Linux Amazing Keypresses & Commands : Set 2

1. Some handy linux keyboard shortcuts!
[alt][tab] Walk through windows. To walk backwards: [alt][shift][tab]
[ctrl][tab] Walk through desktops. To walks backwards: [ctrl][shift][tab]
[ctrl][esc] Show the table of processes running on my system. Allow me to kill any of the processes I started (or send other signals to them).
[alt][f1] Access the K-menu ("Equivalent to MS Windows "Start" menu).
[alt][f12] Emulate the mouse using the arrow keys on the keyboard.
[alt][leftmousebutton] Drag a window to move it. Normally, I move a window by dragging its top title bar, but occassionally I manage to get it off the screen. With this shortcut, I can drag by any part of the window.
[alt][printscreen] Take a snapshot of the current window into the clipboard.
[ctrl][alt][printscreen] Take a snapshot of the entire desktop into the clipboard.
[ctrl][alt][l] Lock the desktop.
[ctrl][alt][d] Toggle hide/show the desktop (great to hide the Solitaire game when your boss walks in).

2.  'xkill' Command :  Kills on X-windows the process that we select by clicking it with the mouse. It's the same as kill but on graphical mode. Hotkey: Ctrl+Alt+ESC.

3. 'at' Command : Scheduling  processes or tasks to be run at a particular time.
Examples:
Sets the computer to play the cd at 7:00.
$at 7:00 cdplayd
List the automatic programmed jobs.
$time atq
Delete automatic job number 8.
$time atrm 8     

4.  rdate : Synchronize system date & time.
Shows the server date and time.
$rdate -p ntp.nasa.gov
Synchronizes your time and date with the server.
$time rdate -s ntp.nasa.gov