Try browsing to the JobTracker:
http://{jobtracker.full.hostname}:50030/
Smoke test using Teragen to generate 10GB of data and then using Terasort to sort the data. Login as
$HDFS_USER
/usr/lib/hadoop/bin/hadoop jar /usr/lib/hadoop/hadoop-examples.jar teragen 100000000 /test/10gsort/input /usr/lib/hadoop/bin/hadoop jar /usr/lib/hadoop/hadoop-examples.jar terasort /test/10gsort/input /test/10gsort/output