Save the NameNode namespace by performing a manual checkpoint - E-MapReduce

A checkpoint saves the current namespace of a NameNode and prevents you from taking an extended period of time to restart the NameNode.

Prerequisites

Before you begin, ensure that you have:

Log on to the cluster over SSH. For more information, see Log on to a cluster.
Switch to the hdfs user.
```
su hdfs
```
Enter safe mode.
```
hdfs dfsadmin -safemode enter
```
Important
Checkpoints on a NameNode must be performed in safe mode. If the checkpoint fails while in safe mode, DfsClient automatically retries. We recommend that you perform this operation during off-peak hours.
Run the checkpoint twice to accelerate the clearance of edit logs. Both commands must complete successfully.
```
hdfs dfsadmin -saveNamespace
hdfs dfsadmin -saveNamespace
```
Exit safe mode.
```
hdfs dfsadmin -safemode leave
```