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

[Rich Freeman]

On Wed, Jan 4, 2012 at 10:19 AM, Steven J Long
<slong@××××××××××××××××××.uk> wrote:
> I was under the impression that anyone using lvm+raid (+luks) on root
> already has an initramfs, and there are docs out there about that, but sure,
> improving those docs and the software is always a good idea.

Anybody running root on lvm+raid(+luks) is already using an initramfs.
 However, the guide I linked does not run root on lvm/luks - just on
raid1, which does not require an initramfs.  That guide puts
everything BUT root on LVM, assuming that baselayout/sysvinit/openrc
on root can mount everything else.

The existing initramfs tools do not yet mount /usr regardless.  I'm
sure RedHat and others pursing a read-only /usr required at time of
boot will be looking to rectify this, so Gentoo is moving along with
upstream for dracut/etc here.

> Yeah I've been using lvm for several years now, with a separate /usr and no
> initramfs, though not on root. For the last few months, I've been running
> with the tweaked udev startup scripts I mentioned before, so /usr is mounted
> before udev starts (which is possible since I don't have any requirement on
> udev-initialised hardware to mount local drives.)

That's basically my configuration as well.  However, I don't really
want to set the goal of making Gentoo support my own configuration.
In any case, having a more robust initramfs solution for separate /usr
should support this and many other configurations.

>
> Regardless of the ability to backup just /usr, I'm still not convinced about
> moving every binary there. It certainly isn't necessary, in that the
> packages we install respect prefix, and there's no need to change the
> ebuilds to make packages work; further most admins already have their own
> backup scripts in-place.

I think that the path of least resistance is to move with upstream -
let's not try to force everything into /usr unless that becomes a
consensus with many other distros.  However, we can at least look to
accomodate things like udev that are moving in this direction so that
it doesn't create sparks within Gentoo.

>
> I for one, would like to be able to run in single-user mode off just the
> rootfs, in case for instance, something goes wrong with lvm and /usr won't
> mount; and I don't want to duplicate all those utilities in an initramfs. If
> that's not going to be possible, fair enough: that's life.
>

I hear you.  No harm in supporting this as long as seems reasonable,
but you're going to be stuck without udev from the sound of things,
and that is a lot to lose.

You should give dracut a shot - it does quite a bit automagically
though for some reason it doesn't set up my raid properly (I can do it
with a simple mdadm --assemble --scan from the dracut shell), and it
doesn't mount /usr yet.  So, it isn't there, but it does quite a bit
just the same.

Rich