Reliance has expanded Polyester manufacturing facilities by 550000 Tons per annum. These have a large scale automation for manufacturing control and automation, manufacturing information, product handling, product quality controls, product storage, retrieval for despatch and supply chain logistics. Deviation has been made from Unix to Linux all over the systems and the experience has been most satisfied. This is the largest and firstever complex application of Linux. The paper presents the application part of Linux in Polyester manufacturing automation. Information Technology is extensively used to achieve advantages in cost, productivity and customer satisfaction in every sector of economy. This article is all about strategic use of IT in achieving these objectives in one of the world's largest single location POY manufacturing set up. Linux OS is the key element in this mission .The success of this example should strengthen the decision to use Linux in mission critical operations by others.