You want to get Hadoop's web UI to work. You have access to the back-end of a Linux server. How do you get the front-end of Hadoop (or hdfs) to work?
1. Deploy Hadoop. See this article if you need help with how to do it.
2. From the NameNode server in a multi-node deployment or from the single Hadoop server, run the start-dfs.sh script (use sudo find / -name start-dfs.sh to find it; use bash /path/to/start-dfs.sh to run it).
3. If it is a single-node cluster, find the external IP address of the server with "curl icanhazip.com". If you have a multi-node Hadoop cluster, find the external IP address of the NameNode with "curl icanhazip.com".
4. Open a web browser from a workstation and go to http://<externalIPaddress>:50070
(The port could be different if you changed it from the default one.)