The OpenStack system has several key projects that are separate installations but can work together depending on your cloud needs: OpenStack Compute, OpenStack Block Storage, OpenStack Object Storage, and the OpenStack Image Service. You can install any of these projects separately and then configure them either as standalone or connected entities. The installation process is documented in the OpenStack Install Guide, for either Ubuntu or RHEL/CentOS/Fedora. You can choose your guide at docs.openstack.org/install.
