1. Don’t bother with the install script. I found it to be broken. And when it breaks during install, it leaves you in a state that’s very hard to understand and fix. In the end it was easier to install FreeSWITCH by hand, get that working, to the extend that you can make inter extension calls, then proceed with the FusionPBX install.
2.  Install FreeSWITCH by following the Quick Install Guide.
3. Commit the entire FreeSWITCH configuration to git so its easy to roll back when you reinstall FusionPBX. Switch to a new branch before making further changes.

   cd /usr/local/freeswitch
         git init
         echo 'db/*' >> .gitignore
         echo 'log/*' >> .gitignore
         echo '.svn*' >> .gitignore
         git add -A
         git commit -m "Initial Commit"
         git checkout -b try1
   

4. Get the latest version of FusionPBX from svn.

   cd /usr/src
            svn checkout http://fusionpbx.googlecode.com/svn/trunk/ fusionpbx
            cd fusionpbx
            cp -a fusionpbx /var/www/fusionpbx
   

5. Create a fusionpbx site for apache and enable it. Note that this makes fusionpbx appear at the root of your site. Create file called fusionpbx in your /etc/apache2/sites-available directory and put the following in it:

         <VirtualHost *:80>
           ServerAdmin webmaster@localhost
           ServerName freepbx.example.com
           DocumentRoot /var/www/fusionpbx
           <Directory />
                   Options FollowSymLinks
                   AllowOverride None
           </Directory>
           <Directory /var/www/fusionpbx/>
                   Options Indexes FollowSymLinks MultiViews
                   AllowOverride None
                   Order allow,deny
                   allow from all
           </Directory>
           ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
           <Directory "/usr/lib/cgi-bin">
                   AllowOverride None
                   Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                   Order allow,deny
                   Allow from all
           </Directory>
           ErrorLog /var/log/apache2/error.log
           # Possible values include: debug, info, notice, warn, error, crit,
           # alert, emerg.
           LogLevel debug
           CustomLog /var/log/apache2/access.log combined
       Alias /doc/ "/usr/share/doc/"
       <Directory "/usr/share/doc/">
           Options Indexes MultiViews FollowSymLinks
           AllowOverride None
           Order deny,allow
           Deny from all
           Allow from 127.0.0.0/255.0.0.0 ::1/128
       </Directory>
   </VirtualHost>
   

   Then enable the site with a2ensite fusionpbx/

6. after installing FusionPBX, commit the entire configuration to git to make rolling back easier. Switch to a new branch before making further changes.
7. set up a FQDN for the box running FreeSWITCH and FusionPBX
8. use ACL to allow www-data to make changes to the /usr/share/freeswitch directory

And after you install and you realise it didn’t quite go as planned

1. Reset the postgresql database:

   root@fusionpbx: # su - postgres
   postgres@fusionpbx:~$ psql
   postgres=# drop database fusionpbx;
   postgres=# create database fusionpbx;
   postgres=# alter user fusionpbx with password 'XXXX';
   grant ALL PRIVILEGES ON DATABASE fusionpbx to fusionpbx;
   

2. revert your FreeSWITCH configuration using git
3. revert your FusionPBX configuration using git