Linux Amazing Keypresses & Commands : Set 3

1. Unmount busy drives
You are probably all too familiar with the situation - you are trying to unmount a drive, but keep getting told by your system that it's busy. But what application is tying it up? A quick one-liner will tell you:
$lsof +D /mnt/windows
This will return the command and process ID of any tasks currently accessing the /mnt/windows directory. You can then locate them, or use the kill command to finish them off.

2. su command  fast execution without logging in.
$su --c [command]
It enables you to issue a command in administrative mode directly after providing the superuser password. And when the command is executed the user is logged off to the previous user.

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.