Use the Terraform CLI (outside of core workflow)

Question 1

What is command fmt?

Answer 1

The terraform fmt command is used to rewrite Terraform configuration
files to a canonical format and style. This command applies a subset
of the Terraform language style conventions, along with other minor
adjustments for readability.

Question 2

What is the recommended approach after upgrading terraform?

Answer 2

The canonical format may change in minor ways between Terraform
versions, so after upgrading Terraform we recommend to proactively
run terraform fmt on your modules along with any other changes you
are making to adopt the new version.

Question 3

What is the command usage?

Answer 3

terraform fmt [options] [DIR]

Question 4

By default,
fmt
scans the current directory for configuration files. Is this true?

Answer 4

True
By default, fmt scans the current directory for configuration files.
If the dir argument is provided then it will scan that given
directory instead. If dir is a single dash (-) then fmt will read
from standard input (STDIN).

Question 5

You are formatting the configuration files and what is the flag you should use to
see the differences?

Answer 5

terraform fmt -diff

Question 6

You are formatting the configuration files and what is the flag you should use to
process the subdirectories as well?

Answer 6

terraform fmt -recursive

Question 7

You are formatting configuration files in a lot of directories and you don’t want to
see the list of file changes. What is the flag that you should use?

Answer 7

terraform fmt -list=false

Question 8

What is the command taint?

Answer 8

The terraform taint command manually marks a Terraform-managed
resource as tainted, forcing it to be destroyed and recreated on the
next apply.

This command will not modify infrastructure, but does modify the
state file in order to mark a resource as tainted. Once a resource is
marked as tainted, the next plan will show that the resource will be
destroyed and recreated and the next apply will implement this
change.

Question 9

What is the command taint usage?

Answer 9

terraform taint [options] address
The address argument is the address of the resource to mark as
tainted. The address is in the resource address syntax syntax

Question 10

When you are tainting a resource terraform reads the default state file
terraform.tfstate. What is the flag you should use to read from a different path?

Answer 10

terraform taint -state=path

Question 11

Give an example of tainting a single resource?

Answer 11

terraform taint aws_security_group.allow_all
The resource aws_security_group.allow_all in the module root has been
marked as tainted.

Question 12

Give an example of tainting a resource within a module?

Answer 12

terraform taint “module.couchbase.aws_instance.cb_node[9]”
Resource instance module.couchbase.aws_instance.cb_node[9] has been
marked as tainted.

Question 13

What is the command import?

Answer 13

The terraform import command is used to import existing resources
into Terraform.
Terraform is able to import existing infrastructure. This allows you
take resources you’ve created by some other means and bring it under
Terraform management.
This is a great way to slowly transition infrastructure to Terraform,
or to be able to be confident that you can use Terraform in the
future if it potentially doesn’t support every feature you need
today.

Question 14

What is the command import usage?

Answer 14

terraform import [options] ADDRESS ID

Question 15

What is the default workspace name?

Answer 15

default

Question 16

What are workspaces?

Answer 16

Each Terraform configuration has an associated backend that defines
how operations are executed and where persistent data such as the
Terraform state are stored.
The persistent data stored in the backend belongs to a workspace.
Initially the backend has only one workspace, called “default”, and
thus there is only one Terraform state associated with that
configuration.
Certain backends support multiple named workspaces, allowing multiple
states to be associated with a single configuration.

Question 17

What is the command to list the workspaces?

Answer 17

terraform workspace list

Question 18

What is the command to create a new workspace?

Answer 18

terraform workspace new

Question 19

What is the command to show the current workspace?

Answer 19

terraform workspace show

Question 20

What is the command to switch the workspace?

Answer 20

terraform workspace select

Question 21

What is the command to delete the workspace?

Answer 21

terraform workspace delete

Question 22

Can you delete the default workspace?

Answer 22

No. You can’t ever delete default workspace

Question 23

You are working on the different workspaces and you want to use a different
number of instances based on the workspace. How do you achieve that?

Answer 23

resource “aws_instance” “example” {
count = “${terraform.workspace == “default” ? 5 : 1}”
}

Question 24

You are working on the different workspaces and you want to use tags based on
the workspace. How do you achieve that?

Answer 24

resource "aws_instance" "example" {
tags = {
Name = "web - ${terraform.workspace}"
}
}

Question 25

You want to create a parallel, distinct copy of a set of infrastructure in order to
test a set of changes before modifying the main production infrastructure. How do
you achieve that?

Answer 25

Workspaces

Question 26

What is the command state?

Answer 26

The terraform state command is used for advanced state management. As
your Terraform usage becomes more advanced, there are some cases
where you may need to modify the Terraform state. Rather than modify
the state directly, the terraform state commands can be used in many
cases instead.
https://www.terraform.io/docs/commands/state/index.html

Question 27

What is the command usage?

