Check file permissions of dfs directory:
``` find /path/to/dfs -group root ```
In general, the user permission group is `hdfs`. Since I started HDFS service with root user, some dfs block file with `root` permissions was generated.
I solved the problem after change to right permissions:
``` sudo chown -R hdfs:hdfs /path/to/dfs ```

Check file permissions of dfs directory:
``` find /path/to/dfs -group root ```
In general, the user permission group is `hdfs`. Since I started HDFS service with root user, some dfs block file with `root` permissions was generated.
I solved the problem after change to right permissions:
``` sudo chown -R hdfs:hdfs /path/to/dfs ```