Generally when we start our computer it will take nearly 1 to 2 minutes of time to load some built in processes. At this time we cannot do any operation like mouse click, typing etc.., at this time we call that our computer is in SAFE MODE.
In the same way when we start our Name Node it loads the following files:
- Loads system config
- Reasonable Replication
- System dependent files
At the time of Name Node start-up HDFS will be in read only mode. In this state we call that our Name Node is in SAFE MODE. After the Name Node start-up is complete is automatically the SAFE MODE will be turned off. If it did not turn off it is the responsibility of Hadoop Admin to turn it OFF. To check the status of SAFE MODE we use the following command.
#hadoop dfsadmin -safemode get
If it is ON, we can use the following command to turn it OFF.
#hadoop dfsadmin -safemode LEAVE
If we want to keep the Name Node in SAFE MODE, we can use the following command.
#hadoop dfsadmin -safemode ENTER
