Installing Mac OSX 10.6 :Snow Leopard

I needed to run an XCode program that uses the features of GCD.
Grand Central Dispatch (GCD) is a technology developed by Apple Inc. to optimize application support for systems with multi-core processors and other symmetric multiprocessing systems.[1] It is an implementation of task parallelism based on the thread pool pattern. It was first released with Mac OS X 10.6. [from wiki]

This event led me to upgrade my system to Snow Leopard. Because GCD is available on Mac OSX 10.6.x. And I was using OSX 10.5.8.

The upgrading job seemed simple as I started.

1. Insert the Snow Leopard into the DVD drive.
2. Double click the install Mac OSX icon.
3. Select the disk where OSX will be installed.
4. Install.

And the happy ride ends :D.

But there is a difference between knowing the path and walking through it. Midway through the installation I was comfounded with an ERROR SCREEN saying that installation could not be done. Most of the possible escape around were tried but gradually situation was becoming grave.

1. Tried to restart computer and started the re-installation.

2. Tried to revert back to my old OSX from the OSX 10.6 DVD. Machine reported that installation not possible.

3. Tried to see what happens if DVD was ejected. Machine shuts down after trying for a while.

4. Inserted OSX 10.5.5 ROM and tried to recover the old OSX.

5. Tried to save the disk content using the disk utility. Machine found that the node structure of the disk has been collapsed. Alas am I going to lose all the files I have!

6. Finally the Terminal window was summoned upon (POPPPOPOOOOOOOOOO). Flash Drive, Portable HD were mustered for transferring data from the Disk. Rigorous usage of UNIX cp command transferred my data to the Portable HD.

7. Old disk was formatted. Then the machine agreed to install the new OSX 10.6.

Sigh of relief.


Lessons:
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1. Always back up the important files from the disk.
Option 1: Use Time Machine to create a disk image of the current state of the Machine so that the saved dmg can be used to revert back if unusual event occurs during installation.
Option 2: Manually save the important files to separate disk.
Option 3: Upload the important file on the web.

2. Think the possible mishaps before committing something new.