apache/hadoop · error · IOException

First node is not root

Error message

First node is not root

What it means

Error "First node is not root" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java:526

     while (numFiles > 0) {
       numFiles -= loadDirectory(in, counter);
     }
     if (numFiles != 0) {
       throw new IOException("Read unexpect number of files: " + -numFiles);
     }
   }
   
    /**
     * Load information about root, and use the information to update the root
     * directory of NameSystem.
     * @param in The {@link DataInput} instance to read.
     * @param counter Counter to increment for namenode startup progress
     */
    private void loadRoot(DataInput in, Counter counter)
        throws IOException {
      // load root
      if (in.readShort() != 0) {
        throw new IOException("First node is not root");
      }
      final INodeDirectory root = loadINode(null, false, in, counter)
        .asDirectory();
      // update the root's attributes
      updateRootAttr(root);
    }
   
    /** Load children nodes for the parent directory. */
    private int loadChildren(INodeDirectory parent, DataInput in,
        Counter counter) throws IOException {
      int numChildren = in.readInt();
      for (int i = 0; i < numChildren; i++) {
        // load single inode
        INode newNode = loadINodeWithLocalName(false, in, true, counter);
        addToParent(parent, newNode);
      }
      return numChildren;
    }

View on GitHub (pinned to 2add963021)

Solutions

1. The fsimage is corrupt (root inode missing); restore the image from a backup or another NameNode storage directory.

When it happens

Trigger: Loading an old-format fsimage whose first inode entry is not the root directory, indicating a corrupt image.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/89ffc3d31e8a72e9. Report an issue: GitHub.