What even is an OS now?

In his latest blog post, security researcher Thomas Ptacek explores the evolving definition of an operating system in the modern computing landscape. As software stacks become increasingly complex, the traditional boundaries between hardware, kernel, and user-space applications are blurring. Ptacek argues that modern environments—heavily reliant on containers, hypervisors, and managed cloud runtimes—have fundamentally shifted what we consider an OS. He examines how the abstraction layers provided by modern infrastructure often replace the core functions once handled by traditional operating systems. By analyzing the shift toward ephemeral, service-oriented architectures, the article questions whether the term 'OS' still holds its original technical meaning or if it has become a legacy label for a vastly different set of responsibilities. The piece invites readers to reconsider the fundamental components that define a platform's role in managing resources, security, and execution in today's cloud-native world.