Linux, usually very old and very well tested Linux. Things that are almost Linux, like LynxOS Lighter RTOSs like VxWorks. If it's simple box it may be bare m

Linux, usually very old and very well tested Linux. Things that are almost Linux, like LynxOS Lighter RTOSs like VxWorks. If it's simple box it may be bare metal. Oh, and sometimes Windows (but generally not for anything with a safety effect).