What are the steps for setting up a completely distributed Hadoop system?

Setting up a fully distributed Hadoop cluster typically involves the following steps:

1. Prepare the environment: Make sure all nodes have the same operating system and Java version, and are capable of network connectivity.
2. Install Hadoop software: Download and install the Hadoop software package on each node.
3. Set up a Hadoop cluster by editing the Hadoop configuration files, including core-site.xml, hdfs-site.xml, mapred-site.xml, and yarn-site.xml, to configure various parameters of the Hadoop cluster.
4. Set up SSH passwordless login: To enable communication between nodes, set up SSH passwordless login in order to avoid having to enter a password each time a connection is made.
5. Set up Hadoop environment variables on each node so that the system can recognize Hadoop commands.
6. Format HDFS: Run the command ‘hadoop namenode -format’ on the master node to format the Hadoop Distributed File System.
7. Start the Hadoop cluster: Initiate various components of the Hadoop cluster, such as NameNode, DataNode, ResourceManager, and NodeManager.
8. Validate the Hadoop cluster: Ensure the proper functioning of the Hadoop cluster by running sample programs such as WordCount or checking the Hadoop web interface.