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

[Gerion Entrup]

Am Freitag, 12. März 2021, 19:28:51 CET schrieb Mike Pagano:
>
> On 3/12/21 1:04 PM, Gerion Entrup wrote:
> > Am Freitag, 12. März 2021, 17:40:02 CET schrieb 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?
> >
> > You are right, but Docker is just an example. Ideally, this would exist
> > for every wiki page that explains which kernel config options need to be
> > set to make XY possible.
> >
> > Gerion
> >
>
> Specific Request -> Bug -> Discussion -> Implementation -> Release
>
> I think we can move past generics and get specific.

Done: https://bugs.gentoo.org/775956

Gerion