Re: deb 'streams', 'capabilities', relocation
"Christopher W. Curtis" <ccurtis@aet-usa.com> wrote:
>As far as stability, I don't see the problem. The SA choses to relocate
>relocatable packages and should be knowledgeable enough about the
>network to do it properly. Not every package would be a candidate for
>relocation (base-files, for instance). But things like the gimp most
>certainly can live in a completely shared space, as can packages like
>amanda, which would need both shared and local settings. If you want to
>put a big disclaimer about relocating packages that's fine, but there's
>no inherant stability problem with them.
The stability problem I see is in the system, not in individual
packages: in particular, dependencies. If I create a package that
depends on, say, vim-rt (>= 5.7), vim-rt (<< 5.8), I can rely on being
able to find vim data files in /usr/share/vim/vim57. If the sysadmin has
relocated /usr/share in vim-rt to /opt/foo, I can't do this any more. I
suppose you could carry out the substitution on all packages (hmm,
quadratic time in an already slow dpkg ...), but the problem is
compounded when packages install binaries which are then expected to be
on the $PATH.
Yes, knowledgeable sysadmins can probably deal with unexpected breakage
like this, but many sysadmins these days (i.e. people installing Debian
on their home computers) are less than knowledgeable, and if they use
relocation unwisely it may cause confusion to the point of making Debian
look badly inconsistent. To quote
/usr/doc/debian-policy/libc6-migration.text.gz, this would "make Debian
systems inconsistent with each other, something we should avoid at
(nearly) all costs".
Sysadmins who really need to relocate a small number of packages can
compile them from source, which apt, the various devscripts, and Debian
policy make a very simple task; this also gives them the opportunity to
intervene in the packaging of delicate-to-integrate programs like trn.
If they want to relocate something more like the whole of Debian, then
perhaps they really ought to be using symlinks and/or mounting, say,
/usr somewhere else, rather than possibly impairing the consistency of
the Debian system for the sake of a relatively infrequent situation.
--
Colin Watson [cjw44@flatline.org.uk]
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