A Linux computer needs to be turned off correctly, to ensure that files are correctly written to the hard drive, and that programs are closed properly.
/sbin/shutdown -r now
/sbin/shutdown -h now
Press Control-Alt-Delete
When the shutdown command starts, it will display information
as each step of the shutdown sequence is completed, until the computer finally
displays:
The system is halted
in which case you can turn off the computer, or
Please stand by while rebooting the system...
for a computer that is being rebooted.