sudo: unable to resolve host ***********: Name or service not known

[Merlincool]

When I wish to do sudo nano /etc/nginx/sites-enabled/default I get this error:

sudo: unable to resolve host ***********: Name or service not known

I have just hide my hostname. Anyways how does that affect, I have said yes for IPaddress while installing procedure. If at all you need any further details, My hostname is not a domain, its just vps(some_number). I have no url directing to my ipaddress of host so how does that matter now?