[oe] [OE-core] RFC: Reference updater filesystem

[Jens Rehsack]

> Am 03.12.2015 um 17:45 schrieb Mariano Lopez <mariano.lopez at linux.intel.com>:
> 
> [...]
> 
> Thanks to all for your input. The conclusion of this thread is:
> 
> 1. One size doesn't fit all.
> 2. Most of the people was fine with the image based update.

Where is the image stored? I read over referred http://sbabic.github.io/swupdate/
and realized that the update image must include a stripped rootfs and the entire
software for rootfs as well as probably the recoveryfs/maintfs and some logic
for updating the data volume (eg. migrator for database of business logic).

This can be very large ... and must be stored somewhere.

Next question: how bullet proof is the swupdate?

Out process is designed (because of typical users can't interact) to can survive
surprising power outage. Unfortunately we didn't manage to split out u-boot into
separate updatable parts, so we can't benefit from it - but technically (if one
has implemented for heir targets), our script updates and continues after power
comes back.

I think, beside the question of having an image containing the update (we have such
an add-on, too - for legacy devices without he modern Yocto based firmware), the
question of stability should be evaluated, too.

> 3. The recommended way to keep the configuration is to have a separated data partition.
> 4. The partition scheme would be:
>    1. boot. This is the usual boot partition
>    2. rootfs. Partition used for normal operation.
>    3. maintenance. This partition will be used to update rootfs.
>    4. data. This will hold the configuration files. Not modified by
>    updates.

Cheers
-- 
Jens Rehsack - rehsack at gmail.com