I was using this guide to make several instances of Joomla work atop of the LAMP stack. I made the changes to all the conf files accordingly, but i still got the error.
Let's say [new_name] is the new instance name, hence directory where your joomla app will reside. It's a notation, so it can be joomla1, mycoolapp, lovelywebsite, etc...
In order for this to work, there are several more steps needed. Here's how:
Do all the changes described in the guide by using [new_name] as your instance name
Update an additional file outside bitnami module and conf files here: /opt/bitnami/php/etc/php-fpm.conf. Open the file using this line (it requires SU permissions, unlike all the other files):
sudo nano /opt/bitnami/php/etc/php-fpm.conf
Find the line with the folder name "joomla"
...and update it to [new_name]:
In the httpd-app.conf - substitute "joomla" with [new_name]:
<Proxy "unix:/opt/bitnami/php/var/run/[new_name].sock|fcgi://[new_name]-fpm" timeout=300>
Inside php-fpm folder edit the pool.conf file: substitute all "joomla" occurrences with [new_name]:
After making any changes, restart:
sudo /opt/bitnami/ctlscript.sh restart
It killed a whole day for me, so hopefully you won't have to suffer.
As for @bitnami, please update the guide, or please implement the --joomla_instance_name parameter during install for joomla modules.
Best of luck!