Several different components of Cluster API leverage infrastructure machine templates,
MachineTemplate resources should be immutable, unless the infrastructure provider
documentation indicates otherwise for certain fields (see below for more details).
The correct process for modifying an infrastructure machine template is as follows:
- Duplicate an existing template.
Users can use
kubectl get <MachineTemplateType> <name> -o yaml > file.yamlto retrieve a template configuration from a running cluster to serve as a starting point.
- Update the desired fields. Fields that might need to be modified could include the SSH key, the AWS instance type, or the Azure VM size. Refer to the provider-specific documentation for more details on the specific fields that each provider requires or accepts.
- Give the newly-modified template a new name by modifying the
metadata.namefield (or by using
- Create the new infrastructure machine template on the API server using
kubectl. (If the template was initially created using the command in step 1, be sure to clear out any extraneous metadata, including the
resourceVersionfield, before trying to send it to the API server.)
Once the new infrastructure machine template has been persisted, users may modify
the object that was referencing the infrastructure machine template. For example,
to modify the infrastructure machine template for the
users would modify the
spec.infrastructureTemplate.name field. For a
MachineSet, users would need to modify the
field. In all cases, the
name field should be updated to point to the newly-modified
infrastructure machine template. This will trigger a rolling update. (This same process
is described in the documentation for upgrading the underlying machine image for
KubeadmControlPlane in the “How to upgrade the underlying
machine image” section.)
Some infrastructure providers may, at their discretion, choose to support in-place modifications of certain infrastructure machine template fields. This may be useful if an infrastructure provider is able to make changes to running instances/machines, such as updating allocated memory or CPU capacity. In such cases, however, Cluster API will not trigger a rolling update.