Terraform Commands/Random Features

Question 1

What does the terraform fmt command do

Answer 1

It is used to rewrite Terraform config files to take care of the overall formatting.

Question 2

How does Terraform load config files if there are a number of them in the working directory?

Answer 2

Terraform loads the config files in the same directory in alphabetical order.

Question 3

What file format will Terraform load using alphabetical order?

Answer 3

The files loaeded must end in either .tf or .tf.json to specify the format that is in use.

Question 4

How can you report Terraform bugs?

Answer 4

You can report bugs in the Terraform Core Github or appropriate provider page

Question 5

Whats debugging?

Answer 5

The process of finding the root cause of a specific issue.

Question 6

What’s an important requirement for debugging?

Answer 6

Getting detailed log information.

Depending on the app, the approach to get detailed logs will differ.

Question 7

What flag do you add to Terraform to output log information?

Answer 7

-v

If you need more log info you’d add more v’s.

Ex. -vvvv

Question 8

How to get detailed logs?

Answer 8

You can set the TF_LOG environment variable to any value.

The value for TF_LOG can be set to the values below where TRACE is the most verbose and ERROR is the least verbose.

TRACE
DEBUG
INFO
WARN
ERROR

Question 9

Can you store log from Terraform to a file?

Answer 9

Yes, you can set the TF_LOG_PATH environment variable to force the log to always be appended to a specific file when logging is enabled.

Question 10

How to set the TF_VAR env variable in Windows?

Answer 10

The command,

set TF_LOG=VALUE

where VALUE is the log level (TRACE,DEBUG,etc)

The command

set TF_LOG_PATH=file.txt
saves the information to a text file

Question 11

How to set the TF_VAR env variable in Linux?

Answer 11

export TF_LOG=VALUE

where VALUE is the log level (TRACE,DEBUG,etc)

Question 12

How do you output to terraform?

Answer 12

output “name” {
value = resource
}

Ex:
output “iam_names” {
value = aws_iam_user.lb[*].name
}

Question 13

Whats the purpose of the terraform output command?

Answer 13

It’s used to extract the value of an output variable from the state file.

terraform output variable

Ex: terraform output iam_names

Question 14

What are terraform settings used for?

Answer 14

Terraform settings are used to configure project specific terraform behaviors, such as requiring a minimum terraform version to apply to your configuration.

Terraform settings are gattered in a “terraform block”

Question 15

What is a terraform block used for?

Answer 15

To configure specific figures.

Ex:
terraform {
required_version = “1.8.1”
}

Question 16

How do you specify a specific terraform version in code?

Answer 16

If your coat is compatible with specific version of terraform, you can use the “required_aversion “block to add your constraints.

Ex:
required_version = “1.8.1”

Question 17

What use cases are best in using terraform blocks?

Answer 17

1. Specificying certain provider versions (using required_version command)
2. Specifying provider requirements (using the required_providers block)
3. Backend configuration setttings
4. Experimental features settings

Question 18

Whats the required_providers block used for?

Answer 18

It can be used to specific certain provider requirements.

Ex:
required_providers {
aws = {
version = “5.6.0”
source = “hashicorp/aws”
}
}

Question 19

What is resource targeting in Terraform used for?

Answer 19

If you only want to create a specific resource even though they may be defined in a .tf file it allows to apply changes to a specific subset of resources rather than applying changes to your entire infrastructure through a terraform plan/apply/destroy

The flag tied to this concept is “-target”

Ex: terraform plan -target resource.name
…
terraform plan -target aws_iam_user.dev

Question 20

Whats a great use case of terraform resource targeting?

Answer 20

Occasionally, you may want to apply only part of a plan, such as when terraform state is become out of sync with your resources due to a network failure, a problem with the upstream cloud platform, or a bug and terraform or its providers.

Targeting individual resources can be useful for troubleshooting errors, but it should not be part of your normal workflow

Question 21

What are some solutions to large infrastructure with Terraform?

