Sample — Code block conventions¶

Approved convention

This page is the canonical sample for lab code blocks. Terminal chrome (dark panel) versus file chrome (green filename bar) is the site-wide standard. Hard-refresh if styles look stale.

What to look for¶

Convention	How it appears
File to create	Light panel + green filename bar (`title="main.tf"`)
Commands to run	Dark terminal chrome (`title="Terminal"`) — not the same as file blocks
Expected output	`!!! example "Expected output"` admonition
Long files	Optional `linenums="1"` (shown once below)
Always tagged	No bare fences

Hands-on Lab¶

Objective¶

Apply a tiny Docker Terraform stack and prove the container with CLI evidence — using the new code-block conventions.

Prerequisites¶

Terraform CLI ≥ 1.5
Docker Engine running

Lab environment¶

Terminal

mkdir -p ~/rebash-labs/sample-code-blocks && cd ~/rebash-labs/sample-code-blocks

Runtime: local Docker Engine + kreuzwerker/docker provider.

Real-world scenario¶

A platform engineer is onboarding a disposable lab pattern: create config as files (not heredocs), run a short terminal session, and prove success with a clear expected-output panel — the same shape learners should see in production interview prep labs.

Step-by-step tasks¶

Task 1 – Author provider and network¶

Create the provider pin and a bridge network.

versions.tf

terraform {
  required_version = ">= 1.5.0"
  required_providers {
    docker = {
      source  = "kreuzwerker/docker"
      version = "~> 3.0"
    }
  }
}

provider "docker" {}

main.tf

resource "docker_network" "lab" {
  name   = "rebash-sample-net"
  driver = "bridge"
}

resource "docker_image" "nginx" {
  name         = "nginx:1.25-alpine"
  keep_locally = true
}

resource "docker_container" "web" {
  name  = "rebash-sample-web"
  image = docker_image.nginx.image_id

  networks_advanced {
    name = docker_network.lab.name
  }

  ports {
    internal = 80
    external = 18080
  }

  labels {
    label = "rebash.sample"
    value = "code-blocks"
  }
}

output "container_name" {
  value = docker_container.web.name
}

Initialise and apply:

Terminal

cd ~/rebash-labs/sample-code-blocks
terraform init
terraform apply -auto-approve
docker ps --filter name=rebash-sample-web --format 'table {{.Names}}\t{{.Status}}\t{{.Ports}}' | tee docker-ps.txt
curl -sS -o /dev/null -w '%{http_code}\n' http://127.0.0.1:18080/ | tee http-code.txt
grep -q rebash-sample-web docker-ps.txt
grep -q 200 http-code.txt

Expected output

terraform apply creates the network and rebash-sample-web
docker-ps.txt lists rebash-sample-web as Up
http-code.txt contains 200

Task 2 – Prove labels (interview-style evidence)¶

Inspect the container label set by Terraform:

Terminal

cd ~/rebash-labs/sample-code-blocks
docker inspect -f '{{index .Config.Labels "rebash.sample"}}' rebash-sample-web | tee label.txt
grep -q code-blocks label.txt
terraform output -raw container_name | tee output-name.txt
grep -q rebash-sample-web output-name.txt

Expected output

label.txt is code-blocks
output-name.txt is rebash-sample-web

Task 3 – Optional: long file with line numbers¶

Use line numbers only when a file is long enough that reviewers discuss specific lines (example shape — do not require this file for the lab):

compose.example.yaml
# Example only — illustrates linenums on longer artefacts
services:
  web:
    image: nginx:1.25-alpine
    ports:
      - "18080:80"
    labels:
      rebash.sample: code-blocks
  # …
  # (truncated in real labs; linenums help when walking line 12 in review)

Validation steps¶

docker ps shows rebash-sample-web
HTTP check returns 200
Label and Terraform output match
Filename titles appear above file fences; Terminal title appears on command fences
Expected output uses green/example admonitions, not plain bold text alone

Common errors and fixes¶

Error	Cause	Fix
Cannot connect to Docker	Daemon not running	Start Docker Desktop / `dockerd`
Port 18080 in use	Another local service	Change `external` port in `main.tf` and re-apply
Provider not found	Skipped init	Run `terraform init` again

Challenge exercise¶

Add an output network_name and prove it with terraform output plus docker network ls.

Learning outcomes¶

File fences carry title="filename" so copy targets are obvious
Terminal fences stay short and labelled
Success criteria sit in an Expected output admonition
Lab still does real apply / proof / cleanup

Cleanup¶

Terminal

cd ~/rebash-labs/sample-code-blocks
terraform destroy -auto-approve
rm -f docker-ps.txt http-code.txt label.txt output-name.txt

Expected output

Terraform reports destroy complete; docker ps -a --filter name=rebash-sample-web is empty.

Authoring cheat sheet (for reviewers)¶

Create `main.tf`:

```hcl title="main.tf"
resource "docker_network" "lab" {
  name = "rebash-sample-net"
}
```

``` {.bash .ra-terminal title="Terminal"}
terraform apply -auto-approve
```

!!! example "Expected output"
    Apply succeeds; resource exists.

Do not use **Expected output:** as the only success signal once this convention is approved.
Do not put multi-line files inside cat <<EOF heredocs.