How to recover a NameNode when it is down ?
![How to recover a NameNode](https://cdn.wikitechy.com/interview-questions/hadoop/how-to-recover-a-name-node.gif)
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- The following steps need to execute to make the Hadoop cluster up and running :
- Use the FsImage which is file system metadata replica to start a new NameNode.
- The following steps need to execute to make the Hadoop cluster up and running :
![Name Node](https://cdn.wikitechy.com/interview-questions/hadoop/how-to-recover-a-namenode-when-it-is-down.png)
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- Configure the DataNodes and also the clients to make them acknowledge the newly started NameNode.
- Once the new NameNode completes loading the last checkpoint FsImage which has received enough block reports from the DataNodes, it will start to serve the client.
- In case of large Hadoop clusters, the NameNode recovery process consumes a lot of time which turns out to be a more significant challenge in case of routine maintenance.