Virtualisation / 'cloud' infrastructure.
http://www.venus.co.uk/ I built their virtualisation, or 'private cloud', or 'VPS', if you will, infrastructure from the ground up, without the aid of a GUI, it is in use providing VPS services to customers to this day.
Member of AICS ([login to view URL]), agree to be bound by their Code Of Practise. Happy to sign an NDA, 10+ year qualified computing (honours) graduate Linux expert, sysadmin, and web developer. Signed up ages ago, only used this site properly since 2012. Will provide a resume to clarify if you're worried about a lack of feedback thus far.