Linux is Very Stable operating system unlike windows.It have very less crashes, stuckes and freezes which is very common with windows.But at rare cases this may occur in Linux.
We have 3 Quick ways to fix this problem without switching off your computer or rebooting it.
1)If only some applications are not responding not the whole desktop is frozen
Take system->Administration->System Monitor.
Then select the frozen application.Now click Kill process.
2)Try the key combination of Ctrl + Alt + Backspace to logout.Then login.
3)Use Virtual console
This way is little complicated than the first one but better method.Press
Ctrl + Alt + F2 to take the virtual console.Then log in and type:
ps -ax | grep startx
This command will return the PID of the Xserver.
Kill Xserver
kill -9 PID_Number
Return to your first console.
Press Alt + F1.
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