Apt

I ran into the following error when I added a new repository to my kubuntu box and ran apt-get update:
E: Dynamic MMap ran out of room. Please increase the size of APT::Cache-Limit. Current value: 123123. (man 5 apt.conf)

To fix this, navigate to /etc/apt/apt.conf.d and edit the file related to debconf which in my case was 70debconf. Add the following line to the bottom of this file and save it:
APT::Cache-Limit "200000000";

Earlier today, I noticed - in htop - that a particular process, let's say 'foo-123', was running even though I had removed the package 'foo' many days earlier. I tried removing it again and found that I was right and that the package had already been removed. The package dependency list was way too long for me to go removing them one by one, or parsing them out and removing the lot.

IRC, however, was very obliging to my query and provided me with the below-pasted nifty solution that did not allow any odd gimmickry:
sudo aptitude search '~i' | grep foo

If you ever find yourself running into a monotonous

"The following packages have been kept back"

error message when you run sudo apt-get upgrade, then the "fix" is to either run apt-get dist-upgrade which is quicker, but sounds more ... dangerous or to run apt-get install [package list] where package list is a list of all packages that have been kept back.