System information

The Resource Library
There are several resources that require external data sources. For example, music on
hold (MOH) can’t happen unless you have some music to play. System prompts also
need to be stored somewhere on the hard drive. The /var/lib/asterisk folder is where
system prompts, AGI scripts, music on hold, and other resource files are stored.
The Spool
The spool is where Linux stores files that are going to change frequently, or will be
processed by other processes at a later time. For example, under Linux print jobs and
pending emails are normally written to the spool until they are processed.
For Asterisk, the spool is used to store transient items such as voice messages, call
recordings,
‖
call files, and so forth.
The Asterisk spool will be found under the /var/spool/asterisk directory.
Logging
Asterisk is capable of generating several different kinds of log files. The /var/log/aster-
isk folder is where things such as call detail records (CDRs), channel events from CEL,
debug logs, queue logs, messages, errors, and other output are written.
This folder will be extremely important for any troubleshooting efforts you undertake.
We will talk more about how to make use of Asterisk logs in Chapter 24.
The Dialplan
The dialplan is the heart of Asterisk. All channels that arrive in the system will be passed
through the dialplan, which contains the call-flow script that determines how the in-
coming calls are handled.
A dialplan can be written in one of three ways:
• Using traditional Asterisk dialplan syntax in /etc/asterisk/extensions.conf
• Using asterisk Extension Logic (AEL) in /etc/asterisk/extensions.ael
• Using LUA in /etc/asterisk/extensions.lua
Later in this book, we’ll have devoted several chapters to the subject of how to write a
dialplan using traditional dialplan syntax (by far the most popular choice). Once you
learn this language, it should be fairly easy to transition to AEL or LUA, should you
desire.
‖ Not call detail records (CDRs), but rather audio recordings of calls generated by the MixMonitor() and related
applications.
The Dialplan | 25