OS Format

A summary of OS formats in Clear Linux


(C) 2018 Intel Corporation, CC-BY-SA-3.0

Manual section





A format defines a range of OS versions that have compatible update metadata and content. An update client can update a system from the oldest version in the format to the latest version in the format without worrying about compatibility issues in the update content for the version it is updating to.

A format bump occurs when the update metadata or content is changed in such a way that will cause client updates to break. In this case the format number must be incremented so clients will not attempt to update to the new versions in the new format without crossing the format boundary. Update clients update only to the latest build in their format. Once that update is complete the update client may then update forward again because the last version in the current format has identical content to the first version in the new format, including the new update client needed to understand the new format.

Because the update system in Clear Linux (swupd) has auto-update turned on by default most users will never be aware of their system changing to a new format. Those users who have disabled auto-update may occasionally see swupd perform two updates in a row when they only invoked swupd update once. This is because swupd detects when it crossed a format boundary and immediately re-executes an update to carry it to the latest version in the new format. This re-execution will actually invoke the new version of swupd that was delivered in the first update.

Format bumps are simply a way for Clear Linux to introduce breaking changes to the OS without breaking user’s update stream or workflow.