Linux Boot Process Explained: From Firmware to Userspace
Overview The Linux boot process is a precisely orchestrated multi-stage sequence — from firmware power-on self-test to kernel loading, all the way to userspace service startup. Each stage has its specific responsibilities. Understanding the complete boot process not only helps troubleshoot boot failures but also enables boot performance optimization. This article proceeds layer by layer from the firmware level through BIOS/UEFI, GRUB2, initramfs, kernel initialization, and systemd startup, covering boot optimization and kernel crash recovery....