A useful side effect of using just the minimum Xserver and Fluxbox setup is not just the ease with which it drops to a server (Ctrl+Alt+F4), but also the uncomplicated way in which you can add new users. There is no need for scripts or GUI programs to add and remove users, just a couple of commands which you can run in Rxvt, it is not necessary to change the run level although you can if needed.
Once the user is added, a new Desktop environment is created
which can be customised to suit.
Add a user in two commands as below.
$ sudo useradd -d /home/anton -s /bin/bash -g users anton
$ sudo passwd anton
and set the passwd.
-d being the directory path, -s the shell and -g the group
See below image of this done in Rxvt with user name 'speccy'
A new Desktop environment is created for the user which can be styled to suit your preference.
And as you can see there are all the basic tools you need for a Desktop Linux environment, file manager, terminal emulator, web browser etc. Check out Centos minimal installation and Fluxbox setup for more info.
If you use Ctrl+Alt+F4 or 'sudo telinit 3' to drop out of the Graphical/Desktop environment, your user will still be logged in (and the Xserver stil running), you can log out the user with
# pkill -KILL -u anton
Replace anton with your user name, you can use the who command as below to see which users are logged in.
You can add multiple users as described above and adjust all the Fluxbox/Desktop styles as required.
You will also have to set permissions for a manually created user
so for the user anton created above. For non encrypted.
# chown -R anton /home/anton
# chmod -R 755 /home/anton
Or whatever permission level you decide on.
See add a user in a Desktop