How does Terraform determine dependencies between resources?

Terraform determines dependencies between resources by automatically building a resource graph. This process involves analyzing the configuration files to understand how different resources relate to one another based on their configurations, inputs, and outputs.

When creating a resource graph, Terraform is able to visualize and manage dependencies without requiring explicit definitions from the user. It takes into account various factors such as resource types, references made within the configuration, and the results of one resource's output that may be needed as an input for another resource. This capability is critical for ensuring that resources are created, updated, or destroyed in the correct order, respecting the defined dependencies.

The automatic nature of this dependency graph helps Terraform efficiently manage provisioning, avoiding potential issues that could arise from manual intervention or an incorrect deployment order. This nuanced dependency management is one of Terraform's key features, enabling complex infrastructure configurations to be handled intelligently and effectively.