HostKernel

Hostkernel is a term used in computing to refer to the kernel that runs directly on the host machine in virtualization and container environments. It is the central component of the host operating system, handling resource management, process scheduling, memory management, device drivers, and hardware access. While guest operating systems run their own kernels inside virtual machines or containers, the hostkernel remains outside those environments and provides the underlying platform for them.

In virtualization, the hostkernel interacts with a hypervisor or VM monitor. It coordinates access to physical CPUs, memory, I/O devices, and network resources, and it may implement virtualization extensions through components such as KVM, Xen, or Hyper-V. The hostkernel must be robust and secure because flaws can affect all hosted workloads and the reliability of the virtual infrastructure.

In containerization, multiple containers share the hostkernel, isolating workloads using mechanisms like namespaces and control groups. This arrangement yields low overhead and near-native performance, but it also means a single kernel vulnerability can impact all containers, and kernel updates affect the entire host. Compatibility between container images and the hostkernel version is an important consideration for stability and security.

Common examples include the Linux kernel acting as the hostkernel on Linux-based hosts, and the Windows kernel in Windows environments used to run hypervisors in some configurations. The term emphasizes the separation between the host’s kernel and the guest environments it supports.