Setting up Craft on Linode Using Ubuntu
I assume you've seen https://www.linode.com/docs/websites/apache/apache-web-server-on-ubuntu-14-04?

Craft really isn't any different than any other PHP application in the way it needs to be setup to execute.  The only extra thing that other apps might not require (because most PHP apps don't auto-update) is that Craft needs to be able to recursively write to its craft/app folder in order for that to work.

There's a handy script here: https://github.com/nystudio107/craft-scripts that can help automate the necessary permissions for your box, but you'll need still need to know what user:group Apache is running as for it to set things up properly.