Linux hosted agents

Buildkite's Linux hosted agents are:

  • Buildkite Agents hosted by Buildkite that run in a Linux environment.

  • Configured as part of a Buildkite hosted queue, where the Buildkite hosted agent's machine type is Linux, has a particular size to efficiently manage jobs with varying requirements, and comes pre-installed with software in the form of agent images, which can be customized with other software.

Learn more about:

Sizes

Buildkite offers a selection of Linux instance types (each based on a different combination of size and architecture, known as an instance shape), allowing you to tailor your hosted agent resources to the demands of your jobs. The architectures supported include AMD64 (x64_86) and ARM64 (AArch64).

Instance shape Size Architecture vCPU Memory Disk space
Instance shape Instance shape LINUX_AMD64_2X4 Size Size Small Architecture Architecture AMD64 vCPU vCPU 2 Memory Memory 4 GB Disk space Disk space 47 GB
Instance shape Instance shape LINUX_AMD64_4X16 Size Size Medium Architecture Architecture AMD64 vCPU vCPU 4 Memory Memory 16 GB Disk space Disk space 95 GB
Instance shape Instance shape LINUX_AMD64_8X32 Size Size Large Architecture Architecture AMD64 vCPU vCPU 8 Memory Memory 32 GB Disk space Disk space 158 GB
Instance shape Instance shape LINUX_AMD64_16X64 Size Size Extra Large Architecture Architecture AMD64 vCPU vCPU 16 Memory Memory 64 GB Disk space Disk space 284 GB
Instance shape Instance shape LINUX_ARM64_2X4 Size Size Small Architecture Architecture ARM64 vCPU vCPU 2 Memory Memory 4 GB Disk space Disk space 47 GB
Instance shape Instance shape LINUX_ARM64_4X16 Size Size Medium Architecture Architecture ARM64 vCPU vCPU 4 Memory Memory 16 GB Disk space Disk space 95 GB
Instance shape Instance shape LINUX_ARM64_8X32 Size Size Large Architecture Architecture ARM64 vCPU vCPU 8 Memory Memory 32 GB Disk space Disk space 158 GB
Instance shape Instance shape LINUX_ARM64_16X64 Size Size Extra Large Architecture Architecture ARM64 vCPU vCPU 16 Memory Memory 64 GB Disk space Disk space 284 GB

Note the following about Linux hosted agent instances.

  • Extra large instances are available on request.

  • To accommodate different workloads, instances are capable of running up to 8 hours.

If you need extra large instances, or longer running hosted agents (over 8 hours), please contact Support at support@buildkite.com.

Concurrency

Linux hosted agents can operate concurrently when running your Buildkite pipeline jobs.

This concurrency is measured by the number of hosted agent machines that are allocated for your jobs at any given time. A machine is counted from the moment it starts booting to acquire a job, since that's when the machine starts consuming capacity. As a result, concurrency may not always match the exact number of running jobs, particularly with short-lived workloads.

The number of Linux hosted agents (of a Buildkite hosted queue) that can process your pipeline jobs concurrently is calculated by your Buildkite plan's maximum combined vCPU value divided by your instance shape's vCPU value. See the Buildkite pricing page for details on the Linux Concurrency that applies to your plan.

For example, if your Buildkite plan provides you with a maximum combined vCPU value of up to 48, and you've configured a Buildkite hosted queue with the LINUX_AMD64_4X16 (Medium AMD64) instance shape, whose vCPU value is 4, then the number of concurrent hosted agents that can run jobs on this queue is 12 (that is, 48 / 4 = 12).

When concurrency limits are exceeded, additional jobs will be queued until sufficient capacity becomes available.

Security

Customer security is paramount to Buildkite, where our source code, build artifacts and deployment processes represent some of our most valuable and sensitive assets.

The shift from a self-hosted to a Buildkite hosted architecture for Buildkite Agents, introduces the potential for new attack vectors and shared responsibility models, and hence, additional security considerations.

The security model for Buildkite hosted agents has the following characteristics to address these security considerations and to mitigate attack risks.

  • Infrastructure and isolation security: Buildkite employs a multi-tenant architecture, where each job runs in a completely isolated virtualized environment. Once a job is complete, regardless of its exit status, the virtualized environment is destroyed, along with all its data (except for cache volumes that persist across jobs). This ephemeral approach ensures that customer workloads remain isolated from each other, even though the underlying hardware is shared across multiple customers.

  • Physical and operational security: The Buildkite hosted agent fleet operates from multiple Tier 3+ data centers with restricted physical access controls and regular security monitoring. The platform maintains SOC 2 compliance through regular audits of both hardware and software security controls.

Agent images

Buildkite provides a Linux agent image pre-configured with common tools and utilities to help you get started quickly. This image also provides tools required for running jobs on hosted agents.

The image is based on Ubuntu 22.04 and includes the following tools:

  • docker
  • docker-compose
  • docker-buildx
  • git-lfs
  • node
  • aws-cli

You can customize the image that your hosted agents use by creating an agent image.