[OE-core] Contents of non-rootfs partitions

[Kristian Amlie]

On 23/11/16 00:45, Khem Raj wrote:
> 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

It's preseeded, but modifiable data, that survives complete rootfs
updates. IOW if you overwrite either of your A/B rootfs partitions, the
data partition and its content survives.

-- 
Kristian