[OE-core] Contents of non-rootfs partitions

[Khem Raj]

On 11/22/16 1:05 AM, Kristian Amlie wrote:
> Hey
> 
> In Mender we are using a dual rootfs partition layout (A/B layout) with a persistent data partition on the side. We're using wic to do the actual image building.
> 
> However, putting files into this data partition is not a straightforward operation ATM. All recipes in OE put files into the rootfs only, and we'd like there to be a way to specify that files should go into the data partition.
> 
> I haven't seen any straightforward way to do this in OE. Some suggestions for how it could be done:
> 
> * A "DATA_FILES" variable (like "IMAGE_BOOT_FILES"), where you can list files you'd like to be included. This is very straightforward, but has the disadvantage of being a bit hairy when paths are involved, and it doesn't allow for much logic.
> 
> * Keep a special "data" directory, something similar to sysroot, where recipes could install files into in order to have it included on the data partition. We could potentially have a bbclass for use in recipes to make this more streamlined.
> 

Firstly, it needs to be defined what the data partition is about.
1. is it some pre-initialized/seeded data that can then be modified during
subsequent boots ?
2. Is it read-only data which is then used to populate r/w data segments in
RAM during boot
3. is it data that does not change over the course of install and reboots of
the device

> * Have a special recipe that users can bbappend, which specifically install to the data partition (this might also need a "data" directory, like above).
> 
> It's also possible that this should be generalized further so that it doesn't only apply to a data partition, but to any non-rootfs partition.
> 
> I'm willing to invest some time in this, but I thought I'd gather some opinions first.
> 
> Thoughts?
> 

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