This will guide you through installing jenkins continuous integration server into ubuntu server using its war file on the tomcat7 container.

Downloading jenkins.war

Go to https://jenkins-ci.org/ and download the latest version of the jenkins war file (right-side of the page, just below Java Web Archive (.war) )

Installing jenkins

I’m following this great article on installing jenkins from its war file.
The only difference is that I needed to replace their use tomcat6 with tomcat7.
Ubuntu, Tomcat, Jenkins, Git, and SSH Together
Other differences:
I’m skipping tomcat installation as it is already done in my setup.