[gentoo-amd64] Re: Installing into a 32-bit chroot?

[Duncan <1i5t5.duncan@cox.net>]

Peter Humphrey posted <200509041702.07690.prh@gotadsl.co.uk>, excerpted
below,  on Sun, 04 Sep 2005 17:02:07 +0100:

> I'd like to see if I can install gambas into my 32-bit chroot jail. It's
> masked out of everything but vanilla x86 systems, which I think is what I
> have in /mnt/gentoo32 (the chroot jail).
> 
> Using emerge to install gambas brings all sorts of other things, including
> a duplicate xorg-x11 installation, which seems a bit excessive to me. How
> do I go about emerging into /mnt/gentoo32 with full X functionality etc,
> but without all the baggage? Perhaps someone's already done this and can
> advise me.
> 
> I don't really understand properly how chroots work, and in particular
> whether it's possible to install, e.g., gambas in /mnt/gentoo32 and have
> it use libraries etc. elsewhere. Or do I really have to install a
> virtually complete gentoo 32-bit system to enable it to work?

I don't really know what that is, but esearch says "a RAD tool for BASIC".
Is it X based?  If so, you'll need the 32-bit xlibs and whatever else it
needs, withh appropriate headers, accessible from the 32-bit chroot so it
(or whatever dependencies it has) can compile against them.

The 32-bit chroot stuff in the technotes explain a bit about how to set it
up and what you can remount in your chroot and what not.  The
compatibility packages do contain the 32-bit xlibs in binary form, but I'm
not sure they have all the headers and the like for you to actually
compile against.  Thus, I'm not sure whether you have to compile X in the
chroot or whether you can short-circuit that by making the binary compat
packages available in the chroot.  Do note, in any case, that the compat
packages aren't all that optimized, so you might be better off compiling x
in 32-bit anyway, if just to get the optimized libs.

Here's how all that works in terms of X.  You'll be running the 64-bit
X-server.  That's fine.  32-bit stuff can connect to it.  However, you
can't mix 32-bit and 64-bit executables and libraries.  You can't load
64-bit X client-libs into your 32-bit X-client app.  That just doesn't
work, for the same reason you can't load 32-bit codecs in a 64-bit mplayer
or 32-bit plugins in a 64-bit browser (tho konqueror has a plugin proxy
that does the job).  As I said, the 32-bit binary compatibility libs do
contain the necessary X client-libs.  However, they may not contain the
headers necessarily to actually compile against them, thus being useful
for 32-bit precompiled stuff only.

So... for now, you'll likely have to compile all of X in 32-bit mode as
well.

FWIW, that's going to change with xorg-7.0, the modular-X now under
development (there's an -rc in portage, hard-masked for testing). 
Upstream is splitting the monolithic package into a rather large number of
component modules, and Gentoo is doing likewise.  When it's all done,
packages won't depend on X, but on the specific X-modules they need, the
client-libs for most X client-apps, and specific other modules as needed. 
Thus, most folks will be able to avoid compiling at least all the extra
drivers for hardware they don't have, and in cases like this, only the
bare minimum necessary packages would be compiled to fill the
dependencies, likely only xlib.

Back to the now.  If gambas isn't an X app, the dependency may be down the
dependency chain a bit.  It's  possible you could avoid it by tweaking
your 32-bit chroot USE flags.  You'll probably want them fairly minimal,
anyway, certainly in the 32-bit make.conf, and make use of  package.use to
turn on specific flags where you /do/ want them.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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