@Somnath Kundu
Step 1: Identify the ambari-server daemon user id.
To check which os user is running ambari-server , use the following os command
# ps -ef |grep -i $(ambari-server status |grep -i PID |awk {'print $5'}) |awk {'print $1'}
The output will be the under which the Ambari server is running.
Step 2: Add the user in step one to custom property in HDFS Core-site.xml
In hdfs config, core-site.xml add the following custom properties.
hadoop.proxyuser.{user_above}.groups=*
hadoop.proxyuser.{user_above}.hosts=*
If your ambari-server daemon is running under a different user, please change the user accordingly and retry you should succeed.Please revert