It very frustrating to read technical literature scattered with acronyms and abbreviations you don't understand or don't know the meaning of. The "FPGA design from scratch" story is also full of acronyms. I try to explain them the first time they are used but if you don't find an explanation in the text you can look here.

Here are some links to web sites that can help you.

• Acronym Finder
• Acronym Server

Acronym	Explanation	Comment
ASIC	Application-Specific Integrated Circuit
CLB	Configurable Logic Block
CMOS	Complementary metal–oxide–semiconductor
DCM	Digital Clock Manager
DSOCM	Data Side On-Chip Memory Controller
DSP	Digital Signal Processor
FIFO	First In First Out
FPGA	Field Programmable Gate Array
ISOCM	Instruction Side On-Chip Memory Controller
JTAG	Joint Test Action Group
LUT	Look-up table
MAC	Media Access Controller
NRE	Non-Recurring Engineering
RISC	Reduced Instruction Set Computer
UNH	University of New Hampshire

This summer we went to Spain to visit our daughter Sara, who was studying Spanish in Sevilla. Sevilla is the capital of Andalucia the most southern province in Spain. To see a map of Spain you can go to Google Maps. We traveled with Spanair from  Stockholm to Malaga. The direct flight took 4 hours.

We had a rental car from AurigaCrown car hire waiting for us at the Malaga Airport, a dark blue Seat Leon, good-looking sporty car. It was too late to drive that far so we decided to stay the first night in Malaga at Hotel Los Naranjos. The second day we planned to arrive in Sevilla late in the afternoon. On the way to Sevilla we wanted to make a stop in Ronda. We took the route E15/A7 driving west from Malaga. Along the way we passed the famous resorts Torremolinos, Fuengirola and Marbella. We didn't see much of Costa del Sol but we saw a lot of ugly looking hotel complex. From Marbella we turned right and drove A-376 towards Ronda. The road started to climb up the mountain and would take us more than 1000 meters up.
Ronda is one of Andalucia's loveliest towns, steeped in history. It stands on a towering plateau in the mountains of Malaga Province, and is famous through Spain for the plunging river gorge which divides the medieval from the 18th century parts of the town. This gorge is known as "El Tajo" - The Cliff and is spanned by a stone bridge, which once housed a prison. Visitors love to peer down into the gorge, to see the waters of the River Guadalevín.

We walked around in Ronda for several hours in the heat and burning sun. We visited the bullring, one of the oldest in Spain and we climbed down all the stairs to the bottom of the gorge. We had lunch in a beautiful restaurant, Restaurante Santa Casa Pola that is built in to the mountain side of the gorge. Here are more photos from Ronda.  After this fantastic start of our journey through Andalucia it was time to get back on the road again and head for Sevilla. On our way to Sevilla we passed Alogodonales a famous center for paragliding and hang gliding in Southern Spain.

Sevilla is a big city with  a population of more than 1 million, ranking as the fourth-largest metropolitan area of Spain. We had a hard time finding our hotel without a good map and not knowing where we were. After we got lost several times in the old town with all its narrow one way streets we at last found our hotel, Catalonia Giralda. When we got out of our car the heat almost knocked us. The thermometer displayed 46 Celcius (115 Farenheit) and we hesitated to leave the air-conditioned car. When we entered the hotel lobby it was 20C (68F) inside. The hotel was nice and perfectly located close to the oldest part of Sevilla. There are so many things to see in Sevilla you could easily spend several week here. The main attractions are the Cathedral with the Giralda bell tower and the Alcazar royal palace.

The Cathedral of Sevilla, formally Catedral de Santa María de la Sede (Cathedral of Saint Mary of the See) was begun in 1402, with construction continuing into the 16th century.It is the largest of all Roman Catholic cathedrals and also the largest Medieval Gothic religious building, in terms of both area and volume. It is 76 by 115 meters, and was built to cover the land previously occupied by the Almohad Mosque. Its central nave rises to an awesome 42 metres and even the side chapels seem tall enough to contain an ordinary church. Its main altarpiece is considered the largest in the Christian world.

