Re: [gentoo-dev] rfc: locations of binaries and separate /usr

[Alex Alexander]

On Fri, Jan 06, 2012 at 08:35:32AM -0500, Rich Freeman wrote:
> On Thu, Jan 5, 2012 at 5:36 PM, Alex Alexander <wired@g.o> wrote:
> > If people are really interested in keeping a tight, self contained root,
> > we need to:
> >
> > - establish a [tight] list of software we consider critical for /
> > - fix/patch software in that list so it can run without /usr there
> > - create /bin => /usr/bin/ symlinks for above software (simplifies
> >  things if packages start hardcoding /usr/bin here and there)
> > - move everything else in /usr/bin/
>
> You're missing one thing:
>
> - establish a list of all the configurations that will actually work
> with this self-contained root
>
> I think this is why there is so much disagreement over whether this is
> a good move.  If you have a really simple configuration, then the
> self-contained root concept works reasonably well (though apparently
> we'll have to heavily patch newer versions of udev or abandon it to
> sustain this).
>
> However, if you have a very complex configuration the current
> self-contained root is already broken and you need an initramfs
> anyway.  For in-between cases things might work now but that is likely
> to change as upstream moves on.
>
> The binary distros don't have users tweaking their kernels and init
> scripts, so they basically have to design for worst-case.  Gentoo can
> get away with designing for more of an average case since we just tell
> anybody with a complex case to go read a howto and configure what is
> necessary (and we like to do that stuff anyway).
>
> We can choose not to like it, but it sounds like maintaining a
> self-contained root for even the typical case will become untenable.
> Those who argue that having /usr on a separate partition simply
> shouldn't be supported are basically just saying that our
> "self-contained root" should include everything in /usr which seems to
> defeat the whole point of a "self-contained root" anyway.
>
> It seems to me that the most reasonable approach is to not force the
> issue, but not deviate greatly from upstream either.  That means
> accepting that over time the rootfs will become less and less capable
> of working on its own, and immediately improving tools like dracut to
> overcome these limitations.  Users who can get away with it can avoid
> using an initramfs, at least for a time.
>
> Sure, it is all open source, and Gentoo can swim upstream if we REALLY
> want to.  However, this only works if developers are willing to spend
> the time constantly fixing upstream's tools.  It sounds to me like the
> maintainers of packages like udev/systemd/etc want to actually move in
> the same direction as upstream so in practice I don't see that
> happening.
>
> Now, Gentoo is about choice, so one thing we should try to do as much
> as possible is understand the limitations of the various
> configurations and make it clear to users when they do and don't need
> an initramfs.  To be honest, tight coupling worries me more than the
> /usr move, since that has a lot more potential to constrain the
> choices we can offer our users (which is a great deal of the value
> that Gentoo offers).  I understand its advantages, but it seems
> somewhat contrary to "the unix way."

That's why I wrote "tight list". I do not expect the self-contained root
to be able to handle everything /usr (or a complete initramfs) would.
What it could and couldn't do is something that needs to be decided, but
some work is already done there - it's just a bit messy and incomplete
and because most people don't care it keeps getting worse.

The important thing here is to make a clear definition of where we draw
the line and make sure things work the way we want them to.

I agree with you in that at some point patching may become too time
consuming, but I still believe that if we do this properly, with a
well-defined plan and list of packages we want to keep in / (with
symlinks to be compatible with whatever others are trying to do), we
won't be alone in this. Gentoo may be one of the most hardcore
power-user distros out there, but we're certainly not the only one.

Now, if only we had people interested enough in doing this... :)
-- 
Alex Alexander | wired
+ Gentoo Linux Developer
++ www.linuxized.com