What is the role of the NameNode in Hadoop?

The NameNode in Hadoop is a vital component of HDFS (Hadoop Distributed File System), responsible for storing the file system’s namespace (files and directory structure) and metadata information (such as file size, permissions, owner, etc). The NameNode also manages the replication of data blocks and the mapping between data blocks and data nodes.

In short, the main role of the NameNode is to manage and maintain the file system structure and metadata information in HDFS, allowing for efficient locating of files and data blocks, as well as coordinating data replication and transfer among data nodes.