Query on hadoop namenode -format command
This question will be prompted only when the dfs.namenode.name.dir already exists i.e., the directory is either formatted already or an existing directory is mapped to dfs.namenode.name.dir.
If you wish to Re-format it again, then give Y else N.
On giving Y, the directory will be formatted, deleting all the existing metadata (fsimage and edits logs). This re-format removes only the metadata, the data dfs.datanode.data.dir directories must be manually removed.