Chapter 8. Next Steps and Where to Go From Here 8.1. Shutting down the system 8.2. If You Are New to Unix 8.3. Orienting Yourself to Ubuntu 8.3.1. Ubuntu Packaging System • /usr (excluding /usr/local ) • /var (you could make /var/local and be safe in there) 1. Under the SysV init system halt had the same effect as poweroff , but with systemd as init system their effects are different. 74 The most important concept to grasp is the Ubuntu packaging system, which may be familiar to those who have already used Debian. In essence, large parts of your system should be considered under the control of the packaging system. These include: Ubuntu is a little different from other distributions. Even if you’re familiar with Linux in other distri- butions, there are things you should know about Ubuntu to help you to keep your system in a good, clean state. This chapter contains material to help you get oriented; it is not intended to be a tutorial for how to use Ubuntu, but just a very brief glimpse of the system for the very rushed. Linux is an implementation of Unix. The Linux Documentation Project (LDP) (http://www.tldp.org/) collects a number of HOWTOs and online books relating to Linux. Most of these documents can be in- stalled locally; just install the doc-linux-html package (HTML versions) or the doc-linux-text package (ASCII versions), then look in /usr/share/doc/HOWTO . International versions of the LDP HOWTOs are also available as Ubuntu packages. If you are new to Unix, you probably should go out and buy some books and do some reading. A lot of valuable information can also be found in the Debian Reference (http://www.debian.org/doc/user- manuals#quick-reference). This list of Unix FAQs (http://www.faqs.org/faqs/unix-faq/) contains a number of UseNet documents which provide a nice historical reference. Just use reboot to reboot the system and halt to halt the system without powering it off $^{1}$. To power off the machine, use poweroff or shutdown -h now . The systemd init system provides additional commands that perform the same functions; for example systemctl reboot or systemctl poweroff . Alternatively you can press the key combination Ctrl - Alt - Del . If the key combinations do not work, a last option is to log in as root and type the necessary commands. To shut down a running Ubuntu system, you must not reboot with the reset switch on the front or back of your computer, or just turn off the computer. Ubuntu should be shut down in a controlled manner, otherwise files might get lost and/or disk damage might occur.