7.2. Creating a Template
Create a template from an existing virtual machine to use as a blueprint for creating additional virtual machines.
You cannot create a sealed virtual machine template based on a RHEL 8.0 virtual machine in Red Hat Virtualization 4.3, because of the following limitations:
- libguestfs tools on Red Hat Enterprise Linux 7 do not support modifying Red Hat Enterprise Linux 8 disk images because of additional XFS functionality added in Red Hat Enterprise Linux 8.
- Red Hat Virtualization 4.3 does not support hypervisors based on Red Hat Enterprise Linux 8.0
When you create a template, you specify the format of the disk to be raw or QCOW2:
- QCOW2 disks are thin provisioned.
- Raw disks on file storage are thin provisioned.
- Raw disks on block storage are preallocated.
Creating a Template
- Click → and select the source virtual machine.
Ensure the virtual machine is powered down and has a status of
- Click More Actions ( ), then click Make Template. For more details on all fields in the New Template window, see Section A.5, “Explanation of Settings in the New Template Window”.
- Enter a Name, Description, and Comment for the template.
- Select the cluster with which to associate the template from the Cluster drop-down list. By default, this is the same as that of the source virtual machine.
- Optionally, select a CPU profile for the template from the CPU Profile drop-down list.
- Optionally, select the Create as a Template Sub-Version check box, select a Root Template, and enter a Sub-Version Name to create the new template as a sub-template of an existing template.
- In the Disks Allocation section, enter an alias for the disk in the Alias text field. Select the disk format in the Format drop-down, the storage domain on which to store the disk from the Target drop-down, and the disk profile in the Disk Profile drop-down. By default, these are the same as those of the source virtual machine.
- Select the Allow all users to access this Template check box to make the template public.
- Select the Copy VM permissions check box to copy the permissions of the source virtual machine to the template.
Select the Seal Template check box (Linux only) to seal the template.Note
Sealing, which uses the
virt-sysprepcommand, removes system-specific details from a virtual machine before creating a template based on that virtual machine. This prevents the original virtual machine’s details from appearing in subsequent virtual machines that are created using the same template. It also ensures the functionality of other features, such as predictable vNIC order. See Appendix B,
virt-sysprepOperations for more information.
- Click .
The virtual machine displays a status of
Image Locked while the template is being created. The process of creating a template may take up to an hour depending on the size of the virtual disk and the capabilities of your storage hardware. When complete, the template is added to the Templates tab. You can now create new virtual machines based on the template.
When a template is made, the virtual machine is copied so that both the existing virtual machine and its template are usable after template creation.