Linux seems to require 'ldconfig' runs after shared libraries are installed. I haven't bothered digging into why, but many debian C library packages run ldconfig as a postinstall step.
I'd like to avoid postinstall actions, so this needs research to see if this is possible.
rubygems on Debian/Ubuntu is not very recent in most cases, and some gems have a requirement of rubygems >= a version you have available.
Further, debian blocks 'gem update --system' which you can get around by doing:
% gem install rubygems-update % ruby /var/lib/gems/1.8/gems/rubygems-update-1.3.1/bin/update_rubygems
I recommend packaging 'rubygems-update' (fpm -s gem -t deb rubygems-update) and possibly running the update_rubygems as a postinstall, even though I don't like postinstalls. I haven't looked yet to see what is required to mimic (if possible) the actions of that script simply in a tarball.
Debian python packages all rely on some form of python-central or python-support (different tools that do similar/same things? I don't know)
As I found, disabling postinst scripts in Debian causes Python to stop working. The postinst scripts generally look like this:
if which update-python-modules >/dev/null 2>&1; then update-python-modules SOMEPACKAGENAME.public fi
I don't believe in postinst scripts, and I also feel like requiring a postinstall step to make a python module work is quite silly - though I'm sure (I hope) Debian had good reason.
So, I'm going to try working on a howto for recommended ways to build python packages with fpm in debian. It will likely require a one-time addition to site.py (/usr/lib/python2.6/site.py) or some other PYTHONPATH hackery, though I don't know just yet.
It will also require special setup.py invocations as Debian has patched distutils to install python packages, by default, to a place that requires again the python-central/support tools to run to make them work.