Codeigniter cache folder requires permission 777

You should use the chown command to create the correct ownership of the cache folder instead of making it writable/readable to all users with chmod.

sudo groupadd www

sudo useradd -g <your username> www

sudo chown -R :www /var/www

sudo chmod -R g+rwX /var/www

This will give the group "www" read and write access to the /var/www folder.