Automate your workflow with GitHub Actions

Create a basic container action by using GitHub Actions

3 min readAug 10, 2020

In this lab I’ll be using the GitHub learning Lab to create a GitHub repository, a container action that will print a greeting in the action’s log file, and a workflow that triggers on a push to this repository

The following are the steps I’ll need to create this container action.

GitHub Actions

This action will use a Docker container so it will require a Dockerfile

Add a Dockerfile

I filled my Dockerfile with the content below:

FROM debian:9.5-slim

ADD entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]

Commit my file

Add an entrypoint script

An entry point script MUST exist in my repository so that Docker has something to execute. What I’m doing is outputting the “Hello world” message using a variable called MY_NAME

I used the command below:

#!/bin/sh -l
sh -c “echo Hello world my name is $INPUT_MY_NAME”

Add an action.yml file

Actions require a metadata file that uses YAML syntax. This data file defines inputs, outputs and main entrypoint for my action

name: "Hello Actions"
description: "Greet someone"
author: "octocat@github.com"

inputs:
MY_NAME:
description: "Who to greet"
required: true
default: "World"

runs:
using: "docker"
image: "Dockerfile"

branding:
icon: "mic"
color: "purple"

Start your workflow file

Work flows can execute based on a chosen even. This pieces together my jobs, and my jobs piece together my steps.

name: A workflow for my Hello World file
on: push

Run an action from your workflow file

jobs:
build:
name: Hello world action
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v1
- uses: ./action-a
with:
MY_NAME: "Mona"

Here are some details as to why each part exists and what each part does:

jobs: is the base component of a workflow run
build: is the identifier we're attaching to this job
name: is the name of the job, this is displayed on GitHub when the workflow is running
steps: the linear sequence of operations that make up a job
uses: actions/checkout@v1 uses a community action called checkout to allow the workflow to access the contents of the repository
uses: ./action-a provides the relative path the action we've created in the action-a directory of the repository
with: is used to specify the input variables that will be available to your action in the runtime environment. In this case, the input variable is MY_NAME, and it is currently initialized to "Mona"