What We Are Using

Host: OSX Lion

VirtualBox: 4.1.0

Guest: Ubuntu Server 11.04 (Natty Narwhal)

I'm assuming you have installed VirtualBox and the VirtualBox Extension Pack from here:

http://www.virtualbox.org/wiki/Downloads

Download Ubuntu Server 11.04 making sure you select 32 bit from the drop down:

http://www.ubuntu.com/download/server/download

Go ahead and install the VM into VirtualBox by select New and following the prompts, it will ask you for the location of the ISO you just downloaded to get started. After starting your new VM and following the prompts, make sure you install SSH server (checkbox) and write down the name of your VM, your username and password.

After creating the Ubuntu guest with SSH server installed, turn the guest OS completely off.

Go to terminal on your Mac (OSX) and type in the following replacing "Narwhal" with whatever you named your guest Ubuntu OS in VirtualBox.:

Start the Ubuntu guest OS.

Make sure your SSH service is running:

From your Mac (OSX) terminal SSH into your guest like this:

Adding Shared Folders

From your Mac (OSX) terminal window that is SSH'd into your Guest Ubuntu VM run the following:

Go to the VirtualBox Devices menu and select "Install Guest Additions"

From your Mac (OSX) terminal window that is SSH'd into your Guest Ubuntu VM type the following:

Don't worry if you see something that says "Installing the Window System drivers …fail!". It fails because we aren't using a GUI.

Now shut down your Ubuntu VM like so:

Go to VirtualBox and select your VM and go into its settings. Find the tab that says "Shared Folders" and click on the green folder icon with the plus sign. Click on the drop-down arrow and select some folder on your Mac you want to share. Select the auto-mount check box. Click OK twice and start up your Ubuntu VM. From your Mac (OSX) terminal ssh into your guest as before and type the following:

See your files? Your done!

But before we plop the DVD into our Mac, we have to do some preparatory work. Make sure you've checked to see that all of your critical applications that you use are compatible with Snow Leopard. You can find a compatibility list here.

Next you will need an external hard drive that you've successfully connected to your Mac. It should have enough space to do a complete backup.

NOTE: You should always do a complete backup of your Mac before doing a clean install. The word "clean" is used in this tutorial because we are going to format our hard drive, wiping it clean of everything. Unless you don't care about losing all your data, back it up! I use SuperDuper to create a bootable image of my entire system, but a TimeMachine backup would work as well.

Now write down or take screenshots of your connected network settings (Ethernet, AirPort, or both). The settings can be found under "System Preferences/Network". Since we will be wiping the hard drive and the external hard drive, you will need to either print the settings out or save them to an external USB thumb-drive.

So first things first:

1. Backup your entire machine with TimeMachine, SuperDuper, or some other method to an external hard drive.
2. If your backup is bootable, SuperDuper's is by default, try it now. Click on "System Preferences" and then double-click on "Startup Disk" near the bottom. Select your external hard drive and click "Restart...". If you can log back into your Mac then you are good to go. Once logged in, complete the same procedure again, this time selecting your Macintosh HD and before clicking "Restart...".
3. Now the fun begins! Put your Snow Leopard DVD into your computer. Make sure no external hard drive or device is connected to your computer.
4. Go to the Apple Menu and select "Restart..." When the computer begins to reboot press and hold down the "c" key on your keyboard. An Apple logo will appear and then you should see a spinning icon. When the spinning icon shows up you can let go of the key.
   
   
5. After a minute or so you should see a Snow Leopard screen appear asking you to pick your language. English is the default. Select your language and hit "Enter".
6. After another minute you should see a screen appear that says Welcome to OS X Snow Leopard. Go to the Utilities menu and select Disk Utility. You should see your hard drive over on the left-hand side of the window. Click on it once to select it. Now, click on the "Erase" tab. Make sure the Format drop-down box is set to "Mac OS Extended (journaled)". Click on the "Name" text box and name your new hard drive. Click on the third button on the bottom right that says "Erase". Snow Leopard will ask you if you are sure. You did back everything up right??? If so, go ahead.
   
   
   
7. Quit the Disk Utility program. Click "Continue" to install Mac OS X. Agree to the terms and select your newly formatted hard drive.
8. Click on the "Customize" button on the lower left. Make sure you add "Rosetta". This will enable you to run applications compiled for the PowerPC family of processors under Snow Leopard. Go ahead and continue the install. You will eventually be prompted to provide your Country and type of Keyboard. Fill both of those in and continue.
9. When you get to the screen that says "Do You Already Own a Mac?" select the "Do no transfer my information now" radio button. You can always transfer your data later using the built in Migration Assistant program which is found under the Applications/Utilities folder. Now would be a good time to get a drink, because after you hit the "Continue" button it will appear as if the Snow Leopard install has hung-up, because nothing seems to change. However, this is not the case, just finish your drink and patiently wait.
10. The next window to appear is called "Your Internet Connection". Select "Using DHCP" for the TCP/IP Connection Type. Follow the prompts to fill in your Apple ID and Registration information. After you've filled out their "A Few More Questions" form and created your user account, you are almost done!
11. Quick, go comb your hair or put on a hat or something, because now Apple will want to take your picture for your user account. Or you can always just pick an icon from the list and change it later. Select your Time Zone, set the date and time, and your install is
    

    done!

12. For extra geek points. When the "Mac OS X Install DVD" appears on the desktop, double-click on Optional Installs. Install the Xcode.mpkg. If your into programming this will install all of the gcc libraries you will need if you are interested in compiling binaries, or wanting to look at Cocoa.
13. Enjoy your new cat.