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Re: Red Hat is moving from / to /usr/

On Wed, 7 Dec 2011 09:00:35 +0000, Simon McVittie <smcv@debian.org> wrote:
> On Wed, 07 Dec 2011 at 01:43:34 +0100, Marco d'Itri wrote:
> > http://git.kernel.org/?p=linux/hotplug/udev.git;a=commitdiff;h=12a362be5c1982f80dbfb75bda070208a2c99cdf
> > 
> > Discuss.
> As far as I can make out, their position is that a separate /usr is now only
> supported if you mount it from the initrd - which to be honest seems a
> reasonable way to keep existing separate-/usr systems working, without
> defeating the "/ is small" justification for a separate /usr by gradually
> migrating more and more of /usr into the root filesystem.
> It doesn't really address the "/ as recovery system" use of a separate /usr
> if your root filesystem can't boot unaided, but I'm far from convinced that
> a separate /usr makes / significantly more reliable, and an entirely
> separate installation (Debian Live on removable media, or a smaller Debian
> install in a separate partition that isn't normally even mounted) makes an
> even more reliable recovery system.

The problem with such rescue partitions is that if anything about your
setup is peculiar, then they are likely to rot in a way that ensures
that they will no longer support new features of the installed kernel on
the machine to be rescued.  Likewise, if you've had to build a custom
kernel to support your hardware, then default rescue media may well not
help you.

RedHat can probably safely ignore that, because their users are not
quite as inventive as ours, and they're only really trying to address
the middle of the bell-curve anyway.  That leaves us with
disproportionately more odd use cases, because they're not being catered
for by the commercial distros.

Also, as far as I've seen the default method for fixing RedHat systems
is to pop in a rescue disk (at least when I was an RHCX that was
certainly the suggested approach in their exams for many of the failure
modes). If that is the default solution anyway, then making it
impossible to use other recovery methods is not so much of a leap.

Personally, I think that resorting to rescue media is something of an
admission of defeat, but I'm probably a bit odd ;-)

I seem to occasionally find myself in situations where the machine
that's failed is the one that you'd use for downloading or burning the
rescue media, or for building the custom kernel needed for the hardware,
so that I'd have real pain if my only solution was getting hold of a
matching rescue disk.  People using ARM seems likely to make this
situation more likely, as there seem to be way to many flavours of ARM.

Having said all that, it would be nice if we made the default setup
include a rescue partition, with hooks to ensure that kernels are
updated on the rescue partition (preferable after the system
successfully boots with the new kernel, say), and it's generally kept
happy and ready for use.

Cheers, Phil.
|)|  Philip Hands [+44 (0)20 8530 9560]    http://www.hands.com/
|-|  HANDS.COM Ltd.                    http://www.uk.debian.org/
|(|  10 Onslow Gardens, South Woodford, London  E18 1NE  ENGLAND

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