Does formatting the HDFS filesystem remove my data?

[skan]

Helo

I'm starting to learn Hadoop.
If I want to format the HDFS filesystem I need to execute

bin/hadoop namenode -format

Does it mean that it will format my filesystem, losing everything I have there?
Or will it just create a kind of big "virtual file" over the local filesystem?

regards

[sicarie]

Yes, it will format your file system and overwrite what you have there. HDFS is complicated and cool, but it does act as a 'file system' and will overwrite what data is there.