Asterisk - The Open Source VoIP PBX - Section D.1. modules.conf

D.1. modules.conf

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.

This file is a key component to building a secure Asterisk installation: best practice suggests that only required modules be loaded.

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 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.

D.1.1. Resources

A resource provides a connection to a static repository of a particular type of information, such as a unique regional requirement or a library of constant elements. This information must be configurable for each system, but once loaded it doesn't need to change in the course of normal operations.

For each resource below, we have outlined the applications and features it provides to other Asterisk modules We've indicated the .conf file used to define the resource, where needed; if no file is listed, then a configuration file isn't required. The resource modules are:

res_adsi.so

Configuration file: adsi.conf

Provides: ADSI functions to ADSIProg( ) and Voicemail( )

res_agi.so

Provides: DeadAGI( ), EAGI( ), AGI( )

res_crypto.so

Provides: Loads public and private keys located in /var/lib/asterisk/keys/

res_features.so

Configuration file: features.conf

Provides: ParkedCall( ), Park( )

res_indications.so

Configuration file: indications.conf

Provides: Playtones( ), StopPlaytones( )

res_monitor.so

Provides: Monitor( ), StopMonitor( ), ChangeMonitor( ), action Monitor, action StopMonitor, action ChangeMonitor

res_musiconhold.so

Configuration file: musiconhold.conf

Provides: MusicOnHold( ), WaitMusicOnHold( ), SetMusicOnHold( ), StartMusicOnHold( ), StopMusicOnHold( )

res_odbc.so

Configuration file: res_odbc.conf

Provides: Connectivity information to the ODBC^[*] driverthe purpose is to store configuration file information in a database and retrieve that information from the database; however, a reload is required to make changes take effect

^[*] Open DataBase Connectivity (ODBC) is a standard by which access to a database can be provided.

D.1.2. Applications

If you build an Asterisk dialplan of any size, you are going to use at least oneand more likely dozensof applications.^[] If an application is never going to be used, it is not strictly required that it be loaded. For performance-challenged systems (or if you just like to keep it lean), you may elect to load only those applications that are referenced in your dialplan.

^[] To be of any use, a self-contained dialplan will always require several applications. Some folks, however, use the dialplan for no other purpose than to pass control to an external application. In this case, it would be possible to have the dialplan use no application other than AGI( ). We're not recommending that you do this, but again, it demonstrates Asterisk's enormous flexibility.

For each application module, we will define any resource requirements and name the applications that the module provides. Unless we have stated otherwise, the application does not require a configuration file or any other modules. The available application modules are:

app_adsiprog.so

Requires: res_adsi.so

Provides: ADSIProg( )

app_alarmreceiver.so

Provides: AlarmReceiver( )

app_authenticate.so

Provides: Authenticate( )

app_cdr.so

Provides: NoCDR( )

app_chanisavail.so

Provides: ChanIsAvail( )

app_chanspy.so

Provides: ChanSpy( )

app_controlplayback.so

Provides: ControlPlayback( )

app_curl.so

Provides: Curl( )

app_cut.so

Provides: Cut( )

app_db.so

Provides: DBget( ), DBput( ), DBdel( ), DBdeltree( )

app_dial.so

Requires: res_features.so, res_musiconhold.so

Provides: Dial( ), RetryDial( )

app_dictate.so

Provides: Dictate( )

app_directory.so

Provides: Directory( )

app_disa.so

Provides: DISA( )

app_dumpchan.so

Provides: DumpChan( )

app_echo.so

Provides: Echo( )

app_enumlookup.so

Configuration file: enum.conf

Provides: EnumLookup( )

app_eval.so

Provides: Eval( )

app_exec.so

Provides: Exec( )

app_festival.so

Provides: Festival( )

app_forkcdr.so

Provides: ForkCDR( )

app_getcpeid.so

Requires: res_adsi.so

Provides: GetCPEID( )

app_groupcount.so

Provides: GetGroupCount( ), SetGroup( ), CheckGroup( ), GetGroupMatchCount( )

app_hasnewvoicemail.so

Provides: HasVoicemail( ), HasNewVoicemail( )

app_ices.so

Provides: ICES( )

app_image.so

Provides: SendImage( )

app_lookupblacklist.so

Provides: LookupBlacklist( )

app_lookupcidname.so

Provides: LookupCIDName( )

app_macro.so

Provides: Macro( ), MacroExit( ), MacroIf( )

app_math.so

Provides: Math( )

app_md5.so

Provides: MD5( ), MD5Check( )

app_milliwatt.so

Provides: Milliwatt( )

app_mp3.so

Provides: MP3Player( )

app_nbscat.so

Provides: NBScat( )

app_parkandannounce.so

Requires: res_features.so

Provides: ParkAndAnnounce( )

app_playback.so

Provides: Playback( )

app_privacy.so

Provides: PrivacyManager( )

app_queue.so

Requires: res_features.so, res_monitor.so, res_musiconhold.so

Provides: Queue( ), AddQueueMember( ), RemoveQueueMember( ), PauseQueueMember( ), UnpauseQueueMember( ), action Queues, action QueueStatus, action QueueAdd, action QueueRemove, action QueuePause

app_random.so

Provides: Random( )

app_read.so

Provides: Read( )

app_readfile.so

Provides: ReadFile( )

app_realtime.so

Provides: RealTime( ), RealTimeUpdate( )

