Checking Ubuntu server version on terminal
Run the following command on terminal to see the Ubuntu server version.
$ lsb_release -a
This prints something like following
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic
From the value of Release you can see the current version. In this case its 18.04