The Giralda is the bell tower of the Cathedral of Seville one of the largest churches in the world and an outstanding example of the Gothic and Baroque architectural styles. The tower is a former Almohad minaret which, when built, was the tallest tower in the world at 97.5 m (320 ft) in height. It was one of the most important symbols in the medieval city.
The Alcázar of Seville is a royal palace. Originally a Moorish fort, the Alcázar(from the Arabic القصر al-qasr, meaning "palace") has been expanded several times. The Almohades were the first to build a palace, called Al-Muwarak, on the site. Most of the modern Alcázar was built over Moorish ruins for King Pedro of Castile  with construction beginning in 1364. Pedro used Moorish workers to build his palace giving it a distinctly Islamic design. The palace is one of the best remaining examples of mudéjar architecture, a style under Christian rule in Spain but using Islamic architectural influence.
The city sits well inland, but a mere 6 metres above sea level. Seville was long an important sea port, prior to the silting up of the Guadalquivir. From Seville Ferdinand Magellan obtained the ships for his circumnavigation. Much of the Spanish Empire's silver from the New World came to Europe in the Spanish treasure fleet that landed in Seville.
Sevilla is especially known for its Flamenco artists. The best Spanish Guitar players are from Andalusia, and many of them from Sevilla. You can also find in Sevilla many Flamenco Shows, with dancers and singers. Here are some photos from Sevilla. The barrio of Triana, across the Rio Guadalquivir from central Sevilla, used to be the quarter of the city's gitanos and the home of Sevillian ceramics. This is also where Sara lives. She share an appartement together with three other students.
The first week we used Sevilla as our starting-point for excursion to exciting places in the south-west of Spain. In a few hours time we can reach Cadiz, Jerez de la Frontera, Gibraltar and Costa de la Luz. One of the most beautiful beaches in Spain is Los Caños de Meca, located 10 km north of Barbate.

After one week in Sevilla we take road A4 to Cordoba. On the way we make a stop in Carmona. Carmona stands on a low hill just off A4, 38km east of Sevilla. It is a charming old town with impressive monuments from many different epochs and with fine views.
We arrive in the afternoon in Cordoba and find our hotel Macia Alfaros a beautiful place with a refreshing outdoor swimming pool. Cordoba is famous for a single architectural  treasure, the Mezquita symbol of the sophisticated Islamic culture. Cordoba's medieval quarter, once the home of the Jewish community, is called "La Judería" (The Jewry), a labyrinth of winding, narrow streets, shady flower-filled courtyards and picturesque squares such as La Plaza del Potro. That night we are having a exquiste diner at restaurant Casa PePe. We are sitting outside at 11 pm and it is still 30 C and it feels cool compared to the 43 C in the middle of the day.

Our next stop on our Spanish tour is Granada. There is no doubt about it - Granada does enchant. The Alhambra palace-fortress stretched along the top of the Sabika hill amid its sumptuos gardens, and the warrenlike Albayzin, Granada's old Islamic quarter, are highlights of any visit to Andalucia. There's no other city in Andalucia where the Islamic past feels so recent. We have booked a room at Parador de Granada Hotel San Fransisco which is part of the famous Palace of Alhambra. We were told we had to make reservations many month in advance but we were lucky and could get a room just a few weeks in advance. Parador hotels can be found all over Spain and they are operated by the Paradores de Turismo de Espana, S.A. which is state owned. Parador hotels are normally found in beautifully restored castles, palaces, fortresses, convents and other fine locations.



Want to read more about Andalucia search for a book at Amazon.

When writing this story I had great help from Wikipedia, the free encyclopedia. Since its creation in 2001, Wikipedia has rapidly grown into the largest reference Web site on the Internet. The content of Wikipedia is free, and is written collaboratively by people from all around the world. This Web site is a wiki, which means that anyone with access to an Internet-connected computer can edit, correct, or improve information throughout the encyclopedia, simply by clicking the edit this page link.

Top

How fast is my MacBook? Let's compare it to some other computers. Here are the contanders.

