The X window system or X11 is most basic component of the graphical environment. You can find many implementations of X11 including servers for Max OSX and Windows (Please insert recommendations!). Most GNU/Linux distributions now use X.Org's implementation (which forked not too long ago from the XFree86 project).
Starting X
Graphical Login and GDM
Most functions of your users graphical experience is actually not handled by X, but rather by the Graphical login managers, such as the Gnome Display Manager(GDM). While other display managers exist, Red Hat and fedora based systems use the Gnome Display Manager as the login manager for their systems.
The X command
In comparison to Graphical Managers such as GDM, "X" contains extremely minimal functionality on its own, but each graphical display manager is actually built atop X, and thus X is important to understand in its own right.
The 'X' window system is:
- a client-server application
- The client is the application using the X-window
- The server controls the keyboard and screen and takes signals from the application and responds with output to display on the screen
- A protocol used by the application to connect to the server
- the 'X' protocol, also known as X11
To start X, one has
The startx command
The X startup scripts
Remote X access with SSH
/etc/ssh/ssh_config
/etc/ssh/sshd_config
VNC
Starting a VNC Server
vncserver :1