this is the step that i done yesterday when my Centos fail to boot because of electricity problem. this is for checking file system concurrency when ask by the system.
fsck /dev/sda1
please be sure to specify file system
fsck -t ext3 /dev/sda1 or
fsck.ext3 /dev/sda1
answer y for all question that came up, tryto use :
fsck -y /dev/sda1
once it has finished, remount file system : mount /usr/u02
read man fsck for further information.