Version method for kernel_module

[aladmit]

Hi! This version method for kernel_module.

issue: #993

[chris-rock]

Thank you @postgred for this great addition. I added ideas for minor improvements.

Right now, rubocop is failing with:

Offenses:
lib/resources/kernel_module.rb:46:42: C: Use delete instead of gsub.
      cmd.exit_status.zero? ? cmd.stdout.gsub("\n", '') : false
                                         ^^^^^^^^^^^^^^

Could you please sign-off your work, too. Instructions are available here: https://github.com/chef/inspec/blob/master/CONTRIBUTING.md#developer-certification-of-origin-dco

[chris-rock]

maybe:

if inspec.os.name == 'centos' && inspec.os.release.to_i == 5
   ...
else
   modinfo_cmd = "modinfo -F version #{@module}"
end

[chris-rock]

It may be better to return nil, since we could not determine a version

[chris-rock]

@postgred Thank you for the quick improvements. The implementation looks great. I was just thinking, we should add this to our integration tests as well, to ensure it works across linux systems. The test is located here: https://github.com/chef/inspec/blob/master/test/integration/default/kernel_module_spec.rb#L21-L23

This will be executed with every travis run. See https://github.com/chef/inspec/blob/master/.travis.yml#L28-L55

[aladmit]

@chris-rock We can't add this to integration tests because modinfo can't work in docker. Example:

root@580f55841391:/# modinfo video
libkmod: ERROR ../libkmod/libkmod.c:556 kmod_search_moddep: could not open moddep file '/lib/modules/4.9.5-200.fc25.x86_64/modules.dep.bin'
modinfo: ERROR: Module alias video not found.

[chris-rock]

@postgred Agreed. Thank you.