Whole document tree
Do not just turn off the computer! You risk losing valuable data!
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.
John Goerzen / Ossama Othman