day38.md

On the thirty eighth day, I learned the following things about Terraform.

Map Variable

• Create a directory by the name of map-variable and get inside it by typing cd map-variable.

• After creating a directory, make a file in it by the name of variable.tf and write the following data inside it.

  variable "userage" {
    type = map
    default = {
      bilal = 25
      ali = 20
    }
  }
  
  output "userage" {
    value = "my name is bilal and my age is ${lookup(var.userage, "bilal")}"
  }
  

• First a variable is declared by the name of userage and inside this variable, there is a type map and values are set to default. The default ages are of bilal and ali.

• After declaring the variables, let's print the output to show the age of a particular key using the lookup function.

Use map variable Dynamically

• Instead of changing the key like bilal or ali every time in a file, how to dynamically use the map variables.

• Create another variable like this and write the following data into it.

  variable "username" {
    type = string
  }
  

• After the variable is created, make some changes in the output like this:

  output "userage" {
      value = "my name is ${var.username} and my age is ${lookup(var.userage, "${var.username}")}"
  }
  

• Now if you write terraform plan, it will ask you for a key to enter. Once you enter a key, it will show you the age according to that key.

• You can also write a key in the terminal like terraform plan -var "username=bilal" and it will show you the value according to it.

TFVARS files in Terraform

• You may face a problem that every time you want a person's data, the command line will ask you everytime to enter the key so that it brings you the value.

• You can automate this process by making a file and write the age and username there.

• To make this happen, first make a directory by the name of tf-var and get into it by using the cd command.

• After that, make a file by the name of first.tf and write the following data into it.

  variable "username" {
    type = string
  }
  
  variable "age" {
    type = number
  }
  
  output printname {
    value = "Hello, ${var.username}, your age is ${var.age}"
  }
  

• Once the data is saved in a file, make another file by the name of terraform.tfvars. Inside this file, write the following data so that it never ask you again.

  age=25
  username="Bilal Khan"
  

• After saving the data in both of the files, if you write terraform plan, it will give you the result without asking you the username and age.

TFVARS File With Different Name.

• If you want to change the name of tfvars file into something else according to your need, you can do this.

• First of all copy the data of tf-var directory into a new directory using the command cp -rvf tf-var tf-var-custom. Get into the newly created directory by writing cd tf-var-custom.

• After that, make a tfvar file by any name that you want like development, production, etc and write the following data into it.

  age=20
  username="Ali Ahmed"
  

• After that, write terraform plan -var-file=filename.tfvars, it will show you the result of that particular file.

• You can find more about this command and other commands by writing terraform plan --help | less.

Read Environment Variable in Terraform Configurations

• If you want to declare the variable in your terminal and then use it in the terraform then you can also do it.

• Create a directory by the name of env-variable and get inside it by typing cd env-variable.

• After creating a directory, make a file in it by the name of first.tf and write the following data.

  variable "username" {
          type = string
  }
  
  output printname {
          value = "Hello, ${var.username}"
  }
  

• Once the file is saved, write terraform plan to get the result. You will see that it will ask you for the value to enter and then it will give you the result.

• To avoid this, you have to first declare an environment variable and then if you run the terraform plan command again, it won't ask you for the value to enter. Instead it will fetch the value from the environment variable.

• First of all, type echo $username. It will show you nothing because an environment variable is not declared yet.

• To declare an environment variable, type export username=Umar and then if you type echo $username again, it will show you result.

• After that, type terraform plan command. You will see that again it is asking you for the value to enter.

• The problem is not in the environment variable. The problem was that the terraform wants the specific name environment variable to be declared.

• You need to declare an environment variable by the name of TF_VAR_username and then it will accept it.

• First export it by writing export TF_VAR_username=Umar and then if you write terraform plan it won't ask you for the value to enter.

Explaining it in a video

Here you can get an explanation in a video. 38/60 Day of DevOps Challenge