Manually perform a checkpoint on a NameNode - E-MapReduce

You can manually perform a checkpoint to save the namespace of a NameNode and prevent you from taking an extended period of time to restart the NameNode. This topic describes how to manually perform a checkpoint on a NameNode.

Procedure

Log on to your cluster in SSH mode. For more information, see Log on to a cluster.
Run the following command to switch to the hdfs user:
```
su hdfs
```
Run the following command to enter the safemode mode:
```
hdfs dfsadmin -safemode enter
```
Important Checkpoints on a NameNode must be performed in safemode mode. In most cases, DfsClient automatically retries to perform a checkpoint if the checkpoint fails to be performed in safemode mode. We recommend that you perform this operation during off-peak hours.
Run the following command to perform a checkpoint on the NameNode.
We recommend that you perform this operation twice to accelerate the clearance of edit logs.
```
hdfs dfsadmin -saveNamespace
hdfs dfsadmin -saveNamespace
```
Run the following command to exit the safemode mode:
```
hdfs dfsadmin -safemode leave
```