System software product lines such as the embedded real-time operating system eCos are a state-of-the-art solution for application scenarios with a very low hardware resource profile. Being highly configurable at compile time, eCos can be tailored to the application in terms of inclusion or exclusion of fine-grained operating system features. The mandatory manual feature selection is carried out by the developer who knows the functionality essential for the application. This process requires profound knowledge of the feature semantics, is very time-consuming, and, in particular, error-prone-most probably resulting in a resource suboptimal or even dysfunctional operating system variant. The contribution of this article is an approach to automate the eCos configuration process to a major degree, therefore reducing the outlined disadvantages significantly. A thorough examination of configurable eCos features exhibits four feature categories of varying complexity: By applying standard model checking techniques and static analysis of the application source code, we show that for at least two feature categories the configuration decisions can be taken automatically. Complementing the approach with configlets-highly eCos specific analysis code-a third category is shown to be also coverable.