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Installing Terraform

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Setting up provider

1. Create a directory with any name and cd  to the directory

2. Create a file named providers.tf with the following content. This will enable the OpenStack provider

   providers.tf

   Code Block
   language hcl
   # Define required providers terraform { required_version = ">= 0.14.0" required_providers { openstack = { source = "terraform-provider-openstack/openstack" version = "~> 1.35.0" } } } provider "openstack" {}

   
   

3. Declare the cloud information. It is recommended that you refer to Using the OpenStack Command Line Interface . You can also declare it in the providers.tf  However  however, you will have to declare your login details in plain text which is not secure.

4. Run terraform init

   Code Block

   $ terraform init Initializing the backend... Initializing provider plugins... - Reusing previous version of terraform-provider-openstack/openstack from the dependency lock file - Using previously-installed terraform-provider-openstack/openstack v1.35.0 Terraform has been successfully initialized! You may now begin working with Terraform. Try running "terraform plan" to see any changes that are required for your infrastructure. All Terraform commands should now work. If you ever set or change modules or backend configuration for Terraform, rerun this command to reinitialize your working directory. If you forget, other commands will detect it and remind you to do so if necessary.

   
   

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I have create an example that will create a set of instances with a volume attached to it.

deploy.tf

# create a security group named secgroup_1
resource "openstack_networking_secgroup_v2" "secgroup_1" {
  # you can access the variables using var.<variable-name>
  name        = var.http_sec_group
  description = "My neutron security group"
}

# create a security group rules
resource "openstack_networking_secgroup_rule_v2" "secgroup_rule_1" {
  direction         = "ingress"
  ethertype         = "IPv4"
  protocol          = "tcp"
  port_range_min    = 80
  port_range_max    = 80
  remote_ip_prefix  = "0.0.0.0/0"
  # you can access the output attribute of other resources using ${<provider>.<name>.<attribute>}
  security_group_id = "${openstack_networking_secgroup_v2.secgroup_1.id}"
}

#creating instances
resource "openstack_compute_instance_v2" "Instance" {
  # the count will create a number of duplicates equal to the number
  count = var.instance_num
  name = format("%s-%02d", var.instance_name, count.index+1)
  image_id = var.image_id
  flavor_id = var.flavor_id
  key_pair = var.key_pair_name
  security_groups = var.security_groups
  network {
    name = var.network_name
  }
}

resource "openstack_blockstorage_volume_v2" "Volume" {
  count = var.instance_num
  name        = format("%s-%02d", var.volume_name, count.index+1)
  size        = var.volume_size
}

resource "openstack_compute_volume_attach_v2" "attachments" {
  count       = var.instance_num
  # if there are multiples of same resources the detail are stored in an array 
  instance_id = "${openstack_compute_instance_v2.Instance[count.index].id}"
  volume_id   = "${openstack_blockstorage_volume_v2.Volume[count.index].id}"
}

# this will create a output which you can use
output "instance_ips" {

   value = {
        for instance in openstack_compute_instance_v2.Instance:
 
       instance.name => instance.access_ip_v4
    }
}

variables.tf

# create a SSH key-pair using other method first since terraform is not secure 
variable "key_pair_name" {
 
  description = "key pair name"
 
  default = "tutorial"
}

variable "http_sec_group" {

   description = "custom security group name"
    default = "HTTP-ingress"
}

variable "network_name" {
    description = "The network to be used."
    default  = "Internal"
}

variable "instance_name" {
 
  description = "The Instance Name to be used."
    default  = "tutorial-machine"
}

variable "image_id" {
    #find#find with: openstack image list

    description = "The image ID to be used."
    default  = "622cb70d-c88c-4dc4-99e6-df8b8f9965d7"
}

variable "flavor_id" {
 
  #find with: openstack flavor list
 
  description = "The flavor id to be used."
 
  default  = "026ace2c-5247-4bdc-8929-81d129cc69bf"
}

# You have to put http sec group here as well
variable "security_groups" {
 
  description = "List of security group"
 
  type = list
 
  default = ["default", "HTTP-ingress"]
}

variable "instance_num" {
    description = "The keypair public keynumber of instances to create."
 
  default = 1
}

variable "volume_name" {
 
  description = "name of volume"

   default = "tutorial_volume"
}

variable "volume_size" {
  #volume size in gigabytes
  description = "size of volume"
 
  default = 3
}

To change the variable you can either change the default in variable.tf  or by passing the -var "<variable-name>=<value>"  flag during terraform plan  or terraform apply . 

On thing to note is that you should create ssh keys via the web interface or OpenStack clients and reference it in terraform since terraform will store configuration in plain text which will expose your ssh key. 

To save the plan to a file you can use the -out=<path> flag. This will make sure when you apply the plan, terraform uses the correct plan

After you have edited the files, you can run

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$ terraform plan -var "instance_num=2" -out plan

# Terraform will compare the configuration witht the desired state and produce a action plan

terrafor apply plan to apply the changes

e.g.

$ terraform apply -var "instance_num=2"

##################################################
Same as above Skipped
###################################################
Apply complete! Resources: 8 added, 0 changed, 0 destroyed.

Outputs:

instance_ips = {
  "tutorial-machine-01" = "172.16.100.135"
  "tutorial-machine-02" = "172.16.101.124"
}

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