Azure Self hosted Agent

Azure Pipelines agents
09/09/2020
23 minutes to read
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Azure Pipelines | Azure DevOps Server 2020 | Azure DevOps Server 2019 | TFS 2018 - TFS 2015

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. An agent is computing infrastructure with installed agent software that runs one job at a time.

Jobs can be run directly on the host machine of the agent or in a container.

Microsoft-hosted agents
If your pipelines are in Azure Pipelines, then you've got a convenient option to run your jobs using a Microsoft-hosted agent. With Microsoft-hosted agents, maintenance and upgrades are taken care of for you. Each time you run a pipeline, you get a fresh virtual machine. The virtual machine is discarded after one use. Microsoft-hosted agents can run jobs directly on the VM or in a container.

Azure Pipelines provides a pre-defined agent pool named Azure Pipelines with Microsoft-hosted agents.

For many teams this is the simplest way to run your jobs. You can try it first and see if it works for your build or deployment. If not, you can use a self-hosted agent.

Tip

You can try a Microsoft-hosted agent for no charge.

Learn more about Microsoft-hosted agents.

Self-hosted agents
An agent that you set up and manage on your own to run jobs is a self-hosted agent. You can use self-hosted agents in Azure Pipelines or Team Foundation Server (TFS). Self-hosted agents give you more control to install dependent software needed for your builds and deployments. Also, machine-level caches and configuration persist from run to run, which can boost speed.

Tip

Before you install a self-hosted agent you might want to see if a Microsoft-hosted agent pool will work for you. In many cases this is the simplest way to get going. Give it a try.

You can install the agent on Linux, macOS, or Windows machines. You can also install an agent on a Docker container. For more information about installing a self-hosted agent, see:

macOS agent
Linux agent (x64, ARM, RHEL6)
Windows agent (x64, x86)
Docker agent
Note

On macOS, you need to clear the special attribute on the download archive to prevent Gatekeeper protection from displaying for each assembly in the tar file when ./config.sh is run. The following command clears the extended attribute on the file:

Bash

Copy
xattr -c vsts-agent-osx-x64-V.v.v.tar.gz ## replace V.v.v with the version in the filename downloaded.

# then unpack the gzip tar file normally:

tar xvfz vsts-agent-osx-x64-V.v.v.tar.gz
After you've installed the agent on a machine, you can install any other software on that machine as required by your jobs.

Azure virtual machine scale set agents
Azure virtual machine scale set agents are a form of self-hosted agents that can be auto-scaled to meet your demands. This elasticity reduces your need to run dedicated agents all the time. Unlike Microsoft-hosted agents, you have flexibility over the size and the image of machines on which agents run.

You specify a virtual machine scale set, a number of agents to keep on standby, a maximum number of virtual machines in the scale set, and Azure Pipelines manages the scaling of your agents for you.

For more information, see Azure virtual machine scale set agents.

Parallel jobs
You can use a parallel job in Azure Pipelines to run a single job at a time in your organization. In Azure Pipelines, you can run parallel jobs on Microsoft-hosted infrastructure or on your own (self-hosted) infrastructure.

Microsoft provides a free tier of service by default in every organization that includes at least one parallel job. Depending on the number of concurrent pipelines you need to run, you might need more parallel jobs to use multiple Microsoft-hosted or self-hosted agents at the same time. For more information on parallel jobs and different free tiers of service, see Parallel jobs in Azure Pipelines.

Capabilities
Every self-hosted agent has a set of capabilities that indicate what it can do. Capabilities are name-value pairs that are either automatically discovered by the agent software, in which case they are called system capabilities, or those that you define, in which case they are called user capabilities.

The agent software automatically determines various system capabilities such as the name of the machine, type of operating system, and versions of certain software installed on the machine. Also, environment variables defined in the machine automatically appear in the list of system capabilities.