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Re: Summary of the 2009-01-06 Packaging Committee meeting



On Wed, 2009-01-07 at 14:48 -0800, Toshio Kuratomi wrote:
> Doug Ledford wrote:
> > On Wed, 2009-01-07 at 11:30 -0800, Toshio Kuratomi wrote:
> > 
> >> So, with the exception of the arch-specific files in %{_datadir} which
> >> has changed for the new release, this seems to be FHS-kosher to me.  If
> >> you can get me a link to the new package I can take a look and see if
> >> the situation there is worse.
> > 
> > Well, not really (unless the FHS changed since I last read it).  The
> > solution was to create an %{mpidir} macro that was
> > %{name}/%{version}-%{opt_cc} and use %{_libdir}/%{mpidir} as a prefix
> > for the entire install.  So, libraries, binaries, man pages, etc config
> > files, they all reside under %{_lidbir}/%{mpidir}.  That's an acceptable
> > layout for things in /opt according to the FHS, but not for distribution
> > provided files in %{_libdir}, and distribution provided files are
> > prohibited from being placed in /opt.  Hence the conundrum.
> > 
> > 
> It depends on how you interpret the FHS, I suppose.  In the old
> packages, the config files are in /etc, the arch independent data (help
> files) are in a subdir or /usr/share/openmpi/, and most of the
> arch-specific files are under /usr/lib/openmpi/.  This satisfies the
> overarching goal of the FHS, separation of sharable and unsharable data.
>  it also satisfies the goal of separating arch specific and arch
> independent files.
> 
> The question is whether the binaries can go there or have to go in
> /usr/bin and whether the libraries can go there or must go directly in
> /usr/lib.  For the libraries, we often put private libraries in a
> subdirectory of /usr/lib.  These differ in that they're public
> libraries.  I lean towards this being okay.  The binaries being in the
> subdirectory of %{_libdir} doesn't have as much precedent.  Perhaps we
> need to make that usage explicit in the Guidelines just like %{_libexecdir}?
> 
> Looking at the new package I see that there's config files under
> %{_libdir}/openmpi.  I think these need to go in %{_sysconfdir} instead.
>  This is more important than binaries and libraries for several reasons:
> 
> 1) Having them in %{_libdir} breaks the sharable/unsharable boundary

Not really, but that's due to typical usage of these specific files.  I
would tend to agree that files normally in /etc are something that are
intended to be edited on a per machine basis.  These files, even though
they are in %{_libdir}/%{mpidir}/etc, are not something that you would
edit on a per machine basis.  If anything, things like the
openmpi-default-hostfile would be edited on a per version basis (and
with this layout they have a per version etc directory to be contained
in).  This is because on a large cluster, you are likely to either allow
all the machines in the cluster to participate and would put all the
machines in the cluster in this config file, or you would have a segment
of the cluster that is dedicated to running this version of openmpi and
only those machines would be in this file.  Either way, for all the
machines you want running this version of openmpi by default, the file
would be the same (this assumes that a person might start the openmpi
job from any machine in the cluster that's part of the appropriate
group, you may have a control machine doing things instead, in which
case you really only have to edit the file on that one machine and all
the others will be passive clients and not care about the contents of
this file).

Now, the even more common scenario is that you have multiple different
MPI apps.  The admins typically would do a login per app so that the
default login environment for a given app is already pre-configured.
Amongst that would be things like selection of the right mpi, and host
files specific to what machines that app is allowed to run on.  Those
would all be in the home directory for the login and wouldn't require
editing the system wide etc files in here.

> 2) They are files edited by system admins and looked at by the user.
> They should be in a predictable place for this reason.

In truth, they aren't edited much at all, and relying upon them is
frowned upon.  But, as I noted above, even if they are edited, they are
still generally shareable due to the nature of MPI clusters.

> As you noted, there's also some FHS regressions compared to the current
> package:
> 
> - include files are under %{_libdir} instead of under %{_includedir} --
> If these are arch specific include files then this makes sense.  If not,
> they belong in %{_includedir}.  What things were broken by doing that?

Two things here.  Remember that we allow simultaneous installs of
different versions of OpenMPI (you can't get it out of the yum channel
this way, and you can't do upgrades of OpenMPI or it wipes older
versions out, but you can download anything after the openmpi-1.2.5 I
think and install different copies of different versions, although that
does not include multiple releases of the same version, I only use n-v
in the naming, not full n-v-r, so for instance you couldn't have 1.2.7-5
and 1.2.7-6 installed, but you can have 1.1.8 and 1.2.7 installed at the
same time) in order to meet user requirements.  Differing versions can
have differing header files, so we can't just use %{_includedir}/%{name}
or they might conflict.  Putting the includes alongside the libs works
for just about any devel package that needs to use it because you can
just use --prefix to configure it to the right place.  Of course, the
gcc wrappers also know about where the right include files are, so it
works with mpicc without doing anything.  The second reason is that for
fortran use in particular, the header file produced during build is
different for different arches.  So aside from the multi-install issue,
there is an arch specific component to the headers that can't be worked
around due to limitations in the fortran language (or that's my
understanding, I haven't touched fortran since 1991 or so).

> - man dirs are now under %{_libdir} instead of under %{_datadir}.  What
> broke by having these under %{_datadir}?

Multiple installs and also if we put it under datadir, then we have to
fiddle with manpath when we set up the environment.  With them where
they are, the presence of %{_libdir}/%{mpidir}/bin in the exec path is
enough for man to track down the right man page automatically.

> -Toshio
> 
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-- 
Doug Ledford <dledford redhat com>
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              http://people.redhat.com/dledford

Infiniband specific RPMs available at
              http://people.redhat.com/dledford/Infiniband

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