Error prompt:“wget: unable to resolve host address”---Solution

//Situation

System prompts that:"wget: unable to resolve host address".

        //Analysis

          Unable to resolve host address means the problem of DNS（Domain Name System）.

        //Solution

          To fix the problem, the configuration file "resolv.conf" should be  modified as follow steps:

             1. Get the root permission:      su -i

             2. Open the file with vi editor:      vi /etc/resolv.conf

             3. Press "i" into edit mode, and modify the content by:

                   nameserver 8.8.8.8 #google's DNS

                   nameserver 8.8.4.4 #google's DNS(backup)