Linux Boot Process

Question 1

BIOS

Answer 1

Basic Input/ Output System

Performs Power On Self Test and executes the MBR (Master Boot Record)

Question 2

MBR

Answer 2

Master Boot Record

Very beginning of the bootable disk, contains the primary bootloader, partition table, and MBR validity check

Question 3

GRUB Phase

Answer 3

Grand Unified Bootloader
-Most important piece of software on the system
Dynamically configurable, changes GRUB is capable of making during boot include:
Altering Boot entries
Selecting different Kernels (OS’s)
Modifying the initial RAM disk (initrd)

Question 4

Kernel Phase

Answer 4

Kernel Phase
Mounts root file system specified in the root= entry in the grub.conf file
Executes /sbin/init daemon, the very first process started with a PID of 1 , parent process for all other processes

Question 5

Init Phase

Answer 5

Init Process Daemon
Used to place and maintain the system in a specific run level or state
there are up to 8 run levels depending on version of UNIX
This mod covers sysvinit

Question 6

Run Level Phase

Answer 6

Run Level Phase
0 Halt mode
1 single user mode
2 Multi User Mode
3 Full Multi User Mode
4 User Defined Mode
5 X11
6 Reboot Mode