Restoring NameNode metadata

If both the NameNode and the secondary NameNode were to suddenly go offline, you can restore the NameNode.

  1. Add a new host to your Hadoop cluster.
  2. Add the NameNode role to the host. Make sure it has the same hostname as the original NameNode.
  3. Create a directory path for the NameNode name.dir (for example, /dfs/nn/current), ensuring that the permissions are set correctly.
  4. Copy the VERSION and latest fsimage file to the /dfs/nn/current directory.
  5. Run the following command to create the md5 file for the fsimage.
    md5sum fsimage > fsimage.md5
  6. Start the NameNode process.