https://community.cloudera.com/t5/Support-Questions/How-can-i-start-Namenode-service-of-Hadoop-without-formating/m-p/239525#M201334 <P>@<A href="https://community.hortonworks.com/users/103244/slimaniibr.html">Slimani Ibrahim</A> </P><P>It's not recommended to format the NameNode more than once except when NameNode loses metadata information.</P><P>The reason could be this property which tells NameNode where to store its metadata information on disk is <EM>dfs.namenode.name.dir</EM> in your case its points to /tmp, so every time you restart your system the<EM> /tmp</EM> directory gets flushed and hence you have to format the NameNode again.</P><P>So, make sure you point the property <EM>dfs.namenode.name.dir</EM> to a more persistent location <BR />(something like <EM>/hadoop/hdfs/namenode</EM> similar for datanode property<EM>/hadoop/hdfs/datanode</EM>) which does not get's cleared every time if you restart your system that will resolve this problem. </P><P>I hope that the above answers your questions. Please accept the answer you found most useful. </P> Fri, 28 Dec 2018 23:31:22 GMT jagadeesan 2018-12-28T23:31:22Z