I tried to change owner and group name,
but it shows following error.
help me to solve this issue.
thanks in advance.
Which user are you using to run NiFi? You have to ensure that user has HDFS super user privileges. ie try changing the user permissions on that folder on command line via (hdfs dfs -chown test:test /tmp/a29)
In this case it is based off the operating system user that started NiFi, not the user that is accessing the NiFi UI... if you started NiFi as root, then root is attempting to access HDFS.