Yes, the Linux kernel is indeed monolithic. In a monolithic kernel, all of the operating system's core services, such as process and memory management, file system, device drivers, network handling, etc., are included in the same address space. This design provides high performance and efficiency since all services are directly accessible without the need for message passing or context switching. However, unlike traditional monolithic architectures, the Linux kernel is also modular. This means that certain elements, usually device drivers, can be compiled and inserted into the kernel at runtime, which allows for greater flexibility without needing to shut down and restart the entire system. This hybrid design combines the efficiency of monolithic kernels with the modularity and extensibility of microkernels.