Added example and KB to create a free ampere instance in Oracle Cloud

terraform/oracle cloud free tier ampere instance/README.md

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+# Oracle free tier Ampere VM
+
+Simple example to create an Ampere VM instance in Oracle Cloud's free tier.
+
+1. [Requirements](#requirements)
+2. [Further readings](#further-readings)
+3. [Sources](#sources)
+
+## Requirements
+
+1. VCN
+1. Public Subnet
+
+For a Subnet to be considered Public, it needs to have associated a Route Table with a default route pointing to an Internet Gateway.
+
+The default route table created using Terraform does not contain this route, nor it is possible to create the single route in it at the time of writing.<br />
+A solution to this is to create a new Route Table **with** the default route above and attach it to the Subnet. See the code for details.
+
+![requirements]
+
+## Further readings
+
+## Sources
+
+- [Ridiculously powerful free server in the cloud]
+- [Always free resources] in Oracle Cloud
+- [Oracle Cloud Infrastructure Provider documentation]
+- [oracle-terraform-modules/terraform-oci-compute-instance]
+
+<!-- internal references -->
+[requirements]: design/requirements.png
+
+<!-- external references -->
+[always free resources]: https://docs.oracle.com/en-us/iaas/Content/FreeTier/freetier_topic-Always_Free_Resources.htm
+[oracle cloud infrastructure provider documentation]: https://registry.terraform.io/providers/oracle/oci/latest/docs
+[ridiculously powerful free server in the cloud]: https://medium.com/codex/ridiculously-powerful-free-server-in-the-cloud-dd4da8524a9c
+[oracle-terraform-modules/terraform-oci-compute-instance]: https://github.com/oracle-terraform-modules/terraform-oci-compute-instance

terraform/oracle cloud free tier ampere instance/design/requirements.py

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+#!/usr/bin/env python3
+
+from diagrams import Cluster, Diagram
+from diagrams.oci.compute import VM
+from diagrams.oci.network import InternetGateway, RouteTable, Vcn
+
+with Diagram("Requirements", show=False):
+
+    vcn = Vcn("VCN")
+    vm = VM("Ampere instance")
+
+    with Cluster("Public Subnet"):
+
+        ig = InternetGateway("Internet Gateway")
+        rt = RouteTable("Route Table")
+
+    vcn >> ig >> rt
+    rt >> vm

terraform/oracle cloud free tier ampere instance/example.tfvars

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+availability_domain = "FIXME" # get it with `oci iam availability-domain list`
+compartment_id      = "FIXME" # get it with `oci iam compartment list`
+
+memory_in_gbs = 24
+ocpus         = 4
+
+# get it with `oci compute image list -c 'tenancy_id'`
+# or check https://docs.oracle.com/en-us/iaas/images/
+source_id = "ocid1.image.oc1.eu-amsterdam-1.aaaaaaaavmra3s4va4fqd4vlcrqc5v5jyqov5vdla3x3b6gzc64n6dkpuqua"
+
+ssh_authorized_keys = <<EOT
+ssh-ed25519 key-1 comment
+ssh-ed25519 key-n comment
+EOT

terraform/oracle cloud free tier ampere instance/main.tf

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+# https://registry.terraform.io/providers/oracle/oci/latest/docs/resources/core_vcn
+resource "oci_core_vcn" "this" {
+  compartment_id = var.compartment_id
+  cidr_blocks    = ["10.0.0.0/16"]
+}
+
+# https://registry.terraform.io/providers/oracle/oci/latest/docs/resources/core_subnet
+resource "oci_core_subnet" "this" {
+  compartment_id = var.compartment_id
+  vcn_id         = oci_core_vcn.this.id
+  cidr_block     = "10.0.0.0/24"
+}
+
+# Needed to be able to connect to the instance from the Internet.
+# Need to create a route table with the default route 0.0.0.0/0 pointing to the
+# internet gateway, and associate the subnet to it.
+# https://registry.terraform.io/providers/oracle/oci/latest/docs/resources/core_internet_gateway
+resource "oci_core_internet_gateway" "this" {
+  compartment_id = var.compartment_id
+  vcn_id         = oci_core_vcn.this.id
+}
+resource "oci_core_route_table" "this" {
+  compartment_id = var.compartment_id
+  vcn_id         = oci_core_vcn.this.id
+
+  route_rules {
+    destination       = "0.0.0.0/0"
+    destination_type  = "CIDR_BLOCK"
+    network_entity_id = oci_core_internet_gateway.this.id
+  }
+}
+resource "oci_core_route_table_attachment" "this" {
+  subnet_id      = oci_core_subnet.this.id
+  route_table_id = oci_core_route_table.this.id
+}
+
+# https://registry.terraform.io/providers/oracle/oci/latest/docs/resources/core_instance
+resource "oci_core_instance" "this" {
+  compartment_id      = var.compartment_id
+  availability_domain = var.availability_domain
+  shape               = var.shape
+
+  create_vnic_details {
+    subnet_id = oci_core_subnet.this.id
+  }
+
+  metadata = {
+    ssh_authorized_keys = var.ssh_authorized_keys
+  }
+
+  shape_config {
+    memory_in_gbs = var.memory_in_gbs
+    ocpus         = var.ocpus
+  }
+
+  source_details {
+    boot_volume_size_in_gbs = var.boot_volume_size_in_gbs
+    source_id               = var.source_id
+    source_type             = var.source_type
+  }
+}

terraform/oracle cloud free tier ampere instance/outputs.tf

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+output "instance" {
+  value = oci_core_instance.this
+}

terraform/oracle cloud free tier ampere instance/variables.tf

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+variable "availability_domain" {
+  type = string
+}
+variable "compartment_id" {
+  type = string
+}
+variable "shape" {
+  type    = string
+  default = "VM.Standard.A1.Flex"
+}
+
+variable "memory_in_gbs" {
+  type    = number
+  default = 24
+}
+variable "ocpus" {
+  type    = number
+  default = 4
+}
+
+variable "boot_volume_size_in_gbs" {
+  type    = number
+  default = 50
+}
+variable "source_id" {
+  type = string
+}
+variable "source_type" {
+  type    = string
+  default = "image"
+}
+
+variable "ssh_authorized_keys" {
+  type = string
+}