Re: [gentoo-dev] Idea: User centric kernel configuration

[Mike Pagano]

On 3/12/21 11:34 AM, Gerion Entrup wrote:
> Am Donnerstag, 11. März 2021, 17:41:45 CET schrieb Peter Stuge:
>> Hi,
>>
>> Gerion Entrup wrote:
>>> the Linux kernel has _a lot of_ configuration options, way too many to configure them by hand.
>>
>> I actually disagree strongly with that; I think it's important to
>> actively decide what kernels include, and I routinely do, but of
>> course not everyone will. I've made sure to include a kernel build
>> when teaching systems administration courses and would again.
>>
>> As the kernel becomes more complex the threshold for the first
>> configuration also rises, but it's still completely possible to learn
>> what you need in order to successfully configure your own kernel.
>> I guess it's on the order of a weekend project given some basic
>> understanding of computer architecture and programming.
>
> I think, we mean two different things here. I for myself also configured
> my own kernel(s) for years. I also actively teach students to do so.
> However, I have never looked into all 18000 configuration options. I
> don't understand them all (by far).
>
> Actually, most of the times, I do a `make localmodconfig`, click through
> various subsystems and activate what I think that it is useful or sounds
> nice. Then, to update a kernel, I use `make oldconfig` and answer the
> questions as good as I can (taking the default otherwise).
>
> If my kernel is not capable to do something (for example run docker
> containers), I take a look in the Gentoo Wiki and "copy" the options
> into my own config.
>
> But for me, this is not an informed decision. Of course, I learn
> something in this process, maybe also more than a precompiled kernel
> user, but I have by far not created a minimal config or even begin
> to understand all subsystems and different configuration options.
>
> I'm sure that this is similar to most Gentoo users.
>
> BTW, here is a project to create a minimal config (kind of "ideal"
> config) based on a "golden run" [1]. However, I have not compared such
> a config with my own homegrown config.
>
>
>>> This requires a mapping between user oriented "features" and the kernel
>>> internal configuration options.
>>
>> So the challenge here is that the kernel is disjoint from user space,
>> and while the kernel API remains stable over time consumer requirements
>> such as "docker" or "cryptsetup" will mean different things for
>> different versions of particular user space software.
>>
>>
>>> Do you think that it is useful and feasible to combine these two mechanisms?
>>
>> AFAIK there's no generic method for formal kernel requirements in user
>> space packages and there's also no sanctioned method for quering
>> kernel capabilities. The only thing available is /proc/config if that
>> was enabled in the kernel build, and there are of course reasons to
>> leave it out, and it only applies to the particular running kernel,
>> e.g. useless for cross-compilation. There, it would be possible to
>> read the kernel configuration file if the kernel source code is
>> available when the userspace package is being built, but that's not
>> guaranteed.
>>
>> In Gentoo, linux-info.eclass provides linux_config_exists() to do all
>> of this, but order to become a widespread success there would have to
>> be one method for upstreams to maintain these requirements as part of
>> their packages, rather than forcing the burden on package maintainers
>> to repeat the same detective task in every single distribution.
>>
>> I think it would be very useful to create something generic for that,
>> but that's certainly no small task.
>>
>> And realistically I only see it succeeding if Linux Foundation decides
>> to push it onto the world.
>
> Sorry, I may have expressed this not clearly. I guess, we actually have
> the same opinion here. I don't want to do this mapping automatically. I
> don't want a "fully automatic" config or touch any (user space) ebuilds.
>
> My idea is to patch Kconfig (as part of gentoo-sources) to provide the
> same "features" (i.e. mappings) that are already present in the Gentoo
> wiki.
>
> For example this could result in this installation description for Docker
> (within the Wiki):
> "To enable kernel support for Docker, enable
> 'Gentoo Linux -> Support for user space programs -> Docker'"
>
> This Kconfig flag than depends on all options that are needed for proper
> Docker support (as already described in the Wiki) like cgroups etc..
>
> This would allow users to configure there kernels the same way as before
> but with some additional convenience shortcuts.
>
> Of course, this is a high maintenance burden for the kernel package
> maintainers. Therefore, this mechanism maybe can be automated:
> Grep the wiki pages for kernel config snippets and automatically
> condense that in a Kconfig readable configuration option.
>
>
>>> A possible way could be to automatically extract the kernel config
>>> flags from the wiki pages and map them to Kconfig options.
>>
>> At very best that will only be valid for some particular point in time,
>> like current CONFIG_CHECK in ebuilds using linux_config_exists() are
>> only valid for particular package versions. At worst it's plain wrong
>> because the requirements have to be reverse-engineered downstream.
>
> Of course, the already existing kernel config snippets in the Wiki are
> best effort. My idea is to combine these snippets directly with Kconfig.
>
>
> Best regards,
> Gerion
>
> [1] https://vamos.informatik.uni-erlangen.de/trac/undertaker/wiki/UndertakerTailor
>


Hello,

If I am reading this correctly, you are looking for something like we 
have for systemd and openrc where you select something and we preselect 
a bunch of required/suggested kernel configs options.

I'm happy to add this to gentoo-sources for Docker based on the 
expertise of the gentoo developer individuals in the project.

Probably a bug to track this would be the best way for me to implement.

Or am I totally off base on your request?

Mike