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Some files and folders are automatically excluded from a backup task

 

Carbon Copy Cloner maintains a list of certain files and folders that are automatically excluded from a 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 configurable, although they can be overridden by a custom filter rule.

Legend:
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 directories are ignored, the directories themselves will be copied.
Items postfixed with a "*" indicate that the filename will be matched up to the asterisk.
Items in bold text are excluded by both cloning methods, other items are excluded only by the "Incremental backup of selected items" cloning method.

Filesystem implementation details

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.

Volume-specific preferences

These items record volume-specific preferences 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.

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 target is not only futile, it will likely corrupt them (and their respective apps will reject them and recreate them).

The dynamic linker share cache

This directory stores the dynamic linker's shared cache. Copying this cache to a new volume will render that volume unbootable. The shared cache must be regenerated on the new volume as the on-disk location of files will have changed.

NetBoot local data store

In the unlikely event that your Macintosh is booted from a Network device, Mac OS X will store local modifications to the filesystem in this directory. 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.

Dynamically-generated devices

These items represent special types of directories on Mac 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

Mac 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 directories. Depending on how you use Mac 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 Mac OS X.

Trash

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 the "Archive modified and deleted items" option to the "Incremental backup of selected 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 directory 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.

Special files

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.