Installing Nexus OSS using the standard Jetty based server distribution bundle is a Sonatype recommended best practice.
General instructions for installing Nexus OSS as a stand-alone server are in the Nexus Book.
Running Nexus OSS WAR file in another application server or servlet container is not recommended.
Several of you have reported issues starting Nexus on Debian or Ubuntu when running under gij. If you see a IOException: Stream Closed during startup, check your JVM or JRE and read this article for the fix.
If Nexus is attempting to bind to a port that is already taken by another process, you will need to change the host or port that Nexus attempts to bind to. To do this read this article.