In this recipe, we will cover how to promote Secondary Namenode to be Primary Namenode.
In production, Datanodes will never talk to the Secondary and only the Primary node knows about the data block mappings. In a non-HA setup, if the Primary Namenode fails, there will be outage, but we can still reduce the downtime by quickly promoting the Secondary to be Primary.
For this recipe, make sure you have completed the previous recipe on Secondary Namenode configuration and have a running Secondary Namenode.
master2.cyrus.commaster node and switch to user
seen_txidfile under location
/data/secondary/current/, to make sure until what ...