From The Eucalyptus Open-Source Private Cloud by Yohan Wadia:
"Eucalyptus is a Linux-based open-source software architecture that implements efficiency-enhancing private and hybrid clouds within an enterprise’s existing IT infrastructure.
Eucalyptus is an acronym for “Elastic Utility Computing Architecture for Linking Your Programs to Useful Systems.”
A Eucalyptus private cloud is deployed across an enterprise’s “on premise” data center infrastructure and is accessed by users over enterprise intranet. Thus, sensitive data remains entirely secure from external intrusion behind the enterprise firewall.
Initially developed to support the high performance computing (HPC) research of Professor Rich Wolski’s research group at the University of California, Santa Barbara, Eucalyptus is engineered according to design principles that ensure compatibility with existing Linux-based data center installations. Eucalyptus can be deployed without modification on all major Linux OS distributions, including Ubuntu, RHEL, Centos, and Debian. And Ubuntu distributions now include the Eucalyptus software core as the key component of the Ubuntu Enterprise Cloud."