Where can I find the docker image which github action uses with pre-installed software

Question

I'm using self hosted runner instead of Github runner for Github Actions because the self hosted runner will have access to private network. I'll also be using containers on top of the self hosted runner.

From the link https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners

One can set the runs-on to ubuntu-latest. I thought this is the same image as docker pull ubuntu with the preinstalled software at https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu2004-README.md

But the ubuntu image at docker hub is not the same as the ubuntu-latest image that Github hosted runner use. Where can I find the docker image that Github runner uses?

After configuring the self hosted runner and installing docker engine I tried with the workflow below. However it fails with no image ubuntu-latest

jobs:
  build:
    runs-on: self-hosted
    container:
      image: ubuntu-latest
    steps:
      - run: echo "🎉 The job was automatically triggered by a ${{ github.event_name }} event."
      - run: echo "🐧 This job is now running on a ${{ runner.os }} server !"

Answer 1

Two options:

1. Build your own from actions/virtual-environments
2. Use medium-sized images created by catthehacker, or full-sized image by nektos