Fetching the most recent GitHub actions runner version

One of the struggles I have with running self-hosted GitHub actions runners is that GitHub releases new versions of the runner quite often and I don’t notice. That’s fine as long as you ignore the scary warnings on action output, until they drop support for whatever random old runner you’re using. They did just that to me this week. The best bit was that the “old runner” was only a month old!

I was left wondering if I could automate this. The answer is thankfully yes.

Specifically, I wanted to automate it with a GitHub action which downloads the runner and puts it into the self-hosted runner image. That looks like this:

- name: Install the github command line
  run: |
    sudo apt update
    sudo apt install -y curl

    curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | sudo dd of=/usr/share/keyrings/githubcli-archive-keyring.gpg
    sudo chmod go+r /usr/share/keyrings/githubcli-archive-keyring.gpg
    echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main" | sudo tee /etc/apt/sources.list.d/github-cli.list > /dev/null
    sudo apt update
    sudo apt install -y gh

- name: Lookup latest version of the GitHub actions runner
  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  run: |
    actions_url=$(gh release view --repo actions/runner --json assets | \
        jq -r '.assets[].url | select (contains("linux-x64-2")) | select (test("[0-9].tar.gz$"))')
    echo "GITHUB_ACTIONS_URL=$actions_url" >> $GITHUB_ENV

- name: Cache github actions runner
  run: |
    curl -o /srv/ci/github-actions-runner.tar.gz ${GITHUB_ACTIONS_URL}

For my setup, this runs in an action which builds a new virtual machine image for the github runners each night. That third step downloads the runner image, and caches it to the virtual machine’s disk. The virtual machine then installs the github actions running on boot for each ephemeral worker.