For many of us developers, testing OS X Lion is very high priority. This is how I installed OS X Lion into a separate partition on my MBP.
Obviously, before you start repartitioning your system, please back it up. A zillion things can go wrong when you start moving and resizing partitions. You’ve been warned.
* The first time you run Mail, your mailbox is “converted” to the new system. I’m assuming that you won’t ever be able to run the old version of Mail!
* If disk utility is unsuccessful in creating your new partition, reboot into the Lion OS X image and select Disk Utility from the menu there. That will run Lion’s new Disk Utility which is more robust that the older version. OS X Snow Leopard was never able to repartition my drive but OS X Lion had no problems.
* Playing with partitions is not for the faint of heart. Installing OS X Lion to a USB drive or external hard drive is a safer but likely slower option.
* Expect to find and be sure to report any bugs you find within Lion.
1. Open Disk Utility
2. Click your drive and select the First Aid tab
3. Verify Disk and Repair Disk if needed
4. Click the Partition tab
5. Click the + sign and create the new partition and name it. I would make sure it is at least 20GB in size. My OS X Lion completed install was just under 10GB.
6. Boot to your OS X Lion image. I mounted mine on a USB drive.
7. Install OS X Lion and be sure to select the new partition you just created.
8. Boot into OS X and enter basic information
9. You will probably want to link your old and new home directories by doing the following:
– a. Open Users & Groups in System Preferences
– b. Unlock to allow changes by clicking the lock and entering password
– c. Right-click on your admin account and select Advanced Options
– d. Choose your old Home Directory and leave everything else alone.
– e. You will be forced to reboot. Upon reboot your system will closely resemble your old setup
10. You may wish to link to your old applications. I just put an alias from my old application directory in my dock. Even after linking home directories and applications, some applications may not work reliably.