Model	Processor	Speed	Memory	Operating_System
Compaq EVO N610c	Pentium 4-M	1.8 GHz	512 MB	RedHat Rel 3.0
SUN SunBlade 1500	Ultra SPARC IIIi	1.5 GHz	1 GB	Solaris 10
HP Proliant DL145	AMD Opteron 200	2.6 GHz	32 GB	RedHat Rel 3.0
Apple MacBook I	Intel Duo Core	2.0 GHz	1 GB  Note 1.	Mac OS X 10.47 Ubuntu 6.06
Apple MacBook II	Intel Duo 2 Core	2.0 GHz	1 GB Note 1.	Mac OS X 10.48 Ubuntu 6.10

Note 1. On the MacBook all files are stored on the local disk. All the others have the files stored on an external file server.

The benchmark consists of two tasks. The first task uses ncvlog to compile a Xilinx macro library including 3100 Verilog files. The second task runs a verilog simulation using ncsim. Here are the results (in seconds) :

Task	Compaq	Sun	HP	Apple I	Apple II
Verilog compilation	58	72	25	24	23
Verilog simulation	60	59	31	28	17

Top

When designing an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) you use a hardware description language (HDL) like Verilog or VHDL. To verify that your design is correct you need a hardware simulator. To find a hardware simulator you have to contact a company that makes computer-aided design (CAD) tools. The three major companies developing CAD tools are Cadence, Mentor Graphics and Synopsys. Cadence has the Incisive Functional Verification Platform, Mentor has the Questa Scalable Verification, and Synopsys has the Discovery Verification Platform.
Ever since I started as an ASIC designer in 1990 I have been using Cadence tools. Back then Verilog-XL was one of the few hardware modeling language available and Cadence owned Verilog-XL. With the increasing success of VHDL at the time, Cadence decided to make the language available for open standardization. Cadence transferred Verilog into the public domain under the Open Verilog International (OVI) (now known as Accellera) organization. Verilog was later submitted to IEEE and became IEEE Standard 1364-1995, commonly referred to as Verilog-95.
Now it's time to install the Cadence hardware simulator. Let's go to the Cadence software download page. Before you can start the download you have to register as a Cadence user. To register you must already have a Cadence product installed. To run the simulator you also need an evaluation license. There is no freeware when it comes to CAD software but try to convince Cadence that you are a presumptive buyer of their software and they may give you access to their download page and an evaluation license. After signing up, go to the Electronic Distribution page and follow these steps:

1. Go to the Linux page.
   
2. Download and install the program InstallScape. InstallScape lets you download and install selected Cadence products in a release in a single step. Create an install directory and download the compressed tar file to this directory. Use the command <tar -zxvf Iscape03.40-s012lnx86.t.z> to unzip and unpack the file at the same time.
   
3. Before starting the installation create two directories, one to temporarily store the downloaded files (archive) and one directory where the final installation will be stored.
   
4. Start Iscape in a terminal window using the script file ../iscape/bin/iscape.sh
5. Click <Select Release> and choose a server near you. Protocol should be <http>.
6. Click the <Select Release> button. Enter user name and password.
7. Select Release and Platform. Click the Linux tab and select IUS58 or later from the list. Click next.
8. Select Release : What do you want to do and select <Download a Release>. Click next.
9. Select Release : Select Source Site to Download. Select one of the releases from the list. Click the download button.
10. Download : What do you want to do. Select <Save Archive and Install>. Click next.
11. Download : Save Archive & Install. Choose <I will select products manually>. Click next.
12. Download : Specify Archive Directory. Select the archive directory. Click next.
13. Download : Specify Install Directory. Select the install directory. Click next.
14. Select Product. Select the full Incisive Unified Simulator (29300) from the list. Click next.
15. Start the installation. You will need 2.7 GB of disk space for the archive and the install directories. When the installation has finished you can delete the archive directory. With a high speed connection the installation will take about 30 minutes. When finished quit the window.
16. Before you can start to use the simulator it must be configured. Select <Configure Product> from the main Installscape window. Select <Install Directory> and click next button.
17. Select product <29300 Incisive Unified Simulator> and click next. The configuration script will start and you have to enter IAGREE before it kicks off. When finished close the report window. The installation is now finished and you can exit InstallScape.
18. To find out if the installation was successful you can start the verilog compiler <ncvlog>. Use the command install_dir/tools/bin/ncvlog. The compiler should start and print the following message:
    ncvlog : 05.82-p002 : ......
    
