HADOOP EROORS

1.There are 0 datanode(s) running and no node(s) are excluded in this operation

solution> 

     stop-all.sh

     rm rf datanode dir in hdfs-site.xml

     datanode format : hadoop datanode format

     start-all.sh

2. outofmemoryerror gc overhead limit exceeded

solution> 

     open hadoop-env.sh an edit below

     export HADOOP_CLIENT_OPTS="-Xmx100000m (much size in a ram)