I am using Ubuntu 14.04 LTS desktop version, I would like to use Ubuntu 14.04 Server.
Is it possible to migrate (change) from Ubuntu desktop to Ubuntu server without losing any data which is currently available?
yes you can do that.
then How ?
Open your terminal and type as
It will open in terminal with options & there you can choose Ubuntu Server with space-bar and then continue. It will download and install Ubuntu Server tools.
hope that helps.