When i try to run "Hadoop" in user "Y" i get error as - No such Command.Is there any way by which the same installation can be used which has been done for user "X" ?
For user Y to have the same access as user x you will need all the Hadoop path variables set in user Y's .bashrc. Depending on how you installed Hadoop you will need to also add user Y to the hadoop user group that X is in. You may also need to create a user directory on HDFS. Also make sure ssh is running for user Y. You could use the namenode you formatted for user x, but you will need to make sure Y has access.
Once you have checked all of the above try typing
xx@yyyy$ bin/hadoop
You should see the documentation for the Hadoop command