Open Source Summit + Embedded Linux Conference North America 2026

From the moment you press the power button to the instant the login prompt appears, a complex sequence of events happens behind the scenes to get your Linux system up and running. This talk aims to demystify the Linux boot process through a deep dive into each stage.
Starting from the role of system firmware, we compare legacy BIOS with modern UEFI and see why there has been a shift to UEFI. From there, we move on to the bootloader stage, discussing its function in loading the kernel and passing control over to it. Using GRUB as an example, we show how to view and customize bootloader configurations. Next, we explore the kernel initialization stage, including the role of initrd/initramfs, how the real root filesystem is mounted, and how the kernel initializes essential system components and launches the first userspace process. From there, control transitions to the init system. We examine SysVinit and its more modern alternative, systemd, and their roles in bringing the rest of the system online.
Finally, we cover practical debugging techniques, such as viewing boot logs, analyzing boot performance, optimizing boot up time, and improving security with features like Secure Boot.