Message-ID: <1342212885.25704.4.camel@lade.trondhjem.org>
Date:	Fri, 13 Jul 2012 20:54:46 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Dave Jones <davej@...hat.com>, Greg Kroah-Hartman <greg@...ah.com>,
	"Ubuntu Kernel Team" <kernel-team@...ts.ubuntu.com>,
	Debian Kernel Team <debian-kernel@...ts.debian.org>,
	OpenSUSE Kernel Team <opensuse-kernel@...nsuse.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Simplifying kernel configuration for distro issues

On Fri, 2012-07-13 at 13:37 -0700, Linus Torvalds wrote:
> So this has long been one of my pet configuration peeves: as a user I
> am perfectly happy answering the questions about what kinds of
> hardware I want the kernel to support (I kind of know that), but many
> of the "support infrastructure" questions are very opaque, and I have
> no idea which of the them any particular distribution actually depends
> on.
> 
> And it tends to change over time. For example, F14 (iirc) started
> using TMPFS and TMPFS_POSIX_ACL/XATTR for /dev. And starting in F16,
> the initrd setup requires DEVTMPFS and DEVTMPFS_MOUNT. There's been
> several times when I started with my old minimal config, and the
> resulting kernel would boot, but something wouldn't quite work right,
> and it can be very subtle indeed.
> 
> Similarly, the distro ends up having very particular requirements for
> exactly *which* security models it uses and needs, and they tend to
> change over time. And now with systemd, CGROUPS suddenly aren't just
> esoteric things that no normal person would want to use, but are used
> for basic infrastructure. And I remember being surprised by OpenSUSE
> suddenly needing the RAW table support for netfilter, because it had a
> NOTRACK rule or something.
> 
> The point I'm slowly getting to is that I would actually love to have
> *distro* Kconfig-files, where the distribution would be able to say
> "These are the minimums I *require* to work". So we'd have a "Distro"
> submenu, where you could pick the distro(s) you use, and then pick
> which release, and we'd have something like
> 
>  - distro/Kconfig:
> 
>     config DISTRO_REQUIREMENTS
>         bool "Pick minimal distribution requirements"
> 
>     choice DISTRO
>         prompt "Distribution"
>         depends on DISTRO_REQUIREMENTS
> 
>     config FEDORA
>     config OPENSUSE
>     config UBUNTU
>     ...
> 
>     endchoice
> 
> and then depending on the DISTRO config, we'd include one of the
> distro-specific ones with lists of supported distro versions and then
> the random config settings for that version:
> 
>  - distro/Kconfig.suse:
> 
>     config OPENSUSE_121
>         select OPENSUSE_11
>         select IP_NF_RAW  # ..
> 
>  - distro/Kconfig.Fedora:
> 
>     config FEDORA_16
>         select FEDORA_15
>         select DEVTMPFS               # F16 initrd needs this
>         select DEVTMPFS_MOUNT  # .. and expects the kernel to mount
> DEVTMPFS automatically
>         ...
> 
>     config FEDORA_17
>         select FEDORA_16
>         select CGROUP_xyzzy
>         ...
> 
> and the point would be that it would make it much easier for a normal
> user (and quite frankly, I want to put myself in that group too) to
> make a kernel config that "just works".
> 
> Sure, you can copy the config file that came with the distro, but it
> has tons of stuff that really isn't required. Not just in hardware,
> but all the debug choices etc that are really a user choice. And it's
> really hard to figure out - even for somebody like me - what a minimal
> usable kernel is.
> 
> And yes, I know about "make localmodconfig". That's missing the point
> for the same reason the distro config is missing the point.
> 
> Comments? It doesn't have to start out perfect, but I think it would
> *really* help make the kernel configuration much easier for people.
> 
> In addition to the "minimal distro settings", we might also have a few
> "common platform" settings, so that you could basically do a "hey, I
> have a modern PC laptop, make it pick the obvious stuff that a normal
> person needs, like USB storage, FAT/VFAT support, the core power
> management etc". The silly stuff that you need, and that
> "localyesconfig" actually misses because if you haven't inserted a USB
> thumb drive, you won't necessarily have the FAT module loaded, but we
> all know you do want it in real life. But that's really independent
> issue, so let's keep it to just distro core things at first, ok?
> 
> Would something like this make sense to people? I really think that
> "How do I generate a kernel config file" is one of those things that
> keeps normal people from compiling their own kernel. And we *want*
> people to compile their own kernel so that they can help with things
> like bisecting etc. The more, the merrier.
> 
>                     Linus

We could at least make selection of a minimal set of drivers for the
more common virtualised platforms a lot easier.
Right now, you need to hunt through 30+ different menus in order to find
what you need to run in a basic KVM virtual machine...

Cheers
  Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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