Running Leopard and Tiger Together

The new version of Mac OS X operating system, 10.5, a.k.a. Leopard is getting ready to be released in October this year. From developer's perspective it comes with large number of improvements and Apple provides members of ADC (Apple Developer Connection) with early access to the system.

I tried to run a few preview releases of Leopard on my MacBook Pro. As much as it is exciting, it is also a pain to reinstall the system. Also, I found that it is not possible to support our current users who still use Tiger. After a few Leopard—Tiger roundtrips I decided to look for a better configuration and run both Tiger and Leopard on my laptop using multiple partitions.

Here is how the final Partition Scheme looks like:

As you can see the 160G disk is split in 3 partitions: two 28G partitions for Tiger and Leopard and 92G partition for /Users files. Both Tiger and Leopard installations have /Users/roustem folder replaced with a symlink to /Volumes/Home/Users/roustem. This makes sure that you use the same home folder in both versions of Mac OS X.

Here is the quick overview of steps I made to configure my system:

1. Make a full backup of your current system. I always use SuperDuper!.
2. Reboot from Tiger DVD.
3. Before installing the system, use Disk Utility to re-partition the disk.
4. Install the system and use the same username that you previously had.
5. Copy /Users folder from your backup drive to the Home disk.
6. Open Terminal and use sudo bash to start a super-user shell
7. Rename the current /Users/{your-user-name} folder to /Users/{your-user-name}.bak and then create a /Users/{your-user-name} symlink to /Volumes/Home/Users/{your-user-name}.
8. Logout and log back in. This should bring back your old desktop and home folder.
9. Reboot from Leopard DVD and install Leopard on the remaining partition and then replace the default user home folder with a shared one.

As you can see the home folder is now a symlink:

Tip: Keep pressing <Option> key during startup to select the disk partition or DVD to boot from.

About the partition size. In the beginning I tried to use a smaller size partitions for Leopard and Tiger and get more space for my own files. This didn't go very well as I started with 12G partition for Leopard only to find later that there is no space left to install Snapz Pro X there. I decided that 28G will be a good partition size for both Leopard and Tiger installations and provide some breathing room when I need to install a system update or Adobe Photoshop that both use the system partition. Note that during the operating system setup I customize the settings and select not to install Additional Languages and Printer Drivers.