Re: [PLUG] /bin and /sbin

[sean finney <seanius@seanius.net>]

On Thu, Nov 03, 2011 at 01:17:13PM -0400, Rich Freeman wrote:
> On Thu, Nov 3, 2011 at 11:54 AM, Amir Tahvildaran <amir@mathforum.org> wrote:
> Yup - on slashdot, and a few weeks ago this was a huge debate on the
> gentoo-dev mailing list.

And quite some debate on the debian side as well.  

> The basic issue is that apparently booting without /usr available is
> already broken on some configurations (mainly involving bluetooth -
> like having a bluetooth keyboard).  The more complex udev rules rely
> on stuff in /usr, and there is a huge pile of dependencies if you want
> to move that stuff to the root.

It used to be that the initramfs was only what you needed to mount /
(and not everyone even needed an initramfs!), and / was just for
everything you needed to fix or mount everything else (including /usr
if seperate).  Having a small / could be advantageous in a number of
specialized situations, and being able to mount it (even read-only)
even when everything else was totally fucked, is consistantly a life-saver.
Hell I even had to do that just a couple weeks ago, when someone forgot
to update some FC drivers in tandem with a kernel upgrade.

> Fedora is basically saying let's forget about the old way of doing
> things and just stick everything in /usr and make our initramfs
> smarter (dracut in their case - btw dracut is worth looking at as a
> general initramfs tool).  Then you can put /usr on a read-only
> filesystem and just about everything associated with your distro is in
> one place, which isn't a bad idea for when you have a million clones
> of a single config in a datacenter.

Basically their / got too complicated and big, so they're giving up on it
and moving everything into the initramfs.  so the initramfs is the new /, and
the bootloader is the new initramfs.  of course your options for fixing the
system from the initramfs are a hell of a lot more limited than from /, and
in debian anyway the complications between / and /usr aren't as big (largely
because we followed closer to this thing called the FHS (which is itself
ironic given Lennart Poetering's deriding statements about the FHS).

so this is yet another example of "linux plumbers" re-inventing the wheel
and managing to make it a bit less round at the same time because their
new tool or subsystem doesn't quite meet the full featureset of what
it's replacing.  Not every linux system is a desktop, especially not servers,
but that's how they seem to be viewing it these days.

On Thu, Nov 03, 2011 at 01:33:27PM -0400, Sean M. Collins wrote:
> Ah, this brings back lots of painful memories about filesystem layouts
> in Linux distros. I switched to FreeBSD just because they have a
> sensible layout.
> 
> FreeBSD uses /bin and /sbin for the base system, then /usr/local/bin and
> /usr/local/sbin for ports (equivalent of packages in Fedora-ese)

Linux systems that more closely adhere to the FHS *do* have a rather sensible
layout, but historically RH/Fedora based systems have not bothered themselves
with such silly ideas.  Debian is probably the most anal on this point,
even in cases when it might otherwise annoy authors of projects where they
want it to work in some other way.

> > The basic issue is that apparently booting without /usr available is
> > already broken on some configurations
> 
> Ah - FreeBSD's layout traditionally is with /usr as separate partition.
> Never assume your partitions will always be readable, let alone
> writable. As long as your root partition mounts you're in business in
> FreeBSD.

That's the same idea on linux, you shouldn't need more than / to get the
rest of your system up and running.  But with the various userlandification
projects (many of them from the same set of people, grr....) it's getting
harder and harder to do.  I'm kinda expecting the next step to be them
requiring the entire OS to be on the same filesystem (i.e. /var).

</rant> :)

	sean
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