Kernel initialization

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.kernel detects the attached devices in the system & loads thier drivers into RAM.

.mounts root filesystem into read-only memory mode.

.Then initializes the ‘init’ process for further processing

init=it is the first process that is started at the boot time.

–init initialization

/etc/inittab – main config file for init

Runlevel

0 – halt

1 – single user mode

2 – 2 to 4 is same text based terminal (f1-f6)

3

4

5 – both text & GUI (f1-f6)+f7

6 – reboot

to system shutdowm

#halt

#poweroff

#init 0

#shutdown -h now

to system reboot

——–

reboot

init 6

shutdown -r now

alt+ctl+del

#shutdown -h +n (shutdown after n minutes)

-r for reboot

#shutdown -c (to cancel the schedule shutdown)