I saw in the list archives that someone recently asked about using newer versions of Linux with Observium. 

I am not an Apache expert, but I got it working by simply changing to "Require all granted" in the recommended Observium config:

http://httpd.apache.org/docs/2.4/upgrading.html

root@observium:/opt/observium/includes# cat /etc/apache2/sites-available/000-default.conf

<VirtualHost *:80>
       ServerAdmin webmaster@localhost
       DocumentRoot /opt/observium/html
       <Directory />
               Options FollowSymLinks
               AllowOverride None
       </Directory>
       <Directory /opt/observium/html/>
               Options Indexes FollowSymLinks MultiViews
               AllowOverride All
               Require all granted
       </Directory>
       ErrorLog  ${APACHE_LOG_DIR}/error.log
       LogLevel warn
       CustomLog  ${APACHE_LOG_DIR}/access.log combined
       ServerSignature On
</VirtualHost>

I also had to manually enable the php5-mcrypt module:


sudo php5enmod mcrypt

sudo service apache2 restart
I hope this was helpful!

Tristan

Tristan Rhodes
Network Engineer
Weber State University
801.626.8549