What exactly is hadoop namenode formatting?

Question

What is namenode formatting? What does it involve. I'm looking to understand namenode formatting and its use.

Answer 1

Namenode is used to specify the default file system and also the  defaults of your local file system.So, you need to set it to a HDFS address. This is important for configuration of client and your Local File system.

<name>filesystem.namenode</name>.

<value>hdfs://192.168.1.2:9000/</value>

The highlighted part is the address.

When we format the Namenode, the original Datanode is not affected but the MetaData related to it gets deleted.So, we can use this space for new Data.

Answer 2

Hadoop NameNode is said to be the centralized place of an HDFS file system. HDFS contains the directory tree-track of all files in the file system. In short, it holds the metadata related to datanodes.

When we format namenode(bin/hadoop namenode -format) it formats the meta-data related to data-nodes. By doing that, all the information on the datanodes are lost and the datanodes becomes reusable for new data.

For more information regarding Hadoop, refer the following link: