terraform-lxd

A Terraform module for Linux Containers (LXD) utilizing terraform-provider-lxd.

Description

The module allows creating and provisioning instance fleets using different mechanisms after implementing a manageable underlying infrastructure.

It is composed of two modules actually:

• lxd-common: creates a storage pool, a volume and an installation image. The module call was appended to provider.tf for the sake of simplicity.
• lxd: runs per instance (or instance group) and adds volumes, prepares the cloud-init image/s, renders the required templates and creates the instances.

Requirements

A host server

A preconfigured host server prepared for LXD. During development I put together an Ansible playbook available from ansible-host-server and tested under CentOS 7.

Terraform

Terraform manual installation is quite straightforward

wget https://releases.hashicorp.com/terraform/1.5.7/terraform_1.5.7_linux_amd64.zip
unzip terraform_1.5.7_linux_amd64.zip
sudo mv terraform /usr/local/bin/terraform

Configuration

main.tf holds the specification for our deployment. The files under examples/ can be renamed and used to that purpose straight away.

Input variables

Name	Type	Description	Default
hostname	string		guest
domain	string	Search domain	local
memory	string	Memory in megabytes	128MB
vcpu	number	Number of virtual cores	1
method	string	Address assign method, eiher static or dhcp	dhcp
address	string	IP address in CIDR notation	""
gateway	string	Default gateway	""
dns_1	string	Primary nameserver	""
dns_2	string	Secondary nameserver	""
deploy_account	string	Deployment account username	deploy
deploy_account_pwd	string	Deployment account password	""
port	number	LXD daemon port	""
trust_pwd	string	LXD daemon trust password	""
host_server	string	Host server IP address	""

Implementing

The infrastructure can be planned, applied and destroyed by means of

terraform init
terraform plan
terraform apply -auto-approve
terraform destroy -auto-approve

During creation Terraform will use cloud-init to create a privileged deployment account inside the instances and provide the SSH key found in keys/id_rsa.pub, so as to prepare the guest systems to be accessed by further provisioning systems.

Examples

Single statically addressed instance

module "guest01" {
  source = "./lxd"
  depends_on = [module.common]
  image_fingerprint = "${module.common.image_fingerprint}"
  hostname = "guest01"
  method = "static"
  address = "10.12.0.111/24"
  gateway = "10.12.0.1"
}

Multiple instances with random hostnames

variable "instances" { default = 3 }

resource "random_string" "hostname" {
  length = 4
  special = false
  upper = false
  count = "${var.instances}"
}

module "guests" {
  source = "./lxd"
  depends_on = [module.common]
  image_fingerprint = "${module.common.image_fingerprint}"
  hostname = "${random_string.hostname[count.index].result}"
  count = "${var.instances}"
}

Which created three instances

[deploy@host ~]$ lxc list
+------+---------+--------------------+------+-----------+-----------+
| NAME |  STATE  |        IPV4        | IPV6 |   TYPE    | SNAPSHOTS |
+------+---------+--------------------+------+-----------+-----------+
| jisf | RUNNING | 10.12.0.234 (eth0) |      | CONTAINER | 0         |
+------+---------+--------------------+------+-----------+-----------+
| wpxk | RUNNING | 10.12.0.233 (eth0) |      | CONTAINER | 0         |
+------+---------+--------------------+------+-----------+-----------+
| xnch | RUNNING | 10.12.0.231 (eth0) |      | CONTAINER | 0         |
+------+---------+--------------------+------+-----------+-----------+

Please, browse the examples/ folder for further scripts.

References

• terraform-lxd/lxd (Terraform Registry)
• Canonical LXD documentation
• cloud-init
• ruanbekker/terraform-lxd-example
• Managing LXC/LXD Linux Containers with Terraform