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Key differences from the Apache HTTP Server

 

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IHS is based on the open source Apache Web server (httpd.apache.org), which can be built with many different capabilities and configuration options.

IHS includes a set of features from the available options.

• Apache modules (directives)
• Apache Portable Runtime (APR) library
• APR-util library
• Multi-processing module (MPM)
• Addressing modes

 

Key features added with IHS

• Support for the WebSphere admin console.

• InstallShield for multiple platforms enables consistent installation of the IHS on different platforms.
• Fast Response Cache Accelerator (FRCA) is available for AIX 5.x and certain Windows operating systems. FRCA significantly improves HTTP Server performance when serving static content such as HTML files or image files.

• Dynamic content generation with FastCGI.

• Installation of IHS in multiple languages

 

Operational differences between Apache and IHS

• The apachectl command is the only supported command to start IBM HTTP Server. You cannot directly invoke the httpd command because it will not find the required libraries. The apachectl command is the preferred command to start Apache V2.0 and higher, but the httpd command might work on the Apache server as expected, depending on the platform and how Apache was built. You can specify httpd options on the apachectl command line.

• IBM HTTP Server supports the suEXEC program, which provides for execution of CGI scripts under a particular user ID.

  • If we use the suEXEC program, install the IBM HTTP Server to the default installation only. The suEXEC program uses the security model which requires that all configuration paths are hard-coded in the executable file, and the paths chosen for IBM HTTP Server are those of the default installation

  • When an Apache user chooses an installation location for Apache at compile time, the suEXEC program is pre-built with the chosen paths, so this issue is seen by the Apache users.

  • Customers who need to use the suEXEC program with arbitrary configuration paths can build it with Apache on their platform and use the generated suEXEC binary with IBM HTTP Server. Customers must save and restore their custom suEXEC file when applying IHS maintenance.

• z/OS: As a more flexible replacement for the suEXEC program (which is for other platforms), IBM HTTP Server supports SAFRunAs. The SAFRunAs directive provides for execution of CGI scripts and access to static files under a particular user ID. You can enable the SAFRunAs directive from the mod_authnz_saf load module.

• IHS provides the new AddServerHeader directive to allow the server response header to be suppressed.

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Related reference

Apache modules (containing directives) supported by IHS
Apache programs supported by IHS
Apache APR and APR-util libraries supported by IHS
Apache MPM and addressing modes supported by IHS