Applications

There are a variety of applications for virtual machines such as UML. The main ones include

• Kernel debugging and development
• Process debugging in situations where the kernel is doing something inexplicable - stepping through the relevant portion of the kernel can quickly uncover the problem
• Sandboxing - this includes jailing potentially hostile code and untrusted services, as well as safely running new versions of the kernel, new distributions, and new services
• Education - using virtual machines instead of physical ones greatly simplifies the logistics of running courses on operating system design, system administration, network administration, and clustering
• Virtual hosting - the applications in the hosting industry are obvious; customers get root access to their own virtual machine without having to colocate a physical server
• A Linux environment for other operating systems - once UML is ported to other operating systems, it provides a completely authentic Linux environment

It has become apparent that UML can be configured in many more ways than just a single virtual machine running on a single host. The rest of this section discusses applications that take advantage of this flexibility.