Page 88 - Asterisk™: The Future of Telephony

firmware/
The firmware/ directory contains firmware for various Asterisk-compatible devi-
ces. It currently contains only the iax/ subdirectory, which holds the binary
firmware image for Digium’s IAXy.
images/
Applications that communicate with channels supporting graphical images look
in the images/ directory. Most channels do not support the transmission of images,
so this directory is rarely used. However, if more devices that support and make
use of graphical images are released, this directory will become more relevant.
keys/
Asterisk can use a public/private key system to authenticate peers connecting to
your box via an RSA digital signature. If you place a peer’s public key in your
keys/ directory, that peer can be authenticated by channels supporting this method
(such as the IAX2 channels). The private key is never distributed to the public. The
reverse is also true: you can distribute your public key to your peers, allowing you
to be authenticated with the use of your private key. Both the public and private
keys—ending in the .pub and .key file extensions, respectively—are stored in the
keys/ directory.
mohmp3/
When you configure Asterisk for Music on Hold, applications utilizing this feature
look for their MP3 files in the mohmp3/ directory. Asterisk is a bit picky about how
the MP3 files are formatted, so you should use constant bitrate (CBR) encoding
and strip the ID3 tags from your files.
sounds/
All of the available voice prompts for Asterisk reside in the sounds/ directory. The
contents of the basic prompts included with Asterisk are in the sounds.txt file lo-
cated in your Asterisk source code directory. Contents of the additional prompts
are located in the sounds-extra.txt file in the directory to which you extracted the
asterisk-sounds package earlier in this chapter.

/var/spool/asterisk/

The Asterisk spool directory contains several subdirectories, including
dictate/, meetme/, monitor/, outgoing/, system/, tmp/, and voicemail/ (see Figure 3-4).
Asterisk monitors the outgoing directory for text files containing call request informa-
tion. These files allow you to generate a call simply by moving the correctly structured
file into the outgoing/ directory.
Call files being placed into the outgoing/ directory can contain useful information, such
as the Context, Extension, and Priority where the answered call should start, or simply
the application and its arguments. You can also set variables and specify an account
code for Call Detail Records. More information about the use of call files is presented
in Chapter 9.

60 | Chapter 3: Installing Asterisk