On firing jps command, if you see that name node is not running during single node hadoop installation , then here are the steps to get Name Node running
Problem: namenode not getting started
Solution: - Please follow the following steps
STEP 1: stop hadoop
hduser@skillmentorz-virtualbox : $ /usr/local/hadoop/sbin/stop-dfs.sh
STEP 2: remove tmp folder
hduser@skillmentorz-virtualbox :$ sudo rm -rf /app/hadoop/tmp/
STEP 3: create /app/hadoop/tmp/
hduser@skillmentorz-virtualbox : $ sudo mkdir -p /app/hadoop/tmp
hduser@skillmentorz-virtualbox : $ sudo chown hduser:hadoop /app/hadoop/tmp
hduser@skillmentorz-virtualbox : $ sudo chmod 750 /app/hadoop/tmp
STEP 4: format namenode
hduser@skillmentorz-virtualbox : $ hdfs namenode -format
STEP 5 : start dfs
hduser@skillmentorz-virtualbox : $ /usr/local/hadoop/sbin/start-dfs.sh
STEP 6: check jps
hduser@skillmentorz-virtualbox : $ jps
You will find all the daemons including Namenode running properly
Namenode
Secondary Namenode
Resource Manager
Data node
Node Manager
Thank you for your time.