unix administrator

My business is in need of a Unix administrator to provide ongoing support when it comes to troubleshooting and problem resolution. We are looking for someone with the knowledge and experience to solve issues which may arise in our system with regard to user management and access control. Having the ability to monitor the system is also important since this is our primary area of concern. As far as communication is concerned, it is preferable that contact be handled primarily over email, though we would also consider Skype or Freelancer messaging system as alternative solutions. Ultimately, we need a highly competent and reliable Unix Administrator to ensure our system is running efficiently and securely.