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What should I do when Ubuntu freezes?

My PC is Dell Optiplex 380, the original OS is Ubuntu 11.04, and I upgraded it to 12.04 right now. After reboot, the keyboard is freezed, and monitor cannot light up.

Seems video card driver is incorrect and USB port is not working.

Please help me, it has very important data in it ......

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marked as duplicate by Jorge Castro, Uri Herrera, Eliah Kagan, SirCharlo, Marco Ceppi Aug 24 '12 at 16:07

This question was marked as an exact duplicate of an existing question.

Did you mean 10.04LTS? – Ross Fleming May 2 '12 at 6:38
My mistake, it is 11.04 not LTS – Freeman Zhang May 2 '12 at 7:08
up vote 0 down vote accepted
  1. Ubuntu 11.04 is no LTS (LTS Versions are released every 2 years, that means ...,8.04, 10.04 or 12.04) -->

  2. If you only want to backup your data, you should boot an Ubuntu Live CD maybe in an older version ( ) and copy the data from the disk to an external drive (USB-HDD, Flash-Disk,...) Most important is in /home/username

  3. Does the console open when you press CTRL+ALT+F2 ?

  4. What is your current graphics card? Still the intel onBoard?

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about 1: sorry my mistake, the original OS is ubuntu 11.04 about 2: I'm trying to recovery by Live CD, but after mounted /dev/sda1 to /mnt and chroot / /mnt, I found /home direcory is empty..... about 3: The keyboard is freezed, cannot change to the console about 4: Yes it is intel on-board – Freeman Zhang May 2 '12 at 7:03
OK, my /home is in /dev/sda2. it is safe to reinstall ubuntu 11.04? – Freeman Zhang May 2 '12 at 7:14
their should be no problem to install 12.04 if the live cd boots properly. You can mount /dev/sda2 to /home during installation. But my advice: rename the username folder in /home to username.old or so and install the system in sda1. Then during the installation mount sda2 in /home and create your user. After installation is finished, copy the needed files from username.old to username. That's because after Upgrade(s) there is also much waste in the home directory and so you can clean it. It's more work, but the cleaner way I think. – Felix Haller May 2 '12 at 16:23

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