GitHub Actions Workflow Syntax: ‘entrypoint’ – Specifying Your Docker Action’s Start Point

In the vast landscape of GitHub Actions, the ‘entrypoint’ keyword plays a pivotal role when you need to define the starting point for Docker container actions. In this blog post, we’ll dive into the ‘entrypoint’ keyword as a part of the GitHub Actions Workflow syntax. We’ll discuss its syntax, usage, and provide examples to solidify understanding.

Introduction

GitHub Actions Workflow offers a powerful way to automate software development processes, such as building, testing, and deploying applications. Workflows are composed of ‘jobs’ and ‘steps’, each performing specific tasks. When you’re running Docker container actions, the ‘entrypoint’ keyword can be used to override the ENTRYPOINT instruction specified in the Dockerfile.

Understanding the ‘entrypoint’ Syntax

In the GitHub Actions Workflow syntax, the ‘entrypoint’ keyword is used within a step to specify or override the entrypoint for a Docker container action.

Here’s a simple structure of how ‘entrypoint’ is used within a step:

jobs:
  job_id:
    runs-on: runner_type
    steps:
    - name: Step name
      uses: docker://image:tag
      with:
        entrypoint: entrypoint_command

jobs:

job_id:

runs-on: runner_type

steps:

- name: Step name

uses: docker://image:tag

with:

entrypoint: entrypoint_command

In this syntax, ‘entrypoint_command’ represents the command that you want to execute as the entrypoint of the Docker container. It overrides the ENTRYPOINT instruction that is defined in the Dockerfile of the specified image.

Example of ‘entrypoint’ in a Workflow

To illustrate the ‘entrypoint’ keyword, let’s look at a workflow that runs a Docker container with a specific entrypoint:

name: Docker container action

on: [push]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - name: Run Docker container
      uses: docker://alpine:3.10
      with:
        entrypoint: /bin/sh

name: Docker container action

on: [push]

jobs:

build:

runs-on: ubuntu-latest

steps:

- name: Run Docker container

uses: docker://alpine:3.10

with:

entrypoint: /bin/sh

In this workflow, the ‘build’ job consists of a single step that uses the docker://alpine:3.10 Docker image to create a container. The ‘entrypoint’ keyword is used to override the entrypoint, setting it to /bin/sh.

Conclusion

The ‘entrypoint’ keyword in the GitHub Actions Workflow syntax gives developers the ability to specify or override the entrypoint for Docker container actions. This functionality allows for increased flexibility and control over the behavior of Docker containers within workflows.