The article provides an overview of Linux online environments based on various virtualization technologies. Linux online virtual environments are systematized, the advantages and disadvantages of considering groups of online virtual environments are listed. The work also gives the comparison of standalone online Unix/Linux terminals in terms of their possible use for a course in operating systems.The author analyzes the experience of teaching a Linux operating system to students of different specialities, and in particular, discusses the virtualization tools used, including Linux online environments (AmazonEC2, Cloud 9, a virtual machine for NDG Linux Essentials course).The study states the need for developing an individually designed system to provide Linux online virtual environments and elaborates the requirements to this system. The work also discusses potential challenges which the developers of Linux online virtual environments for teaching operating systems may face, including the problem of finding a balance between availability and stability of virtual environments on the one hand and the realism of students’ learning experience on the other hand.