    Usage : ncvlog [options] source.file ....

The simulator will not start without a license file. Cadence uses the FLEXlm software license manager and you have to have the license  manager daemon running before starting the simulator (ncsim). You can ask Cadence for an evaluation license file that will last for 45 days. To generate a license file that will only run on your computer (node-locked) they need the MAC address of your machine. To find out the MAC address, execute the following command in a Linux terminal window.
<sudo ifconfig -a>. Look for eth0 and the HWaddr. The MAC address will look like this 00:91:B8:DF:D3:C0. Send the MAC address to Cadence and they will generate a license file for you. When you receive the license file you have to make two changes to the file. The file is in ASCII format and can be edited with a standard text editor. The first three lines of the file will look like this:
SERVER Cadence-SERVER 0091B8DFD3C0 5280
DAEMON cdslmd ./cdslmd
USE_SERVER
........
Replace "Cadence-SERVER" with the hostname of your machine. To find out the hostname execute the following command in a terminal window: <hostname>
Replace ./cdslmd with the full path name of the license daemon program located in the bin directory of the IUS58 installation.
My license file looks like this after the changes:
SERVER svenand-desktop 0091B8DFD3C0 5280
DAEMON cdslmd /home/svenand/cad/Cadence/ius58/tools/bin/cdslmd
USE_SERVER
.........
After editing the license file you start the license daemon using the following command:
install_dir/tools/bin/lmgrd -c license_file
When the license daemon is up and running you can start using the simulator. Good luck.
Don't forget to define the environment variable CDS_LIC_FILE before starting. Use the following command, replacing <hostname> with the host name of your host:
setenv CDS_LIC_FILE 5280@hostname (csh and tcsh)
export CDS_LIC_FILE=5280@hostname (bash)
or
setenv CDS_LIC_FILE license_file
export CDS_LIC_FILE=license_file



The picture shows a screenshot from my MacBook running Mac OS X with Parallels Desktop installed. The virtual machine has Ubuntu Linux booted. In the Ubuntu Linux OS the Cadence waveform viewer Simvision is running. The same thing goes for VMware Fusion.

Top

Now when we have the hardware in place lets go through the process of installing the software we need. The first thing we have to install is the virtualization software that enables us to run multiple operating systems on top of Mac OS X. There are several offers but I have choosen Parallels Desktop from Parallels Inc.

1. Order the program and download it from Parallels download page.
2. Installing Parallels is no different than installing any other OS X program that uses an installer. Double-click the installer, follow the prompts, and wait for it to finish. After installation, you'll find the program in the Parallels folder in the Applications folder. Behind the scenes, Parallels has installed quite a few things on your machine, including a kernel extension (a low-level tool that modifies the core of OS X) to enable its magic.
   
3. The next step is selecting the Linux distribution we would like to use. All CAD vendors  tell us they only support RedHat Enterprise Rel 3 or 4 but that doesn't stop us from using our favorite Linux distribution. I will use Ubuntu 6.10. Ubuntu is a complete Linux-based operating system, freely available with both community and professional support. It is developed by a large community of developers and its small size (it fits on one CD) makes it perfect for our usage.
4. Download the CD image (ubuntu-6.10-desktop-i386.iso) from the Ubuntu download page.
   
5. The file is 700MB so try to find a high-speed connection.
6. Start Parallels Desktop and click the "New VM" button. Click the Next button in the window displayed. The next window will look like this. Select "Create a typical VM" and click the next button.
   
   


7. Select the guest OS to be used. Set guest OS type to  Linux and guest OS  version to Debian Linux and click the next button.
   
