What open source tool is used to manage instances in the cloud using infrastructure as code?

SystemsDeplover is not a widely recognized or standard open-source Infrastructure as Code tool for cloud instance management.

Vault, also by HashiCorp, is an open-source tool for managing secrets and protecting sensitive data, not for provisioning cloud infrastructure.

Terraform, developed by HashiCorp, is an open-source Infrastructure as Code (IaC) tool that allows users to define and provision datacenter infrastructure using a declarative configuration language, managing resources across multiple cloud providers.

Docker is an open-source platform for developing, shipping, and running applications using containers, distinct from an IaC tool for cloud instance management.