Glossary · Operating Systems & Software

Kernel

The kernel is the central part of an operating system that controls hardware, memory, processes, and the way programs request system resources.

Updated October 6, 2026

A kernel is the core component of an operating system. It runs in a privileged mode, manages CPU time, memory, devices, and networking, and exposes system calls that applications use to ask for those resources.

Why it matters

Because the kernel sits between applications and hardware, its bugs and settings affect everything above it. Kernel version determines supported hardware, file systems, and network features, and kernel vulnerabilities are among the most serious because they can give an attacker full control.

On Linux the kernel is only one piece; a distribution adds tools and packages around it.

Example

$ uname -r
6.1.0-18-amd64

This Linux command prints the running kernel release. Comparing it with the newest installed kernel tells you whether a reboot is needed to finish an update.

Common mistakes

  • Calling Linux an operating system when it strictly names the kernel. The full system also needs userland tools.
  • Updating the kernel package but not rebooting, so the old kernel keeps running.
  • Confusing kernel space with user space; a crashing app should not crash the kernel, a faulty driver can.

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