A self-hosted agent is a computer with the Azure Pipelines agent software installed. This allows you to run tasks on your own infrastructure rather than on Microsoft-provided machines. The computer could be a traditional bare-metal machine or a virtual machine in a private or public cloud.
Configuring Self-Hosted Agents
Let’s begin by looking at how to configure a self-hosted agent.
- Install the Agent software: To install the agent software, you first need to download the agent package. Then, on your local machine, create an agent folder, extract the download into the agent folder and configure the agent. The command for configuring the agent could look like this:
./config.cmd –url https://dev.azure.com/myorganization –auth pat –token myToken –pool default –agent myAgent –work _work –runAsService
- Register the Agent: After installing the agent, you’ll need to register it with Azure DevOps. This includes specifying a Personal Access Token (PAT) for the agent to use when it talks back to Azure DevOps.
- Configure Runtime: Finally, you need to set up the runtime for your agent. Depending on the platform, there are different configuration scripts available.
Managing VM templates and Containerization
Now let’s take a look at how VM templates and containerization fit into the picture.
Virtual Machine Templates: In Azure, the approach to managing VMs as self-hosted agents generally involves using VM templates. VM templates allow you to deploy multiple VMs with the same configuration, ensuring consistency and reducing setup time.
The configuration process involves setting up a VM with the desired settings and applications, then deprovisioning the VM and capturing an image of it to create a template. This template can be used to generate new VMs with identical settings.
Containerization: In the context of Azure DevOps, containers present a lightweight alternative to VMs. A container packages an application and its dependencies into a standardized unit for development, shipment, and deployment.
Azure DevOps’ support for Docker containers means you can have your build and release pipelines run on a Docker container. This is especially useful when you have constraint environments or environments with very specific software requirements.
For example, you can have a Dockerfile that will build a container with all the necessary dependencies that your build or release pipeline needs. Your pipeline can then be configured to run on this Docker agent.
# Dockerfile
FROM microsoft/azure-cli:2.0.68
RUN az extension add –name azure-devops
ENTRYPOINT [ “/bin/bash”, “-c”,”az pipelines agent start”]
This Dockerfile builds a container with Azure CLI and the Azure Pipelines agent. It then starts the agent when the container is launched.
Conclusion
In conclusion, understanding how to configure and manage self-hosted agents, as well as containerization and VM templates, is crucial for the AZ-400 “Designing and Implementing Microsoft DevOps Solutions” exam. Practicing these setups in a test or sandbox environment will reinforce your understanding and prepare you for the exam.
Practice Test
True or False: Self-hosted agents are more secure because they are managed directly by Microsoft.
- True
- False
Answer: False
Explanation: Self-hosted agents are hosted either by the user or by a third-party, not Microsoft, thus their security highly depends on the individual or organization managing them.
What is the key benefit of using containerization in a self-hosted agent?
- a) Increased Cost
- b) Enhanced Security
- c) Isolation and Consistency
- d) Reducing agent speed
Answer: c) Isolation and Consistency
Explanation: Containerization provides an isolated and consistent environment for running applications, which is ideal for self-hosted agents.
True or False: Virtual Machine templates can’t be used with self-hosted agents.
- True
- False
Answer: False
Explanation: Virtual machine templates can be used with self-hosted agents to provide a consistent environment for deployments.
In azure DevOps, self-hosted agents are useful for building and deploying applications that require _____.
- a) Other cloud platforms
- b) Specific operating systems
- c) Specific hardware
- d) All of the above
Answer: d) All of the above
Explanation: Self-hosted agents can be tailored to a specific OS, hardware, and can have tools installed that you require for building and deploying your application.
Containerization is responsible for reducing the _____ in self-hosted agents.
- a) speed
- b) dependency
- c) cost
- d) security
Answer: b) dependency
Explanation: Containerization packages an application with its runtime environment, reducing the dependency of the application on the host operating system.
True or False: It is not possible to scale up self-hosted agents.
- True
- False
Answer: False
Explanation: Self-hosted agents can be scaled up according to the requirements, providing flexibility in deployment environments.
_____ can be used with self-hosted agents to provide the benefits of containerization.
- a) Kubernetes
- b) Docker
- c) Both a and b
- d) None of the above
Answer: c) Both a and b
Explanation: Docker is a containerization platform, and Kubernetes is an orchestration platform for Docker containers, both can be used with self-hosted agents.
Virtual machine templates provide a _____ environment for deployments.
- a) inconsistent
- b) consistent
- c) complex
- d) none of the above
Answer: b) consistent
Explanation: Virtual machine templates ensure that the environment is consistent across multiple deployments.
Containerization provides _____ for running applications.
- a) an inconsistent environment
- b) a complex environment
- c) an isolated and consistent environment
- d) a shared and conflicting environment
Answer: c) an isolated and consistent environment
Explanation: Containerization ensures that each application runs in its isolated environment, reducing dependency and conflicts.
True or False: Self-Hosted Agents take less time for setup and maintenance compared to Microsoft-hosted agents.
- True
- False
Answer: False
Explanation: Self-Hosted Agents are likely to need more time for setup and maintenance as compared to Microsoft-hosted agents as they need to be customized to the user’s specifications.
Interview Questions
What is a self-hosted agent in Microsoft Azure?
A self-hosted agent in Azure is any machine with the Azure Pipelines agent software installed. This allows the machine to host deployment jobs and run tasks.
What are the advantages of using self-hosted agents?
Self-hosted agents offer benefits like running the Azure Pipelines agent software on-premise, high-speed local network access, and more control over the environment, including installed software, capacity, and clean-up procedures.
What is a virtual machine template in Azure and why do we use it?
A virtual machine template in Azure is a master copy of a VM that can be used to create multiple identical VMs. It makes it fast and easy to rollout new VMs without the hassle of configuring each new VM from scratch.
What is containerization and how is it used in Azure DevOps?
Containerization in Azure DevOps involves encapsulating or packaging up software code and all its dependencies so that it can run uniformly and consistently on any infrastructure. It allows developers to create predictable environments that are isolated from other applications.
How can you add a self-hosted agent to your Azure DevOps organization?
You can add a self-hosted agent to your DevOps organization by first creating an agent pool, then downloading the agent package, configuring the agent, and finally verifying the installation.
What is a VM Scale Set in Azure and how does it interact with self-hosted agents?
A VM Scale Set in Azure allows you to create and manage a group of identical, load balanced, and autoscaling VMs. With Azure Pipeline’s elasticity features, you can use VM Scale Sets to scale the number of self-hosted agents depending on the workload.
Why might containerization be preferred over VMs?
Containerization could be preferred over VMs as it can be lighter (utilizing less system resources), faster, able to run more instances on the same hardware, and its applications are more easily managed, moved and scaled.
How to remove self-hosted agents from your Azure DevOps Organization?
You can remove self-hosted agents by navigating to the agent pools in Azure DevOps, selecting the specific pool containing the agent to be removed, selecting the specific agent, and then selecting Remove.
Can a self-hosted agent run jobs for public and private projects?
Yes, a self-hosted agent can run jobs for both public and private projects as long as appropriate permissions are set.
How can you secure self-hosted agents in Azure DevOps?
You can secure self-hosted agents by limiting the scope of access tokens, ensuring agents are hosted in a trusted network, hardening the underlying system, regular patching of the operating system, and using firewalls to safeguard the agent machine.
What is the role of Docker in containerization?
Docker is a platform used to develop, ship, and run applications within containers. It allows you to separate your applications from your infrastructure and treat your infrastructure like a managed application.
How do we ensure a self-hosted agent is always online?
You can ensure a self-hosted agent is always online by setting the agent to run as a service on the host machine. That way, the machine will automatically start the agent whenever the machine boots up.
What requirements must be fulfilled to host self-hosted agents?
The host machine for a self-hosted agent must meet certain requirements, including a supported operating system (Windows, macOS, or Linux), minimum hardware requirements, and network requirements to connect to Azure DevOps.
Can Azure Functions be deployed using self-hosted agents?
Yes, Azure Functions can be deployed using self-hosted agents. These agents could be hosted on-premise or in the cloud.
In Azure, how can we distribute the workloads between multiple self-hosted agents?
The workloads between multiple self-hosted agents can be distributed using Azure Pipelines’ parallel jobs. This enables concurrent execution and thus faster completion of tasks.
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