C Y B E R I N S I G H T

Initramfs is a CPIO format archive, that every Linux kernel contains, which is extracted into rootfs when the kernel boots up. It contains a complete root file system for Linux. It then helps to assemble and mount the real root file system. The initramfs or early userspace is necessary for complex setups, like network boot, LVM, raid, which needs additional user space utilities to get rootfs accessed. initramfs does not need to contain every module that a user might want to use, instead it only contains the modules which are required to access the root filesystem. Rest major modules will be loaded later by udev during init process. After extracting, kernel checks for /init file. If it finds, then it is executed as PID 1. This /init program helps in finding real root device if there is any. If kernel does not find /init in rootfs, it falls back to older code to locate and mount a root partition and then executes /sbin/init . Thanks Ayush

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