[docs] [PATCH 1/2] ref-manual/variables.rst: document the IMAGE_CONTAINER_NO_DUMMY variable

[Quentin Schulz]

Hi Antonin,

On 12/12/25 11:22 AM, Antonin Godard via lists.yoctoproject.org wrote:
> Added in OE-Core with commit f0645e172bb8 ("image-container.bbclass:
> Error if not using linux-dummy").
> 
> Signed-off-by: Antonin Godard <antonin.godard at bootlin.com>
> ---
>   documentation/ref-manual/variables.rst | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
> index 71fe11b83..ac7b85992 100644
> --- a/documentation/ref-manual/variables.rst
> +++ b/documentation/ref-manual/variables.rst
> @@ -3955,6 +3955,13 @@ system and gives an overview of their function and contents.
>         variable, see the :ref:`ref-classes-image_types`
>         class file, which is ``meta/classes-recipe/image_types.bbclass``.
>   
> +   :term:`IMAGE_CONTAINER_NO_DUMMY`
> +      When inheriting the :ref:`ref-classes-image-container` class, this variable
> +      can be set to "1" to allow a :term:`PREFERRED_PROVIDER` for the Linux kernel
> +      (``virtual/kernel``) different than ``linux-dummy``.

than the default*

"""
In that case, :term:`PREFERRED_PROVIDER` also needs to be specified for 
``virtual/kernel``. This is only useful if you want to have a kernel 
built for your container images.
"""

Or something like that? I only guessed the last sentence as I'm 
wondering what are the use-cases for setting this variable. We should 
tell the user why they would like to use it maybe? That could help with 
searching on how to do something rather than what the variable does.

> +
> +      This variable should be set from a :term:`Configuration File`.
> +

Are you sure about that? This variable is handled from a recipe class, 
itself inherited only when the IMAGE_FSTYPES contains "container". The 
examples in meta-virtualization all have it set in an image recipe.

Cheers,
Quentin