Problems in YARN: Why only SecondaryNameNode started? [Solved]

I was configuring a YARN cluster and after all set I tried to start services.
./start-dfs.sh
./start-yarn.sh

To my surprise, I only see SecondaryNameNode service got started. What? I didn't configure the SecondaryNameNode service, also where is my NameNode service which I really want?

I also checked the log and it says that:

The log shows that port 50070 already in use. But I run a command:

lsof -i:50070

There is nothing there using the port.

Also the host address is 0.0.0.0, this seems very wrong.
I checked many posts and they all didn't guide me to the root cause. Finally I found out the root cause

[Solution]

in hdfs-site.xml, there is one entry that's necessary:

dfs.http.address
myHostNodename:50070

If you want your secondary namenode, please add another one

dfs.secondary.http.address
my2ndHostNodename:50090

Happy World!

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