    
   


8. The Configuration Editor window will be displayed. In this window you can change the configuration of the virtual machine. Select the CD/DVD-ROM setup to specify the image file to be read during installation. Select "Use image file" and enter the full image file name  .../ubuntu-6.10-desktop-i386.iso. You may also want to change the size of the memory from 256 MB to 512 MB if you have at least 1 GB installed in your Mac. If you need more than 8 GB hard disk you should also change the "Hard Disk" setup. When finished click "OK".
   
   
   


9. Start the virtual machine by clicking the green triangle. The installation will now start and in a few minutes the Ubuntu installation startup window will be displayed.  Double-click the install icon to continue the installation. Then there a is six step process to define the default language, the time zone, the keyboard layout, username and password and to prepare the disk (erase all). From when you click the install button the whole installation will take less than 15 minutes.
   
   
   


10. After the installation has finished you must restart the virtual machine. Before restarting, edit the setup and change CD/DVD-ROM back to default. The Ubuntu Linux will start and you are ready to login.
11. For adding Parallels Tools see this tutorial.

If this didn't help here is an even better  installation guide.

More information

• Home Page of Henk Koster
• Linux On MacBook (Jason Parekh)
• Debian Wiki MacBook
• Gentoo Wiki MacBook

Top  Next
 

After installing Ubuntu Linux on my MacBook I need to add more software and to fix a number of setups to make everything run smoothly. In this chapter I will describe the process to make this Linux installation perfect for my needs. I had much help from reading the book Ubuntu Hacks by Jonathan Oxer, Kyle Rankin and Bill Childers. Here is a link to the Unofficial Ubuntu 7.04 Starter Guide.

Look for help

There are many places where you can look for help when you have a problem with Ubuntu Linux. Here are some places:

• Ubuntu Home
• Ubuntu Forums
  
• Ubuntu Linux Sweden
• Hacking Ubuntu
  

Software packages

One of Ubuntu's key strengths is the quality of the software packages that are included in the main distribution. They have been relentlessly tested, and come together to form a rock-solid Linux distribution. Although the main Ubuntu distribution is integrated and very solid, that stability comes at a price. Many of the optional packages you may want have been excluded from the main distribution. There are several ways to download and install packages. The most common way is to use the command <apt-get>. The use of <apt-get> and other ways of managing packages are well described in the book Ubuntu Hacks (see Package Management).
To install a new package use the following command :
sudo apt-get install <package-name> or use the use the Synaptic package manager found in the menu: System->Administration->Synaptic Package Manager

Here is a list of packages I have added and a description of what they are for:

Package	Description
build-essential	GNU C compiler gcc, g++, make
libx11-dev	Makes it possible to run X11 applications
libdb-4.1	Needed by Xilinx Coregen
alien	Convert rpm package to debian package
sun-java5-jre	Latest version of Java from SUN
sun-java5-plugin	Latest version of Java plugins
mdns-scan	Browse Zeroconf services
avahi-discover	Zeroconf support
avahi-utils	Zeroconf support

libdb-4.1 is an old package not easily found. I downloaded the file libdb4.1-4.1.25-9mdk.i586.rpm and then used the program alien to convert the rpm package to a debian package using the command: sudo alien -c libdb4.1-4.1.25-9mdk.i586.rpm. To install the debian package I used the command: sudo dpkg -i libdb4.1-4.1.25-10_i386.deb.

To install the latest version of Java use the following command:
sudo apt-get install sun-java5-jre sun-java5-plugin
To install Limewire read Torrentfreak.

Other must-have tools and programs.

Ubuntu Linux comes standard with the gedit text editor. My favorite text editor for many years is nedit. To download nedit go to  Nedit home page. Click the download tab and in the download page click stable binaries and download nedit-5.5-Linux-x86.tar.gz

Just found out about a new text editor called jEdit. It is written in Java and runs on Mac OS X, Linux, Unix and Windows. I am going to try it.

Portable Document Format (PDF) is an open file format created and controlled by Adobe Systems, for representing two-dimensional documents in a device independent and resolution independent fixed-layout document format.
Xpdf is an open source PDF viewer for the X Window System and Motif. Xpdf runs on practically any Unix-like operating system. To download Xpdf go to the Xpdf download page. Ubuntu comes with the Evince pdf reader installed.