app_record.so

Provides: Record( )

app_sayunixtime.so

Provides: SayUnixTime( ), DateTime( )

app_senddtmf.so

Provides: SendDTMF( )

app_sendtext.so

Provides: SendText( )

app_setcallerid.so

Provides: SetCallerPres( ), SetCallerID( )

app_setcdruserfield.so

Provides: SetCDRUserField( ), AppendCDRUserField( ), action SetCDRUserField

app_setcidname.so

Provides: SetCIDName( )

app_setcidnum.so

Provides: SetCIDNum( )

app_setrdnis.so

Provides: SetRDNIS( )

app_settransfercapability.so

Provides: SetTransferCapability( )

app_sms.so

Provides: SMS( )

app_softhangup.so

Provides: SoftHangup( )

app_striplsd.so

Provides: StripLSD( )

app_substring.so (deprecated)

Provides: SubString( )

app_system.so

Provides: System( ), TRySystem( )

app_talkdetect.so

Provides: BackgroundDetect( )

app_test.so

Provides: TestClient( ), TestServer( )

app_transfer.so

Provides: transfer( )

app_txtcidname.so

Configuration file: enum.conf

Provides: TXTCIDName( )

app_url.so

Provides: SendURL( )

app_userevent.so

Provides: UserEvent( )

app_verbose.so

Provides: Verbose( )

app_voicemail.so

Configuration file: voicemail.conf

Requires: res_adsi.so

Provides: VoiceMail( ), VoiceMailMain( ), MailboxExists( ), VMAuthenticate( )

app_waitforring.so

Provides: WaitForRing( )

app_waitforsilence.so

Provides: WaitForSilence( )

app_while.so

Provides: While( ), ExecIf( ), EndWhile( )

app_zapateller.so

Provides: Zapateller( )

D.1.3. Database-Stored Call Detail Records

Asterisk normally stores Call Detail Records (CDRs) in a Comma-Separated Values (CSV) file.^[*] If you want CDRs to be stored in a database, you'll need to load the appropriate module and define the relevant .conf file.

^[*] Information stored in a text file as Comma-Separated Values can be imported into pretty much any spreadsheet or database (yes, even stuff from Microsoft). This makes the CSV format extremely portable.

For each module below, we state the database type it supports, and specify the configuration file, if required. The CDR database connector modules are:

cdr_csv.so

Provides: CSV CDR backend

cdr_custom.so

Configuration file: cdr_custom.conf

Provides: Customizable CSV CDR backend

cdr_manager.so

Configuration file: cdr_manager.conf

Provides: Asterisk Call Manager CDR backend

cdr_odbc.so^[]

Configuration file: cdr_odbc.conf

Provides: ODBC CDR backend

cdr_pgsql.so

Configuration file: cdr_pgsql.conf

Provides: PostgreSQL CDR backend

D.1.4. Channels

Next, let's take a look at the channel modules. For each channel module, we identify dependencies and list the capabilities the module provides. We show the configuratin file, if one is required. The available modules are:

chan_agent.so

Configuration file: agents.conf

Requires: res_features.so, res_monitor.so, res_musiconhold.so

Provides: channel Agent, AgentLogin( ), AgentCallbackLogin( ), AgentMonitorOutgoing( ), action Agents

chan_features.so

Provides: channel Feature

chan_iax2.so

Configuration file: iax.conf, iaxprov.conf

Requires: res_crypto.so, res_features.so, res_musiconhold.so

Provides: channel IAX2, IAX2Provision( ), function IAXPEER, action IAXPEERS, action IAXnetstats

chan_local.so

Provides: channel Local

chan_mgcp.so

Configuration file: mgcp.conf

Requires: res_features.so

Provides: channel MGCP

chan_modem.so

Configuration file: modem.conf

Provides: channel Modem

chan_modem_aopen.so

Requires: chan_modem.so

Provides: A/Open (Rockwell Chipset) ITU-2 VoiceModem Driver

chan_modem_bestdata.so

Requires: chan_modem.so

Provides: BestData (Conexant V.90 Chipset) VoiceModem Driver

chan_modem_i4l.so

Requires: chan_modem.so

Provides: ISDN4Linux Emulated Modem Driver

chan_oss.so

Provides: channel Console (soundcard required)

chan_phone.so

Configuration file: phone.conf

Provides: channel Phone

chan_sip.so

Configuration file: sip.conf, sip_notify.conf

Requires: res_features.so

Provides: channel SIP, SIPDtmfMode( ), SIPAddHeader( ), SIPGetHeader( ), action SIPpeers, action SIPshowpeer, function SIP_HEADER

chan_skinny.so

Configuration file: skinny.conf

Requires: res_features.so

Provides: channel Skinny

D.1.5. Codecs

There are several acceptable ways to pass audio information in digital form. The formulas used to encode and decode (or compress and decompress) this information are collectively referred to as codecs. Most of Asterisk's codecs are provided free of license requirements; however, some (such as G.729) are encumbered by patents and thus must be licensed before they can be used.

Asterisk will load these codecs without complaint, but if you attempt to transcode a channel using an unlicensed codec, your calls will be dropped as soon as they connect.

Here, then, are the codec modulesif there are parameters that can be defined, they will be configurable in the codecs.conf file:

codec_a_mu.so

Provides: translator alawtoulaw, translator ulawtoalaw

codec_adpcm.so