In order to research what caused the installation of a given package, I'd like to get a list of packages which depend on that package. I couldn't find anything obvious in
apt-cache rdepends packagename should do what you want
aptitude has a fairly nice way of handling this:
$ aptitude why bash i foomatic-filters PreDepends bash (>= 2.05)
By default, it only lists the "most installed, strongest, tightest, shortest" reason, but you can use
aptitude -v why to make it output everything it finds.
apt-cache showpkg <pkgname>
apt-cache showpkg lightdm
There is more than one way, with each method showing a different output.
For a detailed view of the full reverse dependency tree;
aptitude install apt-rdepends apt-rdepends -r bash
apt-cache showpkg bash
Or a concise list:
apt-cache rdepends bash
In addition to other good answers, doing:
sudo apt -s remove <pkgname>
-s Does a "simulated" removal. )
The removal command will normally list any dependencies/programs/libraries that will be affected or that can removed (orphaned) along with specified pkg. (If they exist.)
The simplest option is still:
apt rdepends package-name
which does not require you to install any package.