OpenIoT & ELC Europe 2016

Configuring the rootfs to be read-only makes embedded systems more robust and reduces the wear on flash storage. In addition, by removing all state from the rootfs it becomes easier to implement system image updates and factory reset.

In this presentation, I show how to identify components that need to store some state, and to split it into volatile state that is needed only until the device shuts down and non-volatile state that is required permanently. I give examples and show various techniques of mapping writes onto volatile or non-volatile storage. To show how this works in practice, I use a standard Yocto Project build and show what changes you have to make to achieve a real-world embedded system with read-only rootfs. In the last section I consider the implications for software image update. Expect a live demonstration