Kernemodulerne

Kernemodulerne are components of an operating system kernel that can be loaded into the kernel at runtime to extend its functionality without requiring a reboot. They enable optional features such as device drivers, file system support, and networking support that would bloat a monolithic kernel if compiled in by default.

Most modern kernels separate core kernel code from modules. Modules are typically compiled separately and placed in a dedicated directory, and they are loaded and unloaded through a module loader. In Linux, modules commonly have the .ko extension and are managed with tools like modprobe, insmod, and rmmod. The current set of loaded modules can be inspected with lsmod, and the kernel validates module dependencies to ensure proper load order.

Lifecycle and management: modules can be inserted when hardware is available or when a new capability is needed, and removed when memory is tight or the feature is no longer required. A module may depend on symbols exported by other modules, and missing dependencies prevent loading. System logs and the kernel message buffer provide diagnostics during load and unload operations.

Security, stability and policy: many systems implement module signing and restrictions to prevent loading unsigned or untrusted modules. Loading modules taints the kernel, which can affect debugging and support. Administrators can blacklist unwanted modules to avoid conflicts or security risks.

Typical examples include device drivers for new hardware, alternative file systems, network drivers and virtualization support such as hypervisors. Kernel modules also allow third-party and proprietary functionality to be added without modifying the core kernel.

Historically, the concept arose in Unix-like systems and was popularized in Linux, where loadable kernel modules became a standard mechanism for extensibility. In Danish technical usage, kernemodulerne refers to this same concept in the kernel architecture.