All Mac OS X computers administrated by Student Computing Labs come with a complete X Window System implementation for running X11-based applications. It includes the full X11R6.6 technology including a window server, libraries and basic utilities such as xterm. With this software, you may log into remote servers and run X11 applications on those servers and have the windows displayed on the Mac you are sitting at.

This webpage's purpose is to instruct you how to log into another department's server while sitting at a computer supported by Student Computing Labs. We offer NO remote X11 access that would allow you to use our software or computers from another department or from home. You must make the trip to a lab supported by us to use our software or computers. You may NOT remotely log into our computers from another department's computer or from home and any attempt to do so is illegal and can result in legal or other disciplinary action.

The intended audience of this webpage is technical users who know a little Unix and are familiar with the command line, but are unfamiliar with X11. The Student Computing Labs technical group does no Unix training and offers only minimal support for X11 users at this time. There will be little to no support from the service counter consultants. If you encounter an X11 problem you believe occurs because of the computer setup, please contact us and we will fix it if we can. But if the problem is with X11 itself, subscribe to Apple's X11 user list or search their archives for help.

For Unix training, see one of the following:

• MacDevCenter tutorial
• OSXFAQ tutorial
• AtomicLearning tutorial
• Take CS 1010, Introduction to Unix (.5 credits)
• Math department's command summary and tutorial
• Unix Manual pages

Quick Links

• X11 Applications

• Aqua vs X11

• Launching Applications

• Instructions on X11 Display Forwarding

X11 Applications

The main application that may introduce users to X11 is that X11 display forwarding to use applications like SAS. SAS is not actually installed (and can't be) on the Apple computers, but users can log into servers that have SAS installed and run it remotely and display the SAS windows using X11's display forwarding abilities. To learn more about these applications and display forwarding, see below.

While you are using X11 applications, you must leave the X11 application open. Quitting X11 will quit any X11 applications that are running.

To see what X11 applications are installed on the Mac computers supported by Student Computing Labs, look in /Applications/X11. X11 command line utilities are located in /usr/X11R6/bin.

There are many more X11 applications. If you would like one installed, please contact us and let us know.

Difference between Aqua and X11

Aqua
The Aqua interface is a graphical user interface (GUI) that Apple Computer created and owns. It is what most users think of when they think of the Mac OS X GUI. It is responsible for the display of the application windows, menus, dock, mouse pointer, and how all of those things interact with each other.

Read more about Aqua.

X11
X11 is also a graphical user interface and serves the same purpose as Aqua. X11 is the interface used on Unix style computers like Sun Solaris, all BSD variants, Linux, SGI's Irix, OS/2, and Cygwin. X11 is maintained by X.org (not Apple Computer). Apple has created an implementation of X11 for Mac OS X, but they do not "own" it. In fact, Apple's X11 uses XFree86, which is open source.

Read more about Apple's X11.

Warning: "Hard to use"
Apple has worked hard to make sure that both Aqua and X11 window systems can work simultaneously, allowing users to run applications that require the X11 window system easily.

However, in the past, Unix style computers were only used by very technical users, like scientists and computer programmers. X11 catered to that audience, and so it is very difficult for "non-geeky" users. Because it is a different user interface, the mouse behavior, the keyboard behavior, and everything you think you know about the computer changes.

Unfortunately, Apple can't make X11 applications look or behave more like applications written for Apple's Aqua interface. It is up to each application developer to do this. And some applications will never do this because the developers want their application to look the same on all platforms, and that is more important to them than looking the same as other applications on the same platform.

