Many of us are using Linux, but how many have ever wondered what exactly happens when a system is powered on, how Linux kernel is loaded, how a login screen prompts? Let's have a deep walk though Linux booting process. After reading this, one would have understanding not only on Linux booting process, but also on BIOS, UEFI firmware, MBR & GPT partitions, bootloaders like GRUB, Linux kernel etc. Let's get started . . . . In order to boot Linux, a Linux capable bootloader such as syslinux or GRUB is needed. They need to be installed in Master Boot Record (MBR) or in GUID Partition Table (GPT). Boot loader loads the kernel and initial ramdisk before actual boot process is initialized. This process is different for different firmwares such as BIOS and UEFI. When the power is on, Power On Self Test (POST) begins which ensures hardwares are ready. After it, BIOS or UEFI firmware is loaded which initializes required hardwares for booting. WHAT IS BIOS? BIOS (Basic Input
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