Discoverable Disk Image (DDI) #

DDIs (Discoverable Disk Images) are self-described file system images that follow the DPS ( Discoverable Partitions Specification), wrapped in a GPT partition table, that may contain root (or /usr/) filesystems, system extensions, configuration extensions, portable services, containers and more, and are all protected by signed dm-verity all combined into one. They are designed to be composable and stackable, and provide security by default.

Image Format #

The images use the GPT partition table verbatim, so it will not be redefined here. Each partition contains a standard Linux filesystem (e.g.: squashfs), so again this will not be redefined here. The DPS defines the GUIDs to use and the format of the dm-verity signature partition’s JSON content.

Image Version #

If the DDI is versioned, the version format described in the Version Format Specification must be used. The underscore character (_) must be used to separate the version from the name of the image. For example: foo_1.2.raw denotes a foo DDI with version 1.2.