Re: [docs] [PATCH 2/4] ref-manual/structure.rst: update with info on PERSISTENT_DIR

["Antonin Godard" <antonin.godard@bootlin.com>]

On Fri Jul 11, 2025 at 11:45 PM CEST, Richard Purdie wrote:
> On Fri, 2025-07-11 at 19:09 +0200, Alexander Kanavin via lists.yoctoproject.org wrote:
>> On Wed, 9 Jul 2025 at 09:57, Antonin Godard via lists.yoctoproject.org
>> <antonin.godard=bootlin.com@lists.yoctoproject.org> wrote:
>> > 
>> > Since we mention that SSTATE_DIR can be shared for multiple builds, also
>> > mention that PERSISTENT_DIR should be shared alongside SSTATE_DIR.
>> 
>> NO. These changes are incorrect, please do not merge or revert if
>> already merged.
>> 
>> PERSISTENT_DIR can be copied from one build directory to another when
>> bitbake is not running, but it cannot be shared between two active
>> builds.
>> 
>> If one wants to share sstate, they either have to setup a hash
>> equivalence server (and then sharing PERSISTENT_DIR is not needed), or
>> disable hash equivalency (in which case it is also not needed).
>
> The changes did merge and definitely are unclear.
>
> The point is that if you share sstate, you also need to have common
> hash equivalence data.
>
> That may be via having common hashequiv server, or, of you have a local
> sstate directory and delete the build directory, you need to preserve
> the hashequiv database file to make the sstate useful.
>
> You cannot have a common PERSISTENT_DIR shared by two builds, that is
> not supported.
>
> Hopefully Antonin can tweak things to make this all clearer. I should
> have caught this, sorry :/

Hi all,

Sorry! I drew a wrong conclusion from bug #15921, I will correct this soon
this week.

Alex, thanks for catching this.

Antonin

-- 
Antonin Godard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com