Answer 27

terraform state [options] [args]

Question 28

You are working on terraform files and you want to list all the resources. What is
the command you should use?

Answer 28

terraform state list

Question 29

How do you list the resources for the given name?

Answer 29

terraform state list

Question 30

What is the command that shows the attributes of a single resource in the state
file?

Answer 30

terraform state show ‘resource name’

Question 31

How do you do debugging terraform?

Answer 31

Terraform has detailed logs which can be enabled by setting the
TF_LOG environment variable to any value.
This will cause detailed logs to appear on stderr.
You can set TF_LOG to one of the log levels TRACE, DEBUG, INFO, WARN
or ERROR to change the verbosity of the logs. TRACE is the most
verbose and it is the default if TF_LOG is set to something other
than a log level name.
To persist logged output you can set TF_LOG_PATH in order to force
the log to always be appended to a specific file when logging is
enabled.
Note that even when TF_LOG_PATH is set, TF_LOG must be set in order
for any logging to be enabled.
https://www.terraform.io/docs/internals/debugging.html

Question 32

If terraform crashes where should you see the logs?

Answer 32

crash.log

If Terraform ever crashes (a “panic” in the Go runtime), it saves a
log file with the debug logs from the session as well as the panic
message and backtrace to crash.log.
https://www.terraform.io/docs/internals/debugging.html

Question 33

What is the first thing you should do when the terraform crashes?

Answer 33

panic message
The most interesting part of a crash log is the panic message itself
and the backtrace immediately following. So the first thing to do is
to search the file for panic
https://www.terraform.io/docs/internals/debugging.html

Question 34

You are building infrastructure for different environments for example test and
dev. How do you maintain separate states?

Answer 34

There are two primary methods to separate state between environments:
directories
workspaces

Question 35

What is the difference between directory-separated and workspace-separated
environments?

Answer 35

Directory separated environments rely on duplicate Terraform code,
which may be useful if your deployments need differ, for example to
test infrastructure changes in development. But they can run the risk
of creating drift between the environments over time.
Workspace-separated environments use the same Terraform code but have
different state files, which is useful if you want your environments
to stay as similar to each other as possible, for example if you are
providing development infrastructure to a team that wants to simulate
running in production.

Question 36

What is the command to pull the remote state?

Answer 36

terraform state pull
This command will download the state from its current location and
output the raw format to stdout.
https://www.terraform.io/docs/commands/state/pull.html

Question 37

What is the command is used manually to upload a local state file to a remote
state

Answer 37

terraform state push
The terraform state push command is used to manually upload a local
state file to remote state. This command also works with local state.
https://www.terraform.io/docs/commands/state/push.html

Question 38

The command terraform taint modifies the state file and doesn’t modify the
infrastructure. Is this true?

Answer 38

True
This command will not modify infrastructure, but does modify the state file in order to mark a resource as tainted. Once a resource is marked as tainted, the next plan will show that the resource will be destroyed and recreated and the next apply will implement this
change.

Question 39

Your team has decided to use terraform in your company and you have existing
infrastructure. How do you migrate your existing resources to terraform and start
using it?

Answer 39

You should use terraform import and modify the infrastrcuture in the
terraform files and do the terraform workflow (init, plan, apply)

Question 40

When you are working with the workspaces how do you access the current
workspace in the configuration files?

Answer 40

${terraform.workspace}

Question 41

When you are using workspaces where does the Terraform save the state file for
the local state?

Answer 41

terraform.tfstate.d
For local state, Terraform stores the workspace states in a directory
called terraform.tfstate.d.

Question 42

When you are using workspaces where does the Terraform save the state file for
the remote state?

Answer 42

For remote state, the workspaces are stored directly in the

configured backend.

Question 43

How do you remove items from the Terraform state?

Answer 43

terraform state rm ‘packet_device.worker’
The terraform state rm command is used to remove items from the
Terraform state. This command can remove single resources, single
instances of a resource, entire modules, and more.
https://www.terraform.io/docs/commands/state/rm.html

Question 44

How do you move the state from one source to another?

Answer 44

terraform state mv ‘module.app’ ‘module.parent.module.app’The terraform state mv command is used to move items in a Terraform
state. This command can move single resources, single instances of a
resource, entire modules, and more. This command can also move items
to a completely different state file, enabling efficient refactoring.
https://www.terraform.io/docs/commands/state/mv.html

Question 45

How do you rename a resource in the terraform state file?

Answer 45

terraform state mv ‘packet_device.worker’ ‘packet_device.helper’
The above example renames the packet_device resource named worker to
helper: