The Root Filesystem Image v2 Update Module does not support this as you have seen as well. But the internal rootfs-image updater supports this as it is using HTTP range-requests to write data in chunks (1MiB), and this way it can keep track of where it is.
You take a look at the code.
Let’s say I want to upload a root fs partition with the A/B mechanic (i.e. a dual rootfs artifact) with the kernel inside, but I also want to upload an extra data partition at the same time (in the same artifact). The two partitions are “linked” but still dissociated on disk. That is why I was talking about extending the dual rootfs update module behavior.
Thanks for clarifying. Now I understand. In this case you have two options:
- deploy the “extra data partition” as part of the rootfs image and e.g install it in one of the Mender state-scripts
- Create two separate Mender Artifacts (
.mender) and deploy them individually.
Even though the specification of the Mender Artifact format does allow multiple payloads with different types (which what you ultimately would like I believe), this is not yet implemented in code and something that will be added further down the road.