[RAUC] Is it possible to change the [system]compatible= string after it has already been set/flashed?

[RAUC] Is it possible to change the [system]compatible= string after it has already been set/flashed?

[Brian Hutchinson via RAUC]

Hi,

Since it's common to produce boards with pre-programmed flash etc., is
it possible to change the [system]compatible= string when hardware
changes happen and the compatible string needs to be updated when it
has already been set previously?

I know that hooks could be used to key in on bundle version
information to implement things like downgrade barriers etc., but it
just feels more elegant to update the compatible string to describe
hardware changes that are human readable than to keep up with a eye
chart truth table of version number combinations to determine what is
safe to downgrade, upgrade etc.

I was thinking if maybe [system]variant-file was used in system.conf,
then a pre-install hook could easily manipulate the compatible string,
but not sure that would work.

This almost feels like the intermediate update that's necessary with
changing rauc versions ... but I searched the mail archives and
couldn't find anyone wondering about this sort of thing so thought I'd
ask Jan, Enrico & Co. their thoughts.

Regards,

Brian

Re: [RAUC] Is it possible to change the [system]compatible= string after it has already been set/flashed?

[Jan Lübbe via RAUC]

On Thu, 2024-12-05 at 22:38 -0500, Brian Hutchinson via RAUC wrote:
> Hi,
> 
> Since it's common to produce boards with pre-programmed flash etc., is
> it possible to change the [system]compatible= string when hardware
> changes happen and the compatible string needs to be updated when it
> has already been set previously?
> 
> I know that hooks could be used to key in on bundle version
> information to implement things like downgrade barriers etc., but it
> just feels more elegant to update the compatible string to describe
> hardware changes that are human readable than to keep up with a eye
> chart truth table of version number combinations to determine what is
> safe to downgrade, upgrade etc.
> 
> I was thinking if maybe [system]variant-file was used in system.conf,
> then a pre-install hook could easily manipulate the compatible string,
> but not sure that would work.
> 
> This almost feels like the intermediate update that's necessary with
> changing rauc versions ... but I searched the mail archives and
> couldn't find anyone wondering about this sort of thing so thought I'd
> ask Jan, Enrico & Co. their thoughts.

You can use a 'install-check' hook [1] in the bundle to override the normal
compatible check. 

Also, the variant handling is built in a way so that you can start setting the
system variant in new systems that behave differently and you can target the
different images correctly.

Regards,
Jan

[1] https://rauc.readthedocs.io/en/latest/using.html#install-hooks

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Pengutronix e.K.                           |                             |
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Re: [RAUC] Is it possible to change the [system]compatible= string after it has already been set/flashed?

[Jan Lübbe via RAUC]

Hi again,

On Thu, 2024-12-05 at 22:38 -0500, Brian Hutchinson via RAUC wrote:
> This almost feels like the intermediate update that's necessary with
> changing rauc versions ...

Enrico pointed me to this part.

Updating RAUC versions normally does *not* require an intermediate
update. An intermediate update is only needed if you explicitly create
bundles which use new features:
https://rauc.readthedocs.io/en/latest/basic.html#forward-and-backward-compatibility

Regards,
Jan
-- 
Pengutronix e.K.                        |                             |
Steuerwalder Str. 21                    | https://www.pengutronix.de/ |
31137 Hildesheim, Germany               | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686        | Fax:   +49-5121-206917-5555 |