Use pre-installed GitHub runner on the AMI

[machulav]

From @jdraymon in #16:

Would it make sense to have a version fixed in our AMI instead? or maybe a download URI with a default? My organization is a bit wary about downloading things off of the web for every build. Maybe a separate enhancement?

Let's keep it separate and collect feedback from the others.

[keithalpichi]

I think this is a great idea. The way I'd like it to work is I prepare the AMI with the Github Runner and any other dependencies. Then I run this Github Action and expect it to just start it for me.

Of course, this Github Action will need to know where the config and run scripts are located so they can be invoked. This could be another input.

[jpalomaki]

FWIW, here's an example AMI build (NOTE: for Ubuntu arm64) that pre-bakes the actions-runner software (and dependencies) in the image, so that we don't need to download/install those at runner boot-time (should somewhat improve reliability and startup time).

Here's how I currently use this AMI (:warning: experimental), which I think is pretty close to what @keithalpichi describes above (plus it uses a non-root user for the runner).

See also: philips-labs/terraform-aws-github-runner scripts

In ec2-github-runner action, the instance user-data script could perhaps be varied based on such action inputs, to allow users to choose between the current behavior of installing stuff on the fly (for backwards-compatibility, and to make it possible to use vanilla-ish AMIs) and that of using a pre-installed runner, depending on what type of AMI is being used?

[jpalomaki]

@machulav @keithalpichi Here's a quick stab at it: #56. Let me know what you think.

[machulav]

Using the changes from the PR above I'm able now to use pre-baked AMI with installed actions-runner software.

I've configured it using the following steps:

1. Create a new EC2 instance based on Amazon Linux 2.
2. Connect to the instance using SSH and install the following tools.

 sudo yum update -y && \
 sudo yum install docker -y && \
 sudo yum install git -y && \
 sudo systemctl enable docker

3. Create a new actions-runner folder in the /root folder using the root user. So the folder with the runner will be /root/actions-runner. For some reason, the runner is not able to run from the /actions-runner folder in the root directory.

mkdir actions-runner && cd actions-runner

4. Determine the architecture and set it into the ENV variable.

case $(uname -m) in aarch64) ARCH="arm64" ;; amd64|x86_64) ARCH="x64" ;; esac && export RUNNER_ARCH=${ARCH}

5. Download the latest version of the runner.

curl -O -L https://github.com/actions/runner/releases/download/v2.278.0/actions-runner-linux-${RUNNER_ARCH}-2.278.0.tar.gz

6. Extract the runner.

tar xzf ./actions-runner-linux-${RUNNER_ARCH}-2.278.0.tar.gz

7. Create a new EC2 image (AMI) from the instance.
8. Use the AMI for creating the runner.
9. Follow the rest of the steps from the How to start
10. Use the runner-home-dir: /root/actions-runner in the start EC2 runner configuration