Set Up Archives

Next, configure your archive backups. As with duplicates, the exact procedure varies from one application to the next, but again, I give you a basic overview.

Tip

You can find detailed instructions for creating Retrospect archives in Set Up a Backup Server Script (page 200).

In your backup application, select the function appropriate for making an archive. (Appendix B has notes on how some applications name this feature.) Note again that 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. If requested, give your archive procedure a descriptive name.

Select your source(s). This may be a simple matter of navigating to your home folder, or it may involve adding many different folders from all over your hard disk. See Archive Strategy (page 105) for details on choosing which files to include in an archive. If you wish (and if supported by your software), choose selectors or exclusions.

Select your destination. If you are archiving files to a hard disk, choose that disk. You may wish to create a new folder on that disk to contain your backups, especially if the disk also holds other files.

If you're storing your archive on optical media or a disk image, some backup software requires that you first mount the volume in the Finder. To do this:

• For blank optical media, simply insert the disc into your drive; when prompted, give the disc a name and choose the (admittedly confusing) action Open Finder. (This is not required in Retrospect, which can write directly to optical media. When creating your backup set, choose "CD/DVD" as the backup set type.)

• For a disk image, launch Disk Utility (located in /Applications/Utilities) and choose Images > New > Blank Image. Specify a name and location for the image. Select Sparse Disk Image as the format, meaning that the image will automatically grow as necessary to accommodate more files, with its initial size being whatever you select from the Size pop-up menu. Optionally (but recommended) choose AES-128 from the Encryption pop-up menu. Click Create, and if you previously chose to encrypt the image, specify a passphrase when prompted. Disk Utility automatically mounts the new image in the Finder, ready to be used by your backup software.

Some software requires you to specify whether your backups should be incremental or additive (though the terminology differs with each application; once again, see Appendix B for notes on how some applications name these features). If so, be sure to select those features now.

If your application offers compression and encryption and you have not already turned them on, consider doing so now. Compression will slow your backup but enable it to occupy much less spacenormally a good thing. If you select encryption, choose a secure passphraseand don't forget it! Also, if the software offers verification (checking to see that files were written properly), turn it on. Verification alerts you to errors in writing files that may otherwise go unnoticed and cause problems when you try to restore the files.

FileVault and Backups

Mac OS X's FileVault feature optionally encrypts the entire contents of your home folder, so that your files are protected from prying eyes and thieves. It accomplishes this behind the scenes by storing your home folder in an encrypted disk image. Using File-Vault may complicate backups.

If you ask your backup software to archive the entire disk image, it will be unable to perform incremental archives of your home folder, instead making a complete copy of the image each time it runs. This is because, from the point of view of the backup software, your entire home folder is a single fileso any change to the data in your home folder, no matter how small, must result in that entire FileVault disk image being copied again.

You can work around this problem by instructing your software to ignore the FileVault disk image and instead look only at the files stored within it; you must then make sure your FileVault-protected home folder is unlocked and mounted when your backup software runs. However, if you have backups running when you are not at your machine, an unlocked FileVault disk image can jeopardize the security of your files. For this reason, if you must use FileVault, you should schedule backups to begin when you are physically present.

But my recommendation, instead, is to avoid using FileVault in the first place. Backup concerns aside, the way FileVault stores your data in day-to-day use makes it extremely vulnerable to corruption; theoretically, even a tiny amount of damage could render your entire home folder unusable.

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

After testing your archive, you can repeat this procedure to set up archives to additional hard drives or other media.