The latest update to Mac OS X includes many enhancements, security fixes, and many people are noticing an overall speed increase, especially on older PowerPC machines. These benefits and the fact that problems, so far, have not been severe, have us recommending this update for most people. Despite this, some people may wish to revert back to the previous OS version.
In our previous articles on the update, we outlined a couple of known incompatibilities and more are sure to be found. Macintosh news Web site "xlr8yourmac" has noted some problems with Adaptec SCSI cards, and potential problems with Apple's 56K modem.
Because of the potential for hardware and software incompatibilities, before applying any OS update we recommend you back up your system using cloning software (Carbon Copy Cloner or SuperDuper), or use a full system restore solution such as Time Machine (set up with no exclusions, especially for system folders). For the sake of restoring to previous versions of the OS and also having access to documents created or edited after updating, we recommend you use Time Machine for the backup.
In the event you run into a problem with the update that you cannot overcome, and choose to restore back to the previous version, the following steps will get you there.
For cloned disks:
If you have a cloned disk, first locate any newly changed documents since the update and back them up. The number of documents will depend on how much the system has been used since updating, and this is the reason we recommend using Time Machine for the backup. However, if you have only one or two documents, then you should be able to back them up easily. Next, make sure the clone drive is attached and reboot the system with the option key held down. From the boot menu, select the clone and click the arrow to boot normally. When the OS has loaded, use the installed cloning program to clone the drive back to the internal one, and restore to the point before the update when the clone was made.
For those with Time Machine backups:
With Time Machine, unlike a clone that only has one instance of the hard drive's "state," you can restore back to a previous state and still maintain changed documents that have been backed up. As such, before updating, be sure to run Time Machine to create a "restore" point. Then, when you're ready to restore to the previous install, be sure to run Time Machine again to save any changed documents. Reboot off your Leopard installation disk and using the "Restore From Backup..." option in the "Utilities" menu, select the "restore" point that you created before updating and restore it. Copying may take some time, but your system should be back to where it was before the update. Be sure to run permissions fixes on the drive after restoring, to ensure files are properly accessible. Check the installation to ensure all software and hardware works, and then you can use the Time Machine interface to locate and restore any files you edited or created after updating the software.
The long way
If you do not have a full system backup of your drive, you will have to reinstall the OS and then update to 10.5.6 using the "Combo" updater. Using your Leopard DVD, perform an "Archive and Install" method of installation, ensuring the option to preserve user accounts and data is checked, and then download and apply the 10.5.6 update. This will get your system back to 10.5.6, but keep in mind that some customized settings may need to be set up again, and some applications will need to be reinstalled. Overall, however, the system will largely be the way it was before you updated to 10.5.7.