oam/examples/terraform/oracle cloud/connect using ssh to an instance through a bastion

Oracle Bastion

Simple example to create a Bastion in Oracle Cloud.

Table of contents

1. Requirements
2. Connect to the instance using SSH through the bastion
3. Further readings
4. Sources

Requirements

1. VCN
2. Private Subnet
3. RSA SSH key

For a Subnet to be considered Private, it needs to have associated a Route Table with a default route pointing to a NAT Gateway.

Note: NAT Gateways are not included in Oracle's free tier.

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.
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.

Connect to the instance using SSH through the bastion

Use this configuration as starting point and fix its values to simplify the command:

Host  bastion
  Hostname                  host.bastion.eu-amsterdam-1.oci.oraclecloud.com
  HostkeyAlgorithms         +ssh-rsa
  PubkeyAcceptedAlgorithms  +ssh-rsa
  LocalForward              8022 10.0.0.230:22
  User                      ocid1.bastionsession.oc1.eu-amsterdam-1.amaaaaaazsnap6iazqwiktq2b7i736d5cgc2vnswuypa3iey754rlj4yyrvq

Host  instance
  Hostname  localhost
  User      opc
  Port      8022

Host  bastion instance
  IdentityFile           ~/.ssh/id_rsa
  IdentitiesOnly         yes
  StrictHostKeyChecking  no
  UserKnownHostsFile     /dev/null

and now use the following command:

ssh -fN bastion && ssh instance

Further readings

• Ridiculously powerful free server in the cloud

Sources

All the references in the further readings section, plus the following:

• Always free resources in Oracle Cloud
• Oracle Cloud Infrastructure Provider documentation
• oracle-terraform-modules/terraform-oci-compute-instance