Re: [OE-core] [PATCH] image_types.bbclass: make fsck optional

[Ross Burton <Ross.Burton@arm.com>]

On 31 Dec 2025, at 22:52, Levi Shafter via lists.openembedded.org <levi.shafter=elder-tomes.com@lists.openembedded.org> wrote:
> 
> The fsck in oe_mkext234fs() was added to prevent an extra reboot on the
> target:
> 
> https://git.openembedded.org/openembedded-core/commit/?id=a93d0059341
> 
> This has the side effect of increasing delta between images which
> prevents reproducibility. In many cases, the added security provided by
> image reproducibility is worth the extra reboot upon first booting the
> target. The use of fsck should be included by default, but left
> configurable.
> 
> [YOCTO #16110]

There’s slightly more information in the bug report than here, which links to a video from YPS 2024.12 talking about how fsck will modify timestamps in file systems, so whilst the initial ext4 from mkfs is reproducible, we do a fsck to clear flags and they’re no longer bit-identical.  Is this the only source of non-determinism that you’re observing?

I don’t think adding an option is the right thing here as you’re swapping one problem (non-reproducible ext4) with another (filesystem dirty, needs a reboot).  As the video shows, we should be passing timestamp information at construction time to avoid this problem. Would you be able to work on a patch to do that instead?

Thanks,
Ross