Example: Suppose you want to create a new user "newuser1" on HDFS.
So first create a user on your Host (client machine) and add it to "hadoop" group
# useradd newuser1 -G hadoop
Create Home directory for this user on HDFS.
# su - hdfs -c "hdfs dfs -mkdir /user/newuser1"
# su - hdfs -c "hdfs dfs -chown newuser1:hadoop /user/newuser1"
# su - hdfs -c "hdfs dfs -chmod 755 /user/newuser1"
Now you can switch to this "newuser1" and then can work on hdfs like putting a file to HDFS.
# su - newuser1
# hdfs dfs -put /etc/passwd /user/newuser1
# hdfs dfs -cat /user/newuser1/passwd