Q1. Answer Booting Sequence and process BIOS[basic input output system]] post - power on self test will check the system integrity if each and hw is working fine or not if not then will display an error if internal speaker are present on the motherboard it will beep once if everything is good. Searches loads and executes the boot loader program(which is part of the mbr) is once the boot loader programs is detected then bios gives control to MBR Bios also holds information related to hardware and firmware and also have stored the booting sequence or the priorities Once the harddisk whichever was in sequence loads mbr will take place MBR[master boot record which has the size of 512 bytes] 512=446[primary boot loader haves the information where boot information is stored]+64[partition table]+2[magicnumber] It is located in the first sector of the bootable disk GRUB(grand unified boot loader)other option available is LILO[linux loader] Its function is to take over from BIOS at boot time, load itself, load the Linux kernel into memory, and then turn over execution to the kernel. Once the kernel takes over, GRUB has done its job and it is no longer needed. Current version which is in market is 2 hence grub2 Boot.img First partition of harddrive begins at sector 63 which stores core.img It loads the linux kernel into ram If you have multiple kernel images installed on your system it gives the screen for temporarily which loads the default kernel if none selected Config file for grub is /boot/grub/grub.conf Consist of the initrd and the kernel image Kernel Mounts sysroot file system as temporarily Oncer kernel starts operating it starts sbin/init process Initrd is used by kernel as temporary root file system until kernel mounts the actually kernel mounts the root filesystem INIT/SYSTEMD [in init] views /etc/inittab file to decide the linux run level [in init] run level decides which initial programs are loaded at startup RUN LEVELS 0 for halt 1 for single user mode 2 for multiuser without nfs 3 full multiuser 4 unused 5 X11 6 reboot [in systemd] system daemon will start fork() system call we'll take the place Whichever target is selected will load graphical.target multiuser.target According the targets required services will start others will start eventually as per requirement RUN LEVELS/TARGETS [when using runlevel]Demanding on your init level setting system will execute the programs from one of the following directories when using runlevel]RUN LEVEL {0..6} -> /etc/rc.d/rc{0..6}.d/ when using runlevel]Under the above mentioned directories programs would be there program which starts withi s will used for start up and k are used during shutdown to kill the proccess -----------------------------------------------------------