Re: [RAUC] Only Application FS Update

["Enrico Jörns" <enricojoerns@web.de>]

Hi Caglar,

Am 18.10.2017 um 14:45 schrieb Kilimci, Caglar:
> Hi all,
> 
> I would like to use RAUC to update just my application FS so I do not have double root FS. In other words, only one root FS but double application FS. If I create an update bundle and install it, RAUC only install "slot.appfs.0". How can I configure RAUC to install different slots?
> 
> Here are my manifest file and system configuration:
> 
> # cat bundle/manifest.raucm
> [update]
> compatible=Phytec
> version=2
> 
> [image.appfs]
> sha256=05f23d6b732519342f265ed2605276585d487e34555be5ae927328164cd83c26
> size=135
> filename=appfs.tar.gz
> 
> # cat /etc/rauc/system.conf
> [system]
> compatible=Phytec
> bootloader=barebox
> 
> [keyring]
> path=ca.cert.pem
> 
> [slot.rootfs.0]
> device=/dev/mmcblk0p2
> type=ext4
> bootname=system1
> 
> [slot.appfs.0]
> device=/dev/mmcblk0p5
> type=ext4
> 
> [slot.appfs.1]
> device=/dev/mmcblk0p6
> type=ext4

well, different things.
First of all, I recommend to install only well-tested software states.
I.e. an appfs tested together with a specific rootfs state.
Now, this does not mean that the rootfs necessarily changes over
different iterations of the appfs and that not each update of an appfs
requires a (real) update of the rootfs.

But, with your design you seem to pin the rootfs to a fixed state that
cannot be changed anymore. It is only possibly to change the appfs.
Is that assumption true? Or do you have another 'factory' slot you can
run RAUC from to update you rootfs?

Now, the normal way RAUC determines how to update a specific slot is by
detecting the booted slot and all other slots being 'active' at the same
time. RAUC will detect your booted rootfs slot and all other slots
having this slot mentiond as their 'parent' as active slots.

In your config, you (intentionally) do not have any relation set between
the appfs and rootfs. This way, RAUC cannot detect that any of your
appfs is 'active' an thus chooses the 'next' one to install.

At the moment, 'next' means the next inactive slot of same class listed
in the system configuration. There is no further metric atm. Thus, you
cannot manually select appfs.1 for installation if that is what you
intended to do.


Now, the key aspect is, if you have only a single rootfs, you must have
a different switching point than 'conventional' approaches.
Thus, my question is where and how you do select which appfs to use?
Here is the point to a) let the RAUC boot selection algorithm interact
with and to b) perform the detection of the slot booted.

If you do not intend to update your rootfs, remove it from the slot list
and set appropriate bootnames for appfs 0 and 1.

But, to lead you in the right way it would help to know a bit more about
your motivations for the design you made.


Best regards

Enrico

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