More tips

Signed-off-by: Marco Emilio "sphakka" Poleggi <marcoep@ieee.org>

SwitchEngines/README.md

@@ -156,7 +156,8 @@ resource "openstack_compute_instance_v2" "app_server" {
 Indeed, all TF files inside a directory constitute a "module". In our case,
 that's the "root" module.
 
-You shall replace all `<...>` tokens with actual values.
+:hammer_and_wrench: **Over to you now.** You shall replace all `<...>`
+tokens with actual values.
 
 :bulb: If you want use explicit provider resource configuration, the values
 shall match those in file `~/.config/openstack/clouds.yaml`.
@@ -536,9 +537,9 @@ Did you try to SSH into the instance you created via TF? It cannot work,
 because we did not instructed TF about networking, login, users, keys or
 anything else.
 
-**This is left to you as an exercise.**
 
-With reference to the official TF documentation for the [OpenStack
+:hammer_and_wrench: **Over to you now.** With reference to the official TF
+documentation for the [OpenStack
 provider](https://registry.terraform.io/providers/terraform-provider-openstack/openstack/latest/docs/),
 you shall:
 
@@ -597,7 +598,7 @@ lcl$ ssh -i keys/tf-cloud-init -o IdentitiesOnly=yes $(terraform output -raw ssh
 
 Now you can provision an instance and have SSH access to it. Let's write a plan variant to provision a cluster of 2 instances.
 
-You shall:
+:hammer_and_wrench: **Over to you now.** You shall:
 
 1. Declare a variable or
    [_local_](https://developer.hashicorp.com/terraform/language/values/locals)
@@ -730,7 +731,7 @@ data "cloudinit_config" "my_config" {
     filename     = "file-1"
     content_type = "text/cloud-config"
     content      = file("file-1.yml")
-	merge_type   = "list(append)+dict(no_replace,recurse_list)"
+    merge_type   = "list(append)+dict(no_replace,recurse_list)"
   }
 
   part {
@@ -748,7 +749,7 @@ data "cloudinit_config" "my_config" {
   * The *merged* result of the whole block is provided by the read-only
     attribute: `data.cloudinit_config.my_config.rendered`.
 
-::hammer_and_wrench:: **Over to you now.** You shall:
+:hammer_and_wrench: **Over to you now.** You shall:
 
 1. Split your cloud-init YAML file above into 2 files:
    - `conf/cloud-init.users.yaml` with basic user-related configuration, and
@@ -774,7 +775,7 @@ before starting this exercise.**
 Now you have all the skills to provision your micro cloud infrastructure based
 on KinD.
 
-You shall:
+:hammer_and_wrench: **Over to you now.** You shall:
 
 1. Modify your `main.tf` to use a more capable flavor instance for your
    `app_server`, like a `m1.medium` or `c1.large`.
@@ -783,7 +784,7 @@ You shall:
      package, install `kubectl` and `kind` via explicit `runcmd` scripts;
    - add any needed extra group for the default user.
 
-Run again terraform apply, wait a couple of minutes to let the installation of
+Run again terraform apply, **wait a couple of minutes** to let the installation of
 all extra packages to complete, then connect to your instance.
 
 Since KinD is not designed for remote use, you'll have to create your cluster
@@ -838,8 +839,8 @@ following:
    provisioners.
 
 
-You shall extend your `main.tf` plan recipe with:
-
+:hammer_and_wrench: **Over to you now.** You shall extend your `main.tf` plan
+recipe with:
 1. At least one `terraform_data` resource declaration that encapsulate all the service
    deployment logic: transferring files and sending commands.
 1. Inside your `terraform_data` declaration:
@@ -877,11 +878,10 @@ resource "terraform_data" "kind_cluster" {
   provisioner "remote-exec" {
     inline = [
 	  "shell command",
-	  ...,
+	  ...
     ]
   }
 }
-
 ```
 
 :bulb: Please mind that:
@@ -890,6 +890,9 @@ resource "terraform_data" "kind_cluster" {
 - For a maximum of flexibility, it is advisable to write 2
 `terraform_data` blocks: one for KinD and another for MetalLB. This way you
 can test the creation of the two resources separately.
+- Since the lines of a `remote-exec` are merged into a script, it is wise to
+  start it with the command `set -o errexit`, so that the whole script exits
+  at the first error.
 
 :warning: You will probably hit some thorny issues: