What is the use of Jenkins?

Jenkins is a software which allows uninterrupted integration which can be installed on a server where the central build takes place. Below flowchart explains very simple workflow of how Jenkins works.

Along with Jenkins, sometimes, Hudson is also associated which is a very popular open-source Java-based uninterrupted integration tool developed by Sun Microsystems and it was later acquired by Oracle. After the acquisition of Sun by Oracle, a fork was created from the Hudson source code, which gave the introduction of Jenkins.

What is Continuous Integration?

Continuous or uninterrupted Integration is a development practice which needs developers to integrate code into a shared repository at regular intervals. Main idea of this is to eliminate the problem of finding upcoming issues in the build lifecycle, but it requires repeated builds. Common practice is that whenever a code commit occurs, a build should be triggered.

System Requirements

JDK	JDK 1.5 or above
Memory	2 GB RAM (recommended)
Disk Space	No minimum requirement. As all the builds will be stored on the Jenkins machines, ensure that sufficient disk space is available for build storage.
Operating System Version	Jenkins can be installed on Windows, Ubuntu/Debian, Red Hat/Fedora/CentOS, Mac OS X, openSUSE, FReeBSD, OpenBSD, Gentoo.
Java Container	The WAR file can be run in any container that supports Servlet 2.4/JSP 2.0 or later.(An example is Tomcat 5).