used to zero out the module list. If the ClearModule directive is not used, then the module precedence is in the order that they were loaded.
After adding the configuration directives to the httpd.conf file, the file syntax can be reviewed prior to restarting the server. The following command directs the server to verify the specified configuration file: