├── LICENSE ├── README.md └── azurerm_example_main.tf /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. By contrast, 15 | the GNU General Public License is intended to guarantee your freedom to 16 | share and change all versions of a program--to make sure it remains free 17 | software for all its users. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Terraform Guide 2 | 3 | > [!WARNING] 4 | > This is an advanced guide and assumes you already know the basics of Terraform. Think of this more like an advanced cheat sheet. I went through various sources, captured any notes that I felt were important, and organized them into the README file you see here. If you are new to Terraform, then I would suggest first going through the [HashiCorp Docs](https://www.terraform.io/docs) or doing a couple [HashiCorp Learn](https://learn.hashicorp.com/) courses. 5 | 6 | > [!NOTE] 7 | > Terraform comes in a few different versions. This guide covers Terraform "*Open Source*" only. It doesn't cover Terraform "*Cloud*" or Terraform "*Enterprise*". 8 | 9 | > [!IMPORTANT] 10 | This is a live document. Some of the sections are still a work in progress. I will be continually updating it over time. 11 | 12 | --- 13 | 14 | # Table of Contents 15 | 16 | Part 1 - Terraform Files, Folder Structure, and Blocks 17 | - [Configuration Files](README.md#configuration-files) 18 | - [Root Module](README.md#root-module) 19 | - [Folder Structure](README.md#typical-root-module-folder-structure) 20 | - [terraform Block](README.md#terraform-block) 21 | - [provider Blocks](README.md#provider-configuration-blocks) 22 | - [terraform init](README.md#terraform-init) 23 | 24 | Part 2 - Terraform State 25 | - [State Files](README.md#state-files) 26 | - [Local Backend](README.md#local-backend) 27 | - [Remote Backend](README.md#remote-backend) 28 | - [Terraform Workspaces](README.md#terraform-workspaces) 29 | 30 | Part 3 - Terraform Code 31 | - [Input Variables](README.md#input-variables-aka-variables) 32 | - [Local Values](README.md#local-values-aka-locals) 33 | - [Data Sources](README.md#data-sources) 34 | - [Resources](README.md#resources) 35 | - [Child Modules](README.md#child-modules-aka-modules) 36 | - [Output Variables](README.md#output-variables-aka-outputs) 37 | 38 | Part 4 - Everything Else 39 | - [Syntax Notes](README.md#syntax-notes) 40 | - [Loops (count and for_each)](README.md#loops) 41 | - [For Expressions](README.md#for-expressions) 42 | - [String Directives](README.md#string-directives) 43 | - [Lifecycle Settings](README.md#lifecycle-settings) 44 | - [Terraform CLI Commands](README.md#terraform-cli-commands) 45 | - [.gitignore File](README.md#gitignore-file) 46 | 47 | --- 48 | 49 | ## Terraform Files, Folder Structure, and Common Code Blocks 50 | 51 | ### Configuration Files 52 | - Files that contain Terraform code are officially called *configuration files* 53 | - Configuration Files can be written in two different formats: 54 | - native format which uses the `.tf` file extension 55 | - alternate JSON format which uses the `.tf.json` file extension 56 | - This guide will only focus on the native format 57 | 58 | ### Root Module 59 | - When you run Terraform commands such as `terraform plan` or `terraform apply` you run it against a directory of Configuration Files. This directory could contain one Configuration File, or it could contain many 60 | - Separating your Terraform code into multiple Configuration Files is totally optional and for you to decide. Using multiple Configuration Files can make it easier for readers and maintainers of your code 61 | - Terraform will automatically evaluate ALL Configuration Files found in the **top level** of the directory you run it against 62 | - This top-level directory is commonly referred to as the *Root Module* 63 | 64 | ### Typical Root Module Folder Structure 65 | - `main.tf` 66 | - Contains all of your `locals` blocks, `resource` blocks, `module` blocks, `data` blocks 67 | - `outputs.tf` 68 | - Contains all of your `output` blocks 69 | - `variables.tf` 70 | - Contains all of your `variable` blocks 71 | - `versions.tf`, `terraform.tf`, `providers.tf` 72 | - Recently, it has been common to put the `terraform` configuration block and all of your `provider` configuration blocks into separate Configuration Files 73 | - Some of the common filenames that I've seen used for this are `versions.tf`, `terraform.tf`, or `providers.tf` 74 | - You may not always find these files. If they don't exist, then these blocks are typically found in `main.tf` instead 75 | - `dependencies.tf` 76 | - Another fairly recent practice is to put all of your `data` blocks (data sources) into this separate Configuration File 77 | - Same as above, you may not always find this file, and if not, the `data` blocks are typically found in `main.tf` instead 78 | 79 | ### terraform block 80 | ```terraform 81 | # ROOT MODULE ONLY 82 | terraform { 83 | 84 | required_version = "=1.2.0" 85 | 86 | required_providers { 87 | azurerm = { 88 | source = "hashicorp/azurerm" 89 | version = "=3.7.0" 90 | } 91 | aws = { 92 | source = "hashicorp/aws" 93 | version = "=4.18.0" 94 | } 95 | } 96 | 97 | backend "azurerm" { 98 | resource_group_name = "value" 99 | storage_account_name = "value" 100 | } 101 | 102 | } 103 | 104 | # CHILD MODULE ONLY 105 | terraform { 106 | 107 | required_version = ">= 1.0.0" # only specify minimum in child modules 108 | 109 | required_providers { 110 | aws = { 111 | source = "hashicorp/aws" 112 | version = ">=2.0.0" # only specify minimum in child modules 113 | configuration_aliases = [ aws.first, aws.second ] 114 | } 115 | } 116 | 117 | # no backend configurations in child modules 118 | 119 | } 120 | ``` 121 | - The `terraform` block supports hard-coded values only 122 | - `required_version` is used to specify which version(s) of Terraform are supported by this module 123 | - You can specify an exact version, a min version, a max version, or even a range of versions. See the [Version Constraints](https://developer.hashicorp.com/terraform/language/expressions/version-constraints) documentation for more info 124 | - In Child Modules, you should only specify a minimum version. Let the Root Module specify the maximum version 125 | - `required_providers` declares which providers are used by this module, so that Terraform can install and use these Providers 126 | - In Root Modules: 127 | - You should include all Providers being used by the Root Module plus any Child Modules being called 128 | - In Child Modules: 129 | - You only need to include Providers being used by that Child Module 130 | - You should only specify a minimum version. Let the Root Module specify the maximum version 131 | - If your Child Module uses multiple copies of the same Provider, then specify the `configuration_aliases` argument, this specifies the exact Providers and their Aliases that must be passed to this Child Module when calling it 132 | - `backend` is used to configure which Backend the Terraform CLI will use 133 | - This block only belongs in Root Modules 134 | - The `terraform` block has a few other uses, but they will not be covered here. Read the [Terraform Settings](https://www.terraform.io/language/settings) docs for more info 135 | 136 | ### provider Configuration Blocks 137 | ```terraform 138 | # ROOT MODULE ONLY 139 | provider "aws" { 140 | region = "us-east-1" 141 | } 142 | 143 | provider "aws" { 144 | alias = "second" 145 | region = "us-west-2" 146 | } 147 | 148 | provider "azurerm" { 149 | # version = "1.0" # DEPRECATED! DO NOT USE! 150 | features {} 151 | } 152 | 153 | provider "google" { 154 | project = "acme-app" 155 | region = "us-central1" 156 | } 157 | ``` 158 | - Each Provider has its own unique settings. This may include things such as the credentials used to authenticate to the vendor's API, which region to use, which subscription to use, etc. 159 | - Do not put sensitive credentials in the `provider` block. Passwords stored directly in code are **bad**! 160 | - Some Providers support alternate ways to provide these values, such as using environment variables. It is recommended to use these alternate methods 161 | - Check out your Provider's documentation for more information 162 | - You may still see code that uses the `version` argument inside of a `provider` block. Do NOT use this, it's deprecated. Instead, you should specify the supported Provider versions in the `terraform` block (see above) 163 | - You can declare multiple `provider` blocks for a single Provider, with each block using a different configuration. See the two `aws` blocks in the example code above 164 | - The first instance you define is considered the *default* Provider and does not need to use the `alias` argument 165 | - Any other instances you define must have a unique `alias` argument that will be used to reference this instance of the Provider 166 | - `provider` configuration blocks go in the Root Module ONLY, they should NOT exist in Child Modules 167 | - Child Modules recieve their provider configurations from the Root Module 168 | 169 | ### terraform init 170 | You must run `terraform init` at least once before you can run any `plan` or `apply` commands. The `terraform init` command is a powerful command that has 3 different purposes: 171 | 172 | 1 - Configures your Providers 173 | - It looks at your Configuration Files, figures out which Providers your code uses, and then automatically downloads those Providers into the `.terraform` folder 174 | - It will automatically create a lock file named `.terraform.lock.hcl` 175 | - The lock file stores the exact versions of the Providers that were downloaded by `init` 176 | - You should store this file in version control along with your code. This way everyone will use the same lock file and as a result everyone will download the same Provider versions 177 | - How do you upgrade to a new Provider version? First, upgrade the Provider version in the `terraform.required_providers` block and then run `terraform init -upgrade`. This will download the new Provider and it will automatically update the `.terraform.lock.hcl` file as well 178 | - Any time you add a new Provider to your code you will need to run `terraform init` again in order to download that Provider 179 | 180 | 2 - Initializes your chosen Backend 181 | - Any time you change to a different Backend you will need to run `terraform init` again in order to initialize the new Backend 182 | 183 | 3 - Configures your Modules 184 | - Any time you add a Module to your Configuration Files, or you change the source of an existing Module, you will need to run `terraform init` again 185 | 186 | --- 187 | 188 | # Terraform State 189 | 190 | ### State Files 191 | - State Files use a custom JSON format 192 | - You should NEVER manually edit State Files. Instead, use commands like `terraform import` and `terraform state` to modify the state 193 | - You should NEVER store your State Files in Version Control Systems like Git: 194 | - State Files are stored in plain text, and they often include passwords and other sensitive information 195 | - Make sure your State Files are stored in a secure location and accessible only by users or accounts who require access 196 | 197 | ### Local Backend 198 | - This is the default backend that Terraform will use unless you specify a different backend 199 | - This will be created as a file named `terraform.tfstate` in the Root Module 200 | - Problems with a Local Backend: 201 | - The State File is local to your computer and can not be shared by other teammates 202 | - You can only use 1 local State File 203 | - (Workspaces are an exception, but they are not recommended) 204 | - You can start with a Local Backend, and later you can change your code to use a Remote Backend. Terraform will recognize the local State File and prompt you to copy it to the new Remote Backend 205 | 206 | ### Remote Backend 207 | - You can only configure 1 Remote Backend per Root Module 208 | - Configuring a Remote Backend is done in the `backend` block inside the `terraform` block: 209 | ```terraform 210 | terraform { 211 | backend "azurerm" { 212 | key1 = value1 213 | key2 = value2 214 | key3 = value3 215 | } 216 | } 217 | ``` 218 | - Remote Backends require configuration parameters, which specify: 219 | - How to find the storage (name, resource group, etc.) 220 | - How to authenticate to the storage (service principal, access key, etc.) 221 | - Read your Remote Backend's documentation for for more info 222 | - `backend` blocks can NOT use Terraform variables or references, they must use hard-coded values 223 | - This is because Terraform sets the Remote Backend as its very first step, even before it processes variables 224 | - Do NOT put sensitive values directly in the `backend` block. Passwords in code are bad! 225 | - You can remove some or all of the key/value pairs from the `backend` block and provide them in other ways: 226 | - Option 1 is individual key/value pairs: `terraform.exe -backend-config="key=value" -backend-config="key=value"` 227 | - Option 2 is to use a separate file: `terraform.exe -backend-config=backend.hcl` 228 | - Where `backend.hcl` is a file which contains only the key/value pairs that are needed by the backend 229 | - If this file contains sensitive values, then do NOT check it into version control 230 | - Option 3 is using environment variables supported by your Backend. Each Backend supports its own special environment variables. Check your Backend's documentation for more information 231 | - This is the preferred option, as credentials are kept out of your code 232 | 233 | ### Terraform Workspaces 234 | - Note: These are different from Terraform "Cloud" Workspaces 235 | - If you create Workspaces, they each get their own State File. However, all Workspaces will still share the same Backend 236 | - State Files for Workspaces are placed in a new subfolder called `env:` and each Workspace gets its own subfolder under that: 237 | - `\env:\workspace1\terraform.tfstate` 238 | - `\env:\workspace2\terraform.tfstate` 239 | - Switching Workspaces is equivalent to changing the path where your State File is stored 240 | - In general, these are confusing. It can be easy to mix up Workspaces and forget which one you are currently working on 241 | - If possible, stay away from using these! 242 | 243 | --- 244 | 245 | # Input Variables (aka Variables) 246 | 247 | ```terraform 248 | # defining a variable 249 | # remember, this is typically done inside a variables.tf file 250 | variable "exampleVarName" { 251 | description = "put a good description here" 252 | type = string | number | bool | list | tuple | set | map | object | any 253 | default = set a default value here 254 | sensitive = true # supported in Terraform 0.14.0 and later 255 | nullable = false # supported in Terraform 1.1.0 and later 256 | 257 | # supported in Terraform 0.13.0 and later 258 | validation { 259 | condition = var.exampleVarName > 10 260 | error_message = "your value needs to be greater than 10" 261 | } 262 | } 263 | 264 | # use a variable by prefixing the variable's name with var. 265 | var.exampleVarName 266 | ``` 267 | - When defining a Variable, all parameters are optional 268 | - If `type` is omitted, then the default is `any` 269 | - If `sensitive` is omitted, then the default is `false` 270 | - If `nullable` is omitted, then the default is `true` 271 | - `type` can be a combination of different options: `list(number)` 272 | - `sensitive = true` prevents showing the value in any `plan` or `apply` commands 273 | - `nullable = false` ensures the value can never be set to `null` 274 | - `validation` blocks 275 | - You can have multiple `validation` blocks pers variable 276 | - `condition` is any condition that resolves to true or false. You can only test against this particular variable and nothing else 277 | - `error_message` is a message that is displayed if the condition is false 278 | 279 | ### How to set values for your Variables: 280 | 1. You can set a `default` value inside the Variable definition 281 | 2. Set an environment variable with the name of `TF_VAR_` and the value that you want to use 282 | - Linux: `export TF_VAR_varName=value` 283 | - PowerShell: `$env:TF_VAR_varName = 'value'` 284 | 3. Use a file with a `.tfvars` extension that lists Variable names and their values 285 | - Option 1: Terraform will automatically load your file if it is placed in your Root Module and it is named `terraform.tfvars` or `*.auto.tfvars` 286 | - Option 2: Pass your tfvars file with the `-var-file` switch: `terraform.exe plan -var-file=somefile.tfvars` 287 | 4. Pass a value with the `-var` switch: `terraform plan -var "name=value"` 288 | 5. If not set by any other method, then Terraform will interactively prompt you for a value at runtime 289 | 290 | Values are loaded in the following order, with the later options taking precedence over earlier ones: 291 | 1. Environment Variables 292 | 2. `terraform.tfvars` files 293 | 3. `*.auto.tfvars` files 294 | 4. `-var` and `-var-file` options, in the order they are given on the commandline 295 | 296 | # Variable Types 297 | 298 | ### Strings 299 | Represented by characters surrounded by double-quotes: `"this is a string"` 300 | 301 | Heredoc / Multi-line Strings 302 | ```terraform 303 | user_data = <<-EOT 304 | indented multi-line 305 | strings will go here 306 | EOT 307 | 308 | user_data = < 439 | # Where `attribute` is specific to the resource that is being fetched by the data source 440 | # In this case it could be id, location, account_kind, etc. 441 | ``` 442 | - Data Sources fetch up-to-date information from your Providers (Azure, AWS, etc.) each time you run Terraform 443 | - Each Provider has their own list of Data Sources that they support 444 | - All Data Sources are Read-Only! 445 | - When defining a Data Source, the argument(s) that you specify can be thought of like search filters to limit what data is returned 446 | - Data Sources support `precondition` and `postcondition` blocks as well (WIP) 447 | 448 | ## Other types of Data Sources 449 |
Click to expand 450 | 451 | ### Remote State Data Source 452 | - Use these when you want to pull info from a foreign Terraform State File 453 | - That foreign Terraform State must have some `outputs` already configured, because that's the information you're pulling from 454 | 455 | ```terraform 456 | # Defining a Remote State Data Source 457 | data "terraform_remote_state" "symbolicName" { 458 | backend = "azurerm" 459 | config = { 460 | key1 = value1 461 | key2 = value2 462 | } 463 | } 464 | 465 | # Using a Remote State Data Source: 466 | `data.teraform_remote_state.symbolicName.outputs.someOutputName` 467 | ``` 468 | - In the `config` block you specify the storage and state file to connect to, as well as how to authenticate to that storage. You can use the same parameters you used for the Remote Backend settings 469 | - Partial config is NOT supported for Remote State Data Sources 470 | 471 | ### External Data Source 472 | - Provides an interface between Terraform and an external program 473 | - Example: 474 | ```terraform 475 | data "external" "symbolicName" { 476 | program = ["python", "${path.module}/example-data-source.py"] 477 | 478 | query = { 479 | id = "abc123" 480 | } 481 | } 482 | ``` 483 | - The `program` must read all of the data passed to it on stdin 484 | - The `program` must parse all of the data that's passed to it as a JSON object 485 | - The JSON object must contain the contents of the `query` 486 | - The `program` must produce a valid JSON object on stdout 487 | - The JSON object must have all of its values as Strings 488 | - On successful completion the `program` must exit with a status of zero 489 | - If there's an error 490 | - The `program` must exit with a non-zero status 491 | - It must print a human-readable error message (ideally a single line) to `stderr` 492 | - `stdout` is ignored for an error 493 | - Terraform will re-run `program` each time that state is refreshed 494 | - `program` is of Type list(string) 495 | - First element is the program to run, and subsequent elements are optional commandline arguments 496 | - Terraform does not execute the program through a shell, so it is not necessary to escape shell metacharacters nor add quotes around arguments containing spaces 497 | - `query` is of Type map(string) 498 | - Optional 499 | - These values are passed to the program as query arguments 500 | - How to reference the data created from the external data source: 501 | - `data.external.symbolicName.result.someAttribute` 502 |
503 | 504 | # Resources 505 | - Resources are the most important element in the Terraform language 506 | - Each `resource` block describes one or more infrastructure objects, such as virtual networks, compute instances, or higher-level components such as DNS records 507 | ```terraform 508 | # defining a resource from the azurerm provider 509 | resource "azurerm_storage_account" "someSymbolicName" { 510 | name = "someName" 511 | location = "someLocation 512 | } 513 | ``` 514 | - In this example, the resource type is `azurerm_storage_account` and if we look at the beginning of the resource type we can tell that it comes from the `azurerm` Provider. 515 | - Each Provider supports its own set of resource types 516 | - Each Provider also defines the acceptable parameters to use for each resource type 517 | - Check your Provider's documentation to learn more about the supported resource types and their supported parameters 518 | - Terraform also supports a number of *Meta-Arguments* that are available to use for each `resource` block, such as `depends_on`, `count`, `for_each`, `provider`, `lifecycle`, and `provisioner` 519 | - This guide will go over the `count`, `for_each`, and `lifecycle` meta-arguments. But, for the others I would suggest reading the [documentation](https://www.terraform.io/language/resources/syntax#meta-arguments) for more information 520 | 521 | # Child Modules (aka Modules) 522 | 523 | - A Module is just a folder full of Configuration Files that is deployed from a Root Module 524 | - This allows you to reuse code 525 | - The Module’s folder should include the usual suspects: `main.tf`, `variables.tf`, `outputs.tf` 526 | - `main.tf` = where you specify the resources that will be created by the module 527 | - `variables.tf` = where you specify the variables that can be passed into the module when you call it 528 | - `outputs.tf` = where you specify the values that will be returned when the module is called 529 | ```terraform 530 | # calling a child Module from your Root Module 531 | module "someSymbolicName" { 532 | source = “path/to/the/module/folder” 533 | 534 | key1 = value1 535 | key2 = value2 536 | } 537 | 538 | # reference an Output value that is generated by a Module 539 | module.someSymbolicName. 540 | ``` 541 | - The keys/value pairs are how you pass Input Variables to the Child Module 542 | - The Child Module defines what it accepts for Input Variables via its own `variables.tf` file in the Module's folder 543 | - Tip: The `source` attribute could point to a git repo if you wanted 544 | - That way you could use git tags to create “versions” of your module, and then you can reference specific versions of each module 545 | - Terraform also supports a number of *Meta-Arguments* that are available to use for each `module` block, such as `depends_on`, `count`, `for_each`, and `providers` 546 | - This guide will go over the `count` and `for_each` meta-arguments. But, for the others I would suggest reading the [documentation](https://www.terraform.io/language/modules/syntax#meta-arguments) for more information 547 | 548 | ### Module Notes 549 | - Some Resource configuration can be provided as inline blocks inside a parent Resource, or it can be provided as totally separate top-level Resources 550 | - Take Subnets for an example. Subnets could be defined as inline blocks on the Virtual Network resource, or Subnets could be defined as their own top-level resources 551 | - When coding your Modules, it is always preferred to use the separate top-level resources whenever possible 552 | - Be careful when using the file() function inside of a Module, as the path to the file can get tricky. Here are some special system variables that can help with this: 553 | - `path.module`: references the folder where the child module is located 554 | - `path.root`: references the folder of the root module 555 | 556 | # Output Variables (aka Outputs) 557 | Outputs are used when you want to output one or more values from one Terraform Root Module, and consume those values in a separate Terraform Root Module 558 | ```terraform 559 | # defining an output 560 | # remember, this is typically done in an outputs.tf file 561 | output "name" { 562 | value = azurerm_storage_account.someSymbolicName.id # can be any terraform expression that you wish to output 563 | description = "put a good description here" 564 | sensitive = true 565 | } 566 | 567 | # using an output 568 | # outputs are displayed in the console after running certain terraform commands 569 | # you can also use a Remote State Data Source (see above) to read Output Variables 570 | ``` 571 | - When defining an Output: 572 | - `value` is the only required parameter 573 | - Setting the `sensitive=true` parameter means that Terraform will not display the output’s value at the end of a `terraform apply` 574 | 575 | --- 576 | 577 | # Syntax Notes 578 | 579 | ### String Interpolation 580 | ```terraform 581 | "some string ${var.name} some more string" 582 | ``` 583 | 584 | ### Comments 585 | ```terraform 586 | # begins a single-line comment, this is the default comment style 587 | 588 | // also begins a single-line comment 589 | 590 | /* 591 | this is a 592 | multi-line comment 593 | */ 594 | ``` 595 | 596 | # Loops 597 | 598 | ### count Meta-Argument 599 | - Every Terraform `resource` or `module` block supports a meta-argument called `count` 600 | - `count` defines how many copies of that item to create 601 | - Example: 602 | ```terraform 603 | resource "azurerm_storage_account" "someSymbolicName" { 604 | count = 5 605 | } 606 | ``` 607 | - `count` must reference hard-coded values, variables, data sources, or lists. It can NOT reference a value that needs to be computed 608 | - When you specify the `count` meta-argument on a resource, you can use a new variable inside that resource: `count.index` 609 | - `count.index` represents the number of the loop that you’re currently on 610 | - For example, say you had a resource with `count = 3` 611 | - The first resource will set `count.index = 0` 612 | - The second resource will set `count.index = 1` 613 | - The third resource will set `count.index = 2` 614 | - You can use this on resource parameters that are required to be unique: `name = "resource-group-${count.index}"` 615 | - You can get creative with this by building a separate List variable that contains the values you would like to use inside of the resource that is using `count` 616 | ```terraform 617 | var.listOfNames = ["will", "dustin", "eleven"] 618 | 619 | resource "azurerm_storage_account" "someSymbolicName" { 620 | count = length(var.listOfNames) 621 | name = var.listOfNames[count.index] 622 | } 623 | ``` 624 | - Important: When you use `count` on a resource, the resource now becomes a List 625 | - To reference a single instance of the resource created by count: `azurerm_storage_account.someSymbolicName[2]` 626 | - To reference all instances of the resource created by count: `azurerm_storage_account.someSymbolicName[*]` (this is called a "splat expression") 627 | 628 | #### Drawback 1: The `count` meta-argument is not supported on inline blocks 629 | - For example, take this resource: 630 | ```terraform 631 | resource "someResource" "someName" { 632 | key1 = value1 633 | key2 = value2 634 | 635 | inline-block { 636 | keyA = valueA 637 | keyB = valueB 638 | } 639 | } 640 | ``` 641 | - If you needed to create multiple inline-blocks, then you may be tempted to just put the `count` meta-argument on the inline-block. However, that is NOT supported 642 | 643 | #### Drawback 2: Deleting a resource from the middle of a List is tricky 644 | - For example, say you used `count = 4` to create some users: 645 | - `user[0] = arnold` 646 | - `user[1] = sylvester` 647 | - `user[2] = jean-claude` 648 | - `user[3] = chuck` 649 | - Now, say you deleted the middle resource `sylvester`. Every resource in the list after that will shift backwards in terms of index count, so you will be left with: 650 | - `user[0] = arnold` 651 | - `user[1] = jean-claude` 652 | - `user[2] = chuck` 653 | - This is a problem because terraform will need to delete the original `jean-claude[2]` and then create a new `jean-claude[1]`. It will also have to delete the original `chuck[3]` and then create a new `chuck[2]` 654 | - **If you remove an item from the middle of the List, Terraform will delete every resource after that item, and then it will recreate those resources again from scratch with new index values.** 655 | 656 | ### for_each Meta-Argument 657 | - Every Terraform `resource` or `module` block supports a meta-argument called `for_each` 658 | ```terraform 659 | resource "azurerm_storage_account" "someSymbolicName" { 660 | for_each = var.Set(string) or var.Map 661 | } 662 | ``` 663 | - So, if your var.Set(string) or var.Map has 5 entries, then you'll get 5 different copies of that Resource 664 | - List variables are NOT supported in Resource Block `for_each`. But, you can convert a List variable to a Set variable: `for_each = toset(var.List)` 665 | - `for_each` must reference hardcoded values, variables, data sources, or lists. It can NOT reference a value that needs to be computed 666 | - When you specify the `for_each` meta-argument on a resource, you can use new variables inside that resource: `each.key` and `each.value` 667 | - For a Set variable: 668 | - `each.key` and `each.value` are both set to the current item in the Set 669 | - Typically, you would just use `each.value` 670 | - For a Map variable: 671 | - `each.key` = the key of the current item in the Map 672 | - `each.value` = the value of the current item in the Map 673 | - Important: When you use `for_each` on a resource, the resource now becomes a Map 674 | - To reference a single instance of the resource created by for_each: `azurerm_storage.someName[key]` 675 | 676 | #### Benefit 1: Deleting from the middle is no problem 677 | - Since the resource is now considered a Map, deleting from the middle will no longer affect items further down the chain 678 | 679 | #### Benefit 2: for_each is supported on inline blocks, by using a dynamic block 680 | ```terraform 681 | resource "someResource" "someName" { 682 | key = value 683 | 684 | dynamic "" { 685 | for_each = any Collection var (list, set, map) or Structural var (tuple, object) 686 | 687 | content { 688 | key1 = .key 689 | key2 = .value 690 | } 691 | } 692 | } 693 | ``` 694 | - So, if your Collection/Structural var has 5 entries, then you'll get 5 different copies of that Inline Block 695 | - `dynamic` block `for_each` supports many types of variables, specifically Lists, Sets, Maps, Tuples, and Objects 696 | - When you specify the `for_each` parameter on a `dynamic` block, you can use new variables inside that Inline Block: `.key` and `.value` 697 | - For a Set variable: 698 | - `.key` and `.value` are both set to the current item in the Set 699 | - Typically, you would just use `.value` 700 | - For a List/Tuple variable: 701 | - `.key` = the numeric index of the current item in the List/Tuple 702 | - `.value` = the value of the current item in the List/Tuple 703 | - For a Map/Obect variable: 704 | - `.key` = the key of the current item in the Map/Object 705 | - `.value` = the value of the current item in the Map/Object 706 | 707 | # For Expressions 708 | - `for` expressions take an input of a List, Set, Tuple, Map, or Object 709 | - `for` expressions will output either: 710 | - a Tuple if you use square brackets `[ ]` 711 | - an Object if you use curly brackets `{ }` 712 | 713 | ### [Square Brackets] return a Tuple 714 | 715 | #### Input a List/Set/Tuple, return a Tuple 716 | - `newTuple = [for in var.List : ]` 717 | - `` is the local variable name to assign to each item in the list/set/tuple 718 | - `` is the value to put into the resultant Tuple, an expression that modifies `` in some way 719 | - `` is optional and you could use it to further refine what values go into the resultant Tuple 720 | - `newTuple = [for , in var.List : ]` 721 | - If your input is a List or Tuple, you can also use this format which gives you access to both the index value and the item value at the same time 722 | - Example: 723 | - `newTuple = [for name in var.List : upper(name) if length(name) < 5]` 724 | - This looks at `var.List` and converts each entry to uppercase, returns only the names that are less than 5 characters, and stores the modified entries in `newList` 725 | 726 | #### Input a Map/Object, return a Tuple 727 | - `newTuple = [for , in var.Map : ]` 728 | - The rest is the same as above 729 | - Example: 730 | - `newTuple = [for first, last in var.Map : “${first} ${last}”]` 731 | - This pulls out each key/value pair from `var.map`, combines them into a new string separated by a space, and puts the new string values into `newTuple` 732 | 733 | ### {Curly Brackets} return an Object 734 | 735 | #### Input a List/Set/Tuple, return an Object 736 | - `newObject = {for in var.List : => }` 737 | - `` is the local variable name to assign to each item in the list/set/tuple 738 | - `` and `` is what to put into the resultant Object, they can be expressions that modify `` in some way 739 | - `` is optional and you could use it to further refine what key/value pairs go into the resultant Object 740 | - `newObject = {for , in var.List : => }` 741 | - If your input is a List or Tuple, you can also use this format which gives you access to both the index value and the item value at the same time 742 | 743 | #### Input a Map/Object, return an Object 744 | - `newObject = {for , in var.Map : => }` 745 | - The rest is the same as above 746 | 747 | # Template Directives 748 | (WIP) 749 | 750 | Template Directives are supported on regular Strings and Heredoc/Multi-line Strings. It is recommended to only use them with Heredoc Strings so that you can use multiple lines for better readability 751 | 752 | - This let’s you loop over a List variable or a Map variable 753 | ```terraform 754 | < in } 756 | do something to 757 | %{ endfor } 758 | EOT 759 | ``` 760 | - Strip Markers ( ~ ) allow you strip out unwanted spaces and newlines 761 | ```terraform 762 | < 5 818 | # an error message to show if the condition is false 819 | error_message = "Something is wrong, zones must be greater than 5" 820 | } 821 | } 822 | } 823 | ``` 824 | - `create_before_destroy` 825 | - By default, when terraform must replace a resource, it will first delete the old/existing one, and then it will create the new one after that 826 | - If your old/existing resource is being referenced by other resources, then terraform will not be able to delete it 827 | - The `create_before_destroy` option flip-flops this, so terraform will first create the new resource, update any references that are needed, and then delete the old/existing resource 828 | - `prevent_destroy` 829 | - The `prevent_destroy` option will cause Terraform to exit on any attempt to delete that resource 830 | - `ignore_changes` 831 | - This is a list of resource attributes that you want Terraform to ignore. If the value of that attribute differs in real life vs. the Terraform code, then Terraform will just ignore it and not try to make any changes 832 | 833 | # terraform CLI Commands 834 | (WIP) 835 | - `terraform apply` 836 | - work in progress 837 | - `terraform console` 838 | - Interactive, read-only console to try out built-in functions, query the state of your infrastructure, etc. 839 | - `terraform destroy` 840 | - Deletes all resources 841 | - There is no "undo" so be very careful! 842 | - `terraform fmt` 843 | - work in progress 844 | - `terraform graph` 845 | - Shows you the dependency graph for the resources 846 | - It outputs into a graph description language called DOT 847 | - You can use tools like Graphviz or GraphvizOnline to convert into an image 848 | - `terraform import` 849 | - work in progress 850 | - `terraform init` 851 | - Downloads any Providers that are found in your code, and puts them here: `\.terraform\` 852 | - You must run `init` each time you change settings for your Remote Backend 853 | - You must run `init` each time you reference a new Module, or change Module settings 854 | - `terraform output` 855 | - Lists all of the Output Variables 856 | - List a specific Output Variable only: `terraform output ` 857 | - Tip: this is great for scripts where you may need to grab an output variable from terraform and use it somewhere else. 858 | - `terraform plan` 859 | - work in progress 860 | - `terraform state` 861 | - work in progress 862 | - `terraform workspace` 863 | - To work with terraform workspaces 864 | 865 | # .gitignore File 866 | (WIP) 867 | - `.terraform` 868 | - Terraform’s scratch directory, is created inside each config folder where you run `terraform init` and includes the downloaded providers. 869 | - `*.tfstate` 870 | - Local state files, never check these into version control as they contain secrets in clear text 871 | - `*.tfstate.backup` 872 | - Backups of local state files 873 | - `backend.hcl` 874 | - The standard filename when you use partial configuration for Remote Backend. 875 | - You only need to ignore this if you're storing **sensitive** keys/values in this file. 876 | 877 | --- 878 | 879 | # References 880 | - Book - [Terraform Up and Running](https://www.terraformupandrunning.com/) 881 | - HashiCorp - [Terraform Settings](https://developer.hashicorp.com/terraform/language/settings) 882 | - HashiCorp - [Backend Configuration](https://developer.hashicorp.com/terraform/language/settings/backends/configuration) 883 | - HashiCorp - [Provider Requirements](https://developer.hashicorp.com/terraform/language/providers/requirements) 884 | - HashiCorp - [Provider Configuration](https://developer.hashicorp.com/terraform/language/providers/configuration) 885 | - HashiCorp - [Providers within Modules](https://developer.hashicorp.com/terraform/language/modules/develop/providers) 886 | - HashiCorp - [Version Constraints](https://developer.hashicorp.com/terraform/language/expressions/version-constraints) 887 | - HashiCorp - [Input Variables](https://developer.hashicorp.com/terraform/language/values/variables) 888 | - HashiCorp - [Types and Values](https://developer.hashicorp.com/terraform/language/expressions/types) 889 | - HashiCorp - [Type Constraints](https://developer.hashicorp.com/terraform/language/expressions/type-constraints) 890 | - HashiCorp - [Local Values](https://developer.hashicorp.com/terraform/language/values/locals) 891 | - HashiCorp - [Modules](https://developer.hashicorp.com/terraform/language/modules) 892 | - HashiCorp - [Module Blocks](https://developer.hashicorp.com/terraform/language/modules/syntax) 893 | - HashiCorp - [Module Sources](https://developer.hashicorp.com/terraform/language/modules/sources) 894 | - HashiCorp - [Output Values](https://developer.hashicorp.com/terraform/language/values/outputs) 895 | -------------------------------------------------------------------------------- /azurerm_example_main.tf: -------------------------------------------------------------------------------- 1 | terraform { 2 | 3 | # Pins the version of Terraform to a specific version 4 | # If this block is in a Child Module, then use a 'minimum' version only 5 | required_version = "=1.2.0" 6 | 7 | # Pins the version of your providers to a specific version 8 | # You should specify all providers used by the Root Module, as well as all providers used by any Child Modules 9 | # If this block is in a Child Module, then use 'minimum' versions only 10 | required_providers { 11 | azurerm = { 12 | source = "hashicorp/azurerm" 13 | version = "=3.7.0" 14 | configuration_aliases = [ azurerm.second ] 15 | } 16 | azuread = { 17 | source = "hashicorp/azuread" 18 | version = "=2.22.0" 19 | } 20 | kubernetes = { 21 | source = "hashicorp/kubernetes" 22 | version = "=2.11.0" 23 | } 24 | helm = { 25 | source = "hashicorp/helm" 26 | version = "=2.5.1" 27 | } 28 | } 29 | 30 | # Backend values must be hard-coded, they can not reference Terraform variables, locals, or data sources 31 | # You can only have one backend block per Root Module 32 | backend "azurerm" { 33 | # Example - Service Principal and Secret 34 | # tenant_id = "value" # think about extracting this from code and using the env var: ARM_TENANT_ID 35 | # client_id = "value" # think about extracting this from code and using the env var: ARM_CLIENT_ID 36 | # client_secret = "value" # think about extracting this from code and using the env var: ARM_CLIENT_SECRET 37 | # subscription_id = "value" # think about extracting this from code and using the env var: ARM_SUBSCRIPTION_ID 38 | resource_group_name = "value" # think about extracting this from code and using Partial Configuration, see below 39 | storage_account_name = "value" # think about extracting this from code and using Partial Configuration, see below 40 | container_name = "value" # think about extracting this from code and using Partial Configuration, see below 41 | key = "value" # think about extracting this from code and using Partial Configuration, see below 42 | } 43 | 44 | # Partial Configuration Option 1. Specify backend settings in an external file 45 | # Still include an empty backend block: backend "azurerm" {} 46 | # terraform init -backend-config=path/to/backend.hcl 47 | # The contents of backend.hcl are just key/value pairs only 48 | 49 | # Partial Configuration Option 2. Specify backend settings on the command-line 50 | # Still include an empty backend block: backend "azurerm" {} 51 | # terraform init -backend-config="resource_group_name=value" -backend-config="storage_account_name=value" 52 | 53 | # Note: Command-line options take priority over the options defined in the terraform backend block 54 | # Note: Command-line options are processed in order, so the last option on the command-line wins 55 | } 56 | 57 | # Provider configuration blocks belong in the Root Module only, and do not belong in Child Modules 58 | provider "azurerm" { 59 | # Example - Service Principal with Secret 60 | # tenant_id = "value" # think about extracting this from code and using the env var: ARM_TENANT_ID 61 | # client_id = "value" # think about extracting this from code and using the env var: ARM_CLIENT_ID 62 | # client_secret = "value" # think about extracting this from code and using the env var: ARM_CLIENT_SECRET 63 | # subscription_id = "value" # think about extracting this from code and using the env var: ARM_SUBSCRIPTION_ID 64 | 65 | features {} # the features block is always required, even if its empty 66 | } 67 | 68 | provider "azurerm" { 69 | alias = "second" 70 | 71 | features {} 72 | } 73 | --------------------------------------------------------------------------------