Hmm.. That's not good..
Generally, the error that you have stated here indicates that there is some sort of problem with the hard drive or partition that is indicated in the message - in your case, this is stating that "/" is the problem, which is the root of your filesystem (where 'Linux is installed').
What happens when you press 'F' to attempt to fix? Are you able to push past and get Ubuntu to boot up?
You may also want to try manually scanning the hard drive for errors... One way to do this would be to put the Ubuntu Live CD (installation CD) in and boot from it. You could then use Disk Utility to browse for the drive/partition in question and scan it for errors via 'Check Filesystem' (this article shows a screenshot of what I am describing: http://www.howtogeek.com/howto/37659/the-beginners-guide-to-linux-disk-utilities/)
The disk drive /tmp is not ready yet or not present.
then you can fix that with above ^-^ flag