Two things worked for me,
STEP 1 : stop hadoop and clean temp files from hduser
sudo rm -R /tmp/*
also, you may need to delete and recreate /app/hadoop/tmp
(mostly when I change hadoop version from 2.2.0
to 2.7.0
)
sudo rm -r /app/hadoop/tmp
sudo mkdir -p /app/hadoop/tmp
sudo chown hduser:hadoop /app/hadoop/tmp
sudo chmod 750 /app/hadoop/tmp
STEP 2: format namenode
hdfs namenode -format
Now, I can see DataNode
hduser@prayagupd:~$ jps
19135 NameNode
20497 Jps
19477 DataNode
20447 NodeManager
19902 SecondaryNameNode
20106 ResourceManager