Re: [RAUC] Question about updating using Casync in RAUC v1.8

["Enrico Jörns via RAUC" <rauc@pengutronix.de>]

Hi Ohara,

Am Mittwoch, dem 02.07.2025 um 02:28 +0000 schrieb 大原 匠汰 via RAUC:
> Hi,
> I have a question about updating using Casync in RAUC v1.8.

Note that this version of RAUC is already 3 years old and should probably not be used for new
developments.

> 1. The documentation says that when updating using Casync,
> the current SLOT in the boot is used as the seed and the differences are downloaded.
> https://rauc.readthedocs.io/en/v1.8/advanced.html#rauc-casync-support 
> If this is the case, will rewriting the current SLOT during the update cause problems?

What's the use case for rewriting the current slot?
In most cases, this should be the slot the system is currently booted from.

> 2.If so, is it necessary to set the SLOT to ReadOnly?

The casync seed store is internally realized using symlinks with storage locations encoded.
After seeding, when actually reading a chunk from the store, this should be hashed and compared
again and produce an error internally if the underlying data changed. This should lead to ignoring
this seed chunk and to download the chunk from the (remote) chunk store instead.

So, yes, in general the seed slot should be read-only.
But it should also work if some of the data gets corrupted between seeding and writing.

Further details on this are probably more a casync-related question.


Regards, Enrico

> 3.If not, or if it is not necessary to set ReadOnly, please tell us why.
> 
> That is all.
> 
> Regards,
>       Ohara
> --------------------------------
> OSAKA NDS Co.,Ltd.
> Ohara Shota
> e-mail: shota.ohara@nds-osk.co.jp
> --------------------------------
> 

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