github.com/danp/terraform@v0.9.5-0.20170426144147-39d740081351/website/source/docs/configuration/terraform.html.md (about)

     1  ---
     2  layout: "docs"
     3  page_title: "Configuring Terraform"
     4  sidebar_current: "docs-config-terraform"
     5  description: |-
     6    The `terraform` configuration section is used to configure Terraform itself, such as requiring a minimum Terraform version to execute a configuration.
     7  ---
     8  
     9  # Terraform Configuration
    10  
    11  The `terraform` configuration section is used to configure Terraform itself,
    12  such as requiring a minimum Terraform version to execute a configuration.
    13  
    14  This page assumes you're familiar with the
    15  [configuration syntax](/docs/configuration/syntax.html)
    16  already.
    17  
    18  ## Example
    19  
    20  Terraform configuration looks like the following:
    21  
    22  ```hcl
    23  terraform {
    24    required_version = "> 0.7.0"
    25  }
    26  ```
    27  
    28  ## Description
    29  
    30  The `terraform` block configures the behavior of Terraform itself.
    31  
    32  The currently only allowed configuration within this block is
    33  `required_version`. This setting specifies a set of version constraints
    34  that must be met to perform operations on this configuration. If the
    35  running Terraform version doesn't meet these constraints, an error
    36  is shown. See the section below dedicated to this option.
    37  
    38  **No value within the `terraform` block can use interpolations.** The
    39  `terraform` block is loaded very early in the execution of Terraform
    40  and interpolations are not yet available.
    41  
    42  ## Specifying a Required Terraform Version
    43  
    44  The `required_version` setting can be used to require a specific version
    45  of Terraform. If the running version of Terraform doesn't match the
    46  constraints specified, Terraform will show an error and exit.
    47  
    48  When [modules](/docs/configuration/modules.html) are used, all Terraform
    49  version requirements specified by the complete module tree must be
    50  satisified. This means that the `required_version` setting can be used
    51  by a module to require that all consumers of a module also use a specific
    52  version.
    53  
    54  The value of this configuration is a comma-separated list of constraints.
    55  A constraint is an operator followed by a version, such as `> 0.7.0`.
    56  Constraints support the following operations:
    57  
    58  - `=` (or no operator): exact version equality
    59  
    60  - `!=`: version not equal
    61  
    62  - `>`, `>=`, `<`, `<=`: version comparison, where "greater than" is a larger
    63    version number
    64  
    65  - `~>`: pessimistic constraint operator. Example: for `~> 0.9`, this means
    66    `>= 0.9, < 1.0`. Example: for `~> 0.8.4`, this means `>= 0.8.4, < 0.9`
    67  
    68  For modules, a minimum version is recommended, such as `> 0.8.0`. This
    69  minimum version ensures that a module operates as expected, but gives
    70  the consumer flexibility to use newer versions.
    71  
    72  ## Syntax
    73  
    74  The full syntax is:
    75  
    76  ```text
    77  terraform {
    78    required_version = VALUE
    79  }
    80  ```