One of the most amazing features of UNIX (yet one of the most unknown to new users) is the great support for remote and distributed execution of applications.
Telnet is a program that allows a person to use a remote computer as if that person was actually at that site. Telnet is one of the most powerful tools for UNIX, allowing for true remote administration. It is also an interesting program from the point of view of users, because it allows remote access to all their files and programs from anywhere in the Internet. Combined with an X server, there is no difference (apart from the delay) between being at the console or in the other side of the planet. Telnet daemons and clients are available with most Linux distributions.
Encrypted remote shell sessions are available through SSH (http://www.cs.hut.fi/ssh/) thus effectively allowing secure remote administration
In Unix, and in particular in Linux, remote commands exist that allow for interaction with other computers from the shell propt. Examples are: rlogin, which allows for login in a remote machine in a similar way to telnet, rcp, that allows for remote transfer of files among machines,etc. Finally, the remote shell command rsh allows the execution of a command on a remote machine without actually logging onto that machine.
The X Window system was developed at MIT in the late 1980s, rapidly becoming the industry standard windowing system for UNIX graphics workstations. The software is freely available, very versatile, and is suitable for a wide range of hardware platforms.Any X window system consists of 2 distinct parts -- the X server and 1 or more X clients. It is important to realise the distinction between the server and the client. The server controls the display directly, and is responsible for all input/output via the keyboard, mouse or display. The clients, on the other hand, do not access the screen directly - they communicate with the server, which handles all input and output. It is the clients which do the "real" computing work - running applications or whatever. The clients communicate with the server, causing the server to open one or more windows to handle input and output for that client.
In short, the X Window system allows an user to log in into a remote machine, execute a process (for example open a web browser) and have the output displayed on his own machine. Because the process is actually being executed on the server, very little CPU power is needed in the client. Indeed it is possible to have computers whose primary purpose is to act as a pure X-Windows servers and they are known as X-terminals.
A free port of the X Window system exists for Linux and can be found at: Xfree It is usually included in most Linux distributions.
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