How to Upgrade Ubuntu 16.04 Server to 18.04 Server LTS

1)
$ sudo apt update
$ sudo apt upgrade

2)
$ sudo apt dist-upgrade
reboot (sudo init 6)




3)
$ sudo apt install update-manager-core

$ sudo vim /etc/update-manager/release-upgrades
set prompt=lts

4)
$ sudo do-release-upgrade -d

reboot (sudo init 6)

5)
$ lsb_release -a