I work for Codethink on a project called Baserock, the goal of which is to solve problems in embedded systems development.

With package-based upgrades you need to be careful to not remove anything that a running program is using, and you need to avoid moving the file-system through invalid states. Distributions generally get this right, but it's a lot of work, and the complicated dance required to make this work, also makes it slow.

We decided to do away with packages to simplify things, so we do image-based updates by applying a binary delta to a snapshot and atomically flip to the new version. Currently the way to do this is reboot or kexec, but requires a service outage, so for Baserock I've been looking at a better way to do this.

In this talk I'm going to explain the various alternative approaches, why I settled on my current approach, the limitations of this approach, and future work to make this more reliable.