In this post we will discuss the GRUB2 (GRand Unified Boot-loader) in Linux. recently i surfing the Linux base concepts then i came to know about grub2. here i ll share what is boot loader?, how grub2 boot loader is works? and how we can customize? and how we apply the themes? What is the Boot Loader Boot loader is small code reside in MBR to load the kernel(core) of the operating system and give the control to OS. When PC is switched on the system controls goes to BIOS. Bios initialize the peripherals and check the booting order of the device then select the highest priority of the device execute the code stored in MBR of that device. Each Operating System shipped with boot loader For Example :- Microsoft Windows up to Windows XP comes with NTLDR boot loader From Windows Vista onward they use BOOTMGR as a boot loader. These boot loaders are specifically designed to load Windows OS. If want use these boot loader to boot other OS (Linux, Mac OS X) then we need t