Hadoop can run in three different modes-
Local/Standalone Mode
This is the single process mode of Hadoop, which is the default mode, wherein which no daemons are running.
This mode is useful for testing and debugging.
Pseudo Distributed Mode
This mode is a simulation of fully distributed mode but on single machine. This means that, all the daemons of Hadoop will run as a separate process.
This mode is useful for development.
Fully Distributed Mode
This mode requires two or more systems as cluster.
Name Node, Data Node and all the processes run on different machines in the cluster.
This mode is useful for the production environment.
