# ASL/SYSTEMRESCUE-OVERLAY/1 - Intake Overlay Layout

Status: Draft
Owner: Architecture
Version: 0.1.0
SoT: No
Last Updated: 2026-01-17
Tags: [ops, rescue, overlay]

**Document ID:** `ASL/SYSTEMRESCUE-OVERLAY/1`
**Layer:** O3 - Rescue overlay profile

**Depends on (normative):**

* `ASL/HOST/1`

**Informative references:**

* `ASL/RESCUE-NODE/1`

---

## 0. Conventions

The key words **MUST**, **MUST NOT**, **REQUIRED**, **SHOULD**, and **MAY** are to be
interpreted as in RFC 2119.

---

## 1. Purpose and Scope

This overlay defines what exists at boot for a rescue intake environment. It
separates immutable tools from mutable runtime state and defines mount points
for local or remote ASL stores.

---

## 2. Overlay Layout

```
overlay/
├── usr/
│   └── local/
│       ├── bin/
│       │   ├── asl-intake
│       │   ├── asl-admin
│       │   └── asl-debug
│       └── lib/
│           └── libasl.so
├── etc/
│   └── asl/
│       ├── asl.conf
│       ├── federation.conf
│       └── logging.conf
├── etc/systemd/system/
│   ├── asl-intake.service
│   └── asl-preflight.service
├── var/
│   └── lib/
│       └── asl/
│           ├── runtime/
│           ├── cache/
│           └── locks/
├── run/
│   └── asl/
│       └── sockets/
└── mnt/
    └── asl/
        ├── local/
        └── remote/
```

---

## 3. Directory Semantics

* `/usr/local/bin` is immutable and MUST NOT be written at runtime.
* `/etc/asl` contains declarative configuration only.
* `/var/lib/asl` contains all mutable state for the rescue session.
* `/mnt/asl/local` is the mount target for a local ASL store.
* `/mnt/asl/remote` is an optional remote mount.

---

## 4. Local Store Layout (Informative)

When mounted, a local store typically exposes:

```
/mnt/asl/local/
├── blocks/
├── segments/
├── snapshots/
└── logs/
```

This internal layout is backend-defined and not mandated by this overlay.

---

## 5. Services

### 5.1 asl-preflight.service

Responsibilities:

* Detect storage backends
* Detect importable pools
* Write mode decisions to `/run/asl/mode`

### 5.2 asl-intake.service

Responsibilities:

* Read `/run/asl/mode`
* Start `asl-intake` with the selected backend

---

## 6. Configuration Defaults

`/etc/asl/asl.conf` SHOULD include at minimum:

```
mode = auto
local.mount = /mnt/asl/local
remote.endpoint = none
```

---

## 7. Versioning

Backward-incompatible overlay changes MUST bump the major version.