ls (list): This command lists directory contents (directory is Linux's word for a folder.) This will show you all of the files and directories available to you in the current directory.

cd <folderdirectory name> (change directory). This command allows you to move into another directory so you can see its contents, in the same way that double-clicking on a directory icon moves you into that directory. You can move through multiple levels of directories in one go by separating the folder directory names with a "/", and you can go up to the parent directory (the directory that contains the current directory) using the special .. directory name.

man <program name> (open manual): This command will bring up lots of information about a particular program, including what it does and how to use it. Very useful if you forget how to use something! Try man ls to see some advanced information on the ls program we tried earlier, and press Q on the keyboard to quit. You can scroll through this information using the arrow keys or the Space Bar.

<program name> (extra information): This is used to start the program, and optionally pass it some extra information. Try typing in scratch to start the Scratch program (we'll cover this in more detail in the next chapter), or if you are connected to the Internet, go to epiphany www.raspberrypi.org to open the Epiphany web browser and then go straight to the Raspberry Pi home page.

My Raspberry Pi doesn't boot (only the red power light comes on): this suggests that the SD card was not written correctly. Try following the instructions again to copy an OS image onto your SD card, and if this fails, try a new SD card.

My Raspberry Pi randomly restarts by itself: this is usually because the Pi is not receiving enough power. Double-check that your power supply is capable of supplying at least 700 mA (0.7A) at 5V. This should be written on the supply somewhere. Perhaps, try upgrading to a 1000 mA (1.0A) supply if you continue to have problems.

Also make sure that you do not have particularly power-hungry peripherals plugged into your Raspberry Pi. Some Wi-Fi dongles and keyboards with extremely bright LEDs can cause problems, for example.

I can't enter my password on the login screen: nothing is shown when the password is entered (not even stars) to minimize the information that others can gain from seeing the screen. It is likely that the keys are still being recognized: try typing in the whole password blindly and pressing Enter.

The display does not fill my screen or extends beyond the edges: this is because of the overscan settings. Many old televisions had cabinets which overlapped part of the screen, so images were given black borders to ensure that none of the picture was lost. Many modern monitors do not have this problem, however, so the black bars are just a nuisance. First, try enabling or disabling overscan by typing sudo raspi-config in a command line and selecting the appropriate option. If this still does not work, search the Internet for Raspberry Pi overscan troubleshooting for detailed guides.

I can't see anything at all on the screen: if the Pi is definitely on, and the OK/ACT light is lit or flashing, try pressing 1, 2, 3, or 4 on your keyboard to select different video modes.

My keyboard is behaving strangely: some wireless keyboards occasionally do not work as expected, for example, by registering double key presses or not noticing a key press at all. This should be fixed in the future by software updates, or you can always try another keyboard if you have one.