forge

Building the GitHub Actions Base Image with Packer

This guide explains how to build the Forge GitHub Actions runner base image using Packer.

Prerequisites

• Packer installed
• AWS CLI configured with credentials and permissions to build AMIs
• The required VPC and subnet exist in your AWS account
• (Optional) Splunk Observability credentials if you want to enable Splunk OTel Collector
• (Optional) Teleport for secure SSH access

Required Variables

You must provide the following variables to Packer:

• subnet_id: The subnet where the instance will be launched
• vpc_id: The VPC where the instance will be launched
• allowed_ssh_cidrs: CIDR blocks allowed to SSH into the instance (for debugging)
• aws_region: The AWS region to build the image in

Example values:

• subnet_id=subnet-0123456789abcdef0
• vpc_id=vpc-0123456789abcdef0
• allowed_ssh_cidrs=10.0.0.0/8
• aws_region=us-west-2

(Optional) Splunk OTel Collector and Teleport

If you want to include the Splunk OpenTelemetry Collector in your image, set the following environment variables before running Packer:

export SPLUNK_ACCESS_TOKEN=<your_splunk_access_token>
export SPLUNK_REALM=<your_splunk_realm>

If you want to include Teleport or Splunk OTel Collector roles in the build, enable them in your Ansible playbook by uncommenting the roles:

forge/examples/build/ansible/build_gh_base_image.yaml

roles:
  - role: teleport  
  - role: splunk_otel_collector

Build Command

Run the following command from the directory containing your Packer template:

cd forge/examples/build/packer
packer build \
  -var "subnet_id=<your_subnet_id>" \
  -var "vpc_id=<your_vpc_id>" \
  -var "allowed_ssh_cidrs=<your_allowed_ssh_cidrs>" \
  -var "aws_region=<your_aws_region>" \
  .

Example:

cd forge/examples/build/packer
packer build \
  -var "subnet_id=subnet-0123456789abcdef0" \
  -var "vpc_id=vpc-0123456789abcdef0" \
  -var "allowed_ssh_cidrs=10.0.0.0/8" \
  -var "aws_region=us-west-2" \
  .

Notes

• Make sure your AWS user/role has permissions to create EC2 instances, AMIs, and related resources.
• If you enable the Splunk OTel Collector, ensure your access token and realm are valid.
• The resulting AMI can be used as the base image for Forge GitHub Actions runners.

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