In all honestly, I'm not familiar with Linux. But you're using Apache then, I presume? Can you actually verify that web services are up and running put making a simple HTML file and navigating out to it?
Is there a way you can ensure that the ColdFusion Application Server services are running as well? (In Windows, we goto Services.msc and can check the status there, I'm sure Linux has an equivalent).
You might want to check the coldfusion-error.log and coldfusion-out.log for additional messages.
If you cannot get to the ACP, there is either a services interruption, configuration issue, or the like. Is there error you're getting when going to the CF ACP the same as navigating to the site itself? Have you recently applied any patches/updates to the server?