If you are an Ubuntu or Linux user, you may have experienced a situation in which the file system may have been damaged for unknown reasons. When this happens, you can repair the damaged file system and return it to its normal state using the Ubuntu boot CD. Accessing the boot menu can help you to detect any errors that may have occurred and help you address the crash correctly.
This article will show you how to address a damaged file system by using command lines to search for and find errors.
How To Repair a File System Error on Ubuntu
Boot your system using the Ubuntu installation CD, and then select Test Ubuntu.
Next, open a terminal, and use the command line
$ sudo fsck.ext3 -f /dev/sdaX
to launch a search for any errors. All errors found should be repaired.
You can ask the system to check the file system at the next reboot by typing