# SmartVM Base Image Bundles

This directory documents the project-owned base image manifest format. The actual kernel and rootfs binaries should be hosted as release assets or in object storage, not committed to git.

## Bundle Layout

A hosted bundle should expose three files:

```text
smartvm-minimal-v1-x86_64.manifest.json
vmlinux
rootfs.ext4
```

The manifest is the only file shape `smartvm` needs to know. It points at the hosted kernel and rootfs artifacts and records checksums.

## Manifest Fields

- `schemaVersion`: currently `1`
- `bundleId`: stable cache key, using letters, numbers, dot, underscore, and dash only
- `arch`: `x86_64` or `aarch64`
- `firecrackerVersion`: Firecracker version validated with this bundle
- `rootfsType`: `ext4` or `squashfs`
- `rootfsIsReadOnly`: use `true` for squashfs or immutable rootfs images
- `bootArgs`: kernel boot args to use with the bundle
- `kernel`: hosted kernel artifact URL/path plus `sha256` for URL artifacts and optional `sizeBytes`
- `rootfs`: hosted rootfs artifact URL/path plus `sha256` for URL artifacts and optional `sizeBytes`
- `fileName`: optional plain output filename; path separators are rejected

`sha256` is required for hosted URL artifacts. `sizeBytes` is optional but helps catch incomplete downloads.

## Cache Behavior

Downloaded bundles are cached under `/tmp/.smartvm/base-images` by default. The cache keeps two bundles unless `maxStoredBaseImages` is configured. Eviction is announced with `console.warn`.