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Today after upgrading to Ubuntu 14.04 (from 13.10), I pressed the key on my laptop (DELL Inspiron N4010) keyboard which is designed to decrease LCD backlight intensity. This key and its opposite (which increases LCD backlight intensity) was working without any problem in 13.10, But today after pressing this key about 5 times, backlight intensity decreased step-by-step by each press and after 6th press a strange thing happened: the screen become black (with backlight is ON) and the mouse pointer doubled in size and was frozen on bottom of the screen. It seems like the situation in which display driver stops working properly!!!

I waited for about 5 minutes and no thing occurred. Everything was frozen. So I turned off my laptop by holding down power button and after restart when I opened a terminal command line history data was something like this: ��^E^L����J2H�Ju^V4���r��^W�
I opened .bash_history file by gedit and it was corrupted!!!
Now I like to know why my command line history is corrupted and how to recover it?

Also there is another symptom on my laptop just after upgrading to 14.04! which may help: That is after restarting and entering my user password to login to my session, the screen is corrupted for 1 second and become normal again. "Corrupted" I mean it is pixelated and pixel size is about 30x30 lcd pixels.

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Possibly a graphic driver issue. Can you log in a tty and see what it looks like there? Press Ctrl+Alt+1, then log in with your username and account, and inspect your bash history with less ~/.bash_history. – Sparhawk Apr 30 '14 at 3:38

How you go about rescuing this really depends on what you mean by corrupted.

  • If it's just got a few weird characters in there on a few lines, sanitise it in your favourite editor and you should be fine.

  • If it's completely junked, that's that I'm afraid. Delete it and move on. The only recourse here is restoring from a backup.

The strange thing is the window for this stuff to happen should be pretty tiny these days. The default filesystems are journalled to minimise loss like this... But unless you have a battery-backed write cache (some enterprise drives and RAID cards do) there's always the possibility the system will be in the middle of writing something when you shut the power off.

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I restored an older version from backup. But I need to know why this problem and how to prevent from occurring again! – PHP Learner May 10 '14 at 11:30

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