Here is the other way Backing Up and Restoring HDFS Metadata Backing Up HDFS Metadata Using Cloudera Manager HDFS metadata backups can be used to restore a NameNode when
both NameNode roles have failed. In addition, Cloudera recommends backing up
HDFS metadata before a major upgrade. Minimum Required Role: (also provided by Full
Administrator) This backup method requires you to shut down the cluster.
Note
the active NameNode.
Stop
the cluster. It is particularly important that the NameNode role process
is not running so that you can make a consistent backup.
Go to
the HDFS service.
Click
the Configuration tab.
In the
Search field, search for "NameNode Data Directories" and note
the value.
On the
active NameNode host, back up the directory listed in the NameNode Data
Directories property. If more than one is listed, make a backup of one
directory, since each directory is a complete copy. For example, if the
NameNode data directory is /data/dfs/nn, do the following as root:
# cd
/data/dfs/nn # tar -cvf /root/nn_backup_data.tar . You should see output like this: ./ ./current/ ./current/fsimage ./current/fstime ./current/VERSION ./current/edits ./image/ ./image/fsimage If there is a file with the extension lock in
the NameNode data directory, the NameNode most likely is still running. Repeat
the steps, starting by shutting down the NameNode role. Restoring HDFS Metadata From a Backup The following process assumes a scenario where both NameNode
hosts have failed and you must restore from a backup.
Remove
the NameNode, JournalNode, and Failover Controller roles from the HDFS
service.
Add
the host on which the NameNode role will run.
Create
the NameNode data directory, ensuring that the permissions, ownership, and
group are set correctly.
Copy
the backed up files to the NameNode data directory.
Add
the NameNode role to the host.
Add
the Secondary NameNode role to another host.
Enable
high availability. If not all roles are started after the wizard
completes, restart the HDFS service. Upon startup, the NameNode reads the
fsimage file and loads it into memory. If the JournalNodes are up and
running and there are edit files present, any edits newer than the fsimage
are applied.
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