How to check if hdfs is running?

Question

I would like to see if the hdfs file system for Hadoop is working properly. I know that jps lists the daemons that are running, but I don't actually know which daemons to look for.

I ran the following commands: $HADOOP_PREFIX/sbin/hadoop-daemon.sh start namenode

$HADOOP_PREFIX/sbin/hadoop-daemon.sh start datanode

$HADOOP_PREFIX/sbin/yarn-daemon.sh start resourcemanager

$HADOOP_PREFIX/sbin/yarn-daemon.sh start nodemanager

Only namenode, resourcemanager, and nodemanager appeared when I entered jps.

Which daemons are supposed to be running in order for hdfs/Hadoop to function? Also, what could you do to fix hdfs if it is not running?

Answer 1

Use any of the following approaches for to check your deamons status

1. JPS command would list all active deamons

2. the below is the most appropriate

      hadoop dfsadmin -report
   

   This would list down details of datanodes which is basically in a sense your HDFS

3. cat any file available in hdfs path.