Carbon Copy Cloner Documentation

			A closer look at how CCC determines the "bootability" of a destination volume

CCC determines whether your destination volume will be bootable and indicates any configuration concerns in the "Cloning Coach" window. If you see a yellow warning icon next to the "Customize these settings" button, you can click on that icon to see these concerns. CCC will also present these concerns to you the first time that you back up to any particular destination volume.

If CCC doesn't raise any configuration concerns, and the destination volume has an OS on it when the backup task is completed, and barring any hardware problems that might interfere, your backup volume *should* be bootable.

Configuration concerns that affect bootability of the destination volume

CCC looks for the following configurations to determine if a destination volume will not be bootable:

The destination volume cannot be a disk image -- you cannot boot your Macintosh from a disk image.
If the Macintosh is a PowerPC Macintosh, the destination device must be an internal volume or on a Firewire hard drive. Intel Macintoshes can boot from either an internal volume, a Firewire hard drive, or a USB hard drive.
The files and folders required by Mac OS X must be present on the source volume. These include: /Library, /System, /bin, /etc, /mach_kernel, /private, /sbin, /tmp, /usr, and /var.
The files and folders that are required by Mac OS X must be selected to be copied to the destination volume (applicable only to the "Incremental backup of selected items" cloning method).
If the Macintosh is a PowerPC-based Macintosh, the hard drive on which the destination volume resides must be partitioned using the APM (Apple Partition Map) partitioning scheme. Intel-based Macintoshes ship with hard drives formatted with the GPT (GUID Partition Table) format, and will not boot a PowerPC Macintosh.
If the Macintosh is an Intel-based Macintosh, the hard drive on which the destination volume resides must be partitioned using the Apple Partition Map or GUID Partition Table partitioning scheme (CCC will indicate, however, that an APM-partitioned disk is not an Apple-supported configuration for Intel-based Macs). You may have difficulty booting or running an Intel-based Macintosh from a hard drive formatted with the MBR (Master Boot Record) partitioning scheme.
CCC will issue a warning if the operating system that you're backing up (or restoring) is older than the OS that your machine shipped with.

CCC does not maintain an exhaustive list of hardware:shipping OS pairs. CCC also cannot determine whether the destination will be bootable when the source or destination are remote Macintosh volumes.

Configuration concerns that affect the preservation of filesystem metadata

CCC will note a concern if there is a compatibility mismatch between the source and destination filesystems. For example, if you are backing up files from an HFS+ volume to a network filesystem, some of the filesystem metadata cannot be preserved. In many cases this is acceptable and you can ignore the message. Each of the possible concerns that CCC might raise are listed below. The "risk" associated with not preserving each type of metadata is explained plainly, so you can decide whether the destination volume will suit your needs.

The destination doesn't support Access Control Lists

Access Control Lists specify a granular list of the privileges that users and groups have for a particular file or folder (e.g., read, write, get information, delete, etc.). These advanced privilege settings generally apply only to user accounts that have been created on your Macintosh — for example, to prevent other users from deleting items from your home directory. If you are backing up your own files to a locally-attached hard drive, or to a network file share on a trusted computer, the Access Control List filesystem metadata is relatively unimportant. If you are backing up to or from a network filesystem in a business or education setting, however, check with your tech support staff for additional advice on whether this metadata must be preserved.

The destination doesn't support hard links

A hard link makes a single file appear to be located in multiple places on your hard drive. If a single file had 20 hard links scattered across the disk, each hard link file would consume no additional space on the hard drive, and editing the content of any one of those files would immediately affect the content of every other hard link to that file.

When you back up the contents of a volume that contains hard links, ideally you want to preserve the hard links. If the destination filesystem doesn't support hard links, each hard linked file will be disassociated from the original file and will become a copy on the destination. This won't result in any loss of data, but your backup set will consume more space on the destination than on the source. Hard links are leveraged quite a bit on Mac OS X by the operating system, though they are generally less common among user data.

The destination doesn't support ownership

File ownership indicates which user account on your Mac has control of a file. The owner of a file can limit access to that file from other users on the same computer. If the destination doesn't support ownership, then the owner of each file copied to the destination will be set to the user that mounted the destination. If the destination volume is accessed elsewhere (e.g. mounted on another Mac or even by a different user on the same Mac), then any restrictions that you have placed on those files may not be honored. If you are backing up files and folders that are not all owned by the same user (e.g. you), you should consider backing up to a local, HFS+ formatted volume or to a disk image instead.

Some filesystems have file size limitations

Some filesystems have restrictions on how large a file can be. FAT32, for example, limits files to 4GB or less. CCC will proactively warn you of this limitation if you choose to back up a volume that does support files larger than 4GB to a filesystem that does not support files larger than 4GB. CCC will then automatically exclude files larger than 4GB from the backup task. Files that were excluded will be reported at the end of the backup task.

If you require that files larger than 4GB are backed up, you must reformat the destination volume with a format that supports larger files.

The destination already has an installation of Mac OS X. Merging a different version of Mac OS X into this destination may cause problems with that installation of Mac OS X

This message appears if you have indicated that files and folders that are only present on the destination should be left alone. While that setting will protect any data that you have on the destination volume that is unique to that volume, it does a disservice to the installation of Mac OS X on your destination.

