The modules.conf file controls which modules are loaded or not loaded at Asterisk startup. This is done through the use of the load => or noload => constructs.

The modules.conf file always starts with the [modules] header. The autoload statement tells Asterisk whether to automatically load all modules contained within the modules directory or to load only those modules specifically defined by load => statements. We recommend you manually load only those modules you need, but many people find it easier to let Asterisk attempt to autoload whatever it finds in /usr/lib/asterisk/modules. You can then exclude^[164] certain modules with noload => statements.

Here’s a sample modules.conf file:

[modules]
    autoload=no                ; set this to yes and Asterisk will load any
                               ; modules it finds in /usr/lib/asterisk/modules

    load => res_adsi.so
    load => pbx_config.so      ; Requires: N/A
    load => chan_iax2.so       ; Requires: res_crypto.so, res_features.so
    load => chan_sip.so        ; Requires: res_features.so
    load => codec_alaw.so      ; Requires: N/A
    load => codec_gsm.so       ; Requires: N/A
    load => codec_ulaw.so      ; Requires: N/A
    load => format_gsm.so      ; Requires: N/A
    load => app_dial.so        ; Requires: res_features.so, res_musiconhold.so

Since we assume Asterisk is built on Linux, all the module names we use end in a .so extension. However, this may not be the case if you have built Asterisk on a different operating system.

As of this writing, there are eight module types: resources, applications, Call Detail Record database connectors, channels, codecs, formats, PBX modules, and standalone functions. Let’s take a look at each of them.