sudo: unable to resolve host ubuntu-server
My /etc/hosts file:
127.0.0.1 localhost 127.0.1.1 ubuntu-server # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes FF02::2 ip6-allrouters
I think there is some other setting that causes the unable to resole host, but I cannot find these.
/etc/hosts, you have a typo
127.0.1.1 is not loopback, change it to
127.0.0.1, save and reboot.