Read only image?

I was just wondering how much writing to the SD cards goes on when using resin images. In my experience using SD cards on Raspberry Pi and other boards is a no-no for remote systems, they will corrupt themselves soon enough.
Ideally any files systems required for boot up should be mounted read only.


Thanks for the question. We are very careful not to write to the SD card at all as far as we can - the root file system is read-only.

However we do expose /data which allows persisting of data across power cycles, but this is entirely user-controlled.

Best, Lorenzo

That is excellent. Thanks.

I will be avoiding /data

Presumably the Docker images are written to a different partition and there is some risk associated with upgrading that which cannot be avoided. Then there is environment variable setting.

Yes, indeed the Docker images are located on a separate partition, with careful use of caching wear can be minimised here! See our docs on optimising builds and Docker best practices for tips.

Best, Lorenzo

Correct me if I’m wrong, but it looks like is using the docker copy-on-write layer to persist runtime state also outside the data partition. This is the default docker behavior.

But I think it would be very useful to (optionally) mount / in the container as read-only. I would consider this best practice for all container based deployment, embedded or not.