Program	Decription	Download
nedit	Text editor	www.nedit.org
jEdit	Text editor	www.jedit.org
Xpdf	PDF reader	http://www.foolabs.com/xpdf/download.html
Inkscape	Vector Graphics Editor	http://www.inkscape.org

Default shell

In Ubuntu the default shell for /bin/sh is dash. If you want to use bash in your script files use /bin/bash.

Keyboard mapping

The MacBook keyboard is setup to run Mac OS X and many keys are not defined the way Unix keyboards are setup. It is possible to map the keys any way you want and there is not one standard setup. I will show my setup and you can modify it to fit your needs.

The xmodmap program is used to edit and display the keyboard modifier map and keymap table that are used by client applications to convert event keycodes into keysyms. It is usually run from the user's session startup script to configure the keyboard according to personal tastes. To map a key to a symbol you have to find the keycode and the keysum. To every key you can map up to four different symbols. To map key "9" to the four symbols : 9 ) }] you use the following command:

keycode 18 = 9 parenright braceright bracketright

To find out the keycode for a key you can use the program xev. Start xev and click in the small window, then hit a key and you will see the keycode and keysum displayed. Put all the mapping commands in a file called .Xmodmap and place this file in your home directory. When you login next time you will be asked to include the .Xmodmap file. You can also setup the mapping by running the command: xmodmap ~/.Xmodmap. To see the current mapping execute : xmodmap -pk. The keysum names can be found in the file keysumdef.h. Remove XK_ before you use the name.

Here is my keyboard mapping for my MacBook (I have a Swedish keyboard):

Keycode	Default	Shift	Alt	Alt shift
64 (Alt left)	Mode_switch
113 (Alt right)	Mode_switch
11	2	quotedbl "	at @
12	3	numbersign #	asciitilde ~
13	4	EuroSign €	dollar $
17	8	parenleft (	bracketleft [	braceleft {
18	9	parenright )	bracketright ]	braceright }
35 (¨^)	backslash	bar |

This is what my .Xmodmap file will look like:

! Map left alt key as mode switch
keycode 64   = Mode_switch
! Map right alt key as mode switch
keycode 113 = Mode_switch
keycode 11    = 2 quotedbl at
keycode 12    = 3 numbersign asciitilde
keycode 13    = 4 EuroSign dollar
keycode 17    = 8 parenleft bracketleft braceleft
keycode 18    = 9 parenright bracketright braceright
keycode 35    = backslash bar

Changing screen resolution

In the latest release of Parallels Desktop (build 3150) this problems has been fixed. Parallels will now set the screen resolution to match the display connected.

When you boot Ubuntu Linux for the first time on your MacBook the maximum screen resolution is set to 1024x768. What happens if you connect an external display with a higher resolution. I have a 23 inch Cinema display (1920x1200) hooked up to my MacBook and without changing the resolution I can't use the fullscreen mode.
It is not possible to set the resolution higher than 1024x768 from the menu System->Preferences->Screen Resolution.
To change the maximum resolution you have to run the program:
sudo dpkg-reconfigure -phigh xserver-xorg. After starting the program a window will be displayed and ask you for a video card driver, leave the vesa marked and then hit Return. In the next window you can enter the video modes to be used . Go down using the arrow down key and when you reach the resolution you would like to use mark it with the space key and then hit Return. The setup will be written to the file /etc/X11/xorg.conf. Next time you boot Ubuntu Linux you will have the maximum resolution changed.

File sharing between Mac OS X and Ubuntu

Parallels has not implemented the same simple file sharing system they have for Windows in Parallels Desktop. But there is a good substitute which I will show you here, the SharePoints program. The SharePoints program lets you setup one or more shared folders in Mac OS X that can be accessed in Ubuntu Linux. Here is a short descriptions on how to use SharePoints to setup file sharing. But first we have to enable personal file sharing and Windows file sharing in the Mac OS system settings:

• In Mac OS X download and install the SharePoints program.
• Start the program.
  

