Linux + Troubleshooting and maintenance part 1 & 2عربي

reboot This will shut down all services and restart
halt Will shutdown all services and then stop the computer with the message
"System Halted"

shutdown When used with a parameter(will tell the system how lont to wait before 
shutting down and whether to reboot or halt)
ex: To halt the system in five minutes shutdown -h r

Ctrl+Alt+Del Executes a shutdown command immediately

telinit 0 Will halt the system (shutting down all services first)

telinit 6 Will reboot the system (shutting down all services first)

This program is controlled by the /etc/inittab configuration file. 
The /etc/inittab file is different in each version of Linux. Most of the files
referred to in /etc/inittab are in the /etc/rc.d subdirectory
Run levels 0,1, and 6 are reserved. 

Logged in as Root, type in the following at the command line to get following results:

init 0 System halts and shutsdown
init 1 System boots in single use mode
init 2 Systme boots in multiuser mode with no networking
init 3 Regular default multiuser mode
init 4 Not Used
init 5 Graphical Login
init 6 System Reboots

part 1
part 2