Demo HCL Basics

In this hands-on lesson, you’ll explore HashiCorp Configuration Language (HCL) fundamentals using OpenTofu. You’ll identify resource types and names, initialize your working directory, and apply changes to a local file resource.

Q1: Identify the HCL File Extension

Navigate to your HCL project directory and list its contents:

cd ~/opentofu-projects/HCL/
ls
# → main.tf

Alternatively, open the folder in VS Code and observe that the filename is main.tf.
Answer: .tf

Q2: Determine the Resource Type

Inspect the resource block in main.tf:

resource "local_file" "games" {
  file    = "/root/favorite-games"
  content = "FIFA 21"
}

Answer: local_file

Q3: Find the Resource Name

Within the same block, the second quoted identifier denotes the resource name:

resource "local_file" "games" { … }

Answer: games

Q4: Identify the Provider Name

The provider is indicated by the prefix of the resource type:

resource "local_file" "games" { … }

Here, local is the provider.
Answer: local

Q5: Valid vs. Invalid Arguments

The local_file resource supports only filename and content. It does not accept resource_type.

Answer: resource_type = "local_file"

Q6: Why tofu plan Fails Initially

Running:

tofu plan

Produces:

Error: Inconsistent dependency lock file
… no version is selected

The directory must be initialized first.

Initialize the Working Directory

tofu init

You should see:

OpenTofu has been successfully initialized!
…

Q7: Locate the Provider Plugin Version

After initialization, OpenTofu downloads provider plugins. You can confirm the version (2.5.1) from the output or by inspecting .terraform:

Answer: 2.5.1

Q8: Re-run tofu plan with Incorrect Arguments

tofu plan

Results in:

Error: Missing required argument
  on main.tf line 1, in resource "local_file" "games":
   1: resource "local_file" "games" {
The argument "filename" is required, but no definition was found.

Error: Unsupported argument
  on main.tf line 2, in resource "local_file" "games":
   2:   file = "/root/favorite-games"
An argument named "file" is not expected here.

You used file instead of filename and omitted filename.

Q9: Identify the Unsupported Argument

Referring to the Local Provider Documentation, file is not supported.
Answer: file

Q10: Correct the Configuration and Apply

Update main.tf:

resource "local_file" "games" {
  filename = "/root/favorite-games"
  content  = "FIFA 21"
}

Run:

tofu plan
tofu apply
# → Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Q11: Switch to a Sensitive File Resource

To mask content in plans, use local_sensitive_file:

resource "local_sensitive_file" "games" {
  filename = "/root/favorite-games"
  content  = "FIFA 21"
}

Attempting to add an unsupported sensitive_content argument will fail:

tofu plan

Error: Unsupported argument
  on main.tf line 4, in resource "local_sensitive_file" "games":
   4:   sensitive_content = "FIFA 21"

Remove sensitive_content; it’s not supported.

Q12: Apply the Sensitive File Resource

With main.tf updated:

resource "local_sensitive_file" "games" {
  filename = "/root/favorite-games"
  content  = "FIFA 21"
}

Run:

tofu plan
tofu apply
# → Apply complete! Resources: 1 added, 0 changed, 1 destroyed.

Plans will now hide the file’s content.

Q13: Destroy the Resource

tofu destroy

Plan: 0 to add, 0 to change, 1 to destroy.
Enter a value: yes

Destroy complete! Resources: 1 destroyed.

Congratulations—you’ve completed the lab! 🎉

Links and References

• OpenTofu Documentation
• Local Provider (OpenTofu)
• HCL Language Overview