Comment 9 for bug 1572485

> Perhaps there's more unwrapped Sigar.new calls in the code.

The actual error in the stack trace [1]

> /usr/lib/ruby/vendor_ruby/ohai/mixin/from_file.rb:29: [BUG] rb_gc_mark(): unknown data type 0x10(0x7fe220c587b8) non object

looks very similar to that in LP: #1463835, see the comment [2] therein. That might be either unwrapped Sigar object,
or a different careless usage of rg_gc_mark

[1] https://bugs.launchpad.net/fuel/+bug/1572485/+attachment/4643100/+files/nailgun-agent.log
[2] https://bugs.launchpad.net/fuel/+bug/1463835/comments/12

Happy debugging,
          Alexey