_Do not just turn off the computer! You risk losing valuable data!_
If you are the only user of your computer, you might want to turn
the computer off when you’re done with it.
To avoid possibly weakening some hardware components, only turn off
the computer when you’re done for the day. Power up and power down
are the two greatest contributors to wear and tear on computer
components. Turning the computer on and off once a day is probably
the best compromise between your electric bill and your computer’s
lifespan.
It’s a bad thing to just press the power switch when you’re done
using the computer. It is also bad to reboot the machine (with the
Reset button) without first taking proper precautions. The Linux
kernel, in order to improve performance, has a disk cache. This
means it temporarily stores information meant for permanent storage
in RAM. Because memory is thousands of times faster than a disk,
this makes many file operations move more quickly. Periodically, the
information Linux has in memory is actually written to the disk.
This is called _syncing_. In order to turn off or reboot the
computer safely, you’ll have to tell the computer to clear
everything out of memory and put it in permanent storage.
To reboot, just type reboot or press Ctrl-Alt-Del (that’s Ctrl, Alt,
and Delete).
To shut down, you’ll have to log in as root. As root, just type the
command shutdown -h now. The sytem will go through the entire
shutdown procedure, including the sync command, which clears the
disk cache as described above. When you see System halted, it’s safe
to turn off the computer. If you have Advanced Power Management
(APM) support in your kernel and BIOS, the computer might shut
itself off and save you the trouble. APM is common in laptops and is
also found in certain desktop mainboards.