* For class methods, prefer calling with `.`  over `::`.  `::` is typically just used to reference namespaces.
* Use LinuxAdmin.run! instead of regular run.  run! raises an exception when exit_status == 0, which is exactly what you want in this case.
* LinuxAdmin::run! take a :params Hash option which represents the params for the command, and handles proper escaping for the command line to prevent command line injection attacks.  So, the way to call it properly in your case is:

```ruby
params = {}
params["--bugzilla="] = "#{uri_opt}/xmlrpc.cgi" unless uri_opt.nil?
params["--debug"]     = nil unless debug_opt.nil? 
params["login"]       = [username, password]

LinuxAdmin.run!(CMD, :params => params)
```