root@ubuntu1204:/etc/apt# do-release-upgrade -p
The program 'do-release-upgrade' is currently not installed.  You can install it by typing:
apt-get install update-manager-core
root@ubuntu1204:/etc/apt# apt-get install update-manager-core
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-generic-lts-raring : Depends: linux-headers-generic-lts-raring but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).