I have upgraded from Ubuntu 16 to Ubuntu 18. And since I restarted my machine, I am not able to connect to the internet. And this seems to be a very popular issue, because I am reading and applying the whole morning different solutions given (for example, tried this one), but that does not seem to do the trick for me.
My laptop is connected to the wifi network. In fact we even have 2 in the house and I am able to successfully see and connect to both of them.
However, when I
ping www.ubuntu.com, I receive "unknown host" as response.
I am able to ping to 127.0.0.1 though.
Any other application is also unable to connect.
Any help is appreciated :)
Resolved this issue by adding
nameserver 18.104.22.168 in the file
/etc/resolv.conf. And then restarted using
sudo /etc/init.d/networking restart. The solution to my issue was given by Zoltán Süle, in the comments of a similar issue like that of mine.