You can apply machine initialization in vRealize Automation Cloud Assembly through vSphere customization specifications, or by running commands directly.
A property in your blueprint code can reference a vSphere customization specification by name. Alternatively, you can add a cloudConfig section to the blueprint, in which you embed specific commands.
Use caution if you attempt to combine embedded commands and customization specification initialization. They aren't formally compatible and might produce inconsistent or unwanted results when used together.
For an example of how a customization specification interferes with commands in a cloudConfig section, see How to deploy a Linux machine with a static IP address.