Suppose, for example, that you have a complete backup of Mac OS 10.6.7 on your backup volume. When you apply the 10.6.8 update to your source volume, many system files are updated, some new files are added, and some files may be deleted. If you use CCC to update your backup volume, but you don't allow CCC to delete the items on the destination that the OS update had deleted from the source, then there will be a bunch of "cruft" left over on the backup volume.

If you should ever need to boot your Mac from your backup volume, these cruft files could cause the OS to behave unexpectedly, and they may prevent it from booting altogether. A notorious example of this is with Mac OS X Tiger in which the database that stores user account information would be corrupted if cruft files weren't removed. In those cases, the destination volume would boot to the loginwindow and the user would be unable to login.

CCC can help you perform a clean upgrade or downgrade of Mac OS X on the destination volume by moving items that should be deleted to an archive folder. Any files and folders that you keep only on the destination would also be moved to the archive folder. See the "Protecting data that is already on your destination volume" section of the documentation for more details on these settings.

Help! My clone won't boot!

We're happy to help you troubleshoot your bootability problems. Before you ask for help, please try the troubleshooting steps below. If you're having trouble with the steps or have run out of options, please let us know how far you got, or how far your Mac gets into the boot process.

If CCC's Cloning Coach didn't report any configuration concerns for your backup volume and you are having trouble booting from it, try the following troubleshooting steps (in order):

If you are using an external hard drive enclosure, confirm with the enclosure vendor whether your enclosure should support booting your Mac. Several Western Digital enclosures, for example, cannot boot a Mac.
Reboot your Mac holding down the Option key.
Wait about 30 seconds to see if the backup volume appears. If your backup volume appears at this step but doesn't complete the boot process, skip to the next section below.
Detach, then reattach the backup volume's firewire or USB cable from/to your Mac and wait up to another 30 seconds.
Shut down your Mac completely, then start it up holding down the Option key, waiting another 30 seconds for the volume to appear.
Repeat the steps above, but using another interface (e.g. USB if you tried Firewire, Firewire if you already tried USB) and see if the volume appears. If you have multiple USB ports, try each port.
If the hard drive enclosure is bus powered, try plugging in its DC power supply before starting up your Mac. Bus powered enclosures often take a bit longer to spin up or simply don't make themselves available that early in the boot process.
Lastly, try resetting your Mac's parameter RAM. PRAM maintains settings related to starting up your Mac, and it's possible that invalid settings are interfering with your Mac's discovery of the external enclosure. To reset your PRAM, hold down Command+Option+P+R on startup. Hold down those keys until you hear the second startup chime. Release all but the Option key after you hear the second startup chime.

If the volume still won't boot, it's possible that the enclosure doesn't support booting your Mac. The Golden Litmus Test for bootability would be to install Mac OS X directly onto the volume. If that fails to make the disk bootable, then it definitely isn't going to happen.

The backup volume starts to boot the Mac, but is slow or never gets to the Finder

There are several visual hints that can indicate how far your backup volume is getting in the startup process:

Apple logo: The "booter" file was found and executed.
Spinning progress indicator: The OS "kernel" was executed and now has control over the startup process. The kernel will load kernel extension caches, mount the startup disk, then execute "launchd" which kicks off all of the other system processes.
Blue screen: The WindowServer has loaded, so the system is ready to start loading regular applications or the loginwindow.
Loginwindow or your Desktop: The system has finished loading, and is ready for user interaction

If your backup volume showed up in the Option key startup disk selection screen, but doesn't display the Apple logo when you choose to start from it, then your Mac is having trouble finding the "booter" file on this volume. This can occur due to hard drive enclosure interference, due to filesystem corruption on the backup volume, or due to the volume being improperly "blessed" (blessing a volume stores certain information about the startup files in the volume's header, and your Mac uses that information to start the boot process). If you can rule out enclosure problems, use Disk Utility to repair any filesystem problems on the backup volume, run your backup task again, then try booting from the backup volume again.

If you see the universal "No access" symbol after selecting your startup disk, this indicates that the booter file could not be executed. This could be caused by a permissions problem, corruption of the booter file, or could be due to trying to run an incompatible operating system on your Mac. If you are booting a different Mac than what the backup volume was cloned from, try installing Mac OS X directly onto the cloned volume while booted from the Mac OS X Installer DVD. If you're booting the same Mac from which you created the backup, try reformatting the backup volume, then re-run your backup task and try again to boot from that volume.

If your Mac never progresses past the spinning progress indicator (below the Apple logo) or hangs at the blue screen while booting from the backup volume, there is probably a problem with some of the system files that are called early in the startup process. The system log on the backup volume can be very useful in troubleshooting these problems. To view the system log:

Boot your Mac from its usual startup disk
Choose "Go to folder" from the Finder's Go menu
Type "/Volumes/Backup volume name/var/log" (no quotes, and substitute the actual name of the volume) and click the Go button
Double-click on the system.log item in this folder

Look for any error messages, indications of crashes, etc., or simply attach the system.log file to a discussion on the Bombich Software Help Desk.

A closer look at how CCC determines the "bootability" of a destination volume