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Using Carbon Copy Cloner to backup to another Macintosh on your network |
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Carbon Copy Cloner offers the option of securely copying your selected data to another Macintosh on your network (or anywhere on the Internet for that matter). After a brief setup procedure to establish trust between your machine and the destination machine, simply indicate the IP address or hostname of the machine to which you have access and CCC will take care of the rest.
Note: Backing up to a remote Macintosh is not the same as backing up to a network filesystem. If you don't require a bootable backup and you are only backing up files for which you are the owner, it will be easier to enable file sharing on the remote machine and back up directly to the mounted sharepoint.
To successfully set up CCC to back up to a remote Macintosh, you will be required to:
- Enable Remote Login on the remote Macintosh
- Determine the Unix path to the folder on that machine that you would like to back up to
- Install an "Authentication Credentials" package on your local machine (CCC will place this package on your Desktop)
- Transfer that same "Authentication Credentials" package to your remote Macintosh and install it there
- Verify that the system time on each Macintosh is reasonably in sync with the other
- Confirm that the backup device on the remote Macintosh is ready and mounted (CCC does not currently perform this verification).
- Manually disable the "Ignore ownership on this volume" setting in the destination volume's Get Info window in the Finder.
- Verify that any firewalls between the two Macs are permitting "secure shell" traffic over port 22.
Configuring CCC to back up to a remote Macintosh is an advanced configuration scenario. If you are unsure of any of these settings, please seek advice at the Bombich Software Help Desk before proceeding.

Enabling Remote Login on the remote Macintosh
To enable Remote Login on your remote Macintosh:
- Log in to that machine as an admin user
- Launch the System Preferences application.
- Open the Sharing Preference Pane
- Check the box next to "Remote Login".
- If you are running Mac OS 10.5 Leopard or greater, be sure to allow access to "All users", or explicitly add the "Administrators" group to the list of restricted users and groups.
Determining the "Remote Macintosh hostname or IP address"
To determine the value to enter into this field:
- Log in to the remote Macintosh as an admin user
- Launch the System Preferences application
- Open the Sharing Preference Pane
- Click on the Remote Login service in the list of services
- In the settings area on the right, you will see a message to the effect of "To log in to this computer remotely, type "ssh username@yourhost.yourdomain.com" at a shell command prompt." The text after the "@" symbol is the hostname or IP address that you will provide in the "Remote Macintosh hostname or IP address" text field.
Determining the "Path to backup directory"
To produce a backup that your source Macintosh can boot from, we recommend that you dedicate a volume to the backup task. The backup volume can be an internal or external volume, though an external volume will be most convenient in a disaster recovery scenario. Be sure to prepare the volume for use with CCC per the instructions in the article titled Preparing a hard drive for use with Carbon Copy Cloner. When you have identified a volume to use on the remote Macintosh for backup, do the following to determine the value to enter in the "Path to backup directory" text field:
- Log in to the remote Macintosh as an admin user
- Launch the Disk Utility application
- Click on the backup volume in the list of devices on the left side of the window
- Locate the "Mount point" value at the bottom of the window — this is the value that you will enter into the "Path to backup directory" field in CCC's Remote Macintosh dialog window on the source machine. The format of this value is typically "/Volumes/Backup Disk".
If you do not intend to create a bootable backup, you may also create a folder on the remote Macintosh that can be used for the backup task:
- Log in to the remote Macintosh as an admin user
- Create a folder in your desired location
- In the Finder, click on the destination folder that you created
- From the Finder's "File" menu, choose "Get Info"
- In the "General" section of the Get Info panel, the "Where" attribute indicates where that folder is located. The path to your backup directory will consist of that location, plus "/", plus the name of your destination directory. For example, I just created a folder named "Backups" in the /Users/Shared directory on my remote Macintosh. The Get Info panel indicates that it is located at "/Users/Shared", therefore the path to my backup directory is "/Users/Shared/Backups".
Bandwidth management options
CCC offers two options that can help you address bandwidth concerns. The option to "Compress data passed over the network" can greatly reduce your backup time and total bandwidth used. The time savings depends on just how slow the connection is between the two Macs. If you have a connection that is slower than 10MB/s, compression will make the transfer faster. If your bandwidth is better than that, compression will actually slow down your transfer. CCC will not compress certain file types that are already compressed, such as graphics files, movies, and compressed archives.
CCC also offers a bandwidth limitation option. If your ISP requires that your transfers stay below a certain rate, you can specify that rate here. Note that CCC errs on the conservative side with this rate, so the average transfer rate may be slightly lower than the limitation that you specify.
The "Authentication Credentials" package installer
Before you can back up to a remote Macintosh, you must first set up "public key authentication" (PKA) between the Macintosh that you're running Carbon Copy Cloner on and the Macintosh that you'd like to back up to. With PKA, you don't need to provide a username/password to access the remote machine. Instead, CCC uses pre-shared, 128-bit key pairs to identify the source and destination machines. When you click on the button to create an Authentication Credentials installer, CCC will generate this key pair and create a package installer. The "Authentication Credentials Installer" installs the key pair into the root account on your machine and then into the root account on the destination machine. You must install them in this order.
Note that you are NOT required to enable the root account on either machine. This is avoided by using public key authentication instead of password-based authentication.
Remote machine requirements
At this time, CCC requires the use of the root account (though it does not have to be enabled) on both the source and destination machines. To successfully back up to a remote machine, you must have administrative privileges on both machines. This may be improved upon in a future release.
CCC also requires that the remote machine be running Mac OS 10.4.8 or later. The ability to back up to non-Mac OS X machines may be improved upon in a future release.
Additional pointers for advanced users
Carbon Copy Cloner's public key-based authentication is designed to work with no additional configuration of the services required for backing up over a network connection. CCC uses rsync over an ssh tunnel (port 22 by default) to perform the backup. If you do make modifications to the sshd configuration, consider how that may affect your backup. For example, CCC requires use of the root account over ssh. If you set the "PermitRootLogin" key in the sshd.conf file to "no", you will not be able to use CCC to or from that machine. It's an important distinction to note that the root account does not have to be *enabled*, but sshd must permit the use of the root account.
A note about access privileges to backed up data
While logged in to your remote Macintosh, you may not have permission to view the contents of your backup in the Finder. Your access to the files will be based on the unique id that is associated with the user account that you're logged in to on the remote Macintosh and the one associated with the account(s) on the other Mac(s) that you're backing up. The first administrator account always gets a uid of "501", and subsequent accounts are assigned incrementally higher uids -- 502, 503, etc. For security and privacy purposes, Mac OS X restricts access to the contents of user home directories to the owners of those home directories, and these restrictions are preserved when your data is backed up to a remote Macintosh.
To learn what user id is associated with your account:
- Open System Preferences and click on the User Accounts preference pane
- Click on the lock and authenticate
- Control+click on your account in the accounts table and choose "Advanced options"
You will see your User ID in the panel that appears.
This may be annoying from the perspective of trying to access those files on your remote Macintosh, but it is important for CCC to preserve the ownership and permissions information when backing up your data. If/when you want to do a restore, you could do either of the following:
a) Attach the external drive directly to the machine that you want to restore files to — the accounts on those systems will be able to access their backed up files
b) Do a restore directly within CCC from the original source Macintosh