[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: from / to /usr/: a summary

On Sat, Dec 24, 2011 at 07:03:10PM +0800, Paul Wise wrote:

> > I'd still like to know what the compelling reason for the change is
> > though.

> Apparently the reason is simply that our upstreams (who it sounds like
> are predominantly driven by Redhat folks) are dropping support for /
> and /usr on different partitions and that re-adding that support or
> maintaining the existing support is too much work for the Debian
> maintainers involved. At least that is what started the thread. Things
> like this is why getting involved upstream is important for Debian
> maintainers and probably why items 2 and 4 exist in our social contract.
> I would encourage those who care about this issue to start getting
> involved in the relevant places and submitting patches. It sounds like
> the ability to run a system with split / and /usr is *very* likely to
> disappear unless people who care decide to work in it.

I don't think that sounds very likely at all, because so far *no one* has
provided *any* evidence in this thread, or in any upstream discussions I've
been able to find, of any regressions that would be introduced into Debian
by upstream's "not supporting" starting udev before mounting /usr.

"It's too much work to move the libraries to /lib" is nonsense and no
justification at all.  Our build systems don't make installing libraries to
/lib as easy as they should, but it's not actually difficult, and no one who
finds this genuinely difficult has any business being the maintainer of a
library so core that it's needed at boot time by the system anyway.  It's
certainly far less work for the handful of affected libraries to be moved
than it is to make countless users repartition their systems!

The one and only example I've ever seen of an upstream decision that would
impact the bootability of existing initramfsless systems with a separate
/usr was a udev rule that would inject name information from
/usr/share/misc/pci.ids into the udev database, *for consumption by other
applications*.  This would be a gratuitous incompatibility; no one appeared
to be arguing that this information needed to be there for the benefit of
udev itself.  But I believe the decision has since been reversed upstream

If someone would give even *one* example where something legitimately needed
by a udev rule could not be moved from /usr to / without breaking interfaces
or otherwise complicating matters, then that would be worth discussing.  But
so far, nobody has done so - having to move shared libraries between
directories certainly doesn't qualify - so I continue to regard this as just
so much upstream FUD.

On Sat, Dec 24, 2011 at 08:00:50PM +0800, Paul Wise wrote:

> The package that started the thread was udev, there are examples of
> libs that need to be in /lib in the beginning of #652011.

Yes, and it's a rather short list.  I'll be happy to provide patches for
these packages.

On Mon, Dec 26, 2011 at 08:25:12PM +0100, Marco d'Itri wrote:
> No, it's not about "patches". More and more things just need /usr at 
> boot time, and the solution is to mount it in the initramfs.
> The only alternative would be to keep moving stuff from /usr to /, which 
> kind of defeats its purpose.

I don't agree that it defeats the purpose to move libraries needed at boot
time to /; I think that given the wide range of uses to which Debian is put,
it's important for us to be disciplined about the size of our base system
and our startup, and keeping track of the libs in /lib is one tool that
helps with this.  So rather than defeating the purpose, I would say that
requiring libs used in early boot to move to /lib provides a useful
deterrent against growing the system unnecessarily.

> Also, mounting /usr in the initramfs allows to explore the / to /usr 
> move, which if practical will bring many benefits and allow supporting 
> new features.

I think I've heard of one new feature, full-filesystem snapshotting, that
this would enable.  I can see that this would be useful and that some people
may want to do it, and that this is worth exploring; I only object to
requiring people to choose between /usr as a separate partition and
initramfsless booting if it's not necessary.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek@ubuntu.com                                     vorlon@debian.org

Attachment: signature.asc
Description: Digital signature

Reply to: