$ lsb_release -a
$ sudo apt-get update && sudo apt-get dist-upgrade
$ sudo reboot
$ sudo apt-get install update-manager-core
$ sudo do-release-upgrade
$ lsb_release -a

Note: if not lts version, need to change file /etc/update-manager/release-upgrades, set Prompt=lts

$ sudo vi /etc/update-manager/release-upgrades
$ sudo do-release-upgrade
$ lsb_release -a