Hadoop HDFS Connection Refused

Today I encounter a problem about connection refused by HDFS, not because of the firewall or something, but because of the /etc/hosts configuration in ubuntu.
By default, the there will have an entry

127.0.1.1   domain.name

It is this entry that direct access back to 127.0.1.1, so the network setup only for local access.
Just removing this entry or replacing the 127.0.1.1 with your ip address could tackle this problem.
More diagnostic, please refer to apache.