namenode format question

[#1]

Hello,

I have a basic question about about namenode format. If we perform namenode format, will clean up all the metadata info in namenode like directory structure, etc.   After it completed, if we restart namenode, would it rebuild the directory structure from datanode information? Or we are lost.

[#2]

Thank you for the info. Yes, I have created with backup with another
directory and I was about to boot restart the namenode from that image.