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| docs | Provisioning Infrastructure - Terraform CLI |
Provisioning Infrastructure with Terraform
Terraform's primary function is to create, modify, and destroy infrastructure resources to match the desired state described in a Terraform configuration.
When people refer to "running Terraform," they generally mean performing these provisioning actions in order to affect real infrastructure objects. The Terraform binary has many other subcommands for a wide variety of administrative actions, but these basic provisioning tasks are the core of Terraform.
Terraform's provisioning workflow relies on three commands: plan, apply, and
destroy. All of these commands require an
initialized working directory, and all of them act
only upon the currently selected workspace.
Planning
The terraform plan command evaluates a Terraform configuration to determine
the desired state of all the resources it declares, then compares that desired
state to the real infrastructure objects being managed with the current working
directory and workspace. It uses state data to determine which real objects
correspond to which declared resources, and checks the current state of each
resource using the relevant infrastructure provider's API.
Once it has determined the difference between the current state and the desired
state, terraform plan presents a description of the changes necessary to
achieve the desired state. It does not perform any actual changes to real
world infrastructure objects; it only presents a plan for making changes.
Plans are usually run to validate configuration changes and confirm that the
resulting actions are as expected. However, terraform plan can also save its
plan as a runnable artifact, which terraform apply can use to carry out those
exact changes.
For details, see the terraform plan command.
Applying
The terraform apply command performs a plan just like terraform plan does,
but then actually carries out the planned changes to each resource using the
relevant infrastructure provider's API. It asks for confirmation from the user
before making any changes, unless it was explicitly told to skip approval.
By default, terraform apply performs a fresh plan right before applying
changes, and displays the plan to the user when asking for confirmation.
However, it can also accept a plan file produced by terraform plan in lieu of
running a new plan. You can use this to reliably perform an exact set of
pre-approved changes, even if the configuration or the state of the real
infrastructure has changed in the minutes since the original plan was created.
For details, see the terraform apply command.
Destroying
The terraform destroy command destroys all of the resources being managed by
the current working directory and workspace, using state data to determine which
real world objects correspond to managed resources. Like terraform apply, it
asks for confirmation before proceeding.
A destroy behaves exactly like deleting every resource from the configuration and then running an apply, except that it doesn't require editing the configuration. This is more convenient if you intend to provision similar resources at a later date.
For details, see the terraform destroy command.