Discussion on config loading mechanism

How Apache httpd does it

The following is based on what's implemented in Ubuntu's Apache httpd 2.2.x package, though the mechanisms should be similar on other operating systems....

The config files are:

• /etc/apache2/apache2.conf

  • sets some initial, global settings (number of threads, default log locations, etc.)

• /etc/apache2/mods-available/*.load

  • contains all module load (but not configuration!) directives for all installed (but not necessarily used!) modules

• /etc/apache2/mods-available/*.conf

  • contains all module configuration directives for all installed (but not necessarily used!) modules

• /etc/apache2/mods-enabled/*.load

  • symlinks to mods-available/*.load files
  • a link here triggers loading of the module
  • loaded in alphanumeric order, so you can play ordering games via:
    • 00-mefirst.load
    • 05-mesecond.load
    • etc.

• /etc/apache2/mods-enabled/*.conf

  • same as mods-enabled/*.load above, but for the config files

• /etc/apache2/httpd.conf

  • user override settings go here

• /etc/apache2/ports.conf

  • network port settings

• /etc/apache2/conf.d/*

  • random collections of settings, e.g. one by default has a bunch of security-related settings in a file conf.d/security

• /etc/apache2/sites-available/*

  • similar to mods-available, but for virtual host settings
  • typically one virtual host per file

• /etc/apache2/sites-enabled/*

  • symlinks similar to mods-enabled, but for virtual host settings

There are also included some unfortunately-named utilities: a2enmod, a2ensite, a2dismod, a2dissite * these handle creating and removing the symlinks in mods-enabled and sites-enabled, e.g.: a2enmod <modulename>