[maemo-developers] Considering /opt and MyDocs in your packages

[From: Andrew Flegg]

On Thu, Sep 10, 2009 at 09:52, Graham Cobb <g+770 at cobb.uk.net> wrote:
> On Thursday 10 September 2009 07:53:37 Andrew Flegg wrote:
>> The use of /opt/_package_/ on Diablo, Fremantle, Mer, Ubuntu is
>> entirely concordant with the FHS:
>
> Well, not really.  That FHS section is clear that if you are using /opt,
> nothing should be installed in (for example) /usr/bin (or even
> /opt/bin).

True. I meant nomenclature and so on. But the following is my FHS++ idea:

    /opt/foo/bin/foo
    /opt/foo/share/some_big_data_file.wad
    /opt/foo/lib/some_bespoke_library.{py,so}
    /usr/bin/foo -> /opt/foo/bin/foo
    /usr/share/applications/hildon/foo.desktop
    /usr/lib/dbus-1/services/foo.service
    /usr/share/icons/..../foo.png

It *seems* much cleaner, architecturally, for end-user apps. Perhaps
with the mass of symlinks from maemo-optify as a solution for
libraries etc.

However, m-vo's apparently got reasons about just having a
"/opt/maemo" prefix over a "/opt/_package_" structure. I look forward
to reading it ;-)

[snip sensible stuff]
>
> I have no idea whether this will work for python -- how does python find
> things like libraries (or whatever the equivalent concept is in python)?

There's a PYTHON_PATH. Python's particularly troublesome as lots of
additional packages (like python-twitter and python-evolution) are
extra dependencies of applications.

How well will dpkg cope when, say, python-core has created
/opt/maemo/usr/lib/python2.5/site-packages and /usr/lib/python2.5 ->
/opt/maemo/usr/lib/python2.5 and then python-evolution comes along and
tries to put /usr/lib/python2.5/site-packages/evolution ->
/opt/maemo/usr/lib/python2.5/site-packages/evolution in? I suspect,
this over symlinking could be problematic.

The real (and best) solution is a unionfs. IIRC, there isn't one in
the mainline, because of problems in some use cases. However for the
use case of "we want to be able to install apps over a single
partition", the solutions are viable, IMHO.

Valerie Aurora recently wrote some LWN articles on the issues, which
make good reading:

    http://lwn.net/Articles/324291/
    http://lwn.net/Articles/325369/
    http://lwn.net/Articles/327738/

Index and more thoughts at:

    http://valerieaurora.org/union/

I would have thought that in the time still available compiling one of
these as a module and mounting the partition over / (or /usr) would be
entirely viable. m-vo, thoughts?

Cheers,

Andrew

-- 
Andrew Flegg -- mailto:andrew at bleb.org  |  http://www.bleb.org/
Maemo Community Council chair