Wednesday, March 20, 2024

How to Setup Self-Hosted Linux Docker Build Agent in Azure DevOps | How to configure Self-Hosted Linux Docker Agents in Azure Pipelines | Create Custom Build Agents in Azure DevOps

 Let us learn how to configure a self-hosted agent using Docker in Azure DevOps pipelines.

What is an Agent?

An agent is computing infrastructure with installed agent software that runs one job at a time.To build your code or deploy your software using Azure Pipelines, you need at least one agent. As you add more code and people, you'll eventually need more.

When your pipeline runs, the system begins one or more jobs. 


In Azure pipelines, there are two types of build agents:

  1. Microsoft-hosted agents - This is a service totally managed by Microsoft and it's cleared on every execution of the pipeline (on each pipeline execution, you have a fresh new environment).
  2. Self-hosted agents - This is a service that you can to set up and manage by yourself. This can be a custom virtual machine on Azure or a custom on-premise machine inside your infrastructure. In a self-hosted agent, you can install all the software you need for your builds, and this is persisted on every pipeline execution. A self-hosted agent can be on Windows, Linux, macOS, or in a Docker container.

You can set up a self-hosted agent in Azure Pipelines to run inside a Windows Server Core (for Windows hosts), or Ubuntu container (for Linux hosts) with Docker. We will learn in this article on how to host Ubuntu Docker container on Linux machines.

Pre-requisites:
How to configure Self-hosted docker build agent?

1. Go to Azure DevOps dashboard - https://dev.azure.com/
2. Select your project dashboard
3. Go to your project settings
4. Click on Agent pools


Create a new Agent pool name

Enter name as myAgentPool or any name
Make sure you select Grant access permission to all pipelines



Login to Azure VM where the docker build agents will be running.

Step #1 - Install Docker CLI so we can build docker image

sudo apt update && sudo apt install docker.io -y

Step #2 - Add logged in user to docker group
sudo usermod -a -G docker $USER

Step #3 - Clone repo which has Dockerfile

git clone https://github.com/akannan1087/ado-docker-agent-repo.git

Sample dockerfile is here.. please feel free to add any software in the docker agent.
FROM ubuntu:22.04

RUN apt update -y && apt upgrade -y && apt install curl git jq libicu70 maven -y

# Also can be "linux-arm", "linux-arm64".
ENV TARGETARCH="linux-x64"

WORKDIR /azp/

COPY ./start.sh ./
RUN chmod +x ./start.sh

# Create agent user and set up home directory
RUN useradd -m -d /home/agent agent
RUN chown -R agent:agent /azp /home/agent

USER agent
# Another option is to run the agent as root.
# ENV AGENT_ALLOW_RUNASROOT="true"

ENTRYPOINT ./start.sh

Step #4 - change directory
cd ado-docker-agent-repo/azp-agent-in-docker/

Step #5 - Build the Docker image
sudo docker build --tag "azp-agent:linux" --file Dockerfile .

Step #6: Run the agent as a container
Run the below command:

sudo docker run -e AZP_URL="https://dev.azure.com/your_org_name" -e AZP_TOKEN="XXXX" -e AZP_POOL=myAgentPool -e AZP_AGENT_NAME="myLinuxDockerBuildAgent" --name "azp-agent" azp-agent:linux

that's it, docker agent is successfully started.

Step #7: Verify if docker agent is running or not
Run the below command:
sudo docker ps


Check the status of build Agent
Click on agentPool name, click on Agents

This confirms that Build agent is successfully configured in Azure DevOps and is available to run builds.

How to use the Docker build agent in your pipelines?

Please use the docker agent in the classic pipeline like below: select the agentPool


run the job. now you can see the jobs under myAgentPool--> Jobs
 

Here is the sample pipeline YAML code for automating Maven build for a Java project:

trigger:
- main
pool:
name: myAgentPool
stages:
- stage: Build
displayName: Build stage
jobs:
- job: MavenPackageAndPublishArtifacts
displayName: Maven Package and Publish Artifacts
steps:
- task: Maven@3
displayName: 'Maven Package'
inputs:
mavenPomFile: 'MyWebApp/pom.xml'

References:

Watch steps in YouTube channel:

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