Hadoop单机启动dfs，为什么各个节点主机名不一样？

[hadoop@localhost hadoop-2.7.2]$ sbin/start-dfs.sh

Starting namenodes on [hadoop1]

hadoop@hadoop1's password:

hadoop1: starting namenode, logging to /home/hadoop/hadoop-2.7.2/logs/hadoop-hadoop-namenode-hadoop1.hadoopdomain.out

hadoop@localhost's password:

localhost: starting datanode, logging to /home/hadoop/hadoop-2.7.2/logs/hadoop-hadoop-datanode-hadoop1.hadoopdomain.out

Starting secondary namenodes [0.0.0.0]

hadoop@0.0.0.0's password:

0.0.0.0: starting secondarynamenode, logging to /home/hadoop/hadoop-2.7.2/logs/hadoop-hadoop-secondarynamenode-hadoop1.hadoopdomain.out