terraform-provider-linuxbox

Linuxbox terraform provider

Basic building block for Seed DevOps.

This provider allows:

• Executing of commands via SSH as a resource.
• Calculating checksum from list of source paths/files.
• Building Docker containers from Dockerfiles.
• Copying built Docker images to destinations hosts vis SSH.
• Controlling Docker containers on destination hosts via SSH.
• Creating Docker networks on destination hosts via SSH.

Installation

Easiest and most efficient way of installing the provider is to generate the provider shim using generate-terraform-provider-shim:

$ generate-terraform-provider-shim numtide/terraform-provider-linuxbox

Generated provider shims (one per found ARCH of the provider) are a small Bash script and can be easily checked in with the rest of the terraform files.

if a version that satisfies Semver constraints is required, this can be specified at generation time:

$ generate-terraform-provider-shim --version '< 0.2.0, >= 0.1.0' numtide/terraform-provider-linuxbox

Use

Configuring Provider

Provider accepts one optional argument: ssh_session_limit. This is the limits number of sessions that will be open through SSH connection to a host. Current default limit is 5.

Sample provider declaration with setting the ssh_session_limit lower looks like this:

provider "linuxbox" {
  ssh_session_limit = 3
}

SSH Configuration used by every SSH resource.

Every Linuxbox resource that uses SSH will accept following parameters:

• ssh_key: This is the private key used to authenticate user when connecting to the destination host.

• ssh_user: Username used to authenticated when connecting to the destination host. By default, this username is root. If the username is not root, make sure that the user has the right permissions on the destination host to execute required operations.

• host_address: Address (dns name or IP address) of the target host.

Performing setup of a remote machine using SSH.

Philosophy of Linuxbox is similar to the one of Ansible. We don't require any kind of agent or a service to be run on the remote machine apart from SSH. Every step of a machine setup can be represented as a separate Terraform resource. By doing so, we make sure that setup steps are executed only once and in order given by depends_on or other dependency resolving mechanism of Terraform. This enables parallelisation of execution of certain tasks (for example: adding a swap and installing Docker) which this will be automatically handled by Terraform.

Every setup step is defined using linuxbox_run_setup resource.

Since setup is a Terraform resource, user has to provide 3 parts to it:

• List of commands to be executed to perform setup (setup). This performed when terraform apply is executed.
• Command that will tell if the result of the setup is available on the machine (check). that is what terraform plan will query)
• Command that will remove the result of the setup ... for examle, removing the installed package or removing the swap.

only setup is mandatory. If check is omitted, plan will alway report resource being present (can be misleading if in the meantime someone has logged in into the machine and has deleted the installed package).

If delete is omitted, removing/destroying the resource in terrafom won't have any effect on what is installed on the destination machine.

For example, following setup will install docker on the target ubuntu 18.04 machine:

resource "linuxbox_run_setup" "install_docker" {
  host_address = digitalocean_droplet.test.ipv4_address
  ssh_key      = tls_private_key.ssh_key.private_key_pem

  setup = [
    "apt update",
    "apt install -y apt-transport-https ca-certificates curl software-properties-common",
    "curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -",
    "add-apt-repository \"deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable\"",
    "apt update",
    "apt install -y docker-ce",
  ]

  check = "docker -v"

  delete = "apt-get purge -y docker-ce docker-ce-cli"

}