Software update is primarily carried out by the Update Daemon. However, the Supervisor and start also have a role to play in rolling-back when updates fail. start also supports installation (via firmware update or other means) of read-only file systems containing full "golden" systems.

The Update Daemon accepts "update pack" files, which contain software/firmware update instructions and associated data, such as libraries, executables, and resource files.

Update packs can be fed to the Update Daemon via the Sofware Update API or through the toolsTarget_update tool.

The Update Daemon includes hooks that allow update packs to be digitally signed and/or encrypted for security reasons.

The mksys tool will automatically generate an update pack file containing the system update.

The update-pack tool can also be used to create update packs containing individual app updates and app removal instructions.

The Update Pack Format update pack file format is documented here.

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