Anatomy of the Linux Boot Process
Boot Camp
A deep dive into the Linux boot process covers UEFI, GRUB, kernel initialization, and userspace startup.
To most users, booting a computer is a passive, 20 second event. You press the power button, a splash screen flashes, and moments later your desktop appears. Behind that familiar sequence, however, control of the machine passes through a carefully orchestrated chain, from firmware to bootloader to kernel to userspace, before your Linux desktop is finally ready to use.
Understanding the boot process will come in handy when something goes wrong and you're dropped into an emergency shell.
Phase 1: Hardware Initialization
Before Linux can boot, the system firmware must first bring the hardware into an operational state. When you power it on, the processor begins executing built-in startup instructions stored in the firmware. This firmware, stored in non-volatile flash memory, initiates the hardware discovery and initialization process, functionally replacing the legacy Power-On Self-Test (POST).
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