Kernel designs 🧱

Types of kernels (with simple diagrams)

Kernels can be built in different ways. This changes performance, safety, and how boot and drivers are handled. Click each section and explore.

1) Monolithic kernel (Linux) 🧱 ▼

Simple definition: Many services (drivers, file systems, networking) run inside one big kernel space.

😊 Apps

User space

⚙️ One big kernel

Drivers + FS + Network inside

⚡ Hardware

Physical parts

Monolithic = “big kernel space”. Often fast and practical.

Strengths ✅	Weaknesses ⚠️	Examples
Fast (many calls stay inside kernel) Common and well-tested	Large trusted code area A buggy driver can crash the system	Linux

2) Microkernel (Minix concept) 🧬 ▼

Simple definition: Keep the kernel very small. Move many services (drivers, file systems) to user space.

🧑‍🔧 Services

Drivers, FS in user space

⚙️ Tiny kernel

Core basics only

⚡ Hardware

Physical parts

Microkernel = “small core + services outside”. Often safer, sometimes slower.

Strengths ✅	Weaknesses ⚠️	Examples
Smaller trusted kernel Better isolation (a driver crash may not crash everything)	More messaging between parts Can be slower or more complex	Minix (classic microkernel example)

3) Hybrid kernel (Windows, macOS) 🧩 ▼

Simple definition: A mix: tries to keep some microkernel ideas but also keeps performance by placing many services in kernel space.

😊 Apps

User space

⚙️ Hybrid core

Mix of ideas

🧑‍🔧 Extra services

Varies by OS

Hybrid = “balance safety + speed” (in practice).

Strengths ✅	Weaknesses ⚠️	Examples
Good performance Can still be modular	Not as small as a microkernel More complexity in design	Windows NT kernel (hybrid), macOS XNU (hybrid)

4) Exokernel (concept overview) 🧠✨ ▼

Simple definition: The kernel gives applications more direct control of hardware resources (with safety rules), and apps build what they need on top.

🧰 App libraries

Custom control

⚙️ Tiny exokernel

Safety + sharing

⚡ Hardware

Resources

Exokernel is often discussed as a research / concept idea.

Strengths ✅	Weaknesses ⚠️	Examples
Potentially very efficient Apps can be more flexible	Harder to build and maintain Not common in everyday PCs	Conceptual overview (research-style designs)

Different OSs, different kernels (table)

Operating System	Kernel Type	Boot Style (high-level)
Windows	Hybrid NT Kernel	UEFI/BIOS → Windows Boot Manager → NT kernel + services
Linux	Monolithic Kernel	UEFI/BIOS → GRUB (or other) → Linux kernel + init
macOS	XNU Hybrid Kernel	Firmware → boot process → XNU kernel + macOS services
Android	Linux Kernel	Boot chain → Linux kernel → Android runtime/services

Next: Windows Boot 🪟 Back: Kernel ⚙️