Screenshot

Definition
The term screenshot usually describes an image taken of a user's graphical environment, or desktop. A screenshot can be either of the entire desktop with everything on it, or it can be of just a single open window. It is also possible to get "screenshots" of non-graphical output, such things as a computer's power on self test messages and/or BIOS interface can be grabbed.

One Screenshot
Gnome: hit the Print Screen key on the keyboard.

A dialog will pop up asking you where to save and which file format you'd like it in.

KDE: hit the Print Screen key on the keyboard.

A dialog will pop up asking you where to save and which file format you'd like it in.

Multiple Screenshots or Video
Xvidcap: Run gvidcap (which comes with xvidcap) because it's better maintained.

Import Tools
If there are no pre-established mechanisms, use xwd > out.xwd
 * GIMP: Go to File -> Aquire -> Screen Shot... Then you can save the image.
 * XWD: Use e.g.
 * the 'import' utility that is part of the ImageMagick collection that ships on most or all distros:

A simple command: import -window root picname.ext will suffice -- where you substitute ext by the filename extension. The choice of extension determines which format the image is saved in. png is a good choice.

To just grab a single client window, something like import -frame picname.ext will do.

To use the mouse to choose which window to capture, use the command: import picname.ext The cursor will change to a '+'. You can then click on the window which has the image you want to capture.

There are many options -- see the import manual for full details. One particularly helpful one is "-pause n". For something a little more convenient, you can write a little script.