https://community.cloudera.com/t5/Support-Questions/Databode-uuid-unassigned/m-p/202367#M164373 <P><A rel="user" href="https://community.cloudera.com/users/3548/bharathwgl.html" nodeid="3548">@Bharath N</A> </P><P>Try to perform the following steps on the failed DataNode:</P><OL><LI>Get the list of DataNode directories from /etc/hadoop/conf/hdfs-site.xml using the following command: <PRE>$ grep -A1 dfs.datanode.data.dir /etc/hadoop/conf/hdfs-site.xml &lt;name&gt;dfs.datanode.data.dir&lt;/name&gt; &lt;value&gt;/data0/hadoop/hdfs/data,/data1/hadoop/hdfs/data,/data2/hadoop/hdfs/data, /data3/hadoop/hdfs/data,/data4/hadoop/hdfs/data,/data5/hadoop/hdfs/data,/data6/hadoop/hdfs/data, /data7/hadoop/hdfs/data,/data8/hadoop/hdfs/data,/data9/hadoop/hdfs/data&lt;/value&gt;</PRE></LI><LI>Get datanodeUuid by grepping the DataNode log: <PRE>$ grep "datanodeUuid=" /var/log/hadoop/hdfs/hadoop-hdfs-datanode-$(hostname).log | head -n 1 | perl -ne '/datanodeUuid=(.*?),/ &amp;&amp; print "$1\n"' 1dacef53-aee2-4906-a9ca-4a6629f21347</PRE></LI><LI>Copy over a VERSION file from one of the &lt;dfs.datanode.data.dir&gt;/current/ directories of a healthy running DataNode: <PRE>$ scp &lt;healthy datanode host&gt;:&lt;dfs.datanode.data.dir&gt;/current/VERSION ./</PRE></LI><LI>Modify the datanodeUuid in the VERSION file with the datanodeUuid from the above grep search: <PRE>$ sed -i.bak -E 's|(datanodeUuid)=(.*$)|\1=1dacef53-aee2-4906-a9ca-4a6629f21347|' VERSION</PRE></LI><LI>Blank out the storageID= property in the VERSION file: <PRE>$ sed -i.bak -E 's|(storageID)=(.*$)|\1=|' VERSION</PRE></LI><LI>Copy this modified VERSION file to the current/ path of every directory listed in dfs.datanode.data.dir property of hdfs-site.xml:<PRE>$ for i in {0..9}; do cp VERSION /data$i/hadoop/hdfs/data/current/; done</PRE></LI><LI>Change permissions on this VERSION file to be owned by hdfs:hdfs with permissions 644:<PRE>$ for i in {0..9}; do chown hdfs:hdfs /data$i/hadoop/hdfs/data/current/VERSION; done $ for i in {0..9}; do chmod 664 /data$i/hadoop/hdfs/data/current/VERSION; done</PRE></LI><LI>One more level down, there is a different VERSION file located under the Block Pool current folder at: <PRE>/data0/hadoop/hdfs/data/current/BP-*/current/VERSION</PRE> This file does not need to be modified -- just place then in the appropriate directories.</LI><LI>Copy over this particular VERSION file from a healthy DataNode into the current/BP-*/current/ folder for each directory listed in dfs.datanode.data.dir of hdfs-site.xml: <PRE>$ scp &lt;healthy datanode host&gt;:&lt;dfs.datanode.data.dir&gt;/current/BP-*/current/VERSION ./VERSION2 $ for i in {0..9}; do cp VERSION2 /data$i/hadoop/hdfs/data/current/BP-*/current/VERSION; done</PRE></LI><LI>Change permissions on this VERSION file to be owned by hdfs:hdfs with permissions 644: <PRE>$ for i in {0..9}; do chown hdfs:hdfs /data$i/hadoop/hdfs/data/current/BP-*/current/VERSION; done $ for i in {0..9}; do chmod 664 /data$i/hadoop/hdfs/data/current/BP-*/current/VERSION; done</PRE></LI><LI>Restart DataNode from Ambari.</LI><LI>The VERSION file located at &lt;dfs.datanode.data.dir&gt;/current/VERSION will have its storageID repopulated with a regenerated ID.</LI></OL><P>If any data is not an issue (say, for example, the node was previously in a different cluster, or was out of service for an extended time), then</P><UL> <LI>delete all data and directories in the dfs.datanode.data.dir (keep that directory, though),</LI><LI>restart the data node daemon or servic</LI></UL> Wed, 23 May 2018 12:49:15 GMT bandarusridhar1 2018-05-23T12:49:15Z