Back up the following critical data before attempting an upgrade. On the node that hosts the NameNode, open the Hadoop Command line shortcut that opens a command window in the Hadoop directory. Run the following commands:
Run the fsck command as the HDFS Service user and fix any errors. (The resulting file contains a complete block map of the file system):
hadoop fsck / -files -blocks -locations > dfs-old-fsck-1.log
Capture the complete namespace directory tree of the file system:
hadoop fs -lsr / > dfs-old-lsr-1.log
Create a list of DataNodes in the cluster:
hadoop dfsadmin -report > dfs-old-report-1.log
Capture output from fsck command:
hadoop fsck / -block -locations -files > fsck-old-report-1.log
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Verify there are no missing or corrupted files/replicas in the |