Creating Linked Clones

A clone is a copy of an existing virtual machine. The result of a cloning operation is a virtual machine that is identical to the original virtual machine. A clone has the same configuration as the original, the same guest OS, and the same installed applications and data. The only exception is the virtual machine UUID and the MAC address of the network adapter, which are reset automatically during the cloning operation.

There are two types of cloning operations in Parallels Desktop:

• Full cloning . When you create a full clone, all of the files comprising the virtual machine are copied, so the new virtual machine is created as completely independent from the original virtual machine.
• Linked cloning . A linked clone is a virtual machine that shares the read-only areas of the virtual hard disk with the original virtual machine. When you create a linked clone, the original virtual hard disk file is not copied. Instead, both the original virtual machine and the clone use the same hard disk with the shared areas of it marked as read-only. When any of the virtual machines make any changes to the hard disk data, a new independent storage is created for it which only that virtual machine can read from and write to. The unaffected areas of the original virtual hard disk are continued to be shared between the original virtual machine and the clone. This functionality allows to save a considerable amount of disk space on the Mac hosting the virtual machines.

Before Your Create a Linked Clone

Before creating a linked clone of an existing virtual machine, make sure that:

• The original virtual machine is stopped.
• The original virtual machine is not encrypted.

Creating a Linked Clone

To create a linked clone of an existing virtual machine:

1. In Parallels Desktop Control Center , select the virtual machine you want to clone.
2. On the Parallels Desktop menu bar, select File > New Linked Clone .
3. Select the target folder. By default, Parallels Desktop saves clones in the Documents > Parallels folder.
4. Click Save to begin the cloning operation.

Creating a Linked Clone from a Snapshot

In addition to creating a linked clone from the current virtual machine state, you can choose an existing snapshot of a virtual machine and create a linked clone from it. You don't have to revert the original virtual machine to the snapshot to create a clone from it.

To create a linked clone from a snapshot:

1. In Parallels Desktop Control Center , select the virtual machine you wish to clone and open its window.
2. On the Parallels Desktop menu bar, select Actions > Manage Snapshots .
3. Select a snapshot from which you wish to create a clone.
4. Click the New Linked Clone button.
5. Select the target folder. By default, Parallels Desktop saves clones in the Documents > Parallels folder.
6. Click Save to begin the cloning operation.

Working with Linked Clones

From the user point of view, a linked clone is just like a regular, completely separate virtual machine. A user of a linked clone doesn't see what's going on in the original virtual machine and other linked clones, and vice versa. The virtual hard disk sharing and independent storage management is done in the background transparently to the virtual machine users.

When you create a linked clone, the virtual hard disk is shared almost completely between the original and the clone(s). When the users of the linked clones begin to install applications, add data, or make any other changes inside their virtual machines, a dedicated disk space is allocated to them where these changes are saved. As a result, the total usage of the host's disk space increases. Still, a large portion of the system and application data on the original virtual disk continues to be shared between the original virtual machine and the linked clones, so the overall host's disk usage remains much lower than if these were independent virtual machines. Provided that the virtual machine users don't do anything drastic, like installing a different operating system, the linked clones normally take much less disk space than independent virtual machines.

For the linked clones to work, the following must be observed:

• You must not delete the original virtual machine. If you do, the linked clones will no longer work.
• If you created a linked clone from a virtual machine snapshot, the snapshot and its entire history in the original virtual machine must not be deleted.
• You should not encrypt the original virtual machine if there are existing linked clones that were created from it. Doing so will make the linked clones inoperable.