Hadoop on a local Ubuntu host
For our exploration of Hadoop outside the cloud, we shall give examples using one or more Ubuntu hosts. A single machine (be it a physical computer or a virtual machine) will be sufficient to run all the parts of Hadoop and explore MapReduce. However, production clusters will most likely involve many more machines, so having even a development Hadoop cluster deployed on multiple hosts will be good experience. However, for getting started, a single host will suffice.
Nothing we discuss will be unique to Ubuntu, and Hadoop should run on any Linux distribution. Obviously, you may have to alter how the environment is configured if you use a distribution other than Ubuntu, but the differences should be slight.
Other operating systems
Hadoop does run well on other platforms. Windows and Mac OS X are popular choices for developers. Windows is supported only as a development platform and Mac OS X is not formally supported at all.
If you choose to use such a platform, the general situation will be similar to other Linux distributions; all aspects of how to work with Hadoop will be the same on both platforms but you will need use the operating system-specific mechanisms for setting up environment variables and similar tasks. The Hadoop FAQs contain some information on alternative platforms and should be your first port of call if you are considering such an approach. The Hadoop FAQs can be found at http://wiki.apache.org/hadoop/FAQ.