You typed the wrong command.That is why it tells you command not found. You need
fsck. Note the spelling. It stands for file system check. You need to do this
as root. If it stops you at boot up you can input your password and run the
command. For how to use the command, try:
beginlinux.com/.../53-touble\
shooting/354-fschk or http://linux.die.net/man/8/fsck.
Ctrl-D will resume.