• Select a folder to used as a shared folder. I used the Public folder.
• Give it a name (ParallelsDesktop)
• Enable both AppleFileServer sharing and Windows sharing.
• Set the permissions in the popup window

• Allow Windows guests and set inheritance of permissions if needed.
• You may have to set group permissions to r/w to allow writing files to Mac OS X.
  
• Save the setup.
• Start Ubuntu Linux and open the Networks Server window in the Places menu
• Hopefully you will see the shared folder (SVEN-KE-ANDERSS).
• If you are using VMware double-click the WIndows Network icon.
  
• Double-click to look inside and read or write files from/to this folder. Voila!
  

File sharing using secure shell (ssh)

Secure Shell or SSH is a set of standards and an associated network protocol that allows establishing a secure channel between a local and a remote computer.
The first thing we have to do on the Mac side is to enable remote login (fjärrinlogging) and to find the ip-address (1x.z.1.y). We should also add the .ssh directory in our home directory.




Here is good description on how to setup and use ssh. Let's follow it.

1. Open a terminal in Ubuntu Linux
2. Generate a new key. Use the command ssh-keygen -d
3. Copy the key to the Mac OS X host using the secure copy cammand.
4. scp ~/.ssh/id_dsa.pub 1x.z.1.y:.ssh/authorized_keys2
5. We are now ready to test the ssh command: ssh -X 1x.z.1.y or use ssh -X userid@1x.z.1.y to connect to user <userid>.
   
6. We are now remotely logging in to the Mac OS X host and can do almost anything, copying files, starting programs and much more. The DISPLAY variable is automatically set to display windows in the Ubuntu desktop.
7. If you execute the command echo $DISPLAY you should see something like this: loacalhost:10.0. If the DISPLAY variable is not set read this link to learn what to do.
   
8. To exit the ssh session use the command: exit or logout
   

Printing using an Airport Express

I use an Airport Express for wireless printing in Mac OS X. Apple uses a technique they call Bonjour to allow printing using a usb printer connected  to their Airport wlan hub. Bonjour lets you create an instant network of computers and and smart devices just by getting them connected to each other. It uses something called Zeroconf or Zero Configuration Networking to setup everything.
To print from Ubuntu Linux to a USB printer connected to an Airport Express we will ignore the Zeroconf method and use the standard Common Unix Printing System (CUPS) instead. To use CUPS we first have to find the IP address of the Airport Express unit. When we open the Airport Utility program under Mac OS X and scan the network for Airport Extreme and Airport Express units, we will see the following display:

   

The IP address of the Airport Express is 10.0.1.200.  When we have the IP address we can scan this address to find all open ports. The port scan function built into the Network Tools (System->Administration->Network Tools) utility didn't display all open ports so I decided to install nmap instead. I downloaded and installed nmap-4.20-1.i386.rpm and here is the print out from the program:

==> nmap 10.0.1.200                                                                                         

Starting Nmap 4.20 ( http://insecure.org ) at 2007-03-05 17:30 CET
Interesting ports on 10.0.1.200:
Not shown: 1693 closed ports
PORT      STATE SERVICE
53/tcp    open  domain
5000/tcp  open  UPnP
9100/tcp  open  jetdirect
10000/tcp open  snet-sensor-mgmt

Nmap finished: 1 IP address (1 host up) scanned in 22.035 seconds

The port 9100 is used for printing and it uses a HP jetdirect printer driver. We are now ready to setup for printing to my Epson Stylus Photo 870. To add a new printer open System->Administration->Printing. Double-click the New Printer icon and follow the instructions.

1. Select Network Printer
2. Select HP JetDirect
   
3. Enter IP address of Airport Express or Airport Extreme where the printer is connected.
   
4. Port number should be 9100
5. Click Forward
   

1. Select printer manufacturer
2. Select printer model
3. Select driver type
4. Click Forward

1. Enter printer name or use default name
2. Enter descriptive text
3. Enter printer location
4. Click Apply

Select the Stylus-Photo-870 and make it the default printer (Edit->Make D