Answer 21

Using a cloud provider does not mean you have access to a limited resources, there are some limits that apply to all of the services

One thing you have to be careful of when using architecture for the cloud is API throttling, particularly the types of calls in the frequency with which they are called

When allotted rate limit for an API call is exceeded, youll receive an error response and the call with be throttled.

Question 22

What are some workarounds for large-infra and possible issues?

Answer 22

1. Convert a big project into multiple smaller projects and when you run terraform commands.
2. Make use of resource targeting
3. Setting refresh=false

Question 23

Whats the zipmap function in Terraform?

Answer 23

The zip map function constructs a map from a list of keys and a corresponding list of values

Ex
zipmap(keyslist, valueslist)

zipmap([“a”, “b”], [1,2])

Output
“a” = 1
“b” = 2

Question 24

What’s a simple used case for zip map function?

Answer 24

When creating multiple EAM users, you need output, which contains direct mapping of IAM names and ARNs

Question 25

How do you add a comment in Terraform?

Answer 25

1. Put a # before the line for a single-line comment 2. Comment a block out by adding start/end delimiters /* */ 3. Put a // before the line for a single-line comment

Question 26

How does terraform apply a configuration as a default behavior?

Answer 26

1. Create resources that exist in the configuration, but are not associated with a real infrastructure object in the state. 2. Destroy resources that exist in the state, but no longer exist in the configuration. 3. Update in place resources whose arguments have changed. 4. Destroy and re-create resources whose arguments have changed, but which cannot be updated in place due to remote API limitations

Question 27

How do you change the default behavior of terraform for config changes? I.e some modifications happen in real infrastructure object that is not part of terraform, but you want to ignore those changes during terraform apply

Answer 27

With the use of meta- arguments "INSIDE" the resource block, this can be accomplished. The meta argument example below is the "lifecycle" meta-argument. There are many other arguments available. Ex. resource "aws_instance" "myec2" { lifecycle { ignore_changes = [tags] }

Question 28

What arguments are available within the life cycle meta – argument block?

Answer 28

1. Create_before_destroy - new replacement object is created first, and the prior object is destroyed after the replacement is created 2. Prevent_destroy - terraform to reject with an error any plan that would destroy the infrastructure object associated with the resource. 3. Ignore_changes - ignore certain changes to the live resource that does not match the configuration. 4. Replace_triggered_by - replace the resource when any of the referenced items change

Question 29

Create_before_destroy lifecycle meta-argument

Answer 29

By default, when terraform must change a resource argument that cannot be updated in place due to remote API limitations, Teflon will instead destroy the existing object and create a new replacement object with the new configured arguments. I.e creating an EC2 instance and then changing the AMI to a different OS triggers Terraform to destroy existing EC2 instance then create the new one based on the new OS/AMI ID Issue: want new EC2 instance to be running prior to destruction of first instance. Solution: use create_before_destroy argument.

Question 30

What are some challenges of the count meta-argument?

Answer 30

If the order of elements of index is changed, this can impact all of the other resources. If your resources are almost identical, count is appropriate. If distinctive values are needed in the arguments, usage of for_each is recommended.

Question 31

What is a list data type?

Answer 31

Lists are used to store multiple items in a single variable and these items can be duplicated The items that you add are indexed starting with an index of 0.

Question 32

What is a SET data type

Answer 32

Sets can only store unique elements but not duplicates, any duplicates are automatically removed. When you define a SET, you also need to define the type of value expected. ex: type = set(string)

Question 33

Whats some distinction of the SET variable

Answer 33

A set does not store the order of the elements like the list data type that stores them based on an index.

Question 34

How does the for_each argument work?

Answer 34

Allows you to manage multiple resources with different configurations for each resource If a resource block includes a for_each meta argument whose value is a map or a set of strings, terraform creates one instance for each member of that map or set.

Question 35

In block where for_each