What is User-mode Linux?

In Linux, user mode is a restricted operating mode in which a user's application or process runs. User mode is a non-privileged mode that prevents user-level processes from accessing sensitive system resources directly.

In user mode, an application can only access hardware resources indirectly, by calling system services or functions provided by the operating system. This ensures that the system's security and stability are maintained by preventing user processes from interfering with or damaging system resources.

Additionally, user mode also provides memory protection to prevent applications from accessing unauthorized memory locations. This is done by assigning each process its own virtual memory space, which is isolated from other processes.

In contrast to user mode, kernel mode is a privileged operating mode in which the operating system's kernel has full access to system resources, and can perform low-level operations, such as accessing hardware devices and managing system resources directly.