Boot Process Demystified
From power button to login screen
What Happens When You Press Power?
From the moment you press the power button to when you see your login screen, your computer executes a carefully orchestrated sequence of events. Let's demystify this process.
Boot Sequence Overview
Power On
0msBIOS/UEFI
~500msBootloader
~2sKernel
~5sInit System
~10sLogin
~15s🤔 What Most People Think
"I press the button and... magic happens?"
"Something loads something else, I guess?"
"The spinning logo means it's thinking?"
💡 What Actually Happens
A precise sequence of hardware and software initialization
Multiple handoffs between firmware, bootloader, and OS
Hundreds of services starting in parallel with dependencies
Why Should You Care?
Troubleshooting
Know where things can go wrong and how to fix them
Optimization
Speed up boot times by understanding bottlenecks
Security
Understand Secure Boot and boot-time security
Quick Facts
Modern Boot Time
5-30 seconds for most systems (NVMe + systemd can boot in under 5s)
Services Started
Typically 100-200 systemd units on a modern Linux desktop
UEFI vs BIOS
UEFI (2005+) replaced legacy BIOS for faster, more secure boots
Boot Disk
GPT replaced MBR to support disks larger than 2TB