Detailed boot-up process for Linux systems from boot to normal service

1. BIOS power-on self-test, detect hardware, find boot partition
2, read and execute MBR (Master boot Record) bootloader (grub program)
3, according to bootloader in the device load Kernel,kernel will start to detect hardware and load driver
/etc/grub.conf is the configuration file in bootloader that needs to load kernel
4. Kernel boot
The file is:/sbin/init, mainly to prepare the software execution Environment
5. Initialize the system
execute/etc/rc.d/rc.sysinit in/etc/init/rcs.conf file
features of the Rc.sysinit script:
host name, mount device, determine whether to start SELinux, network environment, initialize RAID
6. Init find the/etc/inittab file to determine the default RunLevel
operating level:
# Default RunLevel. The runlevels used is:
# 0-halt (do not set Initdefault to this) shutdown
# 1-single User mode single
# 2-multiuser, without NFS (the same as 3, if you don't have networking) multiuser mode, network not supported
# 3-full Multiuser mode multi-user, no network support
# 4-unused reserved Items
# 5-x11 Graphics mode
# 6-reboot (do not set Initdefault to this) reboot
# 
Id:3:initdefault: Default is the graphics mode, the general working scene changed to 3 text mode

7, the system starts to run the program/etc/init/rc.conf
If the system RunLevel is 3, enter/ETC/RC3.D to see many files starting with K, indicating that the level does not start the service; The numbers represent the starting order, from small to large. Start the service view Chkconfig--list
8, the implementation of/etc/rc.d/rc.local
If you want to start a command or execute a script, write to the file.
9, open the terminal or graphical interface (prerequisite system installed desktop software package), enter the account number and password login to the system, open the shell

Note: two drawings (INIT-UPSTART-SYSTEMD)

Figure One:

Figure 2:

Detailed boot-up process for Linux systems from boot to normal service