Purpose

The Base OS defines the common system model and runtime contract implemented by Axis-based Operating Systems.

It specifies the properties that remain consistent across different Operating Systems, Platforms, Devices, and deployment environments without prescribing the software contained in a particular Operating System or the Platform-specific support used to boot and operate it.

Scope

The Base OS specifies the common contracts governing the structure, boot, filesystem, mutable state, update behavior, initialization, and runtime operation of Axis-based Operating Systems.

The Base OS does not define the software packages included by a particular Operating System, the hardware-specific implementation of a Platform, the Platform-specific boot environment or runtime support used by a Device, or the Host-side implementation used to operate a Device.

System Model

An Axis-based Operating System is an immutable Artifact that contains the userspace required to operate the system. A compatible Platform provides the target-side boot environment and runtime support required to use that Operating System on a physical or virtual Device.

During Boot, the Platform establishes the OS Artifact as the root filesystem and transfers execution to /sbin/axisd as PID 1. Mutable runtime and persistent state are kept outside the immutable root filesystem according to the contracts defined by this Specification and its children.


flowchart TD
    Platform["Platform"] -->|provides| Boot["Boot environment"]
    Boot -->|establishes as /| OS["Operating System"]
    OS -->|contains| Axisd["axisd"]
    Boot -->|transfers PID 1 to| Axisd

    class Axisd program

System Lifecycle

An Axis-based system progresses from Platform initialization through the Platform boot chain, establishment of the Operating System as the root filesystem, userspace initialization by axisd, normal runtime operation, and eventually shutdown or restart.

The Platform boot chain MAY include firmware, boot loaders, a Linux kernel, and Platform-specific early userspace before the Base OS runtime begins.

The Operating System itself remains immutable throughout this lifecycle. Runtime changes MUST NOT modify the OS Artifact from which the system was booted.

Filesystem Model

The root filesystem of an Axis-based Operating System is immutable and mounted read-only.

Files required only for the lifetime of a running system and state intended to survive reboots are represented separately from the immutable root filesystem. Their precise locations, lifetime, mounting behavior, and persistence requirements are defined by child Specifications.

Initialization

axisd is the initial userspace process of the Base OS runtime and MUST execute as PID 1.

A Platform MAY execute Platform-specific early userspace before the Base OS root filesystem is established. Such early userspace is not part of the Operating System.

Once the OS Artifact has become the root filesystem, the Platform boot environment MUST transfer execution to /sbin/axisd while preserving PID 1.

axisd is responsible for establishing the runtime environment required by the Operating System and for managing the system after initialization. Its detailed lifecycle and management behavior are defined by the axisd Specification.

Fundamental Invariants

The root filesystem is immutable. Normal runtime operation MUST NOT modify the OS Artifact.
The OS Artifact is used directly as the Base OS root filesystem. Boot MUST NOT require unpacking, reconstructing, or mounting a second root filesystem contained within the OS Artifact.
The Platform boot environment is separate from the OS Artifact. A Platform MAY use firmware, boot loaders, a Linux kernel, an initramfs, or other early userspace without those components becoming part of the OS Artifact.
axisd is PID 1 of the Base OS runtime. Once the OS Artifact has become the root filesystem, the Platform boot environment MUST transfer execution to /sbin/axisd as PID 1.
Mutable state is separate from the Operating System. Runtime and persistent modifications MUST NOT require modifying the immutable root filesystem.
The OS Artifact remains independent of the environment used to boot it. A compatible OS Artifact MUST NOT require modification or repackaging solely because it is booted by a different compatible Platform or operated by a different Runner.
Platform-specific support remains outside the OS Artifact. A Platform MAY provide Platform-specific kernel components, firmware, kernel modules, userspace services, and other runtime support required to operate the Operating System on its Devices.

Conformance

An Operating System conforms to the Base OS when it satisfies this Specification and all applicable child Specifications.

A Platform that boots an Axis-based Operating System MUST satisfy the Base OS contracts delegated to Platforms, including establishing the selected OS Artifact as the Base OS root filesystem and transferring execution to /sbin/axisd as PID 1.