Aqua	X11
Works ok with a 1 button mouse. Holding down modification keys while clicking performs many "optional" click functions, such as display contextual menus. The modification keys are option, control, shift, and command (aka "Apple" key). These types of clicks are called "option-click", "control-click", "shift-click", or "command-click".	Requires 3 button mouse, or emulated 3 button mouse. Apple computers with mice that have multiple buttons, the middle mouse button is the scroll wheel. On Apple computers with one button mice, the middle button is emulated by pressing the option-clicking. The 3rd button is emulated by command-clicking. Control-clicking will also show a contextual menu no matter what type of mouse you have.
Menus are always located on the top of the screen.	Menus are sometimes located at the top of the screen, sometimes in the document window.
Applications mostly have the same look and feel (see snapshot above).	Applications create their own look and feel, often looking very different from each other (see snapshot above).
Graphically appealing, smooth color changes, appealing background textures, "lickable" buttons and widgets (see snapshot above).	Grey and blockly, and often contain no thought for any aesthetics at all (see snapshot above).
Intuitive, often requiring no manual at all.	Ease of use is sometimes never thought of in some X11 applications and require users to read lengthy manuals. But it must be noted that most of these types of applications are specifically targeted for very technical users who are use to reading lengthy manuals. And this doesn't describe all X11 applications.
To copy, you select text, then you select the menu "Edit" and then "Copy" (or press command-c).	To copy, select the text. That is all. Some applications also offer control-c.
To paste, put the cursor where you want to insert the text, then select the menu "Edit" and then "Paste" (or press command-v).	To paste, press the middle mouse button. Some applications also offer control-v.
NOTE: to copy from an X11 application so that you can paste into an Aqua application, you have to select the text and also press command-c. Selecting the text alone will not allow you to paste into Aqua applications. To paste something into an X11 application that you copied from an Aqua application, press the middle mouse button (be sure not to select anything before you paste).
Keyboard shortcuts use the command (aka "Apple") key as the modifier key. For example, command-v is paste.	Keyboard shortcuts use the control key. For example, control-v acts as paste in many (not all) X11 applications. There are also many different key combinations that are completely foreign to Mac OS users.
Nearly every application supports drag and drop so that you can move one item or text straight from one application to another.	Drag and drop does not work at all.
The default way to interact with the computer is by using the Finder application, which shows you a graphical representation of your hard disks, and allows you to find Applications and launch them.	The default way to interact with the computer is through a terminal window called xterm (text based interaction). You type commands into xterm to get a text listing of the hard disk, and you launch applications by typing in the path to the application that you want to launch. To learn the commands to navigate using xterm, see the Unix tutorials above.

Launching X11 applications

Instructions on X11 display forwarding

The X11 user interface allows users to run applications on one computer, but display the graphical interface on a different computer. This is called display forwarding.

Getting an account
To run X11 using display forwarding you must first have an account on a server that supports X11 forwarding and has X11 applications installed. The Math department is an example of one department that has both. In fact, the Math department offers many more X11 programs than our computers.

The Math department will create accounts for University of Utah students who can show justification to use their software. If you would like access to their programs, please visit their lab.

Read more here: www.math.utah.edu/ugrad/lab.html

There are also other departments on campus that will allow X11 display forwarding from their computers. Please contact your department's computer administrators to find out.

When you have an account on another computer, and you can login using "ssh", then you are ready to use X11 display forwarding.

Display forwarding
First, open a Finder window and click on Application on the left pane. Then open X11 in the Utilities folder. Or search for X11 by using Spotlight. This will open an xterm window.

Note, "/Applications/Utilities/Terminal" is very similar to xterm, but it will NOT do X11 display forwarding, only xterm can.

In xterm, enable X11 display forwarding by logging into another computer using ssh and add the "-Y" or "-Y -X" parameter to the ssh command. For example, to use X11 on a Mac to view sas running on a Sun server, in the xterm window, type:

% ssh -Y username@xserver.math.utah.edu or ssh -Y -X username@xserver.math.utah.edu
% sas

or to run only sas

% ssh -Y -f username@xserver.math.utah.edu sas or ssh -Y -X -f username@xserver.math.utah.edu sas

You will not get much feedback that anything is happening. But if you wait, eventually windows should start showing. And that is it. Except you can not close the xterm window or quit X11. If you do, it will quit any X11 applications running in the xterm window.

Note: because of firewall settings on the Apple computers, not all X11 applications will work correctly when displayed locally but running on a remote computer.