sudo : Unable to Resolve Host

This happens after the host-name of the system is changed. Host-name can be changed by editing the file "/etc/hostname".

   sudo gedit /etc/hostname
For resolving the host conflict, we need to edit the file "/etc/hosts". For editing this file use the command:
   sudo gedit /etc/hosts

Edit the name in front of 127.0.1.1 to the new host-name. This will do.

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