if you want to use the interface, install vmware player(free), or virtualbox (free), download iso files from ubuntu/centos site and install whole system in those vm players. if you want it for development use, use vagrant (with command line), either search for the vagrant box you like (basically download installed OS), or you can use puphpet.com to configure the virtualbox setup (download a basic OS and it will setup those applications for you). Or, you just want it to use some common stuff (i.e. you just want linux's python), consider docker. Much lighter.