How can I tell if a hadoop namenode has already been formatted?

Question

When configuring my hadoop namenode for the first time, I know I need to run

bin/hadoop namenode -format

but running this a second time, after loading data into HDFS, will wipe out everything and reformat. Is there an easy way to tell if a namenode has already been formatted?

Answer 1

Well you can check this file store1/name/current/VERSION

If it exist then it is already formatted.

PS: You do format only once in life in production system. Its better to do in the installation process or manually in emergency restoration time.