What is a Cloud ?
Wikipedia defines cloud computing as "Internet-based computing, whereby shared resources, software, and information are provided to computers and other devices on demand, like the electricity grid"
For a discussion of what cloud computing means, and why everything seems to be going that way, check out Matt Zimmerman's On Cloud blog post
Ubuntu Cloud Questions
What is Ubuntu Cloud?
Ubuntu Cloud the family of products that offer cloud functionality in Ubuntu. It includes:
Ubuntu Cloud Infrastructure, which is a software product that you can install on your own servers to create your own cloud computing environment behind the firewall. Ubuntu Cloud Infrastructure provides an Amazon EC2 compatible API interface, such that many tools that configure EC2, can be used readily on it. It is based on the OpenStack project.
- Ubuntu Cloud Guest, which are minimal Ubuntu Server images built specifically for the cloud
Ubuntu over EC2 Questions
Why can't I upgrade the image's kernel in an EC2 AMI?
In 10.04, the -server kernel that is also installed is not usable on EC2. The kernel is present there to aid in moving to Ubuntu Enterprise Cloud (the predecessor to Ubuntu Cloud Infrastructure) if you so desired. Ubuntu Enterprise Cloud uses kvm and full virtualization rather than xen/paravirt. On 10.04 and EC2, you could safely remove that kernel if you wanted.
On 10.10 (maverick), you will both be able to boot the -virtual kernel, and will by default. Maverick images use the pv-grub loader recently released by Amazon, and use a pv-ops kernel, so one kernel can run on xen or on kvm (or actually "bare metal").