I was messing around with my Ubuntu 13.04 and eventually rebooted, now Unity is missing and I can't seem to even install it .
sudo apt-get install unity
karthik@karthik-K55VM:~$ sudo apt-get install unity Reading package lists... Done Building dependency tree Reading state information... Done Package unity is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'unity' has no installation candidate