Namenode not getting started

Question

I was using Hadoop in a pseudo-distributed mode and everything was working fine. But then I had to restart my computer because of some reason. And now when I am trying to st

Answer 1

I ran $hadoop namenode to start namenode manually at foreground.

From the logs I figured out that 50070 is ocuupied, which was defaultly used by dfs.namenode.http-address. After configuring dfs.namenode.http-address in hdfs-site.xml, everything went well.

Answer 2

In conf/hdfs-site.xml, you should have a property like

<property>
    <name>dfs.name.dir</name>
    <value>/home/user/hadoop/name/data</value>
</property>

The property "dfs.name.dir" allows you to control where Hadoop writes NameNode metadata. And giving it another dir rather than /tmp makes sure the NameNode data isn't being deleted when you reboot.

Answer 3

If you kept default configurations when running hadoop the port for the namenode would be 50070. You will need to find any processes running on this port and kill them first.

• Stop all running hadoop with : bin/stop-all.sh

  check all processes running in port 50070

• sudo netstat -tulpn | grep :50070 #check any processes running in port 50070, if there are any the / will appear at the RHS of the output.

• sudo kill -9 <process_id> #kill_the_process.

• sudo rm -r /app/hadoop/tmp #delete the temp folder

• sudo mkdir /app/hadoop/tmp #recreate it

• sudo chmod 777 –R /app/hadoop/tmp (777 is given for this example purpose only)

• bin/hadoop namenode –format #format hadoop namenode

• bin/start-all.sh #start-all hadoop services

Refer this blog