Carbon Copy Cloner maintains a list of certain files and folders that are automatically excluded from a file-level backup task. The contents of this list were determined based on Apple recommendations and years of experience. The following is a list of the items that are excluded along with an explanation of why they are excluded. This list is not (yet) configurable.
Items prefixed with a "/" indicate that they will only be ignored if located at the root of the volume.
Items postfixed with a "/*" indicate that only the contents of those folders are ignored, the folders themselves will be copied.
Items postfixed with a "*" indicate that the filename will be matched up to the asterisk.
Filesystem implementation details
- .HFS+ Private Directory Data*
These items only show up if you're running an older OS than what formatted the source disk. These items should never, ever be manipulated by third-party programs.
- Saved Application State
These items record volume-specific preferences, e.g. for Spotlight, Time Machine, and a custom icon for the volume. Feedback on the exclusion of these items is welcome. Because they are volume-specific preferences, the exclusion of these items from a day-to-day backup seems most appropriate.
The last item is a folder in each user home folder on Lion that stores application state information. Excluding this folder prevents the applications that were open during the backup task from opening when you boot from the backup. This seems appropriate considering that Apple intends the feature to be used to open the applications that were in use when you log out, restart or shutdown, not at an arbitrary point during the backup task.
Apple-proprietary data stores
These items are Apple-proprietary data stores that get regenerated when absent. Attempting to copy these data stores without unmounting the source and destination is not only futile, it will likely corrupt them (and their respective apps will reject them and recreate them).
The DocumentRevisions data store is used by the Versions feature in Lion. The Versions database stored in this folder contains references to the inode of each file that is under version control. File inodes are volume-specific, so this dataset will have no relevance on a cloned volume.
Volume-specific cache files
Copying these caches to a new volume will render that volume unbootable. The caches must be regenerated on the new volume as the on-disk location of system files and applications will have changed.
NetBoot local data store
In the unlikely event that your Macintosh is booted from a Network device, OS X will store local modifications to the filesystem in this folder. These local modifications are not stored in a restorable format, therefore should not be backed up. In general, you should not attempt to back up a NetBooted Mac.
These items represent special types of folders on OS X. These should not be backed up, they are dynamically created every time you start the machine.
Large datastores that are erased on startup
OS X stores virtual memory files and your hibernation image (i.e. the contents of RAM are written to disk prior to sleeping) and temporary items in these folders. Depending on how you use OS X and your hardware configuration, this could be more than 50GB of data, and all of it changes from one hour to the next. Having this data for a full-disk restore does you absolutely no good -- it makes the backup and restore processes take longer and the files get deleted the next time you boot OS X.
Moving an item to the trash is typically considered to be an indication that you are no longer interested in retaining that item. If you use the trash for semi-permanent storage, please consider using CCC's option to archive modified and deleted items to retain a backup of items that are moved to the trash. If you feel strongly that CCC should not exclude the contents of the Trash by default, your feedback is welcome.
Time Machine backup
This folder stores a Time Machine backup. Complete details about the exclusion of a Time Machine backup by Carbon Copy Cloner, including information about how CCC can clone a Time Machine backup, is available in this section of the documentation.
- /Library/Application Support/Comodo/AntiVirus/Quarantine
Files included in this section are application-specific files that have demonstrated unique behavior. The kacta and kactd files, for example, are created by antivirus software and placed into a special type of sandbox that makes them unreadable by any application other than the antivirus software.