Create a Debian package from a Ruby gem

Question

I'm attempting to create a Debian package for a simple utility I wrote with fpm and bundler but am having difficulties. Here's how I generate my .deb (I assume you've checked out sns and are in it's root):

$ bundle install
$ rake install
$ fpm -s gem -t deb --prefix /var/lib/gems/1.8/ pkg/sns-0.1.1.gem 
Successfully installed sns-0.1.1
1 gem installed
md5sum: : No such file or directory
Created /home/blt/projects/com/carepilot/sns/rubygem-sns_0.1.1_all.deb
$ dpkg-deb -c rubygem-sns_0.1.1_all.deb  | grep sns_hosts
-rwxr-xr-x root/root       762 2011-08-18 22:28 ./var/lib/gems/1.8/gems/sns-0.1.1/bin/sns_hosts
-rwxr-xr-x root/root       398 2011-08-18 22:28 ./var/lib/gems/1.8/bin/sns_hosts

Which is how it should be. Unfortunately

$ cat /var/lib/gems/1.8/bin/sns_hosts 
#!/home/blt/.rbenv/versions/1.9.2-p290/bin/ruby
#
# This file was generated by RubyGems.
#
# The application 'sns' is installed as part of a gem, and
# this file is here to facilitate running it.
#

require 'rubygems'

version = ">= 0"

if ARGV.first =~ /^_(.*)_$/ and Gem::Version.correct? $1 then
  version = $1
  ARGV.shift
end

gem 'sns', version
load Gem.bin_path('sns', 'sns_hosts', version)

The gem creates a shunt which incorrectly sets the ruby interpreter to that of my development environment; rather a problem when pushing to other computers. How might I influence the interpreter which is set in the shunt script?

Answer 1

gem install has -E parameter to rewrite the shebang line to use /usr/bin/env. So you need to edit fpm to do this while packaging the gem. /usr/lib/ruby/gems/1.8/gems/fpm-0.3.7/lib/fpm/source/gem.rb line 120 has the parameters, you can try to add it there.