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What is Trident?

Trident is a servicing agent, drawing inspiration from the declarative API principles established by Kubernetes. It ingests a Host Configuration specification as input, and, as it progresses, updates the Host Status to accurately reflect all changes applied in accordance with the provided Host Configuration.

Host Configuration​

The Host Configuration defines the desired state of the host that Trident manages, serving as the authoritative specification from initial installation (when applicable) through all subsequent servicing operations. The Host Configuration API is designed to align closely with the Image Customizer Image Configuration API, ensuring consistency across deployment and servicing workflows.

Basic example of a Host Configuration:

storage:
  disks:
  - id: os
    device: /dev/disk/by-path/pci-0000:00:1f.2-ata-2.0
    partitionTableType: gpt
    partitions:
    - id: esp
      type: esp
      size: 64M
    - id: root
      type: root
      size: 8G
  filesystems:
  - deviceId: esp
    mountPoint:
      path: /boot/efi
      options: umask=0077
  - deviceId: root
    mountPoint: /
image:
  url: file:///path/to/image.cosi
  sha384: ec9a9aa23f02b30f4ec6a168b9bc24733b652eeab4f8abc243630666a5e34cea1667c34313a13ec1564ac4871b80112f

Host Status​

The Host Status provides a snapshot of the current configuration as managed by Trident. This enables Trident to accurately report the operational state to users and facilitates precise determination of required changes when a new Host Configuration is supplied.

Simplifying complexity through integration and reuse​

Trident offers a streamlined abstraction layer over established upstream Linux utilities, including systemd-repart, mdadm, cryptsetup, veritysetup, and others and leverages standard upstream components such as grub2 and systemd-boot. By integrating these proven tools, Trident delivers a consistent and dependable servicing experience while minimizing complexity. Developed in Rust, Trident benefits from enhanced memory safety and performance, ensuring robust and efficient operation.

Architectural principles​

Trident is architected for seamless integration into larger solutions. Its primary responsibility is single-host servicing, delegating orchestration tasks—such as scheduling and input selection—to external logic. Trident is intentionally modular; it can be used solely for image deployment or in conjunction with other tools for OS configuration. However, maximum benefit is achieved when Trident manages the entire servicing workflow.

Further, Trident is designed to be platform and product agnostic. This allows the common servicing logic to be reused across various products and environments, while product-specific logic is handled externally. This separation of concerns simplifies maintenance and enables consistent servicing practices across diverse deployments.

Operating modes​

Trident is capable of operating in two distinct modes: it can execute from a live management operating system to facilitate initial OS installation, or it can run directly within the host OS to perform image-based A/B-style servicing and updates.

Trident-based installer can be deployed through multiple mechanisms, including bootable ISO images, PXE boot, or other provisioning tools. This flexibility allows users to choose the most suitable method for their environment and requirements.

Trident is capable of operating either directly within the host OS root namespace or in a containerized environment. It can be initiated interactively, by product-specific orchestration logic, or managed as a service via systemd. When no servicing operations are pending, the Trident agent remains inactive, ensuring minimal consumption of system resources.