reboot and shutdown

Question 1

we are telling the system to shut down and restart right now.

Answer 1

shutdown -r now

Question 2

broadcasts a message to all logged in user (after message typed you terminate it with Ctrl + D)

Answer 2

wall

Question 3

if you’re on an older upstart or System 5
init system. Which we’ll switch you to run level 0, and halt your computer.

Answer 3

telinit 0

Question 4

Here we use the -h option to indicate that we want to halt and power down the computer, and then we specify a time. And within one minute, the computer will shut down,
and you can also see that wall was invoked to send a message to all logged in users that the computer will be powered down in one minute.

Answer 4

shutdown -h +1

Question 5

Advanced Configuration and Power Interface registers system events (such as pressing power
button or closing laptop lid)

Answer 5

acpid