Appliance image
Also called: OS image, prebuilt image, golden image
An appliance image is a complete, pre-built operating system image that boots straight into a working application with no installation steps.
An appliance image is a full disk image — every dependency, service and configuration baked in — that boots directly into a working system.
The contrast is with an install script. A script runs apt, npm or pip on first
boot, which means the result depends on what upstream published that morning, whether the
network held, and which mirror answered. Two devices flashed a week apart can end up
running different software.
A baked image is deterministic: what shipped is what runs. It can be signed, checksummed and attested, so you can prove the bytes on the card are the bytes that were built. It also works with no network at all, which is what makes an air-gapped tier possible.
The trade-off is size and update cadence — you ship whole images rather than patches, which is why appliances pair the format with A/B slot updates.