How to restore/recreate etc/resolv.conf files

You could reinstall resolvconf to restore the default configuration:

sudo apt-get install --reinstall resolvconf

Another idea would be remove "resolvconf" and then install:

sudo apt-get remove --purge resolvconf && sudo apt-get install resolvconf

If resolvconf -u shows the WARNING that /etc/resolv.conf is not a symbolic link to /run/resolvconf/resolv.conf then just backup that resolv.conf and make the symbolic link:

$ cd /etc
$ sudo ln -s /run/resolvconf/resolv.conf

Try this:

nano /etc/resolv.conf

add:

nameserver 8.8.8.8

nameserver 192.168.x.x (check your ifconfig output for the correct address)

then

sudo service resolvconf start
sudo systemctl enable resolvconf