Question

My problem is ruby recognizes require ‘packetfu’ and include PacketFu in IRB but does not work when I run it as a script. I want to know if it’s due to the way my gem directories are organized or if something odd is going on when I check-in as sudo to run the app.

Here is the error generated when I run it as a regular user:

  1 tMobile:~ cj3kim$ ruby packetfu.rb
  2 Simple sniffer for PacketFu 1.1.5
  3 /Users/cj3kim/.rvm/gems/ruby-1.9.3-p0/gems/packetfu-1.1.5/lib/packetfu/capture.rb:73:in `capture': Not root, so can't capture packets. Error:  (RuntimeError)
  4     from /Users/cj3kim/.rvm/gems/ruby-1.9.3-p0/gems/packetfu-1.1.5/lib/packetfu/capture.rb:46:in `setup_params'
  5     from /Users/cj3kim/.rvm/gems/ruby-1.9.3-p0/gems/packetfu-1.1.5/lib/packetfu/capture.rb:39:in `initialize'
  6     from packetfu.rb:9:in `new'
  7     from packetfu.rb:9:in `sniff'
  8     from packetfu.rb:20:in `<main>'

Does not work with sudo. Why?:

  9 The-BatMobile:~ cj3kim$ sudo ruby packetfu.rb
 10 /Users/cj3kim/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- packetfu (LoadError)
 11     from /Users/cj3kim/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
 12     from packetfu.rb:1:in `<main>'

Sample code from packetfu documentation for the simple sniffer program:

1 require 'packetfu'
  2 include PacketFu
  3 
  4 puts "Simple sniffer for PacketFu #{PacketFu.version}"
  5 
  6 iface = ARGV[0] || "en0"
  7 
  8 def sniff(iface)
  9         cap = Capture.new(:iface => iface, :start => true)
 10         cap.stream.each do |p|
 11                 pkt = Packet.parse p
 12                 if pkt.is_ip?
 13                         next if pkt.ip_saddr == Utils.ifconfig[:ip_saddr]
 14                         packet_info = [pkt.ip_saddr, pkt.ip_daddr, pkt.size, pkt.proto.last]
 15                         puts "%-15s -> %-15s %-4d %s" % packet_info
 16                 end
 17         end
 18 end
 19 
 20 sniff(iface)

Any help is appreciated. Thanks for looking!

Answer 1

Usually, it’s because the sudo environment can’t find any of your gems.

If you’re using RVM (and you should: rvm.io ), you can use rvmsudo instead, and that will preserve your Ruby environment.

If you can’t use RVM for whatever, reason, but you are using a modern version of sudo, you can try sudo -E to retain the environment.