Restorable Apps

Restorable Apps are Compose Apps that can be restored in case of any Docker store damages, without needing to be re-downloaded from the Registry. This is achieved by a distinct way images can pulled and stored on a device.

Images are pulled from registries by the composectl utility, rather than pulling them by utilizing the Docker daemon’s regular functionality normally used for Compose Apps;
Images are stored in two places on a device. In addition to the regular Docker daemon’s image store (/var/lib/docker/image/overlay2 and /var/lib/overlay2), images are also stored in the folder defined in the aktualizr-lite config file. This defaults to /var/sota/reset-apps. The additional store path can be overridden in the *.toml config file by defining a value of [pacman].reset_apps_root.

Image layers are stored in the additional store in tar.gzip format. This helps to reduce the device storage cost of this feature. Effectively, the difference in the Docker store size and the Restorable Apps’ additional storage size is equivalent to the compression ratio of gzip.

Employment of Restorable Apps

Primarily, Restorable Apps are employed to:

Support “Factory Reset” feature;
Provide means to restore a Docker daemon’s store if it gets broken.

Both cases imply that a desired state of Apps can be restored—even if a Docker daemon’s store (/var/lib/docker) is deleted or broken—without needing to re-download images. Effectively, images are injected from the additional storage to the store in such cases.

Restorable Apps are enabled by default. The list of Restorable Apps is equal to the list of Apps enabled on a device (if defined, the value of compose_apps, otherwise all Target Apps). You may extend the default list of Restorable Apps in the following ways:

For manual registration, by invoking lmp-device-register with ‑‑restorable‑apps <comma‑separated app list>.
For auto registration, using --restorable-apps <comma-separated app list> with lmp-device-auto-register.
By setting reset_apps=<a comma-separated list of apps> in [pacman].reset_apps for a device/aklite config. You may change the given configuration for a specific device, a device group, or all devices (see Configuring Devices for details).

To disable Restorable Apps, specify an empty string "" as the value of <a comma-separated list of apps> in one of the previous options. For example, lmp-device-register --restorable-apps "".