[OpenAFS] Storing system binaries in afs redux (/usr /opt /var)

[Russ Allbery]

Kevin <openafs@gnosys.biz> writes:

> It seems that nobody sees this as worth doing, but from the
> documentation, it looks as though this concept was factored into the
> design of afs.  Would anyone care to comment on:

> a) whether or not they are storing any local machine system binaries in
> afs-space (obviously, stuff not needed immediately at boot-time
> like /usr and /opt, maybe /var);
> b) whether or not they think doing so is a good idea, bad idea, or
> neutral;
> c) if someone thinks it's a good/bad idea, reasons for this perspective;
> d) thoughts related to permission problems mentioned by Jim Rees that
> arise from doing this, and the best way (or some ways) to resolve them;

Historically, many sites have done this in many different ways, from
putting /usr in AFS to even running whole machine images out of AFS,
involving a varying degree of hacks and local workarounds for the
differences between AFS file semantics and Unix semantics.

I think part of the reason why you're not getting a lot of response is
that I think there's a general trend away from doing this towards managing
system software on local disk due to a variety of factors (significant
improvements in the capability of native package managers, huge increases
in the average size of disks, loss of expertise in the workarounds
required to keep things running out of AFS, and convergence on
industry-standard practices for system maintenance and away from local
methods, to name a few).  My take on this from a few years back was that
some sites continue to do this and are happy with it and have a large
number of local tools built up around doing it that are fairly specific to
them, but few sites are picking this up as a practice to move towards.
Kind of like Moira.  :)

That being said, it certainly is possible.  /usr is the easiest partition
to move, since most distributions already have support for mounting /usr
from a network file service.  The primary issues, as previously mentioned,
are figuring out how to update the software in AFS with the appropriate
permissions and dealing with cross-directory hard links.

> I've been experimenting with the concept in several Gentoo machines that
> are all on the same afs cell and in fiddling with an OldWorld Apple
> machine with very limited local diskspace and running Debian, I'd like
> to use the concept in order to install a bunch of software that I
> otherwise would not be able to install due to space constraints.

It's certainly far, far easier if you can convince the software to install
in some other path than /usr (/usr/local, for instance) and just mount
that from AFS.  Getting the system software moved into AFS will be more
work than only moving additional add-on software that can be built with a
different prefix.

-- 
Russ Allbery (rra@stanford.edu)             <http://www.eyrie.org/~eagle/>