github.com/bengesoff/terraform@v0.3.1-0.20141018223233-b25a53629922/website/source/docs/configuration/override.html.md (about) 1 --- 2 layout: "docs" 3 page_title: "Overrides" 4 sidebar_current: "docs-config-override" 5 --- 6 7 # Overrides 8 9 Terraform loads all configuration files within a directory and 10 appends them together. Terraform also has a concept of _overrides_, 11 a way to create files that are loaded last and _merged_ into your 12 configuration, rather than appended. 13 14 Overrides have a few use cases: 15 16 * Machines (tools) can create overrides to modify Terraform 17 behavior without having to edit the Terraform configuration 18 tailored to human readability. 19 20 * Temporary modifications can be made to Terraform configurations 21 without having to modify the configuration itself. 22 23 Overrides names must be `override` or end in `_override`, excluding 24 the extension. Examples of valid override files are `override.tf`, 25 `override.tf.json`, `temp_override.tf`. 26 27 Override files are loaded last in alphabetical order. 28 29 Override files can be in Terraform syntax or JSON, just like non-override 30 Terraform configurations. 31 32 ## Example 33 34 If you have a Terraform configuration `example.tf` with the contents: 35 36 ``` 37 resource "aws_instance" "web" { 38 ami = "ami-1234567" 39 } 40 ``` 41 42 And you created a file `override.tf` with the contents: 43 44 ``` 45 resource "aws_instance" "web" { 46 ami = "foo" 47 } 48 ``` 49 50 Then the AMI for the one resource will be replaced with "foo". Note 51 that the override syntax can be Terraform syntax or JSON. You can 52 mix and match syntaxes without issue.