Set Up Duplicates

With your hardware and software installed, it's time to configure your first serious backup: a duplicate of your startup volume. The exact procedure varies from one application to the next, but I walk you through the basics.

Tip

For detailed instructions on setting up duplicates in Retrospect, see Set Up a Duplicate Script (page 196).

In your backup application, select the function for making a bootable backup. Some applications distinguish between commands that are performed immediately and commands that can be performed on a schedule. Given the choice, select the option that can be scheduled.

Some applications require that you select a checkbox or otherwise indicate whether Unix ownership and permissions should be preserved; for duplicates, they should. If the application includes an option to follow aliases and symbolic links, be sure to deselect it.

If requested, give your duplication procedure a descriptive name, and select a source and destination volume. Keep in mind that the destination volume, if a hard disk or partition, must be at least as large as the amount of data on the source volume. Also, check to see that the destination volume does not ignore ownership; if it does, your duplicate will not be bootable. To check this, select the destination volume's icon in the Finder and choose File > Get Info. In the Ownership & Permissions portion of the window, make sure the checkbox labeled Ignore Ownership On This Volume is deselected.

You may have an option to turn incremental duplication on or off. If so, be sure to turn it on! Otherwise, every time you perform the duplication, the application will copy every single file on your hard disk, even though most of them have not changed.

If your application offers compression and encryption, be sure to turn them off. On the other hand, if it offers verification (checking that files were written properly), turn it on. Without verification, errors in writing files may go unnoticed, and even a tiny error in a single file could prevent your duplicate from working properly.

Finally, start the backup. Often this is just a matter of clicking a "Backup" button. (I cover adding a schedule for this script later in Automate Your Backups, page 170.)

Now wait. Even if you have a fast computer, a fast hard drive, and a fast interface, duplicates can take some time. In some cases, you'll be able to continue using your computer while the files are being copied, but remember that if you modify files during this process, the duplicate will no longer be an accurate copy of your entire hard disk as it existed at a single point in time. It may be worth noting how much, if at all, the operation of your computer slows down while a backup is in progress, because this could affect when you schedule backups to run.

After testing your duplicate (next paragraph), you can repeat this procedure to set up duplicates on additional hard disks or other media. If you are creating duplicates of more than one volume, set up those additional volumes at the same time.