Wrong kernel after upgrade --- old kernel still installed?

I just upgraded from 13.10 to 14.04, but when I do uname -r, it says I have kernel 3.11. I want to have the default 14.04 kernel, (3.13 I believe). How can I get this?

This is very similar to Ubuntu 13.10, kernel still 3.8.0-31-generic --- answering here so that this is a more generic question/answer.

Sometime in the upgrade process the kernel meta-packages are "lost". The basic solution is to reinstall the generic kernel package:

sudo apt-get install linux-generic 

which should give you the correct kernel packages and headers after a:

sudo apt-get update; sudo apt-get upgrade 

(obviously if you have -rt or -lowlatency or other "flavored" kernels you have to adapt this to your case)

Sometime the system is (wrongly) convinced it has the newest kernel: in that case, try

sudo apt-get install --reinstall linux-generic